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Anti Iba1, Rabbit antibody

RRID:AB_839504

Antibody ID

AB_839504

Target Antigen

Iba1 human, mouse, rat

Proper Citation

(Wako Cat# 019-19741, RRID:AB_839504)

Clonality

polyclonal antibody

Comments

Applications: IHC. Consolidation on 7/2018: AB_839504, AB_10206679, AB_2665520.

Host Organism

rabbit

Vendor

Wako

Cat Num

019-19741

Publications that use this research resource

Grafts of Olfactory Stem Cells Restore Breathing and Motor Functions after Rat Spinal Cord Injury.

  • Stamegna JC
  • J. Neurotrauma
  • 2018 Aug 1

Literature context:


Abstract:

The transplantation of olfactory ecto-mesenchymal stem cells (OEMSCs) could be a helpful therapeutic strategy for spinal cord repair. Using an acute rat model of high cervical contusion that provokes a persistent hemidiaphragmatic and foreleg paralysis, we evaluated the therapeutic effect of a delayed syngeneic transplantation (two days post-contusion) of OEMSCs within the injured spinal cord. Respiratory function was assessed using diaphragmatic electromyography and neuroelectrophysiological recordings of phrenic nerves (innervating the diaphragm). Locomotor function was evaluated using the ladder-walking locomotor test. Cellular reorganization in the injured area was also studied using immunohistochemical and microscopic techniques. We report a substantial improvement in breathing movements, in activities of the ipsilateral phrenic nerve and ipsilateral diaphragm, and also in locomotor abilities four months post-transplantation with nasal OEMSCs. Moreover, in the grafted spinal cord, axonal disorganization and inflammation were reduced. Some grafted stem cells adopted a neuronal phenotype, and axonal sparing was observed in the injury site. The therapeutic effect on the supraspinal command is presumably because of both neuronal replacements and beneficial paracrine effects on the injury area. Our study provides evidence that nasal OEMSCs could be a first step in clinical application, particularly in patients with reduced breathing/locomotor movements.

Funding information:
  • PHS HHS - 78795(United States)

Cancer Lipid Metabolism Confers Antiangiogenic Drug Resistance.

  • Iwamoto H
  • Cell Metab.
  • 2018 Jul 3

Literature context:


Abstract:

Intrinsic and evasive antiangiogenic drug (AAD) resistance is frequently developed in cancer patients, and molecular mechanisms underlying AAD resistance remain largely unknown. Here we describe AAD-triggered, lipid-dependent metabolic reprogramming as an alternative mechanism of AAD resistance. Unexpectedly, tumor angiogenesis in adipose and non-adipose environments is equally sensitive to AAD treatment. AAD-treated tumors in adipose environment show accelerated growth rates in the presence of a minimal number of microvessels. Mechanistically, AAD-induced tumor hypoxia initiates the fatty acid oxidation metabolic reprogramming and increases uptake of free fatty acid (FFA) that stimulates cancer cell proliferation. Inhibition of carnitine palmitoyl transferase 1A (CPT1) significantly compromises the FFA-induced cell proliferation. Genetic and pharmacological loss of CPT1 function sensitizes AAD therapeutic efficacy and enhances its anti-tumor effects. Together, we propose an effective cancer therapy concept by combining drugs that target angiogenesis and lipid metabolism.

Funding information:
  • British Heart Foundation - G0802266(United Kingdom)

The microbiota influences cell death and microglial colonization in the perinatal mouse brain.

  • Castillo-Ruiz A
  • Brain Behav. Immun.
  • 2018 Jul 11

Literature context:


Abstract:

The mammalian fetus develops in a largely sterile environment, and direct exposure to a complex microbiota does not occur until birth. We took advantage of this to examine the effect of the microbiota on brain development during the first few days of life. The expression of anti- and pro-inflammatory cytokines, developmental cell death, and microglial colonization in the brain were compared between newborn conventionally colonized mice and mice born in sterile, germ-free (GF) conditions. Expression of the pro-inflammatory cytokines interleukin 1β and tumor necrosis factor α was markedly suppressed in GF newborns. GF mice also had altered cell death, with some regions exhibiting higher rates (paraventricular nucleus of the hypothalamus and the CA1 oriens layer of the hippocampus) and other regions exhibiting no change or lower rates (arcuate nucleus of the hypothalamus) of cell death. Microglial labeling was elevated in GF mice, due to an increase in both microglial cell size and number. The changes in cytokine expression, cell death and microglial labeling were evident on the day of birth, but were absent on embryonic day 18.5, approximately one-half day prior to expected delivery. Taken together, our results suggest that direct exposure to the microbiota at birth influences key neurodevelopmental events and does so within hours. These findings may help to explain some of the behavioral and neurochemical alterations previously seen in adult GF mice.

Funding information:
  • NIMH NIH HHS - R21 MH108345()

Behavioural alterations and morphological changes are attenuated by the lack of TRPA1 receptors in the cuprizone-induced demyelination model in mice.

  • Bölcskei K
  • J. Neuroimmunol.
  • 2018 Jul 15

Literature context:


Abstract:

We have recently reported that the Transient Receptor Potential Ankyrin 1 (TRPA1) receptor deficiency significantly attenuated cuprizone-induced demyelination by reducing the apoptosis of mature oligodendrocytes. The aim of the present study was to gather additional data on the role of TRPA1 by investigating the time course of behavioural alterations and morphological changes in cuprizone-treated TRPA1 receptor gene-deficient mice. Demyelination was induced by feeding male wild-type (WT) and TRPA1 gene-deleted (TRPA1 KO) mice with 0.2% cuprizone for 6 weeks. Behavioural tests were performed once per week to follow cuprizone-induced functional changes. Mechanonociceptive thresholds were investigated by a dynamic plantar aesthesiometer and von Frey filaments. Motor performance was assessed by accelerating RotaRod and horizontal grid tests. For the study of spontaneous activity, the open field test was used. The time course of corpus callosum demyelination was also followed weekly by magnetic resonance imaging (MRI). Histological analysis of myelin loss was performed with Luxol Fast Blue (LFB) staining at week 3 and electron microscopy (EM) at week 6. Astrocyte and microglia accumulation at week 3 was assessed by immunohistochemistry (IHC). Cuprizone treatment induced no changes in mechanonociception or motor performance. In the open arena, cuprizone-treated mice spent more time with locomotion, their mean velocity was significantly higher and the distance they travelled was longer than untreated mice. No statistical difference was detected between WT and TRPA1 KO mice in these parameters. On the other hand, significantly increased rearing behaviour was induced in WT mice compared to TRPA1 KO animals. Morphological changes detected with MRI, LFB, IHC and EM analysis revealed reduced damage of the myelin and attenuated accumulation of astrocytes and microglia in cuprizone-treated TRPA1 KO animals, at each examined time point. Our recent data further suggest that inhibition of TRPA1 receptors could be a promising therapeutic approach to limit central nervous system damage in demyelinating diseases.

Funding information:
  • NHLBI NIH HHS - HL59469(United States)

Angiotensin II triggers peripheral macrophage-to-sensory neuron redox crosstalk to elicit pain.

  • Shepherd AJ
  • J. Neurosci.
  • 2018 Jul 5

Literature context:


Abstract:

Injury, inflammation and nerve damage initiate a wide variety of cellular and molecular processes that culminate in hyperexcitation of sensory nerves, which underlies chronic inflammatory and neuropathic pain. Using behavioral readouts of pain hypersensitivity induced by Angiotensin II (Ang II) injection into mouse hindpaws, our study shows that activation of the type 2 Ang II receptor (AT2R) and the cell damage-sensing ion channel TRPA1 are required for peripheral mechanical pain sensitization induced by Ang II in male and female mice. However, we show that AT2R is not expressed in mouse and human dorsal root ganglia (DRG) sensory neurons. Instead, expression/activation of AT2R on peripheral/skin macrophages (MΦs) constitutes a critical trigger of mouse and human DRG sensory neuron excitation. Ang II-induced peripheral mechanical pain hypersensitivity can be attenuated by chemogenetic depletion of peripheral MΦs. Furthermore, AT2R activation in MΦs triggers production of reactive oxygen/nitrogen species, which trans-activate TRPA1 on mouse and human DRG sensory neurons, via cysteine-modification of the channel. Our study thus identifies a translatable immune cell-to-sensory neuron signaling crosstalk underlying peripheral nociceptor sensitization. This form of cell-to-cell signaling represents a critical peripheral mechanism for chronic pain, and thus identifies multiple druggable analgesic targets.Significance Statement: Pain is a widespread problem that is under-managed by currently available analgesics. Findings from a recent clinical trial on a type-II angiotensin II receptor (AT2R) antagonist showed effective analgesia for neuropathic pain. AT2R antagonists have been shown to reduce neuropathy-, inflammation- and bone cancer-associated pain in rodents. We report that activation of AT2R in macrophages that infiltrate the site of injury, but not in sensory neurons, triggers an intercellular redox communication with sensory neurons via activation of the cell damage/pain-sensing ion channel TRPA1. This macrophage-to-sensory neuron crosstalk results in peripheral pain sensitization. Our findings provide an evidence-based mechanism underlying the analgesic action of AT2R antagonists, which could accelerate the development of efficacious non-opioid analgesic drugs for multiple pain conditions.

Funding information:
  • NINDS NIH HHS - R01NS077521(United States)

Male and Female Mice Exhibit Divergent Responses of the Cortical Vasculature to Traumatic Brain Injury.

  • Jullienne A
  • J. Neurotrauma
  • 2018 Jul 15

Literature context:


Abstract:

We previously reported that traumatic brain injuries (TBI) alter the cerebrovasculature near the injury site in rats, followed by revascularization over a 2-week period. Here, we tested our hypothesis that male and female adult mice have differential cerebrovascular responses following a moderate controlled cortical impact (CCI). Using in vivo magnetic resonance imaging (MRI), a new technique called vessel painting, and immunohistochemistry, we found no differences between males and females in lesion volume, neurodegeneration, blood-brain barrier (BBB) alteration, and microglia activation. However, females exhibited more astrocytic hypertrophy and heme-oxygenase-1 (HO-1) induction at 1 day post-injury (dpi), whereas males presented with increased endothelial activation and expression of β-catenin, shown to be involved in angiogenesis. At 7 dpi, we observed an increase in the number of vessels and an enhancement in vessel complexity in the injured cortex of males compared with females. Cerebrovasculature recovers differently after CCI, suggesting biological sex should be considered when designing new therapeutic agents.

Funding information:
  • NICHD NIH HHS - R01HD041462(United States)

Muscarinic receptor M3R signaling prevents efficient remyelination by human and mouse oligodendrocyte progenitor cells.

  • Welliver RR
  • J. Neurosci.
  • 2018 Jun 29

Literature context:


Abstract:

Muscarinic receptor antagonists act as potent inducers of oligodendrocyte differentiation and accelerate remyelination. However, the use of muscarinic antagonists in the clinic is limited by poor understanding of the operant receptor subtype, and questions regarding possible species differences between rodents and humans. Based on high selective expression in human oligodendrocyte progenitor cells (OPCs), we hypothesized that M3R is the functionally relevant receptor. Lentiviral M3R knock-down in human primary CD140a/PDGFαR+ OPCs resulted in enhanced differentiation in vitro and substantially reduced the calcium response following muscarinic agonist treatment. Importantly, following transplantation in hypomyelinating shiverer/rag2 mice, M3R knock-down improved remyelination by human OPCs. Furthermore, conditional M3R ablation in adult NG2-expressing OPCs increased oligodendrocyte differentiation and led to improved spontaneous remyelination in mice. Together, we demonstrate that M3R receptor mediates muscarinic signaling in human OPCs that act to delay differentiation and remyelination, suggesting that M3 receptors are viable targets for human demyelinating disease.SIGNIFICANCE STATEMENTThe identification of drug targets aimed at improving remyelination in patients with demyelination disease is a key step in development of effective regenerative therapies to treat diseases such as multiple sclerosis. Muscarinic receptor antagonists have been identified as effective potentiators of remyelination but the receptor subtypes that mediate these receptors are unclear. In this study, Welliver et al. show that genetic M3R ablation in both mouse and human cells results in improved remyelination and is mediated by acceleration of oligodendrocyte commitment from oligodendrocyte progenitor cells. Therefore, M3R therefore represents an attractive target for induced remyelination in human disease.

Funding information:
  • Medical Research Council - G1000847(United Kingdom)
  • NCATS NIH HHS - UL1 TR001412(United States)
  • NCI NIH HHS - P30 CA016056(United States)
  • NIGMS NIH HHS - R25 GM095459(United States)
  • NINDS NIH HHS - R01 NS104021(United States)

Siglec-H is a microglia-specific marker that discriminates microglia from CNS-associated macrophages and CNS-infiltrating monocytes.

  • Konishi H
  • Glia
  • 2018 Jun 5

Literature context:


Abstract:

Several types of myeloid cell are resident in the CNS. In the steady state, microglia are present in the CNS parenchyma, whereas macrophages reside in boundary regions of the CNS, such as perivascular spaces, the meninges and choroid plexus. In addition, monocytes infiltrate into the CNS parenchyma from circulation upon blood-brain barrier breakdown after CNS injury and inflammation. Although several markers, such as CD11b and ionized calcium-binding adapter molecule 1 (Iba1), are frequently used as microglial markers, they are also expressed by other types of myeloid cell and microglia-specific markers were not defined until recently. Previous transcriptome analyses of isolated microglia identified a transmembrane lectin, sialic acid-binding immunoglobulin-like lectin H (Siglec-H), as a molecular signature for microglia; however, this was not confirmed by histological studies in the nervous system and the reliability of Siglec-H as a microglial marker remained unclear. Here, we demonstrate that Siglec-H is an authentic marker for microglia in mice by immunohistochemistry using a Siglec-H-specific antibody. Siglec-H was expressed by parenchymal microglia from developmental stages to adulthood, and the expression was maintained in activated microglia under injury or inflammatory condition. However, Siglec-H expression was absent from CNS-associated macrophages and CNS-infiltrating monocytes, except for a minor subset of cells. We also show that the Siglech gene locus is a feasible site for specific targeting of microglia in the nervous system. In conclusion, Siglec-H is a reliable marker for microglia that will allow histological identification of microglia and microglia-specific gene manipulation in the nervous system.

Evidence of altered depression and dementia-related proteins in the brains of young rats after ovariectomy.

  • Fang YY
  • J. Neurochem.
  • 2018 Jun 25

Literature context:


Abstract:

Menopause, a risk factor for brain dysfunction in women, is characterized by neuropsychological symptoms including depression and dementia, which are closely related to alterations in different brain regions after menopause. However, little is known about the variability of pathophysiologic changes associated with menopause in the brain. Here, we observed that menopause in rats induced by bilateral ovariectomy (OVX) showed depressive and dementia-related behaviors along with neuronal loss in the prefrontal cortex (PFC), hippocampus (HIP), hypothalamus (HYP) and amygdala (AMY) by Nissl staining. Meanwhile, by immunohistochemical staining, increased microglia in the HIP and AMY and increased astrocytes in the PFC, HYP and AMY were shown. By using quantitative proteomics, we identified 146 differentially expressed proteins in the brains of OVX rats, e.g., 20 in the PFC, 41 in the HIP, 17 in the HYP and 79 in the AMY, and performed further detection by Western blotting. A link between neuronal loss and apoptosis was suggested, as evidenced by increases in adenylate kinase 2 (AK2), B-cell lymphoma 2 associated X (Bax), cleaved caspase-3 and phosphorylated p53 and decreases in Huntingtin-interacting protein K (HYPK), hexokinase (HK), and phosphorylated B-cell lymphoma 2 (Bcl-2), and apoptosis might be triggered by endoplasmic reticulum stress (probed by increased glucose-regulated protein 78 (GRP78), cleaved caspase-12, phosphorylated protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK), inositol-requiring enzyme-1 (IRE-1) and activating transcription factor 6 (ATF6)) and mitochondrial dysfunction (probed by increased cytochrome c and cleaved caspase-3 and decreased sideroflexin-1 (SFXN1) and NADH dehydrogenase (ubiquinone) 1 α subcomplex 11 (NDUFA11)). Activation of autophagy was also indicated by increased autophagy-related 7 (ATG7), γ-aminobutyric acid (GABA) receptor-associated protein-like 2 (GABARAPL2) and oxysterol-binding protein-related protein 1 (ORP1) and confirmed by increased microtubule-associated protein light chain 3 (LC3II/I), autophagy-related 5 (ATG5), and Beclin1 in the HIP and AMY. In the AMY, which is important in emotion, higher GABA transporter 3 (GAT3) and lower vesicular glutamate transporter 1 (VgluT1) levels indicated an imbalance between excitatory and inhibitory neurotransmission, and the increased calretinin and decreased calbindin levels suggested an adjustment of GABAergic transmission after OVX. In addition, cytoskeletal abnormalities including tau hyperphosphorylation, dysregulated Ca²+ signals and glutamic synaptic impairments were observed in the brains of OVX rats. Collectively, our study showed the changes in different brain regions related to depression and dementia during menopause. This article is protected by copyright. All rights reserved.

Funding information:
  • Howard Hughes Medical Institute - 1K08AI097238-01(United States)

Status epilepticus triggers long-lasting activation of complement C1q-C3 signaling in the hippocampus that correlates with seizure frequency in experimental epilepsy.

  • Schartz ND
  • Neurobiol. Dis.
  • 2018 Jun 25

Literature context:


Abstract:

Status epilepticus (SE) triggers a myriad of neurological alterations that include unprovoked seizures, temporal lobe epilepsy (TLE), and cognitive deficits. Although SE-induced loss of hippocampal dendritic structures and synaptic remodeling are often associated with this pathophysiology, the underlying mechanisms remain elusive. Recent evidence points to the classical complement pathway as a potential mechanism. Signaling through the complement protein C1q to C3, which is cleaved into smaller biologically active fragments including C3b and iC3b, contributes to the elimination of synaptic structures in the normal developing brain and in models of neurodegenerative disorders. We recently found increased protein levels of C1q and iC3b fragments in human drug-resistant epilepsy. Thus, to identify a potential role for C1q-C3 in SE-induced epilepsy, we performed a temporal analysis of C1q protein levels and C3 cleavage in the hippocampus along with their association to seizures and hippocampal-dependent cognitive functions in a rat model of SE and acquired TLE. We found significant increases in the levels of C1q, C3, and iC3b in the hippocampus at 2-, 3- and 5-weeks after SE relative to controls (p<0.05). In the SE group, greater iC3b levels were significantly correlated with higher seizure frequency (p<0.05). Together, these data support that hyperactivation of the classical complement pathway after SE parallels the progression of epilepsy. Future studies will determine whether C1q-C3 signaling contributes to epileptogenic synaptic remodeling in the hippocampus.

The neuroregenerative capacity of olfactory stem cells is not limitless: implications for aging.

  • Child KM
  • J. Neurosci.
  • 2018 Jun 22

Literature context:


Abstract:

The olfactory epithelium (OE) of vertebrates is a highly regenerative neuroepithelium, maintained under normal condition by a population of stem and progenitor cells - globose basal cells (GBCs) that also contribute to epithelial reconstitution after injury. However, aging of the OE often leads to neurogenic exhaustion - the disappearance of both GBCs and olfactory sensory neurons (OSNs). Aneuronal tissue may remain as olfactory, with an uninterrupted sheet of apically arrayed microvillar-capped sustentacular cell, or may undergo respiratory metaplasia. We have generated a transgenic mouse model for neurogenic exhaustion using OMP-driven Tet-off regulation of the A subunit of Diphtheria toxin such that the death of mature OSNs is accelerated. As early as 2 months of age the epithelium of transgenic mice, regardless of sex, recapitulates what is seen in the aged OE of humans and rodents. Areas of the epithelium completely lack neurons and GBCs, while the horizontal basal cells, a reserve stem cell population, show no evidence of activation. Surprisingly, other areas that were olfactory undergo respiratory metaplasia. The impact of accelerated neuronal death and reduced innervation on the olfactory bulb (OB) is also examined. Constant neuronal turnover leaves glomeruli shrunken and impacts the dopaminergic interneurons in the periglomerular layer. Moreover, the acceleration of OSN death can be reversed in those areas where some GBCs persist. However, the projection onto the OB recovers incompletely and the reinnervated glomeruli are markedly altered. Thus, the capacity for OE regeneration is tempered when GBCs disappear.SIGNIFICANCE STATEMENTA large percentage of humans lose or suffer a significant decline in olfactory function as they age. Consequently, quality of life suffers, and safety and nutritional status are put at risk. With age, the OE apparently becomes incapable of fully maintaining the neuronal population of the epithelium despite its well-known capacity for recovering from most forms of injury when younger which may contribute to age-related olfactory loss. Efforts to identify the mechanism by which olfactory neurogenesis becomes exhausted with age require a powerful model for accelerating age-related tissue pathology. The current OMP-tTA;TetO-DTA transgenic mouse model, in which olfactory neurons die when they reach maturity and accelerated death can be aborted to assess the capacity for structural recovery, satisfies that need.

Funding information:
  • NICHD NIH HHS - R01 HD008188-36(United States)
  • NIDCD NIH HHS - R01 DC014217(United States)

Epigenetic Promoter DNA Methylation of miR-124 Promotes HIV-1 Tat-Mediated Microglial Activation via MECP2-STAT3 Axis.

  • Periyasamy P
  • J. Neurosci.
  • 2018 Jun 6

Literature context:


Abstract:

The present study demonstrates HIV-1 Tat-mediated epigenetic downregulation of microglial miR-124 and its association with microglial activation. Exposure of mouse primary microglia isolated from newborn pups of either sex to HIV-1 Tat resulted in decreased expression of primary miR-124-1, primary miR-124-2 as well as the mature miR-124. In parallel, HIV-1 Tat exposure to mouse primary microglial cells resulted in increased expression of DNA methylation enzymes, such as DNMT1, DNMT3A, and DNMT3B, which were also accompanied by increased global DNA methylation. Bisulfite-converted genomic DNA sequencing in the HIV-1 Tat-exposed mouse primary microglial cells further confirmed increased DNA methylation of the primary miR-124-1 and primary miR-124-2 promoters. Bioinformatic analyses identified MECP2 as a novel 3'-UTR target of miR-124. This was further validated in mouse primary microglial cells wherein HIV-1 Tat-mediated downregulation of miR-124 resulted in increased expression of MECP2, leading in turn to further repression of miR-124 via the feedback loop. In addition to MECP2, miR-124 also modulated the levels of STAT3 through its binding to the 3'-UTR, leading to microglial activation. Luciferase assays and Ago2 immunoprecipitation determined the direct binding between miR-124 and 3'-UTR of both MECP2 and STAT3. Gene silencing of MECP2 and DNMT1 and overexpression of miR-124 blocked HIV-1 Tat-mediated downregulation of miR-124 and microglial activation. In vitro findings were also confirmed in the basal ganglia of SIV-infected rhesus macaques (both sexes). In summary, our findings demonstrate a novel mechanism of HIV-1 Tat-mediated activation of microglia via downregulation of miR-124, leading ultimately to increased MECP2 and STAT3 signaling.SIGNIFICANCE STATEMENT Despite the effectiveness of combination antiretroviral therapy in controlling viremia, the CNS continues to harbor viral reservoirs. The persistence of low-level virus replication leads to the accumulation of early viral proteins, including HIV-1 Tat protein. Understanding the epigenetic/molecular mechanism(s) by which viral proteins, such as HIV-1 Tat, can activate microglia is thus of paramount importance. This study demonstrated that HIV-1 Tat-mediated DNA methylation of the miR-124 promoter leads to its downregulation with a concomitant upregulation of the MECP2-STAT3-IL6, resulting in microglial activation. These findings reveal an unexplored epigenetic/molecular mechanism(s) underlying HIV-1 Tat-mediated microglial activation, thereby providing a potential target for the development of therapeutics aimed at ameliorating microglial activation and neuroinflammation in the context of HIV-1 infection.

Funding information:
  • Canadian Institutes of Health Research - (Canada)

Brain phospholipid precursors administered post-injury reduce tissue damage and improve neurological outcome in experimental traumatic brain injury.

  • Thau-Zuchman O
  • J. Neurotrauma
  • 2018 May 17

Literature context:


Abstract:

Traumatic brain injury (TBI) leads to cellular loss, destabilisation of membranes, disruption of synapses and altered brain connectivity, and increased risk of neurodegenerative disease. A significant and long-lasting decrease in phospholipids (PL), essential membrane constituents, has recently been reported in plasma and brain tissue, in human and experimental TBI. We hypothesised that supporting PL synthesis post-injury could improve outcome after TBI. We tested this hypothesis using a multi-nutrient combination designed to support the biosynthesis of phospholipids and available for clinical use. The multi-nutrient Fortasyn® Connect (FC) contains polyunsaturated omega-3 fatty acids, choline, uridine, vitamins, co-factors required for PL biosynthesis, and has been shown to have significant beneficial effects in early Alzheimer's disease. Male C57BL/6 mice received a controlled cortical impact injury and then were fed a control diet or a diet enriched with FC for 70 days. FC led to a significantly improved sensorimotor outcome and cognition, reduced lesion size and oligodendrocyte loss, and it restored myelin. It reversed the loss of the synaptic protein synaptophysin and decreased levels of the axon growth inhibitor Nogo-A, thus creating a permissive environment. It decreased microglia activation and the rise in ß-amyloid precursor protein and restored the depressed neurogenesis. The effects of this medical multi-nutrient suggest that support of PL biosynthesis after TBI, a new treatment paradigm, has significant therapeutic potential in this neurological condition for which there is no satisfactory treatment. The multi-nutrient tested has been used in dementia patients, is safe and well-tolerated, which would enable rapid clinical exploration in TBI.

Funding information:
  • Medical Research Council - K-0912(United Kingdom)

Identification of a critical sulfation in chondroitin that inhibits axonal regeneration.

  • Pearson CS
  • Elife
  • 2018 May 15

Literature context:


Abstract:

The failure of mammalian CNS neurons to regenerate their axons derives from a combination of intrinsic deficits and extrinsic factors. Following injury, chondroitin sulfate proteoglycans (CSPGs) within the glial scar inhibit axonal regeneration, an action mediated by the sulfated glycosaminoglycan (GAG) chains of CSPGs, especially those with 4-sulfated (4S) sugars. Arylsulfatase B (ARSB) selectively cleaves 4S groups from the non-reducing ends of GAG chains without disrupting other, growth-permissive motifs. We demonstrate that ARSB is effective in reducing the inhibitory actions of CSPGs both in in vitro models of the glial scar and after optic nerve crush (ONC) in adult mice. ARSB is clinically approved for replacement therapy in patients with mucopolysaccharidosis VI and therefore represents an attractive candidate for translation to the human CNS.

Funding information:
  • National Institutes of Health - 1ZIAHL006135()
  • NIEHS NIH HHS - 2T32ES007329-10(United States)

Oligodendrocyte death, neuroinflammation, and the effects of minocycline in a rodent model of nonarteritic anterior ischemic optic neuropathy (rNAION).

  • Mehrabian Z
  • Mol. Vis.
  • 2018 May 21

Literature context:


Abstract:

Purpose: Optic nerve (ON) damage following nonarteritic anterior ischemic optic neuropathy (NAION) and its models is associated with neurodegenerative inflammation. Minocycline is a tetracycline derivative antibiotic believed to exert a neuroprotective effect by selective alteration and activation of the neuroinflammatory response. We evaluated minocycline's post-induction ability to modify early and late post-ischemic inflammatory responses and its retinal ganglion cell (RGC)-neuroprotective ability. Methods: We used the rodent NAION (rNAION) model in male Sprague-Dawley rats. Animals received either vehicle or minocycline (33 mg/kg) daily intraperitoneally for 28 days. Early (3 days) ON-cytokine responses were evaluated, and oligodendrocyte death was temporally evaluated using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis. Cellular inflammation was evaluated with immunohistochemistry, and RGC preservation was compared with stereology of Brn3a-positive cells in flat mounted retinas. Results: Post-rNAION, oligodendrocytes exhibit a delayed pattern of apoptosis extending over a month, with extrinsic monocyte infiltration occurring only in the primary rNAION lesion and progressive distal microglial activation. Post-induction minocycline failed to improve retinal ganglion cell survival compared with the vehicle treated (893.14 vs. 920.72; p>0.9). Cytokine analysis of the rNAION lesion 3 days post-induction revealed that minocycline exert general inflammatory suppression without selective upregulation of cytokines associated with the proposed alternative or neuroprotective M2 inflammatory pathway. Conclusions: The pattern of cytokine release, extended temporal window of oligodendrocyte death, and progressive microglial activation suggests that selective neuroimmunomodulation, rather than general inflammatory suppression, may be required for effective repair strategies in ischemic optic neuropathies.

Funding information:
  • NEI NIH HHS - R01 EY015304()
  • NINDS NIH HHS - NS065926(United States)

Defining an Analytic Framework to Evaluate Quantitative MRI Markers of Traumatic Axonal Injury: Preliminary Results in a Mouse Closed Head Injury Model.

  • Haber M
  • eNeuro
  • 2018 May 30

Literature context:


Abstract:

Diffuse axonal injury (DAI) is a hallmark of traumatic brain injury (TBI) pathology. Recently, the Closed Head Injury Model of Engineered Rotational Acceleration (CHIMERA) was developed to generate an experimental model of DAI in a mouse. The characterization of DAI using diffusion tensor magnetic resonance imaging (MRI; diffusion tensor imaging, DTI) may provide a useful set of outcome measures for preclinical and clinical studies. The objective of this study was to identify the complex neurobiological underpinnings of DTI features following DAI using a comprehensive and quantitative evaluation of DTI and histopathology in the CHIMERA mouse model. A consistent neuroanatomical pattern of pathology in specific white matter tracts was identified across ex vivo DTI maps and photomicrographs of histology. These observations were confirmed by voxelwise and regional analysis of DTI maps, demonstrating reduced fractional anisotropy (FA) in distinct regions such as the optic tract. Similar regions were identified by quantitative histology and exhibited axonal damage as well as robust gliosis. Additional analysis using a machine-learning algorithm was performed to identify regions and metrics important for injury classification in a manner free from potential user bias. This analysis found that diffusion metrics were able to identify injured brains almost with the same degree of accuracy as the histology metrics. Good agreement between regions detected as abnormal by histology and MRI was also found. The findings of this work elucidate the complexity of cellular changes that give rise to imaging abnormalities and provide a comprehensive and quantitative evaluation of the relative importance of DTI and histological measures to detect brain injury.

The Microglial Innate Immune Receptor TREM2 Is Required for Synapse Elimination and Normal Brain Connectivity.

  • Filipello F
  • Immunity
  • 2018 May 15

Literature context:


Abstract:

The triggering receptor expressed on myeloid cells 2 (TREM2) is a microglial innate immune receptor associated with a lethal form of early, progressive dementia, Nasu-Hakola disease, and with an increased risk of Alzheimer's disease. Microglial defects in phagocytosis of toxic aggregates or apoptotic membranes were proposed to be at the origin of the pathological processes in the presence of Trem2 inactivating mutations. Here, we show that TREM2 is essential for microglia-mediated synaptic refinement during the early stages of brain development. The absence of Trem2 resulted in impaired synapse elimination, accompanied by enhanced excitatory neurotransmission and reduced long-range functional connectivity. Trem2-/- mice displayed repetitive behavior and altered sociability. TREM2 protein levels were also negatively correlated with the severity of symptoms in humans affected by autism. These data unveil the role of TREM2 in neuronal circuit sculpting and provide the evidence for the receptor's involvement in neurodevelopmental diseases.

Funding information:
  • NCI NIH HHS - CA156700(United States)

A Glial Signature and Wnt7 Signaling Regulate Glioma-Vascular Interactions and Tumor Microenvironment.

  • Griveau A
  • Cancer Cell
  • 2018 May 14

Literature context:


Abstract:

Gliomas comprise heterogeneous malignant glial and stromal cells. While blood vessel co-option is a potential mechanism to escape anti-angiogenic therapy, the relevance of glial phenotype in this process is unclear. We show that Olig2+ oligodendrocyte precursor-like glioma cells invade by single-cell vessel co-option and preserve the blood-brain barrier (BBB). Conversely, Olig2-negative glioma cells form dense perivascular collections and promote angiogenesis and BBB breakdown, leading to innate immune cell activation. Experimentally, Olig2 promotes Wnt7b expression, a finding that correlates in human glioma profiling. Targeted Wnt7a/7b deletion or pharmacologic Wnt inhibition blocks Olig2+ glioma single-cell vessel co-option and enhances responses to temozolomide. Finally, Olig2 and Wnt7 become upregulated after anti-VEGF treatment in preclinical models and patients. Thus, glial-encoded pathways regulate distinct glioma-vascular microenvironmental interactions.

Funding information:
  • Intramural NIH HHS - ES016005(United States)

Re-evaluating microglia expression profiles using RiboTag and cell isolation strategies.

