Organic compounds from diesel exhaust particles elicit a proinflammatory response in human airway epithelial cells and induce cytochrome p450 1A1 expression

Biological effects of carbon black nanoparticles are changed by surface coating with polycyclic aromatic hydrocarbons

Background

Carbon black nanoparticles (CBNP) are mainly composed of carbon, with a small amount of other elements (including hydrogen and oxygen). The toxicity of CBNP has been attributed to their large surface area, and through adsorbing intrinsically toxic substances, such as polycyclic aromatic hydrocarbons (PAH). It is not clear whether a PAH surface coating changes the toxicological properties of CBNP by influencing their physicochemical properties, through the specific toxicity of the surface-bound PAH, or by a combination of both.

Methods

Printex^®90 (P90) was used as CBNP; the comparators were P90 coated with either benzo[a]pyrene (BaP) or 9-nitroanthracene (9NA), and soot from acetylene combustion that bears various PAHs on the surface (AS-PAH). Oxidative stress and IL-8/KC mRNA expression were determined in A549 and bronchial epithelial cells (16HBE14o-, Calu-3), mouse intrapulmonary airways and tracheal epithelial cells. Overall toxicity was tested in a rat inhalation study according to Organization for Economic Co-operation and Development (OECD) criteria. Effects on cytochrome monooxygenase (Cyp) mRNA expression, cell viability and mucociliary clearance were determined in acute exposure models using explanted murine trachea.

Results

All particles had similar primary particle size, shape, hydrodynamic diameter and ζ-potential. All PAH-containing particles had a comparable specific surface area that was approximately one third that of P90. AS-PAH contained a mixture of PAH with expected higher toxicity than BaP or 9NA. PAH-coating reduced some effects of P90 such as IL-8 mRNA expression and oxidative stress in A549 cells, granulocyte influx in the in vivo OECD experiment, and agglomeration of P90 and mucus release in the murine trachea ex vivo. Furthermore, P90-BaP decreased particle transport speed compared to P90 at 10 μg/ml. In contrast, PAH-coating induced IL-8 mRNA expression in bronchial epithelial cell lines, and Cyp mRNA expression and apoptosis in tracheal epithelial cells. In line with the higher toxicity compared to P90-BaP and P90-9NA, AS-PAH had the strongest biological effects both ex vivo and in vivo.

Conclusions

Our results demonstrate that the biological effect of CBNP is determined by a combination of specific surface area and surface-bound PAH, and varies in different target cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12989-017-0189-1) contains supplementary material, which is available to authorized users.

Triggering Mechanisms and Inflammatory Effects of Combustion Exhaust Particles with Implication for Carcinogenesis

A number of biological responses may contribute to the carcinogenic effects of combustion-derived particulate matter (CPM). Here, we focus on mechanisms that trigger CPM-induced pro-inflammatory responses. Inflammation has both genotoxic and non-genotoxic implications and is considered to play a central role in development of various health outcome associated with CPM exposure, including cancer. Chronic, low-grade inflammation may cause DNA damage through a persistent increased level of reactive oxygen species (ROS) produced and released by activated immune cells. Moreover, a number of pro-inflammatory cytokines and chemokines display mitogenic, motogenic, morphogenic and/or angiogenic properties and may therefore contribute to tumour growth and metastasis. The key triggering events involved in activation of pro-inflammatory responses by CPM and soluble CPM components can be categorized into (i) formation of ROS and oxidative stress, (ii) interaction with the lipid layer of cellular membranes, (iii) activation of receptors, ion channels and transporters on the cell surface and (iv) interactions with intracellular molecular targets including receptors such as the aryl hydrocarbon receptor (AhR). In particular, we will elucidate the effects of diesel exhaust particles (DEP) using human lung epithelial cells as a model system.

Phytotherapeutic approach: a new hope for polycyclic aromatic hydrocarbons induced cellular disorders, autophagic and apoptotic cell death

Polycyclic aromatic hydrocarbons (PAHs) comprise the major class of cancer-causing chemicals and are ranked ninth among the chemical compounds threatening to humans. Moreover, interest in PAHs has been mainly due to their genotoxic, teratogenic, mutagenic and carcinogenic property. Polymorphism in cytochrome P450 (CYP450) and aryl hydrocarbon receptor (AhR) has the capacity to convert procarcinogens into carcinogens, which is an imperative factor contributing to individual susceptibility to cancer development. The carcinogenicity potential of PAHs is related to their ability to bind to DNA, thereby enhances DNA cross-linking, causing a series of disruptive effects which can result in tumor initiation. They induce cellular toxicity by regulating the generation of reactive oxygen species (ROS), which arbitrate apoptosis. Additionally, cellular toxicity-mediated apoptotic and autophagic cell death and immune suppression by industrial pollutants PAH, provide fertile ground for the proliferation of mutated cells, which results in cancer growth and progression. PAHs play a foremost role in angiogenesis necessary for tumor metastasization by promoting the upregulation of metalloproteinase-9 (MMP-9), vascular endothelial growth factor (VEGF) and hypoxia inducible factor (HIF) in human cancer cells. This review sheds light on the molecular mechanisms of PAHs induced cancer development as well as autophagic and apoptotic cell death. Besides that authors have unraveled how phytotherapeutics is an alternate potential therapeutics acting as a savior from the toxic effects of PAHs for safer and cost effective perspectives.

Characterization of particulate-phase polycyclic aromatic hydrocarbons emitted from incense burning and their bioreactivity in RAW264.7 macrophage

This study investigated the effects of particle-bound polycyclic aromatic hydrocarbons (PAHs) produced from burning three incense types on and their bioreactivity in the RAW 264.7 murine macrophage cell line. Gas chromatography/mass spectrometry was used to determine the levels of 16 identified PAHs. Macrophages were exposed to incense particle extracts at concentrations of 0, 3.125, 6.25, 12.5, 25, 50, and 100 μg/mL for 24 h. After exposure, cell viability and nitric oxide (NO) and inflammatory mediator [tumor necrosis factor (TNF)-α] production of the cells were examined. The mean atomic hydrogen (H) to carbon (C) ratios in the environmentally friendly, binchotan charcoal, and lao shan incenses were 0.69, 1.13, and 1.71, respectively. PAH and total toxic equivalent (TEQ) mass fraction in the incenses ranged from 137.84 to 231.00 and 6.73-26.30 pg/μg, respectively. The exposure of RAW 264.7 macrophages to incense particles significantly increased TNF-α and NO production and reduced cell viability. The cells treated with particles collected from smoldering the environmentally friendly incense produced more NO and TNF-α compared to other incenses. Additionally, the TEQ of fluoranthene (FL), pyrene (Pyr), benzo[a]anthracene (BaA), chrysene (Chr), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (INP), dibenz[a,h]anthracene (DBA), and benzo[g,h,i]perylene [B(ghi)P] had a significant correlation (R² = 0.64-0.98, P < 0.05) with NO and TNF-α production. The current findings indicate that incense particle-bound PAHs are biologically active and that burning an incense with a lower H/C ratio caused higher bioreactivity. The stimulatory effect of PAH-containing particles on molecular mechanisms of inflammation are critical for future study.

Associations between microvascular function and short-term exposure to traffic-related air pollution and particulate matter oxidative potential

BACKGROUND

Short-term exposure to ambient air pollution has been associated with acute increases in cardiovascular hospitalization and mortality. However, causative chemical components and underlying pathophysiological mechanisms remain to be clarified. We hypothesized that endothelial dysfunction would be associated with mobile-source (traffic) air pollution and that pollutant components with higher oxidative potential to generate reactive oxygen species (ROS) would have stronger associations.

