Changes in sputum counts and airway hyperresponsiveness after budesonide: monitoring anti-inflammatory response on the basis of surrogate markers of airway inflammation

The use of the mannitol test as an outcome measure in asthma intervention studies: a review and practical recommendations

BACKGROUND

The mannitol test is an indirect bronchial challenge test widely used in diagnosing asthma. Response to the mannitol test correlates with the level of eosinophilic and mast cell airway inflammation, and a positive mannitol test is highly predictive of a response to anti-inflammatory treatment with inhaled corticosteroids. The response to mannitol is a physiological biomarker that may, therefore, be used to assess the response to other anti-inflammatory treatments and may be of particular interest in early phase studies that require surrogate markers to predict a clinical response. The main objectives of this review were to assess the practical aspects of using mannitol as an endpoint in clinical trials and provide the clinical researcher and respiratory physician with recommendations when designing early clinical trials.

METHODS

The aim of this review was to summarise previous uses of the mannitol test as an outcome measure in clinical intervention studies. The PubMed database was searched using a combination of MeSH and keywords. Eligible studies included intervention or repeatability studies using the standard mannitol test, at multiple timepoints, reporting the use of PD₁₅ as a measure, and published in English.

RESULTS

Of the 193 papers identified, 12 studies met the inclusion criteria and data from these are discussed in detail. Data on the mode of action, correlation with airway inflammation, its diagnostic properties, and repeatability have been summarised, and suggestions for the reporting of test results provided. Worked examples of power calculations for dimensioning study populations are presented for different types of study designs. Finally, interpretation and reporting of the change in the response to the mannitol test are discussed.

CONCLUSIONS

The mechanistic and practical features of the mannitol test make it a useful marker of disease, not only in clinical diagnoses, but also as an outcome measure in intervention trials. Measuring airway hyperresponsiveness to mannitol provides a novel and reproducible test for assessing efficacy in intervention trials, and importantly, utilises a test that links directly to underlying drivers of disease.

COVID-19 with asthma: A case report

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a public health emergency of international concern. The global population lacks immunity to COVID-19 and is generally susceptible. Underlying conditions, especially chronic respiratory diseases, may affect progression, treatment and prognosis of COVID-19.

CASE SUMMARY

We report a patient with confirmed COVID-19 combined with asthma. It took 41 d from disease onset to discharge to obtain two negative tests for this coronavirus.

CONCLUSION

This case indicates the dynamic clinical characteristics, laboratory and computed tomography findings and adjustment of treatment, and the possible relationship between glucocorticoid therapy and coronavirus clearance.

Comparison of methacholine and mannitol challenges: importance of method of methacholine inhalation

Background

Direct inhalation challenges (e.g. methacholine) are stated to be more sensitive and less specific for a diagnosis of asthma than are indirect challenges (e.g. exercise, non-isotonic aerosols, mannitol, etc.). However, data surrounding comparative sensitivity and specificity for methacholine compared to mannitol challenges are conflicting. When methacholine is inhaled by deep total lung capacity (TLC) inhalations, deep inhalation inhibition of bronchoconstriction leads to a marked loss of diagnostic sensitivity when compared to tidal breathing (TB) inhalation methods. We hypothesized that deep inhalation methacholine methods with resulting bronchoprotection may be the explanation for conflicting sensitivity/specificity data.

Methods

We reviewed 27 studies in which methacholine and mannitol challenges were performed in largely the same individuals. Methacholine was inhaled by dosimeter TLC methods in 13 studies and by tidal breathing in 14 studies. We compared the rates of positive methacholine (stratified by inhalation method) and mannitol challenges in both asthmatics and non-asthmatics.

Results

When methacholine was inhaled by TLC inhalations the prevalence of positive tests in asthmatics, 60.2% (548/910), was similar to mannitol, 58.9% (537/912). By contrast, when methacholine was inhaled by tidal breathing the prevalence of positive tests in asthmatics 83.1% (343/413) was more than double that of mannitol, 41.5% (146/351). In non-asthmatics, the two methacholine methods resulted in positive tests in 18.8% (142/756) and 16.2% (27/166) by TLC and TB inhalations respectively. This compares to an overall 8.3% (n = 76) positive rate for mannitol in 913 non-asthmatics.

Conclusion

These data support the hypothesis that the conflicting data comparing methacholine and mannitol sensitivity and specificity are due to the method of methacholine inhalation. Tidal breathing methacholine methods have a substantially greater sensitivity for a diagnosis of asthma than either TLC dosimeter methacholine challenge methods or mannitol challenge. Methacholine challenges should be performed by tidal breathing as per recent guideline recommendations. Methacholine (more sensitive) and mannitol (more specific) will thus have complementary diagnostic features.

Short-term effect of once-daily fluticasone furoate on methacholine-induced bronchoconstriction in mild asthmatics

BACKGROUND

Inhaled corticosteroids (ICS) decrease airway inflammation and airway hyperresponsiveness (AHR). Previous studies have generally investigated the effect of ICS on methacholine-induced AHR following weeks or months of medium to high dose treatment.

PURPOSE

The short-term effects of once-daily fluticasone furoate (FF) 100 mcg on methacholine-induced AHR and airway inflammation were examined over the course of one week.

METHODS

Eleven mild asthmatics completed this randomized, double-blind crossover study. Once-daily FF (100 mcg) and identical appearing placebo Ellipta® inhalers were given for 7 days with a 2-week washout. Methacholine challenges were performed before and 24 h after the first, third and seventh doses. Fractional exhaled nitric oxide (FeNO) was measured initially and at 7 days.

