Residual oil fly ash exposure enhances allergic sensitization to house dust mite

House Dust Mite Allergy Under Changing Environments

Environmental variations induced by industrialization and climate change partially explain the increase in prevalence and severity of allergic disease. One possible mechanism is the increase in allergen production leading to more exposure and sensitization in susceptible individuals. House dust mites (HDMs) are important sources of allergens inducing asthma and rhinitis, and experimentally they have been demonstrated to be very sensitive to microenvironment modifications; therefore, global or regional changes in temperature, humidity, air pollution or other environmental conditions could modify natural HDM growth, survival and allergen production. There is evidence that sensitization to HDMs has increased in some regions of the world, especially in the subtropical and tropical areas; however, the relationship of this increase with environmental changes is not so clear as has reported for pollen allergens. In this review, we address this point and explore the effects of current and predicted environmental changes on HDM growth, survival and allergen production, which could lead to immunoglobulin E (IgE) sensitization and allergic disease prevalence. We also assess the role of adjuvants of IgE responses, such as air pollution and helminth infections, and discuss the genetic and epigenetic aspects that could influence the adaptive process of humans to drastic and relatively recent environmental changes we are experiencing.

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.

Mechanistic impact of outdoor air pollution on asthma and allergic diseases

Over the past decades, asthma and allergic diseases, such as allergic rhinitis and eczema, have become increasingly common, but the reason for this increased prevalence is still unclear. It has become apparent that genetic variation alone is not sufficient to account for the observed changes; rather, the changing environment, together with alterations in lifestyle and eating habits, are likely to have driven the increase in prevalence, and in some cases, severity of disease. This is particularly highlighted by recent awareness of, and concern about, the exposure to ubiquitous environmental pollutants, including chemicals with oxidant-generating capacities, and their impact on the human respiratory and immune systems. Indeed, several epidemiological studies have identified a variety of risk factors, including ambient pollutant gases and airborne particles, for the prevalence and the exacerbation of allergic diseases. However, the responsible pollutants remain unclear and the causal relationship has not been established. Recent studies of cellular and animal models have suggested several plausible mechanisms, with the most consistent observation being the direct effects of particle components on the generation of reactive oxygen species (ROS) and the resultant oxidative stress and inflammatory responses. This review attempts to highlight the experimental findings, with particular emphasis on several major mechanistic events initiated by exposure to particulate matters (PMs) in the exposure-disease relationship.

Adjuvant effect of zymosan after pulmonary treatment in a mouse ovalbumin allergy model

An association has been observed between indoor mold contamination and lung allergy and asthma. This relationship is not fully understood. 1→3-β-Glucan is the major cell wall component of fungi and a good marker of fungi exposure. The objective was to evaluate the adjuvant effect of zymosan, a crude yeast cell wall preparation of 1→3-β-glucan, during ovalbumin (OVA) sensitization in an allergy model. BALB/c mice were sensitized by pharyngeal aspiration with saline, 50 μg of OVA, or OVA with 1, 10, 50, or 75 μg of zymosan on days 0, 7, and 14. One week after sensitization, each sensitized animal group was challenged with an aspiration dose of 50 μg of OVA once a week for 2 weeks. At 1 day after the last aspiration, bronchoalveolar lavage fluid and blood was collected, and markers of lung allergy and inflammation were assessed. An adjuvant effect of zymosan on OVA allergy during sensitization was observed as indicated by significant elevations in lung eosinophils, serum OVA-specific IgE, and lung IL-5 in the groups sensitized with zymosan and OVA. Pulmonary treatment with zymosan also amplified lung inflammation. Elevations were observed in lung neutrophils, TNF-α, and parameters of lung injury in the groups primed with both zymosan and OVA. In nearly all parameters, a non-linear dose-response relationship was observed in the groups primed with OVA and zymosan. The optimum adjuvant dose of zymosan was 10 μg. This study demonstrated an adjuvant effect of zymosan when exposures occurred during the sensitization phase in an OVA-induced allergy model in BALB/c mice.

Airway epithelial regulation of allergic sensitization in asthma

While many of the contributing cell types and mediators of allergic asthma are known, less well understood are the factors that influence the development of allergic responses that lead to the development of allergic asthma. As the first airway cell type to respond to inhaled factors, the epithelium orchestrates downstream interactions between dendritic cells (DCs) and CD4⁺ T cells that quantitatively and qualitatively dictate the degree and type of the allergic asthma phenotype, making the epithelium of critical importance for the genesis of allergies that later manifest in allergic asthma. Amongst the molecular processes of critical importance in airway epithelium is the transcription factor, nuclear factor-kappaB (NF-κB). This review will focus primarily on the genesis of pulmonary allergies and the participation of airway epithelial NF-κB activation therein, using examples from our own work on nitrogen dioxide (NO₂) exposure and genetic modulation of airway epithelial NF-κB activation. In addition, the mechanisms through which Serum Amyloid A (SAA), an NF-κB-regulated, epithelial-derived mediator, influences allergic sensitization and asthma severity will be presented. Knowledge of the molecular and cellular processes regulating allergic sensitization in the airways has the potential to provide powerful insight into the pathogenesis of allergy, as well as targets for the prevention and treatment of asthma.

Epithelial, dendritic, and CD4(+) T cell regulation of and by reactive oxygen and nitrogen species in allergic sensitization

BACKGROUND

While many of the contributing cell types and mediators of allergic asthma are known, less well understood are the factors that induce allergy in the first place. Amongst the mediators speculated to affect initial allergen sensitization and the development of pathogenic allergic responses to innocuous inhaled antigens and allergens are exogenously or endogenously generated reactive oxygen species (ROS) and reactive nitrogen species (RNS).

SCOPE OF REVIEW

The interactions between ROS/RNS, dendritic cells (DCs), and CD4(+) T cells, as well as their modulation by lung epithelium, are of critical importance for the genesis of allergies that later manifest in allergic asthma. Therefore, this review will primarily focus on the initiation of pulmonary allergies and the role that ROS/RNS may play in the steps therein, using examples from our own work on the roles of NO(2) exposure and airway epithelial NF-κB activation.

MAJOR CONCLUSIONS

Endogenously generated ROS/RNS and those encountered from environmental sources interact with epithelium, DCs, and CD4(+) T cells to orchestrate allergic sensitization through modulation of the activities of each of these cell types, which quantitiatively and qualitatively dictate the degree and type of the allergic asthma phenotype.

GENERAL SIGNIFICANCE

Knowledge of the effects of ROS/RNS at the molecular and cellular levels has the potential to provide powerful insight into the balance between inhalational tolerance (the typical immunologic response to an innocuous inhaled antigen) and allergy, as well as to potentially provide mechanistic targets for the prevention and treatment of asthma.

Intrauterine exposure to lead may enhance sensitization to common inhalant allergens in early childhood: a prospective prebirth cohort study

BACKGROUND

Several in vivo and in vitro studies have shown that metal-rich particles may enhance allergic responses to house dust mites and induce an increased release of allergy-related cytokines.