METHODS

We carried out a cohort panel study in 93 elderly non-smoking adults living in the Los Angeles metropolitan area, during July 2012-February 2014. Microvascular function, represented by reactive hyperemia index (RHI), was measured weekly for up to 12 weeks (N = 845). Air pollutant data included daily data from regional air-monitoring stations, five-day average PM chemical components and oxidative potential in three PM size-fractions, and weekly personal nitrogen oxides (NOx). Linear mixed-effect models estimated adjusted changes in microvascular function with exposure.

RESULTS

RHI was inversely associated with traffic-related pollutants such as ambient PM2.5 black carbon (BC), NOx, and carbon monoxide (CO). An interquartile range change increase (1.06 μg/m(3)) in 5-day average BC was associated with decreased RHI, -0.093 (95 % CI: -0.151, -0.035). RHI was inversely associated with other mobile-source components/tracers (polycyclic aromatic hydrocarbons, elemental carbon, and hopanes), and PM oxidative potential as quantified in two independent assays (dithiothreitol and in vitro macrophage ROS) in accumulation and ultrafine PM, and transition metals.

CONCLUSIONS

Our findings suggest that short-term exposures to traffic-related air pollutants with high oxidative potential are major components contributing to microvascular dysfunction.

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.

Biological impact of environmental polycyclic aromatic hydrocarbons (ePAHs) as endocrine disruptors

Polycyclic aromatic hydrocarbons (PAHs) are often detected in the environment and are regarded as endocrine disruptors. We here designated mixtures of PAHs in the environment as environmental PAHs (ePAHs) to discuss their effects collectively, which could be different from the sum of the constituent PAHs. We first summarized the biological impact of environmental PAHs (ePAHs) found in the atmosphere, sediments, soils, and water as a result of human activities, accidents, or natural phenomena. ePAHs are characterized by their sources and forms, followed by their biological effects and social impact, and bioassays that are used to investigate their biological effects. The findings of the bioassays have demonstrated that ePAHs have the ability to affect the endocrine systems of humans and animals. The pathways that mediate cell signaling for the endocrine disruptions induced by ePAHs and PAHs have also been summarized in order to obtain a clearer understanding of the mechanisms responsible for these effects without animal tests; they include specific signaling pathways (MAPK and other signaling pathways), regulatory mechanisms (chromatin/epigenetic regulation, cell cycle/DNA damage control, and cytoskeletal/adhesion regulation), and cell functions (apoptosis, autophagy, immune responses/inflammation, neurological responses, and development/differentiation) induced by specific PAHs, such as benz[a]anthracene, benzo[a]pyrene, benz[l]aceanthrylene, cyclopenta[c,d]pyrene, 7,12-dimethylbenz[a]anthracene, fluoranthene, fluorene, 3-methylcholanthrene, perylene, phenanthrene, and pyrene as well as their derivatives. Estrogen signaling is one of the most studied pathways associated with the endocrine-disrupting activities of PAHs, and involves estrogen receptors and aryl hydrocarbon receptors. However, some of the actions of PAHs are contradictory, complex, and unexplainable. Although several possibilities have been suggested, such as direct interactions between PAHs and receptors and the suppression of their activities through other pathways, the mechanisms underlying the activities of PAHs remain unclear. Thus, standardized assay protocols for pathway-based assessments are considered to be important to overcome these issues.

Human bronchial epithelial cells exposed in vitro to diesel exhaust particles exhibit alterations in cell rheology and cytotoxicity associated with decrease in antioxidant defenses and imbalance in pro- and anti-apoptotic gene expression

Diesel exhaust particles (DEPs) from diesel engines produce adverse alterations in cells of the airways by activating intracellular signaling pathways and apoptotic gene overexpression, and also by influencing metabolism and cytoskeleton changes. This study used human bronchial epithelium cells (BEAS-2B) in culture and evaluates their exposure to DEPs (15ug/mL for 1 and 2 h) in order to determine changes to cell rheology (viscoelasticity) and gene expression of the enzymes involved in oxidative stress, apoptosis, and cytotoxicity. BEAS-2B cells exposed to DEPs were found to have a significant loss in stiffness, membrane stability, and mitochondrial activity. The genes involved in apoptosis [B cell lymphoma 2 (BCL-2 and caspase-3)] presented inversely proportional expressions (p = 0.05, p = 0.01, respectively), low expression of the genes involved in antioxidant responses [SOD1 (superoxide dismutase 1); SOD2 (superoxide dismutase 2), and GPx (glutathione peroxidase) (p = 0.01)], along with an increase in cytochrome P450, family 1, subfamily A, polypeptide 1 (CYP1A1) (p = 0.01). These results suggest that alterations in cell rheology and cytotoxicity could be associated with oxidative stress and imbalance between pro- and anti-apoptotic genes.

Biodiesel exhaust-induced cytotoxicity and proinflammatory mediator production in human airway epithelial cells

Increasing use of biodiesel has prompted research into the potential health effects of biodiesel exhaust exposure. Few studies directly compare the health consequences of mineral diesel, biodiesel, or blend exhaust exposures. Here, we exposed human epithelial cell cultures to diluted exhaust generated by the combustion of Australian ultralow-sulfur-diesel (ULSD), unprocessed canola oil, 100% canola biodiesel (B100), and a blend of 20% canola biodiesel mixed with 80% ULSD. The physicochemical characteristics of the exhaust were assessed and we compared cellular viability, apoptosis, and levels of interleukin (IL)-6, IL-8, and Regulated on Activation, Normal T cell Expressed and Secreted (RANTES) in exposed cultured cells. Different fuel types produced significantly different amounts of exhaust gases and different particle characteristics. All exposures resulted in significant apoptosis and loss of viability when compared with control, with an increasing proportion of biodiesel being correlated with a decrease in viability. In most cases, exposure to exhaust resulted in an increase in mediator production, with the greatest increases most often in response to B100. Exposure to pure canola oil (PCO) exhaust did not increase mediator production, but resulted in a significant decrease in IL-8 and RANTES in some cases. Our results show that canola biodiesel exhaust exposure elicits inflammation and reduces viability of human epithelial cell cultures in vitro when compared with ULSD exhaust exposure. This may be related to an increase in particle surface area and number in B100 exhaust when compared with ULSD exhaust. Exposure to PCO exhaust elicited the greatest loss of cellular viability, but virtually no inflammatory response, likely due to an overall increase in average particle size.

Immunotoxicological impact of occupational and environmental nanoparticles exposure: The influence of physical, chemical, and combined characteristics of the particles

While nanotechnology is growing exponentially, the knowledge of the impact of nanoparticles (NPs) on public health and the environment is limited so far. Current nanomaterial research is focused on the applications of nanotechnology, whereas there is little information on exposure assessment and risk characterization associated with NPs. Therefore, it is essential that the factors influencing NPs associated hazards be studied. This review seeks to survey and evaluate the current literature in order to better understand the impact of both airborne and engineered NPs exposure, the mechanisms at the cellular level, and the factors influencing their immunotoxicity. In fact, NPs do have immunotoxicological significance, as immune cells in the bloodstream and tissues do act to eliminate or interact with NPs.Proper characterization of the NPs as well as understanding the processes occurring on the NPs surface when in contact with biological systems is crucial to predict or exclude toxicological effects.

