MitoTEMPO provides an antiarrhythmic effect in aged-rats through attenuation of mitochondrial reactive oxygen species

The death prevalence from cardiovascular disease is significantly high in elderly-populations, while mitochondrial-aging plays an important in abnormal function of vital organs through high mitochondrial ROS production. Mitochondria have a unique mode of action by providing ATP production and modulating the cytosolic Ca2+-signaling and maintain the redox status of cardiomyocytes. There is an aging-associated impairment in oxidative phosphorylation which causes a marked dysregulation of mitochondrial biogenesis. Therefore, we aimed to examine whether a mitochondria-targeting antioxidant, MitoTEMPO, can directly provide a cardioprotective effect on ventricular cardiomyocyte function under in vitro conditions. The MitoTEMPO-treatment (0.1 μM for 4-h) of aged-ventricular cardiomyocytes (from 24-mo-old rats), compared to those of the adults (from 8-mo-old rats) markedly augmented not only the depressed biochemical parameters but also the ultrastructure of mitochondria. It also provided marked protective action against increased mitochondrial superoxide formation and Bnip3 overexpression, which both markedly induce depolarized mitochondrial potential, increase reactive oxygen species, mitochondrial swelling and fission, and accelerate mitochondrial turnover via autophagy. Furthermore, it provided marked protection against spontaneous action potentials, via shortening the prolonged action potential duration, at most, through recovery in depressed K+-channel currents. Moreover, we determined significant recovery in the depressed intracellular Ca2+-changes under electrical stimulation in MitoTEMPO-treated the aged-cardiomyocytes. Overall, we provided important information associated with an antiarrhythmic action, thereby controlling cytosolic and mitochondrial Ca2+-handling, implying its possible protective role of mitochondria-targeting antioxidant-treatment during aging.