Faculty Bibliography

Inhalation of cadmium oxide (CdO) is a significant form of human exposure to cadmium (Cd). Furthermore, there is epidemiological and experimental data relating Cd inhalation with lung cancer. Animal studies indicate that rats are more susceptible to Cd-induced lung cancer than mice, but interstrain sensitivity differences to Cd-induced pulmonary inflammation or carcinogenesis have not been addressed in either species. We compared pulmonary inflammatory processes in Wistar Furth (WF) rats with those in C57 and DBA mice exposed to freshly generated CdO fumes in nose-only inhalation chambers. Animals were exposed to 1 mg Cd/m3 for 3 hr and terminated immediately or 1, 3, and 5 days after exposure. Control animals were exposed to air/argon furnace gases. Cd-induced lung injury was assessed by bronchoalveolar lavage fluid (BALF) analyses, histopathology, and immunohistochemical detection of cell proliferation. Inhalation of CdO resulted in pulmonary inflammatory processes that varied widely across species and strains. C57 mice responded with faster and greater influx of neutrophils and proliferation of alveolar macrophages, type II epithelial cells, and bronchiolar epithelial cells compared to DBA mice or WF rats. DBA mice retained a greater percentage of inhaled Cd in the lungs and presented higher levels of BALF protein than C57 mice or rats. In comparison to mice, WF rats responded with a more transient inflammatory response in BALF parameters and higher degree of acute inflammation in lung tissue. The more pronounced proliferation of alveolar and bronchiolar epithelial cells observed in C57 mice might indicate higher susceptibility of this mice strain to Cd-induced lung carcinogenesis compared to DBA mice or WF rats. Furthermore, the present results of fewer inflammatory cells and lower proliferation of epithelial cells in DBA mice in association with our previous observation of higher Cd-induced metallothionein protein in this strain suggest that DBA might be less susceptible to the pulmonary carcinogenic effects of inhaled Cd than C57 mice or WF rats. We conclude that mice might not necessarily be more resistant than rats to the carcinogenic effects of inhaled Cd, since intraspecies susceptibility differences are strongly suggested by the present data. An extrapolation of this conclusion is that genetic variations in the human population may determine individual sensitivity differences to inhaled Cd

Soluble and insoluble chromium (Cr) agents are concomitantly released with ozone (O-3) during welding. Although pulmonary implications from exposure to each agent individually have been investigated, the effects from simultaneous exposure, as occurs under actual working conditions, are unclear. To investigate the retention/distribution of inhaled Cr, male F-344 rats were exposed nose-only to atmospheres containing soluble potassium chromate (K2CrO4) or O-3, either alone or in combination, at 360 mu g Cr/m(3) and 0.3 ppm O-3. In a second phase of the study, insoluble barium chromate (BaCrO4) was used in place of K2CrO4. Rats were exposed for 5 h/day, 5 days/wk for 2 or 4 wk. One day after the final exposure, rats were euthanized and their lungs either removed intact or lavaged for quantitation of tissue-, lavaged cell-, and acellular lavage fluid-associated Cr. In general, rats inhaling insoluble Cr had greater total lung Cr burdens than did rats exposed to soluble Cr. Simultaneous inhalation of O-3 and K2CrO4 led to reduced lung Cr levels compared to those in rats receiving K2CrO4 only; with BaCrO4 coexposure to O-3 resulted in increased lung BaCrO, levels compared to BaCrO3 alone. Particle solubility also affected Cr levels in lavageable cells, with those from rats inhaling BaCrO, alone or BaCrO4 + O-3 consistently having greater burdens than their K2CrO4 counterparts; the presence of O-3 itself had no effect upon cell Cr levels when either compound was used. Solubility-dependent differences were also apparent in acellular lavage fluid, with Cr levels initially being greater in fluids from rats inhaling K2CrO4 alone; as exposures continued, these burdens became greater in the rats inhaling BaCrO4 alone. Although inhalation of either Cr/O-3 mixture yielded significant differences in fluid Cr levels, the presence of 4 did lead to reductions in levels compared to those in rats inhaling either Cr agent alone. In postlavage lung tissue, there were time-dependent increases in Cr levels in rats from all exposure groups; however, the most dramatic increase occurred with rats exposed to BaCrO4 + O-3. Lastly, while significant solubility-dependent differences in the relative distribution of Cr among the three pulmonary compartments were discerned, a specific effect attributable to O-3 itself was not evident. The results of this study indicate that Cr retention and distribution within the lungs, as well as any effect from coexposure to O-3, are modulated by the solubility of the inhaled Cr particles

