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Wong TS, Li G, Li S, Gao W, Chen G, Gan S, Zhang M, Li H, Wu S, Du Y. G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders. Signal Transduct Target Ther 2023; 8:177. [PMID: 37137892 PMCID: PMC10154768 DOI: 10.1038/s41392-023-01427-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 02/17/2023] [Accepted: 03/30/2023] [Indexed: 05/05/2023] Open
Abstract
Neuropsychiatric disorders are multifactorial disorders with diverse aetiological factors. Identifying treatment targets is challenging because the diseases are resulting from heterogeneous biological, genetic, and environmental factors. Nevertheless, the increasing understanding of G protein-coupled receptor (GPCR) opens a new possibility in drug discovery. Harnessing our knowledge of molecular mechanisms and structural information of GPCRs will be advantageous for developing effective drugs. This review provides an overview of the role of GPCRs in various neurodegenerative and psychiatric diseases. Besides, we highlight the emerging opportunities of novel GPCR targets and address recent progress in GPCR drug development.
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Affiliation(s)
- Thian-Sze Wong
- Kobilka Institute of Innovative Drug Discovery, Shenzhen Key Laboratory of Steroid Drug Discovery and Development, School of Medicine, The Chinese University of Hong Kong, 518172, Shenzhen, Guangdong, China
- School of Medicine, Tsinghua University, 100084, Beijing, China
| | - Guangzhi Li
- Institute of Urology, The Affiliated Luohu Hospital of Shenzhen University, Shenzhen University, 518000, Shenzhen, Guangdong, China
| | - Shiliang Li
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 200237, Shanghai, China
- Innovation Center for AI and Drug Discovery, East China Normal University, 200062, Shanghai, China
| | - Wei Gao
- Kobilka Institute of Innovative Drug Discovery, Shenzhen Key Laboratory of Steroid Drug Discovery and Development, School of Medicine, The Chinese University of Hong Kong, 518172, Shenzhen, Guangdong, China
- Innovation Center for AI and Drug Discovery, East China Normal University, 200062, Shanghai, China
| | - Geng Chen
- Kobilka Institute of Innovative Drug Discovery, Shenzhen Key Laboratory of Steroid Drug Discovery and Development, School of Medicine, The Chinese University of Hong Kong, 518172, Shenzhen, Guangdong, China
| | - Shiyi Gan
- Kobilka Institute of Innovative Drug Discovery, Shenzhen Key Laboratory of Steroid Drug Discovery and Development, School of Medicine, The Chinese University of Hong Kong, 518172, Shenzhen, Guangdong, China
| | - Manzhan Zhang
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 200237, Shanghai, China
- Innovation Center for AI and Drug Discovery, East China Normal University, 200062, Shanghai, China
| | - Honglin Li
- Shanghai Key Laboratory of New Drug Design, School of Pharmacy, East China University of Science and Technology, 200237, Shanghai, China.
- Innovation Center for AI and Drug Discovery, East China Normal University, 200062, Shanghai, China.
| | - Song Wu
- Institute of Urology, The Affiliated Luohu Hospital of Shenzhen University, Shenzhen University, 518000, Shenzhen, Guangdong, China.
- Department of Urology, South China Hospital, Health Science Center, Shenzhen University, 518116, Shenzhen, Guangdong, China.
| | - Yang Du
- Kobilka Institute of Innovative Drug Discovery, Shenzhen Key Laboratory of Steroid Drug Discovery and Development, School of Medicine, The Chinese University of Hong Kong, 518172, Shenzhen, Guangdong, China.
