Histamine may induce airway remodeling through release of epidermal growth factor receptor ligands from bronchial epithelial cells

Histamine promotes mouse decidualization through stimulating epithelial amphiregulin release

Accumulating evidence shows that inflammation is essential for embryo implantation and decidualization. Histamine, a proinflammatory factor that is present in almost all mammalian tissues, is synthesized through decarboxylating histidine by histidine decarboxylase (HDC). Although histamine is known to be essential for decidualization, the underlying mechanism remains undefined. In the present study, histamine had no obvious direct effects on in vitro decidualization in mice. However, the obvious differences in HDC protein levels between day 4 of pregnancy and day 4 of pseudopregnancy, as well as between delayed and activated implantation, suggested that the blastocyst may be involved in regulating HDC expression. Furthermore, blastocyst-derived tumor necrosis factor α (TNFα) significantly increased HDC levels in the luminal epithelium. Histamine increased the levels of amphiregulin (AREG) and disintegrin and metalloproteinase domain-containing protein 17 (ADAM17) proteins, which was abrogated by treatment with famotidine, a specific histamine type 2 receptor (H2R) inhibitor, or by TPAI-1 (a specific inhibitor of ADAM17). Intraluminal injection of urocanic acid (HDC inhibitor) on day 4 of pregnancy significantly reduced the number of implantation sites on day 5 of pregnancy. TNFα-stimulated increases in HDC, AREG and ADAM17 protein levels was abrogated by urocanic acid, a specific inhibitor of HDC. Additionally, AREG treatment significantly promoted in vitro decidualization. Collectively, our data suggests that blastocyst-derived TNFα induces luminal epithelial histamine secretion, and histamine increases mouse decidualization through ADAM17-mediated AREG release.

Amphiregulin in infectious diseases: Role, mechanism, and potential therapeutic targets

Amphiregulin (AREG) serves as a ligand for the epidermal growth factor receptor (EGFR) and is involved in vital biological functions, including inflammatory responses, tissue regeneration, and immune system function. Upon interaction with the EGFR, AREG initiates a series of signaling cascades necessary for several physiological activities, such as metabolism, cell cycle regulation, and cellular proliferation. Recent findings have provided evidence for the substantial role of AREG in maintaining the equilibrium of homeostasis in damaged tissues and preserving epithelial cell structure in the context of viral infections affecting the lungs. The development of resistance to influenza virus infection depends on the presence of type 1 cytokine responses. Following the eradication of the pathogen, the lungs are subsequently colonized by several cell types that are linked with type 2 immune responses. These cells contribute to the process of repairing and resolving the tissue injury and inflammation caused by infections. Following influenza infection, the activation of AREG promotes the regeneration of bronchial epithelial cells, enhancing the tissue's structural integrity and increasing the survival rate of infected mice. In the same manner, mice afflicted with influenza experience rapid mortality due to a subsequent bacterial infection in the pulmonary region when both bacterial and viral infections manifest concurrently inside the same host. The involvement of AREG in bacterial infections has been demonstrated. The gene AREG experiences increased transcriptional activity inside host cells in response to bacterial infections caused by pathogens such as Escherichia coli and Neisseria gonorrhea. In addition, AREG has been extensively studied as a mitogenic stimulus in epithelial cell layers. Consequently, it is regarded as a prospective contender that might potentially contribute to the observed epithelial cell reactions in helminth infection. Consistent with this finding, mice that lack the AREG gene exhibit a delay in the eradication of the intestinal parasite Trichuris muris. The observed delay is associated with a reduction in the proliferation rate of colonic epithelial cells compared to the infected animals in the control group. The aforementioned findings indicate that AREG plays a pivotal role in facilitating the activation of defensive mechanisms inside the epithelial cells of the intestinal tissue. The precise cellular sources of AREG in this specific context have not yet been determined. However, it is evident that the increased proliferation of the epithelial cell layer in infected mice is reliant on CD4+ T cells. The significance of this finding lies in its demonstration of the crucial role played by the interaction between immunological and epithelial cells in regulating the AREG-EGFR pathway. Additional research is necessary to delve into the cellular origins and signaling mechanisms that govern the synthesis of AREG and its tissue-protective properties, independent of infection.

In vitro human cell-based models to study airway remodeling in asthma

Airway remodeling, as a predominant characteristic of asthma, refers to the structural changes that occurred both in the large and small airways. These pathological changes not only contribute to airway hyperresponsiveness and airway obstruction, but also predict poor outcomes of patients. In vitro models are the alternatives to animal models that facilitate airway remodeling research. Current approaches to mimic airway remodeling in vitro include mono cultures of cell lines and primary cells that are derived from the respiratory tract, and co-culture systems that consist of different cell subpopulations. Moreover, recent advances in microfluid chips and organoids show promise in simulating the complex architecture and functionality of native organs. According, they enable highly physiological-relevant investigations of human diseases in vitro. Here we aim to detail the current human cell-based models regarding their key pros and cons, and to discuss how they may be used to facilitate our understanding of airway remodeling in asthma.

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

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

Lonicerin attenuates house dust mite-induced eosinophilic asthma through targeting Src/EGFR signaling

Eosinophilic asthma is the predominant phenotype of asthma, and although these patients are sensitive to glucocorticoid therapy, they also experience many side effects. Lonicerin is a kind of bioflavonoid isolated from the Chinese herb Lonicera japonica Thunb, which has anti-inflammatory and immunomodulatory effects. The aim of this study was to elucidate the effects of lonicerin on eosinophilic asthma and its potential mechanisms. Here, we established a house dust mite (house dust mite)-induced eosinophilic asthma model in BALB/c mouse, and evaluated the effects of lonicerin on it. Our results showed that lonicerin significantly reduced airway hyperresponsiveness the number of inflammatory cells (especially eosinophils) and the elevation of interleukin (IL)-4, IL-5, IL-13 and eotaxin in bronchoalveolar lavage fluid (BALF) supernatants of mice. Additionally, lonicerin also eminently blunted inflammatory infiltration and mucus secretion, as well as mRNA levels of Mucin 5AC (MUC5AC) in lung tissue. Furthermore, results of network pharmacology and molecular docking revealed that Src kinase and epidermal growth factor receptor may be the potential targets responsible for the effects of lonicerin. Finally, in vivo experiments confirmed that lonicerin inhibited activation of the Src/EGFR pathway by decreasing their phosphorylation. Taken together, the present study demonstrated that lonicerin could suppress HDM-induced eosinophilic asthma in mice through inhibiting the activation of Src/EGFR pathway, which also provides a basis for further research as a new potentially therapeutic agent for eosinophilic asthma and its underlying mechanisms in the future.

Amphiregulin regulates odontogenic differentiation of dental pulp stem cells by activation of mitogen-activated protein kinase and the phosphatidylinositol 3-kinase signaling pathways

Background

Human dental pulp stem cells (hDPSCs) have received widespread attention in the fields of tissue engineering and regenerative medicine. Although amphiregulin (AREG) has been shown to play a vital function in the biological processes of various cell types, its effects on DPSCs remain largely unknown. The aim of this study was to explore the specific role of AREG as a biologically active factor in the regeneration of dental pulp tissue.

Methods

The growth of hDPSCs, together with their proliferation and apoptosis, in response to AREG was examined by CCK-8 assay and flow cytometry. We explored the effects of AREG on osteo/odontogenic differentiation in vitro and investigated the regeneration and mineralization of hDPSCs in response to AREG in vivo. The effects of AREG gain- and loss-of-function on DPSC differentiation were investigated following transfection using overexpression plasmids and shRNA, respectively. The involvement of the mitogen-activated protein kinase (MAPK) or phosphatidylinositol 3-kinase (PI3K)/Akt pathways in the mineralization process and the expression of odontoblastic marker proteins after AREG induction were investigated by using Alizarin Red S staining and Western blotting, respectively.

