All ETDs from UAB

Advisory Committee Chair

Scott W Ballinger

Advisory Committee Members

John Chatham

Victor Darley-Usmar

Roger White

Ed Postlethwait

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

An estimated 70 million Americans have one or more types of cardiovascular disease (CVD). Although the sequence of events leading to CVD are still controversial, there is a general consensus that atherosclerotic lesions result from oxidative stress associated with risk factor. For this study, it was hypothesized that endogenous mitochondrial oxidative stress would influence susceptibility to atherogenesis and mitochondrial damage mediated by CVD risk factor exposure. To test this hypothesis, atherosclerotic lesion formation, oxidant stress, and mitochondrial DNA damage were assessed in hypercholestoremic mice (apolipoprotein E null - apoE -/- SOD2 +/+) and mice with significantly decreased levels of the mitochondrial antioxidant manganese superoxide dismutase (SOD2) (apoE -/-, SOD2 +/- mice) exposed to environmental tobacco smoke (ETS) or filtered air. Measures of atherosclerotic lesion development (oil red-O staining of whole aorta), oxidative stress (protein carbonyl levels, hydrogen peroxide levels, 3-nitrotyrosine levels), and mitochondrial damage (mitochondrial DNA - mtDNA damage) were quantified from aortic and heart tissues. ETS exposure significantly increased atherogenesis, oxidative stress and mitochondrial damage in both apoE -/-, SOD2 +/+ and apoE -/-, SOD2 +/- mice; however, SOD2 compromised mice (apoE -/-, SOD2 +/-) were significantly more susceptible to the deleterious effects of cigarette smoke compared to controls. A second series of studies were performed to determine the effects of decreased SOD2 capacity in vascular endothelial cells. For these studies, SOD2 protein levels were decreased using SOD2 siRNA in human vascular endothelial cells (HUVEC), and cellular ROS levels determined in the absence and presence of the inflammatory cytokine, TNF-α (tumor necrosis factor α). These experiments revealed that endothelial cells with compromised SOD2 protein levels and activity generated significantly higher levels of cellular oxidants, which were further increased in response to TNF-α treatment compared to controls. Overall, the data from these studies are consistent with the hypothesis that endogenous mitochondrial oxidant regulation can modulate susceptibility to known CVD risk factors such as hypercholesterolemia and ETS in mice and furthermore, alter endothelial cell oxidant response under basal and inflammatory conditions thereby influencing the impact of known CVD risk factors on disease susceptibility.

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