The contribution of transforming growth factor-beta and epidermal growth factor signalling to airway remodelling in chronic asthma

Immunological factors, important players in the development of asthma

Asthma is a heterogeneous disease, and its development is the result of a combination of factors, including genetic factors, environmental factors, immune dysfunction and other factors. Its specific mechanism has not yet been fully investigated. With the improvement of disease models, research on the pathogenesis of asthma has made great progress. Immunological disorders play an important role in asthma. Previously, we thought that asthma was mainly caused by an imbalance between Th1 and Th2 immune responses, but this theory cannot fully explain the pathogenesis of asthma. Recent studies have shown that T-cell subsets such as Th1 cells, Th2 cells, Th17 cells, Tregs and their cytokines contribute to asthma through different mechanisms. For the purpose of the present study, asthma was classified into distinct phenotypes based on airway inflammatory cells, such as eosinophilic asthma, characterized by predominant eosinophil aggregates, and neutrophilic asthma, characterized by predominant neutrophil aggregates. This paper will examine the immune mechanisms underlying different types of asthma, and will utilize data from animal models and clinical studies targeting specific immune pathways to inform more precise treatments for this condition.

The epithelium takes the stage in asthma and inflammatory bowel diseases

The epithelium is a dynamic barrier and the damage to this epithelial layer governs a variety of complex mechanisms involving not only epithelial cells but all resident tissue constituents, including immune and stroma cells. Traditionally, diseases characterized by a damaged epithelium have been considered "immunological diseases," and research efforts aimed at preventing and treating these diseases have primarily focused on immuno-centric therapeutic strategies, that often fail to halt or reverse the natural progression of the disease. In this review, we intend to focus on specific mechanisms driven by the epithelium that ensure barrier function. We will bring asthma and Inflammatory Bowel Diseases into the spotlight, as we believe that these two diseases serve as pertinent examples of epithelium derived pathologies. Finally, we will argue how targeting the epithelium is emerging as a novel therapeutic strategy that holds promise for addressing these chronic diseases.

Prostaglandin E2 attenuates lung fibroblast differentiation via inactivation of yes-associated protein signaling

Prostaglandin E2 (PGE2 ) has been implicated in counteracting fibroblast differentiation by TGFβ1 during pulmonary fibrosis. However, the precise mechanism is not well understood. We show here that PGE2 via EP2 R and EP4 R inhibits the expression of mechanosensory molecules Lysyl Oxidase Like 2 (LOXL2), myocardin-related transcription factor A (MRTF-A), ECM proteins, plasminogen activation inhibitor 1 (PAI-1), fibronectin (FN), α-smooth muscle actin (α-SMA), and redox sensor (nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4)) required for TGFβ1-mediated fibroblast differentiation. We further demonstrate that PGE2 inhibits fibrotic signaling via Yes-associated protein (YAP) but does so independently from its actions on SMAD phosphorylation and conserved cylindromatosis (CYLD; deubiquitinase) expression. Mechanistically, PGE2 phosphorylates/inactivates YAP downstream of EP2 R/Gαs and restrains its translocation to the nucleus, thus inhibiting its interaction with TEA domain family members (TEADs) and transcription of fibrotic genes. Importantly, pharmacological or siRNA-mediated inhibition of YAP significantly downregulates TGFβ1-mediated fibrotic gene expression and myofibroblast formation. Notably, YAP expression is upregulated in the lungs of D. farinae-treated wild type (WT) mice relative to saline-treated WT mice. Our results unravel a unique role for PGE2 -YAP interactions in fibroblast differentiation, and that PGE2 /YAP inhibition can be used as a novel therapeutic target in the treatment of pathological conditions associated with myofibroblasts like asthma.

Eosinophils and tissue remodeling: Relevance to airway disease

The ability of human tissue to reorganize and restore its existing structure underlies tissue homeostasis in the healthy airways, but in disease can persist without normal resolution, leading to an altered airway structure. Eosinophils play a cardinal role in airway remodeling both in health and disease, driving epithelial homeostasis and extracellular matrix turnover. Physiological consequences associated with eosinophil-driven remodeling include impaired lung function and reduced bronchodilator reversibility in asthma, and obstructed airflow in chronic rhinosinusitis with nasal polyps. Given the contribution of airway remodeling to the development and persistence of symptoms in airways disease, targeting remodeling is an important therapeutic consideration. Indeed, there is early evidence that eosinophil attenuation may reduce remodeling and disease progression in asthma. This review provides an overview of tissue remodeling in both health and airway disease with a particular focus on eosinophilic asthma and chronic rhinosinusitis with nasal polyps, as well as the role of eosinophils in these processes and the implications for therapeutic interventions. Areas for future research are also noted, to help improve our understanding of the homeostatic and pathological roles of eosinophils in tissue remodeling, which should aid the development of targeted and effective treatments for eosinophilic diseases of the airways.

Airway epithelial development and function: A key player in asthma pathogenesis?

Though asthma is a common and relatively easy to diagnose disease, attempts at primary or secondary prevention, and cure, have been disappointing. The widespread use of inhaled steroids has dramatically improved asthma control but has offered nothing in terms of altering long-term outcomes or reversing airway remodeling and impairment in lung function. The inability to cure asthma is unsurprising given our limited understanding of the factors that contribute to disease initiation and persistence. New data have focused on the airway epithelium as a potentially key factor orchestrating the different stages of asthma. In this review we summarize for the clinician the current evidence on the central role of the airway epithelium in asthma pathogenesis and the factors that may alter epithelial integrity and functionality.

Proline is increased in allergic asthma and promotes airway remodeling

Proline and its synthesis enzyme pyrroline-5-carboxylate reductase 1 (PYCR1) are implicated in epithelial-mesenchymal transition (EMT), yet how proline and PYCR1 function in allergic asthmatic airway remodeling via EMT has not yet been addressed to our knowledge. In the present study, increased levels of plasma proline and PYCR1 were observed in patients with asthma. Similarly, proline and PYCR1 in lung tissues were high in a murine allergic asthma model induced by house dust mites (HDMs). Pycr1 knockout decreased proline in lung tissues, with reduced airway remodeling and EMT. Mechanistically, loss of Pycr1 restrained HDM-induced EMT by modulating mitochondrial fission, metabolic reprogramming, and the AKT/mTORC1 and WNT3a/β-catenin signaling pathways in airway epithelial cells. Therapeutic inhibition of PYCR1 in wild-type mice disrupted HDM-induced airway inflammation and remodeling. Deprivation of exogenous proline relieved HDM-induced airway remodeling to some extent. Collectively, this study illuminates that proline and PYCR1 involved with airway remodeling in allergic asthma could be viable targets for asthma treatment.

Macrophages Orchestrate Airway Inflammation, Remodeling, and Resolution in Asthma

Asthma is a heterogenous chronic inflammatory lung disease with endotypes that manifest different immune system profiles, severity, and responses to current therapies. Regardless of endotype, asthma features increased immune cell infiltration, inflammatory cytokine release, and airway remodeling. Lung macrophages are also heterogenous in that there are separate subsets and, depending on the environment, different effector functions. Lung macrophages are important in recruitment of immune cells such as eosinophils, neutrophils, and monocytes that enhance allergic inflammation and initiate T helper cell responses. Persistent lung remodeling including mucus hypersecretion, increased airway smooth muscle mass, and airway fibrosis contributes to progressive lung function decline that is insensitive to current asthma treatments. Macrophages secrete inflammatory mediators that induce airway inflammation and remodeling. Additionally, lung macrophages are instrumental in protecting against pathogens and play a critical role in resolution of inflammation and return to homeostasis. This review summarizes current literature detailing the roles and existing knowledge gaps for macrophages as key inflammatory orchestrators in asthma pathogenesis. We also raise the idea that modulating inflammatory responses in lung macrophages is important for alleviating asthma.

Bronchial epithelial cells release inflammatory markers linked to airway inflammation and remodeling in response to TLR5 ligand flagellin

Background/Aims

Flagellin, which is abundant in gram-negative bacteria, including Pseudomonas, is reported to influence on inflammatory responses in various lung diseases. However, its effect on airway epithelial cells in contribution to asthma pathogenesis is not elucidated yet. We aimed to investigate the effect of TLR5 ligand flagellin on the transcriptomic profile of primary human epithelial cells and to determine the markers of airway inflammation.

