T(H)17 cells in asthma and inflammation

Effects of environmental exposure to iron powder on healthy and elastase-exposed mice

Prolonged exposure to iron powder and other mineral dusts can threaten the health of individuals, especially those with COPD. The goal of this study was to determine how environmental exposure to metal dust from two different mining centers in Brazil affects lung mechanics, inflammation, remodeling and oxidative stress responses in healthy and elastase-exposed mice. This study divided 72 male C57Bl/6 mice into two groups, the summer group and the winter group. These groups were further divided into six groups: control, nonexposed (SAL); nonexposed, given elastase (ELA); exposed to metal powder at a mining company (SAL-L1 and ELA-L1); and exposed to a location three miles away from the mining company (SAL-L2 and ELA-L2) for four weeks. On the 29th day of the protocol, the researchers assessed lung mechanics, bronchoalveolar lavage fluid (BALF), inflammation, remodeling, oxidative stress, macrophage iron and alveolar wall alterations (mean linear intercept-Lm). The Lm was increased in the ELA, ELA-L1 and ELA-L2 groups compared to the SAL group (p < 0.05). There was an increase in the total number of cells and macrophages in the ELA-L1 and ELA-L2 groups compared to the other groups (p < 0.05). Compared to the ELA and SAL groups, the exposed groups (ELA-L1, ELA-L2, SAL-L1, and SAL-L2) exhibited increased expression of IL-1β, IL-6, IL-10, IL-17, TNF-α, neutrophil elastase, TIMP-1, MMP-9, MMP-12, TGF-β, collagen fibers, MUC5AC, iNOS, Gp91phox, NFkB and iron positive macrophages (p < 0.05). Although we did not find differences in lung mechanics across all groups, there were low to moderate correlations between inflammation remodeling, oxidative stress and NFkB with elastance, resistance of lung tissue and iron positive macrophages (p < 0.05). Environmental exposure to iron, confirmed by evaluation of iron in alveolar macrophages and in air, exacerbated inflammation, initiated remodeling, and induced oxidative stress responses in exposed mice with and without emphysema. Activation of the iNOS, Gp91phox and NFkB pathways play a role in these changes.

Identification of Serum Interleukin-22 as Novel Biomarker in Pulmonary Hypertension: A Translational Study

Growing evidence suggests the crucial involvement of inflammation in the pathogenesis of pulmonary hypertension (PH). The current study analyzed the expression of interleukin (IL)-17a and IL-22 as potential biomarkers for PH in a preclinical rat model of PH as well as the serum levels in a PH patient collective. PH was induced by monocrotalin (60 mg/kg body weight s.c.) in 10 Sprague Dawley rats (PH) and compared to 6 sham-treated controls (CON) as well as 10 monocrotalin-induced, macitentan-treated rats (PH_MAC). Lung and cardiac tissues were subjected to histological and immunohistochemical analysis for the ILs, and their serum levels were quantified using ELISA. Serum IL levels were also measured in a PH patient cohort. IL-22 expression was significantly increased in the lungs of the PH and PH_MAC groups (p = 0.002), whereas increased IL17a expression was demonstrated only in the lungs and RV of the PH (p < 0.05) but not the PH_MAC group (p = n.s.). The PH group showed elevated serum concentrations for IL-22 (p = 0.04) and IL-17a (p = 0.008). Compared to the PH group, the PH_MAC group demonstrated a decrease in IL-22 (p = 0.021) but not IL17a (p = n.s.). In the PH patient collective (n = 92), increased serum levels of IL-22 but not IL-17a could be shown (p < 0.0001). This elevation remained significant across the different etiological groups (p < 0.05). Correlation analysis revealed multiple significant relations between IL-22 and various clinical, laboratory, functional and hemodynamic parameters. IL-22 could serve as a promising inflammatory biomarker of PH with potential value for initial diagnosis, functional classification or even prognosis estimation. Its validation in larger patients' cohorts regarding outcome and survival data, as well as the probability of promising therapeutic target structures, remains the object of further studies.

IL-22 Binding Protein Controls IL-22-Driven Bleomycin-Induced Lung Injury

The high mortality rates of acute lung injury and acute respiratory distress syndrome challenge the field to identify biomarkers and factors that can be exploited for therapeutic approaches. IL-22 is a cytokine that has antibacterial and reparative properties in the lung. However, it also can exacerbate inflammation and requires tight control by the extracellular inhibitory protein known as IL-22 binding protein (IL-22BP) (Il22ra2). This study showed the necessity of IL-22BP in controlling and preventing acute lung injury using IL-22BP knockout mice (Il22ra2-/-) in the bleomycin model of acute lung injury/acute respiratory distress syndrome. Il22ra2-/- mice had greater sensitivity (weight loss and death) and pulmonary inflammation in the acute phase (first 7 days) of the injury compared with wild-type C57Bl/6 controls. The inflammation was driven by excess IL-22 production, inducing the influx of pathogenic IL-17A+ γδ T cells to the lung. Interestingly, this inflammation was initiated in part by the noncanonical IL-22 signaling to macrophages, which express the IL-22 receptor (Il22ra1) in vivo after bleomycin challenge. This study further showed that IL-22 receptor alpha-1+ macrophages can be stimulated by IL-22 to produce a number of IL-17-inducing cytokines such as IL-1β, IL-6, and transforming growth factor-β1. Together, the results suggest that IL-22BP prevents IL-22 signaling to macrophages and reduces bleomycin-mediated lung injury.

Immunomodulatory Effects of Subacute Inhalation Exposure to Copper Oxide Nanoparticles in House Dust Mite-Induced Asthma

It has been shown that inhalation exposure to copper oxide nanoparticles (CuO NPs) results in pulmonary inflammation. However, immunomodulatory consequences after CuO NP inhalation exposure have been less explored. We tested the effect of CuO NP aerosols on immune responses in healthy, house dust mite (HDM) asthmatic, or allergen immunotherapy (AIT)-treated asthmatic mice (BALB/c, females). The AIT consisted of a vaccine comprising HDM allergens and CpG-loaded nanoparticles (CpG NPs). AIT treatment involved mice being immunized (via subcutaneous (sc) injection; 2 doses) while concomitantly being exposed to CuO NP aerosols (over a 2 week period), starting on the day of the first vaccination. Mice were then sensitized twice by sc injection and subsequently challenged with HDM extract 10 times by intranasal instillation. The asthmatic model followed the same timeline except that no immunizations were administered. All mice were necropsied 24 h after the end of the HDM challenge. CuO NP-exposed healthy mice showed a significant decrease in TH1 and TH2 cells, and an elevation in T-bet+ Treg cells, even 40 days after the last exposure to CuO NPs. Similarly, the CuO NP-exposed HDM asthma model demonstrated decreased TH2 responses and increased T-bet+ Treg cells. Conversely, CuO NP inhalation exposure to AIT-treated asthmatic mice resulted in an increase in TH2 cells. In conclusion, immunomodulatory effects of inhalation exposure to CuO NPs are dependent on immune conditions prior to exposure.

Immune cell ratio and coagulation markers in assessing prognosis of asthma: a cross-sectional study from Saudi Arabia

Asthma affects a significant number of individuals in Saudi Arabia, with increasing prevalence worldwide, leading to a considerable impact on their quality of life and frequent hospitalizations. In this study, we aimed to explore the relationship between the immune cell ratio and coagulation markers, specifically to identify the occurrence of coagulation abnormalities associated with asthma. To achieve this, we assessed asthma history and severity using a questionnaire while analyzing coagulation biomarkers through venous blood samples. The biomarkers examined included d-dimer, prothrombin time (PT), partial thromboplastin time (PTT), and the international normalized ratio (INR). In addition, we evaluated various hematological parameters such as blood cell counts and hemoglobin (HGB) levels. Our findings revealed compelling evidence, showing significantly elevated levels of d-dimer and the eosinophil-to-neutrophil (ENR) ratio in asthma cases compared to the controls. Moreover, we observed a positive correlation between d-dimer levels and the ENR, with each unit increase in d-dimer associated with a 0.0006 increase in the ENR among asthma cases. These results highlight the potential of assessing ENR and d-dimer levels as predictive indicators for disease prognosis and the development of coagulation abnormalities in individuals with asthma. By shedding light on the relationship between immune cell ratios and coagulation markers in the context of asthma, our study contributes to a better understanding of disease progression and the associated complications. These insights can potentially lead to improved management strategies and better outcomes for asthma patients.

Asthma-associated bacterial infections: Are they protective or deleterious?

