Altered mitochondrial acetylation profiles in a kainic acid model of temporal lobe epilepsy

Anti-epileptic and Neuroprotective Effects of Ultra-low Dose NADPH Oxidase Inhibitor Dextromethorphan on Kainic Acid-induced Chronic Temporal Lobe Epilepsy in Rats

Neuroinflammation mediated by microglia and oxidative stress play pivotal roles in the development of chronic temporal lobe epilepsy (TLE). We postulated that kainic acid (KA)-Induced status epilepticus triggers microglia-dependent inflammation, leading to neuronal damage, a lowered seizure threshold, and the emergence of spontaneous recurrent seizures (SRS). Extensive evidence from our laboratory suggests that dextromethorphan (DM), even in ultra-low doses, has anti-inflammatory and neuroprotective effects in many animal models of neurodegenerative disease. Our results showed that administration of DM (10 ng/kg per day; subcutaneously via osmotic minipump for 4 weeks) significantly mitigated the residual effects of KA, including the frequency of SRS and seizure susceptibility. In addition, DM-treated rats showed improved cognitive function and reduced hippocampal neuronal loss. We found suppressed microglial activation-mediated neuroinflammation and decreased expression of hippocampal gp91phox and p47phox proteins in KA-induced chronic TLE rats. Notably, even after discontinuation of DM treatment, ultra-low doses of DM continued to confer long-term anti-seizure and neuroprotective effects, which were attributed to the inhibition of microglial NADPH oxidase 2 as revealed by mechanistic studies.

Differential inflammation responses determine the variable phenotypes of epilepsy induced by GABRG2 mutations

OBJECTIVE

To explore the mechanism involved in variable phenotypes of epilepsy models induced by γ-aminobutyric acid type A γ2 subunit (GABRG2) mutations.

METHODS

The zebrafish carrying wild-type (WT) GABRG2, mutant GABRG2(P282S), GABRG2(F343L) and GABRG2(I107T) were established by Tol2kit transgenesis system and Gateway method. Behavioral analysis of different transgenic zebrafish was performed with the DanioVision Video-Track framework and the brain activity was analyzed by field potential recording with MD3000 Bio-signal Acquisition and Processing System. The transcriptome analysis was applied to detect the underlying mechanisms of variable phenotypes caused by different GABRG2 mutations.

RESULTS

The established Tg(hGABRG2P282S ) zebrafish showed hyperactivity and spontaneous seizures, which were more sensitive to chemical and physical epileptic stimulations. Traditional antiepileptic drugs, such as Clonazepam (CBZ) and valproic acid (VPA), could ameliorate the hyperactivity in Tg(hGABRG2P282S ) zebrafish. The metabolic pathway was significantly changed in the brain transcriptome of Tg(hGABRG2P282S ) zebrafish. In addition, the behavioral activity, production of pro-inflammatory factors, and activation of the IL-2 receptor signal pathway varied among the three mutant zebrafish lines.

CONCLUSION

We successfully established transgenic zebrafish epileptic models expressing human mutant GABRG2(P282S), in which CBZ and VPA showed antiepileptic effects. Differential inflammatory responses, especially the SOCS/JAK/STAT signaling pathway, might be related to the phenotypes of genetic epilepsy induced by GABRG2 mutations. Further study will expand the pathological mechanisms of genetic epilepsies and provide a theoretical basis for searching for effective drug treatment.

Nicotinamide mononucleotide alleviates seizures via modulating SIRT1-PGC-1α mediated mitochondrial fusion and fission

Both human and animal experiments have demonstrated that energy metabolism dysfunction in neurons after seizures is associated with an imbalance in mitochondrial fusion/fission dynamics. Effective neuronal mitochondrial dynamics regulation strategies remain elusive. Nicotinamide mononucleotide (NMN) can ameliorate mitochondrial functional and oxidative stress in age-related diseases. But whether NMN improves mitochondrial energy metabolism to exert anti-epileptic effects is unclear. This study aims to clarify if NMN can protect neurons from pentylenetetrazole (PTZ) or Mg2+ -free-induced mitochondrial disorder and apoptosis via animal and cell models. We established a continuous 30-day PTZ (37 mg/kg) intraperitoneal injection-induced epileptic mouse model and a cell model induced by Mg2+ -free solution incubation to explore the neuroprotective effects of NMN. We found that NMN treatment significantly reduced the seizure intensity of PTZ-induced epileptic mice, improved their learning and memory ability, and enhanced their motor activity and exploration desire. At the same time, in vitro and in vivo experiments showed that NMN can inhibit neuronal apoptosis and improve the mitochondrial energy metabolism function of neurons. In addition, NMN down-regulated the expression of mitochondrial fission proteins (Drp1 and Fis1) and promoted the expression of mitochondrial fusion proteins (Mfn1 and Mfn2) by activating the SIRT1-PGC-1α pathway, thereby inhibiting PTZ or Mg2+ -free extracellular solution-induced mitochondrial dysfunction, cell apoptosis, and oxidative stress. However, combined intervention of SIRT1 inhibitor, Selisistat, and PGC-1α inhibitor, SR-18292, eliminated the regulatory effect of NMN pre-treatment on mitochondrial fusion and fission proteins and apoptosis-related proteins. Therefore, NMN intervention may be a new potential treatment for cognitive impairment and behavioral disorders induced by epilepsy, and targeting the SIRT1-PGC-1α pathway may be a promising therapeutic strategy for seizures.

NMNATs expression inhibition mediated NAD+ deficiency plays a critical role in doxorubicin-induced hepatotoxicity in mice

Doxorubicin (DOX) is one of the most widely used antineoplastic drugs with known cardiotoxicity while other organ toxicity, such as hepatotoxicity is not well defined. This study was to explore the role of nicotinamide adenine dinucleotide (NAD+) in DOX-induced hepatotoxicity. DOX (20 mg/kg) induced acute liver injury and oxidative stress in C57BL/6 J mice at 48 h. Notably, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and NAD(P)H dehydrogenase quinone 1 (NQO1) were downregulated. NAD+ deficiency was confirmed due to DOX exposure. Mechanistically, the downregulation of nicotinamide mononucleotide adenylyl transferase 1 (NMNAT1), NMNAT2 and NMNAT3, while no alteration of nicotinamide phosphoribosyl transferase was proved. As a consequence of NAD+ deficiency, the expression of poly-ADP-ribose polymerase1 (PARP1), CD38 and Sirtuin1 (SIRT1) were reduced. Furthermore, supplementation of NAD+ (200 mg/kg/day) or its precursor nicotinamide mononucleotide (NMN) (500 mg/kg/day) alleviated liver injury, attenuated oxidative stress, and elevated the downregulation of Nrf2 and NQO1. More importantly, compromised expression of NMNAT1-3, PARP1, CD38 and SIRT1 were improved by NAD+ and NMN. In conclusion, NAD+ deficiency due to NMNATs expression inhibition may attribute to the pathogenesis of DOX-induced hepatotoxicity, thus providing new insights for mitigating DOX side effects.

