Mechanisms of GM-CSF increase by diesel exhaust particles in human airway epithelial cells

Assessment of inflammatory cytokines in exhaled breath condensate and exposure to mixtures of organic pollutants in brick workers

Brick production causes a lot of pollution in the form of dust, fumes, and toxic substances. Therefore, brick workers are highly exposed to pollutants and present a high risk of developing respiratory diseases. The objective of this research was to determine the exposure to polycyclic aromatic hydrocarbons (PAHs) and toluene in urine and evaluate the effects on health using markers of oxidative stress in exhaled breath condensate (EBC) as well as the exposure to pollutants in suspended particles of the studied area. Exposure to PAHs and toluene was evaluated using hydroxylated markers (OH) of PAHs and hippuric acid in urine, respectively. Cytokines like TNF-α, INF-y, IL-2, IL-4, IL-6, IL-8, IL-10 y GMCSF in EBC were also evaluated. PM_2.5 particles were measured during an 8-h work shift. The results in brick workers presented a total OH-PAHs concentration of 97.3 µg/L and hippuric acid concentration of 0.2 g/L. The environmental concentrations of suspended particles were found within a range of 41.67-3541.6 μg/m³. The median of cytokines oscillated between 11.8 pg/mL to 1041 pg/mL. In conclusion, these results are similar to those of occupations in which there is high exposure to pollutants and populations with lung diseases. For that reason, the brick production sector requires prevention and control strategies against the pollutants emitted.

Oxidized carbon black nanoparticles induce endothelial damage through C-X-C chemokine receptor 3-mediated pathway

Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial and biomedical applications. In this study, we evaluated the cardiopulmonary hazard posed by these nanomaterials using oxidized carbon black (CB) nanoparticles (CBox) as a model particle. Particle surface chemistry was characterized by X-ray photo electron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Colloidal characterization and in vitro dosimetry modeling (particle kinetics, fate and transport modeling) were performed. Lung inflammation was assessed following oropharyngeal aspiration of CB or oxidized CBox particles (20 μg per mouse) in C57BL/6J mice. Toxicity and functional assays were also performed on murine macrophage (RAW 264.7) and endothelial cell lines (C166) with and without pharmacological inhibitors. Oxidant generation was assessed by electron paramagnetic resonance spectroscopy (EPR) and via flow cytometry. Endothelial toxicity was evaluated by quantifying pro-inflammatory mRNA expression, monolayer permeability, and wound closure. XPS and FTIR spectra indicated surface modifications, the appearance of new functionalities, and greater oxidative potential (both acellular and in vitro) of CBox particles. Treatment with CBox demonstrated greater in vivo inflammatory potentials (lavage neutrophil counts, secreted cytokine, and lung tissue mRNA expression) and air-blood barrier disruption (lavage proteins). Oxidant-dependent pro-inflammatory signaling in macrophages led to the production of CXCR3 ligands (CXCL9,10,11). Conditioned medium from CBox-treated macrophages induced significant elevation in endothelial cell pro-inflammatory mRNA expression, enhanced monolayer permeability and impairment of scratch healing in CXCR3 dependent manner. In summary, this study mechanistically demonstrated an increased biological potency of CBox particles and established the role of macrophage-released chemical mediators in endothelial damage.

Combined Toxicity of Metal Nanoparticles: Comparison of Individual and Mixture Particles Effect

Toxicity of metal nanoparticles (NPs) are closely associated with increasing intracellular reactive oxygen species (ROS) and the levels of pro-inflammatory mediators. However, NP interactions and surface complexation reactions alter the original toxicity of individual NPs. To date, toxicity studies on NPs have mostly been focused on individual NPs instead of the combination of several species. It is expected that the amount of industrial and highway-acquired NPs released into the environment will further increase in the near future. This raises the possibility that various types of NPs could be found in the same medium, thereby, the adverse effects of each NP either could be potentiated, inhibited or remain unaffected by the presence of the other NPs. After uptake of NPs into the human body from various routes, protein kinases pathways mediate their toxicities. In this context, family of mitogen-activated protein kinases (MAPKs) is mostly efficient. Despite each NP activates almost the same metabolic pathways, the toxicity induced by a single type of NP is different than the case of co-exposure to the combined NPs. The scantiness of toxicological data on NPs combinations displays difficulties to determine, if there is any risk associated with exposure to combined nanomaterials. Currently, in addition to mathematical analysis (Response surface methodology; RSM), the quantitative-structure-activity relationship (QSAR) is used to estimate the toxicity of various metal oxide NPs based on their physicochemical properties and levels applied. In this chapter, it is discussed whether the coexistence of multiple metal NPs alter the original toxicity of individual NP. Additionally, in the part of "Toxicity of diesel emission/exhaust particles (DEP)", the known individual toxicity of metal NPs within the DEP is compared with the data regarding toxicity of total DEP mixture.

Diesel exhaust particles elevate MUC5AC and MUC5B expression via the TLR4-mediated activation of ERK1/2, p38 MAPK, and NF-κB signaling pathways in human airway epithelial cells

Exposure to diesel exhaust particles (DEPs) is known to cause serious health problems, owing to a steady increase in the number of diesel vehicles worldwide. DEPs comprise approximately 90% particle mass existing in the fine size range (≤2.5 μm) and are mainly absorbed in the respiratory tract. However, limited information is available on the effects of DEP exposure on the respiratory tract in humans. Here, we investigated the effect and signaling pathways of DEPs on the expression of mucin, especially MUC5AC and MUC5B, in human airway epithelial cells by reverse-transcriptase polymerase chain reaction (PCR), real-time PCR, enzyme-linked immunosorbent assay, western blotting, and immunofluorescence staining. The signaling pathways activated following DEP-induced expression of MUC5AC and MUC5B in airway epithelial cells were analyzed by evaluating Toll-like receptor 4 (TLR4), mitogen-activated protein kinase (MAPK; extracellular signal-regulated kinase 1/2 [ERK1/2] and p38), and nuclear factor kappa B (NF-κB) phosphorylation with western blot and small-interfering RNA (siRNA) analyses. DEPs significantly increased MUC5AC and MUC5B expression in human airway epithelial cells that was closely related to TLR4, MAPK (ERK 1/2 and p38), and NF-κB pathway activation. This is the first report to demonstrate the DEP-mediated increase in MUC5AC and MUC5B expression via the TLR4-mediated activation of ERK1/2, p38 MAPK, and NF-κB signaling pathways in human airway epithelial cells.

Variation in doses and duration of particulate matter exposure in bronchial epithelial cells results in upregulation of different genes associated with airway disorders

Exposure to particulate matter < 2.5 μm (PM2.5) is associated with a variety of airway diseases. Although studies have demonstrated that high doses of PM2.5 cause cytotoxicity and changes to gene expression in bronchial epithelial cells, the effect of lower doses and repeated exposure to PM2.5 are less well studied. Here, we treated BEAS-2B cells with varying doses of PM2.5 for 1-7 days and examined the expression of a variety of genes implicated in airway disorders. At high doses, PM2.5 increased the expression of IL6, TNF, TSLP, CSF2, PTGS2, IL4R, and SPINK5. Other genes such as ADAM33, ORMDL3, DPP10 and CYP1A1, however, were increased by PM2.5 at much lower doses (≤1 μg/cm2). Repeated exposure to PM2.5 at 1 or 5 μg/cm2 every day for 7 days increased the sensitivity and magnitude of change for all of the aforementioned genes. Genes such as IL13 and TGFB1, increased only when cells were repeatedly exposed to PM2.5. Treatment with an antioxidant, or inhibitors to aryl hydrocarbon receptor or NF-κB attenuated the effect of PM2.5. These data demonstrate that PM2.5 exerts pleiotropic actions that differ by dose and duration that affect a variety of genes important to the development of airway disease.

