Stabilization of advanced atherosclerosis in low-density lipoprotein receptor-deficient mice by aspirin.

COX-1-dependent eicosanoid formation accelerates atherogenesis, and low-dose aspirin reduces early atherosclerosis. However, the role of aspirin in modulating progression of vascular atherosclerotic lesions once established is less investigated. We wished to determine the effect of low-dose aspirin on vascular inflammation, plaque composition, and progression of established atherosclerosis. Low-density lipoprotein receptor-deficient mice (LDLR(-/-)) were fed a high-fat diet for 3 months. At this time, one group of mice underwent baseline analysis. Two additional groups, while continuing the high-fat diet, were randomized to receive placebo or aspirin for additional 3 months. At the end of the study, LDLR(-/-) mice that had received aspirin had suppressed biosynthesis of thromboxane B2, the major products of COX-1 activity, reduced monocyte chemoattractant protein-1, and soluble intercellular adhesion molecule-1 levels compared with controls. Compared with baseline, the placebo group had significant progression of atherosclerosis. In contrast, aspirin treated mice showed a significant reduction in progression of atherosclerosis, and a significant decrease in foam cell content. These results suggest that in murine atherosclerosis, low-dose aspirin retards progression of established and advanced vascular atherosclerotic lesions by suppressing the formation of bioactive lipids and vascular inflammation.