The role of thromboxane A2 in the development of airway responsiveness after platelet activating factor inhalation in dogs

To determine whether thromboxane A2 (TxA2) is involved in airway hyperresponsiveness after platelet activating factor (PAF) inhalation, we studied the effect of a specific TxA2 receptor antagonist, AA-2414 on the development of airway responsiveness induced by PAF inhalation in six dogs. Airway resistance and airway responsiveness to inhaled methacholine were determined by modified Astograph (7 Hz oscillation method). PAF inhalation (1000 micrograms/ml, ten minutes) caused a significant increase of airway resistance (p less than 0.01), and the increase of airway resistance was not inhibited by pretreated AA-2414. Airway responsiveness to inhaled methacholine increased significantly 3 hr after PAF inhalation (p less than 0.01). Pretreated AA-2414 inhibited the increase of airway responsiveness significantly (p less than 0.01), but the inhibition was partial. After PAF inhalation, total cell counts, neutrophil counts, eosinophil counts and the levels of TxB2 in bronchoalveolar lavage fluid increased significantly (p less than 0.05), and these increase were not affected by pretreated AA-2414. These results suggest that TxA2 is not involved in the bronchoconstriction induced by PAF inhalation, but TxA2 plays a partial role in the development of airway responsiveness after PAF inhalation in dogs.     

The effect of a selective 5-lipoxygenase inhibitor, AA-861 on airway hyperresponsiveness induced by ozone exposure in dogs

To determine whether 5-lipoxygenase products are involved in hyperresponsiveness induced by ozone exposure, we studied the effect of a selective 5-lipoxygenase inhibitor, AA-861 on ozone-induced airway hyperresponsiveness in six dogs. Airway responsiveness to methacholine was measured by modified Astograph (7 Hz oscillation method) before and after ozone exposure, and TxB2 in plasma and in BALF, 6-keto-PGF1 alpha in BALF, numbers of neutrophils in the peripheral blood and differential cell counts in BALF were measured before and after ozone exposure. Ozone exposure was carried out for 2 hr at an ozone level of 3.04 +/- 0.01 ppm (mean +/- SE). There was a significant increase in airway responsiveness to methacholine after ozone exposure in the six dogs (p less than 0.01), and the numbers of neutrophils in the peripheral blood and the neutrophil counts in BALF increased significantly after ozone exposure (P less than 0.01). A selective 5-lipoxygenase inhibitor, AA-861 significantly inhibited the increase of airway responsiveness to methacholine induced by ozone exposure (p less than 0.05), and furthermore, the increase in the numbers of neutrophils in the peripheral blood and the neutrophil counts in BALF after ozone exposure were significantly inhibited by pretreatment with AA-861 (p less than 0.05). There was no significant change in the levels of TxB2 in plasma or in BALF, and also no apparent change in the levels of histamine was observed in BALF after ozone exposure. The levels of 6-keto-PGF1 alpha in BALF decreased after ozone exposure, but the decrease was not significant. These results suggest that 5-lipoxygenase products play an important role in the development of airway hyperresponsiveness and in the infiltration of neutrophils into the airway after ozone exposure in dogs.     

The effect of a specific thromboxane A2 antagonist, AA-2414 on airway hyperresponsiveness induced by ozone exposure in dogs]

