DNASE-I ACUTELY INCREASES CYSTIC-FIBROSIS SPUTUM ELASTASE ACTIVITY AND ITS POTENTIAL TO INDUCE LUNG HEMORRHAGE IN MICE

The potential of DNase I to increase cystic fibrosis sputum elastase a ctivity and lung damage was evaluated, Sputum from CF patients induced little lung hemorrhage when instilled intranasally in C57BL/6 mice, H owever, sputum treated in vitro by the addition of 1 mg/ml bovine DNas e I showed increased neutrophil elastase activity (7.97 +/- 1.56 versu s 3.91 +/- 0.62 mu M, p < 0.01) and induced marked lung hemorrhage in mice (bronchoalveolar lavage fluid hemoglobin = 192.8 +/- 40.7 versus 44.5 +/- 12.0 mu g/ml, p < 0.01), These effects were not observed with DNase I alone in phosphate buffer and were suppressed by the human ne utrophil elastase inhibitor nyl-alanyl-alanyl-prolyl-valine-chlorometh ylketone (MeOSAAPV-CMK). In vivo administration of 2.5 mg aerosolized recombinant human DNase I to patients with CF resulted in a 2.2-fold i ncrease of sputum elastase activity within 1 h of treatment, Elastase levels returned to pre-rhDNase therapy levels 24 h after aerosol treat ment, Sputum collected 1 h after rhDNase on 4 separate days from two o f six patients in which elastase levels were highest, induced lung hem orrhage when instilled intranasally in mice, We conclude that DNase I therapy of patients with cystic fibrosis can acutely increase the elas tase activity of sputum and also its potential to induce hemorrhage in the murine lung.