PFOS-induced black liver and hepatic aging in mice: A new paradigm in environmental hepatotoxicology

Perfluorooctanesulfonic acid (PFOS), a persistent environmental contaminant still imported and widely used in industrial and consumer products, poses poorly defined risks under chronic occupational exposure, with limited research on its role in environmental liver aging. Here, we identify previously unrecognized hepatotoxicity of PFOS in mice exposed to an occupationally relevant dose (10 mg/kg) over subacute (25-day) and chronic (105-day) periods. While both exposures induced mild metabolic-associated steatotic liver disease (MASLD) without fibrosis, only chronic exposure produced a distinct "black liver" phenotype marked by pigmentation, hepatic atrophy, and aging. The black liver discoloration was associated with hepatic congestion and the consequential blood stasis likely contributed to the darkened liver appearance. PFOS also disrupted bile canaliculi by downregulating ZO-1 and mislocalizing BSEP and MRP2, resulting in cholestasis mimicking the Dubin-Johnson Syndrome which displays black liver appearance. Most notably, PFOS activated aging hallmarks, including oxidative stress (superoxide, 4-HNE), genomic instability (γH2AX, 8-oxo-dG), cellular senescence (SA-β-Gal, p21^WAF1/Cip1), and sirtuin reduction (SIRT1 and SIRT7). Mechanistically, chronic PFOS downregulated autophagy complexes (ULK1-FIP200-ATG13 and ATG14L-Beclin1-Vps34) and reduced LC3B-I/II conversion, indicating impaired autophagosome formation and blocked flux. Pharmacological restoration of autophagy in PFOS-treated AML12 cells ameliorated intracellular lipid droplets, canalicular disruption, oxidative stress and aging pigment buildup, suggesting PFOS as a silent driver of irreversible liver aging at least through autophagy suppression. Finally, transcriptomics of PFOS-exposed human liver spheroids recapitulated aging and cholestasis, underscoring translational relevance. These findings redefine the occupational toxicological profile of PFOS, supporting the inclusion of congestion, pigment, and aging biomarkers in occupational PFAS assessments.