Diazoxide triggers cardioprotection against apoptosis induced by oxidative stress

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 284; no. 6; pp. H2235 - H2241
• Main Authors: Ichinose, Masashi, Yonemochi, Hidetoshi, Sato, Toshiaki, Saikawa, Tetsunori
• Format: Journal Article
• Language: English
• Published: United States 01.06.2003
• Subjects: Animals; Animals, Newborn; Apoptosis - drug effects; Cells, Cultured; Diazoxide - pharmacology; Diuretics; Flow Cytometry; Heart Diseases - pathology; Heart Diseases - prevention & control; Hydrogen Peroxide - antagonists & inhibitors; Hydrogen Peroxide - toxicity; Ischemic Preconditioning, Myocardial; L-Lactate Dehydrogenase - metabolism; Membranes - drug effects; Membranes - metabolism; Microscopy, Fluorescence; Mitochondria, Heart - drug effects; Mitochondria, Heart - metabolism; Necrosis; Oxidative Stress - physiology; Rats; Rats, Wistar; Sodium Chloride Symporter Inhibitors - pharmacology
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.01073.2002

1  Department of Laboratory Medicine, Oita Medical University, Oita 879-5593, Japan; and 2  Department of Pharmacology, Chiba University Graduate School of Medicine, Chiba 260-8670, Japan 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 ( ) was measured by flow cytometry of cells stained with rhodamine-123 (Rh-123). Exposure to H 2 O 2 (500 µM) induced apoptosis, and the percentage of apoptotic cells increased progressively and peaked at 2 h. This H 2 O 2 -induced apoptosis was associated with the loss of , 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 before exposure to H 2 O 2 elicited transient and mild depolarization of and consequently suppressed both apoptosis and loss after 2-h exposure to H 2 O 2 . These protective effects of diazoxide were abrogated by the mitoK ATP 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. cardiomyocytes; mitochondria; mitochondrial membrane potential; preconditioning