Diesel exhaust particulates enhance eosinophil adhesion to nasal epithelial cells and cause degranulation

Outdoor Particulate Matter Correlation Analysis and Prediction Based Deep Learning in the Korea

Particulate matter (PM) has become a problem worldwide, with many deleterious health effects such as worsened asthma, affected lungs, and various toxin-induced cancers. The International Agency for Research on Cancer (IARC) under the World Health Organization (WHO) has designated PM as a group 1 carcinogen. Although Korea Environment Corporation forecasts the status of outdoor PM four times a day, whichever is higher among PM10 and PM2.5. Korea Environment Corporation forecasts for the stages of PM. It remains difficult to predict the value of PM when going out. We correlate air quality and solar terms, address format, and weather data, and PM in the Korea. We analyzed the correlation between address format, air quality data, and weather data, and PM. We evaluated performance according to the sequence length and batch size and found the best outcome with a sequence length of 7 days, and a batch size of 96. We performed PM prediction using the Long Short-Term Recurrent Unit (LSTM), the Convolutional Neural Network (CNN), and the Gated Recurrent Unit (GRU) models. The CNN model suffered the limitation of only predicting from the training data, not from the test data. The LSTM and GRU models generated similar prediction results. We confirmed that the LSTM model has higher accuracy than the other two models.

Association between weather seasonality and blood parameters in riverine populations of the Brazilian Amazon

OBJECTIVE

To analyze the seasonality of blood parameters related to iron homeostasis, inflammation, and allergy in two riverine populations from the Brazilian Amazon.

METHODS

This was a cross-sectional study of 120 children and adolescents of school age, living in riverine communities of Porto Velho, Rondonia, Brazil, describing the hematocrit, hemoglobin, ferritin, serum iron, total white blood cell count, lymphocytes, eosinophils, C-reactive protein, and immunoglobulin E levels in the dry and rainy seasons. The chi-squared test and the prevalence ratio were used for the comparison of proportions and mean analysis using paired Student's t-test.

RESULTS

Hemoglobin (13.3g/dL) and hematocrit (40.9%) showed higher average values in the dry season. Anemia prevalence was approximately 4% and 12% in the dry and rainy seasons, respectively. Serum iron was lower in the dry season, with a mean of 68.7 mcg/dL. The prevalence of iron deficiency was 25.8% in the dry season and 9.2% in the rainy season. Serum ferritin did not show abnormal values in both seasons; however, the mean values were higher in the dry season (48.5ng/mL). The parameters of eosinophils, lymphocytes, global leukocyte count, C-reactive protein and immunoglobulin E showed no seasonal differences. C-reactive protein and immunoglobulin E showed abnormal values in approximately 7% and 60% of the examinations, respectively.

CONCLUSION

Hematological parameters of the red cell series and blood iron homeostasis had seasonal variation, which coincided with the dry season in the region, in which an increase in atmospheric pollutants derived from fires is observed.

[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.

Genetic and epigenetic influence on the response to environmental particulate matter

Ambient air pollution, including particulate matter (PM) and gaseous pollutants, represents important environmental exposures that adversely affect human health. Because of their heritable and reversible nature, epigenetic modifications provide a plausible link between the environment and alterations in gene expression that might lead to disease. Epidemiologic evidence supports that environmental exposures in childhood affect susceptibility to disease later in life, supporting the belief that epigenetic changes can affect ongoing development and promote disease long after the environmental exposure has ceased. Indeed, allergic disorders often have their roots in early childhood, and early exposure to PM has been strongly associated with the subsequent development of asthma. The purpose of this review is to summarize recent findings on the genetic and epigenetic regulation of responses to ambient air pollutants, specifically respirable PM, and their association with the development of allergic disorders. Understanding these epigenetic biomarkers and how they integrate with genetic influences to translate the biologic effect of particulate exposure is critical to developing novel preventative and therapeutic strategies for allergic disorders.

Effects of nanoparticle-rich diesel exhaust particles on IL-17 production in vitro

