IL-17A Is Elevated in End-Stage Chronic Obstructive Pulmonary Disease and Contributes to Cigarette Smoke–induced Lymphoid Neogenesis

Reduced Tolerogenic Program Death-Ligand 1-Expressing Conventional Type 1 Dendritic Cells Are Associated with Rapid Decline in Chronic Obstructive Pulmonary Disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is characterized, at least in part, by autoimmunity through amplified T helper 1 and 17 (Th1 and Th17) immune responses. The loss of immune tolerance controlled by programmed death-ligand 1 (PD-L1) may contribute to this.

OBJECTIVES

We studied the tolerogenic role of PD-L1+ dendritic cells (DCs) and their subtypes in relation to specific T cell immunity and the clinical phenotypes of COPD.

METHODS

We used flow cytometry to analyze PD-L1 expression by the DCs and their subtypes in the peripheral blood mononuclear cells (PBMCs) from normal participants and those with COPD. T cell proliferation and the signature cytokines of T cell subtypes stimulated with elastin as autoantigens were measured using flow cytometry and enzyme-linked immunosorbent assays (ELISA), respectively.

MEASUREMENT AND MAIN RESULTS

A total of 83 participants were enrolled (normal, n = 29; COPD, n = 54). A reduced PD-L1+ conventional dendritic cell 1 (cDC1) ratio in the PBMCs of the patients with COPD was shown (13.7 ± 13.7%, p = 0.03). The decrease in the PD-L1+ cDC1 ratio was associated with a rapid decline in COPD (p = 0.02) and correlated with the CD4+ T cells (r = -0.33, p = 0.02). This is supported by the NCBI GEO database accession number GSE56766, the researchers of which found that the gene expressions of PD-L1 and CD4, but not CD8 were negatively correlated from PBMC in COPD patients (r = -0.43, p = 0.002). Functionally, the PD-L1 blockade enhanced CD4+ T cell proliferation stimulated by CD3/elastin (31.2 ± 22.3%, p = 0.04) and interleukin (IL)-17A production stimulated by both CD3 (156.3 ± 54.7, p = 0.03) and CD3/elastin (148 ± 64.9, p = 0.03) from the normal PBMCs. The PD-L1 blockade failed to increase IL-17A production in the cDC1-depleted PBMCs. By contrast, there was no significant change in interferon (IFN)-γ, IL-4, or IL-10 after the PD-L1 blockade. Again, these findings were supported by the NCBI GEO database accession number GSE56766, the researchers of which found that only the expression of RORC, a master transcription factor driving the Th17 cells, was significantly negatively correlated to PD-L1 (r = -0.33, p = 0.02).

CONCLUSIONS

Circulating PD-L1+ cDC1 was reduced in the patients with COPD, and the tolerogenic role was suppressed with susceptibility to self-antigens and linked to rapid decline caused by Th17-skewed chronic inflammation.

Exploring the relationship between Treg-mediated risk in COPD and lung cancer through Mendelian randomization analysis and scRNA-seq data integration

BACKGROUND

Evidence from observational studies suggests an association between chronic obstructive pulmonary disease (COPD) and lung cancer. The potential interactions between the immune system and the lungs may play a causative role in COPD and lung cancer and offer therapeutic prospects. However, the causal association and the immune-mediated mechanisms between COPD and lung cancer remain to be determined.

METHODS

We employed a two-sample Mendelian randomization (MR) approach to investigate the causal association between COPD and lung cancer. Additionally, we examined whether immune cell signals were causally related to lung cancer, as well as whether COPD was causally associated with immune cell signals. Furthermore, through two-step Mendelian randomization, we investigated the mediating effects of immune cell signals in the causal association between COPD and lung cancer. Leveraging publicly available genetic data, our analysis included 468,475 individuals of European ancestry with COPD, 492,803 individuals of European ancestry with lung cancer, and 731 immune cell signatures of European ancestry. Additionally, we conducted single-cell transcriptome sequencing analysis on COPD, lung cancer, and control samples to validate our findings.

FINDINGS

We found a causal association between COPD and lung cancer (odds ratio [OR] = 1.63, 95% confidence interval [CI] = 1.31-2.02, P-value < 0.001). We also observed a causal association between COPD and regulatory T cells (odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.01-1.40, P-value < 0.05), as well as a causal association between regulatory T cells and lung cancer (odds ratio [OR] = 1.02, 95% confidence interval [CI] = 1.002-1.045, P-value < 0.05). Furthermore, our two-step Mendelian randomization analysis demonstrated that COPD is associated with lung cancer through the mediation of regulatory T cells. These findings were further validated through single-cell sequencing analysis, confirming the mediating role of regulatory T cells in the association between COPD and lung cancer.

INTERPRETATION

As far as we are aware, we are the first to combine single-celled immune cell data with two-sample Mendelian randomization. Our analysis indicates a causal association between COPD and lung cancer, with regulatory T cells playing an intermediary role.

Inflammation as the nexus: exploring the link between acute myocardial infarction and chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD), particularly following acute exacerbations (AE-COPD), significantly heightens the risks and mortality associated with acute myocardial infarction (AMI). The intersection of COPD and AMI is characterised by a considerable overlap in inflammatory mechanisms, which play a crucial role in the development of both conditions. Although extensive research has been conducted on individual inflammatory pathways in AMI and COPD, the understanding of thrombo-inflammatory crosstalk in comorbid settings remains limited. The effectiveness of various inflammatory components in reducing AMI infarct size or slowing COPD progression has shown promise, yet their efficacy in the context of comorbidity with COPD and AMI is not established. This review focuses on the critical importance of both local and systemic inflammation, highlighting it as a key pathophysiological connection between AMI and COPD/AE-COPD.

Phenotypes, Etiotypes, and Endotypes of Exacerbations of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease is a major health problem with a high prevalence, a rising incidence, and substantial morbidity and mortality. Its course is punctuated by acute episodes of increased respiratory symptoms, termed exacerbations of chronic obstructive pulmonary disease (ECOPD). ECOPD are important events in the natural history of the disease, as they are associated with lung function decline and prolonged negative effects on quality of life. The present-day therapy for ECOPD with short courses of antibiotics and steroids and escalation of bronchodilators has resulted in only modest improvements in outcomes. Recent data indicate that ECOPD are heterogeneous, raising the need to identify distinct etioendophenotypes, incorporating traits of the acute event and of patients who experience recurrent events, to develop novel and targeted therapies. These characterizations can provide a complete clinical picture, the severity of which will dictate acute pharmacological treatment, and may also indicate whether a change in maintenance therapy is needed to reduce the risk of future exacerbations. In this review we discuss the latest knowledge of ECOPD types on the basis of clinical presentation, etiology, natural history, frequency, severity, and biomarkers in an attempt to characterize these events.

Lymphatic Dysfunction Models an Autoimmune Emphysema Phenotype of Chronic Obstructive Pulmonary Disease

Chronic Obstructive Pulmonary Disease (COPD) is a heterogeneous disease that is characterized by many clinical phenotypes. One such phenotype of COPD is defined by emphysema, pathogenic lung tertiary lymphoid organs (TLOs), and autoantibody production. We have previously shown that lymphatic dysfunction can cause lung TLO formation and lung injury in mice. We now sought to uncover whether underlying lymphatic dysfunction may be a driver of lung injury in cigarette smoke (CS)-induced COPD. We found that lung TLOs in mice with lymphatic dysfunction produce autoantibodies and are associated with a lymphatic endothelial cell subtype that expresses antigen presentation genes. Mice with underlying lymphatic dysfunction develop increased emphysema after CS exposure, with increased size and activation of TLOs. CS further increased autoantibody production in mice with lymphatic dysfunction. B-cell blockade prevented TLO formation and decreased lung injury after CS in mice with lymphatic dysfunction. Using tissue from human COPD patients, we also found evidence of a lymphatic gene signature that was specific to patients with emphysema and prominent TLOs compared to COPD patients without emphysema. Taken together, these data suggest that lymphatic dysfunction may underlie lung injury in a subset of COPD patients with an autoimmune emphysema phenotype.

