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Turbitt J, Brennan L, Moffett RC, Flatt PR, Johnson PRV, Tarasov AI, McClenaghan NH. NKCC transport mediates the insulinotropic effects of taurine and other small neutral amino acids. Life Sci 2023; 316:121402. [PMID: 36669678 DOI: 10.1016/j.lfs.2023.121402] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Revised: 01/04/2023] [Accepted: 01/13/2023] [Indexed: 01/19/2023]
Abstract
AIMS Despite its high concentration in pancreatic islets of Langerhans and broad range of antihyperglycemic effects, the route facilitating the import of dietary taurine into pancreatic β-cell and mechanisms underlying its insulinotropic activity are unclear. We therefore studied the impact of taurine on beta-cell function, alongside that of other small neutral amino acids, L-alanine and L-proline. MAIN METHODS Pharmacological profiling of insulin secretion was conducted using clonal BRIN BD11 β-cells, the impact of taurine on the metabolic fate of glucose carbons was assessed using NMR and the findings were verified by real-time imaging of Ca2+ dynamics in the cytosol of primary mouse and human islet beta-cells. KEY FINDINGS In our hands, taurine, alanine and proline induced secretory responses that were dependent on the plasma membrane depolarisation, import of Ca2+, homeostasis of K+ and Na+ as well as on cell glycolytic and oxidative metabolism. Taurine shifted the balance between the oxidation and anaplerosis towards the latter, in BRIN BD11 beta-cells. Furthermore, the amino acid signalling was significantly attenuated by inhibition of Na+-K+-Cl- symporter (NKCC). SIGNIFICANCE These data suggest that taurine, like L-alanine and L-proline, acutely induces glucose-dependent insulin-secretory responses by modulating electrogenic Na+ transport, with potential role of intracellular K+ and Cl- in the signal transduction. The acute action delineated would be consistent with antidiabetic potential of dietary taurine supplementation.
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Affiliation(s)
- Julie Turbitt
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK
| | - Lorraine Brennan
- UCD Institute of Food and Health, UCD School of Agriculture and Food Science, University College Dublin, Belfield, Dublin 4, Ireland; UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
| | - R Charlotte Moffett
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK.
| | - Peter R Flatt
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK.
| | - Paul R V Johnson
- Nuffeld Department of Surgical Sciences, Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Headington, OX3 7LE Oxford, UK; Oxford Biomedical Research Centre (OxBRC), UK.
| | - Andrei I Tarasov
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK; Nuffeld Department of Surgical Sciences, Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, Churchill Hospital, Headington, OX3 7LE Oxford, UK; Oxford Biomedical Research Centre (OxBRC), UK.
| | - Neville H McClenaghan
- School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, UK; Department of Life Sciences, Atlantic Technological University, Ash Lane, Sligo, F91 YW50, Ireland.
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Khan I, Ali A, Akhter MA, Naeem N, Chotani MA, Mustafa T, Salim A. Preconditioning of mesenchymal stem cells with 2,4-dinitrophenol improves cardiac function in infarcted rats. Life Sci 2016; 162:60-9. [PMID: 27543341 DOI: 10.1016/j.lfs.2016.08.014] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 07/05/2016] [Accepted: 08/14/2016] [Indexed: 12/11/2022]
Abstract
AIMS The aim of this study is to determine if preconditioning of bone marrow derived mesenchymal stem cells (MSCs) with 2,4-dinitrophenol (DNP) improves survival of transplanted stem cells in a rat model of myocardial infarction (MI), and to asses if this strategy has measurable impact on cardiac function. MAIN METHODS MSCs were preconditioned with DNP. In vitro cell adhesion assay and qRT-PCR were performed to analyze the expression of genes involved in cardiomyogenesis, cell adhesion and angiogenesis. MI was produced by occlusion of left anterior descending coronary artery. One million cells were transplanted by intramyocardial injection into the infarcted myocardium. Echocardiography was performed after two and four weeks of cellular transplantation. Hearts were harvested after four weeks and processed for histological analysis. KEY FINDINGS DNP treated MSCs adhered to the surface more (p<0.001) as compared to the normal MSCs. Gene expression levels were significantly upregulated in case of DNP treatment. The number of viable MSCs was more (p<0.001) in animals that received DNP treated MSCs, leading to significant improvement in cardiac function. Histological analysis revealed significant reduction in scar formation (p<0.001), maintenance of left ventricular wall thickness (p<0.001), and increased angiogenesis (p<0.01). SIGNIFICANCE The study evidenced for the first time that MSCs preconditioned with DNP improved cardiac function after transplantation. This can be attributed to improved survival, homing, adhesion, and cardiomyogenic and angiogenic differentiation of DNP treated MSCs in vivo.
