Latency to onset of status epilepticus determines molecular mechanisms of seizure-induced cell death

GABA Administration Ameliorates the Toxicity of Doxorubicin on CSF and the Brain of Albino Rats

Background

Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the mammalian brain and is a non-proteinogenic amino acid. Doxorubcin (DOX) or adriamycin is one of the most potent chemotherapy drugs for breast cancer.

Purpose

This study focused on diminishing the brain injury and neurotoxicity of doxorubicin (DOX) by GABA administration.

Methods

Rats were randomly divided into four groups (8 rats each), which were the control group, DOX group (3 mg/kg for 4 weeks, then 2 mg/kg for 2 weeks), GABA group (2 mg/kg for 21 days), and DOX + GABA group (treated as the second and third groups). Neurotoxicity and brain injury were assessed by determining CSF biomarkers, serum inflammatory markers, and histopathological evaluation of the cerebral cortex.

Results

DOX treatment significantly increased the levels of all CSF biomarkers (S100B, IL-1β, ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), glial fibrillary acidic protein (GFAP), spectrin breakdown products (SBDP145), and C-C motif chemokine ligand 2 (CCL2) and all inflammatory markers (IL-6, TNF-α, and IFN-γ), causing extensive neutrophilic infiltration and great alteration in the cerebral cortex architecture as evidence of neurotoxicity. The oral administration of GABA significantly reduced the levels of all CSF biomarkers and inflammatory markers and restored the normal architecture of the cerebral cortex, with observed ameliorations in neutrophilic infiltration.

Conclusion

GABA administration can ameliorate neurotoxicity and protect the brain against the negative effects of DOX treatment.

Evaluation the cognition-improvement effects of N-acetyl cysteine in experimental temporal lobe epilepsy in rat

Memory impairment is a critical issue in patients with temporal lobe epilepsy (TLE). Neuronal loss within the hippocampus and recurrent seizures may cause cognitive impairment in TLE. N -acetyl cysteine (NAC) is a sulfur-containing amino acid cysteine that is currently being investigated due to its protective effects on neurodegenerative disorders. NAC was orally administrated at a dose of 100 mg/kg for 8 days (7-day pretreatment and 1-day post-surgery). Neuronal viability, mTOR protein level, and spatial memory were detected in the kainite temporal epilepsy model via Nissl staining, western blot method, and Morris water maze task, respectively. Results showed that NAC delayed seizure activity and ameliorated memory deficit induced by Kainic acid. Histological analysis showed that NAC significantly increased the number of intact neurons in CA3 and hilar areas of the hippocampus following the induction of epilepsy. NAC also modulated the mTOR protein level 5 days after epilepsy compared to the KA-induced group. CONCLUSION: These results suggest that NAC improved memory impairment via anticonvulsant and neuroprotective activity and, in all probability, by lowering the level of mTOR.

2-Deoxyglucose protects hippocampal neurons against kainate-induced temporal lobe epilepsy by modulating monocyte-derived macrophages (mo-MΦ) and progranulin production in the hippocampus

Inflammation is an important factor in the pathology of epilepsy with the hallmarks of resident microglia activation and infiltration of circulating monocytes in the damaged area. In the case of recovery and tissue repair, some monocytes change to macrophages (mo-MΦ) to enhance tissue repair. 2-deoxyglucose (2DG) is an analog of glucose capable of protecting the brain, and progranulin is a neurotrophic factor produced mainly by microglia and has an inflammation modulator effect. This study attempted to evaluate if one of the neuroprotective mechanisms of 2-DG is comprised of increasing monocyte-derived macrophages (mo-MΦ) and progranulin production. Status epilepticus (SE) was induced by i.c.v. injection of kainic acid (KA).2DG (125/mg/kg/day) was administered intraperitoneally. Four days later, animals were sacrificed. Their brain sections were then stained with Cresyl violet and Fluoro-Jade B to count the number of necrotic and degenerating neurons in CA3 and Hilus of dentate gyrus of the hippocampus. Lastly, immunohistochemistry was used to detect CD11b + monocyte, macrophage cells, and Progranulin level was evaluated by Western blotting. The histological analysis showed that 2DG can reduce the number of necrotic and degenerating neurons in CA3 and Hilar areas. Following KA administration, a great number of cD11b⁺ cells with monocyte morphology were observed in the hippocampus. 2DG not only reduced cD11b⁺ monocyte cells but was able to convert them to cells with the morphology of macrophages (mo-MΦ). 2DG also caused a significant increase in progranulin level in the hippocampus. Because macrophages and microglia are the most important sources of progranulin, it appears that 2DG caused the derivation of monocytes to macrophages and these cells produced progranulin with a subsequent anti-inflammation effect. In summary, it was concluded that 2DG is neuroprotective and probably one of its neuroprotective mechanisms is by modulating monocyte-derived macrophages by progranulin production.

