Airway Epithelial Repair, Regeneration, and Remodeling after Injury in Chronic Obstructive Pulmonary Disease

Does Rheumatoid Arthritis Increase the Risk of COPD?: A Nationwide Retrospective Cohort Study

BACKGROUND

Most reports of pulmonary manifestations in rheumatoid arthritis (RA) have been related to interstitial lung diseases. RA and COPD are both chronic inflammatory systemic diseases.

RESEARCH QUESTION

Does RA increase the risk of developing COPD? Is there a difference between seropositive and seronegative RA in the risk of COPD?

STUDY DESIGN AND METHODS

Using the Korean National Health Insurance Database, we screened individuals diagnosed with RA between 2010 and 2017. We identified 46,030 patients with RA (32,608 with seropositive RA and 13,422 with seronegative RA) and 230,150 matched control individuals; we monitored them until December 2019. We used multivariate Cox proportional hazard models to estimate the adjusted hazard ratio (aHR) of risk factors for the development of COPD.

RESULTS

The incidence of COPD among patients with RA was 5.04 per 1,000 person-years; it was 2.23 per 1,000 person-years in the control group. Patients with RA showed a higher risk of developing COPD (aHR, 2.11; 95% CI, 1.96-2.28) compared with the control group. Although both seropositive RA and seronegative RA were associated with an increased risk of COPD, patients with seropositive RA had a higher risk for the development of COPD (aHR, 1.26; 95% CI, 1.09-1.46) than patients with seronegative RA. In the subgroup analyses, smoking history did not demonstrate significant interactions between RA and COPD development.

INTERPRETATION

RA was shown to be associated with an increased risk of COPD development, augmented by seropositivity. Physicians should monitor respiratory symptoms and pulmonary function carefully in patients with RA.

Modeling airway persistent infection of Moraxella catarrhalis and nontypeable Haemophilus influenzae by using human in vitro models

Non-typeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (Mcat) are two common respiratory tract pathogens often associated with acute exacerbations in Chronic Obstructive Pulmonary Disease (COPD) as well as with otitis media (OM) in children. Although there is evidence that these pathogens can adopt persistence mechanisms such as biofilm formation, the precise means through which they contribute to disease severity and chronicity remains incompletely understood, posing challenges for their effective eradication. The identification of potential vaccine candidates frequently entails the characterization of the host-pathogen interplay in vitro even though this approach is limited by the fact that conventional models do not permit long term bacterial infections. In the present work, by using air-liquid-interface (ALI) human airway in vitro models, we aimed to recreate COPD-related persistent bacterial infections. In particular, we explored an alternative use of the ALI system consisting in the assembly of an inverted epithelium grown on the basal part of a transwell membrane with the aim to enable the functionality of natural defense mechanisms such as mucociliary clearance and cellular extrusion that are usually hampered during conventional ALI infection experiments. The inversion of the epithelium did not affect tissue differentiation and considerably delayed NTHi or Mcat infection progression, allowing one to monitor host-pathogen interactions for up to three weeks. Notably, the use of these models, coupled with confocal and transmission electron microscopy, revealed unique features associated with NTHi and Mcat infection, highlighting persistence strategies including the formation of intracellular bacterial communities (IBCs) and surface-associated biofilm-like structures. Overall, this study demonstrates the possibility to perform long term host-pathogen investigations in vitro with the aim to define persistence mechanisms adopted by respiratory pathogens and individuate potential new vaccine targets.

Fine particulate matter aggravates smoking induced lung injury via NLRP3/caspase-1 pathway in COPD

BACKGROUND

Exposure to noxious particles, including cigarette smoke and fine particulate matter (PM2.5), is a risk factor for chronic obstructive pulmonary disease (COPD) and promotes inflammation and cell death in the lungs. We investigated the combined effects of cigarette smoking and PM2.5 exposure in patients with COPD, mice, and human bronchial epithelial cells.

METHODS

The relationship between PM2.5 exposure and clinical parameters was investigated in patients with COPD based on smoking status. Alveolar destruction, inflammatory cell infiltration, and pro-inflammatory cytokines were monitored in the smoking-exposed emphysema mouse model. To investigate the mechanisms, cell viability and death and pyroptosis-related changes in BEAS-2B cells were assessed following the exposure to cigarette smoke extract (CSE) and PM2.5.

RESULTS

High levels of ambient PM2.5 were more strongly associated with high Saint George's respiratory questionnaire specific for COPD (SGRQ-C) scores in currently smoking patients with COPD. Combined exposure to cigarette smoke and PM2.5 increased mean linear intercept and TUNEL-positive cells in lung tissue, which was associated with increased inflammatory cell infiltration and inflammatory cytokine release in mice. Exposure to a combination of CSE and PM2.5 reduced cell viability and upregulated NLRP3, caspase-1, IL-1β, and IL-18 transcription in BEAS-2B cells. NLRP3 silencing with siRNA reduced pyroptosis and restored cell viability.

CONCLUSIONS

PM2.5 aggravates smoking-induced airway inflammation and cell death via pyroptosis. Clinically, PM2.5 deteriorates quality of life and may worsen prognosis in currently smoking patients with COPD.

SARS-CoV-2 envelope protein impairs airway epithelial barrier function and exacerbates airway inflammation via increased intracellular Cl- concentration

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection disrupts the epithelial barrier and triggers airway inflammation. The envelope (E) protein, a core virulence structural component of coronaviruses, may play a role in this process. Pathogens could interfere with transepithelial Cl- transport via impairment of the cystic fibrosis transmembrane conductance regulator (CFTR), which modulates nuclear factor κB (NF-κB) signaling. However, the pathological effects of SARS-CoV-2 E protein on airway epithelial barrier function, Cl- transport and the robust inflammatory response remain to be elucidated. Here, we have demonstrated that E protein down-regulated the expression of tight junctional proteins, leading to the disruption of the airway epithelial barrier. In addition, E protein triggered the activation of Toll-like receptor (TLR) 2/4 and downstream c-Jun N-terminal kinase (JNK) signaling, resulting in an increased intracellular Cl- concentration ([Cl-]i) via up-regulating phosphodiesterase 4D (PDE4D) expression in airway epithelial cells. This elevated [Cl-]i contributed to the heightened airway inflammation through promoting the phosphorylation of serum/glucocorticoid regulated kinase 1 (SGK1). Moreover, blockade of SGK1 or PDE4 alleviated the robust inflammatory response induced by E protein. Overall, these findings provide novel insights into the pathogenic role of SARS-CoV-2 E protein in airway epithelial damage and the ongoing airway inflammation during SARS-CoV-2 infection.

Bronchial Progenitor Cells in Obstructive and Neoplastic Lung Disease: A Pilot Study

The alteration of progenitor/stem cells present in the airway epithelium has been observed in patients with COPD. Smoking exposure induces remodeling patterns in bronchial progenitor cells (BPCs), encompassing squamous metaplasia, hyperplasia of basal and of mucus-secreting cells, and the depletion of ciliated and non-mucous secretory cells. Our aim was to assess the expression of p63 and vimentin as potential markers of airway remodeling and the regulation of stem cell populations in obstructive and neoplastic lung disease patients. A retrospective single-center observational study was conducted, including patients undergoing bronchoscopy with bronchial biopsies for suspected lung cancer. p63 and vimentin expression were evaluated via immunohistochemical analysis. There were 25 patients, of which 21 with COPD were included, and 17 were diagnosed with lung cancer. We observed that FEV1% was negatively correlated with p63+ basal cell number (r = -0.614, p = 0.019) and positively correlated with vimentin expression (r = 0.670; p = 0.008). p63 was significantly higher in biopsies from the trachea and main bronchi compared to more distal areas (p = 0.040), whereas vimentin was prevalent in the more distal areas (p = 0.042). Our preliminary data suggest the initial evidence of structural changes in BPCs among patients with COPD and lung cancer. Further research efforts are warranted to investigate additional morphologic and functional respiratory parameters in these patients.

