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Straface M, Koussai MA, Makwana R, Crawley E, Palmer A, Cai W, Gharibans A, Adebibe M, Loy J, O’Grady G, Andrews PLR, Sanger GJ. A multi-parameter approach to measurement of spontaneous myogenic contractions in human stomach: Utilization to assess potential modulators of myogenic contractions. Pharmacol Res 2022; 180:106247. [DOI: 10.1016/j.phrs.2022.106247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 04/22/2022] [Accepted: 05/03/2022] [Indexed: 10/18/2022]
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Drumm BT, Hannigan KI, Lee JY, Rembetski BE, Baker SA, Koh SD, Cobine CA, Sanders KM. Ca 2+ signalling in interstitial cells of Cajal contributes to generation and maintenance of tone in mouse and monkey lower esophageal sphincters. J Physiol 2022; 600:2613-2636. [PMID: 35229888 DOI: 10.1113/jp282570] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/15/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS The lower esophageal sphincter (LES) generates contractile tone preventing reflux of gastric contents into the esophagus. LES smooth muscle cells (SMCs) display depolarized membrane potentials facilitating activation of L-type Ca2+ channels. Interstitial cells of Cajal (ICC) express Ca2+ -activated Cl- channels encoded by Ano1 in mouse and monkey LES. Ca2+ signaling in ICC activates ANO1 currents in ICC. ICC displayed spontaneous Ca2+ transients in mice from multiple firing sites in each cell and no entrainment of Ca2+ firing between sites or between cells. Inhibition of ANO1 channels with a specific antagonist caused hyperpolarization of mouse LES and inhibition of tone in monkey and mouse LES muscles. Our data suggest a novel mechanism for LES tone in which Ca2+ transient activation of ANO1 channels in ICC generates depolarizing inward currents that conduct to SMCs to activate L-type Ca2+ currents, Ca2+ entry and contractile tone. ABSTRACT The lower esophageal sphincter (LES) generates tone and prevents reflux of gastric contents. LES smooth muscle cells (SMCs) are relatively depolarized, facilitating activation of Cav 1.2 channels to sustain contractile tone. We hypothesised that intramuscular interstitial cells of Cajal (ICC-IM), through activation of Ca2+ -activated-Cl- channels (ANO1), set membrane potentials of SMCs favorable for activation of Cav 1.2 channels. In some gastrointestinal muscles, ANO1 channels in ICC-IM are activated by Ca2+ transients, but no studies have examined Ca2+ dynamics in ICC-IM within the LES. Immunohistochemistry and qPCR were used to determine expression of key proteins and genes in ICC-IM and SMCs. These studies revealed that Ano1 and its gene product, ANO1 are expressed in c-Kit+ cells (ICC-IM) in mouse and monkey LES clasp muscles. Ca2+ signaling was imaged in situ, using mice expressing GCaMP6f specifically in ICC (Kit-KI-GCaMP6f). ICC-IM exhibited spontaneous Ca2+ transients from multiple firing sites. Ca2+ transients were abolished by CPA or caffeine but were unaffected by tetracaine or nifedipine. Maintenance of Ca2+ transients depended on Ca2+ influx and store reloading, as Ca2+ transient frequency was reduced in Ca2+ free solution or by Orai antagonist. Spontaneous tone of LES muscles from mouse and monkey was reduced ∼80% either by Ani9, an ANO1 antagonist or by the Cav 1.2 channel antagonist nifedipine. Membrane hyperpolarisation occurred in the presence of Ani9. These data suggest that intracellular Ca2+ activates ANO1 channels in ICC-IM in the LES. Coupling of ICC-IM to SMCs drives depolarization, activation of Cav 1.2 channels, Ca2+ entry and contractile tone. Abstract figure legend Proposed mechanism for generation of contractile tone in the lower esophageal sphincter (LES). Interstitial cells of Cajal (ICC) in the LES generate spontaneous, stochastic Ca2+ transients via Ca2+ release from the endoplasmic reticulum (ER). The Ca2+ transients activate ANO1 Cl- channels causing Cl- efflux (inward current). ANO1 currents have a depolarizing effect on ICC (+++s inside membrane) and this conducts through gap junctions (GJ) to smooth muscle cells (SMCs). Input from thousands of ICC results in depolarized membrane potentials (-40 to -50 mV) which is within the window current range for L-type Ca2+ channels. Activation of these channels causes Ca2+ influx, activation of contractile elements (CE) and development of tonic contraction. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Bernard T Drumm
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA.,Smooth Muscle Research Centre, Dundalk Institute of Technology, Ireland
| | - Karen I Hannigan
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Ji Yeon Lee
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Benjamin E Rembetski
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Salah A Baker
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Sang Don Koh
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Caroline A Cobine
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
| | - Kenton M Sanders
- Department of Physiology & Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA
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Gao Y, Liu JF, Zhang C. The effects of acetylcholine on intracellular calcium fluorescence in smooth muscle cells of human esophagogastric junction cultured in vitro. Neurogastroenterol Motil 2021; 33:e14252. [PMID: 34532931 DOI: 10.1111/nmo.14252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 07/01/2021] [Accepted: 07/22/2021] [Indexed: 02/08/2023]
Abstract
BACKGROUND Most esophageal motility studies are based on animals. It is necessary to explore smooth muscle motility in the human esophagus. This study was undertaken to explore the feasibility of in vitro culture of smooth muscle cells (SMCs) from human esophagogastric junction (EGJ) and to determine changes of intracellular calcium (Ca2+ ) fluorescence ([Ca2+ ]i ) in SMCs stimulated by acetylcholine (ACh). METHODS Primary cells of EGJ (Clasp, Sling, esophageal circular muscle (ECM), and longitudinal muscle (ELM)) were obtained by enzymatic digestion (ED) and explant culture with tissues (EC-T) from 9 upper esophageal carcinoma patients. Cells were cultured in smooth muscle cell medium (SMCM) and DMEM/F-12 medium containing 10% newborn bovine serum (10%-F12), respectively, and then identified by α-SMA staining. After incubation with 5 μM Fluo-3/am, the effect of 10-6 mM ACh on [Ca2+ ]i in Ca2+ -containing and Ca2+ -free buffers was evaluated by confocal microscopy. RESULTS Cultured cells from ED and EC-T were identified as SMCs by α-SMA with spindle surface and "hills and valleys" morphology. Cells cultured in 10%-F12 showed better morphology. The main characteristic of [Ca2+ ]i in Clasp-, Sling- and ECM-SMCs was the release of intracellular Ca2+ stores; the main characteristic in ELM-SMCs was extracellular Ca2+ influx. However, these cells seemed not to rely on a unique Ca2+ activity, instead combining the two activities to maintain [Ca2+ ]i . CONCLUSIONS It was feasible to culture human EGJ SMCs in vitro; moreover, Ach-induced changes of [Ca2+ ]i in EGJ SMCs represent a complex interaction of intracellular Ca2+ release and extracellular Ca2+ influx.
