IL-17A and the Promotion of Neutrophilia in Acute Exacerbation of Chronic Obstructive Pulmonary Disease

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.

The Interplay Between Immune Response and Bacterial Infection in COPD: Focus Upon Non-typeable Haemophilus influenzae

Chronic obstructive pulmonary disease (COPD) is a debilitating respiratory disease and one of the leading causes of morbidity and mortality worldwide. It is characterized by persistent respiratory symptoms and airflow limitation due to abnormalities in the lower airway following consistent exposure to noxious particles or gases. Acute exacerbations of COPD (AECOPD) are characterized by increased cough, purulent sputum production, and dyspnea. The AECOPD is mostly associated with infection caused by common cold viruses or bacteria, or co-infections. Chronic and persistent infection by non-typeable Haemophilus influenzae (NTHi), a Gram-negative coccobacillus, contributes to almost half of the infective exacerbations caused by bacteria. This is supported by reports that NTHi is commonly isolated in the sputum from COPD patients during exacerbations. Persistent colonization of NTHi in the lower airway requires a plethora of phenotypic adaptation and virulent mechanisms that are developed over time to cope with changing environmental pressures in the airway such as host immuno-inflammatory response. Chronic inhalation of noxious irritants in COPD causes a changed balance in the lung microbiome, abnormal inflammatory response, and an impaired airway immune system. These conditions significantly provide an opportunistic platform for NTHi colonization and infection resulting in a "vicious circle." Episodes of large inflammation as the consequences of multiple interactions between airway immune cells and NTHi, accumulatively contribute to COPD exacerbations and may result in worsening of the clinical status. In this review, we discuss in detail the interplay and crosstalk between airway immune residents and NTHi, and their effect in AECOPD for better understanding of NTHi pathogenesis in COPD patients.

Updates on T helper type 17 immunity in respiratory disease

Interleukin-17 (IL-17)-producing cells play a critical role in mucosal immunity including the respiratory tract. This review will highlight recent advances in our understanding of these cells in mucosal immunity in the lung as well as their potential pathogenic roles in respiratory diseases. The IL-17-producing cells include γδ T cells, natural killer cells, group 3 innate lymphoid cells, and T helper type 17 (Th17) cells. There have been recent advances in our understanding of these cell populations in the lung as well as emerging data on how these cells are regulated in the lung. Moreover, Th17 cells may be a key component of tissue-resident memory cells that may be acquired over time or elicited by mucosal immunization that provides the host with enhanced immunity against certain pathogens.

Bronchoscopic mucosal cryobiopsies as a method for studying airway disease

BACKGROUND

Investigating disease mechanisms and treatment responses in obstructive airway diseases with invasive sampling are hampered by the small size and mechanical artefacts that conventional forceps biopsies suffer from. Endoscopic cryobiopsies are larger and more intact and are being increasingly used. However, the technique has not yet been explored for obtaining mucosa biopsies.

OBJECTIVE

To investigate differences in size and quality of endobronchial mucosal biopsies obtained with cryotechnique and forceps. Further, to check for eligibility of cryobiopsies to be evaluated with immunohistochemistry and in situ hybridization and to investigate tolerability and safety of the technique.

METHODS

Endobronchial mucosal biopsies were obtained with cryotechnique and forceps from patients with haemoptysis undergoing bronchoscopy and evaluated by quantitative morphometry, automated immunohistochemistry and in situ hybridization.

RESULTS

A total of 40 biopsies were obtained from 10 patients. Cross-sectional areas were threefold larger in cryobiopsies (median: 3.08 mm² (IQR: 1.79) vs 1.03 mm² (IQR: 1.10), P < 0.001). Stretches of intact epithelium were 8-fold longer (median: 4.61 mm (IQR: 4.50) vs 0.55 mm (IQR: 1.23), P = 0.001). Content of glands (median: 0.095 mm² (IQR: 0.30) vs 0.00 mm² (IQR: 0.01), P = 0.002) and airway smooth muscle (median: 0.25 mm² (IQR: 0.30) vs 0.060 mm² (IQR: 0.11), P = 0.02) was higher in the cryobiopsies compared with forceps biopsies. Further, the cryobiopsies had well-preserved protein antigens and mRNA. Mild to moderate bleeding was the only complication observed.

