Crosstalk with the cholinergic pathway may be responsible for chlorpyrifos-induced reproductive toxicity in fish

Chlorpyrifos (CPF), a commonly applied organophosphate insecticide, is known to disrupt the endocrine systems of aquatic species. However, further research is required to elucidate the molecular mechanisms involved in the reproductive toxicity of fish. In the present study, zebrafish were exposed to environmentally relevant concentrations of CPF (1, 10, and 50 μg/L) for a 21-day period. Within the concentration range at which chlorpyrifos significantly inhibits the activity of acetylcholinesterase in zebrafish, there is a significant decrease in reproductive capacity of 31.65 %. The RNA-seq analysis has revealed that processes such as transporter activity, reproduction, and reproductive function are affected. Elevated FSH and LH levels in CPF-exposed females were observed at concentrations of 10 μg/L and 50 μg/L. Furthermore, the CPF treatment resulted in the upregulation of esr2b, hsd3b1, fshr, gnrh2, vtg1, and vtg2, while cyp19a1a was found to be downregulated. Co-exposure to cetrorelix acetate, a potent GnRH receptor antagonist, has been demonstrated to normalize gene expression and restore E₂ levels. These results suggest that CPF-induced reproductive toxicity involves crosstalk between cholinergic signaling and the HPG axis. These findings underscore the complex toxicity and ecological risks associated with CPF.