Exposure to perfluorooctanoic acid (PFOA) or GenX during gestation disrupts maternal and fetal liver gene expression in CD-1 mice

Per- and polyfluoroalkyl substances (PFAS) are associated with adverse liver outcomes but effects on the developing liver or biologic pathways involved are not known. We implemented whole-transcriptome gene expression analysis to investigate the molecular mechanisms of liver toxicity after developmental exposure to two different PFAS, perfluorooctanoic acid (PFOA) and its replacement, GenX. Pregnant CD-1 mice were exposed via daily oral gavage beginning on embryonic day (E) 1.5 to PFOA (0, 1, or 5 mg/kg) or GenX (0, 2, or 10 mg/kg) until euthanasia on E11.5 or E17.5. Maternal and fetal livers were collected and RNA was isolated. Collected RNA (N=5 per dose/group) was run on Affymetrix Mouse Clariom D arrays, and data sets were normalized and evaluated for outliers. Differentially expressed genes (DEG; fold-change ≥ 1.5, p-value ≤ 0.05) and differentially enriched pathways (DEP; Normalized Pathway Enrichment score ≥ 1.5, p-value ≤ 0.05) were determined using Broad Institute’s Molecular Signature Database Hallmark Pathways. Ingenuity Pathway Analysis was used to identify key genes involved in the hallmark pathways. Alterations in multiple hallmark pathways were consistent across maternal and fetal liver at all doses tested for both PFOA and GenX. Upregulated DEPs identified across all dose and tissue groups included Fatty Acid Metabolism, Peroxisome, Oxidative Phosphorylation, Adipogenesis, and Bile Acid Metabolism. Key altered genes identified in these pathways included reduced cytochrome P450s (Cyp1a2, Cyp3a5), increased lipogenic and lipid transporter genes (Acaa1, Acsl1, Scp2, and Slc27a1), and increased estrogen reductase (Hsd17b7). These findings suggest shared molecular mechanisms of liver toxicity for PFOA and GenX in both maternal and fetal livers in CD-1 mice and provide critical insight into pathways that may underlie latent consequences of developmental exposure. The views expressed are those of the authors and do not necessarily represent the views or policies of the US EPA.

Impact/Purpose

This work explores the gene expression changes in maternal and fetal mouse liver after gestational exposure to two different perfluoroalkyl substances (PFAS), perfluorooctanoic acid (PFOA) or hexafluoropropylene dimer acid (HFPO-DA, commonly referred to by the trade name GenX). The research will be presented to toxicologists at a local chapter meeting for the NC Society of Toxicology. Exposure to PFAS has been associated with adverse health outcomes and the liver is thought to be an important target tissue. However, the mechanism(s) through which PFAS may impact the liver are not well understood, particularly with regard to the developing liver. In this work, we compared the gene expression changes in maternal and fetal mouse liver across the entire transcriptome after pregnant mice were exposed to either PFOA or GenX during gestation. Differentially expressed genes and differentially enriched biologic pathways were identified, which provides insight into the underlying biologic pathways disrupted by exposure to PFOA and GenX. This work is important for improving our understanding of how exposure to PFAS may alter biological processes in the mature and developing liver. 

Citation

Blake, B., T. Phan, H. Nguyen, C. Miller, D. Mav, R. Shah, D. Phadke, AND S. Fenton. Exposure to perfluorooctanoic acid (PFOA) or GenX during gestation disrupts maternal and fetal liver gene expression in CD-1 mice. North Carolina Society of Toxicology Virtual Annual Meeting, Virtual, Virtual, January 19, 2022.