Transforming growth factor-beta 1 in asthma. Measurement in bronchoalveolar lavage fluid

IL-5 antagonism reverses priming and activation of eosinophils in severe eosinophilic asthma

Eosinophils are key effector cells mediating airway inflammation and exacerbation in patients with severe eosinophilic asthma. They are present in increased numbers and activation states in the airway mucosa and lumen. Interleukin-5 (IL-5) is the key eosinophil growth factor that is thought to play a role in eosinophil priming and activation. However, the mechanism of these effects is still not fully understood. The anti-IL-5 antibody mepolizumab reduces eosinophil counts in the airway modestly but has a large beneficial effect on the frequency of exacerbations of severe eosinophilic asthma, suggesting that reduction in eosinophil priming and activation is of central mechanistic importance. In this study, we used the therapeutic effect of mepolizumab and single-cell ribonucleic acid sequencing to investigate the mechanism of eosinophil priming and activation by IL-5. We demonstrated that IL-5 is a dominant driver of eosinophil priming and plays multifaceted roles in eosinophil function. It enhances eosinophil responses to other stimulators of migration, survival, and activation by activating phosphatidylinositol-3-kinases, extracellular signal-regulated kinases, and p38 mitogen-activated protein kinases signaling pathways. It also enhances the pro-fibrotic roles of eosinophils in airway remodeling via transforming growth factor-β pathway. These findings provide a mechanistic understanding of eosinophil priming in severe eosinophilic asthma and the therapeutic effect of anti-IL-5 approaches in the disease.

Investigating dysregulation of TGF-β1/SMAD3 signaling in atopic dermatitis: a molecular and immunohistochemical analysis

Atopic dermatitis (AD) is a persistent and recurring inflammatory condition affecting the skin. An expanding corpus of evidence indicates the potential participation of transforming growth factor-β1 (TGF-β1) in the modulation of inflammation and tissue remodeling in AD. The primary objective of this study was to examine the aberrant modulation of TGF-β1/small mothers against decapentaplegic homolog 3 (SMAD3) signaling through a comprehensive analysis of their molecular and protein expression profiles. The study encompassed an aggregate of 37 participants, which included 25 AD patients and 12 controls. The assessment of mRNA and protein levels of TGF-β1 and SMAD3 was conducted utilizing quantitative real-time PCR and immunohistochemistry (IHC), whereas serum IgE and vitamin D levels were estimated by ELISA and chemiluminescence, respectively. Quantitative analysis demonstrated a 2.5-fold upregulation of TGF-β1 mRNA expression in the lesional AD skin (P < 0.0001). IHC also exhibited a comparable augmented pattern, characterized by moderate to strong staining intensities. In addition, TGF-β1 mRNA showed an association with vitamin D deficiency in serum (P < 0.02), and its protein expression was linked with the disease severity (P < 0.01) Furthermore, a significant decrease in the expression of the SMAD3 gene was observed in the affected skin (P = 0.0004). This finding was further confirmed by evaluating the protein expression and phosphorylation of SMAD3, both of which exhibited a decrease. These findings suggest that there is a dysregulation in the TGF-β1/SMAD3 signaling pathway in AD. Furthermore, the observed augmentation in mRNA and protein expression of TGF-β1, along with its correlation with the disease severity, holds considerable clinical significance and emphasizes its potential role in AD pathogenesis.

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

Rhinovirus infection induces secretion of endothelin-1 from airway epithelial cells in both in vitro and in vivo models

BACKGROUND

Rhinovirus (RV) infection of airway epithelial cells triggers asthma exacerbations, during which airway smooth muscle (ASM) excessively contracts. Due to ASM contraction, airway epithelial cells become mechanically compressed. We previously reported that compressed human bronchial epithelial (HBE) cells are a source of endothelin-1 (ET-1) that causes ASM contraction. Here, we hypothesized that epithelial sensing of RV by TLR3 and epithelial compression induce ET-1 secretion through a TGF-β receptor (TGFβR)-dependent mechanism.

METHODS

To test this, we used primary HBE cells well-differentiated in air-liquid interface culture and two mouse models (ovalbumin and house dust mite) of allergic airway disease (AAD). HBE cells were infected with RV-A16, treated with a TLR3 agonist (poly(I:C)), or exposed to compression. Thereafter, EDN1 (ET-1 protein-encoding gene) mRNA expression and secreted ET-1 protein were measured. We examined the role of TGFβR in ET-1 secretion using either a pharmacologic inhibitor of TGFβR or recombinant TGF-β1 protein. In the AAD mouse models, allergen-sensitized and allergen-challenged mice were subsequently infected with RV. We then measured ET-1 in bronchoalveolar lavage fluid (BALF) and airway hyperresponsiveness (AHR) following methacholine challenge.

RESULTS

Our data reveal that RV infection induced EDN1 expression and ET-1 secretion in HBE cells, potentially mediated by TLR3. TGFβR activation was partially required for ET-1 secretion, which was induced by RV, poly(I:C), or compression. TGFβR activation alone was sufficient to increase ET-1 secretion. In AAD mouse models, RV induced ET-1 secretion in BALF, which positively correlated with AHR.

CONCLUSIONS

Our data provide evidence that RV infection increased epithelial-cell ET-1 secretion through a TGFβR-dependent mechanism, which contributes to bronchoconstriction during RV-induced asthma exacerbations.

Epithelial-Mesenchymal Transition Mechanisms in Chronic Airway Diseases: A Common Process to Target?

Epithelial-to-mesenchymal transition (EMT) is a reversible process, in which epithelial cells lose their epithelial traits and acquire a mesenchymal phenotype. This transformation has been described in different lung diseases, such as lung cancer, interstitial lung diseases, asthma, chronic obstructive pulmonary disease and other muco-obstructive lung diseases, such as cystic fibrosis and non-cystic fibrosis bronchiectasis. The exaggerated chronic inflammation typical of these pulmonary diseases can induce molecular reprogramming with subsequent self-sustaining aberrant and excessive profibrotic tissue repair. Over time this process leads to structural changes with progressive organ dysfunction and lung function impairment. Although having common signalling pathways, specific triggers and regulation mechanisms might be present in each disease. This review aims to describe the various mechanisms associated with fibrotic changes and airway remodelling involved in chronic airway diseases. Having better knowledge of the mechanisms underlying the EMT process may help us to identify specific targets and thus lead to the development of novel therapeutic strategies to prevent or limit the onset of irreversible structural changes.

Unveiling the TGF- β1 paradox: Significant implication of TGF- β1 promoter variants and its mRNA and protein expression in atopic dermatitis

BACKGROUND

Atopic Dermatitis (AD) is a chronic inflammatory skin disorder with evidence of lichenification in later stages. There is mounting evidence supporting the role of TGF- β1 in mediating inflammation as well as subsequent tissue remodeling, often resulting in fibrosis. Given the role of genetic variants in the differential expression of TGF-β1 in various diseases, this study seeks to ascertain the role of TGF-β1 promoter variants (rs1800469 and rs1800468) in AD susceptibility, as well as their association with TGF- β1 mRNA expression, TGF- β1 serum levels and skin prick test positivity in Atopic Dermatitis patients.

METHODS

An aggregate of 246 subjects including 134 AD cases and 112 matched healthy controls were genotyped for TGF-β1 promoter polymorphisms by PCR-RFLP. TGF- β1 mRNA was quantified by quantitative Real-Time PCR (qRT-PCR), Vitamin-D levels by chemiluminescence, and serum TGF- β1, and total IgE levels were determined by ELISA. In-vivo allergy testing was performed for the evaluation of allergic reactions to house dust mites and food allergens.

