Adjuvant activity of diesel-exhaust particulates for the production of IgE antibody in mice

Immunological Findings in a Group of Coke-Oven Workers Exposed to Polycyclic Aromatic Hydrocarbons

Coke-oven workers are exposed to a high concentration of polycyclic aromatic hydrocarbons, which may change the immunologic responses. In this study, we evaluated humoral immunity by measuring serum IgA, IgE, IgG, and tumor necrosis factor-alpha in 251 coke-oven workers and 89 rolling steel workers in Taiwan. Mean values of serum IgE and tumor necrosis factor-alpha levels were 178.8 IU/mL and 8.4 pg/mL in coke-oven workers, respectively, which were significantly higher than in rolling steel workers (102.6 IU/mL and 2.0 pg/mL; P=0.003 and <0.001). In contrast, serum IgA levels were significantly lower in coke-oven workers than in rolling steel workers (mean=264.7 vs 312.0 mg/dL, P<0.001). Our findings suggest that polycyclic aromatic hydrocarbons exposure may alter the immune responses in coke-oven workers.

Use of proteomics to demonstrate a hierarchical oxidative stress response to diesel exhaust particle chemicals in a macrophage cell line

Epidemiological studies demonstrate an association between short term exposure to ambient particulate matter (PM) and cardiorespiratory morbidity and mortality. Although the biological mechanisms of these adverse effects are unknown, emerging data suggest a key role for oxidative stress. Ambient PM and diesel exhaust particles (DEP) contain redox cycling organic chemicals that induce pro-oxidative and pro-inflammatory effects in the lung. These responses are suppressed by N-acetylcysteine (NAC), which directly complexes to electrophilic DEP chemicals and exert additional antioxidant effects at the cellular level. A proteomics approach was used to study DEP-induced responses in the macrophage cell line, RAW 264.7. We demonstrate that in the dose range 10-100 microg/ml, organic DEP extracts induce a progressive decline in the cellular GSH/GSSG ratio, in parallel with a linear increase in newly expressed proteins on the two-dimensional gel. Using matrix-assisted laser desorption ionization time-of-flight mass spectrometry and electrospray ionization-liquid chromatography/mass spectrometry/mass spectrometry analysis, 32 newly induced/NAC-suppressed proteins were identified. These include antioxidant enzymes (e.g. heme oxygenase-1 and catalase), pro-inflammatory components (e.g. p38MAPK and Rel A), and products of intermediary metabolism that are regulated by oxidative stress. Heme oxygenase-1 was induced at low extract dose and with minimal decline in the GSH/GSSG ratio, whereas MAP kinase activation required a higher chemical dose and incremental levels of oxidative stress. Moreover, at extract doses >50 microg/ml, there is a steep decline in cellular viability. These data suggest that DEP induce a hierarchical oxidative stress response in which some of these proteins may serve as markers for oxidative stress during PM exposures.

Adjuvant activity of various diesel exhaust and ambient particles in two allergic models

In the framework of an EU study entitled "Respiratory Allergy and Inflammation Due to Ambient Particles" (RAIAP), various collected particulate matter samples were to be tested for their adjuvant potency in two animal models of allergy. A pollen allergy model in the Brown Norway (BN) rat and an ovalbumin model in the BALB/c mouse were used in this study to compare the discriminatory value of these two models and to evaluate them for later studies of collected RAIAP-samples. Two different sources of diesel exhaust particles (DEP I and DEP II ), a residual oil fly ash source (ROFA), and two sources of ambient particles (Ottawa dust, EHC-93, and road tunnel dust, RTD) were tested. Rats were sensitized intratracheally with Timothy grass pollen (Phleum pratense, 200 microl, 10 mg/ml) on d 0, challenged on d 21, and examined on d 25. Mice were sensitized intranasally at d 0 and 14, challenged intranasally at d 35, 38, and 41 (50 microl, 0.4 mg ovalbumin/ml), and examined at d 42. Particulate matter (PM) was administered either during the sensitization phase only or during the sensitization and challenge phases (for mice only) or during the challenge phase only. In the pollen model, only DEP I, but not DEP II, ROFA, EHC-93, and RTD, stimulated the immunoglobulin (Ig) E and IgG1 response in serum to pollen allergens. In addition to this adjuvant effect noted, no other biomarkers in lung or bronchoalveolar lavage (BAL) revealed adjuvant activity in the pollen model. In the BAL of BN rats exposed to a combination of pollen and PM, the percentages of eosinophilic granulocytes were decreased compared to the BAL of BN rats immunized with pollen only. In the ovalbumin model, the IgE levels in serum were increased in mice after coexposure to ovalbumin and PM (including DEPI, DEPII, ROFA, EHC-93, and RTD) in the sensitization phase but not after coexposure during the challenge phase only. The inflammatory response was greater in the lung, predominantly the influx of eosinophilic granulocytes, as was observed by both histopathological examination and BAL analysis. In addition, BAL levels of inflammatory interleukin (IL)-4 were increased. Based on the IgE antibody response to ovalbumin, the ovalbumin model ranked the adjuvant capacity of the particles in the following order: RTD > ROFA > EHC-93 > DEPI > DEPII. In conclusion, the ovalbumin model is a sensitive system to detect adjuvant activity of airborne particles, whereas the pollen-induced allergy model in rat was less sensitive.

Onset of allergy and asthma symptoms in extra-European immigrants to Milan, Italy: possible role of environmental factors

BACKGROUND

Allergy and asthma are typical disorders of the affluent societies. Migrants from developing to industrialized countries seem to be at increased risk of allergy and asthma development.

OBJECTIVE

To evaluate time of onset, spectrum of sensitization and clinical features in a population of extra-European immigrants to Milan, Italy, complaining of allergy and asthma symptoms.

METHODS

Data regarding 243 extra-European immigrants checked at an allergy clinic from 1994 to 2000 were collected retrospectively. The demographic data were compared with those of the extra-European immigrants living in Milan at the end of 1999.