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Bhattacharya D, Becker C, Readhead B, Goossens N, Novik J, Fiel MI, Cousens LP, Magnusson B, Backmark A, Hicks R, Dudley JT, Friedman SL. Repositioning of a novel GABA-B receptor agonist, AZD3355 (Lesogaberan), for the treatment of non-alcoholic steatohepatitis. Sci Rep 2021; 11:20827. [PMID: 34675338 PMCID: PMC8531016 DOI: 10.1038/s41598-021-99008-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Accepted: 09/14/2021] [Indexed: 01/02/2023] Open
Abstract
Non-alcoholic steatohepatitis (NASH) is a rising health challenge, with no approved drugs. We used a computational drug repositioning strategy to uncover a novel therapy for NASH, identifying a GABA-B receptor agonist, AZD3355 (Lesogaberan) previously evaluated as a therapy for esophageal reflux. AZD3355's potential efficacy in NASH was tested in human stellate cells, human precision cut liver slices (hPCLS), and in vivo in a well-validated murine model of NASH. In human stellate cells AZD3355 significantly downregulated profibrotic gene and protein expression. Transcriptomic analysis of these responses identified key regulatory nodes impacted by AZD3355, including Myc, as well as MAP and ERK kinases. In PCLS, AZD3355 down-regulated collagen1α1, αSMA and TNF-α mRNAs as well as secreted collagen1α1. In vivo, the drug significantly improved histology, profibrogenic gene expression, and tumor development, which was comparable to activity of obeticholic acid in a robust mouse model of NASH, but awaits further testing to determine its relative efficacy in patients. These data identify a well-tolerated clinical stage asset as a novel candidate therapy for human NASH through its hepatoprotective, anti-inflammatory and antifibrotic mechanisms of action. The approach validates computational methods to identify novel therapies in NASH in uncovering new pathways of disease development that can be rapidly translated into clinical trials.
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Affiliation(s)
- Dipankar Bhattacharya
- Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, Box 1123, 1425 Madison Ave. Room 1170, New York, NY, 10029, USA
| | - Christine Becker
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Division of Clinical Immunology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Benjamin Readhead
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Arizona State University-Banner Neurodegenerative Disease Research Center, Arizona, USA
| | - Nicolas Goossens
- Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, Box 1123, 1425 Madison Ave. Room 1170, New York, NY, 10029, USA
- Division of Gastroenterology, Geneva University Hospital, Geneva, Switzerland
| | - Jacqueline Novik
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Maria Isabel Fiel
- Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Leslie P Cousens
- Emerging Innovations, Discovery Sciences, R&D, AstraZeneca, Boston, MA, USA
| | - Björn Magnusson
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Anna Backmark
- Discovery Biology, Discovery Sciences, R&D, AstraZeneca, Gothenburg, Sweden
| | - Ryan Hicks
- BioPharmaceuticals R&D Cell Therapy, Research and Early Development, Cardiovascular, Renal and Metabolism (CVRM), BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Joel T Dudley
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Scott L Friedman
- Division of Liver Diseases, Icahn School of Medicine at Mount Sinai, Box 1123, 1425 Madison Ave. Room 1170, New York, NY, 10029, USA.
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3
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Zheng Z, Shang Y, Wang N, Liu X, Xin C, Yan X, Zhai Y, Yin J, Zhang J, Zhang Z. Current Advancement on the Dynamic Mechanism of Gastroesophageal Reflux Disease. Int J Biol Sci 2021; 17:4154-4164. [PMID: 34803489 PMCID: PMC8579455 DOI: 10.7150/ijbs.65066] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Accepted: 09/19/2021] [Indexed: 12/13/2022] Open
Abstract
Gastroesophageal reflux disease (GERD) is a common clinical disease associated with upper gastrointestinal motility disorders. Recently, with improvements in living standards and changes in lifestyle and dietary habits, the incidence of GERD has been increasing yearly. However, the mechanism of GERD has not been fully elucidated due to its complex pathogenesis, and this had led to unsatisfactory therapeutic outcomes. Currently, the occurrence and development of GERD involve multiple factors. Its pathogenesis is mainly thought to be related to factors, such as lower esophageal sphincter pressure, transient lower esophageal sphincter relaxation, crural diaphragmatic dysfunction, hiatus hernia, and impaired esophageal clearance. Therefore, explaining the pathogenesis of GERD more clearly and systematically, exploring potential and effective therapeutic targets, and choosing the best treatment methods have gradually become the focus of scholars' attention. Herein, we reviewed current advancements in the dynamic mechanism of GERD to better counsel patients on possible treatment options.
