1,25-Dihydroxyvitamin D3 Facilitates M2 Polarization and Upregulates TLR10 Expression on Human Microglial Cells.

Objective: To explore the effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the active metabolite of vitamin D, on M1/M2 polarization of human microglia and the expression of Toll-like receptor 10 (TLR10) on these cells, which has been suggested to play an inhibitory role in inflammation previously.

Methods: Microglial HMO6 cells were treated with 1,25(OH)2D3, and mRNA or protein levels of M1 and M2 cytokines and TLR10 were examined.

Results: 1,25(OH)2D3 upregulated TLR10 in HMO6 cells at both mRNA and protein level.

1,25-Dihydroxyvitamin D3 up-regulates TLR10 while down-regulating TLR2, 4, and 5 in human monocyte THP-1.

In humans, there are ten Toll-like receptors (TLRs), among which TLR10 is the only orphan receptor whose function is unknown. In this study, we examined the effects of IFN-γ, LPS and 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on TLR10 expression of human monocyte THP-1 and compared them with those of other surface TLRs such as TLR2, 4 and 5 to differentiate TLR10 from other TLRs. Surface TLR10 expression on THP-1 was significantly enhanced by the addition of IFN-γ or LPS in a fashion similar to that of other TLRs.