Bronchial responsiveness to methacholine and adenosine 5'-monophosphate in preschool children with bronchopulmonary dysplasia

Bronchial hyperresponsiveness (BHR) is a characteristic feature of asthma, but it is also frequently present in children and adults with chronic obstructive lung diseases. Bronchopulmonary dysplasia (BPD) is a chronic lung disease, most commonly developing after mechanical ventilation and oxygen therapy in premature infants. BHR is usually measured by bronchial challenges, using direct or indirect stimuli. The aim of this study was to evaluate BHR to direct and indirect stimuli in young children with BPD. Methacholine and adenosine 5'-monophosphate (AMP) bronchial challenges were performed on preschool children with BPD (n = 19), using a modified auscultation method. The endpoint was defined as the appearance of wheezing and/or oxygen desaturation. The results obtained were then compared with those of asthmatic (n = 25) and control (n = 23) preschool children. A positive response to methacholine (endpoint concentration, < or = 8 mg/ml) was observed in 89.5% (17/19) of patients with BPD, but a positive response to AMP (endpoint concentration, < or = 200 mg/ml) was observed only in 21.1% (4/19). All patients with asthma responded positively to methacholine, and most (23/25, 92.0%) of them also responded positively to AMP. The majority of controls were unresponsive to both challenges. BHR to methacholine is a frequent finding in preschool-age survivors of BPD, but is usually not accompanied by BHR to AMP. This suggests that most patients with BPD do not have the inflammatory airway response which is characteristic of asthmatic patients.     

Methacholine and adenosine 5'-monophosphate challenges in preschool children with cough-variant and classic asthma

Bronchial challenge with different stimuli provides different information and may be used as an adjunct to understand the pathophysiology of cough variant asthma (CVA) in young children in whom the mechanism of disease is still unresolved. This study was designed to investigate the hypothesis that airway hyperresponsiveness (AHR) to methacholine and adenosine 5'-monophosphate (AMP) is similar in preschool children with CVA and classic asthma. We examined airway response to methacholine and AMP in well-defined 3-6-year-old children with CVA (n = 18), classic persistent asthma (n = 31), and healthy controls (n = 10) by transcutaneous oxygen monitorization. The number of AMP responsive children was significantly lower in the group with CVA (38.9%) than classic persistent asthma (67.7%) (P = 0.049). Mean provocative concentration of AMP causing a 15% fall in transcutaneous oxygen tension (PC15PtcO2 AMP) in children with CVA and classic persistent asthma were 234.58 and 36.35 mg/ml, respectively (P = 0.001). None of the healthy children in the control group responded to AMP. The severity of methacholine responsiveness was found similar in CVA and classic persistent asthma groups (P = 0.738). Although both asthma groups showed a similar pattern in methacholine responsiveness, preschool children with CVA were found to differ from children with classic persistent asthma with regard to response profiles to AMP challenge which may point to different pathophysiologic mechanisms of CVA in the young age group.     

Airway hyperresponsiveness and pulmonary function in adult asthma.

BACKGROUND: Airway hyperresponsiveness (AHR) is a very important factor in the pathogenesis of bronchial asthma. OBJECTIVES: To examine the relationship between airway obstruction and AHR in adult asthma. METHODS: This study was a retrospective study in 161 adult asthmatic patients. Nonspecific AHR to methacholine was measured. We examined the correlations between AHR and pulmonary function, severity of asthma, type of asthma and age. RESULTS: In the moderate and severe groups, peripheral airway obstruction was more aggravated compared to the mild group, and AHR was significantly more severe. Analysis of AHR by age showed that the degree of airway obstruction increased with aging, but age did not clearly correlate with airway sensitivity. Airway reactivity decreased with aging. Aspirin-induced asthma tended to be severe. In fatal asthma, central airway obstruction was significantly more severe. Although AHR in fatal asthma did not significantly differ from that in the severe group, airway sensitivity and airway reactivity tended to be increased. CONCLUSIONS: AHR is an important factor determining the severity of asthma, and airway obstruction is an important index for the prediction of death from asthma. An evaluation of the degree of AHR and airway obstruction is considered to be the first step in controlling asthma.     