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Affiliation(s)
- Yang Gao
- Department of Thoracic Surgery, the Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei Province, China.,Doctoral student of Thoracic Surgery, Graduate School of Hebei Medical University, Shijiazhuang, Hebei Province, China
| | - Jun-Feng Liu
- Department of Thoracic Surgery, the Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei Province, China
| | - Chao Zhang
- Research Center, the Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei Province, China
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Chen Q, Jiang Z, Zhang J, Cao L, Chen Z. Arecoline hydrobromide enhances jejunum smooth muscle contractility via voltage-dependent potassium channels in W/Wv mice. Physiol Res 2021; 70:437-446. [PMID: 33982580 DOI: 10.33549/physiolres.934557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Gastrointestinal motility was disturbed in W/Wv, which were lacking of interstitial cells of Cajal (ICC). In this study, we have investigated the role of arecoline hydrobromide (AH) on smooth muscle motility in the jejunum of W/Wv and wild-type (WT) mice. The jejunum tension was recorded by an isometric force transducer. Intracellular recording was used to identify whether AH affects slow wave and resting membrane potential (RMP) in vitro. The whole-cell patch clamp technique was used to explore the effects of AH on voltage-dependent potassium channels for jejunum smooth muscle cells. AH enhanced W/Wv and WT jejunum contractility in a dose-dependent manner. Atropine and nicardipine completely blocked the excitatory effect of AH in both W/Wv and WT. TEA did not reduce the effect of AH in WT, but was sufficient to block the excitatory effect of AH in W/Wv. AH significantly depolarized the RMP of jejunum cells in W/Wv and WT. After pretreatment with TEA, the RMP of jejunum cells indicated depolarization in W/Wv and WT, but subsequently perfused AH had no additional effect on RMP. AH inhibited the voltage-dependent K+ currents of acutely isolated mouse jejunum smooth muscle cells. Our study demonstrate that AH enhances the contraction activity of jejunum smooth muscle, an effect which is mediated by voltage-dependent potassium channels that acts to enhance the excitability of jejunum smooth muscle cells in mice.
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Affiliation(s)
- Q Chen
- Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, China.
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Adiponectin Exerts Peripheral Inhibitory Effects on the Mouse Gastric Smooth Muscle through the AMPK Pathway. Int J Mol Sci 2020; 21:ijms21249617. [PMID: 33348652 PMCID: PMC7767160 DOI: 10.3390/ijms21249617] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 12/10/2020] [Accepted: 12/15/2020] [Indexed: 12/17/2022] Open
Abstract
Some adipokines, such as adiponectin (ADPN), other than being implicated in the central regulation of feeding behavior, may influence gastric motor responses, which are a source of peripheral signals that also influence food intake. The present study aims to elucidate the signaling pathways through which ADPN exerts its actions in the mouse gastric fundus. To this purpose, we used a multidisciplinary approach. The mechanical results showed that ADPN caused a decay of the strip basal tension, which was abolished by the nitric oxide (NO) synthesis inhibitor, L-NG-nitro arginine (L-NNA). The electrophysiological experiments confirmed that all ADPN effects were abolished by L-NNA, except for the reduction of Ca2+ current, which was instead prevented by the inhibitor of AMP-activated protein kinase (AMPK), dorsomorphin. The activation of the AMPK signaling by ADPN was confirmed by immunofluorescence analysis, which also revealed the ADPN R1 receptor (AdipoR1) expression in glial cells of the myenteric plexus. In conclusion, our results indicate that ADPN exerts an inhibitory action on the gastric smooth muscle by acting on AdipoR1 and involving the AMPK signaling pathway at the peripheral level. These findings provide novel bases for considering AMPK as a possible pharmacologic target for the potential treatment of obesity and eating disorders.
