MITOCHONDRIA AS A SOURCE OF REACTIVE OXYGEN SPECIES DURING REDUCTIVE STRESS IN RAT HEPATOCYTES
MITOCHONDRIA AS A SOURCE OF REACTIVE OXYGEN SPECIES DURING REDUCTIVE STRESS IN RAT HEPATOCYTES
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DOI：
10.1152/ajpcell.1993.264.4.c961
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发表时间：
1993-04-01
影响因子：
--
通讯作者：
LEMASTERS, JJ
中科院分区：
文献类型：
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作者：
DAWSON, TL;GORES, GJ;LEMASTERS, JJ
在糖酵解和呼吸抑制后，测定了大鼠肝细胞的细胞杀伤、耗氧量和过氧化氢形成。这些条件模拟ATP消耗和缺氧的还原性应激（“化学缺氧”）。碘乙酸抑制糖酵解，叠氮化钠、氰化物或粘噻唑阻断线粒体电子转移。叠氮化物对细胞的杀伤、过氧化氢的形成和对抑制剂不敏感的耗氧量比粘噻唑或氰化物更大。去铁胺，一种铁催化羟基自由基形成的抑制剂，在每一种呼吸抑制剂之后延迟细胞杀伤。缺氧也延迟了化学缺氧过程中细胞的死亡。然而，在缺氧孵育期间，地铁胺并没有延迟细胞死亡的发生。这些发现表明活性氧参与了化学缺氧过程中致死性细胞损伤。在离体线粒体中，先前的研究表明，粘噻唑抑制Q循环介导的复合物III（泛醇-细胞色素c氧化还原酶）中乌二半醌的形成，并且乌二半醌可以与分子氧反应形成超氧化物。因此，与叠氮化物相比，粘噻唑对肝细胞的杀伤作用降低，这表明在还原性应激过程中，由络合物III形成的线粒体氧自由基参与了细胞杀伤。为了支持这一假说，粘噻唑降低了叠氮化物或氰化物培养的肝细胞的细胞杀伤率和过氧化氢形成率。线粒体形成氧自由基的机制可能在相对缺氧中起重要作用，而不是绝对缺氧。
Cell killing, oxygen consumption, and hydroperoxide formation were determined in rat hepatocytes after glycolytic and respiratory inhibition. These conditions model the ATP depletion and reductive stress of anoxia (''chemical hypoxia''). Glycolysis was inhibited with iodoacetate, and mitochondrial electron transfer was blocked with sodium azide, cyanide, or myxothiazol. Cell killing, hydroperoxide formation, and inhibitor-insensitive oxygen consumption were greater after azide than after myxothiazol or cyanide. Desferrioxamine, an inhibitor of iron-catalyzed hydroxyl radical formation, delayed cell killing after each of the respiratory inhibitors. Anoxia also delayed cell killing during chemical hypoxia. However, during anoxic incubations, desferrioxamine did not delay the onset of cell death. These findings indicate that reactive oxygen species participate in lethal cell injury during chemical hypoxia. In isolated mitochondria, previous studies have shown that myxothiazol inhibits Q cycle-mediated ubisemiquinone formation in complex III (ubiquinol-cytochrome c oxidoreductase) and that ubisemiquinone can react with molecular oxygen to form superoxide. Decreased killing of hepatocytes with myxothiazol compared with azide suggests, therefore, that mitochondrial oxygen radical formation by complex III is involved in cell killing during reductive stress. In support of this hypothesis, myxothiazol reduced rates of cell killing and hydroperoxide formation in hepatocytes incubated with azide or cyanide. This mitochondrial mechanism for oxygen radical formation may be important in relative but not absolute hypoxia.