Activation of epidermal growth factor receptors is responsible for mucin synthesis induced by cigarette smoke

Mucus Structure, Viscoelastic Properties, and Composition in Chronic Respiratory Diseases

The respiratory mucus, a viscoelastic gel, effectuates a primary line of the airway defense when operated by the mucociliary clearance. In chronic respiratory diseases (CRDs), such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), the mucus is overproduced and its solid content augments, changing its structure and viscoelastic properties and determining a derangement of essential defense mechanisms against opportunistic microbial (virus and bacteria) pathogens. This ensues in damaging of the airways, leading to a vicious cycle of obstruction and infection responsible for the harsh clinical evolution of these CRDs. Here, we review the essential features of normal and pathological mucus (i.e., sputum in CF, COPD, and asthma), i.e., mucin content, structure (mesh size), micro/macro-rheology, pH, and osmotic pressure, ending with the awareness that sputum biomarkers (mucins, inflammatory proteins and peptides, and metabolites) might serve to indicate acute exacerbation and response to therapies. There are some indications that old and novel treatments may change the structure, viscoelastic properties, and biomarker content of sputum; however, a wealth of work is still needed to embrace these measures as correlates of disease severity in association with (or even as substitutes of) pulmonary functional tests.

Discovering genetic mechanisms underlying the co-occurrence of Parkinson's disease and non-motor traits

Understanding the biological mechanisms that underlie the non-motor symptoms of Parkinson's disease (PD) requires comprehensive frameworks that unravel the complex interplay of genetic risk factors. Here, we used a disease-agnostic brain cortex gene regulatory network integrated with Mendelian Randomization analyses that identified 19 genes whose changes in expression were causally linked to PD. We further used the network to identify genes that are regulated by PD-associated genome-wide association study (GWAS) SNPs. Extended protein interaction networks derived from PD-risk genes and PD-associated SNPs identified convergent impacts on biological pathways and phenotypes, connecting PD with established co-occurring traits, including non-motor symptoms. These findings hold promise for therapeutic development. In conclusion, while distinct sets of genes likely influence PD risk and outcomes, the existence of genes in common and intersecting pathways associated with other traits suggests that they may contribute to both increased PD risk and symptom heterogeneity observed in people with Parkinson's.

Serum Allergen-Specific Immunoglobulin E in Cats with Inflammatory Bronchial Disease

The etiology of feline inflammatory bronchial disease is poorly understood. This study compares the degree of allergen-specific serum IgE responses between cats with feline asthma, chronic bronchitis, mixed inflammation, and clinically healthy cats (HCs). The retrospective case-control study used serum from eighteen cats with eosinophilic inflammation (EI), ten with neutrophilic inflammation (NI), six with mixed inflammation (MI), and fourteen HCs. Affected cats were categorized into groups based on bronchoalveolar lavage cytology. The measurement of IgE for 34 different allergens including fungal organisms, weeds, grasses, trees, mites, and insects was performed using an indirect ELISA. Positive reactions to allergens were detected in the serum of 17/18 cats with EI, 8/10 with NI, 6/6 with MI, and 11/14 HCs (p = 0.364). When overall positive reactions were compared between groups, cats with MI (p = <0.01) had significantly more positive reactions against mite allergens than HCs. Blood eosinophils inversely correlated with the absolute amount of allergen-specific serum IgE expressed in ELISA absorbance units (EAs) (p = 0.014). Sensitization against dust mites seems to be more prevalent in cats with MI. However, positive IgE reactions can be observed in healthy and diseased cats, and, therefore, need to be interpreted in the light of clinical findings and environmental conditions of individual patients.

Estrogen Receptor-α Exacerbates EGF-Inducing Airway Remodeling and Mucus Production in Bronchial Epithelium of Asthmatics

PURPOSE

Although estrogen receptors (ERs) signal pathways are involved in the pathogenesis and development of asthma, their expressions and effects remain controversial. This study aimed to investigate the expressions of ERα and ERβ as well as their mechanisms in airway remodeling and mucus production in asthma.

METHODS

The expressions of ERα and ERβ in the airway epithelial cells of bronchial biopsies and induced sputum cells were examined by immunohistochemistry. The associations of ERs expressions with airway inflammation and remodeling were evaluated in asthmatic patients. In vitro, the regulations of ERs expressions in human bronchial epithelial cell lines were examined using western blot analysis. The epidermal growth factor (EGF)-mediated ligand-independent activation of ERα and its effect on epithelial-mesenchymal transitions (EMTs) were investigated in asthmatic epithelial cells by western blot, immunofluorescent staining, and quantitative real-time polymerase chain reaction.

RESULTS

ERα and ERβ were expressed on both bronchial epithelial cells and induced sputum cells, and the expressions showed no sex difference. Compared to controls, male asthmatic patients had higher levels of ERα on the bronchial epithelium, and there were cell-specific expressions of ERα and ERβ in induced sputum. The expression of ERα in the airway epithelium was inversely correlated to forced expiratory volume in 1 second (FEV1) % and FEV1/forced vital capacity. Severe asthmatic patients had significantly greater levels of ERα in the airway epithelium than mild-moderate patients. ERα level was positively correlated with the thickness of the subepithelial basement membrane and airway epithelium. In vitro, co-stimulation of interleukin (IL)-4 and EGF increased the expression of ERα and promoted its nuclear translocation. EGF activated the phosphorylation of ERα via extracellular signal-regulated kinase and c-Jun N-terminal kinase pathways. ERα knockdown alleviated EGF-mediated EMTs and mucus production in airway epithelial cells of asthma.

CONCLUSIONS

ERα contributes to asthmatic airway remodeling and mucus production through the EGF-mediated ligand-independent pathway.

Effects of brake wear nanoparticles on the protection and repair functions of the airway epithelium

Long term exposure to particulate air pollution is known to increase respiratory morbidity and mortality. In urban areas with dense traffic most of these particles are generated by vehicles, via engine exhaust or wear processes. Non-exhaust particles come from wear processes such as those concerning brakes and their toxicity is little studied. To improve our understanding of the lung toxicity mechanisms of the nanometric fraction of brake wear nanoparticles (BWNPs), we studied whether these particles affect the barrier properties of the respiratory epithelium considering particle translocation, mucus production and repair efficiency. The Calu-3 cell line grown in two-compartment chambers was used to mimic the bronchial epithelial barrier. BWNPs detected by single-particle ICP-MS were shown to cross the epithelial tissue in small amounts without affecting the barrier integrity properties, because the permeability to Lucifer yellow was not increased and there was no cytotoxicity as assessed by the release of lactate-dehydrogenase. The interaction of BWNPs with the barrier did not induce a pro-inflammatory response, but increased the expression and production of MU5AC, a mucin, by a mechanism involving the epidermal growth factor receptor pathway. During a wound healing assay, BWNP-loaded cells exhibited the same ability to migrate, but those at the edge of the wound showed higher 5-ethynyl-2'-deoxyuridine incorporation, suggesting a higher proliferation rate. Altogether these results showed that BW. NPs do not exert overt cytotoxicity and inflammation but can translocate through the epithelial barrier in small amounts and increase mucus production, a key feature of acute inflammatory and chronic obstructive pulmonary diseases. Their loading in epithelial cells may impair the repair process through increased proliferation.

Predictive Value of MUC5AC Signature in Pancreatic Ductal Adenocarcinoma: A Hypothesis Based on Preclinical Evidence

Mucin 5AC (MUC5AC) glycoprotein plays a crucial role in carcinogenesis and drug sensitivity in pancreatic ductal adenocarcinoma (PDAC), both individually and in combination with other mucins. Its function and localization are glycoform-specific. The immature isoform (detected by the CLH2 monoclonal antibody, or mab) is usually in the perinuclear (cytoplasmic) region, while the mature (45 M1, 2-11, Nd2) variants are in apical and extracellular regions. There is preclinical evidence suggesting that mature MUC5AC has prognostic and predictive (response to treatment) value. However, these findings were not validated in clinical studies. We propose a MUC5AC signature with three components of MUC5AC-localization, variant composition, and intensity-suggesting a reliable marker in combination of variants than with individual MUC5AC variants alone. We also postulate a theory to explain the occurrence of different MUC5AC variants in abnormal pancreatic lesions (benign, precancerous, and cancerous). We also analyzed the effect of mature MUC5AC on sensitivity to drugs often used in PDAC management, such as gemcitabine, 5-fluorouracil, oxaliplatin, irinotecan, cisplatin, and paclitaxel. We found preliminary evidence of its predictive value, but there is a need for large-scale studies to validate them.