  • Haimon Z
  • Nat. Immunol.
  • 2018 May 20

Literature context:


Abstract:

Transcriptome profiling is widely used to infer functional states of specific cell types, as well as their responses to stimuli, to define contributions to physiology and pathophysiology. Focusing on microglia, the brain's macrophages, we report here a side-by-side comparison of classical cell-sorting-based transcriptome sequencing and the 'RiboTag' method, which avoids cell retrieval from tissue context and yields translatome sequencing information. Conventional whole-cell microglial transcriptomes were found to be significantly tainted by artifacts introduced by tissue dissociation, cargo contamination and transcripts sequestered from ribosomes. Conversely, our data highlight the added value of RiboTag profiling for assessing the lineage accuracy of Cre recombinase expression in transgenic mice. Collectively, this study indicates method-based biases, reveals observer effects and establishes RiboTag-based translatome profiling as a valuable complement to standard sorting-based profiling strategies.

Funding information:
  • NIBIB NIH HHS - EB003537(United States)

Sex differences in the effects of PARP inhibition on microglial phenotypes following neonatal stroke.

  • Charriaut-Marlangue C
  • Brain Behav. Immun.
  • 2018 May 28

Literature context:


Abstract:

Neonatal acute ischemic stroke is a cause of neonatal brain injury that occurs more frequently in males, resulting in associated neurobehavioral disorders. The bases for these sex differences are poorly understood but might include the number, morphology and activation of microglia in the developing brain when subjected to stroke. Interestingly, poly (ADP-ribose) polymerase (PARP) inhibition preferentially protects males against neonatal ischemia. This study aims to examine the effects of PJ34, a PARP inhibitor, on microglial phenotypes at 3 and 8 days and on neurobehavioral disorders in adulthood for both male and female P9 mice subjected to permanent middle cerebral artery occlusion (pMCAo). PJ34 significantly reduced the lesion size by 78% and reduced the density of CX3CR1gfp-labeled microglial cells by 46% when examined 3 days after pMCAo in male but not in female mice. Eight days after pMCAo, the number of Iba1+/Cox-2+ cells did not differ between male and female mice in the cortical peri-infarct region. In the amygdala, Iba1+/Cox-2+ (M1-like) cell numbers were significantly decreased in PJ34-treated males but not in females. Conversely, Iba1+/Arg-1+ (M2-like) and Arg-1+/Cox-2+ (Mtransitional) cell numbers were significantly increased in PJ34-treated females. Regarding neurobehavioral disorders during adulthood, pMCAo induced a motor coordination deficit and a spatial learning deficit in female mice only. PJ34 prevented MBP fibers, motor coordination and learning disorders during adulthood in female mice. Our data show significant sex differences in the effects of PARP inhibition on microglia phenotypes following neonatal ischemia, associated with improved behavior and myelination during adulthood in females only. Our findings suggest that modulating microglial phenotypes may play key roles in behavior disorders and white matter injury following neonatal stroke.

Funding information:
  • NEI NIH HHS - R01 EY016408-03S1(United States)

Cortical hemorrhage-associated neurological deficits and tissue damage in mice are ameliorated by therapeutic treatment with nicotine.

  • Anan J
  • J. Neurosci. Res.
  • 2018 Apr 17

Literature context:


Abstract:

Intracerebral hemorrhage (ICH) is associated with diverse sets of neurological symptoms and prognosis, depending on the site of bleeding. Relative rate of hemorrhage occurring in the cerebral cortex (lobar hemorrhage) has been increasing, but there is no report on effective pharmacotherapeutic approaches for cortical hemorrhage either in preclinical or clinical studies. The present study aimed to establish an experimental model of cortical hemorrhage in mice for evaluation of effects of therapeutic drug candidates. Type VII collagenase at 0.015 U, injected into the parietal cortex, induced hemorrhage expanding into the whole layer of the posterior parts of the sensorimotor cortex in male C57BL/6 mice. Mice with ICH under these conditions exhibited significant motor deficits as revealed by beam-walking test. Daily administration of nicotine (1 and 2 mg/kg), with the first injection given at 3 hr after induction of ICH, improved motor performance of mice in a dose-dependent manner, although nicotine did not alter the volume of hematoma. Immunohistochemical examinations revealed that the number of neurons was drastically decreased within the hematoma region. Nicotine at 2 mg/kg partially but significantly increased the number of remaining neurons within the hematoma at 3 days after induction of ICH. ICH also resulted in inflammatory activation of microglia/macrophages in the perihematoma region, and nicotine (1 and 2 mg/kg) significantly attenuated the increase of microglia. These results suggest that nicotine can provide a therapeutic effect on cortical hemorrhage, possibly via its neuroprotective and anti-inflammatory actions. © 2017 Wiley Periodicals, Inc.

GPNMB ameliorates mutant TDP-43-induced motor neuron cell death.

  • Nagahara Y
  • J. Neurosci. Res.
  • 2018 Apr 17

Literature context:


Abstract:

Glycoprotein nonmetastatic melanoma protein B (GPNMB) aggregates are observed in the spinal cord of amyotrophic lateral sclerosis (ALS) patients, but the detailed localization is still unclear. Mutations of transactive response DNA binding protein 43kDa (TDP-43) are associated with neurodegenerative diseases including ALS. In this study, we evaluated the localization of GPNMB aggregates in the spinal cord of ALS patients and the effect of GPNMB against mutant TDP-43 induced motor neuron cell death. GPNMB aggregates were not localized in the glial fibrillary acidic protein (GFAP)-positive astrocyte and ionized calcium binding adaptor molecule-1 (Iba1)-positive microglia. GPNMB aggregates were localized in the microtubule-associated protein 2 (MAP-2)-positive neuron and neurofilament H non-phosphorylated (SMI-32)-positive neuron, and these were co-localized with TDP-43 aggregates in the spinal cord of ALS patients. Mock or TDP-43 (WT, M337V, and A315T) plasmids were transfected into mouse motor neuron cells (NSC34). The expression level of GPNMB was increased by transfection of mutant TDP-43 plasmids. Recombinant GPNMB ameliorated motor neuron cell death induced by transfection of mutant TDP-43 plasmids and serum-free stress. Furthermore, the expression of phosphorylated ERK1/2 and phosphorylated Akt were decreased by this stress, and these expressions were increased by recombinant GPNMB. These results indicate that GPNMB has protective effects against mutant TDP-43 stress via activating the ERK1/2 and Akt pathways, and GPNMB may be a therapeutic target for TDP-43 proteinopathy in familial and sporadic ALS. © 2016 Wiley Periodicals, Inc.

Funding information:
  • NIMH NIH HHS - R01 MH64547(United States)

Nav1.1-Overexpressing Interneuron Transplants Restore Brain Rhythms and Cognition in a Mouse Model of Alzheimer's Disease.

  • Martinez-Losa M
  • Neuron
  • 2018 Apr 4

Literature context:


Abstract:

Inhibitory interneurons regulate the oscillatory rhythms and network synchrony that are required for cognitive functions and disrupted in Alzheimer's disease (AD). Network dysrhythmias in AD and multiple neuropsychiatric disorders are associated with hypofunction of Nav1.1, a voltage-gated sodium channel subunit predominantly expressed in interneurons. We show that Nav1.1-overexpressing, but not wild-type, interneuron transplants derived from the embryonic medial ganglionic eminence (MGE) enhance behavior-dependent gamma oscillatory activity, reduce network hypersynchrony, and improve cognitive functions in human amyloid precursor protein (hAPP)-transgenic mice, which simulate key aspects of AD. Increased Nav1.1 levels accelerated action potential kinetics of transplanted fast-spiking and non-fast-spiking interneurons. Nav1.1-deficient interneuron transplants were sufficient to cause behavioral abnormalities in wild-type mice. We conclude that the efficacy of interneuron transplantation and the function of transplanted cells in an AD-relevant context depend on their Nav1.1 levels. Disease-specific molecular optimization of cell transplants may be required to ensure therapeutic benefits in different conditions.

Funding information:
  • NCRR NIH HHS - C06 RR018928()
  • NIA NIH HHS - F32 AG043301()
  • NIA NIH HHS - R01 AG030207()
  • NIA NIH HHS - R01 AG036884()
  • NIA NIH HHS - R01 AG047313()
  • NIA NIH HHS - R01 AG051390()
  • NIA NIH HHS - R01 AG054214()
  • NIAID NIH HHS - R01 AI059738-05(United States)
  • NINDS NIH HHS - P30 NS065780()
  • NINDS NIH HHS - R01 NS041787()
  • NINDS NIH HHS - U54 NS100717()

Recombinant interleukin-4 alleviates mechanical allodynia via injury-induced interleukin-4 receptor alpha in spinal microglia in a rat model of neuropathic pain.

  • Okutani H
  • Glia
  • 2018 Apr 25

Literature context:


Abstract:

Glial cells play important roles in the development and maintenance of neuropathic pain. In particular, activated microglia in the spinal cord facilitate the hyper-excitability of dorsal horn neurons after peripheral nerve injury via pro-inflammatory molecules. In this study, we investigated the possible involvement of the anti-inflammatory cytokine, interleukin-4 (IL-4), in neuropathic pain. We did not detect the expression of IL-4 mRNA in the rat dorsal root ganglion or spinal cord; however, peripheral nerve injury induced the expression of IL-4 receptor (IL-4R) alpha mRNA in the spinal cord. A histological analysis revealed that nerve injury induced IL-4R alpha mRNA in activated spinal microglia ipsilateral to the injury site. Additionally, the increases in IL-4R alpha were coincident with the increased expression of phosphorylated signal transducer and activator of transcription 6 (pSTAT6) in spinal microglia. Intrathecal administration of recombinant IL-4 suppressed mechanical hypersensitivity in neuropathic rats, and the analgesic effect of IL-4 was accompanied by further enhancement of pSTAT6 expression in spinal microglia. Taken together, these results suggest that the adaptive responses of microglia to nerve injury involve both inflammatory and anti-inflammatory signaling, including IL-4R alpha and pSTAT6. These findings support that utilizing the endogenous anti-nociceptive activity of IL-4R alpha may modify the cell lineage of pro-nociceptive microglia, thus providing a novel therapeutic strategy for neuropathic pain.

Funding information:
  • NCI NIH HHS - P30 CA006516(United States)

Genetic detection of Sonic hedgehog (Shh) expression and cellular response in the progression of acute through chronic demyelination and remyelination.

  • Sanchez MA
  • Neurobiol. Dis.
  • 2018 Apr 9

Literature context:


Abstract:

Multiple sclerosis is a demyelinating disease in which neurological deficits result from damage to myelin, axons, and neuron cell bodies. Prolonged or repeated episodes of demyelination impair remyelination. We hypothesized that augmenting Sonic hedgehog (Shh) signaling in chronically demyelinated lesions could enhance oligodendrogenesis and remyelination. Shh regulates oligodendrocyte development during postnatal myelination, and maintains adult neural stem cells. We used genetic approaches to detect Shh expression and Shh responding cells in vivo. ShhCreERT2 or Gli1CreERT2 mice were crossed to reporter mice for genetic fate-labeling of cells actively transcribing Shh or Gli1, an effective readout of canonical Shh signaling. Tamoxifen induction enabled temporal control of recombination at distinct stages of acute and chronic cuprizone demyelination of the corpus callosum. Gli1 fate-labeled cells were rarely found in the corpus callosum with tamoxifen given during acute demyelination stages to examine activated microglia, reactive astrocytes, or remyelinating cells. Gli1 fate-labeled cells, mainly reactive astrocytes, were observed in the corpus callosum with tamoxifen given after chronic demyelination. However, Shh expressing cells were not detected in the corpus callosum during acute or chronic demyelination. Finally, SAG, an agonist of both canonical and type II non-canonical Hedgehog signaling pathways, was microinjected into the corpus callosum after chronic demyelination. Significantly, SAG delivery increased proliferation and enhanced remyelination. SAG did not increase Gli1 fate-labeled cells in the corpus callosum, which may indicate signaling through the non-canonical Hedgehog pathway. These studies demonstrate that Hedgehog pathway interventions may have therapeutic potential to modulate astrogliosis and to promote remyelination after chronic demyelination.

Funding information:
  • NCI NIH HHS - K24 CA139054(United States)

Genetic deletion of xCT attenuates peripheral and central inflammation and mitigates LPS-induced sickness and depressive-like behavior in mice.

  • Albertini G
  • Glia
  • 2018 Apr 25

Literature context:


Abstract:

The communication between the immune and central nervous system (CNS) is affected in many neurological disorders. Peripheral injections of the endotoxin lipopolysaccharide (LPS) are widely used to study this communication: an LPS challenge leads to a biphasic syndrome that starts with acute sickness and is followed by persistent brain inflammation and chronic behavioral alterations such as depressive-like symptoms. In vitro, the response to LPS treatment has been shown to involve enhanced expression of system xc-. This cystine-glutamate antiporter, with xCT as specific subunit, represents the main glial provider of extracellular glutamate in mouse hippocampus. Here we injected male xCT knockout and wildtype mice with a single intraperitoneal dose of 5 mg/kg LPS. LPS-injection increased hippocampal xCT expression but did not alter the mainly astroglial localization of the xCT protein. Peripheral and central inflammation (as defined by cytokine levels and morphological activation of microglia) as well as LPS-induced sickness and depressive-like behavior were significantly attenuated in xCT-deficient mice compared with wildtype mice. Our study is the first to demonstrate the involvement of system xc- in peripheral and central inflammation in vivo and the potential therapeutic relevance of its inhibition in brain disorders characterized by peripheral and central inflammation, such as depression.

Funding information:
  • NIGMS NIH HHS - GM091896(United States)

Soluble TNFα Signaling within the Spinal Cord Contributes to the Development of Autonomic Dysreflexia and Ensuing Vascular and Immune Dysfunction after Spinal Cord Injury.

  • Mironets E
  • J. Neurosci.
  • 2018 Apr 25

Literature context:


Abstract:

Cardiovascular disease and susceptibility to infection are leading causes of morbidity and mortality for individuals with spinal cord injury (SCI). A major contributor to these is autonomic dysreflexia (AD), an amplified reaction of the autonomic nervous system (hallmarked by severe hypertension) in response to sensory stimuli below the injury. Maladaptive plasticity of the spinal sympathetic reflex circuit below the SCI results in AD intensification over time. Mechanisms underlying this maladaptive plasticity are poorly understood, restricting the identification of treatments. Thus, no preventative treatments are currently available. Neuroinflammation has been implicated in other pathologies associated with hyperexcitable neural circuits. Specifically, the soluble form of TNFα (sTNFα) is known to play a role in neuroplasticity. We hypothesize that persistent expression of sTNFα in spinal cord underlies AD exacerbation. To test this, we intrathecally administered XPro1595, a biologic that renders sTNFα nonfunctional, after complete, high-level SCI in female rats. This dramatically attenuated the intensification of colorectal distension-induced and naturally occurring AD events. This improvement is mediated via decreased sprouting of nociceptive primary afferents and activation of the spinal sympathetic reflex circuit. We also examined peripheral vascular function using ex vivo pressurized arterial preparations and immune function via flow cytometric analysis of splenocytes. Diminishing AD via pharmacological inhibition of sTNFα mitigated ensuing vascular hypersensitivity and immune dysfunction. This is the first demonstration that neuroinflammation-induced sTNFα is critical for altering the spinal sympathetic reflex circuit, elucidating a novel mechanism for AD. Importantly, we identify the first potential pharmacological, prophylactic treatment for this life-threatening syndrome.SIGNIFICANCE STATEMENT Autonomic dysreflexia (AD), a disorder that develops after spinal cord injury (SCI) and is hallmarked by sudden, extreme hypertension, contributes to cardiovascular disease and susceptibility to infection, respectively, two leading causes of mortality and morbidity in SCI patients. We demonstrate that neuroinflammation-induced expression of soluble TNFα plays a critical role in AD, elucidating a novel underlying mechanism. We found that intrathecal administration after SCI of a biologic that inhibits soluble TNFα signaling dramatically attenuates AD and significantly reduces AD-associated peripheral vascular and immune dysfunction. We identified mechanisms behind diminished plasticity of neuronal populations within the spinal sympathetic reflex circuit. This study is the first to pinpoint a potential pharmacological, prophylactic strategy to attenuate AD and ensuing cardiovascular and immune dysfunction.

Funding information:
  • NHLBI NIH HHS - R01 HL139754()
  • NIDDK NIH HHS - DK62434(United States)
  • NINDS NIH HHS - R01 NS085426()
  • NINDS NIH HHS - R01 NS106908()

Blockade of sustained tumor necrosis factor in a transgenic model of progressive autoimmune encephalomyelitis limits oligodendrocyte apoptosis and promotes oligodendrocyte maturation.

  • Valentin-Torres A
  • J Neuroinflammation
  • 2018 Apr 24

Literature context:


Abstract:

BACKGROUND: Tumor necrosis factor (TNF) is associated with several neurodegenerative disorders including multiple sclerosis (MS). Although TNF-targeted therapies have been largely unsuccessful in MS, recent preclinical data suggests selective soluble TNF inhibition can promote remyelination. This has renewed interest in regulation of TNF signaling in demyelinating disease, especially given the limited treatment options for progressive MS. Using a mouse model of progressive MS, this study evaluates the effects of sustained TNF on oligodendrocyte (OLG) apoptosis and OLG precursor cell (OPC) differentiation. METHODS: Induction of experimental autoimmune encephalomyelitis (EAE) in transgenic mice expressing a dominant-negative interferon-γ receptor under the human glial fibrillary acidic protein promoter (GFAPγR1Δ) causes severe non-remitting disease associated with sustained TNF. Therapeutic effects in GFAPγR1Δ mice treated with anti-TNF compared to control antibody during acute EAE were evaluated by assessing demyelinating lesion size, remyelination, OLG apoptosis, and OPC differentiation. RESULTS: More severe and enlarged demyelinating lesions in GFAPγR1Δ compared to wild-type (WT) mice were associated with increased OLG apoptosis and reduced differentiated CC1+Olig2+ OLG within lesions, as well as impaired upregulation of TNF receptor-2, suggesting impaired OPC differentiation. TNF blockade during acute EAE in GFAPγR1Δ both limited OLG apoptosis and enhanced OPC differentiation consistent with reduced lesion size and clinical recovery. TNF neutralization further limited increasing endothelin-1 (ET-1) expression in astrocytes and myeloid cells noted in lesions during disease progression in GFAPγR1Δ mice, supporting inhibitory effects of ET-1 on OPC maturation. CONCLUSION: Our data implicate that IFNγ signaling to astrocytes is essential to limit a detrimental positive feedback loop of TNF and ET-1 production, which increases OLG apoptosis and impairs OPC differentiation. Interference of this cycle by TNF blockade promotes repair independent of TNFR2 and supports selective TNF targeting to mitigate progressive forms of MS.

Funding information:
  • Biotechnology and Biological Sciences Research Council - 233376(United Kingdom)
  • Cancer Center Support - P30CA014089()
  • National Multiple Sclerosis Society - RG4007B5()

Brimapitide Reduced Neuronal Stress Markers and Cognitive Deficits in 5XFAD Transgenic Mice.

  • Gourmaud S
  • J. Alzheimers Dis.
  • 2018 Apr 18

Literature context:


Abstract:

Alzheimer's disease (AD) is characterized by accumulations of amyloid-β (Aβ42) and hyperphosphorylated tau proteins, associated with neuroinflammation, synaptic loss, and neuronal death. Several studies indicate that c-Jun N-terminal kinase (JNK) is implicated in the pathological features of AD. We have investigated in 5XFAD mice, the therapeutic effects of Brimapitide, a JNK-specific inhibitory peptide previously tested with higher concentrations in another AD model (TgCRND8). Three-month-old 5XFAD and wild-type littermate mice were treated by intravenous injections of low doses (10 mg/kg) of Brimapitide every 3 weeks, for 3 or 6 months (n = 6-9 per group). Cognitive deficits and brain lesions were assessed using Y-maze, fear-conditioning test, and histological and biochemical methods. Chronic treatment of Brimapitide for 3 months resulted in a reduction of Aβ plaque burden in the cortex of 5XFAD treated mice. After 6 months of treatment, cognitive deficits were reduced but also a significant reduction of cell death markers and the pro-inflammatory IL-1β cytokine in treated mice were detected. The Aβ plaque burden was not anymore modified by the 6 months of treatment. In addition to modulating cognition and amyloid plaque accumulation, depending on the treatment duration, Brimapitide seems experimentally to reduce neuronal stress in 5XFAD mice.

Funding information:
  • NIDDK NIH HHS - R01 DK080852(United States)

Functional Divergence of Delta and Mu Opioid Receptor Organization in CNS Pain Circuits.

  • Wang D
  • Neuron
  • 2018 Apr 4

Literature context:


Abstract:

Cellular interactions between delta and mu opioid receptors (DORs and MORs), including heteromerization, are thought to regulate opioid analgesia. However, the identity of the nociceptive neurons in which such interactions could occur in vivo remains elusive. Here we show that DOR-MOR co-expression is limited to small populations of excitatory interneurons and projection neurons in the spinal cord dorsal horn and unexpectedly predominates in ventral horn motor circuits. Similarly, DOR-MOR co-expression is rare in parabrachial, amygdalar, and cortical brain regions processing nociceptive information. We further demonstrate that in the discrete DOR-MOR co-expressing nociceptive neurons, the two receptors internalize and function independently. Finally, conditional knockout experiments revealed that DORs selectively regulate mechanical pain by controlling the excitability of somatostatin-positive dorsal horn interneurons. Collectively, our results illuminate the functional organization of DORs and MORs in CNS pain circuits and reappraise the importance of DOR-MOR cellular interactions for developing novel opioid analgesics.

Funding information:
  • NCI NIH HHS - P30 CA042014(United States)

Histone Deacetylases 1 and 2 Regulate Microglia Function during Development, Homeostasis, and Neurodegeneration in a Context-Dependent Manner.

  • Datta M
  • Immunity
  • 2018 Mar 20

Literature context:


Abstract:

Microglia as tissue macrophages contribute to the defense and maintenance of central nervous system (CNS) homeostasis. Little is known about the epigenetic signals controlling microglia function in vivo. We employed constitutive and inducible mutagenesis in microglia to delete two class I histone deacetylases, Hdac1 and Hdac2. Prenatal ablation of Hdac1 and Hdac2 impaired microglial development. Mechanistically, the promoters of pro-apoptotic and cell cycle genes were hyperacetylated in absence of Hdac1 and Hdac2, leading to increased apoptosis and reduced survival. In contrast, Hdac1 and Hdac2 were not required for adult microglia survival during homeostasis. In a mouse model of Alzheimer's disease, deletion of Hdac1 and Hdac2 in microglia, but not in neuroectodermal cells, resulted in a decrease in amyloid load and improved cognitive impairment by enhancing microglial amyloid phagocytosis. Collectively, we report a role for epigenetic factors that differentially affect microglia development, homeostasis, and disease that could potentially be utilized therapeutically.

Funding information:
  • Austrian Science Fund FWF - P 18613(Austria)

Elevated TREM2 Gene Dosage Reprograms Microglia Responsivity and Ameliorates Pathological Phenotypes in Alzheimer's Disease Models.

  • Lee CYD
  • Neuron
  • 2018 Mar 7

Literature context:


Abstract:

Variants of TREM2 are associated with Alzheimer's disease (AD). To study whether increasing TREM2 gene dosage could modify the disease pathogenesis, we developed BAC transgenic mice expressing human TREM2 (BAC-TREM2) in microglia. We found that elevated TREM2 expression reduced amyloid burden in the 5xFAD mouse model. Transcriptomic profiling demonstrated that increasing TREM2 levels conferred a rescuing effect, which includes dampening the expression of multiple disease-associated microglial genes and augmenting downregulated neuronal genes. Interestingly, 5xFAD/BAC-TREM2 mice showed further upregulation of several reactive microglial genes linked to phagocytosis and negative regulation of immune cell activation. Moreover, these mice showed enhanced process ramification and phagocytic marker expression in plaque-associated microglia and reduced neuritic dystrophy. Finally, elevated TREM2 gene dosage led to improved memory performance in AD models. In summary, our study shows that a genomic transgene-driven increase in TREM2 expression reprograms microglia responsivity and ameliorates neuropathological and behavioral deficits in AD mouse models.

Funding information:
  • NCI NIH HHS - CA-71514(United States)
  • NIA NIH HHS - R01 AG021173()
  • NIA NIH HHS - R01 AG038710()
  • NIA NIH HHS - R01 AG044420()
  • NIA NIH HHS - R21 AG048519()
  • NIA NIH HHS - RF1 AG056114()
  • NIA NIH HHS - RF1 AG056130()
  • NIMH NIH HHS - U01 MH106008()
  • NINDS NIH HHS - R01 NS030549()
  • NINDS NIH HHS - R01 NS046673()
  • NINDS NIH HHS - R01 NS074312()
  • NINDS NIH HHS - R01 NS084298()

Deficient Surveillance and Phagocytic Activity of Myeloid Cells Within Demyelinated Lesions in Aging Mice Visualized by Ex Vivo Live Multiphoton Imaging.

  • Rawji KS
  • J. Neurosci.
  • 2018 Feb 21

Literature context:


Abstract:

Aging impairs regenerative processes including remyelination, the synthesis of a new myelin sheath. Microglia and other infiltrating myeloid cells such as macrophages are essential for remyelination through mechanisms that include the clearance of inhibitory molecules within the lesion. Prior studies have shown that the quantity of myeloid cells and the clearance of inhibitory myelin debris are deficient in aging, contributing to the decline in remyelination efficiency with senescence. It is unknown, however, whether the impaired clearance of debris is simply the result of the reduced number of phagocytes or if the dynamic activity of myeloid cells within the demyelinating plaque also declines with aging and this question is relevant to the proper design of therapeutics to mobilize myeloid cells for repair. Herein, we describe a high-resolution multiphoton ex vivo live imaging protocol that visualizes individual myelinated/demyelinated axons and lipid-containing myeloid cells to investigate the demyelinated lesion of aging female mice. We found that aging lesions have fewer myeloid cells and that these have reduced phagocytosis of myelin. Although the myeloid cells are actively migratory within the lesion of young mice and have protrusions that seem to survey the environment, this motility and surveillance is significantly reduced in aging mice. Our results emphasize the necessity of not only increasing the number of phagocytes, but also enhancing their activity once they are within demyelinated lesions. The high-resolution live imaging of demyelinated lesions can serve as a platform with which to discover pharmacological agents that rejuvenate intralesional remodeling that promotes the repair of plaques.SIGNIFICANCE STATEMENT The repair of myelin after injury depends on myeloid cells that clear debris and release growth factors. As organisms age, remyelination becomes less efficient correspondent with fewer myeloid cells that populate the lesions. It is unknown whether the dynamic activity of cells within lesions is also altered with age. Herein, using high-resolution multiphoton ex vivo live imaging with several novel features, we report that myeloid cells within demyelinated lesions of aging mice have reduced motility, surveillance, and phagocytic activity, suggesting an intralesional impairment that may contribute to the age-related decline in remyelination efficiency. Medications to stimulate deficient aging myeloid cells should not only increase their representation, but also enter into lesions to stimulate their activity.

Funding information:
  • NIAMS NIH HHS - R01 AR057759(United States)

Lentivirus-mediated expression of human secreted amyloid precursor protein-alpha prevents development of memory and plasticity deficits in a mouse model of Alzheimer's disease.

  • Tan VTY
  • Mol Brain
  • 2018 Feb 9

Literature context:


Abstract:

Alzheimer's disease (AD) is a neurodegenerative disease driven in large part by accumulated deposits in the brain of the amyloid precursor protein (APP) cleavage product amyloid-β peptide (Aβ). However, AD is also characterised by reductions in secreted amyloid precursor protein-alpha (sAPPα), an alternative cleavage product of APP. In contrast to the neurotoxicity of accumulated Αβ, sAPPα has many neuroprotective and neurotrophic properties. Increasing sAPPα levels has the potential to serve as a therapeutic treatment that mitigates the effects of Aβ and rescue cognitive function. Here we tested the hypothesis that lentivirus-mediated expression of a human sAPPα construct in a mouse model of AD (APPswe/PS1dE9), begun before the onset of plaque pathology, could prevent later behavioural and electrophysiological deficits. Male mice were given bilateral intra-hippocampal injections at 4 months of age and tested 8-10 months later. Transgenic mice expressing sAPPα performed significantly better than untreated littermates in all aspects of the spatial water maze task. Expression of sAPPα also resulted in partial rescue of long-term potentiation (LTP), tested in vitro. These improvements occurred in the absence of changes in amyloid pathology. Supporting these findings on LTP, lentiviral-mediated expression of sAPPα for 3 months from 10 months of age, or acute sAPPα treatment in hippocampal slices from 18 to 20 months old transgenic mice, completely reversed the deficits in LTP. Together these findings suggest that sAPPα has wide potential to act as either a preventative or restorative therapeutic treatment in AD by mitigating the effects of Aβ toxicity and enhancing cognitive reserve.

Funding information:
  • Health Research Council of New Zealand - 10-170()
  • NIGMS NIH HHS - R01 GM028301-28(United States)

LRRTM1 underlies synaptic convergence in visual thalamus.

  • Monavarfeshani A
  • Elife
  • 2018 Feb 9

Literature context:


Abstract:

It has long been thought that the mammalian visual system is organized into parallel pathways, with incoming visual signals being parsed in the retina based on feature (e.g. color, contrast and motion) and then transmitted to the brain in unmixed, feature-specific channels. To faithfully convey feature-specific information from retina to cortex, thalamic relay cells must receive inputs from only a small number of functionally similar retinal ganglion cells. However, recent studies challenged this by revealing substantial levels of retinal convergence onto relay cells. Here, we sought to identify mechanisms responsible for the assembly of such convergence. Using an unbiased transcriptomics approach and targeted mutant mice, we discovered a critical role for the synaptic adhesion molecule Leucine Rich Repeat Transmembrane Neuronal 1 (LRRTM1) in the emergence of retinothalamic convergence. Importantly, LRRTM1 mutant mice display impairment in visual behaviors, suggesting a functional role of retinothalamic convergence in vision.

Funding information:
  • National Eye Institute - EY021222()
  • National Eye Institute - EY024712()
  • NIGMS NIH HHS - R01 GM059507-09(United States)
  • Virginia Tech Carilion Research Institute - Medical Research Scholars Program()

Astrocytes from old Alzheimer's disease mice are impaired in Aβ uptake and in neuroprotection.

  • Iram T
  • Neurobiol. Dis.
  • 2018 Feb 9

Literature context:


Abstract:

In Alzheimer's disease (AD), astrocytes undergo morphological changes ranging from atrophy to hypertrophy, but the effect of such changes at the functional level is still largely unknown. Here, we aimed to investigate whether alterations in astrocyte activity in AD are transient and depend on their microenvironment, or whether they are irreversible. We established and characterized a new protocol for the isolation of adult astrocytes and discovered that astrocytes isolated from old 5xFAD mice have higher GFAP expression than astrocytes derived from WT mice, as observed in vivo. We found high C1q levels in brain sections from old 5xFAD mice in close vicinity to amyloid plaques and astrocyte processes. Interestingly, while old 5xFAD astrocytes are impaired in uptake of soluble Aβ42, this effect was reversed upon an addition of exogenous C1q, suggesting a potential role for C1q in astrocyte-mediated Aβ clearance. Our results suggest that scavenger receptor B1 plays a role in C1q-facilitated Aβ uptake by astrocytes and that expression of scavenger receptor B1 is reduced in adult old 5xFAD astrocytes. Furthermore, old 5xFAD astrocytes show impairment in support of neuronal growth in co-culture and neurotoxicity concomitant with an elevation in IL-6 expression. Further understanding of the impact of astrocyte impairment on AD pathology may provide insights into the etiology of AD.

Basal Mitophagy Occurs Independently of PINK1 in Mouse Tissues of High Metabolic Demand.

  • McWilliams TG
  • Cell Metab.
  • 2018 Feb 6

Literature context:


Abstract:

Dysregulated mitophagy has been linked to Parkinson's disease (PD) due to the role of PTEN-induced kinase 1 (PINK1) in mediating depolarization-induced mitophagy in vitro. Elegant mouse reporters have revealed the pervasive nature of basal mitophagy in vivo, yet the role of PINK1 and tissue metabolic context remains unknown. Using mito-QC, we investigated the contribution of PINK1 to mitophagy in metabolically active tissues. We observed a high degree of mitophagy in neural cells, including PD-relevant mesencephalic dopaminergic neurons and microglia. In all tissues apart from pancreatic islets, loss of Pink1 did not influence basal mitophagy, despite disrupting depolarization-induced Parkin activation. Our findings provide the first in vivo evidence that PINK1 is detectable at basal levels and that basal mammalian mitophagy occurs independently of PINK1. This suggests multiple, yet-to-be-discovered pathways orchestrating mammalian mitochondrial integrity in a context-dependent fashion, and this has profound implications for our molecular understanding of vertebrate mitophagy.

Funding information:
  • NHLBI NIH HHS - R01 HL074894(United States)

High-Dimensional Single-Cell Mapping of Central Nervous System Immune Cells Reveals Distinct Myeloid Subsets in Health, Aging, and Disease.