Rifampicin ameliorates lithium-pilocarpine-induced seizures, consequent hippocampal damage and memory deficit in rats: Impact on oxidative, inflammatory and apoptotic machineries

Epilepsy is one of the serious neurological sequelae of bacterial meningitis. Rifampicin, the well-known broad spectrum antibiotic, is clinically used for chemoprophylaxis of meningitis. Besides its antibiotic effects, rifampicin has been proven to be an effective neuroprotective candidate in various experimental models of neurological diseases. In addition, rifampicin was found to have promising antioxidant, anti-inflammatory and anti-apoptotic effects. Herein, we investigated the anticonvulsant effect of rifampicin at experimental meningitis dose (20 mg/kg, i.p.) using lithium-pilocarpine model of status epilepticus (SE) in rats. Additionally, we studied the effect of rifampicin on seizure induced histopathological, neurochemical and behavioral abnormalities. Our study showed that rifampicin pretreatment attenuated seizure activity and the resulting hippocampal insults marked by hematoxylin and eosin. Markers of oxidative stress, neuroinflammation and apoptosis were evaluated, in the hippocampus, 24 h after SE induction. We found that rifampicin pretreatment suppressed oxidative stress as indicated by normalized malondialdehyde and glutathione levels. Rifampicin pretreatment attenuated SE-induced neuroinflammation and decreased the hippocampal expression of interleukin-1β, tumor necrosis factor-α, nuclear factor kappa-B, and cyclooxygenase-2. Moreover, rifampicin mitigated SE-induced neuronal apoptosis as indicated by fewer positive cytochrome c immunostained cells and lower caspase-3 activity in the hippocampus. Furthermore, Morris water maze testing at 7 days after SE induction showed that rifampicin pretreatment can improve cognitive dysfunction. Therefore, rifampicin, currently used in the management of meningitis, has a potential additional advantage of ameliorating its epileptic sequelae.

Effect of Naringenin (A naturally occurring flavanone) Against Pilocarpine-induced Status Epilepticus and Oxidative Stress in Mice

BACKGROUND

Epilepsy is a disorder of the central nervous system characterized by recurrent seizures. It is a very common disease in which approximately 30% of patients do not respond favourably to treatment with anticonvulsants. Oxidative stress is associated with neuronal damage arising from epileptic seizures. The present study investigated the effects of naringenin in pilocarpine-induced epilepsy in mice. Naringenin, one of the most frequently occurring flavanone in citrus fruits, was evaluated for its shielding effect against the pilocarpine induced behavioural, oxidative and histopathological alterations in rodent model of epilepsy.

METHODOLOGY

Epilepsy was induced by giving pilocarpine (300mg/kg) and sodium valproate (300mg/kg) was given as standard anti-epileptic drug Pilocarpine was administered (300 mg /kg body weight) intraperitoneally to the mice on 15th day while naringenin was administered orally (20 and 40 mg/kg body weight) for 15 days prior to administration of pilocarpine.

RESULTS

The intraperitoneal administration of pilocarpine enhanced lipid peroxidation, caused reduction in antioxidant enzymes, viz., catalase, superoxide dismutase and glutathione reductase. Treatment of mice orally with naringenin (20 mg/kg body weight and 40 mg/kg body weight) resulted in a significant decrease in lipid peroxidation. There was significant recovery of glutathione content and all the antioxidant enzymes studied. Also in case of behavioural parameters studied, naringenin showed decrease in seizure severity. All these changes were supported by histological observations, which revealed excellent improvement in neuronal damage.

CONCLUSION

The higher dose of naringenin was more potent in our study and was comparable to the standard drug (sodium valproate) in effectiveness.