Oxidative stress induces MUC5AC expression through mitochondrial damage-dependent STING signaling in human bronchial epithelial cells

Oxidative stress increases the production of the predominant mucin MUC5AC in airway epithelial cells and is implicated in the pathogenesis of bronchial asthma and chronic obstructive pulmonary disease. Oxidative stress impairs mitochondria, releasing mitochondrial DNA into the cytoplasm and inducing inflammation through the intracytoplasmic DNA sensor STING (stimulator of interferon genes). However, the role of innate immunity in mucin production remains unknown. We aimed to elucidate the role of innate immunity in mucin production in airway epithelial cells under oxidative stress. Human airway epithelial cell line (NCI-H292) and normal human bronchial epithelial cells were used to confirm MUC5AC expression levels by real-time PCR when stimulated with hydrogen peroxide (H2O2). MUC5AC transcriptional activity was increased and mitochondrial DNA was released into the cytosol by H2O2. Mitochondrial antioxidants were used to confirm the effects of mitochondrial oxidative stress where antioxidants inhibited the increase in MUC5AC transcriptional activity. Cyclic GMP-AMP synthase (cGAS) or STING knockout (KO) cells were generated to investigate their involvement. H2O2-induced MUC5AC expression was suppressed in STING KO cells, but not in cGAS KO cells. The epidermal growth factor receptor was comparably expressed in STING KO and wild-type cells. Thus, mitochondria and STING play important roles in mucin production in response to oxidative stress in airway epithelial cells.

In Vitro Characteristics of Canine Primary Tracheal Epithelial Cells Maintained at an Air-Liquid Interface Compared to In Vivo Morphology

Culturing respiratory epithelial cells at an air-liquid interface (ALI) represents an established method for studies on infection or toxicology by the generation of an in vivo-like respiratory tract epithelial cellular layer. Although primary respiratory cells from a variety of animals have been cultured, an in-depth characterization of canine tracheal ALI cultures is lacking despite the fact that canines are a highly relevant animal species susceptible to various respiratory agents, including zoonotic pathogens such as severe acute respiratory coronavirus 2 (SARS-CoV-2). In this study, canine primary tracheal epithelial cells were cultured under ALI conditions for four weeks, and their development was characterized during the entire culture period. Light and electron microscopy were performed to evaluate cell morphology in correlation with the immunohistological expression profile. The formation of tight junctions was confirmed using transepithelial electrical resistance (TEER) measurements and immunofluorescence staining for the junctional protein ZO-1. After 21 days of culture at the ALI, a columnar epithelium containing basal, ciliated and goblet cells was seen, resembling native canine tracheal samples. However, cilia formation, goblet cell distribution and epithelial thickness differed significantly from the native tissue. Despite this limitation, tracheal ALI cultures could be used to investigate the pathomorphological interactions of canine respiratory diseases and zoonotic agents.

Analyzing cross-talk of EPO and EGF genes along with evaluating therapeutic potential of Cinnamomum verum in cigarette-smoke-induced lung pathophysiology in rat model

The integrity of the distal alveolar epithelium is crucial for lung regeneration following an injury. The present study aimed to evaluate the effect of Cinnamomum verum extract; cross-talk of epidermal growth factor (EGF) and erythropoietin (EPO) genes in a smoke-induced lung injury rat model. For experimentation (n = 27), albino rats were divided equally into three groups, i.e., negative control (NC), positive control (PC), and treatment group (TG). Cigarette smoke was exposed to PC and TG (4 CG/day). C. verum was given orally (350 mg/kg body weight) for 21 days. Decapitation (n = 3) was done on 14th, 18th, and 21st days, respectively. Analyses (hematology, biochemical, high performance liquid chromatography [HPLC], histology, and gene expression) were carried out and results were statistically analyzed by two-way analysis of variance. HPLC analysis of ethanolic extract of C. verum was done to identify the presence of phenolic constituents which showed high concentrations of quercetin and P-coumaric acid. Serum oxidative parameters such as total oxidant status, malondialdehyde, and hematological parameters such as red blood cells, hemoglobin, hematocrit, and white blood cells were significantly (p < .05) elevated in the PC group; however, these parameters were significantly (p < .05) improved in TG. While total antioxidant capacity and serum parameters such as total protein, albumin, and globulin were significantly (p < .05) reduced in the PC group but significantly improved (p < .05) in TG. Histological analysis revealed that smoke exposure resulted in a measurable increase in alveolar septal thickening while ethanolic extract of C. verum greatly ameliorated the histopathological changes in the lung alveoli. The gene expression analysis of EGF and EPO genes showed a significant upregulation (p < .05) of both genes in PC group while in TG, the level of both genes downregulated, in which lung damage was ameliorated due to cytoprotective effects of ethanolic extract of C. verum.

In Vitro Toxicological Investigation and Risk Assessment of E-Cigarette Aerosols Based on a Novel Solvent-Free Extraction Method

Cigarettes, potentially safer alternatives to combustible cigarettes, have been reported to increase the health risk for long-term users, so accumulating information about their potential toxicity is of great concern. However, toxicological evaluations of e-cigarette aerosols are limited, which may be attributed to the lack of a simple and efficient extraction method. Here, we developed a high-speed centrifugal method for extracting e-cigarette aerosol collected mass (ACM) and prepared ACM samples of 26 representative e-cigarettes, and 10 samples were further selected based on their cytotoxicity for systematic toxicological assessments. The average extraction efficiency of ACM, primary aerosol components, and typical carbonyls exceeded 85%. The toxicological evaluation showed that the IC₅₀ value range of e-cigarettes for cytotoxicity was 2-52 mg/mL ACM, all e-cigarettes can induce the risk of DNA damage, mitochondrial depolarization, and c-Jun-related signal disturbances; most e-cigarettes significantly caused disturbance of oxidative stress balance. E-cigarettes with higher cytotoxicity appeared to cause a higher degree of damage, while no e-cigarette promoted mutagenicity and cytochrome c release. The toxicity difference among e-cigarettes using nicotine equivalent was significantly lower than that of ACM. This study provides a novel extraction method and a comprehensive in vitro toxicity risk profile of e-cigarette aerosols.

Systematic Pharmacology-Based Strategy to Explore the Mechanism of Bufei Huoxue Capsule in the Treatment of Chronic Obstructive Pulmonary Disease

OBJECTIVE

To explore the effects and mechanisms of Bufei Huoxue Capsule (BHC) on chronic obstructive pulmonary disease (COPD) based on network pharmacology.

METHODS

The effective components and related targets of BHC were collected by searching TCMSP, HERB, and ETCM databases, after which the related targets of COPD were obtained on GeneCards and OMIM databases. The common targets were imported into the STRING database and Cytoscape database to construct a target interaction network and screen core targets. Next, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed on the Metascape platform. According to the prediction results of network pharmacology, the action mechanism was further examined in an animal model of COPD. The pathological changes of lung tissue were observed by HE staining; goblet cells and mucus secretion in lung tissue were observed by AB-PAS staining, airway collagen deposition was observed by Masson staining, and the expression of NE, TGF-β1, P-EGFR/EGFR, P-ERK1/2/ERK1/2, P-JNK/JNK, and P-P38/P38MAPK protein was detected by Western blot analysis.

RESULTS

A total of 379 targets related to BHC and 7391 targets related to COPD were obtained, including 313 potential targets of BHC in treating chronic obstructive pulmonary disease, with JUN, AKT1, TNF, IL6, EGFR, MAPK1, and MAPK14 as the core targets. Through enrichment analysis, BHC may interfere with COPD by regulating the MAPK signal pathway, HIF-1 signal pathway, NF-κB signal pathway, cAMP signal pathway, cGMP-PKG signal pathway, and so on. Animal experiments showed that the BHC could reduce airway inflammatory cell infiltration, inhibit airway epithelial goblet cell proliferation, reduce mucus secretion, and improve small airway collagen fiber deposition in COPD model rats. Besides, BHC could downregulate the protein expression of NE, TGF-β1, P-EGFR, P-ERK1/2, and P-P38MAPK.

CONCLUSION

BHC can reduce airway inflammation, inhibit mucus hypersecretion, and improve airway remodeling by regulating the MAPK signal transduction pathway.

Autocrine TGF-alpha is associated with Benzo(a)pyrene-induced mucus production and MUC5AC expression during allergic asthma

OBJECTS

Benzo(a)pyrene (BaP), an environmental pollutant, is present in high concentrations in urban smog and cigarette smoke and has been reported to promote high mucin 5AC (MUC5AC) expression. Epithelium-derived inflammatory cytokines are considered an important modulator of mucus oversecretion and MUC5AC overexpression. Here, we investigated whether the effect of BaP on MUC5AC overexpression was associated with cytokine autocrine activity in vivo and in vitro.