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Affiliation(s)
- Irfan Khan
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, 75270 Karachi, Pakistan
| | - Anwar Ali
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, 75270 Karachi, Pakistan; Department of Physiology, University of Karachi, 75270 Karachi, Pakistan
| | - Muhammad Aleem Akhter
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, 75270 Karachi, Pakistan
| | - Nadia Naeem
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, 75270 Karachi, Pakistan
| | - Maqsood Ahmed Chotani
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, 75270 Karachi, Pakistan; Center for Cardiovascular & Pulmonary Research, The Research Institute at Nationwide Children's Hospital, Columbus, OH, USA; Department of Pediatrics, The Ohio State University, Columbus, OH, USA
| | - Tuba Mustafa
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, 75270 Karachi, Pakistan
| | - Asmat Salim
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, 75270 Karachi, Pakistan.
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Ali A, Akhter MA, Haneef K, Khan I, Naeem N, Habib R, Kabir N, Salim A. Dinitrophenol modulates gene expression levels of angiogenic, cell survival and cardiomyogenic factors in bone marrow derived mesenchymal stem cells. Gene 2015; 555:448-57. [PMID: 25445267 DOI: 10.1016/j.gene.2014.10.045] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Revised: 08/29/2014] [Accepted: 10/26/2014] [Indexed: 01/31/2023]
Affiliation(s)
- Anwar Ali
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Muhammad Aleem Akhter
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Kanwal Haneef
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Irfan Khan
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Nadia Naeem
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Rakhshinda Habib
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Nurul Kabir
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan
| | - Asmat Salim
- Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan.
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Conditioned medium enhances the fusion capability of rat bone marrow mesenchymal stem cells and cardiomyocytes. Mol Biol Rep 2014; 41:3099-112. [PMID: 24469729 DOI: 10.1007/s11033-014-3170-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2013] [Accepted: 01/16/2014] [Indexed: 11/10/2022]
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Oreščanin-Dusić Z, Milovanović S, Blagojević D, Nikolić-Kokić A, Radojičić R, Spasojević I, Spasić M. Diethyldithiocarbamate potentiates the effects of protamine sulphate in the isolated rat uterus. Redox Rep 2013; 14:48-54. [DOI: 10.1179/135100009x392476] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
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Das J, Roy A, Sil PC. Mechanism of the protective action of taurine in toxin and drug induced organ pathophysiology and diabetic complications: a review. Food Funct 2013; 3:1251-64. [PMID: 22930035 DOI: 10.1039/c2fo30117b] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Taurine (2-aminoethanesulfonic acid), a conditionally essential amino acid, is found in large concentrations in all mammalian tissues and is particularly abundant in aquatic foods. Taurine exhibits membrane stabilizing, osmoregulatory and cytoprotective effects, antioxidative properties, regulates intracellular Ca(2+) concentration, modulates ion movement and neurotransmitters, reduce the levels of pro-inflammatory cytokines in various organs and controls blood pressure. Recently, emerging evidence from the literature shows the effectiveness of taurine as a protective agent against several environmental toxins and drug-induced multiple organ injuries as the outcome of hepatotoxicity, nephrotoxicity, neurotoxicity, testicular toxicity and cardiotoxicity in several animal models. Besides, taurine is also effective in combating diabetes and its associated complications, including cardiomyopathy, nephropathy, neuropathy, retinopathy and atherosclerosis. These beneficial effects appear to be due to the multiple actions of taurine on cellular functions. This review summarizes the mechanism of the prophylactic role of taurine against several environmental toxins and drug-induced organ pathophysiology and diabetes.
