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Blaustein MP, Hamlyn JM. Sensational site: the sodium pump ouabain-binding site and its ligands. Am J Physiol Cell Physiol 2024; 326:C1120-C1177. [PMID: 38223926 PMCID: PMC11193536 DOI: 10.1152/ajpcell.00273.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 12/22/2023] [Accepted: 01/10/2024] [Indexed: 01/16/2024]
Abstract
Cardiotonic steroids (CTS), used by certain insects, toads, and rats for protection from predators, became, thanks to Withering's trailblazing 1785 monograph, the mainstay of heart failure (HF) therapy. In the 1950s and 1960s, we learned that the CTS receptor was part of the sodium pump (NKA) and that the Na+/Ca2+ exchanger was critical for the acute cardiotonic effect of digoxin- and ouabain-related CTS. This "settled" view was upended by seven revolutionary observations. First, subnanomolar ouabain sometimes stimulates NKA while higher concentrations are invariably inhibitory. Second, endogenous ouabain (EO) was discovered in the human circulation. Third, in the DIG clinical trial, digoxin only marginally improved outcomes in patients with HF. Fourth, cloning of NKA in 1985 revealed multiple NKA α and β subunit isoforms that, in the rodent, differ in their sensitivities to CTS. Fifth, the NKA is a cation pump and a hormone receptor/signal transducer. EO binding to NKA activates, in a ligand- and cell-specific manner, several protein kinase and Ca2+-dependent signaling cascades that have widespread physiological effects and can contribute to hypertension and HF pathogenesis. Sixth, all CTS are not equivalent, e.g., ouabain induces hypertension in rodents while digoxin is antihypertensinogenic ("biased signaling"). Seventh, most common rodent hypertension models require a highly ouabain-sensitive α2 NKA and the elevated blood pressure is alleviated by EO immunoneutralization. These numerous phenomena are enabled by NKA's intricate structure. We have just begun to understand the endocrine role of the endogenous ligands and the broad impact of the ouabain-binding site on physiology and pathophysiology.
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Affiliation(s)
- Mordecai P Blaustein
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland, United States
| | - John M Hamlyn
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland, United States
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Chen Z, Liu X, Shou C, Yang W, Yu J. Advances in the diagnosis of non-occlusive mesenteric ischemia and challenges in intra-abdominal sepsis patients: a narrative review. PeerJ 2023; 11:e15307. [PMID: 37128207 PMCID: PMC10148637 DOI: 10.7717/peerj.15307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 04/06/2023] [Indexed: 05/03/2023] Open
Abstract
Non-occlusive mesenteric ischemia (NOMI) is a type of acute mesenteric ischemia (AMI) with a high mortality rate mainly because of a delayed or misdiagnosis. Intra-abdominal sepsis is one of the risk factors for developing NOMI, and its presence makes early diagnosis much more difficult. An increase in routine abdominal surgeries carries a corresponding risk of abdominal infection, which is a complication that should not be overlooked. It is critical that physicians are aware of the possibility for intestinal necrosis in abdominal sepsis patients due to the poor survival rate of NOMI. This review aims to summarize advances in the diagnosis of NOMI, and focuses on the diagnostic challenges of mesenteric ischemia in patients with intra-abdominal sepsis.
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Prostanoids contribute to regulation of inwardly rectifying K + channels in intrarenal arterial smooth muscle cells. Life Sci 2020; 250:117586. [PMID: 32222464 DOI: 10.1016/j.lfs.2020.117586] [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: 11/24/2019] [Revised: 03/19/2020] [Accepted: 03/19/2020] [Indexed: 11/23/2022]
Abstract
AIM The inward rectifier K+ (Kir) channels and prostanoids are important factors in regulating vascular tone, but the relationship between them has not been well studied. We aimed to study the involvement of prostanoids in regulating Kir activity in the rat intrarenal arteries (RIRAs). MAIN METHODS The vascular tone of isolated RIRAs was recorded with a wire myograph. The intracellular Ca2+ concentrations ([Ca2+]i) and Kir currents were measured with a Ca2+-sensitive fluorescence probe and patch clamp, respectively, in the arterial smooth muscle cell (ASMC) freshly isolated from RIRAs. Kir2.1 expression in RIRAs was assayed by Western blotting. KEY FINDINGS At 0.03-1.0 mM, BaCl2 (a specific Kir blocker) concentration-dependently contracted RIRAs and elevated [Ca2+]i levels. Mild stimulations with various vasoconstrictors at low concentrations significantly potentiated RIRA contraction induced by Kir closure with BaCl2. In both the quiescent and the stimulated RIRAs, cyclooxygenase inhibition and thromboxane-prostanoid receptor (TPR) antagonism depressed BaCl2-induced RIRA contraction, while nitric oxide (NO) synthetase inhibition and endothelium-denudation enhanced the contraction. Kir2.1 expression was significantly more abundant in smaller RIRAs. Ba2+-sensitive Kir currents were depressed by TPR agonist U46619 while increased by NO donor sodium nitroprusside. SIGNIFICANCE The present results reveal that vasoconstrictor stimulation augments RIRA contraction induced by Kir closure with Ba+ and indicate that prostanoid synthesis followed by TPR activation is involved in the modulation of the myocyte Kir activity. This study suggests that prostanoid synthesis and TPR may be potential targets for dysfunctions in renal blood circulation.
