In cystic fibrosis (CF), defective function of the cystic fibrosis transmembrane conductance regulator (CFTR) in airway epithelial cells and submucosal glands results in chronic pulmonary infection with Pseudomonas aeruginosa. The pulmonary infection incites an intense host inflammatory response, causing progressive suppurative pulmonary disease. Mouse models of CF, however, fail to develop pulmonary disease spontaneously. We examined the effects of bronchopulmonary infection on mice homozygous for the S489X mutation of the CFTR gene using an animal model of chronic Pseudomonas endobronchial infection. Slurries of sterile agarose beads or beads containing a clinical isolate of mucoid P. aeruginosa were instilled in the right lung of normal or CF mice. The mortality of CF mice inoculated with Pseudomonas-laden beads was significantly higher than that of normal animals: 82% of infected CF mice, but only 23% of normal mice, died within 10 d of infection (P = 0.023). The concentration of inflammatory mediators, including TNF-alpha, murine macrophage inflammatory protein-2, and KC/N51, in bronchoalveolar lavage fluid in CF mice 3 d after infection and before any mortality, was markedly elevated compared with normal mice. This inflammatory response also correlated with weight loss observed in both CF and normal littermates after inoculation. Thus, this model may permit examination of the relationship of bacterial infections, inflammation, and the cellular and genetic defects in CF.

Poor growth, Pseudomonas aeruginosa endobronchitis, pulmonary inflammation, and decline of lung function are hallmarks of cystic fibrosis (CF), yet the relationship between these features is poorly understood. Because animal models of chronic bronchopulmonary infection with P. aeruginosa used to study pulmonary inflammation in CF have also been associated with weight loss, we sought to determine whether this weight loss was due to the inflammatory process and/or to changes in lung function. P. aeruginosa-laden agarose beads were instilled into the lungs of mice. Weight loss was greatest 3 d after Pseudomonas infection. Infected mice had a rapid though transient rise in absolute neutrophil counts, mTNF-alpha, mIL-1beta, mIL-6, mip-2, and KC in bronchoalveolar lavage fluid. There was no difference in lung resistance or lung compliance measured by body plethysmography between infected and control mice. Weight loss did correlate with the concentration of proinflammatory cytokine levels 3 d after inoculation of mice with Pseudomonas, and body composition analysis revealed loss of skeletal muscle mass. These results suggest that weight loss in P. aeruginosa-infected mice was associated with the inflammatory process and not with altered pulmonary responsiveness. These findings may provide insights into the cause of cachexia and weight loss seen in patients with CF.

Persistent neutrophil infiltration into the airways of patients with cystic fibrosis (CF) results in lung destruction. Eicosanoid lipid mediators, particularly leukotriene B4 (LTB4), may play a role in neutrophil influx and activation. We compared the eicosanoid content of epithelial lining fluid (ELF) obtained by bronchoalveolar lavage (BAL) from 17 patients with CF and 10 healthy subjects. LTB4 was the predominant eicosanoid in the CF airway (16.7 +/- 9.1 ng/ml ELF in CF versus 0.5 +/- 0.1 ng/ml ELF in healthy subjects). Prostaglandins (PG) and thromboxane (TX) were also elevated in CF (PGE2, 8.5 +/- 2.2; PGF2 alpha, 6.0 +/- 2.0; and TXB2, 14.0 +/- 3.0 ng/ml ELF) compared with healthy subjects (PGE2, 0.4 +/- 0.2; PGF2 alpha, 0.5 +/- 0.2; and TXB2, 1.2 +/- 0.4 ng/ml ELF). We also developed a protocol for the storage and subsequent analysis of BAL fluid that assures accurate and reproducible measurements of these eicosanoids. BAL samples stored for up to 8 months retain greater than 80% of their original eicosanoid content if the BAL fluid is immediately treated with methanol, concentrated, and stored at -70 degrees C without further purification. These data suggest that CF airways contain sufficient amounts of LTB4 both to recruit additional neutrophils into the airways and to stimulate neutrophils to release their injurious products. Therapies aimed at interfering with the production or action of LTB4 may be beneficial in CF and other lung diseases with a significant neutrophil response.

Hyperoxic exposure enhances airway reactivity in newborn animals, possibly due to altered relaxation. We sought to define the role of prostaglandinand nitric oxide-mediated mechanisms in impaired airway relaxation induced by hyperoxic stress. We exposed 7-day-old rat pups to either room air or hyperoxia (>95% O2) for 7 days to assess airway relaxation and cAMP and cGMP production after electrical field stimulation (EFS). EFS-induced relaxation of preconstricted trachea was diminished in hyperoxic vs. normoxic animals (P < 0.05). Indomethacin (a cyclooxygenase inhibitor) reduced EFS-induced airway relaxation in tracheae from normoxic (P < 0.05), but not hyperoxic, rat pups; however, in the presence of NG-nitro-L-arginine methyl ester (a nitric oxide synthase inhibitor) EFS-induced airway relaxation was similarly decreased in tracheae from both normoxic and hyperoxic animals. After EFS, the increase from baseline in the production of cAMP was significantly higher in tracheae from normoxic than hyperoxic rat pups, and this was accompanied by greater prostaglandin E2 release only in the normoxic group. cGMP production after EFS stimulation did not differ between normoxic and hyperoxic groups. We conclude that hyperoxia impairs airway relaxation in immature animals via a mechanism primarily involving the prostaglandin-cAMP signaling pathway with an impairment of prostaglandin E2 release and cAMP accumulation.

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