OBJECTIVES

The main goal of this analysis is to define the possible association of intrauterine exposure to lead and mercury with the occurrence of skin sensitization to common aeroallergens in early childhood.

MATERIAL AND METHODS

The present study refers to a sample of 224 women in the second trimester of pregnancy recruited from Krakow inner city area who had full term pregnancies and whose children underwent skin prick testing (SPT) at the age of 5. Lead and mercury levels were assessed in cord blood and retested in children at age of 5 years. Aeroallergen concentrations in house dust were measured at the age of 3 years. The main health outcome (atopic status) was defined as the positive SPT to at least one common aeroallergen (Der f1, Der p1, Can f1 and Fel d1) at the age of 5 years. In the statistical analysis of the association between atopic status of children and exposure to metals, the study considered a set of covariates such as maternal characteristics (age, education, atopy), child's gender, number of older siblings, prenatal (measured via cord blood cotinine) and postnatal environmental tobacco smoke together with exposure to polycyclic aromatic hydrocarbons (PAH) as measured by PAH-DNA adducts.

RESULTS AND CONCLUSION

In the binary regression analysis, which controlled for the confounders, the risk ratio (RR) estimate for atopic sensitization was significantly associated with the lead exposure (RR=2.25, 95%CI: 1.21-4.19). In conclusion, the data suggest that even very low-level of prenatal lead exposure may be implicated in enhancing sensitization to common aeroallergens in early childhood.

Promoting effects of nanoparticles/materials on sensitive lung inflammatory diseases

Although the adverse health effects of nanoparticles/materials have been proposed and are being clarified, their facilitating effects on preexisting pathological conditions have not been fully established. We provide insights into the environmental immunotoxicity of nanoparticles as an aggravating factor in hypersusceptible subjects, especially those with respiratory disorders, using our in vivo models. We first examined the effects of nanoparticles/materials on lung inflammation induced by bacterial endotoxin (lipopolysaccharide) as a test model against innate immunity, and demonstrated that nanoparticles instilled through both an intratracheal tube and an inhalation system can exacerbate lung inflammation. Secondly, we examined the effects of nanoparticles/materials on allergic pathophysiology, and showed that repetitive pulmonary exposure to nanoparticles has aggravating effects on allergic airway inflammation, including adjuvant effects on Th2-milieu. Taken together, nanoparticle exposure may synergistically facilitate pathological inflammatory conditions in the lung via both innate and adaptive immunological abnormalities.

NO2 inhalation induces maturation of pulmonary CD11c+ cells that promote antigenspecific CD4+ T cell polarization

Background

Nitrogen dioxide (NO₂) is an air pollutant associated with poor respiratory health, asthma exacerbation, and an increased likelihood of inhalational allergies. NO₂ is also produced endogenously in the lung during acute inflammatory responses. NO₂ can function as an adjuvant, allowing for allergic sensitization to an innocuous inhaled antigen and the generation of an antigen-specific Th2 immune response manifesting in an allergic asthma phenotype. As CD11c⁺ antigen presenting cells are considered critical for naïve T cell activation, we investigated the role of CD11c⁺ cells in NO₂-promoted allergic sensitization.

Methods

We systemically depleted CD11c⁺ cells from transgenic mice expressing a simian diphtheria toxin (DT) receptor under of control of the CD11c promoter by administration of DT. Mice were then exposed to 15 ppm NO₂ followed by aerosolized ovalbumin to promote allergic sensitization to ovalbumin and were studied after subsequent inhaled ovalbumin challenges for manifestation of allergic airway disease. In addition, pulmonary CD11c⁺ cells from wildtype mice were studied after exposure to NO₂ and ovalbumin for cellular phenotype by flow cytometry and in vitro cytokine production.

Results

Transient depletion of CD11c⁺ cells during sensitization attenuated airway eosinophilia during allergen challenge and reduced Th2 and Th17 cytokine production. Lung CD11c⁺ cells from wildtype mice exhibited a significant increase in MHCII, CD40, and OX40L expression 2 hours following NO₂ exposure. By 48 hours, CD11c⁺MHCII⁺ DCs within the mediastinal lymph node (MLN) expressed maturation markers, including CD80, CD86, and OX40L. CD11c⁺CD11b^- and CD11c⁺CD11b⁺ pulmonary cells exposed to NO₂ in vivo increased uptake of antigen 2 hours post exposure, with increased ova-Alexa 647⁺ CD11c⁺MHCII⁺ DCs present in MLN from NO₂-exposed mice by 48 hours. Co-cultures of ova-specific CD4⁺ T cells from naïve mice and CD11c⁺ pulmonary cells from NO₂-exposed mice produced IL-1, IL-12p70, and IL-6 in vitro and augmented antigen-induced IL-5 production.

Conclusions

CD11c⁺ cells are critical for NO₂-promoted allergic sensitization. NO₂ exposure causes pulmonary CD11c⁺ cells to acquire a phenotype capable of increased antigen uptake, migration to the draining lymph node, expression of MHCII and co-stimulatory molecules required to activate naïve T cells, and secretion of polarizing cytokines to shape a Th2/Th17 response.

Airway epithelial NF-κB activation promotes allergic sensitization to an innocuous inhaled antigen

Activation of NF-κB in airway epithelium is observed in allergic asthma and is induced by inhalation of numerous infectious and reactive substances. Many of the substances that activate NF-κB in the airway epithelium are also capable of acting as adjuvants to elicit antigen-specific sensitization to concomitantly inhaled protein, thereby circumventing the inherent bias of the lung to promote tolerance to innocuous antigens. We have used a transgenic mouse inducibly expressing a constitutively active mutant of the inhibitor of nuclear factor κB (IκB) kinase β ((CA)IKKβ) that activates NF-κB only in nonciliated airway epithelial cells to test whether activation of this intracellular signaling pathway in this specific cell type is sufficient to establish a pulmonary environment permissive to the development of allergic sensitization to inhaled protein. When airway epithelial (CA)IKKβ was transiently expressed in antigen-naive mice only during initial inhalation of ovalbumin, the mice became allergically sensitized to the antigen. As a consequence, subsequent inhalation of ovalbumin alone led to an allergic asthma-like response that included airway hyperresponsiveness to methacholine, eosinophilia, mucus expression, elevated serum levels of antigen-specific IgE and IgG1, and splenic CD4(+) T cells that secreted T helper type 2 and type 17 cytokines in response to in vitro antigen restimulation. Furthermore, CD11c(+) cells in the mediastinal lymph nodes (MLN) of (CA)IKKβ-expressing mice displayed significantly elevated levels of activation markers. These data implicate airway epithelial NF-κB activation as a critical modulator of the adaptive immune response to inhaled antigens via the secretion of soluble mediators that affect the capacity of CD11c(+) cells to undergo maturation and promote antigen-specific allergic responses.

