Mitochondrial Reactive Oxygen Species Control Metabolic Oscillations in Cardiomyocytes at Near-Anoxia

Abstract

Metabolic oscillations frequently occur under conditions simulating ischemia. As oxygen tension is a determinant of mitochondrial function and reactive oxygen species (ROS) production, we studied metabolic oscillations in single resting cardiomyocytes at near-anoxia (pO2 < 0.1 mm Hg) using on-chip picochambers. Activation of current through sarcolemmal KATP channels (IKATP), sensing the cytosolic ATP concentration, was measured simultaneously with either the mitochondrial membrane potential, delta Psi (TMRM fluorescence), or the cellular redox state (H2DCF fluorescence). Upon transition to near anoxia, activation of IKATP started with one or several current oscillations, which were time-correlated with oscillations of delta Psi and H2DCF oxidation. Metabolic oscillations persisted in cells treated with either cytoplasmic ROS scavengers or mitochondrial inhibitors of ROS production, and were stimulated when enhancing the mitochondrial ROS production with either antimycin or rotenone. Oscillations of IKATP could be either initiated or potentiated upon rapid, but not slow, transition to near-anoxia and they were closely paralleled by depolarization of delta Psi, indicative of a transient inability of the F1F0-ATPase to keep delta Psi. At elevated oxidative stress, rapid transition to near-anoxia caused a burst of H2DCF oxidation which correlated with an increased rate of IKATP activation. These results show that metabolic oscillations occur in cardiomyocytes at near-anoxia and that these oscillations are controlled by mitochondria through the rate of ATP hydrolysis which in turn depends on ROS production.