Complex I is the major site of mitochondrial superoxide production by paraquat
Complex I is the major site of mitochondrial superoxide production by paraquat
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DOI：
10.1074/jbc.m708597200
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发表时间：
2008-01-25
影响因子：
4.8
通讯作者：
Murphy, Michael P.
中科院分区：
文献类型：
--
作者：
Cocheme, Helena M.;Murphy, Michael P.
百草枯（1,1'-二甲基-4,4'-二氯化联吡啶）被广泛用作氧化还原循环剂，以刺激生物体、细胞和线粒体中超氧化物的产生。这种超氧化物的产生会导致广泛的线粒体氧化损伤，然而，百草枯还原和超氧化物形成的线粒体位点存在相当大的不确定性。在这里，我们发现，在酵母和哺乳动物线粒体中，百草枯产生的超氧化物发生在线粒体基质中，这一点从锰超氧化物歧化酶敏感的线粒体 DNA 损伤以及在分离的线粒体中进行的超氧化物检测（不受外源超氧化物歧化酶的影响）推断得出。百草枯在线粒体基质中诱导产生超氧化物，需要膜电位，而膜电位对于百草枯吸收到线粒体中至关重要。这种吸收是百草枯双阳离子，而不是自由基单阳离子，并且是载体介导的。线粒体被破坏的实验表明，一旦进入基质，百草枯主要被复合物 I（哺乳动物）或 NADPH 脱氢酶（酵母）还原，形成百草枯自由基阳离子，然后与氧反应形成超氧化物。这种跨线粒体内膜的膜电位依赖性吸收以及随后迅速还原为百草枯自由基阳离子，共同解释了百草枯对线粒体的毒性。
Paraquat (1,1'-dimethyl-4,4'-bipyridinium dichloride) is widely used as a redox cycler to stimulate superoxide production in organisms, cells, and mitochondria. This superoxide production causes extensive mitochondrial oxidative damage, however, there is considerable uncertainty over the mitochondrial sites of paraquat reduction and superoxide formation. Here we show that in yeast and mammalian mitochondria, superoxide production by paraquat occurs in the mitochondrial matrix, as inferred from manganese superoxide dismutase-sensitive mitochondrial DNA damage, as well as from superoxide assays in isolated mitochondria, which were unaffected by exogenous superoxide dismutase. This paraquat-induced superoxide production in the mitochondrial matrix required a membrane potential that was essential for paraquat uptake into mitochondria. This uptake was of the paraquat dication, not the radical monocation, and was carrier-mediated. Experiments with disrupted mitochondria showed that once in the matrix paraquat was principally reduced by complex I (mammals) or by NADPH dehydrogenases (yeast) to form the paraquat radical cation that then reacted with oxygen to form superoxide. Together this membrane potential-dependent uptake across the mitochondrial inner membrane and the subsequent rapid reduction to the paraquat radical cation explain the toxicity of paraquat to mitochondria.