Pulmonary nanoparticle exposure disrupts systemic microvascular nitric oxide signaling

Effect of nanoparticles exposure on fractional exhaled nitric oxide (FENO) in workers exposed to nanomaterials

Fractional exhaled nitric oxide (FENO) measurement is a useful diagnostic test of airway inflammation. However, there have been few studies of FENO in workers exposed to nanomaterials. The purpose of this study was to examine the effect of nanoparticle (NP) exposure on FENO and to assess whether the FENO is increased in workers exposed to nanomaterials (NM). In this study, both exposed workers and non-exposed controls were recruited from NM handling plants in Taiwan. A total of 437 subjects (exposed group = 241, non-exposed group = 196) completed the FENO and spirometric measurements from 2009–2011. The authors used a control-banding (CB) matrix to categorize the risk level of each participant. In a multivariate linear regression analysis, this study found a significant association between risk level 2 of NP exposure and FENO. Furthermore, asthma, allergic rhinitis, peak expiratory flow rate (PEFR), and NF-κB were also significantly associated with FENO. When the multivariate logistic regression model was adjusted for confounders, nano-TiO₂ in all of the NM exposed categories had a significantly increased risk in FENO > 35 ppb. This study found associations between the risk level of NP exposure and FENO (particularly noteworthy for Nano-TiO₂). Monitoring FENO in the lung could open up a window into the role nitric oxide (NO) may play in pathogenesis.

Diesel exhaust particulate increases the size and complexity of lesions in atherosclerotic mice

Objective

Diesel exhaust particulate (DEP), a major component of urban air pollution, has been linked to atherogenesis and precipitation of myocardial infarction. We hypothesized that DEP exposure would increase and destabilise atherosclerotic lesions in apolipoprotein E deficient (ApoE^−/−) mice.

Methods

ApoE^−/− mice were fed a ‘Western diet’ (8 weeks) to induce ‘complex’ atherosclerotic plaques, with parallel experiments in normal chow fed wild-type mice. During the last 4 weeks of feeding, mice received twice weekly instillation (oropharyngeal aspiration) of 35 μL DEP (1 mg/mL, SRM-2975) or vehicle (saline). Atherosclerotic burden was assessed by en-face staining of the thoracic aorta and histological examination of the brachiocephalic artery.

Results

Brachiocephalic atherosclerotic plaques were larger in ApoE^−/− mice treated with DEP (59±10%) than in controls (32±7%; P = 0.017). In addition, DEP-treated mice had more plaques per section of artery (2.4±0.2 vs 1.8±0.2; P = 0.048) and buried fibrous layers (1.2±0.2 vs 0.4±0.1; P = 0.028). These changes were associated with lung inflammation and increased antioxidant gene expression in the liver, but not with changes in endothelial function, plasma lipids or systemic inflammation.

Conclusions

Increased atherosclerosis is caused by the particulate component of diesel exhaust producing advanced plaques with a potentially more vulnerable phenotype. These results are consistent with the suggestion that removal of the particulate component would reduce the adverse cardiovascular effects of diesel exhaust.

Properties that influence the specific surface areas of carbon nanotubes and nanofibers

Commercially available carbon nanotubes and nanofibers were analyzed to examine possible relationships between their Brunauer-Emmett-Teller specific surface areas (SSAs) and their physical and chemical properties. Properties found to influence surface area were number of walls/diameter, impurities, and surface functionalization with hydroxyl and carboxyl groups. Characterization by electron microscopy, energy-dispersive X-ray spectrometry, thermogravimetric analysis, and elemental analysis indicates that SSA can provide insight on carbon nanomaterials properties, which can differ vastly depending on synthesis parameters and post-production treatments. In this study, how different properties may influence surface area is discussed. The materials examined have a wide range of surface areas. The measured surface areas differed from product specifications, to varying degrees, and between similar products. Findings emphasize the multiple factors that influence surface area and mark its utility in carbon nanomaterial characterization, a prerequisite to understanding their potential applications and toxicities. Implications for occupational monitoring are discussed.

Characteristics and popular topics of latest researches into the effects of air particulate matter on cardiovascular system by bibliometric analysis

In recent years, many epidemiological and toxicological studies have investigated the adverse effects of air particulate matter (PM) on the cardiovascular system. However, it is difficult for the researchers to have a timely and effective overall command of the latest characteristics and popular topics in such a wide field. Different from the previous reviews, in which the research characteristics and trends are empirically concluded by experts, we try to have a comprehensive evaluation of the above topics for the first time by bibliometric analysis, a quantitative tool in information exploration. This study aims to introduce the bibliometric method into the field of PM and cardiovascular system. The articles were selected by searching PubMed/MEDLINE (from 2007 to 2012) using Medical Subject Headings (MeSH) terms "particulate matter" and "cardiovascular system". A total of 935 eligible articles and 1895 MeSH terms were retrieved and processed by the software Thomson Data Analyzer (TDA). The bibliographic information and the MeSH terms of these articles were classified and analyzed to summarize the research characteristics. The top 200 high-frequency MeSH terms (the cumulative frequency percentage was 74.2%) were clustered for popular-topic conclusion. We summarized the characteristics of published articles, of researcher collaborations and of the contents. Ten clusters of MeSH terms are presented. Six popular topics are concluded and elaborated for reference. Our study presents an overview of the characteristics and popular topics in the field of PM and cardiovascular system in the past five years by bibliometric tools, which may provide a new perspective for future researchers.

Acute exposure to diesel exhaust impairs nitric oxide-mediated endothelial vasomotor function by increasing endothelial oxidative stress

Exposure to diesel exhaust was recently identified as an important cardiovascular risk factor, but whether it impairs nitric oxide (NO)-mediated endothelial function and increases production of reactive oxygen species (ROS) in endothelial cells is not known. We tested these hypotheses in a randomized, controlled, crossover study in healthy male volunteers exposed to ambient and polluted air (n=12). The effects of skin microvascular hyperemic provocative tests, including local heating and iontophoresis of acetylcholine and sodium nitroprusside, were assessed using a laser Doppler imager. Before local heating, skin was pretreated by iontophoresis of either a specific NO-synthase inhibitor (L-N-arginine-methyl-ester) or a saline solution (Control). ROS production was measured by chemiluminescence using the lucigenin technique in human umbilical vein endothelial cells preincubated with serum from 5 of the subjects. Exposure to diesel exhaust reduced acetylcholine-induced vasodilation (P<0.01) but did not affect vasodilation with sodium nitroprusside. Moreover, the acetylcholine/sodium nitroprusside vasodilation ratio decreased from 1.51 ± 0.1 to 1.06 ± 0.07 (P<0.01) and was correlated to inhaled particulate matter 2.5 (r=-0.55; P<0.01). NO-mediated skin thermal vasodilatation decreased from 466 ± 264% to 29 ± 123% (P<0.05). ROS production was increased after polluted air exposure (P<0.01) and was correlated with the total amount of inhaled particulate matter <2.5 μm (PM2.5). In healthy subjects, acute experimental exposure to diesel exhaust impaired NO-mediated endothelial vasomotor function and promoted ROS generation in endothelial cells. Increased PM2.5 inhalation enhances microvascular dysfunction and ROS production.