To determine whether thromboxane A2 (TxA2) is involved in airway hyperresponsiveness induced by ozone exposure, we studied the effect of a specific TxA2 antagonist, AA-2414 on ozone-induced airway hyperresponsiveness in seven dogs. Airway responsiveness to inhaled methacholine was determined by modified Astograph (7 Hz oscillation method), and numbers of neutrophils in the peripheral blood, neutrophil counts in bronchoalveolar lavage fluid (BALF), the levels of TxB2 and 6-keto-Prostaglandin F1 alpha (6-keto-PGF1 alpha) in BALF were measured before and after ozone exposure, and after ozone exposure with pretreated AA-2414. Ozone exposure was carried out for 2 hr at an ozone level of 3.06 +/- 0.06 ppm (mean +/- SE). Airway responsiveness to inhaled methacholine increased significantly after ozone exposure (p less than 0.01), and the hyperresponsiveness induced by ozone exposure was inhibited significantly by pretreated AA-2414 (p less than 0.01). Numbers of neutrophils in the peripheral blood and neutrophil counts in BALF increased after ozone exposure, and these increase were not inhibited by pretreated AA-2414. There was no apparent change in the levels of TxB2 in BALF after ozone exposure and after ozone exposure with pretreated AA-2414, however the levels of 6-keto-PGF1 alpha in BALF decreased after ozone exposure and after ozone exposure with pretreated AA-2414 (p less than 0.1). These results suggest that TxA2 plays an important role in the development of airway responsiveness after ozone exposure in dogs, and ozone-induced airway hyperresponsiveness may not be associated with the hyperproduction of TxA2 but with the relative increase of TxA2 due to the decrease of PGI2.     

The effect of AH 21-132 on airway hyperresponsiveness induced by ozone exposure

We examined the effect of AH 21-132, which has been reported to relax airway smooth muscle and inhibit platelet activating factor (PAF)-induced airway hyperreactivity, on ozone-induced airway hyperresponsiveness (AHR) with airway inflammation in dogs. Airway responsiveness (AR) to methacholine was measured by modified Astograph (7 Hz oscillation method) before and after ozone exposure, and the numbers of neutrophils in the peripheral blood and total cell counts, differential cell counts and TXB2 in BALF were measured before and after ozone exposure. Ozone exposure was carried out for 2 hr at an ozone level of 3.46 +/- 0.10 ppm (mean +/- SE). There was a significant increase in AR to methacholine after ozone exposure (p less than 0.01), and the numbers of neutrophils in the peripheral blood and the total cell and neutrophil counts in BALF increased significantly (p less than 0.05). Pretreatment with AH 21-132 at an oral dose of 20 mg/kg significantly prevented the ozone-induced AHR to methacholine (p less than 0.01), and also inhibited the increase of neutrophil counts in the peripheral blood, and the total cell counts and the neutrophil counts in BALF after ozone exposure. There was no significant change in the levels of TXB2 in BALF before and after ozone exposure. In dogs not exposed to ozone, AR to methacholine and respiratory resistance to methacholine significantly decreased after administration of AH 21-132 at an oral dose of 20 mg/kg (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibitory effect of prostaglandin I2 on the increase of airway responsiveness induced by inhaled thromboxane A2 mimetic U-46619 in dogs

To investigate the effect of prostaglandin I2 (PGI2) on the increase of airway responsiveness induced by inhaled thromboxane A2 (TxA2), we measured the airway responsiveness to inhaled methacholine (Mch) after inhalation of TxA2 mimetic U-46619 alone and after inhalation of U-46619 in combination with PGI2 (U-46619/PGI2) in six dogs. Airway responsiveness to Mch was determined by Astograph (7Hz oscillation method). Inhalation of U-46619 was carried out for five minutes at a half of minimum threshold concentration, and the concentration of PGI2 was double that of U-46619. Inhaled U-46619 significantly increased airway responsiveness to Mch (p less than 0.01). However the airway responsiveness to Mch did not increase following inhalation of U-46619/PGI2, and the increase of airway responsiveness to Mch induced by inhaled U-46619 was inhibited significantly by PGI2 (p less than 0.01). PGI2 inhalation alone did not affect the basal airway responsiveness to Mch. These results indicate that PGI2 protects the hyperresponsiveness induced by TxA2 inhalation in dogs.     

Eosinophil infiltration and enhancement of airway reactivity by leukocyte chemotactic factor, formyl-methionyl-leucyl-phenylalanine (fMLP), in guinea pigs.

