Diesel exposure favors Th2 cell recruitment by mononuclear cells and alveolar macrophages from allergic patients by differentially regulating macrophage-derived chemokine and IFN-gamma-induced protein-10 production

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.

Particulate matter properties and health effects: consistency of epidemiological and toxicological studies

Identifying the ambient particulate matter (PM) fractions or constituents, critically involved in eliciting adverse health effects, is crucial to the implementation of more cost-efficient abatement strategies to improve air quality. This review focuses on the importance of different particle properties for PM-induced effects, and whether there is consistency in the results from epidemiological and experimental studies. An evident problem for such comparisons is that epidemiological and experimental data on the effects of specific components of ambient PM are limited. Despite this, some conclusions can be drawn. With respect to the importance of the PM size-fractions, experimental and epidemiological studies are somewhat conflicting, but there seems to be a certain consistency in that the coarse fraction (PM10-2.5) has an effect that should not be neglected. Better exposure characterization may improve the consistency between the results from experimental and epidemiological studies, in particular for ultrafine particles. Experimental data indicate that surface area is an important metric, but composition may play an even greater role in eliciting effects. The consistency between epidemiological and experimental findings for specific PM-components appears most convincing for metals, which seem to be important for the development of both pulmonary and cardiovascular disease. Metals may also be involved in PM-induced allergic sensitization, but the epidemiological evidence for this is scarce. Soluble organic compounds appear to be implicated in PM-induced allergy and cancer, but the data from epidemiological studies are insufficient for any conclusions. The present review suggests that there may be a need for improvements in research designs. In particular, there is a need for better exposure assessments in epidemiological investigations, whereas experimental data would benefit from an improved comparability of studies. Combined experimental and epidemiological investigations may also help answer some of the unresolved issues.

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.

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.

Polycyclic aromatic hydrocarbons reciprocally regulate IL-22 and IL-17 cytokines in peripheral blood mononuclear cells from both healthy and asthmatic subjects

Pollution, including polycyclic aromatic hydrocarbons (PAH), may contribute to increased prevalence of asthma. PAH can bind to the Aryl hydrocarbon Receptor (AhR), a transcription factor involved in Th17/Th22 type polarization. These cells produce IL17A and IL-22, which allow neutrophil recruitment, airway smooth muscle proliferation and tissue repair and remodeling. Increased IL-17 and IL-22 productions have been associated with asthma. We hypothesized that PAH might affect, through their effects on AhR, IL-17 and IL-22 production in allergic asthmatics. Activated peripheral blood mononuclear cells (PBMCs) from 16 nonallergic nonasthmatic (NA) and 16 intermittent allergic asthmatic (AA) subjects were incubated with PAH, and IL-17 and IL-22 productions were assessed. At baseline, activated PBMCs from AA exhibited an increased IL-17/IL-22 profile compared with NA subjects. Diesel exhaust particle (DEP)-PAH and Benzo[a]Pyrene (B[a]P) stimulation further increased IL-22 but decreased IL-17A production in both groups. The PAH-induced IL-22 levels in asthmatic patients were significantly higher than in healthy subjects. Among PBMCs, PAH-induced IL-22 expression originated principally from single IL-22- but not from IL-17- expressing CD4 T cells. The Th17 transcription factors RORA and RORC were down regulated, whereas AhR target gene CYP1A1 was upregulated. IL-22 induction by DEP-PAH was mainly dependent upon AhR whereas IL-22 induction by B[a]P was dependent upon activation of PI3K and JNK. Altogether, these data suggest that DEP-PAH and B[a]P may contribute to increased IL22 production in both healthy and asthmatic subjects through mechanisms involving both AhR -dependent and -independent pathways.

Exposure to diesel exhaust particle extracts (DEPe) impairs some polarization markers and functions of human macrophages through activation of AhR and Nrf2