Results

AREG (0.01–0.1 µg/mL) treatment of hDPSCs from 1 to 7 days increased hDPSCs growth and affected apoptosis minimally compared with negative controls. AREG exposure significantly promoted hDPSC differentiation, shown by increased mineralized nodule formation and the expression of odontoblastic marker protein expression. In vivo micro-CT imaging and quantitative analysis showed significantly greater formation of highly mineralized tissue in the 0.1 μg/mL AREG exposure group in DPSC/NF-gelatin-scaffold composites. AREG also promoted extracellular matrix production, with collagen fiber, mineralized matrix, and calcium salt deposition on the composites, as shown by H&E, Masson, and Von Kossa staining. Furthermore, AREG overexpression boosted hDPSC differentiation while AREG silencing inhibited it. During the differentiation of hDPSCs, AREG treatment led to phosphorylation of extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and PI3K/Akt. Notably, a specific inhibitor of ERK, JNK, and PI3K/Akt signaling markedly reduced AREG-induced differentiation, as well as levels of phosphorylated ERK and JNK in hDPSCs.

Conclusions

The data indicated that AREG promoted odontoblastic differentiation and facilitated regeneration and mineralization processes in hDPSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02971-4.

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.

HB-EGF-induced IL-8 secretion from airway epithelium leads to lung fibroblast proliferation and migration

BACKGROUND

We have reported that heparin-binding epidermal growth factor (HB-EGF) is increased in patients with chronic obstructive pulmonary disease (COPD) and associated with collagen deposition, but the mechanisms remain unclear. In the present study, we aimed to investigated the inflammatory cytokines secreted by bronchial epithelial cells following exposure to HB-EGF that promoted proliferation and migration of human lung fibroblast.

METHODS

HB-EGF-induced inflammatory cytokines were assayed in two airway epithelial cells (primary human bronchial epithelial cells [HBECs] and BEAS-2B cells). Moreover, the culture supernatants derived from HB-EGF-treated HBECs and BEAS-2B cells were added to human primary lung fibroblasts. The effect of culture supernatants on proliferation and migration of fibroblasts was assessed.

RESULTS

IL-8 expression was significantly increased in bronchial epithelial cells treated with HB-EGF, which was at least partially dependent on NF-kB pathways activation. HB-EGF-induced IL-8 was found to further promote lung fibroblasts proliferation and migration, and the effects were attenuated after neutralizing IL-8.

CONCLUSIONS

These findings suggest that HB-EGF may be involved in the pathology of airway fibrosis by induction of IL-8 from airway epithelium, subsequently causing lung fibroblasts proliferation and migration. Thus, inhibition of HBEGF and/or IL-8 production could prevent the development of airway fibrosis by modulating fibroblast activation.

Airway Epithelial Cells Drive Airway Smooth Muscle Cell Phenotype Switching to the Proliferative and Pro-inflammatory Phenotype

The increased mass of airway smooth muscle (ASM) in the airways of asthmatic patients may contribute to the pathology of this disease by increasing the capacity for airway narrowing. Evidence for the airway epithelium as a participant in ASM remodeling is accruing. To investigate mechanisms by which airway epithelial cells induce ASM cell (ASMC) proliferation, we have employed a co-culture model to explore markers of ASMC proliferative phenotype. Co-culture with epithelial cells led to incorporation of bromodeoxyuridine into ASMCs, indicating augmented proliferation and an associated increase in mRNA of the pro-proliferative co-transcription factor Elk1. Although the mitogen heparin-binding epidermal growth factor (HB-EGF) was augmented in the co-culture supernatant, the ASMC epidermal growth factor receptor (EGFR), an effector of HB-EGF induced proliferation, did not mediate epithelial-induced proliferation. The co-culture increased the expression of ASMC mRNA for the pro-inflammatory cytokines IL-6 and IL-8 as well as the pro-proliferative microRNA miR-210. The transcriptional repressor Max-binding protein (Mnt), a putative target of miR-210, was transcriptionally repressed in co-cultured ASMCs. Together, these data indicate that the airway epithelium-induced proliferative phenotype of ASMCs is not driven by EGFR signaling, but rather may be dependent on miR210 targeting of tumor suppressor Mnt.

Macrophages in Lung Injury, Repair, and Fibrosis

Fibrosis progression in the lung commonly results in impaired functional gas exchange, respiratory failure, or even death. In addition to the aberrant activation and differentiation of lung fibroblasts, persistent alveolar injury and incomplete repair are the driving factors of lung fibrotic response. Macrophages are activated and polarized in response to lipopolysaccharide- or bleomycin-induced lung injury. The classically activated macrophage (M1) and alternatively activated macrophage (M2) have been extensively investigated in lung injury, repair, and fibrosis. In the present review, we summarized the current data on monocyte-derived macrophages that are recruited to the lung, as well as alveolar resident macrophages and their polarization, pyroptosis, and phagocytosis in acute lung injury (ALI). Additionally, we described how macrophages interact with lung epithelial cells during lung repair. Finally, we emphasized the role of macrophage polarization in the pulmonary fibrotic response, and elucidated the potential benefits of targeting macrophage in alleviating pulmonary fibrosis.

Epithelial Cells and Inflammation in Pulmonary Wound Repair

Respiratory diseases are frequently characterised by epithelial injury, airway inflammation, defective tissue repair, and airway remodelling. This may occur in a subacute or chronic context, such as asthma and chronic obstructive pulmonary disease, or occur acutely as in pathogen challenge and acute respiratory distress syndrome (ARDS). Despite the frequent challenge of lung homeostasis, not all pulmonary insults lead to disease. Traditionally thought of as a quiescent organ, emerging evidence highlights that the lung has significant capacity to respond to injury by repairing and replacing damaged cells. This occurs with the appropriate and timely resolution of inflammation and concurrent initiation of tissue repair programmes. Airway epithelial cells are key effectors in lung homeostasis and host defence; continual exposure to pathogens, toxins, and particulate matter challenge homeostasis, requiring robust defence and repair mechanisms. As such, the epithelium is critically involved in the return to homeostasis, orchestrating the resolution of inflammation and initiating tissue repair. This review examines the pivotal role of pulmonary airway epithelial cells in initiating and moderating tissue repair and restitution. We discuss emerging evidence of the interactions between airway epithelial cells and candidate stem or progenitor cells to initiate tissue repair as well as with cells of the innate and adaptive immune systems in driving successful tissue regeneration. Understanding the mechanisms of intercellular communication is rapidly increasing, and a major focus of this review includes the various mediators involved, including growth factors, extracellular vesicles, soluble lipid mediators, cytokines, and chemokines. Understanding these areas will ultimately identify potential cells, mediators, and interactions for therapeutic targeting.

Effects of Inhalation of STIM-Orai Antagonist SKF 96365 on Ovalbumin-Induced Airway Remodeling in Guinea Pigs

Airway remodeling (AR) consists of wall thickening and hyperreactivity. STIM (stromal interaction molecule) and Orai protein pathways mediate extracellular Ca²⁺ signals involved in AR. This study aims to define the effects on AR of the STIM-Orai antagonist SKF 96365 given by inhalation in three increasing doses in ovalbumin-induced AR. In the control group, the antiasthmatic budesonide and salbutamol were given in the same model. The airway structure was evaluated by histological and immunohistochemistry and reactivity by specific airway resistance, contraction strength of isolated airway smooth muscles, and mucociliary clearance expressed by ciliary beating frequency. The immuno-biochemical markers of chronic inflammation were evaluated by BioPlex and ELISA assays. The AR was mediated by inflammatory cytokines and growth factors. The findings show significant anti-remodeling effects of SKF 96365, which were associated with a decrease in airway hyperreactivity. The anti-remodeling effect of SKF 96365 was mediated via the suppression of IL-4, IL-5, and IL-13 synthesis, and IL-12-INF-γ-TGF-β pathway. The budesonide-related AR suppression had to do with a decrease in proinflammatory cytokines and an increase in the anti-inflammatory IL-10, with negligible influence on growth factors synthesis and mucous glands activity.