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Affiliation(s)
- Joydeep Das
- Division of Molecular Medicine, Bose Institute, P-1/12, CIT Scheme VII M, Kolkata-700054, India
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Du Q, Jovanović S, Sukhodub A, Jovanović A. Infection with AV-SUR2A protects H9C2 cells against metabolic stress: a mechanism of SUR2A-mediated cytoprotection independent from the K(ATP) channel activity. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:405-15. [PMID: 20123112 PMCID: PMC2881534 DOI: 10.1016/j.bbamcr.2010.01.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 12/18/2009] [Accepted: 01/22/2010] [Indexed: 11/17/2022]
Abstract
Transgenic mice overexpressing SUR2A, a subunit of ATP-sensitive K(+) (K(ATP)) channels, acquire resistance to myocardial ischaemia. However, the mechanism of SUR2A-mediated cytoprotection is yet to be fully understood. Adenoviral SUR2A construct (AV-SUR2A) increased SUR2A expression, number of K(ATP) channels and subsarcolemmal ATP in glycolysis-sensitive manner in H9C2 cells. It also increased K(+) current in response to chemical hypoxia, partially preserved subsarcolemmal ATP and increased cell survival. Kir6.2AFA, a mutant form of Kir6.2 with largely decreased K(+) conductance, abolished the effect of SUR2A on K(+) current, did not affect SUR2A-induced increase in subsarcolemmal ATP and partially inhibited SUR2A-mediated cytoprotection. Infection with 193gly-M-LDH, an inactive mutant of muscle lactate dehydrogenase, abolished the effect of SUR2A on K(+) current, subsarcolemmal ATP and cell survival; the effect of 193gly-M-LDH on cell survival was significantly more pronounced than those of Kir6.2AFA. We conclude that AV-SUR2A increases resistance to metabolic stress in H9C2 cells by increasing the number of sarcolemmal K(ATP) channels and subsarcolemmal ATP.
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Affiliation(s)
| | | | | | - Aleksandar Jovanović
- Corresponding author. Division of Medical Sciences/MACHS, Ninewells
Hospital and Medical School, University of Dundee, Dundee, DD1 9SY, Scotland,
UK. Tel.: +44 1382 496 269; fax: +44 1382 632 597.
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M-LDH physically associated with sarcolemmal K ATP channels mediates cytoprotection in heart embryonic H9C2 cells. Int J Biochem Cell Biol 2009; 41:2295-301. [PMID: 19464385 PMCID: PMC2758067 DOI: 10.1016/j.biocel.2009.05.012] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Revised: 04/24/2009] [Accepted: 05/17/2009] [Indexed: 11/21/2022]
Abstract
Muscle form of lactate dehydrogenase (M-LDH) physically associate with KATP channel subunits, Kir6.2 and SUR2A, and is an integral part of the ATP-sensitive K+ (KATP) channel protein complex in the heart. Here, we have shown that concomitant introduction of viral constructs containing truncated and mutated forms of M-LDH (ΔM-LDH) and 193gly-M-LDH respectively, generate a phenotype of rat heart embryonic H9C2 cells that do not contain functional M-LDH as a part of the KATP channel protein complex. The K+ current was increased in wild type cells, but not in cells expressing ΔM-LDH/193gly-M-LDH, when they were exposed to chemical hypoxia induced by 2,4 dinitrophenol (DNP; 10 mM). At the same time, the outcome of chemical hypoxia was much worse in ΔM-LDH/193gly-M-LDH phenotype than in the control one, and that was associated with increased loss of intracellular ATP in cells infected with ΔM-LDH/193gly-M-LDH. On the other hand, cells expressing Kir6.2AFA, a Kir6.2 mutant that abolishes KATP channel conductance without affecting intracellular ATP levels, survived chemical hypoxia much better than cells expressing ΔM-LDH/193gly-M-LDH. Based on the obtained results, we conclude that M-LDH physically associated with Kir6.2/SUR2A regulates the activity of sarcolemmal KATP channels as well as an intracellular ATP production during metabolic stress, both of which are important for cell survival.
