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In a previous study we have shown that inhibition of the endogenous neuropeptide-degrading enzyme, neutral endopeptidase (NEP), potentiates airway narrowing to neurokinin A (NKA) in normal humans in vivo. In the present study, we tested the hypothesis that hyperresponsiveness to NKA in asthma is caused by a reduction in endogenous NEP activity. To that end, we used the NEP inhibitor, thiorphan, or placebo as inhaled pretreatment to NKA challenge in eight atopic asthmatic men, who were controlled by on-demand usage of beta 2-agonists alone. The dose of thiorphan pretreatment was obtained from pilot experiments in which 0.5 ml of a 2.5-mg/ml concentration appeared to be the maximally effective nebulized dose. Dose-response curves to inhaled NKA (1 to 125 micrograms/ml, 0.5 ml/dose) were recorded on 2 randomized days 1 wk apart, in a cross-over study. To detect any effects of thiorphan on bronchoconstriction per se, we also investigated the effect of thiorphan or placebo on the dose-response curve to inhaled methacholine in a separate set of experiments. The response was measured by FEV1 and by partial expiratory flow-volume curves (V40p). The position of the dose-response curves was expressed as the concentration causing a 20% fall in FEV1 (PC20FEV1) or a 40% fall in V40p (PC40V40p). Baseline FEV1 and V40p were not affected by either pretreatment (p > 0.06). PC20FEV1 and PC40V40p to NKA were significantly lower after thiorphan pretreatment as compared with placebo (mean difference +/- SEM: 2.3 +/- 0.6 and 1.6 +/- 0.5 doubling dose, respectively; p < 0.015).(ABSTRACT TRUNCATED AT 250 WORDS)

We studied whether nitric oxide (NO), added at 80 ppm to inspired gas, can exert a bronchodilatory effect in humans. Four groups were studied: (1) healthy adult volunteers (n = 6), (2) adult subjects with hyperreactive airways (n = 6) during provocation with inhaled methacholine (MCh), (3) patients with bronchial asthma (n = 13), and (4) patients with chronic obstructive pulmonary disease (COPD, n = 6). All subjects were studied in a body plethysmograph, measuring volume-corrected specific airway conductance (SGaw). No patient or volunteer reacted with bronchoconstriction during NO inhalation. Nitric oxide did not affect SGaw in healthy volunteers or in patients with COPD. Inhaled NO modulated the MCh-induced bronchoconstriction toward dilatation. In patients with bronchial asthma, SGaw increased (p < 0.05) from 0.4 +/- 0.1 to 0.6 +/- 0.2 (kPa.s)-1. In a succeeding test with inhalation of a beta 2-agonist immediately after NO inhalation, a more marked increase in SGaw was seen, to 1.2 +/- 0.3 (kPa.s)-1 (p < 0.001). We conclude that NO inhaled at 80 ppm has no effect on airway tone in healthy volunteers, but modulates the response to MCh provocation toward bronchodilation. It exerts a weak bronchodilatory effect in bronchial asthma, but not in COPD.

Inhaled glucocorticosteroids have now become first-line therapy for the treatment of chronic asthma in many countries. They are the most effective asthma therapy currently available, and numerous studies have documented their long-term efficacy in asthma control in adults and in children. Inhaled steroids suppress inflammation in asthmatic airways, although their precise molecular mechanism of action is not yet certain. It is likely that steroids affect the transcription of several steroid-responsive genes, and, of particular importance, they may inhibit cytokine gene transcription and cytokine effects, thereby reducing the chronic inflammation in asthmatic airways. Inhaled steroids are now used at a much earlier stage in asthma therapy, and there is a strong argument for their early introduction in both adults and children to prevent asthma morbidity and mortality and possibly the structural changes resulting from uncontrolled chronic inflammation, which may lead to irreversible airflow obstruction in some patients. Of paramount importance is the question of safety as inhaled steroids are likely to be required for a long time. Local side effects caused by oropharyngeal deposition of the inhaled steroid may be reduced by the use of spacer devices and mouthwashing. Systemic side effects caused by gastrointestinal absorption of the fraction deposited in the oropharynx may also be reduced by these devices. There are differences in the systemic bioavailability of the different inhaled steroids currently in use, and inhaled steroids with the lowest bioavailability should be chosen when high doses of inhaled steroids are required for asthma control. Systemic side effects are usually observed only when daily doses of > 800 micrograms are inhaled, and whether effects on very sensitive biochemical indices are relevant to long-term deleterious effects is not yet certain. There is now overwhelming evidence that the doses of inhaled steroids required to control asthma in the majority of adults and children are safe and without systemic side effects. It is important to control asthma with the minimum dose of inhaled steroids possible, however. In the future it may be possible to develop inhaled steroids with even fewer systemic effects if the fraction absorbed from the respiratory tract can be rapidly metabolized in the bloodstream.

In anesthetized guinea pigs, a slow intravenous infusion of platelet activating factor (PAF) (600 ng/kg over 1 h) but not of the carrier molecule bovine serum albumin (0.25%) induced immediate and transient bronchoconstriction and a fall in arterial blood pressure followed by an increase in bronchial responsiveness to histamine (0.56 to 1.8 microgram/kg intravenously). Pretreatment of guinea pigs with capsaicin (55 mg/kg subcutaneously over 2 days) 1 wk before the experiments, or with ruthenium red (5 mg/kg subcutaneously) 1 h before, completely inhibited capsaicin (2.5 micrograms/kg intravenously)-induced bronchoconstriction, and completely inhibited PAF-induced bronchial hyperresponsiveness. On the other hand, PAF-induced immediate bronchoconstriction and decreases in mean arterial blood pressure were not affected by capsaicin and/or ruthenium red pretreatment. However, pretreatment of guinea pigs with the PAF antagonist WEB 2086 resulted in a complete inhibition of PAF-induced direct bronchoconstriction, fall in arterial blood pressure, and bronchial hyperresponsiveness to histamine. It is suggested that in the guinea pig, PAF-induced bronchial hyperresponsiveness to histamine may be secondary to the activation of capsaicin-sensitive sensory fibers.

Long-term variability of bronchial responsiveness has been studied in a random population sample of adults. During a follow-up period of 18 yr, 2,216 subjects contributed 5,012 observations to the analyses. Each subject could have as many as seven observations. Bronchial responsiveness was assessed with a histamine challenge test. The threshold value was defined as the concentration of histamine that caused a decrease in FEV1 of 10% of more (PC10). After a 3-yr interval, a change of the threshold value with two or more doubling concentrations occurred in 21% of the subjects. This proportion increased to 43% if the time between two measurements increased to 18 yr. Of all subjects with multiple observations, 41% were always nonresponders (PC10 > or = 32 mg/ml), 11% were always responders (PC10 < or = 16 mg/ml), and 48% changed responder status. Of the subjects with greater than three observations, 65% changed responder status. Regression analyses, stratified by symptom status, sex, and smoking habit, were used to estimate intraclass correlation coefficients (ICC) as a measure of variability of responsiveness. On average, ICC values were low (0.40), also indicating considerable variability. With adjustment for FEV1, age, area of residence, and eosinophil count, the ICC values decreased slightly. This indicated that with adjustment, the total variability decreased more than the within-subject variability. ICC values did not differ significantly between asymptomatic and symptomatic subjects. Analyses of responsiveness as a binary variable revealed similar results.

The administration by aerosol of the nitric oxide (NO) synthesis inhibitors, N omega-nitro-L-arginine methyl ester (L-NAME) or Ng-monomethyl-L-arginine (L-NMMA), to spontaneously breathing anesthetized guinea pigs resulted in a significant enhancement of lung resistance (RL) after increasing intravenous doses of histamine. The maximal response was increased (p < 0.01) by 126% (L-NAME) and 282% (L-NMMA) compared with the control groups. This effect was inhibited by giving an aerosol of the NO precursor L-arginine (L-Arg) but not by its inactive enantiomer D-arginine (D-Arg). Perfusion through the lumen of guinea pig tracheal tubes in vitro with nitric oxide synthesis inhibitors (120 microM) resulted in a significant increase in basal tone, suggesting a role for NO in the maintenance of basal tone. In addition, the histamine concentration-response curve was significantly shifted upward: the maximal response was increased (p < 0.01) by 335% (L-NAME) and 250% (L-NMMA) compared with the control group. This effect was concentration dependently inhibited by coincubation with L-Arg (120, 200, and 400 microM), but not with D-Arg (200 microM). Furthermore, removal of the epithelium resulted in an upward shift in the histamine concentration-response curve: the maximal response was increased by 185%. However, incubation with L-NAME did not further increase tracheal responsiveness to histamine, but addition of L-Arg (360 microM), when a plateau was reached, relaxed the tissues to control values. Nitric oxide synthesis inhibition did not change the responsiveness of intact tissues in vitro after intraluminal stimulation with leukotriene D4, serotonin, or the cholinergic agonist arecoline.(ABSTRACT TRUNCATED AT 250 WORDS)

A 40-yr-old woman with severe chronic asthma complained that her regular nebulized albuterol was exacerbating her symptoms. Changing to regular nebulized terbutaline resulted in a marked improvement in her peak flow readings. Double-blind challenge with nebulized albuterol and terbutaline confirmed paradoxical bronchoconstriction with albuterol but not with terbutaline. This indicates that paradoxical bronchoconstriction to beta 2-agonists can be specific to the drug preparation used rather than a class effect, as has previously been suggested.