RESULTS

The patients were complaining of asthma (63.7%), rhinoconjunctivitis (56.7%), rhinitis alone (21%) or urticaria (3%). One hundred and eighty-seven out of 222 patients (84.3%) declared they were healthy before migrating and allergy/asthma symptoms started to appear after their arrival in Italy, namely after an average period of 4 years and 7 months. The proportion of male patients was lower than the proportion of men in the extra-European immigrant population (48% vs. 55%), suggesting that in adult immigrants allergy and asthma are more common in women than in men. Furthermore, there was an over-representation of Central-South Americans attending the clinic, which seemed to be due to a genetic predisposition to allergy/asthma development. When data were analysed for single countries, a trend towards an increased risk of allergy and asthma was found in immigrants from all Central-South American countries. A skin test positivity for at least one inhalant allergen was found in 196 out of 232 patients (81%), and the spectrum of allergic sensitization was similar to that of the Italian population living in the North of Italy.

CONCLUSION

Most extra-European immigrants declared that they were healthy at home and that allergy and asthma symptoms had appeared after immigration to Milan; lifestyle and environmental factors in a western industrialized city seem indeed to facilitate allergy/asthma onset in immigrants from developing countries. Allergy/asthma risk seems to be different in different ethnic groups.

Environmental polycyclic aromatic hydrocarbons, benzo(a) pyrene (BaP) and BaP-quinones, enhance IgE-mediated histamine release and IL-4 production in human basophils

Polycyclic aromatic hydrocarbons (PAHs) are major components of diesel exhaust particles found in pollutant respirable particles. There is growing evidence that these fossil fuel combustion products exacerbate allergic inflammation. Basophils contribute to allergic inflammation through the release of preformed and granule-derived mediators. To determine whether allergens and PAHs interact, we incubated human basophils with PAHs and measured the release of histamine and IL-4 with and without added antigen. None of the PAHs induced mediator release by itself and none affected total cellular histamine levels. However, several PAHs enhanced histamine release and IL-4 production in response to crosslinking the high-affinity IgE receptor, Fc epsilon RI. The enhancement seen with 1,6-BaP-quinone involved an increase in tyrosine phosphorylation in several different substrates, including the Fc epsilon RI-associated tyrosine kinase, Lyn, and elevated reactive oxygen species (ROS) levels detected by dichlorofluorescein fluorescence and flow cytometry. The PAH-induced enhancement of mediator release and ROS production could be inhibited with the antioxidant N-acetylcysteine. These data provide further evidence that environmental pollutants can influence allergic inflammation through enhanced Fc epsilon RI-coupled mediator release from human basophils.

Isolation of nitrophenols from diesel exhaust particles (DEP) as vasodilatation compounds

The compounds in diesel exhaust particles (DEP) that are responsible for vasodilatation were isolated and characterized for the first time. From benzene extract of DEP, 2-methyl-4-nitrophenol, 3-methyl-4-nitrophenl and 4-nitrophenol were isolated, and their vasodilatation activities were confirmed. 3-methyl-4-nitrophenol caused dilatation of rat thoracic artery, and the other two nitrophenols, also showed vasodilatation activities.

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

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

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.

Diesel exhaust particle extracts and associated polycyclic aromatic hydrocarbons inhibit Cox-2-dependent prostaglandin synthesis in murine macrophages and fibroblasts

Diesel exhaust particles (DEP) and their organic constituents modulate the immune system and exacerbate allergic airway inflammation. We investigated the role of DEP extract and associated polycyclic aromatic hydrocarbons (PAHs) on prostaglandin synthesis in endotoxin-activated murine macrophages and in mitogen-stimulated fibroblasts. In both macrophages and fibroblasts, DEP extract, phenanthrene, anthracene, phenanthrenequinone, and beta-napthoflavone inhibit prostaglandin production from endogenous arachidonic acid in response to ligand stimulation. However, DEP extract and PAHs do not block ligand induction of cyclooxygenase-2 (COX-2) protein, either in mitogen-stimulated fibroblasts or endotoxin-treated macrophages. Release of total arachidonic acid and total lipid products is not reduced by DEP or PAHs following ligand stimulation of macrophages or fibroblasts. DEP extract and the PAHs inhibit the activity of purified COX-2 enzyme in vitro but do not inhibit COX-1 activity. Thus, DEP and PAHs do not affect ligand-induced COX-2 gene expression, phospholipase activation, or arachidonic acid release in macrophages and fibroblasts but exert their inhibitory effect on prostaglandin production by preferentially blocking COX-2 enzyme activity.

Pollen allergy related to the area of residence in the city of Córdoba, south-west Spain

The aim of this study was to analyse the relationship between the distribution of hay-fever patients in the city of Córdoba, south-western Iberian Peninsula, and the specific atmospheric biological content originating from local sources. Four different districts were established in the metropolitan area of the city, according to vegetational and urbanistic characteristics. Air samples were taken in each area using portable Hirst-type samplers (Lanzoni VPPS 1000) and the spectrum of biological content was defined. Patients attending the Allergy Unit at Córdoba Teaching Hospital in 2000 with allergic rhinitis and/or asthma, and displaying a positive reaction to aeroallergen extracts, were distributed within the areas as a function of their district of residence. Aerobiological results revealed differences in pollen content between areas, in terms of both quantity and number of pollen types recorded. These differences were largely due to proximity to rural areas, prevalence of pollen from typically urban species and the possible effect of urban architecture as a barrier to the dispersal/ concentration of particles and other pollutants. Patients were not uniformly distributed within the city. The majority lived in districts in which pollen from rural species was mixed with pollen from ornamentals. Patients living in typically urban districts displayed a higher prevalence of allergy to pollen from ornamentals. It is concluded that a high degree of exposure to the same environment may influence the development of sensitisation to the particular pollen load associated with that area.

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.

