IL-36γ Promotes Killing of Mycobacterium tuberculosis by Macrophages via WNT5A-Induced Noncanonical WNT Signaling

Mycobacterium tuberculosis , which primarily infects mononuclear phagocytes, remains the leading bacterial cause of enormous morbidity and mortality because of bacterial infections in humans throughout the world. The IL-1 family of cytokines is critical for host resistance to M. tuberculosis As a newly discovered subgroup of the IL-1 family, although IL-36 cytokines have been proven to play roles in protection against M. tuberculosis infection, the antibacterial mechanisms are poorly understood. In this study, we demonstrated that IL-36γ conferred to human monocyte-derived macrophages bacterial resistance through activation of autophagy as well as induction of WNT5A, a reported downstream effector of IL-1 involved in several inflammatory diseases. Further studies showed that WNT5A could enhance autophagy of monocyte-derived macrophages by inducing cyclooxygenase-2 (COX-2) expression and in turn decrease phosphorylation of AKT/mTOR via noncanonical WNT signaling. Consistently, the underlying molecular mechanisms of IL-36γ function are also mediated by the COX-2/AKT/mTOR signaling axis. Altogether, our findings reveal a novel activity for IL-36γ as an inducer of autophagy, which represents a critical inflammatory cytokine that control the outcome of M. tuberculosis infection in human macrophages.