Opposite Production of Reactive Oxygen Species by Complexes I and III during Heart Ischemia/Reperfusion

Abstract

In mitochondria, the main reactive oxygen species (ROS) generators are complexes I and III. Mitochondrial ROS generation has been implicated in cellular damage occurring in a variety of pathologies including ischemia/reperfusion (I/R). Most of the studies have observed an increase of ROS production after I/R. However, there is evidence of an increase of ROS production after cardioprotection by preconditioning interventions.We investigated the differential production of ROS by complex I and III in I/R and sham isolated mitochondria heart mice, and the action of pro-apoptotic drugs (rotenone and antimycin A) on ROS production by these complexes in sham animals.Mitochondrial ROS generation by both complexes was measured using amplex red in the presence of horseradish-peroxidase. Specific substrates for complex I (glutmate/malate) and complex II (succinate), and the inhibitors (rotenone and antimycin-A) were used. Mitochondria from I/R mice produced more ROS than mitochondria from sham when the substrate for complex I was used. In contrast, with the substrate of complex II, mitochondria from I/R mice produced less ROS than sham. Application of rotenone and antimycin-A in mitochondria from sham heart significantly increased ROS production when the substrate for the complex I was used. Surprisingly, these inhibitors decreased the ROS production when the substrate for the complex II was used. This data indicate the ambivalent production of ROS by the respiratory chain complexes I and III, and suggest opposite role of ROS depending on the complex being cardio-deleterious for complex I and cardio-protective for complex III. Supported by NIH and AHA.