422.5: CHOP Promotes ROS-Mediated Liver Ischemia and Reperfusion Injury by Inhibiting Mitophagy in Hepatocytes

Abstract

Background: Liver ischemia and reperfusion (IR) injury represents a major risk factor in both partial hepatectomy and liver transplantation. CCAAT/enhancer-binding protein homologous protein (CHOP) is a key regulator of cell death, its precise molecular basis in regulating hepatocyte death during liver IR has not been delineated. Methods: Hepatocellular CHOP deficient mice were generated by bone marrow chimera models using global CHOP knockout mice. Liver partial warm ischemia model and hypoxia/reoxygenation (H/R) model of primary hepatocytes were applied. Liver injury and mitophagy related signaling pathways were investigated. IR-stressed patient liver tissues and serum samples were analyzed as well. Results: Mice with hepatocellular CHOP deficiency exhibited alleviated cell death, decreased reactive oxygen species (ROS) expression and enhanced mitophagy in hepatocytes after IR, confirmed by in vitro studies of hepatocytes after H/R. Mitochondria ROS scavenge by Mito TEMPO effectively attenuated hepatocyte death and liver IR injury of WT mice, whereas no significant effects were observed in hepatocellular CHOP-deficient mice. CHOP depletion upregulated dynamin-related protein 1 (Drp1) and Beclin-1 activation in the mitochondria of hepatocytes leading to enhanced mitophagy. Following IR, increased CHOP expression and impaired mitophagy activation were observed in the livers of patients undergoing hepatectomy. N-acetylcysteine (NAC) pretreatment significantly improved the liver function of patients after surgery. Conclusion: IR-induced CHOP activation exacerbates ROS-mediated hepatocyte death by inhibiting Drp1-Beclin-1-dependent mitophagy. National Natural Science Foundation of China (82071798, 81901628, 81600450), National Science Foundation of Jiangsu Province (BK20191490), CAMS Innovation Fund for Medical Sciences (No.2019-I2M-5-035).