RESULTS

FF significantly (p = 0.0009-0.0078) increased methacholine PD₂₀ (provocative dose causing 20% fall in forced expiratory volume in 1 s) at all times. Doubling dose shifts (95% CI) were 1.23 (0.60-1.86), 1.17 (0.68-1.67) and 1.44 (0.93-1.94) after the first, third and seventh dose respectively. FeNO (geometric mean, 95% CI) decreased significantly (p = 0.0049) following FF treatment from 37.9 ppb (23.7-60.5) initially to 22.9 ppb (14.8-35.5) at 7 days. Placebo did not affect methacholine PD₂₀ or FeNO.

CONCLUSION

Single-dose FF 100 mcg decreased methacholine AHR at 24 h without significant further improvement with continued daily use over 7 days. The inhibition in AHR after one week of daily dosing coincided with a significant decrease in FeNO at 7 days. Contrary to past assumptions, the ICS FF appears to rapidly reduce AHR to methacholine.

Effect of preoperative inhaled budesonide on pulmonary injury after cardiopulmonary bypass: A randomized pilot study

BACKGROUND

Cardiopulmonary bypass can result in lung injury. This prospective, double-blinded, randomized trial aimed to evaluate the protective effect of inhaled budesonide on lung injury after cardiopulmonary bypass.

METHODS

Sixty patients, aged 25 to 65 years, requiring cardiopulmonary bypass were randomized to groups treated with saline or budesonide inhalation preoperatively. The respiratory mechanics were recorded. Bronchoalveolar lavage fluid was collected before cardiopulmonary bypass and after sternal closure. Serum and bronchoalveolar lavage fluid levels of proinflammatory and anti-inflammatory factors were analyzed. The primary end point was the lowest ratio of the partial pressure of arterial oxygen to the fraction of inspired oxygen after cardiopulmonary bypass. The durations of ventilation and postoperative recovery time were noted.

RESULTS

Budesonide significantly improved respiratory mechanics after cardiopulmonary bypass. Budesonide improved the partial pressure of arterial oxygen to the fraction of inspired oxygen ratio from 8 to 48 hours after the operation. Budesonide shortened the durations of mechanical ventilation and postoperative recovery time. Budesonide decreased the levels of proinflammatory factors while increasing the levels of anti-inflammatory factors in bronchoalveolar lavage fluid and serum (all P < .05). The macrophage and neutrophil counts, and protein and elastase concentrations were decreased by budesonide treatment.

CONCLUSIONS

Budesonide treatment shortened the durations of mechanical ventilation, inhibited local and systemic inflammation, and improved respiratory function after cardiopulmonary bypass.

Extrafine compared to non-extrafine particle inhaled corticosteroids in smokers and ex-smokers with asthma

BACKGROUND

Smoking is as prevalent in asthmatics as in the general population. Asthmatic smokers benefit less from inhaled corticosteroids (ICS) than non-smoking asthmatics, possibly due to more smoking-induced small airways disease. Thus targeting small airways may be important in treating asthmatic (ex-)smokers. We hypothesized that extrafine particle ICS improve small airways function more than non-extrafine particle ICS in asthmatic (ex-)smokers.

METHODS

We performed an open-label, randomized, three-way cross-over study comparing extrafine beclomethasone (HFA-QVAR) to non-extrafine beclomethasone (HFA-Clenil) and fluticasone (HFA-Flixotide) in 22 smokers and 21 ex-smokers with asthma (?5 packyears).

RESULTS

Improvement from baseline in PD₂₀ adenosine after using QVAR, Clenil or Flixotide was 1.04 ± 1.71, 1.09 ± 2.12 and 0.94 ± 1.97 doubling doses, mean ± standard deviation (SD), respectively. The change from baseline in R₅-R₂₀ at PD₂₀ adenosine after using QVAR, Clenil or Flixotide was ?0.02 ± 0.27, 0.02 ± 0.21, and ?0.02 ± 0.31 kPa sL^?1, mean ± SD, respectively. The change in PD₂₀ adenosine and R₅-R₂₀ at PD₂₀ adenosine were neither statistically significant different between QVAR and Clenil (p = 0.86 and p = 0.82) nor between QVAR and Flixotide (p = 0.50 and p = 0.96).

CONCLUSION

Similar effectiveness in improving small airways function was found for extrafine and non-extrafine particle ICS treatment for asthmatic smokers and ex-smokers.

Association of symptom control with changes in lung function, bronchial hyperresponsiveness, and exhaled nitric oxide after inhaled corticosteroid treatment in children with asthma

BACKGROUND

A key therapeutic approach to asthma, which is characterized by chronic airway inflammation, is inhaled corticosteroid (ICS). This study evaluated the association of symptom control with changes in lung function, bronchial hyperresponsiveness (BHR), and exhaled nitric oxide (eNO) after ICS treatment in asthmatic children.

METHODS

A total of 33 children aged between 5 and 12 years with mild to moderate persistent asthma were treated with 160 μg ciclesonide per day for 3 months. At days 0 and 90, the following parameters were assessed: asthma symptom scores; lung function, including forced expiratory volume in one second (FEV₁), forced vital capacity (FVC), and forced expiratory flow at 25-75% of forced vital capacity (FEF_25-75%); BHR to methacholine and adenosine 5-monophosphate (AMP); and eNO.

RESULTS

Asthma symptom scores, lung function parameters, BHR to methacholine and AMP, and eNO levels at day 90 were significantly improved versus day 0 (all p < 0.001). Symptom scores at day 90 were not correlated with changes in lung function and BHR to methacholine during the follow-up period, whereas those at day 90 were more closely correlated with changes in BHR to AMP (r = 0.511, p = 0.003) than with eNO (r = -0.373, p = 0.035). Additionally, changes in PC₂₀ AMP were correlated with changes in PC₂₀ methacholine (r = 0.451, p = 0.011) and eNO (r = -0.474, p = 0.006).

