Effects of 1,25-(OH) 2 D 3 on the expressions of vitamin D receptor, STAT5 and cytoskeletal rearrangement in human monocytes incubated with sera from type 2 diabetes patients and diabetic nephropathy patients with uremia

Objective To explore the effects of 1,25-(OH) 2 D 3 and lipopolysaccharide (LPS) plus human recombinant interleukin-15 (IL-15) on expression of vitamin D receptor (VDR) and STAT5, and cytoskeletal rearrangement in human monocytes incubated with sera from type 2 diabetes (T2DM) patients and diabetic nephropathy (DN) patients with uremia. Materials and methods Peripheral sera were isolated from healthy volunteers (control group, T2DM patients and DN uremic non-dialysis patients). After incubation with or without 1,25(OH) 2 D 3 , THP-1 monocytes were treated with LPS plus IL-15 prior to the collection of cells and supernatants. VDR mRNA transcription was examined by RT-PCR, whilst THP-1 monocytic VDR, STAT5 and p-STAT5 expressions were investigated by Western blotting. Concentrations of IL-6 and monocyte chemoattractant protein-1 (MCP-1) in supernatants were assessed by ELISA. Immunofluorescence and a laser confocal microscopy was used to examine the expression of VDR and cytoskeletal proteins. Results Compared to the normal control, LPS and IL-15 down-regulate monocytic VDR expression in T2DM patients and DN uremic patients, whilst with cytoskeletal rearrangement, they up-regulate p-STAT5 expression as well as IL-6 and MCP-1 activity. Such effects could be in part blocked by 1,25-(OH) 2 D 3 . Conclusion The above results suggest that the anti-inflammatory mechanism of 1,25-(OH) 2 D 3 may be related to cytoskeletal proteins, VDR and STAT5 signaling pathway.