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Internalization and Transportation of Endothelial Cell Surface K Ca2.3 and K Ca3.1 in Normal Pregnancy and Preeclampsia. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2019; 2019:5820839. [PMID: 31871552 PMCID: PMC6906835 DOI: 10.1155/2019/5820839] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 09/25/2019] [Accepted: 11/05/2019] [Indexed: 01/06/2023]
Abstract
Altered redox state modulates the expression levels of endothelial KCa2.3 and KCa3.1 (KCas) in normal pregnancy (NP) and preeclampsia (PE), thereby regulating vascular contractility. The mechanisms underlying KCas endocytosis and transportation remain unknown. We investigated the regulation of KCas expression in plasma membrane (PM) during NP and PE. Cultured human uterine artery endothelial cells were incubated in serum from normal nonpregnant women and women with NP or PE, or in oxidized LDL-, or lysophosphatidylcholine- (LPC-) containing a medium for 24 hours. NP serum elevated PM levels of KCas and reduced caveolin-1 and clathrin levels. PE serum, oxidized LDL, or LPC reduced PM levels of KCas and elevated caveolin-1, clathrin, Rab5c, and early endosome antigen-1 (EEA1) levels. Reduced KCas levels by PE serum or LPC were reversed by inhibition of caveolin-1, clathrin, or EEA1. Catalase and glutathione peroxidase 1 (GPX1) knockdown elevated PM-localized KCas levels and reduced caveolin-1 and clathrin levels. Elevated KCa2.3 levels upon catalase and GPX1 knockdown were reversed by PEG-catalase treatment. An H2O2 donor reduced clathrin and Rab5c. In contrast, elevated clathrin, caveolin-1, or colocalization of caveolin-1 with KCa3.1 by PE serum or LPC was reversed by NADPH oxidase inhibitors or antioxidants. A superoxide donor xanthine+xanthine oxidase elevated caveolin-1 or Rab5c levels. We concluded that KCas are endocytosed in a caveola- or a clathrin-dependent manner and transported in a Rab5c- and EEA1-dependent manner during pregnancy. The endocytosis and transportation processes may slow down via H2O2-mediated pathways in NP and may be accelerated via superoxide-mediated pathways in PE.
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Kloza M, Baranowska-Kuczko M, Toczek M, Kusaczuk M, Sadowska O, Kasacka I, Kozłowska H. Modulation of Cardiovascular Function in Primary Hypertension in Rat by SKA-31, an Activator of KCa2.x and KCa3.1 Channels. Int J Mol Sci 2019; 20:ijms20174118. [PMID: 31450834 PMCID: PMC6747311 DOI: 10.3390/ijms20174118] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 08/17/2019] [Accepted: 08/21/2019] [Indexed: 12/11/2022] Open
Abstract
The aim of this study was to investigate the hemodynamic effects of SKA-31, an activator of the small (KCa2.x) and intermediate (KCa3.1) conductance calcium-activated potassium channels, and to evaluate its influence on endothelium-derived hyperpolarization (EDH)-KCa2.3/KCa3.1 type relaxation in isolated endothelium-intact small mesenteric arteries (sMAs) from spontaneously hypertensive rats (SHRs). Functional in vivo and in vitro experiments were performed on SHRs or their normotensive controls, Wistar-Kyoto rats (WKY). SKA-31 (1, 3 and 10 mg/kg) caused a brief decrease in blood pressure and bradycardia in both SHR and WKY rats. In phenylephrine-pre-constricted sMAs of SHRs, SKA-31 (0.01–10 µM)-mediated relaxation was reduced and SKA-31 potentiated acetylcholine-evoked endothelium-dependent relaxation. Endothelium denudation and inhibition of nitric oxide synthase (eNOS) and cyclooxygenase (COX) by the respective inhibitors l-NAME or indomethacin, attenuated SKA-31-mediated vasorelaxation. The inhibition of KCa3.1, KCa2.3, KIR and Na+/K+-ATPase by TRAM-34, UCL1684, Ba2+ and ouabain, respectively, reduced the potency and efficacy of the EDH-response evoked by SKA-31. The mRNA expression of eNOS, prostacyclin synthase, KCa2.3, KCa3.1 and KIR were decreased, while Na+/K+-ATPase expression was increased. Collectively, SKA-31 promoted hypotension and vasodilatation, potentiated agonist-stimulated vasodilation, and maintained KCa2.3/KCa3.1-EDH-response in sMAs of SHR with downstream signaling that involved KIR and Na+/K+-ATPase channels. In view of the importance of the dysfunction of endothelium-mediated vasodilatation in the mechanism of hypertension, application of activators of KCa2.3/KCa3.1 channels such as SKA-31 seem to be a promising avenue in pharmacotherapy of hypertension.