Cigarette smoke-induced airway hyperresponsiveness is not dependent on elevated immunoglobulin and eosinophilic inflammation in a mouse model of allergic airway disease

Epidemiologic studies suggest that children raised in homes of cigarette smokers have a higher incidence of asthma than children who are raised in homes of nonsmokers. We sought to develop an experimental model to understand the mechanisms involved. Female BALB/c mice were paired with male DO11.10 ovalbumin (OVA)-T cell receptor hemizygous (+/-) mice such that the offspring were either transgene positive (+/-) or negative (-/-). Mice were exposed to either air or mainstream cigarette smoke (100 mg/m(3) total particulate matter, 6 hours/day, 7 days/week) during pregnancy. Immediately after birth, newborn mice were exposed for 4 weeks to either air or sidestream cigarette smoke (SS; 5 mg/m(3) total particulate matter, 6 hours/day, 5 days/week) and then exposed for the following 6 weeks to either air, SS, OVA (5 mg/m(3), 6 hours/day, 5 days/week) or a combination of OVA-SS. DO11.10 +/- offspring exposed to OVA had increased airway hyperresponsiveness (AHR) to methacholine challenge, total IgE, OVA-specific IgE and IgG(1), lymphocytes, and neutrophils in bronchoalveolar lavage and perivascular and peribronchiolar inflammation. Exposure to SS alone caused a significant increase in AHR in both +/- and -/- mice. Transgene -/- mice did not exhibit AHR after OVA exposure unless it was delivered in combination with SS. When compared with OVA-only exposure, OVA-SS exposure decreased total IgE, OVA-specific IgE, and IgG(1) amounts in +/- mice. These results indicate that exposure to SS after birth enhanced AHR in offspring that are both predisposed (+/-) and nonpredisposed (-/-) to develop an allergic response to OVA, but this AHR was not associated with elevated lung eosinophilia or OVA-specific Ig amounts.

Chemical constituents of diesel exhaust particles induce IL-4 production and histamine release by human basophils

BACKGROUND

An epidemiologic relationship between airway allergic diseases and exposure to atmospheric pollutants has been demonstrated and suggested to be one factor in the increasing prevalence of asthma. Diesel exhaust particles (DEPs) have been shown to participate in the development of allergic airway inflammation, in which the targets include macrophages, B and T cells, epithelial cells, and mast cells. In addition to the adjuvant effect of DEPs on total and allergen-specific IgE production, DEPs also act to induce chemokines and cytokines and may play a key role in primary sensitization.

OBJECTIVE

DEPs have been shown to increase local IL-4-containing Kit(+) cells soon after in vivo nasal challenge. The aim of this study was to examine the effects of DEPs on human basophils, a key source of IL-4.

METHODS

Peripheral blood leukocytes from allergic and control subjects were cultured in the presence of organic extracts of DEP (DEPex) with or without allergen. The cultures were analyzed for IL-4-containing cells by using multiparameter flow cytometry, IL-4 secretion with ELISA, and histamine release.

RESULTS

Basophils, when exposed in vitro to DEPex, expressed IL-4 and released histamine significantly (P <.01) more than with antigen activation. DEPex did not synergize with allergen in cytokine production and histamine release. DEPex-induced basophil IL-4 expression peaked at 2 hours and persisted through 20 hours, in contrast to allergen-induced IL-4, which was transient. The effect of DEPex on basophil cytokine expression and histamine release was dose dependent and occurred with cells from both allergic and nonallergic subjects. DEPex induced IL-4 expression and histamine release in highly enriched basophil populations, suggesting it acts directly on basophils. Other peripheral blood leukocytes, including T cells, did not contribute to this cytokine expression. Preincubation with N-acetylcysteine completely abrogated DEPex-driven basophil IL-4 expression.

CONCLUSIONS

Basophils are a direct target for DEPex, inducing IL-4 expression and histamine release in an IgE-allergen independent fashion. N-acetylcysteine inhibition of DEPex-driven IL-4 expression provides evidence that generation of reactive oxygen species is required for the effects observed. The capability of DEPex to activate basophils in both allergic and nonallergic subjects suggests a potential role of this pollutant in the increasing prevalence of allergic diseases.

Effects of birch pollen and traffic particulate matter on Th2 cytokines, immunoglobulin E levels and bronchial hyper-responsiveness in mice

BACKGROUND

Health effects due to air pollution arising from motor vehicles are a major public and political concern world-wide. Epidemiological studies have shown that the manifestations of asthma are increased by air pollution in already affected individuals.

OBJECTIVE

To investigate the potential role of air-polluted tunnel dust (traffic particulate matter, TPM) or pure carbon core particles in the initiation and persistence of experimental allergic inflammation.

METHODS

BP2 mice were immunized with birch pollen alone (group B) or pollen together with TPM (group A), or with birch pollen and Al(OH)3 (group C), or with birch pollen and carbon core particles (group D). Before methacholine challenge they were challenged intranasally and thereafter bronchial hyper-reactivity (BHR) was evaluated in a whole-body plethysmograph. Levels of Th2 cytokines, fibronectin and lactate dehydrogenase (LDH) were determined, and differential counts were performed in the bronchoalveolar lavage (BAL) fluid. Sera were collected for determination of antibody titres and cytokine levels.

RESULTS

Specific IgE titres, BHR, the number of recruited eosinophils and levels of fibronectin and LDH in BAL were increased in mice immunized and challenged with a mixture of birch pollen and TPM. However, mice immunized with birch pollen alone and challenged intranasally with pollen or a mixture of pollen and TPM demonstrated the highest levels of IL-4 and IL-5.

CONCLUSION

This study highlights the importance of the exposure to a combination of particulate matters and pollen allergens, in the induction of allergic disease in the airways, and we have demonstrated that polluted tunnel dust has an effect on both the inflammatory and immunological components of experimental allergy. Immunization and challenge with carbon core particles together with birch pollen increased neither the BHR nor the specific IgE production significantly. Our results therefore strongly suggest that it is most likely to be the organic phase bound to the carbon core of the diesel exhaust particles that might have an important adjuvant effect in the induction of experimental allergy.