RESULTS

A higher frequency of TT genotypes of rs1800469 (OR = 7.7, p = 0.0001) and GA+AA genotypes of rs1800468 (OR-4.4, p < 0.0001) were observed in AD cases than those in controls. Haplotype analysis demonstrated that TG haplotype carriers had an increased risk of AD (p = 0.013). Quantitative analysis revealed a significant upregulation of both mRNA (p = 0.0002) and serum levels (p < 0.0001) of TGF- β1 with a substantial positive correlation between them (Correlation coefficient=0.504; p = 0.01). Moreover, serum TGF-β1 levels were associated with quality of life (p = 0.03), the severity of the disease (p = 0.03), and House dust mite allergy (p = 0.01) whereas TGF-β1 mRNA levels positively correlated with disease severity(p = 0.02). Stratification analysis revealed that the TT genotype of rs1800469 was associated with higher IgE levels (p = 0.01) and eosinophil percentage(p = 0.007) whereas the AA genotype of rs1800468 correlated with elevated serum IgE levels (p = 0.01). Besides, no significant association of genotypes with mRNA and serum expression of TGF-β1 was observed.

CONCLUSION

Our study indicates that TGF-β1 promoter SNPs bear a significant risk of AD development. Moreover, upregulation of TGF-β1 mRNA and serum levels and their association with disease severity, quality of life, and HDM allergy suggests its role as a diagnostic/prognostic biomarker that could help in the development of new therapeutic and prevention strategies.

LXA4 inhibits TGF-β1-induced airway smooth muscle cells proliferation and migration by suppressing the Smad/YAP pathway

The aims of the present study were to examine the signaling mechanisms for transforming growth factor-β1 (TGF-β1)-induced rat airway smooth muscle cells (ASMCs) proliferation and migration and to determine the effect of lipoxin A4 (LXA4) on TGF-β1-induced rat ASMCs proliferation and migration and its underlying mechanisms. TGF-β1 upregulated transcriptional coactivator Yes-associated protein (YAP) expression by activating Smad2/3 and then upregulated cyclin D1, leading to rat ASMCs proliferation and migration. This effect was reversed after treatment with the TGF-β1 receptor inhibitor SB431542. YAP is a critical mediator of TGF-β1-induced ASMCs proliferation and migration. Knockdown of YAP disrupted the pro-airway remodeling function of TGF-β1. Preincubation of rat ASMCs with LXA4 blocked TGF-β1-induced activation of Smad2/3 and changed its downstream targets, YAP and cyclin D1, resulting in the inhibition of rat ASMCs proliferation and migration. Our study suggests that LXA4 suppresses Smad/YAP signaling to inhibit rat ASMCs proliferation and migration and therefore has potential value in the prevention and treatment of asthma by negatively modulating airway remodeling.

Involvement of Transforming Growth Factor-β-Associated Kinase 1 in Fixed Airway Obstruction in Asthmatic Patients with Longer Disease Duration Independent on Airway Eosinophilia

Objective

Transforming growth factor-β-associated kinase 1 (TAK1) mediates non-canonical TGF-β signalling by promoting adhesive, migratory, proliferative and contractile responses of fibroblasts to TGF-β₁. However, TAK1 expression status in asthmatic patients with or without fixed airway obstruction (FAO) is unknown.

Patients and Methods

A total of 60 adult asthmatics with FAO were recruited and compared to 43 those without FAO (nFAO). TGF-β₁ concentrations, and total TAK1 and phosphorylated TAK1 (p-TAK1) levels were determined in sputum supernatants, cytospin, and whole cell lysate by ELISA, immunocytochemistry, and Western blot analysis, respectively, in asthmatics with and without FAO.

Results

Asthmatic patients with FAO had much greater sputum TGF-β₁ concentrations than those without FAO. This was independent of airway eosinophilia as there was no significant difference in TGF-β₁ levels between high and low eosinophil counts within FAO and nFAO groups. In contrast, patients with FAO in the presence of sputum eosinophilia had greater expression of TAK1 and p-TAK1 than those without sputum eosinophilia (P=0.0032 and P=0.0061, respectively). The Western Blot data of total TAK1 and p-TAK1 were consistent with the immunocytochemistry, showing upregulation in all sputum cell types (neutrophils, eosinophils, macrophages, lymphocytes and airway epithelial cells). In addition, total TAK1 expression negatively correlated with pre- and post-bronchodilator FEV₁/FVC ratio.

Conclusion

TAK1 may play a key role in asthmatic patients with fixed airway obstruction, which was independent of eosinophilic airway inflammation. The interruption of TAK1 might have favourable clinical impact.

Apigenin ameliorates non-eosinophilic inflammation, dysregulated immune homeostasis and mitochondria-mediated airway epithelial cell apoptosis in chronic obese asthma via the ROS-ASK1-MAPK pathway

BACKGROUND

Obese asthma is one of the important asthma phenotypes that have received wide attention in recent years. Excessive oxidative stress and different inflammatory endotypes may be important reasons for the complex symptoms, frequent aggravation, and resistance to traditional treatments of obese asthma. Apigenin (API), is a flavonoid natural small molecule compound with good anti-inflammatory and antioxidant activity in various diseases and proved to have the potential efficacy to combat obese asthma.

METHODS

In vivo, this study fed C57BL/6 J mice with high-fat diets(HFD)for 12 weeks and then stimulated them with OVA for 6 weeks to establish a model of chronic obese asthma, while different doses of oral API or dexamethasone were used for therapeutic interventions. In vitro, this study used HDM to stimulate human bronchial cells (HBEs) to establish the model and intervened with API or Selonsertib (SEL).

RESULTS

This study clarified that OVAinduced a type of mixed granulocytic asthma with elevated neutrophils and eosinophils in obese male mice fed with long-term HFD, which also exhibited mixed TH17/TH1/TH2 inflammation. Apigenin effectively suppressed this complex inflammation and acted as a regulator of immune homeostasis. Meanwhile, apigenin reduced AHR, inflammatory cell infiltration, airway epithelial cell apoptosis, airway collagen deposition, and lung oxidative stress via the ROS-ASK1-MAPK pathway in an obese asthma mouse model. In vitro, this study found that apigenin altered the binding status of TRAF6 to ASK1, inhibited ASK1 phosphorylation, and protected against ubiquitin-dependent degradation of ASK1, suggesting that ROS-activated ASK1 may be an important target for apigenin to exert anti-inflammatory and anti-apoptotic effects. To further verify the intervention mechanism, this study clarified that apigenin improved cell viability and mitochondrial function and inhibited apoptosis by interfering with the ROS-ASK1-MAPK pathway.

CONCLUSIONS

This study demonstrates for the first time the therapeutic effect of apigenin in chronic obese asthma and further clarifies its potential therapeutic targets. In addition, this study clarifies the specificity of chronic obese asthma and provides new options for its treatment.

Cell-contact-mediated assembly of contractile airway smooth muscle rings

Microtissues in the shape of toroidal rings provide an ideal geometry to better represent the structure and function of the airway smooth muscle present in the small airways, and to better understand diseases such as asthma. Here, polydimethylsiloxane devices consisting of a series of circular channels surrounding central mandrels are used to form microtissues in the shape of toroidal rings by way of the self-aggregation and -assembly of airway smooth muscle cell (ASMC) suspensions. Over time, the ASMCs present in the rings become spindle-shaped and axially align along the ring circumference. Ring strength and elastic modulus increase over 14 d in culture, without significant changes in ring size. Gene expression analysis indicates stable expression of mRNA for extracellular matrix-associated proteins, including collagen I and lamininsα1 andα4 over 21 d in culture. Cells within the rings respond to TGF-β1 treatment, leading to dramatic decreases in ring circumference, with increases in mRNA and protein levels for extracellular matrix and contraction-associated markers. These data demonstrate the utility of ASMC rings as a platform for modeling diseases of the small airways such as asthma.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

An optimal medicinal and edible Chinese herbal formula attenuates particulate matter-induced lung injury through its anti-oxidative, anti-inflammatory and anti-apoptosis activities

Objective

Identifying novel strategies to prevent particulate matter (PM)-induced lung injury is crucial for the reduction of the morbidity of chronic respiratory diseases. The combined intervention represented by herbal formulae for simultaneously targeting multiple pathological processes can provide a more beneficial effect than the single intervention. The aim of this paper is therefore to design a safe and effective medicinal and edible Chinese herbs (MECHs) formula against PM-induced lung injury.