Insights in particulate matter-induced allergic airway inflammation: Focus on the epithelium

Outdoor air pollution is a major environmental health problem throughout the world. In particular, exposure to particulate matter (PM) has been associated with the development and exacerbation of several respiratory diseases, including asthma. Although the adverse health effects of PM have been demonstrated for many years, the underlying mechanisms have not been fully identified. In this review, we focus on the role of the lung epithelium and specifically highlight multiple cytokines in PM-induced respiratory responses. We describe the available literature on the topic including in vitro studies, findings in humans (ie observations in human cohorts, human controlled exposure and ex vivo studies) and in vivo animal studies. In brief, it has been shown that exposure to PM modulates the airway epithelium and promotes the production of several cytokines, including IL-1, IL-6, IL-8, IL-25, IL-33, TNF-α, TSLP and GM-CSF. Further, we propose that PM-induced type 2-promoting cytokines are important mediators in the acute and aggravating effects of PM on airway inflammation. Targeting these cytokines could therefore be a new approach in the treatment of asthma.

Dung biomass smoke activates inflammatory signaling pathways in human small airway epithelial cells

Animal dung is a biomass fuel burned by vulnerable populations who cannot afford cleaner sources of energy, such as wood and gas, for cooking and heating their homes. Exposure to biomass smoke is the leading environmental risk for mortality, with over 4,000,000 deaths each year worldwide attributed to indoor air pollution from biomass smoke. Biomass smoke inhalation is epidemiologically associated with pulmonary diseases, including chronic obstructive pulmonary disease (COPD), lung cancer, and respiratory infections, especially in low and middle-income countries. Yet, few studies have examined the mechanisms of dung biomass smoke-induced inflammatory responses in human lung cells. Here, we tested the hypothesis that dung biomass smoke causes inflammatory responses in human lung cells through signaling pathways involved in acute and chronic lung inflammation. Primary human small airway epithelial cells (SAECs) were exposed to dung smoke at the air-liquid interface using a newly developed, automated, and reproducible dung biomass smoke generation system. The examination of inflammatory signaling showed that dung biomass smoke increased the production of several proinflammatory cytokines and enzymes in SAECs through activation of the activator protein (AP)-1 and arylhydrocarbon receptor (AhR) but not nuclear factor-κB (NF-κB) pathways. We propose that the inflammatory responses of lung cells exposed to dung biomass smoke contribute to the development of respiratory diseases.

Particulate matter properties and health effects: consistency of epidemiological and toxicological studies

Identifying the ambient particulate matter (PM) fractions or constituents, critically involved in eliciting adverse health effects, is crucial to the implementation of more cost-efficient abatement strategies to improve air quality. This review focuses on the importance of different particle properties for PM-induced effects, and whether there is consistency in the results from epidemiological and experimental studies. An evident problem for such comparisons is that epidemiological and experimental data on the effects of specific components of ambient PM are limited. Despite this, some conclusions can be drawn. With respect to the importance of the PM size-fractions, experimental and epidemiological studies are somewhat conflicting, but there seems to be a certain consistency in that the coarse fraction (PM10-2.5) has an effect that should not be neglected. Better exposure characterization may improve the consistency between the results from experimental and epidemiological studies, in particular for ultrafine particles. Experimental data indicate that surface area is an important metric, but composition may play an even greater role in eliciting effects. The consistency between epidemiological and experimental findings for specific PM-components appears most convincing for metals, which seem to be important for the development of both pulmonary and cardiovascular disease. Metals may also be involved in PM-induced allergic sensitization, but the epidemiological evidence for this is scarce. Soluble organic compounds appear to be implicated in PM-induced allergy and cancer, but the data from epidemiological studies are insufficient for any conclusions. The present review suggests that there may be a need for improvements in research designs. In particular, there is a need for better exposure assessments in epidemiological investigations, whereas experimental data would benefit from an improved comparability of studies. Combined experimental and epidemiological investigations may also help answer some of the unresolved issues.

Toxicology of ambient particulate matter

It is becoming increasingly clear that inhalation exposure to particulate matter (PM) can lead to or exacerbate various diseases, which are not limited to the lung but extend to the cardiovascular system and possibly other organs and tissues. Epidemiological studies have provided strong evidence for associations with chronic obstructive pulmonary disease (COPD), asthma, bronchitis and cardiovascular disease, while the evidence for a link with lung cancer is less strong. Novel research has provided first hints that exposure to PM might lead to diabetes and central nervous system (CNS) pathology. In the current review, an overview is presented of the toxicological basis for adverse health effects that have been linked to PM inhalation. Oxidative stress and inflammation are discussed as central processes driving adverse effects; in addition, profibrotic and allergic processes are implicated in PM-related diseases. Effects of PM on key cell types considered as regulators of inflammatory, fibrotic and allergic mechanisms are described.

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

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

PM10-stimulated airway epithelial cells activate primary human dendritic cells independent of uric acid: application of an in vitro model system exposing dendritic cells to airway epithelial cell-conditioned media

BACKGROUND AND OBJECTIVE

Airway epithelial cells represent the first line of defence against inhaled insults, including air pollution. Air pollution can activate innate immune signalling in airway epithelial cells leading to the production of soluble mediators that can influence downstream inflammatory cells. Our objective was to develop and validate a model of dendritic cell exposure to airway epithelial cell-conditioned media. After establishing the model, we explored how soluble mediators released from airway epithelial cells in response to air pollution influenced the phenotype of dendritic cells.

METHODS

Human airway epithelial cells were cultured under control and urban particulate matter (PM10) exposure conditions with or without pharmacological inhibitors of the uric acid pathway. Culture supernatants were collected for conditioned media experiments with peripheral blood mononuclear cell-derived dendritic cells analysed by flow cytometry.

RESULTS

Monocytes derived from peripheral blood mononuclear cells cultured in interleukin-4 and granulocyte macrophage colony stimulating factor differentiated into immature dendritic cells that phenotypically differentiated into mature dendritic cells in response to conditioned media from phorbol myristate acetate-activated THP-1 monocytes. Exposure of immature dendritic cells to conditioned media from airway epithelial cells exposed to PM10 resulted in dendritic cell maturation that was independent of uric acid.

CONCLUSIONS

We present a conditioned media model useful for interrogating the contribution of soluble mediators produced by airway epithelial cells to dendritic cell phenotype and function. Furthermore, we demonstrate that PM10 exposure induces airway epithelial cell production of soluble mediators that induce maturation of dendritic cells independent of uric acid.

Effect of combined nitrogen dioxide and carbon nanoparticle exposure on lung function during ovalbumin sensitization in Brown Norway rat

The interaction of particulate and gaseous pollutants in their effects on the severity of allergic inflammation and airway responsiveness are not well understood. We assessed the effect of exposure to NO₂ in the presence or absence of repetitive treatment with carbon nanoparticle (CNP) during allergen sensitization and challenges in Borwn-Norway (BN) rat, in order to assess their interactions on lung function and airway responses (AR) to allergen and methacholine (MCH), end-expiratory lung volume (EELV), bronchoalveolar lavage fluid (BALF) cellular content, serum and BALF cytokine levels and histological changes. Animals were divided into the following groups (n = 6): Control; CNP (Degussa-FW2): 13 nm, 0.5 mg/kg instilled intratracheally ×3 at 7-day intervals; OVA: ovalbumin-sensitised; OVA+CNP: both sensitized and exposed to CNP. Rats were divided into equal groups exposed either to air or to NO₂, 10 ppm, 6 h/d, 5d/wk for 4 weeks. Exposure to NO₂, significantly enhanced lung inflammation and airway reactivity, with a significantly larger effect in animals sensitized to allergen, which was related to a higher expression of TH1 and TH2-type cytokines. Conversely, exposure to NO₂ in animals undergoing repeated tracheal instillation of CNP alone, increased BALF neutrophilia and enhanced the expression of TH1 cytokines: TNF-α and IFN-γ, but did not show an additive effect on airway reactivity in comparison to NO₂ alone. The exposure to NO₂ combined with CNP treatment and allergen sensitization however, unexpectedly resulted in a significant decrease in both airway reactivity to allergen and to methacholine, and a reduction in TH2-type cytokines compared to allergen sensitization alone. EELV was significantly reduced with sensitization, CNP treatment or both. These data suggest an immunomodulatory effect of repeated tracheal instillation of CNP on the proinflammatory effects of NO₂ exposure in sensitized BN rat. Furthermore, our findings suggest that NO₂, CNP and OVA sensitization may significantly slow overall lung growth in parenchymally mature animals.

