Combustion-Generated EPFRs: Assessing Cardiovascular Risks of Exposure

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Project Summary/Abstract: Project 2 Particulate matter (PM) is consistently associated with cardiopulmonary and cardiovascular mortality. Despite the risk of exposure, little is known about the mechanisms underlying PM-mediated toxicity. Our Center has shown that PM emissions from the thermal treatment (TT) of hazardous organics or contaminated soils at Superfund sites produce environmentally persistent free radicals (EPFRs). EPFRs are a unique particle- pollutant system capable of redox cycling to generate reactive oxygen species (ROS) in biological systems. EPFRs are present in contaminated Superfund soils and airborne PM near industrialized Superfund sites. Our prior Superfund project focused on the role of EPFRs in modulating cardiac function and disease. Although inhalation of EPFRs decreased baseline cardiac function, we found that these effects were secondary to changes in pulmonary vascular resistance. The mechanism(s) underlying these vascular effects are unknown; however, our preliminary data suggest that EPFR-mediated activation of the aryl hydrocarbon receptor (AhR) in pulmonary epithelial cells resulting in the release of vasoactive factors may play an important pathophysiological role. Our central hypothesis is that EPFR-mediated activation of AhR at the air-blood interface and mobilization of vasoactive mediators leads to activation/dysfunction of the pulmonary and systemic vasculature, resulting in cardiovascular disease. To test this hypothesis, Specific Aim 1 will test whether EPFR-mediated activation of the AhR in lung epithelium is responsible for the increase in pulmonary pressure and decreased diastolic filling that underlies EPFR induced cardiac dysfunction. After establishing the vasculature as the locus of injury, Specific Aim 2 will elucidate the cellular mechanisms of vascular injury by testing whether EPFRs induce vascular dysfunction via activation of the AhR. In both aims, control littermate mice and mice deficient in AhR specifically in alveolar type II will be exposed subchronially to EPFRs, non- EPFR PM, or filtered air using a recently designed inhalation system. Millar pressure-volume catheters will be used to measure left ventricular function and pulmonary arterial pressure in exposed mice. Telemetry devices will be used to record blood pressure. Endothelium-dependent vascular reactivity, as well as markers for both endothelial dysfunction and activation, will be assessed. Specific Aim 3 will identify a putative ligand promoting EPFR-induced AhR activation and test whether this metabolite is associated with EPFR-mediated vascular dysfunction. In collaboration with Project 1, this aim will use novel mass spectrometry approaches to identify and characterize EPFR-induced lipid oxidation products that may serve as endogenous AhR agonists so that we may correlate tissue and blood levels of these metabolites with vascular dysfunction. Completion of these Aims will provide important new data linking EPFR-mediated oxidative stress in epithelial cells, AhR activation, and cardiovascular disease. This information is critical for assessing risks to those living in proximity to sites using TT technologies to remediate Superfund or other hazardous wastes.