Cardiac mitochondrial preconditioning by Big Ca2+-sensitive K+ channel opening requires superoxide radical generation

• Published in: American journal of physiology. Heart and circulatory physiology Vol. 290; no. 1; pp. H434 - H440
• Main Authors: Stowe, David F, Aldakkak, Mohammed, Camara, Amadou K. S, Riess, Matthias L, Heinen, Andre, Varadarajan, Srinivasan G, Jiang, Ming-Tao
• Format: Journal Article
• Language: English
• Published: United States 01.01.2006
• Subjects: Animals; Benzimidazoles - pharmacology; Calcium - metabolism; Ethidium - analogs & derivatives; Guinea Pigs; Ischemic Preconditioning, Myocardial - methods; Large-Conductance Calcium-Activated Potassium Channels - drug effects; Large-Conductance Calcium-Activated Potassium Channels - physiology; Mitochondria, Heart - physiology; NAD; Reactive Oxygen Species - metabolism; Superoxides - metabolism
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00763.2005

Departments of 1 Anesthesiology and 2 Physiology, Anesthesiology Research Laboratories, 3 Cardiovascular Research Center, The Medical College of Wisconsin, Milwaukee; 4 Veterans Affairs Medical Center Research Service, Milwaukee; and 5 Department of Biomedical Engineering, Marquette University, Milwaukee, Wisconsin Submitted 19 July 2005 ; accepted in final form 19 August 2005 ATP-sensitive K + channel opening in inner mitochondrial membranes protects hearts from ischemia-reperfusion (I/R) injury. Opening of the Big conductance Ca 2+ -sensitive K + channel (BK Ca ) is now also known to elicit cardiac preconditioning. We investigated the role of the pharmacological opening of the BK Ca channel on inducing mitochondrial preconditioning during I/R and the role of O 2 -derived free radicals in modulating protection by putative mitochondrial (m)BK Ca channel opening. Left ventricular (LV) pressure (LVP) was measured with a balloon and transducer in guinea pig hearts isolated and perfused at constant pressure. NADH, reactive oxygen species (ROS), principally superoxide (O 2 – ·), and m[Ca 2+ ] were measured spectrophotofluorometrically at the LV free wall using autofluorescence and fluorescent dyes dihydroethidium and indo 1, respectively. BK Ca channel opener 1-(2'-hydroxy-5'-trifluoromethylphenyl)-5-trifluoromethyl-2(3H)benzimid-axolone (NS; NS-1619) was given for 15 min, ending 25 min before 30 min of global I/R. Either Mn(III)tetrakis(4-benzoic acid)porphyrin (TB; MnTBAP), a synthetic dismutator of O 2 – ·, or an antagonist of the BK Ca channel paxilline (PX) was given alone or for 5 min before, during, and 5 min after NS. NS pretreatment resulted in a 2.5-fold increase in developed LVP and a 2.5-fold decrease in infarct size. This was accompanied by less O 2 – · generation, decreased m[Ca 2+ ], and more normalized NADH during early ischemia and throughout reperfusion. Both TB and PX antagonized each preconditioning effect. This indicates that 1 ) NS induces a mitochondrial-preconditioned state, evident during early ischemia, presumably on mBK Ca channels; 2 ) NS effects are blocked by BK Ca antagonist PX; and 3 ) NS-induced preconditioning is dependent on the production of ROS. Thus NS may induce mitochondrial ROS release to initiate preconditioning. cell signaling; ischemic biology; oxidant stress; energy metabolism; heart; mitochondria; reactive oxygen species; redox balance Address for reprint requests and other correspondence: D. F. Stowe, M4280, 8701 Watertown Plank Rd., Medical College of Wisconsin, Milwaukee, WI 53226 (e-mail: dfstowe{at}mcw.edu )