Ganglioside GM3 Synthase Deficiency in Mouse Models and Human Patients.

Gangliosides (glycosphingolipids containing one or more sialic acids) are highly expressed in neural tissues in vertebrates, and four species (GM1a, GD1a, GD1b, GT1b) are predominant in mammalian brains. GM3 is the precursor of each of these four species and is the major ganglioside in many nonneural tissues. GM3 synthase (GM3S), encoded by ST3GAL5 gene in humans, is a sialyltransferase responsible for synthesis of GM3 from its precursor, lactosylceramide. ST3GAL5 mutations cause an autosomal recessive form of severe infantile-onset neurological disease characterized by progressive microcephaly, intellectual disability, dyskinetic movements, blindness, deafness, intractable seizures, and pigment changes. Some of these clinical features are consistently present in patients with ST3GAL5 mutations, whereas others have variable expression. GM3S knockout (KO) mice have deafness and enhanced insulin sensitivity, but otherwise do not display the above-described neurological defects reported in ST3GAL5 patients. The authors present an overview of physiological functions and pathological aspects of gangliosides based on findings from studies of GM3S KO mice and discuss differential phenotypes of GM3S KO mice versus human GM3S-deficiency patients.

The potential impact of CYP2D6 (*2/*4/*10) gene variants among Egyptian epileptic children: A preliminary study.

BACKGROUND: The cytochrome P450 (CYP) isoenzymes have an indispensable role in the metabolic phase of different medications during the treatment of multiple neuropsychiatric disorders. The foremost goal of this study is to evaluate the correlation of the allelic variants within CYP2D6 (*2/*4/*10) gene with the susceptibility for epileptic syndrome as well as the assessment the degree of resistance towards antiepileptic drugs (AEDs). METHODS: This work was designed based on the involvement of 200 participants [100 unrelated healthy controls, 50 AEDs responsive, and 50 AEDs resistant]. Genomic DNA for the CYP2D6 variants was genotyped utilizing the T-ARMS-PCR technique. RESULTS: The distributions of the CYP2D6*2 (rs16947; c.886C > T) and CYP2D6*4 (rs3892097; c.506-1G > A) variants were significantly correlated with elevated risk among epileptic patients compared to healthy controls (P-value < 0.05). Furthermore, the CYP2D6*2 variant was statistically associated with disease risk among AEDs responsive patients, while the CYP2D6*4 variant was statistically correlated with disease risk among AEDs resistant patients (P-value < 0.05). Interestingly, the allelic variants of the CYP2D6*4 (A allele) and CYP2D6*10 (T allele) were associated with elevated risk among AEDs resistant compared to AEDs responsive patients (P-value = 0.008 and 0.040, respectively). CONCLUSIONS: The CYP2D6*2 and CYP2D6*4 variants were recognized as independent risk factors among epileptic patients, but not the CYP2D6*10 variant.

Effects of Sodium Valproate Monotherapy on Blood Liver Enzyme Levels in Patients with Epilepsy: A Meta-Analysis.

We conducted this meta-analysis to assess the effects of sodium valproate (VPA) monotherapy on blood liver enzymes in patients with epilepsy. PubMed, Web of Science, EBSCO, Cochrane Library, Wanfang, China national knowledge infrastructure databases were searched. Nine studies were included. Results showed: (1) The overall SMD for blood AST, ALT, and GGT levels of VPA monotherapy group versus control group were 0.70 (95% CI=0.31 to 1.09, Z=3.52, p=0.0004), 0.47 (95% CI=- 0.01 to 0.95, Z=1.91, p=0.06), 0.44 (95% CI=0.29 to 0.60, Z=5.55, p<0.00001), respectively. (2) In subgroup meta-analysis, increased blood AST and GGT levels were observed in epileptic minors (AST: total SMD=0.85, 95% CI=0.40 to 1.30, Z=3.69, p=0.0002; GGT: total SMD=0.46, 95% CI=0.29 to 0.63, Z=5.25, p<0.00001). Elevated blood ALT level was observed in Asian patients receiving VPA monotherapy (total SMD=0.70, 95% CI=0.51 to 0.90, Z=7.01, p<0.00001), and the early stage of VPA monotherapy (total SMD=0.93, 95% CI=0.57 to 1.29, Z=5.09, p<0.00001). Overall, our results indicated that blood AST and GGT were significantly increased in epileptic minors receiving VPA monotherapy. The elevation of blood ALT was observed in Asian patients and the early stage of VPA monotherapy. However, due to the small number of included studies, our results should be considered with caution.

