Neuroprotective effects of α-lipoic acid on the development of oxidative stress and astrogliosis in the brain of STZ-diabetic rats

Abstract

The aim of this study was to examine whether the antioxidant alpha-lipoic acid protects neurons from diabetic-reperfusion injury. The streptozotocin (STZ) rat model was used to study the glial reactivity and prevention of gliosis by alpha-lipoic acid (alpha-LA) administration. The expression of glial fibrillary acidic protein (GFAP) was determined, as well as lipid peroxidation (LPO) and glu-tathione (GSH) levels in some brain tissues. We observed significant increasing of lipid peroxidation products in both hippocampus and cortex. Changesof polypeptide GFAP were observed in hippocampus and cortex. Both soluble and filamentous forms of GFAP featured the increase in hippocampus of rat with hyperthyreosis. In the filamentfractions, increase in the intensity of 49 kDa polypeptide band was found. In the same fraction of insoluble cytoskeleton proteins degraded HFKB polypeptides with molecular weight in the range of 46–41 kDa appeared. Markedincrease of degraded polypeptides was found in the soluble fraction of the brain stem. The intensity of the intact polypeptide – 49 kDa, as well as in the filament fraction, significantly increased. It is possible that increasing concentrations of soluble subunits glial filaments may be due to dissociation of own filaments during the reorganization of cytoskeleton structures. Given the results of Western blotting for filament fraction, increased content of soluble intact 49 kDa polypeptide is primarily the result of increased expression of HFKB and only partly due to redistribution of existing filament structures. Calculation and analysis of indicators showed high correlation between the increase in content and peroxidation products of HFKB.These results indicate the important role of oxidative stress in the induction of astroglial response under conditions of diabet encefalopathia. Administration of alpha-LA reduced the expression both of glial and neuronal markers. In addition, alpha-LA significantly prevented the increase in LPO levels found in diabetic rats. GSH levels increased by the administration of alpha-LA. This study suggests that alpha-LA prevents neural injury by inhibiting oxidative stress and suppressing reactive gliosis. All these changes were clearly counteracted by alpha-lipoic acid. The results of this study demonstrate that alpha-lipoic acid provides for protection to the GFAP, as a whole, from diabet -reperfusion injuries.