Macrophages (MΦ), well-known to play an important role in immune response, also respond to environmental toxic chemicals such as diesel exhaust particles (DEP). Potential effects of DEPs towards MΦ polarization, a key hall-mark of MΦ physiology, remain however poorly documented. This study was therefore designed to evaluate the effects of a reference DEP extract (DEPe) on human MΦ polarization. Human blood monocytes-derived MΦ were incubated with IFNγ+LPS or IL-4 to obtain M1 and M2 subtypes, respectively; a 24 h exposure of polarizing MΦ to 10 μg/ml DEPe was found to impair expression of some macrophagic M1 and M2 markers, without however overall inhibition of M1 and M2 polarization processes. Notably, DEPe treatment increased the secretion of the M1 marker IL-8 and the M2 marker IL-10 in both MΦ subtypes, whereas it reduced lipopolysaccharide-induced IL-6 and IL-12p40 secretion in M1 MΦ. In M2 MΦ, DEPe exposure led to a reduction of CD200R expression and of CCL17, CCL18 and CCL22 secretion, associated with a lower chemotaxis of CCR4-positive cells. DEPe activated the Nrf2 and AhR pathways and induced expression of their reference target genes such as Hmox-1 and cytochrome P-4501B1 in M1 and M2 MΦ. Nrf2 or AhR silencing through RNA interference prevented DEPe-related down-regulation of IL-6. AhR silencing also inhibited the down-secretion of IL-12p40 and CCL18 in M1- and M2-DEPe-exposed MΦ, respectively. DEPs are therefore likely to alter expression of some M1 and M2 markers in an AhR- and Nrf2-dependent manner; such regulations may contribute to deleterious immune effects of atmospheric DEP.

[Environmental pollution and allergy: immunological mechanisms]

Airborne pollutants, both particulate and gaseous, represent a major environmental factor promoting allergic sensitization and disease expression. These adverse effects of particulate matter are highly dependent upon the nature and size of the particles, their content of chemicals and metals, and the subject's genetic makeup. Diesel exhaust and gases, in particular ozone, have been shown to exacerbate cellular inflammation and to act as mucosal adjuvants to skew the immune response to inhaled antigens toward a Th2-like phenotype. Growing evidence suggests that mechanisms of pollutant-induced amplification of the allergic reaction depend on oxidative stress that is under the control of susceptibility genes, as well as epigenetic mechanisms.

What’s So Special about the Developing Immune System?

The evolution of the subdiscipline of developmental immunotoxicology (DIT) as it exists today has been shaped by significant regulatory pressures as well as key scientific advances. This review considers the role played by legislation to protect children’s health, and on the emergence of immunotoxcity and developmental immunotoxicity guidelines, as well as providing some context to the need for special attention on DIT by considering the evidence that the developing immune system may have unique susceptibilities when compared to the adult immune system. Understanding the full extent of this potential has been complicated by a paucity of data detailing the development of the immune system during critical life stages as well as by the complexities of comparisons across species. Notably, there are differences between humans and nonhuman species used in toxicity testing that include specific differences relative to the timing of the development of the immune system as well as more general anatomic differences, and these differences must be factored into the interpretation of DIT studies. Likewise, understanding how the timing of the immune development impacts on various immune parameters is critical to the design of DIT studies, parameters most extensively characterized to date in young adult animals. Other factors important to DIT, which are considered in this review, are the recognition that effects other than suppression (e.g., allergy and autoimmunity) are important; the need to improve our understanding of how to assess the potential for DIT in humans; and the role that pathology has played in DIT studies in test animals. The latter point receives special emphasis in this review because pathology evaluations have been a major component of standard nonclinical toxicology studies, and could serve an important role in studies to evaluate DIT. This possibility is very consistent with recommendations to incorporate a DIT evaluation into standard developmental and reproductive toxicology (DART) protocols. The overall objective of this review is to provide a ‘snapshot’ of the current state-of-the-science of DIT. Despite significant progress, DIT is still evolving and it is our hope that this review will advance the science.

Distinct requirements for interleukin-6 in airway inflammation induced by diesel exhaust in mice

To clarify the possible role of interleukin-6 in aggravation of inflammatory responses in diesel exhaust-exposed mice, we compared the infiltration of inflammatory cells and the production of chemokines between interleukin-6-deficient and wild-type mice following 0, 1.0, or 3.0 mg diesel particles/m3 diesel exhaust inhalation for 4 weeks. Exposure to diesel exhaust significantly increased the number of inflammatory cells and the amount of CCL17 and CXCL3 in bronchoalveolar lavage fluids from wild-type mice, but not in interleukin-6-deficient mice. These findings suggest that interleukin-6 plays a critical role in airway inflammatory responses induced by diesel exhaust inhalation.