Winter Polycyclic Aromatic Hydrocarbon-Bound Particulate Matter from Peri-urban North China Promotes Lung Cancer Cell Metastasis

On the basis of the close relationship between human exposure to high concentrations of small particulate matter (PM) and increased lung cancer mortality, PM was recently designated as a Group I carcinogen. Considering that PM is highly heterogeneous, the potential health risks of PM promoting tumor metastasis in lung cancer, as well as its chemical characteristics, remain elusive. In the present study, we collected PM2.5 and PM10 in a peri-urban residential site of Taiyuan and determined the concentration and source of polycyclic aromatic hydrocarbons (PAHs). The results indicated that 18 PAHs, ranging from 38.21 to 269.69 ng/m(3) (for PM2.5) and from 44.34 to 340.78 ng/m(3) (for PM10), exhibited seasonal variations, and the PAHs in winter PM mainly originated from coal combustion. We calculated the benzo(a)pyrene-equivalent (BaPeq) and found that the PAH-bound PM in winter exhibited higher carcinogenic risks for humans. Following this result, in vitro bioassays demonstrated that PM2.5 and PM10 induced A549 cell migration and invasion, and the mechanism involved reactive oxygen species (ROS)-mediated epithelial-to-mesenchymal transition (EMT) activation and extracellular matrix (ECM) degradation. Our data indicate the potential risk for winter PAH-bound PM from peri-urban North China promoting lung cancer cell metastasis and reveal a mechanistic basis for treating, ameliorating, or preventing outcomes in polluted environments.

Effects of High-Intensity Swimming on Lung Inflammation and Oxidative Stress in a Murine Model of DEP-Induced Injury

Studies have reported that exposure to diesel exhaust particles (DEPs) induces lung inflammation and increases oxidative stress, and both effects are susceptible to changes via regular aerobic exercise in rehabilitation programs. However, the effects of exercise on lungs exposed to DEP after the cessation of exercise are not clear. Therefore, the aim of this study was to evaluate the effects of high-intensity swimming on lung inflammation and oxidative stress in mice exposed to DEP concomitantly and after exercise cessation. Male Swiss mice were divided into 4 groups: Control (n = 12), Swimming (30 min/day) (n = 8), DEP (3 mg/mL—10 μL/mouse) (n = 9) and DEP+Swimming (n = 8). The high-intensity swimming was characterized by an increase in blood lactate levels greater than 1 mmoL/L between 10th and 30th minutes of exercise. Twenty-four hours after the final exposure to DEP, the anesthetized mice were euthanized, and we counted the number of total and differential inflammatory cells in the bronchoalveolar fluid (BALF), measured the lung homogenate levels of IL-1β, TNF-α, IL-6, INF-ϫ, IL-10, and IL-1ra using ELISA, and measured the levels of glutathione, non-protein thiols (GSH-t and NPSH) and the antioxidant enzymes catalase and glutathione peroxidase (GPx) in the lung. Swimming sessions decreased the number of total cells (p<0.001), neutrophils and lymphocytes (p<0.001; p<0.05) in the BALF, as well as lung levels of IL-1β (p = 0.002), TNF-α (p = 0.003), IL-6 (p = 0.0001) and IFN-ϫ (p = 0.0001). However, the levels of IL-10 (p = 0.01) and IL-1ra (p = 0.0002) increased in the swimming groups compared with the control groups, as did the CAT lung levels (p = 0.0001). Simultaneously, swimming resulted in an increase in the GSH-t and NPSH lung levels in the DEP group (p = 0.0001 and p<0.002). We concluded that in this experimental model, the high-intensity swimming sessions decreased the lung inflammation and oxidative stress status during DEP-induced lung inflammation in mice.

Difference in Pro-Inflammatory Cytokine Responses Induced in THP1 Cells by Particulate Matter Collected on Days with and without ASIAN Dust Storms

The associations between particulate matter from Asian dust storms (ADS) and health disorders differ among studies, and the underlying mechanisms remain unclear. In this study, ADS and non-ADS particles were tested for their potential to induce pro-inflammatory cytokines associated with adverse respiratory effects. Particulate matter was collected in Japan during four periods in 2013 (2 × ADS periods; 2 × non-ADS). THP1 cells were exposed to this particulate matter, and the levels of various interleukins (ILs), and tumor necrosis factor (TNF)-α were measured. Levels of IL-2 increased significantly following exposure to all particulate matter samples (compared to levels in a solvent control). Increased levels of IL-10 and TNF-α were also observed following exposure to particles collected during three (one ADS and two non-ADS) and two (one ADS and one non-ADS) collection periods, respectively. Thus, the effects of particulate matter on cytokine responses differed according to collection period, and the effects of ADS particles differed for each ADS event. Additionally, the levels of pro-inflammatory cytokines induced by ADS particles were not always higher than those induced by non-ADS particles.

Cytokine responses induced by diesel exhaust particles are suppressed by PAR-2 silencing and antioxidant treatment, and driven by polar and non-polar soluble constituents

Adsorbed soluble organics seem to be the main drivers of inflammatory responses induced by diesel exhaust particles (DEP). The specific compounds contributing to this process and the cellular mechanisms behind DEP-induced inflammation are not well known. We have assessed pro-inflammatory effects of DEP and various soluble DEP fractions, in human bronchial epithelial cells (BEAS-2B). DEP increased the expression of interleukin (IL)-6 and CXCL8. Silencing of the aryl hydrocarbon receptor (AhR) by siRNA or pretreatment with AhR-antagonists did not attenuate DEP-induced IL-6 and CXCL8 responses. However, the halogenated aromatic hydrocarbon (HAH)-selective AhR antagonist CH223191 caused a considerable reduction in DEP-induced CYP1A1 expression indicating that this response may be due to dioxin or dioxin-like constituents in DEP. Knock-down of protease activated receptor (PAR)-2 attenuated IL-6 responses without affecting CXCL8. Antioxidants did not affect IL-6 expression after 4h DEP-exposure and only partly reduced CXCL8 expression. However, after 24h exposure antioxidant treatment partly suppressed IL-6 protein release and completely blocked CXCL8 release. Furthermore, a heptane-soluble (non-polar) extract of DEP induced both IL-6 and CXCL8 release, whereas a PBS-soluble (highly polar) extract induced only IL-6. Thus, pro-inflammatory responses in DEP-exposed epithelial cells appear to be the result of both reactive oxygen species and receptor signaling, mediated through combinatorial effects between both non-polar and polar constituents adhered to the particle surface.

Activation of Proinflammatory Responses in Cells of the Airway Mucosa by Particulate Matter: Oxidant- and Non-Oxidant-Mediated Triggering Mechanisms

Inflammation is considered to play a central role in a diverse range of disease outcomes associated with exposure to various types of inhalable particulates. The initial mechanisms through which particles trigger cellular responses leading to activation of inflammatory responses are crucial to clarify in order to understand what physico-chemical characteristics govern the inflammogenic activity of particulate matter and why some particles are more harmful than others. Recent research suggests that molecular triggering mechanisms involved in activation of proinflammatory genes and onset of inflammatory reactions by particles or soluble particle components can be categorized into direct formation of reactive oxygen species (ROS) with subsequent oxidative stress, interaction with the lipid layer of cellular membranes, activation of cell surface receptors, and direct interactions with intracellular molecular targets. The present review focuses on the immediate effects and responses in cells exposed to particles and central down-stream signaling mechanisms involved in regulation of proinflammatory genes, with special emphasis on the role of oxidant and non-oxidant triggering mechanisms. Importantly, ROS act as a central second-messenger in a variety of signaling pathways. Even non-oxidant mediated triggering mechanisms are therefore also likely to activate downstream redox-regulated events.

