Airway smooth muscle as a target for asthma therapy

Long non-coding RNA TCF7 contributes to the growth and migration of airway smooth muscle cells in asthma through targeting TIMMDC1/Akt axis

BACKGROUND

Long noncoding RNAs (lncRNAs) have been revealed to participate in cellular biological processes in multiple diseases, including asthma. Nevertheless, the role of lncRNA TCF7 (lncTCF7) in airway smooth muscle cells (ASMCs) is still covered.

METHODS

The expression of lncTCF7 and TIMMDC1 in ASMCs from 12 asthma patients and 12 healthy controls were detected using qRT-PCR. Then MTT assay, EdU assay and transwell assay were conducted respectively to assess the impact of lncTCF7 on ASMCs viability, proliferation and migration. Besides, western blotting was performed to determine the protein levels of TIMMDC1 and AKT/p-AKT.

RESULTS

We discovered that lncTCF7 and TIMMDC1 were upregulated in asthma groups and lncTCF7 improved ASMCs viability/proliferation and migration. In addition, lncTCF7 regulated TIMMDC1 expression indeed and PDGF-BB treated ASMCs exhibited elevated levels of lncTCF7 and TIMMDC1. Moreover, lncTCF7 suppression diminished both the mRNA and protein levels of TIMMDC1 and markedly reduced p-AKT level which could be enhanced under TIMMDC1 overexpression. Finally, both TIMMDC1 overexpression and AKT activator could restored the inhibitory impacts of lncTCF7 silence on PDGF-BB treated ASMCs.

CONCLUSION

Our study uncovered that lncTCF7 facilitated human ASMCs growth and migration via targeting TIMMDC1 thus activating AKT signaling, providing a novel possible target for asthma therapy.

Effectiveness and Safety of Bronchial Thermoplasty in Severe Asthma in Clinical Practice in Spain

Background

Bronchial thermoplasty (BT) is a minimally invasive procedure consisting of application of thermal energy into the airways to produce ablation of the hypertrophic smooth muscle. It was approved for use in moderate-severe asthma in Spain in 2010.

Objectives

The aims of the present study are to analyze the effectiveness and the safety of BT in clinical practice in our center.

Methods

Participants had a confirmed diagnosis of severe asthma and poor control without therapeutic alternative. Effectiveness was measured by comparing exacerbations, admissions rates, asthma control, and medication 1 year prior and 1 year after BT was completed. All complications appearing during the procedure and in the first year were recorded.

Results

Patients had a mean age of 51 (SD 8) years and were predominantly female (17/23). The average number of activations per patient was 147 (16). The number of severe exacerbations was reduced by 75% (p < 0.001). A 38% reduction in admissions per year was also observed (p = 0.03). The Asthma Control Test improved by 7.1 (3.7) points (p = 0.018). Before BT, the dose of inhaled corticosteroids was 1,621 (1,015) µg of budesonide-equivalent and the dose of oral corticosteroids was 15 (13) mg of prednisone-equivalent. There was a reduction in 430 (731) µg of budesonide-equivalent (p = 0.02) and 4 (11) mg of prednisone (p = 0.094). No changes in lung function were observed. Complications were related mostly to exacerbation of asthma in the days following the procedure.

Conclusions

BT is effective and safe for severe uncontrolled bronchial asthma in real clinical practice.

Bronchial thermoplasty as a treatment for severe asthma: controversies, progress and uncertainties

INTRODUCTION

Bronchial thermoplasty is a licensed non-pharmacological treatment for severe asthma. Area covered: This article considers evidence for the efficacy and safety of bronchial thermoplasty from clinical trials and observational studies in clinical practice. Its place in the management of severe asthma, predictors of response and mechanisms of action are reviewed. Expert commentary: Bronchial thermoplasty improves quality of life and reduces exacerbations in moderate to severe asthma. Morbidity from asthma is increased during treatment. Overall, patients treated in clinical practice have worse baseline characteristics and comparable clinical outcomes to trial data. Follow-up studies provide reassurance on long-term safety. Despite some progress, future research needs to investigate uncertainties about predictors of response, mechanism of action and place in management of asthma.

