Components of diesel exhaust particles differentially affect Th1/Th2 response in a murine model of allergic airway inflammation

Different airborne particulates trigger distinct immune pathways leading to peanut allergy in a mouse model

BACKGROUND

Environmental exposure to peanut through non-oral routes is a risk factor for peanut allergy. Early-life exposure to air pollutants, including particulate matter (PM), is associated with sensitization to foods through unknown mechanisms. We investigated whether PM promotes sensitization to environmental peanut and the development of peanut allergy in a mouse model.

METHODS

C57BL/6J mice were co-exposed to peanut and either urban particulate matter (UPM) or diesel exhaust particles (DEP) via the airways and assessed for peanut sensitization and development of anaphylaxis following peanut challenge. Peanut-specific CD4+ T helper (Th) cell responses were characterized by flow cytometry and Th cytokine production. Mice lacking select innate immune signaling genes were used to study mechanisms of PM-induced peanut allergy.

RESULTS

Airway co-exposure to peanut and either UPM- or DEP-induced systemic sensitization to peanut and anaphylaxis following peanut challenge. Exposure to UPM or DEP triggered activation and migration of lung dendritic cells to draining lymph nodes and induction of peanut-specific CD4+ Th cells. UPM- and DEP-induced distinct Th responses, but both stimulated expansion of T follicular helper (Tfh) cells essential for peanut allergy development. MyD88 signaling was critical for UPM- and DEP-induced peanut allergy, whereas TLR4 signaling was dispensable. DEP-induced peanut allergy and Tfh-cell differentiation depended on IL-1 but not IL-33 signaling, whereas neither cytokine alone was necessary for UPM-mediated sensitization.

CONCLUSION

Environmental co-exposure to peanut and PM induces peanut-specific Tfh cells and peanut allergy in mice.

Differential Pattern of Cell Death and ROS Production in Human Airway Epithelial Cells Exposed to Quinones Combined with Heated-PM2.5 and/or Asian Sand Dust

The combined toxicological effects of airborne particulate matter (PM), such as PM2.5, and Asian sand dust (ASD), with surrounding chemicals, particularly quinones, on human airway epithelial cells remain underexplored. In this study, we established an in vitro combination exposure model using 1,2-naphthoquinones (NQ) and 9,10-phenanthroquinones (PQ) along with heated PM (h-PM2.5 and h-ASD) to investigate their potential synergistic effects. The impacts of quinones and heated PM on tetrazolium dye (WST-1) reduction, cell death, and cytokine and reactive oxygen species (ROS) production were examined. Results revealed that exposure to 9,10-PQ with h-PM2.5 and/or h-ASD dose-dependently increased WST-1 reduction at 1 μM compared to the corresponding control while markedly decreasing it at 10 μM. Higher early apoptotic, late apoptotic, or necrotic cell numbers were detected in 9,10-PQ + h-PM2.5 exposure than in 9,10-PQ + h-ASD or 9,10-PQ + h-PM2.5 + h-ASD. Additionally, 1,2-NQ + h-PM2.5 exposure also resulted in an increase in cell death compared to 1,2-NQ + h-ASD and 1,2-NQ + h-PM2.5 + h-ASD. Quinones with or without h-PM2.5, h-ASD, or h-PM2.5 + h-ASD significantly increased ROS production, especially with h-PM2.5. Our findings suggest that quinones, at relatively low concentrations, induce cell death synergistically in the presence of h-PM2.5 rather than h-ASD and h-PM2.5 + h-ASD, partially through the induction of apoptosis with increased ROS generation.

Air Pollution: Possible Interaction between the Immune and Nervous System?

Exposure to environmental pollutants is a serious and common public health concern associated with growing morbidity and mortality worldwide, as well as economic burden. In recent years, the toxic effects associated with air pollution have been intensively studied, with a particular focus on the lung and cardiovascular system, mainly associated with particulate matter exposure. However, epidemiological and mechanistic studies suggest that air pollution can also influence skin integrity and may have a significant adverse impact on the immune and nervous system. Air pollution exposure already starts in utero before birth, potentially causing delayed chronic diseases arising later in life. There are, indeed, time windows during the life of individuals who are more susceptible to air pollution exposure, which may result in more severe outcomes. In this review paper, we provide an overview of findings that have established the effects of air pollutants on the immune and nervous system, and speculate on the possible interaction between them, based on mechanistic data.

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.

Biological Response-Enhancing Activity with Antigens in A549 Cells Exposed to Representative Polycyclic Aromatic Hydrocarbons

The question of what kinds of airborne particles, including diesel exhaust particles and their adherent chemical constituents, exacerbate the activity of allergic and inflammatory respiratory diseases has not been elucidated in detail. Therefore, chemicals that have amplifying actions on Dermatophagoides farinae (Df) body extract-induced IL-8, the inflammatory cytokines of the innate immune system, were comprehensively examined using commonly used human alveolar epithelial cells, A549, as simple screening for 17 polycyclic aromatic hydrocarbons (PAHs), which are representative organic constituents in atmospheric samples. The significant amplifying actions of two PAHs, dibenzo[a,l]pyrene (DB[a,l]P) at 50 nM and dibenzo[a,i]pyrene (DB[a,i]P) at 2 μM for 48 h, for IL-8 protein release induced by mite antigens in epithelial cells were observed for the first time. In contrast, the enhancement of IL-8 was not observed in protein levels for these PAHs without the antigens. Meanwhile, the significant synergistic amplifying effect of DB[a,l]P at 50 nM on proinflammatory actions was measured in gene expression (i.e., IL-8, IL-6, ICAM-1, and TNF-α) levels in the experimental setting; for the results, the induction of TNF-α may have been the essential factor that enhanced the amplifying activity of DB[a,l]P for IL-8 gene expression and protein release. Examining the exacerbating effect on allergic pathophysiological states for DB[a,l]P is planned for further study.

Traffic-related PM2.5 and diverse constituents disturb the balance of Th17/Treg cells by STAT3/RORγt-STAT5/Foxp3 signaling pathway in a rat model of asthma

Water-soluble ions (WSI) and organic extract (OE) in traffic-related particulate matter with aerodynamic diameters ≤ 2.5 μm (TRPM2.5) are potential risk factors for asthma exacerbation. Although CD4+ T lymphocytes mediated immune response is involved in the pathogenesis of asthma, the effect of WSI-TRPM2.5 and OE-TRPM2.5 on the balance of Th17/Treg cells in asthma remains poorly understood. In this study, the ovalbumin (OVA)-sensitized rats were repeatedly exposure to TRPM2.5 (3 mg/kg·bw), WSI-TRPM2.5 (1.8 mg/kg·bw, 7.2 mg/kg·bw) and OE-TRPM2.5 (0.6 mg/kg·bw, 2.4 mg/kg·bw) every three days for five times. The inflammation response and hyperemia edema were observed in the lung and trachea tissues. DNA methylation levels of STAT3 and RORγt genes in rats with WSI-TRPM2.5 and OE-TRPM2.5 treatment were decreased. DNA methylation level in STAT5 gene tended to decrease, with no change observed on Foxp3 expression. WSI-TRPM2.5 and OE-TRPM2.5 enhanced the mRNA and protein expression of STAT3 and RORγt while inhibited the expression of STAT5 and Foxp3, which may contribute to the imbalance of Th17/Treg cells (P < 0.05). More importantly, recovered balance of Th17/Treg cell subsets, upregulated p-STAT5 and Foxp3 expression and reduced p-STAT3 and RORγt levels were observed after 5-Aza treatment. Our results demonstrate that the STAT3/RORγt-STAT5/Foxp3 signaling pathway is involved in asthma exacerbation induced by WSI-TRPM2.5 and OE-TRPM2.5 through disrupting the balance of Th17/Treg cells. The alteration of DNA methylation of STAT3, STAT5, and RORγt genes may be involved in asthma exacerbation as well.