  • Mrdjen D
  • Immunity
  • 2018 Feb 20

Literature context:


Abstract:

Individual reports suggest that the central nervous system (CNS) contains multiple immune cell types with diverse roles in tissue homeostasis, immune defense, and neurological diseases. It has been challenging to map leukocytes across the entire brain, and in particular in pathology, where phenotypic changes and influx of blood-derived cells prevent a clear distinction between reactive leukocyte populations. Here, we applied high-dimensional single-cell mass and fluorescence cytometry, in parallel with genetic fate mapping systems, to identify, locate, and characterize multiple distinct immune populations within the mammalian CNS. Using this approach, we revealed that microglia, several subsets of border-associated macrophages and dendritic cells coexist in the CNS at steady state and exhibit disease-specific transformations in the immune microenvironment during aging and in models of Alzheimer's disease and multiple sclerosis. Together, these data and the described framework provide a resource for the study of disease mechanisms, potential biomarkers, and therapeutic targets in CNS disease.

Funding information:
  • NHLBI NIH HHS - HL086621(United States)

Corticosterone Production during Repeated Social Defeat Causes Monocyte Mobilization from the Bone Marrow, Glucocorticoid Resistance, and Neurovascular Adhesion Molecule Expression.

  • Niraula A
  • J. Neurosci.
  • 2018 Feb 28

Literature context:


Abstract:

Repeated social defeat (RSD) stress promotes the release of bone marrow-derived monocytes into circulation that are recruited to the brain, where they augment neuroinflammation and cause prolonged anxiety-like behavior. Physiological stress activates the sympathetic nervous system and hypothalamic-pituitary-adrenal gland (HPA) axis, and both of these systems play a role in the physiological, immunological, and behavioral responses to stress. The purpose of this study was to delineate the role of HPA activation and corticosterone production in the immunological responses to stress in male C57BL/6 mice. Here, surgical (adrenalectomy) and pharmacological (metyrapone) interventions were used to abrogate corticosterone signaling during stress. We report that both adrenalectomy and metyrapone attenuated the stress-induced release of monocytes into circulation. Neither intervention altered the production of monocytes during stress, but both interventions enhanced retention of these cells in the bone marrow. Consistent with this observation, adrenalectomy and metyrapone also prevented the stress-induced reduction of a key retention factor, CXCL12, in the bone marrow. Corticosterone depletion with metyrapone also abrogated the stress-induced glucocorticoid resistance of myeloid cells. In the brain, these corticosterone-associated interventions attenuated stress-induced microglial remodeling, neurovascular expression of the adhesion molecule intercellular cell adhesion molecule-1, prevented monocyte accumulation and neuroinflammatory signaling. Overall, these results indicate that HPA activation and corticosterone production during repeated social defeat stress are critical for monocyte release into circulation, glucocorticoid resistance of myeloid cells, and enhanced neurovascular cell adhesion molecule expression.SIGNIFICANCE STATEMENT Recent studies of stress have identified the presence of monocytes that show an exaggerated inflammatory response to immune challenge and are resistant to the suppressive effects of glucocorticoids. Increased presence of these proinflammatory monocytes has been implicated in neuropsychiatric symptoms and the development of chronic cardiovascular, autoimmune, and metabolic disorders. In the current study, we show novel evidence that corticosterone produced during stress enhances the release of proinflammatory monocytes from the bone marrow into circulation, augments their recruitment to the brain and the induction of a neuroinflammatory profile. Overproduction of corticosterone during stress is also the direct cause of glucocorticoid resistance, a key phenotype in individuals exposed to chronic stress. Inhibiting excess corticosterone production attenuates these inflammatory responses to stress.

Funding information:
  • NCI NIH HHS - R21 CA175560(United States)

Immune or Genetic-Mediated Disruption of CASPR2 Causes Pain Hypersensitivity Due to Enhanced Primary Afferent Excitability.

  • Dawes JM
  • Neuron
  • 2018 Feb 21

Literature context:


Abstract:

Human autoantibodies to contactin-associated protein-like 2 (CASPR2) are often associated with neuropathic pain, and CASPR2 mutations have been linked to autism spectrum disorders, in which sensory dysfunction is increasingly recognized. Human CASPR2 autoantibodies, when injected into mice, were peripherally restricted and resulted in mechanical pain-related hypersensitivity in the absence of neural injury. We therefore investigated the mechanism by which CASPR2 modulates nociceptive function. Mice lacking CASPR2 (Cntnap2-/-) demonstrated enhanced pain-related hypersensitivity to noxious mechanical stimuli, heat, and algogens. Both primary afferent excitability and subsequent nociceptive transmission within the dorsal horn were increased in Cntnap2-/- mice. Either immune or genetic-mediated ablation of CASPR2 enhanced the excitability of DRG neurons in a cell-autonomous fashion through regulation of Kv1 channel expression at the soma membrane. This is the first example of passive transfer of an autoimmune peripheral neuropathic pain disorder and demonstrates that CASPR2 has a key role in regulating cell-intrinsic dorsal root ganglion (DRG) neuron excitability.

Funding information:
  • NINDS NIH HHS - NS18400(United States)

Phospholipid localization implies microglial morphology and function via Cdc42 in vitro.

  • Tokizane K
  • Glia
  • 2018 Feb 6

Literature context:


Abstract:

Under a quiescent state, microglia exhibit a ramified shape, rather than the amoeboid-like morphology following injury or inflammation. The manipulation of microglial morphology in vitro has not been very successful, which has impeded the progress of microglial studies. We demonstrate that lysophosphatidylserine (LysoPS), a kind of lysophospholipids, rapidly and substantially alters the morphology of primary cultured microglia to an in vivo-like ramified shape in a receptor independent manner. This mechanism is mediated by Cdc42 activity. LysoPS is incorporated into the plasma membrane and converted to phosphatidylserine (PS) via the Lands' cycle. The accumulated PS on the membrane recruits Cdc42. Both Cdc42 and PS colocalize predominantly in primary and secondary processes, but not in peripheral branches or tips of microglia. Along with the morphological changes LysoPS suppresses inflammatory cytokine production and NF-kB activity. The present study provides a tool to manipulate a microglial phenotype from an amoeboid to a fully ramified in vitro, which certainly contributes to studies exploring microglial physiology and pathology.

Abnormal Microglia and Enhanced Inflammation-Related Gene Transcription in Mice with Conditional Deletion of Ctcf in Camk2a-Cre-Expressing Neurons.

  • McGill BE
  • J. Neurosci.
  • 2018 Jan 3

Literature context:


Abstract:

CCCTC-binding factor (CTCF) is an 11 zinc finger DNA-binding domain protein that regulates gene expression by modifying 3D chromatin structure. Human mutations in CTCF cause intellectual disability and autistic features. Knocking out Ctcf in mouse embryonic neurons is lethal by neonatal age, but the effects of CTCF deficiency in postnatal neurons are less well studied. We knocked out Ctcf postnatally in glutamatergic forebrain neurons under the control of Camk2a-Cre. CtcfloxP/loxP;Camk2a-Cre+ (Ctcf CKO) mice of both sexes were viable and exhibited profound deficits in spatial learning/memory, impaired motor coordination, and decreased sociability by 4 months of age. Ctcf CKO mice also had reduced dendritic spine density in the hippocampus and cerebral cortex. Microarray analysis of mRNA from Ctcf CKO mouse hippocampus identified increased transcription of inflammation-related genes linked to microglia. Separate microarray analysis of mRNA isolated specifically from Ctcf CKO mouse hippocampal neurons by ribosomal affinity purification identified upregulation of chemokine signaling genes, suggesting crosstalk between neurons and microglia in Ctcf CKO hippocampus. Finally, we found that microglia in Ctcf CKO mouse hippocampus had abnormal morphology by Sholl analysis and increased immunostaining for CD68, a marker of microglial activation. Our findings confirm that Ctcf KO in postnatal neurons causes a neurobehavioral phenotype in mice and provide novel evidence that CTCF depletion leads to overexpression of inflammation-related genes and microglial dysfunction.SIGNIFICANCE STATEMENT CCCTC-binding factor (CTCF) is a DNA-binding protein that organizes nuclear chromatin topology. Mutations in CTCF cause intellectual disability and autistic features in humans. CTCF deficiency in embryonic neurons is lethal in mice, but mice with postnatal CTCF depletion are less well studied. We find that mice lacking Ctcf in Camk2a-expressing neurons (Ctcf CKO mice) have spatial learning/memory deficits, impaired fine motor skills, subtly altered social interactions, and decreased dendritic spine density. We demonstrate that Ctcf CKO mice overexpress inflammation-related genes in the brain and have microglia with abnormal morphology that label positive for CD68, a marker of microglial activation. Our findings suggest that inflammation and dysfunctional neuron-microglia interactions are factors in the pathology of CTCF deficiency.

Funding information:
  • NICHD NIH HHS - U54 HD087011()
  • NIGMS NIH HHS - GM007240(United States)

Microbiome Influences Prenatal and Adult Microglia in a Sex-Specific Manner.

  • Thion MS
  • Cell
  • 2018 Jan 25

Literature context:


Abstract:

Microglia are embryonically seeded macrophages that contribute to brain development, homeostasis, and pathologies. It is thus essential to decipher how microglial properties are temporally regulated by intrinsic and extrinsic factors, such as sexual identity and the microbiome. Here, we found that microglia undergo differentiation phases, discernable by transcriptomic signatures and chromatin accessibility landscapes, which can diverge in adult males and females. Remarkably, the absence of microbiome in germ-free mice had a time and sexually dimorphic impact both prenatally and postnatally: microglia were more profoundly perturbed in male embryos and female adults. Antibiotic treatment of adult mice triggered sexually biased microglial responses revealing both acute and long-term effects of microbiota depletion. Finally, human fetal microglia exhibited significant overlap with the murine transcriptomic signature. Our study shows that microglia respond to environmental challenges in a sex- and time-dependent manner from prenatal stages, with major implications for our understanding of microglial contributions to health and disease.

Funding information:
  • NIEHS NIH HHS - R01ES009949(United States)

Progression of histopathological and behavioral abnormalities following mild traumatic brain injury in the male ferret.

  • Schwerin SC
  • J. Neurosci. Res.
  • 2018 Jan 24

Literature context:


Abstract:

White matter damage is an important consequence of traumatic brain injury (TBI) in humans. Unlike rodents, ferrets have a substantial amount of white matter and a gyrencephalic brain; therefore, they may represent an ideal small mammal model to study human-pertinent consequences of TBI. Here we report immunohistochemical and behavioral results after a controlled cortical impact (CCI) injury to the sensorimotor cortex of adult male ferrets. We assessed inflammation in the neocortex and white matter, and behavior at 1 day post injury and 1, 4, and 16 weeks post injury (WPI). CCI in the ferret produced inflammation that originated in the neocortex near the site of the injury and progressed deep into the white matter with time. The density of microglia and astrocytes increased in the neocortex near the injury, peaking at 4WPI and remaining elevated at 16WPI. Microglial morphology in the neocortex was significantly altered in the first 4 weeks, but showed a return toward normal at 16 weeks. Clusters of microglial cells in the white matter persisted until 16WPI. We assessed motor and cognitive behavior using the open field, novel object recognition, T-maze, and gait tests. A transient deficit in memory occurred at 4WPI, with a reduction of rearing and motor ability at 12 and 16WPI. Behavioral impairments coincide with features of the inflammatory changes in the neocortex revealed by immunohistochemistry. The ferret represents an important animal model to explore ongoing damage in the white matter and cerebral cortex after TBI.

Bridging pro-inflammatory signals, synaptic transmission and protection in spinal explants in vitro.

  • Medelin M
  • Mol Brain
  • 2018 Jan 15

Literature context:


Abstract:

Multiple sclerosis is characterized by tissue atrophy involving the brain and the spinal cord, where reactive inflammation contributes to the neurodegenerative processes. Recently, the presence of synapse alterations induced by the inflammatory responses was suggested by experimental and clinical observations, in experimental autoimmune encephalomyelitis mouse model and in patients, respectively. Further knowledge on the interplay between pro-inflammatory agents, neuroglia and synaptic dysfunction is crucial to the design of unconventional protective molecules. Here we report the effects, on spinal cord circuits, of a cytokine cocktail that partly mimics the signature of T lymphocytes sub population Th1. In embryonic mouse spinal organ-cultures, containing neuronal cells and neuroglia, cytokines induced inflammatory responses accompanied by a significant increase in spontaneous synaptic activity. We suggest that cytokines specifically altered signal integration in spinal networks by speeding the decay of GABAA responses. This hypothesis is supported by the finding that synapse protection by a non-peptidic NGF mimetic molecule prevented both the changes in the time course of GABA events and in network activity that were left unchanged by the cytokine production from astrocytes and microglia present in the cultured tissue. In conclusion, we developed an important tool for the study of synaptic alterations induced by inflammation, that takes into account the role of neuronal and not neuronal resident cells.

Funding information:
  • FP7-NMP - 604263()
  • NIEHS NIH HHS - R21ES020010(United States)
  • PRIN-MIUR - n. 2012MYESZW()

Behavioral Changes in Mice Lacking Interleukin-33.

  • Dohi E
  • eNeuro
  • 2018 Jan 31

Literature context:


Abstract:

Interleukin (IL)-33 is a member of the IL-1 family of cytokines. IL-33 is expressed in nuclei and secreted as alarmin upon cellular damage to deliver a danger signal to the surrounding cells. Previous studies showed that IL-33 is expressed in the brain and that it is involved in neuroinflammatory and neurodegenerative processes in both humans and rodents. Nevertheless, the role of IL-33 in physiological brain function and behavior remains unclear. Here, we have investigated the behaviors of mice lacking IL-33 (Il33-/- mice). IL-33 is constitutively expressed throughout the adult mouse brain, mainly in oligodendrocyte-lineage cells and astrocytes. Notably, Il33-/- mice exhibited reduced anxiety-like behaviors in the elevated plus maze (EPM) and the open field test (OFT), as well as deficits in social novelty recognition, despite their intact sociability, in the three-chamber social interaction test. The immunoreactivity of c-Fos proteins, an indicator of neuronal activity, was altered in several brain regions implicated in anxiety-related behaviors, such as the medial prefrontal cortex (mPFC), amygdala, and piriform cortex (PCX), in Il33-/- mice after the EPM. Altered c-Fos immunoreactivity in Il33-/- mice was not correlated with IL-33 expression in wild-type (WT) mice nor was IL-33 expression affected by the EPM in WT mice. Thus, our study has revealed that Il33-/- mice exhibit multiple behavioral deficits, such as reduced anxiety and impaired social recognition. Our findings also indicate that IL-33 may regulate the development and/or maturation of neuronal circuits, rather than control neuronal activities in adult brains.

Funding information:
  • NIMH NIH HHS - R00 MH093458()
  • Wellcome Trust - 078285(United Kingdom)

The cystine-glutamate exchanger (xCT, Slc7a11) is expressed in significant concentrations in a subpopulation of astrocytes in the mouse brain.

  • Ottestad-Hansen S
  • Glia
  • 2018 Jan 20

Literature context:


Abstract:

The cystine-glutamate exchanger (xCT) promotes glutathione synthesis by catalyzing cystine uptake and glutamate release. The released glutamate may modulate normal neural signaling and contribute to excitotoxicity in pathological situations. Uncertainty, however, remains as neither the expression levels nor the distribution of xCT have been unambiguously determined. In fact, xCT has been reported in astrocytes, neurons, oligodendrocytes and microglia, but most of the information derives from cell cultures. Here, we show by immunohistochemistry and by Western blotting that xCT is widely expressed in the central nervous system of both sexes. The labeling specificity was validated using tissue from xCT knockout mice as controls. Astrocytes were selectively labeled, but showed greatly varying labeling intensities. This astroglial heterogeneity resulted in an astrocyte domain-like labeling pattern. Strong xCT labeling was also found in the leptomeninges, along some blood vessels, in selected circumventricular organs and in a subpopulation of tanycytes residing the lateral walls of the ventral third ventricle. Neurons, oligodendrocytes and resting microglia, as well as reactive microglia induced by glutamine synthetase deficiency, were unlabeled. The concentration of xCT protein in hippocampus was compared with that of the EAAT3 glutamate transporter by immunoblotting using a chimeric xCT-EAAT3 protein to normalize xCT and EAAT3 labeling intensities. The immunoblots suggested an xCT/EAAT3 ratio close to one (0.75 ± 0.07; average ± SEM; n = 4) in adult C57BL6 mice. CONCLUSIONS: xCT is present in select blood/brain/CSF interface areas and in an astrocyte subpopulation, in sufficient quantities to support the notion that system xc- provides physiologically relevant transport activity.

Funding information:
  • NIMH NIH HHS - P50 MH106934(United States)

Status Epilepticus Triggers Time-Dependent Alterations in Microglia Abundance and Morphological Phenotypes in the Hippocampus.

  • Wyatt-Johnson SK
  • Front Neurol
  • 2018 Jan 13

Literature context:


Abstract:

Status epilepticus (SE) is defined by the occurrence of prolonged "non-stop" seizures that last for at least 5 min. SE provokes inflammatory responses including the activation of microglial cells, the brain's resident immune cells, which are thought to contribute to the neuropathology and pathophysiology of epilepsy. Microglia are professional phagocytes that resemble peripheral macrophages. Upon sensing immune disturbances, including SE, microglia become reactive, produce inflammatory cytokines, and alter their actin cytoskeleton to transform from ramified to amoeboid shapes. It is widely known that SE triggers time-dependent microglial expression of pro-inflammatory cytokines that include TNFα and IL-1β. However, less is known in regards to the spatiotemporal progression of the morphological changes, which may help define the extent of microglia reactivity after SE and potential function (surveillance, inflammatory, phagocytic). Therefore, in this study, we used the microglia/macrophage IBA1 marker to identify and count these cells in hippocampi from control rats and at 4 h, 3 days, and 2 weeks after a single episode of pilocarpine-induced SE. We identified, categorized, and counted the IBA1-positive cells with the different morphologies observed after SE in the hippocampal areas CA1, CA3, and dentate gyrus. These included ramified, hypertrophic, bushy, amoeboid, and rod. We found that the ramified phenotype was the most abundant in control hippocampi. In contrast, SE provoked time-dependent changes in the microglial morphology that was characterized by significant increases in the abundance of bushy-shaped cells at 4 h and amoeboid-shaped cells at 3 days and 2 weeks. Interestingly, a significant increase in the number of rod-shaped cells was only evident in the CA1 region at 2 weeks after SE. Taken together, these data suggest that SE triggers time-dependent alterations in the morphology of microglial cells. This detailed description of the spatiotemporal profile of SE-induced microglial morphological changes may help provide insight into their contribution to epileptogenesis.

Funding information:
  • NCATS NIH HHS - UL1 TR001108()
  • NCI NIH HHS - P30 CA023168()
  • NCI NIH HHS - P50 CA86306(United States)

Glial scars are permeable to the neurotoxic environment of chronic stroke infarcts.

  • Zbesko JC
  • Neurobiol. Dis.
  • 2018 Jan 15

Literature context:


Abstract:

Following stroke, the damaged tissue undergoes liquefactive necrosis, a stage of infarct resolution that lasts for months although the exact length of time is currently unknown. One method of repair involves reactive astrocytes and microglia forming a glial scar to compartmentalize the area of liquefactive necrosis from the rest of the brain. The formation of the glial scar is a critical component of the healing response to stroke, as well as other central nervous system (CNS) injuries. The goal of this study was to evaluate the toxicity of the extracellular fluid present in areas of liquefactive necrosis and determine how effectively it is segregated from the remainder of the brain. To accomplish this goal, we used a mouse model of stroke in conjunction with an extracellular fluid toxicity assay, fluorescent and electron microscopy, immunostaining, tracer injections into the infarct, and multiplex immunoassays. We confirmed that the extracellular fluid present in areas of liquefactive necrosis following stroke is toxic to primary cortical and hippocampal neurons for at least 7 weeks following stroke, and discovered that although glial scars are robust physical and endocytic barriers, they are nevertheless permeable. We found that molecules present in the area of liquefactive necrosis can leak across the glial scar and are removed by a combination of paravascular clearance and microglial endocytosis in the adjacent tissue. Despite these mechanisms, there is delayed atrophy, cytotoxic edema, and neuron loss in regions adjacent to the infarct for weeks following stroke. These findings suggest that one mechanism of neurodegeneration following stroke is the failure of glial scars to impermeably segregate areas of liquefactive necrosis from surviving brain tissue.

Funding information:
  • NIA NIH HHS - P30 AG019610()
  • NIDDK NIH HHS - R01 DK048006(United States)
  • NINDS NIH HHS - F31 NS105455()
  • NINDS NIH HHS - R01 NS096091()
  • NINDS NIH HHS - U24 NS072026()
  • NINR NIH HHS - K99 NR013593()
  • NINR NIH HHS - R00 NR013593()

Astroglial major histocompatibility complex class I following immune activation leads to behavioral and neuropathological changes.

  • Sobue A
  • Glia
  • 2018 Jan 31

Literature context:


Abstract:

In the central nervous system, major histocompatibility complex class I (MHCI) molecules are mainly expressed in neurons, and neuronal MHCI have roles in synapse elimination and plasticity. However, the pathophysiological significance of astroglial MHCI remains unclear. We herein demonstrate that MHCI expression is up-regulated in astrocytes in the medial prefrontal cortex (mPFC) following systemic immune activation by an intraperitoneal injection of polyinosinic-polycytidylic acid (polyI:C) or hydrodynamic interferon (IFN)-γ gene delivery in male C57/BL6J mice. In cultured astrocytes, MHCI/H-2D largely co-localized with exosomes. To investigate the role of astroglial MHCI, H-2D, or sH-2D was expressed in the mPFC of male C57/BL6J mice using an adeno-associated virus vector under the control of a glial fibrillary acidic protein promoter. The expression of astroglial MHCI in the mPFC impaired sociability and recognition memory in mice. Regarding neuropathological changes, MHCI expression in astrocytes significantly activated microglial cells, decreased parvalbumin-positive cell numbers, and reduced dendritic spine density in the mPFC. A treatment with GW4869 that impairs exosome synthesis ameliorated these behavioral and neuropathological changes. These results suggest that the overexpression of MHCI in astrocytes affects microglial proliferation as well as neuronal numbers and spine densities, thereby leading to social and cognitive deficits in mice, possibly via exosomes created by astrocytes.

The Hypothalamic Inflammatory/Gliosis Response to Neonatal Overnutrition Is Sex and Age Dependent.

  • Argente-Arizón P
  • Endocrinology
  • 2018 Jan 1

Literature context:


Abstract:

Astrocytes participate in both physiological and pathophysiological responses to metabolic and nutrient signals. Although most studies have focused on the astrocytic response to weight gain due to high-fat/high-carbohydrate intake, surplus intake of a balanced diet also induces excess weight gain. We have accessed the effects of neonatal overnutrition, which has both age- and sex-dependent effects on weight gain, on hypothalamic inflammation/gliosis. Although both male and female Wistar rats accumulate excessive fat mass as early as postnatal day (PND) 10 with neonatal overnutrition, no increase in hypothalamic cytokine levels, markers of astrocytes or microglia, or inflammatory signaling pathways were observed. At PND 50, no effect of neonatal overnutriton was found in either sex, whereas at PND 150, males again weighed significantly more than their controls, and this was coincident with an increase in markers of inflammation and astrogliosis in the hypothalamus. Circulating triglycerides and free fatty acids were also elevated in these males, but not in females or in either sex at PND 10. Thus, the effects of fatty acids and estrogens on astrocytes in vitro were analyzed. Our results indicate that changes in circulating fatty acid levels may be involved in the induction of hypothalamic inflammation/gliosis in excess weight gain, even on a normal diet, and that estrogens could participate in the protection of females from these processes. In conclusion, the interaction of developmental influences, dietary composition, age, and sex determines the central inflammatory response and the associated long-term outcomes of excess weight gain.

Dimethyl fumarate treatment after traumatic brain injury prevents depletion of antioxidative brain glutathione and confers neuroprotection.

  • Krämer T
  • J. Neurochem.
  • 2017 Dec 7

Literature context:


Abstract:

Dimethyl fumarate (DMF) is an immunomodulatory compound to treat multiple sclerosis and psoriasis with neuroprotective potential. Its mechanism of action involves activation of the antioxidant pathway regulator Nuclear factor erythroid 2-related factor 2 thereby increasing synthesis of the cellular antioxidant glutathione (GSH). The objective of this study was to investigate whether post-traumatic DMF treatment is beneficial after experimental traumatic brain injury (TBI). Adult C57Bl/6 mice were subjected to controlled cortical impact followed by oral administration of DMF (80 mg/kg body weight) or vehicle at 3, 24, 48, and 72 h after the inflicted TBI. At 4 days after lesion (dal), DMF-treated mice displayed less neurological deficits than vehicle-treated mice and reduced histopathological brain damage. At the same time, the TBI-evoked depletion of brain GSH was prevented by DMF treatment. However, nuclear factor erythroid 2-related factor 2 target gene mRNA expression involved in antioxidant and detoxifying pathways was increased in both treatment groups at 4 dal. Blood brain barrier leakage, as assessed by immunoglobulin G extravasation, inflammatory marker mRNA expression, and CD45+ leukocyte infiltration into the perilesional brain tissue was induced by TBI but not significantly altered by DMF treatment. Collectively, our data demonstrate that post-traumatic DMF treatment improves neurological outcome and reduces brain tissue loss in a clinically relevant model of TBI. Our findings suggest that DMF treatment confers neuroprotection after TBI via preservation of brain GSH levels rather than by modulating neuroinflammation.

Funding information:
  • National Science Foundation - Award IOS-125762(United States)

Calmodulin-like skin protein protects against spatial learning impairment in a mouse model of Alzheimer disease.

  • Kusakari S
  • J. Neurochem.
  • 2017 Nov 23

Literature context:


Abstract:

Humanin and calmodulin-like skin protein (CLSP) inhibits Alzheimer disease (AD)-related neuronal cell death via the heterotrimeric humanin receptor in vitro. It has been suggested that CLSP is a central agonist of the heterotrimeric humanin receptor in vivo. To investigate the role of CLSP in the AD pathogenesis in vivo, we generated mouse CLSP-1 transgenic mice, crossed them with the APPswe/PSEN1dE9 mice, a model mouse of AD, and examined the effect of CLSP over-expression on the pathological phenotype of the AD mouse model. We found that over-expression of the mouse CLSP-1 gene attenuated spatial learning impairment, the loss of a presynaptic marker synaptophysin, and the inactivation of STAT3 in the APPswe/PSEN1dE9 mice. On the other hand, CLSP over-expression did not affect levels of Aβ, soluble Aβ oligomers, or gliosis. These results suggest that the CLSP-mediated attenuation of memory impairment and synaptic loss occurs in an Aβ-independent manner. The results of this study may serve as a hint to the better understanding of the AD pathogenesis and the development of AD therapy.

Transplantation of feeder-free human induced pluripotent stem cell-derived cortical neuron progenitors in adult male Wistar rats with focal brain ischemia.

  • Hermanto Y
  • J. Neurosci. Res.
  • 2017 Nov 8

Literature context:


Abstract:

The use of human induced pluripotent stem cells (hiPSCs) eliminates the ethical issues associated with fetal or embryonic materials, thus allowing progress in cell therapy research for ischemic stroke. Strict regulation of cell therapy development requires the xeno-free condition to eliminate clinical complications. Maintenance of hiPSCs with feeder-free condition presents a higher degree of spontaneous differentiation in comparison with conventional cultures. Therefore, feeder-free derivation might be not ideal for developing transplantable hiPSC derivatives. We developed the feeder-free condition for differentiation of cortical neurons from hiPSCs. Then, we evaluated the cells' characteristics upon transplantation into the sham and focal brain ischemia on adult male Wistar rats. Grafts in lesioned brains demonstrated polarized reactivity toward the ischemic border, indicated by directional preferences in axonal outgrowth and cellular migration, with no influence on graft survival. Following the transplantation, forelimb asymmetry was better restored compared with controls. Herein, we provide evidence to support the use of the xeno-free condition for the development of cell therapy for ischemic stroke.

Contribution of mast cells to injury mechanisms in a mouse model of pediatric traumatic brain injury.

  • Moretti R
  • J. Neurosci. Res.
  • 2017 Nov 20

Literature context:


Abstract:

The cognitive and behavioral deficits caused by traumatic brain injury (TBI) to the immature brain are more severe and persistent than injuries to the adult brain. Understanding this developmental sensitivity is critical because children under 4 years of age of sustain TBI more frequently than any other age group. One of the first events after TBI is the infiltration and degranulation of mast cells (MCs) in the brain, releasing a range of immunomodulatory substances; inhibition of these cells is neuroprotective in other types of neonatal brain injury. This study investigates for the first time the role of MCs in mediating injury in a P7 mouse model of pediatric contusion-induced TBI. We show that various neural cell types express histamine receptors and that histamine exacerbates excitotoxic cell death in primary cultured neurons. Cromoglycate, an inhibitor of MC degranulation, altered the inflammatory phenotype of microglia activated by TBI, reversing several changes but accentuating others, when administered before TBI. However, without regard to the time of cromoglycate administration, inhibiting MC degranulation did not affect cell loss, as evaluated by ventricular dilatation or cleaved caspase-3 labeling, or the density of activated microglia, neurons, or myelin. In double-heterozygous cKit mutant mice lacking MCs, this overall lack of effect was confirmed. These results suggest that the role of MCs in this model of pediatric TBI is restricted to subtle effects and that they are unlikely to be viable neurotherapeutic targets. © 2016 Wiley Periodicals, Inc.

Funding information:
  • BLRD VA - IK2 BX002505(United States)

Pharmacological targeting of GSK-3 and NRF2 provides neuroprotection in a preclinical model of tauopathy.

  • Cuadrado A
  • Redox Biol
  • 2017 Nov 10

Literature context:


Abstract:

Tauopathies are a group of neurodegenerative disorders where TAU protein is presented as aggregates or is abnormally phosphorylated, leading to alterations of axonal transport, neuronal death and neuroinflammation. Currently, there is no treatment to slow progression of these diseases. Here, we have investigated whether dimethyl fumarate (DMF), an inducer of the transcription factor NRF2, could mitigate tauopathy in a mouse model. The signaling pathways modulated by DMF were also studied in mouse embryonic fibroblast (MEFs) from wild type or KEAP1-deficient mice. The effect of DMF on neurodegeneration, astrocyte and microglial activation was examined in Nrf2+/+ and Nrf2-/- mice stereotaxically injected in the right hippocampus with an adeno-associated vector expressing human TAUP301L and treated daily with DMF (100mg/kg, i.g) during three weeks. DMF induces the NRF2 transcriptional through a mechanism that involves KEAP1 but also PI3K/AKT/GSK-3-dependent pathways. DMF modulates GSK-3β activity in mouse hippocampi. Furthermore, DMF modulates TAU phosphorylation, neuronal impairment measured by calbindin-D28K and BDNF expression, and inflammatory processes involved in astrogliosis, microgliosis and pro-inflammatory cytokines production. This study reveals neuroprotective effects of DMF beyond disruption of the KEAP1/NRF2 axis by inhibiting GSK3 in a mouse model of tauopathy. Our results support repurposing of this drug for treatment of these diseases.

Funding information:
  • NCRR NIH HHS - P20 RR16462(United States)

Neuronal aromatase expression in pain processing regions of the medullary and spinal cord dorsal horn.

  • Tran M
  • J. Comp. Neurol.
  • 2017 Nov 1

Literature context:


Abstract:

In both acute and chronic pain conditions, women tend to be more sensitive than men. This sex difference may be regulated by estrogens, such as estradiol, that are synthesized in the spinal cord and brainstem and act locally to influence pain processing. To identify a potential cellular source of local estrogen, here we examined the expression of aromatase, the enzyme that catalyzes the conversion of testosterone to estradiol. Our studies focused on primary afferent neurons and on their central targets in the spinal cord and medulla as well as in the nucleus of the solitary tract, the target of nodose ganglion-derived visceral afferents. Immunohistochemical staining in an aromatase reporter mouse revealed that many neurons in laminae I and V of the spinal cord dorsal horn and caudal spinal trigeminal nucleus and in the nucleus of the solitary tract express aromatase. The great majority of these cells also express inhibitory interneuron markers. We did not find sex differences in aromatase expression and neither the pattern nor the number of neurons changed in a sciatic nerve transection model of neuropathic pain or in the Complete Freund's adjuvant model of inflammatory pain. A few aromatase neurons express Fos after cheek injection of capsaicin, formalin, or chloroquine. In total, given their location, these aromatase neurons are poised to engage nociceptive circuits, whether it is through local estrogen synthesis or inhibitory neurotransmitter release.

Funding information:
  • NINDS NIH HHS - R35 NS097306()
  • NINDS NIH HHS - R37 NS014627()

Microstructural and microglial changes after repetitive mild traumatic brain injury in mice.

