Effect of apocynin on ozone-induced airway hyperresponsiveness to methacholine in asthmatics.

Apocynin is an inhibitor of NADPH oxidase present in inflammatory cells such as eosinophils and neutrophils. We investigated the effect of inhaled apocynin on ozone-induced bronchial hyperresponsiveness in vivo. Seven mild atopic asthmatics participated in a placebo-controlled, cross-over study with two exposures to O(3) at 2-week intervals. Apocynin (3 ml of 0.5 mg/ml) was inhaled 2 times before and 6 times after O(3) exposure at hourly intervals. At 36 h before and 16 h after O(3) exposure, methacholine inhalation challenge tests (Mch) were performed, and PC(20) and maximal % fall from baseline (MFEV(1)) were calculated from dose-response curves. O(3)-induced change in PC(20) (Delta PC(20)) after placebo treatment was -1.94 +/- 0.39 DD (mean +/- SEM doubling dose Mch) (p =.001) and apocynin was -0.6 +/- 0.33 DD (p =.17). The difference between apocynin and placebo treatment was 1.3 DD +/- 0.42 (p =.02). O(3)-induced Delta MFEV(1) was 11.9 +/- 1.5% (p =.008) during placebo inhalation and 3.85 +/- 1.8% during apocynin (p =.47). Apocynin reduced the Delta MFEV(1) by 8.05% compared to placebo (p =.025). We conclude that apocynin markedly reduced O(3)-induced hyperreactivity for Mch as well as maximal airway narrowing. The results suggest that apocynin may have a role in preventing ozone-induced exacerbations of asthma.

Ozone-induced inflammation assessed in sputum and bronchial lavage fluid from asthmatics: a new noninvasive tool in epidemiologic studies on air pollution and asthma.

We investigated correlations between ozone-induced increases in inflammatory markers in induced sputum and in bronchial lavage fluid. Sixteen volunteers with intermittent asthma participated in a placebo-controlled parallel study with two exposures. Six days before and 16 h after the first exposure to ozone (0.4 ppm during 2 h) sputum was induced with hypertonic saline. This resulted in a significant increase in the sputum levels of eosinophil cationic protein (ECP; 1.8-fold; p = .03), neutrophil elastase (5.0-fold; p = .005) and the total cell number (1.6-fold; p = .02). After 4 weeks, a second exposure was randomized for air or ozone. Six days before and 16 h after the second exposure a bronchial lavage was performed. ECP values in sputum and in bronchial lavage fluid obtained after ozone correlated significantly (Rs = .79; p = .04), as did interleukin-8 (IL-8) values (Rs = .86; p = .01), and the percentage eosinophils (Rs = .89; p = .007). Moreover, the ozone-induced changes in percentage eosinophils observed in sputum and lavage fluid were highly correlated (Rs = .93; p = .003). In conclusion, changes in eosinophils, IL-8, and ECP markers induced by ozone and measured in sputum reflect the inflammatory responses in the lower airways of asthmatics, and may provide a noninvasive tool in epidemiologic studies on air pollution and asthma.

The effect of inhaled leukotriene D4 and methacholine on sputum cell differentials in asthma.

The cysteinyl leukotriene LTE4 has been shown to induce airway eosinophilia in asthmatics in vivo. This phenomenon has not yet been reported for LTD4. Hence, we examined the effect of inhaled LTD4 and a control bronchoconstrictor agent, methacholine, on cell differentials in hypertonic saline-induced whole sputum samples of 12 nonsmoking atopic asthmatic subjects (three women, nine men; 21 to 29 yr of age; FEV1, 74 to 120% pred; PC20FEV1 methacholine < 9.6 mg/ml). The study had a cross-over, placebo-controlled design consisting of 4 d separated by > or = 1 wk. On each randomized study day, the subjects inhaled five serial doses of either LTD4 (mean cumulative concentration: 95.7 microM) or methacholine (mean cumulative concentration: 542 mM) or five doses of their respective diluents (PBS/ethanol or PBS). The airway response was measured by FEV1, followed by sputum induction with 4.5% NaCl, 4 h postchallenge. Inflammatory cells (> or = 250) were counted twice on coded cytospins and expressed as percentages of nonsquamous cells. There was no significant difference in the maximal percent fall in FEV1 from baseline between LTD4 (mean +/- SEM, 49.5 +/- 4.4% fall) and methacholine (mean +/- SEM, 55.9 +/- 3.4% fall) (p = 0.11). LTD4 induced a significant increase in the percentage of sputum eosinophils as compared with its diluent (mean +/- SD, 26.6 +/- 21.3% and 10.2 +/- 8.8%, respectively; p = 0.025), whereas a similar trend for methacholine failed to reach significance (mean +/- SD, 19.1 +/- 22.9% and 7.8 +/- 5.8%, respectively; p = 0.11). There was no significant difference in the changes in the percentage of sputum eosinophils between LTD4 and methacholine (mean difference +/- SD, 7.5 +/- 12.5% eosinophils; p = 0.09). We conclude that LTD4 induces eosinophilia in sputum of asthmatic subjects 4 h after inhalation. Our data suggest that LTD4 recruits eosinophils into the airways of asthmatics in vivo, possibly by virtue of direct or indirect chemotactic properties, whereas an additional effect of vigourous airway narrowing per se cannot be excluded.