Eosinophilic, noneosinophilic, or mixed granulocytic inflammations are the hallmarks of asthma heterogeneity. Depending on the priming of lung immune and structural cells, subjects with asthma might generate immune responses that are TH2-prone or TH17-prone immune response. Bacterial infections caused by Haemophilus, Moraxella, or Streptococcus spp. induce the secretion of IL-17, which in turn recruit neutrophils into the airways. Clinical studies and experimental models of asthma indicated that neutrophil infiltration induces a specific phenotype of asthma, characterized by an impaired response to corticosteroid treatment. The understanding of pathways that regulate the TH17-neutrophils axis is critical to delineate and develop host-directed therapies that might control asthma and its exacerbation episodes that course with infectious comorbidities. In this review, we outline clinical and experimental studies on the role of airway epithelial cells, S100A9, and high mobility group box 1, which act in concert with the IL-17-neutrophil axis activated by bacterial infections, and are related with asthma that is difficult to treat. Furthermore, we report critically our view in the light of these findings in an attempt to stimulate further investigations and development of immunotherapies for the control of severe asthma.

Phenotypes and Endotypes in Asthma

Asthma is a broadly encompassing diagnosis of airway inflammation with significant variability in presentation and response. Advances in molecular techniques and imaging have unraveled the delicate mechanistic tapestry responsible for the underlying inflammatory pathways in asthma. The elucidation of biomarkers and cellular components specific to these inflammatory pathways allowed for the categorization of asthma from generic phenotypes to more specific mechanistic endotypes, with two prominent subgroups emerging based on the level of Type 2 inflammation present - T2 high and T2 low (or non-T2). Sophisticated modeling and cluster analyses using a combination of clinical, physiologic, and biomarker parameters have permitted the identification of subendotypes within the broader T2 umbrella. This mechanistic-driven classification schema for asthma has dramatically altered the landscape of asthma management with the discovery and approval of targeted biologic therapies and has ushered in a new era of personalized precision medicine in asthma.

Association between comorbid asthma and prognosis of critically ill patients with severe sepsis: a cohort study

Basic research suggests some contributing mechanisms underlying asthma might at the same time benefit patients with asthma against sepsis, while the potential protective effect of comorbid asthma on prognosis of sepsis has not been well studied in clinical research. The study aimed to assess the association between comorbid asthma and prognosis in a cohort of patients admitted to intensive care unit (ICU) with severe sepsis. Patients with severe sepsis admitted to ICUs were included from the MIMIC-III Critical Care Database, and categorized as patients without asthma, patients with stable asthma, and patients with acute exacerbation asthma. The primary study outcome was 28-day mortality since ICU admission. Difference in survival distributions among groups were evaluated by Kaplan–Meier estimator. Multivariable Cox regression was employed to examine the association between comorbid asthma and prognosis. A total of 2469 patients with severe sepsis were included, of which 2327 (94.25%) were without asthma, 125 (5.06%) with stable asthma, and 17 (0.69%) with acute exacerbation asthma. Compared with patients without asthma, patients with asthma (either stable or not) had a slightly younger age (66.73 ± 16.32 versus 64.77 ± 14.81 years), a lower proportion of male sex (56.81% versus 40.14%), and a lower median SAPS II score (46 versus 43). Patients with acute exacerbation asthma saw the highest 28-day mortality rate (35.29%), but patients with stable asthma had the lowest 28-day mortality rate (21.60%) when compared to that (34.42%) in patients without asthma. Consistent results were observed in Kaplan–Meier curves with a p-value for log-rank test of 0.016. After adjusting for potential confounding, compared to being without asthma, being with stable asthma was associated with a reduced risk of 28-day mortality (hazard ratio (HR) 0.65, 95% confidence interval (CI) 0.44–0.97, p = 0.0335), but being with acute exacerbation asthma was toward an increased risk of 28-day mortality (HR 1.82, 95% 0.80–4.10, p = 0.1513). E-value analysis suggested robustness to unmeasured confounding. These findings suggest comorbid stable asthma is associated with a better prognosis in critically ill patients with severe sepsis, while acute exacerbation asthma is associated with worse prognosis.

The role of macrophage polarization and associated mechanisms in regulating the anti-inflammatory action of acupuncture: a literature review and perspectives

Acupuncture is used in the treatment of a variety of inflammatory conditions and diseases. However, the mechanisms of its anti-inflammatory action are complex and have not been systematically investigated. Macrophages are key components of the innate immune system, thus, balancing the M1/M2 macrophage ratio and modulating cytokine levels in the inflammatory environment may be desirable therapeutic goals. Evidence has shown that acupuncture has anti-inflammatory actions that affect multiple body systems, including the immune, locomotory, endocrine, nervous, digestive, and respiratory systems, by downregulating pro-inflammatory M1 and upregulating anti-inflammatory M2 macrophages, as well as by modulating associated cytokine secretion. Macrophage polarization is controlled by the interlocking pathways of extrinsic factors, the local tissue microenvironment, and the neural-endocrine-immune systems. It has been suggested that polarization of T lymphocytes and cytokine secretions resulting in modulation of the autonomic nervous system and the hypothalamic–pituitary–adrenal axis, may be upstream mechanisms of acupuncture-induced macrophage polarization. We further propose that macrophage polarization could be the principal pathway involved in acupuncture immune regulation and provide the scientific basis for the clinical application of acupuncture in inflammatory conditions.

Asthma Phenotypes as a Guide for Current and Future Biologic Therapies

Asthma has been increasingly recognized as being a heterogeneous disease with multiple distinct mechanisms and pathophysiologies. Evidence continues to build regarding the existence of different cell types, environmental exposures, pathogens, and other factors that produce a similar set of symptoms known collectively as asthma. This has led to a movement from a "one size fits all" symptom-based methodology to a more patient-centered, individualized approach to asthma treatment targeting the underlying disease process. A significant contributor to this shift to more personalized asthma therapy has been the increasing availability of numerous biologic therapies in recent years, providing the opportunity for more targeted treatments. When targeted biologics began to be developed for treatment of asthma, the hope was that distinct biomarkers would become available, allowing the clinician to determine which biologic therapy was best suited for which patients. Presence of certain biomarkers, like eosinophilia or antigen-specific IgE, is important features of specific asthma phenotypes. Currently available biomarkers can help with decision making about biologics, but are generally too broad and non-specific to clearly identify an asthma phenotype or the single biologic best suited to an asthmatic. Identification of further biomarkers is the subject of intense research. Yet, identifying a patient's asthma phenotype can help in predicting disease course, response to treatment, and biologic therapies to consider. In this review, major asthma phenotypes are reviewed, and the evidence for the utility of various biologics, both those currently on the market and those in the development process, in each of these phenotypes is explored.

Sex Hormones and Lung Inflammation

Inflammation is a characteristic marker in numerous lung disorders. Several immune cells, such as macrophages, dendritic cells, eosinophils, as well as T and B lymphocytes, synthetize and release cytokines involved in the inflammatory process. Gender differences in the incidence and severity of inflammatory lung ailments including asthma, chronic obstructive pulmonary disease (COPD), pulmonary fibrosis (PF), lung cancer (LC), and infectious related illnesses have been reported. Moreover, the effects of sex hormones on both androgens and estrogens, such as testosterone (TES) and 17β-estradiol (E2), driving characteristic inflammatory patterns in those lung inflammatory diseases have been investigated. In general, androgens seem to display anti-inflammatory actions, whereas estrogens produce pro-inflammatory effects. For instance, androgens regulate negatively inflammation in asthma by targeting type 2 innate lymphoid cells (ILC2s) and T-helper (Th)-2 cells to attenuate interleukin (IL)-17A-mediated responses and leukotriene (LT) biosynthesis pathway. Estrogens may promote neutrophilic inflammation in subjects with asthma and COPD. Moreover, the activation of estrogen receptors might induce tumorigenesis. In this chapter, we summarize the most recent advances in the functional roles and associated signaling pathways of inflammatory cellular responses in asthma, COPD, PF, LC, and newly occurring COVID-19 disease. We also meticulously deliberate the influence of sex steroids on the development and progress of these common and severe lung diseases.

Low-dose chlorine exposure impairs lung function, inflammation and oxidative stress in mice

AIM

To explore the different consequences of acute and chronic exposure to chlorine gas (Cl₂) on the functional and histological parameters of health mice.

