Biological effects of diesel exhaust particles (DEP). II. Acute toxicity of DEP introduced into lung by intratracheal instillation

Defining the in vivo mechanism of air pollutant toxicity using murine stress response biomarkers

Air pollution can cause a wide range of serious human diseases. For the informed instigation of interventions which prevent these outcomes there is an urgent need to develop robust in vivo biomarkers which provide insights into mechanisms of toxicity and relate pollutants to specific adverse outcomes. We exemplify for a first time the application of in vivo stress response reporters in establishing mechanisms of air pollution toxicity and the application of this knowledge in epidemiological studies. We first demonstrated the utility of reporter mice to understand toxicity mechanisms of air pollutants using diesel exhaust particles compounds. We observed that nitro-PAHs induced Hmox1 and CYP1a1 reporters in a time- and dose-dependent, cell- and tissue-specific manner. Using in vivo genetic and pharmacological approaches we confirmed that the NRF2 pathway mediated this Hmox1-reporter induction stress reporter activity. We then correlated the activation of stress-reporter models (oxidative stress/inflammation, DNA damage and Ah receptor -AhR- activity) with responses in primary human nasal cells exposed to chemicals present in particulate matter (PM; PM2.5-SRM2975, PM10-SRM1648b) or fresh roadside PM10. To exemplify their use in clinical studies, Pneumococcal adhesion was assessed in exposed primary human nasal epithelial cells (HPNEpC). The combined use of HPNEpC and in vivo reporters demonstrated that London roadside PM10 particles induced pneumococcal infection in HPNEpC mediated by oxidative stress responses. The combined use of in vivo reporter models with human data thus provides a robust approach to define the relationship between air pollutant exposure and health risks. Moreover, these models can be used in epidemiological studies to hazard ranking environmental pollutants by considering the complexity of mechanisms of toxicity. These data will facilitate the relationship between toxic potential and the level of pollutant exposure in populations to be established and potentially extremely valuable tools for intervention studies for disease prevention.

Ellagic Acid Prevents Particulate Matter-Induced Pulmonary Inflammation and Hyperactivity in Mice: A Pilot Study

The inhalation of fine particulate matter (PM) is a significant health-related environmental issue. Previously, we demonstrated that repeated PM exposure causes hyperlocomotive activity in mice, as well as inflammatory and hypoxic responses in their lungs. In this study, we evaluated the potential efficacy of ellagic acid (EA), a natural polyphenolic compound, against PM-induced pulmonary and behavioral abnormalities in mice. Four treatment groups were assigned in this study (n = 8): control (CON), particulate-matter-instilled (PMI), low-dose EA with PMI (EL + PMI), and high-dose EA with PMI (EH + PMI). EA (20 and 100 mg/kg body weight for low dose and high dose, respectively) was orally administered for 14 days in C57BL/6 mice, and after the eighth day, PM (5 mg/kg) was intratracheally instilled for 7 consecutive days. PM exposure induced inflammatory cell infiltration in the lungs following EA pretreatment. Moreover, PM exposure induced inflammatory protein expression in the bronchoalveolar lavage fluid and the expression of inflammatory (tumor necrosis factor alpha (Tnfα), interleukin (Il)-1b, and Il-6) and hypoxic (vascular endothelial growth factor alpha (Vegfα), ankyrin repeat domain 37 (Ankrd37)) response genes. However, EA pretreatment markedly prevented the induction of expression of inflammatory and hypoxic response genes in the lungs. Furthermore, PM exposure significantly triggered hyperactivity by increasing the total moving distance with an increase in moving speed in the open field test. On the contrary, EA pretreatment significantly prevented PM-induced hyperactivity. In conclusion, dietary intervention with EA may be a potential strategy to prevent PM-induced pathology and activity.

Gestational exposure to titanium dioxide, diesel exhaust, and concentrated urban air particles affects levels of specialized pro-resolving mediators in response to allergen in asthma-susceptible neonate lungs

Maternal gestational exposures to traffic and urban air pollutant particulates have been linked to increased risk and/or worsening asthma in children; however, mechanisms underlying this vertical transmission are not entirely understood. It was postulated that gestational particle exposure might affect the ability to elicit specialized proresolving mediator (SPM) responses upon allergen encounter in neonates. Lipidomic profiling of 50 SPMs was performed in lungs of neonates born to mice exposed to concentrated urban air particles (CAP), diesel exhaust particles (DEP), or less immunotoxic titanium dioxide particles (TiO2). While asthma-like phenotypes were induced with identical eosinophilia intensity across neonates of all particle-exposed mothers, levels of LXA4, HEPE and HETE isoforms, and HDoHe were only decreased by CAP and DEP only but not by TiO2. However, RvE2 and RvD1 were inhibited by all particles. In contrast, isomers of Maresin1 and Protectin D1 were variably elevated by CAP and DEP, whereas Protectin DX, PGE2, and TxB2 were increased in all groups. Only Protectin D1/DX, MaR1(n-3,DPA), 5(S),15(S)-DiHETE, PGE2, and RvE3 correlated with eosinophilia but the majority of other analytes, elevated or inhibited, showed no marked correlation with inflammation intensity. Evidence indicates that gestational particle exposure leads to both particle-specific and nonspecific effects on the SPM network.

An Exploratory Study of the Relationships Between Diesel Engine Exhaust Particle Inhalation, Pulmonary Inflammation and Anxious Behavior

Recent technical developments brought negative side effects such as air pollution and large-scale fires, increasingly exposing people to diesel engine exhaust particles (DEP). Testing how DEP inhalation triggers pathophysiology in animal models could be useful in determining how it affects humans. To this end, the aim of this study was to investigate the effects of pulmonary exposure to DEP for seven consecutive days in experimental male C5BL6/N mice. Twenty-four C5BL6/N mice were treated with one of the three test materials: distilled water for control, a low DEP exposure (5 mg/kg), or a high DEP exposure (15 mg/kg). Exposure to DEP induced decreased body weight; however, it gradually increased pulmonary weight in a DEP-dose-dependent manner. DEP exposure significantly elevated soot accumulation in the lungs, with the alteration of pulmonary homeostasis. It also elevated infiltrated immune cells, thus significantly increasing inflammatory cytokine mRNA and protein production in the lungs and broncho-alveolar lavage fluid, respectively. Pulmonary DEP exposure also altered behavioral responses in the open field test (OFT). Low exposure elevated moving distance and speed, while significantly decreasing the number of trials to enter the central zone. Different concentrations of DEP resulted in different behavioral changes; however, while anxiety levels increased, their degree was independent of DEP concentrations. Results suggest that DEP exposure may possess pro-inflammatory responses in the lungs and trigger anxiety.

[Toxic Components of PM2.5 and Their Toxicity Mechanisms-On the Toxicity of Sulfate and Carbon Components]

Recently, the main air pollutant has been fine particulate matter (PM_2.5), which is taken up by the whole body with severe adverse health effects. The main chemical components of PM_2.5 are salts of sulfate (and nitrate) and carbons. However, it remains unknown which components are toxic. Here, the author reviewed the literatures to determine which components are toxic and the main mechanisms underlying their toxicity. Many epidemiological studies have shown that sulfate concentration is strongly related to mortality. However, there is no experimental evidence showing that sulfate at environmental concentrations of PM_2.5 causes cardiovascular disease or other disease. On the other hand, carbon components such as elementary carbon (EC) produces high concentrations of reactive oxygen species (ROS) via its phagocytosis by macrophages, and organic carbon (OC) also produces high concentrations of ROS during its metabolic processes, and the ROS cause acute and chronic inflammation. They cause many diseases including cardiovascular disease, asthma and cancer. Furthermore, there are many lines of evidence showing that epigenetic changes such as DNA methylation or microRNA expression induced by particulate matters also induce the development of many diseases such as those mentioned above. It has been reported that carbon components are incorporated into the brain and produce ROS, and that the ROS cause damage to brain cells and Alzheimer's disease and cognitive disorders in the elderly.From these lines of evidence, the author would like to emphasize that the main toxicity of PM_2.5 is due to carbon components, and it is important to take countermeasures to decrease the concentration of carbon components in ambient air.

