1
|
Kang H, Kim J, Park CH, Jeong B, So I. Direct modulation of TRPC ion channels by Gα proteins. Front Physiol 2024; 15:1362987. [PMID: 38384797 PMCID: PMC10880550 DOI: 10.3389/fphys.2024.1362987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 01/26/2024] [Indexed: 02/23/2024] Open
Abstract
GPCR-Gi protein pathways are involved in the regulation of vagus muscarinic pathway under physiological conditions and are closely associated with the regulation of internal visceral organs. The muscarinic receptor-operated cationic channel is important in GPCR-Gi protein signal transduction as it decreases heart rate and increases GI rhythm frequency. In the SA node of the heart, acetylcholine binds to the M2 receptor and the released Gβγ activates GIRK (I(K,ACh)) channel, inducing a negative chronotropic action. In gastric smooth muscle, there are two muscarinic acetylcholine receptor (mAChR) subtypes, M2 and M3. M2 receptor activates the muscarinic receptor-operated nonselective cationic current (mIcat, NSCC(ACh)) and induces positive chronotropic effect. Meanwhile, M3 receptor induces hydrolysis of PIP2 and releases DAG and IP3. This IP3 increases intracellular Ca2+ and then leads to contraction of GI smooth muscles. The activation of mIcat is inhibited by anti-Gi/o protein antibodies in GI smooth muscle, indicating the involvement of Gαi/o protein in the activation of mIcat. TRPC4 channel is a molecular candidate for mIcat and can be directly activated by constitutively active Gαi QL proteins. TRPC4 and TRPC5 belong to the same subfamily and both are activated by Gi/o proteins. Initial studies suggested that the binding sites for G protein exist at the rib helix or the CIRB domain of TRPC4/5 channels. However, recent cryo-EM structure showed that IYY58-60 amino acids at ARD of TRPC5 binds with Gi3 protein. Considering the expression of TRPC4/5 in the brain, the direct G protein activation on TRPC4/5 is important in terms of neurophysiology. TRPC4/5 channels are also suggested as a coincidence detector for Gi and Gq pathway as Gq pathway increases intracellular Ca2+ and the increased Ca2+ facilitates the activation of TRPC4/5 channels. More complicated situation would occur when GIRK, KCNQ2/3 (IM) and TRPC4/5 channels are co-activated by stimulation of muscarinic receptors at the acetylcholine-releasing nerve terminals. This review highlights the effects of GPCR-Gi protein pathway, including dopamine, μ-opioid, serotonin, glutamate, GABA, on various oragns, and it emphasizes the importance of considering TRPC4/5 channels as crucial players in the field of neuroscience.
Collapse
Affiliation(s)
- Hana Kang
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Jinhyeong Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Christine Haewon Park
- Department of Physiology, University of California, San Francisco, San Francisco, CA, United States
| | - Byeongseok Jeong
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Insuk So
- Department of Physiology, Seoul National University College of Medicine, Seoul, Republic of Korea
| |
Collapse
|
2
|
Zholos AV, Melnyk MI, Dryn DO. Molecular mechanisms of cholinergic neurotransmission in visceral smooth muscles with a focus on receptor-operated TRPC4 channel and impairment of gastrointestinal motility by general anaesthetics and anxiolytics. Neuropharmacology 2024; 242:109776. [PMID: 37913983 DOI: 10.1016/j.neuropharm.2023.109776] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 10/13/2023] [Accepted: 10/23/2023] [Indexed: 11/03/2023]
Abstract
Acetylcholine is the primary excitatory neurotransmitter in visceral smooth muscles, wherein it binds to and activates two muscarinic receptors subtypes, M2 and M3, thus causing smooth muscle excitation and contraction. The first part of this review focuses on the types of cells involved in cholinergic neurotransmission and on the molecular mechanisms underlying acetylcholine-induced membrane depolarisation, which is the central event of excitation-contraction coupling causing Ca2+ entry via L-type Ca2+ channels and smooth muscle contraction. Studies of the muscarinic cation current in intestinal myocytes (mICAT) revealed its main molecular counterpart, receptor-operated TRPC4 channel, which is activated in synergy by both M2 and M3 receptors. M3 receptors activation is of permissive nature, while activation of M2 receptors via Gi/o proteins that are coupled to them plays a direct role in TRPC4 opening. Our understanding of signalling pathways underlying mICAT generation has vastly expanded in recent years through studies of TRPC4 gating in native cells and its regulation in heterologous cells. Recent studies using muscarinic receptor knockout have established that at low agonist concentration activation of both M2 receptor and the M2/M3 receptor complex elicits smooth muscle contraction, while at high agonist concentration M3 receptor function becomes dominant. Based on this knowledge, in the second part of this review we discuss the cellular and molecular mechanisms underlying the numerous anticholinergic effects on neuroactive drugs, in particular general anaesthetics and anxiolytics, which can significantly impair gastrointestinal motility. This article is part of the Special Issue on "Ukrainian Neuroscience".
Collapse
Affiliation(s)
- Alexander V Zholos
- Educational and Scientific Centre "Institute of Biology and Medicine", Taras Shevchenko National University of Kyiv, Kyiv, Ukraine.
| | - Mariia I Melnyk
- Educational and Scientific Centre "Institute of Biology and Medicine", Taras Shevchenko National University of Kyiv, Kyiv, Ukraine; A.A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
| | - Dariia O Dryn
- A.A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
| |
Collapse
|
3
|
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.
