Inherent redox properties of diesel exhaust particles: catalysis of the generation of reactive oxygen species by biological reductants.

The toxicity of diesel exhaust particles (DEP) can be due to the particle itself, extractable components, or both. Many studies focus on the biological properties of DEP-extractable components although it is possible that chemical properties inherent to the DEP itself can lead to toxicity. Thus, an examination of the chemistry inherent to DEP was carried out. Herein, we report that DEP are capable of catalyzing the consumption of O2 (monitored using a Clarke electrode) by ascorbate and thiols leading to the generation of reactive oxygen species. Consistent with the idea that DEP are capable of catalyzing the generation of reactive oxygen species, they were also found to catalyze DNA strand breakage via an O2- and reductant-dependent process. Significantly, extraction of DEP with either organic solvent (methylene chloride) or acid (aqueous HCl) did little to abrogate this chemistry. Finally, using electron paramagnetic spectrometry (EPR), DEP were found to have paramagnetic properties. The paramagnetic character of DEP may be important to their ability to catalyze the formation of reactive oxygen species and at least partially responsible for their toxicity. These findings indicate that studies that primarily consider or examine particle extracts as the toxic components of DEP may be insufficient in describing the toxicity associated with DEP exposure.     

Effects of diesel exhaust particles on cytokine production by splenocytes stimulated with lipopolysaccharide

It was previously shown that pulmonary exposure of mice to diesel exhaust particles (DEP) enhances inflammatory conditions induced by allergens or bacterial endotoxin (lipopolysaccharide: LPS) via enhanced local expression of cytokines. However, resolution of the underlying mechanisms, in which DEP exaggerate inflammation, remains uncompleted. Investigation of the actions of DEP on mouse-derived mononuclear cells may provide a clue to the mechanisms, because mononuclear cells produce and release several types of cytokines. The present study elucidated the effects of DEP on mononuclear cell reactions stimulated with LPS in vitro. ICR mouse-derived mononuclear cells, isolated from splenocytes, one of the secondary lymphoid tissues, were co-cultured with LPS (1 microg ml(-1)) and DEP (1, 10 or 100 microg ml(-1)). The protein levels of interferon (IFN)-gamma, interleukin (IL)-2, IL-10, and IL-13 in the culture supernatants were measured 72 h after the co-culture. LPS significantly increased the protein levels of IFN-gamma, IL-2 and IL-10. In the presence of LPS, DEP decreased the protein levels in a concentration-dependent manner with an overall trend, whereas DEP (1, 10 microg ml(-1)) moderately elevated the IL-13 level. These results suggest that DEP suppress cytokine production from mononuclear cells stimulated with LPS and provide a possible hint for DEP facilitation on inflammatory conditions, especially related to Th2 response, in vivo.     

Effect of diesel exhaust particles on allergic reactions and airway responsiveness in ovalbumin-sensitized brown Norway rats.

We have previously demonstrated that exposure to diesel exhaust particles (DEP) prior to ovalbumin (OVA) sensitization in rats reduced OVA-induced airway inflammation. In the present study, Brown Norway rats were first sensitized to OVA (42.3 +/- 5.7 mg/m3) for 30 min on days 1, 8, and 15, then exposed to filtered air or DEP (22.7 +/- 2.5 mg/m3) for 4 h/day on days 24-28, and challenged with OVA on day 29. Airway responsiveness was examined on day 30, and animals were sacrificed on day 31. Ovalbumin sensitization and challenge resulted in a significant infiltration of neutrophils, lymphocytes, and eosinophils into the lung, elevated presence of CD4+ and CD8+ T lymphocytes in lung draining lymph nodes, and increased production of serum OVA-specific immunoglobulin (Ig)E and IgG. Diesel exhaust particles pre-exposure augmented OVA-induced production of allergen-specific IgE and IgG and pulmonary inflammation characterized by marked increases in T lymphocytes and infiltration of eosinophils after OVA challenge, whereas DEP alone did not have these effects. Although OVA-sensitized rats showed modest response to methacholine challenge, it was the combined DEP and OVA exposure that produced significant airway hyperresponsiveness in this animal model. The effect of DEP pre-exposure on OVA-induced immune responses correlated with an interactive effect of DEP with OVA on increased production of reactive oxygen species (ROS) and nitric oxide (NO) by alveolar macrophages (AM) and alveolar type II (ATII) cells, NO levels in bronchoalveolar lavage fluid, the induction of inducible NO synthase expression in AM and ATII cells, and a depletion of total intracellular glutathione (GSH) in AM and lymphocytes. These results show that DEP pre-exposure exacerbates the allergic responses to the subsequent challenge with OVA in OVA-sensitized rats. This DEP effect may be, at least partially, attributed to the elevated generation of ROS in AM and ATII cells, a depletion of GSH in AM and lymphocytes, and an increase in AM and ATII cell production of NO.     