Differential proteomic analysis of mouse macrophages exposed to adsorbate-loaded heavy fuel oil derived combustion particles using an automated sample-preparation workflow

Ship diesel combustion particles are known to cause broad cytotoxic effects and thereby strongly impact human health. Particles from heavy fuel oil (HFO) operated ships are considered as particularly dangerous. However, little is known about the relevant components of the ship emission particles. In particular, it is interesting to know if the particle cores, consisting of soot and metal oxides, or the adsorbate layers, consisting of semi- and low-volatile organic compounds and salts, are more relevant. We therefore sought to relate the adsorbates and the core composition of HFO combustion particles to the early cellular responses, allowing for the development of measures that counteract their detrimental effects. Hence, the semi-volatile coating of HFO-operated ship diesel engine particles was removed by stepwise thermal stripping using different temperatures. RAW 264.7 macrophages were exposed to native and thermally stripped particles in submersed culture. Proteomic changes were monitored by two different quantitative mass spectrometry approaches, stable isotope labeling by amino acids in cell culture (SILAC) and dimethyl labeling. Our data revealed that cells reacted differently to native or stripped HFO combustion particles. Cells exposed to thermally stripped particles showed a very differential reaction with respect to the composition of the individual chemical load of the particle. The cellular reactions of the HFO particles included reaction to oxidative stress, reorganization of the cytoskeleton and changes in endocytosis. Cells exposed to the 280 °C treated particles showed an induction of RNA-related processes, a number of mitochondria-associated processes as well as DNA damage response, while the exposure to 580 °C treated HFO particles mainly induced the regulation of intracellular transport. In summary, our analysis based on a highly reproducible automated proteomic sample-preparation procedure shows a diverse cellular response, depending on the soot particle composition. In particular, it was shown that both the molecules of the adsorbate layer as well as particle cores induced strong but different effects in the exposed cells.

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.

A toxicology suite adapted for comparing parallel toxicity responses of model human lung cells to diesel exhaust particles and their extracts

Epidemiological studies have shown that exposure to airborne particulate matter can be an important risk factor for some common respiratory diseases. While many studies have shown that particulate matter exposures are associated with inflammatory reactions, the role of specific cellular responses in the manifestation of primary hypersensitivities, and the progression of respiratory diseases remains unclear. In order to better understand mechanisms by which particulate matter can exert adverse health effects, more robust approaches to support in vitro studies are warranted. In response to this need, a group of accepted toxicology assays were adapted to create an analytical suite for screening and evaluating the effects of important, ubiquitous atmospheric pollutants on two model human lung cell lines (epithelial and immature macrophage). To demonstrate the utility of this suite, responses to intact diesel exhaust particles, and mass-based equivalent doses of their organic extracts were examined. Results suggest that extracts have the potential to induce greater biological responses than those associated with their colloidal counterpart. Additionally, macrophage cells appear to be more susceptible to the cytotoxic effects of both intact diesel exhaust particles and their organic extract, than epithelial cells tested in parallel. As designed, the suite provided a more robust basis for characterizing toxicity mechanisms than the analysis of any individual assay. Findings suggest that cellular responses to particulate matter are cell line dependent, and show that the collection and preparation of PM and/or their extracts have the potential to impact cellular responses relevant to screening fundamental elements of respiratory toxicity.

Current investigations into the genotoxicity of zinc oxide and silica nanoparticles in mammalian models in vitro and in vivo: carcinogenic/genotoxic potential, relevant mechanisms and biomarkers, artifacts, and limitations

Engineered nanoparticles (NPs) are widely used in many sectors, such as food, medicine, military, and sport, but their unique characteristics may cause deleterious health effects. Close attention is being paid to metal NP genotoxicity; however, NP genotoxic/carcinogenic effects and the underlying mechanisms remain to be elucidated. In this review, we address some metal and metal oxide NPs of interest and current genotoxicity tests in vitro and in vivo. Metal NPs can cause DNA damage such as chromosomal aberrations, DNA strand breaks, oxidative DNA damage, and mutations. We also discuss several parameters that may affect genotoxic response, including physicochemical properties, widely used assays/end point tests, and experimental conditions. Although potential biomarkers of nanogenotoxicity or carcinogenicity are suggested, inconsistent findings in the literature render results inconclusive due to a variety of factors. Advantages and limitations related to different methods for investigating genotoxicity are described, and future directions and recommendations for better understanding genotoxic potential are addressed.

Oxidative stress and aromatic hydrocarbon response of human bronchial epithelial cells exposed to petro- or biodiesel exhaust treated with a diesel particulate filter

The composition of diesel exhaust has changed over the past decade due to the increased use of alternative fuels, like biodiesel, and to new regulations on diesel engine emissions. Given the changing nature of diesel fuels and diesel exhaust emissions, a need exists to understand the human health implications of switching to "cleaner" diesel engines run with particulate filters and engines run on alternative fuels like biodiesel. We exposed well-differentiated normal human bronchial epithelial cells to fresh, complete exhaust from a diesel engine run (1) with and without a diesel particulate filter and (2) using either traditional petro- or alternative biodiesel. Despite the lowered emissions in filter-treated exhaust (a 91-96% reduction in mass), significant increases in transcripts associated with oxidative stress and polycyclic aromatic hydrocarbon response were observed in all exposure groups and were not significantly different between exposure groups. Our results suggest that biodiesel and filter-treated diesel exhaust elicits as great, or greater a cellular response as unfiltered, traditional petrodiesel exhaust in a representative model of the bronchial epithelium.

Differential injurious effects of ambient and traffic-derived particulate matter on airway epithelial cells

BACKGROUND AND OBJECTIVE

Exposure to airborne particulate matter (PM) may promote development of childhood asthma and trigger acute exacerbations of existing asthma via injury to airway epithelial cells (AEC).

METHODS

We compared the response of AEC to ambient particulates with median aerodynamic diameters of <10 μm or <2.5 μm from the Sydney metropolitan region (Sydney PM10 or PM2.5), to traffic-derived particulates from the exhaust stack of a motorway tunnel or to inert carbon black as a control.

RESULTS

Sydney PM10 strongly stimulated messenger RNA expression and secretion of the pro-inflammatory cytokines interleukin 6 (IL-6) and chemokine (C-X-C motif) ligand 1 (CXCL1) by mouse tracheal AEC. In contrast, traffic-derived particulates did not. Similarly, PM10 stimulated expression of IL6, IL8 and IL1B by human AEC. Mass spectrometric analysis showed that PM10 contained much higher levels of elements associated with dusts of geological origin. In contrast, tunnel soot contained much higher levels of various organic compounds, notably including long straight-chain alkanes and diesel-derived polycyclic aromatic hydrocarbons. Sydney PM2.5, as well as PM10 collected during a period including a major dust storm, both of which contained relatively lower levels of iron but similar levels of other crustal elements, did not stimulate expression or secretion of CXCL1 by mouse AEC.

CONCLUSIONS

Ambient PM10 is likely to be more important than traffic-derived PM in causing injury to AEC leading to production of pro-inflammatory cytokines. The injurious effects may be related to the presence of iron in the coarse fraction of airborne PM. These findings are likely to be relevant to the pathogenesis of asthma.

Characteristics and cellular effects of ambient particulate matter from Beijing

In vitro tests using human adenocarcinomic alveolar epithelial cell line A549 and small mouse monocyte-macrophage cell line J774A.1 were conducted to test toxicity of six PM (particulate matter) samples from Beijing. The properties of the samples differ significantly. The production of inflammatory cytokine (TNF-α for J774A.1) and chemokine (IL-8 for A549) and the level of intracellular reactive oxygen species (ROS) were used as endpoints. There was a positive correlation between water soluble organic carbon and DTT-based redox activity. Both cell types produced increased levels of inflammatory mediators and had higher level of intracelllar ROS, indicating the presence of PM-induced inflammatory response and oxidative stress, which were dose-dependent and significantly different among the samples. The releases of IL-8 from A549 and TNF-α from J774A.1 were significantly correlated to PM size, Zeta potential, endotoxin, major metals, and polycyclic aromatic hydrocarbons. No correlation between ROS and these properties was identified.