N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP) is a bacterial-derived chemotactic factor for eosinophils and neutrophils. This study is aimed to examine whether or not eosinophil infiltration induced by intra-airway administration of fMLP causes the damage of the bronchial epithelium and results in airway hyperresponsiveness in normal non-sensitized guinea pigs. In normal guinea pigs fMLP administered by aerosol inhalation or intratracheal injection caused significant infiltration of eosinophils in the tracheal mucosa and enhanced bronchial reactivity to inhaled histamine 6 and 24 hours after exposure. Electron microscopic examination showed damage of the alignment of the epithelial cells in the bronchial mucosa in fMLP-treated guinea pigs. PAF antagonists CV3988 and WEB2086 and a 5-lipoxygenase inhibitor (AA-861) did not prevent fMLP induced eosinophil infiltration, which suggests that fMLP caused eosinophil infiltration mainly by its chemotactic activity, not by the release of platelet activating factor (PAF) or leukotrienes in this experimental condition. These results showed that in normal guinea pigs a bacteria-derived chemoattractant of fMLP could reproduce a sequence of eosinophil infiltration and airway hyperresponsiveness, similar to the inflammatory pathophysiology after antigen challenge in sensitized animals. We concluded that eosinophil infiltration induced by either immunological or non-immunological mechanisms can cause airway damage and airway hyperresponsiveness.     

Role of thromboxane A2 and prostaglandin I2 in the increase of airway responsiveness in dogs after ozone exposure]

To investigate the role of thromboxane (Tx) A2 and prostaglandin (PG) I2 in the development of airway responsiveness after ozone exposure, we measured the airway responsiveness to inhaled methacholine (Mch), TxB2 and 6-keto-PGF1 alpha levels in bronchoalveolar lavage fluid (BALF) in 18 dogs after ozone exposure. Airway responsiveness to Mch was determined by Astograph (7 Hz oscillation method), and ozone exposure was carried out for 2 hr at an ozone level of 3.01 +/- 0.05 ppm (mean +/- SEM). Airway responsiveness to Mch increased significantly after ozone exposure (p less than 0.001). TxB2 levels in BALF were not affected by ozone exposure, but the levels of 6-keto-PGF1 alpha decreased significantly after ozone exposure (p less than 0.001). The ratio of TxB2/6-keto-PGF1 alpha increased significantly after ozone exposure, and the change in this ratio correlated significantly with the change of airway responsiveness to Mch (p less than 0.01, r = 0.654). These results suggest that airway hyperresponsiveness after ozone exposure is induced by the relative increase of TxA2 due to the decrease of PGI2.     

Effects of single and multiple inhalations of platelet-activating factor on airway cell composition and responsiveness in monkeys

Platelet-activating factor (PAF) is a potent pro-inflammatory mediator that may play a role in the pathogenesis of airway hyper-responsiveness and asthma. In man, a single inhalation of PAF induces a small but prolonged increase in airway responsiveness in some individuals. The purpose of this study was to determine the effects of single and multiple inhalations of PAF on airway cell composition and responsiveness in monkeys. Anaesthetized and intubated adult male cynomolgus monkeys were studied. Airway cell composition was measured by bronchoalveolar lavage (BAL). Airway responsiveness was measured by determining the concentration (PC100) of inhaled methacholine that caused a 100% increase in respiratory system resistance (Rrs). Airway cell composition (BAL) and responsiveness (PC100) were determined 1 day before and 20 hr after a single inhalation of PAF (approximately 200 micrograms) or 3 days before (Day 0) and 3 days after (Day 10) 3-alternate-day (Days 3, 5 and 7) inhalations of PAF (each approximately 600 micrograms). The single inhalation of PAF (n = 8) caused an acute increase in Rrs (147 +/- 69%), an increase in BAL granulocytes, and a decrease in PC100 in four of eight animals that was moderate (greater than eight fold) in only one animal. The mean +/- s.e. change in log PC100 was -0.29 +/- 0.18. The multiple inhalations of PAF (n = 8) caused acute increases in Rrs (143 +/- 38%, 175 +/- 44% and 156 +/- 39%, respectively), an increase in BAL granulocytes, and a decrease in PC100 in four of eight animals that was moderate in two animals. The mean +/- s.e. change in log PC100 was -0.43 +/- 0.22.     

