Airway mucus function and dysfunction

The forecasting power of the mucin-microbiome interplay in livestock respiratory diseases

Complex respiratory diseases are a significant challenge for the livestock industry worldwide. These diseases considerably impact animal health and welfare and cause severe economic losses. One of the first lines of pathogen defense combines the respiratory tract mucus, a highly viscous material primarily composed of mucins, and a thriving multi-kingdom microbial ecosystem. The microbiome-mucin interplay protects from unwanted substances and organisms, but its dysfunction may enable pathogenic infections and the onset of respiratory disease. Emerging evidence also shows that noncoding regulatory RNAs might modulate the structure and function of the microbiome-mucin relationship. This opinion paper unearths the current understanding of the triangular relationship between mucins, the microbiome, and noncoding RNAs in the context of respiratory infections in animals of veterinary interest. There is a need to look at these molecular underpinnings that dictate distinct health and disease outcomes to implement effective prevention, surveillance, and timely intervention strategies tailored to the different epidemiological contexts.

Intranasal B5 promotes mucosal defence against Actinobacillus pleuropneumoniae via ameliorating early immunosuppression

Actinobacillus pleuropneumoniae (APP) is an important pathogen of the porcine respiratory disease complex, which leads to huge economic losses worldwide. We previously demonstrated that Pichia pastoris-producing bovine neutrophil β-defensin-5 (B5) could resist the infection by the bovine intracellular pathogen Mycobacterium bovis. In this study, the roles of synthetic B5 in regulating mucosal innate immune response and protecting against extracellular APP infection were further investigated using a mouse model. Results showed that B5 promoted the production of tumour necrosis factor (TNF)-α, interleukin (IL)-1β, and interferon (IFN)-β in macrophages as well as dendritic cells (DC) and enhanced DC maturation in vitro. Importantly, intranasal B5 was safe and conferred effective protection against APP via reducing the bacterial load in lungs and alleviating pulmonary inflammatory damage. Furthermore, in the early stage of APP infection, we found that intranasal B5 up-regulated the secretion of TNF-α, IL-1β, IL-17, and IL-22; enhanced the rapid recruitment of macrophages, neutrophils, and DC; and facilitated the generation of group 3 innate lymphoid cells in lungs. In addition, B5 activated signalling pathways associated with cellular response to IFN-β and activation of innate immune response in APP-challenged lungs. Collectively, B5 via the intranasal route can effectively ameliorate the immune suppression caused by early APP infection and provide protection against APP. The immunization strategy may be applied to animals or human respiratory bacterial infectious diseases. Our findings highlight the potential importance of B5, enhancing mucosal defence against intracellular bacteria like APP which causes early-phase immune suppression.

Electrospun composite-coated endotracheal tubes with controlled siRNA and drug delivery to lubricate and minimize upper airway injury

Endotracheal Tubes (ETTs) maintain and secure a patent airway; however, prolonged intubation often results in unintended injury to the mucosal epithelium and inflammatory sequelae which complicate recovery. ETT design and materials used have yet to adapt to address intubation associated complications. In this study, a composite coating of electrospun polycaprolactone (PCL) fibers embedded in a four-arm polyethylene glycol acrylate matrix (4APEGA) is developed to transform the ETT from a mechanical device to a dual-purpose device capable of delivering multiple therapeutics while preserving coating integrity. Further, the composite coating system (PCL-4APEGA) is capable of sustained delivery of dexamethasone from the PCL phase and small interfering RNA (siRNA) containing polyplexes from the 4APEGA phase. The siRNA is released rapidly and targets smad3 for immediate reduction in pro-fibrotic transforming growth factor-beta 1 (TGFϐ1) signaling in the upper airway mucosa as well as suppressing long-term sequelae in inflammation from prolonged intubation. A bioreactor was used to study mucosal adhesion to the composite PCL-4APEGA coated ETTs and investigate continued mucus secretory function in ex vivo epithelial samples. The addition of the 4APEGA coating and siRNA delivery to the dexamethasone delivery was then evaluated in a swine model of intubation injury and observed to restore mechanical function of the vocal folds and maintain epithelial thickness when observed over 14 days of intubation. This study demonstrated that increase in surface lubrication paired with surface stiffness reduction significantly decreased fibrotic behavior while reducing epithelial adhesion and abrasion.

Thiolated polyglycerol sulfate as potential mucolytic for muco-obstructive lung diseases

Increased disulfide crosslinking of secreted mucins causes elevated viscoelasticity of mucus and is a key determinant of mucus dysfunction in patients with cystic fibrosis (CF) and other muco-obstructive lung diseases. In this study, we describe the synthesis of a novel thiol-containing, sulfated dendritic polyglycerol (dPGS-SH), designed to chemically reduce these abnormal crosslinks, which we demonstrate with mucolytic activity assays in sputum from patients with CF. This mucolytic polymer, which is based on a reportedly anti-inflammatory polysulfate scaffold, additionally carries multiple thiol groups for mucolytic activity and can be produced on a gram-scale. After a physicochemical compound characterization, we compare the mucolytic activity of dPGS-SH to the clinically approved N-acetylcysteine (NAC) using western blot studies and investigate the effect of dPGS-SH on the viscoelastic properties of sputum samples from CF patients by oscillatory rheology. We show that dPGS-SH is more effective than NAC in reducing multimer intensity of the secreted mucins MUC5B and MUC5AC and demonstrate significant mucolytic activity by rheology. In addition, we provide data for dPGS-SH demonstrating a high compound stability, low cytotoxicity, and superior reaction kinetics over NAC at different pH levels. Our data support further development of the novel reducing polymer system dPGS-SH as a potential mucolytic to improve mucus function and clearance in patients with CF as well as other muco-obstructive lung diseases.

Reduced sialylation of airway mucin impairs mucus transport by altering the biophysical properties of mucin

Mucus stasis is a pathologic hallmark of muco-obstructive diseases, including cystic fibrosis (CF). Mucins, the principal component of mucus, are extensively modified with hydroxyl (O)-linked glycans, which are largely terminated by sialic acid. Sialic acid is a negatively charged monosaccharide and contributes to the biochemical/biophysical properties of mucins. Reports suggest that mucin sialylation may be altered in CF; however, the consequences of reduced sialylation on mucus clearance have not been fully determined. Here, we investigated the consequences of reduced sialylation on the charge state and conformation of the most prominent airway mucin, MUC5B, and defined the functional consequences of reduced sialylation on mucociliary transport (MCT). Reduced sialylation contributed to a lower charged MUC5B form and decreased polymer expansion. The inhibition of total mucin sialylation de novo impaired MCT in primary human bronchial epithelial cells and rat airways, and specific α-2,3 sialylation blockade was sufficient to recapitulate these findings. Finally, we show that ST3 beta-galactoside alpha-2,3-sialyltransferase (ST3Gal1) expression is downregulated in CF and partially restored by correcting CFTR via Elexacaftor/Tezacaftor/Ivacaftor treatment. Overall, this study demonstrates the importance of mucin sialylation in mucus clearance and identifies decreased sialylation by ST3Gal1 as a possible therapeutic target in CF and potentially other muco-obstructive diseases.

Mucus plugging on computed tomography and the sputum microbiome in patients with asthma, chronic obstructive pulmonary disease, and asthma-COPD overlap

BACKGROUND

Despite clinical implications, the pathogenesis of mucus plugging in asthma, chronic obstructive pulmonary disease (COPD), and asthma-COPD overlap (ACO) remains unclear. We hypothesized that distinct airway microbiomes might affect mucus plugging differently among ACO, asthma, and COPD and among different extents of airway eosinophilic inflammation.

METHODS

The sputum microbiome, sputum cell differential count, and mucus plug score on computed tomography were cross-sectionally evaluated in patients with chronic airflow limitation.

RESULTS

Patients with ACO, asthma, or COPD were enrolled (n = 56, 10, and 25). Higher mucus plug scores were associated with a greater relative abundance of the phylum Proteobacteria (rho = 0.29) only in patients with ACO and a greater relative abundance of the phylum Actinobacteria (rho = 0.46) only in patients with COPD. In multivariable models including only patients with ACO, the presence of mucus plugs was associated with a greater relative abundance of the phylum Proteobacteria and the genus Haemophilus, independent of smoking status, airflow limitation, and emphysema severity. Moreover, the mucus score was associated with a greater relative abundance of the genus Streptococcus (rho = 0.46) in patients with a high sputum eosinophil count (n = 22) and with that of the genus Haemophilus (rho = 0.46) in those with a moderate sputum eosinophil count (n = 26).

CONCLUSIONS

The associations between mucus plugging and the microbiome in ACO differed from those in COPD and asthma. Greater relative abundances of the phylum Proteobacteria and genus Haemophilus may be involved in mucus plugging in patients with ACO and moderate airway eosinophilic inflammation.