Methods

PM-induced oxidative stress, inflammatory response and apoptosis A549 cell model were used to screen anti-oxidant, anti-inflammatory and anti-apoptotic MECHs, respectively. A network pharmacology method was utilized to rationally design a novel herbal formula. Ultra performance liquid chromatography-mass spectrometer was utilized to assess the quality control of MECHs formula. The excretion of magnetic iron oxide nanospheres of the MECHs formula was estimated in zebrafish. The MECH formula against PM-induced lung injury was investigated with mice experiments.

Results

Five selected herbs were rationally designed to form a new MECH formula, including Citri Exocarpium Rubrum (Juhong), Lablab Semen Album (Baibiandou), Atractylodis Macrocephalae Rhizoma (Baizhu), Mori Folium (Sangye) and Polygonati Odorati Rhizoma (Yuzhu). The formula effectively promoted the magnetic iron oxide nanospheres excretion in zebrafish. The mid/high dose formula significantly prevented PM-induced lung damage in mice by enhancing the activity of SOD and GSH-Px, reducing the MDA and ROS level and attenuating the upregulation of pro-inflammatory cytokine (IL-6, IL-8, IL-1β and TNF-α), down regulating the protein expression of NF-κB, STAT3 and Caspase-3.

Conclusion

Our findings suggest that the effective MECHs formula will become a novel strategy for preventing PM-induced lung injury and provide a paradigm for the development of functional foods using MECHs.

Eosinophilic inflammation: An Appealing Target for Pharmacologic Treatments in Severe Asthma

Severe asthma is characterized by different endotypes driven by complex pathologic mechanisms. In most patients with both allergic and non-allergic asthma, predominant eosinophilic airway inflammation is present. Given the central role of eosinophilic inflammation in the pathophysiology of most cases of severe asthma and considering that severe eosinophilic asthmatic patients respond partially or poorly to corticosteroids, in recent years, research has focused on the development of targeted anti-eosinophil biological therapies; this review will focus on the unique and particular biology of the eosinophil, as well as on the current knowledge about the pathobiology of eosinophilic inflammation in asthmatic airways. Finally, current and prospective anti-eosinophil therapeutic strategies will be discussed, examining the reason why eosinophilic inflammation represents an appealing target for the pharmacological treatment of patients with severe asthma.

Lung Fibrosis and Fibrosis in the Lungs: Is It All about Myofibroblasts?

In the lungs, fibrosis is a growing clinical problem that results in shortness of breath and can end up in respiratory failure. Even though the main fibrotic disease affecting the lung is idiopathic pulmonary fibrosis (IPF), which affects the interstitial space, there are many fibrotic events that have high and dangerous consequences for the lungs. Asthma, chronic obstructive pulmonary disease (COPD), excessive allergies, clearance of infection or COVID-19, all are frequent diseases that show lung fibrosis. In this review, we describe the different kinds of fibrosis and analyse the main types of cells involved-myofibroblasts and other cells, like macrophages-and review the main fibrotic mechanisms. Finally, we analyse present treatments for fibrosis in the lungs and highlight potential targets for anti-fibrotic therapies.

Evaluation of IGF-1, TNF-α, and TGF-β Gene Expression after Oral Vitamin D Supplementation in School-Aged Children with Chronic Bronchial Asthma

BACKGROUND: Airway remodeling in children with bronchial asthma is due to the effect of inflammatory mediators and growth factors on the bronchial epithelium. Vitamin D (VitD) has immunomodulatory effect in many inflammatory diseases as bronchial asthma. The ant-inflammatory and anti-fibrotic role of VitD could prevent or improve air way remodeling in asthmatic patients. AIM: The study investigated the effect of VitD supplementation on the expression of transforming growth factor-beta (TGF-β), tumor necrosis factor-alpha (TNF-α), and insulin growth factor 1(IGF-1) and to correlate them with asthma severity and level of control. METHODS: The serum level of VitD and the mRNA expression of IGF-1, TGF-β, and TNF-α were estimated in 50 patients and 20 healthy controls control subjects using quantitative PCR in real-time. Asthmatic patients with VitD deficiency received VitD supplementation for 2 months followed by remeasurement of serum VitD and the genes expression TGF-β, TNF-α, and IGF-1. RESULT: Pre-intake of VitD and serum level of VitD were lower in all patients than control subjects (p = 0.005). VitD level was directly correlated with IGF-1 mRNA expression, which was indirectly correlated with TGF-β, r = 0.5 and −0.57; p = 0.0001 and 0.002, respectively. After VitD supplementation, the expression of the TGF-β mRNA gene was the only gene that decreased significantly (p = 0.04) together with improved asthma control and spirometric parameters. CONCLUSIONS: VitD supplementation down regulated the gene expression of TGF-β and improved asthma control level, but it did not significantly affect the gene expression of TNF-α and IGF-1.

Emerging Roles of Platelets in Allergic Asthma

Allergic asthma is a complex chronic inflammatory disease of the airways, driven by Th2 immune responses and characterized by eosinophilic pulmonary inflammation, airway hyperresponsiveness, excessive mucus production, and airway remodeling. Overwhelming evidence from studies in animal models and allergic asthmatic patients suggests that platelets are aberrantly activated and recruited to the lungs. It has been established that platelets can interact with other immune cells and secrete various biochemical mediators to promote allergic sensitization and airway inflammatory response, and platelet deficiency may alleviate the pathological features and symptoms of allergic asthma. However, the comprehensive roles of platelets in allergic asthma have not been fully clarified, leaving attempts to treat allergic asthma with antiplatelet agents questionable. In this review, we summarize the role of platelet activation and pulmonary accumulation in allergic asthma; emphasis is placed on the different interactions between platelets with crucial immune cell types and the contribution of platelet-derived mediators in this context. Furthermore, clinical antiplatelet approaches to treat allergic asthma are discussed. This review provides a clearer understanding of the roles of platelets in the pathogenesis of allergic asthma and could be informative in the development of novel strategies for the treatment of allergic asthma.

Pathobiology of Airway Remodeling in Asthma: The Emerging Role of Integrins

Airway remodeling is a complex clinical feature of asthma that involves long-term disruption and modification of airway architecture, which contributes significantly to airway hyperresponsiveness (AHR) and lung function decline. It is characterized by thickening of the airway smooth muscle layer, deposition of a matrix below the airway epithelium, resulting in subepithelial fibrosis, changes within the airway epithelium, leading to disruption of the barrier, and excessive mucous production and angiogenesis within the airway wall. Airway remodeling contributes to stiffer and less compliant airways in asthma and leads to persistent, irreversible airflow obstruction. Current asthma treatments aim to reduce airway inflammation and exacerbations but none are targeted towards airway remodeling. Inhibiting the development of airway remodeling or reversing established remodeling has the potential to dramatically improve symptoms and disease burden in asthmatic patients. Integrins are a family of transmembrane heterodimeric proteins that serve as the primary receptors for extracellular matrix (ECM) components, mediating cell-cell and cell-ECM interactions to initiate intracellular signaling cascades. Cells present within the lungs, including structural and inflammatory cells, express a wide and varying range of integrin heterodimer combinations and permutations. Integrins are emerging as an important regulator of inflammation, repair, remodeling, and fibrosis in the lung, particularly in chronic lung diseases such as asthma. Here, we provide a comprehensive summary of the current state of knowledge on integrins in the asthmatic airway and how these integrins promote the remodeling process, and emphasize their potential involvement in airway disease.