Recent advances in particulate matter and nanoparticle toxicology: a review of the in vivo and in vitro studies

Epidemiological and clinical studies have linked exposure to particulate matter (PM) to adverse health effects, which may be registered as increased mortality and morbidity from various cardiopulmonary diseases. Despite the evidence relating PM to health effects, the physiological, cellular, and molecular mechanisms causing such effects are still not fully characterized. Two main approaches are used to elucidate the mechanisms of toxicity. One is the use of in vivo experimental models, where various effects of PM on respiratory, cardiovascular, and nervous systems can be evaluated. To more closely examine the molecular and cellular mechanisms behind the different physiological effects, the use of various in vitro models has proven to be valuable. In the present review, we discuss the current advances on the toxicology of particulate matter and nanoparticles based on these techniques.

Altered nitric oxide bioavailability contributes to diesel exhaust inhalation-induced cardiovascular dysfunction in man

Background

Diesel exhaust inhalation causes cardiovascular dysfunction including impaired vascular reactivity, increased blood pressure, and arterial stiffness. We investigated the role of nitric oxide (NO) bioavailability in mediating these effects.

Methods and Results

In 2 randomized double‐blind crossover studies, healthy nonsmokers were exposed to diesel exhaust or filtered air. Study 1: Bilateral forearm blood flow was measured during intrabrachial infusions of acetylcholine (ACh; 5 to 20 μg/min) and sodium nitroprusside (SNP; 2 to 8 μg/min) in the presence of the NO clamp (NO synthase inhibitor N^G‐monomethyl‐l‐arginine (l‐NMMA) 8 μg/min coinfused with the NO donor SNP at 90 to 540 ng/min to restore basal blood flow). Study 2: Blood pressure, arterial stiffness, and cardiac output were measured during systemic NO synthase inhibition with intravenous l‐NMMA (3 mg/kg). Following diesel exhaust inhalation, plasma nitrite concentrations were increased (68±48 versus 41±32 nmol/L; P=0.006) despite similar l‐NMMA–induced reductions in basal blood flow (−20.6±14.7% versus −21.1±14.6%; P=0.559) compared to air. In the presence of the NO clamp, ACh and SNP caused dose‐dependent vasodilatation that was not affected by diesel exhaust inhalation (P>0.05 for both). Following exposure to diesel exhaust, l‐NMMA caused a greater increase in blood pressure (P=0.048) and central arterial stiffness (P=0.007), but reductions in cardiac output and increases in systemic vascular resistance (P>0.05 for both) were similar to those seen with filtered air.

Conclusions

Diesel exhaust inhalation disturbs normal vascular homeostasis with enhanced NO generation unable to compensate for excess consumption. We suggest the adverse cardiovascular effects of air pollution are, in part, mediated through reduced NO bioavailability.

Clinical Trial Registration

URL: http://www.ClinicalTrials.gov. Unique identifiers: NCT00845767 and NCT01060930.

Nanotechnology: toxicologic pathology

Nanotechnology involves technology, science, and engineering in dimensions less than 100 nm. A virtually infinite number of potential nanoscale products can be produced from many different molecules and their combinations. The exponentially increasing number of nanoscale products will solve critical needs in engineering, science, and medicine. However, the virtually infinite number of potential nanotechnology products is a challenge for toxicologic pathologists. Because of their size, nanoparticulates can have therapeutic and toxic effects distinct from micron-sized particulates of the same composition. In the nanoscale, distinct intercellular and intracellular translocation pathways may provide a different distribution than that obtained by micron-sized particulates. Nanoparticulates interact with subcellular structures including microtubules, actin filaments, centrosomes, and chromatin; interactions that may be facilitated in the nanoscale. Features that distinguish nanoparticulates from fine particulates include increased surface area per unit mass and quantum effects. In addition, some nanotechnology products, including the fullerenes, have a novel and reactive surface. Augmented microscopic procedures including enhanced dark-field imaging, immunofluorescence, field-emission scanning electron microscopy, transmission electron microscopy, and confocal microscopy are useful when evaluating nanoparticulate toxicologic pathology. Thus, the pathology assessment is facilitated by understanding the unique features at the nanoscale and the tools that can assist in evaluating nanotoxicology studies.

From particles to patients: oxidative stress and the cardiovascular effects of air pollution

Air pollution, especially airborne particulate matter (PM), is associated with an increase in both morbidity and mortality from cardiovascular disease, although the underlying mechanisms remain incompletely established. The one consistent observation that links the pulmonary and cardiovascular effects of inhaled PM is oxidative stress. This article examines the evidence for the role of oxidative stress in the cardiovascular effects of air pollution, beginning with observations from epidemiological and controlled exposure studies and then exploring potential mechanistic pathways involving free radical generation from PM itself, to effects of PM on cell cultures, isolated organs, healthy animals and animal models of disease. Particular emphasis is placed on the vascular and atherosclerotic effects of urban air pollution and diesel exhaust emissions as rich sources of environmental ultrafine particles.

Impairment of coronary arteriolar endothelium-dependent dilation after multi-walled carbon nanotube inhalation: a time-course study

Engineered nanomaterials have been developed for widespread applications due to many highly unique and desirable characteristics. The purpose of this study was to assess pulmonary inflammation and subepicardial arteriolar reactivity in response to multi-walled carbon nanotube (MWCNT) inhalation and evaluate the time course of vascular alterations. Rats were exposed to MWCNT aerosols producing pulmonary deposition. Pulmonary inflammation via bronchoalveolar lavage and MWCNT translocation from the lungs to systemic organs was evident 24 h post-inhalation. Coronary arterioles were evaluated 24-168 h post-exposure to determine microvascular response to changes in transmural pressure, endothelium-dependent and -independent reactivity. Myogenic responsiveness, vascular smooth muscle reactivity to nitric oxide, and α-adrenergic responses all remained intact. However, a severe impact on endothelium-dependent dilation was observed within 24 h after MWCNT inhalation, a condition which improved, but did not fully return to control after 168 h. In conclusion, results indicate that MWCNT inhalation not only leads to pulmonary inflammation and cytotoxicity at low lung burdens, but also a low level of particle translocation to systemic organs. MWCNT inhalation also leads to impairments of endothelium-dependent dilation in the coronary microcirculation within 24 h, a condition which does not fully dissipate within 168 h. The innovations within the field of nanotechnology, while exciting and novel, can only reach their full potential if toxicity is first properly assessed.

Short-term effects of ambient particulates and gaseous pollutants on the incidence of transient ischaemic attack and minor stroke: a case-crossover study

BACKGROUND

While several studies have investigated the effects of short-term air pollution on cardiovascular disease, less is known about its effects on cerebrovascular disease, including stroke and transient ischaemic attack (TIA). The aim of the study was to assess the effects of short-term variation in air pollutants on the onset of TIA and minor stroke.

