Contribution of apoptosis-associated signaling pathways to epileptogenesis: lessons from Bcl-2 family knockouts

(+)-Borneol exerts neuroprotective effects via suppressing the NF-κB pathway in the pilocarpine-induced epileptogenesis rat model

Neuroinflammation plays a crucial role in the development of epilepsy, and suppressing neuroinflammation can delay epileptogenesis. Recent reports have demonstrated that (+)-borneol has neuroprotective effects in several brain disorders by reducing neuroinflammation. However, its effects on epilepsy have not been reported. In this research, we first studied the effect of different doses of (+)-borneol (3, 6, and 12 mg/kg) on neuroinflammation in a pilocarpine model of epileptogenesis by detecting IL-1β, TNF-α, and COX-2 expression. We demonstrated that different doses of (+)-borneol decreased IL-1β, TNF-α, and COX-2 levels, with 12 mg/kg having the most substantial effect. Furthermore, we examined the effects of 12 mg/kg (+)-borneol on neuronal damage, glial cell activation, and apoptosis in the hippocampus at different time points (1, 3, and 7 days) after SE. We found that (+)-borneol significantly ameliorated neuronal injury, decreased glial cell activation, and attenuated apoptosis. We also found that (+)-borneol inhibited the NF-κB pathway activation induced by SE. In conclusion, our results indicated that (+)-borneol reduces neuroinflammation by inhibiting the NF-κB pathway activation, exerts neuroprotective effects, and may have an inhibitory effect in epileptogenesis.

Alpha-Pinene Exerts Antiseizure Effects by Preventing Oxidative Stress and Apoptosis in the Hippocampus in a Rat Model of Temporal Lobe Epilepsy Induced by Kainate

Oxidative stress and apoptosis following seizures play pivotal roles in the consequences of repeated seizures. Beneficial effects of alpha-pinene (APN) have been reported in some experimental models of neurodegenerative diseases. However, its neuroprotective efficacy in a rat model of temporal lobe epilepsy (TLE) induced by kainic acid (KA) has remained unexplored. We aimed to explore the possible antiseizure effects of APN pretreatment and underlying molecular mechanisms in a rat model of TLE induced by KA. TLE was induced in male Wistar rats by intracerebroventricular injection of KA. APN at a dose of 50 mg/kg/day was intraperitoneally injected for 2 weeks before induction of TLE. One day after the induction of TLE, behavioral expressions of seizure were recorded and scored using Racine's scale. Furthermore, the hippocampal levels of oxidative stress markers, B-cell lymphoma 2 (Bcl2), BCL2-associated X protein (BAX), and c-Jun N-terminal kinase (JNK) protein levels were also assessed. Histopathological assessment in the hippocampus was performed with Nissl staining 5 days following induction of TLE. The results revealed that APN pretreatment alleviated epileptic seizures, diminished oxidative stress indicators, blocked the mitochondrial apoptotic pathway via decreasing BAX and raising BCL2 protein levels in the hippocampus at least partly through inhibiting JNK activity, and decreased neuronal death in the CA3 and hilus regions. These findings reveal that APN pretreatment mitigates KA-induced seizures by blocking oxidative stress and neuronal damage factors. It can be concluded that APN has a potent potential to be considered an antiseizure medication, but it needs further investigation.

Dopamine, Immunity, and Disease

The neurotransmitter dopamine is a key factor in central nervous system (CNS) function, regulating many processes including reward, movement, and cognition. Dopamine also regulates critical functions in peripheral organs, such as blood pressure, renal activity, and intestinal motility. Beyond these functions, a growing body of evidence indicates that dopamine is an important immunoregulatory factor. Most types of immune cells express dopamine receptors and other dopaminergic proteins, and many immune cells take up, produce, store, and/or release dopamine, suggesting that dopaminergic immunomodulation is important for immune function. Targeting these pathways could be a promising avenue for the treatment of inflammation and disease, but despite increasing research in this area, data on the specific effects of dopamine on many immune cells and disease processes remain inconsistent and poorly understood. Therefore, this review integrates the current knowledge of the role of dopamine in immune cell function and inflammatory signaling across systems. We also discuss the current understanding of dopaminergic regulation of immune signaling in the CNS and peripheral tissues, highlighting the role of dopaminergic immunomodulation in diseases such as Parkinson's disease, several neuropsychiatric conditions, neurologic human immunodeficiency virus, inflammatory bowel disease, rheumatoid arthritis, and others. Careful consideration is given to the influence of experimental design on results, and we note a number of areas in need of further research. Overall, this review integrates our knowledge of dopaminergic immunology at the cellular, tissue, and disease level and prompts the development of therapeutics and strategies targeted toward ameliorating disease through dopaminergic regulation of immunity. SIGNIFICANCE STATEMENT: Canonically, dopamine is recognized as a neurotransmitter involved in the regulation of movement, cognition, and reward. However, dopamine also acts as an immune modulator in the central nervous system and periphery. This review comprehensively assesses the current knowledge of dopaminergic immunomodulation and the role of dopamine in disease pathogenesis at the cellular and tissue level. This will provide broad access to this information across fields, identify areas in need of further investigation, and drive the development of dopaminergic therapeutic strategies.

The role of peptidyl-prolyl isomerase Pin1 in neuronal signaling in epilepsy

Epilepsy is a common symptom of many neurological disorders and can lead to neuronal damage that plays a major role in seizure-related disability. The peptidyl-prolyl isomerase Pin1 has wide-ranging influences on the occurrence and development of neurological diseases. It has also been suggested that Pin1 acts on epileptic inhibition, and the molecular mechanism has recently been reported. In this review, we primarily focus on research concerning the mechanisms and functions of Pin1 in neurons. In addition, we highlight the significance and potential applications of Pin1 in neuronal diseases, especially epilepsy. We also discuss the molecular mechanisms by which Pin1 controls synapses, ion channels and neuronal signaling pathways to modulate epileptic susceptibility. Since neurotransmitters and some neuronal signaling pathways, such as Notch1 and PI3K/Akt, are vital to the nervous system, the role of Pin1 in epilepsy is discussed in the context of the CaMKII-AMPA receptor axis, PSD-95-NMDA receptor axis, NL2/gephyrin-GABA receptor signaling, and Notch1 and PI3K/Akt pathways. The effect of Pin1 on the progression of epilepsy in animal models is discussed as well. This information will lead to a better understanding of Pin1 signaling pathways in epilepsy and may facilitate development of new therapeutic strategies.

Autophagy and apoptosis cascade: which is more prominent in neuronal death?