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Affiliation(s)
- Monika Kloza
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Marta Baranowska-Kuczko
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
- Department of Clinical Pharmacy, Medical University of Białystok, 15-222 Białystok, Poland
| | - Marek Toczek
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Magdalena Kusaczuk
- Department of Pharmaceutical Biochemistry, Medical University of Białystok, 15-222 Białystok, Poland
| | - Olga Sadowska
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Irena Kasacka
- Department of Histology and Cytophysiology, Medical University of Białystok, 15-222 Białystok, Poland
| | - Hanna Kozłowska
- Department of Experimental Physiology and Pathophysiology, Medical University of Białystok, 15-222 Białystok, Poland.
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Tykocki NR, Boerman EM, Jackson WF. Smooth Muscle Ion Channels and Regulation of Vascular Tone in Resistance Arteries and Arterioles. Compr Physiol 2017; 7:485-581. [PMID: 28333380 DOI: 10.1002/cphy.c160011] [Citation(s) in RCA: 222] [Impact Index Per Article: 31.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Vascular tone of resistance arteries and arterioles determines peripheral vascular resistance, contributing to the regulation of blood pressure and blood flow to, and within the body's tissues and organs. Ion channels in the plasma membrane and endoplasmic reticulum of vascular smooth muscle cells (SMCs) in these blood vessels importantly contribute to the regulation of intracellular Ca2+ concentration, the primary determinant of SMC contractile activity and vascular tone. Ion channels provide the main source of activator Ca2+ that determines vascular tone, and strongly contribute to setting and regulating membrane potential, which, in turn, regulates the open-state-probability of voltage gated Ca2+ channels (VGCCs), the primary source of Ca2+ in resistance artery and arteriolar SMCs. Ion channel function is also modulated by vasoconstrictors and vasodilators, contributing to all aspects of the regulation of vascular tone. This review will focus on the physiology of VGCCs, voltage-gated K+ (KV) channels, large-conductance Ca2+-activated K+ (BKCa) channels, strong-inward-rectifier K+ (KIR) channels, ATP-sensitive K+ (KATP) channels, ryanodine receptors (RyRs), inositol 1,4,5-trisphosphate receptors (IP3Rs), and a variety of transient receptor potential (TRP) channels that contribute to pressure-induced myogenic tone in resistance arteries and arterioles, the modulation of the function of these ion channels by vasoconstrictors and vasodilators, their role in the functional regulation of tissue blood flow and their dysfunction in diseases such as hypertension, obesity, and diabetes. © 2017 American Physiological Society. Compr Physiol 7:485-581, 2017.
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Affiliation(s)
- Nathan R Tykocki
- Department of Pharmacology, University of Vermont, Burlington, Vermont, USA
| | - Erika M Boerman
- Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, Missouri, USA
| | - William F Jackson
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan, USA
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Caniffi C, Cerniello FM, Gobetto MN, Sueiro ML, Costa MA, Arranz C. Vascular Tone Regulation Induced by C-Type Natriuretic Peptide: Differences in Endothelium-Dependent and -Independent Mechanisms Involved in Normotensive and Spontaneously Hypertensive Rats. PLoS One 2016; 11:e0167817. [PMID: 27936197 PMCID: PMC5147996 DOI: 10.1371/journal.pone.0167817] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Accepted: 11/21/2016] [Indexed: 01/30/2023] Open
Abstract
Given that the role of C-type natriuretic peptide (CNP) in the regulation of vascular tone in hypertensive states is unclear, we hypothesized that impaired response of the nitric oxide system to CNP in spontaneously hypertensive rats (SHR) could affect vascular relaxation induced by the peptide in this model of hypertension, and that other endothelial systems or potassium channels opening could also be involved. We examined the effect of CNP on isolated SHR aortas, and the hindlimb vascular resistance (HVR) in response to CNP administration compared to normotensive rats. Aortas were mounted in an isometric organ bath and contracted with phenylephrine. CNP relaxed arteries in a concentration-dependent manner but was less potent in inducing relaxation in SHR. The action of CNP was diminished by removal of the endothelium, inhibition of nitric oxide synthase by Nω-nitro-L-arginine methyl ester, and inhibition of soluble guanylyl cyclase by 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one in both groups. In contrast, blockade of cyclooxygenase or subtype 2 bradykinin receptor increased CNP potency only in SHR. In both Wistar and SHR, CNP relaxation was blunted by tetraethylammonium and partially inhibited by BaCl2 and iberiotoxin, indicating that it was due to opening of the Kir and BKCa channels. However, SHR seem to be more sensitive to Kir channel blockade and less sensitive to BKCa channel blockade than normotensive rats. In addition, CNP decreases HVR in Wistar and SHR, but the effect of CNP increasing blood flow was more marked in SHR. We conclude that CNP induces aorta relaxation by activation of the nitric oxide system and opening of potassium channels, but the response to the peptide is impaired in conductance vessel of hypertensive rats.