CONCLUSIONS

Changes in the BHR to AMP, and to a lesser extent eNO, correlate with asthma symptom control after ICS treatment. BHR to AMP may better reflect the relationship between improved airway inflammation due to ICS treatment and asthma symptoms.

Does airway hyperresponsiveness monitoring lead to improved asthma control?

The current guidelines recommend an approach to asthma management based on asthma control, rather than asthma severity. Although several specific questionnaires have been developed and control criteria have been established based on clinical guidelines, the evaluation of asthma control is still not optimal. In general, these indicators provide adequate assessment of current control, but they are more limited when estimating future risk. There is much evidence demonstrating the persistence of airway inflammation and airway hyperresponsiveness (AHR) in patients with total control. Therefore, the objective of this review was to analyse the possible role of AHR monitoring as an instrument for assessing asthma control. We will evaluate its capacity as an indicator for future risk, both for estimating the possibility of clinical deterioration and loss of lung function or exacerbations. Furthermore, its relationship with inhaled corticosteroid treatment will be analysed, while emphasizing its capacity for predicting response and adjusting dosage, as well as information about the capability of AHR for monitoring treatment. Last of all, we will discuss the main limitations and emerging opportunities of AHR as an assessment instrument for asthma control.

The Asthma-COPD Overlap Syndrome

Although in textbooks asthma and chronic obstructive pulmonary disease (COPD) are viewed as distinct disorders, there is increasing awareness that many patients have features of both. This article reviews the asthma-COPD overlap syndrome.

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

BACKGROUND

Regular 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).

AIM

To determine whether this rapid protective effect of a single dose of FP is also present in COPD.

METHODS

23 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.

RESULTS

In 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.

CONCLUSION

A 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.

Bronchial inflammation and hyperresponsiveness in well controlled asthma

BACKGROUND

Little research has been devoted to the characteristics of bronchial inflammation in patients with stable, well controlled asthma.

OBJECTIVE

The aim of this study was to assess the degree and type of airway inflammation and to investigate the relationship between inflammation and bronchial hyperresponsiveness in patients with well controlled asthma.

METHODS

A cross-sectional study was conducted in 84 adult patients (43 men, mean age 43 years) with documented well controlled asthma. Induced sputum samples were obtained and cell types determined by differential cell count. Spirometry and methacholine challenge testing were performed. Asthma Control Questionnaire (ACQ) was used to assess symptoms. Patients were included if their ACQ score was < 0.75.

RESULTS

A total of 59 patients had persistent bronchial inflammation: 28 cases were considered eosinophilic, 28 neutrophilic, and 3 mixed. Median (range) percentage of eosinophils was 4% (0-64) in patients testing positive to methacholine challenge (n = 66) and 1% (0-3) in those testing negative (n = 18) (P = 0.003). A positive correlation was found between eosinophil percentage and the methacholine dose/response ratio (r = 0.477, P = 0.0001). The geometric mean (95% CI) of the methacholine PC20 was 1.74 mg/mL (1.04-2.93) in patients with eosinophilic inflammation and 4.14 mg/mL (2.5-6.84) in those with neutrophilic inflammation (P = 0.03).

CONCLUSIONS

Inflammation and bronchial hyperresponsiveness persist in most patients with well controlled asthma.

CLINICAL RELEVANCE

The study demonstrates that eosinophilic or neutrophilic inflammation persisted in most well controlled asthma patients despite the fact that their condition was controlled and therefore, measurement of bronchial inflammation seems essential to achieve proper asthma control.

Past, present and future uses of methacholine testing

Methacholine challenge testing is a valuable diagnostic and research tool used by clinicians to assist in the diagnosis of asthma, and by researchers to understand disease pathophysiology and assess novel therapeutic efficacy. The use of methacholine challenge in asthma relates to its direct effect on airway smooth muscle (i.e., bronchoconstriction) as a measure of airway hyperresponsiveness, a cardinal feature of asthma. Airway hyperresponsiveness has been documented in other airway disorders, including chronic obstructive pulmonary disease, cystic fibrosis and allergic rhinitis; however, there is little clinical application of methacholine challenge in these conditions as a diagnostic or disease management tool. The authors will review the aspects of methacholine challenge testing, as they relate to asthma, and point out its usefulness in clinical research. A brief review of past (historical) uses and speculation as to the future uses of methacholine challenge will also be discussed.

Diagnostic exercise challenge testing

This article reviews the diagnostic challenge methods-both exercise and surrogate-for diagnosis of exercise-induced bronchoconstriction (EIB) and EIB with known asthma. Indirect challenges that release the entire repertoire of mediators representative of EIB and asthma are more specific for diagnosis and are recommended over direct challenges such as methacholine challenge, which are sensitive but nonspecific. Self-reported history and empiric therapeutic trials are not adequate for diagnosis of EIB with or without known asthma. Objective pulmonary function documentation with bronchodilator reversibility or exercise or surrogate challenge are optimal for diagnosis of EIB or EIB with known asthma. Such objective pulmonary function documentation is optimal for the proper management and healthy lifestyle of the exercising athlete or individual.

