4-hydroxy-2-nonenal and Seizures

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.

Topics: Acetylcysteine; Aldehydes; Animals; Anticonvulsants; Antipyrine; Cell Survival; Edaravone; Excitatory Amino Acid Antagonists; Free Radical Scavengers; Glutathione; Kainic Acid; Male; Mossy Fibers, Hippocampal; Pentobarbital; Rats; Rats, Sprague-Dawley; Seizures

Our previous work demonstrated the marked decrease of mitochondrial complex I activity in the cerebral cortex of immature rats during the acute phase of seizures induced by bilateral intracerebroventricular infusion of dl-homocysteic acid (600 nmol/side) and at short time following these seizures. The present study demonstrates that the marked decrease ( approximately 60%) of mitochondrial complex I activity persists during the long periods of survival, up to 5 weeks, following these seizures, i.e. periods corresponding to the development of spontaneous seizures (epileptogenesis) in this model of seizures. The decrease was selective for complex I and it was not associated with changes in the size of the assembled complex I or with changes in mitochondrial content of complex I. Inhibition of complex I was accompanied by a parallel, up to 5 weeks lasting significant increase (15-30%) of three independent mitochondrial markers of oxidative damage, 3-nitrotyrosine, 4-hydroxynonenal and protein carbonyls. This suggests that oxidative modification may be most likely responsible for the sustained deficiency of complex I activity although potential role of other factors cannot be excluded. Pronounced inhibition of complex I was not accompanied by impaired ATP production, apparently due to excess capacity of complex I documented by energy thresholds. The decrease of complex I activity was substantially reduced by treatment with selected free radical scavengers. It could also be attenuated by pretreatment with (S)-3,4-DCPG (an agonist for subtype 8 of group III metabotropic glutamate receptors) which had also a partial antiepileptogenic effect. It can be assumed that the persisting inhibition of complex I may lead to the enhanced production of reactive oxygen and/or nitrogen species, contributing not only to neuronal injury demonstrated in this model of seizures but also to epileptogenesis.

Topics: Aldehydes; Animals; Animals, Newborn; Cerebral Cortex; Convulsants; Disease Models, Animal; Down-Regulation; Electron Transport Complex I; Energy Metabolism; Epilepsy; Excitatory Amino Acid Agonists; Free Radical Scavengers; Homocysteine; Male; Metabolic Networks and Pathways; Mitochondria; Mitochondrial Diseases; Oxidative Stress; Rats; Rats, Wistar; Seizures; Survival Rate; Time Factors; Tyrosine

Lysosomal membrane permeabilization (LMP) is implicated in cancer cell death. However, its role and mechanism of action in neuronal death remain to be established. In the present study, we investigate the function of cellular zinc in oxidative stress-induced LMP using hippocampal neurons. Live-cell confocal microscopy with FluoZin-3 fluorescence showed that H(2)O(2) exposure induced vesicles containing labile zinc in hippocampal neurons. Double staining with LysoTracker or MitoTracker disclosed that the majority of the zinc-containing vesicles were lysosomes and not mitochondria. H(2)O(2) additionally augmented the 4-hydroxy-2-nonenal (HNE) adduct level in lysosomes. Intracellular zinc chelation with TPEN [tetrakis(2-pyridylmethyl)ethylenediamine] completely blocked both HNE accumulation and neuronal death. Interestingly, within 1 h after the onset of H(2)O(2) exposure, some of zinc-loaded vesicles lost their zinc signals. Consistent with the characteristics of LMP, a lysosomal enzyme, cathepsin D, was released into the cytosol, and cathepsin inhibitors partially rescued neuronal death. We further examined the possibility that HNE or zinc mediates H(2)O(2)-triggered LMP. Similar to H(2)O(2), exposure to HNE or zinc triggered lysosomal zinc accumulation and LMP. Moreover, isolated lysosomes underwent LMP when exposed to HNE or zinc, but not H(2)O(2), supporting the direct mediation of LMP by HNE and/or zinc. The appearance of zinc-containing vesicles and the increases in levels of cathepsin D and HNE, were also observed in hippocampal neurons of rats after kainate seizures. Thus, under oxidative stress, neuronal lysosomes accumulate zinc and HNE, and eventually undergo LMP, which may constitute a key mechanism of oxidative neuronal death.

Topics: Aldehydes; Animals; Cathepsin D; Cell Death; Cells, Cultured; Cysteine Proteinase Inhibitors; Disease Models, Animal; Embryo, Mammalian; Hippocampus; Hydrogen Peroxide; L-Lactate Dehydrogenase; Lysosomes; Male; Mice; Neurons; Permeability; Polycyclic Compounds; Rats; Rats, Sprague-Dawley; Seizures; Time Factors; Zinc