Immunoregulatory effects of 1, 25(OH)2D3 on Der p stimulating the expression of TLR4 and IL-4 in P815 mast cells

Abstract

Objective To investigate the effects of Dermatophagoides pteronyssinus (Der p) on the expression of TLR4 and IL-4 in P815 mast cells and to further analyze the immunoregulatory effects of 1, 25-(OH)2D3 on Der p treated P815 mast cells. Methods Different concentrations of Der p and 1, 25-(OH)2D3 were used alone or in combination to stimulate P815 mast cells. The supernatants of the stimulated cell culture were analyzed by enzyme-linked immunosorbent assay (ELISA) for the detection of IL-4. The stimulated cells were collected and analyzed by real-time PCR and Western blot assays for the detection of TLR4 at mRNA and protein levels, respectively. Results (1) TLR4 expression was detected in P815 cells. The expression of TLR4 was enhanced in P815 cells treated with various concentrations of Der p. A significant dose-dependent up-regulation of TLR4 was observed in P815 cells after incubation with Der p for 36 h. (2) Der p promoted the release of IL-4 in P815 cells (P 0.05). (4) 10-8 mol/L of 1, 25(OH)2D3 promoted the Der p-induced expression of TLR4 in P815 cells (P<0.01). However, 1, 25(OH)2D3 inhibited the release of IL-4 in a dose-dependent manner (P<0.05 or P<0.01). Conclusion (1) Der p could promote the inflammation and allergic reaction through up-regulating TLR4 and IL-4 in mast cells. (2) The possible mechanism for the inhibitory of 1, 25(OH)2D3 on Der p-induced immune responses was due to the suppression of Th2-type immune responses through inhibiting the synthesis and secretion of IL-4 in mast cells. Key words: Mast cells; P815 cells; Dermatophagoides pteronyssinus; TLR4; 1, 25(OH)2D3