Change over time of the mutagenicity in the lungs of gpt delta transgenic mice by extract of airborne particles collected from ambient air in the Tokyo metropolitan area

BACKGROUND

Previously we found that DNA adducts were accumulated in the lungs of the rats exposed to ambient air in the Tokyo metropolitan area. To examine chronological change in in vivo mutagenicity of airborne particles, extracts produced from samples of total suspended particulates (TSP) collected from urban air in 1980, 1990, and 2010 in the Tokyo metropolitan area were intratracheally administered into the lungs of gpt delta mice, and differences in mutation and mutant frequency were determined by using the gpt assay. In vivo mutations induced by the extracts were characterized and mutation hotspots were identified by DNA sequencing of the mutated gpt gene.

RESULTS

Administration of the 1990 extract at a dose of 0.3 mg/animal significantly elevated total mutant frequency to 3.3-times that in vehicle control, and the in vivo mutagenicity of the extract (induced mutation frequency per milligram extract) was estimated to be 2.0- and 2.4-times higher than that of the 2010 and 1980 extract, respectively. G-to-A transition was the most common base substitution in the vehicle control mice. However, administration of the 1990 extract increased the frequency of G-to-T transversion, which is a landmark base substitution induced by oxidative stress; furthermore, when the extract was administered at a dose of 0.15 mg, the mutant and mutation frequencies of G-to-T transversion were significantly increased to frequencies comparable with those of G-to-A transition. Similar increases in the mutant and mutation frequencies of G-to-T transversion were observed after administration of the 2010 extract. Hotspots (mutation foci identified in three or more mice) of G-to-A transition mutations at nucleotides 64 and 110 were induced by the 1980, 1990, and 2010 extracts; a hotspot of G-to-T transversions at nucleotide 406 was also induced by the 2010 extract. Previously, we showed that diesel exhaust particles or their extract, as well as 1,6-dinitropyrene, administered to mice induced these hotspots of G-to-A transitions.

CONCLUSIONS

The results of the present study suggested that mutagenesis induced by extracts produced from TSP collected in the Tokyo metropolitan area induced in vivo mutagenicity via the same mechanism underlying the induction of in vivo mutagenicity by components of diesel exhaust.

Pulmonary toxicity following acute coexposures to diesel particulate matter and α-quartz crystalline silica in the Sprague-Dawley rat

The effects of acute pulmonary coexposures to silica and diesel particulate matter (DPM), which may occur in various mining operations, were investigated in vivo. Rats were exposed by intratracheal instillation (IT) to silica (50 or 233 µg), DPM (7.89 or 50 µg) or silica and DPM combined in phosphate-buffered saline (PBS) or to PBS alone (control). At one day, one week, one month, two months and three months postexposure bronchoalveolar lavage and histopathology were performed to assess lung injury, inflammation and immune response. While higher doses of silica caused inflammation and injury at all time points, DPM exposure alone did not. DPM (50 µg) combined with silica (233 µg) increased inflammation at one week and one-month postexposure and caused an increase in the incidence of fibrosis at one month compared with exposure to silica alone. To assess susceptibility to lung infection following coexposure, rats were exposed by IT to 233 µg silica, 50 µg DPM, a combination of the two or PBS control one week before intratracheal inoculation with 5 × 105 Listeria monocytogenes. At 1, 3, 5, 7 and 14 days following infection, pulmonary immune response and bacterial clearance from the lung were evaluated. Coexposure to DPM and silica did not alter bacterial clearance from the lung compared to control. Although DPM and silica coexposure did not alter pulmonary susceptibility to infection in this model, the study showed that noninflammatory doses of DPM had the capacity to increase silica-induced lung injury, inflammation and onset/incidence of fibrosis.

Candida Soluble Cell Wall β-D-Glucan Induces Lung Inflammation in Mice

Bioactivity of cell wall component(s) of fungi has not been fully elucidated, especially in vivo. We isolated Candida soluble beta-D-glucan (CSBG) from Candida albicans (C. albicans). We investigated the effects of airway exposure to CSBG on the immune systems in the airways in mice. CSBG exposure induced neutrophilic and eosinophilic inflammation in the lung, which was concomitant with the increased local expression of proinflammatory cytokines including tumor necrosis factor - α, interleukin (IL)-1 β, IL-6, macrophage inflammatory protein -1 α, macrophage chemoattractant protein -1, RANTES (regulated on activation and normal T cells expressed and secreted), and eotaxin. The lung inflammation with enhanced expression of proinflammatory proteins caused by CSBG was directly related to its structure, since structurally degraded products of CSBG by formic acid induced negligible responses in the lung. CSBG enhanced nuclear localization of phosphorylated signal transducer and activator of transcription (STAT)-6 in the lung. These results suggest that airway exposure to CSBG induces lung inflammation, at least partly, via the enhanced expression of proinflammatory cytokines and the activation of STAT-6 pathway, and can be a proper murine model for fungal lung inflammation.

Effects of motor vehicle exhaust on male reproductive function and associated proteins

Air pollution is consistently associated with various diseases and subsequent death among children, adult, and elderly people worldwide. Motor vehicle exhaust contributes to a large proportion of the air pollution present. The motor vehicle exhaust systems emit a variety of toxic components, including carbon monoxide, nitrogen oxides, volatile organic compounds, ozone, particulate matter, and polycyclic aromatic hydrocarbons. Several epidemiological studies and laboratory studies have demonstrated that these components are potentially mutagenic, carcinogenic, and endocrine disrupting agents. However, their impact on male reproductive function and associated proteins is not very clear. Therefore, a comprehensive review on the effects of motor vehicle exhaust on male reproductive function and associated proteins is needed to better understand the risks of exhaust exposure for men. We found that motor vehicle exhaust can cause harmful effects on male reproductive functions by altering organ weights, reducing the spermatozoa qualities, and inducing oxidative stress. Remarkably, motor vehicle exhaust exposure causes significant changes in the expression patterns of proteins that are key components involved in spermatogenesis and testosterone synthesis. In conclusion, this review helps to describe the risks of vehicle exhaust exposure and its relationship to potential adverse effects on the male reproduction system.

Inflammatory airway responses by nasal inoculation of suspended particulate matter in NC/Nga mice

To evaluate the allergic effect of airborne particulate matter (PM) on the airway, separated soluble supernatant (Sup) and insoluble precipitate (Pre) in suspended PM were inoculated into NC/Nga mice with a high sensitivity for mite allergens. Sup, Pre, or both Sup and Pre with or without pronase treatment were inoculated via the nasal route five times for sensitization and a challenge inoculation on the 11th day in NC/Nga mice. On the 14th day, mice were examined for airway hyperresponsiveness (AHR), bronchoalveolar lavage fluid (BALF) cell count, mRNA expression of Th1 and Th2 cytokines in the lung tissue, and histopathology. Synergistic effects of Sup and Pre were observed as increases in AHR and a histopathological change of Periodic acid-Schiff (PAS) staining. Increases in neutrophils, macrophages, and lymphocytes of BALF cells were dependent on Pre. The expression of IL-4 mRNA was increased by Sup, and those of IL-5 mRNA and Il-13 mRNA was increased by Sup and Pre. Augmented AHR, mRNA expression of IL-4, peribronchial inflammation, and PAS staining by Sup plus Pre were attenuated by treatment of Sup with pronase to digest proteins. These results suggest that some proteins of ambient PM may be important environmental factors for AHR and airway inflammation with the aid of insoluble particulates, although some soluble factors such as endotoxins cannot be ruled out.

