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Mitochondrial K ATP channel activation reduces anoxic injury by restoring mitochondrial membrane potential

2001; American Physical Society; Volume: 281; Issue: 3 Linguagem: Inglês

10.1152/ajpheart.2001.281.3.h1295

1522-1539

Meifeng Xu, Yigang Wang, Ahmar Ayub, Muhammad Ashraf,

Mitochondrial Function and Pathology

Mitochondrial membrane potential (ΔΨ 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 ΔΨ 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 and in an electron microscope and exhibited a collapsed ΔΨ 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 cimmunostaining. Activation of mitoK ATP channel with diazoxide (100 μmol/l) resulted in a significant protection against mitochondrial damage, ATP depletion, cytochrome c loss, and stabilized ΔΨ m . This protection was blocked by 5-hydroxydecanoate (500 μmol/l), a mitoK ATP channel-selective inhibitor, but not by HMR-1098 (30 μmol/l), a putative sarcolemmal K ATP channel-selective inhibitor. Dissipation of ΔΨ 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 ΔΨ 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.