Secretome Analysis of Human Nasal Fibroblast Identifies Proteins That Promote Wound Healing

Conditioned medium from cultured fibroblast cells is recognized to promote wound healing and growth through the secretion of enzymes, extracellular matrix proteins, and various growth factors and cytokines. The objective of this study was to profile the secreted proteins present in nasal fibroblast conditioned medium (NFCM). Nasal fibroblasts isolated from human nasal turbinates were cultured for 72 h in Defined Keratinocytes Serum Free Medium (DKSFM) or serum-free F12: Dulbecco's Modified Eagle's Medium (DMEM) to collect conditioned medium, denoted as NFCM_DKSFM and NFCM_FD, respectively. SDS-PAGE was performed to detect the presence of protein bands, followed by MALDI-TOF and mass spectrometry analysis. SignalP, SecretomeP, and TMHMM were used to identify the secreted proteins in conditioned media. PANTHER Classification System was performed to categorize the protein according to protein class, whereas STRING 10 was carried out to evaluate the predicted proteins interactions. SDS-PAGE results showed the presence of various protein with molecular weight ranging from ~10 kDa to ~260 kDa. Four protein bands were identified using MALDI-TOF. The analyses identified 104, 83, and 7 secreted proteins in NFCM_FD, NFCM_DKSFM, and DKSFM, respectively. Four protein classes involved in wound healing were identified, namely calcium-binding proteins, cell adhesion molecules, extracellular matrix proteins, and signaling molecules. STRING10 protein prediction successfully identified various pathways regulated by secretory proteins in NFCM. In conclusion, this study successfully profiled the secreted proteins of nasal fibroblasts and these proteins are predicted to play important roles in RECs wound healing through various pathways.

How does global warming contribute to disorders originating from an impaired epithelial barrier?

The epithelial barrier represents the point of contact between the host and the external environment. It is the first line of defense against external insults in the skin and in the gastrointestinal and upper and lower respiratory tracts. The steep increase in chronic disorders in recent decades, including allergies and autoimmune disorders, has prompted studies to investigate the immune mechanisms of their underlying pathogeneses, all of which point to a thought-provoking shared finding: disrupted epithelial barriers. Climate change with global warming has increased the frequency of unpredictable extreme weather events, such as wildfires, droughts, floods, and aberrant and longer pollination seasons, among many others. These increasingly frequent natural disasters can synergistically damage the epithelial barrier integrity in the presence of environmental pollution. A disrupted epithelial barrier induces proinflammatory activation of epithelial cells and alarmin production, namely, epithelitis. The "opened" epithelial barrier facilitates the entry of the external exposome into and underneath the epithelium, triggering an expulsion response driven by inflammatory cells in the area and chronic inflammation. These changes are associated with microbial dysbiosis with colonizing opportunistic pathogens and decreased commensals. These cellular and molecular events are key mechanisms in the pathogenesis of numerous chronic inflammatory disorders. This review summarizes the impact of global warming on epithelial barrier functions in the context of allergic diseases. Further studies in the impact of climate change on the dysfunction of the epithelial barriers are warranted to improve our understanding of epithelial barrier-related diseases and raise awareness of the environmental insults that pose a threat to our health.

IL-20 Cytokines Are Involved in the Repair of Airway Epithelial Barrier: Implication in Exposure to Cigarette Smoke and in COPD Pathology

BACKGROUND

Dysregulated inflammation as seen in chronic obstructive pulmonary disease (COPD) is associated with impaired wound healing. IL-20 cytokines are known to be involved in wound healing processes. The purpose of this study was to use ex vivo and in vitro approaches mimicking COPD to evaluate the potential modulatory role of interleukin-20 (IL-20) on the inflammatory and healing responses to epithelial wounding.

METHODS

The expression of IL-20 cytokines and their receptors was investigated in lung-derived samples collected from non-COPD and COPD patients, from mice chronically exposed to cigarette smoke and from airway epithelial cells from humans and mice exposed in vitro to cigarette smoke. To investigate the role of IL-20 cytokines in wound healing, experiments were performed using a blocking anti-IL-20Rb antibody.

RESULTS

Of interest, IL-20 cytokines and their receptors were expressed in bronchial mucosa, especially on airway epithelial cells. Their expression correlated with the disease severity. Blocking these cytokines in a COPD context improved the repair processes after a lesion induced by scratching the epithelial layer.

CONCLUSIONS

Collectively, this study highlights the implication of IL-20 cytokines in the repair of the airway epithelium and in the pathology of COPD. IL-20 subfamily cytokines might provide therapeutic benefit for patients with COPD to improve epithelial healing.

Mimicking acute airway tissue damage using femtosecond laser nanosurgery in airway organoids

Airway organoids derived from adult murine epithelial cells represent a complex 3D in vitro system mimicking the airway epithelial tissue's native cell composition and physiological properties. In combination with a precise damage induction via femtosecond laser-based nanosurgery, this model might allow for the examination of intra- and intercellular dynamics in the course of repair processes with a high spatio-temporal resolution, which can hardly be reached using in vivo approaches. For characterization of the organoids' response to single or multiple-cell ablation, we first analyzed overall organoid survival and found that airway organoids were capable of efficiently repairing damage induced by femtosecond laser-based ablation of a single to ten cells within 24 h. An EdU staining assay further revealed a steady proliferative potential of airway organoid cells. Especially in the case of ablation of five cells, proliferation was enhanced within the first 4 h upon damage induction, whereas ablation of ten cells was followed by a slight decrease in proliferation within this time frame. Analyzing individual trajectories of single cells within airway organoids, we found an increased migratory behavior in cells within close proximity to the ablation site following the ablation of ten, but not five cells. Bulk RNA sequencing and subsequent enrichment analysis revealed the differential expression of sets of genes involved in the regulation of epithelial repair, distinct signaling pathway activities such as Notch signaling, as well as cell migration after laser-based ablation. Together, our findings demonstrate that organoid repair upon ablation of ten cells involves key processes by which native airway epithelial wound healing is regulated. This marks the herein presented in vitro damage model suitable to study repair processes following localized airway injury, thereby posing a novel approach to gain insights into the mechanisms driving epithelial repair on a single-cell level.

Effect of smoking on the development of chronic obstructive pulmonary disease in young individuals: a nationwide cohort study

Background

Cigarette smoking is an important risk factor for developing chronic obstructive pulmonary disease (COPD). However, the effect of smoking on the development of COPD in young individuals remains unclear. We aimed to evaluate the effect of smoking on COPD development in young individuals.

Methods

Using the Korean National Health Information Database, we screened individuals aged 20-39 years who participated in the national health check-up between 2009 and 2012. We defined physician-diagnosed COPD based on health insurance claims and searched the database until December 2019. We identified 6,307,576 eligible individuals, and 13,789 had newly developed COPD. We used multivariate Cox proportional hazards models to estimate the adjusted hazard ratio (aHR) of risk factors for COPD.

Results

The incidence rate for developing COPD was 0.26/1000 person-year. The risk of developing COPD was significantly higher in current smokers [aHR 1.46, 95% confidence interval (CI) 1.39-1.53] and former smokers (aHR 1.21, 95% CI 1.14-1.29) than in non-smokers. Furthermore, the risk increased with increasing smoking amounts (≥20 pack-years, aHR 2.24; 10-20 pack-years, aHR 1.55; <10 pack-years, aHR 1.27). Female participants had a higher relative risk of developing COPD due to smoking, compared with their male counterparts.

Conclusion

Cigarette smoking increased the risk of developing COPD in young individuals. Current and heavy smokers had higher risks of developing COPD than non-smokers. Female smokers were more likely to develop COPD than male smokers.

