Dose-dependent in vitro effect of recombinant human DNase on rheological and transport properties of cystic fibrosis respiratory mucus

Abstract

Recombinant human deoxyribonuclease (rhDNase) has been demonstrated to reduce the viscosity of purulent cystic fibrosis (CF) respiratory mucus, to improve pulmonary function and to reduce the risk of respiratory tract infectious exacerbations, but its effect on mucus transportability has not so far been investigated. The dose-dependent effect of rhDNase was analysed in vitro on mucus transport rate (tr) by ciliary activity and by simulated cough (cough transport (ct)), as well as on mucus viscosity and surface properties. Purulent CF sputa (n = 15) were incubated for 30 min at 37 degrees C with either rhDNase at three different concentrations (final concentrations 0.2, 2 or 20 micrograms.ml-1 of mucus) or placebo. No significant dose-dependent effect of rhDNase on the mucociliary transport rate was observed when the samples wer statistically analysed together. However, in the larger group of mucus samples (n = 11) with a low initial mucociliary transport rate, the latter was improved at each rhDNase concentration (tr0.2 = 0.69, tr2 = 0.88 and tr20 = 0.87) as compared to placebo (trp = 0.58). In the smaller group of mucus samples (n = 4) with high initial transport rate, a decrease in mucociliary transport rate was observed, particularly at the highest concentration rhDNase assayed, i.e. 20 micrograms.ml-1 of mucus (tr20 = 0.58) as compared to placebo (trp = 0.86). The mucus cough transport was increased by rhDNase (ct0.2 = 25 mm, ct2 = 27.5 mm and ct20 = 31 mm) as compared to placebo (ctp = 23.5 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of rhDNase on purulent airway secretions in chronic bronchitis

“…In fact, five of the seven sputum samples with an initial relatively high transport rate further increased their transport rate after incubation with rhDNase, either at 2 or 4 µg·mL -1 . Concerning the surface properties of airway secretions, we observed, as we had previously reported in a group of CF patients [11], that rhDNase at a concentration of 4 µg·mL -1 is able to decrease the mucus contact angle. This change reflects a decrease in mucus surface tension, generally associated with a decrease in the adhesive properties of mucus and a parallel improvement in the cough and ciliary transport capacity.…”

“…Huge variations of the viscosity and surface properties were observed from one patient to another (viscosity range 19.4-3750 Pa.s and angle of contact range 0.48-1.23 rd) but we could not demonstrate any significant correlation between the DNA content and the viscosity [8,9]. This is in apparent disagreement with the results reported previously in CF, where a significant and close (r=0.82; p<0.01) relationship was demonstrated between the DNA content and the viscosity of sputum samples [11]. This may result from the fact that, compared to the previous group of CF sputum samples, the range of sputum DNA content is much smaller in this group of CB (range of DNA 0.4-6.8 mg·mL -1 in the CB patients and 2.4-19.5 mg·mL -1 in the CF patients).…”

“…The sputum DNA content of the CB patients was thus much lower (p<0.01) compared to the DNA content of CF sputum samples (median 8.5 mg·mL -1 , range 2.4-19.4 mg·mL -1 ) that we had analysed previously [11]. In our population of CB patients, no correlation could be demonstrated between the DNA content and the mucus viscosity (r=0.10; p>0.78).…”

“…As shown in table 1, the rheological and physical properties of CF sputum samples reported previously [11] appear to be more sensitive to rhDNase as compared to those of this group of CB sputum samples. At a similar concentration of rhDNase (2 µg·mL -1 ), the percentage decrease in viscosity is twofold higher in CF compared to CB.…”

“…In a recent study carried out in CF patients, we demonstrated that mucus viscosity closely correlates with DNA concentration and that the addition of rhDNase to these CF purulent sputum samples decreases the viscosity and improves the mucus transport capacity [11].…”