A review of standard pharmacological therapy for adult asthma – Steps 1 to 5

β-Arrestin-biased proteinase-activated receptor-2 antagonist C781 limits allergen-induced airway hyperresponsiveness and inflammation

BACKGROUND AND PURPOSE

Asthma is a heterogenous disease strongly associated with inflammation that has many different causes and triggers. Current asthma treatments target symptoms such as bronchoconstriction and airway inflammation. Despite recent advances in biological therapies, there remains a need for new classes of therapeutic agents with novel, upstream targets. The proteinase-activated receptor-2 (PAR2) has long been implicated in allergic airway inflammation and asthma and it remains an intriguing target for novel therapies. Here, we describe the actions of C781, a newly developed low MW PAR2 biased antagonist, in vitro and in vivo in the context of acute allergen exposure.

EXPERIMENTAL APPROACH

A human bronchial epithelial cell line expressing PAR2 (16HBE14o- cells) was used to evaluate the modulation in vitro, by C781, of physiological responses to PAR2 activation and downstream β-arrestin/MAPK and Gq/Ca2+ signalling. Acute Alternaria alternata sensitized and challenged mice were used to evaluate C781 as a prophylactically administered modulator of airway hyperresponsiveness, inflammation and mucus overproduction in vivo.

KEY RESULTS

C781 reduced in vitro physiological signalling in response to ligand and proteinase activation. C781 effectively antagonized β-arrestin/MAPK signalling without significant effect on Gq/Ca2+ signalling in vitro. Given prophylactically, C781 modulated airway hyperresponsiveness, airway inflammation and mucus overproduction of the small airways in an acute allergen-challenged mouse model.

CONCLUSION AND IMPLICATIONS

Our work demonstrates the first biased PAR2 antagonist for β-arrestin/MAPK signalling. C781 is efficacious as a prophylactic treatment for allergen-induced airway hyperresponsiveness and inflammation in mice. It exemplifies a key pharmacophore for PAR2 that can be optimized for clinical development.

Airway smooth muscle function in asthma

Known to have affected around 340 million people across the world in 2018, asthma is a prevalent chronic inflammatory disease of the airways. The symptoms such as wheezing, dyspnea, chest tightness, and cough reflect episodes of reversible airway obstruction. Asthma is a heterogeneous disease that varies in clinical presentation, severity, and pathobiology, but consistently features airway hyperresponsiveness (AHR)—excessive airway narrowing due to an exaggerated response of the airways to various stimuli. Airway smooth muscle (ASM) is the major effector of exaggerated airway narrowing and AHR and many factors may contribute to its altered function in asthma. These include genetic predispositions, early life exposure to viruses, pollutants and allergens that lead to chronic exposure to inflammatory cells and mediators, altered innervation, airway structural cell remodeling, and airway mechanical stress. Early studies aiming to address the dysfunctional nature of ASM in the etiology and pathogenesis of asthma have been inconclusive due to the methodological limitations in assessing the intrapulmonary airways, the site of asthma. The study of the trachealis, although convenient, has been misleading as it has shown no alterations in asthma and it is not as exposed to inflammatory cells as intrapulmonary ASM. Furthermore, the cartilage rings offer protection against stress and strain of repeated contractions. More recent strategies that allow for the isolation of viable intrapulmonary ASM tissue reveal significant mechanical differences between asthmatic and non-asthmatic tissues. This review will thus summarize the latest techniques used to study ASM mechanics within its environment and in isolation, identify the potential causes of the discrepancy between the ASM of the extra- and intrapulmonary airways, and address future directions that may lead to an improved understanding of ASM hypercontractility in asthma.

Multivalent stimulation of β1-, but not β2-receptors by adrenaline functionalised gold nanoparticles

In this study, we present a strategy for the synthesis of catecholamine functionalised gold nanoparticles and investigated their multivalent interactions with adrenergic receptors in different biological systems. The catecholamines adrenaline and noradrenaline represent key examples of adrenergic agonists. We used gold nanoparticles as carriers and functionalised them on their surface with a variety of these neurotransmitter molecules. For this purpose, we synthesised each ligand separately using mercaptoundecanoic acid as a bifunctional linking unit and adrenaline (or noradrenaline) as a biogenic amine. This ligand was then immobilised onto the surface of presynthesised spherical monodispersive gold nanoparticles in a ligand exchange reaction. After detailed analytical characterisations, the functionalised gold nanoparticles were investigated for their interactions with adrenergic receptors in intestinal, cardiac and respiratory tissues. Whereas the contractility of respiratory smooth muscle cells (regulated by β₂-receptors) was not influenced, (nor)adrenaline functionalised nanoparticles administered in nanomolar concentrations induced epithelial K⁺ secretion (mediated via different β-receptors) and increased contractility of isolated rat cardiomyocytes (mediated by β₁-receptors). The present results suggest differences in the accessibility of adrenergic agonists bound to gold nanoparticles to the binding pockets of different β-receptor subtypes.