Public health and components of particulate matter: the changing assessment of black carbon

In 2012, the WHO classified diesel emissions as carcinogenic, and its European branch suggested creating a public health standard for airborne black carbon (BC). In 2011, EU researchers found that life expectancy could be extended four to nine times by reducing a unit of BC, vs reducing a unit of PM2.5. Only recently could such determinations be made. Steady improvements in research methodologies now enable such judgments. In this Critical Review, we survey epidemiological and toxicological literature regarding carbonaceous combustion emissions, as research methodologies improved over time. Initially, we focus on studies of BC, diesel, and traffic emissions in the Western countries (where daily urban BC emissions are mainly from diesels). We examine effects of other carbonaceous emissions, e.g., residential burning of biomass and coal without controls, mainly in developing countries. Throughout the 1990s, air pollution epidemiology studies rarely included species not routinely monitored. As additional PM2.5. chemical species, including carbonaceous species, became more widely available after 1999, they were gradually included in epidemiological studies. Pollutant species concentrations which more accurately reflected subject exposure also improved models. Natural "interventions"--reductions in emissions concurrent with fuel changes or increased combustion efficiency; introduction of ventilation in highway tunnels; implementation of electronic toll payment systems--demonstrated health benefits of reducing specific carbon emissions. Toxicology studies provided plausible biological mechanisms by which different PM species, e.g, carbonaceous species, may cause harm, aiding interpretation of epidemiological studies. Our review finds that BC from various sources appears to be causally involved in all-cause, lung cancer and cardiovascular mortality, morbidity, and perhaps adverse birth and nervous system effects. We recommend that the US. EPA rubric for judging possible causality of PM25. mass concentrations, be used to assess which PM2.5. species are most harmful to public health.

IMPLICATIONS

Black carbon (BC) and correlated co-emissions appear causally related with all-cause, cardiovascular, and lung cancer mortality, and perhaps with adverse birth outcomes and central nervous system effects. Such findings are recent, since widespread monitoring for BC is also recent. Helpful epidemiological advances (using many health relevant PM2.5 species in models; using better measurements of subject exposure) have also occurred. "Natural intervention" studies also demonstrate harm from partly combusted carbonaceous emissions. Toxicology studies consistently find biological mechanisms explaining how such emissions can cause these adverse outcomes. A consistent mechanism for judging causality for different PM2.5 species is suggested.

The occurrence of polycyclic aromatic hydrocarbons and their derivatives and the proinflammatory potential of fractionated extracts of diesel exhaust and wood smoke particles

Exposure to combustion emissions, including diesel engine exhaust and wood smoke particles (DEPs and WSPs), has been associated with inflammatory responses. To investigate the possible role of polycyclic aromatic hydrocarbons (PAHs) and PAH-derivatives, the DEPs and WSPs methanol extracts were fractionated by solid phase extraction (SPE), and the fractions were analyzed for more than ∼120 compounds. The pro-inflammatory effects of the fractionated extracts were characterized by exposure of bronchial epithelial lung cells (BEAS-2B). Both native DEPs and WSPs caused a concentration-dependent increase in IL-6 and IL-8 release and cytotoxicity. This is consistent with the finding of a rather similar total content of PAHs and PAH-derivatives. Yet, the samples differed in specific components, suggesting that different species contribute to the toxicological response in these two types of particles. The majority of the IL-6 release and cytotoxicity was induced upon exposure to the most polar (methanol) SPE fraction of extracts from both samples. In these fractions hydroxy-PAHs, carboxy-PAHs were observed along with nitro-amino-PAHs in DEP. However, the biological effects induced by the polar fractions could not be attributed only to the occurrence of PAH-derivatives. The present findings indicate a need for further characterization of organic extracts, beyond an extensive analysis of commonly suspected PAH and PAH-derivatives. Supplemental materials are available for this article. Go to the publisher's online edition of Journal of Environmental Science and Health, Part A, to view the supplemental file.

Biodiesel versus diesel exposure: enhanced pulmonary inflammation, oxidative stress, and differential morphological changes in the mouse lung

The use of biodiesel (BD) or its blends with petroleum diesel (D) is considered to be a viable approach to reduce occupational and environmental exposures to particulate matter (PM). Due to its lower particulate mass emissions compared to D, use of BD is thought to alleviate adverse health effects. Considering BD fuel is mainly composed of unsaturated fatty acids, we hypothesize that BD exhaust particles could induce pronounced adverse outcomes, due to their ability to readily oxidize. The main objective of this study was to compare the effects of particles generated by engine fueled with neat BD and neat petroleum-based D. Biomarkers of tissue damage and inflammation were significantly elevated in lungs of mice exposed to BD particulates. Additionally, BD particulates caused a significant accumulation of oxidatively modified proteins and an increase in 4-hydroxynonenal. The up-regulation of inflammatory cytokines/chemokines/growth factors was higher in lungs upon BD particulate exposure. Histological evaluation of lung sections indicated presence of lymphocytic infiltrate and impaired clearance with prolonged retention of BD particulate in pigment laden macrophages. Taken together, these results clearly indicate that BD exhaust particles could exert more toxic effects compared to D.

Mice exposed in situ to urban air pollution exhibit pulmonary alterations in gene expression in the lipid droplet synthesis pathways

It is clear that particulate air pollution poses a serious risk to human health; however, the underlying mechanisms are not completely understood. We investigated pulmonary transcriptional responses in mice following in-situ exposure to ambient air in a heavily industrialized urban environment. Mature C57BL/CBA male mice were caged in sheds near two working steel mills and a major highway in Hamilton, Ontario, Canada in the spring/summer of 2004. Control mice were housed in the same environment, but received only high-efficiency particle filtered air (HEPA). Whole lung tissues were collected from mice exposed for 3, 10, or for 10 weeks followed by 6 weeks recovery in the laboratory (16 weeks). DNA microarrays were used to profile changes in pulmonary gene expression. Transcriptional profiling revealed changes in the expression of genes implicated in the lipid droplet synthesis (Plin I, Dgat2, Lpl, S3-12, and Agpat2), and antioxidant defense (Ucp1) pathways in mice breathing unfiltered air. We postulate that exposure to urban air, containing an abundance of particulate matter adsorbed with polycyclic aromatic hydrocarbons, triggers lipid droplet (holding depots for lipids and malformed/excess proteins tagged for degradation) synthesis in the lungs, which may act to sequester particulates. Increased lipid droplet synthesis could lead to endogenous/stressor-induced production of reactive oxygen species and activation of antioxidant mechanisms. Further investigation into the stimulation of lipid droplet synthesis in the lung in response to air pollution and the resulting health implications is warranted.

Physico-chemical characterization of African urban aerosols (Bamako in Mali and Dakar in Senegal) and their toxic effects in human bronchial epithelial cells: description of a worrying situation

Background

The involvement of particulate matter (PM) in cardiorespiratory diseases is now established in developed countries whereas in developing areas such as Africa with a high level of specific pollution, PM pollution and its effects are poorly studied. Our objective was to characterize the biological reactivity of urban African aerosols on human bronchial epithelial cells in relation to PM physico-chemical properties to identify toxic sources.

Methods

Size-speciated aerosol chemical composition was analyzed in Bamako (BK, Mali, 2 samples with one having desert dust event BK1) and Dakar (DK; Senegal) for Ultrafine UF, Fine F and Coarse C PM. PM reactivity was studied in human bronchial epithelial cells investigating six biomarkers (oxidative stress responsive genes and pro-inflammatory cytokines).

Results

PM mass concentrations were mainly distributed in coarse mode (60%) and were impressive in BK1 due to the desert dust event. BK2 and DK samples showed a high content of total carbon characteristic of urban areas. The DK sample had huge PAH quantities in bulk aerosol compared with BK that had more water soluble organic carbon and metals. Whatever the site, UF and F PM triggered the mRNA expression of the different biomarkers whereas coarse PM had little or no effect. The GM-CSF biomarker was the most discriminating and showed the strongest pro-inflammatory effect of BK2 PM. The analysis of gene expression signature and of their correlation with main PM compounds revealed that PM-induced responses are mainly related to organic compounds. The toxicity of African aerosols is carried by the finest PM as with Parisian aerosols, but when considering PM mass concentrations, the African population is more highly exposed to toxic particulate pollution than French population. Regarding the prevailing sources in each site, aerosol biological impacts are higher for incomplete combustion sources resulting from two-wheel vehicles and domestic fires than from diesel vehicles (Dakar). Desert dust events seem to produce fewer biological impacts than anthropogenic sources.