Glutathione-S-transferase M1 regulation of diesel exhaust particle-induced pro-inflammatory mediator expression in normal human bronchial epithelial cells

Background

Diesel exhaust particles (DEP) contribute substantially to ambient particulate matter (PM) air pollution in urban areas. Inhalation of PM has been associated with increased incidence of lung disease in susceptible populations. We have demonstrated that the glutathione S-transferase M1 (GSTM1) null genotype could aggravate DEP-induced airway inflammation in human subjects. Given the critical role airway epithelial cells play in the pathogenesis of airway inflammation, we established the GSTM1 deficiency condition in primary bronchial epithelial cells from human volunteers with GSTM1 sufficient genotype (GSTM1+) using GSTM1 shRNA to determine whether GSTM1 deficiency could exaggerate DEP-induced expression of interleukin-8 (IL-8) and IL-1β proteins. Furthermore, the mechanisms underlying GSTM1 regulation of DEP-induced IL-8 and IL-1β expression were also investigated.

Methods

IL-8 and IL-1β protein levels were measured using enzyme-linked immunosorbent assay. GSTM1 deficiency in primary human bronchial epithelial cells was achieved using lentiviral GSTM1 shRNA particles and verified using real-time polymerase chain reaction and immunoblotting. Intracellular reactive oxygen species (ROS) production was evaluated using flow cytometry. Phosphorylation of protein kinases was detected using immunoblotting.

Results

Exposure of primary human bronchial epithelial cells (GSTM1+) to 25-100 μg/ml DEP for 24 h significantly increased IL-8 and IL-1β protein expression. Knockdown of GSTM1 in these cells further elevated DEP-induced IL-8 and IL-1β expression, implying that GSTM1 deficiency aggravated DEP-induced pro-inflammatory response. DEP stimulation induced the phosphorylation of extracellular signal-regulated kinase (ERK) and Akt, the downstream kinase of phosphoinositide 3-kinase (PI3K), in GSTM1+ bronchial epithelial cells. Pharmacological inhibition of ERK kinase and PI3K activity blocked DEP-induced IL-8 and IL-1β expression. DEP-induced ERK and Akt phosphorylation could be increased by GSTM1 knockdown. In addition, pretreatment of HBEC with the antioxidant N-acetyl cysteine significantly inhibited DEP-induced ERK and Akt phosphorylation, and subsequent IL-8 and IL-1β expression.

Conclusion

GSTM1 regulates DEP-induced IL-8 and IL-1β expression in primary human bronchial epithelial cells by modulation of ROS, ERK and Akt signaling.

Role of size and composition of traffic and agricultural aerosols in the molecular responses triggered in airway epithelial cells

The increased levels of fine particles in the atmosphere are suspected of aggravating cardiopulmonary diseases, but the determinants of particle toxicity are poorly understood. This work aims at studying the role of composition and size in the toxicity of size-segregated particulate matter (PM) collected at different sites on human bronchial epithelial cells. PM were sampled at a traffic urban site (Urb S) and a rural site (Rur S) during the pesticide-spreading period. Ultrafine (UF), fine (F), and coarse (C) PM were characterized by their shape and chemical composition. Whatever the site, the finest PM (UF and F) induced the mRNA expression of CYP1A1, a biomarker of polyaromatic hydrocarbons (PAH) exposure, NQO-1 and heme HO-1, two antioxidant responsive element-driven genes; and two effect biomarkers, GM-CSF, a proinflammatory cytokine and amphiregulin (AR), a growth factor. C PM have a low or no effect. Interestingly, AR is more strongly induced by rural PM at the same mass exposure. These discrepancies suggest involvement of PM chemical composition: rural PM bearing the characteristics of aged aerosols with a high content of water-soluble components, and PM at urban kerbside sites containing mainly water-insoluble components. To conclude, we provide evidence that the finest PM fractions, whatever their origin, are more prone to induce exposure and effect biomarkers. The AR differential expression suggests a source-dependent effect requiring further investigation because of the role of this growth factor in airway remodeling, a characteristic feature of chronic lung respiratory diseases exacerbated by particulate pollution.

Impact of air pollution on allergic diseases

The incidence of allergic diseases in most industrialized countries has increased. Although the exact mechanisms behind this rapid increase in prevalence remain uncertain, a variety of air pollutants have been attracting attention as one causative factor. Epidemiological and toxicological research suggests a causative relationship between air pollution and the increased incidence of asthma, allergic rhinitis, and other allergic disorders. These include ozone, nitrogen dioxide and, especially particulate matter, produced by traffic-related and industrial activities. Strong epidemiological evidence supports a relationship between air pollution and the exacerbation of asthma and other respiratory diseases. Recent studies have suggested that air pollutants play a role in the development of asthma and allergies. Researchers have elucidated the mechanisms whereby these pollutants induce adverse effects; they appear to affect the balance between antioxidant pathways and airway inflammation. Gene polymorphisms involved in antioxidant pathways can modify responses to air pollution exposure. While the characterization and monitoring of pollutant components currently dictates pollution control policies, it will be necessary to identify susceptible subpopulations to target therapy/prevention of pollution-induced respiratory diseases.

Size-partitioning of an urban aerosol to identify particle determinants involved in the proinflammatory response induced in airway epithelial cells

Background

The contribution of air particles in human cardio-respiratory diseases has been enlightened by several epidemiological studies. However the respective involvement of coarse, fine and ultrafine particles in health effects is still unclear. The aim of the present study is to determine which size fraction from a chemically characterized background aerosol has the most important short term biological effect and to decipher the determinants of such a behaviour.

Results

Ambient aerosols were collected at an urban background site in Paris using four 13-stage low pressure cascade impactors running in parallel (winter and summer 2005) in order to separate four size-classes (PM_0.03–0.17 (defined here as ultrafine particles), PM_0.17–1 (fine), PM_1–2.5(intermediate) and PM_2.5–10 (coarse)). Accordingly, their chemical composition and their pro-inflammatory potential on human airway epithelial cells were investigated. Considering isomass exposures (same particle concentrations for each size fractions) the pro-inflammatory response characterized by Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF) release was found to decrease with aerosol size with no seasonal dependency. When cells were exposed to isovolume of particle suspensions in order to respect the particle proportions observed in ambient air, the GM-CSF release was maximal with the fine fraction. In presence of a recombinant endotoxin neutralizing protein, the GM-CSF release induced by particles is reduced for all size-fractions, with exception of the ultra-fine fraction which response is not modified. The different aerosol size-fractions were found to display important chemical differences related to the various contributing primary and secondary sources and aerosol age. The GM-CSF release was correlated to the organic component of the aerosols and especially its water soluble fraction. Finally, Cytochrome P450 1A1 activity that reflects PAH bioavailability varied as a function of the season: it was maximal for the fine fraction in winter and for the ultrafine fraction in summer.

Conclusion

In the frame of future regulations, a particular attention should thus be paid to the ultrafine/fine (here referred to as PM1) fraction due to their overwhelming anthropogenic origin and predominance in the urban aerosol and their pro-inflammatory potential.

Environmental exposures and gene regulation in disease etiology

Health or disease is shaped for all individuals by interactions between their genes and environment. Exactly how the environment changes gene expression and how this can lead to disease are being explored in a fruitful new approach to environmental health research, representative studies of which are reviewed here. We searched Web of Science and references of relevant publications to understand the diversity of gene regulatory mechanisms affected by environmental exposures with disease implications. Pharmaceuticals, pesticides, air pollutants, industrial chemicals, heavy metals, hormones, nutrition, and behavior can change gene expression through a broad array of gene regulatory mechanisms. Furthermore, chemically induced changes in gene regulation are associated with serious and complex human diseases, including cancer, diabetes and obesity, infertility, respiratory diseases, allergies, and neurodegenerative disorders such as Parkinson and Alzheimer diseases. The reviewed studies indicate that genetic predisposition for disease is best predicted in the context of environmental exposures. And the genetic mechanisms investigated in these studies offer new avenues for risk assessment research. Finally, we are likely to witness dramatic improvements in human health, and reductions in medical costs, if environmental pollution is decreased.