TOLLIP and MUC5B modulate the effect of ambient NO2 on respiratory symptoms in infancy

BACKGROUND

Current knowledge suggests that the gene region containing MUC5B and TOLLIP plays a role in airway defence and airway inflammation, and hence respiratory disease. It is also known that exposure to air pollution increases susceptibility to respiratory disease. We aimed to study whether the effect of air pollutants on the immune response and respiratory symptoms in infants may be modified by polymorphisms in MUC5B and TOLLIP genes.

METHODS

359 healthy term infants from the prospective Basel-Bern Infant Lung Development (BILD) birth cohort were included in the study. The main outcome was the score of weekly assessed respiratory symptoms in the first year of life. Using the candidate gene approach, we selected 10 single nucleotide polymorphisms (SNPs) from the MUC5B and TOLLIP regions. Nitrogen dioxide (NO2) and particulate matter ≤10 μm in aerodynamic diameter (PM10) exposure was estimated on a weekly basis. We used generalised additive mixed models adjusted for known covariates. To validate our results in vitro, cells from a lung epithelial cell line were downregulated in TOLLIP expression and exposed to diesel particulate matter (DPM) and polyinosinic-polycytidylic acid.

RESULTS

Significant interaction was observed between modelled air pollution (weekly NO2 exposure) and 5 SNPs within MUC5B and TOLLIP genes regarding respiratory symptoms as outcome: E.g., infants carrying minor alleles of rs5744034, rs3793965 and rs3750920 (all TOLLIP) had an increased risk of respiratory symptoms with increasing NO2 exposure. In vitro experiments showed that cells downregulated for TOLLIP react differently to environmental pollutant exposure with DPM and viral stimulation.

CONCLUSION

Our findings suggest that the effect of air pollution on respiratory symptoms in infancy may be influenced by the genotype of specific SNPs from the MUC5B and TOLLIP regions. For validation of the findings, we provided in vitro evidence for the interaction of TOLLIP with air pollution.

Integration of mucus and its impact within in vitro setups for inhaled drugs and formulations: Identifying the limits of simple vs. complex methodologies when studying drug dissolution and permeability

Traditionally, developing inhaled drug formulations relied on trial and error, yet recent technological advancements have deepened the understanding of 'inhalation biopharmaceutics' i.e. the processes that occur to influence the rate and extent of drug exposure in the lungs. This knowledge has led to the development of new in vitro models that predict the in vivo behavior of drugs, facilitating the enhancement of existing formulation and the development of novel ones. Our prior research examined how simulated lung fluid (SLF) affects the solubility of inhaled drugs. Building on this, we aimed to explore drug dissolution and permeability in lung mucosa models containing mucus. Thus, the permeation of four active pharmaceutical ingredients (APIs), salbutamol sulphate (SS), tiotropium bromide (TioBr), formoterol fumarate (FF) and budesonide (BUD), was assayed in porcine mucus covered Calu-3 cell layers, cultivated at an air liquid interface (ALI) or submerged in a liquid covered (LC) culture system. Further analysis on BUD and FF involved their transport in a mucus-covered PAMPA system. Finally, their dissolution post-aerosolization from Symbicort® was compared using 'simple' Transwell and complex DissolvIt® apparatuses, alone or in presence of porcine mucus or polymer-lipid mucus simulant. The presence of porcine mucus impacted both permeability and dissolution of inhaled drugs. For instance, permeability of SS was reduced by a factor of ten in the Calu-3 ALI model while the permeability of BUD was reduced by factor of two in LC and ALI setups. The comparison of dissolution methodologies indicated that drug dissolution performance was highly dependent on the setup, observing decreased release efficiency and higher variability in Transwell system compared to DissolvIt®. Overall, results demonstrate that relatively simple methodologies can be used to discriminate between formulations in early phase drug product development. However, for more advanced stages complex methods are required. Crucially, it was clear that the impact of mucus and selection of its composition in in vitro testing of dissolution and permeability should not be neglected when developing drugs and formulations intended for inhalation.

Exploring Mechanisms of Lipid Nanoparticle-Mucus Interactions in Healthy and Cystic Fibrosis Conditions

Mucus forms the first defense line of human lungs, and as such hampers the efficient delivery of therapeutics to the underlying epithelium. This holds particularly true for genetic cargo such as CRISPR-based gene editing tools which cannot readily surmount the mucosal barrier. While lipid nanoparticles (LNPs) emerge as versatile non-viral gene delivery systems that can help overcome the delivery challenge, many knowledge gaps remain, especially for diseased states such as cystic fibrosis (CF). This study provides fundamental insights into Cas9 mRNA or ribonucleoprotein-loaded LNP-mucus interactions in healthy and diseased states by assessing the impact of the genetic cargo, mucin sialylation, mucin concentration, ionic strength, pH, and polyethylene glycol (PEG) concentration and nature on LNP diffusivity leveraging experimental approaches and Brownian dynamics (BD) simulations. Taken together, this study identifies key mucus and LNP characteristics that are critical to enabling a rational LNP design for transmucosal delivery.

Eosinophil-mucus interplay in severe asthma: Implications for treatment with biologicals

Airway mucus is a hydrogel with unique biophysical properties due to its primary water composition and a small proportion of large anionic glycoproteins or mucins. The predominant mucins in human mucus, MUC5AC and MUC5B, are secreted by specialized cells within the airway epithelium both in normal conditions and in response to various stimuli. Their relative proportions are correlated with specific inflammatory responses and disease mechanisms. The dysregulation of mucin expression is implicated in numerous respiratory diseases, including asthma, COPD, and cystic fibrosis, where the pathogenic role of mucus has been extensively described yet often overlooked. In airway diseases, excessive mucus production or impaired mucus clearance leads to mucus plugging, with secondary airway occlusion that contribute to airflow obstruction, asthma severity and poor control. Eosinophils and Charcot Leyden crystals in sputum contribute to the mucus burden and tenacity. Mucin may also contribute to eosinophil survival. Other mechanisms, including eosinophil-independent IL-13 release, mast-cell activation and non-type-2 (T2) cytokines, are also likely to participate in mucus pathobiology. An accurate assessment of mucus and its clinical and functional consequences require a thorough approach that includes evaluation of cellular predominance in sputum, airway cytokines and other inflammatory markers, mucus characteristics and composition and structural and functional impact measured by advanced lung imaging. This review, illustrated with clinical scenarios, provides an overview of current methods to assess mucus and its relevance to the choice of biologics to treat patients with severe asthma.

Pseudomonas aeruginosa breaches respiratory epithelia through goblet cell invasion in a microtissue model

Pseudomonas aeruginosa, a leading cause of severe hospital-acquired pneumonia, causes infections with up to 50% mortality rates in mechanically ventilated patients. Despite some knowledge of virulence factors involved, it remains unclear how P. aeruginosa disseminates on mucosal surfaces and invades the tissue barrier. Using infection of human respiratory epithelium organoids, here we observed that P. aeruginosa colonization of apical surfaces is promoted by cyclic di-GMP-dependent asymmetric division. Infection with mutant strains revealed that Type 6 Secretion System activities promote preferential invasion of goblet cells. Type 3 Secretion System activity by intracellular bacteria induced goblet cell death and expulsion, leading to epithelial rupture which increased bacterial translocation and dissemination to the basolateral epithelium. These findings show that under physiological conditions, P. aeruginosa uses coordinated activity of a specific combination of virulence factors and behaviours to invade goblet cells and breach the epithelial barrier from within, revealing mechanistic insight into lung infection dynamics.

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.

Cytochrome oxidase requirements in Bordetella reveal insights into evolution towards life in the mammalian respiratory tract

Little is known about oxygen utilization during infection by bacterial respiratory pathogens. The classical Bordetella species, including B. pertussis, the causal agent of human whooping cough, and B. bronchiseptica, which infects nearly all mammals, are obligate aerobes that use only oxygen as the terminal electron acceptor for electron transport-coupled oxidative phosphorylation. B. bronchiseptica, which occupies many niches, has eight distinct cytochrome oxidase-encoding loci, while B. pertussis, which evolved from a B. bronchiseptica-like ancestor but now survives exclusively in and between human respiratory tracts, has only three functional cytochrome oxidase-encoding loci: cydAB1, ctaCDFGE1, and cyoABCD1. To test the hypothesis that the three cytochrome oxidases encoded within the B. pertussis genome represent the minimum number and class of cytochrome oxidase required for respiratory infection, we compared B. bronchiseptica strains lacking one or more of the eight possible cytochrome oxidases in vitro and in vivo. No individual cytochrome oxidase was required for growth in ambient air, and all three of the cytochrome oxidases conserved in B. pertussis were sufficient for growth in ambient air and low oxygen. Using a high-dose, large-volume persistence model and a low-dose, small-volume establishment of infection model, we found that B. bronchiseptica producing only the three B. pertussis-conserved cytochrome oxidases was indistinguishable from the wild-type strain for infection. We also determined that CyoABCD1 is sufficient to cause the same level of bacterial burden in mice as the wild-type strain and is thus the primary cytochrome oxidase required for murine infection, and that CydAB1 and CtaCDFGE1 fulfill auxiliary roles or are important for aspects of infection we have not assessed, such as transmission. Our results shed light on the environment at the surface of the ciliated epithelium, respiration requirements for bacteria that colonize the respiratory tract, and the evolution of virulence in bacterial pathogens.