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Affiliation(s)
- Zhi Zheng
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
| | - Yuxi Shang
- Department of Hematology, Fuxing Hospital, Eighth Clinical Medical College, Capital Medical University, Beijing, China
| | - Ning Wang
- Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Xiaoye Liu
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
| | - Chenglin Xin
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
| | - Xiaosheng Yan
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
| | - Yuhao Zhai
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
| | - Jie Yin
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
| | - Jun Zhang
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
| | - Zhongtao Zhang
- Department of General Surgery, Beijing Friendship Hospital, Capital Medical University, Beijing, China
- Beijing Key Laboratory of Cancer Invasion and Metastasis Research, Beijing, China
- National Clinical Research Center for Digestive Diseases, Beijing, China
- Beijing Institute of Clinical Medicine, Beijing, China
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Vlachou S. A Brief History and the Significance of the GABA B Receptor. Curr Top Behav Neurosci 2021; 52:1-17. [PMID: 34595739 DOI: 10.1007/7854_2021_264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain. GABA type B (GABAB) receptors (GABABRs) are the only metabotropic G protein-coupled receptors for GABA and can be found distributed not only in the central nervous system, but also in the periphery. This chapter introduces important, fundamental knowledge related to GABABR function and the various potential therapeutic applications of the development of novel GABABR-active compounds, as documented through extensive studies presented in subsequent chapters of this Current Topic in Behavioral Neurosciences volume on the role of the neurobiology of GABABR function. The compounds that have received increased attention in the last few years compared to GABABR agonists and antagonists - the positive allosteric modulators - exhibit better pharmacological profiles and fewer side effects. As we continue to unveil the mystery of GABABRs at the molecular and cellular levels, we further understand the significance of these receptors. Future directions should aim for developing highly selective GABABR compounds for treating neuropsychiatric disorders and their symptomatology.
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Affiliation(s)
- Styliani Vlachou
- Neuropsychopharmacology Division, Behavioural Neuroscience Laboratory, School of Psychology, Faculty of Science and Health, Dublin City University, Dublin, Ireland.
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GABA B Receptor Chemistry and Pharmacology: Agonists, Antagonists, and Allosteric Modulators. Curr Top Behav Neurosci 2021; 52:81-118. [PMID: 34036555 DOI: 10.1007/7854_2021_232] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The GABAB receptors are metabotropic G protein-coupled receptors (GPCRs) that mediate the actions of the primary inhibitory neurotransmitter, γ-aminobutyric acid (GABA). In the CNS, GABA plays an important role in behavior, learning and memory, cognition, and stress. GABA is also located throughout the gastrointestinal (GI) tract and is involved in the autonomic control of the intestine and esophageal reflex. Consequently, dysregulated GABAB receptor signaling is associated with neurological, mental health, and gastrointestinal disorders; hence, these receptors have been identified as key therapeutic targets and are the focus of multiple drug discovery efforts for indications such as muscle spasticity disorders, schizophrenia, pain, addiction, and gastroesophageal reflex disease (GERD). Numerous agonists, antagonists, and allosteric modulators of the GABAB receptor have been described; however, Lioresal® (Baclofen; β-(4-chlorophenyl)-γ-aminobutyric acid) is the only FDA-approved drug that selectively targets GABAB receptors in clinical use; undesirable side effects, such as sedation, muscle weakness, fatigue, cognitive deficits, seizures, tolerance and potential for abuse, limit their therapeutic use. Here, we review GABAB receptor chemistry and pharmacology, presenting orthosteric agonists, antagonists, and positive and negative allosteric modulators, and highlight the therapeutic potential of targeting GABAB receptor modulation for the treatment of various CNS and peripheral disorders.