We tested the hypothesis that allergen-induced mediator release augments the magnitude of isocapnic dry gas hyperpnea-induced bronchoconstriction in sensitized guinea pigs. Male Hartley guinea pigs were sensitized by spontaneous inhalation of ovalbumin (OA) aerosol on days 0 and 7 of the study. On day 14, sensitized animals again breathed OA aerosol and were prospectively divided into a group that exhibited labored breathing (LB), presumably reflecting OA-induced inflammatory mediator release, and a group that did not exhibit LB at this time. Control guinea pigs breathed saline aerosol on days 0, 7, and 14. Bronchoalveolar lavage on day 17 disclosed relative eosinophilia in OA+LB, but not in OA-LB, animals. On day 17, the bronchoconstrictor responses to increasing intravenous (i.v.) doses of acetylcholine (ACh), substance P (SP), neurokinin A (NKA), and capsaicin, as well as dry gas hyperpnea, were measured in vivo in animals from each group. Control and OA-LB guinea pigs exhibited similar responses, but OA+LB animals demonstrated augmented bronchoconstriction induced by i.v. administration of ACh, SP, or NKA. However, despite their augmented responsiveness to these exogenous constrictor agonists, OA+LB animals displayed no greater bronchoconstriction after dry gas hyperpnea or i.v. capsaicin administration. It is known that both dry gas hyperpnea and i.v. capsaicin cause bronchoconstriction in guinea pigs by releasing endogenous tachykinins from airway sensory C-fibers. Thus, our results suggest that allergen-induced mediator release impairs endogenous tachykinin release from airway sensory C-fibers in guinea pigs.

We investigated the effect of 5 months of treatment with inhaled beclomethasone dipropionate (BDP) on the airway responsiveness to methacholine (PD20 FEV1) and to toluene diisocyanate (TDI) in 15 sensitized asthmatic subjects who had been removed from occupational exposure to TDI. After the diagnosis was established by a positive inhalation challenge with TDI, each subject was removed from occupational exposure to isocyanates and treated with either BDP (1 mg twice per day, n = 7) or placebo (n = 8) for 5 months. The study was double blind for parallel groups. P20 FEV1 methacholine was measured before and three times during treatment and then at 6 months, that is, 4 wk after cessation of treatment. Airway sensitivity to TDI was assessed with specific inhalation challenge before treatment and at 6 months. Beclomethasone reduced the airway hyperresponsiveness to methacholine but did not affect the response to TDI. In fact, in the subjects on BDP, P20 FEV1 increased from 0.145 to 0.485 mg (p < 0.05) after 2 months of treatment. A further increase was observed at 4 and 5 months (0.548 and 0.629 mg, respectively, p < 0.01), and the improvement in nonspecific airway responsiveness was maintained after a 1-month washout period (0.637 mg, p < 0.01). In contrast, in the subjects on placebo, P20 FEV1 did not change significantly. At the end of the study, the severity of asthmatic reactions induced by bronchial challenge with TDI was significantly reduced in both groups, but no differences were observed between placebo and BDP.(ABSTRACT TRUNCATED AT 250 WORDS)

The purpose of the study was to investigate whether allergen-induced hyperresponsiveness to methacholine and an increase in airway smooth muscle (ASM) in Brown Norway (BN) rats could be mediated by LTD4, an important mediator of allergic airway responses. Male BN rats, 8 to 12 wk of age, were sensitized with ovalbumin (OA). Rats were exposed 2 wk later to aerosols of saline (n = 6), OA (n = 8), or OA after pretreatment with the LTD4 antagonist MK-571 (2 mg/kg intraperitoneally, n = 9), on six occasions at 5-day intervals. Airway responsiveness to methacholine (the concentration required to double pulmonary resistance, EC200 RL) was measured immediately before the first aerosol exposure and 2 days after the last exposure. ASM was quantitated by morphometry, and areas were standardized for size using the epithelial basement membrane length (BM). Following OA challenges EC200 RL decreased from 6.5 to 3.1 mg/ml (p < 0.05) but did not change significantly after saline or OA exposures in MK-571-pretreated animals. ASM/BM2 in the large airways was significantly greater, 3.41 +/- 0.19 x 10(-3), after OA compared with 2.35 +/- 0.22 x 10(-3) for saline exposures (p < 0.01). The ASM/BM2 after OA exposures but with MK-571 pretreatment (2.75 +/- 0.25 x 10(-3)) was intermediate in value. The results indicate that both the increase in airway responsiveness and the increase in ASM following repeated antigen exposures appear to be mediated predominantly by LTD4.

To determine whether oxygen radical scavengers inhibit ozone-induced airway hyperresponsiveness, we examined the protective effect of polyethylene glycol-superoxide dismutase (PEG-SOD) and PEG-catalase (PEG-CAT) on ozone-induced airway hyperresponsiveness in cat airways. Twenty-five cats divided into five groups were anesthetized and mechanically ventilated. There was no difference between the groups in baseline airway responsiveness to inhaled acetylcholine (ACh). In the control group, AChPC, the concentration required to produce a doubling increase in baseline pulmonary resistance, was significantly reduced by ozone exposure (2.0 ppm for 2 h); the ratios of AChPC before ozone exposure to after ozone exposure (AChPC ratio) were 14.8 +/- 5.7 (p < 0.001) and 4.80 +/- 1.6 (p < 0.01) 30 and 120 min after exposure, respectively. Local administration of PEG-SOD (2,000 U/kg) into airways partially but significantly prevented ozone-induced airway hyperresponsiveness. The AChPC ratios were 6.2 +/- 1.4 and 1.5 +/- 0.2 30 and 120 min after exposure, respectively, which were significantly different from those of the control group (p < 0.05), whereas PEG-CAT pretreatment (6,000 U/kg) was without effect. Combined pretreatment with PEG-SOD and PEG-CAT had no additional protective effect compared with PEG-SOD alone. PEG-SOD had no direct effect on airway responsiveness to ACh. These results suggest that superoxide may be involved in ozone-induced airway hyperresponsiveness.

Studies of cotton textile workers have found an association between atopy and drop in FEV1 over a workshift. We studied the response of previously nonexposed volunteers with and without a history of mild atopy to a 5-h exposure to 1 mg/m3 of respirable cotton dust in a model cardroom. All participants were nonsmokers, had no history of asthma, and had normal spirometry. Twenty atopic subjects gave a personal history of mild respiratory allergy to pollen, dusts, or animals that had been confirmed by a physician. Thirty-two nonatopic subjects had no history of allergy. Spirometry and a methacholine challenge test were performed 1 to 2 days prior to exposure. Spirometry was repeated immediately before exposure to cotton dust; spirometry and a methacholine challenge were performed immediately after exposure. Atopic subjects showed a significantly higher mean serum IgE level to Phadiatop, a screening test to common inhalant allergens, than did nonatopic subjects (mean percent binding, 32.1 versus 1.5; p < 0.001). Atopic subjects had a significantly greater mean fall in FEV1 during exposure (8.3% versus 4.9%, p < 0.05). The difference in FEV1 decline between atopic and nonatopic subjects was similar in magnitude to that reported for workshift FEV1 declines between textile workers with and without mild atopy. Atopic subjects had significantly higher baseline methacholine responsiveness than did nonatopic subjects (26% versus 0% reaching a PD20, p < 0.0005). After cotton dust exposure, there was a significant increase in airway reactivity in both groups (68% versus 20% reaching a PD20, p < 0.0005). For all subjects combined baseline responsiveness was significantly related to the change in FEV1 after exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin E2 (PGE2) is produced in the lung but unlike most other lipid mediators has potentially important antiallergic effects. Whether these properties are relevant to asthma has not been established. The effect of inhaled PGE2 on allergen-induced asthma was examined in a double-blind crossover study of eight subjects with asthma. In Study 1 subjects inhaled 100 micrograms PGE2 or placebo 5 min before a normal saline challenge, and FEV1 and bronchial reactivity to methacholine was measured at intervals for 7 h. In Study 2, which had a similar design, subjects inhaled the same dose of PGE2 or placebo followed by a dose of allergen previously shown to cause a fall in FEV1 of 20% or more. On the normal saline challenge day inhaled PGE2 caused a small increase in FEV1 that lasted for around 60 min; there was no difference in the provocative dose of methacholine causing a 20% fall in FEV1 (PD20) at 4 and 7 h compared with placebo. PGE2 caused marked inhibition of the early and late response to allergen. The mean maximum fall in FEV1 0 to 2 h after allergen was 37.8 and 7.7% with placebo and PGE2 pretreatment, respectively (mean difference 30%; 95% CI 15, 45%; p < 0.005). The mean maximum fall in FEV1 from 4 to 7 h after allergen was 25.5 and 8.8% respectively (mean difference 16.7%; 95% CI 4, 29%; p < 0.02). The methacholine PD20 fell significantly after allergen with placebo but not with PGE2. The difference was 1.5 doubling doses at both 4 and 7 h (p < 0.01 and p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