RICH2 decreases the mitochondrial number and affects mitochondrial localization in diffuse low-grade glioma-related epilepsy

Epilepsy, a common complication of diffuse low-grade gliomas (DLGGs; diffuse oligodendroglioma and astrocytoma collectively), severely compromises the quality of life of patients. DLGG epileptogenicity may primarily be generated by interactions between the tumor and the neocortex. Neuronal uptake of dysfunctional mitochondria from the extracellular environment can lead to abnormal neuronal discharge. Mitochondrial dysfunction is frequently observed in gliomas that can transmigrate across the plasma membranes. Here, we examined the role of the Rho GTPase-activating protein 44 (RICH2) in mitochondrial dynamics and DLGG-related epilepsy. We investigated the association between mitochondrial and RICH2 expression in human DLGG tissues using immunohistochemistry. We examined the association between RICH2 and epilepsy in nude mouse glioma models by electrophysiology. The effect of RICH2 on mitochondrial morphology and calcium motility were assessed by single cell fluorescence microscopy. Quantitative RT-PCR (qRT-PCR) and Western blot analysis were performed to characterize RICH2 induced expression changes in the genes related to mitochondrial dynamics, mitogenesis and mitochondrial function. We found that RICH2 expression was higher in oligodendroglioma than in astrocytoma and was correlated with better prognosis and higher epilepsy rate in patients. The expression of mitochondria may be associated with clinical DLGG-related epilepsy and reduced by RICH2 overexpression. And RICH2 could promote DLGG-related epilepsy in tumorigenic nude mice. RICH2 overexpression decreased calcium flow and the mitochondria released from glioma cells (SW1088 and U251) into the extracellular environment, potentially via downregulation of MFN-1/MFN-2 levels which suggests reduced mitochondrial fusion. In addition, we observed decreased mitochondrial trafficking into neurons (released from glioma cells and trafficked into neurons), which could explain the higher incidence of DLGG-related epilepsy due to reduced neuroprotection. Furthermore, RICH2 downregulated MAPK/ERK/HIF-1 pathway. In conclusion, these results suggest that RICH2 could promote epilepsy by (i) inhibiting mitochondrial fusion via MFN downregulation and Drp-1 upregulation; (ii) altering the MAPK/ERK/Hif-1 signaling axis. RICH2 may be a potential target in the treatment of DLGG-related epilepsy.

A Compared Study of Eicosapentaenoic Acid and Docosahexaenoic Acid in Improving Seizure-Induced Cognitive Deficiency in a Pentylenetetrazol-Kindling Young Mice Model

Epilepsy is a chronic neurological disorder that is more prevalent in children, and recurrent unprovoked seizures can lead to cognitive impairment. Numerous studies have reported the benefits of docosahexaenoic acid (DHA) on neurodevelopment and cognitive ability, while comparatively less attention has been given to eicosapentaenoic acid (EPA). Additionally, little is known about the effects and mechanisms of DHA and EPA in relation to seizure-induced cognitive impairment in the young rodent model. Current research indicates that ferroptosis is involved in epilepsy and cognitive deficiency in children. Further investigation is warranted to determine whether EPA or DHA can mitigate seizure-induced cognitive deficits by inhibiting ferroptosis. Therefore, this study was conducted to compare the effects of DHA and EPA on seizure-induced cognitive deficiency and reveal the underlying mechanisms focused on ferroptosis in a pentylenetetrazol (PTZ)-kindling young mice model. Mice were fed a diet containing DHA-enriched ethyl esters or EPA-enriched ethyl esters for 21 days at the age of 3 weeks and treated with PTZ (35 mg/kg, i.p.) every other day 10 times. The findings indicated that both EPA and DHA exhibited ameliorative effects on seizure-induced cognitive impairment, with EPA demonstrating a superior efficacy. Further mechanism study revealed that supplementation of DHA and EPA significantly increased cerebral DHA and EPA levels, balanced neurotransmitters, and inhibited ferroptosis by modulating iron homeostasis and reducing lipid peroxide accumulation in the hippocampus through activating the Nrf2/Sirt3 signal pathway. Notably, EPA exhibited better an advantage in ameliorating iron dyshomeostasis compared to DHA, owing to its stronger upregulation of Sirt3. These results indicate that DHA and EPA can efficaciously alleviate seizure-induced cognitive deficiency by inhibiting ferroptosis in PTZ-kindled young mice.

Neuronal SIRT3 Deletion Predisposes to Female-Specific Alterations in Cellular Metabolism, Memory, and Network Excitability

Mitochondrial dysfunction is an early event in the pathogenesis of neurologic disorders and aging. Sirtuin 3 (SIRT3) regulates mitochondrial function in response to the cellular environment through the reversible deacetylation of proteins involved in metabolism and reactive oxygen species detoxification. As the primary mitochondrial deacetylase, germline, or peripheral tissue-specific deletion of SIRT3 produces mitochondrial hyperacetylation and the accelerated development of age-related diseases. Given the unique metabolic demands of neurons, the role of SIRT3 in the brain is only beginning to emerge. Using mass spectrometry-based acetylomics, high-resolution respirometry, video-EEG, and cognition testing, we report targeted deletion of SIRT3 from select neurons in the cortex and hippocampus produces altered neuronal excitability and metabolic dysfunction in female mice. Targeted deletion of SIRT3 from neuronal helix-loop-helix 1 (NEX)-expressing neurons resulted in mitochondrial hyperacetylation, female-specific superoxide dismutase-2 (SOD2) modification, increased steady-state superoxide levels, metabolic reprogramming, altered neuronal excitability, and working spatial memory deficits. Inducible neuronal deletion of SIRT3 likewise produced female-specific deficits in spatial working memory. Together, the data demonstrate that deletion of SIRT3 from forebrain neurons selectively predisposes female mice to deficits in mitochondrial and cognitive function.SIGNIFICANCE STATEMENT Mitochondrial SIRT3 is an enzyme shown to regulate energy metabolism and antioxidant function, by direct deacetylation of proteins. In this study, we show that neuronal SIRT3 deficiency renders female mice selectively vulnerable to impairment in redox and metabolic function, spatial memory, and neuronal excitability. The observed sex-specific effects on cognition and neuronal excitability in female SIRT3-deficient mice suggest that mitochondrial dysfunction may be one factor underlying comorbid neuronal diseases, such as Alzheimer's disease and epilepsy. Furthermore, the data suggest that SIRT3 dysfunction may predispose females to age-related metabolic and cognitive impairment.

