Activation of endothelial TRPV4 channels mediates flow- induced dilation in human coronary arterioles: role of Ca2+ entry and mitochondrial ROS signaling

Bubolz AH, Mendoza SA, Zheng X, Zinkevich NS, Li R, Gutterman DD, Zhang DX. Activation of endothelial TRPV4 channels mediates flow-induced dilation in human coronary arterioles: role of Ca2+ entry and mitochondrial ROS signaling. Am J Physiol Heart Circ Physiol 302: H634-H642, 2012. First published December 2, 2011; doi:10.1152/ajpheart.00717.2011.-In human coronary arterioles (HCAs) from patients with coronary artery disease, flow-induced dilation is mediated by a unique mechanism involving the release of H2O2 from the mitochondria of endothelial cells (ECs). How flow activates ECs to elicit the mitochondrial release of H2O2 remains unclear. Here, we examined the role of the transient receptor potential vanilloid type 4 (TRPV4) channel, a mechanosensitive Ca2+-permeable cation channel, in mediating ROS formation and flow-induced dilation in HCAs. Using RT-PCR, Western blot analysis, and immunohistochemical analysis, we detected the mRNA and protein expression of TRPV4 channels in ECs of HCAs and cultured human coronary artery ECs (HCAECs). In HCAECs, 4 alpha-phorbol-12,13-didecanoate (4 alpha-PDD), a selective TRPV4 agonist, markedly increased (via Ca2+ influx) intracellular Ca2+ concentration. In isolated HCAs, activation of TRPV4 channels by 4 alpha-PDD resulted in a potent concentration-dependent dilation, and the dilation was inhibited by removal of the endothelium and by catalase, a H2O2-metabolizing enzyme. Fluorescence ROS assays showed that 4 alpha-PDD increased the production of mitochondrial superoxide in HCAECs. 4 alpha-PDD also enhanced the production of H2O2 and superoxide in HCAs. Finally, we found that flow-induced dilation of HCAs was markedly inhibited by different TRPV4 antagonists and TRPV4-specific small interfering RNA. In conclusion, the endothelial TRPV4 channel is critically involved in flow-mediated dilation of HCAs. TRPV4-mediated Ca2+ entry may be an important signaling event leading to the flow-induced release of mitochondrial ROS in HCAs. Elucidation of this novel TRPV4-ROS pathway may improve our understanding of the pathogenesis of coronary artery disease and/or other cardiovascular disorders.