We examined the effect of activated alveolar macrophages (AM) on airway responsiveness to muscarinic stimulation in 33 adult Sprague-Dawley rats. An isolated-perfused lung preparation was used to ensure precise and uniform delivery of cells into peripheral airways. The bronchoconstrictor response to acetylcholine (ACh) delivered into the pulmonary arterial circulation was augmented in 8 rats after infusion of 3 x 10(6) AM activated with 10(-6) M f-met-leu-phe and 5 micrograms/ml of cytochalasin B. Lung resistance (RL) caused by 10(-6) mol ACh increased 2.5-fold from 0.10 +/- 0.004 cm H2O/ml/s before infusion of activated AM to 0.35 +/- 0.05 cm H2O/ml/s after infusion of activated AM (N = 8; p < 0.05); the response to ACh was not augmented after infusion of nonactivated AM (N = 7) or vehicle control (N = 6). Baseline RL before ACh was similar in all three groups (p NS). Perfusion with activated AM also significantly increased the wet/dry (W/D) lung weight ratios (7.1 +/- 0.5) compared with nonactivated AM (5.2 +/- 0.1) or vehicle control (5.5 +/- 0.3) (p < 0.05 versus either nonactivated AM or vehicle control). A63162, a 5-lipoxygenase inhibitor, but not indomethacin, a cyclooxygenase inhibitor, completely inhibited augmentation of bronchoconstrictor responses to ACh caused by activated AM and also completely attenuated the increase in W/D lung weight ratios. A highly significant (p < 0.01) correlation (R = 0.76) between W/D lung weight ratios and RL was observed after 10(-6) mol ACh (the greatest dose of ACh administered). Baseline RL was equivalent for all groups before and after infusion of cells or vehicle.(ABSTRACT TRUNCATED AT 250 WORDS)

Since whole-animal studies suggest that neutrophils play a role in ozone-induced impairment of pulmonary function and increases in airway reactivity, this study was designed to study more precisely the interaction of neutrophils and ozone using the isolated perfused rat lung. Sprague-Dawley rat lungs (n = 60) were ventilated for 3 h with 95% air and 5% CO2 alone or mixed with 1 ppm ozone and perfused with buffer alone or with neutrophils (8 x 10(7)). RL, Cdyn, Ppa, airway reactivity to methacholine, lung/body weight, bronchoalveolar lavage fluid (BALF) protein concentration, and airway lesions were analyzed using a two-way GLM or Kruskal-Wallis test (p < or = 0.05 significant). Both ozone and neutrophils increased RL and decreased Cdyn. Ozone but not neutrophils increased airway reactivity to methacholine. Neutrophils but not ozone increased lung weight/body weight and BALF protein concentration. Ozone damaged airway epithelium. In distal bronchioles, neutrophils enhanced this damage. We conclude that (1) ozone impaired pulmonary function, increased airway reactivity, and damaged airway epithelium without causing measurable microvascular leak; (2) neutrophils impaired pulmonary function, probably a result of microvascular leak, but did not change airway reactivity or damage airway epithelium; and (3) neutrophils had no effect on ozone-induced airway reactivity but had an additive effect on ozone-induced pulmonary function impairment and a synergistic effect on ozone-induced airway epithelial injury.

Major basic protein (MBP) is a highly cationic protein found in the granules of eosinophils. It has been postulated that MBP may participate in the pathogenesis of airway hyperresponsiveness exhibited by asthmatic patients. Accordingly, we used a rat model to investigate the effect of human MBP instillation on airway responsiveness and the possible role of cationic charge in the determination of this effect. Dose-response characteristics to inhaled methacholine (MDRC) were determined at baseline, and the animals were allowed to recover. Then animals in the experimental group received 100 micrograms of purified human MBP via direct instillation into the trachea. One hour after instillation, the MDRC were again assessed. Control animals received (in lieu of MBP) buffer from the void volume pool of the same chromatography column used to purify the MBP. One hour after instillation of MBP there was a significant increase in airway responsiveness to inhaled methacholine, whereas control animals exhibited no increase in airway responsiveness. Some animals from the MBP group were restudied 48 h after MBP instillation, by which time airway responsiveness had returned to baseline level. The effect of the polycations poly-L-arginine and poly-L-lysine on airway responsiveness was also examined. As with MBP, airway responsiveness to inhaled methacholine increased 1 h after the instillation of either polycation. In addition, acetylation of the charged groups on poly-L-lysine resulted in a loss of this effect. Histologic examination of the airways failed to reveal airway epithelial shedding 1 h after MBP or polycation instillation.(ABSTRACT TRUNCATED AT 250 WORDS)

It has previously been demonstrated that human eosinophil-derived granule major basic protein (MBP) can increase airway responsiveness after intratracheal administration in the rat. This effect was mimicked by synthetic polycations, suggesting that charge interactions may be important in the development of airway hyperresponsiveness (AHR). To support this hypothesis, we investigated whether two other cationic proteins, platelet factor 4 (PF4) and cathepsin G, were capable of inducing AHR. Furthermore, to determine whether these effects were dependent on their positive charge, the charge of these proteins was neutralized with low molecular weight heparin. In addition, we have examined whether the effect of a synthetic polycation, poly-L-lysine could be inhibited by low molecular weight heparin, albumin, or dextran sulphate. MBP, PF4, or cathepsin G induced a 2- to 3-fold increase in airway responsiveness 1 h after instillation, as assessed by the dose of inhaled methacholine required to increase total lung resistance by 100%. Admixing these native cationic proteins with low molecular weight heparin inhibited the development of AHR. Similarly, poly-L-lysine increased airway responsiveness that was inhibited not only by low molecular weight heparin but also by two other anionically charged molecules, albumin and dextran sulphate. These findings suggest that charge interactions in the airways are important not only in alterations in airway responsiveness induced by eosinophil-derived MBP, but also because they underlie altered airway responsiveness after treatment with other cationic proteins. The precise mechanisms involved in this phenomenon remain to be determined.

Increased airway hyperresponsiveness is thought to be one of the phenomena underlying nocturnal airway obstruction in asthma. To investigate the mechanisms that influence and modulate this phenomenon, we compared circadian variations in airway responsiveness with AMP and propranolol with the circadian variation in airway responsiveness to methacholine. Inhalation provocation tests were performed at 16.00 and 04.00 h in 16 nonsmoking atopic asthmatic subjects (18 to 42 yr of age), prospectively assigned to Group 1 (mean circadian peak expiratory flow rate [PEFR] variation > or = 15%) and Group 2 (< 15%). The circadian change in airway responsiveness to AMP, in contrast to methacholine, was significantly related to the circadian PEFR-variation of the 16 subjects (r = 0.81, p < 0.001). In Group 1 (n = 7) geometric mean PC20 AMP decreased more than PC20 methacholine during the night (2.3 and 0.9 doubling concentrations respectively, p < 0.05), whereas no difference in baseline FEV1 was found at the same time points during the different study days. Geometric mean PC20 propranolol did not change during the night. Daytime PC20 propranolol and PC20 AMP, in contrast to PC20 methacholine, were significantly lower in Group 1 as compared with Group 2. Together, the results show a higher susceptibility to stimulation of "indirect" airway responsiveness in the subjects with increased circadian PEFR amplitude. This suggests that mast cell activation rather than primary changes in smooth muscle cell contraction may play a role in the development of nocturnal airway obstruction.