METHODS

In vivo, BALB/c mice were treated with ovalbumin (OVA) in the presence or absence of BaP. Allergy-induced mucus production was assessed by Alcian Blue Periodic acid Schiff (AB-PAS) staining. The human airway epithelial cell line NCI-H292 was used in vitro. MUC5AC and transforming growth factor (TGF)-α mRNA levels were assessed with real-time quantitative PCR. The concentration of cytokines was measured by ELISA. The MUC5AC, p-ERK, ERK, p-EGFR and EGFR proteins were detected by Western blotting in cells or by immunohistochemistry in mouse lungs. Small-interfering RNAs were used for gene silencing.

RESULTS

TGF-α was overproduced in the supernatant of NCI-H292 cells treated with BaP. Knockdown of TGF-α expression inhibited the BaP-induced increase in MUC5AC expression and subsequent activation of the EGFR-ERK signalling pathway. Knocking down aryl hydrocarbon receptor (AhR) expression or treatment with an ROS inhibitor (N-acetyl-L-cysteine) could relieve the TGF-α secretion induced by BaP in epithelial cells. In an animal study, coexposure to BaP with OVA increased mucus production, MUC5AC expression and ROS-EGFR-ERK activation in the lung as well as TGF-α levels in bronchoalveolar lavage fluid (BALF). Furthermore, the concentration of TGF-α in BALF was correlated with MUC5AC mRNA levels. Additionally, TGF-α expression was found to be positively correlated with MUC5AC expression in the airway epithelial cells of smokers. Compared with non-smoker asthma patients, TGF-α serum levels were also elevated in smoker asthma patients.

CONCLUSION

Autocrine TGF-α was associated with BaP-induced MUC5AC expression in vitro and in vivo. BaP induced TGF-α secretion by activating AhR and producing ROS, which led to activation of the EGFR-ERK pathway.

Methods of Sputum and Mucus Assessment for Muco-Obstructive Lung Diseases in 2022: Time to “Unplug” from Our Daily Routine!

Obstructive lung diseases, such as chronic obstructive pulmonary disease, asthma, or non-cystic fibrosis bronchiectasis, share some major pathophysiological features: small airway involvement, dysregulation of adaptive and innate pulmonary immune homeostasis, mucus hyperproduction, and/or hyperconcentration. Mucus regulation is particularly valuable from a therapeutic perspective given it contributes to airflow obstruction, symptom intensity, disease severity, and to some extent, disease prognosis in these diseases. It is therefore crucial to understand the mucus constitution of our patients, its behavior in a stable state and during exacerbation, and its regulatory mechanisms. These are all elements representing potential therapeutic targets, especially in the era of biologics. Here, we first briefly discuss the composition and characteristics of sputum. We focus on mucus and mucins, and then elaborate on the different sample collection procedures and how their quality is ensured. We then give an overview of the different direct analytical techniques available in both clinical routine and more experimental settings, giving their advantages and limitations. We also report on indirect mucus assessment procedures (questionnaires, high-resolution computed tomography scanning of the chest, lung function tests). Finally, we consider ways of integrating these techniques with current and future therapeutic options. Cystic fibrosis will not be discussed given its monogenic nature.

Airway Basal Cells, Protectors of Epithelial Walls in Health and Respiratory Diseases

The airway epithelium provides a critical barrier to the outside environment. When its integrity is impaired, epithelial cells and residing immune cells collaborate to exclude pathogens and to heal tissue damage. Healing is achieved through tissue-specific stem cells: the airway basal cells. Positioned near the basal membrane, airway basal cells sense and respond to changes in tissue health by initiating a pro-inflammatory response and tissue repair via complex crosstalks with nearby fibroblasts and specialized immune cells. In addition, basal cells have the capacity to learn from previous encounters with the environment. Inflammation can indeed imprint a certain memory on basal cells by epigenetic changes so that sensitized tissues may respond differently to future assaults and the epithelium becomes better equipped to respond faster and more robustly to barrier defects. This memory can, however, be lost in diseased states. In this review, we discuss airway basal cells in respiratory diseases, the communication network between airway basal cells and tissue-resident and/or recruited immune cells, and how basal cell adaptation to environmental triggers occurs.

Guifu Dihuang Pills Ameliorated Mucus Hypersecretion by Suppressing Muc5ac Expression and Inactivating the ERK-SP1 Pathway in Lipopolysaccharide/Cigarette Smoke-Induced Mice

Mucus hypersecretion is a hallmark of chronic obstructive pulmonary disease (COPD) and is associated with increasing sputum production and declining pulmonary function. Therefore, reducing mucus secretion can be a new therapeutic opportunity for preventing COPD. The Guifu Dihuang pill (GFDHP) is a classical Chinese medicine and has been used as an immunoregulator for treatment of kidney yang deficiency syndrome, including hypothyroidism, adrenocortical hypofunction, chronic bronchitis, and COPD, for more than 2000 years. However, the protective effects and mechanisms of GFDHP against mucus hypersecretion in COPD remain obscure. The aim of the present study was to explore the inhibitory effects of GFDHP on lipopolysaccharide/cigarette smoke- (LPS/CS-) induced Mucin5ac (Muc5ac) overproduction and airway goblet cell hyperplasia in mice. The mice were randomly assigned into 6 groups: control, model, GFDHP-L, GFDHP-M, GFDHP-H, and dexamethasone. The mice were given LPS twice through intranasal inhalation and then exposed to CS daily for 6 weeks. Three doses of GFDHP were orally administered daily during the last 3 weeks of the experiment. Pulmonary function was examined with an EMKA pulmonary system, and pulmonary hyperpermeability and lung damage were evaluated with an in vivo imaging system. Inflammatory cells and cytokines in bronchoalveolar lavage fluid (BALF) were detected with a cell count analyzer and though ELISA analysis, respectively. Lung pathological changes and airway goblet cell hyperplasia were analyzed with hematoxylin and eosin and Alcian blue periodic acid Schiff staining. The protein expression levels of Muc5ac and extracellular signal-regulated kinase (ERK)-specificity protein1 (SP1) signaling pathway were measured with Western blot and immunohistochemistry. The results demonstrated that GFDHP improved pulmonary function and suppressed mouse pulmonary hyperpermeability and edema. GFDHP suppressed inflammatory cell infiltration and cytokine release in BALF, thereby elevating pulmonary function. It ameliorated lung pathological changes and airway goblet cell hyperplasia, and suppressed expression levels of Muc5ac mRNA and protein and phospho-ERK and SP1 levels in the lung tissues of the COPD mice. In conclusion, GFDHP inhibited mucus hypersecretion induced by LPS/CS by suppressing the activation of the ERK-SP1 pathway.

Changes in Eustachian Tube Mucosa in Mice After Short-Term Tobacco and E-cigarette Smoke Exposure

OBJECTIVES

To evaluate histologic changes in middle ear and eustachian tube (ET) mucosa of mice after exposure to tobacco or electronic cigarette (e-cigarette) smoke. To determine whether there were any mitigating effects of middle ear application of anti-IL-13 or the epidermal growth factor receptor antagonist AG1478 on noted changes within ET mucosa.

STUDY DESIGN

Controlled animal study.

METHODS

Fifty BALB/cJ mice were randomly assigned to one of five groups: A control group with no smoke exposure, two groups exposed to tobacco smoke, and two groups exposed to e-cigarette vapor. Within the exposed groups after 4 weeks of exposure, one ear was infiltrated with a saline hydrogel and the other ear with hydrogel of either Anti-IL-13 or AG1478. After four more weeks of exposure, the animals were euthanized and the ETs were evaluated for mucosal changes.

RESULTS

Compared to control animals with no smoke exposure, there were significant decreases in the numbers of goblet cells within the ET mucosa of mice exposed to tobacco smoke and e-cigarette vapor. No significant differences in cilia, mucin, or squamous metaplasia were noted. Neither anti-IL-13 nor AG178 significantly altered goblet cell count in the ET mucosa of mice exposed to tobacco smoke; however, both agents significantly increased goblet cells within the ET mucosa of mice exposed to e-cigarette vapor.

CONCLUSION

Short-term tobacco smoke and e-cigarette vapor significantly decrease goblet cell count in mouse ET mucosa. Middle ear application of both anti-IL-13 and AG1478 resulted in an increase in goblet cell count among mice exposed to e-cigarette vapor, but not to tobacco smoke.

LEVEL OF EVIDENCE

NA Laryngoscope, 2021.