Involvement of CCL18 in allergic asthma

Allergic asthma is associated with a pulmonary recruitment of Th type 2 cells, basophils, and eosinophils, mainly linked to chemokine production. CCL18 is a chemokine preferentially expressed in the lung, secreted by APCs, induced by Th2-type cytokines, and only present in humans. Therefore, CCL18 may be involved in allergic asthma. PBMC from asthmatics allergic to house dust mite cultured in the presence of Dermatophagoides pteronyssinus 1 (Der p 1) allergen secreted CCL18, 48 and 72 h after stimulation, whereas those from healthy donors did not. Part of CCL18 was directly derived from Der p 1-stimulated plasmacytoid dendritic cells, whereas the other part was linked to monocyte activation by IL-4 and IL-13 produced by Der p 1-stimulated T cells. In bronchoalveolar lavages from untreated asthmatic allergic patients, CCL18 was highly increased compared with controls. Functionally, CCL18 preferentially attracted in vitro-polarized Th2 cells and basophils, but not eosinophils and Th1 cells, and induced basophil histamine and intracellular calcium release. These data show a new function for CCL18, i.e., the recruitment of Th2 cells and basophils, and suggest that CCL18 may play a predominant role in allergic asthma.

Modification of allergic inflammation in murine model of rhinitis by different bacterial ligands: involvement of mast cells and dendritic cells

BACKGROUND

It has been suggested that airway bacterial infections exacerbate allergic disorders, and bacterial components in the air affect allergic inflammation via Toll-like receptors expressed on mast cells and dendritic cells in the airway mucosa.

OBJECTIVE

Peptidoglycan (PGN) is a major component of the bacterial cell wall. We investigated the effect of PGN on the effector phase of allergic inflammation, in comparison with the effect of CpG-oligodeoxynucleotides (CpG), which is known to be a Th1 adjuvant.

METHODS

Ovalbumin (OVA)-sensitized mice were challenged intranasally with OVA alone or OVA together with PGN or CpG. Nasal allergic symptoms and eosinophilia were scored, and the OVA-specific cytokine response was examined in the cells of cervical lymph nodes and nasal mucosa. Bone marrow-derived mast cells (BMMCs) and dendritic cells (BMDCs) were stimulated with PGN or CpG in vitro, and the expression level of cytokines and chemokines was examined by RT-PCR. In addition, the expression level of chemokines was examined by RT-PCR in mast cells of OVA-sensitized mice challenged with OVA alone or OVA together with PGN or CpG.

RESULTS

PGN exposure exacerbated the nasal allergic symptoms and eosinophilia, whereas CpG exposure suppressed them. In addition, PGN exposure increased the OVA-specific IL-4 response in the cells, whereas CpG exposure decreased it. On the other hand, there were no significant differences in the OVA-specific IFN-gamma response. PGN but not CpG induced the expression of thymus and activation-regulated chemokine (TARC) and macrophage/monocyte-derived chemokine (MDC) in both BMMCs and mast cells of mice sensitized and challenged with OVA. CpG but not PGN induced the expression of IFN-beta and interferon-inducible protein-10 (IP-10) in BMDCs, and histamine did not influence this effect.

CONCLUSION

These results demonstrate that PGN exposure exacerbates allergic inflammation mainly via mast cells, whereas CpG exposure suppresses allergic inflammation mainly via dendritic cells.

Diesel exhaust particles enhance T-cell activation in severe asthmatics

Prevalence of asthma is increasing in westernized countries. Epidemiological studies showed the impact of traffic pollution on the triggering of asthma symptoms and exacerbations, and this effect is mainly attributed to the polycyclic aromatic hydrocarbon core of diesel exhaust particles (DEP). However, although DEP induce IgE synthesis, little is known of their role on T-cell activation, the main cells orchestrating asthma inflammation. We assessed the effect of DEP on T-cell activation in severe uncontrolled asthmatics during (n = 13) and outside (n = 19) exacerbations. Results were compared with data obtained in healthy controls (n = 14). Peripheral blood mononuclear cells were cultured in the presence of low-dose DEP. T-cell activation markers, CD69 and CD25, interleukin-4 (IL-4) and interferon (IFN)-gamma production and T-cell proliferation were assessed by flow cytometry. DEP exposure increased the proportion of CD3+CD69+ T cells in all subjects. The proportion of CD25+ T cells increased under DEP stimulation in the exacerbation group only. IFN-gamma- and IL-4-producing T cells increased in both asthmatic groups, especially during exacerbations, but not in controls. This effect was more pronounced for IL-4. In response to DEP stimulation, T-cell proliferation increased in higher proportion in asthmatics compared with controls. These results show that DEP activate T cells in asthmatics only, with a higher effect during exacerbations. This is in keeping with epidemiological data which demonstrated that DEP trigger respiratory symptoms in asthmatics but not in controls. The higher effect of DEP in exacerbated asthmatics suggests that uncontrolled asthma is a risk factor for aggravation under exposure to traffic pollutants.

