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Dryn DO, Melnyk MI, Bon RS, Beech DJ, Zholos AV. Pico145 inhibits TRPC4-mediated mI CAT and postprandial small intestinal motility. Biomed Pharmacother 2023; 168:115672. [PMID: 37857250 DOI: 10.1016/j.biopha.2023.115672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 10/04/2023] [Accepted: 10/06/2023] [Indexed: 10/21/2023] Open
Abstract
In intestinal smooth muscle cells, receptor-operated TRPC4 are responsible for the majority of muscarinic receptor cation current (mICAT), which initiates cholinergic excitation-contraction coupling. Our aim was to examine the effects of the TRPC4 inhibitor Pico145 on mICAT and Ca2+ signalling in mouse ileal myocytes, and on intestinal motility. Ileal myocytes freshly isolated from two month-old male BALB/c mice were used for patch-clamp recordings of whole-cell currents and for intracellular Ca2+ imaging using Fura-2. Functional assessment of Pico145's effects was carried out by standard in vitro tensiometry, ex vivo video recordings and in vivo postprandial intestinal transit measurements using carmine red. Carbachol (50 µM)-induced mICAT was strongly inhibited by Pico145 starting from 1 pM. The IC50 value for the inhibitory effect of Pico145 on this current evoked by intracellularly applied GTPγS (200 µM), and thus lacking desensitisation, was found to be 3.1 pM, while carbachol-induced intracellular Ca2+ rises were inhibited with IC50 of 2.7 pM. In contrast, the current activated by direct TRPC4 agonist (-)-englerin A was less sensitive to the action of Pico145 that caused only ∼43 % current inhibition at 100 pM. The inhibitory effect developed rather slowly and it was potentiated by membrane depolarisation. In functional assays, Pico145 produced concentration-dependent suppression of both spontaneous and carbachol-evoked intestinal smooth muscle contractions and delayed postprandial intestinal transit. Thus, Pico145 is a potent GI-active small-molecule which completely inhibits mICAT at picomolar concentrations and which is as effective as trpc4 gene deficiency in in vivo intestinal motility tests.
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Affiliation(s)
- Dariia O Dryn
- A.A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., Kyiv 01024, Ukraine
| | - Mariia I Melnyk
- A.A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., Kyiv 01024, Ukraine; Educational and Scientific Centre "Institute of Biology and Medicine", Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., Kyiv 01601, Ukraine
| | - Robin S Bon
- Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - David J Beech
- Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9JT, United Kingdom
| | - Alexander V Zholos
- Educational and Scientific Centre "Institute of Biology and Medicine", Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., Kyiv 01601, Ukraine.
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2
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Al Kury LT, Papandreou D, Hurmach VV, Dryn DO, Melnyk MI, Platonov MO, Prylutskyy YI, Ritter U, Scharff P, Zholos AV. Single-Walled Carbon Nanotubes Inhibit TRPC4-Mediated Muscarinic Cation Current in Mouse Ileal Myocytes. NANOMATERIALS 2021; 11:nano11123410. [PMID: 34947764 PMCID: PMC8703819 DOI: 10.3390/nano11123410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Revised: 12/10/2021] [Accepted: 12/13/2021] [Indexed: 12/02/2022]
Abstract
Single-walled carbon nanotubes (SWCNTs) are characterized by a combination of rather unique physical and chemical properties, which makes them interesting biocompatible nanostructured materials for various applications, including in the biomedical field. SWCNTs are not inert carriers of drug molecules, as they may interact with various biological macromolecules, including ion channels. To investigate the mechanisms of the inhibitory effects of SWCNTs on the muscarinic receptor cation current (mICAT), induced by intracellular GTPγs (200 μM), in isolated mouse ileal myocytes, we have used the patch-clamp method in the whole-cell configuration. Here, we use molecular docking/molecular dynamics simulations and direct patch-clamp recordings of whole-cell currents to show that SWCNTs, purified and functionalized by carboxylation in water suspension containing single SWCNTs with a diameter of 0.5–1.5 nm, can inhibit mICAT, which is mainly carried by TRPC4 cation channels in ileal smooth muscle cells, and is the main regulator of cholinergic excitation–contraction coupling in the small intestinal tract. This inhibition was voltage-independent and associated with a shortening of the mean open time of the channel. These results suggest that SWCNTs cause a direct blockage of the TRPC4 channel and may represent a novel class of TRPC4 modulators.
