Despite long-term efforts to elucidate the mechanisms responsible for age-related hearing loss (AHL), there is currently no available treatment strategy able to provide a cure. Apoptotic cell death, including that of hair cells and spiral ganglion neurons (SGNs) in the cochlea has been proposed to be the classic theory behind the development of AHL. As calcium signaling plays key roles in signal transduction in apoptosis, in this study, we selected ethosuximide, which is able to block T-type calcium (Ca2+ion) channels, suppressing Ca2+. We hypothesized that the apoptotic pathway may be blocked through the inhibition of T-type Ca2+ channels in cochlear cells in NOD/LtJ mice. NOD/LtJ mice were divided into 2 groups as follows: the ethosuximide-treated and untreated (control) groups. Ethosuximide was administered by intraperitoneal injection every other day from post-natal day seven (P7) until the mice were 8 weeks of age. Following treatment, auditory-evoked brainstem response (ABR) thresholds and distortion product oto-acoustic emission (DPOAE) of the mice in the 2 groups were measured at different time points. Morphometric analysis and the expression of genes involved in the T-type Ca2+-mediated apoptotic pathway were monitored. The ABR and DPOAE results revealed that the NOD/LtJ mice exhibited early-onset and rapidly progressive AHL. A histological examination revealed that hair cell degeneration coincided with the progression of hearing loss. Hair cell and SGN was were significantly lower and auditory function was significantly improved in the ethosuximide-treated group compared to the untreated group. Our data thus indicate that ethosuximide prevents the degeneration of cochlear cells by regulating the expression of genes in apoptotic pathways. Our findings suggest that activating the T-type Ca2+ channel and downstream genes may be key pathological mechanisms responsible for AHL in NOD/LtJ mice.

Ethosuximide is a medication used to treat seizure disorders in humans, and we previously demonstrated that ethosuximide can delay age-related changes and extend the lifespan of the nematode Caenorhabditis elegans. The mechanism of action of ethosuximide in lifespan extension is unknown, and elucidating how ethosuximide functions is important for defining endogenous processes that influence lifespan and for exploring the potential of ethosuximide as a therapeutic for age-related diseases. To identify genes that mediate the activity of ethosuximide, we conducted a genetic screen and identified mutations in two genes, che-3 and osm-3, that cause resistance to ethosuximide-mediated toxicity. Mutations in che-3 and osm-3 cause defects in overlapping sets of chemosensory neurons, resulting in defective chemosensation and an extended lifespan. These findings suggest that ethosuximide extends lifespan by inhibiting the function of specific chemosensory neurons. This model is supported by the observation that ethosuximide-treated animals displayed numerous phenotypic similarities with mutants that have chemosensory defects, indicating that ethosuximide inhibits chemosensory function. Furthermore, ethosuximide extends lifespan by inhibiting chemosensation, since the long-lived osm-3 mutants were resistant to the lifespan extension caused by ethosuximide. These studies demonstrate a novel mechanism of action for a lifespan-extending drug and indicate that sensory perception has a critical role in controlling lifespan. Sensory perception also influences the lifespan of Drosophila, suggesting that sensory perception has an evolutionarily conserved role in lifespan control. These studies highlight the potential of ethosuximide and related drugs that modulate sensory perception to extend lifespan in diverse animals.

We have recently reported that the Cav3.2 T-type calcium channel which is well known for its key role in pain signalling, also mediates a critical function in the transmission of itch/pruritus. Here, we evaluated the effect of the clinically used anti-seizure medication ethosuximide, a well known inhibitor of T-type calcium channels, on male and female mice subjected to histaminergic- and non-histaminergic itch. When delivered intraperitoneally ethosuximide significantly reduced scratching behavior of mice of both sexes in response to subcutaneous injection of either histamine or chloroquine. When co-delivered subcutaneously together with either pruritogenic agent ethosuximide was also effective in inhibiting scratching responses in both male and female animals. Overall, our results are consistent with an important role of Cav3.2 T-type calcium channels in modulating histamine-dependent and histamine-independent itch transmission in the primary sensory pathway. Our findings also suggest that ethosuximide could be explored further as a possible therapeutic for the treatment of itch.