Enhanced radiation sensitivity, decreased DNA damage repair, and differentiation defects in airway stem cells derived from patients with chronic obstructive pulmonary disease

Radiation therapy (RT) is a common treatment for lung cancer. Still, it can lead to irreversible loss of pulmonary function and a significant reduction in quality of life for one-third of patients. Preexisting comorbidities, such as chronic obstructive pulmonary disease (COPD), are frequent in patients with lung cancer and further increase the risk of complications. Because lung stem cells are crucial for the regeneration of lung tissue following injury, we hypothesized that airway stem cells from patients with COPD with lung cancer might contribute to increased radiation sensitivity. We used the air-liquid interface model, a three-dimensional (3D) culture system, to compare the radiation response of primary human airway stem cells from healthy and patients with COPD. We found that COPD-derived airway stem cells, compared to healthy airway stem cell cultures, exhibited disproportionate pathological mucociliary differentiation, aberrant cell cycle checkpoints, residual DNA damage, reduced survival of stem cells and self-renewal, and terminally differentiated cells post-irradiation, which could be reversed by blocking the Notch pathway using small-molecule γ-secretase inhibitors. Our findings shed light on the mechanisms underlying the increased radiation sensitivity of COPD and suggest that airway stem cells reflect part of the pathological remodeling seen in lung tissue from patients with lung cancer receiving thoracic RT.

Role of IL-5 in asthma and airway remodelling

Asthma is a common and burdensome chronic inflammatory airway disease that affects both children and adults. One of the main concerns with asthma is the manifestation of irreversible tissue remodelling of the airways due to the chronic inflammatory environment that eventually disrupts the whole structure of the airways. Most people with troublesome asthma are treated with inhaled corticosteroids. However, the development of steroid resistance is a commonly encountered issue, necessitating other treatment options for these patients. Biological therapies are a promising therapeutic approach for people with steroid-resistant asthma. Interleukin 5 is recently gaining a lot of attention as a biological target relevant to the tissue remodelling process. Since IL-5-neutralizing monoclonal antibodies (mepolizumab, reslizumab and benralizumab) are currently available for clinical use, this review aims to revisit the role of IL-5 in asthma pathogenesis at large and airway remodelling in particular, in addition to exploring its role as a target for biological treatments.

Enhancing pulmonary delivery and immunomodulation of respiratory diseases through virus-mimicking nanoparticles

This study introduces the nanobromhexine lipid particle (NBL) platform designed for effective pulmonary drug delivery. Inspired by respiratory virus transport mechanisms, NBL address challenges associated with mucus permeation and inflammation in pulmonary diseases. Composed of low molecular weight polyethylene glycol-coated lipid nanoparticles with bromhexine hydrochloride, NBL exhibit a size of 118 ± 24 nm, a neutral zeta potential, osmolarity of 358 ± 28 mOsmol/kg, and a pH of 6.5. Nebulizing without leakage and showing no toxicity to epithelial cells, NBL display mucoadhesive properties with a 60% mucin-binding efficiency. They effectively traverse the dense mucus layer of Calu-3 cultures in an air-liquid interface, as supported by a 55% decrease in MUC5AC density and a 29% increase in nanoparticles internalization compared to non-exposed cells. In assessing immunomodulatory effects, NBL treatment in SARS-CoV-2-infected lung cells leads to a 40-fold increase in anti-inflammatory MUC1 gene expression, a proportional reduction in pro-inflammatory IL-6 expression, and elevated anti-inflammatory IL-10 expression. These findings suggest a potential mechanism to regulate the excessive IL-6 expression triggered by virus infection. Therefore, the NBL platform demonstrates promising potential for efficient pulmonary drug delivery and immunomodulation, offering a novel approach to addressing mucus permeation and inflammation in pulmonary diseases.

Computed tomography mucus plugs and airway tree structure in patients with chronic obstructive pulmonary disease: Associations with airflow limitation, health-related independence and mortality

BACKGROUND AND OBJECTIVE

Mucus plugs and underlying airway tree structure can affect airflow limitation and prognosis in patients with chronic obstructive pulmonary disease (COPD), but their relative roles are unclear. This study used two COPD cohorts to examine whether mucus plugs on computed tomography (CT) were associated with airflow limitation and clinical outcomes independent of other airway structural changes and emphysema.

METHODS

Based on visual CT assessment, patients with mucus plugs in 0, 1-2 and ≥3 lung segments were assigned to no-, low- and high-mucus groups. Loss of health-related independence and mortality were prospectively recorded for 3 and 10 years in the Kyoto-Himeji and Hokkaido cohorts, respectively. The percentages of the wall area of the central airways (WA%), total airway count (TAC) and emphysema were quantified on CT.

RESULTS

Of 199 and 96 patients in the Kyoto-Himeji and Hokkaido cohorts, 34% and 30%, respectively, had high mucus scores. In both cohorts, TAC was lower in the high-mucus group than in the no-mucus group, whereas their emphysema severity did not differ. High mucus score and low TAC were independently associated with airflow limitation after adjustment for WA% and emphysema. In multivariable models adjusted for WA% and emphysema, TAC, rather than mucus score, was associated with a greater rate of loss of independence, whereas high mucus score, rather than TAC, was associated with increased mortality.

CONCLUSION

Mucus plugs and lower airway branch count on CT had distinct roles in airflow limitation, health-related independence and mortality in patients with COPD.

Foreign Bodies in Pediatric Otorhinolaryngology: A Review

Foreign bodies (FBs) in pediatric otorhinolaryngology represent up to 10% of cases in emergency departments (ED) and are primarily present in children under five years old. They are probably the result of children's curiosity and tendency to explore the environment. Aural and nasal FBs are the most common and accessible, and the removal methods differ depending on the exact location and type of FB, which can be organic or inorganic. A fish bone stuck in one of the palatine tonsils is the most common pharyngeal FB. Laryngopharyngeal FBs can obstruct the upper respiratory tract and thus become acutely life-threatening, requiring an urgent response. Aspiration of FBs is common in children between 1 and 4 years old. A history of coughing and choking is an indication of diagnostic and therapeutic methods to rule out or confirm a tracheobronchial FB. Regardless of the availability of radiological diagnostics, rigid bronchoscopy is the diagnostic and therapeutic method of choice in symptomatic cases. Radiological diagnostics are more significant in treating esophageal FBs since most are radiopaque. Flexible or rigid esophagoscopy is a successful method of removal. A delayed diagnosis, as with tracheobronchial FBs, can lead to fatal consequences.

Nil per os in the management of oropharyngeal dysphagia-exploring the unintended consequences

Nil per os (NPO), also referred to as Nil by Mouth (NBM), is a health-related intervention of withholding food and fluids. When implemented in the context of a person with dysphagia, NPO aims to mitigate risks of aspiration. However, evidence demonstrating that NPO is beneficial as an intervention for people with dysphagia is lacking. This paper explores the theoretical and empirical evidence relating to the potential benefits and adverse effects of NPO and asserts that NPO is not a benign intervention. This paper argues for applying an ethics framework when making decisions relating to the use of NPO as an intervention for dysphagia, in particular addressing informed consent and a person's right to self-determination.

Eosinophil-Epithelial Cell Interactions in Asthma

BACKGROUND

Eosinophils have numerous roles in type 2 inflammation depending on their activation states in the blood and airway or after encounter with inflammatory mediators. Airway epithelial cells have a sentinel role in the lung and, by instructing eosinophils, likely have a foundational role in asthma pathogenesis.

SUMMARY

In this review, we discuss various topics related to eosinophil-epithelial cell interactions in asthma, including the influence of eosinophils and eosinophil products, e.g., granule proteins, on epithelial cell function, expression, secretion, and plasticity; the effects of epithelial released factors, including oxylipins, cytokines, and other mediators on eosinophils, e.g., on their activation, expression, and survival; possible mechanisms of eosinophil-epithelial cell adhesion; and the role of intra-epithelial eosinophils in asthma.

