Essential role of transcription factor nuclear factor-kappa B in regulation of interleukin-8 gene expression by nitrite reductase from Pseudomonas aeruginosa in respiratory epithelial cells

Persistent infection with Pseudomonas aeruginosa increases interleukin-8 (I L-8) levels and causes dense neutrophil infiltrations in the airways of pat ients with chronic airway diseases. Recently, we have reported that nitrite reductase from P. aeruginosa induces the production of IL-8 in respiratory cells, including bronchial epithelial cells. To determine the molecular me chanism(s) of nitrite reductase-induced IL-8 expression in respiratory cell s, A549 epithelial cells were transfected with plasmids containing serial d eletions of the 5'-flanking region of the IL-8 gene and then exposed to nit rite reductase. Nitrite reductase significantly enhanced IL-8 gene promoter -driven reporter activity. This increased IL-8 gene expression was inhibite d by mutating the nuclear factor-kappa B (NF-kappa B) binding element. Nitr ite reductase enhanced nuclear localization of the NF-kappa B binding compl ex. Furthermore, nitrite reductase induced the degradation of I kappa B alp ha, the major cytoplasmic inhibitor of NF-kappa B, and the expression of I kappa B alpha mRNA. These data support the critical role of the activation of NF-kappa B in nitrite reductase-induced IL-8 gene expression in airway e pithelium.