Administration Of Diesel Exhaust Particles Research Articles

Palliative effects of carnosol on lung-deposited pollutant particles-induced thrombogenicity and vascular injury in mice.

The toxicity of inhaled particulate air pollution perseveres even at lower concentrations than those of the existing air quality limit. Therefore, the identification of safe and effective measures against pollutant particles-induced vascular toxicity is warranted. Carnosol is a bioactive phenolic diterpene found in rosemary herb, with anti-inflammatory and antioxidant actions. However, its possible protective effect on the thrombotic and vascular injury induced by diesel exhaust particles (DEP) has not been studied before. We assessed here the potential alleviating effect of carnosol (20 mg/kg) administered intraperitoneally 1 h before intratracheal (i.t.) instillation of DEP (20 μg/mouse). Twenty-four hours after the administration of DEP, various parameters were assessed. Carnosol administration prevented the increase in the plasma concentrations of C-reactive protein, fibrinogen, and tissue factor induced by DEP exposure. Carnosol inhibited DEP-induced prothrombotic effects in pial microvessels invivo and platelet aggregation invitro. The shortening of activated partial thromboplastin time and prothrombin time induced by DEP was abated by carnosol administration. Carnosol inhibited the increase in pro-inflammatory cytokines (interleukin-6 and tumor necrosis factor α) and adhesion molecules (intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, and P-selectin) in aortic tissue. Moreover, it averted the effects of DEP-induced increase of thiobarbituric acid reactive substances, depletion of antioxidants and DNA damage in the aortic tissue. Likewise, carnosol prevented the decrease in the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) caused by DEP. We conclude that carnosol alleviates DEP-induced thrombogenicity and vascular inflammation, oxidative damage, and DNA injury through Nrf2 and HO-1 activation.

Intratracheal administration of diesel exhaust particles causes male reproductive toxicity and enhances liver cytochrome P450 1A1 activity.

Diesel Exhaust Particles (DEPs) contain Polycyclic Aromatic Hydrocarbons (PAHs) and the Aryl hydrocarbon Receptor (AhR) is closely involved in the endocrine disrupting action of PAHs. Activation of the AhR is thought to cause various effects such as reproductive dysfunction. In our previous studies, Subcutaneous (SC) administration of DEPs to male mice caused reproductive toxicity and increased hepatic Cytochrome P450 1A1 (CYP1A) enzyme activity, as an indirect index of AhR activity. Air pollutants in the environment enter the body through the airways. In this study, we examined the effect of Intratracheally (IT) administered DEP on spermatogenesis and hepatic CYP1A1 in male mice. The amount of DEP administered IT in this study was lower than that administered SC in previous studies. The result showed that similar to SC, IT administered DEP decreased daily sperm production and hepatic CYP1A1 activity significantly. Thus, DEP toxicity was suggested to be more pronounced with IT administration than with SC administration.

Diesel exhaust impairs TREM2 to dysregulate neuroinflammation

BackgroundAir pollution has been linked to neurodegenerative diseases, including Alzheimer’s disease (AD), and the underlying neuroimmune mechanisms remain poorly understood. TREM2 is a myeloid cell membrane receptor that is a key regulator of disease-associated microglia (DAM) cells, where loss-of-function TREM2 mutations are associated with an increased risk of AD. At present, the basic function of TREM2 in neuroinflammation is a point of controversy. Further, the impact of air pollution on TREM2 and the DAM phenotype is largely unknown. Using diesel exhaust (DE) as a model of urban air pollution exposure, we sought to address its impact on TREM2 expression, the DAM phenotype, the association of microglia with the neurovasculature, and the role of TREM2 in DE-induced neuroinflammation.MethodsWYK rats were exposed for 4 weeks to DE (0, 50, 150, 500 μg/m3) by inhalation. DE particles (DEP) were administered intratracheally once (600 μg/mouse) or 8 times (100 μg/mouse) across 28 days to male mice (Trem2+/+, Trem2−/−, PHOX+/+, and PHOX−/−).ResultsRats exposed to DE exhibited inverted-U patterns of Trem2 mRNA expression in the hippocampus and frontal cortex, while TREM2 protein was globally diminished, indicating impaired TREM2 expression. Analysis of DAM markers Cx3Cr1, Lyz2, and Lpl in the frontal cortex and hippocampus showed inverted-U patterns of expression as well, supporting dysregulation of the DAM phenotype. Further, microglial-vessel association decreased with DE inhalation in a dose-dependent manner. Mechanistically, intratracheal administration of DEP increased Tnf (TNFα), Ncf1 (p47PHOX), and Ncf2 (p67PHOX) mRNA expression in only Trem2+/+ mice, where Il1b (IL-1β) expression was elevated in only Trem2−/− mice, emphasizing an important role for TREM2 in DEP-induced neuroinflammation.ConclusionsCollectively, these findings reveal a novel role for TREM2 in how air pollution regulates neuroinflammation and provides much needed insight into the potential mechanisms linking urban air pollution to AD.

