Primary effect of 1α,25(OH)2D3 on IL-10 expression in monocytes is short-term down-regulation

Abstract The biologically most active vitamin D compound, 1α,25-dihydroxyvitamin D 3 (1α,25(OH) 2 D 3 ), influences the status of inflammation by modulating the expression of several cytokine genes. In this study, we have examined the mechanism of transcriptional regulation of interleukin 10 ( IL-10 ) by 1α,25(OH) 2 D 3 in lipopolysaccharide (LPS)-treated human monocytes (THP-1). Quantitative PCR showed that IL-10 mRNA expression was significantly down-regulated (2.8-fold) during the first 8 h of 1α,25(OH) 2 D 3 treatment, while after 48 h it was up-regulated (3-fold). Gel shift and quantitative chromatin immunoprecipitation (ChIP) assays showed that the vitamin D receptor (VDR) binds in a cyclical fashion to a promoter region 1500–1700 bp upstream of the IL-10 transcription start site (TSS) containing two conserved VDR binding sites. Targeting of VDR binding sites by enhancer specific duplex RNAs revealed that only the more distal element is functional and chromosome conformation capture analysis suggested that this region loops 1α,25(OH) 2 D 3 -dependently to the TSS. Quantitative ChIP and micrococcal nuclease assays also revealed 1α,25(OH) 2 D 3 -dependent cyclical epigenetic changes and nucleosome remodeling at this promoter region. In conclusion, in LPS-treated THP-1 cells the primary effect of 1α,25(OH) 2 D 3 on IL-10 expression is down-regulation, which is achieved via a cyclical recruitment of VDR to the promoter.