E-Selectin expression in human endothelial cells exposed to PM10: the role of endotoxin and insoluble fraction

Airborne particulate matter upregulates expression of early and late adhesion molecules and their receptors in a lung adenocarcinoma cell line

BACKGROUND

Epidemiological evidence associates chronic exposure to particulate matter (PM) with respiratory damage and lung cancer. Inhaled PM may induce systemic effects including inflammation and metastasis. This study evaluated whether PM induces expression of adhesion molecules in lung cancer cells promoting interaction with monocytes.

METHODS

The expression of early and late adhesion molecules and their receptors was evaluated in A549 (human lung adenocarcinoma) cells using a wide range of concentrations of PM_2.5 and PM₁₀. Then we evaluated cellular adhesion between A549 cells and U937 (human monocytes) cells after PM exposure.

RESULTS

We found higher expression of both early and late adhesion molecules and their ligands in lung adenocarcinoma cells exposed to PM_2.5 and PM₁₀ particles present in the air pollution at Mexico City from 0.03 μg/cm² with a statistically significant difference (p ≤ 0.05). PM₁₀ had stronger effect than PM_2.5. Both PM also stimulated cellular adhesion between tumor cells and monocytes.

CONCLUSIONS

This study reveals a comprehensive expression profile of adhesion molecules and their ligands upregulated by PM_2.5 and PM₁₀ in A549 cells. Additionally these particles induced cellular adhesion of lung cancer cells to monocytes. This highlights possible implications of PM in two cancer hallmarks i.e. inflammation and metastasis, underlying the high cancer mortality associated with air pollution.

Sources and monthly and seasonal concentration variation study of atmospheric particulates and particles-bound PAEs

The main goal of this study is to measure the ambient air of total suspended particulates at a mixed (traffic, residential and commercial) sampling site. And the concentrations of phthalate acid ester (PAE) which attached on total suspended particles were also analyzed. In addition, the possible sources of PAEs were also analyzed by the method of back trajectories. Finally, appropriate statistical methods were also used to test monthly and seasonal mean pollutants' (particulates, PAEs) concentration differences at this sampling site. The results indicated that the monthly concentration variation trends were similar for DEHP and total PAEs with the results as followed: November > October > July > December > September. In addition, back trajectories results also indicated that the main pollutant parcels were came from the east side of Taiwan in July. And the pollutant parcels were came from the north side of Taiwan during the month of September, October, November and December in this study. Moreover, the results also showed that the DEHP, DNOP, total PAEs' concentrations with TSP and meteorological conditions were not significantly different. But the relationship among DEHP, DNOP and total PAEs was significantly different; particularly, the relationship between DEHP and total PAEs was highly correlated in this study (R² = 0.994). Finally, the statistical analysis of total PAEs T test statistic for mean monthly concentrations results suggested that the sample population means were not differed significantly. In other words, there were not any mean monthly concentration differences for PAEs at this sampling site. The only exception was occurred in the month of September versus November. The results showed that there is a statistically significant PAEs' concentration difference between the input groups (September vs. November).

Urban particulate matter induces the expression of receptors for early and late adhesion molecules on human monocytes

Exposure to urban particulate matter (PM) is correlated with increases in the emergence of health services due to adverse events and deaths and is mainly related to cardiorespiratory complications. The translocation of particles from the lung into circulation has been proposed as a factor that may trigger systemic effects. Monocytes may be exposed to PM, and if the monocytes are activated, then they are likely to adhere to endothelial cells in a distant organ due to the expression of receptors for adhesion molecules. In the present study, we evaluated the expression of receptors for adhesion molecules (sLe^x, PSGL-1, LFA-1, VLA-4 and α_Vβ₃) in monocytes (U937 cells) exposed for 3 or 18 h to PM₁₀ (0.001, 0.003, 0.010, 0.030, 0.300, 3 or 30 µg/mL). Exposed cells were co-cultured with human endothelial cells that were naive or previously exposed to the same particles. When U937 cells were exposed to PM₁₀, similar levels of expression for early and late receptors for adhesion molecules were observed from 30 ng/mL as those induced by TNF-α. Cells exposed to particles at concentrations above 30 ng/mL were more adhesive to naive or exposed human endothelial cells. Taken together, our results suggest that it is plausible that activated monocytes may play a role in systemic effects induced by PM₁₀ due to the size distribution of the particles and the concentrations required to trigger the expression of receptors for adhesion molecules in monocytes.