Activation of NLRP3 in microglia exacerbates diesel exhaust particles-induced impairment in learning and memory in mice

BackgroundThe major components of traffic pollution particulate matter, diesel exhaust particles (DEPs), are airborne ultrafine particles (UFPs). DEPs can enter the central nervous system (CNS), where they may cause neurotoxicity. MethodsWe established murine models with intranasal DEPs instillation in male C57BL/6 and Nlrp3 knock-out (Nlrp3−/−) mice to investigate the effects of DEPs exposure on murine neurobehaviors and related mechanisms. Morris water maze (MWM) tests were performed to evaluate the learning and memory behaviors of mice following DEPs instillation. Metabolomics were assessed using an gas chromatography system coupled to a mass spectrometer. Real-time PCR and immunohistochemistry assays were used to analyze the mRNA and protein expression levels of target genes. Murine microglia, BV2 cells were employed to assay the effects of DEPs exposure in vitro. ResultsIntranasal administration of DEPs in mice led to impairment in hippocampal-dependent learning and memory. Moreover, this phenotype was linked to increased number of Iba-1+ microglia and NLRP3 inflammasome, as well as suppression of mitochondrial gene expression in the hippocampus of mice exposed to DEPs. Nlrp3−/− mice were resistant to DEPs-induced learning and memory impairment, concomitant with protection against the suppression of mitochondrial gene expression. Murine microglia cells (BV2) were exposed to DEPs in vitro and taurine was identified as one of the significantly suppressed metabolites in DEPs-treated microglia by metabolomics analysis. Supplementation with taurine efficiently rescued learning, memory and mitochondrial gene expression levels in the hippocampus of DEPs-exposed mice. ConclusionsMechanistically, our study revealed that microglia-mediated NLRP3 inflammasome activation plays a deleterious role in DEPs-induced neurotoxicity by inhibiting mitochondrial gene expression. These results shed novel light on the potential value of nutritional supplementation against DEPs-induced neurotoxicity in individuals exposed to severe airborne traffic-related air pollutions.

Effects of diesel exhaust particles on the condition of mouse ocular surface

In order to evaluate the effects of diesel exhaust particles (DEP) on the ocular surface, different concentrations (100 and 1000 μg/ml) of DEP eye drops were administered on the mouse ocular surface for a period of 28 days. After DEP treatment, the corneal epithelial permeability to Oregon Green Dextran was studied, which increased proportionally with time. Also, the number of corneal epithelial cell layers significantly increased, which was accompanied with a high Ki67 expression. On the other hand, the number of goblet cells in the conjunctival fornix were reduced, and apoptotic cells were detected in the corneal and conjunctival epithelium by TUNEL assay in the DEP treated group, along with increased Caspase 3/8 expression. Furthermore, the number of CD4 positive cells significantly increased in the conjunctiva, while NF-κB p65 (phospho S536) expression was elevated in the cornea and also the conjunctiva. Our data revealed that the topical administration of DEP on the ocular surface in mouse disrupted the organized structure of the ocular surface and induced an inflammation of the cornea and conjunctiva.

Thrombosis and systemic and cardiac oxidative stress and DNA damage induced by pulmonary exposure to diesel exhaust particles and the effect of nootkatone thereon.