It has been shown that pulmonary exposure to diesel exhaust particles (DEP) disrupt immune systems, presenting as exacerbating effects on allergic manifestations (e.g., allergic asthma). To date, the impact of nano-level DEP on health has not been fully elucidated. Our institute (the National Institute for Environmental Studies) established an 'environmental nanoparticle exposure system applied in animals' in 2005 and, since then, the health effects of exposures to these types of agents have been explored. The present study was designed to investigate the in vitro effects of nanoparticle-rich DEP (NRDEP) on primary splenocytes from atopy-prone hosts. NC/Nga mouse-derived splenic mononuclear cells were co-cultured with NRDEP (0-50 µg/ml); thereafter, cell viability/proliferation was evaluated via a WST-1 assay, production/release of interleukin (IL)-17A in the culture supernatants by ELISA, and expression of RORγt (retinoic acid-related orphan receptor-γt) in cell lysates by Western blot analyses. The results indicated that NRDEP reduced cell viability/proliferation in a dose-related manner-significantly so at a level of 50 µg/ml NRDEP. In contrast, up to 10 µg NRDEP/ml increased RORγt expression in the splenocytes and subsequent IL-17A production/release by the cells in a dose-dependent manner with an overall trend (with significance vs 1 µg NRDEP/ml and 10 µg NRDEP/ml for IL-17A); 50 µg NRDEP/ml tended to inhibit the transcription factor expression and cytokine production/release. These results suggest that NRDEP can activate naïve splenic mononuclear cells from atopy-prone animals in terms of RORγt and IL-17A induction (T(H)17 response).

In vitro study of the effect of nanoparticle-rich diesel exhaust particles on IL-18 production in splenocytes

It has been shown that pulmonary exposure to diesel exhaust particles (DEP) disrupts the immune system, presenting as exacerbating effects on allergic manifestations (e.g., allergic asthma). However, since a model inhalation system has not been developed, the impact of nano-level DEP on health has not been satisfactorily investigated. Our institute (the National Institute for Environmental Studies) established an "environmental nanoparticle exposure system applied in animals" in 2005 and since then, we have explored the health effects of exposure to these types of agent. The present study was conducted to investigate the in vitro effects of nanoparticle-rich DEP (NRDEP) on primary splenocytes from atopy-prone hosts. NC/Nga mouse-derived splenic mononuclear cells were co-cultured with NRDEP (0-50 µg/ml); thereafter, the production/release of interleukin (IL)-18 in the culture supernatants was evaluated by means of ELISA. NRDEP increased IL-18 production/release by splenocytes in a dose-dependent manner with an overall trend (with significance vs. 10 µg/ml of NRDEP). In contrast, 50 µg/ml of NRDEP inhibited production/release. These results suggest that NRDEP can activate naïve splenic mononuclear cells from atopy-prone animals in terms of IL-18 induction.

In vitro effects of nanoparticle-rich diesel exhaust particles on splenic mononuclear cells

It has been shown that pulmonary exposure to diesel exhaust particles (DEP) disrupt immune systems, presenting as exacerbating effects on allergic manifestations (i.e., allergic asthma). However, since inhalation system could not be developed, impact of nano-level DEP on health has not been satisfactorily elucidated. Our institute (National Institute for Environmental Studies) established the "environmental nanoparticle exposure system applied in animals" in 2005, and, since then, we have explored the health effects of the exposure. As part of our ongoing research, the present study was aimed to investigate the effects of nanoparticle-rich DEP (NRDEP) on the characterization of primary atopy-prone splenocytes in vitro. NC/Nga mouse-derived splenic mononuclear cells were co-cultured with NRDEP (0-50 µg/ml); thereafter, the surface expression of CD11c, CD80, CD86, CD69, and CD40L was evaluated by means of flow cytometry. NRDEP increased the surface expression of these molecules on the splenocytes in a dose-dependent manner with an overall trend (with significance vs. 50 µg/ml of NRDEP). These results suggest that NRDEP can activate naïve splenic mononuclear cells from atopy-prone animals.

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.

[Exposure to fine air particles and occurrence of allergic diseases: results of ISAAC-France phase 2]

To evaluate whether fine air particles could be involved in the occurrence of atopy and allergic diseases, we performed a cross-sectional epidemiological survey involving primary schoolchildren living in six French towns with contrasted air pollution levels. Air pollution was measured during a week in the school yards and by standard air monitoring networks. Children get an examination in school looking for atopic dermatitis and bronchial hyperresponsiveness assessed by a standardized run test. Besides, parents or guardians provided past medical history and environmental data, especially on passive smoking. Overall, 5,338 children, aged 10.4 (+/-0.7) years, coming from 108 different schools and 401 different classes were included in the survey. Taking into account potential confounders, high exposure to proximity PM(2.5) was linked to a higher point prevalence of atopic dermatitis and hyperresponsiveness, to a higher cumulative prevalence of allergic asthma and a higher sensitization rate to common indoor allergens. Thus, these data suggest that chronic exposure to urban fine particles could be a risk factor for atopy, hyperresponsiveness and asthma.

