Abstract 4939: Hypercholesterolemia Increases Microparticle Tissue Factor and Activates Coagulation in LDL Receptor Deficient Mice
Objective: Tissue factor (TF) is the initiator of the extrinsic pathway of coagulation and contributes to thrombosis. Previous studies demonstrated that the risk of arterial thrombosis is elevated in patients with increased plasma cholesterol concentrations. In addition, increased levels of circulating TF, bound to microparticles (MPs), may induce thrombosis. Therefore, we tested the hypothesis that hypercholesterolemia increases plasma levels of MP TF and activation of coagulation in low density lipoprotein receptor deficient (LDLr−/−) mice.
Methods and Results: Male LDLr−/− mice were fed a high fat diet (HFD) consisting of 21% saturated fat, and 0.15% cholesterol for 0, 1, 2, 4, and 12 weeks (n=3–7 each time point). Mice were then euthanized, blood was collected from the inferior vena cava (into 3.8% sodium citrate), and plasma prepared. Mice had a sustained elevation in plasma cholesterol concentrations after 1 week of feeding HFD, which were unchanged in all subsequent feeding intervals (945±35 mg/dL). MP TF was analyzed by detection of Factor Xa generation in the presence or absence of an inhibitory rat anti mouse TF antibody. MP TF activity increased in a time-dependent manner at 1 (75%), 2 (112%), 4 (650%), and 12 (1140%) weeks (all times versus 0 week control; P<0.001). Importantly, a similar time-dependent increase in plasma thrombin-antithrombin (TAT) activity was observed at 2 (362%), 4 (1203%), and 12 (927%) weeks (all times versus 0 week control; P<0.001). Moreover, the levels of MP TF activity and TAT were linearly correlated (R=0.70, P<0.001). The inflammatory cytokine IL-6 was also increased in a time-dependent manner from 0 weeks (22.7±10.1 pg/ml) to 12 weeks (112.3±20.2 pg/ml; P<0.023).
Conclusion: These data indicate that hypercholesterolemia results in increased MP TF activity and subsequently activates coagulation. Further studies are required to determine if TF positive MPs are required for hypercholesterolemia -induced coagulation.