Role of the Nrf2-mediated signaling pathway as a negative regulator of inflammation: implications for the impact of particulate pollutants on asthma

Particulate matter (PM) is an environmental factor that may contribute to the exacerbation and possibly the development of asthma. PM contain redox-active chemicals and transition metals which generate reactive oxygen species (ROS). Excessive ROS can induce oxidative stress, which proceeds in hierarchical fashion to generate cellular responses. The most sensitive cellular response to mild oxidative stress is the activation of antioxidant and phase II enzymes (tier 1). If this protection fails, further increase of oxidative stress can induce inflammation (tier 2) and cell death (tier 3). Tier 1 antioxidant defenses are critical for protecting against airway inflammation and asthma. The expression of these antioxidant enzymes is regulated by the transcription factor, Nrf2. In response to oxidative stress, Nrf2 escapes from Keap1-mediated proteasomal degradation resulting in prolonged protein half-life and its nuclear accumulation. Nrf2 interacts with the antioxidant response element (ARE) in the promoters of phase II enzyme genes, leading to their transcriptional activation. Several phase II expression polymorphisms are associated with an increased risk of asthma. The indispensable role of Nrf2 in tier-1 oxidative stress response suggests that polymorphisms of Nrf2-regulated genes may be useful susceptibility markers for asthma. Moreover, chemopreventive Nrf2 inducers may be used for treating PM-exacerbated asthma.

Interleukin-25 and Interleukin-13 Production by Alveolar Macrophages in Response to Particles

Particle inhalation-induced lung inflammation acts as an adjuvant to allergens or respiratory viral infection in a process that is mediated by macrophages and epitheliums. The production of interleukin (IL)-4 and IL-13 by activated T cells is involved in the augmentation of Th2-type immune responses to particles, and IL-25 induces the synthesis of IL-4 and IL-13. However, whether IL-13 and IL-25 are directly regulated by particle instillation in the lung has not been studied. The aim of this study was to reveal particle induction of IL-13 and IL-25 in the lung. TiO(2) instillation potently induced the mRNA expression for IL-25 and IL-13 in lung tissue extracts 24 h after treatment, as compared with the sham group. Immunostaining for IL-25 and IL-13 showed strong positivity for macrophages in the inflammatory lung lesions of TiO(2)-treated rats. The alveolar macrophages expressed IL-25 and IL-13 24 h after in vitro stimulation with TiO(2) particles in dose- and time-dependent manners, with maximal induction at 24 and 48 h after stimulation, respectively. The sequence of the rat IL-25 gene is 95% homologous with the mouse IL-25 gene. These findings indicate that alveolar macrophages play an important role in particle-induced lung inflammation via direct induction of IL-13 and IL-25 production.

CC chemokine receptor 4 ligand production by bronchoalveolar lavage fluid cells in cigarette-smoke-associated acute eosinophilic pneumonia

We examined the production of macrophage-derived chemokine (MDC/CCL22) and thymus- and activation-regulated chemokine (TARC/CCL17) by bronchoalveolar lavage fluid (BALF) cells in cigarette-smoke-associated acute eosinophilic pneumonia (CS-AEP). The CC Chemokine Receptor 4 (CCR4) ligand levels in BALF from patients with CS-AEP were considerably higher than those in healthy volunteers and correlated well with Th2 cytokine levels. Interleukin-4 enhanced CCR4 ligand production. MDC expression was observed in CD68-positive cells from patients with CS-AEP and in healthy control smokers. In contrast, TARC expression in CD68- or CD1a-positive cells was detected only in CS-AEP. An in vivo cigarette smoke challenge test induced increases in CCR4 ligands in the BALF and in the cultured supernatant of BALF adherent cells. These results suggest that alveolar macrophages and dendritic cells contribute to the pathogenesis of CS-AEP by generating CCR4 ligands, probably in response to cigarette smoke.

