Increase In Methacholine Responsiveness Research Articles

Sphingosine-1-phosphate induces airway smooth muscle hyperresponsiveness and proliferation

The emerging role of sphingosine-1-phosphate (S1P) in regulating smooth muscle functions has led to the exploration of the possibility that this sphingolipid could represent a potential therapeutic target in asthma and other lung diseases. Several studies in animal surrogates have suggested a role for S1P-mediated signalling in the regulation of airway smooth muscle contraction, airway hyperresponsiveness and airway remodelling but evidence from human studies is lacking. We have compared the responsiveness of the airways to S1P in healthy and asthmatic individuals in vivo, in isolated human airways ex vivo and in murine airways dissected from healthy and house dust mite (HDM) sensitised animals. Airway responsiveness was measured by spirometry during inhalation challenges and by wire myography in airways isolated from human and mouse lungs. Thymidine incorporation and calcium mobilisation assays were used to study human airway smooth muscle cell responses. S1P did not induce contraction of airways isolated from healthy and HDM exposed mice, nor in human airways. Similarly, there was no airway constriction observed in healthy and asthmatic subjects in response to increasing concentrations of inhaled S1P. However, 30 minutes exposure to S1P induced a significant, concentration-dependent enhancement of airway reactivity to methacholine and to histamine in murine and human airways respectively. HDM-sensitised mice demonstrated a significant increase in methacholine responsiveness which was not further enhanced by S1P treatment. S1P also concentration-dependently enhanced proliferation of human airway smooth muscle cells, an effect mediated through the S1P type 2 receptor, as shown by selective antagonism and S1PR2 siRNA knockdown. Our data suggest that S1P released locally into the airways may be involved in the regulation of airway smooth muscle hyperresponsiveness and hyperplasia, defining a novel target for future therapies.

Clinical Implications of Having Reduced Mid Forced Expiratory Flow Rates (FEF25-75), Independently of FEV1, in Adult Patients with Asthma.

IntroductionFEF25-75 is one of the standard results provided in spirometry reports; however, in adult asthmatics there is limited information on how this physiological measure relates to clinical or biological outcomes independently of the FEV1 or the FEV1/FVC ratio.PurposeTo determine the association between Hankinson’s percent-predicted FEF25-75 (FEF25-75%) levels with changes in healthcare utilization, respiratory symptom frequency, and biomarkers of distal airway inflammation.MethodsIn participants enrolled in the Severe Asthma Research Program 1–2, we compared outcomes across FEF25-75% quartiles. Multivariable analyses were done to avoid confounding by demographic characteristics, FEV1, and the FEV1/FVC ratio. In a sensitivity analysis, we also compared outcomes across participants with FEF25-75% below the lower limit of normal (LLN) and FEV1/FVC above LLN.ResultsSubjects in the lowest FEF25-75% quartile had greater rates of healthcare utilization and higher exhaled nitric oxide and sputum eosinophils. In multivariable analysis, being in the lowest FEF25-75% quartile remained significantly associated with nocturnal symptoms (OR 3.0 [95%CI 1.3–6.9]), persistent symptoms (OR 3.3 [95%CI 1–11], ICU admission for asthma (3.7 [1.3–10.8]) and blood eosinophil % (0.18 [0.07, 0.29]). In the sensitivity analysis, those with FEF25-75% <LLN had significantly more nocturnal and persistent symptoms, emergency room visits, higher serum eosinophil levels and increased methacholine responsiveness.ConclusionsAfter controlling for demographic variables, FEV1 and FEV1/FVC, a reduced FEF25-75% is independently associated with previous ICU admission, persistent symptoms, nocturnal symptoms, blood eosinophilia and bronchial hyperreactivity. This suggests that in some asthmatics, a reduced FEF25-75% is an independent biomarker for more severe asthma.

