Scholz R W, Reddy P V, Wynn M K, Graham K S, Liken A D, Gumpricht E, Reddy C C
Environmental Resources Research Institute and Department of Veterinary Science, The Pennsylvania State University, University Park 16802, USA.
Free Radic Biol Med. 1997;23(5):815-28. doi: 10.1016/s0891-5849(97)00067-1.
The effects of reduced glutathione (GSH) and glutathione disulfide (GSSG) on lipid peroxidation were investigated in rat liver microsomes containing deficient or adequate amounts of alpha-tocopherol (alpha-TH). Rates of formation of thiobarbituric acid reactive substances (TBARS) as well as rates of consumption of alpha-TH and O2 were decreased by GSH and were more pronounced in the NADPH-dependent assay system than in the ascorbate-dependent system. The GSH-dependent inhibition of lipid peroxidation was potentiated by GSSG in the NADPH-dependent assay system, but it had no effect in the nonenzymatic system. Diphenyliodonium chloride, an inhibitor of NADPH cytochrome P-450 reductase, completely prevented lipid peroxidation in the NADPH-dependent assay system whereas it had no effect on the ascorbate-dependent system. This is further evidenced by the fact that purified rat liver microsomal NADPH cytochrome P-450 reductase (EC 1.6.2.4) was inhibited approximately 24% and 52% by 5 mM GSH and 5 mM GSH + 2.5 mM GSSG, respectively. Glutathione disulfide alone had no effect on reductase activity. Similarly, other disulfides such as cystine, cystamine and lipoic acid were without effect on reductase activity. These results clearly delineate different mechanisms underlying the combined effects of GSH and GSSG on microsomal lipid peroxidation in rat liver. One mechanism involves recycling of microsomal alpha-TH by GSH during oxidative stress via a labile protein, ostensibly associated with "free radical reductase" activity. A second glutathione-dependent mechanism appears to be mediated through the inhibition of NADPH cytochrome P-450 reductase. The enhanced inhibition by GSH + GSSG of microsomal lipid peroxidation in the NADPH-dependent assay system suggests suppression of the initiation phase at the level of NADPH cytochrome P-450 reductase which is independent of microsomal alpha-TH.
在含有不足或适量α-生育酚（α-TH）的大鼠肝脏微粒体中，研究了还原型谷胱甘肽（GSH）和氧化型谷胱甘肽（GSSG）对脂质过氧化的影响。GSH降低了硫代巴比妥酸反应性物质（TBARS）的形成速率以及α-TH和O2的消耗速率，且在NADPH依赖性测定系统中比在抗坏血酸依赖性系统中更明显。在NADPH依赖性测定系统中，GSSG增强了GSH对脂质过氧化的抑制作用，但在非酶系统中无作用。二苯基氯化碘鎓，一种NADPH细胞色素P-450还原酶抑制剂，在NADPH依赖性测定系统中完全阻止了脂质过氧化，而对抗坏血酸依赖性系统无作用。纯化的大鼠肝脏微粒体NADPH细胞色素P-450还原酶（EC 1.6.2.4）分别被5 mM GSH和5 mM GSH + 2.5 mM GSSG抑制约24%和52%，这进一步证明了上述情况。单独的GSSG对还原酶活性无影响。同样，其他二硫化物如胱氨酸、胱胺和硫辛酸对还原酶活性也无影响。这些结果清楚地描绘了GSH和GSSG对大鼠肝脏微粒体脂质过氧化联合作用的不同机制。一种机制涉及在氧化应激期间，GSH通过一种不稳定的蛋白质使微粒体α-TH循环利用，这种蛋白质表面上与“自由基还原酶”活性相关。第二种GSH依赖性机制似乎是通过抑制NADPH细胞色素P-450还原酶介导的。在NADPH依赖性测定系统中，GSH + GSSG对微粒体脂质过氧化的增强抑制作用表明在NADPH细胞色素P-450还原酶水平上对起始阶段的抑制，这与微粒体α-TH无关。
