Seizure-induced changes in mitochondrial redox status

Plasma cysteine/cystine redox couple disruption in animal models of temporal lobe epilepsy

Currently the field of epilepsy lacks peripheral blood-based biomarkers that could predict the onset or progression of chronic seizures following an epileptogenic injury. Thiol/disulfide ratios have been shown to provide a sensitive means of assessing the systemic redox potential in tissue and plasma. In this study, we utilized a rapid, simple and reliable method for simultaneous determination of several thiol-containing amino acids in plasma using HPLC with electrochemical detection in kainic acid (KA) and pilocarpine rat models of epilepsy. In contrast to GSH and GSSG levels, the levels of cysteine (Cys) were decreased by 42% and 62% and cystine (Cyss) were increased by 46% and 23% in the plasma of KA- and pilocarpine-injected rats, respectively after 48 h. In chronically epileptic rats, plasma cysteine was decreased by 40.4% and 37.7%, and plasma GSSG increased by 33.8% and 35.0% following KA and pilocarpine, respectively. Treatment of rats with a catalytic antioxidant, 60 min after KA or pilocarpine significant attenuated the decrease of plasma Cys/Cyss ratios at the 48 h time point in both models. These observations suggest that the decreased cysteine and ratio of Cys/Cyss in plasma could potentially serve as redox biomarkers in temporal lobe epilepsy.

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HPLC method for determination thiol-containing amino acids in rat plasma.

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Decreased plasma cysteine/cystine in acute and chronic stages of chemoconvulsant-induced epilepsy.

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Depletion of plasma cysteine/cystine can be ameliorated by a catalytic antioxidant.

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Measurement of plasma cysteine/cystine could serve as redox biomarkers in epilepsy.

Expression pattern of NMDA receptors reveals antiepileptic potential of apigenin 8-C-glucoside and chlorogenic acid in pilocarpine induced epileptic mice

The present study was aimed to evaluate the effect of apigenin 8-C-glucoside (Vitexin) and chlorogenic acid on epileptic mice induced by pilocarpine and explored its possible mechanisms. Intraperitonial administration of pilocarpine (85mg/kg) induced seizure in mice was assessed by behavior observations, which is significantly (p>0.05) reduced by apigenin 8-C-glucoside (AP8CG) (10mg/kg) and chlorogenic acid (CA) (5mg/kg), similar to diazepam. Seizure was accompanied by an imbalance in the levels of Gamma-aminobutyric acid (GABA) and glutamate in the pilocarpine administered group. Moreover, convulsion along with reduced acetylcholinesterase, increased monoamine oxidase and oxidative stress was observed in epileptic mice brain. AP8CG and CA significantly restored back to normal levels even at lower doses. Further, increased lipid peroxidation and nitrite content was also significantly attenuated by AP8CG and CA. However, CA was found to be more effective when compared to AP8CG. In addition, the mRNA expression of N-methyl-d-aspartate receptor (NMDAR), mGluR1 and mGlu5 was significantly (P≤0.05) inhibited by AP8CG and CA in a lower dose. The mRNA expression of GRIK1 did not differ significantly in any of the group and showed a similar pattern of expression. Our result shows that AP8CG and CA selectively inhibit NMDAR, mGluR1 and mGlu5 expression. Modification in the provoked NMDAR calcium response coupled with neuronal death. Hence, these findings underline that the polyphenolics, AP8CG and CA have exerted antiepileptic and neuroprotective activity by suppressing glutamate receptors.

Oxidative Status in Epileptic Children Using Carbamazepine

Background:

There is an increasing attention towards the relationship between oxidative stress and epilepsy. The effect of antiepileptic drugs on oxidant status is of major interest. Antiepileptic drugs can increase levels of free radicals, which consequently might lead to seizures. Carbamazepine (CBZ) is an antiepileptic drug commonly used in childhood and adolescence.

Objectives:

Therefore we aimed to investigate the effects of CBZ on total antioxidant status, total oxidant stress, and oxidative stress index.

Patients and Methods:

The study included 40 epileptic patients and 31 healthy children between 4 and 12 years of age. Serum CBZ level, total antioxidant capacity and total oxidant status were measured. Oxidative stress index was also calculated both in controls and patients.

Results:

In the epileptic group, decreased levels of total antioxidant capacity, increased total oxidative stress and oxidative stress index levels were found. Positive correlation between plasma CBZ levels and total oxidant status was observed.

Conclusions:

Antioxidant action could not be playing any role in antiepileptic effect of CBZ. Furthermore, increased oxidative stress induced by CBZ could be the cause of CBZ-induced seizures. Therefore combining CBZ with antioxidants could be beneficial.

Brain redox imaging in the pentylenetetrazole (PTZ)-induced kindling model of epilepsy by using in vivo electron paramagnetic resonance and a nitroxide imaging probe

Much evidence supports the idea that oxidative stress is involved in the pathogenesis of epilepsy, and therapeutic interventions with antioxidants are expected as adjunct antiepileptic therapy. The aims of this study were to non-invasively obtain spatially resolved redox data from control and pentylenetetrazole (PTZ)-induced kindled mouse brains by electron paramagnetic resonance (EPR) imaging and to visualize the brain regions that are sensitive to oxidative damage. After infusion of the redox-sensitive imaging probe 3-methoxycarbonyl-2,2,5,5-tetramethyl-piperidine-1-oxyl (MCP), a series of EPR images of PTZ-induced mouse heads were measured. Based on the pharmacokinetics of the reduction reaction of MCP in the mouse heads, the pixel-based rate constant of its reduction reaction was calculated as an index of redox status in vivo and mapped as a redox map. The obtained redox map showed heterogeneity in the redox status in PTZ-induced mouse brains compared with control. The co-registered image of the redox map and magnetic resonance imaging (MRI) for both control and PTZ-induced mice showed a clear change in the redox status around the hippocampus after PTZ. To examine the role of antioxidants on the brain redox status, the levels of antioxidants were measured in brain tissues of control and PTZ-induced mice. Significantly lower concentrations of glutathione in the hippocampus of PTZ-kindled mice were detected compared with control. From the results of both EPR imaging and the biochemical assay, the hippocampus was found to be susceptible to oxidative damage in the PTZ-induced animal model of epilepsy.

Reactive oxygen species mediate cognitive deficits in experimental temporal lobe epilepsy

Cognitive dysfunction is an important comorbidity of temporal lobe epilepsy (TLE). However, no targeted therapies are available and the mechanisms underlying cognitive impairment, specifically deficits in learning and memory associated with TLE remain unknown. Oxidative stress is known to occur in the pathogenesis of TLE but its functional role remains to be determined. Here, we demonstrate that oxidative stress and resultant processes contribute to cognitive decline associated with epileptogenesis. Using a synthetic catalytic antioxidant, we show that pharmacological removal of reactive oxygen species (ROS) prevents 1) oxidative stress, 2) deficits in mitochondrial oxygen consumption rates, 3) hippocampal neuronal loss and 4) cognitive dysfunction without altering the intensity of the initial status epilepticus (SE) or epilepsy development in a rat model of SE-induced TLE. Moreover, the effects of the catalytic antioxidant on cognition persisted beyond the treatment period suggestive of disease-modification. The data implicate oxidative stress as a novel mechanism by which cognitive dysfunction can arise during epileptogenesis and suggest a potential disease-modifying therapeutic approach to target it.

Metallothionein expression in the rat brain following KA and PTZ treatment

Epilepsy is a neurological disorder that has been associated with oxidative stress therefore epilepsy models have been develop such as kainic acid and pentylenetetrazol are usually used to understanding of the molecular mechanisms of this disease. We examined the metallothionein expression in rat brains of treated with kainic acid and pentylenetetrazol. Increase in metallothionein and nitrotirosyne immunoreactivity of both seizures epilepsy models was observed. Moreover, we show a significant increase on levels of MT expression. These results suggest that the increase of metallothionein expression is related with kainic acid and pentylenetetrazol treatments as response to damage mediated by oxidative stress.

