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Ca 2+-Activated K + Channels and the Regulation of the Uteroplacental Circulation. Int J Mol Sci 2023; 24:ijms24021349. [PMID: 36674858 PMCID: PMC9867535 DOI: 10.3390/ijms24021349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Revised: 01/06/2023] [Accepted: 01/08/2023] [Indexed: 01/13/2023] Open
Abstract
Adequate uteroplacental blood supply is essential for the development and growth of the placenta and fetus during pregnancy. Aberrant uteroplacental perfusion is associated with pregnancy complications such as preeclampsia, fetal growth restriction (FGR), and gestational diabetes. The regulation of uteroplacental blood flow is thus vital to the well-being of the mother and fetus. Ca2+-activated K+ (KCa) channels of small, intermediate, and large conductance participate in setting and regulating the resting membrane potential of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) and play a critical role in controlling vascular tone and blood pressure. KCa channels are important mediators of estrogen/pregnancy-induced adaptive changes in the uteroplacental circulation. Activation of the channels hyperpolarizes uteroplacental VSMCs/ECs, leading to attenuated vascular tone, blunted vasopressor responses, and increased uteroplacental blood flow. However, the regulation of uteroplacental vascular function by KCa channels is compromised in pregnancy complications. This review intends to provide a comprehensive overview of roles of KCa channels in the regulation of the uteroplacental circulation under physiological and pathophysiological conditions.
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Oduyemi OA, Salami SA, Salahdeen HM, Murtala BA, Raji Y. Mechanisms of inhibitory activity of root extract of Carpolobia lutea G. Don on in vitro contractile responses of rabbit corpus carvernosum. Rev Int Androl 2020; 19:234-241. [PMID: 32593533 DOI: 10.1016/j.androl.2020.04.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 02/08/2020] [Accepted: 04/14/2020] [Indexed: 11/25/2022]
Abstract
INTRODUCTION Carpolobia lutea root extract (CLRE) has been reported to enhance penile erection. However, the mechanism involved is poorly understood. We investigated in vitro mechanisms of CLRE action on contractile activity of rabbit corpus cavernosum (CC). METHODS Corpus cavernosum strips from four healthy male New Zealand rabbits (2.5-3.0kg) were mounted on an organ chamber and contracted with phenylephrine (PE) (10-9 to 10-5M) and Potassium Chloride (KCl) (10-50mM) before treatment with various concentrations of CLRE (0.1-1.2mg/ml). Interactions between CLRE and a Nitric Oxide Synthase (NOS) inhibitor (N-nitro-l-arginine methyl ester - l-NAME 10-4M); guanylyl cyclase inhibitors (Oxalodiazolo 4,3-a quinoxalin-1-one - ODQ 10μM, 20μM, 30μM), and (methylene blue 10-30μM); a cyclooxygenase inhibitor (10-4M indomethacin); potassium-channel inhibitors (100μM tetraethyl ammonium TEA), (100ηM apamin) and (glibenclamide 10μM and 20μM); and a calcium-channel inhibitor (-10-4M nifedipine) were investigated. RESULTS Maximal contractions of KCl and PE contracted CC strips were significantly reduced in a concentration-dependent manner (40.8±3.6% and 38.6±4.0% from 64.6±2.9% and 98.1±4.2% respectively). Relaxant effect of CLRE was significantly reduced by ODQ (38.6±4.0% to 6.4±1.3% and 38.6±4.0% to 7.2±1.2%), nifedipine (38.6±4.0% to 21.1±2.7%) and glibenclamide (40.8±3.6% to 31.5±3.3%). However l-NAME, indomethacin, methylene blue, TEA and apamin did not inhibit relaxation by CLRE. CONCLUSION Concentration-dependent relaxant effect of CLRE in rabbit CC involves the soluble guanylate cyclase/cyclase Guanosine Monophosphate system, and activation of ATP-dependent K+ channels.
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Affiliation(s)
- Oluwatosin Aisha Oduyemi
- Department of Physiology, Reproduction and Developmental Programming Unit, University of Ibadan, Ibadan, Nigeria
| | - Shakiru Ademola Salami
- Department of Physiology, Lagos State University College of Medicine, Ikeja, Lagos, Nigeria.
| | | | | | - Yinusa Raji
- Department of Physiology, Reproduction and Developmental Programming Unit, University of Ibadan, Ibadan, Nigeria
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Guix FX, Sartório CL, Ill-Raga G. BACE1 Translation: At the Crossroads Between Alzheimer's Disease Neurodegeneration and Memory Consolidation. J Alzheimers Dis Rep 2019; 3:113-148. [PMID: 31259308 PMCID: PMC6597968 DOI: 10.3233/adr-180089] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Human life unfolds not only in time and space, but also in the recollection and interweaving of memories. Therefore, individual human identity depends fully on a proper access to the autobiographical memory. Such access is hindered under pathological conditions such as Alzheimer’s disease, which affects millions of people worldwide. Unfortunately, no effective cure exists to prevent this disorder, the impact of which will rise alarmingly within the next decades. While Alzheimer’s disease is largely considered to be the outcome of amyloid-β (Aβ) peptide accumulation in the brain, conceiving this complex disorder strictly as the result of Aβ-neurotoxicity is perhaps a too straight-line simplification. Instead, complementary to this view, the tableau of molecular disarrangements in the Alzheimer’s disease brain may be reflecting, at least in part, a loss of function phenotype in memory processing. Here we take BACE1 translation and degradation as a gateway to study molecular mechanisms putatively involved in the transition between memory and neurodegeneration. BACE1 participates in the excision of Aβ-peptide from its precursor holoprotein, but plays a role in synaptic plasticity too. Its translation is governed by eIF2α phosphorylation: a hub integrating cellular responses to stress, but also a critical switch in memory consolidation. Paralleling these dualities, the eIF2α-kinase HRI has been shown to be a nitric oxide-dependent physiological activator of hippocampal BACE1 translation. Finally, beholding BACE1 as a representative protease active in the CNS, we venture a new perspective on the cellular basis of memory, which may incorporate neurodegeneration in itself as a drift in memory consolidating systems.
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Affiliation(s)
- Francesc X Guix
- Department of Molecular Neuropathology, Centro de Biología Molecular Severo Ochoa-CSIC, Madrid, Spain
| | - Carmem L Sartório
- Division of Physiological Sciences, Federal University of Espírito Santo, Vitória, Espírito Santo, Brazil
| | - Gerard Ill-Raga
- Division of Physiological Sciences, Federal University of Espírito Santo, Vitória, Espírito Santo, Brazil
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Goto K, Ohtsubo T, Kitazono T. Endothelium-Dependent Hyperpolarization (EDH) in Hypertension: The Role of Endothelial Ion Channels. Int J Mol Sci 2018; 19:E315. [PMID: 29361737 PMCID: PMC5796258 DOI: 10.3390/ijms19010315] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Revised: 01/18/2018] [Accepted: 01/19/2018] [Indexed: 12/28/2022] Open
Abstract
Upon stimulation with agonists and shear stress, the vascular endothelium of different vessels selectively releases several vasodilator factors such as nitric oxide and prostacyclin. In addition, vascular endothelial cells of many vessels regulate the contractility of the vascular smooth muscle cells through the generation of endothelium-dependent hyperpolarization (EDH). There is a general consensus that the opening of small- and intermediate-conductance Ca2+-activated K⁺ channels (SKCa and IKCa) is the initial mechanistic step for the generation of EDH. In animal models and humans, EDH and EDH-mediated relaxations are impaired during hypertension, and anti-hypertensive treatments restore such impairments. However, the underlying mechanisms of reduced EDH and its improvement by lowering blood pressure are poorly understood. Emerging evidence suggests that alterations of endothelial ion channels such as SKCa channels, inward rectifier K⁺ channels, Ca2+-activated Cl- channels, and transient receptor potential vanilloid type 4 channels contribute to the impaired EDH during hypertension. In this review, we attempt to summarize the accumulating evidence regarding the pathophysiological role of endothelial ion channels, focusing on their relationship with EDH during hypertension.
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Affiliation(s)
- Kenichi Goto
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
| | - Toshio Ohtsubo
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
| | - Takanari Kitazono
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan.
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Ohta Y, Takaseki S, Yoshitomi T. Effects of ripasudil hydrochloride hydrate (K-115), a Rho-kinase inhibitor, on ocular blood flow and ciliary artery smooth muscle contraction in rabbits. Jpn J Ophthalmol 2017; 61:423-432. [DOI: 10.1007/s10384-017-0524-y] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 04/07/2017] [Indexed: 12/20/2022]
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Nishijima Y, Cao S, Chabowski DS, Korishettar A, Ge A, Zheng X, Sparapani R, Gutterman DD, Zhang DX. Contribution of K V1.5 Channel to Hydrogen Peroxide-Induced Human Arteriolar Dilation and Its Modulation by Coronary Artery Disease. Circ Res 2016; 120:658-669. [PMID: 27872049 DOI: 10.1161/circresaha.116.309491] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 11/11/2016] [Accepted: 11/21/2016] [Indexed: 02/06/2023]
Abstract
RATIONALE Hydrogen peroxide (H2O2) regulates vascular tone in the human microcirculation under physiological and pathophysiological conditions. It dilates arterioles by activating large-conductance Ca2+-activated K+ channels in subjects with coronary artery disease (CAD), but its mechanisms of action in subjects without CAD (non-CAD) when compared with those with CAD remain unknown. OBJECTIVE We hypothesize that H2O2-elicited dilation involves different K+ channels in non-CAD versus CAD, resulting in an altered capacity for vasodilation during disease. METHODS AND RESULTS H2O2 induced endothelium-independent vasodilation in non-CAD adipose arterioles, which was reduced by paxilline, a large-conductance Ca2+-activated K+ channel blocker, and by 4-aminopyridine, a voltage-gated K+ (KV) channel blocker. Assays of mRNA transcripts, protein expression, and subcellular localization revealed that KV1.5 is the major KV1 channel expressed in vascular smooth muscle cells and is abundantly localized on the plasma membrane. The selective KV1.5 blocker diphenylphosphine oxide-1 and the KV1.3/1.5 blocker 5-(4-phenylbutoxy)psoralen reduced H2O2-elicited dilation to a similar extent as 4-aminopyridine, but the selective KV1.3 blocker phenoxyalkoxypsoralen-1 was without effect. In arterioles from CAD subjects, H2O2-induced dilation was significantly reduced, and this dilation was inhibited by paxilline but not by 4-aminopyridine, diphenylphosphine oxide-1, or 5-(4-phenylbutoxy)psoralen. KV1.5 cell membrane localization and diphenylphosphine oxide-1-sensitive K+ currents were markedly reduced in isolated vascular smooth muscle cells from CAD arterioles, although mRNA or total cellular protein expression was largely unchanged. CONCLUSIONS In human arterioles, H2O2-induced dilation is impaired in CAD, which is associated with a transition from a combined large-conductance Ca2+-activated K+- and KV (KV1.5)-mediated vasodilation toward a large-conductance Ca2+-activated K+-predominant mechanism of dilation. Loss of KV1.5 vasomotor function may play an important role in microvascular dysfunction in CAD or other vascular diseases.
