Showing papers in "Particle and Fibre Toxicology in 2009"
TL;DR: The use of MTT assay on THP-1 cells exposed for 24 hours appears to be the most sensitive experimental design to assess the cytotoxic effect of one nanoparticle, and Copper- and Zinc-based nanoparticles appear to beThe most toxic.
Abstract: A critical issue with nanomaterials is the clear understanding of their potential toxicity. We evaluated the toxic effect of 24 nanoparticles of similar equivalent spherical diameter and various elemental compositions on 2 human pulmonary cell lines: A549 and THP-1. A secondary aim was to elaborate a generic experimental set-up that would allow the rapid screening of cytotoxic effect of nanoparticles. We therefore compared 2 cytotoxicity assays (MTT and Neutral Red) and analyzed 2 time points (3 and 24 hours) for each cell type and nanoparticle. When possible, TC50 (Toxic Concentration 50 i.e. nanoparticle concentration inducing 50% cell mortality) was calculated. The use of MTT assay on THP-1 cells exposed for 24 hours appears to be the most sensitive experimental design to assess the cytotoxic effect of one nanoparticle. With this experimental set-up, Copper- and Zinc-based nanoparticles appear to be the most toxic. Titania, Alumina, Ceria and Zirconia-based nanoparticles show moderate toxicity, and no toxicity was observed for Tungsten Carbide. No correlation between cytotoxicity and equivalent spherical diameter or specific surface area was found. Our study clearly highlights the difference of sensitivity between cell types and cytotoxicity assays that has to be carefully taken into account when assessing nanoparticles toxicity.
451 citations
TL;DR: Exposure to iron nanoparticles induces an increase in endothelial cell permeability through ROS oxidative stress-modulated microtubule remodeling, which provides new understandings on the effects of nanoparticles on vascular transport of macromolecules and drugs.
Abstract: Engineered iron nanoparticles are being explored for the development of biomedical applications and many other industry purposes. However, to date little is known concerning the precise mechanisms of translocation of iron nanoparticles into targeted tissues and organs from blood circulation, as well as the underlying implications of potential harmful health effects in human. The confocal microscopy imaging analysis demonstrates that exposure to engineered iron nanoparticles induces an increase in cell permeability in human microvascular endothelial cells. Our studies further reveal iron nanoparticles enhance the permeability through the production of reactive oxygen species (ROS) and the stabilization of microtubules. We also showed Akt/GSK-3β signaling pathways are involved in iron nanoparticle-induced cell permeability. The inhibition of ROS demonstrate ROS play a major role in regulating Akt/GSK-3β – mediated cell permeability upon iron nanoparticle exposure. These results provide new insights into the bioreactivity of engineered iron nanoparticles which can inform potential applications in medical imaging or drug delivery. Our results indicate that exposure to iron nanoparticles induces an increase in endothelial cell permeability through ROS oxidative stress-modulated microtubule remodeling. The findings from this study provide new understandings on the effects of nanoparticles on vascular transport of macromolecules and drugs.
430 citations
TL;DR: It is found that ultrafine particles (<0.18 μm) enhance early atherosclerosis, partly due to their high content in redox cycling chemicals and their ability to synergize with known proatherogenic mediators in the promotion of tissue oxidative stress.
Abstract: Air Pollution has been associated with significant adverse health effects leading to increased morbidity and mortality. Cumulative epidemiological and experimental data have shown that exposure to air pollutants lead to increased cardiovascular ischemic events and enhanced atherosclerosis. It appears that these associations are much stronger with the air particulate matter (PM) component and that in urban areas, the smaller particles could be more pathogenic, as a result of their greater propensity to induce systemic prooxidant and proinflammatory effects. Much is still unknown about the toxicology of ambient particulates as well as the pathogenic mechanisms responsible for the induction of adverse cardiovascular health effects. It is expected that better understanding of these effects will have large implications and may lead to the formulation and implementation of new regulatory policies. Indeed, we have found that ultrafine particles (<0.18 μm) enhance early atherosclerosis, partly due to their high content in redox cycling chemicals and their ability to synergize with known proatherogenic mediators in the promotion of tissue oxidative stress. These changes take place in parallel with increased evidence of phase 2 enzymes expression, via the electrophile-sensitive transcription factor, p45-NFE2 related transcription factor 2 (Nrf2). Exposure to ultrafine particles also results in alterations of the plasma HDL anti-inflammatory function that could be indicative of systemic proatherogenic effects. This article reviews the epidemiological, clinical and experimental animal evidence that support the association of particulate matter with atherogenesis. It also discusses the possible pathogenic mechanisms involved, the physicochemical variables that may be of importance in the greater toxicity exhibited by a small particle size, interaction with genes and other proatherogenic factors as well as important elements to consider in the design of future mechanistic studies. Extensive epidemiological evidence supports the association of air pollution with adverse health effects [13]. It is increasingly being recognized that such effects lead to enhanced morbidity and mortality, mostly due to exacerbation of cardiovascular diseases and predominantly those of ischemic character [4]. Indeed, in addition to the classical risk factors such as serum lipids, smoking, hypertension, aging, gender, family history, physical inactivity and diet, recent data have implicated air pollution as an important additional risk factor for atherosclerosis. This has been the subject of extensive reviews [5,6] and a consensus statement from the American Heart Association [7]. This article reviews the supporting epidemiological and animal data, possible pathogenic mechanisms and future perspectives.
365 citations
TL;DR: Overall, the reviewed literature regarding the physicochemical properties of wood smoke particles provides a relatively clear picture of how these properties vary with the combustion conditions, whereas particle emissions from specific classes of combustion appliances are less well characterised.