Decreased excitatory drive onto hilar neuronal nitric oxide synthase expressing interneurons in chronic models of epilepsy.

Excitation-inhibition imbalance of GABAergic interneurons is predisposed to develop chronic temporal lobe epilepsy (TLE). We have previously shown that virtually every neuronal nitric oxide synthase (nNOS)-positive cell is a GABAergic inhibitory interneuron in the denate gyrus. The present study was designed to quantify the number of nNOS-containing hilar interneurons using stereology in pilocapine- and kainic acid (KA)-exposed transgenic adult mice that expressed GFP under the nNOS promoter. In addition, we studied the properties of miniature excitatory postsynaptic current (mEPSC) and paired-pulse response ratio (PPR) of evoked EPSC in nNOS interneurons using whole cell recording techniques. Results showed that there were fewer nNOS-immunoreactive interneurons of chronically epileptic animals. Importantly, patch-clamp recordings revealed reduction in mEPSC frequency, indicating diminished global excitatory input. In contrast, PPR of evoked EPSC following the granule cell layer stimulation was increased in epileptic animals suggesting reduced neurotransmitter release from granule cell input. In summary, we propose that impaired excitatory drive onto hippocampal nNOS interneurons may be implicated in the development of refractory epilepsy.

Impact of missense mutations in the ALDH7A1 gene on enzyme structure and catalytic function.

Certain mutations in the ALDH7A1 gene cause pyridoxine-dependent epilepsy (PDE), an autosomal recessive metabolic disease characterized by seizures, and in some cases, intellectual disability. The mutational spectrum of PDE is vast and includes over 70 missense mutations. This review summarizes the current state of biochemical and biophysical research on the impact of PDE missense mutations on the structure and catalytic activity of ALDH7A1. Paradoxically, some mutations that target active site residues have a relatively modest impact on structure and function, while those remote from the active site can have profound effects. For example, missense mutations targeting remote residues in oligomer interfaces tend to strongly impact catalytic function by inhibiting formation of the active tetramer. These results shows that it remains very difficult to predict the impact of missense mutations, even when the structure of the wild-type enzyme is known. Additional biophysical analyses of many more disease-causing mutations are needed to develop the rules for predicting the impact of genetic mutations on enzyme structure and catalytic function.

Biallelic variants in ADARB1, encoding a dsRNA-specific adenosine deaminase, cause a severe developmental and epileptic encephalopathy.

BACKGROUND: Adenosine-to-inosine RNA editing is a co-transcriptional/post-transcriptional modification of double-stranded RNA, catalysed by one of two active adenosine deaminases acting on RNA (ADARs), ADAR1 and ADAR2. ADARB1 encodes the enzyme ADAR2 that is highly expressed in the brain and essential to modulate the function of glutamate and serotonin receptors. Impaired ADAR2 editing causes early onset progressive epilepsy and premature death in mice. In humans, ADAR2 dysfunction has been very recently linked to a neurodevelopmental disorder with microcephaly and epilepsy in four unrelated subjects. METHODS: We studied three children from two consanguineous families with severe developmental and epileptic encephalopathy (DEE) through detailed physical and instrumental examinations. Exome sequencing (ES) was used to identify ADARB1 mutations as the underlying genetic cause and in vitro assays with transiently transfected cells were performed to ascertain the impact on ADAR2 enzymatic activity and splicing. RESULTS: All patients showed global developmental delay, intractable early infantile-onset seizures, microcephaly, severe-to-profound intellectual disability, axial hypotonia and progressive appendicular spasticity. ES revealed the novel missense c.1889G>A, p.(Arg630Gln) and deletion c.1245_1247+1 del, p.(Leu415PhefsTer14) variants in ADARB1 (NM_015833.4). The p.(Leu415PhefsTer14) variant leads to incorrect splicing resulting in frameshift with a premature stop codon and loss of enzyme function. In vitro RNA editing assays showed that the p.(Arg630Gln) variant resulted in a severe impairment of ADAR2 enzymatic activity. CONCLUSION: In conclusion, these data support the pathogenic role of biallelic ADARB1 variants as the cause of a distinctive form of DEE, reinforcing the importance of RNA editing in brain function and development.