Characterization of allergen-induced bronchial hyperresponsiveness and airway inflammation in actively sensitized brown-Norway rats.

Bronchial responsiveness to inhaled acetylcholine (ACh) and inflammatory cell recruitment in bronchoalveolar lavage fluid (BALF) were studied in inbred Brown-Norway rats actively sensitized to, and later exposed to, ovalbumin (OA). We examined animals 21 days after initial sensitization at 18 to 24 hours, or 5 days after a single challenge, or after the last of seven repeated exposures administered every 3 days. BALF was examined as an index of inflammatory changes within the lung. Animals repeatedly exposed to OA aerosols had an increased baseline lung resistance and a significant increase in bronchial responsiveness to inhaled ACh compared to control animals at both 18 to 24 hours and 5 days after the last OA exposure. Sensitized animals receiving a single OA aerosol also demonstrated bronchial hyperresponsiveness (BHR) to inhaled ACh (p less than 0.01) at 18 to 24 hours of a similar order as the multiple-exposed group. There was a significant increase in eosinophils, lymphocytes, and neutrophils in BALF at 18 to 24 hours but not at 5 days after single or multiple exposure to OA aerosol in the sensitized groups. Control animals demonstrated no changes in bronchial responsiveness, although a small but significant increase in inflammatory cells was observed compared to saline-only treated animals. There was a significant correlation between bronchial responsiveness and eosinophil counts in the BALF in the single allergen-exposed group (Rs = 0.68; p less than 0.05). We conclude that (1) BHR after allergen exposure in sensitized rats is associated with the presence of pulmonary inflammation but persists despite the regression of inflammatory cells in BALF after multiple OA exposures, and (2) this rat model has many characteristics of human allergen-induced BHR.     

The actions of GR32191B, a thromboxane receptor antagonist, on the effects of inhaled PAF on human airways

We investigated acute bronchoconstriction and changes in airway responsiveness to methacholine following the inhalation of platelet activating factor (PAF) in an open study of 12 non-asthmatic subjects. Ventilatory function was monitored using a flow rate at 30% of vital capacity (V30) and airway responsiveness was measured as PD40V30, i.e. the dose of metacholine causing a 40% fall in V30. PAF (3-422 micrograms) resulted in dose-related acute bronchoconstriction in 10 of the 12 subjects. There was no association between the airway responsiveness to PAF and to methacholine. Ten subjects showed some increase in airway responsiveness to methacholine 1 or 3 days following PAF. Overall, these changes were statistically significant (P less than 0.05) but were of small magnitude (geometric mean PD40V30pre-PAF = 457 micrograms; 24 hr after PAF = 259 micrograms; 72 hr after PAF = 258 micrograms) and variable: only seven subjects showing increased airway responsiveness on both day 1 and day 3 after PAF. Six subjects who appeared to show increases in airway responsiveness following PAF were re-studied with the inhaled PAF pre-medicated by either placebo or a specific thromboxane receptor antagonist (GR32191B) in a double-blind fashion. GR32191B did not reduce the acute bronchoconstriction due to PAF. In this part of the study, these six subjects did not show significant increases in airway responsiveness following the placebo pre-medicated PAF challenge and so no effect of the drug on airway responsiveness could be shown.(ABSTRACT TRUNCATED AT 250 WORDS)     

Airway hyperresponsiveness is associated with inflammatory cell infiltration in allergic brown-Norway rats.