  • Robinson S
  • J. Neurosci. Res.
  • 2017 Nov 16

Literature context:


Abstract:

Traumatic brain injury (TBI) is a major public health issue, with recently increased awareness of the potential long-term sequelae of repetitive injury. Although TBI is common, objective diagnostic tools with sound neurobiological predictors of outcome are lacking. Indeed, such tools could help to identify those at risk for more severe outcomes after repetitive injury and improve understanding of biological underpinnings to provide important mechanistic insights. We tested the hypothesis that acute and subacute pathological injury, including the microgliosis that results from repeated mild closed head injury (rmCHI), is reflected in susceptibility-weighted magnetic resonance imaging and diffusion-tensor imaging microstructural abnormalities. Using a combination of high-resolution magnetic resonance imaging, stereology, and quantitative PCR, we studied the pathophysiology of male mice that sustained seven consecutive mild traumatic brain injuries over 9 days in acute (24 hr) and subacute (1 week) time periods. rmCHI induced focal cortical microhemorrhages and impaired axial diffusivity at 1 week postinjury. These microstructural abnormalities were associated with a significant increase in microglia. Notably, microgliosis was accompanied by a change in inflammatory microenvironment defined by robust spatiotemporal alterations in tumor necrosis factor-α receptor mRNA. Together these data contribute novel insight into the fundamental biological processes associated with repeated mild brain injury concomitant with subacute imaging abnormalities in a clinically relevant animal model of repeated mild TBI. These findings suggest new diagnostic techniques that can be used as biomarkers to guide the use of future protective or reparative interventions. © 2016 Wiley Periodicals, Inc.

Development and Refinement of Functional Properties of Adult-Born Neurons.

  • Wallace JL
  • Neuron
  • 2017 Nov 15

Literature context:


Abstract:

New neurons appear only in a few regions of the adult mammalian brain and become integrated into existing circuits. Little is known about the functional development of individual neurons in vivo. We examined the functional life history of adult-born granule cells (abGCs) in the olfactory bulb using multiphoton imaging in awake and anesthetized mice. We found that abGCs can become responsive to odorants soon after they arrive in the olfactory bulb. Tracking identified abGCs over weeks revealed that the robust and broadly tuned responses of most newly arrived abGCs gradually become more selective over a period of ∼3 weeks, but a small fraction achieves broader tuning with maturation. Enriching the olfactory environment of mice prolonged the period over which abGCs were strongly and broadly responsive to odorants. Our data offer direct support for rapid integration of adult-born neurons into existing circuits, followed by experience-dependent refinement of their functional connectivity.

N-acetylcysteine attenuates the cuprizone-induced behavioral changes and oligodendrocyte loss in male C57BL/7 mice via its anti-inflammation actions.

  • Zhang L
  • J. Neurosci. Res.
  • 2017 Nov 9

Literature context:


Abstract:

Previous animal studies have linked white matter damage to certain schizophrenia-like behaviors in cuprizone (CPZ)-exposed mouse. Mitochondrial dysfunction, oxidative stress, neuroinflammation, and oligodendrocyte loss coexist in the brain of such mice. The aim of this study was to examine effects of the antioxidant N-acetylcysteine (NAC) on CPZ-induced behavioral changes and concurrent oligodendrocyte loss, oxidative stress, and neuroinflammation in these animals. Male C57BL/6 mice were given intraperitoneal saline or NAC at doses of 100, 200, and 400 mg/kg/day for 2 weeks; animals were fed a CPZ-containing diet (0.2%, w/w) during days 5-14. During days 15-17, the mice were examined in open-field, social recognition, and Y-maze tests (1 test per day). Six mice in each group were then used for biochemical and enzyme-linked immunosorbent assay analyses, while the remaining animals were used for immunohistochemical and immunofluorescence staining. The mice exposed to CPZ for 10 days showed significantly lower spontaneous alternation in the Y-maze, lower activity of total superoxide dismutase, and glutathione peroxidase, but higher levels of malondialdehyde in the cerebral cortex and hippocampus, elevated concentrations of interleukin-1β and tumor necrosis factor-α in the brain regions mentioned above and caudate putamen, and a decreased number of mature oligodendrocytes, but increased number of microglia in all the brain regions examined. These changes, however, were not seen or effectively alleviated in NAC-treated mice at all three doses. These results demonstrate that NAC protected mature oligodendrocytes against the toxic effects of CPZ, likely via its antioxidant and anti-inflammatory actions.

Experimental febrile seizures impair interastrocytic gap junction coupling in juvenile mice.

  • Khan D
  • J. Neurosci. Res.
  • 2017 Nov 30

Literature context:


Abstract:

Prolonged and focal febrile seizures (FSs) have been associated with the development of temporal lobe epilepsy (TLE), although the underlying mechanism and the contribution of predisposing risk factors are still poorly understood. Using a kainate model of TLE, we previously provided strong evidence that interruption of astrocyte gap junction-mediated intercellular communication represents a crucial event in epileptogenesis. To elucidate this aspect further, we induced seizures in immature mice by hyperthermia (HT) to study the consequences of FSs on the hippocampal astrocytic network. Changes in interastrocytic coupling were assessed by tracer diffusion studies in acute slices from mice 5 days after experimental FS induction. The results reveal that HT-induced FSs cause a pronounced reduction of astrocyte gap junctional coupling in the hippocampus by more than 50%. Western blot analysis indicated that reduced connexin43 protein expression and/or changes in the phosphorylation status account for this astrocyte dysfunction. Remarkably, uncoupling occurred in the absence of neuronal death and reactive gliosis. These data provide a mechanistic link between FSs and the subsequent development of TLE and further strengthen the emerging view that astrocytes have a central role in the pathogenesis of this disorder. © 2016 Wiley Periodicals, Inc.

Neutrophils Are Critical for Myelin Removal in a Peripheral Nerve Injury Model of Wallerian Degeneration.

  • Lindborg JA
  • J. Neurosci.
  • 2017 Oct 25

Literature context:


Abstract:

Wallerian degeneration (WD) is considered an essential preparatory stage to the process of axonal regeneration. In the peripheral nervous system, infiltrating monocyte-derived macrophages, which use the chemokine receptor CCR2 to gain entry to injured tissues from the bloodstream, are purportedly necessary for efficient WD. However, our laboratory has previously reported that myelin clearance in the injured sciatic nerve proceeds unhindered in the Ccr2-/- mouse model. Here, we extensively characterize WD in male Ccr2-/- mice and identify a compensatory mechanism of WD that is facilitated primarily by neutrophils. In response to the loss of CCR2, injured Ccr2-/- sciatic nerves demonstrate prolonged expression of neutrophil chemokines, a concomitant extended increase in the accumulation of neutrophils in the nerve, and elevated phagocytosis by neutrophils. Neutrophil depletion substantially inhibits myelin clearance after nerve injury in both male WT and Ccr2-/- mice, highlighting a novel role for these cells in peripheral nerve degeneration that spans genotypes.SIGNIFICANCE STATEMENT The accepted view in the basic and clinical neurosciences is that the clearance of axonal and myelin debris after a nerve injury is directed primarily by inflammatory CCR2+ macrophages. However, we demonstrate that this clearance is nearly identical in WT and Ccr2-/- mice, and that neutrophils replace CCR2+ macrophages as the primary phagocytic cell. We find that neutrophils play a major role in myelin clearance not only in Ccr2-/- mice but also in WT mice, highlighting their necessity during nerve degeneration in the peripheral nervous system. These degeneration studies may propel improvements in nerve regeneration and draw critical parallels to mechanisms of nerve degeneration and regeneration in the CNS and in the context of peripheral neuropathies.

Funding information:
  • NEI NIH HHS - P30 EY011373()
  • NIDDK NIH HHS - R01 DK097223()
  • NIDDK NIH HHS - R56 DK097223()
  • NIH HHS - S10 OD016164()
  • NINDS NIH HHS - F31 NS093694()
  • NINDS NIH HHS - R01 NS095017()
  • NINDS NIH HHS - T32 NS067431()

Temporary Depletion of Microglia during the Early Postnatal Period Induces Lasting Sex-Dependent and Sex-Independent Effects on Behavior in Rats.

  • VanRyzin JW
  • eNeuro
  • 2017 Oct 24

Literature context:


Abstract:

Microglia are the primary immune cells of the brain and function in multiple ways to facilitate proper brain development. However, our current understanding of how these cells influence the later expression of normal behaviors is lacking. Using the laboratory rat, we administered liposomal clodronate centrally to selectively deplete microglia in the developing postnatal brain. We then assessed a range of developmental, juvenile, and adult behaviors. Liposomal clodronate treatment on postnatal days 0, 2, and 4 depleted microglia with recovery by about 10 days of age and induced a hyperlocomotive phenotype, observable in the second postnatal week. Temporary microglia depletion also increased juvenile locomotion in the open field test and decreased anxiety-like behaviors in the open field and elevated plus maze. These same rats displayed reductions in predator odor-induced avoidance behavior, but increased their risk assessment behaviors compared with vehicle-treated controls. In adulthood, postnatal microglia depletion resulted in significant deficits in male-specific sex behaviors. Using factor analysis, we identified two underlying traits-behavioral disinhibition and locomotion-as being significantly altered by postnatal microglia depletion. These findings further implicate microglia as being critically important to the development of juvenile and adult behavior.

Interferon-γ-Driven iNOS: A Molecular Pathway to Terminal Shock in Arenavirus Hemorrhagic Fever.

  • Remy MM
  • Cell Host Microbe
  • 2017 Sep 13

Literature context:


Abstract:

Arenaviruses such as Lassa virus (LASV) cause hemorrhagic fever. Terminal shock is associated with a systemic cytokine storm, but the mechanisms are ill defined. Here we used HLA-A2-expressing mice infected with a monkey-pathogenic strain of lymphocytic choriomeningitis virus (LCMV-WE), a close relative of LASV, to investigate the pathophysiology of arenavirus hemorrhagic fever (AHF). AHF manifested as pleural effusions, edematous skin swelling, and serum albumin loss, culminating in hypovolemic shock. A characteristic cytokine storm included numerous pro-inflammatory cytokines and nitric oxide (NO) metabolites. Edema formation and terminal shock were abrogated in mice lacking inducible nitric oxide synthase (iNOS), although the cytokine storm persisted. iNOS was upregulated in the liver in a T cell- and interferon-γ (IFN-γ)-dependent fashion. Accordingly, blockade of IFN-γ or depletion of T cells repressed hepatic iNOS and prevented disease despite unchecked high-level viremia. We identify the IFN-γ-iNOS axis as an essential and potentially druggable molecular pathway to AHF-induced shock.

Spinal nociceptive circuit analysis with recombinant adeno-associated viruses: the impact of serotypes and promoters.

  • Haenraets K
  • J. Neurochem.
  • 2017 Sep 12

Literature context:


Abstract:

Recombinant adeno-associated virus (rAAV) vector-mediated gene transfer into genetically defined neuron subtypes has become a powerful tool to study the neuroanatomy of neuronal circuits in the brain and to unravel their functions. More recently, this methodology has also become popular for the analysis of spinal cord circuits. To date, a variety of naturally occurring AAV serotypes and genetically modified capsid variants are available but transduction efficiency in spinal neurons, target selectivity, and the ability for retrograde tracing are only incompletely characterized. Here, we have compared the transduction efficiency of seven commonly used AAV serotypes after intraspinal injection. We specifically analyzed local transduction of different types of dorsal horn neurons, and retrograde transduction of dorsal root ganglia (DRG) neurons and of neurons in the rostral ventromedial medulla (RVM) and the somatosensory cortex (S1). Our results show that most of the tested rAAV vectors have similar transduction efficiency in spinal neurons. All serotypes analyzed were also able to transduce DRG neurons and descending RVM and S1 neurons via their spinal axon terminals. When comparing the commonly used rAAV serotypes to the recently developed serotype 2 capsid variant rAAV2retro, a > 20-fold increase in transduction efficiency of descending supraspinal neurons was observed. Conversely, transgene expression in retrogradely transduced neurons was strongly reduced when the human synapsin 1 (hSyn1) promoter was used instead of the strong ubiquitous hybrid cytomegalovirus enhancer/chicken β-actin promoter (CAG) or cytomegalovirus (CMV) promoter fragments. We conclude that the use of AAV2retro greatly increases transduction of neurons connected to the spinal cord via their axon terminals, while the hSyn1 promoter can be used to minimize transgene expression in retrogradely connected neurons of the DRG or brainstem. Cover Image for this issue: doi. 10.1111/jnc.13813.

Developmental regulation and localization of carnitine palmitoyltransferases (CPTs) in rat brain.

  • Jernberg JN
  • J. Neurochem.
  • 2017 Sep 21

Literature context:


Abstract:

While the brain's high energy demands are largely met by glucose, brain is also equipped with the ability to oxidize fatty acids for energy and metabolism. The brain expresses the carnitine palmitoyltransferases (CPTs) that mediate carnitine-dependent entry of long-chain acyl-CoAs into the mitochondrial matrix for β-oxidation - CPT1a and CPT2 located on the outer and inner mitochondrial membranes, respectively. Their developmental profile, regional distribution and activity as well as cell type expression remain unknown. We determined that brain CPT1a RNA and total protein expression were unchanged throughout post-natal development (PND0, PND7, PND14, PND21 and PND50); however, CPT2 RNA peaked at PND 21 and remained unchanged through PND50 in all regions studied (cortex, hippocampus, midbrain, and cerebellum). Both long-chain acyl CoA dehydrogenase and medium acyl-CoA dehydrogenase showed a similar developmental profile to CPT2. Acylcarnitines, generated as a result of CPT1a activity, significantly increased with age and peaked at PND21 in all brain regions, concurrent with the increased expression of enzymes involved in mitochondrial β-oxidation. The CPT system is highly enriched in vivo in hippocampus and cerebellum, relative to cortex and midbrain, and is exclusively present in astrocytes and neural progenitor cells, while absent in neurons, microglia, and oligodendrocytes. Using radiolabeled oleate, we demonstrate regional differences in brain fatty acid oxidation that may be blocked by the irreversible CPT1a inhibitor etomoxir. This study contributes to the field of knowledge in brain cell-specific metabolic pathways, which are important for understanding normal brain development and aging, as well as pathophysiology of neurological diseases. Read the Editorial Comment for this article on page 347.

Funding information:
  • NINDS NIH HHS - K08 NS069815()

Light reintroduction after dark exposure reactivates plasticity in adults via perisynaptic activation of MMP-9.

  • Murase S
  • Elife
  • 2017 Sep 6

Literature context:


Abstract:

The sensitivity of ocular dominance to regulation by monocular deprivation is the canonical model of plasticity confined to a critical period. However, we have previously shown that visual deprivation through dark exposure (DE) reactivates critical period plasticity in adults. Previous work assumed that the elimination of visual input was sufficient to enhance plasticity in the adult mouse visual cortex. In contrast, here we show that light reintroduction (LRx) after DE is responsible for the reactivation of plasticity. LRx triggers degradation of the ECM, which is blocked by pharmacological inhibition or genetic ablation of matrix metalloproteinase-9 (MMP-9). LRx induces an increase in MMP-9 activity that is perisynaptic and enriched at thalamo-cortical synapses. The reactivation of plasticity by LRx is absent in Mmp9-/- mice, and is rescued by hyaluronidase, an enzyme that degrades core ECM components. Thus, the LRx-induced increase in MMP-9 removes constraints on structural and functional plasticity in the mature cortex.

Funding information:
  • Canadian Institutes of Health Research - (Canada)

Study of retinal neurodegeneration and maculopathy in diabetic Meriones shawi: A particular animal model with human-like macula.

  • Hammoum I
  • J. Comp. Neurol.
  • 2017 Sep 1

Literature context:


Abstract:

The purpose of this work was to evaluate a potentially useful animal model, Meriones shawi (M.sh)-developing metabolic X syndrome, diabetes and possessing a visual streak similar to human macula-in the study of diabetic retinopathy and diabetic macular edema (DME). Type 2 diabetes (T2D) was induced by high fat diet administration in M.sh. Body weights, blood glucose levels were monitored throughout the study. Diabetic retinal histopathology was evaluated 3 and 7 months after diabetes induction. Retinal thickness was measured, retinal cell types were labeled by immunohistochemistry and the number of stained elements were quantified. Apoptosis was determined with TUNEL assay. T2D induced progressive changes in retinal histology. A significant decrease of retinal thickness and glial reactivity was observed without an increase in apoptosis rate. Photoreceptor outer segment degeneration was evident, with a significant decrease in the number of all cones and M-cone subtype, but-surprisingly-an increase in S-cones. Damage of the pigment epithelium was also confirmed. A decrease in the number and labeling intensity of parvalbumin- and calretinin-positive amacrine cells and a loss of ganglion cells was detected. Other cell types showed no evident alterations. No DME-like condition was noticed even after 7 months. M.sh could be a useful model to study the evolution of diabetic retinal pathology and to identify the role of hypertension and dyslipidemia in the development of the reported alterations. Longer follow up would be needed to evaluate the potential use of the visual streak in modeling human macular diseases.

Visual system pathology in humans and animal models of blast injury.

  • DeWalt GJ
  • J. Comp. Neurol.
  • 2017 Sep 1

Literature context:


Abstract:

Injury from blast exposure is becoming a more prevalent cause of death and disability worldwide. The devastating neurological impairments that result from blasts are significant and lifelong. Progress in the development of effective therapies to treat injury has been slowed by its heterogeneous pathology and the dearth of information regarding the cellular mechanisms involved. Within the last decade, a number of studies have documented visual dysfunction following injury. This brief review examines damage to the visual system in both humans and animal models of blast injury. The in vivo use of the retina as a surrogate to evaluate brain injury following exposure to blast is also highlighted.

Two-photon calcium imaging of the medial prefrontal cortex and hippocampus without cortical invasion.

  • Kondo M
  • Elife
  • 2017 Sep 25

Literature context:


Abstract:

In vivo two-photon calcium imaging currently allows us to observe the activity of multiple neurons up to ~900 µm below the cortical surface without cortical invasion. However, many important brain areas are located deeper than this. Here, we used an 1100 nm laser that underfilled the back aperture of the objective together with red genetically encoded calcium indicators to establish two-photon calcium imaging of the intact mouse brain and detect neural activity up to 1200 μm from the cortical surface. This imaging was obtained from the medial prefrontal cortex (the prelimbic area) and the hippocampal CA1 region. We found that neural activity before water delivery repeated at a constant interval was higher in the prelimbic area than in layer 2/3 of the secondary motor area. Reducing the invasiveness of imaging is an important strategy to reveal the intact brain processes active in cognition and memory.

Loss of Tuberous Sclerosis Complex1 in Adult Oligodendrocyte Progenitor Cells Enhances Axon Remyelination and Increases Myelin Thickness after a Focal Demyelination.

  • McLane LE
  • J. Neurosci.
  • 2017 Aug 2

Literature context:


Abstract:

Although the mammalian target of rapamycin (mTOR) is an essential regulator of developmental oligodendrocyte differentiation and myelination, oligodendrocyte-specific deletion of tuberous sclerosis complex (TSC), a major upstream inhibitor of mTOR, surprisingly also leads to hypomyelination during CNS development. However, the function of TSC has not been studied in the context of remyelination. Here, we used the inducible Cre-lox system to study the function of TSC in the remyelination of a focal, lysolecithin-demyelinated lesion in adult male mice. Using two different mouse models in which Tsc1 is deleted by Cre expression in oligodendrocyte progenitor cells (OPCs) or in premyelinating oligodendrocytes, we reveal that deletion of Tsc1 affects oligodendroglia differently depending on the stage of the oligodendrocyte lineage. Tsc1 deletion from NG2+ OPCs accelerated remyelination. Conversely, Tsc1 deletion from proteolipid protein (PLP)-positive oligodendrocytes slowed remyelination. Contrary to developmental myelination, there were no changes in OPC or oligodendrocyte numbers in either model. Our findings reveal a complex role for TSC in oligodendrocytes during remyelination in which the timing of Tsc1 deletion is a critical determinant of its effect on remyelination. Moreover, our findings suggest that TSC has different functions in developmental myelination and remyelination.SIGNIFICANCE STATEMENT Myelin loss in demyelinating disorders such as multiple sclerosis results in disability due to loss of axon conductance and axon damage. Encouragingly, the nervous system is capable of spontaneous remyelination, but this regenerative process often fails. Many chronically demyelinated lesions have oligodendrocyte progenitor cells (OPCs) within their borders. It is thus of great interest to elucidate mechanisms by which we might enhance endogenous remyelination. Here, we provide evidence that deletion of Tsc1 from OPCs, but not differentiating oligodendrocytes, is beneficial to remyelination. This finding contrasts with the loss of oligodendroglia and hypomyelination seen with Tsc1 or Tsc2 deletion in the oligodendrocyte lineage during CNS development and points to important differences in the regulation of developmental myelination and remyelination.

Funding information:
  • NINDS NIH HHS - R01 NS082203()

Age exacerbates microglial activation, oxidative stress, inflammatory and NOX2 gene expression, and delays functional recovery in a middle-aged rodent model of spinal cord injury.

  • von Leden RE
  • J Neuroinflammation
  • 2017 Aug 18

Literature context:


Abstract:

BACKGROUND: Spinal cord injury (SCI) among people over age 40 has been steadily increasing since the 1980s and is associated with worsened outcome than injuries in young people. Age-related increases in reactive oxygen species (ROS) are suggested to lead to chronic inflammation. The NADPH oxidase 2 (NOX2) enzyme is expressed by microglia and is a primary source of ROS. This study aimed to determine the effect of age on inflammation, oxidative damage, NOX2 gene expression, and functional performance with and without SCI in young adult (3 months) and middle-aged (12 months) male rats. METHODS: Young adult and middle-aged rats were assessed in two groups-naïve and moderate contusion SCI. Functional recovery was determined by weekly assessment with the Basso, Beattie, and Breshnahan general motor score (analyzed two-way ANOVA) and footprint analysis (analyzed by Chi-square analysis). Tissue was analyzed for markers of oxidative damage (8-OHdG, Oxyblot, and 3-NT), microglial-related inflammation (Iba1), NOX2 component (p47PHOX, p22PHOX, and gp91PHOX), and inflammatory (CD86, CD206, TNFα, and NFκB) gene expression (all analyzed by unpaired Student's t test). RESULTS: In both naïve and injured aged rats, compared to young rats, tissue analysis revealed significant increases in 8-OHdG and Iba1, as well as inflammatory and NOX2 component gene expression. Further, injured aged rats showed greater lesion volume rostral and caudal to the injury epicenter. Finally, injured aged rats showed significantly reduced Basso-Beattie-Bresnahan (BBB) scores and stride length after SCI. CONCLUSIONS: These results show that middle-aged rats demonstrate increased microglial activation, oxidative stress, and inflammatory gene expression, which may be related to elevated NOX2 expression, and contribute to worsened functional outcome following injury. These findings are essential to elucidating the mechanisms of age-related differences in response to SCI and developing age-appropriate therapeutics.

Funding information:
  • NINDS NIH HHS - F31 NS090737()
  • NINDS NIH HHS - R01 NS073667()

TREM2 Maintains Microglial Metabolic Fitness in Alzheimer's Disease.

  • Ulland TK
  • Cell
  • 2017 Aug 10

Literature context:


Abstract:

Elevated risk of developing Alzheimer's disease (AD) is associated with hypomorphic variants of TREM2, a surface receptor required for microglial responses to neurodegeneration, including proliferation, survival, clustering, and phagocytosis. How TREM2 promotes such diverse responses is unknown. Here, we find that microglia in AD patients carrying TREM2 risk variants and TREM2-deficient mice with AD-like pathology have abundant autophagic vesicles, as do TREM2-deficient macrophages under growth-factor limitation or endoplasmic reticulum (ER) stress. Combined metabolomics and RNA sequencing (RNA-seq) linked this anomalous autophagy to defective mammalian target of rapamycin (mTOR) signaling, which affects ATP levels and biosynthetic pathways. Metabolic derailment and autophagy were offset in vitro through Dectin-1, a receptor that elicits TREM2-like intracellular signals, and cyclocreatine, a creatine analog that can supply ATP. Dietary cyclocreatine tempered autophagy, restored microglial clustering around plaques, and decreased plaque-adjacent neuronal dystrophy in TREM2-deficient mice with amyloid-β pathology. Thus, TREM2 enables microglial responses during AD by sustaining cellular energetic and biosynthetic metabolism.

Funding information:
  • NCI NIH HHS - T32 CA009547()
  • NIA NIH HHS - P01 AG003991()
  • NIA NIH HHS - P01 AG026276()
  • NIA NIH HHS - P50 AG005681()
  • NIA NIH HHS - RF1 AG051485()
  • NIDDK NIH HHS - R01 DK058177()

Opening a New Time Window for Treatment of Stroke by Targeting HDAC2.

  • Lin YH
  • J. Neurosci.
  • 2017 Jul 12

Literature context:


Abstract:

Narrow therapeutic window limits treatments with thrombolysis and neuroprotection for most stroke patients. Widening therapeutic window remains a critical challenge. Understanding the key mechanisms underlying the pathophysiological events in the peri-infarct area where secondary injury coexists with neuroplasticity over days to weeks may offer an opportunity for expanding the therapeutic window. Here we show that ischemia-induced histone deacetylase 2 (HDAC2) upregulation from 5 to 7 d after stroke plays a crucial role. In this window phase, suppressing HDAC2 in the peri-infarct cortex of rodents by HDAC inhibitors, knockdown or knock-out of Hdac2 promoted recovery of motor function from stroke via epigenetically enhancing cells survival and neuroplasticity of surviving neurons as well as reducing neuroinflammation, whereas overexpressing HDAC2 worsened stroke-induced functional impairment of both WT and Hdac2 conditional knock-out mice. More importantly, inhibiting other isoforms of HDACs had no effect. Thus, the intervention by precisely targeting HDAC2 in this window phase is a novel strategy for the functional recovery of stroke survivors.SIGNIFICANCE STATEMENT Narrow time window phase impedes current therapies for stroke patients. Understanding the key mechanisms underlying secondary injury may open a new window for pharmacological interventions to promote recovery from stroke. Our study indicates that ischemia-induced histone deacetylase 2 upregulation from 5 to 7 d after stroke mediates the secondary functional loss by reducing survival and neuroplasticity of peri-infarct neurons as well as augmenting neuroinflammation. Thus, precisely targeting histone deacetylase 2 in the window phase provides a novel therapeutic strategy for stroke recovery.

Induced-Pluripotent-Stem-Cell-Derived Primitive Macrophages Provide a Platform for Modeling Tissue-Resident Macrophage Differentiation and Function.

  • Takata K
  • Immunity
  • 2017 Jul 18

Literature context:


Abstract:

Tissue macrophages arise during embryogenesis from yolk-sac (YS) progenitors that give rise to primitive YS macrophages. Until recently, it has been impossible to isolate or derive sufficient numbers of YS-derived macrophages for further study, but data now suggest that induced pluripotent stem cells (iPSCs) can be driven to undergo a process reminiscent of YS-hematopoiesis in vitro. We asked whether iPSC-derived primitive macrophages (iMacs) can terminally differentiate into specialized macrophages with the help of growth factors and organ-specific cues. Co-culturing human or murine iMacs with iPSC-derived neurons promoted differentiation into microglia-like cells in vitro. Furthermore, murine iMacs differentiated in vivo into microglia after injection into the brain and into functional alveolar macrophages after engraftment in the lung. Finally, iPSCs from a patient with familial Mediterranean fever differentiated into iMacs with pro-inflammatory characteristics, mimicking the disease phenotype. Altogether, iMacs constitute a source of tissue-resident macrophage precursors that can be used for biological, pathophysiological, and therapeutic studies.

Disrupting IGF Signaling in Adult Mice Conditions Leanness, Resilient Energy Metabolism, and High Growth Hormone Pulses.

  • François JC
  • Endocrinology
  • 2017 Jul 1

Literature context:


Abstract:

Growth hormone (GH) and insulinlike growth factor (IGF) promote aging and age-related pathologies. Inhibiting this pathway by targeting IGF receptor (IGF-1R) is a promising strategy to extend life span, alleviate age-related diseases, and reduce tumor growth. Although anti-IGF-1R agents are being developed, long-term effects of IGF-1R blockade remain unknown. In this study, we used ubiquitous inducible IGF-1R knockout (UBIKOR) to suppress signaling in all adult tissues and screened health extensively. Surprisingly, UBIKOR mice showed no overt defects and presented with rather inconspicuous health, including normal cognition. Endocrine GH and IGF-1 were strongly upregulated without causing acromegaly. UBIKOR mice were strikingly lean with coordinate changes in body composition and organ size. They were insulin resistant but preserved physiological energy expenditure and displayed enhanced fasting metabolic flexibility. Thus, long-term IGF-1R blockade generated beneficial effects on aging-relevant metabolism, but exposed to high GH. This needs to be considered when targeting IGF-1R to protect from neurodegeneration, retard aging, or fight cancer.

Funding information:
  • NEI NIH HHS - R01 EY 015387(United States)

Microglial Inflammatory Signaling Orchestrates the Hypothalamic Immune Response to Dietary Excess and Mediates Obesity Susceptibility.

  • Valdearcos M
  • Cell Metab.
  • 2017 Jul 5

Literature context:


Abstract:

Dietary excess triggers accumulation of pro-inflammatory microglia in the mediobasal hypothalamus (MBH), but the components of this microgliosis and its metabolic consequences remain uncertain. Here, we show that microglial inflammatory signaling determines the immunologic response of the MBH to dietary excess and regulates hypothalamic control of energy homeostasis in mice. Either pharmacologically depleting microglia or selectively restraining microglial NF-κB-dependent signaling sharply reduced microgliosis, an effect that includes prevention of MBH entry by bone-marrow-derived myeloid cells, and greatly limited diet-induced hyperphagia and weight gain. Conversely, forcing microglial activation through cell-specific deletion of the negative NF-κB regulator A20 induced spontaneous MBH microgliosis and cellular infiltration, reduced energy expenditure, and increased both food intake and weight gain even in absence of a dietary challenge. Thus, microglial inflammatory activation, stimulated by dietary excess, orchestrates a multicellular hypothalamic response that mediates obesity susceptibility, providing a mechanistic rationale for non-neuronal approaches to treat metabolic diseases.

Funding information:
  • NIDDK NIH HHS - F32 DK108473()
  • NIDDK NIH HHS - K08 DK088872()
  • NIDDK NIH HHS - P30 DK017047()
  • NIDDK NIH HHS - P30 DK035816()
  • NIDDK NIH HHS - P30 DK098722()
  • NIDDK NIH HHS - R01 DK103175()
  • NIDDK NIH HHS - T32 DK007247()

Early tissue damage and microstructural reorganization predict disease severity in experimental epilepsy.

  • Janz P
  • Elife
  • 2017 Jul 26

Literature context:


Abstract:

Mesial temporal lobe epilepsy (mTLE) is the most common focal epilepsy in adults and is often refractory to medication. So far, resection of the epileptogenic focus represents the only curative therapy. It is unknown whether pathological processes preceding epilepsy onset are indicators of later disease severity. Using longitudinal multi-modal MRI, we monitored hippocampal injury and tissue reorganization during epileptogenesis in a mouse mTLE model. The prognostic value of MRI biomarkers was assessed by retrospective correlations with pathological hallmarks Here, we show for the first time that the extent of early hippocampal neurodegeneration and progressive microstructural changes in the dentate gyrus translate to the severity of hippocampal sclerosis and seizure burden in chronic epilepsy. Moreover, we demonstrate that structural MRI biomarkers reflect the extent of sclerosis in human hippocampi. Our findings may allow an early prognosis of disease severity in mTLE before its first clinical manifestations, thus expanding the therapeutic window.

Local Cues Establish and Maintain Region-Specific Phenotypes of Basal Ganglia Microglia.

  • De Biase LM
  • Neuron
  • 2017 Jul 19

Literature context:


Abstract:

Microglia play critical roles in tissue homeostasis and can also modulate neuronal function and synaptic connectivity. In contrast to astrocytes and oligodendrocytes, which arise from multiple progenitor pools, microglia arise from yolk sac progenitors and are widely considered to be equivalent throughout the CNS. However, little is known about basic properties of deep brain microglia, such as those within the basal ganglia (BG). Here, we show that microglial anatomical features, lysosome content, membrane properties, and transcriptomes differ significantly across BG nuclei. Region-specific phenotypes of BG microglia emerged during the second postnatal week and were re-established following genetic or pharmacological microglial ablation and repopulation in the adult, indicating that local cues play an ongoing role in shaping microglial diversity. These findings demonstrate that microglia in the healthy brain exhibit a spectrum of distinct functional states and provide a critical foundation for defining microglial contributions to BG circuit function.

Lumbee traditional medicine: Neuroprotective activities of medicinal plants used to treat Parkinson's disease-related symptoms.