Regeneration of tracheal neotissue in partially decellularized scaffolds

Extensive tracheal injury or disease can be life-threatening but there is currently no standard of care. Regenerative medicine offers a potential solution to long-segment tracheal defects through the creation of scaffolds that support the generation of healthy neotissue. We developed decellularized tracheal grafts (PDTG) by removing the cells of the epithelium and lamina propria while preserving donor cartilage. We previously demonstrated that PDTG support regeneration of host-derived neotissue. Here, we use a combination of microsurgical, immunofluorescent, and transcriptomic approaches to compare PDTG neotissue with the native airway and surgical controls. We report that PDTG neotissue is composed of native tracheal cell types and that the neoepithelium and microvasculature persisted for at least 6 months. Vascular perfusion of PDTG was established within 2 weeks and the graft recruited multipotential airway stem cells that exhibit normal proliferation and differentiation. Hence, PDTG neotissue recapitulates the structure and function of the host trachea and has the potential to regenerate.

A Diagnostic Classifier Based on Circulating miRNA Pairs for COPD Using a Machine Learning Approach

Chronic obstructive pulmonary disease (COPD) is highly underdiagnosed, and early detection is urgent to prevent advanced progression. Circulating microRNAs (miRNAs) have been diagnostic candidates for multiple diseases. However, their diagnostic value has not yet been fully established in COPD. The purpose of this study was to develop an effective model for the diagnosis of COPD based on circulating miRNAs. We included circulating miRNA expression profiles of two independent cohorts consisting of 63 COPD and 110 normal samples, and then we constructed a miRNA pair-based matrix. Diagnostic models were developed using several machine learning algorithms. The predictive performance of the optimal model was validated in our external cohort. In this study, the diagnostic values of miRNAs based on the expression levels were unsatisfactory. We identified five key miRNA pairs and further developed seven machine learning models. The classifier based on LightGBM was selected as the final model with the area under the curve (AUC) values of 0.883 and 0.794 in test and validation datasets, respectively. We also built a web tool to assist diagnosis for clinicians. Enriched signaling pathways indicated the potential biological functions of the model. Collectively, we developed a robust machine learning model based on circulating miRNAs for COPD screening.

The Tobacco Smoke Component, Acrolein, as a Major Culprit in Lung Diseases and Respiratory Cancers: Molecular Mechanisms of Acrolein Cytotoxic Activity

Acrolein, a highly reactive unsaturated aldehyde, is a ubiquitous environmental pollutant that seriously threatens human health and life. Due to its high reactivity, cytotoxicity and genotoxicity, acrolein is involved in the development of several diseases, including multiple sclerosis, neurodegenerative diseases such as Alzheimer’s disease, cardiovascular and respiratory diseases, diabetes mellitus and even the development of cancer. Traditional tobacco smokers and e-cigarette users are particularly exposed to the harmful effects of acrolein. High concentrations of acrolein have been found in both mainstream and side-stream tobacco smoke. Acrolein is considered one of cigarette smoke’s most toxic and harmful components. Chronic exposure to acrolein through cigarette smoke has been linked to the development of asthma, acute lung injury, chronic obstructive pulmonary disease (COPD) and even respiratory cancers. This review addresses the current state of knowledge on the pathological molecular mechanisms of acrolein in the induction, course and development of lung diseases and cancers in smokers.

Opto-electromechanical quantification of epithelial barrier function in injured and healthy airway tissues

The airway epithelium lining the luminal surface of the respiratory tract creates a protective barrier that ensures maintenance of tissue homeostasis and prevention of respiratory diseases. The airway epithelium, unfortunately, is frequently injured by inhaled toxic materials, trauma, or medical procedures. Substantial or repeated airway epithelial injury can lead to dysregulated intrinsic repair pathways and aberrant tissue remodeling that can lead to dysfunctional airway epithelium. While disruption in the epithelial integrity is directly linked to degraded epithelial barrier function, the correlation between the structure and function of the airway epithelium remains elusive. In this study, we quantified the impact of acutely induced airway epithelium injury on disruption of the epithelial barrier functions. By monitoring alternation of the flow motions and tissue bioimpedance at local injury site, degradation of the epithelial functions, including mucociliary clearance and tight/adherens junction formation, were accurately determined with a high spatiotemporal resolution. Computational models that can simulate and predict the disruption of the mucociliary flow and airway tissue bioimpedance have been generated to assist interpretation of the experimental results. Collectively, findings of this study advance our knowledge of the structure-function relationships of the airway epithelium that can promote development of efficient and accurate diagnosis of airway tissue injury.

cAMP-PDE signaling in COPD: Review of cellular, molecular and clinical features

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death among non-contagious diseases in the world. PDE inhibitors are among current medicines prescribed for COPD treatment of which, PDE-4 family is the predominant PDE isoform involved in hydrolyzing cyclic adenosine monophosphate (cAMP) that regulates the inflammatory responses in neutrophils, lymphocytes, macrophages and epithelial cells The aim of this study is to investigate the cellular and molecular mechanisms of cAMP-PDE signaling, as an important pathway in the treatment management of patients with COPD. In this review, a comprehensive literature review was performed about the effect of PDEs in COPD. Generally, PDEs are overexpressed in COPD patients, resulting in cAMP inactivation and decreased cAMP hydrolysis from AMP. At normal amounts, cAMP is one of the essential agents in regulating metabolism and suppressing inflammatory responses. Low amount of cAMP lead to activation of downstream inflammatory signaling pathways. PDE4 and PDE7 mRNA transcript levels were not altered in polymorphonuclear leukocytes and CD8 lymphocytes originating from the peripheral venous blood of stable COPD subjects compared to healthy controls. Therefore, cAMP-PDE signaling pathway is one of the most important signaling pathways involved in COPD. By examining the effects of different drugs in this signaling pathway critical steps can be taken in the treatment of this disease.

Human lung cell models to study aerosol delivery - considerations for model design and development

Human lung tissue models range from simple monolayer cultures to more advanced three-dimensional co-cultures. Each model system can address the interactions of different types of aerosols and the choice of the model and the mode of aerosol exposure depends on the relevant scenario, such as adverse outcomes and endpoints of interest. This review focuses on the functional, as well as structural, aspects of lung tissue from the upper airway to the distal alveolar compartments as this information is relevant for the design of a model as well as how the aerosol properties determine the interfacial properties with the respiratory wall. The most important aspects on how to design lung models are summarized with a focus on (i) choice of appropriate scaffold, (ii) selection of cell types for healthy and diseased lung models, (iii) use of culture condition and assembly, (iv) aerosol exposure methods, and (v) endpoints and verification process. Finally, remaining challenges and future directions in this field are discussed.

Multiomics Analysis of a DNAH5-Mutated PCD Organoid Model Revealed the Key Role of the TGF-β/BMP and Notch Pathways in Epithelial Differentiation and the Immune Response in DNAH5-Mutated Patients

Dynein axonemal heavy chain 5 (DNAH5) is the most mutated gene in primary ciliary dyskinesia (PCD), leading to abnormal cilia ultrastructure and function. Few studies have revealed the genetic characteristics and pathogenetic mechanisms of PCD caused by DNAH5 mutation. Here, we established a child PCD airway organoid directly from the bronchoscopic biopsy of a patient with the DNAH5 mutation. The motile cilia in the organoid were observed and could be stably maintained for an extended time. We further found abnormal ciliary function and a decreased immune response caused by the DNAH5 mutation through single-cell RNA sequencing (scRNA-Seq) and proteomic analyses. Additionally, the directed induction of the ciliated cells, regulated by TGF-β/BMP and the Notch pathway, also increased the expression of inflammatory cytokines. Taken together, these results demonstrated that the combination of multiomics analysis and organoid modelling could reveal the close connection between the immune response and the DNAH5 gene.