CONCLUSION AND CLINICAL RELEVANCE

By yielding significantly larger and more intact biopsies, the cryotechnique represents a valuable new research tool to explore the bronchi in airway disease. Ultimately with the potential to create better understanding of underlying disease mechanisms and improvement of treatments.

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.

Increased serum IL-17 and decreased serum IL-10 and IL-35 levels correlate with the progression of COPD

Purpose

This study aimed to measure the serum levels of interleukin (IL)-17, IL-10, and IL-35 in patients with stable chronic obstructive pulmonary disease (COPD) and disclose the correlations between their expression levels and clinical factors of patients.

Methods

A total of 75 patients with stable COPD (47 males and 28 females) and 30 healthy controls (15 males and 15 females) were included in this study. The serum levels of IL-17, IL-10, and IL-35 were determined by enzyme-linked immunosorbent assay. The correlations between their expression levels and clinical factors of patients were determined using linear regression methods.

Results

The serum level of IL-17 was upregulated in stable COPD, and increased IL-17 expression was positively correlated with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) grading, modified Medical Research Council (mMRC) score, and long clinical history (P<0.05), but negatively correlated with the pulmonary function (P<0.05) of patients. The serum levels of IL-10 and IL-35 were downregulated in stable COPD, and decreased IL-10 and IL-35 levels negatively correlated with the smoking status, GOLD grading, mMRC score, and long clinical history (P<0.05), but positively correlated with the pulmonary function (P<0.05) of patients. Moreover, the level of IL-17 negatively correlated with IL-10 and IL-35, but IL-10 positively correlated with IL-35.

Conclusion

The serum levels of IL-17, IL-10, and IL-35 correlated with the clinical factors of COPD, indicating that they can serve as indicators to estimate the progression of COPD.

Innate Lymphoid Cells (ILCs) as Mediators of Inflammation, Release of Cytokines and Lytic Molecules

Innate lymphoid cells (ILCs) are an emerging group of immune cells that provide the first line of defense against various pathogens as well as contributing to tissue repair and inflammation. ILCs have been classically divided into three subgroups based on their cytokine secretion and transcription factor profiles. ILC nomenclature is analogous to that of T helper cells. Group 1 ILCs composed of natural killer (NK) cells as well as IFN-γ secreting ILC1s. ILC2s have the capability to produce T_H2 cytokines while ILC3s and lymphoid tissue inducer (LTis) are subsets of cells that are able to secrete IL-17 and/or IL-22. A recent subset of ILC known as ILC4 was discovered, and the cells of this subset were designated as NK17/NK1 due to their release of IL-17 and IFN-γ. In this review, we sought to explain the subclasses of ILCs and their roles as mediators of lytic enzymes and inflammation.

The administration of surfactant decreased oxidative stress in lungs of mice exposed to cigarette smoke

The alveolar surfactant, which composition consists of a unique and complex mixture of lipids and proteins, has immunomodulatory action. This study aimed to evaluate the effects of exogenous surfactant on pulmonary inflammatory response in mice exposed to cigarette smoke (CS). Twenty-four mice C57BL/6 were divided into four groups: control group exposed to ambient air (CG); surfactant treated group (SG); CS exposed group (CSG) and CS exposed group treated with surfactant (CSSG). For five days, CSG and CSSG were exposed to 12 commercial cigarettes/day and SG and CSSG received the surfactant by intranasal instillation. At the end of the experiment, the animals were euthanatized for the collection of bronchoalveolar lavage fluid (BALF) and lungs. The total number of leukocytes in BALF increased in CSG compared to CG, however, there was a decrease in CSSG compared to CSG. There was an increase in lipid peroxidation in SG and CSG compared to CG while there was a decrease in CSSG compared to CSG. Regarding the antioxidant enzymes, the catalase (CAT) activity increased in all groups compared to CG and the superoxide dismutase (SOD) activity decreased in CSG compared to the CG and SG. There was an increase in TNF in SG, CSG and CSSG compared to CG. There was an increase in IL-17 in CSSG compared to CG. There was an increase in CCL5 in SG and CSSG compared to CG. Therefore, our results demonstrated that the administration of exogenous surfactant was able to decrease the oxidative processes in the lungs of mice induced by short-term exposure to CS.