Understanding the Clinical Impact of MUC5AC Expression on Pancreatic Ductal Adenocarcinoma

Simple Summary

Management of pancreatic cancer is challenging as there are limited treatment options, and most cases are diagnosed at advanced stages. In addition, there are no dependable tests available to predict bad outcomes or treatment responses in current clinical practice. Here, we shed light on the available evidence on mucin, MUC5AC in predicting the outcome of pancreatic cancers. We also discuss variants of MUC5AC believed to have a role in the malignant transformation of pancreatic tissues.

Abstract

Mucin-5AC (MUC5AC) is a heavily glycosylated gel-forming secreted mucin with a reliable prognostic value when detected in multiple malignancies. It is highly prevalent (70%) in PDA and is nonexistent in normal pancreatic tissues. Retrospective studies on PDA tumor tissue (detected by immunohistochemistry or IHC)) have investigated the prognostic value of MUC5AC expression but were equivocal. Some studies associated it with poor outcomes (survival or pathological features such as lymph node disease, vascular/neural invasion in resected tumors), while others have concluded that it is a good prognostic marker. The examination of expression level threshold (5%, 10%, or 25%) and the detected region (apical vs. cytoplasmic) were variable among the studies. The maturation stage and glycoform of MUC5AC detected also differed with the Monoclonal antibody (Mab) employed for IHC. CLH2 detects less mature/less glycosylated versions while 45M1 or 21-1 detect mature/more glycosylated forms. Interestingly, aberrantly glycosylated variants of MUC5AC were detected using lectin assays (Wheat Germ Agglutinin-MUC5AC), and Mabs such as NPC-1C and PAM4 have are more specific to malignant pancreatic tissues. NPC-1C and PAM4 antibody reactive epitopes on MUC5AC are immunogenic and could represent specific changes on the native MUC5AC glycoprotein linked to carcinogenesis. It was never studied to predict treatment response.

The development of an in vitro 3D model of goblet cell hyperplasia using MUC5AC expression and repeated whole aerosol exposures

Goblet cell hyperplasia and overproduction of airway mucin are characteristic features of the lung epithelium of smokers and COPD patients. Tobacco heating products (THPs) are a potentially less risky alternative to combustible cigarettes, and through continued use solus THPs may reduce smoking-related disease risk. Using the MucilAir™ in vitro lung model, a 6-week feasibility study was conducted investigating the effect of repeated cigarette smoke (1R6F), THP aerosol and air exposure. Tissues were exposed to nicotine-matched whole aerosol doses 3 times/week. Endpoints assessed were dosimetry, tight-junction integrity, cilia beat frequency (CBF) and active area (AA), cytokine secretion and airway mucin MUC5AC expression. Comparison of incubator and air exposed controls indicated exposures did not have a significant effect on the transepithelial electrical resistance (TEER), CBF and AA of the tissues. Cytokine secretion indicated clear differences in secretion patterns in response to 1R6F and THP exposure. 1R6F exposure resulted in a significant decrease in the TEER and AA (p=0.000 and p=0.000, respectively), and an increase in MUC5AC positive cells (p=0.002). Repeated THP exposure did not result in a significant change in MUC5AC positive cells. This study demonstrates repeated cigarette smoke whole aerosol exposure can induce these morphological changes in vitro.

Pathophysiology of Lung Disease and Wound Repair in Cystic Fibrosis

Cystic fibrosis (CF) is an autosomal recessive, life-threatening condition affecting many organs and tissues, the lung disease being the chief cause of morbidity and mortality. Mutations affecting the CF Transmembrane Conductance Regulator (CFTR) gene determine the expression of a dysfunctional protein that, in turn, triggers a pathophysiological cascade, leading to airway epithelium injury and remodeling. In vitro and in vivo studies point to a dysregulated regeneration and wound repair in CF airways, to be traced back to epithelial CFTR lack/dysfunction. Subsequent altered ion/fluid fluxes and/or signaling result in reduced cell migration and proliferation. Furthermore, the epithelial-mesenchymal transition appears to be partially triggered in CF, contributing to wound closure alteration. Finally, we pose our attention to diverse approaches to tackle this defect, discussing the therapeutic role of protease inhibitors, CFTR modulators and mesenchymal stem cells. Although the pathophysiology of wound repair in CF has been disclosed in some mechanisms, further studies are warranted to understand the cellular and molecular events in more details and to better address therapeutic interventions.

Assessment and treatment of airflow obstruction in patients with chronic obstructive pulmonary disorder: a guide for the clinician

Introduction: Chronic obstructive pulmonary disorder (COPD) is a common cause of disability, morbidity and mortality worldwide. Early diagnosis and adequate treatment maintained over time are crucial to reducing these harmful consequences.Areas covered Persistent, not reversible and naturally progressive airflow obstruction is the functional hallmark of COPD. Therefore, in the presence of individual and environmental risk factors, with or without reported suggestive symptoms, simple spirometry must be performed enough quickly to objectify an obstructive ventilatory defect and assist physicians in making a diagnosis of COPD. Then, to cope with the heterogeneity of COPD patients, more specific functional tests and imaging techniques should be implemented to better define the underlying prevalent disease and its severity. That is necessary to decide whether to introduce ICS and establish the initial level of the treatment with just one or two bronchodilators, to control and freeze, when possible, the underlying pathological process.Expert opinion: The objective assessment of airflow obstruction is mandatory to make a diagnosis of COPD, but the prevalent disease sustaining the disorder should also be investigated to select a targeted therapy, because main determinants of airflow obstruction can be different in COPD patients and may differently respond to treatment.

Onion Bulb Extract Downregulates EGFR/ERK1/2/AKT Signaling Pathway and Synergizes With Steroids to Inhibit Allergic Inflammation

The treatment of allergic diseases, such as asthma, with both conventional and novel therapies presents a challenge both in terms of optimal effect and cost. On the other hand, traditional therapies utilizing natural products such as onion have been in use for centuries with demonstrated efficacy and safety but without much knowledge of their mechanims of action. In this study, we investigated if the anti-inflammatory effects of onion bulb extract (OBE) are mediated via the modulation of the EGFR/ERK1/2/AKT signaling pathway, and whether OBE can synergise with steroids to produce greater anti-inflammatory actions. Treatment with OBE inhibited the house dust mite (HDM)-induced increased phosphorylation of EGFR, ERK1/2 and AKT which resulted in the inhibition of HDM-induced increase in airway cellular influx, perivascular and peribronchial inflammation, goblet cell hyper/metaplasia, and also inhibited ex vivo eosinophil chemotaxis. Moreover, treatment with a combination of a low dose OBE and low dose dexamethasone resulted in a significant inhibition of the HDM-induced cellular influx, perivascular and peribronchial inflammation, goblet cell hyper/metaplasia, and increased the pERK1/2 levels, whereas neither treatment, when given alone, had any discernible effects. This study therefore shows that inhibition of the EGFR/ERK1/2/AKT-dependent signaling pathway is one of the key mechanisms by which OBE can mediate its anti-inflammatory effects in diseases such as asthma. Importantly, this study also demonstrates that combining OBE with steroids results in significantly enhanced anti-inflammatory effects. This action may have important potential implications for future asthma therapy.

Prenatal smoke exposure dysregulates lung epithelial cell differentiation in mouse offspring: role for AREG-induced EGFR signaling

Prenatal smoke exposure is a risk factor for impaired lung development in children. Recent studies have indicated that amphiregulin (AREG), which is a ligand of the epidermal growth factor receptor (EGFR), has a regulatory role in airway epithelial cell differentiation. In this study, we investigated the effect of prenatal smoke exposure on lung epithelial cell differentiation and linked this with AREG-EGFR signaling in 1-day-old mouse offspring. Bronchial and alveolar epithelial cell differentiations were assessed by immunohistochemistry. Areg, epidermal growth factor (Egf), and mRNA expressions of specific markers for bronchial and alveolar epithelial cells were assessed by RT-qPCR. The results in neonatal lungs were validated in an AREG-treated three-dimensional mouse lung organoid model. We found that prenatal smoke exposure reduced the number of ciliated cells and the expression of the cilia-related transcription factor Foxj1, whereas it resulted in higher expression of mucus-related transcription factors Spdef and Foxm1 in the lung. Moreover, prenatally smoke-exposed offspring had higher numbers of alveolar epithelial type II cells (AECII) and lower expression of the AECI-related Pdpn and Gramd2 markers. This was accompanied by higher expression of Areg and lower expression of Egf in prenatally smoke-exposed offspring. In bronchial organoids, AREG treatment resulted in fewer ciliated cells and more basal cells when compared with non-treated bronchiolar organoids. In alveolar organoids, AREG treatment led to more AECII cells than non-treated AECII cells. Taken together, the observed impaired bronchial and alveolar cell development in prenatally smoke-exposed neonatal offspring may be induced by increased AREG-EGFR signaling.