Discussion

Our study shows that combustion sources contribute to the high toxicity of F and UF PM of African urban aerosols, and underlines the importance of emission mitigation and the imperative need to evaluate and to regulate particulate pollution in Africa.

Emerging mechanistic targets in lung injury induced by combustion-generated particles

The mechanism for biological effect following exposure to combustion-generated particles is incompletely defined. The identification of pathways regulating the acute toxicological effects of these particles provides specific targets for therapeutic manipulation in an attempt to impact disease following exposures. Transient receptor potential (TRP) cation channels were identified as "particle sensors" in that their activation was coupled with the initiation of protective responses limiting airway deposition and inflammatory responses, which promote degradation and clearance of the particles. TRPA1, V1, V4, and M8 have a capacity to mediate adverse effects after exposure to combustion-generated particulate matter (PM); relative contributions of each depend upon particle composition, dose, and deposition. Exposure of human bronchial epithelial cells to an organic extract of diesel exhaust particle was followed by TRPV4 mediating Ca(++) influx, increased RAS expression, mitogen-activated protein kinase signaling, and matrix metalloproteinase-1 activation. These novel pathways of biological effect can be targeted by compounds that specifically inhibit critical signaling reactions. In addition to TRPs and calcium biochemistry, humic-like substances (HLS) and cell/tissue iron equilibrium were identified as potential mechanistic targets in lung injury after particle exposure. In respiratory epithelial cells, iron sequestration by HLS in wood smoke particle (WSP) was associated with oxidant generation, cell signaling, transcription factor activation, and release of inflammatory mediators. Similar to WSP, cytotoxic insoluble nanosized spherical particles composed of HLS were isolated from cigarette smoke condensate. Therapies that promote bioelimination of HLS and prevent the disruption of iron homeostasis could function to reduce the harmful effects of combustion-generated PM exposure.

Oxidative DNA damage and inflammatory responses in cultured human cells and in humans exposed to traffic-related particles

Particulate pollution is a major public health concern because epidemiological studies have demonstrated that exposure to particles is associated with respiratory diseases and lung cancer. Diesel exhaust particles (DEP), which is classified as a human carcinogen (IARC, 2012), are considered a major contributor to traffic-related particulate matter (PM) in urban areas. DEP consists of various compounds, including PAHs and metals which are the principal components that contribute to the toxicity of PM. The present study aimed to investigate effects of PM on induction of oxidative DNA damage and inflammation by using lymphocytes in vitro and in human exposed to PM in the environment. Human lymphoblasts (RPMI 1788) were treated with DEP (SRM 2975) at various concentrations (25-100 μg/ml) to compare the extent of responses with alveolar epithelial cells (A549). ROS generation was determined in each cell cycle phase of DEP-treated cells in order to investigate the influence of the cell cycle stage on induction of oxidative stress. The oxidative DNA damage was determined by measurement of 8-hydroxy-deoxyguanosine (8-OHdG) whereas the inflammatory responses were determined by mRNA expression of interleukin-6 and -8 (IL-6 and IL-8), Clara cell protein (CC16), and lung surfactant protein-A (SP-A). The results showed that RPMI 1788 and A549 cells had a similar pattern of dose-dependent responses to DEP in terms of particle uptake, ROS generation with highest level found in G2/M phase, 8-OHdG formation, and induction of IL-6 and IL-8 expression. The human study was conducted in 51 healthy subjects residing in traffic-congested areas. The effects of exposure to PM2.5 and particle-bound PAHs and toxic metals on the levels of 8-OHdG in lymphocyte DNA, IL-8 expression in lymphocytes, and serum CC16 were evaluated. 8-OHdG levels correlated with the exposure levels of PM2.5 (P<0.01) and PAHs (P<0.05), but this was not the case with IL-8. Serum CC16 showed significantly negative correlations with B[a]P equivalent (P<0.05) levels, but positive correlation with Pb (P<0.05). In conclusion, a similar pattern of the dose-dependent responses to DEP in the lymphoblasts and lung cells suggests that circulating lymphocytes could be used as a surrogate for assessing PM-induced oxidative DNA damage and inflammatory responses in the lung. Human exposure to PM leads to oxidative DNA damage whereas PM-induced inflammation was not conclusive and should be further investigated.

Mechanisms of chemokine responses by polycyclic aromatic hydrocarbons in bronchial epithelial cells: sensitization through toll-like receptor-3 priming

We have previously observed that 1-nitropyrene (1-NP) and its amine metabolite 1-aminopyrene (1-AP) induce differential chemokine responses in human bronchial epithelial cells (BEAS-2B) characterized by maximum responses for CXCL8 (IL-8) and CCL5 (RANTES), respectively. In the present study, we further explored the effects of 1-NP and 1-AP on chemokine responses. The results suggest that the differential effect of 1-NP and 1-AP on CXCL8 and CCL5 in BEAS-2B cells was mainly related to effects at higher concentrations, which in the case of 1-NP seemed to be linked to ROS-formation and/or metabolic activation by CYP-enzymes. However, at a low concentration (1 μM) where neither 1-NP, 1-AP nor unsubstituted pyrene had any effect on chemokine responses, we found that all three PAHs potentiated CXCL8 and CCL5 responses induced by the TLR3 ligand polyinosinic:polycytidylic acid (Poly I:C) in BEAS-2B cells. As neither benzo[a]pyrene nor β-naphthoflavone induced a similar effect in Poly I:C-primed cells, the response seemed independent of aryl hydrocarbon receptor-mediated mechanisms. The results show that priming cells with an inflammogenic stimuli like Poly I:C sensitizes the cells toward additional pro-inflammatory effects of certain PAHs. The study underscores that testing on healthy cells or animals may not be sufficient to fully evaluate chemokine responses and the pro-inflammatory potential of organic chemicals.

Inflammation-related effects of diesel engine exhaust particles: studies on lung cells in vitro

Diesel exhaust and its particles (DEP) have been under scrutiny for health effects in humans. In the development of these effects inflammation is regarded as a key process. Overall, in vitro studies report similar DEP-induced changes in markers of inflammation, including cytokines and chemokines, as studies in vivo. In vitro studies suggest that soluble extracts of DEP have the greatest impact on the expression and release of proinflammatory markers. Main DEP mediators of effects have still not been identified and are difficult to find, as fuel and engine technology developments lead to continuously altered characteristics of emissions. Involved mechanisms remain somewhat unclear. DEP extracts appear to comprise components that are able to activate various membrane and cytosolic receptors. Through interactions with receptors, ion channels, and phosphorylation enzymes, molecules in the particle extract will trigger various cell signaling pathways that may lead to the release of inflammatory markers directly or indirectly by causing cell death. In vitro studies represent a fast and convenient system which may have implications for technology development. Furthermore, knowledge regarding how particles elicit their effects may contribute to understanding of DEP-induced health effects in vivo, with possible implications for identifying susceptible groups of people and effect biomarkers.