Direct challenge tests: Airway hyperresponsiveness in asthma: its measurement and clinical significance

Direct bronchoprovocation challenges (eg, methacholine), which act directly on a specific airway smooth muscle receptor, are the most commonly performed challenge tests. Cut points have been arbitrarily selected to give high sensitivity and negative predictive values. In subjects with clinically current symptoms (within a few days) who inhale methacholine without deep inhalations, a normal methacholine test (provocative concentration causing a 20% fall in FEV(1) [PC(20)] > 16 mg/mL) rules out (current) asthma with reasonable certainty. A positive test in the moderate or greater range (PC(20) < 1 mg/mL) has high specificity and positive predictive value, comparable to the indirect challenges. Values between these levels are consistent with, but not diagnostic of, asthma. The positive predictive value (for clinical asthma) will increase the closer the PC(20) is to 1 mg/mL, the higher the pretest probability is for asthma and the more the methacholine-induced symptoms resemble the naturally occurring symptoms. Direct challenges are more sensitive and less specific than indirect challenges (exercise, adenosine monophosphate, mannitol, etc).

Monitoring asthma therapy using indirect bronchial provocation tests

OBJECTIVES

Bronchial provocation tests that assess airway hyperresponsiveness (AHR) are known to be useful in assisting the diagnosis of asthma and in monitoring inhaled corticosteroid therapy. We reviewed the use of bronchial provocation tests that use stimuli that act indirectly for monitoring the benefits of inhaled corticosteroids.

DATA SOURCE

Published clinical trials investigating the effect of inhaled corticosteroids on bronchial hyperresponsiveness in persons with asthma were used for this review.

STUDY SELECTION

Studies using indirect stimuli to provoke airway narrowing such as exercise, eucapnic voluntary hyperventilation, cold air hyperventilation, hypertonic saline, mannitol, or adenosine monophosphate (AMP) to assess the effect of inhaled corticosteroids were selected.

RESULTS

Stimuli acting indirectly result in the release of a variety of bronchoconstricting mediators such as leukotrienes, prostaglandins, and histamine, from cells such as mast cells and eosinophils. A positive response to indirect stimuli is suggestive of active inflammation and AHR that is consistent with a diagnosis of asthma. Persons with a positive response to indirect stimuli benefit from daily treatment with inhaled corticosteroids. Symptoms and lung function are not useful to predict the long-term success of inhaled corticosteroid dose as they usually resolve rapidly, and well before inflammation and AHR has resolved. Following treatment, AHR to indirect stimuli is attenuated. Further, during long-term treatment, asthmatics can become as non-responsive as non-asthmatic healthy persons, suggesting that asthma is not active.

CONCLUSIONS

Non-responsiveness to indirect bronchial provocation tests following inhaled corticosteroids occurs weeks to months following the resolution of symptoms and lung function. Non-responsiveness to indirect stimuli may provide a goal for adequate therapy with inhaled corticosteroids.

Current and future use of the mannitol bronchial challenge in everyday clinical practice

OBJECTIVES

Asthma is a disease associated with inflammation, airway hyperresponsiveness (AHR) and airflow limitation. Clinical diagnosis and management of asthma often relies on assessment of lung function and symptom control, but these factors do not always correlate well with underlying inflammation. Bronchial challenge tests (BCTs) assess AHR, and can be used to assist in the diagnosis and management of asthma.

DATA SOURCE

Data presented at the symposium 'Use of inhaled mannitol for assessing airways disease' organised by the Allied Respiratory Professionals Assembly (9) of the European Respiratory Society (ERS) at the ERS Congress, Berlin 2008.

RESULTS

Indirect challenge tests such as exercise testing, hypertonic saline or adenosine 5'-monophosphate (AMP) are more specific though less sensitive than direct challenge tests (such as methacholine) for identifying patients with active asthma. Indirect BCTs may be used to diagnose exercise-induced bronchoconstriction or AHR consistent with active asthma, to evaluate AHR that will respond to treatment with anti-inflammatory drugs and to determine the effectiveness and optimal dosing of such therapy. An ideal indirect challenge test should be standardised and reproducible, and the test result should correlate with the degree of airway inflammation. The mannitol BCT provides a standardised and rapid point-of-need test to identify currently active asthma, and is clinically useful in the identification of patients with asthma who are likely to benefit from inhaled corticosteroid therapy.

CONCLUSION

In the future, mannitol BCT may be added to lung function and symptom assessment to aid in the everyday management of asthma.

Acute additive effect of montelukast and beclomethasone on AMP induced bronchoconstriction

Bronchial hyperresponsiveness to 5-adenosine mono-phosphate (AMP) is a marker of airway inflammation. Inhaled corticosteroids and antileukotrienes are used as anti-inflammatory drugs for the treatment of asthma. To find out if these two drugs exert their protection in an additive fashion, we compared the effects of acute treatment with inhaled beclomethasone (BDP) and montelukast (ML), alone or in combination, on methacholine and AMP induced bronchoconstriction. 15 asthmatic patients undertook methacholine and AMP challenges at baseline and after receiving ML or BDP, alone or in combination, in a randomized, double-blind, double-dummy placebo-controlled, crossover design. BDP pretreatment significantly increased the AMP PC(20) value (68.34+/-15.9mg/mL) as compared to placebo (22.87+/-5.7mg/mL). Combined treatment, BDP plus ML, afforded a further significant increase of AMP PC(20) (154.57+/-55.0mg/mL) as compared to each single treatment. The significant protection exerted by combined treatment as compared to each single active treatment was also demonstrated by the change of AMP PC(20) doubling dose as compared to placebo and each single active treatment. Our findings suggest that these two agents exert their acute additive protection against AMP induced bronchoconstriction acting on distinct inflammatory pathways and their combined use might provide greater protection against inflammatory response elicited by AMP than either drug alone.

Direct and indirect challenges in the clinical assessment of asthma

OBJECTIVE

To compare direct and indirect bronchoprovocation challenges in the clinical assessment of asthma.

DATA SOURCES

PubMed search using the keywords adenosine monophosphate, eucapnic voluntary hyperpnea, exercise, hypertonic saline, mannitol, and methacholine challenges and asthma.