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Sabti M, Sasaki K, Gadhi C, Isoda H. Elucidation of the Molecular Mechanism Underlying Lippia citriodora(Lim.)-Induced Relaxation and Anti-Depression. Int J Mol Sci 2019; 20:E3556. [PMID: 31330819 PMCID: PMC6678442 DOI: 10.3390/ijms20143556] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 07/16/2019] [Accepted: 07/18/2019] [Indexed: 12/12/2022] Open
Abstract
Lippia citriodora ethanolic extract (VEE) and verbascoside (Vs), a phenypropanoid glycoside, have been demonstrated to exert relaxant and anxiolytic properties. However, the molecular mechanisms behind their effects are still unclear. In this work, we studied the effects and action mechanisms of VEE and Vs in vivo and in vitro, on human neurotypic SH-SY5Y cells.TST was conducted on mice treated orally with VEE (25, 50 and 100 mg/Kg), Vs (2.5 and 5 mg/Kg), Bupropion (20 mg/Kg) and Milli-Q water. Higher dose of VEE-treated mice showed an increase of immobility time compared to control groups, indicating an induction of relaxation. This effect was found to be induced by regulation of genes playing key roles in calcium homeostasis (calcium channels), cyclic AMP (cAMP) production and energy metabolism. On the other hand, low doses of VEE and Vs showed an antidepressant-like effect and was confirmed by serotonin, noradrenalin, dopamine and BDNF expressions. Finally, VEE and Vsenhancedcell viability, mitochondrial activity and calcium uptake in vitro confirming in vivo findings. Our results showed induction of relaxation and antidepressant-like effects depending on the administered dose of VEE and Vs, through modulation of cAMP and calcium.
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Affiliation(s)
- Mouad Sabti
- Alliance for Research on the Mediterranean and North Africa (ARENA), University of Tsukuba, 1-1-1 Tennodai, Tsukuba City 305-8572, Ibaraki, Japan
- Tsukuba Life Science Innovation Program (T-LSI), University of Tsukuba, Tennodai 1-1-1, Tsukuba City 305-8577, Ibaraki, Japan
| | - Kazunori Sasaki
- Alliance for Research on the Mediterranean and North Africa (ARENA), University of Tsukuba, 1-1-1 Tennodai, Tsukuba City 305-8572, Ibaraki, Japan
- Interdisciplinary Research Center for Catalytic Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8560, Japan
| | - Chemseddoha Gadhi
- Faculty of Sciences Semlalia, Cadi Ayyad University, Avenue Prince MoulayAbdellah, BP 2390, 40000 Marrakesh, Morocco
| | - Hiroko Isoda
- Alliance for Research on the Mediterranean and North Africa (ARENA), University of Tsukuba, 1-1-1 Tennodai, Tsukuba City 305-8572, Ibaraki, Japan.
- Tsukuba Life Science Innovation Program (T-LSI), University of Tsukuba, Tennodai 1-1-1, Tsukuba City 305-8577, Ibaraki, Japan.
- Interdisciplinary Research Center for Catalytic Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8560, Japan.
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Gao Y, Liu JF, He X, Liu XB, Zhang LL, Zhao LM, Zhang C. Calcium Receptor and Nitric Oxide Synthase Expression in Circular Muscle of Lower Esophagus from Patients with Achalasia. Chin Med J (Engl) 2019; 131:2882-2885. [PMID: 30511698 PMCID: PMC6278202 DOI: 10.4103/0366-6999.246081] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Affiliation(s)
- Yang Gao
- Department of Thoracic Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011; Graduate School, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Jun-Feng Liu
- Department of Thoracic Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Xin He
- Graduate School, Hebei Medical University, Shijiazhuang, Hebei 050017, China
| | - Xin-Bo Liu
- Department of Thoracic Surgery, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Ling-Ling Zhang
- Department of Pathology, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Lian-Mei Zhao
- Research Center, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, China
| | - Chao Zhang
- Research Center, The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei 050011, China
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Selectivity of Ca 2+ channel blockers for dilator actions on the isolated lower esophageal sphincter and aorta from rats. J Pharmacol Sci 2018; 137:98-100. [PMID: 29709270 DOI: 10.1016/j.jphs.2018.01.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Revised: 01/04/2018] [Accepted: 01/22/2018] [Indexed: 11/22/2022] Open
Abstract
We compared dilator actions of representative four Ca2+ channel blockers on the isolated lower esophagus sphincter (LES) and thoracic aorta from rats. Verapamil, diltiazem, nifedipine and cilnidipine suppressed KCl-induced contractions of LES and thoracic aorta in a concentration-dependent manner. The order of selectivity for LES, which was calculated as ratio of IC50 value for thoracic aorta divided by that for LES, was diltiazem > verapamil > nifedipine > cilnidipine. These results suggest that diltiazem more preferentially dilates the LES whereas cilnidipine is expected to have lower potential risk of gastroesophageal dysfunction during the antihypertensive therapy.
