Changing shear stress‐induced ATP release from erythrocytes increases endothelial calcium and vascular permeability independent from nitric oxide production in intact rat venules (672.2)

Abstract

Disturbed shear stress (SS) promotes atherosclerosis, thrombosis, and inflammation of the vessel wall. Endothelial cell (EC) barrier dysfunction has been implicated to play important roles in the pathogenesis of many cardiovascular diseases. However, how the disturbed blood flow affects EC barrier function in vivo and the involved cellular mechanisms remain to be identified. Our study investigated changing SS‐induced endothelial signaling and permeability in intact rat venules. EC [Ca2+]i and NO were measured in Fura‐2 AM and DAF‐2 DA loaded venules. EC eNOS activation was evaluated by immunofluorescence staining with confocal imaging. ATP released from red blood cells (RBCs) in response to SS is measured by bioluminescent assay. In response to a sudden change of SS, transient shear magnitude‐dependent increases in EC [Ca2+]i occurred only in vessels perfused with whole blood or perfusate containing RBCs, which was correlated with EC gap formation illustrated by fluorescent microsphere accumulation. Carbenoxolone, a Pannexin 1 inhibitor, significantly reduced shear magnitude‐dependent ATP release from RBCs and also abolished SS‐induced increases in EC [Ca2+]i. However, both plasma and whole blood perfusion induced shear magnitude‐dependent NO production and eNOS‐ser1177 phosphorylation. These results indicated that in intact venules ATP released from RBCs in response to the sudden change of SS is accountable for the increases in EC [Ca2+]i and vascular permeability, while SS‐induced NO production can be independent of increased EC [Ca2+]i.Grant Funding Source: Supported by HL56237, HL084338 and AHA 12PRE11470010