Effects of aspirin on atherosclerosis and the cyclooxygenase-2 expression in atherosclerotic rabbits

Background Atherosclerosis is a complex vascular inflammatory disease. Aspirin is a mainstay in the prevention of vascular complications of atherosclerosis. In this study, the effectiveness of aspirin in suppressing atherosclerosis and the inflammation process was evaluated in rabbits fed with a high fat diet. Methods Eighteen male New Zealand rabbits were randomly divided into 3 groups： control group, untreated cholesterol-fed group, aspirin treated cholesterol-fed group, which were fed for 12 weeks. After 12 weeks, the aorta was harvested for pathologic morphology observation. Immunohistochemical analysis of cyclooxygenase-2 （COX-2）, macrophage and vascular smooth muscle cell （VSMC） was performed. The statistical analysis was performed by the statistical program SPSS 10.0. Results The aorta plaque/intima size （P/I） by pathologic morphology observation was 0%, （59.6± 13.7）% and （36.3±16.5）% in the control, untreated cholesterol-fed group and aspirin treated group, respectively. The maximum plaque thickness, the degree of artery stenosis and the proportion of the intimal circumference occupied by atheroma of the 3 groups were significantly different from each other （P〈0.01）. The expression of COX-2 and macrophage in plaque of the aspirin treated group were decreased compared with that in untreated cholesterol-fed group. However, no difference was found in the expression of VSMC between the aspirin treated and the untreated cholesterol-fed group. Conclusion The mechanism of atherosclerosis suppression by aspirin in cholesterol-fed rabbits is related to the inhibition of COX-2 expression together with the reduced inflammation followed by, but not related to the hypolipidemic effects.