Smoking-associated increase in mucins 1 and 4 in human airways

Rationale

Smoking-related chronic obstructive pulmonary disease (COPD) is associated with dysregulated production of mucus. Mucins (MUC) are important both for mucus secretion and epithelial defense. We have examined the distribution of MUC1 and MUC4 in the airway epithelial cells of never-smokers and smokers with and without COPD.

Methods

Mucosal biopsies and bronchial wash samples were obtained by bronchoscopy from age- and sex-matched COPD-patients (n = 38; GOLD I-II/A-B), healthy never-smokers (n = 40) and current smokers with normal lung function (n = 40) from the Karolinska COSMIC cohort (NCT02627872). Cell-specific expressions of MUC1, MUC4 and regulating factors, i.e., epithelial growth factor receptor (EGFR) 1 and 2, were analyzed by immunohistochemistry. Soluble MUC1 was measured by quantitative immunodetection on slot blot.

Results

The levels of cell-bound MUC1 expression in basal cells and in soluble MUC1 in bronchial wash were increased in smokers, regardless of airway obstruction. Patients with chronic bronchitis had higher MUC1 expression. The expression of MUC4 in cells with goblet cell phenotype was increased in smokers. The expression of EGFR2, but not that of EGFR1, was higher in never-smokers than in smokers.

Conclusions

Smoking history and the presence of chronic bronchitis, regardless of airway obstruction, affect both cellular and soluble MUC1 in human airways. Therefore, MUC1 may be a novel marker for smoking- associated airway disease.

MUC1 contributes to goblet cell metaplasia and MUC5AC expression in response to cigarette smoke in vivo

Goblet cell metaplasia (GCM) and mucin overproduction are a hallmark of chronic rhinosinusitis (CRS) and chronic obstructive pulmonary disease (COPD). In the airways, cigarette smoke (CS) induces activation of the epidermal growth factor receptor (EGFR) leading to GCM and overexpression of the gel-forming mucin MUC5AC. Although previous studies have demonstrated that a membrane-bound mucin, MUC1, modulates the activation of CS-induced EGFR, the role of MUC1 in CS-induced GCM and mucin overproduction has not been explored. In response to CS exposure, wild-type (WT) rats displayed Muc1 translocation from the apical surface of airway epithelium to the intracellular compartment of hyperplastic intermediate cells, EGFR phosphorylation, GCM, and Muc5ac overproduction. Similarly, human CRS sinonasal tissues demonstrated hyperplasia of intermediate cells enriched with MUC1 in the intracellular compartment, which was accompanied by GCM and increased MUC5AC expression. To further evaluate the role of Muc1 in vivo, a Muc1 knockout (KO) rat (MUC in humans and Muc in animals) was developed. In contrast to WT littermates, Muc1-KO rats exhibited no activation of EGFR, and were protected from GCM and Muc5ac overproduction. Genetic knockdown of MUC1 in human lung or Muc1 knockout in primary rat airway epithelial cells led to significantly diminished EGF-induced MUC5AC production. Together, these findings suggest that MUC1-dependent EGFR activation mediates CS-induced GCM and mucin overproduction. Strategies designed to suppress MUC1-dependent EGFR activation may provide a novel therapeutic approach for treating mucin hypersecretion in CRS and COPD.

Herbal Combinational Medication of Glycyrrhiza glabra, Agastache rugosa Containing Glycyrrhizic Acid, Tilianin Inhibits Neutrophilic Lung Inflammation by Affecting CXCL2, Interleukin-17/STAT3 Signal Pathways in a Murine Model of COPD

Chronic obstructive pulmonary disease (COPD) is caused by exposure to toxic particles, such as coal fly ash (CFA), diesel-exhaust particle (DEP), and cigarette smoke (CS), leading to chronic bronchitis, mucus production, and a subsequent lung dysfunction. This study, using a mouse model of COPD, aimed to evaluate the effect of herbal combinational medication of Glycyrrhiza glabra (GG), Agastache rugosa (AR) containing glycyrrhizic acid (GA), and tilianin (TN) as active ingredients. GA, a major active component of GG, possesses a range of pharmacological and biological activities including anti-inflammatory, anti-allergic, anti-oxidative. TN is a major flavonoid that is present in AR. It has been reported to have anti-inflammatory effects of potential utility as an anti-COPD agent. The COPD in the mice model was induced by a challenge with CFA and DEP. BALB/c mice received CFA and DEP alternately three times for 2 weeks to induce COPD. The herbal mixture of GG, AR, and TN significantly decreased the number of neutrophils in the lungs and bronchoalveolar lavage (BAL) fluid. It also significantly reduced the production of C-X-C motif chemokine ligand 2 (CXCL-2), IL-17A, CXCL-1, TNF-α, symmetric dimethylarginine (SDMA) in BALF and CXCL-2, IL-17A, CXCL-1, MUC5AC, transient receptor potential vanilloid-1 (TRPV1), IL-6, COX-2, NOS-II, and TNF-α mRNA expression in the lung tissue. Notably, a combination of GG and AR was more effective at regulating such therapeutic targets than GG or AR alone. The histolopathological lung injury was alleviated by treatment with the herbal mixture and their active ingredients (especially TN). In this study, the herbal combinational mixture more effectively inhibited neutrophilic airway inflammation by regulating the expression of inflammatory cytokines and CXCL-2 by blocking the IL-17/STAT3 pathway. Therefore, a herbal mixture of GG and AR may be a potential therapeutic agent to treat COPD.

Strategies for measuring airway mucus and mucins

Mucus secretion and mucociliary transport are essential defense mechanisms of the airways. Deviations in mucus composition and secretion can impede mucociliary transport and elicit airway obstruction. As such, mucus abnormalities are hallmark features of many respiratory diseases, including asthma, cystic fibrosis and chronic obstructive pulmonary disease (COPD). Studying mucus composition and its physical properties has therefore been of significant interest both clinically and scientifically. Yet, measuring mucus production, output, composition and transport presents several challenges. Here we summarize and discuss the advantages and limitations of several techniques from five broadly characterized strategies used to measure mucus secretion, composition and mucociliary transport, with an emphasis on the gel-forming mucins. Further, we summarize advances in the field, as well as suggest potential areas of improvement moving forward.

Construction of a Suite of Computable Biological Network Models Focused on Mucociliary Clearance in the Respiratory Tract

Mucociliary clearance (MCC), considered as a collaboration of mucus secreted from goblet cells, the airway surface liquid layer, and the beating of cilia of ciliated cells, is the airways’ defense system against airborne contaminants. Because the process is well described at the molecular level, we gathered the available information into a suite of comprehensive causal biological network (CBN) models. The suite consists of three independent models that represent (1) cilium assembly, (2) ciliary beating, and (3) goblet cell hyperplasia/metaplasia and that were built in the Biological Expression Language, which is both human-readable and computable. The network analysis of highly connected nodes and pathways demonstrated that the relevant biology was captured in the MCC models. We also show the scoring of transcriptomic data onto these network models and demonstrate that the models capture the perturbation in each dataset accurately. This work is a continuation of our approach to use computational biological network models and mathematical algorithms that allow for the interpretation of high-throughput molecular datasets in the context of known biology. The MCC network model suite can be a valuable tool in personalized medicine to further understand heterogeneity and individual drug responses in complex respiratory diseases.

Ramifications of secreted mucin MUC5AC in malignant journey: a holistic view

Heavily glycosylated secreted mucin MUC5AC, by the virtue of its cysteine-rich repeats, can form inter- and intramolecular disulfide linkages resulting in complex polymers, which in turn craft the framework of the polymeric mucus gel on epithelial cell surfaces. MUC5AC is a molecule with versatile functional implications including barrier functions to epithelial cells, host-pathogen interaction, immune cell attraction to sites of premalignant or malignant lesions and tumor progression in a context-dependent manner. Differential expression, glycosylation and localization of MUC5AC have been associated with a plethora of benign and malignant pathologies. In this era of robust technologies, overexpression strategies and genetically engineered mouse models, MUC5AC is emerging as a potential diagnostic, prognostic and therapeutic target for various malignancies. Considering the clinical relevance of MUC5AC, this review holistically encompasses its genomic organization, domain structure, glycosylation patterns, regulation, functional and molecular connotation from benign to malignant pathologies. Furthermore, we have here explored the incipient and significant experimental tools that are being developed to study this structurally complex and evolutionary conserved gel-forming mucin.