Adverse cardiovascular effects of particulate air pollution persist even at lower concentrations than those of the current air quality limit. Therefore, identification of safe and effective measures against particle-induced cardiovascular toxicity is needed. Nootkatone is a sesquiterpenoid in grapefruit with diverse bioactivities including anti-inflammatory and antioxidant effects. However, its protective effect on the cardiovascular injury induced by diesel exhaust particles (DEPs) has not been studied before. We assessed the possible protective effect of nootkatone (90 mg/kg) administered by gavage 1 h before intratracheal instillation of DEPs (30 μg/mouse). Twenty-four hours after the intratracheal administration of DEPs, various thrombotic and cardiac parameters were assessed. Nootkatone inhibited the prothrombotic effect induced by DEPs in pial arterioles and venules in vivo and platelet aggregation in whole blood in vitro. Also, nootkatone prevented the shortening of activated partial thromboplastin time and prothrombin time induced by DEPs. Nootkatone inhibited the increase of plasma concentration of fibrinogen, plasminogen activator inhibitor-1, interleukin-6, and lipid peroxidation induced by DEPs. Immunohistochemically, hearts showed an analogous increase in glutathione and nuclear factor erythroid-derived 2-like 2 expression by cardiac myocytes and endothelial cells after DEP exposure, and these effects were enhanced in mice treated with nootkatone + DEPs. Likewise, heme oxygenase-1 was increased in mice treated with nootkatone + DEPs compared with those treated with DEPs or nootkatone + saline. The DNA damage caused by DEPs was prevented by nootkatoone pretreatment. In conclusion, nootkatoone alleviates DEP-induced thrombogenicity and systemic and cardiac oxidative stress and DNA damage, at least partly, through nuclear factor erythroid-derived 2-like 2 and heme oxygenase-1 activation. NEW & NOTEWORTHY Nootkatoone, a sesquiterpenoid found in grapefruit, alleviates the thrombogenicity and systemic and cardiac oxidative stress and DNA damage in mice exposed to diesel exhaust particles. Nootkatone-induced boosting of nuclear factor erythroid-derived 2-like 2 and heme oxygenase-1 levels in the heart of mice exposed to diesel exhaust particles suggests that its protective effect is, at least partly, mediated through nuclear factor erythroid-derived 2-like 2 and heme oxygenase-1 activation.

Mechanistic link between diesel exhaust particles and respiratory reflexes

BackgroundDiesel exhaust particles (DEPs) are a major component of particulate matter in Europe's largest cities, and epidemiologic evidence links exposure with respiratory symptoms and asthma exacerbations. Respiratory reflexes are responsible for symptoms and are regulated by vagal afferent nerves, which innervate the airway. It is not known how DEP exposure activates airway afferents to elicit symptoms, such as cough and bronchospasm.ObjectiveWe sought to identify the mechanisms involved in activation of airway sensory afferents by DEPs.MethodsIn this study we use in vitro and in vivo electrophysiologic techniques, including a unique model that assesses depolarization (a marker of sensory nerve activation) of human vagus.ResultsWe demonstrate a direct interaction between DEP and airway C-fiber afferents. In anesthetized guinea pigs intratracheal administration of DEPs activated airway C-fibers. The organic extract (DEP-OE) and not the cleaned particles evoked depolarization of guinea pig and human vagus, and this was inhibited by a transient receptor potential ankyrin-1 antagonist and the antioxidant N-acetyl cysteine. Polycyclic aromatic hydrocarbons, major constituents of DEPs, were implicated in this process through activation of the aryl hydrocarbon receptor and subsequent mitochondrial reactive oxygen species production, which is known to activate transient receptor potential ankyrin-1 on nociceptive C-fibers.ConclusionsThis study provides the first mechanistic insights into how exposure to urban air pollution leads to activation of guinea pig and human sensory nerves, which are responsible for respiratory symptoms. Mechanistic information will enable the development of appropriate therapeutic interventions and mitigation strategies for those susceptible subjects who are most at risk.

Diesel exhaust particles exacerbate allergic rhinitis in mice by disrupting the nasal epithelial barrier.

