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Effect of Diesel Exhaust on Immune Responses in C57BL/6 Mice Intranasally Immunized with Pollen Antigen
Abstract
To investigate the effect of diesel exhaust or particle-free diesel gas on immune responses in IgE low responder mice, C57BL/6 mice immunized intranasally with sugi basic protein were exposed to diesel exhaust or diesel gas components. We evaluated the changes in lymphocyte subpopulations, cell proliferation, chemokine production of cervical lymph nodes cells, and antigen-specific-antibody levels in plasma. Exposure to diesel gas decreased the percentage of CD4+ and TCR-beta+ T cells of cervical lymph nodes from immunized mice. Culture supernatants of cervical lymph nodes cells from diesel gas-exposed mice had significantly increased levels of macrophage inflammatory protein-1alpha and thymus and activation-regulated chemokine, but exposure to diesel exhaust did not affect it. Antigen-specific IgG2a titers in plasma were significantly enhanced after their exposure to diesel exhaust or gas. In contrast, exposure to diesel exhaust or gas markedly decreased antigen-specific IgG1 titers in immunized mice. These facts indicate that concurrent exposure to allergen and diesel exhaust or diesel gas modulates chemokine production in cervical lymph nodes cells and antibody production in plasma differentially.
... For most studies, the mode diameter of particles in whole exhaust was in the range of 22 to 70 nm. One study, Fujimaki et al. 2005, reported a particle diameter of 400 nm, and two studies, Watanabe 2005 andWatanabe et al. 2002, reported that over 90% of particles were smaller than 500 nm. The total particle numbers in whole exhaust ranged from 3.2×10 5 to 4.4×10 6 per cm 3 . ...
... Of the animal toxicological studies, three involved long-term exposure (Fujimaki and Kurokawa 2004;Fujimaki et al. 2005;Tanaka et al. 2013), while one involved exposure through gestation (Watanabe and Ohsawa 2002). Fujimaki and Kurokawa found that filtered and whole exhaust exposure increased chemokine production in cervical lymph node cells from mice treated with sugi basic protein (SBP), a major allergen of Japanese cedar pollen (Fujimaki and Kurokawa 2004). ...
... Fujimaki and Kurokawa found that filtered and whole exhaust exposure increased chemokine production in cervical lymph node cells from mice treated with sugi basic protein (SBP), a major allergen of Japanese cedar pollen (Fujimaki and Kurokawa 2004). Fujimaki et al. found that exposure to filtered and whole exhaust affected levels of anti-SBP antibodies, with decreases in anti-SBP IgG1 and increases in anti-SBP IgG2a (Fujimaki et al. 2005). In Tanaka et al., filtered and whole exhaust-exposed mice treated with ovalbumin showed increased cytokine and chemokine production, as well as increased release of myeloperoxidase into the alveolar space (Tanaka et al. 2013). ...
Background: Diesel exhaust is a complex mixture comprised of gases and particulate matter and is a contributor to ambient air pollution. To reduce health risks, recent changes in diesel engine technology have significantly altered the composition of diesel exhaust, primarily by lowering emissions of particulate matter. However, animal toxicological studies continue to report health effects following exposure to diesel exhaust from engines employing particulate filters. The cause of these effects remains unclear.
Objective and methods: To gain an understanding of the role of both particle-filtered and whole diesel exhaust on specific health outcomes, we conducted a systematic review in which we examined animal toxicological and controlled human exposure studies that included a comparison between inhalation of particle-filtered and whole diesel exhaust on any health endpoint.
Results: We identified 26 studies that met both the inclusion and study evaluation criteria. For most health outcomes, the particle filtration methods employed in the included studies did not appreciably attenuate the health effects associated with exposure to whole diesel exhaust. There were also several health endpoints for which significant effects were associated with exposure to either particle-filtered or whole diesel exhaust, but not to both.
Conclusions: Overall, the results from this systematic review demonstrate that exposure to different components in diesel exhaust can have distinct and independent health effects. Thus, to better inform human health risk assessments, future studies aimed at elucidating the health effects from diesel exhaust should include exposure to both particle-filtered and whole diesel exhaust.
... While a number of pollutants have been associated with these outcomes, particulate air pollution has been prominent among them. In particular Diesel exhaust has been shown to be an adjuvant enhancing response to allergen challenges [11][12][13][14][15]. ...
Background:
Asthma exacerbation and other respiratory symptoms are associated with exposure to air pollution. Since environment affects gene methylation, it is hypothesized that asthmatic responses to pollution are mediated through methylation.
