Anti-inflammatory effect of 1,25-dihydroxyvitamin D3 is associated with crosstalk between signal transducer and activator of transcription 5 and the vitamin D receptor in human monocytes.

1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) has an anti-inflammatory effect on human monocytes incubated with sera from patients with type 2 diabetes/diabetic nephropathy; however, the detailed mechanism behind the effect remains to be explored. The current study further validated the effects of 1,25-(OH)2D3 and lipopolysaccharide (LPS) + human recombinant interleukin (IL)-15 on the expression of the vitamin D receptor (VDR) and phosphorylated signal transducer and activator of transcription 5 (p-STAT5) in human monocytes and explored the possible interaction between VDR and p-STAT5. Synchronized THP-1 cells were divided into pre-intervened groups, namely the control, LPS + IL-15 and 1,25-(OH)2D3, groups, according to their differing treatments. The expression of STAT5 and p-STAT5 was evaluated by western blot analysis; the concentration of IL-6 in the supernatant was determined using an enzyme-linked immunosorbent assay; the expression of cytoskeletal proteins was observed using immunofluorescence and laser confocal microscopy; and the possible intranuclear interaction between VDR and p-STAT5 was investigated using immunofluorescence, immuno-coprecipitation and western blot analysis. LPS + IL-15 upregulated p-STAT5 expression and the IL-6 level (P<0.05), with cytoskeletal rearrangement. These effects were partially prevented through pretreatment with 1,25-(OH)2D3. The LPS + IL-15 group and the 1,25-(OH)2D3 group exhibited an interaction between p-STAT5 and VDR in the nucleus, with the latter group showing a significant increase compared with the former (P<0.05). The immuno-coprecipitation results provided evidence of the interaction between VDR and p-STAT5, which suggests the existence of STAT5-VDR crosstalk in THP-1 monocytes. Cytoskeletal rearrangement, VDR and p-STAT5 potentially have interactions in THP-1 monocytes. The anti-inflammatory effect of 1,25-(OH)2D3 may be associated with crosstalk between STAT5 and VDR, which further induces cytoskeletal rearrangement.