Mechanism of 1α,25-dihydroxyvitamin D3-dependent repression of interleukin-12B

Abstract

Interleukin 12 (IL-12) is a heterodimeric, pro-inflammatory cytokine that plays a central role in activation and differentiation of CD4(+) T cells into interferon-γ secreting T-helper type 1 cells. IL-12B, a gene encoding the larger subunit of active IL-12, has been reported to be down-regulated by the nuclear hormone 1α,25-dihydroxyvitamin D(3) (1α,25(OH)(2)D(3)), but the mechanism of the regulation is unknown. In this study, we have examined the molecular mechanism of transcriptional regulation of the IL-12B gene by 1α,25(OH)(2)D(3) in lipopolysaccharide (LPS)-treated human monocytes (THP-1). Quantitative RT-PCR showed that IL-12B mRNA displays a cyclical expression profile and is down-regulated 2.8-fold during the first 8h and even 12.1-fold 24h after exposure to 1α,25(OH)(2)D(3). Gel shift and quantitative chromatin immunoprecipitation (ChIP) assays demonstrated vitamin D receptor (VDR) binding to genomic regions 480 and 6300bp upstream of the IL-12B transcription start site (TSS). Quantitative ChIP assays also revealed that together with VDR and its partner RXR the above regions recruited the co-repressor NCOR2/SMRT and histone deacetylase 3 leading to a decreased histone 4 acetylation and increased histone 3 trimethylation at the IL-12B promoter and its TSS. We suggest that these repressive epigenetic changes eventually cause down-regulation of IL-12 expression. This article is part of a Special Issue entitled: 11th European Symposium on Calcium.

Oral supplementation with 25(OH)D3 versus vitamin D3: Effects on 25(OH)D levels, lower extremity function, blood pressure, and markers of innate immunity

“…(55) Finally, IL-12, a proinflammatory cytokine that plays a central role in activation and differentiation of CD4(þ) T cells into interferon-g secreting T-helper type 1 cells, has been reported to be downregulated by 1,25-dihydroxyvitamin D treatment. (55,56) In our study, all tested markers of innate immunity showed some response to both types of vitamin D, but it was significantly more pronounced with HyD for four markers of innate immunity (eotaxin, IL-12, MCP-1, and MIP-1b). The response to both types of vitamin D was very rapid in the first 5 days after treatment initiation, during which all but IP-10 and RANTES decreased, followed by an increase of all markers during a 2-day period between day 6 and 8, and a further decline thereafter.…”

Vitamin D in inflammatory diseases

“…An earlier report attributed the down-regulation of IL-12 via interference of 1α,25(OH) 2 D 3 /VDR with NF-κB binding to proximal IL-12 promoter regions (D'Ambrosio et al, 1998). It has been suggested in the more recent report that this suppression of proximal sites is due to epigenetic changes at that location via the distal VDRE binding sites identified in the more recent study (Gynther et al, 2011) (Figure 3). …”

“…IL-12B has been identified as a 1α,25(OH) 2 D 3 -dependently down-regulated gene in LPS-treated THP-1 cells. The gene harbors two VDR binding sites within ~6 kb upstream of the transcription start site to which the VDR and its partner retinoid receptor (RXR) recruit co-repressors and consequently induce epigenetic changes associated with gene repression (Matilainen et al, 2010b; Gynther et al, 2011). An earlier report attributed the down-regulation of IL-12 via interference of 1α,25(OH) 2 D 3 /VDR with NF-κB binding to proximal IL-12 promoter regions (D'Ambrosio et al, 1998).…”

Vitamin D receptor signaling mechanisms: Integrated actions of a well-defined transcription factor

“…For example, 1α,25(OH) 2 D 3 enhances the differentiation of monocytes into functional macrophages with increased phagocytic capacity and altered cytokine-secreting capacity, but impairs the differentiation of monocytes into dendritic cells [100]. The main 1α,25(OH) 2 D 3 targets in differentiating monocytes are anti-microbial peptides, such as cathelicidin, co-stimulatory molecules, such as CD14 [35], and cytokines, such as interleukins 10 and 12b [101,102]. The new insight of the dominant role of VDR in the granulocyte/monocyte module now allows more specific investigations on the functional interplay of VDR with its partner transcription factors, for example with the pioneer factors CEBPA and SPI1.…”