The effect of PM10 on human lung fibroblasts

Asthma diagnoses are increasing nationally with the highest rates in the New England states. Epidemiological studies have suggested a relationship between airborne particulate matter (PM) and severity of an asthma attack. However, because particulate matter, PM, is such a complex mixture, it is difficult to isolate the exacerbating factors. In this paper we investigate the effect of NIST (National Institute of Standards and Technology) and Maine PM and the soluble metals released from the PM on the growth of human lung fibroblasts. While the NIST PM itself had the most pronounced effect on cell survival rates, solutions of metals extracted from the PM also affected cell survival. Treatment of cells with 10, 50, 100 and 200 ug/cm(2) resulted in 84 +/- 13%, 69 +/- 15%, 58 +/- 14% and 58 +/- 16% survival, respectively. Appropriate concentrations of eight acid soluble metals from NIST PM were determined and tested on cells giving 91 +/- 11%, 87 +/- 10%, 72 +/- 18% and 66 +/- 20% survival, respectively. Soluble metals from Maine PM were extracted and mixtures of appropriate concentrations of these metals were used to treat cells, resulting in 88 +/- 5%, 81 +/- 5%, 79 +/- 3% and 57 +/- 9% survival rate. To determine which, if any, of the metals individually affected the cells, Mn, Cu, V and As were used to treat the cells. At the metal concentrations tested, only As and V affected cell survival.

Preexposure to amorphous silica particles attenuates but also enhances allergic reactions in trimellitic anhydride-sensitized brown Norway rats

Irritant-induced inflammation of the airways may aggravate respiratory allergy induced by chemical respiratory allergens. Therefore, the effect of airway irritation by synthetic amorphous silica (SAS) on respiratory allergy to trimellitic anhydride (TMA) was studied. Brown Norway (BN) rats were topically sensitized on day 0 and on day 7, subsequently exposed for 6 h/day for 6 days to 27 mg/m(3) SAS, and challenged by inhalation to a minimally irritating concentration of 12 mg/m(3) TMA, 24 h after the last SAS exposure. An additional group was exposed to SAS before a second challenge to TMA. Control groups were treated with vehicle, and/or did not receive SAS exposure. Breathing parameters, cellular and biochemical changes in bronchoalveolar lavage (BAL) fluid, and histopathological airway changes 24 h after challenge were the main parameters studied. Exposure to SAS alone resulted in transient changes in breathing parameters during exposure, and in nasal and alveolar inflammation with neutrophils and macrophages. Exposure to SAS before a single TMA challenge resulted in a slightly irregular breathing pattern during TMA challenge. SAS also diminished the effect of TMA on tidal volume, laryngeal ulceration, laryngeal inflammation, and the number of BAL (lung) eosinophils in most animals, but aggravated laryngeal squamous metaplasia and inflammation in a single animal. The pulmonary eosinophilic infiltrate and edema induced by a second TMA challenge was diminished by the preceding SAS exposure, but the number of lymphocytes in BAL was increased. Thus, a respiratory particulate irritant like SAS can reduce as well as aggravate certain aspects of TMA-induced respiratory allergy.

Murine lung responses to ambient particulate matter: genomic analysis and influence on airway hyperresponsiveness

BACKGROUND

Asthma is a complex disease characterized by airway hyperresponsiveness (AHR) and chronic airway inflammation. Epidemiologic studies have demonstrated that exposures to environmental factors such as ambient particulate matter (PM), a major air pollutant, contribute to increased asthma prevalence and exacerbations.

OBJECTIVE

We investigated pathophysiologic responses to Baltimore, Maryland, ambient PM (median diameter, 1.78 mum) in a murine model of asthma and attempted to identify PM-specific genomic/molecular signatures.

METHODS

We exposed ovalbumin (OVA)-sensitized A/J mice intratracheally to PM (20 mg/kg), and assayed both AHR and bronchoalveolar lavage (BAL) on days 1, 4, and 7 after PM exposure. Lung gene expression profiling was analyzed in OVA- and PM-challenged mice.

RESULTS

Consistent with this murine model of asthma, we observed significant increases in airway responsiveness in OVA-treated mice, with PM exposure inducing significant changes in AHR in both naive mice and OVA-induced asthmatic mice. PM evoked eosinophil and neutrophil infiltration into airways, elevated BAL protein content, and stimulated secretion of type 1 T helper (T(H)1) cytokines [interferon-gamma, interleukin-6 (IL-6), tumor necrosis factor-alpha] and T(H)2 cytokines (IL-4, IL-5, eotaxin) into murine airways. Furthermore, PM consistently induced expression of genes involved in innate immune responses, chemotaxis, and complement system pathways.

CONCLUSION

This study is consistent with emerging epidemiologic evidence and indicates that PM exposure evokes proinflammatory and allergic molecular signatures that may directly contribute to the asthma susceptibility in naive subjects and increased severity in affected asthmatics.

Effects of residual oil fly ash (ROFA) in mice with chronic allergic pulmonary inflammation

Exposure to particulate matter (PM) air pollution is associated with increased asthma morbidity. Residual oil flash ash (ROFA) is rich in water-soluble transition metals, which are involved in the pathological effects of PM. The objective of this study was to investigate the effects of intranasal administration of ROFA on pulmonary inflammation, pulmonary responsiveness, and excess mucus production in a mouse model of chronic pulmonary allergic inflammation. BALB/c mice received intraperitoneal injections of ovalbumin (OVA) solution (days 1 and 14). OVA challenges were performed on days 22, 24, 26, and 28. After the challenge, mice were intranasally instilled with ROFA. After forty-eight hours, pulmonary responsiveness was performed. Mice were sacrificed, and lungs were removed for morphometric analysis. OVA-exposed mice presented eosinophilia in the bronchovascular space (p < .001), increased pulmonary responsiveness (p < .001), and epithelial remodeling (p = .003). ROFA instillation increased pulmonary responsiveness (p = .004) and decreased the area of ciliated cells in the airway epithelium (p = .006). The combined ROFA instillation and OVA exposure induced a further increase in values of pulmonary responsiveness (p = .043) and a decrease in the number of ciliated cells in the airway epithelium (p = .017). PM exposure results in pulmonary effects that are more intense in mice with chronic allergic pulmonary inflammation.

Lung dendritic cells are stimulated by ultrafine particles and play a key role in particle adjuvant activity

BACKGROUND

The adjuvant activity of air pollution particles on allergic airway sensitization is well known, but the cellular mechanisms underlying this adjuvant potential are not clear.

OBJECTIVE

We sough to study the role of dendritic cells and the costimulatory molecules CD80 and CD86 in the adjuvant activity of ultrafine carbon black particles (CBP).

