Neonatal encephalopathy is associated with high mortality and life-long developmental consequences. Therapeutic options are very limited. We assessed the effects of D-JNKi, a small peptide c-Jun N-terminal kinase (JNK) MAP kinase inhibitor, on neuroinflammation, mitochondrial integrity and neuronal damage in a neonatal rat model of ischemic brain damage. Hypoxic-ischemic (HI) brain injury was induced in postnatal-day 7 rats by unilateral carotid artery occlusion and hypoxia, and was followed by intraperitoneal D-JNKi treatment. We demonstrate here for the first time that a single intraperitoneal injection with D-JNKi directly after HI strongly reduces neonatal brain damage by >85% with a therapeutic window of at least 6h. D-JNKi treatment also restored cognitive and motor function as analyzed at 9weeks post-insult. Neuroprotective D-JNKi treatment inhibited phosphorylation of nuclear c-Jun (P-c-Jun), and consequently reduced activity of the AP-1 transcription factor and production of cerebral cytokines/chemokines as determined at 3 and 24h post-HI. Inhibition of P-c-Jun by D-JNKi is thought to be mediated via inhibition of the upstream phosphorylation of cytosolic and nuclear JNK and/or by preventing the direct interaction of phosphorylated (P-)JNK with c-Jun. Surprisingly, however, HI did not induce a detectable increase in P-JNK in cytosol or nucleus. Notably, we show here for the first time that HI induces P-JNK only in the mitochondrial fraction, which was completely prevented by D-JNKi treatment. The hypothesis that mitochondrial JNK activation is key to HI brain injury was supported by data showing that treatment of rat pups with SabKIM1 peptide, a specific mitochondrial JNK inhibitor, is also neuroprotective. Inhibition of HI-induced mitochondrial JNK activation was associated with preservation of mitochondrial integrity as evidenced by prevention of ATP loss and inhibition of lipid peroxidation. The HI-induced increase in apoptotic markers (cytochrome c release and caspase 3 activation) as analyzed at 24h post-HI were also strongly reduced by D-JNKi and the mitochondrial anti-apoptotic proteins Bcl-2 and Bcl-xL were upregulated. Neuroprotection was lost after repeated 0+3h D-JNKi treatment which was associated with complete inhibition of the second peak of AP-1 activity and disability to upregulate mitochondrial Bcl-2 and Bcl-xL. We show here for the first time that D-JNKi treatment efficiently protects the neonatal brain against ischemic brain damage and subsequent cognitive and motor impairment. We propose that inhibition of phosphorylation of mitochondrial JNK is a pivotal step in preventing early loss of mitochondrial integrity leading to reduced neuroinflammation and inhibition of apoptotic neuronal loss. Moreover we show the crucial role of upregulation of mitochondrial anti-apoptotic proteins to maintain neuroprotection.

Chemotherapy-induced cognitive impairment (CICI) is a commonly reported neurotoxic side effect of chemotherapy, occurring in up to 75% cancer patients. CICI manifests as decrements in working memory, executive functioning, attention, and processing speed, and greatly interferes with patients' daily performance and quality of life. Currently no treatment for CICI has been approved by the US Food and Drug Administration. We show here that treatment with a brain-penetrating histone deacetylase 6 (HDAC6) inhibitor for two weeks was sufficient to fully reverse cisplatin-induced cognitive impairments in male mice, as demonstrated in the Y-maze test of spontaneous alternation, the novel object/place recognition test, and the puzzle box test. Normalization of cognitive impairment was associated with reversal of cisplatin-induced synaptosomal mitochondrial deficits and restoration of synaptic integrity. Mechanistically, cisplatin induced deacetylation of the microtubule protein α-tubulin and hyperphosphorylation of the microtubule-associated protein tau. These cisplatin-induced changes were reversed by HDAC6 inhibition. Our data suggest that inhibition of HDAC6 restores microtubule stability and reverses tau phosphorylation, leading to normalization of synaptosomal mitochondrial function and synaptic integrity and thereby to reversal of CICI. Remarkably, our results indicate that short-term daily treatment with the HDAC6 inhibitor was sufficient to achieve prolonged reversal of established behavioral, structural and functional deficits induced by cisplatin. Because the beneficial effects of HDAC6 inhibitors as add-ons to cancer treatment have been demonstrated in clinical trials, selective targeting of HDAC6 with brain-penetrating inhibitors appears a promising therapeutic approach for reversing chemotherapy-induced neurotoxicity while enhancing tumor control.