PM2.5 collected using cyclonic separation causes stronger biological responses than that collected using a conventional filtration method

Evaluation of the health effects of particulate matter with aerodynamic dias. ≤ 2.5 μm (PM2.5) should reflect realistic condition in ambient atmosphere. However, using conventional filtration methods, only extracts from PM2.5 collected on the filter can be analyzed and not the particle itself. Cyclonic separation is a technique that enables the direct analysis of the effects of the crude "powder form" of PM2.5 on respiratory health. Airway epithelial cells and antigen-presenting cells were exposed to PM2.5 collected during the same period using a conventional filtration method or cyclonic separation. PM2.5 collected using cyclonic separation led to a higher secretion of interleukins 6 and 8 (IL-6, IL-8) from airway epithelial cells, and IL-6, IL-1β, tumor necrosis factor-α (TNF-α) secretion, cluster of differentiation 86 (CD86), and dendritic and epithelial cells 205 (DEC205) expression on antigen-presenting cells, compared with the effects of filter-collected PM2.5. Furthermore, PM2.5 collected using cyclonic separation increased inflammatory cytokine levels and induced lung inflammation in vivo. These results suggest that crude PM2.5 collected using cyclonic separation causes stronger biological responses than filter-collected PM2.5. Hence, PM2.5 collected using cyclonic separation can be utilized for a reliable evaluation of the health effects of ambient PM2.5.

Associations between ambient air pollution and medical care visits for atopic dermatitis

BACKGROUND

Previous studies have reported numerous environmental factors for atopic dermatitis (AD), such as allergens and chemical stimulants. However, few studies have addressed the relationship between ambient air pollution and AD at a population level.

OBJECTIVE

To evaluate the effect of air pollutants on medical care visits for AD and to identify susceptible populations.

METHODS

In this time-series study conducted on 513,870 medical care visits for AD from 2012 to 2015 identified by reviewing national health insurance claim data in Incheon, Republic of Korea. Treating daily number of medical care visits for AD as a dependent variable, generalized additive models with Poisson distributions were constructed, which included air pollutant levels, ambient temperature, relative humidity, day of the week, national holiday, and season. Risks were expressed as relative risks (RR) with 95% confidence intervals (95% CIs) per interquartile range increase of each air pollutant.

RESULTS

Higher levels of particulate matter of diameter ≤10 μm (PM₁₀) (RR, 1.009; 95% CI, 1.007-1.012), ozone (1.028; 1.023-1.033), and sulfur dioxide (1.033; 1.030-1.037) were significantly associated with increased risk of medical care visits for AD on same days. In all age and sex groups, ozone was associated with a significantly higher risk of medical care visits, with the greatest risk among 13- to 18-year-old males (RR, 1.127; 95% CI, 1.095-1.159).

CONCLUSION

This study suggests relationships of ambient PM₁₀, ozone, and sulfur dioxide levels with medical care visits for AD.

Effects of lactational exposure to low-dose BaP on allergic and non-allergic immune responses in mice offspring

Benzo[a]pyrene (BaP) can induce developmental and reproductive toxicity; however, the full scope of its immunotoxic effects remains unknown. This study aimed to assess effects of lactational exposure to low-dose BaP (comparable to human exposure) on potential allergic\non-allergic immune responses in murine offspring. Lactating C3H/HeJ dams were orally dosed with BaP at 0, 0.25, 5.0, or 100 pmol/animal/week) at post-natal days [PND] 1, 8, and 15. Five-weeks-old pups then received intratracheally ovalbumin (OVA) every 2 weeks for 6 weeks. Following the final exposure, mice were processed to permit analyses of bronchoalveolar lavage (BAL) fluid cell profiles as well as levels of lung inflammatory cytokines and chemokines, serum OVA-specific immunoglobulin, and mediastinal lymph node (MLN) cell activation/proliferation. In OVA-sensitized male offspring, lactational low-dose BaP exposure led to enhanced (albeit not significantly) macrophage, neutrophil, and eosinophil infiltration to, and increased T-helper (T_H)-2 cytokine production in, the lungs. In females, BaP exposure, regardless of dose, led to slightly enhanced lung levels of macrophages and eosinophils, and of inflammatory molecules. Protein levels of interleukin (IL)-33 in the OVA + BaP (middle dose) group, and interferon (IFN)-γ in the OVA + BaP (low dose) group, were higher than that of the OVA (no BaP) group. Ex vivo studies showed lactational exposure to BaP partially induced activation of T-cells and antigen-presenting cells (APCs) in the MLN cells of both male and female offspring, with or without OVA sensitization. Further, IL-4 and IFNγ levels in MLN culture supernatants were elevated even without OVA-re-stimulation in OVA + BaP groups. In conclusion, lactational exposure to low-dose BaP appeared to exert slight effects on later allergic and non-allergic immune responses in offspring by facilitating development of modest T_H2 responses and activating MLN cells. In addition, lactational exposures to BaP might give rise to gender differences in allergic/non-allergic immune responses of offspring.

Exposure to low-dose bisphenol A during the juvenile period of development disrupts the immune system and aggravates allergic airway inflammation in mice

Bisphenol A (BPA) is used in the production of polycarbonate plastics and epoxy resins and found in many consumer products. Previous studies have reported that perinatal exposure to BPA through the oral route promotes the development of allergic airway inflammation. We investigated the effects of exposure to low-dose BPA during the juvenile period of development on allergic airway inflammation. Six-week-old male C3H/HeJ mice were intratracheally administered ovalbumin (OVA, 1 μg) every 2 weeks and/or BPA (0, 0.0625, 1.25, and 25 pmol/animal/week) once per week for 6 weeks. Following the final intratracheal instillation, we examined the cellular profile of the bronchoalveolar lavage fluid, histological changes and expression of inflammatory/anti-inflammatory mediators in the lungs, OVA-specific immunoglobulin (Ig) production, serum corticosterone levels, and changes in the lymphoid tissues (mediastinal lymph node (MLN) and spleen). Exposure to OVA + BPA enhanced inflammatory cell infiltration and protein expression of Th2 cytokines/chemokines (e.g. interleukin (IL)-13 and IL-33) in the lungs, OVA-specific immunoglobulin E (IgE) production, the numbers of total cells and activated antigen-presenting cells (MHC class II⁺ CD86⁺, CD11c⁺), as well as the production of Th2 cytokines (i.e. IL-4 and IL-5) and stromal cell-derived factor-1α in MLN cells compared to OVA exposure alone. These effects were more prominent with 0.0625 or 1.25 pmol/animal/week of BPA. Furthermore, exposure to OVA + BPA altered serum levels of anti-inflammatory corticosterone, estrogen receptor 2 messenger RNA (mRNA) expression in the lungs and spleen functionality. These findings suggest that low-dose BPA exposure may aggravate allergic airway inflammation by enhancing Th2 responses via disruption of the immune system.