Many neurodegenerative diseases are associated with protein misfolding/aggregation. Treatments mitigating the effects of such common pathological processes, rather than disease-specific symptoms, therefore have general therapeutic potential.

Recent studies have shown that several strains of transgenic Alzheimer's disease (AD) mice overexpressing the amyloid precursor protein (APP) have cortical hyperexcitability, and their results have suggested that this aberrant network activity may be a mechanism by which amyloid-β (Aβ) causes more widespread neuronal dysfunction. Specific anticonvulsant therapy reverses memory impairments in various transgenic mouse strains, but it is not known whether reduction of epileptiform activity might serve as a surrogate marker of drug efficacy for memory improvement in AD mouse models.

Systemic drug application is the main approach in epilepsy treatment. However, the central nervous system (CNS) is a challenging target for drug delivery as the blood-brain barrier (BBB) restricts the transfer of drugs into the brain. Accordingly, there is a general interest in developing new therapeutic strategies to improve CNS drug accessibility. Intrathecal administration of antiseizure drugs (ASDs) e.g. via pumps or advanced materials could be a possible approach to bypass the BBB and increase the availability of neuroactive compounds in the CNS. The aim of this study was the evaluation of intracerebroventricular (i.c.v.) compared to systemic drug application in generalized epilepsy. The i.c.v. administration of the established ASD ethosuximide (ETX) in Genetic Absence Epilepsy Rats from Strasbourg (GAERS) caused a robust and dose-dependent reduction of spike-wave discharges (SWDs) without causing obvious behavioral abnormalities. Additionally, we could show that i.c.v. treatment with ETX is significantly more effective in seizure suppression than systemic treatment with the same dose. The localized application resulted in reduced systemic drug exposure compared to standard systemic ETX therapy. The tracing of dye distribution throughout the CNS supported the view that i.c.v. applied drugs cross into brain tissue surrounding the ventricles but largely remain restricted to the site of injection. Our data suggest that intrathecal application represents a possible route for the treatment in generalized epilepsy through direct drug penetration from CSF into brain tissue.

Seizures in about 40% of patients with epilepsy fail to respond to anti-seizure medication (ASM) and may lead to uncontrolled and prolonged seizures often inducing status epilepticus (SE). The aim of the study was to evaluate the impact of a long-term treatment with two different generation ASMs: ethosuximide (ETS, a classic ASM) and lacosamide (LCM, a 3rd generation ASM) on neural stem cells' (NSCs') proliferation and learning and memory functions after pilocarpine (PILO)-induced SE in mice. The following drugs were used: LCM (10 mg/kg), ETS (20 mg/kg), and PILO (300 mg/kg). Cell counting was done using confocal microscope and ImageJ software. Cognitive functions were evaluated with the Morris water maze (MWM) test. The level of several selected neurometabolites was measured with magnetic resonance spectroscopy (MRS). Obtained results indicated no significant impact of ETS treatment on the neurogenesis process in PILO mice. Interestingly, LCM significantly decreased the total amount of newborn neurons. The MWM test indicated no significant changes in the time and distance traveled by the ETS and LCM groups compared to PILO control mice, although all measured parameters were more favorable for the PILO mice treated with ASM. Conclusions: The presented results show that long term treatment with LCM and ETS seems to be safe for the cognitive functions and the proper course of neurogenesis in the mouse PILO-induced SE model, although one should remember that LCM administered chronically may act to reduce new neurons' formation.