Effects of exposure to nanoparticle-rich or -depleted diesel exhaust on allergic pathophysiology in the murine lung

Although it has been shown that exposure to diesel exhaust (DE) is linked to the induction or exacerbation of respiratory disorders, the major components responsible have not been fully identified. We examined the effects of airway exposure to nanoparticle-rich DE (NR-DE) or DE without particles on allergic pulmonary inflammation in mice. We also investigated the cellular responses to intratracheal instillation of NR-DE particles (NR-DEP). ICR mice inhaled one of four different mixtures (control air, low-concentration DE, high-concentration DE, and high-concentration DE without particles) for 8 weeks in the presence or absence of repeated intratracheal administration of ovalbumin (OVA). In a separate study, NR-DEP and/or OVA were repeatedly administrated intratracheally to mice. High-concentration NR-DE or DE without particles substantially exacerbated OVA-induced eosinophilic airway inflammation. This exacerbation was concomitant with increases in lung levels of Th2 cytokines such as interleukin (IL)-4, IL-5, and IL-13 and of chemokines such as monocyte chemotactic protein-1. Furthermore, in the presence of allergen, both DE without particles and high-concentration NR-DE strongly enhanced the production and release of myeloperoxidase into the alveolar spaces. Repeated administration of NR-DEP did not substantially affect the allergic asthma. These results strongly suggest that gaseous compounds in NR-DE aggravate murine allergic airway inflammation, mainly via amplification of the Th2 response.

Effects of exposure to nanoparticle-rich diesel exhaust on 8-OHdG synthesis in the mouse asthmatic lung

It has been demonstrated that exposure to diesel exhaust (DE) is associated with the induction and exacerbation of respiratory disorders; however, the impacts of DE containing mainly nanoparticles have been less studied. We have previously demonstrated that inhalation exposure to nanoparticle-rich DE (NR-DE) exacerbated allergic pulmonary inflammation, in the context of enhanced local expression of proinflammatory molecules. However, the underlying mechanisms have not been fully elucidated. 8-Hydroxydeoxyguanosine (8-OHdG) is a marker of oxidative damage, particularly in DNA. This study examined the effects of NR-DE on 8-OHdG synthesis in the lung in the presence or absence of an allergen. Institute for Cancer Research (ICR) mice were exposed by inhalation to four different gas compositions (control air, low-concentration DE, high-concentration DE and high-concentration DE without particulate matter) for 8 weeks, in the presence or absence of repetitive intratracheal administration of ovalbumin (OVA). Thereafter, we assessed the levels of 8-OHdG synthesis and expression in the lungs by means of enzyme immunoassay (EIA) and immunohistochemistry. The EIA revealed that the level of 8-OHdG was significantly higher in the high-concentration NR-DE-exposed and allergen-sensitized/stimulated group compared with that in the control air-exposed and allergen-treated group. The immunohistochemistry results demonstrated that the level of immunoreactive 8-OHdG was higher in the NR-DE-exposed and allergen-treated lungs compared with that in the corresponding control air-exposed lungs. The results suggested that NR-DE exposure enhanced 8-OHdG formation in asthmatic lungs. This, at least in part, is involved in the NR-DE-mediated exacerbation of the allergic pathophysiology that was identified in our previous study.

Organic chemicals in diesel exhaust particles enhance picryl chloride-induced atopic dermatitis in NC/Nga mice

BACKGROUND

Diesel exhaust particles (DEP) have been reported to worsen allergic airway inflammation in mice. Recently, the organic chemical components of DEP (DEP-OC) were found to be important contributors to the aggravation of allergic airway inflammation in mice. The purpose of this study was to examine the effects of DEP-OC on atopic dermatitis (AD)-like skin lesions induced by picryl chloride (PiCl) in NC/Nga mice.

METHODS

DEP were extracted with benzene/ethanol, and the soluble organic fraction formed the DEP-OC. NC/Nga male mice received simultaneous application of DEP-OC and/or PiCl on their ears once a week for 9 or 3 weeks. We evaluated skin lesions by noting scaling, eruption, excoriation, erosion, hemorrhage, pathologic changes, production of cytokines, and IgE level in the serum.

RESULTS

PiCl application alone produced progressively severe AD-like skin lesions. The application of PiCl plus DEP-OC resulted in a marked worsening of skin lesions in the early stages of AD. Moreover, mast cell counts significantly increased in the subcutaneous tissue. Administration of PiCl combined with DEP-OC resulted in a greater increase in the local expression of interleukin-4, keratinocyte chemoattractant, and neutrophils in subcutaneous tissue compared with PiCl treatment alone. In contrast, the combination treatment produced lower levels of IFN-γ compared with PiCl treatment alone.

CONCLUSIONS

DEP-OC application to the skin aggravated PiCl-induced AD. This aggravation may be due to activation of the Th2-associated immune responses by the organic chemicals in DEP.

Organic Chemicals Adsorbed onto Diesel Exhaust Particles Directly Alter the Differentiation of Fetal Thymocytes Through Arylhydrocarbon Receptor but Not Oxidative Stress Responses

Diesel exhaust particles (DEP) were reported to have adverse effects on the immune system of laboratory animals and to induce thymic involution, particularly when exposure occurred during the fetal or lactational period. DEP consist of a carbon core to which many organic compounds are adsorbed, including polyaromatic hydrocarbons (PAHs) and their derivatives (e.g., dioxins and quinones). Although it has been suggested that these organic compounds were responsible for mediating the effects of DEP through their regulation of gene expression, the molecular mechanism of action of DEP has not been fully elucidated. In this study, we examined the direct effect of DEP extracts and their constituents on gene expression and phenotype in the fetal thymus. Fetal thymuses from C57BL/6 mice were exposed to DEP extracts for 24 hrs, after which their gene expression was analyzed using an Affymetrix GeneChip system. DEP extracts up-regulated several genes known as arylhydrocarbon receptor (AhR)-target genes, including cytochrome P450 1a1 (Cyp1a1), 1b1 (Cyp1b1), TCDD-inducible poly(ADP-ribose) polymerase (Tiparp), and scinderin (Scin). Similarly, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and benzo[a]pyrene (B[a]P), which are AhR ligands, induced remarkably similar changes in gene expression compared to DEP extracts. In addition, our data showed little contribution of quinones to DEP extracts-induced changes in gene expression in fetal thymus through oxidative stress responses. These changes in gene expression were also confirmed by semi-quantitative RT-PCR. Furthermore, DEP extracts skewed thymic T-cell differentiation in favor of the production of CD8 T-cells, which was also observed when exposed to AhR ligands. Our results suggest that organic compounds adsorbed onto DEP alter thymic gene expression and directly affect thymocyte development by activating the AhR.

Diesel exhaust particles and airway inflammation

PURPOSE OF REVIEW

Epidemiologic investigation has associated traffic-related air pollution with adverse human health outcomes. The capacity of diesel exhaust particles (DEPs), a major emission source air pollution particle, to initiate an airway inflammation has subsequently been investigated. We review the recent controlled human exposures to diesel exhaust and DEPs, and summarize the investigations into the associations between this emission source air pollution particle and airway inflammation.