Synergistic effect of carbon nuclei and polyaromatic hydrocarbons on respiratory and immune responses

Particulate matter with aerodynamic diameter ≤2.5 μm (PM_2.5 ) is generally composed of carbon nuclei associated with various organic carbons, metals, ions and biological materials. Among these components, polyaromatic hydrocarbons (PAHs) such as benzo(a)pyrene (BaP) and quinones have detrimental effects on airway epithelial cells and immunodisrupting effects, which leads to the exacerbation of respiratory allergies. The effects of PAHs and the carbon nuclei, separately as well as in combination, remain to be established. We investigated the effects of BaP, 9,10-phenanthroquinone (9,10-PQ), and 1,2-napthoquinone (1,2-NQ) and their combined effects with heated diesel exhaust particle (H-DEP) as carbon nuclei of typical PM_2.5 . We exposed human airway epithelial cells (BEAS-2B), murine bone marrow-derived antigen-presenting cells (APCs), and murine splenocytes to BaP, 9,10-PQ, or 1,2-NQ in the presence and absence of H-DEP. Several important inflammatory cytokines and cell surface molecules were measured. PAHs alone did not have apparent cytotoxic effects on BEAS-2B, whereas combined exposure with H-DEP induced noticeable detrimental effects which mainly reflected the action of H-DEP itself. BaP increased CD86 expression as an APC surface molecule regardless of the presence or absence of H-DEP. None of the BaP, 9,10-PQ, or 1,2-NQ exposure alone or their combined exposure with H-DEP resulted in any significant activation of splenocytes. These results suggest that PAHs and carbon nuclei show additive effects, and that BaP with the carbon nuclei may contribute to exacerbations of allergic respiratory diseases including asthma by PM_2.5 , especially via antigen-presenting cell activation.

Diesel exhaust particulate associated chemicals attenuate expression of CXCL10 in human primary bronchial epithelial cells

Air pollution affects a large proportion of the population particularly in urban areas, with diesel particulates recognised as particular causes for concern in respiratory conditions such as asthma. In this study we examined the response of human primary airway epithelial cells to diesel particulate chemical extracts (DE) and characterised gene expression alterations using RNA-SEQ. Using the antagonist CH223191, DE induced CYP1A1 and attenuation of CXCL10 among other genes were observed to be aryl hydrocarbon receptor dependent. Basal and toll like receptor dependent protein levels for CXCL10 were markedly reduced. Investigation of similar regulation in plasmacytoid dendritic GEN2.2 cells did not show DE dependent regulation of CXCL10. Instillation of DE into mice to recapitulate airway epithelial exposure to chemical extracts in an in vivo setting failed to demonstrate a reduction in CXCL10. There was however an increase in the Th2 type epithelial cell derived inflammatory mediators TSLP and SERPINB2. We also observed an increased macrophages and a decrease in the proportion of lymphocytes in bronchoalveolar lavage fluid. CXCL10 can play a role in allergic airway disease through recruitment of Th1 type CD4+ T-cells, which can act to counterbalance Th2 type allergic responses. Modulation of such chemokines within the airway epithelium may represent a mechanism through which pollutant material can modify respiratory conditions such as allergic asthma.

Environmental pollution and allergies

Environmental changes are thought to be the main factor in the rapid increase and worsening of allergic diseases. While there have been significant changes in many environmental factors, including in environments such as residential, health and sanitation, food, and water/soil/atmospheric environments, the root of each of these changes is likely an increase in chemical substances. In fact, various environmental pollutants, such as air pollutants and chemical substances, have been shown to worsen various allergies in experimental studies. For example, diesel exhaust particles (DEPs), which are an agglomeration of particles and a wide array of chemical substances, aggravate asthma, primarily due to the principle organic chemical components of DEPs. In addition, environmental chemicals such as phthalate esters, which are commonly used as plasticizers in plastic products, also aggravate atopic dermatitis. It has also become evident that extremely small nanomaterials and Asian sand dust particles can enhance allergic inflammation. While the underlying mechanisms that cause such aggravation are becoming clearer at the cellular and molecular levels, methods to easily and quickly evaluate (screen) the ever-increasing amount of environmental pollutants for exacerbating effects on allergies are also under development. To eliminate and control allergic diseases, medical measures are necessary, but it is also essential to tackle this issue by ameliorating environmental changes.

Effects of Components of PM2.5 Collected in Japan on the Respiratory and Immune Systems

Epidemiologic studies have reported that particulate matter with aerodynamic diameters ≤2.5 μm (PM_2.5) affect respiratory diseases, including asthma. The components and/or factors of PM_2.5 that contribute to the exacerbation of asthma have not been identified. We investigated the effects of extracts of PM_2.5 collected in Japan on the respiratory and immune systems. PM_2.5 was collected from an industrial area and an urban area in December 2013. Airway epithelial cells and immune cells were exposed to aqueous or organic extracts of PM_2.5. Exposure to extracts from both areas, especially to organic extracts rather than aqueous extracts, caused a pro-inflammatory response via interleukin (IL) 6 production from airway epithelial cells, and it induced the maturation/activation of bone marrow-derived antigen-presenting cells via dendritic and epithelial cell (DEC) 205 and cluster of differentiation (CD) 86 expression and proportional changes in the constitution of the splenocytes. The extracts collected from the industrial area tended to show greater effects than those from the urban area. These results suggest that organic components of PM_2.5 affect the respiratory and immune systems. These effects can differ by the collection areas. In addition, IL-6, DEC205, and CD86 can be predictive biomarkers for the respiratory and immune effects of ambient PM_2.5.

Analysis of morphological and molecular composition changes in allergenic Artemisia vulgaris L. pollen under traffic pollution using SEM and FTIR spectroscopy

Nowadays, pollen allergy becomes an increasing problem for human population. Common mugwort (Artemisia vulgaris L.) is one of the major allergenic plants in Europe. In this study, the influence of air pollution caused by traffic on the structure and chemical composition of common mugwort pollen was investigated. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and curve-fitting analysis of amide I profile was applied to assess the morphological and structural changes of mugwort pollen grains collected from sites with different vehicle pollution levels. Microscopic observations support the conclusion, that the higher the car traffic, the smaller the pollen grains. The obtained results clearly show that air pollution had an impact on different maximum absorbance values of individual functional groups composing the chemical structure of pollen. Moreover, air pollution induced structural changes in macromolecules of mugwort pollen. In pollen collected from the unpolluted site, the content of sporopollenin (850 cm^-1) was the highest, whereas polysaccharide concentration (1032 cm^-1) was the lowest. Significant differences were observed in lipids. Pollen collected from the site with heavy traffic had the lowest content of lipids at 1709, 2071, and 2930 cm^-1. The largest differences were observed in the spectra regions corresponding to proteins. In pollen collected from unpolluted site, the highest level of β-sheet (1600 cm^-1) and α-helix (1650 cm^-1) was detected. The structural changes in proteins, observed in the second derivative of the FTIR spectrum and in the curve-fitting analysis of amide I profile, could be caused inter alia by air pollutants. Alterations in protein structure and in their content in the pollen may increase the sensitization and subsequent risk of allergy in predisposed people. The obtained results suggest that the changes in chemical composition of pollen may be a good indicator of air quality and that FTIR may be successfully applied in biomonitoring.