Several studies have demonstrated that basic fibroblast growth factor (bFGF) can induce neural differentiation of mesenchymal stem cells. In this study, we investigated the neural differentiation of muscle-derived stem cells (MDSCs) following treatment with bFGF and ethosuximide, a small molecule used as an anticonvulsant in humans. Stem cells isolated from rat skeletal muscle (rMDSCs) were pre-induced by culturing with 25 ng/mL bFGF for 24 h and then were transferred to a medium supplemented with or without 4 mM ethosuximide. Neuronal differentiation was assessed by immunocytochemical and western blotting analyses of marker expression. Immunocytochemistry of rMDSCs treated with bFGF and ethosuximide identified abundant cells expressing neuronal markers (TuJ1, neuron-specific class III β-tubulin; NeuN, neuronal nuclear antigen; and NF-MH; neurofilament M and H). Olig2 (oligodendrocyte transcription factor 2)-positive cells were also observed, indicating the presence of oligodendrocyte lineage cells. These findings were substantiated by western blotting analysis of marker proteins. In particular, the expression of NeuN and TuJ1 was significantly higher in rMDSCs treated with ethosuximide and bFGF than in cells stimulated with bFGF alone (NeuN, p < 0.05 and TuJ1, p < 0.001). Expression of the astrocyte marker GFAP (glial fibrillary acidic protein) was not detected in this study. Collectively, the results showed that treatment with bFGF and ethosuximide induced effective transdifferentiation of rMDSCs into cells with a neural-like phenotype. Notably, rMDSCs treated with a combination of bFGF plus ethosuximide showed enhanced differentiation compared with cells treated with bFGF alone, implying that ethosuximide may stimulate neuronal differentiation.

To evaluate the role of ethosuximide, sodium valproate and lamotrigine in children and adolescents with typical absence seizures (AS).

Evidence has been generated that various anticonvulsant agents provide relief of several chronic pain syndromes and therefore as an alternative to opioids, nonsteroidal anti-inflammatory, and tricyclic antidepressant drugs in the treatment of neuropathic pain. The results of these studies thus raise the question of whether all anticonvulsant drugs or particular mechanistic classes may be efficacious in the treatment of neuropathic pain syndromes.

A recent striking advance in the treatment of depression has been the finding of rapid antidepressant effects in over 70% of patients with treatment-resistant depression (TRD) using ketamine. However, the potential risk of addiction may limit its clinical use. Recent research revealed that blockade of N-methyl-D-aspartate receptor (NMDAR) dependent bursting activity in the lateral habenula (LHb) could mediate the fast antidepressant effects of ketamine. Further, LHb bursting plays an important role in the pathophysiology of depression that requires both NMDARs and low-voltage-sensitive T-type calcium channels (T-VSCCs). Ethosuximide, which is used to treat absence seizures, is a T-VSCCs inhibitor, may be a novel drug candidate for depression. The objective of this clinical trial is to investigate the efficacy and safety of ethosuximide in patients with TRD.

A recent study demonstrated that low-voltage-sensitive T-type calcium channel blocker ethosuximide shows rapid antidepressant actions. This study was conducted to compare the antidepressant actions of ethosuximide and (R)-ketamine in a chronic social defeat stress model.

Currently available analgesics are ineffective in 30-50% of patients suffering from neuropathic pain and often induce deleterious side effects. T-type calcium channel blockers (mibefradil, ethosuximide, NNC 55-0396) are of great interest for the development of new symptomatic treatments of neuropathic pain, due to their various effects on pain perception. Interestingly, ethosuximide, which has already been approved for treating epilepsy, is available on the European market for clinical use. Despite numerous preclinical data demonstrating an antinociceptive effect of ethosuximide in various animal models of neuropathic pain, no clinical studies have been published to date on the analgesic efficacy of ethosuximide in patients with neuropathic pain.

The antiepileptic drug ethosuximide has recently been shown to be neuroprotective in various Caenorhabditis elegans and rodent neurodegeneration models. It is therefore a promising repurposing candidate for the treatment of multiple neurodegenerative diseases. However, high concentrations of the drug are required for its protective effects in animal models, which may impact on its translational potential and impede the identification of its molecular mechanism of action. Therefore, we set out to develop more potent neuroprotective lead compounds based on ethosuximide as a starting scaffold. Chemoinformatic approaches were used to identify compounds with structural similarity to ethosuximide and to prioritise these based on good predicated blood-brain barrier permeability and C. elegans bioaccumulation properties. Selected compounds were initially screened for anti-convulsant activity in a C. elegans pentylenetetrazol-induced seizure assay, as a rapid primary readout of bioactivity; and then assessed for neuroprotective properties in a C. elegans TDP-43 proteinopathy model based on pan-neuronal expression of human A315T mutant TDP-43. The most potent compound screened, α-methyl-α-phenylsuccinimide (MPS), ameliorated the locomotion defects and extended the shortened lifespan of TDP-43 mutant worms. MPS also directly protected against neurodegeneration by reducing the number of neuronal breaks and cell body losses in GFP-labelled GABAergic motor neurons. Importantly, optimal neuroprotection was exhibited by external application of 50 μM MPS, compared to 8 mM for ethosuximide. This greater potency of MPS was not due to bioaccumulation to higher internal levels within the worm, based on 1H-nuclear magnetic resonance analysis. Like ethosuximide, the activity of MPS was abolished by mutation of the evolutionarily conserved FOXO transcription factor, daf-16, suggesting that both compounds act via the same neuroprotective pathway(s). In conclusion, we have revealed a novel neuroprotective activity of MPS that is >100-fold more potent than ethosuximide. This increased potency will facilitate future biochemical studies to identify the direct molecular target(s) of both compounds, as we have shown here that they share a common downstream DAF-16-dependent mechanism of action. Furthermore, MPS is the active metabolite of another approved antiepileptic drug, methsuximide. Therefore, methsuximide may have repurposing potential for treatment of TDP-43 proteinopathies and possibly other human neurodegenerative diseases.