Abstract: Background: Residential wood combustion is now recognized as a major particle source in many developed countries, and the number of studies investigating the negative health effects associated with wood smoke exposure is currently increasing. The combustion appliances in use today provide highly variable combustion conditions resulting in large variations in the physicochemical characteristics of the emitted particles. These differences in physicochemical properties are likely to influence the biological effects induced by the wood smoke particles. Outline: The focus of this review is to discuss the present knowledge on physicochemical properties of wood smoke particles from different combustion conditions in relation to wood smoke-induced health effects. In addition, the human wood smoke exposure in developed countries is explored in order to identify the particle characteristics that are relevant for experimental studies of wood smoke-induced health effects. Finally, recent experimental studies regarding wood smoke exposure are discussed with respect to the applied combustion conditions and particle properties. Conclusion: Overall, the reviewed literature regarding the physicochemical properties of wood smoke particles provides a relatively clear picture of how these properties vary with the combustion conditions, whereas particle emissions from specific classes of combustion appliances are less well characterised. The major gaps in knowledge concern; (i) characterisation of the atmospheric transformations of wood smoke particles, (ii) characterisation of the physicochemical properties of wood smoke particles in ambient and indoor environments, and (iii) identification of the physicochemical properties that influence the biological effects of wood smoke particles.
359 citations
TL;DR: This study demonstrates that alteration of anatase TiO2 nanomaterial into a fibre structure of greater than 15 μm creates a highly toxic particle and initiates an inflammatory response by alveolar macrophages, and suggests that any modification of a nanomMaterial, resulting in a wire, fibre, belt or tube, be tested for pathogenic potential.
Abstract: Background
Titanium dioxide (TiO2) nanomaterials have considerable beneficial uses as photocatalysts and solar cells. It has been established for many years that pigment-grade TiO2 (200 nm sphere) is relatively inert when internalized into a biological model system (in vivo or in vitro). For this reason, TiO2 nanomaterials are considered an attractive alternative in applications where biological exposures will occur. Unfortunately, metal oxides on the nanoscale (one dimension < 100 nm) may or may not exhibit the same toxic potential as the original material. A further complicating issue is the effect of modifying or engineering of the nanomaterial to be structurally and geometrically different from the original material.
318 citations
TL;DR: The present study determines the role of TiO2-NP (anatase, ∅ < 100 nm) using several parameters such as cyto- and genotoxicity, DNA-adduct formation and generation of free radicals following its uptake by human lung cells in vitro.
Abstract: Titanium dioxide (TiO2), also known as titanium (IV) oxide or anatase, is the naturally occurring oxide of titanium. It is also one of the most commercially used form. To date, no parameter has been set for the average ambient air concentration of TiO2 nanoparticles (NP) by any regulatory agency. Previously conducted studies had established these nanoparticles to be mainly non-cyto- and -genotoxic, although they had been found to generate free radicals both acellularly (specially through photocatalytic activity) and intracellularly. The present study determines the role of TiO2-NP (anatase, ∅ < 100 nm) using several parameters such as cyto- and genotoxicity, DNA-adduct formation and generation of free radicals following its uptake by human lung cells in vitro. For comparison, iron containing nanoparticles (hematite, Fe2O3, ∅ < 100 nm) were used. The results of this study showed that both types of NP were located in the cytosol near the nucleus. No particles were found inside the nucleus, in mitochondria or ribosomes. Human lung fibroblasts (IMR-90) were more sensitive regarding cyto- and genotoxic effects caused by the NP than human bronchial epithelial cells (BEAS-2B). In contrast to hematite NP, TiO2-NP did not induce DNA-breakage measured by the Comet-assay in both cell types. Generation of reactive oxygen species (ROS) was measured acellularly (without any photocatalytic activity) as well as intracellularly for both types of particles, however, the iron-containing NP needed special reducing conditions before pronounced radical generation. A high level of DNA adduct formation (8-OHdG) was observed in IMR-90 cells exposed to TiO2-NP, but not in cells exposed to hematite NP. Our study demonstrates different modes of action for TiO2- and Fe2O3-NP. Whereas TiO2-NP were able to generate elevated amounts of free radicals, which induced indirect genotoxicity mainly by DNA-adduct formation, Fe2O3-NP were clastogenic (induction of DNA-breakage) and required reducing conditions for radical formation.
317 citations
TL;DR: The data suggest that ApoE-/- model is sensitive for evaluating particle induced inflammation and shows that instillation of CB was more toxic than inhalation of a presumed similar dose with respect to inflammation in the lungs of Apo E-/- mice.
Abstract: The toxic and inflammatory potential of 5 different types of nanoparticles were studied in a sensitive model for pulmonary effects in apolipoprotein E knockout mice (ApoE-/-). We studied the effects instillation or inhalation Printex 90 of carbon black (CB) and compared CB instillation in ApoE-/- and C57 mice. Three and 24 h after pulmonary exposure, inflammation was assessed by mRNA levels of cytokines in lung tissue, cell composition, genotoxicity, protein and lactate dehydrogenase activity in broncho-alveolar lavage (BAL) fluid. Firstly, we found that intratracheal instillation of CB caused far more pulmonary toxicity in ApoE-/- mice than in C57 mice. Secondly, we showed that instillation of CB was more toxic than inhalation of a presumed similar dose with respect to inflammation in the lungs of ApoE-/- mice. Thirdly, we compared effects of instillation in ApoE-/- mice of three carbonaceous particles; CB, fullerenes C60 (C60) and single walled carbon nanotubes (SWCNT) as well as gold particles and quantum dots (QDs). Characterization of the instillation media revealed that all particles were delivered as agglomerates and aggregates. Significant increases in Il-6, Mip-2 and Mcp-1 mRNA were detected in lung tissue, 3 h and 24 h following instillation of SWCNT, CB and QDs. DNA damage in BAL cells, the fraction of neutrophils in BAL cells and protein in BAL fluid increased statistically significantly. Gold and C60 particles caused much weaker inflammatory responses. Our data suggest that ApoE-/- model is sensitive for evaluating particle induced inflammation. Overall QDs had greatest effects followed by CB and SWCNT with C60 and gold being least inflammatory and DNA-damaging. However the gold was used at a much lower mass dose than the other particles. The strong effects of QDs were likely due to Cd release. The surface area of the instilled dose correlated well the inflammatory response for low toxicity particles.