SUMMARY

Naringenin ameliorated the development of ROS formation in hippocamus.Naringenin helped in recovery of antioxidant enzymes.Naringenin decreased seizure severity.Naringenin treatment reduced lipid peroxidation. Abbreviations used: 6-OHDA: 6-hydroxydopamine, AED: Anti epileptic drugs, AIDS: Acquired immune deficiency syndrome, ANOVA: Analysis of variance, ATP: Adenosine triphosphate, CA: Cornu ammonis, CAT: Catalase, DG: Dentate gyrus, EDTA: Ethylenediamine tetra acetic acid, GR: Glutathione reductase, GSH: Glutathione reduced, HCl: Hydrochloric acid, IL-1β: Interleukin 1 beta, LPO: Lipid peroxidation, MDA: Malondialdehyde, NADPH: Nicotinamide adenine dinucleotide phosphate, PMS: post mitochondrial supernatant, SE: Status epilepticus, SEM: Standard error of the mean, SOD Superoxide dismutase, TBA: Thiobarbituric acid, TBARS: Thiobarbituric acid reactive substance, TLE: Temporal lobe epilepsy, TNF-α: Tumor necrosis factor alpha.

Effect of Naringenin (A naturally occurring flavanone) Against Pilocarpine-induced Status Epilepticus and Oxidative Stress in Mice

Background:

Epilepsy is a disorder of the central nervous system characterized by recurrent seizures. It is a very common disease in which approximately 30% of patients do not respond favourably to treatment with anticonvulsants. Oxidative stress is associated with neuronal damage arising from epileptic seizures. The present study investigated the effects of naringenin in pilocarpine-induced epilepsy in mice. Naringenin, one of the most frequently occurring flavanone in citrus fruits, was evaluated for its shielding effect against the pilocarpine induced behavioural, oxidative and histopathological alterations in rodent model of epilepsy.

Methodology:

Epilepsy was induced by giving pilocarpine (300mg/kg) and sodium valproate (300mg/kg) was given as standard anti-epileptic drug Pilocarpine was administered (300 mg /kg body weight) intraperitoneally to the mice on 15th day while naringenin was administered orally (20 and 40 mg/kg body weight) for 15 days prior to administration of pilocarpine.

Results:

The intraperitoneal administration of pilocarpine enhanced lipid peroxidation, caused reduction in antioxidant enzymes, viz., catalase, superoxide dismutase and glutathione reductase. Treatment of mice orally with naringenin (20 mg/kg body weight and 40 mg/kg body weight) resulted in a significant decrease in lipid peroxidation. There was significant recovery of glutathione content and all the antioxidant enzymes studied. Also in case of behavioural parameters studied, naringenin showed decrease in seizure severity. All these changes were supported by histological observations, which revealed excellent improvement in neuronal damage.

Conclusion:

The higher dose of naringenin was more potent in our study and was comparable to the standard drug (sodium valproate) in effectiveness.

SUMMARY

Naringenin ameliorated the development of ROS formation in hippocamus.

Naringenin helped in recovery of antioxidant enzymes.

Naringenin decreased seizure severity.

Naringenin treatment reduced lipid peroxidation.

Abbreviations used: 6-OHDA: 6-hydroxydopamine, AED: Anti epileptic drugs, AIDS: Acquired immune deficiency syndrome, ANOVA: Analysis of variance, ATP: Adenosine triphosphate, CA: Cornu ammonis, CAT: Catalase, DG: Dentate gyrus, EDTA: Ethylenediamine tetra acetic acid, GR: Glutathione reductase, GSH: Glutathione reduced, HCl: Hydrochloric acid, IL-1β: Interleukin 1 beta, LPO: Lipid peroxidation, MDA: Malondialdehyde, NADPH: Nicotinamide adenine dinucleotide phosphate, PMS: post mitochondrial supernatant, SE: Status epilepticus, SEM: Standard error of the mean, SOD Superoxide dismutase, TBA: Thiobarbituric acid, TBARS: Thiobarbituric acid reactive substance, TLE: Temporal lobe epilepsy, TNF-α: Tumor necrosis factor alpha

Metabolic changes in early poststatus epilepticus measured by MR spectroscopy in rats