Time-course effects of systemically administered diesel exhaust particles in rats

Nanosized fraction of particulate air pollution has been reported to translocate from the airways into the bloodstream and act on different organs. However, the direct effect of these translocated particles is not well understood. In this study, we determined the time-course (6h, 18 h, 48 h and 168 h) effects of the systemic administration of 0.02 mg/kg diesel exhaust particles (DEP) on systolic blood pressure (SBP), systemic inflammation, oxidative status, and morphological alterations in lungs, heart, liver and kidneys in Wistar rats. SBP was significantly decreased at 6 h (P < 0.05) but no significant effects have been observed at later time points. The leukocyte numbers were increased at 6 h (P < 0.05) and 18 h (P < 0.05). However, the platelet numbers were significantly decreased (P < 0.05) 6 h following the systemic administration of DEP. The IL-6 concentrations in plasma was increased at 6 h (P < 0.05) and 18 h (P < 0.05). Similarly, superoxide dismutase activity was significantly increased at 6 (P = 0.01) and 18 h (P < 0.05) following DEP exposure. The direct addition of DEP (0.1–1 μg/ml) to untreated rat blood significantly induced in vitro platelet aggregation in a dose-dependent fashion. The activation of intravascular coagulation was confirmed by a dose-dependent shortening of activated partial thromboplastin time and the prothrombin time following in vitro exposure to DEP (0.25–1 μg/ml). Histological analysis revealed the presence of DEP in the lungs, heart, liver and kidneys. However, the morphological changes were only observed in the lungs, where the presence of infiltration of inflammatory cells was observed as early as 6 h, increased at 18 h, and decreased in intensity at 48 h and at 168 h. We conclude that the direct systemic administration of DEP caused acute effect on SBP (6 h) and systemic inflammation and oxidative stress mainly at 6 h and 18 h. Despite the presence of DEP in lungs, heart, liver and kidneys, the histopathological changes were only seen in the lung which suggests that, at the dose and time-points investigated, DEP cause inflammation and have a predilection for pulmonary tissue.     

Differential proinflammatory responses induced by diesel exhaust particles with contrasting PAH and metal content

Exposure to diesel engine exhaust particles (DEPs), representing a complex and variable mixture of components, has been linked with cellular production and release of several types of mediators related to pulmonary inflammation. A key challenge is to identify the specific components, which may be responsible for these effects. The aim of this study was to compare the proinflammatory potential of two DEP‐samples with contrasting contents of polycyclic aromatic hydrocarbons (PAHs) and metals. The DEP‐samples were compared with respect to their ability to induce cytotoxicity, expression and release of proinflammatory mediators (IL‐6, IL‐8), activation of mitogen‐activated protein kinases (MAPKs) and expression of CYP1A1 and heme oxygenase‐1 (HO‐1) in human bronchial epithelial (BEAS‐2B) cells. In addition, dithiothreitol and ascorbic acid assays were performed in order to examine the oxidative potential of the PM samples. The DEP‐sample with the highest PAH and lowest metal content was more potent with respect to cytotoxicity and expression and release of proinflammatory mediators, CYP1A1 and HO‐1 expression and MAPK activation, than the DEP‐sample with lower PAH and higher metal content. The DEP‐sample with the highest PAH and lowest metal content also possessed a greater oxidative potential. The present results indicate that the content of organic components may be determinant for the proinflammatory effects of DEP. The findings underscore the importance of considering the chemical composition of particulate matter‐emissions, when evaluating the potential health impact and implementation of air pollution regulations. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 188–196, 2015.     