Elevated serum immunoglobulin E to Cryptomeria japonica pollen in rats exposed to diesel exhaust during fetal and neonatal periods

BACKGROUND: The possible participation of diesel exhaust inhalation during the fetal period in the elevation of IgE against pollen in postnatal life was investigated. METHOD: The experiment was conducted using rat pups. Group I; exposed to clean air (Control). Group 2, 3; exposed to total or filtered diesel exhaust during the fetal period (Total-C-C, Filtered-C-C). Group 4, 5; exposed to total or filtered diesel exhaust during the suckling period (C-Total-C, C-Filtered-C). Group 6,7; exposed to total or filtered diesel exhaust during the weaning period (C-C-Total, C-C-Filtered). Total diesel engine exhaust contained 1.73 mg/m3 particulate matter and 0.79 ppm nitrogen dioxide; filtered exhaust contained the same gases as the total exhaust without particulate matter. Intraperitoneal injection of 5 mg crude cedar pollen was performed at 2-week intervals from the 49th day after birth. RESULTS: The mean IgE titers measured by the P-K reaction in the Control, Total-C-C, Filtered-C-C, C-Total-C, C-Filtered-C, C-C-Total and C-C-Filtered were 64.0 &PlusMinus; 2.7, 469.5 &PlusMinus; 1.6, 332.0 &PlusMinus; 1.7, 380.4 &PlusMinus; 1.7, 394.8 &PlusMinus; 1.7, 115.9 &PlusMinus; 1.3 and 57.0 &PlusMinus; 2.8 respectively after the fourth immunization. There were significant differences between Total-C-C, Filtered-C-C, C-Total-C, C-Filtered-C and Control (p < 0.01, p < 0.01, p < 0.05, p < 0.01, respectively). The mean IgE titers by ELISA were 0.47 &PlusMinus; 0.06, 0.79 &PlusMinus; 0.35, 0.86 &PlusMinus; 0.46, 0.80 &PlusMinus; 0.22, 0.56 &PlusMinus; 0.08, 0.46 &PlusMinus; 0.04 and 0.45 &PlusMinus; 0.03, respectively. IgE titers in Filtered-C-C and C-Total-C were significantly higher than in Control (p < 0.05 for each). CONCLUSIONS: Inhalation of diesel exhaust during differentiation of the immune system accelerated the elevation of IgE against pollen.

Thiol antioxidants inhibit the adjuvant effects of aerosolized diesel exhaust particles in a murine model for ovalbumin sensitization

Although several epidemiological studies indicate a correlation between exposure to ambient particulate matter and adverse health effects in humans, there is still a fundamental lack of understanding of the mechanisms involved. We set out to test the hypothesis that reactive oxygen species are involved in the adjuvant effects of diesel exhaust particles (DEP) in a murine OVA sensitization model. First, we tested six different antioxidants, N-acetylcysteine (NAC), bucillamine (BUC), silibinin, luteolin, trolox (vitamin E), and ascorbic acid, for their ability to interfere in DEP-mediated oxidative stress in vitro. Of the six agents tested, only the thiol antioxidants, BUC and NAC, were effective at preventing a decrease in intracellular reduced glutathione:glutathione disulfide ratios, protecting cells from protein and lipid oxidation, and preventing heme oxygenase 1 expression. Therefore, we selected the thiol antioxidants for testing in the murine OVA inhalation sensitization model. Our data demonstrate that NAC and BUC effectively inhibited the adjuvant effects of DEP in the induction of OVA-specific IgE and IgG1 production. Furthermore, NAC and BUC prevented the generation of lipid peroxidation and protein oxidation in the lungs of OVA- plus DEP-exposed animals. These findings indicate that NAC and BUC are capable of preventing the adjuvant effects of inhaled DEP and suggest that oxidative stress is a key mechanistic component in the adjuvant effect of DEP. Antioxidant treatment strategies may therefore serve to alleviate allergic inflammation and may provide a rational basis for treating the contribution of particulate matter to asthmatic disease.

Privet pollen (Ligustrum sp.) as potential cause of pollinosis in the city of Cordoba, south-west Spain

BACKGROUND

Privet pollen rarely accounts for more than 1% of the annual total of daily pollen concentrations measured in a city; however in areas where these trees are widely used as ornamentals the amounts collected may be high enough to cause allergy symptoms.

METHODS

Air samples taken with volumetric particle samplers Lanzoni VPPS 1000 (Lanzoni s.r.l., Bologna, Italy) show that there are differences in privet pollen concentrations measured in neighbourhoods with a high incidence of privet trees and in those taken at some distance from the source of emission.

RESULTS

The results suggest that differences are due to the short dispersal range of the pollen grains once released from the plant, resulting from both the entomophilous nature of the plant and the large size of the pollen grains. Urban design, moreover, may play an important role in impeding pollen grain dispersion if the air cannot flow freely through long, narrow avenues. Another important consideration is that the last stages of the flowering period of privet overlaps with the flowering period of olive trees, the main allergen in the area. The fact that the two pollen types share common allergens means that there may be a cross-reaction between olive tree pollen and privet pollen.

CONCLUSIONS

Privet pollen should be considered as a potential causative agent of local allergy problems in areas where its presence is extensive and is in combination with other allergens.

Childhood asthma hospitalization and residential exposure to state route traffic

This study investigated whether pediatric hospitalization for asthma was related to living near a road with heavy traffic. In this case-control study, cases (N=417) consisted of white children aged 0-14 years who were admitted for asthma and who resided in Erie County, New York, excluding the city of Buffalo. Controls (N=461) were children in the same age range admitted during the same time period for nonrespiratory diseases. Subjects' residential addresses were linked to traffic information provided by the New York State Department of Transportation. After adjustments for age and poverty level were made, children hospitalized for asthma were more likely to live on roads with the highest tertile of vehicle miles traveled (VMT) (odds ratio (OR): 1.93, 95% confidence interval (CI): 1.13-3.29) within 200 m and were more likely to have trucks and trailers passing by within 200 m of their residence (OR=1.43, 95% CI: 1.03-1.99) compared to controls. However, childhood asthma hospitalization was not significantly associated with residential distance from state roads, annual VMT within 500 m, or whether trucks or trailers passed by within 500 m. This study suggests that exposure to high volumes of traffic/truck within 200 m of homes contributes to childhood asthma hospitalizations.

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.

Environmental pollution and allergy

OBJECTIVES

Among the theories supporting the increase of allergic diseases in modern western countries during the last several decades is the concept that environmental pollutants may play a vital role. Reading this article will enable the reader to recognize the effect of different types of environmental pollution on the development, modulation, and persistence of allergic reactions.

DATA SOURCES

Data sources include references to relevant articles and texts. To characterize the influence of environmental pollutants on allergic reactions (allergotoxicology), epidemiologic, clinical, and experimental data are considered.

RESULTS

The investigations show that air pollution patterns differ with respect to their effect upon allergies. Classical air pollution (type I) with high sulfur dioxide and dust particles seems not to be associated with allergic disease in humans. However, type II pollution characterized by elevation of oxides of nitrogen (NOx), ozone (O3), tobacco smoke, fine and ultrafine particulate matter, and diesel exhaust particles seems to enhance allergic disease.

