What have recent advances in therapy taught us about severe asthma disease mechanisms?

The nitroxide/antioxidant 3-carbamoyl proxyl attenuates disease severity in murine models of severe asthma

Asthma is characterized by airway inflammation, hyper-responsiveness, symptoms of dyspnea, wheezing and coughing. In most patients, asthma is well controlled using inhaled corticosteroids and bronchodilators. A minority of patients with asthma develop severe disease, which is frequently only partially responsive or even resistant to treatment with corticosteroids. Severe refractory asthma is associated with structural changes in the airways, termed "airway remodeling", and/or with neutrophilic rather than eosinophilic airway inflammation. While oxidative stress plays an important role in the pathophysiology of asthma, cyclic nitroxide stable radicals, which are unique and efficient catalytic antioxidants, effectively protect against oxidative injury. We have demonstrated that the nitroxide 3-carbamoyl proxyl (3-CP) attenuates airway inflammation and hyperresponsiveness in allergic asthma as well as bleomycin-induced fibrosis both using murine models, most probably through modulation of oxidative stress. The present study evaluates the effect of 3-CP on airway inflammation and remodeling using two murine models of severe asthma where mice are sensitized and challenged either by ovalbumin (OVA) or by house dust mite (HDM). 3-CP was orally administered during the entire period of the experiment or during the challenge period alone where its effect was compared to that of dexamethasone. The induced increase by OVA and by HDM of BALf cell counts, airway hyperresponsiveness, fibrosis, transforming growth factor-beta (TGF-β) levels in BALf and protein nitration levels of the lung tissue was significantly reduced by 3-CP. The effect of 3-CP, using two different murine models of severe asthma, is associated at least partially with attenuation of oxidative stress and with TGF-β expression in the lungs. The results of this study suggest a potential use of 3-CP as a novel therapeutic agent in different forms of severe asthma.

Stopping versus continuing long-term mepolizumab treatment in severe eosinophilic asthma (COMET study)

Background

The long-term efficacy and safety of mepolizumab for treatment of severe eosinophilic asthma are well established. Here, we examine the clinical impact of stopping mepolizumab after long-term use.

Methods

COMET (NCT02555371) was a randomised, double-blind, placebo-controlled, parallel-group, multicentre study. Patients who had completed COLUMBA (NCT01691859) or COSMEX (NCT02135692) and received continuous mepolizumab treatment for ≥3 years were randomised 1:1 to stop (switch to placebo) or continue subcutaneous mepolizumab 100 mg every 4 weeks for 52 weeks. Primary end-point: time to first clinically significant exacerbation; secondary end-points: time to first exacerbation requiring hospitalisation/emergency department visit, time to decrease in asthma control (≥0.5-point increase in Asthma Control Questionnaire-5 score from COMET baseline) and blood eosinophil count ratio to COMET baseline. Safety was assessed.

Results

Patients stopping (n=151) versus continuing (n=144) mepolizumab had significantly shorter times to first clinically significant exacerbation (hazard ratio 1.61, 95% CI 1.17–2.22; p=0.004) and decrease in asthma control (hazard ratio 1.52, 95% CI 1.13–2.02; p=0.005), and higher blood eosinophil counts at week 52 (270 versus 40 cells·µL⁻¹; ratio (stopping versus continuing) 6.19, 95% CI 4.89–7.83; p<0.001). Differences in efficacy outcomes between groups were observed when assessed from week 12 (16 weeks after last mepolizumab dose). Exacerbations requiring hospitalisation/emergency department visit were rare. Adverse events in patients continuing mepolizumab were consistent with previous studies. For patients who stopped mepolizumab, the safety profile was consistent with other eosinophilic asthma populations.

Conclusion

Patients who stopped mepolizumab had an increase in exacerbations and reduced asthma control versus those who continued.

This randomised study demonstrates increased exacerbation risk and a decrease in asthma control in patients with severe eosinophilic asthma who stop mepolizumab treatment after long-term use, when compared with those who continue treatment.https://bit.ly/3fsxGV2

Long non-coding RNA TUG1 promotes airway remodeling and mucus production in asthmatic mice through the microRNA-181b/HMGB1 axis

MicroRNA-181b (miR-181b) has been well noted with anti-inflammatory properties in several pathological conditions. It has also been suggested to be downregulated in patients with asthma. In this study, we explored the function of miR-181b in airway remodeling in asthmatic mice and the molecular mechanism. A mouse model with asthma was induced by ovalbumin (OVA) challenge, and miR-181b was found to be downregulated in lung tissues in the OVA-challenged mice. Overexpression of miR-181b was introduced in mice, after which the respiratory resistance, inflammatory infiltration, mucus production, and epithelial-mesenchymal transition (EMT) and fibrosis in mouse airway tissues were decreased. The integrated bioinformatics analysis suggested long non-coding RNA (lncRNA) TUG1 as a sponge for miR-181b. miR-181 directly targeted high mobility group box 1 (HMGB1) mRNA. HMGB1 was suggested to enhance activation of the nuclear factor kappa B (NF-κB) signaling. Further upregulation of lncRNA TUG1 blocked the protective functions of miR-181b in asthmatic mice. To conclude, this study evidenced that lncRNA TUG1 reinforces HMGB1 expression through sequestering microRNA-181b, which activates the NF-κB signaling pathway and promotes airway remodeling in asthmatic mice. This study may provide novel ideas in asthma management.

