Expression of FLIP in synovial tissue from patients with rheumatoid arthritis

AIM: To investigate the expression of Fas-associated death domain-like interleukin 1β-converting enzyme inhibitory protein (FLIP) in synovial tissue from rheumatoid arthritis(RA) patients and its relationship with inflammatory synovial proliferation in RA. METHODS: Immunohistochemistry employing specific rabbit anti-FLIP antibodies was performed on frozen synovial tissue sections from 17 RA and 10 osteoarthritis (OA) patients. The relation of FLIP expression with the degree of synovial inflammation, as well as with caspase-8 activity was then analyzed in RA. RESULTS: Expression of FLIP in synovium of patients with rheumatoid arthritis was significantly higher than that in OA synovial tissues [(30.60±18.90)% vs (1.87±0.57)%, P0.05]. In RA, the expression of FLIP was mainly found in macrophage-like synovocytes. FLIP expression in RA synovial tissues was positively correlated with the severity of synovial inflammation (r=0.425,P0.05), while negatively correlated with caspase-8 activity. CONCLUSION: The FLIP is up-regulated in RA synovial tissues, and is correlated with synovial inflammation, which suggests that FLIP may take a role in the process of inflammatory synovial proliferation in RA.