Institute of Environmental Medicine, Karolinska Institutet, SE-171 77 Stockholm, Sweden; Department of Pharmacology and Toxicology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Fars 71345-1583, Iran.
Department of Pharmacology and Toxicology, School of Pharmacy, Shiraz University of Medical Sciences, Shiraz, Fars 71345-1583, Iran.
Chem Biol Interact. 2016 May 25;252:19-27. doi: 10.1016/j.cbi.2016.03.037. Epub 2016 Apr 1.
The aim of this study was to gain more information about the mechanisms that regulate expression of the aryl hydrocarbon receptor (AHR) target gene CYP1A1. Human hepatoma cells (HepG2 and Huh7) and human immortalized keratinocytes (HaCaT) were treated with different concentrations of the dietary polyphenolic compound curcumin (CUR) alone or in combination with the natural AHR agonist 6-formylindolo[3,2-b]carbazole (FICZ). In an earlier study, we described that CUR can activate the AHR indirectly by inhibiting metabolic clearance of FICZ. Here, we measured cell viability, activation of AHR signaling, oxidative stress and histone modifying activities in response to CUR at concentrations ranging from 0.1 to 50 μM. We observed apparent non-linear responses on cell viability and activation of AHR signaling. The CYP1A1 expression and the CYP1A1 enzyme activity in the presence of CUR reflected the histone acetylation efficiency observed in nuclear extracts. At the lowest concentration, CUR significantly decreased histone deacetylase activity and increased the FICZ-induced CYP1A1 activity. In contrast, at the highest concentration, CUR increased the formation of reactive oxygen species, significantly inhibited histone acetylation, and temporally decreased FICZ-induced CYP1A1 activity. The results suggest that CUR can both increase and decrease the accessibility of DNA and thereby influence transcriptional responses to the ligand-activated AHR. This suggestion was supported by the fact that chromatin remodeling treatments with trichostatin A, p300, or 5-aza-dC increased CYP1A1 transcription. We conclude that the AHR-dependent transcriptional efficiency is modified by factors that influence the cellular redox status and the chromatin structure.
本研究旨在深入了解调节芳香烃受体 (AHR) 靶基因 CYP1A1 表达的机制。我们用不同浓度的膳食多酚化合物姜黄素 (CUR) 单独或与天然 AHR 激动剂 6-甲酰基吲哚并[3,2-b]咔唑 (FICZ) 联合处理人肝癌细胞 (HepG2 和 Huh7) 和人永生化角质形成细胞 (HaCaT)。在之前的研究中，我们描述了 CUR 可以通过抑制 FICZ 的代谢清除来间接激活 AHR。在这里，我们测量了细胞活力、AHR 信号转导的激活、氧化应激和组蛋白修饰活性对 0.1 至 50 μM 浓度 CUR 的反应。我们观察到细胞活力和 AHR 信号转导的激活出现明显的非线性反应。存在 CUR 时，CYP1A1 的表达和 CYP1A1 酶活性反映了核提取物中观察到的组蛋白乙酰化效率。在最低浓度下，CUR 显著降低组蛋白去乙酰化酶活性并增加 FICZ 诱导的 CYP1A1 活性。相比之下，在最高浓度下，CUR 增加活性氧的形成，显著抑制组蛋白乙酰化，并暂时降低 FICZ 诱导的 CYP1A1 活性。结果表明，CUR 既可以增加也可以降低 DNA 的可及性，从而影响配体激活的 AHR 的转录反应。这一假设得到了以下事实的支持：用曲古抑菌素 A、p300 或 5-氮杂-2′-脱氧胞苷进行染色质重塑处理可增加 CYP1A1 转录。我们得出结论，影响细胞氧化还原状态和染色质结构的因素会改变 AHR 依赖性转录效率。
