Abstract Body: Background: Platelet hyperactivity is associated with atherosclerosis, but the mechanisms behind platelets’ contribution to plaque development remain unclear. Hyperlipidemia drives atherosclerosis progression and platelets have been shown to respond to these conditions by secreting various signaling molecules. VAMP8, a primary v-SNARE involved in platelet α-granule secretion, is overexpressed in patients with platelet hyperactivity and is also associated with an increased risk of adverse cardiovascular events. This study examines the role of VAMP8 in the platelet response to hyperlipidemia and its impact on atherosclerosis.
Methods and Results: To assess the role of VAMP8 in platelet function during hyperlipidemia and atherosclerosis development, we first induced hypercholesterolemia in WT and VAMP8-deficient (VAMP8^-/-) mice (8-12 weeks) using an adeno-associated viral (AAV) vector expressing a gain-of-function PCSK9 (D377Y) mutation, followed by a 4-week Western diet. Thrombosis was evaluated using a ferric chloride-induced injury of the carotid artery and laser speckle contrast imaging (LSCI). Atherosclerotic lesions were measured on the intimal surface from the ascending aorta to the descending thoracic aorta (1 mm distal to the left subclavian artery) using Nikon NIS-Elements software (en face method). While hypercholesterolemic animals displayed accelerated thrombosis compared to healthy controls, global deletion of VAMP8 resulted in unstable thrombi formation even in the hypercholesterolemic mice. Loss of VAMP8 also significantly attenuated atherosclerotic lesion development after 4 weeks. To validate these findings in a chronic model, VAMP8^-/- mice were crossed with ApoE^-/- mice to create a hypercholesterolemic double-knockout (ApoE^-/-/VAMP8^-/-) model. After 12 weeks on a Western diet, the double-knockout mice showed a marked reduction in lesion size. Total plasma cholesterol levels were similar between WT and VAMP8^-/- groups in both models. Bulk RNA sequencing of VAMP8-deficient platelets versus WT revealed distinct RNA profiles. Notably, key genes involved in platelet activation and interactions — including Ccl5, Selp, Itga2, Gp6, and Ptgs1 — were among those downregulated in VAMP8-deficient platelets. This suggests a role for VAMP8 in modulating platelet functions that are critical to platelet reactivity.
Conclusion: Global VAMP8 deletion affects platelet function under hypercholesterolemic conditions and attenuates atherosclerosis development.