Collapse
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.
| |
Collapse
|
4
|
Zholos AV, Dryn DO, Melnyk MI. General anaesthesia-related complications of gut motility with a focus on cholinergic mechanisms, TRP channels and visceral pain. Front Physiol 2023; 14:1174655. [PMID: 37275228 PMCID: PMC10232893 DOI: 10.3389/fphys.2023.1174655] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 05/09/2023] [Indexed: 06/07/2023] Open
Abstract
General anesthesia produces multiple side effects. Notably, it temporarily impairs gastrointestinal motility following surgery and causes the so-called postoperative ileus (POI), a multifactorial and complex condition that develops secondary to neuromuscular failure and mainly affects the small intestine. There are currently limited medication options for POI, reflecting a lack of comprehensive understanding of the mechanisms involved in this complex condition. Notably, although acetylcholine is one of the major neurotransmitters initiating excitation-contraction coupling in the gut, cholinergic stimulation by prokinetic drugs is not very efficient in case of POI. Acetylcholine when released from excitatory motoneurones of the enteric nervous system binds to and activates M2 and M3 types of muscarinic receptors in smooth muscle myocytes. Downstream of these G protein-coupled receptors, muscarinic cation TRPC4 channels act as the major focal point of receptor-mediated signal integration, causing membrane depolarisation accompanied by action potential discharge and calcium influx via L-type Ca2+ channels for myocyte contraction. We have recently found that both inhalation (isoflurane) and intravenous (ketamine) anesthetics significantly inhibit this muscarinic cation current (termed mI CAT) in ileal myocytes, even when G proteins are activated directly by intracellular GTPγS, i.e., bypassing muscarinic receptors. Here we aim to summarize Transient Receptor Potential channels and calcium signalling-related aspects of the cholinergic mechanisms in the gut and visceral pain, discuss exactly how these may be negatively impacted by general anaesthetics, while proposing the receptor-operated TRPC4 channel as a novel molecular target for the treatment of POI.
Collapse
Affiliation(s)
- Alexander V. Zholos
- ESC “Institute of Biology and Medicine”, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
| | - Dariia O. Dryn
- O.O. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
| | - Mariia I. Melnyk
- ESC “Institute of Biology and Medicine”, Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
- O.O. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv, Ukraine
| |
Collapse
|
5
|
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.
Collapse
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
| |
Collapse
|
6
|
7,8-Dihydroxyflavone Enhanced Colonic Cholinergic Contraction and Relieved Loperamide-Induced Constipation in Rats. Dig Dis Sci 2021; 66:4251-4262. [PMID: 33528684 DOI: 10.1007/s10620-020-06817-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Accepted: 12/29/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Whether 7,8-dihydroxyflavone (7,8-DHF), a tyrosine kinase receptor B (TrkB) agonist, modulates colonic smooth muscle motility and/or alleviates constipation has not yet been studied. AIMS Here, we aimed to determine how 7,8-DHF influences carbachol (CCh)-stimulated contraction of colonic strips and the in vivo effect of 7,8-DHF on constipation. METHODS Muscle strips were isolated from rat colons for recording contractile tension and performing western blotting. Constipation was induced in rats with loperamide. RESULTS Although it specifically activated TrkB, 7,8-DHF applied alone neither activated PLCγ1 in the colonic strips nor induced colonic strip contraction. However, 7,8-DHF enhanced CCh-stimulated PLCγ1 activation and strip contraction. The PLCγ1 antagonist U73122 suppressed both CCh-stimulated and 7,8-DHF-enhanced/CCh-stimulated contraction. While clarifying the underlying mechanism, we revealed that 7,8-DHF augmented muscarinic M3 receptor expression in the colonic strips. The M3-selective antagonist tarafenacin specifically inhibited the 7,8-DHF-enhanced/CCh-stimulated contraction of the colonic strips. Since 7,8-DHF increased Akt phosphorylation, and LY294002 (an antagonist of PI3K upstream of Akt) dramatically inhibited both 7,8-DHF-augmented M3 expression and 7,8-DHF-enhanced/CCh-stimulated contractions, we assumed that 7,8-DHF/TrkB/Akt was associated with the modulation of M3 expression in the colonic strips. ANA-12, a specific TrkB antagonist, not only inhibited TrkB activation by 7,8-DHF but also suppressed 7,8-DHF-enhanced cholinergic contraction, 7,8-DHF/CCh-mediated activation of PLCγ1/Akt, and M3 overexpression in colonic strips. In vivo 7,8-DHF, also by promoting intestinal motility and M3 expression, significantly alleviated loperamide-induced functional constipation in rats. CONCLUSIONS Our results suggest that 7,8-DHF regulates colonic motility possibly via a TrkB/Akt/M3 pathway and may be applicable for alleviating constipation.