Role of Translocator 18 KDa Ligands in the Activation of Leukotriene B4 Activated G-Protein Coupled Receptor and Toll Like Receptor-4 Pathways in Neutrophils

TSPO (Translocator 18 KDa; tryptophan-rich sensory protein oxygen sensor) is a constitutive outer mitochondrial membrane protein overexpressed in inflammatory cells during local or systemic processes. Despite its expression is characterized, role of TSPO in inflammation remains elusive. For this study, we investigated the role of TSPO ligands on neutrophil functions elicited by two different inflammatory pathways. Peritoneal neutrophils were isolated from male Balb-C mice, treated with TSPO ligand diazepam, Ro5-4864 or PK11195 (1,100 or 1000 nM; 2 h) and further stimulated with lipopolysaccharide from Escherichia coli (LPS), a binding for Toll-Like Receptor-4 (TLR4), or leukotriene B4 (LTB4), a G-protein coupled receptor (GPCR) ligand. LPS treatment did not lead to overexpression of TSPO on neutrophils, and pre-treatment with any TSPO ligand did not alter cytokine expression, adhesion molecule expression, or the production of reactive oxygen and nitrogen species caused by LPS stimulation. Conversely, all TSPO ligands impaired LTB4’s actions, as visualized by reductions in L-selectin shedding, β2 integrin overexpression, neutrophil chemotaxis, and actin filament assembly. TSPO ligands showed distinct intracellular effects on LTB4-induced neutrophil locomotion, with diazepam enhancing cofilin but not modifying Arp2/3 expression, and Ro5-4864 and PK11195 reducing both cofilin and Arp2/3 expression. Taken together, our data exclude a direct role of TSPO ligands in TLR4-elicited pathways, and indicate that TSPO activation inhibits GPCR inflammatory pathways in neutrophils, with a relevant role in neutrophil influx into inflammatory sites.

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.

Emerging pharmaceutical therapies for COPD

COPD, for which cigarette smoking is the major risk factor, remains a worldwide burden. Current therapies provide only limited short-term benefit and fail to halt progression. A variety of potential therapeutic targets are currently being investigated, including COPD-related proinflammatory mediators and signaling pathways. Other investigational compounds target specific aspects or complications of COPD such as mucus hypersecretion and pulmonary hypertension. Although many candidate therapies have shown no significant effects, other emerging therapies have improved lung function, pulmonary hypertension, glucocorticoid sensitivity, and/or the frequency of exacerbations. Among these are compounds that inhibit the CXCR2 receptor, mitogen-activated protein kinase/Src kinase, myristoylated alanine-rich C kinase substrate, selectins, and the endothelin receptor. Activation of certain transcription factors may also be relevant, as a large retrospective cohort study of COPD patients with diabetes found that the peroxisome proliferator-activated receptor γ (PPARγ) agonists rosiglitazone and pioglitazone were associated with reduced COPD exacerbation rate. Notably, several therapies have shown efficacy only in identifiable subgroups of COPD patients, suggesting that subgroup identification may become more important in future treatment strategies. This review summarizes the status of emerging therapeutic pharmaceuticals for COPD and highlights those that appear most promising.

Nasopharyngeal Microbiota, Host Transcriptome, and Disease Severity in Children with Respiratory Syncytial Virus Infection

RATIONALE

Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections and hospitalizations in infants worldwide. Known risk factors, however, incompletely explain the variability of RSV disease severity, especially among healthy children. We postulate that the severity of RSV infection is influenced by modulation of the host immune response by the local bacterial ecosystem.

OBJECTIVES

To assess whether specific nasopharyngeal microbiota (clusters) are associated with distinct host transcriptome profiles and disease severity in children less than 2 years of age with RSV infection.

METHODS

We characterized the nasopharyngeal microbiota profiles of young children with mild and severe RSV disease and healthy children by 16S-rRNA sequencing. In parallel, using multivariable models, we analyzed whole-blood transcriptome profiles to study the relationship between microbial community composition, the RSV-induced host transcriptional response, and clinical disease severity.

