PDF(Pubmed)
Abstract：
The detoxification of quinones through NAD(P)H:quinone oxidoreductase (NQO1) is a crucial mechanism to maintain cellular homeostasis. The exposure to heavy metals, specifically methylmercury (MeHg), induces several antioxidant enzymes, including NQO1. The nuclear factor erythroid 2-related factor-2 (NRF2) is known to regulate the expression of Nqo1 gene and also the aryl hydrocarbon receptor (AHR) is another Nqo1 gene regulator. This co-regulation prompted us to investigate which transcription factor (NRF2 or AHR) orchestrates the regulation of NQO1 expression upon MeHg exposure. Therefore, we investigated how MeHg can modulate the level of NQO1 expression by exposing Hepa-1c1c7 cells to several concentrations of MeHg with and without the addition of NQO1 inducers, DL-sulforaphane (SUL) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We found that the mRNA expression of Nqo1 is up-regulated by MeHg in time- as well as dose-dependent fashions. Additionally, MeHg increased the NQO1 at all expression levels with and without the presence of its inducers, SUL or TCDD. Furthermore, the MeHg-mediated increase of NQO1 expression was in parallel with a concurrent increase in the nuclear localization of NRF2 protein, but not that of AHR. Mechanistically, the antioxidant response element-driven reporter gene activity was induced by 215% upon MeHg exposure. Also, transfecting Hepa-1c1c7 with Nrf2 siRNA reduced the MeHg-induced NQO1 protein expression by 60%. In conclusion, our findings provide evidence supporting the hypothesis that MeHg upregulates the Nqo1 gene through a transcriptional mechanism at least in part via a NRF2-dependent mechanism.
摘要：
通过NAD（P）H：醌氧化还原酶（NQO1）对醌进行解毒是维持细胞稳态的关键机制。接触重金属，特别是甲基汞(MeHg)，诱导几种抗氧化酶，包括NQO1。已知核因子红系2相关因子2（NRF2）调节Nqo1基因的表达，并且芳烃受体（AHR）是另一种Nqo1基因调节因子。这种共调促使我们研究哪种转录因子（NRF2或AHR）在暴露于甲基汞时协调NQO1表达的调节。因此,我们研究了MeHg如何通过将Hepa-1c1c7细胞暴露于有或没有添加NQO1诱导剂的几种浓度的MeHg来调节NQO1表达水平，DL-萝卜硫烷(SUL)和2,3,7,8-四氯二苯并-对二恶英(TCDD)。我们发现Nqo1的mRNA表达在时间和剂量依赖性方式上被MeHg上调。此外,在存在和不存在其诱导物的情况下，MeHg在所有表达水平上增加NQO1，SUL或TCDD。此外，MeHg介导的NQO1表达的增加与NRF2蛋白核定位的同时增加平行，但不是AHR的。机械上,抗氧化剂反应元件驱动的报告基因活性在甲基汞暴露后被诱导215%。此外，用Nrf2siRNA转染Hepa-1c1c7可将MeHg诱导的NQO1蛋白表达降低60%。总之,我们的发现提供了支持以下假设的证据:MeHg通过转录机制上调Nqo1基因,至少部分通过NRF2依赖性机制.
