Comparison of clearance of particles inhaled with bolus and extremely slow inhalation techniques

Ten healthy nonsmokers inhaled 6-microm (aerodynamic diameter) Teflon particles labelled with 111In twice, once with the shallow bolus technique (volumetic lung depth 76+/-20 mL ([+/- SD]) and once with the extremely slow inhalation technique (0.05 L/s). The radioactivity in the lungs was measured at 1 and 24 hours as well as at 1, 2, and 3 weeks after both inhalations. The 24-hour lung retention a percentage of lung deposition was significantly lower for the bolus inhalation, 46%+/-9% (+/- SD) than for the extremely slow inhalation, 56%+/-11%. The retention after 21 days as a percentage of the 24-hour retention was 55%+/-9% for the shallow bolus inhalation and 56%+/-10% for the extremely slow inhalation. Also within the subjects, clearance was similar for the 2 modes of inhalation. Deposition of particles inhaled with the 2 modes of inhalation was calculated with 2 model, one being based on Monte (Carlo particle transport together with an asymmetric lung model. Deposition predicted with this model agreed well with the experimental data under the assumption that there are large retained fractions only in small ciliated airways (bronchioli) and not in large ones. For the bolus inhalation, the model predicted 43% to 50% deposition in the bronchial (BB) region of initial lung deposition, 33% to 38% in the bronchiolar (bb) region, and 16% to 22% in the alveolar region. For the extremely slow inhalation, the model predicted 31% to 34% deposition in the BB region, 45% to 47% in the bb region, and 21% to 22% in the alveolar region. In addition, it predicted about the same ratio between bb and alveolar depositions for the 2 modes of inhalation. Thus, both the experimental and theoretical data indicate that the shallow bolus particles to a considerable extent reach both the bb and the alveolar regions and that they do that at about the same extent as the particles inhaled extremely slow. This conclusion is concerning the experimental data based on the assumption that there are no large retained fractions in the BB region. Another interpretation of the similar clearance for the two modes of inhalation is that there are large retained fractions in both the BB and the bb regions and that individual charactristics of clearance of these fractions are of importance rather than the site of deposition.

All trans-retinoic acid selectively down-regulates matrix metalloproteinase-9 (MMP-9) and up-regulates tissue inhibitor of metalloproteinase-1 (TIMP-1) in human bronchoalveolar lavage cells

BACKGROUND

The balance between proteinases and antiproteinases plays an important role in tissue destruction and remodelling. In chronic obstructive pulmonary disease (COPD) and emphysema, an imbalance between matrix metalloproteinases (MMPs) and inhibitors of tissue metalloproteinase (TIMPs) has been reported. Alveolar macrophages are considered to be the main source of MMPs. We therefore have analyzed the effects of free and liposomal all trans-retinoic acid (ATRA) on the expression of MMP-9 and TIMP-1 in bronchoalveolar lavage (BAL) cells from patients with COPD and patients with other lung diseases.

MATERIAL AND METHODS

BAL cells were incubated 1-3 day with either liposomal or free ATRA. Supernatants were tested for MMP-9 and TIMP-1 protein in specific ELISA systems; mRNA analysis was performed by semi-quantitative RT-PCR and by quantitative LightCycler PCR.

RESULTS

We demonstrate that either liposomal or free ATRA selectively down-regulates MMP-9 and up-regulates TIMP-1. At the protein level, MMP-9 is decreased 3-fold and TIMP-1 is increased 3.5-fold compared to the base line with empty liposomes or untreated cells. The ratio of MMP-9 and its inhibitor TIMP-1, which may be crucial to the overall proteolytic potential decreased by factor 8. That this countercurrent effect of ATRA is not due to an altered protein stability but to transcriptional regulation could be demonstrated by RT-PCR. Quantitative LightCycler analysis revealed a 2.5-fold decrease of MMP-9 mRNA and a 4.5 fold increase of TIMP- 1 mRNA.

CONCLUSIONS

These data suggest that ATRA treatment via its impact on the proteinase/antiproteinase ratio may become a new therapeutic strategy for patients with inflammatory destructive lung diseases.