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Affiliation(s)
- Carolina Caniffi
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Fisiología, CONICET, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA), Buenos Aires, Argentina
- * E-mail:
| | - Flavia M. Cerniello
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Fisiología, CONICET, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA), Buenos Aires, Argentina
| | - María N. Gobetto
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Fisiología, CONICET, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA), Buenos Aires, Argentina
| | - María L. Sueiro
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Fisiología, CONICET, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA), Buenos Aires, Argentina
| | - María A. Costa
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Fisiología, CONICET, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA), Buenos Aires, Argentina
| | - Cristina Arranz
- Universidad de Buenos Aires, Facultad de Farmacia y Bioquímica, Cátedra de Fisiología, CONICET, Instituto de Química y Metabolismo del Fármaco (IQUIMEFA), Buenos Aires, Argentina
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Zheng X, Heaps CL, Fisher SA. Myosin phosphatase isoforms and related transcripts in the pig coronary circulation and effects of exercise and chronic occlusion. Microvasc Res 2014; 98:166-71. [PMID: 24534069 DOI: 10.1016/j.mvr.2014.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 12/19/2013] [Accepted: 02/03/2014] [Indexed: 10/25/2022]
Abstract
Myosin phosphatase (MP) is a key target of signaling pathways that regulate smooth muscle tone and blood flow. Alternative splicing of MP targeting subunit (MYPT1) exon 24 (E24) generates isoforms with variable presence of a C-terminal leucine zipper (LZ) required for activation of MP by NO/cGMP. Here we examined the expression of MP and associated genes in a disease model in the coronary circulation. Female Yucatan miniature swine remained sedentary or were exercise-trained beginning eight weeks after placement of an ameroid constrictor around the left circumflex (LCX) artery. Fourteen weeks later epicardial arteries (~1mm) and resistance arterioles (~125 μm) were harvested and assayed for gene expression. MYPT1 isoforms were distinct in the epicardial arteries (E24-/LZ+) and resistance arterioles (E24+/LZ-) and unchanged by exercise training or coronary occlusion. MYPT1, CPI-17 and PDE5 mRNA levels were not different between arteries and arterioles while Kir2.1 and eNOS were 6.6-fold and 3.9-fold higher in the arterioles. There were no significant changes in transcript abundance in epicardial arteries of the collateralized (LCX) vs. non-occluded left anterior descending (LAD) territories, or in exercise-trained vs. sedentary pigs. There was a significant 1.2 fold increase in CPI-17 in collateral-dependent arterioles, independent of exercise, and a significant 1.7 fold increase in PDE5 in arterioles from exercise-trained pigs, independent of occlusion. We conclude that differences in MYPT1 E24 (LZ) isoforms, eNOS, and Kir2.1 distinguish epicardial arteries and resistance coronary arterioles. Up-regulation of coronary arteriolar PDE5 by exercise and CPI-17 by chronic occlusion could contribute to altered vasomotor responses and requires further study.
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Affiliation(s)
- Xiaoxu Zheng
- Division of Cardiology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA
| | - Cristine L Heaps
- Department of Physiology and Pharmacology, College of Veterinary Medicine & Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA
| | - Steven A Fisher
- Division of Cardiology, School of Medicine, University of Maryland, Baltimore, MD 21201, USA.
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Tajada S, Cidad P, Moreno-Domínguez A, Pérez-García MT, López-López JR. High blood pressure associates with the remodelling of inward rectifier K+ channels in mice mesenteric vascular smooth muscle cells. J Physiol 2012; 590:6075-91. [PMID: 22966162 DOI: 10.1113/jphysiol.2012.236190] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The increased vascular tone that defines essential hypertension is associated with depolarization of vascular smooth muscle cells (VSMCs) and involves a change in the expression profile of ion channels promoting arterial contraction. As a major regulator of VSMC resting membrane potential (V(M)), K(+) channel activity is an important determinant of vascular tone and vessel diameter. However, hypertension-associated changes in the expression and/or modulation of K(+) channels are poorly defined, due to their large molecular diversity and their bed-specific pattern of expression. Moreover, the impact of these changes on the integrated vessel function and their contribution to the development of altered vascular tone under physiological conditions need to be confirmed. Hypertensive (BPH) and normotensive (BPN) mice strains obtained by phenotypic selection were used to explore whether changes in the functional expression of VSMC inward rectifier K(+) channels contribute to the more depolarized resting V(M) and the increased vascular reactivity of hypertensive arteries. We determined the expression levels of inward rectifier K(+) channel mRNA in several vascular beds from BPN and BPH animals, and their functional contribution to VSMC excitability and vascular tone in mesenteric arteries. We found a decrease in the expression of Kir2.1, Kir4.1, Kir6.x and SUR2 mRNA in BPH VSMCs, and a decreased functional contribution of both K(IR) and K(ATP) channels in isolated BPH VSMCs. However, only the effect of K(ATP) channel modulators was impaired when exploring vascular tone, suggesting that decreased functional expression of K(ATP) channels may be an important element in the remodelling of VSMCs in essential hypertension.