Oxidative stress in murine Theiler's virus-induced temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of acquired epilepsy that can be caused by several inciting events including viral infections. However, one-third of TLE patients are pharmacoresistant to current antiepileptic drugs and therefore, there is an urgent need to develop antiepileptogenic therapies that prevent the development of the disease. Oxidative stress and redox alterations have recently been recognized as important etiological factors contributing to seizure-induced neuronal damage. The goal of this study was to determine if oxidative stress occurs in the TMEV (Theiler's murine encephalomyelitis virus) model of temporal lobe epilepsy (TLE). C57Bl/6 mice were injected with TMEV or with PBS intracortically and observed for acute seizures. At various time points after TMEV injection, hippocampi were analyzed for levels of reduced glutathione (GSH), oxidized glutathione (GSSG) and 3-nitrotyrosine (3 NT). Mice infected with TMEV displayed behavioral seizures between days 3 and 7 days post-infection (dpi). The intensity of seizures increased over time with most of the seizures being a stage 4 or 5 on the Racine scale at 6 days p.i. Mice exhibiting at least one seizure during the observation period were utilized for the biochemical analyses. The levels of GSH were significantly depleted in TMEV infected mice at 3, 4 and 14 days p.i. with a concomitant increase in GSSH levels as well as an impairment of the redox status. Additionally, there was a substantial increase in 3 NT levels in TMEV infected mice at these time points. These redox changes correlated with the occurrence of acute seizures in this model. Interestingly, we did not see changes in any of the indices in the cerebellum of TMEV-infected mice at 3 dpi indicating that these alterations are localized to the hippocampus and perhaps other limbic regions. This is the first study to demonstrate the occurrence of oxidative stress in the TMEV model of infection-induced TLE. The redox alterations were observed at time points coinciding with the appearance of acute behavioral seizures suggesting that these changes might be a consequence of seizure activity. Our results support the hypothesis that redox changes correlate with seizure activity in acquired epilepsies, regardless of the inciting insults, and suggest oxidative stress as a potential therapeutic target for their treatment.

Decursin attenuates kainic acid-induced seizures in mice

Epilepsy is a neurological disorder with recurrent unprovoked seizures as the main symptom. Of the coumarin derivatives in Angelica gigas, decursin, a major coumarin component, was reported to exhibit significant protective activity against glutamate-induced neurotoxicity when added to primary cultures of rat cortical cells. This study served to investigate the effects of decursin on a kainic acid (KA)-induced status epilepticus model. Thirty minutes after intraperitoneal injections of decursin (20 mg/kg) in male 7-week-old C57BL/6 mice, the animals were treated with KA (30 mg/kg, intraperitoneally) and then examined for behavioral seizure score, electroencephalogram, seizure-related expressed protein levels, neuronal cell loss, neurodegeneration, and astrogliosis. KA injections significantly enhanced neurodegenerative conditions but treatment with decursin 30 min before KA injection reduced the detrimental effects of KA in mice. The decursin-treated KA-injected group showed significantly decreased behavioral seizure activity and remarkably attenuated intense and high-frequency seizure discharges in the parietal cortex for 2 h compared with the group treated only with KA. Furthermore, in-vivo results indicated that decursin strongly inhibits selective neuronal death, astrogliosis, and oxidative stress induced by KA administration. Therefore decursin is able to attenuate KA-induced seizures and could have potential as an antiepileptic drug.

Microglial ROS production in an electrical rat post-status epilepticus model of epileptogenesis

Reactive oxygen species and inflammatory signaling have been identified as pivotal pathophysiological factors contributing to epileptogenesis. Considering the development of combined anti-inflammatory and antioxidant treatment strategies with antiepileptogenic potential, a characterization of the time course of microglial reactive oxygen species generation during epileptogenesis is of major interest. Thus, we isolated microglia cells and analyzed the generation of reactive oxygen species by flow cytometric analysis in an electrical rat post-status epilepticus model. Two days post status epilepticus, a large-sized cell cluster exhibited a pronounced response with excessive production of reactive oxygen species upon stimulation with phorbol-myristate-acetate. Neither in the latency phase nor in the chronic phase with spontaneous seizures a comparable cell population with induction of reactive oxygen species was identified. We were able to demonstrate in the electrical rat post-status-epilepticus model, that microglial ROS generation reaches a peak after the initial insult, is only marginally increased in the latency phase, and returns to control levels during the chronic epileptic phase. The data suggest that a combination of anti-inflammatory and radical scavenging approaches might only be beneficial during a short time window after an epileptogenic brain insult.

Seizure-induced oxidative stress in temporal lobe epilepsy

An insult to the brain (such as the first seizure) causes excitotoxicity, neuroinflammation, and production of reactive oxygen/nitrogen species (ROS/RNS). ROS and RNS produced during status epilepticus (SE) overwhelm the mitochondrial natural antioxidant defense mechanism. This leads to mitochondrial dysfunction and damage to the mitochondrial DNA. This in turn affects synthesis of various enzyme complexes that are involved in electron transport chain. Resultant effects that occur during epileptogenesis include lipid peroxidation, reactive gliosis, hippocampal neurodegeneration, reorganization of neural networks, and hypersynchronicity. These factors predispose the brain to spontaneous recurrent seizures (SRS), which ultimately establish into temporal lobe epilepsy (TLE). This review discusses some of these issues. Though antiepileptic drugs (AEDs) are beneficial to control/suppress seizures, their long term usage has been shown to increase ROS/RNS in animal models and human patients. In established TLE, ROS/RNS are shown to be harmful as they can increase the susceptibility to SRS. Further, in this paper, we review briefly the data from animal models and human TLE patients on the adverse effects of antiepileptic medications and the plausible ameliorating effects of antioxidants as an adjunct therapy.

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.

Relevance of the glutathione system in temporal lobe epilepsy: evidence in human and experimental models

Oxidative stress, which is a state of imbalance in the production of reactive oxygen species and nitrogen, is induced by a wide variety of factors. This biochemical state is associated with diseases that are systemic as well as diseases that affect the central nervous system. Epilepsy is a chronic neurological disorder, and temporal lobe epilepsy represents an estimated 40% of all epilepsy cases. Currently, evidence from human and experimental models supports the involvement of oxidative stress during seizures and in the epileptogenesis process. Hence, the aim of this review was to provide information that facilitates the processing of this evidence and investigate the therapeutic impact of the biochemical status for this specific pathology.

Widespread pH abnormalities in patients with malformations of cortical development and epilepsy: a phosphorus-31 brain MR spectroscopy study

INTRODUCTION

Neuroimaging studies demonstrate that not only the lesions of malformations of cortical development (MCD) but also the normal-appearing parenchyma (NAP) present metabolic impairments, as revealed with (1)H-MRS. We have previously detected biochemical disturbances in MCD lesions with phosphorus-31 magnetic resonance spectroscopy (31P-MRS). Our hypothesis is that pH abnormalities extend beyond the visible lesions.

METHODS

Three-dimensional 31P-MRS at 3.0 T was performed in 37 patients with epilepsy and MCD, and in 31 matched-control subjects. The patients were assigned into three main MCD subgroups: cortical dysplasia (n=10); heterotopia (n=14); schizencephaly/polymicrogyria (n=13). Voxels (12.5 cm3) were selected in five homologous regions containing NAP: right putamen; left putamen; frontoparietal parasagittal cortex; right centrum semiovale; and left centrum semiovale. Robust methods of quantification were applied, and the intracellular pH was calculated with the chemical shifts of inorganic phosphate (Pi) relative to phosphocreatine (PCr).