AMP-activated protein kinase (AMPK) is an energy-sensing kinase that has emerged as a novel therapeutic target for pain due to its ability to inhibit mechanistic target of rapamycin (mTOR) and mitogen activated protein kinase (MAPK) signaling, two signaling pathways that are linked to pain promotion after injury as well as the development of hyperalgesic priming. MAPK and mTOR signaling are also implicated in chemotherapy induced peripheral neuropathy (CIPN). We conducted a series of experiments to gain further insight into how AMPK activators might best be used to treat pain in both sexes in the setting of CIPN from paclitaxel. We also assessed whether hyperalgesic priming emerges from paclitaxel treatment and if this can be prevented by AMPK targeting. AMPK can be pharmacologically activated indirectly through regulation of upstream kinases like liver kinase B1 (LKB1) or directly using positive allosteric modulators. We used the indirect AMPK activators metformin and narciclasine, both of which have been shown to reduce pain in preclinical models but with much different potencies and different efficacies depending on the sex of the animal. We used the direct AMPK activator MK8722 because it is the most potent and specific such activator described to date. Here, the AMPK activators were used in 2 different treatment paradigms. First the drugs were given concurrently with paclitaxel to test whether they prevent mechanical hypersensitivity. Second the AMPK activators were given after the completion of paclitaxel treatment to test whether they reverse established mechanical hypersensitivity. Consistent with our previously published findings with metformin, narciclasine (1 mg/kg) produced an anti-hyperalgesic effect, preventing paclitaxel-induced neuropathy in outbred mice of both sexes. In contrast to metformin, narciclasine also reversed mechanical hypersensitivity in established CIPN. Both metformin (200 mg/kg) and narciclasine prevented the development of hyperalgesic priming induced by paclitaxel treatment. MK8722 (30 mg/kg) had no effect on mechanical hypersensitivity caused by paclitaxel in either the prevention or reversal treatment paradigms. However, MK8722 did attenuate hyperalgesic priming in male and female mice. We conclude that paclitaxel induces robust hyperalgesic priming that is prevented by AMPK targeting and that narciclasine is a particularly attractive candidate for further development as a CIPN treatment.

Chemotherapy-induced peripheral neuropathy (CIPN) is one of the most frequently reported adverse effects of cancer treatment. CIPN often persists long after treatment completion and has detrimental effects on patient's quality of life. There are no efficacious FDA-approved drugs for CIPN. We recently demonstrated that nasal administration of mesenchymal stem cells (MSC) reverses the cognitive deficits induced by cisplatin in mice. Here we show that nasal administration of MSC after cisplatin- or paclitaxel treatment- completely reverses signs of established CIPN, including mechanical allodynia, spontaneous pain, and loss of intraepidermal nerve fibers (IENF) in the paw. The resolution of CIPN is associated with normalization of the cisplatin-induced decrease in mitochondrial bioenergetics in DRG neurons. Nasally administered MSC enter rapidly the meninges of the brain, spinal cord and peripheral lymph nodes to promote IL-10 production by macrophages. MSC-mediated resolution of mechanical allodynia, recovery of IENFs and restoration of DRG mitochondrial function critically depends on IL-10 production. MSC from IL-10 knockout animals are not capable of reversing the symptoms of CIPN. Moreover, WT MSC do not reverse CIPN in mice lacking IL-10 receptors on peripheral sensory neurons. In conclusion, only two nasal administrations of MSC fully reverse CIPN and the associated mitochondrial abnormalities via an IL-10 dependent pathway. Since MSC are already applied clinically, we propose that nasal MSC treatment could become a powerful treatment for the large group of patients suffering from neurotoxicities of cancer treatment.