The time course of the development of airway hyperresponsiveness (AHR) to inhaled acetylcholine (ACh) and the associated inflammatory cell recovery in bronchoalveolar lavage fluid (BAL) in actively sensitised Brown-Norway rats was studied following challenge with inhaled ovalbumin (OA). IgE for OA was detected in serum obtained from sensitised rats using passive cutaneous anaphylaxis, at titres of 1:10 to 1:30; none was detected in unsensitised animals. There was no significant change in either airway responsiveness to inhaled ACh or in BAL cell counts in rats challenged with saline over the 24 h. Following challenge with a 1% OA aerosol, airway responsiveness to inhaled ACh increased over the 24-hour period, maximal at 18-24 h (saline-challenged group mean -log PC200 1.95 +/- 0.07 M; OA-challenged group mean -log PC200 2.30 +/- 0.05 M; p < 0.01). The composition of the inflammatory cells in the BAL fluid after allergen inhalation varied over the 24-hour period, with an initial neutrophilia at 5-8 h (p < 0.01), followed at 18-24 h by an increase in lymphocytes (p < 0.01) and marked eosinophilia (p < 0.01). There was a significant correlation between airway responsiveness and eosinophil recovery at 5-8 h (p < 0.05), and at 18-24 h after allergen exposure (p < 0.05). At 18-24 h there was also a significant correlation between neutrophils and airway responsiveness (p < 0.05). There was no difference between baseline lung resistance in matched saline- or OA-challenged animals at each time point.(ABSTRACT TRUNCATED AT 250 WORDS)     

Chronic cough with eosinophilic bronchitis: examination for variable airflow obstruction and response to corticosteroid

The purpose of this study was to examine airway responsiveness, sputum cells and the effects of inhaled corticosteroid in the chronic cough syndrome associated with eosinophilic bronchitis. We studied nine consecutive referrals with chronic cough, sputum with >10% eosinophils, normal spirometry, and normal methacholine airway responsiveness. Clinical assessment, sputum analysis, allergy skin tests and a methacholine inhalation test were performed at the first visit. Peak expiratory flow (PEF) was measured twice daily for 1 week followed by an adenosine monophosphate (AMP) inhalation test. Subjects were then treated with inhaled beclomethasone 0.4 mg twice daily for 7 days. Sputum analysis and measurement of methacholine responsiveness were then repeated. Excessive airway narrowing to methacholine was not present in any of the subjects. A methacholine plateau response was present in five subjects. Hyperresponsiveness to AMP was absent in six of the nine subjects, and PEF variability was not increased for eight subjects. Corticosteroid therapy led to a reduction in sputum eosinophil counts from 40.1 (so 21.4)% to 4.0 (4.5)% but there was no significant change in metachromatic cell counts (0.8 so 0.5% vs 0.6 sd 0.6%) or total cell counts. Methacholine responsiveness improved within the normal range in the three subjects in whom it could be determined. Chronic cough associated with eosinophilic airway inflammation can occur in the absence of variable airflow obstruction (asthma) and can improve after treatment with inhaled corticosteroid. This treatment can reduce the level of methacholine responsiveness within the normal range and reduces sputum eosinophils but not mast cells. These results suggest that the occurrence of variable airflow obstruction depends on the baseline level of methacholine responsiveness, the degree of eosinophilic infiltration and the degree to which methacholine responsiveness becomes heightened.     

The onset and recovery from airway hyperresponsiveness: relationship with inflammatory cell infiltrates and release of cytotoxic granule proteins

Previous studies from our laboratory have demonstrated a temporal relationship between eosinophil influx into the airways and the onset of airway hyperresponsiveness to inhaled methacholine. The purpose of the present study was to extend this observation by evaluating changes in airway cellular composition and measuring the levels of granulocyte-derived mediators recovered in BAL fluid during the onset and recovery from antigen-induced airway hyperresponsiveness. Airway cellular composition, airway responsiveness to inhaled methacholine and the levels of BAL fluid EPO and MPO were monitored over a 32 day study in eight adult male Ascaris suum sensitive cynomolgus monkeys. Repeated Ascaris suum inhalation (nine challenges during days 0-21) resulted in a selective, sustained airway eosinophilia that was temporally related with the onset and maintenance of airway hyperresponsiveness (r = 0.67, P less than 0.001). The level of BAL eosinophil-derived EPO was increased and remained elevated concurrent with the increase in airway eosinophils and airway responsiveness. During the recovery phase (days 22-32) the actual number of eosinophils remained elevated, while BAL EPO levels were significantly decreased. The recovery phase was also associated with a transient increase in the number of BAL neutrophils and MPO concentration. We conclude that the number and state of activation of airway eosinophils directly correlate with the onset and maintenance of airway hyperresponsiveness. Recovery from airway hyperresponsiveness is associated with a decrease in eosinophil activation and a transient increase in the number of activated neutrophils.     