MAIN METHODS

Firstly, male BALB/c mice were acute exposed to 3.3 or 33.3 or 70.5 mg/m³ Cl₂. We analyzed the lung function, the inflammatory cells in the bronchoalveolar lavage, cell influx in the peribrochoalveolar space and mucus production. In a second phase, mice were chronic exposed to 70.5 mg/m³ Cl₂. Besides the first phase analyses, we also evaluated the epithelial cells thickness, collagen deposition in the airways, immunohistochemistry stain for IL-1β, iNOS, IL-17 and ROCK-2 and the levels of IL-5, IL-13, IL-17, IL-1β and TNF-α in lung homogenate.

KEY FINDINGS

Acute exposure to chlorine impaired the lung function, increased the number of inflammatory cells in the BALF and in the airways, also increased the mucus production. Furthermore, when chlorine was exposed chronically, increased the airway remodeling with collagen deposition and epithelial cells thickness, positive cells for IL-1β, iNOS, IL-17 in the airways and in the alveolar walls and ROCK-2 in the alveolar walls, lung inflammation with increased levels of IL-5, IL-13, IL-1β and TNF-α in the lung homogenate, and also, induced the acid mucus production by the nasal epithelium.

SIGNIFICANCE

Acute and chronic exposure to low dose of chlorine gas worsens lung function, induces oxidative stress activation and mucus production and contributes to augmenting inflammation in health mice.

Molecular Targets for Biological Therapies of Severe Asthma

Asthma is a heterogeneous respiratory disease characterized by usually reversible bronchial obstruction, which is clinically expressed by different phenotypes driven by complex pathobiological mechanisms (endotypes). Within this context, during the last years several molecular effectors and signalling pathways have emerged as suitable targets for biological therapies of severe asthma, refractory to standard treatments. Indeed, various therapeutic antibodies currently allow to intercept at different levels the chain of pathogenic events leading to type 2 (T2) airway inflammation. In addition to pro-allergic immunoglobulin E (IgE), that chronologically represents the first molecule against which an anti-asthma monoclonal antibody (omalizumab) was developed, today other targets are successfully exploited by biological treatments of severe asthma. In particular, pro-eosinophilic interleukin 5 (IL-5) can be targeted by mepolizumab or reslizumab, whereas benralizumab is a selective blocker of IL-5 receptor. Moreover, dupilumab behaves as a dual receptor antagonist of pleiotropic interleukins 4 (IL-4) and 13 (IL-13). Besides these drugs that are already available in medical practice, other biologics are under clinical development such as those targeting innate cytokines, also including the alarmin thymic stromal lymphopoietin (TSLP), which plays a key role in the pathogenesis of type 2 asthma. Therefore, ongoing and future biological therapies are significantly changing the global scenario of severe asthma management. These new therapeutic options make it possible to implement phenotype/endotype-specific treatments, that are delineating personalized approaches precisely addressing the individual traits of asthma pathobiology. Such tailored strategies are thus allowing to successfully target the immune-inflammatory responses underlying uncontrolled T2-high asthma.

Asthma and Lung Mechanics

This article will discuss in detail the pathophysiology of asthma from the point of view of lung mechanics. In particular, we will explain how asthma is more than just airflow limitation resulting from airway narrowing but in fact involves multiple consequences of airway narrowing, including ventilation heterogeneity, airway closure, and airway hyperresponsiveness. In addition, the relationship between the airway and surrounding lung parenchyma is thought to be critically important in asthma, especially as related to the response to deep inspiration. Furthermore, dynamic changes in lung mechanics over time may yield important information about asthma stability, as well as potentially provide a window into future disease control. All of these features of mechanical properties of the lung in asthma will be explained by providing evidence from multiple investigative methods, including not only traditional pulmonary function testing but also more sophisticated techniques such as forced oscillation, multiple breath nitrogen washout, and different imaging modalities. Throughout the article, we will link the lung mechanical features of asthma to clinical manifestations of asthma symptoms, severity, and control. © 2020 American Physiological Society. Compr Physiol 10:975-1007, 2020.

IL-22 Plays a Critical Role in Maintaining Epithelial Integrity During Pulmonary Infection

Pulmonary infection is a leading cause of hospitalization in world. Lung damage due to infection and host mediated pathology can have life threatening consequences. Factors that limit lung injury and/or promote epithelial barrier function and repair are highly desirable as immunomodulatory therapeutics. Over the last decade, interleukin-22 has been shown to have pulmonary epithelial protective functions at the mucosal immune interface with bacterial and viral pathogens. This article summarizes recent findings in this area and provides perspective regarding the role of IL-22 in mucosal host defense.

IL-17 regulates DC migration to the peribronchial LNs and allergen presentation in experimental allergic asthma

IL-17 is associated with different phenotypes of asthma, however, it is not fully elucidated how it influences induction and maintenance of asthma and allergy. In order to determine the role of IL-17 in development of allergic asthma, we used IL-17A/F double KO (IL-17A/F KO) and WT mice with or without neutralization of IL-17 in an experimental allergic asthma model and analyzed airway hyperresponsiveness, lung inflammation, T helper cell polarization, and DCs influx and activation. We report that the absence of IL-17 reduced influx of DCs into lungs and lung draining LNs. Compared to WT mice, IL-17A/F KO mice or WT mice after neutralization of IL-17A showed reduced airway hyperresponsiveness, eosinophilia, mucus hypersecretion, and IgE levels. DCs from draining LNs of allergen-challenged IL-17A/F KO mice showed a reduction in expression of migratory and costimulatory molecules CCR7, CCR2, MHC-II, and CD40 compared to WT DCs. Moreover, in vivo stimulation of adoptively transferred antigen-specific cells was attenuated in lung-draining LNs in the absence of IL-17. Thus, we report that IL-17 enhances airway DC activation, migration, and function. Consequently, lack of IL-17 leads to reduced antigen-specific T cell priming and impaired development of experimental allergic asthma.

Decreased methylation profiles in the TNFA gene promoters in type 1 macrophages and in the IL17A and RORC gene promoters in Th17 lymphocytes have a causal association with non-atopic asthma caused by obesity: A hypothesis

Obesity is a serious public health problem worldwide and has been associated in epidemiological studies with a unique type of non-atopic asthma, although the causal association of asthma and obesity has certain criteria, such as the strength of association, consistency, specificity, temporality, biological gradient, coherence, analogy and experimentation; nevertheless, the biological plausibility of this association remains uncertain. Various mechanisms have been postulated, such as immunological, hormonal, mechanical, environmental, genetic and epigenetic mechanisms. Our hypothesis favours immunological mechanisms because some cytokines, such as tumour necrosis factor alpha (TNF-α) and interleukin (IL)-17A, are responsible for orchestrating low-grade systemic inflammation associated with obesity; however, these cytokines are regulated by epigenetic mechanisms, such as gene promoter methylation.

Role of IL-17 in asthma pathogenesis and its implications for the clinic

Introduction: Asthma is a respiratory disorder typically characterized by T-helper type 2 (Th2) inflammation that is mediated by cytokines, including IL-4, IL-5, and IL-13. Pathophysiologically, airway inflammation involving prominent eosinophilia, elevated IgE synthesis, airway hyperresponsiveness, mucus hypersecretion, and airway remodeling manifest clinically in patients as wheezing, breathlessness, chest tightness and episodic coughing. However, the Th2 paradigm falls short in interpreting the full spectrum of asthma severity. Areas covered: Severe asthmatics represent a distinct phenotype with their mixed pattern of neutrophilic-eosinophilic infiltration and glucocorticoid insensitivity making them refractory to currently available therapies. Th17 cells and their signature cytokine, IL-17, have been implicated in the development of severe asthma. Here, we review the contribution of IL-17 in the pathological features of asthma, gathered from both human and animal studies published in Pubmed during the past 10 years, and briefly discuss the clinical implications of targeting IL-17 imbalance in asthmatic patients. Expert opinion: With advancement in our understanding of the role of IL-17 in asthma pathology, it is clear that IL-17 is a targetable pathway which may lead to improvement in clinical symptoms of asthma. However, further elucidation of the complex interactions unfurled by IL-17 is essential in the empirical development of effective therapeutic options for refractory asthmatics.

Th17 cells in Bulgarian children with chronic obstructive lung diseases

INTRODUCTION AND OBJECTIVES

Th17 lymphocytes are now widely believed to be critical in various chronic pulmonary diseases. However, there is still a small number of investigations regarding children. We aimed to assess the percentage of Th17 lymphocytes and IL-17A in peripheral blood of children with chronic obstructive lung diseases.

