Critical roles of airway smooth muscle in mediating deep-inspiration-induced bronchodilation: a big stretch?

BACKGROUND

Deep inspiration (DI) has been shown to induce bronchodilation and bronchoprotection in bronchochallenged healthy subjects, but not in asthmatics. Strain-induced relaxation of airway smooth muscle (ASM) is considered one of the factors responsible for these effects. Other factors include the release or redistribution of pulmonary surfactant, alteration in mucus plugs, and changes in airway heterogeneity.

MAIN BODY

The present review is focused on the DI effect on ASM function, based on recent findings from ex vivo sheep lung experiments showing a large change in airway diameter during a DI. The amount of stretch on the airways, when applied to isolated airway rings in vitro, caused a substantial decrease in ASM contractility that takes many minutes to recover. When challenged with a bronchoconstrictor, the increase in pulmonary resistance in the ex vivo ovine lungs is mostly due to the increase in airway resistance.

CONCLUSIONS

Although non-ASM related factors cannot be excluded, the large strain on the airways associated with a DI substantially reduces ASM contractility and thus can account for most of the bronchodilatory and bronchoprotective effects of DI.

Assessing the Effects of Changing Patterns of Inhaled Corticosteroid Dosing and Adherence with Fluticasone Furoate and Budesonide on Asthma Management

INTRODUCTION

Pharmacological asthma management focuses on the use of inhaled corticosteroid (ICS)-containing therapies, which reduce airway inflammation and provide bronchoprotection, improving symptom control and reducing exacerbation risk. ICS underuse due to poor adherence is common, leading to poor clinical outcomes including increased risk of mortality. This article reviews efficacy versus systemic activity profiles for various adherence patterns and dosing regimens of fluticasone furoate (FF)-containing and budesonide (BUD)-containing asthma therapies in clinical trials and real-world studies.

METHODS

We performed a structured literature review (1 January 2000-3 March 2022) and mathematical modelling analysis of FF-containing and BUD-containing regular daily dosing in patients with mild-to-severe asthma, as-needed BUD/formoterol (FOR) in mild asthma, and BUD/FOR maintenance and reliever therapy (MART) dosing in moderate-to-severe asthma, to assess efficacy (bronchoprotection) and systemic activity (cortisol suppression) profiles of dosing patterns of ICS use in multiple adherence scenarios.

RESULTS

A total of 22 manuscripts were included in full-text review and 18 in the model simulations. Focusing on FF-containing or BUD-containing treatments at comparable adherence rates, regular daily FF or FF/vilanterol (VI) dosing provided more prolonged bronchoprotection and fewer systemic effects than daily BUD, daily BUD/FOR, or BUD/FOR MART dosing, especially in low adherence scenarios. In model simulations and the real-world setting, FF/VI generally provided longer bronchoprotection, lower systemic activity, and greater clinical benefits over BUD/FOR as well as consistently higher adherence.

CONCLUSION

In this literature review and modelling analysis, FF/VI was found to show clinical advantages on asthma control over BUD/FOR. These findings have implications for helping clinicians select the most suitable inhaled therapy for their patients with asthma.

New Versus Old: The Impact of Changing Patterns of Inhaled Corticosteroid Prescribing and Dosing Regimens in Asthma Management

Inhaled corticosteroid (ICS)-containing therapies are the mainstay of pharmacological management of asthma. They can be administered alone or in combination with a long-acting bronchodilator, depending on asthma severity, and may also be supplemented with short-acting bronchodilators for as-needed rescue medication. Adherence to asthma therapies is generally poor and characterized by underuse of ICS therapies and over-reliance on short-acting bronchodilators, which leads to poor clinical outcomes. This article reviews efficacy versus systemic activity profiles for various dosing regimens of budesonide (BUD) and fluticasone propionate (FP). We performed a structured literature review of BUD and FP regular daily dosing, and BUD/formoterol (FOR) as-needed dosing, to explore the relationship between various dosing patterns of ICS regimens and the risk–benefit profile in terms of the extent of bronchoprotection and cortisol suppression. In addition, we explored how adherence could potentially affect the risk–benefit profile, in patients with mild, moderate, and moderate-to-severe asthma. With a specific focus on BUD or FP-containing treatments, we found that regular daily ICS and ICS/long-acting β₂-agonist (LABA) dosing had a greater degree of bronchoprotection than as-needed BUD/FOR dosing or BUD/FOR maintenance and reliever therapy (MART) dosing, and still maintained low systemic activity. We also found that the benefits of regular daily ICS dosing regimens were diminished when adherence was low (50%); the shorter duration of bronchoprotection observed was similar to that seen with typical as-needed BUD/FOR usage. These findings have implications for aiding clinicians with selecting the most suitable treatment option for asthma management, and subsequent implications for the advice clinicians give their patients.

