Lung function and inflammation during murine Pseudomonas aeruginosa airway infection

Abstract

BackgroundFollowing any acute irritation lung function declines rapidly. Reasons for pulmonary deterioration in humans had been attributed to the action of either interleukin-6 or interleukin-8 in the lungs. ObjectivesThe present study investigates the association between immune response and decline in lung function in a murine bacterial lung infection model. MethodsUpon intratracheal inoculation of C57BL/6J mice with a sublethal dose of Pseudomonas aeruginosa lung function, cytokine, chemokine and cytometry in bronchoalveolar lavage fluid, bacterial counts and lung histology was assessed at 2, 4, 6, 8, 10, 12, 18, 24, 48, 72, 96 and 120h post inoculation. ResultsLung function measured by non-invasive head-out spirometry decreased most strongly between 6 and 10h post inoculation and required up to 72h to recover for selected parameters. CFU counts in the lungs peaked at 4h post inoculation with subsequent decline until at 24–48h post inoculation background levels were reached. Cytokine and chemokine responses could be separated into an early pro-inflammatory phase (2–8h post inoculation; mainly tumor-necrosis factor α (TNFα) and interleukin-1α driven) and a late anti-inflammatory resolution phase (starting at 24h post inoculation; mainly interleukin-10 and interleukin-4 driven). Interleukin-6 levels correlated with the deterioration of lung function. Lung histology showed maximal changes in terms of inflammation and edema between 24 and 48h post inoculation. ConclusionsIn summary, elevated interleukin-6, high local neutrophil counts and lung edema were found to be the most characteristic signs of the transient period of deterioration of lung function.