抄録
Vascular endothelial cells (ECs) alter their morphology, function, and gene expression in response to shear stress generated by blood flow. However, the molecular mechanism of shear stress sensing by ECs has not been clarified. We investigated the mechanism from the aspect of calcium (Ca) signaling. Human pulmonary artery ECs (HPAECs) loaded with the Ca indicator Indo-1/AM were exposed to laminar flow and changes in intracellular Ca concentrations were monitored. A stepwise increase in flow rate elicited a corresponding stepwise-increase in Ca concentrations. Apyrase or EGTA completely abolished the flow-induced increase in Ca concentrations, indicating that ATP and influx of extracellular Ca are essential for the Ca responses. Flow increased the release of ATP from HPAECs in a shear stress-dependent manner. HPAECs predominantly express a subtype of ATP-operated cation channel P2X4, and antisense oligonucleotides targeted to P2X4 abolished the flow-induced Ca influx. Pulmonary microvascular ECs cultured from P2X4-deficient mice showed no flow-induced Ca influx and nitric oxide production. Human embryonic kidney 293 cells became sensitive to flow and show flow-induced Ca influx when transfected with P2X4 cDNA. Flow-induced dilation of skeletal muscle arterioles was markedly suppressed in P2X4-deficient mice. P2X4-deficient mice had higher systolic blood pressure values than wild-type mice. Thus, ECs transduce the signal of shear stress into Ca influx via P2X4, and that the purinoceptor-mediated blood flow-sensing plays important roles in endothelial NO production and vascular tone control. [J Physiol Sci. 2006;56 Suppl:S48]