Methods

Normal human bronchial epithelial (NHBE) cells were grown and differentiated in air-liquid interface (ALI) culture for 14-16 days. The cells were treated with flagellin in vitro at 10 and 100 ng/ml for 3 and 24 h. The conditioned media and cells were harvested to validate inflammatory markers involved in airway inflammation using ELISA, Western blot, and quantitative PCR methods. RNA-sequencing was performed to investigate the transcriptional response to flagellin in ALI-NHBE cells.

Results

Altered transcriptional responses to flagellin in differentiated bronchial epithelial cells were determined, including genes encoding chemokines, matrix metalloproteinases, and antimicrobial biomolecules. Pathway analysis of the transcriptionally responsive genes revealed enrichment of signaling pathways. Flagellin induced the mRNA expressions of proinflammatory cytokines and chemokines, and secretion of GM-CSF, CXCL5, CCL5 and CXCL10. Flagellin enhanced the protein expression of MMP-13 in TGF-β1 and TGF-β2 pretreated cell lysates and Wnt/β-catenin signaling.

Conclusions

These findings suggest that flagellin could be a potent inducer of inflammatory markers that may contribute to airway inflammation and remodeling.

Epidermal growth factor receptor in asthma: A promising therapeutic target?

Activation of the epidermal growth factor receptor (EGFR) pathway is involved in the pathogenesis of asthma. Although decades of intensive research have focused on the role of EGFR in asthma, the specific mechanisms and pathways of EGFR signaling remain unclear. Various reports have indicated that inhibition of EGFR improves the pathological features in asthma models. However, extending these experimental findings to clinical applications is difficult. Several measures can be adopted to promote clinical application of EGFR inhibitors. This review focuses on the role of EGFR in the pathogenesis of asthma and the development of a potentially novel therapeutic target for asthma.

Understanding fibroblast-immune cell interactions via co-culture models and their role in asthma pathogenesis

Asthma is a chronic lung disease involving airway inflammation and fibrosis. Fibroblasts are the main effector cells important for lung tissue production which becomes abnormal in asthmatics and is one of the main contributors to airway fibrosis. Although fibroblasts were traditionally viewed solely as structural cells, they have been discovered to be highly active, and involved in lung inflammatory and fibrotic processes in asthma. In line with this, using 2D and 3D in vitro co-culture models, a complex interaction between lung fibroblasts and various immune cells important for the pathogenesis of asthma have been recently uncovered. Hence, in this review, we provide the first-ever summary of various studies that used 2D and 3D in vitro co-culture models to assess the nature of aberrant immune cell-fibroblast interactions and their contributions to chronic inflammation and fibrotic mechanisms in asthma pathogenesis.

The anti-asthmatic potential of Rho-kinase inhibitor hydroxyfasudil in the model of experimentally induced allergic airway inflammation

OBJECTIVE

This experimental study evaluated the anti-asthmatic potential of the Rho-kinase inhibitor hydroxyfasudil in the settings of allergen-induced allergen-induced experimental asthma.

METHODS

Chronic allergic airway inflammation was caused by 28 days-sensitisation of guinea pigs with ovalbumin (OVA). Hydroxyfasudil was administered intraperitoneally in two doses for the last two weeks (1 mg/kg b.w.; 10 mg/kg b.w.). The degree of allergic inflammation was determined based on concentrations of inflammatory Th2 cytokines (IL-4, IL-13), Th1 cytokines (TNF-α and IFN-γ) in the lung homogenate and leukocyte count in the bronchoalveolar lavage fluid (BALF). The markers of remodelling and fibrosis, the growth factors (TGF-β1, EGF), EGF receptor, collagen type III and V were estimated in lung homogenate. The changes in specific airway resistance (sRaw) were used as an in vivo bronchial hyperreactivity parameter.

RESULTS

Hydroxyfasudil administration at both doses significantly reduced sRaw after a week of therapy. We observed a decline of IL-13, TNF-α and IFN-γ in lung homogenate and a lower presence of lymphocytes in BALF after 14 days of hydroxyfasudil administration at both tested doses. Hydroxyfasudil 14 days-treatment at both doses effectively reduced the concentrations of TGF-β1, EGF receptors, collagen type III and V in BALF and modulated EGF levels.

CONCLUSIONS

These findings indicate that RhoA/Rho-kinase is involved in the pathophysiology of allergic airway inflammation and suggest that Rho-kinase inhibitor hydroxyfasudil has therapeutic potential for asthma management.

RNA-Seq Analysis of UPM-Exposed Epithelium Co-Cultivated with Macrophages and Dendritic Cells in Obstructive Lung Diseases

Background. Elevated concentrations of airborne pollutants are correlated with an enlarged rate of obstructive lung disease morbidity as well as acute disease exacerbations. This study aimed to analyze the epithelium mRNA profile in response to airborne particulate matter in the control, asthma, and COPD groups. Results. A triple co-culture of nasal epithelium, monocyte-derived macrophages, and monocyte-derived dendritic cells obtained from the controls, asthma, and COPD were exposed to urban particulate matter (UPM) for 24 h. RNA-Seq analysis found differences in seven (CYP1B1, CYP1B1-AS1, NCF1, ME1, LINC02029, BPIFA2, EEF1A2), five (CYP1B1, ARC, ENPEP, RASD1, CYP1B1-AS1), and six (CYP1B1, CYP1B1-AS1, IRF4, ATP1B2, TIPARP, CCL22) differentially expressed genes between UPM exposed and unexposed triple co-cultured epithelium in the control, asthma, and COPD groups, respectively. PCR analysis showed that mRNA expression of BPIFA2 and ENPEP was upregulated in both asthma and COPD, while the expression of CYP1B1-AS1 and TIPARP was increased in the epithelium from COPD patients only. Biological processes changed in UPM exposed triple co-cultured epithelium were associated with epidermis development and epidermal cell differentiation in asthma and with response to toxic substances in COPD. Conclusions. The biochemical processes associated with pathophysiology of asthma and COPD impairs the airway epithelial response to UPM.

The Novel Regulatory Role of the lncRNA–miRNA–mRNA Axis in Chronic Inflammatory Airway Diseases

Chronic inflammatory airway diseases, characterized by airway inflammation and airway remodelling, are increasing as a cause of morbidity and mortality for all age groups and races across the world. The underlying molecular mechanisms involved in chronic inflammatory airway diseases have not been fully explored. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) have recently attracted much attention for their roles in the regulation of a variety of biological processes. A number of studies have confirmed that both lncRNAs and miRNAs can regulate the initiation and progression of chronic airway diseases by targeting mRNAs and regulating different cellular processes, such as proliferation, apoptosis, inflammation, migration, and epithelial–mesenchymal transition (EMT). Recently, accumulative evidence has shown that the novel regulatory mechanism underlying the interaction among lncRNAs, miRNAs and messenger RNAs (mRNAs) plays a critical role in the pathophysiological processes of chronic inflammatory airway diseases. In this review, we comprehensively summarized the regulatory roles of the lncRNA–miRNA–mRNA network in different cell types and their potential roles as biomarkers, indicators of comorbidities or therapeutic targets for chronic inflammatory airway diseases, particularly chronic obstructive pulmonary disease (COPD) and asthma.

A drug-responsive multicellular human spheroid model to recapitulate drug-induced pulmonary fibrosis

Associated with a high mortality rate, pulmonary fibrosis (PF) is the end stage of several interstitial lung diseases. Although many factors are linked to PF progression, initiation of the fibrotic process remains to be studied. Current research focused on generating new strategies to gain a better understanding of the underlying disease mechanism as the animal models remain insufficient to reflect human physiology. Herein, to account complex cellular interactions within the fibrotic tissue, a multicellular spheroid (MCS) model where human bronchial epithelial cells incorporated with human lung fibroblasts was generated and treated with bleomycin (BLM) to emulate drug-induced PF. Recapitulating the epithelial-interstitial microenvironment, the findings successfully reflected the PF disease, where excessive alpha smooth muscle actin (α-SMA) and collagen type I secretion were noted along with the morphological changes in response to BLM. Moreover, increased levels of fibrotic linked COL13A1, MMP2, WNT3 and decreased expression level of CDH1 provide evidence for the model reliability on fibrosis modelling. Subsequent administration of the FDA approved nintedanib and pirfenidone anti-fibrotic drugs proved the drug-responsiveness of the model.

