Effect of regular inhaled salbutamol on airway responsiveness and airway inflammation in rhinitic non-asthmatic subjects

Neuromuscular junction involvement in inherited motor neuropathies: genetic heterogeneity and effect of oral salbutamol treatment

OBJECTIVES

Inherited defects of the neuromuscular junction (NMJ) comprise an increasingly diverse range of diseases. Several recently identified genes highlight the overlap between peripheral neuropathies and congenital myasthenic syndromes (CMS). The beta-2 adrenergic receptor agonist salbutamol has been shown to provide symptomatic benefit in CMS, while improving structural defects at the NMJ. Based on these findings, we identified cases of motor neuropathy with NMJ dysfunction and assessed the effect of salbutamol on motor function.

METHODS

Cases of motor neuropathy with significant NMJ dysfunction, were identified using repetitive nerve stimulation and single fibre electromyography. Oral salbutamol was administered for 12 months. Repeat neurophysiological and clinical assessments were undertaken at baseline, 6 months and 12 months.

RESULTS

Significant defects of neuromuscular transmission were identified in 15 patients harbouring a range of genetic defects, including mutations in GARS1, DNM2, SYT2 and DYNC1H. No clear benefit on motor function was seen following the administration of 12 months of oral salbutamol; however, there was a significant improvement in patient reported fatigue. In addition, no clear effect on neurophysiological parameters was seen in patients treated with salbutamol. Side-effects due to off-target beta-adrenergic effects were significant in the patient cohort.

CONCLUSION

These results highlight the involvement of the NMJ in several subtypes of motor neuropathies, including subtypes of neuropathy due to deficits in mitochondrial fusion-fission, synaptic vesicle transport, calcium channels and tRNA synthetases. Whether the NMJ dysfunction is simply due to muscle reinnervation or a pathology unrelated to denervation is unknown. The involvement of the NMJ may represent a novel therapeutic target in these conditions. However, treatment regimens will need to be more targeted for patients with primary inherited defects of neuromuscular transmission.

Effects of treatment changes on asthma phenotype prevalence and airway neutrophil function

Background

Asthma inflammatory phenotypes are often defined by relative cell counts of airway eosinophils/neutrophils. However, the importance of neutrophilia remains unclear, as does the effect of ICS treatment on asthma phenotypes and airway neutrophil function. The purpose of this study was to assess asthma phenotype prevalence/characteristics in a community setting, and, in a nested preliminary study, determine how treatment changes affect phenotype stability and inflammation, with particular focus on airway neutrophils.

Methods

Fifty adult asthmatics and 39 non-asthmatics were assessed using questionnaires, skin prick tests, spirometry, exhaled nitric oxide (FENO) measurement, and sputum induction. Twenty-one asthmatics underwent further assessment following treatment optimisation (n = 11) or sub-optimisation (n = 10).

Results

Forty percent (20/50) had eosinophilic asthma (EA) and 8% had neutrophilic asthma. EA was associated with increased FENO, bronchodilator reversibility (BDR) and reduced lung function (p < 0.05). Following optimisation/sub-optimisation, the EA/NEA (non-eosinophilic asthma) phenotype changed in 11/21 (52%) asthmatics. In particular, fewer subjects had EA post treatment optimisation, but this was not statistically significant. However, a significant (p < 0.05) reduction in FENO, ACQ7 score, and BDR was observed after treatment optimisation, as well as an increase in FEV₁-% predicted (p < 0.05). It was also associated with reduced eosinophils (p < 0.05) and enhanced neutrophil phagocytosis (p < 0.05) in EA only, and enhanced neutrophil oxidative burst in both EA and NEA (p < 0.05).

Conclusions

In this community based population, non-eosinophilic asthma was common, less severe than EA, and at baseline most asthmatics showed no evidence of inflammation. In the nested change in treatment study, treatment optimisation was associated with reduced sputum eosinophils, improved symptoms and lung function, and enhanced neutrophil function, but a significant reduction in EA could not be demonstrated.

Trial registration

The nested change in treatment component of this study is registered at the Australia and New Zealand Clinical Trial Registry (www.ANZCTR.org.au) ACTRN12617001356358. Registration date 27/09/2017. Retrospectively registered.