METHODS

We performed secondary analyses of data collected prospectively in the North West of England in a multi-centre study (NORTHSTAR) of patients with recent TIA or minor stroke. A case-crossover study was conducted to determine the association between occurrence of TIA and the concentration of ambient PM10 or gaseous pollutants.

RESULTS

A total of 709 cases were recruited from the Manchester (n = 335) and Liverpool (n = 374) areas. Data for the Manchester cohort showed an association between ambient nitric oxide (NO) and risk of occurrence of TIA and minor stroke with a lag of 3 days (odds ratio 1.06, 95% CI: 1.01 - 1.11), whereas negative association was found for the patients from Liverpool. Effects of similar magnitude, although not statistically significant, were generally observed with other pollutants. In a two pollutant model the effect of NO remained stronger and statistically significant when analysed in combination with CO or SO2, but was marginal in combination with NO2 or ozone and non-significant with PM10. There was evidence of effect modification by age, gender and season.

CONCLUSIONS

Our data suggest an association between NO and occurrence of TIA and minor stroke in Greater Manchester.

Changes in cardiopulmonary function induced by nanoparticles

Nanoparticles (NP) are highly applicable in a variety of technological and biomedical fields because of their unique physicochemical properties. The increased development and utilization of NP has amplified human exposure and raised concerns regarding their potential to generate toxicity. The biological impacts of NP exposures have been shown to be dependent on aerodynamic size, chemical composition, and the route of exposure (oral, dermal, intravenous, and inhalation), while recent research has demonstrated the cardiovascular (CV) system as an important site of toxicity. Proposed mechanisms responsible for these effects include inflammation, oxidative stress, autonomic dysregulation, and direct interactions of NP with CV cells. Specifically, NP have been shown to impact vascular endothelial cell (EC) integrity, which may disrupt the dynamic endothelial regulation of vascular tone, possibly altering systemic vascular resistance and impairing the appropriate distribution of blood flow throughout the circulation. Cardiac consequences of NP-induced toxicity include disruption of heart rate and electrical activity via catecholamine release, increased susceptibility to ischemia/reperfusion injury, and modified baroreceptor control of cardiac function. These and other CV outcomes likely contribute to adverse health effects promoting myocardial infarction, hypertension, cardiac arrhythmias, and thrombosis. This review will assess the current knowledge regarding the principle sites of CV toxicity following NP exposure. Furthermore, we will propose mechanisms contributing to altered CV function and hypothesize possible outcomes resulting in decrements in human health.

Manufactured and airborne nanoparticle cardiopulmonary interactions: a review of mechanisms and the possible contribution of mast cells

Human inhalation exposures to manufactured nanoparticles (NP) and airborne ultrafine particles (UFP) continues to increase in both occupational and environmental settings. UFP exposures have been associated with increased cardiovascular mortality and morbidity, while ongoing research supports adverse systemic and cardiovascular health effects after NP exposures. Adverse cardiovascular health effects include alterations in heart rate variability, hypertension, thrombosis, arrhythmias, increased myocardial infarction, and atherosclerosis. Exactly how UFP and NP cause these negative cardiovascular effects is poorly understood, however a variety of mediators and mechanisms have been proposed. UFP and NP, as well as their soluble components, are known to systemically translocate from the lung. Translocated particles could mediate cardiovascular toxicity through direct interactions with the vasculature, blood, and heart. Recent study suggests that sensory nerve stimulation within the lung may also contribute to UFP- and NP-induced acute cardiovascular alterations. Activation of sensory nerves, such as C-fibers, within the lung may result in altered cardiac rhythm and function. Lastly, release of pulmonary-derived mediators into systemic circulation has been proposed to facilitate cardiovascular effects. In general, these proposed pulmonary-derived mediators include proinflammatory cytokines, oxidatively modified macromolecules, vasoactive proteins, and prothrombotic factors. These pulmonary-derived mediators have been postulated to contribute to the subsequent prothrombotic, atherogenic, and inflammatory effects after exposure. This review will evaluate the potential contribution of individual mediators and mechanisms in facilitating cardiopulmonary toxicity following inhalation of UFP and NP. Lastly, we will appraise the literature and propose a hypothesis regarding the possible role of mast cells in contributing to these systemic effects.

Xenobiotic particle exposure and microvascular endpoints: a call to arms

Xenobiotic particles can be considered in two genres: air pollution particulate matter and engineered nanoparticles. Particle exposures can occur in the greater environment, the workplace, and our homes. The majority of research in this field has, justifiably, focused on pulmonary reactions and outcomes. More recent investigations indicate that cardiovascular effects are capable of correlating with established mortality and morbidity epidemiological data following particle exposures. While the preliminary and general cardiovascular toxicology has been defined, the mechanisms behind these effects, specifically within the microcirculation, are largely unexplored. Therefore, the purpose of this review is several fold: first, a historical background on toxicological aspects of particle research is presented. Second, essential definitions, terminology, and techniques that may be unfamiliar to the microvascular scientist will be discussed. Third, the most current concepts and hypotheses driving cardiovascular research in this field will be reviewed. Lastly, potential future directions for the microvascular scientist will be suggested. Collectively speaking, microvascular research in the particle exposure field represents far more than a "niche." The immediate demand for basic, translational, and clinical studies is high and diverse. Microvascular scientists at all career stages are strongly encouraged to expand their research interests to include investigations associated with particle exposures.

Comparison of diffusion charging and mobility-based methods for measurement of aerosol agglomerate surface area

We compare different approaches to measure surface area of aerosol agglomerates. The objective was to compare field methods, such as mobility and diffusion charging based approaches, with laboratory approach, such as Brunauer, Emmett, Teller (BET) method used for bulk powder samples. To allow intercomparison of various surface area measurements, we defined 'geometric surface area' of agglomerates (assuming agglomerates are made up of ideal spheres), and compared various surface area measurements to the geometric surface area. Four different approaches for measuring surface area of agglomerate particles in the size range of 60-350 nm were compared using (i) diffusion charging-based sensors from three different manufacturers, (ii) mobility diameter of an agglomerate, (iii) mobility diameter of an agglomerate assuming a linear chain morphology with uniform primary particle size, and (iv) surface area estimation based on tandem mobility-mass measurement and microscopy. Our results indicate that the tandem mobility-mass measurement, which can be applied directly to airborne particles unlike the BET method, agrees well with the BET method. It was also shown that the three diffusion charging-based surface area measurements of silver agglomerates were similar within a factor of 2 and were lower than those obtained from the tandem mobility-mass and microscopy method by a factor of 3-10 in the size range studied. Surface area estimated using the mobility diameter depended on the structure or morphology of the agglomerate with significant underestimation at high fractal dimensions approaching 3.

