Shimada Tsutomu, Murayama Norie, Okada Kazushi, Funae Yoshihiko, Yamazaki Hiroshi, Guengerich F Peter
Department of Chemical Biology, Osaka City University Medical School, Abeno-ku, Osaka 545-8585, Japan.
Chem Res Toxicol. 2007 Mar;20(3):489-96. doi: 10.1021/tx600299p. Epub 2007 Feb 10.
We have previously shown that several polycyclic aromatic hydrocarbons (PAHs) strongly inhibit their own and other PAH metabolism catalyzed by cytochrome P450 (P450) 1A1, 1A2, and 1B1 [Shimada, T., and Guengerich, F. P. (2006) Chem. Res. Toxicol. 19, 288-294]. In the present study, we examined mechanisms of how PAHs inhibit these P450 enzymes by using 7-ethoxyresorufin O-deethylation (EROD) as a model reaction. First, we examined mechanisms of inhibition of P450 1A1, 1A2, and 1B1 by the synthetic model inhibitors 1-(1-propynyl)pyrene (1PP), 1-ethynylpyrene (1EP), 2-ethynylpyrene (2EP), and 4-(1-propynyl)biphenyl (4Pbi). Both 1PP and 1EP inhibited P450 1A1 in a mechanism-based manner, but P450 1B1 and 1A2 were directly inhibited by 1PP and 1EP. Interestingly, P450 1B1 inactivated 1PP and 1EP to products that were not inhibitory to P450 1B1. 4Pbi was a mechanism-based inhibitor of P450 1A1 and 1B1, but 2EP directly inhibited these P450s. All four of the inhibitors directly inhibited P450 1A2. We also found that benzo[a]pyrene and seven other PAH compounds tested inhibited P450 1A2 in a mechanism-based manner, but fluoranthene directly inhibited P450 1A2. All of the nine PAHs examined were direct inhibitors of P450 1A1 and P450 1B1. These results suggest different mechanisms of inhibition of P450 1A1, 1A2, and 1B1 by PAHs and related chemicals and that interactions between P450 enzymes and PAH inhibitors are involved in differences in inhibition of the enzymes.
我们之前已经表明，几种多环芳烃（PAHs）能强烈抑制由细胞色素P450（P450）1A1、1A2和1B1催化的自身及其他PAH的代谢[岛田，T.，和根特里奇，F.P.（2006年）《化学研究毒理学》19，288 - 294]。在本研究中，我们以7 - 乙氧基试卤灵O - 脱乙基作用（EROD）作为模型反应，研究了PAHs抑制这些P450酶的机制。首先，我们研究了合成模型抑制剂1 -（1 - 丙炔基）芘（1PP）、1 - 乙炔基芘（1EP）、2 - 乙炔基芘（2EP）和4 -（1 - 丙炔基）联苯（4Pbi）对P450 1A1、1A2和1B1的抑制机制。1PP和1EP均以基于机制的方式抑制P450 1A1，但P450 1B1和1A2则被1PP和1EP直接抑制。有趣的是，P450 1B1将1PP和1EP失活为对P450 1B1无抑制作用的产物。4Pbi是P450 1A1和1B1的基于机制的抑制剂，但2EP直接抑制这些P450。所有这四种抑制剂均直接抑制P450 1A2。我们还发现，苯并[a]芘和测试的其他七种PAH化合物以基于机制的方式抑制P450 1A2，但荧蒽直接抑制P450 1A2。所检测的所有九种PAHs均为P450 1A1和P450 1B1的直接抑制剂。这些结果表明PAHs及相关化学物质对P450 1A1、1A2和1B1的抑制机制不同，且P450酶与PAH抑制剂之间的相互作用参与了酶抑制作用的差异。
