Free radicals and oxidative molecular alterations during global cerebral ischemia and reperfusion

Free radical-induced molecular alterations such as lipid peroxidation and protein oxidation have been proposed as one of the major mechanisms involved in cerebral ischemia/reperfusion injury. The objective of this study is to better understand the role of free radical-induced damage in cerebral ischemia/reperfusion injury, and to identify the damage-causing free radical source(s).; A method for the quantification of lipid peroxidation in brain sample using high performance liquid chromatography was developed and lipid peroxidation in a canine global cerebral ischemia/reperfusion model was studied. Lipid peroxidation in the cerebral cortex was found to be significantly increased in all reperfused animal groups as well as in the ischemic group compared with non-ischemic control animals. Free radical-induced, site-specific protein oxidation in the cerebral cortex was also significantly elevated following 2 and 24 hr of reperfusion compared to non-ischemic controls. Post-ischemic intravenous administration of acetyl-L-carnitine, a drug that was found to be neuroprotective in the canine model of cardiac arrest and resuscitation, inhibited both lipid peroxidation and protein oxidation following reperfusion. Normoxic resuscitative ventilatory oxygenation (21%) resulted in significantly less lipid peroxidation than when the normally clinically employed hyperoxic oxygenation (100%) was used. These results provided additional evidence that free radical-mediated lipid and protein oxidation play an important role in global cerebral ischemia/reperfusion injury, and suggest the usefulness of antioxidant therapy in global cerebral ischemia/reperfusion.; A sensitive fluorescent method (p-hydroxyphenylacetic acid plus horseradish perioxidase) for quantifying mitochondrial H{dollar}sb2{dollar}O{dollar}sb2{dollar} generation was developed and the effects of ischemia/reperfusion, Ca{dollar}sp{lcub}2+{rcub}{dollar} and pH on H{dollar}sb2{dollar}O{dollar}sb2{dollar} production by isolated brain mitochondria were systematically studied. Ischemia/reperfusion, increased Ca{dollar}sp{lcub}2+{rcub}{dollar} concentration and decreased pH all inhibited mitochondrial H{dollar}sb2{dollar}O{dollar}sb2{dollar} generation. However, Ca{dollar}sp{lcub}2+{rcub}{dollar} stimulated H{dollar}sb2{dollar}O{dollar}sb2{dollar} production in the presence of the mitochondrial electron transport chain inhibitor antimycin A, a condition simulating severe hypoxia. Thus, the mitochondrial electron transport chain could be a source of damaging reactive oxygen species in global cerebral ischemia/reperfusion injury, where intracellular calcium overload is the primary damaging event.