Obese mice are resistant to eosinophilic airway inflammation induced by diesel exhaust particles

Particulate matter can exacerbate respiratory diseases such as asthma. Diesel exhaust particles are the substantial portion of ambient particulate matter with a <2.5 µm diameter in urban areas. Epidemiological data indicate increased respiratory health effects of particulate matter in obese individuals; however, the association between obesity and diesel exhaust particle‐induced airway inflammation remains unclear. We aimed to investigate the differences in susceptibility to airway inflammation induced by exposure to diesel exhaust particles between obese mice (db/db) and lean mice (db/+m). Female db/db and db/+m mice were intratracheally administered diesel exhaust particles or vehicle every 2 weeks for a total of seven times. The cellular profile of bronchoalveolar lavage fluid and histological changes in the lungs were assessed and the lungs and serum were analyzed for the generation of cytokines, chemokines and soluble intercellular adhesion molecule 1. Diesel exhaust particle exposure‐induced eosinophilic infiltration in db/+m mice accompanied by T‐helper 2 cytokine, chemokine and soluble intercellular adhesion molecule 1 expression in the lungs. In contrast, it induced mild neutrophilic airway inflammation accompanied by elevated cytokines and chemokines in db/db mice. The lungs of db/db mice exhibited decreased expression of eosinophil activators/chemoattractants such as interleukin‐5, interleukin‐13 and eotaxin compared with those of db/+m mice. In addition, serum eotaxin and monocyte chemotactic protein‐1 levels were significantly higher in db/db mice than in db/+m mice. In conclusion, obesity can affect susceptibility to diesel exhaust particle‐induced airway inflammation, which is possibly due to differences in local and systemic inflammatory responses between lean and obese individuals. Copyright © 2013 John Wiley & Sons, Ltd.     

Contrasting actions of diesel exhaust particles on the pulmonary and cardiovascular systems and the effects of thymoquinone

BACKGROUND AND PURPOSE: Acute exposure to particulate air pollution has been linked to acute cardiopulmonary events, but the underlying mechanisms are uncertain. EXPERIMENTAL APPROACH We investigated the acute (at 4 and 18 h) effects of diesel exhaust particles (DEP) on cardiopulmonary parameters in mice and the protective effect of thymoquinone, a constituent of Nigella sativa. Mice were given, intratracheally, either saline (control) or DEP (30 μg·per mouse). KEY RESULTS At 18 h (but not 4 h) after giving DEP, there was lung inflammation and loss of lung function. At both 4 and 18 h, DEP caused systemic inflammation characterized by leucocytosis, increased IL-6 concentrations and reduced systolic blood pressure (SBP). Superoxide dismutase (SOD) activity was decreased only at 18 h. DEP reduced platelet numbers and aggravated in vivo thrombosis in pial arterioles. In vitro, addition of DEP (0.1-1 μg·mL(-1)) to untreated blood-induced platelet aggregation. Pretreatment of mice with thymoquinone prevented DEP-induced decrease of SBP and leucocytosis, increased IL-6 concentration and decreased plasma SOD activity. Thymoquinone also prevented the decrease in platelet numbers and the prothrombotic events but not platelet aggregation in vitro. CONCLUSIONS AND IMPLICATIONS: At 4 h after DEP exposure, the cardiovascular changes did not appear to result from pulmonary inflammation but possibly from the entry of DEP and/or their associated components into blood. However, at 18 h, DEP induced significant changes in pulmonary and cardiovascular functions along with lung inflammation. Pretreatment with thymoquinone prevented DEP-induced cardiovascular changes.     

