Diesel exhaust particles enhance T-cell activation in severe asthmatics

Impact of climate change on immune responses and barrier defense

Climate change is not just jeopardizing the health of our planet but is also increasingly affecting our immune health. There is an expanding body of evidence that climate-related exposures such as air pollution, heat, wildfires, extreme weather events, and biodiversity loss significantly disrupt the functioning of the human immune system. These exposures manifest in a broad range of stimuli, including antigens, allergens, heat stress, pollutants, microbiota changes, and other toxic substances. Such exposures pose a direct and indirect threat to our body's primary line of defense, the epithelial barrier, affecting its physical integrity and functional efficacy. Furthermore, these climate-related environmental stressors can hyperstimulate the innate immune system and influence adaptive immunity-notably, in terms of developing and preserving immune tolerance. The loss or failure of immune tolerance can instigate a wide spectrum of noncommunicable diseases such as autoimmune conditions, allergy, respiratory illnesses, metabolic diseases, obesity, and others. As new evidence unfolds, there is a need for additional research in climate change and immunology that covers diverse environments in different global settings and uses modern biologic and epidemiologic tools.

DEPs Induce Local Ige Class Switching Independent of Their Ability to Stimulate iBALT de Novo Formation

BACKGROUND

Diesel exhaust particles (DEPs) are leading to a general increase in atopic diseases worldwide. However, it is still unknown whether DEPs induce systemic B-cell IgE class switching in secondary lymphoid organs or locally in the lungs in inducible bronchus-associated lymphoid tissue (iBALT). The aim of this work was to identify the exact site of DEP-mediated B-cell IgE class switching and pro-allergic antibody production.

METHODS

We immunized BALB/c mice with different OVA doses (0.3 and 30 µg) intranasally in the presence and absence of two types of DEPs, SRM1650B and SRM2786. We used low (30 µg) and high (150 µg) DEP doses.

RESULTS

Only a high DEP dose induced IgE production, regardless of the particle type. Local IgE class switching was stimulated upon treatment with both types of particles with both low and high OVA doses. Despite the similar ability of the two standard DEPs to stimulate IgE production, their ability to induce iBALT formation and growth was markedly different upon co-administration with low OVA doses.

CONCLUSIONS

DEP-induced local IgE class switching takes place in preexisting iBALTs independent of de novo iBALT formation, at least in the case of SRM1650B co-administered with low OVA doses.

Diesel Exhaust Particles Impair Therapeutic Effect of Human Wharton's Jelly-Derived Mesenchymal Stem Cells against Experimental Colitis through ROS/ERK/cFos Signaling Pathway

Background and Objectives

Epidemiological investigations have shown positive correlations between increased diesel exhaust particles (DEP) in ambient air and adverse health outcomes. DEP are the major constituent of particulate atmospheric pollution and have been shown to induce proinflammatory responses both in the lung and systemically. Here, we report the effects of DEP exposure on the properties of human Wharton’s jelly-derived mesenchymal stem cells (WJ-MSCs), including stemness, regeneration, and immunomodulation.

Methods and Results

Non-apoptotic concentrations of DEP (10 μg/ml) inhibited the migration and osteogenic differentiation capacity of WJ-MSCs. Gene expression profiling showed that DEP increased intracellular reactive oxygen species (ROS) and expression of pro-inflammatory and metabolic-process-related genes including cFos. Furthermore, WJ-MSCs cultured with DEP showed impaired suppression of T cell proliferation that was reversed by inhibition of ROS or knockdown of cFos. ERK inhibition assay revealed that DEP-induced ROS regulated cFos through activation of ERK but not NF-κB signaling. Overall, low concentrations of DEP (10 μg/ml) significantly suppressed the stemness and immunomodulatory properties of WJ-MSCs through ROS/ERK/cFos signaling pathways. Furthermore, WJ-MSCs cultured with DEP impaired the therapeutic effect of WJ-MSCs in experimental colitis mice, but was partly reversed by inhibition of ROS.

Conclusions

Taken together, these results indicate that exposure to DEP enhances the expression of pro-inflammatory cytokines and immune responses through a mechanism involving the ROS/ERK/cFos pathway in WJ-MSCs, and that DEP-induced ROS damage impairs the therapeutic effect of WJ-MSCs in colitis. Our results suggest that modulation of ROS/ERK/cFos signaling pathways in WJ-MSCs might be a novel therapeutic strategy for DEP-induced diseases.

Exacerbation-Prone Asthma: A Biological Phenotype or a Social Construct

Asthma is a complex syndrome with multiple phenotypes and endotypes. Asthma exacerbations are not only the clearest indictor of the morbidity of asthma and of the risk for mortality due to asthma, but also comprise a significant amount of the cost to care for poorly controlled asthma. There continues to be significant disparity in the prevalence, mortality, and morbidity due to asthma. Patients with asthma who suffer recurrent exacerbations are considered to have exacerbation-prone asthma (EPA). Efforts to characterize patients with frequent exacerbations show that the etiology is likely multifactorial. Research to determine the intrinsic risk factors for EPA include studies of both genetic and inflammatory biomarkers. External factors contributing to exacerbations have been extensively reviewed and include viral infection, environmental exposures, air pollution, and psychosocial and economic barriers to optimizing health. It is likely that EPA occurs when patients who have an increased underlying intrinsic/biological risk are placed in a given exposome (environments with a variety of exposures and triggers including allergens, pollution, stress, barriers, and occupational exposures). It is the social construct combined with underlying biology that frequently drives an EPA phenotype.

