Targeting coagulation factor Xa with rivaroxaban reduces the onset and progression of atherosclerosis and enhances plaque stability in ApoE null mice
J. Posthuma1, J. Posma1, R. van Gorp1, A. Jaminon1, P. Leenders1, R. van Oerle1, S. Heitmeier2, L. Schurgers1, H. ten Cate1, H. Spronk1 (1Maastricht, The Netherlands, 2Wuppertal, Germany)
Time: 08:00 - 09:15
Objective: Atherosclerosis is a progressive chronic inflammatory vascular disorder, complicated by plaque rupture and subsequent thrombus formation. In vitro studies indicate that clotting proteases such as thrombin and Xa (FXa) promote a range of cellular actions related to atherosclerosis - e.g. vascular permeability, inflammation, and apoptosis-, presumably mediated through protease activated receptors (PARs). To elucidate the contribution of FXa in atherosclerosis, we investigated the effects of the direct FXa inhibitor rivaroxaban in atherosclerosis prone ApoE-/- mice.
Methods: Female ApoE-/- mice (age 8-9weeks) received high-fat diet with or without rivaroxaban (1.2mg/gram chow) for 8 or 14 weeks (n=8/group). In a second arm, ApoE-/- mice received high-fat diet for 14 weeks, followed by either continuation with standard high-fat diet or high-fat diet supplemented with rivaroxaban (1.2mg/gram chow) for 6 weeks. (n=5/group). Extent of aortic arch atherosclerosis was assessed by haematoxilin & eosin immunohistochemistry (IHC); plaque vulnerability was examined by IHC against collagen, vascular smooth muscle cells (VSMC) and matrix metalloproteinases (MMPs). Furthermore, PAR 1 and 2 expressions in the plaque were determined by IHC. All animal experimental protocols were carried out in compliance with the Dutch government guidelines and were approved by the Animal Care and Use Committee.
Results: Rivaroxaban treated mice reached therapeutic plasma levels (between 150 and 400 ug/mL) and showed less atherosclerotic lesions after 8 and 14 weeks compared to control (-36,92%, p<0,01 and -46,47%, p<0,01). In addition, rivaroxaban mice showed less atherosclerotic lesions after 20 weeks compared to control (-30,93%, p<0,05); this was accompanied by reduced necrotic core size in all rivaroxaban treated mice compared to controls. Additionally, inhibition of FXa resulted in a more stable atherosclerotic phenotype reflected by increased collagen and mean fibrotic cap thickness in all treated groups. These findings were accompanied by increased VSMC’s and reduced expression of MMPs and PARs.
Conclusion: Inhibition of FXa by rivaroxaban delays the onset and progression of atherosclerotic plaque in ApoE-/- mice. This protective effect is associated with reduced plaque vulnerability and possibly mediated through reduced PAR expression.