Sustained effect of inhaled diesel exhaust particles on T-lymphocyte-mediated immune responses against Listeria monocytogenes.

Studies have shown that exposure to diesel exhaust particles (DEP) suppresses pulmonary host defense against bacterial infection. The present study was carried out to characterize whether DEP exposure exerts a sustained effect in which inhaled DEP increase the susceptibility of the lung to bacterial infection occurring at a later time. Brown Norway rats were exposed to filtered air or DEP by inhalation at a dose of 21.2 +/- 2.3 mg/m3, 4 h/day for 5 days, and intratracheally instilled with saline or 100,000 Listeria monocytogenes (Listeria) 7 days after the final DEP exposure. Bacterial growth and cellular responses to DEP and Listeria exposures were examined at 3 and 7 days post-infection. The results showed that inhaled DEP prolonged the growth of bacteria, administered 7 days post DEP exposure, in the lung as compared to the air-exposed controls. Pulmonary responses to Listeria infection were characterized by increased production of interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha, IL-12, and IL-10 by alveolar macrophages (AM) and increased presence of T lymphocytes and their CD4+ and CD8+ subsets in lung draining lymph nodes that secreted elevated levels of IL-2, IL-6, IL-10, and interferon (IFN)-gamma. Diesel exhaust particles were found to inhibit Listeria-induced production of IL-1beta and TNF-alpha, which are responsible for the innate immunity, and IL-12, which initiates the development of T helper (Th)1 responses, but enhance Listeria-induced AM production of IL-10, which prolongs Listeria survival in these phagocytes. The dual action of DEP on AM production of IL-12 and IL-10 correlated with an inhibition of the development of bacteria-specific T lymphocytes by DEP. Cytokine production by lymphocytes from DEP- and Listeria-exposed rats showed a marked decrease in the production of IL-2, IL-10, and IFN-gamma compared to Listeria infection alone, suggesting either that DEP inhibit the production of cytokines by lymphocytes or that these lymphocytes contained T-cell subsets that are different from those of Listeria infection alone and less effective in mediating Th1 immune responses. This study demonstrates that inhaled DEP, after a 7-day resting period, increase the susceptibility of the lung to bacterial infection occurring at a later time by inhibiting macrophage immune function and suppressing the development of T-cell-mediated immune responses. The results support the epidemiological observations that exposure to DEP may be responsible for the pulmonary health effects on humans.     

Exposure of brown Norway rats to diesel exhaust particles prior to ovalbumin (OVA) sensitization elicits IgE adjuvant activity but attenuates OVA-induced airway inflammation.

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

Comparative effects of inhaled diesel exhaust and ambient fine particles on inflammation,atherosclerosis, and vascular dysfunction

