Induction of the imbalance of helper T-cell functions in mice exposed to diesel exhaust

Sensitivity to Ozone, Diesel Exhaust Particles, and Standardized Ambient Particulate Matter in Rats with aListeria Monocytogenes-Induced Respiratory Infection

Ambient particulate matter may increase respiratory allergic skewing of the T-cell-mediated immune response toward a T-helper-2 (Th2) response, with the consequence that the Th1 response develops less well. Successful clearing of a respiratory bacterial infection depends on an adequate Th1 immune response; therefore, the subject would not control the infection as well if exposed to particulate matter. To substantiate this hypothesis, we examined the effect of exposure to diesel exhaust particles (DEP) and urban particulate matter (EHC-93, Ottawa dust) on rats with a Listeria monocytogenes respiratory infection. Since this hypothesis has been confirmed for ozone, we used it as a positive control. Wistar rats were exposed to ozone (2 mg/m3 for 24 h/day for 7 days) and to DEP or to EHC-93 (50 microg/rat intranasally daily for 7 consecutive days). Twenty-four hours after the last exposure, the rats were infected intratracheally with 1 x 10(6) L. monocytogenes bacteria. The number of L. monocytogenes was determined after 3, 4 and 5 days. Statistically significant increases of the number of L. monocytogenes in rats exposed to ozone were observed in the lungs and spleen at all three times. However, we found no significant differences in the numbers of bacteria that were found in rats exposed to DEP or EHC-93 compared to the saline-treated group at any of the three times. In conclusion, the results of this study do not support the hypothesis that exposure to DEP or EHC-93 reduces subsequent resistance to a respiratory infection in rats.

Effect of Formaldehyde Gas Exposure in a Murine Allergic Contact Hypersensitivity Model

To clarify the effect of formaldehyde (FA) gas exposure on contact hypersensitivity (CHS), CHS reactions against 2,4,6-trinitrochlorobenzene (TNCB) was studied in BALB/c mice with a low dose of FA gas exposure. The TNCB-induced CHS reactions were slightly suppressed by the FA gas exposure immediately after sensitization, whereas they were significantly enhanced and prolonged in mice continuously exposed to FA gas before and after sensitization. We showed that exposure to FA gas enhanced the Th2 dominant responses in draining lymph node (LN) in early stage of CHS. In contrast, T cell subsets and their intracellular cytokine production in the draining LN were similar during the early stage of CHS by FA gas exposure during the sensitization phase. The percentage of CD8+ T cells was increased, and the percentage of CD4+CD25+ T cells was decreased in the FA gas-exposed group at 72 hr after elicitation. These results indicate that FA gas-exposed might influence regulatory T cells. Furthermore, in the chronic CHS model that was repetitively elicited with TNCB, more intensive and prolonged CHS reactions, and increased numbers of mast cells were found in the FA gas-exposed group at 4 hr after elicitation than in the control group, FA gas exposure may alter the intensity of allergic CHS.

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

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

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.

Exposure of adult mice to environmental tobacco smoke fails to enhance the immune response to inhaled antigen

Epidemiologic evidence supports a role for environmental tobacco smoke (ETS) in the occurrence and severity of allergies/asthma. However, neither the precise combination of ETS and allergen exposure nor the mechanism (or mechanisms) by which these factors interact and contribute to asthma induction is known. Animal model studies have failed to establish a convincing relationship between ETS exposure and asthma induction, perhaps because of methodological inadequacies. Here, we tested the hypothesis that ETS inhalation would provoke an asthmatic response by overcoming normal airway tolerance to inhaled antigens. Our protocol combined daily ETS exposure with nose-only sensitization to ovalbumin. Three strains of mice were tested, each with a different level of susceptibility to airway hypersensitivity. Immunological responses were assessed by immunoglobulin production. Airway inflammation was assessed by bronchoalveolar lavage differentials and lung histopathology. Airway hyperresponsiveness was determined by methacholine challenge. The mice produced ovalbumin-specific antibodies following ovalbumin exposure in a strain-dependent manner. Only the A/J mice produced detectable levels of ovalbumin-specific immunoglobulin (Ig) E. Both A/J and BALB/c mice produced ovalbumin-specific IgG1 antibodies. The C57Bl/6 mice did not produce detectable levels of antibodies. The A/J mice also exhibited airway inflammation following ovalbumin exposure. Neither the C57Bl/6 nor the BALB/c mice exhibited signs of airway inflammation. Exposure to ETS failed to enhance ovalbumin-specific antibody production, airway inflammation, or hyperresponsiveness. Together these results indicate that ETS exposure accompanied by nose-only allergen sensitization fails to overcome aerosol tolerance in adult mice.

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.