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Affiliation(s)
- Yoshinori Nishijima
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - Sheng Cao
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - Dawid S Chabowski
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - Ankush Korishettar
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - Alyce Ge
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - Xiaodong Zheng
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - Rodney Sparapani
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - David D Gutterman
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI
| | - David X Zhang
- From the Department of Medicine (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Cardiovascular Center (Y.N., S.C., D.S.C., A.K., A.G., X.Z., D.D.G., D.X.Z.), Department of Pharmacology and Toxicology (D.S.C., A.K.), Division of Biostatistics (R.S.), Medical College of Wisconsin, and Zablocki Veterans Affairs Medical Center (D.D.G.), Milwaukee, WI.
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Dorzolamide-induced relaxation of isolated rabbit ciliary arteries mediated by inhibition of extracellular calcium influx. Jpn J Ophthalmol 2016; 60:103-10. [PMID: 26759121 DOI: 10.1007/s10384-015-0423-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 11/04/2015] [Indexed: 10/22/2022]
Abstract
PURPOSE The carbonic anhydrase inhibitor dorzolamide can increase optic nerve blood flow. The aim of the study reported here was to investigate the effect of dorzolamide on isolated rabbit ciliary arteries that supply the optic nerve. METHODS Changes in ciliary artery isometric tension and intracellular Ca(2+) concentration ([Ca(2+)]i) were recorded to elucidate the underlying pharmacologic mechanisms by which dorzolamide regulates blood flow to the optic nerve. RESULTS Dorzolamide induced concentration-dependent relaxation of rabbit ciliary arteries that had been precontracted by exposure to a high potassium (high-K) solution. Neither pretreatment with 10 µM KB-R 7943, an Na(+)/Ca(2+) exchanger inhibitor, nor alkalinization of the high-K solution had an effect on the dorzolamide-induced relaxation. Pretreatment with 100 µM N(G)-nitro-L-arginine methylester, a nitric oxide synthase inhibitor (n = 10), 10 µM indomethacin, a prostacyclin inhibitor (n = 9), or 0.1 µM iberiotoxin, an inhibitor of endothelium-derived hyperpolarizing factor (n = 7), did not change the concentration-dependent relaxation induced by dorzolamide. Incubation with 3 mM dorzolamide in a Ca(2+)-free solution did not change the transient contractions of the rabbit ciliary arteries induced by 1 µM histamine (n = 9). However, 3 mM dorzolamide significantly suppressed the increase in [Ca(2+)]i induced by the reintroduction of Ca(2+) to a calcium-free extracellular medium (P < 0.05). Furthermore, 3 mM dorzolamide significantly suppressed the [Ca(2+)]i increase induced by the high-K solution (P < 0.05). CONCLUSIONS Taken together, our results reveal a novel role for dorzolamide in relaxing the ciliary arteries. Our data support the hypothesis that the vasodilatory action of dorzolamide is mediated by inhibition of Ca(2+) entry through voltage-dependent Ca(2+) channels.
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Hill-Eubanks DC, Gonzales AL, Sonkusare SK, Nelson MT. Vascular TRP channels: performing under pressure and going with the flow. Physiology (Bethesda) 2015; 29:343-60. [PMID: 25180264 DOI: 10.1152/physiol.00009.2014] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelial cells and smooth muscle cells of resistance arteries mediate opposing responses to mechanical forces acting on the vasculature, promoting dilation in response to flow and constriction in response to pressure, respectively. In this review, we explore the role of TRP channels, particularly endothelial TRPV4 and smooth muscle TRPC6 and TRPM4 channels, in vascular mechanosensing circuits, placing their putative mechanosensitivity in context with other proposed upstream and downstream signaling pathways.
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Affiliation(s)
| | - Albert L Gonzales
- Department of Pharmacology, University of Vermont, Burlington, Vermont
| | | | - Mark T Nelson
- Department of Pharmacology, University of Vermont, Burlington, Vermont
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Makino A, Firth AL, Yuan JXJ. Endothelial and smooth muscle cell ion channels in pulmonary vasoconstriction and vascular remodeling. Compr Physiol 2013; 1:1555-602. [PMID: 23733654 DOI: 10.1002/cphy.c100023] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The pulmonary circulation is a low resistance and low pressure system. Sustained pulmonary vasoconstriction and excessive vascular remodeling often occur under pathophysiological conditions such as in patients with pulmonary hypertension. Pulmonary vasoconstriction is a consequence of smooth muscle contraction. Many factors released from the endothelium contribute to regulating pulmonary vascular tone, while the extracellular matrix in the adventitia is the major determinant of vascular wall compliance. Pulmonary vascular remodeling is characterized by adventitial and medial hypertrophy due to fibroblast and smooth muscle cell proliferation, neointimal proliferation, intimal, and plexiform lesions that obliterate the lumen, muscularization of precapillary arterioles, and in situ thrombosis. A rise in cytosolic free Ca(2+) concentration ([Ca(2+)]cyt) in pulmonary artery smooth muscle cells (PASMC) is a major trigger for pulmonary vasoconstriction, while increased release of mitogenic factors, upregulation (or downregulation) of ion channels and transporters, and abnormalities in intracellular signaling cascades are key to the remodeling of the pulmonary vasculature. Changes in the expression, function, and regulation of ion channels in PASMC and pulmonary arterial endothelial cells play an important role in the regulation of vascular tone and development of vascular remodeling. This article will focus on describing the ion channels and transporters that are involved in the regulation of pulmonary vascular function and structure and illustrating the potential pathogenic role of ion channels and transporters in the development of pulmonary vascular disease.
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Affiliation(s)
- Ayako Makino
- Department of Medicine, The University of Illinois at Chicago, Chicago, Illinois, USA
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Itoh T, Maekawa T, Shibayama Y. Characteristics of ACh-induced hyperpolarization and relaxation in rabbit jugular vein. Br J Pharmacol 2013; 167:682-96. [PMID: 22595036 DOI: 10.1111/j.1476-5381.2012.02038.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE The roles played by endothelium-derived NO and prostacyclin and by endothelial cell hyperpolarization in ACh-induced relaxation have been well characterized in arteries. However, the mechanisms underlying ACh-induced relaxation in veins remain to be fully clarified. EXPERIMENTAL APPROACH ACh-induced smooth muscle cell (SMC) hyperpolarization and relaxation were measured in endothelium-intact and -denuded preparations of rabbit jugular vein. KEY RESULTS In endothelium-intact preparations, ACh (≤ 10⁻⁸ M) marginally increased the intracellular concentration of Ca²⁺ ([Ca²⁺](i)) in endothelial cells but did not alter the SMC membrane potential. However, ACh (10⁻¹⁰ -10⁻⁸ M) induced a concentration-dependent relaxation during the contraction induced by PGF(2α) and this relaxation was blocked by the NO synthase inhibitor N(ω) -nitro-l-arginine. ACh (10⁻⁸ -10⁻⁶ M) concentration-dependently increased endothelial [Ca²⁺](i) and induced SMC hyperpolarization and relaxation. These SMC responses were blocked in the combined presence of apamin [blocker of small-conductance Ca²⁺-activated K⁺ (SK(Ca) , K(Ca) 2.3) channel], TRAM 34 [blocker of intermediate-conductance Ca²⁺ -activated K⁺ (IK(Ca) , K(Ca) 3.1) channel] and margatoxin [blocker of subfamily of voltage-gated K⁺ (K(V) ) channel, K(V) 1]. CONCLUSIONS AND IMPLICATIONS In rabbit jugular vein, NO plays a primary role in endothelium-dependent relaxation at very low concentrations of ACh (10⁻¹⁰ -10⁻⁸ M). At higher concentrations, ACh (10⁻⁸ -3 × 10⁻⁶ M) induces SMC hyperpolarization through activation of endothelial IK(Ca) , K(V) 1 and (possibly) SK(Ca) channels and produces relaxation. These results imply that ACh regulates rabbit jugular vein tonus through activation of two endothelium-dependent regulatory mechanisms.
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Affiliation(s)
- Takeo Itoh
- Department of Pharmacology, Graduate School of Medical Sciences, Nagoya City University, Japan.
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Félétou M. The Endothelium, Part I: Multiple Functions of the Endothelial Cells -- Focus on Endothelium-Derived Vasoactive Mediators. ACTA ACUST UNITED AC 2011. [DOI: 10.4199/c00031ed1v01y201105isp019] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Dalsgaard T, Kroigaard C, Simonsen U. Calcium-activated potassium channels - a therapeutic target for modulating nitric oxide in cardiovascular disease? Expert Opin Ther Targets 2010; 14:825-37. [PMID: 20560781 DOI: 10.1517/14728222.2010.500616] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
IMPORTANCE OF THE FIELD Cardiovascular risk factors are often associated with endothelial dysfunction, which is also prognostic for occurrence of cardiovascular events. Endothelial dysfunction is reflected by blunted vasodilatation and reduced nitric oxide (NO) bioavailability. Endothelium-dependent vasodilatation is mediated by NO, prostacyclin, and an endothelium-derived hyperpolarising factor (EDHF), and involves small (SK) and intermediate (IK) conductance Ca(2+)-activated K(+) channels. Therefore, SK and IK channels may be drug targets for the treatment of endothelial dysfunction in cardiovascular disease. AREAS COVERED IN THIS REVIEW SK and IK channels are involved in EDHF-type vasodilatation, but recent studies suggest that these channels are also involved in the regulation of NO bioavailability. Here we review how SK and IK channels may regulate NO bioavailability. WHAT THE READER WILL GAIN Opening of SK and IK channels is associated with EDHF-type vasodilatation, but, through increased endothelial cell Ca(2+) influx, L-arginine uptake, and decreased ROS production, it may also lead to increased NO bioavailability and endothelium-dependent vasodilatation. TAKE HOME MESSAGE Opening of SK and IK channels can increase both EDHF and NO-mediated vasodilatation. Therefore, openers of SK and IK channels may have the potential of improving endothelial cell function in cardiovascular disease.
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Affiliation(s)
- Thomas Dalsgaard
- Department of Pharmacology, Aarhus University, DK-8000 Aarhus C, Denmark.
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Edwards G, Félétou M, Weston AH. Endothelium-derived hyperpolarising factors and associated pathways: a synopsis. Pflugers Arch 2010; 459:863-79. [PMID: 20383718 DOI: 10.1007/s00424-010-0817-1] [Citation(s) in RCA: 279] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2010] [Revised: 02/22/2010] [Accepted: 02/24/2010] [Indexed: 12/29/2022]
Abstract
The term endothelium-derived hyperpolarising factor (EDHF) was introduced in 1987 to describe the hypothetical factor responsible for myocyte hyperpolarisations not associated with nitric oxide (EDRF) or prostacyclin. Two broad categories of EDHF response exist. The classical EDHF pathway is blocked by apamin plus TRAM-34 but not by apamin plus iberiotoxin and is associated with endothelial cell hyperpolarisation. This follows an increase in intracellular [Ca(2+)] and the opening of endothelial SK(Ca) and IK(Ca) channels preferentially located in caveolae and in endothelial cell projections through the internal elastic lamina, respectively. In some vessels, endothelial hyperpolarisations are transmitted to myocytes through myoendothelial gap junctions without involving any EDHF. In others, the K(+) that effluxes through SK(Ca) activates myocytic and endothelial Ba(2+)-sensitive K(IR) channels leading to myocyte hyperpolarisation. K(+) effluxing through IK(Ca) activates ouabain-sensitive Na(+)/K(+)-ATPases generating further myocyte hyperpolarisation. For the classical pathway, the hyperpolarising "factor" involved is the K(+) that effluxes through endothelial K(Ca) channels. During vessel contraction, K(+) efflux through activated myocyte BK(Ca) channels generates intravascular K(+) clouds. These compromise activation of Na(+)/K(+)-ATPases and K(IR) channels by endothelium-derived K(+) and increase the importance of gap junctional electrical coupling in myocyte hyperpolarisations. The second category of EDHF pathway does not require endothelial hyperpolarisation. It involves the endothelial release of factors that include NO, HNO, H(2)O(2) and vasoactive peptides as well as prostacyclin and epoxyeicosatrienoic acids. These hyperpolarise myocytes by opening various populations of myocyte potassium channels, but predominantly BK(Ca) and/or K(ATP), which are sensitive to blockade by iberiotoxin or glibenclamide, respectively.
