Anti-inflammatory effects of 1,25-dihydroxyvitamin D3 in monocytes cultured in serum from patients with type 2 diabetes mellitus and diabetic nephropathy with uremia via Toll-like receptor 4 and nuclear factor-κB p65.

Type 2 diabetes mellitus (T2DM) and diabetic nephropathy (DN) seriously affect the quality of human life. 1,25-dihydroxyvitamin D3 (VD3) is known to exert anti‑inflammatory and immunomodulatory effects. The present study investigated the effects of VD3 on Toll‑like receptor 4 (TLR4) and nuclear factor (NF)‑κB p65 expression in monocytes from patients with T2DM and investigated the underlying mechanisms. Serum from subjects of the control, T2DM and DN with uremia groups was isolated, and THP‑1 monocytes were cultured in these sera with or without VD3. After treatment with lipopolysaccharide (LPS) and interleukin (IL)‑15, monocytes and culture supernatants were collected. The expression of TLR4, TLR9 and IL‑15 mRNA was detected using reverse‑transcription polymerase chain reaction analysis. Furthermore, the protein expression of TLR4, NF‑κB p65 and inhibitor of NF‑κB (IκB) was determined using western blot analysis. The levels of IL‑6 and monocyte chemotactic protein in culture supernatants were detected using ELISAs. The impact of LPS, IL‑15 and VD3 on the TLR/NF‑κB signaling pathway in the T2DM and DN uremia groups was also investigated. In the T2DM and DN uremia groups, LPS and IL‑15 downregulated the expression of IκB and upregulated levels of proteins, including TLR4, NF‑κB p65, IL‑6 and monocyte chemoattractant protein 1, as well as TLR4 and IL‑15 mRNA. There was no significant difference in TLR9 mRNA protein expression among the three groups. VD3 partially blocked the above effects; However, pre‑treatment with VD3 had no significant effect on TLR4 mRNA expression, protein expression of NF-κB p65 and IκB, or the levels of associated inflammatory cytokines. In conclusion, the present study indicated that anti‑inflammatory effects of VD3 in inflammatory immune responses in T2DM and DN uremia are associated with the TLR4/NF-κB p65 signaling pathway.