Curcumin inhibits activation induced by urban particulate material or titanium dioxide nanoparticles in primary human endothelial cells

Curcumin has protective effects against toxic agents and shows preventive properties for various diseases. Particulate material with an aerodynamic diameter of ≤10 μm (PM10) and titanium dioxide nanoparticles (TiO2-NPs) induce endothelial dysfunction and activation. We explored whether curcumin is able to attenuate different events related to endothelial activation. This includes adhesion, expression of adhesion molecules and oxidative stress induced by PM10 and TiO2-NPs. Human umbilical vein endothelial cells (HUVEC) were treated with 1, 10 and 100 μM curcumin for 1 h and then exposed to PM10 at 3 μg/cm2 or TiO2-NPs at 10 μg/cm2. Cell adhesion was evaluated by co-culture with U937 human myelomonocytic cells. Adhesion molecules expression was measured by flow cytometry after 3 or 24 h of exposure. Oxidative stress was determined by 2,7-dichlorodihydrofluorescein (H2DCF) oxidation. PM10 and TiO2-NPs induced the adhesion of U937 cells and the expression of E- and P-selectins, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and platelet-endothelial cell adhesion molecule-1 (PECAM-1). The expression of E- and P-selectins matched the adhesion of monocytes to HUVEC after 3 h. In HUVEC treated with 1 or 10 μM curcumin, the expression of adhesion molecules and monocytes adhesion was significantly diminished. Curcumin also partially reduced the H2DCF oxidation induced by PM10 and TiO2-NPs. Our results suggest an anti-inflammatory and antioxidant role by curcumin attenuating the activation caused on endothelial cells by exposure to particles. Therefore, curcumin could be useful in the treatment of diseases where an inflammatory process and endothelial activation are involved.

Titanium dioxide nanoparticles induce the expression of early and late receptors for adhesion molecules on monocytes

BACKGROUND

There is growing evidence that exposure to titanium dioxide nanoparticles (TiO2 NPs) could be harmful. Previously, we have shown that TiO2 NPs induces endothelial cell dysfunction and damage in glial cells. Considering that inhaled particles can induce systemic effects and the evidence that nanoparticles may translocate out of the lungs, we evaluated whether different types of TiO2 NPs can induce the expression of receptors for adhesion molecules on monocytes (U937 cell line). We evaluated the role of reactive oxygen spices (ROS) on these effects.

METHODS

The expression of receptors for early (sLe(x) and PSGL-1) and late (LFA-1, VLA-4 and αVβ3) adhesion molecules was evaluated in U937 cells on a time course (3-24 h) using a wide range of concentrations (0.001-100 μg/mL) of three types of TiO2 NPs (<25 nm anatase, 50 nm anatase-rutile or < 100 nm anatase). Cells exposed to TNFα were considered positive controls, and unexposed cells, negative controls. In some experiments we added 10 μmolar of N-acetylcysteine (NAC) to evaluate the role of ROS.

RESULTS

All tested particles, starting at a concentration of 0.03 μg/mL, induced the expression of receptors for early and late adhesion molecules. The largest increases were induced by the different molecules after 3 h of exposure for sLe(x) and PSGL-1 (up to 3-fold of the positive controls) and after 18 h of exposure for LFA-1, VLA-4 and αVβ3 (up to 2.5-fold of the positive controls). Oxidative stress was observed as early as 10 min after exposure, but the maximum peak was found after 4 h of exposure. Adhesion of exposed or unexposed monocytes to unexposed or exposed endothelial cells was tested, and we observed that monocytes cells adhere in similar amounts to endothelial cells if one of the two cell types, or both were exposed. When NAC was added, the expression of the receptors was inhibited.