Novel Requirement for Staphylococcal Cell Wall-Anchored Protein SasD in Pulmonary Infection

Staphylococcus aureus can complicate preceding viral infections, including influenza virus. A bacterial infection combined with a preceding viral infection, known as superinfection, leads to worse outcomes than a single infection. Most of the pulmonary infection literature focuses on the changes in immune responses to bacteria between homeostatic and virally infected lungs. However, it is unclear how much of an influence bacterial virulence factors have in single or superinfection. Staphylococcal species express a broad range of cell wall-anchored proteins (CWAs) that have roles in host adhesion, nutrient acquisition, and immune evasion. We screened the importance of these CWAs using mutants lacking individual CWAs in vivo in both bacterial pneumonia and influenza superinfection. In bacterial pneumonia, the lack of individual CWAs leads to various decreases in bacterial burden, lung damage, and immune infiltration into the lung. However, the presence of a preceding influenza infection partially abrogates the requirement for CWAs. In the screen, we found that the uncharacterized CWA S. aureus surface protein D (SasD) induced changes in both inflammatory and homeostatic lung markers. We further characterized a SasD mutant (sasD A50.1) in the context of pneumonia. Mice infected with sasD A50.1 have decreased bacterial burden, inflammatory responses, and mortality compared to wild-type S. aureus. Mice also have reduced levels of interleukin-1β (IL-1β), likely derived from macrophages. Reductions in IL-1β transcript levels as well as increased macrophage viability point at differences in cell death pathways. These data identify a novel virulence factor for S. aureus that influences inflammatory signaling within the lung. IMPORTANCE Staphylococcus aureus is a common commensal bacterium that can cause severe infections, such as pneumonia. In the lung, viral infections increase the risk of staphylococcal pneumonia, leading to combined infections known as superinfections. The most common virus associated with S. aureus pneumonia is influenza, and superinfections lead to worse patient outcomes than either infection alone. While there is much known about how the immune system differs between healthy and virally infected lungs, the role of bacterial virulence factors in single and superinfection is less understood. The significance of our research is identifying bacterial components that play a role in the initiation of lung injury, which could lead to future therapies to prevent pulmonary single or superinfection with S. aureus.

Cigarette Smoke Impairs Airway Epithelial Wound Repair: Role of Modulation of Epithelial-Mesenchymal Transition Processes and Notch-1 Signaling

Cigarette smoke (CS) induces oxidative stress and chronic inflammation in airway epithelium. It is a major risk factor for respiratory diseases, characterized by epithelial injury. The impact of CS on airway epithelial repair, which involves epithelial-mesenchymal transition (EMT) and the Notch-1 pathway, is incompletely understood. In this study, we used primary bronchial epithelial cells (PBECs) to evaluate the effect of CS on epithelial repair and these mechanisms. The effect of CS and/or TGF-beta1 on wound repair, various EMT and Notch-1 pathway markers and epithelial cell markers (TP63, SCGB1A) was assessed in PBECs cultured submerged, at the air–liquid interface (ALI) alone and in co-culture with fibroblasts. TGF-beta1 increased epithelial wound repair, activated EMT (shown by decrease in E-cadherin, and increases in vimentin, SNAIL1/SNAIL2/ZEB1), and increased Notch-1 pathway markers (NOTCH1/JAGGED1/HES1), MMP9, TP63, SCGB1A1. In contrast, CS decreased wound repair and vimentin, NOTCH1/JAGGED1/HES1, MMP9, TP63, SCGB1A1, whereas it activated the initial steps of the EMT (decrease in E-cadherin and increases in SNAIL1/SNAIL2/ZEB1). Using combined exposures, we observed that CS counteracted the effects of TGF-beta1. Furthermore, Notch signaling inhibition decreased wound repair. These data suggest that CS inhibits the physiological epithelial wound repair by interfering with the normal EMT process and the Notch-1 pathway.

In Vitro Evaluation of Leuconostoc mesenteroides Cell-Free-Supernatant GBUT-21 against SARS-CoV-2

The unprecedented health catastrophe derived from the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2 infection) met with a phenomenal scientific response across the globe. Worldwide, the scientific community was focused on finding a cure for the deadly disease. A wide range of research studies has consistently revealed the link between SARS-CoV-2 infection severity and abnormal gut microbiomes, suggesting its potential in developing novel therapeutic approaches. Probiotics have been extensively studied to promote health in human hosts and reestablish a balance in the dysbiotic gut microbiome; however, there is strong skepticism about their safety and efficacy. Consequently, the metabolic signatures of probiotics, often referred to as "postbiotics", could prove of paramount importance for adjuvant cures in patients with SARS-CoV-2. Postbiotics exhibit safety, enhanced shelf-life, and stability and, therefore, could be implemented in SARS-CoV-2 prophylactic strategies with no undue adverse side effects. The current study is a preliminary investigation of the antiviral properties of postbiotic metabolites derived from Leuconostoc mesenteroides GBUT-21. The study focuses on the potential biological role in inactivating SARS-CoV-2 and reducing related inflammatory pathways.

The Role of Proprotein Convertases in Upper Airway Remodeling

Chronic rhinosinusitis (CRS) is a multifactorial, heterogeneous disease characterized by persistent inflammation of the sinonasal mucosa and tissue remodeling, which can include basal/progenitor cell hyperplasia, goblet cell hyperplasia, squamous cell metaplasia, loss or dysfunction of ciliated cells, and increased matrix deposition. Repeated injuries can stimulate airway epithelial cells to produce inflammatory mediators that activate epithelial cells, immune cells, or the epithelial-mesenchymal trophic unit. This persistent inflammation can consequently induce aberrant tissue remodeling. However, the molecular mechanisms driving disease within the different molecular CRS subtypes remain inadequately characterized. Numerous secreted and cell surface proteins relevant to airway inflammation and remodeling are initially synthesized as inactive precursor proteins, including growth/differentiation factors and their associated receptors, enzymes, adhesion molecules, neuropeptides, and peptide hormones. Therefore, these precursor proteins require post-translational cleavage by proprotein convertases (PCs) to become fully functional. In this review, we summarize the roles of PCs in CRS-associated tissue remodeling and discuss the therapeutic potential of targeting PCs for CRS treatment.

Ursodeoxycholic acid ameliorates cell migration retarded by the SARS-CoV-2 spike protein in BEAS-2B human bronchial epithelial cells

BACKGROUND

Coronavirus disease 2019 (COVID-19) is caused by severe acute -respiratory syndrome coronavirus 2 (SARS- CoV-2) through interaction of the spike protein (SP) with the receptor-binding domain (RBD) and its receptor, angiotensin converting enzyme 2(ACE2). Repair mechanisms induced following virus infection can restore the protective barrier through wound healing. Then, cells from the epithelial basal layer repopulate the damaged area, followed by cell proliferation and differentiation, as well as changes in gene expression.

METHODS

Using Beas-2B cells and SP, we investigated whether ursodeoxycholic acid (UDCA) contributes to restoration of the bronchial epithelial layer. ACE2 expression was measured by RT-PCR and Western blotting. SP-ACE2 interaction was analyzed by flow cytometry and visualized through immunostaining. Cell migration was assessed using single cell path tracking and wound healing assay.

RESULTS

Upon ACE2 overexpression in HeLa, HEK293T, and Beas-2B cells following the transfection of pCMV-ACE2 plasmid DNA, SP binding on each cell was increased in the ACE2 overexpression group compared to pCMV-transfected control cells. SP treatment delayed the migration of BEAS-2B cells compared to the control. SP also reduced cell migration, even under ACE2 overexpression; SP binding was greater in ACE2-overexpressed cells than control cells. UDCA interfered significantly with the binding of SP to ACE2 under our experimental conditions. UDCA also restored the inhibitory migration of Beas-2B cells induced by SP treatment.

CONCLSION

Our data demonstrate that UDCA can contribute to the inhibition of abnormal airway epithelial cell migration. These results suggest that UDCA can enhance the repair mechanism, to prevent damage caused by SP-ACE2 interaction and enhance restoration of the epithelial basal layer.