Collapse
|
7
|
Tanahashi Y, Komori S, Matsuyama H, Kitazawa T, Unno T. Functions of Muscarinic Receptor Subtypes in Gastrointestinal Smooth Muscle: A Review of Studies with Receptor-Knockout Mice. Int J Mol Sci 2021; 22:E926. [PMID: 33477687 PMCID: PMC7831928 DOI: 10.3390/ijms22020926] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 01/12/2021] [Accepted: 01/14/2021] [Indexed: 01/25/2023] Open
Abstract
Parasympathetic signalling via muscarinic acetylcholine receptors (mAChRs) regulates gastrointestinal smooth muscle function. In most instances, the mAChR population in smooth muscle consists mainly of M2 and M3 subtypes in a roughly 80% to 20% mixture. Stimulation of these mAChRs triggers a complex array of biochemical and electrical events in the cell via associated G proteins, leading to smooth muscle contraction and facilitating gastrointestinal motility. Major signalling events induced by mAChRs include adenylyl cyclase inhibition, phosphoinositide hydrolysis, intracellular Ca2+ mobilisation, myofilament Ca2+ sensitisation, generation of non-selective cationic and chloride currents, K+ current modulation, inhibition or potentiation of voltage-dependent Ca2+ currents and membrane depolarisation. A lack of ligands with a high degree of receptor subtype selectivity and the frequent contribution of multiple receptor subtypes to responses in the same cell type have hampered studies on the signal transduction mechanisms and functions of individual mAChR subtypes. Therefore, novel strategies such as genetic manipulation are required to elucidate both the contributions of specific AChR subtypes to smooth muscle function and the underlying molecular mechanisms. In this article, we review recent studies on muscarinic function in gastrointestinal smooth muscle using mAChR subtype-knockout mice.
Collapse
Affiliation(s)
- Yasuyuki Tanahashi
- Department of Advanced Life Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan;
| | - Seiichi Komori
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan; (S.K.); (H.M.)
| | - Hayato Matsuyama
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan; (S.K.); (H.M.)
| | - Takio Kitazawa
- Department of Veterinary Science, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan;
| | - Toshihiro Unno
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan; (S.K.); (H.M.)
| |
Collapse
|
8
|
Tanahashi Y, Katsurada T, Inasaki N, Uchiyama M, Sakamoto T, Yamamoto M, Matsuyama H, Komori S, Unno T. Further characterization of the synergistic activation mechanism of cationic channels by M 2 and M 3 muscarinic receptors in mouse intestinal smooth muscle cells. Am J Physiol Cell Physiol 2019; 318:C514-C523. [PMID: 31875697 DOI: 10.1152/ajpcell.00277.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In mouse ileal myocytes, muscarinic receptor-mediated cationic current (mIcat) occurs mainly through synergism of M2 and M3 subtypes involving Gi/o-type GTP-binding proteins and phospholipase C (PLC). We have further studied the M2/M3 synergistic pathway. Carbachol-induced mIcat was markedly depressed by YM-254890, a Gq/11 protein inhibitor. However, the mIcat was unaffected by heparin, calphostin C, or chelerythrine, suggesting that mIcat activation does not involve signaling molecules downstream of phosphatidylinositol 4,5-bisphosphate (PIP2) breakdown. M2-knockout (KO) mice displayed a reduced mIcat (~10% of wild-type mIcat) because of the lack of M2-Gi/o signaling. The impaired mIcat was insensitive to neuropeptide Y possessing a Gi/o-stimulating activity. M3-KO mice also displayed a reduced mIcat (~6% of wild-type mIcat) because of the lack of M3-Gq/11 signaling, and the mIcat was insensitive to prostaglandin F2α possessing a Gq/11-stimulating activity. These results suggest the importance of Gq/11/PLC-hydrolyzed PIP2 breakdown itself in mIcat activation and also support the idea that the M2/M3 synergistic pathway represents a signaling complex consisting of M2-Gi/o and M3-Gq/11-PLC systems in which both G proteins are special for this pathway but not general in receptor coupling.
