Increased phosphorylation of ezrin is associated with the migration and invasion of fibroblast-like synoviocytes from patients with rheumatoid arthritis

Methods. Synovial tissues were obtained from 12 patients with RA and 6 with OA, and then FLSs were separated from synovial tissues. The expression of ezrin and phosphorylated ezrin (p-ezrin) was examined by Western blotting or IF staining. A specific inhibitor of ezrin phosphorylation and small interference RNA-mediated ezrin knockdown were used to inhibit the phosphorylation of ezrin. Migration and invasion of FLSs in vitro were measured by the Boyden chamber assay. Results. Increased expression of p-ezrin protein was found in synovial tissue and FLSs in patients with RA compared with patients with OA. Stimulation with TNF-alpha and IL-1 beta increased ezrin phosphorylation in RA FLSs. Inhibition of p-ezrin protein by a specific inhibitor of phosphorylation of ezrin and small interfering RNA-mediated knockdown reduced in vitro migration and invasion, as well as actin stress fibre formation in RA FLS. Furthermore, rho kinase and p38 mitogen-activated protein kinase (MAPK) signal pathways were involved in the phosphorylation of ezrin and invasion of RA FLSs. Conclusion. Increased expression of p-ezrin may contribute to aberrant aggressive behaviours of RA FLSs, which are mediated by rho kinase and the p38 MAPK pathway. This suggests a novel strategy targeting phosphorylation of ezrin to prevent synovial invasiveness and joint destruction in RA.