Faculty Bibliography

It is becoming increasingly clear that genetic susceptibility is an important host factor determining the effects of exposure to a number of airborne particles and gases. Although numerous studies have identified a genetic component for spontaneous pulmonary tumor development and for chemically induced lung cancer (e.g., urethane) in mice, a systematic examination of murine inter-strain differences in response to cigarette smoke inhalation has not been conducted. We addressed this research gap by examining the strain distribution pattern of lung cancer in nine inbred strains of mice exposed to 258 mg/m(3) mainstream cigarette smoke for 5 months followed by 4 months of rest. Lung tumors were enumerated on fixed lungs visualized at low magnification and on serial step sections examined microscopically. With the low magnification examination, we observed statistically significant increases in the number of lung tumors in cigarette smoke-exposed A/J and the genetically-related A/HeJ mice (p<0.05). While fewer tumors were identified by the microscopic enumeration method, it confirmed that significant increases in lung tumors occurred only in A/J and A/HeJ mice exposed to cigarette smoke (p<0.05). Thus, as predicted by epidemiologic studies and animal experiments using chemically induced lung cancer models, these findings suggest that genetic host factors play a significant role in the pulmonary tumorigenic response of mice to mainstream cigarette smoke

Ozone (O(3)) is a respiratory irritant that leads to airway inflammation and pulmonary dysfunction. Animal studies show that neonates are more sensitive to O(3) inhalation than adults, and children represent a potentially susceptible population. This latter notion is not well established, and biological mechanisms underlying a predisposition to pollution-induced pulmonary effects are unknown. We examined age and strain as interactive factors affecting differential pulmonary responses to inhaled O(3). Male and female adult mice (15 weeks old) and neonates (15-16 days old) from eight genetically diverse inbred strains were exposed to 0.8 ppm O(3) for 5 h. Pulmonary injury and lung inflammation were quantified as total protein concentration and total polymorphonuclear neutrophil (PMN) number in lavage fluid recovered 24-h postexposure. Dose-response and time-course curves were generated using SJL/J pups, and (18)O lung burden dose was assessed in additional mice. Interstrain differences in response to O(3) were seen in neonatal mice: Balb/cJ and SJL/J being most sensitive and A/J and 129x1/SvJ most resistant. The PMN response to O(3) was greater in neonates than in adults, specifically for SJL/J and C3H/HeJ strains, independent of dose. Small gender differences were also observed in adult mice. Variation in protein concentrations and PMN counts between adults and pups were strain dependent, suggesting that genetic determinants do play a role in age-related sensitivity to O(3). Further research will help to determine what genetic factors contribute to these heightened responses, and to quantify the relative contribution of genes vs. environment in O(3)-induced health effects

COMPLAINTS, COMPLAINTS, COMPLAINTS! Where are my results? Why do I have to wait so long? Is anybody listening? Does anybody care? I'm a taxpayer; I am entitled! Sound familiar? These are the kinds of things we hear on a daily basis from patients and family members

Exposure to ambient air pollution has been associated with adverse health effects including lung cancer. A recent epidemiology study has established that each 10mug/m(3) elevation in long-term exposure to average PM(2.5) ambient concentration was associated with approximately 8% of lung cancer mortality. The underlying mechanisms of how PM contributes to lung carcinogenesis, however, remain to be elucidated. We have recently found that transition metals such as nickel and chromium and oxidative stress induced lipid peroxidation metabolites such as aldehydes can greatly inhibit nucleotide excision repair (NER) and enhance carcinogen-induced mutations. Because PM is rich in metal and aldehyde content and can induce oxidative stress, we tested the effect of PM on DNA repair capacity in cultured human lung cells using in vitro DNA repair synthesis and host cell reactivation assays. We found that PM greatly inhibits NER for ultraviolet (UV) light and benzo(a)pyrene diol epoxide (BPDE) induced DNA damage in human lung cells. We further demonstrated that PM exposure can significantly increase both spontaneous and UV-induced mutagenesis. These results together suggest that the carcinogenicity of PM may act through its combined effect on suppression of DNA repair and enhancement of DNA replication errors

Size-fractionated particulate matter (PM) samples were collected from six U.S. cities and chemically analyzed as part of the Multiple Air Pollutant Study. Particles were administered to cultured lung cells and the production of three different proinflammatory markers was measured to explore the association between the health effect markers and PM. Ultrafine, fine, and coarse PM samples were collected between December 2003 and May 2004 over a 4-wk period in each city. Filters were pooled for each city and the PM samples were extracted then analyzed for trace metals, ions, and elemental carbon. Particle extracts were applied to cultured human primary airway epithelial cells, and the secreted levels of interleukin-8 (IL-8), heme oxygenase-1, and cyclooxygenase-2 were measured 1 and 24 h following exposure. Fine PM sources were quantified by the chemical mass balance (CMB) model. The relationship between toxicological measures, PM sources, and individual species were evaluated using linear regression. Ultrafine and fine PM mass were associated with increases in IL-8 (r(2) = .80 for ultrafine and r(2) = .52 for fine). Sources of fine PM and their relative contributions varied across the sampling sites and a strong linear association was observed between IL-8 and secondary sulfate from coal combustion (r(2) = .79). Ultrafine vanadium, lead, copper, and sulfate were also associated with increases in IL-8. Increases in inflammatory markers were not observed for coarse PM mass and source markers. These findings suggest that certain PM size fractions and sources are associated with markers of lung injury or inflammation