Biological factor related to Asian sand dust particles contributes to the exacerbation of asthma

Epidemiologic studies have revealed that Asian sand dust particles (ASDs) can affect respiratory and immune health represented by asthma. Factors responsible for the exacerbation of asthma remain unclear. The fungus Bjerkandera adusta (B.ad) and polycyclic aromatic hydrocarbons such as benzo[a]pyrene (BaP) have been identified in ASDs collected from the atmosphere when an ASD event occurred. We investigated the effects of B.ad and BaP related to ASDs on respiratory and immune systems. Bone marrow-derived antigen-presenting cells (APCs) and splenocytes from atopic prone NC/Nga mice and human airway epithelial cells were exposed to the B.ad or to BaP in the presence and absence of heated-ASDs (H-ASDs). B.ad and BaP in both the presence and absence of H-ASDs increased the expression of cell surface molecules on APCs. H-ASDs alone slightly activated APCs. The expressions induced by B.ad were higher than those induced by BaP in the presence and absence of H-ASDs. There were no remarkable effects on the activation of splenocytes or the proinflammatory responses in airway epithelial cells. These results suggest that B.ad rather than BaP contributes to the exacerbation of asthma regardless of the presence or absence of sand particles, particularly by the activation of the immune system via APCs. Copyright © 2016 John Wiley & Sons, Ltd.

Effects of diesel exhaust particles on macrophage polarization

BACKGROUND

Exposure to diesel exhaust particles (DEP) has long been associated with increased cardiovascular morbidity and mortality. The development of DEP toxicity seems to be linked to inflammation in which macrophages play a critical role. Macrophages can be polarized into proinflammatory M1 or anti-inflammatory M2 macrophages. The aim of this study was to identify the role of inflammation in DEP-induced toxicity by assessing the effects of DEP on macrophage polarization.

METHODS

Monocyte-derived macrophages (Mϕ) were stimulated with interferon γ and lipopolysaccharide or interleukin (IL)-4 to obtain M1 and M2 subtypes, respectively. To test the polarization capacity of DEP, Mϕ cells were exposed to DEP and compared to Mϕ, M1, and M2. We also studied the effects of DEP on already-polarized M1 or M2. The M1 markers assessed were tumor necrosis factor α (TNF-α) and IL-1β, while the M2 markers were the mannose receptor C type 1 (MRC-1) and transglutaminase 2 (TGM2).

RESULTS

Western blots revealed a 31 kDa band corresponding to pro-IL-1β, but only in M1-polarized macrophages. In M1, we also observed an upregulation of TNF-α messenger RNA (mRNA) expression. MRC-1 and TGM2 mRNA expression were only significantly enhanced in M2. DEP had no effect on any of the M1/M2 markers assessed. Moreover, DEP were not able to modify the phenotype of already-polarized M1 or M2.

CONCLUSION

Mϕ incubation with DEP did not have any effect on macrophage polarization, at least on the markers assessed in this study, namely, TNF-α/IL-1β for M1, and MRC-1/TGM2 for M2. Hence, these data argue against an important role of inflammation in DEP-induced vascular toxicity.

Ex vivo effects of naphthoquinones on allergen-sensitized mononuclear cells in mice

Naphthoquinone (NQ), one of the extractable chemical compounds of diesel exhaust particles, enhances allergic asthma traits in mice. However, it remains unknown whether: (1) several types of NQs have the same potential to facilitate allergies; and (2) NQs synergistically disrupt the functional phenotypes of immune cells. The aim of the present study was to investigate the effects of two types (1,2- and 1,4-) of NQs on sensitized mononuclear cells using an ex vivo assay. Male BALB/c mice were repeatedly and intraperitoneally administered ovalbumin (OVA: 20 µg) plus alum with or without two different doses of each NQ. After the final administration, splenocytes (mononuclear cells) were isolated from these mice and cultured in the presence of OVA. Helper T-related cytokines in the culture supernatants and downstream molecules were then evaluated. Protein levels of interferon-γ were higher in the supernatants from 1,2-NQ and 1,4-NQ at low dose + OVA-exposed mononuclear cells following the OVA stimulation than in those from OVA-exposed mononuclear cells. Interleukin (IL)-13 levels were higher in the supernatants from low dose NQs + OVA-exposed mononuclear cells. IL-17 levels were significantly higher in the supernatants from low dose 1,2-NQ + OVA-exposed mononuclear cells. The quantity of phosphorylated STAT6 in the nuclei of these cells was significantly greater in the low dose NQ + OVA groups than in the OVA group. These findings suggest NQs differently enhance allergen sensitization in the context of the Th response against mononuclear cells such as lymphocytes.

Morphometric analysis of inflammation in bronchial biopsies following exposure to inhaled diesel exhaust and allergen challenge in atopic subjects

Background

Allergen exposure and air pollution are two risk factors for asthma development and airway inflammation that have been examined extensively in isolation. The impact of combined allergen and diesel exhaust exposure has received considerably less attention. Diesel exhaust (DE) is a major contributor to ambient particulate matter (PM) air pollution, which can act as an adjuvant to immune responses and augment allergic inflammation. We aimed to clarify whether DE increases allergen-induced inflammation and cellular immune response in the airways of atopic human subjects.

Methods

Twelve atopic subjects were exposed to DE 300 μg.m⁻³ or filtered air for 2 h in a blinded crossover study design with a four-week washout period between arms. One hour following either filtered air or DE exposure, subjects were exposed to allergen or saline (vehicle control) via segmental challenge. Forty-eight hours post-allergen or control exposure, bronchial biopsies were collected. The study design generated 4 different conditions: filtered air + saline (FAS), DE + saline (DES), filtered air + allergen (FAA) and DE + allergen (DEA). Biopsies sections were immunostained for tryptase, eosinophil cationic protein (ECP), neutrophil elastase (NE), CD138, CD4 and interleukin (IL)-4. The percent positivity of positive cells were quantified in the bronchial submucosa.

Results

The percent positivity for tryptase expression and ECP expression remained unchanged in the bronchial submucosa in all conditions. CD4 % positive staining in DEA (0.311 ± 0.060) was elevated relative to FAS (0.087 ± 0.018; p = 0.035). IL-4 % positive staining in DEA (0.548 ± 0.143) was elevated relative to FAS (0.127 ± 0.062; p = 0.034). CD138 % positive staining in DEA (0.120 ± 0.031) was elevated relative to FAS (0.017 ± 0.006; p = 0.015), DES (0.044 ± 0.024; p = 0.040), and FAA (0.044 ± 0.008; p = 0.037). CD138 % positive staining in FAA (0.044 ± 0.008) was elevated relative to FAS (0.017 ± 0.006; p = 0.049). NE percent positive staining in DEA (0.224 ± 0.047) was elevated relative to FAS (0.045 ± 0.014; p = 0.031).

