Interaction between metabolism and transport of toxicological-relevant substances in the gastrointestinal barrier

多环芳烃(PAH)是一大类普遍存在的环境污染物，以致癌物质苯并[a]芘(BP)为代表。非吸烟者摄取多环芳烃的主要来源是日常饮食。多环芳烃只有在加工(加热和干燥)和准备(如烟熏和烧烤)肉类、鱼和植物油和脂肪等高脂肪食品的过程中才会大量形成。在该项目的第一阶段，BP的解毒和肝胆排泄在转运蛋白基因敲除小鼠中进行了研究，调查了两种ABC转运蛋白乳腺癌耐药蛋白(BCRP/ABCG2)和多药耐药相关蛋白2(MRP2/Abcc2)的缺失。数据显示，这两种转运蛋白对人体内BP的排泄起着重要作用。此外，我们可以在体内研究中表明，一种食物成分--显著的类黄酮--栎素，会强烈增加人体肝胆中BP的排泄。但实际上，人类单独接触BP的情况永远不会发生：多环芳烃的混合物总是被营养摄取。这些混合物包括一部分致癌化合物，如BP，但按百分比计算，还有相当比例的非致癌多环芳烃，如芘和荧菲。然而，这种非致癌和致癌的多环芳烃混合物对分子机制的影响仍然没有得到充分的研究和了解。因此，本项目旨在根据上一次资助期间的结果，研究此类真实的多环芳烃混合物对BP的新陈代谢、受体活性和遗传毒性的影响。重要的终点包括通过检测参与生物激活或解毒作用的特征代谢物(DNA加合物，代谢物谱分析)，诱导与代谢相关的基因表达和核受体途径，以及最后，使用人源化的受体小鼠模型对体外数据进行体内验证，从而改变BP的代谢。该项目的结果有望有助于更好地了解真实的人多环芳烃暴露的分子效应，而不是通常具有良好特征的单一暴露，进而允许更好地评估BP的致癌潜力和对人类的相关风险。

Polycyclic aromatic hydrocarbons (PAH) comprise a large group of ubiquitously occurring environmental contaminants with the pro-carcinogen benzo[a]pyrene (BP) as best studied representative. The main source of PAH uptake for non-smokers is the daily diet. PAH are only formed in significant amounts during processing (heating and drying) and preparation (e.g. smoking and grilling) of fatty foods such as meat, fish and vegetable oils and fats. In the first period of this project BP its detoxication and hepatobiliary excretion was studied in transporter knockout mice investigating the lack of the two ABC-transporters Breast Cancer Resistance Protein (Bcrp/Abcg2) and Multidrug Resistance-associated Protein 2 (Mrp2/Abcc2). The data showed an important role of these two transporters for BP excretion from the body. Additionally we could show in an in vivo study that a food component, the prominent flavonoid Quercetin, strongly increases the hepatobiliary excretion of BP from the body.However, in reality a mono-exposure of humans with BP alone never occurs: always mixtures of PAH are taken up by nutrition. These mixtures consist partly of carcinogenic compounds such as BP, but in percentage terms in substantial proportions of non-carcinogenic PAH such as pyrene and fluoranthene. However, the influence of such mixtures of non-carcinogenic and carcinogenic PAHs on the molecular mechanisms is still inadequately investigated and understood. Accordingly, this project is aimed to investigate the impact of such real PAH mixtures on the metabolism, receptor activity and the genotoxicity of BP based on the results of the last funding period. Important endpoints comprise changes of the metabolism of BP by detection of characteristic metabolites involved in bioactivation or detoxification (DNA adducts, analysis of metabolite profile), the induction of gene expression and nuclear receptor pathways associated with the metabolism and finally, the in vivo verification of the in vitro data using humanized receptor mouse models.The results of this project are expected to contribute to a better understanding of molecular effects of real human PAH exposure in contrast to the often well-characterized single exposure and in turn allowing a better assessment of the carcinogenic potential of BP and the associated risk to humans.