Materials & methods:
We study the possibility that airborne particulate matter affects gene methylation in the asthma pathway. We measured methylation array data in clinic visits of 141 subjects from the Normative Aging Study. Black carbon and sulfate measures from a central monitoring site were recorded and 30-day averages were calculated for each clinic visit. Gene-specific methylation scores were calculated for the genes in the asthma pathway, and the association between the methylation in the asthma pathway and the pollution measures was analyzed using sparse Canonical Correlation Analysis.
Results:
The analysis found that exposures to black carbon and sulfate were significantly associated with the methylation pattern in the asthma pathway (p-values 0.05 and 0.02, accordingly). Specific genes that contributed to this association were identified.
Conclusion:
These results suggest that the effect of air pollution on asthmatic and respiratory responses may be mediated through gene methylation.
Recently, our laboratory reported that exposure to nanoparticle-rich diesel exhaust (NRDE) for 3 months impaired hippocampus-dependent spatial learning ability and up-regulated the expressions of memory function-related genes in the hippocampus of female mice. However, whether NRDE affects the hippocampus-dependent non-spatial learning ability and the mechanism of NRDE-induced neurotoxicity was unknown. Female BALB/c mice were exposed to clean air, middle-dose NRDE (M-NRDE, 47 μg/m(3)), high-dose NRDE (H-NRDE, 129 μg/m(3)), or filtered H-NRDE (F-DE) for 3 months. We then investigated the effect of NRDE exposure on non-spatial learning ability and the expression of genes related to glutamate neurotransmission using a novel object recognition test and a real-time RT-PCR analysis, respectively. We also examined microglia marker Iba1 immunoreactivity in the hippocampus using immunohistochemical analyses. Mice exposed to H-NRDE or F-DE could not discriminate between familiar and novel objects. The control and M-NRDE-exposed groups showed a significantly increased discrimination index, compared to the H-NRDE-exposed group. Although no significant changes in the expression levels of the NMDA receptor subunits were observed, the expression of glutamate transporter EAAT4 was decreased and that of glutamic acid decarboxylase GAD65 was increased in the hippocampus of H-NRDE-exposed mice, compared with the expression levels in control mice. We also found that microglia activation was prominent in the hippocampal area of the H-NRDE-exposed mice, compared with the other groups. These results indicated that exposure to NRDE for 3 months impaired the novel object recognition ability. The present study suggests that genes related to glutamate metabolism may be involved in the NRDE-induced neurotoxicity observed in the present mouse model.
Epidemiological studies have indicated associations between day-to-day particulate air pollution and increased risks of various adverse health outcomes. Although an association between exposure to diesel exhaust particles (DEPs) and the development of pulmonary inflammation has been reported, there are limited reports on the neurotoxic effects of DEPs, particularly those of nanoparticle-rich diesel exhaust (NRDE). In this minireview, we highlighted the effects of NRDE which was generated in the National Institute for Environmental Studies, on hippocampus-dependent spatial learning ability and the expression of memory-function-related genes, neurotrophins, and proinflammatory cytokines in a mouse model.
We investigated the effect of exposure to nanoparticle-rich diesel exhaust (NRDE) on hippocampal-dependent spatial learning and memory function-related gene expressions in female mice. Female BALB/c mice were exposed to clean air, middle-dose NRDE (M-NRDE), high-dose NRDE (H-NRDE) or filtered diesel exhaust (F-DE) for three months. A Morris water maze apparatus was used to examine spatial learning. The expression levels of the N-methyl-D-aspartate (NMDA) receptor subunit, proinflammatory cytokines and neurotrophin mRNAs in the hippocampus were then investigated using real-time RT-PCR. Mice exposed to H-NRDE required a longer time to reach the hidden platform and showed higher mRNA expression levels of the NMDA receptor subunit NR2A, the proinflammatory cytokine CCL3, and brain-derived neurotrophic factor (BDNF) in the hippocampus, compared with the findings in the control group. These results indicate that three months of exposure to NRDE affected spatial learning and memory function-related gene expressions in the female mouse hippocampus.