Diesel exhaust particles (DEP), traffic-related air pollutants, are considered environmental factors that affect allergic diseases adversely. However, the exact effect of DEP on allergic rhinitis (AR) is unclear. We thought to investigate the effect of DEP on seasonal AR using a mouse model. Ragweed-pollen-sensitized mice were nasally challenged with ragweed pollen in the presence or absence of DEP. The frequency of sneezing was evaluated immediately after each nasal challenge. The expression of a tight junction (TJ) protein, zonula occludens-1 (ZO-1), was examined by immunohistochemistry in AR mice. RPMI 2650 cells were used for in vitro examination of paracellular permeability. Mice challenged with ragweed pollen plus DEP showed increased frequency of sneezing compared with mice challenged with pollen alone. Interestingly, intranasal DEP pretreatment before ragweed pollen challenge increased ragweed-pollen-induced sneezing to levels comparable with the co-administration group. In vitro examination revealed that DEP reduced ZO-1 expression in RPMI 2650 cells. In addition, intranasal administration of DEP, but not ragweed pollen, disrupted nasal mucosal TJs in vivo. The effect of a single DEP treatment on ragweed-induced sneezing and ZO-1 expression persisted for at least 4 days and was inversely correlated. Finally, an antioxidant substance, N-acetyl-L-cysteine, inhibited DEP-mediated TJ disruption and exacerbation of sneezing in AR. DEP disrupts TJs by a reactive oxygen species-mediated pathway, leading to the increased permeability of nasal epithelial cells. This may result in the promotion of allergen delivery into subepithelial tissues contributing to the exacerbation of immediate allergic responses.

Platelet activation independent of pulmonary inflammation contributes to diesel exhaust particulate-induced promotion of arterial thrombosis.

BackgroundAccelerated thrombus formation induced by exposure to combustion-derived air pollution has been linked to alterations in endogenous fibrinolysis and platelet activation in response to pulmonary and systemic inflammation. We hypothesised that mechanisms independent of inflammation contribute to accelerated thrombus formation following exposure to diesel exhaust particles (DEP).MethodsThrombosis in rats was assessed 2, 6 and 24 h after administration of DEP, carbon black (CB; control carbon nanoparticle), DQ12 quartz microparticles (to induce pulmonary inflammation) or saline (vehicle) by either intra-tracheal instillation (0.5 mg, except Quartz; 0.125 mg) or intravenous injection (0.5 mg/kg). Thrombogenicity was assessed by carotid artery occlusion, fibrinolytic variables and platelet-monocyte aggregates. Measures of inflammation were determined in plasma and bronchoalveolar lavage fluid. Tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI)-1 were measured following direct in vitro exposure of human umbilical vein endothelial cells (HUVECs) to DEP (10–150 μg/mL).ResultsInstillation of DEP reduced the time to thrombotic occlusion in vivo, coinciding with the peak of DEP-induced pulmonary inflammation (6 h). CB and DQ12 produced greater inflammation than DEP but did not alter time to thrombotic occlusion. Intravenous DEP produced an earlier (2 h) acceleration of thrombosis (as did CB) without pulmonary or systemic inflammation. DEP inhibited t-PA and PAI-1 release from HUVECs, and reduced the t-PA/PAI-1 ratio in vivo; similar effects in vivo were seen with CB and DQ12. DEP, but not CB or DQ12, increased platelet-monocyte aggregates.ConclusionDEP accelerates arterial thrombus formation through increased platelet activation. This effect is dissociated from pulmonary and systemic inflammation and from impaired fibrinolytic function.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0116-x) contains supplementary material, which is available to authorized users.

The effects of diesel exhaust particles on neural tube development in the early stage chicken embryo

Particulate matter is an important air-pollutant and its toxicity has been reported. Diesel exhaust particles (DEP) constitute a large portion of particulate matter. Therefore, we established our study to investigate the effects of DEP on neural tissue in early stage chicken embryos. MATERIAL and Four study groups and one control group, each of which included 24 objects were designed. Eggs were incubated for 30 hours. Solutions of DEP containing 10, 50, 100, and 200 μg/0.1 ml were prepared with serum saline. At the end of thirty hours diesel exhaust particle solutions were administered under the embryonic discs. After 72nd hour of the incubation, embryos were excised and evaluated macroscopically and histopathologically. The difference between the embryos that were defined as poorly and well developed, was found statistically significant (p < 0.05). Neural tube defects were detected in 16 of 104 embryos. Statistically significant association between the administration of DEP and development of neural tube defect was identified (p=0.037). Thus, the direct neurotoxic effects of DEP, which the whole population encounters inevitably, have been shown in the early stages of embryonic development. Further studies are needed to identify the effects of these particles in the later stages of embryonic development.