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Zhu Y, Xu X, Zhang M, Si F, Sun H, Yu L, Qiu Z. Pressure and length of the lower esophageal sphincter as predictive indicators of therapeutic efficacy of baclofen for refractory gastroesophageal reflux-induced chronic cough. Respir Med 2021; 183:106439. [PMID: 33962111 DOI: 10.1016/j.rmed.2021.106439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 04/22/2021] [Accepted: 04/24/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Therapeutic efficacy of baclofen is suboptimal in the treatment of refractory gastroesophageal reflux-induced chronic cough (GERC). The purpose of the study is to identify its therapeutic predictors in a prospective clinical study. METHODS 138 patients with suspected refractory GERC were treated with baclofen. Before the therapy, all the patients underwent esophageal manometry and multichannel intraluminal impedance-pH monitoring to establish the diagnosis. After the efficacy of baclofen was evaluated, a stepwise logistic regression analysis was performed to identify the therapeutic predictors of baclofen and to establish a regression prediction model. RESULTS The overall response rate of baclofen treatment was 52.2% (72/138). The lower esophageal sphincter pressure (LESP) (odds ratio (OR) = 0.592, P = 0.000) and lower esophageal sphincter length (LESL) (OR = 0.144, P = 0.008) were independent predictors of baclofen efficacy. The optimal cut-off point to predict baclofen efficacy for LESP was 11.00 mmHg, with a sensitivity of 83.7% and specificity of 79.1% while that for LESL was 2.35 cm, with a sensitivity of 81.6% and specificity of 72.1%. The highest predictive specificity (90.7%) was achieved when both LESP and LESL were jointly used. CONCLUSIONS LESP and LESL may be used to screen the patients with refractory GERC suitable for baclofen therapy and help improve the therapeutic precision. CLINICAL TRIAL REGISTRATION ChiCTR- ONC-13003123.
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Affiliation(s)
- Yiqing Zhu
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Road, Shanghai, 200065, China
| | - Xianghuai Xu
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Road, Shanghai, 200065, China
| | - Mengru Zhang
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Road, Shanghai, 200065, China
| | - Fengli Si
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Road, Shanghai, 200065, China
| | - Huihui Sun
- Department of Gastroenterology, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Road, Shanghai, 200065, China
| | - Li Yu
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Road, Shanghai, 200065, China
| | - Zhongmin Qiu
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, Tongji University School of Medicine, No. 389 Xincun Road, Shanghai, 200065, China.
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Abdou MM. Synopsis of recent synthetic methods and biological applications of phosphinic acid derivatives. Tetrahedron 2020. [DOI: 10.1016/j.tet.2020.131251] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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8
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Martínez-Campos Z, Pastor N, Pineda-Urbina K, Gómez-Sandoval Z, Fernández-Zertuche M, Razo-Hernández RS. In silico structure-based design of GABA B receptor agonists using a combination of docking and QSAR. Chem Biol Drug Des 2019; 94:1782-1798. [PMID: 31207116 DOI: 10.1111/cbdd.13580] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 05/29/2019] [Accepted: 06/02/2019] [Indexed: 12/27/2022]
Abstract
The study of γ-aminobutyric acid B receptor (GABAB ) activation is of great interest for several brain disorders. The search of new GABAB receptor agonists has been carried out by many research groups. As a result, Baclofen has become the prototypical GABAB receptor agonist. However, several attempts have been made to modify its structure to generate derivatives with improved activity. In this work, we carried out a theoretical and computational study for a wide range of GABAB receptor agonists reported in the literature. Molecular docking and QSAR techniques were combined by using the interaction energies of the agonists with the key residues of GABAB receptor, as molecular descriptors for the QSAR construction. The resulting mathematical model suggests that the activity of GABAB receptor agonists is influenced by three factors: their shape and molecular size (PW5 and PJI2), their constitutional features (ELUMO and T(N…O)) and the energy interaction with GABAB receptor (ETRP278 ). This model was validated by the QUIK, REDUNDANCY and OVERFITTING rules, and its predicted ability was tasted by the QLOO , QASYM , R 0 2 and r m 2 rules. Finally, six new compounds are proposed (35-40) with high potential to be used as GABAB receptor agonists.