CircRNA SRRM4 affects glucose metabolism by regulating PKM alternative splicing via SRSF3 deubiquitination in epilepsy

OBJECTIVES

Several reports suggest that epigenetic therapy may be a potential method for treating epilepsy, and circular RNAs (circRNAs) play important roles in mediating the epigenetic mechanisms associated with epilepsy; however, currently there are no effective treatment methods to prevent the progression of epileptogenesis. The circRNA serine/arginine repetitive matrix 4 (circSRRM4) was found to exert regulatory effects in temporal lobe epilepsy (TLE); however, the mechanisms involved are still unknown.

MATERIALS AND METHODS

To elucidate the molecular mechanism of circSRRM4, we investigated human epileptic brain tissue, epileptic rats, neuron and astrocyte cell lines using RT-qPCR, western blot, fluorescence in situ hybridisation, immunofluorescence staining, Nissl stain, micro-PET-CT, RNA-pulldown, liquid chromatography-mass spectrometry, and RBP immunoprecipitation techniques. Furthermore, we evaluated the pyruvate kinase M1/2 (PKM) expression patterns in the human and rat models of TLE.

RESULTS

We detected the increased circSRRM4 expression in the hypometabolic lesions of patients with TLE and discovered that circSrrm4 has specific spatiotemporal characteristics in rats with kainic acid-induced epilepsy. The decreased PKM1 expression and increased PKM2 expression were similar to the Warburg effect in tumours. Notably, circSrrm4 silencing reduced the incidence and frequency of epilepsy, improved local hypometabolism, and prevented neuronal loss and astrocyte activation.

CONCLUSION

PKM2 promotes lactic acid production in the astrocytes by inducing glycolysis, thereby contributing to the energy source for epileptic seizures. Notably, circSRRM4 combines with and inhibits serine and arginine rich splicing factor 3 (SRSF3) from joining the ubiquitin-proteasome pathway, improving the SRSF3-regulated alternative splicing of PKM, and consequently stimulating glycolysis in cells.

Role of SIRT3 in neurological diseases and rehabilitation training

Sirtuin3 (SIRT3) is a deacetylase that plays an important role in normal physiological activities by regulating a variety of substrates. Considerable evidence has shown that the content and activity of SIRT3 are altered in neurological diseases. Furthermore, SIRT3 affects the occurrence and development of neurological diseases. In most cases, SIRT3 can inhibit clinical manifestations of neurological diseases by promoting autophagy, energy production, and stabilization of mitochondrial dynamics, and by inhibiting neuroinflammation, apoptosis, and oxidative stress (OS). However, SIRT3 may sometimes have the opposite effect. SIRT3 can promote the transfer of microglia. Microglia in some cases promote ischemic brain injury, and in some cases inhibit ischemic brain injury. Moreover, SIRT3 can promote the accumulation of ceramide, which can worsen the damage caused by cerebral ischemia-reperfusion (I/R). This review comprehensively summarizes the different roles and related mechanisms of SIRT3 in neurological diseases. Moreover, to provide more ideas for the prognosis of neurological diseases, we summarize several SIRT3-mediated rehabilitation training methods.

Regulation of the Volume-Regulated Anion Channel Pore-Forming Subunit LRRC8A in the Intrahippocampal Kainic Acid Model of Mesial Temporal Lobe Epilepsy

Volume-regulated anion channels (VRACs) are a group of ubiquitously expressed outwardly-rectifying anion channels that sense increases in cell volume and act to return cells to baseline volume through an efflux of anions and organic osmolytes, including glutamate. Because cell swelling, increased extracellular glutamate levels, and reduction of the brain extracellular space (ECS) all occur during seizure generation, we set out to determine whether VRACs are dysregulated throughout mesial temporal lobe epilepsy (MTLE), the most common form of adult epilepsy. To accomplish this, we employed the IHKA experimental model of MTLE, and probed for the expression of LRRC8A, the essential pore-forming VRAC subunit, at acute, early-, mid-, and late-epileptogenic time points (1-, 7-, 14-, and 30-days post-IHKA, respectively). Western blot analysis revealed the upregulation of total dorsal hippocampal LRRC8A 14-days post-IHKA in both the ipsilateral and contralateral hippocampus. Immunohistochemical analyses showed an increased LRRC8A signal 7-days post-IHKA in both the ipsilateral and contralateral hippocampus, along with layer-specific changes 1-, 7-, and 30-days post-IHKA bilaterally. LRRC8A upregulation 1 day post-IHKA was observed primarily in astrocytes; however, some upregulation was also observed in neurons. Glutamate-GABA/glutamine cycle enzymes glutamic acid decarboxylase, glutaminase, and glutamine synthetase were also dysregulated at the 7-day timepoint post status epilepticus. The timepoint-dependent upregulation of total hippocampal LRRC8A and the possible subsequent increased efflux of glutamate in the epileptic hippocampus suggest that the dysregulation of astrocytic VRAC may play an important role in the development of epilepsy.

HAT- and HDAC-Targeted Protein Acetylation in the Occurrence and Treatment of Epilepsy

Epilepsy is a common and severe chronic neurological disorder. Recently, post-translational modification (PTM) mechanisms, especially protein acetylation modifications, have been widely studied in various epilepsy models or patients. Acetylation is regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HATs catalyze the transfer of the acetyl group to a lysine residue, while HDACs catalyze acetyl group removal. The expression of many genes related to epilepsy is regulated by histone acetylation and deacetylation. Moreover, the acetylation modification of some non-histone substrates is also associated with epilepsy. Various molecules have been developed as HDAC inhibitors (HDACi), which have become potential antiepileptic drugs for epilepsy treatment. In this review, we summarize the changes in acetylation modification in epileptogenesis and the applications of HDACi in the treatment of epilepsy as well as the mechanisms involved. As most of the published research has focused on the differential expression of proteins that are known to be acetylated and the knowledge of whole acetylome changes in epilepsy is still minimal, a further understanding of acetylation regulation will help us explore the pathological mechanism of epilepsy and provide novel ideas for treating epilepsy.