Corticosteroid-induced improvement in the PC20 of adenosine monophosphate is more closely associated with reduction in airway inflammation than improvement in the PC20 of methacholine.

It has been suggested in cross-sectional studies that provocation with adenosine 5'-monophosphate (AMP) more closely reflects the inflammatory process in asthma than does provocation with methacholine or histamine. We investigated whether the steroid-induced improvement in the provocative concentration of AMP producing a 20% decline in FEV1 (PC20 AMP) is more closely associated with the concomitant reduction in airway inflammation than is the improvement in PC20 methacholine. In 120 asthmatic patients, we measured PC20 methacholine and PC20 AMP as well as sputum induction and nitric oxide (NO) in exhaled air before and after 2 weeks of treatment with corticosteroids. Improvement in PC20 AMP was solely related to reduction in airway inflammation (i.e., change in the number of sputum eosinophils, lymphocytes, epithelial cells, and concentration of NO in exhaled air). In contrast, improvement in PC20 methacholine was related to both reduction in airway inflammation (i.e., change in the number of sputum eosinophils and lymphocytes) and increase in FEV1 %predicted. The total explained variance of the improvement in bronchial hyperresponsiveness was greater for AMP than for methacholine (36% versus 22%, respectively). We conclude that PC20 AMP is more sensitive to changes in acute airway inflammation than is PC20 methacholine, further reinforcing the notion that PC20 AMP can be a useful tool for monitoring the effects of antiinflammatory therapy.     

PC(20) adenosine 5'-monophosphate is more closely associated with airway inflammation in asthma than PC(20) methacholine

Inhalation of a direct stimulus such as histamine or methacholine is generally used to measure bronchial hyperresponsiveness (BHR). Provocation with adenosine 5'-monophosphate (AMP), an indirect airway challenge, has been suggested to be a better marker of airway inflammation than direct challenges. However, so far little information on this subject is available. The aim of our study was to assess whether the concentration of AMP causing the FEV(1) to drop by 20% (PC(20)) is more closely associated with inflammatory parameters in asthma than PC(20) methacholine. In 120 patients with atopic asthma (median FEV(1) 81% predicted [pred], median age 27 yr), PC(20) methacholine and PC(20) AMP as well as sputum induction, blood sampling, and measurement of nitric oxide in exhaled air were performed. PC(20) methacholine was predominantly predicted by FEV(1) %pred (explained variance [ev] = 18%) with the percentage of peripheral blood monocytes being a weak additional independent predictor (total ev = 23%). By contrast, PC(20) AMP was predominantly predicted by the percentage of eosinophils in sputum (ev = 25%), while FEV(1) %pred was only an additional independent predictor (total ev = 36%). PC(20) AMP reflects more closely the extent of airway inflammation due to asthma than PC(20) methacholine.     

Bronchial hyperresponsiveness is a common feature in patients with chronic urticaria.

BACKGROUND: Chronic urticaria (CU) is a skin disorder characterized by long-lasting release of histamine, and sometimes leukotrienes, from both mast cells and basophils. Although both these substances are potent inductors of contraction of airway smooth muscle, pulmonary function and airway hyperresponsiveness have not been systematically investigated in patients with CU. OBJECTIVE: To assess pulmonary function and airway hyperresponsiveness in patients with CU. METHODS: Twenty-six clinically well-characterized adult patients with CU (M/F 8/18; mean age 47 years) underwent pulmonary function tests and methacholine provocation during a phase of moderate activity of their disease. Twenty-six adult asthmatic patients submitted to methacholine provocation were used as controls. RESULTS: Two patients (8%) had overt asthma on baseline pulmonary function tests. Twenty (77%) patients with a normal baseline pulmonary function showed significant bronchial hyperresponsiveness on methacholine provocation. Altogether, 22/26 (85%) patients had asthma or abnormal bronchial reactivity. Airway hyperresponsiveness was not associated with gender, disease duration, intolerance to NSAID, positive autologous serum skin test or respiratory allergy. On average, asthmatic controls showed a much severer airway hyperresponsiveness than urticaria patients (p < 0.01). CONCLUSION: Patients with CU frequently show bronchial hyperresponsiveness. Prospective studies are needed to assess whether they are at risk for bronchial asthma.     