CRISPR-Cas9-generated zebrafish carrying a 12 base-pair deletion in stxbpb1b, a paralog sharing 79% amino acid sequence identity with human, exhibit spontaneous electrographic seizures during larval stages of development. Zebrafish stxbp1b mutants provide an efficient preclinical platform to test antiseizure therapeutics. The present study was designed to test antiseizure medications approved for clinical use and two recently identified repurposed drugs with antiseizure activity. Larval homozygous stxbp1b zebrafish (4 days postfertilization (dpf)) were agarose-embedded and monitored for electrographic seizure activity using a local field recording electrode placed in midbrain. Frequency of ictal-like events was evaluated at baseline and following 45 min of continuous drug exposure (1 mM, bath application). Analysis was performed on coded files by an experimenter blinded to drug treatment and genotype. Phenytoin (PHT), valproate (VPA), ethosuximide (ESX), levetiracetam (LEV), and diazepam (DZP) had no effect on the ictal-like event frequency in stxbp1b mutant zebrafish. Clemizole and trazodone decreased ictal-like event frequency in stxbp1b mutant zebrafish by 80% and 83%, respectively. These results suggest that repurposed drugs with serotonin receptor-binding affinities could be effective antiseizure treatments. Clemizole and trazodone were previously identified in a larval zebrafish model for Dravet syndrome. Based primarily on these preclinical zebrafish studies, compassionate-use and double-blind clinical trials with both drugs have progressed. The present study extends this approach to a preclinical zebrafish model representing STXBP1 (syntaxin-binding protein 1)-related disorders and suggests that future clinical studies may be warranted.

It was the aim of this study to determine the potential effect of walnut kernel extract (WKE) on experimentally induced seizures in rats and to evaluate the role of benzodiazepines and ethosuximide (ESM) within these pathways.

To determine the effects of antiepileptic drug compounds on glioblastoma cellular growth, we exposed glioblastoma cell lines to select antiepileptic drugs. The effects of selected antiepileptic drugs on glioblastoma cells were measured by MTT assay. For compounds showing significant inhibition, cell cycle analysis was performed. Statistical analysis was performed using SPSS. The antiepileptic compounds selected for screening included carbamazepine, ethosuximide, gabapentin, lamotrigine, levetiracetam, magnesium sulfate, oxcarbazepine, phenytoin, primidone, tiagabine, topiramate, valproic acid, and vigabatrin. Dexamethasone and temozolomide were used as a negative and positive control respectively. Our results showed temozolomide and oxcarbazepine significantly inhibited glioblastoma cell growth and reached IC50 at therapeutic concentrations. The other antiepileptic drugs screened were unable to reach IC50 at therapeutic concentrations. The metabolites of oxcarbazepine were also unable to reach IC50. Dexamethasone, ethosuximide, levetiracetam, and vigabatrin showed some growth enhancement though they did not reach statistical significance. The growth enhancement effects of ethosuximide, levetiracetam, and vigabatrin found in the study may indicate that these compounds should not be used for prophylaxis or short term treatment of epilepsy in glioblastoma. While valproic acid and oxcarbazepine were effective, the required dose of valproic acid was far above that used for the treatment of epilepsy and the metabolites of oxcarbazepine failed to reach significant growth inhibition ruling out the use of oral oxcarbazepine or valproic acid as monotherapy in glioblastoma. The possibility of using these compounds as local treatment is a future area of study.

