In vivo reactive oxygen species production induced by ischemia in muscle arterioles of mice: involvement of xanthine oxidase and mitochondria.

Reactive oxygen species (ROS) participate in tissue injury after ischemia-reperfusion. Their implication in leukocyte adherence and increase in permeability at the venular side of the microcirculation have been reported, but very little is known about ROS production in arterioles. The objective of this work was to evaluate, in the arteriole wall in vivo, the temporal changes in superoxide anion production during ischemia and reperfusion and to identify the source of this production. Mouse cremaster muscle was exposed to 1 h of ischemia followed by 30 min of reperfusion, and superoxide anion production was assessed by a fluorescent probe, i.e., intracellular dihydroethidium oxidation. During ischemia, we found a significant increase in dihydroethidium oxidation; however, we observed no additional increase in fluorescence during the subsequent reperfusion. This phenomenon was significantly inhibited by pretreatment with superoxide dismutase. Allopurinol (xanthine oxidase inhibitor) or stigmatellin [Q(o)-site (oriented toward the intermembrane space) inhibitor of mitochondrial complex III] or simultaneous administration of these two inhibitors significantly reduced superoxide production during ischemia to 80%, 88%, and 72%, respectively, of that measured in the untreated ischemia-reperfusion group. By contrast, no significant inhibition was found when NADPH oxidase was inhibited by apocynin or when mitochondrial complex I or complex II was inhibited by rotenone or thenoyltrifluoroacetone. A significant increase in ROS was found with antimycin A [Q(i)-site (located in the inner membrane and facing the mitochondrial matrix) inhibitor of mitochondrial complex III]. We conclude that a significant increase in ROS production occurs during ischemia in the arteriolar wall. This increased production involves both a cytoplasmic source (i.e., xanthine oxidase) and the mitochondrial complex III at the Q(o) site.