Histopathology and Transcriptomics in Male Zebrafish Livers from a PFOS Multi-Generational Exposure Informs Adverse...

Poly- and perfluoroalkyl substances (PFAS) use in commercial products and industrial applications has resulted in widespread and persistent environmental contamination. Terrestrial and aquatic vertebrates accumulate PFAS in liver tissue potentially inducing hepatotoxicity. The present study investigated tissue-level and molecular effects in 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 (0 [control], 0.1, 0.6, 3.2, 20, and 100 µg/L, nominal, through 180 days post-fertilization (dpf) in both parental (P) and first filial (F1) generations. Histopathological analysis indicated the highest PFOS exposure (100 µg/L, nominal) caused significantly increased incidences of lipid-type hepatocellular vacuolation in both P and F1 generations relative to controls with more prevalent and extensive effects in the F1 generation. RNA sequencing (RNAseq) analysis identified an increased number of transcripts significantly affected in PFOS exposures relative to controls in the F1 (955) versus the P generation (103), where both generations had most effects at the highest PFOS exposure (100 µg/L, nominal). 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 receptors (PPAR) pathway in both generations. To integrate these observations, an adverse outcome pathway (AOP) was developed linking the molecular initiating event (MIE) of a representative chemical stressor (PFOS), binding-initiated interference of PPAR nuclear signaling to disrupted lipid metabolism, lipid accumulation in liver, and ultimately the liver steatosis adverse outcome (AO).