Frequently reported neurotoxic sequelae of cancer treatment include cognitive deficits and sensorimotor abnormalities that have long-lasting negative effects on the quality of life of an increasing number of cancer survivors. The underlying mechanisms are not fully understood and there is no effective treatment. We show here that cisplatin treatment of mice not only caused cognitive dysfunction but also impaired sensorimotor function. These functional deficits are associated with reduced myelin density and complexity in the cingulate and sensorimotor cortex. At the ultrastructural level, myelin abnormalities were characterized by decompaction. We used this model to examine the effect of bexarotene, an agonist of the RXR-family of nuclear receptors. Administration of only five daily doses of bexarotene after completion of cisplatin treatment was sufficient to normalize myelin density and fiber coherency and to restore myelin compaction in cingulate and sensorimotor cortex. Functionally, bexarotene normalized performance of cisplatin-treated mice in tests for cognitive and sensorimotor function. RNAseq analysis identified the TR/RXR pathway as one of the top canonical pathways activated by administration of bexarotene to cisplatin-treated mice. Bexarotene also activated neuregulin and netrin pathways that are implicated in myelin formation/maintenance, synaptic function and axonal guidance. In conclusion, short term treatment with bexarotene is sufficient to reverse the adverse effects of cisplatin on white matter structure, cognitive function, and sensorimotor performance. These encouraging findings warrant further studies into potential clinical translation and the underlying mechanisms of bexarotene for chemobrain.

Chemotherapy-induced peripheral neuropathy (CIPN) and chemotherapy-induced cognitive impairments (CICI) are common, often severe neurotoxic side effects of cancer treatment that greatly reduce quality of life of cancer patients and survivors. Currently, there are no Food and Drug Administration-approved agents for the prevention or curative treatment of CIPN or CICI. The dual leucine zipper kinase (DLK) is a key mediator of axonal degeneration that is localized to axons and coordinates the neuronal response to injury. We developed a novel brain-penetrant DLK inhibitor, IACS'8287, which demonstrates potent and highly selective inhibition of DLK in vitro and in vivo. Coadministration of IACS'8287 with the platinum derivative cisplatin prevents mechanical allodynia, loss of intraepidermal nerve fibers in the hind paws, cognitive deficits, and impairments in brain connectivity in mice, all without interfering with the antitumor activity of cisplatin. The protective effects of IACS'8287 are associated with preservation of mitochondrial function in dorsal root ganglion neurons and in brain synaptosomes. In addition, RNA sequencing analysis of dorsal root ganglia reveals modulation of genes involved in neuronal activity and markers for immune cell infiltration by DLK inhibition. These data indicate that CIPN and CICI require DLK signaling in mice, and DLK inhibitors could become an attractive treatment in the clinic when coadministered with cisplatin, and potentially other chemotherapeutic agents, to prevent neurotoxicities as a result of cancer treatment.