Biologics for the Treatments of Allergic Conditions: Severe Asthma

By selectively targeting specific steps of the immune inflammation cascade, biologic drugs for severe asthma have substantially contributed to increase the standard of care, to reduce drug-related morbidity. and most importantly to ameliorate patients' quality of life. Upcoming molecules are going to provide a chance for severe phenotypes besides Th2 high through the interaction with epithelial and innate immunity. Some practical aspects including optimal treatment duration, the possibility of a dose treatment modulation, the place and relevance of ICS in best responders are still under debate. Long-term safety, especially when interacting with innate immunity needs to be further investigated.

Low adherence to inhaled corticosteroids/long-acting β2-agonists and biologic treatment in severe asthmatics

Eligibility criteria for a biologic treatment for severe asthma include poor disease control despite a full medication plan according to Global Initiative for Asthma steps 4–5 [1]. Adherence to inhaled therapy should be verified as part of that prescription requirement [2]. In fact, it has been demonstrated that poor adherence is a major cause of uncontrolled asthma, regardless of its severity [3]. Furthermore, biologics do not exert a disease-modifying effect [4]; in contrast to allergen immunotherapy, which is able to permanently modulate the way the immune system reacts to allergens beyond the immunotherapy treatment course [5], biologic therapy withdrawal usually leads to asthma relapse [4]. Thus, a low adherence rate to inhaled treatment in patients undergoing biologic therapy raises some issues related to sustainability.

Less than half of severe asthmatic patients show a >80% adherence rate to inhaled treatment just before and during biologic therapy. This has implications in biologic treatment sustainability and disease prevalence estimation.http://bit.ly/3cRTJB0

Inhibition of Virus-Induced Cytokine Production from Airway Epithelial Cells by the Late Addition of Budesonide

Background and objectives: Viral infection is the main cause of asthma and COPD (chronic obstructive pulmonary disease) exacerbation and accumulate inflammatory cells to airway tissue. We have reported poly I:C, a mimic product of the virus and ligand of toll-like receptor 3 (TLR3), induced inflammatory chemokines from airway epithelial cells and found prior incubation with corticosteroids diminishes the effect of TLR3 activation. In clinical practice, mild asthma is recommended as-needed budesonide (BUD) when symptoms occur following a viral infection, etc. However, many questions still surround BUD’s usefulness if taken after a virus has already infected airway tissue. The aim of this study was to investigate the inhibitory effects of BUD on inflammatory cytokines induced by viral infection. Materials and Methods: Normal human bronchial epithelial (NHBE) cells were stimulated with poly I:C or infected with human rhinovirus-16 (HRV16) and BUD was added after the initial stimulation. Expression of both thymic stromal lymphopoietin (TSLP) and CCL26/eotaxin-3 was quantified by real-time RT-PCR and enzyme-linked immunosorbent assay (ELISA), respectively. Knockdown study was performed. Results: Pre-or post-incubation with BUD inhibited both poly I:C- and HRV16-induced mRNAs and proteins of both thymic stromal lymphopoietin (TSLP) and CCL26 with significance. Knockdown of the glucocorticoid receptor diminished these effects of BUD. Under the same conditions of BUD’s experiment, post-incubation with neither fluticasone propionate nor dexamethasone suppressed expression of both TSLP and CCL26, which induced by poly I:C. Conclusion: Post-addition of BUD inhibited the virus-induced TSLP and CCL26 from the airway epithelial cells. These results suggest that inhalation of BUD after viral infection has beneficial effects on asthma. Conclusion: Late addition of BUD may benefit among patient with viral infection and type 2 allergic airway disease such as asthma.

The impact of microRNAs on alterations of gene regulatory networks in allergic diseases

Allergic diseases including asthma are worldwide on the rise and contribute significantly to health expenditures. Allergic diseases are prototypic diseases with a strong gene by environment interaction component and epigenetic mechanisms might mediate the effects of the environment on the disease phenotype. MicroRNAs, small non-coding RNAs (miRNAs), regulate gene expression post-transcriptionally. Functional single-stranded miRNAs are generated in multiple steps of enzymatic processing from their precursors and mature miRNAs are included into the RNA-induced silencing complex (RISC). They imperfectly base-pair with the 3'UTR region of targeted genes leading to translational repression or mRNA decay. The cellular context and microenvironment as well the isoform of the mRNA control the dynamics and complexity of the regulatory circuits induced by miRNAs that regulate cell fate decisions and function. MiR-21, miR-146a/b and miR-155 are among the best understood miRNAs of the immune system and implicated in different diseases including allergic diseases. MiRNAs are implicated in the induction of the allergy reinforcing the Th2 phenotype (miR-19a, miR-24, miR-27), while other miRNAs promote regulatory T cells associated with allergen tolerance or unresponsiveness. In the current chapter we describe in detail the biogenesis and regulatory function of miRNAs and summarize current knowledge on miRNAs in allergic diseases and allergy relevant cell fate decisions focusing mainly on immune cells. Furthermore, we evoke the principles of regulatory loops and feedback mechanisms involving miRNAs on examples with relevance for allergic diseases. Finally, we show the potential of miRNAs and exosomes containing miRNAs present in several biological fluids that can be exploited with non-invasive procedures for diagnostic and potentially therapeutic purposes.