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Affiliation(s)
- Sendoa Tajada
- Departamento de Bioquímica y Biología Molecular y Fisiología e Instituto de Biología y Genética Molecular (IBGM), Universidad de Valladolid y CSIC, Valladolid, Spain
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Choi S, Kim MY, Joo KY, Park S, Kim JA, Jung JC, Oh S, Suh SH. Modafinil inhibits K(Ca)3.1 currents and muscle contraction via a cAMP-dependent mechanism. Pharmacol Res 2012; 66:51-9. [PMID: 22414869 DOI: 10.1016/j.phrs.2012.02.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Revised: 02/23/2012] [Accepted: 02/24/2012] [Indexed: 01/18/2023]
Abstract
Modafinil has been used as a psychostimulant for the treatment of narcolepsy. However, its primary mechanism of action remains elusive. Therefore, we examined the effects of modafinil on K(Ca)3.1 channels and vascular smooth muscle contraction. K(Ca)3.1 currents and channel activity were measured using a voltage-clamp technique and inside-out patches in mouse embryonic fibroblast cell line, NIH-3T3 fibroblasts. Intracellular adenosine 3',5'-cyclic monophosphate (cAMP) concentration was measured, and the phosphorylation of K(Ca)3.1 channel protein was examined using western blotting in NIH-3T3 fibroblasts and/or primary cultured mouse aortic smooth muscle cells (SMCs). Muscle contractions were recorded from mouse aorta and rat pulmonary artery by using a myograph developed in-house. Modafinil was found to inhibit K(Ca)3.1 currents in a concentration-dependent manner, and the half-maximal inhibition (IC(50)) of modafinil for the current inhibition was 6.8 ± 0.7 nM. The protein kinase A (PKA) activator forskolin also inhibited K(Ca)3.1 currents. The inhibitory effects of modafinil and forskolin on K(Ca)3.1 currents were blocked by the PKA inhibitors PKI(14-22) or H-89. In addition, modafinil relaxed blood vessels (mouse aorta and rat pulmonary artery) in a concentration-dependent manner. Modafinil increased cAMP concentrations in NIH-3T3 fibroblasts or primary cultured mouse aortic SMCs and phosphorylated K(Ca)3.1 channel protein in NIH-3T3 fibroblasts. However, open probability and single-channel current amplitudes of K(Ca)3.1 channels were not changed by modafinil. From these results, we conclude that modafinil inhibits K(Ca)3.1 channels and vascular smooth muscle contraction by cAMP-dependent phosphorylation, suggesting that modafinil can be used as a cAMP-dependent K(Ca)3.1 channel blocker and vasodilator.
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Affiliation(s)
- Shinkyu Choi
- Department of Physiology, Medical School, Ewha Womans University, Seoul, South Korea
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Oloyo AK, Sofola OA, Nair RR, Harikrishnan VS, Fernandez AC. Testosterone relaxes abdominal aorta in male Sprague-Dawley rats by opening potassium (K(+)) channel and blockade of calcium (Ca(2+)) channel. ACTA ACUST UNITED AC 2011; 18:247-53. [PMID: 21439799 DOI: 10.1016/j.pathophys.2011.02.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Revised: 02/22/2011] [Accepted: 02/22/2011] [Indexed: 10/18/2022]
Abstract
AIM To investigate the direct effect of testosterone and its precursor/derivative dehydroepiandrosterone (DHEA) on isolated rat abdominal aortic rings. MATERIALS AND METHODS 3mm abdominal aortic rings that were obtained from 3 months old male Sprague-Dawley rats were suspended in organ baths containing Hepes buffered PSS bubbled with 100% oxygen. Relaxation response to testosterone and DHEA was studied in noradrenalin pre-contracted rings. The role of aromatase and androgen receptor was assessed by inhibition using aminogluthetemide and blockade using flutamide respectively. Relaxation responses of the rings to testosterone in the presence of l-NAME, indomethacin, barium chloride, apamin, charybdotoxin, iberiotoxin, and nifedipine were also determined. RESULTS Both aromatase inhibition and androgen receptor blockade did not block the relaxing effect of testosterone on rings from rat abdominal aorta. Also there was no significant difference between testosterone relaxation response in the presence or absence of l-NAME and indomethacin. However 3μM, BaCl(2) almost completely abolished the aortic ring relaxation response to testosterone while 1μM, nifedipine potentiated the vasorelaxing effect of testosterone. CONCLUSION Testosterone relaxes abdominal aorta directly via a non-genomic pathway which is independent of endothelial derived vasoactive substances, but involves activation of inward rectifying potassium channel (K(IR)) and blockade of l-type calcium channel.