Airway Epithelial Dysfunction in Asthma: Relevant to Epidermal Growth Factor Receptors and Airway Epithelial Cells

Airway epithelium plays an important role as the first barrier from external pathogens, including bacteria, viruses, chemical substances, and allergic components. Airway epithelial cells also have pivotal roles as immunological coordinators of defense mechanisms to transfer signals to immunologic cells to eliminate external pathogens from airways. Impaired airway epithelium allows the pathogens to remain in the airway epithelium, which induces aberrant immunological reactions. Dysregulated functions of asthmatic airway epithelium have been reported in terms of impaired wound repair, fragile tight junctions, and excessive proliferation, leading to airway remodeling, which contributes to aberrant airway responses caused by external pathogens. To maintain airway epithelium integrity, a family of epidermal growth factor receptors (EGFR) have pivotal roles in mechanisms of cell growth, proliferation, and differentiation. There are extensive studies focusing on the relation between EGFR and asthma pathophysiology, which describe airway remodeling, airway hypermucus secretion, as well as immunological responses of airway inflammation. Furthermore, the second EGFR family member, erythroblastosis oncogene B2 (ErbB2), has been recognized to be involved with impaired wound recovery and epithelial differentiation in asthmatic airway epithelium. In this review, the roles of the EGFR family in asthmatic airway epithelium are focused on to elucidate the pathogenesis of airway epithelial dysfunction in asthma.

Blood and Salivary Amphiregulin Levels as Biomarkers for Asthma

Background: Amphiregulin (AREG) expression in asthmatic airways and sputum was shown to increase and correlate with asthma. However, no studies were carried out to evaluate the AREG level in blood and saliva of asthmatic patients. Objective: To measure circulating AREG mRNA and protein concentrations in blood, saliva, and bronchial biopsies samples from asthmatic patients. Methods: Plasma and Saliva AREG protein concentrations were measured using ELISA while PBMCs, and Saliva mRNA expression was measured by RT qPCR in non-severe, and severe asthmatic patients compared to healthy controls. Primary asthmatic bronchial epithelial cells and fibroblasts were assessed for AREG mRNA expression and released soluble AREG in their conditioned media. Tissue expression of AREG was evaluated using immunohistochemistry of bronchial biopsies from asthmatic patients and healthy controls. Publicly available transcriptomic databases were explored for the global transcriptomic profile of bronchial epithelium, and PBMCs were explored for AREG expression in asthmatic vs. healthy controls. Results: Asthmatic patients had higher AREG protein levels in blood and saliva compared to control subjects. Higher mRNA expression in saliva and primary bronchial epithelial cells plus higher AREG immunoreactivity in bronchial biopsies were also observed. Both blood and saliva AREG levels showed positive correlations with allergic rhinitis status, atopy status, eczema status, plasma periostin, neutrophilia, Montelukast sodium use, ACT score, FEV1, and FEV1/FVC. In silico analysis showed that severe asthmatic bronchial epithelium with high AREG gene expression is associated with higher neutrophils infiltration. Conclusion: AREG levels measured in a minimally invasive blood sample and a non-invasive saliva sample are higher in non-allergic severe asthma.

CLINICAL IMPLICATIONS

This is the first report to show the higher level of AREG levels in blood and saliva of non-allergic severe asthma.

Mechanical forces induce an asthma gene signature in healthy airway epithelial cells

Bronchospasm compresses the bronchial epithelium, and this compressive stress has been implicated in asthma pathogenesis. However, the molecular mechanisms by which this compressive stress alters pathways relevant to disease are not well understood. Using air-liquid interface cultures of primary human bronchial epithelial cells derived from non-asthmatic donors and asthmatic donors, we applied a compressive stress and then used a network approach to map resulting changes in the molecular interactome. In cells from non-asthmatic donors, compression by itself was sufficient to induce inflammatory, late repair, and fibrotic pathways. Remarkably, this molecular profile of non-asthmatic cells after compression recapitulated the profile of asthmatic cells before compression. Together, these results show that even in the absence of any inflammatory stimulus, mechanical compression alone is sufficient to induce an asthma-like molecular signature.

Serum proteomics analysis based on label-free revealed the protective effect of Chinese herbal formula Gu-Ben-Fang-Xiao

Gubenfangxiao decoction (GBFXD) is a traditional Chinese medicine formula derived from Yupingfengsan, an ancient formula widely used to treat respiratory diseases. In recent years, GBFXD has been applied to efficaciously and safely treat asthma. However, the mechanism of GBFXD is still not fully elucidated. The aim of this study was to employ the label-free proteomic method to explore the protective mechanism of GBFXD in respiratory syncytial virus (RSV)-ovalbumin (OVA) induced chronic persistent asthmatic mice. After RSV-OVA challenge, mice were orally administered GBFXD at a dose of 36 g/kg accompanied with OVA nasal spray once every 3 days for 28 days. The label-free proteomics-based liquid chromatography-tandem mass spectrometry method was used to explore the differentially abundant proteins (DAPs) in the serum from model mice compared with that in control mice (M:C), and in GBFXD-treated mice compared with that in model mice (G:M). The mass spectrometry proteomics data have been deposited to the ProteomeXchange with identifier PXD013244. A total of 69 significant DAPs were identified including 39 in M:C, 46 in G:M, and 16 common differential proteins. Bioinformatics analysis revealed that the DAPs of M:C were mainly involved in inflammatory response and were related to lipid metabolism. However, the DAPs of G:M mostly participated in stress response, inflammatory response, and epithelial cell proliferation. Serum levels of Apoa-1, Apoc-1, Cfd, and Lrg1, EGFR and Lrg1 in the lungs were consistent with the results of proteomic analysis. Apoa-1 and Apoc-1 were closely related to cholesterol transport, lipid metabolism balance, and airway epithelial integrity; Cfd participated in immune response, affecting the occurrence and development of inflammation; EGFR and Lrg1 were involved in epithelial cell proliferation, influencing the process of airway remodeling. In summary, these results indicated that GBFXD may affect inflammatory and immune response of asthma by regulating cholesterol transport and complement factor activation. Furthermore, it could repair damaged airway epithelium and avoid airway remodeling to prevent and treat asthma.

Airway macrophages as the guardians of tissue repair in the lung

The lungs present a challenging immunological dilemma for the host. Anatomically positioned at the environmental interface, they are constantly exposed to antigens, pollutants and microbes, while simultaneously facilitating vital gas exchange. Remarkably, the lungs maintain a functionally healthy state, ignoring harmless inhaled proteins, adapting to toxic environmental insults and limiting immune responses to allergens and pathogenic microbes. This functional strategy of environmental adaptation maintains immune defense, reduces tissue damage, and promotes and sustains lung immune tolerance. At steady state, airway macrophages produce low levels of cytokines, and suppress the induction of innate and adaptive immunity. These cells are primary initiators of lung innate immunity and possess high phagocytic activity to clear particulate antigens and apoptotic cell debris from the airways to regulate the response to infection and inflammation. In response to epithelial injury, resident and recruited macrophages drive tissue repair. In this review, we will focus on the functional importance of macrophages in tissue homeostasis and inflammation in the lung and highlight how environmental cues alter the plasticity and function of lung airway macrophages. We will also discuss mechanisms employed by pulmonary macrophages to promote resolution of tissue inflammation, and how and when this balance is perturbed, they contribute to pathological remodeling in acute and chronic infections and diseases such as asthma, idiopathic pulmonary fibrosis and chronic obstructive pulmonary disease.

Resolvin D1, but not resolvin E1, transactivates the epidermal growth factor receptor to increase intracellular calcium and glycoconjugate secretion in rat and human conjunctival goblet cells

PURPOSE

To identify interactions of the epidermal growth factor receptor (EGFR) with the pro-resolving mediator receptors for RvD1 and RvE1 to stimulate an increase in intracellular [Ca²⁺] ([Ca²⁺]_i) and mucin secretion from cultured human and rat conjunctival goblet cells.