Elevation of macrophage-derived chemokine in eosinophilic pneumonia: a role of alveolar macrophages

Macrophage-derived chemokine (MDC/CCL22) and thymus-and activation-regulated chemokine (TARC/CCL17) are ligands for CC chemokine receptor 4. Recently, TARC has been reported to play a role in the pathogenesis of idiopathic eosinophilic pneumonia (IEP). The purpose of this study was to evaluate the role of MDC in IEP and other interstitial lung diseases (ILDs). MDC and TARC in the bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunosorbent assay in patients with ILDs and healthy volunteers (HV). We also examined the expression of MDC mRNA in alveolar macrophages (AM) by real-time quantitative reverse transcriptase-polymerase chain reaction. Both MDC and TARC were detected only in BALF obtained from IEP patients. The concentration of MDC was higher than that of TARC in all cases. The level of MDC in IEP correlated with that of TARC. AM from IEP patients expressed a significantly higher amount of MDC than that from HV at the levels of protein and mRNA. MDC in BALF from IEP dramatically decreased when patients achieved remission. These findings suggest that MDC, in addition to TARC, might be involved in the pathogenesis of IEP, and AM play a role in the elevation of MDC in IEP.

Symposium summary: children's health risk--what's so special about the developing immune system?

In recent years, there has been increasing regulatory pressure to protect the health of children, with the basic tenet being that children differ significantly from adults in their biological or physiological responses to chemical exposures. In a regulatory context, this has been translated to mean a requirement for an additional 10-fold safety factor for environmental contaminants, specialized tests, or both. Much of the initial focus has been on the developing endocrine and nervous systems; but increasingly, the developing immune system has been identified as a potential target organ for chemically mediated toxicity. More recently, the question has been raised regarding whether the current state of science supports the creation of developmental immunotoxicology (DIT) test guidelines. What is needed is a risk-based evaluation of the biology associated with the proposed differential sensitivity between children and adults and the impact of that assessment on additional regulatory measures to protect children in risk assessment analyses. Additionally, an understanding of whether the developing immune system shows greater susceptibility, either qualitatively or quantitatively, to chemical perturbation is critical. To address the question "What's so special about the developing immune system?" a symposium was organized for the 2003 Society of Toxicology annual meeting that brought together risk assessors, clinicians, immunologists, and toxicologists.

Diesel exhaust particles suppress in vivo IFN-gamma production by inhibiting cytokine effects on NK and NKT cells

Diesel exhaust particles (DEP) have strong, selective Th2 adjuvant activity when inhaled with conventional Ags. We used a novel technique for measuring in vivo cytokine production to investigate possible mechanisms by which DEP might promote a Th2 response. Injection of DEP i.p. stimulated IL-6 secretion, but failed to increase IL-4, IL-10, or TNF-alpha secretion, and decreased basal levels of IFN-gamma. When injected with or before LPS, DEP had little effect on the LPS-induced TNF-alpha responses, but partially inhibited the LPS-induced IL-10 response and strongly inhibited the LPS-induced IFN-gamma response. DEP also inhibited the IFN-gamma responses to IL-12, IL-12 plus IL-18, IL-2, and poly(I.C). DEP treatment had little effect on the percentages of NK and NKT cells in the spleen, but inhibited LPS-induced IFN-gamma production by splenic NK and NKT cells. In contrast, DEP failed to inhibit the IFN-gamma response by anti-CD3 mAb-activated NKT cells. Taken together, these observations suggest that DEP inhibit Toll-like receptor ligand-induced IFN-gamma responses by interfering with cytokine signaling pathways that stimulate NK and NKT cells to produce IFN-gamma. Our observations also suggest that DEP may promote a Th2 response by stimulating production of inflammatory cytokines while simultaneously inhibiting production of IFN-gamma, and raise the possibility that the same mechanisms contribute to the association between DEP exposure and asthma.

Chemokine production and leukocyte recruitment to the lungs of Paracoccidioides brasiliensis-infected mice is modulated by interferon-gamma