Inhaled corticosteroid (ICS)-containing therapies can be administered in a variety of ways depending on a patient’s asthma severity. Patients with mild asthma tend to experience symptom relief with as-needed or regular daily use of an ICS alone, whereas patients with more severe asthma may require regular daily use of an ICS plus a long-acting β₂-agonist (LABA) to experience sufficient asthma control. However, failure to correctly adhere to ICS-containing therapies or an over-reliance on short-acting bronchodilators for symptom relief hinders optimal asthma management, thus negatively affecting overall patient health and wellbeing. Understanding how different dosing regimens affect the degree of bronchoprotection (efficacy) and cortisol suppression (systemic activity) of ICS treatments would benefit physicians by helping them to prescribe the most appropriate treatment for their patient’s asthma. We performed a structured literature review of two ICS molecules—budesonide (BUD) (alone and combined with formoterol [FOR]) and fluticasone propionate (FP)—to explore the relationship between various ICS dosing regimens, and then used these findings to construct models for ICS risk–benefit profiles. Our models factored in different ICS dosing regimens—as-needed, regular daily dosing, and maintenance and reliever therapy (MART)—and various degrees of treatment adherence. We found that regular daily ICS and ICS/LABA dosing provided better bronchoprotection than as-needed BUD/FOR dosing or BUD/FOR MART dosing, but this benefit was diminished with low adherence. Regular daily dosing maintained low cortisol suppression, which indicated a fairly low risk of negative side effects. Our findings have subsequent implications for optimizing treatment in patients with asthma.

Prostaglandin D2 inhibits mediator release and antigen induced bronchoconstriction in the Guinea pig trachea by activation of DP1 receptors

The mechanism by which cyclooxygenase (COX) inhibition increases antigen-induced responses in airways remains unknown. Male albino guinea pigs were sensitized to ovalbumin (OVA). Intact rings of the trachea were isolated and mounted in organ baths for either force measurements or lipid mediator release analysis by UPLC-MS/MS or EIA following relevant pharmacological interventions. First, challenge with OVA increased the release of all primary prostanoids (prostaglandin (PG) D₂/E₂/F_2α/I₂ and thromboxanes). This release was eliminated by unselective COX inhibition (indomethacin) whereas selective inhibition of COX-2 (lumiracoxib) did not inhibit release of PGD₂ or thromboxanes. Additionally, the increased levels of leukotriene B₄ and E₄ after OVA were further amplified by unselective COX inhibition. Second, unselective inhibition of COX and selective inhibition of the prostaglandin D synthase (2-Phenyl-Pyrimidine-5-Carboxylic Acid (2,3-dihydro-indol-1-yl)-amide) amplified the antigen-induced bronchoconstriction which was reversed by exogenous PGD₂. Third, a DP₁ receptor agonist (BW 245c) concentration-dependently reduced the antigen-induced constriction as well as reducing released histamine and cysteinyl-leukotrienes, a response inhibited by the DP₁ receptor antagonist (MK-524). In contrast, a DP₂ receptor agonist (15(R)-15-methyl PGD₂) failed to modulate the OVA-induced constriction. In the guinea pig trachea, endogenous PGD₂ is generated via COX-1 and mediates an inhibitory effect of the antigen-induced bronchoconstriction via DP₁ receptors inhibiting mast cell release of bronchoconstrictive mediators. Removal of this protective function by COX-inhibition results in increased release of mast cell mediators and enhanced bronchoconstriction.

Bronchoprotective effect of deep inspirations in cough variant asthma: A distinguishing feature in the spectrum of airway disease?

PURPOSE

To assess the effect of deep inspirations (DIs) on airway behaviour in individuals with classic asthma (CA), cough variant asthma (CVA), and methacholine (MCh)-induced cough but normal airway sensitivity (COUGH) during bronchoprovocation.

METHODS

Twenty-five adults (18 female; 44.8 ± 12.3 years (Mean ± SD); n = 9 CA, n = 9 CVA, and n = 7 COUGH) completed two single-dose MCh challenges, with and without DIs. Bronchoprotection was assessed by comparing changes in bronchoconstriction (FEV₁, FVC, FEV₁/FVC, FEF₅₀, FEF_25-75), gas trapping (RV, RV/TLC) and impulse oscillometry (IOS) measurements.

RESULTS

The% changes in FEV₁ with and without DIs were not significantly different within any group. Decreases in FEF₅₀ and FEF_25-75 were greater in CA (p = 0.041 and p = 0.029), decreases in FVC (% predicted) and FEV₁/FVC(%) were less in CVA (p = 0.048 and p = 0.010), and increases in RV (L) and RV/TLC (% predicted) were less in COUGH (p = 0.007 and p = 0.028), respectively. No differences in IOS measurements were noted.

CONCLUSIONS

DIs triggered bronchoconstriction in CA, bronchoprotection in CVA, and prevented gas trapping in COUGH.

