Joachim Heyder

Instillation of six different ultrafine carbon particles indicates a surface area threshold dose for acute lung inflammation in mice.

Increased levels of particulate air pollution are associated with increased respiratory and cardiovascular mortality and morbidity. Some epidemiologic and toxicologic research suggests ultrafine particles (UFPs) (< 100 nm) to be more harmful per unit mass than larger particles. Our study was aimed at a quantitative comparison of acute adverse effects of different types of carbonaceous UFPs at a dose range that causes a moderate inflammatory response in lungs. We used six different particle types (primary particle size 10–50 nm, specific surface area 30–800 m2/g, and organic content 1–20%): PrintexG, Printex90, flame soot particles with different organic content (SootL, SootH), spark-generated ultrafine carbon particles (ufCP), and the reference diesel exhaust particles (DEP) SRM1650a. Mice were instilled with 5, 20, and 50 μg of each particle type, and bronchoalveolar lavage was analyzed 24 hr after instillation for inflammatory cells and the level of proinflammatory cytokines. At respective mass-doses, particle-caused detrimental effects ranked in the following order: ufCP > SootL ≥ SootH > Printex90 > PrintexG > DEP. Relating the inflammatory effects to the particle characteristics—organic content, primary particle size, or specific surface area—demonstrates the most obvious dose response for particle surface area. Our study suggests that the surface area measurement developed by Brunauer, Emmett, and Teller is a valuable reference unit for the assessment of causative health effects for carbonaceous UFPs. Additionally, we demonstrated the existence of a threshold for the particle surface area at an instilled dose of approximately 20 cm2, below which no acute proinflammatory responses could be detected in mice.

Aerodynamics and aerosol particle deaggregation phenomena in model oral-pharyngeal cavities

Abstract The results of numerical simulations of the aerodynamics and of solid aerosol deaggregation phenomena arising in the process of airflow through various model human oropharyngeal cavities are reported. Special attention is given to the relevance of these simulations to the inhalation of dry-powder therapeutic aerosols. Several two- and three-dimensional mouth and throat geometries (terminating just beyond the larynx) are considered. Cross-sectional area-averaged viscous stress values are numerically determined as a function of distance from the mouth opening. These values, ranging from approximately 10 to 500 dyn cm −2 , are compared with estimates of Van der Waals attractive forces per unit area of particle-particle contact so as to evaluate the ability of the flowing airstream to deaggregate aerosol particles that enter the mouth in an aggregated state (held together principally by Van der Waals attractive forces). Estimates of airstream viscous stress differ markedly depending on whether the geometry is two- or three-dimensional. Quantitative differences between flow in a 90°-bend model and an oropharyngeal geometry numerically reconstructed from a cast of a human mouth and throat are especially significant in regards to the ability of the airstream to break apart particle agglomerates. For all geometries it is observed that increasingly smaller particle agglomerates may potentially be separated as the airflow rate increases from 30 to 2001 min −1 . At the highest airflows, aggregated particles of diameter near to or even below 1 μm may potentially be separated by the airflow. If separation of particle agglomerates is to occur, it appears far more likely to take place in the throat than in the mouth. This is especially apparent for the more physiologically faithful oropharyngeal geometries considered.

Prostanoids mediate IL-1β-induced β-adrenergic hyporesponsiveness in human airway smooth muscle cells

We have previously reported that pretreatment of cultured human airway smooth muscle (HASM) cells with interleukin-1β (IL-1β) results in decreased β-adrenergic responsiveness. The purpose of this study was to determine whether prostanoids released as a result of cyclooxygenase-2 (COX-2) induction by IL-1β contribute to this effect of the cytokine. Confluent serum-deprived HASM cells were studied in passages 4-7. IL-1β (20 ng/ml for 22 h) reduced the ability of the β-agonist isoproterenol (Iso) to decrease stiffness of HASM cells as measured by magnetic twisting cytometry. The effect of IL-1β on Iso-induced changes in cell stiffness was abolished by nonselective [indomethacin (Indo), 10-6 M] and selective (NS-398, 10-5 M) COX-2 inhibitors. Indo and NS-398 also inhibited both the increased basal cAMP and the decreases in Iso-stimulated cAMP production induced by IL-1β. IL-1β (20 ng/ml for 22 h) caused an increase in both basal (15-fold) and arachidonic acid (AA)-stimulated (10-fold) PGE2 release. Indo blocked basal and AA-stimulated PGE2 release in both control and IL-1β-treated cells. NS-398 also markedly reduced basal and AA-stimulated PGE2release in IL-1β-treated cells but had no significant effect on AA-stimulated PGE2 release in control cells. Western blot analysis confirmed the induction of COX-2 by IL-1β. Exogenously administered PGE2(10-7 M, 22 h) caused a significant reduction in the ability of Iso to decrease cell stiffness, mimicking the effects of IL-1β. Cycloheximide (10 μg/ml for 24 h), an inhibitor of protein synthesis, also abolished the effects of IL-1β on Iso-induced cell stiffness changes and cAMP formation. In summary, our results indicate that IL-1β significantly increases prostanoid release by HASM cells as a result of increased COX-2 expression. The prostanoids appear to contribute to β-adrenergic hyporesponsiveness, perhaps by heterologous desensitization of the β2 receptor.