MEASUREMENTS AND MAIN RESULTS

We identified five nasopharyngeal microbiota clusters characterized by enrichment of either Haemophilus influenzae, Streptococcus, Corynebacterium, Moraxella, or Staphylococcus aureus. RSV infection and RSV hospitalization were positively associated with H. influenzae and Streptococcus and negatively associated with S. aureus abundance, independent of age. Children with RSV showed overexpression of IFN-related genes, independent of the microbiota cluster. In addition, transcriptome profiles of children with RSV infection and H. influenzae- and Streptococcus-dominated microbiota were characterized by greater overexpression of genes linked to Toll-like receptor and by neutrophil and macrophage activation and signaling.

CONCLUSIONS

Our data suggest that interactions between RSV and nasopharyngeal microbiota might modulate the host immune response, potentially affecting clinical disease severity.

Intracellular and Extracellular Cytokines in A549 Cells and THP1 Cells Exposed to Cigarette Smoke

Cigarette smoke (CS) activates inflammatory cells and increases cytokine levels producing local and systemic inflammation. To assess changes in intracellular and extracellular cytokine levels we used human epithelial (A549 cells) and monocyte (THP-1) cell lines grown for 24 h in cigarette smoke-conditioned media. Cytokines were assessed using immunostaining/flow cytometry and ELISA assay. In THP1cells, grown in CS-conditioned media, the intracellular interleukins IL-1β, IL-6, and IL-10 increased by more than tenfold, while less significant increases were found in A549 cells. IL-1α and IL-1β, but not IL-6 or IL-10, were increased in the culture media, while IL-2 was raised by about fivefold only in the culture medium of A549 cells. IL-4, IL-6, IL-8, IL-10, IL-12, and tumor necrosis factor alpha were undetectable, while only a slight increase was observed in extracellular IL-17A (by about 60 %) in the medium of A549 cells and by about 115 % in the medium of THP1 cells. The interferon gamma (IFNγ) was increased by about eightfold, but only in the medium of THP1 cells grown with CS. We conclude that IL-1 and INFγ are the key cytokines responsible for pro-inflammatory signaling in epithelial cells and monocytes, respectively, exposed to cigarette smoke.

IL-17C mediates the recruitment of tumor-associated neutrophils and lung tumor growth

Chronic obstructive pulmonary disease (COPD) is associated with an increased risk for lung cancer and an aberrant microbiota of the lung. Microbial colonization contributes to chronic neutrophilic inflammation in COPD. Nontypeable Haemophilus influenzae (NTHi) is frequently found in lungs of stable COPD patients and is the major pathogen triggering exacerbations. The epithelial cytokine interleukin-17C (IL-17C) promotes the recruitment of neutrophils into inflamed tissues. The purpose of this study was to investigate the function of IL-17C in the pulmonary tumor microenvironment. We subjected mice deficient for IL-17C (IL-17C^-/-) and mice double deficient for Toll-like receptor 2 and 4 (TLR-2/4^-/-) to a metastatic lung cancer model. Tumor proliferation and growth as well as the number of tumor-associated neutrophils was significantly decreased in IL-17C^-/- and TLR-2/4^-/- mice exposed to NTHi. The NTHi-induced pulmonary expression of IL-17C was dependent on TLR-2/4. In vitro, IL-17C increased the NTHi- and tumor necrosis factor-α-induced expression of the neutrophil chemokines keratinocyte-derived chemokine and macrophage inflammatory protein 2 in lung cancer cells but did not affect proliferation. Human lung cancer samples stained positive for IL-17C, and in non-small cell lung cancer patients with lymph node metastasis, IL-17C was identified as a negative prognostic factor. Our data indicate that epithelial IL-17C promotes neutrophilic inflammation in the tumor microenvironment and suggest that IL-17C links a pathologic microbiota, as present in COPD patients, with enhanced tumor growth.

Increased IL-17RA and IL-17RC in End-Stage COPD and the Contribution to Mast Cell Secretion of FGF-2 and VEGF

Mast cells are accumulated in advanced chronic obstructive pulmonary disease (COPD), and interleukin (IL)-17 signaling plays a role in disease progression. The expression, localization and functional relevance of IL-17 receptor (R)A and IL-17RC was explored in COPD by immunodetection, and functional assays.

