PAHs: Balance of Detoxication vs Metabolic Activation

描述（由申请人提供）：多环芳烃（PAH）、亚硝胺和N-杂环化合物存在于燃烧产物中，例如烧烤食品和香烟烟雾。细胞色素P450 1A1和1B1（CYP1A1，CYP1B1）参与多种多环芳烃的代谢，苯并[a]芘（BaP）是其原型。CYP1A2负责代谢亚硝胺和N-杂环化合物，但在较小程度上也代谢多环芳烃（特别是BaP）。使用Cyp1a1（-/-）和Cyp1b1（-/-）基因敲除小鼠，我们已经表明，CYP1A1在解毒中比代谢活化更重要，而CYP1B1导致BaP代谢活化为不需要的活性中间体。换句话说，CYP1A1在摄入BaP的完整小鼠中是好的多于坏的，而CYP1B1在通过各种途径摄入PAHs的完整小鼠中是坏的多于好的。尚不清楚口服BaP时肠系膜血管相对于门静脉系统（肠系膜血管、肝脏、胆汁）的重要性。这个实验室现在有七个-所有三个单，所有三个双，和一个三重Cyp1敲除小鼠品系。我们的假设是：淋巴BaP摄取和远端组织（如免疫细胞、脾脏和骨髓）中的CYP1B1是口服BaP毒性的主要原因，而肝脏和肠道中的诱导型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]鉴定和确定野生型和所有七种Cyp1敲除小鼠品系的肠系膜淋巴、门静脉血、肝脏和胆汁中代谢产物与原型母体BaP的量，以及乳糜微粒在将BaP递送到靶器官中的作用和机制;[B]产生肝和肠上皮特异性Cyp1a1条件敲除品系;[c]用Cyp1a1基因替换Cyp1b1基因（基因组中），反之亦然;[d]在这四个新产生的小鼠品系中重复我们的BaP药代动力学研究（见[a]）。了解接受口服BaP的完整小鼠中三种CYP 1酶中每一种的组织特异性作用将使我们更好地了解BaP解毒与代谢活化。我们期望这些知识将为理解摄入的BaP的消除与传播机制提供蓝图，并将在临床研究中提供信息，我们将确定这三种人类基因的哪些单倍型可能与PAH诱导的毒性和癌症的抗性与敏感性相关。

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.