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Affiliation(s)
- Zuleyma Martínez-Campos
- Instituto de Investigación en Ciencias Básicas y Aplicadas, Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México
| | - Nina Pastor
- Instituto de Investigación en Ciencias Básicas y Aplicadas, Centro de Investigación en Dinámica Celular, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México
| | | | | | - Mario Fernández-Zertuche
- Instituto de Investigación en Ciencias Básicas y Aplicadas, Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México
| | - Rodrigo Said Razo-Hernández
- Instituto de Investigación en Ciencias Básicas y Aplicadas, Centro de Investigación en Dinámica Celular, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, México
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Iftikhar H, Batool S, Deep A, Narasimhan B, Sharma PC, Malhotra M. In silico analysis of the inhibitory activities of GABA derivatives on 4-aminobutyrate transaminase. ARAB J CHEM 2017. [DOI: 10.1016/j.arabjc.2013.03.007] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Scarpellini E, Boecxstaens V, Broers C, Vos R, Pauwels A, Tack J. Effect of baclofen on gastric acid pocket in subjects with gastroesophageal reflux disease symptoms. Dis Esophagus 2016; 29:1054-1063. [PMID: 26541138 DOI: 10.1111/dote.12443] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Postprandial gastroesophageal reflux (PGER) in the distal esophagus (DE) is associated with a gastric juice 'acid pocket' (AP). Baclofen reduces AP extension into the DE in healthy volunteers, in part through increased lower esophageal sphincter (LES) pressure. We aimed to verify whether baclofen also affects postprandial AP location and extent in gastroesophageal reflux disease (GERD) patients. Thirteen treatment-naive heartburn-prevalent GERD patients underwent two AP studies, after pretreatment with baclofen 40 mg or placebo 30 minutes preprandially. We performed pH-probe stepwise pull-throughs (PT) (1 cm/min, LES -10 to +5 cm) before and every 30 minutes from 30 minutes before up to 150 minutes after a test meal. After the meal, both after placebo and baclofen, gastric pH significantly dropped at 30, 60, 90 minutes postprandially (P: nadir pHs of 3.9 ± 0.6, 2.3 ± 0.6, 2.1 ± 0.4; B: nadir pHs of 2.5 ± 0.4, 2.8 ± 0.4, 2.5 ± 0.3; all P < 0.05). After placebo, LES pressure decreased at 60, 90 and 120 minutes postprandially (32.7 ± 6.1 vs. 24.5 ± 3.1, 27.3 ± 5.9, 27.3 ± 6.0 mmHg; analysis of variance [ANOVA], P = 0.037), but this was prevented by baclofen (25.4 ± 3.4 vs. 29.4 ± 2, 32.2 ± 1.4, 35.5 ± 1.7 mmHg, ANOVA, P = not significant (NS)). Baclofen did not significantly decrease the postprandial AP extent above the LES but prevented the postprandial increase in transient lower esophageal sphincter relaxations (TLESRs) (preprandial vs. postprandial, placebo: 1.1 ± 0.3 vs. 3.7 ± 0.7, P < 0.05; baclofen: 1.4 ± 0.4 vs. 2 ± 0.5, P = NS). In GERD patients, baclofen significantly increases postprandial LES pressure, prevents the increase TLESRs but, unlike in healthy volunteers, does not affect AP extension into the DE.