Protective effect of N-acetyl cysteine on the mitochondrial dynamic imbalance in temporal lobe epilepsy: Possible role of mTOR

Understanding the underlying molecular mechanisms involved in epilepsy is critical for the development of more effective therapies. It is believed that mTOR (Mechanistic Target of Rapamycin kinases) activity and the mitochondrial dynamic balance change during epilepsy. mTOR affects mitochondrial fission by stimulating the translation of mitochondrial fission process 1 (MTFP1). In This study, the protective role of N-acetylcysteine was studied in temporal lobe epilepsy (TLE) through the regulation of mTOR and mitochondrial dynamic proteins. Rats received N-acetylcysteine (oral administration) seven days before induction of epilepsy, followed by one day after epilepsy. TLE was induced by microinjection of kainite into the left lateral ventricle. The total mTOR and Drp1 levels in the hippocampus were evaluated by western blotting. MFN1 was assessed using immunohistochemistry, and the expression of Fis.1 and MTFP1 (fission-related proteins) and OPA (fusion-related protein) were detected by real-time PCR. The mitochondrial membrane potential was measured by Rhodamin 123. The results showed that 72 h after induction of epilepsy, the mTOR protein level increased, and the balance of the mitochondrial dynamic was disturbed; however, oral administration of NAC decreased the mTOR protein level and improved the mitochondrial dynamic. These findings indicate that NAC plays a neuroprotective role in temporal lobe epilepsy, probably through decreasing the mTOR protein level, which can improve the imbalance in the mitochondrial dynamic.

The Brain Protein Acylation System Responds to Seizures in the Rat Model of PTZ-Induced Epilepsy

Abnormal energy expenditure during seizures and metabolic regulation through post-translational protein acylation suggest acylation as a therapeutic target in epilepsy. Our goal is to characterize an interplay between the brain acylation system components and their changes after seizures. In a rat model of pentylenetetrazole (PTZ)-induced epilepsy, we quantify 43 acylations in 29 cerebral cortex proteins; levels of NAD⁺; expression of NAD⁺-dependent deacylases (SIRT2, SIRT3, SIRT5); activities of the acyl-CoA-producing/NAD⁺-utilizing complexes of 2-oxoacid dehydrogenases. Compared to the control group, acylations of 14 sites in 11 proteins are found to differ significantly after seizures, with six of the proteins involved in glycolysis and energy metabolism. Comparing the single and chronic seizures does not reveal significant differences in the acylations, pyruvate dehydrogenase activity, SIRT2 expression or NAD⁺. On the contrary, expression of SIRT3, SIRT5 and activity of 2-oxoglutarate dehydrogenase (OGDH) decrease in chronic seizures vs. a single seizure. Negative correlations between the protein succinylation/glutarylation and SIRT5 expression, and positive correlations between the protein acetylation and SIRT2 expression are shown. Our findings unravel involvement of SIRT5 and OGDH in metabolic adaptation to seizures through protein acylation, consistent with the known neuroprotective role of SIRT5 and contribution of OGDH to the Glu/GABA balance perturbed in epilepsy.

Lysine acetylome profiling in mouse hippocampus and its alterations upon FMRP deficiency linked to abnormal energy metabolism

Loss of fragile X retardation protein (FMRP) leads to fragile X syndrome (FXS), a common cause of inherited intellectual disability. Protein lysine acetylation (K-ac), a reversible post-translational modification of proteins, is associated with the regulation of brain development and neuropathies. However, a comprehensive hippocampal K-ac protein profile in response to FMRP deficiency has not been reported until now. Using LC-MS/MS to analyze the enriched K-ac peptides, this study identified 1629 K-ac hits across 717 proteins in the mouse hippocampus, and these proteins were enriched in several metabolic processes. Of them, 51 K-ac hits across 45 proteins were significantly changed upon loss of FMRP. These altered K-ac proteins were enriched in energy metabolic processes including carboxylic acid metabolism process, aerobic respiration and citrate cycle, linking with several neurological disorders such as lactic acidosis, Lewy body disease, Leigh disease and encephalopathies. In the mouse hippocampus and the hippocampal HT-22 cells, FMRP deficiency could induce altered K-ac modification of several key enzymes, decrease in ATP and increase in lactate. Thus, this study identified a global hippocampal lysine acetylome and an altered K-ac protein profile upon loss of FMRP linked to abnormal energy metabolism, implicating in the pathogenesis of FXS. SIGNIFICANCE: Fragile X syndrome (FXS) is a common inherited neurodevelopment disorder characterized by intellectual disability and an increased risk for autism spectrum disorder. FXS is resulted from silencing of the FMR1 gene, which induces loss of its encoding protein FMRP. Molecular and metabolic changes of Fmr1-null animal models of FXS have been identified to potentially contribute to the pathogenesis of FXS. Here, we used a TMT-labeled quantitative proteomic analysis of the peptides enriched by anti-K-ac antibodies and identified a global K-ac protein profile in the mouse hippocampus with a total of 1629 K-ac peptides on 717 proteins. Of them, 51 K-ac peptides regarding 45 proteins altered in response to loss of FMRP, which were enriched in energy metabolic processes and were implicated in several neurological disorders. Thus this study for the first time provides a global hippocampal lysine acetylome upon FMRP deficiency linked to abnormal metabolic pathways, which may contribute to pathogenic mechanism of FXS.