[Measurement of the Fowler dead space in patients with pulmonary emphysema using C18O2]

In patients with lung emphysema, changes in lung volumes as well as changes in airway resistance are well known. The change in airway resistance is caused by obstruction of central airways, which is supposed to reduce the respiratory dead space. Until now, it was not possible to measure the respiratory dead space in patients with lung emphysema using the method of Fowler [2], because in this method distinction of the three phases of an inert gas expirogram is essential. While this distinction is easy in healthy subjects (fig. 1; expirogram 3), the separation of the three phases in patients with lung emphysema is not possible due to gradual transition of phase II into phase III in these patients (fig. 1; expirogram 2). The use of C18O2 as tracer gas allows to separate phase II and phase III even if the patients have severe emphysema (fig. 1; expirogram 1). CO2 labeled with the stable oxygen isotope 18O (C18O2) is completely taken up in the gas exchanging region of the lung, but not from the conducting airways. Therefore C18O2 is only expired from the dead space of the lung, but not from the alveolar region. Hence, C18O2 allows exact measurement of the respiratory dead space in patients with lung emphysema. 21 healthy nonsmoking subjects and 29 patients with clinical signs of lung emphysema participated in this study. There was a good correlation between respiratory dead space, measured by the use of Ar-gas and C18O2-gas in healthy subjects (fig. 2). This indicates, that the use of C18O2 is a valid method to measure the functional dead space. As expected, there was also a correlation between the airway resistance and respiratory dead space in patients with lung emphysema (fig. 3), but not in healty subjects. There was no significant difference of the mean values of the respiratory dead space between these two groups (223 +/- 43 ml in healthy subjects vs. 227 +/- 52 ml in patients), even though there were large differences in airway resistance (0.20 +/- 0.10 kPa/l/s vs. 0.49 +/- 0.27 kPa/l/s). This may be due to a loss of alveolar function in the area of the terminal bronchioli, which is typical for emphysematous patients. This entails a shift of functional dead space towards lung periphery and therefore causes an increase of the volume of functional dead space. But this enlargement may be compensated by the volume reduction, caused by the airway obstruction. Hence, these two oppositional mechanisms may result in only minimal change of dead space volume.

Daily mortality and fine and ultrafine particles in Erfurt, Germany part I: role of particle number and particle mass

Increases in morbidity and mortality have been observed consistently and coherently in association with ambient air pollution. A number of studies on short-term effects have identified ambient particles as a major pollutant in urban air. This study, conducted in Erfurt, Germany, investigated the association of mortality not only with ambient particles but also with gaseous pollutants and indicators of sources. Part I of this study concentrates on particles. Data were collected prospectively over a 3.5-year period from September 1995 to December 1998. Death certificates were obtained from the local authorities and aggregated to daily time series of total counts and counts for subgroups. In addition to standard data for particle mass with diameters < or = 2.5 microm (PM2.5)* or < or = 10 microm (PM10) from impactors, a mobile aerosol spectrometer (MAS) was used to obtain size-specific number and mass concentration data in six size classes between 0.01 microm and 2.5 microm. Particles smaller than 0.1 microm were labeled ultrafine particles (three size classes), and particles between 0.1 and 2.5 microm were termed fine particles (three size classes). Concentrations of the gases sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) were also measured. The daily average total number concentration was 18,000 particles/cm3 with 88% of particles below 0.1 pm and 58% below 0.03 microm in diameter. The average mass concentration (PM2.5) was 26 microg/m3; of this, 75% of particles were between 0.1 and 0.5 microm in diameter. Other average concentrations were 38 microg/m3 for PM10, 17 microg/m3 for SO2, 36 microg/m3 for NO2, and 600 microg/m3 for CO. Ambient air pollution demonstrated a strong seasonality with maximum concentrations in winter. Across the study period, fine particle mass decreased, whereas ultrafine particle number was unchanged. The proportion of ultrafine particles below 0.03 microm diameter increased compared with the proportion of other particles. During the study, concentrations of SO2 and CO also decreased, whereas the concentration of NO2 remained unchanged. The data were analyzed using Poisson regression techniques with generalized additive modeling (GAM) to allow nonparametric adjustment for the confounders. Both the best single-day lag and the overall association of multiple days fitted by a polynomial distributed lag model were used to assess the lag structure between air pollution and death. Mortality increased in association with level of ambient air pollution after adjustment for season, influenza epidemics, day of week, and weather. In the sensitivity analyses, the results proved stable against changes of the confounder model. We saw comparable associations for ultrafine and fine particles in a distributed lag model where the contribution of the previous 4 to 5 days was considered. Furthermore, the data suggest a somewhat more delayed association of ultrafine particles than of fine particles if single-day lags are considered. The associations tended to be stronger in winter than in summer and at ages below 70 years compared to ages above 70 years. Analysis of the prevalent diseases mentioned on death certificates revealed that the overall association for respiratory diseases was slightly stronger than for cardiovascular diseases. In two-pollutant models, associations of ultrafine and fine particles seemed to be largely independent of each other, and the risk was enhanced if both were considered at the same time. Furthermore, when the associations were summed for the six size classes between 0.01 and 2.5 microm, the overall association was clearly stronger than the associations of the individual size classes alone. Associations were observed for SO2, NO2, and CO with mortality despite low concentrations of these gases. These associations disappeared in two-pollutant models for NO2 and CO, but they remained stable for SO2. The persistence of the SO2 effect was interpreted as artifact, however, because the SO2 concentration was much below levels at which effects are usually expected. Furthermore, the results for SO2 were inconsistent with those from earlier studies conducted in Erfurt. We conclude that both fine particles (represented by particle mass) and ultrafine particles (represented by particle number) showed independent effects on mortality at ambient concentrations. Comparable associations for gaseous pollutants were interpreted as artifacts of collinearity with particles from the same sources.

