Ascorbate is a pro-oxidant in chromium-treated human lung cells
Ascorbate is a pro-oxidant in chromium-treated human lung cells
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DOI：
10.1016/j.mrgentox.2006.06.014
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发表时间：
2006-11-07
影响因子：
1.9
通讯作者：
Sugden, Kent D.
中科院分区：
文献类型：
--
作者：
Martin, Brooke D.;Schoenhard, J. Andy;Sugden, Kent D.
本研究使用人类A549肺细胞系作为评估铬毒性和诱变的模型，因为吸入这种金属会引起一种流行病学，表明肺是铬毒性的靶器官。六价铬被认为是铬的致癌形式，然而，它必须在吸收到细胞后被还原激活，以便与细胞内的成分发生反应。我们已经证实，荧光染料二氯荧光素(DCF)和二氢罗丹明是铬还原活化的有效指示剂，是细胞内高活性铬物种(RCS)形成的敏感手段。为了研究两种常见的细胞内还原剂谷胱甘肽和抗坏血酸(维生素C)在细胞内生成RCS中的作用，我们通过使用丁硫氨酸亚磺胺(BSO)或在培养基中添加抗坏血酸来调节它们在细胞内的水平。我们发现，该癌细胞中高水平的谷胱甘肽显著降低了内源性氧化水平，并且，通过减少细胞内谷胱甘肽，BSO不仅产生了更高的本底水平的内源性细胞内氧化，而且铬刺激的氧化也显著增加。与其被称为抗氧化剂相反，抗坏血酸在铬处理后激发了强烈的促氧化反应，这种促氧化反应明显，与细胞中谷胱甘肽的水平无关。根据这些结果，我们得出结论，在铬处理的细胞中，抗坏血酸起到了促氧化剂的作用。(C)2006爱思唯尔B.V.保留所有权利。
The human A549 lung cell line is used in this study as a model to evaluate chromium toxicity and mutagenesis since inhalation exposure of this metal gives rise to an epidemiology that indicates the lung as a target organ of chromium toxicity. Hexavalent chromium is considered the carcinogenic form of chromium, however it must be reductively activated following uptake into cells in order to react with intracellular constituents. We have previously established that the fluorescent dyes, dichlorofluorescein (DCF) and dihydrorhodamine, are effective indicators of the reductive activation of chromium and are sensitive measures of the formation of highly reactive chromium species (RCS) intracellularly. In order to examine the role of the two common intracellular reductants, glutathione and ascorbic acid (Vitamin C) in generating RCS intracellularly, we manipulated their intracellular levels through the use of buthionine sulfoximine (BSO) or by the addition of ascorbate into the culture media. We found that the high levels of glutathione in this cancer cell line lowered endogenous oxidation levels markedly, and that, by decreasing intracellular glutathione, BSO not only generated a higher background level of endogenous intracellular oxidation but the chromium-stimulated oxidation also increased markedly. Contrary to it appellation as an anti-oxidant, ascorbic acid stimulated a strong pro-oxidant response upon chromium treatment and this pro-oxidant response was evident regardless of the levels of glutathione in the cells. Based on these results, we conclude that ascorbic acid acts as a pro-oxidant in chromium-treated cells. (c) 2006 Elsevier B.V. All rights reserved.