OBJECTIVES To examine whether inhibition of NF-κB induces apoptosis of human synovial cells stimulated by tumour necrosis factor α (TNFα), interleukin 1β (IL1β), and anti-Fas monoclonal antibody (mAb).

RESULTS Abundant PCNA+ synovial cells were found in rheumatoid arthritis (RA) synovial tissue, though a few apoptotic synovial cells were also detected in the RA synovial tissues. Nuclear NF-κB was expressed in RA synovial cells. Electrophoretic mobility shift assay showed that treatment of cells with TNFα or IL1β significantly stimulated nuclear NF-κB activity. A small number of apoptotic synovial cells expressing intracellular active caspase-3 were found after treatment of cells with LLL-CHO. Although treatment of RA synovial cells with TNFα or IL1β alone did not induce apoptosis, apoptosis induced by LLL-CHO and caspase-3 activation were clearly enhanced in TNFα or IL1β stimulated synovial cells compared with unstimulated synovial cells. Furthermore, induction of apoptosis of synovial cells with caspase-3 activation by anti-Fas mAb was clearly increased by LLL-CHO. The expression of cIAP2 and XIAP in synovial cells may not directly influence the sensitivity of synovial cells to apoptosis induced by LLL-CHO.

CONCLUSION The results suggest that NF-κB inhibition may be a potentially important therapeutic approach for RA by correcting the imbalance between apoptosis and proliferation of synovial cells in RA synovial tissue.