Perfluorooctane sulfonate (PFOS) exposure and alcohol-associated liver disease severity in a mouse chronic-binge ethanol feeding model
Background: Exposure to pollutants including the ubiquitous 'forever chemical', Perfluorooctane sulfonate (PFOS) has increasingly been associated with metabolic dysfunction-associated steatotic liver disease (MASLD). Recent epidemiological evidence has identified associations between Per- and polyfluoroalkyl substances (PFAS) exposure and increased liver injury in alcohol consumers, suggesting potential interactions between these exposures. However, the intersection of pollutant exposures and alcohol-associated liver disease (ALD) is not well studied. We hypothesize that pollutants may disrupt hepatic metabolism to modify ALD severity. Recently, we developed a two-hit (ethanol plus pollutant) mouse model, enabling testing of this hypothesis. Here, we elucidate the metabolic and disease-modifying effects of PFOS in this model. Methods: Male C57BL/6J mice were fed isocaloric control or 5% Ethanol (EtOH) Lieber-DeCarli diet for 15 days. From day 6 of feeding, mice were concurrently gavaged with 1 mg/kg PFOS or 2% tween-80 vehicle for 10 days, followed by a 5 g/kg EtOH binge dose and euthanized 5-6 hours later. Results: Approximately 60% of the administered PFOS dose accumulated in liver. PFOS exacerbated EtOH-induced hepatic steatosis and was associated by higher levels of plasma very low-density lipoprotein (vLDL) and alanine aminotransferase (ALT). PFOS upregulated hepatic ethanol-metabolizing enzymes and lowered blood alcohol levels. Ingenuity Pathway Analysis (IPA) Top Toxicity Functions/Lists associated with hepatic gene expression following PFOS co-exposure in EtOH-fed mice included: fatty acid metabolism and liver steatosis; nuclear receptor activation, cytochrome P450, and reactive oxygen species (ROS); apoptosis; liver fibrosis; and hepatocellular carcinoma (HCC). GO/KEGG analyses similarly revealed enrichment in fatty acid, xenobiotic, alcohol, or glutathione metabolic processes; and Peroxisome proliferator-activated receptor (PPAR) signaling. PFOS upregulated hepatic expression of several nuclear receptors (e.g., Ppara, Car, and Pxr) and their P450 target genes (e.g., Cyp4a10, Cyp2b10, and Cyp3a11) by RT-PCR or Western blot, confirming key IPA predictions. Conclusions: PFOS is a metabolism disrupting chemical that worsened ALD severity. PFOS activated hepatic nuclear receptors and enriched hepatic transcriptional pathways associated with steatosis, xenobiotic metabolism, oxidative stress, cell death, fibrosis, and HCC. These data demonstrate a novel mechanism whereby PFOS exacerbates ALD through coordinated dysregulation of lipid homeostasis and liver injury, potentially mediated by nuclear receptor activation. The identification of PFOS as an ALD risk modifier highlight the critical need to evaluate environmental pollutants as potential contributors to liver disease progression in vulnerable populations. More data are required on environmental pollution as a disease modifying factor in ALD. Overall design: Total RNA was extracted from liver tissue samples (n=6), and RNA-seq libraries were prepared using the NEBNext Ultra II RNA Library Prep Kit for Illumina (NEB, Ipswich, MA). Sequencing was performed on an Illumina NovaSeq 6000 S4 flow cell using a 2 x 150 bp paired-end configuration.