Diesel Exhaust and Atherosclerotic Plaque Stability

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DESCRIPTION (provided by applicant): There is epidemiological, clinical, and experimental data linking chronic and acute exposure to air pollution with morbidity and mortality from cardiovascular disease. The mechanisms by which pollutants such as diesel exhaust contribute to cardiovascular disease are unknown but multiple possibilities have been posited. These include responses to common molecular mediators elicited by the pollutants in the lungs. Small particulates have been shown to induce oxidative stress and expression of pro-inflammatory cytokines by many cell types within the lungs. It is likely therefore that this inflammatory response in the lungs also impacts the ongoing inflammation in the blood vessels. Inflammatory mechanisms are associated with both atherosclerotic lesion initiation and progression. Cytokines and other proinflammatory factors are expressed by leukocytes, endothelial cells, and smooth muscle cells in atherosclerotic lesions and are thought to contribute to the destabilization of the plaques by further inducing localized oxidant stress with consequent loss of nitric oxide mediated dilation, increasing expression and secretion of matrix metalloproteinases, and causing cell death. The death of macrophages and smooth muscle cells is largely responsible for the formation of the necrotic core and thinning of the fibrous cap. These changes in turn, reduce the tensile strength of the plaques and lead to plaque rupture, occlusive thrombosis and ischemia, the ultimate causes of myocardial infarction and stroke. In this proposal, the investigators will draw on their extensive experience with mouse models of unstable atherosclerosis and oxidant stress and their experience in measuring cardiac and vascular function in mice. They will investigate how acute and chronic exposures to diesel exhaust in a unique controlled exposure chamber impact on cytokine secretion, flow mediated dilation, the electrical properties of the heart and the progression and stability of advanced atherosclerofic lesions. The investigators will also directly address the role of oxidant stress in mediating the effects of diesel exhaust by employing unique mouse models that have either an increased capacity to produce the main endogenous antioxidant glutathione specifically in macrophages or conversely, mice that have a reduced capacity to produce glutathione.