Conclusions

In vivo allergen and DE co-exposure results in elevated CD4, IL-4, CD138 and NE in the respiratory submucosa of atopic subjects, while eosinophils and mast cells are not changed.

Trial registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT01792232.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-016-0114-z) contains supplementary material, which is available to authorized users.

Activation of Proinflammatory Responses in Cells of the Airway Mucosa by Particulate Matter: Oxidant- and Non-Oxidant-Mediated Triggering Mechanisms

Inflammation is considered to play a central role in a diverse range of disease outcomes associated with exposure to various types of inhalable particulates. The initial mechanisms through which particles trigger cellular responses leading to activation of inflammatory responses are crucial to clarify in order to understand what physico-chemical characteristics govern the inflammogenic activity of particulate matter and why some particles are more harmful than others. Recent research suggests that molecular triggering mechanisms involved in activation of proinflammatory genes and onset of inflammatory reactions by particles or soluble particle components can be categorized into direct formation of reactive oxygen species (ROS) with subsequent oxidative stress, interaction with the lipid layer of cellular membranes, activation of cell surface receptors, and direct interactions with intracellular molecular targets. The present review focuses on the immediate effects and responses in cells exposed to particles and central down-stream signaling mechanisms involved in regulation of proinflammatory genes, with special emphasis on the role of oxidant and non-oxidant triggering mechanisms. Importantly, ROS act as a central second-messenger in a variety of signaling pathways. Even non-oxidant mediated triggering mechanisms are therefore also likely to activate downstream redox-regulated events.

Aggravation of ovalbumin-induced murine asthma by co-exposure to desert-dust and organic chemicals: an animal model study

BACKGROUND

The organic chemicals present in Asian sand dust (ASD) might contribute to the aggravation of lung eosinophila. Therefore, the aggravating effects of the Tar fraction from ASD on ovalbumin (OVA)-induced lung eosinophilia were investigated.

METHODS

The Tar fraction was extracted from ASD collected from the atmosphere in Fukuoka, Japan. ASD collected from the Gobi desert was heated at 360°C to inactivate toxic organic substances (H-ASD). ICR mice were instilled intratracheally with 12 different test samples prepared with Tar (1 μg and 5 μg), H-ASD, and OVA in a normal saline solution containing 0.02% Tween 80. The lung pathology, cytological profiles in the bronchoalveolar lavage fluid (BALF), inflammatory cytokines/chemokines in BALF and OVA-specific immunoglobulin in serum were investigated.

RESULTS

Several kinds of polycyclic aromatic hydrocarbons (PAHs) were detected in the Tar sample. H-ASD + Tar 5 μg induced slight neutrophilic lung inflammation. In the presence of OVA, Tar 5 μg increased the level of eosinophils slightly and induced trace levels of Th2 cytokines IL-5 and IL-13 in BALF. Also mild to moderate goblet cell proliferation and mild infiltration of eosinophils in the submucosa of airway were observed. These pathological changes caused by H-ASD + OVA were relatively small. However, in the presence of OVA and H-ASD, Tar, at as low a level as 1 μg, induced severe eosinophil infiltration and proliferation of goblet cells in the airways and significantly increased Th2 cytokines IL-5 and IL-13 in BALF. The mixture showed an adjuvant effect on OVA-specific IgG1 production.

CONCLUSIONS

These results indicate that H-ASD with even low levels of Tar exacerbates OVA-induced lung eosinophilia via increases of Th2-mediated cytokines. These results suggest that ASD-bound PAHs might contribute to the aggravation of lung eosinophila.

Interplay of air pollution and asthma immunopathogenesis: a focused review of diesel exhaust and ozone

Controlled human exposure experiments with diesel exhaust particles (DEPs) and ozone serve to illustrate the important role pollutants play in modulating both allergic mechanisms and immune responses to affect the immunopathogenesis of airway diseases such as asthma. For DEP, evidence is stronger for the exacerbation of existing asthma rather than for the development of new disease. To the extent that this enhancement occurs, the augmentation of Th2-type immunity seems to be a common element. For ozone, neutrophilic inflammation, altered immune cell phenotype and function and oxidative stress are all marked responses that likely contribute to underlying immune-inflammatory features of asthma. Evidence is also emerging that unique gene signatures and epigenetic control of immune and inflammatory-based genes are playing important roles in the magnitude of the impact ozone is having on respiratory health. Indeed, the interplay between air pollutants such as DEP and ozone and asthma immunopathogenesis is an ongoing concern in terms of understanding how exposure to these agents can lead to worsening of disease. To this end, asthmatics may be pre-disposed to the deleterious effects of pollutants like ozone, having constitutively modified host defense functions and gene signatures. Although this review has utilized DEP and ozone as example pollutants, more research is needed to better understand the interplay between air pollution in general and asthma immumopathogenesis.

Effects of exposure to nanoparticle-rich or -depleted diesel exhaust on allergic pathophysiology in the murine lung

Although it has been shown that exposure to diesel exhaust (DE) is linked to the induction or exacerbation of respiratory disorders, the major components responsible have not been fully identified. We examined the effects of airway exposure to nanoparticle-rich DE (NR-DE) or DE without particles on allergic pulmonary inflammation in mice. We also investigated the cellular responses to intratracheal instillation of NR-DE particles (NR-DEP). ICR mice inhaled one of four different mixtures (control air, low-concentration DE, high-concentration DE, and high-concentration DE without particles) for 8 weeks in the presence or absence of repeated intratracheal administration of ovalbumin (OVA). In a separate study, NR-DEP and/or OVA were repeatedly administrated intratracheally to mice. High-concentration NR-DE or DE without particles substantially exacerbated OVA-induced eosinophilic airway inflammation. This exacerbation was concomitant with increases in lung levels of Th2 cytokines such as interleukin (IL)-4, IL-5, and IL-13 and of chemokines such as monocyte chemotactic protein-1. Furthermore, in the presence of allergen, both DE without particles and high-concentration NR-DE strongly enhanced the production and release of myeloperoxidase into the alveolar spaces. Repeated administration of NR-DEP did not substantially affect the allergic asthma. These results strongly suggest that gaseous compounds in NR-DE aggravate murine allergic airway inflammation, mainly via amplification of the Th2 response.

