Induced sputum inflammatory mediator concentrations in eosinophilic bronchitis and asthma

Eosinophilic bronchitis is a common cause of chronic cough, which like asth ma is characterized by sputum eosinophilia, but in contrast to asthma there is no variable airflow obstruction or airway hyperresponsiveness. Our hypo thesis was that the differences in airway pathophysiology maybe due to less active airway inflammation in eosinophilic bronchitis, with reduced releas e of important effector mediators. We measured the concentration of various proinflammatory mediators in induced sputum cell-free supernatant in eight patients with eosinophilic bronchitis, 17 patients with asthma matched for sputum eosinophil count, and 10 normal subjects. Cysteinyl-leukotrienes (c ys-LT) were measured by enzyme immunoassay, eosinophilic cationic protein ( ECP) by fluoroimmunoassay, prostanoids (PGE(2), PGD(2), TXB2, and PGF(2 alp ha)) by gas chromatography-negative ion chemical ionization-mass spectrosco py, and histamine by radioenzymic assay. The geometric mean sputum eosinoph il count was similar in asthma (13.4%) and eosinophilic bronchitis (12.5%). Sputum cys-LT and ECP were a mean (95% CI) 1.6-fold (1.1, 2.5) and 6.4-fol d (1.4, 28) higher in eosinophilic bronchitis and 1.9-fold (1.3, 2.9) and 7 .7-fold (1.2, 46) higher in asthma compared with that in control subjects ( geometric mean, 5.9 and 95 ng/ml, respectively). In eosinophilic bronchitis the mean concentration of sputum PGD(2) (0.79 ng/ml) and histamine (968 ng /ml) were significantly higher than in asthma (mean absolute difference in PGD(2) concentration, 0.47 ng/ml [95% CI, 0.19 to 0.74] and mean-fold diffe rence in histamine concentration, 6.7 [95% CI 1.7 to 26]) and normal subjec ts (0.64 ng/ml [0.36 to 0.90] and 11-fold [3.3 to 36]), respectively. In co nclusion, eosinophilic bronchitis is associated with active airway inflamma tion with increased release of vasoactive and bronchoconstrictor mediators.