Bronchial hyperresponsiveness in the assessment of asthma control: Airway hyperresponsiveness in asthma: its measurement and clinical significance

Daily Inhaled Corticosteroids Treatment Abolishes Airway Hyperresponsiveness to Mannitol in Defence and Police Recruits

Background

Airway hyperresponsiveness (AHR) is a key pathophysiological feature of asthma and causes exercise-induced bronchoconstriction (EIB). Indirect bronchial provocation tests (BPTs) (e.g., exercise, mannitol) aid to diagnose asthma and identify EIB. Daily inhaled corticosteroids (ICS) can abolish AHR caused by indirect stimuli. Where strenuous physical exertion is integral to an occupation, identification of those at risk of EIB is important and documentation of inhibition of AHR with ICS is required before recruitment.

Methods/Objectives

A retrospective analysis was performed on 155 potential recruits with AHR to mannitol who underwent follow-up assessment after daily ICS treatment to determine the proportion that can abolish AHR using ICS and to determine any predictors of the persistence of AHR.

Results

Airway hyperresponsiveness was abolished in the majority (84%, n = 130) over the treatment period (mean ± SD 143 ± 72days), and it was defined as the provoking dose of mannitol to cause a 15% fall in FEV1 (cumulative inhaled dose of mannitol to cause 15% fall in FEV₁, PD₁₅) improved from (GeoMean) 183 to 521 mg. Compared with recruits in whom AHR was abolished with daily ICS (i.e., no 15% fall in FEV₁ to the maximum cumulative dose of mannitol of 635 mg), in those where AHR remained (16%, n = 25), baseline AHR was more severe (PD15: 85 mg vs. 213 mg, P < 0.001), baseline FEV₁% was lower (89 vs. 96%; 95%CI:2–12, P=0.004), and they had a longer follow-up duration (180 vs. 136 days; 13–74, P = 0.006). Baseline FEV₁% (adjusted odds ratio 0.85; 95%CI:0.77–0.93), FEV₁/FVC (0.78; 0.67–0.90), FEF_25−75% (1.15; 1.06–1.25), and airway reactivity to mannitol (%Fall/cumulative dose of mannitol multiplied by 100) (1.07; 1.03–1.11) predicted AHR remaining after daily ICS.

Conclusion

Airway hyperresponsiveness to mannitol can be abolished after 20 weeks of daily treatment with ICS. Inhibition of AHR is likely due to attenuation of airway inflammation in response to ICS treatment. Increased airway reactivity and lower spirometry variables predicted the persistence of AHR. Thus, those with a slower response to daily ICS on AHR can potentially be identified at the commencement of monitoring ICS using inhaled mannitol.

RSV Promotes Epithelial Neuroendocrine Phenotype Differentiation through NODAL Signaling Pathway

Background

Respiratory syncytial virus (RSV) infects infants and children, predisposing them to development of asthma during adulthood. Epithelial neuroendocrine phenotypes may be associated with development of asthma. This study hopes to ascertain if RSV infection promotes epithelial neuroendocrine phenotypes through the NODAL signaling pathway.

Methods

The GSE6802 data set was obtained from the GEO database, and the differential genes were analyzed using the R language. An in vitro model was constructed with RSV infected human respiratory epithelial cells, and then real-time qPCR and immunofluorescence were used to detect the expression of different epithelial biomarkers and airway neuropeptides. The acute and chronic infection model of RSV infection was established by intranasal injection of RSV into guinea pigs. Immunohistochemistry and Western blot were used to detect the expression of pulmonary neuroendocrine cells markers ENO2 and neuropeptides.

Results

The expression levels of ENO2, SP, CGRP, and NODAL/ACTRII were significantly higher in the RSV infection group than those of the control group, which were abrogated by siRNA-NODAL. In vivo, we found that the expression levels of ENO2, SP, and CGRP were significantly higher than that of the control group.

Conclusion

RSV promotes epithelial neuroendocrine phenotypes through the NODAL signaling pathway.

Zhike pingchuan granules improve bronchial asthma by regulating the IL-6/JAK2/STAT3 pathway

The present study aimed to investigate the effects of zhike pingchuan granules (ZKPC) on bronchial asthma and the underlying mechanism. A bronchial asthma mouse model was established by aerosol inhalation of ovalbumin. The changes in lung pathomorphology were observed by hematoxylin and eosin staining. The levels of IL-1β, TNF-α and IL-6 in bronchoalveolar lavage fluid (BALF) and serum were detected by corresponding ELISA kits. Levels of reactive oxygen species, malondialdehyde and superoxide dismutase in lung tissues were analyzed using corresponding kits. The expression of proteins related to apoptosis and the IL-6/janus kinase 2 (JAK2)/STAT3 pathway was detected by western blot analysis. The results showed that ZKPC significantly restored the dry/wet ratio and alleviated lung pathomorphology of bronchial asthmatic mice. In addition, ZKPC inhibits inflammation, oxidative stress levels and cell apoptosis in bronchial asthmatic mice and also suppressed the IL-6/JAK2/STAT3 pathway. Fedratinib (a JAK2 inhibitor) further strengthened the alleviative effects of ZKPC on bronchial asthma. In conclusion, ZKPC improved bronchial asthma by suppressing the IL-6/JAK2/STAT3 pathway.

Bronchial Provocation Testing for the Identification of Exercise-Induced Bronchoconstriction

Exercise-induced bronchoconstriction (EIB) occurs in patients with asthma, children, and otherwise healthy athletes. Poor diagnostic accuracy of respiratory symptoms during exercise requires objective assessment of EIB. The standardized tests currently available are based on the assumption that the provoking stimulus to EIB is dehydration of the airway surface fluid due to conditioning large volumes of inhaled air. "Indirect" bronchial provocation tests that use stimuli to cause endogenous release of bronchoconstricting mediators from airway inflammatory cells include dry air hyperpnea (eg, exercise and eucapnic voluntary hyperpnea) and osmotic aerosols (eg, inhaled mannitol). The airway response to different indirect tests is generally similar in patients with asthma and healthy athletes with EIB. Furthermore, the airway sensitivity to these tests is modified by the same pharmacotherapy used to treat asthma. In contrast, pharmacological agents such as methacholine, given by inhalation, act directly on smooth muscle to cause contraction. These "direct" tests have been used traditionally to identify airway hyperresponsiveness in clinical asthma but are less useful to diagnose EIB. The mechanistic differences between indirect and direct tests have helped to elucidate the events leading to airway narrowing in patients with asthma and elite athletes, while improving the clinical utility of these tests to diagnose and manage EIB.

Performance Characteristics of Spirometry With Negative Bronchodilator Response and Methacholine Challenge Testing and Implications for Asthma Diagnosis

BACKGROUND

In patients with a history suggestive of asthma, diagnosis is usually confirmed by spirometry with bronchodilator response (BDR) or confirmatory methacholine challenge testing (MCT).

RESEARCH QUESTION

We examined the proportion of participants with negative BDR testing who had a positive MCT (and its predictors) result and characteristics of MCT, including effects of controller medication tapering and temporal variability (and predictors of MCT result change), and concordance between MCT and pulmonologist asthma diagnosis.

STUDY DESIGN AND METHODS

Adults with self-reported physician-diagnosed asthma were recruited by random-digit dialing across Canada. Subjects performed spirometry with BDR testing and returned for MCT if testing was nondiagnostic for asthma. Subjects on controllers underwent medication tapering with serial MCTs over 3 to 6 weeks. Subjects with a negative MCT (the provocative concentration of methacholine that results in a 20% drop in FEV₁ [PC₂₀] > 8 mg/mL) off medications were examined by a pulmonologist and had serial MCTs after 6 and 12 months.

