Thrombin generation by intimal tissue factor contributes to thrombus formation on macrophage-rich neointima but not normal intima of hyperlipidemic rabbits

Arterial thrombosis occurs in atherosclerotic, but rarely in non-atherosclerotic arteries. The present study investigates how hyperlipidemic condition affects thrombus formation on macrophage-rich neointima or normal intima in rabbits. Rabbits were fed with a 0.5% cholesterol diet, and then the femoral artery on one side of each rabbit was injured with a balloon catheter. Three weeks later, bilateral femoral arteries were similarly injured with a balloon catheter to produce thrombi on neointima and normal intima. We compared the expression and activity of intimal tissue factor (TF) as well as thrombus size and composition between these femoral arteries. 0.5% cholesterol diet combined with a balloon injury induced macrophage-rich neointima in injured arteries. The whole blood coagulation activity or plasma thrombin generation activity did not differ after consuming the 0.5% cholesterol diet for 4 weeks, and an anti-TF antibody did not affect the measured parameters. TF activities were increased in the neointima/media compared with normal intima/media. Balloon injury induced large platelet-fibrin thrombi on macrophage-rich neointima, whereas small platelet thrombi were produced in normal arteries even under hyperlipidemic conditions. Recombinant human tissue factor pathway inhibitor (25 mu g/(kg min)) and argatroban (100 mu g/(kg min)), a specific thrombin inhibitor, significantly reduced thrombus formation on induced neointima, but not on normal intima. Thrombin generation mediated by TF in intima contributes to thrombus formation on macrophage-rich neointima, but not on normal intima. The TF content in disrupted atherosclerotic plaques might play a more important role than hyperlipidemia in the development of atherothrombosis. (C) 2009 Elsevier Ireland Ltd. All rights reserved.