Chrysin, baicalein and galangin are indirect activators of the human constitutive androstane receptor (CAR)
Chrysin, baicalein and galangin are indirect activators of the human constitutive androstane receptor (CAR)
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DOI：
10.1016/j.toxlet.2015.01.013
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发表时间：
2015-03-04
影响因子：
3.5
通讯作者：
Pavek, Petr
中科院分区：
文献类型：
--
作者：
Carazo, Alejandro;Smutny, Tomas;Pavek, Petr
结构性雄烷受体(CAR)是细胞色素P450、细胞色素P3A4、细胞色素P2C9和细胞色素P2B6等关键异源代谢酶的重要转录调控因子。黄酮类化合物白杨素、黄芩素和高良姜素可激活CAR并干扰EGFR信号转导。然而，这些黄酮类化合物是直接的CAR配体还是通过抑制表皮生长因子受体(EGFR)信号的间接苯巴比妥类CAR激活剂尚不清楚。我们分析了白杨素、高良姜素、黄芩素及其苷类黄芩苷与CAR的相互作用。我们已经采用并验证了可以研究与CAR配体结合口袋的直接相互作用的方法。其次，我们确定了这些化合物是否影响人EGFR信号转导并与EGFR相互作用。利用重组CAR-FRET共激活试验或CAR组装试验，没有观察到CAR与黄酮类和苯巴比妥的一致激活。结果表明，高良姜素、白杨素和黄芩素可轻微抑制原代人肝细胞经EGF处理后的EGFR-Tyr1068自磷酸化、下游转录因子ELK1的磷酸化和刺激EGFP-CAR核转位，提示黄酮类白杨素、白杨素和黄芩素是间接的人CAR激活剂。这项研究还展示了如何测试CAR与其配体的直接相互作用的新方法。(C)2015爱思唯尔爱尔兰有限公司。保留所有权利。
The constitutive androstane receptor (CAR) is a crucial transcriptional regulator of key xenobiotic-metabolizing enzymes such as cytochrome P450 CYP3A4, CYP2C9 and CYP2B6. The flavonoids chrysin, baicalein and galangin have been reported to activate CAR and interfere with EGFR signaling. Nevertheless, it is not known if these flavonoids are direct CAR ligands or indirect phenobarbital-like CAR activators via the inhibition of epidermal growth factor receptor (EGFR) signaling.We analyze the interactions of chrysin, galangin and baicalein and its glycoside baicalin with human CAR. We have employed and validated methods that can study direct interaction with the CAR ligand binding pocket. Secondly, we determined if the compounds affect human EGFR signaling and interact with EGFR.Employing a TR-FRET coactivator assay with recombinant CAR or CAR assembly assay, a consistent activation of CAR with flavonoids and phenobarbital was not observed. It was determined, however, that galangin, chrysin, and baicalein may slightly repress EGFR-Tyr1068 autophosphorylation after EGF treatment, phosphorylation of downstream transcription factor ELK1 and stimulate EGFP-CAR nuclear translocation in primary human hepatocytes.These data suggest that flavonoids chrysin, galangin and baicalein are indirect human CAR activators. This study also demonstrates new approach how to test the direct CAR interaction with its ligands. (C) 2015 Elsevier Ireland Ltd. All rights reserved.