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Affiliation(s)
- Ahmed Kolade Oloyo
- Department of Physiology, College of Medicine, University of Lagos, Idi - Araba Lagos, Nigeria
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Chung IM, Kim YM, Yoo MH, Shin MK, Kim CK, Suh SH. Immobilization stress induces endothelial dysfunction by oxidative stress via the activation of the angiotensin II/its type I receptor pathway. Atherosclerosis 2010; 213:109-14. [DOI: 10.1016/j.atherosclerosis.2010.08.052] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 07/13/2010] [Accepted: 08/11/2010] [Indexed: 01/22/2023]
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Potentiation of EDHF-mediated relaxation by chloride channel blockers. Acta Pharmacol Sin 2010; 31:1303-11. [PMID: 20835269 DOI: 10.1038/aps.2010.157] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
AIM To investigate the involvement of Cl⁻ channels in endothelium-derived hyperpolarizing factor (EDHF)-mediated relaxation in rat mesenteric arteries. METHODS Cl⁻ channel and K(ir) channel activities were studied using whole-cell patch clamping in rat mesenteric arterial smooth muscle cells. Isometric tension of arterial rings was measured in organ chambers. RESULTS The volume-activated Cl⁻ current in rat mesenteric arterial smooth muscle cells was abolished by Cl⁻ channel blockers NPPB or DIDS. The EDHF-mediated vasorelaxation was potentiated by NPPB and DIDS. The EDHF response was diminished by a combination of apamin and charybdotoxin, which agreed with the hypothesis that EDHF response involves the release of K(+) via the Ca²(+)-activated K(+) channels in endothelial cells. The elevation of K(+) concentration in bathing solution from 1.2 mmol/L to 11.2 mmol/L induced an arterial relaxation, which was abolished by the combination of BaCl₂ and ouabain. It is consistent to the hypothesis that K(+) activates K(+)/Na(+)-ATPase and inward rectifier K(+) (K(ir)) channels, leading to the hyperpolarization and relaxation of vascular smooth muscle. The K(+)-induced relaxation was augmented by NPPB, DIDS, or withdrawal of Cl⁻ from the bathing solution, which could be reversed by BaCl₂, but not ouabain. The potentiating effect of Cl⁻ channel blockers on K(+)-induced relaxation was probably due to the interaction between Cl⁻ channels and K(ir) channels. Moreover, the K(+)-induced relaxation was potentiated when the arteries were incubated in hyperosmotic solution, which is known to inhibit volume-activated Cl⁻ channels. CONCLUSION The inhibition of Cl⁻ channels, particularly the volume-activated Cl⁻ channels, may potentiate the EDHF-induced vasorelaxation through the K(ir) channels.
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14
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Choi SS. Effect of pH Change on Vascular Smooth Muscle Contractility in Rat Superior Mesenteric Artery and Its Branches. THE KOREAN JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2010. [DOI: 10.5090/kjtcs.2010.43.4.345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Soo Seung Choi
- Department of Thoracic and Cardiovascular Surgery, Ewha Womans University School of Medicine
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15
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de Boer TP, Houtman MJC, Compier M, van der Heyden MAG. The mammalian K(IR)2.x inward rectifier ion channel family: expression pattern and pathophysiology. Acta Physiol (Oxf) 2010; 199:243-56. [PMID: 20331539 DOI: 10.1111/j.1748-1716.2010.02108.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Inward rectifier currents based on K(IR)2.x subunits are regarded as essential components for establishing a stable and negative resting membrane potential in many excitable cell types. Pharmacological inhibition, null mutation in mice and dominant positive and negative mutations in patients reveal some of the important functions of these channels in their native tissues. Here we review the complex mammalian expression pattern of K(IR)2.x subunits and relate these to the outcomes of functional inhibition of the resultant channels. Correlations between expression and function in muscle and bone tissue are observed, while we recognize a discrepancy between neuronal expression and function.
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Affiliation(s)
- T P de Boer
- Department of Medical Physiology, UMCU, Utrecht, the Netherlands
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16
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Wang S, Zhang Y, Wier WG, Yu X, Zhao M, Hu H, Sun L, He X, Wang Y, Wang B, Zang W. Role of store-operated Ca(2+) entry in adenosine-induced vasodilatation of rat small mesenteric artery. Am J Physiol Heart Circ Physiol 2009; 297:H347-54. [PMID: 19429831 DOI: 10.1152/ajpheart.00060.2009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Store-operated Ca(2+) entry (SOCE) has recently been proposed to contribute to Ca(2+) influx in vascular smooth muscle cells (VSMCs). Adenosine is known for its protective role against hypoxia and ischemia by increasing nutrient and oxygen supply through vasodilation. This study was designed to examine the hypothesis that SOCE have a functional role in adenosine-induced vasodilation. Small mesenteric resistance arteries and mesenteric VSMCs were obtained from rats. Isometric tensions of isolated artery rings were measured by a sensitive myograph system. Laser-scanning confocal microscopy was used to determine the intracellular Ca(2+) concentration of fluo 3-loaded VSMCs. Adenosine (0.1-100 microM) relaxed artery rings that were precontracted by phenylephrine in a concentration-dependent manner. In cultured mesenteric VSMCs, passive store depletion by thapsigargin and active store depletion by phenylephrine both induced Ca(2+) influx due to SOCE. Adenosine inhibited SOCE-mediated increases in cytosolic Ca(2+) levels evoked by the emptying of the stores. In isolated artery rings, adenosine inhibited SOCE-induced contractions due to store depletion. A(2A) receptor antagonism with SCH-58261 and adenylate cyclase inhibition with SQ-22536 largely attenuated adenosine responses. The cAMP analog 8-bromo-cAMP mimicked the effects of adenosine on SOCE. Our results indicate a novel mechanism of vasodilatation by adenosine that involves regulation of SOCE through the cAMP signaling pathway due to activation of adenosine A(2A) receptors.