Peripheral neuropathic pain induced by the chemotherapeutic cisplatin can persist for months to years after treatment. Histone deacetylase 6 (HDAC6) inhibitors have therapeutic potential for cisplatin-induced neuropathic pain since they persistently reverse mechanical hypersensitivity and spontaneous pain in rodent models. Here, we investigated the mechanisms underlying reversal of mechanical hypersensitivity in male and female mice by a 2 week treatment with an HDAC6 inhibitor, administered 3 d after the last dose of cisplatin. Mechanical hypersensitivity in animals of both sexes treated with the HDAC6 inhibitor was temporarily reinstated by a single injection of the neutral opioid receptor antagonist 6β-naltrexol or the peripherally restricted opioid receptor antagonist naloxone methiodide. These results suggest that tonic peripheral opioid ligand-receptor signaling mediates reversal of cisplatin-induced mechanical hypersensitivity after treatment with an HDAC6 inhibitor. Pointing to a specific role for δ opioid receptors (DORs), Oprd1 expression was decreased in DRG neurons following cisplatin administration, but normalized after treatment with an HDAC6 inhibitor. Mechanical hypersensitivity was temporarily reinstated in both sexes by a single injection of the DOR antagonist naltrindole. Consistently, HDAC6 inhibition failed to reverse cisplatin-induced hypersensitivity when DORs were genetically deleted from advillin+ neurons. Mechanical hypersensitivity was also temporarily reinstated in both sexes by a single injection of a neutralizing antibody against the DOR ligand met-enkephalin. In conclusion, we reveal that treatment with an HDAC6 inhibitor induces tonic enkephalin-DOR signaling in peripheral sensory neurons to suppress mechanical hypersensitivity.SIGNIFICANCE STATEMENT Over one-fourth of cancer survivors suffer from intractable painful chemotherapy-induced peripheral neuropathy (CIPN), which can last for months to years after treatment ends. HDAC6 inhibition is a novel strategy to reverse CIPN without negatively interfering with tumor growth, but the mechanisms responsible for persistent reversal are not well understood. We built on evidence that the endogenous opioid system contributes to the spontaneous, apparent resolution of pain caused by nerve damage or inflammation, referred to as latent sensitization. We show that blocking the δ opioid receptor or its ligand enkephalin unmasks CIPN in mice treated with an HDAC6 inhibitor (latent sensitization). Our work provides insight into the mechanisms by which treatment with an HDAC6 inhibitor apparently reverses CIPN.

Early phase diabetes is often accompanied by pain sensitization. In Drosophila, the insulin receptor (InR) regulates the persistence of injury-induced thermal nociceptive sensitization. Whether Drosophila InR also regulates the persistence of mechanical nociceptive sensitization remains unclear. Mice with a sensory neuron deletion of the insulin receptor (Insr) show normal nociceptive baselines; however, it is uncertain whether deletion of Insr in nociceptive sensory neurons leads to persistent nociceptive hypersensitivity. In this study, we used fly and mouse nociceptive sensitization models to address these questions. In flies, InR mutants and larvae with sensory neuron-specific expression of RNAi transgenes targeting InR exhibited persistent mechanical hypersensitivity. Mice with a specific deletion of the Insr gene in Nav1.8+ nociceptive sensory neurons showed nociceptive thermal and mechanical baselines similar to controls. In an inflammatory paradigm, however, these mutant mice showed persistent mechanical (but not thermal) hypersensitivity, particularly in female mice. Mice with the Nav1.8+ sensory neuron-specific deletion of Insr did not show metabolic abnormalities typical of a defect in systemic insulin signaling. Our results show that some aspects of the regulation of nociceptive hypersensitivity by the insulin receptor are shared between flies and mice and that this regulation is likely independent of metabolic effects.

We recently demonstrated that inhibition of the NF-kappaB-pathway by the specific peptide inhibitor TAT-NBD markedly reduced cerebral injury in a rat model of perinatal hypoxic-ischemic (HI) brain damage. The aim of the current study was to assess whether neuroprotection by TAT-NBD is associated with long-term functional improvements after neonatal HI. Postnatal-day 7 rats subjected to HI showed motor deficits in the cylinder rearing test and adhesive removal task. HI-treated animals also showed cognitive impairments in a visuo-spatial learning task (modified hole board) as defined by an increased latency to complete this task and increased numbers of short- and long-term memory errors. HI animals treated with TAT-NBD [20mg/kg i.p.] at 0 and 3h post-HI did not show impairments in the cylinder rearing test, adhesive removal task and modified hole board. In conclusion, the almost complete reduction in lesion size observed after TAT-NBD treatment was associated with long-lasting normalization of sensorimotor and cognitive functions.

