Involvement of MAPKs and NF-kappa B in Tumor Necrosis Factor alpha-Induced Vascular Cell Adhesion Molecule 1 Expression in Human Rheumatoid Arthritis Synovial Fibroblasts

Objective. To investigate the roles of MAPKs and NF-kappa B in tumor necrosis factor alpha (TNF alpha)-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in human rheumatoid arthritis synovial fibroblasts (RASFs). Methods. Human RASFs were isolated from synovial tissue obtained from patients with RA who underwent knee or hip surgery. The involvement of MAPKs and NF-kappa B in TNF alpha-induced VCAM-1 expression was investigated using pharmacologic inhibitors and transfection with short hairpin RNA (shRNA) and measured using Western blot, reverse transcriptase-polymerase chain reaction, and gene promoter assay. NF-kappa B translocation was determined by Western blot and immunofluorescence staining. The functional activity of VCAM-1 was evaluated by lymphocyte adhesion assay. Results. TNF alpha-induced VCAM-1 expression, phosphorylation of p42/p44 MAPK, p38 MAPK, and JNK, and translocation of NF-kappa B were attenuated by the inhibitors of MEK-1/2 (U0126), p38 (SB202190), JNK (SP600125), and NF-kappa B (helenalin) or by transfection with their respective shRNA. TNF alpha-stimulated translocation of NF-kappa B into the nucleus and NF-kappa B promoter activity were blocked by Bay11-7082, but not by U0126, SB202190, or SP600125. VCAM-1 promoter activity was enhanced by TNF alpha in RASFs transfected with VCAM-1-Luc, and this promoter activity was inhibited by Bay11-7082, U0126, SB202190, and SP600125. Moreover, up-regulation of VCAM-1 increased the adhesion of lymphocytes to the RASF monolayer, and this adhesion was attenuated by pretreatment with helenalin, U0126, SP600125, or SB202190 prior to exposure to TNF alpha or by anti-VCAM-1 antibody before the addition of lymphocytes. Conclusion. In RASFs, TNF alpha-induced VCAM-1 expression is mediated through activation of the p42/p44 MAPK, p38 MAPK, JNK, and NF-kappa B pathways. These results provide new insights into the mechanisms underlying cytokine-initiated joint inflammation in RA and may inspire new targeted therapeutic approaches.