Ambient air PM_2.5 (particulate matter less than 2.5 μm in diameter) has been associated with cardiovascular diseases (CVDs), but the underlying mechanisms affecting CVDs are unknown. The authors investigated whether subchronic inhalation of concentrated ambient PM_2.5 (CAPs), whole diesel exhaust (WDE), or diesel exhaust gases (DEGs) led to exacerbation of atherosclerosis, pulmonary and systemic inflammation, and vascular dysfunction; and whether DEG interactions with CAPs alter cardiovascular effects. ApoE^?/? mice were simultaneously exposed via inhalation for 5 hours/day, 4 days/week, for up to 5 months to one of five different exposure atmospheres: (1) filtered air (FA); (2) CAPs (105 μg/m³); (3) WDE (DEP = 436 μg/m³); (4) DEG (equivalent to gas levels in WDE group); and (5) CAPs+DEG (PM_2.5: 113 μg/m³; with DEG equivalent to WDE group). After 3 and 5 months, lung lavage fluid and blood sera were analyzed, and atherosclerotic plaques were quantified by ultrasound imaging, hematoxylin and eosin (H&E stain), and en face Sudan IV stain. Vascular functions were assessed after 5 months of exposure. The authors showed that (1) subchronic CAPs, WDE, and DEG inhalations increased serum vascular cell adhesion molecule (VCAM)-1 levels and enhanced phenylephrine (PE)-induced vasoconstriction; (2) for plaque exacerbation, CAPs > WDE > DEG?=?FA, thus PM components (not present in WDE) were responsible for plaque development; (3) atherosclerosis can exacerbated through mechanistic pathways other than inflammation and vascular dysfunction; and (4) although there were no significant interactions between CAPs and DEG on plaque exacerbation, it is less clear whether the effects of CAPs on vasomotor dysfunction and pulmonary/systemic inflammation were enhanced by the DEG coexposure.     

Oxidative DNA damage in vitamin C-supplemented guinea pigs after intratracheal instillation of diesel exhaust particles

The health effects of diesel exhaust particles (DEP) are thought to involve oxidative damage. We have investigated the effect of intratracheal DEP instillation to guinea pigs in three groups of 12 animals each given 0, 0.7, or 2.1 mg. Five days later guinea pigs exposed to DEP had increased levels of oxidized amino acids (gamma-glutamyl semialdehyde), DNA strand breaks, and 7-hydro-8-oxo-2'-deoxyguanosine (8-oxodG) in the lung. Bulky DNA ad- ducts were not significantly elevated in the lung. The antioxidant enzyme activity of glutathione reductase was increased in the lung of DEP-exposed guinea pigs, whereas glutathione peroxidase and superoxide dismutase enzyme activities were unaltered. There was no difference in DNA strand breaks in lymphocytes or urinary excretion of 8-oxodG at the two doses tested. Protein oxidations in plasma and in erythrocytes were not altered by DEP exposure. The concentrations of ascorbate in liver, lung, and plasma were unaltered by the DEP exposure. The results indicate that in guinea pigs DEP causes oxidative DNA damage rather than bulky DNA adducts in the lung. Guinea pigs, which are similar to humans with respect to vitamin C metabolism, may serve as a new model for the study of oxidative damage induced by particulate matter.     

Suppression of cell-mediated immune responses to listeria infection by repeated exposure to diesel exhaust particles in brown Norway rats.

Diesel exhaust particles (DEP) have been shown to alter pulmonary immune responses to bacterial infection. Exposure of rats to 100 mg/m(3) DEP for 4 h was found to aggravate Listeria monocytogenes(Listeria) infection at 3 days postinfection, but the bacteria were largely cleared at 7 days postinfection due to the development of a strong T cell-mediated immunity. In the present study, we examined the effects of repeated DEP exposure at lower doses on pulmonary responses to bacterial infection. Brown Norway rats were exposed to DEP by inhalation at 20.62 +/- 1.31 mg/m 3 for 4 h/day for 5 days, followed by intratracheal inoculation with 100,000 Listeria at 2 h after the last DEP exposure. DEP-exposed rats showed a significant increase in lung bacterial load at both 3 and 7 days postinfection. The repeated DEP exposure was shown to suppress both the innate, orchestrated by alveolar macrophages (AM), and T cell-mediated responses to Listeria. DEP inhibited AM production of interleukin- (IL-) 1beta, tumor necrosis factor- (TNF-) alpha, and IL-12 but enhanced Listeria-induced AM production of IL-10, which has been shown to prolong the survival of intracellular pathogens such as Listeria. DEP exposure also suppressed the development of bacteria-specific lymphocytes from lung-draining lymph nodes, as indicated by the decreased numbers of T lymphocytes and their CD4(+) and CD8(+) subsets. Furthermore, the DEP exposure markedly inhibited the Listeria-induced lymphocyte secretion of IL-2 at day 7, IL-10 at days 3 and 7, and interferon- (IFN-) gamma at days 3 to 10 postinfection when compared to air-exposed controls. These results show a sustained pattern of downregulation of T cell-mediated immune responses by repeated low-dose DEP exposure, which is different from the results of a single high-dose exposure where the acute effect of DEP aggravated bacteria infection but triggered a strong T cell-mediated immunity.     