314 citations
TL;DR: Investigating the effects of maternal exposure to nano-sized anatase titanium dioxide (TiO2) on gene expression in the brain during the developmental period using cDNA microarray analysis combined with Gene Ontology (GO) and Medical Subject Headings (MeSH) terms information indicated that expression levels of genes associated with apoptosis and those associated with brain development were altered in newborn pups.
Abstract: Nanotechnology is developing rapidly throughout the world and the production of novel man-made nanoparticles is increasing, it is therefore of concern that nanomaterials have the potential to affect human health. The purpose of this study was to investigate the effects of maternal exposure to nano-sized anatase titanium dioxide (TiO2) on gene expression in the brain during the developmental period using cDNA microarray analysis combined with Gene Ontology (GO) and Medical Subject Headings (MeSH) terms information. Analysis of gene expression using GO terms indicated that expression levels of genes associated with apoptosis were altered in the brain of newborn pups, and those associated with brain development were altered in early age. The genes associated with response to oxidative stress were changed in the brains of 2 and 3 weeks old mice. Changes of the expression of genes associated with neurotransmitters and psychiatric diseases were found using MeSH terms. Maternal exposure of mice to TiO2 nanoparticles may affect the expression of genes related to the development and function of the central nervous system.
249 citations
TL;DR: Results indicate that for low toxicity low solubility materials, surface area of particles administered rather than mass burden of particles may be a more appropriate dose metric for pulmonary toxicity studies.
Abstract: Nanoparticles are characterized by having a high surface area per mass. Particulate surface area has been reported to play an important role in determining the biological activity of nanoparticles. However, recent reports have questioned this relationship. This study was conducted to determine whether mass of particles or surface area of particles is the more appropriate dose metric for pulmonary toxicity studies. In this study, rats were exposed by intratracheal instillation to various doses of ultrafine and fine carbon black. At 1, 7, or 42 days post-exposure, inflammatory and cytotoxic potential of each particle type was compared on both a mass dosage (mg/rat) as well as an equal surface area dosage (cm2 of particles per cm2 of alveolar epithelium). In an additional study, the pulmonary responses to instillation of ultrafine carbon black were compared to equivalent particle surface area doses of ultrafine titanium dioxide. Ultrafine carbon black particles caused a dose dependent but transient inflammatory and cytotoxic response. On a mass basis, these responses were significantly (65 fold) greater than those for fine sized carbon black. However, when doses were equalized based on surface area of particles given, the ultrafine carbon black particles were only slightly (non-significantly) more inflammogenic and cytotoxic compared to the fine sized carbon black. At one day post-exposure, inflammatory potencies of the ultrafine carbon black and ultrafine titanium dioxide particles were similar. However, while the pulmonary reaction to ultrafine carbon black resolved with time, the inflammatory effects of ultrafine titanium dioxide were more persistent over a 42 day post-exposure period. These results indicate that for low toxicity low solubility materials, surface area of particles administered rather than mass burden of particles may be a more appropriate dose metric for pulmonary toxicity studies. In addition, ultrafine titanium dioxide appears to be more bioactive than ultrafine carbon black on an equivalent surface area of particles delivered basis.
224 citations
TL;DR: The ALICE is a useful tool for dose-controlled nanoparticle (or solute) exposure of cells at the air-liquid interface and indicates that ZnO nanoparticles are not toxic at occupationally allowed exposure levels.
Abstract: Engineered nanoparticles are becoming increasingly ubiquitous and their toxicological effects on human health, as well as on the ecosystem, have become a concern. Since initial contact with nanoparticles occurs at the epithelium in the lungs (or skin, or eyes), in vitro cell studies with nanoparticles require dose-controlled systems for delivery of nanoparticles to epithelial cells cultured at the air-liquid interface. A novel air-liquid interface cell exposure system (ALICE) for nanoparticles in liquids is presented and validated. The ALICE generates a dense cloud of droplets with a vibrating membrane nebulizer and utilizes combined cloud settling and single particle sedimentation for fast (~10 min; entire exposure), repeatable (<12%), low-stress and efficient delivery of nanoparticles, or dissolved substances, to cells cultured at the air-liquid interface. Validation with various types of nanoparticles (Au, ZnO and carbon black nanoparticles) and solutes (such as NaCl) showed that the ALICE provided spatially uniform deposition (<1.6% variability) and had no adverse effect on the viability of a widely used alveolar human epithelial-like cell line (A549). The cell deposited dose can be controlled with a quartz crystal microbalance (QCM) over a dynamic range of at least 0.02-200 μg/cm2. The cell-specific deposition efficiency is currently limited to 0.072 (7.2% for two commercially available 6-er transwell plates), but a deposition efficiency of up to 0.57 (57%) is possible for better cell coverage of the exposure chamber. Dose-response measurements with ZnO nanoparticles (0.3-8.5 μg/cm2) showed significant differences in mRNA expression of pro-inflammatory (IL-8) and oxidative stress (HO-1) markers when comparing submerged and air-liquid interface exposures. Both exposure methods showed no cellular response below 1 μg/cm2 ZnO, which indicates that ZnO nanoparticles are not toxic at occupationally allowed exposure levels. The ALICE is a useful tool for dose-controlled nanoparticle (or solute) exposure of cells at the air-liquid interface. Significant differences between cellular response after ZnO nanoparticle exposure under submerged and air-liquid interface conditions suggest that pharmaceutical and toxicological studies with inhaled (nano-)particles should be performed under the more realistic air-liquid interface, rather than submerged cell conditions.
222 citations
TL;DR: This review focuses on outlining the toxicity of titanium dioxide (TiO2) particulates in vitro and in vivo, in order to understand their ability to detrimentally impact on human health.