Collapse
Affiliation(s)
- Yasuyuki Tanahashi
- Department of Animal Medical Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan
| | - Taisuke Katsurada
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| | - Noriko Inasaki
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| | - Mai Uchiyama
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| | - Takashi Sakamoto
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| | - Masayuki Yamamoto
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| | - Hayato Matsuyama
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| | - Seiichi Komori
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| | - Toshihiro Unno
- Laboratory of Veterinary Pharmacology, Department of Veterinary Medicine, Faculty of Applied Biological Science, Gifu University, Gifu, Japan
| |
Collapse
|
9
|
He B, Qu Z, Tian Z, Zhao K, Wei L, Ma L. 7,8-dihydroxyflavone enhanced cholinergic contraction of rat gastric smooth muscle via augmenting muscarinic M3 receptor expression. Clin Exp Pharmacol Physiol 2018; 45:1170-1180. [PMID: 29927500 DOI: 10.1111/1440-1681.12999] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Revised: 06/18/2018] [Accepted: 06/19/2018] [Indexed: 12/27/2022]
Affiliation(s)
- Baoguo He
- Department of Gastroenterology, Affiliated Hospital; Qingdao University; Qingdao China
| | - Zhiqiang Qu
- Center for Medical Research, Affiliated Hospital; Qingdao University; Qingdao China
| | - Zibin Tian
- Department of Gastroenterology, Affiliated Hospital; Qingdao University; Qingdao China
| | - Kun Zhao
- Department of Gastroenterology, Affiliated Hospital; Qingdao University; Qingdao China
| | - Liangzhou Wei
- Department of Gastroenterology, Affiliated Hospital; Qingdao University; Qingdao China
| | - Li Ma
- Department of Clinical Nutrition, Affiliated Hospital; Qingdao University; Qingdao China
| |
Collapse
|
10
|
Dryn D, Luo J, Melnyk M, Zholos A, Hu H. Inhalation anaesthetic isoflurane inhibits the muscarinic cation current and carbachol-induced gastrointestinal smooth muscle contractions. Eur J Pharmacol 2017; 820:39-44. [PMID: 29198958 DOI: 10.1016/j.ejphar.2017.11.044] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 11/28/2017] [Indexed: 02/02/2023]
Abstract
Gastrointestinal tract motility may be demoted significantly after surgery operations at least in part due to anaesthetic agents, but there is no comprehensive explanation of the molecular mechanism(s) of such adverse effects. Anesthetics are known to interact with various receptors and ion channels including several subtypes of transient receptor potential (TRP) channels. Two members of the canonical subfamily of TRP channels (TRPC), TRPC4 and TRPC6 are Ca2+-permeable cation channels involved in visceral smooth muscle contractility induced by acetylcholine, the primary excitatory neurotransmitter in the gut. In the present study, we aimed to study the effect of anesthetics on muscarinic receptor-mediated excitation and contraction of intestinal smooth muscle. Here we show that muscarinic cation current (mICAT) mediated by TRPC4 and TRPC6 channels in mouse ileal myocytes was strongly inhibited by isoflurane (0.5mM), one of the most commonly used inhalation anesthetics. Carbachol-activated mICAT was reduced by 63 ± 11% (n = 5), while GTPγS-induced (to bypass muscarinic receptors) current was inhibited by 44 ± 9% (n = 6). Furthermore, carbachol-induced ileum and colon contractions were inhibited by isoflurane by about 30%. We discuss the main sites of isoflurane action, which appear to be G-proteins and muscarinic receptors, rather than TRPC4/6 channels. These results contribute to our better understanding of the signalling pathways affected by inhalation anesthetics, which may cause ileus, and thus may be important for the development of novel treatment strategies during postoperative recovery.
Collapse
Affiliation(s)
- Dariia Dryn
- Washington University School of Medicine in St. Louis, 660 South Euclid Avenue, St. Louis, MO, USA; A.A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv 01024, Ukraine; Institute of Pharmacology and Toxicology, Academy of Medical Sciences of Ukraine, 14 Eugene Pottier Street, Kyiv 03680, Ukraine
| | - Jialie Luo
- Washington University School of Medicine in St. Louis, 660 South Euclid Avenue, St. Louis, MO, USA
| | - Mariia Melnyk
- A.A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv 01024, Ukraine; Institute of Pharmacology and Toxicology, Academy of Medical Sciences of Ukraine, 14 Eugene Pottier Street, Kyiv 03680, Ukraine
| | - Alexander Zholos
- A.A. Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv 01024, Ukraine; ESC "Institute of Biology and Medicine", Taras Shevchenko Kyiv National University, 64/13 Volodymyrska Street, Kyiv 01601, Ukraine.
| | - Hongzhen Hu
- Washington University School of Medicine in St. Louis, 660 South Euclid Avenue, St. Louis, MO, USA
| |
Collapse
|
11
|
Species-Related Differences in the Properties of TRPC4 Channels in Intestinal Myocytes of Rodents. NEUROPHYSIOLOGY+ 2016. [DOI: 10.1007/s11062-016-9592-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
12
|
Cholinergic and glutamatergic transmission at synapses between pedunculopotine tegmental nucleus axonal terminals and A7 catecholamine cell group noradrenergic neurons in the rat. Neuropharmacology 2016; 110:237-250. [PMID: 27422407 DOI: 10.1016/j.neuropharm.2016.07.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Revised: 06/23/2016] [Accepted: 07/11/2016] [Indexed: 11/20/2022]
Abstract
We characterized transmission from the pedunculopotine tegmental nucleus (PPTg), which contains cholinergic and glutamatergic neurons, at synapses with noradrenergic (NAergic) A7 neurons. Injection of an anterograde neuronal tracer, biotinylated-dextran amine, into the PPTg resulted in labeling of axonal terminals making synaptic connection with NAergic A7 neurons. Consistent with this, extracellular stimulation using a train of 10 pulses at 100 Hz evoked both fast and slow excitatory synaptic currents (EPSCs) that were blocked, respectively, by DNQX, a non-N-methyl-d-aspartate receptor blocker, or atropine, a cholinergic muscarinic receptor (mAChR) blocker. Interestingly, many spontaneous-like, but stimulation-dependent, EPSCs, were seen for up to one second after the end of stimulation and were blocked by DNQX and decreased by EGTA-AM, a membrane permeable form of EGTA, showing they are glutamatergic EPSCs causing by asynchronous release of vesicular quanta. Moreover, application of atropine or carbachol, an mAChR agonist, caused, respectively, an increase in the number of asynchronous EPSCs or a decrease in the frequency of miniature EPSCs, showing that mAChRs mediated presynaptic inhibition of glutamatergic transmission of the PPTg onto NAergic A7 neurons. In conclusion, our data show direct synaptic transmission of PPTg afferents onto pontine NAergic neurons that involves cooperation of cholinergic and glutamatergic transmission. This dual-transmitter transmission drives the firing rate of NAergic neurons, which may correlate with axonal and somatic/dendritic release of NA.