Non-histone substrates of histone deacetylases as potential therapeutic targets in epilepsy.

Introduction: Epilepsy is a network-level neurological disorder characterized by unprovoked recurrent seizures and associated comorbidities. Aberrant activity and localization of histone deacetylases (HDACs) have been reported in epilepsy and HDAC inhibitors (HDACi) have been used for therapeutic purposes. Several non-histone targets of HDACs have been recognized whose reversible acetylation can modulate protein functions and can contribute to disease pathology. Areas covered: This review provides an overview of HDACs in epilepsy and reflects its action on non-histone substrates involved in the pathogenesis of epilepsy and explores the effectiveness of HDACi as anti-epileptic drugs (AEDs). It also covers the efforts undertaken to target the interaction of HDACs with their substrates. We have further discussed non-deacetylase activity possessed by specific HDACs that might be essential in unraveling the molecular mechanism underlying the disease. For this purpose, relevant literature from 1996 to 2020 was derived from PubMed. Expert opinion: The interaction of HDACs and their non-histone substrates can serve as a promising therapeutic target for epilepsy. Pan-HDACi offers limited benefits to the epileptic patients. Thus, identification of novel targets of HDACs contributing to the disease and designing inhibitors targeting these complexes would be more effective and holds a greater potential as an anti-epileptogenic therapy.

Impaired proteasome activity and neurodegeneration with brain iron accumulation in FBXO7 defect.

FBXO7 is implicated in the ubiquitin-proteasome system and parkin-mediated mitophagy. FBXO7defects cause a levodopa-responsive parkinsonian-pyramidal syndrome(PPS). METHODS: We investigated the disease molecular bases in a child with PPS and brain iron accumulation. RESULTS: A novel homozygous c.368C>G (p.S123*) FBXO7 mutation was identified in a child with spastic paraplegia, epilepsy, cerebellar degeneration, levodopa nonresponsive parkinsonism, and brain iron deposition. Patient's fibroblasts assays demonstrated an absence of FBXO7 RNA expression leading to impaired proteasome degradation and accumulation of poly-ubiquitinated proteins. CONCLUSION: This novel FBXO7 phenotype associated with impaired proteasome activity overlaps with neurodegeneration with brain iron accumulation disorders.

A novel ITPA variant causes epileptic encephalopathy with multiple-organ dysfunction.

Inborn errors of metabolism can cause epileptic encephalopathies. Biallelic loss-of-function variants in the ITPA gene, encoding inosine triphosphate pyrophosphatase (ITPase), have been reported in epileptic encephalopathies with lack of myelination of the posterior limb of the internal capsule, brainstem tracts, and tracts to the primary visual and motor cortices (MIM:616647). ITPase plays an important role in purine metabolism. In this study, we identified two novel homozygous ITPA variants, c.264-1 G > A and c.489-1 G > A, in two unrelated consanguineous families. The probands had epilepsy, microcephaly with characteristic magnetic resonance imaging findings (T2 hyperintensity signals in the pyramidal tracts of the internal capsule, delayed myelination, and thin corpus callosum), hypotonia, and developmental delay; both died in early infancy. Our report expands the knowledge of clinical consequences of biallelic ITPA variants.

A novel PAK1 variant causative of neurodevelopmental disorder with postnatal macrocephaly.

p21-activated kinases (PAKs) are protein serine/threonine kinases stimulated by Rho-family p21 GTPases such as CDC42 and RAC. PAKs have been implicated in several human disorders, with pathogenic variants in PAK3 associated with intellectual disability and several PAK members, especially PAK1 and PAK4, overexpressed in human cancer. Recently, de novo PAK1 variants were reported to be causative of neurodevelopmental disorder (ND) with secondary macrocephaly in three patients. We herein report a fourth patient with ND, epilepsy, and macrocephaly caused by a de novo PAK1 missense variant. Two previously reported missense PAK1 variants functioned as activating alleles by reducing PAK1 homodimerization. To examine the pathogenicity of the identified novel p.Ser110Thr variant, we carried out in silico structural analysis. Our findings suggest that this variant also prevents PAK1 homodimerization, leading to constitutive PAK1 activation.