Abstract: This review focuses on outlining the toxicity of titanium dioxide (TiO2) particulates in vitro and in vivo, in order to understand their ability to detrimentally impact on human health. Evaluating the hazards associated with TiO2 particles is vital as it enables risk assessments to be conducted, by combining this information with knowledge on the likely exposure levels of humans. This review has concentrated on the toxicity of TiO2, due to the fact that the greatest number of studies by far have evaluated the toxicity of TiO2, in comparison to other metal oxide particulates. This derives from historical reasons (whereby the size dependency of particulate toxicity was first realised for TiO2) and due to its widespread application within consumer products (such as sunscreens). The pulmonary and dermal hazards of TiO2 have been a particular focus of the available studies, due to the past use of TiO2 as a (negative) control when assessing the pulmonary toxicity of particulates, and due to its incorporation within consumer products such as sunscreens. Mechanistic processes that are critical to TiO2 particulate toxicity will also be discussed and it is apparent that, in the main, the oxidant driven inflammatory, genotoxic and cytotoxic consequences associated with TiO2 exposure, are inherently linked, and are evident both in vivo and in vitro. The attributes of TiO2 that have been identified as being most likely to drive the observed toxicity include particle size (and therefore surface area), crystallinity (and photocatalytic activity), surface chemistry, and particle aggregation/agglomeration tendency. The experimental set up also influences toxicological outcomes, so that the species (or model) used, route of exposure, experiment duration, particle concentration and light conditions are all able to influence the findings of investigations. In addition, the applicability of the observed findings for particular TiO2 forms, to TiO2 particulates in general, requires consideration. At this time it is inappropriate to consider the findings for one TiO2 form as being representative for TiO2 particulates as a whole, due to the vast number of available TiO2 particulate forms and large variety of potential tissue and cell targets that may be affected by exposure. Thus emphasising that the physicochemical characteristics are fundamental to their toxicity.
TL;DR: Wearing a facemask appears to abrogate the adverse effects of air pollution on blood pressure and heart rate variability, and has the potential to protect susceptible individuals and prevent cardiovascular events in cities with high concentrations of ambient air pollution.
Abstract: Exposure to air pollution is an important risk factor for cardiovascular morbidity and mortality, and is associated with increased blood pressure, reduced heart rate variability, endothelial dysfunction and myocardial ischaemia. Our objectives were to assess the cardiovascular effects of reducing air pollution exposure by wearing a facemask. In an open-label cross-over randomised controlled trial, 15 healthy volunteers (median age 28 years) walked on a predefined city centre route in Beijing in the presence and absence of a highly efficient facemask. Personal exposure to ambient air pollution and exercise was assessed continuously using portable real-time monitors and global positional system tracking respectively. Cardiovascular effects were assessed by continuous 12-lead electrocardiographic and ambulatory blood pressure monitoring. Ambient exposure (PM2.5 86 ± 61 vs 140 ± 113 μg/m3; particle number 2.4 ± 0.4 vs 2.3 ± 0.4 × 104 particles/cm3), temperature (29 ± 1 vs 28 ± 3°C) and relative humidity (63 ± 10 vs 64 ± 19%) were similar (P > 0.05 for all) on both study days. During the 2-hour city walk, systolic blood pressure was lower (114 ± 10 vs 121 ± 11 mmHg, P 0.05). Over the 24-hour period heart rate variability increased (SDNN 65.6 ± 11.5 vs 61.2 ± 11.4 ms, P < 0.05; LF-power 919 ± 352 vs 816 ± 340 ms2, P < 0.05) when subjects wore the facemask. Wearing a facemask appears to abrogate the adverse effects of air pollution on blood pressure and heart rate variability. This simple intervention has the potential to protect susceptible individuals and prevent cardiovascular events in cities with high concentrations of ambient air pollution.
TL;DR: The overall medium to high likelihood ratings of causality of health effects of UFP exposure and the high likelihood rating of at least one of the proposed causal mechanisms explaining associations between UFP and cardiac events, stresses the importance of considering UFP in future health impact assessments of (transport-related) air pollution, and the need for further research on U FP exposure and health effects.
Abstract: Background
Exposure to fine ambient particulate matter (PM) has consistently been associated with increased morbidity and mortality. The relationship between exposure to ultrafine particles (UFP) and health effects is less firmly established. If UFP cause health effects independently from coarser fractions, this could affect health impact assessment of air pollution, which would possibly lead to alternative policy options to be considered to reduce the disease burden of PM. Therefore, we organized an expert elicitation workshop to assess the evidence for a causal relationship between exposure to UFP and health endpoints.
TL;DR: The data suggest that the presence of contaminants, such as sodium citrate, on the surface of gold nanoparticles might play a pivotal role in inducing cytotoxicity in vitro, but does not influence the uptake of the particles in human ATII-like cell lines.
Abstract: During the last years engineered nanoparticles (NPs) have been extensively used in different technologies and consequently many questions have arisen about the risk and the impact on human health following exposure to nanoparticles. Nevertheless, at present knowledge about the cytotoxicity induced by NPs is still largely incomplete. In this context, we have investigated the cytotoxicity induced by gold nanoparticles (AuNPs), which differed in size and purification grade (presence or absence of sodium citrate residues on the particle surface) in vitro, in the human alveolar type-II (ATII)-like cell lines A549 and NCIH441. We found that the presence of sodium citrate residues on AuNPs impaired the viability of the ATII-like cell lines A549 and NCIH441. Interestingly, the presence of an excess of sodium citrate on the surface of NPs not only reduced the in vitro viability of the cell lines A549 and NCIH441, as shown by MTT assay, but also affected cellular proliferation and increased the release of lactate dehydrogenase (LDH), as demonstrated by Ki-67 and LDH-release assays respectively. Furthermore, we investigated the internalization of AuNPs by transmission electron microscopy (TEM) and we observed that particles were internalized by active endocytosis in the cell lines A549 and NCIH441 within 3 hr. In addition, gold particles accumulated in membrane-bound vesicles and were not found freely dispersed in the cytoplasm. Our data suggest that the presence of contaminants, such as sodium citrate, on the surface of gold nanoparticles might play a pivotal role in inducing cytotoxicity in vitro, but does not influence the uptake of the particles in human ATII-like cell lines.
