Knockout Attenuates Inflammatory Response and Mitochondrial Dysfunction after Hepatic Ischemia-reperfusion Injury

Abstract

Background: Ischemia-reperfusion (IR) injury is an inevitable consequence during liver transplantation. IL-17a initiates mitochondrial permeability transition pore (mPTP) opening in human platelets. Onset of mPTP plays a pivotal role on IR injury by inducing apoptotic and necrotic cell death. We aimed to investigate the role of IL-17a on mitochondria-driven hepatocyte apoptosis after IR injury. Methods: The association between IL-17a expression and inflammatory response was analyzed both in human and rat liver transplantation. Wild-type (WT) and IL-17a knockout (KO) mice fed with high fat diet were subject to hepatic IR injury and major hepatectomy. Mitochondrial depolarization in hepatocytes was observed in live mice longitudinally using intra-vital imaging system. The cell adhesion and migration capacity was compared between the primary bone marrow neutrophils isolated from WT and IL-17a KO mice when co-cultured with liver sinusoidal endothelial cells. Results: Serum IL-17a was significantly increased by 1.9 and 2.7 folds in normal graft and fatty graft respectively after human (Fig.A p=0.014) and rat (p=0.042) liver transplantation. It had a positive correlation with pro-inflammatory cytokines and serum transaminase levels. In our mouse hepatic IR injury model, knockout of IL-17a notably attenuated pro-inflammatory cytokines expression (Fig.B), neutrophils infiltration (Fig.C) and hepatocytes apoptosis (Fig.D) in fatty liver. Less mitochondrial depolarization (mPTP opening) in hepatocytes was observed in IL-17a knockout mice compared with wild-type mice (Fig.E 8% vs 30%) both in normal and fatty liver. Increased mitochondrial reactive oxygen species (mROS), phosphorylation of NF-?B and MAPK after hepatic IR injury could be suppressed by knockout of IL-17a (Fig.F). In vitro, IL-17a deficiency decreased neutrophils migration and adhesion activity in response to liver sinusoidal endothelial cells. Conclusions: Knockout of IL-17a protected fatty liver against IR injury through suppression of inflammatory response and improvement of mitochondrial function.