Comparison of transcriptomic profiles between HFPO-DA and positive controls for PPARa, PPARg or cytotoxicity in mouse, rat, and pooled human hepatocytes
Like many per- or polyfluorinated alkyl substances (PFAS), toxicity studies with HFPO-DA (ammonium, 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)-propanoate; CASRN 62037-80-3), a short-chain PFAS used in the manufacture of some types of fluorinated polymers, indicate that the liver is the primary target of toxicity in rodents following oral exposure. Although the current weight of evidence supports the PPARa mode of action (MOA) for liver effects in HFPO-DA-exposed mice, alternate MOAs have also been hypothesized including PPARg or cytotoxicity. To further evaluate the MOA for HFPO-DA in rodent liver, transcriptomic analyses were conducted on samples from primary mouse, rat and pooled human hepatocytes treated for 12, 24 or 72 hours with various concentrations of HFPO-DA, or established agonists of PPARa (GW7647), PPARg (rosiglitazone), or cytotoxic agents (i.e., acetaminophen or d-galactosamine). Concordance analyses of enriched pathways across chemicals within each species demonstrated greatest concordance between HFPO-DA and PPARa agonist GW7647-treated hepatocytes compared to the other chemicals evaluated. These findings were supported by benchmark concentration modeling and predicted upstream regulator results. In addition, transcriptomic analyses across species demonstrated a greater transcriptomic response in rodent hepatocytes treated with HFPO-DA or agonists of PPARa or PPARg, indicating rodent hepatocytes are more sensitive to HFPO-DA or PPARa/g agonist treatment. These results are consistent with previously published transcriptomic analyses and further support that liver effects in HFPO-DA-exposed rodents are mediated through rodent-specific PPARa signaling mechanisms as part of the MOA for PPARa activator-induced rodent hepatocarcinogenesis. Overall design: Comparative gene expression profiling analysis of RNA-seq data from lysed mouse, rat and human primary hepatocytes treated for 12, 24 or 72 h with supplemented MCM media containing solvent control in the presence or absence of HFPO-DA (0.1, 5, 50 or 500 µM) or one of the following positive controls: GW7647 (0.01, 0.1, 1 or 10 µM), rosiglitazone (0.01, 0.1, 1 or 10 µM), acetaminophen (0.3, 1, 3 or 10 mM) or d-galactosamine (0.3, 1, 3 or 10 mM).