Electronic supplementary material

The online version of this article (10.1186/s12890-017-0511-6) contains supplementary material, which is available to authorized users.

Airway injury as a mechanism for exercise-induced bronchoconstriction in elite athletes

Exercise-induced bronchoconstriction (EIB) is a consequence of evaporative water loss in conditioning the inspired air. The water loss causes cooling and dehydration of the airway surface. One acute effect of dehydration is the release of mediators, such as prostaglandins, leukotrienes, and histamine, that can stimulate smooth muscle, causing contraction and a change in vascular permeability. Inspiring cold air increases dehydration of the surface area and causes changes in bronchial blood flow. This article proposes that the pathogenesis of EIB in elite athletes relates to the epithelial injury arising from breathing poorly conditioned air at high flows for long periods of time or high volumes of irritant particles or gases. The evidence to support this proposal comes from many markers of injury. The restorative process after injury involves plasma exudation and movement of cells into the airways, a process repeated many times during a season of training. This process has the potential to expose smooth muscle to a wide variety of plasma- and cell-derived substances. The exposure to these substances over time can lead to an alteration in the contractile properties of the smooth muscle, making it more sensitive to mediators of bronchoconstriction. It is proposed that cold-weather athletes have airway hyperresponsiveness (AHR) to pharmacologic agents as a result of epithelial injury. In those who are allergic, AHR can also be expressed as EIB. The role of beta(2)-receptor agonists in inhibiting and enhancing the development of AHR and EIB is discussed.

Beta2-agonists and exercise-induced asthma

Beta2-agonists taken immediately before exercise provide significant protection against exercise- induced asthma (EIA) in most patients. However, when they are taken daily, there are some negative aspects regarding severity, control, and recovery from EIA. First, there is a significant minority (15-20%) of asthmatics whose EIA is not prevented by beta2-agonists, even when inhaled corticosteroids are used concomitantly. Second, with daily use, there is a decline in duration of the protective effect of long-acting beta2-agonists. Third, if breakthrough EIA occurs, recovery of lung function is slower in response to a beta2-agonist, and additional doses are often required to achieve pre-exercise values. If a person who takes a beta2-agonist daily experiences problems with exercise, then the physician should consider changing the treatment regimen to achieve better control of EIA. These problems likely result from desensitization of the beta2-receptor on the mast cell, which enhances mediator release, and on the bronchial smooth muscle, which enhances the bronchoconstrictor response and delays recovery from EIA. These effects are reversed within 72 h after cessation of a beta2-agonists. The important clinical question is: Are we actually compromising the beneficial effects of beta2-agonists on the prevention and recovery from EIA by prescribing them daily? Patients with EIA need to ensure that their doses of inhaled corticosteroid or other anti-inflammatory therapy are optimized so that, if necessary, a beta2-agonist can be used intermittently as prophylactic medication with greater confidence in the outcome.

Exercise-induced bronchoconstriction: pathogenesis

There is still active debate on the acute mechanism of exercise-induced bronchoconstriction (EIB). Although it is unlikely that vasoconstriction and hyperemia of the bronchial vasculature are essential events for EIB, it is likely that this vasculature enhances the airway response to dehydration and contributes to the pathogenesis of EIB, particularly in elite athletes. Accumulating evidence suggests that airway smooth muscle (ASM) becomes more sensitive as a result of repeated exposure to bulk plasma in response to airway injury from dehydration. Recent evidence also demonstrates sufficient concentrations of mediators that could affect ASM. Paradoxically, mediator release from mast cells may be enhanced and their contractile effects greater when beta(2)-receptor agonists are taken daily. The effect of drugs that have the potential to reduce microvascular leak and reduce or inhibit release or action of these mediators needs to be investigated in elite athletes.