Autophagy and apoptosis are two crucial self-destructive processes that maintain cellular homeostasis, which are characterized by their morphology and regulated through signal transduction mechanisms. These pathways determine the fate of cellular organelle and protein involved in human health and disease such as neurodegeneration, cancer, and cardiovascular disease. Cell death pathways share common molecular mechanisms, such as mitochondrial dysfunction, oxidative stress, calcium ion concentration, reactive oxygen species, and endoplasmic reticulum stress. Some key signaling molecules such as p53 and VEGF mediated angiogenic pathway exhibit cellular and molecular responses resulting in the triggering of apoptotic and autophagic pathways. Herein, based on previous studies, we describe the intricate relation between cell death pathways through their common genes and the role of various stress-causing agents. Further, extensive research on autophagy and apoptotic machinery excavates the implementation of selective biomarkers, for instance, mTOR, Bcl-2, BH3 family members, caspases, AMPK, PI3K/Akt/GSK3β, and p38/JNK/MAPK, in the pathogenesis and progression of neurodegenerative diseases. This molecular phenomenon will lead to the discovery of possible therapeutic biomolecules as a pharmacological intervention that are involved in the modulation of apoptosis and autophagy pathways. Moreover, we describe the potential role of micro-RNAs, long non-coding RNAs, and biomolecules as therapeutic agents that regulate cell death machinery to treat neurodegenerative diseases. Mounting evidence demonstrated that under stress conditions, such as calcium efflux, endoplasmic reticulum stress, the ubiquitin-proteasome system, and oxidative stress intermediate molecules, namely p53 and VEGF, activate and cause cell death. Further, activation of p53 and VEGF cause alteration in gene expression and dysregulated signaling pathways through the involvement of signaling molecules, namely mTOR, Bcl-2, BH3, AMPK, MAPK, JNK, and PI3K/Akt, and caspases. Alteration in gene expression and signaling cascades cause neurotoxicity and misfolded protein aggregates, which are characteristics features of neurodegenerative diseases. Excessive neurotoxicity and misfolded protein aggregates lead to neuronal cell death by activating death pathways like autophagy and apoptosis. However, autophagy has a dual role in the apoptosis pathways, i.e., activation and inhibition of the apoptosis signaling. Further, micro-RNAs and LncRNAs act as pharmacological regulators of autophagy and apoptosis cascade, whereas, natural compounds and chemical compounds act as pharmacological inhibitors that rescue neuronal cell death through inhibition of apoptosis and autophagic cell death.

Inhibition of microRNA-129-2-3p protects against refractory temporal lobe epilepsy by regulating GABRA1

BACKGROUND

Accumulating evidence demonstrates that certain microRNAs play critical roles in epileptogenesis. Our previous studies found microRNA (miR)-129-2-3p was induced in patients with refractory temporal lobe epilepsy (TLE). In this study, we aimed to explore the role of miR-129-2-3p in TLE pathogenesis.

METHOD

By bioinformatics, we predicted miR-129-2-3p may target the gene GABRA1 encoding the GABA type A receptor subunit alpha 1. Luciferase assay was used to investigate the regulation of miR-129-2-3p on GABRA1 3'UTR. The dynamic expression of miR-129-2-3p and GABRA1 mRNA and protein levels were measured in primary hippocampal neurons and a rat kainic acid (KA)-induced seizure model by quantitative reverse transcription-polymerase chain reaction (qPCR), Western blotting, and immunostaining. MiR-129-2-3p agomir and antagomir were utilized to explore their role in determining GABRA1 expression. The effects of targeting miR-129-2-3p and GABRA1 on epilepsy were assessed by electroencephalography (EEG) and immunostaining.

RESULTS

Luciferase assay, qPCR, and Western blot results suggested GABRA1 as a direct target of miR-129-2-3p. MiR-129-2-3p level was significantly upregulated, whereas GABRA1 expression downregulated in KA-treated rat primary hippocampal neurons and KA-induced seizure model. In vivo knockdown of miR-129-2-3p by antagomir alleviated the seizure-like EEG findings in accordance with the upregulation of GABRA1. Furthermore, the seizure-suppressing effect of the antagomir was partly GABRA1 dependent.

CONCLUSIONS

The results suggested GABRA1 as a target of miR-129-2-3p in rat primary hippocampal neurons and a rat kainic acid (KA) seizure model. Silencing of miR-129-2-3p exerted a seizure-suppressing effect in rats. MiR-129-2-3p/GABRA1 pathway may represent a potential target for the prevention and treatment of refractory 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.

Two Faces of Autophagy in the Struggle against Cancer

Autophagy can play a double role in cancerogenesis: it can either inhibit further development of the disease or protect cells, causing stimulation of tumour growth. This phenomenon is called "autophagy paradox", and is characterised by the features that the autophagy process provides the necessary substrates for biosynthesis to meet the cell's energy needs, and that the over-programmed activity of this process can lead to cell death through apoptosis. The fight against cancer is a difficult process due to high levels of resistance to chemotherapy and radiotherapy. More and more research is indicating that autophagy may play a very important role in the development of resistance by protecting cancer cells, which is why autophagy in cancer therapy can act as a "double-edged sword". This paper attempts to analyse the influence of autophagy and cancer stem cells on tumour development, and to compare new therapeutic strategies based on the modulation of these processes.

[Structural heterogeneity of epileptic foci in local drug-resistant epilepsy]

BACKGROUND

To study etiopathogenesis is one of the most important tasks of modern neurology. Various types of structural changes occur in drug-resistant epilepsy (DRE); however, they are described as distinct phenomena.

OBJECTIVE

To provide a comprehensive characterization of structural changes in the cortex and adjacent white matter in the electrophysiological activity zone (in the epileptic focus) in patients undergoing surgery for DRE.

MATERIAL AND METHODS

Biopsy material of fragments of the temporal lobe and hippocampus from 16 patients aged 21 to 54 years (mean age, 25 years) with DRE were intraoperatively obtained at the Prof. A.L. Polenov Russian Research Institute of Neurosurgery. The investigators studied histological sections stained with H&E, toluidine blue according to the Nissl method and the Spielmeyer method, as well as the results of immunohistochemical reactions with glial fibrillary acidic protein (GFAP), vimentin, and neurofilaments (NF) (Dako antibodies, Denmark).

RESULTS

Histological examination revealed a set of heterogeneous changes, reflecting the complex pathogenetic interactions that developed during the formation of an epileptic focus. Structural brain damage involved both gray and white matter. Focal cortical dysplasia was diagnosed in 14 (87.5%) cases; white matter neuronal heterotopia in 100%; neuronal reactive and destructive changes in 100%; epileptic leukoencephalopathy (vascular demyelination, microcysts, sclerosis and dystonia, gliosis) in 100%, cortical atrophy in 12.5%, and hippocampal sclerosis in 20% (in 2 out of the 10 examinees).

CONCLUSION

The morphopathological heterogeneity in the structure of epileptic foci reflects the complexity of etiopathogenetic interactions, the polymorphism of epileptic manifestations, and the individual nature of formation of the epileptic system, which requires an integral approach to understanding the pathogenesis and morphogenesis of formation of the epileptic system and provides a direction for a personalized approach to epilepsy treatment.

Blood biomarkers predictive of epilepsy after an acute stroke event

OBJECTIVE

Blood biomarkers have not been widely investigated in poststroke epilepsy. In this study, we aimed to describe clinical factors and biomarkers present during acute stroke and analyze their association with the development of epilepsy at long term.