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Affiliation(s)
- Gillian Edwards
- Faculty of Life Sciences, University of Manchester, CTF Building, 46 Grafton St, Manchester, M13 9NT, UK
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Dong Y, Watabe H, Cui J, Abe S, Sato N, Ishikawa H, Yoshitomi T. Reduced effects of endothelium-derived hyperpolarizing factor in ocular ciliary arteries from spontaneous hypertensive rats. Exp Eye Res 2010; 90:324-9. [DOI: 10.1016/j.exer.2009.11.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2009] [Revised: 11/12/2009] [Accepted: 11/16/2009] [Indexed: 11/25/2022]
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16
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Abstract
The endothelium controls vascular tone not only by releasing NO and prostacyclin, but also by other pathways causing hyperpolarization of the underlying smooth muscle cells. This characteristic was at the origin of the term 'endothelium-derived hyperpolarizing factor' (EDHF). However, this acronym includes different mechanisms. Arachidonic acid metabolites derived from the cyclo-oxygenases, lipoxygenases and cytochrome P450 pathways, H(2)O(2), CO, H(2)S and various peptides can be released by endothelial cells. These factors activate different families of K(+) channels and hyperpolarization of the vascular smooth muscle cells contribute to the mechanisms leading to their relaxation. Additionally, another pathway associated with the hyperpolarization of both endothelial and vascular smooth muscle cells contributes also to endothelium-dependent relaxations (EDHF-mediated responses). These responses involve an increase in the intracellular Ca(2+) concentration of the endothelial cells, followed by the opening of SK(Ca) and IK(Ca) channels (small and intermediate conductance Ca(2+)-activated K(+) channels respectively). These channels have a distinct subcellular distribution: SK(Ca) are widely distributed over the plasma membrane, whereas IK(Ca) are preferentially expressed in the endothelial projections toward the smooth muscle cells. Following SK(Ca) activation, smooth muscle hyperpolarization is preferentially evoked by electrical coupling through myoendothelial gap junctions, whereas, following IK(Ca) activation, K(+) efflux can activate smooth muscle Kir2.1 and/or Na(+)/K(+)-ATPase. EDHF-mediated responses are altered by aging and various pathologies. Therapeutic interventions can restore these responses, suggesting that the improvement in the EDHF pathway contributes to their beneficial effect. A better characterization of EDHF-mediated responses should allow the determination of whether or not new drugable targets can be identified for the treatment of cardiovascular diseases.
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17
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Félétou M. Calcium-activated potassium channels and endothelial dysfunction: therapeutic options? Br J Pharmacol 2009; 156:545-62. [PMID: 19187341 DOI: 10.1111/j.1476-5381.2009.00052.x] [Citation(s) in RCA: 187] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The three subtypes of calcium-activated potassium channels (K(Ca)) of large, intermediate and small conductance (BK(Ca), IK(Ca) and SK(Ca)) are present in the vascular wall. In healthy arteries, BK(Ca) channels are preferentially expressed in vascular smooth muscle cells, while IK(Ca) and SK(Ca) are preferentially located in endothelial cells. The activation of endothelial IK(Ca) and SK(Ca) contributes to nitric oxide (NO) generation and is required to elicit endothelium-dependent hyperpolarizations. In the latter responses, the hyperpolarization of the smooth muscle cells is evoked either via electrical coupling through myo-endothelial gap junctions or by potassium ions, which by accumulating in the intercellular space activate the inwardly rectifying potassium channel Kir2.1 and/or the Na(+)/K(+)-ATPase. Additionally, endothelium-derived factors such as cytochrome P450-derived epoxyeicosatrienoic acids and under some circumstances NO, prostacyclin, lipoxygenase products and hydrogen peroxide (H(2)O(2)) hyperpolarize and relax the underlying smooth muscle cells by activating BK(Ca). In contrast, cytochrome P450-derived 20-hydroxyeicosatetraenoic acid and various endothelium-derived contracting factors inhibit BK(Ca). Aging and cardiovascular diseases are associated with endothelial dysfunctions that can involve a decrease in NO bioavailability, alterations of EDHF-mediated responses and/or enhanced production of endothelium-derived contracting factors. Because potassium channels are involved in these endothelium-dependent responses, activation of endothelial and/or smooth muscle K(Ca) could prevent the occurrence of endothelial dysfunction. Therefore, direct activators of these potassium channels or compounds that regulate their activity or their expression may be of some therapeutic interest. Conversely, blockers of IK(Ca) may prevent restenosis and that of BK(Ca) channels sepsis-dependent hypotension.
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Affiliation(s)
- Michel Félétou
- Department of Angiology, Institut de Recherches Servier, Suresnes, France.
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18
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Does Endothelium-derived Hyperpolarizing Factor Play a Role in Endothelium-dependent Component of Electrical Field Stimulation-induced Vasorelaxation of Rat Mesenteric Arterial Rings? J Cardiovasc Pharmacol 2009; 53:30-7. [DOI: 10.1097/fjc.0b013e3181953e27] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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19
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Ma X, Li YF, Gao Q, Ye ZG, Lu XJ, Wang HP, Jiang HD, Bruce IC, Xia Q. Inhibition of superoxide anion-mediated impairment of endothelium by treatment with luteolin and apigenin in rat mesenteric artery. Life Sci 2008; 83:110-7. [DOI: 10.1016/j.lfs.2008.05.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 04/01/2008] [Accepted: 05/13/2008] [Indexed: 10/22/2022]
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20
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Ledoux J, Bonev AD, Nelson MT. Ca2+-activated K+ channels in murine endothelial cells: block by intracellular calcium and magnesium. ACTA ACUST UNITED AC 2008; 131:125-35. [PMID: 18195387 PMCID: PMC2213563 DOI: 10.1085/jgp.200709875] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The intermediate (IK(Ca)) and small (SK(Ca)) conductance Ca(2+)-sensitive K(+) channels in endothelial cells (ECs) modulate vascular diameter through regulation of EC membrane potential. However, contribution of IK(Ca) and SK(Ca) channels to membrane current and potential in native endothelial cells remains unclear. In freshly isolated endothelial cells from mouse aorta dialyzed with 3 microM free [Ca(2+)](i) and 1 mM free [Mg(2+)](i), membrane currents reversed at the potassium equilibrium potential and exhibited an inward rectification at positive membrane potentials. Blockers of large-conductance, Ca(2+)-sensitive potassium (BK(Ca)) and strong inward rectifier potassium (K(ir)) channels did not affect the membrane current. However, blockers of IK(Ca) channels, charybdotoxin (ChTX), and of SK(Ca) channels, apamin (Ap), significantly reduced the whole-cell current. Although IK(Ca) and SK(Ca) channels are intrinsically voltage independent, ChTX- and Ap-sensitive currents decreased steeply with membrane potential depolarization. Removal of intracellular Mg(2+) significantly increased these currents. Moreover, concomitant reduction of the [Ca(2+)](i) to 1 microM caused an additional increase in ChTX- and Ap-sensitive currents so that the currents exhibited theoretical outward rectification. Block of IK(Ca) and SK(Ca) channels caused a significant endothelial membrane potential depolarization (approximately 11 mV) and decrease in [Ca(2+)](i) in mesenteric arteries in the absence of an agonist. These results indicate that [Ca(2+)](i) can both activate and block IK(Ca) and SK(Ca) channels in endothelial cells, and that these channels regulate the resting membrane potential and intracellular calcium in native endothelium.
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Affiliation(s)
- Jonathan Ledoux
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington 05405, USA
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21
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Leuranguer V, Vanhoutte PM, Verbeuren T, Félétou M. C-type natriuretic peptide and endothelium-dependent hyperpolarization in the guinea-pig carotid artery. Br J Pharmacol 2007; 153:57-65. [PMID: 17906681 PMCID: PMC2199393 DOI: 10.1038/sj.bjp.0707476] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE C-type natriuretic peptide (CNP) has been proposed to make a fundamental contribution in arterial endothelium-dependent hyperpolarization to acetylcholine. The present study was designed to address this hypothesis in the guinea-pig carotid artery. EXPERIMENTAL APPROACH The membrane potential of vascular smooth muscle cells was recorded in isolated arteries with intracellular microelectrodes. KEY RESULTS Acetylcholine induced endothelium-dependent hyperpolarizations in the presence or absence of N (G)-nitro-L-arginine, indomethacin and/or thiorphan, inhibitors of NO-synthases, cyclooxygenases or neutral endopeptidase, respectively. Acetycholine hyperpolarized smooth muscle cells in resting arteries and produced repolarizations in phenylephrine-stimulated arteries. CNP produced hyperpolarizations with variable amplitude. They were observed only in the presence of inhibitors of NO-synthases and cyclooxygenases and were endothelium-independent, maintained in phenylephrine-depolarized carotid arteries, and not affected by the additional presence of thiorphan. In arteries with endothelium, the hyperpolarizations produced by CNP were always significantly smaller than those induced by acetylcholine. Upon repeated administration, a significant tachyphylaxis of the hyperpolarizing effect of CNP was observed, while consecutive administration of acetycholine produced sustained responses. The hyperpolarizations evoked by acetylcholine were abolished by the combination of apamin plus charybdotoxin, but unaffected by glibenclamide or tertiapin. In contrast, CNP-induced hyperpolarizations were abolished by glibenclamide and unaffected by the combination of apamin plus charybdotoxin. CONCLUSIONS AND IMPLICATIONS In the isolated carotid artery of the guinea-pig, CNP activates K(ATP) and is a weak hyperpolarizing agent. In this artery, the contribution of CNP to EDHF-mediated responses is unlikely.
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Affiliation(s)
| | - P M Vanhoutte
- Department of Pharmacology, Faculty of Medicine, University of Hong Kong Hong Kong, China
| | - T Verbeuren
- Institut Recherches Servier Suresnes, France
| | - M Félétou
- Institut Recherches Servier Suresnes, France
- Author for correspondence:
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22
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Abstract
Endothelium-dependent relaxations are attributed to the release of various factors, such as nitric oxide, carbon monoxide, reactive oxygen species, adenosine, peptides and arachidonic acid metabolites derived from the cyclooxygenases, lipoxygenases, and cytochrome P450 monooxygenases pathways. The hyperpolarization of the smooth muscle cell can contribute to or be an integral part of the mechanisms underlying the relaxations elicited by virtually all these endothelial mediators. These endothelium-derived factors can activate different families of K(+) channels of the vascular smooth muscle. Other events associated with the hyperpolarization of both the endothelial and the vascular smooth muscle cells (endothelium-derived hyperpolarizing factor (EDHF)-mediated responses) contribute also to endothelium-dependent relaxations. These responses involve an increase in the intracellular Ca(2+) concentration of the endothelial cells followed by the opening of Ca(2+)-activated K(+) channels of small and intermediate conductance and the subsequent hyperpolarization of these cells. Then, the endothelium-dependent hyperpolarization of the underlying smooth muscle cells can be evoked by direct electrical coupling through myoendothelial junctions and/or the accumulation of K(+) ions in the intercellular space between the two cell types. These various mechanisms are not necessarily mutually exclusive and, depending on the vascular bed and the experimental conditions, can occur simultaneously or sequentially, or also may act synergistically.
