RIP3 Blockade Drives Myeloid-Derived Suppressor Cell-Mediated Immune Tolerance in Immune-Mediated Hepatitis

Abstract

Background: Excessive and uncontrolled immune activation plays a deleterious role in liver damage of autoimmune hepatitis (AIH), thus, it`s of great significance to identify the regulation of immune tolerance. Receptor-interacting protein kinase 3 (RIP3) has been found to be down-regulated in tumor tissues and mediates tumor immune evasion. However, the role of RIP3 in AIH remains elusive. We aimed to investigate the role of RIP3 in the regulation of inflammation and immune tolerance in immune-mediated hepatitis (IMH). Methods: RIP3 expression was evaluated in the livers of AIH patients and mice models. Mice were treated with GSK872, a RIP3 specific inhibitor, or glucocorticoid dexamethasone before concanavalin A (ConA)-induced IMH. Real-time PCR, western blotting, and flow cytometry served to explore the molecular mechanisms involved. The depleting anti-mouse Gr-1 antibody and isotype control were used for further determine the role of MDSCs in GSK872 treatment. Findings: AIH patients and mice model displayed pronounced RIP3 activation in the liver tissues. RIP3 blockade by GSK872 prevented ConA-induced IMH by reduced hepatic proinflammatory cytokines and immune cells including Th17 cells and macrophages. Further experiments revealed that RIP3 inhibition resulted in an increase in CD11b+ Gr-1+ MDSCs with immunoregulatory properties in the livers, spleen, and peripheral blood. Moreover, the depletion of Gr-1+ MDSCs abrogated the protective effect and immune suppression function of GSK872 in ConA-induced IMH. Interpretation: RIP3 blockade prevents ConA-induced IMH through a MDSC-dependent mechanism. Inhibition of RIP3 kinase may be a novel therapeutic avenue for AIH treatment. Funding Statement: The study was supported by the National Natural Science Foundation of China (81860109). Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: This study was approved by the Ethics Committee of Tianjin Medical University General Hospital, and all participants provided signed informed consents. The animal use protocol has been reviewed and approved by the Animal Ethical and Welfare Committee of Tianjin Medical University, Approval No. IRB2020-WZ-175.