Mitochondrial K(ATP) channel activation reduces anoxic injury by restoring mitochondrial membrane potential.
Mitochondrial membrane potential (DeltaPsi(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 DeltaPsi(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 DeltaPsi(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 micromol/l) resulted in a significant protection against mitochondrial damage, ATP depletion, cytochrome c loss, and stabilized DeltaPsi(m). This protection was blocked by 5-hydroxydecanoate (500 micromol/l), a mitoK(ATP) channel-selective inhibitor, but not by HMR-1098 (30 micromol/l), a putative sarcolemmal K(ATP) channel-selective inhibitor. Dissipation of DeltaPsi(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 DeltaPsi(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.
Xu
M
M
Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, Ohio 45267-0529, USA.
Wang
Y
Y
Ayub
A
A
Ashraf
M
M
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides / Q000494:pharmacology; D015687:Cell Hypoxia / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism; D019610:Cytoprotection / Q000187:drug effects; D003652:Decanoic Acids / Q000494:pharmacology; D003981:Diazoxide / Q000494:pharmacology; D006880:Hydroxy Acids / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D014665:Vasodilator Agents / Q000494:pharmacology
D001549:Benzamides; D003574:Cytochrome c Group; D003652:Decanoic Acids; D006880:Hydroxy Acids; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D014665:Vasodilator Agents; C052853:5-hydroxydecanoic acid; C410297:HMR 1098; D003981:Diazoxide