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Jovanović S, Du Q, Sukhodub A, Jovanović A. A dual mechanism of cytoprotection afforded by M-LDH in embryonic heart H9C2 cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:1379-86. [PMID: 19406174 PMCID: PMC2719797 DOI: 10.1016/j.bbamcr.2009.04.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2009] [Revised: 04/05/2009] [Accepted: 04/21/2009] [Indexed: 01/01/2023]
Abstract
Muscle form of lactate dehydrogenase (M-LDH), a minor LDH form in cardiomyocytes, physically interacts with ATP-sensitive K+ (K ATP) channel-forming subunits. Here, we have shown that expression of 193gly-M-LDH, an inactive mutant of M-LDH, inhibit regulation of the K ATP channels activity by LDH substrates in embryonic rat heart H9C2 cells. In cells expressing 193gly-M-LDH chemical hypoxia has failed to activate K ATP channels. The similar results were obtained in H9C2 cells expressing Kir6.2AFA, a mutant form of Kir6.2 with largely decreased K+ conductance. Kir6.2AFA has slightly, but significantly, reduced cellular survival under chemical hypoxia while the deleterious effect of 193gly-M-LDH was significantly more pronounced. The levels of total and subsarcolemmal ATP in H9C2 cells were not affected by Kir6.2AFA, but the expression of 193gly-M-LDH led to lower levels of subsarcolemmal ATP during chemical hypoxia. We conclude that M-LDH regulates both the channel activity and the levels of subsarcolemmal ATP and that both mechanism contribute to the M-LDH-mediated cytoprotection.
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Affiliation(s)
- Sofija Jovanović
- Division of Medical Sciences, Centre for Cardiovascular and Lung Biology, Ninewells Hospital and Medical School, University of Dundee, Dundee, DD1 9SY Scotland, UK
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Murzaeva SV, Belosludtseva NV, Gavrovskaya L, Mironova GD. The effect of taurine on the ion transport system in mitochondria. Biophysics (Nagoya-shi) 2008; 53:515-518. [DOI: 10.1134/s0006350908060080] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023] Open
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Cuong DV, Kim N, Youm JB, Joo H, Warda M, Lee JW, Park WS, Kim T, Kang S, Kim H, Han J. Nitric oxide-cGMP-protein kinase G signaling pathway induces anoxic preconditioning through activation of ATP-sensitive K+ channels in rat hearts. Am J Physiol Heart Circ Physiol 2005; 290:H1808-17. [PMID: 16339835 DOI: 10.1152/ajpheart.00772.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Nitric oxide (NO) plays an important role in anoxic preconditioning to protect the heart against ischemia-reperfusion injuries. The present work was performed to study better the NO-cGMP-protein kinase G (PKG) signaling pathway in the activation of both sarcolemmal and mitochondrial ATP-sensitive K+ (KATP) channels during anoxic preconditioning (APC) and final influence on reducing anoxia-reperfusion (A/R)-induced cardiac damage in rat hearts. The upstream regulating elements controlling NO-cGMP-PKG signal-induced KATP channel opening that leads to cardioprotection were investigated. The involvement of both inducible and endothelial NO synthases (iNOS and eNOS) in the progression of this signaling pathway was followed. Final cellular outcomes of ischemia-induced injury after different preconditioning in the form of lactate dehydrogenase release, DNA strand breaks, and malondialdehyde formation as indexes of cell injury and lipid peroxidation, respectively, were investigated. The lactate dehydrogenase and malondialdehyde values decreased in the groups that underwent preconditioning periods with specific mitochondrial KATP channels opener diazoxide (100 microM), nonspecific mitochondrial KATP channels opener pinacidil (50 microM), S-nitroso-N-acetylpenicillamine (SNAP, 300 microM), or beta-phenyl-1,N2-etheno-8-bromoguanosine-3',5'-cyclicmonophosphorothioate, Sp-isomer (10 microM) before the A/R period. Preconditioning with SNAP significantly reduced the DNA damage. The effect was blocked by glibenclamide (50 microM), 5-hydroxydecanoate (100 microM), NG-nitro-L-arginine methyl ester (200 microM), and beta-phenyl-1,N2-etheno-8-bromoguanosine-3',5'-cyclic monophosphorothioate, Rp-isomer (1 microM). The results suggest iNOS, rather than eNOS, as the major contributing NO synthase during APC treatment. Moreover, the PKG shows priority over NO as the upstream regulator of NO-cGMP-PKG signal-induced KATP channel opening that leads to cardioprotection during APC treatment.
