Mitochondrial KATP channel activation reduces anoxic injury by restoring mitochondrial membrane potential

Mitochondrial membrane potential (Delta Psi (m)) is severely compromised in the myocardium after ischemia-reperfusion and triggers apoptotic events leading to cell demise. This study tests the hypothesis that mitochondrial ATP-sensitive K+ (mitoK(ATP)) channel activation prevents the collapse of Delta Psi (m) in myocytes during anoxia-reoxygenation (A-R) and is responsible for cell protection via inhibition of apoptosis. After 3-h anoxia and 2-h reoxygenation, the cultured myocytes underwent extensive damage, as evidenced by decreased cell viability, compromised membrane permeability, increased apoptosis, and decreased ATP concentration. Mitochondria in A-R myocytes were swollen and fuzzy as shown after staining with Mito Tracker Orange CMTMRos an in an electron microscope and exhibited a collapsed Delta Psi (m), as monitored by 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide (JC-1). Cytochrome c was released from mitochondria into the cytosol as demonstrated by cytochrome c immunostaining. Activation of mitoK(ATP) channel with diazoxide (100 mu mol/l) resulted in a significant protection against mitochondrial damage, ATP depletion, cytochrome c loss, and stabilized This protection was blocked by 5-hydroxydecanoate (500 mu mol/l), a mitoK(ATP) channel-selective inhibitor, but not by HMR-1098 (30 mu mol/l), a putative sarcolemmal K-ATP channel-selective inhibitor. Dissipation of Delta Psi (m) also leads to opening of mitochondrial permeability transition pore, which was prevented by cyclosporin A. The data support the hypothesis that A-R disrupts Delta Psi (m) and induces apoptosis, which are prevented by the activation of the mitoK(ATP) channel. This further emphasizes the therapeutic significance of mitoK(ATP) channel agonists in the prevention of ischemia-reperfusion cell injury.