METHODS

A panel of 14 blood biomarkers was evaluated in patients with ischemic and hemorrhagic stroke. Biomarkers were normalized and standardized using Z-scores. Stroke and epilepsy-related variables were also assessed: stroke severity, determined by National Institutes of Health Stroke Scale (NIHSS) score, stroke type and cause, time from stroke to onset of late seizures, and type of seizure. Multiple Cox regression models were used to identify clinical variables and biomarkers independently associated with epilepsy.

RESULTS

From a cohort of 1115 patients, 895 patients were included. Mean ± standard deviation (SD) age was 72.0 ± 13.1 years, and 57.8% of patients were men. Fifty-one patients (5.7%) developed late seizures, with a median time to onset of 232 days (interquartile range [IQR] 86-491). NIHSS score ≥8 (P < .001, hazard ratio [HR] 4.013, 95% confidence interval [CI] 2.123-7.586) and a history of early onset seizures (P < .001, HR 4.038, 95% CI 1.802-9.045) were factors independently associated with a risk of developing epilepsy. Independent blood biomarkers predictive of epilepsy were high endostatin levels >1.203 (P = .046, HR 4.300, 95% CI 1.028-17.996) and low levels of heat shock 70 kDa protein-8 (Hsc70) <2.496 (P = .006, HR 3.795, 95% CI 1.476-9.760) and S100B <1.364 (P = .001, HR 2.955, 95% CI 1.534-5.491). The risk of epilepsy when these biomarkers were combined increased to 17%. The area under the receiver-operating characteristic (ROC) curve of the predictive model was stronger when clinical variables were combined with blood biomarkers (74.3%, 95% CI 65.2%-83.3%) than when they were used alone (68.9%, 95% CI 60.3%-77.6%).

SIGNIFICANCE

Downregulated S100B and Hsc70 and upregulated endostatin may assist in prediction of poststroke epilepsy and may provide additional information to clinical risk factors. In addition, these data are hypothesis-generating for the epileptogenic process.

Genetic and molecular basis of epilepsy-related cognitive dysfunction

Epilepsy is a common neurological disease characterized by recurrent seizures. About 70 million people were affected by epilepsy or epileptic seizures. Epilepsy is a complicated complex or symptomatic syndromes induced by structural, functional, and genetic causes. Meanwhile, several comorbidities are accompanied by epileptic seizures. Cognitive dysfunction is a long-standing complication associated with epileptic seizures, which severely impairs quality of life. Although the definitive pathogenic mechanisms underlying epilepsy-related cognitive dysfunction remain unclear, accumulating evidence indicates that multiple risk factors are probably involved in the development and progression of cognitive dysfunction in patients with epilepsy. These factors include the underlying etiology, recurrent seizures or status epilepticus, structural damage that induced secondary epilepsy, genetic variants, and molecular alterations. In this review, we summarize several theories that may explain the genetic and molecular basis of epilepsy-related cognitive dysfunction.

De novo variants in RHOBTB2, an atypical Rho GTPase gene, cause epileptic encephalopathy

By whole exome sequencing, we identified three de novo RHOBTB2 variants in three patients with epileptic encephalopathies (EEs). Interestingly, all three patients showed acute encephalopathy (febrile status epilepticus), with magnetic resonance imaging revealing hemisphere swelling or reduced diffusion in various brain regions. RHOBTB2 encodes Rho-related BTB domain-containing protein 2, an atypical Rho GTPase that is a substrate-specific adaptor or itself is a substrate for the Cullin-3 (CUL3)-based ubiquitin ligase complex. Transient expression experiments in Neuro-2a cells revealed that mutant RHOBTB2 was more abundant than wild-type RHOBTB2. Coexpression of CUL3 with RHOBTB2 decreased the level of wild-type RHOBTB2 but not the level of any of the three mutants, indicating impaired CUL3 complex-dependent degradation of the three mutants. These data indicate that RHOBTB2 variants are a rare genetic cause of EEs, in which acute encephalopathy might be a characteristic feature, and that precise regulation of RHOBTB2 levels is essential for normal brain function.

Notch Signaling Regulates Microglial Activation and Inflammatory Reactions in a Rat Model of Temporal Lobe Epilepsy

The inflammatory response mediated by microglia in the central nervous system is closely related to epilepsy. Notch signaling plays an important role in the microglial activation during hypoxia. This study aimed to investigate whether Notch signaling is involved in microglial activation and subsequent inflammation-related neuronal injury during the process of epileptogenesis in a rat model of temporal lobe epilepsy. By using western blotting, real-time quantitative PCR, immunohistochemistry and immunofluorescence labeling, we found that the expression of Notch signaling increased after status epilepticus and that a γ-secretase inhibitor could significantly inhibit the upregulation of Notch signaling, the activation of microglia, and the release of proinflammatory cytokines. Likewise, the neuronal apoptosis and loss in the hippocampus after SE were attenuated by the γ-secretase inhibitor. These results suggest that Notch signaling plays a key role in neuroinflammation and inflammation-related neuronal damage in epilepsy, and γ-secretase inhibitors may become a novel prospective therapeutic agent for epilepsy.

Targeting of microRNA-21-5p protects against seizure damage in a kainic acid-induced status epilepticus model via PTEN-mTOR

OBJECTIVE

Studies have shown that microRNAs play a role in the development of epilepsy by regulating downstream target messenger (m)RNA. The present study aims to determine the changes associated with microRNA-21-5p (miR-21-5p) during epileptogenesis in a kainic acid rat model, and to assess whether the PTEN-mTOR pathway is a target of miR-21-5p.

METHOD

Reverse transcription polymerase chain reaction (RT-PCR) was used to examine the quantitative expressions of miR-21-5p and PTEN, and Western blotting was used to test the activity of mTOR in the acute, latent, and chronic stages of epileptogenesis. The antagomir of miR-21-5p was injected into the intracerebroventricular space using a microsyringe. Neuronal death and epilepsy discharge were assessed by Nissl staining and electroencephalography (EEG), respectively. The Morris water maze (MWM) was used to assess the cognitive impairment in rats after status epilepticus (SE).

RESULTS

Both miR-21-5p and mTOR were upregulated and PTEN was downregulated in rats during acute, latent, and chronic stages of epileptogenesis when compared with those of the control. After using antagomir miR-21-5p in vivo, miR-21-5p and mTOR decreased and the expression of PTEN increased compared with that in the SE model. The silencing of miR-21-5p diminished the number of abnormal spikes on EEG and decreased the number of neuron deletions on Nissl staining. The cognitive and memory impairment caused by epilepsy could also be improved after miR-21-5p knockdown in vivo.

CONCLUSION

The results of the present study demonstrate that PTEN-mTOR is the target of miR-21-5p in a kainic acid model of epilepsy. The knockout of miR-21-5p decreases the neuronal damage in stages of epileptogenesis. The miR-21-5p/PTEN/mTOR axis may be a potential target for preventing and treating seizures and epileptic damage.

