The role of albumin and other serum factors in Per- and polyfluoroalkyl substance (PFAS) accumulation and toxicity - SUMMARY Per- and polyfluoroalkyl substances (PFAS) are a family of highly fluorinated aliphatic compounds widely used in commercial applications such as food packaging, textiles, and non-stick cookware. Exposure to the legacy PFAS perfluorosulfonic acid (PFOS) exposure is associated with hepatotoxicity, non-alcoholic fatty liver disease, and lipid dysregulation. PFOS and other long-chain PFAS possess serum half-lives of ~3-8 years in humans, and their elimination half-life is hypothesized to result from tight binding to abundant serum and tissue proteins that are known to bind fatty acids and xenobiotics. Albumin, the most abundant plasma protein, is hypothesized to play a key role in PFAS retention, contributing to the long elimination half-lives observed in humans. This hypothesis is based on in vitro studies using purified protein and has never been verified under physiological conditions in vivo, where other macromolecules (e.g., immunoglobulins) are present that potentially bind PFAS. Our preliminary data demonstrated that plasma PFOS levels are lower in mice lacking albumin (Alb-/-), confirming the long-held theory that albumin is a crucial binding protein for PFOS in the body. However, we have observed that PFOS still binds and is retained in mice lacking albumin, suggesting additional binding mechanisms, possibly involving immunoglobulins, as indicated by our in vitro binding studies. Albumin also modulates liver pathophysiology and contributes to fatty acid balance. Our pilot data indicate that albumin is a potential mediator for PFOS-induced liver effects and may contribute to PFAS-induced adverse liver effects in humans. Aim 1 will determine whether albumin is a key factor for PFAS distribution among mouse plasma and tissues and associated elimination half-lives. We will determine PFAS tissue accumulation in Alb-/- and wild-type mice (Alb+/+), which is conceptually innovative for the PFAS field. Using in vitro binding assays, we will quantify binding of novel and emerging PFAS to tissues from Alb+/+ and Alb-/- mice and to plasma samples from human with disease-associated alterations in plasma protein levels. Aim 2 will investigate the role of albumin as mediator of PFAS-induced adverse liver effects and hepatoxicity. Because albumin binds fatty acid, we hypothesize that lack of albumin will increase PFAS-induced fatty acid update by liver and steatosis in albumin deficient mice. Aim 3 will determine the impact of genetic and disease-related variations in albumin and globulin levels on PFAS exposure and susceptibility to hepatotoxicity in humans. We will use a physiologically-based toxicokinetic (PBTK) model parameterized with data from Aim 1 and our previous work to evaluate how these variations influence PFAS distribution, accumulation, and elimination, identifying populations at higher risk for PFAS-induced liver diseases. Outcome of Proposed Aims: PFAS tend to show high tissue and blood protein binding in vitro, however our rigorous in vivo studies will determine whether albumin is a relevant factor for the physiologic response of the liver to PFAS, and whether albumin is relevant for tissue binding when other macromolecules like immunoglobulins are present. The outcome of this work is to define whether albumin is a key factor for PFAS-induced hepatoxicity and bioaccumulation, compared to other macromolecules like immunoglobulins. This R01 proposal will serve as a basis for further animal studies combined with toxicokinetic modeling in the context of PFAS accumulation and hepatotoxicity.