RESULTS

Of 500 subjects (50.5 ± 16.6 years old, 68.0% female) with a negative BDR test for asthma, 215 (43.0%) had a positive MCT. Subjects with prebronchodilator airflow limitation were more likely to have a positive MCT (OR, 1.90; 95% CI, 1.17-3.04). MCT converted from negative to positive, with medication tapering in 18 of 94 (19.1%) participants, and spontaneously over time in 25 of 165 (15.2%) participants. Of 231 subjects with negative MCT, 28 (12.1%) subsequently received an asthma diagnosis from a pulmonologist.

INTERPRETATION

In subjects with a self-reported physician diagnosis of asthma, absence of bronchodilator reversibility had a negative predictive value of only 57% to exclude asthma. A finding of spirometric airflow limitation significantly increased chances of asthma. MCT results varied with medication taper and over time, and pulmonologists were sometimes prepared to give a clinical diagnosis of asthma despite negative MCT. Correspondingly, in patients for whom a high clinical suspicion of asthma exists, repeat testing appears to be warranted.

Bronchoprovocation Testing in Asthma: An Update

Bronchial hyperresponsiveness (BHR) is defined as a heightened bronchoconstrictive response to airway stimuli. It complements the cardinal features in asthma, such as variable or reversible airflow limitation and airway inflammation. Although BHR is considered a pathophysiologic hallmark of asthma, it should be acknowledged that this property of the airway is dynamic, because its severity and even presence can vary over time with disease activity, triggers or specific exposure, and with treatment. In addition, it is important to recognize that there is a component that is not reflective of a specific disease entity.

Prevalence of airway hyperresponsiveness and its seasonal variation in children with asthma

BACKGROUND

Airway hyperresponsiveness (AHR) is a key feature of asthma and can be detected using various bronchoprovocation tests. In pediatric populations, the percentage of a positive methacholine challenge test (MCCTs) in children with asthma varies among studies, and some have reported seasonal variability. However, these studies have mostly been conducted in temperate regions. This study evaluated the prevalence of AHR to methacholine and its seasonal variation in asthmatic children in Taiwan, a subtropical country.

METHODS

A total of 276 children with asthma and their MCCT results were retrospectively reviewed. All were diagnosed with asthma and received asthma controllers regularly. They were assigned to four season groups depending in which season MCCTs were administered, with seasons categorized by the Central Weather Bureau of Taiwan. Subgroup analyses, including for sex, age, and atopy level, were compared for seasonal difference.

RESULTS

The prevalence of methacholine hyperresponsiveness was 70.7% (n = 195), and the children who were younger and had higher total serum IgE were more sensitive to methacholine (p = 0.019 and p < 0.005, respectively). No significant difference in AHR prevalence among seasons was observed (p = 0.480). The percentage of borderline, mild, and moderate severity of MCCT results was almost equally distributed among the seasons. In subgroup analysis, the children with a higher IgE level (≥75th percentile of all data) had a higher proportion of positive MCCTs in summer (88.6%, p = 0.016).

CONCLUSION

In total, 70% of the children with asthma in Taiwan had AHR to methacholine, which varied among seasons. Children with a higher total serum IgE level may be more seasonally dependent, particularly in summer.

Enhanced pause correlates with airway neutrophils and airway-epithelial injury in asthmatic mice treated with dexamethasone

OBJECTIVE

To investigate the correlations among airway inflammation, airway epithelial injury and airway hyperresponsiveness (AHR) in asthmatic mice treated with dexamethasone.

METHODS

Female BALB/c mice were sensitized with intraperitoneal and hypodermic injections of ovalbumin (OVA) and aluminum on days 0, 7 and 14, challenged with OVA starting on day 21 for 10 days, and treated with dexamethasone via intraperitoneal injection starting on day 28 for 3 days. Female C57BL/6 mice were treated intranasally with house dust mite (HDM) on days 1 and 14, challenged intranasally with HDM on days 21, 23, 25, 27 and 29, and treated with sivelestat (a selective neutrophil elastase inhibitor) via intraperitoneal injection after each challenge. Following the final challenge, enhanced pause (Penh) and differential cell counts in the broncho-alveolar lavage fluid were measured and the correlations were analyzed.

RESULTS

Compared with OVA-challenged BALB/c mice, the counterpart mice treated with dexamethasone showed reduced Penh and shedding of airway epithelial cells. In addition, we found that Penh 50 (an indicator of AHR) had positive correlations with airway neutrophils and shedding of airway epithelial cells, but no correlation with eosinophils, lymphocytes or macrophages. Moreover, shedding of airway epithelial cells had positive correlations with airway neutrophils, but no correlation with eosinophils, lymphocytes or macrophages. Further, sivelestat decreased Penh 50 and shed airway-epithelial cells in HDM-challenged C57BL/6 mice.

CONCLUSIONS

Collectively, our findings suggest that airway neutrophils and excessive shedding of airway epithelial cells, but not eosinophils, lymphocytes or macrophages, may be involved in AHR in asthmatic mice treated with dexamethasone.

Does Continuous Positive Airway Pressure (CPAP) treatment of obstructive sleep apnoea (OSA) improve asthma-related clinical outcomes in patients with co-existing conditions?- A systematic review

INTRODUCTION

A high prevalence of OSA has been observed in asthma populations, with detrimental impact on clinical outcomes.

AIM

To determine if CPAP treatment of co-existing OSA improves asthma-related symptoms and quality of life.

METHODS

Literature review of EMBASE and MEDLINE databases prior to July 2017. Study populations included asthmatics with co-existing OSA treated with CPAP, and ≥1 asthma-related clinical outcome measure.

RESULTS

12 studies; 8 prospective quasi-experimental and 4 observational. Mean CPAP duration; 19.5 (2-100) weeks. Meta-analysis demonstrated significant improvement in mean Asthma Quality of Life Questionnaire scores (AQLQ and mini-AQLQ); 0.59 (95%CI; 0.25, 0.92), p = 0.0006. No significant improvement was demonstrated in forced expiratory volume in 1 s (FEV1)% predicted; 0.32 (95%CI; -2.84, 3.47), p = 0.84. Asthma Control Test/Asthma Control Questionnaire improved in 2 studies, with no improvement in 1 study. 4 studies demonstrated improvement in asthma daytime/night-time symptoms, and 3 studies showed improved asthma severity.

CONCLUSION

Asthmatics with co-existing OSA can experience improved quality of life with CPAP treatment. This effect appears more pronounced in severe OSA or poorly controlled asthma.

The airway hyperresponsiveness to methacholine may be predicted by impulse oscillometry and plethysmography in children with well-controlled asthma

OBJECTIVE

Airway hyperresponsiveness (AHR) is a hallmark of asthma. Methacholine challenge test which is mostly used to confirm AHR is not routinely available. The aim of this study was to investigate the predictive values of fractional exhaled nitric oxide (FeNO), impulse oscillometry (IOS), and plethysmography for the assessment of AHR in children with well-controlled asthma.

METHODS

60 children with controlled allergic asthma aged 6-18 years participated in the study. FeNO measurement, spirometry, IOS, and plethysmography were performed. Methacholine challenge test was done to assess AHR. PC20 and dose response slope (DRS) of methacholine was calculated.