The measurement of bronchial hyperreactivity (BHR) may give additional information to questionnaire-based studies of asthma prevalence. It is desirable to have a provocation method with high specificity that avoids the use of pharmacologic provocations in large numbers of healthy children. It was the aim of this study to establish a range of values for responsiveness to cold-air challenge in normal children, to describe its specificity and sensitivity for a diagnosis of asthma in a large unselected sample of schoolchildren in a field study, and to measure factors associated with hyperresponsiveness. All fourth-grade schoolchildren (9 to 11 yr of age) in Munich and several southern Bavarian communities (n = 9,403) were surveyed with a questionnaire (response rate, 87%), baseline lung function, and cold-air hyperventilation challenge (n = 5,697). A diagnosis of asthma was reported in 7.9% of children. In the reference group, the ninety-fifth percentile (%ile) for the change of FEV1 (DFEV1) was -9.0%; the 90%ile was -7.3%. Asymptomatic children fulfilling all criteria for the reference group showed a significantly increased reactivity if they had a family history of asthma (p = 0.038). With a cutoff for DFEV1 of -9.0% or -7.3% the respective sensitivities to "detect" a diagnosis of asthma were 21.6 and 30.7%, and for asthma with symptoms during the previous 12 months it was 26.2 and 35.1%. Reactivity to cold air increased with the number of episodes of asthma in the previous 12 months. In a multiple linear regression model, factors associated with increased reactivity to cold air were diagnosed asthma, hay fever, male sex, younger age, and a positive skin test.(ABSTRACT TRUNCATED AT 250 WORDS)

In contrast to methacholine, a stimulus that induces airway constriction mainly by "direct" stimulation of airway smooth muscle cells, AMP airway responsiveness reflects "indirectly" induced airway narrowing via inflammatory or neural reflex mechanisms. In order to determine inflammatory contribution to airway narrowing in COPD, we performed AMP and methacholine inhalation provocation tests in nonatopic subjects with COPD and compared the results with those obtained from atopic nonsmoking asthmatics and from healthy smoking volunteers. AMP caused airway narrowing in all but two subjects with COPD and in only three of the 12 healthy smoking subjects. Patients with COPD were significantly more responsive to AMP and methacholine than were healthy smoking volunteers. Geometric mean PC20 AMP was significantly lower in the smokers with COPD (7.2 mg/ml) than in the nonsmokers with COPD (58.5 mg/ml), whereas PC20 methacholine values and baseline FEV1 were comparable. In the nonatopic nonsmoking subjects with COPD, PC20 AMP was significantly higher than in the atopic nonsmoking asthmatics (3.8 mg/ml), whereas they responded similar to methacholine provocation. These results indicate that most subjects with COPD respond to AMP provocation and that smoking determines the degree of airway responsiveness to AMP in COPD. We suggest that increased susceptibility to mediator release by mast cells or neural reflex mechanisms are involved in AMP-induced airway constriction in asthma and in COPD.

Previously it was demonstrated that during delayed-type hypersensitivity reactions (DTH) to picryl chloride (PCl) in murine lungs, as a model for cellular IgE-independent immunity, tracheal hyperreactivity and increased pulmonary resistance are induced. In the present study it is demonstrated that after pretreatment with 5HT-2 antagonists, such as ketanserin and methysergide, DTH lung reactions to PCl in mice are suppressed. The increase in vascular permeability, detectable at 2 h after intranasal hapten challenge and probably necessary for the development of a classic DTH reaction, as was demonstrated in skin DTH models, as well as the classic late inflammatory component of lung DTH, is inhibited. However, in vitro tracheal hyperreactivity to the cholinergic receptor agonist carbachol and increased pulmonary resistance in vivo, both induced during the development of these inflammatory DTH lung reactions, are not affected by 5HT-2 receptor antagonist pretreatment. These results indicate that the actual presence of increased vascular permeability and mononuclear infiltrates is not a prerequisite for the development of changed lung functions and tracheal hyperresponsiveness. Thus in mice, serotonin-independent mechanisms that appear during T cell-dependent lung immune reactions induce airway hyperresponsiveness and increased pulmonary resistance.

We previously showed that oxygen radicals can induce airway hyperresponsiveness (AHR) in allergic sheep. The purpose of this study was to determine whether antigen challenge results in the generation of free oxygen radicals and if these radicals contribute to antigen-induced AHR. We first determined baseline airway responsiveness in seven Ascaris suum-sensitive sheep by calculating the cumulative provocative concentration of carbachol in breath units (BU; one BU defined as one breath of a 1% wt/vol carbachol solution) that increased specific lung resistance (SRL) 400% over baseline (PC400). On a different day, the sheep underwent inhalation challenge with A. suum antigen, SRL was measured before and immediately after challenge and then hourly for 2 h, at which time SRL had returned to baseline. The postchallenge PC400 was then measured. This procedure was repeated on separate occasions, each at least 14 days apart, except that the sheep were treated with an aerosol of catalase (CAT; 38 mg in 3 ml deionized water), the enzyme that catalyzes the decomposition of hydrogen peroxide (H2O2), at three different times: Trial 1, before antigen and then every 30 min after antigen challenge for 2 h; Trial II, 1 and 2 h after antigen challenge; and Trial III, only at 2 h after antigen challenge. In the control trial, antigen challenge caused a transient (mean +/- SEM) 303 +/- 48% increase in SRL over baseline (p < 0.05), and 2 h later, PC400 was reduced to 11.0 +/- 1.7 BU from a prechallenge value of 24.8 +/- 1.9 BU (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The association between sinusitis and asthma has been clinically recognized, but its precise nature is controversial. We studied the relationship between sinusitis and lower airways function in a rabbit model of sterile maxillary sinusitis induced by the chemotactic complement fragment C5a des arg. Animals kept in a head-up position following experimental sinusitis demonstrated a significant increase in airways responsiveness (AWR) to histamine. In contrast, animals of which the sinuses were injected with a saline diluent and in which no sinus inflammation developed had no increase in AWR. Experiments were subsequently carried out to investigate some of the potential mechanisms for these observations. A group of rabbits in which a distal site of inflammation was induced did not demonstrate increased AWR. Likewise, when sinus inflammation was established but passage of fluid to the lower airways was prevented, either by intubation or by head-down positioning, there was no change in AWR. A fourth experiment was designed to decrease complement factor activity before placing the animals in a head-up position. This led to the same degree of increased AWR. Neither the histology nor the bronchoalveolar lavage data demonstrated significant lower airways inflammation in any group. We conclude that sterile sinusitis can increase lower airways responsiveness to histamine in a rabbit model. The most likely mechanism for this effect is the postnasal dripping of cells or cell products into the lower airway. The role of a nasobronchial reflex or inflammatory mediator absorption could not be demonstrated in this model.

Smokers with chronic bronchitis and/or chronic obstructive pulmonary disease (COPD) have been reported to have an increased bronchial reactivity (BR). It has been discussed whether increased BR is a risk factor for the development of COPD in smokers. We studied 10 monozygotic twin pairs who were discordant for tobacco smoking by means of histamine provocation tests, lung function tests, and serum samples for total IgE. The smokers had a mild obstructive ventilatory impairment, with FEV1 significantly lower than that of the partner both when it was determined from the flow-volume loops (3.2 +/- 1.0 L for smokers and 3.4 +/- 0.8 L for nonsmokers) and by the Vitalograph spirometer (3.5 +/- 1.0 L for smokers and 3.8 +/- 0.8 L for nonsmokers). Forced midexpiratory flow (FEF25-75%) and forced expiratory flow at 75 to 85% of vital capacity (FEF75-85%) were both significantly lower in the smokers (p < 0.05). The alveolar plateau phase N2-delta test and lung clearing index in the multibreath nitrogen washout test were both significantly affected in the smokers (p < 0.05 and p < 0.01, respectively). We found no significant difference in histamine reactivity between smokers and nonsmokers and no correlation between differences in reactivity and differences in lung function within pairs. Total serum IgE was significantly higher in the smokers than in their nonsmoking siblings. These data suggest that obstructive ventilatory impairment and raised serum IgE are earlier and more constant manifestations of tobacco smoking than increased bronchial reactivity. Thus, bronchial hyperreactivity does not seem to be a major risk factor for the development of early airways obstruction in smokers.

