The role of Pseudomonas aeruginosa elastase as a potent inflammatory factor in a rat air pouch inflammation model

Pseudomonas aeruginosa, an opportunistic pathogen, call cause life threaten ing infections in patients compromised by underlying respiratory disease li ke bronchiectasis, cystic fibrosis and diffuse panbronchiolitis. Most strai ns of P. aeruginosa produce some kind of protease with broad substrate spec ificities during the infectious stare in the host. P. aeruginosa elastase, one of the strongest exotoxins, has a tissue-damaging proteolytic activity and is capable of degrading such plasma proteins as immunoglobulins, comple ment factor and cytokines. The present study focused on the effect of P. ae ruginosa elastase and was designed to evaluate the neutrophil accumulation at the inflammation site mediated by P. aeruginosa elastase in the inflamma tory response in the host. An air pouch model in rats, considered as a usef ul model of inflammation, was used to analyze the number of leukocytes, the volume of exudate and the concentration of interleukin-8 after the injecti on of P. aeruginosa elastase into the pouch cavity. The number of neutrophi ls and the volume of exudate in the pouch cavity increased significantly at 4 h, peaked at 8 h in a dose-dependent manner and then decreased at 24 h. The concentration of interleukine-8 in pouch fluid peaked 4 h earlier than the peak of the neutrophil number. The enzymatic activity Of P. aeruginosa elastase seemed to reinforce the inflammation process. The influence of lip opolysaccharide contamination was negligible. Although these observations w ere made in the subcutaneous cavity, they indicate that P. aeruginosa elast ase plays a role as an immunoprovocative factor in the inflammatory respons e in cases of infection with P. aeruginosa. (C) 1999 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights r eserved.