By virtue of their target cell specificity, chemokines have the potential to selectively recruit leukocyte subpopulations into sites of inflammation. Their role in regulation of T lymphocyte traffic into lymph nodes during the development of an immune response has not previously been explored. The sensitization phase of contact hypersensitivity induced by the hapten, dinitrofluorobenzene (DNFB) in the mouse was used as a model of T lymphocyte trafficking in response to antigenic stimulation. Rapid accumulation of CD8+ and CD4+ T cells in the draining lymph nodes was closely associated with strongly enhanced expression of macrophage inflammatory protein (MIP)-1α and MIP-1β mRNAs and proteins. Mast cells accumulating in the nodes during DNFB sensitization were the predominant source of MIP-1β, whereas MIP-1α was expressed by multiple cell types. Neutralization of these chemokines profoundly inhibited T lymphocyte trafficking into lymph nodes and altered the outcome of a subsequent challenge to DNFB. Thus, β-chemokines regulate T lymphocyte emigration from the circulation into lymph nodes during an immune response and contribute significantly to the immunologic outcome.
The increasing prevalence of allergic rhinitis in many countries is becoming a social problem. It is important to determine whether air pollutants are related to the increase in the prevalence rate of allergic rhinitis or not. In this respect, it is necessary to elucidate whether exposure to air pollutants affects the nasal mucosa and causes nasal mucosal hyperresponsiveness to chemical mediators released by antigen-antibody reactions. A previous study revealed that diesel exhaust particulates are potent in augmenting increases in nasal congestion and nasal secretion induced by histamine (T. Kobayashi and T. Ito, 1995, Fundam. Appl. Toxicol. 27, 195-202). In the present study, using a rhinitis model of guinea pigs, we investigated whether short-term (3-hr) exposure to diesel exhaust induces nasal mucosal hyperresponsiveness to histamine. Guinea pigs of each group were exposed to filtered air or to a low or high concentration of diesel exhaust (1 and 3.2 mg/m3 particulates in diluted diesel exhaust, respectively) for 3 hr. After diesel exhaust exposure, sneezing frequency, nasal secretion from the nostril, and intranasal airway resistance induced by histamine were measured as indices of sneezing response, rhinorrhea, and nasal congestion, respectively. Short-term exposure to a low or high concentration of diesel exhaust itself did not induce sneezing, nasal secretion, or nasal congestion. However, short-term exposure to a high concentration of diesel exhaust augmented sneezing and nasal secretion, but not nasal congestion, induced by histamine. In conclusion, short-term exposure to diesel exhaust potently induces nasal mucosal hyperresponsiveness.
In this study using guinea pigs, we investigated the effects of diesel exhaust (DE) containing diesel exhaust particulate (DEP) on 1) vascular permeability induced by histamine, 2) nasal mucosal permeability to horseradish peroxidase (HRP), and 3) eosinophilic epithelial infiltration. The vascular permeability induced by histamine was enhanced significantly and dose-dependently in DE-exposed guinea pigs. The HRP reaction products in epithelial cells and intercellular spaces were significantly and dose-dependently increased in those guinea pigs. Eosinophil infiltration into the epithelial layer was significantly increased in guinea pigs exposed to DE containing 3.2 mg/m³ DEP, and the reactivity of the nasal mucosa to histamine solution applied on the nasal mucosa was significantly enhanced in those guinea pigs. These findings suggest that DE may play an important role not only in promoting nasal hyperreactivity induced by the enhancement of absorption of antigen through the nasal epithelium, but also in inducing eosinophil infiltration in nasal mucosa and enhancing nasal mucosal reactivity.
Epidemiological evidence suggests that air pollutants may increase the prevalence of bronchial hyperresponsiveness and exacerbate the asthma. However, the role of the ambient level of NO2 in the induction of allergic disease is still unclear. In this study, we investigated whether exposure of mice of low concentrations of NO2 before or after sensitization with ovalbumin (OVA) enhances an antigen-specific immune response. Sensitization of mice with an aerosol of OVA at 3-wk intervals after initiation of 2 ppm NO2 exposure resulted in suppression of OVA-specific immunoglobulin (Ig) E, IgG1, and IgG(2a) antibody production in plasma. OVA-specific IgG1 and IgG(2a) antibody production was also significantly decreased in the bronchoalveolar lavage (BAL) fluid by exposed mice. In contrast, when mice were exposed to NO2 after intraperitoneal immunization with OVA and sensitization with OVA aerosol at 3-wk intervals during NO2 exposure, OVA-specific IgE antibody production in the plasma of mice exposed to 0.5 and 1.0 ppm NO2 was significantly increased when compared with control mice. Moreover, antigen-specific IgG1 and IgG(2a) antibody production in the plasma of exposed mice showed a trend to be increased, but not significantly. OVA-specific IgG1 and IgG(2a) antibody production was significantly increased in the BAL fluid of mice exposed to 1 ppm NO2 and 2 ppm NO2, respectively. To assess the factors modulating antibody production in the NO2-exposed mice before or after immunization with OVA, the local level of cytokine in BAL fluid was measured using an enzyme-linked immunosorbent assay (ELISA). In the BAL fluid of mice exposed to NO2 after immunization there were no differences in interleukin-4 (IL-4) and IL-10 levels, while IL-12 production showed a significant decrease. Although IL-10 in the BAL fluid of mice exposed to 2.0 ppm NO2 before immunization was increased significantly, IL-4 levels showed a significant decreases in mice exposed to 1.0 and 2.0 ppm NO2. These results suggest that ambient levels of NO2 increase antibody production in mice preimmunized with antigen, but not in mice without preimmunization.