STUDY SELECTION

Articles were selected based on their relevance to the topic of this review.

RESULTS

Methacholine is the most widely used direct challenge. Methacholine is highly sensitive, provided symptoms are clinically current and deep inhalations are avoided during inhalation. There are many causes of a false-positive test result. Specificity is increased if the pretest probability of asthma is greater, if the methacholine responsiveness is moderate or greater, and if the methacholine-induced symptoms mimic the natural symptoms. Indirect challenges are more specific for asthma but are insensitive, particularly for mild and/or well-controlled asthma. The lower sensitivity may relate to the fact that many indirect challenges (eg, exercise, eucapnic voluntary hyperpnea, adenosine monophosphate) are dose limited (ie, the dose of stimulus cannot be increased above a level based on physiology or solubility). Indirect challenges also correlate better with airway inflammation and are more responsive to anti-inflammatory treatments.

CONCLUSIONS

Direct challenges (ie, methacholine), because of the high sensitivity, function best to exclude clinically current asthma; a positive test result is consistent with but not diagnostic of asthma. By contrast, indirect challenges are superior for confirming asthma and are the challenges of choice when exercise bronchospasm is the question (eg, certification for international athletic competition, armed forces, scuba diving). Indirect challenges would be preferred for monitoring of asthma control and used serially to help diagnose occupational asthma.

Diagnostic and therapeutic value of airway challenges in asthma

Airway challenges are of value in the assessment of asthma. Direct challenges (histamine and methacholine) are highly sensitive for clinically current symptomatic asthma and particularly useful to exclude current asthma when they are negative. Indirect challenges (exercise, eucapnic voluntary hyperventilation, adenosine monophosphate, hypertonic saline, mannitol) are more specific but very insensitive for clinical asthma. They are of particular value to confirm asthma and to differentiate asthma from other airway diseases, such as chronic airflow limitation. The indirect stimuli are the challenges of choice for evaluating exercise-induced bronchoconstriction.

The effect of low-dose inhaled budesonide on PC20 AMP levels in patients with mild asthma: a 3-month follow-up study

Adenosine monophosphate (AMP) challenge is a diagnostic tool for asthma. The aim of this study is to evaluate the effect of low dose inhaled budesonide (IB) on PC(20)AMP levels. Seventeen stable mild asthmatic patients were prospectively recruited. After initial testing, patients were administered 400 microg of inhaled budesonide. AMP challenge was then repeated at the 12th hour and 5th,15th, 30th, and 90th days of the treatment. AMP challenge resulted in negative in 47% of the patients at 12(-)hour testing. This study suggests that low-dose IB may return airway responsiveness as early as 12 hours and AMP challenge may be effectively used for treatment monitorization.

Effect of age on relationship between exhaled nitric oxide and airway hyperresponsiveness in asthmatic children

BACKGROUND

Numerous studies have examined the relationship between the fractional concentration of exhaled nitric oxide (Feno) and airway hyperresponsiveness (AHR). Our objective was to determine the effects of age on the relationship between Feno and AHR in asthmatic children.

METHODS

AHR was examined in 267 asthmatic patients (age range, 5 to 20 years). A challenge test was performed using acetylcholine chloride (Ach). We determined the provocative concentration of Ach producing a 20% decrease in FEV(1) from baseline (PC(20)). Feno was examined using the recommended online method before the Ach challenge test.

RESULTS

In children < 12 years of age (range, 5 to 11 years), decreasing AHR (PC(20)) was significantly related to higher Feno (r = -0.43; beta = -0.28; p < 0.001). In adolescents >or= 12 years of age (range, 12 to 20 years), decreasing PC(20) was associated with peripheral airway obstruction (FEV(1): r = 0.32; beta = 5.5; p = 0.002; forced expiratory flow at 50% of the FVC: r = 0.24; beta=8.4; p = 0.006; and forced expiratory flow at 25% of FVC: r = 0.28; beta=11.4; p = 0.002). AHR and Feno were weakly related (r = -0.18; beta = -0.14; p = 0.02).

CONCLUSIONS

In children with asthma, AHR is associated with airway inflammation. AHR in children with asthma may consist of variable components mainly reflecting airway inflammation. In contrast, in adolescents with asthma, AHR is associated with airway structural changes and weakly with airway inflammation. AHR in adolescents with asthma may consist of chronic components mainly reflecting airway remodeling.

Glucocorticoid actions on airway epithelial responses in immunity: functional outcomes and molecular targets

Research on the biology of airway epithelium in the last decades has progressively uncovered the many roles of this cell type during the immune response. Far from the early view of the epithelial layer simply as a passive barrier, the airway epithelium is now considered a central player in mucosal immunity, providing innate mechanisms of first-line host defense as well as facilitating adaptive immune responses. Alterations of the epithelial phenotype are primarily involved in the pathogenesis of allergic airways disease, particularly in severe asthma. Appreciation of the epithelium as target of glucocorticoid therapy has also grown, because of studies defining the pathways and mediators affected by glucocorticoids, and studies illustrating the relevance of the control of the response from epithelium in the overall efficacy of topical and systemic therapy with glucocorticoids. Studies of the mechanism of action of glucocorticoids within the biology of the immune response of the epithelium have uncovered mechanisms of gene regulation involving both transcriptional and posttranscriptional events. The view of epithelium as therapeutic target therefore has plenty of room to evolve, as new knowledge on the role of epithelium in immunity is established and novel pathways mediating glucocorticoid regulation are elucidated.