Eosinophilic bronchitis in asthma: a model for establishing dose-response and relative potency of inhaled corticosteroids

BACKGROUND: Newer generations and formulations of inhaled corticosteroids have necessitated the development of a clinically relevant model to compare their clinical potency. OBJECTIVE: We evaluated whether sputum eosinophil counts could demonstrate a dose-response to inhaled corticosteroids, and compared the response with other inflammatory markers. METHODS: Fourteen steroid-naive patients with asthma with an initial sputum eosinophilia of > or = 2.5% entered a 6-week sequential, placebo-controlled, patient-blinded, cumulative dose-response study. After 7 days of placebo, they received incremental doses of fluticasone propionate (FP), 50, 100, 200, and 400 microg/d, each for 7 days. Measurements were made of sputum and blood eosinophils, exhaled nitric oxide, spirometry, airway responsiveness to methacholine (methacholine PC20), and symptom scores before and after each dose. RESULTS: Sputum eosinophils and exhaled nitric oxide were extremely sensitive to the effects of FP, and exhibited significant dose-dependent reductions of 99.4% and 99.8 parts per billion, respectively, where each variable was expressed per 100 microg/d FP. This compared with a 0.5 doubling dose increase of airway responsiveness to methacholine and a 0.3 decrease in symptom scores. Airway responsiveness to methacholine was the only variable that increased throughout the study. CONCLUSION: These results suggest that the model of eosinophilic bronchitis could be used to compare the effect of cumulative doses of an inhaled corticosteroid delivered by different types of delivery systems or preparations using a relatively small number of patients. CLINICAL IMPLICATIONS: Future clinical studies based on this model will allow clinicians to make informed decisions regarding the relative potencies of different inhaled corticosteroids.     

The effect of aerosol distribution on airway responsiveness to inhaled methacholine in patients with asthma.

It has been demonstrated that airway deposition of inhaled aerosols is more heterogeneous in patients with asthma than in normal subjects. Nevertheless, the influence of abnormal airway deposition on responses to bronchoactive aerosols is poorly understood. We altered bronchopulmonary deposition heterogeneity of methacholine aerosol in nine asymptomatic patients with asthma by controlling inspiratory flow at high (approximately 60 L/min) versus low (approximately 12 L/min) rates on 2 study days and determined the effect on the provocative dose of methacholine causing a 20% fall in FEV1 (PD20) (often used as a measure of airway responsiveness). Deposition uniformity was quantified from gamma-camera scans of the lungs in terms of the distribution of a technetium-labeled aerosol that was inhaled rapidly or slowly before the inhalation of methacholine. Increased deposition in an inner (large, central airways) versus an outer (peripheral airways and alveoli) zone of the right lung (inner/outer ratio, greater than 1) and higher values of skew (an index of deposition asymmetry) and kurtosis (an index of deposition range) indicated enhanced heterogeneity of deposition. Mean (+/- SD) inner/outer ratio was significantly higher during rapid inspiration compared to slow inspiration with 2.91 +/- 0.51 and 1.84 +/- 0.30, respectively (p less than 0.01). Mean skew and kurtosis were also significantly higher after rapid inspiration, with 1.12 +/- 0.35 and 3.86 +/- 1.25, respectively, compared to 0.74 +/- 0.36 and 2.64 +/- 0.77 after slow inhalation (p less than 0.01). Geometric mean PD20 methacholine was significantly reduced when the aerosol was inhaled rapidly, with 5.9 cumulative methacholine units compared to 15.7 units after slow inhalation (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)     