Allergic airway inflammation is characterized by peribronchial eosinophil accumulation within the submucosa of the airway of the lung. In the present study we have utilized a model of airway inflammation induced by intratracheal challenge with parasite (Schistosoma mansoni) egg antigen (SEA) in presensitized mice. The recruitment of neutrophils and eosinophils into the airway was found to be maximal at 8 and 48 h post challenge, respectively. Since macrophage inflammatory protein-1α (MIP-1α) has previously been found to be chemotactic for eosinophils, in vitro, we postulated that MIP-1α was involved in the airway inflammation and more specifically in eosinophil recruitment into the airway. Initial studies demonstrated an increase in MIP-1α mRNA expression at 8 h post-SEA challenge, as compared to vehicle-treated control mice. We next demonstrated a significant increase in MLP-1α protein in the lungs of SEA-challenged mice at 8 h compared to control challenged mice, correlating to the mRNA data. Immunohistochemical staining of lungs from SEA-challenged mice demonstrated MIP-1α protein expression in airway epithelial cells, alveolar macrophages and in recruited mononuclear cell populations. Immunolocalization of MIP-1α to cells within the bronchoalveolar lavage fluid demonstrated that macrophages and eosinophils stained positive for the protein. To determine the contribution of MIP-1α expression to eosinophil accumulation, SEA-challenged mice were passively immunized with either neutralizing MIP-1α antibodies or normal rabbit IgG, 3-4 h prior to the intratracheal SEA challenge. These studies demonstrated a > 50% decrease in eosinophil recruitment to the lungs and airway in animals receiving neutralizing MIP-1α antibodies with no effect on early neutrophil recruitment. These results suggest that the production of MIP-1α, induced by an antigen-specific response, lays an important role in recruitment of eosinophils in this airway model of inflammation.
Several specific conclusions can be drawn from these studies: 1. IL-4 is required for the generation of both primary polyclonal and secondary antigen-specific IgE responses in vivo. 2. IL-4 is required to maintain established, ongoing, antigen-specific and polyclonal IgE responses. 3. Most, but not all, polyclonal IgE production during a secondary immune response is IL-4-dependent. Memory B cells that have already switched to IgE at the DNA level may no longer require stimulation with IL-4 to be induced to secrete IgE. 4. The generation of a secondary IgE response is not dependent upon the presence of IL-4 during primary immunization. However, if IL-4 is not present during primary immunization, it is required during secondary immunization for the generation of an IgE response. 5. IL-4 does not appear to be required for the generation of in vivo IgG1 responses, and in at least some instances, does not contribute significantly to the generation of IgG1 responses in vivo. 6. A late-acting form of T-cell help other than IL-4 appears to be required for the generation of an IgE, but not an IgG1 response. 7. An antibody that inhibits IL-4 binding to IL-4 receptors affects Ig isotype selection in the same way as an antibody that neutralizes IL-4. 8. IFN-gamma can act in both spontaneous and induced immune responses to suppress IgE production. 9. IFN-gamma can also suppress IgG1 production and stimulate IgG2a production. However, IFN-gamma appears to suppress polyclonal IgG1 responses more than antigen-specific IgG1 responses, and it enhances, but is not required for, the generation of IgG2a responses. 10. IFN-alpha appears to resemble IFN-gamma in its ability to inhibit IgE and enhance IgG2a responses in GaM delta-injected mice, but it requires the presence of IFN-gamma to suppress IgG1 production in these mice. 11. Both IFN-alpha and IFN-gamma appear to be able to decrease IgE production in some human patients. 12. There is no direct evidence that IL-5 contributes to the generation of in vivo antibody responses. Two general conclusions may also be drawn.(ABSTRACT TRUNCATED AT 400 WORDS)
Our previous study indicated that the IgE antibody responses in mice immunized with intraperitoneal injection of the antigens mixed with diesel-exhaust particulates (DEP) were higher than those in the animals immunized with the antigens alone. We examined the adjuvant activity of DEP inoculated by the intranasal route, i.e., the natural entrance of DEP. In 3-week interval immunization, the IgE antibody responses in mice immunized with intranasal inoculation of ovalbumin (OA) mixed with DEP were higher than responses in the animals immunized with OA alone. DEP had an adjuvant activity for anti-OA IgE antibody production, even in a small dose such as 1 micrograms administered with a 3-week interval. Also in 1-week interval immunization, the enhancing effect of DEP on anti-OA IgE antibody production was demonstrated when mice were immunized with intranasal inoculation of OA and DEP. The possibility cannot be excluded that DEP, which are kept buoyant in the environmental atmosphere of urban districts, may exert an adjuvant activity for IgE antibody production after being inhaled into the human body and have some relation to the mechanism of the outbreak of allergic rhinitis caused by pollens in Japan.