Cytokine production by co-cultures exposed to monodisperse amorphous silica nanoparticles: the role of size and surface area

The aim of this study was to test the influence of nanoparticle size and surface area (SA) on cytokine secretion by co-cultures of pulmonary epithelial cells (A549), macrophages (differentiated THP-1 cells) and endothelium cells (EA.hy926) in a two-compartment system. We used monodisperse amorphous silica nanoparticles (2, 16, 60 and 104 nm) at concentrations of 5 μg/cm² cell culture SA or 10 cm² particle SA/cm². A549 and THP-1 cells were exposed to nanoparticles for 24h, in the presence of EA.hy926 cells cultured in an insert introduced above the bi-culture after 12h. Supernatants from both compartments were recovered and TNF-α, IL-6, IL-8 and MIP-1α were measured. Significant secretion of all cytokines was observed for the 2 nm particles at both concentrations and in both compartments. Larger particles of 60 nm induced significant cytokine secretion at the dose of 10 cm² particle SA/cm². The use of multiple cellular types showed that cytokine secretion in single cell cultures is amplified or mitigated in co-cultures. The release of pro-inflammatory mediators by endothelial cells not directly exposed to nanoparticles indicates a possible endothelium activation after inhalation of silica particles. This work shows the role of size and SA in cellular response to amorphous nanosilica.

Health implications of engineered nanomaterials

With the development of nanotechnology, a growing number of people are expected to be exposed to its products, the engineered nanomaterials (ENMs). Some physico-chemical properties of ENMs, linked to their size in the nanoscale (1-100 nm), make them potentially more reactive, and therefore raise concern about possible adverse effects in humans. In this article, I discuss human diseases which may be predicted after exposure to ENMs, and how their pathogenetic mechanisms may be linked to exposure; in this regard, special emphasis has been given to the triad of oxidative stress/inflammation/genotoxicity and to the interaction of ENMs/proteins in different biological compartments. The analysis of possible adverse effects has been made on an organ-by-organ basis, starting from the skin, respiratory system and gastrointestinal tract. These sites are in fact not only those exposed to the highest amounts of ENMs, but are also the portals of entry to internal organs for possible systemic effects. Although the list and the relevance of possible human disorders linked to ENM exposure are at least as impressive as that of their direct or indirect beneficial effects for human health, we must be clear that ENM-linked diseases belong to the realm of possible risk (i.e. cannot be excluded, but are unlikely), whereas ENMs with proven beneficial effects are on the market. Therefore, the mandatory awareness about possible adverse effects of ENMs should in no way be interpreted as a motivation to disregard the great opportunity represented by nanotechnology.

Changes in eNOS phosphorylation contribute to increased arteriolar NO release during juvenile growth

Nitric oxide (NO) mediates a major portion of arteriolar endothelium-dependent dilation in adults, but indirect evidence has suggested that NO contributes minimally to these responses in the young. Isolated segments of arterioles were studied in vitro to verify this age-related increase in NO release and investigate the mechanism by which it occurs. Directly measured NO release induced by ACh or the Ca(2+) ionophore A-23187 was five- to sixfold higher in gracilis muscle arterioles from 42- to 46-day-old (juvenile) rats than in those from 25- to 28-day-old (weanling) rats. There were no differences between groups in arteriolar endothelial NO synthase (eNOS) expression or tetrahydrobiopterin levels, and arteriolar l-arginine levels were lower in juvenile vessels than in weanling vessels (104 ± 6 vs.126 ± 3 pmol/mg). In contrast, agonist-induced eNOS Thr(495) dephosphorylation and eNOS Ser(1177) phosphorylation (events required for maximal activity) were up to 30% and 65% greater, respectively, in juvenile vessels. Juvenile vessels did not show increased expression of enzymes that mediate these events [protein phosphatases 1 and 2A and PKA and PKB (Akt)] or heat shock protein 90, which facilitates Ser(1177) phosphorylation. However, agonist-induced colocalization of heat shock protein 90 with eNOS was 34-66% greater in juvenile vessels than in weanling vessels, and abolition of this difference with geldanamycin also abolished the difference in Ser(1177) phosphorylation between groups. These findings suggest that growth-related increases in arteriolar NO bioavailability may be due at least partially to changes in the regulation of eNOS phosphorylation and increased signaling activity, with no change in the abundance of eNOS signaling proteins.

Serum proteins prevent aggregation of Fe2O3 and ZnO nanoparticles

Aggregation of metal oxide nanoparticles in aqueous media complicates interpretation of in vitro studies of nanoparticle-cell interactions. We used dynamic light scattering to investigate the aggregation dynamics of iron oxide and zinc oxide nanoparticles. Our results show that iron oxide particles aggregate more readily than zinc oxide particles. Pretreatment with serum stabilises iron oxide and zinc oxide nanoparticles against aggregation. Serum-treated iron oxide is stable only in pure water, while zinc oxide is stable in water or cell culture media. These findings, combined with zeta potential measurements and quantification of proteins adsorbed on particle surface, suggest that serum stabilisation of iron oxide particles occurs primarily through protein adsorption and resulting net surface charge. Zinc oxide stabilisation, however, also involves steric hindrance of particle aggregation. Fluid shear at levels used in flow experiments breaks up iron oxide particle aggregates. These results enhance our understanding of nanoparticle aggregation and its consequences for research on the biological effects of nanomaterials.

Modest effect on plaque progression and vasodilatory function in atherosclerosis-prone mice exposed to nanosized TiO(2)

Background

There is growing evidence that exposure to small size particulate matter increases the risk of developing cardiovascular disease.

Methods

We investigated plaque progression and vasodilatory function in apolipoprotein E knockout (ApoE^-/-) mice exposed to TiO₂. ApoE^-/- mice were intratracheally instilled (0.5 mg/kg bodyweight) with rutile fine TiO₂ (fTiO₂, 288 nm), photocatalytic 92/8 anatase/rutile TiO₂ (pTiO₂, 12 nm), or rutile nano TiO₂ (nTiO₂, 21.6 nm) at 26 and 2 hours before measurement of vasodilatory function in aorta segments mounted in myographs. The progression of atherosclerotic plaques in aorta was assessed in mice exposed to nanosized TiO₂ (0.5 mg/kg bodyweight) once a week for 4 weeks. We measured mRNA levels of Mcp-1, Mip-2, Vcam-1, Icam-1 and Vegf in lung tissue to assess pulmonary inflammation and vascular function. TiO₂-induced alterations in nitric oxide (NO) production were assessed in human umbilical vein endothelial cells (HUVECs).

Results

The exposure to nTiO₂ was associated with a modest increase in plaque progression in aorta, whereas there were unaltered vasodilatory function and expression levels of Mcp-1, Mip-2, Vcam-1, Icam-1 and Vegf in lung tissue. The ApoE^-/- mice exposed to fine and photocatalytic TiO₂ had unaltered vasodilatory function and lung tissue inflammatory gene expression. The unaltered NO-dependent vasodilatory function was supported by observations in HUVECs where the NO production was only increased by exposure to nTiO₂.

Conclusion

Repeated exposure to nanosized TiO₂ particles was associated with modest plaque progression in ApoE^-/- mice. There were no associations between the pulmonary TiO₂ exposure and inflammation or vasodilatory dysfunction.

