Health effects of ambient particulate matter--biological mechanisms and inflammatory responses to in vitro and in vivo particle exposures.

In this article, we review and analyze different modes of exposure to ultrafine particles in order to assess particle-induced inflammatory responses and the underlying mechanisms in vitro and in vivo. Based on results from monocytic cells cultured under submerged conditions, we discuss (1) the impact of particle properties such as surface area and oxidative potential on lipid metabolism as a highly sensitive regulatory pathway and (2) the interference of diesel exhaust particles with toll-like receptor-mediated inflammatory responses. Furthermore, new developments of air-liquid interface exposure used as an alternative approach to simulate cell particle interactions are presented. In addition to the in vitro approaches, animal exposure studies are described that apply selected mouse models to elucidate potential allergic and inflammatory pulmonary responses and mast-cell-related mechanisms after particle exposure. Long-term inhalation of ultrafine particles might lead to irreversible changes in lung structure and function. Clinical studies addressing the characteristics of inflammatory airway cells are a promising approach to understand underlying pathophysiological mechanisms in chronic obstructive pulmonary disease. Finally, a potential outcome of human particle exposure is chronic cough in children. Here, discrimination between asthmatic and nonasthmatic cough by means of immunological parameters appears to be an important step toward improving diagnosis and therapy.

Sulfur-related air pollutants induce the generation of platelet-activating factor, 5-lipoxygenase- and cyclooxygenase-products in canine alveolar macrophages via activation of phospholipases A2.

Recent studies have shown that long-term in vivo exposure of dogs to neutral sulfur(IV)/sulfite aerosols induces mild inflammatory reactions, whereas the combination of neutral sulfite with acidic sulfur(VI)/sulfate aerosols evokes less pronounced effects. To understand underlying mechanisms, we studied in vitro the role of lipid mediators in the responses of alveolar macrophages (AMs) to sulfur-related compounds under neutral (pH 7) or moderate acidic (pH 6) conditions. Canine AMs incubated with sulfite at pH 7 released threefold higher amounts of platelet-activating factor than control (P < 0.005). Generation of arachidonic acid, leukotriene B4, 5-hydroxy-eicosatetraenoic acid, prostaglandin E2, thromboxane B2 and 12-hydroxyheptadecatrienoic acid increased twofold (P < 0.0005). However, these metabolites remained unchanged following incubation of AMs with sulfite at pH 6 or with sulfate at pH 7 or pH 6. Mediator release by sulfite-treated AMs at pH 7 stimulated respiratory burst activity of neutrophils. Inhibition of MAPK pathway by PD 98059, of cytosolic (cPLA2) and secretory phospholipases A2 by AACOCF3 and thioetheramide-PC, respectively, reduced sulfite-induced eicosanoid formation in AMs. Sulfite activated cPLA2 activity twofold at pH 7. This mechanism of sulfite-stimulated responses in phospholipid metabolism predicts that chronic exposure to sulfur(IV)/sulfite is associated with a considerable health risk.

Cardiovascular responses in unrestrained WKY rats to inhaled ultrafine carbon particles.

Based on epidemiologic observations, the issue of adverse health effects of inhaled ultrafine particles (UFP) is currently under intensive discussion. We therefore examined cardiovascular effects of UFP in a controlled animal exposure on young, healthy WKY rats. Short-term exposure (24 h) to carbon UFPs (38 nm, 180 microg m (-3)), generated by spark discharging, induced a mild but consistent increase in heart rate (18 bpm, 4.8%), which was associated with a significant decrease in heart-rate variability during particle inhalation. The timing and the transient character of these responses point to a particle induced alteration of cardiac autonomic balance, mediated by a pulmonary receptor activation. After 24 h of inhalation exposure, bronchoalveolar lavage revealed significant but low-grade pulmonary inflammation (clean air 1.9% vs. UFPs 6.9% polymorphonuclear cells) and on histopathology sporadic accumulation of particle-laden macrophages was found in the alveolar region. There was no evidence of an inflammation-mediated increase in blood coagulability, as UFP inhalation did not induce any significant changes in plasma fibrinogen or factor VIIa levels and there were no prothrombotic changes in the lung or the heart at both the protein and mRNA level. Histological analysis revealed no signs of cardiac inflammation or cardiomyopathy. This study therefore provides toxicological evidence for UFP-associated pulmonary and cardiac effects in healthy rats. Our findings suggest that the observed changes are mediated by an altered sympatho-vagal balance in response to UFP inhalation, but do not support the concept of an inflammation-mediated prothrombotic state by UFP.

Inbred strain variation in lung function.