Repeated exposure of high-IgE-responder Brown Norway (BN) rats to an aerosol of ovalbumin (OVA) once weekly triggered progressively increasing levels of OVA-specific IgG in serum. In contrast, responses in the IgE class were transient, declining from peak titers during the third week to background levels by Week 5, despite continuing aerosol exposure. Subsequent parenteral challenge of these animals revealed a state of antigen- and IgE isotype-specific tolerance. Adoptive transfer of splenocytes or pooled respiratory tract lymph node (RTLN) cells from aerosol-exposed animals to naive rats abrogated subsequent OVA-specific primary IgE responses in the recipients, but did not affect specific IgG responses, and kinetic studies indicated that these suppressor cells arose first in the RTLN. Transfer studies employing individual lymph node groups which constituted the RTLN pool pinpointed the superficial cervical nodes, which drain the uppermost portion of the respiratory tract, as the major source of suppressor cells. Fractionation of cell populations before adoptive transfer employing monoclonal antibodies directed against T-cell markers, defined a population of suppressor cells generated by aerosol exposure which expressed both the W3/13 (pan T-cell) and OX8 (cytotoxic/suppressor T-cell) antigens, but which was negative for the W3/25 (helper T-cell) marker. Analysis of the IgE and IgG responses induced by OVA inhalation was performed employing the ELISA plaque technique, recently developed in this laboratory. These studies revealed the parathymic and posterior mediastinal nodes draining the lower lung, as the major sites of specific IgE and IgG production; smaller numbers of OVA-specific IgG-secreting cells (but none secreting specific IgE) were detected in the nodes draining the upper respiratory tract, while antibody secretion outside the respiratory tract was restricted to comparatively few cells in the spleen. The ELISA plaque assay was also employed to enumerate total numbers of cells secreting the IgE isotype in aerosol-exposed and control rats, employing samples from 10 different lymphoid organs. Approximately 50% of the IgE-secreting cells in these animals were localized in RTLN, as opposed to 25% in gut-associated lymphoid tissues. These data are discussed in relation to the pivotal role of respiratory-tract associated lymphoid tissues in regulation of IgE responses to aeroallergens.
To investigate cytokine production stimulated by diesel exhaust particulates (DEP) and antigen through the intranasal route, mice were administered with DEP mixed with ovalbumin (OA) 3 times at an interval of 3 weeks. After the last instillation, cervical lymph node cells (LNC) were cultured in vitro with OA and antigen-presenting cells. The proliferative response to OA in cervical LNC from mice instilled with DEP and OA was noted to have increased significantly compared to mice instilled with OA alone. Interleukin 4 (IL-4) and interferon (IFN)-gamma in culture supernatants were measured with ELISA. OA-stimulated IL-4 production in cervical LNC from mice instilled with DEP and OA markedly increased beyond that in the control mice. In contrast, OA-stimulated IFN-gamma production in cervical LNC from mice instilled with OA was 3 times that for DEP and OA-instilled mice. OA-specific IgE antibody in sera showed a trend to be increased in mice intranasally instilled with DEP and OA. These results suggest that intranasal instillation of DEP and antigen in mice may modulate in vitro antigen-stimulated cytokine production from cervical LNC with a consequent increase in IgE antibody production.