On-chip evaluation of shear stress effect on cytotoxicity of mesoporous silica nanoparticles

In this work, nanotoxicity in the bloodstream was modeled, and the cytotoxicity of sub-50 nm mesoporous silica nanoparticles to human endothelial cells was investigated under microfluidic flow conditions. Compared to traditional in vitro cytotoxicity assays performed under static conditions, unmodified mesoporous silica nanoparticles show higher and shear stress-dependent toxicity to endothelial cells under flow conditions. Interestingly, even under flow conditions, highly organo-modified mesoporous silica nanoparticles show no significant toxicity to endothelial cells. This paper clearly demonstrates that shear stress is an important factor to be considered in in vitro nanotoxicology assessments and provides a simple device for pursuing this consideration.

Nanoparticle inhalation alters systemic arteriolar vasoreactivity through sympathetic and cyclooxygenase-mediated pathways

The widespread increase in the production and use of nanomaterials has increased the potential for nanoparticle exposure; however, the biological effects of nanoparticle inhalation are poorly understood. Rats were exposed to nanosized titanium dioxide aerosols (10 μg lung burden); at 24 h post-exposure, the spinotrapezius muscle was prepared for intravital microscopy. Nanoparticle exposure did not alter perivascular nerve stimulation (PVNS)-induced arteriolar constriction under normal conditions; however, adrenergic receptor inhibition revealed a more robust effect. Nanoparticle inhalation reduced arteriolar dilation in response to active hyperaemia (AH). In both PVNS and AH experiments, nitric oxide synthase (NOS) inhibition affected only controls. Whereas cyclooxygenase (COX) inhibition only attenuated AH-induced arteriolar dilation in nanoparticle-exposed animals. This group displayed an enhanced U46619 constriction and attenuated iloprost-induced dilation. Collectively, these studies indicate that nanoparticle exposure reduces microvascular NO bioavailability and alters COX-mediated vasoreactivity. Furthermore, the enhanced adrenergic receptor sensitivity suggests an augmented sympathetic responsiveness.

Relationship between pulmonary and systemic markers of exposure to multiple types of welding particulate matter

Welding results in a unique and complex occupational exposure. Recent epidemiological studies have shown an increased risk of cardiovascular disease following welding fume exposure. In this study, we compared the induction of pulmonary and systemic inflammation following exposure to multiple types of welding fumes. Mice were exposed to 340μg of manual metal arc stainless steel (MMA-SS), gas metal arc-SS (GMA-SS) or GMA-mild steel (GMA-MS) by pharyngeal aspiration. Mice were sacrificed at 4 and 24h post-exposure to evaluate various parameters of pulmonary and systemic inflammation. Alterations in pulmonary gene expression by a custom designed TaqMan array showed minimal differences between the fumes at 4h. Conversely at 24h, gene expression changes were further increased by SS but not GMA-MS exposure. These findings were associated with the surrogate marker of systemic inflammation, liver acute phase gene induction. Interestingly, stress response genes in cardiovascular tissues were only increased following MMA-SS exposure. These effects were related to the initial level of pulmonary cytotoxicity, as measured by lactate dehydrogenase activity, which was greatest following MMA-SS exposure. In conclusion, varying types of welding fumes elicit quantitatively different systemic inflammatory and/or stress responses.

Toxicological effects of titanium dioxide nanoparticles: a review of in vitro mammalian studies

BACKGROUND AND OBJECTIVE

Recent rapid advances in nanotechnology raise concerns about development, production route, and diffusion in industrial and consumer products of titanium dioxide nanoparticles (TiO2-NPs). In fact, compared to recent increase in applications of this nanomaterial, the health effects of human exposure have not been systematically investigated. The aim of this review was to provide a comprehensive overview on the current knowledge regarding the effects of TiO2-NPs on mammalian cells.

EVIDENCE AND INFORMATION SOURCES

This review is based on an analysis of the current literature on this topic.

STATE OF THE ART

Fine TiO2 particles have been considered as safe and to pose little risk to humans, suggesting that exposure to this material is relatively harmless. However, available data in the literature showed that TiO2-NPs can cause several adverse effects on mammalian cells such as increase of reactive oxygen species (ROS) production and cytokines levels, reduction of cell viability and proliferation, induction of apoptosis and genotoxicity.

PERSPECTIVES AND CONCLUSIONS

Additional research is needed to obtain up-to-date knowledge on health effects of TiO2-NPs and to avoid any potential risk correlated to their exposure. Consequently, future studies need to: (1) use an homogeneous and rigorous exposure classification to clarify how the physicochemical properties of TiO2-NPs correlate with their toxicological effects; (2) assess the potential adverse effects of low level exposures to TiO2-NPs, as most of the information currently available originates from studies in which exposure levels were excessively and unrealistically high; (3) identify the possible roles of TiO2-NPs in genotoxicity and carcinogenicity (4) carry out epidemiologic studies of exposed workers to provide an assessment of possible risks correlated to the occupational exposure to TiO2-NPs.

Hazard identification of particulate matter on vasomotor dysfunction and progression of atherosclerosis

The development and use of nanoparticles have alerted toxicologists and regulators to issues of safety testing. By analogy with ambient air particles, it can be expected that small doses are associated with a small increase in risk of cardiovascular diseases, possibly through oxidative stress and inflammatory pathways. We have assessed the effect of exposure to particulate matter on progression of atherosclerosis and vasomotor function in humans, animals, and ex vivo experimental systems. The type of particles that have been tested in these systems encompass TiO(2), carbon black, fullerene C(60), single-walled carbon nanotubes, ambient air particles, and diesel exhaust particles. Exposure to ambient air particles is associated with accelerated progression of atherosclerosis and vasomotor dysfunction in both healthy and susceptible animal models and humans at risk of developing cardiovascular diseases. The vasomotor dysfunction includes increased vasoconstriction as well as reduced endothelium-dependent vasodilatation; endothelium-independent vasodilatation is often unaffected indicating mainly endothelial dysfunction. Pulmonary exposure to TiO(2), carbon black, and engineered nanoparticles generate vasomotor dysfunction; the effect size is similar to that generated by combustion-derived particles, although the effect could depend on the exposure period and the administered dose, route, and mode. The relative risk associated with exposure to nanoparticles may be small compared to some traditional risk factors for cardiovascular diseases, but superimposed on these and possible exposure to large parts of the population it is a significant public health concern. Overall, assessment of vasomotor dysfunction and progression of atherosclerosis are promising tools for understanding the effects of particulate matter.

[Importance of researches on chronic effects by manufactured nanomaterials]

Manufactured nanomaterials are the most important substances for the nanotechnology. The nanomaterials possess different physico-chemical properties from bulk materials. The new properties may lead to biologically beneficial effects and/or adverse effects. However, there are no standardized evaluation methods at present. Some domestic research projects and international OECD programs are ongoing, in order to share the health impact information of nanomaterials or to standardize the evaluation methods. From 2005, our institutes have been conducting the research on the establishment of health risk assessment methodology of manufactured nanomaterials. In the course of the research project, we revealed that the nanomaterials were competent to cause chronic effects, by analyzing the intraperitoneal administration studies and carcinogenic promotion studies. These studies suggested that even aggregated nanomaterials were crumbled into nanosized particles inside the body during the long-term, and the particles were transferred to other organs. Also investigations of the toxicokinetic properties of nanomaterials after exposure are important to predict the chronically targeted tissues. The long lasting particles/fibers in the particular tissues may cause chronic adverse effects. Therefore, focusing on the toxicological characterization of chronic effects was considered to be most appropriate approach for establishing the risk assessment methods of nanomaterials.