Human WWOX gene resides in the chromosomal common fragile site FRA16D and encodes a tumor suppressor WW domain-containing oxidoreductase. Loss-of-function mutations in both alleles of WWOX gene lead to autosomal recessive abnormalities in pediatric patients from consanguineous families, including microcephaly, cerebellar ataxia with epilepsy, mental retardation, retinal degeneration, developmental delay and early death. Here, we report that targeted disruption of Wwox gene in mice causes neurodevelopmental disorders, encompassing abnormal neuronal differentiation and migration in the brain. Cerebral malformations, such as microcephaly and incomplete separation of the hemispheres by a partial interhemispheric fissure, neuronal disorganization and heterotopia, and defective cerebellar midline fusion are observed in Wwox-/- mice. Degenerative alterations including severe hypomyelination in the central nervous system, optic nerve atrophy, Purkinje cell loss and granular cell apoptosis in the cerebellum, and peripheral nerve demyelination due to Schwann cell apoptosis correspond to reduced amplitudes and a latency prolongation of transcranial motor evoked potentials, motor deficits and gait ataxia in Wwox-/- mice. Wwox gene ablation leads to the occurrence of spontaneous epilepsy and increased susceptibility to pilocarpine- and pentylenetetrazol (PTZ)-induced seizures in preweaning mice. We determined that a significantly increased activation of glycogen synthase kinase 3β (GSK3β) occurs in Wwox-/- mouse cerebral cortex, hippocampus and cerebellum. Inhibition of GSK3β by lithium ion significantly abolishes the onset of PTZ-induced seizure in Wwox-/- mice. Together, our findings reveal that the neurodevelopmental and neurodegenerative deficits in Wwox knockout mice strikingly recapitulate the key features of human neuropathies, and that targeting GSK3β with lithium ion ameliorates epilepsy.

Channel blocking, anti-oscillatory, and anti-epileptic effects of clinically used anti-absence substances (ethosuximide, valproate) and the T-type Ca2+ current (IT) blocker mibefradil were tested by analyzing membrane currents in acutely isolated local circuit interneurons and thalamocortical relay (TC) neurons, slow intrathalamic oscillations in brain slices, and spike and wave discharges (SWDs) occurring in vivo in Wistar Albino Glaxo rats from Rijswijk (WAG/Rij). Substance effects in vitro were compared between WAG/Rij and a non-epileptic control strain, the ACI rats. Ethosuximide (ETX) and valproate were found to block IT in acutely isolated thalamic neurons. Block of IT by therapeutically relevant ETX concentrations (0.25-0.75 mM) was stronger in WAG/Rij, although the maximal effect at saturating concentrations (>or=10 mM) was stronger in ACI. Ethosuximide delayed the onset of the low threshold Ca2+ spike (LTS) of neurons recorded in slice preparations. Mibefradil (>or=2 microM) completely blocked IT and the LTS, dampened evoked thalamic oscillations, and attenuated SWDs in vivo. Computational modeling demonstrated that the complete effect of ETX can be replicated by a sole reduction of IT. However, the necessary degree of IT reduction was not induced by therapeutically relevant ETX concentrations. A combined reduction of IT, the persistent sodium current, and the Ca2+ activated K+ current resulted in an LTS alteration resembling the experimental observations. In summary, these results support the hypothesis of IT reduction as part of the mechanism of action of anti-absence drugs and demonstrate the ability of a specific IT antagonist to attenuate rhythmic burst firing and SWDs.

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer death among women in the United States (5 % of cancer deaths). The standard treatment for patients with advanced EOC is initial debulking surgery followed by carboplatin-paclitaxel combination chemotherapy. Unfortunately, with chemotherapy most patients relapse and die resulting in a five-year overall survival around 45 %. Thus, finding novel therapeutics for treating EOC is essential. Connectivity Mapping (CMAP) has been used widely in cancer drug discovery and generally has relied on cancer cell line gene expression and drug phenotype data. Therefore, we took a CMAP approach based on tumor information and clinical endpoints from high grade serous EOC patients.