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Affiliation(s)
- Dang Van Cuong
- Mitochondrial Signaling Laboratory, Department of Physiology and Biophysics, College of Medicine, Cardiovascular and Metabolic Disease Center, Biohealth Products Research Center, Inje University, Busan, Korea
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Lim JG, Lee HY, Yun JE, Kim SP, Park JW, Suh SI, Jang BC, Cho CH, Bae JH, Kim SS, Han J, Park MJ, Song DK. Taurine block of cloned ATP-sensitive K+ channels with different sulfonylurea receptor subunits expressed in Xenopus laevis oocytes. Biochem Pharmacol 2004; 68:901-10. [PMID: 15294453 DOI: 10.1016/j.bcp.2004.05.050] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2004] [Accepted: 05/26/2004] [Indexed: 11/29/2022]
Abstract
Taurine has been found to inhibit ATP-sensitive K+ (KATP) channels in rat pancreatic beta-cells [Park et al., Biochem Pharmacol 2004;67:1089-1096] which could be due to its interaction with a benzamido-binding site on SUR1. In present study, we further evaluated the mechanism of taurine action on the KATP-channel inhibition, using cloned KATP-channels with different types of SUR subunit expressed in Xenopus laevis oocytes. The oocytes were coinjected with Kir6.2 mRNA, and mRNA encoding SUR1, SUR2A or SUR2B. Macroscopic currents were recorded from giant excised inside-out patches. The binding of glibenclamide to SUR1 was assessed by using a glibenclamide-fluorescent probe. Intracellular taurine inhibited all three types of KATP-channels to a similar extent. They were fit to the Hill equation, showing IC50 of 11.0 mM for Kir6.2/SUR1, 10.9 mM for Kir6.2/SUR2A, and 9.0 mM for Kir6.2/SUR2B currents. Taurine at the concentration of 10 mM enhanced the high-affinity bindings of glibenclamide and repaglinide on all types of SUR, whereas the low-affinity binding on Kir6.2 was not affected. The intensity of glibenclamide fluorescence was higher in the plasma membrane of taurine-pretreated oocytes. The high-affinity binding of tolbutamide or gliclazide on SUR was not modified by taurine. These results suggest that the taurine inhibition of KATP-channels is mediated by an interaction with the site on SUR where the benzamido group is bound. Therefore, intracellular concentrations of taurine in different tissues may be more important in determining taurine modulation of the KATP-channel rather than distinct types of SUR subunit.
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Affiliation(s)
- Jeong-Geun Lim
- Department of Neurology, Keimyung University School of Medicine, 194 Dongsan-Dong, Jung-Gu, Daegu 700-712, South Korea
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Park EJ, Bae JH, Kim SY, Lim JG, Baek WK, Kwon TK, Suh SI, Park JW, Lee IK, Ashcroft FM, Song DK. Inhibition of ATP-sensitive K+ channels by taurine through a benzamido-binding site on sulfonylurea receptor 1. Biochem Pharmacol 2004; 67:1089-96. [PMID: 15006545 DOI: 10.1016/j.bcp.2003.11.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2003] [Accepted: 11/03/2003] [Indexed: 10/26/2022]
Abstract
ATP-sensitive potassium (K(ATP)) channels in pancreatic beta-cells comprise sulfonylurea receptor (SUR) 1 and inwardly-rectifying potassium channel (Kir) 6.2 subunits. We have evaluated the effect of intracellular taurine on K(ATP) channel activity in rat pancreatic beta-cells using the patch-clamp technique. The mechanism of taurine action was also examined using recombinant K(ATP) channels. The islets and single beta-cells from male Sprague-Dawley rats were collected by collagenase digestion technique. Single K(ATP) channel currents were recorded by the inside-out mode at a membrane potential of -60mV. Cytosolic free-Ca(2+) concentration ([Ca(2+)](c)) and insulin secretory capacity were measured by the dual-excitation fluorimetry and radioimmunoassay, respectively. The native beta-cell K(ATP) channel was directly inhibited by taurine in a dose-dependent manner. Taurine did not influence ATP-mediated inhibition or MgADP-induced activation of the channel activity. The sensitivity of the K(ATP) channel to glybenclamide, but not gliclazide, was enhanced by taurine. Glybenclamide elicited a greater increase in [Ca(2+)](c) and increased insulin secretion in the beta-cells when pretreated with taurine. Taurine did not inhibit Kir6.2DeltaC36 currents, a truncated form of Kir6.2, expressed in Xenopus oocytes without SUR. These results demonstrate that taurine inhibits the K(ATP) channel activity in the beta-cells, interacting with a benzamido-binding site on SUR1, but not Kir6.2.
