Abstract 606: Antithrombin Nanoparticle Therapy Safely Restores Endothelial Barrier Integrity and Reduces Vessel Hypercoagulability in Atherosclerotic Mice
Introduction: Thrombin plays a major role in regulating signaling pathways responsible for atherogenesis, hypercoagulability and plaque permeability. Herein, we report the therapeutic effects of perfluorocarbon core nanoparticles (PFC-NP) conjugated to the thrombin inhibitor D-phenylalanyl-L-prolyl-L-chloromethylketone (PPACK-NP) on vascular barrier integrity and hypercoagulability.
Methods and Results: ApoE-/- mice were fed a Western diet for 4 months, and received 3 doses/week of saline or 1 ml/kg PPACK-NP for the final month of feeding. Endothelial barrier integrity was assessed by quantifying the ability of atherosclerotic aortas to take up circulating semipermeable PFC-NP (~250 nm diameter). Whole aortas (arch to iliacs) were excised after 2 hour in vivo exposure to PFC-NP and underwent fluorine magnetic resonance spectroscopy (19F-MRS) to quantify plaque-permeating PFC-NP. 19F-MRS data revealed a significant decrease in plaque permeability to PFC-NP after PPACK-NP treatment compared to saline control (0.081 ± 0.011 μl PFC-NP/g aorta, N = 5 vs. 0.122 ± 0.014 μl PFC-NP/g aorta, N = 8 for PPACK-NP treated vs. saline control, p = 0.027). To assess hypercoagulability, carotid artery injury was induced photochemically to measure the time to complete occlusion as an index of thrombotic risk. Occlusion times were significantly prolonged with PPACK-NP treatment compared to untreated mice (49.8 ± 6.7 min, N = 5 vs. 26.1 ± 4.6 min, N = 9 for PPACK-NP treated vs. saline control, p = 0.019), indicating a decrease in vessel hypercoagulability after therapeutic intervention. Furthermore, PPACK-NP treatment of human aortic endothelial cells in vitro abrogated thrombin-mediated activation of surface PAR-1 receptors as measured by flow cytometry, suggesting a potential dual role for PPACK-NP in the localized modulation of both thrombosis and PAR-1 signaling. Moreover, this sustained therapeutic benefit is obtained without systemic anticoagulation as all clotting parameters and bleeding times are completely normalized within 60 minutes after i.v. injection.
Conclusion: Thrombin inhibition with PPACK-NP is effective in restoring vascular barrier integrity and reducing focal thrombotic risk within a single month without incurring bleeding risk.
Author Disclosures: R.U. Palekar: None. A.P. Jallouk: None. H. Pan: None. S.A. Wickline: Ownership Interest; Significant; Acuplaq, LLC.
- © 2015 by American Heart Association, Inc.