Thermal ablation for asthma: current status and technique

Bronchial thermoplasty (BT) is a novel technique used in the treatment of severe asthma. A catheter is advanced through the bronchoscope and directed radiofrequency waves are applied to the segmental bronchi to reduce airway smooth muscle mass. Several randomized clinical trials demonstrate improvement in quality of life and reduction in exacerbation rates after treatment. BT is a safe and cost effective treatment option for severe asthma which is refractory to medical treatment. Further studies are needed in order to better describe the mechanism of action and the asthma subphenotype that was best benefit from this treatment.

Bronchial thermoplasty and biological therapy as targeted treatments for severe uncontrolled asthma

Although a small proportion of patients with asthma have severe disease, it accounts for the majority of morbidity related to the illness. Severe asthma comprises a heterogeneous group of phenotypes. Targeted treatments for these phenotypes represent a major advancement in the management of severe asthma. Omalizumab, a monoclonal antibody to IgE, improves asthma control in patients with a predominant allergic phenotype. Monoclonal antibodies targeted to interleukin 4α and interleukin 5 have shown substantial benefit in patients with the eosinophilic asthma phenotype; so too have monoclonal antibodies targeted to interleukin 13 in patients with a type 2 allergic phenotype. Bronchial thermoplasty, a new technique to reduce airway smooth muscle mass, improves symptoms and reduces exacerbations in patients with severe uncontrolled asthma and the chronic airflow obstruction phenotype. While awaiting comparative trials, we can now use a targeted approach with these phenotypes, guiding our treatment selection with the best evidence. This Review will focus on the latest developments in these new treatments and inform the clinician on how to select the appropriate patient for these treatments.

Advances in Bronchial Thermoplasty

Bronchial thermoplasty (BT) is a therapeutic intervention that delivers targeted thermal energy to the airway walls with the goal of ablating the smooth muscle in patients with severe persistent asthma. Since the publication of the original preclinical studies, three large randomized clinical trials evaluating its impact on asthma control have been performed. These trials have shown improvements in asthma-related quality of life and a reduction in asthma exacerbations following treatment with BT. However, there remains significant controversy regarding the true efficacy of BT and the interpretation of these studies, particularly the Asthma Intervention Research 2 trial. In this article, we will discuss these controversies and present the latest evidence on the use of BT in asthma, specifically the 5-year longitudinal evaluation of patients. In addition, we will discuss new insights into the histopathologic changes that occur in the airways following BT, as well as the feasibility of performing the procedure in patients with very severe asthma. We also will discuss the ongoing translational and clinical investigations regarding the underlying mechanism of action and methods to improve patient selection for this procedure.

Long-term efficacy and safety of bronchial thermoplasty in patients with moderate-to-severe persistent asthma: a systemic review and meta-analysis

OBJECTIVE

To evaluate the long-term efficacy and safety of bronchial thermoplasty (BT) in the treatment of patients with moderate-to-severe persistent asthma.

METHODS

We therefore performed a systematic literature review of peer-reviewed studies focusing on BT intervention in asthma control published between January 2000 and June 2014. Three randomized controlled studies and extension studies met the inclusion criteria (n = 6). Outcomes assessed after BT included spirometric data, adverse respiratory events, emergency room (ER) visits and hospitalization for respiratory illness. One-year and 5-year follow-up data were defined as V1 and V5, respectively.

RESULTS

There were 249 BT-treated subjects in total who had a 1-year follow-up (V1), whereas 216 of them finished a 5-year follow-up (V5). No evidence of significant decline was found in pre-bronchodilator FEV1 (% predicted) (WMD = 0.75; 95% CI: 3.36 to 1.85; p = 0.57), or in post-bronchodilator FEV1 (% predicted) (WMD = 0.62; 95% CI: 3.32 to 2.08; p = 0.65) between V1 and V5. In addition, the frequency of respiratory adverse events was reduced significantly during the follow-up (RR = 3.41, 95% CI: 2.96-3.93, p < 0.00001). The number of ER visits for adverse respiratory events remained unchanged (RR = 1.06, 95% CI: 0.77-1.46, p = 0.71) after BT treatment. There was no statistically significant increase in the incidence of hospitalization for respiratory adverse events (V5 vs. V1, RR = 1.47, 95% CI: 0.69-3.12, p = 0.32).