Association Between IL-17 and Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-Analysis

Background

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease characterized by neutrophils airway infiltration. It is currently known that Interleukin-17 (IL-17) is an important pro-inflammatory factor. It can promote the accumulation of neutrophils and participate in the chronic inflammatory process of COPD. However, the value of IL-17 levels in the diagnosis and assessment of COPD remains controversial. In view of this, we conducted a systematic review and meta-analysis to assess its relevance.

Methods

We searched databases such as PubMed, Web of Science, Cochrane Library and Embase to extract original research.

Results

A total of 10 studies with 2268 participants were included in this meta-analysis. The results showed that the level of serum IL-17 in patients with stable COPD was significantly higher than that in healthy controls (standard mean difference SMD, 1.59, 95% CI 0.84-2.34; p<0.001). Compared with the stable COPD group, the serum IL-17 level in acute exacerbation (AECOPD) was significantly higher (SMD, 1.78, 95% CI 1.22-2.33; p<0.001). The level of IL-17 in sputum of COPD patients was also higher than that of healthy controls (SMD, 2.03, 95% CI 0.74-3.31; p<0.001).

Conclusion

Our results showed that IL-17 levels were elevated in serum and sputum in COPD patients compared with healthy controls, and IL-17 levels increased with disease progression. IL-17 serves as a potential biomarker to indicate the persistence of neutrophilic inflammation and exacerbation of COPD.

Neutrophil Extracellular Traps in Airway Diseases: Pathological Roles and Therapeutic Implications

Neutrophils are important effector cells of the innate immune response that fight pathogens by phagocytosis and degranulation. Neutrophil extracellular traps (NETs) are released into the extracellular space to defend against invading pathogens. Although NETs play a defensive role against pathogens, excessive NETs can contribute to the pathogenesis of airway diseases. NETs are known to be directly cytotoxic to the lung epithelium and endothelium, highly involved in acute lung injury, and implicated in disease severity and exacerbation. This review describes the role of NET formation in airway diseases, including chronic rhinosinusitis, and suggests that targeting NETs could be a therapeutic strategy for airway diseases.

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.

Biologic therapies for chronic obstructive pulmonary disease

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is a disorder characterized by a complicated chronic inflammatory response that is resistant to corticosteroid therapy. As a result, there is a critical need for effective anti-inflammatory medications to treat people with COPD. Using monoclonal antibodies (mAbs) to inhibit cytokines and chemokines or their receptors could be a potential approach to treating the inflammatory component of COPD.

AREAS COVERED

The therapeutic potential that some of these mAbs might have in COPD is reviewed.

EXPERT OPINION

No mAb directed against cytokines or chemokines has shown any therapeutic impact in COPD patients, apart from mAbs targeting the IL-5 pathway that appear to have statistically significant, albeit weak, effect in patients with eosinophilic COPD. This may reflect the complexity of COPD, in which no single cytokine or chemokine has a dominant role. Because the umbrella term COPD encompasses several endotypes with diverse underlying processes, mAbs targeting specific cytokines or chemokines should most likely be evaluated in limited and focused populations.

Seeds of Ginkgo biloba L. inhibit oxidative stress and inflammation induced by cigarette smoke in COPD rats through the Nrf2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional medicine, seeds of Ginkgo biloba L. (Gbs) have been used to treat cough or asthma for a long time. It is commonly used in clinic for lung diseases. However, its mechanism of lung protection is not completely clear.

AIMS OF THE STUDY

This research was designed to explore the protective effects of Gbs on antioxidant and inflammation during the chronic obstructive pulmonary disease (COPD) pathological process provoked by cigarette smoking (CS) in rats.

MATERIALS AND METHODS

Six random groups including control group, CS model group, Gbs intervention groups (25 mg/kg, 50 mg/kg, and 100 mg/kg) and aminophylline group were composed of forty-eight rats. Smoking and intratracheal instillation of lipopolysaccharide (LPS) were used to establish the COPD rat model. Glutathione peroxidase (GSH-PX), malondialdehyde (MDA), superoxide dismutase (SOD), and enzyme-linked immunosorbent assay (ELISA) was used for quantifying the inflammatory factors such as IL-8, IL-6, IL-10, IL-17 and TNF-α. Western blotting were used for detecting the protein expressions of Nrf2, Keap1 and HO-1 in the lung tissues.

RESULTS

Gbs inhibits lung histological changes and decreased the inflammatory factors in both bronchoalveolar lavage fluid (BALF) and serum of CS-exposed rats, including IL-10, IL-17, IL-6, IL-8 and TNF-α. Gbs also inhibited the MDA level, increased SOD and GSH-PX activity in serum and changed expressions of Nrf2, Keap1 and HO-1 in the lung tissues.

CONCLUSION

Gbs inhibit oxidative stress and inflammation induced by cigarette smoke in COPD rats through the Nrf2 Pathway.

YPL-001 Shows Various Beneficial Effects against Cigarette Smoke Extract-Induced Emphysema Formation: Anti-Inflammatory, Anti-Oxidative, and Anti-Apoptotic Effects

Inflammation, oxidative stress, and apoptosis are thought to be important causes of chronic obstructive pulmonary disease (COPD). We investigated the effect of YPL-001 (under phase 2a study, ClinicalTrials.gov identifier NCT02272634), a drug derived from Pseudolysimachion rotundum var. subintegrum, on cigarette smoke extract (CSE)-induced inflammation, the anti-oxidative pathway, and apoptosis in human lung epithelial cells and on CSE-induced emphysema in mice. YPL-001 suppressed CSE-induced expression of IL8 mRNA and protein. This was due to the reduction in NF-κB transcriptional activity by YPL-001, which resulted from the blockade of acetylation of the NF-κB subunit p65 (Lys310). Histone deacetylases (HDACs) prevent gene transcription by condensing the DNA structure and affecting NF-κB nuclear binding. YPL-001 alone increased HDAC2 activity and enhanced CSE-induced activation of HDAC2. YPL-001-induced suppression of NF-κB transcriptional activity might be caused by increased HDAC2 activity. YPL-001 increased nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression via both degradation of its inhibitory protein, Kelch-like ECH-associated protein 1, and an increase in de novo protein synthesis. YPL-001 increased the DNA binding activity of Nrf2. Consequently, YPL-001 upregulated the expression of Nrf2-targeted anti-oxidant genes such as NAD(P)H quinone dehydrogenase 1 and heme oxygenase 1. Moreover, YPL-001 significantly suppressed CSE-induced apoptotic cell death. In vivo study showed that CSE-induced emphysematous changes, neutrophilic inflammation, protein leakage into bronchoalveolar space, and lung cell apoptosis in mice were suppressed by YPL-001 treatment. Taken together, these results suggest that YPL-001 is a good therapeutic candidate for the treatment of COPD by blocking inflammation and apoptosis and activating the anti-oxidative pathway.

IL-17A Promotes Epithelial ADAM9 Expression in Cigarette Smoke-Related COPD

Background

It has been reported that a disintegrin and metalloproteinase 9 (ADAM9) is involved in the pathogenesis of cigarette smoke (CS)-associated chronic obstructive pulmonary disease (COPD). But how CS exposure leads to upregulation of ADAM9 remains unknown.

Methods

Patients who underwent lobectomy for a solitary pulmonary nodule were enrolled and divided into three groups: non-smokers with normal lung function, smokers without COPD and smoker patients with COPD. Immunoreactivity of interleukin (IL)-17A and ADAM9 in small airways and alveolar walls was measured by immunohistochemistry. Wild-type and Il17a^−/− C57BL/6 mice were exposed to CS for six months, and ADAM9 expression in the airway epithelia was measured by immunoreactivity. In addition, the protein and mRNA expression levels of IL-17A and ADAM9 were assessed in CS extract (CSE) and/or IL-17A-treated human bronchial epithelial (HBE) cells.

Results

The immunoreactivity of ADAM9 was increased in the airway epithelia and alveolar walls of patients with COPD compared to that of the controls. The expression of IL-17A was also upregulated in airway epithelial cells of patients with COPD and correlated positively with the level of ADAM9. The results from the animal model showed that Il17a^−/− mice were protected from emphysema induced by CS exposure, together with a reduced level of ADAM9 expression in the airway epithelia, suggesting a possible link between ADAM9 and IL-17A. Consistently, our in vitro cell model showed that CSE stimulated the expression of ADAM9 and IL-17A in HBE cells in a dose- and time-dependent manner. Recombinant IL-17A induced ADAM9 upregulation in HBE cells and had a synergistic effect with CSE, whereas blocking IL-17A inhibited CSE-induced ADAM9 expression. Further analysis revealed that IL-17A induced c-Jun N-terminal kinase (JNK) phosphorylation, thereby increasing ADAM9 expression.