Louqin Zhisou Decoction Inhibits Mucus Hypersecretion for Acute Exacerbation of Chronic Obstructive Pulmonary Disease Rats by Suppressing EGFR-PI3K-AKT Signaling Pathway and Restoring Th17/Treg Balance

Airway mucus hypersecretion is the main pathogenic factor in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and the control of mucus secretion is closely associated with survival. Louqin Zhisou decoction (LQZS) has been found to improve lung function and reduce sputum in AECOPD patients, but the mechanism remains unclear. This study aimed to explore the mechanism of LQZS against mucus hypersecretion in lung tissues of rat AECOPD model. Wistar rats were used to establish AECOPD model by intratracheal instillation of LPS in combination with the continuous cigarette smoking. Rats were administrated LQZS/clarithromycin (CAM)/distilled water via gavage every day and all rats were sacrificed after 30 days. BALF and lung tissues were obtained. Lung morphology, cytokines levels, MUC5AC mRNA transcription and protein expression, phosphorylation of the EGFR-PI3K-AKT signaling pathway, and molecules involved in Th17/Treg balance were evaluated. The results demonstrated that LQZS protected rats from decline in pulmonary function and ameliorated lung injury. LQZS treatment decreased the number of goblet cells in airway and suppressed MUC5AC mRNA and protein expression of lung tissues. Furthermore, LQZS attenuated the level of phospho-EGFR, phospho-PI3K and phospho-AKT in AECOPD rats. In addition, LQZS could inhibit the production of proinflammatory cytokines in BALF, including IL-6 and IL-17A and downregulate the secretion of NE and MCP-1, indicating that LQZS could limit inflammatory responses in AECOPD. Moreover, LQZS reversed RORγt and Foxp3 expression, the key transcription factors of Th17 and Treg, respectively. In conclusion, this research demonstrated the inhibitory effects of LQZS against mucus hypersecretion in AECOPD via suppressing EGFR-PI3K-AKT signaling pathway and restoring Th17/Treg balance.

Resolvin D1 treatment on goblet cell mucin and immune responses in the chronic allergic eye disease (AED) model

Severe, chronic eye allergy is an understudied, vision-threatening condition. Treatments remain limited. We used a mouse model of severe allergic eye disease (AED) to determine whether topical application of the pro-resolution mediator Resolvin D1 (RvD1) terminates the response. AED was induced by injection of ovalbumin (OVA) followed by topical challenge of OVA daily. RvD1 was applied topically prior to OVA. Clinical symptoms were scored. Eye washes were assayed for MUC5AC. After 7 days, eyes were removed and the number of goblet cells, T helper cell responses and presence of immune cells in draining lymph nodes and conjunctiva determined. Topical RvD1 treatment significantly reduced symptoms of AED. RvD1 did not alter the systemic type 2 immune response in the lymph nodes. AED increased the total amount of goblet cell mucin secretion, but not the number of goblet cells. RvD1 prevented this increase, but did not alter goblet cell number. Absolute numbers of CD4 + T cells, total CD11b + myeloid cells, eosinophils, neutrophils, and monocytes, but not macrophages increased in AED versus RvD1-treated mice. We conclude that topical application of RvD1 reduced the ocular allergic response by local actions in conjunctival immune response and a decrease in goblet cell mucin secretion.

The Importance of Tyrosine Phosphorylation Control of Cellular Signaling Pathways in Respiratory Disease: pY and pY Not

Reversible phosphorylation of proteins on tyrosine residues is an essential signaling mechanism by which diverse cellular processes are closely regulated. The tight temporal and spatial control of the tyrosine phosphorylation status of proteins by protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs) is critical to cellular homeostasis as well as to adaptations to the external environment. Via regulation of cellular signaling cascades involving other protein kinases and phosphatases, receptors, adaptor proteins, and transcription factors, PTKs and PTPs closely control diverse cellular processes such as proliferation, differentiation, migration, inflammation, and maintenance of cellular barrier function. Given these key regulatory roles, it is not surprising that dysfunction of PTKs and PTPs is important in the pathogenesis of human disease, including many pulmonary diseases. The roles of various PTKs and PTPs in acute lung injury and repair, pulmonary fibrosis, pulmonary vascular disease, and inflammatory airway disease are discussed in this review. It is important to note that although there is overlap among many of these proteins in various disease states, the mechanisms by which they influence the pathogenesis of these conditions differ, suggesting wide-ranging roles for these enzymes and their potential as therapeutic targets.

A Small Molecule BH3-mimetic Suppresses Cigarette Smoke-Induced Mucous Expression in Airway Epithelial Cells

Cigarette smoke (CS) exposure is one of the primary risk factors associated with the chronic mucous hypersecretion (CMH). The antiapoptotic protein, Bcl-2 sustains hyperplastic mucous cells, and the airway epithelium of ex-smokers with CMH as well as mice exposed to chronic CS showed increased Bcl-2 expression. Therefore, we investigated whether Bcl-2 plays a role in CS-induced mucous expression. Primary airway epithelial cells (AECs) of murine and human origin were treated with CS extract (CSE), and there was a concentration- and time-dependent increase in secretory mucin (MUC5AC), mucous regulator (SPDEF) and Bcl-2 expression. Using differentiated human AECs cultured on air-liquid interface, EGFR and ERK1/2 pathways were interrogated. Bcl-2 activity was blocked using a small molecule BH3 mimetic ABT-263 that disrupts the Bcl-2 interaction with pro-apoptotic proteins. The ABT-263 treatment resulted in the downregulation of CSE-induced mucus expression and disrupted the EGFR-signaling while inducing the apoptosis and the pro-apoptotic protein, Bik expression. This strategy significantly suppressed the mainstream CS-induced mucous phenotype in a 3-D human airway epithelium model. Therefore, the present study suggests that CS induces Bcl-2 expression to help promote mucous cell survival; and small molecule BH3 mimetics targeting Bcl-2 could be useful in suppressing the CS-induced mucous response.

New targets for resolution of airway remodeling in obstructive lung diseases

Airway remodeling (AR) is a progressive pathological feature of the obstructive lung diseases, including asthma and chronic obstructive pulmonary disease (COPD). The pathology manifests itself in the form of significant, progressive, and (to date) seemingly irreversible changes to distinct respiratory structural compartments. Consequently, AR correlates with disease severity and the gradual decline in pulmonary function associated with asthma and COPD. Although current asthma/COPD drugs manage airway contraction and inflammation, none of these effectively prevent or reverse features of AR. In this review, we provide a brief overview of the features and putative mechanisms affecting AR. We further discuss recently proposed strategies with promise for deterring or treating AR.

Relationship between advanced glycation end-product accumulation in the skin and pulmonary function

. [Purpose] This study aimed to evaluate the relationship between advanced glycation end-product accumulation and pulmonary function in a general population with normal spirometry results. [Subjects and Methods] A total of 201 subjects (mean age, 56 ± 11 years; males, 58%) enrolled in this study. Subjects were classified into two groups (younger group [<65 years old] and elderly group [≥65 years old]). Skin autofluorescence was assessed as an estimate of advanced glycation end-product. Forced vital capacity and forced expiratory volume in one second were measured using a spirometer, and the forced expiratory volume in one second/forced vital capacity ratio (FEV1/FVC) was calculated. [Results] Skin autofluorescence was not an independent factor associated with FEV1/FVC in the younger group, but both skin autofluorescence and pack-years of smoking were significant independent factors associated with FEV1/FVC in the elderly group. [Conclusion] Advanced glycation end-product accumulation, assessed by skin autofluorescence, is an independent factor negatively associated with FEV1/FVC in elderly people with normal spirometry results.

Aberrant epithelial differentiation by cigarette smoke dysregulates respiratory host defence

It is currently unknown how cigarette smoke-induced airway remodelling affects highly expressed respiratory epithelial defence proteins and thereby mucosal host defence.

Localisation of a selected set of highly expressed respiratory epithelial host defence proteins was assessed in well-differentiated primary bronchial epithelial cell (PBEC) cultures. Next, PBEC were cultured at the air–liquid interface, and during differentiation for 2–3 weeks exposed daily to whole cigarette smoke. Gene expression, protein levels and epithelial cell markers were subsequently assessed. In addition, functional activities and persistence of the cigarette smoke-induced effects upon cessation were determined.

Expression of the polymeric immunoglobulin receptor, secretory leukocyte protease inhibitor and long and short PLUNC (palate, lung and nasal epithelium clone protein) was restricted to luminal cells and exposure of differentiating PBECs to cigarette smoke resulted in a selective reduction of the expression of these luminal cell-restricted respiratory host defence proteins compared to controls. This reduced expression was a consequence of cigarette smoke-impaired end-stage differentiation of epithelial cells, and accompanied by a significant decreased transepithelial transport of IgA and bacterial killing.

These findings shed new light on the importance of airway epithelial cell differentiation in respiratory host defence and could provide an additional explanation for the increased susceptibility of smokers and patients with chronic obstructive pulmonary disease to respiratory infections.