CONCLUSIONS

These data demonstrate long-term benefits of BT with regard to both asthma control and safety for moderate-to-severe asthmatic patients.

Bronchial thermoplasty: a new therapeutic option for the treatment of severe, uncontrolled asthma in adults

Bronchial thermoplasty is a young yet promising treatment for severe asthma whose benefit for long-term asthma control outweighs the short-term risk of deterioration and hospitalisation in the days following the treatment. It is an innovative treatment whose clinical efficacy and safety are beginning to be better understood. Since this is a device-based therapy, the overall evaluation of risk-benefit is unlike that of pharmaceutical products; safety aspects, regulatory requirements, study design and effect size assessment may be unfamiliar. The mechanisms of action and optimal patient selection need to be addressed in further rigorous clinical and scientific studies. Bronchial thermoplasty fits in perfectly with the movement to expand personalised medicine in the field of chronic airway disorders. This is a device-based complimentary asthma treatment that must be supported and developed in order to meet the unmet needs of modern severe asthma management. The mechanisms of action and the type of patients that benefit from bronchial thermoplasty are the most important challenges for bronchial thermoplasty in the future.

Bronchial thermoplasty in asthma: current perspectives

Bronchial thermoplasty (BT) is a novel therapy for patients with severe asthma. Using radio frequency thermal energy, it aims to reduce the airway smooth muscle mass. Several clinical trials have demonstrated improvements in asthma-related quality of life and a reduction in the number of exacerbations following treatment with BT. In addition, recent data has demonstrated the long-term safety of the procedure as well as sustained improvements in rates of asthma exacerbations, reduction in health care utilization, and improved quality of life. Further study is needed to elucidate the underlying mechanisms that result in these improvements. In addition, improved characterization of the asthma subphenotypes likely to exhibit the largest clinical benefit is a critical step in determining the precise role of BT in the management of severe asthma.

[Bronchial thermoplasty in the treatment of severe adult asthma]

Bronchial thermoplasty is a recent endoscopic technique for the treatment of severe asthma. It is an innovative treatment whose clinical efficacy and safety are beginning to be better understood. Since this is a device-based treatment, the evaluation procedure of risks and benefits is different that for pharmaceutical products; safety aspects, regulatory requirements, study design and the assessment of the magnitude of effects may all be different. The mechanism of action and optimal patient selection need to be assessed further in rigorous clinical and scientific studies. This technique is in harmony with the development of personalised medicine in the 21st century. It should be developed further in response to the numerous challenges and needs not yet met in the management of severe asthma.

Cost-effectiveness of bronchial thermoplasty in commercially-insured patients with poorly controlled, severe, persistent asthma

OBJECTIVES

We examined the cost-effectiveness of treating poorly controlled, severe, persistent asthma patients with bronchial thermoplasty (BT), a novel technology that uses thermal energy to reduce airway smooth muscle mass, with 5-year outcome data demonstrating a durable reduction in asthma exacerbations.

STUDY DESIGN

We conducted a model-based cost-effectiveness analysis assessing 5-year healthcare utilization, patient quality of life and adverse events.

METHODS

We utilized Markov modeling to estimate the costs and quality-of-life impact of BT compared with high-dose combination therapy among poorly controlled, severe, persistent asthma patients: those requiring high-dose combination therapy and having experienced an asthma exacerbation-related ER visit in the past year.

RESULTS

The cost-effectiveness of BT was US$5495 per quality-adjusted life year; and approximately 22% of sensitivity analysis iterations estimated BT to reduce costs and increase quality of life.