Differences in the effect of allergen avoidance on bronchial hyperresponsiveness as measured by methacholine,adenosine 5′-monophosphate,and exercise in asthmatic children

Asthma is now considered as an inflammatory airway disease. There is evidence that allergen avoidance reduces clinical symptoms in atopic asthma. We investigated the effect of a month's stay in the hypoallergenic environment of Davos, Switzerland (1560 m) which is relatively free of house dust mite (HDM) on changes in bronchial hyperresponsiveness (BHR), using the challenge tests of adenosine 5′ monophosphate (AMP), exercise and methacholine to test for BHR. Thirteen asthmatic children with an allergy to HDM participated in the study. We measured BHR on admission to the Davos Asthma Center and after 1 month in the house dust-free environment. The medications used by the patients at the time of admission were kept unchanged during this month. No significant difference in BHR was found to methacholine challenge after a 1-month stay at high altitude (P > 0.05). By contrast, the response to AMP was significantly different as indicated by displacement of the dose-response curve to the right by 2.15 doubling concentrations (P = 0.005). We also observed a significant difference in response to exercise (P = 0.03). These results indicate that a month's stay in a hypoallergenic environment caused a reduction in BHR to AMP and exercise, but not to methacholine. In addition, the results support the concept of differences in trigger mechanisms for BHR, and that responses to a methacholine challenge are not the same as responses to an exercise challenge. The observed reduction in BHR in asthmatic children to the indirect bronchial stimuli of AMP and exercise suggest reduced airway inflammation following avoidance of house dust aeroallergens. AMP and exercise challenges may therefore be better indicators of asthmatic airway inflammation than the direct stimulus of methacholine. Pediatr Pulmonol. 1996; 22:147–153. © 1996 Wiley-Liss, Inc.     

Airway hyperresponsiveness: the usefulness of airway hyperresponsiveness testing in epidemiology,in diagnosing asthma and in the assessment of asthma severity

The present PhD thesis was conducted at the Respiratory Research Unit at the Pulmonary Department L in Bispebjerg Hospital, Copenhagen, Denmark and describes airway hyperresponsiveness in asthma patients in four studies. The first study concerned risk factors for the development of asthma in young adults in a 12‐year prospective follow‐up study of a random population sample of 291 children and adolescents from Copenhagen, who were followed up from the age of 7–17 years (1986) until the age of 19–29 years (1998). During follow‐up, 16.1% developed asthma, and in these subjects, the most important predictor of asthma development was airway hyperresponsiveness to histamine at baseline. Airway hyperresponsiveness is associated with more severe asthma and a poorer prognosis in terms of more exacerbations and less chance of remission of the disease. The second study described the relation between airway hyper‐responsiveness to methacholine and the quality of life in 691 asthma patients: In asthma patients with airway hyperresponsiveness to methacholine, the quality of life measured with a validated questionnaire (Junipers Asthma Quality of Life Questionnaire) was significantly reduced compared to asthma patients who did not respond to bronchial provocation with methacholine. Airway hyperresponsiveness is not uncommonly observed in non‐asthmatics, and the response to bronchial provocation with methacholine is therefore relatively non‐specific. The mannitol test is a relatively new bronchial provocation test that acts indirectly on the smooth airway muscle cells through the release of mediators from inflammatory cells in the airways; the mannitol could consequently be a more specific test compared with methacholine. The third study showed that out of 16 non‐asthmatics with airway hyperresponsiveness to methacholine, 15 did not respond to bronchial provocation with mannitol Because of the mechanism of action of mannitol, it seems plausible that the response to mannitol is more closely correlated to airway inflammation in asthma compared with the response to methacholine. The fourth study showed that in 53 adult asthma patients, who did not receive treatment with inhaled steroids, there was a positive correlation between the degree of airway inflammation and the degree of airway responsiveness to mannitol as well as to methacholine. The mannitol does, however, have the advantage of being a faster and simpler test to perform, requiring no additional equipment apart from a spirometer. Conclusions: Airway hyperresponsiveness in children and in adolescents without asthma predicts asthma development in adulthood. Asthma patients with airway hyperresponsiveness to methacholine have a poorer quality of life as well as more severe disease and a poorer prognosis compared with asthma patients without airway hyperresponsiveness. Bronchial provocation with mannitol as well as with methacholine were useful for evaluating the severity of asthma and the degree of airway inflammation, and accordingly for determining the need for steroid statement. The mannitol test does, however, have practical advantages over the methacholine test that make it preferable for clinical use.     