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.

Impact of Air Pollution in Airway Diseases: Role of the Epithelial Cells (Cell Models and Biomarkers)

Biomedical research is multidisciplinary and often uses integrated approaches performing different experimental models with complementary functions. This approach is important to understand the pathogenetic mechanisms concerning the effects of environmental pollution on human health. The biological activity of the substances is investigated at least to three levels using molecular, cellular, and human tissue models. Each of these is able to give specific answers to experimental problems. A scientific approach, using biological methods (wet lab), cell cultures (cell lines or primary), isolated organs (three-dimensional cell cultures of primary epithelial cells), and animal organisms, including the human body, aimed to understand the effects of air pollution on the onset of diseases of the respiratory system. Biological methods are divided into three complementary models: in vitro, ex vivo, and in vivo. In vitro experiments do not require the use of whole organisms (in vivo study), while ex vivo experiments use isolated organs or parts of organs. The concept of complementarity and the informatic support are useful tools to organize, analyze, and interpret experimental data, with the aim of discussing scientific notions with objectivity and rationality in biology and medicine. In this scenario, the integrated and complementary use of different experimental models is important to obtain useful and global information that allows us to identify the effect of inhaled pollutants on the incidence of respiratory diseases in the exposed population. In this review, we focused our attention on the impact of air pollution in airway diseases with a rapid and descriptive analysis on the role of epithelium and on the experimental cell models useful to study the effect of toxicants on epithelial cells.

Primary Cilium by Polyinosinic:Polycytidylic Acid Regulates the Regenerative Migration of Beas-2B Bronchial Epithelial Cells

The airway epithelium is equipped with the ability to resist respiratory disease development and airway damage, including the migration of airway epithelial cells and the activation of TLR3, which recognizes double-stranded (ds) RNA. Primary cilia on airway epithelial cells are involved in the cell cycle and cell differentiation and repair. In this study, we used Beas-2B human bronchial epithelial cells to investigate the effects of the TLR3 agonist polyinosinic:polycytidylic acid [Poly(I:C)] on airway cell migration and primary cilia (PC) formation. PC formation increased in cells incubated under serum deprivation. Migration was faster in Beas-2B cells pretreated with Poly(I:C) than in control cells, as judged by a wound healing assay, single-cell path tracking, and a Transwell migration assay. No changes in cell migration were observed when the cells were incubated in conditioned medium from Poly(I:C)-treated cells. PC formation was enhanced by Poly(I:C) treatment, but was reduced when the cells were exposed to the ciliogenesis inhibitor ciliobrevin A (CilioA). The inhibition of Beas-2B cell migration by CilioA was also assessed and a slight decrease in ciliogenesis was detected in SARS-CoV-2 spike protein (SP)-treated Beas-2B cells overexpressing ACE2 compared to control cells. Cell migration was decreased by SP but restored by Poly(I:C) treatment. Taken together, our results demonstrate that impaired migration by SP-treated cells can be attenuated by Poly(I:C) treatment, thus increasing airway cell migration through the regulation of ciliogenesis.

Pathogenesis of Respiratory Viral and Fungal Coinfections

Individuals suffering from severe viral respiratory tract infections have recently emerged as "at risk" groups for developing invasive fungal infections. Influenza virus is one of the most common causes of acute lower respiratory tract infections worldwide. Fungal infections complicating influenza pneumonia are associated with increased disease severity and mortality, with invasive pulmonary aspergillosis being the most common manifestation. Strikingly, similar observations have been made during the current coronavirus disease 2019 (COVID-19) pandemic. The copathogenesis of respiratory viral and fungal coinfections is complex and involves a dynamic interplay between the host immune defenses and the virulence of the microbes involved that often results in failure to return to homeostasis. In this review, we discuss the main mechanisms underlying susceptibility to invasive fungal disease following respiratory viral infections. A comprehensive understanding of these interactions will aid the development of therapeutic modalities against newly identified targets to prevent and treat these emerging coinfections.

Transferring Microclusters of P. aeruginosa Biofilms to the Air-Liquid Interface of Bronchial Epithelial Cells for Repeated Deposition of Aerosolized Tobramycin

As an alternative to technically demanding and ethically debatable animal models, the use of organotypic and disease-relevant human cell culture models may improve the throughput, speed, and success rate for the translation of novel anti-infectives into the clinic. Besides bacterial killing, host cell viability and barrier function appear as relevant but seldomly measured readouts. Moreover, bacterial virulence factors and signaling molecules are typically not addressed in current cell culture models. Here, we describe a reproducible protocol for cultivating barrier-forming human bronchial epithelial cell monolayers on Transwell inserts and infecting them with microclusters of pre-grown mature Pseudomonas aeruginosa PAO1 biofilms under the air-liquid interface conditions. Bacterial growth and quorum sensing molecules were determined upon tobramycin treatment. The host cell response was simultaneously assessed through cell viability, epithelial barrier function, and cytokine release. By repeated deposition of aerosolized tobramycin after 1, 24, and 48 h, bacterial growth was controlled (reduction from 10 to 4 log₁₀ CFU/mL), which leads to epithelial cell survival for up to 72 h. E-cadherin's cell-cell adhesion protein expression was preserved with the consecutive treatment, and quorum sensing molecules were reduced. However, the bacteria could not be eradicated and epithelial barrier function was impaired, similar to the currently observed situation in the clinic in lack of more efficient anti-infective therapies. Such a human-based in vitro approach has the potential for the preclinical development of novel anti-infectives and nanoscale delivery systems for oral inhalation.

Immunoglobulin A Mucosal Immunity and Altered Respiratory Epithelium in Cystic Fibrosis

The respiratory epithelium represents the first chemical, immune, and physical barrier against inhaled noxious materials, particularly pathogens in cystic fibrosis. Local mucus thickening, altered mucociliary clearance, and reduced pH due to CFTR protein dysfunction favor bacterial overgrowth and excessive inflammation. We aimed in this review to summarize respiratory mucosal alterations within the epithelium and current knowledge on local immunity linked to immunoglobulin A in patients with cystic fibrosis.

Redox Dysregulation in Aging and COPD: Role of NOX Enzymes and Implications for Antioxidant Strategies

With a rapidly growing elderly human population, the incidence of age-related lung diseases such as chronic obstructive pulmonary disease (COPD) continues to rise. It is widely believed that reactive oxygen species (ROS) play an important role in ageing and in age-related disease, and approaches of antioxidant supplementation have been touted as useful strategies to mitigate age-related disease progression, although success of such strategies has been very limited to date. Involvement of ROS in ageing is largely attributed to mitochondrial dysfunction and impaired adaptive antioxidant responses. NADPH oxidase (NOX) enzymes represent an important enzyme family that generates ROS in a regulated fashion for purposes of oxidative host defense and redox-based signalling, however, the associations of NOX enzymes with lung ageing or age-related lung disease have to date only been minimally addressed. The present review will focus on our current understanding of the impact of ageing on NOX biology and its consequences for age-related lung disease, particularly COPD, and will also discuss the implications of altered NOX biology for current and future antioxidant-based strategies aimed at treating these diseases.

An innate contribution of human nicotinic receptor polymorphisms to COPD-like lesions

Chronic Obstructive Pulmonary Disease is a generally smoking-linked major cause of morbidity and mortality. Genome-wide Association Studies identified a locus including a non-synonymous single nucleotide polymorphism in CHRNA5, rs16969968, encoding the nicotinic acetylcholine receptor α5 subunit, predisposing to both smoking and Chronic Obstructive Pulmonary Disease. Here we report that nasal polyps from rs16969968 non-smoking carriers exhibit airway epithelium remodeling and inflammation. These hallmarks of Chronic Obstructive Pulmonary Disease occur spontaneously in mice expressing human rs16969968. They are significantly amplified after exposure to porcine pancreatic elastase, an emphysema model, and to oxidative stress with a polymorphism-dependent alteration of lung function. Targeted rs16969968 expression in epithelial cells leads to airway remodeling in vivo, increased proliferation and production of pro-inflammatory cytokines through decreased calcium entry and increased adenylyl-cyclase activity. We show that rs16969968 directly contributes to Chronic Obstructive Pulmonary Disease-like lesions, sensitizing the lung to the action of oxidative stress and injury, and represents a therapeutic target.

