Overexpression of Smad2 drives house dust mite-mediated airway remodeling and airway hyperresponsiveness via activin and IL-25

The integrin receptor beta7 subunit mediates airway remodeling and hyperresponsiveness in allergen exposed mice

BACKGROUND

Fibroblast differentiation to a myofibroblast phenotype is a feature of airway remodeling in asthma. Lung fibroblasts express the integrin receptor α4β7 and fibronectin induces myofibroblast differentiation via this receptor.

OBJECTIVES

To investigate the role of the β7 integrin receptor subunit and α4β7 integrin complex in airway remodeling and airway hyperresponsiveness (AHR) in a murine model of chronic allergen exposure.

METHODS

C57BL/6 wild type (WT) and β7 integrin null mice (β7 -/-) were sensitized (days 1,10) and challenged with ovalbumin (OVA) three times a week for one or 4 weeks. Similar experiments were performed with WT mice in the presence or absence of α4β7 blocking antibodies. Bronchoalveolar (BAL) cell counts, AHR, histological evaluation, soluble collagen content, Transforming growth factor-β (TGFβ) and Interleukin-13 (IL13) were measured. Phenotype of fibroblasts cultured from WT and β7 -/- saline (SAL) and OVA treated mice was evaluated.

RESULTS

Eosinophil numbers were similar in WT vs β7-/- mice. Prolonged OVA exposure in β7-/- mice was associated with reduced AHR, lung collagen content, peribronchial smooth muscle, lung tissue TGFβ and IL13 expression as compared to WT. Similar findings were observed in WT mice treated with α4β7 blocking antibodies. Fibroblast migration was enhanced in response to OVA in WT but not β7 -/- fibroblasts. α-SMA and fibronectin expression were reduced in β7-/- fibroblasts relative to WT.

CONCLUSIONS

The β7 integrin subunit and the α4β7 integrin complex modulate AHR and airway remodeling in a murine model of allergen exposure. This effect is, at least in part, explained by inhibition of fibroblast activation and is independent of eosinophilic inflammation.

Evaluation of 6-PPD quinone toxicity on lung of male BALB/c mice by quantitative proteomics

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ), a transformation product of tyre-derived 6-PPD, has been frequently detected in different environments. After 6-PPDQ exposure, we here aimed to examine dynamic lung bioaccumulation, lung injury, and the underlying molecular basis in male BALB/c mice. After single injection at concentration of 4 mg/kg, 6-PPDQ remained in lung up to day 28, and higher level of 6-PPDQ bioaccumulation in lung was observed after repeated injection. Severe inflammation was observed in lung after both single and repeated 6-PPDQ injection as indicated by changes of inflammatory cytokines (TNF-α, IL-6 and IL-10). Sirius red staining and hydroxyproline content analysis indicated that repeated rather than single 6-PPDQ injection induced fibrosis in lung. Repeated 6-PPDQ injection also severely impaired lung function in mice by influencing chord compliance (Cchord) and enhanced pause (Penh). Proteomes analysis was further carried out to identify molecular targets of 6-PPDQ after repeated injection, which was confirmed by transcriptional expression analysis and immunohistochemistry staining. Alterations in Ripk1, Fadd, Il-6st, and Il-16 expressions were identified to be associated with inflammation induction of lung after repeated 6-PPDQ injection. Alteration in Smad2 expression was identified to be associated with fibrosis formation in lung of 6-PPDQ exposed mice. Therefore, long-term and repeated 6-PPDQ exposure potentially resulted in inflammation and fibrosis in lung by affecting certain molecular signals in mammals. Our results suggested several aspects of lung injury caused by 6-PPDQ and provide the underlying molecular basis. These observations implied the possible risks of long-term 6-PPDQ exposure to human health.

Activin A levels are raised during human tuberculosis and blockade of the activin signaling axis influences murine responses to M. tuberculosis infection

Activin A strongly influences immune responses; yet, few studies have examined its role in infectious diseases. We measured serum activin A levels in two independent tuberculosis (TB) patient cohorts and in patients with pneumonia and sarcoidosis. Serum activin A levels were increased in TB patients compared to healthy controls, including those with positive tuberculin skin tests, and paralleled severity of disease, assessed by X-ray scores. In pneumonia patients, serum activin A levels were also raised, but in sarcoidosis patients, levels were lower. To determine whether blockade of the activin A signaling axis could play a functional role in TB, we harnessed a soluble activin type IIB receptor fused to human IgG1 Fc, ActRIIB-Fc, as a ligand trap in a murine TB model. The administration of ActRIIB-Fc to Mycobacterium tuberculosis-infected mice resulted in decreased bacterial loads and increased numbers of CD4 effector T cells and tissue-resident memory T cells in the lung. Increased frequencies of tissue-resident memory T cells corresponded with downregulated T-bet expression in lung CD4 and CD8 T cells. Altogether, the results suggest a disease-exacerbating role of ActRIIB signaling pathways. Serum activin A may be useful as a biomarker for diagnostic triage of active TB or monitoring of anti-tuberculosis therapy.

IMPORTANCE

Tuberculosis remains the leading cause of death by a bacterial pathogen. The etiologic agent of tuberculosis, Mycobacterium tuberculosis, can remain dormant in the infected host for years before causing disease. Significant effort has been made to identify biomarkers that can discriminate between latently infected and actively diseased individuals. We found that serum levels of the cytokine activin A were associated with increased lung pathology and could discriminate between active tuberculosis and tuberculin skin-test-positive healthy controls. Activin A signals through the ActRIIB receptor, which can be blocked by administration of the ligand trap ActRIIB-Fc, a soluble activin type IIB receptor fused to human IgG1 Fc. In a murine model of tuberculosis, we found that ActRIIB-Fc treatment reduced mycobacterial loads. Strikingly, ActRIIB-Fc treatment significantly increased the number of tissue-resident memory T cells. These results suggest a role for ActRIIB signaling pathways in host responses to Mycobacterium tuberculosis and activin A as a biomarker of ongoing disease.

Lignosus rhinocerotis extract ameliorates airway inflammation and remodelling via attenuation of TGF-β1 and Activin A in a prolonged induced allergic asthma model

Allergic asthma is associated with chronic airway inflammation and progressive airway remodelling. The sclerotium of Lignosus rhinocerotis (Cooke) Ryvarden (Tiger Milk mushroom) is used traditionally to treat various illnesses, including asthma in Southeast Asia. This study was carried out to evaluate the effect of L. rhinocerotis extract (LRE) on airway inflammation and remodelling in a chronic model of asthma. The present study investigated the therapeutic effects of LRE on airway inflammation and remodelling in prolonged allergen challenged model in allergic asthma. Female Balb/C mice were sensitised using ovalbumin (OVA) on day 0 and 7, followed by OVA-challenged (3 times/week) for 2, 6 and 10 weeks. LRE (125, 250, 500 mg/kg) were administered by oral gavage one hour after every challenge. One group of mice were left untreated after the final challenge for two weeks. LRE suppressed inflammatory cells and Th2 cytokines (IL-4, IL-5 and IL-13) in BALF and reduced IgE level in the serum. LRE also attenuated eosinophils infiltration and goblet cell hyperplasia in the lung tissues; as well as ameliorated airway remodelling by reducing smooth muscle thickness and reducing the expressions of TGF-β1 and Activin A positive cell in the lung tissues. LRE attenuated airway inflammation and remodelling in the prolonged allergen challenge of allergic asthma model. These findings suggest the therapeutic potential of LRE as an alternative for the management of allergic asthma.

Role of transforming growth factor-β in airway remodelling in bronchiolitis obliterans

Airway remodelling is the main pathological mechanism of bronchiolitis obliterans (BO). Several studies have found that transforming growth factor-β (TGF-β) expression is increased in BO during airway remodelling, where it plays an important role in various biological processes by binding to its receptor complex to activate multiple signalling proteins and pathways. This review examines the role of TGF-β in airway remodelling in BO and its potential as a therapeutic target, highlighting the mechanisms of TGF-β activation and signalling, cellular targets of TGF-β actions, and research progress in TGF-β signalling and TGF-β-mediated processes.

