6533b7dafe1ef96bd126e31a

RESEARCH PRODUCT

0152 : Effects of connexin 43 inhibition on mitochondrial function in cardiac skinned fibers and isolated mitochondria

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Connexin 43 (Cx43) is a main component of intercellular gap junction channels in cardiomyocytes. The presence of Cx43 in heart mitochondria has been also reported, where it may participate in energy metabolism and protection against ischemia. Given the key role for mitochondria in pathogenesis of heart diseases, we examined how mitochondrial function could be altered in case of Cx43 pharmacological inhibition by carbenoxolone (CBX). Oxygen consumption rates under various substrate conditions were determined either in ventricles from pig hearts using saponin-permeabilized fibers, or in isolated mitochondria from rat hearts. Measurements of mitochondrial membrane potential (ΔΨ) and reactive oxygen species (ROS) by fluorescence, as well as calcium-induced matrix swelling by light scattering were recorded in cardiac mitochondria exposed to increasing CBX concentrations. At high dose (100μM), CBX substantially decreased the ADP-stimulated respiration while increasing mitochondrial protons leak in permeabilized ventricular fibers. In isolated mitochondria, we found a similar response accompanied by a collapse of ΔΨand ROS production. At lower CBX concentrations (≤25μM), the substrates oxidation rates by mitochondria were not changed (except for ADPstimulated complex I respiration which was slightly reduced), but ΔΨ remained stable. More interestingly, low CBX concentrations increased calcium sensitivity of mitochondria when incubated in a KCl versus sucrose medium. This phenomenon was partly prevented by cyclosporin A, an inhibitor of the permeability transition pore (PTP) involved in apoptosis. These data suggest a possible interaction between the function of Cx43 and the mitochondrial PTP. Further investigations will resolve the impact of Cx43 on bioenergetics in order to better understand some mitochondrial disorders in failing hearts.