Aims: 

ATP signalling in the airways might play a role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and bronchial asthma by triggering airway inflammation and bronchoconstriction. Airway ATP level is increased in COPD and asthma and can be monitored using non-invasive measures.

Methods: 

We collected exhaled breath condensate (EBC), a non-invasive airway sample, from patients with acute hypoxic exacerbation of COPD or stable asthma and relevant control subjects. EBC ATP concentration was measured in a luciferase-luciferin assay, and was correlated to clinical parameters of the diseases. Airway ATP level was estimated in asthmatic patients and healthy controls from the measured dilution of the airway lining fluid in EBC.

Results: 

We developed a luminescent assay to successfully measure EBC ATP concentration and demonstrated that ATP in the condensate mainly derives from the lower airways. No difference was found in EBC ATP concentration between patients with COPD exacerbation or stable asthma and control subjects. We found that the improvement of blood oxygenation and clinical condition in COPD or the level of disease control and airway inflammation in asthma did not influence EBC ATP concentrations. Dilution of airway lining fluid highly influenced EBC ATP concentration. The calculated airway ATP level was similar in asthmatic patients and healthy controls, and showed a significant negative correlation to airway calibre.

Conclusion: 

ATP measured in EBC cannot be considered as a biomarker for COPD or bronchial asthma but airway ATP might be involved in the regulation of airway calibre. ATP concentration measured in EBC is in close correlation with the extent of airway lining fluid dilution. Hence the assessment of respiratory droplet dilution in the condensate fluid might also be of importance for other biomarkers measured in EBC.

Support: 

OTKA (grant No.68808) and Hungarian Respiratory Foundation (grant to Zsófia Lázár).