Polluted Air Exposure Compromises Corneal Immunity and Exacerbates Inflammation in Acute Herpes Simplex Keratitis

Air pollution is a serious environmental issue worldwide in developing countries’ megacities, affecting the population’s health, including the ocular surface, by predisposing or exacerbating other ocular diseases. Herpes simplex keratitis (HSK) is caused by the herpes simplex virus type 1 (HSV-1). The primary or recurring infection in the ocular site causes progressive corneal scarring that may result in visual impairment. The present study was designed to study the immunopathological changes of acute HSK under urban polluted air, using the acute HSK model combined with an experimental urban polluted air exposure from Buenos Aires City. We evaluated the corneal clinical outcomes, viral DNA and pro-inflammatory cytokines by RT-PCR and ELISA assays, respectively. Then, we determined the innate and adaptive immune responses in both cornea and local lymph nodes after HSV-1 corneal by immunofluorescence staining and flow cytometry. Our results showed that mice exposed to polluted air develop a severe form of HSK with increased corneal opacity, neovascularization, HSV-1 DNA and production of TNF-α, IL-1β, IFN-γ, and CCL2. A high number of corneal resident immune cells, including activated dendritic cells, was observed in mice exposed to polluted air; with a further significant influx of bone marrow-derived cells including GR1+ cells (neutrophils and inflammatory monocytes), CD11c+ cells (dendritic cells), and CD3+ (T cells) during acute corneal HSK. Moreover, mice exposed to polluted air showed a predominant Th1 type T cell response over Tregs in local lymph nodes during acute HSK with decreased corneal Tregs. These findings provide strong evidence that urban polluted air might trigger a local imbalance of innate and adaptive immune responses that exacerbate HSK severity. Taking this study into account, urban air pollution should be considered a key factor in developing ocular inflammatory diseases.

Viruses and non-allergen environmental triggers in asthma

Asthma is a complex inflammatory disease with many triggers. The best understood asthma inflammatory pathways involve signals characterized by peripheral eosinophilia and elevated immunoglobulin E levels (called T2-high or allergic asthma), though other asthma phenotypes exist (eg, T2-low or non-allergic asthma, eosinophilic or neutrophilic-predominant). Common triggers that lead to poor asthma control and exacerbations include respiratory viruses, aeroallergens, house dust, molds, and other organic and inorganic substances. Increasingly recognized non-allergen triggers include tobacco smoke, small particulate matter (eg, PM2.5), and volatile organic compounds. The interaction between respiratory viruses and non-allergen asthma triggers is not well understood, though it is likely a connection exists which may lead to asthma development and/or exacerbations. In this paper we describe common respiratory viruses and non-allergen triggers associated with asthma. In addition, we aim to show the possible interactions, and potential synergy, between viruses and non-allergen triggers. Finally, we introduce a new clinical approach that collects exhaled breath condensates to identify metabolomics associated with viruses and non-allergen triggers that may promote the early management of asthma symptoms.

Causation by Diesel Exhaust Particles of Endothelial Dysfunctions in Cytotoxicity, Pro-inflammation, Permeability, and Apoptosis Induced by ROS Generation

Epidemiological studies suggest that an increase of diesel exhaust particles (DEP) in ambient air corresponds to an increase in hospital-recorded myocardial infarctions within 48 h after exposure. Among the many theories to explain this data are endothelial dysfunction and translocation of DEP into vasculature. The mechanisms for such DEP-induced vascular permeability remain unknown. One of the major mechanisms underlying the effects of DEP is suggested to be oxidative stress. Experiments have shown that DEP induce the generation of reactive oxygen species (ROS), such as superoxide anion and H₂O₂ in the HUVEC tube cells. Transcription factor Nrf2 is translocated to the cell nucleus, where it activates transcription of the antioxidative enzyme HO-1 and sequentially induces the release of vascular permeability factor VEGF-A. Furthermore, a recent study shows that DEP-induced intracellular ROS may cause the release of pro-inflammatory TNF-α and IL-6, which may induce endothelial permeability as well by promoting VEGF-A secretion independently of HO-1 activation. These results demonstrated that the adherens junction molecule, VE-cadherin, becomes redistributed from the membrane at cell-cell borders to the cytoplasm in response to DEP, separating the plasma membranes of adjacent cells. DEP were occasionally found in endothelial cell cytoplasm and in tube lumen. In addition, the induced ROS is cytotoxic to the endothelial tube-like HUVEC. Acute DEP exposure stimulates ATP depletion, followed by depolarization of their actin cytoskeleton, which sequentially inhibits PI3K/Akt activity and induces endothelial apoptosis. Nevertheless, high-dose DEP augments tube cell apoptosis up to 70 % but disrupts the p53 negative regulator Mdm2. In summary, exposure to DEP affects parameters influencing vasculature permeability and viability, i.e., oxidative stress and its upregulated antioxidative and pro-inflammatory responses, which sequentially induce vascular permeability factor, VEGF-A release and disrupt cell-cell junction integrity. While exposure to a low dose of DEP actin triggers cytoskeleton depolarization, reduces PI3K/Akt activity, and induces a p53/Mdm2 feedback loop, a high dose causes apoptosis by depleting Mdm2. Addition of ROS scavenger N-acetyl cysteine suppresses DEP-induced oxidative stress efficiently and reduces subsequent damages by increasing endogenous glutathione.

Radical containing combustion derived particulate matter enhance pulmonary Th17 inflammation via the aryl hydrocarbon receptor

Background

Pollutant particles containing environmentally persistent free radicals (EPFRs) are formed during many combustion processes (e.g. thermal remediation of hazardous wastes, diesel/gasoline combustion, wood smoke, cigarette smoke, etc.). Our previous studies demonstrated that acute exposure to EPFRs results in dendritic cell maturation and Th17-biased pulmonary immune responses. Further, in a mouse model of asthma, these responses were enhanced suggesting exposure to EPFRs as a risk factor for the development and/or exacerbation of asthma. The aryl hydrocarbon receptor (AHR) has been shown to play a role in the differentiation of Th17 cells. In the current study, we determined whether exposure to EPFRs results in Th17 polarization in an AHR dependent manner.