Collapse
|
13
|
Regulator of G-protein signalling and GoLoco proteins suppress TRPC4 channel function via acting at Gαi/o. Biochem J 2016; 473:1379-90. [PMID: 26987813 DOI: 10.1042/bcj20160214] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 03/16/2016] [Indexed: 01/09/2023]
Abstract
Transient receptor potential canonical 4 (TRPC4) forms non-selective cation channels implicated in the regulation of diverse physiological functions. Previously, TRPC4 was shown to be activated by the Gi/o subgroup of heterotrimeric G-proteins involving Gαi/o, rather than Gβγ, subunits. Because the lifetime and availability of Gα-GTP are regulated by regulators of G-protein signalling (RGS) and Gαi/o-Loco (GoLoco) domain-containing proteins via their GTPase-activating protein (GAP) and guanine-nucleotide-dissociation inhibitor (GDI) functions respectively, we tested how RGS and GoLoco domain proteins affect TRPC4 currents activated via Gi/o-coupled receptors. Using whole-cell patch-clamp recordings, we show that both RGS and GoLoco proteins [RGS4, RGS6, RGS12, RGS14, LGN or activator of G-protein signalling 3 (AGS3)] suppress receptor-mediated TRPC4 activation without causing detectable basal current or altering surface expression of the channel protein. The inhibitory effects are dependent on the GAP and GoLoco domains and facilitated by enhancing membrane targeting of the GoLoco protein AGS3. In addition, RGS, but not GoLoco, proteins accelerate desensitization of receptor-activation evoked TRPC4 currents. The inhibitory effects of RGS and GoLoco domains are additive and are most prominent with RGS12 and RGS14, which contain both RGS and GoLoco domains. Our data support the notion that the Gα, but not Gβγ, arm of the Gi/o signalling is involved in TRPC4 activation and unveil new roles for RGS and GoLoco domain proteins in fine-tuning TRPC4 activities. The versatile and diverse functions of RGS and GoLoco proteins in regulating G-protein signalling may underlie the complexity of receptor-operated TRPC4 activation in various cell types under different conditions.
Collapse
|
14
|
Nagy JI, Urena-Ramirez V, Ghia JE. Functional alterations in gut contractility after connexin36 ablation and evidence for gap junctions forming electrical synapses between nitrergic enteric neurons. FEBS Lett 2014; 588:1480-90. [PMID: 24548563 PMCID: PMC4043341 DOI: 10.1016/j.febslet.2014.02.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2013] [Revised: 02/05/2014] [Accepted: 02/06/2014] [Indexed: 02/02/2023]
Abstract
Neurons in the enteric nervous system utilize numerous neurotransmitters to orchestrate rhythmic gut smooth muscle contractions. We examined whether electrical synapses formed by gap junctions containing connexin36 also contribute to communication between enteric neurons in mouse colon. Spontaneous contractility properties and responses to electrical field stimulation and cholinergic agonist were altered in gut from connexin36 knockout vs. wild-type mice. Immunofluorescence revealed punctate labelling of connexin36 that was localized at appositions between somata of enteric neurons immunopositive for the enzyme nitric oxide synthase. There is indication for a possible functional role of gap junctions between inhibitory nitrergic enteric neurons.
Collapse
Affiliation(s)
- James Imre Nagy
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada
| | - Viridiana Urena-Ramirez
- Department of Physiology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada; Department of Immunology and Internal Medicine section of Gastroenterology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada
| | - Jean-Eric Ghia
- Department of Immunology and Internal Medicine section of Gastroenterology, Faculty of Medicine, University of Manitoba, Winnipeg, Canada.
| |
Collapse
|
15
|
Priyashree S, Jha S, Pattanayak SP. Bronchodilatory and mast cell stabilising activity of Cressa cretica L.: evaluation through in vivo and in vitro experimental models. ASIAN PAC J TROP MED 2012; 5:180-6. [PMID: 22305781 DOI: 10.1016/s1995-7645(12)60021-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 12/15/2011] [Accepted: 01/15/2012] [Indexed: 11/17/2022] Open
Abstract
OBJECTIVE To evaluate the effect of ethylacetate fraction (Fr-Et) and methanolic fraction (Fr-Me) obtained from Cressa cretica L.(C. cretica) L. on experimental models for bronchodilatory activity and mast cell stabilising activity. METHODS The effect of Fr-Et and Fr-Me were studied on acetylcholine and histamine aerosol-induced broncospasm using guinea pigs as experimental animals. Also, the effects of these fractions were evaluated on the isolated guinea pig tracheal preparations. Besides this mast cell degranulation effect was assessed using egg albumin and compound 48/80 on rat peritoneal mast cells. RESULTS Significant increase in preconvulsion time was observed due to pretreatment with the fractions when guinea pigs were exposed to histamine and acetylcholine aerosol. Fr-Et and Fr-Me significantly increased the preconvulsion in a dose depended manner that suggestive of bronchodilating activity. Fr-Et and Fr-Me exhibited a significant concentration dependant relaxant effect on guinea pig trachea pre-contracted with CCh, K(+) and histamine. The results revealed that Fr-Et to be more potent than Fr-Me in relaxing histamine and K(+) and calcium induced contraction than CCh induced contractions. Studies on the fractions in protecting mast cell degranulation, which were elicited by the egg albumin as well as synthetic compound 48/80 revealed both the fractions significantly protect the mast cell degranulation, which release mediators such as histamine and proinflammatory cytokines through various stimuli in a dose depended manner. CONCLUSIONS Thus our study established the bronchodilator activity, and mast cell stabilizing activity which are important mediators that provoke or sustain in asthma.