TL;DR: Findings suggest that the metals on brake wear particles damage tight junctions with a mechanism involving oxidative stress and increase pro-inflammatory responses, however, this might be due to another mechanism than via oxidative stress.
Abstract: Fine particulate matter originating from traffic correlates with increased morbidity and mortality. An important source of traffic particles is brake wear of cars which contributes up to 20% of the total traffic emissions. The aim of this study was to evaluate potential toxicological effects of human epithelial lung cells exposed to freshly generated brake wear particles. An exposure box was mounted around a car's braking system. Lung cells cultured at the air-liquid interface were then exposed to particles emitted from two typical braking behaviours („full stop“ and „normal deceleration“). The particle size distribution as well as the brake emission components like metals and carbons was measured on-line, and the particles deposited on grids for transmission electron microscopy were counted. The tight junction arrangement was observed by laser scanning microscopy. Cellular responses were assessed by measurement of lactate dehydrogenase (cytotoxicity), by investigating the production of reactive oxidative species and the release of the pro-inflammatory mediator interleukin-8. The tight junction protein occludin density decreased significantly (p < 0.05) with increasing concentrations of metals on the particles (iron, copper and manganese, which were all strongly correlated with each other). Occludin was also negatively correlated with the intensity of reactive oxidative species. The concentrations of interleukin-8 were significantly correlated with increasing organic carbon concentrations. No correlation was observed between occludin and interleukin-8, nor between reactive oxidative species and interleukin-8. These findings suggest that the metals on brake wear particles damage tight junctions with a mechanism involving oxidative stress. Brake wear particles also increase pro-inflammatory responses. However, this might be due to another mechanism than via oxidative stress.
TL;DR: The enhanced cytotoxicity upon exposure to MCP230 correlated with its ability to generate more cellular oxidative stress and concurrently reduce the antioxidant defenses of the epithelial cells (i.e. reduced GSH, SOD activity, and GPx).
Abstract: Background: Combustion generated particulate matter is deposited in the respiratory tract and pose a hazard to the lungs through their potential to cause oxidative stress and inflammation. We have previously shown that combustion of fuels and chlorinated hydrocarbons produce semiquinone-type radicals that are stabilized on particle surfaces (i.e. environmentally persistent free radicals; EPFRs). Because the composition and properties of actual combustion-generated particles are complex, heterogeneous in origin, and vary from day-to-day, we have chosen to use surrogate particle systems. In particular, we have chosen to use the radical of 2-monochlorophenol (MCP230) as the EPFR because we have previously shown that it forms a EPFR on Cu(II)O surfaces and catalyzes formation of PCDD/F. To understand the physicochemical properties responsible for the adverse pulmonary effects of combustion by-products, we have exposed human bronchial epithelial cells (BEAS-2B) to MCP230 or the CuO/silica substrate. Our general hypothesis was that the EPFR-containing particle would have greater toxicity than the substrate species. Results: Exposure of BEAS-2B cells to our combustion generated particle systems significantly increased reactive oxygen species (ROS) generation and decreased cellular antioxidants resulting in cell death. Resveratrol treatment reversed the decline in cellular glutathione (GSH), glutathione peroxidase (GPx), and superoxide dismutase (SOD) levels for both types of combustion-generated particle systems. Conclusion: The enhanced cytotoxicity upon exposure to MCP230 correlated with its ability to generate more cellular oxidative stress and concurrently reduce the antioxidant defenses of the epithelial cells (i.e. reduced GSH, SOD activity, and GPx). The EPFRs in MCP230 also seem to be of greater biological concern due to their ability to induce lipid peroxidation. These results are consistent with the oxidizing nature of the CuO/silica ultrafine particles and the reducing nature and prolonged environmental and biological lifetimes of the EPFRs in MCP230.
TL;DR: If the findings are confirmed in larger cohorts of susceptible populations, this simple non-invasive method of assessing arterial stiffness may become a useful technique in measuring the impact of real world exposures to combustion derived-air pollution.
Abstract: Exposure to air pollution is associated with increased cardiovascular morbidity, although the underlying mechanisms are unclear. Vascular dysfunction reduces arterial compliance and increases central arterial pressure and left ventricular after-load. We determined the effect of diesel exhaust exposure on arterial compliance using a validated non-invasive measure of arterial stiffness. In a double-blind randomized fashion, 12 healthy volunteers were exposed to diesel exhaust (approximately 350 μg/m3) or filtered air for one hour during moderate exercise. Arterial stiffness was measured using applanation tonometry at the radial artery for pulse wave analysis (PWA), as well as at the femoral and carotid arteries for pulse wave velocity (PWV). PWA was performed 10, 20 and 30 min, and carotid-femoral PWV 40 min, post-exposure. Augmentation pressure (AP), augmentation index (AIx) and time to wave reflection (Tr) were calculated. Blood pressure, AP and AIx were generally low reflecting compliant arteries. In comparison to filtered air, diesel exhaust exposure induced an increase in AP of 2.5 mmHg (p = 0.02) and in AIx of 7.8% (p = 0.01), along with a 16 ms reduction in Tr (p = 0.03), 10 minutes post-exposure. Acute exposure to diesel exhaust is associated with an immediate and transient increase in arterial stiffness. This may, in part, explain the increased risk for cardiovascular disease associated with air pollution exposure. If our findings are confirmed in larger cohorts of susceptible populations, this simple non-invasive method of assessing arterial stiffness may become a useful technique in measuring the impact of real world exposures to combustion derived-air pollution.
TL;DR: This review will summarize the current state of knowledge about the biological effects of CNTs and will discuss to what extent they present similarities to those of asbestos fibres.