  • de Rus Jacquet A
  • J Ethnopharmacol
  • 2017 Jul 12

Literature context:


Abstract:

ETHNOPHARMACOLOGICAL RELEVANCE: Parkinson's disease (PD) is a neurodegenerative disorder characterized by a loss of dopaminergic neurons in the substantia nigra pars compacta and the presence in surviving neurons of Lewy body inclusions enriched with aggregated forms of the presynaptic protein α-synuclein (aSyn). Although current therapies provide temporary symptomatic relief, they do not slow the underlying neurodegeneration in the midbrain. In this study, we analyzed contemporary herbal medicinal practices used by members of the Lumbee tribe to treat PD-related symptoms, in an effort to identify safe and effective herbal medicines to treat PD. AIM OF THE STUDY: The aims of this study were to (i) document medicinal plants used by Lumbee Indians to treat PD and PD-related symptoms, and (ii) characterize a subset of plant candidates in terms of their ability to alleviate neurotoxicity elicited by PD-related insults and their potential mechanisms of neuroprotection. MATERIALS AND METHODS: Interviews of Lumbee healers and local people were carried out in Pembroke, North Carolina, and in surrounding towns. Plant samples were collected and prepared as water extracts for subsequent analysis. Extracts were characterized in terms of their ability to induce activation of the nuclear factor E2-related factor 2 (Nrf2) antioxidant response in cortical astrocytes. An extract prepared from Sambucus caerulea flowers (elderflower extract) was further examined for the ability to induce Nrf2-mediated transcription in induced pluripotent stem cell (iPSC)-derived astrocytes and primary midbrain cultures, to ameliorate mitochondrial dysfunction, and to alleviate rotenone- or aSyn-mediated neurotoxicity. RESULTS: The ethnopharmacological interviews resulted in the documentation of 32 medicinal plants used to treat PD-related symptoms and 40 plants used to treat other disorders. A polyphenol-rich extract prepared from elderflower activated the Nrf2-mediated antioxidant response in cortical astrocytes, iPSC-derived astrocytes, and primary midbrain cultures, apparently via the inhibition of Nrf2 degradation mediated by the ubiquitin proteasome system. Furthermore, the elderflower extract rescued mitochondrial functional deficits in a neuronal cell line and alleviated neurotoxicity elicited by rotenone and aSyn in primary midbrain cultures. CONCLUSIONS: These results highlight potential therapeutic benefits of botanical extracts used in traditional Lumbee medicine, and they provide insight into mechanisms by which an elderflower extract could suppress neurotoxicity elicited by environmental and genetic PD-related insults.

Hepcidin attenuates amyloid beta-induced inflammatory and pro-oxidant responses in astrocytes and microglia.

  • Urrutia PJ
  • J. Neurochem.
  • 2017 Jul 7

Literature context:


Abstract:

Alzheimer's disease (AD) is characterized by extracellular senile plaques, intracellular neurofibrillary tangles, and neuronal death. Aggregated amyloid-β (Aβ) induces inflammation and oxidative stress, which have pivotal roles in the pathogenesis of AD. Hepcidin is a key regulator of systemic iron homeostasis. Recently, an anti-inflammatory response to hepcidin was reported in macrophages. Under the hypothesis that hepcidin mediates anti-inflammatory response in the brain, in this study, we evaluated the putative anti-inflammatory role of hepcidin on Aβ-activated astrocytes and microglia. Primary culture of astrocytes and microglia were treated with Aβ, with or without hepcidin, and cytokine levels were then evaluated. In addition, the toxicity of Aβ-treated astrocyte- or microglia-conditioned media was tested on neurons, evaluating cellular death and oxidative stress generation. Finally, mice were injected in the right lateral ventricle with Aβ, with or without hepcidin, and hippocampus glial activation and oxidative stress were evaluated. Pre-treatment with hepcidin reduced the expression and secretion of TNF-α and IL-6 in astrocytes and microglia treated with Aβ. Hepcidin also reduced neurotoxicity and oxidative damage triggered by conditioned media obtained from astrocytes and microglia treated with Aβ. Stereotaxic intracerebral injection of hepcidin reduced glial activation and oxidative damage triggered by Aβ injection in mice. Overall, these results are consistent with the hypothesis that in astrocytes and microglia hepcidin down-regulates the inflammatory and pro-oxidant processes induced by Aβ, thus protecting neighboring neurons. This is a newly described property of hepcidin in the central nervous system, which may be relevant for the development of strategies to prevent the neurodegenerative process associated with AD.

Microglia Are Irrelevant for Neuronal Degeneration and Axon Regeneration after Acute Injury.

  • Hilla AM
  • J. Neurosci.
  • 2017 Jun 21

Literature context:


Abstract:

The role of microglia in degenerative and regenerative processes after damage of the nervous system remains ambiguous, partially due to the paucity of appropriate investigative methods. Here, we show that treatment with the pharmacological colony stimulating factor 1 receptor inhibitor PLX5622 specifically eliminated microglia in murine retinae and optic nerves with high efficiency. Interestingly, time course and extent of retinal ganglion cell (RGC) degeneration after optic nerve crush remained unaffected upon microglia depletion, although remnants of prelabeled apoptotic RGCs were not cleared from the retina in these animals. In addition, microglia depletion neither affected the induction of regeneration associated genes upon optic nerve injury nor the increased regenerative potential of RGCs upon lens injury (LI). However, although the repopulation of the optic nerve lesion site by astrocytes was significantly delayed upon microglia depletion, spontaneous and LI-induced axon regeneration were unaffected by PLX5622 treatment or peripheral macrophage depletion by clodronate liposome treatment. Only concurrent double depletion of microglia and infiltrated macrophages slightly, but significantly, compromised optic nerve regeneration. Therefore, microglia are not essentially involved in RGC degeneration or axonal regeneration after acute CNS injury.SIGNIFICANCE STATEMENT The roles of microglia, the phagocytosing cells of the CNS, and invading macrophages in degenerative and regenerative processes after injury are still controversial and insufficiently characterized. Here, we show that application of a CSF1R inhibitor eliminated virtually all microglia from the visual system, whereas macrophages were spared. Specific microglia depletion impaired the removal of dead labeled retinal ganglion cells after optic nerve crush, but remarkable had no influence on their degeneration. Similarly, optic nerve regeneration was completely unaffected, although repopulation of the lesion site by astrocytes was delayed significantly. Therefore, contrary to previous reports, this experimental approach revealed that microglia seemingly neither promote nor inhibit neuronal degeneration or axonal regrowth within the injured visual system.

Establishing the ferret as a gyrencephalic animal model of traumatic brain injury: Optimization of controlled cortical impact procedures.

  • Schwerin SC
  • J. Neurosci. Methods
  • 2017 Jun 15

Literature context:


Abstract:

BACKGROUND: Although rodent TBI studies provide valuable information regarding the effects of injury and recovery, an animal model with neuroanatomical characteristics closer to humans may provide a more meaningful basis for clinical translation. The ferret has a high white/gray matter ratio, gyrencephalic neocortex, and ventral hippocampal location. Furthermore, ferrets are amenable to behavioral training, have a body size compatible with pre-clinical MRI, and are cost-effective. NEW METHODS: We optimized the surgical procedure for controlled cortical impact (CCI) using 9 adult male ferrets. We used subject-specific brain/skull morphometric data from anatomical MRIs to overcome across-subject variability for lesion placement. We also reflected the temporalis muscle, closed the craniotomy, and used antibiotics. We then gathered MRI, behavioral, and immunohistochemical data from 6 additional animals using the optimized surgical protocol: 1 control, 3 mild, and 1 severely injured animals (surviving one week) and 1 moderately injured animal surviving sixteen weeks. RESULTS: The optimized surgical protocol resulted in consistent injury placement. Astrocytic reactivity increased with injury severity showing progressively greater numbers of astrocytes within the white matter. The density and morphological changes of microglia amplified with injury severity or time after injury. Motor and cognitive impairments scaled with injury severity. COMPARISON WITH EXISTING METHOD(S): The optimized surgical methods differ from those used in the rodent, and are integral to success using a ferret model. CONCLUSIONS: We optimized ferret CCI surgery for consistent injury placement. The ferret is an excellent animal model to investigate pathophysiological and behavioral changes associated with TBI.

Neuroprotection and Blood-Brain Barrier Restoration by Salubrinal After a Cortical Stab Injury.

  • Barreda-Manso MA
  • J. Cell. Physiol.
  • 2017 Jun 18

Literature context:


Abstract:

Following a central nervous system (CNS) injury, restoration of the blood-brain barrier (BBB) integrity is essential for recovering homeostasis. When this process is delayed or impeded, blood substances and cells enter the CNS parenchyma, initiating an additional inflammatory process that extends the initial injury and causes so-called secondary neuronal loss. Astrocytes and profibrotic mesenchymal cells react to the injury and migrate to the lesion site, creating a new glia limitans that restores the BBB. This process is beneficial for the resolution of the inflammation, neuronal survival, and the initiation of the healing process. Salubrinal is a small molecule with neuroprotective properties in different animal models of stroke and trauma to the CNS. Here, we show that salubrinal increased neuronal survival in the neighbourhood of a cerebral cortex stab injury. Moreover, salubrinal reduced cortical blood leakage into the parenchyma of injured animals compared with injured controls. Adjacent to the site of injury, salubrinal induced immunoreactivity for platelet-derived growth factor subunit B (PDGF-B), a specific mitogenic factor for mesenchymal cells. This effect might be responsible for the increased immunoreactivity for fibronectin and the decreased activation of microglia and macrophages in injured mice treated with salubrinal, compared with injured controls. The immunoreactivity for PDGF-B colocalized with neuronal nuclei (NeuN), suggesting that cortical neurons in the proximity of the injury were the main source of PDGF-B. Our results suggest that after an injury, neurons play an important role in both, the healing process and the restoration of the BBB integrity. J. Cell. Physiol. 232: 1501-1510, 2017. © 2016 Wiley Periodicals, Inc.

Funding information:
  • Wellcome Trust - 102645(United Kingdom)

Neurons and Glial Cells Are Added to the Female Rat Anteroventral Periventricular Nucleus During Puberty.

  • Mohr MA
  • Endocrinology
  • 2017 Jun 5

Literature context:


Abstract:

The anteroventral periventricular nucleus (AVPV) orchestrates the neuroendocrine-positive feedback response that triggers ovulation in female rodents. The AVPV is larger and more cell-dense in females than in males, and during puberty, only females develop the capacity to show a positive feedback response. We previously reported a potential new mechanism to explain this female-specific gain of function during puberty, namely a female-biased sex difference in the pubertal addition of new cells to the rat AVPV. Here we first asked whether this sex difference is due to greater cell proliferation and/or survival in females. Female and male rats received the cell birthdate marker 5-bromo-2'-deoxyuridine (BrdU; 200 mg/kg, ip) on postnatal day (P) 30; brains were collected at short and long intervals after BrdU administration to assess cell proliferation and survival, respectively. Overall, females had more BrdU-immunoreactive cells in the AVPV than did males, with no sex differences in the rate of cell attrition over time. Thus, the sex difference in pubertal addition of AVPV cells appears to be due to greater cell proliferation in females. Next, to determine the phenotype of pubertally born AVPV cells, daily BrdU injections were given to female rats on P28-56, and tissue was collected on P77 to assess colocalization of BrdU and markers for mature neurons or glia. Of the pubertally born AVPV cells, approximately 15% differentiated into neurons, approximately 19% into astrocytes, and approximately 23% into microglia. Thus, both neuro- and gliogenesis occur in the pubertal female rat AVPV and potentially contribute to maturation of female reproductive function.

Funding information:
  • NIMH NIH HHS - R01 MH059950(United States)

Serotonin axons in the neocortex of the adult female mouse regrow after traumatic brain injury.

  • Kajstura TJ
  • J. Neurosci. Res.
  • 2017 May 10

Literature context:


Abstract:

It is widely held that injured neurons in the central nervous system do not undergo axonal regrowth. However, there is mounting evidence that serotonin axons are a notable exception. Serotonin axons undergo long-distance regrowth in the neocortex after amphetamine lesion, and, following a penetrating stab injury, they can regrow from cut ends to traverse the stab rift. Traumatic brain injury (TBI) is clinically prevalent and can lead to pathologies, such as depression, that are related to serotonergic dysfunction. Thus, whether serotonin axons can regrow after TBI is an important question. We used two models for TBI-a persistent open skull condition and controlled cortical impact-to evoke injury in adult female mouse neocortex, and assessed serotonin axon density 1 week, 1 month, and 3 months after injury by serotonin transporter immunohistochemistry. We found that after both forms of TBI, serotonin axon density is decreased posterior but not anterior to the injury site when measured in layer 1 at 1 week post surgery, and that serotonin axons are capable of regrowing into the distal zone to increase density by 1 month post surgery. This pattern is consistent with the anterior-to-posterior course of serotonin axons in the neocortex. TBI in these models is associated with significant reactive astrogliosis both anterior and posterior to the impact, but the degree of reactive astrogliosis is not correlated with serotonin axon density when measured 1 week after TBI. Microglial density remains constant following both types of injuries, but microglial condensation was detected 1 week after controlled cortical impact.

Funding information:
  • NINDS NIH HHS - R21 NS081467()

Developmental microglial priming in postmortem autism spectrum disorder temporal cortex.

  • Lee AS
  • Brain Behav. Immun.
  • 2017 May 4

Literature context:


Abstract:

Microglia can shift into different complex morphologies depending on the microenvironment of the central nervous system (CNS). The distinct morphologies correlate with specific functions and can indicate the pathophysiological state of the CNS. Previous postmortem studies of autism spectrum disorder (ASD) showed neuroinflammation in ASD indicated by increased microglial density. These changes in the microglia density can be accompanied by changes in microglia phenotype but the individual contribution of different microglia phenotypes to the pathophysiology of ASD remains unclear. Here, we used an unbiased stereological approach to quantify six structurally and functionally distinct microglia phenotypes in postmortem human temporal cortex, which were immuno-stained with Iba1. The total density of all microglia phenotypes did not differ between ASD donors and typically developing individual donors. However, there was a significant decrease in ramified microglia in both gray matter and white matter of ASD, and a significant increase in primed microglia in gray matter of ASD compared to typically developing individuals. This increase in primed microglia showed a positive correlation with donor age in both gray matter and white of ASD, but not in typically developing individuals. Our results provide evidence of a shift in microglial phenotype that may indicate impaired synaptic plasticity and a chronic vulnerability to exaggerated immune responses.

Development of a systems-based in situ multiplex biomarker screening approach for the assessment of immunopathology and neural tissue plasticity in male rats after traumatic brain injury.

  • Bogoslovsky T
  • J. Neurosci. Res.
  • 2017 May 4

Literature context:


Abstract:

Traumatic brain injuries (TBIs) pose a massive burden of disease and continue to be a leading cause of morbidity and mortality throughout the world. A major obstacle in developing effective treatments is the lack of comprehensive understanding of the underlying mechanisms that mediate tissue damage and recovery after TBI. As such, our work aims to highlight the development of a novel experimental platform capable of fully characterizing the underlying pathobiology that unfolds after TBI. This platform encompasses an empirically optimized multiplex immunohistochemistry staining and imaging system customized to screen for a myriad of biomarkers required to comprehensively evaluate the extent of neuroinflammation, neural tissue damage, and repair in response to TBI. Herein, we demonstrate that our multiplex biomarker screening platform is capable of evaluating changes in both the topographical location and functional states of resident and infiltrating cell types that play a role in neuropathology after controlled cortical impact injury to the brain in male Sprague-Dawley rats. Our results demonstrate that our multiplex biomarker screening platform lays the groundwork for the comprehensive characterization of changes that occur within the brain after TBI. Such work may ultimately lead to the understanding of the governing pathobiology of TBI, thereby fostering the development of novel therapeutic interventions tailored to produce optimal tissue protection, repair, and/or regeneration with minimal side effects, and may ultimately find utility in a wide variety of other neurological injuries, diseases, and disorders that share components of TBI pathobiology.

Migrating Interneurons Secrete Fractalkine to Promote Oligodendrocyte Formation in the Developing Mammalian Brain.

  • Voronova A
  • Neuron
  • 2017 May 3

Literature context:


Abstract:

During development, newborn interneurons migrate throughout the embryonic brain. Here, we provide evidence that these interneurons act in a paracrine fashion to regulate developmental oligodendrocyte formation. Specifically, we show that medial ganglionic eminence (MGE) interneurons secrete factors that promote genesis of oligodendrocytes from glially biased cortical precursors in culture. Moreover, when MGE interneurons are genetically ablated in vivo prior to their migration, this causes a deficit in cortical oligodendrogenesis. Modeling of the interneuron-precursor paracrine interaction using transcriptome data identifies the cytokine fractalkine as responsible for the pro-oligodendrocyte effect in culture. This paracrine interaction is important in vivo, since knockdown of the fractalkine receptor CX3CR1 in embryonic cortical precursors, or constitutive knockout of CX3CR1, causes decreased numbers of oligodendrocyte progenitor cells (OPCs) and oligodendrocytes in the postnatal cortex. Thus, in addition to their role in regulating neuronal excitability, interneurons act in a paracrine fashion to promote the developmental genesis of oligodendrocytes.

Diverse Requirements for Microglial Survival, Specification, and Function Revealed by Defined-Medium Cultures.

  • Bohlen CJ
  • Neuron
  • 2017 May 17

Literature context:


Abstract:

Microglia, the resident macrophages of the CNS, engage in various CNS-specific functions that are critical for development and health. To better study microglia and the properties that distinguish them from other tissue macrophage populations, we have optimized serum-free culture conditions to permit robust survival of highly ramified adult microglia under defined-medium conditions. We find that astrocyte-derived factors prevent microglial death ex vivo and that this activity results from three primary components, CSF-1/IL-34, TGF-β2, and cholesterol. Using microglial cultures that have never been exposed to serum, we demonstrate a dramatic and lasting change in phagocytic capacity after serum exposure. Finally, we find that mature microglia rapidly lose signature gene expression after isolation, and that this loss can be reversed by engrafting cells back into an intact CNS environment. These data indicate that the specialized gene expression profile of mature microglia requires continuous instructive signaling from the intact CNS.

Funding information:
  • NIDA NIH HHS - R01 DA015043()
  • NIMH NIH HHS - K08 MH112120()
  • NIMH NIH HHS - T32 MH019938()

RNA Sequencing Exposes Adaptive and Immune Responses to Intrauterine Growth Restriction in Fetal Sheep Islets.

  • Kelly AC
  • Endocrinology
  • 2017 Apr 1

Literature context:


Abstract:

The risk of type 2 diabetes is increased in children and adults who exhibited fetal growth restriction. Placental insufficiency and intrauterine growth restriction (IUGR) are common obstetrical complications associated with fetal hypoglycemia and hypoxia that reduce the β-cell mass and insulin secretion. In the present study, we have defined the underlying mechanisms of reduced growth and proliferation, impaired metabolism, and defective insulin secretion previously established as complications in islets from IUGR fetuses. In an IUGR sheep model that recapitulates human IUGR, high-throughput RNA sequencing showed the transcriptome of islets isolated from IUGR and control sheep fetuses and identified the transcripts that underlie β-cell dysfunction. Functional analysis expanded mechanisms involved in reduced proliferation and dysregulated metabolism that include specific cell cycle regulators and growth factors and mitochondrial, antioxidant, and exocytotic genes. These data also identified immune responses, wnt signaling, adaptive stress responses, and the proteasome as mechanisms of β-cell dysfunction. The reduction of immune-related gene expression did not reflect a change in macrophage density within IUGR islets. The present study reports the islet transcriptome in fetal sheep and established processes that limit insulin secretion and β-cell growth in fetuses with IUGR, which could explain the susceptibility to premature islet failure in adulthood. Islet dysfunction formed by intrauterine growth restriction increases the risk for diabetes.

Funding information:
  • NIDDK NIH HHS - R01 DK084842()

K+ Channel Modulatory Subunits KChIP and DPP Participate in Kv4-Mediated Mechanical Pain Control.

  • Kuo YL
  • J. Neurosci.
  • 2017 Apr 19

Literature context:


Abstract:

The K+ channel pore-forming subunit Kv4.3 is expressed in a subset of nonpeptidergic nociceptors within the dorsal root ganglion (DRG), and knockdown of Kv4.3 selectively induces mechanical hypersensitivity, a major symptom of neuropathic pain. K+ channel modulatory subunits KChIP1, KChIP2, and DPP10 are coexpressed in Kv4.3+ DRG neurons, but whether they participate in Kv4.3-mediated pain control is unknown. Here, we show the existence of a Kv4.3/KChIP1/KChIP2/DPP10 complex (abbreviated as the Kv4 complex) in the endoplasmic reticulum and cell surface of DRG neurons. After intrathecal injection of a gene-specific antisense oligodeoxynucleotide to knock down the expression of each component in the Kv4 complex, mechanical hypersensitivity develops in the hindlimbs of rats in parallel with a reduction in all components in the lumbar DRGs. Electrophysiological data further indicate that the excitability of nonpeptidergic nociceptors is enhanced. The expression of all Kv4 complex components in DRG neurons is downregulated following spinal nerve ligation (SNL). To rescue Kv4 complex downregulation, cDNA constructs encoding Kv4.3, KChIP1, and DPP10 were transfected into the injured DRGs (defined as DRGs with injured spinal nerves) of living SNL rats. SNL-evoked mechanical hypersensitivity was attenuated, accompanied by a partial recovery of Kv4.3, KChIP1, and DPP10 surface levels in the injured DRGs. By showing an interdependent regulation among components in the Kv4 complex, this study demonstrates that K+ channel modulatory subunits KChIP1, KChIP2, and DPP10 participate in Kv4.3-mediated mechanical pain control. Thus, these modulatory subunits could be potential drug targets for neuropathic pain.SIGNIFICANCE STATEMENT Neuropathic pain, a type of moderate to severe chronic pain resulting from nerve injury or disorder, affects 6.9%-10% of the global population. However, less than half of patients report satisfactory pain relief from current treatments. K+ channels, which act to reduce nociceptor activity, have been suggested to be novel drug targets for neuropathic pain. This study is the first to show that K+ channel modulatory subunits KChIP1, KChIP2, and DPP10 are potential drug targets for neuropathic pain because they form a channel complex with the K+ channel pore-forming subunit Kv4.3 in a subset of nociceptors to selectively inhibit mechanical hypersensitivity, a major symptom of neuropathic pain.

Dopamine neuronal loss contributes to memory and reward dysfunction in a model of Alzheimer's disease.

  • Nobili A
  • Nat Commun
  • 2017 Apr 3

Literature context:


Abstract:

Alterations of the dopaminergic (DAergic) system are frequently reported in Alzheimer's disease (AD) patients and are commonly linked to cognitive and non-cognitive symptoms. However, the cause of DAergic system dysfunction in AD remains to be elucidated. We investigated alterations of the midbrain DAergic system in the Tg2576 mouse model of AD, overexpressing a mutated human amyloid precursor protein (APPswe). Here, we found an age-dependent DAergic neuron loss in the ventral tegmental area (VTA) at pre-plaque stages, although substantia nigra pars compacta (SNpc) DAergic neurons were intact. The selective VTA DAergic neuron degeneration results in lower DA outflow in the hippocampus and nucleus accumbens (NAc) shell. The progression of DAergic cell death correlates with impairments in CA1 synaptic plasticity, memory performance and food reward processing. We conclude that in this mouse model of AD, degeneration of VTA DAergic neurons at pre-plaque stages contributes to memory deficits and dysfunction of reward processing.

Hallmarks of Alzheimer's Disease in Stem-Cell-Derived Human Neurons Transplanted into Mouse Brain.

  • Espuny-Camacho I
  • Neuron
  • 2017 Mar 8

Literature context:


Abstract:

Human pluripotent stem cells (PSCs) provide a unique entry to study species-specific aspects of human disorders such as Alzheimer's disease (AD). However, in vitro culture of neurons deprives them of their natural environment. Here we transplanted human PSC-derived cortical neuronal precursors into the brain of a murine AD model. Human neurons differentiate and integrate into the brain, express 3R/4R Tau splice forms, show abnormal phosphorylation and conformational Tau changes, and undergo neurodegeneration. Remarkably, cell death was dissociated from tangle formation in this natural 3D model of AD. Using genome-wide expression analysis, we observed upregulation of genes involved in myelination and downregulation of genes related to memory and cognition, synaptic transmission, and neuron projection. This novel chimeric model for AD displays human-specific pathological features and allows the analysis of different genetic backgrounds and mutations during the course of the disease.

Neurogenic Radial Glia-like Cells in Meninges Migrate and Differentiate into Functionally Integrated Neurons in the Neonatal Cortex.

  • Bifari F
  • Cell Stem Cell
  • 2017 Mar 2

Literature context:


Abstract:

Whether new neurons are added in the postnatal cerebral cortex is still debated. Here, we report that the meninges of perinatal mice contain a population of neurogenic progenitors formed during embryonic development that migrate to the caudal cortex and differentiate into Satb2+ neurons in cortical layers II-IV. The resulting neurons are electrically functional and integrated into local microcircuits. Single-cell RNA sequencing identified meningeal cells with distinct transcriptome signatures characteristic of (1) neurogenic radial glia-like cells (resembling neural stem cells in the SVZ), (2) neuronal cells, and (3) a cell type with an intermediate phenotype, possibly representing radial glia-like meningeal cells differentiating to neuronal cells. Thus, we have identified a pool of embryonically derived radial glia-like cells present in the meninges that migrate and differentiate into functional neurons in the neonatal cerebral cortex.

Funding information:
  • NINDS NIH HHS - R01 NS036715(United States)

Cell- and region-specific expression of depression-related protein p11 (S100a10) in the brain.

  • Milosevic A
  • J. Comp. Neurol.
  • 2017 Mar 1

Literature context:


Abstract:

P11 (S100a10), a member of the S100 family of proteins, has widespread distribution in the vertebrate body, including in the brain, where it has a key role in membrane trafficking, vesicle secretion, and endocytosis. Recently, our laboratory has shown that a constitutive knockout of p11 (p11-KO) in mice results in a depressive-like phenotype. Furthermore, p11 has been implicated in major depressive disorder (MDD) and in the actions of antidepressants. Since depression affects multiple brain regions, and the role of p11 has only been determined in a few of these areas, a detailed analysis of p11 expression in the brain is warranted. Here we demonstrate that, although widespread in the brain, p11 expression is restricted to distinct regions, and specific neuronal and nonneuronal cell types. Furthermore, we provide comprehensive mapping of p11 expression using in situ hybridization, immunocytochemistry, and whole-tissue volume imaging. Overall, expression spans multiple brain regions, structures, and cell types, suggesting a complex role of p11 in depression. J. Comp. Neurol. 525:955-975, 2017. © 2016 Wiley Periodicals, Inc.

Funding information:
  • NINDS NIH HHS - R01 NS085232(United States)

miR-219 Cooperates with miR-338 in Myelination and Promotes Myelin Repair in the CNS.

  • Wang H
  • Dev. Cell
  • 2017 Mar 27

Literature context:


Abstract:

A lack of sufficient oligodendrocyte myelination contributes to remyelination failure in demyelinating disorders. miRNAs have been implicated in oligodendrogenesis; however, their functions in myelin regeneration remained elusive. Through developmentally regulated targeted mutagenesis, we demonstrate that miR-219 alleles are critical for CNS myelination and remyelination after injury. Further deletion of miR-338 exacerbates the miR-219 mutant hypomyelination phenotype. Conversely, miR-219 overexpression promotes precocious oligodendrocyte maturation and regeneration processes in transgenic mice. Integrated transcriptome profiling and biotin-affinity miRNA pull-down approaches reveal stage-specific miR-219 targets in oligodendrocytes and further uncover a novel network for miR-219 targeting of differentiation inhibitors including Lingo1 and Etv5. Inhibition of Lingo1 and Etv5 partially rescues differentiation defects of miR-219-deficient oligodendrocyte precursors. Furthermore, miR-219 mimics enhance myelin restoration following lysolecithin-induced demyelination as well as experimental autoimmune encephalomyelitis, principal animal models of multiple sclerosis. Together, our findings identify context-specific miRNA-regulated checkpoints that control myelinogenesis and a therapeutic role for miR-219 in CNS myelin repair.

Funding information:
  • NINDS NIH HHS - R01 NS065808()
  • NINDS NIH HHS - R01 NS072427()
  • NINDS NIH HHS - R01 NS075243()
  • NINDS NIH HHS - R21 NS087474()
  • NINDS NIH HHS - R37 NS096359()

Tamoxifen Provides Structural and Functional Rescue in Murine Models of Photoreceptor Degeneration.

  • Wang X
  • J. Neurosci.
  • 2017 Mar 22

Literature context:


Abstract:

Photoreceptor degeneration is a cause of irreversible vision loss in incurable blinding retinal diseases including retinitis pigmentosa (RP) and atrophic age-related macular degeneration. We found in two separate mouse models of photoreceptor degeneration that tamoxifen, a selective estrogen receptor modulator and a drug previously linked with retinal toxicity, paradoxically provided potent neuroprotective effects. In a light-induced degeneration model, tamoxifen prevented onset of photoreceptor apoptosis and atrophy and maintained near-normal levels of electroretinographic responses. Rescue effects were correlated with decreased microglial activation and inflammatory cytokine production in the retina in vivo and a reduction of microglia-mediated toxicity to photoreceptors in vitro, indicating a microglia-mediated mechanism of rescue. Tamoxifen also rescued degeneration in a genetic (Pde6brd10) model of RP, significantly improving retinal structure, electrophysiological responses, and visual behavior. These prominent neuroprotective effects warrant the consideration of tamoxifen as a drug suitable for being repurposed to treat photoreceptor degenerative disease.SIGNIFICANCE STATEMENT Photoreceptor degeneration is a cause of irreversible blindness in a number of retinal diseases such as retinitis pigmentosa (RP) and atrophic age-related macular degeneration. Tamoxifen, a selective estrogen receptor modulator approved for the treatment of breast cancer and previously linked to a low incidence of retinal toxicity, was unexpectedly found to exert marked protective effects against photoreceptor degeneration. Structural and functional protective effects were found for an acute model of light-induced photoreceptor injury and for a genetic model for RP. The mechanism of protection involved the modulation of microglial activation and the production of inflammatory cytokines, highlighting the role of inflammatory mechanisms in photoreceptor degeneration. Tamoxifen may be suitable for clinical study as a potential treatment for diseases involving photoreceptor degeneration.

Astrocytes Control Circadian Timekeeping in the Suprachiasmatic Nucleus via Glutamatergic Signaling.

  • Brancaccio M
  • Neuron
  • 2017 Mar 22

Literature context:


Abstract:

The suprachiasmatic nucleus (SCN) of the hypothalamus orchestrates daily rhythms of physiology and behavior in mammals. Its circadian (∼24 hr) oscillations of gene expression and electrical activity are generated intrinsically and can persist indefinitely in temporal isolation. This robust and resilient timekeeping is generally regarded as a product of the intrinsic connectivity of its neurons. Here we show that neurons constitute only one "half" of the SCN clock, the one metabolically active during circadian daytime. In contrast, SCN astrocytes are active during circadian nighttime, when they suppress the activity of SCN neurons by regulating extracellular glutamate levels. This glutamatergic gliotransmission is sensed by neurons of the dorsal SCN via specific pre-synaptic NMDA receptor assemblies containing NR2C subunits. Remarkably, somatic genetic re-programming of intracellular clocks in SCN astrocytes was capable of remodeling circadian behavioral rhythms in adult mice. Thus, SCN circuit-level timekeeping arises from interdependent and mutually supportive astrocytic-neuronal signaling.

Macrophage Transcriptional Profile Identifies Lipid Catabolic Pathways That Can Be Therapeutically Targeted after Spinal Cord Injury.

  • Zhu Y
  • J. Neurosci.
  • 2017 Mar 1

Literature context:


Abstract:

Although infiltrating macrophages influence many pathological processes after spinal cord injury (SCI), the intrinsic molecular mechanisms that regulate their function are poorly understood. A major hurdle has been dissecting macrophage-specific functions from those in other cell types as well as understanding how their functions change over time. Therefore, we used the RiboTag method to obtain macrophage-specific mRNA directly from the injured spinal cord in mice and performed RNA sequencing to investigate their transcriptional profile. Our data show that at 7 d after SCI, macrophages are best described as foam cells, with lipid catabolism representing the main biological process, and canonical nuclear receptor pathways as their potential mediators. Genetic deletion of a lipoprotein receptor, CD36, reduces macrophage lipid content and improves lesion size and locomotor recovery. Therefore, we report the first macrophage-specific transcriptional profile after SCI and highlight the lipid catabolic pathway as an important macrophage function that can be therapeutically targeted after SCI.SIGNIFICANCE STATEMENT The intrinsic molecular mechanisms that regulate macrophage function after spinal cord injury (SCI) are poorly understood. We obtained macrophage-specific mRNA directly from the injured spinal cord and performed RNA sequencing to investigate their transcriptional profile. Our data show that at 7 d after SCI, macrophages are best described as foam cells, with lipid catabolism representing the main biological process and canonical nuclear receptor pathways as their potential mediators. Genetic deletion of a lipoprotein receptor, CD36, reduces macrophage lipid content and improves lesion size and locomotor recovery. Therefore, we report the first macrophage-specific transcriptional profile after SCI and highlight the lipid catabolic pathway as an important macrophage function that can be therapeutically targeted after SCI.