The Dual Role of the Airway Epithelium in Asthma: Active Barrier and Regulator of Inflammation

Chronic airway inflammation is the cornerstone on which bronchial asthma arises, and in turn, chronic inflammation arises from a complex interplay between environmental factors such as allergens and pathogens and immune cells as well as structural cells constituting the airway mucosa. Airway epithelial cells (AECs) are at the center of these processes. On the one hand, they represent the borderline separating the body from its environment in order to keep inner homeostasis. The airway epithelium forms a multi-tiered, self-cleaning barrier that involves an unstirred, discontinuous mucous layer, the dense and rigid mesh of the glycocalyx, and the cellular layer itself, consisting of multiple, densely interconnected cell types. On the other hand, the airway epithelium represents an immunologically highly active tissue once its barrier has been penetrated: AECs play a pivotal role in releasing protective immunoglobulin A. They express a broad spectrum of pattern recognition receptors, enabling them to react to environmental stressors that overcome the mucosal barrier. By releasing alarmins-proinflammatory and regulatory cytokines-AECs play an active role in the formation, strategic orientation, and control of the subsequent defense reaction. Consequently, the airway epithelium is of vital importance to chronic inflammatory diseases, such as asthma.

Mitochondria signaling pathways in allergic asthma

Mitochondria, as the powerhouse organelle of cells, are greatly involved in regulating cell signaling pathways, including those related to the innate and acquired immune systems, cellular differentiation, growth, death, apoptosis, and autophagy as well as hypoxic stress responses in various diseases. Asthma is a chronic complicated airway disease characterized by airway hyperresponsiveness, eosinophilic inflammation, mucus hypersecretion, and remodeling of airway. The asthma mortality and morbidity rates have increased worldwide, so understanding the molecular mechanisms underlying asthma progression is necessary for new anti-asthma drug development. The lung is an oxygen-rich organ, and mitochondria, by sensing and processing O2, contribute to the generation of ROS and activation of pro-inflammatory signaling pathways. Asthma pathophysiology has been tightly associated with mitochondrial dysfunction leading to reduced ATP synthase activity, increased oxidative stress, apoptosis induction, and abnormal calcium homeostasis. Defects of the mitochondrial play an essential role in the pro-remodeling mechanisms of lung fibrosis and airway cells' apoptosis. Identification of mitochondrial therapeutic targets can help repair mitochondrial biogenesis and dysfunction and reverse related pathological changes and lung structural remodeling in asthma. Therefore, we here overviewed the relationship between mitochondrial signaling pathways and asthma pathogenic mechanisms.

Airway Exposure to 1,3-Beta-d-Glucan Induces Airway Hyperresponsiveness in Guinea Pigs

1,3-Beta-d-glucan (β-glucan) is a component of mold cell walls and is frequently found in fungi and house dust mites. The studies of β-glucan are inconsistent, although it has been implicated in airway adverse responses. This study was carried out to determine whether airway hyperresponsiveness was seen 24 h after airway exposure to β-glucan in guinea pigs. Two matching guinea pigs were exposed intratracheally to either β-glucan or its vehicle. Twenty-four hours after intratracheal instillation, there was no difference between these two groups in the baseline of the total pulmonary resistance (R _L), dynamic lung compliance (C _dyn), arterial blood pressure, and heart rate. In contrast, the responses of R _L to capsaicin injection were significantly increased in β-glucan animals; capsaicin at the same dose of 3.2 μg/kg increased R _L by 184% in vehicle animals and by 400% in β-glucan animals. The effective dose 200% to capsaicin injection was lower in the β-glucan animals. Furthermore, the increases in R _L were partially reduced after transient lung hyperinflation to recruit the occluding airways; however, the R _L induced by capsaicin injection after lung hyperinflation was significantly larger than the baseline in β-glucan animals; also, the lung wet-to-dry ratio in capsaicin-injected animals was augmented in the β-glucan group. Moreover, the airway hyperresponsiveness was accompanied by increases in neutrophils in the bronchoalveolar lavage fluid in the β-glucan animals. Furthermore, the levels of substance P and the calcitonin gene-related peptide in the bronchoalveolar lavage fluid collected after capsaicin injection were increased in β-glucan animals. We provide definitive evidence that β-glucan can induce airway hyperresponsiveness in guinea pigs, and the neuropeptide releases play an important role in this airway hyperresponsiveness.

Caspase-11 regulates lung inflammation in response to house dust mites

Asthma is an inflammatory lung disorder characterized by mucus hypersecretion, cellular infiltration, and bronchial hyper-responsiveness. House dust mites (HDM) are the most prevalent cause of allergic sensitization. Canonical and noncanonical inflammasomes are multiprotein complexes that assemble in response to pathogen or danger-associated molecular patterns (PAMPs or DAMPs). Murine caspase-11 engages the noncanonical inflammasome. We addressed the role of caspase-11 in mediating host responses to HDM and subsequent allergic inflammation using caspase-11-/- mice, which lack caspase-11 while express caspase-1. We found that HDM induce caspase-11 expression in vitro. The presence of IL-4 and IL-13 promote caspase-11 expression. Additionally, caspase-11-/- macrophages show reduced release of IL-6, IL-12, and KC, and express lower levels of costimulatory molecules (e.g., CD40, CD86 and MHCII) in response to HDM stimulation. Notably, HDM sensitization of caspase-11-/- mice resulted in similar levels of IgE responses and hypothermia in response to nasal HDM challenge compared to WT. However, analysis of cell numbers and cytokines in bronchiolar alveolar lavage fluid (BALF) and histopathology of representative lung segments demonstrate altered inflammatory responses and reduced neutrophilia in the airways of the caspase-11-/- mice. These findings indicate that caspase-11 regulates airway inflammation in response to HDM exposure.

Quantification of increased MUC5AC expression in airway mucus of smoker using an automated image-based approach

Microscopic analysis of mucus quantity and composition is crucial in research and diagnostics on muco-obstructive diseases. Currently used image-based methods are unable to extract concrete numeric values of mucosal proteins, especially on the expression of the key mucosal proteins MUC5AC and MUC5B. Since their levels increase under pathologic conditions such as extensive exposure to cigarette smoke, it is imperative to quantify them to improve treatment strategies of pulmonary diseases. This study presents a simple, image-based, and high-processing computational method that allows determining the ratio of MUC5AC and MUC5B within the overall airway mucus while providing information on their spatial distribution. The presented pipeline was optimized for automated downstream analysis using a combination of bright field and immunofluorescence imaging suitable for tracheal and bronchial tissue samples, and air-liquid interface (ALI) cell cultures. To validate our approach, we compared tracheal tissue and ALI cell cultures of isolated primary normal human bronchial epithelial cells derived from smokers and nonsmokers. Our data indicated 18-fold higher levels of MUC5AC in submucosal glands of smokers covering about 8% of mucosal areas compared to <1% in nonsmoking individuals, confirming results of previous studies. We further identified a subpopulation of nonsmokers with slightly elevated glandular MUC5AC levels suggesting moderate exposure to second-hand smoke or fine particulate air pollution. Overall, this study demonstrates a novel, user-friendly and freely available tool for digital pathology and the analysis of therapeutic interventions tested in ALI cell cultures.

HDAC inhibitor sodium butyrate prevents allergic rhinitis and alters lncRNA and mRNA expression profiles in the nasal mucosa of mice

Our previous study demonstrated that intranasal administration of histone deacetylase inhibitor sodium butyrate (NaB) exhibits therapeutic effects on a mouse model of allergic rhinitis (AR). However, whether NaB is effective on AR when administered orally and prophylactically, as well as its potential effects on gene expression, remained unknown. The present study aimed to investigate the preventive effect of NaB on AR when added to the diet of newly weaned mice and to evaluate the changes in long non-coding (lnc)RNA and mRNA expression profiles in the nasal mucosa. Mice were randomly divided into three groups as follows: i) Control (C) group, (no treatment); ii) AR group [treated with ovalbumin (OVA)]; and iii) NaB + AR group (treated with OVA and NaB). The NaB + AR group was administered NaB in their feed (30 g/kg chow), whereas the other two groups were fed normal feed between 3 and 6 weeks of age. At 7 weeks of age, OVA administration was initiated to induce AR in the AR and NaB + AR groups. Following model establishment, behavioral assessments, western blotting and gene expression analysis were performed. NaB exhibited a preventive effect in the murine AR model, diminished the increases in histone deacetylase 1 (HDAC1) and HDAC8 expression and increased OVA-induced acetylation of histone H3 at lysine 9. In addition, NaB increased the AR-associated low expression of interleukin 2 (IL-2), interferon γ and IL-17 and decreased the expression of IL-4, IL-5 and transforming growth factor β1. Gene Ontology and pathway analyses revealed the top 10 pathways among the groups. Octamer-binding transcription factor 1, ecotropic viral integration site 1 and paired box 4 were predicted to be target genes of lncRNA (NONMMUT057309). Thus, NaB may exhibit a preventive effect on AR. Additionally, the lncRNA and mRNA expression profiles in the nasal mucosa of mice with AR differed significantly following NaB treatment. These results may provide insights into the pathogenesis of AR and suggest new treatment targets.