RESULTS

Mild to severe AHR with PC20 < 4 mg/ml was confirmed in 31 (51.7%) patients. Baseline FeNO and total specific airway resistance (SRtot)%pred and residual volume (RV)%pred levels in plethysmography were significantly higher and FEV1%pred, FEV1/FVC%pred, MMEF%pred values were lower in the group with PC20 < 4 mg/ml. FeNO, SRtot%pred, and RV%pred levels were found to be positively correlated with DRS methacholine. The higher baseline FeNO, frequency dependence of resistance (R5-R20) in IOS and SRtot%pred in plethysmography were found to be significantly related to DRS methacholine in linear regression analysis (β: 1.35, p = 0.046, β: 4.58, p = 0.002, and β: 0.78, p = 0.035, respectively). The cut-off points for FeNO and SRtot% for differentiating asthmatic children with PC20 < 4 mg/ml from those with PC20 ≥ 4 mg/ml were 28 ppb (sensitivity: 67.7%, specificity: 72.4%, p < 0.001) and 294.9% (sensitivity: 35.5%, specificity: 96.6%, p = 0.013), respectively.

CONCLUSION

IOS and plethysmography may serve as reliable and practical tools for prediction of mild to severe methacholine induced AHR in otherwise "seemingly well-controlled'' asthma.

Clinical markers of asthma and IgE assessed in parents before conception predict asthma and hayfever in the offspring

BACKGROUND

Mice models suggest epigenetic inheritance induced by parental allergic disease activity. However, we know little of how parental disease activity before conception influences offspring's asthma and allergy in humans.

OBJECTIVE

We aimed to assess the associations of parental asthma severity, bronchial hyperresponsiveness (BHR), and total and specific IgEs, measured before conception vs. after birth, with offspring asthma and hayfever.

METHODS

The study included 4293 participants (mean age 34, 47% men) from the European Community Respiratory Health Survey (ECRHS) with information on asthma symptom severity, BHR, total and specific IgEs from 1991 to 1993, and data on 9100 offspring born 1972-2012. Adjusted relative risk ratios (aRRR) for associations of parental clinical outcome with offspring allergic disease were estimated with multinomial logistic regressions.

RESULTS

Offspring asthma with hayfever was more strongly associated with parental BHR and specific IgE measured before conception than after birth [BHR: aRRR = 2.96 (95% CI: 1.92, 4.57) and 1.40 (1.03, 1.91), respectively; specific IgEs: 3.08 (2.13, 4.45) and 1.83 (1.45, 2.31), respectively]. This was confirmed in a sensitivity analysis of a subgroup of offspring aged 11-22 years with information on parental disease activity both before and after birth.

CONCLUSION & CLINICAL RELEVANCE

Parental BHR and specific IgE were associated with offspring asthma and hayfever, with the strongest associations observed with clinical assessment before conception as compared to after birth of the child. If the hypothesis is confirmed in other studies, parental disease activity assessed before conception may prove useful for identifying children at risk for developing asthma with hayfever.

Relationship between Fractional Exhaled Nitric Oxide Level and Efficacy of Inhaled Corticosteroid in Asthma-COPD Overlap Syndrome Patients with Different Disease Severity

This study explored the relationship between the fractional exhaled nitric oxide (FeNO) level and the efficacy of inhaled corticosteroid (ICS) in asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) patients with different disease severity. A total of 127 ACOS patients with ACOS (case group) and 131 healthy people (control group) were enrolled in this study. Based on the severity of COPD, the ACOS patients were divided into: mild ACOS; moderate ACOS; severe ACOS; and extremely severe ACOS groups. We compared FeNO levels, pulmonary function parameters including percentage of forced expiratory volume in 1 second (FEV1) to predicted value (FEV1%pred), ratio of FEV1 to forced vital capacity (FEV1/FVC), inspiratory capacity to total lung capacity (IC/TLC) and residual volume to total lung capacity (RV/TLC), arterial blood gas parameters, including PH, arterial partial pressure of oxygen (PaO₂) and arterial partial pressure of carbon dioxide (PaCO₂), total serum immunoglobulin E (IgE), induced sputum eosinophil (EOS), plasma surfactant protein A (SP-A), plasma soluble receptor for advanced glycation end products (sRAGE), sputum myeloperoxidase (MPO), sputum neutrophil gelatinase-associated lipocalin (NGAL) and Asthma Control Test (ACT) scores, and COPD Assessment Test (CAT) scores. Compared with pre-treatment parameters, the FeNO levels, RV/TLC, PaCO₂, total serum IgE, induced sputum EOS, plasma SP-A, sputum MPO, sputum NGAL, and CAT scores were significantly decreased after 6 months of ICS treatment, while FEV1%pred, FEV1/FVC, IC/TLC, PH, PaO2, plasma sRAGE, and ACT scores were significantly increased in ACOS patients with different disease severity after 6 months of ICS treatment. This finding suggests that the FeNO level may accurately predict the efficacy of ICS in the treatment of ACOS patients.

Diagnostic Value of Serum Baseline Tryptase Levels in Childhood Asthma and Its Correlation with Disease Severity

BACKGROUND

The aim of this study was to explore whether serum baseline tryptase (sBT) levels might be a useful marker not only for the accurate diagnosis of childhood asthma, but also for the prediction of disease severity.

METHODS

A total of 114 asthmatic children were enrolled in this study, 36 of whom had mild intermittent asthma, 38 had mild persistent asthma, and 40 had moderate to severe persistent asthma. Additionally, 34 age-matched healthy children were enrolled as controls. The sBT levels of these populations were measured using a fluoroenzymeimmunoassay kit. The diagnostic performance of sBT levels and their correlation with asthma severity were systematically investigated using receiver operating characteristic (ROC) analysis and correlation analysis.

RESULTS

Children with mild and moderate to severe persistent asthma had significantly increased sBT levels as compared to those with mild intermittent asthma and healthy controls. ROC analysis further demonstrated that sBT levels not only appear to be highly sensitive and specific for distinguishing asthmatic children from healthy controls, but also show good accuracy for the differentiation of various asthmatic subgroups. Correlation analysis revealed that in all asthmatic subgroups sBT levels were significantly correlated with a variety of key markers that reflect the disease severity of asthma, including childhood asthma control test scores, serum IgE and interleukin-13 levels, blood eosinophil counts, and pulmonary test parameters.

CONCLUSIONS

sBT levels may have a potential use in supporting a diagnosis of asthma in children and as a predictor of disease severity.

Fluticasone/formoterol association favors long-lasting decrease in bronchial reactivity to methacholine and weekly PEF variability

Inhaled corticosteroids (ICS)/long-acting beta-agonists (LABA) association offers a better asthma control than a higher steroid dose with short-acting beta-agonists as needed. In this study, we evaluated the effect of the association on bronchial hyperreactivity (BHR) and peak expiratory flow (PEF) variability, as such parameters are positively correlated with increased asthma morbidity and exacerbations. Thirty-six adult patients with mild persistent asthma were enrolled. After a 7-day run-in, they were randomly assigned to three therapy regimens for 6 weeks: Group 1, fluticasone 125 μg + formoterol 5 μg in the same device; Group 2, fluticasone 125 μg + formoterol 12 μg as needed; Group 3, fluticasone 250 μg + formoterol 12 μg as needed. We evaluated changes induced in weekly PEF variability (measured during the entire study and 4 weeks of follow-up) and pre- and post-study PD20 methacholine (MCH). Weekly PEF variability decreased in all groups during treatment with the greatest reduction in Group 1, followed by Group 3, and finally Group 2. During the follow-up, no significant changes were detected in Group 1, whereas a trend towards an increased variability was found in Groups 2 and 3. Post-treatment PD20 MCH was significantly higher versus the pre-treatment. The increase observed in Group 1 was significantly higher compared to Groups 2 and 3 and that observed in Group 3 in respect to Group 2. The study proves that both BHR and PEF variability are influenced by ICS. This effect was greater with fluticasone/formoterol association compared to fluticasone alone with formoterol as needed even at higher steroid dose.

