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

Abstract

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.