Cigarette smoke-induced epithelial expression of WNT-5B: implications for COPD

A 3D Epithelial-Mesenchymal Co-Culture Model of the Airway Wall Using Native Lung Extracellular Matrix

Chronic obstructive pulmonary disease (COPD) is a chronic lung disease characterized by ongoing inflammation, impaired tissue repair, and aberrant interplay between airway epithelium and fibroblasts, resulting in an altered extracellular matrix (ECM) composition. The ECM is the three-dimensional (3D) scaffold that provides mechanical support and biochemical signals to cells, now recognized not only as a consequence but as a potential driver of disease progression. To elucidate how the ECM influences pathophysiological changes occurring in COPD, in vitro models are needed that incorporate the ECM. ECM hydrogels are a novel experimental tool for incorporating the ECM in experimental setups. We developed an airway wall model by combining lung-derived ECM hydrogels with a co-culture of primary human fibroblasts and epithelial cells at an air-liquid interface. Collagen IV and a mixture of collagen I, fibronectin, and bovine serum albumin were used as basement membrane-mimicking coatings. The model was initially assembled using porcine lung-derived ECM hydrogels and subsequently with COPD and non-COPD human lung-derived ECM hydrogels. The resulting 3D construct exhibited considerable contraction and supported co-culture, resulting in a differentiated epithelial layer. This multi-component 3D model allows the investigation of remodelling mechanisms, exploring ECM involvement in cellular crosstalk, and holds promise as a model for drug discovery studies exploring ECM involvement in cellular interactions.

Cigarette Smoke-Induced Epithelial-to-Mesenchymal Transition: Insights into Cellular Mechanisms and Signaling Pathways

This review delves into the molecular complexities underpinning the epithelial-to-mesenchymal transition (EMT) induced by cigarette smoke (CS) in human bronchial epithelial cells (HBECs). The complex interplay of pathways, including those related to WNT//β-catenin, TGF-β/SMAD, hypoxia, oxidative stress, PI3K/Akt, and NF-κB, plays a central role in mediating this transition. While these findings significantly broaden our understanding of CS-induced EMT, the research reviewed herein leans heavily on 2D cell cultures, highlighting a research gap. Furthermore, the review identifies a stark omission of genetic and epigenetic factors in recent studies. Despite these shortcomings, the findings furnish a consolidated foundation not only for the academic community but also for the broader scientific and industrial sectors, including large tobacco companies and manufacturers of related products, both highlighting areas of current understanding and identifying areas for deeper exploration. The synthesis herein aims to propel further research, hoping to unravel the complexities of the EMT in the context of CS exposure. This review not only expands our understanding of CS-induced EMT but also reveals critical limitations in current methodologies, primarily the reliance on 2D cell cultures, which may not adequately simulate more complex biological interactions. Additionally, it highlights a significant gap in the literature concerning the genetic and epigenetic factors involved in CS-induced EMT, suggesting an urgent need for comprehensive studies that incorporate these types of experiments.

Use of human airway smooth muscle in vitro and ex vivo to investigate drugs for the treatment of chronic obstructive respiratory disorders

Isolated airway smooth muscle has been extensively investigated since 1840 to understand the pharmacology of airway diseases. There has often been poor predictability from murine experiments to drugs evaluated in patients with asthma or chronic obstructive pulmonary disease (COPD). However, the use of isolated human airways represents a sensible strategy to optimise the development of innovative molecules for the treatment of respiratory diseases. This review aims to provide updated evidence on the current uses of isolated human airways in validated in vitro methods to investigate drugs in development for the treatment of chronic obstructive respiratory disorders. This review also provides historical notes on the pioneering pharmacological research on isolated human airway tissues, the key differences between human and animal airways, as well as the pivotal differences between human medium bronchi and small airways. Experiments carried out with isolated human bronchial tissues in vitro and ex vivo replicate many of the main anatomical, pathophysiological, mechanical and immunological characteristics of patients with asthma or COPD. In vitro models of asthma and COPD using isolated human airways can provide information that is directly translatable into humans with obstructive lung diseases. Regardless of the technique used to investigate drugs for the treatment of chronic obstructive respiratory disorders (i.e., isolated organ bath systems, videomicroscopy and wire myography), the most limiting factors to produce high-quality and repeatable data remain closely tied to the manual skills of the researcher conducting experiments and the availability of suitable tissue.

Plasma sCD146 is a potential biomarker for acute exacerbation of chronic obstructive pulmonary disease

This study examined the levels of soluble CD146 (sCD146) in plasma samples from patients with chronic obstructive pulmonary disease (COPD) and assessed the relationship between sCD146 and the severity of COPD. A total of 97 COPD patients were recruited from 20 medical centers in Jiangsu, China, including 13 stable subjects and 84 exacerbated subjects. The plasma sCD146 level in exacerbated subjects (28.77 ± 10.80 ng/mL) was significantly lower than that in stable subjects (38.84 ± 15.00 ng/mL). In the high sCD146 group, the proportion of subjects with modified Medical Research Council (mMRC) scores of 0-1 was higher, the proportion of subjects with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage 4 was lower, and the proportion of subjects with ≥1 hospitalizations in the past year was lower. The plasma sCD146 level was negatively correlated with the COPD Assessment Test (CAT) score (r = -0.2664, p = 0.0087). Logistic regression analysis showed that sCD146 was an independent risk factor for acute exacerbation of COPD (AECOPD). Receiver operating characteristic (ROC) analysis suggested that sCD146 combined with sex, age, pulmonary function, and acute exacerbations in the past year had clinical value for the accurate identification of AECOPD, with an area under the ROC curve (AUC) of 0.908 (95% CI: 0.810-1.000, p < 0.001). In addition, there was a significant negative correlation between plasma sCD146 and S100A9 (r = -0.3939, p < 0.001).

8-Bromo-cAMP attenuates human airway epithelial barrier disruption caused by titanium dioxide fine and nanoparticles

Titanium dioxide fine particles (TiO2-FPs) and nanoparticles (TiO2-NPs) are the most widely used whitening pigments worldwide. Inhalation of TiO2-FPs and TiO2-NPs can be harmful as it triggers toxicity in the airway epithelial cells. The airway epithelium serves as the respiratory system's first line of defense in which airway epithelial cells are significant targets of inhaled pathogens and environmental particles. Our group previously found that TiO2-NPs lead to a disrupted barrier in the polarized airway epithelial cells. However, the effect of TiO2-FPs on the respiratory epithelial barrier has not been examined closely. In this study, we aimed to compare the effects of TiO2-FPs and TiO2-NPs on the structure and function of the airway epithelial barrier. Additionally, we hypothesized that 8-Bromo-cAMP, a cyclic adenosine monophosphate (cAMP) derivative, would alleviate the disruptive effects of both TiO2-FPs and TiO2-NPs. We observed increased epithelial membrane permeability in both TiO2-FPs and TiO2-NPs after exposure to 16HBE cells. Immunofluorescent labeling showed that both particle sizes disrupted the structural integrity of airway epithelial tight junctions and adherens junctions. TiO2-FPs had a slightly more, but insignificant impact on the epithelial barrier disruption than TiO2-NPs. Treatment with 8-Bromo-cAMP significantly attenuated the barrier-disrupting impact of both TiO2-FPs and TiO2-NPs on cell monolayers. Our study demonstrates that both TiO2-FPs and TiO2-NPs cause comparable barrier disruption and suggests a protective role for cAMP signaling. The observed effects of TiO2-FPs and TiO2-NPs provide a necessary understanding for characterizing the pathways involved in the defensive role of the cAMP pathway on TiO2-induced airway barrier disruption.