RESULTS

In comparison to controls and considering a Bonferroni adjusted p-value <0.01, MCD patients presented significant reduction in intracellular pH in the frontoparietal parasagittal cortex (6.985±0.022), right centrum semiovale (7.004±0.029), and left centrum semiovale (6.995±0.030), compared to controls (mean values±standard deviations of 7.087±0.048, 7.096±0.042, 7.088±0.045, respectively). Dunnet and Dunn tests demonstrated that the differences in pH values remained statistically significant in all MCD subgroups. No significant differences were found for the putamina.

CONCLUSION

The present study demonstrates widespread acidosis in the NAP, and reinforces the idea that MCD visible lesions are only the tip of the iceberg.

Seizure activity results in calcium- and mitochondria-independent ROS production via NADPH and xanthine oxidase activation

Seizure activity has been proposed to result in the generation of reactive oxygen species (ROS), which then contribute to seizure-induced neuronal damage and eventually cell death. Although the mechanisms of seizure-induced ROS generation are unclear, mitochondria and cellular calcium overload have been proposed to have a crucial role. We aim to determine the sources of seizure-induced ROS and their contribution to seizure-induced cell death. Using live cell imaging techniques in glioneuronal cultures, we show that prolonged seizure-like activity increases ROS production in an NMDA receptor-dependent manner. Unexpectedly, however, mitochondria did not contribute to ROS production during seizure-like activity. ROS were generated primarily by NADPH oxidase and later by xanthine oxidase (XO) activity in a calcium-independent manner. This calcium-independent neuronal ROS production was accompanied by an increase in intracellular [Na(+)] through NMDA receptor activation. Inhibition of NADPH or XO markedly reduced seizure-like activity-induced neuronal apoptosis. These findings demonstrate a critical role for ROS in seizure-induced neuronal cell death and identify novel therapeutic targets.

Oxidative stress in immature brain following experimentally-induced seizures

The existing data indicate that status epilepticus (SE) induced in immature animals is associated with oxidative stress and mitochondrial dysfunction. This has been demonstrated using two models of SE, induced by substances with a different mechanism of action (DL-homocysteic acid and 4-aminopyridine) which suggests that the findings are not model-dependent but they reflect more general phenomenon. Oxidative stress occurring in immature brain during and following seizures is apparently due to both the increased free radicals production and the limited antioxidant defense. Pronounced inhibition of mitochondrial complex I in immature brain was demonstrated not only during the acute phase of SE, but it persisted during long periods of survival, corresponding to the development of spontaneous seizures (epileptogenesis). The findings suggest that oxidative modification is most likely responsible for the sustained deficiency of complex I activity. It can be assumed that the substances with antioxidant properties combined with conventional therapies might provide a beneficial effect in treatment of epilepsy.

3-Methyl-1-phenyl-2-pyrazolin-5-one or N-acetylcysteine prevents hippocampal mossy fiber sprouting and rectifies subsequent convulsive susceptibility in a rat model of kainic acid-induced seizure ceased by pentobarbital

There is accumulating evidence that reactive oxygen species are involved in the development of seizures under pathological conditions, and antioxidant treatments are a novel therapeutic approach for epilepsy. The kainic acid (KA) model of induced seizures has been widely used to study temporal lobe epilepsy. However, research on the use of free radical scavengers following KA-induced status epilepticus (SE) is limited. We examined whether antioxidants already used in humans could reduce hippocampal neuronal cell loss, mossy fiber sprouting and the acquisition of hyperexcitability when administered as a single dose after SE. The antioxidant 3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone) (30mg/kg) or N-acetylcysteine (NAC) (30mg/kg) was administered after KA-induced SE ceased by pentobarbital. We evaluated neuronal cell viability 1 week after SE, determined the threshold for seizures induced by inhalation of flurothyl ether 12 weeks after SE, and examined the extent of mossy fiber sprouting 12 weeks after SE. We found that edaravone or NAC prevented neuronal cell loss and mossy fiber sprouting, and increased the threshold for seizures induced by flurothyl ether, even when administered after KA-induced SE. These results demonstrate that a single dose of edaravone or NAC can protect against neuronal cell loss and epileptogenesis when administered after SE ceased by pentobarbital.

Brain mitochondria from DJ-1 knockout mice show increased respiration-dependent hydrogen peroxide consumption

Mutations in the DJ-1 gene have been shown to cause a rare autosomal-recessive genetic form of Parkinson's disease (PD). The function of DJ-1 and its role in PD development has been linked to multiple pathways, however its exact role in the development of PD has remained elusive. It is thought that DJ-1 may play a role in regulating reactive oxygen species (ROS) formation and overall oxidative stress in cells through directly scavenging ROS itself, or through the regulation of ROS scavenging systems such as glutathione (GSH) or thioredoxin (Trx) or ROS producing complexes such as complex I of the electron transport chain. Previous work in this laboratory has demonstrated that isolated brain mitochondria consume H2O2 predominantly by the Trx/Thioredoxin Reductase (TrxR)/Peroxiredoxin (Prx) system in a respiration dependent manner (Drechsel et al., Journal of Biological Chemistry, 2010). Therefore we wanted to determine if mitochondrial H2O2 consumption was altered in brains from DJ-1 deficient mice (DJ-1(-/-)). Surprisingly, DJ-1(-/-) mice showed an increase in mitochondrial respiration-dependent H2O2 consumption compared to controls. To determine the basis of the increased H2O2 consumption in DJ1(-/-) mice, the activities of Trx, Thioredoxin Reductase (TrxR), GSH, glutathione disulfide (GSSG) and glutathione reductase (GR) were measured. Compared to control mice, brains from DJ-1(-/-) mice showed an increase in (1) mitochondrial Trx activity, (2) GSH and GSSG levels and (3) mitochondrial glutaredoxin (GRX) activity. Brains from DJ-1(-/-) mice showed a decrease in mitochondrial GR activity compared to controls. The increase in the enzymatic activities of mitochondrial Trx and total GSH levels may account for the increased H2O2 consumption observed in the brain mitochondria in DJ-1(-/-) mice perhaps as an adaptive response to chronic DJ-1 deficiency.

Nicotinamide nucleotide transhydrogenase (Nnt) links the substrate requirement in brain mitochondria for hydrogen peroxide removal to the thioredoxin/peroxiredoxin (Trx/Prx) system

Mitochondrial reactive oxygen species are implicated in the etiology of multiple neurodegenerative diseases, including Parkinson disease. Mitochondria are known to be net producers of ROS, but recently we have shown that brain mitochondria can consume mitochondrial hydrogen peroxide (H2O2) in a respiration-dependent manner predominantly by the thioredoxin/peroxiredoxin system. Here, we sought to determine the mechanism linking mitochondrial respiration with H2O2 catabolism in brain mitochondria and dopaminergic cells. We hypothesized that nicotinamide nucleotide transhydrogenase (Nnt), which utilizes the proton gradient to generate NADPH from NADH and NADP(+), provides the link between mitochondrial respiration and H2O2 detoxification through the thioredoxin/peroxiredoxin system. Pharmacological inhibition of Nnt in isolated brain mitochondria significantly decreased their ability to consume H2O2 in the presence, but not absence, of respiration substrates. Nnt inhibition in liver mitochondria, which do not require substrates to detoxify H2O2, had no effect. Pharmacological inhibition or lentiviral knockdown of Nnt in N27 dopaminergic cells (a) decreased H2O2 catabolism, (b) decreased NADPH and increased NADP(+) levels, and (c) decreased basal, spare, and maximal mitochondrial oxygen consumption rates. Nnt-deficient cells possessed higher levels of oxidized mitochondrial Prx, which rendered them more susceptible to steady-state increases in H2O2 and cell death following exposure to subtoxic levels of paraquat. These data implicate Nnt as the critical link between the metabolic and H2O2 antioxidant function in brain mitochondria and suggests Nnt as a potential therapeutic target to improve the redox balance in conditions of oxidative stress associated with neurodegenerative diseases.