Chemical pollution, respiratory allergy and asthma: a perspective

The European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) convened a workshop in June 2005 to address the speculation that exposure to specific chemicals, and/or chemical pollutants in general, may play an important role in the increased prevalence of allergy and asthma in 'westernized' societies. This paper summarises one perspective arrived at during this workshop. It was acknowledged that certain chemicals and certain types of pollution might trigger or exacerbate asthmatic reactions in sensitised subjects. However, overall levels of pollution appear not to have had a major impact upon the prevalence of atopic allergy. Epidemiological studies suggest that pollution may in some circumstances protect from acquisition of sensitisation. Increasing exposure to household chemicals may enhance pre-existing allergies, but evidence for their causation of allergy is lacking. Other risk factors considered included societal dietary changes and exposure to endotoxins. Future research needs were identified which included epidemiological studies employing exposure and biomonitoring data, studies on domestic exposure to chemicals and their association with the incidence of allergy and asthma, and prospective birth cohort studies employing well-defined aspects of lifestyle, diet, chemical and endotoxin exposure as factors that may drive susceptibility to allergy and asthma.

Effects of phenanthraquinone on allergic airway inflammation in mice

BACKGROUND

Diesel exhaust particles (DEP) enhance allergic airway inflammation in mice (Takano et al., Am J Respir Crit Care Med 1997; 156: 36-42). DEP consist of carbonaceous nuclei and a vast number of organic chemical compounds. However, it remains to be identified which component(s) from DEP are responsible for the enhancing effects. 9,10-Phenanthraquinone (PQ) is a quinone compound involved in DEP.

OBJECTIVE

To investigate the effects of PQ inoculated intratracheally on allergic airway inflammation related to ovalbumin (OVA) challenge.

MATERIALS AND METHODS

We evaluated effects of PQ on airway inflammation, local expression of cytokine proteins, and allergen-specific immunoglobulin production in mice in the presence or absence of OVA. Results In the presence of OVA, PQ (2.1 ng/animal) significantly increased the numbers of eosinophils and mononuclear cells in bronchoalveolar lavage fluid as compared with OVA alone. In contrast, the numbers of these cells around the airways were not significantly different between OVA challenge and OVA plus PQ challenge in lung histology. PQ exhibited adjuvant activity for the allergen-specific production of IgG1 and IgE. OVA challenge induced significant increases in the lung expression of IL-4, IL-5, eotaxin, macrophage chemoattractant protein-1, and keratinocyte chemoattractant as compared with vehicle challenge. However, the combination of PQ with OVA did not alter the expression levels of these proteins as compared with OVA alone.

CONCLUSION

These results indicate that PQ can enhance the immunoglobulin production and the infiltration of inflammatory cells into alveolar spaces that are related to OVA, whereas PQ seems to be partially responsible for the DEP toxicity on the allergic airway inflammation.

Additive effect of diesel exhaust particulates and ozone on airway hyperresponsiveness and inflammation in a mouse model of asthma

Allergic airway diseases are related to exposure to atmospheric pollutants, which have been suggested to be one factor in the increasing prevalence of asthma. Little is known about the effect of ozone and diesel exhaust particulates (DEP) on the development or aggravation of asthma. We have used a mouse asthma model to determine the effect of ozone and DEP on airway hyperresponsiveness and inflammation. Methacholine enhanced pause (P(enh)) was measured. Levels of IL-4 and IFN-gamma were quantified in bronchoalveolar lavage fluids by enzyme immunoassays. The OVA-sensitized-challenged and ozone and DEP exposure group had higher P(enh) than the OVA-sensitized-challenged group and the OVA-sensitized-challenged and DEP exposure group, and the OVA-sensitized-challenged and ozone exposure group. Levels of IFN-gamma were decreased in the OVA-sensitized-challenged and DEP exposure group and the OVA-sensitized-challenged and ozone and DEP exposure group compared to the OVA-sensitized-challenged and ozone exposure group. Levels of IL-4 were increased in the OVA-sensitized-challenged and ozone exposure group and the OVA-sensitized-challenged and DEP exposure group, and the OVA-sensitized-challenged and ozone and DEP exposure group compared to OVA-sensitized-challenged group. Co-exposure of ozone and DEP has additive effect on airway hyperresponsiveness by modulation of IL-4 and IFN-gamma suggesting that DEP amplify Th2 immune response.