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Affiliation(s)
- Michel Félétou
- Department of Angiology, Institut de Recherches Servier, Suresnes, France
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23
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Abstract
The endothelium controls vascular tone not only by releasing nitric oxide (NO) and prostacyclin but also by other pathways causing hyperpolarization of the underlying smooth muscle cells. This characteristic was at the origin of the denomination endothelium-derived hyperpolarizing factor (EDHF). We know now that this acronym includes different mechanisms. In general, EDHF-mediated responses involve an increase in the intracellular calcium concentration, the opening of calcium-activated potassium channels of small and intermediate conductance and the hyperpolarization of the endothelial cells. This results in an endothelium-dependent hyperpolarization of the smooth muscle cells, which can be evoked by direct electrical coupling through myo-endothelial junctions and/or the accumulation of potassium ions in the intercellular space. Potassium ions hyperpolarize the smooth muscle cells by activating inward rectifying potassium channels and/or Na+/K(+)-ATPase. In some blood vessels, including large and small coronary arteries, the endothelium releases arachidonic acid metabolites derived from cytochrome P450 monooxygenases. The epoxyeicosatrienoic acids (EET) generated are not only intracellular messengers but also can diffuse and hyperpolarize the smooth muscle cells by activating large conductance calcium-activated potassium channels. Additionally, the endothelium can produce other factors such as lipoxygenases derivatives or hydrogen peroxide (H2O2). These different mechanisms are not necessarily exclusive and can occur simultaneously.
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Affiliation(s)
- Michel Félétou
- Department of Angiology, Institut de Recherches Servier, Suresnes, France
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24
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Siegl D, Koeppen M, Wölfle SE, Pohl U, de Wit C. Myoendothelial Coupling Is Not Prominent in Arterioles Within the Mouse Cremaster Microcirculation In Vivo. Circ Res 2005; 97:781-8. [PMID: 16166558 DOI: 10.1161/01.res.0000186193.22438.6c] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
A smooth muscle hyperpolarization is essential for endothelium-dependent hyperpolarizing factor–mediated dilations. It is debated whether the hyperpolarization is induced by a factor (endothelium-derived hyperpolarizing factor) and/or is attributable to direct current transfer from the endothelium via myoendothelial gap junctions. Here, we measured membrane potential in endothelial cells (EC) and smooth muscle cells (SMC) in vivo at rest and during acetylcholine (ACh) application in the cremaster microcirculation of mice using sharp microelectrodes before and after application of specific blockers of Ca
2+
-dependent K
+
channels (K
Ca
). Moreover, diameter changes in response to ACh were studied. Membrane potential at rest was lower in EC than SMC (−46.6±1.0 versus −36.5±1.0mV,
P
<0.05). Bolus application of ACh induced robust hyperpolarizations in EC and SMC, but the amplitude (11.1±0.9 versus 5.1±0.9mV,
P
<0.05) and duration of the response (10.7±0.8 versus 7.5±1.0s,
P
<0.05) were larger in EC. Blockers of large conductance K
Ca
(charybdotoxin or iberiotoxin) abrogated ACh-induced hyperpolarizations in SMC but did not alter endothelial hyperpolarizations. In contrast, apamin, a blocker of small conductance K
Ca
abolished ACh-induced hyperpolarizations in EC and had only small effects on SMC. ACh-induced dilations were strongly attenuated by iberiotoxin but only slightly by apamin. We conclude that myoendothelial coupling in arterioles in vivo in the murine cremaster is weak, as EC and SMC behaved electrically different. Small conductance K
Ca
mediate endothelial hyperpolarization in response to ACh, whereas large conductance K
Ca
are important in SMC. Because tight myoendothelial coupling was found in vitro in previous studies, we suggest that it is differentially regulated between vascular beds and/or by mechanisms acting in vivo.
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Affiliation(s)
- Daniel Siegl
- Physiologisches Institut, Universität Lübeck,Lübeck, Germany
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25
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Martínez AC, Prieto D, Hernández M, Rivera L, Recio P, García-Sacristán A, Benedito S. Endothelial mechanisms underlying responses to acetylcholine in the horse deep dorsal penile vein. Eur J Pharmacol 2005; 515:150-9. [PMID: 15894308 DOI: 10.1016/j.ejphar.2005.04.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2005] [Revised: 04/01/2005] [Accepted: 04/08/2005] [Indexed: 11/23/2022]
Abstract
This study evaluates the mechanisms underlying endothelium-dependent responses to acetylcholine in horse deep dorsal penile veins. Acetylcholine-induced relaxation was abolished by endothelium removal, the soluble guanylyl cyclase-inhibitor, and the nitric oxide (NO) synthase inhibitors. Acetylcholine-induced relaxation was inhibited by high K+ concentrations and blockade of large-conductance Ca(2+)-activated potassium (BK(Ca)) channels, and voltage-dependent potassium (K(v)) channels. Relaxations were unaffected by a small-conductance K(Ca) (SK(Ca)) channel blocker, or an ATP-sensitive potassium (K(ATP)) channel blocker. Relaxation in response to a NO donor was unaffected by K(Ca) channel blockers, but inhibited by high K+ concentrations and a K(v) channel blocker. In the presence of a NO synthase inhibitor, acetylcholine-induced contractions were inhibited by a cyclooxygenase blocker and abolished by endothelial removal. The contractile response was competitively inhibited by muscarinic receptor antagonists, high affinity M1 and M3 antagonists, while the M2 antagonist had no effect. The pharmacological profile suggests that acetylcholine contraction is mediated by muscarinic M1 receptors. Our findings indicate that acetylcholine-induced relaxation in the horse deep dorsal penile vein is essentially mediated by NO, acting via the cGMP-dependent pathway and opening of K+ channels. The contraction elicited by acetylcholine is prostanoid-mediated and induced by endothelial muscarinic M1 receptor activation.
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Affiliation(s)
- Ana Cristina Martínez
- Sección Departamental de Fisiología, Facultad de Farmacia, Universidad Complutense, UCM, 28040 Madrid, Spain
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26
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Sato A, Terata K, Miura H, Toyama K, Loberiza FR, Hatoum OA, Saito T, Sakuma I, Gutterman DD. Mechanism of vasodilation to adenosine in coronary arterioles from patients with heart disease. Am J Physiol Heart Circ Physiol 2005; 288:H1633-40. [PMID: 15772334 DOI: 10.1152/ajpheart.00575.2004] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Adenosine is a key myocardial metabolite that elicits coronary vasodilation in a variety of pathophysiological conditions. We examined the mechanism of adenosine-induced vasodilation in coronary arterioles from patients with heart disease. Human coronary arterioles (HCAs) were dissected from pieces of the atrial appendage obtained at the time of cardiac surgery and cannulated for the measurement of internal diameter with videomicroscopy. Adenosine-induced vasodilation was not inhibited by endothelial denudation, but A(2) receptor antagonism with 3,7-dimethyl-1-propargylxanthine and adenylate cyclase (AC) inhibition with SQ22536 significantly attenuated the dilation. In contrast, A(1) receptor antagonism with 8-cyclopentyl-1,3-dipropylxanthine significantly augmented the sensitivity to adenosine. Moreover, dilation to A(2a) receptor activation with 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido-adenosine hydrochloride was reduced by the A(1) receptor agonist (2S)-N(6)-(2-endo-norbornyl)adenosine. The nonspecific calcium-activated potassium (K(Ca)) channel blocker tetrabutylammonium attenuated adenosine-induced dilation, as did the intermediate-conductance K(Ca) blocker clotrimazole. Neither the large-conductance K(Ca) blocker iberiotoxin nor small-conductance K(Ca) blocker apamin altered the dilation. In conclusion, adenosine endothelium independently dilates HCAs from patients with heart disease through a receptor-mediated mechanism that involves the activation of intermediate-conductance K(Ca) channels via an AC signaling pathway. The roles of A(1) and A(2) receptor subtypes are opposing, with the former being inhibitory to AC-mediated dilator actions of the latter. These observations identify unique fundamental physiological characteristics of the human coronary circulation and may help to target the use of novel adenosine analogs for vasodilation in perfusion imaging or suggest new strategies for myocardial preconditioning.
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Affiliation(s)
- Atsushi Sato
- Dept. of Medicine, Cardiovascular Center, and Veterans Administration Medical Center, Medical College of Wisconsin, 8701 Watertown Plank Rd., Milwaukee, WI 53226, USA
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27
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Griffith TM. Endothelium-dependent smooth muscle hyperpolarization: do gap junctions provide a unifying hypothesis? Br J Pharmacol 2005; 141:881-903. [PMID: 15028638 PMCID: PMC1574270 DOI: 10.1038/sj.bjp.0705698] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
An endothelium-derived hyperpolarizing factor (EDHF) that is distinct from nitric oxide (NO) and prostanoids has been widely hypothesized to hyperpolarize and relax vascular smooth muscle following stimulation of the endothelium by agonists. Candidates as diverse as K(+) ions, eicosanoids, hydrogen peroxide and C-type natriuretic peptide have been implicated as the putative mediator, but none has emerged as a 'universal EDHF'. An alternative explanation for the EDHF phenomenon is that direct intercellular communication via gap junctions allows passive spread of agonist-induced endothelial hyperpolarization through the vessel wall. In some arteries, eicosanoids and K(+) ions may themselves initiate a conducted endothelial hyperpolarization, thus suggesting that electrotonic signalling may represent a general mechanism through which the endothelium participates in the regulation of vascular tone.
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Affiliation(s)
- Tudor M Griffith
- Department of Diagnostic Radiology, Wales Heart Research Institute, University of Wales College of Medicine, Heath Park, Cardiff CF14 4XN.
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28
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Gluais P, Edwards G, Weston AH, Vanhoutte PM, Félétou M. Hydrogen peroxide and endothelium-dependent hyperpolarization in the guinea-pig carotid artery. Eur J Pharmacol 2005; 513:219-24. [PMID: 15862803 DOI: 10.1016/j.ejphar.2005.02.042] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2005] [Revised: 02/14/2005] [Accepted: 02/24/2005] [Indexed: 10/25/2022]
Abstract
This study was designed to determine whether or not endothelium-dependent hyperpolarizations evoked by acetylcholine in the isolated guinea-pig carotid artery involve hydrogen peroxide. Membrane potential was recorded in the vascular smooth muscle cells of that artery. Under control conditions, acetylcholine induced endothelium-dependent hyperpolarization of the vascular smooth muscle cells which was not affected by the presence of catalase, superoxide dismutase or their combination. Neither the superoxide dismutase mimetic, tiron nor the thiol-reducing agent N-acetyl-L-cysteine modified the hyperpolarization evoked by 0.1 microM acetylcholine but each produced a partial and significant inhibition of the hyperpolarization induced by 1 microM acetylcholine. Neither 10 nor 100 microM hydrogen peroxide influenced the resting membrane potential of the smooth muscle cells and the higher concentration did not significantly influence the hyperpolarization elicited by acetylcholine. These data indicate that, in the guinea-pig isolated carotid artery, hydrogen peroxide is unlikely to contribute to the endothelium-dependent hyperpolarization evoked by acetylcholine.