Clinical implications of airway hyperresponsiveness in COPD

COPD represents one of the leading causes of mortality in the general population. This study aimed at evaluating the relationship between airway hyperresponsiveness (AHR) and COPD and its relevance for clinical practice. We performed a MEDLINE search that yielded a total of 1919 articles. Eligible studies were defined as articles that addressed specific aspects of AHR in COPD, such as prevalence, pathogenesis, or prognosis. AHR appears to be present in at least one out of two individuals with COPD. The occurrence of AHR in COPD is influenced by multiple mechanisms, among which impairment of factors that oppose airway narrowing plays an important role. The main determinants of AHR are reduction in lung function and smoking status. We envision a dual role of AHR: in suspected COPD, specific determinants of AHR, such as reactivity and the plateau response, may help the physician to discriminate COPD from asthma; in definite COPD, AHR may be relevant for the prognosis. Indeed, AHR is an independent predictor of mortality in COPD patients. Smoking cessation has been shown to reduce AHR. Further studies are needed to elucidate whether this functional change is associated with improvement in lung function and respiratory symptoms.

Changes in airway hyperresponsiveness following smoking cessation: comparisons between Mch and AMP

BACKGROUND

Given the observed association between smoking, inflammation and airway hyperresponsiveness (AHR) one may predict that smoking cessation may improve AHR. However, only a few studies have investigated the effect of smoking on AHR and their results appear to be conflicting depending on the stimulus used in their bronchoprovocation protocol. The aim of the current study was to compare changes in AHR between direct (methacholine (Mch)) and indirect (adenosine 5'monophosphate (AMP)) stimuli before and at different time points after smoking cessation in smokers with allergic rhinitis (+/-asthma).

METHODS

We have prospectively studied changes in AHR to inhaled Mch and AMP in smokers with allergic rhinitis (+/-asthma), before and at 6 and 12 months after smoking cessation.

RESULTS

It was found that 28% (16/57) of the participants had quit smoking by the end of the study. No significant change in AHR was observed in smoking cessation failures. A significant improvement in AHR to AMP but not Mch was observed 6 months after smoking cessation in quitters; a 1.2 doubling concentrations change in PC20 AMP was measured whereas only a 0.4 doubling concentrations change was observed for PC20 Mch. However, after 12 months smoking cessation the improvement in AHR became significant for both AMP and Mch, their dose-response curves being displaced to the right to a similar extent (1.4 and 1.1 doubling concentrations for AMP and Mch, respectively).

CONCLUSION

Smoking cessation can improve AHR in smokers who quit with a 6 months improvement being reported for the airways response to AMP but not Mch. AMP challenge may detect earlier changes in AHR in smokers during smoking cessation.

Adenosine receptors: promising targets for the development of novel therapeutics and diagnostics for asthma

Interest in the role of adenosine in asthma has escalated considerably since the early observation of its powerful bronchoconstrictor effects in asthmatic but not normal airways. A growing body of evidence has emerged in support of a proinflammatory and immunomodulatory role for the purine nucleoside adenosine in the pathogenic mechanisms of chronic inflammatory disorders of the airways such as asthma. The fact that adenosine enhances mast cell allergen-dependent activation, that elevated levels of adenosine are present in chronically inflamed airways, and that adenosine given by inhalation cause dose-dependent bronchoconstriction in subjects with asthma emphasizes the importance of adenosine in the initiation, persistence and progression of these common inflammatory disorders of the airways. These distinctive features of adenosine have been recently exploited in the clinical and research setting to identify innovative diagnostic applications for asthma. In addition, because adenosine exerts its multiple biological activities by interacting with four adenosine receptor subtypes, selective activation or blockade of these receptors may lead to the development of novel therapies for asthma.

Adenosine signaling in asthma and chronic obstructive pulmonary disease

PURPOSE OF REVIEW

The chronic lung diseases, asthma and chronic obstructive pulmonary disease, are pulmonary disorders in which persistent inflammation and alterations in lung structure contribute to a progressive loss of lung function. Although the exact type of inflammation and damage in each disease is distinct, they share the common feature that they are chronic in nature. Despite efforts, little is known about the cellular and molecular mechanisms that drive the chronicity of these two diseases. This review will summarize important findings regarding the role of adenosine, a signaling nucleoside implicated in the pathogenesis of these two disorders.

RECENT FINDINGS

Aerosolized adenosine induces bronchoconstriction in patients with asthma and chronic obstructive pulmonary disease primarily through the release of mast cell mediators. In this setting it can not only be used to aid in diagnosis but also to monitor patient responses to steroid therapy. Adenosine levels are elevated in the lungs of asthma patients, indicating greater flux through adenosine receptor signaling pathways. In-vitro studies have shown adenosine to access pathways leading to the genesis of chronic inflammation via the release of proinflammatory cytokines and chemokines. Animal studies demonstrate that merely elevating adenosine levels in the mouse is sufficient to induce a pulmonary phenotype with features of asthma and chronic obstructive pulmonary disease.

SUMMARY

Identifying mediators regulating the chronic nature of asthma and chronic obstructive pulmonary disease is critical towards advancements in treatment options. Adenosine has been implicated in promoting the inflammation and airway remodeling seen in chronic lung disease and thus makes an attractive therapeutic target.

A critical appraisal of methods used in early clinical development of novel drugs for the treatment of asthma

Asthma is a heterogeneous disorder characterized by chronic airway inflammation, hyperresponsiveness and remodeling. Being the hallmark of asthma, airway inflammation has become the most important target for therapeutic agents. Consequently, during the past decade various semi-and non-invasive methods have been explored to sample the airway inflammation in asthma. In this review, we provide a practical overview of the current status of various sampling techniques including sputum induction, exhaled breath analysis, and bronchoprovocation tests (BPTs). We focus on their applicability for monitoring in clinical practice and in intervention trials in asthma.

