Ischemia-induced shortening of the cardiac action potential and its heterogeneous recovery upon reperfusion are thought to set the stage for reentrant arrhythmias and sudden cardiac death. We have recently reported that the collapse of mitochondrial membrane potential (ΔΨm) through a mechanism triggered by reactive oxygen species (ROS), coupled to the opening of sarcolemmal ATP-sensitive potassium (KATP) channels, contributes to electrical dysfunction during ischemia-reperfusion. Here we present a computational model of excitation-contraction coupling linked to mitochondrial bioenergetics that incorporates mitochondrial ROS-induced ROS release with coupling between the mitochondrial energy state and electrical excitability mediated by the sarcolemmal KATP current (I K,ATP). Whole-cell model simulations demonstrate that increasing the fraction of oxygen diverted from the respiratory chain to ROS production triggers limit-cycle oscillations of ΔΨm, redox potential, and mitochondrial respiration through the activation of a ROS-sensitive inner membrane anion channel. The periods of transient mitochondrial uncoupling decrease the cytosolic ATP/ADP ratio and activate IK,ATP, consequently shortening the cellular action potential duration and ultimately suppressing electrical excitability. The model simulates emergent behavior observed in cardiomyocytes subjected to metabolic stress and provides a new tool for examining how alterations in mitochondrial oxidative phosphorylation will impact the electrophysiological, contractile, and Ca2+ handling properties of the cardiac cell. Moreover, the model is an important step toward building multiscale models that will permit investigation of the role of spatiotemporal heterogeneity of mitochondrial metabolism in the mechanisms of arrhythmogenesis and contractile dysfunction in cardiac muscle.
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