Exacerbation of cigarette smoke-induced pulmonary inflammation by Staphylococcus aureus enterotoxin B in mice

Qing-Kai-Ling oral liquid alleviated pneumonia via regulation of intestinal flora and metabolites in rats

Background

Qing-Kai-Ling (QKL) oral liquid, evolving from a classical Chinese formula known as An-Gong-Niu-Huang pills, is a well-established treatment for pneumonia with its mechanism remaining muddled. Studies have shown that the regulation of both intestinal flora and host-microbiota co-metabolism may contribute to preventing and treating pneumonia. The study aimed to investigate the potential mechanism by which QKL alleviates pneumonia from the perspective of 'microbiota-metabolites-host' interaction.

Methods

We evaluated the therapeutic effects of QKL on lipopolysaccharide (LPS)-induced pneumonia rats. To explore the protective mechanism of QKL treatment, a multi-omics analysis that included 16S rDNA sequencing for disclosing the key intestinal flora, the fecal metabolome to discover the differential metabolites, and whole transcriptome sequencing of lung tissue to obtain the differentially expressed genes was carried out. Then, a Spearman correlation was employed to investigate the association between the intestinal flora, the fecal metabolome and inflammation-related indices.

Results

The study demonstrated that pneumonia symptoms were significantly attenuated in QKL-treated rats, including decreased TNF-α, NO levels and increased SOD level. Furthermore, QKL was effective in alleviating pneumonia and provided protection equivalent to that of the positive drug dexamethasone. Compared with the Model group, QKL treatment significantly increased the richness and αlpha diversity of intestinal flora, and restored multiple intestinal genera (e.g., Bifidobacterium, Ruminococcus_torques_group, Dorea, Mucispirillum, and Staphylococcus) that were correlated with inflammation-related indices. Interestingly, the intestinal flora demonstrated a strong correlation with several metabolites impacted by QKL. Furthermore, metabolome and transcriptome analyses showed that enrichment of several host-microbiota co-metabolites [arachidonic acid, 8,11,14-eicosatrienoic acid, LysoPC (20:0/0:0), LysoPA (18:0e/0:0), cholic acid, 7-ketodeoxycholic acid and 12-ketodeoxycholic acid] levels and varying lung gene (Pla2g2a, Pla2g5, Alox12e, Cyp4a8, Ccl19, and Ccl21) expression were observed in the QKL group. Moreover, these metabolites and genes were involved in arachidonic acid metabolism and inflammation-related pathways.

Conclusion

Our findings indicated that QKL could potentially modulate intestinal flora dysbiosis, improve host-microbiota co-metabolism dysregulation and regulate gene expression in the lungs, thereby mitigating LPS-induced pneumonia in rats. The study may provide new ideas for the clinical application and further development of QKL.

Global Research Trends on the Link Between the Microbiome and COPD: A Bibliometric Analysis

Background

The pathogenesis of chronic obstructive pulmonary disease (COPD) has been studied in relation to the microbiome, providing space for more targeted interventions and new treatments. Numerous papers on the COPD microbiome have been reported in the last 10 years, yet few publications have used bibliometric methods to evaluate this area.

Methods

We searched the Web of Science Core Collection for all original research articles in the field of COPD microbiome from January 2011 to August 2022 and used CiteSpace for visual analysis.

Results

A total of 505 relevant publications were obtained, and the number of global publications in this field is steadily increasing every year, with China and the USA occupying the first two spots in international publications. Imperial College London and the University of Leicester produced the most publications. Brightling C from the UK was the most prolific writer, while Huang Y and Sze M from the USA were first and second among the authors cited. The American Journal of Respiratory and Critical Care Medicine had the highest frequency of citations. The top 10 institutions, cited authors and journals are mostly from the UK and the US. In the ranking of citations, the first article was a paper published by Sze M on changes in the lung tissue's microbiota in COPD patients. The keywords "exacerbation", "gut microbiota", "lung microbiome", "airway microbiome", "bacterial colonization", and "inflammation" were identified as cutting-edge research projects for 2011-2022.

Conclusion

Based on the visualization results, in the future, we can use the gut-lung axis as the starting point to explore the immunoinflammatory mechanism of COPD, and study how to predict the effects of different treatments of COPD by identifying the microbiota, and how to achieve the optimal enrichment of beneficial bacteria and the optimal consumption of harmful bacteria to improve COPD.