There is little experimental in vivo data on how differences in seizure duration in experimental status epilepticus influence metabolic injury. This is of interest given that in humans, status duration is a factor that influences the probability of subsequent development of epilepsy. This question is studied using 7-T magnetic resonance (MR) spectroscopy, T2 relaxometry in the incremented kainate rodent model of temporal lobe epilepsy, using two durations of status epilepticus, 1.5 and 3 hours. Histologic evaluation was performed in a subset of animals. Three days after status, single-voxel (8 mm(3)) point resolved spectroscopy (PRESS) MR spectroscopic measurements were acquired at 7 T to assess the cerebral metabolites measured as a ratio to total creatine (tCr). The status injury resulted in decreased N-acetylaspartate NAA/tCr, increased myo-inositol/tCr and glutamine/tCr, increased T2, and significant declines in NeuN-stained neuronal counts in both status groups. Regressions were identified in the status groups that provide evidence for neuronal injury and astrocytic reaction after status in both the short and long status duration groups. The long status group displays changes in glutathione/tCr that are not identified in the short status group, this difference possibly representing a maturation of injury and antioxidant response that occurs in synchrony with glutamatergic injury and glial activation.

3,4-Methylenedioxymethamphetamine enhances kainic acid convulsive susceptibility

Kainic acid (KA) causes seizures and neuronal loss in the hippocampus. The present study investigated whether a recreational schedule of 3,4-methylenedioxymethamphetamine (MDMA) favours the development of a seizure state in a model of KA-induced epilepsy and potentiates the toxicity profile of KA (20 or 30mg/kg). Adolescent male C57BL/6 mice received saline or MDMA t.i.d. (s.c. every 3h), on 1day a week, for 4 consecutive weeks. Twenty-four hours after the last MDMA exposure, the animals were injected with saline or KA (20 or 30mg/kg). After this injection, we evaluated seizures, hippocampal neuronal cell death, microgliosis, astrogliosis, and calcium binding proteins. MDMA pretreatment, by itself, did not induce neuronal damage but increased seizure susceptibility in all KA treatments and potentiated the presence of Fluoro-Jade-positive cells in CA1. Furthermore, MDMA, like KA, significantly decreased parvalbumin levels in CA1 and dentate gyrus, where it potentiated the effects of KA. The amphetamine derivative also promoted a transient decrease in calbindin and calretinin levels, indicative of an abnormal neuronal discharge. In addition, treatment of cortical neurons with MDMA (10-50μM) for 6 or 48h significantly increased basal Ca(2+), reduced basal Na(+) levels and potentiated kainate response. These results indicate that MDMA potentiates KA-induced neurodegeneration and also increases KA seizure susceptibility. The mechanism proposed includes changes in Calcium Binding Proteins expression, probably due to the disruption of intracellular ionic homeostasis, or/and an indirect effect through glutamate release.

A Molecular Approach to Epilepsy Management: from Current Therapeutic Methods to Preconditioning Efforts

Epilepsy is the most common and chronic neurological disorder characterized by recurrent unprovoked seizures. The key aim in treating patients with epilepsy is the suppression of seizures. An understanding of focal changes that are involved in epileptogenesis may therefore provide novel approaches for optimal treatment of the seizure. Although the actual pathogenesis of epilepsy is still uncertain, recently growing lines of evidence declare that microglia and astrocyte activation, oxidative stress and reactive oxygen species (ROS) production, mitochondria dysfunction, and damage of blood-brain barrier (BBB) are involved in its pathogenesis. Impaired GABAergic function in the brain is probably the most accepted hypothesis regarding the pathogenesis of epilepsy. Clinical neuroimaging of patients and experimental modeling have demonstrated that seizures may induce neuronal apoptosis. Apoptosis signaling pathways are involved in the pathogenesis of several types of epilepsy such as temporal lobe epilepsy (TLE). The quality of life of patients is seriously affected by treatment-related problems and also by unpredictability of epileptic seizures. Moreover, the available antiepileptic drugs (AED) are not significantly effective to prevent epileptogenesis. Thus, novel therapies that are proficient to control seizure in people who are suffering from epilepsy are needed. The preconditioning method promises to serve as an alternative therapeutic approach because this strategy has demonstrated the capability to curtail epileptogenesis. For this reason, understanding of molecular mechanisms underlying brain tolerance induced by preconditioning is crucial to delineate new neuroprotective ways against seizure damage and epileptogenesis. In this review, we summarize the work to date on the pathogenesis of epilepsy and discuss recent therapeutic strategies in the treatment of epilepsy. We will highlight that novel therapy targeting such as preconditioning process holds great promise. In addition, we will also highlight the role of gene reprogramming and mitochondrial biogenesis in the preconditioning-mediated neuroprotective events.

