Inflammation in cystic fibrosis airways: Relationship to increased bacterial adherence

Abstract

It is unclear whether inflammation in the cystic fibrosis (CF) lung relates predominantly to bacterial infection, or occurs as a direct consequence of mutant cystic fibrosis transmembrane conductance regulator (CFTR) protein. Interleukin (IL)-8 secretion from CF and non-CF cell lines, and from CF and non-CF human primary nasal epithelial cells incubated with or without Pseudomonas aeruginosa, was measured. Activation of nuclear factor-κB (NF-κB) in unstimulated CF and non-CF nasal epithelial cells, cell lines and murine tissues was measured by gelshift assays. No significant difference in basal IL-8 production or NF-κB activation was observed between CF and non-CF primary nasal cells. However, CF cells exhibited a significantly (p<0.01) increased IL-8 secretion following P. aeruginosa stimulation. Equalization of the increased P. aeruginosa adherence observed in CF cells, to non-CF levels, resulted in comparable IL-8 secretion. Further, IL-8 production did not differ with mutations which result in either correctly localized CFTR, or in partial/total mislocalization of this protein. Similar levels of NF-κB activation were observed in a number of organs of wild-type and CF mice. Finally, IL-8 secretion and NF-κB activity were not consistently increased in CF cell lines. Cos-7 cell transfection with plasmids expressing ΔF508 or G551D mutant CFTR protein resulted in increased activation of a p50-containing NF-κB complex, but IL-8 secretion was similar to wild-type cells. The authors conclude that the stimulus produced by Pseudomonas aeruginosa is the predominant inflammatory trigger in their models.