METABOLIC ACTIVATION OF AROMATIC CARCINOGENS

芳香族致癌物的代谢激活

• 批准号: 2087880
• 负责人: SHEN K. YANG
• 金额: $ 14.88万
• 依托单位: HENRY M. JACKSON FDN FOR THE ADV MIL/MED
• 依托单位国家: 美国
• 财政年份: 1981
• 资助国家: 美国
• 起止时间: 1981-08-01 至 1996-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2087880
• 关键词: benzanthracenes; benzopyrenes; chemical carcinogen; cytochrome P450; detoxification; environment related neoplasm /cancer; genetic strain; high performance liquid chromatography; laboratory mouse; laboratory rat; methylcholanthrene; toxin metabolism

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants and some are believed to be causal in human cancer. This proposal has two objectives. The first objective is to elucidate the mechanism(s) of metabolic activation of 3-methylcholanthrene (3MC), which is a potent carcinogen and a cytochrome P450 isozyme inducer widely used as a model compound in cancer and drug research. The second objective is to examine the formation of proximate carcinogenic metabolites and subsequent oxidation to ultimate carcinogenic product in the metabolism of benzo[a]pyrene (BaP) and 3MC respectively in an enzyme system containing one of thirteen forms of human liver P450s. Specific forms of human P450s (1A2, 2A3, 2B7, 2C8, 2C9, 2D6, 2E1, 2F1, 3A3, 3A4, 3A5, and 4B1) are each contained in human hepatoma Hep G2 cells infected with recombinant vaccinia virus containing a human P450 cDNA or in AHH-1 lymphoblastoid cells in which the cDNA encoding for human P450 1A1 is incorporated in a herpes-like vector. BaP is known to be metabolically activated along the BaP->BaP 7,8-epoxide->BaP 7,8-dihydrodiol->BaP 7,8-diol-9,10-epoxide pathway. However, pathway(s) of metabolic activation of 3MC is less clear. We propose to employ in vitro and in vivo methods to elucidate the activation pathways of 3MC. Individual cDNA-expressed human P450s will be used to determine P450-specific activation/detoxification metabolic pathways. 3MC is metabolized by mammalian drug metabolizing enzyme system to form a complex mixture of metabolites. Among synthetic 3MC derivatives, 2-hydroxy-3MC (2-OH-3MC) and 3MC-2-one are known to be potent carcinogens. Based on recent findings in our laboratory, we have developed a hypothesis that three highly optically active 9, 10-diol-7,8-epoxides derived from further metabolism of 2S-hydroxy- 3MC (2S-OH-3MC), 3MC-2-one, and 3-hydroxymethylcholanthrene (3-OHMC) may be responsible for the carcinogenic activities of 3MC. Each activation pathway differs in detail from that of BaP and involves four or five enantioselective enzymatic steps catalyzed by cytochrome P450s and epoxide hydrolase in the microsomal enzyme complex. Experiments including high-performance liquid chromatographic isolation and physicochemical characterization of metabolites, DNA binding, and tumor-initiating activity test on mouse skin are designed to determine activation/detoxification pathways of 3MC. The well-established species differences in P450 expression indicate that it is unlikely to reliably extrapolate rodent carcinogen activation data to humans. Direct analysis of human P450-based carcinogen metabolite formations is therefore essential to identify the form(s) responsible for carcinogen activation and detoxification. The results may eventually allow us to specifically induce certain P450s engaged in detoxification processes relative to those involved in carcinogen activation and thus reduce toxicity. This research will contribute to the much needed human enzyme-based risk assessment of environmental carcinogens.

多环芳烃(PAHs)是一种普遍存在的环境污染物 污染物和一些被认为是人类癌症的因果关系。这 提案有两个目标。第一个目标是澄清 3-甲基胆蒽代谢活化机理(S) 是一种强有力的致癌物和细胞色素P450同工酶诱导剂，应用广泛 作为癌症和药物研究的模型化合物。第二个目标是 检查最接近致癌代谢物的形成和 在代谢过程中随后氧化为最终致癌产物 苯并[a]芘(BaP)和3MC在酶体系中的作用 含有十三种人类肝脏P450中的一种。特定形式的 人P450(1A2、2A3、2B7、2C8、2C9、2D6、2E1、2F1、3A3、3A4、3A5和 4B1)分别存在于感染人肝癌Hep G2细胞中 含人P450基因或AHH-1基因的重组痘苗病毒 人P450 1A1基因编码区的淋巴母细胞 合并成疱疹病毒的载体。众所周知，BaP是一种新陈代谢 沿着BaP-&>BaP-7，8-环氧化物-->BaP-7，8-二氢二醇->BaP； 7，8-二醇-9，10-环氧化物途径。然而，代谢途径(S) 3mc的激活还不是很清楚。我们建议在体外和体外使用 体内方法阐明3mc的激活途径。个体 表达的人P450将用于确定P450的特异性 激活/解毒代谢途径。 3MC由哺乳动物药物代谢酶系统代谢而成 代谢物的复杂混合物。在合成的3MC衍生物中， 已知2-羟基-3mc(2-羟基-3mc)和3mc-2-酮是有效的 致癌物质。根据我们实验室的最新发现，我们已经 提出了一个假设，即三个高度光学活性的9， 2S-羟基-3MC进一步代谢衍生的10-二醇-7，8-环氧化物 (2S-OH-3mc)、3mc-2-酮和3-羟甲基胆蒽(3-OHMC)可以是 对3mc的致癌活性负责。每次激活 路径与bap路径不同，涉及四、五个路径。 细胞色素P450催化的对映体选择性酶促步骤 微粒体酶复合体中的环氧化物水解酶。实验 包括高效液相色谱分离和 代谢物的物理化学特征、DNA结合和 小鼠皮肤上的肿瘤启动活性测试旨在确定 3mc的激活/解毒途径。 P450表达的物种差异表明 不太可能可靠地推断啮齿动物致癌物的激活数据 对人类来说。人P450致癌物代谢物的直接分析 因此，确定队形(S)负责的队形是必不可少的 激活致癌物质，解毒解毒。最终的结果可能是 允许我们特定地诱导某些参与解毒的P450 与致癌物激活相关的过程，因此 降低毒性。这项研究将对人类的急需做出贡献 基于酶的环境致癌物风险评估。