Department of Applied Chemistry, Kinki University, Kowakae, Higashiosaka-Shi, Osaka, Japan.
Environ Mol Mutagen. 2011 Oct;52(8):646-57. doi: 10.1002/em.20665. Epub 2011 Jul 22.
This study was designed to investigate the antigenotoxic effects of a series of naturally occurring furanocoumarins (NOFs) including isoimperatorin, imperatorin, (+)-oxypeucedanin, (+)-byakangelicol, and (+)-byakangelicine on antigenotoxic activities against genotoxicity induced by carcinogens [furylfuramide and N-methyl-N'-nitro-N-nitrosoguanidine], and procarcinogens 2-[2-(acetylamino)-4-amino-5-methoxyphenyl]-5-amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-4) and 2-amino-3,4-dimethyl-3H-imidazo-[4,5-f] quinoline (MeIQ)] to genotoxic metabolites catalyzed by rat S9 or rat and human recombinant cytochrome P450 (CYP) 1As by using the umu test based on SOS response. Five different NOFs, which were found in the human diets, strongly inhibited the umuC induction by procarcinogens, but did not be affected by carcinogens. Notably, isoimperatorin and (+)-byakangelicol were found to be potent inhibitors on the metabolic activation of PBTA-4 and MeIQ to genotoxic metabolites catalyzed by rat and human CYP1A1, or rat and human CYP1A2, respectively. In addition, to elucidate the mechanism of their antigenotoxic effects against procarcinogens, the effects of NOFs on rat and human CYP1A1- or rat and human CYP1A2-related enzyme activities of 7-ethoxyresorufin-O-deethylase (EROD) were also investigated. Reduction of the EROD activities by some of the NOFs with IC(50) values of 0.23-20.64 μM was found to be due to strong inhibition of CYP1A1 and CYP1A2 dependent monooxygenases. Furthermore, the mechanism of inhibitions by NOFs on human CYP1A1 and CYP1A2 was analyzed by means of Dixon plots plus Cornish-Bowden plots. The kinetic studies of inhibition types revealed that these compounds inhibited the human CYP1A1 and CYP1A2 a variety of modes rather than by a uniform one. Moreover, experiments with a two-stage incubation indicated that NOFs, except for imperatorin, inhibited human CYP1A1 in a mechanism-based manner, but directly inhibited human CYP1A2. This data suggest that certain NOFs, to which humans are exposed in the diet, may be capable of affecting the metabolic activation of procarcinogens due to inhibitions of CYP1A1 and CYP1A2 enzymes.
本研究旨在探讨一系列天然呋喃香豆素（NOF），包括异茴芹素、茴芹素、（+）-氧化前胡素、（+）-比克白芷素和（+）-比克白芷宁，对致癌剂[呋喃氟酰胺和 N-甲基-N'-硝基-N-亚硝胍]和前致癌剂 2-[2-（乙酰氨基）-4-氨基-5-甲氧基苯基]-5-氨基-7-溴-4-氯-2H-苯并三唑（PBTA-4）和 2-氨基-3,4-二甲基-3H-咪唑[4,5-f]喹啉（MeIQ）]诱导的遗传毒性代谢物的抗原毒性作用。五种在人类饮食中发现的不同的 NOF 强烈抑制前致癌剂诱导的 umuC 诱导，但不受致癌剂的影响。值得注意的是，异茴芹素和（+）-比克白芷素被发现是 PBTA-4 和 MeIQ 代谢激活为遗传毒性代谢物的有效抑制剂，分别由大鼠和人细胞色素 P450（CYP）1A1 或大鼠和人 CYP1A2 催化。此外，为了阐明它们对前致癌剂的抗原毒性作用的机制，还研究了 NOF 对大鼠和人 CYP1A1 或大鼠和人 CYP1A2 相关的 7-乙氧基荧光素-O-去乙基酶（EROD）酶活性的影响。发现一些 NOF 以 IC50 值为 0.23-20.64 μM 降低 EROD 活性，这是由于强烈抑制 CYP1A1 和 CYP1A2 依赖性单加氧酶。此外，通过 Dixon 图和 Cornish-Bowden 图分析了 NOF 对人 CYP1A1 和 CYP1A2 的抑制机制。抑制类型的动力学研究表明，这些化合物以多种方式而非单一方式抑制人 CYP1A1 和 CYP1A2。此外，两阶段孵育实验表明，除了茴芹素外，NOF 以基于机制的方式抑制人 CYP1A1，但直接抑制人 CYP1A2。这些数据表明，某些在饮食中接触到人类的 NOF 可能由于对 CYP1A1 和 CYP1A2 酶的抑制作用，能够影响前致癌剂的代谢激活。