Mesenchymal stem cell (MSC) treatment is an effective strategy to reduce brain damage after neonatal hypoxia-ischemia (HI) in mice. We recently showed that a single injection with MSC at either 3 or 10 days after HI (MSC-3 or MSC-10) increases neurogenesis. In case of two injections (MSC-3+10), the second MSC application does not increase neurogenesis, but promotes corticospinal tract remodeling. Here we investigated GFP(+)-MSC engraftment level in the brain using quantitative-PCR analysis. We show for the first time that in the neonatal ischemic brain survival of transplanted MSC is very limited. At 3 days after injection ∼22% of transplanted MSC were still detectable and 18 days after the last administration barely ∼1%. These findings indicate that engraftment of MSC is not likely the underlying mechanism of the efficient regenerative process. Therefore, we tested the hypothesis that the effects of MSC-treatment on regenerative processes are related to specific changes in the gene expression of growth factors and cytokines in the damaged area of the brain using PCR-array analysis. We compared the effect of one (MSC-10) or two (MSC-3+10) injections of 10(5) MSC on gene expression in the brain. Our data show that MSC-10 induced expression of genes regulating proliferation/survival. In response to MSC-3+10-treatment a pattern functionally categorized as growth stimulating genes was increased. Collectively, our data indicate that specific regulation of the endogenous growth factor milieu rather than replacement of damaged tissue by exogenous MSC mediates regeneration of the damaged neonatal brain by MSC-treatment.

G protein-coupled receptor (GPCR) kinase 2 (GRK2) regulates cellular signaling via desensitization of GPCRs and by direct interaction with intracellular signaling molecules. We recently described that ischemic brain injury decreases cerebral GRK2 levels. Here we studied the effect of astrocyte GRK2-deficiency on neonatal brain damage in vivo. As astrocytes protect neurons by taking up glutamate via plasma-membrane transporters, we also studied the effect of GRK2 on the localization of the GLutamate ASpartate Transporter (GLAST). Brain damage induced by hypoxia-ischemia was significantly reduced in GFAP-GRK2(+/-) mice, which have a 60% reduction in astrocyte GRK2 compared to GFAP-WT littermates. In addition, GRK2-deficient astrocytes have higher plasma-membrane levels of GLAST and an increased capacity to take up glutamate in vitro. In search for the mechanism by which GRK2 regulates GLAST expression, we observed increased GFAP levels in GRK2-deficient astrocytes. GFAP and the cytoskeletal protein ezrin are known regulators of GLAST localization. In line with this evidence, GRK2-deficiency reduced phosphorylation of the GRK2 substrate ezrin and enforced plasma-membrane GLAST association after stimulation with the group I mGluR-agonist DHPG. When ezrin was silenced, the enhanced plasma-membrane GLAST association in DHPG-exposed GRK2-deficient astrocytes was prevented. In conclusion, we identified a novel role of astrocyte GRK2 in regulating plasma-membrane GLAST localization via an ezrin-dependent route. We demonstrate that the 60% reduction in astrocyte GRK2 protein level that is observed in GFAP-GRK2(+/-) mice is sufficient to significantly reduce neonatal ischemic brain damage. These findings underline the critical role of GRK2 regulation in astrocytes for dampening the extent of brain damage after ischemia.

Transient stimulation of the innate immune system by an intraperitoneal injection of lipopolysaccharide (LPS) activates peripheral and central expression of the tryptophan degrading enzyme indoleamine 2,3 dioxygenase (IDO) which mediates depressive-like behavior. It is unknown whether direct activation of the brain with LPS is sufficient to activate IDO and induce depressive-like behavior.

Pain and depression often co-occur, but the underlying mechanisms have not been elucidated. Here, we used the spared nerve injury (SNI) model in mice to induce both neuropathic pain and depression-like behavior. We investigated whether brain interleukin (IL)-1 signaling and activity of kynurenine 3-monoxygenase (KMO), a key enzyme for metabolism of kynurenine into the neurotoxic NMDA receptor agonist quinolinic acid, are necessary for comorbid neuropathic pain and depression-like behavior. SNI mice showed increased expression levels of Il1b and Kmo mRNA in the contralateral side of the brain. The SNI-induced increase of Kmo mRNA was associated with increased KMO protein and elevated quinolinic acid and reduced kynurenic acid in the contralateral hippocampus. The increase in KMO-protein in response to SNI mostly took place in hippocampal NeuN-positive neurons rather than microglia. Inhibition of brain IL-1 signaling by intracerebroventricular administration of IL-1 receptor antagonist after SNI prevented the increase in Kmo mRNA and depression-like behavior measured by forced swim test. However, inhibition of brain IL-1 signaling has no effect on mechanical allodynia. In addition, intracerebroventricular administration of the KMO inhibitor Ro 61-8048 abrogated depression-like behavior without affecting mechanical allodynia after SNI. We show for the first time that the development of depression-like behavior in the SNI model requires brain IL-1 signaling and activation of neuronal KMO, while pain is independent of this pathway. Inhibition of KMO may represent a promising target for treating depression.