Previous data suggest that regular tobacco smoking may lead to nonspecific airway hyperresponsiveness (AHR) independent of airway obstruction, possibly because of effects on bronchial inflammation or mucosal permeability. Little is known concerning the effects on AHR of other widely smoked substances besides tobacco such as marijuana or cocaine. The smoke of both marijuana and cocaine contains respiratory irritants that elicit cough and produce abnormalities in airway dynamics and bronchial mucosal histopathology in habitual smokers. Therefore, regular smoking of one or both of these illicit substances could cause AHR or augment the AHR associated with tobacco smoking. The present study examined the influence of habitual smoking of marijuana, cocaine, and/or tobacco on nonspecific AHR in 542 (456 male) healthy participants (mean age, 34.8 +/- 6.8 SD yr) in an ongoing cohort study of the pulmonary effects of habitual smoking of illicit substances. Subjects with a history of intravenous drug abuse, significant occupational exposures, asthma, or recent upper respiratory tract infection were excluded. Inhalation challenge studies were performed using solutions of diluent and methacholine chloride (1.25 to 25 mg/ml) aerosolized by a DeVilbiss no. 646 nebulizer attached to a breath-activated dosimeter inhaled by three to five inspiratory capacity breaths. Positive responses to methacholine were defined by > or = 20% or > or = 10% declines in FEV1 from the postdiluent control value after inhalation of each concentration of methacholine. Participants were categorized by smoking status (nonsmoking and smoking of marijuana, cocaine, and/or tobacco alone and in combination); most analyses were performed in men and women separately.(ABSTRACT TRUNCATED AT 250 WORDS)

We recently found that exposure of 21-day-old rats to hyperoxia (> 95% O2 for 8 days) significantly increased in vivo airway cholinergic responsiveness and that O2 exposure also increased airway epithelial and smooth muscle layer thicknesses in a separate cohort of animals. There was substantial variation in the magnitude of both the functional and structural responses to hyperoxia. The present study was designed to test whether the magnitude of O2-induced airway remodeling could account for individual differences in airway responsiveness after O2 exposure, as well as for the difference in responsiveness between air- and O2-exposed animals. We assessed in vivo airway responsiveness to aerosolized acetylcholine (ACh) and airway architecture in 14 O2- and 5 air-exposed, immature rats. Total respiratory system resistance was determined using a plethysmographic method. The mean thicknesses and fractional areas of the airway epithelial and smooth muscle layers were determined by contour tracing using a digitizing pad and microcomputer. Both the small (circumference < 1,000 microns) and central (circumference 1,000 to 4,000 microns) airways were studied. For O2-exposed rats, individual values of EC200 ACh correlated negatively with small airway smooth muscle layer thickness (r = -0.59, p < 0.05; ANOVA), small airway smooth muscle layer fractional area (r = -0.75, p < 0.01), small airway epithelial thickness (r = -0.54, p < 0.05), small airway epithelial fractional area (r = -0.69, p < 0.01), and central airway smooth muscle layer thickness (r = -0.53, p < 0.05). When both air- and O2-exposed animals were considered, EC200 ACh correlated negatively with all eight parameters of airway layer thickness and fractional area.(ABSTRACT TRUNCATED AT 250 WORDS)

We investigated the role of platelet-activating factor (PAF) in ozone-induced airway responses by examining the effects of L659,989, a potent PAF antagonist, on bronchial hyperresponsiveness and airway inflammation. Twenty-four male guinea pigs were studied in four equal groups. Total lung resistance (RL) in intubated and spontaneously breathing animals was measured in a constant-volume body plethysmograph. Dose-response curves to methacholine were determined in all animals at the start of the experiment. These were repeated on a separate day after the following types of treatments: air exposure in Group 1, intraperitoneally administered alcohol and air exposure in Group 2; intraperitoneally administered alcohol and ozone exposure in Group 3, and intraperitoneally administered L659,989 (a specific PAF antagonist), 5 mg/kg dissolved in alcohol, and ozone exposure in Group 4. Bronchoalveolar lavage (BAL) was performed after the second methacholine challenge, and the bronchial mucosa was also examined for inflammatory cells. Exposure to 3 ppm ozone for 2 h resulted in a three-doubling concentration increase in bronchial responsiveness, which was not significantly inhibited by prior treatment with L659,989. Ozone induced a 1.8-fold increase in BAL total cell count, increased eosinophilic influx into the airways, and increased eosinophilic infiltration in the bronchial mucosa, which were all not inhibited by L659,989 pretreatment. The results suggest that PAF may not have an essential role in ozone-induced airway hyperresponsiveness and nonallergic airway inflammation.

Longitudinal lung function data from four occupational health surveys was used to explore the relationship between nonspecific bronchial responsiveness (NSBR) and the rate of decline of FEV1 (RDFEV) and to address other factors that may predict or influence RDFEV. Of the 1,203 subjects with baseline methacholine and lung function data, follow-up data were available for 733 individuals (61%). The data-available and data-unavailable groups were well matched with respect to baseline lung function, atopy, and smoking status. Compared with the unavailable group, those available for follow-up were younger (42.5 versus 37.7 yr; p less than 0.0001) and slightly less responsive to methacholine (p less than 0.01). Somewhat unexpectedly, RDFEV was lower in the 30 asthmatic subjects than in the nonasthmatics. Among the nonasthmatic subgroup (96% of those available for follow-up), age, occupational group, and baseline FEV1 (% predicted) were independent predictive factors for RDFEV. When these factors were included in the model, RDFEV was found to be increased among current smokers compared with never-smokers or ex-smokers. In the final regression model, a relationship was found between methacholine sensitivity (calculated as a dose-response slope) and RDFEV in nonasthmatics (p less than 0.05). Stratification by smoking status revealed that the relationship between RDFEV and bronchial responsiveness was confined to current smokers and that atopy was an additional risk factor in this subgroup only. This relationship was valid among current smokers in each of the three occupational groups studies. However, reinclusion of the 30 asthmatic subjects in the study population obscured the relationship between NSBR and RDFEV.(ABSTRACT TRUNCATED AT 250 WORDS)

For describing bronchial responsiveness, it has been suggested that the dose-response slope (DRS), which is the linear slope of the dose-response curve, is a more useful measure of severity than the provoking dose that causes a 20% fall in FEV1 (PD20FEV1). To determine the distribution of DRS measurements and their relation to respiratory illness in adults, we have reanalyzed data collected in 1981 from a random sample of the population of Busselton, Western Australia. We measured bronchial responsiveness to histamine by the rapid method and atopy by skin prick tests to 15 common allergens. Satisfactory bronchial challenge data were recorded for 858 subjects. Subjects were classified as having asthma symptoms by self-reported history or as having chronic airflow limitation by abnormality of lung function. In normal subjects, DRS values were symmetrically distributed on a logarithmic scale so that a value that represented abnormal responsiveness could be calculated. The dose-response slope had a significant independent association with past and current asthma symptoms, smoking history, sex, atopy, and FEV1/FVC ratio but not with chronic airflow limitation. In subjects in whom a PD20FEV1 could not be measured, the DRS had a significant relation to asthma symptoms, smoking history, and FEV1/FVC. Thus, DRS values, which could be obtained for most subjects, contributed additional information to PD20FEV1 values and discriminated more accurately between groups classified according to respiratory history. These data confirm that DRS values should be used in preference to PD20FEV1 values for describing the severity of bronchial responsiveness in populations.

Because there is no "gold standard" for defining asthma for epidemiology, we have defined current asthma as bronchial hyperresponsiveness (BHR) plus recent wheeze (in the 12 months prior to study). To describe the characteristics of groups categorized by these measurements, we studied two samples of children aged 7 to 12 yr: 210 from a population sample and 142 self-identified asthmatics. Bronchial responsiveness to histamine was measured by the rapid method, respiratory symptom history, and asthma medication use by self-administered questionnaire to parents and atopy by skin prick tests to 14 allergens. Children recorded daily Airflometer readings and symptom scores for 2 wk. Children with current asthma had more severe bronchial responsiveness, greater Airflometer variability, more symptoms, more atopy (particularly to house dust mites), and used more asthma medication than children with BHR or recent wheeze alone. Children with BHR, but not with recent wheeze, were intermediate between the current asthma and normal groups in terms of bronchial responsiveness, Airflometer variability, and atopy. Children with recent wheeze and normal responsiveness differed from the normal group only in symptoms and medication use. Our definition of current asthma discriminates a group of children that is clearly different in terms of both clinical features and physiologic measures. As such, it is the most useful definition to date for measuring the prevalence of clinically important asthma in populations.