Comprehensive analysis of elastase-induced pulmonary emphysema in mice: Effects of ambient existing particulate matters

Pulmonary exposure of rodents to porcine pancreatic elastase (PPE) induces lesions that morphologically resemble human panacinar emphysema. However, there has been little work on the comprehensive analysis of this model. The present study was designed to extensively examine the biological effects of PPE on inflammation, cell damage, emphysematous change, and cholinergic reactivity in the lungs of mice. Furthermore, we evaluated the effects of pulmonary exposure to diesel exhaust particles (DEP) on the disease model. Intratracheal administration of PPE induced (1) proinflammatory response in the lungs that was characterized by significant infiltration of leukocytes such as macrophages, eosinophils, and lymphocytes and an increased level of interleukin-1β in lung homogenates, (2) lung cell damage, indicated by higher levels of total protein, lactate dehydrogenase, and alkaline phosphatase in lung homogenates, (3) emphysema-related morphological changes including airspace enlargement and progressive destruction of alveolar wall structures, and (4) airway responsiveness to methacholine in the context of the compliance value of the respiratory system in a dose-dependent manner showing an overall trend. A single intratracheal administration of DEP did not significantly facilitate the hallmark of the disease. This is the first study to extensively analyze PPE-induced lung emphysema in mice with evaluation of the effects of DEP. Furthermore, this bioassay may be applied to future investigations that evaluate new therapeutic agents or risk factors for pulmonary emphysema.

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.

Cacao Liquor Proanthocyanidins Inhibit Lung Injury Induced by Diesel Exhaust Particles

Epidemiological and experimental studies have suggested that diesel exhaust particles (DEPs), which generate reactive oxygen species, may be involved in the recent increase in the prevalence of lung diseases. Cacao liquor proanthocyanidins (CPs) are naturally occurring polyphenols with antioxidative activities. We carried out a study in mice to investigate the effects of dietary supplementation of CPs on lung injury induced by intratracheal administration of DEPs (500 microg/body). Dietary supplementation with 1.0 percent CPs inhibited DEP-induced lung injury, characterized by neutrophil sequestration and edema. Immunohistochemical analyses showed that CPs prevented enhanced expression of vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 caused by DEPs in the lung injury. Numerous adducts of nitrotyrosine, N-(hexanonyl) lysine, 4-hydroxy-2-nonenal, and 8-OHdG were also observed immunohistochemically in the lungs of mice treated with DEPs. However, these indicators of oxidative stress were barely visible in mice pretreated with CP supplementation. In addition, the level of thiobarbituric acid reactive substances in the lung was decreased by CP supplementation in the presence of DEPs. These results suggest that CPs inhibit DEP-induced lung injury by reducing oxidative stress, in association with a reduction in the expression of adhesion molecules.

Dietary exposure to diesel exhaust particles and oxidatively damaged DNA in young oxoguanine DNA glycosylase 1 deficient mice

Pulmonary exposure to diesel exhaust particles (DEP) has been associated with high levels of oxidized DNA in lung cells, whereas long-term oral DEP exposure appears to induce the DNA repair system with concomitant unaltered levels of oxidized DNA in the colon and liver of rats. Here we studied the generation of oxidatively damaged DNA in young wild type (WT) and oxoguanine DNA glycosylase 1 (OGG1) deficient mice after dietary exposure to 0 mg/kg, 0.8 mg/kg, or 8 mg/kg Standard Reference Material 1650 in the feed for 21 days. The ingestion of DEP did not increase the levels of 8-oxo-7,8-dihydro-2′-deoxyguanosine and comet assay endpoints in terms of strand break, endonuclease III, and formamidopyrimidine glycosylase (FPG) in the colon, liver, and lung tissue of WT or Ogg1 −/− mice. The level of OGG1 mRNA could only be measured in WT mice and it was not increased by DEP feeding. On the contrary, the level of FPG sites was twofold higher in the liver and lung of Ogg1 −/− mice compared to the levels in the WT mice tissues. In conclusion, although Ogg1 −/− mice have high levels of oxidized guanine lesions, they do not appear to be markedly vulnerable to the genotoxicity by oral administration of DEP.