PATIENTS AND METHODS

We included a total of 42 children: 20 with bronchial asthma (BA), 12 with cystic fibrosis (CF) and 10 healthy children without a history of allergies, aged 4-17 years. Th17 cells (CD3+CD4+CD161+CCR6+) were determined in peripheral blood by flow cytometry. The concentration of serum IL-17A was measured by ELISA.

RESULTS

The BA patients had a significantly higher percentage of Th17 (12.40±1.16%) compared to the CF children (7.64±0.87%, p=0.0035) and healthy (7.25±0.45%, p=0.008). Stratifying the BA group, we found higher levels of Th17 in patients with severe BA (p=0.03), whereas patients with moderate BA had Th17 cells close to those in CF and healthy children. We found that patients with better control of BA had Th17 closer to those with CF (p=0.98) than BA children with poor control (p<0.001) (post hoc, Bonferroni correction). CF patients with concomitant P. aeruginosa infection showed slightly higher percentages of Th17 cells than those without infection (8.08±3.09% vs. 6.25±2.42%, p=0.294).

CONCLUSIONS

The percentage of Th17 cells was significantly increased in the peripheral blood of children with severe BA compared to the children with moderate BA, which suggests that the former could possibly benefit from future target therapies.

Increased pro-inflammatory cytokine-secreting regulatory T cells are correlated with the plasticity of T helper cell differentiation and reflect disease status in asthma

BACKGROUND

Human regulatory T cells (Tregs) are a heterogeneous population which consists of three distinct subpopulations: CD25⁺CD45RA⁺ resting Treg (rTreg) cells; CD25^hiCD45RA^- activated Treg (aTreg) cells, which are both suppressive; and CD25⁺CD45RA^- cytokine-secreting T cells with pro-inflammatory capacity.

OBJECTIVE

We investigated variation in peripheral Treg subpopulations of asthma and explored their potential roles in asthma inflammation.

METHODS

Twenty-eight mild asthma patients, 26 moderate asthma patients, 18 severe asthma patients, and 36 healthy controls were recruited for a cross-sectional study. Phenotyping of peripheral CD4⁺ Tregs was performed based on flow cytometry results.

RESULTS

The proportions of rTreg and aTreg cells among CD4⁺ T cells were higher in mild and moderate asthma patients than in healthy controls. All three groups of asthmatics had a higher proportion of pro-inflammatory Tregs than healthy controls, and these increased with asthma severity. The proportion of IL-17-producing Foxp3⁺ cells and IFN-ɤ-producing Foxp3⁺ cells strongly correlated with T helper 17 (Th17) cells (r = 0.66, p < 0.001) and Th1 cells (r = 0.48, p < 0.001). The pro-inflammatory Treg subpopulation was correlated with the severity of asthma and may be insensitive to corticosteroids.

CONCLUSIONS

Our data suggest that pro-inflammatory Treg subpopulations may be relevant to the plasticity of Th17 and Th1 differentiation and play an important role in the pathogenesis of asthma.

Lung health in era of climate change and dust storms

Dust storms are strong winds which lead to particle exposure over extensive areas. These storms influence air quality on both a local and global scale which lead to both short and long-term effects. The frequency of dust storms has been on the rise during the last decade. Forecasts suggest that their incidence will increase as a response to the effects of climate change and anthropogenic activities. Elderly people, young children, and individuals with chronic cardiopulmonary diseases are at the greatest risk for health effects of dust storms. A wide variety of infectious and non-infectious diseases have been associated with dust exposure. Influenza A virus, pulmonary coccidioidomycosis, bacterial pneumonia, and meningococcal meningitis are a few examples of dust-related infectious diseases. Among non-infectious diseases, chronic obstructive pulmonary disease, asthma, sarcoidosis and pulmonary fibrosis have been associated with dust contact. Here, we review two molecular mechanisms of dust induced lung disease for asthma and sarcoidosis. We can also then further understand the mechanisms by which dust particles disturb airway epithelial and immune cells.

From Infections to Anthropogenic Inflicted Pathologies: Involvement of Immune Balance

A temporal trend can be seen in recent human history where the dominant causes of death have shifted from infectious to chronic diseases in industrialized societies. Human influences in the current "Anthropocene" epoch are exponentially impacting the environment and consequentially health. Changing ecological niches are suggested to have created health transitions expressed as modifications of immune balance from infections inflicting pathologies in the Holocene epoch (12,000 years ago) to human behaviors inflicting pathologies beginning in the Anthropocene epoch (300 years ago). A review of human immune health and adaptations responding to environmental (biological, chemical, physical, and psychological) stresses, which are influenced by social conditions, emphasize the involvement of fluctuations in immune cell subsets affecting influential gene-environment interactions. The literature from a variety of fields (anthropological, immunological, and environmental) is incorporated to present an expanded perspective on shifts in diseases within the context of immune balance and function and environmental immunology. The influences between historical and contemporary human ecology are examined in relation to human immunity. Several examples of shifts in human physiology and immunity support the premise that increased incidences of chronic diseases are a consequence of human modification of environment and lifestyle. Although the development of better health care and a broader understanding of human health have helped with better life quality and expectancy, the transition of morbidity and mortality rates from infections to chronic diseases is a cause for concern. Combinations of environmental stressors/pollutants and human behaviors and conditions are modulating the immune-neuroendocrine network, which compromises health benefits.

STAT1 Is Required for Suppression of Type 17 Immunity during Influenza and Bacterial Superinfection

Influenza is an annual, global health care concern. Secondary bacterial pneumonia is a severe complication associated with primary influenza virus infection, often resulting in critical morbidity and mortality. Our laboratory has identified influenza-induced suppression of anti-bacterial Type 17 immunity as a mechanism for enhanced susceptibility to bacterial super-infection. We have shown that influenza-induced type I interferon impairs Type 17 activation. STAT1 is a transcription factor involved in interferon signaling, shared by type I, II, and III interferon. In this work, we investigated the role of STAT1 signaling during influenza, methicillin-resistant Staphylococcus aureus (MRSA) super-infection. STAT1-/- mice had increased morbidity and airway inflammation compared to control mice during influenza mono-infection. Despite this worsened anti-viral response, STAT1-/- mice were protected from super-infection bacterial burden and mortality compared to controls. Type 17 immune activation was increased in lymphocytes in STAT1-/- mice during super-infection. The elevation in Type 17 immunity was not related to increased IL-23 production, as type I interferon could inhibit IL-23 expression in a STAT1 independent manner. STAT1-/- antigen presenting cells were inherently biased towards Type 17 polarization compared to control cells. Further, STAT1-/- dendritic cells produced attenuated IL-6 and TNFα upon heat-killed S. aureus stimulation compared to control. Overall, these data indicate that STAT1 signaling plays a detrimental role in influenza, MRSA super-infection by controlling the magnitude of Type 17 immune activation.

Targeting transcription factor lysine acetylation in inflammatory airway diseases

Asthma and chronic obstructive pulmonary disease are inflammatory airway diseases for which alternative therapeutic strategies are urgently needed. Interestingly, HDAC inhibitors show anti-inflammatory effects in mouse models for these diseases. Here we explore underlying mechanisms that may explain these effects. In previous studies, effects of HDAC inhibitors on histone acetylation are often correlated with their effects on gene expression. However, effects of HDAC inhibitors on transcription factors and their acetylation status may be particularly important in explaining these effects. These effects are also cell type-specific. Recent developments (including chemoproteomics and acetylomics) allow for a more detailed understanding of the selectivity of HDAC inhibitors, which will drive their further development into applications in inflammatory airway diseases.

Adenosine Triphosphate Promotes Allergen-Induced Airway Inflammation and Th17 Cell Polarization in Neutrophilic Asthma

Adenosine triphosphate (ATP) is a key mediator to alert the immune dysfunction by acting on P2 receptors. Here, we found that allergen challenge caused an increase of ATP secretion in a murine model of neutrophilic asthma, which correlated well with neutrophil counts and interleukin-17 production. When ATP signaling was blocked by intratracheal administration of the ATP receptor antagonist suramin before challenge, neutrophilic airway inflammation, airway hyperresponsiveness, and Th17-type responses were reduced significantly. Also, neutrophilic inflammation was abrogated when airway ATP levels were locally neutralized using apyrase. Furthermore, ATP promoted the Th17 polarization of splenic CD4⁺ T cells from DO11.10 mice in vitro. In addition, ovalbumin (OVA) challenge induced neutrophilic inflammation and Th17 polarization in DO11.10 mice, whereas administration of suramin before challenge alleviated these parameters. Thus, ATP may serve as a marker of neutrophilic asthma, and local blockade of ATP signaling might provide an alternative method to prevent Th17-mediated airway inflammation in neutrophilic asthma.