Mannitol and AMP do not induce bronchoconstriction in eosinophilic bronchitis: Further evidence for dissociation between airway inflammation and bronchial hyperresponsiveness

Background and objective: Eosinophilic bronchitis (EB) shares many pathological features with asthma. However, patients with EB do not develop the characteristic physiological abnormalities of asthma: variable airflow obstruction and bronchial hyperresponsiveness (BHR) to a direct bronchial challenge with methacholine. Indirect bronchial challenges with AMP and mannitol are dependent on the presence of airway inflammation, and positive in 10% of asthmatic subjects who have a negative response to methacholine. We have therefore investigated whether subjects with EB are responsive to indirect airway challenge with AMP and mannitol. Methods: Subjects with asthma, EB and healthy controls attended on up to four occasions. After screening, subjects performed bronchial provocation tests to methacholine and then either AMP or mannitol. Each challenge was followed immediately by sputum induction for the measurement of airway inflammation and mast cell‐derived histamine. Results: No subjects with EB responded to either AMP (n = 5) or mannitol (n = 7) while 4/8 and 7/10 subjects with asthma responded to the respective challenges (P = 0.057 for AMP, P = 0.004 for mannitol). There was no difference in induced sputum concentrations of histamine or eosinophil cell counts following methacholine challenge compared with AMP or mannitol. Conclusions: The airways of patients with EB are not responsive to either direct or indirect bronchial challenge. This supports the view that it is the presence of functionally abnormal airway smooth muscle that is the key determinant of BHR in asthma, and that while this may be aggravated by the presence of mucosal airway inflammation, it is not caused by it.     

Adenosine 5'-monophosphate increases levels of leukotrienes in breath condensate in asthma

Hyperresponsiveness (AHR) is a key physiological abnormality in asthma. In clinical and research studies AHR is measured bronchial challenge, with methacholine (MCh), but more recently with adenosine-5'-monophosphate (AMP). In the search for markers of airway inflammation in asthmatic patients, we measured the concentrations of histamine and cysteinyl-leukotrienes (cys-LTs) before and after MCh and AMP challenges in the exhaled breath condensate of 13 patients with mild asthma (FEV1 78.5%pred) and nine healthy non-smokers, using specific enzyme immunoassays. With methacholine challenge we did not find any differences between asthmatics and normal subjects in the pre- and post-challenge concentrations of cys-LTs: 27.2+/-1.4 vs. 29.2+/-1.2 pg/ml and 26.3+/-2.2 vs. 27.5+/-4.2 pg/ml, respectively or histamine: 5.1+/-0.4 vs. 5.1+/-0.6 nM and 4.5+/-0.4 vs. 4.4+/-0.3 nM; P>0.05). In asthmatic patients cys-LT levels were significantly higher after AMP challenge (56.2+/-9.7 vs. 31.7+/-6.9 pg/ml; P<0.05); but there was no difference in healthy subjects (27.2+/-4.6 vs. 30.3+/-4.7 pg/ml). There was no difference in histamine concentrations in asthmatic (5.9+/-1.8 vs. 4.5+/-0.5 nM), or healthy subjects (5.5+/-0.4 vs.5.7+/-0.9 nM) after AMP challenge. In conclusion, our results show that the cys-LTs are increased in exhaled breath condensate after AMP challenge, which may indicate that the AMP acts indirectly by releasing cys-LTs from primed mast cells. The detection of LTs and histamine in exhaled breath condensate may be useful in monitoring asthma.     