CONCLUSIONS

The data suggest that environmental pollution can act at different levels and by complex interactions both outside and inside the individual and influence allergic diseases.

Why are allergies increasing?

The incidence of atopic allergy is increasing in certain 'Western' countries but this remains unexplained. Various hypotheses with differing amounts of evidence and/or relevance have been assessed, including increased awareness of the diseases, improved diagnostics, genetic susceptibility, psycho-social influences, allergen exposure, decreased immune-system stimulation, underlying disease, anti-allergic therapy and pollution.

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.

A prospective study of the association between home gas appliance use during infancy and subsequent dust mite sensitization and lung function in childhood

BACKGROUND

Home gas appliance use has been associated with child respiratory illness but prospective data on the relationship between infant exposure and the development of child allergic disease has not been readily available.

OBJECTIVES

(a) To determine if home gas appliance use is associated with increased risk of house dust mite (HDM) sensitization. (b) To examine whether any association between current home gas use and airway obstruction is influenced by HDM sensitization.

METHODS

DESIGN

an 8-year follow-up birth cohort study of children born during 1988 and 1989.

PARTICIPANTS

a population-based sample (n = 498) of children who participated in the Tasmanian Infant Health Survey (TIHS) and resided in Northern Tasmania in 1997 (84% of eligible children).

MAIN OUTCOME MEASURES

(a) Skin prick test reaction to nine allergens, including Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1). (b) Spirometric lung function indices, including forced expiratory volume in one second (FEV(1)) and forced vital capacity (FVC).

RESULTS

The relative risk for home gas appliance use at 1 month of age and HDM sensitization was 1.98 (1.04, 3.79) in a cohort analysis with confounder matching. Current home gas use was also associated with HDM sensitization (ARR 1.73 (1.43, 2.76)). Current home gas use was related to a stronger (P = 0.006) reduction in the FEV(1) : FVC ratio among HDM-sensitive children (adjusted difference - 6.2% (- 10.0 to - 2.4)) than non-HDM-sensitive children (adjusted difference - 0.3% (- 2.5 to 1.8)).

CONCLUSION

Indoor pollutants from gas combustion may increase the likelihood of initial sensitization to HDM and play a role in the development of atopic asthma. HDM-sensitized children may be more vulnerable to indoor pollutant-induced airway obstruction. The ability of this study to detect such effects may partly reflect unflued gas appliance use among this sample.

Accelerated DNA adduct formation in the lung of the Nrf2 knockout mouse exposed to diesel exhaust

Diesel exhaust (DE) has been recognized as a noxious mutagen and/or carcinogen, because its components can form DNA adducts. Mechanisms governing the susceptibility to DE and the efficiency of such DNA adduct formation require clarification. The transcription factor Nrf2 is essential for inducible and/or constitutive expression of a group of detoxification and antioxidant enzymes, and we hypothesized that the nrf2 gene knockout mouse might serve as an excellent model system for analyzing DE toxicity. To address this hypothesis, lungs from nrf2(-/-) and nrf2(+/-) mice were examined for the production of xenobiotic-DNA adducts after exposure to DE (3 mg/m(3) suspended particulate matter) for 4 weeks. Whereas the relative adduct levels (RAL) were significantly increased in the lungs of both nrf2(+/-) and nrf2(-/-) mice upon exposure to DE, the increase of RAL in the lungs from nrf2(-/-) mice exposed to DE were approximately 2.3-fold higher than that of nrf2(+/-) mice exposed to DE. In contrast, cytochrome P4501A1 mRNA levels in the nrf2(-/-) mouse lungs were similar to those in the nrf2(+/-) mouse lungs even after exposure to DE, suggesting that suppressed activity of phase II drug-metabolizing enzymes is important in giving rise to the increased level of DNA adducts in the Nrf2-null mutant mouse subjected to DE. Importantly, severe hyperplasia and accumulation of the oxidative DNA adduct 8-hydroxydeoxyguanosine were observed in the bronchial epidermis of nrf2(-/-) mice following DE exposure. These results demonstrate the increased susceptibility of the nrf2 germ line mutant mouse to DE exposure and indicate the nrf2 gene knockout mouse may represent a valuable model for the assessment of respiratory DE toxicity.

Outdoor air pollutants derived from industrial processes may be causally related to the development of asthma in children

BACKGROUND

There is no consistent evidence that outdoor air pollutants are involved in the development of asthma.

OBJECTIVE

The aim of this study was to determine whether outdoor air pollutants derived from industrial processes were related to the prevalence of asthma, bronchial hyperresponsiveness, and atopy in exposed children.

METHODS

A total of 7,511 children from 7 to 12 years of age were recruited in the study. Eight hundred eighty-eight of 1,009 (88%) of the subjects living around industrial factories and 5,998 of 6,502 (92%) living in a less polluted neighboring area responded to the ISAAC questionnaire. A total of 1,492 subjects 8 to 9 years old underwent skin prick tests for 11 common aeroallergens. A total of 732 of the subjects from 8 to 9 years of age underwent bronchial provocation tests with hypertonic saline (BPT-HS).

RESULTS

The prevalence of ever experiencing wheezing and wheeze during the last 12 months was 25.6%, and 18.8% among the children living in the more polluted area. This was significantly higher than for those living in the less polluted area (14.2% and 9.0%, respectively). The positive rate of BPT-HS (the provocative dose of hypertonic saline causing 20% fall of FEV, < or = 23 mL) was higher among those in the more polluted area than in children living in the less polluted area (12.2% vs 7.5%). However, the rate of atopy based on the skin tests was the same in the two groups (28.3% vs 30.6%).

CONCLUSIONS

The prevalence of asthma and bronchial hyperresponsiveness was higher among children living around the heavily industrial area compared with those living in the less polluted area, despite similar atopic sensitization.

