Geiger P G, Thomas J P, Girotti A W
Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.
Arch Biochem Biophys. 1991 Aug 1;288(2):671-80. doi: 10.1016/0003-9861(91)90250-m.
The effect of selenium deprivation on the viability of murine L1210 cells exposed to various exogenous lipid hydroperoxides has been investigated. Selenoperoxidase activities of cells grown for longer than 1 week in 1% serum with no added selenium [Se(-) cells] were less than 10% of the activities of selenium-satisfied controls [Se(+) cells] or selenium-repleted counterparts [Se(-/+) cells]. The enzymes measured were classical glutathione peroxidase (GPX) and phospholipid hydroperoxide glutathione peroxidase (PHGPX). Se(-) cells exhibited a compensatory increase in catalase activity. Dye exclusion and clonal survival assays indicated that Se(-) and Se(+) cells were relatively insensitive to photochemically generated phospholipid hydroperoxides in liposomal form. However, both cell types were sensitive to liposomal cholesterol hydroperoxides, e.g., 7-hydroperoxycholesterol (7-OOH), Se(-) being much more so (LD50 approximately 10 microM) than Se(+) (LD50 approximately 75 microM). By contrast, 7-hydroxycholesterol over a comparable concentration range was minimally toxic to Se(-) and Se(+) cells. Cell killing by 7-OOH was inhibited by desferrioxamine and by butylated hydroxytoluene, suggesting that iron-mediated free radical reactions are involved. The involvement of glutathione in cytoprotection was confirmed by showing that Se(+) cells were more sensitive to 7-OOH after treating with buthionine sulfoximine, an inhibitor of GSH synthesis. Cellular detoxification of 7-OOH is provisionally attributed to PHGPX rather than GPX, since 7-OOH and other cholesterol hydroperoxides were found to be good substrates for PHGPX in a cell free system, but were unreactive with GPX.
研究了缺硒对暴露于各种外源性脂质氢过氧化物的小鼠L1210细胞活力的影响。在无添加硒的1%血清中培养超过1周的细胞（硒缺乏细胞[Se(-)细胞]）的硒过氧化物酶活性不到硒充足对照细胞[Se(+)细胞]或硒补充对应细胞[Se(-/+）细胞]活性的10%。所检测的酶为经典谷胱甘肽过氧化物酶（GPX）和磷脂氢过氧化物谷胱甘肽过氧化物酶（PHGPX）。Se(-)细胞过氧化氢酶活性出现代偿性增加。染料排斥和克隆存活试验表明，Se(-)和Se(+)细胞对脂质体形式的光化学产生的磷脂氢过氧化物相对不敏感。然而，两种细胞类型对脂质体胆固醇氢过氧化物均敏感，例如7-氢过氧胆固醇（7-OOH），Se(-)细胞比Se(+)细胞更敏感（半数致死剂量约为10μM）（Se(+)细胞半数致死剂量约为75μM）。相比之下，在相当的浓度范围内，7-羟基胆固醇对Se(-)和Se(+)细胞的毒性极小。去铁胺和丁基化羟基甲苯可抑制7-OOH对细胞的杀伤作用，表明涉及铁介导的自由基反应。通过显示用谷胱甘肽合成抑制剂丁硫氨酸亚砜胺处理后Se(+)细胞对7-OOH更敏感，证实了谷胱甘肽在细胞保护中的作用。7-OOH的细胞解毒作用暂时归因于PHGPX而非GPX，因为在无细胞体系中发现7-OOH和其他胆固醇氢过氧化物是PHGPX的良好底物，但与GPX无反应。