Asthma is associated with dysfunction of the beta-adrenergic receptor adenylyl cyclase signal transduction pathway. It has been argued that this results from receptor down-regulation by beta-agonist therapy. This study examined the relationship between nonspecific bronchial responsiveness (NSBR) to methacholine (Newcastle dosimeter method) and beta-adrenergic receptor density (Bmax) and affinity (%KH) in membranes from peripheral blood mononuclear leukocytes (MNL) in 12 male (27.3 +/- 1.7 yr old) and 14 female (31.4 +/- 1.7 yr old) drug-naive subjects with and without symptoms of mild intermittent wheezing. None had ever smoked or received any antiasthma medication. "Hyperresponsive" subjects were defined as those (n = 11) whose simplified slope of FEF50 (calculated as the percent fall in FEF50 divided by the dose of methacholine) was more than one SD above the mean for asymptomatic subjects. The log of the slope was reproducible (repeatability coefficient = 0.43) on two nonconsecutive days. Multiple regression analysis (overall R2 = 0.57) revealed negative relationships between the log of the slope and both Bmax (p = 0.016) and %KH (p = 0.011). Analysis of variance confirmed a lower mean (+/- SEM) value of %KH in "hyperresponsives" (45.7 +/- 5.5%) than in "normoresponsives" (60.4 +/- 4.1%, p = 0.04) with a similar trend for Bmax (hyperresponsives = 33.5 +/- 4.1 fmol/mg, normoresponsives = 45.9 +/- 7.1 fmol/mg, p = 0.18). These relationships between bronchial responsiveness, Bmax, and %KH cannot be explained by drug therapy, and they provide further evidence that there is an intrinsic impairment in the function of beta-adrenergic receptors on peripheral MNLs from subjects with high levels of nonspecific bronchial responsiveness.

Subjects with asymptomatic airway hyperresponsiveness in epidemiologic studies may have variable airway obstruction that is not perceived as dyspnea. We tested the hypothesis that such subjects are less likely to report an increase in dyspnea during histamine-induced bronchoconstriction than symptomatic hyperresponders. A random population sample of 412 middle-aged subjects was studied. Before and after a standardized histamine challenge test, subjects recorded Borg scores for dyspnea: any increase in Borg score was considered significant. More than 80% of hyperresponsive subjects (PC10 histamine < or = 16 mg/ml) had no symptoms. The presence of prechallenge dyspnea was related to increased airways responsiveness and current smoking. An increase in Borg score was associated with younger age, more severe airway responsiveness, atopy, and female sex. The level of and increase in the Borg score were not significantly related to level and change in airway caliber (FEV1). In hyperresponsive subjects (PC10 < or = 16 mg/ml), subjects who reported dyspnea, wheeze, or asthma were more likely to show an increase in Borg score during histamine provocation than asymptomatic subjects (adjusted odds ratio 4.01, 95% confidence interval 1.01 to 16.00, p = 0.049), after adjustment for age, sex, smoking habits, FEV1, and atopy. This suggests that asymptomatic hyperresponders may have variable airway obstruction that is not recognized as breathlessness.

The aim of this study was to develop an in vitro system in which an isolated bronchus from human lung was exposed, during 30 min, to a constant flow of either air or nitrogen dioxide (NO2), and to examine subsequently the contractile response of airway smooth muscle rings to carbachol, histamine, and substance P. Two proximal bronchi were mounted in an organ bath, perfused externally with Krebs-Henseleit solution and ventilated with clean air, 1.0 or 2.0 ppm NO2. The exposed bronchi were then cut into rings and mounted in a computerized organ bath system. Contractile responses to agonists were measured isometrically. In each ring, a cumulative concentration response curve was obtained to the desired agonist. We found that in vitro exposure of human lumen bronchus to a constant flow of air did not alter the contractility of the smooth muscle. Whereas in vitro exposure of the bronchus to 1.0 ppm NO2 did not significantly increase the efficacy or the potency of carbachol, exposure to 2.0 ppm NO2 increased airway smooth muscle contractions in response to carbachol, histamine, and substance P. These results indicate that our experimental preparation is well suited to study the respiratory toxicity of inhaled pollutants in order to understand further the mechanisms underlying toxicant-induced airway hyperresponsiveness.

We examined the effect of phospholipase A2 (PLA2; Naja naja) on isometric tracheal smooth muscle force generation in guinea pig trachealis in situ. Direct application of PLA2 to the surface of the trachea caused dose-related contraction of tracheal smooth muscle. In seven guinea pigs, a dose/density of 100 micrograms/cm2 PLA2 caused active tension (AT) that began immediately and was maximum (1.32 +/- 0.13 g/cm) at 5 min (p less than 0.01 versus baseline tension). PLA2 also augmented the contractile response to intravenously administered acetylcholine (ACh); AT caused by 3 x 10(-7) mol/kg ACh was 0.98 +/- 0.13 g/cm after PLA2 versus 0.64 +/- 0.09 g/cm in control animals (p = 0.003). PLA2 inactivated with bromophenacyl bromide (BPB) prior to topical application neither caused contraction (-0.18 +/- 0.18 g/cm AT, p = NS versus baseline tension) nor altered muscarinic responsiveness to 3 x 10(-7) mol/kg ACh. Contraction caused by 100 micrograms/cm2 PLA2 was greater after epithelium removal (2.73 +/- 0.40 g/cm AT versus 1.32 +/- 0.13 g/cm AT in epithelium-intact animals, p less than 0.005). However, epithelium removal (confirmed histologically) attenuated completely augmentation of muscarinic contraction caused by PLA2. Augmentation of muscarinic contraction also was blocked with 15 mg/kg 3-amino-1-(3-trifluoromethylphenyl)-2-pyrazoline hydrochloride (BW 755c), an inhibitor of eicosanoid synthesis, administered intravenously 30 min prior to topical application of 100 micrograms/cm2 PLA2. In contrast, contraction of tracheal smooth muscle caused by PLA2 was not affected significantly by blockade of eicosanoid synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboxane A2(TxA2) has been implicated in the pathogenesis of airway hyperresponsiveness. The effects of inhaled TxA2 on human airway function have not been studied because of its short half-life. U46619 is a chemical that mimics the effects of TxA2. The purpose of this study was to evaluate the effects of inhaled U46619 on human airway function and methacholine airway responsiveness. Airway responsiveness to methacholine and U46619 was measured in 19 subjects (13 asthmatic and six normal) and expressed as the provocative concentration causing a 20% fall in FEV1 (PC20). On one day, methacholine alone was inhaled. On a second day, U46619 was inhaled, then 1 h later methacholine was inhaled. On a third day, U46619 was inhaled, then repeated 1 h later. In six subjects, the effects of isotonic saline or a subthreshold concentration of histamine or U46619 were examined on methacholine airway responsiveness. U46619 was 178 times more potent as a bronchoconstrictor than was methacholine. Airway responsiveness to methacholine was correlated to airway responsiveness to U46619 (r = 0.87, p = 0.001). Subthreshold concentrations of U46619, but not of histamine, increased methacholine airway responsiveness. The mean maximal fall in FEV1 after inhaled methacholine was 13.2% (SEM, 3.4%) after saline, 12.4% (SEM, 2.4%) after histamine, and 25.7% (SEM, 2.0%) after U46619 (p = 0.0004). This effect lasted less than 1 h. There was no tachyphylaxis to repeated inhalations of U46619. These results indicate that in human subjects inhaled U46619 is a potent bronchoconstrictor that, when present in the airways, can cause airway hyperresponsiveness to inhaled methacholine in asthmatic subjects.

