Acute Pseudomonas challenge in cystic fibrosis mice causes prolonged nuclear factor-κB activation, cytokine secretion, and persistent lung inflammation

BackgroundCystic fibrosis (CF) is characterized by an excessive and prolonged inflammatory response to Pseudomonas aeruginosa in the lung. There are high levels of cytokines and chemokines and an exaggerated PMN influx causing significant morbidity and mortality.ObjectiveTo compare the kinetics of the inflammatory response with the kinetics of clearance of acute bacterial challenge in the lungs of CF and wild-type (WT) mice.MethodsWe challenged CF knockout (KO) and WT mice intratracheally with P aeruginosa in suspension and evaluated bacteria counts, nuclear factor-κB (NF-κB), and inhibitor of NF-κB alpha protein (I-κBα) in lung tissue, cytokines, and PMN in bronchoalveolar lavage (BAL).ResultsBoth groups of mice cleared the infection with the same kinetics. CF-KO mice had more PMN in BAL than WT mice. CF-KO mice had high concentrations of proinflammatory cytokines in BAL on days 2 and 4, whereas cytokines in BAL from WT mice were only slightly elevated. CF-KO mice failed to regenerate I-κBα once it was degraded, and consequently had prolonged and excessive activation of NF-κB for the entire 6-day duration of the study. In contrast, WT mice showed only slight NF-κB activation, which plateaued at day 4.ConclusionThese data suggest that NF-κB is dysregulated in CF lung infection and could be a good target for therapy. Prolonged responses to initial acute infections may contribute to the eventual establishment of chronic persistent inflammation.Clinical implicationsDysregulation of the I-κB/NF-κB pathway in cystic fibrosis leads to prolonged cytokine secretion and persistent inflammation in response to acute challenges and may be important in the development of chronic lung inflammation and infection.