Staphylococcal Enterotoxin-Specific IgE Sensitization: A Potential Predictor of Fixed Airflow Obstruction in Elderly Asthma

PURPOSE

Staphylococcus aureus enterotoxin-specific immunoglobulin E (SE-sIgE) sensitization tends to increase with age and is known to be associated with asthma and severity in older adults. However, the long-term impact of SE-sIgE in the elderly remains unknown. This study aimed to examine the relationships between SE-sIgE and fixed airflow obstruction (FAO) in a cohort of elderly asthmatics.

METHODS

A total of 223 elderly asthmatics and 89 controls were analyzed. Patients were assessed for demographics, history of chronic rhinosinusitis (CRS), asthma duration, acute exacerbation frequency, and lung function at baseline and then were prospectively followed up for 2 years. Serum total IgE and SE-sIgE levels were measured at baseline. Airflow obstruction was defined as forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio < 0.7 at baseline and FAO was defined as FEV1/FVC ratio < 0.7 over the 2-year follow-up.

RESULTS

At baseline, the prevalence of airflow obstruction was 29.1%. Patients with airflow obstruction were significantly more likely to be male, and have a positive smoking history, comorbid CRS, and higher levels of SE-sIgE than those without airflow obstruction. Multivariate logistic regression analysis showed that airflow obstruction was significantly associated with current smoking and SE-sIgE sensitization at baseline. After the 2-year follow-up, baseline SE-sIgE sensitization was consistently related to FAO. Meanwhile, the number of exacerbations per year was significantly correlated with SE-sIgE levels.

CONCLUSIONS

Baseline SE-sIgE sensitization was significantly associated with the number of asthma exacerbations and FAO after the 2-year follow-up in elderly asthmatics. These findings warrant further investigation of the direct and mediating roles of SE-sIgE sensitization on airway remodeling.

Identification of Survival-Associated Gene Signature in Lung Cancer Coexisting With COPD

Background: Chronic obstructive pulmonary disease (COPD) and lung cancer often coexist, which is associated with a worse prognosis. Thousands of biomarkers related to the survival of lung cancer have been investigated. However, those which can predict the survival of lung cancer coexisting with COPD are currently lacking. The present study aimed to identify novel gene signatures to predict the survival of patients with lung cancer coexisting COPD.

Method: RNA-sequence data of lung cancer and control accompanying with matched clinical information were retrieved from the Cancer Genome Atlas (TCGA). Differently expressed genes (DEGs) associated with lung cancer coexisting COPD were screened. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were performed. Univariate and multivariate Cox regression analyses were applied to identify survival-associated DEGs and to construct survival-associated gene signature. Kaplan-Meier survival analysis and calibration plots of the nomogram were performed to test the predictive accuracy of the gene signature. qPCR was performed to validate the genes in the prognostic signature.

Results: Sequence data from 70 patients with lung cancer coexisting COPD, 127 with lung cancer alone and 108 control tissues were included for analysis. A total of 2424 DEGs were identified when comparing lung cancer coexisting COPD with controls. The biological process was primarily associated with DNA-binding transcription activator activity, peptidase inhibitor activity, endopeptidase inhibitor activity, et al. KEGG pathways were mainly enriched in neuroactive ligand-receptor interaction, cell cycle, and Staphylococcus aureus infection. A survival-associated gene signature consisting of CEACAM5, RASAL1, CSTL1, CNGB1, and SLC4A3 was identified and represented as risk score. The high-risk score group had significantly worse survival than the low-risk score group (P < 0.001). Areas under receiver operating characteristic curves were 0.943, 0.773, 0.888 for predicting overall survival at 1-, 3-, and 5-year, respectively. The risk score was an independent predictor of survival, independent of clinical factors. High conformity of the actual survival and the nomogram–predicted probability of survival by applying the risk score. Upregulation of the five genes in patients with lung cancer coexisting COPD were confirmed by qPCR in an independent cohort.

Conclusion: Our study constructed and validated a novel prognostic gene signature for predicting survival of patient with lung cancer coexisting COPD, which may contribute to the clinical treatment decisions.

Animal models of emphysema

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a common chronic respiratory disease of human beings characterized by not fully reversible airflow limitation. Emphysema is the main pathological feature of COPD which causes high mortality worldwide every year and consumes a large amount of medical expenses. This paper was to review the establishment and evaluation methods of animal models of emphysema or COPD, and put forward some new ideas on animal selection, method of modeling, and model evaluation.

DATA SOURCES

The author retrieved information from the PubMed database up to July 2019, using various combinations of search terms, including emphysema, model, and animal.