Mechanisms and implications of air pollution particle associations with chemokines

Inflammation induced by inhalation of air pollutant particles has been implicated as a mechanism for the adverse health effects associated with exposure to air pollution. The inflammatory response is associated with upregulation of various pro-inflammatory cytokines and chemokines. We have previously shown that diesel exhaust particles (DEP), a significant constituent of air pollution particulate matter in many urban areas, bind and concentrate IL-8, an important human neutrophil-attracting chemokine, and that the chemokine remains biologically active. In this report, we examine possible mechanisms of this association and the effects on clearance of the chemokine. The binding appears to be the result of ionic interactions between negatively charged particles and positively charged chemokine molecules, possibly combined with intercalation into small pores in the particles. The association is not limited to diesel exhaust particles and IL-8: several other particle types also adsorb the chemokine and several other cytokines are adsorbed onto the diesel particles. However, there are wide ranges in the effectiveness of various particle types and various cytokines. Finally, male Fisher 344 rats were intratracheally instilled with chemokine alone or combined with diesel exhaust or silica particles under isofluorane anesthesia. In contrast to silica particles, which do not bind the chemokine, the presence of diesel exhaust particles, which bind the chemokine, prolonged the retention of the chemokine.

The effects of organic extract of diesel exhaust particles on ischemia/reperfusion-related arrhythmia and on pulmonary inflammation

Since our previous study demonstrated the exacerbation of acute myocardial ischemia/reperfusion (AMIR)-related arrhythmia by intratracheal instillation (IT) of diesel exhaust particles (DEP), the influence of IT with extracts of DEP in organic solvents on AMIR-related arrhythmia was examined in rats. Oxidative activity in a non-biological assay system and proinflammatory activity in mice of DEP extracts were examined. The dichloromethane-soluble fraction (DMSF) of DEP was further fractionated into n-hexane-soluble (n-HSF) and n-hexane-insoluble (n-HISF) fractions. The oxidative activities of the fractions evaluated by dithiothreitol assay were ranked as follows: n-HISF>DMSF>n-HSF. Twenty-one to 34 hr after IT, the AMIR experiment was performed. Exacerbation of AMIR-related arrhythmia and increased reperfusion-related mortality were observed only in rats treated with DMSF. In fact, n-HSF and n-HISF did not affect arrhythmia up to 5 mg/kg. Twelve hr after IT, a significant increase in neutrophil count was observed only with DMSF. The levels of granulocyte colony-stimulating factor and interleukin-6 in bronchoalveolar lavage fluid were significantly elevated in the group treated with DMSF, while neither, n-HSF nor n-HISF, affected the level of cytokines up to 5 mg/kg. In fact, tumor necrosis factor-alpha, IL-10 and granulocyte-macrophage colony-stimulating factor were unchanged with any of the fractions. In conclusion, exacerbation of AMIR-related arrhythmia by DMSF suggests the contribution of non-particle components of DEP to arrhythmia while the component contributed to the effects did not become clear. Furthermore, it is confirmed that exacerbation of AMIR-related arrhythmia is accompanied by an increased neutrophil count in the circulatory blood.

Increased transcription of immune and metabolic pathways in naive and allergic mice exposed to diesel exhaust

Diesel exhaust (DE) has been shown to enhance allergic sensitization in animals following high-dose instillation or chronic inhalation exposure scenarios. The purpose of this study was to determine if short-term exposures to diluted DE enhance allergic immune responses to antigen, and identify possible mechanisms using microarray technology. BALB/c mice were exposed to filtered air or diluted DE to yield particle concentrations of 500 or 2000 mug/m(3) 4 h/day on days 0-4. Mice were immunized intranasally with ovalbumin (OVA) antigen or saline on days 0-2, challenged on day 18 with OVA or saline, and all mice were challenged with OVA on day 28. Mice were necropsied either 4 h after the last DE exposure on day 4, or 18, 48, and 96 h after the last challenge. Immunological endpoints included OVA-specific serum IgE, biochemical and cellular profiles of bronchoalveolar lavage (BAL), and cytokine production in the BAL. OVA-immunized mice exposed to both concentrations of DE had increased eosinophils, neutrophils, lymphocytes, and interleukin-6 (high dose only) post-challenge compared with OVA control, whereas DE/saline exposure yielded increases in neutrophils at the high dose only. Transcriptional microarray analysis 4 h after the last DE exposure demonstrated distinct gene expression profiles for the high-dose DE/OVA and DE/saline groups. DE/OVA induced oxidative stress and metabolism pathways, whereas DE in the absence of immunization modulated cell cycle control, growth and differentiation, G-proteins, and cell adhesion pathways. This study shows for the first time early changes in gene expression induced by the combination of DE inhalation and mucosal immunization, which resulted in stronger development of allergic eosinophilia.

Diesel exhaust particle-exposed human bronchial epithelial cells induce dendritic cell maturation and polarization via thymic stromal lymphopoietin

Human exposure to air pollutants, including ambient particulate matter, has been proposed as a mechanism for the rise in allergic disorders. Diesel exhaust particles, a major component of ambient particulate matter, induce sensitization to neoallergens, but the mechanisms by which sensitization occur remain unclear. We show that diesel exhaust particles upregulate thymic stromal lymphopoietin in human bronchial epithelial cells in an oxidant-dependent manner. Thymic stromal lymphopoietin induced by diesel exhaust particles was associated with maturation of myeloid dendritic cells, which was blocked by anti-thymic stromal lymphopoietin antibodies or silencing epithelial cell-derived thymic stromal lymphopoietin. Dendritic cells exposed to diesel exhaust particle-treated human bronchial epithelial cells induced Th2 polarization in a thymic stromal lymphopoietin-dependent manner. These findings provide new insight into the mechanisms by which diesel exhaust particles modify human lung mucosal immunity.

Environmental exposures and gene regulation in disease etiology

OBJECTIVE

Health or disease is shaped for all individuals by interactions between their genes and environment. Exactly how the environment changes gene expression and how this can lead to disease are being explored in a fruitful new approach to environmental health research, representative studies of which are reviewed here.

DATA SOURCES

We searched Web of Science and references of relevant publications to understand the diversity of gene regulatory mechanisms affected by environmental exposures with disease implications.

DATA SYNTHESIS

Pharmaceuticals, pesticides, air pollutants, industrial chemicals, heavy metals, hormones, nutrition, and behavior can change gene expression through a broad array of gene regulatory mechanisms. Mechanisms include regulation of gene translocation, histone modifications, DNA methylation, DNA repair, transcription, RNA stability, alternative RNA splicing, protein degradation, gene copy number, and transposon activation. Furthermore, chemically induced changes in gene regulation are associated with serious and complex human diseases, including cancer, diabetes and obesity, infertility, respiratory diseases, allergies, and neurodegenerative disorders such as Parkinson and Alzheimer diseases. One of the best-studied areas of gene regulation is epigenetics, especially DNA methylation. Our examples of environmentally induced changes in DNA methylation are presented in the context of early development, when methylation patterns are initially laid down. This approach highlights the potential role for altered DNA methylation in fetal origins of adult disease and inheritance of acquired genetic change.

CONCLUSIONS

The reviewed studies indicate that genetic predisposition for disease is best predicted in the context of environmental exposures. Second, the genetic mechanisms investigated in these studies offer new avenues for risk assessment research. Finally, we are likely to witness dramatic improvements in human health, and reductions in medical costs, if environmental pollution is decreased.

Determination of oxygenated polycyclic aromatic hydrocarbons in particulate matter using high-performance liquid chromatography–tandem mass spectrometry

A high-performance liquid chromatography-tandem mass spectrometric (LC-MS/MS) method with a rapid and simple sample preparation was optimized and validated for the determination of phenanthrene-9,10-dione, chrysene-5,6-dione, benzo[a]pyrene-1,6-dione, benzo[a]pyrene-3,6-dione, benzo[a]pyrene-4,5-dione, benzo[a]pyrene-6,12-dione, benzo[a]pyrene-7,8-dione, benzo[a]pyrene-11,12-dione and 6-oxo-7-oxa-benzo[a]pyrene in particulate matter. The mass spectrometer was operated in the multiple reaction monitoring (MRM) mode leading to high sensitivity and selectivity. The limits of quantification (S/N=10) ranged from ca. 0.1 pg/microl to ca. 5.8 pg/microl and matrix dependent recoveries varied between 49 and 92%. The applicability of the LC-MS/MS method was shown by the analysis of particulate matter (PM(2.5)) collected during the course of 2005 in the Munich area, Germany. All oxy-PAHs determined exhibited higher mean and peak concentrations in the winter months compared to the concentration levels in the warmer season.