KEY MESSAGES

We suggest that eosinophils and their products can have both injurious and beneficial effects on airway epithelial cells in asthma and that there are bidirectional interactions and signaling between eosinophils and airway epithelial cells in asthma.

The Modulation of Respiratory Epithelial Cell Differentiation by the Thickness of an Electrospun Poly-ε-Carprolactone Mesh Mimicking the Basement Membrane

The topology of the basement membrane (BM) affects cell physiology and pathology, and BM thickening is associated with various chronic lung diseases. In addition, the topology of commercially available poly (ethylene terephthalate) (PET) membranes, which are used in preclinical in vitro models, differs from that of the human BM, which has a fibrous and elastic structure. In this study, we verified the effect of BM thickness on the differentiation of normal human bronchial epithelial (NHBE) cells. To evaluate whether the thickness of poly-ε-carprolactone (PCL) mesh affects the differentiation of NHBE cells, cells were grown on thin- (6-layer) and thick-layer (80-layer) meshes consisting of electrospun PCL nanofibers using an air-liquid interface (ALI) cell culture system. It was found that the NHBE cells formed a normal pseudostratified epithelium composed of ciliated, goblet, and basal cells on the thin-layer PCL mesh; however, goblet cell hyperplasia was observed on the thick-layer PCL mesh. Differentiated NHBE cells cultured on the thick-layer PCL mesh also demonstrated increased epithelial-mesenchymal transition (EMT) compared to those cultured on the thin-layer PCL mesh. In addition, expression of Sox9, nuclear factor (NF)-κB, and oxidative stress-related markers, which are also associated with goblet cell hyperplasia, was increased in the differentiated NHBE cells cultured on the thick-layer PCL mesh. Thus, the use of thick electrospun PCL mesh led to NHBE cells differentiating into hyperplastic goblet cells via EMT and the oxidative stress-related signaling pathway. Therefore, the topology of the BM, for example, thickness, may affect the differentiation direction of human bronchial epithelial cells.

Ozonolysis of Terpene Flavor Additives in Vaping Emissions: Elevated Production of Reactive Oxygen Species and Oxidative Stress

The production of e-cigarette aerosols through vaping processes is known to cause the formation of various free radicals and reactive oxygen species (ROS). Despite the well-known oxidative potential and cytotoxicity of fresh vaping emissions, the effects of chemical aging on exhaled vaping aerosols by indoor atmospheric oxidants are yet to be elucidated. Terpenes are commonly found in e-liquids as flavor additives. In the presence of indoor ozone (O3), e-cigarette aerosols that contain terpene flavorings can undergo chemical transformations, further producing ROS and reactive carbonyl species. Here, we simulated the aging process of the e-cigarette emissions in a 2 m3 FEP film chamber with 100 ppbv of O3 exposure for an hour. The aged vaping aerosols, along with fresh aerosols, were collected to detect the presence of ROS. The aged particles exhibited 2- to 11-fold greater oxidative potential, and further analysis showed that these particles formed a greater number of radicals in aqueous conditions. The aging process induced the formation of various alkyl hydroperoxides (ROOH), and through iodometric quantification, we saw that our aged vaping particles contained significantly greater amounts of these hydroperoxides than their fresh counterparts. Bronchial epithelial cells exposed to aged vaping aerosols exhibited an upregulation of the oxidative stress genes, HMOX-1 and GSTP1, indicating the potential for inhalation toxicity. This work highlights the indirect danger of vaping in environments with high ground-level O3, which can chemically transform e-cigarette aerosols into new particles that can induce greater oxidative damage than fresh e-cigarette aerosols. Given that the toxicological characteristics of e-cigarettes are mainly associated with the inhalation of fresh aerosols in current studies, our work may provide a perspective that characterizes vaping exposure under secondhand or thirdhand conditions as a significant health risk.

An antibacterial, multifunctional nanogel for efficient treatment of neutrophilic asthma

Asthma is a chronic and heterogeneous disease affecting the lungs and respiratory tract. In particular, the neutrophil subtype of asthma was described as persistent, more severe, and corticosteroid-resistant. Growing evidence suggested that nontypeable Haemophilus influenzae (NTHi) infection contributes to the development of neutrophilic asthma, exacerbating clinical symptoms and increasing the associated medical burden. In this work, arginine-grafted chitosan (CS-Arg) was ionically cross-linked with tris(2-carboxyethyl) phosphine (TCEP), and a highly-efficient antimicrobial agent, poly-ε-L-Lysine (ε-PLL), was incorporated to prepare ε-PLL/CS-Arg/TCEP (ECAT) composite nanogels. The results showed that ECAT nanogels exhibited highly effective inhibition against the proliferation of NTHi, Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). In addition, ECAT nanogels could effectively inhibit the formation of mucins aggregates in vitro, suggesting that the nanogel might have the potential to destroy mucin in respiratory disease. Furthermore, in the ovalbumin (OVA)/NTHi-induced Balb/c mice model of neutrophilic asthma, the number of neutrophils in the alveolar lavage fluid and the percentage of inflammatory cells in the blood were effectively reduced by exposure to tower nebulized administration of ECAT nanogels, and reversing airway hyperresponsiveness (AHR) and reducing inflammation in neutrophilic asthma mice. In conclusion, the construction of ECAT nanogels was a feasible anti-infective and anti-inflammatory therapeutic strategy, which demonstrated strong potential in the clinical treatment of neutrophilic asthma.

Mucus polymer concentration and in vivo adaptation converge to define the antibiotic response of Pseudomonas aeruginosa during chronic lung infection

The airway milieu of individuals with muco-obstructive airway diseases (MADs) is defined by the accumulation of dehydrated mucus due to hyperabsorption of airway surface liquid and defective mucociliary clearance. Pathological mucus becomes progressively more viscous with age and disease severity due to the concentration and overproduction of mucin and accumulation of host-derived extracellular DNA (eDNA). Respiratory mucus of MADs provides a niche for recurrent and persistent colonization by respiratory pathogens, including Pseudomonas aeruginosa, which is responsible for the majority of morbidity and mortality in MADs. Despite high concentration inhaled antibiotic therapies and the absence of antibiotic resistance, antipseudomonal treatment failure in MADs remains a significant clinical challenge. Understanding the drivers of antibiotic tolerance is essential for developing more effective treatments that eradicate persistent infections. The complex and dynamic environment of diseased airways makes it difficult to model antibiotic efficacy in vitro. We aimed to understand how mucin and eDNA concentrations, the two dominant polymers in respiratory mucus, alter the antibiotic tolerance of P. aeruginosa. Our results demonstrate that polymer concentration and molecular weight affect P. aeruginosa survival post antibiotic challenge. Polymer-driven antibiotic tolerance was not explicitly associated with reduced antibiotic diffusion. Lastly, we established a robust and standardized in vitro model for recapitulating the ex vivo antibiotic tolerance of P. aeruginosa observed in expectorated sputum across age, underlying MAD etiology, and disease severity, which revealed the inherent variability in intrinsic antibiotic tolerance of host-evolved P. aeruginosa populations.

IMPORTANCE

Antibiotic treatment failure in Pseudomonas aeruginosa chronic lung infections is associated with increased morbidity and mortality, illustrating the clinical challenge of bacterial infection control. Understanding the underlying infection environment, as well as the host and bacterial factors driving antibiotic tolerance and the ability to accurately recapitulate these factors in vitro, is crucial for improving antibiotic treatment outcomes. Here, we demonstrate that increasing concentration and molecular weight of mucin and host eDNA drive increased antibiotic tolerance to tobramycin. Through systematic testing and modeling, we identified a biologically relevant in vitro condition that recapitulates antibiotic tolerance observed in ex vivo treated sputum. Ultimately, this study revealed a dominant effect of in vivo evolved bacterial populations in defining inter-subject ex vivo antibiotic tolerance and establishes a robust and translatable in vitro model for therapeutic development.

Dynamic measurement of airway surface liquid volume with an ex vivo trachea-chip

The volume and composition of airway surface liquid (ASL) is regulated by liquid secretion and absorption across airway epithelia, controlling the pH, solute concentration, and biophysical properties of ASL in health and disease. Here, we developed a method integrating explanted tracheal tissue with a micro-machined device (referred to as "ex vivo trachea-chip") to study the dynamic properties of ASL volume regulation. The ex vivo trachea-chip allows real-time measurement of ASL transport (Jv) with intact airway anatomic structures, environmental control, high-resolution, and enhanced experimental throughput. Applying this technology to freshly excised tissue we observed ASL absorption under basal conditions. The apical application of amiloride, an inhibitor of airway epithelial sodium channels (ENaC), reduced airway liquid absorption. Furthermore, the basolateral addition of NPPB, a Cl- channel inhibitor, reduced the basal rate of ASL absorption, implicating a role for basolateral Cl- channels in ASL volume regulation. When tissues were treated with apical amiloride and basolateral methacholine, a cholinergic agonist that stimulates secretion from airway submucosal glands, the net airway surface liquid production shifted from absorption to secretion. This ex vivo trachea-chip provides a new tool to investigate ASL transport dynamics in pulmonary disease states and may aid the development of new therapies targeting ASL regulation.