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Affiliation(s)
- Shengpeng Wang
- Department of Pharmacology, School of Medicine, Xi'an Jiaotong University, Xi'an, PR China
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17
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Scherer D, Kiesecker C, Kulzer M, Günth M, Scholz EP, Kathöfer S, Thomas D, Maurer M, Kreuzer J, Bauer A, Katus HA, Karle CA, Zitron E. Activation of inwardly rectifying Kir2.x potassium channels by beta 3-adrenoceptors is mediated via different signaling pathways with a predominant role of PKC for Kir2.1 and of PKA for Kir2.2. Naunyn Schmiedebergs Arch Pharmacol 2007; 375:311-22. [PMID: 17534603 DOI: 10.1007/s00210-007-0167-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2006] [Accepted: 05/07/2007] [Indexed: 01/22/2023]
Abstract
beta(3)-adrenoceptors have recently been shown to induce a complex modulation of intracellular signaling pathways including cyclic guanine monophosphate, cyclic adenosine monophosphate, nitric oxide, and protein kinases A and C. They are expressed in a broad variety of tissues including the myocardium, vascular smooth muscle, and endothelium. In those tissues, resting membrane potential is controlled mainly by inwardly rectifying potassium channels of the Kir2 family namely, Kir2.1 in the vascular smooth muscle, Kir2.1-2.3 in the myocardium, and Kir2.1-2.2 in the endothelium. In the present study, we investigated the possible modulation of Kir2 channel function by beta(3)-adrenoceptors in an expression system. Human-cloned beta(3)-adrenoceptors and Kir2.1 (KCNJ2), Kir2.2 (KCNJ12), and Kir2.3 (KCNJ4) channels were coexpressed in Xenopus oocytes, and currents were measured with double-microelectrode voltage clamp. Activation of beta(3)-adrenoceptors with isoproterenol resulted in markedly increased currents in Kir2.1 and in Kir2.2 potassium channels with EC50 values of 27 and 18 nM, respectively. In contrast, Kir2.3 currents were not modulated. Coapplication of specific inhibitors of protein kinase A (KT-5720) and calmodulin kinase II (KN-93) had no effects on the observed regulation in Kir2.1. However, coapplication of protein kinase C (PKC) inhibitors staurosporine and chelerythrine suppressed the observed effect. In Kir2.2, coapplication of KT-5720 reduced the effect of beta(3)-adrenoceptor activation. No differences in current increase after application of isoproterenol were observed between mutant Kir2.2 potassium channels lacking all functional PKC phosphorylation sites and Kir2.2 wild-type channels. In heteromeric Kir2.x channels, all types of heteromers were activated. The effect was most pronounced in Kir2.1/Kir2.2 and in Kir2.2/Kir2.3 channels. In summary, homomeric and heteromeric Kir2.x channels are activated by beta(3)-adrenoceptors via different protein kinase-dependent pathways: Kir2.1 subunits are modulated by PKC, whereas Kir2.2 is modulated by protein kinase A. In heteromeric composition, a marked activation of currents can be observed particularly with involvement of Kir2.2 subunits. This regulation may contribute to the hyperpolarizing effects of beta(3)-adrenoceptors in tissues that exhibit modulation by Kir2 channel function.
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Affiliation(s)
- Daniel Scherer
- Department of Cardiology, Medical University Hospital Heidelberg, Im Neuenheimer Feld 410, 69120, Heidelberg, Germany
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18
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Brochet DXP, Langton PD. Dual effect of initial [K] on vascular tone in rat mesenteric arteries. Pflugers Arch 2006; 453:33-41. [PMID: 16847697 DOI: 10.1007/s00424-006-0106-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2006] [Revised: 04/08/2006] [Accepted: 05/04/2006] [Indexed: 10/24/2022]
Abstract
A slight increase in extracellular concentration of potassium ([K(+)](o)) can act as a vasodilator in rat mesenteric vascular bed. However, in recent years, several groups have failed to consistently observe relaxation of rat mesenteric arteries in these conditions. The aim of the present study was to provide a mechanistic understanding of this discrepancy. In rat small mesenteric arteries, 37 of 40 arteries mounted for measurement of isometric force and pre-contracted with phenylephrine (PE) did not relax when ([K(+)](o) was raised from 5.9 mM (control ([K(+)](o) to 11.2 or 21.2 mM. However, when ([K(+)](o) was briefly lowered to 1.2 mM, increasing ([K(+)](o) to between 5.9 and 41.2 mM evoked relaxation. This relaxation was not reduced by barium or by removal of the endothelium, but was abolished by 0.1 mM ouabain. Raising ([K(+)](o) from concentrations between 0 and 5.9 mM to 13.8 mM elicited a relaxation of PE-induced tone that was inversely proportional to initial ([K(+)](o). Relaxation was associated with a ouabain-sensitive hyperpolarization of smooth muscle cells. In arteries exposed to dihydroouabain (DHO), raising ([K(+)](o) from 5.9 to 13.8 mM and simultaneously washing out DHO resulted in relaxation of PE-induced force. These results suggest that only when the initial ([K(+)](o) is less than approximately 5 mM do small elevations in ([K(+)](o) evoke smooth muscle hyperpolarization and relaxation via activation of Na,K-ATPase, and not inwardly rectifying K(+) channels. Therefore, small differences in the initial ([K(+)](o) (4.6 vs 5.9 mM) can strongly influence the variations of vascular tone to increases in ([K(+)](o).