Collapse
Affiliation(s)
- Sunita Priyashree
- Govt. Pharmacy Institute, Department of Health and Family Welfare, Govt. of Jharkhand, Ranchi, India.
| | | | | |
Collapse
|
16
|
Kim H, Dwyer L, Song JH, Martin-Cano FE, Bahney J, Peri L, Britton FC, Sanders KM, Koh SD. Identification of histamine receptors and effects of histamine on murine and simian colonic excitability. Neurogastroenterol Motil 2011; 23:949-e409. [PMID: 21806740 PMCID: PMC3173574 DOI: 10.1111/j.1365-2982.2011.01760.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
BACKGROUND Inflammatory responses can include recruitment of cells of hematopoietic origin to the tunica muscularis. These cells can secrete a variety of factors which can reset the gain of smooth muscle cells (SMC) and influence motor patterns. Histamine (H), a major mediator in inflammation, is released by mast cells and exerts diverse effects in SMC by binding to H receptors. The profiles of H receptor expression in animal models used to study inflammatory diseases are unknown. METHODS Histamine receptor expression and electro-mechanical responses to H were tested in simian and murine colonic smooth muscle using qualitative and quantitative PCR, isometric force measurements, microelectrode recordings and patch clamp techniques. KEY RESULTS H1, H2, and H4 receptor transcripts were expressed at similar levels in simian colonic tissue whereas only the H2 receptor transcript was detected in murine colonic tissue. Stimulation of simian colonic muscles with H caused depolarization and contraction in the presence of tetrodotoxin. Histamine activated non-selective cation channels in simian SMC. In contrast, H caused hyperpolarization and inhibited contractions of murine colon. The hyperpolarization was inhibited by the K(ATP) channel blocker, glibenclamide. Histamine-activated K(+) currents were inhibited by glibenclamide in murine colonic SMC. CONCLUSIONS & INFERENCES Histamine receptor expression in simian SMC was similar to that reported in humans. However, H receptor profile and responses to H were considerably different in mice. Thus, monkey colon may be a more suitable model to study how inflammatory mediators affect the gain of smooth muscle excitability.
Collapse
Affiliation(s)
- H Kim
- Department of Internal Medicine, School of Medicine, Gyeongsang National University, Jinju, Korea
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Comparative effects of menthol and icilin on the induced contraction of the smooth muscles of the vas deferens of normal and castrated rats. ACTA ACUST UNITED AC 2011. [DOI: 10.15407/fz57.04.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
18
|
Dwyer L, Kim HJ, Koh BH, Koh SD. Phospholipase C-independent effects of 3M3FBS in murine colon. Eur J Pharmacol 2009; 628:187-94. [PMID: 19931239 DOI: 10.1016/j.ejphar.2009.11.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 10/22/2009] [Accepted: 11/05/2009] [Indexed: 11/30/2022]
Abstract
The muscarinic receptor subtype M(3) is coupled to Gq/11 proteins. Muscarinic receptor agonists such as carbachol stimulate these receptors that result in activation of phospholipase C (PLC) which hydrolyzes phosphatidylinositol 4,5-bisphosphate into diacylglycerol and Ins(1,4,5)P(3). This pathway leads to excitation and smooth muscle contraction. In this study the PLC agonist, 2, 4, 6-trimethyl-N-(meta-3-trifluoromethyl-phenyl)-benezenesulfonamide (m-3M3FBS), was used to investigate whether direct PLC activation mimics carbachol-induced excitation. We examined the effects of m-3M3FBS and 2, 4, 6-trimethyl-N-(ortho-3-trifluoromethyl-phenyl)-benzenesulfonamide (o-3M3FBS), on murine colonic smooth muscle tissue and cells by performing conventional microelectrode recordings, isometric force measurements and patch clamp experiments. Application of m-3M3FBS decreased spontaneous contractility in murine colonic smooth muscle without affecting the resting membrane potential. Patch clamp studies revealed that delayed rectifier K(+) channels were reversibly inhibited by m-3M3FBS and o-3M3FBS. The PLC inhibitor, 1-(6-((17b-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U73122), did not prevent this inhibition by m-3M3FBS. Both m-3M3FBS and o-3M3FBS decreased two components of delayed rectifier K(+) currents in the presence of tetraethylammonium chloride or 4-aminopyridine. Ca(2+) currents were significantly suppressed by m-3M3FBS and o-3M3FBS with a simultaneous increase in intracellular Ca(2+). Pretreatment with U73122 did not prevent the decrease in Ca(2+) currents upon m-3M3FBS application. In conclusion, both m-3M3FBS and o-3M3FBS inhibit inward and outward currents via mechanisms independent of PLC acting in an antagonistic manner. In contrast, both compounds also caused an increase in [Ca(2+)](i) in an agonistic manner. Therefore caution must be employed when interpreting their effects at the tissue and cellular level.
