Chronic perfluorobutanoic acid (PFBA) exposure induces apoptosis and inflammation of gill in zebrafish (Danio rerio).

Abstract

Perfluorobutanoic acid (PFBA), a short-chain perfluoroalkyl substance (PFAS), has been widely adopted as an alternative to regulated long-chain PFAS; however, its chronic ecotoxicological effects remain poorly understood. Herein, an integrated analysis combining transcriptomic, histopathological, and molecular approaches was performed to investigate the impacts of environmentally relevant PFBA exposure (1000 ng/L) on the gill tissue of zebrafish (Danio rerio) over a 63 days post-exposure (dpe). A total of 120 zebrafish were randomly assigned to 4 groups (control, 7 dpe, 35 dpe, and 63 dpe groups), with 3 biological replicates (10 fish per tank) per group. The 1000 ng/L exposure concentration was selected based on published environmental PFBA monitoring data and preliminary dose-response trial results. Histopathological observations revealed progressive gill impairment, characterized by epithelial hyperplasia and tissue disintegration, with prolonged PFBA exposure. Transcriptomic analysis demonstrated sustained dysregulation of genes associated with the nucleotide excision repair pathway, p53 signaling pathway, and apoptotic pathway throughout the exposure period. Molecular assays indicated that PFBA exposure significantly inhibited the expression of key DNA repair proteins (tyms, fen1, and rad51b); in silico molecular docking analyses predicted that PFBA may bind to the active sites of these proteins. Meanwhile, PFBA exposure coordinately upregulated the expression of atm, p53, bax, and casp3 genes, while suppressing bcl-2 expression, thereby activating the mitochondrial apoptotic pathway. Additionally, PFBA exposure induced the activation of inflammatory factors, which further exacerbated gill tissue damage. TUNEL assays confirmed a time-dependent increase in apoptotic signals, which were strongly correlated with cumulative DNA damage. Collectively, our findings suggest a potential mechanistic link between chronic PFBA exposure and gill injury in zebrafish, mediated through the DNA damage-p53-apoptosis cascade. These results underscore the previously underestimated ecological risks posed by short-chain PFAS in aquatic ecosystems.