The Non-Invasive Detection of Pulmonary Exacerbations in Disorders of Mucociliary Clearance with Breath Analysis: A Systematic Review

Background: Disorders of mucociliary clearance, such as cystic fibrosis (CF), primary ciliary dyskinesia (PCD) and bronchiectasis of unknown origin, are characterised by periods with increased respiratory symptoms, referred to as pulmonary exacerbations. These exacerbations are hard to predict and associated with lung function decline and the loss of quality of life. To optimise treatment and preserve lung function, there is a need for non-invasive and reliable methods of detection. Breath analysis might be such a method. Methods: We systematically reviewed the existing literature on breath analysis to detect pulmonary exacerbations in mucociliary clearance disorders. Extracted data included the study design, technique of measurement, definition of an exacerbation, identified compounds and diagnostic accuracy. Results: Out of 244 identified articles, 18 were included in the review. All studies included patients with CF and two also with PCD. Age and the definition of exacerbation differed between the studies. There were five that measured volatile organic compounds (VOCs) in exhaled breath using gas chromatography with mass spectrometry, two using an electronic nose and eleven measured organic compounds in exhaled breath condensate. Most studies showed a significant correlation between pulmonary exacerbations and one or multiple compounds, mainly hydrocarbons and cytokines, but the validation of these results in other studies was lacking. Conclusions: The detection of pulmonary exacerbations by the analysis of compounds in exhaled breath seems possible but is not near clinical application due to major differences in results, study design and the definition of an exacerbation. There is a need for larger studies, with a longitudinal design, international accepted definition of an exacerbation and validation of the results in independent cohorts.

Reduced Sialylation of Airway Mucin Impairs Mucus Transport by Altering the Biophysical Properties of Mucin

Mucus stasis is a pathologic hallmark of muco-obstructive diseases, including cystic fibrosis (CF). Mucins, the principal component of mucus, are extensively modified with hydroxyl (O)-linked glycans, which are largely terminated by sialic acid. Sialic acid is a negatively charged monosaccharide and contributes to the biochemical/biophysical properties of mucins. Reports suggest that mucin sialylation may be altered in CF; however, the consequences of reduced sialylation on mucus clearance have not been fully determined. Here, we investigated the consequences of reduced sialylation on the charge state and conformation of the most prominent airway mucin, MUC5B, and defined the functional consequences of reduced sialylation on mucociliary transport (MCT). Reduced sialylation contributed to a lower charged MUC5B form and decreased polymer expansion. The inhibition of total mucin sialylation de novo impaired MCT in primary human bronchial epithelial cells and rat airways, and specific α-2,3 sialylation blockade was sufficient to recapitulate these findings. Finally, we show that ST3 beta-galactoside alpha-2,3-sialyltransferase (ST3Gal1) expression is downregulated in CF and partially restored by correcting CFTR via Elexacaftor/Tezacaftor/Ivacaftor treatment. Overall, this study demonstrates the importance of mucin sialylation in mucus clearance and identifies decreased sialylation by ST3Gal1 as a possible therapeutic target in CF and potentially other muco-obstructive diseases.

Mucus-Inspired Self-Healing Hydrogels: A Protective Barrier for Cells against Viral Infection

Mucus is a dynamic biological hydrogel, composed primarily of the glycoprotein mucin, exhibits unique biophysical properties and forms a barrier protecting cells against a broad-spectrum of viruses. Here, this work develops a polyglycerol sulfate-based dendronized mucin-inspired copolymer (MICP-1) with ≈10% repeating units of activated disulfide as cross-linking sites. Cryo-electron microscopy (Cryo-EM) analysis of MICP-1 reveals an elongated single-chain fiber morphology. MICP-1 shows potential inhibitory activity against many viruses such as herpes simplex virus 1 (HSV-1) and SARS-CoV-2 (including variants such as Delta and Omicron). MICP-1 produces hydrogels with viscoelastic properties similar to healthy human sputum and with tuneable microstructures using linear and branched polyethylene glycol-thiol (PEG-thiol) as cross-linkers. Single particle tracking microrheology, electron paramagnetic resonance (EPR) and cryo-scanning electron microscopy (Cryo-SEM) are used to characterize the network structures. The synthesized hydrogels exhibit self-healing properties, along with viscoelastic properties that are tuneable through reduction. A transwell assay is used to investigate the hydrogel's protective properties against viral infection against HSV-1. Live-cell microscopy confirms that these hydrogels can protect underlying cells from infection by trapping the virus, due to both network morphology and anionic multivalent effects. Overall, this novel mucin-inspired copolymer generates mucus-mimetic hydrogels on a multi-gram scale. These hydrogels can be used as models for disulfide-rich airway mucus research, and as biomaterials.

Effects of Thickening Agents on the Mucociliary Transport Function: Comparison by the Type of Thickening Agents and the Viscosity of Thickened Water

Thickening agents effectively prevent liquid aspiration, but their impact on the ease of discharging aspirated liquids from the trachea remains unclear due to alterations in the physical properties of liquids. This study clarifies the effects of thickening agents, comprising various raw materials, on mucociliary transport function, focusing on the viscosities of thickened waters. The subjects were 23 healthy adults. Five types of saccharin solution were prepared: a solution without a thickening agent, a starch-based nectar-like solution, a starch-based honey-like solution, a xanthan-gum-based nectar-like solution, and a xanthan-gum-based honey-like solution. Using these five types of saccharin solutions randomly, each subject underwent five trials of the saccharine dye test to evaluate the mucociliary transport function of the respiratory tract. The saccharin time was defined as the time from the placement of the saccharin solution on the nasal vestibule of the subject to when the subject reported that they became aware of the sweetness. The saccharin transit times for all samples of thickened water were longer compared to those of water without a thickening agent (p < 0.01). A comparison between thickened water samples with different viscosities showed that the saccharin transit time was longer when thickened water samples with high viscosity were prepared using the same thickening agent (p < 0.01). This suggests that while thickening reduces aspiration, the use of thickening agents may increase the difficulty in discharging aspirated fluids from the trachea.

Airway Mucus Plugs in Community-Living Adults: A Study Protocol

Introduction

Mucus pathology plays a critical role in airway diseases like chronic bronchitis (CB) and chronic obstructive pulmonary disease (COPD). Up to 32% of community-living persons report clinical manifestations of mucus pathology (e.g., cough and sputum production). However, airway mucus pathology has not been systematically studied in community-living individuals. In this study, we will use an objective, reproducible assessment of mucus pathology on chest computed tomography (CT) scans from community-living individuals participating in the Coronary Artery Risk Development in Young Adults (CARDIA) and Framingham Heart Study (FHS) cohorts.

Methods and analysis

We will determine the clinical relevance of CT-based mucus plugs and modifiable and genetic risk and protective factors associated with this process. We will evaluate the associations of mucus plugs with lung function, respiratory symptoms, and chronic bronchitis and examine whether 5-yr. persistent CT-based mucus plugs are associated with the decline in FEV1 and future COPD. Also, we will assess whether modifiable factors, including air pollution and marijuana smoking are associated with increased odds of CT-based mucus plugs and whether cardiorespiratory fitness is related in an opposing manner. Finally, we will determine genetic resilience/susceptibility to mucus pathology. We will use CT data from the FHS and CARDIA cohorts and genome-wide sequencing data from the TOPMed initiative to identify common and rare variants associated with CT-based mucus plugging.

Ethics and Dissemination

The Mass General Brigham Institutional Review Board approved the study. Findings will be disseminated through peer-reviewed journals and at professional conferences.

The association between humidex and tuberculosis: a two-stage modelling nationwide study in China

BACKGROUND

Under a changing climate, the joint effects of temperature and relative humidity on tuberculosis (TB) are poorly understood. To address this research gap, we conducted a time-series study to explore the joint effects of temperature and relative humidity on TB incidence in China, considering potential modifiers.

METHODS

Weekly data on TB cases and meteorological factors in 22 cities across mainland China between 2011 and 2020 were collected. The proxy indicator for the combined exposure levels of temperature and relative humidity, Humidex, was calculated. First, a quasi-Poisson regression with the distributed lag non-linear model (DLNM) was constructed to examine the city-specific associations between humidex and TB incidence. Second, a multivariate meta-regression model was used to pool the city-specific effect estimates, and to explore the potential effect modifiers.