The Multifaceted Role of GPCRs in Amyotrophic Lateral Sclerosis: A New Therapeutic Perspective?

Amyotrophic lateral sclerosis (ALS) is a degenerating disease involving the motor neurons, which causes a progressive loss of movement ability, usually leading to death within 2 to 5 years from the diagnosis. Much effort has been put into research for an effective therapy for its eradication, but still, no cure is available. The only two drugs approved for this pathology, Riluzole and Edaravone, are onlyable to slow down the inevitable disease progression. As assessed in the literature, drug targets such as protein kinases have already been extensively examined as potential drug targets for ALS, with some molecules already in clinical trials. Here, we focus on the involvement of another very important and studied class of biological entities, G protein-coupled receptors (GPCRs), in the onset and progression of ALS. This workaimsto give an overview of what has been already discovered on the topic, providing useful information and insights that can be used by scientists all around the world who are putting efforts into the fight against this very important neurodegenerating disease.

Packaging and Delivery of Asthma Therapeutics

Asthma is a life-altering, chronic disease of heterogenous origin that features a complex interplay of immune and environmental signaling. Although very little progress has been made in prevention, diverse types of medications and delivery systems, including nanoscale systems, have been or are currently being developed to control airway inflammation and prevent exacerbations and fibrosis. These medications are delivered through mechanical methods, with various inhalers (with benefits and drawbacks) existing, and new types offering some variety in delivery. Of particular interest is the progress being made in nanosized materials for efficient penetration into the epithelial mucus layer and delivery into the deepest parts of the lungs. Liposomes, nanoparticles, and extracellular vesicles, both natural and synthetic, have been explored in animal models of asthma and have produced promising results. This review will summarize and synthesize the latest developments in both macro-(inhaler) and micro-sized delivery systems for the purpose of treating asthma patients.

Reasons and outcomes for patients receiving ICS/LABA agents prior to, and one month after, emergency department presentations for acute asthma

Objective: Asthma is a common emergency department (ED) presentation. This study examined factors associated with inhaled corticosteroids/long-acting beta-agonist (ICS/LABA) use; and management and outcomes before and after ED presentation. Methods: Secondary analysis of a prospective cohort study; adults treated for acute asthma in Canadian EDs underwent a structured interview before discharge and were followed-up four weeks later. Patients received oral corticosteroids (OCS) at discharge and, at physician discretion, most received ICS or ICS/LABA inhaled agents. Analyses focused on ICS/LABA vs "other" treatment groups at ED presentation. Results: Of 807 enrolled patients, 33% reported receiving ICS/LABA at ED presentation; 62% were female, median age was 31 years. Factors independently associated with ICS/LABA treatment prior to ED presentation were: having an asthma action plan; using an asthma diary/peak flow meter; influenza immunization; not using the ED as usual site for prescriptions; ever using OCS and currently using ICS. Patients were treated similarly in the ED and at discharge; however, relapse was higher in the ICS/LABA group, even after adjustment. Conclusion: One-third of patients presenting to the ED with acute asthma were already receiving ICS/LABA agents; this treatment was independently associated with preventive measures. While ICS/LABA management improves control of chronic asthma, patients using these agents who develop acute asthma reflect higher severity and increased risk of future relapse.

Synthesis, Pharmacological Profile and Docking Studies of New Sulfonamides Designed as Phosphodiesterase-4 Inhibitors

Prior investigations showed that increased levels of cyclic AMP down-regulate lung inflammatory changes, stimulating the interest in phosphodiesterase (PDE)4 as therapeutic target. Here, we described the synthesis, pharmacological profile and docking properties of a novel sulfonamide series (5 and 6a-k) designed as PDE4 inhibitors. Compounds were screened for their selectivity against the four isoforms of human PDE4 using an IMAP fluorescence polarized protocol. The effect on allergen- or LPS-induced lung inflammation and airway hyper-reactivity (AHR) was studied in A/J mice, while the xylazine/ketamine-induced anesthesia test was employed as a behavioral correlate of emesis in rodents. As compared to rolipram, the most promising screened compound, 6a (LASSBio-448) presented a better inhibitory index concerning PDE4D/PDE4A or PDE4D/PDE4B. Accordingly, docking analyses of the putative interactions of LASSBio-448 revealed similar poses in the active site of PDE4A and PDE4C, but slight unlike orientations in PDE4B and PDE4D. LASSBio-448 (100 mg/kg, oral), 1 h before provocation, inhibited allergen-induced eosinophil accumulation in BAL fluid and lung tissue samples. Under an interventional approach, LASSBio-448 reversed ongoing lung eosinophilic infiltration, mucus exacerbation, peribronchiolar fibrosis and AHR by allergen provocation, in a mechanism clearly associated with blockade of pro-inflammatory mediators such as IL-4, IL-5, IL-13 and eotaxin-2. LASSBio-448 (2.5 and 10 mg/kg) also prevented inflammation and AHR induced by LPS. Finally, the sulfonamide derivative was shown to be less pro-emetic than rolipram and cilomilast in the assay employed. These findings suggest that LASSBio-448 is a new PDE4 inhibitor with marked potential to prevent and reverse pivotal pathological features of diseases characterized by lung inflammation, such as asthma.

