Faculty Bibliography

Chronic exposure to inhaled cadmium (Cd) has been shown to induce lung tumors in rats (Wistar strain) but not in mice (NMRI strain). The protein metallothionein (MT) plays an important role in Cd detoxification, and it has been suggested that differential inducibility of pulmonary MT may lead to interspecies susceptibility differences to inhaled Cd. Interstrain differences in the pulmonary response of the MT gene to Cd stimuli have not been examined in rats or mice. We compared pulmonary MT expression in Wistar Furth (WF) rats with that in DBA and C57 mice, following a single 3-h exposure to CdO fumes containing 1 mg Cd/m3. Induction of the MT gene was assessed by the levels of MT-I and MT-II transcripts, MT-protein content, and number of MT-labeled alveolar and bronchiolar epithelial cells immediately after Cd exposure and 1, 3, and 5 days later. Control animals were exposed to air/argon furnace gases. We observed differential intra- and interspecies inducibility of the MT gene in the lung following Cd inhalation. DBA mice exhibited greater levels of MT-mRNA, mainly for the MT-I isoform, MT-protein content, and number of MT positive cells relative to C57 mice. WF rats showed lower transcription and translation responses of the MT gene upon Cd stimuli than C57 mice. The present results, in concert with our previous findings of higher lung cell proliferation in Cd-exposed C57 relative to DBA mice, predict greater susceptibility of C57 to the carcinogenic effects of inhaled Cd. Furthermore, the low transcriptional and translation responses of the MT gene to Cd stimuli in WF rats might explain the higher susceptibility of this rat strain to develop malignant lung tumors after chronic exposure to Cd via inhalation. Parallel to our findings in mice, differences in the responsiveness of lung MT gene may exist across rat strains. Thus intraspecies genetic variability in pulmonary MT may influence the susceptibility of rats or mice to lung carcinogenesis induced by inhalation of Cd compounds.

To examine the biological plausibility of the adverse health effects of ambient particulate matter (PM), we have studied the cardio-pulmonary effects of PM in an animal model of pulmonary hypertension. Normal and monocrotaline-treated rats were exposed, nose-only, for 3 h to filtered air or concentrated ambient PM. At 3 h--but not 24 h--post-exposure, the percentage of neutrophils in peripheral blood was significantly elevated in PM-exposed animals while the percentage of lymphocytes was decreased with no change in white blood cell counts. These changes in white blood cell differential occurred in both normal and monocrotaline-treated animals. Small, but consistent changes in heart rate, but not core temperature, were observed after exposure to concentrated ambient PM. Pulmonary injury, as evidenced by increased protein levels in lavage fluid, occurred only in monocrotaline-treated animals exposed to > 360 microg/m3 PM. The observed pattern of hematological and cardiac changes suggests an activation of the sympathetic stress response

Epidemiological studies have shown that the prevalence of coal workers' pneumoconiosis (CWP) differed remarkably between different coal mine regions despite comparable exposures to respirable dust. In the United States, CWP was found to be most common in Pennsylvania coal miners and least common in miners from Utah. The active component(s) responsible for the regional differences in CWP has not yet been identified. In the present study, we found that coals from Pennsylvania, compared with Utah coals, showed a much lower buffering capacity as determined by the amount of acid consumed in order to reach pH 4.5, which is the pH of the phagolysosomes of macrophages. Moreover, the coals from Pennsylvania released large amounts of Fe2+ in the acidified extract, whereas the coals from Utah released little Fe2+. Using electron spin resonance (ESR), we found that the coals from Pennsylvania, but not from Utah, were effective in oxidizing formate by a radical pathway. Two coals, one from Utah with high buffering capacity and low acid-soluble Fe2+ and the other from Pennsylvania with low buffering capacity and high acid-soluble Fe2+, were then selected for cell treatment. We found that human tracheal epithelial (HTE) cells treated with the coal from Pennsylvania (10 microg/cm2) showed a 36% increase in oxidant formation over the control as detected by dichlorofluorescein assay, whereas the coal from Utah had no effect. An electrophoretic mobility shift assay was used to test the binding affinity of nuclear proteins extracted from the coal-treated HTE cells to an oxidative stress-responsive transcription factor activator protein-1 (AP-1) element. The coal from Pennsylvania with high acid-soluble Fe2+ (1 microg/cm2) activated AP-1 to the same extent as 10 microM H2O2, while the coal from Utah without acid-soluble Fe2+ had no effect. These results support our hypothesis that the prevalence of CWP may be higher in coal workers exposed to coal with high acid-soluble Fe2+ and low buffering capacity than in workers exposed to coal with low acid-soluble Fe2+ and high buffering capacity