Airway Hyperresponsiveness in Children With Sickle Cell Anemia

The high prevalence of airway hyperresponsiveness (AHR) among children with sickle cell anemia (SCA) remains unexplained. To determine the relationship between AHR, features of asthma, and clinical characteristics of SCA, we conducted a multicenter, prospective cohort study of children with SCA. Dose response slope (DRS) was calculated to describe methacholine responsiveness, because 30% of participants did not achieve a 20% decrease in FEV1 after inhalation of the highest methacholine concentration, 25 mg/mL. Multiple linear regression analysis was done to identify independent predictors of DRS. Methacholine challenge was performed in 99 children with SCA aged 5.6 to 19.9 years (median, 12.8 years). Fifty-four (55%) children had a provocative concentration of methacholine producing a 20% decrease in FEV1<4 mg/mL. In a multivariate analysis, independent associations were found between increased methacholine responsiveness and age (P<.001), IgE (P=.009), and lactate dehydrogenase (LDH) levels (P=.005). There was no association between methacholine responsiveness and a parent report of a doctor diagnosis of asthma (P=.986). Other characteristics of asthma were not associated with methacholine responsiveness, including positive skin tests to aeroallergens, exhaled nitric oxide, peripheral blood eosinophil count, and pulmonary function measures indicating airflow obstruction. In children with SCA, AHR to methacholine is prevalent. Younger age, serum IgE concentration, and LDH level, a marker of hemolysis, are associated with AHR. With the exception of serum IgE, no signs or symptoms of an allergic diathesis are associated with AHR. Although the relationship between methacholine responsiveness and LDH suggests that factors related to SCA may contribute to AHR, these results will need to be validated in future studies.

Maternal smoking during pregnancy induces airway remodelling in mice offspring

Children from smoking mothers have an increased risk of developing asthma for reasons largely unknown. The effects of maternal smoking during pregnancy on remodelling, allergic airway inflammation and hyperresponsiveness in offspring were investigated in an experimental asthma model. Mice were exposed to fresh air or cigarette smoke from 3 weeks prior to conception until birth. Offspring were exposed to house dust mite (HDM) or PBS intranasally four times per week from week 5 to week 10 after birth onwards. Maternal smoking increased airway smooth muscle layer, collagen III deposition and HDM-induced goblet cell numbers in offspring. It additionally increased methacholine responsiveness, which correlated significantly with increased airway smooth muscle layer and collagen deposition. Maternal smoking increased HDM-induced numbers of neutrophils and mast cells in lung tissue. No further effects were observed. Smoking during pregnancy induces airway remodelling in mice offspring, which may contribute to increased methacholine responsiveness. This takes place irrespective of allergen exposure but may worsen the outcome of the allergic stimulus, resulting in higher methacholine responsiveness in house dust mite-exposed offspring from smoking mothers when compared to nonsmoking mothers. The results provide a possible mechanism behind the association between maternal smoking and asthma.

Subclinical immunologic and physiologic responses in hexamethylene diisocyanate-exposed auto body shop workers.

Diisocyanates are potent sensitizing agents and currently the most commonly identified cause of occupational asthma in industrialized countries. However, diisocyanate asthma is difficult to diagnose and exposure and host risk factors are unclear. Auto body shops, one of the most common hexamethylene diisocyanate (HDI) exposure settings, are particularly difficult to study due to their small size and episodic exposures. Surveillance studies of such workers are limited. We have initiated a cross-sectional field epidemiologic study, Survey of Painters and Repairers of Auto bodies by Yale (SPRAY), to characterize the effects of diisocyanate exposures on actively employed auto body shop workers. Methods and Results We present here questionnaire, physiologic, immunologic, and exposure data on 75 subjects enrolled in the study. No overt cases of clinically apparent diisocyanate asthma were identified based on spirometry, methacholine challenge, peak flows, and symptoms. HDI-specific lymphocyte proliferation was present in 30% of HDI-exposed workers and HDI-specific IgG in 34% of HDI-exposed workers, but they were not associated. HDI-specific IgE was detected in two workers. HDI-specific lymphocyte proliferation, increased methacholine responsiveness, and symptoms of chest tightness and shortness of breath were more common in the most heavily HDI-exposed workers, the painters. More long-term follow-up of this cohort should clarify the significance of these HDI-specific immunologic responses, physiologic changes, and symptoms. These findings demonstrate the presence of HDI-specific immune responses in a large proportion of healthy HDI-exposed workers.

An improved murine model of asthma: selective airway inflammation, epithelial lesions and increased methacholine responsiveness following chronic exposure to aerosolised allergen

BACKGROUNDExisting murine models of asthma lack many of the inflammatory and epithelial changes that are typical of the human disease. Moreover, these models are frequently complicated by allergic alveolitis.METHODSHigh IgE...

A seven-year follow-up study of lung function and methacholine responsiveness in sensitized and non-sensitized workers handling laboratory animals.

