Inhibition of Cytokine-Induced NF-κB Activation by Adenovirus-Mediated Expression of a NF-κB Super-Repressor Prevents β-Cell Apoptosis

Abstract

Cytokine-induced β-cell death is an important event in the pathogenesis of type 1 diabetes. The transcription factor nuclear factor-κB (NF-κB) is activated by interleukln-1β (IL-1β), and its activity promotes the expression of several β-cell genes, including pro- and antiapoptotic genes. To elucidate the role of cytokine (IL-1β + γ-interferon [IFN-γ])-induced expression of NF-κB in β-cell apoptosis, rat β-cells were infected with the recombinant adenovirus AdIκB(SA)2, which contained a nondegradable mutant form of inhibitory κB (IκB(SA)2, with S32A and S36A) that locks NF-κB in a cytosolic protein complex, preventing its nuclear action. Expression of IκB(SA)2 inhibited cytokine-stimulated nuclear translocation and DNA-binding of NF-κB. Cytokine-induced gene expression of several NF-κB targets, namely inducible nitric oxide synthase, Fas, and manganese superoxide dismutase, was prevented by AdIκB(SA)2, as established by reverse transcriptasepolymerase chain reaction, protein blot, and measurement of nitrite in the medium. Finally, α-cell survival after IL-1β + IFN-γ treatment was significantly improved by IκB(SA)2 expression, mostly through inhibition of the apoptotic pathway. Based on these findings, we conclude that NF-κB activation, under in vitro conditions, has primarily a pro-apoptotic function in β-cells.