Acute unilateral emphysema induced by Pseudomonas aeruginosa in mice

Background: Pulmonary emphysema, a major form of chronic obstructive pulmonary disease (COPD), has long been regarded as a chronic airway response result from cigarette smoking. Airway infection on the other hand, is not considered to play a major role in emphysema pathogenesis. Acute emphysema caused by airway infection has never been reported. Until recently, we accidentally found that the secretion from Pseudomonas aeruginosa could cause significant lung emphysema in mice rapidly. Using a unilateral lung injury model, we further studied the unique pathological change and tested if it can be induced by direct P. aeruginosa airway infection. Method: P. aeruginosa secretion was extracted and instilled intratracheally into the left lung of C57BL/6 and C3HHeJ mice, while the right lung used as self-control. Alveolar diameter and lung compliance were measured and compared. The dynamic change of emphysema in different mice were closely watched. C57BL/6, immunosuppressed C57BL/6 and C3HHeJ mice were used to examine if the emphysema can be caused by P. aeruginosa infection. Results: P. aeruginosa secretion extract containing metal-dependent hydrolase and other enzymes caused acute panacinar emphysema and a decrease of dynamic lung compliance in mice. However, the P. aeruginosa infection could only elicit emphysema in immunocompromised mice but not in immunocompetent mice. Panacinar emphysema interwoven with inflammation developed into various types of emphysema and bullae. Conclusion: P. aeruginosa lung infection in mice recapitulates main features of human pulmonary emphysema and COPD. Key words: Emphysema, COPD, pathology, unilateral lung injury, Pseudomonas aeruginosa