Involvement of caspase-3-like protease in the mechanism of cell death following focally evoked limbic seizures

A network pharmacology approach to explore pharmacological mechanisms of Asparagus racemosus for ameliorative effect in epilepsy and comorbid progressive memory dysfunction

Background

Network pharmacology approach has been observed a powerful tool to predict underlying complex pharmacological mechanism of herbs. Asparagus racemosus has been reported to show ameliorative effects in treating epilepsy and comorbid memory dysfunction but mechanism of this amelioration is elusive. Hence a network pharmacology approach was employed to investigate the plausible mechanism of A. recemosus.

Methodology

: Bioactive compounds of A. racemosus were extracted based on the TCMSP, PCIDB, and BATMAN-TCM database. The potential targets of bioactive compounds were collected using target fishing. Epilepsy and comorbid dementia genes were collected from DISGENET. A PPI network among these targets was constructed using the intersecting key targets between herb targets and disease targets. Besides, DAVID bioinformatics resource was utilized for the pathway enrichment analysis on GO and KEGG. Ultimately, phytochemical compound-target genes-Pathways network has been assembled utilizing Cytoscape to decipher the mechanism of the herb.

Results

The network analysis revealed that 5 targets (CASP3, TNF, VEGFA, PTGS2 and CNR1) might be the key therapeutic targets of asparagus on Epilepsy comorbid Alzheimer's disease. Based on high connectivity, four hub compounds with the highest connectivity were noted and it includes Shatavarin V, Sarsasapogenin, Shatavarin IX, and Shatavarin VI. A total of 19 KEGG terms were enriched as the potential pathways of A. racemosus in Epilepsy comorbid Alzheimer's disease.

Conclusion

This study envisaged the pharmacological and molecular mechanism of A. racemosus against epilepsy comorbid Alzheimer's disease and put forward a strategy to uncover the mechanisms of Traditional Indian Medicine based on network pharmacology.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40203-023-00169-x.

Anti-inflammatory and antioxidative effects of elderberry diet in the rat model of seizure: a behavioral and histological investigation on the hippocampus

The present study was designed to evaluate whether elderberry (EB) effectively reduces inflammation and oxidative stress in hippocampal cells to modify seizure damage. Seizure was induced in rats by the injection of pentylenetetrazol (PTZ). In the Seizure + EB group, EB powder was added to the rats' routine diet for eight consecutive weeks. The study included several behavioral tests, immunohistopathology, Voronoi tessellation (to estimate the spatial distribution of cells in the hippocampus), and Sholl analysis. The results in the Seizure + EB group showed an improvement in the behavioral aspects of the study, a reduction in astrogliosis, astrocyte process length, number of branches, and intersections distal to the soma in the hippocampus of rats compared to controls. Further analysis showed that EB diet increased nuclear factor-like 2 expression and decreased caspase-3 expression in the hippocampus in the Seizure + EB group. In addition, EB protected hippocampal pyramidal neurons from PTZ toxicity and improved the spatial distribution of hippocampal neurons in the pyramidal layer and dentate gyrus. The results of the present study suggest that EB can be considered a potent modifier of astrocyte reactivation and inflammatory responses.

Neuroprotective effect of Berberine Nanoparticles Against Seizures in Pentylenetetrazole Induced Kindling Model of Epileptogenesis: Role of Anti-Oxidative, Anti-Inflammatory, and Anti-Apoptotic Mechanisms

There is an unmet need to develop alternative therapeutic strategies to not only restrain seizures but also to alleviate the underlying pathologies and sequelae. Berberine (BBR), an isoquinoline alkaloid, has shown promising effect in the kindling model of epileptogenesis, but due to the poor oral bioavailability its clinical application is limited. So, the present study was designed to study the neuroprotective effect of BBR nanoparticles (enhanced bioavailability as compared to BBR) against seizures in pentylenetetrazole (PTZ) induced kindling model of epileptogenesis. Kindling model was established in male Wistar rats by intraperitoneal (i.p.) administration of PTZ (30 mg/kg) on every alternate day till the animal became fully kindled or till 6 weeks. Three doses of BBR (50, 100, and 200 mg/kg) and nano-BBR (25, 50, 100 mg/kg) were studied for seizure score, percentage of animal kindled, histopathological score, oxidative stress, inflammation, and apoptosis in PTZ treated rats by conducting cytokines, gene expression and protein expression analysis. BBR nanoparticles showed significant effect on the seizure score and percentage of animal kindled, histopathological score, neurobehavioral parameters (Forced swim test, Rotarod), oxidative (MDA, SOD, GSH, GPx) and inflammatory (IL-1beta, TNF-alpha) parameters, apoptotic parameters (Bax and iNOS), and gene (Nrf2, NQO1, HO1) and protein expression (Nrf2) as compared to both PTZ and BBR. BBR nanoparticles showed neuroprotective effect in PTZ induced kindling model of epileptogenesis and proves to be a promising antiepileptogenic therapy for the patients who are at high risk of developing seizures.

Administration of Kainic Acid Differentially Alters Astrocyte Markers and Transiently Enhanced Phospho-tau Level in Adult Rat Hippocampus

Kainic acid (KA), an analogue of the excitatory neurotransmitter glutamate, when administered systemically can trigger seizures and neuronal loss in a manner that mirrors the neuropathology of human mesial temporal lobe epilepsy (mTLE), which affects ∼50 million people globally. Evidence suggests that changes in astrocytes which precede neuronal damage play an important role in the degeneration of neurons and/or development of seizures in TLE pathogenesis. Additionally, a role for microtubule associated tau protein, involved in various neurodegenerative diseases including Alzheimer's disease, has also been suggested in the development of seizure and/or neurodegeneration in TLE pathogenesis. At present, possible alterations of different subtypes of astrocytes and their association, if any, with tau protein in TLE remain unclear. In this study, we evaluated alterations of different subtypes of astrocytes and phospho-/cleaved-tau levels in KA-treated rat model of TLE. Our results reveal that levels/expression of various astrocyte markers such as GFAP, vimentin, S100B, Aldh1L1, but not GS, are increased in the hippocampus of KA-treated rats. The levels/expression of both A1(C3+) and A2(S100A10+)-like astrocytes are also increased in KA-treated rats. Concurrently, the total (Tau1 and Tau5) and phospho-tau (AT270 and PHF1) levels are transiently enhanced following KA administration. Furthermore, the level/expression of cleaved-tau, which is apparent in a subset of GFAP-, S100B- and A2-positive astrocytes, are increased in KA-treated rats. These results, taken together, suggest a differential role for various astrocytic subpopulations and tau protein in the development of seizure and/or loss of neurons in KA model of TLE and possibly in human mTLE pathogenesis.

Exploring the mechanism of Chaihujia Longgu Muli decoction in the treatment of epilepsy in rats based on the RhoA/ROCK signaling pathway

BACKGROUND

The Chinese herbal formula Chaihujia Longgu Muli Decoction (CD) has a good antiepileptic effect, but its mechanisms remain unclear. Therefore, in this study we explored the molecular mechanisms of CD against epilepsy.

METHODS

Twelve-day-old SD rats were randomly divided into a normal group, model group, valproic acid group, and CD high, medium, and low groups. Except for the normal group, the other groups were given an intraperitoneal injection of pentylenetetrazol (PTZ) to establish epilepsy models, and the Racine score was applied for model judgment. After 14 consecutive days of dosing, the Morris water maze test was performed. Then, hippocampal Nissl staining and immunofluorescence staining were performed, and synaptic ultrastructure was observed by transmission electron microscopy (TEM). RhoA/ROCK signaling pathway proteins were detected.

