The protective effect of vitamin E, idebenone and reduced glutathione on free radical mediated injury in rat brain synaptosomes

Abstract

In the present study the effect of ascorbate (0.8 mM)/iron (2.5 microM) on lipid and protein oxidation, in Synaptosomes isolated from rat brain cortex, was evaluated. Vitamin E, idebenone and reduced glutathione were used as free radicals scavengers, in order to analyze the mechanism involved in ascorbate/iron-induced oxidative stress. An increased formation of reactive oxygen species (ROS) in the cytosol and in the mitochondria was observed, in ascorbate/iron treated synaptosomes. Idebenone (50 microM) prevented the increased formation of ROS in both synaptosomal compartments, vitamin E (150 microM) protected partially this formation in mitochondria, whereas reduced glutathione (250 microM) (GSH) was ineffective. After ascorbate/iron treatment an increase in lipid peroxidation occurred as compared to control, which was completely inhibited by idebenone. A decrease in protein-SH content was also observed, and it was prevented by Vitamin E, idebenone and GSH. When synaptosomes were treated with ascorbate/iron the levels of GSH decreased, and the levels of oxidized glutathione (GSSG) increased as compared to controls under these conditions. Glutathione peroxidase activity was unchanged, whereas an inhibition of glutathione reductase activity was observed. These data suggest that the increased formation of free radicals in synaptosomes leads to lipid and protein oxidation, the role of the endogenous GSH being essential to protect protein thiol-groups against oxidative damage in order to maintain enzyme activity.