Central Role of IL-23 and IL-17 Producing Eosinophils as Immunomodulatory Effector Cells in Acute Pulmonary Aspergillosis and Allergic Asthma

Aspergillus fumigatus causes invasive pulmonary disease in immunocompromised hosts and allergic asthma in atopic individuals. We studied the contribution of lung eosinophils to these fungal diseases. By in vivo intracellular cytokine staining and confocal microscopy, we observed that eosinophils act as local sources of IL-23 and IL-17. Remarkably, mice lacking eosinophils had a >95% reduction in the percentage of lung IL-23p19⁺ cells as well as markedly reduced IL-23 heterodimer in lung lavage fluid. Eosinophils killed A. fumigatus conidia in vivo. Eosinopenic mice had higher mortality rates, decreased recruitment of inflammatory monocytes, and decreased expansion of lung macrophages after challenge with conidia. All of these functions underscore a potential protective role for eosinophils in acute aspergillosis. Given the postulated role for IL-17 in asthma pathogenesis, we assessed whether eosinophils could act as sources of IL-23 and IL-17 in models where mice were sensitized to either A. fumigatus antigens or ovalbumin (OVA). We found IL-23p19⁺ IL-17AF⁺ eosinophils in both allergic models. Moreover, close to 95% of IL-23p19⁺ cells and >90% of IL-17AF⁺ cells were identified as eosinophils. These data establish a new paradigm in acute and allergic aspergillosis whereby eosinophils act not only as effector cells but also as immunomodulatory cells driving the IL-23/IL-17 axis and contributing to inflammatory cell recruitment.

The opportunistic fungus, Aspergillus fumigatus, causes a spectrum of diseases ranging from invasive aspergillosis in the severely immunosuppressed to allergic asthma in atopic individuals. Here we explored the contribution of eosinophils, a type of white blood cell, to host defenses and pathogenesis in murine models of invasive pulmonary aspergillosis and asthma. We found eosinophils co-produce the cytokines IL-23 and IL-17 in both aspergillosis models as well as a model of OVA-induced asthma. Eosinophils killed the conidia (spores) of A. fumigatus in vivo and mice that lacked eosinophils were more susceptible to invasive aspergillosis. These observations suggest eosinophils play a more prominent role in defenses against invasive pulmonary aspergillosis than heretofore appreciated and identify eosinophil-derived IL-23 and IL-17 as potential therapeutic targets in allergic asthma.

Development of eosinophilic inflammation is independent of B-T cell interaction in a chronic house dust mite-driven asthma model

BACKGROUND

Chronic exposure to environmental triggers, such as house dust mite (HDM), drives T helper 2 (Th2) cell-mediated asthma. Recent evidence has shown that B-T cell interaction, and in particular germinal centre reactions and follicular T helper (Tfh) cells are required for the development of eosinophilic airway inflammation in HDM-driven models containing a sensitization and challenge phase. Whether B-T cell interactions are essential for pulmonary eosinophilic inflammation following chronic allergen provocation remains unknown.

AIMS

In this study, we investigated the importance of B-T cell interaction in the development of eosinophilic airway inflammation and pulmonary remodelling in a chronic HDM-driven asthma model.

METHODS

We exposed C57BL/6, Cd40l^-/- , and Mb1^-/- mice to HDM three times a week for five consecutive weeks.

RESULTS

Chronic HDM exposure induced a pronounced eosinophilic allergic airway inflammation in broncho-alveolar lavage fluid (BALf) and lung tissue, associated with the formation of immunologically active inducible bronchus-associated lymphoid tissue (iBALT) in the lungs. The absence of B cells or lack of CD40L signalling did not hamper eosinophilic inflammation in the airways, although the number of Tfh and Th2 cells was substantially reduced in the lungs. Importantly, type 2 innate lymphoid cell (ILC2) numbers in BALf and lung were not affected by the absence of B cells or B-T cell interaction. Furthermore, eosinophilic airway inflammation is not sufficient to induce pulmonary remodelling and airway hyperresponsiveness.

CONCLUSION AND CLINICAL RELEVANCE

From these findings, we conclude that B-T cell interaction is required for robust Tfh and Th2 cell induction, but not essential for eosinophilic airway inflammation during a chronic HDM-driven asthma model.

NFATc1 deletion in T lymphocytes inhibits the allergic trait in a murine model of asthma

BACKGROUND

NFATc1 isoforms are highly regulated in peripheral T cells where they contribute to the effector function and cell homeostasis.

OBJECTIVE

Here, we investigated the role of NFATc1 in asthma and in T cells.

METHODS

In a murine model of allergic asthma, we analysed differences in T-cell development in this allergic disease model, between wild-type and NFATc1 conditional knockout mice. Thus, we performed quantitative real-time PCR to investigate the mRNA expression of Th2-associated genes as well as genes that are involved in IgE immunoglobulin class-switch. Additionally, we used ELISA, Western blot and flow cytometry (FACS) to analyse protein concentrations of Th1-, Th2- and Th17-specific transcription factors and cytokines and the Th2 chemokine, thymus and activation-regulated chemokine/chemokine ligand 17 (TARC/CCL17) by ELISA.

RESULTS

Mice lacking NFATc1 in CD4(+) T cells display a significant reduction in lung Th2 and Th17 as well as an increase of Th1 cells in an experimental asthma model. Additionally, Batf gene, a recently described transcription factor of the Th2 and Th17 cell differentiation as well as a key T and B transcription factor involved in the IgE immunoglobulin class-switch, was found decreased in the lungs of these mice. As a consequence, serum OVA-specific IgE and IgG1 levels were found significantly decreased after allergen exposure and in the absence of NFATc1 in T cells in experimental allergic asthma.

CONCLUSIONS AND CLINICAL RELEVANCE

Targeting NFATc1 in T lymphocytes ameliorated the allergic trait in the airways of NFATc1(fl/fl) xCD4Cre mice. NFATc1 emerges as a novel target for anti-allergy intervention.

Airway inflammation in asthma: key players beyond the Th2 pathway

PURPOSE OF REVIEW

The Th2 pathway starts with the binding of IL-4 to the IL-4 receptor followed by the phosphorylation of signal transducer and activator of transcription 6 and the activation of GATA3. The most important question relates to the sources of IL-4 and IL-4 related inflammation. Which cells other than Th2 cells are responsible for airway inflammation in asthma?

RECENT FINDINGS

Accumulating data indicate that basophils contribute to endothelium-related IL-4-dependent inflammation. There is also a dendritic cell-related alternative for the induction of Th2 cells via Notch signalling. GATA3 deoxyribozyme improves asthma that is not clearly related to T-cells. The innate immune response in allergy is linked to mast cells, basophils, and the innate lymphoid cell type 2 (ILC2). ILC2s respond to IL-25, IL-33, thymic stromal lymphopoietin, and leukotrienes by producing IL-4, IL-5, and IL-13. In addition to all this inflammatory-cell-driven asthma, increasing evidence has emerged relating to smooth muscle cell activation, the endothelial and epithelial barrier functions, and improvements in the barrier function. The elevation of intracellular cyclic adenosine monophosphate because of the use of phosphodiesterase inhibitors adds to the prevention of epithelial-endothelial leakage, supports airway smooth muscle relaxation, and is immunosuppressive.

CONCLUSION AND SUMMARY

IL-4 is the predominant Th2 cell cytokine. Many more cells, including eosinophils, basophils, mast cells, and ILC2, contribute to the production of IL-4 in the airways. Epithelial cells and endothelial cells lose barrier function in the context of allergic airway inflammation, and this could be at least partially remedied by increasing the intracellular cyclic adenosine monophosphate levels through phosphodiesterase inhibition.

TCDD-Induced Activation of Aryl Hydrocarbon Receptor Inhibits Th17 Polarization and Regulates Non-Eosinophilic Airway Inflammation in Asthma

The aryl hydrocarbon receptor (AhR), a transcription factor of the bHLH/PAS family, has recently been demonstrated to regulate T cell differentiation. Whether AhR activation participates in allergic airway inflammation remains unknown. In the current study, using a non-eosinophilic asthma model, we demonstrate that 2, 3, 7, 8-tetrachlorodibenzo-P-dioxin (TCDD), a potent AhR ligand, reduced the airway infiltration of neutrophils, airway hyperresponsiveness and Th17 cytokine expression. Furthermore, stimulation with TCDD promoted Treg differentiation and inhibited Th17 differentiation. However, the maturation of dendritic cells may not be inhibited by AhR activation. This study thus indicates a critical role of TCDD-induced AhR activation in the regulation of non-eosinophilic airway inflammation.

