Thomas J P, Geiger P G, Girotti A W
Department of Biochemistry, Medical College of Wisconsin, Milwaukee 53226.
J Lipid Res. 1993 Mar;34(3):479-90.
Oxidized low density lipoprotein (LDLox) is believed to be an important contributor to endothelial cytodamage and atherogenesis. The purpose of this study was to examine the role of glutathione (GSH) and GSH-dependent selenoperoxidases in cytoprotection against the damaging effects of LDLox. When irradiated in the presence of a phthalocyanine sensitizing dye, human LDL accumulated chromatographically detectable and iodometrically measurable lipid hydroperoxides (LOOHs). Photogenerated LDLox caused lethal damage to bovine aortic endothelial (BAE) cells in vitro, as determined by lactate dehydrogenase release and inhibition of thiazolyl blue reduction. When depleted of GSH by buthionine sulfoximine treatment, BAE cells became more sensitive to LDLox. Cells grown in 2% serum/DME-HAM's F-12 medium without added selenium [Se(-) cells] exhibited far lower GSH-peroxidase and phospholipid hydroperoxide GSH-peroxidase activities than selenium-supplemented controls [Se(+) cells], and were much more sensitive to oxidative injury induced by t-butyl hydroperoxide, liposomal cholesterol hydroperoxides, and LDLox. Preincubation of LDLox with GSH and Ebselen (a selenoperoxidase mimetic) resulted in a dramatic reduction in both LOOH content and cytotoxicity. Moreover, treating Se(-) cells themselves with Ebselen substantially restored their resistance to LDLox-induced damage. LDLox toxicity to Se(-) cells was strongly inhibited by desferrioxamine and stimulated by ferric-8-hydroxyquinoline (a lipophilic chelate), indicating that iron is an active participant in oxidative damage. These results demonstrate that the GSH-dependent selenoperoxidase(s) play(s) an important role in cellular defense against oxidized low density lipoprotein, presumably by detoxifying lipid hydroperoxides and thereby preventing their iron-catalyzed decomposition to damaging free radical intermediates.
氧化型低密度脂蛋白（LDLox）被认为是导致内皮细胞损伤和动脉粥样硬化形成的重要因素。本研究的目的是探讨谷胱甘肽（GSH）和GSH依赖性硒过氧化物酶在细胞保护中对LDLox损伤作用的影响。当在酞菁敏化染料存在下进行辐照时，人低密度脂蛋白会积累可通过色谱检测和碘量法测量的脂质氢过氧化物（LOOHs）。光生成的LDLox在体外对牛主动脉内皮（BAE）细胞造成致命损伤，这可通过乳酸脱氢酶释放和噻唑蓝还原抑制来确定。用丁硫氨酸亚砜胺处理使BAE细胞内的GSH耗竭后，细胞对LDLox变得更加敏感。在不添加硒的2%血清/DME-HAM's F-12培养基中培养的细胞[硒缺乏（Se(-)）细胞]，其谷胱甘肽过氧化物酶和磷脂氢过氧化物谷胱甘肽过氧化物酶活性远低于补充硒的对照细胞[硒充足（Se(+)）细胞]，并且对叔丁基氢过氧化物、脂质体胆固醇氢过氧化物和LDLox诱导的氧化损伤更为敏感。LDLox与GSH和依布硒啉（一种硒过氧化物酶模拟物）预孵育后，LOOH含量和细胞毒性均显著降低。此外，用依布硒啉处理Se(-)细胞本身可显著恢复其对LDLox诱导损伤的抗性。去铁胺强烈抑制LDLox对Se(-)细胞的毒性，而亲脂性螯合剂铁-8-羟基喹啉则刺激该毒性，这表明铁是氧化损伤的积极参与者。这些结果表明，GSH依赖性硒过氧化物酶在细胞防御氧化型低密度脂蛋白中起重要作用，可能是通过解毒脂质氢过氧化物，从而防止其铁催化分解为具有损伤性的自由基中间体。
