Abstract 623: Role Of Cd73-derived Adenosine In Atherosclerosis

We recently reported that mice with targeted deletion of ecto-5′-nucleotidase (CD73) are characterized by enhanced platelet activation and increased adherence of monocytes to the endothelium. Wire-induced injury of the carotid artery resulted in enhanced neointima formation associated with increased macrophage content and VCAM-1 expression in CD73−/−mice. In order to study a possible modulation of atherogenesis and vascular inflammation by CD73-derived adenosine, we generated ApoE−/−/CD73−/− double mutant mice. Quantification and characterisation of atherosclerotic lesions was performed in WT, ApoE−/−, and ApoE−/− / CD73−/− mice on chow diet after 6 and 12 month, respectively, by macroscopic analysis of the descending thoracic aorta after oil red staining and by histological stainings for cholesterol, hyaloronic acid, and collagen in cryo sections of the aortic sinus. Immunohistological analysis of lesion morphology included primary antibodies for ICAM-1, VCAM-1, CD4, CD73, and CD11b. Determination of the plaque score by oil red staining revealed enhanced development of atherosclerotic lesions over the entire thoracic aorta after 6 month in the double mutant compared with ApoE−/− (2.5-fold increased, n=8, P<0.05). Atherosclerotic plaques in the aortic sinus were substantially enlarged as compared to ApoE−/− mice. Changes in extracellular matrix composition were not detected. However, we found enhanced VCAM-1 expression in ApoE−/−/CD73−/− mice after 6 month, which was accompanied by an increased infiltration of monocytes and macrophages but unchanged T-cells. We also noted that in atherosclerotic plaques of ApoE−/− mice the expression and activity of CD73 was significantly increased compared to WT. Measurements of cytokines in plasma support the notion of an increased inflammatory state in the double knockout. Interestingly, after 12 months all double mutant mice showed multiple scattered myocardial infarcts associated with myocardial hypertrophy and fibrosis. Our findings demonstrate that CD73-derived adenosine acts as an endogenous modulator protecting against chronic vascular inflammation and monocyte recruitment. Thus in the murine model, extracellular adenosine appears to limit the progression of atherosclerosis.