Metabolism of Selenite in Human Lung Cancer Cells: X-Ray Absorption and Fluorescence Studies

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• 作者：Claire M. Weekley ; Jade B. Aitken ; Stefan Vogt ; Lydia A. Finney ; David J. Paterson ; Martin D. de Jonge ; Daryl L. Howard ; Paul K. Witting ; Ian F. Musgrave ; Hugh H. Harris
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：November 16, 2011
• 年：2011
• 卷：133
• 期：45
• 页码：18272-18279
• 全文大小：1012K
• 年卷期：v.133,no.45(November 16, 2011)
• ISSN：1520-5126

文摘

Selenite is an inorganic form of selenium that has a cytotoxic effect against several human cancer cell lines: one or more selenite metabolites are considered to be responsible for its toxicity. X-ray absorption spectroscopy was used to monitor Se speciation in A549 human lung cancer cells incubated with selenite over 72 h. As anticipated, selenodiglutathione and elemental Se both comprised a large proportion of Se in the cells between 4 and 72 h after treatment, which is in accordance with the reductive metabolism of selenite in the presence of glutathione and glutathione reductase/NADPH system. Selenocystine was also present in the cells but was only detected as a significant component between 24 and 48 h concomitant with a decrease in the proportion of selenocysteine and the viability of the cells. The change in speciation from the selenol, selenocysteine, to the diselenide, selenocystine, is indicative of a change in the redox status of the cells to a more oxidizing environment, likely brought about by metabolites of selenite. X-ray fluorescence microscopy of single cells treated with selenite for 24 h revealed a punctate distribution of Se in the cytoplasm. The accumulation of Se was associated with a greater than 2-fold increase in Cu, which was colocalized with Se. Selenium K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy revealed Se鈥揝e and Se鈥揝 bonding, but not Se鈥揅u bonding, despite the spatial association of Se and Cu. Microprobe X-ray absorption near-edge structure spectroscopy (渭-XANES) showed that the highly localized Se species was mostly elemental Se.