RECENT FINDINGS

Using bronchoalveolar lavage, bronchial biopsies, and sputum collection, studies have demonstrated inflammation in the airways of healthy individuals after exposure to diesel exhaust and DEPs. This inflammation has included neutrophils, eosinophils, mast cells, and lymphocytes. Elevated expression and concentrations of inflammatory mediators have similarly been observed in the respiratory tract after diesel exhaust and DEP exposure. An increased sensitivity of asthmatic individuals to the proinflammatory effects of DEPs has not been confirmed.

SUMMARY

Inflammation after diesel exhaust and DEP exposure is evident at higher concentrations only; there appears to be a threshold dose for DEPs approximating 300 μg/m. The lack of a biological response to DEPs at lower concentrations may reflect a contribution of gaseous constituents or interactions between DEPs and gaseous air pollutants to the human inflammatory response and function loss.

Physiological and inflammatory responses in an anthropomorphically relevant model of acute diesel exhaust particle exposure are sex and dose-dependent

CONTEXT

Diesel exhaust particles (DEP) are an important contributor to suspended particulate matter (PM) in urban areas. While epidemiological evidence exists for a sex-influenced dose-response relationship between acute PM exposure and respiratory health, similar data are lacking for DEP. Further, experimental evidence showing deleterious effects on respiratory health due to acute DEP exposure is sparse.

OBJECTIVE

To establish and characterize a mouse model of acute DEP exposure, comparing male and female mice and assessing the kinetics of the elemental carbon content of alveolar macrophages (AMs) to relate our model to human exposure.

MATERIALS AND METHODS

Adult BALB/c mice were intranasally inoculated with 0 (control), 10, 30 or 100 µg DEP in saline. Bronchoalveolar lavage cellular inflammation and cytokine levels were assessed 3, 6, 12, 24, 48 and 168 hours post exposure. Elemental carbon uptake by AMs was additionally assessed at 336 and 672 hours post DEP exposure. Thoracic gas volume and lung mechanics were measured 6 and 24 hours post exposure.

RESULTS

DEP resulted in dose-dependent cellular inflammation and cytokine production in both sexes. Males and females responded differently with females having more severe and prolonged neutrophilia, monocyte chemoattractant protein-1 and developing greater abnormalities in lung function. The sexual dimorphism in response was not related to the capacity of AMs to phagocytise DEP.

CONCLUSIONS

Our mouse model of acute diesel exhaust particle exposure shows a dose dependency and sexual dimorphism in response. Quantification of elemental carbon in AMs allows for comparison of the results of our study with human studies.

Composition of air pollution particles and oxidative stress in cells, tissues, and living systems

Epidemiological studies demonstrated an association between increased levels of ambient air pollution particles and human morbidity and mortality. Production of oxidants, either directly by the air pollution particles or by the host response to the particles, appears to be fundamental in the biological effects seen after exposure to particulate matter (PM). However, the precise components and mechanisms responsible for oxidative stress following PM exposure are yet to be defined. Direct oxidant generation by air pollution particles is attributed to organic and metal components. Organic compounds generate an oxidative stress through redox cycling of quinone-based radicals, by complexing of metal resulting in electron transport, and by depletion of antioxidants by reactions between quinones and thiol-containing compounds. Metals directly support electron transport to generate oxidants and also diminish levels of antioxidants. In addition to direct generation of oxidants by organic and metal components, cellular responses contribute to oxidative stress after PM exposure. Reactive oxygen species (ROS) production occurs in the mitochondria, cell membranes, phagosomes, and the endoplasmic reticulum. Oxidative stress following PM exposure initiates a series of cellular reactions that includes activation of kinase cascades and transcription factors and release of inflammatory mediators, which ultimately lead to cell injury or apoptosis. Consequently, oxidative stress in cells and tissues is a central mechanism by which PM exposure leads to injury, disease, and mortality.

Effects of carbon black nanoparticles on elastase-induced emphysematous lung injury in mice

Although adverse health effects of particulate matter with a diameter of <100 nm (nanoparticles) have been proposed, biological evidence supporting their promotion of the inflammatory lung response in vivo is limited. This study investigated the impact of pulmonary exposure to carbon black nanoparticles (CBNP) on emphysematous lung injury induced by porcine pancreatic elastase (PPE) in mice. Vehicle, two sizes (14 and 56 nm) of CBNP (50 μg/body: 4 mg/kg), PPE (0.03 U/body: 1 U/kg) or PPE + CBNP was administered intratracheally; thereafter, parameters of inflammatory lung changes were evaluated at several time-points. CBNP of 14 nm significantly induced acute lung inflammation in non-elicited subjects and aggravated PPE-elicited airway neutrophilic inflammation at an early stage (day 1), which was concomitant with the enhanced lung expression of pro-inflammatory cytokines such as interleukin-1β and chemokine such as keratinocyte-derived chemoattractant. Further, 14-nm CBNP exaggerated emphysematous lung structural changes at a delayed stage (day 14). On the other hand, 56-nm CBNP induced lung inflammation but did not influence PPE-elicited pathophysiology in the lung. Taken together, CBNP at an optimal size and dose can exacerbate PPE-induced pulmonary inflammation and emphysema. This enhancement may be mediated, at least partly, via the increased local expression of pro-inflammatory molecules.

Promoting effects of nanoparticles/materials on sensitive lung inflammatory diseases

Although the adverse health effects of nanoparticles/materials have been proposed and are being clarified, their facilitating effects on preexisting pathological conditions have not been fully established. We provide insights into the environmental immunotoxicity of nanoparticles as an aggravating factor in hypersusceptible subjects, especially those with respiratory disorders, using our in vivo models. We first examined the effects of nanoparticles/materials on lung inflammation induced by bacterial endotoxin (lipopolysaccharide) as a test model against innate immunity, and demonstrated that nanoparticles instilled through both an intratracheal tube and an inhalation system can exacerbate lung inflammation. Secondly, we examined the effects of nanoparticles/materials on allergic pathophysiology, and showed that repetitive pulmonary exposure to nanoparticles has aggravating effects on allergic airway inflammation, including adjuvant effects on Th2-milieu. Taken together, nanoparticle exposure may synergistically facilitate pathological inflammatory conditions in the lung via both innate and adaptive immunological abnormalities.

Mouse models to unravel the role of inhaled pollutants on allergic sensitization and airway inflammation

Air pollutant exposure has been linked to a rise in wheezing illnesses. Clinical data highlight that exposure to mainstream tobacco smoke (MS) and environmental tobacco smoke (ETS) as well as exposure to diesel exhaust particles (DEP) could promote allergic sensitization or aggravate symptoms of asthma, suggesting a role for these inhaled pollutants in the pathogenesis of asthma. Mouse models are a valuable tool to study the potential effects of these pollutants in the pathogenesis of asthma, with the opportunity to investigate their impact during processes leading to sensitization, acute inflammation and chronic disease. Mice allow us to perform mechanistic studies and to evaluate the importance of specific cell types in asthma pathogenesis. In this review, the major clinical effects of tobacco smoke and diesel exhaust exposure regarding to asthma development and progression are described. Clinical data are compared with findings from murine models of asthma and inhalable pollutant exposure. Moreover, the potential mechanisms by which both pollutants could aggravate asthma are discussed.