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Affiliation(s)
- Eun-Jee Park
- Chronic Disease Research Center, Keimyung University School of Medicine, 194 Dongsan-Dong, Jung-Gu, Daegu 700-712, South Korea
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Schaffer S, Azuma J, Takahashi K, Mozaffari M. Why is taurine cytoprotective? ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2004; 526:307-21. [PMID: 12908615 DOI: 10.1007/978-1-4615-0077-3_39] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Stephen Schaffer
- Department of Pharmacology, University of South Alabama, College of Medicine, Mobile, AL, USA
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Brochiero E, Wallendorf B, Gagnon D, Laprade R, Lapointe JY. Cloning of rabbit Kir6.1, SUR2A, and SUR2B: possible candidates for a renal K(ATP) channel. Am J Physiol Renal Physiol 2002; 282:F289-300. [PMID: 11788443 DOI: 10.1152/ajprenal.00063.2001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
In rabbit proximal tubules, a basolateral ATP- and taurine-sensitive K(+) channel (K(ATP)) was shown to be involved in the regulation of the basolateral K(+) conductance as a function of the rate of apical Na(+) entry. To establish the molecular identity of this channel, we used degenerated primers to look for cDNA transcripts for an inwardly rectifying K(+) channel (Kir6.1 and Kir6.2) and sulfonylurea receptors (SUR1, SUR2A, and SUR2B) in a cDNA library obtained from rabbit proximal tubules. PCR products were found only for Kir6.1, SUR2A, and SUR2B. Expression of Kir6.1 in Xenopus oocytes generated an additional K(+) current that was found to be sensitive to external barium and intracellular taurine and to changes in intracellular ATP concentrations. To study the specificity of the taurine sensitivity, intracellular taurine was tested on several members of the Kir family expressed in Xenopus oocytes. K(+) currents induced by Kir1.1A, Kir2.1, Kir3.2, Kir4.1, or Kir5.1 were insensitive to taurine, but all tested combinations of Kir6.x with or without the SUR subunit were significantly inhibited by taurine. This study suggests that the taurine-sensitive K(ATP) channel of rabbit proximal tubules is formed by a combination of Kir6.1 plus SUR2A and/or SUR2B.
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Affiliation(s)
- Emmanuelle Brochiero
- Groupe de Recherche en Transport Membranaire, Département de Physiologie, Université de Montréal, Montreal, Quebec H3C 3J7, Canada
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Expanding the Circle 1975–1999: Sulfur Biochemistry and Insights on the Biological Functions of Taurins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2002. [DOI: 10.1007/0-306-46838-7_1] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Brochiero E, Coady MJ, Klein H, Laprade R, Lapointe JY. Activation of an ATP-dependent K(+) conductance in Xenopus oocytes by expression of adenylate kinase cloned from renal proximal tubules. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1510:29-42. [PMID: 11342145 DOI: 10.1016/s0005-2736(00)00333-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
In rabbit proximal convoluted tubules, an ATP-sensitive K(+) (K(ATP)) channel has been shown to be involved in membrane cross-talk, i.e. the coupling (most likely mediated through intracellular ATP) between transepithelial Na(+) transport and basolateral K(+) conductance. This K(+) conductance is inhibited by taurine. We sought to isolate this K(+) channel by expression cloning in Xenopus oocytes. Injection of renal cortex mRNA into oocytes induced a K(+) conductance, largely inhibited by extracellular Ba(2+) and intracellular taurine. Using this functional test, we isolated from our proximal tubule cDNA library a unique clone, which induced a large K(+) current which was Ba(2+)-, taurine- and glibenclamide-sensitive. Surprisingly, this clone is not a K(+) channel but an adenylate kinase protein (AK3), known to convert NTP+AMP into NDP+ADP (N could be G, I or A). AK3 expression resulted in a large ATP decrease and activation of the whole-cell currents including a previously unknown, endogenous K(+) current. To verify whether ATP decrease was responsible for the current activation, we demonstrated that inhibition of glycolysis greatly reduces oocyte ATP levels and increases an inwardly rectifying K(+) current. The possible involvement of AK in the K(ATP) channel's regulation provides a means of explaining their observed activity in cytosolic environments characterized by high ATP concentrations.
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Affiliation(s)
- E Brochiero
- Département de Physiologie, Université de Montréal, Quebec, Canada.