Exposure of human tracheal epithelial (TE) cells to ozone (0.1-0.5 ppm) leads to a transient increase followed by decreased production of prostaglandin (PG) E2 concomitant with dose-dependent loss and delayed recovery of cyclooxygenase (CO) activity [S.E. Alpert and R.W. Walenga. Am. J. Physiol. 269 (Lung Cell. Mol. Physiol. 13): L734-L743, 1995]. Formation of reactive oxygen species (ROS) in cultured tracheobronchial epithelial cells during ozone exposure was recently demonstrated (L.C. Chen and Q.Qu. Toxicol. Appl. Pharmacol. 143: 96-101, 1997). In the present study, we investigated if ROS generated by ozone-exposed human TE cells contribute to PGE2 production and/or CO inactivation and whether the delay in recovery of CO activity after ozone reflects impaired gene transcription and/or protein synthesis. Rapid, dose-dependent ROS generation, assessed by fluorescence of dihydrorhodamine 123, was detected in human TE monolayers exposed to 0.21-0.63 ppm ozone. In a different system, TE cells were exposed to air or 0.5 ppm ozone for 1 h by serial renewal/collection of an adherent film of media. Ozone-induced ROS formation, the transient increase and decline in PGE2, and CO inactivation were attenuated by an intracellular hydroxyl radical scavenger, 1,3-dimethyl-2-thiourea. Ibuprofen, a reversible CO inhibitor, prevented PGE2 release during ozone exposure (and hence autocatalytic CO inactivation) but not loss of CO activity. Although CO activity remained depressed for hours after ozone exposure, compared with air-exposed cultures, no differences were detected in mRNA and protein levels of prostaglandin endoperoxide G/H synthase 2 (PGHS-2), the only CO isoform present in human TE cells, or in the rate of de novo PGHS-2 synthesis. Our findings suggest that ozone-induced PGE2 production and CO inactivation are primarily the result of formation of intracellular oxidant molecules and that delayed recovery of CO activity in human TE cells after short-term ozone exposure is due to persistent inactivation of PGHS-2, rather than to interference with its synthesis

Ozone is a ubiquitous air pollutant which can affect numerous function s of the respiratory system. However, previous work has not provided any information concerning its ability to modulate pharmacological receptors of pulmonary macrophages. This study examined, using a chemiluminescence assay, the beta-adrenergic modulation of pulmonary macrophages harvested from rabbits exposed for 3 hr/day for 5 days to 0.1, 0.3 or 0.6 ppm ozone (O3) or to 3 hr/day for 20 days to 0.1 or 0.3 ppm. Receptor activity was monitored using release of reactive oxygen species (ROS) following administration to the cells of the beta2-receptor agonist, isoproterenol. An O3-exposure concentration-dependent response was observed for isoproterenol efficacy following 5-day exposures, in that 0.1 ppm O3 induced a significant enhancement of beta-adrenergic inhibition of ROS production, 0.3 ppm ozone produced no significant change from control, and 0.6 ppm decreased inhibition. No significant effects on beta-adrenergic modulation were noted following the 20-day exposures. The results of this study suggest that short-term repeated exposures to O3 are capable of inducing alterations in the pharmacological functioning of pulmonary macrophages, while longer term exposures may result in adaptation. Alterations in receptor function have implications in terms of pulmonary defense and disease