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.

Cerebrospinal fluid protein biomarker panel for assessment of neurotoxicity induced by kainic acid in rats

Glutamate excitotoxicity plays a key role in the etiology of a variety of neurological, psychiatric, and neurodegenerative disorders. The goal of this study was to investigate spatiotemporal distribution in the brain and cerebrospinal fluid (CSF) concentrations of ubiquitin C-terminal hydrolase-1 (UCH-L1), glial fibrillary acidic protein (GFAP), αII-spectrin breakdown products (SBDP150, SBDP145, and SBDP120), and their relationship to neuropathology in an animal model of kainic acid (KA) excitotoxicity. Triple fluorescent labeling and Fluoro-Jade C staining revealed a reactive gliosis in brain and specific localization of degenerating neurons in hippocampus and entorhinal cortex of KA-treated rats. Immunohistochemistry showed upregulation of GFAP expression in hippocampus and cortex beginning 24h post KA injection and peaking at 48h. At these time points concurrent with extensive neurodegeneration all SBDPs were observed throughout the brain. At 24h post KA injection, a loss of structural integrity was observed in cellular distribution of UCH-L1 that correlated with an increase in immunopositive material in the extracellular matrix. CSF levels of UCH-L1, GFAP, and SBDPs were significantly increased in KA-treated animals compared with controls. The temporal increase in CSF biomarkers correlated with brain tissue distribution and neurodegeneration. This study provided evidence supporting the use of CSF levels of glial and neuronal protein biomarkers to assess neurotoxic damage in preclinical animal models that could prove potentially translational to the clinic. The molecular nature of these biomarkers can provide critical information on the underlying mechanisms of neurotoxicity that might facilitate the development of novel drugs and allow physicians to monitor drug safety.

Content and traffic of taurine in hippocampal reactive astrocytes

Taurine is one of the most abundant free amino acids in the mammalian central nervous system, where it is crucial to proper development. Moreover, taurine acts as a neuroprotectant in various diseases; in epilepsy, for example, it has the capacity to reduce or abolish seizures. In the present study, taurine levels has been determine in mice treated with Kainic Acid (KA) and results showed an increase of this amino acid in hippocampus but not in whole brain after 3 and 7 days of KA treatment. This increase occurs when gliosis was observed. Moreover, taurine transporter (TAUT) was found in astrocytes 3 and 7 days after KA treatment, together with an increase in cysteine sulfinic acid decarboxylase (csd) mRNA, that codifies for the rate-limiting enzyme of taurine synthesis, in the hippocampus at the same times after KA treatment. Glial cultures enriched in astrocytes were developed to demonstrate that these cells are responsible for changes in taurine levels after an injury to the brain. The cultures were treated with proinflammatory cytokines to reproduce gliosis. In this experimental model, an increase in the immunoreactivity of GFAP was observed, together with an increase in CSD and taurine levels. Moreover, an alteration in the taurine uptake-release kinetics was detected in glial cells treated with cytokine. All data obtained indicate that astrocytes could play a key role in taurine level changes induced by neuronal damage. More studies are, therefore, needed to clarify the role taurine has in relation to neuronal death and repair.

Deletion of Puma protects hippocampal neurons in a model of severe status epilepticus

Prolonged seizures (status epilepticus) can activate apoptosis-associated signaling pathways. The extent to which such pathways contribute to cell death might depend on the insult intensity, whereby the programmed or apoptotic cell death component is reduced when seizures are more severe or protracted. We recently showed that mice lacking the pro-apoptotic Bcl-2 homology domain 3-only protein Puma (Bbc3) were potently protected against damage caused by status epilepticus. In the present study we examined whether Puma deficiency was protective when the seizure episode was more severe. Intra-amygdala microinjection of 1 microg kainic acid (KA) into C57BL/6 mice triggered status epilepticus that lasted about twice as long as with 0.3 microg KA prior to lorazepam termination. Hippocampal damage was also significantly greater in the higher-dose group. Over 80% of degenerating neurons after seizures were positive for DNA fragmentation assessed by terminal deoxynucleotidyl dUTP nick end labeling (TUNEL). Microscopic analysis of neuronal nuclear morphology in TUNEL-positive cells revealed the proportion displaying large rounded clumps of condensed chromatin was approximately 50% lower in the high-dose versus low-dose KA group. Nevertheless, compared to heterozygous and wild-type mice subject to status epilepticus by high-dose KA, neuronal death was reduced by approximately 50% in the hippocampus of Puma-deficient mice. These data suggest aspects of the apoptotic component of seizure-induced neuronal death are insult duration- or severity-dependent. Moreover, they provide further genetic evidence that seizure-induced neuronal death is preventable by targeting so-called apoptosis-associated signaling pathways and Puma loss likely disrupts caspase-independent or non-apoptotic seizure-induced neuronal death.

