Environmental exposure to triazole fungicide causes left-right asymmetry defects and contributes to abnormal heart development in zebrafish embryos by activating PPARγ-coupled Wnt/β-catenin signaling pathway.

Triazole fungicides have been widely used all over the world. However, their potential ecological safety and health risks remain unclear, especially their cardiac developmental toxicity. This study systematically investigated whether and how triazole fungicides could activate peroxisome proliferative activity receptor γ (PPARγ) to cause abnormal heart development. Among ten triazole fungicides, difenoconazole (DIF) exhibited the strongest agonistic activity and caused severe pericardial edema in zebrafish embryos, accompanied by a reduction in heart rate, blood flow and cardiac function. In vitro transcriptomic profile implicated that DIF inhibited the Wnt signaling pathway, and in vivo DIF exposure significantly increased the phosphorylation of β-catenin (p = 0.0002) and altered the expression of related genes in zebrafish embryos. Importantly, exposure to DIF could activate PPARγ and inhibit the Wnt/β-catenin signaling pathway, which changed the size of Kupffer's vesicle (KV) (p = 0.02), altered the expression of left-right (LR) asymmetry-related genes, caused cardiac LR asymmetry defect, and eventually led to abnormal heart development. These findings provide evidence for potential developmental toxicity of triazole fungicides and highlight the necessity of assessing their ecological safety and human health risks.