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Affiliation(s)
- E Scarpellini
- TARGID (Translational Research Centre for Gastrointestinal Disorders), University of Leuven, Leuven, Belgium
| | - V Boecxstaens
- TARGID (Translational Research Centre for Gastrointestinal Disorders), University of Leuven, Leuven, Belgium
| | - C Broers
- TARGID (Translational Research Centre for Gastrointestinal Disorders), University of Leuven, Leuven, Belgium
| | - R Vos
- TARGID (Translational Research Centre for Gastrointestinal Disorders), University of Leuven, Leuven, Belgium
| | - A Pauwels
- TARGID (Translational Research Centre for Gastrointestinal Disorders), University of Leuven, Leuven, Belgium
| | - J Tack
- TARGID (Translational Research Centre for Gastrointestinal Disorders), University of Leuven, Leuven, Belgium
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11
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Scarpellini E, Boecxstaens V, Farré R, Bisschops R, Dewulf D, Gasbarrini A, Pauwels A, Blondeau K, Tack J. Effect of baclofen on the acid pocket at the gastroesophageal junction. Dis Esophagus 2015; 28:488-95. [PMID: 24758736 DOI: 10.1111/dote.12224] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Previous studies established that a pocket of highly acidic gastric juice is present postprandially at the gastroesophageal junction in man. The GABA-B agonist baclofen inhibits postprandial reflux events through its effects on the lower esophageal sphincter (LES). The aim of the current study was to investigate whether baclofen would affect the location and the extent of the postprandial acid pocket in healthy volunteers. Twelve healthy volunteers underwent acid pocket studies on two different occasions, at least 1 week apart. LES position was determined preprandially with pull-through manometry. Dual pH electrode and manometry probe stepwise pull-through (1 cm/minute, LES-10 to +5 cm) was performed at 30-minute intervals for 150 minutes, with administration of placebo or baclofen 40 mg after the first and ingestion of a liquid meal after the second pull-through. After placebo, a significant drop in intragastric gastric pH was present at the gastroesophageal junction after the meal, reflecting the acid pocket, and this was associated with a drop in LES pressure. Baclofen did not affect the presence of the acid pocket, but prevented the postprandial drop in LES pressure, and the extent of the acid pocket above the upper margin of the manometrically located LES was significantly decreased by baclofen (1.6 ± 0.7 vs. 0.3 ± 0.4 cm at 60 minutes, 2.2 ± 0.6 vs. 0.2 ± 0.6 at 90 minutes, and 1.5 ± 0.5 vs. 0.7 ± 0.7 cm at 120 minutes, all P < 0.05). Baclofen does not alter the intragastric acid pocket, but limits its extension into the distal esophagus, probably through an increase in postprandial LES pressure.
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Affiliation(s)
- E Scarpellini
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - V Boecxstaens
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - R Farré
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - R Bisschops
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - D Dewulf
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - A Gasbarrini
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - A Pauwels
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - K Blondeau
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
| | - J Tack
- Department of Internal Medicine, Division of Gastroenterology, University Hospital Gasthuisberg, Catholic University of Leuven, Leuven, Belgium
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Auteri M, Zizzo MG, Serio R. GABA and GABA receptors in the gastrointestinal tract: from motility to inflammation. Pharmacol Res 2015; 93:11-21. [PMID: 25526825 DOI: 10.1016/j.phrs.2014.12.001] [Citation(s) in RCA: 153] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 11/28/2014] [Accepted: 12/01/2014] [Indexed: 12/16/2022]
Abstract
Although an extensive body of literature confirmed γ-aminobutyric acid (GABA) as mediator within the enteric nervous system (ENS) controlling gastrointestinal (GI) function, the true significance of GABAergic signalling in the gut is still a matter of debate. GABAergic cells in the bowel include neuronal and endocrine-like cells, suggesting GABA as modulator of both motor and secretory GI activity. GABA effects in the GI tract depend on the activation of ionotropic GABAA and GABAC receptors and metabotropic GABAB receptors, resulting in a potential noteworthy regulation of both the excitatory and inhibitory signalling in the ENS. However, the preservation of GABAergic signalling in the gut could not be limited to the maintenance of physiologic intestinal activity. Indeed, a series of interesting studies have suggested a potential key role of GABA in the promising field of neuroimmune interaction, being involved in the modulation of immune cell activity associated with different systemic and enteric inflammatory conditions. Given the urgency of novel therapeutic strategies against chronic immunity-related pathologies, i.e. multiple sclerosis and Inflammatory Bowel Disease, an in-depth comprehension of the enteric GABAergic system in health and disease could provide the basis for new clinical application of nerve-driven immunity. Hence, in the attempt to drive novel researches addressing both the physiological and pathological importance of the GABAergic signalling in the gut, we summarized current evidence on GABA and GABA receptor function in the different parts of the GI tract, with particular focus on the potential involvement in the modulation of GI motility and inflammation.
