Systemic Effect of Particulate Air Pollution

Airway exposure to silica-coated TiO2 nanoparticles induces pulmonary neutrophilia in mice

The importance of nanotechnologies and engineered nanoparticles has grown rapidly. It is therefore crucial to acquire up-to-date knowledge of the possible harmful health effects of these materials. Since a multitude of different types of nanosized titanium dioxide (TiO(2)) particles are used in industry, we explored their inflammatory potential using mouse and cell models. BALB/c mice were exposed by inhalation for 2 h, 2 h on 4 consecutive days, or 2 h on 4 consecutive days for 4 weeks to several commercial TiO(2) nanoparticles, SiO(2) nanoparticles, and to nanosized TiO(2) generated in a gas-to-particle conversion process at 10 mg/m(3). In addition, effects of in vitro exposure of human macrophages and fibroblasts (MRC-9) to the different particles were assessed. SiO(2)-coated rutile TiO(2) nanoparticles (cnTiO(2)) was the only sample tested that elicited clear-cut pulmonary neutrophilia. Uncoated rutile and anatase as well as nanosized SiO(2) did not induce significant inflammation. Pulmonary neutrophilia was accompanied by increased expression of tumor necrosis factor-alpha (TNF-alpha) and neutrophil-attracting chemokine CXCL1 in the lung tissue. TiO(2) particles accumulated almost exclusively in the alveolar macrophages. In vitro exposure of murine and human macrophages to cnTiO(2) elicited significant induction of TNF-alpha and neutrophil-attracting chemokines. Stimulation of human fibroblasts with cnTiO(2)-activated macrophage supernatant induced high expression of neutrophil-attracting chemokines, CXCL1 and CXCL8. Interestingly, the level of lung inflammation could not be explained by the surface area of the particles, their primary or agglomerate particle size, or radical formation capacity but is rather explained by the surface coating. Our findings emphasize that it is vitally important to take into account in the risk assessment that alterations of nanoparticles, e.g., by surface coating, may drastically change their toxicological potential.

Delayed Exacerbation of Acute Myocardial Ischemia/Reperfusion-Induced Arrhythmia by Tracheal Instillation of Diesel Exhaust Particles

For understanding the relationship between the increased incidence of sudden cardiac death and air pollution, we examined the effects of intratracheal instillation of diesel exhaust particles (DEP) on acute myocardial ischemia/reperfusion-induced arrhythmia in rats. The animals received 1 mg DEP 24-48 h before the ischemia/reperfusion (DEP-pretreated group, DEP-PRE), and were subjected to 3 successive brief ischemia/reperfusion (3 min ischemia followed by 5 min reperfusion) procedures. These were to make the animals tolerant to ischemia/reperfusion-related myocardial deterioration. Thereafter the animals were subjected to a 10-min ischemia followed by a 30-min reperfusion. In the experiments, an increased mortality was observed in the DEP-PRE group compared to the vehicle (0.05% Tween 80-PBS)-treated group. Forty-six percent of the animals in DEP-PRE died during the first 3-min reperfusion period. The animals of other groups were intratracheally instilled with DEP at the beginning of ischemia/reperfusion experiment, or were pretreated with polyethylene glycol-conjugated superoxide dismutase (1000 IU kg(-1), iv). In these animals, incidences of both arrhythmia and mortality were similar to those in the animals treated with the vehicle. In experiments to investigate the effects of DEP on the biochemical and hematological parameters, neutrophil count was elevated by a higher dose (5 mg) of DEP at 24 h after the intratracheal instillation, and oxygen radical production, which was induced by 12-O-tetradecanoylphorbol 13-acetate, was enhanced at 72 h. These results indicate that intratracheal DEP instillation exacerbates short-period ischemia/reperfusion-induced arrhythmia. Delivery and activation of peripheral neutrophils and oxygen radicals produced in neutrophils might participate in this exacerbation. This is the first article that demonstrates the arrhythmogenicity of DEP using intratracheal instillation in rats.