Results

Exposure to EPFRs resulted in Th17 and IL17A dependent pulmonary immune responses including airway neutrophilia. EPFR exposure caused a significant increase in pulmonary Th17 cytokines such as IL6, IL17A, IL22, IL1β, KC, MCP-1, IL31 and IL33. To understand the role of AHR activation in EPFR-induced Th17 inflammation, A549 epithelial cells and mouse bone marrow-derived dendritic cells (BMDCs) were exposed to EPFRs and expression of Cyp1a1 and Cyp1b1, markers for AHR activation, was measured. A significant increase in Cyp1a1 and Cyp1b1 gene expression was observed in pulmonary epithelial cells and BMDCs in an oxidative stress and AHR dependent manner. Further, in vivo exposure of mice to EPFRs resulted in oxidative stress and increased Cyp1a1 and Cyp1b1 pulmonary gene expression. To further confirm the role of AHR activation in pulmonary Th17 immune responses, mice were exposed to EPFRs in the presence or absence of AHR antagonist. EPFR exposure resulted in a significant increase in pulmonary Th17 cells and neutrophilic inflammation, whereas a significant decrease in the percentage of Th17 cells and neutrophilic inflammation was observed in mice treated with AHR antagonist.

Conclusion

Exposure to EPFRs results in AHR activation and induction of Cyp1a1 and in vitro this is dependent on oxidative stress. Further, our in vivo studies demonstrated a role for AHR in EPFR-induced pulmonary Th17 responses including neutrophilic inflammation.

Electronic supplementary material

The online version of this article (10.1186/s12989-018-0255-3) contains supplementary material, which is available to authorized users.

Urban Particulate Matter-Activated Human Dendritic Cells Induce the Expansion of Potent Inflammatory Th1, Th2, and Th17 Effector Cells

Exposure to urban particulate matter (UPM) exacerbates asthmatic lung inflammation. Lung dendritic cells (DCs) are critical for stimulating T cell immunity and in maintaining airway tolerance, but they also react to airway UPM. The adjuvant role of UPM in enhancing primary immune responses by naive cells to allergen has been reported, but the direct effects of UPM-activated DCs on the functionality of human memory CD4 T cells (Tms), which constitute the majority of T cells in the lung, has not been investigated. Blood CD1c(+) DCs were purified and activated with UPM in the presence or absence of house dust mite or tetanus toxoid control antigen. 5-(and -6)-Carboxyfluorescein diacetate succinimidyl ester-labeled blood Tms were cocultured with autologous DCs, T cell proliferation and effector function were assessed using flow cytometry, and secreted cytokines were measured by combined bead array. UPM-DCs elicited IFN-γ and IL-13 secretion and induced proliferation in Tms isolated from both allergic patients with asthma and healthy control subjects, whereas only IL-13 was produced by Tms from patients with atopic asthma stimulated by house dust mite-loaded DCs. UPM-DCs drove the expansion and differentiation of a mixed population of Th1, Th2, and Th17 cell effectors through a mechanism that was dependent on major histocompatibility class II but not on cytokine-driven expansion. The data suggest that UPM not only has adjuvant properties but is also a source of antigen that stimulates the generation of Th2, Th1, and Th17 effector phenotypes, which have been implicated in both exacerbations of asthma and chronic inflammatory diseases.

Strategies targeting the IL-4/IL-13 axes in disease

IL-4 and IL-13 are pleiotropic Th2 cytokines produced by a wide variety of different cell types and responsible for a broad range of biology and functions. Physiologically, Th2 cytokines are known to mediate host defense against parasites but they can also trigger disease if their activities are dysregulated. In this review we discuss the rationale for targeting the IL-4/IL-13 axes in asthma, atopic dermatitis, allergic rhinitis, COPD, cancer, inflammatory bowel disease, autoimmune disease and fibrotic disease as well as evaluating the associated clinical data derived from blocking IL-4, IL-13 or IL-4 and IL-13 together.

Long-Term Effects of Diesel Exhaust Particles on Airway Inflammation and Remodeling in a Mouse Model

Purpose

Diesel exhaust particles (DEPs) can induce and trigger airway hyperresponsiveness (AHR) and inflammation. The aim of this study was to investigate the effect of long-term DEP exposure on AHR, inflammation, lung fibrosis, and goblet cell hyperplasia in a mouse model.

Methods

BALB/c mice were exposed to DEPs 1 hour a day for 5 days a week for 3 months in a closed-system chamber attached to a ultrasonic nebulizer (low dose: 100 µg/m³ DEPs, high dose: 3 mg/m³ DEPs). The control group was exposed to saline. Enhanced pause was measured as an indicator of AHR. Animals were subjected to whole-body plethysmography and then sacrificed to determine the performance of bronchoalveolar lavage and histology.

Results

AHR was higher in the DEP group than in the control group, and higher in the high-dose DEP than in the low-dose DEP groups at 4, 8, and 12 weeks. The numbers of neutrophils and lymphocytes were higher in the high-dose DEP group than in the low-dose DEP group and control group at 4, 8, and 12 weeks. The levels of interleukin (IL)-5, IL-13, and interferon-γ were higher in the low-dose DEP group than in the control group at 12 weeks. The level of IL-10 was higher in the high-dose DEP group than in the control group at 12 weeks. The level of vascular endothelial growth factor was higher in the low-dose and high-dose DEP groups than in the control group at 12 weeks. The level of IL-6 was higher in the low-dose DEP group than in the control group at 12 weeks. The level of transforming growth factor-β was higher in the high-dose DEP group than in the control group at 4, 8, and 12 weeks. The collagen content and lung fibrosis in lung tissue was higher in the high-dose DEP group at 8 and 12 weeks.