CONCLUSIONS

These results show that small concentrations of particles may activate monocytes that attach to endothelial cells. These results suggest that distal effects can be induced by small amounts of particles that may translocate from the lungs. ROS play a central role in the induction of the expression of these receptors.

Particulate matter (PM₁₀) induces metalloprotease activity and invasion in airway epithelial cells

Airborne particulate matter with an aerodynamic diameter ≤ 10 μm (PM10) is a risk factor for the development of lung diseases and cancer. The aim of this work was to identify alterations in airway epithelial (A549) cells induced by PM10 that could explain how subtoxic exposure (10 μg/cm(2)) promotes a more aggressive in vitro phenotype. Our results showed that cells exposed to PM10 from an industrial zone (IZ) and an urban commercial zone (CZ) induced an increase in protease activity and invasiveness; however, the cell mechanism is different, as only PM10 from CZ up-regulated the activity of metalloproteases MMP-2 and MMP-9 and disrupted E-cadherin/β-catenin expression after 48 h of exposure. These in vitro findings are relevant in terms of the mechanism action of PM10 in lung epithelial cells, which could be helpful in understanding the pathogenesis of some human illness associated with highly polluted cities.

Docosahexaenoic acid regulates gene expression in HUVEC cells treated with polycyclic aromatic hydrocarbons

The molecular mechanism of inflammation and carcinogenesis induced by exposure of polycyclic aromatic hydrocarbons (PAHs) is not clearly understood. Our study was undertaken due to the strong pro-carcinogenic potential and reactivity of PAH-metabolites, as well as the susceptibility of polyunsaturated fatty acids to oxidation. The aim of this study was to evaluate the pro- or anti-inflammatory impact of n-3 docosahexaenoic acid on human primary umbilical vein endothelial cells (HUVEC) exposed to polycyclic aromatic hydrocarbons. We analysed the influence of docosahexaenoic acid (DHA) and/or PAHs supplementation on the fatty acid profile of cell membranes, on cyclooxygenase-2 (COX-2), aryl hydrocarbon receptor (AHR), and glutathione S transferase Mu1 (GSTM1) protein expression as well as on the prostaglandin synthase 2 (PTGS2), AHR, GSTM1, PLA2G4A, and cytochrome P450 CYP1A1 gene expression. We observed that COX-2 and AHR protein expression was increased while GSTM1 expression was decreased in cells exposed to DHA and PAHs. Docosahexaenoic acid down-regulated CYP1A1 and up-regulated the AHR and PTGS2 genes. Our findings suggested that DHA contributes significantly to alleviate the harmful effects caused by PAHs in endothelial cells. Moreover, these results suggest that a diet rich in n-3 fatty acids is helpful to reduce the harmful effects of PAHs exposure on human living in heavily polluted areas.

Toxicology of ambient particulate matter

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

In vitro and in vivo toxicity of urban and rural particulate matter from California

Particulate matter (PM) varies in chemical composition and mass concentration based on location, source, and particle size. This study sought to evaluate the in vitro and in vivo toxicity of coarse (PM_10-2.5) and fine (PM₂₅) PM samples collected at 5 diverse sites within California. Coarse and fine PM samples were collected simultaneously at 2 rural and 3 urban sites within California during the summer. A human pulmonary microvascular endothelial cell line (HPMEC-ST1.6R) was exposed to PM suspensions (50 μg/mL) and analyzed for reactive oxygen species (ROS) after 5 hours of treatment. In addition, FVB/N mice were exposed by oropharyngeal aspiration to 50 μg PM, and lavage fluid was collected 24 hrs post-exposure and analyzed for total protein and %PMNs. Correlations between trace metal concentrations, endotoxin, and biological endpoints were calculated, and the effect of particle size range, locale (urban vs. rural), and location was determined. Absolute principal factor analysis was used to identify pollution sources of PM from elemental tracers of those sources. Ambient PM elicited an ROS and pro-inflammatory-related response in the cell and mouse models, respectively. These responses were dependent on particle size, locale, and location. Trace elements associated with soil and traffic markers were most strongly linked to the adverse effects in vitro and in vivo. Particle size, location, source, and composition of PM collected at 5 locations in California affected the ROS response in human pulmonary endothelial cells and the inflammatory response in mice.