RESULTS

In PTZ model rats, the passing times were reduced, and the escape latency was prolonged in the Morris water maze test. Nissl staining showed that some hippocampal neurons swelled and ruptured, Nissl bodies in the cytoplasm were significantly reduced, and neurons were lost. Immunofluorescence detection revealed that the expression of PSD95 and SYP was significantly reduced. Electron microscopy results revealed that the number of synapses in hippocampal neurons was significantly reduced and the postsynaptic membrane length was significantly reduced. Western blot analysis showed that the RhoA/ROCK signaling pathway was activated, while SYP, SPD95, and PTEN expression was significantly decreased. After treatment with CD, neurobehavioral abnormalities and neuronal damage caused by epileptic seizures were improved.

CONCLUSION

CD exerted an antiepileptic effect by inhibiting the activation of the RhoA/ROCK signaling pathway.

Potential Pleiotropic Genes and Shared Biological Pathways in Epilepsy and Depression Based on GWAS Summary Statistics

Current epidemiological and experimental studies have indicated the overlapping genetic foundation of epilepsy and depression. However, the detailed pleiotropic genetic etiology and neurobiological pathways have not been well understood, and there are many variants with underestimated effect on the comorbidity of the two diseases. Utilizing genome-wide association study (GWAS) summary statistics of epilepsy (15,212 cases and 29,677 controls) and depression (170,756 cases and 329,443 controls) from large consortia, we assessed the integrated gene-based association with both diseases by Multimarker Analysis of Genomic Annotation (MAGMA) and Fisher's meta-analysis. On the one hand, shared genes with significantly altered transcripts in Gene Expression Omnibus (GEO) data sets were considered as possible pleiotropic genes. On the other hand, the pathway enrichment analysis was conducted based on the gene lists with nominal significance in the gene-based association test of each disease. We identified a total of two pleiotropic genes (CD3G and SLCO3A1) with gene expression analysis validated and interpreted twenty-five common biological process supported with literature mining. This study indicates the potentially shared genes associated with both epilepsy and depression based on gene expression, meta-data analysis, and pathway enrichment strategy along with traditional GWAS and provides insights into the possible intersecting pathways that were not previously reported.

Programmed Mechanisms of Status Epilepticus-induced Neuronal Necrosis

Excitotoxicity is the underlying mechanism for all acute neuronal injury, from cerebral ischemia, status epilepticus, traumatic CNS injury and hypoglycemia. It causes morphological neuronal necrosis, and it triggers a programmed cell death program. Excessive calcium entry through the NMDA-receptor-operated cation channel activates two key enzymes-calpain I and neuronal nitric oxide synthase (nNOS). Calpain I, a cytosolic enzyme, translocates to mitochondrial and lysosomal membranes, causing release of cytochrome c, endonuclease G and apoptosis-inducing factor (AIF) from mitochondria and DNase II and cathepsins B and D from lysosomes. These all translocate to neuronal nuclei, creating DNA damage, which activates poly(ADP) ribose polymerase-1 (PARP-1) to form excessive amounts of poly(ADP) ribose (PAR) polymers, which translocate to mitochondrial membranes, causing release of truncated AIF (tAIF). The free radicals that are released from mitochondria and peroxynitrite, formed from nitric oxide (NO) from nNOS catalysis of L-arginine to L-citrulline, damage mitochondrial and lysosomal membranes and DNA. The end result is the necrotic death of neurons. Another programmed necrotic pathway, necroptosis, occurs through a parallel pathway. As investigators of necroptosis do not recognize the excitotoxic pathway, it is unclear to what extent each contributes to programmed neuronal necrosis. We are studying the extent to which each contributes to acute neuronal necrosis and the extent of cross-talk between these pathways.

Organophosphorus diisopropylfluorophosphate (DFP) intoxication in zebrafish larvae causes behavioral defects, neuronal hyperexcitation and neuronal death

With millions of intoxications each year and over 200,000 deaths, organophosphorus (OP) compounds are an important public health issue worldwide. OP poisoning induces cholinergic syndrome, with respiratory distress, hypertension, and neuron damage that may lead to epileptic seizures and permanent cognitive deficits. Existing countermeasures are lifesaving but do not prevent long-lasting neuronal comorbidities, emphasizing the urgent need for animal models to better understand OP neurotoxicity and identify novel antidotes. Here, using diisopropylfluorophosphate (DFP), a prototypic and moderately toxic OP, combined with zebrafish larvae, we first showed that DFP poisoning caused major acetylcholinesterase inhibition, resulting in paralysis and CNS neuron hyperactivation, as indicated by increased neuronal calcium transients and overexpression of the immediate early genes fosab, junBa, npas4b, and atf3. In addition to these epileptiform seizure-like events, DFP-exposed larvae showed increased neuronal apoptosis, which were both partially alleviated by diazepam treatment, suggesting a causal link between neuronal hyperexcitation and cell death. Last, DFP poisoning induced an altered balance of glutamatergic/GABAergic synaptic activity with increased NR2B-NMDA receptor accumulation combined with decreased GAD65/67 and gephyrin protein accumulation. The zebrafish DFP model presented here thus provides important novel insights into the pathophysiology of OP intoxication, making it a promising model to identify novel antidotes.

Anterior thalamic nucleus stimulation protects hippocampal neurons by activating autophagy in epileptic monkeys

Deep brain stimulation of the anterior nucleus of the thalamus (ANT-DBS) is effective in treating temporal lobe epilepsy (TLE) and protects hippocampal neurons. Autophagy plays an essential role in epileptogenesis; however, the underlying effect of autophagy on ANT-DBS-mediated neuroprotection remains unclear. A monkey model of epilepsy was established by injecting kainic acid into the hippocampus and amygdala using a robot-assisted system. ANT-DBS was delivered in the chronic stage of the epileptic model and continued for 8 weeks. We found that ANT-DBS reduced the frequency of seizures and exerted neuroprotective effects via activating autophagy in hippocampal neurons. ANT-DBS increased light chain 3 (LC3) II level and co-localization of LC3 and lysosomal-associated membrane protein-1, accompanied by decreased expression of the autophagy substrate ubiquitin-binding protein p62, suggesting increased autophagosome formation. Most importantly, brain-derived neurotrophic factor (BDNF) –tropomyosin-related kinase type B (TrkB) pathway were involved in the regulation of autophagy. Both protein levels were reduced by ANT-DBS, and there was less phosphorylation of downstream regulators, extracellular signal-regulated kinase and Akt, followed by inactivation of mammalian target of rapamycin complex 1. Taken together, chronic ANT-DBS exerts neuroprotective effects on hippocampal neurons through inducing autophagy via suppressing the BDNF–TrkB pathway in a TLE monkey model.