Collapse
Affiliation(s)
- Laura Dwyer
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557, USA
| | | | | | | |
Collapse
|
19
|
Otsuguro KI, Tang J, Tang Y, Xiao R, Freichel M, Tsvilovskyy V, Ito S, Flockerzi V, Zhu MX, Zholos AV. Isoform-specific inhibition of TRPC4 channel by phosphatidylinositol 4,5-bisphosphate. J Biol Chem 2008; 283:10026-36. [PMID: 18230622 DOI: 10.1074/jbc.m707306200] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Full-length transient receptor potential (TRP) cation channel TRPC4alpha and shorter TRPC4beta lacking 84 amino acids in the cytosolic C terminus are expressed in smooth muscle and endothelial cells where they regulate membrane potential and Ca(2+) influx. In common with other "classical" TRPCs, TRPC4 is activated by G(q)/phospholipase C-coupled receptors, but the underlying mechanism remains elusive. Little is also known about any isoform-specific channel regulation. Here we show that TRPC4alpha but not TRPC4beta was strongly inhibited by intracellularly applied phosphatidylinositol 4,5-bisphosphate (PIP(2)). In contrast, several other phosphoinositides (PI), including PI(3,4)P(2), PI(3,5)P(2), and PI(3,4,5)P(3), had no effect or even potentiated TRPC4alpha indicating that PIP(2) inhibits TRPC4alpha in a highly selective manner. We show that PIP(2) binds to the C terminus of TRPC4alpha but not that of TRPC4beta in vitro. Its inhibitory action was dependent on the association of TRPC4alpha with actin cytoskeleton as it was prevented by cytochalasin D treatment or by the deletion of the C-terminal PDZ-binding motif (Thr-Thr-Arg-Leu) that links TRPC4 to F-actin through the sodium-hydrogen exchanger regulatory factor and ezrin. PIP(2) breakdown appears to be a required step in TRPC4alpha channel activation as PIP(2) depletion alone was insufficient for channel opening, which additionally required Ca(2+) and pertussis toxin-sensitive G(i/o) proteins. Thus, TRPC4 channels integrate a variety of G-protein-dependent stimuli, including a PIP(2)/cytoskeleton dependence reminiscent of the TRPC4-like muscarinic agonist-activated cation channels in ileal myocytes.
Collapse
Affiliation(s)
- Ken-ichi Otsuguro
- Cardiovascular Biomedical Research Centre, School of Medicine and Dentistry, Queen's University Belfast, Belfast, United Kingdom
| | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Ma KT, Guan BC, Yang YQ, Zhao H, Jiang ZG. ACh-induced depolarization in inner ear artery is generated by activation of a TRP-like non-selective cation conductance and inactivation of a potassium conductance. Hear Res 2008; 239:20-33. [PMID: 18313244 DOI: 10.1016/j.heares.2008.01.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2007] [Revised: 01/03/2008] [Accepted: 01/15/2008] [Indexed: 10/22/2022]
Abstract
Adequate cochlear blood supply by the spiral modiolar artery (SMA) is critical for normal hearing. ACh may play a role in neuroregulation of the SMA but several key issues including its membrane action mechanisms remain poorly understood. Besides its well-known endothelium-dependent hyperpolarizing action, ACh can induce a depolarization in vascular cells. Using intracellular and whole-cell recording techniques on cells in guinea pig in vitro SMA, we studied the ionic mechanism underlying the ACh-depolarization and found that: (1) ACh induced a DAMP-sensitive depolarization when intermediate conductance KCa channels were blocked by charybdotoxin or nitrendipine. The ACh-depolarization was associated with a decrease in input resistance (R(input)) in high membrane potential (V(m)) ( approximately -40 mV) cells but with no change or an increase in R input in low Vm ( approximately -75 mV) cells. ACh-depolarization was attenuated by background membrane depolarization from approximately -70 mV in the majority of cells; (2) ACh-induced inward current in smooth muscle cells embedded in a SMA segment often showed a U-shaped I/V curve, the reversal potential of its two arms being near EK and 0 mV, respectively; (3) ACh-depolarization was reduced by low Na+, zero K+ or 20mM K+ bath solutions; (4) ACh-depolarization was inhibited by La3+ in all cells tested, by 4-AP and flufenamic acid in low Vm cells, but was not sensitive to Cd2+, Ni2+, nifedipine, niflumic acid, DIDS, IAA94, linopirdine or amiloride. We conclude that ACh-induced vascular depolarization was generated mainly by activation of a TRP-like non-selective cation channel and by inactivation of an inward rectifier K+ channel.