Lung function, studied with spirometry, nitrogen washout technique, and methacholine responsiveness, was prospectively investigated in a seven-year follow-up study of 35 laboratory animal workers (19 women and 16 men) of whom 11 were skin prick test (SPT) positive to laboratory animal allergens; five had asthma and six had rhinitis symptoms. During the follow-up, 82% of the SPT positive subjects had stopped animal work, compared with 29% of the SPT-negative subjects. In baseline spirometry, there was no decrement in the lung volumes or differences between SPT-positive and SPT-negative subjects. At follow-up, no difference was found in vital capacity (VC), forced expiratory volume during one second (FEV1), or residual volume (RV), but the volume of trapped gas (VTG), which is assumed to measure small airways, had increased with a median of 11 mL (P = 0.03). Subjects sensitized to laboratory animals had a minor increase in methacholine responsiveness in FEV1 at follow-up (P = 0.03). The VTG responsiveness was already increased in the first examination (P = 0.035) and remained so at follow-up. Furthermore, the FEV1 responsiveness could predict a subsequent decline in baseline VC and FEV1. In conclusion, our results support the hypothesis that airway responsiveness in immunoglobulin E-mediated allergy might start in small airways and subsequently affect large airways.

Beclomethasone given after the early asthmatic response inhibits the late response and the increased methacholine responsiveness and cromolyn does not

Background: Single doses of inhaled beclomethasone or inhaled cromolyn, given before allergen inhalation, inhibit allergen-induced late asthmatic responses (LARs) and increased airway responsiveness (Δ log methacholine PC 20). We hypothesized that when given 2 hours after allergen, beclomethasone might work better than cromolyn. Methods: In 10 patients with mild, stable, atopic asthma with LARs or Δ log PC 20 or both, we performed a double-blind, double-dummy, random-order trial comparing a single dose of inhaled beclomethasone (500 μg), cromolyn (20 mg), and placebo, administered 2 hours after allergen challenge on LAR and Δ log PC 20. Results: The treatment effect on LAR was significant ( p < 0.001). The LAR after beclomethasone (7.3% ± 6.1%) was significantly less than after cromolyn (20.4% ± 15.2%) or placebo (26.4% ± 8.2%); cromolyn was not different from placebo. There was a borderline treatment effect on Δ log PC 20 ( p = 0.056) with beclomethasone (0.12 ± 0.31) less than placebo (0.37 ± 0.39) but not less than cromolyn (0.34 ± 0.18). Conclusion: Beclomethasone (500 μg) administered 2 hours after allergen challenge markedly inhibited the LAR and had a small effect on allergen-induced airway responsiveness. Cromolyn (20 mg) was not effective on maximal LAR; a small effect on the early part of the LAR was suggested.

The effect of repirinast on airway responsiveness to methacholine and allergen

Repirinast, a novel ingested antiallergic asthma medication from Japan, was compared versus placebo on airway responsiveness to methacholine and was compared versus placebo and cromolyn on airway responses to allergen. In 14 patients with mild, stable, atopic asthma, we performed a double-blind, double-dummy, random-order trial with ingested repirinast 300 mg twice daily for 7 days, inhaled cromolyn 40 mg spincaps single dose, and double placebo on allergen-induced early (EAR) and late (LAR) asthmatic responses and increased airway responsiveness. In the 14 subjects, no difference occurred in methacholine PC 20 after 6 days of repirinast or 6 days of placebo. In the 13 subjects who completed the allergen study, single-dose cromolyn significantly reduced the EAR by 63% and the LAR by 65% versus placebo ( p < 0.02); repirinast was not significantly different from placebo, both the EAR and LAR being reduced by less than 10%. Allergen-induced increase in methacholine responsiveness was borderline ( p = 0.052), and no significant drug effects occurred. In these models, a 1-week treatment period with repirinast, like other oral antiallergic asthma medications (e.g., ketotifen, fumarate), provides no protection against airway responses to methacholine or allergen.

The Effects of Sequential Exposure to Acidic Fog and Ozone on Pulmonary Function in Exercising Subjects

In Southern California coastal regions, morning fog is often acidified by the presence of nitric acid (HNO3). Peak exposure to ozone (O3) usually occurs in the afternoon and evening, after the fog has dissipated. To determine whether fog containing HNO3 might enhance pulmonary responses to O3, we studied a group of healthy, athletic subjects selected for lung function sensitivity to O3. On 3 separate days, the subjects exercised for 2 h in atmospheres containing HNO3 fog (0.5 mg/ml), H2O fog, or clean, filtered air. After a 1-h break, they exercised for an additional 3 h in an atmosphere containing 0.20 ppm O3. Surprisingly, the mean O3-induced decrements in FEV1 and FVC were smaller after exercise in each fog-containing atmosphere than they were after exercise in clean, filtered air. The mean (+/- SEM) O3-induced decrements in FEV1 were 26.4 +/- 5.3% after air, 17.1 +/- 3.7% after H2O fog, and 18.0 +/- 4.3% after HNO3 fog, and in FVC they were 19.9 +/- 4.7% after air, 13.6 +/- 2.8% after H2O fog, and 13.6 +/- 4.2% after HNO3 fog.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of an inhaled leukotriene antagonist, L-648,051, on early and late asthmatic reactions and subsequent increase in airway responsiveness in man