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Affiliation(s)
- Lina T. Al Kury
- College of Natural and Health Sciences, Zayed University, Abu Dhabi 144534, United Arab Emirates; (L.T.A.K.); (D.P.)
| | - Dimitrios Papandreou
- College of Natural and Health Sciences, Zayed University, Abu Dhabi 144534, United Arab Emirates; (L.T.A.K.); (D.P.)
| | - Vasyl V. Hurmach
- ESC “Institute of Biology and Medicine”, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., 01601 Kyiv, Ukraine; (V.V.H.); (D.O.D.); (M.I.M.); (Y.I.P.)
| | - Dariia O. Dryn
- ESC “Institute of Biology and Medicine”, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., 01601 Kyiv, Ukraine; (V.V.H.); (D.O.D.); (M.I.M.); (Y.I.P.)
- O.O. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., 01024 Kyiv, Ukraine
- Institute of Pharmacology and Toxicology, National Academy of Medical Sciences of Ukraine, 14 Anton Tsedik Str., 03057 Kyiv, Ukraine
| | - Mariia I. Melnyk
- ESC “Institute of Biology and Medicine”, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., 01601 Kyiv, Ukraine; (V.V.H.); (D.O.D.); (M.I.M.); (Y.I.P.)
- O.O. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, 4 Bogomoletz Str., 01024 Kyiv, Ukraine
- Institute of Pharmacology and Toxicology, National Academy of Medical Sciences of Ukraine, 14 Anton Tsedik Str., 03057 Kyiv, Ukraine
| | - Maxim O. Platonov
- Institute of Molecular Biology and Genetics, National Academy of Sciences of Ukraine, 150 Zabolotnogo Str., 03143 Kyiv, Ukraine;
| | - Yuriy I. Prylutskyy
- ESC “Institute of Biology and Medicine”, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., 01601 Kyiv, Ukraine; (V.V.H.); (D.O.D.); (M.I.M.); (Y.I.P.)
| | - Uwe Ritter
- Institute of Chemistry and Biotechnology, Technical University of Ilmenau, 25 Weimarer Str., 98693 Ilmenau, Germany; (U.R.); (P.S.)
| | - Peter Scharff
- Institute of Chemistry and Biotechnology, Technical University of Ilmenau, 25 Weimarer Str., 98693 Ilmenau, Germany; (U.R.); (P.S.)
| | - Alexander V. Zholos
- ESC “Institute of Biology and Medicine”, Taras Shevchenko National University of Kyiv, 64 Volodymyrska Str., 01601 Kyiv, Ukraine; (V.V.H.); (D.O.D.); (M.I.M.); (Y.I.P.)
- Correspondence: ; Tel.: +380-44-4312-0403
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Kim J, Moon SH, Kim T, Ko J, Jeon YK, Shin YC, Jeon JH, So I. Analysis of interaction between intracellular spermine and transient receptor potential canonical 4 channel: multiple candidate sites of negatively charged amino acids for the inward rectification of transient receptor potential canonical 4. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2020; 24:101-110. [PMID: 31908579 PMCID: PMC6940491 DOI: 10.4196/kjpp.2020.24.1.101] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/28/2019] [Revised: 10/16/2019] [Accepted: 10/16/2019] [Indexed: 01/05/2023]
Abstract
Transient receptor potential canonical 4 (TRPC4) channel is a nonselective calcium-permeable cation channels. In intestinal smooth muscle cells, TRPC4 currents contribute more than 80% to muscarinic cationic current (mIcat). With its inward-rectifying current-voltage relationship and high calcium permeability, TRPC4 channels permit calcium influx once the channel is opened by muscarinic receptor stimulation. Polyamines are known to inhibit nonselective cation channels that mediate the generation of mIcat. Moreover, it is reported that TRPC4 channels are blocked by the intracellular spermine through electrostatic interaction with glutamate residues (E728, E729). Here, we investigated the correlation between the magnitude of channel inactivation by spermine and the magnitude of channel conductance. We also found additional spermine binding sites in TRPC4. We evaluated channel activity with electrophysiological recordings and revalidated structural significance based on Cryo-EM structure, which was resolved recently. We found that there is no correlation between magnitude of inhibitory action of spermine and magnitude of maximum current of the channel. In intracellular region, TRPC4 attracts spermine at channel periphery by reducing access resistance, and acidic residues contribute to blocking action of intracellular spermine; channel periphery, E649; cytosolic space, D629, D649, and E687.