Human polymorphisms in nicotinic acetylcholine receptor genes have been linked to both smoking and lung diseases like Chronic Obstructive Pulmonary Disease (COPD) or lung cancer. Here the authors identify a direct role for a human coding polymorphism in COPD-like lesions independent of smoke or nicotine exposure.

MiR-361-5p/abca1 and MiR-196-5p/arhgef12 Axis Involved in γ-Sitosterol Inducing Dual Anti-Proliferative Effects on Bronchial Epithelial Cells of Chronic Obstructive Pulmonary Disease

Purpose

Chronic obstructive pulmonary disease (COPD), a progressive and irreversible respiratory disease, becomes the third leading cause of death and results in enormous economic burden on healthcare costs and productivity loss worldwide by 2020. Thus, it is urgent to develop effective anti-COPD drugs.

Materials and Methods

In the present study, two published GEO profiles were used to re-analyze and ascertain the relationships between circulating miRNAs and bronchial epithelial cells (BECs) mRNAs in COPD. The microRNA levels of miR-361-5p and miR-196-5p in plasma of COPD patients and healthy volunteers were detected by qRT-PCR. Next, the effects of γ-sitosterol (GS) on the expression of miR-361-5p and miR-196-5p and cell proliferation were investigated in BEC and H292 cell lines. Finally, whether specific miRNA-mRNA pathways involved in the effect of GS on BECs was assayed using Western Blot, real-time PCR and immunofluorescence.

Results

miR-196-5p and miR-361-5p were, respectively, up- and down-regulated in COPD patients compared with healthy controls. Luciferase assays demonstrated that miR-361-5p and miR-196-5p were, respectively, targeting abca1 and arhgef12 3ʹUTR in BEAS-2B cells. GS significantly suppressed miR-196-5p and promoted miR-361-5p levels in BEAS-2B cells and inhibited BECs proliferation in vitro. GS promoted miR-361-5p expression, which inhibited BCAT1 mRNA and protein levels and weaken mTOR-pS6K pathway, resulted in anti-proliferation in BEAS-2B cells. In addition, RhoA was activated by ARHGEF12 due to the inhibitory effect of miR-196-5p on arhgef12-3ʹUTR which was partially abolished by GS suppressing miR-196-5p expression. Activated RhoA further activated ROCK1-PTEN pathway and finally inhibited mTOR pathway, resulting in induced BECs proliferation. The anti-proliferation effect of GS was not observed in H292 cells.

Conclusion

These findings indicate that miR-361-5p/abca1 and miR-196-5p/arhgef12 axis mediated GS inducing dual anti-proliferation effects on BECs.

Expression/Activation of PAR-1 in Airway Epithelial Cells of COPD Patients: Ex Vivo/In Vitro Study

The role of PAR-1 expression and activation was described in epithelial cells from the central and distal airways of COPD patients using an ex vivo/in vitro model. PAR-1 immunoreactivity was studied in epithelial cells from surgical specimens of the central and distal airways of COPD patients and healthy control (HC). Furthermore, PAR-1 expression and activation were measured in both the human bronchial epithelial cell line (16HBE) and normal human bronchial epithelial cells (NHBEs) exposed to cigarette smoke extract (CSE) (10%) or thrombin. Finally, cell proliferation, apoptosis, and IL-8 release were detected in stimulated NHBEs. We identified higher levels of PAR-1 expression/activation in epithelial cells from the central airways of COPD patients than in HC. Active PAR-1 increased in epithelial cells from central and distal airways of COPD, with higher levels in COPD smokers (correlated with pack-years) than in COPD ex-smokers. 16HBE and NHBEs exposed to CSE or thrombin showed increased levels of active PAR-1 (localized in the cytoplasm) than baseline conditions, while NHBEs treated with thrombin or CSE showed increased levels of IL-8 proteins, with an additional effect when used in combination. Smoking habits generate the upregulation of PAR-1 expression/activation in airway epithelial cells, and promoting IL-8 release might affect the recruitment of infiltrating cells in the airways of COPD patients.

Pulmonary Tuberculosis and the Incidence of Lung Cancer among Patients with Chronic Obstructive Pulmonary Disease

RATIONALE

While the history of pulmonary tuberculosis (PTB) is a risk factor for developing both chronic obstructive pulmonary disease (COPD) and lung cancer, it remains unclear whether the history of PTB affects lung cancer development in COPD patients.

OBJECTIVES

To investigate whether a history of PTB is associated with an increased risk of lung cancer development in a population with COPD.

METHODS

This cohort study included a nationwide representative sample of 13,165 Korean men and women with COPD, aged between 50-84 years. In addition, to assess whether the relationship between PTB and lung cancer risk differs between participants with and without COPD, a matched cohort without COPD was included. Participants were matched 1:3 for age, sex, smoking history, and PTB status based on the index health screening exam of corresponding participants with COPD. The two cohorts were followed up for 13 years (January 1st, 2003, to December 31st, 2015). PTB was diagnosed based on the results of chest radiography, and incident lung cancer was identified from hospitalization and outpatient visit claims (International Classification of Diseases, Tenth Revision diagnosis code C33 or C34).

RESULTS

During 370,617 person-years (PY) of follow-up (median follow-up, 7.7 years), in the COPD group, we observed 430 incident cases of lung cancer in participants without a history of PTB (incidence rate 524 per 100,000 PY) and 148 cases in those with a history of PTB (incidence rate 931 per 100,000 PY). Compared to participants without a PTB history, the fully adjusted subdistribution hazard ratio (95% confidence interval) for lung cancer in those with a history of PTB was 1.24 (1.03, 1.50). The association of PTB history and lung cancer development was more evident in never-smokers with COPD. In contrast, among participants without COPD, the corresponding hazard ratio (95% confidence interval) was 0.98 (0.78, 1.22). There was no interaction between PTB, smoking status, and COPD.

CONCLUSIONS

The history of PTB was associated with an increased risk of developing lung cancer among COPD patients in our country with an intermediate TB burden. COPD patients with a history of PTB, particularly the never-smokers, might benefit from periodical screening or assessment for lung cancer development.

Cigarette Smoke Specifically Affects Small Airway Epithelial Cell Populations and Triggers the Expansion of Inflammatory and Squamous Differentiation Associated Basal Cells

Smoking is a major risk factor for chronic obstructive pulmonary disease (COPD) and causes remodeling of the small airways. However, the exact smoke-induced effects on the different types of small airway epithelial cells (SAECs) are poorly understood. Here, using air–liquid interface (ALI) cultures, single-cell RNA-sequencing reveals previously unrecognized transcriptional heterogeneity within the small airway epithelium and cell type-specific effects upon acute and chronic cigarette smoke exposure. Smoke triggers detoxification and inflammatory responses and aberrantly activates and alters basal cell differentiation. This results in an increase of inflammatory basal-to-secretory cell intermediates and, particularly after chronic smoke exposure, a massive expansion of a rare inflammatory and squamous metaplasia associated KRT6A⁺ basal cell state and an altered secretory cell landscape. ALI cultures originating from healthy non-smokers and COPD smokers show similar responses to cigarette smoke exposure, although an increased pro-inflammatory profile is conserved in the latter. Taken together, the in vitro models provide high-resolution insights into the smoke-induced remodeling of the small airways resembling the pathological processes in COPD airways. The data may also help to better understand other lung diseases including COVID-19, as the data reflect the smoke-dependent variable induction of SARS-CoV-2 entry factors across SAEC populations.