Ozone is one of the most common air pollutants humans routinely inhale. We have previously shown that in vitro ozone exposure induces the DNA-binding activities of NF-kappaB and NF-IL6 as well as the expression of interleukin 8 in respiratory epithelial cells. In this study, we investigated intracellular signaling steps mediating ozone-induced inflammatory mediator release. A549 cells, a type II like alveolar epithelial cell line, were exposed in vitro to air or 0.1 ppm of ozone in the presence of several kinase inhibitors. Exposure to ozone increased interleukin 8 expression and transcription factor activities in a protein tyrosine kinase (PTK)-dependent and protein kinase A (PKA)-dependent, yet protein kinase C (PKC)-independent, manner. Furthermore, ozone-induced PTK and PKA activities but failed to induce PKC activity. In addition, our results suggest that ozone-induced PTK and PKA activities were reactive oxygen intermediate dependent and occurred in parallel, because specific inhibitors for PTK and PKA failed to block the other kinase's activity. These results indicate that PTK and PKA activities are early events in the signal transduction cascade mediating the ozone-induced activation of NF-kappaB and NF-IL6 as well as the release of interleukin 8

In ambient air, organic chemicals are common constituents of aerosol particles, and many of them are surface-active. If these compounds are present as surface films on aqueous droplets, mass transfer of gaseous molecules into or out of the droplets could be impeded, and the hygroscopic growth of acidic droplets could be reduced. In this work, the effects of organic films on the hygroscopic growth rate of ultrafine H2SO4 aerosols (40-120 nm) were investigated under relative humidity conditions of 20-85% and over time scales of 6 and 10 s. Lauric (C-12 saturated),stearic(C-18,saturated),and oleic acids were chosen as the film coating materials. The experimental results showed that the presence of monolayer films of some fatty acids retards the hygroscopic growth rate of H2SO4 aerosol due to the obstructive effect of the films on the permeation of water vapor. The retardation effects depend on the original film coating thickness. Molecular structure of the film-forming compounds is an important factor for determining the effectiveness of the film. Linear molecules, such as lauric and stearic acids, have stronger effects on mass transport of water vapor than those of nonlinear molecules, such as oleic acid

To investigate whether aerosol droplet size influences structural changes in the lung produced by short-term, concomitant exposure to ozone and sulfuric acid, groups of 10 rats were exposed 4 hr/day for 2 days to filtered air, 0.6 ppm ozone, 0.5 mg/m3 fine (aerosol mass median diameter (MMD) = 0.3 microm) or ultrafine (MMD = 0.06 microm) sulfuric acid, or a mixture of ozone and 0.5 mg/m3 fine or ultrafine sulfuric acid. The volume percentage of total parenchyma containing markedly to severely injured alveolar septae was measured morphometrically. There were no differences between the ultrafine or fine acid exposure groups and the sham group for any of the morphologic endpoints. Volume percentage of markedly to severely injured tissue was increased in the ultrafine, but not fine, mixture animals when compared with the ozone-only group. In addition, a synergistic interaction between ozone and ultrafine, but not fine, sulfuric acid was found for this endpoint. The bromodeoxyuridine cell labeling index in the periacinar region was greater in the rats exposed to the fine sulfuric acid and ozone mixture than that in rats exposed to ozone alone, and a synergistic interaction between ozone and fine sulfuric acid was found for this end point. None of the exposures produced any changes in ventilatory parameters. Thus, acid aerosol droplet size was found to influence the effect of sulfuric acid in modifying ozone-induced structural changes in the rat lung