Biology of diesel exhaust effects on respiratory function

In recent decades, clinicians and scientists have witnessed a significant increase in the prevalence of allergic rhinitis and asthma. The factors underlying this phenomenon are clearly complex; however, this rapid increase in the burden of atopic disease has undeniably occurred in parallel with rapid industrialization and urbanization in many parts of the world. Consequently, more people are exposed to air pollutants than at any point in human history. Worldwide, increases in allergic respiratory disease have mainly been observed in urban communities. Epidemiologic and clinical investigations have suggested a strong link between particulate air pollution and detrimental health effects, including cardiopulmonary morbidity and mortality. The purpose of this review is to provide an evidence-based summary of the health effects of air pollutants on asthma, focusing on diesel exhaust particles (DEPs) as a model particulate air pollutant. An overview of observational and experimental studies linking DEPs and asthma will be provided, followed by consideration of the mechanisms underlying DEP-induced inflammation and a brief discussion of future research and clinical directions.

Effects of a single intratracheal administration of phenanthraquinone on murine lung

Although several studies have reported that diesel exhaust particles (DEP) affect cardiorespiratory health in animals and humans, the responsible components in DEP for the effects remain to be defined. Diesel exhaust particles contain quinones that can catalyse the generation of reactive oxygen species, resulting in the induction of oxidative stress. Oxidative stress can correlate with a variety of diseases and health effects. In the present study, we investigated the effects of phenanthraquinone--a relatively abundant quinone in DEP--on lung inflammation and the local expression of cytokine proteins in mice as a measure of oxidative damage. The animals were randomized into two experimental groups that received vehicle or phenanthraquinone by intratracheal instillation. The cellular profiles of bronchoalveolar lavage fluid (BALF) and local expression of cytokines were evaluated 24 and 48 h after the instillation. Phenanthraquinone challenge revealed an increase in the numbers of neutrophils and eosinophils in BALF as compared to vehicle challenge (P < 0.05 at 48 h post-instillation). Phenanthraquinone induced the lung expression of interleukin (IL)-5 and eotaxin 48 h and 24 h after the challenge, respectively. These results indicate that intratracheal exposure to phenanthraquinone induces recruitment of inflammatory cells, at least partly, through the local expression of IL-5 and eotaxin.

A review of experimental studies on diesel exhaust particles and nasal epithelium alterations

The aim of the present review is to summarize biological events in nasal epithelium after short-term exposure to diesel exhaust particles (DEP). Therefore human, animal, and in vitro studies carried out since 1987 are reviewed. Short-term exposure results included qualitative alterations characterized by immediate nasal hyperresponsiveness, antioxidant responses, marked epithelial inflammation, and a specific humoral response. In addition, studies on combined DEP/allergen challenge reported that, besides their intrinsic deleterious properties, DEP produced adjuvant-like effects on the immediate and late-phase response to allergen challenge, since they are able to mimic effects occurring after allergen challenge. DEP act deeply in nasal epithelium by (1) directing cytokine gene expression toward a Th2 profile, (2) enhancing local antigen-specific immunoglobulin E (IgE) production, and (3) driving in vivo isotype switch to IgE. Furthermore, DEP can induce in allergic subjects sensitization to a neoallergen, sensitization that did not occur with exposure to the neoantigen alone. Particulate pollutants such as DEP, encountered in urban areas, are therefore thought to be contributing causal factors to the exaggerated sensitization to allergens in subjects with appropriate genetic predisposition, sensitization that they might not otherwise have experienced. These findings add weight to the hypothesis that DEP are involved in the increased prevalence of airway allergic diseases.

Enhancement of acute lung injury related to bacterial endotoxin by components of diesel exhaust particles

BACKGROUND

Diesel exhaust particles (DEP) synergistically aggravate acute lung injury related to lipopolysaccharide (LPS) in mice, but the components in DEP responsible for this have not been identified. A study was undertaken to examine the effects of the organic chemicals (DEP-OC) and residual carbonaceous nuclei (washed DEP) derived from DEP on LPS related lung injury.

METHODS

ICR mice were divided into experimental groups and vehicle, LPS, washed DEP, DEP-OC, washed DEP+LPS, and DEP-OC+LPS were administered intratracheally. The cellular profile of the bronchoalveolar lavage (BAL) fluid, pulmonary oedema, lung histology, and expression of proinflammatory molecules and Toll-like receptors in the lung were evaluated.

RESULTS

Both DEP-OC and washed DEP enhanced the infiltration of neutrophils into BAL fluid in the presence of LPS. Washed DEP combined with LPS synergistically exacerbated pulmonary oedema and induced alveolar haemorrhage, which was concomitant with the enhanced lung expression of interleukin-1beta, macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant, whereas DEP-OC combined with LPS did not. Gene expression of Toll-like receptors 2 and 4 was increased by combined treatment with washed DEP and LPS. The enhancement effects of washed DEP on LPS related changes were comparable to those of whole DEP.

