Effects of RANKL on the proliferation and apoptosis of fibroblast-like synoviocytes in rheumatoid arthritis through regulating the NF-κB signaling pathway.

Objective The aim of this study is to investigate the regulatory effects of receptor activator of nuclear factor-kappa B ligand (RANKL) on the proliferation and apoptosis of fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA), and to explore its regulatory mechanism. Materials and methods Synoviocytes were primarily cultured in rats of recognized collagen-induced arthritis (CIA) model. Meanwhile, they were induced into FLS models by lipopolysaccharides (LPS). All cells were divided into three groups, including blank group, model group and RANKL inhibitor group. The levels of tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) in the cells were detected by enzyme-linked immunosorbent assay (ELISA). The proliferation and apoptosis of FLS were detected via 3-(4,5)-dimethylthiazol (-z-y1)-3,5-diphenytetrazoliumromide (MTT) assay and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, respectively. Reverse transcription-polymerase chain reaction (RT-PCR) was conducted to measure the messenger ribonucleic acid (mRNA) expression levels of nuclear factor-kappa B ligand (NF-κB) and Caspase-3 in FLS. Furthermore, Western blotting was adopted to detect the protein expression levels of NF-κB and Caspase-3 in FLS. Results Compared with the blank group, the expression levels of TNF-α and IL-1β in the cells of the model group increased significantly. Cell proliferation rate increased significantly, whereas the cell apoptosis rate decreased remarkably in the model group. Meanwhile, the mRNA and protein levels of NF-κB and Caspase-3 in FLS were significantly up-regulated. Compared with the model group, the levels of TNF-α and IL-1β in cells of RANKL inhibitor group notably declined. Similarly, cell proliferation rate was significantly reduced, whereas the cell apoptosis rate increased significantly. Furthermore, the mRNA and protein levels of NF-κB and Caspase-3 in FLS were evidently down-regulated. Conclusions RANKL inhibitors can inhibit the proliferation and promote the apoptosis of FLS in RA. In addition, its mechanism may be related to the inhibition of NF-κB signaling pathway.