Conclusions

These results suggest that long-term DEP exposure may increase AHR, inflammation, lung fibrosis, and goblet cell hyperplasia in a mouse model.

Diesel exhaust particle exposure in vitro impacts T lymphocyte phenotype and function

Background

Diesel exhaust particles (DEP) are major constituents of ambient air pollution and their adverse health effect is an area of intensive investigations. With respect to the immune system, DEP have attracted significant research attention as a factor that could influence allergic diseases interfering with cytokine production and chemokine expression. With this exception, scant data are available on the impact of DEP on lymphocyte homeostasis. Here, the effects of nanoparticles from Euro 4 (E4) and Euro 5 (E5) light duty diesel engines on the phenotype and function of T lymphocytes from healthy donors were evaluated.

Methods

T lymphocytes were isolated from peripheral blood obtained from healthy volunteers and subsequently stimulated with different concentration (from 0.15 to 60 μg/ml) and at different time points (from 24 h to 9 days) of either E4 or E5 particles. Immunological parameters, including apoptosis, autophagy, proliferation levels, mitochondrial function, expression of activation markers and cytokine production were evaluated by cellular and molecular analyses.

Results

DEP exposure caused a pronounced autophagic-lysosomal blockade, thus interfering with a key mechanism involved in the maintaining of T cell homeostasis. Moreover, DEP decreased mitochondrial membrane potential but, unexpectedly, this effect did not result in changes of the apoptosis and/or necrosis levels, as well as of intracellular content of adenosine triphosphate (ATP). Finally, a down-regulation of the expression of the alpha chain of the interleukin (IL)-2 receptor (i.e., the CD25 molecule) as well as an abnormal Th1 cytokine expression profile (i.e., a decrease of IL-2 and interferon (IFN)-γ production) were observed after DEP exposure. No differences between the two compounds were detected in all studied parameters.

Conclusions

Overall, our data identify functional and phenotypic T lymphocyte parameters as relevant targets for DEP cytotoxicity, whose impairment could be detrimental, at least in the long run, for human health, favouring the development or the progression of diseases such as autoimmunity and cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-014-0074-0) contains supplementary material, which is available to authorized users.

Pediatric asthma and ambient pollutant levels in industrializing nations

Asthma is one of the most common chronic diseases in childhood and its prevalence has been increasing within industrializing nations. The contribution of ambient pollutants to asthma symptomatology has been explored in some countries through epidemiological investigations, molecular analysis and monitoring functional outcomes. The health effects of rising environmental pollution have been of increasing concern in industrializing nations with rising urbanization patterns. This review article provides an overview of the link between pediatric asthma and exposure to rising sources of urban air pollution. It primarily focuses on the asthma-specific effects of sulfur dioxide, nitrogen dioxide, ozone and particulate matter. Worldwide trends of asthma prevalence are also provided which detail the prominent rise in asthma symptoms in many urban areas of Africa, Latin America and Asia. The molecular and functional correlation of ambient pollutants with asthma-specific airway inflammation in the pediatric population are also highlighted. The final aspect of the review considers the correlation of motor vehicle, industrial and cooking energy sources, ascribed as the major emitters among the pollutants in urban settings, with asthma epidemiology in children.

The biological effects of individual-level PM(2.5) exposure on systemic immunity and inflammatory response in traffic policemen

BACKGROUND

Ambient fine-particle particulate matter (PM2.5) exposure is associated with the decline in pulmonary function, prevalence of coronary heart disease and incidence of myocardial infarction. The study is to observe the effects of ambient PM2.5 on the cardiovascular system and to explore the potential inflammatory and immune mechanisms.

METHODS

The subjects included 110 traffic policemen in Shanghai, China, who were aged 25-55 years. Two-times continuous 24 h individual-level PM2.5 measurements were performed in winter and summer, respectively. The inflammatory marker (high-sensitivity C-reactive protein, hs-CRP), immune parameters (IgA, IgG, IgM and IgE) and lymphocyte profiles (CD4 T cells, CD8 T cells, CD4/CD8 T cells) were measured in blood. The associations between individual-level PM2.5 and inflammatory marker and immune parameters were analysed by multiple linear regression.

RESULTS

The average concentration of 24 h personal PM2.5 for participants was 116.98 μg/m(3) and 86.48 μg/m(3) in winter and summer, respectively. In the main analysis, PM2.5 exposure is associated with the increases in hs-CRP of 1.1%, IgG of 6.7%, IgM of 11.2% and IgE of 3.3% in participants, and decreases in IgA of 4.7% and CD8 of 0.7%, whereas we found no statistical association in CD4 T cells and CD4/CD8 T cells. In the adjusted model, the results showed that the increase of PM2.5 was associated with the changes of inflammatory markers and immune markers both in winter and summer.

CONCLUSIONS

Traffic policeman have been a high-risk group suffering inflammatory response or immune injury because of the high exposure to PM2.5. These findings provided new insight into the mechanisms linking ambient PM2.5 and inflammatory and immune response.

Current treatment of severe asthma

Severe asthma is considered a heterogeneous disease in which a variety of clinical, physiological and inflammatory markers determine disease severity. Pivotal studies in the last 5 years have led to substantial progress in many areas, ranging from a more accurate definition of truly severe, refractory asthma, to classification of the disease into distinct clinical phenotypes, and introduction of new therapies. This review focuses on three common clinical phenotypes of severe asthma in adults (early onset severe allergic asthma, late onset non-atopic eosinophilic asthma, late onset non-eosinophilic asthma with obesity), and provides an overview of recent developments regarding treatment options that are best suited for each of these phenotypes.