Generating controlled test atmospheres of known chemical identity and airborne concentration upon demand is a significant technical obstacle that limits the scope and repeatability of studies of inhaled substances. We addressed this problem as applied to the generation of atmospheres that result from heating crack cocaine, which include both cocaine and its pyrolyzate methylecgonidine (MEG). A condensation aerosol generator was used to generate atmospheres comprised of monodisperse particles of cocaine, MEG, or mixtures of both that are of submicron size suitable for deposition in the alveolar region of primates. Compressed air seeded with nanometer-size sodium chloride particles was passed through a constant depth of molten cocaine or MEG in a bead bed, reheated, and condensed to an aerosol within an annulus of cold air. To achieve control of a mixture of both compounds, MEG was condensed onto cocaine particles in a separate coating step. On-line analytical instruments provided verification of airborne concentration, estimates of particle size, and dispersion as well as chemical identity. Specific airway conductance (SGaw), heart rate, and rectal and skin temperatures were measured in squirrel monkeys breathing atmospheres containing condensation aerosols of cocaine or MEG free base. SGaw was reduced after inhalation of either base, and both induced temperature and cardiovascular changes, demonstrating that the aerosols so generated had biological activity

In addition to being the single greatest known environmental cause of cancer, cigarette smoke (CS) is also a major contributor to heart disease. We reported previously that 1) inhalation of either mainstream or sidestream CS promotes aortic arteriosclerotic plaque development; 2) 1,3 butadiene, a vapor-phase component of CS, promotes plaque development at 20 ppm, which at the time was only 2 times higher than the threshold limit value; and 3) individual tar fraction carcinogens in CS, including polynuclear aromatic hydrocarbons (PAHs) and nitrosamines, either do not promote plaque development or do so only at high concentrations. These results suggested that the tar fraction is not the primary source of plaque-promoting agents in CS. We asked whether repeated exposure to the tar fraction of CS, collected in a cold trap (TAR), promotes plaque development in an avian model of arteriosclerosis. Acetone extracts of mainstream CS tar from burning, unfiltered reference cigarettes were solubilized in dimethyl sulfoxide (DMSO) and injected weekly into cockerels for 16 weeks (25 mg/kg/week). Positive controls were injected weekly with the synthetic PAH carcinogen, 7,12 dimethylbenz(a)anthracene (DMBA) dissolved in DMSO and negative controls were injected with DMSO. Plaque location and prevalence did not differ from group to group. Morphometric analysis of plaque cross-sectional areas showed that plaque sizes, which are log-normally distributed, were significantly larger in the DMBA cockerels compared to both the TAR and DMSO groups. There were no significant differences in plaque size between DMSO and TAR cockerels. The results reported here, combined with other recent findings, support the conclusion that the primary arteriosclerotic plaque-promoting components of CS are in the vapor phase

We previously demonstrated that rats in a late stage of pregnancy and throughout lactation were more susceptible to pulmonary inflammation induced by exposure to 1 ppm ozone than were age-matched virgin females or rats following lactation. The purpose of the study reported here was to extend the comparison of ozone-induced pulmonary inflammation in lactating and postlactating rats to lower concentrations of ozone and to investigate the hypothesis that the enhanced response demonstrated by lactating rats is attributable to a greater inhaled ozone dose. During pregnancy and lactation the metabolic demands on the female are substantially increased above prepregnancy levels, In response to this metabolic demand, it was shown in this study that the minute volume of air-breathing postpartum rats on day 13 of lactation increased to approximately 150%, of that of age-matched postlactating rats with the same lung size. Heightened ventilation in lactating rats was maintained during exposure to 0.3, 0.5, and 1.0 ppm ozone for 6 h, resulting in greater inhaled ozone doses in lactating rats compared to postlactating rats exposed identically The pulmonary inflammatory response to ozone was assessed in the same rats 18 h after exposure by comparison of protein concentration and polymorphonuclear cell (PMN) numbers in bronchoalveolar lavage fluid (BALF). Both of these parameters were significantly greater in lactating than postlactating rats at 0.3, 0.5, and 1.0 ppm ozone. Statistical analysis indicated that most or all of the greater BALF protein in lactating rats could be accounted for by their greater inhaled dose, whereas a significant portion of the enhanced PMN influx in lactating rats remained unexplained by inhaled ozone dose

