Abstract 1212: Increased Oxidative Stress in the Atherosclerosis-Predisposed Region of Mouse Aorta
In the arterial circulation, regions of disturbed flow are susceptible to atherogenesis, whereas regions of undisturbed laminar flow appear protected. The mechanisms underlying the regional susceptibility to atherosclerosis are yet to be determined. Recently, a low grade chronic inflammation has been reported in the atherosclerosis-predisposed regions. In addition, exposure of endothelial cells to disturbed flow leads to both oxidative and inflammatory responses. We sought to investigate the association of regional susceptibility to atherosclerosis and oxidative stress. En face confocal microscopy was employed in C57BL/6 mice (n = 8) to asses oxidative stress in the endothelium of atherosclerosis susceptible and protected regions (lesser and greater curvature of the ascending aortic arch, LC and GC). Intravenous injection of redox-sensitive fluorescent dyes, Dehydroethidium (nuclear) and Dihydrorhodamine-123 (cytosolic) revealed an increased production of reactive oxygen species (ROS) in atherosclerosis susceptible regions relative to the protected regions (67±7 VS 34±4 PMI P = 0.01). DHE oxidation was significantly reduced by administration of 10 μM diphenyliodonium, a NADPH oxidase inhibitor. Hoeschst, a fluorescent nuclear dye with no reaction to ROS distributed evenly in the LC and GC regions. To determine the source of elevated oxidative stress, endothelial cells were isolated and pooled from the LC and GC regions of 3– 4 mice and transcript profile of ROS and antioxidant producing genes were compared using real time PCR technique (n = 4). mRNA levels of super oxide producing enzymes, NADH oxidase (P47phox and gp91phox subunits) and xanthine dehydrogenase were increased in the regions predisposed to atherosclerosis (5.7±0.4, 6.2±0.6, and 2.7±0.3 fold, respectively). Genes involved in antioxidant defense (Super oxide dismutase-2, Hemeoxogenase, Glutathione reductase, Glucose 6 phosphate dehydrogenase, Glutaredoxin) also showed an increased expression in LC region except for Thioredoxin mRNA level which was lower. Expression of redox-sensitive transcription factor, c-fos was elevated in LC region. Our study for the first time demonstrated an augmented oxidative stress in atherosclerosis susceptible regions of mouse aorta.