METHODS

The proliferation of CFSE-labeled DO11.10 CD4 cells was studied after intranasal exposure to particles and ovalbumin (OVA). Next the frequency of myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells and their expression of CD80 and CD86 were studied in the peribronchial lymph nodes (PBLNs). The expression of costimulatory molecules was also studied on bone marrow-derived mDCs after exposure to CBPs in vitro, and the importance of costimulation in CBP adjuvant activity was assessed by using CD80/CD86-deficient mice or cytotoxic T lymphocyte-associated antigen 4 (CTLA4)-Ig in vivo.

RESULTS

Our data show that CBPs plus OVA caused proliferation of DO11.10 CD4 cells and high levels of cytokine production in the PBLNs. Furthermore, the combined CBP plus OVA exposure increased the number of mDCs and expression of costimulatory molecules in the PBLNs. In addition, CBPs upregulated the expression of CD80/CD86 molecules on dendritic cells in vitro, which are necessary for the particle adjuvant effects in vivo.

CONCLUSION

Together this study shows the importance of dendritic cells and costimulation in particle adjuvant activity. Furthermore, we show for the first time that CBPs can also directly induce maturation of dendritic cells.

Assessing the health effects and risks associated with children's inhalation exposures--asthma and allergy

Adults and children may have different reactions to inhalation exposures due to differences in target tissue doses following similar exposures, and/or different stages in lung growth and development. In the case of asthma and allergy both the developing immune system and initial encounters with common allergens contribute to this differential susceptibility. Asthma, the most common chronic childhood disease, has significant public health impacts and is characterized by chronic lung inflammation, reversible airflow obstruction, and immune sensitization to allergens. Animal studies described here suggest that air pollutants exacerbate asthma symptoms and may also play a role in disease induction. Changes characteristic of asthma were observed in rhesus monkeys sensitized to house dust mite antigen (HDMA) as infants and exposed repeatedly thereafter to ozone (O3) and HDMA. O3 exposure compromised airway growth and development and exacerbated the allergen response to favor intermittent airway obstruction and wheeze. In Brown Norway rats a variety of air pollutants enhanced sensitization to HDMA such that symptoms elicited in response to subsequent allergen challenge were more severe. Although useful for assessing air pollutants effects on initial sensitization, the rodent immune system is immature at birth relative to humans, making this model less useful for studying differential effects between adults and children. Because computational models available to address children's inhalation exposures are limited, default adjustments and their associated uncertainty will continue to be used in children's inhalation risk assessment. Because asthma is a complex (multiple genes, phenotypes, organ systems) disease, this area is ripe for systems biology approaches.

Ultrafine but not fine particulate matter causes airway inflammation and allergic airway sensitization to co-administered antigen in mice

BACKGROUND

Airborne particulate matter (PM) is an important factor associated with the enhanced prevalence of respiratory allergy. The PM adjuvant activity on allergic sensitization is a possible mechanism of action involved, and the induction of airway inflammation is suggested to be of importance in PM-induced adjuvant activity.

OBJECTIVE

Because differently sized PM have different toxic potentials, we studied the role of particle size in the induction of airway inflammation and allergic sensitization. This was done using fine (0.250 and 0.260 micro m) and ultrafine (0.029 and 0.014 micro m) titanium dioxide (TiO(2)) and carbon black particles (CBP) with known differences in airway toxicity.

METHODS

Mice were intranasally exposed to ovalbumin (OVA) alone or in combination with one of the different particles. The induction of airway inflammation and the immune adjuvant activity were studied in the lungs and lung-draining peribronchial lymph nodes (PBLN) at day 8. OVA-specific antibodies were measured at day 21, and the development of allergic airway inflammation was studied after OVA challenges (day 28).

RESULTS

When administered at the same total particle mass (200 micro g), exposure to ultrafine TiO(2) and CBP-induced airway inflammation, and had immune adjuvant activity. The latter was shown by increasing both the PBLN cell numbers and the production of OVA-specific T-helper type 2 (Th2) cytokines (IL-4, IL-5, IL-10 and IL-13). Whereas OVA-specific IgE and IgG1 levels in serum were only increased in animals exposed to the ultrafine TiO(2), allergic airway inflammation could be detected in both ultrafine TiO(2)-and CBP-treated groups after challenges with OVA.

CONCLUSION

Our data show that only the ultrafine particles, with a small diameter and a large total surface area/mass, cause airway inflammation and have immune adjuvant activity in the current model supporting the hypothesis that particle toxicity is site-dependent and related to adjuvant activity.

Animal models for protein respiratory sensitizers

Protein induced respiratory hypersensitivity, particularly atopic disease in general, and allergic asthma in particular, has increased dramatically over the last several decades in the US and other industrialized nations as a result of ill-defined changes in living conditions in modern western society. In addition, work-related asthma has become the most frequently diagnosed occupational respiratory illness. Animal models have demonstrated great utility in developing an understanding of the etiology and mechanisms of many diseases. A few models been developed as predictive models to identify a protein as an allergen or to characterize its potency. Here we describe animal models that have been used to investigate and identify protein respiratory sensitizers. In addition to prototypical experimental design, methods for exposure route, sample collection, and endpoint assessment are described. Some of the most relevant endpoints in assessing the potential for a given protein to induce atopic or allergic asthma respiratory hypersensitivity are the development of cytotropic antibodies (IgE, IgG1), eosinophil influx into the lung, and airway hyperresponsiveness to the sensitizing protein and/or to non-antigenic stimuli (Mch). The utility of technologies such as PCR and multiplexing assay systems is also described. These models and methods have been used to elucidate the potential for protein sources to induce allergy, identify environmental conditions (pollutants) to impact allergy responsiveness, and establish safe exposure limits. As an example, data are presented from an experiment designed to compare the allergenicity of a fungal biopesticide Metarhizium anisopliae (MACA) crude extract with the one of its components, conidia (CON) extract.

Relation between sources of particulate air pollution and biological effect parameters in samples from four European cities: an exploratory study

Given that there are widely different prevalence rates of respiratory allergies and asthma between the countries of Europe and that exposure to ambient particulate matter (PM) is substantial in urban environments throughout Europe, an EU project entitled "Respiratory Allergy and Inflammation Due to Ambient Particles" (RAIAP) was set up. The project focused on the role of physical and chemical composition of PM on release of cytokines of cells in vitro, on respiratory inflammation in vivo, and on adjuvant potency in allergy animal models. Coarse (2.5-10 microm) and fine (0.15-2.5 microm) particles were collected during the spring, summer and winter in Rome (I), Oslo (N), Lodz (PL), and Amsterdam (NL). Markers within the same model were often well correlated. Markers of inflammation in the in vitro and in vivo models also showed a high degree of correlation. In contrast, correlation between parameters in the different allergy models and between allergy and inflammation markers was generally poor. This suggests that various bioassays are needed to assess the potential hazard of PM. The present study also showed that by clustering chemical constituents of PM based on the overall response pattern in the bioassays, five distinct groups could be identified. The clusters of traffic, industrial combustion and/or incinerators (TICI), and combustion of black and brown coal/wood smoke (BBCW) were associated primarily with adjuvant activity for respiratory allergy, whereas clusters of crustal of material (CM) and sea spray (SS) are predominantly associated with measures for inflammation and acute toxicity. The cluster of secondary inorganic aerosol and long-range transport aerosol (SIALT) was exclusive associated with systemic allergy. The present study has shown that biological effect of PM can be linked to one or more PM emission sources and that this linkage requires a wide range of bioassays.