Kerosene space heaters are widely used as a major source of home heat in the United States and in countries such as Japan and Korea. Based on a report that evaluated particle emissions from unvented kerosene space heaters in an environmental chamber, kerosene space heaters can be an important indoor source of fine particles and a major source of sulfate and acidic aerosols. In this study, guinea pigs were exposed to filtered air or kerosene space heater (9000 Btu radiant heater) emissions for 3 h/day for 1 wk or 6 h/day, 5 days/wk for 4 wk. The following pollutant concentrations were measured during the exposure period: total mass loading, 69 mu g/ms(3); NO2, 0.17 ppm; particle number concentration, 2.7 x 10(5)/cm(3); SO2, 0.093 ppm; SO42-, 28.7 mu g/m(3). Nonspecific airway responsiveness was monitored before and during the 4-wk exposure period. Biochemical parameters in lavage fluid as well as functional characteristics of pulmonary macrophages were determined 24 h after the final exposure. In comparison to preexposure valves, the concentration of acetylcholine that decreased specific airway conductance by 50% was significantly decreased after 1 and 4 wk of exposure. These functional changes were accompanied by a small increase in lavage fluid protein following 4 wk of exposure (58%, p < .05) and by a number of alterations in pulmonary macrophages. Intracellular free Ca2+ concentration ([Ca2+](i) increased by 85% at the end of the 4-wk exposure. Small but statistically significant decreases in intracellular pH (pH(i)) of recovered lavage cells were also observed at the end of the 1-wk and 4-wk exposures. Furthermore, the in vitro phagocytic function of pulmonary macrophages was enhanced by 51% at the end of the 1-wk exposure and depressed by 79% at the end of the 4-wk exposure. Other changes in biochemical parameters or cell numbers were not observed. We conclude that repeated exposure to kerosene space heater emissions at concentrations relevant to those encountered in home use can produce alterations in airway responsiveness and pulmonary macrophage function in guinea pigs

Nitric acid (HNO3) vapor is a component of ambient photochemical pollution. Because of its high water solubility and reactivity, it would be anticipated to undergo significant removal within the upper respiratory tract (URT). However, recent studies have shown that inhaled vapor can alter bronchial responsiveness and other functions of the lower respiratory tract (LRT). The penetration of HNO3 into the lungs was assessed using a physical system that mimicked the residence time of inhaled air in the URT of the animal used in this laboratory for toxicologic studies, namely, the rabbit. The system allowed for mixing of precisely metered concentrations of ammonia (NH3), which is present in the URT, under conditions of controlled relative humidity. The size of particles produced when HNO3 was introduced into humid atmospheres was also determined. In an NH3-free atmosphere maintained at 77% relative humidity, ultrafine particles (0.003 mu m) were formed When NH3 was added, the particle size increased to 0.15 mu m. While there was greater production of particles when NH3 was present at various humidity levels, even in the absence of NH3 almost 50% of HNO3 vapor formed particles at high humidity. The ability of other particles to act as vectors for adsorbed/absorbed HNO3 was also examined; such particles could then be carried into the LRT. The results indicate that HNO3 vapor is likely transformed into particle Form al some point following inhalation. Furthermore, endogenous ammonia may react with inhaled HNO3 producing particulate ammonium nitrate. Once formed these particles, and others present in the respiratory-tract air, may serve as vectors for HNO3 delivery to the LRT