Conclusion

Our results revealed a novel role of IL-17A in CS-related COPD, where IL-17A contributes to ADAM9 expression by activating JNK signaling.

Dynamically upregulated mast cell CPA3 patterns in chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis

Background

The mast cell-specific metalloprotease CPA3 has been given important roles in lung tissue homeostasis and disease pathogenesis. However, the dynamics and spatial distribution of mast cell CPA3 expression in lung diseases remain unknown.

Methods

Using a histology-based approach for quantitative spatial decoding of mRNA and protein single cell, this study investigates the dynamics of CPA3 expression across mast cells residing in lungs from control subjects and patients with severe chronic obstructive pulmonary disease (COPD) or idiopathic lung fibrosis (IPF).

Results

Mast cells in COPD lungs had an anatomically widespread increase of CPA3 mRNA (bronchioles p &lt; 0.001, pulmonary vessels p &lt; 0.01, and alveolar parenchyma p &lt; 0.01) compared to controls, while granule-stored CPA3 protein was unaltered. IPF lungs had a significant upregulation of both mast cell density, CPA3 mRNA (p &lt; 0.001) and protein (p &lt; 0.05), in the fibrotic alveolar tissue. Spatial expression maps revealed altered mast cell mRNA/protein quotients in lung areas subjected to disease-relevant histopathological alterations. Elevated CPA3 mRNA also correlated to lung tissue eosinophils, CD3 T cells, and declined lung function. Single-cell RNA sequencing of bronchial mast cells confirmed CPA3 as a top expressed gene with potential links to both inflammatory and protective markers.

Conclusion

This study shows that lung tissue mast cell populations in COPD and IPF lungs have spatially complex and markedly upregulated CPA3 expression profiles that correlate with immunopathological alterations and lung function. Given the proposed roles of CPA3 in tissue homeostasis, remodeling, and inflammation, these alterations are likely to have clinical consequences.

IL-17 Cytokines and Chronic Lung Diseases

IL-17 cytokines are expressed by numerous cells (e.g., gamma delta (γδ) T, innate lymphoid (ILC), Th17, epithelial cells). They contribute to the elimination of bacteria through the induction of cytokines and chemokines which mediate the recruitment of inflammatory cells to the site of infection. However, IL-17-driven inflammation also likely promotes the progression of chronic lung diseases, such as chronic obstructive pulmonary disease (COPD), lung cancer, cystic fibrosis, and asthma. In this review, we highlight the role of IL-17 cytokines in chronic lung diseases.

Advancing Lung Immunology Research: An Official American Thoracic Society Workshop Report

The mammalian airways and lungs are exposed to a myriad of inhaled particulate matter, allergens, and pathogens. The immune system plays an essential role in protecting the host from respiratory pathogens, but a dysregulated immune response during respiratory infection can impair pathogen clearance and lead to immunopathology. Furthermore, inappropriate immunity to inhaled antigens can lead to pulmonary diseases. A complex network of epithelial, neural, stromal, and immune cells has evolved to sense and respond to inhaled antigens, including the decision to promote tolerance versus a rapid, robust, and targeted immune response. Although there has been great progress in understanding the mechanisms governing immunity to respiratory pathogens and aeroantigens, we are only beginning to develop an integrated understanding of the cellular networks governing tissue immunity within the lungs and how it changes after inflammation and over the human life course. An integrated model of airway and lung immunity will be necessary to improve mucosal vaccine design as well as prevent and treat acute and chronic inflammatory pulmonary diseases. Given the importance of immunology in pulmonary research, the American Thoracic Society convened a working group to highlight central areas of investigation to advance the science of lung immunology and improve human health.

Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity, mortality, and health-care use worldwide. COPD is caused by exposure to inhaled noxious particles, notably tobacco smoke and pollutants. However, the broad range of factors that increase the risk of development and progression of COPD throughout the life course are increasingly being recognised. Innovations in omics and imaging techniques have provided greater insight into disease pathobiology, which might result in advances in COPD prevention, diagnosis, and treatment. Although few novel treatments have been approved for COPD in the past 5 years, advances have been made in targeting existing therapies to specific subpopulations using new biomarker-based strategies. Additionally, COVID-19 has undeniably affected individuals with COPD, who are not only at higher risk for severe disease manifestations than healthy individuals but also negatively affected by interruptions in health-care delivery and social isolation. This Seminar reviews COPD with an emphasis on recent advances in epidemiology, pathophysiology, imaging, diagnosis, and treatment.

An inhibitor of RORγ for chronic pulmonary obstructive disease treatment

The role of RORγ as a transcription factor for Th17 cell differentiation and thereby regulation of IL-17 levels is well known. Increased RORγ expression along with IL-17A levels was observed in animal models, immune cells and BAL fluid of COPD patients. Increased IL-17A levels in severe COPD patients are positively correlated with decreased lung functions and increased severity symptoms and emphysema, supporting an urgency to develop novel therapies modulating IL-17 or RORγ for COPD treatment. We identified a potent RORγ inhibitor, PCCR-1 using hit to lead identification followed by extensive lead optimization by structure–activity relationship. PCCR-1 resulted in RORγ inhibition with a high degree of specificity in a biochemical assay, with > 300-fold selectivity over other isoforms of ROR. Our data suggest promising potency for IL-17A inhibition in human and canine PBMCs and mouse splenocytes with no significant impact on Th1 and Th2 cytokines. In vivo, PCCR-1 exhibited significant efficacy in the acute CS model with dose-dependent inhibition of the PD biomarkers that correlated well with the drug concentration in lung and BAL fluid, demonstrating an acceptable safety profile. This inhibitor effectively inhibited IL-17A release in whole blood and BALf samples from COPD patients. Overall, we identified a selective inhibitor of RORγ to pursue further development of novel scaffolds for COPD treatment.

Tissue-Dependent Adaptations and Functions of Innate Lymphoid Cells

Tissue-resident immune cells reside in distinct niches across organs, where they contribute to tissue homeostasis and rapidly respond to perturbations in the local microenvironment. Innate lymphoid cells (ILCs) are a family of innate immune cells that regulate immune and tissue homeostasis. Across anatomical locations throughout the body, ILCs adopt tissue-specific fates, differing from circulating ILC populations. Adaptations of ILCs to microenvironmental changes have been documented in several inflammatory contexts, including obesity, asthma, and inflammatory bowel disease. While our understanding of ILC functions within tissues have predominantly been based on mouse studies, development of advanced single cell platforms to study tissue-resident ILCs in humans and emerging patient-based data is providing new insights into this lymphocyte family. Within this review, we discuss current concepts of ILC fate and function, exploring tissue-specific functions of ILCs and their contribution to health and disease across organ systems.

[Population rearrangement of B-lymphocytes expressing chemokine receptors in patients with chronic obstructive pulmonary disease]

To date, there are no drugs that can prevent progressive destruction of lung tissue and small airway fibrosis in patients with chronic obstructive pulmonary disease (COPD). Therefore, molecular mechanisms of this disease are being studied. The aim of this study was to determine the chemokine receptor expression pattern of B-lymphocytes from peripheral blood and airways of patients with COPD. Peripheral blood was collected from 51 smokers with COPD, 21 healthy smokers, and 20 healthy non-smokers. Seven smokers with COPD and 7 healthy smokers were recruited to undergo bronchoscopy with bronchoalveolar lavage (BAL). The expression of chemokine receptors CCR5, CCR6, CCR7, CXCR3, CXCR4, and CXCR5 on the surface of blood and BAL B-lymphocytes was determined by flow cytometry. It was found that the percentage of blood B-lymphocytes expressing chemokine receptors CCR5 and CXCR3 was higher in smokers with COPD compared with healthy smokers and healthy non-smokers. The percentage of CD27⁺ B-cells expressing CCR5 and CXCR3 receptors exceeded the proportion of CD27⁻ B-lymphocytes expressing these receptors in peripheral blood of patients with COPD and healthy controls. In smoking patients with COPD, the percentage of BAL B-cells expressing receptors CCR5 and CXCR3 was also increased compared with healthy smokers. There were no differences in the percentage of B-lymphocytes expressing receptors CXCR4, CXCR5, CCR6, and CCR7 in both peripheral blood and BAL between smokers with COPD and healthy smokers. A greater percentage of CD27⁻ B-lymphocytes than CD27⁺ B-cells expressed receptors CXCR4, CXCR5, CCR6, and CCR7 in the peripheral blood of smokers with COPD and healthy controls. The results of this study indicate a modification in the chemokine receptor profile of B-lymphocytes in COPD.