Inhibition of TRIB3 Protects Against Neurotoxic Injury Induced by Kainic Acid in Rats

Epilepsy refers to a group of neurological disorders of varying etiologies characterized by recurrent seizures, resulting in brain dysfunction. Endoplasmic reticulum (ER) stress is highly activated in the process of epilepsy-related brain injury. However, the mechanisms by which ER stress triggers neuronal apoptosis remain to be fully elucidated. Tribbles pseudokinase 3 (TRIB3) is a pseudokinase that affects a number of cellular functions, and its expression is increased during ER stress. Here, we sought to clarify the role of TRIB3 in neuronal apoptosis mediated by ER stress. In the kainic acid (KA) (10 mg/kg)-induced rat seizure model, we characterized neuronal injury and apoptosis after KA injection. KA induced an ER stress response, as indicated by elevated expression of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP). TRIB3 protein was upregulated concomitantly with the downregulation of phosphorylated-protein kinase B (p-AKT) in rats following KA administration. In rat cortical neurons treated with KA, TRIB3 knockdown by siRNA reduced the number of dying neurons, decreased the induction of GRP78 and CHOP and the activation of caspase-3, and blocked the dephosphorylation of AKT after KA treatment. Our findings indicate that TRIB3 is involved in neuronal apoptosis occurring after KA-induced seizure. The knockdown of TRIB3 effectively protects against neuronal apoptosis in vitro, suggesting that TRIB3 may be a potential therapeutic target for the treatment of epilepsy.

Neuroprotective effect of curcumin nanoparticles against rat model of status epilepticus induced by pilocarpine

Background

The present study aims to investigate the neuroprotective effect of curcumin nanoparticles (Cur-NP) on the rat model of status epilepticus (SE) induced by pilocarpine.

Methods

In the present study, animals were divided into three groups: control animals, rat model of SE induced by a single dose of pilocarpine (380 mg/kg) injected intraperitoneally, and rat model of SE that received a daily intraperitoneal injection of Cur-NP (50 mg/kg) for four consecutive days prior to pilocarpine administration.

Results

The present results revealed a state of oxidative stress in the cortex and hippocampus of rat model of SE as compared to control. This was evident from the significant increase in lipid peroxidation and the significant decrease in reduced glutathione and nitric oxide. In addition, a significant increase in the levels of tumor necrosis factor-alpha (TNF-α) and caspase-3 was detected in the two studied brain regions of rat model of SE. The activities of acetylcholinesterase (AchE) and Na+/K+-ATPase decreased significantly in the cortex and hippocampus of rat model of SE. Protection with Cur-NP prevented oxidative stress and improved the elevated level of caspase-3 in the hippocampus and cortex and the hippocampal TNF-α to nonsignificant changes. Although Cur-NP prevented the decrease in AchE activity in the two studied brain regions, it failed to return Na+/K+-ATPase activity to its normal value.

Conclusions

It is clear from the present findings that Cur-NP could prevent the oxidative stress and neuroinflammation and cell death that were induced during SE. This in turn may help in ameliorating the subsequent cascades of events that follow SE and its development into epileptogenesis.

Metabolic and Homeostatic Changes in Seizures and Acquired Epilepsy-Mitochondria, Calcium Dynamics and Reactive Oxygen Species

Acquired epilepsies can arise as a consequence of brain injury and result in unprovoked seizures that emerge after a latent period of epileptogenesis. These epilepsies pose a major challenge to clinicians as they are present in the majority of patients seen in a common outpatient epilepsy clinic and are prone to pharmacoresistance, highlighting an unmet need for new treatment strategies. Metabolic and homeostatic changes are closely linked to seizures and epilepsy, although, surprisingly, no potential treatment targets to date have been translated into clinical practice. We summarize here the current knowledge about metabolic and homeostatic changes in seizures and acquired epilepsy, maintaining a particular focus on mitochondria, calcium dynamics, reactive oxygen species and key regulators of cellular metabolism such as the Nrf2 pathway. Finally, we highlight research gaps that will need to be addressed in the future which may help to translate these findings into clinical practice.

Pathophysiology of status epilepticus

Status epilepticus (SE) is the maximal expression of epilepsy with a high morbidity and mortality. It occurs due to the failure of mechanisms that terminate seizures. Both human and animal data indicate that the longer a seizure lasts, the less likely it is to stop. Recent evidence suggests that there is a critical transition from an ictal to a post-ictal state, associated with a transition from a spatio-temporally desynchronized state to a highly synchronized state, respectively. As SE continues, it becomes progressively resistant to drugs, in particular benzodiazepines due partly to NMDA receptor-dependent internalization of GABA(A) receptors. Moreover, excessive calcium entry into neurons through excessive NMDA receptor activation results in activation of nitric oxide synthase, calpains, and NADPH oxidase. The latter enzyme plays a critical part in the generation of seizure-dependent reactive oxygen species. Calcium also accumulates in mitochondria resulting in mitochondrial failure (decreased ATP production), and opening of the mitochondrial permeability transition pore. Together these changes result in status epilepticus-dependent neuronal death via several pathways. Multiple downstream mechanisms including inflammation, break down of the blood-brain barrier, and changes in gene expression can contribute to later pathological processes including chronic epilepsy and cognitive decline.

Neuroprotective Effect of Electric Conduction Treatment on Hippocampus Cell Apoptosis in KA Induced Acute Temporal Lobe Epileptic Rats

BACKGROUND

Electronic conduction, a new treatment approach for epilepsy, has been confirmed to reduce epileptiform discharge on EEG and convulsive behaviors, particularly epileptic discharge propagation and serious behavioral seizures, in rats with kainic acid (KA)-induced acute temporal lobe epilepsy (TLE).

OBJECTIVE

Hippocampal cell apoptosis was examined to confirm the neuroprotective effect of electronic conduction therapy in rats with KA-induced acute TLE.

METHODS

Rats were divided into four groups: control group (right CA3 injection of saline), KA group (right CA3 injection of KA), sham conduction group (KA rats with sham conduction), and conduction group (KA rats with electric conduction). Apoptotic cells were evaluated by flow cytometry, TUNEL staining, and mRNA expression levels of caspase-3, tumor necrosis factor-alpha, and glial fibrillary acidic protein measured by real-time quantitative PCR (qRT-PCR).

RESULTS

The frequency of convulsive behaviors in the conduction group decreased significantly compared with the KA group and the sham conduction group. Significantly fewer apoptotic cells were detected in rats with conduction based on flow cytometry and TUNEL staining results. The qRT-PCR results indicated that KA-induced up-regulation of hippocampal caspase-3 mRNA expression was reduced 24 hours after KA injection in rats that received conduction treatment.

CONCLUSION

Electronic conduction treatment can reduce seizure frequency and hippocampal cell apoptosis in rats with KA-induced acute TLE.

Continuous neurodegeneration and death pathway activation in neurons and glia in an experimental model of severe chronic epilepsy

Whether seizures might determine the activation of cell death pathways and what could be the relevance of seizure-induced cell death in epilepsy are still highly debated issues. We recently developed an experimental model of acquired focal cortical dysplasia (the MAM-pilocarpine or MP rat) in which the occurrence of status epilepticus--SE--and subsequent seizures induced progressive cellular/molecular abnormalities and neocortical/hippocampal atrophy. Here, we exploited the same model to verify when, where, and how cell death occurred in neurons and glia during epilepsy course. We analyzed Fluoro Jade (FJ) staining and the activation of c-Jun- and caspase-3-dependent pathways during epilepsy, from few hours post-SE up to six months of spontaneous recurrent seizures. FJ staining revealed that cell injury in MP rats was not temporally restricted to SE, but extended throughout the different epileptic stages. The region-specific pattern of FJ staining changed during epilepsy, and FJ(+) neurons became more prominent in the dorsal and ventral hippocampal CA at chronic epilepsy stages. Phospho-c-Jun- and caspase-3-dependent pathways were selectively activated respectively in neurons and glia, at early but even more conspicuously at late chronic stages. Phospho-c-Jun activation was associated with increased cytochrome-c staining, particularly at chronic stages, and the staining pattern of cytochrome-c was suggestive of its release from the mitochondria. Taken together, these data support the content that at least in the MP rat model the recurrence of seizures can also sustain cell death mechanisms, thus continuously contributing to the pathologic process triggered by the occurrence of SE.