Ozone, one of the most reactive oxidant gases to which humans are routinely exposed, induces inflammation in the lower airways. The airway epithelium is one of the first targets that inhaled ozone will encounter, but its role in airway inflammation is not well understood. Expression of inducible genes involved in the inflammatory response, such as interleukin (IL)-8, is controlled by transcription factors. Expression of the IL-8 gene is regulated by the transcription factors nuclear factor (NF)-kappaB, NF-IL-6, and possibly activator protein-1 (AP-1). Type II-like epithelial cells (A549) were grown on a collagen-coated membrane and exposed in vitro to 0.1 ppm ozone or air. Exposure to ozone induced DNA-binding activity of NF-kappaB, NF-IL-6, and AP-1. IL-8 mRNA and IL-8 protein levels were also increased after ozone exposure. These results link ozone-induced DNA-binding activity of transcription factors and the production of IL-8 by epithelial cells thus demonstrating a potential cellular cascade resulting in the recruitment of inflammatory cells into the airway lumen

In vivo exposure to ozone (O3) has been shown to cause airway epithelial damage and lipid peroxidation. The oxidation of polyunsaturated fatty acids has been shown to produce hydrogen peroxide and aldehydes with reactive oxygen species (ROS) as intermediates. These products of ozonation may react with other bioorganic molecules and cause cellular damage. To assess the production of ROS, confluent primary cultures of guinea pig airway epithelial cells were grown on Costar membrane with a liquid-air interface and exposed to 0.2, 0.4, and 0.6 ppm O3. The concentrations of intracellular ROS during the exposure were monitored using the fluorescent dye dihydrorhodamine-123. The intracellular concentration of ROS increased immediately upon the commencement of the O3 exposure and persisted until the end of the exposure period (up to 1 hr). The concentration of ROS increased with increasing O3 concentration. To determine the species of ROS produced during O3 exposure, airway epithelial cells were perfused with dimethyl sulfoxide (DMSO), sodium formate (hydroxyl radical scavengers), NaN3 (catalase inhibitor), or diethyl-dithio carbamate (DEDC, superoxide dismutase inhibitor) prior to and during the exposure period and the fluorescent intensity was monitored continuously. While both DMSO and sodium formate decreased the concentration of ROS, DEDC and NaN3 had no effect. We concluded that hydroxyl radicals instead of H2O2 or superoxide anions were produced immediately following the commencement of O3 exposure in guinea pig airway epithelial cells in an exposure concentration-dependent fashion

Results from animal and preliminary human exposure studies have called into question whether the 5 mg/m3 8-hour time-weighted average threshold limit value (TLV) for zinc oxide fume is sufficient to protect workers against metal fume fever. The objectives of this study were to determine the clinical effects of exposures to low concentrations of zinc oxide and to ascertain whether these exposures elevated circulating levels of specific cytokines, which could account for the symptoms of the metal fume fever syndrome. Thirteen resting naive subjects inhaled, on separate days, air and 2.5 and 5 mg/m3 of furnace-generated zinc oxide fume for 2 hours. Subjects recorded symptoms and temperature and had blood drawn before and after each exposure. The mean (+/- SE) maximum rise in oral temperature at 6 to 12 hours after exposure was 1.4 +/- 0.3 degrees F after 5 mg/m3, compared with 0.6 +/- 0.5 degrees F after air exposure (P < 0.05). Mean temperature was also elevated after exposure to 2.5 mg/m3 zinc oxide (1.2 +/- 0.3 degrees F). In a parallel fashion, plasma levels of interleukin 6 (IL-6), a pyrogen, were significantly elevated after exposure to 5 mg/m3 zinc oxide. Mean IL-6 values (pg/mL) at pre-exposure and at 3 and 6 hours post-exposure were 1.9 (+/- 0.6), 2.8 (+/- 0.7), and 2.9 (+/- 0.6), respectively, on the air day and 1.6 (+/- 0.6), 4.4 (+/- 1.2), and 6.4 (+/- 1.1) on the 5 mg/m3 zinc oxide day. Zinc oxide exposure did not significantly affect plasma levels of tumor necrosis factor. Total symptom scores peaked 9 hours after the 5 mg/m3 zinc oxide exposure. Myalgias, cough, and fatigue were the predominant symptoms reported. Inhalation of zinc oxide for 2 hours at the current TLV of 5 mg/m3 produces fever and symptoms along with elevation in plasma IL-6 levels