Immune induction of airway remodeling

Airway remodeling is accepted to be a determining component within the natural history of asthma. It is a phenomenon characterized by changes in the airways structures that marches in parallel with and can be influenced by airway inflammation, floating at the interface between both natural and adaptive immunity and physical and mechanical cells behavior. In this review we aimed to highlight the comprehensive, yet not exhaustive, evidences of how immune cells induce, regulate and adapt to the recognized markers of airway remodeling. Mucous cell hyperplasia, epithelial dysfunction and mesenchymal transition, extracellular matrix protein synthesis and restructuration, fibroblast to myofibroblast transition, airway smooth muscle proliferation, bioactive and contractile properties, and vascular remodeling encompass complex physiopathological mechanisms that can be induced, suppressed or regulated by different cellular and molecular pathways. Growth factors, cytokines, chemokines and adhesion molecules expressed or derived either from the immune network of cells infiltrating the asthmatic airways and involving T helper lymphocytes, immune lymphoid cells, dendritic cells, eosinophils, neutrophils, mast cells or by the structural components such as epithelial cells, fibroblasts, myocytes, airway smooth muscle cells concur with protein cellular matrix component and metalloproteases in modifying the airway structure in a detrimental way. The consequences in lung function decline, fixed airway obstruction and clinical severity of the disease suggest the possibility of identify among the immune molecular pathway of remodeling some biological parameters or signal pathway to be either a good tracer for monitoring the disease evolution or a target for hypothetical phenotypes and endotypes. In the era of personalized medicine, a biomarker of remodeling might predict a response to small-molecule inhibitors or biologicals potentially targeting a fundamental aspect of asthma pathogenesis that impacts on the low responsiveness to airway inflammation directed treatments.

Allergen-induced asthma, chronic rhinosinusitis and transforming growth factor-β superfamily signaling: mechanisms and functional consequences

Introduction: Often co-associated, asthma and chronic rhinosinusitis (CRS) are complex heterogeneous disease syndromes. Severity in both is related to tissue inflammation and abnormal repair (termed remodeling). Understanding signaling factors that can modulate, integrate the activation, and regulation of such key processes together is increasingly important. The transforming growth factor (TGF)-β superfamily of ligands comprise a versatile system of immunomodulatory molecules that are gaining recognition as having an essential function in the immunopathogenesis of asthma. Early data suggest an important role in CRS as well. Abnormal or dysregulated signaling may contribute to disease pathogenesis and severity.Areas covered: The essential biology of this complex family of growth factors in relation to the excess inflammation and remodeling that occurs in allergic asthma and CRS is reviewed. The need to understand the integration of signaling pathways together is highlighted. Studies in human airway tissue are evaluated and only selected key animal models relevant to human disease discussed given the highly context-dependent signaling and function of these ligands.Expert opinion: Abnormal or dysregulated TGF-β superfamily signaling may be central to the excess inflammation and tissue remodeling in asthma, and possibly CRS. Therefore, the TGF-β superfamily signaling pathways represent an emerging and attractive therapeutic target.

An extracellular matrix fragment drives epithelial remodeling and airway hyperresponsiveness

It is anticipated that bioactive fragments of the extracellular matrix (matrikines) can influence the development and progression of chronic diseases. The enzyme leukotriene A₄ hydrolase (LTA₄H) mediates opposing proinflammatory and anti-inflammatory activities, through the generation of leukotriene B₄ (LTB₄) and degradation of proneutrophilic matrikine Pro-Gly-Pro (PGP), respectively. We show that abrogation of LTB₄ signaling ameliorated inflammation and airway hyperresponsiveness (AHR) in a murine asthma model, yet global loss of LTA₄H exacerbated AHR, despite the absence of LTB₄ This exacerbated AHR was attributable to a neutrophil-independent capacity of PGP to promote pathological airway epithelial remodeling. Thus, we demonstrate a disconnect between airway inflammation and AHR and the ability of a matrikine to promote an epithelial remodeling phenotype that negatively affects lung function. Subsequently, we show that substantial quantities of PGP are detectable in the sputum of moderate-severe asthmatics in two distinct cohorts of patients. These studies have implications for our understanding of remodeling phenotypes in asthma and may rationalize the failure of LTA₄H inhibitors in the clinic.

IL-25 Orchestrates Activation of Th Cells via Conventional Dendritic Cells in Tissue to Exacerbate Chronic House Dust Mite-Induced Asthma Pathology

House dust mite (HDM) extract is a common trigger of asthma in humans. Chronic exposure to HDM also induces asthma-like pathology in mice. Allergic responses to HDM and other allergens are linked to release of IL-25, IL-33, and TSLP by epithelial cells; these cytokines, especially IL-33, target innate lymphoid cells type 2 to produce type 2 cytokines. To what extent and by what mechanisms IL-25 contributes to chronic HDM-induced pathology is not well understood. In humans, elevated levels of IL-25 appear to be associated with cases of uncontrolled asthma and exacerbated attacks. In this article, we demonstrate that blockade of IL-25 signaling in either lung conventional dendritic cells or in T cells resulted in similar decreases in production of IL-13 and IL-9 by T cells, reduced mast cell accumulation and tissue remodeling, and improved lung function but had only modest effects on eosinophilia. Stimulation of conventional dendritic cells by IL-25 promoted proximal accumulation of Th cells, and stimulation of Th cells by IL-25 locally promoted IL-13 and IL-9 production. IL-25 made notable contributions to chronic HDM-induced allergic asthma pathology by facilitating clustering and cross-stimulation of different cell types in tissue. Therapeutic targeting of IL-25 in combination with other treatments may be beneficial.

Genes and Pathways Regulating Decline in Lung Function and Airway Remodeling in Asthma

Asthma is a common disorder of the airways characterized by airway inflammation and by decline in lung function and airway remodeling in a subset of asthmatics. Airway remodeling is characterized by structural changes which include airway smooth muscle hypertrophy/hyperplasia, subepithelial fibrosis due to thickening of the reticular basement membrane, mucus metaplasia of the epithelium, and angiogenesis. Epidemiologic studies suggest that both genetic and environmental factors may contribute to decline in lung function and airway remodeling in a subset of asthmatics. Environmental factors include respiratory viral infection-triggered asthma exacerbations, and tobacco smoke. There is also evidence that several asthma candidate genes may contribute to decline in lung function, including ADAM33, PLAUR, VEGF, IL13, CHI3L1, TSLP, GSDMB, TGFB1, POSTN, ESR1 and ARG2. In addition, mediators or cytokines, including cysteinyl leukotrienes, matrix metallopeptidase-9, interleukin-33 and eosinophil expression of transforming growth factor-β, may contribute to airway remodeling in asthma. Although increased airway smooth muscle is associated with reduced lung function (i.e. forced expiratory volume in 1 second) in asthma, there have been few long-term studies to determine how individual pathologic features of airway remodeling contribute to decline in lung function in asthma. Clinical studies with inhibitors of individual gene products, cytokines or mediators are needed in asthmatic patients to identify their individual role in decline in lung function and/or airway remodeling.

