Role of mitochondrial ATP-sensitive potassium channels in apoptosis

Research Project

Project/Area Number	12670681
Research Category	Grant-in-Aid for Scientific Research (C)
Allocation Type	Single-year Grants
Section	一般
Research Field	Circulatory organs internal medicine
Research Institution	OITA MEDICAL UNIVERSITY
Principal Investigator	YONEMOCHI Hidetoshi OITA MEDICAL UNIVERSITY, MEDICAL DEPARTMENT, ASSOCIATED PROFESSOR, 医学部, 助教授 (40191671)
Co-Investigator(Kenkyū-buntansha)	SATO Toshiaki CHIBA UNIVERSITY, GRADUATED SCHOOL OF MEDICINE, ASSOCIATED PROFESSOR, 大学院・医学研究院, 助教授 (60244159)
Project Period (FY)	2000 – 2001
Project Status	Completed (Fiscal Year 2001)
Budget Amount *help	¥3,400,000 (Direct Cost: ¥3,400,000) Fiscal Year 2001: ¥1,600,000 (Direct Cost: ¥1,600,000) Fiscal Year 2000: ¥1,800,000 (Direct Cost: ¥1,800,000)
Keywords	Cardioprotection / apoptosis / K^+ channel / mitochondria / ischemia / ATP感受性K^+チャネル
Research Abstract	Although mitochondrial ATP-sensitive potassium (mitoK_<ATP>) channels have been reported to reduce the extent of apoptosis, the critical timing of mitoK_<ATP> channel opening required to protect myocytes against apoptosis remains unclear. In the present study, we examined whether the mitoK_<ATP> channel serves as a trigger of cardioprotection against apoptosis induced by oxidative stress. Apoptosis of cultured neonatal rat cardiomyocytes was determined by flow cytometry (light scatter and propidium iodide/annexin V-FITC fluorescence) and by nuclear staining with Hoechst 33342. Mitochondrial membrane potential (ΔΨ) was measured by flow cytometry of cells stained with rhodamine-123 (Rh-123). Exposure to H_2O_2 (500 μM) induced apoptosis and the percentage of apoptotic cells increased progressively and peaked at 2 hours. This H_2O_2-induced apoptosis was associated with the loss of ΔΨ, and the time-course of decrease in Rh-123 fluorescence paralleled that of apoptosis. Pretreatment of cardiomyocytes with diazoxide (100 μM), a putative mitoK_<ATP> channel opener, for 30 min prior to exposure to H_2O_2 elicited the transient and mild depolarization of AW, and consequently suppressed both apoptosis and ΔΨ loss after 2 hours exposure to H_2O_2. These protective effects of diazoxide were abrogated by the, mitoKATP channel blocker 5-hydroxydecanoate (500 μM), but not by the sarcolemmal K_<ATP> channel blocker HMR 1098 (30 μM). Our results suggest for the first time that diazoxide-induced opening of mitoK_<ATP> channels triggers cardioprotection against apoptosis induced by oxidative stress in rat cardiomyocytes.