IL-36/LXR axis modulates cholesterol metabolism and immune defense to Mycobacterium tuberculosis

Mycobacterium tuberculosis (Mtb) is a life-threatening pathogen in humans. Bacterial infection of macrophages usually triggers strong innate immune mechanisms, including IL-1 cytokine secretion. The newer member of the IL-1 family, IL-36, was recently shown to be involved in cellular defense against Mtb. To unveil the underlying mechanism of IL-36 induced antibacterial activity, we analyzed its role in the regulation of cholesterol metabolism, together with the involvement of Liver X Receptor (LXR) in this process. Here we report that, in Mtb-infected macrophages, IL-36 signaling modulates cholesterol biosynthesis and efflux via LXR. Moreover, IL-36 induces the expression of cholesterol-converting enzymes and the accumulation of LXR ligands, such as oxysterols. Ultimately, both IL-36 and LXR signaling play a role in the regulation of antimicrobial peptides expression and in Mtb growth restriction. These data provide novel evidence for the importance of IL‑36 and cholesterol metabolism mediated by LXR in cellular host defense against Mtb. THP-1 macrophages (scramble and IL36R knockdown) were infected with Mycobacterium tuberculosis for 24 hour and RNA from the sample lysates were extracted for further microarray analyses. Three independent experiments were included.