Acute and durable effect of inhaled hypertonic saline on mucociliary clearance in adult asthma

Recent advances in asthma mucus biology and emerging treatment strategies

PURPOSE OF REVIEW

To describe the recent advances in the pathobiology and treatment of mucus hypersecretion in asthma, a critical factor contributing to airway obstruction, inflammation, and impaired lung function.

RECENT FINDINGS

Significant progress has been made in understanding how mucin protein regulation, mucus viscosity, and adhesion are affected by cytokine-driven inflammation, especially interleukin-13, and defects in ion transport mechanisms. Advances in imaging techniques, such as multidetector computed tomography (MDCT) and hyperpolarized gas MRI, allow for a more precise assessment of mucus plugging and associated ventilation defects. Emerging therapies, including biologicals targeting type-2 (T2) inflammation, and novel mucolytics aimed at modifying mucus properties and secretion, offer promising effects in reducing mucus in severe asthmatics.

SUMMARY

The growing understanding of mucus biology and the development of advanced imaging and therapeutic strategies could significantly improve the management of mucus-related complications in asthma. By targeting mucus characteristics, these findings support future approaches to reduce airway obstruction, enhance lung function, and improve clinical outcomes in patients with severe asthma. A deeper understanding of the glycobiology of mucus is critical to develop new therapies.

Effect of prednisone on woodsmoke-induced sputum inflammation in healthy volunteers: A randomized, placebo-controlled pilot study

Background

Inhalation of biomass smoke is associated with adverse respiratory effects in those with chronic pulmonary conditions. There are few published data regarding the effects of anti-inflammatory interventions on these outcomes.

Objective

Our aim was to assess the effects of postexposure prednisone on woodsmoke (WS)-induced sputum neutrophilia.

Methods

We carried out a randomized, placebo-controlled, crossover pilot study assessing the effect of a postexposure dose of 60 mg prednisone on induced sputum inflammation after controlled exposure to WS (500 μg/m3 for 2 hours) in healthy adults who had been identified in a separate screening protocol as being "PMN responsive" to WS. Secondary end points were sputum cytokine level and mucociliary clearance as measured by γ-scintigraphy.

Results

A total of 11 subjects yielded complete data for the primary analysis. At 24 hours after WS exposure, there was a significant increase in sputum percentage of PMNs (%PMN) versus at baseline after placebo (median = 42% [IQR = 31%-53%]) (P = .02) but not after prednisone (median = 32% [IQR = 18%-40%]) (P = .09). Prednisone reduced Δ%PMN at 24 hours, but this difference did not reach statistical significance. However, for the 8 of 11 subjects who were PMN responsive after placebo, prednisone reduced Δ%PMN significantly (P = .05). Prednisone had no significant effects on sputum levels of IL-1β, IL-6, IL-8, or TNF-α. WS exposure tended to reduce mucociliary clearance in the placebo arm but not in the prednisone arm.

Conclusions

Prednisone taken immediately after exposure to WS mitigated short-term increase in sputum %PMN among healthy volunteers selected for their underlying inflammatory responsiveness to WS. Our data support future studies assessing anti-inflammatory interventions and the role of mucus clearance in WS-induced respiratory health effects.

Outpatient Medications Deimplemented by the AAP Bronchiolitis Guidelines: An Umbrella Review of Meta-Analyses

BACKGROUND

The 2014 AAP Bronchiolitis Guidelines deimplemented or recommended against the routine therapeutic use of albuterol, hypertonic saline, and epinephrine for infants and children presenting in the outpatient setting. Our objective was to perform an umbrella review of all meta-analyses that included outpatient subanalyses or network meta-analyses with medication treatment comparisons to study the clinical benefits of these deimplemented medications in the outpatient (i.e., primary care, urgent care, and emergency department) setting.

METHODS

Searches were performed in the databases PubMed and Scopus and the Web search engine Google Scholar on the following three topics: albuterol and bronchiolitis, epinephrine and bronchiolitis, and hypertonic saline and bronchiolitis. Article types were limited to systematic reviews and meta-analyses with outpatient subanalyses, with English language and age restrictions. The search strategy was based on the Population, Intervention, Comparator, Outcomes, Studies (PICOS) framework. The studies were uploaded to Rayyan, a Web-based platform for managing articles of systematic reviews. Citation tracking and manual review of references were performed for the included studies. The meta-analyses and network meta-analyses were reviewed for outpatient subanalyses focused on clinical responses and risk of hospital admission.

RESULTS

A total of 6 meta-analyses for albuterol, 4 meta-analyses for epinephrine, and 11 meta-analyses for hypertonic saline were included. Our review identified evidence from predominantly low and moderate evidence meta-analyses (assessed using GRADE and AMSTAR 2) indicating that all three deimplemented medications exhibit one or more therapeutic effects and benefits for infants with the bronchiolitis syndrome in the outpatient setting. Effect sizes ranged from medium to near medium. These clinical benefits include decreased hospital admissions and lower clinical severity scores.

