VanDenBerg Kelly R, Freeborn Robert A, Liu Sheng, Kennedy Rebekah C, Zagorski Joseph W, Rockwell Cheryl E
Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan, United States of America.
Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan, United States of America.
PLoS One. 2017 Oct 19;12(10):e0185579. doi: 10.1371/journal.pone.0185579. eCollection 2017.
Nuclear factor erythroid 2-related factor 2 (Nrf2) is a stress-activated transcription factor that induces a variety of cytoprotective genes. Nrf2 also mediates immunosuppressive effects in multiple inflammatory models. Upon activation, Nrf2 dissociates from its repressor protein, Keap1, and translocates to the nucleus where it induces Nrf2 target genes. The Nrf2-Keap1 interaction is disrupted by the environmental toxicant and chemotherapeutic agent arsenic trioxide (ATO). The purpose of the present study was to determine the effects of ATO on early events of T cell activation and the role of Nrf2 in those effects. The Nrf2 target genes Hmox-1, Nqo-1, and Gclc were all upregulated by ATO (1-2 μM) in splenocytes derived from wild-type, but not Nrf2-null, mice, suggesting that Nrf2 is activated by ATO in splenocytes. ATO also inhibited IFNγ, IL-2, and GM-CSF mRNA and protein production in wild-type splenocytes activated with the T cell activator, anti-CD3/anti-CD28. However, ATO also decreased production of these cytokines in activated splenocytes from Nrf2-null mice, suggesting the inhibition is independent of Nrf2. Interestingly, ATO inhibited TNFα protein secretion, but not mRNA expression, in activated splenocytes suggesting the inhibition is due to post-transcriptional modification. In addition, c-Fos DNA binding was significantly diminished by ATO in wild-type and Nrf2-null splenocytes activated with anti-CD3/anti-CD28, consistent with the observed inhibition of cytokine production by ATO. Collectively, this study suggests that although ATO activates Nrf2 in splenocytes, inhibition of early T cell cytokine production by ATO occurs independently of Nrf2 and may instead be due to impaired AP-1 DNA binding.
核因子红细胞2相关因子2（Nrf2）是一种应激激活的转录因子，可诱导多种细胞保护基因。Nrf2在多种炎症模型中也介导免疫抑制作用。激活后，Nrf2与其抑制蛋白Keap1解离，并转移至细胞核，在细胞核中诱导Nrf2靶基因。环境毒物和化疗药物三氧化二砷（ATO）可破坏Nrf2-Keap1相互作用。本研究的目的是确定ATO对T细胞激活早期事件的影响以及Nrf2在这些影响中的作用。在野生型而非Nrf2基因敲除小鼠的脾细胞中，ATO（1-2μM）上调了Nrf2靶基因Hmox-1、Nqo-1和Gclc，这表明ATO在脾细胞中激活了Nrf2。ATO还抑制了用T细胞激活剂抗CD3/抗CD28激活的野生型脾细胞中IFNγ、IL-2和GM-CSF的mRNA和蛋白质产生。然而，ATO也降低了Nrf2基因敲除小鼠激活的脾细胞中这些细胞因子的产生，这表明这种抑制作用与Nrf2无关。有趣的是，ATO抑制了激活的脾细胞中TNFα蛋白的分泌，但不影响其mRNA表达，这表明这种抑制作用是由于转录后修饰。此外，在抗CD3/抗CD28激活的野生型和Nrf2基因敲除脾细胞中，ATO显著降低了c-Fos与DNA的结合，这与观察到的ATO对细胞因子产生的抑制作用一致。总的来说，这项研究表明，尽管ATO在脾细胞中激活了Nrf2，但ATO对早期T细胞细胞因子产生的抑制作用独立于Nrf2发生，可能是由于AP-1与DNA结合受损所致。