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Ovide-Bordeaux S, Ventura-Clapier R, Veksler V. Do modulators of the mitochondrial K(ATP) channel change the function of mitochondria in situ? J Biol Chem 2000; 275:37291-5. [PMID: 10970894 DOI: 10.1074/jbc.m005772200] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Pharmacological opening of mitochondrial cardiac ATP-sensitive potassium (K(ATP)) channels has the chance to be a promising but still controversial cardioprotective mechanism. Physiological roles of mitochondrial K(ATP) channels in the myocardium remain unclear. We studied the effects of diazoxide, a specific opener of these channels, on the function of rat mitochondria in situ in saponin-permeabilized fibers using an ionic medium that mimics the cytosol. In the presence of NADH-producing substrates (malate + glutamate), neither 100 microm diazoxide nor 100 microm glibenclamide (a K(ATP) channel blocker) changed the mitochondrial respiration in the absence or presence of ADP. Because the K(ATP) channel function could be modified by changes in adenine nucleotide concentrations near the mitochondria, we studied the effects of diazoxide and glibenclamide on the functional activity of mitochondrial kinases. Both diazoxide and glibenclamide did not change the in situ ADP sensitivity in the presence or absence of creatine (apparent K(m) values for ADP were, respectively, 59 +/- 9 and 379 +/- 45 microm). Similarly, stimulation of the mitochondrial respiration with AMP in the presence of ATP due to adenylate kinase activity was not affected by the modulators of K(ATP) channels. However, when succinate was used as substrate, diazoxide significantly inhibited basal respiration by 22% and maximal respiration by 24%. Thus, at a cardioprotective dose, the main functional effect of diazoxide depends on respiratory substrates and seems not to be related to K(ATP) channel activity.
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Affiliation(s)
- S Ovide-Bordeaux
- Laboratoire de Cardiologie Cellulaire et Moléculaire INSERM U-446, Faculté de Pharmacie, Université Paris-Sud, 92296 Ch atenay-Malabry, France
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Tricarico D, Barbieri M, Camerino DC. Taurine blocks ATP-sensitive potassium channels of rat skeletal muscle fibres interfering with the sulphonylurea receptor. Br J Pharmacol 2000; 130:827-34. [PMID: 10864889 PMCID: PMC1572140 DOI: 10.1038/sj.bjp.0703385] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/1999] [Revised: 03/24/2000] [Accepted: 03/24/2000] [Indexed: 11/09/2022] Open
Abstract
Taurine is a sulphonic aminoacid present in high amounts in various tissues including cardiac and skeletal muscles showing different properties such as antioxidative, antimyotonic and anti-schaemic effects. The cellular mechanism of action of taurine is under investigation and appears to involve the interaction of the sulphonic aminoacid with several ion channels. Using the patch-clamp technique we studied the effects of taurine in rat skeletal muscle fibres on ATP-sensitive K(+) channel (K(ATP)) immediately after excision and on channels that underwent rundown. The cytoplasmic application of 20 mM of taurine reduced the K(ATP) current; this effect was reverted by washout of the drug solution. In this experimental condition the IC(50) was 20.1 mM. After rundown, taurine inhibited the K(ATP) current with similar efficacy. Competition experiments showed that taurine shifted the dose-response inhibition curve of glybenclamide to the left on the log-dose axis without significantly affecting those of ATP or Ca(2+) ion. Single channel recording revealed that taurine affects the close state of the channel prolonging it and reducing the bursts duration. Our data indicate that taurine inhibits the muscular K(ATP) channel interfering with the glybenclamide site on the sulphonylurea receptor of the channel or on the site allosterically coupled to it. During ischaemia and hypoxia, the skeletal and heart muscles undergo several changes; for example, the activation of K(ATP) channels and loss of the intracellular taurine content. The depletion of taurine during ischaemia would contribute to the early activation of K(ATP) channels and salvage the intracellular ATP content.