The pro-apoptotic protein Bmf co-operates with Bim and Puma in neuron death induced by β-amyloid or NGF deprivation

The pro-apoptotic Bcl-2 homology 3 domain only (BH3-only) proteins are central regulators of cell death in various physiological and pathological conditions, including Alzheimer's disease (AD). Bcl-2 modifying factor (Bmf) is one such BH3-only protein that is implicated in various death paradigms such as anoikis, seizures, cancer and autoimmunity. It also co-operates with other BH3-only proteins such as Bim in various death paradigms. However, its role in neurodegeneration is under-investigated. Here, we report for the first time the essential role of Bmf and its co-operativity with direct activator BH3-only proteins Bim and Puma in neuron death induced by beta-amyloid (Aβ) toxicity or NGF deprivation. Oligomeric Aβ is main pathologic species in AD and NGF deprivation is relevant for both developmental as well as pathologic neuron death. We find that Bmf over-expression causes cell death and Bmf knockdown protects neurons against death evoked by Aβ or NGF deprivation. We also find that Bmf co-operates with other important BH3-only proteins such as Bim and Puma in neuron death induced by Aβ or NGF deprivation. Simultaneous knocking down of these molecules by their respective shRNAs provide enhanced protection against Aβ. Taken together, our results elucidate the essential role of Bmf and its co-operative effects with already known neuron death inducers, Bim and Puma, in neuron death evoked by Aβ treatment or NGF deprivation.

Follow-Up of Peripheral IL-1β and IL-6 and Relation with Apoptotic Death in Drug-Resistant Temporal Lobe Epilepsy Patients Submitted to Surgery

Increasing amounts of evidence support the role of inflammation in epilepsy. This study was done to evaluate serum follow-up of IL-1β and IL-6 levels, as well as their concentration in the neocortex, and the relationship of central inflammation with NF-κB and annexin V in drug-resistant temporal lobe epileptic (DRTLE) patients submitted to surgical treatment. Peripheral and central levels of IL-1β and IL-6were measured by ELISA in 10 DRTLE patients. The sera from patients were taken before surgery, and 12 and 24 months after surgical treatment. The neocortical expression of NF-κB was evaluated by western blotting and annexin V co-localization with synaptophysin by immunohistochemistry. The neocortical tissues from five patients who died by non-neurological causes were used as control. Decreased serum levels of IL-1 and IL-6 were observed after surgery; at this time, 70% of patients were seizure-free. No values of IL-1 and IL-6 were detected in neocortical control tissue, whereas cytokine levels were evidenced in DRTLE. Increased NF-κB neocortex expression was found and the positive annexin V neurons were more obvious in the DRTLE tissue, correlating with IL-6 levels. The follow-up study confirmed that the inflammatory alterations disappeared one year after surgery, when the majority of patients were seizure-free, and the apoptotic death process correlated with inflammation.

Metabolic Dysfunction and Oxidative Stress in Epilepsy

The epilepsies are a heterogeneous group of disorders characterized by the propensity to experience spontaneous recurrent seizures. Epilepsies can be genetic or acquired, and the underlying mechanisms of seizure initiation, seizure propagation, and comorbid conditions are incompletely understood. Metabolic changes including the production of reactive species are known to result from prolonged seizures and may also contribute to epilepsy development. In this review, we focus on the evidence that metabolic and redox disruption is both cause and consequence of epileptic seizures. Additionally, we discuss the promise of targeting redox processes as a therapeutic option in epilepsy.

Dysregulation of zinc/lipid metabolism‑associated genes in the rat hippocampus and cerebral cortex in early adulthood following recurrent neonatal seizures

Although it has been established that recurrent or prolonged clinical seizures during infancy may cause lifelong brain damage, the underlying molecular mechanism is still not well elucidated. The present study, to the best of our knowledge, is the first to investigate the expression of twenty zinc (Zn)/lipid metabolism-associated genes in the hippocampus and cerebral cortex of rats following recurrent neonatal seizures. In the current study, 6-day-old Sprague-Dawley rats were randomly divided into control (CONT) and recurrent neonatal seizure (RS) groups. On postnatal day 35 (P35), mossy fiber sprouting and gene expression were assessed by Timm staining and reverse transcription-quantitative polymerase chain reaction, respectively. Of the twenty genes investigated, seven were significantly downregulated, while four were significantly upregulated in the RS group compared with CONT rats, which was observed in the hippocampus but not in the cerebral cortex. Meanwhile, aberrant mossy fiber sprouting was observed in the supragranular region of the dentate gyrus and Cornu Ammonis 3 subfield of the hippocampus in the RS group. In addition, linear correlation analysis identified significant associations between the expression of certain genes in the hippocampus, which accounted for 40% of the total fifty-five gene pairs among the eleven regulated genes. However, only eight gene pairs in the cerebral cortex exhibited significant positive associations, which accounted for 14.5% of the total. The results of the present study indicated the importance of hippocampal Zn/lipid metabolism-associated genes in recurrent neonatal seizure-induced aberrant mossy fiber sprouting, which may aid the identification of novel potential targets during epileptogenesis.

Mechanisms of epileptogenesis and preclinical approach to antiepileptogenic therapies

The prevalence of epilepsy is estimated 5-10 per 1000 population and around 70% of patients with epilepsy can be sufficiently controlled by antiepileptic drugs (AEDs). Epileptogenesis is the process responsible for converting normal into an epileptic brain and mechanisms responsible include among others: inflammation, neurodegeneration, neurogenesis, neural reorganization and plasticity. Some AEDs may be antiepileptiogenic (diazepam, eslicarbazepine) but the correlation between neuroprotection and inhibition of epileptogenesis is not evident. Antiepileptogenic activity has been postulated for mTOR ligands, resveratrol and losartan. So far, clinical evidence gives some hope for levetiracetam as an AED inhibiting epileptogenesis in neurosurgical patients. Biomarkers for epileptogenesis are needed for the proper selection of patients for evaluation of potential antiepileptogenic compounds.

Antiepileptogenic and Neuroprotective Effects of Pergularia daemia on Pilocarpine Model of Epilepsy

In this study, we investigated antiepileptogenic and neuroprotective effects of the aqueous extract of Pergularia daemia roots (PDR) using in vivo and in vitro experimental models. In in vivo studies, status epilepticus caused by pilocarpine injection triggers epileptogenesis which evolves during about 1–2 weeks. After 2 h of status epilepticus, mice were treated during the epileptogenesis period for 7 days with sodium valproate and vitamin C (standards which demonstrated to alter epileptogenesis), or Pergularia daemia. The animals were then, 1 week after status epilepticus, challenged with acute pentylenetetrazole (PTZ) administration to test behaviorally the susceptibility to a convulsant agent of animals treated or not with the plan extract. Memory was assessed after PTZ administration in the elevated plus maze and T-maze paradigms at 24 and 48 h. Antioxidant and acetylcholinesterase activities were determined in the hippocampus after sacrifice, in vitro studies were conducted using embryonic rat primary cortical cultures exposed to L-glutamate. Cell survival rate was measured and apoptotic and necrotic cell death determined. The results showed that chronic oral administration of PDR significantly and dose-dependently increased the latency to myoclonic jerks, clonic seizures and generalized tonic–clonic seizures, and the seizure score. In addition, PDR at all doses (from 4.9 to 49 mg/kg) significantly decreased the initial and retention transfer latencies in the elevated plus maze. Interestingly PDR at the same doses significantly increased the time spent and the number of entries in T-maze novel arm. PDR significantly increased the activities of acetylcholinesterase and antioxidant enzymes superoxide dismutase, catalase, and total glutathione and proteins, and decreased malondialdehyde level. Furthermore, PDR increased viability rate of primary cortical neurons after L-glutamate-induced excitotoxicity, in a dose dependent manner. Altogether these results suggest that PDR has antiepileptogenic and neuroprotective effects, which could be mediated by antioxidant and antiapoptotic activities.