Activin-A in the regulation of immunity in health and disease

The TGF-β superfamily of cytokines plays pivotal roles in the regulation of immune responses protecting against or contributing to diseases, such as, allergy, autoimmunity and cancer. Activin-A, a member of the TGF-β superfamily, was initially identified as an inducer of follicle-stimulating hormone secretion. Extensive research over the past decades illuminated fundamental roles for activin-A in essential biologic processes, including embryonic development, stem cell maintenance and differentiation, haematopoiesis, cell proliferation and tissue fibrosis. Activin-A signals through two type I and two type II receptors which, upon ligand binding, activate their kinase activity, phosphorylate the SMAD2 and 3 intracellular signaling mediators that form a complex with SMAD4, translocate to the nucleus and activate or silence gene expression. Most immune cell types, including macrophages, dendritic cells (DCs), T and B lymphocytes and natural killer cells have the capacity to produce and respond to activin-A, although not in a similar manner. In innate immune cells, including macrophages, DCs and neutrophils, activin-A exerts a broad range of pro- or anti-inflammatory functions depending on the cell maturation and activation status and the spatiotemporal context. Activin-A also controls the differentiation and effector functions of Th cell subsets, including Th9 cells, T_FH cells, Tr1 Treg cells and Foxp3⁺ Treg cells. Moreover, activin-A affects B cell responses, enhancing mucosal IgA secretion and inhibiting pathogenic autoantibody production. Interestingly, an array of preclinical and clinical studies has highlighted crucial functions of activin-A in the initiation, propagation and resolution of human diseases, including autoimmune diseases, such as, systemic lupus erythematosus, rheumatoid arthritis and pulmonary alveolar proteinosis, in allergic disorders, including allergic asthma and atopic dermatitis, in cancer and in microbial infections. Here, we provide an overview of the biology of activin-A and its signaling pathways, summarize recent studies pertinent to the role of activin-A in the modulation of inflammation and immunity, and discuss the potential of targeting activin-A as a novel therapeutic approach for the control of inflammatory diseases.

Rhinovirus Attributes that Contribute to Asthma Development

Early-life wheezing-associated infections with human rhinovirus (HRV) are strongly associated with the inception of asthma. The immune system of immature mice and humans is skewed toward a type 2 cytokine response. Thus, HRV-infected 6-day-old mice but not adult mice develop augmented type 2 cytokine expression, eosinophilic inflammation, mucous metaplasia, and airway hyperresponsiveness. This asthma phenotype depends on interleukin (IL)-13-producing type 2 innate lymphoid cells, the expansion of which in turn depends on release of the innate cytokines IL-25, IL-33, and thymic stromal lymphopoietin from the airway epithelium. In humans, certain genetic variants may predispose to HRV-induced childhood asthma.

Pulmonary environmental cues drive group 2 innate lymphoid cell dynamics in mice and humans

Group 2 innate lymphoid cells (ILC2s) are enriched in mucosal tissues (e.g., lung) and respond to epithelial cell-derived cytokines initiating type 2 inflammation. During inflammation, ILC2 numbers are increased in the lung. However, the mechanisms controlling ILC2 trafficking and motility within inflamed lungs remain unclear and are crucial for understanding ILC2 function in pulmonary immunity. Using several approaches, including lung intravital microscopy, we demonstrate that pulmonary ILC2s are highly dynamic, exhibit amoeboid-like movement, and aggregate in the lung peribronchial and perivascular spaces. They express distinct chemokine receptors, including CCR8, and actively home to CCL8 deposits located around the airway epithelium. Within lung tissue, ILC2s were particularly motile in extracellular matrix-enriched regions. We show that collagen-I drives ILC2 to markedly change their morphology by remodeling their actin cytoskeleton to promote environmental exploration critical for regulating eosinophilic inflammation. Our study provides previously unappreciated insights into ILC2 migratory patterns during inflammation and highlights the importance of environmental guidance cues in the lung in controlling ILC2 dynamics.

Anti-inflammatory cytokines in endometriosis

Although the pathogenesis of endometriosis is not fully understood, it is often considered to be an inflammatory disease. An increasing number of studies suggest that differential expression of anti-inflammatory cytokines (e.g., interleukin-4 and -10, and transforming growth factor-β1) occurs in women with endometriosis, including in serum, peritoneal fluid and ectopic lesions. These anti-inflammatory cytokines also have indispensable roles in the progression of endometriosis, including by promoting survival, growth, invasion, differentiation, angiogenesis, and immune escape of the endometriotic lesions. In this review, we provide an overview of the expression, origin, function and regulation of anti-inflammatory cytokines in endometriosis, with brief discussion and perspectives on their future clinical implications in the diagnosis and therapy of the disease.

Regulatory cytokine function in the respiratory tract

The respiratory tract is an important site of immune regulation; required to allow protective immunity against pathogens, while minimizing tissue damage and avoiding aberrant inflammatory responses to inhaled allergens. Several cell types work in concert to control pulmonary immune responses and maintain tolerance in the respiratory tract, including regulatory and effector T cells, airway and interstitial macrophages, dendritic cells and the airway epithelium. The cytokines transforming growth factor β, interleukin (IL-) 10, IL-27, and IL-35 are key coordinators of immune regulation in tissues such as the lung. Here, we discuss the role of these cytokines during respiratory infection and allergic airway disease, highlighting the critical importance of cellular source and immunological context for the effects of these cytokines in vivo.

TGF-β Upregulated Mitochondria Mass through the SMAD2/3→C/EBPβ→PRMT1 Signal Pathway in Primary Human Lung Fibroblasts

Tissue remodeling of subepithelial mesenchymal cells is a major pathologic condition of chronic obstructive pulmonary disease and asthma. Fibroblasts contribute to fibrotic events and inflammation in both airway diseases. Recent mechanistic studies established a link between mitochondrial dysfunction or aberrant biogenesis leading to tissue remodeling of the airway wall in asthma. Protein arginine methyltransferase-1 (PRMT1) participated in airway wall remodeling in pulmonary inflammation. This study investigated the mechanism by which PRMT1 regulates mitochondrial mass in primary human airway wall fibroblasts. Fibroblasts from control or asthma patients were stimulated with TGF-β for up to 48 h, and the signaling pathways controlling PRMT1 expression and mitochondrial mass were analyzed. PRMT1 activity was suppressed by the pan-PRMT inhibitor AMI-1. The SMAD2/3 pathway was blocked by SB203580 and C/EBPβ by small interference RNA treatment. The data obtained from unstimulated cells showed a significantly higher basal expression of PRMT1 and mitochondrial markers in asthmatic compared with control fibroblasts. In all cells, TGF-β significantly increased the expression of PRMT1 through SMAD2/3 and C/EBPβ. Subsequently, PRMT1 upregulated the expression of the mitochondria regulators PGC-1α and heat shock protein 60. Both the inhibition of the SAMD2/3 pathway or PRMT1 attenuated TGF-β-induced mitochondrial mass and C/EBPβ and α-SMA expression. These findings suggest that the signaling sequence controlling mitochondria in primary human lung fibroblasts is as follows: TGF-β→SMAD2/3→C/EBPβ→PRMT1→PGC-1α. Therefore, PRMT1 and C/EBPβ present a novel therapeutic and diagnostic target for airway wall remodeling in chronic lung diseases.

TRPC1 intensifies house dust mite-induced airway remodeling by facilitating epithelial-to-mesenchymal transition and STAT3/NF-κB signaling

Airway remodeling with progressive epithelial alterations in the respiratory tract is a severe consequence of asthma. Although dysfunctional signaling transduction is attributed to airway inflammation, the exact mechanism of airway remodeling remains largely unknown. TRPC1, a member of the transient receptor potential canonical Ca²⁺ channel family, possesses versatile functions but its role in airway remodeling remains undefined. Here, we show that ablation of TRPC1 in mice alleviates airway remodeling following house dust mite (HDM) challenge with decreases in mucus production, cytokine secretion, and collagen deposition. HDM challenge induces Ca²⁺ influx via the TRPC1 channel, resulting in increased levels of signal transducer and activator of transcription 3 (STAT3) and proinflammatory cytokines. In contrast, STAT3 expression was significantly decreased in TRPC1^-/- mouse lungs compared with wild-type controls after HDM challenge. Mechanistically, STAT3 promotes epithelial-to-mesenchymal transition and increases mucin 5AC expression. Collectively, these findings identify TRPC1 as a modulator of HDM-induced airway remodeling via STAT3-mediated increase in mucus production, which provide new insight in our understanding of the molecular basis of airway remodeling, and identify novel therapeutic targets for intervention of severe chronic asthma.-Pu, Q., Zhao, Y., Sun, Y., Huang, T., Lin, P., Zhou, C., Qin, S., Singh, B. B., Wu, M. TRPC1 intensifies house dust mite-induced airway remodeling by facilitating epithelial-to-mesenchymal transition and STAT3/NF-κB signaling.