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9
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Bai X, Ihara E, Hirano K, Tanaka Y, Nakano K, Kita S, Iwamoto T, Ogino H, Hirano M, Oda Y, Nakamura K, Ogawa Y. Endogenous Hydrogen Sulfide Contributes to Tone Generation in Porcine Lower Esophageal Sphincter Via Na +/Ca 2+ Exchanger. Cell Mol Gastroenterol Hepatol 2017; 5:209-221. [PMID: 29379856 PMCID: PMC5782486 DOI: 10.1016/j.jcmgh.2017.11.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Accepted: 11/14/2017] [Indexed: 12/16/2022]
Abstract
BACKGROUND AND AIMS Hydrogen sulfide (H2S) is a major physiologic gastrotransmitter. Its role in the regulation of the lower esophageal sphincter (LES) function remains unknown. The present study addresses this question. METHODS Isometric contraction was monitored in circular smooth muscle strips of porcine LES. Changes in cytosolic Ca2+ concentration ([Ca2+]i) and force were simultaneously monitored in fura-2-loaded strips with front-surface fluorometry. The contribution of endogenous H2S to LES contractility was investigated by examining the effects of inhibitors of H2S-generating enzymes, including cystathionine-β-synthase, cystathionine-γ-lyase, and 3-mercaptopyruvate sulfurtransferase, on the LES function. RESULTS Porcine LES strips myogenically maintained a tetrodotoxin-resistant basal tone. Application of AOA (cystathionine-β-synthase inhibitor) or L-aspartic acid (L-Asp; 3-mercaptopyruvate sulfurtransferase inhibitor) but not DL-PAG (cystathionine-γ-lyase inhibitor), decreased this basal tone. The relaxant effects of AOA and L-Asp were additive. Maximum relaxation was obtained by combination of 1 mM AOA and 3 mM L-Asp. Immunohistochemical analyses revealed that cystathionine-β-synthase and 3-mercaptopyruvate sulfurtransferase, but not cystathionine-γ-lyase, were expressed in porcine LES. AOA+L-Asp-induced relaxation was accompanied by a decrease in [Ca2+]i and inversely correlated with the extracellular Na+ concentration ([Na+]o) (25-137.4 mM), indicating involvement of an Na+/Ca2+ exchanger. The reduction in the basal [Ca2+]i level by AOA was significantly augmented in the antral smooth muscle sheets of Na+/Ca2+ exchanger transgenic mice compared with wild-type mice. CONCLUSIONS Endogenous H2S regulates the LES myogenic tone by maintaining the basal [Ca2+]i via Na+/Ca2+ exchanger. H2S-generating enzymes may be a potential therapeutic target for esophageal motility disorders, such as achalasia.
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Key Words
- 3MST, 3-mercaptopyruvate sulfurtransferase
- AOA, amino-oxyacetic acid
- CBS, cystathionine-β-synthase
- CCh, carbachol
- CSE, cystathionine-γ-lyase
- ES, extracellular solution
- H2S, hydrogen sulfide
- Hydrogen Sulfate
- KATP channels, ATP-sensitive K+ channels
- KES, K+ extracellular solution
- L-Asp, L-aspartic acid
- L-Cys, L-cysteine
- L-NAME, Nω-nitro-L-arginine methyl ester
- LES, lower esophageal sphincter
- Lower Esophageal Sphincter
- Myogenic Tone Regulation
- NCX, Na+/Ca2+ exchanger
- NES, normal extracellular solution
- Na+/Ca2+ Exchanger
- PAG, propargylglycine
- TEA, tetraethylammonium
- TG, transgenic
- TTX, tetrodotoxin
- [Ca2+]i, cytosolic Ca2+ concentration
- [Na+]o, extracellular Na+ concentration
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Affiliation(s)
- Xiaopeng Bai
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Eikichi Ihara
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan,Correspondence Address correspondence to: Eikichi Ihara, MD, PhD, Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. fax +81-92-642-5287.Department of Medicine and Bioregulatory ScienceGraduate School of Medical SciencesKyushu University3-1-1 Maidashi, Higashi-kuFukuoka812-8582Japan
| | - Katsuya Hirano
- Department of Cardiovascular Physiology, Faculty of Medicine, Kagawa University, Kagawa Prefecture, Japan
| | - Yoshimasa Tanaka
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Kayoko Nakano
- Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Satomi Kita
- Department of Pharmacology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan,Department of Pharmacology, Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Tokushima, Japan
| | - Takahiro Iwamoto
- Department of Pharmacology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan
| | - Haruei Ogino
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Mayumi Hirano
- Division of Molecular Cardiology, Research Institute of Angiocardiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshinao Oda
- Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Kazuhiko Nakamura
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Yoshihiro Ogawa
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan,Department of Molecular and Cellular Metabolism, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan
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Meng XM, Huang X, Zhang CM, Liu DH, Lu HL, Kim YC, Xu WX. Hydrogen sulfide-induced enhancement of gastric fundus smooth muscle tone is mediated by voltage-dependent potassium and calcium channels in mice. World J Gastroenterol 2015; 21:4840-4851. [PMID: 25944997 PMCID: PMC4408456 DOI: 10.3748/wjg.v21.i16.4840] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 10/17/2014] [Accepted: 12/22/2014] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effect of hydrogen sulfide (H2S) on smooth muscle motility in the gastric fundus.
METHODS: The expression of cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) in cultured smooth muscle cells from the gastric fundus was examined by the immunocytochemistry technique. The tension of the gastric fundus smooth muscle was recorded by an isometric force transducer under the condition of isometric contraction with each end of the smooth muscle strip tied with a silk thread. Intracellular recording was used to identify whether hydrogen sulfide affects the resting membrane potential of the gastric fundus in vitro. Cells were freshly separated from the gastric fundus of mice using a variety of enzyme digestion methods and whole-cell patch-clamp technique was used to find the effects of hydrogen sulfide on voltage-dependent potassium channel and calcium channel. Calcium imaging with fura-3AM loading was used to investigate the mechanism by which hydrogen sulfide regulates gastric fundus motility in cultured smooth muscle cells.