RESULTS

A total of 849,676 TB cases occurred in the 22 cities between 2011 and 2020. Overall, a conspicuous J-shaped relationship between humidex and TB incidence was discerned. Specifically, a decrease in humidex was positively correlated with an increased risk of TB incidence, with a maximum relative risk (RR) of 1.40 (95% CI: 1.11-1.76). The elevated RR of TB incidence associated with low humidex (5th humidex) appeared on week 3 and could persist until week 13, with a peak at approximately week 5 (RR: 1.03, 95% CI: 1.01-1.05). The effects of low humidex on TB incidence vary by Natural Growth Rate (NGR) levels.

CONCLUSION

A J-shaped exposure-response association existed between humidex and TB incidence in China. Humidex may act as a better predictor to forecast TB incidence compared to temperature and relative humidity alone, especially in regions with higher NGRs.

Understanding the Risk Factors and Pathogenesis of Disseminated Nocardiosis in Immunocompromised Patients

Nocardia is a genus of aerobic, Gram-positive, partially acid-fast, filamentous bacilli notoriously known for causing multisystemic infections in immunocompromised individuals. Notably, this genus of bacteria commonly infects the pleural and central nervous system, leading to pneumonia and brain abscesses, respectively. Our patient is a 71-year-old female who initially presented to the emergency department complaining of shortness of breath and altered mental status. Imaging revealed multiple enhancing brain lesions, a pleural effusion, and a paraspinal abscess, which upon aspiration and culture demonstrated Nocardia farcinica/kroppenstedtii. The patient underwent antibiotic treatment, including intravenous (IV) imipenem and trimethoprim/sulfamethoxazole (TMP-SMX), before being transitioned to oral TMP-SMX and amoxicillin/clavulanate. This case demonstrates the importance of diagnosing nocardiosis acutely and treating it appropriately.

Assessing susceptibility for polycyclic aromatic hydrocarbon toxicity in an in vitro 3D respiratory model for asthma

There is increased emphasis on understanding cumulative risk from the combined effects of chemical and non-chemical stressors as it relates to public health. Recent animal studies have identified pulmonary inflammation as a possible modifier and risk factor for chemical toxicity in the lung after exposure to inhaled pollutants; however, little is known about specific interactions and potential mechanisms of action. In this study, primary human bronchial epithelial cells (HBEC) cultured in 3D at the air-liquid interface (ALI) are utilized as a physiologically relevant model to evaluate the effects of inflammation on toxicity of polycyclic aromatic hydrocarbons (PAHs), a class of contaminants generated from incomplete combustion of fossil fuels. Normal HBEC were differentiated in the presence of IL-13 for 14 days to induce a profibrotic phenotype similar to asthma. Fully differentiated normal and IL-13 phenotype HBEC were treated with benzo[a]pyrene (BAP; 1-40 μg/mL) or 1% DMSO/PBS vehicle at the ALI for 48 h. Cells were evaluated for cytotoxicity, barrier integrity, and transcriptional biomarkers of chemical metabolism and inflammation by quantitative PCR. Cells with the IL-13 phenotype treated with BAP result in significantly (p < 0.05) decreased barrier integrity, less than 50% compared to normal cells. The effect of BAP in the IL-13 phenotype was more apparent when evaluating transcriptional biomarkers of barrier integrity in addition to markers of mucus production, goblet cell hyperplasia, type 2 asthmatic inflammation and chemical metabolism, which all resulted in dose-dependent changes (p < 0.05) in the presence of BAP. Additionally, RNA sequencing data showed that the HBEC with the IL-13 phenotype may have increased potential for uncontrolled proliferation and decreased capacity for immune response after BAP exposure compared to normal phenotype HBEC. These data are the first to evaluate the role of combined environmental factors associated with inflammation from pre-existing disease and PAH exposure on pulmonary toxicity in a physiologically relevant human in vitro model.

The airway microbiome of persons with cystic fibrosis correlates with acquisition and microbiological outcomes of incident Stenotrophomonas maltophilia infection

Rationale

Chronic infection with Stenotrophomonas maltophilia in persons with cystic fibrosis (pwCF) has been linked to an increased risk of pulmonary exacerbations and lung function decline. We sought to establish whether baseline sputum microbiome associates with risk of S. maltophilia incident infection and persistence in pwCF.

Methods

pwCF experiencing incident S. maltophilia infections attending the Calgary Adult CF Clinic from 2010-2018 were compared with S. maltophilia-negative sex, age (+/-2 years), and birth-cohort-matched controls. Infection outcomes were classified as persistent (when the pathogen was recovered in ≥50% of cultures in the subsequent year) or transient. We assessed microbial communities from prospectively biobanked sputum using V3-V4 16S ribosomal RNA (rRNA) gene sequencing, in the year preceding (Pre) (n = 57), at (At) (n = 22), and after (Post) (n = 31) incident infection. We verified relative abundance data using S. maltophilia-specific qPCR and 16S rRNA-targeted qPCR to assess bioburden. Strains were typed using pulse-field gel electrophoresis.

Results

Twenty-five pwCF with incident S. maltophilia (56% female, median 29 years, median FEV1 61%) with 33 total episodes were compared with 56 uninfected pwCF controls. Demographics and clinical characteristics were similar between cohorts. Among those with incident S. maltophilia infection, sputum communities did not cluster based on infection timeline (Pre, At, Post). Communities differed between the infection cohort and controls (n = 56) based on Shannon Diversity Index (SDI, p = 0.04) and clustered based on Aitchison distance (PERMANOVA, p = 0.01) prior to infection. At the time of incident S. maltophilia isolation, communities did not differ in SDI but clustered based on Aitchison distance (PERMANOVA, p = 0.03) in those that ultimately developed persistent infection versus those that were transient. S. maltophilia abundance within sputum was increased in samples from patients (Pre) relative to controls, measuring both relative (p = 0.004) and absolute (p = 0.001). Furthermore, S. maltophilia abundance was increased in sputum at incident infection in those who ultimately developed persistent infection relative to those with transient infection, measured relatively (p = 0.04) or absolute (p = 0.04), respectively.

Conclusion

Microbial community composition of CF sputum associates with S. maltophilia infection acquisition as well as infection outcome. Our study suggests sputum microbiome may serve as a surrogate for identifying infection risk and persistence risk.

Chloride/Multiple Anion Exchanger SLC26A Family: Systemic Roles of SLC26A4 in Various Organs

Solute carrier family 26 member 4 (SLC26A4) is a member of the SLC26A transporter family and is expressed in various tissues, including the airway epithelium, kidney, thyroid, and tumors. It transports various ions, including bicarbonate, chloride, iodine, and oxalate. As a multiple-ion transporter, SLC26A4 is involved in the maintenance of hearing function, renal function, blood pressure, and hormone and pH regulation. In this review, we have summarized the various functions of SLC26A4 in multiple tissues and organs. Moreover, the relationships between SLC26A4 and other channels, such as cystic fibrosis transmembrane conductance regulator, epithelial sodium channel, and sodium chloride cotransporter, are highlighted. Although the modulation of SLC26A4 is critical for recovery from malfunctions of various organs, development of specific inducers or agonists of SLC26A4 remains challenging. This review contributes to providing a better understanding of the role of SLC26A4 and development of therapeutic approaches for the SLC26A4-associated hearing loss and SLC26A4-related dysfunction of various organs.

Nanomedicines for intranasal delivery: understanding the nano-bio interactions at the nasal mucus-mucosal barrier

INTRODUCTION

Intranasal administration is an effective drug delivery routes in modern pharmaceutics. However, unlike other in vivo biological barriers, the nasal mucosal barrier is characterized by high turnover and selective permeability, hindering the diffusion of both particulate drug delivery systems and drug molecules. The in vivo fate of administrated nanomedicines is often significantly affected by nano-biointeractions.

AREAS COVERED

The biological barriers that nanomedicines encounter when administered intranasally are introduced, with a discussion on the factors influencing the interaction between nanomedicines and the mucus layer/mucosal barriers. General design strategies for nanomedicines administered via the nasal route are further proposed. Furthermore, the most common methods to investigate the characteristics and the interactions of nanomedicines when in presence of the mucus layer/mucosal barrier are briefly summarized.

EXPERT OPINION

Detailed investigation of nanomedicine-mucus/mucosal interactions and exploration of their mechanisms provide solutions for designing better intranasal nanomedicines. Designing and applying nanomedicines with mucus interaction properties or non-mucosal interactions should be customized according to the therapeutic need, considering the target of the drug, i.e. brain, lung or nose. Then how to improve the precise targeting efficiency of nanomedicines becomes a difficult task for further research.