Deficient Follistatin-like 3 Secretion by Asthmatic Airway Epithelium Impairs Fibroblast Regulation and Fibroblast-to-Myofibroblast Transition

Bronchial epithelial cells (BECs) from healthy children inhibit human lung fibroblast (HLF) expression of collagen and fibroblast-to-myofibroblast transition (FMT), whereas asthmatic BECs do so less effectively, suggesting that diminished epithelial-derived regulatory factors contribute to airway remodeling. Preliminary data demonstrated that secretion of the activin A inhibitor follistatin-like 3 (FSTL3) by healthy BECs was greater than that by asthmatic BECs. We sought to determine the relative secretion of FSTL3 and activin A by asthmatic and healthy BECs, and whether FSTL3 inhibits FMT. To quantify the abundance of the total proteome FSTL3 and activin A in supernatants of differentiated BEC cultures from healthy children and children with asthma, we performed mass spectrometry and ELISA. HLFs were cocultured with primary BECs and then HLF expression of collagen I and α-smooth muscle actin (α-SMA) was quantified by qPCR, and FMT was quantified by flow cytometry. Loss-of-function studies were conducted using lentivirus-delivered shRNA. Using mass spectrometry and ELISA results from larger cohorts, we found that FSTL3 concentrations were greater in media conditioned by healthy BECs compared with asthmatic BECs (4,012 vs. 2,553 pg/ml; P = 0.002), and in media conditioned by asthmatic BECs from children with normal lung function relative to those with airflow obstruction (FEV1/FVC ratio < 0.8; n = 9; 3,026 vs. 1,922 pg/ml; P = 0.04). shRNA depletion of FSTL3 in BECs (n = 8) increased HLF collagen I expression by 92% (P = 0.001) and α-SMA expression by 88% (P = 0.02), and increased FMT by flow cytometry in cocultured HLFs, whereas shRNA depletion of activin A (n = 6) resulted in decreased α-SMA (22%; P = 0.01) expression and decreased FMT. Together, these results indicate that deficient FSTL3 expression by asthmatic BECs impairs epithelial regulation of HLFs and FMT.

Epithelial-derived TGF-β1 acts as a pro-viral factor in the lung during influenza A infection

Mucosal surfaces are under constant bombardment from potentially antigenic particles and so must maintain a balance between homeostasis and inappropriate immune activation and consequent pathology. Epithelial cells have a vital role orchestrating pulmonary homeostasis and defense against pathogens. TGF-β regulates an array of immune responses-both inflammatory and regulatory-however, its function is highly location- and context-dependent. We demonstrate that epithelial-derived TGF-β acts as a pro-viral factor suppressing early immune responses during influenza A infection. Mice specifically lacking bronchial epithelial TGF-β1 (epTGFβKO) displayed marked protection from influenza-induced weight loss, airway inflammation, and pathology. However, protection from influenza-induced pathology was not associated with a heightened lymphocytic immune response. In contrast, the kinetics of interferon beta (IFNβ) release into the airways was significantly enhanced in epTGFβKO mice compared with control mice, with elevated IFNβ on day 1 in epTGFβKO compared with control mice. This induced a heighted antiviral state resulting in impaired viral replication in epTGFβKO mice. Thus, epithelial-derived TGF-β acts to suppress early IFNβ responses leading to increased viral burden and pathology. This study demonstrates the importance of the local epithelial microenvironmental niche in shaping initial immune responses to viral infection and controlling host disease.

Contraction-dependent TGF-β1 activation is required for thrombin-induced remodeling in human airway smooth muscle cells

AIMS

Thrombin is a serine proteinase that is not only involved in coagulation cascade, but also mediates a number of biological responses relevant to tissues repair, and induces bronchoconstriction. TGF-β plays a pivotal role in airway remodeling due to its effects on airway smooth muscle proliferation and extracellular matrix (ECM) deposition. Recently, bronchoconstriction itself is found to constitute a form of strain and is highly relevant to asthmatic airway remodeling. However, the underlying mechanisms remain unknown. Here, we investigated the role of contraction- dependent TGF-β activation in thrombin-induced remodeling in human airway smooth muscle (HASM) cells.

MATERIALS AND METHODS

Primary HASM cells were treated with or without thrombin in the absence or presence of anti-TGF-β antibody, cytochalasin D and formoterol. CFSE labeling index or CCK-8 assay were performed to test cell proliferation. RT-PCR and Western blotting were used to examined ECM mRNA level and collagen Iα1, α-actin protein expression, respectively. Immunofluorescence was also used to confirm contraction induced by thrombin in HASM cells.

KEY FINDING

Thrombin stimulation enhanced HASM cells proliferation and activated TGF-β signaling. Thrombin induced ECM mRNA and collagen Iα1 protein expression, and these effects are mediated by TGF-β. Abrogation of TGF-β activation by contraction inhibitors cytochalasin D and formoterol prevents the thrombin-induced effects.

SIGNIFICANCE

These findings suggest that contraction-dependent TGF-β activation could be a mechanism by which thrombin leads to the development of asthmatic airway remodeling. Blocking physical forces with bronchodilator would be an intriguing way in reducing airway remodeling in asthma.

Manipulation of dipeptidylpeptidase 10 in mouse and human in vivo and in vitro models indicates a protective role in asthma

We previously identified dipeptidylpeptidase 10 (DPP10) on chromosome 2 as a human asthma susceptibility gene, through positional cloning. Initial association results were confirmed in many subsequent association studies but the functional role of DPP10 in asthma remains unclear. Using the MRC Harwell N-ethyl-N-nitrosourea (ENU) DNA archive, we identified a point mutation in Dpp10 that caused an amino acid change from valine to aspartic acid in the β-propeller region of the protein. Mice carrying this point mutation were recovered and a congenic line was established (Dpp10^145D). Macroscopic examination and lung histology revealed no significant differences between wild-type and Dpp10^145D/145D mice. However, after house dust mite (HDM) treatment, Dpp10 mutant mice showed significantly increased airway resistance in response to 100 mg/ml methacholine. Total serum IgE levels and bronchoalveolar lavage (BAL) eosinophil counts were significantly higher in homozygotes than in control mice after HDM treatment. DPP10 protein is present in airway epithelial cells and altered expression is observed in both tissue from asthmatic patients and in mice following HDM challenge. Moreover, knockdown of DPP10 in human airway epithelial cells results in altered cytokine responses. These results show that a Dpp10 point mutation leads to increased airway responsiveness following allergen challenge and provide biological evidence to support previous findings from human genetic studies.

This article has an associated First Person interview with the first author of the paper.

Summary: Here, we show a novel mouse model carrying a point mutation in dipeptidylpeptidase 10 (Dpp10). Our data provide evidence that DPP10 might play a protective role in asthma.

Thymic stromal lymphopoietin contribution to the recruitment of circulating fibrocytes to the lung in a mouse model of chronic allergic asthma

Objective: Fibrocyte localization to the airways and thymic stromal lymphopoietin (TSLP) overexpression in the lung are features of severe asthma. The aim of this study was to determine whether TSLP contributes to fibrocyte trafficking and airway remodeling in a mouse model of allergic asthma. Methods: We established a chronic asthma animal model by administering house dust mite (HDM) extracts intranasally for up to 5 consecutive weeks. Mouse anti-TSLP monoclonal antibody (mAb) was given intraperitoneally starting the 4^th week. Fluorescence-labeled CD34/collagen I (Col I)-dual-positive fibrocytes were examined by confocal microscopy. The level of TGF-β1 in the bronchoalveolar lavage (BAL) fluid was determined by ELISA. Results: We found significantly increased levels of TSLP and TGF-β1 in the lung of the mice subjected to repeated allergen exposure, which was accompanied by increased number of fibrocytes in the sub-epithelial zone and the BAL fluid. However, blocking TSLP markedly decreased the production of TGF-β1, reduced the number of fibrocytes and subsequently prevented alterations of both airway and vascular structures. Conclusions: Our data suggested that TSLP might function in airway remodeling by promoting circulating fibrocyte recruitment to the lung in the mice subjected to chronic allergen exposure. These results provide a better rationale for targeting the interaction between TSLP and fibrocytes as a therapeutic approach for chronic allergic asthma.