The role of excitotoxic programmed necrosis in acute brain injury

Excitotoxicity involves the excessive release of glutamate from presynaptic nerve terminals and from reversal of astrocytic glutamate uptake, when there is excessive neuronal depolarization. N-methyl-d-aspartate (NMDA) receptors, a subtype of glutamate receptor, are activated in postsynaptic neurons, opening their receptor-operated cation channels to allow Ca^2 + influx. The Ca^2 + influx activates two enzymes, calpain I and neuronal nitric oxide synthase (nNOS). Calpain I activation produces mitochondrial release of cytochrome c (cyt c), truncated apoptosis-inducing factor (tAIF) and endonuclease G (endoG), the lysosomal release of cathepsins B and D and DNase II, and inactivation of the plasma membrane Na⁺–Ca^2 + exchanger, which add to the buildup of intracellular Ca^2 +. tAIF is involved in large-scale DNA cleavage and cyt c may be involved in chromatin condensation; endoG produces internucleosomal DNA cleavage. The nuclear actions of the other proteins have not been determined. nNOS forms nitric oxide (NO), which reacts with superoxide (O₂⁻) to form peroxynitrite (ONOO⁻). These free radicals damage cellular membranes, intracellular proteins and DNA. DNA damage activates poly(ADP-ribose) polymerase-1 (PARP-1), which produces poly(ADP-ribose) (PAR) polymers that exit nuclei and translocate to mitochondrial membranes, also releasing AIF. Poly(ADP-ribose) glycohydrolase hydrolyzes PAR polymers into ADP-ribose molecules, which translocate to plasma membranes, activating melastatin-like transient receptor potential 2 (TRPM-2) channels, which open, allowing Ca^2 + influx into neurons. NADPH oxidase (NOX1) transfers electrons across cellular membranes, producing O₂⁻. The result of these processes is neuronal necrosis, which is a programmed cell death that is the basis of all acute neuronal injury in the adult brain.

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.

Calpain I activity and its relationship with hippocampal neuronal death in pilocarpine-induced status epilepticus rat model

This study aims to establish pilocarpine-induced rat model of status epilepticus (SE), observe the activity of calpain I in the rat hippocampus and the subsequent neuronal death, and explore the relationship between calpain I activity and neuronal death in the hippocampus. Fifty-eight adult male Wistar rats were assigned randomly into either control group (n = 8) or epilepsy group (n = 50). SE was induced in the epilepsy group using pilocarpine. Before the injection, the rats were given atropine sulfate to reduce the side effect of pilocarpine. All rats in the seizure group were grouped into either SE or non-SE, depending on whether they developed convulsive seizures. The rats in SE group were treated with chloral hydrate to stop seizures after 60 min. Control animals were treated with the same dose of 0.9 % saline. All rats were monitored for seizures. At 24 h after SE, the rats' left brain tissues were stained by HE and TUNEL. Neuronal necrosis and apoptosis in the hippocampal CA3 area were observed. Calpain I activity in the right hippocampus was also observed using western blotting. Eighty percent of the rats in the seizure group developed SE, of which 35 % died. No rat died in both the control and non-SE groups. At 24 h after SE, the number of HE-stained neurons decreased (SE group: 55.19 ± 8.23; control group: 102.13 ± 3.73; non-SE group: 101.2 ± 2.86) and the number of TUNEL-positive neurons increased (SE group: 4.91 ± 1.35; non-SE and control group: 0). No obvious changes were observed in the neurons of the control and non-SE group animals. The 76 kDa cleavage of calpain I (the average optical density ratio is 0.096 ± 0.015) emerged in the SE group. Neuronal death has a direct relationship with calpain I activity. There is high success rate and lower death rate for pilocarpine to induce SE. At 24 h after SE, activity of calpain I, neuronal necrosis and apoptosis increased in the hippocampus. Neuronal death has a direct relationship with calpain I activity, which suggests that calpain I plays an important role in neuronal damage during SE.

Caspase 3 involves in neuroplasticity, microglial activation and neurogenesis in the mice hippocampus after intracerebral injection of kainic acid

BACKGROUND

The roles of caspase 3 on the kainic acid-mediated neurodegeneration, dendritic plasticity alteration, neurogenesis, microglial activation and gliosis are not fully understood. Here, we investigate hippocampal changes using a mouse model that receive a single kainic acid-intracerebral ventricle injection. The effects of caspase 3 inhibition on these changes were detected during a period of 1 to 7 days post kainic acid injection.

RESULT

Neurodegeneration was assessed by Fluoro-Jade B staining and neuronal nuclei protein (NeuN) immunostaining. Neurogenesis, gliosis, neuritic plasticity alteration and caspase 3 activation were examined using immunohistochemistry. Dendritic plasticity, cleavvage-dependent activation of calcineurin A and glial fibrillary acidic protein cleavage were analyzed by immunoblotting. We found that kainic acid not only induced neurodegeneration but also arouse several caspase 3-mediated molecular and cellular changes including dendritic plasticity, neurogenesis, and gliosis. The acute caspase 3 activation occurred in pyramidal neurons as well as in hilar interneurons. The delayed caspase 3 activation occurred in astrocytes. The co-injection of caspase 3 inhibitor did not rescue kainic acid-mediated neurodegeneration but seriously and reversibly disturb the structural integrity of axon and dendrite. The kainic acid-induced events include microglia activation, the proliferation of radial glial cells, neurogenesis, and calcineurin A cleavage were significantly inhibited by the co-injection of caspase 3 inhibitor, suggesting the direct involvement of caspase 3 in these events. Alternatively, the kainic acid-mediated astrogliosis is not caspase 3-dependent, although caspase 3 cleavage of glial fibrillary acidic protein occurred.

CONCLUSIONS

Our results provide the first direct evidence of a causal role of caspase 3 activation in the cellular changes during kainic acid-mediated excitotoxicity. These findings may highlight novel pharmacological strategies to arrest disease progression and control seizures that are refractory to classical anticonvulsant treatment.

A new therapy for refractory partial epilepsy: current shunt

A large number of epileptic patients suffer from refractory epilepsy, despite optimal treatment; thus these patients require new therapeutic approaches. Focal seizure activity is typically initiated in a fixed and localized region, which subsequently spreads to neighboring regions or more distant areas. At the initial onset of a seizure, the epileptic discharge will generate a relatively high voltage in seizure focus, and the discharge subsequently spreads to other relatively low-voltage regions. However, it is unknown whether seizure can be controlled through current shunt using a conduction microelectrode to conduct the epileptic discharge with a relatively high voltage in the seizure focus outside the brain. The current therapies for epilepsy, including drugs, resective surgery and neuromodulation, focus on inhibiting abnormal excessive or synchronous neuronal activity to control seizures; thus, the basic mechanism underlying these therapies is "inhibition". In contrast, we proposed a "conduction" mechanism, whereby a current shunt with conduction electrode is used to control seizures. To our knowledge, this therapeutic strategy has not been previously reported, and we propose that this approach might be an alternative choice for the treatment of refractory partial epilepsy in the future.