(-)-Epigallocatechin-3-gallate Reduces Cigarette Smoke-Induced Airway Neutrophilic Inflammation and Mucin Hypersecretion in Rats

Background: Cigarette smoking is the leading cause of chronic obstructive pulmonary disease. (-)-Epigallocatechin-3-gallate (EGCG), the major catechins in Chinese green tea, has been studied for its anti-oxidative and anti-inflammatory properties in cell and animal models. In this study, we aimed to analyze the effects of EGCG on cigarette smoke (CS)-induced airway inflammation and mucus secretion in the CS-exposed rat model. Methods: Male Sprague-Dawley rats were randomly divided into either sham air (SA) or CS exposure. EGCG (50 mg/kg b.wt.) was given by oral gavage every other day in both SA and CS-exposed animals. Oxidative stress and inflammatory markers were determined in serum and/or bronchoalveolar lavage fluid by biochemical assays or ELISA. Lung morphological changes were examined by Periodic Acid-Schiff, Masson's Trichrome staining and immunohistochemical analysis. Western blot analysis was performed to explore the effects of EGCG on epidermal growth factor receptor (EGFR)-mediated signaling pathway. Results: (-)-Epigallocatechin-3-gallate treatment attenuated CS-induced oxidative stress, lung cytokine-induced neutrophil chemoattractant-1 release and neutrophil recruitment. CS exposure caused an increase in the number of goblet cells in line with MUC5AC upregulation, and increased lung collagen deposition, which were alleviated in the presence of EGCG. In addition, CS-induced phosphorylation of EGFR in rat lung was abrogated by EGCG treatment. Conclusion: (-)-Epigallocatechin-3-gallate treatment ameliorated CS-induced oxidative stress and neutrophilic inflammation, as well as airway mucus production and collagen deposition in rats. The present findings suggest that EGCG has a therapeutic effect on chronic airway inflammation and abnormal airway mucus production probably via inhibition of EGFR signaling pathway.

Chronic Cigarette Smoke Mediated Global Changes in Lung Mucoepidermoid Cells: A Phosphoproteomic Analysis

Proteomics analysis of chronic cigarette smoke exposure is a rapidly emerging postgenomics research field. While smoking is a major cause of lung cancer, functional studies using proteomics approaches could enrich our mechanistic understanding of the elusive lung cancer global molecular signaling and cigarette smoke relationship. We report in this study on a stable isotope labeling by amino acids in cell culture-based quantitative phosphoproteomic analysis of a human lung mucoepidermoid carcinoma cell line, H292 cells, chronically exposed to cigarette smoke. Using high resolution Orbitrap Velos mass spectrometer, we identified the hyperphosphorylation of 493 sites, which corresponds to 341 proteins and 195 hypophosphorylated sites, mapping to 142 proteins upon smoke exposure (2.0-fold change). We report differential phosphorylation of multiple kinases, including PAK6, EPHA4, LYN, mitogen-activated protein kinase, and phosphatases, including TMEM55B, PTPN14, TIGAR, among others, in response to chronic cigarette smoke exposure. Bioinformatics analysis revealed that the molecules differentially phosphorylated upon chronic exposure of cigarette smoke are associated with PI3K/AKT/mTOR and CDC42-PAK signaling pathways. These signaling networks are involved in multiple cellular processes, including cell polarity, cytoskeletal remodeling, cellular migration, protein synthesis, autophagy, and apoptosis. The present study contributes to emerging proteomics insights on cigarette smoke mediated global signaling in lung cells, which in turn may aid in development of precision medicine therapeutics and postgenomics biomarkers.

Functional characterization of a novel 3D model of the epithelial-mesenchymal trophic unit

BACKGROUND/AIM

Epithelial-mesenchymal communication plays a key role in tissue homeostasis and abnormal signaling contributes to chronic airways disease such as COPD. Most in vitro models are limited in complexity and poorly represent this epithelial-mesenchymal trophic unit. We postulated that cellular outgrowth from bronchial tissue would enable development of a mucosal structure that recapitulates better in vivo tissue architecture.

MATERIALS AND METHODS

Bronchial tissue was embedded in Matrigel and outgrowth cultures monitored using time-lapse microscopy, electrical resistance, light and electron microscopy. Cultures were challenged repetitively with cigarette smoke extract (CSE).

RESULTS

The outgrowths formed as a multicellular sheet with motile cilia becoming evident as the Matrigel was remodeled to provide an air interface; cultures were viable for more than one year. Immunofluorescence and electron microscopy (EM) identified an upper layer of mucociliary epithelium and a lower layer of highly organized extracellular matrix (ECM) interspersed with fibroblastic cells separated by a basement membrane. EM analysis of the mucosal construct after repetitive exposure to CSE revealed epithelial damage, loss of cilia, and ECM remodeling, as occurs in vivo.

CONCLUSIONS

We have developed a robust bronchial mucosal model. The structural changes observed following CSE exposure suggest the model should have utility for drug discovery and preclinical testing, especially those targeting airway remodeling.

The Contribution of Small Airway Obstruction to the Pathogenesis of Chronic Obstructive Pulmonary Disease

The hypothesis that the small conducting airways were the major site of obstruction to airflow in normal lungs was introduced by Rohrer in 1915 and prevailed until Weibel introduced a quantitative method of studying lung anatomy in 1963. Green repeated Rohrer's calculations using Weibels new data in 1965 and found that the smaller conducting airways offered very little resistance to airflow. This conflict was resolved by seminal experiments conducted by Macklem and Mead in 1967, which confirmed that a small proportion of the total lower airways resistance is attributable to small airways <2 mm in diameter. Shortly thereafter, Hogg, Macklem, and Thurlbeck used this technique to show that small airways become the major site of obstruction in lungs affected by emphysema. These and other observations led Mead to write a seminal editorial in 1970 that postulated the small airways are a silent zone within normal lungs where disease can accumulate over many years without being noticed. This review provides a progress report since the 1970s on methods for detecting chronic obstructive pulmonary disease, the structural nature of small airways' disease, and the cellular and molecular mechanisms that are thought to underlie its pathogenesis.

Measuring the Effect of Environmental Tobacco Smoke on Lung Function: Results From a Small Observational Investigation of Acute Exposure

OBJECTIVE

Exposure to environmental tobacco smoke (ETS) in smoky venues puts patrons and employees at risk for immediate respiratory symptoms. Although much literature focuses on outcomes associated with chronic ETS exposure, the current study assesses changes in lung function after acute exposure.

METHODS

Ninety-six nonsmoking, healthy adults were exposed to ETS at a bar. Lung function [eg, forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1)] was assessed at baseline, immediately after 3 hours of ETS exposure, and 2 hours after exiting the bar. PM2.5 recordings were also measured.

RESULTS

Repeated-measures analysis of variance found significant decreases in FEV1, FVC and FEF25-75%, and peak expiratory flow after ETS exposure compared with baseline that remained significantly decreased after a 2-hour recovery period.

CONCLUSIONS

Acute exposure to ETS in a natural environment significantly attenuates lung function. A subgroup experienced heightened reductions in lung function.

Identification of non-coding genetic variants in samples from hypoxemic respiratory disease patients that affect the transcriptional response to hypoxia

A wide range of diseases course with an unbalance between the consumption of oxygen by tissues and its supply. This situation triggers a transcriptional response, mediated by the hypoxia inducible factors (HIFs), that aims to restore oxygen homeostasis. Little is known about the inter-individual variation in this response and its role in the progression of disease. Herein, we sought to identify common genetic variants mapping to hypoxia response elements (HREs) and characterize their effect on transcription. To this end, we constructed a list of genome-wide HIF-binding regions from publicly available experimental datasets and studied the genetic variability in these regions by targeted re-sequencing of genomic samples from 96 chronic obstructive pulmonary disease and 144 obstructive sleep apnea patients. This study identified 14 frequent variants disrupting potential HREs. The analysis of the genomic regions containing these variants by means of reporter assays revealed that variants rs1009329, rs6593210 and rs150921338 impaired the transcriptional response to hypoxia. Finally, using genome editing we confirmed the functional role of rs6593210 in the transcriptional regulation of EGFR. In summary, we found that inter-individual variability in non-coding regions affect the response to hypoxia and could potentially impact on the progression of pulmonary diseases.

