Airway inflammatory response to ozone in subjects with different asthma severity

Abstract

The aim of this study was to evaluate whether ozone exposure induces a similar airway inflammatory response in subjects with different degrees of asthma severity. Two groups of asthmatic subjects were studied: seven with intermittent mild asthma not requiring regular treatment (group A); and seven with persistent mild asthma requiring regular treatment with inhaled corticosteroids and long-acting β2-agonists (group B). All subjects were exposed, in a randomized cross-over design, to air or O3 (0.26 parts per million (ppm) for 2 h with intermittent exercise); subjects in group B withdrew from regular treatment 72 h before each exposure. Before the exposure, and 1 and 2 h after the beginning of the exposure they performed a pulmonary function test, and a questionnaire was completed to obtain a total symptom score (TSS). Six hours after the end of the exposure, hypertonic saline (HS) sputum induction was conducted. Sputum cell percentages, eosinophil cationic protein (ECP) and interleukin (IL)-8 concentrations in the sputum supernatant were measured. TSS significantly increased and forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) significantly decreased after O3 exposure in comparison with air exposure in group A, whereas no changes were observed in group B except for a significant decrement of FEV1 2 h after the beginning of O3 exposure. Sputum neutrophil percentage was significantly higher after O3 exposure than after air exposure in both groups (Group A: 70.2% (28-87) versus 26.6% (8.6-73.2); Group B: 62.1% (25-82.4) versus 27.9% (14.4-54)). IL-8 was higher in sputum supernatant collected 6 h after O3 exposure than after air, only in group A. No change due to O3 has been found in sputum eosinophil percentage and ECP concentration in both groups. In conclusion, the degree of airway response to a short-term exposure to ozone is different in subjects with asthma of different severity. The available data do not allow elucidation of whether this difference depends on the severity of the disease or on the regular anti-inflammatory treatment.