Mechanisms of concanavalin A-induced cytokine synthesis by hepatic stellate cells: Distinct roles of interferon regulatory factor-1 in liver injury

Richa Rani,Sudhir Kumar,Akanksha Sharma,Sujit K Mohanty,Bryan Donnelly,Gregory M Tiao,Chandrashekhar R Gandhi

doi:10.1074/jbc.ra118.005583

Abstract

Mice depleted of hepatic stellate cells (HSCs) are protected from concanavalin A (ConA)-induced liver injury that is mediated by the activation of interferon regulatory factor 1 (IRF1). The aim of this study was to determine the mechanisms of ConA-mediated signaling and synthesis/release of mediators by HSCs that damage hepatocytes. Primary cultures of wildtype (WT) and IRF1-knockout (KO) HSCs and hepatocytes were used, and ConA-induced liver damage in interferon (IFN)αβ receptor-deficient (IFNαβR-KO) mice was determined. Specific binding of ConA to HSCs induced rapid activation of JAK2 and STAT1. ConA-induced expression of IRF1, IFNβ, tumor necrosis factor α, and CXCL1 was abrogated by selective inhibition of JAK2 and STAT1. Despite activating JAK2/STAT1, ConA failed to stimulate expression of inflammatory cytokines in HSCs from IRF1-KO mice. ConA-conditioned WT-HSC medium caused activation of JNK and caspase 3, and apoptosis of hepatocytes from WT but not from IRF1-KO or IFNαβR-KO mice. Conversely, ConA-conditioned medium of IRF1-KO HSCs failed to cause apoptosis of WT or IRF1-KO hepatocytes. IFNαβR-KO mice were protected from ConA-induced liver damage, and ConA-induced hepatic expression of IRF1 and pro-inflammatory cytokines and chemokines, and infiltration of neutrophils were significantly lower in IFNαβR-KO than in WT mice. These results demonstrate distinct roles of IRF1 in hepatic inflammation (HSCs) and injury (hepatocytes) and can be an important target for intervention in acute liver injury.

Highlights

Mice depleted of hepatic stellate cells (HSCs) are protected from concanavalin A (ConA)-induced liver injury that is mediated by the activation of interferon regulatory factor 1 (IRF1)
We found that ConA stimulates JAK2/STAT1 signaling in HSCs that is coupled to increased nuclear translocation of IRF1 and expression of cytokines and chemokines including IFN␤
We reported that ConA increases expression of the transcription factor IRF1, inflammatory cytokines TNF␣ and IFN␤, and the neutrophil/monocyte chemoattractant CXCL1 in HSCs [16]

Summary

Introduction

Mice depleted of hepatic stellate cells (HSCs) are protected from concanavalin A (ConA)-induced liver injury that is mediated by the activation of interferon regulatory factor 1 (IRF1). IFN␣␤R-KO mice were protected from ConA-induced liver damage, and ConA-induced hepatic expression of IRF1 and pro-inflammatory cytokines and chemokines, and infiltration of neutrophils were significantly lower in IFN␣␤R-KO than in WT mice These results demonstrate distinct roles of IRF1 in hepatic inflammation (HSCs) and injury (hepatocytes) and can be an important target for intervention in acute liver injury. We found that ConA stimulates JAK2/STAT1 signaling in HSCs that is coupled to increased nuclear translocation of IRF1 and expression of cytokines and chemokines including IFN␤ This effect was strongly mitigated in HSCs from IRF1knockout (IRF1-KO) mice, and hepatocytes from IRF1-KO or IFN␣␤R-KO mice were protected from WT-HSC/ConA-induced apoptosis. The data demonstrate that IRF1, by stimulating JAK/STAT-mediated synthesis of IFN␤ in HSCs and by causing IFN␤-induced hepatocyte injury, plays distinct roles in ConA-induced liver damage

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Conclusion