Air pollution, inflammation and preterm birth: a potential mechanistic link

Preterm birth is a public health issue of global significance, which may result in mortality during the perinatal period or may lead to major health and financial consequences due to lifelong impacts. Even though several risk factors for preterm birth have been identified, prevention efforts have failed to halt the increasing rates of preterm birth. Epidemiological studies have identified air pollution as an emerging potential risk factor for preterm birth. However, many studies were limited by study design and inadequate exposure assessment. Due to the ubiquitous nature of ambient air pollution and the potential public health significance of any role in causing preterm birth, a novel focus investigating possible causal mechanisms influenced by air pollution is therefore a global health priority. We hypothesize that air pollution may act together with other biological factors to induce systemic inflammation and influence the duration of pregnancy. Evaluation and testing of this hypothesis is currently being conducted in a prospective cohort study in Mexico City and will provide an understanding of the pathways that mediate the effects of air pollution on preterm birth. The important public health implication is that crucial steps in this mechanistic pathway can potentially be acted on early in pregnancy to reduce the risk of preterm birth.

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.

Dehydroepiandrosterone protects endothelial cells against inflammatory events induced by urban particulate matter and titanium dioxide nanoparticles

Particulate matter (PM) and nanoparticles (NPs) induce activation and dysfunction of endothelial cells characterized by inhibition of proliferation, increase of adhesion and adhesion molecules expression, increase of ROS production, and death. DHEA has shown anti-inflammatory and antioxidant properties in HUVEC activated with proinflammatory agents. We evaluated if DHEA could protect against some inflammatory events produced by PM10 and TiO2 NPs in HUVEC. Adhesion was evaluated by a coculture with U937 cells, proliferation by crystal violet staining, and oxidative stress through DCFDA and Griess reagent. PM10 and TiO2 NPs induced adhesion and oxidative stress and inhibited proliferation of HUVEC; however, when particles were added in combination with DHEA, the effects previously observed were abolished independently from the tested concentrations and the time of addition of DHEA to the cultures. These results indicate that DHEA exerts significant anti-inflammatory and antioxidative effects on the damage induced by particles in HUVEC, suggesting that DHEA could be useful to counteract the harmful effects and inflammatory diseases induced by PM and NPs.

Feasibility of using biomarkers in blood serum as markers of effect following exposure of the lungs to particulate matter air pollution

Particulate matter (PM) air pollution has significant cardiopulmonary health effects. Serum biomarkers may elucidate the disease mechanisms involved and provide a means for biomonitoring exposed populations, thereby enabling accurate policy decisions on air quality standards to be made. For this review, research investigating association of blood serum biomarkers and exposure to PM was identified, finding 26 different biomarkers that were significantly associated with exposure. Recent evidence links different effects to different components of PM. Future research on biomarkers of effect will need to address exposure by all PM size fractions.

TiO2 nanoparticles induce endothelial cell activation in a pneumocyte-endothelial co-culture model

The effects of particulate matter (PM) on endothelial cells have been evaluated in vitro by exposing isolated endothelial cells to different types of PM. Although some of the findings from these experiments have been corroborated by in vivo studies, an in vitro model that assesses the interaction among different cell types is necessary to achieve more realistic assays. We developed an in vitro model that mimics the alveolar-capillary interface, and we challenged the model using TiO nanoparticles (TiO-NPs). Human umbilical endothelial cells (HUVECs) were cultured on the basolateral side of a membrane and pneumocytes (A549) on the apical side. Confluent co-cultures were exposed on the apical side to 10 μg/cm of TiO-NPs or 10 ng/mL of TNFα for 24 h. Unexposed cultures were used as negative controls. We evaluated monocyte adhesion to HUVECs, adhesion molecule expression, nitric oxide concentration and proinflammatory cytokine release. The TiO-NPs added to the pneumocytes induced a 3- to 4-fold increase in monocyte adhesion to the HUVECs and significant increases in the expression of adhesion molecules (4-fold for P-selectin at 8 h, and about 8- and 10-fold for E-selectin, ICAM-1, VCAM-1 and PECAM-1 at 24 h). Nitric oxide production also increased significantly (2-fold). These results indicate that exposing pneumocytes to TiO-NPs causes endothelial cell activation.

