Huang Zhi, Li Jun, Zhang Sichun, Zhang Xinrong
Department of Chemistry, Key Laboratory for Atomic and Molecular Nanosciences of Education Ministry, Tsinghua University, 100084 Beijing, PR China.
Toxicol Lett. 2009 Jun 1;187(2):69-76. doi: 10.1016/j.toxlet.2009.01.024. Epub 2009 Jan 30.
At least 25 selenoproteins in humans and 24 homologues in rodents have been identified. They play important roles in antioxidation, redox regulation and detoxification. The modulation of the expression of selenoproteins by inorganic arsenic (iAs) exposure may highlight the molecular mechanism for the arsenic toxicity. To investigate the effects of iAs exposure on the expression of selenoproteins, we determined how addition of iAs to culture medium affected all known selenoproteins in the mouse embryonic stem (ES) cells. Separated groups of ES cells were treated with arsenite (iAsIII) (0.25-0.5microM), arsenate (iAsV) (1.0-2.0microM) and co-treatment with sodium selenite (SeIV) (0.5microM). The mRNA levels of all selenoproteins were detected by real time quantitative PCR. The up-regulated selenoproteins were confirmed by immunoblotting analysis and enzymatic activity detection. Results showed that CGR8 cells treated with iAsIII (0.25-0.5microM) and iAsV (2.0microM) displayed significant increases of cellular reactive oxygen species (ROS) generation and nuclear accumulation of the transcription factor NF-E2-related factor 2 (Nrf2). Treatments of iAsIII (0.5microM) or iAsV (2.0microM) for 24h caused significant increases in the expression of the antioxidant selenoproteins (Gpx1, Gpx4, and Tr1), whereas led to significant decreases in the mRNA levels of selenoprotein H and some endoplasmic reticulum (ER) located selenoproteins (15-Sep, SelK, SelM, and SelS). Additionally, supplement of SeIV (0.5microM) could restore most of the down-regulated selenoproteins. These results suggested that iAs exposure modulated not only the antioxidant selenoproteins but also the ER stress associated selenoproteins. Further studies are required to clarify whether these modulated selenoproteins genes are targets for selenium supplement in the defense against the toxicity of iAs.
在人类中已鉴定出至少25种硒蛋白，在啮齿动物中鉴定出24种同源物。它们在抗氧化、氧化还原调节和解毒中发挥重要作用。无机砷（iAs）暴露对硒蛋白表达的调节可能揭示砷毒性的分子机制。为了研究iAs暴露对硒蛋白表达的影响，我们确定了向培养基中添加iAs如何影响小鼠胚胎干细胞（ES）中所有已知的硒蛋白。将分离的ES细胞组分别用亚砷酸盐（iAsIII）（0.25 - 0.5微摩尔）、砷酸盐（iAsV）（1.0 - 2.0微摩尔）处理，并与亚硒酸钠（SeIV）（0.5微摩尔）共同处理。通过实时定量PCR检测所有硒蛋白的mRNA水平。通过免疫印迹分析和酶活性检测对上调的硒蛋白进行确认。结果显示，用iAsIII（0.25 - 0.5微摩尔）和iAsV（2.0微摩尔）处理的CGR8细胞表现出细胞活性氧（ROS）生成显著增加以及转录因子NF-E2相关因子2（Nrf2）的核积累。用iAsIII（0.5微摩尔）或iAsV（2.0微摩尔）处理24小时导致抗氧化硒蛋白（Gpx1、Gpx4和Tr1）的表达显著增加，而硒蛋白H和一些内质网（ER）定位的硒蛋白（15-Sep、SelK、SelM和SelS）的mRNA水平显著降低。此外，补充SeIV（0.5微摩尔）可以恢复大多数下调的硒蛋白。这些结果表明，iAs暴露不仅调节抗氧化硒蛋白，还调节与ER应激相关的硒蛋白。需要进一步研究以阐明这些被调节的硒蛋白基因是否是硒补充剂抵御iAs毒性的靶点。