Determinants of airway responsiveness to adenosine 5'-monophosphate in school-age children with asthma

Airway responsiveness to adenosine 5'-monophosphate (AMP) is more specific than that to direct stimuli for asthma diagnosis and response to treatment, but is not detected in all patients with asthma. This study was planned to determine predictive factors for responsiveness to AMP in asthmatic children between 7-16 years old. We performed a retrospective analysis of data from 71 asthmatic children who were challenged by AMP in our department. All children were characterized by skin-prick and lung function tests and bronchial challenge with AMP. Data on simultaneous methacholine challenge tests were available for 46 children, 34 of whom were also challenged with a third stimulus, exercise. Potential demographic factors for responsiveness to AMP were assessed by logistic regression analysis within the study group. The proportion of school-age children with asthma responsive to AMP was 39.4%. The geometric mean provocative concentration of AMP causing a 20% decrease in forced expiratory volume in 1 sec (PC20AMP) was 20.50 mg/ml (range, 0.31-377 mg/ml). There were no significant differences either in response to methacholine below 16 mg/ml (P = 0.66) or in PC20 methacholine level (P = 0.075) when we compared AMP-responsive and -nonresponsive children. These two groups also did not differ with respect to their response to exercise challenge in subgroup analysis (P = 0.34). Among school-age children with asthma, allergic rhinitis (P = 0.004) and sensitizaton to grass mix (P = 0.001), cereal mix (P = 0.003), house dust mite (P = 0.024), and cat (P = 0.043) were found to be more frequent in AMP-responsive children than the others. There was no difference in lung function test parameters between children responsive to AMP and the others. Grass pollen sensitization was found to be the only independent predictive factor for determining AMP responsiveness in school-age children with asthma (odds ratio, 5.65; 95% confidence interval, 1.84-17.45; P = 0.003). In conclusion, atopic sensitization is the most important predictive factor for responsiveness to AMP in school-age children with asthma, as in adults.     

Long-term asthma treatment guided by airway hyperresponsiveness in children: a randomised controlled trial.

Management plans for childhood asthma show limited success in optimising asthma control. The aim of the present study was to assess whether a treatment strategy guided by airway hyperresponsiveness (AHR) increased the number of symptom-free days and improved lung function in asthmatic children, compared with a symptom-driven reference strategy. In a multicentre, double-blind, parallel-group, randomised, 2-yr intervention trial, 210 children (aged 6-16 yrs) with moderate atopic asthma, selected on the basis of symptom scores and/or the presence of AHR, were studied. At 3-monthly visits, symptom scores, forced expiratory volume in one second (FEV(1)) and methacholine challenge results were obtained, and medication (five levels of fluticasone with or without salmeterol) adjusted according to algorithms based on symptom score (reference strategy, n = 104) or AHR and symptom score (AHR strategy, n = 102). After 2 yrs, no difference was found in the percentage of symptom-free days between treatment strategies. Pre-bronchodilator FEV(1) was higher in the AHR strategy (2.3% predicted). This was entirely explained by a gradual worsening of FEV(1) in a subgroup of 91 hyperresponsive children enrolled with low symptom scores (final difference between study arms was 6%). Asthma treatment guided by airway hyperresponsiveness showed no benefits in terms of number of symptom-free days, but produced a better outcome in terms of pre-bronchodilator forced expiratory volume in one second in allergic asthmatic children, especially those characterised by low symptom scores despite airway hyperresponsiveness.     

Airway responsiveness to adenosine after a single dose of fluticasone propionate discriminates asthma from COPD