Adjuvant Activity of Ambient Particulate Matter in Macrophage Activity-Suppressed,N-Acetylcysteine-Treated, iNOS- and IL-4-Deficient Mice

In previous studies, we have shown strong adjuvant activity for Ottawa dust (EHC-93) after coexposure of the BALB/c mouse to EHC-93 and ovalbumin. Mice were intranasally sensitized at days 0 and 14 with 200 microg ovalbumin and 150 microg EHC-93, and challenged with ovalbumin at days 35, 38, and 41 with 200 microg ovalbumin. Mice were autopsied at day 42. This adjuvant activity was shown for the antibody response to ovalbumin (immunoglobulins E, G1, and G2a), histopathological lesions in the lung, cytokines, and the numbers of eosinophils in lung lavages. To study the mechanisms of this adjuvant activity, mice (BALB/cC.D2-Vil6) with natural-resistance-associated macrophage protein (Nramp1s), BALB/c mice pretreated with the antioxidant N-acetylcysteine (NAC), mice (B6.129P2-Nos2tmLau) deficient in inducible nitric oxide synthase (iNOS), and mice with interleukin-4 (IL-4) deficiency (BALB/cIl4< tm2Nnt) were coexposed to ovalbumin and EHC-93. Our studies have shown that the adjuvant activity induced after such coexposure does not change if the macrophage activation of the mice is disturbed or if the mice have been pretreated with N-acetylcysteine. In addition, the adjuvant activity does not develop through the pathway in which inducible nitric oxide synthase is involved. Because the histopathological lesions are statistically significant less in the IL-4 knockout strain in comparison with the wild type, we conclude that interleukin-4 might play an important role in the adjuvant activity caused by EHC-93.

Effects of pulmonary exposure to carbon nanotubes on lung and systemic inflammation with coagulatory disturbance induced by lipopolysaccharide in mice

Despite intensive research as to the pathogenesis of lipopolysaccharide (LPS)-related inflammation with coagulatory disturbance, their exacerbating factors have not been well explored. This study examined the effects of pulmonary exposure to two types of nano-sized materials (carbon nano-tubes: CNT [single-wall: SWCNT, and multi-wall: MWCNT]) on lung inflammation and consequent systemic inflammation with coagulatory disturbance induced by pulmonary exposure to LPS in mice and their cellular mechanisms in vitro. ICR male mice were divided into 6 experimental groups that intra-tracheally received the vehicle, two types of CNT (4 mg/kg), LPS (33 mu g/kg), or LPS plus either type of CNT. Twenty-four hours after treatment, both types of CNT alone induced lung inflammation with enhanced lung expression of proinflammatory cytokines, but did not synergistically exacerbate lung inflammation elicited by LPS. SWCNT significantly induced/ enhanced pulmonary permeability and hyperfibrinogenemia and reduced activated protein C in the absence or presence of LPS, whereas MWCNT did moderately. Both CNT moderately, but not significantly, elevated circulatory levels of proinflammatory cytokines and chemokines. In the presence of LPS, CNT tended to elevate the levels of the mediators with an overall trend, which was more prominent with SWCNT than with MWCNT. In vitro study showed that both CNT amplified LPS-induced cytokine production from peripheral blood monocytes. These results suggest that CNT can facilitate systemic inflammation with coagulatory disturbance, at least in part, via the activation of mononuclear cells, which is accompanied by moderate enhancement of acute lung inflammation related to LPS.

Size effects of latex nanomaterials on lung inflammation in mice

Effects of nano-sized materials (nanomaterials) on sensitive population have not been well elucidated. This study examined the effects of pulmonary exposure to (latex) nanomaterials on lung inflammation related to lipopolysaccharide (LPS) or allergen in mice, especially in terms of their size-dependency. In protocol 1, ICR male mice were divided into 8 experimental groups that intratracheally received a single exposure to vehicle, latex nanomaterials (250 microg/animal) with three sizes (25, 50, and 100 nm), LPS (75 microg/animal), or LPS plus latex nanomaterials. In protocol 2, ICR male mice were divided into 8 experimental groups that intratracheally received repeated exposure to vehicle, latex nanomaterials (100 microg/animal), allergen (ovalbumin: OVA; 1 microg/animal), or allergen plus latex nanomaterials. In protocol 1, latex nanomaterials with all sizes exacerbated lung inflammation elicited by LPS, showing an overall trend of amplified lung expressions of proinflammatory cytokines. Furthermore, LPS plus nanomaterials, especially with size less than 50 nm, significantly elevated circulatory levels of fibrinogen, macrophage chemoattractant protein-1, and keratinocyte-derived chemoattractant, and von Willebrand factor as compared with LPS alone. The enhancement tended overall to be greater with the smaller nanomaterials than with the larger ones. In protocol 2, latex nanomaterials with all sizes did not significantly enhance the pathophysiology of allergic asthma, characterized by eosinophilic lung inflammation and Igs production, although latex nanomaterials with less than 50 nm significantly induced/enhanced neutrophilic lung inflammation. These results suggest that latex nanomaterials differentially affect two types of (innate and adaptive immunity-dominant) lung inflammation.

Size effects of nanomaterials on lung inflammation and coagulatory disturbance

Effects of nano-sized materials (nanomaterials) on subjects with predisposing inflammatory disorders have not been well elucidated. This study examined the effects of pulmonary exposure to TiO2 nanomaterials on lung inflammation induced by lipopolysaccharide (LPS) and consequent systemic inflammation with coagulatory disturbance in mice, in particular regarding their size-dependency. Also, gene expression pattern in the lung was compared among the experimental groups using cDNA microarray analysis. ICR male mice were divided into 8 experimental groups that intratracheally received vehicle, three sizes (15, 50, 100 nm) of TiO2 nanomaterials (8 mg/kg), LPS (2.5 mg/kg), or LPS plus nanomaterials. Twenty four h after the treatment, these nanomaterials exacerbated the lung inflammation and vascular permeability elicited by LPS, with an overall trend of amplified lung expressions of cytokines such as interleukin (IL)-1beta, macrophage chemoattractant protein (MCP)-1, and keratinocyte chemoattractant (KC). LPS plus nanomaterials, especially of a size less than 50 nm, elevated circulatory levels of fibrinogen, IL-1beta, MCP-1, and KC, and von Willebrand factor as compared with LPS alone. The enhancement tended overall to be greater with the smaller nanomaterials than with the larger ones. cDNA microarray analyses revealed that there was no difference in gene expression pattern between the LPS group and the LPS + nanomaterial. These results suggest that nanomaterials exacerbate lung inflammation related to LPS with systemic inflammation and coagulatory disturbance, and that the exacerbation is more prominent with smaller nanomaterials than with larger ones.

The role of oxidative stress in ambient particulate matter-induced lung diseases and its implications in the toxicity of engineered nanoparticles

Ambient particulate matter (PM) is an environmental factor that has been associated with increased respiratory morbidity and mortality. The major effect of ambient PM on the pulmonary system is the exacerbation of inflammation, especially in susceptible people. One of the mechanisms by which ambient PM exerts its proinflammatory effects is the generation of oxidative stress by its chemical compounds and metals. Cellular responses to PM-induced oxidative stress include activation of antioxidant defense, inflammation, and toxicity. The proinflammatory effect of PM in the lung is characterized by increased cytokine/chemokine production and adhesion molecule expression. Moreover, there is evidence that ambient PM can act as an adjuvant for allergic sensitization, which raises the possibility that long-term PM exposure may lead to increased prevalence of asthma. In addition to ambient PM, rapid expansion of nanotechnology has introduced the potential that engineered nanoparticles (NP) may also become airborne and may contribute to pulmonary diseases by novel mechanisms that could include oxidant injury. Currently, little is known about the potential adverse health effects of these particles. In this communication, the mechanisms by which particulate pollutants, including ambient PM and engineered NP, exert their adverse effects through the generation of oxidative stress and the impacts of oxidant injury in the respiratory tract will be reviewed. The importance of cellular antioxidant and detoxification pathways in protecting against particle-induced lung damage will also be discussed.