Effects of organic chemicals from diesel exhaust particles on adipocytes differentiated from human mesenchymal stem cells

Exposure to fine particulate matter (PM_2.5) from incomplete fossil fuel combustion (coal, oil, gas and diesel) has been linked to increased morbidity and mortality due to metabolic diseases. PM_2.5 exaggerate adipose inflammation and insulin resistance in mice with diet-induced obesity. Here, we elucidate the hypothesis that such systemic effects may be triggered by adhered particle components affecting adipose tissue directly. Studying adipocytes differentiated from primary human mesenchymal stem cells, we found that lipophilic organic chemicals (OC) from diesel exhaust particles induced inflammation-associated genes and increased secretion of the chemokine CXLC8/interleukin-8 as well as matrix metalloprotease 1. The oxidative stress response gene haem oxygenase-1 and tumour necrosis factor alpha were seemingly not affected, while aryl hydrocarbon receptor-regulated genes, cytochrome P450 1A1 (CYP1A1) and CYP1B1 and plasminogen activator inhibitor-2, were clearly up-regulated. Finally, expression of β-adrenergic receptor, known to regulate adipocyte homoeostasis, was down-regulated by exposure to these lipophilic OC. Our results indicate that low concentrations of OC from combustion particles have the potential to modify expression of genes in adipocytes that may be linked to metabolic disease. Further studies on mechanisms linking PM exposure and metabolic diseases are warranted.     

Nitrogen dioxide: no influence on allergic sensitization in an intranasal mouse model with ovalbumin and diesel exhaust particles

The role of traffic-related air pollution in the development of allergic diseases is still unclear. We therefore investigated if NO₂, an important constituent of traffic-related air pollution, promotes allergic sensitization to the allergen ovalbumin (OVA). We also examined if NO₂ influenced the allergy adjuvant activity of diesel exhaust particles (DEP). For this purpose, mice were exposed intranasally to OVA with or without DEP present, immediately followed by exposure to NO₂ (5 or 25 parts per million [ppm]) or room air for 4?h in whole body exposure chambers. Eighteen hours after the last of three exposures, the lungs of half of the animals were lavaged with saline and markers of lung damage and lung inflammation in the bronchoalveolar lavage fluid (BALF) were measured. Three weeks later, after intranasal booster immunizations with OVA, the levels of OVA-specific IgE and IgG2a antibodies in serum were determined. Both NO₂ (25?ppm) and DEP gave lung damage, measured as increased total protein concentration in BALF, whereas only NO₂ seemed to stimulate release of the proinflammatory cytokine tumor necrosis factor alpha (TNF-α). In contrast, only DEP significantly increased the number of neutrophils. Furthermore, DEP in combination with OVA stimulated the production of serum allergen-specific IgE antibodies. NO₂, however, neither increased the production of allergen-specific IgE antibodies, nor influenced the IgE adjuvant activity of DEP. Thus, based on our findings, NO₂ seems to be of less importance than combustion particles in the development of allergic diseases after exposure to traffic-related air pollution.     