Adenosine in the airways: implications and applications

Adenosine in a signaling nucleoside eliciting many physiological responses. Elevated levels of adenosine have been found in bronchoalveolar lavage, blood and exhaled breath condensate of patients with asthma a condition characterized by chronic airway inflammation. In addition, inhaled adenosine-5'-monophosphate induces bronchoconstriction in asthmatics but not in normal subjects. Studies on animals and humans have shown that bronchoconstriction is most likely due to the release of inflammatory mediators from mast cells. However a number of evidences suggest that adenosine modulates the function of many other cells involved in airway inflammation such as neutrophils, eosinophils, lymphocytes and macrophages. Although this clear pro-inflammatory role in the airways, adenosine may activate also protective mechanisms particularly against lung injury. For many years this dual role of adenosine in the respiratory system has represented an enigma, and only recently it has become clear that biological functions of adenosine are mediated by four distinct subtypes of receptors (A1, A2A, A2B, and A3) and that biological responses are determined by the different pattern of receptors distribution in specific cells. Therefore, pharmacological modulation of adenosine receptors, particularly A2B, may represent a novel therapeutic approach for inflammatory diseases. Moreover, as bronchial response to adenosine strictly reflects airway inflammation in asthma, bronchial challenge with adenosine is considered a valuable clinical tool to monitor airway inflammation, to follow the response to anti-inflammatory treatments and to help in the diagnostic discrimination between asthma and chronic obstructive lung disease.

Effect of fluticasone propionate-salmeterol therapy on seasonal changes in airway responsiveness and exhaled nitric oxide levels in patients with pollen-induced asthma

BACKGROUND

There has been concern that in allergic asthmatic patients there might be an interactive effect on inflammation between regular salmeterol use and exposure to allergens, resulting in increased airway responsiveness.

OBJECTIVE

To determine the effects of salmeterol on allergen-induced changes in airway responsiveness and exhaled nitric oxide (ENO) levels in allergic asthmatic patients concomitantly taking inhaled corticosteroids.

METHODS

Forty-two asthmatic patients sensitized to pollen allergens were randomly allocated to treatment with fluticasone propionate-salmeterol (n=21) or fluticasone propionate alone (n=21). Spirometry, the methacholine provocation concentration causing a 20% decline in forced expiratory volume in 1 second (PC20), the adenosine 5'-monophosphate (AMP) PC20, and ENO levels were measured before and at the height of the pollen season after 6 weeks of treatment.

RESULTS

Changes in the methacholine PC20, the AMP PC20, and ENO levels were not significantly different between treatment groups. No significant changes in the AMP PC20 were observed among the fluticasone propionate-salmeterol and fluticasone propionate groups during natural pollen exposure. However, a significant increase in the methacholine PC20 was observed in the fluticasone propionate-salmeterol group (P = .03) and in the fluticasone propionate group (P = .04); ENO concentrations decreased significantly in both groups during natural allergen exposure (P = .009 and .005).

CONCLUSIONS

In patients with pollen-induced asthma, treatment with either fluticasone propionate or fluticasone propionate-salmeterol is associated with significant reductions in methacholine responsiveness and ENO concentrations, even during natural pollen exposure. Furthermore, at least in patients with mild asthma, natural allergen exposure and the regular use of fluticasone propionate-salmeterol are not associated with a greater increase in ENO levels and airway responsiveness than natural allergen exposure and fluticasone propionate use alone.

Beclomethasone dipropionate attenuates airways hyperresponsiveness to neurokinin A and histamine in asthma

BACKGROUND

Inhaled corticosteroids (ICS) are the most effective anti-inflammatory agents available for the treatment of asthma but they produce only modest effects on airway inflammation and non-specific bronchial hyperresponsiveness (BHR). However, little is known about the possibility that treatment with ICS might cause additional protection on BHR to inhaled tachykinins such as neurokinin A (NKA).

OBJECTIVE

Therefore, we compared the effects of beclomethasone dipropionate (BDP) on the degree of BHR to inhaled histamine and NKA in a double-blind, controlled, cross-over study of asthmatic patients.

METHODS

Patients attended the laboratory before and after each 6 weeks treatment period to undertake concentration-response studies with histamine and NKA. Bronchial responsiveness to both funs was expressed as the provocative concentration producing a 20% decrease in FEV(1) from baseline (PC(20)).

RESULTS

BDP therapy attenuated the constrictor response to both agonists to a similar degree, their geometric mean (range) PC(20) values increasing from 0.47 (0.21-1.41) mg/ml to 2.43 (0.51-4.50) mg/ml (P<0.01, post-salb vs. post-BDP treatment) and from 101.7 (27.3-356.1) microg/ml to 666.7 (151.5-1,000) microg/ml (P<0.01, post-salb vs. post-BDP treatment) for histamine and NKA, respectively.

CONCLUSION

Airway responsiveness to histamine and NKA is reduced by BDP to the same extent. As a result of these findings, provocation with NKA is unlikely to provide additional useful information in the assessment of airway inflammation in asthma.

Dose-response comparison of budesonide dry powder inhalers using adenosine monophosphate bronchial challenge

BACKGROUND

Bronchial hyperresponsiveness to adenosine monophosphate, an indirect measure of airway inflammation, is a sensitive marker of inhaled corticosteroid efficacy.

OBJECTIVE

To evaluate the relative therapeutic efficacy of budesonide delivered via Clickhaler and Turbuhaler dry powder inhalers in patients with mild-to-moderate persistent asthma.

METHODS

In a double-masked, dose-response crossover study, 27 patients received inhaled budesonide in cumulative sequential doubling dose increments, 2 weeks per dose, of 200, 400, and 800 microg/d. Each treatment block was preceded by 1- to 3-week placebo run-in and washout periods. End points were measured after each placebo (ie, baseline) and treatment period. Adenosine monophosphate bronchial challenge was the primary outcome, and exhaled nitric oxide, serum eosinophilic cationic protein, spirometry, domiciliary peak expiratory flow, symptoms, and rescue medication use were the secondary outcomes.

