Vitamin D Induces Interleukin-1β Expression: Paracrine Macrophage Epithelial Signaling Controls M. tuberculosis Infection

Abstract

Although vitamin D deficiency is a common feature among patients presenting with active tuberculosis, the full scope of vitamin D action during Mycobacterium tuberculosis (Mtb) infection is poorly understood. As macrophages are the primary site of Mtb infection and are sites of vitamin D signaling, we have used these cells to understand the molecular mechanisms underlying modulation of the immune response by the hormonal form of vitamin D, 1,25-dihydroxyvitamin D (1,25D). We found that the virulent Mtb strain H37Rv elicits a broad host transcriptional response. Transcriptome profiling also revealed that the profile of target genes regulated by 1,25D is substantially altered by infection, and that 1,25D generally boosts infection-stimulated cytokine/chemokine responses. We further focused on the role of 1,25D- and infection-induced interleukin 1β (IL-1β) expression in response to infection. 1,25D enhanced IL-1β expression via a direct transcriptional mechanism. Secretion of IL-1β from infected cells required the NLRP3/caspase-1 inflammasome. The impact of IL-1β production was investigated in a novel model wherein infected macrophages were co-cultured with primary human small airway epithelial cells. Co-culture significantly prolonged survival of infected macrophages, and 1,25D/infection-induced IL-1β secretion from macrophages reduced mycobacterial burden by stimulating the anti-mycobacterial capacity of co-cultured lung epithelial cells. These effects were independent of 1,25D-stimulated autophagy in macrophages but dependent upon epithelial IL1R1 signaling and IL-1β-driven epithelial production of the antimicrobial peptide DEFB4/HBD2. These data provide evidence that the anti-microbial actions of vitamin D extend beyond the macrophage by modulating paracrine signaling, reinforcing its role in innate immune regulation in humans.

Engagement of the Aryl Hydrocarbon Receptor in Mycobacterium tuberculosis–Infected Macrophages Has Pleiotropic Effects on Innate Immune Signaling

“…Previous studies showed that IL1B is also induced by M. tuberculosis infection of primary human macrophages (25), a result that we confirmed in this study (Supplemental Fig. 2H).…”

“…Analysis of the microarray data revealed that AHR, ARNT, and RELB transcripts were well expressed in both uninfected and infected cells (25). Expression of AHR and RELB in THP-1 cells was enhanced modestly (1.5-2-fold) and 3-4-fold, respectively, after 24 h of infection with either H37Ra or H37Rv, whereas that of ARNT was slightly inhibited (25) (Supplemental Fig.…”

“…PBMCs were isolated, as previously described (25). Briefly, after PBMC isolation, monocytes were left to adhere to tissue culture dishes in RPMI 1640-10% FBS.…”

“…The immune complexes were collected using 40 ml Protein A Beads for 2 h at 4˚C with rotation. The beads were washed for 4 min on a rotating platform, as previously described (25), and the immune complexes were eluted twice using 200 ml elution buffer (1% SDS, 100 mM NaHCO 3 ). The supernatants were combined, and the immune complexes were reverse cross-linked for 6 h at 65˚C in the presence of proteinase K (20 mM).…”

High Serum 25-Hydroxyvitamin D Levels Are Associated with Pediatric Sepsis

“…Production of 1,25-dihydroxyvitamin D 3 is further increased by interferon γ. In addition to cathelicidin and B-defensin, 1,25-dihydroxyvitamin D 3 induces other important antimicrobial factors, including reactive oxygen species, nitric oxide synthase and active form of interleukin-1β that trigger the beginning of inflammation cascade (Verway et al 2013).…”