Step 4: stick or twist? A review of asthma therapy

Many people with asthma do not achieve disease control, despite bronchodilators and inhaled corticosteroid therapy. People with uncontrolled asthma are at higher risk of an asthma attack and death, with mortality rates estimated at 1000 deaths/year in England and Wales. The recent National Review of Asthma Deaths (NRAD) report, ‘Why asthma still kills’, recommended that patients at step 4 or 5 of the British Thoracic Society/Scottish Intercollegiate Guidelines Network (BTS/SIGN) guidance must be referred to a specialist asthma service. This article reviews the 2014 evidence base for therapy of asthma patients at BTS/SIGN step 4 of the treatment cascade, in response to key findings of the NRAD report and lack of preferred treatment option at this step.

Lipid mediators as regulators of human ILC2 function in allergic diseases

Group 2 innate lymphoid cells (ILC2) are specialized in type 2 immunity. ILC2 are activated early in immune responses and, despite their low abundance, are able to initiate and amplify allergic inflammation by orchestrating other type 2 immune cells. Based on recent discoveries, the spectrum of ILC2 regulating factors has been extended. It is now well established that not only epithelial cell-derived innate cytokines, but also bioactive lipids can regulate ILC2 activity and accumulation. Additionally, ILC2 appear to be susceptible to changes in the cytokine milieu and can acquire an ILC1-like phenotype due to a high degree of cellular plasticity. As ILC2 are fundamentally involved in the pathogenesis of type 2 diseases, they represent a promising therapeutic target for allergic airway and skin diseases. In this review we summarize the current knowledge about ILC2 biology in the allergy context, with a particular focus on the emerging role of lipid mediators in regulating ILC2 function.

Glucocorticoid and TNF signaling converge at A20 (TNFAIP3) to repress airway smooth muscle cytokine expression

Airway smooth muscle is a major target tissue for glucocorticoid (GC)-based asthma therapies, however, molecular mechanisms through which the GC receptor (GR) exerts therapeutic effects in this key airway cell type have not been fully elucidated. We previously identified the nuclear factor-κB (NF-κB) inhibitor, A20 (TNFAIP3), as a mediator of cytokine repression by glucocorticoids (GCs) in airway epithelial cells and defined cooperative regulation of anti-inflammatory genes by GR and NF-κB as a key mechanistic underpinning of airway epithelial GR function. Here, we expand on these findings to determine whether a similar mechanism is operational in human airway smooth muscle (HASM). Using HASM cells derived from normal and fatal asthma samples as an in vitro model, we demonstrate that GCs spare or augment TNF-mediated induction of A20 (TNFAIP3), TNIP1, and NFKBIA, all implicated in negative feedback control of NF-κB-driven inflammatory processes. We applied chromatin immunoprecipitation and reporter analysis to show that GR and NF-κB directly regulate A20 expression in HASM through cooperative induction of an intronic enhancer. Using overexpression, we show for the first time that A20 and its interacting partner, TNIP1, repress TNF signaling in HASM cells. Moreover, we applied small interfering RNA-based gene knockdown to demonstrate that A20 is required for maximal cytokine repression by GCs in HASM. Taken together, our data suggest that inductive regulation of A20 by GR and NF-κB contributes to cytokine repression in HASM.

Olodaterol for the treatment of asthma

INTRODUCTION

Long-acting β-agonist (LABA)/inhaled corticosteroid (ICS) combinations are still the mainstay of asthma therapy but there is a pressing need to increase adherence to the prescribed treatment achievable in general by reducing the dose frequency. Consequently, there is considerable interest within the pharmaceutical industry in the discovery of once-daily β2-agonists (ultra-LABAs) to be used as a part of a combination therapy for treating asthma.

AREAS COVERED

The authors review the preclinical and clinical development of olodaterol, a new ultra-LABA characterized by an improved selectivity for β2-adrenoceptors and a rather high intrinsic efficacy profile, in asthma. The clinical results were generated by 4 Phase 2 trials, which have enrolled 731 asthmatic patients.

EXPERT OPINION

The available results indicate that olodaterol is able to induce an effective 24-h bronchodilation and is safe. However, one cannot formulate a solid conclusion on the best dose and/or dose frequency to be used in asthma because trials were not powered to assess the differences between doses and dose frequencies. Apparently, there is no Phase 3 trial planned or ongoing for olodaterol monotherapy in patients with asthma and also no attempt to combine olodaterol with an ICS, which is surprising.