Novel Approach by Nanobiomaterials in Vascular Tissue Engineering

Interactions between vascular endothelial cells (ECs) and biomaterials are important for engineered tissue substitute. The modification of biomaterial surfaces are designed to modulate EC adhesion and responses in order to improve implantation success rate. Specifically, it has now been well established that increased vascular tissue regeneration can be achieved on almost any surface by employing novel nanofabricated surface features. To enhance EC adhesion and growth, material surfaces have been modified with physicochemical and mechanical properties, such as bioactive molecules from the matrix, peptides, and/or growth factors to control EC behavior. The advances in nanotechnology can bring additional functionality to vascular tissue engineering, optimize internal vascular graft surface, help to direct the differentiation of stem cells into the vascular cell phenotype, and, most importantly, also provide a biomaterials-based cellularization process. Nanomaterials could promote in situ endothelialization by mobilizing endothelial progenitor cells (EPCs) from the bone marrow, by encouraging cell-specific adhesion to the vascular graft, and, once attached, by controlling the proliferation and differentiation of these cells. Interaction between different cell types and extracellular matrix continue to be a principal source of inspiration for material biological function and, therefore, the understanding of the molecular mechanism trigger by the interaction is discussed.

Acute effects of COREXIT EC9500A on cardiovascular functions in rats

These studies characterized cardiovascular responses after an acute inhalation exposure to COREXIT EC9500A, the oil dispersant used in the Deepwater Horizon oil spill. Male Sprague-Dawley rats underwent a single 5-h inhalation exposure to COREXIT EC9500A (average exposure level 27.12 mg/m(3)) or air. On d 1 and 7 following the exposure, rats were implanted with indwelling catheters and changes in heart rate and blood pressure were assessed in response to increasing levels of adrenoreceptor agonists. A separate group of rats was euthanized at the same time points, ventral tail arteries were dissected, and vascular tone along with dose-dependent responses to vasoconstricting and dilating factors were assessed in vitro. Agonist-induced dose-dependent increases in heart rate and blood pressure were greater in COREXIT EC9500A-exposed than in air-exposed rats at 1 d but not 7 d after the exposure. COREXIT EC9500A exposure also induced a rise in basal tone and reduced responsiveness of tail arteries to acetylcholine-induced vasodilation at 1 d but not 7 d following the exposure. These findings demonstrate that an acute exposure to COREXIT EC9500A exerts transient effects on cardiovascular and peripheral vascular functions.

Assessment of neurobehavioral and biochemical effects in rats exposed to copper smelter dusts

Female Wistar rats were instilled per os by gavage with different copper dust samples: P-25 obtained by passing the test material through a 25 μmsieve, and P-0.1 containing soluble matter and ultra-fine, non-soluble<100 nm particulate matter (PM) fraction. The control group received sterile saline. The effects were studied at day 1, 7, and 30 post-exposure, focusing on bronchoalveolar lavage fluid (BALF) analysis (including biochemistry, cell morphology, cell viability, and Clara cell 16 protein concentration) and pathomorphology of lung. Results of biochemical tests showed a strong pro-inflammatory effect of both particulate fractions. The morphological studies after exposure to P-25 and P-0.1 fractions showed multi-focal infiltrations in the alveoli. Changes in behavioral (radial maze and passive avoidance tests) have shown that memory in groups exposed to dust was impaired. Our findings indicate that both samples of dust from Copper Smelter cause greater and lesser intensity (P-25 > P-0.1) of the symptoms of acute inflammatory reaction immediately 24 h after instillation to rats. Exposure results in dropping CC16 protein level in serum of rats. After one month, previous acute inflammation was resolved and transformed in persistent low-grade inflammation. The low-grade inflammation resulted in induction of neurobehavioral effects probably by changes in "cholinergic anti-inflammatory pathway" in which acetylcholine modulates neurotransmission.

Formation of vascular S-nitrosothiols and plasma nitrates/nitrites following inhalation of diesel emissions

Epidemiological studies have associated traffic-related airborne pollution with adverse cardiovascular outcomes. Nitric oxide (NO) is a common component of fresh diesel and gasoline engine emissions that rapidly transforms both in the atmosphere and once inhaled. Because of this rapid transformation, limited information is available in terms of potential human exposures and adverse health effects. Young rats were exposed to whole diesel emissions (DE) adjusted to 300 μg/m(3) of particulate matter (containing 3.5 ppm NO) or 0, 3, or 10 ppm NO as a positive control. Animals were also pre-injected (ip) with either saline or N-acetylcysteine (NAC), a precursor of glutathione. Predictably, pure NO exposures led to a concentration-dependent increase in plasma nitrates compared to controls, which lasted for roughly 4 h postexposure. Whole DE exposure for 1 h also led to a doubling of plasma NOx. NAC injection increased the levels of plasma nitrates and nitrites (NOx) in the DE exposure group. Inhibition of nitric oxide symthase (NOS) by N(G)-nitro-L-arginine (L-NNA) did not block the rise in plasma NOx, demonstrating that the increase was entirely due to exogenous sources. Both DE and pure NO exposures paradoxically led to elevated eNOS expression in aortic tissue. Furthermore, coronary arterioles from NO-exposed animals exhibited greater constriction to endothelin-1 compared to controls, consistent with a derangement of the NOS system. Thus, NO may be an important contributor to traffic-related cardiovascular morbidity, although further research is necessary for proper hazard identification.

Mechanisms of diesel-induced endothelial nitric oxide synthase dysfunction in coronary arterioles

BACKGROUND AND OBJECTIVE

Increased air pollutants correlate with increased incidence of cardiovascular disease potentially due to vascular dysfunction. We have reported that acute diesel engine exhaust (DE) exposure enhances vasoconstriction and diminishes acetylcholine (ACh)-induced dilation in coronary arteries in a nitric oxide synthase (NOS)-dependent manner. We hypothesize that acute DE inhalation leads to endothelial dysfunction by uncoupling NOS.

METHODS

Rats inhaled fresh DE (300 µg particulate matter/m3) or filtered air for 5 hr. After off-gassing, intraseptal coronary arteries were isolated and dilation to ACh recorded using videomicroscopy.

RESULTS

Arteries from DE-exposed animals dilated less to ACh than arteries from air-exposed animals. NOS inhibition did not affect ACh dilation in control arteries but increased dilation in the DE group, suggesting NOS does not normally contribute to ACh-induced dilation in coronary arteries but does contribute to endothelial dysfunction after DE inhalation. Cyclooxygenase (COX) inhibition did not affect ACh dilation in the DE group, but combined inhibition of NOS and COX diminished dilation in both groups and eliminated intergroup differences, suggesting that the two pathways interact. Superoxide scavenging increased ACh dilation in DE arteries, eliminating differences between groups. Tetrahydrobiopterin (BH4) supplementation with sepiapterin restored ACh-mediated dilation in the DE group in a NOS-dependent manner. Superoxide generation (dihydroethidium staining) was greater in DE arteries, and superoxide scavenging, BH4 supplementation, or NOS inhibition reduced the signal in DE but not air arteries.