Maternal exposure to air pollution before and during pregnancy related to changes in newborn's cord blood lymphocyte subpopulations. The EDEN study cohort

Background

Toxicants can cross the placenta and expose the developing fetus to chemical contamination leading to possible adverse health effects, by potentially inducing alterations in immune competence. Our aim was to investigate the impacts of maternal exposure to air pollution before and during pregnancy on newborn's immune system.

Methods

Exposure to background particulate matter less than 10 μm in diameter (PM₁₀) and nitrogen dioxide (NO₂) was assessed in 370 women three months before and during pregnancy using monitoring stations. Personal exposure to four volatile organic compounds (VOCs) was measured in a subsample of 56 non-smoking women with a diffusive air sampler during the second trimester of pregnancy. Cord blood was analyzed at birth by multi-parameter flow cytometry to determine lymphocyte subsets.

Results

Among other immunophenotypic changes in cord blood, decreases in the CD4+CD25+ T-cell percentage of 0.82% (p = 0.01), 0.71% (p = 0.04), 0.88% (p = 0.02), and 0.59% (p = 0.04) for a 10 μg/m³ increase in PM₁₀ levels three months before and during the first, second and third trimester of pregnancy, respectively, were observed after adjusting for confounders. A similar decrease in CD4+CD25+ T-cell percentage was observed in association with personal exposure to benzene. A similar trend was observed between NO₂ exposure and CD4+CD25+ T-cell percentage; however the association was stronger between NO₂ exposure and an increased percentage of CD8+ T-cells.

Conclusions

These data suggest that maternal exposure to air pollution before and during pregnancy may alter the immune competence in offspring thus increasing the child's risk of developing health conditions later in life, including asthma and allergies.

Radical-containing particles activate dendritic cells and enhance Th17 inflammation in a mouse model of asthma

We identified a previously unrecognized component of airborne particulate matter (PM) formed in combustion and thermal processes, namely, environmentally persistent free radicals (EPFRs). The pulmonary health effects of EPFRs are currently unknown. In the present study, we used a model EPFR-containing pollutant-particle system referred to as MCP230. We evaluated the effects of MCP230 on the phenotype and function of bone marrow-derived dendritic cells (BMDCs) in vitro and lung dendritic cells (DCs) in vivo, and the subsequent T-cell response. We also investigated the adjuvant role of MCP230 on airway inflammation in a mouse model of asthma. MCP230 decreased intracellular reduced glutathione (GSH) and the GSH/oxidized glutathione ratio in BMDCs, and up-regulated the expression of costimulatory molecules CD80 and CD86 on DCs. The maturation of DCs was blocked by inhibiting oxidative stress or the uptake of MCP230. BMDCs exposed to MCP230 increased their antigen-specific T-cell proliferation in vitro. In a model of asthma, exposure to MCP230 exacerbated pulmonary inflammation, which was attributed to the increase of neutrophils and macrophages but not eosinophils. This result correlated with an increase in Th17 cells and cytokines, compared with non-MCP230-treated but ovalbumin (OVA)-challenged mice. The percentage of Th2 cells was comparable between OVA and OVA + MCP230 mice. Our data demonstrate that combustion-generated, EPFR-containing PM directly induced the maturation of DCs in an uptake-dependent and oxidative stress-dependent manner. Furthermore, EPFR-containing PM induced a Th17-biased phenotype in lung, accompanied by significant pulmonary neutrophilia. Exposure to EPFR-containing PM may constitute an important and unrecognized risk factor in the exacerbation and development of a severe asthma phenotype in humans.

Preventing asthma exacerbations: what are the targets?

Exacerbations of asthma are the main cause of asthma morbidity. They induce acute respiratory failure, and sometimes death. Two immunological signals acting in synergy are necessary for inducing asthma exacerbations. The first, triggered by allergens and/or unknown agents leads to the chronic Th2 inflammation characteristic of asthma. The second, caused by either viral infection, allergens, pollutants or a combination of these, results in an acute Th1 and Th2 inflammation precipitating symptoms. In both, innate and adaptive immunities are involved, providing a series of potential targets for therapy. Molecules associated to the first, chronic inflammation constitute targets for preventing therapies, when these related to the second, acute signal provide the rationale for curative treatments. Toll like receptors and bronchial epithelial cell-derived cytokines, engaged upstream of inflammation constitute interesting candidates for future treatments. The great heterogeneity of asthma has to be taken into account when considering targets for therapy to identify clusters of responders and nonresponders, and an integrative system biology approach will be necessary to go further.

Activation of pulmonary dendritic cells and Th2-type inflammatory responses on instillation of engineered, environmental diesel emission source or ambient air pollutant particles in vivo

The biological effects of acute particulate air pollution exposure in host innate immunity remain obscure and have relied largely on in vitro models. We hypothesized that single acute exposure to ambient or engineered particulate matter (PM) in the absence of other secondary stimuli would activate lung dendritic cells (DC) in vivo and provide information on the early immunological events of PM exposure and DC activation in a mouse model naïve to prior PM exposure. Activation of purified lung DC was studied following oropharyngeal instillation of ambient particulate matter (APM). We compared the effects of APM exposure with that of diesel-enriched PM (DEP), carbon black particles (CBP) and silver nanoparticles (AgP). We found that PM species induced variable cellular infiltration in the lungs and only APM exposure induced eosinophilic infiltration. Both APM and DEP activated pulmonary DC and promoted a Th2-type cytokine response from naïve CD4+ T cells ex vivo. Cultures of primary peribronchial lymph node cells from mice exposed to APM and DEP also displayed a Th2-type immune response ex vivo. We conclude that exposure of the lower airway to various PM species induces differential immunological responses and immunomodulation of DC subsets. Environmental APM and DEP activated DC in vivo and provoked a Th2 response ex vivo. By contrast, CBP and AgP induced altered lung tissue barrier integrity but failed to stimulate CD4+ T cells as effectively. Our work suggests that respirable pollutants activate the innate immune response with enhanced DC activation, pulmonary inflammation and Th2-immune responsiveness.