Toluene diisocyanate (TDI) induces production of inflammatory cytokines and chemokines by bronchial epithelial cells via the epidermal growth factor receptor and p38 mitogen-activated protein kinase pathways

Toluene diisocyanate (TDI) is known as one of causes of occupational asthma and hypersensitivity pneumonitis. To investigate the stimulatory effect on bronchial epithelial cells in response to TDI, the authors examined production of cytokines by the bronchial epithelial cell line BEAS-2B and intercellular signal transduction stimulated by TDI-human serum albumin (HSA) conjugate. The production of interleukin (IL)-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and regulated on activation normal T cell expressed and secreted (RANTES) from the bronchial epithelial cells were augmented by the TDI-HSA conjugate. Extracellular signal-regulated kinase (Erk) 1/2 and p38 mitogen-activated protein kinase (MAPK) were phosphorylated by the TDI-HSA conjugate. AG1478, SB203580, and dexamethasone prevented augmentation of these cytokine production. TDI-HSA conjugate did not augment release of epidermal growth factor (EGF) ligands from BEAS-2B. These results suggest that TDI directly induces production of proinflammatory cytokines and chemokines through p38 MAPK and EGF receptor (EGFR)-Erk pathway without an autocrine mechanism. Thus, TDI was shown to have a stimulatory effect on bronchial epithelial cells, suggesting the potent role of bronchial epithelial cells in TDI-induced asthma.

The potential risks of nanomaterials: a review carried out for ECETOC

During the last few years, research on toxicologically relevant properties of engineered nanoparticles has increased tremendously. A number of international research projects and additional activities are ongoing in the EU and the US, nourishing the expectation that more relevant technical and toxicological data will be published. Their widespread use allows for potential exposure to engineered nanoparticles during the whole lifecycle of a variety of products. When looking at possible exposure routes for manufactured Nanoparticles, inhalation, dermal and oral exposure are the most obvious, depending on the type of product in which Nanoparticles are used. This review shows that (1) Nanoparticles can deposit in the respiratory tract after inhalation. For a number of nanoparticles, oxidative stress-related inflammatory reactions have been observed. Tumour-related effects have only been observed in rats, and might be related to overload conditions. There are also a few reports that indicate uptake of nanoparticles in the brain via the olfactory epithelium. Nanoparticle translocation into the systemic circulation may occur after inhalation but conflicting evidence is present on the extent of translocation. These findings urge the need for additional studies to further elucidate these findings and to characterize the physiological impact. (2) There is currently little evidence from skin penetration studies that dermal applications of metal oxide nanoparticles used in sunscreens lead to systemic exposure. However, the question has been raised whether the usual testing with healthy, intact skin will be sufficient. (3) Uptake of nanoparticles in the gastrointestinal tract after oral uptake is a known phenomenon, of which use is intentionally made in the design of food and pharmacological components. Finally, this review indicates that only few specific nanoparticles have been investigated in a limited number of test systems and extrapolation of this data to other materials is not possible. Air pollution studies have generated indirect evidence for the role of combustion derived nanoparticles (CDNP) in driving adverse health effects in susceptible groups. Experimental studies with some bulk nanoparticles (carbon black, titanium dioxide, iron oxides) that have been used for decades suggest various adverse effects. However, engineered nanomaterials with new chemical and physical properties are being produced constantly and the toxicity of these is unknown. Therefore, despite the existing database on nanoparticles, no blanket statements about human toxicity can be given at this time. In addition, limited ecotoxicological data for nanomaterials precludes a systematic assessment of the impact of Nanoparticles on ecosystems.

Responses of well-differentiated nasal epithelial cells exposed to particles: role of the epithelium in airway inflammation

Numerous epidemiological studies support the contention that ambient air pollution particles can adversely affect human health. To explain the acute inflammatory process in airways exposed to particles, a number of in vitro studies have been performed on cells grown submerged on plastic and poorly differentiated, and on cell lines, the physiology of which is somewhat different from that of well-differentiated cells. In order to obtain results using a model system in which epithelial cells are similar to those of the human airway in vivo, apical membranes of well-differentiated human nasal epithelial (HNE) cells cultured in an air-liquid interface (ALI) were exposed for 24 h to diesel exhaust particles (DEP) and Paris urban air particles (PM(2.5)). DEP and PM(2.5) (10-80 microg/cm(2)) stimulated both IL-8 and amphiregulin (ligand of EGFR) secretion exclusively towards the basal compartment. In contrast, there was no IL-1beta secretion and only weak non-reproducible secretion of TNF-alpha. IL-6 and GM-CSF were consistently stimulated towards the apical compartment and only when cells were exposed to PM(2.5). ICAM-1 protein expression on cell surfaces remained low after particle exposure, although it increased after TNF-alpha treatment. Internalization of particles, which is believed to initiate oxidative stress and proinflammatory cytokine expression, was restricted to small nanoparticles (< or =40 nm). Production of reactive oxygen species (ROS) was detected, and DEP were more efficient than PM(2.5). Collectively, our results suggest that airway epithelial cells exposed to particles augment the local inflammatory response in the lung but cannot alone initiate a systemic inflammatory response.

Physicochemical characterisation of combustion particles from vehicle exhaust and residential wood smoke

Background

Exposure to ambient particulate matter has been associated with a number of adverse health effects. Particle characteristics such as size, surface area and chemistry seem to influence the negative effects of particles. In this study, combustion particles from vehicle exhaust and wood smoke, currently used in biological experiments, were analysed with respect to microstructure and chemistry.

Methods

Vehicle exhaust particles were collected in a road tunnel during two seasons, with and without use of studded tires, whereas wood smoke was collected from a stove with single-stage combustion. Additionally, a reference diesel sample (SRM 2975) was analysed. The samples were characterised using transmission electron microscopy techniques (TEM/HRTEM, EELS and SAED). Furthermore, the elemental and organic carbon fractions were quantified using thermal optical transmission analysis and the content of selected PAHs was determined by gas chromatography-mass spectrometry.

Results

Carbon aggregates, consisting of tens to thousands of spherical primary particles, were the only combustion particles identified in all samples using TEM. The tunnel samples also contained mineral particles originating from road abrasion. The geometric diameters of primary carbon particles from vehicle exhaust were found to be significantly smaller (24 ± 6 nm) than for wood smoke (31 ± 7 nm). Furthermore, HRTEM showed that primary particles from both sources exhibited a turbostratic microstructure, consisting of concentric carbon layers surrounding several nuclei in vehicle exhaust or a single nucleus in wood smoke. However, no differences were detected in the graphitic character of primary particles from the two sources using SAED and EELS. The total PAH content was higher for combustion particles from wood smoke as compared to vehicle exhaust, whereas no source difference was found for the ratio of organic to total carbon.

Conclusion

Combustion particles from vehicle exhaust and residential wood smoke differ in primary particle diameter, microstructure, and PAH content. Furthermore, the analysed samples seem suitable for assessing the influence of physicochemical characteristics of particles on biological responses.

Diesel exhaust particles and their effect on induced cytokine expression in human bronchial epithelial cells

PURPOSE OF REVIEW

It has been demonstrated that particulate air pollutants such as diesel exhaust particles (DEPs) are associated with allergic respiratory disorders, including asthma and allergic rhinitis. Recent in-vivo and in-vitro studies strongly suggest that DEPs induce both anti-inflammatory and proinflammatory products by activating their transcription. If pollutants are to be controlled in the environment in a cost-effective manner, it is important that the molecular target(s) of DEP-induced responses be elucidated. Bronchial epithelial cells are the key regulators of airway inflammation, and therefore it is crucial to clarify the cellular and molecular mechanisms that are active in these cells. It is also important to compare responses to DEP exposure between healthy and susceptible populations.