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Affiliation(s)
- Michelangelo Auteri
- Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), Laboratorio di Fisiologia generale, Università di Palermo, Viale delle Scienze, I-90128 Palermo, Italy
| | - Maria Grazia Zizzo
- Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), Laboratorio di Fisiologia generale, Università di Palermo, Viale delle Scienze, I-90128 Palermo, Italy
| | - Rosa Serio
- Dipartimento di Scienze e Tecnologie Biologiche, Chimiche e Farmaceutiche (STEBICEF), Laboratorio di Fisiologia generale, Università di Palermo, Viale delle Scienze, I-90128 Palermo, Italy.
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Curcic J, Schwizer A, Kaufman E, Forras-Kaufman Z, Banerjee S, Roy S, Pal A, Hebbard GS, Boesiger P, Fried M, Steingoetter A, Schwizer W, Fox M. Effects of baclofen on the functional anatomy of the oesophago-gastric junction and proximal stomach in healthy volunteers and patients with GERD assessed by magnetic resonance imaging and high-resolution manometry: a randomised controlled double-blind study. Aliment Pharmacol Ther 2014; 40:1230-40. [PMID: 25230154 DOI: 10.1111/apt.12956] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 05/23/2014] [Accepted: 08/25/2014] [Indexed: 12/14/2022]
Abstract
BACKGROUND The mechanism of reflux protection may involve a 'flap valve' at the oesophago-gastric junction (OGJ). AIM To assess the effects of baclofen, a gamma-aminobutyric acid receptor type-B (GABA-B) agonist known to suppress reflux events, on the 'functional anatomy' of the OGJ and proximal stomach after a large test meal. METHODS Twelve healthy volunteers (HVs) and 12 patients with gastro-oesophageal reflux disease (GERD); with erosive oesophagitis or pathological oesophageal acid exposure completed a randomised, double-blind, cross-over study. On 2 test days participants received 40-mg baclofen or placebo before ingestion of a large test meal. OGJ structure and function were assessed by high-resolution manometry (HRM) and magnetic resonance imaging (MRI) using validated methods. Measurements of the oesophago-gastric angle were derived from three-dimensional models reconstructed from anatomic MRI images. Cine-MRI and HRM identified postprandial reflux events. Mixed model analysis and Wilcoxon rank signed tests assessed differences between participant groups and treatment conditions. RESULTS In both HVs and GERD patients, baclofen reduced the frequency of postprandial reflux events. The oesophago-gastric insertion angle in GERD patients was reduced (-4.1 ± 1.8, P = 0.025), but was unchanged in healthy controls. In both study groups, baclofen augmented lower oesophageal sphincter (LES) pressure (HVs: +7.3 ± 1.8 mmHg, P < 0.0001, GERD: +4.50 ± 1.49 mmHg, P < 0.003) and increased LES length (HVs: +0.48 ± 0.11 cm, P < 0.0003, GERD: +0.35 ± 0.06 cm, P < 0.0001). CONCLUSIONS Baclofen inhibits transient LES relaxations and augments LES pressure and length. Additionally, baclofen has effects on the 'functional anatomy' of the OGJ and proximal stomach in GERD patients, which may suppress reflux by means of a 'flap valve' mechanism.