Dysregulated Notch Signaling in the Airway Epithelium of Children with Wheeze

The airway epithelium of children with wheeze is characterized by defective repair that contributes to disease pathobiology. Dysregulation of developmental processes controlled by Notch has been identified in chronic asthma. However, its role in airway epithelial cells of young children with wheeze, particularly during repair, is yet to be determined. We hypothesized that Notch is dysregulated in primary airway epithelial cells (pAEC) of children with wheeze contributing to defective repair. This study investigated transcriptional and protein expression and function of Notch in pAEC isolated from children with and without wheeze. Primary AEC of children with and without wheeze were found to express all known Notch receptors and ligands, although pAEC from children with wheeze expressed significantly lower NOTCH2 (10-fold, p = 0.004) and higher JAG1 (3.5-fold, p = 0.002) mRNA levels. These dysregulations were maintained in vitro and cultures from children with wheeze displayed altered kinetics of both NOTCH2 and JAG1 expression during repair. Following Notch signaling inhibition, pAEC from children without wheeze failed to repair (wound closure rate of 76.9 ± 3.2%). Overexpression of NOTCH2 in pAEC from children with wheeze failed to rescue epithelial repair following wounding. This study illustrates the involvement of the Notch pathway in airway epithelial wound repair in health and disease, where its dysregulation may contribute to asthma development.

Molecular mechanisms of oxidative stress in asthma

The lungs are exposed to reactive oxygen species oxygen (ROS) produced as a result of inhalation of oxygen, as well as smoke and other air pollutants. Cell metabolism and the NADPH oxidases (Nox) generate low levels of intracellular ROS that act as signal transduction mediators by inducing oxidative modifications of histones, enzymes and transcription factors. Redox signalling is also regulated by localised production and sensing of ROS in mitochondria, the endoplasmic reticulum (ER) and inside the nucleus. Intracellular ROS are maintained at low levels through the action of a battery of enzymatic and non-enzymatic antioxidants. Asthma is a heterogeneous airway inflammatory disease with different immune endotypes; these include atopic or non-atopic Th2 type immune response associated with eosinophilia, or a non-Th2 response associated with neutrophilia. Airway remodelling and hyperresponsiveness accompany the inflammatory response in asthma. Over-production of ROS resulting from infiltrating immune cells, particularly eosinophils and neutrophils, and a concomitant impairment of antioxidant responses lead to development of oxidative stress in asthma. Oxidative stress is augmented in severe asthma and during exacerbations, as well as by air pollution and obesity, and causes oxidative damage of tissues promoting airway inflammation and hyperresponsiveness. Furthermore, deregulated Nox activity, mitochondrial dysfunction, ER stress and/or oxidative DNA damage, resulting from exposure to irritants, inflammatory mediators or obesity, may lead to redox-dependent changes in cell signalling. ROS play a central role in airway epithelium-mediated sensing, development of innate and adaptive immune responses, and airway remodelling and hyperresponsiveness. Nonetheless, antioxidant compounds have proven clinically ineffective as therapeutic agents for asthma, partly due to issues with stability and in vivo metabolism of these compounds. The compartmentalised nature of ROS production and sensing, and the role of ROS in homeostatic responses and in the action of corticosteroids and β2-adrenergic receptor agonists, adds another layer of complexity to antioxidant therapy development. Nox inhibitors and mitochondrial-targeted antioxidants are in clinical development for a number of diseases but they have not yet been investigated in asthma. A better understanding of the complex role of ROS in the pathogenesis of asthma will highlight new opportunities for more targeted and effective redox therapies.

Eosinophils as Drivers of Severe Eosinophilic Asthma: Endotypes or Plasticity?

Asthma is now recognized as a heterogeneous disease, encompassing different phenotypes driven by distinct pathophysiological mechanisms called endotypes. Common phenotypes of asthma, referred to as eosinophilic asthma, are characterized by the presence of eosinophilia. Eosinophils are usually considered invariant, terminally differentiated effector cells and have become a primary therapeutic target in severe eosinophilic asthma (SEA) and other eosinophil-associated diseases (EADs). Biological treatments that target eosinophils reveal an unexpectedly complex role of eosinophils in asthma, including in SEA, suggesting that "not all eosinophils are equal". In this review, we address our current understanding of the role of eosinophils in asthma with regard to asthma phenotypes and endotypes. We further address the possibility that different SEA phenotypes may involve differences in eosinophil biology. We discuss how these differences could arise through eosinophil "endotyping", viz. adaptations of eosinophil function imprinted during their development, or through tissue-induced plasticity, viz. local adaptations of eosinophil function through interaction with their lung tissue niches. In doing so, we also discuss opportunities, technical challenges, and open questions that, if addressed, might provide considerable benefits in guiding the choice of the most efficient precision therapies of SEA and, by extension, other EADs.

New Insights on the Role of pentraxin-3 in Allergic Asthma

Pentraxins are soluble pattern recognition receptors that play a major role in regulating innate immune responses. Through their interaction with complement components, Fcγ receptors, and different microbial moieties, Pentraxins cause an amplification of the inflammatory response. Pentraxin-3 is of particular interest since it was identified as a biomarker for several immune-pathological diseases. In allergic asthma, pentraxin-3 is produced by immune and structural cells and is up-regulated by pro-asthmatic cytokines such as TNFα and IL-1β. Strikingly, some recent experimental evidence demonstrated a protective role of pentraxin-3 in chronic airway inflammatory diseases such as allergic asthma. Indeed, reduced pentraxin-3 levels have been associated with neutrophilic inflammation, Th17 immune response, insensitivity to standard therapeutics and a severe form of the disease. In this review, we will summarize the current knowledge of the role of pentraxin-3 in innate immune response and discuss the protective role of pentraxin-3 in allergic asthma.

MicroRNA-21 inhibition attenuates airway inflammation and remodelling by modulating the transforming growth factor β-Smad7 pathway

BACKGROUND/AIMS

Current asthma therapies remain unsatisfactory for controlling airway remodelling in asthma. MicroRNA-21 is a key player in asthma pathogenesis, but the molecular mechanisms underlying its effects on airway remodelling are not completely understood. We investigated the effects of inhibition of microRNA-21 on allergic airway inflammation and remodelling.

METHODS

Female BALB/c mice were divided into four groups: control, ovalbumin-sensitized and -challenged for 3 months, microRNA-negative control-treated ovalbumin-treated, and microRNA-21 inhibitor-treated ovalbumin-treated groups. Parameters related to airway remodelling, cytokine production, airway inflammation, and airway hyperresponsiveness were compared between groups. Human bronchial smooth muscle cells were used in a mechanism study.

RESULTS

In this asthma model, ovalbumin-sensitized and -challenged mice exhibited allergic airway inf lammation and airway remodelling. MicroRNA-21 inhibitor-treated mice had fewer inflammatory cells, lower TH2 cytokine production, and suppressed parameters related to remodelling such as goblet cell hyperplasia, collagen deposition, hydroxyproline content, and expression of smooth muscle actin. Inhibition of microRNA-21 decreased transforming growth factor β1 expression and induced Smad7 expression in lung tissue. In human bronchial smooth muscle cells stimulated with transforming growth factor β1, microRNA-21 inhibition upregulated Smad7 expression and decreased markers of airway remodelling.

CONCLUSION

Inhibition of microRNA-21 had both anti-inflammatory and anti-remodelling effects in this model of ovalbumin-induced chronic asthma. Our data suggest that the microRNA-21-transforming growth factor β1-Smad7 axis modulates the pathogenesis of ovalbumin-induced chronic asthma and in human bronchial smooth muscle cells. MicroRNA-21 inhibitors may be a novel therapeutic target in patients with allergic asthma, especially those with airway remodelling.

Cellular and mitochondrial calcium communication in obstructive lung disorders

Calcium (Ca²⁺) signalling is well known to dictate cellular functioning and fate. In recent years, the accumulation of Ca²⁺ in the mitochondria has emerged as an important factor in Chronic Respiratory Diseases (CRD) such as Asthma and Chronic Obstructive Pulmonary Disease (COPD). Various reports underline an aberrant increase in the intracellular Ca²⁺, leading to mitochondrial ROS generation, and further activation of the apoptotic pathway in these diseases. Mitochondria contribute to Ca²⁺ buffering which in turn regulates mitochondrial metabolism and ATP production. Disruption of this Ca²⁺ balance leads to impaired cellular processes like apoptosis or necrosis and thus contributes to the pathophysiology of airway diseases. This review highlights the key role of cytoplasmic and mitochondrial Ca²⁺ signalling in regulating CRD, such as asthma and COPD. A better understanding of the dysregulation of mitochondrial Ca²⁺ homeostasis in these diseases could provide cues for the development of advanced therapeutic interventions in these diseases.