Interleukin-17A mediates tobacco smoke-induced lung cancer epithelial-mesenchymal transition through transcriptional regulation of ΔNp63α on miR-19

Interleukin-17A (IL-17A) is an essential inflammatory cytokine in the progress of carcinogenesis. Tobacco smoke (TS) is a major risk factor of lung cancer that influences epithelial-mesenchymal transition (EMT) process. However, the potential mechanism by which IL-17A mediates the progression of lung cancer in TS-induced EMT remains elusive. In the present study, it was revealed that the IL-17A level was elevated in lung cancer tissues, especially in tumor tissues of cases with experience of smoking, and a higher IL-17A level was correlated with induction of EMT in those specimens. Moreover, the expression of ΔNp63α was increased in IL-17A-stimulated lung cancer cells. ΔNp63α functioned as a key oncogene that bound to the miR-17-92 cluster promoter and transcriptionally increased the expression of miR-19 in lung cancer cells. Overexpression of miR-19 promoted EMT in lung cancer with downregulation of E-cadherin and upregulation of N-cadherin, while its inhibition suppressed EMT. Finally, the upregulated levels of IL-17A, ΔNp63α, and miR-19 along with the alteration of EMT-associated biomarkers were found in lung tissues of TS-exposed mice. Taken together, the abovementioned results suggest that IL-17A increases ΔNp63α expression, transcriptionally elevates miR-19 expression, and promotes TS-induced EMT in lung cancer. These findings may provide a new insight for the identification of therapeutic targets for lung cancer.

Pathogenesis of COPD at the cellular and molecular level

Chronic inflammatory responses in the lung of patients with stable mild-to severe forms of COPD play a central role in the definition, comprehension and monitoring of the disease state. A better understanding of the COPD pathogenesis can't avoid a detailed knowledge of these inflammatory changes altering the functional health of the lung during the disease progression. We here summarize and discuss the role and principal functions of the inflammatory cells populating the large, small airways and lung parenchyma of patients with COPD of increasing severity in comparison with healthy control subjects: T and B lymphocytes, NK and Innate Lymphoid cells, macrophages, and neutrophils. The differential inflammatory distribution in large and small airways of patients is also discussed. Furthermore, relevant cellular mechanisms controlling the homeostasis and the "normal" balance of these inflammatory cells and of structural cells in the lung, such as autophagy, apoptosis, necroptosis and pyroptosis are as well presented and discussed in the context of the COPD severity.

Characterization of the COPD alveolar niche using single-cell RNA sequencing

Chronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide, however our understanding of cell specific mechanisms underlying COPD pathobiology remains incomplete. Here, we analyze single-cell RNA sequencing profiles of explanted lung tissue from subjects with advanced COPD or control lungs, and we validate findings using single-cell RNA sequencing of lungs from mice exposed to 10 months of cigarette smoke, RNA sequencing of isolated human alveolar epithelial cells, functional in vitro models, and in situ hybridization and immunostaining of human lung tissue samples. We identify a subpopulation of alveolar epithelial type II cells with transcriptional evidence for aberrant cellular metabolism and reduced cellular stress tolerance in COPD. Using transcriptomic network analyses, we predict capillary endothelial cells are inflamed in COPD, particularly through increased CXCL-motif chemokine signaling. Finally, we detect a high-metallothionein expressing macrophage subpopulation enriched in advanced COPD. Collectively, these findings highlight cell-specific mechanisms involved in the pathobiology of advanced COPD.

Effect of physical training on cytokine expression in CD4+ T lymphocytes in subjects with stable COPD

Introduction:

Although evidence suggests that physical exercise reduces systemic inflammation, at the plasma level, there are still contradictions in chronic obstructive pulmonary disease (COPD). In this sense, analysis of intracellular cytokines could clear off the effect of physical exercise on the inflammatory profile of these subjects.

Aim:

The aim was to evaluate the effect of physical training on cytokine expression in CD4+ T lymphocytes from subjects with COPD.

Methods:

This is a randomized controlled trial. Subjects with stable COPD were grouped into two groups, exercise and control. In total, 23 subjects with stable COPD were evaluated, of which 15 underwent aerobic strength training [physical exercise group (PEG)] and 8 underwent breathing exercises [respiratory physiotherapy group (RPG)]. Intracellular cytokines [interleukin (IL)-8, IL-13, IL-17, IL-6, IL-2, IL-10, and tumor necrosis factor alpha (TNF-α)] from CD4+ T lymphocytes were analyzed from peripheral blood through flow cytometry, before and after 8 weeks of intervention.

Results:

The PEG and RPG groups had a mean age of 68 ± 5.96 and 72.25 ± 6.86 years and predicted forced expiratory volume in the first second (FEV₁) of 58.6 ± 15.99% and 39.75 ± 10.39%, respectively. It was possible to detect a significant reduction in IL-8 (p = 0.0125) and an increase in IL-13 (p = 0.0014) and an increase in TNF-α (p < 0.001) in both groups.

Conclusion:

Eight weeks of physical training, both peripheral and respiratory, were able to reduce concentrations of IL-8 and to increase IL-13, and TNF-α in CD4+ T lymphocytes in subjects with stable COPD. The findings reinforce the benefits of interventions in subjects with COPD, revealing data not previously investigated.

The functions of CD4 T-helper lymphocytes in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) has been increasingly accounted for global morbidity and mortality worldwide. Although it is partially reversible, the obstructive ventilatory schema of COPD often causes chronic inflammation that primarily affects peripheral airways, pulmonary parenchyma, and the development of lung lymphoid follicles. Among various T-helper (Th) cell types associated with COPD, Th1, Th2 and Th17 cell numbers are increased in COPD patients, whereas Treg cell number is reduced. Here, we reviewed recent advance in understanding the roles of Th1/Th2 and Th17/Treg in the pathogenesis of COPD and discussed the potential underlying mechanism.

Alteration of immune profiles is associated with pulmonary function and symptoms in patients with chronic obstructive pulmonary disease

Inflammation serves a key role in chronic obstructive pulmonary disease (COPD). However, changes in the immune profiles of patients with COPD remain unclear. The present prospective observational study aimed to determine the expression profiles of immune cells and inflammatory factors of patients with COPD and healthy controls, and to analyze the relationship between immune profiles and smoking history. A total of 140 subjects were enrolled in the present study between September 2018 and April 2019 at West China Hospital of Sichuan University (Chengdu, China). These included 87 patients with stable COPD and 24 patients with acute exacerbated COPD, as well as 29 healthy controls. Baseline characteristics were recorded during the screening period, and levels of immune cells were examined using flow cytometry. In addition, levels of inflammatory factors were measured using ELISAs. The results revealed increased expression of the CD64⁺/CD14⁺ mononuclear phagocyte system (MPS) and CD16⁺CD66⁺ neutrophils, and decreased expression of CD3⁺CD4⁺ T cells and CD3⁺ CD8⁺ T cells (all P<0.05) in the peripheral blood of patients with COPD and smokers relative to non-smoking controls. In addition, significant differences were observed in protein levels of IL-6, IL-1β, TNF-α, TGF-α, IFN-γ, IL-8, IL-17A and CRP among the three groups (all P<0.05). Furthermore, the IL-17A, TNF and NF-κB signaling pathways were found to serve a key role in the inflammatory network of COPD. Pearson's correlation analysis revealed a positive correlation between CD3⁺T lymphocyte counts and pulmonary function, and a negative correlation with smoking and exacerbations. Furthermore, neutrophils and MPS were negatively associated with pulmonary function, and IL-8 was positively associated with cough. There was also a negative association between CRP and IL-17A with pulmonary function but a positive correlation with symptoms and exacerbation. Club cell secretory protein was also negatively associated with emphysema parameters. In conclusion, the present findings revealed significant differences in profiles of immune factors among patients with COPD, smokers and non-smoking controls and their association with clinical characteristics. The clinical trial registration number of the present study is: ChiCTR1800015700 (registered with http://www.chictr.org.cn/index.aspx, 2018/04/16).