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 μg/body). Dietary supplementation with 1.0% 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.

Effects of components derived from diesel exhaust particles on lung physiology related to antigen

Our previous study has shown that diesel exhaust particles (DEP), main constituents in ambient particulate matters (PM), enhance airway hyperresponsivness in a murine model of allergic asthma (Takano et al., 1998). However, it remains unknown which components in DEP are responsible for the enhancement. The present study investigated the effects of repeated pulmonary exposure to DEP components (extracted organic chemicals in DEP; DEP-OC, carbonaceous nuclei of DEP after extraction; washed DEP) on lung physiology in the presence or absence of antigen. ICR mice were divided into six experimental groups. Vehicle, DEP components, ovalbumin (OVA), or DEP components plus OVA was administered intratrachally for 6 weeks. Twenty-four hr after the last instillation, cholinergic lung reactivity was examined. DEP components alone did not induce any facilitation of lung function as compared to vehicle alone. The values of total respiratory system resistance (R), elastance (E), Newtonian resistance (R(n)), tissue damping (G), and tissue elastance (H) were higher and the value of compliance (C) was lower in the OVA or the DEP component + OVA groups than in the vehicle group. In particular, the hyperreactivity was most prominent in the washed DEP + OVA group. The values in the DEP-OC + OVA group were not significantly different from those in the OVA group. These data suggest that carboneous component in DEP, rather than organic chemical one, can be attributable to the enhancement of lung hyperresponsiveness in allergic asthma.

Effects of nanoparticles on lung physiology in the presence or absence of antigen

Ambient particulate matter (PM) exacerbates allergic airway diseases. Our previous study showed that diesel exhaust particles, the main constituents in urban PM, enhance airway hyperresponsivness in mice. In addition, health effects of PM with a diameter of less than 100 nm, called nanoparticles, have been reported, and we have also demonstrated that carbon nanoparticles exacerbate antigen-related airway inflammation. The present study investigates the effects of pulmonary exposure to two sizes of carbon nanoparticles on lung physiology and lung expression of Muc5ac in the presence or absence of antigen in mice. Nanoparticles alone or ovalbumin (OVA) alone moderately enhanced cholinergic airway reactivity, as assessed by total respiratory system resistance (R) and Newtonian resistance (Rn). In the nanoparticle + OVA groups, all the parameters for lung responsiveness, such as R, compliance, elastance, Rn, tissue damping, and tissue elastance, were worse than those in the vehicle group, the corresponding nanoparticle groups or the OVA group. The lung mRNA level for Muc5ac was significantly higher in the OVA group than in the vehicle group, and further increased in the nanoparticle + OVA groups than in the OVA or the nanoparticle groups. These data suggest that carbon nanoparticles can enhance lung hyperresponsiveness, especially in the presence of antigen. The effects may be mediated, at least partly, through the enhanced lung expression of Muc5ac.

[Development of new cytoxicity testing systems that include toxicokinetic processes]

Conventional in vitro cytotoxicity tests usually do not include toxicokinetic processes that affect final toxicity in the entire body. To overcome this limitation, we have been developing several types of new toxicity test systems and applying them to evaluate hazardous chemicals or environmental samples. In this review, we described two of these new systems; one is a batch-type gas exposure system based on air-liquid interface culture of lung epithelial cells, and the other is a simple double-layered coculture system incorporating permeation and biotransformation processes occurring in the small intestine. In addition, we introduce our latest approach toward further miniaturization of existing tests, that is, determination of minimum cell number necessary for obtaining physiologically-relevant tissue responses.

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.

Pulmonary exposure to diesel exhaust particles enhances coagulatory disturbance with endothelial damage and systemic inflammation related to lung inflammation

Pulmonary exposure to diesel exhaust particles (DEP) enhances lung inflammation related to bacterial endotoxin (lipopolysaccharide [LPS]) in mice. Severe lung inflammation can reportedly induce coagulatory abnormalities and systemic inflammation. This study examined the effects of components of DEP on lung inflammation, pulmonary permeability, coagulatory changes, systemic inflammatory response, and lung-to-systemic translocation of LPS in a murine model of lung inflammation. ICR mice were divided into six experimental groups that intratracheally received vehicle, LPS (2.5 mg/kg), organic chemicals in DEP (DEP-OC; 4 mg/kg) extracted with dicloromethane), residual carbonaceous nuclei of DEP (washed DEP: 4 mg/kg), DEP-OC + LPS, or washed DEP + LPS. Both DEP components exacerbated lung inflammation, vascular permeability, and the increased fibrinogen and E-selectin levels induced by LPS. With overall trends, the exacerbation was more prominent with washed DEP than with DEP-OC. Washed DEP + LPS significantly decreased activated protein C and antithrombin-III and elevated circulatory levels of interleukin (IL)-6, keratinocyte chemoattractant (KC), and LPS as compared with LPS alone, whereas DEP-OC + LPS elevated IL-6, KC, and LPS without significance. These results show that DEP components, especially washed DEP, amplify the effects if LPS on the respiratory system and suggest that they contribute to the adverse health effects of particulate air pollution on the sensitive populations with predisposing vascular and/or pulmonary diseases, including ischemic vascular diseases and respiratory infection.

ROS scavenging effects of organic extract of diesel exhaust particles on human neutrophil granulocytes and rat alveolar macrophages

Diesel exhaust particles are major constituents of ambient air pollution, and are associated with respiratory and cardiovascular diseases and lung cancer. The organic part of the particles is heterogenic and complex, and seems to be responsible for many of the adverse effects. Increased formation of ROS is often connected to the adverse effects. We have therefore investigated the effect of an organic extract of diesel exhaust particles on the reactive oxygen species (ROS) status in human neutrophil granulocytes and rat alveolar macrophages in vitro. ROS formation were studied by three different assays namely the use of DCFH-DA, lucigenin and luminol. The organic extract increased ROS assayed with DCFH-DA, but it decreased the amount of ROS in cells stimulated by PMA in all three assays. The identities of the ROS affected were further studied in cell free systems. The cell free studies confirmed that the extract had scavenging effects against superoxide, hypochlorite and to a smaller extent against peroxynitrite, but not against the hydroxyl radical and nitric oxide. ROS take part in the intracellular signalling pathways as well as in the defence against invading microorganisms, and the possible effects of interference of the redox status in the cells are discussed.

