Beta2-agonists and bronchial hyperresponsiveness

Treat to target approach for asthma

Recognition that about half of asthma deaths might be preventable if recommended guidelines are followed suggests that better implementation of established management strategies is needed. However, to achieve a further substantive reduction in asthma mortality, novel strategies will also be required. It is well established that asthma is a disease of chronic inflammation, with episodes of worsening inflammation associated with increased symptoms and/or exacerbations; however, current guidelines paradoxically recommend that initial treatment is only symptomatic, rather than directed at the underlying inflammatory mechanism. The "Treat to target" (TTT) approach has become a popular concept in the medical management of several common chronic conditions, including rheumatoid arthritis (RA), diabetes, hypertension and hyperlipidemia. For example, as part of a TTT approach, rheumatologists recommend methotrexate for RA with onset within 6 months. Applying the TTT approach to asthma, the primary target could be clinical remission and the primary goals as follows: eliminate symptoms and exacerbation risk; prevent airway remodeling; and normalize lung function. To construct a TTT algorithm for chronic asthma, the proposal is to eradicate short-acting β2-agonists (SABA) at all asthma severity levels and replace SABA with "Anti-Inflammatory Reliever Therapy" (AIR), using inhaled corticosteroids (ICS)/SABA or ICS/formoterol. For individuals with equal to or less than 12 months' history of symptoms, fewer than two symptoms per month, no exacerbations in the last 12 months and normal lung function, the recommendation is early initiation of ICS/SABA or ICS/formoterol as AIR.

Tolerogenic Dendritic Cells Reduce Airway Inflammation in a Model of Dust Mite Triggered Allergic Inflammation

PURPOSE

The use of tolerogenic dendritic cells (TolDCs) to control exacerbated immune responses may be a prophylactic and therapeutic option for application in autoimmune and allergic conditions. The objective of this work was to evaluate the effects of TolDC administration in a mouse model of allergic airway inflammation caused by mite extract.

METHODS

Mouse bone marrow-derived TolDCs were induced by incubation with granulocyte-macrophage colony-stimulating factor (GM-CSF) and dexamethasone, and then characterized by flow cytometry and cytokine production by enzyme-linked immunosorbent assay (ELISA). For the in vivo model of Blomia tropicalis-induced allergy, mice transplanted with antigen-pulsed TolDCs were sensitized intraperitoneally with B. tropicalis mite extract (BtE) adsorbed to aluminium hydroxide. After challenge by nasal administration of BtE, bronchoalveolar lavage fluid (BALF), lungs, spleen and serum were collected for analysis.

RESULTS

Induction of TolDCs was efficiently achieved as shown by low expression of major histocompatibility complex (MHC) II, programmed death-ligand (PD-L) 2 and pro-inflammatory cytokine production, and up-regulation of interleukin (IL)-10, upon LPS stimulation in vitro. Transplantation of 1 or 2 doses of BtE-pulsed TolDCs reduced the number of inflammatory cells in BALF and lungs as well as mucus deposition. Moreover, compared to saline-injected controls, TolDC-treated mice showed lower serum levels of anti-BtE immunoglobulin E (IgE) antibodies as well as reduced Gata3 and IL-4 gene expression in the lungs and decreased IFN-γ levels in the supernatant of splenocyte cultures Transplantation of TolDCs increased the percentage of the regulatory T cells in the spleen and the lungs.

CONCLUSIONS

Preventive treatment with TolDCs protects against dust mite-induced allergy in a mouse model, reinforcing the use of tolerogenic dendritic cells for the management of allergic conditions.

A new approach to the classification and management of airways diseases: identification of treatable traits

This review outlines a new, personalized approach for the classification and management of airway diseases. The current approach to airways disease is, we believe, no longer fit for purpose. It is impractical, overgeneralizes complex and heterogeneous conditions and results in management that is imprecise and outcomes that are worse than they could be. Importantly, the assumptions we make when applying a diagnostic label have impeded new drug discovery and will continue to do so unless we change our approach. This review suggests a new mechanism-based approach where the emphasis is on identification of key causal mechanisms and targeted intervention with treatment based on possession of the relevant mechanism rather than an arbitrary label. We highlight several treatable traits and suggest how they can be identified and managed in different healthcare settings.

Exposure to Allergen Causes Changes in NTS Neural Activities after Intratracheal Capsaicin Application, in Endocannabinoid Levels and in the Glia Morphology of NTS

Allergen exposure may induce changes in the brainstem secondary neurons, with neural sensitization of the nucleus solitary tract (NTS), which in turn can be considered one of the causes of the airway hyperresponsiveness, a characteristic feature of asthma. We evaluated neurofunctional, morphological, and biochemical changes in the NTS of naive or sensitized rats. To evaluate the cell firing activity of NTS, in vivo electrophysiological experiments were performed before and after capsaicin challenge in sensitized or naive rats. Immunohistochemical studies, endocannabinoid, and palmitoylethanolamide quantification in the NTS were also performed. This study provides evidence that allergen sensitization in the NTS induced: (1) increase in the neural firing response to intratracheal capsaicin application, (2) increase of endocannabinoid anandamide and palmitoylethanolamide, a reduction of 2-arachidonoylglycerol levels in the NTS, (3) glial cell activation, and (4) prevention by a Group III metabotropic glutamate receptor activation of neural firing response to intratracheal application of capsaicin in both naïve and sensitized rats. Therefore, normalization of ovalbumin-induced NTS neural sensitization could open up the prospect of new treatments based on the recovery of specific brain nuclei function and for extensive studies on acute or long-term efficacy of selective mGlu ligand, in models of bronchial hyperreactivity.