Aerosol morphometry and aerosol bolus dispersion in patients with CT-determined combined pulmonary emphysema and lung fibrosis

The simultaneous occurrence of pulmonary fibrosis and emphysema may present considerable problems in clinical assessment. Recent studies have shown that Aerosol Derived Airway Morphometry (ADAM) and Aerosol Bolus Dispersion (ABD) are changed in patients with pulmonary emphysema. This study was performed to assess the effect of simultaneous lung fibrosis in patients with emphysema on ADAM and ABD. ADAM and ABD measurements were performed in 20 patients with lone high resolution CT scan (HRCT) confirmed emphysema (E), and compared to those in 15 emphysematics with HRCT-confirmed superimposed pulmonary fibrosis (FE). In both groups the peripheral effective airspace dimension (EAD) (E: 0.63 +/- 0.20 mm; FE: 0.60 +/- 0.27 mm, N.S.) was increased by more than a factor of two compared to that of healthy subjects (0.28 +/- 0.05 mm) (p < 0.001). Patients with E showed a significantly higher bolus dispersion than patients with FE (724 +/- 122 cm3 vs. 546 +/- 80 cm3; p < 0.001). However, in patients with FE, bolus dispersion was still significantly higher than in previously published control groups of healthy subjects (546 +/- 80 cm3 vs. 455 +/- 68 cm3; p < 0.001). The results of this study confirm that ADAM and ABD are powerful tools for identifying emphysema even in patients with superimposed pulmonary fibrosis.

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.

Total deposition of therapeutic particles during spontaneous and controlled inhalations

Treatment of systemic diseases by means of the inhalation route is hampered by uncertainties of the drug dose applied by inhalation. In this study, the hypothesis was tested that by standardization of the breathing maneuver used for inhalation, the interindividual variability of the dose deposited intrathoracically can be reduced. Therefore, breathing pattern during routine inhalations with jet nebulizers was measured in 18 patients with lung disease. Using monodisperse 3 microm particles, total deposition was then assessed for the measured spontaneous and for three controlled, slow breathing patterns. Particle deposition for the three controlled breathing patterns was additionally measured in 14 healthy subjects. The study has shown that within the study population the inhaled air volume and flow rate were quite different. Consequently, total particle deposition varied between 20 and 95%, depending on breathing pattern. For controlled, slow breathing patterns, deposition was on average higher, intersubject variability of deposition was smaller, and differences in deposition between healthy subjects and patients were negligible. Therefore, to perform efficient systemic treatment with aerosolized drugs, controlled, slow breathing patterns should be used.