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

Neuronal cell death is a pathophysiological consequence of many brain insults that trigger epilepsy and has been implicated as a causal factor in epileptogenesis. Seizure-induced neuronal death features excitotoxic necrosis and apoptosis-associated signaling pathways, including activation of multiple members of the Bcl-2 gene family. The availability of mice in which individual Bcl-2 family members have been deleted has provided the means to determine whether they have causal roles in neuronal death and epileptogenesis in vivo. Studies show that multiple members of the Bcl-2 family are activated following status epilepticus and the seizure and damage phenotypes of eight different knockouts of the Bcl-2 family have now been characterized. Loss of certain pro-apoptotic members, including Puma, protected against seizure-induced neuronal death whereas loss of anti-apoptotic Mcl-1 and Bcl-w enhanced hippocampal damage. Notably, loss of two putatively pro-apoptotic members, Bak and Bmf, resulted in more seizure-damage while deletion of Bid had no effect, indicating the role of certain Bcl-2 family proteins in epileptic brain injury is distinct from their contributions following other stressors or in non-CNS tissue. Notably, Puma-deficient mice develop fewer spontaneous seizures after status epilepticus suggesting neuroprotection may preserve functional inhibition, either directly by preserving neuronal networks or indirectly, for example by limiting reactive gliosis and pro-inflammatory responses to neuronal death. Together, these studies support apoptosis-associated molecular mechanisms controlling neuronal death as a component of epileptogenesis which might be targetable to protect against seizure-damage, cognitive deficits and mitigate the severity of syndrome following epilepsy-precipitating injuries to the brain.

Effect of different mild hypoxia manipulations on kainic acid-induced seizures in the hippocampus of rats

The protective effect of the mild hypoxia to the epilepsy has been widely tested. Although it is found that the hypoxia protects the brain by up-regulation of hypoxia-inducible factor-1α, few focused on systematic comparisons between different mild hypoxia manipulations and their effects. The male Sprague-Dawley rats were observed following exposure to hypoxia before and after epilepsy for 3 days with 90 min per day. The effects of different mild hypoxia manipulations on kainic acid-induced epilepsy were compared from the perspective of morphology, molecular biology and behavioral test. Results showed that different mild hypoxia manipulations could inhibit the cell apoptosis of kainic acid-induced rat hippocampus and improve their physiological functions. The effect of preconditioning group was better than that of postconditioning group and that of preconditioning and postconditioning with mild hypoxia group was the best among all the groups. The result showed that the preconditioning and postconditioning of mild hypoxia was recommended pre- and post-epilepsy and exposure to mild hypoxia should be prolonged. These findings might provide new ideas and methods for the clinical treatment of epilepsy.

A swell in the armamentarium of antiepileptic drug targets

Although long granted the status of immune privilege, the central nervous system is not completely isolated from the immune system. Increasing evidence suggests that this system contributes to seizures and epilepsy and that the molecular mediators of inflammation and immunity may serve as appropriate targets in the quest to develop novel antiepileptic drugs that are more efficacious and potentially disease modifying.

Cell signaling underlying epileptic behavior

Epilepsy is a complex disease, characterized by the repeated occurrence of bursts of electrical activity (seizures) in specific brain areas. The behavioral outcome of seizure events strongly depends on the brain regions that are affected by overactivity. Here we review the intracellular signaling pathways involved in the generation of seizures in epileptogenic areas. Pathways activated by modulatory neurotransmitters (dopamine, norepinephrine, and serotonin), involving the activation of extracellular-regulated kinases and the induction of immediate early genes (IEGs) will be first discussed in relation to the occurrence of acute seizure events. Activation of IEGs has been proposed to lead to long-term molecular and behavioral responses induced by acute seizures. We also review deleterious consequences of seizure activity, focusing on the contribution of apoptosis-associated signaling pathways to the progression of the disease. A deep understanding of signaling pathways involved in both acute- and long-term responses to seizures continues to be crucial to unravel the origins of epileptic behaviors and ultimately identify novel therapeutic targets for the cure of epilepsy.

Functional aspects of redox control during neuroinflammation

Neuroinflammation is a CNS reaction to injury in which some severe pathologies, regardless of their origin, converge. The phenomenon emphasizes crosstalk between neurons and glia and reveals a complex interaction with oxidizing agents through redox sensors localized in enzymes, receptors, and transcription factors. When oxidizing pressures cause reversible molecular changes, such as minimal or transitory proinflammatory cytokine overproduction, redox couples provide a means of translating the presence of reactive oxygen or nitrogen species into useful signals in the cell. Additionally, thiol-based redox sensors convey information about localized changes in redox potential induced by physiologic or pathologic situations. They are susceptible to oxidative changes and become key events during neuroinflammation, altering the course of a signaling response or the behavior of specific transcription factors. When oxidative stress augments the pressure on the intracellular environment, the effective reduction potential of redox pairs diminishes, and cell signaling shifts toward proinflammatory and proapoptotic signals, creating a vicious cycle between oxidative stress and neuroinflammation. In addition, electrophilic compounds derived from the oxidative cascade react with key protein thiols and interfere with redox signaling. This article reviews the relevant functional aspects of redox control during the neuroinflammatory process.

Transcriptome analysis of the hippocampal CA1 pyramidal cell region after kainic acid-induced status epilepticus in juvenile rats

Molecular mechanisms involved in epileptogenesis in the developing brain remain poorly understood. The gene array approach could reveal some of the factors involved by allowing the identification of a broad scale of genes altered by seizures. In this study we used microarray analysis to reveal the gene expression profile of the laser microdissected hippocampal CA1 subregion one week after kainic acid (KA)-induced status epilepticus (SE) in 21-day-old rats, which are developmentally roughly comparable to juvenile children. The gene expression analysis with the Chipster software generated a total of 1592 differently expressed genes in the CA1 subregion of KA-treated rats compared to control rats. The KEGG database revealed that the identified genes were involved in pathways such as oxidative phosporylation (26 genes changed), and long-term potentiation (LTP; 18 genes changed). Also genes involved in Ca²⁺ homeostasis, gliosis, inflammation, and GABAergic transmission were altered. To validate the microarray results we further examined the protein expression for a subset of selected genes, glial fibrillary protein (GFAP), apolipoprotein E (apo E), cannabinoid type 1 receptor (CB1), Purkinje cell protein 4 (PEP-19), and interleukin 8 receptor (CXCR1), with immunohistochemistry, which confirmed the transcriptome results. Our results showed that SE resulted in no obvious CA1 neuronal loss, and alterations in the expression pattern of several genes during the early epileptogenic phase were comparable to previous gene expression studies of the adult hippocampus of both experimental epileptic animals and patients with temporal lobe epilepsy (TLE). However, some changes seem to occur after SE specifically in the juvenile rat hippocampus. Insight of the SE-induced alterations in gene expression and their related pathways could give us hints for the development of new target-specific antiepileptic drugs that interfere with the progression of the disease in the juvenile age group.