Cytochrome P450-mediated antiseizure medication interactions influence apoptosis, modulate the brain BAX/Bcl-XL ratio and aggravate mitochondrial stressors in human pharmacoresistant epilepsy

Polytherapy with antiseizure medications (ASMs) is often used to control seizures in patients suffering from epilepsy, where about 30% of patients are pharmacoresistant. While drug combinations are intended to be beneficial, the consequence of CYP-dependent drug interactions on apoptotic protein levels and mitochondrial function in the epileptic brain remains unclear. We examined the interactions of ASMs given prior to surgery in surgically resected brain tissues and of three ASMs (lacosamide, LCM; oxcarbazepine, OXC; levetiracetam LEV) in isolated brain cells from patients with drug-resistant epilepsy (n = 23). We divided the patients into groups-those who took combinations of NON-CYP + CYP substrate ASMs, NON-CYP + CYP inducer ASMs, CYP substrate + CYP substrate or CYP substrate + CYP inducer ASMs-to study the 1) pro- and anti-apoptotic protein levels and other apoptotic signaling proteins and levels of reactive oxygen species (reduced glutathione and lipid peroxidation) in brain tissues; 2) cytotoxicity at blood-brain barrier epileptic endothelial cells (EPI-ECs) and subsequent changes in mitochondrial membrane potential in normal neuronal cells, following treatment with LCM + OXC (CYP substrate + CYP inducer) or LCM + LEV (CYP substrate + NON-CYP-substrate) after blood-brain barrier penetration, and 3) apoptotic and mitochondrial protein targets in the cells, pre-and post-CYP3A4 inhibition by ketoconazole and drug treatments. We found an increased BAX (pro-apoptotic)/Bcl-XL (anti-apoptotic) protein ratio in epileptic brain tissue after treatment with CYP substrate + CYP substrate or inducer compared to NON-CYP + CYP substrate or inducer, and subsequently decreased glutathione and elevated lipid peroxidation levels. Further, increased cytotoxicity and Mito-ID levels, indicative of compromised mitochondrial membrane potential, were observed after treatment of LCM + OXC in combination compared to LCM + LEV or these ASMs alone in EPI-ECs, which was attenuated by pre-treatment of CYP inhibitor, ketoconazole. A combination of two CYP-mediated ASMs on EPI-ECs resulted in elevated caspase-3 and cytochrome c with decreased SIRT3 levels and activity, which was rescued by CYP inhibition. Together, the study highlights for the first time that pro- and anti-apoptotic proteins levels are dependent on ASM combinations in epilepsy, modulated via a CYP-mediated mechanism that controls free radicals, cytotoxicity and mitochondrial activity. These findings lead to a better understanding of future drug selection choices offsetting pharmacodynamic CYP-mediated interactions.

Electroacupuncture Promotes Autophagy by Regulating the AKT/mTOR Signaling Pathway in Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) is a complex neurological disease, and its occurrence and development are closely related to the autophagy signaling pathway. However, the mechanism by which electroacupuncture (EA) affects the regulation of autophagy has not been fully elucidated. TLE gene chip dataset GSE27166 and data from rats without epilepsy (n = 6) and rats with epilepsy (n = 6) were downloaded from Gene Expression Omnibus. The differentially expressed genes (DEGs) in the TLE and control groups were identified with the online tool GEO2R. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were used to analyse the functional and pathway enrichment of genes in the most important modules. A rat model of TLE induced by lithium-pilocarpine treatment was established. EA treatment at DU20 and DU14 in TLE rats was performed for 2 weeks. Neuronal regeneration was determined using immunofluorescence staining. The protein levels of AKT/mTOR signaling pathway and autophagy markers were detected through western blotting and immunohistochemistry. This study identified 1837 DEGs, including 798 upregulated genes and 1039 downregulated genes. GO enrichment and KEGG analyses were performed on DEGs and revealed functional enrichment mainly in the mTOR signaling pathway and autophagy-animal. Furthermore, the number of mature neurons was significantly increased upon coexpressing BrdU/NeuN in TLE rats treated with EA. Western blotting and immunohistochemistry results showed significantly decreased levels of the phosphorylated-AKT and p-mTOR in the hippocampal CA3 and DG regions of TLE rats with EA treatment. And increased p-ULK1/ULK1, LC3-II/LC3-I and p62 levels in TLE rats with EA stimulation. Therefore, this study suggested that EA promoted autophagy in hippocampal neurons during the onset of epilepsy by regulating the AKT/mTOR signaling pathway to treat epilepsy.

Pathological Targets for Treating Temporal Lobe Epilepsy: Discoveries From Microscale to Macroscale

Temporal lobe epilepsy (TLE) is one of the most common and severe types of epilepsy, characterized by intractable, recurrent, and pharmacoresistant seizures. Histopathology of TLE is mostly investigated through observing hippocampal sclerosis (HS) in adults, which provides a robust means to analyze the related histopathological lesions. However, most pathological processes underlying the formation of these lesions remain elusive, as they are difficult to detect and observe. In recent years, significant efforts have been put in elucidating the pathophysiological pathways contributing to TLE epileptogenesis. In this review, we aimed to address the new and unrecognized neuropathological discoveries within the last 5 years, focusing on gene expression (miRNA and DNA methylation), neuronal peptides (neuropeptide Y), cellular metabolism (mitochondria and ion transport), cellular structure (microtubule and extracellular matrix), and tissue-level abnormalities (enlarged amygdala). Herein, we describe a range of biochemical mechanisms and their implication for epileptogenesis. Furthermore, we discuss their potential role as a target for TLE prevention and treatment. This review article summarizes the latest neuropathological discoveries at the molecular, cellular, and tissue levels involving both animal and patient studies, aiming to explore epileptogenesis and highlight new potential targets in the diagnosis and treatment of TLE.

Acetylation Profiles in the Metabolic Process of Glioma-Associated Seizures

Objective: We test the hypothesis that lysine acetylation is involved in the metabolic process of glioma-associated seizures (GAS). Methods: We used label-free mass spectrometry-based quantitative proteomics to quantify dynamic changes of protein acetylation between gliomas with seizure (CA1 group) and gliomas without seizure (CA2 group). Furthermore, differences of acetyltransferase and deacetylase expression between CA1 and CA2 groups were performed by a quantitative proteomic study. We further classified acetylated proteins into groups according to cell component, molecular function, and biological process. In addition, metabolic pathways and protein interaction networks were analyzed. Regulated acetyltransferases and acetylated profiles were validated by PRM and Western blot. Results: We detected 169 downregulated lysine acetylation sites of 134 proteins and 39 upregulated lysine acetylation sites of 35 proteins in glioma with seizures based on acetylome. We detected 407 regulated proteins by proteomics, from which ACAT2 and ACAA2 were the differentially regulated enzymes in the acetylation of GAS. According to the KEGG analysis, the upregulated acetylated proteins within the PPIs were mapped to pathways involved in the TCA cycle, oxidative phosphorylation, biosynthesis of amino acids, and carbon metabolism. The downregulated acetylated proteins within the PPIs were mapped to pathways involved in fatty acid metabolism, oxidative phosphorylation, TCA cycle, and necroptosis. Regulated ACAT2 expression and acetylated profiles were validated by PRM and Western blot. Conclusions: The data support the hypothesis that regulated protein acetylation is involved in the metabolic process of GAS, which may be induced by acetyl-CoA acetyltransferases.