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Affiliation(s)
- Jinsung Kim
- Department of Physiology, College of Medicine, Seoul National University, Seoul 03080, Korea
| | - Sang Hui Moon
- Office of Medical Education, College of Medicine, Seoul National University, Seoul 03080, Korea.,Department of Surgery, College of Medicine, Seoul National University, Seoul 03080, Korea
| | - Taewook Kim
- Department of Physiology, College of Medicine, Seoul National University, Seoul 03080, Korea
| | - Juyeon Ko
- Department of Physiology, College of Medicine, Seoul National University, Seoul 03080, Korea
| | - Young Keul Jeon
- Department of Physiology, College of Medicine, Seoul National University, Seoul 03080, Korea
| | - Young-Cheul Shin
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ju-Hong Jeon
- Department of Physiology, College of Medicine, Seoul National University, Seoul 03080, Korea
| | - Insuk So
- Department of Physiology, College of Medicine, Seoul National University, Seoul 03080, Korea
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Structure-Function Relationship and Physiological Roles of Transient Receptor Potential Canonical (TRPC) 4 and 5 Channels. Cells 2019; 9:cells9010073. [PMID: 31892199 PMCID: PMC7017149 DOI: 10.3390/cells9010073] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 12/24/2019] [Accepted: 12/24/2019] [Indexed: 12/11/2022] Open
Abstract
The study of the structure–function relationship of ion channels has been one of the most challenging goals in contemporary physiology. Revelation of the three-dimensional (3D) structure of ion channels has facilitated our understanding of many of the submolecular mechanisms inside ion channels, such as selective permeability, voltage dependency, agonist binding, and inter-subunit multimerization. Identifying the structure–function relationship of the ion channels is clinically important as well since only such knowledge can imbue potential therapeutics with practical possibilities. In a sense, recent advances in the understanding of the structure–relationship of transient receptor potential canonical (TRPC) channels look promising since human TRPC channels are calcium-permeable, non-selective cation channels expressed in many tissues such as the gastrointestinal (GI) tract, kidney, heart, vasculature, and brain. TRPC channels are known to regulate GI contractility and motility, pulmonary hypertension, right ventricular hypertrophy, podocyte injury, seizure, fear, anxiety-like behavior, and many others. In this article, we tried to elaborate recent findings of Cryo-EM (cryogenic-electron microscopy) based structural information of TRPC 4 and 5 channels and domain-specific functions of the channel, such as G-protein mediated activation mechanism, extracellular modification of the channel, homo/hetero-tetramerization, and pharmacological gating mechanisms.
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Aird SD, Villar Briones A, Roy MC, Mikheyev AS. Polyamines as Snake Toxins and Their Probable Pharmacological Functions in Envenomation. Toxins (Basel) 2016; 8:toxins8100279. [PMID: 27681740 PMCID: PMC5086639 DOI: 10.3390/toxins8100279] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 09/05/2016] [Indexed: 12/19/2022] Open
Abstract
While decades of research have focused on snake venom proteins, far less attention has been paid to small organic venom constituents. Using mostly pooled samples, we surveyed 31 venoms (six elapid, six viperid, and 19 crotalid) for spermine, spermidine, putrescine, and cadaverine. Most venoms contained all four polyamines, although some in essentially trace quantities. Spermine is a potentially significant component of many viperid and crotalid venoms (≤0.16% by mass, or 7.9 µmol/g); however, it is almost completely absent from elapid venoms assayed. All elapid venoms contained larger molar quantities of putrescine and cadaverine than spermine, but still at levels that are likely to be biologically insignificant. As with venom purines, polyamines impact numerous physiological targets in ways that are consistent with the objectives of prey envenomation, prey immobilization via hypotension and paralysis. Most venoms probably do not contain sufficient quantities of polyamines to induce systemic effects in prey; however, local effects seem probable. A review of the pharmacological literature suggests that spermine could contribute to prey hypotension and paralysis by interacting with N-methyl-d-aspartate (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, nicotinic and muscarinic acetylcholine receptors, γ-Aminobutyric acid (GABA) receptors, blood platelets, ryanodine receptors, and Ca2+-ATPase. It also blocks many types of cation-permeable channels by interacting with negatively charged amino acid residues in the channel mouths. The site of envenomation probably determines which physiological targets assume the greatest importance; however, venom-induced liberation of endogenous, intracellular stores of polyamines could potentially have systemic implications and may contribute significantly to envenomation sequelae.
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Affiliation(s)
- Steven D Aird
- Division of Faculty Affairs, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa-ken 904-0495, Japan.