Long-acting beta 2-adrenoceptor agonists and exercise-induced asthma: lessons to guide us in the future

The safety and efficacy of long-acting beta(2)-adrenoceptor agonists (LABAs) taken intermittently for the prevention of exercise-induced asthma (EIA) in children is well established. However, the safety and efficacy of LABAs taken twice daily, either alone or in combination with inhaled corticosteroids, for the prevention of EIA is not as clear because of issues of tolerance (defined as being less responsive to the influence of LABAs). There have been many observations on short-acting beta(2)-adrenoceptor agonists (SABAs) and EIA that should have alerted us to the potential for tolerance and desensitization to occur with LABAs. For example, we expected that the use of LABAs for EIA would overcome the problem of the short duration of protection of SABAs, and to some extent they have. The protective period of a LABA is two to three times longer in duration than that of a SABA. However, when a LABA is taken daily it is apparent that the duration of its protective effect is reduced and there is a risk of EIA occurring well within the 12-hour administration schedules. Furthermore, daily use of LABAs attenuates the bronchodilator effect of SABAs, an effect that is greater the more severe the bronchoconstriction. This 'tolerance' increases both the time and the amount of therapy that is needed to recover from bronchoconstriction, and thus, could potentially impact on the success of rescue therapy should severe EIA occur. The daily use of LABAs also increases the sensitivity of the bronchial smooth muscle to contractile agents. This increase in sensitivity is almost equivalent to the extent to which inhaled corticosteroids reduce sensitivity to the same contractile agents. The increased sensitivity to contractile agents may occur either by a reduction in the inhibitory effect of beta(2)-adrenoceptor agonists on release of mediators from mast cells or by a direct effect on the bronchial smooth muscle. These unwanted effects of LABAs are not necessarily reduced by concomitant treatment with inhaled corticosteroids. As the number of children being treated with LABAs increases, it is predicted that problems with breakthrough EIA will also increase. We need to know the percentage of children taking a LABA daily who are requiring either extra doses of a beta(2)-adrenoceptor agonist to prevent (or reverse) EIA or other provocative stimuli. If this percentage is significant then we may need to reconsider the position of LABAs in the treatment of children with asthma who regularly perform strenuous physical activity.

Preserved bronchial dilatation after salbutamol does not guarantee protection against bronchial hyperresponsiveness

Racemic salbutamol, a beta2-adrenoceptor agonist used for dilatation of airways, has recently been shown to induce lessened relaxation of bronchial smooth muscle and partial loss of bronchoprotection, seen as increased hyperresponsiveness, after regular treatment. The racemate undergoes stereo-selective disposition, giving higher plasma levels of S-salbutamol than that of bronchodilating R-salbutamol, thus raising S : R ratios after repeated administration. Our aim was to evaluate whether increased bronchial hyperresponsiveness (BHR) could be found even after 1 day of repeated salbutamol inhalations, with beta2-receptor-induced bronchial smooth muscle relaxation remaining and whether this would be associated with plasma levels of either enantiomer. Fifteen patients with stable asthma, aged 19-54 years, were included in a randomized, cross-over study. An indirect bronchial challenge method was used [voluntary isocapnic hyperventilation of cold air (IHCA)], and airway condition tested by means of impulse oscillometry. Racemic salbutamol was inhaled three times during a 6-h period. IHCA was performed and plasma concentrations of enantiomers were measured 4 h after the last dose. Tests were also performed without preceding drug treatment. beta2-Agonist-produced bronchial dilatation and protection persisted in the majority of the 15 patients 4 h after repeated inhalations of salbutamol during 1 day. In only two of the 15 patients we could trace increased BHR after salbutamol. Neither dilatation nor protection could be linked to plasma levels of either R- or S-salbutamol. The underlying mechanisms of BHR remain unknown and are dissociated from beta2-receptor-mediated dilatation.

Adverse effects of beta-agonists

Short-acting beta-adrenergic receptor agonists have pharmacologically predictable dose-related and potency-related adverse effects, including tachycardia and tremor, and they also affect serum potassium and glucose. These effects all show tolerance with continued exposure. The potential for arrhythmia is increased by comorbidity and hypoxemia. Nonpharmacologically predictable effects include airway hyperresponsiveness to nonspecific and specific stimuli, including allergen and exercise, and increased airway inflammation. Genetic variants of the beta-adrenergic receptor alter susceptibility to adverse effects of beta-agonists on airway function. The impact of the enantiomers of beta-agonists on adverse effects remains unclear. The two epidemics of asthma death among young people were temporally associated with introduction of potent short-acting beta-agonists (isoproterenol and fenoterol) and appear to be related to adverse effects of these drugs on airway function and airway hyperresponsiveness rather than to cardiotoxicity. Compared with short-acting agents, long-acting beta-agonists show similar but less pronounced pharmacologically predictable effects, and they have not been shown to increase airway hyperresponsiveness in adults. Postmarketing surveillance studies have not suggested significant adverse effects of long-acting beta-agonists on morbidity and mortality.

