Yan L, Spallholz J E
Center for Food and Nutrition, Texas Tech University, Lubbock 79409.
Biochem Pharmacol. 1993 Jan 26;45(2):429-37.
Sodium selenite, sodium selenate, selenocystine and selenomethionine were tested for their abilities to generate superoxide by the oxidation of glutathione and other thiols in the absence and presence of cells of the human mammary tumor cell line HTB123/DU4475. Free radical generation was measured by lucigenin- or luminol-amplified chemiluminescence. In the absence of tumor cells, lucigenin-dependent chemiluminescence was observed from the reaction of selenite with the thiols glutathione, 2-mercaptoethanol and L-cysteine, but not with oxidized glutathione. Superoxide dismutase, catalase, and glutathione peroxidase all suppressed the observed chemiluminescence; but when these enzymes were heat inactivated they had little suppressive inhibition on chemiluminescence. Luminol-dependent chemiluminescence from the reaction of selenite with glutathione was much less than that observed by lucigenin-amplified chemiluminescence. In the presence of the HTB123/DU4475 mammary tumor cells, lucigenin-dependent chemiluminescence was observed from the reactions of selenite and selenocystine with glutathione which were 5 and 23 times greater than their respective reactions with glutathione in the absence of tumor cells. The enhanced chemiluminescence generated by selenite and selenocystine in the presence of the tumor cells was also suppressed by superoxide dismutase, catalase and glutathione peroxidase. These data suggest that a free radical, the superoxide anion (O2-), and H2O2 are produced from the reaction of selenite and selenocystine with glutathione. These free radical reactions may account for the toxicity of selenite and selenocystine in vitro in comparison to a near absence of acute tumor cell toxicity and superoxide generation by selenate and selenomethionine with thiols. Enhanced chemiluminescence in the presence of tumor cells may be an expression of cellular selenium metabolism and the capability of cells to form selenium metabolites that more easily oxidize glutathione and other thiols producing reactive free radicals and peroxides.
在不存在和存在人乳腺肿瘤细胞系HTB123/DU4475细胞的情况下，测试了亚硒酸钠、硒酸钠、硒代胱氨酸和硒代蛋氨酸通过氧化谷胱甘肽和其他硫醇来产生超氧化物的能力。通过光泽精或鲁米诺放大的化学发光来测量自由基的产生。在不存在肿瘤细胞的情况下，观察到亚硒酸盐与硫醇谷胱甘肽、2-巯基乙醇和L-半胱氨酸反应产生的依赖于光泽精的化学发光，但与氧化型谷胱甘肽反应则未观察到。超氧化物歧化酶、过氧化氢酶和谷胱甘肽过氧化物酶均抑制了观察到的化学发光；但当这些酶被热灭活时，它们对化学发光的抑制作用很小。亚硒酸盐与谷胱甘肽反应产生的依赖于鲁米诺的化学发光远低于光泽精放大的化学发光所观察到的。在存在HTB123/DU4475乳腺肿瘤细胞的情况下，观察到亚硒酸盐和硒代胱氨酸与谷胱甘肽反应产生的依赖于光泽精的化学发光，分别比它们在不存在肿瘤细胞时与谷胱甘肽的反应大5倍和23倍。超氧化物歧化酶、过氧化氢酶和谷胱甘肽过氧化物酶也抑制了在肿瘤细胞存在下亚硒酸盐和硒代胱氨酸产生的增强的化学发光。这些数据表明，亚硒酸盐和硒代胱氨酸与谷胱甘肽反应会产生自由基超氧阴离子（O2-）和H2O2。与硒酸盐和硒代蛋氨酸与硫醇几乎不产生急性肿瘤细胞毒性和超氧化物相比，这些自由基反应可能解释了亚硒酸盐和硒代胱氨酸在体外的毒性。在肿瘤细胞存在下增强的化学发光可能是细胞硒代谢以及细胞形成更容易氧化谷胱甘肽和其他硫醇以产生活性自由基和过氧化物的硒代谢物能力的一种表现。