Exercise-induced bronchoconstriction update-2016

The first practice parameter on exercise-induced bronchoconstriction (EIB) was published in 2010. This updated practice parameter was prepared 5 years later. In the ensuing years, there has been increased understanding of the pathogenesis of EIB and improved diagnosis of this disorder by using objective testing. At the time of this publication, observations included the following: dry powder mannitol for inhalation as a bronchial provocation test is FDA approved however not currently available in the United States; if baseline pulmonary function test results are normal to near normal (before and after bronchodilator) in a person with suspected EIB, then further testing should be performed by using standardized exercise challenge or eucapnic voluntary hyperpnea (EVH); and the efficacy of nonpharmaceutical interventions (omega-3 fatty acids) has been challenged. The workgroup preparing this practice parameter updated contemporary practice guidelines based on a current systematic literature review. The group obtained supplementary literature and consensus expert opinions when the published literature was insufficient. A search of the medical literature on PubMed was conducted, and search terms included pathogenesis, diagnosis, differential diagnosis, and therapy (both pharmaceutical and nonpharmaceutical) of exercise-induced bronchoconstriction or exercise-induced asthma (which is no longer a preferred term); asthma; and exercise and asthma. References assessed as relevant to the topic were evaluated to search for additional relevant references. Published clinical studies were appraised by category of evidence and used to document the strength of the recommendation. The parameter was then evaluated by Joint Task Force reviewers and then by reviewers assigned by the parent organizations, as well as the general membership. Based on this process, the parameter can be characterized as an evidence- and consensus-based document.

Evaluation of exhaled nitric oxide's ability to predict methacholine challenge in adults with nonobstructive spirometry

BACKGROUND

Compared with methacholine challenge, exhaled nitric oxide is less expensive, is performed as a simpler point-of-care maneuver, and may provide treatment guiding information.

OBJECTIVE

To determine whether exhaled nitric oxide levels can predict the outcome of methacholine challenge in patients without obvious baseline obstruction.

METHODS

This retrospective database and medical record review included adults presenting to a tertiary care center from November 1, 2009, through August 31, 2013, who underwent methacholine challenge and exhaled nitric oxide measurement within 2 weeks of each other. Database extraction identified age, sex, body mass index, baseline corticosteroid use, testing indication, forced expiratory volume in 1 second (FEV₁), and testing results. Individuals taking corticosteroid-containing medication or who had an FEV₁ less than the lower limit of normal at baseline were excluded.

RESULTS

A total of 1,322 individuals were identified, with 774 meeting the eligibility criteria. A total of 123 methacholine challenges (16%) had positive results. Fractional exhaled nitric oxide was statistically higher in those with positive methacholine challenge results (mean [SD], 41.9 [54.5] ppb vs 25.2 [19.7] ppb; P < .01). Receiver operating characteristic curve revealed an area under the curve of 0.572 (P < .01), suggesting a poor correlation between exhaled nitric oxide level and methacholine challenge outcome. Fractional exhaled nitric oxide of greater than 50 ppb has a sensitivity, specificity, positive predictive value, and negative predictive value of 12%, 89%, 17%, and 84%, respectively, for a positive methacholine challenge result.

CONCLUSION

In this large, retrospective cohort of corticosteroid-naive pulmonary patients with normal FEV₁ on baseline spirometry, exhaled nitric oxide poorly predicts the outcome of a methacholine challenge.

Pheretima aspergillum decoction suppresses inflammation and relieves asthma in a mouse model of bronchial asthma by NF-κB inhibition

ETHNOPHARMACOLOGICAL RELEVANCE AND AIM OF THE STUDY

Guang-Pheretima, the live form of the earthworm Pheretima aspergillum, is a traditional Chinese medicine commonly used for the treatment of asthma, cough, stroke, epilepsy and other diseases due to its anti-inflammatory, anti-asthmatic, anti-seizure, thrombolytic and diuretic properties. Although Guang-Pheretima is effective in the relief of asthma, its pharmacological activity and the underlying molecular mechanisms are not fully understood. Hence, we investigated the effects of a Pheretima aspergillum decoction (PAD) against inflammation in a model of ovalbumin (OVA)-induced asthma in BALB/c mice, as well as the nuclear factor-κB (NF-κB) pathway involved in this process.

MATERIALS AND METHODS

OVA was used to sensitize and challenge the airway of the mice, and PAD was administrated by gavage. We measured airway hyperresponsiveness (AHR) in the mice 24h following a final methacholine challenge with whole-body plethysmography. The bronchoalveolar lavage fluid (BALF), serum and pulmonary tissues were collected 48h after the last challenge. The levels of inflammatory factors and the related mRNAs were determined by enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR), respectively. The number of differential inflammatory cells in the BALF was counted. Serum total and OVA-specific IgE levels were measured with ELISA. The activation of NF-κB signaling in the lung was detected by western blotting. In addition, the lung tissues were stained with hematoxylin and eosin or periodic acid Schiff stain for histopathological examination.

RESULTS

PAD treatment significantly alleviated AHR in the asthmatic mice, decreased the mRNA and protein levels of IL-4, IL-5 and IL-13 and downregulated IgE. In addition, PAD treatment attenuated mucus secretion and infiltration of inflammatory cells in the lung while inhibiting the activation of NF-κB signaling.

CONCLUSIONS

PAD effectively inhibited the activation of NF-κB signaling in the lungs of mice with OVA-induced asthma, and mitigated AHR and Th2 type inflammatory reactions. Therefore, PAD may serve as a drug candidate for asthma treatment.

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 contractile lability of smooth muscle in asthmatic airway hyperresponsiveness

The contractile capacity of airway smooth muscle is not fixed but modulated by an impressive number of extracellular inflammatory mediators. Targeting the transient component of airway hyperresponsiveness ascribed to this contractile lability of ASM is a quest of great promises in order to alleviate asthma symptoms during inflammatory flares. However, owing to the plethora of mediators putatively involved and the molecular heterogeneity of asthma, it is more likely that many mediators conspire to increase the contractile capacity of ASM, each of which contributing to a various extent and in a time-varying fashion in individuals suffering from asthma. The task of identifying a common mend for a tissue rendered hypercontractile by imponderable assortments of inflammatory mediators is puzzling.

The potential role of direct and indirect bronchial challenge testing to identify overtreatment of community managed asthma

BACKGROUND

Although airway hyperresponsiveness (AHR) is a defining feature of asthma pathophysiology, bronchial challenge testing is not routinely used in primary care asthma management.

OBJECTIVE

The aim of this study was to evaluate the potential role of direct (methacholine) and indirect (mannitol) challenge testing in community managed asthma.

METHODS

Patients currently treated for asthma from Tayside and Fife were identified by the Health Informatics Centre (HIC) and invited to take part in the study. At screening, the following tests were carried out: spirometry, methacholine and mannitol challenge, exhaled nitric oxide (FeNO); Asthma Control Questionnaire (ACQ) and Mini Asthma Quality of Life Questionnaire (AQLQ).

