Environment and Non-Communicable Disease Research Center, Key Laboratory of Arsenic-related Biological Effects and Prevention and Treatment in Liaoning Province, School of Public Health, China Medical University, Shenyang, PR China; Key Laboratory of Health Ministry for Congenital Malformation, Shengjing Hospital, China Medical University, Shenyang, PR China.
Environment and Non-Communicable Disease Research Center, Key Laboratory of Arsenic-related Biological Effects and Prevention and Treatment in Liaoning Province, School of Public Health, China Medical University, Shenyang, PR China.
Toxicol Appl Pharmacol. 2021 Feb 15;413:115404. doi: 10.1016/j.taap.2021.115404. Epub 2021 Jan 9.
Arsenic is a ubiquitous metalloid element present in both inorganic and organic forms in the environment. The liver is considered to be a primary organ of arsenic biotransformation and methylation, as well as the main target of arsenic toxicity. Studies have confirmed that Chang human hepatocytes have an efficient arsenic methylating capacity. Our previous studies have proven that arsenite activates nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in hepatocytes. This study aimed to explore the activation of the Nrf2 pathway upon treatment of arsenic in various forms, including inorganic and organic arsenic. Our results showed that inorganic arsenic-both AsO and NaHAsO significantly induced the expression of Nrf2 protein and mRNA, enhanced the transcription activity of Nrf2, and induced the expression of downstream target genes. These results confirmed the inorganic arsenic-induced Nrf2 pathway activation in hepatocytes. Although all arsenic chemicals used in the study induced Nrf2 protein accumulation, the organic arsenic CHAsO did not affect the expression of Nrf2 downstream genes which were elevated by inorganic arsenic exposures. Through qRT-PCR and Nrf2 luciferase reporter assays, we further confirmed that CHAsO neither increased Nrf2 mRNA level nor activated the Nrf2 transcription activity. Mechanistically, our results confirmed inorganic arsenic-induced both the nuclear import of Nrf2 and export of Bach1 (BTB and CNC homology 1), which is an Nrf2 transcriptional repressor, while organic arsenic only induced Nrf2 translocation. The unique pattern of Nrf2 regulation by organic arsenic underlines the critical role of Nrf2 and Bach1 in the arsenic toxicology.
砷是一种普遍存在的类金属元素，以无机和有机形式存在于环境中。肝脏被认为是砷生物转化和甲基化的主要器官，也是砷毒性的主要靶器官。研究证实，Chang 人肝细胞具有高效的砷甲基化能力。我们之前的研究已经证明，亚砷酸盐在肝细胞中激活核因子红细胞 2 相关因子 2（Nrf2）通路。本研究旨在探讨不同形式的砷（包括无机砷和有机砷）处理对 Nrf2 通路的激活作用。我们的结果表明，无机砷——AsO 和 NaHAsO——均显著诱导 Nrf2 蛋白和 mRNA 的表达，增强 Nrf2 的转录活性，并诱导下游靶基因的表达。这些结果证实了无机砷诱导肝细胞中 Nrf2 通路的激活。虽然研究中使用的所有砷化学物质都诱导了 Nrf2 蛋白的积累，但有机砷 CHAsO 并未影响无机砷暴露引起的 Nrf2 下游基因的表达。通过 qRT-PCR 和 Nrf2 荧光素酶报告基因测定，我们进一步证实 CHAsO 既不增加 Nrf2 mRNA 水平，也不激活 Nrf2 转录活性。从机制上讲，我们的结果证实，无机砷诱导 Nrf2 的核内输入和 Bach1（BTB 和 CNC 同源性 1）的核输出，Bach1 是 Nrf2 的转录抑制剂，而有机砷仅诱导 Nrf2 易位。有机砷对 Nrf2 的独特调控模式突出了 Nrf2 和 Bach1 在砷毒理学中的关键作用。