BackgroundRegular treatment with inhaled corticosteroids (ICS) is known to reduce airway hyperresponsiveness (AHR) to adenosine 5′-monophosphate (AMP) in asthma even after a single dose of fluticasone propionate (FP).AimTo determine whether this rapid protective effect of a single dose of FP is also present in COPD.Methods23 mild asthmatic and 24 COPD subjects with documented AHR to both AMP and methacholine took part in a randomized, double-blind, placebo-controlled, crossover study to measure AHR to inhaled AMP and methacholine 2 h after either 1000 μg FP or matched placebo.ResultsIn subjects with asthma, 1000 μg FP in a single dose significantly attenuated the constrictor response to AMP, geometric mean (range) PC20AMP values increasing from a 19.2 (1.3–116.3) to 81.5 (9.6–1600.0) (p < 0.001; post-placebo vs post-FP) mg/ml. Change in the airways response to inhaled AMP after FP was well within test variability in patients with COPD, with PC20AMP values 59.6 (11.3–183.9) and 76.3 (21.0–445.3) (p = 0.022; post-placebo vs post-FP) mg/ml. Additionally, FP failed to significantly attenuate the bronchial response to methacholine in both asthma and COPD subjects. A change in doubling dilution, between placebo and following a single dose of FP, in AMP had a better sensitivity and specificity of 95.8% and 65.2%, compared to methacholine of 79.2% and 43.5% respectively in delineating between COPD and asthma.ConclusionA single dose of 1000 μg FP rapidly improves AHR to AMP in asthmatics but not in COPD subjects. This may provide a convenient way by which provocation challenge with inhaled AMP may help in discriminating asthma from COPD.     

Asymptomatic airway hyperresponsiveness: relationships with airway inflammation and remodelling.

To study the physiopathology and significance of asymptomatic airway hyperresponsiveness (AHR), the clinical and bronchial immunohistological parameters were evaluated in subjects with asymptomatic and symptomatic AHR. Asymptomatic subjects with AHR (eight females/two males, no respiratory symptoms, provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (PC20) <8 mg x mL(-1) and no treatment) were compared with asthmatic subjects paired for age, sex and PC20, and with nonatopic, nonasthmatic controls paired for age and sex. All three groups were evaluated once at baseline, whilst the asymptomatic AHR subjects were re-evaluated after 1 and 2 yrs. Measurements included spirometry, methacholine challenge, serum immunoglobulin (Ig)E, blood eosinophils, and bronchoscopy (at baseline and after 2 yrs only). At first evaluation, the mean blood eosinophil count, total serum IgE level, atopic index, baseline forced expiratory volume in one second (FEV1) and the degree of bronchial epithelial desquamation of the asymptomatic AHR subjects were similar to those of asthmatic subjects. However, they presented focal rather than the continuous bronchial subepithelial fibrosis observed in asthmatics. Their mucosal CD3, CD4, CD25, EG1 and EG2-positive cell counts were intermediate between those of the control subjects and asthmatics. At the end of the 2-yr follow-up, four of them had developed asthma symptoms. At this time, bronchial biopsies revealed an increase in the extent of subepithelial fibrosis and in the number of CD25 and CD4-positive cells, and a decrease in the number of CD8+ cells, particularly in subjects who developed asthma symptoms. These data suggest that asymptomatic airway hyperresponsiveness is associated with airway inflammation and remodelling, and that the appearance of asthma symptoms is associated with an increase in these features, particularly the CD4/CD8 ratio and airway fibrosis. Consequently, this study proposes an association between asymptomatic airway hyperresponsiveness and airway inflammation, structural changes and asthma although these relationships remain to be further evaluated.     

Airway hyperresponsiveness,peak flow variability and inflammatory markers in non‐asthmatic subjects with respiratory infections

Objective: The aim of this study was to characterise non‐asthmatic subjects with asthma‐like symptoms during a common cold, particularly in relation to airway hyperresponsiveness (AHR). Materials and Methods: Subjects with acute respiratory infections and a group of controls (n = 20 + 20), age 20–65 years, underwent bronchial provocations with methacholine, adenosine and cold air. All were non‐smokers and had no history of asthma or heart disease. Those with infection had asthma‐like symptoms (>2). Measurements of exhaled nitric oxide (eNO), serum levels of eosinophil cationic protein (ECP), eosinophil peroxidase, myeloperoxidase and human neutrophil lipocalin were made at each provocation. A 17‐day symptom and peak flow diary was calculated. Results: No differences between the two groups were found, regarding responsiveness to methacholine, adenosine or cold air challenge, as well as the inflammatory markers measured. In the infected group, the mean (standard deviation) ECP was higher in those with AHR to methacholine or cold air [15.7 (6.5) and 11.4 (4.2) µg/L, respectively; P < 0.05]; furthermore, eNO was higher in the infected group [116 (54) and 88 (52) nL/min, respectively; P = 0.055]. The infected group had, at all times, more symptoms and higher peak flow, with a decrease in the symptoms (P = 0.02) and a tendency to change in peak flow variation (P = 0.06). Conclusion: AHR does not seem to be the main cause of asthma‐like symptoms in adults with infectious wheezing. Peak flow variation and symptom prevalence during the post‐infection period may imply airway pathology different from AHR. Please cite this paper as: Björnsson E, Lúdvíksdóttir D, Hedenström H, Eriksson B‐M, Högman M, Venge P and Janson C. Airway hyperresponsiveness, peak flow variability and inflammatory markers in non‐asthmatic subjects with respiratory infections. The Clinical Respiratory Journal 2007;1:42–50.     