Effects of Diesel Exhaust on Lung Inflammation Related to Bacterial Endotoxin in Mice

We have previously shown that intratracheal instillation of diesel exhaust particles enhances lung inflammation and lung expression of proinflammatory cytokines and chemokines related to bacterial endotoxin (lipopolysaccharide) in mice. The present study was designed to elucidate the effects of inhalation of diesel exhaust on lung inflammation related to lipopolysaccharide. ICR mice were exposed for 12 hr to clean air or diesel exhaust at a soot concentration of 0.3, 1.0, or 3.0 mg/m(3) after intratracheal challenge with 125 microg/kg of lipopolysaccharide. Lung inflammation and lung expression of proinflammatory chemokines such as macrophage chemoattractant protein-1 and keratinocyte chemoattractant were evaluated 24 hr after intratracheal administration. Diesel exhaust inhalation decreased lipopolysaccharide-elicited inflammatory cell recruitment into the bronchoalveolar lavage fluid as compared with clean air inhalation. Histological study demonstrated that exposure to diesel exhaust did not affect lipopolysaccharide-enhanced neutrophil recruitment into the lung parenchyma. Lipopolysaccharide instillation elevated lung expression of macrophage chemoattractant protein-1 and keratinocyte chemoattractant under clean air or diesel exhaust inhalation. However, diesel exhaust exposure did not influence but rather did suppress these levels in the presence of lipopolysaccharide. These results suggest that short-term exposure to diesel exhaust did not exacerbate lung inflammation related to bacterial endotoxin.

Effects of airway exposure to nanoparticles on lung inflammation induced by bacterial endotoxin in mice

BACKGROUND

Although adverse health effects of particulate matter with a diameter of < 100 nm (nanoparticles) have been proposed, molecular and/or experimental evidence for their facilitation of lung inflammation in vivo is not fully defined.

OBJECTIVE

In the present study we investigated the effects of nanoparticles on lung inflammation related to bacterial endotoxin [lipopolysaccharide (LPS) ] in mice.

RESULTS

We intratracheally administered vehicle, two sizes (14 nm, 56 nm) of carbon black nanoparticles (4 mg/kg) , LPS (2.5 mg/kg) , or LPS plus nanoparticles and evaluated parameters for lung inflammation and coagulation. Nanoparticles alone induced slight lung inflammation and significant pulmonary edema compared with vehicle. Fourteen-nanometer nanoparticles intensively aggravated LPS-elicited lung inflammation and pulmonary edema that was concomitant with the enhanced lung expression of interleukin-1beta (IL-1beta) , macrophage inflammatory protein-1alpha (MIP-1alpha) , macrophage chemoattractant protein-1, MIP-2, and keratinocyte chemoattractant in overall trend, whereas 56-nm nanoparticles did not show apparent effects. Immunoreactivity for 8-hydroxyguanosine, a marker for oxidative stress, was more intense in the lungs from the LPS + 14-nm nanoparticle group than in those from the LPS group. Circulatory fibrinogen levels were higher in the LPS + plus 14-nm nanoparticle group than in the LPS group.

CONCLUSIONS

Taken together, evidence indicates that nanoparticles can aggravate lung inflammation related to bacterial endotoxin, which is more prominent with smaller particles. The enhancement may be mediated, at least partly, via the increased local expression of proinflammatory cytokines and via the oxidative stress. Furthermore, nanoparticles can promote coagulatory disturbance accompanied by lung inflammation.

Effects of Volatile Constituents of Rosemary Extract on Lung Inflammation Induced by Diesel Exhaust Particles

Epidemiological and experimental studies have implicated that diesel exhaust particles are involved in increases in morbidity and mortality from lung diseases. Recently, we have demonstrated that rosmarinic acid, a polyphenolic liquid component in perilla, inhibits lung inflammation induced by diesel exhaust particles in vivo, partly through its antioxidative property. We have also shown the antioxidative activities of volatile constituents of rosemary extract, the gaseous component in perilla, in vitro. The purpose of this study was to evaluate the effects of intratracheal administration of volatile rosemary extract on lung inflammation induced by diesel exhaust particles. ICR mice were treated with intratracheal administration of volatile rosemary extract before intratracheal exposure to diesel exhaust particles. Twenty-four hr later, diesel exhaust particles exposure elicited lung inflammation characterized by the infiltration of neutrophils and eosinophils, which was confirmed by cellular profile of bronchoalveolar lavage fluid and histological examination. Diesel exhaust particles enhanced the protein expressions of interleukin-1beta, macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant in the lung. Pretreatment with rosemary extract significantly inhibited the diesel exhaust particles-induced lung inflammation. Rosemary extract treatment also suppressed the diesel exhaust particles-enhanced lung expression of macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant. These results suggest that intratracheal administration of rosemary extract can prevent lung inflammation induced by diesel exhaust particles. The preventive effect is mediated, at least partly, through the inhibition of the enhanced lung expressions of macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractants.

Effects of organic chemicals derived from ambient particulate matter on lung inflammation related to lipopolysaccharide

The effects of components of ambient particulate matter (PM) on individuals with predisposing respiratory disorders are not well defined. We have previously demonstrated that airway exposure to diesel exhaust particles (DEP) or organic chemicals (OC) extracted from DEP (DEP-OC) enhances lung inflammation related to bacterial endotoxin (lipopolysaccharide, LPS). The present study aimed to examine the effects of airway exposure to OC extracted from urban PM (PM-OC) on lung inflammation related to LPS. ICR mice were divided into four experimental groups that intratracheally received vehicle, LPS (2.5 mg/kg), PM-OC (4 mg/kg), or PM-OC + LPS. Lung inflammation, lung water content, and lung expression of cytokines were evaluated 24 h after intratracheal administration. LPS challenge elicited lung inflammation evidenced by cellular profiles of bronchoalveolar lavage fluid and lung histology, which was further aggravated by the combined challenge with PM-OC. The combination with PM-OC and LPS did not significantly exaggerate LPS-elicited pulmonary edema. LPS instillation induced elevated lung expression of interleukin-1beta, macrophage inflammatory protein-1alpha, macrophage chemoattractant protein-1, and keratinocyte chemoattractant, whereas the combined challenge with PM-OC did not influence these levels. All the results were consistent with our previous reports on DEP-OC. These results suggest that the extracted organic chemicals from PM exacerbate infectious lung inflammation. The mechanisms underlying the enhancing effects are not mediated via the enhanced local expression of proinflammatory cytokines.

Components of diesel exhaust particles differentially affect Th1/Th2 response in a murine model of allergic airway inflammation

BACKGROUND

Diesel exhaust particles (DEP) can enhance various respiratory diseases. However, it is unclear as to which components in DEP are associated with the enhancement. We investigated the effects of DEP components on antigen-related airway inflammation, using residual carbonaceous nuclei of DEP after extraction (washed DEP), extracted organic chemicals (OC) in DEP (DEP-OC), and DEP-OC plus washed DEP (whole DEP) in the presence or absence of ovalbumin (OVA).

METHODS

Male ICR mice were intratracheally administrated with OVA and/or DEP components. We examined the cellular profile of bronchoalveolar lavage (BAL) fluid, histological changes, lung expression of inflammatory molecules, and antigen-specific production of IgG1 in the serum.

RESULTS

DEP-OC, rather than washed DEP, enhanced infiltration of inflammatory cells into BAL fluid, magnitude of airway inflammation, and proliferation of goblet cells in the airway epithelium in the presence of OVA, which was paralleled by the enhanced lung expression of eotaxin and IL-5 as well as the elevated concentration of OVA-specific IgG1. In contrast, washed DEP with OVA showed less change and increased the lung expression of IFN-gamma. The combination of whole DEP and OVA caused the most remarkable changes in the entire enhancement, which was also accompanied by the enhanced expression of IL-13 and macrophage inflammatory protein-1 alpha.

CONCLUSION

DEP-OC, rather than washed DEP, exaggerated allergic airway inflammation through the enhancement of T-helper type 2 responses. The coexistence of OC with carbonaceous nuclei caused the most remarkable aggravation. DEP components might diversely affect various types of respiratory diseases, while whole DEP might mostly aggravate respiratory diseases.