CONCLUSION

Acute DE exposure appears to uncouple NOS, increasing reactive oxygen species generation and causing endothelial dysfunction, potentially because of depletion of BH4 limiting its bioavailability.

Air Pollution and the microvasculature: a cross-sectional assessment of in vivo retinal images in the population-based multi-ethnic study of atherosclerosis (MESA)

BACKGROUND

Long- and short-term exposures to air pollution, especially fine particulate matter (PM(2.5)), have been linked to cardiovascular morbidity and mortality. One hypothesized mechanism for these associations involves microvascular effects. Retinal photography provides a novel, in vivo approach to examine the association of air pollution with changes in the human microvasculature.

METHODS AND FINDINGS

Chronic and acute associations between residential air pollution concentrations and retinal vessel diameters, expressed as central retinal arteriolar equivalents (CRAE) and central retinal venular equivalents (CRVE), were examined using digital retinal images taken in Multi-Ethnic Study of Atherosclerosis (MESA) participants between 2002 and 2003. Study participants (46 to 87 years of age) were without clinical cardiovascular disease at the baseline examination (2000-2002). Long-term outdoor concentrations of PM(2.5) were estimated at each participant's home for the 2 years preceding the clinical exam using a spatio-temporal model. Short-term concentrations were assigned using outdoor measurements on the day preceding the clinical exam. Residential proximity to roadways was also used as an indicator of long-term traffic exposures. All associations were examined using linear regression models adjusted for subject-specific age, sex, race/ethnicity, education, income, smoking status, alcohol use, physical activity, body mass index, family history of cardiovascular disease, diabetes status, serum cholesterol, glucose, blood pressure, emphysema, C-reactive protein, medication use, and fellow vessel diameter. Short-term associations were further controlled for weather and seasonality. Among the 4,607 participants with complete data, CRAE were found to be narrower among persons residing in regions with increased long- and short-term levels of PM(2.5). These relationships were observed in a joint exposure model with -0.8 µm (95% confidence interval [CI] -1.1 to -0.5) and -0.4 µm (95% CI -0.8 to 0.1) decreases in CRAE per interquartile increases in long- (3 µg/m(3)) and short-term (9 µg/m(3)) PM(2.5) levels, respectively. These reductions in CRAE are equivalent to 7- and 3-year increases in age in the same cohort. Similarly, living near a major road was also associated with a -0.7 µm decrease (95% CI -1.4 to 0.1) in CRAE. Although the chronic association with CRAE was largely influenced by differences in exposure between cities, this relationship was generally robust to control for city-level covariates and no significant differences were observed between cities. Wider CRVE were associated with living in areas of higher PM(2.5) concentrations, but these findings were less robust and not supported by the presence of consistent acute associations with PM(2.5).

CONCLUSIONS

Residing in regions with higher air pollution concentrations and experiencing daily increases in air pollution were each associated with narrower retinal arteriolar diameters in older individuals. These findings support the hypothesis that important vascular phenomena are associated with small increases in short-term or long-term air pollution exposures, even at current exposure levels, and further corroborate reported associations between air pollution and the development and exacerbation of clinical cardiovascular disease. Please see later in the article for the Editors' Summary.

Acute respiratory and systemic toxicity of pulmonary exposure to rutile Fe-doped TiO(2) nanorods

Nanomaterials are extensively used in medicines, industry and daily life, but little is known about their possible health effects. Titanium dioxide (TiO₂) nonmaterial-based photocatalysis is useful in the complete mineralization of organic pollutants in waste water and air. While the Fe-doping of TiO₂ enhances their photocatalytic activity, their potential pathophysiologic effects are unknown. Here, rutile Fe-doped (9%) pure titanium dioxide (TiO₂) nanorods were prepared and characterized. Subsequently, we assessed the acute (24 h) pulmonary and extrapulmonary effects of intratracheal (i.t.) instillation of these nanorods (1 and 5 mg/kg) in Wistar rats. In the bronchoalveolar lavage, the treatment induced a significant and dose-dependent increase of neutrophils, an increase of interleukin-6 (IL-6, at 5 mg/kg), and caused a dose-dependent-decrease of superoxide dismutase (SOD) activity. The lung sections of rats exposed to rutile Fe-TiO₂ nanorods showed infiltration of inflammatory cells in dose-dependent manner. Similarly, the heart rate, systolic blood pressure, plasma IL-6, and leukocyte and platelet numbers were increased at 5 mg/kg. The plasma SOD and reduced glutathaione activities were dose-dependently decreased after exposure to the nanorods. Histopathologically, the liver showed mild inflammatory cells infiltration of few portal tracts, but the kidneys and heart were unaffected. In plasma, the levels of lactate dehydrogenase and hepatic enzymes, i.e., alanine aminotranferease and aspartate aminotransferase were increased significantly. The in vitro exposure of human lung cancer cells NCI-H460-Luc2 and human hepatoma cells HepG2 to FeTiO₂ (6.25-100 μg/ml) dose-dependently reduced cellular viability. Also, the In vitro direct addition of these nanorods (0.1-1 μg/ml) to untreated rat blood, significantly and dose-dependently induced platelet aggregation. In conclusion, exposure to rutile Fe-TiO₂ promotes pulmonary and systemic inflammation and oxidative stress. It affects the liver, enhances thrombotic potential, heart rate and systolic blood pressure. Moreover, the rutile Fe-TiO₂ elicited direct toxicity on NCI-H460-Luc2 and HepG2 cells.

Pulmonary exposure to carbon black nanoparticles and vascular effects

BACKGROUND

Exposure to small size particulates is regarded as a risk factor for cardiovascular diseases.

METHODS

We exposed young and aged apolipoprotein E knockout mice (apoE-/-) to carbon black (Printex 90, 14 nm) by intratracheal instillation, with different dosing and timing, and measured vasomotor function, progression of atherosclerotic plaques, and VCAM-1, ICAM-1, and 3-nitrotyrosine in blood vessels. The mRNA expression of VCAM-1, ICAM-1, HO-1, and MCP-1 was examined in lung tissue.

RESULTS

Young apoE-/- mice exposed to two consecutive 0.5 mg/kg doses of carbon black exhibited lower acetylcholine-induced vasorelaxation in aorta segments mounted in myographs, whereas single doses of 0.05-2.7 mg/kg produced no such effects. The phenylephrine-dependent vasocontraction response was shifted toward a lower responsiveness in the mice exposed once to a low dose for 24 hours. No effects were seen on the progression of atherosclerotic plaques in the aged apoE-/- mice or on the expression of VCAM-1 and ICAM-1 and the presence of 3-nitrotyrosine in the vascular tissue of either young or aged apoE-/- mice. The expression of MCP-1 mRNA was increased in the lungs of young apoE-/- mice exposed to 0.9-2.7 mg/kg carbon black for 24 hours and of aged apoE-/- mice exposed to two consecutive 0.5 mg/kg doses of carbon black seven and five weeks prior to sacrifice.