Regular inhaled salbutamol : effect on airway responsiveness to methacholine and adenosine 5'-monophosphate and tolerance to bronchoprotection

OBJECTIVE

Regular treatment with inhaled beta(2)-agonists increases airway responsiveness consistently to indirect bronchoconstrictors (allergen, exercise, hypertonic saline solution, etc) and inconsistently to direct bronchoconstrictors (histamine, methacholine). Studies demonstrating tolerance to beta(2)-agonist bronchoprotection against the indirect bronchoconstrictor adenosine 5'-monophosphate (AMP) have not examined changes in baseline AMP responsiveness. This study assessed the effect of regular salbutamol on AMP and methacholine responsiveness and on tolerance to bronchoprotection.

DESIGN

Double-blind, randomized, crossover study.

SETTING

University hospital bronchoprovocation laboratory.

PATIENTS

Fourteen atopic asthmatic subjects with FEV(1) > 65% predicted, and methacholine provocative concentration causing a 20% fall in FEV(1) (PC(20)) < 8 mg/mL.

INTERVENTIONS

Salbutamol, 100 microg, and placebo inhalers, two puffs qid, each for 10 days.

MEASUREMENTS

Methacholine PC(20) and AMP PC(20) measured 12 h after blinded inhaler after each treatment period. Methacholine PC(20) and AMP PC(20) repeated 10 min after salbutamol, 200 microg (eight subjects).

RESULTS

There was no difference between placebo and salbutamol treatment in geometric mean methacholine PC(20) (0.85 mg/mL vs 0.82 mg/mL, p = 0.86) or AMP PC(20) (22 mg/mL vs 17.4 mg/mL, p = 0.21; n = 14). The acute bronchoprotective effect of salbutamol was greater vs. AMP than vs methacholine (5.1 doubling concentrations vs. 3.5 doubling concentrations, p = 0.06) and loss of protective effect of salbutamol (mean +/- SD) was greater vs AMP than vs. methacholine (2.4 +/- 0.33 doubling concentration loss vs 0.8 +/- 0.21 doubling concentration loss, p = 0.008; n = 8).

CONCLUSION

Regular salbutamol (mean +/- SD) treatment did not enhance airway responsiveness to either the indirect bronchoconstrictor AMP or the direct bronchoconstrictor methacholine. Compared to its effect on methacholine, salbutamol had a greater acute protective effect vs AMP and produced greater loss of protection vs AMP when used regularly.

Salbutamol via Easyhaler is at least as effective as salbutamol via Turbuhaler in the treatment of histamine-induced bronchoconstriction

The aim of this study was to compare the clinical efficacy and acceptability of salbutamol inhaled via Easyhaler and Turbuhaler multi-dose dry powder inhalers in the treatment of histamine-induced bronchoconstriction. Thirty-two adult patients with asthma and/or bronchial hyper-reactivity were included in the study, which was carried out according to a randomized, double-blind, double-dummy, cross-over design. Histamine challenge test was performed on 2 study days separated by at least 7 days. The challenge test was continued until a > or = 20% fall in forced expiratory volume in 1 sec (FEV1) was achieved. The patients then inhaled a single 100 microg dose of salbutamol from Easyhaler, or from Turbuhaler. FEV1 was assessed by flow-volume spirometry before and after histamine challenge and 1.5, 3, 5, 10, 15, 20, 30 and 60 min after salbutamol inhalation. The primary efficacy variable was the maximum percentage change in FEV1 from the post-challenge value. The secondary efficacy variable was area under the curve (AUC) of FEV1. At the end of the study, acceptability of salbutamol Easyhaler was evaluated using a questionnaire and Easyhaler was also compared with the inhalation device the patient had used earlier. Twenty-six patients completed the study. Both salbutamol Easyhaler and salbutamol Turbuhaler produced a rapid and significant increase in FEV1, with maximum percentage changes being 43.9% (+/-15.3) and 40.5% (+/-21.9) from the post-challenge value, respectively. There were no significant differences between the two inhalation devices in terms of changes in FEV1 or AUC of FEV1. The use of Easyhaler and getting a new dose from Easyhaler was considered to be very easy by 65% and easy by 35% of the patients. None considered it difficult. Of 16 patients who had used Turbuhaler earlier, 19% considered Easyhaler much better, 44% better, and 38% the same as Turbuhaler, and none considered it worse. In conclusion, the results show that salbutamol Easyhaler was at least as effective as salbutamol Turbuhaler in the treatment of histamine-induced bronchoconstriction. In addition, the patients considered Easyhaler very easy or easy to use. The majority of patients who reported Turbuhaler as their own inhaler considered Easyhaler better or much better than Turbuhaler.

