THE PROTECTIVE EFFECT OF VITAMIN-E, IDEBENONE AND REDUCED GLUTATHIONEON FREE-RADICAL MEDIATED INJURY IN RAT-BRAIN SYNAPTOSOMES

In the present study the effect of ascorbate (0.8 mM)/iron (2.5 mu M) on lipid and protein oxidation, in Synaptosomes isolated from rat brai n cortex, was evaluated. Vitamin E, idebenone and reduced glutathione were used as free radicals scavengers, in order to analyze the mechani sm involved in ascorbate/iron-induced oxidative stress, An increased f ormation of reactive oxygen species (ROS) in the cytosol and in the mi tochondria was observed, in ascorbate/iron treated synaptosomes, Idebe none (50 mu M) prevented the increased formation of ROS in both synapt osomal compartments, vitamin E (150 mu M) protected partially this for mation in mitochondria, whereas reduced glutathione (250 mu M) (GSH) w as ineffective. After ascorbate/iron treatment an increase in lipid pe roxidation occurred as compared to control, which was completely inhib ited by idebenone. A decrease in protein-SH content was also observed, and it was prevented by Vitamin E, idebenone and GSH. When synaptosom es were treated with ascorbate/iron the levels of GSH decreased, and t he levels of oxidized glutathione (GSSG) increased as compared to cont rols under these conditions. Glutathione peroxidase activity was uncha nged, whereas an inhibition of glutathione reductase activity was obse rved, 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 agains t oxidative damage in order to maintain enzyme activity. (C) 1998 Acad emic Press.