Calcium Signaling in Airway Epithelial Cells: Current Understanding and Implications for Inflammatory Airway Disease

Airway epithelial cells play an indispensable role in protecting the lung from inhaled pathogens and allergens by releasing an array of mediators that orchestrate inflammatory and immune responses when confronted with harmful environmental triggers. While this process is undoubtedly important for containing the effects of various harmful insults, dysregulation of the inflammatory response can cause lung diseases including asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis. A key cellular mechanism that underlies the inflammatory responses in the airway is calcium signaling, which stimulates the production and release of chemokines, cytokines, and prostaglandins from the airway epithelium. In this review, we discuss the role of major Ca2+ signaling pathways found in airway epithelial cells and their contributions to airway inflammation, mucociliary clearance, and surfactant production. We highlight the importance of store-operated Ca2+ entry as a major signaling hub in these processes and discuss therapeutic implications of targeting Ca2+ signaling for airway inflammation.

Strategies for non-viral vectors targeting organs beyond the liver

In recent years, nanoparticles have evolved to a clinical modality to deliver diverse nucleic acids. Rising interest in nanomedicines comes from proven safety and efficacy profiles established by continuous efforts to optimize physicochemical properties and endosomal escape. However, despite their transformative impact on the pharmaceutical industry, the clinical use of non-viral nucleic acid delivery is limited to hepatic diseases and vaccines due to liver accumulation. Overcoming liver tropism of nanoparticles is vital to meet clinical needs in other organs. Understanding the anatomical structure and physiological features of various organs would help to identify potential strategies for fine-tuning nanoparticle characteristics. In this Review, we discuss the source of liver tropism of non-viral vectors, present a brief overview of biological structure, processes and barriers in select organs, highlight approaches available to reach non-liver targets, and discuss techniques to accelerate the discovery of non-hepatic therapies.

In silico identification of viral loads in cough-generated droplets - Seamless integrated analysis of CFPD-HCD-EWF

BACKGROUND AND OBJECTIVE

Respiratory diseases caused by respiratory viruses have significantly threatened public health worldwide. This study presents a comprehensive approach to predict viral dynamics and the generation of stripped droplets within the mucus layer of the respiratory tract during coughing using a larynx-trachea-bifurcation (LTB) model.

METHODS

This study integrates computational fluid-particle dynamics (CFPD), host-cell dynamics (HCD), and the Eulerian wall film (EWF) model to propose a potential means for seamless integrated analysis. The verified CFPD-HCD coupling model based on a 3D-shell model was used to characterize the severe acute respiratory syndrome, coronavirus 2 (SARS-CoV-2) dynamics in the LTB mucus layer, whereas the EWF model was employed to account for the interfacial fluid to explore the generation mechanism and trace the origin site of droplets exhaled during a coughing event of an infected host.

RESULTS

The results obtained using CFPD delineated the preferential deposition sites for droplets in the laryngeal and tracheal regions. Thus, the analysis of the HCD model showed that the viral load increased rapidly in the laryngeal region during the peak of infection, whereas there was a growth delay in the tracheal region (up to day 8 after infection). After two weeks of infection, the high viral load gradually migrated towards the glottic region. Interestingly, the EWF model demonstrated a high concentration of exhaled droplets originating from the larynx. The coupling technique indicated a concurrent high viral load in the mucus layer and site of origin of the exhaled droplets.

CONCLUSIONS

This interdisciplinary research underscores the seamless analysis from initial exposure to virus-laden droplets, the dynamics of viral infection in the LTB mucus layer, and the re-emission from the coughing activities of an infected host. Our efforts aimed to address the complex challenges at the intersection of viral dynamics and respiratory health, which can contribute to a more detailed understanding and targeted prevention of respiratory diseases.

Relationship of computed tomography-based measurements with symptom perception and quality of life in patients with severe asthma

BACKGROUND

Symptom perception and quality of life (QOL) are important domains for properly managing severe asthma. This study aimed to assess the relationship between airway structural and parenchymal variables measured using chest computed tomography (CT) and subjective symptom perception and QOL in patients with severe asthma enrolled in the Korean Severe Asthma Registry.

METHODS

This study used CT-based objective measurements, including airway wall thickness (WT), hydraulic diameter, functional small airway disease (fSAD), and emphysematous lung (Emph), to assess their association with subjective symptom (cough, dyspnea, wheezing, and sputum) perception measured using the visual analog scale, and QOL measured by the Severe Asthma Questionnaire (SAQ).

RESULTS

A total of 94 patients with severe asthma were enrolled in this study. The WT and fSAD% were significantly positively associated with cough and dyspnea, respectively. For QOL, WT and Emph% showed significant negative associations with the SAQ. However, there was no significant association between lung function and symptom perception or between lung function and QOL.

CONCLUSION

Overall, WT, fSAD%, and Emph% measured using chest CT were associated with subjective symptom perception and QOL in patients with severe asthma. This study provides a basis for clarifying the clinical correlates of imaging-derived metrics and for understanding the mechanisms of respiratory symptom perception.

Dictamnus dasycarpus Turcz. attenuates airway inflammation and mucus hypersecretion by modulating the STAT6-STAT3/FOXA2 pathway

BACKGROUND

Effects of Dictamnus dasycarpus Turcz. on allergic asthma and their underlying mechanisms remain unclarified. Thus, we investigated the effects of D. dasycarpus Turcz. water extract (DDW) on mucus hypersecretion in mice with ovalbumin (OVA)-induced asthma and human bronchial epithelial cells.

METHODS

BALB/c mice were used to establish an OVA-induced allergic asthma model. Mice were grouped into the OVA sensitization/challenge, 100 and 300 mg/kg DDW treatment, and dexamethasone groups. In mice, cell counts in bronchoalveolar lavage fluid (BALF), serum and BALF analyses, and histopathological lung tissue analyses were performed. Furthermore, we confirmed the basic mechanism in interleukin (IL)-4/IL-13-treated human bronchial epithelial cells through western blotting.

RESULTS

In OVA-induced asthma mice, DDW treatment reduced inflammatory cell number and airway hyperresponsiveness and ameliorated histological changes (immune cell infiltration, mucus secretion, and collagen deposition) in lung tissues and serum total immunoglobulin E levels. DDW treatment lowered BALF IL-4, IL-5, and IL-13 levels; reduced levels of inflammatory mediators, such as thymus- and activation-regulated chemokine, macrophage-derived chemokine, and interferon gamma-induced protein; decreased mucin 5AC (MUC5AC) production; decreased signal transducer and activator of transcription (STAT) 6 and STAT3 expression; and restored forkhead box protein A2 (FOXA2) expression. In IL-4/IL-13-treated human bronchial epithelial cells, DDW treatment inhibited MUC5AC production, suppressed STAT6 and STAT3 expression (related to mucus hypersecretion), and increased FOXA2 expression.

CONCLUSIONS

DDW treatment modulates MUC5AC expression and mucus hypersecretion by downregulating STAT6 and STAT3 expression and upregulating FOXA2 expression. These findings provide a novel approach to manage mucus hypersecretion in asthma using DDW.

The airway epithelium: an orchestrator of inflammation, a key structural barrier and a therapeutic target in severe asthma

Asthma is a disease of heterogeneous pathology, typically characterised by excessive inflammatory and bronchoconstrictor responses to the environment. The clinical expression of the disease is a consequence of the interaction between environmental factors and host factors over time, including genetic susceptibility, immune dysregulation and airway remodelling. As a critical interface between the host and the environment, the airway epithelium plays an important role in maintaining homeostasis in the face of environmental challenges. Disruption of epithelial integrity is a key factor contributing to multiple processes underlying asthma pathology. In this review, we first discuss the unmet need in asthma management and provide an overview of the structure and function of the airway epithelium. We then focus on key pathophysiological changes that occur in the airway epithelium, including epithelial barrier disruption, immune hyperreactivity, remodelling, mucus hypersecretion and mucus plugging, highlighting how these processes manifest clinically and how they might be targeted by current and novel therapeutics.

