Atheroprone shear stress stimulates noxious endothelial extracellular vesicle uptake by MCAM and PECAM-1 cell adhesion molecules

Abstract

Atherosclerotic lesions mainly form in arterial areas exposed to low shear stress (LSS), where endothelial cells express a senescent and inflammatory phenotype. Conversely, high shear stress (HSS) has atheroprotective effects on the endothelium. Endothelial cell-derived extracellular vesicles have been shown to regulate inflammation, senescence and angiogenesis and therefore play a crucial role in vascular homeostasis and disease. While previous studies have shown links between hemodynamic forces and extracellular vesicle release, the exact consequences of shear stress on the release and uptake of endothelial EVs remains elusive. Our aim is therefore to decipher the interplay between these processes in endothelial cells exposed to atheroprone or atheroprotective shear stress. Confluent human umbilical vein endothelial cells (HUVEC) were exposed to either LSS or HSS for 24 hours. Large and small EVs were isolated from conditioned medium by sequential centrifugation and size exclusion chromatography. They were characterized by TEM, Western blot analysis of EV markers, tunable resistive pulse sensing, flow cytometry and proteomics. Uptake experiments were performed using fluorescently-labeled EVs and differences between groups were assessed by flow cytometry and confocal microscopy. We found that levels of large and small EVs in HUVEC conditioned media were fifty and five times higher in HSS than in LSS conditions, respectively. In vivo and in vitro uptake experiments revealed greater EV incorporation by cells exposed to LSS conditions compared to HSS. Additionally, endothelial LSS-EVs appeared to have a greater affinity for HUVECs than HSS-EVs or EVs derived from platelets, red blood cells, granulocytes and peripheral blood mononuclear cells. Proteomic analysis revealed that LSS-EVs were enriched in adhesion proteins such as PECAM1, MCAM, which were involved in EV uptake by endothelial cells. LSS-EVs also carried mitochondrial material, which may be involved in elevating reactive oxygen species levels in recipient cells. These findings suggest that endothelial shear stress has a significant impact during EV biogenesis and uptake. Given the major role of EVs and shear stress in vascular health, deciphering the relation between these processes may yield innovative strategies for the early detection and treatment of endothelial dysfunction.