Exaggerated activation of nuclear factor-κB and altered IκB-β processing in cystic fibrosis bronchial epithelial cells

In cystic fibrosis (CF), inflammatory mediator production by airway epithelial cells is a critical determinant of chronic airway inflammation. To determine whether altered signal transduction through the nuclear factor (NF)-kappa B pathway occurs in CF epithelial cells and results in excessive generation of inflammatory cytokines, we evaluated tumor necrosis factor (TNF)-alpha-induced production of the NF-kappa B-dependent cytokine interleukin (IL)-8 and activation of NF-KB in three different human bronchial epithelial cell lines: (1) BEAS cells that express wild-type CF transmembrane conductance regulator (CFTR), (2) IB3 cells with mutant CFTR, and (3) C38 cells, which are "corrected" IB3 cells complemented with wild-type CFTR, Treatment of cells with TNF-alpha (30 ng/ml) resulted in markedly elevated NF-kappa B activation and production of IL-8 by IB3 cells compared with BEAS and C38 cells. Despite the differences in NF-kappa B activation, no differences in basal levels of I kappa B-alpha or TNF-alpha-induced I kappa B-alpha processing and degradation were detected among the cell lines. In contrast, the basal level of I kappa B-beta was increased in the IB3 cells. Treatment with TNF-alpha resulted in increased formation of hypophosphorylated I kappa B-beta and increased nuclear localization of I kappa B-beta in IB3 cells compared with the other cell types, These findings provide additional evidence of a dysregulated inflammatory response in CF.