Features of amygdala in patients with mesial temporal lobe epilepsy and hippocampal sclerosis: An MRI volumetric and histopathological study

OBJECTIVE

It is well-known that there is a correlation between the neuropathological grade of hippocampal sclerosis (HS) and neuroradiological atrophy of the hippocampus in mesial temporal lobe epilepsy (mTLE) patients. However, there is no strict definition or criterion regarding neuron loss and atrophy of the amygdala neighboring the hippocampus. We examined the relationship between HS and neuronal loss in the amygdala.

MATERIALS AND METHODS

Nineteen mTLE patients with neuropathological proof of HS were assigned to Group A, while seven mTLE patients without HS were assigned to Group B. We used FreeSurfer software to measure amygdala volume automatically based on pre-operation magnetic resonance images. Neurons observed using Klüver-Barrera (KB) staining in resected amygdala tissue were counted. and the extent of immunostaining with stress marker antibodies was semiquantitatively evaluated.

RESULTS

There was no significant difference in amygdala volume between the two groups (Group A: 1.41±0.24; Group B: 1.41±0.29cm³; p=0.98), nor in the neuron cellularity of resected amygdala specimens (Group A: 3.98±0.97; Group B: 3.67±0.67 10×^-4 number of neurons/μm²; p=0.40). However, the HSP70 level, representing acute stress against epilepsy, in Group A patients was significantly larger than that in Group B. There was no significant difference in the level of Bcl-2, which is known as a protein that inhibits cell death, between the two groups.

CONCLUSIONS

Neuronal loss and volume loss in the amygdala may not necessarily follow hippocampal sclerosis. From the analysis of stress proteins, epileptic attacks are as likely to damage the amygdala as the hippocampus but do not lead to neuronal death in the amygdala.

The Protective Effect of Aucubin from Eucommia ulmoides Against Status Epilepticus by Inducing Autophagy and Inhibiting Necroptosis

Eucommia ulmoides Oliv. is a famous traditional Chinese medicine which exhibits anti-oxidative stress ability and neuro-protective effects. Aucubin is the predominant component of Eucommia ulmoides Oliv. Our present study is intended to investigate aucubin's potential protective effects on neurons against epilepsy in the hippocampus by establishing the lithium-pilocarpine induced status epilepticus (SE) rat model in vivo. Aucubin (at a low dose and a high dose of 5[Formula: see text]mg/kg and 10[Formula: see text]mg/kg, respectively) was administered through gavage for two weeks before lithium-pilocarpine injection. Rats were sacrificed at 4, 24 and 72[Formula: see text]h after SE induction. Pretreatment with both low-dose and high-dose aucubin significantly reduced the number of death neurons ([Formula: see text]) and increased the number of surviving neurons ([Formula: see text]) in DG, Hilus, CA1 and CA3 hippocampal regions post SE. Meanwhile, it significantly inhibited necroptosis proteins (MLKL and RIP-1) ([Formula: see text] or [Formula: see text]) and enhanced autophagy protein (Beclin-1 and LC3BII/LC3BI) prevalence in the hippocampus ([Formula: see text] or [Formula: see text]). In conclusion, aucubin appeared to ameliorate damages in lithium-pilocarpine induced SE in hippocampus, reduce the number of apoptotic neurons, and increased the number of survival neurons by inducing autophagy and inhibiting necroptosis. These original findings might provide an important basis for the further investigation of the therapeutic role of aucubin in treatment or prevention of epilepsy-related neuronal damages.

Down-regulation of Pin1 in Temporal Lobe Epilepsy Patients and Mouse Model

Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (Pin1) is a unique PPIase belonging to the parvulin family, and it isomerizes peptide bond between phospho-(Ser/Thr) and Pro. Pin1 has been linked to the pathogenesis of various human diseases; however, its exact biological functions remain unclear. The aim of the present study is to explore the expression pattern of Pin1 in patients with refractory epilepsy and in a chronic pilocarpine-induced epileptic mouse model. Using Western blot, immunofluorescence and immunoprecipitation analysis, we found that Pin1 protein was mainly distributed in neurons, demonstrated by colocalization with the dendritic marker, MAP2. However, the expression of Pin1 decreased remarkably in epileptic patients and experimental mice. Furthermore, the reciprocal coimmunoprecipitation analysis showed that Pin1 interacted with NR2A and NR2B-containing NMDA receptors not AMPA receptors in epileptic mouse models. Our results are the first to indicate that the expression of Pin1 in epileptic brain tissue could play important roles in epilepsy.

Stimulation of Anterior Thalamic Nuclei Protects Against Seizures and Neuronal Apoptosis in Hippocampal CA3 Region of Kainic Acid-induced Epileptic Rats

Background:

The antiepileptic effect of the anterior thalamic nuclei (ANT) stimulation has been demonstrated; however, its underlying mechanism remains unclear. The aim of this study was to investigate the effect of chronic ANT stimulation on hippocampal neuron loss and apoptosis.

Methods:

Sixty-four rats were divided into four groups: The control group, the kainic acid (KA) group, the sham-deep brain stimulation (DBS) group, and the DBS group. KA was used to induce epilepsy. Seizure count and latency to the first spontaneous seizures were calculated. Nissl staining was used to analyze hippocampal neuronal loss. Polymerase chain reaction and Western blotting were conducted to assess the expression of caspase-3 (Casp3), B-cell lymphoma-2 (Bcl2), and Bcl2-associated X protein (Bax) in the hippocampal CA3 region. One-way analysis of variance was used to determine the differences between the four groups.

Results:

The latency to the first spontaneous seizures in the DBS group was significantly longer than that in the KA group (27.50 ± 8.05 vs. 16.38 ± 7.25 days, P = 0.0005). The total seizure number in the DBS group was also significantly reduced (DBS vs. KA group: 11.75 ± 6.80 vs. 23.25 ± 7.72, P = 0.0002). Chronic ANT-DBS reduced neuronal loss in the hippocampal CA3 region (DBS vs. KA group: 23.58 ± 6.34 vs. 13.13 ± 4.00, P = 0.0012). After chronic DBS, the relative mRNA expression level of Casp3 was decreased (DBS vs. KA group: 1.18 ± 0.37 vs. 2.09 ± 0.46, P = 0.0003), and the relative mRNA expression level of Bcl2 was increased (DBS vs. KA group: 0.92 ± 0.21 vs. 0.48 ± 0.16, P = 0.0004). The protein expression levels of CASP3 (DBS vs. KA group: 1.25 ± 0.26 vs. 2.49 ± 0.38, P < 0.0001) and BAX (DBS vs. KA group: 1.57 ± 0.49 vs. 2.80 ± 0.63, P = 0.0012) both declined in the DBS group whereas the protein expression level of BCL2 (DBS vs. KA group: 0.78 ± 0.32 vs. 0.36 ± 0.17, P = 0.0086) increased in the DBS group.

