Abstract 3674: Ionic Mechanisms Underlying Angiotensin Ii Induced Endothelial Dysfunction in Human Coronary Endothelial Cells; A Role of TRPV4 Channel
Endothelial dysfunction is an initial step in the pathogenesis of cardiovascular diseases and a significant predictor of mortality in heart failure patients. A rise of intracellular Ca2+ concentration ([Ca2+]i) is an important stimulus for endothelial nitric oxide production. However, the ionic mechanism underlying the endothelial dysfunction remains unclear. Recent notable finding is an identification of transient receptor potential V4 channel (TRPV4) as endoth1elial mechanosensor, which is involved in endothelial Ca2+ transport induced by shear stress and resultant NO production. The purpose of this study was to explore the potential involvement of TRPV4 channels in the endothelial dysfunction induced by angiotensin II (Ang II). We studied human coronary artery endothelial cells (hCAECs), which constitutively express TRPV4. By using the most specific ligand 4 alpha-phorbol 12, 13-didecanoate (4αPDD) as a tool to stimulate endothelial TRPV4, we evaluated TRPV4 mediated Ca2+ entry in impaired endothelial cells which were treated with Ang II (100nM) for 24 – 48 h. 4αPDD induced an increase in [Ca2+]i in Ang II treated hCAECs but was 50% less effective than that in control hCAECs. Ang II exerted the inhibitory effects upon TRPV4 activity in a dose dependent manner (10 nM - 1 μM) and even by using other TRPV4 stimuli, 30% hypotonic stress and 5′,6′-epoxyeicosatrienoic acid. Likewise, 4αPDD induced TRPV4 current density at −80 mV was significantly decreased in Ang II treated hCAECs. In NO measurement using DAF2, 4αPDD induced NO production was markedly attenuated in Ang II treated cells. Although quantitative real time RT-PCR analysis showed no difference in mRNA expression of TRPV4, protein expression of TRPV4 was decreased in Ang II treated hCAECs.
Conclusion: Down-regulation of TRPV4 in human endothelial cells might contribute to endothelial dysfunction induced by Ang II.