IL-17RA and IL-17RC was increased in very severe COPD, and expressed by mast cells. Increased secretion of the pro-angiogenic basic fibroblast growth factor and vascular endothelial growth factor was observed in vitro-maintained mast cells stimulated with IL-17A. Expression of these mediators was confirmed in end-stage COPD. Thus, accumulation of mast cells in COPD may contribute to vascular remodeling.

Nontypeable Haemophilus influenzae-Promoted Proliferation of Kras-Induced Early Adenomatous Lesions Is Completely Dependent on Toll-Like Receptor Signaling

Chronic obstructive pulmonary disease (COPD) is a risk factor for lung cancer. COPD is characterized by chronic airway inflammation and lung infections. The airways of patients with COPD are frequently colonized with bacteria [eg, nontypeable Haemophilus influenzae (NTHi)] that cause pulmonary inflammation and exacerbations. Pulmonary adenocarcinomas are frequently associated with an activating mutation in the KRAS gene. We determined the function of Toll-like receptor (TLR) signaling on the progression of Kras-induced early adenomatous lesions in the lung. Wild-type (WT) mice and mice doubly deficient in Tlr-2 and -4 (Tlr2/4^-/-), both with an oncogenic Kras allele in lung epithelium, were exposed to NTHi for 4 weeks. Exposure to NTHi resulted in increased tumor proliferation and growth in WT mice, but not in Tlr2/4^-/- mice. Alveolar adenomatous hyperplasia and adenocarcinoma were significantly increased in WT mice compared with Tlr2/4^-/- mice. The average size of tumors was significantly larger in WT mice, whereas there was no difference in the number of alveolar lesions between WT and Tlr2/4^-/- mice. NTHi-induced pulmonary neutrophilic inflammation and tumor-associated neutrophils were reduced in Tlr2/4^-/- mice. Thus, subsequent to a driver mutation, NTHi-induced inflammation promotes proliferation of early adenomatous lesions in a TLR-dependent manner.

Non-Typeable Haemophilus influenzae Infection of the Junbo Mouse

Acute otitis media, inflammation of the middle ear bulla, is the most common bacterial infection in children. For one of the principal otopathogens, non-typeable Haemophilus influenzae (NTHi), animal models allow us to investigate host-microbial interactions relevant to the onset and progression of infection and to study treatment of middle ear disease. We have established a robust model of NTHi middle ear infection in the Junbo mouse. Intranasal inoculation with NTHi produces high rates of bulla infection and high bacterial titers in bulla fluids; bacteria can also spread down the respiratory tract to the mouse lung. An innate immune response is detected in the bulla of Junbo mice following NTHi infection, and bacteria are maintained in some ears at least up to day 56 post-inoculation. The Junbo/NTHi infection model facilitates studies on bacterial pathogenesis and antimicrobial intervention regimens and vaccines for better treatment and prevention of NTHi middle ear infection. © 2017 by John Wiley & Sons, Inc.

Immune-mediated inflammation in the pathogenesis of emphysema: insights from mouse models

The cellular mechanisms that result in the initiation and progression of emphysema are clearly complex. A growing body of human data combined with discoveries from mouse models utilizing cigarette smoke exposure or protease administration have improved our understanding of emphysema development by implicating specific cell types that may be important for the pathophysiology of chronic obstructive pulmonary disease. The most important aspects of emphysematous damage appear to be oxidative or protease stress and sustained macrophage activation and infiltration of other immune cells leading to epithelial damage and cell death. Despite the identification of these associated processes and cell types in many experimental studies, the reasons why cigarette smoke and other pollutants result in unremitting damage instead of injury resolution are still uncertain. We propose an important role for macrophages in the sequence of events that lead and maintain this chronic tissue pathologic process in emphysema. This model involves chronic activation of macrophage subtypes that precludes proper healing of the lung. Further elucidation of the cross-talk between epithelial cells that release damage-associated signals and the cellular immune effectors that respond to these cues is a critical step in the development of novel therapeutics that can restore proper lung structure and function to those afflicted with emphysema.

