Liu Yanping, Yang Xi-Ming, Iliodromitis Efstathios K, Kremastinos Dimitrios T, Dost Turhan, Cohen Michael V, Downey James M
Department of Physiology, MSB 3074, University of South Alabama College of Medicine, Mobile, AL 36688, USA.
Basic Res Cardiol. 2008 Jan;103(1):54-9. doi: 10.1007/s00395-007-0683-y. Epub 2007 Nov 12.
Redox signaling prior to a lethal ischemic insult is an important step in triggering the protected state in ischemic preconditioning. When the preconditioned heart is reperfused a second sequence of signal transduction events, the mediator pathway, occurs which is believed to inhibit mitochondrial permeability transition pore formation that normally destroys mitochondria in much of the reperfused tissue. Prominent among the mediator pathway's events is activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase. Recently it was found that both activation of PKC and generation of reactive oxygen species (ROS) at the time of reperfusion are required for protection in preconditioned hearts. To establish their relative order we tested whether ROS formation at reperfusion is required in hearts protected by direct activation of PKC at reperfusion. Isolated rabbit hearts were exposed to 30 min of regional ischemia and 2 h of reperfusion. Preconditioned hearts received 5 min of global ischemia and 10 min of reperfusion prior to the index ischemia. Another group of preconditioned hearts was exposed to 300 microM of the ROS scavenger N-(2-mercaptopropionyl) glycine (MPG) for 20 min starting 5 min prior to reperfusion. Infarct size was measured by triphenyltetrazolium staining. Preconditioning reduced infarct size from 36% +/- 2% of the ischemic zone in control hearts to only 18 +/- 2%. MPG during early reperfusion completely blocked preconditioning's protection (33 +/- 3% infarction). MPG given in the same dose and schedule to non-preconditioned hearts had no effect on infarct size. In the last group phorbol 12-myristate 13-acetate (PMA) (0.05 nM) was given to non-preconditioned hearts from 1 min before to 5 min after reperfusion in addition to MPG administered as in the other groups. MPG did not block protection from an infusion of PMA as infarct size was only 9 +/- 2% of the risk zone. We conclude that while redox signaling during the first few minutes of reperfusion is an essential component of preconditioning's protective mechanism, this step occurs upstream of PKC activation.
在致死性缺血损伤之前的氧化还原信号传导是触发缺血预处理中保护状态的重要步骤。当预处理过的心脏再次灌注时,会发生第二序列的信号转导事件,即介质途径,据信该途径可抑制线粒体通透性转换孔的形成,而这种孔通常会破坏大部分再灌注组织中的线粒体。介质途径事件中突出的是磷脂酰肌醇3激酶和细胞外信号调节激酶的激活。最近发现,在预处理过的心脏中,再灌注时蛋白激酶C(PKC)的激活和活性氧(ROS)的产生都是保护所必需的。为了确定它们的相对顺序,我们测试了在再灌注时通过直接激活PKC来保护的心脏中是否需要再灌注时形成ROS。将离体兔心脏暴露于30分钟的局部缺血和2小时的再灌注。预处理过的心脏在指数缺血之前接受5分钟的全心缺血和10分钟的再灌注。另一组预处理过的心脏在再灌注前5分钟开始暴露于300微摩尔的ROS清除剂N-(2-巯基丙酰基)甘氨酸(MPG)20分钟。通过三苯基四氮唑染色测量梗死面积。预处理将梗死面积从对照心脏缺血区的36%±2%减少到仅18±2%。早期再灌注期间的MPG完全阻断了预处理的保护作用(梗死率为33±3%)。以相同剂量和方案给予未预处理心脏的MPG对梗死面积没有影响。在最后一组中,除了按照其他组的方式给予MPG外,在再灌注前1分钟至再灌注后5分钟向未预处理心脏给予佛波酯12-肉豆蔻酸酯13-乙酸酯(PMA)(0.05纳摩尔)。由于梗死面积仅为危险区的9±2%,MPG并未阻断PMA输注的保护作用。我们得出结论,虽然再灌注最初几分钟的氧化还原信号传导是预处理保护机制的重要组成部分,但这一步骤发生在PKC激活的上游。