Transcriptomic analysis reveals the toxic effects of Clothianidin on the embryonic development of zebrafish.

Clothianidin (CLO) is a neonicotinoid insecticide containing a nitro active group and a chlorinated thiazole heterocycle. It is classified as a second generation thianicotin compound. It is recognized for its augmented stability and broad spectrum of biological toxicity. Numerous studies have shown that CLO exerts toxic effects on the nervous, immunal, reproductive, cardiovascular and multiple organ systems. These effects have been shown to result in mucous membrane and skin damage. In this study, zebrafish embryos were exposed to different concentrations of CLO to observe morphological development and behavioral characteristics. In addition, reactive oxygen species (ROS), neutrophils, apoptosis and erythrocyte production were measured. The results demonstrated that the administration of CLO had a significant effect on several parameters, including embryo hatching rate, mortality, malformation rate, swim-up rate and heart rate. The analysis revealed the presence of abnormalities in embryos, such as pericardial cysts and spinal curvature. Furthermore, the exposure of cells to CLO resulted in increased levels of ROS and neutrophils in the embryos. O-Dianisidine and acridine orange staining revealed an increase in erythrocyte production in the yolk sac, which was accompanied by an increase in cardiac cell apoptosis following exposure. Subsequent analysis via RNA-seq and KEGG pathway analysis identified differentially expressed genes and functional pathways, demonstrating enrichment in the TCA cycle, peroxisomal function, and glutathione metabolism. These findings were subsequently validated by RT-qPCR. These findings suggest that CLO may induce toxic effects in zebrafish embryos by disrupting development, triggering oxidative stress and inflammation, and promoting apoptosis and erythrocyte production.