Overexpression of ATP5b promotes cell proliferation in asthma

Asthma is a complicated systemic disease of the airways, which is characterized by variable symptoms, including bronchial hyper‑responsive-ness, inflammation and airflow obstruction. The prevalence of asthma has increased 2‑3‑fold over recent decades in developed countries; however, the molecular mechanism of asthma remains unclear. In the current study, the expression of recombinant protein Dermatophagoides farinaeI (Derf I) was induced by isopropyl β‑D‑1‑thiogalactoside (IPTG) and purified using Ni‑NTA. Derf I, an important antigen of asthma, was used to establish the animal model of asthma. Airway hyper‑responsiveness was mea-sured using unrestrained whole‑body plethysmography with a four‑chamber system. Immunoglobulin (Ig)E, IgG and IgG2a were analyzed using indirect enzyme‑linked immunosorbent assay (ELISA). Proteomic technology was applied to detect the difference between the normal lung tissue and asthma lung tissue samples of the asthma model. Cytokines in bronchoalveolar lavage fluid and the splenocyte culture medium were measured by ELISA and reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was performed to detect the mRNA expression of ATP synthase, H+ transporting, mitochondrial F1 complex, β polypeptide (ATP5b). In addition, cell growth of arterial smooth muscle cells (ASMCs) was evaluated by MTT assay. In the current study, Derf I was successfully used to construct the animal model of asthma. Out of 23 proteins that exhibit 3‑fold upregulation or downregulation, ATP5b was chosen for further investigation. The data indicated that ATP5b was overexpressed in the asthma lung tissue when compared with the normal lung tissue. However, when ATP5b was knocked down, cell growth decreased. Therefore, overexpressed ATP5b leads to airway smooth muscle cell (ASMC) proliferation and finally to ASM thickening. Thus, to the best of our knowledge, this is the first study to report that the expression level of ATP5b was markedly increased in lung tissue samples of an asthma model compared with the tissue samples from normal lungs, which promoted ASMC proliferation and contributed to airway remodeling.

EPO modified MSCs can inhibit asthmatic airway remodeling in an animal model

There was no effective measures can be obtained at present to reverse or prevent airway remodeling. We investigated the therapeutic effect of Erythropoietin (EPO) gene modified mesenchymal stem cells (MSCs) on asthmatic airway remodeling and the possible underlied molecular mechanisms. EPO gene was transfected into MSCs via lentivirus vector. The transfected cells (EPO-MSCs) were identified by flow cytometry and the EPO secreting function was detected by PCR and Western blot. MSCs or EPO-MSCs were administrated to albumin (OVA)-induced chronic asthmatic mouse model via tail veins. The asthmatic phenotype was analyzed. Number of cells in bronchoalveolar lavage fluid (BALF) was counted using a hemocytometer. Histological findings of airways were evaluated by microscopic examination. The concentrations of interleukin 4(IL-4), interleukin 5(IL-5), and interleukin 13(IL-13) in lung homogenate were determined by ELISA. The activation state of transforming growth factor-β 1 (TGF-β1), Transforming growth factor beta-activated kinase 1 (TAK1), and p38 Mitogen Activated Protein Kinase (p38MAPK) signaling was detected by Real-Time PCR and Western blotting. EPO-MSCs were successfully constructed. EPO-MSCs showed a more potently suppressive effect on local asthmatic airway inflammation and the level of IL-4, IL-5, and IL-13 in lung tissue than MSCs. Moreover, the numbers of goblet cells, the thicknesses of smooth muscle layer, collagen density, percentage of proliferating cell nuclear antigen positive (PCNA⁺ ) mesenchymal cells, and von Willebrand factor positive(vWF⁺ ) vessels were also significantly inhibited by EPO-MSCs. Furthermore, EPO-MSCs could downregulate the expression of TGF-β1, TAK1, and p38MAPK in lung tissue both in mRNA level and in protein level. EPO gene modified MSCs may more efficiently attenuate asthmatic airway remodeling, which maybe related with the downregulation of TGF-β1-TAK1-p38MAPK pathway activity.

The Innate Cytokines IL-25, IL-33, and TSLP Cooperate in the Induction of Type 2 Innate Lymphoid Cell Expansion and Mucous Metaplasia in Rhinovirus-Infected Immature Mice

Early-life respiratory viral infection is a risk factor for asthma development. Rhinovirus (RV) infection of 6-d-old mice, but not mature mice, causes mucous metaplasia and airway hyperresponsiveness that are associated with the expansion of lung type 2 innate lymphoid cells (ILC2s) and are dependent on IL-13 and the innate cytokine IL-25. However, contributions of the other innate cytokines, IL-33 and thymic stromal lymphopoietin (TSLP), to the observed asthma-like phenotype have not been examined. We reasoned that IL-33 and TSLP expression are also induced by RV infection in immature mice and are required for maximum ILC2 expansion and mucous metaplasia. We inoculated 6-d-old BALB/c (wild-type) and TSLP receptor-knockout mice with sham HeLa cell lysate or RV. Selected mice were treated with neutralizing Abs to IL-33 or recombinant IL-33, IL-25, or TSLP. ILC2s were isolated from RV-infected immature mice and treated with innate cytokines ex vivo. RV infection of 6-d-old mice increased IL-33 and TSLP protein abundance. TSLP expression was localized to the airway epithelium, whereas IL-33 was expressed in epithelial and subepithelial cells. RV-induced mucous metaplasia, ILC2 expansion, airway hyperresponsiveness, and epithelial cell IL-25 expression were attenuated by anti-IL-33 treatment and in TSLP receptor-knockout mice. Administration of intranasal IL-33 and TSLP was sufficient for mucous metaplasia. Finally, TSLP was required for maximal ILC2 gene expression in response to IL-25 and IL-33. The generation of mucous metaplasia in immature RV-infected mice involves a complex interplay among the innate cytokines IL-25, IL-33, and TSLP.

Transforming Growth Factor-β: Master Regulator of the Respiratory System in Health and Disease

In this article, we review the biology and physiological importance of transforming growth factor-β (TGF-β) to homeostasis in the respiratory system, its importance to innate and adaptive immune responses in the lung, and its pathophysiological role in various chronic pulmonary diseases including pulmonary arterial hypertension, chronic obstructive pulmonary disease, asthma, and pulmonary fibrosis. The TGF-β family is responsible for initiation of the intracellular signaling pathways that direct numerous cellular activities including proliferation, differentiation, extracellular matrix synthesis, and apoptosis. When TGF-β signaling is dysregulated or essential control mechanisms are unbalanced, the consequences of organ and tissue dysfunction can be profound. The complexities and myriad checkpoints built into the TGF-β signaling pathways provide attractive targets for the treatment of these disease states, many of which are currently being investigated. This review focuses on those aspects of TGF-β biology that are most relevant to pulmonary diseases and that hold promise as novel therapeutic targets.

Therapeutic efficacy of a co-blockade of IL-13 and IL-25 on airway inflammation and remodeling in a mouse model of asthma

Repeated airway inflammation and unremitting remodeling provoke irreversible pulmonary dysfunction and resistance to current drugs in patients with chronic bronchial asthma. Interleukin (IL)-13 and IL-25 play an important role in airway inflammation and remodeling in asthma. We aimed to investigate whether co-inhibiting IL-13 and IL-25 can effectively down-regulate allergen-induced airway inflammation and remodeling in mice. Mice with asthma induced by chronic exposure to ovalbumin (OVA) were given soluble IL-13 receptor α2 (sIL-13R) or soluble IL-25 receptor (sIL-25R) protein alone and in combination to neutralize the bioactivity of IL-13 and IL-25, and relevant airway inflammation and remodeling experiments were performed. We found that the co-blockade of IL-13 and IL-25 with sIL-13R and sIL-25R was more effective than either agent alone at decreasing inflammatory cell infiltration, airway hyperresponsiveness (AhR) and airway remodeling including mucus production, extracellular collagen deposition, smooth muscle cell hyperplasia and angiogenesis in mice exposed to OVA. These results suggest that the combined inhibition of IL-13 and IL-25 may provide a novel therapeutic strategy for asthma, especially for patients who are resistant to current treatments.

Airway remodeling in asthma: what really matters

Airway remodeling is generally quite broadly defined as any change in composition, distribution, thickness, mass or volume and/or number of structural components observed in the airway wall of patients relative to healthy individuals. However, two types of airway remodeling should be distinguished more clearly: (1) physiological airway remodeling, which encompasses structural changes that occur regularly during normal lung development and growth leading to a normal mature airway wall or as an acute and transient response to injury and/or inflammation, which ultimately results in restoration of a normal airway structures; and (2) pathological airway remodeling, which comprises those structural alterations that occur as a result of either disturbed lung development or as a response to chronic injury and/or inflammation leading to persistently altered airway wall structures and function. This review will address a few major aspects: (1) what are reliable quantitative approaches to assess airway remodeling? (2) Are there any indications supporting the notion that airway remodeling can occur as a primary event, i.e., before any inflammatory process was initiated? (3) What is known about airway remodeling being a secondary event to inflammation? And (4), what can we learn from the different animal models ranging from invertebrate to primate models in the study of airway remodeling? Future studies are required addressing particularly pheno-/endotype-specific aspects of airway remodeling using both endotype-specific animal models and “endotyped” human asthmatics. Hopefully, novel in vivo imaging techniques will be further advanced to allow monitoring development, growth and inflammation of the airways already at a very early stage in life.