In vitro toxicity evaluation of diesel exhaust particles on human eosinophilic cell

Diesel exhaust particles (DEPs), comprised mainly of particles less than 2.5 μm (PM 2.5) in aerodynamic diameter, have been assumed to enhance the response of asthma to allergen inhalation. Although eosinophilic infiltration is remarkable in the event of bronchial asthma induced by DEPs, the precise mechanisms leading to eosinophilia are unknown. To examine the effect of DEPs on eosinophils, we measured the cytokine products and activity of nuclear factor-kappa B (NF-κB) after addition of the proteasomal inhibitor MG132 in HL-60 clone 15 cells differentiated into eosinophils. We measured eotaxin-induced chemotaxis of cells and their activity of p38 mitogen-activated protein (MAP) kinase was analysed. Interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1) were increased markedly in DEPs-treated cells. The active form of NF-κB in cells treated with DEPs was increased, and this effect was significantly decreased by the administration of MG132. Cell migration in the presence of DEPs was significantly greater, and inhibited by adding N-acetyl l-cysteine. P38 MAP kinase activity was highly influenced by DEPs-treatment. DEPs induce MCP-1 and IL-8 production by up-regulating NF-κB activity, which is inhibited in the presence of an inhibitor of proteasomal degradation. DEP also promotes eotaxin-induced chemotaxis in a p38-dependent manner.     

Enhancement of antigen-induced eosinophilic inflammation in the airways of mast-cell deficient mice by diesel exhaust particles

The present study was conducted to clarify the involvement of mast cells in the exacerbating effect of diesel exhaust particles (DEP) toward allergic airway inflammation and airway hyperresponsiveness (AHR). Airway inflammation by the infiltration of cosinophils with goblet cell proliferation and AHR, as well as by the production of antigen-specific IgG1 and IgE, in plasma were examined using mast cell-deficient mice (W/W^v) and normal mice (W/W⁺). Both groups of mice received ovalbumin (OVA) or OVA+DEP intratracheally. The eosinophilic airway inflammation and goblet cell proliferation promoted by OVA were significantly greater in W/W⁺ than in W/W^v. A similar result was observed in AHR, but was not significant among both groups of mice. DEP enhanced OVA induced-allergic airway inflammation, goblet cell proliferation, and development of AHR in W/W^v, but not in W/W⁺. DEP decreased production of antigen-specific IgG1 and IgE in both groups of mice. Mast cells were observed in the submucosal layer of the main bronchus in W/W^v. The number of mast cells was significantly decreased by OVA treatment. The results indicate that mast cells are not necessary to enhance airway damage and development of AHR in W/W^v by DEP. However, mast cells may be required for the OVA-induced cosinophilic inflammation, airway damage with goblet cell proliferation, and AHR in W/W⁺.     

Effect of diesel exhaust particles on renal vascular responses in rats with chronic kidney disease

Several recent studies have indicated the possible association between exposure to particulate air pollution and the increased rate of morbidity and mortality in patients with kidney diseases. The link of this observation to vascular damage has not been adequately addressed. Therefore, this study aims to investigate possible vascular damage that might be associated with exposure to diesel exhaust particles (DP) in adenine (AD)‐induced chronic kidney disease (CKD) in rats, and the possible ameliorative effect of gum acacia (GA). CKD was induced by feeding AD (0.75%, w/w), and DP (0.5 mg/kg) was instilled intratracheally every second day and GA was given concomitantly in the drinking water at a dose of 15% w/v. All treatments were given concomitantly for 28 days. Changes in renal blood flow (RBF) and systolic and diastolic blood pressure were monitored in these animals after anesthesia, together with several other endpoints. Exposure to DP significantly reduced RBF and this was significantly potentiated in AD‐treated rats. Phenylephrine‐induced decreases in RBF and increases in systolic and diastolic blood pressure were severely potentiated in rats exposed to DP, and these actions were significantly augmented in AD‐treated rats. GA did not significantly affect the vascular impairment induced by AD and DP given together. This study provides experimental evidence that exposure to particulate air pollution can exacerbate the vascular damage seen in patients with CKD. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 541–549, 2017.     