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.

Epithelial-Mesenchymal Transition in Atopy: A Mini-Review

Atopic diseases, particularly atopic dermatitis (AD), asthma, and allergic rhinitis (AR) share a common pathogenesis of inflammation and barrier dysfunction. Epithelial to mesenchymal transition (EMT) is a process where epithelial cells take on a migratory mesenchymal phenotype and is essential for normal tissue repair and signal through multiple inflammatory pathways. However, while links between EMT and both asthma and AR have been demonstrated, as we outline in this mini-review, the literature investigating AD and EMT is far less well-elucidated. Furthermore, current studies on EMT and atopy are mostly animal models or ex vivo studies on cell cultures or tissue biopsies. The literature covered in this mini-review on EMT-related barrier dysfunction as a contributor to AD as well as the related (perhaps resultant) atopic diseases indicates a potential for therapeutic targeting and carry treatment implications for topical steroid use and environmental exposure assessments. Further research, particularly in vivo studies, may greatly advance the field and translate into benefit for patients and families.

The Airway Epithelium-A Central Player in Asthma Pathogenesis

Asthma is a chronic inflammatory airway disease characterized by variable airflow obstruction in response to a wide range of exogenous stimuli. The airway epithelium is the first line of defense and plays an important role in initiating host defense and controlling immune responses. Indeed, increasing evidence indicates a range of abnormalities in various aspects of epithelial barrier function in asthma. A central part of this impairment is a disruption of the airway epithelial layer, allowing inhaled substances to pass more easily into the submucosa where they may interact with immune cells. Furthermore, many of the identified susceptibility genes for asthma are expressed in the airway epithelium. This review focuses on the biology of the airway epithelium in health and its pathobiology in asthma. We will specifically discuss external triggers such as allergens, viruses and alarmins and the effect of type 2 inflammatory responses on airway epithelial function in asthma. We will also discuss epigenetic mechanisms responding to external stimuli on the level of transcriptional and posttranscriptional regulation of gene expression, as well the airway epithelium as a potential treatment target in asthma.

Bidirectional interaction of airway epithelial remodeling and inflammation in asthma

Asthma is a chronic disease of the airways that has long been viewed predominately as an inflammatory condition. Accordingly, current therapeutic interventions focus primarily on resolving inflammation. However, the mainstay of asthma therapy neither fully improves lung function nor prevents disease exacerbations, suggesting involvement of other factors. An emerging concept now holds that airway remodeling, another major pathological feature of asthma, is as important as inflammation in asthma pathogenesis. Structural changes associated with asthma include disrupted epithelial integrity, subepithelial fibrosis, goblet cell hyperplasia/metaplasia, smooth muscle hypertrophy/hyperplasia, and enhanced vascularity. These alterations are hypothesized to contribute to airway hyperresponsiveness, airway obstruction, airflow limitation, and progressive decline of lung function in asthmatic individuals. Consequently, targeting inflammation alone does not suffice to provide optimal clinical benefits. Here we review asthmatic airway remodeling, focusing on airway epithelium, which is critical to maintaining a healthy respiratory system, and is the primary defense against inhaled irritants. In asthma, airway epithelium is both a mediator and target of inflammation, manifesting remodeling and resulting obstruction among its downstream effects. We also highlight the potential benefits of therapeutically targeting airway structural alterations. Since pathological tissue remodeling is likewise observed in other injury- and inflammation-prone tissues and organs, our discussion may have implications beyond asthma and lung disease.

Enhanced asthma-related fibroblast to myofibroblast transition is the result of profibrotic TGF-β/Smad2/3 pathway intensification and antifibrotic TGF-β/Smad1/5/(8)9 pathway impairment

Airway remodelling with subepithelial fibrosis, which abolishes the physiological functions of the bronchial wall, is a major issue in bronchial asthma. Human bronchial fibroblasts (HBFs) derived from patients diagnosed with asthma display in vitro predestination towards TGF-β₁-induced fibroblast-to-myofibroblast transition (FMT), a key event in subepithelial fibrosis. As commonly used anti-asthmatic drugs do not reverse the structural changes of the airways, and the molecular mechanism of enhanced asthma-related TGF-β₁-induced FMT is poorly understood, we investigated the balance between the profibrotic TGF-β/Smad2/3 and the antifibrotic TGF-β/Smad1/5/9 signalling pathways and its role in the myofibroblast formation of HBF populations derived from asthmatic and non-asthmatic donors. Our findings showed for the first time that TGF-β-induced activation of the profibrotic Smad2/3 signalling pathway was enhanced, but the activation of the antifibrotic Smad1/5/(8)9 pathway by TGF-β₁ was significantly diminished in fibroblasts from asthmatic donors compared to those from their healthy counterparts. The impairment of the antifibrotic TGF-β/Smad1/5/(8)9 pathway in HBFs derived from asthmatic donors was correlated with enhanced FMT. Furthermore, we showed that Smad1 silencing in HBFs from non-asthmatic donors increased the FMT potential in these cells. Additionally, we demonstrated that activation of antifibrotic Smad signalling via BMP7 or isoliquiritigenin [a small-molecule activator of the TGF-β/Smad1/5/(8)9 pathway] administration prevents FMT in HBFs from asthmatic donors through downregulation of profibrotic genes, e.g., α-SMA and fibronectin. Our data suggest that influencing the balance between the antifibrotic and profibrotic TGF-β/Smad signalling pathways using BMP7-mimetic compounds presents an unprecedented opportunity to inhibit subepithelial fibrosis during airway remodelling in asthma.

Leonurus sibiricus root extracts decrease airway remodeling markers expression in fibroblasts

Bronchial asthma is believed to be provoked by the interaction between airway inflammation and remodeling. Airway remodeling is a complex and poorly understood process, and controlling it appears key for halting the progression of asthma and other obstructive lung diseases. Plants synthesize a number of valuable compounds as constitutive products and as secondary metabolites, many of which have curative properties. The aim of this study was to evaluate the anti-remodeling properties of extracts from transformed and transgenic Leonurus sibiricus roots with transformed L. sibiricus roots extract with transcriptional factor AtPAP1 overexpression (AtPAP1). Two fibroblast cell lines, Wistar Institute-38 (WI-38) and human fetal lung fibroblast (HFL1), were incubated with extracts from transformed L. sibiricus roots (TR) and roots with transcriptional factor AtPAP1 over-expression (AtPAP1 TR). Additionally, remodeling conditions were induced in the cultures with rhinovirus 16 (HRV16). The expressions of metalloproteinase 9 (MMP)-9, tissue inhibitor of metalloproteinases 1 (TIMP-1), arginase I and transforming growth factor (TGF)-β were determined by quantitative polymerase chain reaction (qPCR) and immunoblotting methods. AtPAP1 TR decreased arginase I and MMP-9 expression with no effect on TIMP-1 or TGF-β mRNA expression. This extract also inhibited HRV16-induced expression of arginase I, MMP-9 and TGF-β in both cell lines (P < 0·05) Our study shows for the first time to our knowledge, that transformed AtPAP1 TR extract from L. sibiricus root may affect the remodeling process. Its effect can be attributed an increased amount of phenolic acids such as: chlorogenic acid, caffeic acid or ferulic acid and demonstrates the value of biotechnology in medicinal research.

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.