Interleukin-22 protects against non-typeable Haemophilus influenzae infection: alteration during chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is a major health problem becoming a leading cause of morbidity and mortality worldwide. A large part of these disorders is associated with acute exacerbations resulting from infection by bacteria, such as non-typeable Haemophilus influenzae (NTHi). Our understanding of the pathogenesis of these exacerbations is still elusive. We demonstrate herein that NTHi infection of mice chronically exposed to cigarette smoke (CS), an experimental model of chronic obstructive pulmonary disease (COPD), not only causes acute pulmonary inflammation but also impairs the production of interleukin (IL)-22, a cytokine with potential anti-bacterial activities. We also report that mice lacking IL-22, as well as mice exposed to CS, have a delayed clearance of NTHi bacteria and display enhanced alveolar wall thickening and airway remodeling compared with controls. Supplementation with IL-22 not only boosted bacterial clearance and the production of anti-microbial peptides but also limited lung damages induced by infection both in IL-22-/- and CS-exposed mice. In vitro exposure to CS extract altered the NTHi-induced IL-22 production by spleen cells. This study shows for the first time that a defect in IL-22 is involved in the acute exacerbation induced by NTHi infection during experimental COPD and opens the way to innovative therapeutic strategies.

Immune Imbalances in Non-Alcoholic Fatty Liver Disease: From General Biomarkers and Neutrophils to Interleukin-17 Axis Activation and New Therapeutic Targets

Non-alcoholic fatty liver disease (NAFLD) is an increasing problem worldwide and is associated with negative outcomes such as cirrhosis, hepatocellular carcinoma, insulin resistance, diabetes, and cardiovascular events. Current evidence shows that the immune response has an important participation driving the initiation, maintenance, and progression of the disease. So, various immune imbalances, from cellular to cytokines levels, have been studied, either for better compression of the disease pathophysiology or as biomarkers for severity assessment and outcome prediction. In this article, we performed a thorough review of studies that evaluated the role of inflammatory/immune imbalances in the NAFLD. At the cellular level, we gave special focus on the imbalance between neutrophils and lymphocytes counts (the neutrophil-to-lymphocyte ratio), and that which occurs between T helper 17 (Th17) and regulatory T cells as emerging biomarkers. By extension, we reviewed the reflection of these imbalances at the molecular level through pro-inflammatory cytokines including those involved in Th17 differentiation (IL-6, IL-21, IL-23, and transforming growth factor-beta), and those released by Th17 cells (IL-17A, IL-17F, IL-21, and IL-22). We gave particular attention to the role of IL-17, either produced by Th17 cells or neutrophils, in fibrogenesis and steatohepatitis. Finally, we reviewed the potential of these pathways as new therapeutic targets in NAFLD.

Human innate lymphoid cells

Innate lymphoid cells (ILCs) are increasingly acknowledged as important mediators of immune homeostasis and pathology. ILCs act as early orchestrators of immunity, responding to epithelium-derived signals by expressing an array of cytokines and cell-surface receptors, which shape subsequent immune responses. As such, ILCs make up interesting therapeutic targets for several diseases. In patients with allergy and asthma, group 2 innate lymphoid cells produce high amounts of IL-5 and IL-13, thereby contributing to type 2-mediated inflammation. Group 3 innate lymphoid cells are implicated in intestinal homeostasis and psoriasis pathology through abundant IL-22 production, whereas group 1 innate lymphoid cells are accumulated in chronic inflammation of the gut (inflammatory bowel disease) and lung (chronic obstructive pulmonary disease), where they contribute to IFN-γ-mediated inflammation. Although the ontogeny of mouse ILCs is slowly unraveling, the development of human ILCs is far from understood. In addition, the growing complexity of the human ILC family in terms of previously unrecognized functional heterogeneity and plasticity has generated confusion within the field. Here we provide an updated view on the function and plasticity of human ILCs in tissue homeostasis and disease.