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Affiliation(s)
- Didier X P Brochet
- Department of Physiology, School of Medical Sciences, University of Bristol, Bristol, BS8 1TD, UK
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19
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Haddy FJ, Vanhoutte PM, Feletou M. Role of potassium in regulating blood flow and blood pressure. Am J Physiol Regul Integr Comp Physiol 2006; 290:R546-52. [PMID: 16467502 DOI: 10.1152/ajpregu.00491.2005] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Unlike sodium, potassium is vasoactive; for example, when infused into the arterial supply of a vascular bed, blood flow increases. The vasodilation results from hyperpolarization of the vascular smooth muscle cell subsequent to potassium stimulation by the ion of the electrogenic Na+-K+ pump and/or activating the inwardly rectifying Kir channels. In the case of skeletal muscle and brain, the increased flow sustains the augmented metabolic needs of the tissues. Potassium ions are also released by the endothelial cells in response to neurohumoral mediators and physical forces (such as shear stress) and contribute to the endothelium-dependent relaxations, being a component of endothelium-derived hyperpolarization factor-mediated responses. Dietary supplementation of potassium can lower blood pressure in normal and some hypertensive patients. Again, in contrast to NaCl restriction, the response to potassium supplementation is slow to appear, taking approximately 4 wk. Such supplementation reduces the need for antihypertensive medication. "Salt-sensitive" hypertension responds particularly well, perhaps, in part, because supplementation with potassium increases the urinary excretion of sodium chloride. Potassium supplementation may even reduce organ system complications (e.g., stroke).
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Affiliation(s)
- Francis J Haddy
- Department of Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine, Rochester, Minnesota, USA
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20
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Kim MY, Seol GH, Liang GH, Kim JA, Suh SH. Na+-K+ pump activation inhibits endothelium-dependent relaxation by activating the forward mode of Na+/Ca2+ exchanger in mouse aorta. Am J Physiol Heart Circ Physiol 2005; 289:H2020-9. [PMID: 15994853 DOI: 10.1152/ajpheart.00908.2004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of Na+-K+ pump activation on endothelium-dependent relaxation (EDR) and on intracellular Ca2+ concentration ([Ca2+]i) was examined in mouse aorta and mouse aortic endothelial cells (MAECs). The Na+-K+ pump was activated by increasing extracellular K+ concentration ([K+]o) from 6 to 12 mM. In aortic rings, the Na+ ionophore monensin evoked EDR, and this EDR was inhibited by the Na+/Ca2+ exchanger (NCX; reverse mode) inhibitor KB-R7943. Monensin-induced Na+ loading or extracellular Na+ depletion (Na+ replaced by Li+) increased [Ca2+]i in MAECs, and this increase was inhibited by KB-R7943. Na+-K+ pump activation inhibited EDR and [Ca2+]i increase (K+-induced inhibition of EDR and [Ca2+]i increase). The Na+-K+ pump inhibitor ouabain inhibited K+-induced inhibition of EDR. Monensin (>0.1 microM) and the NCX (forward and reverse mode) inhibitors 2'4'-dichlorobenzamil (>10 microM) or Ni2+ (>100 microM) inhibited K+-induced inhibition of EDR and [Ca2+]i increase. KB-R7943 did not inhibit K+-induced inhibition at up to 10 microM but did at 30 microM. In current-clamped MAECs, an increase in [K+]o from 6 to 12 mM depolarized the membrane potential, which was inhibited by ouabain, Ni2+, or KB-R7943. In aortic rings, the concentration of cGMP was significantly increased by acetylcholine and decreased on increasing [K+]o from 6 to 12 mM. This decrease in cGMP was significantly inhibited by pretreating with ouabain (100 microM), Ni2+ (300 microM), or KB-R7943 (30 microM). These results suggest that activation of the forward mode of NCX after Na+-K+ pump activation inhibits Ca2+ mobilization in endothelial cells, thereby modulating vasomotor tone.
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Affiliation(s)
- Moon Young Kim
- Dept. of Physiology, College of Medicine, Ewha Women's Univ., 911-1 Mok-6-dong, Yang Chun-gu, Seoul, Republic of Korea 158-710
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