CONCLUSIONS

These results suggest that the residual carbonaceous nuclei of DEP rather than the extracted organic chemicals predominantly contribute to the aggravation of LPS related lung injury. This may be mediated through the expression of proinflammatory cytokines, chemokines, and Toll-like receptors.

Relationship of outdoor air quality to pediatric asthma exacerbations

BACKGROUND

Although exposure to outdoor air pollutants has been shown to be associated with exacerbations of asthma, there are relatively few admissions for asthma to Cincinnati Children's Hospital, Cincinnati, OH during the summer months when air quality tends to be worst.

OBJECTIVE

The objective of this study was to determine the relationship of outdoor air quality parameters to asthma exacerbations in children.

METHODS

The number of emergency room visits and hospitalizations for asthma were determined by review of emergency department logs and the hospital computer database. Outdoor air concentrations of ozone, particulates of < 10 microm diameter (PM-10), pollens, and fungal spores were obtained from the Hamilton County Department of Environmental Services. Multiple regression analysis was performed, looking for relationships between the daily number of asthma visits and the air quality data for the same day and for 1 through 5 days before the visits.

RESULTS

A significant association was found between the number of asthma visits and the daily pollen count (P = 0.014, SE = 0.001). The effect was stronger for visits 1, 2, and 3 days after the pollen count (P < 0.001 for pollen count lagged 3 days). High PM-10 counts were synergistic with the pollen count as a predictor of asthma visits. There was no association between asthma visits and the ozone concentration or fungal spore count.

CONCLUSIONS

Exacerbations of asthma severe enough to require visits to the hospital were associated with elevated concentrations of airborne pollens and particulates, with a significant delayed effect. Ozone, in the concentrations measured here, was not a risk factor for severe asthma exacerbations in children.

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 exhausts and their associated organic compounds may be involved in the recent increase in the prevalence of allergic disorders, through their ability to favor a type 2 immune response. Type 2 T cells have been shown to be preferentially recruited by the chemokines eotaxin (CCL11), macrophage-derived chemokine (MDC, CCL22), and thymus activation-regulated chemokine (CCL17) through their interaction with CCR3 and CCR4, respectively, whereas type 1 T cells are mainly recruited by IFN-gamma-induced protein-10 (CXCL10) through CXCR3 binding. The aim of the study was to evaluate the effect of diesel exposure on the expression of chemokines involved in type 1 and 2 T cell recruitment. PBMC and alveolar macrophages from house dust mite allergic patients were incubated with combinations of diesel extracts and Der p 1 allergen, and chemokine production was analyzed. Diesel exposure alone decreased the constitutive IP-10 production, while it further augmented allergen-induced MDC production, resulting in a significantly increased capacity to chemoattract human Th2, but not Th1 clones. Inhibition experiments with anti-type 1 or type 2 cytokine Abs as well as cytokine mRNA kinetic evaluation showed that the chemokine variations were not dependent upon IL-4, IL-13, or IFN-gamma expression. In contrast, inhibition of the B7:CD28 pathway using a CTLA-4-Ig fusion protein completely inhibited diesel-dependent increase of allergen-induced MDC production. This inhibition was mainly dependent upon the CD86 pathway and to a lesser extent upon the CD80 pathway. These results suggest that the exposure to diesel exhausts and allergen may likely amplify a deleterious type 2 immune response via a differential regulation of chemokine production through the CD28 pathway.

Diesel particles increase phosphatidylcholine release through a NO pathway in alveolar type II cells

Diesel exhaust particles (DEPs) have been shown in vivo as well as in vitro to affect the respiratory function and in particular the immune response to infection and allergens. In the current study, we investigated the effect of DEPs on the production of phosphatidylcholine (PC), a major constituent of surfactant, by rat alveolar type II (ATII) primary cells in vitro. Our results demonstrate that incubation of ATII cells with DEPs lead to a time- and dose-dependent increase in labeled PC release. This effect was mimicked by nitric oxide (NO) donors and cGMP and was abolished by inhibitors of NO synthase (NOS). In addition, a NOS inhibitor inhibits by itself the basal secretion of PC. We next examined the effects of DEPs on NOS gene expression and showed that DEPs increase NO production and upregulate both protein content and mRNA levels of the inducible NOS (NOS II). Together our data demonstrate that DEPs alter the production of surfactant by ATII cells through a NO-dependent signaling pathway.

