Curcumin protects against difenoconazole-induced kidney injury in carp by inhibiting ferroptosis through the Nrf2/GPX4 axis

Difenoconazole (DFZ) is a persistent triazole fungicide that leads to aquatic toxicity and ecosystem damage due to its environmental persistence and high toxicity. Curcumin (CUR), a natural polyphenol derived from turmeric, exhibits strong anti-inflammatory, antioxidant, and antitumor properties. This study assesses CUR's protective role against DFZ-induced kidney injury in carp and investigates its mechanisms. Carp were exposed to DFZ for 30 days, with dietary supplementation of 400 mg/kg CUR. H&E staining revealed that CUR significantly reduced DFZ-induced histopathological damage in the kidneys. Dihydroethidium staining and biochemical assays demonstrated that CUR effectively lowered Reactive Oxygen Species levels and lipid peroxidation. Through biochemical kits, qPCR, and Western blotting, it was found that CUR decreased T-AOC and iron content, while activating the Nrf2/HO-1 pathway, thereby alleviating ferroptosis. CUR also upregulated the expression of xCT and GPX4, increased GSH levels, and further suppressed ferroptosis. In terms of inflammation, CUR improved the response by reducing pro-inflammatory cytokines (iNOS, IL-1β, IL-6, TNF-α) and increasing anti-inflammatory factors (IL-10, TGF-β1). With regard to apoptosis, CUR inhibited pro-apoptotic proteins (Bax, Cleaved-caspase3, Cleaved-caspase9, Cytochrome c) and restored the anti-apoptotic protein Bcl-2. In conclusion, CUR alleviates DFZ-induced kidney injury in carp by inhibiting ferroptosis through the Nrf2/GPX4 axis, while reducing oxidative stress, inflammation, and apoptosis. This study highlights CUR as a promising natural agent for mitigating environmental toxicity caused by triazole fungicides.