RECENT FINDINGS

Studies have shown that DEPs activate several signalling pathways such as mitogen-activated protein kinases and transcription factors, in particular nuclear factor-kappa and activator protein-1, in human bronchial epithelial cells; these effects are thought to occur via production of reactive oxygen species. Antioxidants effectively reduce the allergic inflammatory effects of DEPs both in vitro and in mice.

SUMMARY

Host responses to DEPs are regulated by a balance between antioxidants and proinflammatory responses. DEP-induced oxidants play a key role in proinflammatory reactions. Recent human studies suggest that chemoprevention against DEP-induced adverse effects in susceptible individuals is possible.

Physicochemical characteristics and biological activities of seasonal atmospheric particulate matter sampling in two locations of Paris

Fine particulate matter present in urban areas seems to be incriminated in respiratory disorders. The aim of this study was to relate physicochemical characteristics of PM2.5 (particulate matter collected with a 50% efficiency for particles with an aerodynamic diameter of 2.5 microm) to their biological activities toward a bronchial epithelial cell line 16-HBE. Two seasonal sampling campaigns of particles were realized, respectively, in a kerbside and an urban background station in Paris. Sampled-PM2.5 mainly consist of particles with a size below 1 microm and are mainly composed of soot as assessed by analytical scanning electron microscopy. The different PM2.5 samples contrasted in their PAH content, which was the highest in the kerbside station in winter, as well as in their metal content. Kerbside station samples were characterized by the highest Fe and Cu content, which appears correlated to their hydroxyl radical generating properties measured by electron paramagnetic resonance. Particles were compared by their capacity to induce cytotoxicity, intracellular ROS production, and proinflammatory cytokine release (GM-CSF and TNF-alpha). At a concentration of 10 microg/cm2, all samples induced peroxide production and cytokine release to the similar extent in the absence of cytotoxicity. In conclusion, whereas the PM2.5 samples differ by their PAH and metal composition, they induce the same biological responses likely either due to components bioavailability and/ or interactions between PM components.

Signal transduction pathways relevant for neoplastic effects of fibrous and non-fibrous particles

Apart from their genotoxic effects, both fibrous and non-fibrous particles are known to induce signalling pathways involved in the development of malignant lung diseases. Different direct effects of particles as well as indirect cellular effects are believed to induce changes in apoptosis or proliferation in target cells. Signalling events, e.g. the induction of mitogen-activated protein kinase (MAPK) cascades resulting in the activation of the transcription factor AP-1, as well as the induction of the transcription factor NFkappaB which mainly mediates the expression of pro-inflammatory genes are discussed. There is some insight into the molecular mechanisms eliciting these pathways. Therefore, this review aims to give an overview on signalling pathways as well as initial events including effects of reactive oxygen and nitrogen species, membrane receptors and particle uptake.

Induction of granulocyte-macrophage colony-stimulating factor by a new cytokine, ML-1 (IL-17F), via Raf I-MEK-ERK pathway

BACKGROUND

ML-1 (IL-17F) is a recently discovered cytokine, and its function remains elusive. GM-CSF is a crucial cytokine for the maturation of various cell types and regulates allergic airway inflammation.

OBJECTIVE

The functional effect of ML-1 in the expression of GM-CSF was investigated.

METHODS

The levels of gene and protein expression in normal human bronchial epithelial cells (NHBEs) in the presence or absence of various kinase inhibitors or, in some cases, of a Raf1 dominant-negative mutant were determined by RT-PCR and ELISA, respectively. Western blotting was performed to investigate kinase activation.

RESULTS

The results showed first that ML-1 induces, in a time-dependent and dose-dependent manner, the gene and protein expression for GM-CSF NHBEs, which are associated with activation of Raf1 and MAP kinase kinase (MEK) kinases. Selective MEK inhibitors, PD98059 and U0126, and Raf1 kinase inhibitor I significantly inhibited ML-1-induced GM-CSF production. Furthermore, overexpression of Raf1 dominant-negative mutants inhibited IL-17F-induced GMCSF expression. The combination of PD98059 and Raf1 kinase inhibitor I completely blocked GM-CSF production, whereas 2 protein kinase C inhibitors, Ro-31-7549 and GF109203X, and a phosphatidylinositol 3-kinase inhibitor, LY294002, showed no inhibitory effect.

CONCLUSION

These findings suggest that ML-1 induces GM-CSF expression through the activation of the Raf1-MEK-extracellular signal-regulated kinase 1/2 pathway.

A comparison of murine and human alveolar macrophage responses to urban particulate matter

There is increasing evidence linking mortality, increased asthma morbidity, and other respiratory disorders to increases in fine airborne particulate matter (PM) concentrations. However, there are only limited data dealing with the biological mechanisms that ultimately lead to the reported health effects. Rodents are frequently used as an animal model to help elucidate the mechanisms of toxicity that may provide clues for the understanding of PM toxicity in humans; however, the relationships between murine and human PM toxicity have not been established. PM is known to target the pulmonary epithelium and resident alveolar macrophages (AM). PM can initiate cytotoxic effects on the AM including apoptosis and necrosis, depending on the particle concentration, which may be central to the pathological effects just described. This study examined AM apoptosis and necrosis initiated by PM in AM from humans and BALB/c mice in an in vitro exposure model. Freshly isolated AM from human volunteers were incubated with seven different residual fractions of PM1648 derived from organic solvent extractions, high-temperature heating and acid digestions that change the surface characteristics of the original PM. These results were compared to the analogous murine experiments. The results suggested that, at the same concentration of PM, the trend of toxicity and the posttreatment effects observed in BALB/c and human AM have a similar pattern. Altering the surface chemistry by removal of one or more PM components, such as through the various treatments conducted in this study, is sufficient to alter PM bioactivity in both human and murine AM in a similar manner. In addition, the human and murine models were compared with regard to in vitro cytotoxicity using PM(2.5) particles. The cytotoxic PM(2.5) effects were identical in both human and mouse models. Regression analysis revealed that the BALB/c mouse is a suitable model for PM cytotoxicity of AM as it is a good predictive model for the human AM responses.

Staphylococcus aureus peptidoglycan stimulates granulocyte macrophage colony-stimulating factor production from human epidermal keratinocytes via mitogen-activated protein kinases

Epidermal keratinocytes with atopic dermatitis (AD) overproduce mediators such as granulocyte macrophage colony-stimulating factor (GM-CSF), which are associated with pathology of AD. We found that peptidoglycan (PGN) of Staphylococcus aureus, which is frequently observed in lesion with AD, induced the production of numerous mediators such as GM-CSF and regulated on activation, normal T-cell expressed and secreted. Moreover, PGN phosphorylated extracellular-signal-regulated kinases and p38 mitogen-activated protein kinase, which were involved in the induction of GM-CSF expression. These results suggested that PGN of S. aureus directly exacerbates inflammation of inflammatory skin disease.

Activation of nuclear factor kappa B by diesel exhaust particles in mouse epidermal cells through phosphatidylinositol 3-kinase/Akt signaling pathway

Diesel exhaust particles (DEP) induce intense inflammatory and allergic immune responses. The epidermal cells receive much exposure to DEP, and are an important source of pro-inflammatory cytokines and other inflammatory mediators. Transcription factors, such as nuclear factor kappa B (NF-kappaB) and activator protein 1 (AP-1), regulate the expression of these mediators. We hypothesize that the transcription factors are target of DEP action. The current study sought to determine whether DEP-activated NF-kappaB and AP-1 in a mouse epidermal cell line, JB6 P(+) cells. Using stable transfectants of JB6 P(+) cells expressing NF-kappaB or AP-1 luciferase reporter constructs, we demonstrated that exposure to DEP at a non-cytotoxic concentration significantly enhanced the transactivation of NF-kappaB, but not AP-1. Furthermore, DEP promoted phosphorylation of Akt, a substrate of phosphatidylinositol 3-kinase (PI3K), on Ser-473 and Thr-308 in a PI3K-dependent manner, and enhanced phosphorylation of down-stream p70/p85 S6 kinases (p70/p85S6K) as well as glycogen synthase kinase-3beta (GSK-3beta). Blockage of PI3K activation eliminated DEP-stimulated NF-kappaB transactivation. Although SAPK/JNK pathway was modestly activated by DEP, it was not involved in NF-kappaB transactivation. DEP had little effect on the phosphorylation of ERKs and p38 MAPK. Thus, DEP-induced transactivation of NF-kappaB is mediated by PI3K/Akt signaling pathway.

