Isoprocarb causes neurotoxicity of zebrafish embryos through oxidative stress-induced apoptosis

Isoprocarb is a widely used carbamate insecticide in agriculture and aquaculture. Overuse of isoprocarb always leaves toxic residues in soil and water, however, the potential ecotoxicity of isoprocarb to organisms is still confusing. In this study, zebrafish embryo was used as a model to evaluate the toxicity of isoprocarb. Zebrafish embryos (96 hpf) were separately exposed at different concentrations of isoprocarb. The mortality rate, hatchability rate, average heart beat of the zebrafish embryo were separately calculated. Our results suggested that exposure to isoprocarb induced developmental toxicity in zebrafish embryos. HE staining showed that exposure to isoprocarb caused developmental defect in the hindbrain of zebrafish embryos. As expected, the behavioral analysis also showed that the motor ability of zebrafish embryos were significantly inhibited following exposure to isoprocarb. In terms of mechanism, The expressions of genes involved in neurodevelopment signaling pathways, such as foxo3a, gfap, syn2a, elavl3 and sox19b, were inhibited in zebrafish embryos after exposure to isoprocarb. The acetylcholinesterase (AChE) activity was also reduced in isoprocarb-treated zebrafish embryos. Moreover, oxidative stress was induced by increasing the reactive oxygen species (ROS) level and decreasing the activity of antioxidant enzyme (SOD) after exposure to isoprocarb. Expectedly, acridine orange (AO) staining and the detection of some apoptosis-related genes revealed that oxidative stress resulted in apoptosis. In short, the expressions of genes associated with the neurodevelopmental signaling pathway are inhibited, and oxidative stress is also induced in zebrafish embryos after exposure to isoprocarb, which may be the molecular basics of isoprocarb-induced neurotoxicity in zebrafish embryos.