Molecular pathogenesis of subretinal fibrosis in neovascular AMD focusing on epithelial-mesenchymal transformation of retinal pigment epithelium

Age-related macular degeneration (AMD) is a leading cause of vision loss among elderly people in developed countries. Neovascular AMD (nAMD) accounts for more than 90% of AMD-related vision loss. At present, intravitreal injection of anti-vascular endothelial growth factor (anti-VEGF) is widely used as the first-line therapy to decrease the choroidal and retinal neovascularizations, and thus to improve or maintain the visual acuity of the patients with nAMD. However, about 1/3 patients still progress to irreversible visual impairment due to subretinal fibrosis even with adequate anti-VEGF treatment. Extensive literatures support the critical role of epithelial-mesenchymal transformation (EMT) of retinal pigment epithelium (RPE) in the pathogenesis of subretinal fibrosis in nAMD, but the underlying mechanisms still remain largely unknown. This review summarized the molecular pathogenesis of subretinal fibrosis in nAMD, especially focusing on the transforming growth factor-β (TGF-β)-induced EMT pathways. It was also discussed how these pathways crosstalk and respond to signals from the microenvironment to mediate EMT and contribute to the progression of nAMD-related subretinal fibrosis. Targeting EMT signaling pathways might provide a promising and effective therapeutic strategy to treat subretinal fibrosis secondary to nAMD.

Cigarette smoke extract-mediated FABP4 upregulation suppresses viability and induces apoptosis, inflammation and oxidative stress of bronchial epithelial cells by activating p38 MAPK/MK2 signaling pathway

Background

Long-term inhalation of cigarette smoke is considered to be one of the main causes of bronchial epithelioid cell damage, but its underlying mechanism has to be further clarified.

Methods

Gene expression at mRNA level and protein levels were detected by qRT-PCR and western blot analysis respectively. CCK-8, TUNEL assays, ELISA, western blot analysis and commercial kits were utilized to test cell viability, apoptosis inflammatory response and oxidative stress. The correlation between fatty acid binding protein 4 (FABP4) and the p38 mitogen-activated protein kinase (MAPK)/MAPK activated kinase 2 (MK2) signaling pathway was verified by western blot analysis and rescue assays.

Results

Cigarette smoke extract (CSE) exposure decreased viability, induced apoptosis and inflammatory response in 16HBE cells. Moreover, the expression of FABP4 in CSE-treated 16HBE cells was up-regulated in a time and dose-dependent manner. Ablation of FABP4 in 16HBE cells significantly protected against CSE-mediated cell viability decline and apoptosis. Further, FABP4 knockdown suppressed inflammatory response by down-regulating the elevated levels of cellular inflammatory factors including TNF-α, IL-1β, IL-6, Cyclooxygenase-2 (Cox-2) and inducible nitric oxide synthase (iNOS) in CSE-treated 16HBE cells. The oxidative stress induced by CSE in 16HBE cells was also inhibited by FABP4 silence as evidence by reduced ROS and MDA level but increased SOD activity caused by FABP4 silence. Finally, all the above effects of FABP4 silence on CSE-treated 16HBE cells were reversed by asiatic acid, an agonist of p38 mitogen-activated protein kinase (MAPK).

Conclusions

The up-regulation of FABP4 expression mediated by CSE exerted pro-inflammatory, pro-oxidative stress and pro-apoptotic effects on bronchial epithelial cells by activating the p38 MAPK/MK2 signaling pathway. Our findings help to further understand the underlying mechanism of cigarette smoke-induced bronchial inflammation.

From Differential DNA Methylation in COPD to Mitochondria: Regulation of AHRR Expression Affects Airway Epithelial Response to Cigarette Smoke

Cigarette smoking causes hypomethylation of the gene Aryl Hydrocarbon Receptor Repressor (AHRR), which regulates detoxification and oxidative stress-responses. We investigated whether AHRR DNA methylation is related to chronic obstructive pulmonary disease (COPD) and studied its function in airway epithelial cells (AECs). The association with COPD was assessed in blood from never and current smokers with/without COPD, and in AECs from ex-smoking non-COPD controls and GOLD stage II-IV COPD patients cultured with/without cigarette smoke extract (CSE). The effect of CRISPR/Cas9-induced AHRR knockout on proliferation, CSE-induced mitochondrial membrane potential and apoptosis/necrosis in human bronchial epithelial 16HBE cells was studied. In blood, DNA methylation of AHRR at cg05575921 and cg21161138 was lower in smoking COPD subjects than smoking controls. In vitro, AHRR DNA methylation at these CpG-sites was lower in COPD-derived than control-derived AECs only upon CSE exposure. Upon AHRR knockout, we found a lower proliferation rate at baseline, stronger CSE-induced decrease in mitochondrial membrane potential, and higher CSE-induced late apoptosis/necroptosis. Together, our results show lower DNA methylation of AHRR upon smoking in COPD patients compared to non-COPD controls. Our data suggest that higher airway epithelial AHRR expression may lead to impaired cigarette smoke-induced mitochondrial dysfunction and apoptosis/necroptosis, potentially promoting unprogrammed/immunogenic cell death.

Impaired Alveolar Re-Epithelialization in Pulmonary Emphysema

Alveolar type II (ATII) cells are progenitors in alveoli and can repair the alveolar epithelium after injury. They are intertwined with the microenvironment for alveolar epithelial cell homeostasis and re-epithelialization. A variety of ATII cell niches, transcription factors, mediators, and signaling pathways constitute a specific environment to regulate ATII cell function. Particularly, WNT/β-catenin, YAP/TAZ, NOTCH, TGF-β, and P53 signaling pathways are dynamically involved in ATII cell proliferation and differentiation, although there are still plenty of unknowns regarding the mechanism. However, an imbalance of alveolar cell death and proliferation was observed in patients with pulmonary emphysema, contributing to alveolar wall destruction and impaired gas exchange. Cigarette smoking causes oxidative stress and is the primary cause of this disease development. Aberrant inflammatory and oxidative stress responses result in loss of cell homeostasis and ATII cell dysfunction in emphysema. Here, we discuss the current understanding of alveolar re-epithelialization and altered reparative responses in the pathophysiology of this disease. Current therapeutics and emerging treatments, including cell therapies in clinical trials, are addressed as well.

Advances in cGAS-STING Signaling Pathway and Diseases

Pathogens can produce conserved pathogen-associated molecular patterns (PAMPs) after invading the body, which can be specifically recognized by host pattern recognition receptors (PRRs). In recent years, it has been found that cytoplasmic DNA receptors recognize exogenous DNA inducing activation of interferon 1 (IFN1), which is a rapid advance in various research areas. The cyclic GMP–AMP synthase (cGAS) stimulator of interferon gene (STING) signaling pathway is a critical natural immune pathway in cells. Early studies revealed that it plays a crucial regulatory role in pathogen infection and tumor, and it is associated with various human autoimmune diseases. Recently studies have found that activation of cGAS-STING signaling pathway is related to different organ injuries. The present review elaborates on the regulation of the cGAS-STING signaling pathway and its role in various diseases, aiming to provide a theoretical basis for immunotherapy targeting this pathway.

MicroRNAs Associated with Chronic Mucus Hypersecretion in COPD Are Involved in Fibroblast-Epithelium Crosstalk

We recently identified microRNAs (miRNAs) associated with chronic mucus hypersecretion (CMH) in chronic obstructive pulmonary disease (COPD), which were expressed in both airway epithelial cells and fibroblasts. We hypothesized that these miRNAs are involved in communication between fibroblasts and epithelium, contributing to airway remodeling and CMH in COPD. Primary bronchial epithelial cells (PBECs) differentiated at the air–liquid interface, and airway fibroblasts (PAFs) from severe COPD patients with CMH were cultured alone or together. RNA was isolated and miRNA expression assessed. miRNAs differentially expressed after co-culturing were studied functionally using overexpression with mimics in mucus-expressing human lung A549 epithelial cells or normal human lung fibroblasts. In PBECs, we observed higher miR-708-5pexpression upon co-culture with fibroblasts, and miR-708-5p expression decreased upon mucociliary differentiation. In PAFs, let-7a-5p, miR-31-5p and miR-146a-5p expression was significantly increased upon co-culture. miR-708-5p overexpression suppressed mucin 5AC (MUC5AC) secretion in A549, while let-7a-5poverexpression suppressed its target gene COL4A1 in lung fibroblasts. Our findings suggest that let-7a-5p, miR-31-5p and miR-146a-5p may be involved in CMH via fibroblasts–epithelium crosstalk, including extracellular matrix gene regulation, while airway epithelial expression of miR-708-5p may be involved directly, regulating mucin production. These findings shed light on miRNA-mediated mechanisms underlying CMH, an important symptom in COPD.