In vivo glutamate decline associated with kainic acid-induced status epilepticus

Neurophysiological, biochemical, and anatomical evidence implicates glutamatergic mechanisms in epileptic seizures. Until recently, however, longitudinal characterization of in vivo glutamate dynamics was not possible. Here, we present data using in vivo magnetic resonance spectroscopy (MRS) optimized for the detection of glutamate to identify changes that evolve following kainic acid (KA)-induced status epilepticus. Wild-type male Wistar rats underwent whole-brain MR imaging and single-voxel MRS on a clinical 3 T scanner equipped with a high-strength insert gradient coil. Scanning took place before and then 3 days, 28-32 days, and 42-50 days after induction of status epilepticus. Analyses compared 5 seizure (Sz), 5 no-seizure (NoSz; received KA but did not exhibit seizures), and 6 control (Con) animals. This longitudinal study demonstrated reduced glutamate levels in vivo in the dorsal hippocampus 3 days and 1 month following status epilepticus in Sz animals compared with Con animals. Additionally, previous results were replicated: in the Sz group, computed T2 was higher in the ventral hippocampus and limbic cortex 3 days after seizure activity compared with baseline but resolved in both regions at the 1 month scan, suggesting a transient edema. Three days following seizure activity, N-acetylaspartate (NAA) declined and lactate increased in the dorsal hippocampus of the Sz group compared with the Con and NoSz group; both metabolites approached baseline levels by the third scan. Taken together, these results support the conclusion that seizure activity following KA infusion causes loss of glutamatergic neurons.

Large differences in blood measures, tissue weights, and focal areas of damage 1 year after postseizure treatment with acepromazine or ketamine

Approximately 1 year after rats were seized as young adults with lithium (3 mEq/kg) and pilocarpine (30 mg/kg) and given acepromazine or ketamine, 18 blood measures, wet tissue weights, and detailed damage scores for 107 brain structures were completed. Compared with normal and ketamine-treated rats, acepromazine-treated seized rats (total n=54) had lighter pancreata and spleens and elevated aspartate aminotransferase and alanine aminotransferase blood levels. Even though average damage did not differ, the mosaic of brain damage completely discriminated the two seized groups. Differential effects of postseizure treatment on functions of the thyroid, pancreas, and spleen were indicated. Ketamine-treated seized rats were healthier than acepromazine-treated seized rats or normal rats. This experiment demonstrates the importance of whole-organism assessment and that the single administration of a specific drug after onset of status epilepticus can produce marked differences in the evolution of brain damage and its influence on specific organs for the rest of the animal's life.

Prevention of epilepsy by taurine treatments in mice experimental model

An experimental model based on kainic acid (KA) injections replicates many phenomenological features of human temporal lobe epilepsy, the most common type of epilepsy in adults. Taurine, 2-aminoethanesulfonic acid, present in high concentrations in many invertebrate and vertebrate systems, is believed to serve several important biological functions. In addition, it is believed to have a neuroprotective role against several diseases. In the present study, an experimental mouse model based on taurine pretreatment prior to KA administration has been improved to study whether taurine has a neuroprotective effect against KA-induced behavior and cell damage. Under different treatments tested, taurine's most neuroprotective effects were observed with intraperitoneal taurine injection (150 mg/kg dosage) 12 hr before KA administration. Thus, a reduction in or total absence of seizures, together with a reduction in or even disappearance of cellular and molecular KA-derived effects, was detected in mice pretreated with taurine compared with those treated only with KA. Moreover, the use of tritiated taurine revealed taurine entry into the brain, suggesting possible changes in intracellular:extracellular taurine ratios and the triggering of pathways related to neuroprotective effects.

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.