CONCLUSIONS

BT is a cost-effective treatment option for patients with poorly controlled, severe, persistent asthma.

Airway smooth muscle: a potential target for asthma therapy

PURPOSE OF REVIEW

Asthma is a major public health problem that afflicts nearly one in 20 people worldwide. Despite available treatments, asthma symptoms remain poorly controlled in a significant minority of asthma patients, especially those with severe disease. Accordingly, much ongoing effort has been directed at developing new therapeutic strategies; these efforts are described in detail below.

RECENT FINDINGS

Although mucus hypersecretion is an important component of asthma pathobiology, the primary mechanism of morbidity and mortality in asthma is excessive narrowing of the airway. The key end- effector of excessive airway narrowing is airway smooth muscle (ASM) contraction; overcoming ASM contraction is therefore a prominent therapeutic strategy. Here, we review exciting new advances aimed at ASM relaxation.

SUMMARY

Exciting advances in ASM biology have identified new therapeutic targets for the prevention or reversal of bronchoconstriction in asthma.

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.

Effect of tumor suppressor PTEN gene on apoptosis and cell cycle of human airway smooth muscle cells

It is well established that hyperplasia and decreased apoptosis of airway smooth muscle cells (ASMCs) play an important role in the asthmatic airway remodeling. Tumor suppressor PTEN gene with phosphatase activity plays an important regulatory role in embryonic development, cell proliferation, and apoptosis, cell cycle regulation, migration (invasion) of the cytoskeleton. We hypotheses that PTEN gene could affect the growth and viability of ASMCs through the regulation of PI3K/Akt, MAPK, and cell cycle-related gene expression. We constructed a recombinant adenovirus to transfect ASMCs. Cells were divided into the overexpression of PTEN gene group (Ad-PTEN-GFP), negative control group (Ad-GFP), and blank control group (DMEM). The cell apoptosis of ASMCs were evaluated by Hoechst-33342 staining and PE-7AAD double-labeled flow cytometry. The cell cycle distribution was observed by flow cytometry with PI staining. The expression of PTEN, p-Akt, total-Akt, p-ERK1/2, total-ERK1/2, cleaved-Caspases-3, Caspases-9, p21, and Cyclin D1 were tested by the Western blotting. Our study revealed that overexpression of PTEN gene did not induce apoptosis of human ASMCs cultured in vitro. However, overexpression of PTEN inhibited proliferation of human ASMCs cultured in vitro and was associated with downregulation of Akt phosphorylation levels, while did not affect ERK1/2 phosphorylation levels. Moreover, overexpression of PTEN could induce ASMCs arrested in the G0/G1 phase through the downregulation of Cyclin D1 and upregulation of p21 expressions.

Bronchial thermoplasty for severe asthma

PURPOSE OF REVIEW

Bronchial thermoplasty, which involves the delivery of radio frequency energy to the airways to reduce airway smooth muscle mass, has been recently introduced for the treatment of severe asthma. This review summarizes the preclinical development, efficacy and adverse effects of bronchial thermoplasty. In addition, the potential mechanisms of action and place in management of severe asthma are discussed.

RECENT FINDINGS

The efficacy and adverse profile of bronchial thermoplasty has been assessed in three randomized controlled trials, the first two of which showed clinical benefits of bronchial thermoplasty compared with usual care in patients with moderate or severe asthma. The third trial reports the results of a comparison with sham bronchial thermoplasty in 288 adults with severe asthma. Bronchial thermoplasty improved asthma quality of life questionnaire scores compared with sham bronchial thermoplasty; in the posttreatment period, there were fewer severe exacerbations and emergency department visits. Bronchial thermoplasty causes short-term increases in asthma-related morbidity. Follow-up data to date support the long-term safety of the procedure.

SUMMARY

Bronchial thermoplasty has a role in the management of patients with severe asthma who have uncontrolled symptoms despite current therapies. Future studies need to identify factors that predict a beneficial clinical response.