Mitochondrial DNA profiling via genomic analysis in mesial temporal lobe epilepsy patients with hippocampal sclerosis

INTRODUCTION

Mitochondria have an essential role in neuronal excitability and neuronal survival. In addition to energy production, mitochondria also play a crucial role in the maintenance of intracellular calcium homeostasis, generation of reactive oxygen species and mechanisms of cell death. There is a relative paucity of data about the role of mitochondria in epilepsy. Mitochondrial genome analysis is rarely carried out in the investigation of some diseases. In mesial temporal lobe epilepsies (MTLE) cases, genome analysis has never been used previously. The aim of this study is to show mitochondrial dysfunctions using genome analysis in patients with MTLE-hippocampal sclerosis (HS).

METHODS

44 patients with MTLE-HS and 86 matched healthy unrelated controls were included in this study. The patients were divided into four groups according to their clinical presentation as the following: Group 1 consists of patients with intractable epilepsy who refused operation; Group 2 of operated seizure free patients; Group 3 of operated patients with seizures; and Group 4 unoperated seizure free patients with or without antiepileptic drugs. Blood samples were used to isolate DNA. Parallel tagged sequencing was employed to allow pyrosequencing of 130 samples. Complete mtDNA is amplified in two overlapping fragments (11 and 9 kb). The PCR amplicons were pooled in equimolar ratios. Titanium kits were used to produce shotgun libraries according to the manufacturer's protocol.

RESULTS

The average coverage in total was 130 ± 30 and an average of 2365127 bases and 337 bp fragment length was received from all samples. The mean mtDNA heteroplasmy in patients was 26.35 ± 12.3 and in controls 25.03 ± 9.34. Three mutations had prominently high significance in patient samples. The most significantly associated variation was located in the MT-ATP-8 gene (8502 A>T, Asn46Ile) whereas the other two were in the MT-ND4 (11994 C>T, Thr412Ile) and MT-ND5 (13231 A>C, Lys299Gln) genes.

CONCLUSIONS

We have observed that three mutations were significantly related to the presence of epilepsy. These mutations were found at the 8502, 11994, and 13,231 bp of mtDNA, which resulted in amino acid changes at the MT-ATP-8, MT-ND4 and MT-ND5 genes. Finding mutations can lead us to knowing more about the pathophysiology of the MTLE disease.

Berberine exerts an anticonvulsant effect and ameliorates memory impairment and oxidative stress in a pilocarpine-induced epilepsy model in the rat

Though new antiepileptic drugs are emerging, approximately a third of epileptic patients still suffer from recurrent convulsions and cognitive dysfunction. Therefore, we tested whether berberine (Ber), a vegetable drug, has an anticonvulsant property and attenuates memory impairment in a pilocarpine (Pilo)-induced epilepsy model in rats. The rats were injected with 400 mg/kg Pilo to induce convulsions, and Ber 25, 50, and 100 mg/kg were administrated by the intragastric route once daily 7 days before Pilo injection until the experiment was over. Convulsions were observed after Pilo injection. For the rats that developed status epilepticus (SE), malondialdehyde, glutathione levels, superoxide dismutase, and catalase activity in the hippocampus were measured 24 hours after SE. The rats received the Morris water-maze test 2 weeks after SE, and then were killed for fluoro-jade B staining to detect the degenerating neurons. We found Ber delayed latency to the first seizure and the time to develop SE in a dose-dependent manner. Malondialdehyde levels were decreased, while glutathione and catalase activity were strengthened in Ber-injected SE rats. In the Morris water-maze test, Ber decreased escape latency compared to saline-treated SE rats. Additionally, Ber reduced the number of fluoro-jade B-positive cells in the hippocampal CA1 region. Our data suggest that Ber exerts anticonvulsant and neuroprotective effects on Pilo-induced epilepsy in rats. Simultaneously, Ber attenuates memory impairment. The beneficial effect may be partly due to mitigation of the oxidative stress burden.

Temporal and spatial increase of reactive nitrogen species in the kainate model of temporal lobe epilepsy

Steady-state levels of reactive oxygen species (ROS) and oxidative damage to cellular macromolecules are increased in the rodent hippocampus during epileptogenesis. However, the role of reactive nitrogen species (RNS) in epileptogenesis remains to be explored. The goal of this study was to determine the spatial and temporal occurrence of RNS i.e. nitric oxide levels in a rat model of temporal lobe epilepsy (TLE). Rats were injected with a single high dose of kainate and monitored by video for behavioral seizures for 6weeks to determine the onset and severity of chronic seizures. RNS and tissue/mitochondrial redox status (glutathione redox couple and coenzyme A:glutathione redox couple) were measured in the hippocampus at 8h, 24h, 48h, 1wk, 3wk and 6wk following kainate to assess the level of reactive species in subcellular compartments. We observed a biphasic increase in RNS levels with a return to control values at the 48h time point. However, both tissue and mitochondrial redox status showed permanent and significant decreases during the entire time course of epilepsy development. 3 nitrotyrosine (3NT) protein adducts were found to gradually increase throughout epileptogenesis, conceivably as a result of the local environment under oxidative and nitrosative stress. Colocalization of 3NT immunostaining with neuron- or astrocyte-specific markers revealed neuron-specific localization of 3NT in hippocampal principal neurons. Persistent and concurrent glutathione oxidation and nitrosative stress occur during epileptogenesis suggesting a favorable environment for posttranslational modifications.

Oxidative stress markers in the neocortex of drug-resistant epilepsy patients submitted to epilepsy surgery

PURPOSE

While there is solid experimental evidence of brain oxidative stress in animal models of epilepsy, it has not been thoroughly verified in epileptic human brain. Our purpose was to determine and to compare oxidative stress markers in the neocortex of epileptic and non-epileptic humans, with the final objective of confirming oxidative stress phenomena in human epileptic brain.

METHODS

Neocortical samples from drug-resistant epilepsy patients submitted to epilepsy surgery (n=20) and from control, non-epileptic cortex samples (n=11) obtained from brain bank donors without neurological disease, were studied for oxidative stress markers: levels of reactive oxygen species (ROS), such as superoxide anion (O2(-)); activity of antioxidant enzymes: superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), and glutathione reductase (GR); and markers of damage to biomolecules (lipid peroxidation and DNA oxidation).

RESULTS

Compared with non-epileptic controls, the neocortex of epileptic patients displayed increased levels of superoxide anion (P≤0.001), catalase (P≤0.01), and DNA oxidation (P≤0.001); a decrease in GPx (P≤0.05), and no differences in SOD, GR and lipid peroxidation.

CONCLUSIONS

Our findings in humans are in agreement with those found in animal models, supporting oxidative stress as a relevant mechanism also in human epilepsy. The concurrent increase in catalase and decrease in GPx, together with unchanged SOD levels, suggests catalase as the main antioxidant enzyme in human epileptic neocortex. The substantial increase in the levels of O2(-) and 8-oxo-dG in epileptic patients supports a connection between chronic seizures and ROS-mediated neural damage.

Mitochondrial involvement and oxidative stress in temporal lobe epilepsy

A role for mitochondria and oxidative stress is emerging in acquired epilepsies such as temporal lobe epilepsy (TLE). TLE is characterized by chronic unprovoked seizures arising from an inciting insult with a variable seizure-free "latent period." The mechanism by which inciting injury induces chronic epilepsy, known as epileptogenesis, involves multiple cellular, molecular, and physiological changes resulting in altered hyperexcitable circuitry. Whether mitochondrial and redox mechanisms contribute to epileptogenesis remains to be fully clarified. Mitochondrial impairment is revealed in studies from human imaging and tissue analysis from TLE patients. The collective data from animal models suggest that steady-state mitochondrial reactive oxygen species and resultant oxidative damage to cellular macromolecules occur during different phases of epileptogenesis. This review discusses evidence for the role of mitochondria and redox changes occurring in human and experimental TLE. Potential mechanisms by which mitochondrial energetic and redox mechanisms contribute to increased neuronal excitability and therapeutic approaches to target TLE are delineated.

