Targeted RNA-Seq analysis of the livers of male mice treated with the perfluorinated alkyl substance PFESA-BP2 (Nafion byproduct 2)

The perfluorinated alkyl substance PFESA-BP2 (1,1,2,2-tetrafluoro-2-[1,1,1,2,3,3-hexafluoro-3-(1,1,2,2-tetrafluoroethoxy)propan-2-yl]oxyethane-1-sulfonic acid; also known as nafion BP2) has been detected in the blood of people living in the North Carolina Cape Fear River basin downstream of an industrial manufacturing facility. Given that almost nothing is known about the potential toxicity of PFESA-BP2 and safe exposure levels have not yet been determined, we performed a benchmark dose analysis of phenotypic and genomic effects. Male mice were exposed to PFESA-BP2 at 0, 0.03, 0.3, 3, and 6 mg/kg-day each day for 7 days by oral gavage. Transcript profiling showed that PFESA-BP2 activates a number of transcription factors linked to liver toxicity including constitutive activated/androstane receptor, pregnane X receptor, and Nrf2, but unlike other long-chain PFAS, there was only weak activation of peroxisome proliferator-activated receptor α. Steatosis was coincident with activation of sterol response element binding proteins as well as increases in the expression of the very low density lipoprotein receptor. Balb-C male mice at 10-12 weeks of age were dosed by gavage for 7 consecutive days using 20-gauge stainless steel feeding needles. Doses of 0, 0.03, 0.3, 3.0, and 6.0 mg/kg-day were administered once daily in the afternoon. Control animals were administered an equal volume of deionized water. Four biological replicates consisting of individual animals were included in each dose group. RNA was isolated and gene expression was determined using the mouse TempO-Seq targeted RNA-Seq platform (BioSpyder, Inc; Carlsbad CA).