- Ecology and Evolution Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa-ken 904-0495, Japan.
| | - Alejandro Villar Briones
- Division of Research Support, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa-ken 904-0495, Japan.
| | - Michael C Roy
- Division of Research Support, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa-ken 904-0495, Japan.
| | - Alexander S Mikheyev
- Ecology and Evolution Unit, Okinawa Institute of Science and Technology Graduate University, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa-ken 904-0495, Japan.
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6
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Kim J, Moon SH, Shin YC, Jeon JH, Park KJ, Lee KP, So I. Intracellular spermine blocks TRPC4 channel via electrostatic interaction with C-terminal negative amino acids. Pflugers Arch 2015; 468:551-61. [PMID: 26631167 DOI: 10.1007/s00424-015-1753-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 10/27/2015] [Accepted: 10/29/2015] [Indexed: 01/09/2023]
Abstract
Transient receptor potential canonical (TRPC) 4 channels are calcium-permeable, nonselective cation channels and are widely expressed in mammalian tissue, especially in the GI tract and brain. TRPC4 channels are known to be involved in neurogenic contraction of ileal smooth muscle cells via generating cationic current after muscarinic stimulation (muscarinic cationic current (mIcat)). Polyamines exist in numerous tissues and are believed to be involved in cell proliferation, differentiation, scar formation, wound healing, and carcinogenesis. Besides, physiological polyamines are essential to maintain inward rectification of cardiac potassium channels (Kir2.1). At membrane potentials more positive than equilibrium potential, intracellular polyamines plug the cytosolic surface of the Kir2.1 so that potassium ions cannot pass through the pore. Recently, it was reported that polyamines inhibit not only cardiac potassium channels but also nonselective cation channels that mediate the generation of mIcat. Here, we report that TRPC4, a definite mIcat mediator, is inhibited by intracellular spermine with great extent. The inhibition was specific to TRPC4 and TRPC5 channels but was not effective to TRPC1/4, TRPC1/5, and TRPC3 channels. For this inhibition to occur, we found that glutamates at 728th and 729th position of TRPC4 channels are essential whereby we conclude that spermine blocks the TRPC4 channel with electrostatic interaction between negative amino acids at the C-terminus of the channel.
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Affiliation(s)
- Jinsung Kim
- College of Medicine, Catholic University of Korea, Seoul, 137-701, Republic of Korea.,Department of Physiology, College of Medicine, Seoul National University, Seoul, 110-799, Republic of Korea
| | - Sang Hui Moon
- Department of Surgery, College of Medicine, Seoul National University, Seoul, 110-799, Republic of Korea
| | - Young-Cheul Shin
- Department of Physiology, College of Medicine, Seoul National University, Seoul, 110-799, Republic of Korea
| | - Ju-Hong Jeon
- Department of Physiology, College of Medicine, Seoul National University, Seoul, 110-799, Republic of Korea
| | - Kyu Joo Park
- Department of Surgery, College of Medicine, Seoul National University, Seoul, 110-799, Republic of Korea
| | - Kyu Pil Lee
- Department of Physiology, College of Veterinary Medicine, Chungnam National University, Daejeon, 305-764, Republic of Korea.
| | - Insuk So
- Department of Physiology, College of Medicine, Seoul National University, Seoul, 110-799, Republic of Korea.
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Role of β-adrenoceptors, cAMP phosphodiesterase and external Ca2+ on polyamine-induced relaxation in isolated bovine tracheal strips. Pharmacol Rep 2010; 62:1127-38. [DOI: 10.1016/s1734-1140(10)70375-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2009] [Revised: 06/04/2010] [Indexed: 11/21/2022]
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Kim YC, Sim JH, Choi W, Kim CH, You RY, Xu WX, Lee SJ. Relaxant Effect of Spermidine on Acethylcholine and High K-induced Gastric Contractions of Guinea-Pig. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2008; 12:59-64. [PMID: 20157395 DOI: 10.4196/kjpp.2008.12.2.59] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In our previous study, we found that spermine and putrescine inhibited spontaneous and acetylcholine (ACh)-induced contractions of guinea-pig stomach via inhibition of L-type voltage-dependent calcium current (VDCC(L)). In this study, we also studied the effect of spermidine on mechanical contractions and calcium channel current (I(Ba)), and then compared its effects to those by spermine and putrescine. Spermidine inhibited spontaneous contraction of the gastric smooth muscle in a concentration-dependent manner (IC(50)=1.1+/-0.11 mM). Relationship between inhibition of contraction and calcium current by spermidine was studied using 50 mM high K(+)-induced contraction: Spermidine (5 mM) significantly reduced high K(+) (50 mM)-induced contraction to 37+/-4.7% of the control (p<0.05), and inhibitory effect of spermidine on I(Ba) was also observed at a wide range of test potential in current/voltage (I/V) relationship. Pre- and post-application of spermidine (5 mM) also significantly inhibited carbachol (CCh) and ACh-induced initial and phasic contractions. Finally, caffeine (10 mM)-induced contraction which is activated by Ca(2+)-induced Ca(2+) release (CICR),' was also inhibited by pretreatment of spermidine (5 mM). These findings suggest that spermidine inhibits spontaneous and CCh-induced contraction via inhibition of VDCC(L) and Ca(2+) releasing mechanism in guinea-pig stomach.