Phosphatidylserine Exposure Controls Viral Innate Immune Responses by Microglia.

  • Tufail Y
  • Neuron
  • 2017 Feb 8

Literature context:


Abstract:

Microglia are the intrinsic immune sentinels of the central nervous system. Their activation restricts tissue injury and pathogen spread, but in some settings, including viral infection, this response can contribute to cell death and disease. Identifying mechanisms that control microglial responses is therefore an important objective. Using replication-incompetent adenovirus 5 (Ad5)-based vectors as a model, we investigated the mechanisms through which microglia recognize and respond to viral uptake. Transgenic, immunohistochemical, molecular-genetic, and fluorescence imaging approaches revealed that phosphatidylserine (PtdSer) exposure on the outer leaflet of transduced cells triggers their engulfment by microglia through TAM receptor-dependent mechanisms. We show that inhibition of phospholipid scramblase 1 (PLSCR1) activity reduces intracellular calcium dysregulation, prevents PtdSer externalization, and enables months-long protection of vector-transduced, transgene-expressing cells from microglial phagocytosis. Our study identifies PLSCR1 as a potent target through which the innate immune response to viral vectors, and potentially other stimuli, may be controlled.

Funding information:
  • NIAID NIH HHS - R01 AI101400()
  • NINDS NIH HHS - DP2 NS083038()
  • NINDS NIH HHS - R01 NS085296()
  • NINDS NIH HHS - R01 NS085938()

Developmental time course and effects of immunostressors that alter hormone-responsive behavior on microglia in the peripubertal and adult female mouse brain.

  • Holder MK
  • PLoS ONE
  • 2017 Feb 3

Literature context:


Abstract:

In female mice, the experience of being shipped from the breeder facility or a single injection of the bacterial endotoxin, lipopolysaccharide (LPS), during pubertal development alters the behavioral response to estradiol in adulthood as demonstrated by perturbations of estradiol's effects on sexual behavior, cognitive function, as well as its anxiolytic and anti-depressive properties. Microglia, the primary type of immunocompetent cell within the brain, contribute to brain development and respond to stressors with marked and long-lasting morphological and functional changes. Here, we describe the morphology of microglia and their response to shipping and LPS in peripubertal and adult female mice. Peripubertal mice have more microglia with long, thick processes in the hippocampus, amygdala and hypothalamus as compared with adult mice in the absence of an immune challenge. An immune challenge also increases immunoreactivity (IR) of ionized calcium binding adaptor molecule 1 (Iba1), which is constitutively expressed in microglia. In the hippocampus, the age of animal was without effect on the increase in Iba1- IR following shipping from the breeder facility or LPS exposure. In the amygdala, we observed more Iba1-IR following shipping or LPS treatment in peripubertal mice, compared to adult mice. In the hypothalamus, there was a disassociation of the effects of shipping and LPS treatment as LPS treatment, but not shipping, induced an increase in Iba1-IR. Taken together these data indicate that microglial morphologies differ between pubertal and adult mice; moreover, the microglial response to complex stressors is greater in pubertal mice as compared to adult mice.

Parkinson Sac Domain Mutation in Synaptojanin 1 Impairs Clathrin Uncoating at Synapses and Triggers Dystrophic Changes in Dopaminergic Axons.

  • Cao M
  • Neuron
  • 2017 Feb 22

Literature context:


Abstract:

Synaptojanin 1 (SJ1) is a major presynaptic phosphatase that couples synaptic vesicle endocytosis to the dephosphorylation of PI(4,5)P2, a reaction needed for the shedding of endocytic factors from their membranes. While the role of SJ1's 5-phosphatase module in this process is well recognized, the contribution of its Sac phosphatase domain, whose preferred substrate is PI4P, remains unclear. Recently a homozygous mutation in its Sac domain was identified in early-onset parkinsonism patients. We show that mice carrying this mutation developed neurological manifestations similar to those of human patients. Synapses of these mice displayed endocytic defects and a striking accumulation of clathrin-coated intermediates, strongly implicating Sac domain's activity in endocytic protein dynamics. Mutant brains had elevated auxilin (PARK19) and parkin (PARK2) levels. Moreover, dystrophic axonal terminal changes were selectively observed in dopaminergic axons in the dorsal striatum. These results strengthen evidence for a link between synaptic endocytic dysfunction and Parkinson's disease.

Funding information:
  • NCATS NIH HHS - UL1 TR001863()
  • NIDA NIH HHS - P30 DA018343()
  • NIGMS NIH HHS - P41 GM103412()
  • NINDS NIH HHS - R01 NS036251()
  • NINDS NIH HHS - R01 NS036942()
  • NINDS NIH HHS - R37 NS036251()
  • NINDS NIH HHS - R37 NS036942()

Promoted Interaction of C/EBPα with Demethylated Cxcr3 Gene Promoter Contributes to Neuropathic Pain in Mice.

  • Jiang BC
  • J. Neurosci.
  • 2017 Jan 18

Literature context:


Abstract:

DNA methylation has been implicated in the pathogenesis of chronic pain. However, the specific genes regulated by DNA methylation under neuropathic pain condition remain largely unknown. Here we investigated how chemokine receptor CXCR3 is regulated by DNA methylation and how it contributes to neuropathic pain induced by spinal nerve ligation (SNL) in mice. SNL increased Cxcr3 mRNA and protein expression in the neurons of the spinal cord. Meanwhile, the CpG (5'-cytosine-phosphate-guanine-3') island in the Cxcr3 gene promoter region was demethylated, and the expression of DNA methyltransferase 3b (DNMT3b) was decreased. SNL also increased the binding of CCAAT (cytidine-cytidine-adenosine-adenosine-thymidine)/enhancer binding protein α (C/EBPα) with Cxcr3 promoter and decreased the binding of DNMT3b with Cxcr3 promoter in the spinal cord. C/EBPα expression was increased in spinal neurons after SNL, and inhibition of C/EBPα by intrathecal small interfering RNA attenuated SNL-induced pain hypersensitivity and reduced Cxcr3 expression. Furthermore, SNL-induced mechanical allodynia and heat hyperalgesia were markedly reduced in Cxcr3-/- mice. Spinal inhibition of Cxcr3 by shRNA or CXCR3 antagonist also attenuated established neuropathic pain. Moreover, CXCL10, the ligand of CXCR3, was increased in spinal neurons and astrocytes after SNL. Superfusing spinal cord slices with CXCL10 enhanced spontaneous EPSCs and potentiated NMDA-induced and AMPA-induced currents of lamina II neurons. Finally, intrathecal injection of CXCL10 induced CXCR3-dependent pain hypersensitivity in naive mice. Collectively, our results demonstrated that CXCR3, increased by DNA demethylation and the enhanced interaction with C/EBPα, can be activated by CXCL10 to facilitate excitatory synaptic transmission and contribute to the maintenance of neuropathic pain. SIGNIFICANCE STATEMENT: Peripheral nerve injury induces changes of gene expression in the spinal cord that may contribute to the pathogenesis of neuropathic pain. CXCR3 is a chemokine receptor. Whether it is involved in neuropathic pain and how it is regulated after nerve injury remain largely unknown. Our study demonstrates that spinal nerve ligation downregulates the expression of DNMT3b, which may cause demethylation of Cxcr3 gene promoter and facilitate the binding of CCAAT/enhancer binding protein α with Cxcr3 promoter and further increase CXCR3 expression in spinal neurons. The upregulated CXCR3 may contribute to neuropathic pain by facilitating central sensitization. Our study reveals an epigenetic mechanism underlying CXCR3 expression and also suggests that targeting the expression or activation of CXCR3 signaling may offer new therapeutics for neuropathic pain.

Immunohistochemical analysis of huntingtin-associated protein 1 in adult rat spinal cord and its regional relationship with androgen receptor.

  • Islam MN
  • Neuroscience
  • 2017 Jan 6

Literature context:


Abstract:

Huntingtin-associated protein 1 (HAP1) is a neuronal interactor with causatively polyglutamine (polyQ)-expanded huntingtin in Huntington's disease and also associated with pathologically polyQ-expanded androgen receptor (AR) in spinobulbar muscular atrophy (SBMA), being considered as a protective factor against neurodegenerative apoptosis. In normal brains, it is abundantly expressed particularly in the limbic-hypothalamic regions that tend to be spared from neurodegeneration, whereas the areas with little HAP1 expression, including the striatum, thalamus, cerebral neocortex and cerebellum, are targets in several neurodegenerative diseases. While the spinal cord is another major neurodegenerative target, HAP1-immunoreactive (ir) structures have yet to be determined there. In the current study, HAP1 expression was immunohistochemically evaluated in light and electron microscopy through the cervical, thoracic, lumbar, and sacral spinal cords of the adult male rat. Our results showed that HAP1 is specifically expressed in neurons through the spinal segments and that more than 90% of neurons expressed HAP1 in lamina I-II, lamina X, and autonomic preganglionic regions. Double-immunostaining for HAP1 and AR demonstrated that more than 80% of neurons expressed both in laminae I-II and X. In contrast, HAP1 was specifically lacking in the lamina IX motoneurons with or without AR expression. The present study first demonstrated that HAP1 is abundantly expressed in spinal neurons of the somatosensory, viscerosensory, and autonomic regions but absent in somatomotor neurons, suggesting that the spinal motoneurons are, due to lack of putative HAP1 protectivity, more vulnerable to stresses in neurodegenerative diseases than other HAP1-expressing neurons probably involved in spinal sensory and autonomic functions.

Granulocyte colony-stimulating factor promotes behavioral recovery in a mouse model of traumatic brain injury.

  • Song S
  • J. Neurosci. Res.
  • 2016 Dec 13

Literature context:


Abstract:

Hematopoietic growth factors such as granulocyte colony-stimulating factor (G-CSF) represent a novel approach for treatment of traumatic brain injury (TBI). After mild controlled cortical impact (CCI), mice were treated with G-CSF (100 μg/kg) for 3 consecutive days. The primary behavioral endpoint was performance on the radial arm water maze (RAWM), assessed 7 and 14 days after CCI. Secondary endpoints included 1) motor performance on a rotating cylinder (rotarod), 2) measurement of microglial and astroglial response, 3) hippocampal neurogenesis, and 4) measures of neurotrophic factors (brain-derived neurotrophic factor [BDNF] and glial cell line-derived neurotrophic factor [GDNF]) and cytokines in brain homogenates. G-CSF-treated animals performed significantly better than vehicle-treated mice in the RAWM at 1 and 2 weeks but not on the rotarod. Cellular changes found in the G-CSF group included increased hippocampal neurogenesis as well as astrocytosis and microgliosis in both the striatum and the hippocampus. Neurotrophic factors GDNF and BDNF, elaborated by activated microglia and astrocytes, were increased in G-CSF-treated mice. These factors along with G-CSF itself are known to promote hippocampal neurogenesis and inhibit apoptosis and likely contributed to improvement in the hippocampal-dependent learning task. Six cytokines that were modulated by G-CSF treatment following CCI were elevated on day 3, but only one of them remained altered by day 7, and all of them were no different from vehicle controls by day 14. The pro- and anti-inflammatory cytokines modulated by G-CSF administration interact in a complex and incompletely understood network involving both damage and recovery processes, underscoring the dual role of inflammation after TBI.

Gut Microbiota Regulate Motor Deficits and Neuroinflammation in a Model of Parkinson's Disease.

  • Sampson TR
  • Cell
  • 2016 Dec 1

Literature context:


Abstract:

The intestinal microbiota influence neurodevelopment, modulate behavior, and contribute to neurological disorders. However, a functional link between gut bacteria and neurodegenerative diseases remains unexplored. Synucleinopathies are characterized by aggregation of the protein α-synuclein (αSyn), often resulting in motor dysfunction as exemplified by Parkinson's disease (PD). Using mice that overexpress αSyn, we report herein that gut microbiota are required for motor deficits, microglia activation, and αSyn pathology. Antibiotic treatment ameliorates, while microbial re-colonization promotes, pathophysiology in adult animals, suggesting that postnatal signaling between the gut and the brain modulates disease. Indeed, oral administration of specific microbial metabolites to germ-free mice promotes neuroinflammation and motor symptoms. Remarkably, colonization of αSyn-overexpressing mice with microbiota from PD-affected patients enhances physical impairments compared to microbiota transplants from healthy human donors. These findings reveal that gut bacteria regulate movement disorders in mice and suggest that alterations in the human microbiome represent a risk factor for PD.

Funding information:
  • NCI NIH HHS - P30 CA060553(United States)

Mouse Tmem135 mutation reveals a mechanism involving mitochondrial dynamics that leads to age-dependent retinal pathologies.

  • Lee WH
  • Elife
  • 2016 Nov 15

Literature context:


Abstract:

While the aging process is central to the pathogenesis of age-dependent diseases, it is poorly understood at the molecular level. We identified a mouse mutant with accelerated aging in the retina as well as pathologies observed in age-dependent retinal diseases, suggesting that the responsible gene regulates retinal aging, and its impairment results in age-dependent disease. We determined that a mutation in the transmembrane 135 (Tmem135) is responsible for these phenotypes. We observed localization of TMEM135 on mitochondria, and imbalance of mitochondrial fission and fusion in mutant Tmem135 as well as Tmem135 overexpressing cells, indicating that TMEM135 is involved in the regulation of mitochondrial dynamics. Additionally, mutant retina showed higher sensitivity to oxidative stress. These results suggest that the regulation of mitochondrial dynamics through TMEM135 is critical for protection from environmental stress and controlling the progression of retinal aging. Our study identified TMEM135 as a critical link between aging and age-dependent diseases.

In vivo inhibition of miR-155 significantly alters post-stroke inflammatory response.

  • Pena-Philippides JC
  • J Neuroinflammation
  • 2016 Nov 9

Literature context:


Abstract:

BACKGROUND: MicroRNA miR-155 is implicated in modulation of the inflammatory processes in various pathological conditions. In our previous studies, we demonstrated that in vivo inhibition of miR-155 promotes functional recovery after mouse experimental stroke. In the present study, we explored if this beneficial effect is associated with miR-155 inhibition-induced alterations in post-stroke inflammatory response. METHODS: Intravenous injections of a specific miR-155 inhibitor were initiated at 48 h after mouse distal middle cerebral artery occlusion (dMCAO). Temporal changes in the expression of cytokines and key molecules associated with cytokine signaling were assessed at 7, 14, and 21 days after dMCAO, using mouse cytokine gene and protein arrays and Western blot analyses. Electron and immunofluorescence confocal microscopy techniques were used to evaluate the ultrastructural changes, as well as altered expression of specific phenotypic markers, at different time points after dMCAO. RESULTS: In the inhibitor-injected mice (inhibitor group), there was a significant decrease in CCL12 and CXCL3 cytokine expression at 7 days and significantly increased levels of major cytokines IL-10, IL-4, IL-6, MIP-1α, IL-5, and IL-17 at 14 days after dMCAO. These temporal changes correlated with altered expression of miR-155 target proteins SOCS-1, SHIP-1, and C/EBP-β and phosphorylation levels of cytokine signaling regulator STAT-3. Electron microscopy showed decreased number of phagocytically active peri-vascular microglia/macrophages in the inhibitor samples. Immunofluorescence and Western blot of these samples demonstrated that expression of leukocyte/ macrophage marker CD45 and phagocytosis marker CD68 was reduced at 7 days, and in contrast, significantly increased at 14 days after dMCAO, as compared to controls. CONCLUSIONS: Based on our findings, we propose that in vivo miR-155 inhibition following mouse stroke significantly alters the time course of the expression of major cytokines and inflammation-associated molecules, which could influence inflammation process and tissue repair after experimental cerebral ischemia.

Neonatal disease environment limits the efficacy of retinal transplantation in the LCA8 mouse model.

  • Cho SH
  • BMC Ophthalmol
  • 2016 Nov 4

Literature context:


Abstract:

BACKGROUND: Mutations of Crb1 gene cause irreversible and incurable visual impairment in humans. This study aims to use an LCA8-like mouse model to identify host-mediated responses that might interfere with survival, retinal integration and differentiation of grafted cells during neonatal cell therapy. METHODS: Mixed retinal donor cells (1 ~ 2 × 104) isolated from neural retinas of neonatal eGFP transgenic mice were injected into the subretinal space of LCA8-like model neonatal mice. Markers of specific cell types were used to analyze microglial attraction, CSPG induction and retinal cell differentiation. The positions of host retinal cells were traced according to their laminar location during disease progression to look for host cell rearrangements that might inhibit retinal integration of the transplanted cells. RESULTS: Transplanted retinal cells showed poor survival and attracted microglial cells, but CSPG was not greatly induced. Retinas of the LCA8 model hosts underwent significant cellular rearrangement, including rosette formation and apical displacement of inner retinal cells. CONCLUSIONS: Local disease environment, particularly host immune responses to injected cells and formation of a physical barrier caused by apical migration of host retinal cells upon disruption of outer limiting membrane, may impose two major barriers in LCAs cell transplantation therapy.

Funding information:
  • NINDS NIH HHS - R01 NS083726(United States)

Distinct subcellular localization of alternative splicing variants of EFA6D, a guanine nucleotide exchange factor for Arf6, in the mouse brain.

  • Fukaya M
  • J. Comp. Neurol.
  • 2016 Sep 1

Literature context:


Abstract:

EFA6D (guanine nucleotide exchange factor for ADP-ribosylation factor 6 [Arf6]D) is also known as EFA6R, Psd3, and HCA67. It is the fourth member of the EFA6 family with guanine nucleotide exchange activity for Arf6, a small guanosine triphosphatase (GTPase) that regulates endosomal trafficking and actin cytoskeleton remodeling. We propose a classification and nomenclature of 10 EFA6D variants deposited in the GenBank database as EFA6D1a, 1b, 1c, 1d, 1s, 2a, 2b, 2c, 2d, and 2s based on the combination of N-terminal and C-terminal insertions. Polymerase chain reaction analysis showed the expression of all EFA6D variants except for variants a and d in the adult mouse brain. Immunoblotting analysis with novel variant-specific antibodies showed the endogenous expression of EFA6D1b, EFA6D1c, and EFA6D1s at the protein level, with the highest expression being EFA6D1s, in the brain. Immunoblotting analysis of forebrain subcellular fractions showed the distinct subcellular distribution of EFA6D1b/c and EFA6D1s. The immunohistochemical analysis revealed distinct but overlapping immunoreactive patterns between EFA6D1b/c and EFA6D1s in the mouse brain. In immunoelectron microscopic analyses of the hippocampal CA3 region, EFA6D1b/c was present predominantly in the mossy fiber axons of dentate granule cells, whereas EFA6D1s was present abundantly in the cell bodies, dendritic shafts, and spines of hippocampal pyramidal cells. These results provide the first anatomical evidence suggesting the functional diversity of EFA6D variants, particularly EFA6D1b/c and EFA6D1s, in neurons. J. Comp. Neurol. 524:2531-2552, 2016. © 2016 Wiley Periodicals, Inc.

Funding information:
  • NIMH NIH HHS - R15 MH099590(United States)

Neuroprotective effect of bee venom is mediated by reduced astrocyte activation in a subchronic MPTP-induced model of Parkinson's disease.

  • Kim ME
  • Arch. Pharm. Res.
  • 2016 Aug 30

Literature context:


Abstract:

Bee venom (BV), also known as apitoxin, is widely used in traditional oriental medicine to treat immune-related diseases. Recent studies suggest that BV could be beneficial for the treatment of neurodegenerative diseases. Parkinson's disease (PD) is the second most common neurodegenerative disease next to Alzheimer's disease, and PD pathologies are closely associated with neuroinflammation. Previous studies have suggested the neuroprotective effects of BV in animal models of PD are due to the modulation of inflammation. However, the molecular mechanisms responsible for the anti-neuroinflammatory effect of BV have not been elucidated in astrocytes. Here, the authors investigated the neuroprotective effects of BV and pramipexole (PPX; a positive control) in a subchronic MPTP-induced murine PD model. Both BV and PPX prevented MPTP-induced impairments in motor performance and reduced dopaminergic neuron loss, and furthermore, these neuroprotective effects of BV and PPX were found to be associated with reduced astroglial activation in vivo PD model. However, in MPP(+) treated primary cultured astrocytes, BV modulated astrocyte activation, whereas PPX did not, indicating that the neuroprotective effects of PPX were not mediated by neuroinflammation. These findings suggest that BV should be considered a potential therapeutic or preventive agent for PD and other neuroinflammatory associated disorders.

Environmental Enrichment Potently Prevents Microglia-Mediated Neuroinflammation by Human Amyloid β-Protein Oligomers.

  • Xu H
  • J. Neurosci.
  • 2016 Aug 31

Literature context:


Abstract:

Microglial dysfunction is increasingly recognized as a key contributor to the pathogenesis of Alzheimer's disease (AD). Environmental enrichment (EE) is well documented to enhance neuronal form and function, but almost nothing is known about whether and how it alters the brain's innate immune system. Here we found that prolonged exposure of naive wild-type mice to EE significantly altered microglial density and branching complexity in the dentate gyrus of hippocampus. In wild-type mice injected intraventricularly with soluble Aβ oligomers (oAβ) from hAPP-expressing cultured cells, EE prevented several morphological features of microglial inflammation and consistently prevented oAβ-mediated mRNA changes in multiple inflammatory genes both in vivo and in primary microglia cultured from the mice. Microdialysis in behaving mice confirmed that EE normalized increases in the extracellular levels of the key cytokines (CCL3, CCL4, TNFα) identified by the mRNA analysis. Moreover, EE prevented the changes in microglial gene expression caused by ventricular injection of oAβ extracted directly from AD cerebral cortex. We conclude that EE potently alters the form and function of microglia in a way that prevents their inflammatory response to human oAβ, suggesting that prolonged environmental enrichment could protect against AD by modulating the brain's innate immune system. SIGNIFICANCE STATEMENT: Environmental enrichment (EE) is a potential therapy to delay Alzheimer's disease (AD). Microglial inflammation is associated with the progression of AD, but the influence of EE on microglial inflammation is unclear. Here we systematically applied in vivo methods to show that EE alters microglia in the dentate gyrus under physiological conditions and robustly prevents microglial inflammation induced by human Aβ oligomers, as shown by neutralized microglial inflammatory morphology, mRNA changes, and brain interstitial fluid cytokine levels. Our findings suggest that EE alters the innate immune system and could serve as a therapeutic approach to AD and provide new targets for drug discovery. Further, we propose that the therapeutic benefits of EE could extend to other neurodegenerative diseases involving microglial inflammation.

East Coast Fever Caused by Theileria parva Is Characterized by Macrophage Activation Associated with Vasculitis and Respiratory Failure.

  • Fry LM
  • PLoS ONE
  • 2016 May 20

Literature context:


Abstract:

Respiratory failure and death in East Coast Fever (ECF), a clinical syndrome of African cattle caused by the apicomplexan parasite Theileria parva, has historically been attributed to pulmonary infiltration by infected lymphocytes. However, immunohistochemical staining of tissue from T. parva infected cattle revealed large numbers of CD3- and CD20-negative intralesional mononuclear cells. Due to this finding, we hypothesized that macrophages play an important role in Theileria parva disease pathogenesis. Data presented here demonstrates that terminal ECF in both Holstein and Boran cattle is largely due to multisystemic histiocytic responses and resultant tissue damage. Furthermore, the combination of these histologic changes with the clinical findings, including lymphadenopathy, prolonged pyrexia, multi-lineage leukopenia, and thrombocytopenia is consistent with macrophage activation syndrome. All animals that succumbed to infection exhibited lymphohistiocytic vasculitis of small to medium caliber blood and lymphatic vessels. In pulmonary, lymphoid, splenic and hepatic tissues from Holstein cattle, the majority of intralesional macrophages were positive for CD163, and often expressed large amounts of IL-17. These data define a terminal ECF pathogenesis in which parasite-driven lymphoproliferation leads to secondary systemic macrophage activation syndrome, mononuclear vasculitis, pulmonary edema, respiratory failure and death. The accompanying macrophage phenotype defined by CD163 and IL-17 is presented in the context of this pathogenesis.

Tau hyperphosphorylation in synaptosomes and neuroinflammation are associated with canine cognitive impairment.

  • Smolek T
  • J. Comp. Neurol.
  • 2016 Mar 1

Literature context:


Abstract:

Canine cognitive impairment syndrome (CDS) represents a group of symptoms related to the aging of the canine brain. These changes ultimately lead to a decline of memory function and learning abilities, alteration of social interaction, impairment of normal housetraining, and changes in sleep-wake cycle and general activity. We have clinically examined 215 dogs, 28 of which underwent autopsy. With canine brains, we performed extensive analysis of pathological abnormalities characteristic of human Alzheimer's disease and frontotemporal lobar degeneration, including β-amyloid senile plaques, tau neurofibrillary tangles, and fused in sarcoma (FUS) and TAR DNA-binding protein 43 (TDP43) inclusions. Most demented dogs displayed senile plaques, mainly in the frontal and temporal cortex. Tau neurofibrillary inclusions were found in only one dog. They were identified with antibodies used to detect tau neurofibrillary lesions in the human brain. The inclusions were also positive for Gallyas silver staining. As in humans, they were distributed mainly in the entorhinal cortex, hippocampus, and temporal cortex. On the other hand, FUS and TDP43 aggregates were not present in any of the examined brain samples. We also found that CDS was characterized by the presence of reactive and senescent microglial cells in the frontal cortex. Our transcriptomic study revealed a significant dysregulation of genes involved in neuroinflammation. Finally, we analyzed tau phosphoproteome in the synaptosomes. Proteomic studies revealed a significant increase of hyperphosphorylated tau in synaptosomes of demented dogs compared with nondemented dogs. This study suggests that cognitive decline in dogs is related to the tau synaptic impairment and neuroinflammation. J. Comp. Neurol. 524:874-895, 2016. © 2015 Wiley Periodicals, Inc.

Funding information:
  • NIDCR NIH HHS - U01 DE024427(United States)

Glial activation in the periaqueductal gray promotes descending facilitation of neuropathic pain through the p38 MAPK signaling pathway.

  • Ni HD
  • J. Neurosci. Res.
  • 2016 Jan 28

Literature context:


Abstract:

The midbrain ventrolateral periaqueductal gray (VL-PAG) is a key component that mediates pain modulation. Although spinal cord glial cells appear to play an important role in chronic pain development, the precise mechanisms involving descending facilitation pathways from the PAG following nerve injury are poorly understood. This study shows that cellular events that occur during glial activation in the VL-PAG may promote descending facilitation from the PAG during neuropathic pain. Chronic constriction nerve injury (CCI) was induced by ligature construction of the sciatic nerve in male Sprague-Dawley rats. Behavioral responses to noxious mechanical (paw withdrawal threshold; PWT) and thermal (paw withdrawal latency; PWL) stimuli were evaluated. After CCI, immunohistochemical and Western blot analysis of microglia and astrocytes in the VL-PAG showed morphological and quantitative changes indicative of activation in microglia and astrocytes. Intra-VL-PAG injection of microglial or astrocytic inhibitors attenuated PWT and PWL at days 7 and 14, respectively, following CCI. We also evaluated the effects of intra-VL-PAG administration of the phosphorylated p38 mitogen-activated protein kinase (p-p38 MAPK) inhibitor SB 203580 at day 7 after CCI. This treatment abolished microglial activation and produced a significant time-dependent attenuation of PWT and PWL. Western blot analysis showed localized expression of p-p38 in the VL-PAG after CCI. P-p38 was expressed in labeled microglia of the VL-PAG but was not present in astrocytes and neurons on day 7 after CCI. These results demonstrate that CCI-induced neuropathic pain is associated with glial activation in the VL-PAG, which likely participates in descending pain facilitation through the p38 MAPK signaling pathway.

Funding information:
  • NCI NIH HHS - CA173903(United States)

Increase of transcription factor EB (TFEB) and lysosomes in rat DRG neurons and their transportation to the central nerve terminal in dorsal horn after nerve injury.

  • Jung J
  • Neuroscience
  • 2016 Jan 28

Literature context:


Abstract:

In the spinal dorsal horn (DH), nerve injury activates microglia and induces neuropathic pain. Several studies clarified an involvement of adenosine triphosphate (ATP) in the microglial activation. However, the origin of ATP together with the release mechanism is unclear. Recent in vitro study revealed that an ATP marker, quinacrine, in lysosomes was released from neurite terminal of dorsal root ganglion (DRG) neurons to extracellular space via lysosomal exocytosis. Here, we demonstrate a possibility that the lysosomal ingredient including ATP released from DRG neurons by lysosomal-exocytosis is an additional source of the glial activation in DH after nerve injury. After rat L5 spinal nerve ligation (SNL), mRNA for transcription factor EB (TFEB), a transcription factor controlling lysosomal activation and exocytosis, was induced in the DRG. Simultaneously both lysosomal protein, LAMP1- and vesicular nuclear transporter (VNUT)-positive vesicles were increased in L5 DRG neurons and ipsilateral DH. The quinacrine staining in DH was increased and co-localized with LAMP1 immunoreactivity after nerve injury. In DH, LAMP1-positive vesicles were also co-localized with a peripheral nerve marker, Isolectin B4 (IB4) lectin. Injection of the adenovirus encoding mCherry-LAMP1 into DRG showed that mCherry-positive lysosomes are transported to the central nerve terminal in DH. These findings suggest that activation of lysosome synthesis including ATP packaging in DRG, the central transportation of the lysosome, and subsequent its exocytosis from the central nerve terminal of DRG neurons in response to nerve injury could be a partial mechanism for activation of microglia in DH. This lysosome-mediated microglia activation mechanism may provide another clue to control nociception and pain.

Funding information:
  • NIMH NIH HHS - 1R01 MH084803(United States)

Involvement of endoplasmic reticulum stress in optic nerve degeneration after chronic high intraocular pressure in DBA/2J mice.

  • Ojino K
  • J. Neurosci. Res.
  • 2015 Nov 19

Literature context:


Abstract:

DBA/2J mice are one of several animal strains used for experimental models of both intraocular hypertension and glaucoma. This study investigates the relationship between endoplasmic reticulum (ER) stress and optic nerve degeneration in DBA/2J mice. Intraocular pressure (IOP) was measured in DBA/2J mice between the ages of 6 and 15 months. Optic nerve damage was assessed at 15 months of age. The nerve was immunostained with antibodies to either neurofilament heavy chain (NFH) or phosphorylated NFH (pNFH), and optic nerve damage was assessed by performing NFH- and pNFH-positive axon counts. Expression levels of the ER stress proteins 78-kDa glucose-regulated protein, also known as binding immunoglobulin protein, and C/EBP homologous protein were assayed with Western blotting. We also investigated ER stress localization in the optic nerve by double immunostaining with antibodies to ionized calcium-binding adaptor molecule 1, myelin basic protein, and glial fibrillary acidic protein (GFAP). In DBA/2J mice, IOP began to rise at 8 months of age, and retinal degeneration was detected at 15 months of age. DBA/2J mice had fewer axons than controls at 15 months of age. ER stress-related protein levels were higher in the optic nerves of DBA/2J mice and were colocalized with GFAP-positive astrocytes. Our findings suggest that ER stress plays a role in optic nerve degeneration during chronic ocular hypertension. Furthermore, ER stress may be related in some way to astrocyte activation.

Funding information:
  • NIAMS NIH HHS - R01 AR066703(United States)

A stereological analysis of NPY, POMC, Orexin, GFAP astrocyte, and Iba1 microglia cell number and volume in diet-induced obese male mice.

  • Lemus MB
  • Endocrinology
  • 2015 May 18

Literature context:


Abstract:

The hypothalamic arcuate nucleus (ARC) contains 2 key neural populations, neuropeptide Y (NPY) and proopiomelanocortin (POMC), and, together with orexin neurons in the lateral hypothalamus, plays an integral role in energy homeostasis. However, no studies have examined total neuronal number and volume after high-fat diet (HFD) exposure using sophisticated stereology. We used design-based stereology to estimate NPY and POMC neuronal number and volume, as well as glial fibrillary acidic protein (astrocyte marker) and ionized calcium-binding adapter molecule 1 (microglia marker) cell number in the ARC; as well as orexin neurons in the lateral hypothalamus. Stereological analysis indicated approximately 8000 NPY and approximately 9000 POMC neurons in the ARC, and approximately 7500 orexin neurons in the lateral hypothalamus. HFD exposure did not affect total neuronal number in any population. However, HFD significantly increased average NPY cell volume and affected NPY and POMC cell volume distribution. HFD reduced orexin cell volume but had a bimodal effect on volume distribution with increased cells at relatively small volumes and decreased cells with relatively large volumes. ARC glial fibrillary acidic protein cells increased after 2 months on a HFD, although no significant difference after 6 months on chow diet or HFD was observed. No differences in ARC ionized calcium-binding adapter molecule 1 cell number were observed in any group. Thus, HFD affects ARC NPY or POMC neuronal cell volume number not cell number. Our results demonstrate the importance of stereology to perform robust unbiased analysis of cell number and volume. These data should be an empirical baseline reference to which future studies are compared.

Funding information:
  • NEI NIH HHS - EY012135(United States)

Prostacyclin prevents pericyte loss and demyelination induced by lysophosphatidylcholine in the central nervous system.