Regulatory T Cells in Bioactive Peptides-Induced Oral Tolerance; a Two-Edged Sword Related to the Risk of Chronic Diseases: A Systematic Review

This systematic review assesses the literature regarding beneficial and potential detrimental effects of bioactive peptides (BPs), focusing on evidence of regulatory T cells (T-regs) mediated oral tolerance (OT), collagen hydrolysate (CH) supplementation in osteoarthritis (OA) and the association of T-regs with chronic disease. The systematic search was done for articles published from inception to April 2019 using the PubMed and Scopus databases. About 3081 papers were identified by three different search strategies and screened against inclusion criteria which resulted in the inclusion of 22 articles. From the included articles, 12 papers were related to treatment of different disease in vivo by oral administration of BPs, six articles evaluated the effects of CH supplementation, as a rich source of BPs, on OA pain-relief and four observational studies assessed the association of circulating T-regs and risk of cancer and cardiovascular disease (CVD). The evidence obtained from first search strategy, indicated that oral administration of BPs improve clinical manifestations of animal models of allergy, arthritis, atherosclerosis, ulcerative colitis and allograft rejection by T-regs expansion; while, observational studies showed that although higher levels of circulating T-regs reduced risk of CVD and allergy, but, increased risk of solid cancers.

MiRNA-620 promotes TGF-β1-induced proliferation of airway smooth muscle cell through controlling PTEN/AKT signaling pathway

Asthma is an inflammatory syndrome characterized by airway hyperresponsiveness, bronchial inflammation, and airway remodeling. The hypertrophy and hyperplasia of airway smooth muscle cells (ASMCs) are hallmarks of bronchial remodeling in asthma. In this study, the regulatory effects of microRNA-620 (miR-620) on ASMC proliferation and apoptosis in response to transforming growth factor β1 (TGF-β1) stimulation was investigated. The expression of miR-620 was significantly upregulated in TGF-β1-treated ASMCs compared with vehicle-treated cells. Downregulation of miR-620 suppressed the proliferation and increased apoptosis in TGF-β1-stimulated ASMCs. Phosphatase and tensin homolog (PTEN) was predicted and confirmed as a downstream target of miR-620. PTEN was upregulated in miR-620-inhibitor transfected ASMCs, but decreased in cells delivered with miR-620 mimics. Moreover, knocking down miR-620 alone efficiently reduced the phosphorylation of protein kinase B (AKT), decreased TGF-β1-induced proliferation and promoted apoptosis in ASMCs, whereas downregulation of PTEN in miR-620 inhibitor-transfected cells restored the activation of AKT, increased TGF-β1-triggered proliferation, and partially inhibited ASMC apoptosis. Taken together, the present study provided evidence that miR-620 increased TGF-β1-mediated proliferation and suppressed apoptosis in ASMCs via the regulation of PTEN and AKT expression. These findings suggest that miR-620/PTEN/AKT axis may be considered as a therapeutic target for asthma treatment.

Regulation of Human Innate Lymphoid Cells in the Context of Mucosal Inflammation

Since their identification as a unique cell population, innate lymphoid cells (ILCs) have revolutionized our understanding of immune responses, leaving their impact on multiple inflammatory and fibrotic pathologies without doubt. Thus, a tightly controlled regulation of local ILC numbers and their activity is of crucial importance. Even though this has been extensively studied in murine ILCs in the last few years, our knowledge of human ILCs is still lagging behind. Our review article will therefore summarize recent insights into the function of human ILCs and will particularly focus on their regulation under inflammatory conditions. The quality and intensity of ILC involvement into local immune responses at mucosal sites of the human body can potentially be modulated via three different axes: (1) activation of tissue-resident mature ILCs, (2) plasticity and local transdifferentiation of specific ILC subsets, and (3) tissue migration and accumulation of peripheral ILCs. Despite a still ongoing scientific effort in this field, already existing data on the fate of human ILCs under different pathologic conditions clearly indicate that all three of these mechanisms are of relevance for the clinical course of chronic inflammatory and autoimmune diseases and might likewise provide new target structures for future therapeutic strategies.

Aberrant cell migration contributes to defective airway epithelial repair in childhood wheeze

Abnormal wound repair has been observed in the airway epithelium of patients with chronic respiratory diseases, including asthma. Therapies focusing on repairing vulnerable airways, particularly in early life, present a potentially novel treatment strategy. We report defective lower airway epithelial cell repair to strongly associate with common pre-school-aged and school-aged wheezing phenotypes, characterized by aberrant migration patterns and reduced integrin α5β1 expression. Next generation sequencing identified the PI3K/Akt pathway as the top upstream transcriptional regulator of integrin α5β1, where Akt activation enhanced repair and integrin α5β1 expression in primary cultures from children with wheeze. Conversely, inhibition of PI3K/Akt signaling in primary cultures from children without wheeze reduced α5β1 expression and attenuated repair. Importantly, the FDA-approved drug celecoxib - and its non-COX2-inhibiting analogue, dimethyl-celecoxib - stimulated the PI3K/Akt-integrin α5β1 axis and restored airway epithelial repair in cells from children with wheeze. When compared with published clinical data sets, the identified transcriptomic signature was also associated with viral-induced wheeze exacerbations highlighting the clinical potential of such therapy. Collectively, these results identify airway epithelial restitution via targeting the PI3K-integrin α5β1 axis as a potentially novel therapeutic avenue for childhood wheeze and asthma. We propose that the next step in the therapeutic development process should be a proof-of-concept clinical trial, since relevant animal models to test the crucial underlying premise are unavailable.

SMAD Signaling Restricts Mucous Cell Differentiation in Human Airway Epithelium

Mucin-secreting goblet cell metaplasia and hyperplasia (GCMH) is a common pathological phenotype in many human respiratory diseases, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, primary ciliary dyskinesia, and infections. A better understanding of how goblet cell quantities or proportions in the airway epithelium are regulated may provide novel therapeutic targets to mitigate GCMH in these devastating diseases. We identify canonical SMAD signaling as the principal pathway restricting goblet cell differentiation in human airway epithelium. Differentiated goblet cells express low levels of phosphorylated SMAD. Accordingly, inhibition of SMAD signaling markedly amplifies GCMH induced by mucous mediators. In contrast, SMAD signaling activation impedes goblet cell generation and accelerates the resolution of preexisting GCMH. SMAD signaling inhibition can override the suppressive effects imposed by a GABAergic receptor inhibitor, suggesting the GABAergic pathway likely operates through inhibition of SMAD signaling in regulating mucous differentiation. Collectively, our data demonstrate that SMAD signaling plays a determining role in mucous cell differentiation, and thus raise the possibility that dysregulation of this pathway contributes to respiratory pathophysiology during airway inflammation and pulmonary diseases. In addition, our study also highlights the potential for SMAD modulation as a therapeutic target in mitigating GCMH.

Icariside II attenuates eosinophils-induced airway inflammation and remodeling via inactivation of NF-κB and STAT3 in an asthma mouse model

Asthma is a chronic inflammatory airway disease. Icariside II has been reported to exert anti-inflammatory effect in multiple human diseases. The present study aimed to investigate the effects and mechanisms of Icariside II on airway inflammation and remodeling in asthma. We established an asthma mouse model with ovalbumin (OVA) immunization. Histological analysis using H&E, PAS and Masson staining showed that administration of Icariside II attenuated OVA-induced airway inflammation and remodeling. Icariside II reduced the numbers of total white blood cells and eosinophils in bronchoalveolar lavage fluid (BALF). The levels of interleukin (IL)-4, IL-5, IL-13 and transforming growth factor (TGF)-β1 in peripheral blood and the expression of α-smooth muscle actin (α-SMA), connective tissue growth factor (CTGF), eotaxin-1, CC-chemokine receptor-3 (CCR-3), Toll-like receptor (TLR)-2 and TLR-4 were significantly down-regulated in lung tissues of OVA-induced mouse model. These results suggested that Icariside II inhibited eosinophil activation and thus decreased eosinophils-induced airway inflammation and remodeling in asthma. Moreover, Icariside II suppressed TGF-β1-induced cell proliferation, migration, and CTGF expression in airway smooth muscle cells (ASMCs). In both OVA-induced mouse model of asthma and TGF-β1-induced ASMCs, Icariside II decreased IκBα degradation, nuclear translocation of NF-κB p65 and STAT3 phophorylation, indicating an inactivation of NF-κB and STAT3 in the presence of Icariside II. Therefore, we demonstrate that Icariside II attenuates eosinophils-induced airway inflammation and remodeling in asthmatic mice and inhibits TGF-β1-induced cell proliferation and migration in ASMCs via suppressing NF-κB and STAT3 signalings.