Effects of terbutaline and budesonide on sputum cells and bronchial hyperresponsiveness in asthma

Previous studies have shown that the regular administration of short acting beta-agonists can be associated with adverse effects on airway caliber and bronchial hyperresponsiveness (BHR) and that this may occur through a proinflammatory mechanism. The aim was to explore possible adverse effects of high-dose beta-agonist therapy and to assess any adverse interaction with corticosteroids. We undertook a randomized, crossover study to investigate the effects of 6 wk of treatment with regular terbutaline (1 mg four times a day), regular budesonide (400 microg twice a day), combined treatment, and placebo in subjects with mild to moderate asthma. Major endpoints were PD(15) saline, PD(20) methacholine, and induced sputum differential cell counts. Thirty-four subjects were randomized and 28 completed the study. PD(15) saline decreased on terbutaline alone compared with placebo treatment and on combined treatment compared with budesonide alone (mean fold decrease of 0.57 [95% CI = 0.36, 0.90] and 0.65 [95% CI = 0.43, 0.97], respectively). PD(20) methacholine was not affected by the use of terbutaline either alone or in combination with budesonide. The percentage of eosinophils in induced sputum increased during terbutaline treatment alone compared with placebo (median 8.3% versus 4.4%, p = 0.049). The addition of terbutaline to budesonide did not affect the percentage of eosinophils compared with budesonide treatment alone. These findings support the hypothesis that short-acting beta-agonists have a permissive effect on airway inflammation and that when used in high dose there may be an unfavorable interaction with inhaled corticosteroids.

Recent advances in the sleep apnoea/hypopnoea syndrome

This review highlights some of the advances in sleep apnoea/hypopnoea syndrome made over the last few years, particularly in diagnosis and treatment. Recent evidence of the controversial associations of sleep apnoea/hypopnoea syndrome with increased morbidity and mortality, particularly from cardiovascular disease, is presented.

The effect of regular salbutamol on lung function and bronchial responsiveness in patients with primary ciliary dyskinesia

STUDY OBJECTIVE

There is growing evidence that regular beta(2)-agonist use in patients with asthma is associated with decreased airway caliber and increased bronchial responsiveness. The aim of this study was to determine whether regular treatment with beta(2)-agonists induces changes in lung function and bronchial responsiveness in patients with primary ciliary dyskinesia.

DESIGN

A randomized, double-blind, placebo-controlled, crossover study.

PATIENTS

Nineteen children with primary ciliary dyskinesia.

INTERVENTIONS

Subjects received inhaled salbutamol or identical placebo (2 x 100 microg qid) for periods of 6 weeks with a wash-out period of 4 weeks.

MEASUREMENTS AND RESULTS

FEV(1) was measured before and 3 weeks and 6 weeks after salbutamol or placebo treatment. High-dose methacholine inhalation tests were performed before and 6 weeks after each treatment. The provocative concentration of methacholine producing a 20% fall in FEV(1) (PC(20)) and maximal airway narrowing (MDeltaFFEV(1)) was measured. No significant change in FEV(1) was observed during the salbutamol or placebo periods. No significant differences in the parameters of bronchial responsiveness (PC(20) and MDeltaFFEV(1)) were noted as the result of either salbutamol or placebo treatment.

CONCLUSION

Our data have shown that salbutamol, inhaled regularly for 6 weeks, did not cause either a decline in lung function or an increase in bronchial responsiveness in subjects with primary ciliary dyskinesia.

