Increased S-nitrosothiol levels in nonasthmatic eosinophilic bronchitis compared with cough variant asthma.

摘要

BACKGROUND: Nonasthmatic eosinophilic bronchitis (NAEB) and cough variant asthma (CVA) are common causes of chronic cough. Both are characterized by eosinophilic inflammation in the airways. However, airway hyperresponsiveness, which is a characteristic feature of CVA, is not observed in NAEB. We hypothesized that endogenous bronchodilator S-nitrosothiol (SNO) levels are different between patients with NAEB and CVA. METHODS: SNO concentrations in sputum supernatant were measured using a commercially available kit in 20 NAEB and 21 CVA patients. RESULTS: The mean sputum eosinophil counts and exhaled nitric oxide values were similar in patients with NAEB (12.4 +/- 2.3%, 80.6 +/- 8.1 ppb) and CVA (15.3 +/- 3.7%, 97.7 +/- 9.2 ppb). By contrast, SNO levels in the airway lining fluid of NAEB patients were substantially higher than those of CVA patients (87.1 +/- 9.8 vs. 46.8 +/- 4.8 muM; p < 0.05). CONCLUSIONS: SNOs may be an important factor in determining the development of airway hyperresponsiveness in the presence of eosinophilic inflammation.