Diesel exhaust and asthma: hypotheses and molecular mechanisms of action

Several components of air pollution have been linked to asthma. In addition to the well-studied critera air pollutants, such as nitrogen dioxide, sulfur dioxide, and ozone, diesel exhaust and diesel exhaust particles (DEPs) also appear to play a role in respiratory and allergic diseases. Diesel exhaust is composed of vapors, gases, and fine particles emitted by diesel-fueled compression-ignition engines. DEPs can act as nonspecific airway irritants at relatively high levels. At lower levels, DEPs promote release of specific cytokines, chemokines, immunoglobulins, and oxidants in the upper and lower airway. Release of these mediators of the allergic and inflammatory response initiates a cascade that can culminate in airway inflammation, mucus secretion, serum leakage into the airways, and bronchial smooth muscle contraction. DEPs also may promote expression of the T(subscript)H(/subscript)2 immunologic response phenotype that has been associated with asthma and allergic disease. DEPs appear to have greater immunologic effects in the presence of environmental allergens than they do alone. This immunologic evidence may help explain the epidemiologic studies indicating that children living along major trucking thoroughfares are at increased risk for asthmatic and allergic symptoms and are more likely to have objective evidence of respiratory dysfunction.

Diesel particles are taken up by alveolar type II tumor cells and alter cytokines secretion

Diesel exhaust particles can reach the alveolar space and interact with alveolar type II cells. The authors investigated whether diesel exhaust particles lead to an internalization process and alter the production of proinflammatory cytokines, such as interleukin-8 and granulocyte macrophage-colony-stimulating factor by human alveolar type II cells. Cells from the human lung epithelial cell line A-549 were incubated with diesel exhaust particles or with inert particles for different periods of time. Phagocytosis was studied with electron microscopic analysis and flow cytometry. Cytokines were quantified in supernatants with enzyme-linked immunosorbent assay. Both diesel exhaust particles and inert particles were similarly engulfed by alveolar type II cells. Diesel exhaust particles induced a dose- and a time-dependent increase in granulocyte macrophage-colony-stimulating factor release and a transient inhibition of interleukin-8 release, but inert particles did not. Diesel exhaust particles were taken up by alveolar type II cells, and they altered cytokine production. Alveolar type II cells, therefore, may represent a target site for the deleterious effects of diesel exhaust particles.

Is diesel the cause for the increase in allergic disease?

LEARNING OBJECTIVES

The purpose of this review is to objectively critique available data regarding the role of diesel exhaust particles (DEPs) in allergic disease. Readers of this review should understand the ways in which diesel particulates can affect human airways and the extent of the scientific data which are currently available.

DATA SOURCES

Data were obtained from published studies and reviews.

STUDY SELECTION

The specific reviewed studies selected for this review met the following criteria: human and animal in vivo, in vitro, and pulmonary dosimetry studies, as well as epidemiologic studies to examine the role of DEPs and particulates on the airways.

RESULTS

The results of the published studies show that although DEPs may play a role in the increased levels of allergic disorders through a number of immunologic mechanisms, it remains to be proven whether it is responsible for the recent rise in the prevalence of asthma and other allergic disorders.

CONCLUSIONS

Further studies in humans are needed to elucidate the mechanisms by which DEPs may be responsible for the increased prevalence of allergic disorders.

Health effects of diesel exhaust emissions

Epidemiological studies have demonstrated an association between different levels of air pollution and various health outcomes including mortality, exacerbation of asthma, chronic bronchitis, respiratory tract infections, ischaemic heart disease and stroke. Of the motor vehicle generated air pollutants, diesel exhaust particles account for a highly significant percentage of the particles emitted in many towns and cities. This review is therefore focused on the health effects of diesel exhaust, and especially the particular matter components. Acute effects of diesel exhaust exposure include irritation of the nose and eyes, lung function changes, respiratory changes, headache, fatigue and nausea. Chronic exposures are associated with cough, sputum production and lung function decrements. In addition to symptoms, exposure studies in healthy humans have documented a number of profound inflammatory changes in the airways, notably, before changes in pulmonary function can be detected. It is likely that such effects may be even more detrimental in asthmatics and other subjects with compromised pulmonary function. There are also observations supporting the hypothesis that diesel exhaust is one important factor contributing to the allergy pandemic. For example, in many experimental systems, diesel exhaust particles can be shown to act as adjuvants to allergen and hence increase the sensitization response. Much of the research on adverse effects of diesel exhaust, both in vivo and in vitro, has however been conducted in animals. Questions remain concerning the relevance of exposure levels and whether findings in such models can be extrapolated into humans. It is therefore imperative to further assess acute and chronic effects of diesel exhaust in mechanistic studies with careful consideration of exposure levels. Whenever possible and ethically justified, studies should be carried out in humans.

