1,25 ‑Dihydroxyvitamin D regulates macrophage polarization and ameliorates experimental inflammatory bowel disease by suppressing miR-125b.

This study aimed to explore whether 1,25(OH)2D3 modulates macrophage polarization in inflammation. Peripheral blood mononuclear cells and colitis mice were treated with 1,25(OH)2D3. Macrophages were transfected with siRNA-vitamin D receptor (VDR) or miR-125b mimic or inhibitor, and 1,25(OH)2D3-pretreated colitis mice were injected with a miR-125b agomir. The distribution of macrophage subsets and macrophage subtype characteristics was analyzed. As expected, 1,25(OH)2D3 transformed lipopolysaccharide-induced M1 macrophages to the M2 subset, downregulated tumor necrosis factor-α and interleukin (IL)-6 expression and interferon regulatory factor 5 (IRF5) phosphorylation, and upregulated IL-10, arginase-1, VDR, and IRF4 expression. SiRNA-VDR and miR-125b mimic significantly impaired 1,25(OH)2D3 activity. In colitis mice, 1,25(OH)2D3 pretreatment ameliorated disease activity, converted M1 macrophages to the M2 subtype, suppressed IRF5 phosphorylation, and increased IRF4 expression in lamina propria mononuclear cells (LPMC). miR-125b agomir injections reversed 1,25(OH)2D3 action. Collectively, the results demonstrate that 1,25(OH)2D3 downregulates miR-125b expression and promotes M1 macrophage polarization to the M2 subtype. 1,25(OH)2D3 pretreatment ameliorated colitis by restoring the LPMC macrophage subtype balance. PMID: 30540970 [PubMed - as supplied by publisher]
Source: International Immunopharmacology - Category: Allergy & Immunology Authors: Tags: Int Immunopharmacol Source Type: research