[Adult asthma exacerbations in questions]

In this article a French working party critically review the international literature to revise the definition, pathophysiology, treatment and cost of exacerbations of adult asthma. The various guidelines do not always provide a consistent definition of exacerbations of asthma. An exacerbation can be defined as deterioration of clinical and/or functional parameters lasting more than 24 hours, without return to baseline, requiring a change of treatment. No single clinical or functional criterion can be used as an early marker of an exacerbation. Innate and acquired immune mechanisms, modified by contact with infectious, irritant or allergenic agents, participate in the pathogenesis of exacerbations, which are accompanied by bronchial inflammation. In 2010, mortality is related to progression of exacerbations, often occurring before the patient seeks medical attention. The objective of treatment is to control asthma and prevent exacerbations. However, many factors can trigger exacerbations and often cannot be controlled. The efficacy of inhaled corticosteroids has been demonstrated on reduction of the number of exacerbations and the number of asthma-related deaths. This treatment is cost-effective, especially in terms of reduction of exacerbations.

Mouse models to unravel the role of inhaled pollutants on allergic sensitization and airway inflammation

Air pollutant exposure has been linked to a rise in wheezing illnesses. Clinical data highlight that exposure to mainstream tobacco smoke (MS) and environmental tobacco smoke (ETS) as well as exposure to diesel exhaust particles (DEP) could promote allergic sensitization or aggravate symptoms of asthma, suggesting a role for these inhaled pollutants in the pathogenesis of asthma. Mouse models are a valuable tool to study the potential effects of these pollutants in the pathogenesis of asthma, with the opportunity to investigate their impact during processes leading to sensitization, acute inflammation and chronic disease. Mice allow us to perform mechanistic studies and to evaluate the importance of specific cell types in asthma pathogenesis. In this review, the major clinical effects of tobacco smoke and diesel exhaust exposure regarding to asthma development and progression are described. Clinical data are compared with findings from murine models of asthma and inhalable pollutant exposure. Moreover, the potential mechanisms by which both pollutants could aggravate asthma are discussed.

Exacerbation of allergic inflammation in mice exposed to diesel exhaust particles prior to viral infection

Background

Viral infections and exposure to oxidant air pollutants are two of the most important inducers of asthma exacerbation. Our previous studies have demonstrated that exposure to diesel exhaust increases the susceptibility to influenza virus infections both in epithelial cells in vitro and in mice in vivo. Therefore, we examined whether in the setting of allergic asthma, exposure to oxidant air pollutants enhances the susceptibility to respiratory virus infections, which in turn leads to increased virus-induced exacerbation of asthma. Ovalbumin-sensitized (OVA) male C57BL/6 mice were instilled with diesel exhaust particles (DEP) or saline and 24 hours later infected with influenza A/PR/8. Animals were sacrificed 24 hours post-infection and analyzed for markers of lung injury, allergic inflammation, and pro-inflammatory cytokine production.

Results

Exposure to DEP or infection with influenza alone had no significant effects on markers of injury or allergic inflammation. However, OVA-sensitized mice that were exposed to DEP and subsequently infected with influenza showed increased levels of eosinophils in lung lavage and tissue. In addition Th2-type cytokines, such as IL-4 and IL-13, and markers of eosinophil chemotaxis, such as CCL11 and CCR3, were increased in OVA-sensitized mice exposed to DEP prior to infection with influenza. These mice also showed increased levels of IL-1α, but not IL-10, RANTES, and MCP-1 in lung homogenates.

Conclusion

These data suggest that in the setting of allergic asthma, exposure to diesel exhaust could enhance virus-induced exacerbation of allergic inflammation.

Total serum IgE levels are associated with ambient ozone concentration in asthmatic adults

BACKGROUND

Effects of air pollution exposure on IgE-mediated response in asthmatics are poorly investigated. The aim was to examine the relationship between air pollution concentrations and total IgE levels in adult asthmatics.

METHODS

The present study relates to the 369 asthmatic adults from the French Epidemiological study on Genetics and Environment of Asthma (EGEA), with availability of data on both total serum IgE measurements and air pollution concentrations. Geo-statistical models were performed on 4 x 4 km grids to assess individual outdoor air pollution exposure. Annual outdoor concentrations of ozone (O(3)), nitrogen dioxide (NO(2)), sulphur dioxide (SO(2)), and particulate matter smaller than 10 microm size (PM(10)), and concentrations of summer ozone were assigned to subject's home address.

RESULTS

The geometric mean of total IgE was 161 IU/ml and the average of O(3) exposure was 44.9 +/- 9.5 microg/m(3). Ozone concentrations were positively related to total IgE levels and an increase of 10 microg/m(3) of O(3) resulted in an increase of 20.4% (95% CI = 3.0-40.7) in total IgE levels. Adjustment for age, gender, smoking habits and previous life in the countryside did not change the results, and an increase of 19.1% (2.4-38.6) in total IgE was observed with O(3). Negative associations observed between NO(2) and total IgE levels disappeared after including O(3) in the models. Neither SO(2) nor PM(10) were correlated with total IgE levels.

CONCLUSIONS

Results suggest that O(3) or related ambient pollutants may up-regulate total IgE levels among asthmatic adults.

