PROJECTS

Project 1: Contribution of Primary and Secondary PM Sources to Exposure and Evaluation of their Relative Toxicity
Contantinos Sioutas, PI; Philip Fine, Michael Geller, William Hinds, Yifang Zhu, James Schauer, Martin Shafer
While all four projects proposed to be undertaken by the SCPC are inter-related, Project 1 is central, based on its hypotheses that chemical composition and physical characteristics related to sources have crucial relevance to the toxicity and exposure-response characteristics of PM and that variations in exposure according to source, season, and location influence the eventual human health response. The other Projects build upon these hypotheses, and Project 1 is an integral part of Projects 2, 3 and 4, by serving as the field operations for concentrating ambient PM for toxicity testing and animal exposure studies. The extensive PM characterization at sites relevant to the Project 4 human population study will have direct relevance to the interpretation of the toxicological and health outcomes in that study. To achieve their primary objective of examining the relationships between PM sources, exposure and toxicity, Drs. Sioutas and his colleagues will conduct extensive sampling at major PM sources in the LAB with a range of temporal and geographical characteristics, using the mobile, size-selective particle concentrators developed by Dr. Sioutas. Several locations have been selected to overlap with the Children’s Health Study (CHS). Indoor sources are included as is a study of non-volatile vs. semi-volatile PM. The PM collected from a range of sources will be extensively characterized for chemical composition, size, and airborne concentration. Source apportionment by chemical mass balance methods will involve analysis of defined source tracers. A particular focus of this research will be the determination of how the toxicity, composition, and exposure to the multiple sources varies from source to receptor areas as the aerosol ages and undergoes atmospheric chemistry to learn more about the impact of atmospheric processes in relation to toxicological outcomes. In addition to mobile vehicle sources and wood combustion, we will expand our understanding of the potential consequences of exposure to PM from major sources in the LAB which have received inadequate attention including air and marine ports.

Project 2: The Role of Oxidative Stress in the Susceptibility to PM-Induced Adverse Health Effects
Andre Nel, PI; Aldons Lusis, Jack Harkema, Michael Kleinman
Project 3: Chemical Reactivity of Particulate Matter from Primary and Secondary Sources, Modification of Chemical and Cellular Properties of PM-Assocaited Components by the Patricle Matrix
Arthur Cho, PI; John Froines, John Fukuto, Yoshito Kumagai.
Projects 2 and 3 propose toxicological research that seeks to 1) identify the important chemical/physical characteristics of PM in relation to a wide array of toxicological endpoints; 2) identify physiological, cellular, biochemical, and molecular mechanisms that explain specific health effects associated with exposure to PM and/or specific PM components with particular reference to the mechanism(s) of PM-induced asthma and atherosclerosis exacerbation; 3) investigate whether a failure of appropriate antioxidant defense could constitute the basis of PM susceptibility; 4) assess the dose-dependent exacerbation of allergic airway inflammation and aortic atherosclerotic lesions by concentrated PM; and 5) study the intracellular disposition and toxicokinetics of PM and its chemical components. Our principal mechanistic hypothesis for the toxicological research is that PM-induced oxidative stress initiates airway and arterial wall inflammation due to reactive chemical species. These chemical species can be organic or inorganic and act through several possible chemical reactions with biological substrates; we are focusing on redox and electrophilic reactions. We propose that the biological response to oxidative stress is a hierarchical event, in which the induction of antioxidant defense at the lowest tier (Tier 1) of oxidative stress protects against the pro-inflammatory (Tier 2) and cytotoxic effects (Tier 3) of higher levels of oxidative stress. Integral to this hypothesis is that a weakened antioxidant defense may define disease susceptibility. This hypothesis has relevance to the study of both acute and chronic health endpoints. Chemical assays developed during the first 5 years of the Center will be employed to study the quantitative formation of catalytically generated reactive oxygen species (ROS) and to determine the magnitude of electrophilic activity (Project 3). In vitro studies will examine the intracellular activity of PM in relation to ROS generation and oxidative stress, using a variety of assays. The importance of the PM matrix in relation to the adsorbed components will be analyzed with extraction techniques as well as the use of synthetic particles. A series of in vivo studies will rigorously investigate the mechanistic details of the health effects of PM linked to oxidative stress. We will use normal and genetically susceptible murine models to study PM-induced exacerbation of asthma and atherosclerosis. These experiments will seek to demonstrate that exposure to ambient PM, especially fine and ultrafine particles: (i) lead to asthma and atherosclerosis exacerbation in susceptible murine models; (ii) lead to airway and arterial wall inflammation as a result of oxidative stress; (iii) act in a dose-dependent manner; and (iv) differ in their relative potency due to differences in their content of redox cycling organic chemicals. The experiments to be conducted in Projects 2 and 3 will couple in vitro assays with in vivo experiments, carried out at a range of exposure concentrations. The findings will enable us to determine the strongest statistical predictors of in vivo outcomes in murine models, using in vitro and chemical assay results as exposure metrics of biological activity.

Project 4: Oxidative Stress Responses to PM Exposure in Elderly Individuals with Coronary Heart Disease
Ralph Delfino, PI; Susan Neuhausen, Nostratola Vaziri; Norbert Staimer
The overall goal of Project 4 is to advance knowledge on the importance of particle size and composition to the induction of oxidative stress and systemic inflammatory responses that may be responsible for observed cardiovascular outcomes in epidemiological time series studies of PM exposure. The design is a repeated measures panel study of high-risk elderly people with coronary heart disease (CHD). Aspects of this panel study have been previously funded; SCPC activities will add critical data to the exposure assessment, measure biomarkers of oxidative damage, and develop a genetic susceptibility component for the study. Intensive exposure assessments are planned that include indoor and outdoor home PM mass, number concentration, and particle composition. Accumulation and ultrafine mode PM will be extracted to measure concentrations of transition metals and tracer compounds for use in apportioning PM exposures to specific sources including vehicular emissions, photochemical activity, cooking, and wood smoke. Circulating biomarkers indicating systemic oxidative stress responses will be measured. Changes in these biomarkers are expected to be associated with cardiovascular outcomes and with the inflammatory biomarkers measured in the parent NIEHS study. The panel study will be coupled with Project 2 through the study of PM-induced oxidative modification of LDL and HDL, leading to altered pro-inflammatory and anti-inflammatory properties, respectively. The association between biomarkers of oxidative stress and exposure to a variety of PM measures including elemental and organic carbon, and specific metals and organic components used as source tracers will be ascertained. Statistical analysis of biomarker associations with ROS and electrophilic activity provides a direct linkage to Project 3. In addition, genetic susceptibility to oxidative damage will be explored, by genotyping each study subject for polymorphisms in genes likely to be involved in oxidative stress responses.