Collapse
Affiliation(s)
- Ke-Tao Ma
- Oregon Hearing Research Center, Department of Otolaryngology, Oregon Health and Science University, Portland, OR 97239, USA
| | | | | | | | | |
Collapse
|
21
|
Krustev A, Sirakov V, Turiiski V, Getova D, Velkova K, Prissadova N. Delayed evacuatory function due to specific smooth muscle reactivity in the gastrointestinal tracts of tacrine-treated rats. Pharmacology 2007; 81:50-6. [PMID: 17827979 DOI: 10.1159/000107969] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Accepted: 06/11/2007] [Indexed: 11/19/2022]
Abstract
Most of the side effects induced by tacrine are associated with the gastrointestinal (GI) tract. The aim of the study was to analyze the nature of radiographically registered, tacrine-induced changes in evacuatory function, as well as to find a possible correlation with the immediate in vitro action of the drug on smooth muscles from the GI tracts of rats. The tacrine dose we used reliably delayed GI passage: contrast matter was not fully evacuated, predominantly from the stomach and cecum. The delay resulted from changes in tone and peristaltic activity, specific for the various regions of the tract. These changes were associated with a superposing of the responses due to the anticholinesterase and noncholinergic action of tacrine.
Collapse
Affiliation(s)
- A Krustev
- Department of Biophysics, Medical University, Plovdiv, Bulgaria
| | | | | | | | | | | |
Collapse
|
22
|
Gordienko DV, Harhun MI, Kustov MV, Pucovský V, Bolton TB. Sub-plasmalemmal [Ca2+]i upstroke in myocytes of the guinea-pig small intestine evoked by muscarinic stimulation: IP3R-mediated Ca2+ release induced by voltage-gated Ca2+ entry. Cell Calcium 2007; 43:122-41. [PMID: 17570487 PMCID: PMC2268754 DOI: 10.1016/j.ceca.2007.04.012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 03/29/2007] [Accepted: 04/20/2007] [Indexed: 11/23/2022]
Abstract
Membrane depolarization triggers Ca2+ release from the sarcoplasmic reticulum (SR) in skeletal muscles via direct interaction between the voltage-gated L-type Ca2+ channels (the dihydropyridine receptors; VGCCs) and ryanodine receptors (RyRs), while in cardiac muscles Ca2+ entry through VGCCs triggers RyR-mediated Ca2+ release via a Ca2+-induced Ca2+ release (CICR) mechanism. Here we demonstrate that in phasic smooth muscle of the guinea-pig small intestine, excitation evoked by muscarinic receptor activation triggers an abrupt Ca2+ release from sub-plasmalemmal (sub-PM) SR elements enriched with inositol 1,4,5-trisphosphate receptors (IP3Rs) and poor in RyRs. This was followed by a lesser rise, or oscillations in [Ca2+]i. The initial abrupt sub-PM [Ca2+]i upstroke was all but abolished by block of VGCCs (by 5 μM nicardipine), depletion of intracellular Ca2+ stores (with 10 μM cyclopiazonic acid) or inhibition of IP3Rs (by 2 μM xestospongin C or 30 μM 2-APB), but was not affected by block of RyRs (by 50–100 μM tetracaine or 100 μM ryanodine). Inhibition of either IP3Rs or RyRs attenuated phasic muscarinic contraction by 73%. Thus, in contrast to cardiac muscles, excitation–contraction coupling in this phasic visceral smooth muscle occurs by Ca2+ entry through VGCCs which evokes an initial IP3R-mediated Ca2+ release activated via a CICR mechanism.
Collapse
Affiliation(s)
- D V Gordienko
- Division of Basic Medical Sciences, Ion Channels and Cell Signalling Centre, St. George's University of London, UK.
| | | | | | | | | |
Collapse
|
23
|
Meis S, Munsch T, Sosulina L, Pape HC. Postsynaptic mechanisms underlying responsiveness of amygdaloid neurons to cholecystokinin are mediated by a transient receptor potential-like current. Mol Cell Neurosci 2007; 35:356-67. [PMID: 17482476 DOI: 10.1016/j.mcn.2007.03.012] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Revised: 03/16/2007] [Accepted: 03/27/2007] [Indexed: 10/23/2022] Open
Abstract
Projection neurons of mouse basolateral amygdala responded to CCK with an inward current at a holding potential of -70 mV. This response was mediated by CCK2 receptors as indicated by agonist and antagonist effectiveness, and conveyed via G-proteins of the G(q/11) family as it was abolished in gene knockout mice. Maximal current amplitude was insensitive to extracellular potassium, cesium, and calcium ions, respectively, whereas amplitude and reversal potential critically depended upon extracellular sodium concentration. The current reversed near -20 mV consistent with activation of a mixed cationic channel reminiscent of transient receptor potential (TRP) channels. Extracellular application of the non-selective TRP channel blockers 2-APB, flufenamic acid, Gd3+, and ruthenium red, respectively, inhibited CCK induced inward currents. Single cell PCR confirmed the expression of TRPC1,4,5 and coexpression of TRPC1 with TRPC4 or TRPC5 in some cells. CCK responses were associated with depolarization leading to an increase in cell excitability.
Collapse
Affiliation(s)
- Susanne Meis
- Institut für Physiologie, Medizinische Fakultät, Otto-von-Guericke-Universität, Leipziger Str. 44, D-39120 Magdeburg, Germany.
| | | | | | | |
Collapse
|