Weekley Claire M, Jeong Gloria, Tierney Michael E, Hossain Farjaneh, Maw Aung Min, Shanu Anu, Harris Hugh H, Witting Paul K
School of Chemistry and Physics, The University of Adelaide, Adelaide, SA, 5005, Australia.
J Biol Inorg Chem. 2014 Aug;19(6):813-28. doi: 10.1007/s00775-014-1113-x. Epub 2014 Feb 15.
Selenite may exert its cytotoxic effects against cancer cells via the generation of reactive oxygen species (ROS). We investigated sources of, and the cellular response to, superoxide radical anion (O2 (·-)) generated in human A549 lung cancer cells after treatment with selenite. A temporal delay was observed between selenite treatment and increases in O2 (·-) production and biomarkers of apoptosis/necrosis, indicating that the reduction of selenite by the glutathione reductase/NADPH system (yielding O2 (·-)) is a minor contributor to ROS production under these conditions. By contrast, mitochondrial and NADPH oxidase O2 (·-) generation were the major contributors. Treatment with a ROS scavenger [poly(ethylene glycol)-conjugated superoxide dismutase (SOD) or sodium 4,5-dihydroxybenzene-1,3-disulfonate] 20 h after the initial selenite treatment inhibited both ROS generation and apoptosis determined at 24 h. In addition, SOD1 was selectively upregulated and its perinuclear cytoplasmic distribution was colocalised with the cellular distribution of selenium. Interestingly, messenger RNA for manganese superoxide dismutase, catalase, inducible haem oxygenase 1 and glutathione peroxidase either remained unchanged or showed a delayed response to selenite treatment. Colocalisation of Cu and Se in these cells (Weekley et al. in J. Am. Chem. Soc. 133:18272-18279, 2011) potentially results from the formation of a Cu-Se species, as indicated by Cu K-edge extended X-ray absorption fine structure spectra. Overall, SOD1 is upregulated in response to selenite-mediated ROS generation, and this likely leads to an accumulation of toxic hydrogen peroxide that is temporally related to decreased cancer cell viability. Increased expression of SOD1 gene/protein coupled with formation of a Cu-Se species may explain the colocalisation of Cu and Se observed in these cells.
亚硒酸盐可能通过产生活性氧（ROS）对癌细胞发挥细胞毒性作用。我们研究了亚硒酸盐处理后人A549肺癌细胞中产生的超氧阴离子自由基（O2(·-)）的来源及其细胞反应。在亚硒酸盐处理与O2(·-)产量增加以及凋亡/坏死生物标志物之间观察到时间延迟，这表明在这些条件下，谷胱甘肽还原酶/NADPH系统将亚硒酸盐还原（产生O2(·-)）对ROS产生的贡献较小。相比之下，线粒体和NADPH氧化酶产生的O2(·-)是主要贡献者。在初始亚硒酸盐处理20小时后用ROS清除剂[聚（乙二醇）缀合的超氧化物歧化酶（SOD）或4,5-二羟基苯-1,3-二磺酸钠]处理，可抑制24小时时测定的ROS产生和凋亡。此外，SOD1被选择性上调，其核周细胞质分布与硒的细胞分布共定位。有趣的是，锰超氧化物歧化酶、过氧化氢酶、诱导型血红素加氧酶1和谷胱甘肽过氧化物酶的信使RNA要么保持不变，要么对亚硒酸盐处理表现出延迟反应。这些细胞中铜和硒的共定位（Weekley等人，《美国化学会志》133:18272 - 18279，2011）可能是由于形成了铜 - 硒物种，如铜K边扩展X射线吸收精细结构光谱所示。总体而言，SOD1响应亚硒酸盐介导的ROS产生而上调，这可能导致有毒过氧化氢的积累，这在时间上与癌细胞活力降低相关。SOD1基因/蛋白表达增加以及铜 - 硒物种的形成可能解释了在这些细胞中观察到的铜和硒的共定位。
