Shear stress-induced pathological changes in endothelial cells occur through Piezo1 activation of TRPV4

Although the ion channels Piezo1 and TRPV4 have been implicated in high venous pressure- and fluid shear stress-induced vascular hyperpermeability, they have been described as working independently. Moreover, the mechanism by which Piezo1 and TRPV4 channels in endothelial cells execute the same function is poorly understood. Here we demonstrate that Piezo1 regulates TRPV4 channel activation in endothelial cells and that Piezo1-mediated TRPV4 channel opening is a function of the strength and duration of fluid shear stress. Application of the Piezo1 antagonist, GsMTx4, completely blocked the elevation in intracellular calcium ([Ca2+]i) induced by both fluid shear stress and the Piezo1 agonist, Yoda1. High and prolonged shear stress caused sustained [Ca2+]i elevation which required TRPV4 opening and was responsible for fluid shear stress- and Piezo1-mediated disruption of adherens junctions and actin remodeling. We found that Piezo1s effects were mediated by phospholipase A2 activation. Blockade of TRPV4 channels with the selective TRPV4 blocker, HC067047, prevented the loss of endothelial cell integrity and actin disruption induced by Yoda1 or shear stress and prevented Piezo1-induced monocyte adhesion to endothelial cell monolayers. These findings demonstrate that Piezo1 activation by fluid shear stress initiates a calcium signal that causes TRPV4 opening which in turn is responsible for the sustained phase calcium elevation that triggers pathological events in endothelial cells.