Effect of Volatile Organic Compounds on Pulmonary Functions Among Paint Industry Workers of Unorganized Sectors

Background Paint industry workers are constantly exposed to paints and organic solvents that contain a substantial quantity of volatile organic compounds (VOCs). Exposure to VOC emissions could result in pulmonary, neurobehavioral, and hematological consequences. Limited studies have been undertaken in India to assess the health consequences of VOCs among paint industry workers in unorganized sectors. Aim To assess the effects of VOCs on pulmonary function in paint industry workers of unorganized sectors. Methodology A hundred and twenty full-time male construction painters and small-scale paint manufacturing workers aged 25-60 were assessed for respiratory symptoms using a questionnaire, and pulmonary functions using Wright's Peak Expiratory Flow Meter (PEFR). Participants were randomly selected for VOC assessment and the cumulative solvent exposure index was calculated. A pulmonary function test (PFT) was performed on a subset of construction painters (n=30) using a Koko spirometer. Results The concentration of VOCs such as benzene, ethylbenzene, toluene, and xylene (BETX) and dichloromethane levels exceeded American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs) among the paint manufacturing workers. About 52% of paint workers reported respiratory symptoms. Around 22% of the participants showed reduced pulmonary function (PEFR<400 L/min). There was a significant weak negative correlation between PEFR and work experience (r = -0.2, p=0.03). PFT parameters among a subset of construction painters revealed a significant moderate negative correlation with work experience [forced expiratory volume at the onset of the first second (FEV1) (r = -0.6, p=0.001) and forced vital capacity (FVC) (r = -0.53, p=0.005)] and cumulative VOC exposure index [FEV1 (r = -0.53, p = 0.004) and FVC (r = -0.5, p = 0.008)]. Conclusion The concentration of VOCs was higher among paint industry workers of unorganized sectors and they reported respiratory symptoms and diminished pulmonary function. To reduce morbidity, it is critical to enhance awareness about occupational safety and services in these unorganized sectors.

Nursing Practice of Airway Care Interventions and Prone Positioning in ICU Patients with COVID-19-A Dutch National Survey

Background: Airway care interventions and prone positioning are used in critically ill patients with coronavirus disease 2019 (COVID-19) admitted to the intensive care unit (ICU) to improve oxygenation and facilitate mucus removal. At the onset of the COVID-19 pandemic, the decision-making process regarding the practice of airway care interventions and prone positioning was challenging. Objective: To provide an overview of the practice of airway care interventions and prone positioning during the second wave of the pandemic in the Netherlands. Method: Web-based survey design. Seventy ICU nurses, each representing one intensive care in the Netherlands, were contacted for participation. Potential items were generated based on a literature search and formulated by a multidisciplinary team. Questions were pilot tested for face and construct validity by four intensive care nurses from four different hospitals. Results: The response rate was 53/77 (69%). This survey revealed widespread use of airway care interventions in the Netherlands in COVID-19 patients, despite questionable benefits. Additionally, prone positioning was used in invasively and non-invasively ventilated patients. Conclusions: The use of airway care interventions and prone positioning is time consuming and comes with the production of waste. Further research is needed to assess the effectiveness, workload, and environmental impact of airway care interventions and prone positioning.

Effects of Anti-Fibrotic Drugs on Transcriptome of Peripheral Blood Mononuclear Cells in Idiopathic Pulmonary Fibrosis

Two anti-fibrotic drugs, pirfenidone (PFD) and nintedanib (NTD), are currently used to treat idiopathic pulmonary fibrosis (IPF). Peripheral blood mononuclear cells (PBMCs) are immunocompetent cells that could orchestrate cell-cell interactions associated with IPF pathogenesis. We employed RNA sequencing to examine the transcriptome signature in the bulk PBMCs of patients with IPF and the effects of anti-fibrotic drugs on these signatures. Differentially expressed genes (DEGs) between "patients with IPF and healthy controls" and "before and after anti-fibrotic treatment" were analyzed. Enrichment analysis suggested that fatty acid elongation interferes with TGF-β/Smad signaling and the production of oxidative stress since treatment with NTD upregulates the fatty acid elongation enzymes ELOVL6. Treatment with PFD downregulates COL1A1, which produces wound-healing collagens because activated monocyte-derived macrophages participate in the production of collagen, type I, and alpha 1 during tissue damage. Plasminogen activator inhibitor-1 (PAI-1) regulates wound healing by inhibiting plasmin-mediated matrix metalloproteinase activation, and the inhibition of PAI-1 activity attenuates lung fibrosis. DEG analysis suggested that both the PFD and NTD upregulate SERPINE1, which regulates PAI-1 activity. This study embraces a novel approach by using RNA sequencing to examine PBMCs in IPF, potentially revealing systemic biomarkers or pathways that could be targeted for therapy.

Nontuberculous Mycobacteria, Mucociliary Clearance, and Bronchiectasis

Nontuberculous mycobacteria (NTM) are environmental and ubiquitous, but only a few species are associated with disease, often presented as nodular/bronchiectatic or cavitary pulmonary forms. Bronchiectasis, airways dilatations characterized by chronic productive cough, is the main presentation of NTM pulmonary disease. The current Cole's vicious circle model for bronchiectasis proposes that it progresses from a damaging insult, such as pneumonia, that affects the respiratory epithelium and compromises mucociliary clearance mechanisms, allowing microorganisms to colonize the airways. An important bronchiectasis risk factor is primary ciliary dyskinesia, but other ciliopathies, such as those associated with connective tissue diseases, also seem to facilitate bronchiectasis, as may occur in Lady Windermere syndrome, caused by M. avium infection. Inhaled NTM may become part of the lung microbiome. If the dose is too large, they may grow excessively as a biofilm and lead to disease. The incidence of NTM pulmonary disease has increased in the last two decades, which may have influenced the parallel increase in bronchiectasis incidence. We propose that ciliary dyskinesia is the main promoter of bronchiectasis, and that the bacteria most frequently involved are NTM. Restoration of ciliary function and impairment of mycobacterial biofilm formation may provide effective therapeutic alternatives to antibiotics.

Severe Atelectasis due to Aspirated Valproic Acid Tablet

A 60-year-old man treated with valproic acid (VPA) for epilepsy developed atelectasis and respiratory failure after an accidentally aspirated VPA tablet-induced mucus hypersecretion. Following bronchoscopic removal of the aspirated tablet, his respiratory status improved and massive sputum production did not recur. We hypothesized that the aspirated VPA tablet increased the expression of mucin-related genes, thereby increasing mucus production. Our in vitro experiments using a human respiratory epithelial cell line revealed that VPA directly upregulates the airway mucin-related genes. We believe that this is the first case report of aspirated VPA-induced severe atelectasis and respiratory failure, which were successfully treated with the bronchoscopic removal of the VPA tablet.

Water Sorption and Structural Properties of Human Airway Mucus in Health and Muco-Obstructive Diseases

Muco-obstructive diseases change airway mucus properties, impairing mucociliary transport and increasing the likelihood of infections. To investigate the sorption properties and nanostructures of mucus in health and disease, we investigated mucus samples from patients and cell cultures (cc) from healthy, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) airways. Atomic force microscopy (AFM) revealed mucin monomers with typical barbell structures, where the globule to spacer volume ratio was the highest for CF mucin. Accordingly, synchrotron small-angle X-ray scattering (SAXS) revealed more pronounced scattering from CF mucin globules and suggested shorter carbohydrate side chains in CF mucin and longer side chains in COPD mucin. Quartz crystal microbalance with dissipation (QCM-D) analysis presented water sorption isotherms of the three types of human airway mucus, where, at high relative humidity, COPD mucus had the highest water content compared to cc-CF and healthy airway mucus (HAM). The higher hydration of the COPD mucus is consistent with the observation of longer side chains of the COPD mucins. At low humidity, no dehydration-induced glass transition was observed in healthy and diseased mucus, suggesting mucus remained in a rubbery state. However, in dialyzed cc-HAM, a sorption-desorption hysteresis (typically observed in the glassy state) appeared, suggesting that small molecules present in mucus suppress the glass transition.

Inhaled "Muco-Trapping" Monoclonal Antibody Effectively Treats Established Respiratory Syncytial Virus (RSV) Infections

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in infants, the immunocompromised, and the elderly. RSV infects the airway epithelium via the apical membrane and almost exclusively sheds progeny virions back into the airway mucus (AM), making RSV difficult to target by systemically administered therapies. An inhalable "muco-trapping" variant of motavizumab (Mota-MT), a potent neutralizing mAb against RSV F is engineered. Mota-MT traps RSV in AM via polyvalent Fc-mucin bonds, reducing the fraction of fast-moving RSV particles in both fresh pediatric and adult AM by ≈20-30-fold in a Fc-glycan dependent manner, and facilitates clearance from the airways of mice within minutes. Intranasal dosing of Mota-MT eliminated viral load in cotton rats within 2 days. Daily nebulized delivery of Mota-MT to RSV-infected neonatal lambs, beginning 3 days after infection when viral load is at its maximum, led to a 10 000-fold and 100 000-fold reduction in viral load in bronchoalveolar lavage and lung tissues relative to placebo control, respectively. Mota-MT-treated lambs exhibited reduced bronchiolitis, neutrophil infiltration, and airway remodeling than lambs receiving placebo or intramuscular palivizumab. The findings underscore inhaled delivery of muco-trapping mAbs as a promising strategy for the treatment of RSV and other acute respiratory infections.