We have investigated the protective effects of the inhaled cysteinyl leukotriene antagonist, L-648,051, on allergen-induced early asthmatic response (EAR) and late asthmatic response (LAR) and the subsequent changes in bronchial responsiveness to methacholine. Ten atopic men with asthma participated in a double-blind, crossover, placebo-controlled trial. All subjects had documented EAR and LAR to house dust-mite extract. Responsiveness to methacholine was measured the day before and the day after a standardized allergen-challenge test. L-648,051 was inhaled in two doses of 12 mg 20 minutes before and 3 hours after the allergen challenge. The response was obtained from FEV, and flows from maximal (V 40m) and partial (V 40p) expiratory flow-volume curves. All subjects had an EAR and LAR during placebo therapy, but only a minority demonstrated an increase in methacholine responsiveness of more than one doubling dose. The ratio of V 40m to V 40p during methacholine challenge was higher than during both EAR and LAR ( p < 0.05). There was no difference between drug- and placebo-therapy periods in baseline function, EAR, LAR, ratio of V 40m to V 40p, and the allergen-induced hyperresponsiveness ( p > 0.1). These results indicate that an effective aerosolized leukotriene antagonist in man does not protect against allergen-induced airflow obstruction, despite the evidence of an inflammatory response to allergen challenge. This suggests that either the potency or duration of activity of L-648,051 is limited or that leukotrienes C 4 and D 4 do not play a causative role in human allergic asthma.

Substance P-induced Bronchoconstriction in the Guinea Pig: Enhancement by Inhibitors of Neutral Metalloendopeptidase and Angiotensin-converting Enzyme

We tested the effects of the neutral metalloendopeptidase (NEP) inhibitor, thiorphan (0.17, 0.5, and 1.7 mg i.v), and the angiotensin-converting enzyme (ACE) inhibitor, captopril (0.5, 1.7, and 5.0 mg i.v.), on the bronchoconstrictor response to rapid intravenous infusions of substance P (0.1 to 30 nmol/kg) in anesthetized, mechanically ventilated guinea pigs. The decreases in pulmonary conductance and dynamic compliance caused by substance P were greater in animals treated with either thiorphan or captopril than in control animals. Thiorphan (0.5 mg) had no effect on airway responsiveness to intravenously administered methacholine, whereas captopril (1.7 mg) caused a small increase in methacholine responsiveness. Both drugs significantly increased the recovery of immunoreactive substance P in arterial plasma after exogenous administration of the peptide. We conclude that degradation of substance P by both NEP and ACE is important for determining the magnitude of the bronchoconstriction caused by intravenous administration of this neuropeptide. These data suggest that conditions associated with diminished peptidase activity could result in enhanced responses to stimuli which cause the release of endogenous substance P.

Effects of two doses of cromolyn on allergen-induced late asthmatic response and increased responsiveness

We selected five atopic children with asthma with previously documented late asthmatic response (LAR) associated with increased hyperresponsiveness to methacholine after the inhalation of Dermatophagoides pteronyssinus. The children had four allergen inhalation tests on 4 different days, at least 14 days apart. On days 1 and 4, saline placebo was inhaled 1 hour before the expected onset of LAR, and FEV 1 was measured hourly until FEV 1 returned within 10% of baseline value; then methacholine challenge was performed. On days 2 and 3, 20 and 40 mg of cromolyn was inhaled double blind 1 hour before the expected onset of LAR. FEV 1 and methacholine responsiveness were measured as on days 1 and 4. The two doses of cromolyn significantly delayed the LAR onset without altering the overall LAR magnitude and prevented the allergen-induced increase in methacholine responsiveness. Both these effects were greater at the maximal dose used. We conclude that cromolyn can prevent the allergen-induced increase in methacholine responsiveness and that this effect is not due to alteration in the magnitude of LAR. Our findings reveal a possible explanation of the effectiveness of this drug in the treatment of allergic asthma.