Wwox deficiency leads to neurodevelopmental and degenerative neuropathies and glycogen synthase kinase 3ß-mediated epileptic seizure activity in mice.

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 3ß (GSK3ß) occurs in Wwox-/- mouse cerebral cortex, hippocampus and cerebellum. Inhibition of GSK3ß 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 GSK3ß with lithium ion ameliorates epilepsy.

[Altered expressions of SphK1 and S1PR2 in hippocampus of epileptic rats].

OBJECTIVE: To observe the expressions of sphingosine kinase 1 (SphK1) and sphingosine-1-phosphate receptor 2 (S1PR2) in hippocampus of epileptic rats and to investigate the pathogenesis of SphK1 and S1PR2 in epilepsy. METHODS: One hundred and eight male Sprague-Dawley (SD) rats were randomly divided into control group (n=48) and pilocarpine (PILO) group (n=60). A robust convulsive status epilepticus (SE) was induced in PILO group rats by the application of pilocarpine. Control group rats were injected with respective of physiological saline. Pilocarpine group was randomly divided into 6 subgroups (n=8): acute group (E6 h, E1 d, E3 d), latent group (E7 d) and chronic group (E30 d, E56 d). Each subgroup has 8 control rats and 8 epileptic rats. Hippocampal tissue and brain slices were obtained from control rats and rats subjected to the Li-PILO model of epilepsy at 6 h, 1 d, 3 d,7 d,30 d and 56 d after status epilepticus (SE). Western blot technique was used to determine the expressions of SphK1 and S1PR2 in hippocampus at different point of time after pilocarpine treatment. Immunofluorescence was applied to detect the activation and proliferation of hippocampal astrocytes and the localization of SphK1 and S1PR2 in rat hippocampal astrocytes. RESULTS: Compared with control group, the levels of SphK1 in acute phase (E3 d), latent phase (E7 d) and chronic phase (E30 d, E56 d) were significantly increased while the expressions of S1PR2 were decreased in acute phase (E3 d), latent phase (E7 d) and chronic phase (E30 d, E56 d)(P＜0.05 or P＜0.01). Immunofluorescence results showed astrocyte activation and proliferation in hippocampus of epileptic (E7 d) rats (P＜0.05). Confocal microscopy confirmed the preferential expressions of SphK1 and S1PR2 in epileptic rat(E7 d)hippocampal astrocytes. CONCLUSION: The results indicate that SphK1 and S1PR2 may play an important role in the pathogenesis of epilepsy by regulating the activation and proliferation of hippocampal astrocytes and altering neuronal excitability.

Cyclooxygenase-2 (COX-2) inhibitors: future therapeutic strategies for epilepsy management.

Epilepsy, a common multifactorial neurological disease, affects about 69 million people worldwide constituting nearly 1% of the world population. Despite decades of extensive research on understanding its underlying mechanism and developing the pharmacological treatment, very little is known about the biological alterations leading to epileptogenesis. Due to this gap, the currently available antiepileptic drug therapy is symptomatic in nature and is ineffective in 30% of the cases. Mounting evidences revealed the pathophysiological role of neuroinflammation in epilepsy which has shifted the focus of epilepsy researchers towards the development of neuroinflammation-targeted therapeutics for epilepsy management. Markedly increased expression of key inflammatory mediators in the brain and blood-brain barrier may affect neuronal function and excitability and thus may increase seizure susceptibility in preclinical and clinical settings. Cyclooxygenase-2 (COX-2), an enzyme synthesizing the proinflammatory mediators, prostaglandins, has widely been reported to be induced during seizures and is considered to be a potential neurotherapeutic target for epilepsy management. However, the efficacy of such therapy involving COX-2 inhibition depends on various factors viz., therapeutic dose, time of administration, treatment duration, and selectivity of COX-2 inhibitors. This article reviews the preclinical and clinical evidences supporting the role of COX-2 in seizure-associated neuroinflammation in epilepsy and the potential clinical use of COX-2 inhibitors as a future strategy for epilepsy treatment.