The environmental predictors of allergic disease

The prevalence of allergic diseases has been on the rise for the last 200 years, when hay fever, an easy and obvious-to-recognize illness, was virtually unknown in Europe and North America. Genetic factors are unlikely to explain these rapid increases. Among the potential environmental factors, exposure to ambient air pollution has been intensely debated. Besides passive smoking, which has convincingly been shown to increase the risk for asthma and bronchial hyperresponsiveness among exposed children, the evidence to suggest that outdoor pollution to sulfur dioxide, particulate matter, diesel exhaust, and ozone is causally related with the inception of allergic diseases is poor. Rather, factors associated with the lifestyle of populations or families, such as socioeconomic status, allergen exposure, sibship size, early childhood infections, dietary habits, and growing up in anthroposophic families or a farming environment, may prove to be of greater relevance. The future challenge is to tackle the complex interplay between environmental factors and genetic determinants that will eventually contribute to a better understanding and to better prevention strategies for such multifactorial conditions as asthma and allergies.

Passive smoking causes an 'allergic' cell infiltrate in the nasal mucosa of non-atopic children

Environmental tobacco smoke (ETS) is one of the most common indoor pollutants to which many children are exposed. This study was set up to determine possible effects on cellular infiltrates in the nasal mucosa of children exposed to ETS. The research population consisted of a group of ten children exposed to more then 15 cigarettes/day and a control group of ten children without exposure. The groups were matched for age and gender. None of the children had an atopic constitution. Immunohistochemical staining techniques were used to determine the number of Langerhans cells, T cells, B cells, granulocytes, macrophages, mast cells and eosinophils in the nasal mucosa. IgE+ cells and eosinophils were seen in significantly higher cell numbers in the nasal mucosa of children exposed to ETS (Mann-Whitney U-test). IgE+ mast cells were not found to be more numerous in the ETS-exposed group. We can conclude that exposure to ETS causes changes in cellular infiltrates which partly resemble those seen in the nasal mucosa of allergic children. However, no sign of allergic sensitisation can be found in the nasal mucosa. Children with a genetic predisposition to allergic disease will probably suffer most from the 'unstable' nasal mucosa due to ETS.

Chemicals in Diesel Exhaust Particles Generate Reactive Oxygen Radicals and Induce Apoptosis in Macrophages

There is increasing evidence that particulate air pollutants, such as diesel exhaust particles (DEP), potentiate chronic inflammatory processes as well as acute symptomatic responses in the respiratory tract. The mechanisms of action as well as the cellular targets for DEP remain to be elucidated. We show in this paper that the phagocytosis of DEP by primary alveolar macrophages or macrophage cell lines, RAW 264.7 and THP-1, leads to the induction of apoptosis through generation of reactive oxygen radicals (ROR). This oxidative stress initiates two caspase cascades and a series of cellular events, including loss of surface membrane asymmetry and DNA damage. The apoptotic effect on macrophages is cell specific, because DEP did not induce similar effects in nonphagocytic cells. DEP that had their organic constituents extracted were no longer able to induce apoptosis or generate ROR. The organic extracts were, however, able to induce apoptosis. DEP chemicals also induced the activation of stress-activated protein kinases, which play a role in cellular apoptotic pathways. The injurious effects of native particles or DEP extracts on macrophages could be reversed by the antioxidant, N-acetyl-cysteine. Taken together, these data suggest that organic compounds contained in DEP may exert acute toxic effects via the generation of ROR in macrophages.

Effect of diesel exhaust on guinea pig nasal mucosa

In this study using guinea pigs, we investigated the effects of diesel exhaust (DE) containing diesel exhaust particulate (DEP) on 1) vascular permeability induced by histamine, 2) nasal mucosal permeability to horseradish peroxidase (HRP), and 3) eosinophilic epithelial infiltration. The vascular permeability induced by histamine was enhanced significantly and dose-dependently in DE-exposed guinea pigs. The HRP reaction products in epithelial cells and intercellular spaces were significantly and dose-dependently increased in those guinea pigs. Eosinophil infiltration into the epithelial layer was significantly increased in guinea pigs exposed to DE containing 3.2 mg/m3 DEP, and the reactivity of the nasal mucosa to histamine solution applied on the nasal mucosa was significantly enhanced in those guinea pigs. These findings suggest that DE may play an important role not only in promoting nasal hyperreactivity induced by the enhancement of absorption of antigen through the nasal epithelium, but also in inducing eosinophil infiltration in nasal mucosa and enhancing nasal mucosal reactivity.

Effects of diesel organic extracts on chemokine production by peripheral blood mononuclear cells

BACKGROUND

Polyaromatic hydrocarbons (PAHs) associated with diesel exhaust particles (DEPs) are found in the atmospheric urban pollution. Such compounds have been shown to favor IgE production, bronchial hyperresponsiveness, and airway inflammation. Chemokines are a group of chemotactic cytokines involved in the recruitment of inflammatory cells.

