PFOS and its substitute F-53B suppress growth and alter cAMP/PKA signaling and the GH/IGF axis in juvenile cyprinid fish

Replacement of legacy PFASs by structurally related alternatives has raised increasing concern because the ecological safety of these substitutes remains insufficiently evaluated. F-53B has been widely used as a substitute for PFOS, but its growth-related endocrine toxicity in freshwater aquaculture fish remains poorly understood. In this study, juvenile Spinibarbus hollandi and Megalobrama terminalis were exposed to PFOS and F-53B at a nominal concentration of 5 μg/L for 60 days. Growth performance, tissue accumulation, histopathology, GH/IGF-axis hormones, cAMP/PKA signaling, transcriptomic responses, molecular docking and primary pituitary cell responses were integrated to evaluate the growth-related effects and associated mechanisms. PFOS and F-53B significantly reduced body length and body weight growth in both fish species. Both compounds accumulated in multiple tissues, with relatively high accumulation in the liver and generally higher residue levels of F-53B than PFOS. Histological alterations were observed in the pituitary and liver. Serum GH, IGF-1 and IGF-2 levels were markedly decreased, accompanied by reduced cAMP content and PKA activity in pituitary tissues. Transcriptomic and qPCR analyses further showed alterations in growth- and endocrine-related pathways, including neuroactive ligand-receptor interaction, PI3K-Akt, JAK-STAT, HIF-1 and Notch signaling. Molecular docking predicted possible interactions of PFOS and F-53B with GHRHR and GHR, while primary pituitary cell assays showed changes in cAMP/PKA signaling and intracellular GH levels following exposure. Overall, growth inhibition was accompanied by alterations in cAMP/PKA signaling and the GH/IGF axis, suggesting their possible involvement in the observed growth effects. These findings identify growth-related endocrine effects of F-53B under the tested conditions and support further assessment of its toxicity as a PFOS substitute.