Allergen inhalation causes airway inflammation and an increase in histamine airway responsiveness. We have used cell counts in sputum induced by hypertonic saline aerosol to assess airway inflammation before and 32 h after asthmatic responses to allergen. Twelve asthmatic subjects (mean age, 27.4 yr; range, 20-38 yr) had an inhalation test with D. farinae, ragweed pollen, or cat extract. All of them developed an early response with a fall in FEV1, of 24.8% (SD, 6.3%); nine of 12 had a definite late response (fall in FEV1 greater than or equal to 15%), and 10 of 12 had an increase in airway responsiveness to histamine at 32 h (PC20 reduced by greater than twofold). Sputum was induced by hypertonic saline after the histamine test, before and 32 h after the allergen challenge, at the same time of day. The quality of the sample was scored according to visual inspection and inverted microscopy and by salivary contamination. Plugs arising from the lower respiratory tract were selected for further evaluation. Differential cell counts of eosinophils (Eo) and metachromatic cells (MCC) (mast cell and basophils) were obtained from direct smears, blind to the clinical procedures. The mean fall in FEV1 after hypertonic saline was 6.4% (range, zero to 28%). The sputum samples were adequate in 79.5% of attempts. Eo and MCC increased significantly from 3.8 (4.4) to 18.2 (22.8)% (p = 0.01) and from 0.05 (0.17) to 0.25 (0.76)% (p = 0.04), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

We studied the effects of dexamethasone and cyclosporin A on the airway hyperresponsiveness (AHR) and the influx of inflammatory cells into the bronchoalveolar lavage (BAL) fluid seen 18 to 24 hr after exposure to aerosolized ovalbumin in actively ovalbumin-sensitized Brown-Norway rats. Allergen exposure resulted in an approximately sevenfold increase in bronchial responsiveness to inhaled acetylcholine associated with a significant increase in eosinophils and lymphocytes in BAL fluid. Dexamethasone (0.5 mg/kg administered intraperitoneally for 3 days) abolished the AHR and the increase in eosinophil and lymphocyte counts. However, cyclosporin A at two doses (5 and 50 mg given orally for 5 days) did not significantly prevent the induction of AHR while producing a significant inhibition of the eosinophil and lymphocyte influx. Dexamethasone (0.5 mg/kg for 3 days) or cyclosporin A (5 mg/kg for 5 days) on their own had no effect on airway responsiveness. We conclude that specific inhibition of T-lymphocyte activation in this Brown-Norway rat model is not sufficient to inhibit the induction of AHR despite suppressing allergen-induced eosinophilia in BAL fluid. However, corticosteroids, which have inhibitory effects on a wider range of inflammatory cells, are more effective. Our observations are in line with the potent effect of corticosteroids in airway inflammatory conditions such as asthma.

Inflammation of the airway wall and airway hyperresponsiveness are consistent features of chronic asthma. We investigated how damage of the bronchial epithelium is related to airway hyperresponsiveness and how bronchial infiltration of eosinophils and lymphocytes is related to bronchial epithelial damage. We examined the biopsy specimens of bronchial mucosa taken from 19 patients with chronic asthma by electron microscopy. We also measured the incidence of opening of epithelial tight junctions, the widening of intercellular spaces in the epithelium, and the density of infiltrated eosinophils and lymphocytes in bronchial mucosa. Airway responsiveness was accessed by measuring PC20-acetylcholine (PC20-ACh). The inflammatory cells in the airway mucosa were counted by electron microscopy. Lymphocytes were most abundant, being 54.5% of the cells counted; eosinophils were 22.1%, neutrophils were 4.9%, and mast cells were 4.6%. A significant correlation was noted between the density of eosinophils and that of lymphocytes infiltrated in the airway mucosa (r = 0.80, p less than 0.01), suggesting that T cells may potentiate eosinophil infiltration. With increased density of eosinophils infiltrated in bronchial mucosa, both the incidence of opening of tight junctions of epithelial ciliary cells and the degree of widening of intercellular spaces in epithelium increased significantly (r = 0.51, p less than 0.05; r = 0.52, p less than 0.05), suggesting that eosinophils are related to damage of the bronchial epithelium. No correlation was observed between the density of lymphocyte infiltration and the degree of epithelial damage.(ABSTRACT TRUNCATED AT 250 WORDS)

This study was performed to determine whether lipoxin A4 (LXA4) inhalation in asthmatic subjects has an effect on airways response. Eight subjects (six asthmatic, two normal) attended for bronchial inhalation challenge with LXA4. In three of these subjects (two asthmatics, one normal) blood pressure, pulse, and symptoms before and after challenge were recorded. Subsequently five male patients with mild asthma (22 to 34 yr of age) reattended for bronchial inhalation challenge with either leukotriene C4 (LTC4) or the combination of LTC4 and 1 x 10(-4) M LXA4. After inhalation of each dose of agonist SGaw and V25 were measured. Airway responsiveness was determined by the concentration of agonist in the nebulizer required to induce a 35% fall in SGaw (PC35). There was no effect of LXA4 inhalation on SGaw, V25, blood pressure, pulse, or symptoms. There was a significant shift of the SGaw and V25 dose-response curve to the right after inhalation challenge with LTC4 combined with 1 x 10(-4) M LXA4 as compared with that after inhalation challenge with LTC4 alone (p less than 0.01 and p less than 0.025, respectively). Thus, LXA4 may modulate LTC4-induced airway obstruction and may act as an endogenous sulfidopeptide leukotriene receptor antagonist.

To assess the role of T lymphocytes in the initiation of the allergic asthmatic response we have investigated T-cells subsets and their activation markers in bronchoalveolar lavage (BAL) fluid recovered 10 min after local challenge of the bronchial mucosa with allergen or saline. Endobronchial challenge was performed in 13 mildly atopic asthmatic patients (FEV1% predicted range, 78.2 to 116.5) and 10 normal volunteers. In all of the asthmatics but in none of the normal subjects allergen but not saline exposure resulted in visible bronchoconstriction. Analysis of BAL by flow cytometry showed no differences in the overall number of T cells (CD3+) and their CD4+ and CD8+ subsets per milliliter of BAL between the groups of normal subjects and asthmatics. However, within 10 min of allergen challenge, in the asthmatics but not in the normal subjects, there occurred a significant loss of CD3+ cells (p less than 0.01) comprising mostly CD4+ (p less than 0.05) but also CD8+ cells, with a consequent decrease in the CD4:CD8 ratio. At this early time point no differences in the extent of expression of the T-cell activation markers, IL-2 receptor, and HLA-DR were found. These results provide evidence to support a role of T lymphocytes early in the allergen-induced inflammatory response in asthma.

To investigate whether survivors of heart/lung and double-lung transplantations have normal or increased nonspecific bronchial responsiveness, nine heart/lung and four double-lung transplant recipients with normal lung histology underwent methacholine challenge and voluntary isocapnic dry air hyperventilation (VIH) in a randomized order at a mean time of 14.8 +/- 12.1 months after surgery. Transplant recipients were compared with 10 normal subjects and 11 patients with mild asthma. Asthmatic patients had a mean provocative concentration of methacholine inducing a 20% fall (PC20) in FEV1 of 3.4 +/- 3.6 mg/ml (SD). Seventy seven percent of the transplant recipients and 70% of the normal subjects had PC20 superior to 32 mg/ml. The percentage fall from baseline FEV1 after VIH was 12.6 +/- 10.4% in asthmatic patients as compared with 1.9 +/- 2.9% in transplant recipients (p = 0.002) and 0.45 +/- 1.2% in normal subjects (p = 0.001). The decrease in FEV1 after VIH was similar in transplant recipients and normal subjects (p = 0.14). These results show that heart/lung or double-lung transplant recipients with normal lung histology have a normal response to nonspecific bronchial stimulation.

Bronchial hyperresponsiveness (BHR) is a major characteristic of bronchial asthma. The pathogenesis of BHR remains to be fully elucidated, but is considered to be closely linked to airway inflammation. Animal models might provide us with useful data for a better understanding of the interrelationship between these phenomena. In the present study we investigated the effect of a single and chronic exposure to inhaled antigen on bronchial responsiveness and airway morphology in actively sensitized Brown Norway rats. Immunization to ovalbumin (OA) did not cause airway inflammation, but induced a small, transient decrease in bronchial responsiveness to 5-hydroxytryptamine (5HT) on Day 10, which returned to baseline on Day 16. By 24 h after a single exposure to aerosolized OA, a significant decrease in the provocative concentration of 5HT causing a 50% increase in lung resistance (PC50RL 5HT) was observed, compared with immunized, saline-exposed animals (7.7 +/- 0.8 versus 10.8 +/- 1.0 micrograms/kg). This was accompanied by the influx of neutrophils and few eosinophils in bronchoalveolar lavage fluid. Repeated daily or intermittent exposure to aerosolized OA enhanced airway inflammation, characterized by the presence of neutrophils, eosinophils, and lymphocytes in bronchoalveolar lavage fluid. Histologic analysis revealed patchy inflammatory infiltrates, located predominantly around bronchi and bronchioli. Despite these inflammatory changes, bronchial responsiveness was not significantly different from that of control animals. We therefore conclude that the induction of airway inflammation is not always associated with BHR.

