RF22 | PSUN318 Hepatocytes Exposed to PFOA Prior to Differentiation Leads to Epigenetic Changes in Genes Linked With NAFLD
Authors: Fu Weixuan , Joshi Apoorva , Pinney Sara Elizabeth , Tarapore Pheruza , Wang Zhiping , Green Stephanie 
Published: November 2022

Abstract

Background
Perfluorooctanoic acid (PFOA), is a persistent fluorinated compound with oil and water repelling properties found in cookware, food packaging and municipal water systems. Adult animals exposed to PFOA develop hepatomegaly, fatty liver, peroxisome proliferation, and immunotoxicity. Rodents exposed to PFOA in utero have altered hepatic lipid metabolism, increased hepatic de novo lipogenesis and susceptibility to non-alcoholic fatty liver disease (NAFLD), but underlying molecular mechanisms remain unknown. With increasing rates of obesity, diabetes, and NAFLD it is critical to examine the mechanisms by which in utero exposure to PFOA contributes to the development of metabolic syndrome in offspring.

Objectives
To characterize how PFOA exposure during hepatocyte differentiation leads to the development of NAFLD through alterations in DNA methylation profiles and changes in the availability of transcription factor binding sites.

Methods
HepaRG cells (human-derived hepatocyte progenitor cells) were treated with 0.5uM PFOA or vehicle for 48 hours followed by differentiation. Undifferentiated and differentiated hepatocytes exposed to PFOA were assessed relative to controls (n=4). RNASeq was completed; DESeq2 identified differentially expressed genes via false discovery rate (FDR) of &lt;0.05 after Bonferroni correction. Genome-wide DNA methylation analysis via MethylSeq was completed to identify differentially methylated regions (DMRs) defined as minimum number of CpN =5, absolute change in percent methylation &gt;10%, and FDR of &lt;0.05. Enrichment analysis of transcription factor binding motifs within DMRs and single CpG sites (± 200 bp) was performed using HOMER.

Results
PFOA treatment resulted in decreased expression of the transcription factors early growth response protein 1 (EGR1), nuclear receptor Nur77 (NR4A1), early growth response protein 2 (EGR2), krueppel-like factor 10 (KLF10) and fos-related antigen 1 (FOSL1), which are key genes linked to impaired hepatic insulin signaling, lipid metabolism, steatosis and fibrosis (q&lt;0.05) in undifferentiated hepatocytes. Differentiated hepatocytes showed decreased expression of peroxisome proliferator-activated receptor γ coactivator 1-α (PGC1α), peroxisome proliferator-activated receptor γ (PPARγ), forkhead box protein O1 (FOXO1) and increased expression of pyruvate dehydrogenase kinase isozyme 4 (PDK4), genes linked to regulation of lipid metabolism and insulin signaling (q &lt;0.05). MethylSeq analysis identified changes in DMRs located in exons, introns, and intergenic regions, with 57 DMRs in undifferentiated hepatocytes (46 with gains; 11 with losses; q &lt;0.05) and 75 DMRs in differentiated hepatocytes (32 with gains; 41 with losses; q&lt;0.05). HOMER identified 29 known transcription factor binding motifs with changes in methylation in undifferentiated hepatocytes (p&lt;0.05) and 19 in differentiated hepatocytes after PFOA treatment (p&lt;0.05), with significant changes in the EGR1 consensus sequence identified in both comparisons.

Conclusions
We conclude hepatocyte progenitor cells exposed to low dose PFOA results in changes in DNA methylation and expression of key metabolic genes linked to NAFLD, notably EGR1, a gene previously linked to NAFLD, suggesting PFOA exposure in utero has lasting effects.
Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Sunday, June 12, 2022 12:48 p.m. - 12:53 p.m.