T-cell activation during exacerbations: a longitudinal study in refractory asthma

BACKGROUND

Asthma exacerbations represent the main source of costs and morbidity in asthma care, and drugs specifically designed to prevent exacerbations are needed. A prerequisite is to dispose of a precise knowledge of inflammatory events leading to exacerbations.

OBJECTIVE

To study T-cell activation during exacerbations from severe refractory asthmatics.

METHODS

Proportions of blood T-cell interleukin (IL)-13, interferon-gamma, IL-4, IL-5, IL-10 production and of CD4+CD25+(high)CD62L+CD45RO+ [T regulatory (Treg)] cells were determined by flow cytometry. Blood cytokine mRNA was studied by reverse transcription-polymerase chain reaction and the respective protein levels were determined by cytokine beads array. Depletion of Treg cells was performed to study their activation. T-cell cytokines were detected in parallel in induced sputum.

RESULTS

At baseline, T helper 2 (Th2) cells were increased in asthmatics, whereas T helper 1 (Th1) and Treg T cells were decreased. T helper 2 cells increased before exacerbations, followed by Th1 cells, in blood and induced sputum, albeit Treg cells decreased in parallel with IL-10-producing T cells. Concordant results were found at the mRNA level. The suppressive activity of Treg cells was impaired during exacerbations compared to baseline.

CONCLUSIONS

New insights are given into pathophysiology of asthma exacerbations: Although at baseline T-cell activation is Th2-biased, a mixed Th1/Th2 activation occurs during exacerbations. The Treg cell deficiency found at baseline in SRA increases during exacerbations.

Asthma history and presentation

Asthma is suspected from a history of key symptoms, including cough, wheezing, dyspnea, chest tightness, and increased mucus production. A positive family or personal history of atopic diseases and diseases that are comorbid with asthma, such as allergic rhinitis and rhinosinusitis, is also important. The differential diagnosis of asthma is broad and includes potentially life-threatening diseases. Pediatric asthma and psychiatric mimics require special attention to prevent misdiagnosis. Differentiating asthma from these other disease states by history alone is not always possible. Because accurate diagnosis is critical to successful treatment, objective testing by spirometry and methacholine challenge should be employed.

L-Xylulose reductase is involved in 9,10-phenanthrenequinone-induced apoptosis in human T lymphoma cells

9,10-Phenanthrenequinone (9,10-PQ), a major component in diesel exhaust particles, is suggested to generate reactive oxygen species (ROS) through its redox cycling, leading to cell toxicity. l-Xylulose reductase (XR), a NADPH-dependent enzyme in the uronate pathway, strongly reduces alpha-dicarbonyl compounds and was thought to act as a detoxification enzyme against reactive carbonyl compounds. Here, we have investigated the role of intracellular ROS generation in apoptotic signaling in human acute T-lymphoblastic leukemia MOLT-4 cells treated with 9,10-PQ and the role of XR in the generation of ROS. Treatment with 9,10-PQ elicited not only apoptotic signaling, including mitochondrial membrane dysfunction and activation of caspases and poly(ADP-ribose) polymerase, but also intracellular ROS generation and consequent glutathione depletion. The apoptotic effects of 9,10-PQ were drastically mitigated by pretreatment with intracellular ROS scavengers, such as N-acetyl-l-cysteine, glutathione monoethyl ester, and polyethylene glycol-conjugated catalase, indicating that intracellular ROS generation is responsible for the 9,10-PQ-evoked apoptosis. Surprisingly, the ROS generation and cytotoxicity by 9,10-PQ were augmented in an XR-transformed cell line. XR indeed reduced 9,10-PQ and produced superoxide anion through redox cycling. In addition, the expression levels of XR and its mRNA in the T lymphoma cells were markedly enhanced after the exposure to 9,10-PQ, and the induction was completely abolished by the ROS scavengers. Moreover, the 9,10-PQ-induced apoptosis was partially inhibited by the pretreatment with XR-specific inhibitors. These results suggest that initially produced ROS induce XR, which accelerates the generation of ROS.

[Exacerbation in asthma: definitions and immunopathology]

There is no unequivocal definition of exacerbation in asthma. These are defined as episodes of increased or aggravated respiratory symptoms or as use of oral corticosteroid therapy. Viral infection is the most frequent cause of exacerbations. Inflammation during exacerbations is heterogeneous. It may be associated with bronchial hypereosinophilia, which is used as a predictive marker for exacerbation, and with neutrophilia, which is more resistant to corticosteroids. During viral infection, an inappropriate Th1 antiviral inflammation develops, associated with the intrinsic Th2 activity that leads to an aberrant immune response. Exacerbations secondary to allergen exposure are classically described as due to a Th2-type inflammation; but Th1 response also seems to play a role. Exposure to air pollutants appears able not only to induce bronchial inflammation but also to potentiate the inflammatory reactions of patients with exacerbations.

Diesel-enriched particulate matter functionally activates human dendritic cells

Epidemiologic studies have associated exposure to airborne particulate matter (PM) with exacerbations of asthma. It is unknown how different sources of PM affect innate immunity. We sought to determine how car- and diesel exhaust-derived PM affects dendritic cell (DC) activation. DC development was modeled using CD34+ hematopoietic progenitors. Airborne PM was collected from exhaust plenums of Fort McHenry Tunnel providing car-enriched particles (CEP) and diesel-enriched particles (DEP). DC were stimulated for 48 hours with CEP, DEP, CD40-ligand, or lipopolysaccharide. DC activation was assessed by flow cytometry, enzyme-linked immunosorbent assay, and standard culture techniques. DEP increased uptake of fluorescein isothiocyanate-dextran (a model antigen) by DC. Diesel particles enhanced cell-surface expression of co-stimulatory molecules (e.g., CD40 [P < 0.01] and MHC class II [P < 0.01]). By contrast, CEP poorly affected antigen uptake and expression of cell surface molecules, and did not greatly affect cytokine secretion by DC. However, DEP increased production of TNF, IL-6, and IFN-gamma (P < 0.01), IL-12 (P < 0.05), and vascular endothelial growth factor (P < 0.001). In co-stimulation assays of PM-exposed DC and alloreactive CD4+ T cells, both CEP and DEP directed a Th2-like pattern of cytokine production (e.g., enhanced IL-13 and IL-18 and suppressed IFN-gamma production). CD4+ T cells were not functionally activated on exposure to either DEP or CEP. Car- and diesel-enriched particles exert a differential effect on DC activation. Our data support the hypothesis that DEP (and to a lesser extent CEP) regulate important functional aspects of human DC, supporting an adjuvant role for this material.