Neuropeptides such as neurokinin A (NKA) have been proposed as important mediators of bronchoconstriction and airway hyperresponsiveness in asthma. Inhaled NKA causes bronchoconstriction in patients with asthma, but not in normal subjects. This is possibly due to the activity of an endogenous neuropeptide-degrading enzyme: neutral endopeptidase (NEP). We investigated whether a NEP-inhibitor, thiorphan, reveals bronchoconstriction to NKA or NKA-induced changes in airway responsiveness to methacholine in normal humans in vivo. Eight normal male subjects participated in a double-blind crossover study, using thiorphan as pretreatment to NKA challenge. Dose-response curves to inhaled NKA (8 to 1,000 micrograms/ml, 0.5 ml/dose) were recorded on 2 randomized days 1 wk apart, and methacholine tests were performed 48 h before and 24 h after the NKA challenge. Ten minutes prior to NKA challenge the subjects inhaled either thiorphan (2.5 mg/ml, 0.5 ml) or placebo. To detect a possible nonspecific effect of thiorphan, we investigated the effect of the same pretreatment with thiorphan or placebo on the dose-response curve to methacholine in a separate set of experiments. The response was measured by the flow from standardized partial expiratory flow-volume curves (V40p), expressed in percent fall from baseline. NKA log dose-response curves were analyzed using the area under the curve (AUC) and the response to the highest dose of 1,000 micrograms/ml (V40p,1000). The methacholine dose-response curves were characterized by their position (PC40V40p) and the maximal-response plateau (MV40p). Baseline V40p was not affected by either pretreatment (p greater than 0.15).(ABSTRACT TRUNCATED AT 250 WORDS)

We have examined the effect of airway wall thickening, loss of lung recoil, and airway smooth muscle shortening on the increase in airway resistance using a model of the human tracheobronchial tree. The values for airway wall thickening were determined morphometrically on the postmortem or surgically resected lungs of normal subjects, patients with moderate chronic obstructive pulmonary disease, and patients with severe asthma. Loss of recoil was simulated by deflating airways along their pressure-area curves by 1 to 3 cm H2O. Values of smooth muscle shortening between 20 and 40% were used in the model to generate sigmoidal-shaped "dose-response" curves. The analysis shows that moderate amounts of airway wall thickening, which have little effect on baseline resistance, can profoundly affect the airway narrowing caused by smooth muscle shortening--especially if the wall thickening is localized in peripheral airways. The combination of a loss of recoil and airway wall thickening are more than additive in their effect on simulated airway responsiveness. We conclude that airway wall thickening and a loss of lung recoil can partially explain the airway hyperresponsiveness observed in patients with chronic obstructive lung disease and asthma.

Bronchial hyperresponsiveness can be demonstrated in asthmatic subjects by inhalation of adenosine, but the action of adenosine at the level of the human airway smooth muscle has received comparatively little attention. We have previously observed that bronchi isolated from one asthmatic patient contracted in response to adenosine. We have therefore, during the course of a 3-yr study, further characterized the effects of adenosine in bronchi prepared from surgical specimens of lung tissue of asthmatics and of nonasthmatics. Contraction responses were always studied in vitro the same day the tissues were obtained. Bronchi from asthmatics (19 strips from six patients) were more sensitive to adenosine than were bronchi from nonasthmatics (21 strips, seven patients). In contrast, there was no difference in sensitivity to histamine or leukotriene C4 between the two groups, nor was the maximal tissue contractility different. The contractile effect of adenosine was inhibited by the adenosine A1-antagonist 2-thio-[(1,3-dipropyl)-8-cyclopentyl]-xanthine as well as by the dual A1 and A2 antagonists 8-(p-sulfo)-phenyltheophylline and theophylline. The combination of leukotriene antagonism (receptor-antagonist ICI 198,615 or biosynthesis inhibitor MK-886) and histamine antagonism (antihistamines mepyramine and metiamide) blocked the contractile effects of adenosine, suggesting that adenosine acts indirectly by liberation of leukotrienes and histamine, possibly from mast cells. The findings of increased sensitivity to adenosine in bronchi from asthmatics to our knowledge represents the first evidence of increased bronchial reactivity in vitro in asthmatics.

A total of 645 cotton mill operatives were administered a respiratory questionnaire. Of these, 85 (13.2%) complained of one or more work-related respiratory symptoms: 23 (3.6%) had byssinosis and the remaining 62 had symptoms not conforming to byssinosis (nonbyssinotic symptomatics, NBS). All byssinotic, 56 NBS, and 84 matched asymptomatic operatives underwent pulmonary function testing (FEV1 and FVC), skin testing to common allergens, and histamine bronchial challenge. Work area and personal breathing zone cotton dust concentrations were assessed, and a cumulative cotton dust exposure index was calculated for each individual. Byssinotic, NBS, and asymptomatic operatives all had reduced FEV1; observed mean liters (95% CI); predicted mean: byssinosis, 2.36 (2.09 to 2.63), 3.02; NBS, 2.94 (2.71 to 3.17), 3.29; and asymptomatic, 3.12 (2.95 to 3.29), 3.31. Only byssinotic subjects had evidence of impaired FVC: 3.31 (2.97 to 3.65), 3.69. The majority of byssinotic operatives (18 of 23) had bronchial hyperreactivity (BHR) in comparison with 21 of 56 NBS and 14 of 84 asymptomatic operatives. Mean log PD20 (95% CI) values were significantly lower in the byssinotic group -0.72 (-1.42, -0.02) than in NBS 0.57 (0.08, 1.06) and asymptomatic subjects 0.57 (-0.26, 1.39). The distribution of atopy did not differ significantly between groups, and lung function did not differ significantly between atopic and nonatopic subjects. The cumulative cotton dust exposure index was the only dust parameter to be significantly greater in those with BHR (mean mg-yr/m3 [95% CI] 14.13 [13.1 to 15.1]) than those with normal reactivity [5.35 (3.9 to 6.8)].

Lung volume has been shown to be a major determinant of the bronchoconstrictor response to inhaled methacholine (MCh). Because a change in body posture from sitting to supine is associated with a reduction in lung volume, we hypothesized that airway responsiveness to inhaled MCh should be affected by body posture. Responsiveness to MCh was assessed in both sitting and supine postures on separate days in 10 subjects aged 24 to 42 yr. Subjects inhaled aerosols of saline and MCh in progressively doubling concentration (0.125 to 256 mg/ml). Responses were assessed by measuring partial and complete forced expiratory flow-volume curves (PEFV and MEFV, respectively). As indices of airway responsiveness, we took the MCh concentration ([MCh]) at which the FEV1 fell by 10% relative to postsaline (PC10), the maximal percentage fall in FEV1 (MR), the [MCh] at which FEV1 reached 50% of MR (EC50), and the [MCh] at which the flow at 20% vital capacity on PEFV curves fell by 20% relative to postsaline (FP20). Responsiveness to MCh was increased in the supine compared with the sitting posture. In the sitting posture, the geometric mean values of MR, PC10, and FP20 were 16.3%, 16.3 mg/ml, and 2.0 mg/ml; supine they were 29.9% (p less than 0.009), 3.0 mg/ml (p less than 0.02), and 0.6 mg/ml (NS), respectively. EC50 did not change with posture. These results are consistent with the notion that airway responsiveness is influenced by airway-parenchymal interdependence and indicate that the results of bronchial provocation testing in the supine posture cannot be directly compared with those in the upright posture.

We measured the competitive antagonistic effect of atropine in bronchi of 8 normal and 15 asthmatic subjects. Classic pharmacologic theory states that the degree of competitive antagonism depends only upon (1) antagonist concentration at the receptor and (2) receptor affinity. Delivery and affinity also influence agonist responsiveness, but measurement of bronchial antagonism allows study of these factors in isolation. Bronchial responsiveness to methacholine was measured as the cumulative dose required to produce a 35% fall in specific airway conductance (PD35). On different days three measurements of control PD35 were made on each subject. On 2 days PD35 was measured after inhalation of 0.14 mg atropine and, on another day, after intravenous injection of 0.32 mg atropine. The antagonist effect of atropine was measured as dose ratio - 1 (DR - 1), where DR = PD35 after atropine/control PD35. Geometric mean DR - 1 with inhaled atropine in asthmatic subjects (11.7) was 6.3 times that of normal subjects (1.9) (p less than 0.001), and DR - 1 with intravenous atropine in asthmatic subjects (8.0) was 5.6 times that of normal subjects (1.4) (p less than 0.001). In conclusion, there is enhanced muscarinic blockade from inhaled and intravenously administered atropine in asthmatic bronchi. We suggest that this is due to increased access of the drug to bronchial muscarinic receptors.