STUDY SELECTION

Original articles, reviews, and other articles were searched and reviewed for animal models of emphysema.

RESULTS

This review summarized animal models of emphysema from the perspectives of animal selection, emphysema mechanism, modeling method and model evaluation, and found that passive smoking is the classic method for developing animal model of emphysema, mice are more suitable for experimental study on emphysema. Compared with pulmonary function indicators, airway inflammation indicators and oxidative stress indicators, pathomorphological indicators of lung tissue are the most important parameters for evaluating the establishment of the animal model of emphysema.

CONCLUSIONS

Mice model induced by passive smoking is the classic animal model of emphysema. Pathomorphological indicators are the most important parameters for evaluating the establishment of the animal model of emphysema.

The acute pulmonary toxicity in mice induced by Staphylococcus aureus, particulate matter, and their combination

Inhalation of pathogenic bacteria transported by particulate matter (PM) presents an important potential threat to human health. Therefore, the pulmonary toxicity in mice caused by Staphylococcus aureus (S. aureus) and PM as individual matter and mixtures was studied. PM and S. aureus were instilled intratracheally into Kunming mice at doses of 0.2 mg/mouse and 5.08 × 10⁶ CFU /mouse, respectively, as individual matter and in combination two times at 5-day intervals. After the exposure period, oxidative stress markers and nitric oxide (NO) in the lung, cellular infiltration, neurotrophins, chemokines, and cytokines in bronchoalveolar lavage fluid (BALF), and immunoglobulin (Ig) in sera were examined. Exposure to the combination of PM and S. aureus caused significant increases in malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD), and NO and significant decreases in total antioxidant capacity (T-AOC) and the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) in the lung. Meanwhile, the ratio of interleukin (IL)-4 to interferon (INF)-γ, the IL-4 level in BALF, and the IgE concentration in sera were significantly increased in the groups exposed to S. aureus or the combination of PM and S. aureus. Substance P and IL-8 in BALF were significantly increased in mice exposed to PM, S. aureus or their combination. In addition, PM, S. aureus, and their combination caused infiltration of leukocytes into the alveolar tissue spaces. The results suggested that exposure to the combination of PM and S. aureus induced a lung inflammatory response that was at least partly caused by oxidative stress and mediators from the activated eosinophils, neutrophils, alveolar macrophages, and epithelial cells.

Sensitization to Staphylococcus aureus enterotoxins in smokers with asthma

BACKGROUND

Sensitization to Staphylococcus aureus enterotoxins (SEs) augments eosinophilic inflammation in asthma. Recent epidemiologic studies demonstrate that sensitization to SEs is increased in healthy smokers; however, there is no evidence on the association between sensitization to SEs and eosinophilic inflammation in smokers with asthma.

OBJECTIVE

To clarify the role of SEs on clinical indexes, including eosinophilic inflammation and lung function in smokers with asthma.

METHODS

The frequency of atopic sensitization to SEs was examined in adult patients with asthma. In current or ex-smokers with asthma, the association of sensitization to SEs with eosinophilic inflammation, airflow limitation, or treatment steps was determined. Clinical indexes were examined at the first visit, and treatment steps were assessed 6 months after enrollment.

RESULTS

Overall, 23 current smokers, 40 ex-smokers, and 118 never smokers with asthma were enrolled. The frequency of sensitization to SEs, but not to other aeroallergens, was significantly higher in current, ex-, and never smokers, in decreasing order. In current or ex-smokers with asthma, patients with sensitization to SEs exhibited higher serum levels of total and specific IgE to aeroallergens, higher blood eosinophil counts, greater airflow limitation, and more severe disease 6 months later than those without sensitization to SE. A longer smoking abstinence period was associated with serum specific IgE levels to SEs, and 3 years was the best cutoff of abstinence period to predict the absence of sensitization to SEs.

CONCLUSION

Sensitization to SEs is increased in smokers with asthma, and it may be a marker of eosinophilic inflammation and severe asthma in smokers with asthma.

TRIAL REGISTRATION

umin.ac.jp Identifier: UMIN000007818.

