Per- and polyfluoroalkyl substances (PFAS) are a class of ubiquitous man-made chemicals utilized for their surfactant properties in industrial and consumer products (cookware, clothing, carpets) as well as in firefighting foams. PFAS are highly resistant to degradation, leading to their bioaccumulation in the environment and in humans. Because of this, PFAS are currently circulating in humans at blood concentrations that are magnitudes higher than other legacy contaminants. Exposure to PFAS have been associated with increased risk factors for cardiometabolic disease (i.e., increased circulating cholesterol), or major clinical outcomes related to atherosclerosis that include stroke and heart attack. However, no studies have yet reported on whether exposure to PFAS can induce the development of atherosclerosis. The overarching objective of this proposal is to determine if PFAS exposure induces atherosclerosis and to characterize the underlying mechanisms leading to PFAS-induced development of atherosclerosis risk factors. We have shown in our preliminary studies that Low Density Lipoprotein Receptor deficient mice (Ldlr -/-) fed an atherogenic diet and exposed to a simple mixture of 5 environmentally relevant PFAS (PFOS, PFOA, PFNA, PFHxS, and GenX) for 7 weeks resulted in increased circulating cholesterol and bile acids as well as decreased bile acid excretion. We also observed that PFAS exposure results in induction of ileal bile acid transporters, especially the ileal reuptake apical sodium dependent bile acid transporter (ASBT). Therefore, the central hypothesis of this proposal is that PFAS exposure induces atherosclerosis through mechanisms related to ASBT-mediated bile acid transport and excretion. To test this hypothesis, I will utilize Ldlr -/- mice, which is the gold standard for mechanistically investigating atherosclerosis because this genetically modified model has cholesterol profiles that closely mirror those seen in humans and is a model sensitive to dietary manipulation. Experiments proposed in Aim 1 will investigate the development of atherosclerosis in hyperlipidemic mice by monitoring lesion development in the aorta and aortic roots, quantifying lipid, sterol, and bile acid levels, and transcriptomic profiling. Aim 2 will investigate mechanisms underlying the PFAS-mediated increases in circulating cholesterol and atherosclerosis. Experiments proposed in Aim 2 will explore how ASBT inhibition modulates circulating cholesterol and bile acids, as well as the development of atherosclerosis. Collectively, these data will describe new mechanisms linking exposure to PFAS and increased risk of atherosclerosis. This proposed work will have broad implications for the use of well-tolerated pharmaceuticals as effective interventions against PFAS-mediated toxicity.