Mitochondrial Unfolded Protein Response Regulates Copper-Induced Oxidative Stress via a Sirt3/FOXO3a Signaling Pathway in Chicken Hepatocytes

Copper (Cu) is an essential trace element but also an agricultural pollutant with hepatotoxic risks. This study investigated the relationship among UPRmt, the Sirt3/FOXO3a pathway, and oxidative stress in chicken hepatocytes under Cu exposure. Here, broilers were fed diets containing 11, 110, 220, or 330 mg/kg Cu for 49 days, and primary hepatocytes were treated with Cu combined with OTC overexpression, Sirt3 agonist ADTL-SA1215, Sirt3 inhibitor 3-TYP, and FOXO3a overexpression or silencing. Cu exposure causes liver injury and activates UPRmt (upregulated HSP60 and LonP1) and was associated with Sirt3/FOXO3a inhibition. OTC-overexpression-induced UPRmt activation further correlated with Sirt3/FOXO3a inhibition, decreased antioxidant enzymes (GPX4 and SOD2), increased oxidative markers (8-OhdG and LPO), and aggravated liver injury. Pharmacological and genetic modulation confirmed Sirt3/FOXO3a as a key downstream mediator. These results suggest that Cu-induced UPRmt activation, association with Sirt3/FOXO3a inhibition, may disrupt the redox balance and promote hepatocyte injury, providing new insights into Cu hepatotoxicity.