IL-25 blockade augments antiviral immunity during respiratory virus infection

IL-25 is implicated in the pathogenesis of viral asthma exacerbations. However, the effect of IL-25 on antiviral immunity has yet to be elucidated. We observed abundant expression and colocalization of IL-25 and IL-25 receptor at the apical surface of uninfected airway epithelial cells and rhinovirus infection increased IL-25 expression. Analysis of immune transcriptome of rhinovirus-infected differentiated asthmatic bronchial epithelial cells (BECs) treated with an anti-IL-25 monoclonal antibody (LNR125) revealed a re-calibrated response defined by increased type I/III IFN and reduced expression of type-2 immune genes CCL26, IL1RL1 and IL-25 receptor. LNR125 treatment also increased type I/III IFN expression by coronavirus infected BECs. Exogenous IL-25 treatment increased viral load with suppressed innate immunity. In vivo LNR125 treatment reduced IL-25/type 2 cytokine expression and increased IFN-β expression and reduced lung viral load. We define a new immune-regulatory role for IL-25 that directly inhibits virus induced airway epithelial cell innate anti-viral immunity.

Genome-Wide Association Study of Fluorescent Oxidation Products Accounting for Tobacco Smoking Status in Adults from the French EGEA Study

Oxidative stress (OS) is the main pathophysiological mechanism involved in several chronic diseases, including asthma. Fluorescent oxidation products (FlOPs), a global biomarker of damage due to OS, is of growing interest in epidemiological studies. We conducted a genome-wide association study (GWAS) of the FlOPs level in 1216 adults from the case-control and family-based EGEA study (mean age 43 years old, 51% women, and 23% current smokers) to identify genetic variants associated with FlOPs. The GWAS was first conducted in the whole sample and then stratified according to smoking status, the main exogenous source of reactive oxygen species. Among the top genetic variants identified by the three GWAS, those located in BMP6 (p = 3 × 10⁻⁶), near BMPER (p = 9 × 10⁻⁶), in GABRG3 (p = 4 × 10⁻⁷), and near ATG5 (p = 2 × 10⁻⁹) are the most relevant because of both their link to biological pathways related to OS and their association with several chronic diseases for which the role of OS in their pathophysiology has been pointed out. BMP6 and BMPER are of particular interest due to their involvement in the same biological pathways related to OS and their functional interaction. To conclude, this study, which is the first GWAS of FlOPs, provides new insights into the pathophysiology of chronic OS-related diseases.

FGF2 is overexpressed in asthma and promotes airway inflammation through the FGFR/MAPK/NF-κB pathway in airway epithelial cells

BACKGROUND

Airway inflammation is the core pathological process of asthma, with the key inflammatory regulators incompletely defined. Recently, fibroblast growth factor 2 (FGF2) has been reported to be an inflammatory regulator; however, its role in asthma remains elusive. This study aimed to investigate the immunomodulatory role of FGF2 in asthma.

METHODS

First, FGF2 expression was characterised in clinical asthma samples and the house dust mite (HDM)-induced mouse chronic asthma model. Second, recombinant mouse FGF2 (rm-FGF2) protein was intranasally delivered to determine the effect of FGF2 on airway inflammatory cell infiltration. Third, human airway epithelium-derived A549 cells were stimulated with either HDM or recombinant human interleukin-1β (IL-1β) protein combined with or without recombinant human FGF2. IL-1β-induced IL-6 or IL-8 release levels were determined using enzyme-linked immunosorbent assay, and the involved signalling transduction was explored via Western blotting.

RESULTS

Compared with the control groups, the FGF2 protein levels were significantly upregulated in the bronchial epithelium and alveolar areas of clinical asthma samples (6.70 ± 1.79 vs. 16.32 ± 2.40, P = 0.0184; 11.20 ± 2.11 vs. 21.00 ± 3.00, P = 0.033, respectively) and HDM-induced asthmatic mouse lung lysates (1.00 ± 0.15 vs. 5.14 ± 0.42, P < 0.001). Moreover, FGF2 protein abundance was positively correlated with serum total and anti-HDM IgE levels in the HDM-induced chronic asthma model (R² = 0.857 and 0.783, P = 0.0008 and 0.0043, respectively). Elevated FGF2 protein was mainly expressed in asthmatic bronchial epithelium and alveolar areas and partly co-localised with infiltrated inflammatory cell populations in HDM-induced asthmatic mice. More importantly, intranasal instillation of rm-FGF2 aggravated airway inflammatory cell infiltration (2.45 ± 0.09 vs. 2.88 ± 0.14, P = 0.0288) and recruited more subepithelial neutrophils after HDM challenge [(110.20 ± 29.43) cells/mm² vs. (238.10 ± 42.77) cells/mm², P = 0.0392] without affecting serum IgE levels and Th2 cytokine transcription. In A549 cells, FGF2 was upregulated through HDM stimulation and promoted IL-1β-induced IL-6 or IL-8 release levels (up to 1.41 ± 0.12- or 1.44 ± 0.14-fold change vs. IL-1β alone groups, P = 0.001 or 0.0344, respectively). The pro-inflammatory effect of FGF2 is likely mediated through the fibroblast growth factor receptor (FGFR)/mitogen-activated protein kinase (MAPK)/nuclear factor kappa B (NF-κB) pathway.

CONCLUSION

Our findings suggest that FGF2 is a potential inflammatory modulator in asthma, which can be induced by HDM and acts through the FGFR/MAPK/NF-κB pathway in the airway epithelial cells.

Novel regulators of airway epithelial barrier function during inflammation: potential targets for drug repurposing

INTRODUCTION

Endogenous inflammatory signaling molecules resulting from deregulated immune responses, can impair airway epithelial barrier function and predispose individuals with airway inflammatory diseases to exacerbations and lung infections. Targeting the specific endogenous factors disrupting the airway barrier therefore has the potential to prevent disease exacerbations without affecting the protective immune responses.

AREAS COVERED

Here, we review the endogenous factors and specific mechanisms disrupting airway epithelial barrier during inflammation and reflect on whether these factors can be specifically targeted by repurposed existing drugs. Literature search was conducted using PubMed, drug database of US FDA and European Medicines Agency until and including September 2021.

EXPERT OPINION

IL-4 and IL-13 signaling are the major pathways disrupting the airway epithelial barrier during airway inflammation. However, blocking IL-4/IL-13 signaling may adversely affect protective immune responses and increase susceptibility of host to infections. An alternate approach to modulate airway epithelial barrier function involves targeting specific downstream component of IL-4/IL-13 signaling or different inflammatory mediators responsible for regulation of airway epithelial barrier. Airway epithelium-targeted therapy using inhibitors of HDAC, HSP90, MIF, mTOR, IL-17A and VEGF may be a potential strategy to prevent airway epithelial barrier dysfunction in airway inflammatory diseases.

The Impact of Environmental Pollutants on Barrier Dysfunction in Respiratory Disease

Respiratory epithelial cells form a selective barrier between the outside environment and underlying tissues. Epithelial cells are polarized and form specialized cell-cell junctions, known as the apical junctional complex (AJC). Assembly and disassembly of the AJC regulates epithelial morphogenesis and remodeling processes. The AJC consists of tight and adherens junctions, functions as a barrier and boundary, and plays a role in signal transduction. Endothelial junction proteins play important roles in tissue integrity and vascular permeability, leukocyte extravasation, and angiogenesis. Air pollutants such as particulate matter, ozone, and biologic contaminants penetrate deep into the airways, reaching the bronchioles and alveoli before entering the bloodstream to trigger airway inflammation. Pollutants accumulating in the lungs exacerbate the symptoms of respiratory diseases, including asthma and chronic obstructive lung disease. Biological contaminants include bacteria, viruses, animal dander and cat saliva, house dust mites, cockroaches, and pollen. Allergic inflammation develops in tissues such as the lung and skin with large epithelial surface areas exposed to the environment. Barrier dysfunction in the lung allows allergens and environmental pollutants to activate the epithelium and produce cytokines that promote the induction and development of immune responses. In this article, we review the impact of environmental pollutants on the cell barrier in respiratory diseases.

Abnormal ADAM17 expression causes airway fibrosis in chronic obstructive asthma

Patients with chronic obstructive asthma (COA) develop airflow obstruction caused by subepithelial fibrosis. Although a disintegrin and metalloproteinase 17 (ADAM17) has been implicated in lung inflammation and tissue fibrosis, its role in airway fibrosis in COA has not been explored. Here, we found marked overexpression of ADAM17, phosphorylated ADAM17, and connective tissue growth factor (CTGF) in human airway fibroblasts from COA patients, compared with those of normal subjects. Similarly, levels of ADAM17, CTGF, α-smooth muscle actin (α-SMA), and collagen were increased in endobronchial biopsies from COA patients, but not in controls. In an ovalbumin-challenge asthma model, airway fibrosis was inhibited in ADAM17^f/f/Cre⁺ mice compared to control mice. TGF-β- and thrombin-induced fibrotic protein expression was reduced by ADAM17 small interfering (si)RNA, TAPI-0 (an ADAM17 inhibitor), and EGFR siRNA. In addition, exogenous HB-EGF reversed fibrotic response in ADAM17 knockdown human lung fibroblasts. ADAM17 causes subepithelial fibrosis through regulation of enhanced extracellular matrix production and fibroblast differentiation and is the common pathway for airway fibrosis mediated by TGF-β and thrombin through an aberrant ADAM17/EGFR signalling pathway.