Mucociliary and long-term particle clearance in airways of patients with immotile cilia.

Spherical monodisperse ferromagnetic iron oxide particles of 1.9 μm geometric and 4.2 μm aerodynamic diameter were inhaled by seven patients with primary ciliary dyskinesia (PCD) using the shallow bolus technique, and compared to 13 healthy non-smokers (NS) from a previous study. The bolus penetration front depth was limiting to the phase1 dead space volume. In PCD patients deposition was 58+/-8 % after 8 s breath holding time. Particle retention was measured by the magnetopneumographic method over a period of nine months. Particle clearance from the airways showed a fast and a slow phase. In PCD patients airway clearance was retarded and prolonged, 42+/-12 % followed the fast phase with a mean half time of 16.8+/-8.6 hours. The remaining fraction was cleared slowly with a half time of 121+/-25 days. In healthy NS 49+/-9 % of particles were cleared in the fast phase with a mean half time of 3.0+/-1.6 hours, characteristic of an intact mucociliary clearance. There was no difference in the slow clearance phase between PCD patients and healthy NS. Despite non-functioning cilia the effectiveness of airway clearance in PCD patients is comparable to healthy NS, with a prolonged kinetics of one week, which may primarily reflect the effectiveness of cough clearance. This prolonged airway clearance allows longer residence times of bacteria and viruses in the airways and may be one reason for increased frequency of infections in PCD patients.

Magnetic Phagosome Motion in J774A.1 Macrophages: Influence of Cytoskeletal Drugs

The role of the different cytoskeletal structures like microfilaments (MF), microtubuli (MT), and intermediate filaments (IF) in phagosome motion is unclear. These cytoskeletal units play an important role in macrophage function (migration, phagocytosis, phagosome transport). We investigated ferromagnetic phagosome motions by cell magnetometry. J774A.1 macrophages were incubated with 1.3-microm spherical magnetite particles for 24 h, after which more than 90% of the particles had been phagocytized. Phagosome motions can be caused either by the cell itself (relaxation) or by applying magnetic twisting forces, yielding cell stiffness and viscoelastic properties of the cytoskeleton. Apparent viscosity of the cytoplasm was non-Newtonian and showed a shear-rate-dependent power law behavior. Elastically stored energy does not force the magnetic phagosomes back to their initial orientation: 57% of the twisting shear was not recoverable. Cytoskeletal drugs, like Cytochalasin D (CyD, 2 - 4 microM), Colchicine (CoL, 10 microM), or Acrylamide (AcL, 40 mM) were added in order to disturb the different cytoskeletal structures. AcL disintegrates IF, but affected neither stochastic (relaxation) nor directed phagosome motions. CyD disrupts MF, resulting in a retarded stochastic phagosome motion (relative decay 0.53 +/- 0.01 after 5 min versus 0.34 +/- 0.01 in control), whereas phagosome twisting shows only a small response with a 9% increase of stiffness and a small reduction of recoverable strain. CoL depolymerizes the MT, inducing a moderately accelerated relaxation (relative decay 0.28 +/- 0.01 after 5 min) and a 10% increase of cell stiffness, where the pure viscous shear is increased and the viscoelastic recoil is inhibited by 40%. Combining the two drugs conserves both effects. After disintegrating either MF or MT, phagosome motion and cytoskeletal stiffness reflect the behavior of either MT or MF, respectively. The results verify that the dominant phagosome transport mechanism is MF-associated. MT depolymerization by CoL induces an activation of the F-actin synthesis, which may induce an accelerated relaxation and an increase of stiffness. Cell mechanical properties are not modulated by MF depolymerization, whereas MT depolymerization causes a loss of viscous resistance and a loss of cell elasticity. The mean energy for stochastic phagosome transport is 5*10(-18) Joules and corresponds to a force of 7 pN on a single 1.3-microm phagosome.