RESULTS: We found that both CBS and CSE were expressed in the cultured smooth muscle cells from the gastric fundus and that H2S increased the smooth muscle tension of the gastric fundus in mice at low concentrations. In addition, nicardipine and aminooxyacetic acid (AOAA), a CBS inhibitor, reduced the tension, whereas Nω-nitro-L-arginine methyl ester, a nonspecific nitric oxide synthase, increased the tension. The AOAA-induced relaxation was significantly recovered by H2S, and the NaHS-induced increase in tonic contraction was blocked by 5 mmol/L 4-aminopyridine and 1 μmol/L nicardipine. NaHS significantly depolarized the membrane potential and inhibited the voltage-dependent potassium currents. Moreover, NaHS increased L-type Ca2+ currents and caused an elevation in intracellular calcium ([Ca2+]i).
CONCLUSION: These findings suggest that H2S may be an excitatory modulator in the gastric fundus in mice. The excitatory effect is mediated by voltage-dependent potassium and L-type calcium channels.
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MESH Headings
- Animals
- Calcium Channel Agonists/pharmacology
- Calcium Channels, L-Type/drug effects
- Calcium Channels, L-Type/metabolism
- Calcium Signaling/drug effects
- Cells, Cultured
- Cystathionine gamma-Lyase/metabolism
- Dose-Response Relationship, Drug
- Enzyme Inhibitors/pharmacology
- Gastric Fundus/drug effects
- Gastric Fundus/metabolism
- Gastrointestinal Motility/drug effects
- Hydrogen Sulfide/pharmacology
- Lyases/antagonists & inhibitors
- Lyases/metabolism
- Male
- Membrane Potentials
- Mice, Inbred ICR
- Muscle Contraction/drug effects
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/metabolism
- Nitric Oxide Synthase/antagonists & inhibitors
- Nitric Oxide Synthase/metabolism
- Potassium Channel Blockers/pharmacology
- Potassium Channels, Voltage-Gated/antagonists & inhibitors
- Potassium Channels, Voltage-Gated/metabolism
- Time Factors
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11
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Bhetwal BP, An C, Baker SA, Lyon KL, Perrino BA. Impaired contractile responses and altered expression and phosphorylation of Ca(2+) sensitization proteins in gastric antrum smooth muscles from ob/ob mice. J Muscle Res Cell Motil 2013; 34:137-49. [PMID: 23576331 DOI: 10.1007/s10974-013-9341-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/27/2013] [Indexed: 12/21/2022]
Abstract
Diabetic gastroparesis is a common complication of diabetes, adversely affecting quality of life with symptoms of abdominal discomfort, nausea, and vomiting. The pathogenesis of this complex disorder is not well understood, involving abnormalities in the extrinsic and enteric nervous systems, interstitial cells of Cajal (ICCs), smooth muscles and immune cells. The ob/ob mouse model of obesity and diabetes develops delayed gastric emptying, providing an animal model for investigating how gastric smooth muscle dysfunction contributes to the pathophysiology of diabetic gastroparesis. Although ROCK2, MYPT1, and CPI-17 activities are reduced in intestinal motility disorders, their functioning has not been investigated in diabetic gastroparesis. We hypothesized that reduced expression and phosphorylation of the myosin light chain phosphatase (MLCP) inhibitory proteins MYPT1 and CPI-17 in ob/ob gastric antrum smooth muscles could contribute to the impaired antrum smooth muscle function of diabetic gastroparesis. Spontaneous and carbachol- and high K(+)-evoked contractions of gastric antrum smooth muscles from 7 to 12 week old male ob/ob mice were reduced compared to age- and strain-matched controls. There were no differences in spontaneous and agonist-evoked intracellular Ca(2+) transients and myosin light chain kinase expression. The F-actin:G-actin ratios were similar. Rho kinase 2 (ROCK2) expression was decreased at both ages. Basal and agonist-evoked MYPT1 and myosin light chain 20 phosphorylation, but not CPI-17 phosphorylation, was reduced compared to age-matched controls. These findings suggest that reduced MLCP inhibition due to decreased ROCK2 phosphorylation of MYPT1 in gastric antrum smooth muscles contributes to the antral dysmotility of diabetic gastroparesis.
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Affiliation(s)
- Bhupal P Bhetwal
- Department of Physiology & Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, CMM 203E-MS 0575, 1664 N Virginia St, Reno, NV 89557, USA
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12
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Kovac JR, Mak SK, Garcia MM, Lue TF. A pathophysiology-based approach to the management of early priapism. Asian J Androl 2012. [PMID: 23202699 DOI: 10.1038/aja.2012.83] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Priapism is a rare condition that involves persistent penile erection for greater than 4 h. Distinct variants exist, each with unique characteristics. Ischemic priapism is a painful medical emergency that may occur as a result of veno-occlusion leading to hypoxia and tissue death. Recurrent bouts of ischemic priapism, or stuttering priapism, require treatment for individual attacks as well as long-term prevention. Non-ischemic priapism is associated with trauma and may be managed conservatively. Recent advances into the pathophysiology of priapism have allowed the development of treatment algorithms that specifically target the mechanisms involved. In this review, we outline the basics of smooth muscle contraction and describe how derangement of these pathways results in priapism. A pathophysiological approach to the treatment of priapism is proposed with duration-based algorithms presented to assist in management.