Oxidative stress, inflammatory biomarkers, and toxicity in mouse lung and liver after inhalation exposure to 100% biodiesel or petroleum diesel emissions

Over the past decade, soy biodiesel (BD) has become a first alternative energy source that is economically viable and meets requirements of the Clean Air Act. Due to lower mass emissions and reduced hazardous compounds compared to diesel combustion emissions (CE), BD exposure is proposed to produce fewer adverse health effects. However, considering the broad use of BD and its blends in different industries, this assertion needs to be supported and validated by mechanistic and toxicological data. Here, adverse effects were compared in lungs and liver of BALB/cJ mice after inhalation exposure (0, 50, 150, or 500 μg/m3; 4 h/d, 5 d/wk, for 4 wk) to CE from 100% biodiesel (B100) and diesel (D100). Compared to D100, B100 CE produced a significant accumulation of oxidatively modified proteins (carbonyls), an increase in 4-hydroxynonenal (4-HNE), a reduction of protein thiols, a depletion of antioxidant gluthatione (GSH), a dose-related rise in the levels of biomarkers of tissue damage (lactate dehydrogenase, LDH) in lungs, and inflammation (myeloperoxidase, MPO) in both lungs and liver. Significant differences in the levels of inflammatory cytokines interleukin (IL)-6, IL-10, IL-12p70, monocyte chemoattractant protein (MCP)-1, interferon (IFN) γ, and tumor necrosis factor (TNF)-α were detected in lungs and liver upon B100 and D100 CE exposures. Overall, the tissue damage, oxidative stress, inflammation, and cytokine response were more pronounced in mice exposed to BD CE. Further studies are required to understand what combustion products in BD CE accelerate oxidative and inflammatory responses.

Development of a repeated exposure protocol of human bronchial epithelium in vitro to study the long-term effects of atmospheric particles

Chronic exposure to atmospheric particles is suspected of exacerbating chronic inflammatory respiratory diseases but the underlying mechanisms remain poorly understood. An experimental strategy using human bronchial epithelial cells (NHBE) known to be one of the main target cells of particles in the lung was developed to investigate the long term effects of repeated exposure to particles. Primary cultures of NHBE cells were grown at an air-liquid interface and subjected to repeated treatments to particles. Fate of particles, pro inflammatory response and epithelial differentiation were studied during the 5 weeks following the final treatment. Ultrastructural observations revealed the biopersistence of particles in the bronchial epithelium. The expression of cytochrome P450 1A1, was transiently induced, suggesting that organic compounds could have been metabolized. The release of GM-CSF and IL-6 (biomarkers of pro-inflammatory response), was induced by particle treatments and was maintained up to 5weeks after treatments. The release of amphiregulin and TGFα (Growth Factor) was induced after each treatment. The number of cells expressing the mucin MUC5AC, a differentiation marker, was increased in particle-exposed epithelium. The experimental strategy we developed is suitable for investigating in greater depth the long term effects of particles on bronchial epithelial cells repeatedly exposed to atmospheric particles in vitro.

Investigating the potential for interaction between the components of PM(10)

The adverse health effects of elevated exposures to PM(10) (particulate matter collected through a size selective inlet with an efficiency of 50% for particles with an aerodynamic diameter of 10 μm) in relation to morbidity and mortality, especially in susceptible individuals, are now well recognised. PM(10) consists of a variable cocktail of components differing in chemical composition and size. Epidemiological and toxicological data suggest that transition metals and ultrafine particles are both able to drive the cellular and molecular changes that underlie PM(10)-induced inflammation and so worsen disease status. Toxicological evidence also suggest roles for the biological components of PM(10) including volatile organic compounds (VOC's), allergens and bacterial-derived endotoxin. Many of these components, in particular transition metals, ultrafine particles, endotoxin and VOC's induce a cellular oxidative stress which initiates an intracellular signaling cascade involving the activation of phosphatase and kinase enzymes as well as transcription factors such as nuclear factor kappa B. Activation of these signaling mechanisms results in an increase in the expression of proinflammatory mediators, and hence enhanced inflammation. Given that many of the components of PM(10) stimulate similar or even identical intracellular signaling pathways, it is conceivable that this will result in synergistic or additive interactions so that the biological response induced by PM(10) exposure is a response to the composition rather than the mass alone. A small number of studies suggest that synergistic interactions occur between ultrafine particles and transition metals, between particles and allergens, and between particles and VOC's. Elucidation of the consequences of interaction between the components of PM(10) in relation to their biological activity implies huge consequences for the methods used to monitor and to legislate pollution exposure in the future, and may drive a move from mass based measurements to composition.

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.

The Role of Nuclear Factor Kappa B in the Pathogenesis of Pulmonary Diseases: Implications for Therapy

The nuclear factor kappa B (NF-kappaB) transcription factor plays a key role in the induction of pro-inflammatory gene expression, leading to the synthesis of cytokines, adhesion molecules, chemokines, growth factors and enzymes. Results of studies in in vitro and in vivo models of inflammation and malignancy have also suggested central roles for NF-kappaB in programmed cell death, or apoptosis. NF-kappaB plays a central role in a variety of acute and chronic inflammatory diseases. In the common lung diseases associated with a significant inflammatory component such as severe sepsis, acute lung injury, acute respiratory distress syndrome, cystic fibrosis and asthma, the pathogenic roles of NF-kappaB have been extensively investigated. In COPD, activation of NF-kappaB has been implicated in disease pathogenesis but its exact role is less clearly demonstrable in this heterogeneous patient population. However, the principal risk factor for COPD, cigarette smoking, is strongly associated with NF-kappaB activation. Activation of NF-kappaB has been demonstrated in mineral dust diseases and probably plays a role in the pathogenesis of these chronic illnesses. NF-kB also plays a variety of roles in lung cancer including resistance to chemotherapy, inhibition of tumorigenesis and inducing expression of antiapoptotic genes. The complex NF-kappaB pathway offers a variety of potential molecular targets for chemotherapeutic intervention. A variety of agents aimed at modulating NF-kappaB activity are in various stages of investigation.

Traffic-related air pollution and DNA damage: a longitudinal study in Taiwanese traffic conductors

BACKGROUND

There is accumulating epidemiologic evidence that exposure to traffic-related air pollutants, including particulate matter (PM) and polyaromatic hydro carbons (PAHs), plays a role in etiology and prognosis of a large scale of illnesses, although the role of specific causal agents and underlying mechanisms for different health outcomes remains unknown.

OBJECTIVE

Our general objective was to assess the relations between personal exposure to traffic exhausts, in particular ambient PM(2.5) and PAHs, and the occurrence of DNA strand breaks by applying personal monitoring of PM and biomarkers of exposure (urinary 1-hydroxypyrene-glucuronide, 1-OHPG) and effect (urinary 8-hydroxydeoxyguanosine, 8-OHdG and DNA strand breaks).

METHODS

We recruited 91 traffic conductors and 53 indoor office workers between May 2009 and June 2011 in Taipei City, Taiwan. We used PM(2.5) personal samplers to collect breathing-zone particulate PAHs samples. Spot urine and blood samples after work shift of 2 consecutive days were analyzed for 1-OHPG, 8-OHdG and DNA strand breaks, respectively. Statistical methods included linear regression and mixed models.

RESULTS

Urinary 8-OHdG levels and the occurrence of DNA strand breaks in traffic conductors significantly exceeded those in indoor office workers in mixed models. Particulate PAHs levels showed a positive association with urinary 1-OHPG in the regression model (β = 0.056, p = 0.01). Urinary 1-OHPG levels were significantly associated with urinary 8-OHdG levels in the mixed model (β = 0.101, p = 0.023). Our results provide evidence that exposure to fine particulates causes DNA damage. Further, particulate PAHs could be biologically active constituents of PM(2.5) with reference to the induction of oxidative DNA damages.