Dysregulated Cell Signaling in Pulmonary Emphysema

Pulmonary emphysema is characterized by the destruction of alveolar septa and irreversible airflow limitation. Cigarette smoking is the primary cause of this disease development. It induces oxidative stress and disturbs lung physiology and tissue homeostasis. Alveolar type II (ATII) cells have stem cell potential and can repair the denuded epithelium after injury; however, their dysfunction is evident in emphysema. There is no effective treatment available for this disease. Challenges in this field involve the large complexity of lung pathophysiological processes and gaps in our knowledge on the mechanisms of emphysema progression. It implicates dysregulation of various signaling pathways, including aberrant inflammatory and oxidative responses, defective antioxidant defense system, surfactant dysfunction, altered proteostasis, disrupted circadian rhythms, mitochondrial damage, increased cell senescence, apoptosis, and abnormal proliferation and differentiation. Also, genetic predispositions are involved in this disease development. Here, we comprehensively review studies regarding dysregulated cell signaling, especially in ATII cells, and their contribution to alveolar wall destruction in emphysema. Relevant preclinical and clinical interventions are also described.

Effects of intranasal azithromycin on features of cigarette smoke-induced lung inflammation

Airflow limitation in chronic obstructive pulmonary disease (COPD) is the result of exaggerated airway fibrosis and obliteration of the small airways due to persistent inflammation, and an impaired anti-oxidant response. EMT has been implicated as an active signalling process in cigarette smoke (CS)-induced lung pathology, and macrolide Azithromycin (AZT) use has gained interest in treating COPD. Here, we tested effectiveness of intra-nasal AZT alone and in combination with dexamethasone (DEX) on CS-induced acute lung inflammation. Human alveolar epithelial cells (A549) were treated with CS extract (CSE) for 48 h, and male Balb/c mice were exposed to CS (3 cigarettes-3 times/day) for 4 days. The effects of AZT alone (0.25 and 1.25 μM, in vitro; 0.5 and 5 mg/kg, in vivo) or in combination with DEX (1 μM, in vitro; 1 mg/kg, in vivo) on CS-induced cellular cytotoxicity, oxidative stress, inflammation, and lung function were assessed. AZT alone and in combination with DEX significantly inhibited the CS (E)-induced expression of mesenchymal protein markers and the regulatory protein β-catenin. Furthermore, AZT by itself or in combination with DEX significantly suppressed CS-induced expression of the proinflammtory cytokines TNFα, IL1β and IL6 and prevented pNFkB. Mechanistically, AZT restored the CS-induced reduction in anti-oxidant transcription factor NRF2 and upregulated HDAC2 levels, thereby repressing inflammatory gene expression. Beneficial effects of AZT functionally translated in improved lung mechanics in vivo. Further preclinical and clinical studies are warranted to fully establish and validate the therapeutic efficacy of AZT as a mono- or combination therapy for the treatment of COPD.

Increased LGR6 Expression Sustains Long-Term Wnt Activation and Acquisition of Senescence in Epithelial Progenitors in Chronic Lung Diseases

Chronic lung diseases (CLDs) represent a set of disorders characterized by the progressive loss of proper lung function. Among severe CLDs, the incidence of chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF) has grown over the last decades, mainly in the elderly population. Several studies have highlighted an increased expression of senescence-related markers in the resident progenitor cells in COPD and IPF, possibly undermining epithelial integrity and contributing to the progression and the aggravation of both diseases. Recently, the chronic activation of the canonical Wnt/β-catenin pathway was shown to induce cellular senescence. Here, we investigated the localization and the expression of leucin-rich repeat-containing G-protein-coupled receptor 6 (LGR6), a protein that activates and potentiates the canonical Wnt signalling. Through immunohistochemical analyses, we identified a lesion-associated rise in LGR6 levels in abnormal lung epithelial progenitors in COPD and IPF when compared to histologically normal tissues. Moreover, in areas of aberrant regeneration, chronic damage and fibrosis, LGR6-expressing epithelial progenitors displayed a major increase in the expression of senescence-associated markers. Our study suggests the involvement of LGR6 in the chronic activation of the Wnt/β-catenin pathway, mediating the impairment and exhaustion of epithelial progenitors in COPD and IPF.

Noncanonical Wnt Signaling Promotes Myofibroblast Differentiation in Pulmonary Fibrosis

The Wnt/β-catenin pathway initiates a signaling cascade that is critical in cell differentiation and the normal development of multiple organ systems. The reactivation of this pathway has been documented in experimental and human idiopathic pulmonary fibrosis, wherein Wnt/β-catenin activation has been implicated in epithelial-cell repair. Furthermore, the canonical ligand Wnt3a is known to induce myofibroblast differentiation; however, the role of noncanonical Wnt ligands remains unclear. This study showed significantly higher levels of Wnt11 expression in cells from both patients with idiopathic pulmonary fibrosis and bleomycin-treated mice, as well as in TGFβ-treated mouse lung fibroblasts. Moreover, Wnt11 induced myofibroblast differentiation as manifested by increased α-SMA (ACTA2) expression, which was similar to that induced by canonical Wnt3a/β-catenin signaling. Further investigation revealed that Wnt11 induction of α-SMA was associated with the activation of JNK (c-Jun N-terminal kinase)/c-Jun signaling and was inhibited by a JNK inhibitor. The potential importance of this signaling pathway was supported by in vivo evidence showing significantly increased levels of Wnt11 and activated JNK in the lungs of mice with bleomycin-induced pulmonary fibrosis. Interestingly, fibroblasts did not express canonical Wnt3a, but treatment of these cells with exogenous Wnt3a induced endogenous Wnt11 and Wnt5a, resulting in repression of the Wnt3a/β-catenin target gene Axin2. These findings suggested that the noncanonical Wnt induction of myofibroblast differentiation mediated by the JNK/c-Jun pathway might play a significant role in pulmonary fibrosis, in addition to or in synergy with canonical Wnt3a/β-catenin signaling. Moreover, Wnt3a activation of noncanonical Wnt signaling might trigger a switch from canonical to noncanonical Wnt signaling to induce myofibroblast differentiation.

Allergen-specific immunotherapy induces the suppressive secretoglobin 1A1 in cells of the lower airways

BACKGROUND

While several systemic immunomodulatory effects of allergen-specific immunotherapy (AIT) have been discovered, local anti-inflammatory mechanisms in the respiratory tract are largely unknown. We sought to elucidate local and epithelial mechanisms underlying allergen-specific immunotherapy in a genome-wide approach.

METHODS

We induced sputum in hay fever patients and healthy controls during the pollen peak season and stratified patients by effective allergen immunotherapy or as untreated. Sputum was directly processed after induction and subjected to whole transcriptome RNA microarray analysis. Nasal secretions were analyzed for Secretoglobin1A1 (SCGB1A1) and IL-24 protein levels in an additional validation cohort at three defined time points during the 3-year course of AIT. Subsequently, RNA was extracted and subjected to an array-based whole transcriptome analysis.