Emerging Biological Functions of IL-17A: A New Target in Chronic Obstructive Pulmonary Disease?

Chronic obstructive pulmonary disease (COPD) is a chronic inflammatory disease that causes high rates of disability and mortality worldwide because of severe progressive and irreversible symptoms. During the period of COPD initiation and progression, the immune system triggers the activation of various immune cells, including Regulatory T cells (Tregs), dendritic cells (DCs) and Th17 cells, and also the release of many different cytokines and chemokines, such as IL-17A and TGF-β. In recent years, studies have focused on the role of IL-17A in chronic inflammation process, which was found to play a highly critical role in facilitating COPD. Specially, IL-17A and its downstream regulators are potential therapeutic targets for COPD. We mainly focused on the possibility of IL-17A signaling pathways that involved in the progression of COPD; for instance, how IL-17A promotes airway remodeling in COPD? How IL-17A facilitates neutrophil inflammation in COPD? How IL-17A induces the expression of TSLP to promote the progression of COPD? Whether the mature DCs and Tregs participate in this process and how they cooperate with IL-17A to accelerate the development of COPD? And above associated studies could benefit clinical application of therapeutic targets of the disease. Moreover, four novel efficient therapies targeting IL-17A and other molecules for COPD are also concluded, such as Bufei Yishen formula (BYF), a Traditional Chinese Medicine (TCM), and curcumin, a natural polyphenol extracted from the root of Curcuma longa.

Quantification and role of innate lymphoid cell subsets in Chronic Obstructive Pulmonary Disease

Objectives

Innate lymphoid cells (ILCs) secrete cytokines, such as IFN‐γ, IL‐13 and IL‐17, which are linked to chronic obstructive pulmonary disease (COPD). Here, we investigated the role of pulmonary ILCs in COPD pathogenesis.

Methods

Lung ILC subsets in COPD and control subjects were quantified using flow cytometry and associated with clinical parameters. Tissue localisation of ILC and T‐cell subsets was determined by immunohistochemistry. Mice were exposed to air or cigarette smoke (CS) for 1, 4 or 24 weeks to investigate whether pulmonary ILC numbers and activation are altered and whether they contribute to CS‐induced innate inflammatory responses.

Results

Quantification of lung ILC subsets demonstrated that ILC1 frequency in the total ILC population was elevated in COPD and was associated with smoking and severity of respiratory symptoms (COPD Assessment Test [CAT] score). All three ILC subsets localised near lymphoid aggregates in COPD. In the COPD mouse model, CS exposure in C57BL/6J mice increased ILC numbers at all time points, with relative increases in ILC1 in bronchoalveolar lavage (BAL) fluid. Importantly, CS exposure induced increases in neutrophils, monocytes and dendritic cells that remained elevated in Rag2/Il2rg‐deficient mice that lack adaptive immune cells and ILCs. However, CS‐induced CXCL1, IL‐6, TNF‐α and IFN‐γ levels were reduced by ILC deficiency.

Conclusion

The ILC1 subset is increased in COPD patients and correlates with smoking and severity of respiratory symptoms. ILCs also increase upon CS exposure in C57BL/6J mice. In the absence of adaptive immunity, ILCs contribute to CS‐induced pro‐inflammatory mediator release, but are redundant in CS‐induced innate inflammation.

Exposure to biomass smoke induces pulmonary Th17 cell differentiation by activating TLR2 on dendritic cells in a COPD rat model

Almost three billion people in developing countries are exposed to biomass smoke (BS), which predisposes them to developing chronic obstructive pulmonary disease (COPD). COPD is associated with abnormal innate and adaptive immune responses in the lungs and systemic circulation, but the mechanisms underlying BS-COPD development are uncertain. We investigated the role of dendritic cells (DCs) and interleukin (IL)-17A in BS-COPD. We investigated T helper cell responses in the BS-exposed COPD rat model by flow cytometry, quantitative PCR, and enzyme-linked immunosorbent assays. We conducted ex vivo experiments to determine which antigen-presenting cells induce Th17 cell responses. We evaluated the in vitro effects of BS-related particulate matter (BRPM) (2.5 μm) on the function of bone marrow-derived dendritic cells (BMDCs). We found that BS exposure enhanced Th17 responses in the lungs of the COPD-modelled rats, and the stimulated DCs (but not the macrophages) were sufficient to induce naïve CD4 + T cells to produce IL-17A in ex vivo experiments. BRPM significantly enhanced the maturation and activation of DCs through Toll-like receptor 2 (TLR2), but not TLR4, and induced Th17 responses. Therefore, BS activated lung DCs through TLR2, which led to Th17 responses and emphysema in the rats. This process is possibly therapeutically targetable.

Preclinical studies and the function of IL-17 cytokines in COPD

Chronic obstructive pulmonary disease (COPD) is among the leading causes of death worldwide and imposes a high economic burden to the health systems. COPD is characterized by chronic inflammation of the lung leading to airflow limitation, alveolar tissue destruction, and emphysema. Therefore, anti-inflammatory therapies for the treatment of COPD are of interest. In this review, we focus on the function of the IL-17 cytokines IL-17A and IL-17C, both known to mediate the recruitment of inflammatory cells, in the pathogenesis of COPD. We highlight that the expression of IL-17A and IL-17C is induced by pathogens frequently found in lungs of COPD patients and that targeting IL-17-signaling is an interesting option for the treatment of acute exacerbation of COPD.

Cigarette Smoke-Induced Lymphoid Neogenesis in COPD Involves IL-17/RANKL Pathway

IL-17 is critical in lung lymphoid neogenesis in COPD, but the cellular and molecular mechanisms remain to be elucidated. Receptor activator of nuclear factor-κB ligand (RANKL) functions in lymphoid follicle formation in other organs, whether it is involved in IL-17A-dependent lymphoid neogenesis in COPD is unknown. To elucidate the expression and functional role of IL-17A/RANKL pathway in COPD. We first quantified and localized RANKL, its receptor RANK and IL-17A in lungs of patients with COPD, smokers and non-smokers. Next, IL-17A-/- and wild-type (WT) mice were exposed to air or cigarette smoke (CS) for 24 weeks, and lung lymphoid follicles and RANKL-RANK expression were measured. Lastly, we studied the in vitro biological function of RANKL pertaining to lymphoid neogenesis. We found that the expressions of RANKL-RANK and IL-17A, together with lymphoid follicles, were increased in lung tissues from patients with COPD. In WT mice exposed to CS, RANKL-RANK expressions were prominent in lung lymphoid follicles, which were absent in IL-17A-/- mice exposed to CS. In the lymphoid follicles, RANKL+ cells were identified mostly as B cells and RANK was localized in dendritic cells (DCs). In vitro IL-17A increased the expressions of RANKL in B cells and RANK in DCs, which in turn responded to RANKL stimulation by upregulation of CXCL13. Altogether, these results suggest that B lymphocyte RANKL pathway is involved in IL-17A-dependent lymphoid neogenesis in COPD.