Preservation of mitochondrial integrity and energy metabolism during experimental status epilepticus leads to neuronal apoptotic cell death in the hippocampus of the rat

Status epilepticus results in mitochondrial damage or dysfunction and preferential neuronal cell loss in the hippocampus. Since a critical determinant of the eventual cell death fate resides in intracellular ATP concentration, we investigated whether mitochondrial integrity and level of energy metabolism are related with apoptotic cell death in specific hippocampal neuronal populations. A kainic acid (KA)-induced experimental temporal lobe status epilepticus model was used. Qualitative and quantitative analysis of DNA fragmentation, TUNEL immunohistochemistry, double immunofluorescence staining for activated caspase-3, electron microscopy or measurement of ATP level in the bilateral hippocampus was carried out 1, 3 or 7 days after microinjection unilaterally of a low dose of KA (0.5 nmol) into the CA3 hippocampal subfield. Characteristic biochemical (DNA fragmentation), histochemical (TUNEL or activated caspase-3 staining) or ultrastructural (electron microscopy) features of apoptotic cell death were presented bilaterally in the hippocampus 7 days after the elicitation of sustained hippocampal seizure activity by microinjection of KA into the unilateral CA3 subfield. At the same time, CA3 or CA1 subfield on either side manifested a maintained ATP level; alongside relatively intact mitochondria, rough endoplasmic reticulum, Golgi apparatus or cytoplasmic membrane in hippocampal neurons that exhibited ultrastructural features of apoptotic cell death. Our results demonstrated that preserved mitochondrial ultrastructural integrity and maintained energy metabolism during experimental temporal lobe status epilepticus is associated specifically with apoptotic, not necrotic, cell death in hippocampal CA3 or CA1 neurons.

The effects of topiramate on caspase-3 expression in hippocampus of basolateral amygdala (BLA) electrical kindled epilepsy rat

Caspase-3 expression was determined in the hippocampus of electrically kindled rats with and without topiramate treatment. Bipolar electrotrodes were implanted for chronic stimulation of the basolateral amygdala (BLA) to achieve a kindled state. Seizure and behavioral responses were observed, and video-electroencephalograms were recorded during and after kindling. After topiramate treatment (80 mg/kg, p.o.), the hippocampi were extracted and caspase-3 mRNA analyzed by semiquantitative RT-PCR. Caspase-3 immunoreactivity was determined with immunohistochemical staining. Topiramate treatment resulted in a significant decrease in the mean duration of seizures from 52 s in kindled rats to 13 s. The after-discharge duration was significantly decreased by 70% after topiramate treatment. Significant upregulations of both caspase-3 mRNA and caspase-3 immunoreactivity were observed in the kindled rats. These kindling-mediated increases in caspase-3 were prevented by topiramate treatment, and these levels were not different from those of sham-operated controls. In BLA-kindled rats, mRNA and immunoreactivity for caspase-3 were increased. Treatment with topiramate prevented the kindling-associated increases in caspase-3 as well as the increases in seizure duration and after-discharge duration. These data suggest that topiramate may have a neuroprotective role in addition to its action as an anticonvulsant.

The ketogenic diet and epilepsy

PURPOSE OF REVIEW

The ketogenic diet has long been used to treat medically refractory epilepsy. The mechanisms underlying its clinical effects, however, have remained a mystery. The evidence to date suggests that a fundamental shift from glycolysis to intermediary metabolism induced by the ketogenic diet is necessary and sufficient for clinical efficacy. This notion is supported by a growing number of studies indicating that glucose restriction, ketone bodies and polyunsaturated fatty acids may all play mechanistic roles, possibly by enhancing mitochondrial respiration and ATP production, and decreasing reactive oxygen species production.

RECENT FINDINGS

Recent reports indicate that ketone bodies can reduce oxidative stress and that fatty acid-induced mitochondrial uncoupling may also yield similar protective effects. Ketone bodies may attenuate spontaneous firing of ATP-sensitive potassium channels in central neurons, and pharmacological inhibition of glycolysis has been shown to retard epileptogenesis in a rat kindling model.

SUMMARY

While the mechanisms underlying the broad clinical efficacy of the ketogenic diet remain unclear, there is growing evidence that the ketogenic diet alters the fundamental biochemistry of neurons in a manner that not only inhibits neuronal hyperexcitability but also induces a protective effect. Thus, the ketogenic diet may ultimately be useful in the treatment of a variety of neurological disorders.

Mu-calpain mediates hippocampal neuron death in rats after lithium-pilocarpine-induced status epilepticus

Status epilepticus (SE) is a severe clinical manifestation of epilepsy which causes brain damage. The pathological process and underlying mechanisms involved in the programmed cell death (PCD) are still not fully clear. In the current study, rats were induced SE by lithium-pilocarpine administration. Our data showed hippocampal neurons death appeared at 6h after SE and sustained for 7 days. By blotting the activation of mu-calpain and its specific cleavage of nonerythroid alpha-spectrin (alphaSpII) (145 kDa) was evident at 1 and 3 days after SE, which coincided with Bid activation, apoptosis inducing factor (AIF) translocation and cytochrome c release from mitochondria, whereas, activated caspase-3 and caspase-3-specific fragments of alphaSpII (120 kDa) predominantly appeared at 5 and 7 days after SE. Moreover, MDL-28170, a calpain inhibitor, partially rescued the neuron death and attenuated the expression of activated mu-calpain, cleavage of Bid (15 kDa), AIF translocation and cytochrome c release. Taken together, our study indicated that mu-calpain mediated hippocampal neuron PCD is prior to caspase-3 activation. It functioned via translocation of Bid, AIF and cytochrome c release.

Calpain activation is involved in early caspase-independent neurodegeneration in the hippocampus following status epilepticus

Evidence for increased calpain activity has been described in the hippocampus of rodent models of temporal lobe epilepsy. However, it is not known whether calpains are involved in the cell death that accompanies seizures. In this work, we characterized calpain activation by examining the proteolysis of calpain substrates and in parallel we followed cell death in the hippocampus of epileptic rats. Male Wistar rats were injected with kainic acid (10 mg/kg) intraperitoneally and killed 24 h later, after development of grade 5 seizures. We observed a strong Fluoro-Jade labeling in the CA1 and CA3 areas of the hippocampus in the rats that received kainic acid, when compared with saline-treated rats. Immunohistochemistry and western blot analysis for the calpain-derived breakdown products of spectrin showed evidence of increased calpain activity in the same regions of the hippocampus where cell death is observed. No evidence was found for caspase activation, in the same conditions. Treatment with the calpain inhibitor MDL 28170 significantly prevented the neurodegeneration observed in CA1. Taken together, our data suggest that early calpain activation, but not caspase activation, is involved in neurotoxicity in the hippocampus after status epilepticus.

Dynamic changes of proteases and protease inhibitors revealed by microarray analysis in CA3 and entorhinal cortex during epileptogenesis in the rat

We investigated expression of genes involved in the proteolytic process during epileptogenesis in a rat model of temporal lobe epilepsy (TLE). In a previous microarray study we found prominent activation of this process, which reached highest expression during the acute and latent phase (1 week after SE) in CA3 and entorhinal cortex (EC). Detailed analysis shows differences in dynamics of the changes of several protease genes such as cathepsins, caspases, matrix metalloproteinases, and plasminogen activators. Most genes were acutely upregulated while others were mainly activated during the latent phase. Interestingly several proteolytic genes were still elevated in the chronic epileptic phase. Various protease inhibitors followed a similar time course. The identification of changes in the activation of genes involved in proteolysis at critical phases during epileptogenesis could point to potential time specific targets for intervention. The fact that several proteolytic genes were still activated in the chronic epileptic phase makes them interesting candidates to modify and slow down seizure progression.