RESULTS

For the adenosine monophosphate provocation concentration that caused a decrease in forced expiratory volume in 1 second of 20% (PC20), a significant overall dose-response effect (P = .006) was found, and there was no significant difference between the devices (P = .8). The relative microgram dose potency ratio between Clickhaler and Turbuhaler was 1.11 (95% confidence interval [CI], 0.50-2.46). After administration of the highest dose of budesonide, the mean doubling dilution shift in adenosine monophosphate PC20 from placebo baseline was 3.46 (95% CI, 2.66-4.27) with the Clickhaler vs 3.41 (95% CI, 2.47-4.35) with the Turbuhaler. A significant overall dose-response effect was demonstrated for exhaled nitric oxide (P = .03) but not for any of the other secondary outcome measures. There were no significant differences between the devices for any of the outcome measures.

CONCLUSION

Inhaled budesonide exhibited overall dose-response effects on adenosine monophosphate PC20 delivered via Turbuhaler and Clickhaler, with no significant difference between the devices.

Monitoring response to treatment in asthma management: food for thought

Asthma is a chronic inflammatory disorder of the airways that is characterized by episodic symptoms. In this regard, asthma management has classically involved periodic re-assessment by the health-care provider, during which therapy is altered mainly based on clinical and physiological parameters, such as assessment of symptoms, spirometry and peak expiratory flow monitoring. In this context, various markers of airway inflammation (e.g. eosinophils in the induced sputum, nitric oxide in the exhaled air) have been proposed to assess the severity of asthma and to adjust the therapy accordingly. The evaluation of airway hyper-responsiveness with different stimuli has also been suggested as a new tool to monitor asthma. However, the lack of definite relationships between airway inflammation and asthmatic symptoms strongly limit the use of markers of asthma severity in the clinical setting. Therefore, the need of new tools to assess the severity of asthma is raised. The ideal measurement employed to establish the proper asthmatic therapy should be safe, non-invasive, easy to perform, reproducible and accurate, and have the capability to monitor the changes induced by the therapeutic interventions. A careful review of the available techniques, and the evaluation of their sensitivity and specificity in the clinical setting is warranted.

Tools to assess (and achieve?) long-term asthma control

Assessment tools are needed to monitor asthma control and to detect exacerbations before the alteration of functional parameters and the occurrence of symptoms. The ability to effectively monitor asthma control would enable clinicians to increase corticosteroid dose or to stop corticosteroid tapering before symptoms occur. As a few severe exacerbations are expected per year in treated patients, these tools must be suitable for long-term use. They must also be reproducible, acceptable to patients and be non-invasive. Tools currently available to assess asthma control include assessment of: clinical parameters (e.g. nocturnal awakenings; bronchodilator intake; symptom scores); lung function (e.g. peak expiratory flow and forced expiratory volume in 1 s); subjective parameters of asthma control (e.g. asthma control questionnaire (ACQ)); bronchial hyper-responsiveness; eosinophilia in induced sputum; and exhaled nitric oxide (NO) concentration. Clinical symptoms, lung function and the ACQ have proved to be inadequate markers of asthma control, as changes in these parameters occur at the same time as symptom manifestation. By contrast, sputum eosinophilia and exhaled NO concentrations are truly predictive of asthma exacerbations; monitoring these parameters are useful in preventing exacerbations from occurring in the first instance. They also assess, and help to achieve asthma control in the long term.

Brain-derived neurotrophic factor in platelets and airflow limitation in asthma

Brain-derived neurotrophic factor (BDNF), a key mediator of neuronal plasticity, contributes to airway obstruction and hyperresponsiveness in a model of allergic asthma. BDNF is stored in human platelets and circulates in human plasma, but the significance of BDNF in this compartment is poorly understood. We investigated the relationship between platelet and plasma BDNF levels and pulmonary function in a cohort of 26 adult patients with recently diagnosed allergic asthma. BDNF levels in serum, platelets, and plasma were significantly increased in participants with asthma, as compared with 26 age- and sex-matched control subjects. In steroid-naive patients, but not in patients using inhaled corticosteroids, enhanced platelet BDNF levels correlated with parameters of airway obstruction and airway hyperresponsiveness to histamine. Experiments with activated peripheral blood mononuclear cells revealed that corticosteroids such as fluticasone effectively suppress BDNF secretion. In conclusion, we demonstrate that enhanced platelet BDNF is associated with airflow limitation and airway hyperresponsiveness in asthma. In addition, we provide evidence that corticosteroids suppress BDNF production by activated immune cells.

Research applications and implications of adenosine in diseased airways

Adenosine, when given by inhalation, initiates the narrowing of airways in subjects with asthma or chronic obstructive pulmonary disease (COPD). The underlying mechanism of this narrowing appears to involve the stimulation of specific mast cell surface adenosine receptors with the subsequent release of mediators and contraction of airway smooth muscle. Although methacholine and histamine have become gold standards as bronchial provocants used to quantify bronchial hyperresponsiveness, the airways response to the indirect stimulus adenosine more closely reflects bronchial inflammation. This distinctive feature of adenosine could be exploited to enable superior diagnostic discrimination between asthma and COPD, allow better monitoring of disease activity and progression, and improve the individual adjustment of long-term asthma management with topical glucocorticosteroids. In this article, we review recent developments in this area of rapidly evolving clinical research, focusing on the putative role of adenosine as a mediator of airway inflammation and as a useful bronchoprovocant in several clinical and research applications.