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

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

Potential of coculture in vitro models to study inflammatory and sensitizing effects of particles on the lung

Exposure to particulate matter (PM) like nanoparticles (NPs) has increased in the last century due to increased combustion processes, road traffic, etc. In addition, the progress in chemical and cosmetic industry led to many new compounds, e.g. fragrances, which humans are exposed to every day. Many chemicals are known to act as contact and some as respiratory sensitizers, causing allergic reactions. Exposure to small particles of less than 100 nm in diameter is linked with an increased risk of respiratory diseases, such as asthma or rhinitis. To date already more than 1000 customer products contain eNPs without knowing much about the health effects. In comparison to chemicals, the mechanisms by which PM and eNPs can cause sensitization are still not fully understood. Validated and regulatory accepted in vitro models to assess this hazard in its full range are still missing. While a huge number of animal studies contributed to our knowledge about sensitization processes, knowledge on involved cellular mechanisms is still limited. In this review relevant in vitro models to study and elucidate these mechanisms in more detail are presented and their potential to serve as part of a tiered testing strategy is discussed.

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.

Endotoxin and polycyclic aromatic hydrocarbons in ambient fine particulate matter from Fresno, California initiate human monocyte inflammatory responses mediated by reactive oxygen species

In urban areas, a correlation between exposure to particulate matter (PM) from air pollution and increased cardiovascular morbidity and mortality has been observed. Components of PM include bacterial contaminants, transition metals, salts, polycyclic aromatic hydrocarbons (PAH), and carbonaceous material, which could interact with various cell types to produce systemic responses when inhaled. We examined the effects of PM collected from Fresno, California on activation of human monocytes and their interaction with vascular endothelium, a key event in atherogenesis. PM exposure increased cytokine expression and secretion from monocytes and enhanced monocyte adhesion to human aortic endothelial cells, both of which were attenuated by neutralizing endotoxin. PM also increased monocyte CYP1a1 expression, and inhibition of the aryl hydrocarbon receptor reduced the CYP1a1 and inflammatory responses. PM-treated monocytes accumulated intracellular reactive oxygen species (ROS), and antioxidants attenuated inflammatory and xenobiotic responses. Finally, supernatants from PM-treated pulmonary microvascular endothelial cells induced monocyte inflammatory responses that were not a consequence of endotoxin transfer. These results suggest that certain components of urban PM, namely endotoxin and PAH, activate circulating monocytes directly or indirectly by first stimulating other cells such as pulmonary endothelial cells, providing several mechanisms by which PM inhalation could induce pulmonary and/or systemic inflammation.

Cytological damage of nasal epithelium associated with decreased glutathione peroxidase in residents from a heavily polluted city

OBJECTIVE

To evaluate the cytological damage and glutathione peroxidase (GPX) content in the nasal epithelium of residents of Southwest Metropolitan Mexico City (SWMMC) along 1 year of ozone and PM(10) exposure.

METHOD

Four nasal scrapings were obtained in 20 volunteers from a control low polluted city and SWMMC permanent residents (n = 20) during 1 year. The scrapings were obtained in September and December 2004, and February and May 2005. One part of the scraping was stained by hematoxylin-eosin technique for cytological evaluation and a second part was stained by immunocytochemistry method to evaluate GPX concentration by morphometry.

RESULTS

Control subjects: in total, 30% had no cytological alterations and 70% showed only mild or moderate inflammation in four nasal scrapings. All SWMMC residents showed moderate to severe inflammatory processes in some scrapings. Additionally, dysplasia was found once (in 2 cases) or more than on scraping in five cases (25%). GPX concentration in the control group remained highest in median values throughout the study. SWMMC residents with the highest median values of GPX content were found in the May and September scrapings, and the lowest median values were found in December and February when Ozone and PM(10) levels are increased (P < or = 0.05). A lower GPX content was found as the cytological damage increased (P < or = 0.001).