RESULTS

Allergen-specific immunotherapy inhibited pro-inflammatory CXCL8, IL24, and CCL26mRNA expression, while SCGB1A1, IL7, CCL5, CCL23, and WNT5BmRNAs were induced independently of the asthma status and allergen season. In our validation cohort, local increase of SCGB1A1 occurred concomitantly with the reduction of local IL-24 in upper airways during the course of AIT. Additionally, SCGB1A1 was identified as a suppressor of epithelial gene expression.

CONCLUSIONS

Allergen-specific immunotherapy induces a yet unknown local gene expression footprint in the lower airways that on one hand appears to be a result of multiple regulatory pathways and on the other hand reveals SCGB1A1 as novel anti-inflammatory mediator of long-term allergen-specific therapeutic intervention in the local environment.

Resveratrol and Pterostilbene Inhibit SARS-CoV-2 Replication in Air-Liquid Interface Cultured Human Primary Bronchial Epithelial Cells

The current COVID-19 pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has an enormous impact on human health and economy. In search for therapeutic options, researchers have proposed resveratrol, a food supplement with known antiviral, anti-inflammatory, and antioxidant properties as an advantageous antiviral therapy for SARS-CoV-2 infection. Here, we provide evidence that both resveratrol and its metabolically more stable structural analog, pterostilbene, exhibit potent antiviral properties against SARS-CoV-2 in vitro. First, we show that resveratrol and pterostilbene antiviral activity in African green monkey kidney cells. Both compounds actively inhibit virus replication within infected cells as reduced virus progeny production was observed when the compound was added at post-inoculation conditions. Without replenishment of the compound, antiviral activity was observed up to roughly five rounds of replication, demonstrating the long-lasting effect of these compounds. Second, as the upper respiratory tract represents the initial site of SARS-CoV-2 replication, we also assessed antiviral activity in air-liquid interface (ALI) cultured human primary bronchial epithelial cells, isolated from healthy volunteers. Resveratrol and pterostilbene showed a strong antiviral effect in these cells up to 48 h post-infection. Collectively, our data indicate that resveratrol and pterostilbene are promising antiviral compounds to inhibit SARS-CoV-2 infection. Because these results represent laboratory findings in cells, we advocate evaluation of these compounds in clinical trials before statements are made whether these drugs are advantageous for COVID-19 treatment.

A Protective Role of FAM13A in Human Airway Epithelial Cells Upon Exposure to Cigarette Smoke Extract

Background

Chronic Obstructive Pulmonary Disease (COPD) is a progressive lung disease characterized by chronic inflammation upon inhalation of noxious particles, e.g., cigarette smoke. FAM13A is one of the genes often found to be associated with COPD, however its function in the pathophysiology of COPD is incompletely understood. We studied its role in airway epithelial barrier integrity and cigarette smoke-induced epithelial responses.

Materials and Methods

Protein level and localization of FAM13A was assessed with immunohistochemistry in lung tissue from COPD patients and non-COPD controls. In vitro, FAM13A expression was determined in the absence or presence of cigarette smoke extract (CSE) in primary airway epithelial cells (AECs) from COPD patients and controls by western blotting. FAM13A was overexpressed in cell line 16HBE14o- and its effect on barrier function was monitored real-time by electrical resistance. Expression of junctional protein E-cadherin and β-catenin was assessed by western blotting. The secretion of neutrophil attractant CXCL8 upon CSE exposure was measured by ELISA.

Results

FAM13A was strongly expressed in airway epithelium, but significantly weaker in airways of COPD patients compared to non-COPD controls. In COPD-derived AECs, but not those of controls, FAM13A was significantly downregulated by CSE. 16HBE14o- cells overexpressing FAM13A built up epithelial resistance significantly more rapidly, which was accompanied by higher E-cadherin expression and reduced CSE-induced CXCL8 levels.

Conclusion

Our data indicate that the expression of FAM13A is lower in airway epithelium of COPD patients compared to non-COPD controls. In addition, cigarette smoking selectively downregulates airway epithelial expression of FAM13A in COPD patients. This may have important consequences for the pathophysiology of COPD, as the more rapid build-up of epithelial resistance upon FAM13A overexpression suggests improved (re)constitution of barrier function. The reduced epithelial secretion of CXCL8 upon CSE-induced damage suggests that lower FAM13A expression upon cigarette smoking may facilitate epithelial-driven neutrophilia.

Air-liquid interface cultures of the healthy and diseased human respiratory tract: promises, challenges and future directions

Air-liquid interface (ALI) culture models currently represent a valid instrument to recreate the typical aspects of the respiratory tract in vitro in both healthy and diseased state. They can help reducing the number of animal experiments, therefore, supporting the 3R principle. This review discusses ALI cultures and co-cultures derived from immortalized as well as primary cells, which are used to study the most common disorders of the respiratory tract, in terms of both pathophysiology and drug screening. The article displays ALI models used to simulate inflammatory lung diseases such as chronic obstructive pulmonary disease (COPD), asthma, cystic fibrosis, lung cancer, and viral infections. It also includes a focus on ALI cultures described in literature studying respiratory viruses such as SARS-CoV-2 causing the global Covid-19 pandemic at the time of writing this review. Additionally, commercially available models of ALI cultures are presented. Ultimately, the aim of this review is to provide a detailed overview of ALI models currently available and to critically discuss them in the context of the most prevalent diseases of the respiratory tract.

WNT5B in Physiology and Disease

WNT5B, a member of the WNT family of proteins that is closely related to WNT5A, is required for cell migration, cell proliferation, or cell differentiation in many cell types. WNT5B signals through the non-canonical β-catenin-independent signaling pathway and often functions as an antagonist of canonical WNT signaling. Although WNT5B has a high amino acid identity with WNT5A and is often assumed to have similar activities, WNT5B often exhibits unique expression patterns and functions. Here, we describe the distinct effects and mechanisms of WNT5B on development, bone, adipose tissue, cardiac tissue, the nervous system, the mammary gland, the lung and hematopoietic cells, compared to WNT5A. We also highlight aberrances in non-canonical WNT5B signaling contributing to diseases such as osteoarthritis, osteoporosis, obesity, type 2 diabetes mellitus, neuropathology, and chronic diseases associated with aging, as well as various cancers.

Abnormalities in reparative function of lung-derived mesenchymal stromal cells in emphysema

Mesenchymal stromal cells (MSCs) may provide crucial support in the regeneration of destructed alveolar tissue (emphysema) in chronic obstructive pulmonary disease (COPD). We hypothesized that lung-derived MSCs (LMSCs) from patients with emphysema are hampered in their repair capacity, either intrinsically or due to their interaction with the damaged microenvironment. LMSCs were isolated from the lung tissue of controls and patients with severe emphysema and characterized at baseline. In addition, LMSCs were seeded onto control and emphysematous decellularized lung tissue scaffolds and assessed for deposition of extracellular matrix (ECM). We observed no differences in surface markers, differentiation/proliferation potential, and expression of ECM genes between control- and COPD-derived LMSCs. Notably, COPD-derived LMSCs displayed lower expression of FGF10 and HGF messenger RNA (mRNA) and hepatocyte growth factor (HGF) and decorin protein. When seeded on control decellularized lung tissue scaffolds, control- and COPD-derived LMSCs showed no differences in engraftment, proliferation, or survival within 2  wk, with similar ability to deposit new matrix on the scaffolds. Moreover, LMSC numbers and the ability to deposit new matrix were not compromised on emphysematous scaffolds. Collectively, our data show that LMSCs from patients with COPD compared with controls show less expression of FGF10 mRNA, HGF mRNA and protein, and decorin protein, whereas other features including the mRNA expression of various ECM molecules are unaffected. Furthermore, COPD-derived LMSCs are capable of engraftment, proliferation, and functioning on native lung tissue scaffolds. The damaged, emphysematous microenvironment as such does not hamper the potential of LMSCs. Thus, specific intrinsic deficiencies in growth factor production by diseased LMSCs may contribute to impaired alveolar repair in emphysema.