Lung Mast Cells Have a High Constitutive Expression of Carboxypeptidase A3 mRNA That Is Independent from Granule-Stored CPA3

The mast cell granule metalloprotease CPA3 is proposed to have important tissue homeostatic functions. However, the basal CPA3 mRNA and protein expression among mast cell populations has remained poorly investigated. Using a novel histology-based methodology that yields quantitative data on mRNA and protein expression at a single-cell level, the present study maps CPA3 mRNA and protein throughout the MCT and MCTC populations in healthy skin, gut and lung tissues. MCTC cells had both a higher frequency of CPA3 protein-containing cells and a higher protein-staining intensity than the MCT population. Among the tissues, skin MCs had highest CPA3 protein intensity. The expression pattern at the mRNA level was reversed. Lung mast cells had the highest mean CPA3 mRNA staining. Intriguingly, the large alveolar MCT population, that lack CPA3 protein, had uniquely high CPA3 mRNA intensity. A broader multi-tissue RNA analysis confirmed the uniquely high CPA3 mRNA quantities in the lung and corroborated the dissociation between chymase and CPA3 at the mRNA level. Taken together, our novel data suggest a hitherto underestimated contribution of mucosal-like MCT to baseline CPA3 mRNA production. The functional consequence of this high constitutive expression now reveals an important area for further research.

The role of genomic profiling in identifying molecular phenotypes in obstructive lung diseases

PURPOSE OF REVIEW

The biology underlying asthma and chronic obstructive pulmonary disease (COPD) is heterogeneous. Targeting therapies to patient subgroups, or 'molecular phenotypes', based on their underlying biology is emerging as an efficacious treatment strategy. This review summarizes the role of airway sample gene expression profiling in understanding molecular phenotypes in obstructive lung disease.

RECENT FINDINGS

Recent gene expression studies have reinforced the importance of Type two (T2) inflammation in asthma and COPD subgroups. Studies in asthma also suggest that the molecular phenotype with enhanced T2 inflammation is itself heterogeneous with a subgroup that has steroid-refractory inflammation. Other inflammatory pathways are also emerging as implicated in asthma and COPD molecular phenotypes, including Type one and Type 17 adaptive immune responses and proinflammatory cytokines, such as interleukin-6.

SUMMARY

Genomic profiling studies are advancing our understanding of the complex biology contributing to asthma and COPD molecular phenotypes. Recent studies suggest that asthma and COPD subgroups may benefit from different treatment strategies than those currently in practice.

IL-17C contributes to NTHi-induced inflammation and lung damage in experimental COPD and is present in sputum during acute exacerbations

Neutrophilic inflammation results in loss of lung function in chronic obstructive pulmonary disease (COPD). Gram-negative bacteria, such as nontypeable Haemophilus influenzae (NTHi), trigger acute exacerbations of COPD (AECOPD) and contribute to chronic lung inflammation. The pro-inflammatory cytokine interleukin-17C (IL-17C) is expressed by airway epithelial cells and regulates neutrophilic chemotaxis. Here, we explored the function of IL-17C in NTHi- and cigarette smoke (CS)-induced models of COPD. Neutrophilic inflammation and tissue destruction were decreased in lungs of IL-17C-deficient mice (Il-17c-/-) chronically exposed to NTHi. Numbers of pulmonary neutrophils were decreased in Il-17c-/- mice after acute exposure to the combination of NTHi and CS. However, Il-17c-/- mice were not protected from CS-induced lung inflammation. In a preliminary patient study, we show that IL-17C is present in sputum samples obtained during AECOPD and associates with disease severity. Concentrations of IL-17C were significantly increased during advanced COPD (GOLD III/IV) compared to moderate COPD (GOLD I/II). Concentrations of IL-17A and IL-17E did not associate with disease severity. Our data suggest that IL-17C promotes harmful pulmonary inflammation triggered by bacteria in COPD.

Human Lung Conventional Dendritic Cells Orchestrate Lymphoid Neogenesis during Chronic Obstructive Pulmonary Disease

Rationale: Emerging evidence supports a crucial role for tertiary lymphoid organs (TLOs) in chronic obstructive pulmonary disease (COPD) progression. However, mechanisms of immune cell activation leading to TLOs in COPD remain to be defined.Objectives: To examine the role of lung dendritic cells (DCs) in T follicular helper (Tfh)-cell induction, a T-cell subset critically implicated in lymphoid organ formation, in COPD.Methods: Myeloid cell heterogeneity and phenotype were studied in an unbiased manner via single-cell RNA sequencing on HLA-DR⁺ cells sorted from human lungs. We measured the in vitro capability of control and COPD lung DC subsets, sorted using a fluorescence-activated cell sorter, to polarize IL-21⁺CXCL13⁺ (IL-21-positive and C-X-C chemokine ligand type 13-positive) Tfh-like cells. In situ imaging analysis was performed on Global Initiative for Chronic Obstructive Lung Disease stage IV COPD lungs with TLOs.Measurements and Main Results: Single-cell RNA-sequencing analysis revealed a high degree of heterogeneity among human lung myeloid cells. Among these, conventional dendritic type 2 cells (cDC2s) showed increased induction of IL-21⁺CXCL13⁺ Tfh-like cells. Importantly, the capacity to induce IL-21⁺ Tfh-like cells was higher in cDC2s from patients with COPD than in those from control patients. Increased Tfh-cell induction by COPD cDC2s correlated with increased presence of Tfh-like cells in COPD lungs as compared with those in control lungs, and cDC2s colocalized with Tfh-like cells in TLOs of COPD lungs. Mechanistically, cDC2s exhibited a unique migratory signature and (transcriptional) expression of several pathways and genes related to DC-induced Tfh-cell priming. Importantly, blocking the costimulatory OX40L (OX40 ligand)-OX40 axis reduced Tfh-cell induction by control lung cDC2s.Conclusions: In COPD lungs, we found lung EBI2⁺ (Epstein-Barr virus-induced gene 2-positive) OX-40L-expressing cDC2s that induced IL-21⁺ Tfh-like cells, suggesting an involvement of these cells in TLO formation.

Recent advances in chronic obstructive pulmonary disease pathogenesis: from disease mechanisms to precision medicine

Chronic obstructive pulmonary disease (COPD) is a devastating lung disease with a high personal and societal burden. Exposure to toxic particles and gases, including cigarette smoke, is the main risk factor for COPD. Together with smoking cessation, current treatment strategies of COPD aim to improve symptoms and prevent exacerbations, but there is no disease-modifying treatment. The biggest drawback of today's COPD treatment regimen is the 'one size fits all' pharmacological intervention, mainly based on disease severity and symptoms and not the individual's disease pathology. To halt the worrying increase in the burden of COPD, disease management needs to be advanced with a focus on personalized treatment. The main pathological feature of COPD includes a chronic and abnormal inflammatory response within the lungs, which results in airway and alveolar changes in the lung as reflected by (small) airways disease and emphysema. Here we discuss recent developments related to the abnormal inflammatory response, ECM and age-related changes, structural changes in the small airways and the role of sex-related differences, which are all relevant to explain the individual differences in the disease pathology of COPD and improve disease endotyping. Furthermore, we will discuss the most recent developments of new treatment strategies using biologicals to target specific pathological features or disease endotypes of COPD. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Interleukin-17A Deficiency Attenuated Emphysema and Bone Loss in Mice Exposed to Cigarette Smoke

Background and Purpose

Chronic obstructive pulmonary disease (COPD) is a common chronic inflammatory disease, which is associated with various comorbidities including osteoporosis. Interleukin(IL)-17 has been reported to play important roles in the pathogenesis of COPD and also associated with bone destruction in inflammatory diseases. However, the role of IL-17A in COPD-related osteoporosis is yet unknown. The purpose of our study was to investigate the potential contribution of IL-17A in COPD-related bone loss.

Materials and Methods

We examined the bone mass and bone microarchitecture in wild-type and IL-17A^-/- mice exposed to long-term cigarette smoke (CS). Osteoclast activities and the expression of receptor activator of nuclear factor-κB ligand (RANKL) in bone tissues were assessed, and the blood levels of inflammatory cytokines were measured.

Results

Less bone loss as well as attenuated emphysema were shown in IL-17A^-/- mice compared with wild-type mice. CS-exposed IL-17A^-/- mice had decreased TRAP+ osteoclast numbers and lower RANKL expression compared with CS-exposed wild-type mice. Inflammatory cytokines including IL-6 and IL-1β in circulation were decreased in IL-17A^-/- mice exposed to CS compared with wild-type mice.

Conclusion

This study indicates that IL-17A is involved in CS-induced bone loss and may be a common link between COPD and osteoporosis.

