Hmgb1-TLR4-IL-23-IL-17A Axis Promote Ischemia-Reperfusion Injury in a Cardiac Transplantation Model

Background. Cardiac transplantation is the last resort for patients with end-stage heart failure. Ischemia-reperfusion (IR) injury is a major issue in cardiac transplantation. Inflammatory processes play a major role in myocardial IR injury. However, the cellular and molecular immune mechanisms of myocardial IR injury remain elusive. Methods. Hearts of C57BL/6 mice were flushed and stored in cold Bretschneider solution for 8 hr and then transplanted into syngeneic recipient. The involvement of high-mobility group box 1 (Hmgb1) and interleukin (IL)-17A was assessed in functional assays by neutralizing Hmgb1 or IL-17A. Results. IL-17A was elevated after myocardial IR injury in cardiac transplantation. IL-17A was predominantly produced by gamma delta T cells rather than CD4(+) or CD8(+) T cells infiltrated into the cardiac isografts. Neutralizing antibody against IL-17A or gamma delta TCR attenuated cardiomyocyte apoptosis and neutrophil recruitment. Furthermore, a neutralizing IL-23p19 antibody decreased the level of IL-17A and neutrophil infiltration. Importantly, IL-23 and IL-17A were reduced after inhibition of macrophages and could not be induced in TLR4(-/-) mice after IR injury. Meanwhile, Hmgb1 increased after IR injury and the Hmgb1 inhibitor glycyrrhizin markedly reduced the production of IL-23 and IL-17A and ameliorated myocardial IR injury. Conclusion. The Hmgb1-TLR4-IL-23-IL-17A axis contributes to cardiomyocyte apoptosis, neutrophil accumulation and IR injury in cardiac transplantation.