Current and novel bronchodilators in respiratory disease

PURPOSE OF REVIEW

β2-Agonists and muscarinic antagonists are widely used to treat asthma and chronic obstructive pulmonary disease (COPD), and a number of novel drug targets are being investigated for potential clinical utility. This review will summarize current developments in the field.

RECENT FINDINGS

The clinical effectiveness of a number of once a day inhaled β2-agonists and muscarinic antagonists is a major advance providing sustained bronchodilation in asthma and COPD. The identification of novel targets (e.g. bitter taste receptor TASR2), the demonstration of clinical effectiveness of others [e.g. phosphodiesterase (PDE)3/4] and exploring the potential of inverse agonists/biased agonists are evidence of continuing interest in the development of novel bronchodilators.

SUMMARY

Novel long-acting β2-agonists (e.g. indacaterol, vilanterol, olodaterol and carmoterol) and muscarinic antagonists (e.g. tiotropium, aclidinium, glycopyrronium and umeclidinium bromide) document sustained bronchodilation and their combination provides additional benefits over monotherapy. Not surprisingly, inhaled long-acting β2-agonist and long-acting muscarinic antagonists remain the drugs of choice for maintenance bronchodilation. However, there is a continued interest in developing novel bronchodilators illustrated by the clinical effectiveness of long acting mixed PDE3/4 inhibitors, vasointestinal peptide adenylyl cyclase agonists and inverse agonists/biased agonists for the β2-adrenoceptor, and the identification of intracellular (e.g. Rho kinase, exchange proteins activated by cyclic AMP) and cell surface (e.g. TAS2R, natriuretic peptide receptor) targets.

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.

Provoked models of asthma: what have we learnt?

Asthma is a chronic inflammatory disease of the airways characterized by physiological abnormalities of variable airflow obstruction and airway hyperresponsiveness (AHR) to a wide variety of physical and inhaled chemical stimuli and the presence of symptoms. AHR is measured by challenging the airways with a variety of agonists and naturally occurring stimuli, which results in constriction of the airway smooth muscle, leading to airway narrowing and airflow limitation. There are two distinct mechanisms by which the airways can narrow to a constrictor stimulus and these are defined by the pathways they take to induce AHR. Direct stimuli are pharmacological agents administered exogenously (such as histamine or methacholine) that act 'directly' on specific receptors on the bronchial smooth muscle to cause constriction. The other mechanism by which the airway can narrow is via the inhalation of indirect stimuli, which include natural stimuli, such as allergen or exercise, and pharmacological agents such as adenosine monophosphate and hyper-osmotic agents (e.g. hypertonic saline or dry powder mannitol). These stimuli induce airway narrowing 'indirectly' by causing the endogenous release of mediators of bronchoconstriction from airway inflammatory cells. Provoked models of asthma have been extremely valuable in understanding the pathobiology of asthma, in aiding diagnosis, in helping to clarify the mechanisms of actions of effective drugs and in the development of new entities to treat asthma. Some provoked models are valuable clinically, particularly those that measure direct AHR, while others, particularly allergen challenge, have been used in animal models and in humans to study the mechanisms of allergen-induced airway inflammation and the associated physiological changes, as well in the development of new drugs for asthma. An emerging role for measurements of AHR is in the evaluation of the optimal treatment for patients with asthma.

Pharmaceutical treatment of asthma symptoms in elite athletes - doping or therapy?

Asthma, exercise-induced bronchoconstriction, and airway hyper-responsiveness are often found in elite athletes, perhaps as a consequence of their sport or maybe because asthma is a common disorder in young adults. Inhaled beta2-agonists (IBA) are frequently used in elite athletes, but due to regulations introduced by the International Olympic Committee, the use of anti-asthmatic therapy might change. Drugs that make ergogenic effect persist are prohibited in all athletes, whether or not they take part in competitions and systemic steroids and beta2-agonists are among such drugs. On the other hand, opinion is more divided about the use of inhaled corticosteroids (ICS) and IBA. In humans, no effect has been found on the oxygen uptake, performance or distance run with therapeutic doses of IBA, either in asthmatics or non-asthmatics, whereas others report an ergogenic effect and better lung function of high doses of a beta2-agonist in non-asthmatics. Anti-asthmatic treatment is necessary for asthmatics, but should not be used by non-asthmatic elite athletes due to both possible systemic effects and furthermore, side effects of both ICS and IBA.