Effects of two Asian sand dusts transported from the dust source regions of Inner Mongolia and northeast China on murine lung eosinophilia

The quality and quantity of toxic materials adsorbed onto Asian sand dust (ASD) are different based on dust source regions and passage routes. The aggravating effects of two ASDs (ASD1 and ASD2) transported from the source regions of Inner Mongolia and northeast China on lung eosinophilia were compared to clarify the role of toxic materials in ASD. The ASDs contained different amounts of lipopolysaccharides (LPS) and β-glucan (ASD1<ASD2) and SiO2 (ASD1>ASD2). CD-1 mice were instilled intratracheally with ASD1, ASD2 and/or ovalbumin (OVA) four times at 2-week intervals. ASD1 and ASD2 enhanced eosinophil recruitment induced by OVA in the submucosa of the airway, with goblet cell proliferation in the bronchial epithelium. ASD1 and ASD2 synergistically increased OVA-induced eosinophil-relevant cytokines interleukin-5 (IL-5), IL-13 (ASD1<ASD2) and chemokine eotaxin (ASD1>ASD2) in bronchoalveolar lavage fluid. ASD2 aggravating effects on lung eosinophilia were greater than ASD1. The role of LPS and β-glucan in ASD2 on the production of pro-inflammatory mediators was assessed using in vitro bone marrow-derived macrophages (BMDMs) from wild type, Toll-like receptor 2-deficient (TLR2-/-), TLR4-/-, and MyD88-/- mice (on Balb/c background). ASD2-stimulated TLR2-/- BMDMs enhanced IL-6, IL-12, TNF-α, MCP-1 and MIP-1α secretion compared with ASD2-stimulated TLR4-/- BMDMs. Protein expression from ASD2-stimulated MyD88-/- BMDM were very low or undetectable. The in vitro results indicate that lung eosinophilia caused by ASD is TLR4 dependent. Therefore, the aggravation of OVA-related lung eosinophilia by ASD may be dependent on toxic substances derived from microbes, such as LPS, rather than SiO2.

Organic chemicals in diesel exhaust particles enhance picryl chloride-induced atopic dermatitis in NC/Nga mice

BACKGROUND

Diesel exhaust particles (DEP) have been reported to worsen allergic airway inflammation in mice. Recently, the organic chemical components of DEP (DEP-OC) were found to be important contributors to the aggravation of allergic airway inflammation in mice. The purpose of this study was to examine the effects of DEP-OC on atopic dermatitis (AD)-like skin lesions induced by picryl chloride (PiCl) in NC/Nga mice.

METHODS

DEP were extracted with benzene/ethanol, and the soluble organic fraction formed the DEP-OC. NC/Nga male mice received simultaneous application of DEP-OC and/or PiCl on their ears once a week for 9 or 3 weeks. We evaluated skin lesions by noting scaling, eruption, excoriation, erosion, hemorrhage, pathologic changes, production of cytokines, and IgE level in the serum.

RESULTS

PiCl application alone produced progressively severe AD-like skin lesions. The application of PiCl plus DEP-OC resulted in a marked worsening of skin lesions in the early stages of AD. Moreover, mast cell counts significantly increased in the subcutaneous tissue. Administration of PiCl combined with DEP-OC resulted in a greater increase in the local expression of interleukin-4, keratinocyte chemoattractant, and neutrophils in subcutaneous tissue compared with PiCl treatment alone. In contrast, the combination treatment produced lower levels of IFN-γ compared with PiCl treatment alone.

CONCLUSIONS

DEP-OC application to the skin aggravated PiCl-induced AD. This aggravation may be due to activation of the Th2-associated immune responses by the organic chemicals in DEP.

Inflammation-related effects of diesel engine exhaust particles: studies on lung cells in vitro

Diesel exhaust and its particles (DEP) have been under scrutiny for health effects in humans. In the development of these effects inflammation is regarded as a key process. Overall, in vitro studies report similar DEP-induced changes in markers of inflammation, including cytokines and chemokines, as studies in vivo. In vitro studies suggest that soluble extracts of DEP have the greatest impact on the expression and release of proinflammatory markers. Main DEP mediators of effects have still not been identified and are difficult to find, as fuel and engine technology developments lead to continuously altered characteristics of emissions. Involved mechanisms remain somewhat unclear. DEP extracts appear to comprise components that are able to activate various membrane and cytosolic receptors. Through interactions with receptors, ion channels, and phosphorylation enzymes, molecules in the particle extract will trigger various cell signaling pathways that may lead to the release of inflammatory markers directly or indirectly by causing cell death. In vitro studies represent a fast and convenient system which may have implications for technology development. Furthermore, knowledge regarding how particles elicit their effects may contribute to understanding of DEP-induced health effects in vivo, with possible implications for identifying susceptible groups of people and effect biomarkers.

In vivo immunoamplifying effects of di-(2-ethylhexyl) phthalate on cytokine response

A recent epidemiological study has revealed the positive association between atopy morbidity in children and phthalate esters, environmental chemicals in house dust. Nonetheless, experimental and molecular evidences regarding the correlation between phthalates and allergic response/pathophysiology are not fully investigated. Among phthalate esters, di-(2-ethylhexyl) phthalate (DEHP) has been widely used for flexible polyvinyl chloride products including vinyl flooring and wall covering. In the present study, we examined the effects of exposure to DEHP on allergen (ovalbumin: OVA) -induced peritonitis in ICR mice. Repeated administration of OVA via intraperitoneal route induced peritoneal inflammation characterized by infiltration of granulocytes (neutrophils and eosinophils) into the cavity. DEHP synergistically exaggerated the OVA-related neutrophilic inflammation. Furthermore, DEHP + OVA profoundly amplified OVA-elicited inflammation- and allergy-related molecules such as interleukin-5, eotaxin, and keratinocyte-derived chemoattractant production/release in the peritoneal cavity. Taken together, DEHP aggravated OVA-related peritoneal inflammation, which is concomitant with local enhanced production/release of inflammation- and allergy-related molecules.

Nano-titanium dioxide modulates the dermal sensitization potency of DNCB

We determined the ability of a model nanoparticle (NP) (titanium dioxide, TiO(2)) to modulate sensitization induced by a known potent dermal sensitizer (dinitrochlorobenzene) using a variant of the local lymph node assay called lymph node proliferation assay.BALB/c mice received sub-cutaneous injections of vehicle (2.5 mM sodium citrate), TiO(2) NPs (0.004, 0.04 or 0.4 mg/ml) or pigment particles (0.04 mg/ml) both stabilized in sodium citrate buffer at the base of each ear (2x50μl), before receiving dermal applications (on both ears) of 2,4-Dinitrochlorobenzene (DNCB) (2x25μl of 0.1%) or its vehicle (acetone olive oil - AOO (4:1)) on days 0, 1 and 2. On day 5, the stimulation index (SI) was calculated as a ratio of (3)HTdR incorporation in lymphocytes from DNBC-treated mice and AOO-treated controls. In a second experiment the EC(3)-value for DNCB (0 to 0.1%) was assessed in the absence or presence of 0.04 mg/ml TiO(2). In a third experiment, the lymphocyte subpopulations and the cytokine secretion profile were analyzed after TiO(2) (0.04 mg/ml) and DNCB (0.1%) treatment. Injection of NPs in AOO-treated control mice did not have any effect on lymph node (LN) proliferation. DNCB sensitization resulted in LN proliferation, which was further increased by injection of TiO(2) NPs before DNCB sensitization. The EC(3) of DNCB, with prior injection of vehicle control was 0.041%, while injection with TiO(2) decreased the EC(3) of DNCB to 0.015%. TiO(2) NPs pre-treatment did not alter the lymphocyte subpopulations, but significantly increased the level of IL-4 and decreased IL-10 production in DNCB treated animals.In conclusion, our study demonstrates that administration of nano-TiO(2) increases the dermal sensitization potency of DNCB, by augmenting a Th(2) response, showing the immunomodulatory abilities of NPs.

