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

Abstract

In human coronary arterioles (HCAs) from patients with coronary artery disease, flow-induced dilation is mediated by a unique mechanism involving the release of H(2)O(2) from the mitochondria of endothelial cells (ECs). How flow activates ECs to elicit the mitochondrial release of H(2)O(2) remains unclear. Here, we examined the role of the transient receptor potential vanilloid type 4 (TRPV4) channel, a mechanosensitive Ca(2+)-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, 4α-phorbol-12,13-didecanoate (4α-PDD), a selective TRPV4 agonist, markedly increased (via Ca(2+) influx) intracellular Ca(2+) concentration. In isolated HCAs, activation of TRPV4 channels by 4α-PDD resulted in a potent concentration-dependent dilation, and the dilation was inhibited by removal of the endothelium and by catalase, a H(2)O(2)-metabolizing enzyme. Fluorescence ROS assays showed that 4α-PDD increased the production of mitochondrial superoxide in HCAECs. 4α-PDD also enhanced the production of H(2)O(2) 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 Ca(2+) 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.

Thirty Years of Saying NO

“…Indeed, although there is consensus that exaggerated oxidative stress is a major villain in causing endothelial dysfunction, one cannot ignore the fact that physiological amounts of ROS can activate eNOS, thus increasing NO production and evoking/potentiating endothelium-dependent relaxations. [180][181][182][183][184][185] Even when accepting that ROS are villains at least in rats and mice, the therapeutic relevance of experimental animal findings appears maybe questionable because chronic treatment with antioxidants usually fails to improve endothelial function in humans 15,94,[186][187][188] ; this lack of efficacy may be explained by the largely ignored observation of large amounts of extracellular SOD contained in the human vascular wall 189 ; (8) understanding why in resistance arteries the relative lack of NO production is brought about, permitting the emergence of EDH-mediated dilatations; (9) understanding how at the molecular level NO tempers the occurrence of endothelium-dependent vasoconstrictions; (10) understanding the link between overexpression/presence of adipocyte-fatty acid binding protein and the accelerated production of oxidized-LDL leading to selective loss of G i -mediated endothelium-dependent relaxations; and (11) understanding why under hypoxic conditions (or during exposure to thymoquinone) NO stimulates the biased activity of sGC leading to the production of the vasoconstrictor cyclic nucleotide cIMP. Hypoxic vasospasm has been demonstrated in vivo in coronary arteries of the pig previously exposed to ischemia-reperfusion injury; if they were to occur in humans, they may help to understand the greater cardiovascular risk associated with sleep apnea 15 and raise concerns on the use of sGC activators/stimulators in coronary patients with a history of ischemia-reperfusion.…”

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,…”

“…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] . A unique mechanism has been described in human coronary arterioles isolated from patients suffering from coronary artery disease, where the endothelial TRPV4 stimulate mitochondria to release ROS, which in turn cause VSMCs to relax [300] . Conversely, TRPV4 signaling induced by mechanical strain is mediated by direct force transfer from β1 integrins to the integrin-associated transmembrane CD98 protein within focal adhesions [293] .…”

“…NO, PGI2, and IKCa/SKCa/MaxiKmediated EDHF are vasodilatory pathways that are activated following by pharmacological activation of TRPV4 [27,291,[302][303][304] . 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] .…”

TRPV4 channels: physiological and pathological role in cardiovascular system

“…The widespread presence of TRPV4 channels in different body organs indicates the important physiological functions of these channels. The major physiological function of TRPV4 channels is mediating flow-induced vasodilation [7]. The physiological role of these channels is further emphasized from the studies implicating developmental abnormalities in TRPV4-knockout mice.…”