Chemokines and chemokine receptors play a role in cell recruitment during granulomatous inflammatory reactions. Here, we evaluated the expression of chemokines and chemokine receptors and their regulation by IFN-gamma in the course of Paracoccidioides brasiliensis (Pb) infection in mice. We found an association between KC and MIP-1alpha (CCL3) production and neutrophil infiltration in the lungs of Pb-infected mice during the early acute phase of infection. High levels of RANTES/CCL5, MCP-1/CCL2, IP-10/CXCL10, and Mig/CXCL9 simultaneously with mononuclear cell infiltration in the lungs was found. In the absence of IFN-gamma (GKO mice) we observed increased production of KC and MIP-1alpha and chronic neutrophilia. Moreover, we found a change in the chemokine receptor profiles expressed by wild-type (WT) versus GKO animals. Increased expression of CXCR3 and CCR5, and low levels of CCR3 and CCR4 were observed in the lungs of Pb-infected WT mice, whereas the opposite effect was observed in the lungs of GKO mice. Consistent with these results, infected cells from WT mice preferentially migrated in response to IP-10 (CXCR3 ligand), while those from GKO mice migrated in response to eotaxin/CCL11 (CCR3 ligand). These results suggest that IFN-gamma modulates the expression of chemokines and chemokine receptors as well as the kind of cells that infiltrate the lungs of Pb-infected mice.

Effect of diesel on chemokines and chemokine receptors involved in helper T cell type 1/type 2 recruitment in patients with asthma

The objective of this study was to evaluate if diesel exhausts could favor helper T cell type (Th) 2-associated allergic reactions either through an increased production of Th2-associated chemokines and of their associated receptors or through a decrease of Th1-attracting chemokines and chemokine receptors. Diesel but not allergen exposure of peripheral blood mononuclear cells from subjects with allergy induced a release of I-309, whereas both diesel and Der p 1 induced an early but transient release of monokine induced by IFN-gamma and a late release of pulmonary and activation-regulated chemokine. Although both Th1- and Th2-attracting chemokines were induced, the resulting effect was an increased chemotactic activity on Th2 but not Th1 cells. Surprisingly, diesel induced a late increase in the expression of the Th1-associated CXC receptor 3 and CC receptor 5. T cell CXC receptor 3 upregulation was not associated with an increased migration to its ligands. These two antagonistic effects have been previously reported as a scavenger mechanism to clear chemokines. Altogether, these results suggest that diesel, even without allergen, may amplify a type 2 immune response but that it can also increase late Th1-associated chemokine receptor expression, perhaps as a scavenger mechanism to clear pro-Th1 chemokines and promote the Th2 pathway.

Increased susceptibility to RSV infection by exposure to inhaled diesel engine emissions

Although epidemiologic data strongly suggest a role for inhaled environmental pollutants in modulating the susceptibility to respiratory infection in humans, the underlying cellular and molecular mechanisms have not been well studied in experimental systems. The current study assessed the impact of inhaled diesel engine emissions (DEE) on the host response in vivo to a common pediatric respiratory pathogen, respiratory syncytial virus (RSV). Using a relatively resistant mouse model of RSV infection, prior exposure to either 30 microg/m3 particulate matter (PM) or 1,000 microg/m3 PM of inhaled DEE (6 h/d for seven consecutive days) increased lung inflammation to RSV infection as compared with air-exposed RSV-infected C57Bl/6 mice. Inflammatory cells in bronchoalveolar lavage fluid were increased in a dose-dependent manner with regard to the level of DEE exposure, concomitant with increased levels of inflammatory mediators. Lung histology analysis indicated pronounced peribronchial and peribronchiolar inflammation concordant with the level of DEE exposure during infection. Mucous cell metaplasia was markedly increased in the airway epithelium of DEE-exposed mice following RSV infection. Interestingly, both airway and alveolar host defense and immunomodulatory proteins were attenuated during RSV infection by prior DEE exposure. DEE-induced changes in inflammatory and lung epithelial responses to infection were associated with increased RSV gene expression in the lungs following DEE exposure. These findings are consistent with the concept that DEE exposure modulates the lung host defense to respiratory viral infections and may alter the susceptibility to respiratory infections leading to increased lung disease.

Diesel fumes and the rising prevalence of atopy: an urban legend?

Recently, the incidence of allergic diseases has increased in most industrialized countries of the world. Persistent exposure to particulate air pollution from motor vehicles has been implicated as one of the factors that is responsible for the observed increased prevalence of atopy. Epidemiologic studies conducted in different parts of the world have demonstrated an important association between ambient levels of motor vehicle traffic emissions and increased symptoms of asthma and rhinitis. Additionally, recent human and animal laboratory-based studies have shown that particulate toxic pollutants, and in particular diesel exhaust particles (DEP), can enhance allergic inflammation and induce the development of allergic immune responses. In this article, our current understanding of the mechanisms by which pollutants such as DEPs enhance the underlying allergic inflammatory response is reviewed, and the evidence that supports the causative link between particulate air pollution from motor vehicles and increasing allergic diseases is discussed.