Background: In familial hypercholesterolemia (FH), high-density lipoprotein (HDL) often becomes dysfunctional and enriched with lipid peroxidation products, potentially contributing to increased thrombotic risk. However, its specific effects on platelet function and thrombosis remain unclear. Whether targeting HDL oxidation can restore its protective role has yet to be determined. Methods: Platelet function in healthy and FH subjects was assessed via flow cytometry, TEM, western blotting, and transcriptome analysis. The effects of HDL from healthy and FH subjects and lipid peroxidation-modified HDL on oxidized low-density lipoprotein (oxLDL)-induced platelet activation and apoptosis were evaluated. In vivo thrombosis was assessed in LDL-receptor-deficient (Ldlr-/-) mice fed a Western-style diet and treated with 2-hydroxybenzylamine (2-HOBA), a lipid peroxidation scavenger. The roles of SR-B1 and CD36 in platelet activation were examined using inhibitors. Results: Platelet activity was elevated in FH subjects compared to healthy controls, with FH platelets showing increased apoptosis, higher pro-apoptotic and reduced anti-apoptotic proteins. HDL from healthy subjects attenuated oxLDL-induced platelet activation and apoptosis, whereas FH-HDL exacerbated these effects. Western blot and immunofluorescence confirmed that control HDL prevented platelet activation, while FH-HDL promoted apoptosis in oxLDL-stimulated platelets. FH-HDL was enriched with peroxidation products, and lipid peroxidation-modified HDL from healthy volunteers exhibited similar pro-apoptotic effects. Treatment with 2-HOBA mitigated dysfunctional HDL-induced apoptosis, improved thrombosis outcomes, and enhanced blood flow in Ldlr-/- mice. Blocking SR-B1 abolished the protective effects of healthy HDL but had no impact on FH-HDL, whereas inhibiting CD36 prevented the pro-apoptotic effects of FH-HDL. Conclusion: Our research shows that while HDL normally protects against platelet apoptosis, in familial hypercholesterolemia it turns prothrombotic, enhancing platelet dysfunction and thrombosis. Treatment with 2-HOBA effectively counters these adverse effects, highlighting a potential therapeutic strategy for managing cardiovascular risks in FH patients.

Dr. MacRae F. Linton and Dr. Sean S. Davies are inventors on patents and patent applications for the use of 2-HOBA and related dicarbonyl scavengers for the treatment of atherosclerosis. Dr. Linton has received research support from Amgen, Regeneron, Ionis, Merck, REGENXBIO, Sanofi, and Novartis, and has served as a consultant for Esperion, Alexion Pharmaceuticals, and REGENXBIO. Dr. Wen-Liang Song has received research support from Amgen and Novartis and has served as a consultant for RONA Therapeutics. All other authors declare no competing financial interests.

This work was funded by the NIH (K08HL145075) and HL116263 and 1R01HL159204-01A1.

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