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29
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Molin JC, Bendhack LM. Clonidine induces rat aorta relaxation by nitric oxide-dependent and -independent mechanisms. Vascul Pharmacol 2004; 42:1-6. [PMID: 15664881 DOI: 10.1016/j.vph.2004.11.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2004] [Accepted: 11/19/2004] [Indexed: 11/21/2022]
Abstract
The alpha1- and alpha2-adrenoceptors coexist in vascular smooth muscle cells producing vascular contraction and relaxation. This study was designed to investigate which is the mechanism activated by clonidine in the rat aorta, and the endothelial factors possibly involved in the relaxation induced by clonidine. The alpha2-adrenoceptors agonist clonidine relaxed rat aortas pre-contracted with phenylephrine, with or without endothelium. In non-contracted denuded arteries, clonidine produced contractions instead of relaxation. In intact endothelium aortic rings, clonidine induced greater relaxation than in denuded aortic rings. In aortas with intact endothelium, the NO-synthase inhibitor L-NAME (10 micromol/L) and the NO-scavenger hemoglobin (10 micromol/L) reduced the relaxation to clonidine. On the other hand, indomethacin (10 micromol/L) failed to alter the relaxation induced by clonidine. These results suggest the participation of NO, but not prostacyclin in clonidine-induced relaxation. In aortic rings pre-contracted with KCl (60 mmol/L) the relaxation induced by clonidine was abolished; however, the K+ channel blockers glibenclamide (K(ATP)), tetraethylamonium (K(Ca)), and the combination of apamin and charybdotoxin (K(Ca)) did not change the relaxation induced by clonidine. The relaxation induced by clonidine on PGF2alpha-contracted arteries was not affected by prazosin. However, in the absence of prazosin, clonidine had an additional contractile effect in PGF2alpha-contracted arteries. In conclusion, our results show that in rat aorta clonidine can activate alpha2-adrenoceptors in the smooth muscle cells and alpha2-adrenoceptors in the endothelial cells that activates NO production, but not prostacyclin and/or EDHF. In the absence of phenylephrine and prazosin, clonidine can also activate alpha1-adrenoceptors and rat aorta contraction.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Animals
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/physiology
- Clonidine/antagonists & inhibitors
- Clonidine/pharmacology
- Dinoprost/antagonists & inhibitors
- Dinoprost/pharmacology
- Dose-Response Relationship, Drug
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/pathology
- Endothelium, Vascular/physiology
- Endothelium-Dependent Relaxing Factors/pharmacology
- Indomethacin/pharmacology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- NG-Nitroarginine Methyl Ester/pharmacology
- Nitric Oxide/physiology
- Ouabain/pharmacology
- Phenylephrine/pharmacology
- Potassium Chloride/pharmacology
- Prazosin/pharmacology
- Rats
- Rats, Wistar
- Receptors, Adrenergic, alpha-1/drug effects
- Receptors, Adrenergic, alpha-1/physiology
- Vasodilation/drug effects
- Vasodilation/physiology
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Affiliation(s)
- Josiane C Molin
- Laboratório de Farmacologia, Dept. Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, Av. do Café s/no. 14040-903 Ribeirão Preto, SP, Brasil
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30
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Félétou M, Busse R, Edwards G, Fleming I, Weston AH, Vanhoutte PM. [Communication between endothelial and smooth muscle cells]. Med Sci (Paris) 2004; 19:1242-50. [PMID: 14691749 DOI: 10.1051/medsci/200319121242] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Vascular endothelial cells play a fundamental role in the control of vascular tone, and therefore in the control of local blood flow, by releasing various contracting (endothelin, prostaglandins) and relaxing (prostacycline, NO) factors. An additional mechanism involving the hyperpolarization of the vascular smooth muscle cells is observed mainly in the coronary vascular bed and in the periphery. This phenomenon was attributed to an elusive endothelial factor called endothelium-derived hyperpolarizing factor (EDHF). This mechanism is now better understood. It involves first an increase in the endothelial intracellular concentration of calcium, the activation of endothelial potassium channels and the resulting hyperpolarization of the endothelial cells. The hyperpolarization of the endothelial cells is transmitted to the smooth muscle cells by different pathways. This hyperpolarization propagates along the vessels not only via the smooth muscle cells but also via the endothelial cells. Therefore, the endothelial layer can also be considered as a conducting tissue. The discovery of specific inhibitors of the endothelial cell hyperpolarization allows the assessment of the contribution of EDHF-mediated responses in the control of vascular tone.
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31
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Woodman OL, Boujaoude M. Chronic treatment of male rats with daidzein and 17 beta-oestradiol induces the contribution of EDHF to endothelium-dependent relaxation. Br J Pharmacol 2003; 141:322-8. [PMID: 14691049 PMCID: PMC1574190 DOI: 10.1038/sj.bjp.0705603] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. We investigated the effect of chronic (7 days) treatment of male rats with the isoflavone daidzein (0.2 mg kg(-1) sc per day) or 17beta-oestradiol (0.1 mg kg(-1) sc per day) on the contribution of nitric oxide (NO), prostaglandins and endothelium-derived hyperpolarising factor (EDHF) to endothelium-dependent relaxation of isolated aortic rings. 2. The sensitivity and maximum relaxation to acetylcholine (ACh) were significantly greater in aortic rings from rats treated with daidzein or 17beta-oestradiol, in comparison to vehicle-treated rats. Inhibition of nitric oxide synthase with N-nitro-l-arginine (l-NOARG) abolished ACh-induced relaxation in the aortae from vehicle-treated rats, but only attenuated relaxation in aortae from daidzein or 17beta-oestradiol-treated rats. The presence of haemoglobin in addition to l-NOARG did not cause any further inhibition of relaxation. 3. The cyclooxygenase inhibitor indomethacin had no effect on endothelium-dependent relaxation in aortae from any treatment group. Charybdotoxin (ChTX), which blocks large-conductance calcium-activated potassium channels (BK(Ca)) and intermediate-conductance calcium-activated potassium channels (IK(Ca)), plus apamin, which blocks small-conductance calcium-activated potassium channels (SK(Ca)), but not iberiotoxin, which only blocks BK(Ca), attenuated endothelium-dependent relaxation of aortae from daidzein or 17beta-oestradiol-treated rats. Blockade of K(Ca) channels had no effect on the responses to ACh in aortae from vehicle-treated rats. In aortae from daidzein- or 17beta-oestradiol-treated rats, endothelium-dependent relaxation was also attenuated by inhibition of cytochrome P450 (CYP450) epoxygenase with 6-(2-propargylloxyphenyl)hexanoic acid (PPOH) or inhibition of K(IR) channels and Na(+)/K(+)-ATPase with barium and oubain, respectively. 4. This study demonstrates that endothelium-dependent relaxation of male rat aorta is normally entirely mediated by NO, whereas treatment with daidzein or 17beta-oestradiol stimulates a contribution from a non-NO, nonprostaglandin factor acting through the opening of SK(Ca) and IK(Ca) channels, and involving activation of Na/K-ATPase, K(IR) and CYP450 epoxygenase. This pattern of sensitivity to the tested inhibitors is consistent with the contribution of EDHF to relaxation. Thus, EDHF contributes to the enhanced endothelium-dependent relaxation that is observed after chronic treatment with the phytoestrogen daidzein or with 17beta-oestradiol.
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Affiliation(s)
- Owen L Woodman
- Department of Pharmacology, University of Melbourne, Victoria 3010, Australia.
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Quignard JF, Harley EA, Duhault J, Vanhoutte PM, Félétou M. K+ channels in cultured bovine retinal pericytes: effects of beta-adrenergic stimulation. J Cardiovasc Pharmacol 2003; 42:379-88. [PMID: 12960683 DOI: 10.1097/00005344-200309000-00009] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Retinal pericytes are key cells involved in the regulation of retinal blood flow. The purpose of this work was to identify the K+ channel population expressed in cultured bovine retinal pericytes and to determine whether beta-adrenergic stimulation alters the activity of these channels. Isolated pericytes were obtained by homogenization and filtration of bovine retina and K+ channels were studied with the whole-cell configuration of the patch-clamp technique on 3-5 passaged pericytes. Pericytes expressed an inward current dependent on extracellular K+ concentration which was sensitive to micromolar concentrations of barium, a characteristic of an inward-rectifying K+ current. Furthermore, two voltage-dependent outward currents were also observed. Their activation and inactivation properties, as well as their respective sensitivity to 4-aminopyridine and iberiotoxin, were indicative of voltage-sensitive and large-conductance calcium-activated K+ channels (BKCa). Isoproterenol and dibutyryl cyclic adenosine monophosphate enhanced the activity of BKCa without affecting the other potassium currents. In conclusion, bovine retinal pericytes express mainly two outward potassium currents, KV and BKCa, as well as an inward rectifying K+ current, Kir. Physiologic stimuli such as an increase in extracellular potassium concentration or beta-adrenergic receptor stimulation enhance the activity of Kir and BKCa, respectively, suggesting a potential role for these channels in the control of retinal blood flow.
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Affiliation(s)
- Jean-François Quignard
- Département Diabète et Maladies Métaboliques, Institut de Recherches Servier, Suresnes, France
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Nishimura H, Yang Y, Hubert C, Gasc JM, Ruijtenbeek K, De Mey J, Boudier HAJS, Corvol P. Maturation-dependent changes of angiotensin receptor expression in fowl. Am J Physiol Regul Integr Comp Physiol 2003; 285:R231-42. [PMID: 12702485 DOI: 10.1152/ajpregu.00481.2002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An angiotensin (ANG) receptor homologous to the type 1 receptor (AT1) has been cloned in chickens (cAT1). We investigated whether cAT1 expression in various tissues shows maturation/age-dependent changes. cAT1 mRNA levels detected in renal glomeruli [in situ hybridization (ISH)] and kidney extract (RT-PCR) are significantly (P < 0.01) higher in 19-day embryos (EB) than in chicks (CH, 2-3 wk) and pullets/cockerels (PL/CK, 14-16 wk). The levels in adrenal glands (concentrated in subcapsular regions) are high in EB and further increased in CH and PL/CK. cAT1 mRNA is also detectable in smooth muscle (SM)/adventitia of EB and CH aorta and in the adventitia, but not SM, from PL/CK aortas. The endothelia from small arteries and arterioles, but not from aorta, express cAT1 mRNA (ISH). In all age groups, ANG II induces profound endothelium-dependent relaxation of abdominal aorta, partly (37-47%) inhibitable (P < 0.01) by Nomega-nitro-l-arginine methyl ester (l-NAME, 10(-4) M), suggesting the presence of ANG receptor in endothelium. l-NAME-resistant ANG II relaxation, examined in a limited number of EB or CH aortas, was reduced by 125 mM K+ or apamin plus charybdotoxin. The results suggest that 1) cAT1 is present in kidney, adrenal gland, and vascular endothelium (heterogeneity exists among arteries) of EB, CH, and PL/CK, and in aortic SM/adventitia of EB/CH but only in adventitia of PL/CK; 2) levels of cAT1 gene expression change during maturation in a tissue-specific manner; and 3) ANG II-induced relaxation may be partly attributable to nitric oxide and potassium channel activation.
