Inducible gene expression of IκB-kinase ε is dependent on nuclear factor-κB in human pulmonary epithelial cells

While I kappa B-kinase-epsilon kappa B-kinase- epsilon (IKK epsilon) epsilon ) induces immunomodulatory genes following viral stimuli, its up- regulation by inflammatory cytokines remains under-explored. Since airway epithelial cells respond to airborne insults and potentiate inflammation, IKK epsilon epsilon expression was characterized in pulmonary epithelial cell lines (A549, BEAS-2B) and primary human bronchial epithelial cells grown as submersion or differentiated air-liquid interface cultures. IKK epsilon epsilon expression was up-regulated by the pro-inflammatory cytokines, interleukin-1 beta beta (IL-1 beta) beta ) and tumour necrosis factor-alpha alpha (TNF alpha). alpha ). Thus, mechanistic interrogations in A549 cells were used to demonstrate the NF-kappa B kappa B dependence of cytokine-induced IKK epsilon. epsilon . Furthermore, chromatin immunoprecipitation in A549 and BEAS-2B cells revealed robust recruitment of the NF-kappa B kappa B subunit, p65, to one 5' ' and two intronic regions within the IKK epsilon epsilon locus (IKBKE). In addition, IL-1 beta beta and TNF alpha alpha induced strong RNA polymerase 2 recruitment to the 5' ' region, the first intron, and the transcription start site. Stable transfection of the p65- binding regions into A549 cells revealed IL-1 beta- beta- and TNF alpha-inducible alpha-inducible reporter activity that required NF-kappa B, kappa B, but was not repressed by glucocorticoid. While critical NF-kappa B kappa B motifs were identified in the 5' ' and downstream intronic regions, the first intronic region did not contain functional NF-kappa B kappa B motifs. Thus, IL-1 beta- beta- and TNF alpha-induced alpha-induced IKK epsilon epsilon expression involves three NF-kappa B-binding kappa B-binding regions, containing multiple functional NF-kappa B kappa B motifs, and potentially other mechanisms of p65 binding through non-classical NF-kappa B kappa B binding motifs. By enhancing IKK epsilon epsilon expression, IL-1 beta beta may prime, or potentiate, responses to alternative stimuli, as modelled by IKK epsilon epsilon phosphorylation induced by phorbol 12-myristate 13- acetate. However, since IKK epsilon epsilon expression was only partially repressed by glucocorticoid, IKK epsilon-dependent epsilon-dependent responses could contribute to glucocorticoid-resistant disease.