Impact of tobacco smoking on cytokine signaling via interleukin-17A in the peripheral airways

There is excessive accumulation of neutrophils in the airways in chronic obstructive pulmonary disease (COPD) but the underlying mechanisms remain poorly understood. It is known that extracellular cytokine signaling via interleukin (IL)-17A contributes to neutrophil accumulation in the airways but nothing is known about the impact of tobacco smoking on extracellular signaling via IL-17A. Here, we characterized the impact of tobacco smoking on extracellular cytokine signaling via IL-17A in the peripheral airways in long-term smokers with and without COPD and in occasional smokers before and after short-term exposure to tobacco smoke. We quantified concentrations of IL-17A protein in cell-free bronchoalveolar lavage (BAL) fluid samples (Immuno-quantitative PCR) and cytotoxic T-cells (immunoreactivity for CD8⁺ and CD3⁺) in bronchial biopsies. Matrix metalloproteinase-8 and human beta defensin 2 proteins were also quantified (enzyme-linked immunosorbent assay) in the BAL samples. The concentrations of IL-17A in BAL fluid were higher in long-term smokers without COPD compared with nonsmoking healthy controls, whereas those with COPD did not differ significantly from either of the other groups. Short-term exposure to tobacco smoke did not induce sustained alterations in these concentrations in occasional smokers. Long-term smokers displayed higher concentrations of IL-17A than did occasional smokers. Moreover, these concentrations correlated with CD8⁺ and CD3⁺ cells in biopsies among long-term smokers with COPD. In healthy nonsmokers, BAL concentrations of matrix metalloproteinase-8 and IL-17A correlated, whereas this was not the case in the pooled group of long-term smokers with and without COPD. In contrast, BAL concentrations of human beta defensin 2 and IL-17A correlated in all study groups. This study implies that long-term but not short-term exposure to tobacco smoke increases extracellular cytokine signaling via IL-17A in the peripheral airways. In the smokers with COPD, this signaling may involve cytotoxic T-cells. Long-term exposure to tobacco smoke leads to a disturbed association of extracellular IL-17A signaling and matrix metalloproteinase-8, of potential importance for the coordination of antibacterial activity.

Interleukin-17A Is Associated With Alveolar Inflammation and Poor Outcomes in Acute Respiratory Distress Syndrome

OBJECTIVE

Interleukin-17A is a proinflammatory cytokine known to play a role in host defense and pathologic inflammation in murine models of lung injury. The relationship between interleukin-17A and inflammation in human lung injury is unknown. Our primary objective was to determine whether interleukin-17A levels are associated with alveolar measures of inflammation and injury in patients with acute respiratory distress syndrome. Our secondary objective was to test whether interleukin-17A levels are associated with acute respiratory distress syndrome-related outcomes.

DESIGN

Observational study.

SETTING

Six North American medical centers.

PATIENTS

We studied two groups of patients with acute respiratory distress syndrome: 1) patients previously enrolled in a placebo-controlled clinical trial of omega-3 fatty acids performed at five North American medical centers (n = 86, acute respiratory distress syndrome 1), and 2) patients with systemic inflammatory response syndrome admitted to an ICU who developed acute respiratory distress syndrome (n = 140, acute respiratory distress syndrome 2). In acute respiratory distress syndrome 1, we used paired serum and bronchoalveolar lavage fluid samples obtained within 48 hours of acute respiratory distress syndrome onset, whereas in acute respiratory distress syndrome 2, we used plasma obtained within the first 24 hours of ICU admission.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured circulating interleukin-17A in acute respiratory distress syndrome 1 and acute respiratory distress syndrome 2. We also measured interleukin-17A, neutrophil counts, and total protein in bronchoalveolar lavage fluid from acute respiratory distress syndrome 1. We found that bronchoalveolar lavage interleukin-17A was strongly associated with higher bronchoalveolar lavage percent neutrophils (p < 0.001) and bronchoalveolar lavage total protein (p < 0.01) in acute respiratory distress syndrome1. In both acute respiratory distress syndrome 1 and acute respiratory distress syndrome 2, elevated interleukin-17A was associated with higher Sequential Organ Failure Assessment scores (p < 0.05).

CONCLUSIONS

Elevated circulating and alveolar levels of interleukin-17A are associated with increased percentage of alveolar neutrophils, alveolar permeability, and organ dysfunction in acute respiratory distress syndrome.