METHODS

Goblet cells from human and rat conjunctiva were grown in culture using RPMI media. Cultured goblet cells were pre-incubated with inhibitors, and then stimulated with RvD1, RvE1, EGF or the cholinergic agonist carbachol (Cch). Increase in [Ca²⁺]_i was measured using fura-2/AM. Goblet cell secretion was measured using an enzyme-linked lectin assay with UEA-1. Western blot analysis was performed with antibodies against AKT and ERK 1/2.

RESULTS

In cultured human conjunctival goblet cells RvE1 -stimulated an increase in [Ca²⁺]_i. RvD1-, but not the RvE1-, stimulated increase in [Ca²⁺]_i and mucin secretion was blocked by the EGFR inhibitor AG1478 and siRNA for the EGFR. RvD1-, but not RvE1-stimulated an increase in [Ca²⁺]_i that was also inhibited by TAPI-1, an inhibitor of the matrix metalloprotease ADAM 17. Inhibition of the EGFR also blocked RvD1-stimulated increase in AKT activity and both RvD1-and RvE1-stimulated increase in ERK 1/2 activity. Pretreatment with either RvD1 or RvE1 did not block the EGFR-stimulated increase in [Ca²⁺]_i.

CONCLUSIONS

We conclude that in cultured rat and human conjunctival goblet cells, RvD1 activates the EGFR, increases [Ca²⁺]_i, activates AKT and ERK1/2 to stimulate mucin secretion. RvE1 does not transactivate the EGFR to increase [Ca²⁺]_I and stimulate mucin secretion, but does interact with the receptor to increase ERK 1/2 activity.

Activation of the EGF Receptor by Histamine Receptor Subtypes Stimulates Mucin Secretion in Conjunctival Goblet Cells

Purpose

The purpose of this study was to determine if histamine receptors interact with the epidermal growth factor receptor (EGFR) in cultured rat conjunctival goblet cells.

Methods

Goblet cells from rat conjunctiva were grown in organ culture. First-passage goblet cells were used in all experiments. Phosphorylated (active) and total EGFR, AKT, and extracellular signal-regulated kinase (ERK)1/2 were measured by Western blot analysis. Cells were preincubated with the EGFR antagonist AG1478 for 30 minutes or small interfering RNA specific to the EGFR for 3 days prior to stimulation with histamine or agonists specific for histamine receptor subtypes for 2 hours. Goblet cell secretion was measured using an enzyme-linked lectin assay. Goblet cells were incubated for 1 hour with the calcium indicator molecule fura-2/AM, and intracellular [Ca2+] ([Ca2+]i) was determined. Data were collected in real time and presented as the actual [Ca2+]i with time and as the change in peak [Ca2+]i.

Results

Histamine increased the phosphorylation of the EGFR. Mucin secretion and increase in [Ca2+]i stimulated by histamine, and agonists specific for each histamine receptor subtype were blocked by inhibition of the EGFR. Increase in [Ca2+]i stimulated by histamine and specific agonists for each histamine receptor was also inhibited by TAPI-1, a matrix metalloproteinase (MMP) inhibitor. The histamine-stimulated increase in activation of AKT, but not ERK1/2, was blocked by AG1478.

Conclusions

In conjunctival goblet cells, histamine, using all four receptor subtypes, transactivates the EGFR via an MMP. This in turn phosphorylates AKT to increase [Ca2+]i and stimulate mucin secretion.

Poly (ethylene-co-vinyl alcohol) is a suitable substrate for human olfactory neuroepithelial cell differentiation in vitro through a defined regulatory pathway

Olfactory dysfunction significantly influences patients' life quality, but currently has no adequate treatment. Poly (ethylene-co-vinyl alcohol) (EVAL) mediates cell adhesion, growth and modulates differentiation of neural stem cells. However, whether EVAL is a suitable substrate to establish an in vitro culture system that can promote development and differentiation of human olfactory neuroepithelial cells (HONCs) remains unexplored. This study isolates and cultures HONCs on controls and EVAL films for 21 days. The effects of treatment are assessed using immunocytochemistry, microarray analysis, quantitative PCR, ELISA and western blots following culturing. Most of the cell morphology on controls is epithelial and expresses markers of sustentacular cells (SCs), cadherin-1 and cytokeratin18, whereas the main population on EVAL presents as morphology with extended thin processes and possesses markers of mature olfactory sensory neurons (OSNs), olfactory marker protein (OMP). Microarray analyses reveal neuropeptide Y (NPY) and amphiregulin (AREG) are the two important regulating factors on EVAL films. HONCs cultured on EVAL films enhance the development of mature OSNs through NPY signaling, and significantly decrease the growth of SCs by blocking epidermal growth factor receptor (EGFR) activation. EVAL is a potential biomaterial to serve as an ideal substrate for treating olfactory dysfunction in the future.

STATEMENT OF SIGNIFICANCE

Olfaction not only contributes to enjoyments of food, but provides a clue to escape from dangerous environmental hazards. However, loss of smell is commonly progressive and there is no good prognostic approach for olfactory dysfunction. Here, we use poly (ethylene-co-vinyl alcohol) (EVAL) to establish an in vitro culture system that promotes development and differentiation of human olfactory neuroepithelial cells. We show that EVAL not only enhances the development of mature olfactory sensory neurons through neuronpeptide Y signaling, but significantly protects the olfactory neuroepithelium from metaplasia by inhibiting EGFR activation. Therefore, EVAL is a potential biomaterial to serve as an ideal substrate for treating olfactory dysfunction in the future.

The EGFR-ADAM17 Axis in Chronic Obstructive Pulmonary Disease and Cystic Fibrosis Lung Pathology

Chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF) share molecular mechanisms that cause the pathological symptoms they have in common. Here, we review evidence suggesting that hyperactivity of the EGFR/ADAM17 axis plays a role in the development of chronic lung disease in both CF and COPD. The ubiquitous transmembrane protease A disintegrin and metalloprotease 17 (ADAM17) forms a functional unit with the EGF receptor (EGFR), in a feedback loop interaction labeled the ADAM17/EGFR axis. In airway epithelial cells, ADAM17 sheds multiple soluble signaling proteins by proteolysis, including EGFR ligands such as amphiregulin (AREG), and proinflammatory mediators such as the interleukin 6 coreceptor (IL-6R). This activity can be enhanced by injury, toxins, and receptor-mediated external triggers. In addition to intracellular kinases, the extracellular glutathione-dependent redox potential controls ADAM17 shedding. Thus, the epithelial ADAM17/EGFR axis serves as a receptor of incoming luminal stress signals, relaying these to neighboring and underlying cells, which plays an important role in the resolution of lung injury and inflammation. We review evidence that congenital CFTR deficiency in CF and reduced CFTR activity in chronic COPD may cause enhanced ADAM17/EGFR signaling through a defect in glutathione secretion. In future studies, these complex interactions and the options for pharmaceutical interventions will be further investigated.

Epithelial Cells Induce a Cyclo-Oxygenase-1-Dependent Endogenous Reduction in Airway Smooth Muscle Contractile Phenotype

Airway smooth muscle cells (ASMCs) are phenotypically regulated to exist in either a proliferative or a contractile state. However, the influence of other airway structural cell types on ASMC phenotype is largely unknown. Although epithelial cells are known to drive ASM proliferation, their effects on the contractile phenotype are uncertain. In the current study, we tested the hypothesis that epithelial cells reduce the contractile phenotype of ASMCs. To do so, we measured force production by traction microscopy, gene and protein expression, as well as calcium release by Fura-2 ratiometric imaging. ASMCs incubated with epithelial-derived medium produced less force after histamine stimulation. We observed reduced expression of myocardin, α-smooth muscle actin, and calponin within ASMCs after coculture with epithelial cells. Peak calcium release in response to histamine was diminished, and depended on the synthesis of cyclo-oxygenase-1 products by ASM and on prostaglandin E receptors 2 and 4. Together, these in vitro results demonstrate that epithelial cells have the capacity to coordinately reduce ASM contraction by functional antagonism and by reduction of the expression of certain contractile proteins.

