Enzymatic activity, histological slices, and hepatic transcriptomics analysis of isoprothiolane effects on juvenile...

The present study evaluated the toxic effects of isoprothiolane (IPT) on juvenile Nile tilapia (Oreochromis niloticus). A total of 500 fish (102.7 ± 11.66 mm; 21.72 ± 0.9 g) were used to determine the 96-hour median lethal concentration (LC₅₀) using six IPT concentrations. In addition, fish were exposed for 21 days to sub-lethal IPT concentrations of 0.24 and 1.2 mg·L^-1, alongside a control group. Liver tissues were sampled on days 7, 14, and 21 for histological examination, enzymatic assays, and transcriptomic analysis. The 96-h LC₅₀ of IPT was calculated as 9.79 mg·L^-1. Histopathological observations revealed clear liver damage in exposed fish, including vacuolation, hepatocyte degeneration, sinusoidal dilation, and nuclear displacement. Superoxide dismutase activity remained unchanged across treatments. At 0.24 mg·L^-1, antioxidant and detoxification enzymes showed time-dependent fluctuations, with early increases in AKP, GSH-Px, CAT, and CES, followed by altered oxidative stress markers and metabolic enzymes at later exposure periods. Similar but more pronounced effects were observed at 1.2 mg·L^-1. KEGG pathway analysis indicated significant enrichment of ferroptosis and necroptosis pathways in IPT-exposed livers. Overall, the findings demonstrate that IPT induces hepatic damage, oxidative stress, and metabolic disruption in Nile tilapia, suggesting potential ecological risks associated with its presence in aquatic environments.