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

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

Inflammation, edema, and peripheral blood changes in lung-compromised rats after instillation with combustion-derived and manufactured nanoparticles

Increased exposure to pollution has been implicated in cardiovascular malfunction, and although studies show a relationship between PM10 and mortality, the exact biological causes are unclear. This study investigated how compromised lungs respond to instillation of nanoparticles, and the links between exposure to nanoparticles and the subsequent effects on the blood. Instillation of diesel exhaust particles and Cabosil caused significant permeability and inflammatory changes in both bleomycin-treated and control lungs, as shown by increased lung surface protein and lung:body weight ratio. This was true in edematous and maximally repairing lungs, but without significant hematological alterations. Plasma viscosity, a renowned marker for cardiovascular disease, correlated strongly statistically with free cell numbers, type I cell marker rT140, and lung acellular protein. These correlations are a new and novel insight into the mechanisms linking air pollution to cardiovascular mortality.

Differential responses of rat alveolar macrophages to carpet dust in vitro

Epidemiological studies of workers in carpet weaving units in carpet industries have shown a direct relation between the concentration of carpet dust in the air and respiratory symptoms. To predict the health risk of carpet weavers, this preliminary study was conducted to evaluate the toxic potential of different types of workplace dust by using alveolar macrophages (AMs). Several parameters were observed for cytotoxicity such as cell viability, the release of lactate dehydrogenase (LDH) in rat AMs treated with different concentration of carpet dust and haemolytic potential of erythrocytes. In addition, reactive oxygen/nitrogen species-inducing effects of carpet dust were assessed by nitric oxide (NO), reduced glutathione (GSH) release and hydrogen peroxide (H2O2) generation in AMs. Results of cell viability and hemolytic assay showed a direct correlation between increasing the dust concentration with enhancing the toxic effect. Knotted and tufted carpet dust increases the release of LDH, NO, GSH and H2O2 production with increasing dust concentration. Present observations have revealed that dusts collected from tufted carpet weaving units exhibited more toxicity to AMs than knotted carpet dust. These data further suggest that injurious effects of carpet dust to AMs could pave a way to evaluate the toxic potential of the different types of workplace dusts and component(s) involved in it.

Histone acetylation regulates epithelial IL-8 release mediated by oxidative stress from environmental particles

Increases in the levels of environmental particulate matter with a diameter of <10 microm diameter (PM(10)) in the air are associated with a variety of adverse health effects, particularly chronic lung and cardiovascular diseases. The expression of many inflammatory genes involves the remodeling of the chromatin structure provided by histone proteins. Histone acetylation causes the unwinding of chromatin structure, therefore allowing transcription factor access to promoter sites. Acetylation is reversible and is regulated by histone acetyltransferases (HATs), which promote acetylation, and deacetylases, which promote deacetylation. PM(10) and H(2)O(2) increased IL-8 protein release from A549 cells after 24-h treatment, and this was enhanced by histone deacetylase inhibition by trichostatin A (cotreatment). PM(10) and H(2)O(2) treatment also increased HAT activity as well as the level of acetylated histone 4 (H4). PM(10) enhanced H4 acetylation that was mediated by oxidative stress as shown by thiol antioxidant inhibition. Acetylation of H4 mediated by PM(10) was associated with the promoter region of the IL-8 gene. These data suggest that remodeling of chromatin by histone acetylation plays a role in PM(10)-mediated responses in the lungs.

Ambient particulate matter induces relaxation of rat aortic rings in vitro

Epidemiological studies have shown an association between ambient levels of particulate matter (PM) and increased mortality from cardiovascular diseases. However, the underlying mechanisms are still not clear. We hypothesised that PM, when translocated after inhalation, could affect vascular smooth muscle function. Therefore, total suspended particulate matter (TSP) was sampled and investigated for its ability to affect aortic muscle contraction. Both TSP and TSP supernatant (TSP-sup) induced a concentration-dependent relaxation of phenylephrine (PE)-precontracted aortic rings. Relaxation induced by 100 microg/ml TSP was 51.5 +/- 3.1% of total contraction. At 60 and 100 microg/ml, relaxation induced by TSP was significantly higher compared to TSP-sup. Ultrafine TiO2, used as a model to investigate the role of ultrafine particles, did not show an effect. Soluble iron, present in TSP suspensions, seems not to be involved, as chelating with deferoxamine did not affect TSP-induced relaxation. However, TSP effects were inhibited by Trolox, suggesting a role of oxidants. Nudation of aortic rings showed that effects of TSP were only partly endothelium-dependent, while preincubation with L-NAME increased TSP-induced relaxation. From these data, we conclude that both the particle core and soluble components of TSP can affect the smooth muscle function, leading to changes in the vascular contractile response.