Trichostatin A abrogates airway constriction, but not inflammation, in murine and human asthma models

Histone deacetylase (HDAC) inhibitors may offer novel approaches in the treatment of asthma. We postulate that trichostatin A (TSA), a Class 1 and 2 inhibitor of HDAC, inhibits airway hyperresponsiveness in antigen-challenged mice. Mice were sensitized and challenged with Aspergillus fumigatus antigen (AF) and treated with TSA, dexamethasone, or vehicle. Lung resistance (R(L)) and dynamic compliance were measured, and bronchial alveolar lavage fluid (BALF) was analyzed for numbers of leukocytes and concentrations of cytokines. Human precision-cut lung slices (PCLS) were treated with TSA and their agonist-induced bronchoconstriction was measured, and TSA-treated human airway smooth muscle (ASM) cells were evaluated for the agonist-induced activation of Rho and intracellular release of Ca(2+). The activity of HDAC in murine lungs was enhanced by antigen and abrogated by TSA. TSA also inhibited methacholine (Mch)-induced increases in R(L) and decreases in dynamic compliance in naive control mice and in AF-sensitized and -challenged mice. Total cell counts, concentrations of IL-4, and numbers of eosinophils in BALF were unchanged in mice treated with TSA or vehicle, whereas dexamethasone inhibited the numbers of eosinophils in BALF and concentrations of IL-4. TSA inhibited the carbachol-induced contraction of PCLS. Treatment with TSA inhibited the intracellular release of Ca(2+) in ASM cells in response to histamine, without affecting the activation of Rho. The inhibition of HDAC abrogates airway hyperresponsiveness to Mch in both naive and antigen-challenged mice. TSA inhibits the agonist-induced contraction of PCLS and mobilization of Ca(2+) in ASM cells. Thus, HDAC inhibitors demonstrate a mechanism of action distinct from that of anti-inflammatory agents such as steroids, and represent a promising therapeutic agent for airway disease.

Phosphoinositide 3-kinase gamma regulates airway smooth muscle contraction by modulating calcium oscillations

Phosphoinositide 3-kinase gamma (PI3Kgamma) has been implicated in the pathogenesis of asthma, but its mechanism has been considered indirect, through release of inflammatory cell mediators. Because airway smooth muscle (ASM) contractile hyper-responsiveness plays a critical role in asthma, the aim of the present study was to determine whether PI3Kgamma can directly regulate contractility of ASM. Immunohistochemistry staining indicated expression of PI3Kgamma protein in ASM cells of mouse trachea and lung, which was confirmed by Western blot analysis in isolated mouse tracheal ASM cells. PI3Kgamma inhibitor II inhibited acetylcholine (ACh)-stimulated airway contraction of cultured precision-cut mouse lung slices in a dose-dependent manner with 75% inhibition at 10 muM. In contrast, inhibitors of PI3Kalpha, PI3Kbeta, or PI3Kdelta, at concentrations 40-fold higher than their reported IC(50) values for their primary targets, had no effect. It is noteworthy that airways in lung slices pretreated with PI3Kgamma inhibitor II still exhibited an ACh-induced initial contraction, but the sustained contraction was significantly reduced. Furthermore, the PI3Kgamma-selective inhibitor had a small inhibitory effect on the ACh-stimulated initial Ca(2+) transient in ASM cells of mouse lung slices or isolated mouse ASM cells but significantly attenuated the sustained Ca(2+) oscillations that are critical for sustained airway contraction. This report is the first to show that PI3Kgamma directly controls contractility of airways through regulation of Ca(2+) oscillations in ASM cells. Thus, in addition to effects on airway inflammation, PI3Kgamma inhibitors may also exert direct effects on the airway contraction that contribute to pathologic airway hyper-responsiveness.

Interventional bronchoscopy from bench to bedside: new techniques for central and peripheral airway obstruction

This article discusses how basic scientific concepts, based on a greater understanding of airway physiology, support the development and dissemination of multidimensional classification systems for tracheal stenosis, expiratory central airway collapse, and innovative interventional bronchoscopic procedures for patients with asthma and chronic obstructive pulmonary disease.