Periostin: contributor to abnormal airway epithelial function in asthma?

Periostin (POSTN) may serve as a biomarker for Type-2 mediated eosinophilic airway inflammation in asthma. We hypothesised that a Type-2 cytokine, interleukin (IL)-13, induces airway epithelial expression of POSTN, which in turn contributes to epithelial changes observed in asthma.We studied the effect of IL-13 on POSTN expression in BEAS-2B and air-liquid interface differentiated primary bronchial epithelial cells (PBECs). Additionally, the effects of recombinant human POSTN on epithelial-to-mesenchymal transition (EMT) markers and mucin genes were assessed. POSTN single cell gene expression and protein levels were analysed in bronchial biopsies and induced sputum from asthma patients and healthy controls.IL-13 increased POSTN expression in both cell types and this was accompanied by EMT-related features in BEAS-2B. In air-liquid interface differentiated PBECs, IL-13 increased POSTN basolateral and apical release. Apical administration of POSTN increased the expression of MMP-9, MUC5B and MUC5AC In bronchial biopsies, POSTN expression was mainly confined to basal epithelial cells, ionocytes, endothelial cells and fibroblasts, showing higher expression in basal epithelial cells from asthma patients versus those from controls. A higher level of POSTN protein expression in epithelial and subepithelial layers was confirmed in bronchial biopsies from asthma patients when compared to healthy controls. Although sputum POSTN levels were not higher in asthma, levels correlated with eosinophil numbers and with the coughing-up of mucus.POSTN expression is increased by IL-13 in bronchial epithelial cells and is higher in bronchial biopsies from asthma patients. This may have important consequences, as administration of POSTN increases epithelial expression of mucin genes, supporting the relationship of POSTN with Type-2 mediated asthma and mucus secretion.

WNT Signalling in Lung Physiology and Pathology

The main physiological function of the lung is gas exchange, mediated at the interface between the alveoli and the pulmonary microcapillary network and facilitated by conducting airway structures that regulate the transport of these gases from and to the alveoli. Exposure to microbial and environmental factors such as allergens, viruses, air pollution, and smoke contributes to the development of chronic lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and lung cancer. Respiratory diseases as a cluster are the commonest cause of chronic disease and of hospitalization in children and are among the three most common causes of morbidity and mortality in the adult population worldwide. Many of these chronic respiratory diseases are associated with inflammation and structural remodelling of the airways and/or alveolar tissues. They can often only be treated symptomatically with no disease-modifying therapies that normalize the pathological tissue destruction driven by inflammation and remodelling. In search for novel therapeutic strategies for these diseases, several lines of evidence revealed the WNT pathway as an emerging target for regenerative strategies in the lung. WNT proteins, their receptors, and signalling effectors have central regulatory roles under (patho)physiological conditions underpinning lung function and (chronic) lung diseases and we summarize these roles and discuss how pharmacological targeting of the WNT pathway may be utilized for the treatment of chronic lung diseases.

Canonical WNT pathway is activated in the airway epithelium in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a devastating lung disease, mainly due to cigarette smoking, which represents the third cause of mortality worldwide. The mechanisms driving its epithelial salient features remain largely elusive. We aimed to evaluate the activation and the role of the canonical, β-catenin-dependant WNT pathway in the airway epithelium from COPD patients.

METHODS

The WNT/β-catenin pathway was first assessed by WNT-targeted RNA sequencing of the air/liquid interface-reconstituted bronchial epithelium from COPD and control patients. Airway expression of total and active β-catenin was assessed in lung sections, as well as WNT components in laser-microdissected airway epithelium. Finally, we evaluated the role of WNT at the bronchial epithelial level by modulating the pathway in the reconstituted COPD epithelium.

FINDINGS

We show that the WNT/β-catenin pathway is upregulated in the COPD airway epithelium as compared with that of non-smokers and control smokers, in targeted RNA-sequencing of in vitro reconstituted airway epithelium, and in situ in lung tissue and laser-microdissected epithelium. Extrinsic activation of this pathway in COPD-derived airway epithelium inhibited epithelial differentiation, polarity and barrier function, and induced TGF-β-related epithelial-to-mesenchymal transition (EMT). Conversely, canonical WNT inhibition increased ciliated cell numbers, epithelial polarity and barrier function, whilst inhibiting EMT, thus reversing COPD features.

INTERPRETATION

In conclusion, the aberrant reactivation of the canonical WNT pathway in the adult airway epithelium recapitulates the diseased phenotype observed in COPD patients, suggesting that this pathway or its downstream effectors could represent a future therapeutic target.

FUNDING

This study was supported by the Fondation Mont-Godinne, the FNRS and the WELBIO.

Cigarette smoke promotes chronic obstructive pulmonary disease (COPD) through the miR-130a/Wnt1 axis

Cigarette smoke (CS) is a crucial factor in chronic obstructive pulmonary disease (COPD). Wnt/β-catenin signaling deregulation may further contribute to COPD progression. The deregulation and dysfunction of miRNAs in COPD have been reported. Investigating the deregulated miRNAs and their potential role in COPD progression may provide novel strategies for COPD treatment. In the present study, we analyzed significantly differentially-expressed miRNAs in COPD according to GSE44531 and miR-130a was selected. We revealed the upregulation of miR-130a in COPD, both in cigarette smoke extract (CSE)-treated BEAS-2B cells and CS-exposed mice. MiR-130a negatively regulated three critical factors in Wnt/β-catenin signaling, Wnt1, β-Catenin, and LEF1. MiR-130a inhibition rescued CSE-blocked activation of Wnt/β-catenin signaling in vitro. MiR-130a targets WNT1 3'UTR to inhibit its expression. Moreover, in CSE-stimulated BEAS-2B cells, miR-130a overexpression aggravated, while miR-130a inhibition partially attenuated CSE-caused suppression on cell migration and proliferation. MiR-130a aggravates CSE-induced cellular injury in BEAS-2B cells by targeting Wnt signaling. In summary, miR-130a has a pathogenetic role in CS-induced COPD and regulates Wnt/β-catenin signaling via targeting Wnt1. Our findings indicate that miR-130a is a potential therapeutic target for the treatment of CS-induced COPD.

Integrative analysis of genetic and epigenetic profiling of lung squamous cell carcinoma (LSCC) patients to identify smoking level relevant biomarkers

BACKGROUND

Incidence and mortality of lung cancer have dramatically decreased during the last decades, yet still approximately 160,000 deaths per year occurred in United States. Smoking intensity, duration, starting age, as well as environmental cofactors including air-pollution, showed strong association with major types of lung cancer. Lung squamous cell carcinoma is a subtype of non-small cell lung cancer, which represents 25% of the cases. Thus, exploring the molecular pathogenic mechanisms of lung squamous cell carcinoma plays crucial roles in lung cancer clinical diagnosis and therapy.

RESULTS

In this study, we performed integrative analyses on 299 comparative datasets of RNA-seq and methylation data, collected from 513 lung squamous cell carcinoma cases in The Cancer Genome Atlas. The data were divided into high and low smoking groups based on smoking intensity (Numbers of packs per year). We identified 1002 significantly up-regulated genes and 534 significantly down-regulated genes, and explored their cellular functions and signaling pathways by bioconductor packages GOseq and KEGG. Global methylation status was analyzed and visualized in circular plot by CIRCOS. RNA-and methylation data were correlatively analyzed, and 24 unique genes were identified, for further investigation of regional CpG sites' interactive patterns by bioconductor package coMET. AIRE, PENK, and SLC6A3 were the top 3 genes in the high and low smoking groups with significant differences.

