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Epithelial cell damage is induced by neutrophil-derived, not pseudomonas-derived, proteases in cystic fibrosis sputum
T J Venaille1, G Ryan, B W Robinson
1University Department of Medicine, QEII Medical Centre, Perth, Western Australia.
Abstract:
Airway histopathological changes in cystic fibrosis (CF) include damage to the epithelial tissue and accumulation of polymorphonuclear leukocytes (PMN). Airways of CF patients are usually colonized with bacteria such as mucoid Pseudomonas aeruginosa (PA). Bacteria and PMN can both release proteolytic enzymes capable of causing tissue damage. This study aims to clarify and compare the roles of these agents in epithelium damage. Epithelial cell (EC) damage and detachment induced by sputum samples from CF or non-CF patients, with and without lung infection, were assessed on amnionic EC in an in vitro model of airway epithelium. Protease activity was determined using inhibitor profiles, and compared to the proteolytic activity of isolated neutrophils and bacteria. Sputa from CF patients and infected non-CF patients induced high levels of detachment. PA also induced high levels of EC detachment but Staphylococcus aureus and Haemophilus influenzae, two other bacteria commonly isolated from CF sputa, induced no detachment. Antiprotease inhibition profiles were similar for PMN and sputa-induced EC detachment, but different for PA-induced detachment. These results suggest that PMN proteolytic enzymes, probably elastase and cathepsin G, are more likely to be the inducers of tissue damage in the airways of CF patients than PA proteolytic enzymes.
Insights
Polymorphonuclear leukocytes (PMN) in cystic fibrosis (CF) airways likely cause more epithelial damage than Pseudomonas aeruginosa (PA). PMN enzymes, not bacterial proteases, are the primary culprits in CF airway tissue damage.
Area of Science:
- Pulmonary Medicine
- Cell Biology
- Microbiology
Background:
- Cystic Fibrosis (CF) involves airway epithelial damage and inflammation.
- Airways in CF patients are often colonized by bacteria like Pseudomonas aeruginosa (PA).
- Both bacteria and polymorphonuclear leukocytes (PMN) release proteases that can damage tissue.
Purpose of the Study:
- To compare the roles of PMN and bacterial proteases in airway epithelial damage in CF.
- To investigate the specific enzymes responsible for tissue damage in CF airways.
Main Methods:
- An in vitro model using amnionic epithelial cells (EC) to assess EC damage and detachment.
- Analysis of protease activity in sputum from CF and non-CF patients, and from isolated neutrophils and bacteria.
- Comparison of protease inhibitor profiles for PMN, PA, and sputum-induced EC detachment.
Main Results:
- Sputa from CF and infected non-CF patients induced significant EC detachment.
- PA also caused high EC detachment, while Staphylococcus aureus and Haemophilus influenzae did not.
- Protease activity profiles suggested PMN enzymes, not PA enzymes, are the main drivers of sputum-induced EC detachment.
Conclusions:
- PMN proteolytic enzymes, likely elastase and cathepsin G, are the probable inducers of airway tissue damage in CF patients.
- The contribution of Pseudomonas aeruginosa proteolytic enzymes to CF airway damage appears less significant than that of PMN enzymes.