Epithelial Barrier Dysfunction in Chronic Respiratory Diseases

Mucosal surfaces are lined by epithelial cells, which provide a complex and adaptive module that ensures first-line defense against external toxics, irritants, antigens, and pathogens. The underlying mechanisms of host protection encompass multiple physical, chemical, and immune pathways. In the lung, inhaled agents continually challenge the airway epithelial barrier, which is altered in chronic diseases such as chronic obstructive pulmonary disease, asthma, cystic fibrosis, or pulmonary fibrosis. In this review, we describe the epithelial barrier abnormalities that are observed in such disorders and summarize current knowledge on the mechanisms driving impaired barrier function, which could represent targets of future therapeutic approaches.

Epithelial cell plasticity: breaking boundaries and changing landscapes

Epithelial tissues respond to a wide variety of environmental and genotoxic stresses. As an adaptive mechanism, cells can deviate from their natural paths to acquire new identities, both within and across lineages. Under extreme conditions, epithelial tissues can utilize "shape-shifting" mechanisms whereby they alter their form and function at a tissue-wide scale. Mounting evidence suggests that in order to acquire these alternate tissue identities, cells follow a core set of "tissue logic" principles based on developmental paradigms. Here, we review the terminology and the concepts that have been put forward to describe cell plasticity. We also provide insights into various cell intrinsic and extrinsic factors, including genetic mutations, inflammation, microbiota, and therapeutic agents that contribute to cell plasticity. Additionally, we discuss recent studies that have sought to decode the "syntax" of plasticity-i.e., the cellular and molecular principles through which cells acquire new identities in both homeostatic and malignant epithelial tissues-and how these processes can be manipulated for developing novel cancer therapeutics.

RSV attenuates epithelial cell restitution by inhibiting actin cytoskeleton-dependent cell migration

The airway epithelium's ability to repair itself after injury, known as epithelial restitution, is an essential mechanism enabling the respiratory tract's normal functions. Respiratory Syncytial Virus (RSV) is the leading cause of lower respiratory tract infections worldwide. We sought to determine whether RSV delays the airway epithelium wound repair process both in vitro and in vivo. We found that RSV infection attenuated epithelial cell migration, a step in wound repair, promoted stress fiber formation, and mediated assembly of large focal adhesions (FA). Inhibition of Rho kinase (ROCK), a master regulator of actin function, reversed these effects. There was increased RhoA and phospho-myosin light chain (pMLC2) following RSV infection. In vivo, mice were intraperitoneally inoculated with naphthalene to induce lung injury, followed by RSV infection. RSV infection delayed re-epithelialization. There were increased concentrations of pMLC2 in day 7 naphthalene plus RSV animals which normalized by day 14. This study suggests a key mechanism by which RSV infection delays wound healing.

Understanding potential mechanisms of harm: the drivers of electronic cigarette-induced changes in alveolar macrophages, neutrophils, and lung epithelial cells

Electronic (e-) cigarettes are growing in popularity despite uncertainties regarding their long-term health implications. The link between cigarette smoking and initiation of chronic lung disease took decades to unpick so in vitro studies mimicking e-cigarette exposure aim to detect early indicators of harm. In response to e-cigarette exposure, alveolar macrophages adopt a proinflammatory phenotype of increased secretion of proinflammatory cytokines, reduction in phagocytosis, and efferocytosis and reactive oxygen species generation. These effects are largely driven by free radical exposure, changes in PI3K/Akt signaling pathways, nicotine-induced reduction in phagocytosis receptors, and impaired lipid homeostasis leading to a foam-like lipid-laden phenotype. Neutrophils exhibit disrupted chemotaxis and transmigration to chemokines, reduced phagocytosis and bacterial killing, and an increase in protease secretion without corresponding antiproteases in response to e-cigarette exposure. This is driven by an altered ability to respond and to polarize toward chemoattractants, an activation of the p38 MAPK signaling pathway and inability to assemble NADPH oxidase. E-cigarettes induce lung epithelial cells to display decreased ciliary beat frequency and ion channel conductance as well as changes in chemokine secretion and surface protein expression. Changes in gene expression, mitochondrial function, and signaling pathways have been demonstrated in lung epithelial cells to explain these changes. Many functional outputs of alveolar macrophages, neutrophils, and lung epithelial cells have not been fully explored in the context of e-cigarette exposure and the underlying driving mechanisms are poorly understood. This review discusses current evidence surrounding the effects of e-cigarettes on alveolar macrophages, neutrophils, and lung epithelial cells with particular focus on the cellular mechanisms of change.

EFFECTS OF DOXYCYCLINE HYCLATE, ONE PERCENT POLIDOCANOL, AND ABSOLUTE ETHANOL ON THE CUTANEOUS AND SUBCUTANEOUS TISSUES OF CHICKENS (GALLUS GALLUS DOMESTICUS) AND THE POTENTIAL IMPLICATIONS IN TREATING CERVICOCEPHALIC DIVERTICULA RUPTURE

The objective of this pilot study was to examine the histologic effects associated with three known sclerosing agents and their ability to induce fibrosis in the subcutaneous space between the cervicocephalic air sac and skin. In the future, these drugs may prove useful in treating birds experiencing cervicocephalic diverticula rupture. The agents used were 1% polidocanol, absolute ethanol, and doxycycline hyclate. Twelve healthy adult chickens (Gallus gallus domesticus) were used in this study. The chickens were randomly allocated into three groups denoting day of euthanasia (day 4, 7, or 14). On day 0, all agents were injected (0.2 ml) subcutaneously, in a four-point grid fashion, in both the cervical and pectoral region of each bird. After euthanasia, the skin and subcutaneous tissues corresponding to the injection sites were harvested for histologic assessment. Tissue sections were assessed for fibrosis and lymphocytic and histiocytic inflammation. A scoring system was established to rank sclerosing agents by fibrosing and inflammatory ability. In the cervical region of chickens, 1% polidocanol induced the greatest inflammatory changes by day 7. Data suggest that doxycycline hyclate may produce the greatest cutaneous and subcutaneous fibrosis overall among all groups of birds. No adverse reactions were associated with any injection. Sterile saline produced the least amount of inflammation when assessed with the scoring system. Further investigation is needed to determine the safety of injections of larger volume with these chemicals and whether these findings can be extrapolated to birds with disease.

Integration of transcriptome analysis with pathophysiological endpoints to evaluate cigarette smoke toxicity in an in vitro human airway tissue model

Exposure to cigarette smoke (CS) is a known risk factor in the pathogenesis of smoking-caused diseases, such as chronic obstructive pulmonary diseases (COPD) and lung cancer. To assess the effects of CS on the function and phenotype of airway epithelial cells, we developed a novel repeated treatment protocol and comprehensively evaluated the progression of key molecular, functional, and structural abnormalities induced by CS in a human in vitro air-liquid-interface (ALI) airway tissue model. Cultures were exposed to CS (diluted with 0.5 L/min, 1.0 L/min, and 4.0 L/min clean air) generated from smoking five 3R4F University of Kentucky reference cigarettes under the International Organization for Standardization (ISO) machine smoking regimen, every other day for 4 weeks (3 days per week, 40 min/day). By integrating the transcriptomics-based approach with the in vitro pathophysiological measurements, we demonstrated CS-mediated effects on oxidative stress, pro-inflammatory cytokines and matrix metalloproteinases (MMPs), ciliary function, expression and secretion of mucins, and squamous cell differentiation that are highly consistent with abnormalities observed in airways of smokers. Enrichment analysis on the transcriptomic profiles of the ALI cultures revealed key molecular pathways, such as xenobiotic metabolism, oxidative stress, and inflammatory responses that were perturbed in response to CS exposure. These responses, in turn, may trigger aberrant tissue remodeling, eventually leading to the onset of respiratory diseases. Furthermore, changes of a panel of genes known to be disturbed in smokers with COPD were successfully reproduced in the ALI cultures exposed to CS. In summary, findings from this study suggest that such an integrative approach may be a useful tool for identifying genes and adverse cellular events caused by inhaled toxicants, like CS.