Intrapulmonary distribution of deposited particles

Inhalation drug delivery for both topical and systemic treatments has many advantages over oral, intravenous, or subcutaneous drug delivery. Because some drugs should be deposited within the bronchial tree and others should deposit within the respiratory zone of the lung, it should be possible to determine and influence the preferential site of drug deposition to develop efficient inhalation therapy strategies. In this article, a method that allows estimation of the longitudinal distribution of deposited particles in the lungs of individual subjects is introduced. From the photometrically measured deposition of monodisperse di-2-ethylhexyl sebacate (DEHS) droplets, the longitudinal distribution of deposited particles (i.e., the number of particles that are deposited in a certain lung volume element) can be assessed. In this study in four healthy volunteers the distribution of deposited particles was assessed for different airflow rates, tidal volumes (VTS), and particle sizes. The results showed that there are considerable differences in the longitudinal distribution of deposited particles between subjects and that the distribution is strongly dependent on particle size: if particle size is increased, the site of particle deposition is shifted proximally. Particles with diameters greater than approximately 5 microns cannot penetrate to a volumetric lung depth (VP) greater than approximately 600 cm3 even if the VT is increased. Airflow rate has a minor effect on the distribution of deposited particles, but if airflow rate increases, the site of particle deposition is slightly shifted peripherally. This method can be used to investigate individual patterns of drug deposition in human lungs noninvasively and to develop and optimize inhalation strategies for inhalation drug delivery.

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

We have previously reported that interleukin (IL)-1beta decreases responsiveness of cultured human airway smooth muscle (HASM) cells to beta-agonists. The purpose of this study was to determine whether glucocorticoids inhibit this IL-1beta 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-1beta (20 ng/ml)-treated cells. In addition, Dex had no effect on Iso-stimulated cAMP formation in control cells but prevented the IL-1beta-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-1beta-induced hyporesponsiveness to PGE(2) stimulation. In contrast, neither IL-1beta nor glucocorticoids had any effect on cell stiffness responses to dibutyryl cAMP. We have previously reported that the IL-1beta effect on beta-adrenergic responsiveness is mediated through cyclooxygenase-2 expression and prostanoid formation. Consistent with these observations, IL-1beta-induced cyclooxygenase-2 expression was virtually abolished by FP at concentrations of 10(-10) M and greater, with a resultant decrease in PGE(2) formation. However, Dex did not inhibit IL-1beta-induced nuclear translocation of nuclear factor-kappaB or activator protein-1 in HASM cells. In summary, our results indicate that, in HASM cells, glucocorticoids alone do not alter responses to beta-agonists but do inhibit IL-1beta-induced beta-adrenergic hyporesponsiveness. Glucocorticoids mediate this effect by inhibiting prostanoid formation but without altering nuclear factor-kappaB or activator protein-1 translocation.

Noninvasive diagnosis of emphysema. Aerosol morphometry and aerosol bolus dispersion in comparison to HRCT

Aerosol-derived airway morphometry (ADAM) and aerosol bolus dispersion (ABD) test are altered in patients with emphysema. We examined the diagnostic power of these aerosol methods in comparison with the noninvasive "gold-standard" HRCT in 50 consecutive patients with various lung diseases. The severity of airflow limitation was mild to moderate in the group of patients without emphysema and moderate to severe in the group of patients with HRCT-confirmed emphysema (FEV(1), 78 +/- 23% pred versus 53 +/- 33% pred; p < 0. 001). Among all lung function parameters under consideration ADAM showed the highest sensitivity and specificity for separating patients with emphysema from those without emphysema (area under the operating characteristics curve: p(ROC), 0.92), followed by ABD (p(ROC), 0.90), a marker for ventilation inhomogeneities. In patients with HRCT-confirmed macroscopic emphysema, peripheral air-space dimensions (EAD) at a relative volumetric lung depth V(pr) of 0.20 measured by ADAM were 155% larger, and bolus dispersion (ABD) at a lung depth of V(p) 600 ml was 53% larger than those observed in patients with other lung diseases (EAD = 0.84 +/- 0.53 mm versus 0.33 +/- 0.10 mm, p < 0.0001; ABD = 706 +/- 154 cm(3) versus 462 +/- 109 cm(3); p < 0.0001). EAD showed a significant correlation with the HRCT visual score (r = 0.78, p = 0.01). ABD showed weak significant correlations with all HRCT parameters under consideration (visual score, pixel density, mean lung density) (r = 0.45 to 0.66; p < 0.05). ADAM and ABD are powerful tools for the noninvasive diagnosis of macroscopic emphysema.

