Ischemia/Reperfusion-induced oxidative stress causes structural changes of brain membrane proteins and lipids

Oxidative stress is a recognized factor of ischemia reperfusion injury. It shares damage of lipids (LPO) and proteins (PPO), and consequently might cause changes in activity of transport systems. Global 15 min ischemia followed by 2, 24 and 48 hour reperfusion was induced by four-vessel occlusion in Wistar rats of both sexes. Levels of TBARS and conjugated dienes as parameters of LPO were analyzed in forebrain homogenates. Concentrations of total free sulfhydryl (SH) groups and emission spectra of tryptophan were measured to quantify PPO. Our results indicate that lipid peroxidation and protein oxidation occurs mainly during the period of reperfusion. However, significant increase in the level of conjugated dienes can be detected already after 15 min ischemia. Attack of proteins by free radicals leads to modification in structure of proteins seen as a decrease of free SH groups and tryptophan fluorescence. Ischemia/reperfusion induces formation of lipid peroxidation products as well as protein modifications.