Abstract 265: Platelet C-Type Lectinlike (CLEC)-2 Receptor Plays a Protective Role Against Development of Atherosclerosis in Atherosclerosis-Prone Mice

Abstract

Background: Platelets can influence progression of plaque formation by facilitating recruitment of inflammatory cells at the sites of atherosclerotic lesions. A C-type lectin-like receptor, CLEC-2, abundantly expressed on the platelet surface, has been shown to regulate lymphatic development in utero though an interaction with Podoplanin. Interestingly, lymphatic vasculature is increased in ischemic and inflamed hearts, and in cholesterol-rich atherosclerotic lesions. Moreover, Podoplanin expression is up-regulated on inflammatory macrophages and on T-helper 17 cells. However, the role of the Podoplanin - CLEC-2 interaction in atherosclerosis remains unknown. Aim: We sought to investigate the role of CLEC-2 on atherosclerotic development in ApoE-deficient mice. Methods: CreERT.CLEC-2fl/fl x ApoE-/- and litter-matched ApoE-/- mice were treated with tamoxifen at the age of 9 weeks and were put on a high-fat diet for 6 weeks. Animals were killed at the age of 16 weeks, when platelet function assays and atherosclerosis assays were carried out. Results: Expression of CLEC-2 was abolished in tamoxifen-treated CreERT.CLEC-2fl/fl x ApoE-/- mice (n=8), whereas normal levels were seen in ApoE-/- controls (n=10) also treated with tamoxifen. CreERT.CLEC-2fl/fl x ApoE-/- and ApoE-/- mice had similar baseline characteristics, comparable levels of platelet glycoprotein expression (GPIb, GPIIbIIIa and GPVI) and normal platelet responses to platelet agonists (collagen-related peptide, PAR-4 peptide, ADP and arachidonic acid). Blood lipid levels were comparable between CreERT.CLEC-2fl/fl x ApoE-/- and control animals. Atherosclerotic plaque burden was significantly higher in the aortas of CreERT.CLEC-2fl/fl x ApoE-/- mice fed a high-fat diet for 6 weeks compared with their ApoE-/- counterparts. The higher plaque burden was seen consistently throughout the aorta, but reached significance at the level of whole aorta, abdominal aorta, outer curvature and the left subclavian region. This was seen in both male and female animals. Conclusions: The platelet-borne CLEC-2 receptor appears to have a protective role against atherogenesis in atheroprone mice. Further research to investigate the underlying mechanisms is warranted.