No abstract

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(OH)₂D₃ enhanced basal mRNA expression of M2 cytokines, such as IL-10 and CCL17, but did not affect the expression of M1 cytokines, including IL-12 and TNF-α. 1,25(OH)₂D₃ downregulated the lipopolysaccharide (LPS)-induced mRNA expression of M1 cytokines IL-12 and TNF-α. Concomitantly, it upregulated not only the M2 cytokines IL-10 and CCL17, but also TLR10 in microglial cells treated with LPS, in a concentration-dependent manner. Conclusions: Our results suggest that 1,25(OH)₂D₃ may exert anti-inflammatory action by facilitating the M2 polarization of human microglial cells.