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Affiliation(s)
- H Nishimura
- Dept. of Physiology, Univ. of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163, USA.
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Suzuki H. [Recent advances in the study of endothelium-dependent hyperpolarizing factor (EDHF)]. Nihon Yakurigaku Zasshi 2003; 121:85-90. [PMID: 12616853 DOI: 10.1254/fpj.121.85] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Recent advances in the properties and physiological functions of endothelium-dependent hyperpolarizing factor (EDHF) in vascular tissues were reviewed briefly. The EDHF-induced hyperpolarization is inhibited by charybdotoxin, indicating that the potential is produced mainly by activation of intermediate conductance Ca-sensitive K-channels. During generation of EDHF responses, endothelial Ca2+ concentration was elevated, suggesting that the activated K-channels were distributed on the endothelial membrane. This was confirmed by direct recording of membrane potentials from endothelial and smooth muscle cells using double patch electrodes. Measurement of the propagation of potentials applied to endothelial or smooth muscle cells to surrounding cells revealed that there were tight electrical connections between endothelial cells much more than between endothelial and smooth muscle cells or between smooth muscle cells, and these observations yielded a possible spread of electrical signal along the endothelial layer first, and then the signals would be conducted to smooth muscle cell layers. These properties of vascular tissues allow speculating that EDHF is an electrical signal propagated from endothelial cells electrotonically through myoendothelial gap junctions. Several candidates have been proposed as EDHF, and possibilities of individual substances for EDHF were discussed. The cellular mechanism of the hyperpolarization-induced vasodilatation remains unclear, and this should be clarified in the future for further understanding of the EDHF-induced vasodilatation.
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Affiliation(s)
- Hikaru Suzuki
- Nagoya City University Graduate School of Medical Sciences, Mizuho-ku, Nagoya 467-8601, Japan.
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Eichler I, Wibawa J, Grgic I, Knorr A, Brakemeier S, Pries AR, Hoyer J, Köhler R. Selective blockade of endothelial Ca2+-activated small- and intermediate-conductance K+-channels suppresses EDHF-mediated vasodilation. Br J Pharmacol 2003; 138:594-601. [PMID: 12598413 PMCID: PMC1573692 DOI: 10.1038/sj.bjp.0705075] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. Activation of Ca(2+)-activated K(+)-channels (K(Ca)) has been suggested to play a key role in endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilation. However, due to the low selectivity of commonly used K(Ca)-channel blockers it is still elusive which endothelial K(Ca)-subtypes mediate hyperpolarization and thus initiate EDHF-mediated vasodilation. 2. Using the non-cytochrome P450 blocking clotrimazole-derivatives, 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) and 2-(2-chlorophenyl)-2,2-diphenylacetonitrile (TRAM-39) as highly selective IK1-inhibitors, we investigated the role of the intermediate-conductance K(Ca) (rIK1) in endothelial hyperpolarization and EDHF-mediated vasodilation. 3. Expression and function of rIK1 and small-conductance K(Ca) (rSK3) were demonstrated in situ in single endothelial cells of rat carotid arteries (CA). rIK1-currents were blocked by TRAM-34 or TRAM-39, while rSK3 was blocked by apamin. In current-clamp experiments, endothelial hyperpolarization in response to acetylcholine was abolished by the combination of apamin and TRAM-34. 4. In phenylephrine-preconstricted CA, acetylcholine-induced NO and prostacyclin-independent vasodilation was almost completely blocked by ChTX, CLT, TRAM-34, or TRAM-39 in combination with the SK3-blocker apamin. Apamin, TRAM-34, and CLT alone or sulphaphenzole, a blocker of the cytochrome P450 isoform 2C9, were ineffective in blocking the EDHF-response. 5. In experiments without blocking NO and prostacyclin synthesis, the combined blockade of SK3 and IK1 reduced endothelium-dependent vasodilation. 6. In conclusion, the use of selective IK1-inhibitors together with the SK3-blocker apamin revealed that activation of both K(Ca), rIK1 and rSK3 is crucial in mediating endothelial hyperpolarization and generation of the EDHF-signal while the cytochrome P450 pathway seems to play a minor or no role in rat CA.
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Affiliation(s)
- Ines Eichler
- Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany
| | - Judith Wibawa
- Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany
| | - Ivica Grgic
- Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany
| | - Andrea Knorr
- Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany
| | - Susanne Brakemeier
- Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany
| | - Axel R Pries
- Institute of Physiology, Freie Universität, Berlin, Germany
| | - Joachim Hoyer
- Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany
| | - Ralf Köhler
- Department of Nephrology, Benjamin Franklin Medical Center, Berlin, Germany
- Author for correspondence:
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Allen T, Iftinca M, Cole WC, Plane F. Smooth muscle membrane potential modulates endothelium-dependent relaxation of rat basilar artery via myo-endothelial gap junctions. J Physiol 2002; 545:975-86. [PMID: 12482900 PMCID: PMC2290719 DOI: 10.1113/jphysiol.2002.031823] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The release of endothelium-derived relaxing factors, such as nitric oxide (NO), is dependent on an increase in intracellular calcium levels ([Ca(2+)](i)) within endothelial cells. Endothelial cell membrane potential plays a critical role in the regulation of [Ca(2+)](i) in that calcium influx from the extracellular space is dependent on membrane hyperpolarization. In this study, the effect of inhibition of vascular smooth muscle delayed rectifier K(+) (K(DR)) channels by 4-aminopyridine (4-AP) on endothelium-dependent relaxation of rat basilar artery to acetylcholine (ACh) was assessed. ACh-evoked endothelium-dependent relaxations were inhibited by N-(Omega)-nitro-L-arginine (L-NNA) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), confirming a role for NO and guanylyl cyclase. 4-AP (300 microM) also suppressed ACh-induced relaxation, with the maximal response reduced from approximately 92 to approximately 33 % (n = 11; P < 0.01). However, relaxations in response to exogenous NO, applied in the form of authentic NO, sodium nitroprusside or diethylamineNONOate (DEANONOate), were not affected by 4-AP treatment (n = 3-11). These data are not consistent with the view that 4-AP-sensitive K(DR) channels are mediators of vascular hyperpolarization and relaxation in response to endothelium-derived NO. Inhibition of ACh-evoked relaxation by 4-AP was reversed by pinacidil (0.5-1 microM; n = 5) or 18beta-glycyrrhetinic acid (18betaGA; 5 microM; n = 5), indicating that depolarization and electrical coupling of the smooth muscle to the endothelium were involved. 4-AP caused depolarization of both endothelial and vascular smooth muscle cells of isolated segments of basilar artery (mean change 11 +/- 1 and 9 +/- 2 mV, respectively; n = 15). Significantly, 18betaGA almost completely prevented the depolarization of endothelial cells (n = 6), but not smooth muscle cells (n = 6) by 4-AP. ACh-induced hyperpolarization of endothelium and smooth muscle cells was also reduced by 4-AP, but this inhibition was not observed in the combined presence of 4-AP and 18betaGA. These data indicate that 4-AP can induce an indirect inhibition of endothelium-dependent relaxation in the rat basilar artery by electrical coupling of smooth muscle membrane depolarization to the endothelium via myo-endothelial gap junctions.
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Affiliation(s)
- Tracy Allen
- The Smooth Muscle Research Group, Canadian Institutes of Health Research Group in Regulation of Vascular Contractility, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1
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Bychkov R, Burnham MP, Richards GR, Edwards G, Weston AH, Félétou M, Vanhoutte PM. Characterization of a charybdotoxin-sensitive intermediate conductance Ca2+-activated K+ channel in porcine coronary endothelium: relevance to EDHF. Br J Pharmacol 2002; 137:1346-54. [PMID: 12466245 PMCID: PMC1573623 DOI: 10.1038/sj.bjp.0705057] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. This study characterizes the K(+) channel(s) underlying charybdotoxin-sensitive hyperpolarization of porcine coronary artery endothelium. 2. Two forms of current-voltage (I/V) relationship were evident in whole-cell patch-clamp recordings of freshly-isolated endothelial cells. In both cell types, iberiotoxin (100 nM) inhibited a current active only at potentials over +50 mV. In the presence of iberiotoxin, charybdotoxin (100 nM) produced a large inhibition in 38% of cells and altered the form of the I/V relationship. In the remaining cells, charybdotoxin also inhibited a current but did not alter the form. 3. Single-channel, outside-out patch recordings revealed a 17.1+/-0.4 pS conductance. Pipette solutions containing 100, 250 and 500 nM free Ca(2+) demonstrated that the open probability was increased by Ca(2+). This channel was blocked by charybdotoxin but not by iberiotoxin or apamin. 4. Hyperpolarizations of intact endothelium elicited by substance P (100 nM; 26.1+/-0.7 mV) were reduced by apamin (100 nM; 17.0+/-1.8 mV) whereas those to 1-ethyl-2-benzimidazolinone (1-EBIO, 600 microM, 21.0+/-0.3 mV) were unaffected (21.7+/-0.8 mV). Substance P, bradykinin (100 nM) and 1-EBIO evoked charybdotoxin-sensitive, iberiotoxin-insensitive whole-cell perforated-patch currents. 5 A porcine homologue of the intermediate-conductance Ca(2+)-activated K(+) channel (IK1) was identified in endothelial cells. 6. In conclusion, porcine coronary artery endothelial cells express an intermediate-conductance Ca(2+)-activated K(+) channel and the IK1 gene product. This channel is opened by activation of the EDHF pathway and likely mediates the charybdotoxin-sensitive component of the EDHF response.
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Affiliation(s)
- Rostislav Bychkov
- Département Diabète et Maladies Métaboliques, Institut de Recherches Servier, 92150 Suresnes, France
| | - Matthew P Burnham
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Gillian R Richards
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Gillian Edwards
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Arthur H Weston
- School of Biological Sciences, University of Manchester, Manchester M13 9PT
| | - Michel Félétou
- Département Diabète et Maladies Métaboliques, Institut de Recherches Servier, 92150 Suresnes, France
- Author for correspondence:
| | - Paul M Vanhoutte
- Institut de Recherches Internationales Servier, 92410 Courbevoie, France
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Quignard JF, Chataigneau T, Corriu C, Edwards G, Weston A, Félétou M, Vanhoutte PM. Endothelium-dependent hyperpolarization to acetylcholine in carotid artery of guinea pig: role of lipoxygenase. J Cardiovasc Pharmacol 2002; 40:467-77. [PMID: 12198333 DOI: 10.1097/00005344-200209000-00016] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
This study was designed to determine whether lipoxygenase-dependent metabolites of arachidonic acid are involved in the endothelium-dependent hyperpolarization of the guinea pig carotid artery. The membrane potential of vascular smooth muscle cells was measured with intracellular microelectrodes and potassium channels were studied on freshly isolated cells with the patch-clamp technique. Acetylcholine-induced hyperpolarizations were not affected by arachidonyl trifluoromethyl ketone (AACOCF3), quinacrine (phospholipase A inhibitors), or eicosatetraenoic acid (nonspecific inhibitor of lipoxygenase, cytochrome P450, and cyclooxygenase). In contrast, cinnamyl-3,4 dihydroxy-alpha-cyanocinnamate (CDC) and AA861 (lipoxygenase inhibitors) as well as 1-(6-(17beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino) hexyl)-1H-pyrrole-2,5-dione (U-73122) (phospholipase C inhibitor) produced a significant inhibition of the hyperpolarization. An opener of intermediate conductance calcium-activated potassium channels, 1-ethyl-2-benzamidazolinone (1-EBIO), induced a hyperpolarization that was unaffected by AACOCF3, CDC, AA861, or U-73122 but was inhibited by charybdotoxin. (+/-)12-hydroxy-eicosatetraenoic acid (12-HETE) and 12(S)-hydroperoxy-eicosatetraenoic acid (12(S)-HpETE) did not induce any significant changes in membrane potential. CDC inhibited the voltage-gated potassium current and increased the large conductance calcium-activated potassium current whereas AA861 inhibited both potassium currents. These results confirm that, in the isolated carotid artery of the guinea pig, stimulation of endothelial muscarinic receptors involves phospholipase C activation and indicate that the activation of phospholipase A2 and the release of lipoxygenase metabolites is unlikely to explain endothelium-dependent hyperpolarization.