TGF-β3 Induces Autophagic Activity by Increasing ROS Generation in a NOX4-Dependent Pathway

Higher concentrations of reactive oxygen species (ROS) have been associated with epithelial cell damage, cell shedding, and airway hyperresponsiveness. Previous studies have indicated that transforming growth factor-beta (TGF-β) mediates ROS production and NADPH oxidase (NOX) activity. In our previous study, we also observed that TGF-β3 increases mucus secretion in airway epithelial cells in an autophagy-dependent fashion. Although it is well known that the relationship between ROS and autophagy is cell context-dependent, the exact mechanism of action remains unclear. The following study examined whether ROS act as upstream of autophagy activation in response to TGF-β3 induction. Using an allergic inflammation mouse model induced by house dust mite (HDM), we observed elevated lung amounts of TGF-β3 accompanied by increased ROS levels. And we found that ROS levels were elevated and NOX4 expression was increased in TGF-β3-induced epithelial cells, while the lack of NOX4 in the epithelial cells could reduce ROS generation and autophagy-dependent MUC5AC expression treated with TGF-β3. Furthermore, our studies demonstrated that the Smad2/3 pathway was involved in TGF-β3-induced ROS generation by promoting NOX4 expression. The inhibition of ROS generation by N-Acetyl-L-cysteine (NAC) resulted in a decrease in mucus expression and autophagy activity in vivo as well as in vitro. Finally, TGF-β3-neutralizing antibody significantly reduced the ROS generation, mucus expression, and autophagy activity and also decreased the phosphorylation of Smad2 and Smad3. Taken together, the obtained results revealed that persistent TGF-β3 activation increased ROS levels in a NOX4-dependent pathway and subsequently induced autophagy as well as MUC5AC expression in the epithelial cells.

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.

Exhaled TGF-β1 levels before and after an exercise challenge in asthmatic and healthy children, and during exacerbation

BACKGROUND

There is conflicting data regarding the role of transforming growth factor-β1 (TGF-β1) in the pathogenesis of airway hyper-reactivity and asthma exacerbation.

OBJECTIVE

To investigate the role of exhaled-TGF-β1 in exercise-induced bronchospasm (EIB) in asthmatic and nonasthmatic healthy children, and in asthma exacerbation and asthma control.

METHODS

The exhaled-TGF-β1 levels of 56 stable asthmatic children and 15 nonasthmatic healthy children were evaluated before and 30 min after an exercise challenge. The exhaled-TGF-β1 levels of 20 additional children with asthma exacerbation were evaluated.

RESULTS

While no significant difference in the exhaled-TGF-β1 levels was found at the baseline, exhaled-TGF-β1 levels after the exercise challenge were significantly higher in the non-EIB (n = 31) asthmatics when compared to the asthmatic children with EIB (n = 25) (p = 0.04). Although there was a statistically significant increase in the concentration of the exhaled-TGF-β1 after the exercise challenge in the non-EIB asthmatics (p = 0.008), the concentration of the TGF-β1 was not increased after the exercise challenge in EIB + asthmatics. The exhaled-TGF-β1 was significantly correlated with the ACT score (p = 0.01, r = 0.49) and the baseline FEV₁ level (p = 0.02, r = 0.35). The exhaled-TGF-β1 levels were significantly higher in the stable asthmatic children when compared to the nonasthmatic children (p < 0.0001). There was no significant difference in exhaled-TGF-β1 levels after the exercise challenge in the nonasthmatics. The exhaled-TGF-β1 levels were significantly lower in those children with asthma exacerbation when compared to the stable asthmatic children (p = 0.0003).

CONCLUSION

Our results suggest that TGF-β1 may play a role in suppressing airway reactivity and its deficiency is associated with asthma exacerbation.

Neutrophils from severe asthmatic patients induce epithelial to mesenchymal transition in healthy bronchial epithelial cells

BACKGROUND

Asthma is a heterogenous disease characterized by chronic inflammation and airway remodeling. An increase in the severity of airway remodeling is associated with a more severe form of asthma. There is increasing interest in the epithelial to mesenchymal transition process and mechanisms involved in the differentiation and repair of the airway epithelium, especially as they apply to severe asthma. Growing evidence suggests that Epithelial-Mesenchymal transition (EMT) could contribute to airway remodeling and fibrosis in asthma. Severe asthmatic patients with remodeled airways have a neutrophil driven inflammation. Neutrophils are an important source of TGF-β1, which plays a role in recruitment and activation of inflammatory cells, extracellular matrix (ECM) production and fibrosis development, and is a potent inducer of EMT.

OBJECTIVE

As there is little data examining the contribution of neutrophils and/or their mediators to the induction of EMT in airway epithelial cells, the objective of this study was to better understand the potential role of neutrophils in severe asthma in regards to EMT.

METHODS

We used an in vitro system to investigate the neutrophil-epithelial cell interaction. We obtained peripheral blood neutrophils from severe asthmatic patients and control subjects and examined for their ability to induce EMT in primary airway epithelial cells.

RESULTS

Our data indicate that neutrophils from severe asthmatic patients induce changes in morphology and EMT marker expression in bronchial epithelial cells consistent with the EMT process when co-cultured. TGF-β1 levels in the culture medium of severe asthmatic patients were increased compared to that from co-cultures of non-asthmatic neutrophils and epithelial cells.

CONCLUSIONS AND CLINICAL RELEVANCE

As an inducer of EMT and an important source of TGF-β1, neutrophils may play a significant role in the development of airway remodeling and fibrosis in severe asthmatic airways.

Crosstalk Between Signaling Pathways Involved in the Regulation of Airway Smooth Muscle Cell Hyperplasia

Increased ASM mass, primarily due to ASM hyperplasia, has been recognized as a hallmark of airway remodeling in asthma. Increased ASM mass is the major contributor to the airway narrowing, thus worsening the bronchoconstriction in response to stimuli. Inflammatory mediators and growth factors released during inflammation induce increased ASM mass surrounding airway wall via increased ASM proliferation, diminished ASM apoptosis and increased ASM migration. Several major pathways, such as MAPKs, PI3K/AKT, JAK2/STAT3 and Rho kinase, have been reported to regulate these cellular activities in ASM and were reported to be interrelated at certain points. This article aims to provide an overview of the signaling pathways/molecules involved in ASM hyperplasia as well as the mapping of the interplay/crosstalk between these major pathways in mediating ASM hyperplasia. A more comprehensive understanding of the complexity of cellular signaling in ASM cells will enable more specific and safer drug development in the control of asthma.

Advanced Molecular Knowledge of Therapeutic Drugs and Natural Products Focusing on Inflammatory Cytokines in Asthma

Asthma is a common respiratory disease worldwide. Cytokines play a crucial role in the immune system and the inflammatory response to asthma. Abnormal cytokine expression may lead to the development of asthma, which may contribute to pathologies of this disease. As cytokines exhibit pleiotropy and redundancy characteristics, we summarized them according to their biologic activity in asthma development. We classified cytokines in three stages as follows: Group 1 cytokines for the epithelial environment stage, Group 2 cytokines for the Th2 polarization stage, and Group 3 cytokines for the tissue damage stage. The recent cytokine-targeting therapy for clinical use (anti-cytokine antibody/anti-cytokine receptor antibody) and traditional medicinal herbs (pure compounds, single herb, or natural formula) have been discussed in this review. Studies of the Group 2 anti-cytokine/anti-cytokine receptor therapies are more prominent than the studies of the other two groups. Anti-cytokine antibodies/anti-cytokine receptor antibodies for clinical use can be applied for patients who did not respond to standard treatments. For traditional medicinal herbs, anti-asthmatic bioactive compounds derived from medicinal herbs can be divided into five classes: alkaloids, flavonoids, glycosides, polyphenols, and terpenoids. However, the exact pathways targeted by these natural compounds need to be clarified. Using relevant knowledge to develop more comprehensive strategies may provide appropriate treatment for patients with asthma in the future.

