Alqahtani Mohammed A, El-Ghiaty Mahmoud A, El-Mahrouk Sara R, El-Kadi Ayman O S
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada.
Curr Res Toxicol. 2023 Sep 17;5:100126. doi: 10.1016/j.crtox.2023.100126. eCollection 2023.
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 gene and also the aryl hydrocarbon receptor (AHR) is another 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 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 siRNA reduced the MeHg-induced NQO1 protein expression by 60%. In conclusion, our findings provide evidence supporting the hypothesis that MeHg upregulates the gene through a transcriptional mechanism at least in part via a NRF2-dependent mechanism.
通过NAD(P)H:醌氧化还原酶（NQO1）对醌进行解毒是维持细胞内稳态的关键机制。接触重金属，特别是甲基汞（MeHg），会诱导包括NQO1在内的几种抗氧化酶。已知核因子红细胞2相关因子2（NRF2）可调节基因表达，芳烃受体（AHR）也是另一种基因调节因子。这种共同调节促使我们研究在MeHg暴露后，哪个转录因子（NRF2或AHR）协调NQO1表达的调节。因此，我们通过将Hepa-1c1c7细胞暴露于几种浓度的MeHg，并添加或不添加NQO1诱导剂DL-萝卜硫素（SUL）和2,3,7,8-四氯二苯并对二恶英（TCDD），研究了MeHg如何调节NQO1表达水平。我们发现，MeHg以时间和剂量依赖性方式上调mRNA表达。此外，无论有无诱导剂SUL或TCDD，MeHg均在所有表达水平上增加NQO1。此外，MeHg介导的NQO1表达增加与NRF2蛋白核定位的同时增加平行，但与AHR无关。从机制上讲，MeHg暴露后抗氧化反应元件驱动的报告基因活性增加了215%。此外，用NRF2 siRNA转染Hepa-1c1c7可使MeHg诱导的NQO1蛋白表达降低60%。总之，我们的研究结果提供了证据支持以下假设：MeHg至少部分通过NRF2依赖性机制，通过转录机制上调NQO1基因。