Effects of nebulised magnesium sulphate on inflammation and function of the guinea-pig airway

Magnesium sulphate is a potential treatment for acute severe asthma. However, the mechanisms and dose-response relationships are poorly understood. The first objective of this study was to examine whether inhaled magnesium sulphate exerts bronchodilator activity measured as bronchoprotection against histamine-induced bronchoconstriction in conscious guinea-pigs alone and combined with salbutamol. Secondly, we examined whether inhaled magnesium sulphate inhibits airways inflammation and function in models of neutrophilic and eosinophilic lung inflammation induced, respectively, by inhaled lipopolysaccharide or the inhaled antigen, ovalbumin (OVA). Airway function was measured in conscious guinea-pigs as specific airway conductance (sG_aw) by whole-body plethysmography. Anti-inflammatory activity was measured against lung inflammatory cell influx induced by OVA inhalation in OVA-sensitised animals or by lipopolysaccharide (LPS) exposure of non-sensitised animals. Airway function (sG_aw) was measured over 24h after OVA exposure. Airway hyperresponsiveness to inhaled histamine and inflammatory cells in bronchoalveolar lavage fluid were recorded 24h after OVA or LPS challenge. Histamine-induced bronchoconstriction was inhibited by inhaled magnesium sulphate or salbutamol alone and in combination, they produced synergistic bronchoprotection. LPS-induced neutrophil influx was inhibited by 6 days pretreatment with magnesium sulphate. Early and late asthmatic responses in OVA sensitised and challenged animals were attenuated by magnesium sulphate. Lung inflammatory cells were increased by OVA, macrophages being significantly reduced by magnesium sulphate. Nebulised magnesium sulphate protects against histamine-induced bronchoconstriction in conscious guinea-pigs and exerts anti-inflammatory activity against pulmonary inflammation induced by allergen (OVA) or LPS. These properties of magnesium sulphate explain its beneficial actions in acute asthma.

Duration of bronchoprotection of the long-acting muscarinic antagonists tiotropium & glycopyrronium against methacholine-induced bronchoconstriction in mild asthmatics

The duration of bronchoprotection against methacholine-induced bronchoconstriction by long-acting muscarinic antagonists (LAMA's) in asthmatics and whether these drugs differ in their pharmacodynamic properties remain to be determined. The most recent published guidelines for methacholine challenge testing (MCT) suggest that LAMA's should be abstained from for 48 h prior to testing, perhaps one week in the case of tiotropium. The objectives were to determine and compare the duration of protection of a single dose of two different LAMA's, tiotropium and glycopyrronium, against methacholine-induced bronchoconstriction. Thirteen mild-to-moderate asthmatics [with a forced expiratory volume in 1 s (FEV1) > 65% of predicted and a baseline methacholine provocation concentration causing a 20% reduction in FEV1 (PC20) ≤ 8 mg/mL] completed this double-blind, double-dummy, crossover study. Methacholine challenges were performed before treatment (5 μg tiotropium or 50 μg glycopyrronium) and at 1, 24, 48, 72, 96 and 168 h post-treatment. The minimum duration between treatment administration was 11 days. Both drugs provided significant bronchoprotection, each producing greater than a 16-fold increase in mean PC20 by 1 h. Tiotropium still provided statistically significant protection at 7 days (p = 0.0282) while glycopyrronium provided bronchoprotection until day 7 (p = 0.0590). Tiotropium provided statistically superior bronchoprotection at 24 and 72 h compared to glycopyrronium. To minimize the occurrence of false negatives, MCT guidelines should be updated to recommend a minimum one-week abstinence period from all LAMA's. MCT was also able to statistically differentiate between tiotropium and glycopyrronium with respect to the degree and duration of bronchoprotection provided by each.

CLINICAL TRIAL REGISTRATION NUMBER

NCT02622243.

Nonprescription racemic epinephrine for asthma

BACKGROUND

Inhaled racepinephrine (RE) (Asthmanefrin) became available in September 2012 as a nonprescription treatment for bronchospasm based on a 1986 US Food and Drug Administration rule. It contains 11.25 mg RE in 0.5 mL and is delivered by a handheld electronic nebulizer. In 2001, we conducted a pilot study that was never published. Now that the product is promoted as a replacement for epinephrine chlorofluorocarbon metered-dose inhaler (Primatene), we provide the results of that study. Methacholine challenge was used as a bioassay.

OBJECTIVE

To determine the dose of RE that is equivalent to nebulized albuterol.

METHODS

Four subjects, 18 to 45 years old, with mild stable asthma completed the pilot study. Methacholine challenge was performed on the first screening day, without pretreatment, and then on different days, 15 minutes after 1.25 mg albuterol and 2.5, 5, 10, and 20 mg RE delivered by a Pari LC Plus nebulizer. The end point was the provocative concentration of methacholine that caused a 20% decrease in FEV1. Data were log transformed and analyzed by an ANOVA for repeated measures.

RESULTS

There was a significant dose response for RE. The geometric mean provocative concentration of methacholine that caused a 20% decrease in FEV1 was 44 mg/mL (95% CI, 23-85 mg/mL) after albuterol, and 10.2 mg/mL (95% CI, 3.5-30 mg/mL) after the 10-mg dose of RE (approximate nonprescription dose) (P = .001). There were no adverse effects.

CONCLUSION

RE provides less bronchoprotection from methacholine than does albuterol and may be less effective in treating acute bronchospasm.