Effects of nano particles on cytokine expression in murine lung in the absence or presence of allergen

Particulate matter (PM) can exacerbate allergic airway diseases. Health effects of PM with a diameter of less than 100 nm, called nano particles, have been focused. We have recently demonstrated that carbon nano particles (14, 56 nm) exaggerate allergic airway inflammation in mice. In the present study, we investigated the effects of repeated pulmonary exposure to carbon nano particles on the expression of a variety of cytokines in the absence or presence of allergen in mice. ICR mice were divided into six experimental groups. Vehicle, two sizes of carbon nano particles, ovalbumin (OVA), and OVA + nano particles were administered intratracheally. Nano particles increased the lung protein levels of thymus and activation-regulated chemokine (TARC), macrophage inflammatory protein (MIP)-1alpha, and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the absence or presence of allergen. The enhancement was more prominent with 14 nm of nano particles than with 56 nm of nano particles in overall trend. 14 nm nano particle exposure significantly enhanced the lung expressions of interleukin (IL)-2 and IL-10 in the presence of allergen as compared with allergen exposure. These results suggest that pulmonary exposure to nano particles can induce the lung expression of TARC, MIP-1alpha, GM-CSF in the absence of allergen and can enhance that of TARC, MIP-1alpha, GM-CSF, IL-2, and IL-10 in the presence of allergen. The enhancing effects are more prominent with smaller particles.

Effects of nano particles on antigen-related airway inflammation in mice

Background

Particulate matter (PM) can exacerbate allergic airway diseases. Although health effects of PM with a diameter of less than 100 nm have been focused, few studies have elucidated the correlation between the sizes of particles and aggravation of allergic diseases. We investigated the effects of nano particles with a diameter of 14 nm or 56 nm on antigen-related airway inflammation.

Methods

ICR mice were divided into six experimental groups. Vehicle, two sizes of carbon nano particles, ovalbumin (OVA), and OVA + nano particles were administered intratracheally. Cellular profile of bronchoalveolar lavage (BAL) fluid, lung histology, expression of cytokines, chemokines, and 8-hydroxy-2'-deoxyguanosine (8-OHdG), and immunoglobulin production were studied.

Results

Nano particles with a diameter of 14 nm or 56 nm aggravated antigen-related airway inflammation characterized by infiltration of eosinophils, neutrophils, and mononuclear cells, and by an increase in the number of goblet cells in the bronchial epithelium. Nano particles with antigen increased protein levels of interleukin (IL)-5, IL-6, and IL-13, eotaxin, macrophage chemoattractant protein (MCP)-1, and regulated on activation and normal T cells expressed and secreted (RANTES) in the lung as compared with antigen alone. The formation of 8-OHdG, a proper marker of oxidative stress, was moderately induced by nano particles or antigen alone, and was markedly enhanced by antigen plus nano particles as compared with nano particles or antigen alone. The aggravation was more prominent with 14 nm of nano particles than with 56 nm of particles in overall trend. Particles with a diameter of 14 nm exhibited adjuvant activity for total IgE and antigen-specific IgG₁ and IgE.

Conclusion

Nano particles can aggravate antigen-related airway inflammation and immunoglobulin production, which is more prominent with smaller particles. The enhancement may be mediated, at least partly, by the increased local expression of IL-5 and eotaxin, and also by the modulated expression of IL-13, RANTES, MCP-1, and IL-6.

Exposure of Brown Norway Rats to Diesel Exhaust Particles Prior to Ovalbumin (OVA) Sensitization Elicits IgE Adjuvant Activity but Attenuates OVA-Induced Airway Inflammation

Exposure to diesel exhaust particles (DEP) during the sensitization process has been shown to increase antigen-specific IgE production and aggravate allergic airway inflammation in human and animal models. In this study, we evaluated the effect of short-term DEP exposure on ovalbumin (OVA)-mediated responses using a post-sensitization model. Brown Norway rats were first exposed to filtered air or DEP (20.6 +/- 2.7 mg/m3) for 4 h/day for five consecutive days. One day after the final air or DEP exposure (day 1), rats were sensitized with aerosolized OVA (40.5 +/- 6.3 mg/m3), and then again on days 8 and 15, challenged with OVA on day 29, and sacrificed on days 9 or 30, 24 h after the second OVA exposure or the final OVA challenge, respectively. Control animals received aerosolized saline instead of OVA. DEP were shown to elicit an adjuvant effect on the production of antigen-specific IgE and IgG on day 30. At both time points, no significant airway inflammatory responses and lung injury were found for DEP exposure alone. However, the OVA-induced inflammatory cell infiltration, acellular lactate dehydrogenase activity and albumin content in bronchoalveolar lavage (BAL) fluid, and numbers of T cells and their CD4+ and CD8+ subsets in lung-draining lymph nodes were markedly reduced by DEP on day 30 compared with the air-plus-OVA exposure group. The OVA-induced nitric oxide (NO) in the BAL fluid and production of NO, interleukin (IL)-10, and IL-12 by alveolar macrophages (AM) were also significantly lowered by DEP on day 30 as well as day 9. DEP or OVA alone decreased intracellular glutathione (GSH) in AM and lymphocytes on days 9 and 30. The combined DEP and OVA exposure resulted in further depletion of GSH in both cell types. These results show that short-term DEP exposure prior to sensitization had a delayed effect on enhancement of the sensitization in terms of allergen-specific IgE and IgG production, but caused an attenuation of the allergen-induced airway inflammatory responses.

Ultrafine carbon black particles cause early airway inflammation and have adjuvant activity in a mouse allergic airway disease model

To gain more insight into the mechanisms of particulate matter (PM)-induced adjuvant activity, we studied the kinetics of airway toxicity/inflammation and allergic sensitization to ovalbumin (OVA) in response to ultrafine carbon black particles (CBP). Mice were exposed intranasally to OVA alone or in combination with different concentrations of CBP. Airway toxicity and inflammation were assessed at days 4 and 8. Immune adjuvant effects were studied in the lung draining peribronchial lymph nodes (PBLN) at day 8. Antigen-specific IgE was measured at days 21 and 28, whereas allergic airway inflammation was studied after OVA challenges (day 28). Results show that a total dose of 200 microg CBP per mouse, but not 20 microg or 2 microg, induced immediate airway inflammation. This 200 microg CBP was the only dose that had immune adjuvant activity, by inducing enlargement of the PBLN and increasing OVA-specific production of Th2 cytokines (IL-4, IL-5, and IL-10). The immune adjuvant activity of 200 microg CBP dosing was further examined. Whereas increased OVA-specific IgE levels in serum on day 21 confirms systemic sensitization, this was further supported by allergic airway inflammation after challenges with OVA. Our data show a link between early airway toxicity and adjuvant effects of CBP. In addition, results indicate that local cytokine production early after exposure to CBP is predictive of allergic airway inflammation. In addition this model appears suitable for studying the role of airway toxicity, inflammation and other mechanisms of particle adjuvant activity, and predicting the adjuvant potential of different particles.