Positive feedback of the amphiregulin-EGFR-ERK pathway mediates PM2.5 from wood smoke-induced MUC5AC expression in epithelial cells

Biomass fuel smoke is thought to contribute to chronic obstructive pulmonary disease, which is characterized by mucous cell metaplasia and enhanced mucus secretion. We investigated the effect of particulate matter (PM) with a diameter <2.5 μm (PM2.5) from wood smoke (WSPM2.5) on the expression of the most prominent secreted mucin, MUC5AC. Wood smoke was able to induce MUC5AC expression in the rat respiratory tract after 3 months of exposure. WSPM2.5 could induce MUC5AC production in both primary human airway epithelial cells and the NCI-H292 cell line. This induction process was mediated by activation of epithelial growth factor receptor (EGFR)-extracellular signal-regulated kinase (ERK) signaling through an EGFR ligand-dependent mechanism. Amphiregulin (AR) was identified as the major ligand responsible for EGFR-ERK signaling activation and MUC5AC expression. In turn, EGFR-ERK pathway activation was found to contribute to the de novo synthesis of AR. This positive feedback loop might play an important role in a sustained mucus hypersecretion response.

MicroRNA-145 down-regulates mucin 5AC to alleviate airway remodeling and targets EGFR to inhibit cytokine expression

This study aims to explore how microRNA-145 (miR-145) affects airway remodeling and cytokine expression by targeting epidermal growth factor receptor (EGFR) to regulate mucin 5AC (MUC5AC).Mice alveolar epithelial cells (AECs) were divided into a control, blank, miR-145 mimics, mimic control, miR-145 inhibitors, inhibitor control, si-EGFR and miR-145 inhibitors + si-EGFR group. Asthma mice models with airway remodeling were induced with an Ovalbumin (OVA) solution and randomly divided into a normal, asthma, asthma + miR-145 mimics, asthma + miR-145 mimic control, asthma + si-EGFR or asthma + si-EGFR NC group. Airway remodeling degree and histomorphology was measured using hematoxylin-eosin (HE), Masson and periodic acid-Schiff (PAS) staining. Flow cytometry was used to detect Th2 and Th17 cells in peripheral blood, ELISA was used to measure inflammatory factors. qRT-PCR and western blotting was adapted to detect the expressions of EGFR and the relevant cytokines that are regulated by miR-145.The control, miR-145 mimics and si-EGFR groups showed a higher expression of miR-145 and a lower expression of EGFR and cytokines than the blank, mimic control, inhibitor control and miR-145 inhibitor + si-EGFR groups. Mice in the asthma + miR-145 mimics and asthma + si-EGFR groups showed lower WAt/Pbm, WAi/Pbm and WAm/Pbm, less inflammatory cells, less airway modeling and alleviated goblet cell hyperplasia and mucus obstruction than the asthma group. Furthermore, the expressions of EGFR and cytokines of transfected cells and lung tissues were negatively related to those of miR-145. MiR-145 can down-regulate MUC5AC by negatively targeting EGFR and thereby relieving airway remodeling.

EGF-Amphiregulin Interplay in Airway Stem/Progenitor Cells Links the Pathogenesis of Smoking-Induced Lesions in the Human Airway Epithelium

The airway epithelium of cigarette smokers undergoes dramatic remodeling with hyperplasia of basal cells (BC) and mucus-producing cells, squamous metaplasia, altered ciliated cell differentiation and decreased junctional barrier integrity, relevant to chronic obstructive pulmonary disease and lung cancer. In this study, we show that epidermal growth factor receptor (EGFR) ligand amphiregulin (AREG) is induced by smoking in human airway epithelium as a result of epidermal growth factor (EGF)-driven squamous differentiation of airway BC stem/progenitor cells. In turn, AREG induced a unique EGFR activation pattern in human airway BC, distinct from that evoked by EGF, leading to BC- and mucous hyperplasia, altered ciliated cell differentiation and impaired barrier integrity. Further, AREG promoted its own expression and suppressed expression of EGF, establishing an autonomous self-amplifying signaling loop in airway BC relevant for promotion of EGF-independent hyperplastic phenotypes. Thus, EGF-AREG interplay in airway BC stem/progenitor cells is one of the mechanisms that mediates the interconnected pathogenesis of all major smoking-induced lesions in the human airway epithelium. Stem Cells 2017;35:824-837.

Amphiregulin suppresses epithelial cell apoptosis in lipopolysaccharide-induced lung injury in mice

BACKGROUND AND OBJECTIVE

As a member of the epidermal growth factor family, amphiregulin contributes to the regulation of cell proliferation. Amphiregulin was reported to be upregulated in damaged lung tissues in patients with chronic obstructive pulmonary disease and asthma and in lung epithelial cells in a ventilator-associated lung injury model. In this study, we investigated the effect of amphiregulin on lipopolysaccharide (LPS)-induced acute lung injury in mice.

METHODS

Acute lung injury was induced by intranasal instillation of LPS in female C57BL/6 mice, and the mice were given intraperitoneal injections of recombinant amphiregulin or phosphate-buffered saline 6 and 0.5 h before and 3 h after LPS instillation. The effect of amphiregulin on apoptosis and apoptotic pathways in a murine lung alveolar type II epithelial cell line (LA-4 cells) were examined using flow cytometry and western blotting, respectively.

RESULTS

Recombinant amphiregulin suppressed epithelial cell apoptosis in LPS-induced lung injury in mice. Western blotting revealed that amphiregulin suppressed epithelial cell apoptosis by inhibiting caspase-8 activity.

CONCLUSION

Amphiregulin signaling may be a therapeutic target for LPS-induced lung injury treatment through its prevention of epithelial cell apoptosis.

Classically Activated Macrophages Protect against Lipopolysaccharide-induced Acute Lung Injury by Expressing Amphiregulin in Mice

BACKGROUND

Alveolar macrophages (AMs) activated into M1 phenotype are involved in the development of lipopolysaccharide-induced acute lung injury (ALI). However, whether AMs express amphiregulin and what roles amphiregulin plays in lipopolysaccharide-induced ALI remain poorly understood.

METHODS

Acute lung injury was induced by intratracheal instillation of lipopolysaccharide in male C57BL/6 mice. Lung injury scores, level of protein, and level of neutrophils in bronchial alveolar lavage fluid of lipopolysaccharide-induced ALI mice were compared with those in mice challenged with recombinant exogenous amphiregulin and antiamphiregulin antibody. Amphiregulin expression in macrophages and neutrophils in bronchial alveolar lavage fluid of lipopolysaccharide-induced ALI mice was determined by using immunofluorescence technique and further detected in M0, M1, and M2 phenotypes of both peritoneal macrophages and AMs. The effect of amphiregulin on apoptosis of MLE12 cells and activation of epithelial growth factor receptor-AKT pathway were, respectively, examined by using flow cytometry and western blotting.

RESULTS

Alveolar macrophages were found to highly express amphiregulin in ALI mice. Amphiregulin neutralization aggravated, whereas recombinant exogenous amphiregulin attenuated lipopolysaccharide-induced ALI in mice (n = 6). In cultured AMs and peritoneal macrophages, amphiregulin was mainly generated by M1, rather than M0 or M2 phenotype (n = 5). Apoptosis ratio of lipopolysaccharide-challenged MLE12 cells was significantly reduced by recombinant exogenous amphiregulin from 16.60 ± 1.82 to 9.47 ± 1.67% (n = 5) but significantly increased from 17.45 ± 1.13 to 21.67 ± 1.10% (n = 5) after stimulation with supernatant of M1-polarized AM media conditioned with amphiregulin-neutrolizing antibody. Western blotting revealed that amphiregulin activated epithelial growth factor receptor and AKT in the lung tissues and MLE12 cells (n = 5).

CONCLUSIONS

Different from the common notion that classically activated AMs have just a detrimental effect on the lung tissues, the results of this study showed that classically activated AMs also exerted a protective effect on the lung tissues by producing high-level amphiregulin in lipopolysaccharide-induced ALI.