Aerosol-derived airway morphometry and aerosol bolus dispersion in patients with lung fibrosis and lung emphysema

OBJECTIVE

Patients with lung emphysema show increased aerosol-derived dimensions of peripheral airspaces and increased aerosol bolus dispersion (AD). To apply these tests in epidemiologic studies, the objective of this pilot study was to investigate whether morphometric changes caused by lung fibrosis can be distinguished from those caused by emphysema.

DESIGN

This study was designed as a cross-sectional study in which airspace dimensions and AD in patients with emphysema and in patients with fibrosis were compared. Forty patients participated in the study: 20 patients had high-resolution CT (HRCT)-proved lung emphysema and 20 patients had HRCT-proved lung fibrosis. All patients underwent conventional lung function tests, aerosol-derived airway morphometry (ADAM), and AD measurements.

RESULTS

Patients with lung emphysema showed normal dimensions of small airways but enlarged airspace dimensions in the lung periphery. Patients with fibrosis showed in all lung depths increased airspace dimensions. AD was increased in patients with emphysema but was normal in patients with fibrosis.

CONCLUSIONS

These results show that when using ADAM and AD, morphometric changes caused by emphysema can be distinguished from those caused by fibrosis with high sensitivity and specificity.

Anatomic localization of 24- and 96-h particle retention in canine airways

Long-term retention of particles in airways is controversial. However, precise anatomic localization of the particles is not possible in people. In this study the anatomic location of retained particles after shallow bolus inhalation was determined in anesthetized, ventilated beagle dogs. Fifty 30-cm(3) boluses containing monodisperse 2.5-micron polystyrene particles (PSL) were delivered to a shallow lung depth of 81-129 cm(3). At 96 h before euthanasia, red fluorescent PSL were used; at 24 h, green fluorescent PSL and (99m)Tc-labeled PSL were used. Clearance of (99m)Tc-PSL was measured during the next 24 h. Sites of particle retention were determined in systematic, volume-weighted random samples of microwave-fixed lung tissue. Precise particle localization and distribution was analyzed by using gamma counting, conventional fluorescence microscopy, and confocal microscopy. Within 24 h after shallow bolus inhalation, 50-95% of the deposited (99m)Tc-PSL were cleared, but the remaining fraction was cleared slowly in all dogs, similar to previous human results. The three-dimensional deposition patterns showed particles across the entire cross-sectional plane of the lungs at the level of the carina. In these locations, 33 +/- 9.9% of the retained particles were found in small, nonrespiratory airways (0.3- to 1-mm diameter) and 49 +/- 10% of the particles in alveoli; the remaining fraction was found in larger airways. After 96 h, a similar pattern was found. These findings suggest that long-term retention in airways is at the bronchiolar level.

[Diagnostic pneumology using model aerosols]

Clearance of Aerosol Particles from the Airways: Measurement of the efficiency and kinetics of particle clearance from the airways is dependent on the site of particle deposition within the lungs. Insoluble particles deposited in the alveolar region are mainly cleared by macrophages over a period of hundreds of days, whereas particles from the tracheobronchial airways are mainly cleared within hours or days by mucociliary clearance. We introduce a method for mucociliary clearance measurements called 'Radio-Bolus-Scintigraphy'. A small volume of radiolabelled aerosol particles sandwiched in clean air (aerosol bolus) is inhaled near the end of a tidal breath which leads to a preferential deposition of the particles in the airways. Particles were Fe3O4 labelled with 99mTc with an aerodynamic particle diameter of 3.5 microns (monodisperse). The retention of the particles within the lungs was detected by Gamma Camera and Human Scintillation Counter. 26 healthy subjects volunteered in this study (14 nonsmokers and 12 smokers). The half width of the mucociliary clearance was found to be 2.4 h in nonsmokers and 3.3 h in smokers (p < 0.05). Intersubject variability was small, 24 hours after inhalation 55% (+/- 6%) of the inhaled particles were still found in the airways of the subjects. No difference was found between nonsmokers and smokers. Good intersubject reproducibility makes this method useful in therapy control as well as in early diagnosis of changes in mucociliary clearance kinetics and efficiency.