Recent studies have suggested a link between inhaled particulate matter (PM) exposure and atherogenesis. We investigated tissue factor (TF) expression with ambient fine particulate matter (diameter < 2.5 microm, PM(2.5)) exposure and in response to in vitro exposure to fine and ultrafine PM in cultured human bronchial epithelial cells, vascular smooth muscle cells (hSMCs), and monocytes. ApoE-/- mice, fed with normal chow (NC) or high-fat chow (HFC), were exposed to concentrated PM(2.5) or filtered air (FA) for 6 mo (6 h/day, 5 day/wk, n = 28). Following in vivo ultrasound bio-microscopy (UBM) assessment of plaque area, macrophage infiltration (CD68) and TF expression in the aorta were quantified. Cultured cells were incubated with size-fractionated PM from cascade impactors, or with standard reference PM material (SRM, number 1649a) and assayed for TF protein, mRNA, and activity. UBM-derived plaque areas were 7 +/- 1% larger in the PM(2.5)-HFC than the FA-HFC group (p = .04), but not significantly different between the PM(2.5)-NC and FA-NC groups (p = .07). Immunohistochemistry revealed increased TF (15 +/- 3% vs. 8 +/- 2%, p < .01) and macrophage infiltration (19 +/- 2% vs. 14 +/- 3%, p < .01) in the plaques of PM(2.5)-HFC compared with FA-HFC groups. Impactor-collected PM(2.5) and ultrafine particles consistently increased TF protein in bronchial epithelial cells, monocytes, and hSMCs. TF mRNA expression increased rapidly (within 1 h) in response to SRM PM. We conclude that in vivo and in vitro exposure to ambient air PM(2.5) induces TF expression

In December 2006, the U.S. Environmental Protection Agency (EPA) sponsored a 2-day workshop on 'Interpretation of Epidemiologic Studies of Multipollutant Exposure and Health Effects' in Chapel Hill, NC. The final session at this workshop was devoted to assessing the biological plausibility of epidemiological findings with regard to criteria air pollutants. The presentations and the panel contributions of this last session primarily focused on controlled exposure studies and led to wide-ranging discussions, some of which were provocative. The panel summary provides some guidance to future evaluations of the biological plausibility of the epidemiological reports on criteria pollutants and is intended to stimulate thinking, without drawing any definitive conclusions. This paper does not approach, nor was it intended to approach, the more formal analytical approach such as that used in EPA's development of its Science Assessment Document for the criteria pollutants

The Clean Air Act mandates the U.S. Environmental Protection Agency to periodically reassess existing and new science that underlie the regulation of major ambient pollutants -- particulate matter (PM) and tropospheric ozone being most notable. While toxic effects have been ascribed individually to these and other pollutants in the air, it is clear that mixtures of these contaminants have the potential to interact and thereby influence their overall toxic outcomes. It follows that a more comprehensive assessment of the potential health effects of the air pollution complex might better protect human health; however, traditional regulatory drivers and funding constraints have impeded progress to such a goal. Despite difficulties in empirically conducting studies of complex mixtures of air pollutants and acquiring relevant exposure data, there remains a need to develop integrated, interdisciplinary research and analytical strategies to provide more comprehensive (and relevant) assessments of associated health outcomes and risks. The research and assessment communities are endeavoring to dissect this complexity using varied approaches Here we present five interdisciplinary perspectives of this evolving line of thought among researchers and those who use such data in assessment: (1) analyses that coordinate air quality-health analyses utilizing representative polluted U.S. air sheds to apportion source and component-specific health risks; (2) novel approaches to characterize air quality in terms of emission sources and how emission reduction strategies might effectively impact pollutant levels; (3) insights from present-day studies of effects of single ambient pollutants in animal and controlled clinical toxicology studies and how these are evolving to address air pollution; (4) refinements in epidemiologic health assessments that take advantage of the complexities of existent air quality conditions; and (5) new approaches to integrative analyses to establish the criteria for regulation of PM and other criteria pollutants. As these examples illustrate, implementing multidisciplined and integrative strategies offer the promise of more realistic and relevant science, greater reductions in uncertainty, and improved overall air pollution assessment. The regulatory mandate may lag behind the science, but real gains both in public health benefit and the science to dissect complex problems will result