Fine particulate matter induces amphiregulin secretion by bronchial epithelial cells

Particulate matter (PM) is thought to be responsible for respiratory health problems. Epithelial cells exposed to particles release pro-inflammatory cytokines leading to inflammation of airways. However, the signaling cascades triggered by particles are poorly understood. We demonstrate that PM with an aerodynamic diameter < 2.5 microm (PM2.5) or diesel exhaust particles upregulate the expression of amphiregulin (AR), a ligand of the epidermal growth factor receptor (EGFR), in human bronchial epithelial cells. AR secretion was blocked by an inhibitor of the EGFR tyrosine kinase (AG1478), or a selective mitogen-activated protein (MAP) kinase/extracellular regulated kinase (Erk) inhibitor (PD98059), but not by the p38 MAP kinase inhibitor (SB203580). Thus, AR secretion is mediated through the activation of the EGFR and Erk MAP kinase pathway. In addition, AR secretion was inhibited by the antioxidant N-acetyl cysteine, but not by a neutralizing anti-EGFR, suggesting an EGFR transactivation via oxidative stress. AR may be involved in cytokine secretion, as AR can induce granulocyte macrophage-colony-stimulating factor (GM-CSF) release and a neutralizing anti-EGFR reduces the particle-induced GM-CSF release. This study indicates that PM2.5 induces the expression and secretion of AR, an EGFR ligand contributing to GM-CSF release, which may reflect an important mechanism for sustaining the proinflammatory response.

Effect of OFR and [Ca2+]i on the activation of p38 MAPK in isolated rabbit liver during cold preservation and reperfusion period

AIM

To study the effect of OFR (oxygen-derieved free radicals) and calcium on the activation of p38 MAPK in isolated rabbit liver during cold preservation and reperfusion period.

METHODS

Based on the cold preservation-reperfusion model of isolated rabbit liver, isolated livers were divided into 4 groups according to the concentration of allopurinol or verapamil in the preservation solution. Liver tissue samples were harvested at the time points of before cold preservation, at the end of cold preservation, and during reperfusion period (5 min, 10 min, 60 min, 120 min). The phosphorylation level of p38MAPK and its activity in liver tissue were detected by Western-Blotting and immunoprecipitation respectively. The content of OFR and concentration of intracellular calciumion ([Ca²⁺]_i) were also measured by the corresponding method.

RESULTS

The content of OFR was increased to its peak value at 5 min during reperfusion period, the difference among the four groups was significant (groups A, B, C, D: 2.32±0.22, 1.82±0.15, 1.63±0.11, 1.29±0.10, P<0.05, t = 2.57). At 10 min during reperfusion period, the phosphorylation level and its activity of p38MAPK reached its peak value, and there was significant difference among the four groups (Groups A, B, C, D: p38MAPK phosphorylation level (76.2±7.0, 61.4±5.9, 47.3±2.5, 37.7±3.0, P<0.05, t = 2.61.Groups A, B, C, D: p38MAPK activity) 82.7±6.8, 69.7±5.2, 54.5±5.5, 41.2±3.1, P<0.05, t = 2.61. Groups A, E, F, G: p38MAPK phosphorylation level (80.3±8.7, 63.3±4.2, 50.4±5.6, 39.2±5.7, P<0.05, t = 2.61. Groups A, E, F, G: p38MAPK activity (80.8±8.9, 66.7±4.2, 53.7±4.1, 39.4±5.5, P<0.05, t = 2.61). The peak value of OFR content and [Ca²⁺]_i was significantly and positively correlated with the peak value of p38MAPK phosphorylation level and activity (P<0.05, R_OFR = 0.976, R_Ca = 0.970).

CONCLUSION

Allopurinol can significantly inhibit the OFR content of isolated liver tissues while verapamil can significantly inhibit the overload of Ca²⁺ concentration of isolated liver cells. The OFR content and overload of intracellular calciumion concentration are closely related with p38MAPK activation during cold preservation and reperfusion period. So activation of p38MAPK signal pathway may be an important mechanism of OFR and Ca²⁺ , which play a critical role in the ischemia-reperfusion injury of donor liver.

DEP-induced fra-1 expression correlates with a distinct activation of AP-1-dependent gene transcription in the lung

Recent studies indicate a potential role for Fra-1, a heterodimeric partner of activator protein (AP)-1, in toxicant-induced epithelial injury, repair, and cellular transformation. Here we have investigated the effects of diesel exhaust particles (DEP) on fra-1 expression in C10 cells, a murine lung epithelial cell line. DEP markedly upregulated fra-1, but not fra-2, expression. The increase in fra-1 mRNA expression correlated well with its protein- and DNA-binding activity. DNA-binding assays also revealed a predominant presence of Jun-B and Jun-D in the AP-1 complex. Interestingly, DEP did not alter Jun-B and Jun-D protein levels. Transcriptional analysis revealed that fra-1 induction is regulated in part at the transcriptional level. The -379 to +32 bp 5'-flanking region mediated this induction. Furthermore, inhibitors of ERK1/2, JNK1, and p38 mitogen-activated protein kinases (MAPKs) significantly suppressed DEP-stimulated fra-1 transcription, suggesting their involvement in the induction process. Consistent with this finding, DEP stimulated phosphorylation of ERK1/2, JNK1, and p38 MAPKs with a distinct activation pattern. Overexpression of Fra-1 downregulated c-Jun and Nrf2 enhanced AP-1- and ARE-mediated reporter gene expression, respectively. In contrast, Fra-1 had the opposite effect on matrix metalloproteinase (MMP)-9 promoter activity. In particular, it bound to the functional AP-1 site of the MMP-9 promoter after DEP stimulation. Consistent with this result, DEP also markedly upregulated MMP-9 promoter activity. Collectively, these findings suggest that fra-1 induction by DEP may play a role in selectively regulating gene expression involved in alveolar epithelial cell injury and repair.

Involvement of reactive oxygen species in the metabolic pathways triggered by diesel exhaust particles in human airway epithelial cells

Diesel exhaust particles (DEP) induce a proinflammatory response in human bronchial epithelial cells (16HBE) characterized by the release of proinflammatory cytokines after activation of transduction pathways involving MAPK and the transcription factor NF-kappaB. Because cellular effects induced by DEP are prevented by antioxidants, they could be mediated by reactive oxygen species (ROS). Using fluorescent probes, we detected ROS production in bronchial and nasal epithelial cells exposed to native DEP, organic extracts of DEP (OE-DEP), or several polyaromatic hydrocarbons. Carbon black particles mimicking the inorganic part of DEP did not increase ROS production. DEP and OE-DEP also induced the expression of genes for phase I [cytochrome P-450 1A1 (CYP1A1)] and phase II [NADPH quinone oxidoreductase-1 (NQO-1)] xenobiotic metabolization enzymes, suggesting that DEP-adsorbed organic compounds become bioavailable, activate transcription, and are metabolized since the CYP1A1 enzymatic activity is increased. Because NQO-1 gene induction is reduced by antioxidants, it could be related to the ROS generated by DEP, most likely through the activation of the stress-sensitive Nrf2 transcription factor. Indeed, DEP induced the translocation of Nrf2 to the nucleus and increased protein nuclear binding to the antioxidant responsive element. In conclusion, we show that DEP-organic compounds generate an oxidative stress, activate the Nrf2 transcription factor, and increase the expression of genes for phase I and II metabolization enzymes.

Oxidative stress and calcium signaling in the adverse effects of environmental particles (PM10)

This review focuses on the potential role that oxidative stress plays in the adverse effects of PM(10). The central hypothesis is that the ability of PM(10) to cause oxidative stress underlies the association between increased exposure to PM(10) and both exacerbations of lung disease and lung cancer. Pulmonary inflammation may also underlie the cardiovascular effects seen following increased PM(10), although the mechanisms of the cardiovascular effects of PM(10) are not well understood. PM(10) is a complex mix of various particle types and several of the components of PM(10) are likely to be involved in the induction of oxidative stress. The most likely of these are transition metals, ultrafine particle surfaces, and organic compounds. In support of this hypothesis, oxidative stress arising from PM(10) has been shown to activate a number of redox-responsive signaling pathways in lung target cells. These pathways are involved in expression of genes that play a role in responses relevant to inflammation and pathological change, including MAPKs, NF-kappaB, AP-1, and histone acetylation. Oxidative stress from particles is also likely to play an important role in the carcinogenic effects associated with PM(10) and hydroxyl radicals from PM(10) cause DNA damage in vitro.