Bovine retinal extract (RE) is a heterologous mixture of highly uveitogenic proteins including S-Antigen (S-Ag), interphotoreceptor retinol binding protein (IRBP) and rhodopsin, and is a potent inducer of experimental autoimmune uveoretinitis (EAU). Intranasal inoculation of Lewis rats with RE performed daily for 10 days prior to immunization with RE suppresses both the severity and the incidence of the clinical response and histopathological changes in EAU. Significant suppression of the disease in treated animals could be achieved with a total (cumulative) intranasal inoculum of 42 micrograms of antigen. Animals which were treated with extract exhibited a normal total antibody response to S-Ag, IRBP and retinal extract when compared with controls [phosphate-buffered saline (PBS) treated] animals. The antibody response in tolerized animals was predominantly anti-S-Ag IgG2a with suppression of anti-S-Ag IgM response. Treated animals had a significantly suppressed delayed-type hypersensitivity (DTH) response to retinal extract but normal response to purified protein derivative (PPD) compared to control animals. Adoptive transfer of splenocytes from treated animals also demonstrated some protection against RE-induced EAU. These results demonstrate that tolerance induction impairs the onset and severity of EAU by inhibiting the DTH response to heterologous mixture of retinal antigens.
Intranasal administration of protein antigen is an efficient way to induce mucosal tolerance. Suppressive mechanisms that might be involved in this phenomenon include down-regulation of T-helper type-1 (Th1)-mediated processes by Th2 cells. However, since Th2 responses can also be subjected to mucosal tolerance, we wanted to investigate whether suppression of a typical Th1 response, such as a delayed-type hypersensitivity (DTH) reaction by intranasal tolerance induction, was causally related to up-regulation of Th2 responses. We therefore treated mice either systemically or locally with anti-interleukin-4 (IL-4) or anti-IL-10 antibodies before intranasal tolerance induction or before sensitization for DTH to see whether we could prevent or abrogate tolerance. Although the up-regulation of antigen-specific IgE levels in tolerant mice could be prevented by anti-IL-4 treatment, the extent of tolerance as measured by suppression of DTH was not affected. We therefore conclude that up-regulation of Th2 responses observed after intranasal tolerance induction is an additional or consequential rather than a necessary reaction.
We investigated the effect of diesel exhaust particles (DEP) on oral tolerance. Oral tolerance was induced by feeding mice with 10 mg of hen egg lysozyme (HEL) daily over a period of 5 days before immunization with the antigen. Varying doses of DEP were orally administered immediately before each feeding of HEL. The results showed that oral administration of HEL significantly suppressed production of anti-HEL IgG, IgG1 and IgG2a antibodies, delayed-type hypersensitivity and proliferative responses of lymph node cells to the antigen. The suppression of these immune responses to HEL by the oral antigen was associated with a marked decrease in secretion of interferon-gamma and interleukin-4 from the lymphoid cells. Administration of DEP dose-dependently blocked suppression by oral HEL of antigen-specific IgG, IgG1 and IgG2a antibody production, delayed-type hypersensitivity and lymphoid cell proliferation. The suppression by the fed antigen of secretion of interferon-gamma and interleukin-4 was also markedly diminished by the particles. Thus, DEP appear to be effective in blocking induction of oral tolerance.
It has been reported that diesel exhaust (DE) particulates augment increases in nasal congestion and nasal secretion induced by histamine (His). We also showed that short-term (3-h) exposure to DE induces nasal mucosal hyperresponsiveness to His. Therefore, in the present study we investigated that whether 4-week exposure of guinea pigs to diesel exhaust would likewise induce nasal mucosal hyperresponsiveness to His. Sneezing number, nasal secretion from the nostril, and intranasal airway resistance induced by His were measured as indices of sneezing response, rhinorrhea, and nasal congestion, respectively. Guinea pigs of each group were exposed to filtered air, with or without a low or high concentration of DE for 3, 7, or 28 days. Exposure to a low or high concentration of DE itself did not induce sneezing, nasal secretion, or nasal congestion. However, exposure to a high concentration of DE augmented that the number of sneezes induced by His, whereas exposure to a low concentration of DE had no significant effect. Exposure to DE for 7 and days tended to augment an increase in nasal secretion induced by exposure to His aerosol in a DE concentration-dependent fashion. The augmentation, however, was not statistically significant. Exposure to high or low DE for 3 or 7 days had no significant effect on the increase in intranasal pressure (INP) induced by a 10-min exposure to His aerosol, but exposure to high DE for 28 days augmented the increase in INP induced by His, significantly. Exposure to low DE for 28 days did not augment the increase in INP immediately after inhalation of His aerosol. These results reveal that 4-week exposure to high DE induces nasal mucosal hyperresponsiveness in guinea pigs.