Conclusions:

This study demonstrated that chronic ANT stimulation could exert a neuroprotective effect on hippocampal neurons. This neuroprotective effect is likely to be mediated by the inhibition of apoptosis in the epileptic hippocampus.

Deletion of the BH3-only protein Noxa alters electrographic seizures but does not protect against hippocampal damage after status epilepticus in mice

Several members of the Bcl-2 gene family are dysregulated in human temporal lobe epilepsy and animal studies show that genetic deletion of some of these proteins influence electrographic seizure responses to chemoconvulsants and associated brain damage. The BH3-only proteins form a subgroup comprising direct activators of Bax–Bak that are potently proapoptotic and a number of weaker proapoptotic BH3-only proteins that act as sensitizers by neutralization of antiapoptotic Bcl-2 family members. Noxa was originally characterized as a weaker proapoptotic, ‘sensitizer' BH3-only protein, although recent evidence suggests it too may be potently proapoptotic. Expression of Noxa is under p53 control, a known seizure-activated pathway, although Noxa has been linked to energetic stress and autophagy. Here we characterized the response of Noxa to prolonged seizures and the phenotype of mice lacking Noxa. Status epilepticus induced by intra-amygdala kainic acid caused a rapid increase in expression of noxa in the damaged CA3 subfield of the hippocampus but not undamaged CA1 region. In vivo upregulation of noxa was reduced by pifithrin-α, suggesting transcription may be partly p53-dependent. Mice lacking noxa developed less severe electrographic seizures during status epilepticus in the model but, surprisingly, displayed equivalent hippocampal damage to wild-type animals. The present findings indicate Noxa does not serve as a proapoptotic BH3-only protein during seizure-induced neuronal death in vivo. This study extends the comprehensive phenotyping of seizure and damage responses in mice lacking specific Bcl-2 gene family members and provides further evidence that these proteins may serve roles beyond control of cell death in the brain.

NR4A1 Knockdown Suppresses Seizure Activity by Regulating Surface Expression of NR2B

Nuclear receptor subfamily 4 group A member 1 (NR4A1), a downstream target of CREB that is a key regulator of epileptogenesis, has been implicated in a variety of biological processes and was previously identified as a seizure-associated molecule. However, the relationship between NR4A1 and epileptogenesis remains unclear. Here, we showed that NR4A1 protein was predominantly expressed in neurons and up-regulated in patients with epilepsy as well as pilocarpine-induced mouse epileptic models. NR4A1 knockdown by lentivirus transfection (lenti-shNR4A1) alleviated seizure severity and prolonged onset latency in mouse models. Moreover, reciprocal coimmunoprecipitation of NR4A1 and NR2B demonstrated their interaction. Furthermore, the expression of p-NR2B (Tyr1472) in epileptic mice and the expression of NR2B in the postsynaptic density (PSD) were significantly reduced in the lenti-shNR4A1 group, indicating that NR4A1 knockdown partly decreased surface NR2B by promoting NR2B internalization. These results are the first to indicate that the expression of NR4A1 in epileptic brain tissues may provide new insights into the molecular mechanisms underlying epilepsy.

Involvement of microRNAs in epileptogenesis

Patients who have sustained brain injury or had developmental brain lesions present a non-negligible risk for developing delayed epilepsy. Finding therapeutic strategies to prevent development of epilepsy in at-risk patients represents a crucial medical challenge. Noncoding microRNA molecules (miRNAs) are promising candidates in this area. Indeed, deregulation of diverse brain-specific miRNAs has been observed in animal models of epilepsy as well as in patients with epilepsy, mostly in temporal lobe epilepsy (TLE). Herein we review deregulated miRNAs reported in epilepsy with potential roles in key molecular and cellular processes underlying epileptogenesis, namely neuroinflammation, cell proliferation and differentiation, migration, apoptosis, and synaptic remodeling. We provide an up-to-date listing of miRNAs altered in epileptogenesis and assess recent functional studies that have interrogated their role in epilepsy. Last, we discuss potential applications of these findings for the future development of disease-modifying therapeutic strategies for antiepileptogenesis.

Chikusetsu saponin V attenuates H2O2-induced oxidative stress in human neuroblastoma SH-SY5Y cells through Sirt1/PGC-1α/Mn-SOD signaling pathways

Oxidative stress plays a vital role in the pathogenesis of neurodegenerative diseases. Chikusetsu saponin V (CsV), the most abundant member of saponins from Panax japonicus (SPJ), has attracted increasing attention for its potential to treat neurodegenerative diseases. However, the mechanisms are unclear. Our study intended to investigate the antioxidative effects of CsV in human neuroblastoma SH-SY5Y cells. Our data showed that CsV attenuated H2O2-induced cytotoxicity, inhibited ROS accumulation, increased the activities of superoxide dismutase (SOD) and GSH, and increased mitochondrial membrane potential dose-dependently. Further exploration of the mechanisms showed that CsV exhibited these effects through increasing the activation of oxidative-stress-associated factors including Sirt1, PGC-1α, and Mn-SOD. Moreover, CsV inhibited H2O2-induced down-regulation of Bcl-2 and up-regulation of Bax in a dose-dependent manner and, thus, increased the ratio of Bcl-2/Bax. In conclusion, our study demonstrated that CsV exhibited neuroprotective effects possibly through Sirt1/PGC-1α/Mn-SOD signaling pathways.

Chronic Trigeminal Nerve Stimulation Protects Against Seizures, Cognitive Impairments, Hippocampal Apoptosis, and Inflammatory Responses in Epileptic Rats

Trigeminal nerve stimulation (TNS) has recently been demonstrated effective in the treatment of epilepsy and mood disorders. Here, we aim to determine the effects of TNS on epileptogenesis, cognitive function, and the associated hippocampal apoptosis and inflammatory responses. Rats were injected with pilocarpine to produce status epilepticus (SE) and the following chronic epilepsy. After SE induction, TNS treatment was conducted for 4 consecutive weeks. A pilocarpine re-injection was then used to induce a seizure in the epileptic rats. The hippocampal neuronal apoptosis induced by seizure was assessed by TUNEL staining and inflammatory responses by immunohistochemistry and enzyme-linked immunosorbent assay (ELISA). The spontaneous recurrent seizure (SRS) number was counted through video monitoring, and the cognitive function assessed through Morris Water Maze (MWM) test. TNS treatment attenuated the SRS attacks and improved the cognitive impairment in epileptic rats. A pilocarpine re-injection resulted in less hippocampal neuronal apoptosis and reduced level of interleukin-1 beta (IL-1β), tumor necrosis factor-α (TNF-α), and microglial activation in epileptic rats with TNS treatment in comparison to the epileptic rats without TNS treatment. It is concluded that TNS treatment shortly after SE not only protected against the chronic spontaneous seizures but also improved cognitive impairments. These antiepileptic properties of TNS may be related to its attenuating effects on hippocampal apoptosis and pro-inflammatory responses.

