Objective: Tumor necrosis factor alpha (TNFalpha) increases the survival and proliferation of human rheumatoid arthritis (RA) cell lines. These experiments were designed to determine if inhibition of nuclear factor kappaB (NF-kappaB) nuclear translocation leads to increased apoptosis of TNFalpha-treated human RA cell lines.
Methods: We constructed an inhibitor of nuclear factor kappaB(IkappaB) dominant-negative adenovirus (AdCMVIkappaB-DN) and an X-linked inhibitor of apoptosis (XIAP) antisense adenovirus (AdCMVXIAP-AS). Primary RA synovial fibroblast (RASF) cell lines were transfected in vitro, and SV40-transformed RA synovial cell lines in SCID mice were transfected in vivo. Cells were treated with TNFalpha and analyzed for apoptosis.
Results: There was no apoptosis of primary RASF transfected in vitro with AdCMVIkappaB-DN alone. In contrast, there was apoptosis of >85% of cells treated with AdCMVIkappaB-DN plus TNFalpha. Primary RASF in SCID mice also exhibited high levels of apoptosis after in vivo transfection with AdCMVIkappaB-DN followed by treatment with TNFalpha. There was no apoptosis after treatment with AdCMVIkappaB-DN in the absence of TNFalpha. XIAP is an inhibitor of apoptosis which was up-regulated by TNFalpha, and this up-regulation was inhibited by AdCMVIkappaB-DN plus TNFalpha. Transfection of an AdCMVXIAP-AS gene therapy resulted in increased TNFa-induced apoptosis.
Conclusion: AdCMVIkappaB-DN gene therapy greatly enhances apoptosis due to inhibition of an NF-kappaB-mediated antiapoptosis signaling pathway, and XIAP is a TNFalpha-inducible specific inhibitor of apoptosis in RA synovial cell lines. This and other modulators of TNF receptor or the Fas apoptosis pathway may be therapeutically beneficial in facilitating apoptosis of synovial tissue in patients with RA.