Cytosolic phospholipase A2 is a key regulator of blood-brain barrier function in epilepsy.

Blood-brain barrier dysfunction in epilepsy contributes to seizures and resistance to antiseizure drugs. Reports show that seizures increase brain glutamate levels, leading to barrier dysfunction. One component of barrier dysfunction is overexpression of the drug efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). Based on our previous studies, we hypothesized that glutamate released during seizures activates cytosolic phospholipase A2 (cPLA2), resulting in P-gp and BCRP overexpression. We exposed isolated rat brain capillaries to glutamate ex vivo and used an in vivo-ex vivo approach of isolating brain capillaries from rats after status epilepticus (SE) and in chronic epileptic (CE) rats. Glutamate increased cPLA2, P-gp, and BCRP protein and activity levels in isolated brain capillaries. We confirmed the role of cPLA2 in the signaling pathway in brain capillaries from male and female mice lacking cPLA2. We also demonstrated, in vivo, that cPLA2 inhibition prevents overexpression of P-gp and BCRP at the blood-brain barrier in rats after status epilepticus and in CE rats. Our data support the hypothesis that glutamate signals cPLA2 activation, resulting in overexpression of blood-brain barrier P-gp and BCRP.-Hartz, A. M. S., Rempe, R. G., Soldner, E. L. B., Pekcec, A., Schlichtiger, J., Kryscio, R., Bauer, B. Cytosolic phospholipase A2 is a key regulator of blood-brain barrier function in epilepsy.

Neurovascular Drug Biotransformation Machinery in Focal Human Epilepsies: Brain CYP3A4 Correlates with Seizure Frequency and Antiepileptic Drug Therapy.

Pharmacoresistance is a major clinical challenge for approximately 30% of patients with epilepsy. Previous studies indicate nuclear receptors (NRs), drug efflux transporters, and cytochrome P450 enzymes (CYPs) control drug passage across the blood-brain barrier (BBB) in drug-resistant epilepsy. Here, we (1) evaluate BBB changes, neurovascular nuclear receptors, and drug transporters in lesional/epileptic (EPI) and non-lesional/non-epileptic (NON-EPI) regions of the same brain, (2) examine regional CYP expression and activity, and (3) investigate the association among CYP brain expression, seizure frequency, duration of epilepsy, and antiepileptic drug (AED) combination. We used surgically resected brain specimens from patients with medically intractable epilepsy (n = 22) where the epileptogenic loci were well-characterized by invasive and non-invasive methods; histology confirmed distinction of small NON-EPI regions from EPI tissues. NRs, transporters, CYPs, and tight-junction proteins were assessed by western blots/immunohistochemistry, and CYP metabolic activity was determined and compared. The relationship of CYP expression with seizure frequency, duration of epilepsy, and prescribed AEDs was evaluated. Decreased BBB tight-junction proteins accompanied IgG leakage in EPI regions and correlated with upregulated NR and efflux transporter levels. CYP expression and activity significantly increased in EPI compared to NON-EPI tissues. Change in EPI and NON-EPI CYP3A4 expression increased in patients taking AEDs that were CYP substrates, was downregulated when CYP- and non-CYP-substrate AEDs were given together, and correlated with seizure frequency. Our studies suggest focal neurovascular CYP-NR-transporter alterations, as demonstrated by the relationship of seizure frequency and AED combination to brain CYP3A4, might together impact biotransformation machinery of human pharmacoresistant epilepsy.

Biallelic mutations in valyl-tRNA synthetase gene VARS are associated with a progressive neurodevelopmental epileptic encephalopathy.

Aminoacyl-tRNA synthetases (ARSs) function to transfer amino acids to cognate tRNA molecules, which are required for protein translation. To date, biallelic mutations in 31 ARS genes are known to cause recessive, early-onset severe multi-organ diseases. VARS encodes the only known valine cytoplasmic-localized aminoacyl-tRNA synthetase. Here, we report seven patients from five unrelated families with five different biallelic missense variants in VARS. Subjects present with a range of global developmental delay, epileptic encephalopathy and primary or progressive microcephaly. Longitudinal assessment demonstrates progressive cortical atrophy and white matter volume loss. Variants map to the VARS tRNA binding domain and adjacent to the anticodon domain, and disrupt highly conserved residues. Patient primary cells show intact VARS protein but reduced enzymatic activity, suggesting partial loss of function. The implication of VARS in pediatric neurodegeneration broadens the spectrum of human diseases due to mutations in tRNA synthetase genes.

