首页> 外文期刊>The Journal of Nutritional Biochemistry >Superoxide dictates the mode of U937 cell ascorbic acid uptake and prevents the enhancing effects of the vitamin to otherwise nontoxic levels of reactive oxygenitrogen species.
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Superoxide dictates the mode of U937 cell ascorbic acid uptake and prevents the enhancing effects of the vitamin to otherwise nontoxic levels of reactive oxygenitrogen species.

机译:超氧化物决定了U937细胞抗坏血酸的吸收方式,并阻止了维生素对活性氧/氮物质无毒水平的增强作用。

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Exposure of U937 cells to low micromolar levels of ascorbic acid or dehydroascorbic acid, while resulting in identical ascorbic acid accumulation, is unexpectedly associated with remarkably different responses to exogenous oxidants. We observed that otherwise nontoxic levels of hydrogen peroxide, tert-butylhydroperoxide or peroxynitrite promote toxicity in cells preloaded with ascorbic acid, whereas hardly any effect was detected in cells pretreated with dehydroascorbic acid. Further experiments performed with peroxynitrite in cells preloaded with ascorbic acid provided evidence for a very rapid nonapoptotic death, preceded by early Bax mitochondrial translocation and by mitochondrial permeability transition. The notion that conversion of extracellular ascorbic acid to dehydroascorbic acid prevents the enhancing effects on oxidant toxicity and nevertheless preserves the net amount of vitamin C accumulated was also established using ascorbate oxidase as well as various sources of superoxide, namely, xanthine/xanthine oxidase or ATP-driven NADPH oxidase activation. These findings suggest that superoxide-dependent conversion of extracellular ascorbic acid to dehydroascorbic acid represents an important component of the overall survival strategy of some cell types to reactive oxygenitrogen species. All rights reserved, Elsevier.
机译:U937细胞暴露于低微摩尔水平的抗坏血酸或脱氢抗坏血酸,导致相同的抗坏血酸积累,却出乎意料地与对外源氧化剂的反应明显不同。我们观察到,否则无毒水平的过氧化氢,叔丁基过氧化氢或过氧亚硝酸盐会在预装有抗坏血酸的细胞中促进毒性,而在经脱氢抗坏血酸预处理的细胞中几乎没有发现任何作用。用过氧亚硝酸盐在预装有抗坏血酸的细胞中进行的进一步实验提供了非常迅速的非凋亡死亡的证据,随后是早期Bax线粒体易位和线粒体通透性转变。还使用抗坏血酸氧化酶以及各种超氧化物源(即黄嘌呤/黄嘌呤氧化酶或ATP)建立了将细胞外抗坏血酸转化为脱氢抗坏血酸可防止增强氧化剂毒性的观点,但仍保留了积累的维生素C的净量这一观点。驱动的NADPH氧化酶激活。这些发现表明,细胞外抗坏血酸至脱氢抗坏血酸的超氧化物依赖性转化代表了某些细胞类型向活性氧/氮物种的总体存活策略的重要组成部分。保留所有权利,Elsevier。

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