Saotome Masao, Katoh Hideki, Yaguchi Yasuhiro, Tanaka Takamitsu, Urushida Tsuyoshi, Satoh Hiroshi, Hayashi Hideharu
Division of Cardiology, Internal Medicine III, Hamamatsu Univ. School of Medicine, 1-20-1 Handayama, Higashi-ku, Hamamatsu, 431-3192, Japan.
Am J Physiol Heart Circ Physiol. 2009 Apr;296(4):H1125-32. doi: 10.1152/ajpheart.00436.2008. Epub 2009 Feb 6.
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+)) 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+) without the change in DeltaPsi(m) might be a possible mechanism for the protection.
缺血再灌注（I/R）期间活性氧（ROS）的产生被认为是心肌损伤的关键因素。然而，缺血预处理（IPC）期间少量的ROS可能提供心脏保护信号。我们之前报道过，重复预处理少量ROS [过氧化氢（H₂O₂），2微摩尔] 可模拟IPC对Langendorff灌注大鼠心脏的心脏保护作用。我们进一步研究了ROS诱导的心脏保护对抗I/R损伤的机制，并测试了其是否能介导线粒体通透性转换孔（mPTP）开放的假说。对Langendorff灌注的大鼠心脏进行35分钟缺血和40分钟再灌注，H₂O₂（2微摩尔）预处理显著改善了缺血后左心室发展压力、细胞内磷酸肌酸和ATP水平的恢复。一种特异性mPTP抑制剂环孢素A（CsA；0.2微摩尔）消除了这些H₂O₂诱导的效应。在分离的透化心肌细胞中，H₂O₂（1微摩尔）以CsA敏感的方式加速了钙黄绿素从线粒体的泄漏，表明H₂O₂导致mPTP开放。然而，即使在存在寡霉素（F₁/F₀ ATP酶抑制剂；1微摩尔）的情况下，H₂O₂也不会使线粒体膜电位（ΔΨm）去极化，并且通过mPTP加速线粒体Ca²⁺外排降低了线粒体Ca²⁺浓度（[Ca²⁺]m）。我们得出结论，短暂的mPTP开放可能参与了H₂O₂诱导的对抗再灌注损伤的心脏保护作用，并且[Ca²⁺]m的降低而ΔΨm不变可能是这种保护的一种可能机制。