Oral exposure to cadmium and mercury alone and in combination causes damage to the lung tissue of Sprague-Dawley rats

Environmental presence and human exposure to heavy metals in air and cigarette smoke has led to a worldwide increase in respiratory disease. The effects of oral exposure to heavy metals in liver and kidney structure and function have been widely investigated and the respiratory system as a target is often overlooked. The aim of the study was to investigate the possible structural changes in the lung tissue of Sprague-Dawley rats after oral exposure for 28 days to cadmium (Cd) and mercury (Hg), alone and in combination at 1000 times the World Health Organization's limit for each metal in drinking water. Following exposure, the general morphology of the bronchiole and lungs as well as collagen and elastin distribution was evaluated using histological techniques and transmission electron microscopy. In the lungs, structural changes to the alveoli included collapsed alveolar spaces, presence of inflammatory cells and thickening of the alveolar walls. In addition, exposure to Cd and Hg caused degeneration of the alveolar structures resulting in confluent alveoli. Changes in bronchiole morphology included an increase in smooth muscle mass with luminal epithelium degeneration, detachment and aggregation. Prominent bronchiole-associated lymphoid tissue was present in the group exposed to Cd and Hg. Ultrastructural examination confirmed the presence of fibrosis where in the Cd exposed group, collagen fibrils arrangement was dense, while in the Hg exposed group, additional prominent elastin was present. This study identified the lungs as target of heavy metals toxicity following oral exposure resulting in cellular damage, inflammation and fibrosis and increased risk of respiratory disease where Hg showed the greatest fibrotic effect, which was further, aggravated in combination with Cd.

Genetic evidence for the role of transforming growth factor-β in atopic phenotypes

New evidence in humans and mice supports a role for transforming growth factor-β (TGF-β) in the initiation and effector phases of allergic disease, as well as in consequent tissue dysfunction. This pleiotropic cytokine can affect T cell activation and differentiation and B cell immunoglobulin class switching following initial encounter with an allergen. TGF-β can also act on mast cells during an acute allergic episode to modulate the strength of the response, in addition to driving tissue remodeling following damage caused by an allergic attack. Accordingly, genetic disorders leading to altered TGF-β signaling can result in increased rates of allergic disease.

Molecular changes during TGFβ-mediated lung fibroblast-myofibroblast differentiation: implication for glucocorticoid resistance

Airway remodeling is an important process in response to repetitive inflammatory-mediated airway wall injuries. This is characterized by profound changes and reorganizations at the cellular and molecular levels of the lung tissue. It is of particular importance to understand the mechanisms involved in airway remodeling, as this is strongly associated with severe asthma leading to devastating airway dysfunction. In this study, we have investigated the transforming growth factor-β (TGFβ, a proinflammatory mediator)-activated fibroblast to myofibroblast transdifferentiation pathway, which plays a key role in asthma-related airway remodeling. We show that TGFβ induces fibroblast to myofibroblast transdifferentiation by the expression of αSMA, a specific myofibroblast marker. Furthermore, Smad2/Smad3 gene and protein expression patterns are different between fibroblasts and myofibroblasts. Such a change in expression patterns reveals an important role of these proteins in the cellular phenotype as well as their regulation by TGFβ during cellular transdifferentiation. Interestingly, our data show a myofibroblastic TGFβ-mediated increase in glucocorticoid receptor (GR) expression and a preferential localization of GR in the nucleus, compared to in fibroblasts. Furthermore, the GRβ (nonfunctional GR isoform) is increased relative to GRα (functional isoform) in myofibroblasts. These results are interesting as they support the idea of a GRβ-mediated glucocorticoid resistance observed in the severe asthmatic population. All together, we provide evidence that key players are involved in the TGFβ-mediated fibroblast to myofibroblast transdifferentiation pathway in a human lung fibroblast cell line. These players could be the targets of new treatments to limit airway remodeling and reverse glucocorticoid resistance in severe asthma.

IRAK-M Associates with Susceptibility to Adult-Onset Asthma and Promotes Chronic Airway Inflammation

IL-1R-associated kinase (IRAK)-M regulates lung immunity during asthmatic airway inflammation. However, the regulatory effect of IRAK-M differs when airway inflammation persists. A positive association between IRAK-M polymorphisms with childhood asthma has been reported. In this study, we investigated the role of IRAK-M in the susceptibility to adult-onset asthma and in chronic airway inflammation using an animal model. Through genetic analysis of IRAK-M polymorphisms in a cohort of adult-onset asthma patients of Chinese Han ethnicity, we identified two IRAK-M single nucleotide polymorphisms, rs1624395 and rs1370128, genetically associated with adult-onset asthma. Functionally, the top-associated rs1624395, with an enhanced affinity to the transcription factor c-Jun, was associated with a higher expression of IRAK-M mRNA in blood monocytes. In contrast to the protective effect of IRAK-M in acute asthmatic inflammation, we found a provoking impact of IRAK-M on chronic asthmatic inflammation. Following chronic OVA stimulation, IRAK-M knockout (KO) mice presented with significantly less inflammatory cells, a lower Th2 cytokine level, a higher IFN-γ concentration, and increased percentage of Th1 cells in the lung tissue than wild type mice. Moreover, lung dendritic cells (DC) from OVA-treated IRAK-M KO mice expressed a higher percentage of costimulatory molecules PD-L1 and PD-L2. Mechanistically, in vitro TLR ligation led to a greater IFN-γ production by IRAK-M KO DCs than wild type DCs. These findings demonstrated a distinctive role of IRAK-M in maintaining chronic Th2 airway inflammation via inhibiting the DC-mediated Th1 activation and indicated a complex role for IRAK-M in the initiation and progression of experimental allergic asthma.

Surfactant protein D alleviates eosinophil-mediated airway inflammation and remodeling in patients with aspirin-exacerbated respiratory disease

BACKGROUND

Surfactant protein D (SPD) is a member of the collectin family that lines the airway epithelial cells with host defense. However, the role of SPD in the pathogenesis of aspirin-exacerbated respiratory disease (AERD) is still unclear.

METHODS

The serum SPD level was measured in patients with AERD (n = 336), those with aspirin-tolerant asthma (ATA, n = 442), and healthy controls (HC, n = 104). Polymorphisms of SFTPD in the study subjects were analyzed. The effect of LTE4 on SPD production through eosinophil infiltration was investigated in BALB/c mice. The protective function of SPD against eosinophils inducing inflammation and remodeling was assessed in vitro/vivo. The potential efficacy of nintedanib against airway remodeling through the production of SPD was evaluated.

RESULTS

The serum SPD level was significantly lower (P < .001) in AERD compared with ATA patients, and negatively correlated with fall in FEV₁ (%) after lysine-aspirin bronchoprovocation test and/or the urinary LTE4 level. In addition, polymorphism of SFTPD at rs721917 was significantly different in the study subjects (odds ratio, 1.310; 95% confidence intervals, 2.124-3.446; P = .002). LTE4-exposed mice showed an increased eosinophil count with a decreased SPD level in bronchoalveolar lavage fluid. Eosinophils increased α-smooth muscle actin expression in airway epithelial cells, which was attenuated by SPD treatment. Furthermore, nintedanib protected the airway epithelial cells against eosinophils by enhancing the production of SPD.

CONCLUSION

The decreased level of SPD in AERD was associated with airway inflammation/remodeling under the eosinophilic condition, suggesting that modulation of SPD may provide a potential benefit in AERD.