W. H. M. Stevens

Ozone-induced oxygen radical release from bronchoalveolar lavage cells and airway hyper-responsiveness in dogs.

1. Ozone inhalation causes airway hyper‐responsiveness and airway inflammation in dogs. The purpose of this study was to determine whether these effects are associated with increases in oxygen radical production from bronchoalveolar lavage (BAL) cells. 2. Twelve randomly selected dogs were studied twice, 4 weeks apart. On each study day, acetylcholine (ACh) airway responsiveness was measured before and 1 h after ozone (3 p.p.m., 30 min) or dry air inhalation, followed by BAL. The response to ACh was expressed as the concentration causing an increase in lung resistance of 5 cmH2O l‐1 s‐1 above baseline. Spontaneous and phorbol myristate acetate (PMA) (2.4 mumol l‐1)‐stimulated oxygen radical release from washed BAL cells (4 x 10(6) cells ml‐1) was measured by luminol‐enhanced chemiluminescence in a luminometer at 37 degrees C. 3. Ozone inhalation caused airway hyper‐responsiveness. The concentration of ACh causing an increase in lung resistance of 5 cmH2O l‐1 s‐1 (the ‘provocative’ concentration) fell from 4.68 mg ml‐1 (% S.E.M., 1.43) before, to 0.48 mg ml‐1 (% S.E.M., 1.60) after ozone (P < 0.0001). Spontaneous chemiluminescence area under the curve (AUC) significantly increased after ozone from 4.08 mV (10 min) (% S.E.M., 1.28) after dry air to 8.25 mV (10 min; % S.E.M., 1.29) after ozone (P = 0.007). Ozone inhalation also increased PMA‐stimulated chemiluminescence AUC from 18.97 mV (10 min; % S.E.M., 1.18) after dry air to 144.03 mV (10 min; % S.E.M., 1.45) after ozone (P = 0.0001). The increase in PMA‐stimulated chemiluminescence was significantly correlated with ozone‐induced ACh airway hyper‐responsiveness (r = 0.83, P < 0.001). 4. These results indicate that inhaled ozone increases oxygen radical release from BAL cells and suggest that oxygen radicals are important in causing ozone‐induced airway hyper‐responsiveness.

The effects of an inhaled corticosteroid on oxygen radical production by bronchoalveolar cells after allergen or ozone in dogs.

Both ozone and allergen inhalation increase the capacity to produce oxygen radicals by bronchoalveolar lavage cells in dogs. The purpose of these studies was to determine whether inhaled corticosteroids inhibits these increases in oxygen radical production from bronchoalveolar lavage cells. Six random source dogs were studied after dry air or ozone inhalation (3 ppm, 30 min). Seven random source dogs were studied after diluent or allergen inhalation. The dogs inhaled budesonide (2.74 mg/day) or lactose powder, twice daily for 7 days before ozone and allergen. 90 min after ozone or dry air, and 24 h after Ascaris suum or diluent a bronchoalveolar lavage was carried out. Spontaneous luminol-enhanced chemiluminescence was measured from bronchoalveolar lavage cells (4 x 10(6) cells) for 10 min, followed by a measurement of phorbol myristate acetate (PMA 2.4 micromol/l) stimulated chemiluminescence for 10 min. Both ozone and allergen inhalation caused an increase in PMA stimulated chemiluminescence (P<0.05). Budesonide pretreatment inhibited ozone-induced (P<0.008), but not allergen-induced PMA stimulated chemiluminescence (P>0.90). Both ozone and allergen inhalation caused an increase in the bronchoalveolar lavage neutrophils. Budesonide pretreatment significantly inhibited the ozone-induced (P=0.007), but not the ascaris-induced neutrophil influx (P=0.93). These results demonstrate that ozone, but not allergen, stimulated oxygen radical release and neutrophil influx are attenuated by inhaled corticosteroids. This suggests that luminol-enhanced chemiluminescence from bronchoalveolar lavage cells measures oxygen radicals derived from neutrophils, and that ozone-and allergen-induced bronchoalveolar lavage neutrophilia are caused by different mechanisms.

Ozone-Induced Bronchial Hyperreactivity

Ozone (03) is a powerful oxidizing agent which is classified as a “secondary air pollutant”. Secondary air pollutants are not emitted into the atmosphere but formed from subsequent atmospheric chemical reactions of primary pollutants (nitrogen dioxide, sulfur dioxide, particles, carbon monoxide, lead).

Effect of Inhaled Prostaglandin E2 on Methacholine and Leukotriene D4 Airway Responsiveness in Asthmatic Subjects

Previous studies in asthmatics have demonstrated that the endogenous release of inhibitory prostaglandins limits the bronchoconstrictor response to repeated challenges with exercise and histamine, and that inhaled prostaglandin (PG) E2 attenuates allergen-induced asthmatic responses and exercise bronchoconstriction in asthmatics. Inhaled PGE2 does not significantly attenuate methacholine airway responsiveness. These results, taken together, indicate that inhaled PGE2 attenuates the bronchoconstriction caused by stimuli, such as allergen and exercise, that result in bronchoconstriction through cysteinyl leukotriene (LT) release. The purpose of this study was to determine whether inhaled PGE2 could selectively attenuate LTD4-induced bronchoconstriction in seven stable asthmatic subjects. Each subject was studied on four different study days. On two occasions the subjects inhaled 100 mg PGE2, 30 mins before a methacholine, or LTD4 challenge test. On the other two study days, the subjects were pretreated with its diluent. Results were expressed as the provocation concentration causing a 20% fall in forced expiratory volume in 1 s (FEV1) (PC20). PGE2 pretreatment significantly increased the LTD4 PC20, but not the methacholine PC20. The mean LTD4 PC20 increased from 2.00 mg/mL (%SEM 1.65) after diluent pretreatment to 3.01 mg/mL (%SEM 1.64) after PGE2 pretreatment (P=0.008). The mean methacholine PC20 was 1.28 mg/mL (%SEM 1.68) after diluent pretreatment and 1.62 mg/mL (%SEM 1.46) after PGE2 pretreatment (P=0.28). These results suggest that PGE2 partially attenuates LTD4-induced bronchoconstriction; however, the magnitude of the effect is unlikely to account for its attenuation of exercise and allergen-induced bronchoconstriction.