Impact of Dysfunctional HDL on Platelet Function and in vivo Thrombosis

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PROJECT SUMMARY/ABSTRACT The studies outlined in this proposal will explore novel mechanisms by which dysfunctional high-density lipoprotein (HDL) impairs platelet function and promotes the prothrombotic phenotype and will test an innovative potential therapeutic strategy to reduce atherothrombosis. This proposal is for a Mentored Career Development Award by Dr. Wenliang Song in the Division of Cardiovascular Medicine of the Department of Medicine at Vanderbilt University. Dr. Song has a long-term career goal of being an independently funded physician-scientist focused on the role of lipid metabolism in cardiovascular disease. He has already invested heavily in this career path. He has extensive research background on lipoperoxidation and oxidative stress, platelet biology and rodent models of cardiovascular diseases. Recent evidence suggests that HDL function may be a better indicator than HDL cholesterol (HDL-C). Mounting evidence supports the concept that dysfunctional HDL, for example, oxidized HDL, loses its beneficial properties and actually contributes to the development of cardiovascular disease. Preliminary data in this proposal suggest that HDL from patients with Familial Hypercholesterolemia (FH) is enriched with peroxidation products, including malondialdehyde (MDA) and isolevuglandins(IsoLG), and is strikingly dysfunctional. Novel aldehyde scavengers, which targeted mitigate the adverse effects of reactive oxidative stress(ROS) without abrogating normal signaling of ROS, can reduce the peroxidation modification of the HDL and prevent formation of dysfunctional HDL. Previous studies suggest normal HDL can reduce agonist- stimulated platelet activation and aggregation, while oxidized HDL enhances platelet aggregation, yet the mechanisms are not clear. Interestingly, recent studies demonstrated that apoptosis also occurs in anucleate platelets, and apoptotic platelets accelerate in vivo arterial thrombosis formation. It is known that normal HDL is anti-apoptotic and oxidized HDL is pro-apoptotic in macrophages and endothelial cells, but no studies have ever investigated HDL’s effect on platelets apoptosis. Dr. Song hypothesizes that dysfunctional HDL, such as oxidized HDL and HDL from FH patient (FH-HDL), increase platelet activation in vivo leading to enhance thrombosis through inducing apoptosis. The effect of peroxidation modification of HDL, as well as FH-HDL, on platelet apoptosis and activity will be tested. Two in vivo thrombosis mouse models (acute and chronic) will also be used. Wild type, LDLr-/- and ApoA1-/-LDLr-/- mice will be used to mimic the FH condition, and to assess the contribution of HDL. Novel aldehyde scavengers will be used to protect HDL from dysfunction and rescue the phenotypes. This proposed research will provide novel insights into the impact of HDL on platelet biology and advance the field of HDL function in atherothrombosis. The principal investigator has assembled a multidisciplinary mentorship committee. He and his mentor have outlined a detailed well thought training plan. He will have 80% protected time for research. Vanderbilt offers an exceptional environment and strong institutional commitment to foster this candidate's transition to becoming an independent investigator.