MiR-21-5p in Macrophage-Derived Exosomes Targets Smad7 to Promote Epithelial Mesenchymal Transition of Airway Epithelial Cells

Background

Asthma is usually associated with airway inflammation and airway remodeling. Epithelial mesenchymal transition (EMT) often occurs in airway remodeling. The purpose of this study is to identify the effect of miR-21-5p and Smad7 signaling pathway in macrophage-derived exosomes on EMT of airway epithelial cells.

Methods

HE staining and Masson staining were used to verify the successful establishment of the asthma model. The levels of epithelial cell adhesion factor and stromal cell markers were detected by Western blot. The levels of miR-21-5p were detected by qRT-PCR. The expression of miR-21-5p in lung tissue was further verified by fluorescence in situ hybridization (FISH). Exosome morphology was observed by transmission electron microscopy (TEM) and nanoparticle tracking analysis (NTA). Luciferase reporter assay was applied to analyze the interaction of miR-21-5p with Smad7.

Results

The expression of miR-21-5p was upregulated in macrophages of rats in vivo with OVA-induced asthma. In vitro cultured alveolar macrophages stimulated by LPS could secrete exosomes with high levels of miR-21-5p. The exosome-derived miR-21-5p promotes EMT in rat tracheal epithelial cells through TGFβ1/Smad signaling pathway by downregulating Smad7. This process can be blocked by miR-21-5p inhibitor.

Conclusion

Rat alveolar macrophages produced high levels of miR-21-5p-containing exosomes, which transported miR-21-5p to tracheal epithelial cells, thus promoting EMT through TGF-β1/Smad signaling pathway by targeting Smad7.

Circulating MicroRNA: Incident Asthma Prediction and Vitamin D Effect Modification

Of children with recurrent wheezing in early childhood, approximately half go on to develop asthma. MicroRNAs have been described as excellent non-invasive biomarkers due to their prognostic utility. We hypothesized that circulating microRNAs can predict incident asthma and that that prediction might be modified by vitamin D. We selected 75 participants with recurrent wheezing at 3 years old from the Vitamin D Antenatal Asthma Reduction Trial (VDAART). Plasma samples were collected at age 3 and sequenced for small RNA-Seq. The read counts were normalized and filtered by depth and coverage. Logistic regression was employed to associate miRNAs at age 3 with asthma status at age 5. While the overall effect of miRNA on asthma occurrence was weak, we identified 38 miRNAs with a significant interaction effect with vitamin D and 32 miRNAs with a significant main effect in the high vitamin D treatment group in VDAART. We validated the VDAART results in Project Viva for both the main effect and interaction effect. Meta-analysis was performed on both cohorts to obtain the combined effect and a logistic regression model was used to predict incident asthma at age 7 in Project Viva. Of the 23 overlapped miRNAs in the stratified and interaction analysis above, 9 miRNAs were replicated in Project Viva with strong effect size and remained in the meta-analysis of the two populations. The target genes of the 9 miRNAs were enriched for asthma-related Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathways. Using logistic regression, microRNA hsa-miR-574-5p had a good prognostic ability for incident asthma prognosis with an area under the receiver operating characteristic (AUROC) of 0.83. In conclusion, miRNAs appear to be good biomarkers of incident asthma, but only when vitamin D level is considered.

Initiation and Pathogenesis of Severe Asthma with Fungal Sensitization

Fungi represent one of the most diverse and abundant eukaryotes on earth, and their ubiquity and small proteolytically active products make them pervasive allergens that affect humans and other mammals. The immunologic parameters surrounding fungal allergies are still not fully elucidated despite their importance given that a large proportion of severe asthmatics are sensitized to fungal allergens. Herein, we explore fungal allergic asthma with emphasis on mouse models that recapitulate the characteristics of human disease, and the main leukocyte players in the pathogenesis of fungal allergies. The endogenous mycobiome may also contribute to fungal asthma, a phenomenon that we discuss only superficially, as much remains to be discovered.

Protective effects of total flavonoids from Qu Zhi Qiao (fruit of Citrus paradisi cv. Changshanhuyou) on OVA-induced allergic airway inflammation and remodeling through MAPKs and Smad2/3 signaling pathway

Allergic asthma is one of the inflammatory diseases, which has become a major public health problem. Qu zhi qiao (QZQ), a dry and immature fruit of Citrus paradisi cv. Changshanhuyou, has various flavonoids with pharmacological properties. However, there is a knowledge gap on the pharmacological properties of QZQ on allergic asthma. Therefore, here, we explored the efficacy and mechanism of total flavonoids from QZQ (TFCH) on allergic asthma. We extracted and purified TFCH and conducted animal experiments using an Ovalbumin (OVA)-induced mice model. Bronchoalveolar lavage fluid and Swiss-Giemsa staining were used to count different inflammatory cells in allergic asthma mice. We conducted histopathology and immunohistochemistry to evaluate the changes in the lungs of allergic asthma mice. Moreover, we used ELISA assays to analyze chemokines and inflammatory cytokines. Furthermore, western blot analyses were conducted to elucidate the mechanism of TFCH on allergic asthma. We established that TFCH has anti-inflammatory effects and inhibits airway remodeling, providing a potential therapeutic strategy for allergic asthma.

RGD-binding integrins and TGF-β in SARS-CoV-2 infections - novel targets to treat COVID-19 patients?

The new coronavirus SARS-CoV-2 is a global pandemic and a severe public health crisis. SARS-CoV-2 is highly contagious and shows high mortality rates, especially in elderly and patients with pre-existing medical conditions. At the current stage, no effective drugs are available to treat these patients. In this review, we analyse the rationale of targeting RGD-binding integrins to potentially inhibit viral cell infection and to block TGF-β activation, which is involved in the severity of several human pathologies, including the complications of severe COVID-19 cases. Furthermore, we demonstrate the correlation between ACE2 and TGF-β expression and the possible consequences for severe COVID-19 infections. Finally, we list approved drugs or drugs in clinical trials for other diseases that also target the RGD-binding integrins or TGF-β. These drugs have already shown a good safety profile and, therefore, can be faster brought into a trial to treat COVID-19 patients.

TGF-β: The missing link in obesity-associated airway diseases?

Obesity is emerging as a global public health epidemic. The co-morbidities associated with obesity significantly contribute to reduced quality of life, mortality, and global healthcare burden. Compared to other asthma comorbidities, obesity prominently engenders susceptibility to inflammatory airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), contributes to greater disease severity and evokes insensitivity to current therapies. Unlike in other metabolic diseases associated with obesity, the mechanistic link between obesity and airway diseases is only poorly defined. Transforming growth factor-β (TGF-β) is a pleiotropic inflammatory cytokine belonging to a family of growth factors with pivotal roles in asthma. In this review, we summarize the role of TGF-β in major obesity-associated co-morbidities to shed light on mechanisms of the diseases. Literature evidence shows that TGF-β mechanistically links many co-morbidities with obesity through its profibrotic, remodeling, and proinflammatory functions. We posit that TGF-β plays a similar mechanistic role in obesity-associated inflammatory airway diseases such as asthma and COPD. Concerning the role of TGF-β on metabolic effects of obesity, we posit that TGF-β has a similar mechanistic role in obesity-associated inflammatory airway diseases in interplay with different comorbidities such as hypertension, metabolic diseases like type 2 diabetes, and cardiomyopathies. Future studies in TGF-β-dependent mechanisms in obesity-associated inflammatory airway diseases will advance our understanding of obesity-induced asthma and help find novel therapeutic targets for prevention and treatment.

[Management strategies for chronic rhinosinusitis with nasal polyps in adults]

INTRODUCTION

Chronic rhinosinusitis with nasal polyps (CRSwNP) is one of the categories of chronic rhinosinusitis and is defined by the presence of bilateral polyps. It is frequently associated with other conditions (asthma, atopy, aspirin intolerance), which worsen its prognosis.

