Arterial Response to Shear Stress Critically Depends on Endothelial TRPV4 Expression

Abstract

BackgroundIn blood vessels, the endothelium is a crucial signal transduction interface in control of vascular tone and blood pressure to ensure energy and oxygen supply according to the organs' needs. In response to vasoactive factors and to shear stress elicited by blood flow, the endothelium secretes vasodilating or vasocontracting autacoids, which adjust the contractile state of the smooth muscle. In endothelial sensing of shear stress, the osmo- and mechanosensitive Ca2+-permeable TRPV4 channel has been proposed to be candidate mechanosensor. Using TRPV4−/− mice, we now investigated whether the absence of endothelial TRPV4 alters shear-stress-induced arterial vasodilation.Methodology/Principal FindingsIn TRPV4−/− mice, loss of the TRPV4 protein was confirmed by Western blot, immunohistochemistry and by in situ-patch–clamp techniques in carotid artery endothelial cells (CAEC). Endothelium-dependent vasodilation was determined by pressure myography in carotid arteries (CA) from TRPV4−/− mice and wild-type littermates (WT). In WT CAEC, TRPV4 currents could be elicited by TRPV4 activators 4α-phorbol-12,13-didecanoate (4αPDD), arachidonic acid (AA), and by hypotonic cell swelling (HTS). In striking contrast, in TRPV4−/− mice, 4αPDD did not produce currents and currents elicited by AA and HTS were significantly reduced. 4αPDD caused a robust and endothelium-dependent vasodilation in WT mice, again conspicuously absent in TRPV4−/− mice. Shear stress-induced vasodilation could readily be evoked in WT, but was completely eliminated in TRPV4−/− mice. In addition, flow/reperfusion-induced vasodilation was significantly reduced in TRPV4−/− vs. WT mice. Vasodilation in response to acetylcholine, vasoconstriction in response to phenylephrine, and passive mechanical compliance did not differ between genotypes, greatly underscoring the specificity of the above trpv4-dependent phenotype for physiologically relevant shear stress.Conclusions/SignificanceGenetically encoded loss-of-function of trpv4 results in a loss of shear stress-induced vasodilation, a response pattern critically dependent on endothelial TRPV4 expression. Thus, Ca2+-influx through endothelial TRPV4 channels is a molecular mechanism contributing significantly to endothelial mechanotransduction.

Update on vascular endothelial Ca2+signalling: A tale of ion channels, pumps and transporters

“…TRPC3-and TRPC6-induced Ca 2+ inflow underpin the stimulatory effect of VEGF on endothelial proliferation, migration and permeability [18,231,236] , while ATP exploits TRPC3 to activate NF-κB and increase vascular cell adhesion molecule-1 expression [237] . TRPC3-driven NO synthesis and vasore- TRPV1 TRPV2 TRPV3 TRPV4 TRPV5 TRPV6 PCa/PNa and conductance (pS) [202] 10, 35-80 1-3, NM 12, 172 6, 90 > 100, 75 > 100, 40-70 Human coronary artery ECs [300] (+RT-PCR, WB, IHC) Human pulmonary artery ECs [415] +(RT-PCR) +(RT-PCR) +(RT-PCR) Human pulmonary microvascular ECs +(RT-PCR) Human cerebral microvascular ECs [272] +(RT-PCR, IC) Human cerebral arterioles ECs [305] +(RT-PCR, IHC) Human dermal microvascular ECs [319] +(RT-PCR, WB) Breast cancer derived microvascular ECs [319] +(RT-PCR, WB) Human umbilical vein ECs [227,277,296,301] +(RT-PCR) +(WB, IHC) Mouse aortic ECs [280,285,299,306] +(WB) +(RT-PCR, WB, NM, IHC) Mouse pulmonary artery ECs [313] +(WB, IHC) Mouse mesenteric artery ECs [27,280,302] +(RT-PCR, WB, IC) +(RT-PCR, IC) Mouse cerebral microvascular ECs +(RT-PCR) +(RT-PCR, WB) +(RT-PCR) Mouse dermal microvascular ECs [307] +(RT-PCR, WB) Mouse carotid artery ECs [290,296] +(IHC) Rat mesenteric artery ECs [226,275,302] +(WB) +(WB, IC, IHC) Rat femoral artery ECs [312] +(RT-PCR, IC) Rat pulmonary artery ECs [303] +(WB, IHC) Rat renal artery ECs [303] +(IHC) Rat cardiac microvascular ECs [303,…”

“…TRPV4: TRPV4 is the most polymodal TRP channel, being a molecular integrator of both chemical and physical stimuli [200,270] , and may be expressed in both native and cultured ECs (Table 3). More specifically, endothelial TRPV4 may be activated by non-noxious temperatures (> 24 ℃) [288] , hypo-osmotic cell swelling [289] , shear stress [290,291] , cyclic strain [292,293] , and pharmacologically, by the non-PKC-activating phorbol ester, 4α-phorbol-12,13-didecanoate (4αPDD) [294] and by the plant-derived flavone, apigenin [295] . Cell swelling and shear stress do not gate TRPV4 directly, but via the PLA2-dependent synthesis of AA, and its subsequent metabolization to 5',6'-epoxyeicosatrienoic acid (EET) through a CYP epoxygenase-dependent pathway [290,291,[296][297][298][299] .…”

“…An alternative mechanism has been unravelled in human coronary arterioles from patients with coronary artery disease, where flow-induced TRPV4 activation causes ECs to release mitochondrial ROS, thereby relaxing the adjoining VSMCs [300] . Under physiological conditions, TRPV4-mediated vasodilation, mainly via NO and EDHF production, is induced by both shear stress [27,290,291,296] and extracellular autacoids, such as Ach and UTP [297,301,305,306] . Although the cellular mechanisms linking membrane receptors to TRPV4 opening are still unclear, UTP utilizes PLA2 to gate the channel [297] , while PKCα mediates Ach-dependent activation [307] .…”

Imbalance and dysfunction of transient receptor potential channels contribute to the pathogenesis of hypertension

“…TRPV4 channels in the vascular ECs and SMCs are critically involved in the vasodilatation of mesenteric arteries in response to endothelial-derived factors [28]. One study found that the genetically encoded loss-of-function of trpv4 resulted in a loss of shear stress-induced vasodilatation, a response pattern largely dependent on endothelial TRPV4 expression [55]. In a previous study, we demonstrated that TRPM8 activation, by its agonist menthol, antagonized vasoconstriction by inhibiting Ca 2+ signaling-mediated RhoA/ROCK activation in the vasculature [56].…”

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

“…Ca 2+ entry through endothelial TRPV4 triggered NO-dependent vasodilation in rat conduit arteries, and NO-dependent and EDHF-dependent vasodilaton in small-sized A gracilis. Furthermore, shear stress induced vasodilation is significantly reduced in carotid arteries from TRPV4 knockout (-/-) mice [27].…”