Abstract: Carbon nanotubes (CNTs), the product of new technology, may be used in a wide range of applications Because they present similarities to asbestos fibres in terms of their shape and size, it is legitimate to raise the question of their safety for human health Recent animal and cellular studies suggest that CNTs elicit tissue and cell responses similar to those observed with asbestos fibres, which increases concern about the adverse biological effects of CNTs While asbestos fibres' mechanisms of action are not fully understood, sufficient results are available to develop hypotheses about the significant factors underlying their damaging effects This review will summarize the current state of knowledge about the biological effects of CNTs and will discuss to what extent they present similarities to those of asbestos fibres Finally, the characteristics of asbestos known to be associated with toxicity will be analyzed to address the possible impact of CNTs
TL;DR: The results provided novel information that both TiO2 nanoparticles and C60 were taken up by cells and induced kilo-base pair deletion mutations in a transgenic mouse mutation system and the induction of ONOO- may be a critical signaling event for nanoparticle genotoxicity.
Abstract: Titanium dioxide (TiO2) nanoparticles and fullerene (C60) are two attractive manufactured nanoparticles with great promise in industrial and medical applications. However, little is known about the genotoxic response of TiO2 nanoparticles and C60 in mammalian cells. In the present study, we determined the mutation fractions induced by either TiO2 nanoparticles or C60 in gpt delta transgenic mouse primary embryo fibroblasts (MEF) and identified peroxynitrite anions (ONOO-) as an essential mediator involved in such process. Both TiO2 nanoparticles and C60 dramatically increased the mutation yield, which could be abrogated by concurrent treatment with the endocytosis inhibitor, Nystatin. Under confocal scanning microscopy together with the radical probe dihydrorhodamine 123 (DHR 123), we found that there was a dose-dependent formation of ONOO- in live MEF cells exposed to either TiO2 nanoparticles or C60, and the protective effects of antioxidants were demonstrated by the nitric oxide synthase (NOS) inhibitor, NG-methyl-L-arginine (L-NMMA). Furthermore, suppression of cyclooxygenase-2 (COX-2) activity by using the chemical inhibitor NS-398 significantly reduced mutation frequency of both TiO2 nanoparticles and C60. Our results provided novel information that both TiO2 nanoparticles and C60 were taken up by cells and induced kilo-base pair deletion mutations in a transgenic mouse mutation system. The induction of ONOO- may be a critical signaling event for nanoparticle genotoxicity.
TL;DR: It is pointed out here that 3 different conventional pathogenic particle types, PM10, asbestos and quartz, which cause diverse pathological effects, have been reported to cause very similar oxidative stress effects in cells in culture.
Abstract: In vitro studies with particles are a major staple of particle toxicology, generally used to investigate mechanisms and better understand the molecular events underlying cellular effects. However, there is ethical and financial pressure in nanotoxicology, the new sub-specialty of particle toxicology, to avoid using animals. Therefore an increasing amount of studies are being published using in vitro approaches and such studies require careful interpretation. We point out here that 3 different conventional pathogenic particle types, PM10, asbestos and quartz, which cause diverse pathological effects, have been reported to cause very similar oxidative stress effects in cells in culture. We discuss the likely explanation and implications of this apparent paradox, and its relevance for testing in nanotoxicology.
TL;DR: In the frame of future regulations, a particular attention should be paid to the ultrafine/fine fraction due to their overwhelming anthropogenic origin and predominance in the urban aerosol and their pro-inflammatory potential.
Abstract: 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. 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 (PM0.03–0.17 (defined here as ultrafine particles), PM0.17–1 (fine), PM1–2.5(intermediate) and PM2.5–10 (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. 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.
TL;DR: Manufactured nano/microparticles, CB, C60 and kaolin, were shown to be genotoxic in in vitro and in vivo assay systems.
Abstract: Recently, manufactured nano/microparticles such as fullerenes (C60), carbon black (CB) and ceramic fiber are being widely used because of their desirable properties in industrial, medical and cosmetic fields. However, there are few data on these particles in mammalian mutagenesis and carcinogenesis. To examine genotoxic effects by C60, CB and kaolin, an in vitro micronuclei (MN) test was conducted with human lung cancer cell line, A549 cells. In addition, DNA damage and mutations were analyzed by in vivo assay systems using male C57BL/6J or gpt delta transgenic mice which were intratracheally instilled with single or multiple doses of 0.2 mg per animal of particles. In in vitro genotoxic analysis, increased MN frequencies were observed in A549 cells treated with C60, CB and kaolin in a dose-dependent manner. These three nano/microparticles also induced DNA damage in the lungs of C57BL/6J mice measured by comet assay. Moreover, single or multiple instillations of C60 and kaolin, increased either or both of gpt and Spi- mutant frequencies in the lungs of gpt delta transgenic mice. Mutation spectra analysis showed transversions were predominant, and more than 60% of the base substitutions occurred at G:C base pairs in the gpt genes. The G:C to C:G transversion was commonly increased by these particle instillations. Manufactured nano/microparticles, CB, C60 and kaolin, were shown to be genotoxic in in vitro and in vivo assay systems.
TL;DR: In this article, the authors found that co-exposure to carbon black and Fe2O3 nanoparticles significantly increased protein oxidation and lipid peroxidation in cultured human lung epithelial cells.
Abstract: There is a need to better understand synergism in the biological effects of particles composed of multiple substances. The objective of this study was to determine if the oxidative stress in cultured cells caused by co-exposure to carbon black and Fe2O3 nanoparticles was significantly greater than the additive effects of exposure to either type of particles alone; and to determine a possible cause for such synergistic effect if one was found. Cultured A549 human lung epithelial cells were exposed to (1) carbon black nanoparticles alone, (2) Fe2O3 nanoparticles alone, and (3) both types of particles simultaneously. Protein oxidation, lipid peroxidation, and cellular uptake of Fe in these cells were measured after 25 hours of exposure. The reduction of solubilized Fe3+ by the carbon black nanoparticles was measured separately in a cell-free assay, by incubating the carbon black and the Fe2O3 nanoparticles in 0.75 M sulfuric acid at 40°C and measuring the amount of reduced Fe3+ at different time points up to 24 hours. Cells exposed to carbon black particles alone did not show protein oxidation, nor did the cells exposed to Fe2O3 particles alone, relative to the control. However, cells co-exposed to both carbon black and Fe2O3 particles showed up to a two-fold increase in protein oxidation relative to the control. In addition, co-exposure induced significant lipid peroxidation, although exposure to either particle type alone did not. No significant difference in cellular iron uptake was found between single exposure and co-exposure, when the Fe2O3 dosing concentration was the same in each case. In the cell-free assay, significant reduction of Fe3+ ions by carbon black nanoparticle was found within 2 hour, and it progressed up to 24 hours. At 24 hours, the carbon black nanoparticles showed a reductive capacity of 0.009 g/g, defined as the mass ratio of reduced Fe3+ to carbon black. Co-exposure to carbon black and Fe2O3 particles causes a synergistic oxidative effect that is significantly greater than the additive effects of exposures to either particle type alone. The intracellular redox reaction between carbon black and Fe3+ is likely responsible for the synergistic oxidative effect. Therefore elemental carbon particles and fibres should be considered as potential reducing agents rather than inert materials in toxicology studies. Acidified cell organelles such as the lysosomes probably play a critical role in the solubilization of Fe2O3. Further research is necessary to better understand the mechanisms.