Molecular Mechanisms of Airway Hyperresponsiveness in a Murine Model of Steroid-Resistant Airway Inflammation

IL-13 and IL-17A, produced mainly by Th2 and Th17 cells, respectively, have an influential role in asthma pathogenesis. We examined the role of IL-13 and IL-17A in mediating airway hyperresponsiveness (AHR), lung inflammation, and mucus metaplasia in a dual Th2/Th17 model of asthma. IL-13 and/or IL-17A were neutralized using mAbs. Th2/Th17 adoptive transfer induced a mixed asthma phenotype characterized by elevated eosinophilia and neutrophilia, tissue inflammation, mucus metaplasia, and AHR that were partially reversible with steroid treatment. Pulmonary inflammation and quasi-static lung compliance were largely unaffected by neutralization of IL-13 and/or IL-17A. However, neutralization of IL-13 alone or in combination with IL-17A significantly attenuated AHR and mucus metaplasia. Further, STAT6 activation was attenuated following IL-13 and IL-13/IL-17A Ab treatment. We next assessed the role of STAT6 in Th2/Th17-mediated allergic airway disease using STAT6(-/-) mice. STAT6(-/-) mice adoptively transferred with Th2/Th17 cells had decreased AHR compared with controls. These data suggest that IL-13 drives AHR and mucus metaplasia in a STAT6-dependent manner, without directly contributing to airway or tissue inflammation. IL-17A independently contributes to AHR, but it only partially mediates inflammation and mucus metaplasia in a mixed Th2/Th17 model of steroid-resistant asthma.

Rhinovirus inhibits IL-17A and the downstream immune responses in allergic asthma

The proinflammatory cytokine interleukin-17A (IL-17A) is known to mediate antimicrobial activity, but its role during rhinovirus (RV) infections and in asthma needs further investigation. Therefore, we addressed the role of IL-17A during allergic asthma and antiviral immune response in human and murine immunocompetent cells. In this study we found that asthmatic children with a RV infection in their upper airways have upregulated mRNA levels of the antiviral cytokine interferon type I (IFN)-β and the transcription factor T-box 21 (TBX21) and reduced levels of IL-17A protein in their peripheral blood mononuclear cells (PBMCs). We also found that IL-17A inhibited RV1b replication in infected human lung epithelial cells A549. Furthermore, by using gene array analysis we discovered that targeted deletion of Il17a in murine lung CD4(+) T cells impaired Oas1g mRNA downstream of Ifnβ, independently from RV infection. Additionally, in PBMCs of children with a RV infection in their nasalpharyngeal fluid OAS1 gene expression was found downregulated. Finally RV1b inhibited IL-17A production in lung CD4(+) T cells in a setting of experimental asthma. These results indicate that the RV1b inhibits IL-17A in T helper type 17 cells and IL-17A clears RV1b infection in epithelial cells. In both cases IL-17A contributes to fend off RV1b infection by inducing genes downstream of interferon type I pathway.

Acupuncture Attenuated Inflammation and Inhibited Th17 and Treg Activity in Experimental Asthma

Acupuncture is an effective therapeutic method in asthma treatment in traditional Chinese medicine. Here, we evaluated the effect of acupuncture on airway hyperresponsiveness (AHR) and the associated inflammatory changes as well as Th17 and Treg activity in ovalbumin- (OVA-) induced experimental asthma. Our results revealed that acupuncture treatment significantly inhibited AHR, lung inflammation, and mucus secretion of experimental asthma mice. Furthermore, a decrease in lymphocytes and eosinophils as well as neutrophils was observed in bronchoalveolar lavage fluid (BALF) of mice treated with acupuncture. Acupuncture reduced the OVA specific IgE level as well as the Th17 cytokine levels including IL-17A, IL-17F, and IL-22 in the serum of the experimental asthma mice. Acupuncture treatment group also had reduced CD4+IL-17A+ cell numbers and increased CD4+Foxp3+ cell numbers in BALF. In addition, acupuncture could inhibit IL-17R, RORγt, p65, and the inhibitor of NF-κB kinase-α (IKKα) protein expression. Our results indicated that acupuncture was effective in inhibiting AHR and inflammation in OVA-induced experimental asthma, which may be associated with the regulation of Th17 and Treg activity and NF-κB pathway.

A randomised, placebo-controlled study of the CXCR2 antagonist AZD5069 in bronchiectasis

This randomised double-blind placebo-controlled parallel-group multicentre phase IIa study evaluated the effect of the CXCR2 antagonist AZD5069 on sputum neutrophil counts in adults with bronchiectasis.Patients were randomised 1:1 to receive AZD5069 80 mg or placebo orally twice daily for 28 days. Assessments included blood cell counts, inflammatory markers in blood, morning spontaneous sputum, lung function, safety and tolerability and patients completed daily BronkoTest diary cards. The primary outcome measure was the change in absolute sputum neutrophil count.Of 52 randomised patients, 45 completed treatment, 20 (76.9%) out of 26 receiving AZD5069 and 25 (96.2%) out of 26 receiving placebo. AZD5069 reduced the absolute neutrophil cell count in morning sputum by 69% versus placebo (p=0.004); percentage sputum neutrophil count was reduced by 36% (p=0.008). The number of infections/exacerbations was similar with AZD5069 and placebo (nine versus eight), but these led to more study discontinuations with AZD5069 (four versus zero). Sputum interleukin (IL)-6 and growth-regulated oncogene (GRO)-α and serum GRO-α, IL-1ß and IL-8 levels increased with AZD5069 versus placebo (all p<0.001), while serum high-sensitivity C-reactive protein levels did not change. AZD5069 was well tolerated.AZD5069 markedly reduced absolute sputum neutrophil counts in bronchiectasis patients, although this was not associated with improvements in clinical outcomes in this exploratory study.

Influenza-induced type I interferon enhances susceptibility to gram-negative and gram-positive bacterial pneumonia in mice

Suppression of type 17 immunity by type I interferon (IFN) during influenza A infection has been shown to enhance susceptibility to secondary bacterial pneumonia. Although this mechanism has been described in coinfection with gram-positive bacteria, it is unclear whether similar mechanisms may impair lung defense against gram-negative infections. Furthermore, precise delineation of the duration of type I IFN-associated susceptibility to bacterial infection remains underexplored. Therefore, we investigated the effects of preceding influenza A virus infection on subsequent challenge with the gram-negative bacteria Escherichia coli or Pseudomonas aeruginosa and the temporal association between IFN expression with susceptibility to Staphylococcus aureus challenge in a mouse model of influenza and bacterial coinfection. Here we demonstrate that preceding influenza A virus led to increased lung E. coli and P. aeruginosa bacterial burden, which was associated with suppression of type 17 immunity and attenuation of antimicrobial peptide expression. Enhanced susceptibility to S. aureus coinfection ceased at day 14 of influenza infection, when influenza-associated type I IFN levels had returned to baseline levels, further suggesting a key role for type I IFN in coinfection pathogenesis. These findings further implicate type I IFN-associated suppression of type 17 immunity and antimicrobial peptide production as a conserved mechanism for enhanced susceptibility to both gram-positive and gram-negative bacterial coinfection during influenza infection.

Bu-Shen-Yi-Qi formulae suppress chronic airway inflammation and regulate Th17/Treg imbalance in the murine ovalbumin asthma model

ETHNOPHARMACOLOGICAL RELEVANCE

Bu-Shen-Yi-Qi formulae (BSYQF) are frequently used in the treatment of chronic inflammatory diseases in the respiratory system in traditional Chinese medicine (TCM). However, the regulatory effect of BSYQF on T helper 17 (Th17) and regulatory T (Treg) cells in murine ovalbumin (OVA) asthma model remains poorly understood. In the present study, we sought to determine the effect of high-performance liquid chromatography/mass spectrometry (HPLC/MS) standardized BSYQF on chronic airway inflammation and Th17/Treg imbalance in the murine OVA asthma model.