Sex differences in lymphoid follicles in COPD airways

Background

Female smokers have increased risk for chronic obstructive pulmonary disease (COPD) compared with male smokers who have a similar history of cigarette smoke exposure. Tertiary lymphoid follicles are often found in the lungs of patients with severe COPD but sex-related differences have not been previously investigated. We determined the impact of female sex hormones on chronic cigarette smoke-induced expression of lymphoid aggregates in mice with COPD-like pathologies.

Methods

Lymphoid aggregate counts, total aggregate cross-sectional area and foamy macrophage counts were determined morphometrically in male, female, and ovariectomized mice exposed to air or cigarette smoke for 6 months. B-cell activating factor (BAFF) protein expression and markers of oxidative stress were evaluated in mouse lung tissues by immunofluorescence staining and gene expression analyses. Quantitative histology was performed on lung tissue sections of human COPD lungs to evaluate follicle formation.

Results

Lymphoid follicle and foamy macrophage counts as well as the total follicle cross-sectional area were differentially increased in lung tissues of female mice compared to male mice, and these differences were abolished by ovariectomy. These lymphoid aggregates were positive for CD45, CD20, CD21 and BAFF expression. Differential increases in Mmp12 and Cxcl2 gene expression correlated with an increase in foamy macrophages in parenchymal tissues of female but not male mice after smoke exposure. Parenchymal tissues from female mice failed to induce antioxidant-related genes in response to smoke exposure, and this effect was restored by ovariectomy. 3-nitrotyrosine, a stable marker of oxidative stress, positively correlated with Mmp12 and Cxcl2 gene expression. Hydrogen peroxide induced BAFF protein in mouse macrophage cell line. In human lung tissues, female smokers with severe COPD demonstrated increased numbers of lymphoid follicles compared with males.

Conclusions

Chronic smoke exposure increases the risk of lymphoid aggregate formation in female mice compared with male mice, which is mediated female sex hormones and BAFF expression in an oxidative environment.

Friend or Foe: The Protective and Pathological Roles of Inducible Bronchus-Associated Lymphoid Tissue in Pulmonary Diseases

Inducible bronchus-associated lymphoid tissue (iBALT) is a tertiary lymphoid structure that resembles secondary lymphoid organs. iBALT is induced in the lung in response to Ag exposure. In some cases, such as infection with Mycobacterium tuberculosis, the formation of iBALT structure is indicative of an effective protective immune response. However, with persistent exposure to Ags during chronic inflammation, allergy, or autoimmune diseases, iBALT may be associated with exacerbation of inflammation. iBALT is characterized by well-organized T and B areas enmeshed with conventional dendritic cells, follicular dendritic cells, and stromal cells, usually located surrounding airways or blood vessels. Several of the molecular signals and cellular contributors that mediate formation of iBALT structures have been recently identified. This review will outline the recent findings associated with the formation and maintenance of iBALT and their contributions toward a protective or pathogenic function in pulmonary disease outcome.

Chronic Inflammation: A Common Promoter in Tertiary Lymphoid Organ Neogenesis

Tertiary lymphoid organs (TLOs) frequently develop locally in adults in response to non-resolving inflammation. Chronic inflammation leads to the differentiation of stromal fibroblast cells toward lymphoid tissue organizer-like cells, which interact with lymphotoxin α1β2+ immune cells. The interaction initiates lymphoid neogenesis by recruiting immune cells to the site of inflammation and ultimately leads to the formation of TLOs. Mature TLOs harbor a segregated T-cell zone, B-cell follicles with an activated germinal center, follicular dendritic cells, and high endothelial venules, which architecturally resemble those in secondary lymphoid organs. Since CXCL13 and LTα₁β₂ play key roles in TLO neogenesis, they might constitute potential biomarkers of TLO activity. The well-developed TLOs actively regulate local immune responses and influence disease progression, and they are thereby regarded as the powerhouses of local immunity. In this review, we recapitulated the determinants for TLOs development, with great emphasis on the fundamental role of chronic inflammation and tissue-resident stromal cells for TLO neogenesis, hence offering guidance for therapeutic interventions in TLO-associated diseases.

Targeting Chronic Obstructive Pulmonary Disease Phenotypes, Endotypes, and Biomarkers

Chronic obstructive pulmonary disease (COPD) is now well recognized to be a phenotypically heterogeneous disease, and this heterogeneity is underpinned by biological heterogeneity. An "endotype" is a group of patients who share the same observed characteristic(s) because of shared underlying biology, and the "endotype" concept has emerged as one way of bringing order to this phenotypic heterogeneity by focusing on its biological underpinnings. In principle, biomarkers can help identify endotypes and mark these specific groups of patients as suitable candidates for targeted biological therapies. Among the better-described endotypes of COPD are alpha-1 antitrypsin deficiency and eosinophilic COPD. Both of these endotypes have biomarkers and at least some evidence of preferential benefit from targeted therapy. Other biological pathways that may define endotypes of COPD include more general pathways of type 2 inflammation, IL-17-driven inflammation (due to autoimmunity or deposition of nanoparticulate carbon black), bacterial colonization, pathological alterations of the airway mucus gel, and others that are beyond the scope of this review. Whether these biological pathways ultimately are found to segregate patients into very distinct endotypes or subsets (like alpha-1 antitrypsin deficiency) or, instead, are present as "treatable traits" in various combinations is uncertain. However imperfect, the endotype concept forces a focus on heterogeneity at a biological level, and the development of biomarkers of biological heterogeneity should help advance the goal of developing new therapies for COPD.

Increased IFN-γ-producing Th17/Th1 cells and their association with lung function and current smoking status in patients with chronic obstructive pulmonary disease

Background

Th17 cells are believed to be important proinflammatory cells in the pathogenesis of chronic obstructive pulmonary disease (COPD). Recent evidence demonstrates that Th17 cells display substantial developmental plasticity, giving rise to Th17/Th1 cells that secret both IL-17 and IFN-γ and are more pathogenic in inflammatory diseases. The aim of this study was to examine the distribution of circulating Th17/Th1 subpopulation and its association with disease severity in patients with COPD.

Methods

Blood samples were obtained from 21 never-smokers, 31 smokers with normal lung function and 83 patients with COPD. The frequencies of Th17 cells and the Th17/Th1 subset were measured using flow cytometry. Plasma concentrations of IL-6, transforming growth factor (TGF)-β1 and IL-12 were determined by ELISA. The associations of Th17/Th1 cells with lung function and smoking were evaluated.

Results

In peripheral blood, significantly increased proportions of Th17/Th1 cells among CD4 cells and Th17 cells were found in COPD patients compared with never-smokers and smokers with normal lung function. The percentages of Th17/Th1 cells showed correlations with forced expiratory volume in 1 (FEV₁) % predicted value (r = − 0.244, p < 0.05), and higher proportions of Th17/Th1 cells in GOLD stage IV patients compared with stage I patients. The percentages of Th17/Th1 cells were significantly higher in current smokers compared with ex-smoker COPD patients, and positively correlated with pack-years of smoking (r = 0.352, p < 0.01). The plasma concentrations of IL-6, TGF-β1 and IL-12 were significantly increased in patients with COPD compared with never-smokers and smokers with normal lung function.

Conclusion

Our results revealed correlations of proportions of IFN-γ-producing Th17/Th1 cells with lung function and smoking, suggesting that increased Th17/Th1 cells may play a role in COPD progression.

Innate Lymphoid Cells in Mucosal Immunity

Innate lymphoid cells (ILCs) are innate counterparts of T cells that contribute to immune responses by secreting effector cytokines and regulating the functions of other innate and adaptive immune cells. ILCs carry out some unique functions but share some tasks with T cells. ILCs are present in lymphoid and non-lymphoid organs and are particularly abundant at the mucosal barriers, where they are exposed to allergens, commensal microbes, and pathogens. The impact of ILCs in mucosal immune responses has been extensively investigated in the gastrointestinal and respiratory tracts, as well as in the oral cavity. Here we review the state-of-the-art knowledge of ILC functions in infections, allergy and autoimmune disorders of the mucosal barriers.

An airway epithelial IL-17A response signature identifies a steroid-unresponsive COPD patient subgroup

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a heterogeneous smoking-related disease characterized by airway obstruction and inflammation. This inflammation may persist even after smoking cessation and responds variably to corticosteroids. Personalizing treatment to biologically similar "molecular phenotypes" may improve therapeutic efficacy in COPD. IL-17A is involved in neutrophilic inflammation and corticosteroid resistance, and thus may be particularly important in a COPD molecular phenotype.