Autism and dietary therapy: case report and review of the literature

We report the history of a child with autism and epilepsy who, after limited response to other interventions following her regression into autism, was placed on a gluten-free, casein-free diet, after which she showed marked improvement in autistic and medical symptoms. Subsequently, following pubertal onset of seizures and after failing to achieve full seizure control pharmacologically she was advanced to a ketogenic diet that was customized to continue the gluten-free, casein-free regimen. On this diet, while still continuing on anticonvulsants, she showed significant improvement in seizure activity. This gluten-free casein-free ketogenic diet used medium-chain triglycerides rather than butter and cream as its primary source of fat. Medium-chain triglycerides are known to be highly ketogenic, and this allowed the use of a lower ratio (1.5:1) leaving more calories available for consumption of vegetables with their associated health benefits. Secondary benefits included resolution of morbid obesity and improvement of cognitive and behavioral features. Over the course of several years following her initial diagnosis, the child's Childhood Autism Rating Scale score decreased from 49 to 17, representing a change from severe autism to nonautistic, and her intelligence quotient increased 70 points. The initial electroencephalogram after seizure onset showed lengthy 3 Hz spike-wave activity; 14 months after the initiation of the diet the child was essentially seizure free and the electroencephalogram showed only occasional 1-1.5 second spike-wave activity without clinical accompaniments.

Glutathione deficiency in Gclm null mice results in complex I inhibition and dopamine depletion following paraquat administration

Depletion of glutathione has been shown to occur in autopsied brains of patients with Parkinson's disease (PD) and in animal models of PD. The goal of this study was to determine whether chronic glutathione (GSH) deficiency per se resulted in complex I inhibition and/or dopamine depletion and whether these indices were further potentiated by aging or administration of paraquat, a redox-cycling herbicide that produces a PD-like neurodegeneration model in rodents (Brooks, A. I., Chadwick, C. A., Gelbard, H. A., Cory-Slechta, D. A., and Federoff, H. J. [1999]. Paraquat elicited neurobehavioral syndrome caused by dopaminergic neuron loss. Brain Res. 823, 1-10; McCormack, A. L., Thiruchelvam, M., Manning-Bog, A. B., Thiffault, C., Langston, J. W., Cory-Slechta, D. A., and Di Monte, D. A. [2002]. Environmental risk factors and Parkinson's disease: Selective degeneration of nigral dopaminergic neurons caused by the herbicide paraquat. Neurobiol. Dis. 10, 119-127.) Deletion of the rate-limiting GSH synthesis gene, glutamate-cysteine ligase modifier subunit (Gclm), leads to significantly lower GSH concentrations in all tissues including brain. Gclm null (Gclm (-/-)) mice provide a model of prolonged GSH depletion to explore the relationship between GSH, complex I inhibition, and dopamine loss in vivo. Despite ~60% depletion of brain GSH in Gclm (-/-) mice of ages 3-5 or 14-16 months, striatal complex I activity, dopamine levels, 3-nitrotyroine/tyrosine ratios, aconitase activity, and CoASH remained unchanged. Administration of paraquat (10mg/kg, twice/week, 3 weeks) to 3- to 5-month-old Gclm (-/-) mice resulted in significantly decreased aconitase activity, complex I activity, and dopamine levels but not in 3- to 5-month-old Gclm (+/+) mice. Furthermore, paraquat-induced inhibition of complex I and aconitase activities in Gclm (-/-) mice was observed in the striatum but not in the cortex. The results suggest that chronic deficiency of GSH in Gclm (-/-) mice was not sufficient to result in complex I inhibition or dopamine depletion perhaps due to homeostatic mechanisms but required an additional oxidative stress insult as shown with paraquat exposure.

Changes in gene expression in the frontal cortex of rats with pilocarpine-induced status epilepticus after sleep deprivation

Sleep and epilepsy present a bidirectional interaction. Sleep complaints are common in epilepsy, and sleep deprivation may provoke seizures. However, the mechanisms underlying this relationship are unknown. Thus, this study investigated the effects of paradoxical sleep deprivation (PSD24h) and total sleep deprivation (TSD6h) in the expression of genes related to reactive oxygen species and nitric oxide production in the frontal cortex of a rodent model of temporal lobe epilepsy (PILO). The data show that PILO rats had increased NOX-2 expression and decreased SOD expression, independent of sleep. Higher NOX-2 expression was observed only in PILO rats subjected to the control condition and TSD6h. Also, eNOS and DDAH1 were increased in the PILO group submitted to TSD6h. Moreover, CAT expression in the frontal cortex of PILO rats submitted to PSD24h was reduced compared to that of PILO rats that were not sleep-deprived. The molecular changes found in the frontal cortex of PILO rats following sleep deprivation suggest a mechanism via oxidative stress.

Post-translational oxidative modification and inactivation of mitochondrial complex I in epileptogenesis

Mitochondrial oxidative stress and damage have been implicated in the etiology of temporal lobe epilepsy, but whether or not they have a functional impact on mitochondrial processes during epilepsy development (epileptogenesis) is unknown. One consequence of increased steady-state mitochondrial reactive oxygen species levels is protein post-translational modification (PTM). We hypothesize that complex I (CI), a protein complex of the mitochondrial electron transport chain, is a target for oxidant-induced PTMs, such as carbonylation, leading to impaired function during epileptogenesis. The goal of this study was to determine whether oxidative modifications occur and what impact they have on CI enzymatic activity in the rat hippocampus in response to kainate (KA)-induced epileptogenesis. Rats were injected with a single high dose of KA or vehicle and evidence for CI modifications was measured during the acute, latent, and chronic stages of epilepsy. Mitochondrial-specific carbonylation was increased acutely (48 h) and chronically (6 week), coincident with decreased CI activity. Mass spectrometry analysis of immunocaptured CI identified specific metal catalyzed carbonylation to Arg76 within the 75 kDa subunit concomitant with inhibition of CI activity during epileptogenesis. Computational-based molecular modeling studies revealed that Arg76 is in close proximity to the active site of CI and carbonylation of the residue is predicted to induce substantial structural alterations to the protein complex. These data provide evidence for the occurrence of a specific and irreversible oxidative modification of an important mitochondrial enzyme complex critical for cellular bioenergetics during the process of epileptogenesis.

Brain region-specific altered expression and association of mitochondria-related genes in autism

BACKGROUND

Mitochondrial dysfunction (MtD) has been observed in approximately five percent of children with autism spectrum disorders (ASD). MtD could impair highly energy-dependent processes such as neurodevelopment, thereby contributing to autism. Most of the previous studies of MtD in autism have been restricted to the biomarkers of energy metabolism, while most of the genetic studies have been based on mutations in the mitochondrial DNA (mtDNA). Despite the mtDNA, most of the proteins essential for mitochondrial replication and function are encoded by the genomic DNA; so far, there have been very few studies of those genes. Therefore, we carried out a detailed study involving gene expression and genetic association studies of genes related to diverse mitochondrial functions.

METHODS

For gene expression analysis, postmortem brain tissues (anterior cingulate gyrus (ACG), motor cortex (MC) and thalamus (THL)) from autism patients (n=8) and controls (n=10) were obtained from the Autism Tissue Program (Princeton, NJ, USA). Quantitative real-time PCR arrays were used to quantify the expression of 84 genes related to diverse functions of mitochondria, including biogenesis, transport, translocation and apoptosis. We used the delta delta Ct (∆∆Ct) method for quantification of gene expression. DNA samples from 841 Caucasian and 188 Japanese families were used in the association study of genes selected from the gene expression analysis. FBAT was used to examine genetic association with autism.