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.

Health effects of sulfur-related environmental air pollution. IV. Respiratory lung function

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-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. Before and at the end of exposure, respiratory lung function was evaluated in both groups in anesthetized and mechanically ventilated animals. Lung volumes as well as static and dynamic lung compliances were measured. Series dead-space volumes and slopes of the alveolar plateau for respiratory (O2, CO2) and inert test gases (He, SF6) were determined from single-breath washout tracings. Monodisperse 0.9-microm DEHS droplets were used to assess convective mixing in the lungs and to evaluate airway dimensions in vivo. Gas exchange across the alveolar-capillary layer was characterized by membrane diffusing capacity for carbon monoxide and alveolar-arterial pressure differences for respiratory gases. A bronchial challenge with carbachol was used to assess airway responsiveness. In comparison to the control group, dogs exposed to sulfur(IV) and acidic aerosol exhibited no significant changes in any respiratory lung function parameter. Also the responsiveness of the bronchial airways to carbachol was not affected. In view of the results obtained in this and previous studies, we conclude that anticipated synergistic effects of the two air pollutants on pulmonary lung function were not observed. It is hypothesized that antagonistic effects of the air pollutants on the activity of phospholipase A2 play an important role and account for counteracting physiological compensatory mechanisms. The results emphasize the complexity of health effects on lung function in response to the complex mixtures of ambient air pollutants and witness the precariousness in the risk assessment of air pollutants for humans.

Health effects of sulfur-related environmental air pollution. V. Lung structure

The lungs of 8 male beagle dogs were examined morphologically and morphometrically after exposure for 13 mo to a respirable sulfur(IV) aerosol at a mass concentration of 1.53 mg m(-3) (16.5 h/day), and to an acidic sulfate aerosol carrying 15.2 micromol m(-3) hydrogen ions into the lungs (6 h/day). An additional eight dogs served as unexposed controls. Standard morphometric analyses of both the surface epithelia of the conducting airways and the alveolar region were performed. These analyses showed no difference between the exposure group and control group. However, there was a tendency to an increase in the volume density of bronchial glands in the exposure group. Five of eight exposed animals showed thickened ridges (knob-like structures) at the entrance to alveoli in the alveolar duct and alveolar sac. Transmission electron microscopy revealed that the thickening was mainly due to type II cell proliferation. As the previous experiment using sulfite aerosol only showed no alterations in the proximal alveolar regions, the changes observed may be considered as effects of acidic sulfate aerosol alone or in combination with sulfite. These findings suggest that sulfur aerosols have the potential to induce epithelial alterations in the proximal alveolar region, which is a primary target for air pollutants.

Health effects of sulfur-related environmental air pollution. I. Executive summary