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Affiliation(s)
- Jean-François Quignard
- Département Diabète et Maladies Métaboliques, Institut de Recherches Servier, Suresnes, France
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Sollini M, Frieden M, Bény JL. Charybdotoxin-sensitive small conductance K(Ca) channel activated by bradykinin and substance P in endothelial cells. Br J Pharmacol 2002; 136:1201-9. [PMID: 12163354 PMCID: PMC1573447 DOI: 10.1038/sj.bjp.0704819] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1 In cultured porcine coronary artery endothelial cells, we have recently shown that substance P and bradykinin stimulated different types of Ca(2+)-dependent K(+) (K(Ca)) current. A large part of this current was insensitive to iberiotoxin and apamin. The aim of the present study was to characterize the K(Ca) channel responsible for this current. 2 In cell-attached configuration and asymmetrical K(+) concentration, 100 nM bradykinin or substance P activated a 10 pS K(+) channel. In inside-out configuration, the channel was half-maximally activated by 795 nM free Ca(2+). 3 Apamin (1 micro M) added to the pipette solution failed to inhibit the channel activity while charybdotoxin (50 nM), completely blocked it. Perfusion at the intracellular face of the cell, of an opener of intermediate conductance K(Ca) channel, 500 micro M 1-ethyl-benzimidazolinone (1-EBIO) increased the channel activity by about 4.5 fold. 4 In whole-cell mode, bradykinin and substance P stimulated an outward K(+) current of similar amplitude. Charybdotoxin inhibited by 75% the bradykinin-induced current and by 80% the substance P-induced current. Charybdotoxin plus iberiotoxin (50 nM each) inhibited by 97% the bradykinin-response. Charybdotoxin plus apamin did not increase the inhibition of the substance P-response obtained in the presence of charybdotoxin alone. 5 1-EBIO activated a transient outward K(+) current and hyperpolarized the membrane potential by about 13 mV. Charybdotoxin reduced the hyperpolarization to about 3 mV. 6 Taken together these results show that bradykinin and substance P activate a 10 pS K(Ca) channel, which largely contributes to the total K(+) current activated by these agonists. Despite its small conductance, this channel shares pharmacological characteristics with intermediate conductance K(Ca) channels.
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Affiliation(s)
- M Sollini
- Department of Zoology and Animal Biology, Sciences III, 30 quai E. Ansermet 1211 Geneva 4, Switzerland
| | - M Frieden
- Department of Zoology and Animal Biology, Sciences III, 30 quai E. Ansermet 1211 Geneva 4, Switzerland
| | - J-L Bény
- Department of Zoology and Animal Biology, Sciences III, 30 quai E. Ansermet 1211 Geneva 4, Switzerland
- Author for correspondence:
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Miller AW, Tulbert C, Puskar M, Busija DW. Enhanced endothelin activity prevents vasodilation to insulin in insulin resistance. Hypertension 2002; 40:78-82. [PMID: 12105142 DOI: 10.1161/01.hyp.0000022806.87281.62] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Although insulin-mediated vasodilation is impaired in insulin resistance, the mechanisms of this are unknown. We investigated factors mediating vasoactive responses to insulin in control and insulin-resistant rats. Responses to insulin in small mesenteric arteries from control and insulin-resistant rats were investigated after blocking endothelin-A receptors, cyclooxygenase, nitric oxide synthase, and potassium channels. In addition, insulin's effect on prostacyclin production in small mesenteric blood vessels was assessed by enzyme immunoassay. Insulin induced a concentration-dependent vasodilation in control arteries that was absent in arteries from insulin-resistant rats. However, in the presence of BQ610, an endothelin-A receptor antagonist, the response to insulin was normalized in insulin-resistant arteries. In control arteries, insulin-induced vasodilation was completely inhibited by indomethacin, meclofenamate, glibenclamide, or potassium chloride. In contrast, neither n-nitro-L-arginine nor the combination of charybdotoxin and apamin altered vasodilation to insulin. In insulin-resistant arteries in the presence of BQ610, vasodilation was also inhibited by indomethacin, glibenclamide, and potassium chloride. Insulin increased prostacyclin production in small mesenteric blood vessels from both groups of rats to a similar degree. Insulin-induced vasodilation in small rat mesenteric arteries is mediated through prostacyclin- and ATP-dependent potassium channels. However, insulin-resistant arteries do not vasodilate to insulin unless endothelin-A receptors are blocked. Thus, impaired relaxation to insulin in insulin-resistant rats is due to enhanced vasoconstriction by endothelin, which offsets a normal vasodilatory response to insulin.
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Affiliation(s)
- Allison W Miller
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA.
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Ungvari Z, Csiszar A, Koller A. Increases in endothelial Ca(2+) activate K(Ca) channels and elicit EDHF-type arteriolar dilation via gap junctions. Am J Physiol Heart Circ Physiol 2002; 282:H1760-7. [PMID: 11959641 DOI: 10.1152/ajpheart.00676.2001] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In skeletal muscle arterioles, the pathway leading to non-nitric oxide (NO), non-prostaglandin-mediated endothelium-derived hyperpolarizing factor (EDHF)-type dilations is not well characterized. To elucidate some of the steps in this process, simultaneous changes in endothelial intracellular Ca(2+) concentration ([Ca(2+)](i)) and the diameter of rat gracilis muscle arterioles (approximately 60 microm) to acetylcholine (ACh) were measured by fura 2 microfluorimetry (in the absence of NO and prostaglandins). ACh elicited rapid increases in endothelial [Ca(2+)](i) (101 +/- 7%), followed by substantial dilations (73 +/- 2%, coupling time: 1.3 +/- 0.2 s) that were prevented by endothelial loading of an intracellular Ca(2+) chelator [1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid]. Arteriolar dilations to ACh were also inhibited by intraluminal administration of the Ca(2+)-activated K(+) (K(Ca)) channel blockers charybdotoxin plus apamin or by palmitoleic acid, an uncoupler of myoendothelial gap junctions without affecting changes in endothelial [Ca(2+)](i). The presence of large conductance K(Ca) channels on arteriolar endothelial cells was demonstrated with immunohistochemisty. We propose that in skeletal muscle arterioles, EDHF-type mediation is evoked by an increase in endothelial [Ca(2+)](i), which by activating endothelial K(Ca) channels elicits hyperpolarization that is conducted via myoendothelial gap junctions to the smooth muscle resulting in decreases in [Ca(2+)](i) and consequently dilation.
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Affiliation(s)
- Zoltan Ungvari
- Department of Physiology, New York Medical College, Valhalla, New York 10595, USA
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42
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McGuire JJ, Hollenberg MD, Andrade-Gordon P, Triggle CR. Multiple mechanisms of vascular smooth muscle relaxation by the activation of proteinase-activated receptor 2 in mouse mesenteric arterioles. Br J Pharmacol 2002; 135:155-69. [PMID: 11786491 PMCID: PMC1573127 DOI: 10.1038/sj.bjp.0704469] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Activation of PAR2 in second-order mesenteric arteriole (MA) rings from C57BL/6J, NOS3 (-/-) and PAR2 (-/-) mice was assessed for the contributions of NO, cyclo-oxygenases, guanylyl cyclase, adenylyl cyclase, and of K(+) channel activation to vascular smooth muscle relaxation. 2. PAR2 agonist, SLIGRL-NH(2) (0.1 to 30 microM), induced relaxation of cirazoline-precontracted MA from C57BL/6J and NOS3 (-/-), but not PAR2 (-/-) mice. Maximal relaxation (E(max)) was partially reduced by a combination of L-(G)N-nitroarginine methyl ester (L-NAME), 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and indomethacin. An ODQ/L-NAME/indomethacin resistant relaxation was also caused by trypsin (30 nM) in PAR2 (+/+), but not in PAR2 (-/-) mice. Relaxation was endothelium-dependent and inhibited by either 30 mM KCl-precontraction, or pretreatment with apamin, charybdotoxin, and their combination; iberiotoxin did not substitute for charybdotoxin nor did scyllatoxin substitute fully for apamin. 3. Tetraethylammonium (TEA), glibenclamide, tetrodotoxin, 17-octadecynoic acid, carboxy-2-phenyl-4,4,5,5,-tetramethyl-imidazoline-1-oxyl-3-oxide, SQ22536, carbenoxolone, arachidonyl trifluoromethyl ketone, 7-nitroindazole, N-(3-(aminomethyl)benzyl)acetamidine (1400W), N-(2-cyclohexyloxy-4-nitrophenyl)-methanesulfonamide (NS-398) and propanolol did not inhibit relaxation. 4-aminopyridine significantly increased the potency of SLIGRL-NH(2). A combination of 30 microM BaCl(2) and 10 microM ouabain significantly reduced the potency for relaxation, and in the presence of L-NAME, ODQ and indomethacin, E(max) was reduced. 4. We conclude PAR2-mediated relaxation of mouse MA utilizes multiple mechanisms that are both NO-cGMP-dependent, and -independent. The data are also consistent with a role for endothelium-dependent hyperpolarization of vascular smooth muscle that involves the activation of an apamin/charybdotoxin-sensitive K(+) channel(s) and, in part, may be mediated by K(+).
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MESH Headings
- Acetylcholine/pharmacology
- Animals
- Biological Factors/pharmacology
- Cyclic GMP/physiology
- Cyclooxygenase Inhibitors/metabolism
- Dose-Response Relationship, Drug
- Endothelium, Vascular/physiology
- Guanylate Cyclase
- Male
- Membrane Potentials/drug effects
- Mesenteric Arteries/drug effects
- Mesenteric Arteries/physiology
- Mice
- Mice, Inbred C57BL
- Muscle Relaxation/drug effects
- Muscle Relaxation/physiology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- NG-Nitroarginine Methyl Ester/pharmacology
- Nitric Oxide/physiology
- Nitric Oxide Donors/pharmacology
- Nitric Oxide Synthase/antagonists & inhibitors
- Nitric Oxide Synthase Type II
- Nitric Oxide Synthase Type III
- Oligopeptides/metabolism
- Potassium/pharmacology
- Potassium Channel Blockers/pharmacology
- Receptor, PAR-2
- Receptors, Cytoplasmic and Nuclear/antagonists & inhibitors
- Receptors, Thrombin/metabolism
- Soluble Guanylyl Cyclase
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Affiliation(s)
- John J McGuire
- Smooth Muscle Research Group, Faculty of Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 4N1.