Targeting Interleukin-17 signalling in cigarette smoke-induced lung disease: Mechanistic concepts and therapeutic opportunities

It is widely accepted that compromised lung function in chronic obstructive pulmonary disease (COPD) is, at least in part, a consequence of persistent airway inflammation caused by particles and noxious gases present in cigarette smoke and indoor air pollution from burning biomass fuel. Currently, the World Health Organization estimates that 80 million people have moderate or severe COPD worldwide. While there is a global need for effective medical treatment, current therapeutic interventions have shown limited success in preventing disease pathology and progression. This is, in large part, due to the complexity and heterogeneity of COPD, and an incomplete understanding of the molecular mechanisms governing inflammatory processes in individual patients. This review discusses recent discoveries related to the pro-inflammatory cytokine interleukin (IL)-17A, and its potential role in the pathogenesis of COPD. We propose that an intervention strategy targeting IL-17 signalling offers an exciting opportunity to mitigate inflammatory processes, and prevent the progression of tissue pathologies associated with COPD.

Bacteria-driven peribronchial lymphoid neogenesis in bronchiectasis and cystic fibrosis

We aimed to characterise lymphoid neogenesis in bronchiectasis and cystic fibrosis (CF) lungs and to examine the role of bacterial infection.

Lymphoid aggregates were examined using immunohistochemical staining and morphometric analysis in surgical lung sections obtained from nonsmokers and patients with bronchiectasis or CF. Sterile, Pseudomonas aeruginosa- or Staphylococcus aureus-coated agarose beads were instilled intratracheally in mice. Kinetics of lymphoid neogenesis and chemokine expression were examined over 14 days.

Lymphoid aggregates were scarce in human lungs of nonsmokers, but numerous peribronchial lymphoid aggregates containing B-lymphocytes, T-lymphocytes, germinal centres and high endothelial venules were found in bronchiectasis and CF. Mouse lungs contained no lymphoid aggregate at baseline. During persistent P. aeruginosa or S. aureus airway infection peribronchial lymphoid neogenesis occurred. At day 14 after instillation, lymphoid aggregates expressed markers of tertiary lymphoid organs and the chemokines CXCL12 and CXCL13. The airway epithelium was an important site of CXCL12, CXCL13 and interleukin-17A expression, which began at day 1 after instillation.

Peribronchial tertiary lymphoid organs are present in bronchiectasis and in CF, and persistent bacterial infection triggered peribronchial lymphoid neogenesis in mice. Peribronchial localisation of tertiary lymphoid organs and epithelial expression of chemokines suggest roles for airway epithelium in lymphoid neogenesis.

Interference of the T Cell and Antigen-Presenting Cell Costimulatory Pathway Using CTLA4-Ig (Abatacept) Prevents Staphylococcal Enterotoxin B Pathology

Staphylococcal enterotoxin B (SEB) is a bacterial superantigen that binds the receptors in the APC/T cell synapse and causes increased proliferation of T cells and a cytokine storm syndrome in vivo. Exposure to the toxin can be lethal and cause significant pathology in humans. The lack of effective therapies for SEB exposure remains an area of concern, particularly in scenarios of acute mass casualties. We hypothesized that blockade of the T cell costimulatory signal by the CTLA4-Ig synthetic protein (abatacept) could prevent SEB-dependent pathology. In this article, we demonstrate mice treated with a single dose of abatacept 8 h post SEB exposure had reduced pathology compared with control SEB-exposed mice. SEB-exposed mice showed significant reductions in body weight between days 4 and 9, whereas mice exposed to SEB and also treated with abatacept showed no weight loss for the duration of the study, suggesting therapeutic mitigation of SEB-induced morbidity. Histopathology and magnetic resonance imaging demonstrated that SEB mediated lung damage and edema, which were absent after treatment with abatacept. Analysis of plasma and lung tissues from SEB-exposed mice treated with abatacept demonstrated significantly lower levels of IL-6 and IFN-γ (p < 0.0001), which is likely to have resulted in less pathology. In addition, exposure of human and mouse PBMCs to SEB in vitro showed a significant reduction in levels of IL-2 (p < 0.0001) after treatment with abatacept, indicating that T cell proliferation is the main target for intervention. Our findings demonstrate that abatacept is a robust and potentially credible drug to prevent toxic effects from SEB exposure.

Emerging pathogenic links between microbiota and the gut-lung axis

The microbiota is vital for the development of the immune system and homeostasis. Changes in microbial composition and function, termed dysbiosis, in the respiratory tract and the gut have recently been linked to alterations in immune responses and to disease development in the lungs. In this Opinion article, we review the microbial species that are usually found in healthy gastrointestinal and respiratory tracts, their dysbiosis in disease and interactions with the gut-lung axis. Although the gut-lung axis is only beginning to be understood, emerging evidence indicates that there is potential for manipulation of the gut microbiota in the treatment of lung diseases.