STATE OF ART

The pathophysiology of CRSwNP is still poorly understood. The genesis of polyps is thought to be based on an initial epithelial lesion caused by environmental factors in the context of self-maintained chronic local inflammation. Multiple local and general factors can be involved in this inflammation, which is mainly of Th2 type in Europe. Abnormalities of the epithelial barrier and the immune system (eosinophilia, cytokines, T and B lymphocytes), genetic factors and pathogens, including Staphylococcus aureus, have been incriminated. The treatment of CRSwNP is mainly based on the application of local corticosteroids. Surgery remains an important part of patient management where CRSwNP becomes resistant to topical therapy. The management of CRSwNP may be at a turning point thanks to the arrival of biological therapies (anti-IgE, anti-IL-5, anti-IL-4/IL-13) the initial results of which are promising.

PERSPECTIVES/CONCLUSIONS

With the new concept of endotypes, current avenues of research are moving towards a better understanding of the inflammatory mechanisms of CRSwNP. Immunotherapy appears to be a promising future for the treatment of CRSwNP.

Airway epithelial integrin β4 suppresses allergic inflammation by decreasing CCL17 production

Airway epithelial cells (AECs) play a key role in asthma susceptibility and severity. Integrin β4 (ITGB4) is a structural adhesion molecule that is down-regulated in the airway epithelium of asthma patients. Although a few studies hint toward the role of ITGB4 in asthmatic inflammation pathogenesis, their specific resultant effects remain unexplored. In the present study, we determined the role of ITGB4 of AECs in the regulation of Th2 response and identified the underpinning molecular mechanisms. We found that ITGB4 deficiency led to exaggerated lung inflammation and AHR with higher production of CCL17 in house dust mite (HDM)-treated mice. ITGB4 regulated CCL17 production in AECs through EGFR, ERK and NF-κB pathways. EFGR-antagonist treatment or the neutralization of CCL17 both inhibited exaggerated pathological marks in HDM-challenged ITGB4-deficient mice. Together, these results demonstrated the involvement of ITGB4 deficiency in the development of Th2 responses of allergic asthma by down-regulation of EGFR and CCL17 pathway in AECs.

Epithelial cell dysfunction, a major driver of asthma development

Airway epithelial barrier dysfunction is frequently observed in asthma and may have important implications. The physical barrier function of the airway epithelium is tightly interwoven with its immunomodulatory actions, while abnormal epithelial repair responses may contribute to remodelling of the airway wall. We propose that abnormalities in the airway epithelial barrier play a crucial role in the sensitization to allergens and pathogenesis of asthma. Many of the identified susceptibility genes for asthma are expressed in the airway epithelium, supporting the notion that events at the airway epithelial surface are critical for the development of the disease. However, the exact mechanisms by which the expression of epithelial susceptibility genes translates into a functionally altered response to environmental risk factors of asthma are still unknown. Interactions between genetic factors and epigenetic regulatory mechanisms may be crucial for asthma susceptibility. Understanding these mechanisms may lead to identification of novel targets for asthma intervention by targeting the airway epithelium. Moreover, exciting new insights have come from recent studies using single‐cell RNA sequencing (scRNA‐Seq) to study the airway epithelium in asthma. This review focuses on the role of airway epithelial barrier function in the susceptibility to develop asthma and novel insights in the modulation of epithelial cell dysfunction in asthma.

Role of biomarkers and effect of FIP-fve in acute and chronic animal asthma models

BACKGROUND

Asthma is a consequence of complex gene-environment interactions. Exploring the heterogeneity of asthma in different stages is contributing to our understanding of its pathogenesis and the development of new therapeutic strategies, especially in severe cases.

OBJECTIVE

This study aimed to further understand the relationship between manifestations of acute and chronic asthma and various endotypes, and explore the severity of lung inflammation, cell types, cytokine/chemokine differences, and the effects of FIP-fve.

MATERIALS AND METHODS

Acute and chronic OVA-sensitization mouse asthma models, based on our previously published method, were used and FIP-fve was used to evaluate the effect on these two models. BALF cytokines/chemokines were detected according to the manufacturer's protocol.

RESULTS

Seventeen cytokine/chemokine secretions were higher in the chronic stage than in the acute stage. Whether in acute stage or chronic stage, the FIP-fve treatment groups had reduced airway hyperresponsiveness, infiltration of airway inflammatory cells, secretion of cytokines, chemokines by Th2 cells, and TNF-α, IL-8, IL-17, CXCL-1, CXCL-10, CCL-17, and CCL-22, and it was also found that the Treg cell cytokine IL-10 had increased significantly. PCA (Principal Component Analysis) was also used to compare statistics and laboratory data to find the important biomarkers in different stages and after treatment with FIP-fve.

CONCLUSIONS

There are many different immune responses in the different stages of the asthma process. Drug treatment at the appropriate times might help reduce the worsening of asthma.

What Have In Vitro Co-Culture Models Taught Us about the Contribution of Epithelial-Mesenchymal Interactions to Airway Inflammation and Remodeling in Asthma?

As the lung develops, epithelial-mesenchymal crosstalk is essential for the developmental processes that drive cell proliferation, differentiation, and extracellular matrix (ECM) production within the lung epithelial-mesenchymal trophic unit (EMTU). In asthma, a number of the lung EMTU developmental signals have been associated with airway inflammation and remodeling, which has led to the hypothesis that aberrant activation of the asthmatic EMTU may lead to disease pathogenesis. Monoculture studies have aided in the understanding of the altered phenotype of airway epithelial and mesenchymal cells and their contribution to the pathogenesis of asthma. However, 3-dimensional (3D) co-culture models are needed to enable the study of epithelial-mesenchymal crosstalk in the setting of the in vivo environment. In this review, we summarize studies using 3D co-culture models to assess how defective epithelial-mesenchymal communication contributes to chronic airway inflammation and remodeling within the asthmatic EMTU.

Asthma and Lung Mechanics

This article will discuss in detail the pathophysiology of asthma from the point of view of lung mechanics. In particular, we will explain how asthma is more than just airflow limitation resulting from airway narrowing but in fact involves multiple consequences of airway narrowing, including ventilation heterogeneity, airway closure, and airway hyperresponsiveness. In addition, the relationship between the airway and surrounding lung parenchyma is thought to be critically important in asthma, especially as related to the response to deep inspiration. Furthermore, dynamic changes in lung mechanics over time may yield important information about asthma stability, as well as potentially provide a window into future disease control. All of these features of mechanical properties of the lung in asthma will be explained by providing evidence from multiple investigative methods, including not only traditional pulmonary function testing but also more sophisticated techniques such as forced oscillation, multiple breath nitrogen washout, and different imaging modalities. Throughout the article, we will link the lung mechanical features of asthma to clinical manifestations of asthma symptoms, severity, and control. © 2020 American Physiological Society. Compr Physiol 10:975-1007, 2020.

Chlorella vulgaris α-L-arabino-α-L-rhamno-α,β-D-galactan structure and mechanisms of its anti-inflammatory and anti-remodelling effects

Microalgal exopolysaccharides (EPSs) are given great attention due to their potential biotechnology applications. Purified C. vulgaris EPS was subjected to compositional and sugar linkage analyses, and partial acid hydrolysis. Hydrolysate separation by gel chromatography afforded oligosaccharide fractions. Both, EPS and oligomers were studied by NMR spectroscopy. Data suggest very complex highly branched α-L-arabino-α-L-rhamno-α,β-D-galactan structure. Backbone repeating unit is formed by →2)-α-L-Rha (1 → 3)-α-L-Rha(1 → sequence, highly branched by long 1,6-linked α-D-Galp side chains, further branched at C2, C3 or C4 by α-L-Araf, α-D-Galf and β-D-Galf residues. α-L-Araf form longer 1,2-linked chains branched at C3, C4 or C5. Galf residues are localized as terminal units predominantly in the β configuration, while α-D-Galp and α-L-Araf may be partially O-methylated. Ex vivo biological assays showed increased interleukin-12 (IL-12) and interferon-gamma (INF-γ) levels corresponding to transforming growth factor beta (TGF-β) decrease in guinea pig model experimental asthma. These facts point to the anti-remodelling effect of Chlorella EPS and suggest its possible application in the treatment of asthma and chronic obstructive pulmonary disorder.