RESULTS

A total of 3388 asthmatics were initially identified by HIC with 423 positive responses and 123 completing the study. Seventy percent had either a positive methacholine (PC20  < 8 mg/mL) or mannitol challenge (PD15  < 635 mg), and 30% were non-responsive to both challenges. Fourteen percent of methacholine responders (n = 74) were negative to mannitol, and 16% of mannitol responders (n = 76) were negative to methacholine. Spirometry, FeNO, ACQ and AQLQ were significantly better in the non-responder group who were exposed to high-dose inhaled corticosteroids and frequent long-acting beta-agonists.

CONCLUSIONS AND CLINICAL RELEVANCE

We found that 30% of unselected patients with community managed asthma were challenge negative and could be potentially misdiagnosed or overtreated, in turn suggesting the need for supervised step-down.

Genetic variation in uncontrolled childhood asthma despite ICS treatment

Genetic variation may partly explain asthma treatment response heterogeneity. We aimed to identify common and rare genetic variants associated with asthma that was not well controlled despite inhaled corticosteroid (ICS) treatment. Data of 110 children was collected in the Children Asthma Therapy Optimal trial. Associations of genetic variation with measures of lung function (FEV1%pred), airway hyperresponsiveness (AHR) to methacholine (Mch PD20) and treatment response outcomes were analyzed using the exome chip. The 17q12-21 locus (containing ORMDL3 and GSMDB) previously associated with childhood asthma was investigated separately. Single-nucleotide polymorphisms (SNPs) in the 17q12-21 locus were found nominally associated with the outcomes. The strongest association in this region was found for rs72821893 in KRT25 with FEV1%pred (P=3.75*10(-5)), Mch PD20 (P=0.00095) and Mch PD20-based treatment outcome (P=0.006). No novel single SNPs or burden tests were significantly associated with the outcomes. The 17q12-21 region was associated with FEV1%pred and AHR, and additionally with ICS treatment response.

Glucocorticoids decrease Treg cell numbers in lungs of allergic mice

Glucocorticoids have been the hallmark anti-inflammatory drug used to treat asthma. It has been shown that glucocorticoids ameliorate asthma by increasing numbers and activity of Tregs, in contrast recent data show that glucocorticoid might have an opposite effect on Treg cells from normal mice. Since Tregs are target cells that act on the resolution of asthma, the aim of this study was to elucidate the effect of glucocorticoid treatment on lung Tregs in mouse models of asthma. Allergen challenged mice were treated with either oral dexamethasone or nebulized budesonide. Broncoalveolar lavage and airway hyperresponsiveness were evaluated after allergenic challenge. Lung, thymic and lymph node cells were phenotyped on Treg through flow cytometry. Lung cytokine secretion was detected by ELISA. Although dexamethasone inhibited airway inflammation and hyperresponsiveness, improving resolution, we have found that both dexamethasone and budesonide induce a reduction of Treg numbers on lungs and lymphoid organs of allergen challenged mice. The reduction of lung Treg levels was independent of mice strain or type of allergen challenge. Our study also indicates that both glucocorticoids do not increase Treg activity through production of IL-10. Glucocorticoid systemic or localized treatment induced thymic atrophy. Taken together, our results demonstrate that glucocorticoids decrease Treg numbers and activity in different asthma mouse models, probably by reducing thymic production of T cells. Therefore, it is possible that glucocorticoids do not have beneficial effects on lung populations of Treg cells from asthmatic patients.

Variability of methacholine bronchoprovocation and the effect of inhaled corticosteroids in mild asthma

BACKGROUND

The methacholine challenge test quantifies airway hyper-responsiveness, which is measured by the provocative concentration of methacholine causing a 20% decrease in forced expiration volume in 1 second (PC20). The dose-response effect of inhaled corticosteroids (ICS) on PC20 has been inconsistent and within-patient variability of PC20 is not well established.

OBJECTIVE

To determine the effect of high- vs low-dose ICS on PC20 and within-patient variability in those with repeated measurements of PC20.

METHODS

A randomized, double-masked, crossover trial was conducted in patients with asthma on controller medications with PC20 of 8 mg/mL or lower (n = 64) to evaluate the effect of high-dose (1,000 μg/d) vs low-dose (250 μg/d) fluticasone for 4 weeks on PC20. In addition, the variability of PC20 was assessed in participants who underwent 2 or 3 PC20 measurements on the same dose of ICS (n = 27) over a 4-week interval.

RESULTS

Because there was a significant period effect, dose comparison of the change in PC20 was assessed in the first treatment period. There was no significant difference in the change in PC20 for high- vs low-dose ICS (39% vs 30% increase, respectively; P = .87). The within- and between-participant variances for log PC20 were 0.84 and 0.96, respectively, with an intra-class correlation of 0.53, and 37% of participants had more than 2 doubling dose changes in PC20 in those with repeated measurements.

CONCLUSION

The effect of ICS on PC20 is not dose dependent at fluticasone levels of 250 and 1,000 μg/d. Interpersonal variability for PC20 is large. A lack of precise measurements should be taken into account when interpreting any change in PC20.

Nasal hyper-reactivity is a common feature in both allergic and nonallergic rhinitis

BACKGROUND

Nasal hyper-reactivity is an increased sensitivity of the nasal mucosa to various nonspecific stimuli. Both allergic rhinitis (AR) and nonallergic rhinitis (NAR) patients can elicit nasal hyper-reactivity symptoms. Differences in the prevalence or type of nasal hyper-reactivity in AR and NAR patients are largely unknown. In this study, we quantitatively and qualitatively assessed nasal hyper-reactivity in AR and NAR.

METHODS

In the first part, an analysis of a prospectively collected database was performed to reveal patient-reported symptoms of hyper-reactivity. In the second part, cold dry air provocation (CDA) was performed as a hyper-reactivity measure in AR and NAR patients and healthy controls, and symptoms scores, nasal secretions and peak nasal inspiratory flow were measured. Comparisons were made between AR and NAR patients in both studies.

RESULTS

The database analysis revealed high hyper-reactivity prevalence in AR (63.4%) and NAR (66.9%). There were no differences between AR and NAR in terms of the number or type of hyper-reactivity stimuli. Hyper-reactivity to physical stimuli did not exclude a response to chemical stimuli, or vice versa. CDA provocation resulted in a significant increase in rhinitis symptoms and the amount of nasal secretions in AR and NAR patients, but not in controls.

CONCLUSIONS

We found no quantitative or qualitative differences in nasal hyper-reactivity between AR and NAR patients. It is not possible to differentiate NAR subpopulations based on physical or chemical stimuli.

