1,25(OH)2D3 promotes chondrocyte apoptosis and restores physical function in rheumatoid arthritis through the NF-κB signal pathway

We explored the modulatory effect of 1,25(OH)2D3 on chondrocytes and physical function in rats with RA and its mechanism underlying the regulation of NF-κB signal pathway. RA patients and healthy volunteers were selected. Sprague-Dawley (SD) rats were used to establish RA models. The paw volume of rats was estimated. Chondrocytes were isolated from RA rats. The protein levels in both cartilage tissues and chondrocytes were determined using western blotting. Apoptosis was evaluated using TUNEL assay. Serum levels of IL-1β, IL-6, IL-10 and IL-17 were measured by enzyme-linked immunosorbent assay (ELISA). Serum levels of 1,25(OH)2D3 were lower in RA patients than in healthy volunteers. Rats in the RA + VD3 group were lighter than those in normal and PBS groups, with an increased paw volume, severer joint swelling, higher expression levels of p-IκBα, p-p65, IL-1β, IL-6, and IL-17, and lower expression level of IL-10, while those in RA and RA + VD3 + NF-κB group differed more significantly. In addition, by comparing RA rats and RA + NF-κB rats, we found that TNF-α stimulation exacerbated RA, increased expression levels of p-IκBα, p-p65, IL-1β, IL-6, and IL-17, and decreased the expression level of IL-10. Compared with RA chondrocytes, chondrocytes from RA + VD3 rats exhibited lower expression levels of p-IκBα and p-p65, and had more apoptotic cells, while those from RA + NF-κB rats showed an opposite trend. Taken together, 1,25(OH)2D3 accelerates chondrocyte apoptosis and improve physical function in rats with RA by the inhibition of NF-κB signal pathway.