Cardiovascular and lung inflammatory effects induced by systemically administered diesel exhaust particles in rats

Pollution by particulates has consistently been associated with increased cardiorespiratory morbidity and mortality. It has been suggested that ultrafine particles, of which diesel exhaust particles (DEP) are significant contributors, are able to translocate from the airways into the bloodstream in vivo. In the present study, we assessed the effect of systemic administration of DEP on cardiovascular and respiratory parameters. DEP were administered into the tail vein of rats, and heart rate, blood pressure, blood platelet activation, and lung inflammation were studied 24 h later. Doses of 0.02, 0.1, or 0.5 mg DEP/kg (8, 42, or 212 microg DEP/rat) induced a significant decrease of heart rate and blood pressure compared with saline-treated rats. Although the number of platelets was not affected, all the doses of DEP caused a shortening of the bleeding time. Similarly, in addition to triggering lung edema, the bronchoalveolar lavage analysis revealed the presence of neutrophil influx in DEP-treated rats in a dose-dependent manner. We conclude that the presence of DEP in the systemic circulation leads not only to cardiovascular and haemostatic changes but it also triggers pulmonary inflammation.

DNA damage in lung after oral exposure to diesel exhaust particles in Big Blue ® rats

Several chemical mutagens and carcinogens, including polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs, are adsorbed to the surface of diesel exhaust particles (DEP). DEP can induce formation of reactive oxygen species and cause oxidative DNA damage as well as bulky carcinogen DNA adducts. Lung tissue is a target organ for DEP induced cancer following inhalation. Recent studies have provided evidence that the lung is also a target organ for DNA damage and cancer after oral exposure to other complex mixtures of PAHs. The genotoxic effect of oral administration of DEP was investigated, in terms of markers of DNA damage, mutations and repair, in the lung of Big Blue ® rats fed a diet with 0, 0.2, 0.8, 2, 8, 20 or 80 mg DEP/kg feed for 21 days. There was no significant increase in the mutation frequency in the cII gene. However, an increase of DNA damage measured as DNA strand breaks (comet assay) and bulky DNA adducts ( 32 P post labeling) was observed. The level of DNA strand breaks increased significantly at all dose levels while the level of DNA adducts increased significantly only at the intermediate dose levels. Similarly, the number of oxidized DNA bases measured as endonuclease III and fapyguanine glycosylase (FPG) sensitive sites increased at the intermediate dose levels. The induction of DNA damage by DEP exposure did not increase the expression of the repair genes OGG1 and ERCC1 at the mRNA level. The present study indicates that the lung is a target organ for primary DNA damage following oral exposure to DEP. DNA damage was induced following exposure to relatively low levels of DEP, but under the conditions used in the present experiment DNA damage did not result in an increased mutation rate.

Rosmarinic acid inhibits lung injury induced by diesel exhaust particles.

Epidemiological and experimental studies have suggested that diesel exhaust particles (DEP) may be involved in recent increases in lung diseases. DEP has been shown to generate reactive oxygen species. Intratracheal instillation of DEP induces lung inflammation and edema in mice. Rosmarinic acid is a naturally occurring polyphenol with antioxidative and anti-inflammatory activities. We investigated the effects of rosmarinic acid on lung injury induced by intratracheal administration of DEP (500 microg/body) in mice. Oral supplementation with administration of rosmarinic acid (2 mg/body for 3 d) inhibited DEP-induced lung injury, which was characterized by neutrophil sequestration and interstitial edema. DEP enhanced the lung expression of keratinocyte chemoattractant (KC), interleukin-1beta, monocyte chemoattractant protein-1, and macrophage inflammatory protein-1alpha, which was inhibited by treatment with rosmarinic acid. DEP enhanced expression of iNOS mRNA and formation of nitrotyrosine and 8-OHdG in the lung, which was also inhibited by rosmarinic acid. These results suggest that rosmarinic acid inhibits DEP-induced lung injury by the reduction of proinflammatory molecule expression. Antioxidative activities of rosmarinic acid may also contribute to its protective effects.