RESULTS

Several genes showed brain region-specific expression alterations in autism patients compared to controls. Metaxin 2 (MTX2), neurofilament, light polypeptide (NEFL) and solute carrier family 25, member 27 (SLC25A27) showed consistently reduced expression in the ACG, MC and THL of autism patients. NEFL (P = 0.038; Z-score 2.066) and SLC25A27 (P = 0.046; Z-score 1.990) showed genetic association with autism in Caucasian and Japanese samples, respectively. The expression of DNAJC19, DNM1L, LRPPRC, SLC25A12, SLC25A14, SLC25A24 and TOMM20 were reduced in at least two of the brain regions of autism patients.

CONCLUSIONS

Our study, though preliminary, brings to light some new genes associated with MtD in autism. If MtD is detected in early stages, treatment strategies aimed at reducing its impact may be adopted.

Thiol oxidation and altered NR2B/NMDA receptor functions in in vitro and in vivo pilocarpine models: implications for epileptogenesis

Hippocampal sclerosis, the main pathological sign of chronic temporal lobe epilepsy (TLE), is associated with oxidative injury, altered N-methyl d-aspartate receptor (NMDAR) stoichiometry, and loss of hippocampal neurons. However, the mechanisms that drive the chronic progression of TLE remain elusive. Our previous studies have shown that NADPH oxidase activation and ERK 1/2 phosphorylation are required for the up-regulation of the predominantly pre-synaptic NR2B subunit auto-receptor in both in vitro and in vivo pilocarpine (PILO) models of TLE. To provide further understanding of the cellular responses during the early-stages of hyper excitability, we investigated the role of oxidative damage and altered NR2B functions. In rat primary hippocampal cultures, we found that N-acetylcysteine (NAC) prevented PILO-mediated thiol oxidation, apoptosis, cell death and NR2B subunit over-expression. Interestingly, NAC did not block thiol oxidation when added to the neurons 6h after the PILO exposure, suggesting that disulfide formation could rapidly become an irreversible phenomenon. Moreover, NAC pre-treatment did not prevent PILO-induced NR2A subunit over-expression, a critical event in hippocampal sclerosis. Pre-treatment with the highly specific NR2B subunit inhibitor, ifenprodil, partially decreased PILO-mediated thiol oxidation and was not effective in preventing apoptosis and cell death. However, if acutely administered 48h after PILO exposure, ifenprodil blocked glutamate-induced aberrant calcium influx, suggesting the crucial role of NR2B over-expression in triggering neuronal hyper-excitability. Furthermore, ifenprodil treatment was able to prevent NR2A subunit over-expression by means of ERK1/2 phosphorylation. Our findings indicate oxidative stress and NR2B/NMDA signaling as promising therapeutic targets for co-treatments aimed to prevent chronic epilepsy following the seizure onset.

Oxidative stress and epilepsy: literature review

Backgrounds. The production of free radicals has a role in the regulation of biological function, cellular damage, and the pathogenesis of central nervous system conditions. Epilepsy is a highly prevalent serious brain disorder, and oxidative stress is regarded as a possible mechanism involved in epileptogenesis. Experimental studies suggest that oxidative stress is a contributing factor to the onset and evolution of epilepsy. Objective. A review was conducted to investigate the link between oxidative stress and seizures, and oxidative stress and age as risk factors for epilepsy. The role of oxidative stress in seizure induction and propagation is also discussed. Results/Conclusions. Oxidative stress and mitochondrial dysfunction are involved in neuronal death and seizures. There is evidence that suggests that antioxidant therapy may reduce lesions induced by oxidative free radicals in some animal seizure models. Studies have demonstrated that mitochondrial dysfunction is associated with chronic oxidative stress and may have an essential role in the epileptogenesis process; however, few studies have shown an established link between oxidative stress, seizures, and age.

Mitochondrial oxidative stress and epilepsy in SOD2 deficient mice: attenuation by a lipophilic metalloporphyrin

Epileptic seizures are a common feature associated with inherited mitochondrial diseases. This study investigated the role of mitochondrial oxidative stress in epilepsy resulting from mitochondrial dysfunction using cross-bred mutant mice lacking mitochondrial manganese superoxide dismutase (MnSOD or SOD2) and a lipophilic metalloporphyrin catalytic antioxidant. Video-EEG monitoring revealed that in the second to third week of postnatal life (P14-P21) B6D2F2 Sod2(-/-) mice exhibited frequent spontaneous motor seizures providing evidence that oxidative stress-induced mitochondrial dysfunction may contribute to epileptic seizures. To confirm the role of mitochondrial oxidative stress in epilepsy a newly developed lipophilic metalloporphyrin, AEOL 11207, with high potency for catalytic removal of endogenously generated reactive oxygen species was utilized. AEOL 11207-treated Sod2(-/-) mice showed a significant decrease in both the frequency and duration of spontaneous seizures but no effect on seizure severity. A significant increase in the average lifespan of AEOL 11207-treated Sod2(-/-) mice compared to vehicle-treated Sod2(-/-) mice was also observed. Indices of mitochondrial oxidative stress and damage (aconitase inactivation, 3-nitrotyrosine formation, and depletion of reduced coenzyme A) and ATP levels affecting neuronal excitability were significantly attenuated in the brains of AEOL 11207-treated Sod2(-/-) mice compared to vehicle-treated Sod2(-/-) mice. The occurrence of epileptic seizures in Sod2(-/-) mice and the ability of catalytic antioxidant therapy to attenuate seizure activity, mitochondrial dysfunction, and ATP levels suggest that ongoing mitochondrial oxidative stress can contribute to epilepsy associated with mitochondrial dysfunction and disease.

Antitumor indolequinones induced apoptosis in human pancreatic cancer cells via inhibition of thioredoxin reductase and activation of redox signaling

Indolequinones (IQs) were developed as potential antitumor agents against human pancreatic cancer. IQs exhibited potent antitumor activity against the human pancreatic cancer cell line MIA PaCa-2 with growth inhibitory IC(50) values in the low nanomolar range. IQs were found to induce time- and concentration-dependent apoptosis and to be potent inhibitors of thioredoxin reductase 1 (TR1) in MIA PaCa-2 cells at concentrations equivalent to those inducing growth-inhibitory effects. The mechanism of inhibition of TR1 by the IQs was studied in detail in cell-free systems using purified enzyme. The C-terminal selenocysteine of TR1 was characterized as the primary adduction site of the IQ-derived reactive iminium using liquid chromatography-tandem mass spectrometry analysis. Inhibition of TR1 by IQs in MIA PaCa-2 cells resulted in a shift of thioredoxin-1 redox state to the oxidized form and activation of the p38/c-Jun NH(2)-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) signaling pathway. Oxidized thioredoxin is known to activate apoptosis signal-regulating kinase 1, an upstream activator of p38/JNK in the MAPK signaling cascade and this was confirmed in our study providing a potential mechanism for IQ-induced apoptosis. These data describe the redox and signaling events involved in the mechanism of growth inhibition induced by novel inhibitors of TR1 in human pancreatic cancer cells.

Modulation of oxidative stress and mitochondrial function by the ketogenic diet

The ketogenic diet (KD) is a high-fat, low carbohydrate diet that is used as a therapy for intractable epilepsy. However, the mechanism(s) by which the KD achieves neuroprotection and/or seizure control are not yet known. The broad efficacy of the KD in diverse epilepsies coupled with its profound influence on metabolism suggests that mitochondrial functions may be critical in its mechanism(s) of seizure control. Mitochondria subserve important cellular functions that include the production of cellular ATP, control of apoptosis, maintenance of calcium homeostasis and the production and elimination of reactive oxygen species (ROS). This review will focus on recent literature reporting the regulation of mitochondrial functions and redox signaling by the KD. The review highlights a potential mechanism of the KD involving the production of low levels of redox signaling molecules such as H(2)O(2) and electrophiles e.g. 4-hydroxynonenal (4-HNE), which in turn activate adaptive pathways such as the protective transcription factor, NF E2-related factor 2 (Nrf2). This can ultimately result in increased production of antioxidants (e.g. GSH) and detoxification enzymes which may be critical in mediating the protective effects of the KD.