Coarse(PM(2.5-10)), fine(PM(2.5)), and ultrafine air pollution particles induce/increase immune costimulatory receptors on human blood-derived monocytes but not on alveolar macrophages

Diesel particles have been shown to possess adjuvant activity and influence the development of allergic sensitization. Also, more heterogeneous mixtures of pollution particles have been shown to affect host defenses and development of immunity in animal models. In the present study it was determined whether freshly collected particulate matter (PM(10)) in the size ranges 2.5-10 micro m (PM(2.5-10), coarse), 0.1-2.5 micro m (PM(2.5), fine), and </=0.1 micro m (ultrafine) in diameter affected the development of antigen presenting cells by evaluating the expression of surface receptors involved in T-cell interaction on both human alveolar macrophages (AM) and blood-derived monocytes (Mo). A Mo-AM coculture was exposed to 50 micro g/ml of particles and expression of HLA-DR, CD40, CD80, and CD86 on each cell type was assessed by flow cytometry. Mo upregulated the expression of all four receptors in response to each of the particle fractions, while expression was unaffected in AM. The cells were also exposed to two model air pollution particles, diesel dust and volcanic ash, neither of which affected receptor expression. Furthermore, Mo and AM were separately exposed to the three PM size fractions and supernatants assessed for the T-helper (CD4(+)) lymphocyte chemoattractant interleukin-16 (IL-16). AM, but not Mo, produced IL-16, and this chemoattractant was released only in response to PM(2.5-10). These data suggest that a wide size range of pollution particles contain materials that may promote antigen presentation by Mo, while the capability to specifically recruit CD4(+) lymphocytes is contained in AM stimulated with the coarse PM fraction.

Phenotypic comparison of allergic airway responses to house dust mite in three rat strains

Brown Norway (BN) rats develop a robust response to antigens in the lung, characterized by a large increase in allergen-specific immune function and pulmonary eosinophilia. The objective of this study was to investigate alternative models by determining whether other rat strains could be sensitized to house dust mite (HDM) antigen and whether the allergic disease process could be worsened with repeated allergen exposure. In general, BN rats sensitized by either subcutaneous or intratracheal routes exhibited increased pulmonary allergy compared with Sprague-Dawley (SD) and Lewis (L) rats. Multiple intratracheal allergen exposures incrementally increased HDM-specific immune function in BN rats but progressively decreased eosinophil recruitment and markers of lung injury. SD rats had more moderate responses, whereas L rats were relatively unresponsive. Because BN rats developed stronger clinical hallmarks of allergic asthma under various immunization regimes compared with SD and L rats, we conclude that the BN is the most appropriate strain for studying allergic asthma-like responses in rats. Phenotypic differences in response to HDM were associated with differences in the Th1/Th2 cytokine balance and antioxidant capacity.

An association between plastic mattress covers and sheepskin underbedding use in infancy and house dust mite sensitization in childhood: a prospective study

BACKGROUND

Higher house dust mite (HDM) allergen exposure during infancy has been associated with increased HDM sensitization. Infant bedding has been associated with the accumulation of varying levels of HDM. Prospective data on the relationship between infant bedding and the development of HDM sensitization has not been previously examined.

OBJECTIVES

To determine if particular types of bedding used in infancy are associated with increased risk of house dust mite sensitization in childhood.

METHODS

A population-based sample (n = 498) of children born in 1988 or 1989, and who were resident in Northern Tasmania in 1997, participated in this study. These children were part of a birth cohort study (1988-95), the Tasmanian Infant Health Survey. Data on infant underbedding and mattresses was available on 460 and 457 children, respectively. The main outcome measure was HDM sensitization defined as a skin prick test (SPT) reaction of 3 mm or more to the allergens of Dermatophagoides pteronyssinus and/or Dermatophagoides farinae.

RESULTS

The use of either sheepskin underbedding or plastic mattress covers in infancy was associated with an increased risk of sensitization to HDM allergens at age 8 years. The adjusted risk ratio (RR) for sensitization to HDM with sheepskin in infancy was 2.27 (95% CI: 1.14, 4.55), P = 0.020. The adjusted RR for sensitization to HDM with the use of plastic mattress covers in infancy was 2.06 (95% CI: 1.22, 3.51), P = 0.007. The use of a foam mattress in infancy was not related to subsequent HDM sensitization.

CONCLUSION

Infant's bedding plays a role in the development of HDM sensitization in childhood. Intervention studies to examine mite allergen levels and the role of underbedding on the development of HDM sensitization are required.

The dual effect of the particulate and organic components of diesel exhaust particles on the alteration of pulmonary immune/inflammatory responses and metabolic enzymes

Exposure to diesel exhaust particles (DEP) is an environmental and occupational health concern. This review examines the cellular actions of the organic and the particulate components of DEP in the development of various lung diseases. Both the organic and the particulate components cause oxidant lung injury. The particulate component is known to induce alveolar epithelial damage, alter thiol levels in alveolar macrophages (AM) and lymphocytes, and activate AM in the production of reactive oxygen species (ROS) and pro-inflammatory cytokines. The organic component, on the other hand, is shown to generate intracellular ROS, leading to a variety of cellular responses including apoptosis. There are a number of differences between the biological actions exerted by these two components. The organic component is responsible for DEP induction of cytochrome P450 family 1 enzymes that are critical to the polycyclic aromatic hydrocarbons (PAH) and nitro-PAH metabolism in the lung as well as in the liver. The particulate component, on the other hand, causes a sustained down-regulation of CYP2B1 in the rat lung. The significance of this effect on pulmonary metabolism of xenobiotics and endobiotics remains to be seen, but may prove to be an important factor governing the interplay of the pulmonary metabolic and inflammatory systems. Long-term exposures to various particles including DEP, carbon black (CB), TiO2, and washed DEP devoid of the organic content, have been shown to produce similar tumorigenic responses in rodents. There is a lack of correlation between tumor development and DEP chemical-derived DNA adduct formation. But the organic component has been shown to generate ROS that produce 8-hydroxydeoxyguanosine (8-OHdG) in cell culture. The organic, but not the particulate, component of DEP suppresses the production of pro-inflammatory cytokines by AM and the development of Th1 cell-mediated immunity. The mechanism for this effect is not yet clear, but may involve the induction of heme oxygenase-1 (HO-1), a cellular genetic response to oxidative stress. Both the organic and the particulate components of DEP enhance respiratory allergic sensitization. Part of the DEP effects may be due to a depletion of glutathione in lymphocytes. The organic component, which is shown to induce IL-4 and IL-10 productions, may skew the immunity toward Th2 response, whereas the particulate component may stimulate both the Th1 and Th2 responses. In conclusion, the literature shows that the particulate and organic components of DEP exhibit different biological actions but both involve the induction of cellular oxidative stress. Together, these effects inhibit cell-mediated immunity toward infectious agents, exacerbate respiratory allergy, cause DNA damage, and under long-term exposure, induce the development of lung tumors.