Transient Receptor Potential Vanilloid channel regulates fibroblast differentiation and airway remodeling by modulating redox signals through NADPH Oxidase 4

Asthma is characterized by pathological airway remodeling resulting from persistent myofibroblast activation. Although transforming growth factor beta 1 (TGFβ1), mechanical signals, and reactive oxygen species (ROS) are implicated in fibroblast differentiation, their integration is still elusive. We identified that Transient Receptor Potential Vanilloid 4 (TRPV4), a mechanosensitive ion channel mediates lung fibroblast (LF) differentiation and D. farinae-induced airway remodeling via a novel TRPV4-NADPH Oxidase 4 (NOX4) interaction. NOX4-mediated ROS production is essential for TGFβ1-induced LF differentiation via myocardin-related transcription factor-A (MRTF-A) and plasminogen activator inhibitor 1 (PAI-1). Importantly, TRPV4 inhibition prevented TGFβ1-induced NOX4 expression and ROS production. Both TRPV4 and NOX4 are activated by phosphatidylinositol 3-kinase (PI3K) downstream of TGFβ1, and signals from both TRPV4 and Rac are necessary for NOX4 upregulation. Notably, NOX4 expression is higher in fibroblasts derived from asthmatic patients (disease human LF; DHLF) in comparison to non-asthmatics (normal human LF; NHLF). Further, NOX4 expression is up-regulated in the lungs of D.farinae-treated wild type mice (WT) relative to saline-treated WT, which was attenuated in TRPV4 knockout (KO) mice. Our findings suggest that TRPV4 integrates TGFβ1 and ROS signaling through NOX4 and, TRPV4-NOX4 interaction is amenable to target lung remodeling during asthma.

CRISPRi-mediated functional analysis of lung disease-associated loci at non-coding regions

Genome-wide association studies have identified lung disease-associated loci; however, the functions of such loci are not well understood in part because the majority of such loci are located at non-coding regions. Hi-C, ChIP-seq and eQTL data predict potential roles (e.g. enhancer) of such loci; however, they do not elucidate the molecular function. To determine whether these loci function as gene-regulatory regions, CRISPR interference (CRISPRi; CRISPR/dCas9-KRAB) has been recently used. Here, we applied CRISPRi along with Hi-C, ChIP-seq and eQTL to determine the functional roles of loci established as highly associated with asthma, cystic fibrosis (CF), chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). Notably, Hi-C, ChIP-seq and eQTL predicted that non-coding regions located at chromosome 19q13 or chromosome 17q21 harboring single-nucleotide polymorphisms (SNPs) linked to asthma/CF/COPD and chromosome 11p15 harboring an SNP linked to IPF interact with nearby genes and function as enhancers; however, CRISPRi indicated that the regions with rs1800469, rs2241712, rs12603332 and rs35705950, but not others, regulate the expression of nearby genes (single or multiple genes). These data indicate that CRISPRi is useful to precisely determine the roles of non-coding regions harboring lung disease-associated loci as to whether they function as gene-regulatory regions at a genomic level.

Emerging biomarkers in chronic lung allograft dysfunction

Introduction: Lung transplantation remains an important treatment for patients with end stage lung disease. Chronic lung allograft dysfunction (CLAD) remains the greatest limiting factor for long term survival. As the diagnosis of CLAD is based on pulmonary function tests, significant lung injury is required before a diagnosis is feasible, likely when irreversible damage has already occurred. Therefore, research is ongoing for early CLAD recognition, with biomarkers making up a substantial amount of this research.Areas covered: The purpose of this review is to describe available biomarkers, focusing on those which aid in predicting CLAD and distinguishing between different CLAD phenotypes. We describe biomarkers presenting in bronchial alveolar lavage (BAL) as well as circulating in peripheral blood, both of which offer an appealing alternative to lung biopsy.Expert opinion: Development of CLAD involves complex, multiple immune and nonimmune mechanisms. Therefore, evaluation of potential CLAD biomarkers serves a dual purpose: clinically, the goal remains early detection and identification of patients at increased risk. Simultaneously, biomarkers offer insight into the different mechanisms involved in the pathophysiology of CLAD, leading to the development of possible interventions. The ultimate goal is the development of both preventive and early intervention strategies for CLAD to improve the overall survival of our lung transplant recipients.

Cordyceps polysaccharide ameliorates airway inflammation in an ovalbumin-induced mouse model of asthma via TGF-β1/Smad signaling pathway

Allergic asthma is a chronic inflammatory disease characterized by airflow obstruction, airway hyperresponsiveness (AHR), airway inflammation, and mucus overproduction. Cordyceps polysaccharide (CPS) is one of the main bioactive compounds of Cordyceps militarisis, a traditional Chinese medicine. In this study, we established a mouse model of asthma using ovalbumin (OVA) challenge and evaluated the potential regulatory effect of CPS (25, 50, and 100 mg/kg) on asthmatic mice. These results showed that the asthmatic mice treated with CPS suppressed the secretion of eotaxin, IL-4, IL-5, IL-13, and IFN-γ in the blood and bronchoalveolar lavage fluid (BALF), and decreased serum IgE levels compared to the vehicle-treated mice. CPS also alleviated inflammatory cell infiltration, goblet cell hyperplasia, and the increases of inflammatory cells in the mouse model of asthma. In addition, OVA-induced AHR was inhibited by CPS treatment. Further analyses of protein expression revealed that CPS inhibited the activation of transforming growth factor β1 (TGF-β1)/Smad pathway in mice with asthma. These findings indicated that CPS might serve as a potential therapeutic agent for the management of allergic asthma.

Transcriptomic changes during TGF-β-mediated differentiation of airway fibroblasts to myofibroblasts

Asthma is the most common chronic lung disease in children and young adults worldwide. Airway remodelling (including increased fibroblasts and myofibroblasts in airway walls due to chronic inflammation) differentiates asthmatic from non-asthmatic airways. The increase in airway fibroblasts and myofibroblasts occurs via epithelial to mesenchymal transition (EMT) where epithelial cells lose their tight junctions and are transdifferentiated to mesenchymal cells, with further increases in myofibroblasts occurring via fibroblast-myofibroblast transition (FMT). Transforming growth factor (TGF)-β is the central EMT- and FMT-inducing cytokine. In this study, we have used next generation sequencing to delineate the changes in the transcriptome induced by TGF-β treatment of WI-38 airway fibroblasts in both the short term and after differentiation into myofibroblasts, to gain an understanding of the contribution of TGF-β induced transdifferentiation to the asthmatic phenotype. The data obtained from RNAseq analysis was confirmed by quantitative PCR (qPCR) and protein expression investigated by western blotting. As expected, we found that genes coding for intermediates in the TGF-β signalling pathways (SMADs) were differentially expressed after TGF-β treatment, SMAD2 being upregulated and SMAD3 being downregulated as expected. Further, genes involved in cytoskeletal pathways (FN1, LAMA, ITGB1) were upregulated in myofibroblasts compared to fibroblasts. Importantly, genes that were previously shown to be changed in asthmatic lungs (ADAMTS1, DSP, TIMPs, MMPs) were similarly differentially expressed in myofibroblasts, strongly suggesting that TGF-β mediated differentiation of fibroblasts to myofibroblasts may underlie important changes in the asthmatic airway. We also identified new intermediates of signalling pathways (PKB, PTEN) that are changed in myofibroblasts compared to fibroblasts. We have found a significant number of genes that are altered after TGF-β induced transdifferentiation of WI-38 fibroblasts into myofibroblasts, many of which were expected or predicted. We also identified novel genes and pathways that were affected after TGF-β treatment, suggesting additional pathways are activated during the transition between fibroblasts and myofibroblasts and may contribute to the asthma phenotype.

Autophagy Activation in Asthma Airways Remodeling

Current asthma therapies fail to target airway remodeling that correlates with asthma severity driving disease progression that ultimately leads to loss of lung function. Macroautophagy (hereinafter "autophagy") is a fundamental cell-recycling mechanism in all eukaryotic cells; emerging evidence suggests that it is dysregulated in asthma. We investigated the interrelationship between autophagy and airway remodeling and assessed preclinical efficacy of a known autophagy inhibitor in murine models of asthma. Human asthmatic and nonasthmatic lung tissues were histologically evaluated and were immunostained for key autophagy markers. The percentage area of positive staining was quantified in the epithelium and airway smooth muscle bundles using ImageJ software. Furthermore, the autophagy inhibitor chloroquine was tested intranasally in prophylactic (3 wk) and treatment (5 wk) models of allergic asthma in mice. Human asthmatic tissues showed greater tissue inflammation and demonstrated hallmark features of airway remodeling, displaying thickened epithelium (P < 0.001) and reticular basement membrane (P < 0.0001), greater lamina propria depth (P < 0.005), and increased airway smooth muscle bundles (P < 0.001) with higher expression of Beclin-1 (P < 0.01) and ATG5 (autophagy-related gene 5) (P < 0.05) together with reduced p62 (P < 0.05) compared with nonasthmatic control tissues. Beclin-1 expression was significantly higher in asthmatic epithelium and ciliated cells (P < 0.05), suggesting a potential role of ciliophagy in asthma. Murine asthma models demonstrated effective preclinical efficacy (reduced key features of allergic asthma: airway inflammation, airway hyperresponsiveness, and airway remodeling) of the autophagy inhibitor chloroquine. Our data demonstrate cell context-dependent and selective activation of autophagy in structural cells in asthma. Furthermore, this pathway can be effectively targeted to ameliorate airway remodeling in asthma.