CONCLUSIONS

Gene functions and DNA methylation patterns of these 24 genes are important and useful in disclosing the differences of gene expression and methylation profiling caused by different smoking levels.

Mesenchymal WNT-5A/5B Signaling Represses Lung Alveolar Epithelial Progenitors

Chronic obstructive pulmonary disease (COPD) represents a worldwide concern with high morbidity and mortality, and is believed to be associated with accelerated ageing of the lung. Alveolar abnormalities leading to emphysema are a key characteristic of COPD. Pulmonary alveolar epithelial type 2 cells (AT2) produce surfactant and function as progenitors for type 1 cells. Increasing evidence shows elevated WNT-5A/B expression in ageing and in COPD that may contribute to the disease process. However, supportive roles for WNT-5A/B in lung regeneration were also reported in different studies. Thus, we explored the role of WNT-5A/B on alveolar epithelial progenitors (AEPs) in more detail. We established a Precision-Cut-Lung Slices (PCLS) model and a lung organoid model by co-culturing epithelial cells (EpCAM⁺/CD45^-/CD31^-) with fibroblasts in matrigel in vitro to study the impact of WNT-5A and WNT-5B. Our results show that WNT-5A and WNT-5B repress the growth of epithelial progenitors with WNT-5B preferentially restraining the growth and differentiation of alveolar epithelial progenitors. We provide evidence that both WNT-5A and WNT-5B negatively regulate the canonical WNT signaling pathway in alveolar epithelium. Taken together, these findings reveal the functional impact of WNT-5A/5B signaling on alveolar epithelial progenitors in the lung, which may contribute to defective alveolar repair in COPD.

Epithelial-mesenchymal transition is driven by transcriptional and post transcriptional modulations in COPD: implications for disease progression and new therapeutics

COPD is a common and highly destructive disease with huge impacts on people and health services throughout the world. It is mainly caused by cigarette smoking though environmental pollution is also significant. There are no current treatments that affect the overall course of COPD; current drugs focus on symptomatic relief and to some extent reducing exacerbation rates. There is an urgent need for in-depth studies of the fundamental pathogenic mechanisms that underpin COPD. This is vital, given the fact that nearly 40%-60% of the small airway and alveolar damage occurs in COPD well before the first measurable changes in lung function are detected. These individuals are also at a high risk of lung cancer. Current COPD research is mostly centered around late disease and/or innate immune activation within the airway lumen, but the actual damage to the airway wall has early onset. COPD is the end result of complex mechanisms, possibly triggered through initial epithelial activation. To change the disease trajectory, it is crucial to understand the mechanisms in the epithelium that are switched on early in smokers. One such mechanism we believe is the process of epithelial to mesenchymal transition. This article highlights the importance of this profound epithelial cell plasticity in COPD and also its regulation. We consider that understanding early changes in COPD will open new windows for therapy.

Perspectives on Wnt Signal Pathway in the Pathogenesis and Therapeutics of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a chronic lung disease with progressive airflow limitation and functional decline. The pathogenic mechanisms for this disease include oxidative stress, inflammatory responses, disturbed protease/antiprotease equilibrium, apoptosis/proliferation imbalance, senescence, autophagy, metabolic reprogramming, and mitochondrial dysfunction. The Wnt signaling pathway is an evolutionarily conserved signaling pathway that is abnormal in COPD, including chronic bronchitis and pulmonary emphysema. Furthermore, Wnt signaling has been shown to modulate aforementioned cellular processes involved in COPD. From this perspective, we provide an updated understanding of the crosstalk between Wnt signal and these cellular processes, and highlight the crucial role of the Wnt signal during the development of COPD. We also discuss the potential for targeting the Wnt signal in future translational and pharmacological therapeutics aimed at prevention and treatment of this disease.

miR-145-5p is associated with smoke-related chronic obstructive pulmonary disease via targeting KLF5

Increasing evidence illustrate that dysregulation of microRNAs (miRNAs) is involved in the pathogenesis of chronic obstructive pulmonary disease (COPD), which is mainly resulted from cigarette smoke (CS) exposure. However, the role of miR-145-5p in CS-mediated COPD remains largely unknown. Thus, the aim of this study was to investigate the expression level of miR-145-5p in 31 human lung tissues samples, and to explore its regulatory role in the apoptosis and inflammation of human bronchial epithelial cells (HBECs) following CS extract (CSE) exposure. We found that miR-145-5p was significantly down-regulated in lung tissues from smokers without or with COPD compared to non-smokers. Functional assays showed that miR-145-5p overexpression remarkably alleviated CSE-induced apoptosis and inflammation response by regulating p53-mediated apoptotic signaling and pre-inflammatory factors such as necrosis factor-α (TNF-α), interleukins (IL)-6, IL-8 in HBECs, whereas, down-regulation of miR-145-5p showed opposite effects. Furthermore, luciferase reporter assays verified that Kruppel-like 5 (KLF5) was a direct target of miR-145-5p. Western blot assay also confirmed that KLF5 was up-regulated in COPD tissues and was negatively associated with miR-145-5p expression. Restoration of miR-145-5p expression significantly abrogated the suppressive effect of miR-145-5p on CSE-stimulated apoptosis and inflammation. In addition, the CSE-induced NF-κB signaling activation was suppressed by miR-145-5p overexpression. Therefore, our data suggested that miR-145-5p conferred protection against CSE-induced airway epithelial cell apoptosis and inflammation partially via targeting KLF5, which might be a potential therapeutic biomarker in COPD treatment.

Cigarette smoke-induced RANKL expression enhances MMP-9 production by alveolar macrophages

Background and purpose

Cigarette smoke (CS) induces alveolar destruction through overproduction of proteinases including matrix metalloproteinase (MMP)-9 by alveolar macrophages (AMs). Receptor activator of nuclear factor-κB ligand (RANKL) functions in immune regulation and cytokine secretion; whether it is involved in CS-induced MMP-9 expression is unknown. The purpose of our study was to investigate the expression and functional role of RANKL pathway in MMP-9 production pertaining to the pathogenesis of COPD.

Materials and methods

We first localized RANKL and its receptor RANK in the lungs of mice exposed to long-term CS exposure. Next, we studied RANKL and RANK expression under CS extract (CSE) stimulation in vitro. Lastly, we studied the in vitro biological function of RANKL in CS-induced production of MMP-9.

Results

Both RANKL and RANK were highly expressed in AMs in CS-exposed mice, but not in the control mice. In vitro, CSE increased the expressions of RANKL and RANK in macrophages. AMs responded to CSE and RANKL stimulation by overexpressing MMP-9, and CSE-induced MMP-9 expression was partly blocked by using monoclonal anti-RANKL antibody.

Conclusion

RANKL/RANK pathway mediates CS-induced MMP-9 expression in AMs, suggesting a novel mechanism for CS-associated emphysema.

microRNA-mRNA regulatory networks underlying chronic mucus hypersecretion in COPD

Chronic mucus hypersecretion (CMH) is a common feature in chronic obstructive pulmonary disease (COPD) and is associated with worse prognosis and quality of life. This study aimed to identify microRNA (miRNA)-mRNA regulatory networks underlying CMH.The expression profiles of miRNA and mRNA in bronchial biopsies from 63 COPD patients were associated with CMH using linear regression. Potential mRNA targets of each CMH-associated miRNA were identified using Pearson correlations. Gene set enrichment analysis (GSEA) and STRING (search tool for the retrieval of interacting genes/proteins) analysis were used to identify key genes and pathways.20 miRNAs and 539 mRNAs were differentially expressed with CMH in COPD. The expression of 10 miRNAs was significantly correlated with the expression of one or more mRNAs. Of these, miR-134-5p, miR-146a-5p and the let-7 family had the highest representation of CMH-associated mRNAs among their negatively correlated predicted targets. KRAS and EDN1 were identified as key regulators of CMH and were negatively correlated predicted targets of miR-134-5p and let-7a-5p, let-7d-5p, and let-7f-5p, respectively. GSEA suggested involvement of MUC5AC-related genes and several other relevant gene sets in CMH. The lower expression of miR-134-5p was confirmed in primary airway fibroblasts from COPD patients with CMH.We identified miR-134-5p, miR-146a-5p and let-7 family, along with their potential target genes including KRAS and EDN1, as potential key miRNA-mRNA networks regulating CMH in COPD.