Suppression of the NF-κB pathway by diesel exhaust particles impairs human antimycobacterial immunity

Epidemiological studies suggest that chronic exposure to air pollution increases susceptibility to respiratory infections, including tuberculosis in humans. A possible link between particulate air pollutant exposure and antimycobacterial immunity has not been explored in human primary immune cells. We hypothesized that exposure to diesel exhaust particles (DEP), a major component of urban fine particulate matter, suppresses antimycobacterial human immune effector cell functions by modulating TLR-signaling pathways and NF-κB activation. We show that DEP and H37Ra, an avirulent laboratory strain of Mycobacterium tuberculosis, were both taken up by the same peripheral human blood monocytes. To examine the effects of DEP on M. tuberculosis-induced production of cytokines, PBMC were stimulated with DEP and M. tuberculosis or purified protein derivative. The production of M. tuberculosis and purified protein derivative-induced IFN-γ, TNF-α, IL-1β, and IL-6 was reduced in a DEP dose-dependent manner. In contrast, the production of anti-inflammatory IL-10 remained unchanged. Furthermore, DEP stimulation prior to M. tuberculosis infection altered the expression of TLR3, -4, -7, and -10 mRNAs and of a subset of M. tuberculosis-induced host genes including inhibition of expression of many NF-κB (e.g., CSF3, IFNG, IFNA, IFNB, IL1A, IL6, and NFKBIA) and IFN regulatory factor (e.g., IFNG, IFNA1, IFNB1, and CXCL10) pathway target genes. We propose that DEP downregulate M. tuberculosis-induced host gene expression via MyD88-dependent (IL6, IL1A, and PTGS2) as well as MyD88-independent (IFNA, IFNB) pathways. Prestimulation of PBMC with DEP suppressed the expression of proinflammatory mediators upon M. tuberculosis infection, inducing a hyporesponsive cellular state. Therefore, DEP alters crucial components of antimycobacterial host immune responses, providing a possible mechanism by which air pollutants alter antimicrobial immunity.

Differential effects of the particle core and organic extract of diesel exhaust particles

Exposure to diesel engine exhaust particles (DEPs), representing a complex and variable mixture of components, has been associated with lung disease and induction of pro-inflammatory mediators and CYP1A1 expression. The aim of this study was to further characterise DEP-components accounting for these effects. Human bronchial epithelial cells (BEAS-2B) were exposed to either native DEPs, or corresponding methanol DEP-extract or residual DEPs, and investigated with respect to cytotoxicity and expression and release of multiple inflammation-related mediators. Both native DEPs and DEP-extract, but not residual DEPs, induced marked mRNA expression of COX-2, IL-6 and IL-8, as well as cytotoxicity and release of IL-6. However, CYP1A1 was primarily induced by the native and residual DEPs. Overall, the results of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and gas chromatography with mass spectrometry (GC/MS) analysis of DEP-extracts indicated that the majority of the analysed PAHs and PAH-derivatives were extracted from the particles, but that certain PAH-derivatives, probably their carboxylic isomers, tended to be retained on the residual DEPs. Moreover, it appeared that certain components of the methanol extract may suppress CYP1A1 expression. These results provide insight into how different components of the complex DEP-mixture may be differently involved in DEP-induced pro-inflammatory responses and underscore the importance of identifying and clarifying the roles of active DEP-components in relation to different biological effects.

Threat of allergenic airborne grass pollen in Szczecin, NW Poland: the dynamics of pollen seasons, effect of meteorological variables and air pollution

The dynamics of Poaceae pollen season, in particularly that of the Secale genus, in Szczecin (western Poland) 2004-2008 was analysed to establish a relationship between the meteorological variables, air pollution and the pollen count of the taxa studied. Consecutive phases during the pollen season were defined for each taxon (1, 2.5, 5, 25, 50, 75, 95, 97.5, 99% of annual total), and duration of the season was determined using the 98% method. On the basis of this analysis, the temporary differences in the dynamics of the seasons were most evident for Secale in 2005 and 2006 with the longest main pollen season (90% total pollen). The pollen season of Poaceae started the earliest in 2007, when thermal conditions were the most favourable. Correlation analysis with meteorological factors demonstrated that the relative humidity, mean and maximum air temperature, and rainfall were the factors influencing the average daily pollen concentrations in the atmosphere; also, the presence of air pollutants such as ozone, PM(10) and SO(2) was statistically related to the pollen count in the air. However, multiple regression models explained little part of the total variance. Atmospheric pollution induces aggravation of symptoms of grass pollen allergy.

Biology of diesel exhaust effects on allergic pulmonary inflammation

Although the adverse health effects of diesel exhaust particles (DEP) have been proposed and are being clarified, their facilitating effects on preexisting pathological conditions (pathological conditions) have not been fully identified. On the other hand, there exist hypersensitive subjects against particulate matters. In this review, we provide insights into the immunotoxicity of DEP as an aggravating factor in hypersusceptible subjects, especially those with allergic pulmonary diseases using our in vivo experimental model. In brief, we examined the effects of DEP on allergic asthma in vivo, and showed that repetitive pulmonary exposure to DEP has promoting effects on allergic airway inflammation, including adjuvanticity on Th2-milieu. Further, we propose a causal machinery regarding the adverse impacts, i.e., via inappropriate activation of antigen-presenting cells such as dendritic cells.

Components of diesel exhaust particles diversely enhance a variety of respiratory diseases related to infection or allergy: extracted organic chemicals and the residual particles after extraction differently affect respiratory diseases

Experimental and epidemiological studies have reported that diesel exhaust particles (DEP) can aggravate a variety of respiratory diseases including infection or allergy. However, the responsible components in DEP for the enhancement have not been identified. The present review demonstrates the different effects of the components of DEP on the respiratory diseases related to infection or allergy. We exposed mice to the organic chemicals (DEP-OC) and the residual carbonaceous nuclei (washed DEP) derived from DEP in the presence or absence of bacterial endotoxin (lipopolysaccharide: LPS) or allergen. In our first series of experiments, washed DEP combined with LPS synergistically exacerbated lung injury, which was concomitant with the enhanced lung expression of proinflammatory cytokines and chemokines, whereas DEP-OC combined with LPS did not. In contrast, our second series of experiments showed that DEP-OC, rather than washed DEP, enhanced allergen-related eosinophilic inflammation and proliferation of goblet cells in the airway epithelium, which was paralleled by the enhanced lung expression of eotaxin and interleukin-5. However, washed DEP with ovalbmin showed less change and increased the lung expression of interferon-γ. It is suggested that DEP components diversely affect various types of respiratory diseases, while the combination of organic chemicals and carbonaceous nuclei (whole DEP) mostly aggravate respiratory diseases.

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.