Heavy Cigarette Smokers in a Chinese Population Display a Compromised Permeability Barrier

Cigarette smoking is associated with various cutaneous disorders with defective permeability. Yet, whether cigarette smoking influences epidermal permeability barrier function is largely unknown. Here, we measured skin biophysical properties, including permeability barrier homeostasis, stratum corneum (SC) integrity, SC hydration, skin surface pH, and skin melanin/erythema index, in cigarette smokers. A total of 99 male volunteers were enrolled in this study. Smokers were categorized as light-to-moderate (<20 cigarettes/day) or heavy smokers (≥20 cigarettes/day). An MPA5 was used to measure SC hydration and skin melanin/erythema index on the dorsal hand, forehead, and cheek. Basal transepidermal water loss (TEWL) and barrier recovery rates were assessed on the forearm. A Skin-pH-Meter pH900 was used to measure skin surface pH. Our results showed that heavy cigarette smokers exhibited delayed barrier recovery after acute abrogation (1.02% ± 13.06 versus 16.48% ± 6.07), and barrier recovery rates correlated negatively with the number of daily cigarettes consumption (p = 0.0087). Changes in biophysical parameters in cigarette smokers varied with body sites. In conclusion, heavy cigarette smokers display compromised permeability barrier homeostasis, which could contribute, in part, to the increased prevalence of certain cutaneous disorders characterized by defective permeability. Thus, improving epidermal permeability barrier should be considered for heavy cigarette smokers.

Cigarette Smoke-Induced Lung Disease Predisposes to More Severe Infection with Nontypeable Haemophilus influenzae: Protective Effects of Andrographolide

Cigarette smoke (CS) is associated with many maladies, one of which is chronic obstructive pulmonary disease (COPD). As the disease progresses, patients are more prone to develop COPD exacerbation episodes by bacterial infection, particularly to nontypeable Haemophilus influenza (NTHi) infection. The present study aimed to develop a CS-exposed mouse model that increases inflammation induced by NTHi challenge and investigate the protective effects of andrographolide, a bioactive molecule with anti-inflammatory and antioxidant properties isolated from the plant Andrographis paniculata. Female BALB/c mice exposed to 2 weeks of CS followed by a single intratracheal instillation of NTHi developed increased macrophage and neutrophil pulmonary infiltration, augmented cytokine levels, and heightened oxidative damage. Andrographolide effectively reduced lung cellular infiltrates and decreased lung levels of TNF-α, IL-1β, CXCL1/KC, 8-OHdG, matrix metalloproteinase-8 (MMP-8), and MMP-9. The protective actions of andrographolide on CS-predisposed NTHi inflammation might be attributable to increased nuclear factor erythroid-2-related factor 2 (Nrf2) activation and decreased Kelch-like ECH-associated protein 1 (Keap1) repressor function, resulting in enhanced gene expression of antioxidant enzymes including heme oxygenase-1 (HO-1), glutathione reductase (GR), glutathione peroxidase-2 (GPx-2), glutamate-cysteine ligase modifier (GCLM), and NAD(P)H quinone oxidoreductase 1 (NQO1). Taken together, these findings strongly support a therapeutic potential for andrographolide in preventing lung inflammation caused by NTHi in cigarette smokers.

Murine models of cardiovascular comorbidity in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) have an increased risk for cardiovascular disease (CVD). Currently, COPD patients with atherosclerosis (i.e., the most important underlying cause of CVD) receive COPD therapy complemented with standard CVD therapy. This may, however, not be the most optimal treatment. To investigate the link between COPD and atherosclerosis and to develop specific therapeutic strategies for COPD patients with atherosclerosis, a substantial number of preclinical studies using murine models have been performed. In this review, we summarize the currently used murine models of COPD and atherosclerosis, both individually and combined, and discuss the relevance of these models for studying the pathogenesis and development of new treatments for COPD patients with atherosclerosis. Murine and clinical studies have provided complementary information showing a prominent role for systemic inflammation and oxidative stress in the link between COPD and atherosclerosis. These and other studies showed that murine models for COPD and atherosclerosis are useful tools and can provide important insights relevant to understanding the link between COPD and CVD. More importantly, murine studies provide good platforms for studying the potential of promising (new) therapeutic strategies for COPD patients with CVD.