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Affiliation(s)
- Young Chul Kim
- Department of Physiology, Chungbuk National University College of Medicine, Cheongju 361-763, Korea
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Kim YC, Sim JH, Kim YH, Kwon SC, Lee SJ, Kim SR, Kim DW, Park SM, Youn SJ, Lee SJ, Xing DG, Xu WX, Kim KW. Effects of polyamines on contractility of guinea-pig gastric smooth muscle. J Korean Med Sci 2007; 22:48-56. [PMID: 17297251 PMCID: PMC2693568 DOI: 10.3346/jkms.2007.22.1.48] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study was designed to investigate the effects of polyamines on mechanical contraction and voltage-dependent calcium current (VDCC) of guinea-pig gastric smooth muscle. Mechanical contraction and calcium channel current I(Ba) were recorded by isometric tension recording and whole-cell patch clamp technique. Spermine, spermidine and putrescine inhibited spontaneous contraction of the gastric smooth muscle in a concentration-dependent manner. Spermine (2 mM) reduced high K+ (50 mM)-induced contraction to 16+/-6.4% of the control (n=9), and significantly inhibited I(Ba) in a reversible manner (p<0.05; IC50=0.8 mM). Pre- and post-treatment of tissue with spermine (2-5 mM, n=10) also inhibited acetylcholine (10 microM)-induced phasic contraction to 5+/-6.4% of the control. Inhibitory effect of spermine on I(Ba) was observed at a wide range of test potentials of current/voltage (I/V) relationship (p<0.05), and steady-state activation of I(Ba) was shifted to the right by spermine (p<0.05). Spermidine and putrescine (1 mM each) also inhibited I(Ba) to 51+/-5.7% and 81+/-5.3% of the control, respectively. And putrescine (1 mM) inhibited I(Ba) at whole tested potentials (p<0.05) without significant change of kinetics (p<0.05). Finally, 5 mM putrescine also inhibited high K+-induced contraction to 53+/-7.1% of the control (n=4). These findings suggest that polyamines inhibit contractions of guinea-pig gastric smooth muscle via inhibition of VDCC.
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Affiliation(s)
- Young Chul Kim
- Department of Physiology, Chungbuk National University, College of Medicine, Cheongju, Korea.
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Zholos AV. Regulation of TRP-like muscarinic cation current in gastrointestinal smooth muscle with special reference to PLC/InsP3/Ca2+ system. Acta Pharmacol Sin 2006; 27:833-42. [PMID: 16787566 DOI: 10.1111/j.1745-7254.2006.00392.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Acetylcholine, the main enteric excitatory neuromuscular transmitter, evokes membrane depolarization and contraction of gastrointestinal smooth muscle cells by activating G protein-coupled muscarinic receptors. Although the cholinergic excitation is generally underlined by the multiplicity of ion channel effects, the primary event appears to be the opening of cation-selective channels; among them the 60 pS channel has been recently identified as the main target for the acetylcholine action in gastrointestinal myocytes. The evoked cation current, termed mI(CAT), causes either an oscillatory or a more sustained membrane depolarization response, which in turn leads to increases of the open probability of voltage-gated Ca2+ channels, thus providing Ca2+ entry in parallel with Ca2+ release for intracellular Ca2+ concentration rise and contraction. In recent years there have been several significant developments in our understanding of the signaling processes underlying mICAT generation. They have revealed important synergistic interactions between M2 and M3 receptor subtypes, single channel mechanisms, and the involvement of TRPC-encoded proteins as essential components of native muscarinic cation channels. This review summarizes these recent findings and in particular discusses the roles of the phospholipase C/InsP3/intracellular Ca2+ release system in the mI(CAT) physiological regulation.
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