Effects of phenanthraquinone on allergic airway inflammation in mice

BACKGROUND

Diesel exhaust particles (DEP) enhance allergic airway inflammation in mice (Takano et al., Am J Respir Crit Care Med 1997; 156: 36-42). DEP consist of carbonaceous nuclei and a vast number of organic chemical compounds. However, it remains to be identified which component(s) from DEP are responsible for the enhancing effects. 9,10-Phenanthraquinone (PQ) is a quinone compound involved in DEP.

OBJECTIVE

To investigate the effects of PQ inoculated intratracheally on allergic airway inflammation related to ovalbumin (OVA) challenge.

MATERIALS AND METHODS

We evaluated effects of PQ on airway inflammation, local expression of cytokine proteins, and allergen-specific immunoglobulin production in mice in the presence or absence of OVA. Results In the presence of OVA, PQ (2.1 ng/animal) significantly increased the numbers of eosinophils and mononuclear cells in bronchoalveolar lavage fluid as compared with OVA alone. In contrast, the numbers of these cells around the airways were not significantly different between OVA challenge and OVA plus PQ challenge in lung histology. PQ exhibited adjuvant activity for the allergen-specific production of IgG1 and IgE. OVA challenge induced significant increases in the lung expression of IL-4, IL-5, eotaxin, macrophage chemoattractant protein-1, and keratinocyte chemoattractant as compared with vehicle challenge. However, the combination of PQ with OVA did not alter the expression levels of these proteins as compared with OVA alone.

CONCLUSION

These results indicate that PQ can enhance the immunoglobulin production and the infiltration of inflammatory cells into alveolar spaces that are related to OVA, whereas PQ seems to be partially responsible for the DEP toxicity on the allergic airway inflammation.

Thioredoxin-1 suppresses lung injury and apoptosis induced by diesel exhaust particles (DEP) by scavenging reactive oxygen species and by inhibiting DEP-induced downregulation of Akt

Diesel exhaust particles (DEP) are reactive oxygen species (ROS)-inducing toxic agents that damage lungs. Thioredoxin-1 (Trx-1) is a thiol protein with antioxidant and redox-regulating effects. In this study, we demonstrate that Trx-1 scavenges ROS generated by DEP and attenuates the lung injury. Intratracheal instillation of DEP resulted in the generation of more hydroxyl radicals in control mice than in human Trx-1 (hTrx-1)-transgenic mice as measured by noninvasive L-band in vivo electron spin resonance. DEP caused acute lung damage with massive infiltration of inflammatory cells in control mice, but much less damage in hTrx-1-transgenic mice. The hTrx-1 transgene protected the mice against DEP toxicity. To investigate further the molecular mechanism of the protective role of Trx-1 against DEP-induced lung injury, we used hTrx-1-transfected L-929 cells and recombinant hTrx-1 (rhTrx-1)-pretreated A-549 cells. DEP-induced ROS generation was suppressed by hTrx-1 transfection or pretreatment with rhTrx-1. Endogenous Trx-1 expression was induced by DEP in control cells. The downregulation of Akt phosphorylation by DEP resulted in apoptosis, which was prevented by Trx-1. Moreover, an Akt inhibitor canceled this protective effect of Trx-1. Collectively, the results suggest that Trx-1 exerts antioxidant effects in vivo and in vitro and that this plays a role in protection against DEP-induced lung damage by regulating Akt-mediated antiapoptotic signaling.

Conference overview: Molecular mechanisms of metal toxicity and carcinogenesis

Chronic exposure to many heavy metals and metal-derivatives is associated with an increased risk of cancer, although the mechanisms of tumorigenesis are largely unknown. Approximately 125 scientists attended the 3rd Conference on Molecular Mechanisms of Metal Toxicity and Carcinogenesis and presented the latest research concerning these mechanisms. Major areas of focus included exposure assessment and biomarker identification, roles of ROS and antioxidants in carcinogenesis, mechanisms of metal-induced DNA damage, metal signalling, and the development of animal models for use in metal toxicology studies. Here we highlight some of the research presented, and summarize the conference proceedings.

Additive effect of diesel exhaust particulates and ozone on airway hyperresponsiveness and inflammation in a mouse model of asthma

Allergic airway diseases are related to exposure to atmospheric pollutants, which have been suggested to be one factor in the increasing prevalence of asthma. Little is known about the effect of ozone and diesel exhaust particulates (DEP) on the development or aggravation of asthma. We have used a mouse asthma model to determine the effect of ozone and DEP on airway hyperresponsiveness and inflammation. Methacholine enhanced pause (P(enh)) was measured. Levels of IL-4 and IFN-gamma were quantified in bronchoalveolar lavage fluids by enzyme immunoassays. The OVA-sensitized-challenged and ozone and DEP exposure group had higher P(enh) than the OVA-sensitized-challenged group and the OVA-sensitized-challenged and DEP exposure group, and the OVA-sensitized-challenged and ozone exposure group. Levels of IFN-gamma were decreased in the OVA-sensitized-challenged and DEP exposure group and the OVA-sensitized-challenged and ozone and DEP exposure group compared to the OVA-sensitized-challenged and ozone exposure group. Levels of IL-4 were increased in the OVA-sensitized-challenged and ozone exposure group and the OVA-sensitized-challenged and DEP exposure group, and the OVA-sensitized-challenged and ozone and DEP exposure group compared to OVA-sensitized-challenged group. Co-exposure of ozone and DEP has additive effect on airway hyperresponsiveness by modulation of IL-4 and IFN-gamma suggesting that DEP amplify Th2 immune response.

Pulmonary toxicity induced by intratracheal instillation of Asian yellow dust (Kosa) in mice

Asian yellow dust (Kosa) causes adverse respiratory health effects in humans. The objective of this study was to clarify the lung toxicity of Kosa. ICR mice (5 weeks of age) were administered intratracheally with Kosa samples-two samples from Maowusu desert and Shapotou desert, one sample consisted of Shapotou Kosa plus sulfate, and natural Asian dust (NAD) from the atmosphere of Beijing-at doses of 0.05, 0.10 or 0.20mg/mouse at four weekly intervals. The four Kosa samples tested had similar compositions of minerals and concentrations of elements. Instillation of dust particles caused bronchitis and alveolitis in treated mice. The magnitude of inflammation was much greater in NAD-treated mice than in the other particles tested. Increased neutrophils, lymphocytes or eosinophils in bronchoalveolar lavage fluids (BALF) of treated mice were dose dependent. The number of neutrophils in BALF at the 0.2mg level was parallel to the content of β-glucan in each particle. The numbers of lymphocytes and eosinophils in BALF at the 0.2mg level were parallel to the concentration of SO(4)(2-) in each particle. Pro-inflammatory mediators-such as interleukin (IL)-12, tumor necrosis factor-(TNF)-α, keratinocyte chemoattractant (KC), monocyte chemotactic protein (MCP)-l and macrophage inflammatory protein-(MIP)-lα in BALF-were greater in the treated mice. Specifically, NAD considerably increased pro-inflammatory mediators at a 0.2mg dose. The increased amounts of MlP-lα and TNF-α at 0.2mg dose corresponded to the amount of β-glucan in each particle. The amounts of MCP-l or IL-12 corresponded to the concentration of sulfate (SO(4)(2-)) at a 0.2mg dose. These results suggest that inflammatory lung injury was mediated by β-glucan or SO(4)(2-), which was adsorbed into the particles, via the expression of these pro-inflammatory mediators. The results also suggest that the variations in the magnitude of inflammation of the tested Kosa samples depend on the amounts of these toxic materials.