Association between air pollution and daily consultations with general practitioners for allergic rhinitis in London, United Kingdom

Few published studies have looked at the health effects of air pollution in the primary care setting, and most have concentrated on lower rather than upper respiratory diseases. The authors investigated the association of daily consultations with general practitioners for allergic rhinitis with air pollution in London, United Kingdom. Generalized additive models were used to regress time series of daily numbers of patients consulting for allergic rhinitis against 1992--1994 measures of air pollution, after control for possible confounders and adjustment for overdispersion and serial correlation. In children, a 10th--90th percentile increase in sulfur dioxide (SO(2)) levels 4 days prior to consultation (13-31 microg/m(3)) was associated with a 24.5% increase in consultations (95% confidence interval: 14.6, 35.2; p < 0.00001); a 10th--90th percentile increase in averaged ozone (O(3)) concentrations on the day of consultation and the preceding 3 days (6--29 parts per billion) was associated with a 37.6% rise (95% confidence interval: 23.3, 53.5; p < 0.00001). For adults, smaller effect sizes were observed for SO(2) and O(3). The association with SO(2) remained highly significant in the presence of other pollutants. This study suggests that air pollution worsens allergic rhinitis symptoms, leading to substantial increases in consultations. SO(2) and O(3) seem particularly responsible, and both seem to contribute independently.

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.

Childhood risk factors for atopy and the importance of early intervention

The increasing prevalence of atopic diseases, particularly atopy-associated asthma, has become a major challenge for allergists and public health authorities in many countries. The understanding of the natural history of the atopic march, including the determinants that are modifiable and might become candidates for preventive intervention, is still very limited. Information provided by cross-sectional studies can only generate hypotheses, which need to be supported by prospective, longitudinal, cohort studies. Ultimately, it will depend on the results of well-controlled intervention studies to identify which nutritional, environmental, or lifestyle-related factors should be considered for early intervention and might be useful to reverse the epidemiologic trend.

Effect of diesel exhaust particles and their components on the allergen-specific IgE and IgG1 response in mice

Increased antigen-specific IgE expression is a hallmark of the allergic response in mice. IgG1 may also be involved. Co-injection of mice with diesel exhaust particles (DEP) and ovalbumin three times over a 2 week period lead to a rapid and marked elevation of ovalbumin-specific IgE, IgG1 and also IgG2a, compared with ovalbumin alone. When DEP were injected 1 day before or after ovalbumin on each occasion, their adjuvant effect was considerably muted, suggesting that the adjuvant effect of DEP is short-lived, or that a physical interaction between ovalbumin and DEP is required. DEP were extracted with methylene chloride. Both the resulting core carbon particles and the organic extract enhanced ovalbumin specific IgE and IgG1 levels. Thus the adjuvant effect of DEP in this model is due both to the physical and the chemical attributes of the particles. The tricyclic hydrocarbons phenanthene (the most prevalent polycyclic aromatic hydrocarbon in DEP) and anthracene were both capable of enhancing antigen-specific IgE and IgG1 production. The phenolic antioxidant, butylated hydroxyanisole, which can affect gene expression via the antioxidant responsive element (ARE), had a lesser effect. Two agonists for the aryl hydrocarbon receptor, 3-methychloranthrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin, either were without effect or suppressed the response, suggesting that DEP adjuvancy may not be mediated by this receptor.

Fine particles of widely different composition have an adjuvant effect on the production of allergen-specific antibodies

Diesel exhaust particles (DEP) are reported to increase the specific IgE response to allergens, and results from our laboratory suggest that the particle core of DEP contribute to this adjuvant activity. The purpose of the present study was to explore further the adjuvant effect of particles per se, that is particles by themselves. NIH/Ola mice were given two intraperitoneal injections with ovalbumin (OVA; 10 microg) alone or OVA in combination with PSP, polytetrafluoroethylene (teflon), titanium dioxide (TiO(2)) or amorphous silica particles (2.8x10(10)-2.8x10(12)). Blood samples were drawn 7 days after the last injection, and serum levels of allergen-specific and total IgE and IgG2a were measured. All types of particles gave increased levels of allergen-specific IgE and IgG2a. Similar results were obtained after intranasal or intratracheal instillation with OVA plus PSP or silica. Our results indicate that fine particles of widely different composition may have an adjuvant effect on the production of allergen-specific antibodies.

IgE adjuvant effect caused by particles - immediate and delayed effects

Diesel exhaust particles are reported to increase the specific IgE response to ovalbumin (OVA) and pollen. Evidence has been provided that the particle core contributes to this adjuvant activity. The purpose of our study was to investigate the effect of well-defined simple particles, polystyrene particles (PSP), on the production of allergen-specific IgE in a mouse model. The IgE adjuvant effect of PSP was investigated in experiments using intranasal (i.n.) instillation, intratracheal (i.t.) instillation or intraperitoneal (i.p.) injection. Delayed and cumulative adjuvant effects were investigated by giving mice i.p. injections with PSP 1-3 days, or on 4 consecutive days before OVA, respectively. The levels of allergen-specific and total IgE were measured. Irrespectively of immunisation route and protocol, OVA in combination with PSP elicited increased levels of both allergen-specific and total IgE when compared with OVA alone. Therefore, in the experimental model, particles were found to augment the specific IgE response to an allergen even when the allergen was introduced several days after the particles. These findings imply that individuals exposed to particulate air pollution at one point of time may develop an increased reaction towards allergens inhaled later that day or even several days after the particle exposure.

The role of particulate pollutants in pulmonary inflammation and asthma: evidence for the involvement of organic chemicals and oxidative stress

We review the literature indicating that the adverse health effects of ambient particulate matter involve the generation of oxidative stress and inflammation, as well as immunomodulating effects by particle-associated chemicals. We discuss evidence that diesel exhaust particle organic extracts induce reactive oxygen species in macrophages and bronchial epithelial cells, two key cell types targeted by particulate matter in the lung. Reactive oxygen species activate the promoters of cytokines and chemokines involved in allergic inflammation through activator protein-1 and nuclear factor- kappaB signaling pathways, which may explain exacerbation of allergic inflammation. Organic diesel exhaust particle chemicals also induce apoptosis and necrosis in bronchial epithelial cells via a mitochondrial pathway. This may be responsible for epithelial shedding and bronchial hyperreactivity in asthma.