TL;DR: It is concluded that high concentrations of DEP can modulate the tight junction occludin mRNA in the cells of the defence system and that those cells play an important role maintaining the epithelial integrity following exposure to particulate antigens in lung cells.
Abstract: Background
Using an in vitro triple cell co-culture model consisting of human epithelial cells (16HBE14o-), monocyte-derived macrophages and dendritic cells, it was recently demonstrated that macrophages and dendritic cells create a transepithelial network between the epithelial cells to capture antigens without disrupting the epithelial tightness. The expression of the different tight junction proteins in macrophages and dendritic cells, and the formation of tight junction-like structures with epithelial cells has been demonstrated. Immunofluorescent methods combined with laser scanning microscopy and quantitative real-time polymerase chain reaction were used to investigate if exposure to diesel exhaust particles (DEP) (0.5, 5, 50, 125 μg/ml), for 24 h, can modulate the expression of the tight junction mRNA/protein of occludin, in all three cell types.
TL;DR: Elevated concentrations of air pollution are associated with changes in some blood markers of inflammation and coagulation in patients with chronic pulmonary disease, and Von Willebrand factor antigen showed a consistent decrease in association with almost all air pollutants.
Abstract: Growing evidence indicates that ambient air pollution is associated with exacerbation of chronic diseases like chronic pulmonary disease. A prospective panel study was conducted to investigate short-term changes of blood markers of inflammation and coagulation in response to daily changes in air pollution in Erfurt, Germany. 12 clinical visits were scheduled and blood parameters were measured in 38 male patients with chronic pulmonary disease during winter 2001/2002. Additive mixed models with random patient intercept were applied, adjusting for trend, weekday, and meteorological parameters. Hourly data on ultrafine particles (UFP, 0.01-0.1 μm), accumulation mode particles (ACP, 0.1-1.0 μm), PM10 (particulate matter <10 μm in diameter), elemental (EC) and organic carbon (OC), gaseous pollutants (nitrogen monoxide [NO], nitrogen dioxide [NO2], carbon monoxide [CO], and sulphur dioxide [SO2]) were collected at a central monitoring site and meteorological data were received from an official network. For each person and visit the individual 24-hour average of pollutants immediately preceding the blood withdrawal (lag 0) up to day 5 (lag1-4) and 5-day running means were calculated. Increased levels of fibrinogen were observed for an increase in one interquartile range of UFP, PM10, EC, OC, CO, and NO revealing the strongest effect for lag 3. E-selectin increased in association with ACP and PM10 with a delay of one day. The ACP effect was also seen with the 5-day-mean. The pattern found for D-dimer was inconsistent. Prothrombin fragment 1+2 decreased with lag 4 consistently for all particulate pollutants. Von Willebrand factor antigen (vWF) showed a consistent decrease in association with almost all air pollutants with all lags except for lag 0. No associations were found for C-reactive protein, soluble intercellular adhesion molecule 1, serum amyloid A and factor VII. These results suggest that elevated concentrations of air pollution are associated with changes in some blood markers of inflammation and coagulation in patients with chronic pulmonary disease. The clinical implications of these findings need further investigation.
TL;DR: It is suggested that Sap, Saa1 and Saa3 are not induced in livers of mice exposed to DEP or CB, and global transcriptional profiling of liver did not reveal any hepatic response following exposure by inhalation.
Abstract: Background
Epidemiologic and animal studies have shown that particulate air pollution is associated with increased risk of lung and cardiovascular diseases. Although the exact mechanisms by which particles induce cardiovascular diseases are not known, studies suggest involvement of systemic acute phase responses, including C-reactive protein (CRP) and serum amyloid A (SAA) in humans. In this study we test the hypothesis that diesel exhaust particles (DEP) – or carbon black (CB)-induced lung inflammation initiates an acute phase response in the liver.
TL;DR: Considering the role of VEGF, FGF2 and EDN1 in lung development and morphogenesis together with the lack of any evident tissue damage the authors suggest a protective/homeostatic machinery to be associated in lungs of stable organisms to counter the CNP challenge as a precautionary measure.