MATERIALS AND METHODS

The murine asthma model was induced by OVA sensitization and challenge and BSYQF was oral administrated. 24h after last OVA exposure, airway hyperresponsiveness (AHR) to methacholine (Mch) was assessed, and inflammatory cell counts and classification in bronchoalveolar lavage fluid (BALF) were analysed. Histopathological evaluation of the lung tissue was performed by hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) staining. Th17 and Treg associated cytokine levels in serum and BALF as well as transcription factors expression in the lung tissue were measured by ELISA, Bio-Plex and western blot assay. We also analysed the CD4(+)RORγt(+) and CD4(+)Foxp3(+) T cells in BALF and spleen by flow cytometric analysis.

RESULTS

Our results demonstrated that oral administration of BSYQF inhibited the markedly increased AHR and lung inflammation (p<0.05), resulted in a dramatic reduction in total inflammatory cells as well as neutrophils (Neu), lymphocytes (Lym), monocytes (Mon), eosinophils (Eos) and basophils (Bas) of OVA-induced asthmatic mice (p<0.05). Furthermore, BSYQF treatment caused a distinct reduction in IL-6, IL-10 and IL-17A levels in serum (p<0.05), and induced a significant improvement in IL-6 and IL-10 as well as a marked decrease in TGF-β1 and IL-17A levels in BALF of OVA-induced asthmatic mice (p<0.05). Mice in BSYQF treated groups also had decreased RORγt and increased Foxp3 expression in the lung tissue (p<0.05). Flow cytometry analysis revealed that CD4(+)RORγt(+) T cells elevated markedly and CD4(+)Foxp3(+) T cells decreased prominently in BALF and spleen in murine OVA asthma model (p<0.05), and BSYQF and DEX treatment lead to an obvious reduction in CD4(+)RORγt(+) T cells in BALF (p<0.05) but not in spleen. BSYQF and DEX treatment resulted in an obvious elevation in CD4(+)Foxp3(+) T cells in BALF and spleen (p<0.05).

CONCLUSIONS

Collectively, these results demonstrated that BSYQF could suppress chronic airway inflammation and regulate Th17/Treg imbalance by inhibition of Th17 and enhancement of Treg functions in the murine OVA asthma model, which may help to elucidate the underlying regulatory mode of BSYQF on asthma treatment.

Cellular mechanisms underlying eosinophilic and neutrophilic airway inflammation in asthma

Asthma is a phenotypically heterogeneous chronic disease of the airways, characterized by either predominant eosinophilic or neutrophilic, or even mixed eosinophilic/neutrophilic inflammatory patterns. Eosinophilic inflammation can be associated with the whole spectrum of asthma severity, ranging from mild-to-moderate to severe uncontrolled disease, whereas neutrophilic inflammation occurs mostly in more severe asthma. Eosinophilic asthma includes either allergic or nonallergic phenotypes underlying immune responses mediated by T helper (Th)2 cell-derived cytokines, whilst neutrophilic asthma is mostly dependent on Th17 cell-induced mechanisms. These immune-inflammatory profiles develop as a consequence of a functional impairment of T regulatory (Treg) lymphocytes, which promotes the activation of dendritic cells directing the differentiation of distinct Th cell subsets. The recent advances in the knowledge of the cellular and molecular mechanisms underlying asthmatic inflammation are contributing to the identification of novel therapeutic targets, potentially suitable for the implementation of future improvements in antiasthma pharmacologic treatments.

Chitinase-like proteins promote IL-17-mediated neutrophilia in a tradeoff between nematode killing and host damage

Enzymatically inactive chitinase-like proteins (CLPs) such as BRP-39, Ym1 and Ym2 are established markers of immune activation and pathology, yet their functions are essentially unknown. We found that Ym1 and Ym2 induced the accumulation of neutrophils through the expansion of γδ T cell populations that produced interleukin 17 (IL-17). While BRP-39 did not influence neutrophilia, it was required for IL-17 production in γδ T cells, which suggested that regulation of IL-17 is an inherent feature of mouse CLPs. Analysis of a nematode infection model, in which the parasite migrates through the lungs, revealed that the IL-17 and neutrophilic inflammation induced by Ym1 limited parasite survival but at the cost of enhanced lung injury. Our studies describe effector functions of CLPs consistent with innate host defense traits of the chitinase family.

Interleukin-22 exacerbates airway inflammation induced by short-term exposure to cigarette smoke in mice

AIM

Interleukin-22 (IL-22) exhibits both proinflammatory and anti-inflammatory properties in various biological processes. In this study we explored the effects of exogenous recombinant IL-22 (rIL-22) on cigarette smoke (CS)-induced airway inflammation in mice.

METHODS

Male C57BL/6 mice were divided into groups: (1) CS group exposed to tobacco smoke for 3 consecutive days, (2) rIL-22 group received rIL-22 (100 mg/kg, ip), and (3) CS plus rIL-22 group, received rIL-22 (100 mg/kg, ip) before the CS exposure. The airway resistance (Rn), lung morphology, inflammatory cells in the airways, and inflammatory cytokines and CXCR3 ligands in both bronchoalveolar lavage (BAL) fluids and lung tissues were analyzed.

RESULTS

CS alone significantly elevated IL-22 level in the BAL fluid. Both CS and rIL-22 significantly augmented airway resistance, an influx of inflammatory cells into the airways and lung parenchyma, and significantly elevated levels of pro-inflammatory cytokines (TGFβ1 and IL-17A) and CXCR3 chemokines (particularly CXCL10) at the mRNA and/or protein levels. Furthermore, the effects of rIL-22 on airway resistance and inflammation were synergistic with those of CS, as demonstrated by a further increased Rn value, infiltration of greater numbers of inflammatory cells into the lung, higher levels of inflammatory cytokines and chemokines, and more severe pathological changes in CS plus rIL-22 group as compared to those in CS group.

CONCLUSION

Exogenous rIL-22 exacerbates the airway inflammatory responses to CS exposure in part by inducing expression of several proinflammatory cytokines and CXCR3 ligands.

Mode of dendritic cell activation: the decisive hand in Th2/Th17 cell differentiation. Implications in asthma severity?

Asthma is a heterogeneous chronic inflammatory disease of the airways, with reversible airflow limitations and airway remodeling. The classification of asthma phenotypes was initially based on different combinations of clinical symptoms, but they are now unfolding to link biology to phenotype. As such, patients can suffer from a predominant eosinophilic, neutrophilic or even mixed eosinophilic/neutrophilic inflammatory response. In adult asthma patients, eosinophilic inflammation is usually seen in mild-to-moderate disease and neutrophilic inflammation in more severe disease. The underlying T cell response is predominated by T helper (Th) 2, Th17, or a mixed Th2/Th17 cell immune response. Dendritic cells (DCs) are "professional" antigen presenting cells (APCs), since their principal function is to present antigens and induce a primary immune response in resting naive T cells. DCs also drive the differentiation into distinctive Th subsets. The expression of co-stimulatory molecules and cytokines by DCs and surrounding cells determines the outcome of Th cell differentiation. The nature of DC activation will determine the expression of specific co-stimulatory molecules and cytokines, specifically needed for induction of the different Th cell programs. Thus DC activation is crucial for the subsequent effector Th immune responses. In this review, we will discuss underlying mechanisms that initiate DC activation in favor of Th2 differentiation versus Th1/Th17 and Th17 differentiation in the development of mild versus moderate to severe asthma.

The complex relationship between inflammation and lung function in severe asthma

Asthma is a common respiratory disease affecting ∼300 million people worldwide. Airway inflammation is thought to contribute to asthma pathogenesis, but the direct relationship between inflammation and airway hyperresponsiveness (AHR) remains unclear. This study investigates the role of inflammation in a steroid-insensitive, severe allergic airway disease model and in severe asthmatics stratified by inflammatory profile. First, we used the T-helper (T(H))-17 cells adoptive transfer mouse model of asthma to induce pulmonary inflammation, which was lessened by tumor necrosis factor (TNF)-α neutralization or neutrophil depletion. Although decreased airspace inflammation following TNFα neutralization and neutrophil depletion rescued lung compliance, neither intervention improved AHR to methacholine, and tissue inflammation remained elevated when compared with control. Further, sputum samples were collected and analyzed from 41 severe asthmatics. In severe asthmatics with elevated levels of sputum neutrophils, but low levels of eosinophils, increased inflammatory markers did not correlate with worsened lung function. This subset of asthmatics also had significantly higher levels of T(H)17-related cytokines in their sputum compared with severe asthmatics with other inflammatory phenotypes. Overall, this work suggests that lung compliance may be linked with cellular inflammation in the airspace, whereas T-cell-driven AHR may be associated with tissue inflammation and other pulmonary factors.