HUMAN ALVEOLAR LONG-TERM CLEARANCE OF FERROMAGNETIC IRON OXIDE MICROPARTICLES IN HEALTHY AND DISEASED SUBJECTS

Monodisperse ferrimagnetic microparticles (Fe3O4) with 1.3 microm geometric diameter were inhaled to study alveolar long-term clearance in healthy and diseased human subjects. Nineteen younger (age 20 to 39 years) and 20 older (age 40 to 65 years) healthy volunteers participated in the study as well as 15 patients with sarcoidosis (SAR), 12 patients with idiopathic pulmonary fibrosis (IPF), and 15 patients with chronic obstructive bronchitis (COB). In each group the subjects were divided into never smokers (NS) and active smokers (S). Clearance was measured by magnetopneumography (MPG) for 300 days after inhalation. In COB, 50% of the deposited particles were removed from the lungs after 2 days, indicating high bronchial deposits due to bronchial obstructions. In healthy NS, only 10% of the particles were removed after 2 days and cigarette smoking enhanced the fraction of fast-cleared particles. In subjects who smoked, slow clearance was significantly impaired (P < . 02). Clearance half-lives (in days) for younger, healthy, NS were 124 +/- 66 (mean +/- SD) compared to 220 +/- 74 for S. Similarly for older subjects, the timeswere 162 +/- 120 for NS and 459 +/- 334 for S. The impairment of alveolar clearance due to cigarette smoking increases by 5.7 +/- 1.3 days/pack-year (P < .01). Alveolar clearance was impaired in SAR and in IPF; half-lives were 275 +/- 109 days (P < .05) and 756 +/- 345 days (P < .02), respectively, compared to healthy NS. Most COB patients were ex-smokers, their long-term clearance was 240 +/- 74 days, which is more than healthy NS (P < .01), but less than healthy S and might indicate a recovery of alveolar clearance. In view of studies using totally inert particles like Teflon, we conclude that the lung clearance measured with iron oxide tracer particles primarily reflects clearance by intraphagosomal particle dissolution within alveolar macrophages, which is impaired by cigarette smoke consumption and in patients.

Diesel exhaust particles increase LPS‐stimulated COX‐2 expression and PGE2 production in human monocytes

Little is known about health effects of ultrafine particles (UFP) found in ambient air, but much of their action may be on cells of the lung, including cells of the monocyte/macrophage lineage. We have analyzed the effects of diesel exhaust particles (DEP; SRM1650a) on human monocytes in vitro. DEP, on their own, had little effect on cyclooxygenase (COX)‐2 gene expression in the Mono Mac 6 cell line. However, when cells were preincubated with DEP for 1 h, then stimulation with the Toll‐like receptor 4 (TLR4) ligand lipopolysaccharide (LPS) induced an up‐to fourfold‐higher production of COX‐2 mRNA with an average twofold increase. This costimulatory effect of DEP led to enhanced production of COX‐2 protein and to increased release of prostaglandin E2 (PGE2). The effect was specific in that tumor necrosis factor gene expression was not enhanced by DEP costimulation. Furthermore, costimulation with the TLR2 ligand Pam3Cys also led to enhanced COX‐2 mRNA. DEP and LPS showed similar effects on COX‐2 mRNA in primary blood mononuclear cells, in highly purified CD14‐positive monocytes, and in monocyte‐derived macrophages. Our data suggest that UFP such as DEP may exert anti‐inflammatory effects mediated by enhanced PGE2 production.

Glucocorticoids ablate IL-1β-induced β-adrenergic hyporesponsiveness in human airway smooth muscle cells