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Tare M, Coleman HA, Parkington HC. Glycyrrhetinic derivatives inhibit hyperpolarization in endothelial cells of guinea pig and rat arteries. Am J Physiol Heart Circ Physiol 2002; 282:H335-41. [PMID: 11748079 DOI: 10.1152/ajpheart.2002.282.1.h335] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glycyrrhetinic acid (GA) derivatives have been used to implicate gap junctions in vasorelaxation attributed to endothelium-derived hyperpolarizing factor (EDHF). The aim of this study was to assess whether GA compounds affect endothelial cell hyperpolarization. Membrane potentials were recorded from dye-identified endothelial and smooth muscle cells of guinea pig coronary and rat mesenteric arteries. GA derivatives had varied effects on the resting membrane potential: depolarization, hyperpolarization, or no effect, depending on the artery. 18alpha-GA (50 microM) had a small variable effect on ACh-induced hyperpolarizations in endothelial cells. 18beta-GA (30 microM) and carbenoxolone (100 microM) significantly reduced ACh-induced hyperpolarizations in both endothelial and smooth muscle cells. Smooth muscle action potentials in rat tail arteries were smaller and slower in the presence of 18beta-GA. Nerve-induced excitatory junction potentials were inhibited by 18beta-GA and carbenoxolone, whereas the time course of their decay initially increased and then decreased. In conclusion, the GA compounds had a range of effects. Their inhibition of the EDHF hyperpolarization and relaxation in the smooth muscle may stem from the inhibition of endothelial cell hyperpolarization.
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Affiliation(s)
- Marianne Tare
- Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia
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Ghisdal P, Morel N. Cellular target of voltage and calcium-dependent K(+) channel blockers involved in EDHF-mediated responses in rat superior mesenteric artery. Br J Pharmacol 2001; 134:1021-8. [PMID: 11682450 PMCID: PMC1573040 DOI: 10.1038/sj.bjp.0704348] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. We have investigated the cellular target of K(+) channel blockers responsible for the inhibition of the EDHF-mediated relaxation in the rat mesenteric artery by studying their effects on tension, smooth muscle cell (SMC) membrane potential and endothelial cell Ca(2+) signal ([Ca(2+)](endo)). 2. In arteries contracted with prostaglandin F(2 alpha) (2.5 - 10 microM), relaxation evoked by ACh (0.01 - 3 microM) was abolished by a combination of charybdotoxin (ChTX, 0.1 microM) plus apamin (Apa, 0.1 microM) and was inhibited by 68+/-6% (n=6) by 4-aminopyridine (4-AP, 5 mM). 3. ACh(0.001 - 3 microM) increased [Ca(2+)](endo) and hyperpolarized SMCs with the same potency, the pD(2) values were equal to 7.2+/-0.08 (n=4) and 7.2+/-0.07 (n=9), respectively. SMCs hyperpolarization to ACh (1 microM) was abolished by high K(+) solution or by ChTX/Apa. It was decreased by 66+/-5% (n=6) by 4-AP. 4. The increase in [Ca(2+)](endo) evoked by ACh (1 microM) was insensitive to ChTX/Apa but was depressed by 58+/-16% (n=6) and 27+/-4% (n=7) by raising external K(+) concentration and by 4-AP, respectively. 5. The effect of 4-AP on [Ca(2+)](endo) was not affected by increasing external K(+) concentration. In Ca-free/EGTA solution, the transient increase in [Ca(2+)](endo) evoked by ACh (1 microM) was abolished by thapsigargin (1 microM) and was decreased by 75+/-7% (n=5) by 4-AP. 6. These results show that inhibition of EDHF-evoked responses by 4-AP may be attributed to a decrease in the Ca(2+) release activated by ACh in endothelial cells. The abolition of SMCs hyperpolarization to ACh by ChTX/Apa is not related to an interaction with the [Ca(2+)](endo).
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MESH Headings
- 4-Aminopyridine/pharmacology
- Acetylcholine/pharmacology
- Animals
- Apamin/pharmacology
- Biological Factors/physiology
- Calcium/metabolism
- Calcium Signaling/drug effects
- Charybdotoxin/pharmacology
- Cytosol/drug effects
- Cytosol/metabolism
- Dose-Response Relationship, Drug
- Endothelium, Vascular/cytology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- In Vitro Techniques
- Male
- Membrane Potentials/drug effects
- Mesenteric Artery, Superior/drug effects
- Mesenteric Artery, Superior/physiology
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiology
- Potassium/pharmacology
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Calcium-Activated/antagonists & inhibitors
- Potassium Channels, Calcium-Activated/physiology
- Rats
- Rats, Inbred WKY
- Vasodilation/drug effects
- Vasodilator Agents/pharmacology
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Affiliation(s)
- Philippe Ghisdal
- Laboratoire de Pharmacologie, Université Catholique de Louvain, UCL 5410, Avenue Hippocrate, 54 - B 1200 Bruxelles, Belgium
| | - Nicole Morel
- Laboratoire de Pharmacologie, Université Catholique de Louvain, UCL 5410, Avenue Hippocrate, 54 - B 1200 Bruxelles, Belgium
- Author for correspondence:
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Stuart-Smith K, Jeremy JY. Microvessel damage in acute respiratory distress syndrome: the answer may not be NO. Br J Anaesth 2001; 87:272-9. [PMID: 11493501 DOI: 10.1093/bja/87.2.272] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- K Stuart-Smith
- Department of Anaesthesia, Birmingham Heartlands Hospital, Birmingham B9 5SS, UK
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McGuire JJ, Ding H, Triggle CR. Endothelium-derived relaxing factors: A focus on endothelium-derived hyperpolarizing factor(s). Can J Physiol Pharmacol 2001. [DOI: 10.1139/y01-025] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Endothelium-derived hyperpolarizing factor (EDHF) is defined as the non-nitric oxide (NO) and non-prostacyclin (PGI2) substance that mediates endothelium-dependent hyperpolarization (EDH) of vascular smooth muscle cells (VSMC). Although both NO and PGI2 have been demonstrated to hyperpolarize VSMC by cGMP- and cAMP-dependent mechanisms, respectively, and in the case of NO by cGMP-independent mechanisms, a considerable body of evidence suggests that an additional cellular mechanism must exist that mediates EDH. Despite intensive investigation, there is no agreement as to the nature of the cellular processes that mediates the non-NO/PGI2 mediated hyperpolarization. Epoxyeicosatrienoic acids (EET), an endogenous anandamide, a small increase in the extracellular concentration of K+, and electronic coupling via myoendothelial cell gap junctions have all been hypothesized as contributors to EDH. An attractive hypothesis is that EDH is mediated via both chemical and electrical transmissions, however, the contribution from chemical mediators versus electrical transmission varies in a tissue- and species-dependent manner, suggesting vessel-specific specialization. If this hypothesis proves to be correct then the potential exists for the development of vessel and organ-selective vasodilators. Because endothelium-dependent vasodilatation is dysfunctional in disease states (i.e., atherosclerosis), selective vasodilators may prove to be important therapeutic agents.Key words: endothelium, nitric oxide, potassium channels, hyperpolarization, gap junctions.
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Jiang F, Dusting GJ. Endothelium-dependent vasorelaxation independent of nitric oxide and K(+) release in isolated renal arteries of rats. Br J Pharmacol 2001; 132:1558-64. [PMID: 11264250 PMCID: PMC1572700 DOI: 10.1038/sj.bjp.0703965] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
1. We investigated whether K(+) can act as an endothelium-derived hyperpolarizing factor (EDHF) in isolated small renal arteries of Wistar-Kyoto rats. 2. Acetylcholine (0.001 - 3 microM) caused relaxations that were abolished by removal of the endothelium. However, acetylcholine-induced relaxations were not affected by the nitric oxide (NO) synthase inhibitor N:(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM), by L-NAME plus the soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one (ODQ, 1 microM) or by L-NAME plus the cyclo-oxygenase inhibitor indomethacin (10 microM). In rings precontracted with high-K(+)(60 mM) physiological salt solution in the presence of L-NAME, acetylcholine-induced relaxations were abolished. 3. L-NAME-resistant relaxations were abolished by the large-conductance Ca(2+)-activated K(+) channel inhibitor charybdotoxin plus the small-conductance Ca(2+)-activated K(+) channel inhibitor apamin, while the inward rectifier K(+) channel inhibitor Ba(2+) or the gap junction inhibitor 18alpha-glycyrrhetinic acid had no effect. Acetylcholine-induced relaxation was unchanged by ouabain (10 microM) but was partially inhibited by a higher concentration (100 microM). 4. In half of the tissues tested, K(+)(10 mM) itself produced L-NAME-resistant relaxations that were blocked by ouabain (10 microM) and partially reduced by charybdotoxin plus apamin, but not affected by 18alpha-glycyrrhetinic acid or Ba(2+). However, K(+) did not induce relaxations in endothelium-denuded tissues. 5. In conclusion, acetylcholine-induced relaxations in this tissue are largely dependent upon hyperpolarization mechanisms that are initiated in the endothelium but do not depend upon NO release. K(+) release cannot account for endothelium-dependent relaxation and cannot be an EDHF in this artery. However, K(+) itself can initiate endothelium-dependent relaxations via a different pathway from acetylcholine, but the mechanisms of K(+)-induced relaxations remain to be clarified.
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Affiliation(s)
- F Jiang
- Howard Florey Institute, The University of Melbourne, Victoria 3010, Australia.
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Quignard J, Félétou M, Corriu C, Chataigneau T, Edwards G, Weston AH, Vanhoutte PM. 3-Morpholinosydnonimine (SIN-1) and K(+) channels in smooth muscle cells of the rabbit and guinea pig carotid arteries. Eur J Pharmacol 2000; 399:9-16. [PMID: 10876017 DOI: 10.1016/s0014-2999(00)00372-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Experiments were designed to determine the subtype of K(+) channels activated by the nitrovasodilator 3-morpholinosydnonimine (SIN-1) in smooth muscle cells of the rabbit and guinea pig carotid arteries. Membrane potential was recorded in isolated segments with intracellular microelectrode and K(+) currents in freshly dissociated smooth muscle cells, with the patch-clamp technique. In the guinea pig carotid artery, SIN-1 caused a glibenclamide-sensitive hyperpolarization. The nitrovasodilator did not affect the whole-cell K(+) current, but activated a glibenclamide-sensitive K(+) current. In the rabbit carotid artery, SIN-1 induced only an iberiotoxin-sensitive repolarization in phenylephrine-depolarized tissue and in isolated cells, enhanced the activity of an iberiotoxin-sensitive K(+) current. These findings demonstrate that the population of K(+) channels activated by nitric oxide (NO) is species-dependent and support the conclusion that, in the guinea pig carotid artery, in contrast to the rabbit carotid artery, the release of NO cannot account for the responses attributed to endothelium-derived hyperpolarizing factor (EDHF).
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Affiliation(s)
- J Quignard
- Département Diabète et Maladies Métaboliques, Institut de Recherche Servier, 92150, Suresnes, France
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