Similarities in diesel exhaust particles induced alterations in expression of cytochrome P-450 and glutathione S-transferases in rat lymphocytes and lungs

Freshly prepared peripheral blood lymphocytes (PBL) are known to express cytochrome P450s (CYPs) and glutathione S-transferases (GSTs) involved in the bioactivation and detoxification of organic components of diesel exhaust particles (DEPs). To validate that blood lymphocyte expression profiles could be used as a biomarker to predict exposure to vehicular emissions, similarities in the alterations in the mRNA expression of CYPs and GSTs were studied in PBL and lungs of rats exposed to DEPs. Adult male Wistar rats were treated transtracheally with different doses of DEPs (3.75- or 7.5- or 15- or 30-mg/kg b.wt.). The animals were anaesthetized after 24 h and blood was drawn and lungs were taken out and processed. DEP produced a similar pattern of increase in the mRNA expression of CYPs (CYP1A1, 1A2, 1B1, 2E1), associated arylhydrocarbon receptor (Ahr) and arylhydrocarbon nuclear translocator (Arnt) and GSTs (GSTPi, GSTM1 and GSTM2) at all the doses in lungs and PBL. The protein expression of CYP1A1/1A2 and 2E1 and catalytic activity of CYPs and GSTs also showed a similar pattern of increase in blood lymphocyte and in lungs isolated from DEP treated rats. Our data indicating similarities in the alterations in the expression of carcinogen metabolizing CYPs and GSTs in PBL with the lung enzymes suggests the suitability of using expression profiles of blood lymphocyte CYPs and GSTs as a biomarker to predict exposure to vehicular emissions.

PM10-biogenic fraction drives the seasonal variation of proinflammatory response in A549 cells

PM10 was collected in a Milan urban site, representative of the city air quality, during winter and summer 2006. Mean daily PM10 concentration was 48 μg m(-3) during summer and 148 μg m(-3) during winter. Particles collected on Teflon filters were chemically characterized and the endotoxin content determined by the LAL test. PM10-induced cell toxicity, assessed with MTT and LDH methods, and proinflammatory potential, monitored by IL-6 and IL-8 cytokines release, were investigated on the human alveolar epithelial cell line A549 exposed to increasing doses of PM. Besides untreated cells, exposure to inert carbon particles (2-12 μm) was also used as additional control. Both cell toxicity and proinflammatory potency resulted to be higher for summer PM10 with respect of winter PM10, with IL-6 showing the highest dose-dependent release. The relevance of biogenic components adsorbed onto PM10 in eliciting the proinflammatory mediators release was investigated by inhibition experiments. Polymixin B (Poly) was used to inhibit particle-bind LPS while Toll-like receptor-2 antibody (a-TLR2) to specifically block the activation of this receptor. While cell viability was not modulated in cells coexposed to PM10 and Poly or a-TLR2 or both, inflammatory response did it, with IL-6 release being the most inhibited. In conclusion, Milan PM10-induced seasonal-dependent biological effects, with summer particles showing higher cytotoxic and proinflammatory potential. Cytotoxicity seemed to be unaffected by the PM biogenic components, while inflammation was significantly reduced after the inhibition of some biogenic activated pathways. Besides, the PM-associated biogenic activity does not entirely justify the PM-induced inflammatory effects. © 2010 Wiley Periodicals, Inc. Environ Toxicol 2012.

Differential effects of the particle core and organic extract of diesel exhaust particles

Exposure to diesel engine exhaust particles (DEPs), representing a complex and variable mixture of components, has been associated with lung disease and induction of pro-inflammatory mediators and CYP1A1 expression. The aim of this study was to further characterise DEP-components accounting for these effects. Human bronchial epithelial cells (BEAS-2B) were exposed to either native DEPs, or corresponding methanol DEP-extract or residual DEPs, and investigated with respect to cytotoxicity and expression and release of multiple inflammation-related mediators. Both native DEPs and DEP-extract, but not residual DEPs, induced marked mRNA expression of COX-2, IL-6 and IL-8, as well as cytotoxicity and release of IL-6. However, CYP1A1 was primarily induced by the native and residual DEPs. Overall, the results of near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and gas chromatography with mass spectrometry (GC/MS) analysis of DEP-extracts indicated that the majority of the analysed PAHs and PAH-derivatives were extracted from the particles, but that certain PAH-derivatives, probably their carboxylic isomers, tended to be retained on the residual DEPs. Moreover, it appeared that certain components of the methanol extract may suppress CYP1A1 expression. These results provide insight into how different components of the complex DEP-mixture may be differently involved in DEP-induced pro-inflammatory responses and underscore the importance of identifying and clarifying the roles of active DEP-components in relation to different biological effects.

Epithelial nuclear factor-κB signaling promotes lung carcinogenesis via recruitment of regulatory T lymphocytes

The mechanisms by which chronic inflammatory lung diseases, particularly chronic obstructive pulmonary disease (COPD), confer enhanced risk for lung cancer are not well defined. To investigate whether nuclear factor (NF)-κB, a key mediator of immune and inflammatory responses, provides an interface between persistent lung inflammation and carcinogenesis, we utilized tetracycline-inducible transgenic mice expressing, constitutively active IκB kinase β in airway epithelium (IKTA mice). Intraperitoneal injection of ethyl carbamate (urethane) or 3-methylcholanthrene (MCA) and butylated hydroxytoluene (BHT) was used to induce lung tumorigenesis. Doxycycline-treated IKTA mice developed chronic airway inflammation and markedly increased numbers of lung tumors in response to urethane, even when transgene expression (and therefore epithelial NF-κB activation) was begun after exposure to carcinogen. Studies using a separate tumor initiator/promoter model (MCA+BHT) indicated that NF-κB functions as an independent tumor promoter. Enhanced tumor formation in IKTA mice was preceded by increased proliferation and reduced apoptosis of alveolar epithelium, resulting in increased formation of premalignant lesions. Investigation of inflammatory cells in lungs of IKTA mice revealed a substantial increase in macrophages and lymphocytes, including functional CD4+/CD25+/FoxP3+ regulatory T lymphocytes (Tregs). Importantly, Treg depletion using repetitive injections of anti-CD25 antibodies limited excessive tumor formation in IKTA mice. At 6 weeks following urethane injection, antibody-mediated Treg depletion in IKTA mice reduced the number of premalignant lesions in the lungs in association with an increase in CD8 lymphocytes. Thus, persistent NF-κB signaling in airway epithelium facilitates carcinogenesis by sculpting the immune/inflammatory environment in the lungs.

Particle-associated organic compounds and symptoms in myocardial infarction survivors

CONTEXT

The aerosol components responsible for the adverse health effects of the exposure to particulate matter (PM) have not been conclusively identified, and there is especially little information on the role of particulate organic compounds (POC).

OBJECTIVE

This study evaluated the role of PM and POC with regard to daily symptoms.

METHODS

One hundred and fifty-three myocardial infarction survivors from Augsburg, Germany, recorded daily occurrence of different symptoms in winter 2003/2004. Ambient concentrations of PM with a diameter <2.5 μm (PM(2.5)), particle number concentration (PNC), PM(2.5)-bound hopanes, and polycyclic aromatic hydrocarbons (PAH) were quantified. Data were analyzed using generalized estimating equations adjusting for meteorological and other time-variant confounders.

RESULTS

The odds for avoidance of physically demanding activities due to heart problems increased immediately associated with most POC measures (e.g. 5% per 1.08 ng/m(3) increase in benzo[a]pyrene, 95%-confidence interval (CI):1-9%) and tended to a delayed decrease. After a 2-day delayed decrease associated with hopanes, the odds for shortness of breath increased consistently after 3 days with almost all POC measures (e.g. 4% per 0.21 ng/m(3) increase in 17α(H), 21β(H)-hopane, CI: 1-8%). The odds for heart palpitations marginally increased immediately in association with PNC (8% per 8146 cm(-3) increase in PNC, CI: 0-16%).

CONCLUSIONS

The study showed an association between PM, particle-bound POC, and daily symptoms. The organic compounds may be causally related with cardiovascular health or act rather as indicators for traffic- and combustion-related particles.