Department of Environmental and Occupational Health, National Cheng Kung University Medical College, Tainan 701, Taiwan.
Arch Toxicol. 2012 Jun;86(6):879-96. doi: 10.1007/s00204-012-0845-z. Epub 2012 Apr 10.
Chronic arsenic exposure has been linked to an increased risk of vascular diseases. To clarify the molecular mechanisms through which arsenic causes injuries to blood vessels, we analyzed the effects of arsenic trioxide on the cytotoxicity, intracellular reactive oxygen species (ROS), the expression of related genes, and signaling pathways involved in the SVEC4-10 mouse endothelial cells. Arsenic dose-dependently caused SVEC4-10 cell death, which is completely inhibited by α-lipoic acid (LA), a thioreductant, but partially ameliorated by Tiron, a potent superoxide scavenger. The mRNA levels of heme oxygenase-1 (HO-1), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), and vascular endothelial growth factor (VEGF) were significantly increased by arsenic. The up-regulation of these can be blocked by LA instead of Tiron, suggesting ROS is not important in their increase. HO-1 competitive inhibitor zinc protoporphyrin improved the cytotoxicity of arsenic in an inverted-U dose-response curve, indicating the biphasic hormetic effect of HO-1. HO-1 siRNA decreased VEGF expression in response to arsenic. Arsenic exposure also enhanced NF-E2-related factor 2 (Nrf2) expression and increased activation of nuclear factor-κB (NF-κB). NF-κB inhibitor Bay 11-7082 reduced arsenic-mediated expression of HO-1 and IL-6. Selective blocking of the MAPK pathways with p38 inhibitor SB203580 significantly decreased arsenic-induced HO-1 and VEGF expression, while JNKs inhibitor SP600125 increased IL-6 expression. These results suggest that in arsenic-treated SVEC4-10 cells, HO-1 expression is mediated through Nrf2-, NF-κB-, and p38 MAPK-dependent signaling pathways and serves as an upstream regulator of VEGF. IL-6 expression is regulated by NF-κB and JNKs. In conclusion, oxidative stress may be associated with arsenic-induced cytotoxicity and endothelial gene up-regulation, but signaling transduction dominates the direct effects of ROS.
慢性砷暴露与血管疾病风险增加有关。为了阐明砷引起血管损伤的分子机制，我们分析了三氧化二砷对 SVEC4-10 小鼠内皮细胞的细胞毒性、细胞内活性氧（ROS）、相关基因表达和信号通路的影响。砷呈剂量依赖性地导致 SVEC4-10 细胞死亡，该作用可被硫醇还原剂 α-硫辛酸（LA）完全抑制，但可被强超氧化物清除剂 Tiron 部分缓解。砷显著增加血红素加氧酶-1（HO-1）、白细胞介素 6（IL-6）、单核细胞趋化蛋白-1（MCP-1）和血管内皮生长因子（VEGF）的 mRNA 水平。LA 而非 Tiron 可阻断这些基因的上调，表明 ROS 对其增加并不重要。HO-1 竞争抑制剂锌原卟啉 IX 以倒 U 型剂量反应曲线改善砷的细胞毒性，表明 HO-1 呈双相适应性反应效应。HO-1 siRNA 降低了砷刺激的 VEGF 表达。砷暴露还增强了核因子-E2 相关因子 2（Nrf2）的表达，并增加了核因子-κB（NF-κB）的激活。NF-κB 抑制剂 Bay 11-7082 降低了砷介导的 HO-1 和 IL-6 的表达。MAPK 途径的选择性阻断，p38 抑制剂 SB203580 显著降低了砷诱导的 HO-1 和 VEGF 表达，而 JNKs 抑制剂 SP600125 增加了 IL-6 的表达。这些结果表明，在砷处理的 SVEC4-10 细胞中，HO-1 的表达是通过 Nrf2、NF-κB 和 p38 MAPK 依赖性信号通路介导的，是 VEGF 的上游调节剂。IL-6 的表达受 NF-κB 和 JNKs 调控。总之，氧化应激可能与砷诱导的细胞毒性和内皮基因上调有关，但信号转导主导了 ROS 的直接作用。