The present study was undertaken to examine whether oral administration of soluble antigen together with diesel exhaust particles (DEP) induced the systemic immune response in mice. Mice were orally given 1 mg of hen egg lysozyme (HEL) with varying doses of DEP every 3 days over a period of 15 days. The results showed that oral administration of HEL plus DEP produced anti-HEL IgG antibodies in serum in a dose-related fashion, while either HEL or DEP alone failed to show the antigen-specific IgG antibody production. Production of anti-HEL IgG2a and IgG1 antibodies, which are dependent on Th1 and Th2 CD4(+) T cells, respectively, was seen in mice fed with combined HEL and DEP, although anti-HEL IgG1 antibodies appeared to be more efficiently produced by lower doses of DEP than anti-HEL IgG2a antibodies. There was marked antigen-specific proliferation of spleen cells in mice treated with HEL and DEP. The anti-HEL antibody production and lymphoid cell proliferation to the antigen were associated with marked secretion of the Th1 cytokine IFN-gamma as well as the Th2 cytokine IL-4. These results suggest that DEP may act as a mucosal adjuvant in the gut enhancing systemic Th1 and Th2 immune responses and might play a role in oral immunization and food allergy.
The ambient atmosphere contains a large number of non-biological particles produced by human inhabitation. Following inhalation, ultrafine particles deposit in large numbers in the conducting and gas exchange areas of the lung. By virtue of their extremely small size, they have a large surface area capable of carrying large numbers of toxic substances and free radicals on their surface. This provides the opportunity for surface chemistry of the particles to have a profound biological effect on the cells which come in contact with them. Alveolar macrophages rapidly phagocytose particles which deposit in the airways, however, their phagocytic capacity decreases when the particle load is high. This results in their prolonged retention in the lung and increased interaction with epithelial and other cells. Free radicals generated via transition metals associated with particles lead to oxidative damage and activation of macrophages resulting in the release of several pro-inflammatory mediators, which initiate an acute cellular and mediator inflammatory response in the airways. Epithelial cells on coming in contact with ultrafine particles actively phagocytose them, followed by increased production and release of a large number of pro- inflammatory cytokines, which further amplify the inflammatory response. Particles generated from diesel exhaust on reaching the airway submucosa produce a qualitative and quantitative increase in IgE levels, which further trigger an allergic inflammatory response. Ultrafine particles which penetrate the interstitium make contact with interstitial macrophages and other sensitive cell populations and release inflammatory mediators which can enter the blood stream to produce a low-grade systemic inflammatory response, with effects on blood platelets and clotting factors, thereby increasing plasma viscosity. This could lead to cardiovascular dysfunction, especially in patients with an already compromised cardiovascular status.
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.
Through an imbalance in Th1 and Th2 cytokine profiles, diesel exhaust particles (DEP) are thought to induce Th2-dominated IgE and IgG1 production. However, the roles of CD4+ and CD8+ T-cell subtypes in the increased immune responses to antigen in mice exposed to DEP are unclear. In the present study, we investigated whether treatment with anti-CD4 or anti-CD8 mAb abrogated the adjuvant activity of DEP. On day -1 and day 1, each group of mice was injected intraperitoneally with anti-CD4, anti-CD8, or rat IgG (vehicle). On day 0, the mice were immunized with ovalbumin (OVA) or OVA plus DEP. After 3 weeks, each mouse was boosted with 10 microg of OVA alone. On day 7 after the first injection with OVA+DEP or OVA alone, the numbers of total, IA+, CD80+/IA+ and CD86+/IA+ cells in peritoneal exudate cells (PEC) were higher in OVA+DEP-immunized mice than in OVA-immunized mice. Depletion of CD8+ cells resulted in a modulation of the production of granulocyte-macrophage colony-stimulating factor, IL-12 and PGE(2) in peritoneal exudate fluid from OVA+DEP-immunized mice. On day 28, DEP injection markedly increased IL-4 production in the culture supernatants of spleen cells from CD4+ or CD8+-depleted mice. Depletion of CD8+ cells in OVA+DEP-immunized mice resulted in a decrease in IFN-gamma production compared with that in OVA-immunized mice. Adjuvant activity of DEP was observed in anti-OVA IgE, anti-OVA IgG1, anti-OVA IgG3, and total IgE production. Depletion of CD4+ T cells abrogated the adjuvant effect of DEP on anti-OVA IgE, and anti-OVA IgG1 production in plasma. However, depletion of CD8+ T cell inhibited the upregulated anti-OVA IgG3 production. These findings suggest that DEP injection may affect not only the function of CD4+ cells but also that of CD8+ T-cell subsets to modulate the synthesis of proinflammatory cytokine in PEC and type-1 and type-2 cytokine production in spleens.