Increased expression of HLA-DR and CD86 in nasal epithelial cells in allergic rhinitics: antigen presentation to T cells and up-regulation by diesel exhaust particles

BACKGROUND

A proportion of nasal epithelial cells (NEC) in patients with allergic rhinitis (AR) are known to express the major histocompatibility complex Class II molecule (HLA-DR).

OBJECTIVE

We hypothesized that NEC may play a role in antigen presentation to T cells. To elucidate the possible role of NEC in antigen presentation, we examined the expression of HLA-DR, CD80 and CD86 in NEC, their regulation by cytokines and the capacity of NEC to induce antigen-specific proliferation of T cells.

METHODS

We examined the expression of HLA-DR, CD80 and CD86 in nasal epithelial scrapings of patients with seasonal allergic rhinitis (SAR) to Japanese cedar pollen pre-season and in-season, by immunohistochemistry. Next, we examined the effect of IL-1beta, TNF-alpha, (IFN-gamma), IL-4 alpha, IL-13 and diesel exhaust particles (DEP) on the HLA-DR, CD80 and CD86 expression in cultured nasal epithelial cells (CNEC), by flow cytometry. Further, we analysed the capacity of mite antigen (Der f II)-pulsed mitomycin-C-treated CNEC to induce proliferation of autologous T cells from patients with perennial allergic rhinitis.

RESULTS

NEC constitutively expressed HLA-DR and CD86, but not CD80. The expression of HLA-DR and CD86 in NEC was significantly increased in-season, in patients with SAR as compared with that of pre-season. While IFN-gamma up-regulated the expression of HLA-DR, IL-1beta and TNF-alpha up-regulated the expression of CD86 in CNEC. Furthermore, in the presence of mite antigen, CNEC induced the proliferation of autologous peripheral blood T lymphocytes. Anti-CD86 and anti-HLA-DR monoclonal antibody but not anti-CD80 inhibited the epithelial cell-induced T cell proliferation. Stimulation with a combination of DEP and mite antigen significantly up-regulated HLA-DR and CD86 expression in CNEC.

CONCLUSIONS

These studies suggest that NEC in patients with AR may play a role in antigen presentation through the enhanced expression of HLA-DR and CD86. Furthermore, these results suggest the possibility that DEP may enhance the antigen-presenting function of CNEC.

Particulate matter in the environment: pulmonary and cardiovascular effects

PURPOSE OF REVIEW

The mechanisms related to adverse respiratory and cardiovascular effects in populations exposed to particulate matter are under debate and different models have been used to further our understanding of the various aspects of those effects. In this review we present some studies that may give new insights into the cellular and systemic mechanisms related to particulate matter toxicity.

RECENT FINDINGS

Strong epidemiological evidence is now available regarding exposure markers and health effects. This is evident in the correlation between carbon content in macrophages and decrease in lung function, an increase in the risk of chronic obstructive pulmonary disease, lung cancer and postnatal mortality. The role of outdoor temperature and a missing allele for GSTM1 and the impact of these factors on cardiovascular effects are also reported. At the experimental level, the effects of particulate matter and the interactions between different cell types, the role of toll-like receptor-2 and 4, the translocation of particles through cell monolayers and the activation of endothelial cells by particulate matter are also discussed. The role of composition is under intense debate, and different statistical analyses have been proposed.

SUMMARY

Experimental studies on the effects of particulate matter are giving plausibility to the epidemiological findings, but the possible mechanisms of action are also becoming a hot topic.

Effects of diesel exhaust particles on cytokine production by splenocytes stimulated with lipopolysaccharide

It was previously shown that pulmonary exposure of mice to diesel exhaust particles (DEP) enhances inflammatory conditions induced by allergens or bacterial endotoxin (lipopolysaccharide: LPS) via enhanced local expression of cytokines. However, resolution of the underlying mechanisms, in which DEP exaggerate inflammation, remains uncompleted. Investigation of the actions of DEP on mouse-derived mononuclear cells may provide a clue to the mechanisms, because mononuclear cells produce and release several types of cytokines. The present study elucidated the effects of DEP on mononuclear cell reactions stimulated with LPS in vitro. ICR mouse-derived mononuclear cells, isolated from splenocytes, one of the secondary lymphoid tissues, were co-cultured with LPS (1 microg ml(-1)) and DEP (1, 10 or 100 microg ml(-1)). The protein levels of interferon (IFN)-gamma, interleukin (IL)-2, IL-10, and IL-13 in the culture supernatants were measured 72 h after the co-culture. LPS significantly increased the protein levels of IFN-gamma, IL-2 and IL-10. In the presence of LPS, DEP decreased the protein levels in a concentration-dependent manner with an overall trend, whereas DEP (1, 10 microg ml(-1)) moderately elevated the IL-13 level. These results suggest that DEP suppress cytokine production from mononuclear cells stimulated with LPS and provide a possible hint for DEP facilitation on inflammatory conditions, especially related to Th2 response, in vivo.