Evidence for a Functional Role of Endothelial Transient Receptor Potential V4 in Shear Stress–Induced Vasodilatation

Abstract

Objective-Ca2ϩ -influx through transient receptor potential (TRP) channels was proposed to be important in endothelial function, although the precise role of specific TRP channels is unknown. Here, we investigated the role of the putatively mechanosensitive TRPV4 channel in the mechanisms of endothelium-dependent vasodilatation. Methods and Results-Expression and function of TRPV4 was investigated in rat carotid artery endothelial cells (RCAECs) by using in situ patch-clamp techniques, single-cell RT-PCR, Ca 2ϩ measurements, and pressure myography in carotid artery (CA) and Arteria gracilis. In RCAECs in situ, TRPV4 currents were activated by the selective TRPV4 opener 4␣-phorbol-12,13-didecanoate (4␣PDD), arachidonic acid, moderate warmth, and mechanically by hypotonic cell swelling. Single-cell RT-PCR in endothelial cells demonstrated mRNA expression of TRPV4. In FURA-2 Ca 2ϩ measurements, 4␣PDD increased [Ca 2ϩ ] i by Ϸ140 nmol/L above basal levels. In pressure myograph experiments in CAs and A gracilis, 4␣PDD caused robust endothelium-dependent and strictly endothelium-dependent vasodilatations by Ϸ80% (K D 0.3 mol/L), which were suppressed by the TRPV4 blocker ruthenium red (RuR). Shear stress-induced vasodilatation was similarly blocked by RuR and also by the phospholipase A 2 inhibitor arachidonyl trifluoromethyl ketone (AACOCF 3 ). 4␣PDD produced endothelium-derived hyperpolarizing factor (EDHF)-type responses in A gracilis but not in rat carotid artery. Shear stress did not produce EDHF-type vasodilatation in either vessel type. Conclusions-Ca2ϩ entry through endothelial TRPV4 channels triggers NO-and EDHF-dependent vasodilatation. Moreover, TRPV4 appears to be mechanistically important in endothelial mechanosensing of shear stress. Key Words: endothelium-dependent vasodilatation Ⅲ transient receptor potential Ⅲ TRPV4 Ⅲ calcium Ⅲ shear stress Ⅲ nitric oxide Ⅲ 4␣PDD Ⅲ rat carotid artery C a 2ϩ -influx in response to mechanical or humoral stimulation plays a significant role in a variety of endothelial functions and especially in the Ca 2ϩ -dependent synthesis of endothelium-derived vasodilators such as NO, prostacyclin, or the endothelium-derived hyperpolarizing factor (EDHF). 1

Nitric Oxide–Dependent Feedback Loop Regulates Transient Receptor Potential Vanilloid 4 (TRPV4) Channel Cooperativity and Endothelial Function in Small Pulmonary Arteries

“…ATP can be released from sympathetic nerves during synaptic transmission, or can be released into the circulation by ECs, SMCs, or erythrocytes 25, 26, 64, 65. Shear stress, which is a well‐known activator of endothelial TRPV4 channels,66, 67, 68 also induces the release of ATP,65 suggesting a possible involvement of P2 purinergic receptor‐TRPV4 signaling in flow‐induced vasodilation. Endothelial Gq‐protein coupled receptor agonists carbachol and bradykinin activated TRPV4 channels through a phospholipase C‐diacylglycerol‐protein kinase C mechanism in MAs 5.…”

Salt Sensitivity in Blacks

“…Asymmetrical dimethylarginine (ADMA) is a major endogenous inhibitor of vasodilatation by inhibiting the endothelial synthesis of NO, which relaxes vascular smooth muscle. 7,8 In isolated rat arterioles, 9 and likely in small resistance arteries, 10 ADMA inhibits vasodilatation otherwise induced by increased flow/shear stress. Intravenously administered ADMA acutely increases systemic vascular resistance (SVR) and BP in humans and animals.…”

Vascular Responses to Shear Stress: The Involvement of Mechanosensors in Endothelial Cells

“…TRPP1/TRPP2, TRPV4, TRPC3 and TRPM7 have been localized in endothelial cells and/or smooth muscle cells. They have been reported to be mechanosensors responding to shear stress [10][11][12][13].…”

“…In addition, it has been shown to be opened by diverse physical and chemical stimuli such as cell swelling [21] and shear stress [11,22], moderate warmth (>27°C) [23], low pH [24], 4 -phorbol 12,13-didecanoate (4 PDD), arachidonic acid (AA) and its metabolite 5,6 epoxyeicosatrienoic acid [25].…”

“…The role of TRPV4 in shear stress-induced vasodilation was also investigated in rat conduit arteries and small-sized Austroboletus gracilis [11]. Shear stress induced vasodilation in conduit arteries and A gracilis, and this response was greatly blocked by the TRPV4 inhibitor ruthenium red.…”