Risk assessment of difenoconazole pollution in carp (Cyprinus carpio): Involvement of liver metabolism disorder and IP3R-Sig1R mediated mitochondrial Ca2+ overload

Environmental residues of the fungicide difenoconazole (DFZ) have been shown to pose a threat to mammals. However, the risk assessment of DFZ for cultured carp remains unclear. The aim of this study was to investigate the adverse effects of DFZ on carp liver and their molecular mechanisms by simulating the environmental contamination concentrations of DFZ. Our results showed that DFZ induced structural damage in the liver, including edema, vacuolation, and congestion. In addition, DFZ residues were detected in liver tissues. Mechanistically, DFZ causes mitochondrial dysfunction by promoting Ca²⁺ transfer from the endoplasmic reticulum (ER) to mitochondria via IP3R, leading to the onset of ROS burst and apoptosis, and the inhibition of Nrf2 antioxidant function by DFZ also results in uncontrolled ROS. Mitophagy was also activated intracellularly to counteract mitochondrial damage. Interestingly, treatment with 2-APB alleviated mitochondrial dysfunction, restored the mitochondrial membrane potential, and inhibited apoptosis by blocking the translocation of Ca²⁺ from the ER to the mitochondria. Metabolomic analysis revealed that DFZ disrupted energy metabolism in carp liver, whereas 2-APB reversed DFZ-induced metabolic alterations. In conclusion, the present study elucidates the threat of DFZ to carp liver and highlights the mechanism of damage, thereby helping to explain the impact of agriculture on the aquatic environment.