Airway Epithelium Dysfunction in Cystic Fibrosis and COPD

Cystic fibrosis is a genetic disease caused by mutations in the CFTR gene, whereas chronic obstructive pulmonary disease (COPD) is mainly caused by environmental factors (mostly cigarette smoking) on a genetically susceptible background. Although the etiology and pathogenesis of these diseases are different, both are associated with progressive airflow obstruction, airway neutrophilic inflammation, and recurrent exacerbations, suggesting common mechanisms. The airway epithelium plays a crucial role in maintaining normal airway functions. Major molecular and morphologic changes occur in the airway epithelium in both CF and COPD, and growing evidence suggests that airway epithelial dysfunction is involved in disease initiation and progression in both diseases. Structural and functional abnormalities in both airway and alveolar epithelium have a relevant impact on alteration of host defences, immune/inflammatory response, and the repair process leading to progressive lung damage and impaired lung function. In this review, we address the evidence for a critical role of dysfunctional airway epithelial cells in chronic airway inflammation and remodelling in CF and COPD, highlighting the common mechanisms involved in the epithelial dysfunction as well as the similarities and differences of the two diseases.

SIRT1/FoxO3 axis alteration leads to aberrant immune responses in bronchial epithelial cells

Inflammation and ageing are intertwined in chronic obstructive pulmonary disease (COPD). The histone deacetylase SIRT1 and the related activation of FoxO3 protect from ageing and regulate inflammation. The role of SIRT1/FoxO3 in COPD is largely unknown. This study evaluated whether cigarette smoke, by modulating the SIRT1/FoxO3 axis, affects airway epithelial pro-inflammatory responses. Human bronchial epithelial cells (16HBE) and primary bronchial epithelial cells (PBECs) from COPD patients and controls were treated with/without cigarette smoke extract (CSE), Sirtinol or FoxO3 siRNA. SIRT1, FoxO3 and NF-κB nuclear accumulation, SIRT1 deacetylase activity, IL-8 and CCL20 expression/release and the release of 12 cytokines, neutrophil and lymphocyte chemotaxis were assessed. In PBECs, the constitutive FoxO3 expression was lower in patients with COPD than in controls. Furthermore, CSE reduced FoxO3 expression only in PBECs from controls. In 16HBE, CSE decreased SIRT1 activity and nuclear expression, enhanced NF-κB binding to the IL-8 gene promoter thus increasing IL-8 expression, decreased CCL20 expression, increased the neutrophil chemotaxis and decreased lymphocyte chemotaxis. Similarly, SIRT1 inhibition reduced FoxO3 expression and increased nuclear NF-κB. FoxO3 siRNA treatment increased IL-8 and decreased CCL20 expression in 16HBE. In conclusion, CSE impairs the function of SIRT1/FoxO3 axis in bronchial epithelium, dysregulating NF-κB activity and inducing pro-inflammatory responses.

WNT receptor signalling in lung physiology and pathology

The WNT signalling cascades have emerged as critical regulators of a wide variety of biological aspects involved in lung development as well as in physiological and pathophysiological processes in the adult lung. WNTs (secreted glycoproteins) interact with various transmembrane receptors and co-receptors to activate signalling pathways that regulate transcriptional as well as non-transcriptional responses within cells. In physiological conditions, the majority of WNT receptors and co-receptors can be detected in the adult lung. However, dysregulation of WNT signalling pathways contributes to the development and progression of chronic lung pathologies, including idiopathic pulmonary fibrosis (IPF), chronic obstructive pulmonary disease (COPD), asthma and lung cancer. The interaction between a WNT and the (co-)receptor(s) present at the cell surface is the initial step in transducing an extracellular signal into an intracellular response. This proximal event in WNT signal transduction with (cell-specific) ligand-receptor interactions is of great interest as a potential target for pharmacological intervention. In this review we highlight the diverse expression of various WNT receptors and co-receptors in the aforementioned chronic lung diseases and discuss the currently available biologicals and pharmacological tools to modify proximal WNT signalling.

The IARA Model as an Integrative Approach to Promote Autonomy in COPD Patients through Improvement of Self-Efficacy Beliefs and Illness Perception: A Mixed-Method Pilot Study

Chronic obstructive pulmonary disease (COPD) is one of the most deadly and costly chronic diseases in the world characterized by many breathing problems. The management of COPD and the prevention of exacerbations are a priority goals to improve the quality of life in patients affected by this illness. In addition, it is also crucial to improve the patients' adherence to care which, in turn, depends on their knowledge and understanding of some factors such as the prescribed medical treatment, changes in dailylife, and the process of breathing. In turn, the adherence to care leads to greater autonomy for the patient who is thus able to better manage his illness. Here we presented the application of the Model IARA in patients affected by COPD in order to achieve their autonomy in illness management which, in turn, leads to a better quality of life. IARA is an intervention program which improve the awareness and knowledge of patients with respect to both the disease and symptoms through health education. Moreover, through IARA the patients are encouraged to become more actively involved in COPD care process, also regarding drug therapy adherence. Using St. George's Respiratory Questionnaire combined with qualitative analysis, we demonstrated that IARA could be considered a useful approach in COPD management.

Lung development, regeneration and plasticity: From disease physiopathology to drug design using induced pluripotent stem cells

Lungs have a complex structure composed of different cell types that form approximately 17 million airway branches of gas-delivering bronchioles connected to 500 million gas-exchanging alveoli. Airways and alveoli are lined by epithelial cells that display a low rate of turnover at steady-state, but can regenerate the epithelium in response to injuries. Here, we review the key points of lung development, homeostasis and epithelial cell plasticity in response to injury and disease, because this knowledge is required to develop new lung disease treatments. Of note, canonical signaling pathways that are essential for proper lung development during embryogenesis are also involved in the pathophysiology of most chronic airway diseases. Moreover, the perfect control of these interconnected pathways is needed for the successful differentiation of induced pluripotent stem cells (iPSC) into lung cells. Indeed, differentiation of iPSC into airway epithelium and alveoli is based on the use of biomimetics of normal embryonic and fetal lung development. In vitro iPSC-based models of lung diseases can help us to better understand the impaired lung repair capacity and to identify new therapeutic targets and new approaches, such as lung cell therapy.

β-catenin, Twist and Snail: Transcriptional regulation of EMT in smokers and COPD, and relation to airflow obstruction

COPD is characterised by poorly reversible airflow obstruction usually due to cigarette smoking. The transcription factor clusters of β-catenin/Snail1/Twist has been implicated in the process of epithelial mesenchymal transition (EMT), an intermediate between smoking and airway fibrosis, and indeed lung cancer. We have investigated expression of these transcription factors and their "cellular localization" in bronchoscopic airway biopsies from patients with COPD, and in smoking and non-smoking controls. An immune-histochemical study compared cellular protein expression of β-catenin, Snail1 and Twist, in these subject groups in 3 large airways compartment: epithelium (basal region), reticular basement membrane (Rbm) and underlying lamina propria (LP). β-catenin and Snail1 expression was generally high in all subjects throughout the airway wall with marked cytoplasmic to nuclear shift in COPD (P < 0.01). Twist expression was generalised in the epithelium in normal but become more basal and nuclear with smoking (P < 0.05). In addition, β-catenin and Snail1 expression, and to lesser extent of Twist, was related to airflow obstruction and to expression of a canonical EMT biomarker (S100A4). The β-catenin-Snail1-Twist transcription factor cluster is up-regulated and nuclear translocated in smokers and COPD, and their expression is closely related to both EMT activity and airway obstruction.