Biallelic VARS variants cause developmental encephalopathy with microcephaly that is recapitulated in vars knockout zebrafish.

Aminoacyl tRNA synthetases (ARSs) link specific amino acids with their cognate transfer RNAs in a critical early step of protein translation. Mutations in ARSs have emerged as a cause of recessive, often complex neurological disease traits. Here we report an allelic series consisting of seven novel and two previously reported biallelic variants in valyl-tRNA synthetase (VARS) in ten patients with a developmental encephalopathy with microcephaly, often associated with early-onset epilepsy. In silico, in vitro, and yeast complementation assays demonstrate that the underlying pathomechanism of these mutations is most likely a loss of protein function. Zebrafish modeling accurately recapitulated some of the key neurological disease traits. These results provide both genetic and biological insights into neurodevelopmental disease and pave the way for further in-depth research on ARS related recessive disorders and precision therapies.

Selective deletion of glutamine synthetase in the mouse cerebral cortex induces glial dysfunction and vascular impairment that precede epilepsy and neurodegeneration.

Glutamate-ammonia ligase (glutamine synthetase; Glul) is enriched in astrocytes and serves as the primary enzyme for ammonia detoxification and glutamate inactivation in the brain. Loss of astroglial Glul is reported in hippocampi of epileptic patients, but the mechanism by which Glul deficiency might cause disease remains elusive. Here we created a novel mouse model by selectively deleting Glul in the hippocampus and neocortex. The Glul deficient mice were born without any apparent malformations and behaved unremarkably until postnatal week three. There were reductions in tissue levels of aspartate, glutamate, glutamine and GABA and in mRNA encoding glutamate receptor subunits GRIA1 and GRIN2A as well as in the glutamate transporter proteins EAAT1 and EAAT2. Adult Glul-deficient mice developed progressive neurodegeneration and spontaneous seizures which increased in frequency with age. Importantly, progressive astrogliosis occurred before neurodegeneration and was first noted in astrocytes along cerebral blood vessels. The responses to CO2-provocation were attenuated at four weeks of age and dilated microvessels were observed histologically in sclerotic areas of cKO. Thus, the abnormal glutamate metabolism observed in this model appeared to cause epilepsy by first inducing gliopathy and disrupting the neurovascular coupling.

ATP Synthase Subunit Beta Immunostaining is Reduced in the Sclerotic Hippocampus of Epilepsy Patients.

Epilepsy is a common disease presenting with recurrent seizures. Hippocampal sclerosis (HS) is the commonest histopathological alteration in patients with temporal lobe epilepsy (TLE) undergoing surgery. HS physiopathogenesis is debatable. We have recently studied, by using mass spectrometry-based proteomics, an experimental model of TLE induced by electrical stimulation. Specifically, protein expressions of both the beta subunit of mitochondrial ATP synthase (ATP5B) and of membrane ATPases were found to be reduced. Here, we investigated tissue distribution of ATP5B and sodium/potassium-transporting ATPase subunit alpha-3 (NKAα3), a protein associated with neuromuscular excitability disorders, in human hippocampi resected "en bloc" for HS treatment (n = 15). We used immunohistochemistry and the stained area was digitally evaluated (increase in binary contrast of microscopic fields) in the hippocampal sectors (CA1-CA4) and dentate gyrus. All HS samples were classified as Type 1, according to the International League Against Epilepsy (ILAE) 2013 Classification (predominant cell loss in CA1 and CA4). ATP5B was significantly decreased in all sectors and dentate gyrus of HS patients compared with individuals submitted to necropsy and without history of neurological alterations (n = 10). NKAα3 expression showed no difference. Moreover, we identified a negative correlation between frequency of pre-operative seizures and number of neurons in CA1. In conclusion, our data showed similarity between changes in protein expression in a model of TLE and individuals with HS. ATP5B reduction would be at least in part due to neuronal loss. Future investigations on ATP5B activity could provide insights into the process of such cell loss.