Bcl-w protects hippocampus during experimental status epilepticus

Experimentally evoked seizures can activate the intrinsic mitochondrial cell death pathway, components of which are modulated in the hippocampus of patients with temporal lobe epilepsy. Bcl-2 family proteins are critical regulators of mitochondrial dysfunction, but their significance in this setting remains primarily untested. Presently, we investigated the mitochondrial pathway and role of anti-apoptotic Bcl-2 proteins using a mouse model of seizure-induced neuronal death. Status epilepticus was evoked in mice by intra-amygdala kainic acid, causing cytochrome c release, processing of caspases 9 and 7, and death of ipsilateral hippocampal pyramidal neurons. Seizures caused a rapid decline in hippocampal Bcl-w levels not seen for either Bcl-2 or Bcl-xl. To test whether endogenous Bcl-w was functionally significant for neuronal survival, we investigated hippocampal injury after seizures in Bcl-w-deficient mice. Seizures induced significantly more hippocampal CA3 neuronal loss and DNA fragmentation in Bcl-w-deficient mice compared with wild-type mice. Quantitative electroencephalography analysis also revealed that Bcl-w-deficient mice display a neurophysiological phenotype whereby there was earlier polyspike seizure onset. Finally, we detected higher levels of Bcl-w in hippocampus from temporal lobe epilepsy patients compared with autopsy controls. These data identify Bcl-w as an endogenous neuroprotectant that may have seizure-suppressive functions.

Neuroprotective strategies to avert seizure-induced neurodegeneration in epilepsy

Neurodegeneration in limbic circuits is a hallmark feature of chronic temporal lobe epilepsy (TLE). Studies in experimental animal models and human patients indicate that seizure-induced neuronal injury involves some active, as well as passive cell death processes. Experimental approaches that inhibit active steps in cell death programs have been shown to reduce neuronal cell death and sclerosis, but not to prevent epileptogenesis in animal models of TLE. These findings suggest that we need additional research using both animal models and brain slices from human patients to understand the pathological mechanisms underlying seizure generation. Such comparative studies will also aid in evaluating the potential therapeutic value of inhibiting cell death in seizure disorders.

Increased expression of caspase 2 in experimental and human temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is often caused by a neurodegenerative brain insult that triggers epileptogenesis, and eventually results in spontaneous seizures, i.e., epilepsy. Understanding the mechanisms of cell death is a key for designing new drug therapies for preventing the neurodegeneration associated with TLE. Here, we investigated the expression of caspase 2, a protein involved in programmed cell death, during the course of epilepsy. We investigated caspase 2 expression in hippocampal samples derived from patients operated on for drug refractory TLE. To understand the evolution of altered-caspase 2 expression during the epileptic process, we also examined caspase 2 expression and activity in the rat hippocampus after status epilepticus-induced acute damage, during epileptogenesis, and after the onset of epilepsy. Caspase 2 expression was enhanced in the hippocampal neurons in chronic TLE patients. In rats, status epilepticus-induced caspase 2 labeling paralleled the progression of neurodegeneration. Proteolytic activation and cleavage of caspase 2 was also detected in the rat brain undergoing epileptogenesis. Our data suggest that caspase 2-mediated programmed cell death participates in the seizure-induced degenerative process in experimental and human TLE.

Apoptosis signalling pathways in seizure-induced neuronal death and epilepsy

Delineating the molecular pathways underlying seizure-induced neuronal death may yield novel strategies for brain protection against prolonged or repetitive seizures. Glutamate-mediated excitotoxicity and necrosis is a primary contributing mechanism but seizures also activate programmed (apoptotic) cell death pathways. Apoptosis signalling pathways are typically initiated following perturbation of intracellular organelle function (intrinsic pathway) or by activated cell-surface-expressed death receptors (extrinsic pathway), with signalling cascades orchestrated in part by the Bcl-2 and caspase gene families. In this review, evidence for these pathways from experimental seizure modelling and clinical material from patients with intractable temporal lobe epilepsy is examined. Seizures cause mitochondrial dysfunction and activate intrinsic pathway components including pro-apoptotic Bcl-2 family proteins and caspases, processes that may be partly calcium-induced. The ER (endoplasmic reticulum) has emerged as a major intrinsic pathway trigger for apoptosis and its function may also be compromised following seizures and in epilepsy. The extrinsic, death-receptor-dependent pathway is also rapidly engaged following experimental seizures and in patient brain, supporting a previously unexpected apical role for a calcium-independent pathway. When considered alongside emerging functions of apoptosis-regulatory proteins in non-cell-death processes, including regulating intracellular calcium release and neuronal (re)structuring, apoptosis signalling pathways can be viewed as an important developing focus of research into how to obviate the deleterious impact of seizures on the brain.

Caspase-dependent programmed cell death pathways are not activated in generalized seizure-induced neuronal death

Activation of the caspase-dependent cell death pathways has been shown in focal seizures, but whether this occurs in prolonged generalized seizures is not known. We investigated whether the initiator caspase in the extrinsic pathway, caspase-8, or the intrinsic pathway, caspase-9, is activated during the first 24 h following lithium-pilocarpine-induced status epilepticus, when neuronal death is maximal and widespread. The thymuses of rats given methamphetamine were used as positive controls for caspase-3-activated cellular apoptosis. Following methamphetamine treatment, caspase-9 but not caspase-8 was activated in thymocytes. However, 6 or 24 h following status epilepticus, none of 26 brain regions studied showed either caspase-8 or -9 activation by immunohistochemistry, western blotting and enzyme activity assays. Our results provide evidence against the activation of the extrinsic and intrinsic caspase pathways in generalized seizures, which produce morphologically necrotic neurons with internucleosomal DNA cleavage (DNA laddering), a programmed process. In contrast, there is increasing evidence that caspase-independent programmed mechanisms play a prominent role in seizure-induced neuronal death.

Proteolysis consistent with activation of caspase-7 after severe traumatic brain injury in humans

The expression and proteolysis of caspase family proteins are involved in the initiation and execution of apoptosis, which has been reported to occur in human and experimental traumatic brain injury (TBI). Caspase-3, -6, and -7 belong to the group of executioner caspases, which are cleaved and activated at the late, irreversible stage of apoptosis. Our previous studies demonstrated roles for caspase-1, -3, and -8 in humans after severe TBI. Here we report expression of caspase-7 mRNA and protein in humans after TBI (n = 16) and control brain-bank tissue (n = 6). Semiquantitative reverse transcription polymerase chain reaction showed no differences between caspase-7 mRNA in TBI patients versus controls (73 +/- 24 vs. 85 +/- 56 relative optical density [ROD], respectively). In contrast, Western blot analysis showed increased pro-caspase-7 in TBI patients versus controls (214 +/- 30 vs. 1 +/- 1 ROD, respectively), as well as an increase in the approximately 20 kD proteolytic fragment in TBI patients versus controls (86 +/- 13 vs. 22 +/- 12 ROD, respectively), consistent with activation of caspase-7 after TBI in humans. Immunohistochemical analysis showed that cells expressing caspase-7 included astrocytes and neurons and possibly other glial cell types and infiltrated inflammatory cells. These data show that caspase-7 and its cleavage product are increased in human brain after TBI in many central nervous system, as well as noncentral nervous system, cell types. Thus, caspase-7 may play a role in the glial and inflammatory responses, and possibly neuronal death, after TBI in humans.