  • Muramatsu R
  • J. Biol. Chem.
  • 2015 May 1

Literature context:


Abstract:

Pericytes play pivotal roles in physiological and pathophysiological conditions in the central nervous system. As pericytes prevent vascular leakage, they can halt neuronal damage stemming from a compromised blood-brain barrier. Therefore, pericytes may be a good target for the treatment of neurodegenerative disorders, although evidence is lacking. In this study, we show that prostacyclin attenuates lysophosphatidylcholine (LPC)-mediated vascular dysfunction through pericyte protection in the adult mouse spinal cord. LPC decreased the number of pericytes in an in vitro blood-brain barrier model, and this decrease was prevented by iloprost treatment, a prostacyclin analog. Intrathecal administration of iloprost attenuated vascular barrier disruption after LPC injection in the mouse spinal cord. Furthermore, iloprost treatment diminished demyelination and motor function deficits in mice injected with LPC. These results support the notion that prostacyclin acts on pericytes to maintain vascular barrier integrity.

Funding information:
  • Canadian Institutes of Health Research - 89904(Canada)
  • NEI NIH HHS - R01-EY18005(United States)

Blocking stroke-induced immunodeficiency increases CNS antigen-specific autoreactivity but does not worsen functional outcome after experimental stroke.

  • Römer C
  • J. Neurosci.
  • 2015 May 20

Literature context:


Abstract:

Stroke-induced immunodepression (SIDS) is an essential cause of poststroke infections. Pharmacological inhibition of SIDS appears promising in preventing life-threatening infections in stroke patients. However, SIDS might represent an adaptive mechanism preventing autoreactive immune responses after stroke. To address this, we used myelin oligodendrocyte glycoprotein (MOG) T-cell receptor transgenic (2D2) mice where >80% of peripheral CD4(+) T cells express a functional receptor for MOG. We investigated in a murine model of middle cerebral artery occlusion the effect of blocking SIDS by inhibiting body's main stress axes, the sympathetic nervous system (SNS) with propranolol and the hypothalamic-pituitary-adrenal axis (HPA) with mifepristone. Blockade of both stress axes robustly reduced infarct volumes, decreased infection rate, and increased long-term survival of 2D2 and C57BL/6J wild-type mice. Despite these protective effects, blockade of SIDS increased CNS antigen-specific Type1 T helper cell (Th1) responses in the brains of 2D2 mice 14 d after middle cerebral artery occlusion. One month after experimental stroke, 2D2 mice developed signs of polyradiculitis, which were diminished by SIDS blockade. Adoptive transfer of CD4(+) T cells, isolated from 2D2 mice, into lymphocyte-deficient Rag-1KO mice did not reveal differences between SIDS blockade and vehicle treatment in functional long-term outcome after stroke. In conclusion, inhibiting SIDS by pharmacological blockade of body's stress axes increases autoreactive CNS antigen-specific T-cell responses in the brain but does not worsen functional long-term outcome after experimental stroke, even in a mouse model where CNS antigen-specific autoreactive T-cell responses are boosted.

Brain innate immunity regulates hypothalamic arcuate neuronal activity and feeding behavior.

  • Reis WL
  • Endocrinology
  • 2015 Apr 21

Literature context:


Abstract:

Hypothalamic inflammation, involving microglia activation in the arcuate nucleus (ARC), is proposed as a novel underlying mechanism in obesity, insulin and leptin resistance. However, whether activated microglia affects ARC neuronal activity, and consequently basal and hormonal-induced food intake, is unknown. We show that lipopolysaccharide, an agonist of the toll-like receptor-4 (TLR4), which we found to be expressed in ARC microglia, inhibited the firing activity of the majority of orexigenic agouti gene-related protein/neuropeptide Y neurons, whereas it increased the activity of the majority of anorexigenic proopiomelanocortin neurons. Lipopolysaccharide effects in agouti gene-related protein/neuropeptide Y (but not in proopiomelanocortin) neurons were occluded by inhibiting microglia function or by blocking TLR4 receptors. Finally, we report that inhibition of hypothalamic microglia altered basal food intake, also preventing central orexigenic responses to ghrelin. Our studies support a major role for a TLR4-mediated microglia signaling pathway in the control of ARC neuronal activity and feeding behavior.

Funding information:
  • NIMH NIH HHS - MH090963(United States)

Differential contributions of microglial and neuronal IKKβ to synaptic plasticity and associative learning in alert behaving mice.

  • Kyrargyri V
  • Glia
  • 2015 Apr 16

Literature context:


Abstract:

Microglia are CNS resident immune cells and a rich source of neuroactive mediators, but their contribution to physiological brain processes such as synaptic plasticity, learning, and memory is not fully understood. In this study, we used mice with partial depletion of IκB kinase β, the main activating kinase in the inducible NF-κB pathway, selectively in myeloid lineage cells (mIKKβKO) or excitatory neurons (nIKKβKO) to measure synaptic strength at hippocampal Schaffer collaterals during long-term potentiation (LTP) and instrumental conditioning in alert behaving individuals. Resting microglial cells in mIKKβKO mice showed less Iba1-immunoreactivity, and brain IL-1β mRNA levels were selectively reduced compared with controls. Measurement of field excitatory postsynaptic potentials (fEPSPs) evoked by stimulation of the CA3-CA1 synapse in mIKKβKO mice showed higher facilitation in response to paired pulses and enhanced LTP following high frequency stimulation. In contrast, nIKKβKO mice showed normal basic synaptic transmission and LTP induction but impairments in late LTP. To understand the consequences of such impairments in synaptic plasticity for learning and memory, we measured CA1 fEPSPs in behaving mice during instrumental conditioning. IKKβ was not necessary in either microglia or neurons for mice to learn lever-pressing (appetitive behavior) to obtain food (consummatory behavior) but was required in both for modification of their hippocampus-dependent appetitive, not consummatory behavior. Our results show that microglia, through IKKβ and therefore NF-κB activity, regulate hippocampal synaptic plasticity and that both microglia and neurons, through IKKβ, are necessary for animals to modify hippocampus-driven behavior during associative learning.

α-Synuclein-independent histopathological and motor deficits in mice lacking the endolysosomal Parkinsonism protein Atp13a2.

  • Kett LR
  • J. Neurosci.
  • 2015 Apr 8

Literature context:


Abstract:

Accumulating evidence from genetic and biochemical studies implicates dysfunction of the autophagic-lysosomal pathway as a key feature in the pathogenesis of Parkinson's disease (PD). Most studies have focused on accumulation of neurotoxic α-synuclein secondary to defects in autophagy as the cause of neurodegeneration, but abnormalities of the autophagic-lysosomal system likely mediate toxicity through multiple mechanisms. To further explore how endolysosomal dysfunction causes PD-related neurodegeneration, we generated a murine model of Kufor-Rakeb syndrome (KRS), characterized by early-onset Parkinsonism with additional neurological features. KRS is caused by recessive loss-of-function mutations in the ATP13A2 gene encoding the endolysosomal ATPase ATP13A2. We show that loss of ATP13A2 causes a specific protein trafficking defect, and that Atp13a2 null mice develop age-related motor dysfunction that is preceded by neuropathological changes, including gliosis, accumulation of ubiquitinated protein aggregates, lipofuscinosis, and endolysosomal abnormalities. Contrary to predictions from in vitro data, in vivo mouse genetic studies demonstrate that these phenotypes are α-synuclein independent. Our findings indicate that endolysosomal dysfunction and abnormalities of α-synuclein homeostasis are not synonymous, even in the context of an endolysosomal genetic defect linked to Parkinsonism, and highlight the presence of α-synuclein-independent neurotoxicity consequent to endolysosomal dysfunction.

Funding information:
  • NINDS NIH HHS - R01 NS090390(United States)

Cytogenesis in the adult monkey motor cortex: perivascular NG2 cells are the major adult born cell type.

  • Stanton GB
  • J. Comp. Neurol.
  • 2015 Apr 15

Literature context:


Abstract:

We used confocal microscopy and immunohistochemistry (IHC) to look for new cells in the motor cortex of adult macaque monkeys that might form the cellular bases of improved brain function from exercise. Twenty-four female Macaca fascicularis monkeys divided into groups by age (10-12 years, 15-17 years), postexercise survival periods, and controls, received 10 weekly injections of the thymidine analog, bromodeoxyuridine (BrdU) to mark new cells. Sixteen monkeys survived 15 weeks (5 weeks postexercise) and 8 monkeys survived 27 weeks (12 weeks postexercise) after initial BrdU injections. Additionally, five Macaca mulatta female monkeys (∼5.5-7 years) received single injections of BrdU and survived 2 days, 2 weeks, and 6 weeks after BrdU injections. Neural and glial antibodies were used to identify new cell phenotypes and to look for changes in proportions of these cells with respect to time and experimental conditions. No BrdU(+) /DCx(+) cells were found but about 7.5% of new cells were calretinin-positive (Cr(+) ). BrdU(+) /GABA(+) (gamma-aminobutyric acid) cells were also found but no new Cr(+) or GABA(+) cells colabeled with a mature neuron marker, NeuN or chondroitin sulfate antibody, NG2. The proportion of new cells that were NG2(+) was about 85% for short and long survival monkeys of which two, newly described perivascular phenotypes (Pldv and Elu) and a small percentage of pericytes (2.5%) comprised 44% and 51% of the new NG2(+) cells, respectively. Proportions of NG2(+) phenotypes were affected by post-BrdU survival periods, monkey age, and possibly a postexercise sedentary period but no direct effect of exercise was found.

A novel and robust conditioning lesion induced by ethidium bromide.

  • Hollis ER
  • Exp. Neurol.
  • 2015 Mar 2

Literature context:


Abstract:

Molecular and cellular mechanisms underlying the peripheral conditioning lesion remain unsolved. We show here that injection of a chemical demyelinating agent, ethidium bromide, into the sciatic nerve induces a similar set of regeneration-associated genes and promotes a 2.7-fold greater extent of sensory axon regeneration in the spinal cord than sciatic nerve crush. We found that more severe peripheral demyelination correlates with more severe functional and electrophysiological deficits, but more robust central regeneration. Ethidium bromide injection does not activate macrophages at the demyelinated sciatic nerve site, as observed after nerve crush, but briefly activates macrophages in the dorsal root ganglion. This study provides a new method for investigating the underlying mechanisms of the conditioning response and suggests that loss of the peripheral myelin may be a major signal to change the intrinsic growth state of adult sensory neurons and promote regeneration.

Funding information:
  • NINDS NIH HHS - 1F31NS084706-01(United States)

Olfactory ensheathing cells are the main phagocytic cells that remove axon debris during early development of the olfactory system.

  • Nazareth L
  • J. Comp. Neurol.
  • 2015 Feb 15

Literature context:


Abstract:

During development of the primary olfactory system, axon targeting is inaccurate and axons inappropriately project within the target layer or overproject into the deeper layers of the olfactory bulb. As a consequence there is considerable apoptosis of primary olfactory neurons during embryonic and postnatal development and axons of the degraded neurons need to be removed. Olfactory ensheathing cells (OECs) are the glia of the primary olfactory nerve and are known to phagocytose axon debris in the adult and postnatal animal. However, it is unclear when phagocytosis by OECs first commences. We investigated the onset of phagocytosis by OECs in the developing mouse olfactory system by utilizing two transgenic reporter lines: OMP-ZsGreen mice which express bright green fluorescent protein in primary olfactory neurons, and S100β-DsRed mice which express red fluorescent protein in OECs. In crosses of these mice, the fate of the degraded axon debris is easily visualized. We found evidence of axon degradation at embryonic day (E)13.5. Phagocytosis of the primary olfactory axon debris by OECs was first detected at E14.5. Phagocytosis of axon debris continued into the postnatal animal during the period when there was extensive mistargeting of olfactory axons. Macrophages were often present in close proximity to OECs but they contributed only a minor role to clearing the axon debris, even after widespread degeneration of olfactory neurons by unilateral bulbectomy and methimazole treatment. These results demonstrate that from early in embryonic development OECs are the primary phagocytic cells of the primary olfactory nerve.

Distribution of microsomal prostaglandin E synthase-1 in the mouse brain.

  • Eskilsson A
  • J. Comp. Neurol.
  • 2014 Oct 1

Literature context:


Abstract:

Previous studies in rats have demonstrated that microsomal prostaglandin E synthase-1 (mPGES-1) is induced in brain vascular cells that also express inducible cyclooxygenase-2, suggesting that such cells are the source of the increased PGE2 levels that are seen in the brain following peripheral immune stimulation, and that are associated with sickness responses such as fever, anorexia, and stress hormone release. However, while most of what is known about the functional role of mPGES-1 for these centrally evoked symptoms is based on studies on genetically modified mice, the cellular localization of mPGES-1 in the mouse brain has not been thoroughly determined. Here, using a newly developed antibody that specifically recognizes mouse mPGES-1 and dual-labeling for cell-specific markers, we report that mPGES-1 is constitutively expressed in the mouse brain, being present not only in brain endothelial cells, but also in several other cell types and structures, such as capillary-associated pericytes, astroglial cells, leptomeninges, and the choroid plexus. Regional differences were seen with particularly prominent labeling in autonomic relay structures such as the area postrema, the subfornical organ, the paraventricular hypothalamic nucleus, the arcuate nucleus, and the preoptic area. Following immune stimulation, mPGES-1 in brain endothelial cells, but not in other mPGES-1-positive cells, was coexpressed with cyclooxygenase-2, whereas there was no coexpression between mPGES-1 and cyclooxygenase-1. These data imply a widespread synthesis of PGE2 or other mPGES-1-dependent products in the mouse brain that may be related to inflammation-induced sickness symptom as well as other functions, such as blood flow regulation.

Characterization of neural estrogen signaling and neurotrophic changes in the accelerated ovarian failure mouse model of menopause.

  • Van Kempen TA
  • Endocrinology
  • 2014 Sep 25

Literature context:


Abstract:

Accelerated ovarian failure (AOF) can be induced in young mice with low doses of 4-vinylcyclohexene diepoxide (VCD), modeling the hormone changes observed across menopause. We assessed markers of synaptic plasticity in the hippocampus, anxiety-like behavior, and spatial learning longitudinally at 4 time points across the AOF model: premenopause, early perimenopause, late perimenopause, and postmenopause (POST). As others have shown, VCD administration decreased ovarian follicle counts and increased acyclicity as the model progressed to POST but with no impact on organ or body weights. The morphology of Iba1 immunoreactive microglia did not differ between vehicle- and VCD-administered mice. Hippocampal postsynaptic density 95 levels were minimally altered across the AOF model but decreased at POST in CA3b 24 hours after exogenous estradiol benzoate (EB). In contrast, hippocampal phosphorylated AKT levels transiently decreased in premenopause but increased at POST after 24 hours of EB in select subregions. Electron microscopy revealed fewer estrogen receptor α containing dendritic spines and terminals in CA1 stratum radiatum at POST. mRNA levels of most brain-derived neurotrophic factor exons (except V and VI) were lower in POST compared with ovariectomized mice. Exon V was sensitive to 24 hours of EB administration in POST-VCD. Anxiety-like behavior was unaffected at any menopause phase. Spatial learning was unaffected in all groups, but POST-VCD mice performed below chance. Our results suggest that the AOF model is suitable for longitudinal studies of neurobiological changes across the menopause transition in mice. Our findings also point to complex interactions between estrogen receptors and pathways involved in synaptic plasticity.

Funding information:
  • NINDS NIH HHS - R56 NS046367(United States)

Substance P exacerbates dopaminergic neurodegeneration through neurokinin-1 receptor-independent activation of microglial NADPH oxidase.

  • Wang Q
  • J. Neurosci.
  • 2014 Sep 10

Literature context:


Abstract:

Although dysregulated substance P (SP) has been implicated in the pathophysiology of Parkinson's disease (PD), how SP affects the survival of dopaminergic neurons remains unclear. Here, we found that mice lacking endogenous SP (TAC1(-/-)), but not those deficient in the SP receptor (neurokinin-1 receptor, NK1R), were more resistant to lipopolysaccharide (LPS)- and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced nigral dopaminergic neurodegeneration than wild-type controls, suggesting a NK1R-independent toxic action of SP. In vitro dose-response studies revealed that exogenous SP enhanced LPS- and 1-methyl-4-phenylpyridinium (MPP(+))-induced dopaminergic neurodegeneration in a bimodal manner, peaking at submicromolar and subpicomolar concentrations, but was substantially less effective at intermediate concentrations. Mechanistically, the actions of submicromolar levels of SP were NK1R-dependent, whereas subpicomolar SP-elicited actions required microglial NADPH oxidase (NOX2), the key superoxide-producing enzyme, but not NK1R. Subpicomolar concentrations of SP activated NOX2 by binding to the catalytic subunit gp91(phox) and inducing membrane translocation of the cytosolic subunits p47(phox) and p67(phox). The importance of NOX2 was further corroborated by showing that inhibition or disruption of NOX2 blocked subpicomolar SP-exacerbated neurotoxicity. Together, our findings revealed a critical role of microglial NOX2 in mediating the neuroinflammatory and dopaminergic neurodegenerative effects of SP, which may provide new insights into the pathogenesis of PD.

Funding information:
  • NINDS NIH HHS - 5R01NS039444(United States)

n-3 polyunsaturated fatty acids supplementation enhances hippocampal functionality in aged mice.

  • Cutuli D
  • Front Aging Neurosci
  • 2014 Sep 9

Literature context:


Abstract:

As major components of neuronal membranes, omega-3 polyunsaturated acids (n-3 PUFA) exhibit a wide range of regulatory functions, modulating from synaptic plasticity to neuroinflammation, from oxidative stress to neuroprotection. Recent human and animal studies indicated the n-3 PUFA neuroprotective properties in aging, with a clear negative correlation between n-3 PUFA levels and hippocampal deficits. The present multidimensional study was aimed at associating cognition, hippocampal neurogenesis, volume, neurodegeneration and metabolic correlates to verify n-3 PUFA neuroprotective effects in aging. To this aim 19 month-old mice were given n-3 PUFA mixture, or olive oil or no dietary supplement for 8 weeks during which hippocampal-dependent mnesic functions were tested. At the end of behavioral testing morphological and metabolic correlates were analyzed. n-3 PUFA supplemented aged mice exhibited better object recognition memory, spatial and localizatory memory, and aversive response retention, without modifications in anxiety levels in comparison to controls. These improved hippocampal cognitive functions occurred in the context of an enhanced cellular plasticity and a reduced neurodegeneration. In fact, n-3 PUFA supplementation increased hippocampal neurogenesis and dendritic arborization of newborn neurons, volume, neuronal density and microglial cell number, while it decreased apoptosis, astrocytosis and lipofuscin accumulation in the hippocampus. The increased levels of some metabolic correlates (blood Acetyl-L-Carnitine and brain n-3 PUFA concentrations) found in n-3 PUFA supplemented mice also pointed toward an effective neuroprotection. On the basis of the present results n-3 PUFA supplementation appears to be a useful tool in health promotion and cognitive decline prevention during aging.

Funding information:
  • NIMH NIH HHS - R01 MH059950(United States)

Opposing effects of membrane-anchored CX3CL1 on amyloid and tau pathologies via the p38 MAPK pathway.

  • Lee S
  • J. Neurosci.
  • 2014 Sep 10

Literature context:


Abstract:

Several Alzheimer's disease (AD) risk genes are specifically expressed by microglia within the CNS. However, the mechanisms by which microglia regulate the pathological hallmarks of AD--extracellular deposition of β-amyloid (Aβ) and intraneuronal hyperphosphorylation of microtubule-associated protein tau (MAPT)--remain to be established. Notably, deficiency for the microglial CX3CR1 receptor has opposing effects on Aβ and MAPT pathologies. CX3CL1, the neuronally derived cognate ligand for CX3CR1, signals both in membrane-anchored and soluble forms. In this study, we sought to determine the relative contribution on membrane-anchored versus soluble CX3CL1 in regulating the microglia-mediated amelioration of Aβ pathology, as well as provide insight into the potential downstream microglial-based mechanisms. As expected, CX3CL1 deficiency reduced Aβ deposition in APPPS1 animals in a similar manner to CX3CR1 deficiency. Surprisingly, however, CX3CL1-deficient APPPS1 animals exhibited enhanced neuronal MAPT phosphorylation despite reduced amyloid burden. Importantly, neither of these phenotypes was altered by transgenic expression of the soluble CX3CL1 isoform, suggesting that it is the membrane-anchored version of CX3CL1 that regulates microglial phagocytosis of Aβ and neuronal MAPT phosphorylation. Analysis of transcript levels in purified microglia isolated from APPPS1 mice with the various CX3CL1/CX3CR1 genotypes revealed increased expression of inflammatory cytokines and phagocytic markers, which was associated with activation of p38 mitogen-activated protein kinase and Aβ internalization within microglia. Together, these studies challenge the "frustrated phagocytosis" concept and suggest that neuronal-microglial communication link the two central AD pathologies.

ZPK/DLK and MKK4 form the critical gateway to axotomy-induced motoneuron death in neonates.

  • Itoh T
  • J. Neurosci.
  • 2014 Aug 6

Literature context:


Abstract:

Motoneuron death after transection of the axons (axotomy) in neonates is believed to share the same mechanistic bases as naturally occurring programmed cell death during development. The c-Jun N-terminal kinase pathway is activated in both forms of motoneuron death, but it remains unknown to what extent these two forms of motoneuron death depend on this pathway and which upstream kinases are involved. We found that numbers of facial motoneurons are doubled in neonatal mice deficient in either ZPK/DLK (zipper protein kinase, also known as dual leucine zipper kinase), a mitogen-activated protein kinase kinase kinase, or in MKK4/MAP2K4, a mitogen-activated protein kinase kinase directly downstream of ZPK/DLK, and that the facial motoneurons in those mutant mice are completely resistant to axotomy-induced death. Conditional deletion of MKK4/MAP2K4 in neurons further suggested that ZPK/DLK and MKK4/MAP2K4-dependent mechanisms underlying axotomy-induced death are motoneuron autonomous. Nevertheless, quantitative analysis of facial motoneurons during embryogenesis revealed that both ZPK/DLK and MKK4/MAP2K4-dependent and -independent mechanisms contribute to developmental elimination of excess motoneurons. In contrast to MKK4/MAP2K4, mice lacking MKK7/MAP2K7, another mitogen-activated protein kinase kinase directly downstream of ZPK/DLK, conditionally in neurons did not have excess facial motoneurons. However, some MKK7/MAP2K7-deficient facial motoneurons were resistant to axotomy-induced death, indicating a synergistic effect of MKK7/MAP2K7 on axotomy-induced death of these facial motoneurons. Together, our study provides compelling evidence for the pivotal roles of the ZPK/DLK and MKK4/MAP2K4-dependent mechanism in axotomy-induced motoneuron death in neonates and also demonstrates that axotomy-induced motoneuron death is not identical to developmental motoneuron death with respect to the involvement of ZPK/DLK, MKK4/MAP2K4 and MKK7/MAP2K7.

Hypothalamic gliosis associated with high-fat diet feeding is reversible in mice: a combined immunohistochemical and magnetic resonance imaging study.

  • Berkseth KE
  • Endocrinology
  • 2014 Aug 19

Literature context:


Abstract:

Gliosis, the activation of astrocyte and microglial cell populations, is a hallmark of central nervous system injury and is detectable using either immunohistochemistry or in vivo magnetic resonance imaging (MRI). Obesity in rodents and humans is associated with gliosis of the arcuate nucleus, a key hypothalamic region for the regulation of energy homeostasis and adiposity, but whether this response is permanent or reversible is unknown. Here we combine terminal immunohistochemistry analysis with serial, noninvasive MRI to characterize the progression and reversibility of hypothalamic gliosis in high-fat diet (HFD)-fed mice. The effects of HFD feeding for 16 weeks to increase body weight and adiposity relative to chow were nearly normalized after the return to chow feeding for an additional 4 weeks in the diet-reversal group. Mice maintained on the HFD for the full 20-week study period experienced continued weight gain associated with the expected increases of astrocyte and microglial activation in the arcuate nucleus, but these changes were not observed in the diet-reversal group. The proopiomelanocortin neuron number did not differ between groups. Although MRI demonstrated a positive correlation between body weight, adiposity, and the gliosis-associated T2 signal in the mediobasal hypothalamus, it did not detect the reversal of gliosis among the HFD-fed mice after the return to chow diet. We conclude that hypothalamic gliosis associated with 16-week HFD feeding is largely reversible in rodents, consistent with the reversal of the HFD-induced obesity phenotype, and extend published evidence regarding the utility of MRI as a tool for studying obesity-associated hypothalamic gliosis in vivo.

Funding information:
  • Canadian Institutes of Health Research - 89904(Canada)

Huntingtin is required for normal excitatory synapse development in cortical and striatal circuits.

  • McKinstry SU
  • J. Neurosci.
  • 2014 Jul 9

Literature context:


Abstract:

Huntington's disease (HD) is a neurodegenerative disease caused by the expansion of a poly-glutamine (poly-Q) stretch in the huntingtin (Htt) protein. Gain-of-function effects of mutant Htt have been extensively investigated as the major driver of neurodegeneration in HD. However, loss-of-function effects of poly-Q mutations recently emerged as potential drivers of disease pathophysiology. Early synaptic problems in the excitatory cortical and striatal connections have been reported in HD, but the role of Htt protein in synaptic connectivity was unknown. Therefore, we investigated the role of Htt in synaptic connectivity in vivo by conditionally silencing Htt in the developing mouse cortex. When cortical Htt function was silenced, cortical and striatal excitatory synapses formed and matured at an accelerated pace through postnatal day 21 (P21). This exuberant synaptic connectivity was lost over time in the cortex, resulting in the deterioration of synapses by 5 weeks. Synaptic decline in the cortex was accompanied with layer- and region-specific reactive gliosis without cell loss. To determine whether the disease-causing poly-Q mutation in Htt affects synapse development, we next investigated the synaptic connectivity in a full-length knock-in mouse model of HD, the zQ175 mouse. Similar to the cortical conditional knock-outs, we found excessive excitatory synapse formation and maturation in the cortices of P21 zQ175, which was lost by 5 weeks. Together, our findings reveal that cortical Htt is required for the correct establishment of cortical and striatal excitatory circuits, and this function of Htt is lost when the mutant Htt is present.

Funding information:
  • NIGMS NIH HHS - R01 GM072881(United States)

Inflammation-inducible type 2 deiodinase expression in the leptomeninges, choroid plexus, and at brain blood vessels in male rodents.

  • Wittmann G
  • Endocrinology
  • 2014 May 21

Literature context:


Abstract:

Thyroid hormone regulates immune functions and has antiinflammatory effects. In promoter assays, the thyroid hormone-activating enzyme, type 2 deiodinase (D2), is highly inducible by the inflammatory transcription factor nuclear factor-κ B (NF-κB), but it is unknown whether D2 is induced in a similar fashion in vivo during inflammation. We first reexamined the effect of bacterial lipopolysaccharide (LPS) on D2 expression and NF-κB activation in the rat and mouse brain using in situ hybridization. In rats, LPS induced very robust D2 expression in normally non-D2-expressing cells in the leptomeninges, adjacent brain blood vessels, and the choroid plexus. These cells were vimentin-positive fibroblasts and expressed the NF-κB activation marker, inhibitor κ B-α mRNA, at 2 hours after injection, before the increase in D2 mRNA. In mice, LPS induced intense D2 expression in the choroid plexus but not in leptomeninges, with an early expression peak at 2 hours. Moderate D2 expression along numerous brain blood vessels appeared later. D2 and NF-κB activation was induced in tanycytes in both species but with a different time course. Enzymatic assays from leptomeningeal and choroid plexus samples revealed exceptionally high D2 activity in LPS-treated rats and Syrian hamsters and moderate but significant increases in mice. These data demonstrate the cell type-specific, highly inducible nature of D2 expression by inflammation, and NF-κB as a possible initiating factor, but also warrant attention for species differences. The results suggest that D2-mediated T₃ production by fibroblasts regulate local inflammatory actions in the leptomeninges, choroid plexus and brain blood vessels, and perhaps also in other organs.

Funding information:
  • NICHD NIH HHS - R24 HD050838(United States)

Migration of bone marrow-derived cells into the central nervous system in models of neurodegeneration.

  • Lampron A
  • J. Comp. Neurol.
  • 2013 Dec 1

Literature context:


Abstract:

Microglia are the brain-resident macrophages tasked with the defense and maintenance of the central nervous system (CNS). The hematopoietic origin of microglia has warranted a therapeutic potential for the hematopoietic system in treating diseases of the CNS. However, migration of bone marrow-derived cells (BMDC) into the CNS is a marginal event under normal, healthy conditions. A busulfan-based chemotherapy regimen was used for bone marrow transplantation in wild-type mice before subjecting them to a hypoxic-ischemic brain injury or in APP/PS1 mice prior to the formation of amyloid plaques. The cells were tracked and analyzed throughout the development of the pathology. The efficacy of a preventive macrophage colony-stimulating factor (M-CSF) treatment was also studied to highlight the effects of circulating monocytes in hypoxic-ischemic brain injury. Such an injury induces a strong migration of BMDC into the CNS, without the need for irradiation. These migrating cells do not replace the entire microglial pool but rather are confined to the sites of injury for several weeks, suggesting that they could perform specific functions. M-CSF showed neuroprotective effects as a preventive treatment. In APP/PS1 mice, the formation of amyloid plaques was sufficient to induce the entry of cells into the parenchyma, though in low numbers. This study confirms that BMDC infiltrate the CNS in animal models for stroke and Alzheimer's disease and that peripheral cells can be targeted to treat affected regions of the CNS.

Funding information:
  • Cancer Research UK - C355/A6253(United Kingdom)

Dim light at night exaggerates weight gain and inflammation associated with a high-fat diet in male mice.

  • Fonken LK
  • Endocrinology
  • 2013 Oct 23

Literature context:


Abstract:

Elevated nighttime light exposure is associated with symptoms of metabolic syndrome. In industrialized societies, high-fat diet (HFD) and exposure to light at night (LAN) often cooccur and may contribute to the increasing obesity epidemic. Thus, we hypothesized that dim LAN (dLAN) would provoke additional and sustained body mass gain in mice on a HFD. Male mice were housed in either a standard light/dark cycle or dLAN and fed either chow or HFD. Exposure to dLAN and HFD increase weight gain, reduce glucose tolerance, and alter insulin secretion as compared with light/dark cycle and chow, respectively. The effects of dLAN and HFD appear additive, because mice exposed to dLAN that were fed HFD display the greatest increases in body mass. Exposure to both dLAN and HFD also change the timing of food intake and increase TNFα and MAC1 gene expression in white adipose tissue after 4 experimental weeks. Changes in MAC1 gene expression occur more rapidly due to HFD as compared with dLAN; after 5 days of experimental conditions, mice fed HFD already increase MAC1 gene expression in white adipose tissue. HFD also elevates microglia activation in the arcuate nucleus of the hypothalamus and hypothalamic TNFα, IL-6, and Ikbkb gene expression. Microglia activation is increased by dLAN, but only among chow-fed mice and dLAN does not affect inflammatory gene expression. These results suggest that dLAN exaggerates weight gain and peripheral inflammation associated with HFD.

Funding information:
  • NIGMS NIH HHS - R01 GM049831(United States)

RANTES has a potential to play a neuroprotective role in an autocrine/paracrine manner after ischemic stroke.

  • Tokami H
  • Brain Res.
  • 2013 Jun 23

Literature context:


Abstract:

Regulated upon Activation, Normal T-cell Expressed, and Secreted (RANTES) is a well-known pro-inflammatory chemokine and its role in ischemic stroke remains controversial. We examined the significance of RANTES in ischemic stroke and aimed to elucidate the direct effect of RANTES on neurons. Plasma concentrations of major C-C chemokines, including RANTES, and neurotrophic factors were examined in 171 ischemic stroke patients and age- and gender- matched healthy subjects. Plasma concentrations of RANTES at day 0 after onset were significantly elevated in stroke patients, compared with controls, and were highly correlated with those of BDNF, EGF, and VEGF. In a mouse middle cerebral artery occlusion model (MCAO), plasma RANTES was significantly elevated and the expression of RANTES was markedly upregulated in neurons particularly in peri-infarct areas. The expression of CCR3 and CCR5, receptors for RANTES, was also induced in neurons, while another receptor, CCR1, was observed in vascular cells, in peri-infarct areas after MCAO. We examined the effects of RANTES on differentiated PC12 cells, a model of neuronal cells. Treatment with RANTES induced the activation of Akt and Erk1/2, and attenuated the cleavage of caspase-3 in the cells. RANTES increased the expression of BDNF, EGF, and VEGF in the cells. Moreover, RANTES maintained the number of cells under serum free conditions. The RANTES-mediated upregulation of neurotrophic factors and cell survival were significantly attenuated by the inhibition of Akt or Erk1/2. Taken together, RANTES is an interesting chemokine that is produced from neurons after ischemic stroke and has the potential to protect neurons directly or indirectly through the production of neurotrophic factors in peri-infarct areas.