Suspended particulate matter in indoor air: adjuvants and allergen carriers

The overall purpose of this study was to investigate how airborne house dust particles may contribute to an allergic immune response, and thereby also to asthma and other respiratory symptoms. The following aims were set: first, to quantify and characterize indoor suspended particulate matter (SPM) with regard to amount, as well as elemental and size distribution, second, to identify possible mechanisms by which SPM may affect the allergic immune response. A vast majority of the particles in SPM samples from homes in Oslo were found to be less than 2.5 microm in diameter. This PM(2.5) fraction contained, in addition to a large amount of sulfur aerosols and silicates, a lot of soot particles. Most of these were less than 1 microm in diameter. Using an immunogold labeling technique, we found that these soot particles carried cat, dog and birch allergens on their surface. These results show that indoor SPM contains a lot of potential allergen carriers, i.e. soot particles (carbon aggregates), most of them less that 1 microm in diameter and therefore able to transport allergens deep into the respiratory tree. We further found that diesel exhaust particles (DEP), which is likely the main soot component of SPM, adsorbed several well-known allergens in vitro. Furthermore, SPM was found to elicit a local lymph node inflammatory response, and to have an adjuvant activity on the production of IgE antibodies to ovalbumin (OA).

Adjuvant activity of particulate pollutants in different mouse models

Particulate air pollutants may play a role in the increasing prevalence of respiratory allergy by acting as adjuvants for a T helper 2 (Th2) mediated immune response to common allergens. The immunomodulating capacity of well-defined polystyrene particles as well as different particles as present in our environment (diesel exhaust, carbon black, and silica particles) was investigated in different models. Polystyrene particles were injected intraperitoneally or installed intratracheally, while the environmentally relevant particles were injected subcutaneously. From these studies, it becomes clear that all particles exert an adjuvant effect on the immune response to the co-administered antigen. The particle core rather than attached chemical factors seems to be mainly responsible for this effect. The different particles, however, stimulate different types of immune responses, indicating that physicochemical properties of particles may be of importance in steering the response towards a T helper 1 (Th1) or a Th2-like response.

Study of adjuvant effect of model surfactants from the groups of alkyl sulfates, alkylbenzene sulfonates, alcohol ethoxylates and soaps

The sodium salts of representatives of anionic surfactants, dodecylbenzene sulfonate (SDBS), dodecyl sulfate (SDS) and coconut oil fatty acids, and a nonionic surfactant, dodecyl alcohol ethoxylate, were studied for adjuvant effect on the production of specific IgE antibodies in mice. The surfactants were injected subcutaneously (sc) in concentrations of 1000, 100, 10 or 1 mg/l, respectively, together with 1 microg of ovalbumin (OVA). In addition, groups of mice received OVA in saline (control group) or in Al(OH)(3) (positive adjuvant control group). After the primary immunization the mice were boosted up to three times with OVA (0.1 microg sc) in saline. OVA-specific IgE antibodies were determined by the heterologous mouse rat passive cutaneous anaphylaxis test. The results were confirmed by a specific ELISA method. After the first booster, the Al(OH)(3) group and the 10 mg/l SDS group showed a statistically significant increase in OVA specific IgE levels. After two boosters, a statistically significant suppression in OVA-specific IgE production occurred with SDS (1000 mg/l), SDBS (1000 and 100 mg/l), coconut soap (1000 mg/l) and the alcohol ethoxylate (10 mg/l). This study suggests that a limited number of surfactants possess an adjuvant effect whereas all surfactants at certain levels can suppress specific IgE production.

Diesel exhaust, carbon black, and silica particles display distinct Th1/Th2 modulating activity

Certain particulate air pollutants may play an important role in the increasing prevalence of respiratory allergy by stimulating T helper 2 cell (Th2)-mediated immune responses to common antigens. The study described here examined different particles, diesel exhaust particles (DEP), carbon black particles (CBP), and silica particles (SIP) for their immunomodulating capacity in both primary and secondary immune responses in female BALB/C mice. The primary response was studied after subcutaneous injection of 1 mg of particle together with 10 microgram of reporter antigen TNP-OVA (2,4,6-trinitrophenyl coupled to ovalbumin) into the hind paw. Interferon-gamma (IFN-gamma) and interleukin 4 (IL-4) production was assessed in the popliteal lymph node (PLN) at Day 2 and Day 5 after injection by flow cytometry and ELISA. The number of IL-4-containing CD4(+) T cells increased between Day 2 and Day 5 in DEP- and CBP-exposed mice, in contrast to SIP-treated animals. IL-4 production by cultured PLN cells was also significantly increased for DEP- and CBP-treated animals. The secondary response was studied in different organs after an intranasal challenge with TNP-OVA (50 microgram), which was given 4 weeks after the initial subcutaneous injection. Five days after challenge the number of antibody-forming cells (AFCs) was assessed in peribronchial lymph nodes (PBLN), spleen, bone marrow, and PLN, and antibody levels were determined in weekly obtained blood samples. It appeared that all particles acted as adjuvant, but the different particles stimulated distinct types of immune responses to TNP-OVA. DEP-treated animals show high IgG1 and IgE levels in serum and high IgG1 and IgE-forming AFC numbers in PBLN, bone marrow, and spleen. CBP-treated animals show even higher IgG1 and IgE levels and AFC numbers, and in addition display IgG2a production. SIP-injected animals display predominantly IgG2a responses. It is concluded that DEP are able to skew the immune response toward the T helper 2 (Th2) side, whereas SIP stimulate a Th1 response and CBP have a mixed activity, stimulating both Th1 and Th2 responses in this model.

Induction of heme oxygenase-1 expression in macrophages by diesel exhaust particle chemicals and quinones via the antioxidant-responsive element

Diesel exhaust particles (DEP) contain organic chemicals that contribute to the adverse health effects of inhaled particulate matter. Because DEP induce oxidative stress in the lung and in macrophages, effective antioxidant defenses are required. One type of defense is through the expression of the antioxidant enzyme, heme oxygenase I (HO-1). HO-1 as well as phase II detoxifying enzymes are induced via antioxidant response elements (ARE) in their promoters of that gene. We show that a crude DEP total extract, aromatic and polar DEP fractions, a benzo(a)pyrene quinone, and a phenolic antioxidant induce HO-1 expression in RAW264.7 cells in an ARE-dependent manner. N-acetyl cysteine and the flavonoid, luteolin, inhibited HO-1 protein expression. We also demonstrate that the same stimuli induce HO-1 mRNA expression in parallel with the activation of the SX2 enhancer of that gene. Mutation of the ARE core, but not the overlapping AP-1 binding sequence, disrupted SX2 activation. Finally, we show that biological agents, such as oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, could also induce HO-1 expression via an ARE-dependent mechanism. Prior induction of HO-1 expression, using cobalt-protoporphyrin, protected RAW264.7 cells against DEP-induced toxicity. Taken together, these data show that HO-1 plays an important role in cytoprotection against redox-active DEP chemicals, including quinones.