Platelet activating factor does not cause a reproducible increase in bronchial responsiveness in normal man

The reproducibility of acute effects of inhaled PAF on airway calibre, circulating neutrophil count and any subsequent increase in bronchial responsiveness has been studied in six normal subjects and compared to the effects of inhaled lyso-PAF, the inactive precursor and metabolite of PAF. PAF caused acute bronchoconstriction and a transient fall in neutrophil count on two separate occasions in five out of six subjects (minimum percentage of baseline values (mean): first PAF challenge; sGaw 69%, Vmax30 72%; neutrophil count 70%; second PAF challenge; sGaw 61%, Vmax30 74%, neutrophil count 63%). In one subject inhaled PAF caused bronchoconstriction and a transient fall in neutrophil count once, but a second challenge resulted in no detectable changes. There was no significant increase in bronchial responsiveness to methacholine in any subject studied on five occasions over a 2-week period following each PAF challenge. Challenge with lyso-PAF did not cause acute effects or any subsequent changes in bronchial responsiveness. These findings demonstrate that any effects of inhaled PAF on bronchial responsiveness in normal man are small and probably not of clinical significance. It would also be inappropriate to use this human model to study the mechanisms of bronchial hyperresponsiveness or for the preliminary assessment of potential new anti-asthma drugs.     

Sodium cromoglycate attenuates pulmonary inflammation without influencing bronchial responsiveness in healthy subjects exposed to organic dust

BACKGROUND: Inhalation of organic dust from a pig house induces airway inflammation and increases bronchial responsiveness to methacholine in healthy subjects. OBJECTIVE: To study whether sodium cromoglycate influences the airway inflammatory reaction and the increase in airway responsiveness induced by inhalation of organic dust. METHODS: Bronchoalveolar and nasal lavages, and bronchial methacholine challanges were performed and blood samples were drawn in 32 healthy subjects before and after exposure to dust in a pig farm. Sodium cromoglycate was inhaled (20 mg, twice a day) and administered intranasally (5.2 mg, twice a day) by 16 and a corresponding placebo was given to the other 16 healthy controls for two weeks prior to exposure. RESULTS: Exposure induced a significant increase in inflammatory cells and soluble components (pro-inflammatory cytokines, inflammatory mediators) in bronchoalveolar and nasal lavage fluid in both groups. The increase in neutrophils, interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha as well as myeloperoxidase and soluble intracellular adhesion molecule (ICAM)-1 in bronchoalveolar lavage (BAL) fluid was significantly reduced by treatment with sodium cromoglycate. Although sodium cromoglycate inhalation largely influenced a variety of inflammatory indices in bronchoalveolar lavage fluid it had no effect on the increase in bronchial responsiveness to methacholine. CONCLUSION: Sodium cromoglycate alters the airway inflammatory response to inhaled organic dust without influencing the dust-induced increase in bronchial responsiveness to methacholine.     

Changes in sputum cell counts after exposure to occupational agents: what do they mean?

