Opening of mitochondrial BK(Ca) channels at reoxygenation protects ventricular myocytes against injury via redox signaling

Abstract

The aim was to find out whether opening of mitochondrial large conductance calcium‐activated potassium channels [BK(Ca)] protects cardiomyocytes against injury associated with simulated reoxygenation. Cells isolated from the left ventricles of adult male Wistar rats were subjected to 25‐min metabolic inhibition with NaCN and 2‐deoxyglucose followed by 30‐min reenergization. NS11021 (0.1 μM), a novel BK(Ca) channel opener, or hydrogen peroxide (2 μM) added at reenergization increased cell survival by about 30% and reduced the release of lactate dehydrogenase (LDH). The cytoprotective effects of NS11021 were completely abolished by paxilline, a BK(Ca) blocker, or tempol, a superoxide dismutase mimetic, but not by wortmannin, an inhibitor of phosphatidylinositol 3 kinase (PI3K). NS11021 significantly increased fluorescence of cells loaded with dichlorofluorescein diacetate (DCFDA) indicating an increased formation of reactive oxygen species (ROS). The NS11021‐induced ROS signal was abolished by paxilline or tempol. NS13558, an inactive structural analogue of NS11021, affected neither cell survival nor DCFDA fluorescence. These results suggest that opening of mitochondrial BK(Ca) channels protects isolated cardiomyocytes against simulated reoxygenation injury; the protective mechanism requires ROS formation but not the activation of PI3K/Akt pathway. Supported by the grant IAA500110804.