Bourdonnay Emilie, Morzadec Claudie, Fardel Olivier, Vernhet Laurent
Inserm U620, Group Toxicité des contaminants de l'environnement, 2 avenue du Pr. Léon Bernard, 35043 Rennes, France.
J Cell Biochem. 2009 Jun 1;107(3):537-47. doi: 10.1002/jcb.22155.
Inorganic arsenic is an environmental contaminant toxic for key immune cells. We recently reported that low micromolar concentrations of arsenic trioxide (As(2)O(3)) alter functions and differentiation gene program of human macrophages. Particularly, prolonged treatment with As(2)O(3) concomitantly reverses expression of a macrophage-specific gene subset and triggers reactive oxygen species (ROS) production, suggesting a possible role of cell stress in As(2)O(3) gene effects. This study was thus designed to determine whether redox-sensitive signaling pathways could mediate gene expression in metalloid-exposed macrophages. Our results show that As(2)O(3)-dependent alterations of stress (HMOX1 and GCLM) and macrophage-specific (MMP9, CCL22, and CXCL2) gene expression are not mediated by ROS or related signaling pathways. Notably, As(2)O(3) alters neither activity of the redox-sensitive transcription factor Sp1 nor that of AP-1 or NF-kappaB. In contrast, N-acetylcysteine, a potent cysteine reductive compound, significantly prevents up-regulation of HMOX1, GCLM, and CXCL2 genes, and repression of MMP9 and CCL22 genes induced by As(2)O(3). In addition, we demonstrate that As(2)O(3) markedly alters nuclear levels of Nrf2 and Bach1, two redox-sensitive regulators of stress genes, and represses expression of the transcription factor EGR2 which is involved in mouse macrophage differentiation; such effects are reduced by N-acetylcysteine. Finally, we report that genetic invalidation of EGR2 gene partially mimics metalloid effects; it significantly represses CCL22 gene expression and weakly induces that of CXCL2. In conclusion, our results demonstrate that As(2)O(3) alters macrophage gene expression through redox-sensitive signaling pathways unrelated to ROS production and reveal the transcription factor EGR2 as a new molecular target of arsenic.
无机砷是一种对关键免疫细胞有毒的环境污染物。我们最近报道，低微摩尔浓度的三氧化二砷（As₂O₃）会改变人类巨噬细胞的功能和分化基因程序。特别是，As₂O₃的长期处理会同时逆转巨噬细胞特异性基因子集的表达并触发活性氧（ROS）的产生，这表明细胞应激可能在As₂O₃的基因效应中起作用。因此，本研究旨在确定氧化还原敏感信号通路是否能介导金属类物质暴露的巨噬细胞中的基因表达。我们的结果表明，As₂O₃对应激（HMOX1和GCLM）和巨噬细胞特异性（MMP9、CCL22和CXCL2）基因表达的依赖性改变并非由ROS或相关信号通路介导。值得注意的是，As₂O₃既不改变氧化还原敏感转录因子Sp1的活性，也不改变AP - 1或NF - κB的活性。相反，N - 乙酰半胱氨酸是一种有效的半胱氨酸还原化合物，它能显著阻止As₂O₃诱导的HMOX1、GCLM和CXCL2基因的上调以及MMP9和CCL22基因的抑制。此外，我们证明As₂O₃显著改变了应激基因的两个氧化还原敏感调节因子Nrf2和Bach1的核水平，并抑制了参与小鼠巨噬细胞分化的转录因子EGR2的表达；N - 乙酰半胱氨酸可降低这种效应。最后，我们报告EGR2基因的基因敲除部分模拟了金属类物质的效应；它显著抑制CCL22基因的表达，并微弱诱导CXCL2基因的表达。总之，我们的结果表明，As₂O₃通过与ROS产生无关的氧化还原敏感信号通路改变巨噬细胞基因表达，并揭示转录因子EGR2是砷的一个新分子靶点。
