Endocrine disruptor mediated activation of PXR causes dyslipidemia and atherosclerosis

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PROJECT SUMMARY Despite major advances in developing diagnostic techniques and effective treatments, atherosclerotic cardiovascular disease (CVD) is still the leading cause of mortality and morbidity worldwide. Recent large- scale human studies have implicated a novel link between exposure to endocrine disrupting chemicals (EDCs) and CVD. However, how exposure to EDCs influences CVD risk is still poorly understood, and continues to hamper rational assessment of the health risks of EDC exposure. We have previously identified many plastic- associated EDCs as potent agonists of the xenobiotic sensor pregnane X receptor (PXR), which has provided an important tool for the study of new mechanisms through which EDC exposure impacts diseases. Our laboratory was the first to reveal the novel function of PXR in the regulation of atherosclerosis development, and has also demonstrated that several widely-used EDCs increase atherosclerosis and dyslipidemia through PXR signaling in mouse models. To understand the detailed mechanisms underlying EDC-induced dyslipidemia and atherosclerosis, novel tissue-specific PXR knockout mice have been generated, and preliminary studies demonstrated that exposure to a newly identified PXR agonistic EDC increased intestinal lipid absorption, hyperlipidemia, and hepatic steatosis in a PXR-dependent manner. Further, EDC-mediated PXR activation led to elevated circulating levels of ceramides, a class of bioactive sphingolipids that has been independently associated with increased CVD risk in humans. Our exciting preliminary findings support a central hypothesis that plastic-associated EDCs that activate PXR stimulate intestinal lipid absorption and ceramide production, leading to increased dyslipidemia, hepatic steatosis, and atherosclerosis. We propose three specific aims to test this hypothesis: 1) Determine the tissue-specific contribution of PXR signaling towards EDC-induced dyslipidemia and ceramide production using novel conditional knockout mice; 2) Define the enterohepatic signaling through which PXR agonistic EDCs regulate lipid and ceramide homeostasis; and 3) Determine the impact of EDC-mediated PXR activation on atherosclerosis development. Influences of the chemical environment on human health have become the subject of intense interest but very few studies in the EDC research field have focused on the impact of EDCs on atherosclerosis development. This renewal application will expand our initial research scope, pursue new research directions, utilize newly developed animal models, and combine in vitro, ex vivo, and in vivo approaches to investigate EDCs’ atherogenic effects. The proposed studies will contribute to our understanding of “gene-EDC interactions” in predisposing individuals to atherosclerosis and other chronic diseases.