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Affiliation(s)
- Jason R Kovac
- Scott Department of Urology, Baylor College of Medicine, Houston, TX 77030, USA
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13
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Seretis C, Seretis F, Gemenetzis G, Liakos N, Pappas A, Gourgiotis S, Lagoudianakis E, Keramidaris D, Salemis N. Calcium channel blockers and esophageal sclerosis: should we expect exacerbation of interstitial lung disease? Case Rep Gastroenterol 2012; 6:82-7. [PMID: 22423244 PMCID: PMC3304075 DOI: 10.1159/000336584] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Esophageal sclerosis is the most common visceral manifestation of systemic sclerosis, resulting in impaired esophageal clearance and retention of ingested food; in addition, co-existence of lung fibrosis with esophageal scleroderma is not uncommon. Both the progression of generalized connective tissue disorders and the damaging effect of chronic aspiration due to esophageal dysmotility appear to be involved in this procedure of interstitial fibrosis. Nifedipine is a widely prescribed calcium antagonist in a significant percentage of rheumatologic patients suffering from Raynaud syndrome, in order to inhibit peripheral vasospasm. Nevertheless, blocking calcium channels has proven to contribute to exacerbation of gastroesophageal reflux, which consequently can lead to chronic aspiration. We describe the case of severe exacerbation of interstitial lung disease in a 76-year-old female with esophageal sclerosis who was treated with oral nifedipine for Raynaud syndrome.
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Affiliation(s)
- Charalampos Seretis
- 2nd Department of Surgery, 401 General Army Hospital of Athens, Athens, Argos, Greece
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14
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Bhetwal BP, An CL, Fisher SA, Perrino BA. Regulation of basal LC20 phosphorylation by MYPT1 and CPI-17 in murine gastric antrum, gastric fundus, and proximal colon smooth muscles. Neurogastroenterol Motil 2011; 23:e425-36. [PMID: 21883701 PMCID: PMC3173524 DOI: 10.1111/j.1365-2982.2011.01769.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
BACKGROUND Myosin light chain kinase (MLCK) and myosin light chain phosphatase (MLCP) govern myosin light chain (LC20) phosphorylation and smooth muscle contraction. Rho kinase (ROK) inhibits MLCP, resulting in greater LC20 phosphorylation and force generation at a given [Ca(2+) ](i) . Here, we investigate the role of ROK in regulating LC20 phosphorylation and spontaneous contractions of gastric fundus, gastric antrum, and proximal colon smooth muscles. METHODS Protein and phosphorylation levels were determined by western blotting. The effects of Y27632, nicardipine, and GF109203X on phosphorylation levels and contraction were measured. KEY RESULTS γ-Actin expression is similar in all three smooth muscles. LC20 and pS19 are highest, but ROK1 and ROK2 are lowest, in antrum and proximal colon smooth muscles. LZ +/- myosin phosphatase targeting subunit 1 (MYPT1), CPI-17, and pT696, pT853, and pT38 are highest in fundus and proximal colon smooth muscles. Myosin phosphatase-rho interacting protein (M-RIP) expression is lowest in fundus, and highest in antrum and proximal colon smooth muscles. Y27632 reduced pT853 in each smooth muscle, but reduced pT696 only in fundus smooth muscles. Nicardipine had no effect on pT38 in each smooth muscle, while GF109203X reduced pT38 in proximal colon and fundus smooth muscles. Y27632 or nicardipine reduced pS19 in proximal colon and fundus smooth muscles. Y27632 or nicardipine inhibited antrum and proximal colon smooth muscle spontaneous contractions, but only Y27632 reduced fundus smooth muscle tone. Zero external Ca(2+) relaxed each smooth muscle and abolished LC20 phosphorylation. CONCLUSIONS & INFERENCES Organ-specific mechanisms involving the MLCP interacting proteins LZ +/- MYPT1, M-RIP, and CPI-17 are critical to regulating basal LC20 phosphorylation in gastrointestinal smooth muscles.
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Affiliation(s)
- Bhupal P. Bhetwal
- Department of Physiology & Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Reno, NV, USA
| | - Chang Long An
- Department of Physiology & Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Reno, NV, USA
| | - Steven A. Fisher
- Departments of Medicine (Cardiology), and Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Brian A. Perrino
- Department of Physiology & Cell Biology, Center of Biomedical Research Excellence, University of Nevada School of Medicine, Reno, NV, USA
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15
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Braverman AS, Vegesna AK, Miller LS, Barbe MF, Tiwana M, Hussain K, Ruggieri MR. Pharmacologic specificity of nicotinic receptor-mediated relaxation of muscarinic receptor precontracted human gastric clasp and sling muscle fibers within the gastroesophageal junction. J Pharmacol Exp Ther 2011; 338:37-46. [PMID: 21464333 PMCID: PMC3126643 DOI: 10.1124/jpet.110.177097] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Relaxation of gastric clasp and sling muscle fibers is involved the transient lower esophageal sphincter relaxations underlying the pathophysiology of gastroesophageal reflux disease (GERD). These fibers do not contribute tone to the high-pressure zone in GERD patients, indicating their role in pathophysiology. This study identifies some mediators of the nicotine-induced relaxation of muscarinic receptor precontracted gastric clasp and sling fibers. Muscle strips from organ donors precontracted with bethanechol were relaxed with nicotine and then rechallenged after washing and adding inhibitors tetrodotoxin (TTX), the nitric-oxide synthase inhibitor L-nitro-arginine methyl ester (L-NAME), the β-adrenoceptor antagonist propranolol, the glycine receptor antagonist strychnine or ginkgolide B, and the GABA(A) receptor antagonist bicuculline or 2-(3-carboxypropyl)-3-amino-6-(4 methoxyphenyl)pyridazinium bromide [(gabazine) SR95531]. TTX only inhibited clasp fiber relaxations. L-NAME and propranolol inhibited, and ginkgolide B was ineffective in both. SR95531 was ineffective in clasp fibers and partially effective in sling fibers. Strychnine and bicuculline prevented relaxations with low potency, indicating actions not on glycine or GABA(A) receptors but more consistent with nicotinic receptor blockade. Bethanechol-precontracted fibers were relaxed by the nitric oxide donor S-nitroso-N-acetyl-DL-penicillamine and by the β-adrenergic agonist isoproterenol (clasp fibers only) but not by the glycine receptor agonist taurine or glycine or the GABA(A) agonist muscimol. These data indicate that nicotinic receptor activation mediates relaxation via release of nitric oxide in clasp and sling fibers, norepinephrine acting on β-adrenoceptors in clasp fibers, and GABA acting on GABA(A) receptors in sling fibers. Agents that selectively prevent these relaxations may be useful in the treatment of GERD.
