Cilostazol inhibits accumulation of triglyceride in aorta and platelet aggregation in cholesterol-fed rabbits

Abstract

Cilostazol is clinically used for the treatment of ischemic symptoms in patients with chronic peripheral arterial obstruction and for the secondary prevention of brain infarction. Recently, it has been reported that cilostazol has preventive effects on atherogenesis and decreased serum triglyceride in rodent models. There are, however, few reports on the evaluation of cilostazol using atherosclerotic rabbits, which have similar lipid metabolism to humans, and are used for investigating the lipid content in aorta and platelet aggregation under conditions of hyperlipidemia. Therefore, we evaluated the effect of cilostazol on the atherosclerosis and platelet aggregation in rabbits fed a normal diet or a cholesterol-containing diet supplemented with or without cilostazol. We evaluated the effects of cilostazol on the atherogenesis by measuring serum and aortic lipid content, and the lesion area after a 10-week treatment and the effect on platelet aggregation after 1- and 10-week treatment. From the lipid analyses, cilostazol significantly reduced the total cholesterol, triglyceride and phospholipids in serum, and moreover, the triglyceride content in the atherosclerotic aorta. Cilostazol significantly reduced the intimal atherosclerotic area. Platelet aggregation was enhanced in cholesterol-fed rabbits. Cilostazol significantly inhibited the platelet aggregation in rabbits fed both a normal diet and a high cholesterol diet. Cilostazol showed anti-atherosclerotic and anti-platelet effects in cholesterol-fed rabbits possibly due to the improvement of lipid metabolism and the attenuation of platelet activation. The results suggest that cilostazol is useful for prevention and treatment of atherothrombotic diseases with the lipid abnormalities.

Figure 1. Comparison of atherosclerotic areas in aorta.

Plaques areas in the aorta of a typical animal in each group are shown by black areas (A). Individual values in the control group are shown by closed triangles (previous study) and closed circles (present study) and those in the cilostazol group by opened triangles (previous study) and opened circles (present study) and the horizontal bars in each group represent the mean and the vertical bars are the SD (B). Control [n = 10], cilostazol [n = 10]. *: p<0.05, **: p<0.01 versus control by a two-way ANOVA.

Figure 2. Effects of cilostazol on the lipid contents in the atherosclerotic aorta.

Amounts of triglyceride (A), total cholesterol (B), free cholesterol (C) and phospholipid (D) in different regions of the aorta. Individual values of the control group are shown by closed columns and those of the cilostazol group by opened columns. Data represent means ± S.D. Control [n = 5], cilostazol [n = 5]. *: p<0.05, **: p<0.01 versus control by t-test.

Figure 3. Immunohistochemical staining of macrophages in the proximal ascending aorta.

Cross sections of the proximal ascending aorta were stained by an anti-macrophage RAM11 antibody. The brown part represents the macrophage-positive area. Typical images are shown for the control and cilostazol groups. Two of the five samples in the cilostazol group were not stained by the RAM11 antibody (the right image of cilostazol), although all samples were stained in the control group.

Figure 4. Platelet aggregation in rabbits.

Comparison of platelet aggregation between normal and hypercholesterolemic rabbits (A). Effect of cilostazol on platelet aggregation in normal rabbits (B) or hypercholesterolemic rabbits (C). The control group are shown by closed circles and the cilostazol group by open circles. Correlation between serum TC and PATI values (D). Normal rabbits are shown by closed triangles and hypercholesterolemic rabbits by open triangles. Data represent means ± S.D. Normal rabbit study: control [n = 8], cilostazol [n = 8], hypercholesterolemic rabbit study: control [n = 5], cilostazol [n = 5]. **: p<0.01 versus control by t-test. PATI: Platelet aggregatory threshold index, TC: total cholesterol, R: correlative rate.

Figure 5. Serum TG analysis by HPLC.

Lipoproteins in 10 week treatment serum samples were analyzed by HPLC. The mean value of the control group is shown by a red line and the cilostazol group by the blue line and the normal diet group by the green line. Control [n = 5], cilostazol [n = 5], normal diet [n = 3].