Targeting of microRNA-199a-5p protects against pilocarpine-induced status epilepticus and seizure damage via SIRT1-p53 cascade

OBJECTIVE

MicroRNAs (miRNAs) are noncoding small RNAs that control gene expression at the posttranscriptional level. Some dysregulated miRNAs have been shown to play important roles in epileptogenesis. The aim of this study was to determine if miR-199a-5p regulates seizures and seizure damage by targeting the antiapoptotic protein silent information regulator 1 (SIRT1).

METHODS

Hippocampal expression levels of miR-199a-5p, SIRT1, and acetylated p53 were quantified by quantitative real-time polymerase chain reaction (RT-PCR) and Western blotting in the acute, latent, and chronic stages of epilepsy in a rat lithium-pilocarpine epilepsy model. Silencing of miR-199a-5p expression in vivo was achieved by intracerebroventricular injection of antagomirs. The effects of targeting miR-199a-5p and SIRT1 protein on seizure and epileptic damage post-status epilepticus were assessed by electroencephalography (EEG) and immunohistochemistry, respectively.

RESULTS

miR-199a-5p expression was up-regulated, SIRT1 levels were decreased, and neuron loss and apoptosis were induced in epilepsy model rats compared with normal controls, as determined by up-regulation of acetylated p53 and cleaved caspase-3 expression. In vivo knockdown of miR-199a-5p by an antagomir alleviated the seizure-like EEG findings and protected against neuron damage, in accordance with up-regulation of SIRT1 and subsequent deacetylation of p53. Furthermore, the seizure-suppressing effect of the antagomir was partly SIRT1 dependent.

SIGNIFICANCE

The results of this study suggest that silencing of miR-199a-5p exerts a seizure-suppressing effect in rats, and that SIRT1 is a direct target of miR-199a-5p in the hippocampus. The effect of miR-199a-5p on seizures and seizure damage is mediated via down-regulation of SIRT1. The miR-199a-5p/SIRT1 pathway may thus represent a potential target for the prevention and treatment of epilepsy and epileptic damage.

Peroxisome proliferator-activated receptor-γ coactivator-1α mediates neuroprotection against excitotoxic brain injury in transgenic mice: role of mitochondria and X-linked inhibitor of apoptosis protein

Peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α) is a transcriptional coactivator involved in the regulation of mitochondrial biogenesis and cell defense. The functions of PGC-1α in physiology of brain mitochondria are, however, not fully understood. To address this we have studied wild-type and transgenic mice with a two-fold overexpression of PGC-1α in brain neurons. Data showed that the relative number and basal respiration of brain mitochondria were increased in PGC-1α transgenic mice compared with wild-type mitochondria. These changes occurred concomitantly with altered levels of proteins involved in oxidative phosphorylation (OXPHOS) as studied by proteomic analyses and immunoblottings. Cultured hippocampal neurons from PGC-1α transgenic mice were more resistant to cell degeneration induced by the glutamate receptor agonist kainic acid. In vivo kainic acid induced excitotoxic cell death in the hippocampus at 48 h in wild-type mice but significantly less so in PGC-1α transgenic mice. However, at later time points cell degeneration was also evident in the transgenic mouse hippocampus, indicating that PGC-1α overexpression can induce a delay in cell death. Immunoblotting showed that X-linked inhibitor of apoptosis protein (XIAP) was increased in PGC-1α transgenic hippocampus with no significant changes in Bcl-2 or Bcl-X. Collectively, these results show that PGC-1α overexpression contributes to enhanced neuronal viability by stimulating mitochondria number and respiration and increasing levels of OXPHOS proteins and the anti-apoptotic protein XIAP.

Time-dependent variation of pathways and networks in a 24-hour window after cerebral ischemia-reperfusion injury

Background

Cerebral ischemia-reperfusion injury may simultaneously result in functional variation of multiple genes/pathways. However, most prior time-sequence studies on its pathomechanism only focused on a single gene or pathway. Our study aimed to systematically analyze the time-dependent variation in the expression of multiple pathways and networks within 24 h after cerebral ischemia-reperfusion injury.

Results

By uploading 374 ischemia-related genes into the MetaCore software, the variation in the expression of multiple pathways and networks in 3 h, 12 h, and 24 h after cerebral ischemia-reperfusion injury had been analyzed. The conserved TNFR1-signaling pathway, among the top 10 pathways, was consistently enriched in 3 h, 12 h, and 24 h groups. Three overlapping pathways were found between 3 h and 12 h groups; 2 between 12 h and 24 h groups; and 1 between 3 h and 24 h groups. Five, 4, and 6 non-overlapping pathways were observed in 3 h, 12 h, and 24 h groups, respectively. Apart from pathways reported by earlier studies, we identified a novel pathway related to the time-dependent development of cerebral ischemia pathogenesis. The process of apoptosis stimulation by external signals, among the top 10 processes, was consistently enriched in 3 h, 12 h, and 24 h groups; 2, 1, and 2 processes overlapped between 3 h and 12 h groups, 12 h and 24 h groups, and 3 h and 24 h groups, respectively. Four, 5, and 5 non-overlapping processes were found in 3 h, 12 h and 24 h groups, respectively. The presence of apoptotic processes was observed in all the 3 groups; while anti-apoptotic processes only existed in 3 h and 12 h groups. Additionally, according to node degree, network comparison identified 1, 8,and 5 important genes or proteins (e.g. Pyk2, PKC, E2F1, and VEGF-A) in 3 h, 12 h, and 24 h groups, respectively. The Jaccard similarity index revealed a higher level of similarity between 12 h and 24 h groups than that between 3 h and 12 h groups.

Conclusion

Time-dependent treatment can be utilized to reduce apoptosis, which may activate anti-apoptotic pathways within 12 h after cerebral ischemia-reperfusion injury. Pathway and network analyses may help identify novel pathways and genes implicated in disease pathogenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0152-4) contains supplementary material, which is available to authorized users.

Overexpression of 14-3-3ζ Increases Brain Levels of C/EBP Homologous Protein CHOP

Recent studies demonstrated that overexpression of the molecular chaperone 14-3-3ζ protects the brain against endoplasmic reticulum (ER) stress and prolonged seizures. The 14-3-3 targets responsible for improved neuronal survival after seizures remain unknown. Here we explored the mechanism, finding that protein levels of the ER-stress-associated transcription factor C/EBP homologous protein (CHOP) were significantly higher in 14-3-3ζ-overexpressing mice. Since previous studies by us demonstrated that loss of CHOP increased vulnerability to seizure damage, we explored whether elevated CHOP levels result from 14-3-3ζ overexpression and contribute to the protection. Pull-down experiments suggested that 14-3-3ζ could bind CHOP as well as sequester a CHOP-targeting microRNA. However, 14-3-3ζ overexpression remained protective against seizure-induced hippocampal injury in mice lacking CHOP. These studies reveal a novel function for 14-3-3ζ in regulating CHOP levels but show that this is not required for protection against seizure-induced neuronal death.

