RhDNase and Biodistribution of PMN Serine Proteases in Cystic Fibrosis Sputum
Status:
Completed
Trial end date:
2013-04-01
Target enrollment:
Participant gender:
Summary
Serine proteases belonging to the elastase family are mainly responsible for lung tissue
destruction as observed during cystic fibrosis. But anti-inflammatory therapies based on
systemic or aerosolized protease-inhibitors administration, have not given the expected
results until now. One reason would be the impaired access of therapeutic inhibitors to their
molecular targets. It was recently shown that neutrophils actively secrete neutrophil
extracellular traps (NETs) made of DNA that binds cationic proteases among other molecules.
NETs together with DNA passively released from dead neutrophils contribute to the viscosity
of CF expectorations which explains that rhDNase treatment fluidifies expectorations and
improves the patient status. Preliminary experiments in our laboratory have shown that DNA
degradation was associated with a significant increase of proteolytic activity in the sputum
soluble fraction. However the efficacy of exogenous inhibitors is also improved in these
conditions. Using the specific substrates and methodologies that we developed previously to
measure cell-surface associated proteolytic activities, we will study the effects of DNase on
the activity of individual proteases, their biodistribution in sputum and their regulation by
potential therapeutic inhibitors. Enzymatic, immunochemical and microscopic (confocal and
scanning) techniques will first be used for ex vivo studies on sputa freshly collected at the
adult and paediatric CRCM in Tours, then on sputa from patients before and after
administration of aerosolized rhDNase. We hypothesize that a better understanding of the
biodistribution of neutrophil serine proteases and especially their binding to DNA will help
designing new therapeutic strategies that facilitate inhibitor access to their protease
targets.