Histopathology and transcriptomics in male zebrafish livers from a perfluorooctanesulfonic acid multigenerational exposure inform adverse outcome pathway development for liver steatosis

Poly- and perfluoroalkyl substance use in commercial products and industrial applications has resulted in widespread and persistent environmental contamination. Terrestrial and aquatic vertebrates accumulate poly- and perfluoroalkyl substances in liver tissue, potentially inducing hepatotoxicity. The present study investigated tissue-level and molecular effects in the livers of male zebrafish (Danio rerio) exposed for two generations to perfluorooctanesulfonic acid (PFOS). Histopathology and transcriptomic expression analysis (RNA sequencing) were performed for males exposed to PFOS at a control concentration (0 µg/L) and five nominal concentrations (0.1, 0.6, 3.2, 20, and 100 µg/L) through 180 days postfertilization in the parental (P) and first filial (F1) generations. Histopathological analysis indicated that the highest PFOS exposure (100 µg/L, nominal) caused significantly increased incidences of lipid-type hepatocellular vacuolation in P and F1 generations relative to controls with more prevalent and extensive effects in the F1 generation. The RNA sequencing analysis identified an increased number of transcripts significantly affected in PFOS exposures relative to controls in the F1 generation (955) versus the P generation (103), where both generations had most effects at the highest PFOS exposure (100 µg/L). Histopathological observations of disrupted lipid phenotypes in liver corresponded with transcriptomic identification of significantly enriched metabolic pathways underlying lipid metabolism, including cholesterol biosynthesis and the peroxisome proliferator-activated receptor (PPAR) pathway in both generations. To integrate these observations, an adverse outcome pathway was developed linking the molecular initiating event of a representative chemical stressor (PFOS) binding PPAR isoforms, binding-initiated interference of PPAR nuclear signaling to disrupted lipid metabolism, lipid accumulation in liver, and ultimately the liver steatosis adverse outcome.