Size fractions of ambient particulate matter induce granulocyte macrophage colony-stimulating factor in human bronchial epithelial cells by mitogen-activated protein kinase pathways

Environmental pollutants, including ambient particulate matter (PM), increase respiratory morbidity. Studies of model PM particles, including residual oil fly ash and freshly generated diesel exhaust particles, have demonstrated that PM affects inflammatory airway responses. Neither of these particles completely represents ambient PM, and therefore questions remain about ambient particulates. We hypothesized that ambient PM of different size fractions collected from an urban environment (New York City air), would activate primary culture human bronchial epithelial cells (HBECs). Because of the importance of granulocyte-macrophage colony-stimulating factor (GM-CSF) on inflammatory and immunomodulatory processes, we focused our studies on this cytokine. We demonstrated that the smallest size fraction (ultrafine/fine; < 0.18 micro m) of ambient PM (11 micro g/cm(2)), upregulated GM-CSF production (2-fold increase). The absence of effect of carbon particles of similar size, and the day-to-day variation in response, suggested that the chemical composition, but not the particle itself, was necessary for GM-CSF induction. Activation of the extracellular signal-regulated kinase and the p38 mitogen-activated protein kinase was associated with, and necessary for, GM-CSF release. These studies serve to corroborate and extend those on model particles. Moreover, they emphasize the role of the smallest size ambient particles in airway epithelial cell responses.

Effects of fractions of traffic particulate matter on TH2-cytokines, IgE levels, and bronchial hyperresponsiveness in mice

In recent decades an increased prevalence of allergic conditions has been observed in developed countries. Although lifestyles, exposure to infection, and diet are all likely important factors, many studies have also shown a strong link between industrialization and allergy. The aim of this study was to investigate which extract fractions from traffic particulate matter (TPM, collected in a tunnel in Prague) have the greatest impact on different inflammatory and immunological parameters, such as cytokine production, levels of immunoglobulin E (IgE) antibodies, and bronchial hyperresponsiveness (BHR) in mice, when the extracts are used together with birch pollen for immunization. BP2 mice were immunized with birch pollen and different fractions of TPM (fractions 1-8). They were provoked intranasally with a mixture of pollen and TPM or pollen alone before they were challenged with methacholine. The BHR was evaluated in a whole-body plethysmograph. Th2 cytokines and fibronectin concentrations were measured, and differential cell counts were performed in the bronchioalveolar lavage (BAL) fluid. Sera were collected for determination of antibody titers. The highest titers of IgE and the highest BHR were found in the positive control mice (immunized and provoked with a mixture of pollen and TPM), followed by mice immunized with pollen and fraction 2 (which contains organic acids). Fraction 2 also induced the highest number of eosinophils and increased levels of interleukin 5 (IL-5) in the BAL fluid. The highest levels of IL-5, in BAL fluid and sera, were obtained in mice immunized with fraction 6 (moderately polar compounds), a somewhat surprising result since those mice did not produce any IgE, did not have any eosinophils in their BAL, or showed almost no BHR. Our data demonstrate that fractions 2 (organic acids) and 7 (highly polar compounds) seem to contain potential adjuvants stimulating the IL-5 production, the IgE synthesis, the eosinophil recruitment, and the bronchial hyperreactivity. Further characterization at the molecular level is now necessary to be able to identify the exact nature of those potential adjuvants. This will be of help in the future to improve the quality of the urban air aerosol.

Pulmonary function assessment by whole-body plethysmography in restrained versus unrestrained mice

INTRODUCTION

The evaluation of pulmonary physiological measurements in laboratory animals is an essential tool in many biomedical and toxicological research areas. Recently, an unrestrained single chambered whole-body plethysmograph that utilizes a barometric analysis technique to quantify pulmonary physiological values has gained widespread use. However, results generated with the single chamber plethysmograph have come under increased scrutiny because airflow in the lung is indirectly measured. The purpose of the present study was to use mice with known interstrain differences in pulmonary physiology (A/J, BALB/c, CD-1, and B6C3F1) and compare the physiological data generated with a single chamber plethysmograph to data obtained in the widely accepted double chamber noninvasive airway mechanics (NAM) plethysmograph in which the animals are restrained.

METHODS

Animals were placed into the plethysmographs and baseline physiological data acquired. The mice were then subjected to challenge with aerosols generated from isotonic saline (control) and methacholine solutions of increasing concentration (2.5-320 mg/ml) for 3 min for determination of the concentration of methacholine that induced a 200% increase in airway resistance (PC(200)R).

RESULTS

Repeated physiological measurements on the same animals in both the single and double chamber plethysmographs demonstrated that each instrument generated reproducible baseline physiological data. However, comparison of physiological data generated with the double-chambered instrument to that generated with the single chamber plethysmograph revealed several significant differences. While the single chamber plethysmograph appeared to give inaccurate measurements of tidal volume, it provided much better analysis of airway reactivity based on PC(200)R results. In contrast, the double chamber plethysmograph provided accurate physiological data such as tidal volume and respiratory rate, but provided inaccurate and irreproducible airway reactivity results based on PC(200)R.

DISCUSSION

Our results indicate that the choice of single or double chamber plethysmograph for physiological measurements should be linked to the study objectives and the type of data required.

Coadministration of antigen and particles optimally stimulates the immune response in an intranasal administration model in mice

Some particulate matter is known to affect human health, yet the mechanism(s) by which it acts is largely unknown. One of the factors that may play a role in the immune- stimulating activity of particles is binding of allergen to particles. This may turn the particles into allergen carriers, resulting in antigen deposition within the altered inflammatory microenvironment created by the particles. We compared the efficacy of simultaneous versus separate administration of antigen and particles during sensitization in an intranasal exposure model in BALB/c mice. Sensitization consisted of three separate doses (10 microg) of TNP-OVA at Days 1, 2, and 3. Two hundred micrograms of carbon black particles (CBP) were administered either 1 day before sensitization (Day 0), 1 day after sensitization (Day 4), or during sensitization. The latter was performed either at Day 1 (200 microg) or at Days 1, 2, and 3 (67 microg/day). At Day 10 a challenge with 10 microg of TNP-OVA was performed, and at Day 15 the immune response was assessed. The total number of cells as well as antibody-forming cells (AFC) in lymph nodes draining the lung (peribronchial lymph nodes [PBLN]) were determined, and immunoglobulin levels in blood were assessed. Cell numbers of PBLN increased significantly in all particle-treated groups compared to controls. The number of TNP-specific IgG1-forming cells in the groups receiving particles during sensitization was significantly higher than control level. Only groups receiving particles during or before sensitization displayed significantly higher IgG1 levels than controls, in contrast to the group receiving particles after sensitization. Only in animals receiving three doses of 67 microg during sensitization did TNP-specific IgE increase significantly compared to controls. IgG2a did not show significant differences compared to controls, indicating that the response is predominantly Th2 mediated. These data indicate that coadministration of particles at all time points of antigen dosing is the most effective way to stimulate an immune response in our model compared to separate particle and antigen dosing. Also, administration shortly before antigen administration was effective in stimulating an immune response, suggesting that time-dependent processes are involved in immune-stimulating activity of particles, supporting the important role of the altered inflammatory microenvironment created by the particles.