Exposure to diesel exhaust (DE) increased airway inflammatory responses and airway responsiveness to allergen challenge. To clarify the roles of T cells in DE exposure-induced early inflammation, we studied the effect of CD4 and CD8 cells on the effect DE might have on allergic inflammation by using monoclonal antibody-mediated cellular depletion assays. In the bronchoalveolar lavage (BAL) fluid, the numbers of inflammatory cells from 3 mg/m(3) DE-exposed and ovalbumin (OVA)-immunized mice markedly increased. Depletion of CD4(+) cells resulted in reduced accumulation of inflammatory cells. DE exposure to OVA-immunized mice significantly increased interleukin (IL)-1 beta production but decreased IL-12 production. DE exposure significantly enhanced production of the macrophage inflammatory proteins (MIP)-1 alpha and MIP-2, but not monocyte chemoattractant protein (MCP)-1 and regulated upon activation normal T cells expressed and secreted (RANTES). Treatment with anti-CD4 and anti-CD8 mAbs abrogated the adverse effect of DE exposure. In CLN cells from OVA + DE-exposed mice, CD45R/B220-, CD3-, CD4-, and CD8-positive cells were significantly increased, but the OVA-stimulated cytokine production remained at the same levels with OVA-immunized mice. These findings suggest that the induction of early inflammatory responses by DE exposure may initially be related to the modulated function of lymphocyte subpopulations.
The objective of this study was to evaluate if diesel exhausts could favor helper T cell type (Th) 2-associated allergic reactions either through an increased production of Th2-associated chemokines and of their associated receptors or through a decrease of Th1-attracting chemokines and chemokine receptors. Diesel but not allergen exposure of peripheral blood mononuclear cells from subjects with allergy induced a release of I-309, whereas both diesel and Der p 1 induced an early but transient release of monokine induced by IFN-gamma and a late release of pulmonary and activation-regulated chemokine. Although both Th1- and Th2-attracting chemokines were induced, the resulting effect was an increased chemotactic activity on Th2 but not Th1 cells. Surprisingly, diesel induced a late increase in the expression of the Th1-associated CXC receptor 3 and CC receptor 5. T cell CXC receptor 3 upregulation was not associated with an increased migration to its ligands. These two antagonistic effects have been previously reported as a scavenger mechanism to clear chemokines. Altogether, these results suggest that diesel, even without allergen, may amplify a type 2 immune response but that it can also increase late Th1-associated chemokine receptor expression, perhaps as a scavenger mechanism to clear pro-Th1 chemokines and promote the Th2 pathway.
Previously, we showed that exposure to diesel exhaust (DE) increased inflammatory cells in the airway and cytokine production from local lymph-node cells after antigen stimulation. To clarify the role of particle-free diesel gas components in induction of allergic inflammation, we compared the effect of DE and gas components on pollen-antigen-stimulated chemokine production by cervical lymph nodes (CLN) cells in BALB/c mice. Groups of mice were exposed to 0 (control), 1.0 mg diesel exhaust particles (DEP)/m(3) (DE), or filtered 1.0 mg DEP/m(3) DE (gas) for 12 h daily for 5 wk. Each group of mice was injected intraperitoneally with sugi basic protein (SBP), a major allergen of Japanese cedar pollen, immediately before their exposure to DE or gas. On days 14 and 35, each mouse received an additional SBP intranasally. Exposure to DE or gas did not affect the lymphocyte subpopulations of CLN. Culture supernatants of CLN cells from DE-exposed, SBP-immunized mice had significantly increased levels of monocyte chemoattractant protein-1. Exposure to gas significantly increased the amount of thymus- and activation-regulated chemokine and macrophage inflammatory proteins-1 alpha in the CLN cells from SBP-immunized mice. These results suggest that Gas components as well as DEP may differentially regulate production of chemokines at local sites.
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