OBJECTIVE

We investigated the effect of DEP-PAHs on the release and mRNA expression of IL-8, MCP-1, and RANTES by PBMCs obtained from healthy subjects.

METHODS

Protein production in supernatants was assessed by ELISA, and mRNA expression was evaluated by semiquantitative RT-PCR.

RESULTS

Secretion of IL-8 and RANTES increased in a dose-dependent manner with increasing concentrations of DEP-PAHs (range, 0.5 ng to 50 ng/mL). On the contrary, the release of MCP-1 was significantly inhibited, also in a dose-dependent manner. Messenger RNA production coding for IL-8, RANTES, and MCP-1 showed parallel variations to the production of the correspondent proteins. Effects of DEP-PAHs became significant at 7 hours and up to 48 hours time culture for MCP-1, and up to 24 hours time culture for IL-8 and RANTES. Moreover, supernatants from DEP-PAH-activated cells, compared with those of controls, exhibited a significantly enhanced chemotactic activity for neutrophils and eosinophils, which was significantly inhibited by pretreatment with anti-IL-8 and anti-RANTES neutralizing antibodies, respectively.

CONCLUSION

These findings suggest that the chemokine pathways are modulated by DEP-PAHs at the transcriptional level, reinforcing the idea that the development of inflammatory reactions might be affected by diesel exhaust emission.

Diesel exhaust particles are taken up by human airway epithelial cells in vitro and alter cytokine production

The involvement of diesel exhaust particles (DEPs) in respiratory diseases was evaluated by studying their effects on two in vitro models of human airway epithelial cells. The cytotoxicity of DEPs, their phagocytosis, and the resulting immune response were investigated in a human bronchial epithelial cell line (16HBE14o-) as well as in human nasal epithelial cells in primary culture. DEP exposure induced a time- and dose-dependent membrane damage. Transmission electron microscopy showed that DEPs underwent endocytosis by epithelial cells and translocated through the epithelial cell sheet. Flow cytometric measurements allowed establishment of the time and dose dependency of this phagocytosis and its nonspecificity with different particles (DEPs, carbon black, and latex particles). DEPs also induced a time-dependent increase in interleukin-8, granulocyte-macrophage colony-stimulating factor, and interleukin-1beta release. This inflammatory response occurred later than phagocytosis, and its extent seems to depend on the content of adsorbed organic compounds because carbon black had no effect on cytokine release. Furthermore, exhaust gas posttreatments, which diminished the adsorbed organic compounds, reduced the DEP-induced increase in granulocyte-macrophage colony-stimulating factor release. These results suggest that DEPs could 1) be phagocytosed by airway epithelial cells and 2) induce a specific inflammatory response.

Effect of environmental pollutants on the production of pro-inflammatory cytokines by normal human dermal keratinocytes

The effect of the environmental pollutants, diesel exhaust particles (DEP) and formaldehyde (FA), on the production of pro-inflammatory cytokines (interleukin (IL)-1alpha, IL-1beta, tumor necrosis factor (TNF)-alpha and IL-8) by normal human dermal keratinocytes (hKCs) was investigated. Normal hKCs were incubated with various concentrations of DEP (0.4, 0.8, 4, or 20 microg/ml) or FA (0.25, 0.5, 1, or 5 microg/ml), and cytokine production was then determined by enzyme-linked immunosorbent assay (ELISA). DEP (20 microg/ml) induced IL-1beta production without altering cell growth. The increased production of IL-1beta induced by this concentration of DEP was further enhanced by the presence of phorbol 12-myristate 13-acetate (PMA), although PMA alone did not affect the levels of IL-1beta. IL-8 production was also increased by DEP (0.4 and 0.8 microg/ml), which is consistent with the results that these concentrations of DEP increased the number of cells significantly after 72 h incubation. Although FA alone did not stimulate the production of IL-1beta or IL-8 by keratinocytes, FA (0.5 microg/ml and 5 microg/ml) significantly increased IL-8 and IL-1beta production, respectively, in cells stimulated with PMA. IL-1alpha production was not modulated by FA or DEP even in the presence of PMA. TNF-alpha was produced by unstimulated keratinocytes at barely detectable levels after 48 h incubation. Although basal levels of TNF-alpha in the culture supernatants were increased after stimulation with PMA, neither pollutant alone nor combination with PMA affected the levels of TNF-alpha. These in vitro findings suggest that environmental pollutants may act as modulating factors of cutaneous inflammation by affecting the ability of keratinocytes to release pro-inflammatory cytokines.