Phosphorus magnetic resonance spectroscopy in malformations of cortical development

PURPOSE

The aim of this study was to evaluate phospholipid metabolism in patients with malformations of cortical development (MCDs).

METHODS

Thirty-seven patients with MCDs and 31 control subjects were studied using three-dimensional phosphorus magnetic resonance spectroscopy ((31)P-MRS) at 3.0 T. The voxels in the lesions and in the frontoparietal cortex of the control subjects were compared (the effective volumes were 12.5 cm(3)). Robust quantification methods were applied to fit the time-domain data to the following resonances: phosphoethanolamine (PE); phosphocholine (PC); inorganic phosphate (Pi); glycerophosphoethanolamine (GPE); glycerophosphocholine (GPC); phosphocreatine (PCr); and α-, β-, and γ-adenosine triphosphate (ATP). We also estimated the total ATP (ATP(t) = α-+β-+γ-ATP), phosphodiesters (PDE = GPC+GPE), phosphomonoesters (PME = PE+PC), and the PME/PDE, PCr/ATP(t) and PCr/Pi ratios. The magnesium (Mg(2+)) levels and pH values were calculated based on PCr, Pi, and β-ATP chemical shifts.

KEY FINDINGS

Compared to controls and assuming that a p-value < 0.05 indicates statistical significance, the patients with MCDs exhibited significantly lower pH values and higher Mg(2+) levels. In addition, the patients with MCDs had lower GPC and PDE and an increased PME/PDE ratio.

SIGNIFICANCE

Mg(2+) and pH are important in the regulation of bioenergetics and are involved in many electrical activity pathways in the brain. Our data support the idea that neurometabolic impairments occur during seizure onset and propagation. The GPC, PDE, and PME/PDE abnormalities also demonstrate that there are membrane turnover disturbances in patients with MCDs.

Role of oxidative stress in epileptic seizures

Oxidative stress resulting from excessive free-radical release is likely implicated in the initiation and progression of epilepsy. Therefore, antioxidant therapies aimed at reducing oxidative stress have received considerable attention in epilepsy treatment. However, much evidence suggests that oxidative stress does not always have the same pattern in all seizures models. Thus, this review provides an overview aimed at achieving a better understanding of this issue. We summarize work regarding seizure models (i.e., genetic rat models, kainic acid, pilocarpine, pentylenetetrazol, and trimethyltin), oxidative stress as an etiologic factor in epileptic seizures (i.e., impairment of antioxidant systems, mitochondrial dysfunction, involvement of redox-active metals, arachidonic acid pathway activation, and aging), and antioxidant strategies for seizure treatment. Combined, this review highlights pharmacological mechanisms associated with oxidative stress in epileptic seizures and the potential for neuroprotection in epilepsy that targets oxidative stress and is supported by effective antioxidant treatment.

Mitochondrial matters of the brain: mitochondrial dysfunction and oxidative status in epilepsy

Epilepsy is a neurological disorder characterized by spontaneous, recurrent and paroxysmal cerebral discharge, clinically leading to persistent alterations in function and morphology of neurons. Oxidative stress is one of possible mechanisms in the pathogenesis of epilepsy. Oxidative stress resulting from mitochondrial dysfunction gradually disrupts the intracellular calcium homeostasis, which modulates neuronal excitability and synaptic transmission making neurons more vulnerable to additional stress, and leads to neuronal loss in epilepsy. In addition, the high oxidative status is associated with the severity and recurrence of epileptic seizure. Hence, treatment with antioxidants is critically important in epileptic patients through scavenging the excessive free radicals to protect the neuronal loss. In this review, we reviewed the recent findings that focus on the role for antioxidants in prevention of mitochondrial dysfunction and the correlation between oxidative status and disease prognosis in patients with epilepsy.

Mitochondrial dysfunction and oxidative stress: a contributing link to acquired epilepsy?

Mitochondrial dysfunction and oxidative stress contribute to several neurologic disorders and have recently been implicated in acquired epilepsies such as temporal lobe epilepsy (TLE). Acquired epilepsy is typically initiated by a brain injury followed by a "latent period" whereby molecular, biochemical and other cellular alterations occur in the brain leading to chronic epilepsy. Mitochondrial dysfunction and oxidative stress are emerging as factors that not only occur acutely as a result of precipitating injuries such as status epilepticus (SE), but may also contribute to epileptogenesis and chronic epilepsy. Mitochondria are the primary site of reactive oxygen species (ROS) making them uniquely vulnerable to oxidative damage that may affect neuronal excitability and seizure susceptibility. This mini-review provides an overview of evidence suggesting the role of mitochondrial dysfunction and oxidative stress as acute consequences of injuries that are known to incite chronic epilepsy and their involvement in the chronic stages of acquired epilepsy.

Stable isotope labeling by essential nutrients in cell culture for preparation of labeled coenzyme A and its thioesters

Stable isotope dilution mass spectrometry (MS) represents the gold standard for quantification of endogenously formed cellular metabolites. Although coenzyme A (CoA) and acyl-CoA thioester derivatives are central players in numerous metabolic pathways, the lack of a commercially available isotopically labeled CoA limits the development of rigorous MS-based methods. In this study, we adapted stable isotope labeling by amino acids in cell culture (SILAC) methodology to biosynthetically generate stable isotope labeled CoA and thioester analogues for use as internal standards in liquid chromatography/multiple reaction monitoring mass spectrometry (LC/MRM-MS) assays. This was accomplished by incubating murine hepatocytes (Hepa 1c1c7) in media in which pantothenate (a precursor of CoA) was replaced with [¹³C₃¹⁵N₁]-pantothenate. Efficient incorporation into various CoA species was optimized to >99% [¹³C₃¹⁵N₁]-pantothenate after three passages of the murine cells in culture. Charcoal−dextran-stripped fetal bovine serum (FBS) was found to be more efficient for serum supplementation than dialyzed or undialyzed FBS, due to lower contaminating unlabeled pantothenate content. Stable isotope labeled CoA species were extracted and utilized as internal standards for CoA thioester analysis in cell culture models. This methodology of stable isotope labeling by essential nutrients in cell culture (SILEC) can serve as a paradigm for using vitamins and other essential nutrients to generate stable isotope standards that cannot be readily synthesized.

O papel da dieta cetogênica no estresse oxidativo presente na epilepsia experimental

INTRODUÇÃO: A epilepsia é um dos transtornos neurológicos mais comuns, sendo definido como uma condição de crises recorrentes espontâneas. Existe uma importante relação entre radicais livres e enzimas antioxidantes no fenômeno epiléptico, e as espécies reativas de oxigênio (EROs) têm sido implicadas na neurodegeneração induzida pelas crises. OBJETIVO: A presente revisão teve como objetivo investigar a relação existente entre o estresse oxidativo e a epilepsia, destacando o efeito da dieta cetogênica sob condições experimentais. MATERIAL E MÉTODOS: Procedeu-se a pesquisa em artigos científicos publicados nos Bancos de Dados Medline, PubMed, Periódicos CAPES, ScienceDirect e Scielo. As palavras-chave selecionadas para a pesquisa incluíram epilepsia, status epilepticus, pilocarpina, estresse oxidativo, espécies reativas de oxigênio, disfunção mitocondrial. RESULTADOS E DISCUSSÃO: Terapia dietética tem sido utilizada, como é o caso da dieta cetogênica (DC), a qual é rica em lipídeos e pobre em carboidratos e utilizada por mais de oito décadas para o tratamento de epilepsia refratária, principalmente em crianças. A DC modula a bionergética mitocondrial, diminui a formação de EROs, aumenta a capacidade antioxidante celular e ainda, previne alterações do DNA mitocondrial. CONCLUSÃO: Evidências de atuação da DC na disfunção mitocondrial, como ocorre na epilepsia, são muitas e demonstram claramente efeitos benéficos dessa terapêutica.