Bronchoconstriction induced by inhaled adenosine 5'-monophosphate in subjects with allergic rhinitis.

Adenosine and its related nucleotide, adenosine 5'-monophosphate (AMP) induce bronchoconstriction in asthmatics, probably caused by histamine release from airway mast cells. The objective of this study was to determine the effect of inhaled AMP on lung function in subjects with allergic rhinitis. A total of 52 adults (28 subjects with allergic rhinitis, 14 asthmatics and 10 healthy subjects) were challenged with increasing concentrations of AMP and methacholine. Airflow was assessed after each concentration and the response to each bronchoconstrictor agent was measured by the provocative concentration required to produce a 20% fall (PC20) in forced expired volume in one second (FEV1). All 14 asthmatics, 10 subjects with allergic rhinitis and none of the healthy controls were hyperresponsive to AMP. Subjects with allergic rhinitis had higher prevalence of hyperresponsiveness to AMP than healthy controls (p=0.038). Although the prevalence of hyperresponsiveness for methacholine and for AMP in subjects with allergic rhinitis was similar (39% and 36%, respectively), four subjects had hyperresponsiveness to methacholine but not to AMP, whereas three subjects had hyperresponsiveness to AMP but not to methacholine. To conclude, inhaled adenosine 5'-monophosphate causes airway narrowing in a significantly higher proportion of subjects with allergic rhinitis than healthy volunteers. Furthermore, methacholine and adenosine 5'-monophosphate hyperresponsiveness are not detected in the same individuals with allergic rhinitis, thus suggesting that responsiveness to the two bronchoconstrictor stimuli is not reflecting the same abnormalities of the airways.     

Smoking cessation improves both direct and indirect airway hyperresponsiveness in COPD.

Smoking induces chronic obstructive pulmonary disease (COPD) and is associated with airway inflammation and airway hyperresponsiveness (AHR). It has not been studied in COPD whether direct (methacholine) and indirect (adenosine-5'-monophosphate (AMP)) stimuli are associated with airway inflammation and neither whether smoking cessation improves these features. The current authors cross-sectionally investigated the relationship of AHR to methacholine and AMP with lung function and inflammatory cells in the sputum of 33 smokers with COPD. In addition, changes in these parameters were prospectively assessed in 14 smokers who successfully quit smoking for 1 yr. The presence of AHR to both methacholine and AMP was associated with lower lung function, but not with sputum inflammation. AHR to methacholine and AMP improved significantly after a 1-yr smoking cessation, yet this was unrelated to changes in sputum cell counts. The numbers of neutrophils and epithelial cells significantly increased with smoking cessation. Both direct and indirect airway hyperresponsiveness are associated with lower lung function, but not with sputum inflammation in chronic obstructive pulmonary disease. Interestingly, 1-yr smoking cessation improved both direct and indirect airway hyperresponsiveness, yet without a significant association with changes in lung function or sputum inflammation. Thus, other factors are likely to induce these improvements, e.g. a reduction in stimulation of irritant receptors, airway wall changes or mucus hypersecretion.     