Clinical significance of changes in serum inflammatory factors in patients with chronic obstructive pulmonary disease and pulmonary infection

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is often accompanied by pulmonary infection, inflammatory responses, decreased immunity, and decreased lung function. The relationships among the pulmonary inflammation index (PII), lung function, and immunity in COPD patients with pulmonary infection remain unclear.

METHODS

This retrospective observational study enrolled 234 participants (patients with COPD and pulmonary infection, patients with COPD without pulmonary infection, and healthy individuals) from January 2017 to December 2019.

RESULTS

Levels of interleukin (IL)-6 were lower and levels of IL-8 were higher in patients with COPD and pulmonary infection. Levels of white blood cells (WBCs), C-reactive protein (CRP), IL-6, IL-8, tumor necrosis factor (TNF)-α and CD8+ cells were higher, while levels of CD3+ and CD4+ cells, the CD4+/CD8+ ratio, forced expiratory volume in 1 s (FEV1), FEV1 % predicted (FEV1%pred), and FEV1/forced vital capacity (FVC) (FEV1%FVC) were lower in patients with COPD and pulmonary infection. Levels of WBCs, CRP, IL-6, IL-8, and TNF-α were negatively associated with FEV1, FEV1%pred and FEV1%FVC.

CONCLUSIONS

Patients with COPD and pulmonary infection have high PIIs, decreased immunity, and poor lung function. PII is closely related to lung function and may represent a useful biomarker for the assessment of patients with COPD and pulmonary infection.

In Vitro Lung Models and Their Application to Study SARS-CoV-2 Pathogenesis and Disease

SARS-CoV-2 has spread across the globe with an astonishing velocity and lethality that has put scientist and pharmaceutical companies worldwide on the spot to develop novel treatment options and reliable vaccination for billions of people. To combat its associated disease COVID-19 and potentially newly emerging coronaviruses, numerous pre-clinical cell culture techniques have progressively been used, which allow the study of SARS-CoV-2 pathogenesis, basic replication mechanisms, and drug efficiency in the most authentic context. Hence, this review was designed to summarize and discuss currently used in vitro and ex vivo cell culture systems and will illustrate how these systems will help us to face the challenges imposed by the current SARS-CoV-2 pandemic.

Impaired Differentiation of Chronic Obstructive Pulmonary Disease Bronchial Epithelial Cells Grown on Bronchial Scaffolds

Chronic obstructive pulmonary disease (COPD) is characterized by airway inflammation, small airway remodeling, and emphysema. Airway remodeling in patients with COPD involves both the airway epithelium and the subepithelial extracellular matrix (ECM). However, it is currently unknown how epithelial remodeling in COPD airways depends on the relative influence from inherent defects in the epithelial cells and alterations in the ECM. To address this, we analyzed global gene expression in COPD human bronchial epithelial cells (HBEC) and normal HBEC after repopulation on decellularized bronchial scaffolds derived from patients with COPD or donors without COPD. COPD HBEC grown on bronchial scaffolds showed an impaired ability to initiate ciliated-cell differentiation, which was evident on all scaffolds regardless of their origin. In addition, although normal HBEC were less affected by the disease state of the bronchial scaffolds, COPD HBEC showed a gene expression pattern indicating increased proliferation and a retained basal-cell phenotype when grown on COPD bronchial scaffolds compared with normal bronchial scaffolds. By using mass spectrometry, we identified 13 matrisome proteins as being differentially abundant between COPD bronchial scaffolds and normal bronchial scaffolds. These observations are consistent with COPD pathology and suggest that both epithelial cells and the ECM contribute to epithelial-cell remodeling in COPD airways.

SARS-CoV-2 Switches 'on' MAPK and NFκB Signaling via the Reduction of Nuclear DUSP1 and DUSP5 Expression

Mitogen-activated protein kinases (MAPK) and NF-kappaB (NF-κB) pathway regulate many cellular processes and are essential for immune cells function. Their activity is controlled by dual-specificity phosphatases (DUSPs). A comprehensive analysis of publicly available gene expression data sets of human airway epithelial cells (AECs) infected with SARS-CoV-2 identified DUSP1 and DUSP5 among the lowest induced transcripts within these pathways. These proteins are known to downregulate MAPK and NF-κB pathways; and their lower expression was associated with increased activity of MAPK and NF-κB signaling and enhanced expression of proinflammatory cytokines such as TNF-α. Infection with other coronaviruses did not have a similar effect on these genes. Interestingly, treatment with chloroquine and/or non-steroidal anti-inflammatory drugs counteracted the SARS-CoV-2 induced reduction of DUSP1 and DUSP5 genes expression. Therapeutically, impeding this evasion mechanism of SARS-CoV-2 may help control the exaggerated activation of these immune regulatory pathways during a COVID-19 infection.

Influence of Hypoxia on the Epithelial-Pathogen Interactions in the Lung: Implications for Respiratory Disease

Under normal physiological conditions, the lung remains an oxygen rich environment. However, prominent regions of hypoxia are a common feature of infected and inflamed tissues and many chronic inflammatory respiratory diseases are associated with mucosal and systemic hypoxia. The airway epithelium represents a key interface with the external environment and is the first line of defense against potentially harmful agents including respiratory pathogens. The protective arsenal of the airway epithelium is provided in the form of physical barriers, and the production of an array of antimicrobial host defense molecules, proinflammatory cytokines and chemokines, in response to activation by receptors. Dysregulation of the airway epithelial innate immune response is associated with a compromised immunity and chronic inflammation of the lung. An increasing body of evidence indicates a distinct role for hypoxia in the dysfunction of the airway epithelium and in the responses of both innate immunity and of respiratory pathogens. Here we review the current evidence around the role of tissue hypoxia in modulating the host-pathogen interaction at the airway epithelium. Furthermore, we highlight the work needed to delineate the role of tissue hypoxia in the pathophysiology of chronic inflammatory lung diseases such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease in addition to novel respiratory diseases such as COVID-19. Elucidating the molecular mechanisms underlying the epithelial-pathogen interactions in the setting of hypoxia will enable better understanding of persistent infections and complex disease processes in chronic inflammatory lung diseases and may aid the identification of novel therapeutic targets and strategies.

Cellular and mitochondrial calcium communication in obstructive lung disorders

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

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.

TP63 basal cells are indispensable during endoderm differentiation into proximal airway cells on acellular lung scaffolds

The use of decellularized whole-organ scaffolds for bioengineering of organs is a promising avenue to circumvent the shortage of donor organs for transplantation. However, recellularization of acellular scaffolds from multicellular organs like the lung with a variety of different cell types remains a challenge. Multipotent cells could be an ideal cell source for recellularization. Here we investigated the hierarchical differentiation process of multipotent ES-derived endoderm cells into proximal airway epithelial cells on acellular lung scaffolds. The first cells to emerge on the scaffolds were TP63⁺ cells, followed by TP63⁺/KRT5⁺ basal cells, and finally multi-ciliated and secretory airway epithelial cells. TP63⁺/KRT5⁺ basal cells on the scaffolds simultaneously expressed KRT14, like basal cells involved in airway repair after injury. Removal of TP63 by CRISPR/Cas9 in the ES cells halted basal and airway cell differentiation on the scaffolds. These findings suggest that differentiation of ES-derived endoderm cells into airway cells on decellularized lung scaffolds proceeds via TP63⁺ basal cell progenitors and tracks a regenerative repair pathway. Understanding the process of differentiation is key for choosing the cell source for repopulation of a decellularized organ scaffold. Our data support the use of airway basal cells for repopulating the airway side of an acellular lung scaffold.