Persistent impairment of mitochondrial and tissue redox status during lithium-pilocarpine-induced epileptogenesis

Mitochondrial dysfunction and oxidative stress are known to occur following acute seizure activity but their contribution during epileptogenesis is largely unknown. The goal of this study was to determine the extent of mitochondrial oxidative stress, changes to redox status, and mitochondrial DNA (mtDNA) damage during epileptogenesis in the lithium-pilocarpine model of temporal lobe epilepsy. Mitochondrial oxidative stress, changes in tissue and mitochondrial redox status, and mtDNA damage were assessed in the hippocampus and neocortex of Sprague-Dawley rats at time points (24h to 3months) following lithium-pilocarpine administration. A time-dependent increase in mitochondrial hydrogen peroxide (H(2)O(2)) production coincident with increased mtDNA lesion frequency in the hippocampus was observed during epileptogenesis. Acute increases (24-48h) in H(2)O(2) production and mtDNA lesion frequency were dependent on the severity of convulsive seizure activity during initial status epilepticus. Tissue levels of GSH, GSH/GSSG, coenzyme A (CoASH), and CoASH/CoASSG were persistently impaired at all measured time points throughout epileptogenesis, that is, acutely (24-48h), during the 'latent period' (48h to 7days), and chronic epilepsy (21days to 3months). Together with our previous work, these results demonstrate the model independence of mitochondrial oxidative stress, genomic instability, and persistent impairment of mitochondrial specific redox status during epileptogenesis. Lasting impairment of mitochondrial and tissue redox status during the latent period, in addition to the acute and chronic phases of epileptogenesis, suggests that redox-dependent processes may contribute to the progression of epileptogenesis in experimental temporal lobe epilepsy.

Acute oxidative stress and systemic Nrf2 activation by the ketogenic diet

The mechanisms underlying the efficacy of the ketogenic diet (KD) remain unknown. Recently, we showed that the KD increased glutathione (GSH) biosynthesis. Since the NF E2-related factor 2 (Nrf2) transcription factor is a primary responder to cellular stress and can upregulate GSH biosynthesis, we asked whether the KD activates the Nrf2 pathway. Here we report that rats consuming a KD show acute production of H(2)O(2) from hippocampal mitochondria, which decreases below control levels by 3 weeks, suggestive of an adaptive response. 4-Hydroxy-2-nonenal (4-HNE), an electrophilic lipid peroxidation end product known to activate the Nrf2 detoxification pathway, was also acutely increased by the KD. Nrf2 nuclear accumulation was evident in both the hippocampus and liver, and the Nrf2 target, NAD(P)H:quinone oxidoreductase (NQO1), exhibited increased activity in both the hippocampus and liver after 3 weeks. We also found chronic depletion of liver tissue GSH, while liver mitochondrial antioxidant capacity was preserved. These data suggest that the KD initially produces mild oxidative and electrophilic stress, which may systemically activate the Nrf2 pathway via redox signaling, leading to chronic cellular adaptation, induction of protective proteins, and improvement of the mitochondrial redox state.

Spinal levels of nonprotein thiols are related to nociception in mice

Oxidative stress markers are thought to be related to nociception. Because thiolic compounds are important antioxidants, we investigated the relationship between thiols, endogenous or exogenous, and nociception. Systemic or spinal, but not peripheral, administration of the exogenous thiolic compound N-acetyl-L-cysteine (NAC) reduced nociception induced by intraplantar capsaicin injection. Moreover, we detected an increase in lipid peroxidation and 3-nitrotyrosine and a decrease in nonprotein thiolic levels in the lumbar spinal cord of capsaicin-injected animals. All these effects were prevented by NAC treatment (i.p. and i.t.). Our findings confirm a role for the spinal cord in NAC actions because systemic NAC administration also reduced the nociception trigged by intrathecal injection of capsaicin. Moreover, adjuvant-induced arthritis, but not paw incision, also -decreases nonprotein thiol levels in the spinal cord. Similarly, NAC produced antinociception in adjuvant-treated animals, but not in paw-incised animals. Finally, we investigated the role of endogenous thiol compounds in the nociceptive process administrating buthionine-suphoxamine (BSO), an inhibitor of glutathione-synthesis. Intrathecal BSO treatment decreased nonprotein thiol levels in the spinal cord, as well as induced mechanical allodynia and chemical and thermal hyperalgesia. In conclusion, our results indicate a critical role for nonprotein thiols in nociception at the level of the spinal cord.

PERSPECTIVE

The results presented here indicate that the loss of nonprotein thiols in the spinal cord is involved in pain development. Therefore, the administration of thiolic compounds or other strategies allow thiol levels to be maintained and could be a beneficial action in the therapy of painful conditions.

Mitochondria, oxidative stress, and temporal lobe epilepsy

Mitochondrial oxidative stress and dysfunction are contributing factors to various neurological disorders. Recently, there has been increasing evidence supporting the association between mitochondrial oxidative stress and epilepsy. Although certain inherited epilepsies are associated with mitochondrial dysfunction, little is known about its role in acquired epilepsies such as temporal lobe epilepsy (TLE). Mitochondrial oxidative stress and dysfunction are emerging as key factors that not only result from seizures, but may also contribute to epileptogenesis. The occurrence of epilepsy increases with age, and mitochondrial oxidative stress is a leading mechanism of aging and age-related degenerative disease, suggesting a further involvement of mitochondrial dysfunction in seizure generation. Mitochondria have critical cellular functions that influence neuronal excitability including production of adenosine triphosphate (ATP), fatty acid oxidation, control of apoptosis and necrosis, regulation of amino acid cycling, neurotransmitter biosynthesis, and regulation of cytosolic Ca(2+) homeostasis. Mitochondria are the primary site of reactive oxygen species (ROS) production making them uniquely vulnerable to oxidative stress and damage which can further affect cellular macromolecule function, the ability of the electron transport chain to produce ATP, antioxidant defenses, mitochondrial DNA stability, and synaptic glutamate homeostasis. Oxidative damage to one or more of these cellular targets may affect neuronal excitability and increase seizure susceptibility. The specific targeting of mitochondrial oxidative stress, dysfunction, and bioenergetics with pharmacological and non-pharmacological treatments may be a novel avenue for attenuating epileptogenesis.

Protection against kainate neurotoxicity by ginsenosides: attenuation of convulsive behavior, mitochondrial dysfunction, and oxidative stress

We previously demonstrated that kainic acid (KA)-mediated mitochondrial oxidative stress contributed to hippocampal degeneration and that ginsenosides attenuated KA-induced neurotoxicity and neuronal degeneration. Here, we examined whether ginsenosides affected KA-induced mitochondrial dysfunction and oxidative stress in the rat hippocampus. Treatment with ginsenosides attenuated KA-induced convulsive behavior dose-dependently. KA treatment increased lipid peroxidation and protein oxidation and decreased the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio to a greater degree in the mitochondrial fraction than in the hippocampal homogenate. KA treatment resulted in decreased Mn-superoxide dismutase expression and diminished the mitochondrial membrane potential. Furthermore, KA treatment increased intramitochondrial Ca(2+) and promoted ultrastructural degeneration in hippocampal mitochondria. Treatment with ginsenosides dose-dependently attenuated convulsive behavior and the KA-induced mitochondrial effects. Protection appeared to be more evident in mitochondria than in tissue homogenates. Collectively, the results suggest that ginsenosides prevent KA-induced neurotoxicity by attenuating mitochondrial oxidative stress and mitochondrial dysfunction.