Cytosolic and mitochondrial systems for NADH- and NADPH-dependent reduction of alpha-lipoic acid
Cytosolic and mitochondrial systems for NADH- and NADPH-dependent reduction of alpha-lipoic acid
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DOI：
10.1016/s0891-5849(96)00400-5
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发表时间：
1997-01-01
影响因子：
7.4
通讯作者：
Packer, L
中科院分区：
文献类型：
--
作者：
Haramaki, N;Han, D;Packer, L
在细胞、组织和生物体系统中，外源性供应的α-硫辛酸（硫辛酸）具有多种显着作用，包括直接清除自由基、细胞代谢的氧化还原调节以及抑制氧化诱导损伤的潜力。由于还原硫辛酸二氢硫辛酸是许多这些过程中的一个关键步骤，我们研究了其还原机制。线粒体NADH依赖性二氢硫辛酰胺脱氢酶对R（+）-硫辛酸有明显的偏好，而NADPH依赖性谷胱甘肽还原酶对S（-）-硫辛酸立体异构体的活性略高。大鼠肝线粒体也减少外源性硫辛酸。还原率的刺激，增加线粒体的NADH含量的底物，并抑制甲氧基吲哚-2-羧酸，二氢硫辛酰胺脱氢酶抑制剂。在大鼠肝胞液中，NADPH依赖性还原大于NADH，硫辛酸还原被谷胱甘肽二硫化物抑制。在大鼠心脏、肾脏和脑全细胞可溶性组分中，NADH比NADPH对还原的贡献更大（70-90%），而在肝脏中，NADH和NADPH的活性大致相同。一个完整的器官，离体灌注的大鼠心脏，减少R-硫辛酸比S-硫辛酸快6至8倍，与高线粒体二氢硫辛酰胺脱氢酶活性和结果与分离的心脏线粒体一致。另一方面，红细胞，缺乏线粒体，有点更积极地减少S-比R-硫辛酸。这些结果证明了完整细胞和组织的不同立体特异性还原。因此，α-硫辛酸的还原机制具有高度的组织特异性，外源性α-硫辛酸的作用由组织谷胱甘肽还原酶和二氢硫辛酰胺脱氢酶活性决定。版权所有（C）1996 Elsevier Science Inc.
In cellular, tissue, and organismal systems, exogenously supplied alpha-lipoic acid (thioctic acid) has a variety of significant effects, including direct radical scavenging, redox modulation of cell metabolism, and potential to inhibit oxidatively-induced injury. Because reduction of lipoate to dihydrolipoate is a crucial step in many of these processes, we investigated mechanisms of its reduction. The mitochondrial NADH-dependent dihydrolipoamide dehydrogenase exhibits a marked preference for R(+)-lipoate, whereas NADPH-dependent glutathione reductase shows slightly greater activity toward the S(-)-lipoate stereoisomer. Rat liver mitochondria also reduced exogenous lipoic acid. The rate of reduction was stimulated by substrates which increased the NADH content of the mitochondria, and was inhibited by methoxyindole-2-carboxylic acid, a dihydrolipoamide dehydrogenase inhibitor. In rat liver cytosol, NADPH-dependent reduction was greater than NADH, and lipoate reduction was inhibited by glutathione disulfide. In rat heart, kidney, and brain whole cell-soluble fractions, NADH contributed more to reduction (70-90%) than NADPH, whereas with liver, NADH and NADPH were about equally active. An intact organ, the isolated perfused rat heart, reduced R-lipoate six to eight times more rapidly than S-lipoate, consistent with high mitochondrial dihydrolipoamide dehydrogenase activity and results with isolated cardiac mitochondria. On the other hand, erythrocytes, which lack mitochondria, somewhat more actively reduced S- than R-lipoate. These results demonstrate differing stereospecific reduction by intact cells and tissues. Thus, mechanisms of reduction of alpha-lipoate are highly tissue-specific and effects of exogenously supplied alpha-lipoate are determined by tissue glutathione reductase and dihydrolipoamide dehydrogenase activity. Copyright (C) 1996 Elsevier Science Inc.