ATP/AMP Challenge in Healthy Non-smokers, Smokers, Patients With Asthma, and Patients With Chronic Obstructive Pulmonary Disease (COPD)

Overview

In this randomised, cross-over, controlled study, a total of 84 subjects will be included: 12 healthy non-smoking volunteers; 12 current smokers; 30 patients with mild steroid-naïve asthma; and 30 patients with mild-moderate COPD. Each subject will have 1 screening visit (if necessary) and 2 study visits. At visits 2 and 3 the effects of adenosine 5'-triphosphate (ATP) or adenosine 5'-monophosphate (AMP) challenge, given in a random order, will be tested.

Background: Extracellular adenosine 5'-triphosphate (ATP) stimulates vagal C and Aδ fibers in the lung, resulting in pronounced bronchoconstriction and cough mediated by P2X2/3 receptors located on vagal sensory nerve terminals. We investigated the effects of nebulized ATP on cough and symptoms in control subjects, healthy smokers, and patients with COPD and compared these responses to the effects of inhaled adenosine, the metabolite of ATP. Methods: We studied the effects of inhaled ATP and adenosine monophosphate (AMP) on airway caliber, perception of dyspnea assessed by the Borg score, cough sensitivity, and ATP in exhaled breath condensate in healthy nonsmokers (n = 10), healthy smokers (n = 14), and patients with COPD (n = 7). Results: In comparison with healthy subjects, ATP induced more dyspnea, cough, and throat irritation in smokers and patients with COPD, and the effects of ATP were more pronounced than those of AMP. The concentration of ATP in the exhaled breath condensate of patients with COPD was elevated compared with that of healthy subjects. Conclusions: Smokers and patients with COPD manifest hypersensitivity to extracellular ATP, which may play a mechanistic role in COPD.

Conditions