BACKGROUND: Exposure to occupational agents can induce eosinophilic inflammation in subjects with occupational asthma (OA). It might also induce nonspecific changes in airway inflammation in subjects without OA. OBJECTIVES: We sought to investigate the changes in airway inflammation induced by exposure to occupational agents in subjects with and without OA and to determine which changes in sputum eosinophil numbers and bronchial responsiveness to methacholine should be regarded as clinically significant for predicting a 20% fall in FEV(1). METHODS: We performed specific inhalation challenges (SICs) in 3 groups of subjects: subjects reporting a history consistent with OA with a positive SIC response (n = 17); subjects reporting a history consistent with OA with a negative SIC response (n = 14); and asthmatic subjects without any history of OA (n = 10). Induced sputum and methacholine challenges were performed at the end of the control day and again at the end of the last day of exposure; the last day of exposure was always performed in the laboratory. RESULTS: There was an increase in median sputum eosinophil and neutrophil numbers in subjects with positive SIC responses. Cell counts remained unchanged after exposure in asthmatic subjects without OA. A combination of a greater than 0.26 10(6)/mL increase in sputum eosinophil numbers and a decrease in the concentration of methacholine inducing a 20% fall in FEV(1) of at least 1.8-fold compared with baseline values predicted a 20% fall in FEV(1) in 96% (95% CI, 70%-99%) of patients. CONCLUSION: Exposure to occupational agents per se does not induce airway inflammation. Changes in both sputum eosinophil counts and methacholine responsiveness are satisfactory predictors of a significant bronchial responsiveness to occupational agents.     

The effects of inhaled leukotriene E4 on the airway responsiveness to histamine in subjects with asthma and normal subjects

Eight subjects with asthma inhaled on separate occasions leukotriene E4 (LTE4) (6.1 nmol, geometric mean), methacholine, and diluent, which produced an average 41.0%, 37.0%, and 3.3% decrease in specific airway conductance (SGaw), respectively. When the SGaw had recovered to baseline levels at 60 minutes after challenge, the provocative dose of inhaled histamine that produced a 35% decrease in SGaw (PD35) was determined. The histamine PD35 observed after inhalation of LTE4 was 0.46 mumol, and this was significantly less than the histamine PD35 observed after inhalation of methacholine (0.88 mumol; p less than 10(-4) and diluent (0.97 mumol; p less than 10(-5). Histamine responsiveness was also enhanced by a fiftyfold lower dose of LTE4 (p = 0.005), and the enhancement was less than that elicited by the higher dose of LTE4 in the same individuals (p = 0.02). The changes in histamine PD35 during a 1-week period after LTE4 and methacholine challenges were compared in four subjects with asthma. There was a time-dependent enhancement in histamine responsiveness that reached a maximal of 3.5-fold at 7 hours after LTE4. The enhancement had disappeared by 1 week. Similar changes were not observed after methacholine challenge, which elicited the same degree of bronchoconstriction as LTE4. Inhalation of LTE4 in five normal subjects that produced a mean 37.6% decrease in SGaw did not change histamine responsiveness for up to 7 hours. These findings suggest that LTE4 may play a role in the perpetuation of nonspecific airway hyperresponsiveness in bronchial asthma.     

Time course of the increase in airway responsiveness associated with late asthmatic reactions to toluene diisocyanate in sensitized subjects

To understand better the mechanism of the increase in airway responsiveness associated with late asthmatic reactions, we determined the time course of toluene diisocyanate (TDI) effect on airway responsiveness in six sensitized subjects who exhibited a late asthmatic response after TDI exposure (0.018 +/- 0.005 ppm, 30 min) in the laboratory. Airway responsiveness was assessed before TDI exposure and then at 8 hr, 1 day, 1 wk, and 1 mo after TDI exposure. To assess responsiveness we determined the provocative dose of methacholine causing a decrease in FEV1 of 20% (PD20FEV1). The methacholine PD20 decreased from 0.50 mg geometric standard error of the mean (GSEM = 1.54) to 0.06 mg (GSEM = 1.55) (p less than 0.001) at 8 hr after exposure to TDI, was still decreased to 0.15 mg (GSEM = 1.93) (p less than 0.05) at 1 day, returned to 0.26 mg (GSEM = 1.91) (p greater than 0.05) at 1 wk, and returned to 0.43 mg (GSEM = 1.71) at 1 mo, indicating that full recovery occurred within 1 to 4 wk. These results demonstrate that TDI-induced late asthmatic response is associated with a reversible increase in airway responsiveness to methacholine and suggest that the TDI effect is linked to an acute inflammatory response in the airways.