Cerebral antioxidant status and free radical generation following glutathione depletion and subsequent recovery

Abstract

This study was aimed to evaluate the oxidative damage, production of reactive oxygen species and the status of antioxidative defenses following cerebral GSH depletion induced by two classical depletors, diethylmaleate (DEM, 3 mmol/kg, i.p.) and phorone (PHO, 4 mmol/kg, i.p.). The treatment decreased (40-43%) brain glutathione levels at 2 h, followed by a partial recovery at 24 h. Cerebral glutathione depletion by these agents increased the levels of superoxide anion and hydroxyl radical at both the time intervals; however, hydrogen peroxide was high at 24 h only. It also produced a dramatic increase in the protein carbonyls at 2 h but not at 24h, without any significant effect on lipid peroxidation and conjugated diene levels. These rats showed a significantly lowered superoxide dismutase activity both at 2 h and 24 h of exposure, as compared to controls. Glutathione depletion enhanced catalase activity markedly at 2 h, followed by some recovery at 24 h. While Se-independent glutathione peroxidase (GPx) and glutathione S-transferase activities were increased at both 2 and 24 h time intervals, Se-dependent GPx and glucose-6-phosphate dehydrogenase were induced at 2 h only. Glutathione depletion decreased ceruloplasmin and vitamin E levels significantly at 2 h. However, ascorbic acid remained unaffected. It may be concluded that an acute cerebral glutathione depletion generates higher levels of reactive oxygen species, which may be responsible for oxidative modification of proteins. Some of these changes appear to recover soon after an activation of a variety of cellular antioxidant defense mechanisms and glutathione restoration. It appears that central nervous system is highly vulnerable to oxidative damage following a moderate glutathione depletion that may result from certain diseases or xenobiotic exposures.