Animal models of asthma: potential usefulness for studying health effects of inhaled particles

Asthma is now recognized to be a chronic inflammatory disease that affects the whole lung. Incidence appears to be increasing despite improved treatment regimens. There is substantial epidemiological evidence suggesting a relationship between the incidence and severity of asthma (e.g., hospitalizations) and exposure to increased levels of air pollution, especially fine and ultrafine particulate material, in susceptible individuals. There have been a few studies in animal models that support this concept, but additional animal studies to test this hypothesis are needed. However, such studies must be performed with awareness of the strengths and weaknesses of the currently available animal models. For studies in mice, the most commonly used animal, a broad spectrum of molecular and immunological tools is available, particularly to study the balance between Th1 and Th2 responses, and inbred strains may be useful for genetic dissection of susceptibility to the disease. However, the mouse is a poor model for bronchoconstriction or localized immune responses that characterize the human disease. In contrast, allergic lung diseases in dogs and cats may more accurately model the human condition, but fewer tools are available for characterization of the mechanisms. Finally, economic issues as well as reagent availability limit the utility of horses, sheep, and primates.

Exposure to diesel exhaust aggravates nasal allergic reaction in guinea pigs

Diesel exhaust particulates (DEP) () and exposure to diesel exhaust (DE) induce nasal mucosal hyperresponsiveness to histamine. Therefore, in the present study, we investigated whether or not exposing guinea pigs to DE aggravates the nasal allergic reaction induced by repeated nasal administration of ovalbumin (OVA). Guinea pigs were exposed to filtered air or to DE (DE containing 0.3 or 1.0 mg/m(3) of DEP) for 5 wk. During exposure to filtered air or to DE, guinea pigs were administered 1% of OVA in saline into the nasal cavities once a week. Sneezes were counted and nasal secretions were measured as indices of sneezing responses and rhinorrhea for 20 min after OVA administration. Titers of specific anti-OVA-IgG and anti-OVA-IgE and the number of eosinophils infiltrated into both nasal epithelium and subepithelium were measured at the end of the exposure to DE. Exposure to DE enhanced the number of sneezes and the amount of nasal secretions induced by OVA. Titers of specific anti-OVA-IgG and anti-OVA-IgE also significantly increased in DE-exposed animals. Exposure to DE also augmented the number of eosinophils that infiltrated both the nasal epithelium and the subepithelium induced by OVA. These results suggest that exposure to DE enhances the nasal allergic reaction induced by repeated antigen administration in guinea pigs.

Exposure to motor vehicle traffic and allergic sensitization. The Swiss Study on Air Pollution and Lung Diseases in Adults (SAPALDIA) Team

We examined the association between the presence of an allergic sensitization and seasonal allergic diseases or symptoms and the exposure to road traffic in Basel, Switzerland. Traffic counts at the domiciles of subjects ranged from 24 to 32,504 cars per 24 hours, with a median of 1,624. To investigate the relation of road traffic and allergies, we matched the data of the traffic inventory of Basel with those of the 820 participants of the SAPALDIA study (Swiss Study on Air Pollution and Lung Diseases in Adults), ages 18-60 years, who had completed a detailed respiratory health questionnaire and had undergone allergy testing (skin prick tests and serologic examinations). We observed a positive association with a sensitization to pollen that was most pronounced among persons with a duration of residence of at least 10 years. The odds ratios (adjusted for educational level, smoking behavior, number of siblings, age, sex, and family history of atopy) for cars, contrasting four exposure categories with the lowest quartile as referent category, were 1.99 [95% confidence interval (CI) = 0.91-4.38], 2.47 (95% CI = 1.06-5.73), and 2.83 (95% CI = 1.26-6.31). These results suggest that living on busy roads is associated with a higher risk for a sensitization to pollen and could possibly be interpreted as an indication for interactions between pollen and air pollutants. We did not, however, find a similar relation between motor vehicle traffic and hay fever or seasonal allergic symptoms, and we saw no trend that increasing traffic exposure was associated with a rise in sensitization rates to indoor allergens.

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.

Resistance of very young mice to inhaled allergen sensitization is overcome by coexposure to an air-pollutant aerosol

The role of air pollution in the initiation of asthma is controversial. We sought to model the potential effects of air pollution on immune responses to inhaled allergens in developing lungs by using very young mice. Neonatal mice were repeatedly exposed to aerosolized ovalbumin (OVA; 3% in phosphate-buffered saline for 10 min/d, from Days 5 to 15 of age). Some mice were also exposed to leachate of residual oil fly ash (ROFA-s), a surrogate for ambient air particles, for 30 min, on Days 6, 8, and 10 of age). Repeated exposure of very young mice to allergen alone (OVA) or pollutant alone (ROFA-s) had no effect on airway hyperresponsiveness (AHR, measured as enhanced pause (Penh) with noninvasive plethysmography at Day 16 of age), and did not cause inflammation or OVA-specific antibody production. Similar exposures of adult mice to either OVA alone or to OVA + ROFA-s did result in AHR, without evidence of enhancement by combined exposure. In contrast, very young mice exposed to both OVA and ROFA-s showed significantly increased AHR (e.g., Penh with 50 mg/ml methacholine for OVA + ROFA-s versus OVA alone = 2.6 +/- 0.4 [mean +/- SE], versus 1.2 +/- 0.1; p < 0.01, n >/= 15), and produced OVA-specific IgE and IgG upon allergen challenge a week later. Immunostaining of airways taken from mice at Day 11 showed a marked increase in Ia(+) cells after OVA + ROFA-s exposure. We conclude that exposure to pollutant aerosols can disrupt normal resistance to sensitization to inhaled allergens, and can thereby promote development of airway hypersensitivity in this neonatal/juvenile mouse model.