Bronchial responsiveness to adenosine 5'-monophosphate (AMP) and methacholine differ in their relationship with airway allergy and baseline FEV(1)

Bronchial hyperresponsiveness (BHR) and inflammation are central hallmarks of asthma. Studies in patients with asthma suggest that BHR to adenosine 5'-monophosphate (AMP) is a better marker of bronchial inflammation than BHR to methacholine. The association between markers of airway inflammation and BHR to methacholine and AMP in a population of young adults, with mild symptoms if any, was evaluated. A total of 230 subjects who participated in a follow-up study on occupational allergy were included. Before exposure to occupational allergens, subjects completed a questionnaire on respiratory symptoms and were tested for atopy, blood eosinophilia (> or =275/mm(3)), and BHR to methacholine and AMP (> or =15% fall in FEV(1)). Risk estimates were expressed as prevalence ratios (PR) and 95% confidence intervals (95% CI). Dose-response slopes (DRS) for methacholine and AMP were compared between healthy control subjects, self-reported allergic rhinitis, and allergic asthma. BHR to AMP was associated with allergic rhinitis (PR 2.51, 95% CI: 1.22;5.17), allergic asthma (PR 4.38, 95% CI: 1.98;9.66), with atopy (PR 3.87, 95% CI: 1.76;8.52), and blood eosinophilia (PR 3.57, 95% CI: 1.48;8.77), but not with baseline FEV(1). BHR to methacholine was inversely related to prechallenge FEV(1) (PR 0.97, 95% CI: 0.96;0.99). For both methacholine and AMP the geometric mean DRS increased along the axis asymptomatic-allergic rhinitis-allergic asthma, but for AMP the increase was the strongest. In this population study among young adults, BHR to AMP refers to allergic background of airway lability and BHR to methacholine is related to a diminished airway caliber.     

Non-invasive evaluation of lower airway inflammation in hyper-responsive elite cross-country skiers and asthmatics

Asthma-like symptoms and bronchial hyper-responsiveness (BHR) to methacholine are prevalent in competitive cross-country skiers. Whether these symptoms (ski asthma) in these athletes are caused by asthma remains uncertain. Bronchial responsiveness to adenosine 5'-monophosphate (AMP) and nitric oxide (NO) concentration in exhaled air, both indirect markers of asthmatic airway inflammation, were investigated in two non-smoking study populations of skiers and asthmatics. Of 18 skiers with ski asthma, 15 non-steroid and 14 steroid-treated asthmatics, BHR to AMP was present in five (28%), six (40%) and 10 (71%) subjects respectively. Although the groups were not significantly different in responsiveness to methacholine, responsiveness to AMP increased in order of magnitude from ski asthma < non-steroid-treated < steroid-treated asthma. Exhaled NO in 44 (nine with ski asthma) skiers was not significantly different from 82 healthy non-atopic controls [median [interquartile range (IQR)] 6.5 (4.1-9.9) vs. 5.2 (4.2-6.5) ppb]. Exhaled NO in 29 subjects with mild intermittent asthma was three-fold greater [median (IQR) 19.2 (5.1-25.6) ppb, P < 0.01] than in skiers. Exhaled NO was two- and four-fold greater in atopic than non-atopic subjects in the skier (P < 0.001) and asthmatic (P < 0.01) groups, respectively, and was correlated to methacholine responsiveness in atopic asthmatics (n = 22, rho = 0.55, P < 0.01). Exhaled NO was not elevated in ski asthma and may be more useful as a marker of atopic status than inflammation in the lower airway in skiers. Few skiers were hyper-responsive to AMP, indicating that pre-activated mucosal mast cells are not a predominant feature in ski asthma.     

支气管哮喘气道高反应易感基因原钙黏蛋白1研究进展

支气管哮喘关键病理生理特征之一是气道高反应性,气道高反应发生与气道上皮屏障功能缺陷密切相关。研究表明原钙黏蛋白1（protocadherin-1,PCDH1）基因通过影响气道上皮屏障功能进而调控气道高反应性的发生发展。而PCDH1基因影响气道上皮屏障功能的作用机制尚不清楚,需要进一步研究其在气道上皮屏障功能发生发展中的表达、功能以及分子机制,并探索其作用的信号通路。该文对目前气道高反应易感基因PCDH1的研究进展作一综述。