Department of Pharmacology and Toxicology, School of Pharmacy , Shiraz University of Medical Sciences , Shiraz , Iran.
Department of Pharmacology and Toxicology, Faculty of Pharmacy , Hormozgan University of Medical Sciences , Bandar Abbas , Iran.
Chem Res Toxicol. 2019 Apr 15;32(4):691-697. doi: 10.1021/acs.chemrestox.8b00371. Epub 2019 Mar 4.
The mechanisms underlying aryl hydrocarbon receptor (AHR) activation by agonists and circumstances that increase the sensitivity toward agonists and AHR inhibition by antagonists are diverse and still not fully understood. AHR antagonist, 2-methyl-2 H-pyrazole-3-carboxylic acid (2-methyl-4- o-tolylazo-phenyl)-amide, CH223191, has been reported to inhibit the AHR transcription activity. However, CH223191 antagonist activity toward an AHR endogenous ligand, 6-formylindolo[3,2- b]carbazole (FICZ), and its mode of action remain to be elusive. Male BALB/c albino mice, HepG2 cells, and HepG2-XRE-Luc carrying cytochrome P4501A1 (CYP1A1) gene linked to a luciferase reporter were exposed to FICZ alone or in combination with CH223191, buthionine-( S, R)-sulfoximine (BSO), and N-acetyl-l-cysteine (NAC) for 5 h. Microsomal and cellular CYP1A1 enzyme activities, cellular FICZ levels, CYP1A1 reporter activity, mitochondrial membrane potential, and mitochondrial-dependent reactive oxygen species (ROS) formation were measured. In this study, we showed that AHR activity induced by an AHR endogenous ligand, FICZ, in a dose-dependent manner could be suppressed by CH223191. Indeed, we observed that CH223191 is able to inhibit the catalytic activity of CYP1A1, with an IC value of 1.48 μM. Our experiments with silencing RNA sequences showed that ROS formation by mitochondria might take part as a primary event in the downregulation of CYP1A1 by CH223191. We describe a new mechanism for inhibition of AHR-induced CYP1A1 by CH223191. The sensitivity of the AHR to oxidants and its possible reversibility by antioxidants supports the view that CH223191-induced mitochondrial dysfunction might be involved in this pharmacological event.
芳基烃受体（AHR）激动剂激活的机制以及增加激动剂敏感性和拮抗剂抑制 AHR 的情况多种多样，仍未完全了解。AHR 拮抗剂 2-甲基-2H-吡唑-3-羧酸（2-甲基-4-邻甲苯基偶氮-苯基）-酰胺，CH223191，已被报道可抑制 AHR 转录活性。然而，CH223191 对 AHR 内源性配体 6-甲氧基吲哚并[3,2-b]咔唑（FICZ）的拮抗剂活性及其作用方式仍不清楚。雄性 BALB/c 白化小鼠、HepG2 细胞和携带与荧光素酶报告基因相连的细胞色素 P4501A1（CYP1A1）基因的 HepG2-XRE-Luc 细胞分别单独或与 CH223191、丁硫氨酸-（S，R）-亚砜（BSO）和 N-乙酰-l-半胱氨酸（NAC）一起暴露于 FICZ 中 5 小时。测量了细胞色素 P4501A1 酶活性、细胞内 FICZ 水平、CYP1A1 报告基因活性、线粒体膜电位和线粒体依赖性活性氧（ROS）形成。在这项研究中，我们表明，AHR 内源性配体 FICZ 以剂量依赖性方式诱导的 AHR 活性可被 CH223191 抑制。事实上，我们观察到 CH223191 能够抑制 CYP1A1 的催化活性，IC 值为 1.48 μM。我们用沉默 RNA 序列进行的实验表明，线粒体产生的 ROS 可能作为 CH223191 下调 CYP1A1 的初始事件之一发挥作用。我们描述了一种新的机制，即 CH223191 抑制 AHR 诱导的 CYP1A1。AHR 对氧化剂的敏感性及其被抗氧化剂逆转的可能性支持这样一种观点，即 CH223191 诱导的线粒体功能障碍可能参与了这种药理事件。
