COMPLEX III AUGMENTS OXIDANTS DAMAGE IN ISCHEMIC AGED HEART

老年心脏缺血再灌注后心肌损伤增加。老化降低氧化磷酸化的速率和电子传递链的复合物HI和IV的活性在24个月。Fischer 344大鼠心脏，与6 mo.成人对照组衰老损伤对心肌线粒体原纤维间群体具有选择性 存在于肌原纤维之间，而位于质膜下的肌膜下线粒体（SSM）不变。复合物III含有11个肽亚基，包括三个催化中心：细胞色素B、细胞色素c1和Rieske铁硫蛋白（ISP）。老化修饰IFM中底物氧化位点（Qo位点）的细胞色素B。IFM中复合物III的老化缺陷导致基线状态下活性氧（ROS）的产生增加。 线粒体损伤发生在成人和老年心脏缺血期间。缺血损伤复合物III的ISP，并降低复合物III在成年和老年心脏的线粒体群体中的活性。与成人心脏相反，老年心脏在缺血期间对SSM和IFM都承受额外的氧化损伤。心磷脂是一种重要的线粒体内膜磷脂，仅在老年心脏中发生修饰，产生一种新的心磷脂分子。位于心磷脂附近的细胞色素c也仅在老年心脏中发生改变。老年心脏缺血后细胞色素氧化酶活性降低，与成人心脏不同，加入外源性磷脂后不能恢复活性。在老年心脏中的这一观察结果表明，缺血导致细胞色素氧化酶的肽亚基的持续性损伤，而不是可逆的损伤复杂的内膜环境，在成人心脏。因此，在缺血期间，电子传递链中的特定分子靶点，包括心磷脂，仅在心肌缺血时维持氧化损伤。 老的心。 线粒体是心肌缺血时产生活性氧的主要来源。复合物III是成年心脏线粒体内ROS产生的主要位点。复合物III在缺血期间老年心脏所持续的氧化损伤中的作用尚不清楚。我们发现，限制电子流到复合物III在缺血期间实现了通过阻断复合物I与鱼藤酮缺血前即刻通过复合物III和IV在老年心脏中保持氧化磷酸化的速率。 我们提出，在缺血复合物III是一个关键机制，在老年心脏中观察到的氧化损伤增强，我们推测，活性氧从复合物III损害细胞色素氧化酶在老年心脏。在IFM中，缺血期间的氧化损伤通过复合物III的Qo位点处存在的老化缺陷而加速。我们推测，细胞色素氧化酶的损害反过来导致细胞色素c和心磷脂的氧化修饰。我们假设，缺血性损伤后，老年心脏线粒体，活性氧的生产和释放增加，设置阶段的氧化损伤再灌注。 增强的ROS从线粒体释放，反过来，放大心脏损伤和功能障碍，在再灌注过程中，可以通过可逆地限制电子流到复合物III在缺血过程中减少。

Myocardial injury is increased following ischemia and reperfusion in the aged heart. Aging decreases the rate of oxidative phosphorylation and the activity of complexes HI and IV of the electron transport chain in the 24 mo. Fischer 344 rat heart, compared to 6 mo. adult controls. The aging impairment is selective to the interfibrillar population of cardiac mitochondria 0FM) that reside among the myofibrils, whereas subsarcolemmal mitochondria (SSM), located beneath the plasma membrane, are unaltered. Complex III contains 11 peptide subunits, including three catalytic centers: cytochrome b, cytochrome c1, and the Rieske iron-sulfur protein (ISP). Aging modifies cytochrome b at the site of substrate oxidation, the Qo site, in IFM. The aging defect in complex III in IFM leads to an increased production of reactive oxygen species (ROS) in the baseline state. Mitochondrial damage occurs during ischemia in the adult and aged heart. Ischemia damages the ISP of complex III and decreases complex III activity in both populations of mitochondria in adult and aged hearts. In contrast to the adult heart, the aged heart sustains additional oxidative damage to both SSM and IFM during ischemia. Cardiolipin, a key inner mitochondrial membrane phospholipid, is modified only in the aged heart, generating a new molecular species of cardiolipin. Cytochrome c, located in proximity to cardiolipin, is modified, again, only in the aged heart. Cytochrome oxidase activity decreases following ischemia in the aged heart, and, unlike in the adult heart, activity cannot be restored following the addition of exogenous phospholipid. This observation in the aged heart indicates that ischemia led to persistent damage to a peptide subunit of cytochrome oxidase, rather than reversible damage to the inner membrane environment of the complex as in the adult heart. Thus, during ischemia, specific molecular targets in the electron transport chain, including cardiolipin, sustain oxidative damage only in the aged heart. Mitochondria are the major source of the ROS generated during myocardial ischemia. Complex III is the major site of ROS production within mitochondria in the adult heart The role of complex III in the oxidative damage sustained by the aged heart during ischemia is unknown. We found that limitation of electron flow into complex III during ischemia achieved by blockade of complex I with rotenone immediately prior to ischemia preserves the rate of oxidative phosphorylation through complexes III and IV in the aged heart. We propose that during ischemia complex III is a key mechanism of the enhanced oxidative damage observed in the aged heart, We hypothesize that ROS from complex III damage cytochrome oxidase in the aged heart. Oxidative damage during ischemia is accelerated in IFM by the aging defect present at Qo site of complex III. We hypothesize that damage to cytochrome oxidase leads in turn to oxidative modification of cytochrome c and cardiolipin. We hypothesize that following ischemic damage to aged heart mitochondria, ROS production and release is increased, setting the stage for oxidative damage during reperfusion. Enhanced ROS release from mitochondria, in turn, amplifies cardiac damage and dysfunction during reperfusion that can be decreased by reversibly limiting electron flow into complex III during ischemia.