HB-EGF-Promoted Airway Smooth Muscle Cells and Their Progenitor Migration Contribute to Airway Smooth Muscle Remodeling in Asthmatic Mouse

The airway smooth muscle (ASM) cells' proliferation, migration, and their progenitor's migration are currently regarded as causative factors for ASM remodeling in asthma. Heparin-binding epidermal growth factor (HB-EGF), a potent mitogen and chemotactic factor, could promote ASM cell proliferation through MAPK pathways. In this study, we obtained primary ASM cells and their progenitors from C57BL/6 mice and went on to explore the role of HB-EGF in these cells migration and the underlying mechanisms. We found that recombinant HB-EGF (rHB-EGF) intratracheal instillation accelerated ASM layer thickening in an OVA-induced asthmatic mouse. Modified Boyden chamber assay revealed that rHB-EGF facilitate ASM cell migration in a dose-dependent manner and ASM cells from asthmatic mice had a greater migration ability than that from normal counterparts. rHB-EGF could stimulate the phosphorylation of ERK1/2 and p38 in ASM cells but further migration assay showed that only epidermal growth factor receptor inhibitor (AG1478) or p38 inhibitor (SB203580), but not ERK1/2 inhibitor (PD98059), could inhibit rHB-EGF-mediated ASM cells migration. Actin cytoskeleton experiments exhibited that rHB-EGF could cause actin stress fibers disassembly and focal adhesions formation of ASM cells through the activation of p38. Finally, airway instillation of rHB-EGF promoted the recruitment of bone marrow-derived smooth muscle progenitor cells, which were transferred via caudal vein, migrating into the airway from the circulation. These observations demonstrated that ASM remodeling in asthma might have resulted from HB-EGF-mediated ASM cells and their progenitor cells migration, via p38 MAPK-dependent actin cytoskeleton remodeling.

Immunohistochemical localization of epidermal growth factor system in the lung of the Japanese quail (Coturnix coturnix japonica) during the post-hatching period

The purpose of this study is to determine the possible changes in the localization of the four Epidermal Growth Factor Receptors and three ligands in quail lungs from the first day of hatching until the 125th after hatching using immunohistochemical methods. Immunohistochemical results demonstrated that four EGFRs and their ligands are chiefly located in the cytoplasm of cells. Additionally, ErbB4, AREG, and NRG1 are localized to the nucleus and nucleolus, but EGF is present in the nucleolus. ErbB2 was also found in the cell membrane. In the epithelium of secondary bronchi, the goblet cells only exhibited ErbB1 and ErbB2, whereas the basal and ciliated cells exhibited EGFRs and ligands immunoreactivity. The atrial granular cells displayed moderate levels of ErbB1-ErbB3 and EGF and strong levels of ErbB4, AREG, and NRG1 immunoreactivity. While the squamous atrial cells and squamous respiratory cells of air capillaries and endothelial cells of blood capillaries exhibited moderate to strong ErbB2, ErbB4, AREG, and NRG1 immunoreactivity, they had negative or weak ErbB1, ErbB3, and EGF immunoreactivity. The expression levels of ErbB2-ErbB4, EGF, AREG, and NRG1 were also detected in fibroblasts. Although ErbB2 was highly expressed in the bronchial and vascular smooth muscle cells, weak expression of ErbB1, ErbB3, AREG and EGF and moderate expression of ErbB4 and NRG1 were observed. Macrophages were only negative for ErbB1. In conclusion, these data indicate that the EGFR-system is functionally active at hatching, which supports the hypothesis that the members of EGFR-system play several cell-specific roles in quail lung growth after hatching.

Putting the Squeeze on Airway Epithelia

Asthma is characterized by chronic inflammation, airway hyperresponsiveness, and progressive airway remodeling. The airway epithelium is known to play a critical role in the initiation and perpetuation of these processes. Here, we review how excessive epithelial stress generated by bronchoconstriction is sufficient to induce airway remodeling, even in the absence of inflammatory cells.

Mast cells in airway diseases and interstitial lung disease

Mast cells are major effector cells of inflammation and there is strong evidence that mast cells play a significant role in asthma pathophysiology. There is also a growing body of evidence that mast cells contribute to other inflammatory and fibrotic lung diseases such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis. This review discusses the role that mast cells play in airway diseases and highlights how mast cell microlocalisation within specific lung compartments and their cellular interactions are likely to be critical for their effector function in disease.

Genetic variation within the histamine pathway among patients with asthma--a pilot study

OBJECTIVE

Histamine is an important mediator in the pathophysiology of asthma. We have previously reported that HRH1 is differentially expressed among those with asthma compared to those without asthma. Single histamine-related genes have also been associated with asthma. We aimed to evaluate known single nucleotide polymorphisms (SNPs) in genes along the histamine biotransformation and response pathway, and determine their association with asthma and HRH1 mRNA expression.

METHODS

We enrolled children and adults (n = 93) with/without asthma who met inclusion/exclusion criteria. Genotyping was performed for nine known SNPs in the HDC, HRH1, HRH4, HNMT and ABP1 genes. HRH1 mRNA expression was determined on RNA from buccal tissue. General linear model, Fisher's exact test and Chi-square test were used to determine differences in allele, genotype and haplotype frequency between subjects with and without asthma and differential HRH1 mRNA expression relative to genotype. Statistical significance was determined by p < 0.05.

RESULTS

No difference was observed in genotype/allele frequency for the nine SNPs between subjects with and without asthma. The HNMT-1639C/-464C/314C/3'UTRA haplotype was more frequently observed in those without asthma than those with asthma (p = 0.03). We also observed genetic differences relative to race and gender. HNMT 314 genotype CT was more frequent in males with asthma compared to those without asthma (p = 0.04).

CONCLUSIONS

Histamine pathway haplotype was associated with a diagnosis of asthma in our cohort but allele and genotype were not. Subgroup evaluations may also be important. Further studies are needed to determine the potential biological/clinical significance of our findings.

Effects of intravenous and subcutaneous heartworm homogenate from doxycycline-treated and untreated donor dogs on bronchial reactivity and lung in cats

A controlled, blind research study was conducted to define the innate response of lungs in specific pathogen free (SPF) cats to intravenous (n=10) or subcutaneous (n=4) administration of homogenate of adult Dirofilaria immitis from donor dogs compared with lung response in control cats (n=6). There was no difference in cats that received heartworm homogenate IV for 18 days from donor dogs treated with doxycycline for 1 month compared with cats given heartworm homogenate from untreated donor dogs. Cats did not develop clinical signs, and no radiographic changes were noted. Cats given SC heartworm homogenate at lower concentration than IV groups did not develop histologic changes. Cats that received IV heartworm homogenate for 18 days developed mild interstitial and peribronchial myofibrocyte proliferation and smooth muscle proliferation of the pulmonary arteries. Bronchial ring contractility in vitro was blunted in the IV homogenate cats to the agonists acetylcholine and 5-hydroxytryptamine. Cats in the SC group had increased sensitivity to histamine at high concentrations but normal contractility and relaxation responses to other agonists. No increase in mast cells was noted in lung tissues of cats given homogenate. In the absence of bronchial wall remodeling, cats given IV homogenate had blunted responses to bronchial constriction, but normal relaxation to nitroprusside and substance P and increased sensitivity to histamine. In the absence adult heartworms, the homogenate of adult heartworms in the circulation of SPF cats induced a direct effect on lung parenchyma and altered bronchial ring reactivity.

Lung remodeling mechanisms in chronic lung diseases

PURPOSE OF REVIEW

To summarize the new knowledge on tissue remodeling in the context of lung diseases. Tissue remodeling includes changes in cells: differentiation; response to growths factors, hormones, or environmental factors; and composition of the extracellular matrix. So, can one trigger cause them all or are they independently regulated?

RECENT FINDINGS

New evidence from clinical and experimental studies strengthened the view that a susceptibility to remodeling can be initiated in early life and be re-activated by environmental triggers later in life. Many studies further support the idea that TGF-β plays the central role in the pathogenesis of remodeling and fibrosis. However, the activation pathways and the end-effect of TGF-β activation seems to be distinctive of disease and effecter cell specific patterns. The existing animal models do not properly reflect the human disease and thus have to be further improved.