Kainic acid dose affects delayed cell death mechanism after status epilepticus

Kainic acid (KA)-induced status epilepticus (SE) produces hippocampal neuronal death, which varies from necrosis to apoptosis or programmed cell death (PCD). We examined whether the type of neuronal death was dependent on KA dose. Adult rats were induced SE by intraperitoneal injection of KA at 9 mg/kg (K9) or 12 mg/kg (K12). Hippocampal neuronal death was assessed by TUNEL staining, electron microscopy, and Western blotting of caspase-3 on days 1, 3 and 7 after SE induction. K12 rats showed higher a mortality rate and shorter latency to the onset of SE when compared with K9 rats. In both groups, acidophilic and pyknotic neurons were evident in CA1 at 24h after SE and neuronal loss developed from day 3. The degenerated neurons became TUNEL-positive on days 3 and 7 in K9 rats but not in K12 rats. Caspase-3 activation was detected on days 3 and 7 in K9 rats but was undetectable in K12 rats. Ultrastructural study revealed shrunken neurons exhibiting pyknotic nuclei containing small and dispersed chromatin clumps 24h after SE in CA1. No cells exhibited apoptosis. On days 3 and 7, the degenerated neurons were necrotic with high electron density and small chromatin clumps. There were no ultrastructural differences between the K9 and K12 groups. These results revealed that differences in KA dose affected the delayed cell death (3 and 7 days after SE); however, no effect was seen on the early cell death (24h after SE). Moderate-dose KA induced necrosis, while low-dose KA induced PCD.

Epilepsy and apoptosis pathways

Epilepsy is a common, chronic neurologic disorder characterized by recurrent unprovoked seizures. Experimental modeling and clinical neuroimaging of patients has shown that certain seizures are capable of causing neuronal death. Such brain injury may contribute to epileptogenesis, impairments in cognitive function or the epilepsy phenotype. Research into cell death after seizures has identified the induction of the molecular machinery of apoptosis. Here, the authors review the clinical and experimental evidence for apoptotic cell death pathway function in the wake of seizure activity. We summarize work showing intrinsic (mitochondrial) and extrinsic (death receptor) apoptotic pathway function after seizures, activation of the caspase and Bcl-2 families of cell death modulators and the acute and chronic neuropathologic impact of intervening in these molecular cascades. Finally, we describe evolving data on nonlethal roles for these proteins in neuronal restructuring and cell excitability that have implications for shaping the epilepsy phenotype. This review highlights the work to date on apoptosis pathway signaling during seizure-induced neuronal death and epileptogenesis, and speculates on how emerging roles in brain remodeling and excitability have enriched the number of therapeutic strategies for protection against seizure-damage and epileptogenesis.

Soman-induced convulsions: the neuropathology revisited

The organophosphorus compound soman, an irreversible inhibitor of cholinesterases, produces seizure activity and related brain damage. Studies using various biochemical markers of programmed cell death (PCD) suggested that soman-induced cell damage in the brain was apoptotic rather than necrotic. However, it has recently become clear that not all PCD is apoptotic, and the unequivocal demonstration of apoptosis requires ultrastructural examination. Therefore, the present study was undertaken to reinvestigate the damage produced in the brains of mice sacrificed at various times within the first 24 h or at 7 days after a convulsive dose of soman. Classical histology and ultrastructural examination were performed. The immunohistochemical expression of proteins (p53, Bax) involved in PCD, DNA fragmentation (TUNEL method at light and electron microscopy levels) and the glial reaction were also explored. Our study confirms that the severity of lesions depended on the duration of convulsions and shows that cerebral changes were still occurring as late as 7 days after the onset of long-lasting convulsions. Our observations also establish that there was a large variety of ultrastructurally distinct types of cell damage, including hybrid forms between apoptosis and necrosis, but that pure apoptosis was very rare. A prominent expression of p53 and Bax proteins was detected indicating that PCD mechanisms were certainly involved in the morphologically diverse forms of cell death. Since purely apoptotic cells were very rare, these protein expressions were presumably involved either in nonapoptotic cell death mechanisms or in apoptotic mechanisms occurring in parallel with nonapoptotic ones. Moreover, evidence for DNA fragmentation by the TUNEL method was found in apoptotic but also in numerous other morphotypes of cell damage. Therefore, TUNEL-positivity and the expression of PCD-related proteins, in the absence of ultrastructural confirmation, were here shown not to provide proof of apoptosis. In soman poisoning as well as in other cerebral pathologies, premature conclusions on this question can potentially be misleading and might even lead to detrimental therapies.