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Affiliation(s)
- D Tricarico
- Department of Pharmacobiology, Faculty of Pharmacy, University of Bari, Via Orabona n degrees 4, 70120 Bari, Italy
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Noulin JF, Brochiero E, Lapointe JY, Laprade R. Two types of K(+) channels at the basolateral membrane of proximal tubule: inhibitory effect of taurine. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:F290-7. [PMID: 10444584 DOI: 10.1152/ajprenal.1999.277.2.f290] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cell-attached configuration of the patch-clamp technique was used to investigate the effects of taurine on the basolateral potassium channels of rabbit proximal convoluted tubule. In the absence of taurine, the previously reported ATP-blockable channel, K(ATP), was observed in 51% of patches. It is characterized by an inwardly rectifying current-voltage curve with an inward slope conductance of 49 +/- 5 pS (n = 15) and an outward slope conductance of 13 +/- 6 pS (n = 15). The K(ATP) channel open probability (P(o)) is low, 0.15 +/- 0.06 (n = 15) at a -V(p) = -100 mV (V(p) is the pipette potential), and increases slightly with depolarization. The gating kinetics are characterized by one open time constant (tau(o) = 5.0 +/- 1.9 ms, n = 6) and two closed time constants (tau(C1) = 5. 2 +/- 1.5 ms, tau(C2) = 140 +/- 40 ms; n = 6). In 34% of patches, a second type of potassium channel, sK, with distinct properties was recorded. Its current-voltage curve is characterized by a sigmoidal shape, with an inward slope conductance of 12 +/- 2 pS (n = 4). Its P(o) is voltage independent and averages 0.67 +/- 0.03 (n = 4) at -V(p) = -80 mV. Both its open time and closed time distributions are described by a single time constant (tau(o) = 96 +/- 19 ms, tau(C) = 10.5 +/- 3.6 ms; n = 4). Extracellular perfusion of 40 mM taurine fails to affect sK channels, whereas K(ATP) channel P(o) decreases by 75% (from 0.17 +/- 0.06 to 0.04 +/- 0.02, n = 7, P < 0.05). In conclusion, the absolute basolateral potassium conductance of rabbit proximal tubules is the resulting combination of, at least, two types of potassium channels of roughly equal importance: a high-conductance low-open probability K(ATP) channel and a low-conductance high-open probability sK channel. The previously described decrease in the basolateral absolute potassium conductance by taurine is, however, mediated by a single type of K channel: the ATP-blockable K channel.
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Affiliation(s)
- J F Noulin
- Groupe de Recherche en Transport Membranaire, Université de Montréal, Montreal, Quebec, Canada H3C 3J7
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Abstract
The aim of this review is to provide basic information on the electrophysiological changes during acute ischemia and reperfusion from the level of ion channels up to the level of multicellular preparations. After an introduction, section II provides a general description of the ion channels and electrogenic transporters present in the heart, more specifically in the plasma membrane, in intracellular organelles of the sarcoplasmic reticulum and mitochondria, and in the gap junctions. The description is restricted to activation and permeation characterisitics, while modulation is incorporated in section III. This section (ischemic syndromes) describes the biochemical (lipids, radicals, hormones, neurotransmitters, metabolites) and ion concentration changes, the mechanisms involved, and the effect on channels and cells. Section IV (electrical changes and arrhythmias) is subdivided in two parts, with first a description of the electrical changes at the cellular and multicellular level, followed by an analysis of arrhythmias during ischemia and reperfusion. The last short section suggests possible developments in the study of ischemia-related phenomena.
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Affiliation(s)
- E Carmeliet
- Centre for Experimental Surgery and Anesthesiology, University of Leuven, Leuven, Belgium
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Satoh H, Sperelakis N. Review of some actions of taurine on ion channels of cardiac muscle cells and others. GENERAL PHARMACOLOGY 1998; 30:451-63. [PMID: 9522160 DOI: 10.1016/s0306-3623(97)00309-1] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
1. Taurine has recently been known to protect against ischemia and heart failure. Taurine possesses plenty of actions on the ion channels and transports, but is very non-specific. 2. Taurine may directly and indirectly help to regulate the [Ca]i level by modulating the activity of the voltage-dependent Ca2+ channels (also dependent on [Ca]i/[Ca]o), by regulation of Na+ channels, and secondly via Na-Ca exchange and Na(+)-taurine cotransport. 3. Taurine can prevent the Ca2+ ([Ca]o or [Ca]i)-induced cardiac functions. 4. Therefore, it seems possible that taurine could exert the potent cardioprotective actions even under the condition of low [Ca]i levels as well as under the Ca2+ overload condition. 5. The electrophysiological actions of taurine on cardiomyocytes, smooth muscle cells, and neurons from recent studies are summarized.
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Affiliation(s)
- H Satoh
- Department of Pharmacology, Nara Medical University, Japan
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