Late bronchial response and increase in methacholine hyperresponsiveness after exercise and distilled water challenge in atopic subjects with asthma with dual asthmatic response to allergen inhalation

We investigated the occurrence of late asthmatic response and increased methacholine responsiveness after exercise and ultrasonically nebulized distilled water (UNDW) inhalation in 12 subjects with asthma with dual asthmatic response and increased responsiveness after allergen challenge. On 3 separate days, allergen, exercise, and UNDW challenges were performed 2 hours after methacholine. FEV 1 was measured for 8 hours to detect any delayed change in airway caliber. If there were a further significant reduction in FEV 1 after the recovery from the immediate bronchoconstriction, methacholine challenge was performed again when FEV 1 had returned to baseline. Reproducibility of any observed late response to exercise and UNDW was also investigated by repeating these challenges on 2 subsequent days. After allergen inhalation only nine subjects had an early asthmatic response, whereas all the tested subjects demonstrated a late reaction and increased methacholine responsiveness. Ten subjects had an immediate response to exercise, and this was followed by a late response in only four patients. Nine subjects demonstrated early response to UNDW inhalation, and five subjects also had a late reaction. These late responses were associated with an increase in methacholine responsiveness in a subset of the tested subjects. Late-phase reactions to exercise and UNDW were not reproducible.

Antigen-induced Enhancement of Bronchial Reactivity

Bronchial hyperreactivity as determined by the airway response to methacholine was evaluated pre- and post-antigen challenge in three patients with specific antigen sensitivity. No significant change in pulmonary function was noticed after inhalation of antigen alone. However, transient but significant increase in methacholine responsiveness followed the antigen challenge. The studies indicate a need for a nonspecific inhalation challenge following a negative antigen challenge when clinically indicated.

Asymptomatic bronchial hyperresponsiveness in rhinitis

Methacholine inhalation tests are used to help in the diagnosis of asthma when spirometry is normal. However, the significance of increased methacholine responsiveness in patients with rhinitis and no symptoms of asthma is not known. One possibility is that it is a false positive result; another possibility is that it indicates subclinical asthma. We investigated these possibilities in 25 patients with rhinitis, whose attending physician had not made a diagnosis of asthma, by comparing responsiveness to methacholine expressed as the provocation concentration to cause a fall in FEV 1 of 20% (PC 20) with responsiveness to the natural stimulus of isocapnic hyperventilation of cold air and the diurnal variation of peak flow rate. Asthma was recognized objectively by variable airflow obstruction documented by one of the latter two tests. The PC 20 ranged between 4 and >64 mg/ml. In 10 patients the PC 20 was <16 mg1ml. Five of these patients had bronchoconstriction in response to hyperventilation, and a further two patients demonstrated increased variability of peak flow rates. Thus, in seven of 10 patients, increased bronchial responsiveness was confirmed by the use of two different methods, although they were asymptomatic, and the increased response to methacholine was not a false positive result. In the remaining three patients the PC 20 was borderline increased (8 to 16 mg/ml). The results indicate that methacholine responsiveness in the asthmatic range in patients with rhinitis is associated with variable airflow obstruction and subclinical asthma.

Asthma and increases in nonallergic bronchial responsiveness from seasonal pollen exposure

Serial measurements of symptoms, peak flow rates, methacholine bronchial responsiveness, and ragweed-specific IgE antibodies were made before and during the ragweed pollen season in 13 sensitized subjects. Allergen inhalation tests were carried out with aerosols of pollen extract out of season in nine subjects; isolated early asthmatic responses were provoked in four, and dual responses (early followed by late) were provoked in five. During the pollen season all subjects developed hay fever and eight had symptoms of asthma. There was a real increase in methacholine responsiveness during the ragweed season. This increase appeared before or after the occurrence of asthma symptoms and changes in flow rates and was greater in subjects with symptoms in the pollen season, dual responses after allergen inhalation tests, and higher levels of ragweed-specific IgE antibodies. The results confirm the occurrence of seasonal asthma and increases in nonallergic (nonspecific) bronchial responsiveness to methacholine from seasonal pollen exposure. They suggest that the occurrence of symptoms is closely linked to the allergic inflammatory reaction and the induction of increased nonallergic responsiveness.

Prolonged asthmatic responses to inhaled methacholine

The pattern of asthmatic response after inhalation of atropine and methacholine was studied in six adult asthmatics. After pretreatment with atropine, the provocation concentration of methacholine to cause a fall in FEV 1 of 20% was increased from 0.66 ± 2.09 to 94.90 ± 1.78 mg/ml. In the subsequent 7 hr, four subjects developed prolonged asthmatic responses. These occurred after concentrations of methacholine higher than those used clinically but did not directly relate to the dose of methacholine or to the increase in dose after atropine. In one subject the prolonged response was not accompanied by increased methacholine responsiveness and was not prevented by pretreatment with cromolyn sodium (40 mg). These results show that high doses of methacholine inhaled after pretreatment with atropine can induce prolonged asthmatic responses but the mechanism is unclear.