Negative impact of DEP exposure on human airway epithelial cell adhesion, stiffness, and repair

Epidemiological and experimental studies suggest that diesel exhaust particles (DEPs) may be associated with increased respiratory mortality and morbidity. Several recent studies have also shown that DEPs increase the production of inflammatory cytokines by human bronchial epithelium (HBE) cells in vitro. The present study investigates the effects of DEPs on the interaction of l-HBE cells (16HBE14o-) with the cell and matrix microenvironment based on evaluation of integrin-type cell/matrix ligand expression, cytoskeleton (CSK) stiffness, and matrix remodeling via matrix metalloproteinase (MMP)-1, MMP-2, and MMP-9 expression. The results showed that DEP exposure induced: 1) a net dose-dependent decrease in CSK stiffness through actin fibers, 2) a concomitant specific reduction of both alpha(3)- and beta(1)-integrin subunits extensively expressed on the HBE cell surface, 3) a decrease in the level of CD44, which is a major HBE cell-cell and HBE cell-matrix adhesion molecule; and 4) an isolated decrease in MMP-1 expression without any change in tissue inhibitor of matrix metalloproteinase (TIMP)-1 or TIMP-2 tissue inhibitors. Restrictive modulation of cell-matrix interaction, cell-cell connection, CSK stiffness, and fibrillary collagen remodeling results in a decreased wound closure capacity and an increased deadhesion capacity. In conclusion, on the basis of these results, we can propose that, in addition to their ability to increase the production of inflammatory cytokines, DEPs could also alter the links between actin CSK and the extracellular matrix, suggesting that they might facilitate HBE cell detachment in vivo.

Isoflavones protect against diesel engine exhaust injury in organotypic culture of lung tissue

The wide range of potential health beneficial effects of isoflavones, including a chemoprentive action, have prompted us to study the potential benefits of genistein and daidzein in an experimental model of environmental pollution impact on lung tissue. A diesel engine placed was used to generate reproducible emissions including both gaseous and particulate matters that are commonly found in urban atmospheres. Isoflavones were added to culture medium of rat lung slices 2 h prior to their exposure to pollutants for 3 h. Intracellular ATP and GSH levels, TNFα production, nucleosome assay and TUNEL labeling were monitored. Isoflavones showed almost total in vitro protection against inflammatory and pro-apoptotic responses in lung slices. Isoflavones 0.3 and 1 μmol/l protected against exhaust induced GSH depletion. Isoflavones 0.3 μmol/l appeared to exert the most beneficial effects. In conclusion, this study points out the potential interest of soy isoflavones consumption in polluted areas. Further studies should be undertaken to verify that similar effects could be obtained after in vivo administration of isoflavones.

Comparison of the pro-oxidative and proinflammatory effects of organic diesel exhaust particle chemicals in bronchial epithelial cells and macrophages

Inhaled diesel exhaust particles (DEP) exert proinflammatory effects in the respiratory tract. This effect is related to the particle content of redox cycling chemicals and is involved in the adjuvant effects of DEP in atopic sensitization. We demonstrate that organic chemicals extracted from DEP induce oxidative stress in normal and transformed bronchial epithelial cells, leading to the expression of heme oxygenase 1, activation of the c-Jun N-terminal kinase cascade, IL-8 production, as well as induction of cytotoxicity. Among these effects, heme oxygenase 1 expression is the most sensitive marker for oxidative stress, while c-Jun N-terminal kinase activation and induction of apoptosis-necrosis require incremental amounts of the organic chemicals and increased levels of oxidative stress. While a macrophage cell line (THP-1) responded in similar fashion, epithelial cells produced more superoxide radicals and were more susceptible to cytotoxic effects than macrophages. Cytotoxicity is the result of mitochondrial damage, which manifests as ultramicroscopic changes in organelle morphology, a decrease in the mitochondrial membrane potential, superoxide production, and ATP depletion. Epithelial cells also differ from macrophages in not being protected by a thiol antioxidant, N-acetylcysteine, which effectively protects macrophages against cytotoxic DEP chemicals. These findings show that epithelial cells exhibit a hierarchical oxidative stress response that differs from that of macrophages by more rapid transition from cytoprotective to cytotoxic responses. Moreover, epithelial cells are not able to convert N-acetylcysteine to cytoprotective glutathione.

Size fractions of ambient particulate matter induce granulocyte macrophage colony-stimulating factor in human bronchial epithelial cells by mitogen-activated protein kinase pathways

Environmental pollutants, including ambient particulate matter (PM), increase respiratory morbidity. Studies of model PM particles, including residual oil fly ash and freshly generated diesel exhaust particles, have demonstrated that PM affects inflammatory airway responses. Neither of these particles completely represents ambient PM, and therefore questions remain about ambient particulates. We hypothesized that ambient PM of different size fractions collected from an urban environment (New York City air), would activate primary culture human bronchial epithelial cells (HBECs). Because of the importance of granulocyte-macrophage colony-stimulating factor (GM-CSF) on inflammatory and immunomodulatory processes, we focused our studies on this cytokine. We demonstrated that the smallest size fraction (ultrafine/fine; < 0.18 micro m) of ambient PM (11 micro g/cm(2)), upregulated GM-CSF production (2-fold increase). The absence of effect of carbon particles of similar size, and the day-to-day variation in response, suggested that the chemical composition, but not the particle itself, was necessary for GM-CSF induction. Activation of the extracellular signal-regulated kinase and the p38 mitogen-activated protein kinase was associated with, and necessary for, GM-CSF release. These studies serve to corroborate and extend those on model particles. Moreover, they emphasize the role of the smallest size ambient particles in airway epithelial cell responses.

Interaction of alveolar macrophages and airway epithelial cells following exposure to particulate matter produces mediators that stimulate the bone marrow

Exposure to ambient air pollution particles with a diameter of < 10 microm (PM(10)) has been associated with increased cardiopulmonary morbidity and mortality. We postulate that these adverse health effects are related to proinflammatory mediators produced in the lung and released into the circulation where they initiate a systemic inflammatory response. The present study was designed to determine if alveolar macrophages (AMs) and primary human bronchial epithelial cells (HBECs) interact to amplify the production of certain cytokines when exposed to ambient PM(10) (EHC-93). Candidate cytokines were measured at the mRNA level using a RNase protection assay and at the protein level by enzyme-linked immunosorbent assay (ELISA). When AM/HBEC cocultures were exposed to 100 microg/ml of PM(10), levels of tumor necrosis factor (TNF)-alpha, granulocyte macrophage colony stimulating factor (GM-CSF), interleukin (IL)-1beta, IL-6, leukemia inhibitory factor (LIF), oncostatin M (OSM), and IL-8 mRNA increased within 2 h (P < 0.05) and 8 h following exposure compared with control cells. GM-CSF mRNA expression was more rapidly induced in cocultured cells compared with HBECs or AMs alone. The concentrations of TNF-alpha, GM-CSF, IL-1beta, IL-6, and IL-8 in the cocultured supernatants collected after 24 h PM(10) exposure increased significantly compared with control cells. There was a significant synergistic effect between AMs and HBECs in the production of GM-CSF and of IL-6 (P < 0.05). Instillation of supernatants from HBECs cultured with PM(10) into lungs of rabbits failed to increase circulating band cell counts or stimulate the bone marrow. However, those from AM/HBEC cocultures exposed to PM(10) increased circulating band cell counts (P < 0.05) and shortened the transit time of polymorphonuclear leukocytes (PMNs) through the bone marrow compared with control co-cultures (P < 0.01). These results suggest that the interaction between AMs and HBECs during PM(10) exposure contributes to the production of mediators that induce a systemic inflammatory response.