Up to seventy-five percent of patients treated for cancer suffer from cognitive deficits which can persist for months to decades, severely impairing quality of life. Although the number of cancer survivors is increasing tremendously, no efficacious interventions exist. Cisplatin, most commonly employed for solid tumors, leads to cognitive impairment including deficits in memory and executive functioning. We recently proposed deficient neuronal mitochondrial function as its underlying mechanism. We hypothesized nasal administration of mitochondria isolated from human mesenchymal stem cells to mice, can reverse cisplatin-induced cognitive deficits. Methods: Puzzle box, novel object place recognition and Y-maze tests were used to assess the cognitive function of mice. Immunofluorescence and high-resolution confocal microscopy were employed to trace the nasally delivered mitochondria and evaluate their effect on synaptic loss. Black Gold II immunostaining was used to determine myelin integrity. Transmission electron microscopy helped determine mitochondrial and membrane integrity of brain synaptosomes. RNA-sequencing was performed to analyse the hippocampal transcriptome. Results: Two nasal administrations of mitochondria isolated from human mesenchymal stem cells to mice, restored executive functioning, working and spatial memory. Confocal imaging revealed nasally delivered mitochondria rapidly arrived in the meninges where they were readily internalized by macrophages. The administered mitochondria also accessed the rostral migratory stream and various other brain regions including the hippocampus where they colocalized with GFAP+ cells. The restoration of cognitive function was associated with structural repair of myelin in the cingulate cortex and synaptic loss in the hippocampus. Nasal mitochondrial donation also reversed the underlying synaptosomal mitochondrial defects. Moreover, transcriptome analysis by RNA-sequencing showed reversal of cisplatin-induced changes in the expression of about seven hundred genes in the hippocampus. Pathway analysis identified Nrf2-mediated response as the top canonical pathway. Conclusion: Our results provide key evidence on the therapeutic potential of isolated mitochondria - restoring both brain structure and function, their capability to enter brain meninges and parenchyma upon nasal delivery and undergo rapid cellular internalization and alter the hippocampal transcriptome. Our data identify nasal administration of mitochondria as an effective strategy for reversing chemotherapy-induced cognitive deficits and restoring brain health, providing promise for the growing population of both adult and pediatric cancer survivors.

Exposure to synthetic glucocorticoids (GCs) or other stimuli around birth may affect neuroendocrine and immune responsiveness in the offspring. Experiments were conducted to investigate whether maternal manipulation with saline or with GCs alters the corticosterone (CORT) response to a mild stressor in the offspring, and whether maternal manipulation results in long-term altered in vivo humoral and cellular immune responsiveness in the offspring. Pregnant rats were given dexamethasone (DEX, 1.2 mg/kg body weight, i.p.) or saline (SAL) at day 17 and 19 of gestation. A third group of pregnant rats was left undisturbed (UNTR-group). After maternal DEX treatment, no altered CORT response was seen to a novel environment at 20 days of age, as compared to both the SAL-treated group and the UNTR-group. However, saline administration to pregnant rats caused an increased CORT response in female offspring, but not male offspring, as compared to the UNTR-group (P < or = 0.01). Furthermore, no effects of maternal DEX exposure were seen on IgG2a production after immunization with a conjugated pneumococcal polysaccharide (PPS-14-CRM197) at 6 weeks of age. However, maternal SAL treatment enhanced anti-PPS-14 IgG2a antibody levels in female offspring, but not in male offspring, as compared to the UNTR-group (P < or = 0.05). Cellular immune responses were measured by an oxazolone-induced contact hypersensitivity response (CHS-response), at 8 weeks of age. Maternal SAL treatment increased the CHS response in adult male rats, but not in female rats, as compared to both the UNTR-group and the DEX-group (P < or = 0.005). These data suggest that manipulations during late pregnancy not only affect endocrine responsiveness, but also influence immune responsiveness in the rat offspring. Furthermore, these effects may be long-term and gender-specific.

