Extracellular ATP as a biomarker of severity of chronic obstructive pulmonary disease

Introduction: Cigarette smoking is the main etiologic factor for chronic obstructive pulmonary disease (COPD), characterized by chronic airway inflammation. Extracellular ATP (eATP) is a damage-associated molecular pattern (DAMP) molecule that may induce activation of inflammatory cells. Aims and Objectives: The aim of this study was to assess eATP concentration in stable COPD patients in relation to the severity of the disease and smoking status. Methods: We obtained blood samples from stable COPD patients (N=137) and healthy volunteers (N=95), matched by age and sex. COPD patients were divided into subgroups according to GOLD (Global Initiative for Chronic Obstructive Lung Disease) or “ABCD” classifications, by both mMRC (modified Medical Research Council) and CAT (COPD assessment test) questionnaires. Plasma eATP concentrations were determined using the commercially available luminescence assay. Nonparametric statistics using the MedCalc software was used for data analysis. Results: Plasma eATP concentration was significantly increased in COPD patients compared to healthy controls (P<0.001) and was also elevated in healthy smokers compared to healthy non-smokers (P<0.001). We found significant negative correlation between eATP and both FEV1 (r=-0.764) and FEV1/FVC (r=-0.661) in COPD patients, P<0.001. Moreover, plasma eATP concentration showed a severity of the disease-associated increase according to both GOLD and “ABCD” classifications (by mMRC and CAT questionnaires), P<0.001. Finally, eATP correlated with the number of exacerbations in COPD patients (r=0.505, P<0.001). Conclusions: Plasma eATP concentration might be a simple biomarker of severity and disease progression in COPD patients.