SUMMARY

The central role of TGF-β on pathological mechanisms leading to remodeling and fibrosis has been further confirmed. However, the questions of why TGF-β is activated as well as its disease and cell type specific mode of action remain to be answered. Based on clinical data redefining the term 'tissue remodeling' in a disease and cell type specific way should be considered.

Plasminogen-stimulated airway smooth muscle cell proliferation is mediated by urokinase and annexin A2, involving plasmin-activated cell signalling

BACKGROUND AND PURPOSE

The conversion of plasminogen into plasmin by interstitial urokinase plasminogen activator (uPA) is potentially important in asthma pathophysiology. In this study, the effect of uPA-mediated plasminogen activation on airway smooth muscle (ASM) cell proliferation was investigated.

EXPERIMENTAL APPROACH

Human ASM cells were incubated with plasminogen (0.5-50 μg·mL(-1) ) or plasmin (0.5-50 mU·mL(-1) ) in the presence of pharmacological inhibitors, including UK122, an inhibitor of uPA. Proliferation was assessed by increases in cell number or MTT reduction after 48 h incubation with plasmin(ogen), and by earlier increases in [(3) H]-thymidine incorporation and cyclin D1 expression.

KEY RESULTS

Plasminogen (5 μg·mL(-1) )-stimulated increases in cell proliferation were attenuated by UK122 (10 μM) or by transfection with uPA gene-specific siRNA. Exogenous plasmin (5 mU·mL(-1) ) also stimulated increases in cell proliferation. Inhibition of plasmin-stimulated ERK1/2 or PI3K/Akt signalling attenuated plasmin-stimulated increases in ASM proliferation. Furthermore, pharmacological inhibition of cell signalling mediated by the EGF receptor, a receptor trans-activated by plasmin, also reduced plasmin(ogen)-stimulated cell proliferation. Knock down of annexin A2, which has dual roles in both plasminogen activation and plasmin-signal transduction, also attenuated ASM cell proliferation following incubation with either plasminogen or plasmin.

CONCLUSIONS AND IMPLICATIONS

Plasminogen stimulates ASM cell proliferation in a manner mediated by uPA and involving multiple signalling pathways downstream of plasmin. Targeting mediators of plasminogen-evoked ASM responses, such as uPA or annexin A2, may be useful in the treatment of asthma.

Histamine stimulates hydrogen peroxide production by bronchial epithelial cells via histamine H1 receptor and dual oxidase

Oxidative stress has been implicated in the pathogenesis of bronchial asthma. Besides granulocytes, the airway epithelium can produce large amounts of reactive oxygen species and can contribute to asthma-related oxidative stress. Histamine is a major inflammatory mediator present in large quantities in asthmatic airways. Whether histamine triggers epithelium-derived oxidative stress is unknown. We therefore aimed at characterizing human airway epithelial H2O2 production stimulated by histamine. We found that air-liquid interface cultures of primary human bronchial epithelial cells (BECs) and an immortalized BEC model (Cdk4/hTERT HBEC) produce H2O2 in response to histamine. The main source of airway epithelial H2O2 is an NADPH dual oxidase, Duox1. Out of the four histamine receptors (H1R-H4R), H1R has the highest expression in BECs and mediates the H2O2-producing effects of histamine. IL-4 induces Duox1 gene and protein expression levels and enhances histamine-induced H2O2 production by epithelial cells. Using HEK-293 cells expressing Duox1 or Duox2 and endogenous H1R, histamine triggers an immediate intracellular calcium signal and H2O2 release. Overexpression of H1R further increases the oxidative output of Duox-expressing HEK-293 cells. Our observations show that BECs respond to histamine with Duox-mediated H2O2 production. These findings reveal a mechanism that could be an important contributor to oxidative stress characteristic of asthmatic airways, suggesting novel therapeutic targets for treating asthmatic airway disease.

Variants of CEP68 gene are associated with acute urticaria/angioedema induced by multiple non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are the most consumed drugs worldwide because of their efficacy and utility in the treatment of pain and inflammatory diseases. However, they are also responsible for an important number of adverse effects including hypersensitivity reactions. The most important group of these reactions is triggered by non-immunological, pharmacological mechanisms catalogued under the denomination of cross-intolerance (CRI), with acute urticaria/angioedema induced by multiple NSAIDs (MNSAID-UA) the most frequently associated clinical entity. A recent genome-wide association study identified the gene encoding the centrosomal protein of 68 KDa (CEP68) as the major locus associated with aspirin intolerance susceptibility in asthmatics. In this study, we aimed to assess the role of this locus in susceptibility to CRI to NSAIDs by examining 53 common gene variants in a total of 635 patients that were classified as MNSAID-UA (n = 399), airway exacerbations (n = 110) or blended pattern (n = 126), and 425 controls. We found in the MNSAID-UA group a number of variants (17) associated (lowest p-value = 1.13×10⁻⁶), including the non-synonymous Gly74Ser variant (rs7572857) previously associated with aspirin intolerance susceptibility in asthmatics. Although not being significant in the context of multiple testing, eight of these variants were also associated with exacerbated respiratory disease or blended reactions. Our results suggest that CEP68 gene variants may play an important role in MNSAID-UA susceptibility and, despite the different regulatory mechanisms involved depending on the specific affected organ, in the development of hypersensitivity reactions to NSAIDs.

Amphiregulin

Amphiregulin (AREG) is a ligand of the epidermal growth factor receptor (EGFR), a widely expressed transmembrane tyrosine kinase. AREG is synthesized as a membrane-anchored precursor protein that can engage in juxtacrine signaling on adjacent cells. Alternatively, after proteolytic processing by cell membrane proteases, mainly TACE/ADAM17, AREG is secreted and behaves as an autocrine or paracrine factor. AREG gene expression and release is induced by a plethora of stimuli including inflammatory lipids, cytokines, hormones, growth factors and xenobiotics. Through EGFR binding AREG activates major intracellular signaling cascades governing cell survival, proliferation and motility. Physiologically, AREG plays an important role in the development and maturation of mammary glands, bone tissue and oocytes. Chronic elevation of AREG expression is increasingly associated with different pathological conditions, mostly of inflammatory and/or neoplastic nature. Here we review the essential aspects of AREG structure, function and regulation, discuss the basis for its differential role within the EGFR family of ligands, and identify emerging aspects in AREG research with translational potential.

Mechanisms of airway remodeling

Airway remodeling comprises the structural changes of airway walls, induced by repeated injury and repair processes. It is characterized by the changes of tissue, cellular, and molecular composition, affecting airway smooth muscle, epithelium, blood vessels, and extracellular matrix. It occurs in patients with chronic inflammatory airway diseases such as asthma, COPD, bronchiectasis, and cystic fibrosis. Airway remodeling is arguably one of the most intractable problems in these diseases, leading to irreversible loss of lung function. Current therapeutics can ameliorate inflammation, but there is no available therapy proven to prevent or reverse airway remodeling, although reversibility of airway remodeling is suggested by studies in animal models of disease. Airway remodeling is often considered the result of longstanding airway inflammation, but it may be present to an equivalent degree in the airways of children with asthma, raising the necessity for early and specific therapeutic interventions. In this review, we consider the factors that may contribute to airway remodeling and discuss the current and potential therapeutic interventions.

