In Vitro Inhibition of Neutrophil Elastase Activity by Inhaled Anti-Pseudomonas Antibiotics Used in Cystic Fibrosis Patients

BACKGROUND Inhaled antibiotics are commonly used in the treatment of cystic fibrosis lung disease. A previous study suggested neutrophil elastase activation by colistin in vitro. Here, we investigated direct effects of the commonly used antibiotics colistin and tobramycin on neutrophil elastase activity. METHODS Neutrophil elastase was measured spectrophotometrically. The antibiotics colistin and tobramycin were added in different concentrations with or without the addition of albumin. RESULTS Generally, neutrophil elastase activity was lower in the absence of albumin compared to its presence. Both antibiotics, colistin and tobramycin, had inhibitory effects on neutrophil elastase activity except for high concentrations of colistin when albumin was absent. CONCLUSIONS Our results suggest inhibitory effects of colistin and tobramycin in vitro. There was a clear dependency of neutrophil elastase measurements on the presence of albumin. Clinical studies are needed to investigate potential direct effects of inhaled antibiotics on neutrophil elastase activity in cystic fibrosis airways.