Pregnancy is widely viewed as dependent upon an intimate dialogue, mediated by locally secreted factors between a developmentally competent embryo and a receptive endometrium. Reproductive success in humans is however limited, largely because of the high prevalence of chromosomally abnormal preimplantation embryos. Moreover, the transient period of endometrial receptivity in humans uniquely coincides with differentiation of endometrial stromal cells (ESCs) into highly specialized decidual cells, which in the absence of pregnancy invariably triggers menstruation. The role of cyclic decidualization of the endometrium in the implantation process and the nature of the decidual cytokines and growth factors that mediate the crosstalk with the embryo are unknown.

Loss of integrity of the epithelial and endothelial barriers is thought to be a prominent feature of ventilator-induced lung injury (VILI). Based on its function in vascular integrity, we hypothesize that the angiopoietin (Ang)-Tie2 system plays a role in the development of VILI. The present study was designed to examine the effects of mechanical ventilation on the Ang-Tie2 system in lung tissue. Moreover, we evaluated whether treatment with Ang-1, a Tie2 receptor agonist, protects against inflammation, vascular leakage and impaired gas exchange induced by mechanical ventilation.

Subarachnoid hemorrhage (SAH) represents a considerable health problem. To date, limited therapeutic options are available. In order to develop effective therapeutic strategies for SAH, the mechanisms involved in SAH brain damage should be fully explored. Here we review the mechanisms of SAH brain damage induced by the experimental endovascular puncture model. We have included a description of similarities and distinctions between experimental SAH in animals and human SAH pathology. Moreover, several novel treatment options to diminish SAH brain damage are discussed.SAH is accompanied by cerebral inflammation as demonstrated by an influx of inflammatory cells into the cerebral parenchyma, upregulation of inflammatory transcriptional pathways and increased expression of cytokines and chemokines. Additionally, various cell death pathways including cerebral apoptosis, necrosis, necroptosis and autophagy are involved in neuronal damage caused by SAH.Treatment strategies aiming at inhibition of inflammatory or cell death pathways demonstrate the importance of these mechanisms for survival after experimental SAH. Moreover, neuroregenerative therapies using stem cells are discussed as a possible strategy to repair the brain after SAH since this therapy may extend the window of treatment considerably. We propose the endovascular puncture model as a suitable animal model which resembles the human pathology of SAH and which could be applied to investigate novel therapeutic therapies to combat this debilitating insult.

For the treatment of patients with multiple sclerosis there are no regenerative approaches to enhance remyelination. Mesenchymal stem cells (MSC) have been proposed to exert such regenerative functions. Intravenous administration of human MSC reduced the clinical severity of experimental autoimmune encephalomyelitis (EAE), an animal model mimicking some aspects of multiple sclerosis. However, it is not clear if this effect was achieved by systemic immunomodulation or if there is an active neuroregeneration in the central nervous system (CNS). In order to investigate remyelination and regeneration in the CNS we analysed the effects of intravenously and intranasally applied murine and human bone marrow-derived MSC on cuprizone induced demyelination, a toxic animal model which allows analysis of remyelination without the influence of the peripheral immune system. In contrast to EAE no effects of MSC on de- and remyelination and glial cell reactions were found. In addition, neither murine nor human MSC entered the lesions in the CNS in this toxic model. In conclusion, MSC are not directed into CNS lesions in the cuprizone model where the blood-brain-barrier is intact and thus cannot provide support for regenerative processes.

For clinical translation, we assessed whether intranasal mesenchymal stem cell (MSC) treatment after hypoxia-ischemia (HI) induces neoplasia in the brain or periphery at 14 mo. Furthermore, the long-term effects of MSCs on behavior and lesion size were determined.