The Role of MAPK Signaling of 1,25(OH)2D3-induced CYP24 Expression in Activated Human Macrophages / 대한류마티스학회지

ABSTRACT

OBJECTIVE: Several important roles of 1,25(OH)2D3 have been recognized in the immune system. The availability of 1,25(OH)2D3 at the cellular level is significantly influenced by the relative abundance of enzymes to synthesize (CYP27B1) and catabolize (CYP24) 1,25(OH)2D3. In this study, we examined the effect of 1,25(OH)2D3 on the expression of the CYP24 gene and the role of MAPK for the induction of CYP24 by 1,25(OH)2D3 in activated human macrophages. METHODS: For obtaining human activated macrophages, we treated U937 cells with PMA and we cultured these cells for 24 hours to adhere. After 24 hours treatment with PMA, the differentiated cells were washed with phosphate buffered saline (PBS), and then they were used for examining the effect of 1,25(OH)2D3 on the expression of the CYP24 gene. The mRNA expressions of the vitamin-D3 inducible genes were measured by real-time PCR, and the change of the protein expression by 1,25(OH)2D3 was measured by immunoblotting. RESULTS: 1,25(OH)2D3 significantly induced the expression of CYP24 in the U937 cells and the 1,25(OH)2D3-induced expression of CYP24 was strongly augmented in the PMA-differentiated U937 cells. The 1,25(OH)2D3-induced expression of CYP24 was mediated by Erk1/2 and p38 MAPKs. Parallel to the induced expression of CYP24, 1,25(OH)2D3 induced the expression and phosphorylation of the CCAAT enhancer-binding protein (C/EBPbeta). CONCLUSION: In this study, we found that 1,25(OH)2D3 inducedthe expression of CYP24 via activation of MAPKs. These results suggest that MAPK inhibitors may be useful for the treatment of inflammatory conditions, in which active vitamin D3 can be used as the therapeutic molecule, by increasing the availability of 1,25(OH)2D3.