Embryonic toxicity of epoxiconazole exposure to the early life stage of zebrafish

Epoxiconazole (EPX), as a broad-spectrum triazole fungicide, is widely used in agriculture to resist pests and diseases, while it may have potential toxicity to non-target organisms. In the present study, early developmental stage zebrafish were used as the subject organisms to assess the toxicity of EPX, and the possible mechanism of toxicity was also discussed by biochemical and transcriptomic analysis. Through embryo toxicity test, we had made it clear that the 96 h LC₅₀ of embryo was 7.204 mg/L, and acute exposure to EPX effected hatching rate, heartbeats, body length and even morphological defects. Then, by being exposed to EPX for 7 days at concentrations of 175 (1/40 LC₅₀), 350 (1/20 LC₅₀) and 700 (1/10 LC₅₀), biochemical parameters were affected, mainly manifested as increase of the triglyceride (TG) level and decrease of glucose content. Correspondingly, the transcription of genes related of glucose metabolism, lipid metabolism and cholesterol metabolism were also affected significantly in larval zebrafish. Moreover, some pathways, including lipid metabolism, glucose metabolism and amino acid metabolism were affected through transcriptome sequencing analysis in the larval zebrafish. Further data analysis based on the sequencing, EPX exposure also affected the expression of genes related to cell apoptosis. We further conformed that the bright fluorescence on the liver and bright spots near the liver by acridine orange staining. In addition, the mRNA levels of apoptosis related genes were also significantly affected in the EPX exposed larval zebrafish. Taken together, the work could provide an insight into toxic effects of EPX on the zebrafish larvae at embryo toxicity and transcriptional levels, providing some evidences for the toxic effects of triazole fungicides on non-target organisms.