Suppression of allergic immune responses to house dust mite (HDM) in rats exposed to 2,3,7,8-TCDD

Exposure to various xenobiotics, including oxidant gases, diesel exhaust, and certain pesticides, has been reported to exacerbate pulmonary allergic hypersensitivity responses. Increased lymphocyte proliferative responses to parasite antigens or increased antibody responses to sheep erythrocyte have also been reported in rats exposed to TCDD before infection or immunization. As a result, these studies were conducted to test the hypothesis that TCDD exposure exacerbates the allergic response to house dust mite antigen. Brown Norway rats were injected, ip, with 0, 1, 10, or 30 microg TCDD/kg 7 days before intratracheal (it) sensitization to semipurified house dust mite allergen (HDM). Fourteen days later, rats were challenged with HDM and immediate bronchospasm was measured. At this time point, plus 2 and 7 days later, inflammatory cells in bronchoalveolar lavage fluid (BALF), HDM-specific IgE levels in serum, and HDM-driven cell proliferation in bronchial lymph nodes and spleen were evaluated. TCDD exposure decreased both immediate bronchoconstriction and specific IgE synthesis after the HDM challenge; 7 days later, HDM-specific IgE responses remained suppressed. Total serum IgE levels were similar in all groups. HDM challenge alone significantly increased cellular and biochemical indicators of lung injury, both of which were suppressed by TCDD exposure. The proliferative response of lymph node cells, but not of spleen cells, to HDM was also suppressed at the highest TCDD dose, although the splenic response to Concanavalin A was elevated. It appears that early events in the response to HDM are affected by TCDD exposure, since message for IL5 was dramatically reduced 2 days after sensitization, but not after challenge. We therefore conclude that TCDD exposure suppressed, rather than enhanced the development of allergic immune responses and the expression of immune-mediated lung disease.

Animal models to assess the effects of air pollutants on allergic lung disease

Animal models provide toxicologists with useful tools for assessing risks associated with respiratory allergy. Both the mouse and BN rat models described exhibit many of the features of human allergic asthma. It is clear that environmental contaminants can exacerbate the expression of these features. Work is under way to explore underlying mechanisms and to develop methods for applying these data to human health risk assessment.

The role of particulate matter in exacerbation of atopic asthma

Increasing evidence shows that elevated levels of particulate matter (PM) can exacerbate existing asthma, while evidence that PM can promote the induction of asthma is limited. PM in ambient air has been associated with increased emergency room visits and medication use by asthmatics. Controlled human exposure studies of acid aerosols suggest increased responses among adolescent asthmatics. Increased ambient and indoor levels of bioaerosols (e.g., house dust mite, fungal spores, endotoxin) have been associated with exacerbation of asthma. Environmental Protection Agency (EPA) studies focus on the effects of exposing humans and animal models to a combination of various PM samples (e.g., diesel exhaust particles, oil fly ash) and allergens (e.g., house dust mite, ovalbumin). These research efforts to understand the mechanisms by which PM exposure can promote allergic sensitization and exacerbate existing asthma concentrate on the role of transition metals. Exposure of animal models to combined PM and allergen promotes allergic sensitization and increases allergic inflammation and airway hyperresponsiveness. Exposure of healthy human volunteers to emission source PM samples promotes inflammation and increased indices of oxidant formation correlating with the quantity of transition metals in the samples. Results of these studies suggest that transition metals in ambient PM promote the formation of reactive oxygen species and subsequent lung injury, inflammation, and airway hyperresponsiveness leading to airflow limitation and symptoms of asthma.

Inhalation toxicology models of endotoxin- and bioaerosol-induced inflammation

Inhalation toxicology studies in rodents have proven their usefulness for furthering our understanding of the causal agents, mechanisms, and pathology associated with exposures to environmental endotoxins and bioaerosols. Inhalation animal models are used to determine which components of a mixture are the most important toxicants for inducing the observed adverse outcome. They are used to obtain exposure-response relationships for allergens and pro-inflammatory agents to help elucidate disease mechanisms and contribute quantitative data to the risk assessment process. Inhalation models serve as important adjuncts to epidemiology studies and human exposure studies. They are also useful for establishing phenotype in studies of genetic polymorphisms and disease susceptibility and are widely applied for evaluation of safety and efficacy for potential therapeutic agents. In order to produce reliable data, rigorous exposure chamber design, aerosol generation systems, exposure quantitation and experimental protocols must be utilized.

Enhanced allergic sensitization by residual oil fly ash particles is mediated by soluble metal constituents

Epidemiological studies have demonstrated an association between elevated levels of particulate matter (PM) air pollutants and exacerbation of asthma symptoms. We have shown in a Brown Norway (BN) rat model of house dust mite (HDM) allergy that preexposure to residual oil fly ash (ROFA) particles enhanced the sensitization phase such that the secondary immune response and associated lung injury were increased after allergen challenge. To determine whether the metals present in ROFA mediated this effect, BN rats were intratracheally instilled with either ROFA (1000 microg) or acidified saline + NiSO(4) (105.12 microg), VSO(4) (98.2 microg), FeSO(4) (58.49 microg), or a mixture (Mix) of each metal. HDM-specific IgE was higher in the serum of the ROFA, Ni, V, and Mix groups than in the HDM group after challenge, and antigen-induced bronchoconstriction responses were increased in the Ni group. Lymphocyte proliferation to antigen was increased in the ROFA, Ni, and V groups compared to controls. Total protein and eosinophil peroxidase levels were elevated in the Fe group, and eosinophil numbers in the bronchoalveolar lavage fluid (BALF) were increased in the ROFA and Fe groups compared to HDM control. IL-5 and IL-13 mRNA expression was also increased in the lung tissue of all metal and ROFA-treated groups, while BALF IL-10 was elevated in the Fe and Mix groups, and IL-6 and TNF-alpha were elevated in the metal and ROFA-treated groups compared to controls. These results suggest that ROFA's metallic constituents mediate enhancement of sensitization to HDM and that pulmonary inflammation may play a role in this adjuvant effect.