The motivation of simulating real-world environmental exposure in a number of long-term studies with dogs was to address the question of whether or not perpetual inhalation of air pollutants can initiate diseases in healthy lungs and can thus contribute to the increasing prevalence of respiratory diseases in industrialized countries. The major conclusion of this article is that this question has to be answered in the negative for the simultaneous inhalation of the major constituents of combustion-related air pollution, particle-associated sulfur(IV), and particle-associated hydrogen ions. Over 13 mo, 8 healthy beagle dogs were exposed in 2 whole-body chambers daily for 16.5 h to 1 microm neutral sulfite [sulfur(IV)] particles at a mass concentration of 1.5 mg m-3 and for 6 h to 1.1 microm acidic sulfate particles carrying 15 micromol m-3 hydrogen ions into the canine lungs. This longitudinal study was characterized by repeated observations of individual respiratory response patterns. To establish baseline data the dogs were repeatedly examined preexposure while the chambers were ventilated over 16 mo with clean air. Each individual served thus as its own control. Another eight dogs served as additional controls. They were housed in 2 chambers ventilated with clean air over the entire study period of 29 mo. To assess response patterns, respiratory lung function tests were performed pre- and postexposure, segmental lung lavages were repeatedly performed to obtain epithelial lining fluid from the lungs for analysis of cell content, cell function, and biochemical indicators of lung injury, and radiolabeled test particles were used to study pathways of intrapulmonary particle elimination. At the end of the study, the lungs of all animals were morphologically and morphometrically examined. Functional and structural responses were finally compared to those observed previously as a result of a sole exposure of canine lungs to neutral sulfite particles over 10 mo (Heyder et al., 1992). Interactions between responses induced by neutral sulfite and acidic sulfate particles occurred, but antagonism rather than synergism was observed. The responses induced by sulfur(IV) were less pronounced, not detectable, or even reversed when hydrogen ions were also delivered to the lungs. On the other hand, responses not induced by the sole exposure to sulfur(IV) were observed: The activity of alkaline phosphatase was elevated and type II pneumocytes proliferated. It can, however, be concluded that long-term exposure of healthy lungs to particle-associated neutral sulfur(IV) and hydrogen ions at concentration close to ambient levels causes subtle respiratory responses but does not initiate pathological processes in the lungs. In other words, the perpetual inhalation of sulfur(IV) and hydrogen ions from the atmospheric environment presents no health risk to the healthy lungs. It is thus also very unlikely that respiratory diseases can be initiated by the inhalation of these pollutants.

Health effects of sulfur-related environmental air pollution. II. Cellular and molecular parameters of injury

Recently, concern has been raised about effects related to environmental sulfur and/or acidic aerosols. To assess long-term effects on nonrespiratory lung function, 8 beagle dogs were exposed over a period of 13 mo for 16.5 h/day to a neutral sulfite aerosol at a sulfur(IV) concentration of 0.32 mg m(-3) and for 6 h/day to an acidic sulfate aerosol providing a hydrogen 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 animal. A second group of eight dogs (control) was kept for the entire study under clean air conditions. No clinical symptoms were identified that could be related to the combined exposure. Biochemical and cellular parameters were analyzed in sequential bronchoalveolar lavage (BAL) fluids. The permeability of the alveolo-capillary membrane and diethylenetriaminepentaacetic acid (DTPA) clearance was not affected. Similarly, oxidant burden of the epithelial lining fluid evaluated by levels of oxidation products in the BAL fluid protein fraction remained unchanged. Both the lysosomal enzyme beta-N-acetylglucosaminidase and the alpha-1-AT were increased (p <.05). In contrast, the cytoplasmic marker lactate dehydrogenase remained unchanged, indicating the absence of severe damages to epithelial cells or phagocytes. Various surfactant functions were not altered during exposure. Three animals showed elevated levels of the type II cell-associated alkaline phosphatase (AP), indicating a nonuniform response of type II cells. Significant correlations were found between AP and total BAL protein, but not between AP and lactate dehydrogenase, suggesting proliferation of alveolar type II cells. Absolute and relative cell counts in the BAL fluid were not influenced by exposure. Alveolar macrophages showed no alterations with regard to their respiratory burst upon stimulation with opsonized zymosan. The percentage of alveolar macrophages capable of phagocytozing latex particles was significantly decreased (p<.05), while the phagocytosis index was not altered. In view of the results of this and previous studies, we conclude that there is no synergism of effects of these two air pollutants on nonrespiratory lung functions. It is hypothesized that antagonistic effects of these air pollutants on phospholipase A2-dependent pathways account for compensatory physiological mechanisms. The results emphasize the complexity of health effects on lung functions in response to the complex mixture of air pollutants and disclose the precariousness in the risk assessment of air pollutants for humans.

