β‐catenin regulates innate and adaptive immunity in mouse liver ischemia‐reperfusion injury

Dendritic cells (DCs) are critical mediators of immune responses that integrate signals from the innate immune system to orchestrate adaptive host immunity. This study was designed to investigate the role and molecular mechanisms of STAT3‐induced β‐catenin in the regulation of DC function and inflammatory responses in vitro and in vivo. STAT3 induction in lipopolysaccharide (LPS)‐stimulated mouse bone marrow‐derived DCs (BMDCs) triggered β‐catenin activation by way of GSK‐3β phosphorylation. The activation of β‐catenin inhibited phosphatase and tensin homolog delete on chromosome 10 (PTEN) and promoted the phosphoinositide 3‐kinase (PI3K)/Akt pathway, which in turn down‐regulated DC maturation and function. In contrast, knockdown of β‐catenin increased PTEN/TLR4 (Toll‐like receptor 4), interferon regulatory factor‐3 (IRF3), nuclear factor kappa B (NF‐κB) activity, and proinflammatory cytokine programs in response to LPS stimulation. In a mouse model of warm liver ischemia and reperfusion injury (IRI), disruption of β‐catenin signaling increased the hepatocellular damage, enhanced hepatic DC maturation/function, and PTEN/TLR4 local inflammation in vivo. Conclusion: These findings underscore the role of β‐catenin to modulate DC maturation and function at the innate‐adaptive interface. Activation of β‐catenin triggered PI3K/Akt, which in turn inhibited TLR4‐driven inflammatory response in a negative feedback regulatory mechanism. By identifying the molecular pathways by which β‐catenin regulates DC function, our findings provide the rationale for novel therapeutic approaches to manage local inflammation and injury in IR‐stressed liver. (HEPATOLOGY 2013)