METHODS

We generated a gene expression signature of IL-17A response in bronchial airway epithelial brushings from smokers with and without COPD (n = 238), and validated it using data from 2 randomized trials of IL-17 blockade in psoriasis. This IL-17 signature was related to clinical and pathologic characteristics in 2 additional human studies of COPD: (a) SPIROMICS (n = 47), which included former and current smokers with COPD, and (b) GLUCOLD (n = 79), in which COPD participants were randomized to placebo or corticosteroids.

RESULTS

The IL-17 signature was associated with an inflammatory profile characteristic of an IL-17 response, including increased airway neutrophils and macrophages. In SPIROMICS the signature was associated with increased airway obstruction and functional small airways disease on quantitative chest CT. In GLUCOLD the signature was associated with decreased response to corticosteroids, irrespective of airway eosinophilic or type 2 inflammation.

CONCLUSION

These data suggest that a gene signature of IL-17 airway epithelial response distinguishes a biologically, radiographically, and clinically distinct COPD subgroup that may benefit from personalized therapy.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01969344.

FUNDING

Primary support from the NIH, grants K23HL123778, K12HL11999, U19AI077439, DK072517, U01HL137880, K24HL137013 and R01HL121774 and contracts HHSN268200900013C, HHSN268200900014C, HHSN268200900015C, HHSN268200900016C, HHSN268200900017C, HHSN268200900018C, HHSN268200900019C and HHSN268200900020C.

Bronchioloalveolar lung tumors induced in “mice only” by non-genotoxic chemicals are not useful for quantitative assessment of pulmonary adenocarcinoma risk in humans

Chemicals classified as known human carcinogens by International Agency for Research on Cancer (IARC) show a low level of concordance between rodents and humans for induction of pulmonary carcinoma. Rats and mice exposed via inhalation for 2 years show a low level of concordance in both tumor development and organ site location. In 2-year inhalation studies using rats and mice, when pulmonary tumors are seen in only male or female mice or both, but not in either sex of rat, there is a high probability that the murine pulmonary tumor has been produced via Clara cell or club cell (CC) metabolism of the inhaled chemical to a cytotoxic metabolite. Cytotoxicity-induced mitogenesis increases mutagenesis via amplification of the background mutation rate. If the chemical being tested is also negative in the Ames Salmonella mutagenicity assay, and only mouse pulmonary tumors are induced, the probability that this pulmonary tumor is not relevant to human lung cancer risk goes even higher. Mice have a larger percentage of CCs in their distal airways than rats, and a much larger percentage than in humans. The CCs of mice have a much higher concentration of metabolic enzymes capable of metabolizing xenobiotics than CCs in either rats or humans. A principal threat to validity of extrapolating from the murine model lies in the unique capacity of murine CCs to metabolize a significant spectrum of xenobiotics which in turn produces toxicants not seen in rat or human pulmonary pathophysiology.

Role of inflammatory cells in airway remodeling in COPD

COPD is characterized by chronic bronchitis, chronic airway obstruction, and emphysema, leading to a progressive and irreversible decline in lung function. Inflammation is central for the development of COPD. Chronic inflammation in COPD mainly involves the infiltration of neutrophils, macrophages, lymphocytes, and other inflammatory cells into the small airways. The contribution of resident airway structural cells to the inflammatory process is also important in COPD. Airway remodeling consists of detrimental changes in structural tissues and cells including airway wall thickening, epithelial metaplasia, goblet cell hypertrophy, and smooth muscle hyperplasia. Persistent airway inflammation might contribute to airway remodeling and small airway obstruction. However, the underlying mechanisms remain unclear. In this review, we will provide an overview of recent insights into the role of major immunoinflammatory cells in COPD airway remodeling.

IL-17A Attenuates IFN-λ Expression by Inducing Suppressor of Cytokine Signaling Expression in Airway Epithelium

IFN-λ is a cytokine expressed in epithelial tissues and plays a central role in antiviral mucosal immune response. The expression of IFN-λ in the airway is impaired in chronic airway diseases (e.g., asthma, chronic obstructive pulmonary disease), which renders patients susceptible to viral infection. IL-17A is associated with asthma and chronic obstructive pulmonary disease pathogenesis; however, IL-17A regulation of IFN-λ expression remains unclear. The aim of the current study is to clarify IL-17A-mediated regulatory mechanisms of IFN-λ expression in human airway epithelial cells. In this study, we have shown that polyinosinic:polycytidylic acid (polyI:C) and influenza A virus (IAV) infection increased IFN-λ expression at mRNA and protein levels in primary cultures of normal human bronchial epithelial cells, whereas IL-17A attenuated polyI:C- or IAV-induced IFN-λ expression. IFN-λ receptor 1 knockdown and a JAK inhibitor, ruxolitinib, attenuated polyI:C-induced IFN-λ expression, confirming that a positive autocrine feedback loop, the IFN-λ receptor-JAK-STAT pathway, was involved in IFN-λ expression. In Western blotting analysis, we demonstrated that polyI:C and IAV infection induced STAT1 phosphorylation in normal human bronchial epithelial cells, whereas IL-17A suppressed polyI:C- or IAV-mediated STAT1 phosphorylation. Furthermore, we found that cotreatment with IL-17A and polyI:C or IAV infection synergistically increased suppressor of cytokine signaling (SOCS)1 and SOCS3 expression. SOCS1 small interfering RNA and SOCS3 small interfering RNA negated the inhibitory effect of IL-17A in polyI:C-induced IFN-λ expression by restoring attenuated STAT1 phosphorylation. Taken together, these findings indicate that IL-17A attenuates virus-induced IFN-λ expression by enhancing SOCS1 and SOCS3 expression to inhibit autocrine signaling loops in human airway epithelial cells.

Tertiary Lymphoid Structures: Autoimmunity Goes Local

Tertiary lymphoid structures (TLS) are frequently observed in target organs of autoimmune diseases. TLS present features of secondary lymphoid organs such as segregated T and B cell zones, presence of follicular dendritic cell networks, high endothelial venules and specialized lymphoid fibroblasts and display the mechanisms to support local adaptive immune responses toward locally displayed antigens. TLS detection in the tissue is often associated with poor prognosis of disease, auto-antibody production and malignancy development. This review focuses on the contribution of TLS toward the persistence of the inflammatory drive, the survival of autoreactive lymphocyte clones and post-translational modifications, responsible for the pathogenicity of locally formed autoantibodies, during autoimmune disease development.

Influenza A Virus Infection Causes Chronic Lung Disease Linked to Sites of Active Viral RNA Remnants

Clinical and experimental observations suggest that chronic lung disease is linked to respiratory viral infection. However, the long-term aspect of this relationship is not yet defined using a virus that replicates at properly high levels in humans and a corresponding animal model. In this study, we show that influenza A virus infection achieves 1 × 10⁶-fold increases in viral load in the lung and dose-dependent severity of acute illness in mice. Moreover, these events are followed by persistence of negative- and positive-strand viral RNA remnants for 15 wk and chronic lung disease for at least 26 wk postinfection. The disease is manifested by focal areas of bronchiolization and mucus production that contain increased levels of viral RNA remnants along with mucin Muc5ac and Il13 mRNA compared with uninvolved areas of the lung. Excess mucus production and associated airway hyperreactivity (but not fibrosis or emphysema) are partially attenuated with loss of IL-13 production or signaling (using mice with IL-13 or STAT6 deficiency). These deficiencies cause reciprocal increases in l17a mRNA and neutrophils in the lung; however, none of these disease endpoints are changed with IL-13/IL-17a compared with IL-13 deficiency or STAT6/IL-17a compared with STAT6 deficiency. The results establish the capacity of a potent human respiratory virus to produce chronic lung disease focally at sites of active viral RNA remnants, likely reflecting locations of viral replication that reprogram the region. Viral dose dependency of disease also implicates high-level viral replication and severity of acute infection as determinants of chronic lung diseases such as asthma and COPD with IL-13-dependent and IL-13/IL-17-independent mechanisms.