IL-22 Defect During Streptococcus pneumoniae Infection Triggers Exacerbation of Chronic Obstructive Pulmonary Disease

Progression of chronic obstructive pulmonary disease (COPD) is linked to episodes of exacerbations caused by bacterial infections due to Streptococcus pneumoniae. Our objective was to identify during COPD, factors of susceptibility to bacterial infections among cytokine network and their role in COPD exacerbations. S. pneumoniae was used to sub-lethally challenge mice chronically exposed to air or cigarette smoke (CS) and to stimulate peripheral blood mononuclear cells (PBMC) from non-smokers, smokers and COPD patients. The immune response and the cytokine production were evaluated. Delayed clearance of the bacteria and stronger lung inflammation observed in infected CS-exposed mice were associated with an altered production of IL-17 and IL-22 by innate immune cells. This defect was related to a reduced production of IL-1β and IL-23 by antigen presenting cells. Importantly, supplementation with recombinant IL-22 restored bacterial clearance in CS-exposed mice and limited lung alteration. In contrast with non-smokers, blood NK and NKT cells from COPD patients failed to increase IL-17 and IL-22 levels in response to S. pneumoniae, in association with a defect in IL-1β and IL-23 secretion. This study identified IL-17 and IL-22 as susceptibility factors in COPD exacerbation. Therefore targeting such cytokines could represent a potent strategy to control COPD exacerbation.

Second-hand cigarette smoke impairs bacterial phagocytosis in macrophages by modulating CFTR dependent lipid-rafts

Introduction

First/Second-hand cigarette-smoke (FHS/SHS) exposure weakens immune defenses inducing chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are not fully understood. Hence, we evaluated if SHS induced changes in membrane/lipid-raft (m-/r)-CFTR (cystic fibrosis transmembrane conductance regulator) expression/activity is a potential mechanism for impaired bacterial phagocytosis in COPD.

Methods

RAW264.7 murine macrophages were exposed to freshly prepared CS-extract (CSE) containing culture media and/or Pseudomonas-aeruginosa-PA01-GFP for phagocytosis (fluorescence-microscopy), bacterial survival (colony-forming-units-CFU), and immunoblotting assays. The CFTR-expression/activity and lipid-rafts were modulated by transient-transfection or inhibitors/inducers. Next, mice were exposed to acute/sub-chronic-SHS or room-air (5-days/3-weeks) and infected with PA01-GFP, followed by quantification of bacterial survival by CFU-assay.

Results

We investigated the effect of CSE treatment on RAW264.7 cells infected by PA01-GFP and observed that CSE treatment significantly (p<0.01) inhibits PA01-GFP phagocytosis as compared to the controls. We also verified this in murine model, exposed to acute/sub-chronic-SHS and found significant (p<0.05, p<0.02) increase in bacterial survival in the SHS-exposed lungs as compared to the room-air controls. Next, we examined the effect of impaired CFTR ion-channel-activity on PA01-GFP infection of RAW264.7 cells using CFTR172-inhibitor and found no significant change in phagocytosis. We also similarly evaluated the effect of a CFTR corrector-potentiator compound, VRT-532, and observed no significant rescue of CSE impaired PA01-GFP phagocytosis although it significantly (p<0.05) decreases CSE induced bacterial survival. Moreover, induction of CFTR expression in macrophages significantly (p<0.03) improves CSE impaired PA01-GFP phagocytosis as compared to the control. Next, we verified the link between m-/r-CFTR expression and phagocytosis using methyl-β-cyclodextran (CD), as it is known to deplete CFTR from membrane lipid-rafts. We observed that CD treatment significantly (p<0.01) inhibits bacterial phagocytosis in RAW264.7 cells and adding CSE further impairs phagocytosis suggesting synergistic effect on CFTR dependent lipid-rafts.

Conclusion

Our data suggest that SHS impairs bacterial phagocytosis by modulating CFTR dependent lipid-rafts.

Combined exposure to bacteria and cigarette smoke resembles characteristic phenotypes of human COPD in a murine disease model

Abundant microbial colonization is a hallmark of COPD and smoke exposure likely increases the susceptibility to colonization and infection. The aim of the present study was to characterize the pulmonary changes of a combined exposure to cigarette smoke (CS) and microbial challenge in a preclinical murine COPD model. Animals were exposed to CS for 2 weeks, 3, and 6 months. Low and high doses of heat inactivated nontypeable Haemophilus influenzae (NTHi) were administered by inhalation during the whole exposure time. Pulmonary changes were analyzed by stereology, pulmonary function tests, measurements of inflammatory cells and mediators, and histopathology. Exposure of smoke in a relatively low concentration caused COPD-like changes of pulmonary function and only little inflammation. The coadministration of low dose NTHi (ld-NTHi) augmented a macrophage dominated inflammatory profile, while high dose NTHi (hd-NTHi) induced a neutrophilic inflammatory pattern. IL-17A secretion was solely dependent on the exposure to NTHi. Also goblet cell metaplasia and the formation of lymphoid aggregates depended on exposure to bacteria. In conclusion, the combination of exposure to smoke and bacterial compounds resulted in a mouse model that resembles several aspects of human disease. Exposure to microbial structural components appears necessary to model important pathologic features of the disease and the quantity of the exposure with microorganisms has a strong effect on the phenotype.