Isoform- and subcellular fraction-specific differences in hippocampal 14-3-3 levels following experimentally evoked seizures and in human temporal lobe epilepsy

14-3-3 proteins are a family of signaling molecules involved in diverse cellular functions, which can mediate anti-apoptotic effects. Seizure-induced neuronal death may involve programmed (apoptotic) cell death pathways and is associated with a decline in brain 14-3-3 levels. Presently, we investigated the subcellular localization and effects of seizures on isoforms of 14-3-3 in rat hippocampus, and contrasted these to findings in human temporal lobe epilepsy (TLE). All brain isoforms of 14-3-3 were detected in the cytoplasmic compartment of rat hippocampus, while 14-3-3gamma and -zeta were also present in mitochondrial and microsome-enriched fractions. Focally evoked seizures in rats significantly reduced 14-3-3gamma levels within the microsome-enriched compartment at 4 h, with similar responses for 14-3-3zeta, while cytoplasm-localized 14-3-3beta, -epsilon and -eta remained unchanged. Analysis of human autopsy control hippocampus revealed similar 14-3-3 isoform expression profiles. In TLE samples, the microsome-enriched fraction also showed differences, but here 14-3-3epsilon and -zeta levels were higher than controls. TLE sample 14-3-3 isoform abundance within the cytoplasmic fraction was not different to controls. This study defines the subcellular localization of 14-3-3 isoforms in rat and human hippocampus and identifies the microsome-enriched fraction as the main site of altered 14-3-3 levels in response to acute prolonged and chronic recurrent seizures.

Neuroprotection of Tat-GluR6-9c against neuronal death induced by kainate in rat hippocampus via nuclear and non-nuclear pathways

Previous studies have suggested that glutamate receptor 6 (GluR6) subunit- and JNK-deficient mice can resist kainate-induced epileptic seizure and neuronal toxicity (Yang, D. D., Kuan, C.-Y., Whitmarsh, A. J., Rinoćn, M., Zheng, T. S., Davis, R. J., Rakic, P., and Flavell, R. A. (1997) Nature 389, 865-870; Mulle, C., Seiler, A., Perez-Otano, I., Dickinson-Anson, H., Castillo, P. E., Bureau, I., Maron, C., Gage, F. H., Mann, J. R., Bettler, B., and Heinemmann, S. F. (1998) Nature 392, 601-605). In this study, we show that kainate can enhance the assembly of the GluR6-PSD95-MLK3 module and facilitate the phosphorylation of JNK in rat hippocampal CA1 and CA3/dentate gyrus (DG) subfields. More important, a peptide containing the Tat protein transduction sequence (Tat-GluR6-9c) perturbed the assembly of the GluR6-PSD95-MLK3 signaling module and suppressed the activation of MLK3, MKK7, and JNK. As a result, the inhibition of JNK activation by Tat-GluR6-9c diminished the phosphorylation of the transcription factor c-Jun and down-regulated Fas ligand expression in hippocampal CA1 and CA3/DG regions. The inhibition of JNK activation by Tat-Glur6-9c attenuated Bax translocation, the release of cytochrome c, and the activation of caspase-3 in CA1 and CA3/DG subfields. Furthermore, kainate-induced neuronal loss in hippocampal CA1 and CA3 subregions was prevented by intracerebroventricular injection of Tat-Glur6 - 9c. Taken together, our findings strongly suggest that the GluR6-PSD95-MLK3 signaling module mediates activation of the nuclear and non-nuclear pathways of JNK, which is involved in brain injury induced by kainate. Tat-GluR6-9c, the peptide we constructed, gives new insight into seizure therapy.

Serum Fas and Bcl-2 in patients with epilepsy

OBJECTIVES

The present study aimed to investigate the levels of the biochemical markers of apoptosis (soluble Fas and Bcl-2) in the sera of children and adolescents with idiopathic epilepsy.

MATERIALS AND METHODS

The study included 30 children and adolescents (mean age 8.03 +/- 4.49 years) with idiopathic epilepsy, 16 of them were newly diagnosed, and 15 clinically healthy control subjects. Of the included patients, 22 had focal seizures and eight had generalized seizures. In addition to laboratory and radiological investigations needed for diagnosis and follow-up, soluble Fas (s.Fas) and Bcl-2 were assayed in sera of patients and controls by enzyme-linked immunosorbent assay technique.

RESULTS

Serum levels of s.Fas and Bcl-2 were significantly higher in the patients group than in the control group; however, their levels were comparable in patients with different seizure types. Levels of s.Fas correlated positively with seizure severity and negatively with the duration from the last attack. Bcl-2 levels were positively correlated to each of the duration of epilepsy, the severity of seizures and its frequency. There was a significant positive correlation between serum levels of s.Fas and that of Bcl-2 and both were significantly increased in patients with uncontrolled epilepsy.

CONCLUSION

The present data demonstrate that markers of apoptosis, both the proapoptotic Fas and the anti-apoptotic Bcl-2, were proportionately elevated in sera of patients with idiopathic epilepsy, and their levels were related to the seizure severity and frequency.

Apoptotic interactions of cytochrome c: redox flirting with anionic phospholipids within and outside of mitochondria

Since the (re)discovery of cytochrome c (cyt c) in the early 1920s and subsequent detailed characterization of its structure and function in mitochondrial electron transport, it took over 70 years to realize that cyt c plays a different, not less universal role in programmed cell death, apoptosis, by interacting with several proteins and forming apoptosomes. Recently, two additional essential functions of cyt c in apoptosis have been discovered that are carried out via its interactions with anionic phospholipids: a mitochondria specific phospholipid, cardiolipin (CL), and plasma membrane phosphatidylserine (PS). Execution of apoptotic program in cells is accompanied by substantial and early mitochondrial production of reactive oxygen species (ROS). Because antioxidant enhancements protect cells against apoptosis, ROS production was viewed not as a meaningless side effect of mitochondrial disintegration but rather playing some - as yet unidentified - role in apoptosis. This conundrum has been resolved by establishing that mitochondria contain a pool of cyt c, which interacts with CL and acts as a CL oxygenase. The oxygenase is activated during apoptosis, utilizes generated ROS and causes selective oxidation of CL. The oxidized CL is required for the release of pro-apoptotic factors from mitochondria into the cytosol. This redox mechanism of cyt c is realized earlier than its other well-recognized functions in the formation of apoptosomes and caspase activation. In the cytosol, released cyt c interacts with another anionic phospholipid, PS, and catalyzes its oxidation in a similar oxygenase reaction. Peroxidized PS facilitates its externalization essential for the recognition and clearance of apoptotic cells by macrophages. Redox catalysis of plasma membrane PS oxidation constitutes an important redox-dependent function of cyt c in apoptosis and phagocytosis. Thus, cyt c acts as an anionic phospholipid specific oxygenase activated and required for the execution of essential stages of apoptosis. This review is focused on newly discovered redox mechanisms of complexes of cyt c with anionic phospholipids and their role in apoptotic pathways in health and disease.