PAHs: Balance of Detoxication vs Metabolic Activation

描述(由申请人提供)：燃烧产物中存在多环芳烃(PAHs)、亚硝胺和N-杂环化合物，例如烧烤食品和香烟烟雾。细胞色素P450 1A1和1B1(CYP1A1，CYP1B1)负责多种多环芳烃的代谢，其原型是苯并[a]芘(BaP)。CYP1A2负责代谢亚硝胺和N-杂环化合物，但也在较小程度上代谢多环芳烃(特别是BaP)。使用Cyp1a1(-/-)和CyP1B1(-/-)基因敲除小鼠，我们已经证明了CyP1A1在解毒方面比代谢激活更重要，而CyP1B1导致BaP的代谢激活到不需要的反应中间体。换句话说，在通过不同途径摄入多环芳烃的完整小鼠中，CYP1A1是利大于弊，而CYP1B1则是利大于利。肠系膜淋巴管与门静脉系统(肠系膜血管、肝脏、胆汁)的重要性对于口服BaP尚不为人所知。这个实验室现在有七个--三个都是单人，三个都是双人，还有一个三个Cyp1基因敲除小鼠品系。我们的假设是：淋巴摄取和远端组织(如免疫细胞、脾和骨髓)中的CYP1B1是口服BaP中毒的主要原因，而肝脏和肠道中可诱导的CyP1A1是BaP解毒的主要原因。因此，在这个拟议的项目中，我们将：[a)鉴定和测定野生型和所有七个Cyp1基因敲除小鼠系的肠系膜淋巴、门静脉血、肝脏和胆汁中代谢物的数量，以及乳糜粒在将BaP运送到靶器官中的作用和机制；[b)产生肝脏和肠上皮特异的Cyp1a1条件基因敲除系；[c]用Cyp1a1基因替换(基因组中的)CYP1B1基因，反之亦然；以及[d]在这四个新产生的小鼠系中重复我们的BaP药代动力学研究(见[a])。了解三种CYP1酶在口服BaP的完整小鼠中的组织特异性作用将使我们更好地理解BaP的解毒与代谢激活。我们希望这些知识将为了解摄入的苯并苯的消除和传播机制提供蓝图，并将在临床研究中提供信息，在临床研究中，我们将确定这三个人类基因的哪些单倍型可能与对多环芳烃诱导的毒性和癌症的抗性和敏感性有关。

DESCRIPTION (provided by applicant): Polycyclic aromatic hydrocarbons (PAHs), nitrosamines, and N-heterocyclics are present in combustion products, e.g. grilled foods & cigarette smoke. Cytochromes P450 1A1 & 1B1 (CYP1A1, CYP1B1) are responsible for the metabolism of numerous PAHs, the prototype of which is benzo[a]pyrene (BaP). CYP1A2 is responsible for metabolizing nitrosamines and N-heterocyclics, but also PAHs (in particular, BaP) to a lesser extent. Using Cyp1a1(-/-) and Cyp1b1(-/-) knockout mice, we have shown that CYP1A1 is more important in detoxication than metabolic activation, whereas CYP1B1 causes metabolic activation of BaP to unwanted reactive intermediates. In other words, CYP1A1 is more good than bad in the intact mouse ingesting BaP, and CYP1B1 is more bad than good in the intact mouse administered PAHs by various routes. The importance of mesenteric lymphatics vs. the portal system (mesenteric blood vessels, liver, bile) is not known for oral BaP. This lab now has seven-all three single, all three double, and the one triple-Cyp1 knockout mouse lines. Our hypothesis is: lymph BaP uptake and CYP1B1 in distal tissues (e.g. immune cells, spleen, and bone marrow) are the principal causes of oral BaP toxicity, whereas inducible CYP1A1 in liver and intestine is the principal cause of BaP detoxication. In this proposed project, we therefore will: [a] identify and determine the amounts of metabolites vs. unchanged parent BaP in mesenteric lymph, portal vein blood, liver, and bile in wild-type and all seven Cyp1 knockout mouse lines, and the role and mechanism of chylomicrons in delivering BaP to target organs; [b] generate liver- and intestinal epithelium-specific Cyp1a1 conditional knockout lines; [c] replace the Cyp1b1 gene (in the genome) with the Cyp1a1 gene, and vice versa; and [d] repeat our BaP pharmacokinetics studies (see [a]) in these four newly generated mouse lines. Understanding the tissue- specific roles for each of the three CYP1 enzymes in the intact mouse receiving oral BaP will provide us with a greater understanding of BaP detoxification vs. metabolic activation. We expect this knowledge will provide a blueprint for understanding the mechanisms of elimination vs. dissemination of ingested BaP and will be informative in clinical studies in which we would determine which haplotypes of these three human genes might be associated with resistance vs. sensitivity to PAH-induced toxicity and cancer.