Exogenous Nicotinamide Adenine Dinucleotide Attenuates Postresuscitation Myocardial and Neurologic Dysfunction in a Rat Model of Cardiac Arrest

OBJECTIVES

To investigate the therapeutic potential and underlying mechanisms of exogenous nicotinamide adenine dinucleotide+ on postresuscitation myocardial and neurologic dysfunction in a rat model of cardiac arrest.

DESIGN

Thirty-eight rats were randomized into three groups: 1) Sham, 2) Control, and 3) NAD. Except for the sham group, untreated ventricular fibrillation for 6 minutes followed by cardiopulmonary resuscitation was performed in the control and NAD groups. Nicotinamide adenine dinucleotide+ (20 mg/kg) was IV administered at the onset of return of spontaneous circulation.

SETTING

University-affiliated research laboratory.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

Nicotinamide adenine dinucleotide+.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic and myocardial function were measured at baseline and within 4 hours following return of spontaneous circulation. Survival analysis and Neurologic Deficit Score were performed up to 72 hours after return of spontaneous circulation. Adenosine triphosphate (adenosine triphosphate) level was measured in both brain and heart tissue. Mitochondrial respiratory chain function, acetylation level, and expression of Sirtuin3 and NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 9 (NDUFA9) in isolated mitochondrial protein from both brain and heart tissue were evaluated at 4 hours following return of spontaneous circulation. The results demonstrated that nicotinamide adenine dinucleotide+ treatment improved mean arterial pressure (at 1 hr following return of spontaneous circulation, 94.69 ± 4.25 mm Hg vs 89.57 ± 7.71 mm Hg; p < 0.05), ejection fraction (at 1 hr following return of spontaneous circulation, 62.67% ± 6.71% vs 52.96% ± 9.37%; p < 0.05), Neurologic Deficit Score (at 24 hr following return of spontaneous circulation, 449.50 ± 82.58 vs 339.50 ± 90.66; p < 0.05), and survival rate compared with that of the control group. The adenosine triphosphate level and complex I respiratory were significantly restored in the NAD group compared with those of the control group. In addition, nicotinamide adenine dinucleotide+ treatment activated the Sirtuin3 pathway, down-regulating acetylated-NDUFA9 in the isolated mitochondria protein.

CONCLUSIONS

Exogenous nicotinamide adenine dinucleotide+ treatment attenuated postresuscitation myocardial and neurologic dysfunction. The responsible mechanisms may involve the preservation of mitochondrial complex I respiratory capacity and adenosine triphosphate production, which involves the Sirtuin3-NDUFA9 deacetylation.

Progress on mitochondrial silence information regulator family in epilepsy

SIRT3, SIRT4 and SIRT5 are located in mitochondria and also known as mitochondrial sirtuins. They play important roles in regulating many cellular functions including cell survival, cell cycle or apoptosis, DNA repair and metabolism. Mitochondrial sirtuins are involved in the protection of mitochondrial integrity and energy metabolism under stress regulating the expression of neurotransmitter receptors, neurotrophins, extracellular matrix proteins and various transcription factors, thus involved in epileptogenesis triggered by both genetic or acquired factors. Here we review research progress on the actions of mitochondrial sirtuin in epilepsy; and discuss the challenges and perspectives of mitochondrial sirtuin as a potential therapeutic target for epilepsy.

A link between protein acetylation and mitochondrial dynamics under energy metabolism: A comprehensive overview

Cells adjust mitochondrial morphologies to coordinate between the cellular demand for energy and the availability of resources. Mitochondrial morphology is regulated by the balance between two counteracting mitochondrial processes of fusion and fission. Fission and fusion are dynamic and reversible processes that depend on the coordination of a number of proteins and are primarily regulated by posttranslational modifications. In the mitochondria, more than 20% of proteins are acetylated in proteomic surveys, partly involved in the dynamic regulation of mitochondrial fusion and fission. This article focuses on the molecular mechanism of the mitochondrial dynamics of fusion and fission, and summarizes the related mechanisms and targets of mitochondrial protein acetylation to regulate the mitochondrial dynamics of fusion and fission in energy metabolism.

The Kainic Acid Models of Temporal Lobe Epilepsy

Experimental models of epilepsy are useful to identify potential mechanisms of epileptogenesis, seizure genesis, comorbidities, and treatment efficacy. The kainic acid (KA) model is one of the most commonly used. Several modes of administration of KA exist, each producing different effects in a strain-, species-, gender-, and age-dependent manner. In this review, we discuss the advantages and limitations of the various forms of KA administration (systemic, intrahippocampal, and intranasal), as well as the histologic, electrophysiological, and behavioral outcomes in different strains and species. We attempt a personal perspective and discuss areas where work is needed. The diversity of KA models and their outcomes offers researchers a rich palette of phenotypes, which may be relevant to specific traits found in patients with temporal lobe epilepsy.

Reviving mitochondrial bioenergetics: A relevant approach in epilepsy

Epileptogenesis is most commonly associated with neurodegeneration and a bioenergetic defect attributing to the fact that mitochondrial dysfunction plays a key precursor for neuronal death. Mitochondria are the essential organelle of neuronal cells necessary for certain neurophysiological processes like neuronal action potential activity and synaptic transmission. The mitochondrial dysfunction disrupts calcium homeostasis leading to inhibitory interneuron dysfunction and increasing the excitatory postsynaptic potential. In epilepsy, the prolonged repetitive neuronal activity increases the excessive demand for energy and acidosis in the brain further increasing the intracellular calcium causing neuronal death. Similarly, the mitochondrial damage also leads to the decline of energy by dysfunction of the electron transport chain and abnormal production of the ROS triggering the apoptotic neuronal death. Thus, the elevated level of cytosolic calcium causes the mitochondria DNA damage coinciding with mtROS and releasing the cytochrome c binding to Apaf protein further initiating the apoptosis resulting in epileptic encephalopathies. The various genetic and mRNA studies of epilepsy have explored the various pathogenic mutations of genes affecting the mitochondria functioning further initiating the neuronal excitotoxicity. Based on the results of previous studies, the recent therapeutic approaches are targeting basic mitochondrial processes, such as energy metabolism or free-radical generation, or specific interactions of disease-related proteins with mitochondria and hold great promise to attenuate epileptogenesis. Therefore, the current review emphasizes the emerging insights to uncover the relation between mitochondrial dysfunction and ROS generation contributing to mechanisms underlying epileptic seizures.