Funding information:
  • NIDDK NIH HHS - 5R01DK069983-02(United States)

Peripubertal proliferation of progenitor cells in the preoptic area of Japanese quail (Coturnix japonica).

  • Mouriec K
  • Brain Res.
  • 2013 Jun 21

Literature context:


Abstract:

Brain structures related to reproduction are thought to depend on the action of gonadal steroids acting either during early life (organizing irreversible effects) or adulthood (activating transient effects). More recently puberty has become a focus of attention and it was demonstrated that action of sex steroid hormones at this time plays a critical role in the final organization of brain and behavior. We studied by BrdU immunohistochemistry the ontogeny from hatching to sexual maturity of a previously identified cell population in the preoptic area labeled by a BrdU injection at the end of embryonic period (E12) of sexual differentiation in male and female Japanese quail. After an initial increase between E12 and hatching, the density of BrdU-immunoreactive cells decreased until the beginning of puberty but then increased again during sexual maturation in the caudal preoptic area specifically. Divisions of these cells took place in the brain parenchyma as indicated by the large numbers of pairs of labeled cells. No sex difference affecting these processes could be detected at any stage of development. Large numbers of new cells thus arise around puberty in the caudal preoptic area and presumably contribute to the reorganization of this structure that precedes the emergence of adult reproductive behaviors.

Funding information:
  • NHGRI NIH HHS - R01-HG004885(United States)

Striatal oligodendrogliogenesis and neuroblast recruitment are increased in the R6/2 mouse model of Huntington's disease.

  • McCollum MH
  • Brain Res.
  • 2013 Jun 26

Literature context:


Abstract:

The subventricular zone (SVZ) is one of the two major neurogenic regions in the adult mammalian brain. Its close proximity to the striatum suggests that a cell-based therapeutic strategy for the treatment of Huntington's disease (HD) is possible. To achieve this, it is important to understand how adult cell production, migration and differentiation may be altered in the HD brain. In this study, we quantified the number of adult-born striatal cells and characterized their fate in the R6/2 transgenic mouse model of HD. We found that the number of new striatal cells was approximately two-fold greater in R6/2 vs. wild type mice, while SVZ cell proliferation was not affected. Using cell-type specific markers, we demonstrated that the majority of new striatal cells were mature oligodendrocytes or oligodendroglial precursors that were intrinsic to the striatum. We also detected a significant increase in the number of migrating neuroblasts that appeared to be recruited from the SVZ to the striatum. However, these neuroblasts did not mature into neurons and most were lost between 1 and 2 weeks of cell age. Crossing the R6/2 mice with mice the over-expressing brain-derived neurotrophic factor in the striatum increased the numbers of neuroblasts that survived to 2 weeks, but did not promote their differentiation. Together, our data indicate that the potential treatment of HD based on manipulating endogenous progenitor cells should take into consideration the apparent enhancement in striatal oligodendrogliogenesis and the limited ability of recruited SVZ neuroblasts to survive long-term and differentiate in the diseased striatum.

Funding information:
  • Canadian Institutes of Health Research - (Canada)

Novel objective classification of reactive microglia following hypoglossal axotomy using hierarchical cluster analysis.

  • Yamada J
  • J. Comp. Neurol.
  • 2013 Apr 1

Literature context:


Abstract:

A total of 136 microglia were intracellularly labeled and their morphological features were evaluated by 3D morphometric measurement. According to hierarchical cluster analysis, microglia were objectively categorized into four groups termed types I-IV. The validity of this classification was confirmed by principal component analysis and linear discriminant analysis. Type I microglia were found in sham-operated mice and in mice sacrificed 28 days (D28) after axotomy. The appearance of type I cells was similar to so-called ramified microglia in a resting state. Type II microglia were mainly seen in D14 mice, which exhibited small cell bodies with thin and short processes. Interestingly, none of the already-known morphological types of microglia seemed to be comparable to type II cells. We thus named type II microglia "small ramified" cells. Types III and IV microglia were mainly seen in D3 and D7 mice and their appearances were similar to hypertrophied and bushy cells, respectively. Proliferating cell nuclear antigen (PCNA), a mitosis marker, was almost exclusively expressed in D3 mice. On the other hand, voltage-dependent potassium channels (Kv1.3/1.5), neurotoxicity-related molecules, were most highly expressed in D14 mice. Increased expression of Kv1.3/1.5 in D14 mice was suppressed by minocycline treatment. These findings indicate that type II and III microglia may be involved in neurotoxicity and mitosis, respectively. Type IV microglial cells are assumed to be in the process of losing mitotic activity and gaining neurotoxicity. Our data also suggest that type II microglia can be a potential therapeutic target against neurodegenerative diseases.

Funding information:
  • NHLBI NIH HHS - U01-HL-061744(United States)
  • Wellcome Trust - (United Kingdom)

A cell population that strongly expresses the CB1 cannabinoid receptor in the ependyma of the rat spinal cord.

  • Garcia-Ovejero D
  • J. Comp. Neurol.
  • 2013 Jan 1

Literature context:


Abstract:

The cells surrounding the central canal of the spinal cord are a source of stem/precursor cells that may give rise to neurons, astrocytes, or oligodendrocytes. However, they are a heterogeneous population that remains poorly understood. Here we describe a subpopulation characterized by their strong expression of the CB(1) cannabinoid receptor, oval/round soma, apical nucleus, a variable number of cilia (0, 1, or 2), and the presence of a single short and occasionally ramified basal process. These cells are mainly located in the lateral and dorsal central canal throughout the spinal cord. These CB(1)(HIGH) cells are closely related to the basal lamina labyrinths or fractones derived from subependymal microglia. In addition, CB(1)(HIGH) cells express some stem/precursor cell markers, including vimentin, nestin, Sox2, Sox9, and GLAST, but not others such as CD15 or GFAP. In addition, this cell population does not proliferate in the intact adult spinal cord, although up to 50% of these cells express the proliferation marker Ki67 in newly born rats or after a spinal cord contusion. The present findings contribute to our understanding of the spinal cord central canal structure and reveal the targets for endocannabinoids inside this neurogenic niche.

Funding information:
  • Howard Hughes Medical Institute - NS072360(United States)
  • NIGMS NIH HHS - GM068118(United States)

Long-term interaction between microglial cells and cochlear nucleus neurons after bilateral cochlear ablation.

  • Fuentes-Santamaría V
  • J. Comp. Neurol.
  • 2012 Sep 1

Literature context:


Abstract:

The removal of afferent activity has been reported to modify neuronal activity in the cochlear nucleus of adult rats. After cell damage, microglial cells are rapidly activated, initiating a series of cellular responses that influences neuronal function and survival. To investigate how this glial response occurs and how it might influence injured neurons, bilateral cochlear ablations were performed on adult rats to examine the short-term (16 and 24 hours and 4 and 7 days) and long-term (15, 30, and 100 days) changes in the distribution and morphology of microglial cells (immunostained with the ionized calcium-binding adaptor molecule 1; Iba-1) and the interaction of microglial cells with deafferented neurons in the ventral cochlear nucleus. A significant increase in the mean cross-sectional area and Iba-1 immunostaining of microglial cells in the cochlear nucleus was observed at all survival times after the ablation compared with control animals. These increases were concomitant with an increase in the area of Iba-1 immunostaining at 24 hours and 4, 7, and 15 days postablation. Additionally, microglial cells were frequently seen apposing the cell bodies and dendrites of auditory neurons at 7, 15, and 30 days postablation. In summary, these results provide evidence for persistent glial activation in the ventral cochlear nucleus and suggest that long-term interaction occurs between microglial cells and deafferented cochlear nucleus neurons following bilateral cochlear ablation, which could facilitate the remodeling of the affected neuronal circuits.

Funding information:
  • NEI NIH HHS - EY-03592(United States)
  • NIAID NIH HHS - HHSN272201400048C(United States)

SPARC-like 1 (SC1) is a diversely expressed and developmentally regulated matricellular protein that does not compensate for the absence of SPARC in the CNS.

  • Lloyd-Burton S
  • J. Comp. Neurol.
  • 2012 Aug 15

Literature context:


Abstract:

SPARC-like 1 (SC1) is a member of the SPARC family of matricellular proteins that has been implicated in the regulation of processes such as cell migration, proliferation, and differentiation. Here we show that SC1 exhibits remarkably diverse and dynamic expression in the developing and adult nervous system. During development, SC1 localizes to radial glia and pial-derived structures, including the vasculature, choroid plexus, and pial membranes. SC1 is not downregulated in postnatal development, but its expression shifts to distinct time windows in subtypes of glia and neurons, including astrocytes, large projection neurons, Bergmann glia, Schwann cells, and ganglionic satellite cells. In addition, SC1 expression levels and patterns are not altered in the SPARC null mouse, suggesting that SC1 does not compensate for the absence of SPARC. We conclude that SC1 and SPARC may share significant homology, but are likely to have distinct but complementary roles in nervous system development.

Funding information:
  • NINDS NIH HHS - R01 NS085387(United States)

Increase of close homolog of cell adhesion molecule L1 in primary afferent by nerve injury and the contribution to neuropathic pain.

  • Yamanaka H
  • J. Comp. Neurol.
  • 2011 Jun 1

Literature context:


Abstract:

The L1 family of cell adhesion molecules (L1-CAMs) is known to be involved in various neuronal functions such as cell adhesion, axon guidance, and synaptic plasticity. We investigated the detailed expression/changes of a close homolog of the L1 cell adhesion molecule (CHL1) after nerve injury and the possible role on neuropathic pain using the rat spared nerve injury (SNI) model. SNI induced the expression of CHL1 in L4/5 DRG neurons, particularly in small-size injured neurons and in satellite cells. In the spinal cord, CHL1 immunoreactivity increased mainly in laminae I-II of the dorsal horn on the side ipsilateral to the nerve injury. Ultrastructural study clarified the fine localization of CHL1 in axons of primary afferents in the dorsal horn. CHL1 immunoreactivities were localized in the adherence such as axon-axon, axon-dorsal horn neurons (dendrite, soma), and axon-glial cells (astrocyte and microglia). Experimental inhibition of CHL1 adhesion by intrathecal administration of the antibody for CHL1 extracellular domain significantly prevented and reversed SNI-induced mechanical allodynia. Thus, alterations of CHL1 may be involved in the structural plasticity after peripheral nerve injury and have important roles in neuropathic pain.

Funding information:
  • NIBIB NIH HHS - EB006733(United States)
  • NINDS NIH HHS - NS19865(United States)

Early microglia activation in a mouse model of chronic glaucoma.

  • Bosco A
  • J. Comp. Neurol.
  • 2011 Mar 1

Literature context:


Abstract:

Changes in microglial cell activation and distribution are associated with neuronal decline in the central nervous system (CNS), particularly under pathological conditions. Activated microglia converge on the initial site of axonal degeneration in human glaucoma, yet their part in its pathophysiology remains unresolved. To begin with, it is unknown whether microglia activation precedes or is a late consequence of retinal ganglion cell (RGC) neurodegeneration. Here we address this critical element in DBA/2J (D2) mice, an established model of chronic inherited glaucoma, using as a control the congenic substrain DBA/2J Gpnmb(+/SjJ) (D2G), which is not affected by glaucoma. We analyzed the spatial distribution and timecourse of microglial changes in the retina, as well as within the proximal optic nerve prior to and throughout ages when neurodegeneration has been reported. Exclusively in D2 mice, we detected early microglia clustering in the inner central retina and unmyelinated optic nerve regions, with microglia activation peaking by 3 months of age. Between 5 and 8 months of age, activated microglia persisted and concentrated in the optic disc, but also localized to the retinal periphery. Collectively, our findings suggest microglia activation is an early alteration in the retina and optic nerve in D2 glaucoma, potentially contributing to disease onset or progression. Ultimately, detection of microglial activation may have value in early disease diagnosis, while modulation of microglial responses may alter disease progression.

Funding information:
  • NHGRI NIH HHS - P01 HG004120(United States)

Characterization of retinal function and glial cell response in a mouse model of oxygen-induced retinopathy.

  • Vessey KA
  • J. Comp. Neurol.
  • 2011 Feb 15

Literature context:


Abstract:

Retinal neovascularization, such as that occurring in proliferative diabetic retinopathy and retinopathy of prematurity, can have serious effects on visual function. By using a mouse model of neovascularization, oxygen-induced retinopathy (OIR), the interplay among angiogenesis, neuronal function, and the macro- and micro-glial response was explored. OIR was induced by exposure of mice to 75% oxygen from postnatal day 7 (P7) to P11 and then room air until P18. Controls were reared in room air. Blood vessel development was assessed by using fluorescence histochemistry. Aberrant intravitreal neovascularization was present across all eccentricities of retina in mice with OIR, whereas the number of vessels present in the deep plexus was reduced in the central regions. Neuronal function of both the rod and cone pathways, assessed by using the electroretinogram, was found to be significantly reduced in OIR. This may in part be explained by an alteration in photoreceptor outer segment morphology and also a loss of neurons and their synapses in the inner nuclear and plexiform layers of the central retina. In addition, there was an increase in the number of gliotic Müller cells and microglia in mice with OIR and the increase in the number of these cells correlated with the absence of the deep plexus. This indicates that the activity of both macro- and microglia is altered in regions where the deep plexus blood supply is deficient. Treatments or genetic manipulations directed toward amelioration of proliferative retinopathy need to address not only the vascular changes but also the alterations in neuronal and macro- and microglial function.

Funding information:
  • NCI NIH HHS - RC2CA148317(United States)

Progranulin expression in the developing and adult murine brain.

  • Petkau TL
  • J. Comp. Neurol.
  • 2010 Oct 1

Literature context:


Abstract:

Frontotemporal lobar degeneration (FTLD) is a neurodegenerative condition characterized by focal degeneration of the frontal and temporal lobes of the brain. Autosomal dominantly inherited mutations of the progranulin gene (GRN) have been identified as the cause of a subset of cases of familial FTLD. In order to better understand the function of progranulin in the central nervous system (CNS), we have assessed the spatiotemporal expression pattern of both the murine progranulin gene (Grn) and the protein (Grn) by using transgenic knock-in mice expressing a reporter gene from the Grn locus and by immunohistochemistry, respectively. We compared Grn expression with a panel of established markers for distinct neuronal developmental stages and specific cell lineages at time points ranging from embryonic day 13.5 through to the mature adult. We find that Grn is expressed in both neurons and microglia within the CNS, but that it shows a different developmental expression pattern in each cell type. Grn expression in neurons increases as the cells mature, whereas expression in microglia varies with the cells' state of activation, being specifically upregulated in microglia in response to excitotoxic injury. Our results suggest that progranulin plays distinct roles in neurons and microglia, both of which likely contribute to overall neuronal health and function.

Funding information:
  • NCATS NIH HHS - UL1 TR000127(United States)

Beneficial effects of antioxidant-enriched diet for tyrosine hydroxylase-positive neurons in ventral mesencephalic tissue in oculo grafts.

  • Berglöf E
  • J. Comp. Neurol.
  • 2009 Jul 1

Literature context:


Abstract:

Supplementation of antioxidants to the diet has been proved to be beneficial in aging and after brain injury. Furthermore, it has been postulated that the locus coeruleus promotes survival of dopamine neurons. Thus, this study was performed to elucidate the effects of a blueberry-enriched diet on fetal ventral mesencephalic tissue in the presence or absence of locus coeruleus utilizing the in oculo grafting method. Sprague-Dawley rats were given control diet or diet supplemented with 2% blueberries, and solid tissue pieces of fetal locus coeruleus and ventral mesencephalon were implanted as single and co-grafts. The results revealed that the presence of locus coeruleus tissue or the addition of blueberries enhanced the survival of ventral mesencephalic tyrosine hydroxylase (TH)-positive neurons, whereas no additive effects were observed for the two treatments. The density of TH-positive nerve fibers in ventral mesencephalic tissue was significantly elevated when it was attached to the locus coeruleus or by blueberry treatment, whereas the innervation of dopamine-beta-hydroxylase-positive nerve fibers was not altered. The presence of locus coeruleus tissue or bluberry supplementation reduced the number of Iba-1-positive microglia in the ventral mesencephalic portion of single and co-grafts, respectively, whereas almost no OX6 immunoreactivity was found. Furthermore, neither the attachment of ventral mesencephalic tissue nor the addition of blueberries improved the survival of TH-positive neurons in the locus coerulean grafts. To conclude, locus coeruleus and blueberries are beneficial for the survival of fetal ventral mesencephalic tissue, findings that could be useful when grafting tissue in Parkinson's disease.

Close homologue of adhesion molecule L1 promotes survival of Purkinje and granule cells and granule cell migration during murine cerebellar development.

  • Jakovcevski I
  • J. Comp. Neurol.
  • 2009 Apr 10

Literature context:


Abstract:

Several L1-related adhesion molecules, expressed in a well-coordinated temporospatial pattern during development, are important for fine tuning of specific cerebellar circuitries. We tested the hypothesis that CHL1, the close homologue of L1, abundantly expressed in the developing and adult cerebellum, is also required for normal cerebellar histogenesis. We found that constitutive ablation of CHL1 in mice caused significant loss (20-23%) of Purkinje and granule cells in the mature 2-month-old cerebellum. The ratio of stellate/basket interneurons to Purkinje cells was abnormally high (+38%) in CHL1-deficient (CHL1-/-) mice compared with wild-type (CHL1+/+) littermates, but the gamma-aminobutyric acid (GABA)ergic synaptic inputs to Purkinje cell bodies and dendrites were normal, as were numbers of Golgi interneurons, microglia, astrocytes, and Bergmann glia. Purkinje cell loss occurred before the first postnatal week and was associated with enhanced apoptosis, presumably as a consequence of CHL1 deficiency in afferent axons. In contrast, generation of granule cells, as indicated by in vivo analyses of cell proliferation and death, was unaffected in 1-week-old CHL1-/- mice, but numbers of migrating granule cells in the molecular layer were increased. This increase was likely related to retarded cell migration because CHL1-/- granule cells migrated more slowly than CHL1+/+ cells in vitro, and Bergmann glial processes guiding migration in vivo expressed CHL1 in wild-type mice. Granule cell deficiency in adult CHL1-/- mice appeared to result from decreased precursor cell proliferation after the first postnatal week. Our results indicate that CHL1 promotes Purkinje and granule cell survival and granule cell migration during cerebellar development.

Funding information:
  • NICHD NIH HHS - P30 HD15052(United States)

Neonatal hypoxic/ischemic brain injury induces production of calretinin-expressing interneurons in the striatum.

  • Yang Z
  • J. Comp. Neurol.
  • 2008 Nov 1

Literature context:


Abstract:

Ischemia-induced striatal neurogenesis from progenitors in the adjacent subventricular zone (SVZ) in young and adult rodents has been reported. However, it has not been established whether the precursors that reside in the SVZ retain the capacity to produce the full range of striatal neurons that has been destroyed. By using a neonatal rat model of hypoxic/ischemic brain damage, we show here that virtually all of the newly produced striatal neurons are calretinin (CR)-immunoreactive (+), but not DARPP-32(+), calbindin-D-28K(+), parvalbumin(+), somatostatin(+), or choline acetyltransferase(+). Retroviral fate-mapping studies confirm that these newly born CR(+) neurons are indeed descendants of the SVZ. Our studies indicate that, although the postnatal SVZ has the capacity to produce a range of neurons, only a subset of this repertoire is manifested in the brain after injury.

Tauopathy with paired helical filaments in an aged chimpanzee.

  • Rosen RF
  • J. Comp. Neurol.
  • 2008 Jul 20

Literature context:


Abstract:

An enigmatic feature of age-related neurodegenerative diseases is that they seldom, if ever, are fully manifested in nonhuman species under natural conditions. The neurodegenerative tauopathies are typified by the intracellular aggregation of hyperphosphorylated microtubule-associated protein tau (MAPT) and the dysfunction and death of affected neurons. We document the first case of tauopathy with paired helical filaments in an aged chimpanzee (Pan troglodytes). Pathologic forms of tau in neuronal somata, neuropil threads, and plaque-like clusters of neurites were histologically identified throughout the neocortex and, to a lesser degree, in allocortical and subcortical structures. Ultrastructurally, the neurofibrillary tangles consisted of tau-immunoreactive paired helical filaments with a diameter and helical periodicity indistinguishable from those seen in Alzheimer's disease. A moderate degree of Abeta deposition was present in the cerebral vasculature and, less frequently, in senile plaques. Sequencing of the exons and flanking intronic regions in the genomic MAPT locus disclosed no mutations that are associated with the known human hereditary tauopathies, nor any polymorphisms of obvious functional significance. Although the lesion profile in this chimpanzee differed somewhat from that in Alzheimer's disease, the copresence of paired helical filaments and Abeta-amyloidosis indicates that the molecular mechanisms for the pathogenesis of the two canonical Alzheimer lesions--neurofibrillary tangles and senile plaques--are present in aged chimpanzees.

CD11c/EYFP transgene illuminates a discrete network of dendritic cells within the embryonic, neonatal, adult, and injured mouse brain.

  • Bulloch K
  • J. Comp. Neurol.
  • 2008 Jun 10

Literature context:


Abstract:

The CD11c enhanced yellow fluorescent protein (EYFP) transgenic mouse was constructed to identify dendritic cells in the periphery (Lindquist et al. [2004] Nat. Immunol. 5:1243-1250). In this study, we used this mouse to characterize dendritic cells within the CNS. Our anatomic results showed discrete populations of EYFP(+) brain dendritic cells (EYFP(+) bDC) that colocalized with a small fraction of microglia immunoreactive for Mac-1, Iba-1, CD45, and F4/80 but not for NeuN, Dcx, NG2 proteoglycan, or GFAP. EYFP(+) bDC, isolated by fluorescent activated cell sorting (FACS), expressed mRNA for the Itgax (CD11c) gene, whereas FACS anlaysis of EYFP(+) bDC cultures revealed the presence of CD11c protein. Light microscopy studies revealed that EYFP(+) bDC were present in the embryonic CNS when the blood-brain barrier is formed and postnatally when brain cells are amenable to culturing. In adult male mice, EYFP(+) bDC distribution was prominent within regions of the CNS that 1) are subject to structural plasticity and neurogenesis, 2) receive sensory and humoral input from the external environment, and 3) lack a blood-brain barrier. Ultrastructural analysis of EYFP(+) bDC in adult neurogenic niches showed their proximity to developing neurons and a morphology characteristic of immune/microglia cells. Kainic acid-induced seizures revealed that EYFP(+) bDC responded to damage of the hippocampus and displayed morphologies similar to those described for seizure-activated EGFP(+) microglia in the hippocampus of cfms (CSF-1R) EGFP mice. Collectively, these findings suggest a new member of the dendritic cell family residing among the heterogeneous microglia population.

Funding information:
  • NIGMS NIH HHS - GM 074746(United States)

Griffonia simplicifolia isolectin B4 identifies a specific subpopulation of angiogenic blood vessels following contusive spinal cord injury in the adult mouse.

  • Benton RL
  • J. Comp. Neurol.
  • 2008 Mar 1

Literature context:


Abstract:

After traumatic spinal cord injury (SCI), disruption and plasticity of the microvasculature within injured spinal tissue contribute to the pathological cascades associated with the evolution of both primary and secondary injury. Conversely, preserved vascular function most likely results in tissue sparing and subsequent functional recovery. It has been difficult to identify subclasses of damaged or regenerating blood vessels at the cellular level. Here, adult mice received a single intravenous injection of the Griffonia simplicifolia isolectin B4 (IB4) at 1-28 days following a moderate thoracic (T9) contusion. Vascular binding of IB4 was maximally observed 7 days following injury, a time associated with multiple pathologic aspects of the intrinsic adaptive angiogenesis, with numbers of IB4 vascular profiles decreasing by 21 days postinjury. Quantitative assessment of IB4 binding shows that it occurs within the evolving lesion epicenter, with affected vessels expressing a temporally specific dysfunctional tight junctional phenotype as assessed by occludin, claudin-5, and ZO-1 immunoreactivities. Taken together, these results demonstrate that intravascular lectin delivery following SCI is a useful approach not only for observing the functional status of neovascular formation but also for definitively identifying specific subpopulations of reactive spinal microvascular elements.

Funding information:
  • NINDS NIH HHS - R01 NS087988(United States)

Embryonic and postnatal development of microglial cells in the mouse retina.

  • Santos AM
  • J. Comp. Neurol.
  • 2008 Jan 10

Literature context:


Abstract:

Macrophage/microglial cells in the mouse retina during embryonic and postnatal development were studied by immunocytochemistry with Iba1, F4/80, anti-CD45, and anti-CD68 antibodies and by tomato lectin histochemistry. These cells were already present in the retina of embryos aged 11.5 days (E11.5) in association with cell death. At E12.5 some macrophage/microglial cells also appeared in peripheral regions of the retina with no apparent relationship with cell death. Immediately before birth microglial cells were present in the neuroblastic, inner plexiform (IPL), and ganglion cell (GCL) layers, and their distribution suggested that they entered the retina from the ciliary margin and the vitreous. The density of retinal microglial cells strongly decreased at birth, increased during the first postnatal week as a consequence of the entry of microglial precursors into the retina from the vitreous, and subsequently decreased owing to the cessation of microglial entry and the increase in retina size. The mature topographical distribution pattern of microglia emerged during postnatal development of the retina, apparently by radial migration of microglial cells from the vitreal surface in a vitreal-to-scleral direction. Whereas microglial cells were only seen in the GCL and IPL at birth, they progressively appeared in more scleral layers at increasing postnatal ages. Thus, microglial cells were present within all layers of the retina except the outer nuclear layer at the beginning of the second postnatal week. Once microglial cells reached their definitive location, they progressively ramified.

Funding information:
  • NEI NIH HHS - EY002520(United States)

Time course and distribution of inflammatory and neurodegenerative events suggest structural bases for the pathogenesis of experimental autoimmune encephalomyelitis.

  • Brown DA
  • J. Comp. Neurol.
  • 2007 May 10

Literature context:


Abstract:

Murine models of experimental autoimmune encephalomyelitis (EAE) are important vehicles for studying the effects of genetic manipulation on disease processes related to multiple sclerosis (MS). Currently, a comprehensive assessment of EAE pathogenesis with respect to inflammatory and degenerating neuronal elements is lacking. By using Fluoro-jade histochemistry to mark neurodegeneration and dual immunostaining to follow T-cell, microglial, and vascular responses, the time course and distribution of pathological events in EAE was surveyed. C57BL/6J mice were killed at 7, 10, 14, 21 or 35 days after vaccination with the myelin oligodendrocyte glycoprotein peptide MOG(35-55). Disease onset occurred at day 14 and peaked at day 21. Early T-cell infiltration and microglial activation in periventricular and superficial white matter structures adjacent to meninges suggested initial recruitment of effector T cells via the cerebrospinal fluid and choroid plexus. This was associated with microglial activation at distal sites along the same white matter tracts, with subsequent vascular recruitment of T cells associated with further injury. Systematic examination of the entire CNS supported this two-step model of EAE pathogenesis, with inflammation and neurodegeneration commencing at similar times and affecting multiple levels of predominantly sensory central pathways, including their terminal fields. This included aspects of the visual, auditory/vestibular, somatosensory (lemniscal), and proprioceptive (spinocerebellar) systems. The early targeting of visual and periventricular structures followed by more widespread CNS involvement is consistent with common presenting signs in human MS patients and suggestive of a similar basis in neuropathology.

Funding information:
  • NINDS NIH HHS - R01 NS083898(United States)

Glial influence on nerve fiber formation from rat ventral mesencephalic organotypic tissue cultures.

  • Berglöf E
  • J. Comp. Neurol.
  • 2007 Mar 20

Literature context:


Abstract:

Rat fetal ventral mesencephalic organotypic cultures have demonstrated two morphologically different dopamine nerve fiber growth patterns, in which the initial nerve fibers are formed in the absence of astrocytes and the second wave is guided by astrocytes. In this study, the presence of subpopulations of dopamine neurons, other neuronal populations, and glial cells was determined. We used "roller-drum" organotypic cultures, and the results revealed that beta-tubulin-positive/tyrosine hydroxylase (TH)-negative nerve fibers were present as early as 1 day in vitro (DIV). A similar growth pattern produced by TH-positive neurons was present from 2 DIV. These neurites grew to reach distances over 4 mm and over time appeared to be degenerating. Thin, vimentin-positive processes were found among these nerve fibers. As the first growth was retracted, a second outgrowth was initiated and formed on migrating astrocytes. TH- and aldehyde dehydrogenase-1 (ALDH1)-positive nerve fibers formed both the nonglia-associated and the glia-associated outgrowth. In cultures with membrane inserts, only the glia-associated outgrowth was found. Vimentin-positive cells preceded migration of NG2-positive oligodendrocytes and Iba-1-positive microglia. Oligodendrocytes appeared not to be involved in guiding neuritic growth, but microglia was absent over areas dense with TH-positive neurons. In conclusion, in "roller-drum" cultures, nerve fibers are generally formed in two sequences. The early-formed nerve fibers grow in the presence of thin, vimentin-positive processes. The second nerve fiber outgrowth is formed on astroglia, with no correlation to the presence of oligodendrocytes or microglia. ALDH1-positive nerve fibers, presumably derived from A9 dopamine neurons, participate in formation of both sequences of outgrowth.

Funding information:
  • NIDA NIH HHS - R01 DA031833(United States)

Proinflammatory cytokine synthesis in the injured mouse spinal cord: multiphasic expression pattern and identification of the cell types involved.

  • Pineau I
  • J. Comp. Neurol.
  • 2007 Jan 10

Literature context:


Abstract:

We have studied the spatial and temporal distribution of six proinflammatory cytokines and identified their cellular source in a clinically relevant model of spinal cord injury (SCI). Our findings show that interleukin-1beta (IL-1beta) and tumor necrosis factor (TNF) are rapidly (<5 and 15 minutes, respectively) and transiently expressed in mice following contusion. At 30-45 minutes post SCI, IL-1beta and TNF-positive cells could already be seen over the entire spinal cord segment analyzed. Multilabeling analyses revealed that microglia and astrocytes were the two major sources of IL-1beta and TNF at these times, suggesting a role for these cytokines in gliosis. Results obtained from SCI mice previously transplanted with green fluorescent protein (GFP)-expressing hematopoietic stem cells confirmed that neural cells were responsible for the production of IL-1beta and TNF for time points preceding 3 hours. From 3 hours up to 24 hours, IL-1beta, TNF, IL-6, and leukemia inhibitory factor (LIF) were strongly upregulated within and immediately around the contused area. Colocalization studies revealed that all populations of central nervous system resident cells, including neurons, synthesized cytokines between 3 and 24 hours post SCI. However, work done with SCI-GFP chimeric mice revealed that at least some infiltrating leukocytes were responsible for cytokine production from 12 hours on. By 2 days post-SCI, mRNA signal for all the above cytokines had nearly disappeared. Notably, we also observed another wave of expression for IL-1beta and TNF at 14 days. Overall, these results indicate that following SCI, all classes of neural cells initially contribute to the organization of inflammation, whereas recruited immune cells mostly contribute to its maintenance at later time points.

Funding information:
  • Howard Hughes Medical Institute - 5U24CA143858(United States)
  • NEI NIH HHS - R01-EY12654(United States)

Differential response of arcuate proopiomelanocortin- and neuropeptide Y-containing neurons to the lesion produced by gold thioglucose administration.

  • Homma A
  • J. Comp. Neurol.
  • 2006 Nov 1

Literature context:


Abstract:

The effect of gold thioglucose (GTG) administration on neurons containing feeding-related peptides in the hypothalamic arcuate nucleus was examined in mice. Intraperitoneal GTG injection increased the body weight and produced a hypothalamic lesion that extended from the ventral part of the ventromedial nucleus to the dorsal part of the arcuate nucleus. Neurons containing proopiomelanocortin (POMC) and neuropeptide Y (NPY) present in the dorsal part of the arcuate nucleus were destroyed by GTG. In addition, the peptide-containing fibers that extended from the remaining arcuate neurons were degenerated at the lesion site. The number of POMC-containing fibers in the paraventricular nucleus, dorsomedial nucleus, and lateral hypothalamus was found to have decreased significantly when examined at 2 days and 2 weeks after the GTG treatment. In contrast, the number of NPY-containing fibers in the lateral hypothalamus remained unchanged after the GTG treatment, probably because of the presence of an unaffected NPY-containing fiber pathway passing through the tuberal region and projecting onto the lateral hypothalamus. The number of NPY-immunoreactive fibers in the paraventricular and dorsomedial nuclei showed a moderate but significant decrease at 2 days after the GTG treatment, but it recovered to the normal levels 2 weeks later. The NPY-containing fibers were found to have regenerated across the lesion site 2 weeks later, and this might contribute to the recovery of the NPY-immunoreactive fibers in these regions. The present results first demonstrate that POMC- and NPY-containing neurons in the arcuate nucleus respond differently to the lesion produced by the GTG treatment.

Funding information:
  • NEI NIH HHS - EY11105(United States)
  • NIGMS NIH HHS - R01-GM65466-01(United States)