Cheonggukjang ethanol extracts inhibit a murine allergic asthma via suppression of mast cell-dependent anaphylactic reactions

Cheonggukjang (CGJ), a traditional Korean fermented soybean food, exerts immunomodulatory effects. Asthma is the most common chronic allergic disease to be associated with immune response to environmental allergens. In the pathogenesis of asthma, histamine is one of the important inflammatory mediators released from granules of mast cells. In this study, we evaluated the therapeutic effect of CGJ on a mouse model of ovalbumin (OVA)-induced asthma via the suppression of histamine release. C57BL/6 mice were sensitized by intraperitoneal injection of OVA or a phosphate-buffered saline (PBS) control and then challenged with OVA inhalation. Mice were treated intraperitoneally with either 70% ethanol-extracted CGJ (CGJE) (100 mg/kg/day) or equivalent PBS. Asthma-related inflammation was assessed by bronchoalveolar lavage fluid cell counts and histopathological and immunohistochemical analysis of lung tissues. To elucidate the mechanisms of asthma inhibition by CGJE treatment, we also examined degranulation and histamine release of compound 48/80-induced rat peritoneal mast cells (RPMCs). Treatment with CGJE downregulated the number of eosinophils and monocytes in the lungs of mice challenged with OVA and suppressed histopathological changes, such as eosinophil infiltration, mucus accumulation, goblet cell hyperplasia, and collagen fiber deposits. Moreover, CGJE alleviated compound 48/80-induced mast cell degranulation and histamine release from RPMCs through inhibition of calcium (Ca²⁺) uptake as well as ear swelling by infiltration of inflammatory cells. These findings demonstrated that CGJE can be used as an antiasthmatic dietary supplements candidate for histamine-mediated asthma.

Airway smooth muscle in airway reactivity and remodeling: what have we learned?

It is now established that airway smooth muscle (ASM) has roles in determining airway structure and function, well beyond that as the major contractile element. Indeed, changes in ASM function are central to the manifestation of allergic, inflammatory, and fibrotic airway diseases in both children and adults, as well as to airway responses to local and environmental exposures. Emerging evidence points to novel signaling mechanisms within ASM cells of different species that serve to control diverse features, including 1) [Ca(2+)]i contractility and relaxation, 2) cell proliferation and apoptosis, 3) production and modulation of extracellular components, and 4) release of pro- vs. anti-inflammatory mediators and factors that regulate immunity as well as the function of other airway cell types, such as epithelium, fibroblasts, and nerves. These diverse effects of ASM "activity" result in modulation of bronchoconstriction vs. bronchodilation relevant to airway hyperresponsiveness, airway thickening, and fibrosis that influence compliance. This perspective highlights recent discoveries that reveal the central role of ASM in this regard and helps set the stage for future research toward understanding the pathways regulating ASM and, in turn, the influence of ASM on airway structure and function. Such exploration is key to development of novel therapeutic strategies that influence the pathophysiology of diseases such as asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis.

BRET Biosensor Analysis of Receptor Tyrosine Kinase Functionality

Bioluminescence resonance energy transfer (BRET) is an improved version of earlier resonance energy transfer technologies used for the analysis of biomolecular protein interaction. BRET analysis can be applied to many transmembrane receptor classes, however the majority of the early published literature on BRET has focused on G protein-coupled receptor (GPCR) research. In contrast, there is limited scientific literature using BRET to investigate receptor tyrosine kinase (RTK) activity. This limited investigation is surprising as RTKs often employ dimerization as a key factor in their activation, as well as being important therapeutic targets in medicine, especially in the cases of cancer, diabetes, neurodegenerative, and respiratory conditions. In this review, we consider an array of studies pertinent to RTKs and other non-GPCR receptor protein-protein signaling interactions; more specifically we discuss receptor-protein interactions involved in the transmission of signaling communication. We have provided an overview of functional BRET studies associated with the RTK superfamily involving: neurotrophic receptors [e.g., tropomyosin-related kinase (Trk) and p75 neurotrophin receptor (p75NTR)]; insulinotropic receptors [e.g., insulin receptor (IR) and insulin-like growth factor receptor (IGFR)] and growth factor receptors [e.g., ErbB receptors including the EGFR, the fibroblast growth factor receptor (FGFR), the vascular endothelial growth factor receptor (VEGFR) and the c-kit and platelet-derived growth factor receptor (PDGFR)]. In addition, we review BRET-mediated studies of other tyrosine kinase-associated receptors including cytokine receptors, i.e., leptin receptor (OB-R) and the growth hormone receptor (GHR). It is clear even from the relatively sparse experimental RTK BRET evidence that there is tremendous potential for this technological application for the functional investigation of RTK biology.

Histamine-induced changes in rat tracheal goblet cell mucin store and mucosal edema

The pathology of chronic asthma in human and mouse is characterized by inflammation and remodeling of airway tissues. As a result of repeated inflammatory insults to the lower airways, smooth muscle thickening, mucin secretion and airway hyperreactivity may develop. In ovalbumin (OVA)-sensitized mice with repeated challenges with OVA to the lower airways, the trachea and bronchi are characterized by goblet cell hyperplasia and mucus hypersecretion from goblet cells. Previous study reports that intravenous (i.v.) application of a high dose of capsaicin releases tachykinin from capsaicin-sensitive nerves, producing acute plasma leakage and mucosal edema formation and causing depletion of mucin granules in goblet cells that results in a reduction in the number and size of Alcian blue (AB)-positive goblet cells in the rat trachea within a few minute after capsaicin application. Histamine is an important non-neural mediator of asthma from mast cells. The present study investigated whether i.v. application of a high dose of histamine (18 μmol/ml/kg) could result in these acute changes and the similar time-course changes in rat trachea. The tracheal whole mounts stained with chloroacetate esterase reagent and AB and tracheal methacrylate sections stained with AB and periodic acid-Schiff reagent were used for evaluation of histological and cellular changes. At 5 min after histamine application, mucosal leaky venules were numerous and subepithelial edema ratio (% of length of edema along the mucosal epithelial circumference of tracheal cross section) was found to be 48.2 ± 4.9, which was greater (P < 0.01) than saline-treated rats. But, the number of AB-positive goblet cells, 2,030 ± 170/mm(2) of mucosal surface epithelium, was similar to saline-treated group (P > 0.05). One day later, edema ratio remained large and the number of AB-positive goblet cells was 1,140 ± 150/mm(2) epithelium, reduced to half the number of the group at 5 min after histamine (P < 0.01). It is suggested that mucus hypersecretion occurred at this time point. At 3 or 5 days after histamine, edema ratio gradually decreased. The number of AB-positive goblet cells continued to remain small on day 3. On day 5 after histamine, the number of AB-positive goblet cells restored to the level of rat group at 5 min after histamine application. At 7 days after histamine, edema ratio returned to the level of saline-treated group. It is concluded that degranulation and thinning of tracheal goblet cells and mucus hypersecretion lagged behind histamine-induced acute plasma leakage and edema, and restoration of mucin store in goblet cells was associated with remission of mucosal edema.

Tissue remodeling in eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a recently recognized, immune-mediated disease characterized clinically by symptoms of esophageal dysfunction and histologically by eosinophil-predominant inflammation. The chronic esophageal eosinophilia of EoE is associated with tissue remodeling that includes epithelial hyperplasia, subepithelial fibrosis, and hypertrophy of esophageal smooth muscle. This remodeling causes the esophageal rings and strictures that frequently complicate EoE and underlies the mucosal fragility that predisposes to painful mucosal tears in the EoE esophagus. The pathogenesis of tissue remodeling in EoE is not completely understood, but emerging studies suggest that secretory products of eosinophils and mast cells, as well as cytokines produced by other inflammatory cells, epithelial cells, and stromal cells in the esophagus, all contribute to the process. Interleukin (IL)-4 and IL-13, Th2 cytokines overproduced in allergic disorders, have direct profibrotic and remodeling effects in EoE. The EoE esophagus exhibits increased expression of transforming growth factor (TGF)-β1, which is a potent activator of fibroblasts and a strong inducer of epithelial-mesenchymal transition. In addition, IL-4, IL-13, and TGF-β all have a role in regulating periostin, an extracellular matrix protein that might influence remodeling by acting as a ligand for integrins, by its effects on eosinophils or by activating fibrogenic genes in the esophagus. Presently, few treatments have been shown to affect the tissue remodeling that causes EoE complications. This report reviews the potential roles of fibroblasts, eosinophils, mast cells, and profibrotic cytokines in esophageal remodeling in EoE and identifies potential targets for future therapies that might prevent EoE complications.