title: Role of protein kinase C in mitochondrial KATP channel-mediated protection against Ca2+ overload injury in rat myocardium.
abstract: Growing evidence exists that ATP-sensitive mitochondrial potassium channels (MitoKATP channel) are a major contributor to the cardiac protection against ischemia. Given the importance of mitochondria in the cardiac cell, we tested whether the potent and specific opener of the MitoKATP channel diazoxide attenuates the lethal injury associated with Ca2+overload. The specific aims of this study were to test whether protection by diazoxide is mediated by MitoKATP channels; whether diazoxide mimics the effects of Ca2+ preconditioning; and whether diazoxide reduces Ca2+ paradox (PD) injury via protein kinase C (PKC) signaling pathways. Langendorff-perfused rat hearts were subjected to the Ca2+ PD (10 minutes of Ca2+ depletion followed by 10 minutes of Ca2+ repletion). The effects of the MitoKATP channel and other interventions on functional, biochemical, and pathological changes in hearts subjected to Ca2+ PD were assessed. In hearts treated with 80 micromol/L diazoxide, left ventricular end-diastolic pressure and coronary flow were significantly preserved after Ca2+ PD; peak lactate dehydrogenase release was also significantly decreased, although ATP content was less depleted. The cellular structures were well preserved, including mitochondria and intercalated disks in diazoxide-treated hearts compared with nontreated Ca2+ PD hearts. The salutary effects of diazoxide on the Ca2+ PD injury were similar to those in hearts that underwent Ca2+ preconditioning or pretreatment with phorbol 12-myristate 13-acetate before Ca2+ PD. The addition of sodium 5-hydroxydecanoate, a specific MitoKATP channel inhibitor, or chelerythrine chloride, a PKC inhibitor, during diazoxide pretreatment completely abolished the beneficial effects of diazoxide on the Ca2+ PD. Blockade of Ca2+ entry during diazoxide treatment by inhibiting L-type Ca2+ channel with verapamil or nifedipine also completely reversed the beneficial effects of diazoxide on the Ca2+ PD. PKC-delta was translocated to the mitochondria, intercalated disks, and nuclei of myocytes in diazoxide-pretreated hearts, and PKC-alpha and PKC-epsilon were translocated to sarcolemma and intercalated disks, respectively. This study suggests that the effect of the MitoKATP channel is mediated by PKC-mediated signaling pathway.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Cincinnati Medical Center, Cincinnati, Ohio 45267-0529, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Ashraf
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000470:Alkaloids; D000818:Animals; D053119:Benzophenanthridines; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D020746:Calcium Channels, L-Type; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology; D003981:Diazoxide / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry; D019194:Ischemic Preconditioning; D007527:Isoenzymes / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000737:chemistry* / Q000201:enzymology; D017202:Myocardial Ischemia / Q000378:metabolism; D009206:Myocardium / Q000737:chemistry / Q000201:enzymology*; D009543:Nifedipine / Q000494:pharmacology; D010617:Phenanthridines / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism*; D011493:Protein Kinase C / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D051381:Rats; D017207:Rats, Sprague-Dawley; D014665:Vasodilator Agents / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000470:Alkaloids; D053119:Benzophenanthridines; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010617:Phenanthridines; D015221:Potassium Channels; D014665:Vasodilator Agents; D000255:Adenosine Triphosphate; D014700:Verapamil; C016299:chelerythrine; D007770:L-Lactate Dehydrogenase; C497260:Prkcd protein, rat; C497257:Prkce protein, rat; D011493:Protein Kinase C; D064546:Protein Kinase C beta; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051744:Protein Kinase C-epsilon; D009543:Nifedipine; D003981:Diazoxide; D002118:Calcium