The IL-17A/IL-17RA axis in pulmonary defence and immunopathology

The interleukin (IL)-17A/IL-17 receptor A (IL-17RA) axis is emerging as a key player in host defence. Several studies have demonstrated that IL-17A-mediated responses play a critical role in both acute and chronic inflammation induced by infectious agents, environmental stimuli and genetic diseases in the airways. In this regard, it is becoming evident that IL-17A/IL-17RA signalling may have a protective and beneficial impact on health, but that it can also result in detrimental outcomes. On one hand, the IL-17A/IL-17RA axis can contribute to the elimination of noxious stimuli and to the resolution of acute inflammatory processes; on the other hand, it can exacerbate immunopathological responses, contributing to the development and progression of chronic respiratory illnesses. In addition, cellular and molecular signatures underlying IL-17A/IL-17RA signalling have been increasingly identified, although further studies are needed to clarify such complex responses. Here, we discuss the latest discoveries on the role of the IL-17A/IL-17RA axis in driving host pulmonary defence and immunopathology.

IL-17A increases TNF-α-induced COX-2 protein stability and augments PGE2 secretion from airway smooth muscle cells: impact on β2 -adrenergic receptor desensitization

BACKGROUND

IL-17A plays an important role in respiratory disease and is a known regulator of pulmonary inflammation and immunity. Recent studies have linked IL-17A with exacerbation in asthma and COPD. We have shown that the enzyme cyclooxygenase-2 (COX-2) and its prostanoid products, prostaglandin E2 (PGE2 ) in particular, are key contributors in in vitro models of infectious exacerbation; however, the impact of IL-17A was not known.

METHODS AND RESULTS

We address this herein and show that IL-17A induces a robust and sustained upregulation of COX-2 protein and PGE2 secretion from airway smooth muscle (ASM) cells. COX-2 can be regulated at transcriptional, post-transcriptional and/or post-translational levels. We have elucidated the underlying molecular mechanisms responsible for the sustained upregulation of TNF-α-induced COX-2 by IL-17A in ASM cells and show that is not via increased COX-2 gene expression. Instead, TNF-α-induced COX-2 upregulation is subject to regulation by the proteasome, and IL-17A acts to increase TNF-α-induced COX-2 protein stability as confirmed by cycloheximide chase experiments. In this way, IL-17A acts to amplify the COX-2-mediated effects of TNF-α and greatly enhances PGE2 secretion from ASM cells.

CONCLUSION

As PGE2 is a multifunctional prostanoid with diverse roles in respiratory disease, our studies demonstrate a novel function for IL-17A in airway inflammation by showing for the first time that IL-17A impacts on the COX-2/PGE2 pathway, molecules known to contribute to disease exacerbation.

A new model for non-typeable Haemophilus influenzae middle ear infection in the Junbo mutant mouse

Acute otitis media, inflammation of the middle ear, is the most common bacterial infection in children and, as a consequence, is the most common reason for antimicrobial prescription to this age group. There is currently no effective vaccine for the principal pathogen involved, non-typeable Haemophilus influenzae (NTHi). The most frequently used and widely accepted experimental animal model of middle ear infection is in chinchillas, but mice and gerbils have also been used. We have established a robust model of middle ear infection by NTHi in the Junbo mouse, a mutant mouse line that spontaneously develops chronic middle ear inflammation in specific pathogen-free conditions. The heterozygote Junbo mouse (Jbo/+) bears a mutation in a gene (Evi1, also known as Mecom) that plays a role in host innate immune regulation; pre-existing middle ear inflammation promotes NTHi middle ear infection. A single intranasal inoculation with NTHi produces high rates (up to 90%) of middle ear infection and bacterial titres (10⁴-10⁵ colony-forming units/µl) in bulla fluids. Bacteria are cleared from the majority of middle ears between day 21 and 35 post-inoculation but remain in approximately 20% of middle ears at least up to day 56 post-infection. The expression of Toll-like receptor-dependent response cytokine genes is elevated in the middle ear of the Jbo/+ mouse following NTHi infection. The translational potential of the Junbo model for studying antimicrobial intervention regimens was shown using a 3 day course of azithromycin to clear NTHi infection, and its potential use in vaccine development studies was shown by demonstrating protection in mice immunized with killed homologous, but not heterologous, NTHi bacteria.

Summary: Acute otitis media is an important disease in children. We describe a new infection model for translational research that uses the Junbo mouse mutant intranasally inoculated with non-typeable Haemophilus influenzae.

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.