Activin A and follistatin in patients with asthma. Does severity make the difference?

BACKGROUND AND OBJECTIVE

Activin A is a pleiotropic cytokine holding a fundamental role in inflammation and tissue remodelling. Follistatin can modulate the bioactivity of activin. We aimed to measure activin A and follistatin in sputum supernatants and bronchoalveolar lavage (BAL) of asthmatic patients and to determine the possible associations with severity as well as with inflammatory and remodelling indices.

METHODS

A total of 58 asthmatic patients (33 with severe refractory asthma (SRA)) and 10 healthy controls underwent sputum induction for % cells, activin A, follistatin, eosinophilic cationic protein (ECP), transforming growth factor beta 1 (TGF-β1), IL-13 and IL-8 measurements. In 22 asthmatic patients, BAL and bronchial biopsies were also performed for the assessment of the above-mentioned variables, measurement of remodelling indices and immunostaining for different activin A receptors.

RESULTS

Sputum activin A (pg/mL) was higher in patients with SRA (median (interquartile ranges): 76 (33-185)) compared to mild-to-moderate asthma (44 (18-84); P = 0.005), whereas follistatin did not differ between the two groups. BAL activin A (pg/mL) was higher in patients with SRA compared to those with mild-to-moderate disease. A significant association was observed between activin A and TGF-β1, eosinophils in sputum and/or in BAL, while reticular basement membrane (RBM) thickness was significantly associated with BAL activin levels only. No difference in immunostaining for activin receptor type IB was observed between patients with SRA and those with mild-to-moderate asthma.

CONCLUSION

Sputum and BAL levels of activin A are higher in SRA. The association of activin A with TGF-β1, eosinophils and RBM thickness may indicate a role of this cytokine in the inflammatory and remodelling process in SRA.

Anti-inflammatory effect of Yu-Ping-Feng-San via TGF-β1 signaling suppression in rat model of COPD

OBJECTIVES

Yu-Ping-Feng-San (YPFS) is a classical traditional Chinese medicine that is widely used for treatment of the diseases in respiratory systems, including chronic obstructive pulmonary disease (COPD) recognized as chronic inflammatory disease. However, the molecular mechanism remains unclear. Here we detected the factors involved in transforming growth factor beta 1 (TGF-β1)/Smad2 signaling pathway and inflammatory cytokines, to clarify whether YPFS could attenuate inflammatory response dependent on TGF-β1/Smad2 signaling in COPD rats or cigarette smoke extract (CSE)-treated human bronchial epithelial (Beas-2B) cells.

MATERIALS AND METHODS

The COPD rat model was established by exposure to cigarette smoke and intratracheal instillation of lipopolysaccharide, YPFS was administered to the animals. The efficacy of YPFS was evaluated by comparing the severity of pulmonary pathological damage, pro-inflammation cytokines, collagen related genes and the activation of TGF-β1/Smad2 signaling pathway. Furthermore, CSE-treated cells were employed to confirm whether the effect of YPFS was dependent on the TGF-β1/Smad2 signaling via knockdown Smad2 (Si-RNA), or pretreatment with the inhibitor of TGF-β1.

RESULTS

Administration of YPFS effectively alleviated injury of lung, suppressed releasing of pro-inflammatory cytokines and collagen deposition in COPD animals (P<0.05), whereas exogenous TGF-β1 promoted releasing of IL-1β, IL-6, TNFα (P<0.05). Administration YPFS reduced inflammatory response significantly, also down-regulated TGF-β1/Smad2 signaling in vivo and in vitro. Unexpectedly, knockdown Smad2 or inhibition of TGF-β1 abolished anti-inflammatory effect of YPFS in CSE-treated cells.

CONCLUSION

YPFS accomplished anti-inflammatory effects mainly by suppressing phosphorylation of Smad2, TGF-β1/Smad2 signaling pathway was required for YPFS-mediated anti-inflammation in COPD rats or CSE-treated Beas-2B cells.

The immunoregulatory and fibrotic roles of activin A in allergic asthma

Activin A, a member of the TGF-β superfamily of cytokines, was originally identified as an inducer of follicle stimulating hormone release, but has since been ascribed roles in normal physiological processes, as an immunoregulatory cytokine and as a driver of fibrosis. In the last 10–15 years, it has also become abundantly clear that activin A plays an important role in the regulation of asthmatic inflammation and airway remodelling. This review provides a brief introduction to the activin A/TGF-β superfamily, focussing on the regulation of receptors and signalling pathways. We examine the contradictory evidence for generalized pro- vs. anti-inflammatory effects of activin A in inflammation, before appraising its role in asthmatic inflammation and airway remodelling specifically by evaluating data from both murine models and clinical studies. We identify key issues to be addressed, paving the way for safe exploitation of modulation of activin A function for treatment of allergic asthma and other inflammatory lung diseases.

Regulation of group 2 innate lymphoid cells

Group 2 innate lymphoid cells (ILC2) exert critical roles in type 2 immune responses, epithelial repair at mucosal tissues and metabolic homeostasis. ILC2 rapidly provide large amounts of type 2 signature cytokines, thereby driving type 2 immune responses such as the defense against helminths. However, if deregulated, ILC2 facilitate tissue fibrosis and trigger unwanted type 2 immunopathologies such as allergies, asthma and atopic dermatitis. Therefore, ILC2 need to be tightly regulated and we are just beginning to understand which mediators activate or inhibit this rare but important cell population. In this review, we summarize current knowledge about positive and negative regulation of ILC2 and discuss its immunological consequences.

Pulmonary Epithelial Cell-Derived Cytokine TGF-β1 Is a Critical Cofactor for Enhanced Innate Lymphoid Cell Function

Epithelial cells orchestrate pulmonary homeostasis and pathogen defense and play a crucial role in the initiation of allergic immune responses. Maintaining the balance between homeostasis and inappropriate immune activation and associated pathology is particularly complex at mucosal sites that are exposed to billions of potentially antigenic particles daily. We demonstrated that epithelial cell-derived cytokine TGF-β had a central role in the generation of the pulmonary immune response. Mice that specifically lacked epithelial cell-derived TGF-β1 displayed a reduction in type 2 innate lymphoid cells (ILCs), resulting in suppression of interleukin-13 and hallmark features of the allergic response including airway hyperreactivity. ILCs in the airway lumen were primed to respond to TGF-β by expressing the receptor TGF-βRII and ILC chemoactivity was enhanced by TGF-β. These data demonstrate that resident epithelial cells instruct immune cells, highlighting the central role of the local environmental niche in defining the nature and magnitude of immune reactions.

Novel concepts in airway inflammation and remodelling in asthma

The hallmark pathological features of asthma include airway eosinophilic inflammation and structural changes (remodelling) which are associated with an irreversible loss in lung function that tracks from childhood to adulthood. In parallel with changes in function, pathological abnormalities occur early, during the pre-school years, are established by school age and subsequently remain (even though symptoms may remit for periods during adulthood). Given the equal importance of inflammation and remodelling in asthma pathogenesis, there is a significant disparity in studies undertaken to investigate the contribution of each. The majority focus on the role of inflammation, and although novel therapeutics such as those targeted against T-helper cell type 2 (Th2) mediators have arisen, it is apparent that targeting inflammation alone has not allowed disease modification. Therefore, unless airway remodelling is addressed for future therapeutic strategies, it is unlikely that we will progress towards a cure for asthma. Having acknowledged these limitations, the focus of this review is to highlight the gaps in our current knowledge about the mechanisms underlying airway remodelling, the relationships between remodelling, inflammation and function, remodelling and clinical phenotypes, and the importance of utilising innovative and realistic pre-clinical models to uncover effective, disease-modifying therapeutic strategies.