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Affiliation(s)
- Alan S Braverman
- Department of Urology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA
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16
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L’Heureux MC, Muinuddin A, Gaisano HY, Diamant NE. Nitric oxide activation of a potassium channel (BK Ca) in feline lower esophageal sphincter. World J Gastroenterol 2010; 16:5852-60. [PMID: 21155007 PMCID: PMC3001977 DOI: 10.3748/wjg.v16.i46.5852] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To assess the effect of nitric oxide (NO) on the large conductance potassium channel (BKCa) in isolated circular (CM) and sling (SM) muscle cells and muscle strips from the cat lower esophageal sphincter (LES) to determine its regulation of resting tone and relaxation.
METHODS: Freshly enzymatically-digested and isolated circular smooth muscle cells were prepared from each LES region. To study outward K+ currents, the perforated patch clamp technique was employed. To assess LES resting tone and relaxation, muscle strips were mounted in perfused organ baths.
RESULTS: (1) Electrophysiological recordings from isolated cells: (a) CM was more depolarized than SM (-39.7 ± 0.8mV vs -48.1 ± 1.6 mV, P < 0.001), and maximal outward current was similar (27.1 ± 1.5 pA/pF vs 25.7 ± 2.0 pA/pF, P > 0.05); (b) The NO donor sodium nitroprusside (SNP) increased outward currents only in CM (25.9 ± 1.9 to 46.7 ± 4.2 pA/pF, P < 0.001) but not SM (23.2 ± 3.1 to 27.0 ± 3.4 pA/pF, P > 0.05); (c) SNP added in the presence of the BKCa antagonist iberiotoxin (IbTX) produced no increase in the outward current in CM (17.0 ± 2.8 vs 13.7 ± 2.2, P > 0.05); and (d) L-NNA caused a small insignificant inhibition of outward K+ currents in both muscles; and (2) Muscle strip studies: (a) Blockade of the nerves with tetrodotoxin (TTX), or BKCa with IbTX had no significant effect on resting tone of either muscle; and (b) SNP reduced tone in both muscles, and was unaffected by the presence of TTX or IbTX.
CONCLUSION: Exogenous NO activates BKCa only in CM of the cat. However, as opposed to other species, exogenous NO-induced relaxation is predominantly by a non-BKCa mechanism, and endogenous NO has minimal effect on resting tone.
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Sims SM, Chrones T, Preiksaitis HG. Calcium sensitization in human esophageal muscle: role for RhoA kinase in maintenance of lower esophageal sphincter tone. J Pharmacol Exp Ther 2008; 327:178-86. [PMID: 18628484 DOI: 10.1124/jpet.108.140806] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
A rise in intracellular-free calcium ([Ca(2+)](i)) concentration is important for initiating contraction of smooth muscles, and Ca(2+) sensitization involving RhoA kinase can sustain tension. We previously found that [Ca(2+)](i) was comparable in cells from the esophageal body (EB) and lower esophageal sphincter (LES) muscles, despite the fact that the LES maintains resting tone. We hypothesized that Ca(2+) sensitization contributes to contraction in human esophageal muscle. Tension and [Ca(2+)](i) were measured simultaneously in intact human EB and LES muscles using the ratiometric Ca(2+)-sensitive dye fura-2. Spontaneous oscillations in EB muscle tension were associated with transient elevations of [Ca(2+)](i). Carbachol caused a large increase in tension, compared with spontaneous oscillations, although the rise of [Ca(2+)](i) was similar, suggesting Ca(2+) sensitization. The RhoA-kinase blockers (R)-(+)-trans-4-(1-aminoethyl)-N-(4-pyridyl) cyclohexanecarboxamide dihydrochloride monohydrate (Y-27632) and 1-(5-isoquinolinesulfonyl)-homopiperazine hydrochloride (HA-1077) reduced carbachol- and nerve-evoked contraction of the EB, accompanied by smaller reduction in the rise of [Ca(2+)](i). Protein kinase C inhibitors reduced force to a lesser extent. RhoA-kinase blockers caused concentration-dependent reduction of tension in spontaneously contracted LES muscles. Moreover, RhoA-kinase blockers reduced intrinsic nerve-evoked and carbachol-evoked contraction. However, there was no effect on nerve- or nitric oxide-mediated relaxation of LES. Ca(2+) sensitization mediated by the RhoA-kinase pathway has an important role in contraction of human EB muscles and LES tonic contraction, a feature not previously recognized.
