Regulation of TNF-Related Apoptosis-Inducing Ligand-Mediated Death-Signal Pathway in Human β Cells by Fas-Associated Death Domain and Nuclear Factor κB

Transfectants of human CM and NES2Y β cell lines and primary islets transfected by FADD-DN (dominant-negative form of Fas-associated death domain), a mutant of FADD and/or a superrepressor of nuclear factor κB (NF-κB) (AdIκB(SA)2), were examined for their susceptibility to the TRAIL (TNF-related apoptosis-inducing ligand)-induced death signal pathway, compared with controls, wild-type cells, and vector transfectants in caspase fluorescence, Western blot, electrophoretic mobility shift, apoptosis, and cytotoxicity assays. FADD-DN inhibited caspase-8 activation induced by TRAIL in the transfectants of CM and NES2Y cells. TRAIL-induced apoptosis and cytotoxicity to the FADD-DN transfectants were decreased in comparison to those responses in controls (CM, p < 0.01 and p < 0.01; NES2Y, p < 0.05, and p < 0.02, respectively). When CM, NES2Y, and primary islet cells were transfected by AdIκB(SA)2, TRAIL-induced IκB degradation and nuclear translocation of NF-κB p50/p65 were blocked. TRAIL-induced apoptosis and cytotoxicity to AdIκB(SA)2transfectants of these cells were also reduced (CM, p < 0.02 and p < 0.02; NES2Y, p < 0.01 and p < 0.01, respectively, and islet p < 0.01 for cytotoxicity). Finally, cytotoxicity induced by TRAIL in CM and NES2Y cells transfected with both FADD-DN and AdIκB(SA)2 was reduced, compared with that observed in these cells transfected with either FADD-DN alone or AdIκB(SA)2 alone, suggesting that FADD and NF-κB have synergistic proapoptotic regulatory effects on the susceptibility of β cell lines and islet cells to TRAIL-induced destruction.