Abstract 1946: Regulation OF Entpdase1 (CD39) Expression by Fluid-phase Shear Forces
Sudden death due to thrombotic occlusion of a ruptured plaque is the leading cause of mortality in patients with atherosclerosis. Little is known about how the apyrase ENTPDase1 (CD39), a primary regulator of platelet activation in vivo, is affected at the plaque surface. By examining coronal sections of atherosclerotic plaques from apoE−/− mice, we determined that CD39 is lost specifically in endothelium overlying the plaque surface, but not in adjacent endothelium. This led to the hypothesis that CD39 expression in the vascular wall may be driven by laminar, fluid-phase shear forces. To distinguish the effects of hyperlipidemia from that of shear forces, coronal aortic arch sections from wild type mice were examined at the greater curvature (an area defined by laminar shear stresses) and the ostia of the left subclavian artery (an area defined by non-laminar blood flow). Fluorescent intensity quantification revealed a near 6-fold induction of CD39 staining in areas exposed to laminar shear stresses. This finding was confirmed by confocal microscopy of en face aorta preparations as well. In vitro studies with human umbilical vein endothelial cells in a cone plate viscometer showed a 10.8-fold induction of CD39 mRNA by laminar shear stress (~15 dyne/cm2) when compared to fluid stasis (p<0.001). By comparison oscillatory flow (0 ± 5 dyne/cm2, 1 Hz) did not induce a significant change in CD39 mRNA when compared to static control. Western blotting revealed that the CD39 mRNA induced by laminar shear manifested as a more than 4.3-fold induction of protein (p<0.01). Flow cytometry confirmed the western blotting results showing a 3.8-fold induction of CD39 protein on the surface of cells exposed to laminar shear. These are the first data to show that CD39 is regulated by shear, and that it is lost from endothelium overlying atherosclerotic plaque in regions of turbulent flow. These results could be of great clinical relevance as they demonstrate that CD39, the enzyme that prevents aberrant platelet activation, is lost on the plaque surface. These data support the hypothesis that regional vascular zones are athero- and thrombo-resistant due to local ectonucleotidase expression modulated by dynamic/shear forces in flowing blood.
This research has received full or partial funding support from the American Heart Association, AHA Midwest Affiliate (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota & Wisconsin).