Comparison of direct and indirect bronchoprovocation testing using ventilator-acquired pulmonary mechanics in healthy cats and cats with experimental allergic asthma

Airway hyperresponsiveness (AHR) is a key feature of asthma and can be measured using bronchoprovocation. Direct (methacholine, MCh) or indirect (adenosine-5-monophosphate, AMP; or mannitol) bronchoprovocants are used in human patients, the latter inducing AHR only with pre-existing airway inflammation. The present study compared the responses to direct (MCh) and indirect (mannitol, AMP) bronchoprovocation in healthy and asthmatic cats (n=6/group). The order of bronchoprovocant was randomized using a published table of random numbers and there was a 1-month washout before crossover to the next treatment. Pulmonary mechanics were measured in anesthetized and mechanically ventilated cats using a critical care ventilator. Saline at baseline and increasing doses of each bronchoprovocant were aerosolized for 30 s, followed by 4 min of data collection between doses. The endpoint for each bronchoprovocant was reached when airway resistance exceeded 200% of baseline values (EC200Raw). There was a significant difference (P<0.001) in the airway response of asthmatic vs. healthy cats over the range of MCh concentrations, despite there being no significant difference in the EC200Raw between the groups. Response to MCh was significantly greater (P<0.05) in asthmatic than in healthy cats at MCh concentrations as low as 0.0625 mg/mL. For AMP, a small subset of asthmatics (n=2/6) responded at low concentrations; four asthmatic cats and all healthy cats failed to respond even to the highest concentrations of AMP. One asthmatic cat but no healthy cats responded to mannitol. In conclusion, MCh discriminated asthmatic from healthy cats but neither AMP nor mannitol was an effective bronchoprovocant in this model.

Macrolides for the long-term management of asthma--a meta-analysis of randomized clinical trials

BACKGROUND

Macrolide antibiotics, which have anti-inflammatory and immune modulatory effects, have been studied as adjuncts for the management of asthma. However, results have been contradictory and trials underpowered. We therefore sought to conduct a meta-analysis of randomized controlled trials (RCT).

METHODS

All RCT of prolonged macrolides (3+ weeks) for asthma treatment, published up to January 2013 in MEDLINE, Scopus, CINAHL, Highwire, and The Cochrane Collaboration Library, were included. Fixed- or random-effects models were used to calculate pooled weighted or standard mean differences (WMD or SMD, respectively).

RESULTS

A total of 12 studies were included for analysis. The pooled effect of macrolides on FEV1 (eight trials, 381 subjects) was not significant (SMD 0.05, 95% CI -0.14-0.25), but there was a significant increase in peak expiratory flow (four trials, 419 subjects; WMD 6.7, 95% CI 1.35-12.06). Pooled analysis also showed significant improvements in symptom scores (eight studies, 478 subjects; WMD -0.46, 95% CI -0.60 to -0.32), quality of life (five trials, 346 subjects; WMD 0.18, 95% CI 0.001-0.37), and airway hyper-reactivity (two trials, 131 subjects; SMD 1.99, 95% CI 0.46-3.52). Post hoc evaluation showed limited statistical power to detect significant differences in FEV1.

CONCLUSIONS

Macrolide administration for asthma for three or more weeks was not associated with improvement in FEV1, but produced significant improvements in peak expiratory flow, symptoms, quality of life, and airway hyper-reactivity. Macrolides may therefore be beneficial as adjunct asthma therapy. Future trials, focusing on long-term safety and effectiveness, should use standardized outcomes and procedures.

Phenotyping airways disease: an A to E approach

The airway diseases asthma and chronic obstructive pulmonary disease (COPD) are heterogeneous conditions with overlapping pathophysiological and clinical features. It has previously been proposed that this heterogeneity may be characterized in terms of five relatively independent domains labelled from A to E, namely airway hyperresponsiveness (AHR), bronchitis, cough reflex hypersensitivity, damage to the airways and surrounding lung parenchyma, and extrapulmonary factors. Airway hyperresponsiveness occurs in both asthma and COPD, accounting for variable day to day symptoms, although the mechanisms most likely differ between the two conditions. Bronchitis, or airway inflammation, may be predominantly eosinophilic or neutrophilic, with different treatments required for each. Cough reflex hypersensitivity is thought to underlie the chronic dry cough out of proportion to other symptoms that can occur in association with airways disease. Structural changes associated with airway disease (damage) include bronchial wall thickening, airway smooth muscle hypertrophy, bronchiectasis and emphysema. Finally, a variety of extrapulmonary factors may impact upon airway disease, including rhinosinusitis, gastroesophageal reflux disease, obesity and dysfunctional breathing. This article discusses the A to E concept in detail and describes how this framework may be used to assess and treat patients with airway diseases in the clinic.

Assessment of exercise-induced bronchoconstriction in adolescents and young children

Recent research shows important differences in exercise-induced bronchoconstriction (EIB) between children and adults, suggesting a different pathophysiology of EIB in children. Although exercise can trigger classic symptoms of asthma, in children symptoms can be subtle and nonspecific; parents, children, and clinicians often do not recognize EIB. With an age-adjusted protocol, an exercise challenge test can be performed in children as young as 3 years of age. However, an alternative challenge test is sometimes necessary to assess potential for EIB in children. This review summarizes age-related features of EIB and recommendations for assessing EIB in young children and adolescents.

Airway smooth muscle in the pathophysiology and treatment of asthma

Airway smooth muscle (ASM) plays an integral part in the pathophysiology of asthma. It is responsible for acute bronchoconstriction, which is potentiated by constrictor hyperresponsiveness, impaired relaxation and length adaptation. ASM also contributes to airway remodeling and inflammation in asthma. In light of this, ASM is an important target in the treatment of asthma.

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.

Exhaled RANTES and interleukin 4 levels after exercise challenge in children with asthma

BACKGROUND

Despite the universality and clinical significance of exercise-induced bronchospasm (EIB), the mechanisms responsible for it are incompletely understood.

OBJECTIVE

To investigate the role of exhaled RANTES (regulated on activation, normal T-cell expressed and secreted) and interleukin (IL) 4 in EIB in children with asthma.

METHODS

Fifty-six children with asthma were evaluated with exercise challenge and exhaled RANTES and IL-4 levels. Exhaled breath condensate was collected before and 30 minutes after exercise challenge. RANTES and IL-4 concentrations were determined using a specific immunoassay kit.

RESULTS

A significant increase was found in RANTES levels after exercise challenge in the asthmatic children (P<.001). A statistically significant increase in RANTES levels was noted after exercise challenge in both the asthmatic children with EIB (n=25, P=.007) and in the non-EIB asthmatic group (n=31, P=.005). Our study revealed that exhaled RANTES level correlates significantly well with percentage of forced expiratory volume in 1 second (FEV1), exacerbation frequency, serum IgE, and body mass index. No statistically significant increase was found in IL-4 levels after exercise challenge. The maximal postexercise decrease in FEV1 strongly correlated with total eosinophil count (P<.001, r = -0.61) and baseline ratio of FEV1 to forced vital capacity (FVC) (P=.002, r=0.40). Results from multivariate regression analysis adjusted for age, sex, and atopy as covariates showed that eosinophil count and FEV1/FVC ratio were significantly associated with EIB.

CONCLUSION

We found that exercise challenge, leading to hyperosmolar stimulus, may increase exhaled RANTES levels in children with asthma. In addition, exhaled RANTES levels correlate well with serum IgE, severity of asthma, FEV1/FVC ratio, and body mass index. RANTES and IL-4 may not be independent predictors for EIB. Furthermore, eosinophil count and FEV1/FVC ratio may predict the presence and severity of EIB in asthmatic children.