Asiatic Acid Prevents Cognitive Deficits by Inhibiting Calpain Activation and Preserving Synaptic and Mitochondrial Function in Rats with Kainic Acid-Induced Seizure

Cognitive impairment is not only associated with seizures but also reported as an adverse effect of antiepileptic drugs. Thus, new molecules that can ameliorate seizures and maintain satisfactory cognitive function should be developed. The antiepileptic potential of asiatic acid, a triterpene derived from the medicinal herb Centella asiatica, has already been demonstrated; however, its role in epilepsy-related cognitive deficits is yet to be determined. In this study, we evaluated the effects of asiatic acid on cognitive deficits in rats with kainic acid (KA)-induced seizure and explored the potential mechanisms underlying these effects. Our results revealed that asiatic acid administrated intraperitoneally 30 min prior to KA (15 mg/kg) injection ameliorated seizures and significantly improved KA-induced memory deficits, as demonstrated by the results of the Morris water maze test. In addition, asiatic acid ameliorated neuronal damage, inhibited calpain activation, and increased protein kinase B (AKT) activation in the hippocampus of KA-treated rats. Asiatic acid also increased the levels of synaptic proteins and the number of synaptic vesicles as well as attenuated mitochondrial morphology damage in the hippocampus of KA-treated rats. Furthermore, proteomic and Western blot analyses of hippocampal synaptosomes revealed that asiatic acid reversed KA-induced changes in mitochondria function-associated proteins, including lipoamide dehydrogenase, glutamate dehydrogenase 1 (GLUD1), ATP synthase (ATP5A), and mitochondrial deacetylase sirtuin-3 (SIRT3). Our data suggest that asiatic acid can prevent seizures and improve cognitive impairment in KA-treated rats by reducing hippocampal neuronal damage through the inhibition of calpain activation and the elevation of activated AKT, coupled with an increase in synaptic and mitochondrial function.

Neuroproteomics in Epilepsy: What Do We Know so Far?

Epilepsies are chronic neurological diseases that affect approximately 2% of the world population. In addition to being one of the most frequent neurological disorders, treatment for patients with epilepsy remains a challenge, because a proportion of patients do not respond to the antiseizure medications that are currently available. This results in a severe economic and social burden for patients, families, and the healthcare system. A characteristic common to all forms of epilepsy is the occurrence of epileptic seizures that are caused by abnormal neuronal discharges, leading to a clinical manifestation that is dependent on the affected brain region. It is generally accepted that an imbalance between neuronal excitation and inhibition generates the synchronic electrical activity leading to seizures. However, it is still unclear how a normal neural circuit becomes susceptible to the generation of seizures or how epileptogenesis is induced. Herein, we review the results of recent proteomic studies applied to investigate the underlying mechanisms leading to epilepsies and how these findings may impact research and treatment for these disorders.

Antioxidants Targeting Mitochondrial Oxidative Stress: Promising Neuroprotectants for Epilepsy

Mitochondria are major sources of reactive oxygen species (ROS) within the cell and are especially vulnerable to oxidative stress. Oxidative damage to mitochondria results in disrupted mitochondrial function and cell death signaling, finally triggering diverse pathologies such as epilepsy, a common neurological disease characterized with aberrant electrical brain activity. Antioxidants are considered as promising neuroprotective strategies for epileptic condition via combating the deleterious effects of excessive ROS production in mitochondria. In this review, we provide a brief discussion of the role of mitochondrial oxidative stress in the pathophysiology of epilepsy and evidences that support neuroprotective roles of antioxidants targeting mitochondrial oxidative stress including mitochondria-targeted antioxidants, polyphenols, vitamins, thiols, and nuclear factor E2-related factor 2 (Nrf2) activators in epilepsy. We point out these antioxidative compounds as effectively protective approaches for improving prognosis. In addition, we specially propose that these antioxidants exert neuroprotection against epileptic impairment possibly by modulating cell death interactions, notably autophagy-apoptosis, and autophagy-ferroptosis crosstalk.

A unifying mechanism of ketogenic diet action: The multiple roles of nicotinamide adenine dinucleotide

The ability of a ketogenic diet to treat seizures and render a neuronal network more resistant to strong electrical activity has been observed for a century in clinics and for decades in research laboratories. Alongside ongoing efforts to understand how this therapy works to stop seizures, metabolic health is increasingly appreciated as critical buffer to resisting and recovering from acute and chronic disease. Accordingly, links between metabolism and health, and the broader emerging impact of the ketogenic diet in improving diverse metabolic, immunological and neurological conditions, have served to intensify the search for its key and/or common mechanisms. Here we review diverse evidence for increased levels of NAD⁺, and thus an altered ratio of NAD⁺/NADH, during metabolic therapy with a ketogenic diet. We propose this as a potential unifying mechanism, and highlight some of the evidence linking altered NAD⁺/NADH with reduced seizures and with a range of short and long-term changes associated with the beneficial effects of a ketogenic diet. An increase in NAD⁺/NADH is consistent with multiple lines of evidence and hypotheses, and therefore we suggest that increased NAD⁺ may be a common mechanism underlying beneficial effects of ketogenic diet therapy.

Inhibition of miR-181a-5p reduces astrocyte and microglia activation and oxidative stress by activating SIRT1 in immature rats with epilepsy

MicroRNAs regulate gene expression at the posttranscriptional level, and this process has been shown to be implicated in the pathological processes of temporal lobe epilepsy. At present, studies about the impact of microRNA-181a (miR-181a) on epilepsy have focused on hippocampal neurons, and the effect of miR-181a on other cells in the hippocampus remains poorly understood. Herein, we explored the role of miR-181a-5p in a lithium-pilocarpine model of epilepticus in immature rats. We found that the hippocampal expression level of miR-181a-5p was increased. Inhibition of miR-181a-5p protected the hippocampus against epilepsy, including hippocampal insults, neuronal apoptosis, astrocyte and microglia activation, neuroinflammation, oxidative stress, mitochondrial function, and cognitive dysfunction. Moreover, miR-181a-5p inhibition exerted a seizure-suppressing effect via SIRT1 upregulation. Overall, our findings reveal the potential role of the miR-181a-5p/SIRT1 pathway in the development of temporal lobe epilepsy, and this pathway may represent a novel target for ameliorating epilepsy and its sequelae.

