title: Transient opening of mitochondrial permeability transition pore by reactive oxygen species protects myocardium from ischemia-reperfusion injury.
abstract: Reactive oxygen species (ROS) production during ischemia-reperfusion (I/R) is thought to be a critical factor for myocardial injury. However, a small amount of ROS during the ischemic preconditioning (IPC) may provide a signal for cardioprotection. We have previously reported that the repetitive pretreatment of a small amount of ROS [hydrogen peroxide (H(2)O(2)), 2 microM] mimicked the IPC-induced cardioprotection in the Langendorff-perfused rat hearts. We further investigated the mechanisms of the ROS-induced cardioprotection against I/R injury and tested the hypothesis whether it could mediate the mitochondrial permeability transition pore (mPTP) opening. The Langendorff-perfused rat hearts were subjected to 35 min ischemia and 40 min reperfusion, and the pretreatment of H(2)O(2) (2 microM) significantly improved the postischemic recoveries in left ventricular developed pressure, intracellular phosphocreatine, and ATP levels. A specific mPTP inhibitor cyclosporin A (CsA; 0.2 microM) canceled these H(2)O(2)-induced effects. In isolated permeabilized myocytes, H(2)O(2) (1 microM) accelerated the calcein leakage from mitochondria in a CsA-sensitive manner, indicating the opening of mPTP by H(2)O(2). However, H(2)O(2) did not depolarize mitochondrial membrane potential (DeltaPsi(m)) even in the presence of oligomycin (F(1)/F(0) ATPase inhibitor; 1 microM) and decreased mitochondrial Ca(2+) concentration ([Ca(2+)](m)) by accelerating the mitochondrial Ca(2+) extrusion via an mPTP. We conclude that the transient mPTP opening could be involved in the H(2)O(2)-induced cardioprotection against reperfusion injury, and the reduction of [Ca(2+)](m) without the change in DeltaPsi(m) might be a possible mechanism for the protection.
authors.affiliation: Division of Cardiology, Internal Medicine III, Hamamatsu Univ. School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan. msaotome@hama-med.ac.jp
authors.forename: Masao
authors.initials: M
authors.lastname: Saotome
authors.forename: Hideki
authors.initials: H
authors.lastname: Katoh
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Yaguchi
authors.forename: Takamitsu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Urushida
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Satoh
authors.forename: Hideharu
authors.initials: H
authors.lastname: Hayashi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D016572:Cyclosporine / Q000494:pharmacology; D005452:Fluoresceins / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000494:pharmacology*; D015427:Reperfusion Injury / Q000378:metabolism / Q000517:prevention & control*; D016277:Ventricular Function, Left / Q000187:drug effects
chemical_list: D005452:Fluoresceins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017382:Reactive Oxygen Species; D016572:Cyclosporine; D006861:Hydrogen Peroxide; D002118:Calcium; C007740:fluorexon