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Affiliation(s)
- Stephen M Sims
- Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, The University of Western Ontario, London, Ontario, Canada N6A 5C1.
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18
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Abstract
Smooth muscle cells (SMC) make up the muscular portion of the gastrointestinal (GI) tract from the distal oesophagus to the internal anal sphincter. Coordinated contractions of these cells produce the motor patterns of GI motility. Considerable progress was made during the last 20 years to understand the basic mechanisms controlling excitation-contraction (E-C) coupling. The smooth muscle motor is now understood in great molecular detail, and much has been learned about the mechanisms that deliver and recover Ca2+ during contractions. The majority of Ca2+ that initiates contractions comes from the external solution and is supplied by voltage-dependent Ca2+ channels (VDCC). VDCC are regulated largely by the effects of K+ and non-selective cation conductances (NSCC) on cell membrane potential and excitability. Ca2+ entry is supplemented by release of Ca2+ from IP(3) receptor-operated stores and by mechanisms that alter the sensitivity of the contractile apparatus to changes in cytoplasmic Ca2+. Molecular studies of the regulation of smooth muscle have been complicated by the plasticity of SMC and difficulties in culturing these cells without dramatic phenotypic changes. Major questions remain to be resolved regarding the details of E-C coupling in human GI smooth muscles. New discoveries regarding molecular expression that give GI smooth muscle their unique properties, the phenotypic changes that occur in SMC in GI motor disorders, tissue engineering approaches to repair or replace defective muscular regions, and molecular manipulations of GI smooth muscles in animals models and in cell culture will be topics for exciting investigations in the future.
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Affiliation(s)
- K M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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19
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Kovac JR, Chrones T, Sims SM. Temporal and spatial dynamics underlying capacitative calcium entry in human colonic smooth muscle. Am J Physiol Gastrointest Liver Physiol 2008; 294:G88-98. [PMID: 17975132 DOI: 10.1152/ajpgi.00305.2007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Following smooth muscle excitation and contraction, depletion of intracellular Ca(2+) stores activates capacitative Ca(2+) entry (CCE) to replenish stores and sustain cytoplasmic Ca(2+) (Ca(2+)(i)) elevations. The objectives of the present study were to characterize CCE and the Ca(2+)(i) dynamics underlying human colonic smooth muscle contraction by using tension recordings, fluorescent Ca(2+)-indicator dyes, and patch-clamp electrophysiology. The neurotransmitter acetylcholine (ACh) contracted tissue strips and, in freshly isolated colonic smooth muscle cells (SMCs), caused elevation of Ca(2+)(i) as well as activation of nonselective cation currents. To deplete Ca(2+)(i) stores, the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitors thapsigargin and cyclopiazonic acid were added to a Ca(2+)-free bathing solution. Under these conditions, addition of extracellular Ca(2+) (3 mM) elicited increased tension that was inhibited by the cation channel blockers SKF-96365 (10 microM) and lanthanum (100 microM), suggestive of CCE. In a separate series of experiments on isolated SMCs, SERCA inhibition generated a gradual and sustained inward current. When combined with high-speed Ca(2+)-imaging techniques, the CCE-evoked rise of Ca(2+)(i) was associated with inward currents carrying Ca(2+) that were inhibited by SKF-96365. Regional specializations in Ca(2+) influx and handling during CCE were observed. Distinct "hotspot" regions of Ca(2+) rise and plateau were evident in 70% of cells, a feature not previously recognized in smooth muscle. We propose that store-operated Ca(2+) entry occurs in hotspots contributing to localized Ca(2+) elevations in human colonic smooth muscle.
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Affiliation(s)
- Jason R Kovac
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, ON N6A 5C1, Canada
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Regulation of basal tone, relaxation and contraction of the lower oesophageal sphincter. Relevance to drug discovery for oesophageal disorders. Br J Pharmacol 2007; 153:858-69. [PMID: 17994108 DOI: 10.1038/sj.bjp.0707572] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The lower oesophageal sphincter (LOS) is a specialized region of the oesophageal circular smooth muscle that allows the passage of a swallowed bolus to the stomach and prevents the reflux of gastric contents into the oesophagus. The anatomical arrangement of the LOS includes semicircular clasp fibres adjacent to the lesser gastric curvature and sling fibres following the greater gastric curvature. Such anatomical arrangement together with an asymmetric intrinsic innervation and distinct proportion of neurotransmitters in both regions produces an asymmetric pressure profile. The LOS tone is myogenic in origin and depends on smooth muscle properties that lead to opening of L-type Ca(2+) channels; however it can be modulated by enteric motor neurons, the parasympathetic and sympathetic extrinsic nervous system and several neurohumoral substances. Nitric oxide synthesized by neuronal NOS is the main inhibitory neurotransmitter involved in LOS relaxation. Different putative neurotransmitters have been proposed to play a role together with NO. So far, only ATP or related purines have shown to be co-transmitters with NO. Acetylcholine and tachykinins are involved in the LOS contraction acting through acetylcholine M(3) and tachykinin NK(2) receptors. Nitric oxide can also be involved in the regulation of LOS contraction. The understanding of the mechanisms that originate and modulate LOS tone, relaxation and contraction and the characterization of neurotransmitters and receptors involved in LOS function are important to develop new pharmacological tools to treat primary oesophageal motor disorders and gastro-oesophageal reflux disease.
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