Identification of estrogenic and antiestrogenic activities of respirable diesel exhaust particles by bioassay-directed fractionation

Bioassay-directed fractionation was performed to identify causative chemical groups of DEPs with estrogenic and antiestrogenic activities. Bioassay-directed fractionation consists of a cell bioassay (E-SCREEN) in conjunction with acid-base partitoning (F1 and F2) and silica gel column fractionation of neutral fractions (F3-F7). Crude extract (CE) of DEPs in dichloromethane (DCM) exhibited both estrogenic and antiestrogenic activity. Estrogenic activity of CE and some fractions (F1, F2, F3, F5 and F6) was induced through estrogen receptor (ER)-mediated pathways. In particular, the acid polar fraction (F2) of DEPs, which contains phenols, induced high levels of estrogenic activity compared to other fractions. The estrogenic activity of F2 (610.80 pg-bio-EEQ/g-DEPs) was higher than that of the total estrogenic activity of CE (222.22 pg-bio-EEQ/g-DEPs). This result indicates that the estrogenic activity induced by causative estrogenic fraction (F2) may be antagonized by unidentified chemicals in DEPs. On the other hand, non-polar fractions (F3 and F4) of DEPs include aliphatic and chlorinated hydrocarbon, polyaromatic hydrocarbons, and their alkyl derivatives, which play an important role in the antiestrogenic activity of DEPs. In particular, F4, which contains PAH and its derivatives, showed the highest antiestrogenic activity. Since in our previous study, dibenzo(a, h)anthracene and chrysene were identified in F4, and these chemicals have antiestrogenic activity, we assume that these chemicals are the major causative chemicals with antiestrogenic activity in DEPs. In contrast to the estrogenic activity of DEPs, antiestrogenic activity of CE was stronger than that of antiestrogenic fractions (F3 and F4) at non-cytotoxic concentrations, indicating that additive or synergistic effects by unidentified chemicals contained in DEPs occurred.     

Roles of reactive oxygen species and heme oxygenase-1 in modulation of alveolar macrophage-mediated pulmonary immune responses to Listeria monocytogenes by diesel exhaust particles.

Diesel exhaust particles (DEP) have been shown to suppress alveolar macrophage (AM)-mediated pulmonary immune responses to Listeria monocytogenes in vivo. In this study, effects of DEP-derived reactive oxygen species (ROS) and heme oxygenase (HO)-1 on AM-mediated immune responses to L. monocytogenes were investigated. Brown Norway rats were intratracheally inoculated with 100,000 L. monocytogenes, and AM were isolated at 7 days post-infection. Exposure to DEP or their organic extract (eDEP), but not the washed DEP (wDEP) or carbon black, increased intracellular ROS and HO-1 expression in AM. Induction of ROS and HO-1 by eDEP was partially reversed by alpha-naphthoflavone, a cytochrome P450 1A1 inhibitor, and totally blocked by N-acetylcysteine. In addition, exposure to eDEP, but not wDEP, inhibited lipopolysacchride-stimulated secretion of tumor necrosis factor-alpha (TNF-alpha) and interleukin-12 (IL-12), but augmented production of IL-10 by AM. Kinetic studies showed that modulation of cytokines by eDEP was preceded by ROS and HO-1 induction. Furthermore, pretreatment of AM with superoxide dismutase (SOD) or zinc protoporphrin IX (Znpp), which attenuated eDEP-induced HO-1 expression/activity, substantially inhibited eDEP effect on IL-10. Finally, direct stimulation with pyrogallol (PYR), a superoxide donor, upregulated HO-1 and IL-10 but decreased secretion of IL-12 in L. monocytogenes-infected AM. These results show that DEP, through eDEP-mediated ROS, induce HO-1 expression and IL-10 production and at the same time inhibit AM production of TNF-alpha and IL-12 to dampen the host immune responses. The results also suggest that HO-1 may play an important role in regulating production of IL-10 by DEP-exposed and L. monocytogenes-infected AM.