Host Components Contributing to Respiratory Syncytial Virus Pathogenesis

Respiratory syncytial virus (RSV) is the most prevalent viral etiological agent of acute respiratory tract infection. Although RSV affects people of all ages, the disease is more severe in infants and causes significant morbidity and hospitalization in young children and in the elderly. Host factors, including an immature immune system in infants, low lymphocyte levels in patients under 5 years old, and low levels of RSV-specific neutralizing antibodies in the blood of adults over 65 years of age, can explain the high susceptibility to RSV infection in these populations. Other host factors that correlate with severe RSV disease include high concentrations of proinflammatory cytokines such as interleukins (IL)-6, IL-8, tumor necrosis factor (TNF)-α, and thymic stromal lymphopoitein (TSLP), which are produced in the respiratory tract of RSV-infected individuals, accompanied by a strong neutrophil response. In addition, data from studies of RSV infections in humans and in animal models revealed that this virus suppresses adaptive immune responses that could eliminate it from the respiratory tract. Here, we examine host factors that contribute to RSV pathogenesis based on an exhaustive review of in vitro infection in humans and in animal models to provide insights into the design of vaccines and therapeutic tools that could prevent diseases caused by RSV.

Induction of airway remodeling and persistent cough by repeated citric acid exposure in a guinea pig cough model

BACKGROUND

A previous study involving guinea pigs showed that repeated cough could increase peripheral airway smooth muscle area, which can also aggravate cough. The airway pathologic changes produced by prolonged cough are still unknown.

OBJECTIVE

To study the airway pathologic changes in prolonged cough models of guinea pigs.

METHODS

Guinea pigs were assigned to three treatment groups: citric acid inhalation (CA) alone, citric acid inhalation with codeine pretreatment (COD), or saline solution inhalation (SA). Animals were challenged with citric acid or saline solution three times weekly. The intervention period was 22 or 43 days. Animals were challenged with citric acid on the first and last days of exposure. Lung specimens were obtained for pathologic analysis 72 h after the last exposure.

RESULTS

Compared with the other two groups, the CA group had increased frequency of cough on both 22 and 43 days of exposure. Tracheal basement membrane (BM) thickness was increased after 43 days of exposure, correlating with the frequency of cough. The area of airway smooth muscles (ASM index) in small airways increased in the CA group after both 22 and 43 days of exposure, compared with the SA group. Compared with the COD group, the ASM index in small airways increased in the CA group after 22 days of exposure instead of 43 days of exposure.

CONCLUSIONS

An increase in peripheral smooth muscle area by repeated cough was confirmed. Moreover, this is the first study to show that tracheal BM thickness increased after prolonged exposure (43 days). Repeated cough may lead to airway remodeling, which was also associated with an increased frequency of cough.

A Guinea Pig Model of Airway Smooth Muscle Hyperreactivity Induced by Chronic Allergic Lung Inflammation: Contribution of Epithelium and Oxidative Stress

Asthma is a heterogeneous disease of the airways characterized by chronic inflammation associated with bronchial and smooth muscle hyperresponsiveness. Currently, different murine models for the study of asthma show poor bronchial hyperresponsiveness due to a scarcity of smooth muscle and large airways, resulting in a failure to reproduce smooth muscle hyperreactivity. Thus, we aimed to standardize a guinea pig model of chronic allergic lung inflammation mimicking airway smooth muscle hyperreactivity observed in asthmatics (Asth). Animals were randomly divided into a control group (Ctrl), which received saline (0.9% NaCl), and the Asth group, subjected to in vivo sensitization with ovalbumin (OVA) nebulization. Morphological analysis was performed by hematoxylin-eosin staining. Bronchial hyperresponsiveness was evaluated by nebulization time in the fifth, sixth, and seventh inhalations (NT5-7) and tracheal isometric contractions were assessed by force transducer. Total antioxidant capacity was measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method and protein expression by Western blot. Histologically, the Asth group developed peribronchial cellular infiltrate, epithelial hyperplasia and smooth muscle thickening. After the fourth nebulization, the Asth group developed bronchial hyperreactivity. The trachea from the Asth group contracted after in vitro stimulation with OVA, differing from the Ctrl group, which showed no response. Additionally, airway smooth muscle hyperreactivity to carbachol and histamine was observed in the Asth group only in intact epithelium preparations, but not to KCl, and this effect was associated with an augmented production of reactive oxygen species. Moreover, lung inflammation impaired the relaxant potency of isoproterenol only in intact epithelium preparations, without interfering with nifedipine, and it was found to be produced by transforming growth factor-β negative modulation of β adrenergic receptors and, furthermore, big-conductance Ca2+-sensitive K+ channels. These effects were also associated with increased levels of phosphatidylinositol 3-kinases but not extracellular signal-regulated kinases 1/2 or phosphorylation, and augmented α-actin content as well, explaining the increased smooth muscle mass. Furthermore, pulmonary antioxidant capacity was impaired in the Asth group. Therefore, we developed a standardized and easy-to-use, reproducible guinea pig model of lung inflammation that mimics airway smooth muscle hypercontractility, facilitating the investigation of the mechanisms of bronchial hyperresponsiveness in asthma and new therapeutic alternatives.

Phyllanthin and hypophyllanthin from Phyllanthus amarus ameliorates immune-inflammatory response in ovalbumin-induced asthma: role of IgE, Nrf2, iNOs, TNF-α, and IL's

Background: Asthma is a chronic airway immunoinflammatory disorder characterized by airway remodeling. Phyllanthus amarus has been reported to possess antioxidant and anti-inflammatory potential. Aim: To evaluate the possible mechanism of action of isolated phytoconstituents from P. amarus (PA) against ovalbumin (OVA)-induced experimental airway hyperresponsiveness (AHR). Material and method: Phyllanthin and hypophyllanthin were isolated and characterized (HPLC) from the methanolic extract of PA. AHR was induced in Sprague-Dawley rats by OVA-challenged, and animals were treated with PA (50, 100, and 200 mg/kg, p.o.) for 28 days. Results: The HPLC analysis showed the presence of phyllanthin and hypophyllanthin in methanolic extract of PA at RT of 25.243 and 26.832 min, respectively. OVA-induced alterations in hemodynamic parameters, lung functions test, peripheral blood oxygen level, total, and differential cell count in Bronchoalveolar Lavage Fluid was significantly attenuated (p < .05) by PA (100 and 200 mg/kg). It also significantly decreased (p < .05) the levels of total protein and albumin in serum, BALF, and lungs. OVA-induced increase in IgE (total and OVA-specific), and oxido-nitrosative stress (SOD, GSH, MDA, and NO) levels were significantly (p < .05) decreased by PA. RT-PCR analysis revealed that elevated oxido-nitrosative stress (Nrf2 and iNOs), immune-inflammatory makers (HO-1, TNF-α, IL-1β, and TGF-β1), Th2 cytokines (IL-4 and IL-6) levels were significantly attenuated (p < .05) by PA. PA also attenuated histological and ultrastructural aberrations induced by OVA. Conclusion: Results of the present investigation demonstrated that the presence of phyllanthin and hypophyllanthin in P. amarus alleviated Th2 response in OVA-induced AHR via modulation of endogenous markers in a murine model of asthma. Thus, phyllanthin and hypophyllanthin may be a new therapeutic approach for the management of asthma.