Airway hyperresponsiveness in asthma: mechanisms, clinical significance, and treatment

Airway hyperresponsiveness (AHR) and airway inflammation are key pathophysiological features of asthma. Bronchial provocation tests (BPTs) are objective tests for AHR that are clinically useful to aid in the diagnosis of asthma in both adults and children. BPTs can be either “direct” or “indirect,” referring to the mechanism by which a stimulus mediates bronchoconstriction. Direct BPTs refer to the administration of pharmacological agonist (e.g., methacholine or histamine) that act on specific receptors on the airway smooth muscle. Airway inflammation and/or airway remodeling may be key determinants of the response to direct stimuli. Indirect BPTs are those in which the stimulus causes the release of mediators of bronchoconstriction from inflammatory cells (e.g., exercise, allergen, mannitol). Airway sensitivity to indirect stimuli is dependent upon the presence of inflammation (e.g., mast cells, eosinophils), which responds to treatment with inhaled corticosteroids (ICS). Thus, there is a stronger relationship between indices of steroid-sensitive inflammation (e.g., sputum eosinophils, fraction of exhaled nitric oxide) and airway sensitivity to indirect compared to direct stimuli. Regular treatment with ICS does not result in the complete inhibition of responsiveness to direct stimuli. AHR to indirect stimuli identifies individuals that are highly likely to have a clinical improvement with ICS therapy in association with an inhibition of airway sensitivity following weeks to months of treatment with ICS. To comprehend the clinical utility of direct or indirect stimuli in either diagnosis of asthma or monitoring of therapeutic intervention requires an understanding of the underlying pathophysiology of AHR and mechanisms of action of both stimuli.

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.

Airway contractility and remodeling: links to asthma symptoms

Respiratory symptoms are largely caused by obstruction of the airways. In asthma, airway narrowing mediated by airway smooth muscle (ASM) contraction contributes significantly to obstruction. The spasmogens produced following exposure to environmental triggers, such as viruses or allergens, are initially responsible for ASM activation. However, the extent of narrowing of the airway lumen due to ASM shortening can be influenced by many factors and it remains a real challenge to decipher the exact role of ASM in causing asthmatic symptoms. Innovative tools, such as the forced oscillation technique, continue to develop and have been proven useful to assess some features of ASM function in vivo. Despite these technologic advances, it is still not clear whether excessive narrowing in asthma is driven by ASM abnormalities, by other alterations in non-muscle factors or simply because of the overexpression of spasmogens. This is because a multitude of forces are acting on the airway wall, and because not only are these forces constantly changing but they are also intricately interconnected. To counteract these limitations, investigators have utilized in vitro and ex vivo systems to assess and compare asthmatic and non-asthmatic ASM contractility. This review describes: 1- some muscle and non-muscle factors that are altered in asthma that may lead to airway narrowing and asthma symptoms; 2- some technologies such as the forced oscillation technique that have the potential to unveil the role of ASM in airway narrowing in vivo; and 3- some data from ex vivo and in vitro methods that probe the possibility that airway hyperresponsiveness is due to the altered environment surrounding the ASM or, alternatively, to a hypercontractile ASM phenotype that can be either innate or acquired.

Gastroesophageal reflux disease and airway hyperresponsiveness: concomitance beyond the realm of chance?

Gastroesophageal reflux disease and asthma are both quite common the world over, and they can coexist. However, the nature of the relationship between these two diseases remains unclear. In this study, we review controversial aspects of the relationships among asthma, airway hyperresponsiveness, and gastroesophageal reflux disease in adults and in children.

Feasibility and acceptability of using bronchial hyperresponsiveness to manage asthma in primary care: a pilot study

AIMS

To determine if indirect testing for bronchial hyperresponsiveness (BHR) to monitor inhaled corticosteroid (ICS) treatment in asthma is feasible and acceptable in primary care.

METHODS

Fourteen adult patients with asthma aged 22-70 years (4M:10F, forced expiratory volume in 1 s >70% predicted) taking ICS performed a test for BHR using mannitol on three visits 6 weeks apart. ICS dose adjustments were made based on the presence of BHR. The Asthma Quality of Life Questionnaire (AQLQ) and the Asthma Control Questionnaire were used at each visit. A semi structured interview at study exit assessed subject acceptability.

RESULTS

BHR did not return in those with no BHR at study entry (n=9) with decreasing ICS dose. Improvements in BHR with increasing ICS dose (n=5) were observed with clinically significant improvements in AQLQ (mean score increase >0.5, p=0.02). Feasibility and acceptability of BHR testing was demonstrated.

CONCLUSIONS

It is feasible and acceptable to perform BHR testing using mannitol to help identify patients with asthma who would benefit from ICS dose increases and those with no BHR who could have a dose reduction.

TRIAL REGISTRATION

Australia New Zealand Clinical Trial Registry ACTRN12610000807055.

Methacholine challenge test: diagnostic characteristics in asthmatic patients receiving controller medications

BACKGROUND

The methacholine challenge test (MCT) is commonly used to assess airway hyperresponsiveness, but the diagnostic characteristics have not been well studied in asthmatic patients receiving controller medications after the use of high-potency inhaled corticosteroids became common.

OBJECTIVES

We investigated the ability of the MCT to differentiate participants with a physician's diagnosis of asthma from nonasthmatic participants.

METHODS

We conducted a cohort-control study in asthmatic participants (n= 126) who were receiving regular controller medications and nonasthmatic control participants (n= 93) to evaluate the sensitivity and specificity of the MCT.

RESULTS

The overall sensitivity was 77% and the specificity was 96% with a threshold PC(20) (the provocative concentration of methacholine that results in a 20% drop in FEV(1)) of 8 mg/mL. The sensitivity was significantly lower in white than in African American participants (69% vs 95%, P= .015) and higher in atopic compared with nonatopic (82% vs 52%, P= .005). Increasing the PC(20) threshold from 8 to 16 mg/mL did not noticeably improve the performance characteristics of the test. African American race, presence of atopy, and lower percent predicted FEV(1) were associated with a positive test result.

CONCLUSIONS

The utility of the MCT to rule out a diagnosis of asthma depends on racial and atopic characteristics. Clinicians should take into account the reduced sensitivity of the MCT in white and nonatopic asthmatic patients when using this test for the diagnosis of asthma.

Effect of an intranasal corticosteroid on exercise induced bronchoconstriction in asthmatic children

RATIONALE

Allergic rhinitis and exercise induced bronchoconstriction (EIB) are common in asthmatic children. The aim of this study was to investigate whether treatment of allergic rhinitis with an intranasal corticosteroid protects against EIB in asthmatic children.

METHODS

This was a double-blind, randomized, placebo-controlled, parallel group study. Subjects aged 12-17 years, with mild-to-moderate asthma, intermittent allergic rhinitis and ≥ 10% fall in FEV(1) at a screening exercise challenge were randomized to 22 ± 3 days treatment with intranasal fluticasone furoate or placebo. The primary outcome was change in exercise induced fall in FEV(1) . Secondary outcomes were changes in the area under the curve (AUC), asthma control questionnaire (ACQ), pediatric asthma quality of life questionnaire (PAQLQ), and exhaled nitric oxide (FeNO).

RESULTS

Twenty-five children completed the study. Mean exercise induced fall in FEV(1) (± SD) decreased significantly (95% CI: 0.7-18.2%, P = 0.04) in the fluticasone furoate group from 28.4 ± 15.8% to 19.0 ± 13.8%, compared to the placebo group (27.4 ± 16.0% to 27.4 ± 19.2%). The change in AUC was not significantly different between treatment groups. However, within the fluticasone furoate group the AUC decreased significantly (P = 0.01). Although total PAQLQ score did not improve, the activity limitation domain score improved significantly within the fluticasone furoate group (P = 0.03). No significant changes were observed in FeNO and ACQ.

CONCLUSION

Treatment of allergic rhinitis in asthmatic children with an intranasal corticosteroid reduces EIB and tends to improve quality of life.