Animal models of chronic obstructive pulmonary disease

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a leading global cause of mortality and chronic morbidity. Inhalation of cigarette smoke is the principal risk factor for development of this disease. COPD is a progressive disease that is typically characterised by chronic pulmonary inflammation, mucus hypersecretion, airway remodelling and emphysema that collectively reduce lung function. There are currently no therapies that effectively halt or reverse disease progression. It is hoped that the development of animal models that develop the hallmark features of COPD, in a short time frame, will aid in the identifying and testing of new therapeutic approaches.

AREAS COVERED

The authors review the recent developments in mouse models of chronic cigarette smoke-induced COPD as well as the principal findings. Furthermore, the authors discuss the use of mouse models to understand the pathogenesis and the contribution of infectious exacerbations. They also discuss the investigations of the systemic co-morbidities of COPD (pulmonary hypertension, cachexia and osteoporosis).

EXPERT OPINION

Recent advances in the field mark a point where animal models recapitulate the pathologies of COPD patients in a short time frame. They also reveal novel insights into the pathogenesis and potential treatment of this debilitating disease.

Combined exposure to cigarette smoke and nontypeable Haemophilus influenzae drives development of a COPD phenotype in mice

BACKGROUND

Cigarette smoke (CS) is the major etiologic factor of chronic obstructive pulmonary disease (COPD). CS-exposed mice develop emphysema and mild pulmonary inflammation but no airway obstruction, which is also a prominent feature of COPD. Therefore, CS may interact with other factors, particularly respiratory infections, in the pathogenesis of airway remodeling in COPD.

METHODS

C57BL/6 mice were exposed to CS for 2 h a day, 5 days a week for 8 weeks. Mice were also exposed to heat-killed non-typeable H. influenzae (HK-NTHi) on days 7 and 21. One day after the last exposure to CS, mice were sacrificed and lung inflammation and mechanics, emphysematous changes, and goblet cell metaplasia were assessed. Mice exposed to CS or HK-NTHi alone or room air served as controls. To determine the susceptibility to viral infections, we also challenged these mice with rhinovirus (RV).

RESULTS

Unlike mice exposed to CS or HK-NTHi alone, animals exposed to CS/HK-NTHi developed emphysema, lung inflammation and goblet cell metaplasia in both large and small airways. CS/HK-NTHi-exposed mice also expressed increased levels of mucin genes and cytokines compared to mice in other groups. CS/HK-NTHi-exposed mice infected with RV demonstrated increased viral persistence, sustained neutrophilia, and further increments in mucin gene and chemokine expression compared to other groups.

CONCLUSIONS

These findings indicate that in addition to CS, bacteria may also contribute to development of COPD, particularly changes in airways. Mice exposed to CS/HK-NTHi are also more susceptible to subsequent viral infection than mice exposed to either CS or HK-NTHi alone.

MAPK/NF-κB-dependent upregulation of kinin receptors mediates airway hyperreactivity: a new perspective for the treatment

Airway hyperreactivity (AHR) is a major feature of asthmatic and inflammatory airways. Cigarette smoke exposure, and bacterial and viral infections are well-known environmental risk factors for AHR, but knowledge about the underlying molecular mechanisms on how these risk factors lead to the development of AHR is limited. Activation of intracellular mitogen-activated protein kinase (MAPK)/nuclear factor-kappa B (NF-κB) and their related signal pathways including protein kinase C (PKC), phosphoinositide 3-kinase (PI3K) and protein kinase A (PKA) signaling pathways may result in airway kinin receptor upregulation, which is suggested to play an important role in the development of AHR. Environmental risk factors trigger the production of pro-inflammatory mediators such as tumor necrosis factor-α (TNF-α) and interleukins (ILs) that activate intracellular MAPK- and NF-κB-dependent inflammatory pathways, which subsequently lead to AHR via kinin receptor upregulation. Blockage of intracellular MAPK/NF-κB signaling prevents kinin B₁ and B₂ receptor expression in the airways, resulting in a decrease in the response to bradykinin (kinin B₂ receptor agonist) and des-Arg⁹-bradykinin (kinin B₁ receptor agonist). This suggests that MAPK- and NF-κB-dependent kinin receptor upregulation can provide a novel option for treatment of AHR in asthmatic as well as in other inflammatory airway diseases.