Wound-healing effects of 635-nm low-level laser therapy on primary human vocal fold epithelial cells: an in vitro study

Low-level laser therapy (LLLT) has been promoted for its beneficial effects on tissue healing and pain relief for skin and oral applications. However, there is no corresponding literature reporting on vocal fold wound healing. Our purpose was to assess the potential wound-healing effects of LLLT on primary human vocal fold epithelial cells (VFECs). In this study, normal vocal fold tissue was obtained from a 58-year-old male patient who was diagnosed with postcricoid carcinoma without involvement of the vocal folds and underwent total laryngectomy. Primary VFECs were then cultured. Cells were irradiated at a wavelength of 635 nm with fluences of 1, 4, 8, 12, 16, and 20 J/cm² (50 mW/cm²), which correspond to irradiation times of 20, 80, 160, 240, 320, and 400 s, respectively. Cell viability of VFECs in response to varying doses of LLLT was investigated by the Cell Counting Kit-8 (CCK-8) method. The most effective irradiation dose was selected to evaluate the cell migration capacity by using the scratch wound-healing assay. Real-time polymerase chain reaction (RT-PCR) was used to detect the gene expression of TGF-β1, TGF-β3, EGF, IL-6, and IL-10. Irradiation with doses of 8 J/cm² resulted in 4% increases in cell proliferation differing significantly from the control group (p < 0.05). With subsequent doses at 48 and 72 h after irradiation, the differences between the experimental and the control groups became greater, up to 9.8% (p < 0.001) and 19.5% (p < 0.001), respectively. It also increased cell migration and the expression of some genes, such as EGF, TGF-β1, TGF-β3, and IL-10, involved in the tissue healing process. This study concludes that LLLT at the preset parameters was capable of stimulating the proliferation and migration of human vocal fold epithelial cells in culture as well as increase the expression of some genes involved in tissue healing process. Additionally, successive laser treatments at 24 h intervals have an additive beneficial effect on the healing of injured tissues.

Role of Matrix Metalloproteinase-2 in Eosinophil-Mediated Airway Remodeling

Airway remodeling is responsible for the progressive decline of lung function in bronchial asthma. Matrix metalloproteinase-2 and fibroblast-to-myofibroblast transition are involved in tissue remodeling. Here we evaluated whether eosinophils play a role in fibroblasts-to-myofibroblasts transition and in the expression of matrix metalloproteinase-2. We co-cultured human eosinophils with human fetal lung fibroblast-1 cells, assessed the expression of remodeling-associated molecules by immunoassays and polymerase-chain reaction, and eosinophils-mediated migration of human fetal lung fibroblast-1 cells using a Boyden chamber. To clarify the participation of matrix metalloproteinase-2 in airway remodeling we administered bone marrow-derived eosinophils by intra-tracheal route to transgenic mice overexpressing the human matrix metalloproteinase-2. The expression of α-smooth muscle actin significantly increased in human fetal lung fibroblast-1 cells co-cultured with human eosinophils compared to controls. There was enhanced expression of matrix metalloproteinase-2 during fibroblast-to-myofibroblast transition. An inhibitor of matrix metalloproteinases blocked eosinophils-associated fibroblast-to-myofibroblast transition and increased migration of fibroblasts. The human matrix metalloproteinase-2 transgenic mice receiving adoptive transfer of mouse eosinophils exhibited increased inflammation and advanced airway remodeling compared to wild type mice. This study demonstrated that eosinophils induce fibroblast-to-myofibroblast transition, secretion of matrix metalloproteinase-2, accelerated migration of fibroblasts, and promote matrix metalloproteinase-2-related airway remodeling. These findings provide a novel mechanistic pathway for eosinophil-associated airway remodeling in bronchial asthma.

Hyaluronan antagonizes the differentiation effect of TGF-β1 on nasal epithelial cells through down-regulation of TGF-β type I receptor

Although hyaluronan (HA)-based biomaterials have been proposed to promote mucociliary differentiation of nasal epithelial cells (NECs), the mechanism by which HA affects the growth and differentiation of NECs has not been thoroughly explored. This study investigates the effect and mechanism of HA on the differentiation of NECs. The experiment cultures human NECs in four conditions, namely controls, transforming growth factor (TGF)-β1, TGF-β1 + HA and HA groups. In the TGF group, the NECs become irregular shape without formation of tight junction and mucociliary differentiation of NECs is inhibited. Epithelial-mesenchymal transition (EMT) of NECs also occurs in the TGF group. However, with addition of HA in TGF groups, NECs reveal the mucociliary phenotypes of epithelial cells with tight junction expression. Incubation of TGF-β1 in an NEC culture leads to an increase in phosphorylated type 1 TGF-β receptors (p-TβRI). This increase is attenuated when NECs are cultured in the presence of HA. Similar expressions are observed in phosphorylated smad2/smad3. Additionally, HA-dependent inhibition of TGF-β1 signalling is inhibited by co-incubation with a blocking antibody to CD44. Experimental results indicate that HA can antagonize TGF-β1 effect on EMT and mucociliary differentiation of NECs by down-regulation of TβR I, which is via CD44.

Therapeutic Effects of Kangzhi Syrup in a Guinea Pig Model of Ovalbumin-Induced Cough Variant Asthma

Purpose

This study aimed to investigate the possible effects and underlying mechanisms of Kangzhi syrup on ovalbumin- (OVA-) induced cough variant asthma (CVA) in guinea pigs.

Methods

All 48 guinea pigs were randomly assigned to four experimental groups: normal, OVA model with or without Kangzhi syrup (OVA and OVA + KZ), and OVA with Dexamethasone (OVA + DM). After sensitizing the guinea pigs, a cough challenge was performed by the inhalation of capsaicin. The antitussive effect, inflammatory cells, cytokines in bronchoalveolar lavage fluid (BALF) and lung tissue, and morphological changes were examined.

Results

Compared with model group, Kangzhi syrup effectively exerted an antitussive effect (p < 0.0001) and reduced the pneumonic anaphylacticitis by inhibiting the infiltration of total inflammatory cells (p < 0.0001) and reducing the percentage of eosinophil in BALF (p < 0.0001). Moreover, evidence from morphological studies also demonstrated that Kangzhi syrup inhibited the infiltration of inflammatory cells and ameliorated the structure changes. NF-κB and TGF-β1 expression were attenuated in the OVA + KZ group versus the OVA group (p < 0.0001). Additionally, a semiquantitative analysis of TGF-β1 expression also demonstrated that the Kangzhi syrup attenuated this profibrogenic growth factor (p < 0.001).

Conclusions

The results demonstrated that Kangzhi syrup exerted a considerable antitussive effect in CVA animal model, which depended on its marked impact on the anti-anaphylactic inflammation. Additionally, it could ameliorate the airway remodeling by inhibiting NF-κB and TGF-β1 signal pathway.

TGF-β1 Signaling and Tissue Fibrosis

Activation of TGF-β1 initiates a program of temporary collagen accumulation important to wound repair in many organs. However, the outcome of temporary extracellular matrix strengthening all too frequently morphs into progressive fibrosis, contributing to morbidity and mortality worldwide. To avoid this maladaptive outcome, TGF-β1 signaling is regulated at numerous levels and intimately connected to feedback signals that limit accumulation. Here, we examine the current understanding of the core functions of TGF-β1 in promoting collagen accumulation, parallel pathways that promote physiological repair, and pathological triggers that tip the balance toward progressive fibrosis. Implicit in better understanding of these processes is the identification of therapeutic opportunities that will need to be further advanced to limit or reverse organ fibrosis.

Activation of Activin receptor-like kinases curbs mucosal inflammation and proliferation in chronic rhinosinusitis with nasal polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a widespread disease causing obstruction of the nasal cavity. Its cause remains unclear. The transforming growth-factor beta (TGF-β) superfamily and their receptors, termed Activin receptor-like kinases (ALKs), have recently been suggested to play a role in local airway inflammation, but have so far not been evaluated in human nasal epithelial cells (HNECs) from CRSwNP patients. We demonstrated that ALK1–7 were expressed in the nasal polyp epithelium, and the expression of ALK1-6 was markedly elevated in polyps compared to nasal mucosa from healthy controls. Stimulation with the ALK ligand TGF-β1 decreased Ki67 expression in HNECs from CRSwNP patients, not evident in controls. Likewise, TGF-β1, Activin A and Activin B, all ALK ligands, decreased IL-8 release and Activin A and Activin B reduced ICAM1 expression on HNECs from CRSwNP patients, not seen in controls. Pre-stimulation with TGF-β1, Activin A, BMP4 and Activin B attenuated a TNF-α-induced ICAM1 upregulation on HNECs of CRSwNP. No effect was evident in controls. In conclusion, an increased expression of ALK1-6 was found on polyp epithelial cells and ligand stimulation appeared to reduce proliferation and local inflammation in polyps.