Urban particulate matter in Beijing, China, enhances allergen-induced murine lung eosinophilia

It has been reported that ambient particulate matter (PM) in some large cities, such as Beijing, China, causes adverse respiratory health effects. However, there is currently no experimental report on the relationship between bronchial asthma and urban PM (UPM) in northeast Asia. In this study, the microbial and chemical substances adsorbed onto UPM collected in Beijing were excluded by heat-treatment at 360 degrees C for 30 min. The effects of UPM or heated UPM (H-UPM) toward allergic lung inflammation were compared in murine lungs to investigate the role of organic substances. ICR mice were administrated intratracheally with the two kinds of UPM and/or ovalbumin (OVA) 4 times at 2-week intervals. UPM and H-UPM enhanced eosinophil recruitment induced by OVA in the alveoli and in the submucosa of the airway, which has a goblet cell proliferation in the bronchial epithelium. UPM and H-UPM synergistically increased Th-2 cytokines--interleukin (IL)-4 and IL-13, eosinophil-relevant cytokines and chemokines, such as IL-5 and monocyte chemotactic protein-3 (MCP-3), induced by OVA in bronchoalveolar lavage fluid (BALF). The enhancing effects were much greater in UPM than in H-UPM. UPM induced adjuvant effects on specific immunoglobulin E (IgE) and IgG1 production by OVA. In an in vitro study using RAW264.7 cells, UPM increased the expression of Toll-like receptor 2 (TLR2) mRNA, but not TLR4 mRNA. H-UPM caused no expression of both TLR mRNAs. These results suggest that the aggravated lung eosinophilia in UPM was due to activation of a Th2-associated immune response via the activation of TLR2 by microbial materials. Chemical materials of air pollutant origin contained in UPM, and inorganic components (elemental carbon, mineral elements) in H-UPM, could also cause the aggravation.

Differential Transcriptional Changes in Mice Exposed to Chemically Distinct Diesel Samples

Epidemiological studies have linked exposure to ambient particulate matter (PM) with increased asthmatic symptoms. Diesel exhaust particles (DEP) are a predominant source of vehicle derived ambient PM, and experimental studies have demonstrated that they may have adjuvant potential when given with an antigen. We previously compared 3 DEP samples: N-DEP, A-DEP, and C-DEP in a murine ovalbumin (OVA) mucosal sensitization model and reported the adjuvant activity to be: C-DEP ≈ A-DEP > N-DEP. The present study analyzed gene expression changes from the lungs of these mice. Transcription profiling demonstrated that all the DEP samples altered cytokine and toll-like receptor pathways regardless of type, with or without antigen sensitization. Further analysis of DEP exposure with OVA showed that all DEP treatments altered networks involved in immune and inflammatory responses. The A- and C-DEP/OVA treatments induced differential expression of apoptosis pathways in association with stronger adjuvant responses, while expression of cell cycle control and DNA damage pathways were also altered in the C-DEP/OVA treatment. This comprehensive approach using gene expression analysis to examine changes at a pathway level provides detailed information on events occurring in the lung after DEP exposure, and confirms that the most bioactive sample induced many more individual genes and changes in immunoregulatory and homeostatic pathways.

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.

Susceptibility of inflamed alveolar and airway epithelial cells to injury induced by diesel exhaust particles of varying organic carbon content

Exposure to traffic-related ambient air pollution, such as diesel exhaust particles (DEP), is associated with adverse health outcomes, especially in individuals with preexisting inflammatory respiratory diseases. Using an analogous novel in vitro system to model both the healthy and inflamed lung, the susceptibility of epithelial cells exposed to DEP of varying organic carbon content was studied. Murine LA-4 alveolar type II-like epithelial cells, as well as primary murine tracheal epithelial cells (MTE), were treated with exogenous cytokines (tumor necrosis factor [TNF] alpha + interleukin [IL]-1 beta + interferon [IFN] gamma) to model a mild inflammatory state. Epithelial cells were subsequently exposed to DEP of varying organic carbon content, and the resultant cytotoxic, cytoprotective, or antioxidant cell responses were inferred by changes in lactate dehydrogenase (LDH) release, heme oxygenase-1 (HO-1) expression, or glutathione levels, respectively. Data showed that exposure of healthy LA-4 cells to organic carbon-rich DEP (25 microg/cm(2); 24 h) induced adaptive cytoprotective/antioxidant responses with no apparent cell injury. In contrast, exposure of inflamed LA-4 cells resulted in oxidative stress culminating in significant cytotoxicity. Exposure of healthy MTE cells to organic carbon-rich DEP (20 microg/cm(2); 24 h) was seemingly without effect, whereas exposure of inflamed MTE cells resulted in increased epithelial solute permeability. Thus, surface lung epithelial cells stressed by a state of inflammation and then exposed to organic carbon-rich DEP appear unable to respond to the additional oxidative stress, resulting in epithelial barrier dysfunction and injury. Adverse health outcomes associated with exposure to traffic-related air pollutants, like DEP, in patients with preexisting inflammatory respiratory diseases may be due, in part, to similar mechanisms.

The immune effects of naturally occurring and synthetic nanoparticles

Ultrafine particles and engineered nanoparticles have unique aerodynamic and biochemical properties that affect the immune system and human health in ways that are different from or exceed those seen with gases or larger particulates. These effects result from a unique set of physical characteristics and surface moieties, which generate an ability of UFPs to enter tissues and cells, interact with proteins and DNA at a molecular level and directly and indirectly modulate the immune system by novel mechanisms. In recent years, a new field known as nanotechnology has impacted multiple industries by taking advantage of the special qualities of these small "atomic-sized" particles. Nanomedicine has already opened up a new avenue of research in cancer therapy, drug delivery and immune regulation. While the benefits of this new science to human civilization are seemingly immeasurable, it is also important to appreciate that these particles can also lead to harmful effects on human health. In vitro and animal studies are showing that nanoparticles and UFPs are capable of activating proinflammatory cytokines, chemokines and adhesion molecules, with recruitment of inflammatory cells including basophils, macrophages, dendritic cells, T cells, neutrophils and eosinophils. These changes may have an impact on immune defense, but also on the Th1/Th2 balance, and even on non-immunologic function. Resulting immune system derangement can lead to increases in incidence of autoimmune, allergic and even neoplastic diseases. Cardiorespiratory effects have been observed to occur in humans. Much further research is needed to establish safe exposure levels for this important new class of particulates.

Nano titanium dioxide particles promote allergic sensitization and lung inflammation in mice

The purpose of this study was to investigate whether photocatalytic TiO₂ nanoparticles have adjuvant effect, when administered in combination with ovalbumin (OVA) in mice. Mice were immunized via intraperitoneal injections of OVA, OVA + TiO₂ or OVA + Al(OH)₃ and challenged with aerosols of OVA. At the end of the study, serum was analysed for content of OVA-specific IgE, IgG1 and IgG2a antibodies, and the bronchoalveolar lavage fluid (BALF) was analysed for content of inflammatory cells and levels of interleukin (IL)-4, IL-5, IL-10 and interferon-γ. The TiO₂ particles promoted a Th2 dominant immune response with high levels of OVA-specific IgE and IgG1 in serum and influx of eosinophils, neutrophils and lymphocytes in BALF. The TiO₂ particles induced a significantly higher level of OVA-specific IgE than the standard adjuvant Al(OH)₃. However, the two substances were comparable regarding the level of eosinophilic inflammation and interleukins present in BALF.