Oxidative stress associated with neuronal apoptosis in experimental models of epilepsy

Epilepsy is considered one of the most common neurological disorders worldwide. Oxidative stress produced by free radicals may play a role in the initiation and progression of epilepsy; the changes in the mitochondrial and the oxidative stress state can lead mechanism associated with neuronal death pathway. Bioenergetics state failure and impaired mitochondrial function include excessive free radical production with impaired synthesis of antioxidants. This review summarizes evidence that suggest what is the role of oxidative stress on induction of apoptosis in experimental models of epilepsy.

Chikusetsu saponin V attenuates MPP+-induced neurotoxicity in SH-SY5Y cells via regulation of Sirt1/Mn-SOD and GRP78/caspase-12 pathways

Studies have shown that saponins from Panax japonicus (SPJ) possess neuroprotective effects. However, whether Chikusetsu saponin V (CsV), the most abundant member of SPJ, can exert neuroprotective effects against 1-methyl-4-phenylpyridinium ion (MPP⁺)-induced cytotoxicity is not known. In this study, we aimed to investigate the neuroprotective effects of CsV on MPP⁺-induced cytotoxicity in human neuroblastoma SH-SY5Y cells and explore its possible mechanisms. Our results show that CsV attenuates MPP⁺-induced cytotoxicity, inhibits ROS accumulation, and increases mitochondrial membrane potential dose-dependently. We also found that levels of Sirt1 protein and Mn-SOD mRNA significantly decreased in MPP⁺-treated group but were restored with CsV treatment in a dose-dependent manner. Furthermore, GRP78 protein and Caspase-12 mRNA levels were elevated by MPP⁺ exposure but reversed by CsV treatment. CsV inhibited the MPP⁺-induced downregulation of Bcl-2 and up-regulation of Bax in a dose-dependent manner and, thus, increased the ratio of Bcl-2/Bax. Overall, these results suggest that Sirt1/Mn-SOD and GRP78/Caspase-12 pathways might be involved in the CsV-mediated neuroprotective effects.

Effects of glutathione S-transferase M1 and T1 deletions on epilepsy risk among a Tunisian population

Glutathione-S-transferases enzymes are involved in the detoxification of several endogenous and exogenous substances. In this present study, we evaluated the effects of two glutathione-S-transferase polymorphisms, (GSTM1 and GSTT1) on epilepsy risk susceptibility in a Tunisian population. These polymorphisms were analyzed in 229 healthy subjects and 98 patients with epilepsy, using a polymerase chain reaction (PCR). Odds ratio (ORs) was used for analyzing results. The study results demonstrated that individuals with the GSTM1 null genotype were at an increased risk of developing epilepsy [OR=3.80, 95% confidence interval (CI) (2.15-4.78)], whereas no significant effects were observed between individuals with GSTT1 null genotype and epilepsy risk [OR=1.15, 95% CI (0.62-2.12)]. These genotyping finding revealed that the absence of GSTM1 activity could be contributor factor for the development of epilepsy disease.

Serine racemase: a key player in apoptosis and necrosis

A fine balance between cell survival and cell death is required to sculpt the nervous system during development. However, an excess of cell death can occur following trauma, exposure to neurotoxins or alcohol, and some developmental and neurodegenerative diseases, such as Alzheimer's disease (AD). N-Methyl-D-aspartate receptors (NMDARs) support synaptic plasticity and survival of many neuronal populations whereas inappropriate activation may promote various forms of cell death, apoptosis, and necrosis representing the two extremes of a continuum of cell death processes both “in vitro” and “in vivo.” Hence, by identifying the switches controlling pro-survival vs. apoptosis and apoptosis vs. pro-excitotoxic outcome of NMDAR stimulation, NMDAR modulators could be developed that selectively block the cell death enhancing pro-survival signaling or synaptic plasticity mediated by NMDAR. Among these modulators, a role is emerging for the enzyme serine racemase (SR) that synthesizes D-serine, a key co-agonist with glutamate at NMDAR. This review summarizes the experimental evidence from “in vitro” neuronal cultures—with special emphasis on cerebellar granule neurons (CGNs)—and “in vivo” models of neurodegeneration, where the dual role of the SR/D-serine pathway as a master regulator of apoptosis and the apoptosis-necrosis shift will be discussed.

MicroRNAs in the pathophysiology and treatment of status epilepticus

MicroRNA (miRNA) are an important class of non-coding RNA which function as post-transcriptional regulators of gene expression in cells, repressing and fine-tuning protein output. Prolonged seizures (status epilepticus, SE) can cause damage to brain regions such as the hippocampus and result in cognitive deficits and the pathogenesis of epilepsy. Emerging work in animal models has found that SE produces select changes to miRNAs within the brain. Similar changes in over 20 miRNAs have been found in the hippocampus in two or more studies, suggesting conserved miRNA responses after SE. The miRNA changes that accompany SE are predicted to impact levels of multiple proteins involved in neuronal morphology and function, gliosis, neuroinflammation, and cell death. miRNA expression also displays select changes in the blood after SE, supporting blood genomic profiling as potential molecular biomarkers of seizure-damage or epileptogenesis. Intracerebral delivery of chemically modified antisense oligonucleotides (antagomirs) has been shown to have potent, specific and long-lasting effects on brain levels of miRNAs. Targeting miR-34a, miR-132 and miR-184 has been reported to alter seizure-induced neuronal death, whereas targeting miR-134 was neuroprotective, reduced seizure severity during status epilepticus and reduced the later emergence of recurrent spontaneous seizures. These studies support roles for miRNAs in the pathophysiology of status epilepticus and miRNAs may represent novel therapeutic targets to reduce brain injury and epileptogenesis.

The role of dopamine signaling in epileptogenesis

Clinical and experimental studies implicate most neuromodulatory systems in epileptogenesis. The dopaminergic system has a seizure-modulating effect that crucially depends on the different subtypes of dopamine (DA) receptors involved and the brain regions in which they are activated. Specifically, DA plays a major role in the control of seizures arising in the limbic system. Studies performed in a wide variety of animal models contributed to illustrate the opposite actions of D1-like and D2-like receptor signaling in limbic epileptogenesis. Indeed, signaling from D1-like receptors is generally pro-epileptogenic, whereas D2-like receptor signaling exerts an anti-epileptogenic effect. However, this view might appear quite simplistic as the complex neuromodulatory action of DA in the control of epileptogenesis likely requires a physiological balance in the activation of circuits modulated by these two major DA receptor subtypes, which determines the response to seizure-promoting stimuli. Here we will review recent evidences on the identification of molecules activated by DA transduction pathways in the generation and spread of seizures in the limbic system. We will discuss the intracellular signaling pathways triggered by activation of different DA receptors in relation to their role in limbic epileptogenesis, which lead to the activation of neuronal death/survival cascades. A deep understanding of the signaling pathways involved in epileptogenesis is crucial for the identification of novel targets for the treatment of epilepsy.