Inhaled short acting beta2-agonist use in asthma: regular vs as needed treatment

BACKGROUND

Inhaled beta2-adrenergic agonists delivered by inhalation are very widely used in asthma. There has been much controversy of the use and possible consequences of the use of these agents for regular, as opposed as-needed use in asthma.

OBJECTIVES

This review to assessed the clinical trial evidence to test whether using regular use of short-acting beta2-agonists reduced asthma control and pulmonary function; worsened symptoms, airway reactivity and quality of life; and increased the rate of exacerbations.

SEARCH STRATEGY

A search was carried out of the Cochrane Airways Group "Asthma and Wheez* RCT" register using the terms: regular AND [beta agonist OR bronchodilator OR salbutamol OR albuterol Or terbutaline OR isoproterenol OR reproterol OR fenoterol]. Bibliographies of existing trials were searched and primary trial authors and pharmaceutical companies were approached for additional trials.

SELECTION CRITERIA

Randomised controlled trials in which the short-acting beta2-agonist was given regularly in the experimental group, together with an inhaled bronchodilator for relief of symptoms ('rescue use'). The control group consisted of matching placebo inhaled regularly, with an inhaled bronchodilator for as-needed 'rescue use'.

DATA COLLECTION AND ANALYSIS

Data were extracted and quality assessments were made by both reviewers. Parallel group and cross-over trials were analysed separately. Where possible data were pooled using a fixed effects model.

MAIN RESULTS

Over 800 abstracts were identified, following a review, 60 papers were requested for full assessment by both reviewers. 34 trials from 30 papers met the entry criteria. Data from 31 outcomes were analyzable. There was little difference between the treatments for nearly all outcomes. In cross-over studies, evening peak flow was better with regular treatment, weighted mean difference (WMD) 13.1 l/min (95% confidence interval 24.3, 1.9). In contrast, the FEV1 was better with as-needed treatment (WMD 157 ml (95% CI: 123, 192). Bronchial hyper reactivity was slightly better in the as-needed group, standardised mean difference 0.23, 95% CI: 0.52, 1.12.

REVIEWER'S CONCLUSIONS

These results support current guidelines. There is little advantage in using short-acting beta2-agonists regularly, and potentially some small clinical disadvantage.

Pharmacotherapy of asthma in children, with special reference to leukotriene receptor antagonists

Asthma in adults is generally recognized as a chronic inflammatory airway disease, although this association is less well established in childhood asthma. Thus, recent asthma guidelines have emphasized that asthma treatment should be directed toward the underlying inflammatory aspects of the disease. The prevalence of asthma and resultant hospitalizations and deaths have increased or remained stable over the past 10 years in the United States. In part, this appears to be caused by shortcomings of available antiasthma therapeutic agents. Because these trends are particularly troublesome in children and young adults, there is a need for effective anti-inflammatory therapies that are safe and tolerable. The leukotrienes are a family of lipid mediators that appear to play an important role in the symptomology and pathogenesis of asthma. The results of clinical trials in adults with asthma demonstrated that antileukotriene drugs such as zafirlukast, montelukast, and zileuton improve pulmonary function, decrease asthma symptoms, and decrease the concomitant use of other antiasthma drugs. Most antileukotriene agents are orally bioavailable and well tolerated, offering the potential for improved patient compliance. Montelukast and zafirlukast have received approval for use in pediatric asthma patients, and approval of zafirlukast in this patient population is pending.

Selective airway responsiveness in asthma

Hyperresponsiveness of airway smooth muscle accounts for the susceptibility of asthmatic subjects to diverse bronchoconstrictor agents. It is widely presumed that hyperresponsiveness is not spasmogen selective. Hence, inhalation of methacholine is used routinely for clinical assessment of asthma and for evaluation of anti-asthma drugs. Comparative studies employing multiple spasmogens have revealed hyperresponsiveness to be markedly spasmogen selective. Because of this pronounced heterogeneity of hyperresponsiveness, sensitivity to methacholine cannot provide a reliable index of responsiveness. Development of exceptional hyperresponsiveness to bradykinin and to peptidoleukotrienes during allergic and other reactions could warrant the development of specific antagonists for asthma therapy. These issues are discussed here by Brian O'Connor, Simon Crowther, John Costello and John Morley.