Gefitinib, an EGFR Tyrosine Kinase inhibitor, Prevents Smoke-Mediated Ciliated Airway Epithelial Cell Loss and Promotes Their Recovery

Cigarette smoke exposure is a major health hazard. Ciliated cells in the epithelium of the airway play a critical role in protection against the noxious effects of inhaled cigarette smoke. Ciliated cell numbers are reduced in smokers which weakens host defense and leads to disease. The mechanisms for the loss of ciliated cells are not well understood. The effects of whole cigarette smoke exposure on human airway ciliated ciliated cells were examined using in vitro cultures of normal human bronchial epithelial cells and a Vitrocell^® VC 10^® Smoking Robot. These experiments showed that whole cigarette smoke causes the loss of differentiated ciliated cells and inhibits differentiation of ciliated cells from undifferentiated basal cells. Furthermore, treatment with the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, Gefitinib, during smoke exposure prevents ciliated cell loss and promotes ciliated cell differentiation from basal cells. Finally, restoration of ciliated cells was inhibited after smoke exposure was ceased but was enhanced by Gefitinib treatment. These data suggest that inhibition of EGFR activity may provide therapeutic benefit for treating smoke related diseases.

Pathogenesis of COPD (Persistence of Airway Inflammation): Why Does Airway Inflammation Persist After Cessation of Smoking?

The structural features of airways in patients with COPD are airway wall inflammation, fibrosis, muscle hypertrophy, and goblet cell metaplasia. These structural cellular changes contribute to mucus hypersecretion and destruction of the alveolar walls and a decline in forced expiratory volume in one second (FEV₁). At the cellular level, macrophages, T lymphocytes, and neutrophils, driven by cytokines including interleukin-8 (IL-8), gather on the airways. The main cause of COPD inflammation is cigarette smoke. Smoke causes an increase in the secretion of matrix metalloproteinase (MMPs) and neutrophilic elastase from epithelial cells and neutrophils, which are responsible for mucin production and destruction of the lung. Initially, cigarette smoke influences the expression of pattern recognition receptors (PRRs) including Toll-like receptors (TLRs), the intracellularly located nucleotide-binding oligomerization domain (NOD)-like receptors (NLRs), retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs), and receptors for advanced glycation end products (RAGE) on lung epithelial cells, endothelial cells, and leukocytes in the lung. These actions bring about the production of cytokines and activation of inflammatory cells, leading to production of MMPs and neutrophilic elastase. The inflammatory changes persist for several months and years after smoking cessation and are sometimes irreversible. Damage-associated molecular patterns (DAMPs) released from dying cells after cigarette smoking increase the number of apoptotic cells, suppress efferocytosis, induce hypoxia and oxidative stress, and prolong the inflammatory changes, even after smoking cessation. Viral and bacterial infections of the respiratory tract then fortify these inflammatory responses. Exacerbations of COPD then worsen the deterioration of COPD.

Kinases as Novel Therapeutic Targets in Asthma and Chronic Obstructive Pulmonary Disease

Multiple kinases play a critical role in orchestrating the chronic inflammation and structural changes in the respiratory tract of patients with asthma and chronic obstructive pulmonary disease (COPD). Kinases activate signaling pathways that lead to contraction of airway smooth muscle and release of inflammatory mediators (such as cytokines, chemokines, growth factors) as well as cell migration, activation, and proliferation. For this reason there has been great interest in the development of kinase inhibitors as anti-inflammatory therapies, particular where corticosteroids are less effective, as in severe asthma and COPD. However, it has proven difficult to develop selective kinase inhibitors that are both effective and safe after oral administration and this has led to a search for inhaled kinase inhibitors, which would reduce systemic exposure. Although many kinases have been implicated in inflammation and remodeling of airway disease, very few classes of drug have reached the stage of clinical studies in these diseases. The most promising drugs are p38 MAP kinases, isoenzyme-selective PI3-kinases, Janus-activated kinases, and Syk-kinases, and inhaled formulations of these drugs are now in development. There has also been interest in developing inhibitors that block more than one kinase, because these drugs may be more effective and with less risk of losing efficacy with time. No kinase inhibitors are yet on the market for the treatment of airway diseases, but as kinase inhibitors are improved from other therapeutic areas there is hope that these drugs may eventually prove useful in treating refractory asthma and COPD.

Autocrine Acetylcholine, Induced by IL-17A via NFκB and ERK1/2 Pathway Activation, Promotes MUC5AC and IL-8 Synthesis in Bronchial Epithelial Cells

IL-17A is overexpressed in the lung during acute neutrophilic inflammation. Acetylcholine (ACh) increases IL-8 and Muc5AC production in airway epithelial cells. We aimed to characterize the involvement of nonneuronal components of cholinergic system on IL-8 and Muc5AC production in bronchial epithelial cells stimulated with IL-17A. Bronchial epithelial cells were stimulated with recombinant human IL-17A (rhIL-17A) to evaluate the ChAT expression, the ACh binding and production, the IL-8 release, and the Muc5AC production. Furthermore, the effectiveness of PD098,059 (inhibitor of MAPKK activation), Bay11-7082 (inhibitor of IkBα phosphorylation), Hemicholinium-3 (HCh-3) (choline uptake blocker), and Tiotropium bromide (Spiriva®) (anticholinergic drug) was tested in our in vitro model. We showed that rhIL-17A increased the expression of ChAT, the levels of ACh binding and production, and the IL-8 and Muc5AC production in stimulated bronchial epithelial cells compared with untreated cells. The pretreatment of the cells with PD098,059 and Bay11-7082 decreased the ChAT expression and the ACh production/binding, while HCh-3 and Tiotropium decreased the IL-8 and Muc5AC synthesis in bronchial epithelial cells stimulated with rhIL-17A. IL-17A is involved in the IL-8 and Muc5AC production promoting, via NFκB and ERK1/2 pathway activation, the synthesis of ChAT, and the related activity of autocrine ACh in bronchial epithelial cells.

Kallikreins - The melting pot of activity and function

The human tissue kallikrein and kallikrein-related peptidases (KLKs), encoded by the largest contiguous cluster of protease genes in the human genome, are secreted serine proteases with diverse expression patterns and physiological roles. Because of the broad spectrum of processes that are modulated by kallikreins, these proteases are the subject of extensive investigations. This review brings together basic information about the biochemical properties affecting enzymatic activity, with highlights on post-translational modifications, especially glycosylation. Additionally, we present the current state of knowledge regarding the physiological functions of KLKs in major human organs and outline recent discoveries pertinent to the involvement of kallikreins in cell signaling and in viral infections. Despite the current depth of knowledge of these enzymes, many questions regarding the roles of kallikreins in health and disease remain unanswered.

Aloe vera affects changes induced in pulmonary tissue of mice caused by cigarette smoke inhalation

This study was undertaken to determine the influence of Aloe vera (AV) on changes induced in pulmonary tissue of cigarette smoke (CS) inhaling mice. CS inhalation for 4 weeks caused pulmonary damage as evident by histoarchitectural alterations and enhanced serum and tissue lactate dehydrogenase (LDH) activities. CS inhalation also led to increased mucin production as revealed by mucicarmine and Alcian Blue-Periodic Acid Schiff (AB-PAS) staining. Studies on bronchoalveolar lavage fluid (balf) of CS exposed animals revealed structural changes in phospholipids and increase in surface tension when compared with control counterparts. These changes were accompanied by enhanced nitric oxide (NO) levels, citrulline levels, peroxidative damage, and differential modulation of antioxidant defense system. AV administration (seven weeks, 500 mg/kg b.w. daily) to CS inhaling mice led to modulation of CS induced pulmonary changes as revealed by lesser degree of histoarchitectural alterations, lesser mucin production, decreased NO levels, citrulline levels, peroxidative damage, and serum LDH activity. AV treatment to CS inhaling mice was associated with varying response to antioxidant defense system, however balf of CS + AV treated animals did not exhibit appreciable changes when compared with that of CS exposed animals. These observations suggest that AV has the potential to modulate CS induced changes in the pulmonary tissue which could have implications in management of CS associated pulmonary diseases, however, further investigations are required to explore its complete mechanism of action.

Causes of chronic productive cough: An approach to management

A chronic 'productive' or 'wet' cough is a common presenting complaint for patients attending the adult respiratory clinic. Most reviews and guidelines suggest that the causes of a productive cough are the same as those of a non-productive cough and as such the same diagnostic pathway should be followed. We suggest a different diagnostic approach for patients with a productive cough, focussing on the conditions that are the most likely causes of this problem. This review is intended to briefly summarise the epidemiology, clinical features, pathophysiology and treatment of a number of conditions which are often associated with chronic productive cough to aid decision making when encountering a patient with this often distressing symptom. The conditions discussed include bronchiectasis, chronic bronchitis, asthma, eosinophilic bronchitis and immunodeficiency. We also propose an adult version of the paediatric diagnosis of protracted bacterial bronchitis (PBB) in patients with idiopathic chronic productive cough who appear to respond well to low dose macrolide therapy.