CONCLUSIONS

Given the heterogeneity of patients under the umbrella term "acute bronchiolitis" and the potential for some patients to respond clinically to albuterol, hypertonic saline, and epinephrine, current evidence supports conducting therapeutic trials in infants with acute bronchiolitis in outpatient settings. However, further well-designed and adequately powered randomized controlled trials and high-quality meta-analyses are still needed.

In vivo detection of pulmonary mucociliary clearance: present challenges and future directions

Pulmonary mucociliary clearance (MCC) is an important defence mechanism of the respiratory system and clears pathogens and foreign particles from the airways. Understanding the effect of disease states, drugs, toxins and airway manipulations on MCC could be beneficial in preventing early pulmonary disease and developing new pulmonary therapeutics. This review summarises the current methods and future efforts to detect pulmonary MCC in vivo.

Emerging cell and molecular targets for treating mucus hypersecretion in asthma

Mucus provides a protective barrier that is crucial for host defense in the lungs. However, excessive or abnormal mucus can have pathophysiological consequences in many pulmonary diseases, including asthma. Patients with asthma are treated with agents that relax airway smooth muscle and reduce airway inflammation, but responses are often inadequate. In part, this is due to the inability of existing therapeutic agents to directly target mucus. Accordingly, there is a critical need to better understand how mucus hypersecretion and airway plugging are affected by the epithelial cells that synthesize, secrete, and transport mucus components. This review highlights recent advances in the biology of mucin glycoproteins with a specific focus on MUC5AC and MUC5B, the chief macromolecular components of airway mucus. An improved mechanistic understanding of key steps in mucin production and secretion will help reveal novel potential therapeutic strategies.

Physiology and pathophysiology of human airway mucus

The mucus clearance system is the dominant mechanical host defense system of the human lung. Mucus is cleared from the lung by cilia and airflow, including both two-phase gas-liquid pumping and cough-dependent mechanisms, and mucus transport rates are heavily dependent on mucus concentration. Importantly, mucus transport rates are accurately predicted by the gel-on-brush model of the mucociliary apparatus from the relative osmotic moduli of the mucus and periciliary-glycocalyceal (PCL-G) layers. The fluid available to hydrate mucus is generated by transepithelial fluid transport. Feedback interactions between mucus concentrations and cilia beating, via purinergic signaling, coordinate Na+ absorptive vs Cl- secretory rates to maintain mucus hydration in health. In disease, mucus becomes hyperconcentrated (dehydrated). Multiple mechanisms derange the ion transport pathways that normally hydrate mucus in muco-obstructive lung diseases, e.g., cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD), non-CF bronchiectasis (NCFB), and primary ciliary dyskinesia (PCD). A key step in muco-obstructive disease pathogenesis is the osmotic compression of the mucus layer onto the airway surface with the formation of adherent mucus plaques and plugs, particularly in distal airways. Mucus plaques create locally hypoxic conditions and produce airflow obstruction, inflammation, infection, and, ultimately, airway wall damage. Therapies to clear adherent mucus with hydrating and mucolytic agents are rational, and strategies to develop these agents are reviewed.

Halotherapy-An Ancient Natural Ally in the Management of Asthma: A Comprehensive Review

The increasing production of modern medication emerges as a new source of environmental pollution. The scientific community is interested in developing alternative, ecological therapies in asthma. Halotherapy proved its benefits in asthma diagnosis, treatment, and prevention and may represent a reliable therapeutic addition to the allopathic treatment, due to its ecological and environment-friendly nature, in order to prevent or prolong the time to exacerbations in patients with asthma. We aimed to review up-to-date research regarding halotherapy benefits in asthma comprehensively. We searched the electronic databases of PubMed, MEDLINE, EMBASE for studies that evaluated the exposure of asthmatic patients to halotherapy. Eighteen original articles on asthma were included. Five studies in adults and five in children assessed the performance of hypertonic saline bronchial challenges to diagnose asthma or vocal cord dysfunction in asthmatic patients. Three papers evaluated the beneficial effects of halotherapy on mucociliary clearance in asthmatic adults. The therapeutic effect of halotherapy on acute or chronic asthma was appraised in three studies in adults and one in children. The preventive role was documented in one paper reporting the ability of halotherapy to hinder nocturnal asthma exacerbations. All studies seem to sustain the overall positive effects of halotherapy as adjuvant therapy on asthma patients with no reported adverse events. Halotherapy is a crucial natural ally in asthma, but further evidence-based studies on larger populations are needed.