Diesel Exhaust Particle-Induced Alterations of Pulmonary Phase I and Phase II Enzymes of Rats

Although diesel exhaust particles (DEP) are known to produce pulmonary disorders, the xenobiotic metabolic pathways associated with DEP detoxification and bioactivation remain unclear. In this study, the effect of acute exposure of DEP on phase I and phase II enzymes of rat lung was investigated. Intratracheal administration of DEP produced an induction of cytochrome P-450 (CYP) 1A1 enzyme protein and activity at 1 d postexposure, with the enzyme level returning to control at 5 d postexposure. On the other hand, carbon black (CB), a particle control, did not show any induction of CYP1A1 protein or enzyme activity. However, both DEP and CB significantly decreased CYP2B1 protein and enzyme activity at 1 d postexposure. The decrease in CYP2B1 enzyme protein and activity by DEP or CB treatment was observed up to 7 d postexposure. DEP and CB treatments also significantly attenuated glutathione S-transferase (GST)- ~ protein at 1 d postexposure. Both DEP and CB at 35 mg/kg significantly decreased the activities of GST and catalase at 1 and 7 d postexposure. DEP, but not CB, significantly induced quinone reductase (QR) activity at 7 d postexposure. This study suggests that DEP may induce CYP1A1 and QR enzymes via a chemical effect, while the carbonaceous core may be involved in the attenuation of CYP2B1, GST, and catalase proteins and enzyme activities.

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

Administration of diesel exhaust particles (DEP) increases antigen-specific IgE production and IgE-secreting cells, and induces Th2-type cytokine profiles in the airway in mice and humans. To determine the early effects of diesel exhaust (DE) inhalation on the cytokine production profile, BALB/c mice were exposed to 0 (controls) and 1.0 mg/m 3 DE inhalation for 4 weeks. Intraperitoneal sensitization with ovalbumin (OVA) was conducted immediately before DE inhalation. Mice were treated with anti-CD4 or anti-CD8 mAb 1 day before and after the sensitization. On day 21, these mice were boosted with OVA and blood; bronchoalveolar lavage (BAL) fluid, and spleens were collected on day 28. In BAL fluid, both TNFα and IL-10 production in DE-exposed and control mice remained basically the same. IL-6 production in the anti-CD4 treatment group of DE-exposed mice, however, significantly increased compared with that of the controls. In vitro antigen-stimulated interleukin-4 (IL-4) and -10 (IL-10) production in spleen cells of exposed mice were not affected by low-dose DE inhalation. In vitro interferon (IFN)-γ production in the anti-CD4 treated group of exposed mice decreased markedly. Although anti-OVA IgE production in the plasma of sham-treated mice exposed to DE was the same level as for controls, anti-CD4 mAb treatment in DE-exposed mice significantly reduced IgE production compared to controls. In anti-OVA IgG1 production, anti-CD4 or anti-CD8 mAb treatment in DE-exposed groups also significantly reduced. Anti-OVA IgG2a production was reduced by treatment with anti-CD4 mAb, but increased by anti-CD8 mAb treatment in DE-exposed mice. Low dose DE inhalation is thus shown to adversely affect the cytokine and antibody production in mice by altering CD4 + and CD8 + T-cell functions.

Changes in levels of 8-hydroxyguanine in DNA, its repair and OGG1 mRNA in rat lungs after intratracheal administration of diesel exhaust particles

Diesel exhaust particles (DEP), an environmental pollutant, are known to induce lung cancer in experimental animals. To clarify whether reactive oxygen species (ROS) are involved in its carcinogenic mechanism, we examined the levels of 8-hydroxyguanine (8-OH-Gua), its total repair and the repair enzyme OGG1 mRNA in female Fischer 344 rat lungs, as markers of the response to ROS, after DEP was intratracheally instilled. The 8-OH-Gua levels in both DEP-treated groups (2 and 4 mg) were increased during the 2-8 h following exposure to DEP. The 8-OH-Gua repair activities in the DEP-treated groups decreased during the period from 2 h to 2 days following DEP exposure and then recovered to the level of the control group at 5 days after exposure. OGG1 mRNA was induced in rats treated with 4 mg DEP for 5-7 days after administration. In conclusion, the 8-OH-Gua level in rat lung DNA increases markedly at an early phase after DEP exposure, by the generation of ROS and the inhibition of 8-OH-Gua repair activity, and induction of OGG1 mRNA is also a good marker of cellular oxidative stress during carcinogenesis.