Use of airway epithelial cell culture to unravel the pathogenesis and study treatment in obstructive airway diseases

Asthma and chronic obstructive pulmonary disease (COPD) are considered as two distinct obstructive diseases. Both chronic diseases share a component of airway epithelial dysfunction. The airway epithelium is localized to deal with inhaled substances, and functions as a barrier preventing penetration of such substances into the body. In addition, the epithelium is involved in the regulation of both innate and adaptive immune responses following inhalation of particles, allergens and pathogens. Through triggering and inducing immune responses, airway epithelial cells contribute to the pathogenesis of both asthma and COPD. Various in vitro research models have been described to study airway epithelial cell dysfunction in asthma and COPD. However, various considerations and cautions have to be taken into account when designing such in vitro experiments. Epithelial features of asthma and COPD can be modelled by using a variety of disease-related invoking substances either alone or in combination, and by the use of primary cells isolated from patients. Differentiation is a hallmark of airway epithelial cells, and therefore models should include the ability of cells to differentiate, as can be achieved in air-liquid interface models. More recently developed in vitro models, including precision cut lung slices, lung-on-a-chip, organoids and human induced pluripotent stem cells derived cultures, provide novel state-of-the-art alternatives to the conventional in vitro models. Furthermore, advanced models in which cells are exposed to respiratory pathogens, aerosolized medications and inhaled toxic substances such as cigarette smoke and air pollution are increasingly used to model e.g. acute exacerbations. These exposure models are relevant to study how epithelial features of asthma and COPD are affected and provide a useful tool to study the effect of drugs used in treatment of asthma and COPD. These new developments are expected to contribute to a better understanding of the complex gene-environment interactions that contribute to development and progression of asthma and COPD.

Distinct Roles of Wnt/β-Catenin Signaling in the Pathogenesis of Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis

Wnt signaling pathways are tightly controlled under a physiological condition, under which they play key roles in many biological functions, including cell fate specification and tissue regeneration. Increasing lines of evidence recently demonstrated that a dysregulated activation of Wnt signaling, particularly the Wnt/β-catenin signaling, was involved in the pathogenesis of chronic pulmonary diseases, such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). In this respect, Wnt signaling interacts with other cellular signaling pathways to regulate the initiation and pathogenic procedures of airway inflammation and remodeling, pulmonary myofibroblast proliferation, epithelial-to-mesenchymal transition (EMT), and development of emphysema. Intriguingly, Wnt/β-catenin signaling is activated in IPF; an inhibition of this signaling leads to an alleviation of pulmonary inflammation and fibrosis in experimental models. Conversely, Wnt/β-catenin signaling is inactivated in COPD tissues, and its reactivation results in an amelioration of airspace enlargement with a restored alveolar epithelial structure and function in emphysema models. These studies thus imply distinct mechanisms of Wnt/β-catenin signaling in the pathogenesis of these two chronic pulmonary diseases, indicating potential targets for COPD and IPF treatments. This review article aims to summarize the involvement and pathogenic roles of Wnt signaling pathways in the COPD and IPF, with a focus on the implication of Wnt/β-catenin signaling as underlying mechanisms and therapeutic targets in these two incurable diseases.

'WNT-er is coming': WNT signalling in chronic lung diseases

Chronic lung diseases represent a major public health problem with only limited therapeutic options. An important unmet need is to identify compounds and drugs that target key molecular pathways involved in the pathogenesis of chronic lung diseases. Over the last decade, there has been extensive interest in investigating Wingless/integrase-1 (WNT) signalling pathways; and WNT signal alterations have been linked to pulmonary disease pathogenesis and progression. Here, we comprehensively review the cumulative evidence for WNT pathway alterations in chronic lung pathologies, including idiopathic pulmonary fibrosis, pulmonary arterial hypertension, asthma and COPD. While many studies have focused on the canonical WNT/β-catenin signalling pathway, recent reports highlight that non-canonical WNT signalling may also significantly contribute to chronic lung pathologies; these studies will be particularly featured in this review. We further discuss recent advances uncovering the role of WNT signalling early in life, the potential of pharmaceutically modulating WNT signalling pathways and highlight (pre)clinical studies describing promising new therapies for chronic lung diseases.

Role of Proteases in Lung Disease: A Brief Overview

Proteases play an important role in health and disease of the lung. In the normal lungs, proteases maintain their homeostatic functions that regulate processes like its regeneration and repair. Dysregulation of proteases–antiproteases balance is crucial in the manifestation of different types of lung diseases. Chronic inflammatory lung pathologies are associated with a marked increase in protease activities. Thus, in addition to protease activities, inhibition of anti-proteolytic control mechanisms are also important for effective microbial infection and inflammation in the lung. Herein, we briefly summarize the role of different proteases and to some extent antiproteases in regulating a variety of lung diseases.

Emerging concepts in smooth muscle contributions to airway structure and function: implications for health and disease

Airway structure and function are key aspects of normal lung development, growth, and aging, as well as of lung responses to the environment and the pathophysiology of important diseases such as asthma, chronic obstructive pulmonary disease, and fibrosis. In this regard, the contributions of airway smooth muscle (ASM) are both functional, in the context of airway contractility and relaxation, as well as synthetic, involving production and modulation of extracellular components, modulation of the local immune environment, cellular contribution to airway structure, and, finally, interactions with other airway cell types such as epithelium, fibroblasts, and nerves. These ASM contributions are now found to be critical in airway hyperresponsiveness and remodeling that occur in lung diseases. This review emphasizes established and recent discoveries that underline the central role of ASM and sets the stage for future research toward understanding how ASM plays a central role by being both upstream and downstream in the many interactive processes that determine airway structure and function in health and disease.

Noncanonical WNT-5B signaling induces inflammatory responses in human lung fibroblasts

COPD is a progressive chronic lung disease characterized by pulmonary inflammation. Several recent studies indicate aberrant expression of WNT ligands and Frizzled receptors in the disease. For example, WNT-5A/B ligand expression was recently found to be increased in lung fibroblasts of COPD patients. However, possible effects of WNT-5A and WNT-5B on inflammation have not been investigated yet. In this study, we assessed the regulation of inflammatory cytokine release in response to WNT-5A/B signaling in human lung fibroblasts. Primary human fetal lung fibroblasts (MRC-5), and primary lung fibroblasts from COPD patients and non-COPD controls were treated with recombinant WNT-5A or WNT-5B to assess IL-6 and CXCL8 cytokine secretion and gene expression levels. Following WNT-5B, and to a lesser extent WNT-5A stimulation, fibroblasts showed increased IL-6 and CXCL8 cytokine secretion and mRNA expression. WNT-5B-mediated IL-6 and CXCL8 release was higher in fibroblasts from COPD patients than in non-COPD controls. In MRC-5 fibroblasts, WNT-5B-induced CXCL8 release was mediated primarily via the Frizzled-2 receptor and TAK1 signaling, whereas canonical β-catenin signaling was not involved. In further support of noncanonical signaling, we showed activation of JNK, p38, and p65 NF-κB by WNT-5B. Furthermore, inhibition of JNK and p38 prevented WNT-5B-induced IL-6 and CXCL8 secretion, whereas IKK inhibition prevented CXCL8 secretion only, indicating distinct pathways for WNT-5B-induced IL-6 and CXCL8 release. WNT-5B induces IL-6 and CXCL8 secretion in pulmonary fibroblasts. In summary, WNT-5B mediates this via Frizzled-2 and TAK1. As WNT-5 signaling is increased in COPD, this WNT-5-induced inflammatory response could represent a therapeutic target.