Increased fine particle deposition in women with asymptomatic nonspecific airway hyperresponsiveness

Previous studies suggest that lung function tests using monodisperse aerosols can help to identify early stages of lung diseases. We investigated intrapulmonary particle loss and aerosol bolus dispersion-a marker of convective gas transport-in 32 women with asymptomatic nonspecific bronchial hyperresponsiveness (BHR) compared with 60 women without BHR. Deposition of inhaled particles (0.9 micrometer mass median aerodynamic diameter [MMAD]) was calculated from particle losses of inhaled aerosol boluses consisting of di-2-ethylhexyl sebacate droplets. Convective gas mixing was assessed by the aerosol bolus dispersion method. Women with BHR, nonsmokers as well as smokers, showed significantly increased deposition of aerosol particles (nonsmokers: 45.6 +/- 8.8%; smokers: 49.2 +/- 5.4%; mean +/- SD) compared with the control group of female nonsmokers without BHR (38.2 +/- 9.1%; mean +/- SD) (p < 0.01). Aerosol bolus dispersion values showed a trend for higher values in subjects with BHR (nonsmokers: 572 +/- 122 cm3; smokers: 587 +/- 85 cm3) compared with the control group (542 +/- 88 cm3) (p = 0.2). Also, the maximal expiratory flow at 25% vital capacity (MEF25) showed a trend for decreased values in nonsmokers with BHR compared with nonsmokers without BHR (64 +/- 16% of predicted versus 78 +/- 24% of predicted; p = 0.03). These results suggest that deposition of inhaled particles (0.9 micrometer MMAD) administered by the aerosol bolus technique is a sensitive index of peripheral lung injury that is usually not assessable by conventional methods.

Aerosol bolus dispersion in patients with bronchiolitis obliterans after heart-lung and double-lung transplantation. The Munich Lung Transplantation Group

Bronchiolitis obliterans (BO) is one of the main late complications in patients after lung transplantation. Because BO is located in small airways, conventional lung function tests are supposed to be rather insensitive to detect early stages of this disease. In this study, the capability of the aerosol bolus dispersion test to detect BO was tested in 12 subjects with heart-lung and double-lung transplantation. Four of these patients had histological evidence of BO. The broadening (dispersion) of inhaled boluses consisting of monodispersed inert test particles during respiration was repeatedly measured in each subject. Additional measurements of spirometric and bodyplethysmographic measurements were performed. Patients with evidence of BO showed significantly increased aerosol bolus dispersion and significantly reduced maximal airflow parameters. Calculation of receiver operating characteristics (ROCs) revealed that from all lung function parameters under consideration, aerosol bolus dispersion divided by the maximum expiratory flow rate at 50% of vital capacity (MEF50) and MEI50 had the highest sensitivity and specificity for the detection of BO. Both parameters showed a sensitivity and specificity of 100%. Therefore, it may be speculated that even in early stages of disease, the combination of MEF50 measurement with aerosol bolus dispersion measurements may be a powerful tool for the detection of BO in patients with lung transplantation.

Regional deposition and retention of particles in shallow, inhaled boluses: effect of lung volume

The regional deposition of particles in boluses delivered to shallow lung depths and their subsequent retention in the airways may depend on the lung volume at which the boluses are delivered. To evaluate the effect of end-inspiratory lung volume on aerosol bolus delivery, we had healthy subjects inhale radiolabeled, monodisperse aerosol (99mTc-iron oxide, 3.5-microm mass median aerodynamic diameter) boluses (40 ml) to a volumetric front depth of 70 ml into the lung at lung volumes of 50, 70, and 85% of total lung capacity (TLC) end inhalation. By gamma camera analysis, we found significantly greater deposition in the left (L) vs. right (R) lungs at the 70 and 85% TLC end inhalation; ratio of deposition in L to R lung, normalized to L-to-R ratio of lung volume (mean L/R), was 1.60 +/- 0.45 (SD) and 1. 96 +/- 0.72, respectively (P < 0.001 for comparison to 1.0) for posterior images. However, at 50% TLC, L/R was 1.23 +/- 0.37, not significantly different from 1.0. These data suggest that the L and R lungs may be expanding nonuniformly at higher lung volumes. On the other hand, subsequent retention of deposited particles at 2 and 24 h postdeposition was independent of L/R at the various lung volumes. Thus asymmetric bolus ventilation for these very shallow boluses does not lead to significant increases in peripheral alveolar deposition. These data may prove useful for 1) designing aerosol delivery techniques to target bronchial airways and 2) understanding airway retention of inhaled particles.