Mutational effects at the tetramerization site of nonerythroid alpha spectrin

Spectrin, a prominent cytoskeletal protein, exerts its fundamental role in cellular function by forming a sub-membrane filamentous network. An essential aspect of spectrin network formation is the tetramerization of spectrin alphabeta heterodimers. We used laboratory methods, the yeast two-hybrid system and random mutagenesis, to investigate, for the first time, effects of amino acid mutations on tetramerization of nonerythroid (brain) spectrin (fodrin). Based on high sequence homology with erythroid spectrin, we assume the putative tetramerization region of nonerythroid alpha-spectrin at the N-terminal region. We introduced mutations in the region consisting of residues 1-45 and studied mutational effects on spectrin alphabeta association to form tetramers. We detected single, double, and triple mutations involving 24 residues in this region. These amino acid mutations of nonerythroid alpha-spectrin exhibit full, partial, or no effect on the association with nonerythroid beta-spectrin. Single amino acid mutations in the region of residues 1-9 (D2Y, G5V, V6D, and V8M) did not affect the association. However, seven single mutations (I15F, I15N, R18G, V22D, R25P, Y26N, and R28P) affected the alphabeta association. These mutations were clustered in the region predicted by sequence alignment to be crucial in nonerythroid alpha-spectrin for tetramerization, a region that spanned residues 12-36, corresponding to the partial domain Helix C' (residues 21-45) in erythroid alpha-spectrin. In addition, two other mutations, one upstream and one downstream of this region at positions 10 (E10D) and 37 (R37P), also affected the alphabeta association. Our results implied nonerythroid alpha-spectrin partial domain helix may be longer than Helix C' (residues 21-45 and a total of 25 residues) in erythroid alpha-spectrin and spanned at least residues 10-37. It is interesting to note that seven out of these nine single mutations (I15F, I15N, R18G, V22D, R25P, Y26N, R37P) were at the a, d, e or g heptad positions based on sequence alignment with erythroid alpha-spectrin. Four of the mutated residues (I15, R18, V22, R25) are conserved in both erythroid and nonerythroid spectrin. These positions were previously identified as hot spots in erythroid alpha-spectrin that lead to severe hematological symptoms. This study clearly demonstrated that single mutation in a region predicted to be critical functionally in nonerythroid alpha-spectrin indeed leads to functional abnormalities and may lead to neurological disorders.

Seizures induced in immature rats by homocysteic acid and the associated brain damage are prevented by group II metabotropic glutamate receptor agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate

The present study has examined the anticonvulsant and neuroprotective effect of group II metabotropic glutamate receptor (mGluR) agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) in the model of seizures induced in immature 12-day-old rats by bilateral intracerebroventricular infusion of dl-homocysteic acid (DL-HCA, 600 nmol/side). For biochemical analyses, rat pups were sacrificed during generalized clonic-tonic seizures, approximately 45-50 min after infusion. Comparable time intervals were used for sacrificing the pups which had received 2R,4R-APDC. Low doses of 2R,4R-APDC (0.05 nmol/side) provided a pronounced anticonvulsant effect which was abolished by pretreatment with a selective group II mGluR antagonist LY341495. Generalized clonic-tonic seizures were completely suppressed and cortical energy metabolite changes which normally accompany these seizures were either normalized (decrease of glucose and glycogen) or markedly reduced (an accumulation of lactate). EEG recordings support the marked anticonvulsant effect of 2R,4R-APDC, nevertheless, this was only partial. In spite of the absence of obvious motor phenomena, isolated spikes or even short periods of partial ictal activity could be observed. Isolated spikes could also be seen in some animals after application of 2R,4R-APDC alone, reflecting most likely subclinical proconvulsant activity of this agonist. The neuroprotective effect of 2R,4R-APDC was evaluated after 24 h and 6 days of survival following DL-HCA-induced seizures. Massive neuronal degeneration, as revealed by Fluoro-Jade B staining, was observed in a number of brain regions following infusion of DL-HCA alone (seizure group), whereas 2R,4R-APDC pretreatment provided substantial neuroprotection. The present findings support the possibility that group II mGluRs are a promising target for a novel approach to treating epilepsy.