Kv7 potassium channels in airway smooth muscle cells: signal transduction intermediates and pharmacological targets for bronchodilator therapy

Expression and function of Kv7 (KCNQ) voltage-activated potassium channels in guinea pig and human airway smooth muscle cells (ASMCs) were investigated by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR), patch-clamp electrophysiology, and precision-cut lung slices. qRT-PCR revealed expression of multiple KCNQ genes in both guinea pig and human ASMCs. Currents with electrophysiological and pharmacological characteristics of Kv7 currents were measured in freshly isolated guinea pig and human ASMCs. In guinea pig ASMCs, Kv7 currents were significantly suppressed by application of the bronchoconstrictor agonists methacholine (100 nM) or histamine (30 μM), but current amplitudes were restored by addition of a Kv7 channel activator, flupirtine (10 μM). Kv7 currents in guinea pig ASMCs were also significantly enhanced by another Kv7.2-7.5 channel activator, retigabine, and by celecoxib and 2,5-dimethyl celecoxib. In precision-cut human lung slices, constriction of airways by histamine was significantly reduced in the presence of flupirtine. Kv7 currents in both guinea pig and human ASMCs were inhibited by the Kv7 channel blocker XE991. In human lung slices, XE991 induced robust airway constriction, which was completely reversed by addition of the calcium channel blocker verapamil. These findings suggest that Kv7 channels in ASMCs play an essential role in the regulation of airway diameter and may be targeted pharmacologically to relieve airway hyperconstriction induced by elevated concentrations of bronchoconstrictor agonists.

A 'Good' muscle in a 'Bad' environment: the importance of airway smooth muscle force adaptation to airway hyperresponsiveness

Asthma is characterized by airway inflammation, with a consequent increase in spasmogens, and exaggerated airway narrowing in response to stimuli, termed airway hyperresponsiveness (AHR). The nature of any relationship between inflammation and AHR is less clear. Recent ex vivo data has suggested a novel mechanism by which inflammation may lead to AHR, in which increased basal ASM-tone, due to the presence of spasmogens in the airways, may "strengthen" the ASM and ultimately lead to exaggerated airway narrowing. This phenomenon was termed "force adaptation" [Bossé, Y., Chin, L.Y., Paré, P.D., Seow, C.Y., 2009. Adaptation of airway smooth muscle to basal tone: relevance to airway hyperresponsiveness. Am. J. Respir. Cell Mol. Biol. 40, 13-18]. However, it is unknown whether the magnitude of the effect of force adaptation ex vivo could contribute to exaggerated airway narrowing in vivo. Our aim was to utilize a computational model of ASM shortening in order to quantify the potential effect of force adaptation on airway narrowing when all other mechanical factors were kept constant. The shortening in the model is dictated by a balance between physiological loads and ASM force-generating capacity at different lengths. The results suggest that the magnitude of the effect of force adaptation on ASM shortening would lead to substantially more airway narrowing during bronchial challenge at any given airway generation. We speculate that the increased basal ASM-tone in asthma, due to the presence of inflammation-derived spasmogens, produces an increase in the force-generating capacity of ASM, predisposing to AHR during subsequent challenge.

Bronchial provocation testing: the future

PURPOSE OF REVIEW

Performing a bronchial provocation test (BPT) using a direct or indirect stimulus to identify bronchial hyper-responsiveness (BHR) reduces the possibility of over and under-diagnosis of asthma based on history and symptoms. This review discusses some long-held beliefs of BPTs to include or exclude a diagnosis of asthma or exercise-induced bronchoconstriction (EIB).

RECENT FINDINGS

A high frequency of negative methacholine tests has been reported in 240 patients given a diagnosis of asthma at the end of the study, many of whom had documented EIB. This suggests that a negative methacholine test should not be relied upon to rule out asthma. Further, a positive methacholine test alone should be interpreted with caution as it may reflect airway injury rather than asthma or EIB. Mannitol, an indirect stimulus, identified a similar prevalence of BHR to methacholine and identified more patients than a single exercise test in three studies. However, neither mannitol nor methacholine identified all patients with EIB. Mannitol has a higher specificity for a physician diagnosis of asthma than methacholine.

SUMMARY

It is likely that both a direct test and an indirect test result may be required in some patients in order to confirm or exclude a diagnosis of asthma with certainty.

Endotracheal nebulization of N-acetylcysteine increases airway resistance in cats with experimental asthma

N-acetylcysteine (NAC), a mucolytic and antioxidant, is speculated to cause bronchoconstriction in cats when delivered via aerosol. We hypothesized that in cats with experimental asthma, aerosol delivery of NAC (400mg cumulative dose) via an endotracheal tube would increase airflow limitation as measured by ventilator-acquired mechanics. After endotracheal drug delivery, airway resistance and inspiratory plateau pressure (Pplat) measurements were obtained in six mechanically ventilated asthmatic cats. Results demonstrated significantly increased airway resistance (P=0.0007) compared with aerosolized saline control; Pplats were not significantly different (P=0.059). All cats exhibited at least one adverse effect: excessive airway secretions (n=3), spontaneous cough (n=2), unilateral strabismus (n=1) and post-anesthetic death (n=1). No adverse reactions were noted with saline aerosol; cough was noted in one cat with methacholine challenge. In conclusion, airway resistance and adverse reactions were documented in all cats after NAC aerosol delivery. Further studies must be performed to evaluate if it is an effective mucolytic and/or antioxidant in cats and to determine if bronchodilator pre-treatment will negate NAC-induced bronchoconstriction.

The inflammatory basis of exercise-induced bronchoconstriction

Exercise-induced bronchoconstriction (EIB) is common in individuals with asthma, and may be observed even in the absence of a clinical diagnosis of asthma. Exercise-induced bronchoconstriction can be diagnosed via standardized exercise protocols, and anti-inflammatory therapy with inhaled corticosteroids (ICS) is often warranted. Exercise-related symptoms are commonly reported in primary care; however, access to standardized exercise protocols to assess EIB are often restricted because of the need for specialized equipment, as well as time constraints. Symptoms and lung function remain the most accessible indicators of EIB, yet these are poor predictors of its presence and severity. Evidence suggests that exercise causes the airways to narrow as a result of the osmotic and thermal consequences of respiratory water loss. The increase in airway osmolarity leads to the release of bronchoconstricting mediators (eg, histamine, prostaglandins, leukotrienes) from inflammatory cells (eg, mast cells and eosinophils). The objective assessment of EIB suggests the presence of airway inflammation, which is sensitive to ICS in association with a responsive airway smooth muscle. Surrogate tests for EIB, such as eucapnic voluntary hyperpnea or the osmotic challenge tests, cause airway narrowing via a similar mechanism, and a response indicates likely benefit from ICS therapy. The complete inhibition of EIB with ICS therapy in individuals with asthma may be a useful marker of control of airway pathology. Furthermore, inhibition of EIB provides additional, useful information regarding the identification of clinical control based on symptoms and lung function. This article explores the inflammatory basis of EIB in asthma as well as the effect of ICS on the pathophysiology of EIB.

Introduction: Airway hyperresponsiveness in asthma: its measurement and clinical significance

This supplement to CHEST, titled "Airway Hyperresponsiveness in Asthma: Its Measurement and Clinical Significance," resulted from a symposium that brought together experts from Canada, the United States, and Australia to discuss the progress in the understanding of measurements of airway hyperresponsiveness. There was an additional focus on the indirect measurement of airway inflammation and its interaction with airway hyperresponsiveness, as well as the role of measuring airway inflammation in the management of asthma.