A workshop was held February 14, 2007, in Arlington, VA, under the auspices of the Phosgene Panel of the American Chemistry Council. The objective of this workshop was to convene inhalation toxicologists and medical experts from academia, industry and regulatory authorities to critically discuss past and recent inhalation studies of phosgene in controlled animal models. This included presentations addressing the benefits and limitations of rodent (mice, rats) and nonrodent (dogs) species to study concentration x time (C x t) relationships of acute and chronic types of pulmonary changes. Toxicological endpoints focused on the primary pulmonary effects associated with the acute inhalation exposure to phosgene gas and responses secondary to injury. A consensus was reached that the phosgene-induced increased pulmonary extravasation of fluid and protein can suitably be probed by bronchoalveolar lavage (BAL) techniques. BAL fluid analyses rank among the most sensitive methods to detect phosgene-induced noncardiogenic, pulmonary high-permeability edema following acute inhalation exposure. Maximum protein concentrations in BAL fluid occurred within 1 day after exposure, typically followed by a latency period up to about 15 h, which is reciprocal to the C x t exposure relationship. The C x t relationship was constant over a wide range of concentrations and single exposure durations. Following intermittent, repeated exposures of fixed duration, increased tolerance to recurrent exposures occurred. For such exposure regimens, chronic effects appear to be clearly dependent on the concentration rather than the cumulative concentration x time relationship. The threshold C x t product based on an increased BAL fluid protein following single exposure was essentially identical to the respective C x t product following subchronic exposure of rats based on increased pulmonary collagen and influx of inflammatory cells. Thus, the chronic outcome appears to be contingent upon the acute pulmonary threshold dose. Exposure concentrations high enough to elicit an increased acute extravasation of plasma constituents into the alveolus may also be associated with surfactant dysfunction, intra-alveolar accumulation of fibrin and collagen, and increased recruitment and activation of inflammatory cells. Although the exact mechanisms of toxicity have not yet been completely elucidated, consensus was reached that the acute pulmonary toxicity of phosgene gas is consistent with a simple, irritant mode of action at the site of its initial deposition/retention. The acute concentration x time mortality relationship of phosgene gas in rats is extremely steep, which is typical for a local, directly acting pulmonary irritant gas. Due to the high lipophilicity of phosgene gas, it efficiently penetrates the lower respiratory tract. Indeed, more recent published evidence from animals or humans has not revealed appreciable irritant responses in central and upper airways, unless exposure was to almost lethal concentrations. The comparison of acute inhalation studies in rats and dogs with focus on changes in BAL fluid constituents demonstrates that dogs are approximately three to four times less susceptible to phosgene than rats under methodologically similar conditions. There are data to suggest that the dog may be useful particularly for the study of mechanisms associated with the acute extravasation of plasma constituents because of its size and general morphology and physiology of the lung as well as its oronasal breathing patterns. However, the study of the long-term sequelae of acute effects is experimentally markedly more demanding in dogs as compared to rats, precluding the dog model to be applied on a routine base. The striking similarity of threshold concentrations from single exposure (increased protein in BAL fluid) and repeated-exposure 3-mo inhalation studies (increased pulmonary collagen deposition) in rats supports the notion that chronic changes depend on acute threshold mechanisms

Cor pulmonale is a significant cause of morbidity and mortality in patients with emphysema, but it is not known whether alveolar destruction is directly involved in the disease pathogenesis. The purpose of this study was to examine the relationship between susceptibility to smoking-induced cor pulmonale and alveolar destruction in eight inbred strains of mice: 129XI/SvJ, A/J, A/HeJ, BALB/cJ, C3H/HeJ, C57BL/6J, DBA/2J, and SWR/J. The mice were exposed to filtered air or mainstream cigarette smoke at a concentration of 250 mg/m(3) for 5.5 h/day, 5 days/wk for 5 mo, housed for 4 more months, and killed. The ratio of the weight of the right ventricle/left ventricle plus septum [RV/(LV + S)] was used to assess right ventricular hypertrophy. Alveolar mean linear intercept was used to quantify severity of alveolar destruction. Morphometric determination of blood vessel muscularization was done on sections from four mouse strains. Smoke exposure resulted in significant increases in RV/(LV + S) in the A/J and A/HeJ strains compared with air-exposed controls. The magnitude of the smoking-induced increase in RV/(LV + S) decreased as a function of the genetic distance of the other strains from the A/J and A/HeJ strains. Pulmonary vascular muscularization was significantly increased in smoke-exposed A/J and BALB/cJ mice but not in C3H/HeJ and C57BL/6 mice. Also, mouse strain susceptibility to smoking-induced pulmonary vascular muscularization did not correlate with changes in mean linear intercept. The data from this study suggest that alveolar destruction by itself is not sufficient to cause smoking-induced cor pulmonale in inbred mice