Murine models of infectious exacerbations of airway inflammation

Airway inflammation underpins the pathogenesis of the major human chronic respiratory diseases. It is now well recognized that respiratory infections with bacteria and viruses are important in the induction, progression and exacerbation of these diseases. There are no effective therapies that prevent or reverse these events. The development and use of mouse models are proving valuable in understanding the role of infection in disease pathogenesis. They have recently been used to show that infections in early life alter immune responses and lung structure to increase asthma severity, and alter immune responses in later life to induce steroid resistance. Infection following smoke exposure or in experimental chronic obstructive pulmonary disease exacerbates inflammation and remodeling, and worsens cystic fibrosis. Further exploration of these models will facilitate the identification of new therapeutic approaches and the testing of new preventions and treatments.

The adjuvant-like activity of staphylococcal enterotoxin B in a murine asthma model is independent of IL-1R signaling

BACKGROUND

Staphylococcal enterotoxin B (SEB) is a superantigen known to be a modulator of chronic airway inflammation in mice and humans, yet little is known about the mechanisms that regulate its interaction with the innate immune system. We investigated this mechanism in a murine model of allergic airway inflammation induced by OVA (ovalbumin) in the presence of SEB.

METHODS

Superantigen-induced allergic inflammation was studied in IL-1R knockout (KO) mice exposed to OVA+SEB. Multicolor flow cytometry was used to analyze the inflammatory cell profile in airways and lymph nodes. Production of IL-4, IL-5, IL-10, and IL-13 in lymph nodes was assessed by Luminex technology.

RESULTS

In wild-type mice, endonasal instillation of OVA+SEB induced a pulmonary inflammation, characterized by an increase in the number of eosinophils, T cells, and dendritic cells and in the production of Th2 cytokines and OVA-specific IgE. In IL-1R KO mice exposed to OVA+SEB, attraction of CD4+ cells and production of Th2 cytokines were reduced. However, knocking out IL-1R did not affect any of the features of allergic airway inflammation, such as bronchial eosinophilia, OVA-specific IgE production and goblet cell metaplasia.

CONCLUSION

We provide new insights into the mechanisms of airways allergy development in the presence of bacterial superantigen. The asthma features induced by OVA+SEB, such as bronchial eosinophilia, goblet cell proliferation, production of OVA-specific IgE and increase in inflammatory dendritic cells, are IL-1R independent. Yet, IL-1R signaling is crucial for CD4 cell accumulation and Th2 cytokine production.

Cigarette smoke increases Staphylococcus aureus biofilm formation via oxidative stress

The strong epidemiological association between cigarette smoke (CS) exposure and respiratory tract infections is conventionally attributed to immunosuppressive and irritant effects of CS on human cells. Since pathogenic bacteria such as Staphylococcus aureus are members of the normal microbiota and reside in close proximity to human nasopharyngeal cells, we hypothesized that bioactive components of CS might affect these organisms and potentiate their virulence. Using Staphylococcus aureus as a model organism, we observed that the presence of CS increased both biofilm formation and host cell adherence. Analysis of putative molecular pathways revealed that CS exposure decreased expression of the quorum-sensing agr system, which is involved in biofilm dispersal, and increased transcription of biofilm inducers such as sarA and rbf. CS contains bioactive compounds, including free radicals and reactive oxygen species, and we observed transcriptional induction of bacterial oxidoreductases, including superoxide dismutase, following exposure. Moreover, pretreatment of CS with an antioxidant abrogated CS-mediated enhancement of biofilms. Exposure of bacteria to hydrogen peroxide alone increased biofilm formation. These observations are consistent with the hypothesis that CS induces staphylococcal biofilm formation in an oxidant-dependent manner. CS treatment induced transcription of fnbA (encoding fibronectin binding protein A), leading to increased binding of CS-treated staphylococci to immobilized fibronectin and increased adherence to human cells. These observations indicate that the bioactive effects of CS may extend to the resident microbiota of the nasopharynx, with implications for the pathogenesis of respiratory infection in CS-exposed humans.