IL-17A induces Pendrin expression and chloride-bicarbonate exchange in human bronchial epithelial cells

The epithelium plays an active role in the response to inhaled pathogens in part by responding to signals from the immune system. Epithelial responses may include changes in chemokine expression, increased mucin production and antimicrobial peptide secretion, and changes in ion transport. We previously demonstrated that interleukin-17A (IL-17A), which is critical for lung host defense against extracellular bacteria, significantly raised airway surface pH in vitro, a finding that is common to a number of inflammatory diseases. Using microarray analysis of normal human bronchial epithelial (HBE) cells treated with IL-17A, we identified the electroneutral chloride-bicarbonate exchanger Pendrin (SLC26A4) as a potential mediator of this effect. These data were verified by real-time, quantitative PCR that demonstrated a time-dependent increase in Pendrin mRNA expression in HBE cells treated with IL-17A up to 48 h. Using immunoblotting and immunofluorescence, we confirmed that Pendrin protein expression is increased in IL-17 treated HBE cells and that it is primarily localized to the mucosal surface of the cells. Functional studies using live-cell fluorescence to measure intracellular pH demonstrated that IL-17A induced chloride-bicarbonate exchange in HBE cells that was not present in the absence of IL-17A. Furthermore, HBE cells treated with short interfering RNA against Pendrin showed substantially reduced chloride-bicarbonate exchange. These data suggest that Pendrin is part of IL-17A-dependent epithelial changes and that Pendrin may therefore be a therapeutic target in IL-17A-dependent lung disease.

Aligning mouse models of asthma to human endotypes of disease

Substantial gains in understanding the pathophysiologic mechanisms underlying asthma have been made using preclinical mouse models. However, because asthma is a complex, heterogeneous syndrome that is rarely due to a single allergen and that often presents in the absence of atopy, few of the promising therapeutics that demonstrated effectiveness in mouse models have translated into new treatments for patients. This has resulted in an urgent need to characterize T helper (Th) 2-low, non-eosinophilic subsets of asthma, to study models that are resistant to conventional treatments such as corticosteroids and to develop therapies targeting patients with severe disease. Classifying asthma based on underlying pathophysiologic mechanisms, known as endotyping, offers a stratified approach for the development of new therapies for asthma. In preclinical research, new models of asthma are being utilized that more closely resemble the clinical features of different asthma endotypes, including the presence of interleukin-17 and a Th17 response, a biomarker of severe disease. These models utilize more physiologically relevant sensitizing agents, exacerbating factors and allergens, as well as incorporate time points that better reflect the natural history and chronicity of clinical asthma. Importantly, some models better represent non-classical asthma endotypes that facilitate the study of non-Th2-driven pathology and resemble the complex nature of clinical asthma, including corticosteroid resistance. Placing mouse asthma models into the context of human asthma endotypes will afford a more relevant approach to the understanding of pathophysiological mechanisms of disease that will afford the development of new therapies for those asthmatics that remain difficult to treat.

Refractory asthma: mechanisms, targets, and therapy

Asthma is a common medical condition affecting 300 million people worldwide. Airway inflammation, smooth muscle bronchoconstriction leading to airflow obstruction, and mucous hypersecretion are clinical hallmarks of asthma. The NHLBI Expert Panel Report 3 recommends inhaled corticosteroids (ICS) for patients with moderate to severe persistent asthma. Inhaled corticosteroids (ICS) target gene transcription through their interactions with the glucocorticoid (GC) receptor (GR) at the glucocorticoid response element (GRE). The GC/GR complex enhances anti-inflammatory but inhibits pro-inflammatory mediator production. Classically, asthma has been described as a Th2-associated eosinophil-predominant disease, but recently alternative models have been described including a Th17-mediated neutrophil-predominant phenotype resulting in patients with more severe disease who may be less responsive to steroids. Additional mechanisms of steroid resistance include increased activity of GR phosphorylating kinases which modify the interactions of GR with transcription factors to inhibit the ability of GR to bind with GRE, leading to an increase in pro-inflammatory gene transcription. Oxidative stress also affects the balance between pro-inflammatory and anti-inflammatory gene transcription through the modification of transcription factors and cofactors (such as PI3K) leading to the inhibition of histone deacetylase 2. Continued investigations into the mechanisms behind glucocorticoid resistance will lead to novel treatments that improve control of severe refractory asthma.

Dual role of interleukin-23 in epicutaneously-sensitized asthma in mice

BACKGROUND

Interleukin (IL)-23/Th17 axis plays an important role in the pathophysiology of asthma and eczema, however, there are some conflicting data about the effects of this system on allergic airway inflammation. In the present study, we aim to dissect the spatiotemporal differences in the roles of IL-23 in an epicutaneously-sensitized asthma model of mice.

METHODS

C57BL/6 mice were sensitized to ovalbumin (OVA) by patch application on the skin, followed by airway exposure to aerosolized OVA. During sensitization and/or challenge phase, either a specific neutralizing antibody (Ab) against IL-23 or control IgG was injected intraperitoneally. On days 1 and 8 after the final OVA exposure, airway inflammation and responsiveness to methacholine, immunoglobulin levels in serum, and cytokine release from splenocytes were evaluated. Skin Il23a mRNA levels were evaluated with quantitative RT-PCR.

RESULTS

Patch application time-dependently increased the expression of Il23a mRNA expression in the skin. Treatment with the anti-IL-23 Ab during sensitization phase alone significantly reduced the number of eosinophils in bronchoalveolar lavage fluids and peribronchial spaces after allergen challenge compared with treatment with control IgG. Anti-IL-23 Ab also reduced serum levels of OVA-specific IgG1. In contrast, treatment with the anti-IL-23 Ab during the challenge phase alone rather exacerbated airway hyperresponsiveness to methacholine with little effects on airway eosinophilia or serum IgG1 levels.

CONCLUSIONS

IL-23 expressed in the skin during the sensitization phase plays an essential role in the development of allergic phenotypes, whereas IL-23 in the airways during the challenge phase suppresses airway hyperresponsiveness.

IL-6 activated integrated BATF/IRF4 functions in lymphocytes are T-bet-independent and reversed by subcutaneous immunotherapy

IL-6 plays a central role in supporting pathological T_H2 and T_H17 cell development and inhibiting the protective T regulatory cells in allergic asthma. T_H17 cells have been demonstrated to regulate allergic asthma in general and T-bet-deficiency-induced asthma in particular. Here we found an inverse correlation between T-bet and Il-6 mRNA expression in asthmatic children. Moreover, experimental subcutaneous immunotherapy (SIT) in T-bet^(−/−) mice inhibited IL-6, IL-21R and lung T_H17 cells in a setting of asthma. Finally, local delivery of an anti-IL-6R antibody in T-bet^(−/−) mice resulted in the resolution of this allergic trait. Noteworthy, BATF, crucial for the immunoglobulin-class-switch and T_H2,T_H17 development, was found down-regulated in the lungs of T-bet^(−/−) mice after SIT and after treatment with anti-IL-6R antibody, indicating a critical role of IL-6 in controlling BATF/IRF4 integrated functions in T_H2, T_H17 cells and B cells also in a T-bet independent fashion in allergic asthma.

Clinical consequences of targeting IL-17 and TH17 in autoimmune and allergic disorders

The TH17 lineage of T cells and its canonical cytokine IL-17 have been the focus of many recent studies in autoimmune, allergic, and infectious disease. In this review, we will briefly discuss the current knowledge about the role of these cells and IL-17 in a spectrum of disorders. It is clear that IL-17 plays pathogenic roles in certain conditions while the same pathway is critically important to immunity in others. Targeting of TH17 cells or IL-17 therapeutically may impart many benefits, but this approach is not without potentially serious implications regarding host defense. These issues will be discussed herein as we evaluate pharmacological approaches targeting this pathway that are just beginning to be fully tested in human disease.

A tale of two cytokines: IL-17 and IL-22 in asthma and infection

The Th17 pathway has recently been shown to play a critical role in host defense, allergic responses and autoimmune inflammation. Th17 cells predominantly produce IL-17 and IL-22, which are two cytokines with broad effects in the lung and other tissues. This review summarizes not only what is currently known about the molecular regulation of this pathway and Th17-related cytokine signaling, but also the roles of these cytokines in pathogen immunity and asthma. In the last 5 years, the Th17 field has rapidly grown and research has revealed that the Th17 pathway is essential in lung pathogenesis in response to exogenous stimuli. As work in the field continues, it is expected that many exciting therapeutic advances will be made for a broad range of diseases.