Treatment with rhDNase in patients with cystic fibrosis alters in‐vitro CHIT‐1 activity of isolated leucocytes

Summary Recent data suggest a possible relationship between cystic fibrosis (CF) pharmacotherapy, Aspergillus fumigatus colonization (AC) and/or allergic bronchopulmonary aspergillosis (ABPA). The aim of this study was to determine if anti‐fungal defence mechanisms are influenced by CF pharmacotherapy, i.e. if (1) neutrophils form CF and non‐CF donors differ in their ability to produce chitotriosidase (CHIT‐1); (2) if incubation of isolated neutrophils with azithromycin, salbutamol, prednisolone or rhDNase might influence the CHIT‐1 activity; and (3) if NETosis and neutrophil killing efficiency is influenced by rhDNase. Neutrophils were isolated from the blood of CF patients ( n  = 19; mean age 26·8 years or healthy, non‐CF donors ( n  = 20; 38·7 years) and stimulated with phorbol‐12‐myristate‐13‐acetate (PMA), azithromycin, salbutamol, prednisolone or rhDNase. CHIT‐1 enzyme activity was measured with a fluorescent substrate. NETosis was induced by PMA and neutrophil killing efficiency was assessed by a hyphae recovery assay. Neutrophil CHIT‐1 activity was comparable in the presence or absence of PMA stimulation in both CF and non‐CF donors. PMA stimulation and preincubation with rhDNase increased CHIT‐1 activity in culture supernatants from non‐CF and CF donors. However, this increase was significant in non‐CF donors but not in CF patients ( P <  0·05). RhDNase reduced the number of NETs in PMA‐stimulated neutrophils and decreased the killing efficiency of leucocytes in our in‐vitro model. Azithromycin, salbutamol or prednisolone had no effect on CHIT‐1 activity. Stimulation of isolated leucocytes with PMA and treatment with rhDNase interfered with anti‐fungal defence mechanisms. However, the impact of our findings for treatment in CF patients needs to be proved in a clinical cohort.