Role of cytochrome P450 1a1 and 1b1 in the metabolic activation of 7,12-dimethylbenz[a]anthracene and the effects of naturally occurring furanocoumarins on skin tumor initiation
Role of cytochrome P450 1a1 and 1b1 in the metabolic activation of 7,12-dimethylbenz[a]anthracene and the effects of naturally occurring furanocoumarins on skin tumor initiation
复制标题
DOI：
10.1021/tx010151v
复制
发表时间：
2002-02-01
影响因子：
4.1
通讯作者：
DiGiovanni, J
中科院分区：
文献类型：
--
作者：
Kleiner, HE;Vulimiri, SV;DiGiovanni, J
本研究旨在确定天然存在的呋喃香豆素对7，12-二甲基苯并[a]蒽（DMBA）引发皮肤肿瘤的影响差异的机制基础。雌性SENCAR小鼠在用DMBA（10 nmol）局部处理前5分钟用香柠檬素、欧前胡素或异茴芹素（100-3200 nmol）、7，8-苯并异丁酮（7，8-BF，5-40 nmol，小鼠中DMBA皮肤致癌作用的已知抑制剂）或丙酮（载体对照）局部预处理。欧前胡素、异欧前胡素和7，8-BF显著阻断总DMBA-DNA加合物的形成，但香柠檬素不阻断。DNA加合物的HPLC分析表明，香柠檬素优先抑制反-DMBA二醇-环氧化物（DMBADE）衍生的DNA加合物的形成，欧前胡素和异茴芹素抑制反-和顺-衍生的加合物，而7，8-BF对顺-DMBADE-DNA加合物的还原显示出一定的选择性。小鼠胚胎成纤维细胞C3 H/10 T1/2（10 T1/2）细胞和小鼠肝癌衍生的1c 1c 7（Hepa-1）细胞分别优先表达P450 1b 1和P450 1a 1，将它们与2 μ M香柠檬素、欧前胡素、异茴芹素和7，8-BF以及DMBA（2 μ M）共孵育。Hepa-1细胞（P4501 a1）主要形成抗DMBADE-DNA加合物。而10 T1/2细胞（P450 1b 1）主要形成syn-DMBADE-DNA加合物。在Hepa-1细胞中，佛手柑内酯抑制DMBA代谢为DMBA-3，4-二醇，并阻断DNA加合物的形成，但在10 T1/2细胞中几乎没有影响。相反，7，8-BF在10 T1/2细胞中完全阻断DMBA代谢和DNA加合物的形成，但在Hepa-1细胞中几乎没有影响。欧前胡素和异欧前胡素在两种细胞系中抑制DMBA生物活化。这些结果表明，香柠檬素是一个更有选择性的抑制剂P450 1a 1和整体的DMBA代谢活化的抑制剂在小鼠表皮中的有效性较低。相反，欧前胡素，isopimpinellin，尤其是7，8-BF，它阻止DMBA在小鼠表皮中的代谢活化，似乎对P450 1b 1更具选择性。基于我们使用10 T1/2细胞和Hepa-1细胞的研究，似乎P450 1a 1主要负责将DMBA-3，4-二醇转化为抗DMBADE，而P450 1b 1主要负责将DMBA-3，4-二醇转化为syn-DMBADE。这些数据证明了P450 1a 1和1b 1在小鼠表皮DMBA代谢活化中的作用，并为天然存在的呋喃香豆素（和7，8-BF）对多环芳烃皮肤致癌作用的差异效应提供了机制解释。
The current study was designed to determine the mechanistic basis for differences in the effects of naturally occurring furanocoumarins on skin tumor initiation by 7,12-dimethylbenz[a]anthracene (DMBA). Female SENCAR mice were pretreated topically with bergamottin, imperatorin, or isopimpinellin (100-3200 nmol), 7,8-benzoflavone (7,8-BF, 5-40 nmol, a known inhibitor of DMBA skin carcinogenesis in mice), or acetone (vehicle control) 5 min prior to topical treatment with DMBA (10 nmol). Imperatorin, isopimpinellin, and 7,8-BF, but not bergamottin, significantly blocked total DMBA-DNA adduct formation. HPLC analysis of DNA adducts revealed that bergamottin preferentially inhibited formation of anti-DMBA diol-epoxide (DMBADE) derived DNA adducts, imperatorin, and isopimpinellin inhibited both anti- and syn- derived adducts, whereas 7,8-BF showed some selectivity for reduction of syn-DMBADE-DNA adducts. Mouse embryo fibroblast C3H/10T1/2 (10T1/2) cells, and mouse hepatoma-derived 1c1c7 (Hepa-1) cells, which preferentially express P450 1b1 and P450 1a1, respectively, were co-incubated with 2 muM bergamottin, imperatorin, isopimpinellin, and 7,8-BF, and with DMBA (2 muM). Hepa-1 cells (P450 1a1) formed mainly anti-DMBADE-DNA adducts. In contrast, 10T1/2 cells (P450 1b1) formed mainly syn-DMBADE-DNA adducts. Bergamottin inhibited DMBA metabolism to DMBA-3,4-diol and blocked DNA adduct formation in Hepa-1 cells, but had little effect in 10T1/2 cells. In contrast, 7,8-BF completely blocked DMBA metabolism and DNA adduct formation in 10T1/2 cells, but had little effect in Hepa-1 cells. Imperatorin and isopimpinellin inhibited DMBA bioactivation in both cell lines. These results indicate that bergamottin is a more selective inhibitor of P450 1a1 and overall a less effective inhibitor of the metabolic activation of DMBA in mouse epidermis. In contrast, imperatorin, isopimpinellin, and especially 7,8-BF, which block metabolic activation of DMBA in mouse epidermis, appear more selective for P450 1b1. On the basis of our studies using 10T1/2 cells and Hepa-1 cells, it appears that P450 1a1 is primarily responsible for converting DMBA-3,4-diol to anti-DMBADE, whereas P450 1b1 is primarily responsible for converting DMBA-3,4-diol to syn-DMBADE. These data demonstrate the role of P450 1a1 and 1b1 in the metabolic activation of DMBA in mouse epidermis and provide a mechanistic explanation for the differential effects of naturally occurring furanocoumarins (and 7,8-BF) on polycyclic aromatic hydrocarbon skin carcinogenesis.