Glycyrrhizic acid protects juvenile epileptic rats against hippocampal damage through activation of Sirtuin3

Glycyrrhizic acid (GA) and Sirtuin3 (Sirt3) were both found to be involved in epilepsy (EP), but their interaction was rarely studied. Herein, we aim to investigate the underlying mechanism of GA with the interaction of Sirt3 in juvenile EP rats. The EP model in juvenile rats was established by lithium chloride-pilocarpine and treated with different concentrations of GA, GA + DMSO or GA + 3-TYP [a selective inhibitor of Sirtuin3 (Sirt3)]. The expression of Sirt3, mitochondrial autophagy-related genes (C-III core 1, COX IV, LC3-I, LC3-II), apoptosis-related genes (Bcl-2, Bax, Caspase-3), glutathione (GSH), superoxide dismutase (SOD), malondialchehyche (MDA) and reactive oxygen species (ROS) as well as mitochondrial membrane potential were subsequently detected. The juvenile EP rats treated with GA showed increased level of C-III core 1 and COX IV, increased LC3-I/LC3-II, GSH and SOD, decreased MDA, increased expression of Sirt3, and Bcl-2, and decreased expression of Bax and Caspase-3. However, inhibition of Sirt3 caused reverse results. Collectively, GA could alleviate hippocampal pathological damage, promote mitochondrial autophagy and reduce oxidative stress in juvenile EP rats through activation of Sirt3. Understanding of these mechanisms may allow devising of novel therapeutics for pediatric EP.

Seizing the Alzheimer's Brain: A Role for Sirtuin 3 in Hyperexcitability

[Box: see text]

Quantification of [18F]UCB-H Binding in the Rat Brain: From Kinetic Modelling to Standardised Uptake Value

PURPOSE

[¹⁸F]UCB-H is a specific positron emission tomography (PET) biomarker for the Synaptic Vesicle protein 2A (SV2A), the binding site of the antiepileptic drug levetiracetam. With a view to optimising acquisition time and simplifying data analysis with this radiotracer, we compared two parameters: the distribution volume (Vt) obtained from Logan graphical analysis using a Population-Based Input Function, and the Standardised Uptake Value (SUV).

PROCEDURES

Twelve Sprague Dawley male rats, pre-treated with three different doses of levetiracetam were employed to develop the methodology. Three additional kainic acid (KA) treated rats (temporal lobe epilepsy model) were also used to test the procedure. Image analyses focused on: (i) length of the dynamic acquisition (90 versus 60 min); (ii) correlations between Vt and SUV over 20-min consecutive time-frames; (iii) and (iv) evaluation of differences between groups using the Vt and the SUV; and (v) preliminary evaluation of the methodology in the KA epilepsy model.

RESULTS

A large correlation between the Vt issued from 60 to 90-min acquisitions was observed. Further analyses highlighted a large correlation (r > 0.8) between the Vt and the SUV. Equivalent differences between groups were detected for both parameters, especially in the 20-40 and 40-60-min time-frames. The same results were also obtained with the epilepsy model.

CONCLUSIONS

Our results enable the acquisition setting to be changed from a 90-min dynamic to a 20-min static PET acquisition. According to a better image quality, the 20-40-min time-frame appears optimal. Due to its equivalence to the Vt, the SUV parameter can be considered in order to quantify [¹⁸F]UCB-H uptake in the rat brain. This work, therefore, establishes a starting point for the simplification of SV2A in vivo quantification with [¹⁸F]UCB-H, and represents a step forward to the clinical application of this PET radiotracer.

Metabolism-based drug discovery in zebrafish: An emerging strategy to uncover new anti-seizure therapies

As one of the most common neurological disorders, epilepsy can occur throughout the lifespan and from a multiplicity of causes, including genetic mutations, inflammation, neurotrauma, or brain malformations. Although pharmacological agents are the mainstay of treatment for seizure control, an unyielding 30-40% of patients remain refractory to these medications and continue to experience spontaneous recurrent seizures with attendant life-long cognitive, behavioural, and mental health issues, as well as an increased risk for sudden unexpected death. Despite over eight decades of antiseizure drug (ASD) discovery and the approval of dozens of new medications, the percentage of this refractory population remains virtually unchanged, suggesting that drugs with new and unexpected mechanisms of action are needed. In this brief review, we discuss the need for new animal models of epilepsy, with a particular focus on the advantages and disadvantages of zebrafish. We also outline the evidence that epilepsy is characterized by derangements in mitochondrial function and introduce the rationale and promise of bioenergetics as a functional readout assay to uncover novel ASDs. We also consider limitations of a zebrafish metabolism-based drug screening approach. Our goal is to discuss the opportunities and challenges of further development of mitochondrial screening strategies for the development of novel ASDs. This article is part of the special issue entitled 'New Epilepsy Therapies for the 21st Century - From Antiseizure Drugs to Prevention, Modification and Cure of Epilepsy'.

The role of astrocytes in seizure generation: insights from a novel in vitro seizure model based on mitochondrial dysfunction

Approximately one-quarter of patients with mitochondrial disease experience epilepsy. Their epilepsy is often severe and resistant towards conventional antiepileptic drugs. Despite the severity of this epilepsy, there are currently no animal models available to provide a mechanistic understanding of mitochondrial epilepsy. We conducted neuropathological studies on patients with mitochondrial epilepsy and found the involvement of the astrocytic compartment. As a proof of concept, we developed a novel brain slice model of mitochondrial epilepsy by the application of an astrocytic-specific aconitase inhibitor, fluorocitrate, concomitant with mitochondrial respiratory inhibitors, rotenone and potassium cyanide. The model was robust and exhibited both face and predictive validity. We then used the model to assess the role that astrocytes play in seizure generation and demonstrated the involvement of the GABA-glutamate-glutamine cycle. Notably, glutamine appears to be an important intermediary molecule between the neuronal and astrocytic compartment in the regulation of GABAergic inhibitory tone. Finally, we found that a deficiency in glutamine synthetase is an important pathogenic process for seizure generation in both the brain slice model and the human neuropathological study. Our study describes the first model for mitochondrial epilepsy and provides a mechanistic insight into how astrocytes drive seizure generation in mitochondrial epilepsy.