S100A8/A9: a mediator of severe asthma pathogenesis and morbidity?

Nearly 12% of children and 6% of adults in Canada have been diagnosed with asthma. Although in most patients symptoms are controlled by inhaled steroids, a subpopulation (approximately 10%) characterized by excessive airway neutrophilia, is refractory to treatment; these patients exhibit severe disease, and account for more than 50% of asthma health care costs. These numbers underscore the need to better understand the biology of severe asthma and identify pro-asthma mediators released by cells, such as neutrophils, that are unresponsive to common steroid therapy. This review focuses on a unique protein complex consisting of S100A8 and S100A9. These subunits belong to the large Ca2+-binding S100 protein family and are some of the most abundant proteins in neutrophils and macrophages. S100A8/A9 is a damage-associated molecular pattern (DAMP) protein complex released in abundance in rheumatoid arthritis, inflammatory bowel disease, and cancer, but there are no definitive studies on its role in inflammation and obstructive airways disease. Two receptors for S100A8/A9, the multiligand receptor for advanced glycation end products (RAGE) and Toll-like receptor 4 (TLR4), are expressed in lung. TLR4 is linked with innate immunity that programs local airway inflammation, and RAGE participates in mediating fibroproliferative remodeling in idiopathic pulmonary fibrosis. S100A8/A9 can induce cell proliferation, or apoptosis, inflammation, collagen synthesis, and cell migration. We hypothesize that this capacity suggests S100A8/A9 could underpin chronic airway inflammation and airway remodeling in asthma by inducing effector responses of resident and infiltrating airway cells. This review highlights some key issues related to this hypothesis and provides a template for future research.

Disrupting actin-myosin-actin connectivity in airway smooth muscle as a treatment for asthma?

Breathing is known to functionally antagonize bronchoconstriction caused by airway muscle contraction. During breathing, tidal lung inflation generates force fluctuations that are transmitted to the contracted airway muscle. In vitro, experimental application of force fluctuations to contracted airway smooth muscle strips causes them to relengthen. Such force fluctuation-induced relengthening (FFIR) likely represents the mechanism by which breathing antagonizes bronchoconstriction. Thus, understanding the mechanisms that regulate FFIR of contracted airway muscle could suggest novel therapeutic interventions to increase FFIR, and so to enhance the beneficial effects of breathing in suppressing bronchoconstriction. Here we propose that the connectivity between actin filaments in contracting airway myocytes is a key determinant of FFIR, and suggest that disrupting actin-myosin-actin connectivity by interfering with actin polymerization or with myosin polymerization merits further evaluation as a potential novel approach for preventing prolonged bronchoconstriction in asthma.

The synergistic interactions of allergic lung inflammation and intratracheal cationic protein

RATIONALE

Airways hyperresponsiveness (AHR) is a hallmark feature of asthma, and can be caused by various disparate mechanisms. Mouse models of AHR have been useful for studying these mechanisms in isolation, but such models still typically do not exhibit the same degree of AHR as seen in severe human asthma. We hypothesized that more severe AHR in mice could be achieved by imbuing them with more than one mechanism of AHR.

OBJECTIVES

We sought to determine if the airway wall thickening accompanying allergic inflammation and the exaggerated smooth muscle shortening induced by intratracheal cationic protein could act together to produce a severe form of AHR.

METHODS

We used the forced oscillation technique to measure methacholine responsiveness in BALB/c mice that had been sensitized and challenged with ovalbumin followed by an intratracheal instillation of poly-l-lysine.

MEASUREMENTS AND MAIN RESULTS

We found that both ovalbumin and poly-l-lysine treatment alone caused moderate levels of AHR. When the two treatments were combined, however, they synergized in terms of their effect on lung stiffness to an extent that could even be fatal, reflecting a significantly enhanced level of airway closure.

CONCLUSIONS

Our results suggest that mechanistic synergy between airway wall thickening and exaggerated smooth muscle shortening produces a more germane mouse model of asthma that may have particular relevance to the pathophysiology of the acute severe asthma exacerbation.