We have previously reported that interleukin (IL)-1β decreases responsiveness of cultured human airway smooth muscle (HASM) cells to β-agonists. The purpose of this study was to determine whether glucocorticoids inhibit this IL-1β effect. Dexamethasone (Dex; 10-6 M) had no effect on concentration-related decreases in cell stiffness in response to isoproterenol (Iso) in control cells as measured by magnetic twisting cytometry but prevented the decreased responsiveness to Iso observed in IL-1β (20 ng/ml)-treated cells. In addition, Dex had no effect on Iso-stimulated cAMP formation in control cells but prevented the IL-1β-induced reduction in Iso-stimulated cAMP formation. Similar effects on cell stiffness and cAMP responses were seen after pretreatment with the glucocorticoid fluticasone proprionate (FP). Dex and FP also prevented IL-1β-induced hyporesponsiveness to PGE2 stimulation. In contrast, neither IL-1β nor glucocorticoids had any effect on cell stiffness responses to dibutyryl cAMP. We have previously reported that the IL-1β effect on β-adrenergic responsiveness is mediated through cyclooxygenase-2 expression and prostanoid formation. Consistent with these observations, IL-1β-induced cyclooxygenase-2 expression was virtually abolished by FP at concentrations of 10-10 M and greater, with a resultant decrease in PGE2formation. However, Dex did not inhibit IL-1β-induced nuclear translocation of nuclear factor-κB or activator protein-1 in HASM cells. In summary, our results indicate that, in HASM cells, glucocorticoids alone do not alter responses to β-agonists but do inhibit IL-1β-induced β-adrenergic hyporesponsiveness. Glucocorticoids mediate this effect by inhibiting prostanoid formation but without altering nuclear factor-κB or activator protein-1 translocation.

Health effects of sulfur-related environmental air pollution. III. Nonspecific respiratory defense capacities.

Recently concern has been raised about health effects related to environmental sulfur and/or acidic aerosols. To assess long-term effects on respiratory lung function, 8 beagle dogs were exposed over a period of 13 mo for 16.5 h/day to 1.0 microm neutral sulfite aerosol with a particle associated sulfur(IV) concentration of 0.32 mg m(-3) and for 6 h/day to 1.1 microm acidic sulfate aerosol providing an hydrogen ion concentration of 15.2 micromol m(-3) for inhalation. Prior to exposure the dogs were kept under clean air conditions for 16 mo to establish physiological baseline values for each dog. A second group of eight dogs (control) was kept for the entire study under clean air conditions. Nonspecific defense mechanisms in the airways and in the peripheral lung were studied during chronic exposure of the combination of neutral sulfur(IV) and acidic sulfur(VI) aerosols. No functional changes of tracheal mucus velocity were found, in agreement with unchanged morphometry of the airways. However, the exposure resulted in changes of several alveolar macrophage (AM) mediated particle clearance mechanisms: (1) Based on in vivo clearance analysis and cultured AM studies using moderately soluble cobalt oxide particles, intracellular particle dissolution was significantly reduced since phagolysosomal proton concentration was decreased. We deduce exposure-related malfunction of proton pumps bound to the phagolysosomal membrane as a result of an increase of cytosolic proton concentration. (2) Based on in vivo clearance analysis using insoluble polystyrene particles, AM-mediated particle transport from the lung periphery toward ciliated terminal bronchioli and further to the larynx was significantly reduced. Activation of epithelial type II cells at the entrance of alveoli was inferred from observed type II cell proliferation at those alveolar ridges and enhanced secretion of alkaline phosphatase in the fluid of bronchoalveolar lavages. As a result, hypersecretion of chemotactic mediators by activated type II cells at these loci led to the observed decrease of particle transport toward ciliated bronchioli. (3) Based on in vivo clearance analysis using insoluble polystyrene particles, particle transport from the alveolar epithelium into interstitial tissues was increased and (4) particle transport to the tracheobronchial lymph nodes was significantly enhanced. Particle transport into interstitial tissues is the most prominent clearance pathway from the canine alveolar epithelium. We conclude that the deteriorated particle transport toward ciliated terminal bronchioli resulted in an enhanced particle transport across the epithelial membrane into interstitial tissues and the lymphatic drainage. The observed alterations in alveolar macrophage-mediated clearance mechanisms during chronic exposure of these air pollutants indicate an increased risk of health.

Smoking impairs alveolar macrophage activation after inert dust exposure

Magnetopneumography was applied to investigate intracellular phagosome motion in alveolar macrophage cells of healthy subjects (non-smokers and smokers). Ingested magnetic microparticles are inhaled and phagocytized by alveolar macrophages within hours. Thereby the particles are transferred into phagolysosomes. After magnetization the particles produce a macroscopic magnetic field of the lungs. Cellular motility causes a decay of the field (relaxation) by stochastic disorientation of the dipole particles (phagolysosomes) in the cells. Our studies have shown that the deposition of magnetite test particles induces a non-specific activation of the macrophage cells with a faster relaxation. This activation vanishes within the first day after particle deposition. This macrophage activation due to dust exposure was not present in smokers. It follows that cigarette smoking either causes a damage of the cellular defense or causes an adaptation of the macrophage cells to the permanent cigarette smoke inhalation.