CONCLUSION

Cytological evaluation of nasal epithelium and GPX immunodetection are satisfactory methods to evaluate the earliest damage produced by atmospheric pollution in heavily contaminated cities.

PM2.5 and PM10 induce the expression of adhesion molecules and the adhesion of monocytic cells to human umbilical vein endothelial cells

Exposure to airborne particles has been associated with an increase in cardiopulmonary events. Endothelial cells could be playing an important role in the response to airborne particles due their involvement in proinflammatory events, and there is some evidence of particle translocation from lung into circulation. One of the initiating events of inflammation is endothelial activation. We determined the concentration-response effect of a particulate matter with different aerodynamic sizes (PM2.5 [particulate matter with aerodynamic diameter of 2.5 microm and less] and PM10 [particulate matter with aerodynamic diameter of 10 microm and less]) obtained from Mexico City on human umbilical vein endothelial cells (HUVEC). The adhesion of monocytic U937 cells to HUVEC and the expression of early (E- and P-selectins) and late (ICAM-1, PECAM-1, VCAM-1) adhesion molecules were tested. Adhesion of U937 cells to HUVEC was evaluated by coculture experiments using [3H]thymidine-labeled U937 cells and the expression of adhesion molecules was evaluated by flow cytometry. Tumor necrosis factor (TNF)-alpha was used as a positive control of endothelial activation. Our results showed that both PM2.5 and PM10 induced the adhesion of U937 cells to HUVEC, and their maximal effect was observed at 20 microg/cm2. This adhesion was associated with an increase in the expression of all adhesion molecules evaluated for PM10, and E-selectin, P-selectin, and ICAM-1 for PM2.5. In general, maximum expression of adhesion molecules induced by PM2.5 and PM10 was obtained with 20 microg/cm2; however, PM10-induced expression was observed from 5 microg/cm2. E-selectin and ICAM-1 had the strongest expression in response to particles. In conclusion, PM2.5 and PM10 induce the activation of HUVEC, leading to monocytic adhesion via the expression of adhesion molecules, suggesting that these particles may participate in the development of inflammatory diseases. The role of these events in the development of diseases such as atherosclerosis is likely to be evaluated.

Enhanced peripheral thrombogenicity after lung inflammation is mediated by platelet-leukocyte activation: role of P-selectin

BACKGROUND

Inhaled ultrafine particles trigger peripheral thrombotic complications.

METHODS

We have analyzed the systemic prothrombotic risk following lung inflammation induced by pulmonary carbon nanotubes (CNTs).

RESULTS

Intratracheal instillation in Swiss mice of 200 and 400 microg of multiwall ground CNTs triggered substantial lung neutrophil, but not macrophage influx, 24 h later. The detection of circulating platelet-leukocyte conjugates exclusively 6 h after CNT instillation pointed to early but transient activation of circulating platelets. At 24 h, elevated plasma procoagulant microvesicular tissue factor activity was found in CNT-exposed but not in saline-exposed mice. However, at 24 h, both the tail and jugular vein bleeding times were prolonged in CNT-exposed but not in saline-exposed mice, arguing against strong CNT-induced platelet activation at this point. Nevertheless, at 24 h, enhanced peripheral thrombogenicity was detected in CNT-exposed but not in saline-exposed mice, via quantitative photochemically induced carotid artery thrombosis measurements. P-selectin neutralization abrogated platelet-leukocyte conjugate formation and microvesicular tissue factor generation, and abolished the CNT-induced thrombogenicity amplification. In contrast, the weak vascular injury-triggered thrombus formation in saline-treated mice was not affected by P-selectin neutralization at 24 h.

CONCLUSIONS

The mild CNT-induced lung inflammation translates via rapid but mild and transient activation of platelets into P-selectin-mediated systemic inflammation. Leukocyte activation leads to tissue factor release, in turn eliciting inflammation-induced procoagulant activity and an associated prothrombotic risk.