Oral fungal immunomodulatory protein-Flammulina velutipes has influence on pulmonary inflammatory process and potential treatment for allergic airway disease: A mouse model

BACKGROUND/PURPOSE

House dust mite (HDM) is well known as one of the major indoor allergens that trigger allergic inflammation, especially asthma, and accounts for 85% of all cases. So far, asthma has been thought of as a condition of imbalance between T helper (Th)1 and Th2. Fungal immunomodulatory protein-Flammulina velutipes (FIP-fve) has been seemingly demonstrated to modulate the response to Th1 cytokine production. The aim of this study was to investigate if the oral administration of FIP-fve can inhibit HDM-induced asthma inflammation in the mouse model.

METHODS

We divided the mice (female BALB/c, 4-6 weeks) into four groups: the prevention group, which consisted of mice sensitized by HDM (intraperitoneally on Day 1, Day 7, and Day 14, and intranasally on Day 14, Day 17, Day 21, Day 24, and Day 27) fed with FIP-fve from Day 1 to Day 14; the treatment group, which comprised mice that received treatment from Day 14 to Day 28; the positive control (PC, sensitized by HDM fed without FIP-fve) group; and the negative control group (NC, nonsensitized). Airway hyperresponsiveness induced by methacholine challenge was determined using whole-body barometric plethysmography. In addition, cytokines were analyzed from bronchoalveolar lavage fluid and serum. Histopathological studies and Liu's staining method in mice lungs were also performed.

RESULTS

The results showed that both pre- and posttreated FIP-fve groups had significantly reduced airway hyperresponsiveness compared with the PC group after methacholine challenge. In addition, a significantly decreased level of HDM-specific immunoglobulin E in serum and decreased production of Th2 cytokines in bronchoalveolar lavage fluid and serum were observed in these two FIP-fve fed groups. Moreover, more decreased amounts of infiltrating inflammatory cells were present in the lungs of FIP-fve fed groups than those of the PC group.

CONCLUSION

Oral FIP-fve had an anti-inflammatory effect on the acute phase of the airway inflammatory process induced by HDM in the mouse model and might have a potentially therapeutic role for allergic airway diseases.

Transforming growth factor-β superfamily in obstructive lung diseases. more suspects than TGF-β alone

Asthma and chronic obstructive pulmonary disease are respiratory disorders and a major global health problem with increasing incidence and severity. Genes originally associated with lung development could be relevant in the pathogenesis of chronic obstructive pulmonary disease/asthma, owing to either an early-life origin of adult complex diseases or their dysregulation in adulthood upon exposure to environmental stressors (e.g., smoking). The transforming growth factor (TGF)-β superfamily is conserved through evolution and is involved in a range of biological processes, both during development and in adult tissue homeostasis. TGF-β1 has emerged as an important regulator of lung and immune system development. However, considerable evidence has been presented for a role of many of the other ligands of the TGF-β superfamily in lung pathology, including activins, bone morphogenetic proteins, and growth differentiation factors. In this review, we summarize the current knowledge on the mechanisms by which activin, bone morphogenetic protein, and growth differentiation factor signaling contribute to the pathogenesis of obstructive airway diseases.

The TNF Family Molecules LIGHT and Lymphotoxin αβ Induce a Distinct Steroid-Resistant Inflammatory Phenotype in Human Lung Epithelial Cells

Lung epithelial cells are considered important sources of inflammatory molecules and extracellular matrix proteins that contribute to diseases such as asthma. Understanding the factors that stimulate epithelial cells may lead to new insights into controlling lung inflammation. This study sought to investigate the responsiveness of human lung epithelial cells to the TNF family molecules LIGHT and lymphotoxin αβ (LTαβ). Bronchial and alveolar epithelial cell lines, and primary human bronchial epithelial cells, were stimulated with LIGHT and LTαβ, and expression of inflammatory cytokines and chemokines and markers of epithelial-mesenchymal transition and fibrosis/remodeling was measured. LTβ receptor, the receptor shared by LIGHT and LTαβ, was constitutively expressed on all epithelial cells. Correspondingly, LIGHT and LTαβ strongly induced a limited but highly distinct set of inflammatory genes in all epithelial cells tested, namely the adhesion molecules ICAM-1 and VCAM-1; the chemokines CCL5, CCL20, CXCL1, CXCL3, CXCL5, and CXCL11; the cytokines IL-6, activin A and GM-CSF; and metalloproteinases matrix metalloproteinase-9 and a disintegrin and metalloproteinase domain-8. Importantly, induction of the majority of these inflammatory molecules was insensitive to the suppressive effects of the corticosteroid budesonide. LIGHT and LTαβ also moderately downregulated E-cadherin, a protein associated with maintaining epithelial integrity, but did not significantly drive production of extracellular matrix proteins or α-smooth muscle actin. Thus, LIGHT and LTαβ induce a distinct steroid-resistant inflammatory signature in airway epithelial cells via constitutively expressed LTβ receptor. These findings support our prior murine studies that suggested the receptors for LIGHT and LTαβ contribute to development of lung inflammation characteristic of asthma and idiopathic pulmonary fibrosis.

The activin A antagonist follistatin inhibits cystic fibrosis-like lung inflammation and pathology

Cystic fibrosis (CF) is the most common life-limiting genetically acquired respiratory disorder. Patients with CF have thick mucus obstructing the airways leading to recurrent infections, bronchiectasis and neutrophilic airway inflammation culminating in deteriorating lung function. Current management targets airway infection and mucus clearance, but despite recent advances in care, life expectancy is still only 40 years. We investigated whether activin A is elevated in CF lung disease and whether inhibiting activin A with its natural antagonist follistatin retards lung disease progression. We measured serum activin A levels, lung function and nutritional status in CF patients. We studied the effect of activin A on CF lung pathogenesis by treating newborn CF transgenic mice (β-ENaC) intranasally with the natural activin A antagonist follistatin. Activin A levels were elevated in the serum of adult CF patients, and correlated inversely with lung function and body mass index. Follistatin treatment of newborn β-ENaC mice, noted for respiratory pathology mimicking human CF, decreased the airway activin A levels and key features of CF lung disease including mucus hypersecretion, airway neutrophilia and levels of mediators that regulate inflammation and chemotaxis. Follistatin treatment also increased body weight and survival of β-ENaC mice, with no evidence of local or systemic toxicity. Our findings demonstrate that activin A levels are elevated in CF and provide proof-of-concept for the use of the activin A antagonist, follistatin, as a therapeutic in the long-term management of lung disease in CF patients.

Virus-induced modulation of lower airway diseases: pathogenesis and pharmacologic approaches to treatment

Uncomplicated upper respiratory viral infections are the most common cause of days lost from work and school and exert a major economic burden. In susceptible individuals, however, common respiratory viruses, particularly human rhinoviruses, also can have a major impact on diseases that involve the lower airways, including asthma, chronic obstructive pulmonary diseases (COPD) and cystic fibrosis (CF). Respiratory virus-induced wheezing illnesses in early life are a significant risk factor for the subsequent development of asthma, and virus infections may also play a role in the development and progression of airway remodeling in asthma. It is clear that upper respiratory tract virus infections can spread to the lower airway and trigger acute attacks of asthma, COPD or CF. These exacerbations can be life-threatening, and exert an enormous burden on health care systems. In recent years we have gained new insights into the mechanisms by which respiratory viruses may induce acute exacerbations of lower airway diseases, as well as into host defense pathways that may regulate the outcomes to viral infections. In the current article we review the role of viruses in lower airway diseases, including our current understanding on pathways by which they may cause remodeling and trigger acute exacerbations. We also review the efficacy of current and emerging therapies used to treat these lower airway diseases on the outcomes due to viral infection, and discuss alternative therapeutic approaches for the management of virus-induced airway inflammation.

Transforming growth factor β and severe asthma: a perfect storm

Asthma is a chronic inflammatory airway disease involving complex interplay between resident and infiltrative cells, which in turn are regulated by a wide range of host mediators. Identifying useful biomarkers correlating with clinical symptoms and degree of airway obstruction remain important to effective future asthma treatments. Transforming growth factor β (TGF-β) is a major mediator involved in pro-inflammatory responses and fibrotic tissue remodeling within the asthmatic lung. Its role however, as a therapeutic target remains controversial. The aim of this review is to highlight its role in severe asthma including interactions with adaptive T-helper cells, cytokines and differentiation through regulatory T-cells. Associations between TGF-β and eosinophils will be addressed and the effects of genetic polymorphisms of the TGF-β1 gene explored in the context of asthma. We highlight TGF-β1 as a potential future therapeutic target in severe asthma including its importance in identifying emerging clinical phenotypes in asthmatic subjects who may be suitable for individualized therapy through TGF-β modulation.