Abstract: Carbonaceous nanoparticles possess an emerging source of human exposure due to the massive release of combustion products and the ongoing revolution in nanotechnology. Pulmonary inflammation caused by deposited nanoparticles is central for their adverse health effects. Epidemiological studies suggest that individuals with favourable lung physiology are at lower risk for particulate matter associated respiratory diseases probably due to efficient control of inflammation and repair process. Therefore we selected a mouse strain C3H/HeJ (C3) with robust lung physiology and exposed it to moderately toxic carbon nanoparticles (CNP) to study the elicited pulmonary inflammation and its resolution. 5 μg, 20 μg and 50 μg CNP were intratracheally (i.t.) instilled in C3 mice to identify the optimal dose for subsequent time course studies. Pulmonary inflammation was assessed using histology, bronchoalveolar lavage (BAL) analysis and by a panel of 62 protein markers. 1 day after instillation of CNP, C3 mice exhibited a typical dose response, with the lowest dose (5 μg) representing the 'no effect level' as reflected by polymorphonuclear leucocyte (PMN), and BAL/lung concentrations of pro-inflammatory proteins. Histological analysis and BAL-protein concentration did not reveal any evidence of tissue injury in 20 μg CNP instilled animals. Accordingly time course assessment of the inflammatory response was performed after 3 and 7 days with this dose (20 μg). Compared to day 1, BAL PMN counts were significantly decreased at day 3 and completely returned to normal by day 7. We have identified protein markers related to the acute response and also to the time dependent response in lung and BAL. After complete resolution of PMN influx on day 7, we detected elevated concentrations of 20 markers that included IL1B, IL18, FGF2, EDN1, and VEGF in lung and/or BAL. Biological pathway analysis revealed these factors to be involved in a closely regulated molecular cascade with IL1B/IL18 as upstream and FGF2/EDN1/VEGF as downstream molecules. Considering the role of VEGF, FGF2 and EDN1 in lung development and morphogenesis together with the lack of any evident tissue damage we suggest a protective/homeostatic machinery to be associated in lungs of stable organisms to counter the CNP challenge as a precautionary measure.
TL;DR: Data suggest that in the setting of allergic asthma, exposure to diesel exhaust could enhance virus-induced exacerbation of allergic inflammation.
Abstract: Background
Viral infections and exposure to oxidant air pollutants are two of the most important inducers of asthma exacerbation. Our previous studies have demonstrated that exposure to diesel exhaust increases the susceptibility to influenza virus infections both in epithelial cells in vitro and in mice in vivo. Therefore, we examined whether in the setting of allergic asthma, exposure to oxidant air pollutants enhances the susceptibility to respiratory virus infections, which in turn leads to increased virus-induced exacerbation of asthma. Ovalbumin-sensitized (OVA) male C57BL/6 mice were instilled with diesel exhaust particles (DEP) or saline and 24 hours later infected with influenza A/PR/8. Animals were sacrificed 24 hours post-infection and analyzed for markers of lung injury, allergic inflammation, and pro-inflammatory cytokine production.
TL;DR: These findings represent an important step in the hazard characterization of C60 fullerenes by showing that intraperitoneal administration is associated with a moderate decrease in the vascular function of mice with atherosclerosis.
Abstract: Exposure to small size particulate matter in urban air is regarded as a risk factor for cardiovascular effects, whereas there is little information about the impact on the cardiovascular system by exposure to pure carbonaceous materials in the nano-size range. C60 fullerenes are nano-sized particles that are expected to have a widespread use, including cosmetics and medicines. We investigated the association between intraperitoneal injection of pristine C60 fullerenes and vasomotor dysfunction in the aorta of 11–13 and 40–42 weeks old apolipoprotein E knockout mice (apoE-/-) with different degree of atherosclerosis. The aged apoE-/-mice had lower endothelium-dependent vasorelaxation elicited by acetylcholine in aorta segments mounted in myographs and the phenylephrine-dependent vasoconstriction response was increased. One hour after an intraperitoneal injection of 0.05 or 0.5 mg/kg of C60 fullerenes, the young apoE-/- mice had slightly reduced maximal endothelium-dependent vasorelaxation. A similar tendency was observed in the old apoE-/- mice. Hampered endothelium-independent vasorelaxation was also observed as slightly increased EC50 of sodium nitroprusside-induced vasorelaxation response in young apoE-/- mice. Treatment with C60 fullerenes affected mainly the response to vasorelaxation in young apoE-/- mice, whereas the vasomotor dysfunction in old apoE-/- mice with more advanced atherosclerosis was less affected by acute C60 fullerene treatment. These findings represent an important step in the hazard characterization of C60 fullerenes by showing that intraperitoneal administration is associated with a moderate decrease in the vascular function of mice with atherosclerosis.
TL;DR: Fe2O3 particle-induced neutrophilic inflammatory response in vivo and pro-inflammatory cytokine release in vitro might be modulated by intracellular soluble iron via PGE2 synthesis.
Abstract: Ambient particulate matter (PM)-associated metals have been shown to play an important role in cardiopulmonary health outcomes. To study the modulation of PM-induced inflammation by leached off metals, we investigated intracellular solubility of radio-labeled iron oxide (59Fe2O3) particles of 0.5 and 1.5 μm geometric mean diameter. Fe2O3 particles were examined for the induction of the release of interleukin 6 (IL-6) as pro-inflammatory and prostaglandin E2 (PGE2) as anti-inflammatory markers in cultured alveolar macrophages (AM) from Wistar Kyoto (WKY) rats. In addition, we exposed male WKY rats to monodispersed Fe2O3 particles by intratracheal instillation (1.3 or 4.0 mg/kg body weight) to examine in vivo inflammation. Particles of both sizes are insoluble extracellularly in the media but moderately soluble in AM with an intracellular dissolution rate of 0.0037 ± 0.0014 d-1 for 0.5 μm and 0.0016 ± 0.0012 d-1 for 1.5 μm 59Fe2O3 particles. AM exposed in vitro to 1.5 μm particles (10 μg/mL) for 24 h increased IL-6 release (1.8-fold; p < 0.05) and also PGE2 synthesis (1.9-fold; p < 0.01). By contrast, 0.5 μm particles did not enhance IL-6 release but strongly increased PGE2 synthesis (2.5-fold, p < 0.005). Inhibition of PGE2 synthesis by indomethacin caused a pro-inflammatory phenotype as noted by increased IL-6 release from AM exposed to 0.5 μm particles (up to 3-fold; p < 0.005). In the rat lungs, 1.5 but not 0.5 μm particles (4.0 mg/kg) induced neutrophil influx and increased vascular permeability. Fe2O3 particle-induced neutrophilic inflammatory response in vivo and pro-inflammatory cytokine release in vitro might be modulated by intracellular soluble iron via PGE2 synthesis. The suppressive effect of intracellular released soluble iron on particle-induced inflammation has implications on how ambient PM-associated but soluble metals influence pulmonary toxicity of ambient PM.