CONCLUSION

Exposure to nano-sized carbon black particles is associated with modest vasomotor impairment, which is associated neither with nitrosative stress nor with any obvious increases in the expression of cell adhesion proteins on endothelial cells or in plaque progression. Evidence of pulmonary inflammation was observed, but only in animals exposed to higher doses.

Nanoparticles-containing spray can aerosol: characterization, exposure assessment, and generator design

This is the first report demonstrating that a commercially available household consumer product produces nanoparticles in a respirable range. This report describes a method developed to characterize nanoparticles that were produced under typical exposure conditions when using a consumer spray product. A well-controlled indoor environment was simulated for conducting spray applications approximating a human exposure scenario. Results indicated that, while aerosol droplets were large with a count median diameter of 22 µm during spraying, the final aerosol contained primarily solid TiO(2) particles with a diameter of 75 nm. This size reduction was due to the surface deposition of the droplets and the rapid evaporation of the aerosol propellant. In the breathing zone, the aerosol, containing primarily individual particles (>90%), had a mass concentration of 3.4 mg/m(3), or 1.6 × 10(5) particles/cm(3), with a nanoparticle fraction limited to 170 µg/m(3), or 1.2 × 10(5) particles/cm(3). The results were used to estimate the pulmonary dose in an average human (0.075 µg TiO(2) per m(2) alveolar epithelium per minute) and rat (0.03 µg TiO(2)) and, consequently, this information was used to design an inhalation exposure system. The system consisted of a computer-controlled solenoid ''finger'' for generating constant concentrations of spray can aerosols inside a chamber. Test results demonstrated great similarity between the solenoid ''finger''-dispersed aerosol compared to human-generated aerosol. Future investigations will include an inhalation study to obtain information on dose-response relationships in rats and to use it to establish a No Effect Exposure Level for setting guidelines for this consumer product.

Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association

In 2004, the first American Heart Association scientific statement on "Air Pollution and Cardiovascular Disease" concluded that exposure to particulate matter (PM) air pollution contributes to cardiovascular morbidity and mortality. In the interim, numerous studies have expanded our understanding of this association and further elucidated the physiological and molecular mechanisms involved. The main objective of this updated American Heart Association scientific statement is to provide a comprehensive review of the new evidence linking PM exposure with cardiovascular disease, with a specific focus on highlighting the clinical implications for researchers and healthcare providers. The writing group also sought to provide expert consensus opinions on many aspects of the current state of science and updated suggestions for areas of future research. On the basis of the findings of this review, several new conclusions were reached, including the following: Exposure to PM <2.5 microm in diameter (PM(2.5)) over a few hours to weeks can trigger cardiovascular disease-related mortality and nonfatal events; longer-term exposure (eg, a few years) increases the risk for cardiovascular mortality to an even greater extent than exposures over a few days and reduces life expectancy within more highly exposed segments of the population by several months to a few years; reductions in PM levels are associated with decreases in cardiovascular mortality within a time frame as short as a few years; and many credible pathological mechanisms have been elucidated that lend biological plausibility to these findings. It is the opinion of the writing group that the overall evidence is consistent with a causal relationship between PM(2.5) exposure and cardiovascular morbidity and mortality. This body of evidence has grown and been strengthened substantially since the first American Heart Association scientific statement was published. Finally, PM(2.5) exposure is deemed a modifiable factor that contributes to cardiovascular morbidity and mortality.

Nanoparticle inhalation impairs coronary microvascular reactivity via a local reactive oxygen species-dependent mechanism

We have shown that nanoparticle inhalation impairs endothelium-dependent vasodilation in coronary arterioles. It is unknown whether local reactive oxygen species (ROS) contribute to this effect. Rats were exposed to TiO(2) nanoparticles via inhalation to produce a pulmonary deposition of 10 microg. Coronary arterioles were isolated from the left anterior descending artery distribution, and responses to acetylcholine, arachidonic acid, and U46619 were assessed. Contributions of nitric oxide synthase and prostaglandin were assessed via competitive inhibition with N(G)-Monomethyl-L-Arginine (L-NMMA) and indomethacin. Microvascular wall ROS were quantified via dihydroethidium (DHE) fluorescence. Coronary arterioles from rats exposed to nano-TiO(2) exhibited an attenuated vasodilator response to ACh, and this coincided with a 45% increase in DHE fluorescence. Coincubation with 2,2,6,6-tetramethylpiperidine-N-oxyl and catalase ameliorated impairments in ACh-induced vasodilation from nanoparticle exposed rats. Incubation with either L-NMMA or indomethacin significantly attenuated ACh-induced vasodilation in sham-control rats, but had no effect in rats exposed to nano-TiO(2). Arachidonic acid induced vasoconstriction in coronary arterioles from rats exposed to nano-TiO(2), but dilated arterioles from sham-control rats. These results suggest that nanoparticle exposure significantly impairs endothelium-dependent vasoreactivity in coronary arterioles, and this may be due in large part to increases in microvascular ROS. Furthermore, altered prostanoid formation may also contribute to this dysfunction. Such disturbances in coronary microvascular function may contribute to the cardiac events associated with exposure to particles in this size range.

Nanoparticle inhalation impairs endothelium-dependent vasodilation in subepicardial arterioles

Exposure to fine particulate matter (PM, mean aerodynamic diameter <or=2.5 microm) has been shown to be a risk factor for cardiovascular disease mortality and may contribute to acute coronary events such as myocardial infarction (MI). There is sufficient reason to believe that smaller particles, such as nanoparticles, might be even more detrimental than larger sized particles due to their increased surface area and higher pulmonary deposition. Our laboratory showed that nanoparticle inhalation impairs endothelium-dependent arteriolar vasodilation in skeletal muscle. However, it is not known whether coronary microvascular endothelial function is affected in a similar manner. Rats were exposed to filtered air (control) or TiO(2) nanoparticles (primary particle diameter, approximately 21 nm) via inhalation at concentrations that produced measured depositions (10 microg) relevant to ambient air pollution. Subepicardial arterioles ( approximately 150 mum in diameter) were isolated and responses to transmural pressure, flow-induced dilation (FID), acetylcholine (ACh), the Ca(2+) ionophore A23187, and sodium nitroprusside (SNP) were assessed. Myogenic responsiveness was preserved between groups. In addition, there was no difference in the vasodilation to SNP, signifying that smooth muscle sensitivity to nitric oxide (NO) is unaffected by nano-TiO(2) exposure. However, inhalation of nano-TiO(2) produced an increase in spontaneous tone in coronary arterioles and also impaired endothelium-dependent FID. In addition, ACh-induced and A23187-induced vasodilation was also blunted in arterioles after inhalation of nano-TiO(2). Data showed that nanoparticle exposure significantly impairs endothelium-dependent vasodilation in subepicardial arterioles. Such disturbances in coronary microvascular function are consistent with the cardiac events associated with particle pollution exposure.