1,25-Dihydroxyvitamin D3 Inhibits the RANKL Pathway and Impacts on the Production of Pathway-Associated Cytokines in Early Rheumatoid Arthritis

Objectives. To study effects of 1,25-dihydroxyvitamin D3 (1,25(OH)(2)D-3) on RANKL signaling pathway and pathway-associated cytokines in patients with rheumatoid arthritis (RA). Methods. Receptor activator of nuclear factor-kappa B ligand (RANKL), osteoprotegerin (OPG), IFN-gamma, IL-6, TNF-alpha, IL-17, and IL-4 were examined in 54 patients with incipient RA using a cytometric bead array (CBA) or an enzyme-linked immunosorbent assay (ELISA). Results. After 72 hours of incubation of peripheral blood mononuclear cells (PBMCs) with 1,25(OH)(2)D-3 in RA patients, the levels of RANKL, TNF-alpha, IL-17 and IL-6 significantly decreased compared to those of the control. 1,25(OH)(2)D-3 had no significantly impact on the levels of OPG, RANKL/OPG, and IL-4. Conclusions. The present study demonstrated that 1,25(OH)(2)D-3 reduced the production of RANKL and the secretion of TNF-alpha, IL-17, and IL-6 in PBMCs of RA patients, which indicated that 1,25(OH)(2)D-3 might be able to decrease damage of cartilage and bone in RA patients by regulating the expression of RANKL signaling pathway and pathway-associated cytokines.