The purpose of the present study was to determine the strain-specific phenotype variance of lung function parameters among common inbred laboratory mouse strains. In accordance with the "Mouse Phenome Project" run by The Jackson Laboratory (http://www.jax.org/phenome), lung volumes, lung mechanics, and diffusing capacity of 16 males and 16 females of the strains C3H/HeJ, BALB/cByJ, C57B1/6J, A/J, FVB/J, 129SV/ImJ, and SWR/J were determined in a standardized manner. The defined respiratory maneuvers for lung function testing were performed with a custom-made, computer-controlled servo-ventilator in anesthetized animals. Sex differences within the strains were found in most (83%) of the absolute lung function parameters. Usually, normalization to body or lung size completely compensates for the observed gender differences. There was great diversity between strains for all of the lung function parameters studied; for example, the total lung capacity as well as the pulmonary diffusing capacity for carbon monoxide varied by 50% and the static lung compliance by a factor of almost two among the strains. Little, but statistically significant variability was detectable for the dead space volume and the respiratory system resistance. There was no clear-cut evidence for any strain exhibiting either the smallest or the largest values for all parameters studied, suggesting that there were no simple allometric relationships of lung size between the strains. Well-established genealogical relationships among strains were not constantly reflected in phenotype similarities of pulmonary function. Therefore, these data strongly support heritable genetic traits for pulmonary function. Moreover, it constitutes a basis for further genetic lung function-related studies.

Ultrafine particles cause cytoskeletal dysfunctions in macrophages.

Essential cytoskeletal functions of macrophages are migration, phagocytosis of foreign materials, and intracellular transport and digestion The influence of fine and ultrafine test particles (UFP), such as TiO(2), elemental carbon, commercial carbon black, diesel exhaust particulate matter, and urban dust (UrbD), on cytoskeleton-related functions of macrophages, such as phagocytosis, phagosome transport mechanisms, and mechanical cytoskeletal integrity, were studied by flow cytometry and by cytomagnetometry. Additionally, necrosis and apoptosis caused by the test particles was detected. The diameter of the test particles ranged from 12 to 220 nm and the Brunauer-Emmet-Teller specific surface area ranged from 6 to 600 m(2)/g. Primary alveolar macrophages from beagle dogs (BD-AM), obtained by bronchoalveolar lavage, were used as well as macrophages originating from the cell line J774A.1. For cytomagnetometry studies, spherical 1.8-microm ferromagnetic particles served as probes for cytoskeletal functions and were incubated together with the macrophages 24 h prior to UFP exposure. Macrophages were exposed in vitro with 10-320 microg UFP/ml/10(6) cells up to 24 h. In all experiments, J774A.1 macrophages were more sensitive than BD-AM to UFP exposure. Cytoskeletal dysfunctions evaluated by cytomagnetometry were an impaired phagosome transport and an increased cytoskeletal stiffness and occurred at concentrations of 100 microg UFP/ml/10(6) cells and above, in both BD-AM and J774A.1. Only fine TiO(2) did not show any effect. Urban dust (standard reference material 1649a) and diesel exhaust particles (DEP, standard reference material 1650) caused comparable cytoskeletal dysfunctions to elemental carbon with high specific surface area. Cytoskeletal dysfunctions induced by DEP or UrbD could be reduced after washing the particles by dichloromethane. UFP caused an impaired phagocytosis of 1-microm diameter fluorescent latex beads, inhibited cell proliferation, and decreased cell viability. All recorded cytotoxic parameters showed only weak correlations with the specific surface area or the total number of UFP, which can result from the different types of particles and different surface compositions. UFP cause cytoskeletal toxicity in vitro in macrophages, which can cause cellular dysfunctions, such as impaired proliferation, impaired phagocytic activity, and retarded intracellular transport processes as well as increased cell stiffness and can result in impaired defense ability in the lung.

Pulmonary and systemic effects of short-term inhalation exposure to ultrafine carbon black particles.

While environmental particles are associated with mortality and morbidity related to pulmonary and cardiovascular (CV) disease, the mechanisms involved in CV health effects are not known. Changes in systemic clotting factors have been associated with pulmonary inflammation. We hypothesized that inhaled ultrafine particles result in an inflammatory response which may stimulate systemic clotting factor release. Adult male Wistar rats were exposed to either fine or ultrafine carbon black (CB) for 7 h. The attained total suspended particle concentrations were 1.66 mg/m(3) for ultrafine CB and 1.40 mg/m(3) for fine CB. Particle concentration of ultrafine particles was more than 10 times greater than that of fine particles and the count median aerodynamic diameter averaged 114 nm for the ultrafine and 268 nm for the fine carbon particles. Data were collected immediately, 16 and 48 h following exposure. Only ultrafine CB caused an increase in total bronchoalveolar lavage (BAL) leukocytes, whereas both fine (2-fold) and ultrafine (4-fold) carbon particles caused an increase in BAL neutrophils at 16 h postexposure. Exposure to the ultrafine, but not fine, carbon was also associated with significant increases in the total numbers of blood leukocytes. Plasma fibrinogen, factor VII and von Willebrand factor (vWF) were unaffected by particle treatments as was plasma Trolox equivalent antioxidant status (TEAC). Macrophage inflammatory protein-2 mRNA was significantly increased in BAL cells 48 h following exposure to ultrafine CB. The data show that there is a small but consistent significant proinflammatory effect of this exposure to ultrafine particles that is greater than the effect of the same exposure to fine CB.