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Affiliation(s)
- J Curcic
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland; Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland
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Andrade FJC, de Almeida ER, dos Santos MTBR, Soares-Filho E, Lopes JB, Veras e Silva RC. Quality of life of patients undergoing surgery by videolaparoscopy for GERD treatment. ABCD-ARQUIVOS BRASILEIROS DE CIRURGIA DIGESTIVA 2013; 25:154-60. [PMID: 23411803 DOI: 10.1590/s0102-67202012000300004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2012] [Accepted: 06/08/2012] [Indexed: 02/08/2023]
Abstract
BACKGROUND Gastroesophageal reflux disease is a chronic disease of high prevalence in Western countries, with negative effects on quality of life. Surgery is indicated for patients with intolerance to continuous medication, prolonged treatment or control, or in complicated forms of the disease. AIM To evaluate the quality of life of patients undergoing surgery by videolaparoscopy for gastroesophageal reflux disease treatment. METHODS Sample comprised 43 patients of both genders (mean age = 51.4 years). For quality of life evaluation was made using the questionnaire Gastroesophageal Reflux Disease Health Related Quality of Life, translated and validated into Portuguese. Data were analyzed by Epi Info version 3.5.1, using Duncan test and Pearson's correlation coefficient, with 5% for null hypothesis (p ≤ 0.05). RESULTS Over 50% of participants showed good quality of life (scores <5 of the questionnaire), more than 90% indicated satisfaction with their health. A significant positive correlation between most variables related to heartburn and the time after surgery was observed (p ≤ 0.05). CONCLUSION Patients presented good quality of life and high level of satisfaction with their postoperative condition.
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Sharma N, Anderson SHC. The relevance of transient lower oesophageal sphincter relaxations in the pathophysiology and treatment of GORD. Frontline Gastroenterol 2013; 4:171-174. [PMID: 28839723 PMCID: PMC5369794 DOI: 10.1136/flgastro-2012-100261] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Revised: 11/19/2012] [Accepted: 11/23/2012] [Indexed: 02/04/2023] Open
Abstract
Gastro-oesophageal reflux disease (GORD) is associated with the passage of gastric contents into the oesophagus resulting in potential oesophageal damage and impaired quality of life. GORD is a frequently encountered problem in today's population, with 25% of people in western populations reporting such symptoms at least once a month. Proton pump inhibitors (PPI) are the drug of choice, with surgery being employed in refractory cases. Although acid suppression is often effective, some patients remain symptomatic despite maximal PPI therapy. By delving into the mechanisms of the disease, it is clear that transient lower oesophageal sphincter relaxations are a key component of its pathophysiology. Research has demonstrated various therapeutic targets for reducing the frequency of such relaxations through GABA and glutamate modulation, for instance. This review highlights such modulations and hopes to explore these mechanisms and therapeutic targets in an area that will no doubt see a change in its pharmacological management in the near future.
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Affiliation(s)
- Neel Sharma
- Li Ka Shing Faculty of Medicine, Institute of Medical and Health Sciences Education, The University of Hong Kong, Hong Kong, China
| | - Simon H C Anderson
- Department of Gastroenterology, Guy's and St Thomas’ Hospital, London, UK
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Brozmanová M, Mazúrová L, Tatár M, Kollárik M. Evaluation of the effect of GABA(B) agonists on the vagal nodose C-fibers in the esophagus. Physiol Res 2013; 62:285-95. [PMID: 23489191 DOI: 10.33549/physiolres.932429] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Clinical studies showed that GABA(B) receptor agonists improve symptoms in patients with gastroesophageal reflux disease. One proposed mechanism of this effect is direct inhibition of the gastroesophageal vagal tension mechanosensors by GABA(B) agonists leading to reduction of reflux. In addition to tension mechanosensors, the vagal nodose ganglion supplies the esophagus with nociceptive C-fibers that likely contribute to impairment of esophageal reflex regulation in diseases. We hypothesized that GABA(B) agonists inhibit mechanically-induced activation of vagal esophageal nodose C-fibers in baseline and/or in sensitized state induced by inflammatory mediators. Ex vivo extracellular recordings were made from the esophageal nodose C-fibers in the isolated vagally-innervated guinea pig esophagus. We found that the selective GABA(B) agonist baclofen (100-300 microM) did not inhibit activation of esophageal nodose C-fibers evoked by esophageal distention (10-60 mmHg). The mechanical response of esophageal nodose C-fibers can be sensitized by different pathways including the stimulation of the histamine H(1) receptor and the stimulation the adenosine A(2A) receptor. Baclofen failed to inhibit mechanical sensitization of esophageal nodose C-fibers induced by histamine (100 microM) or the selective adenosine A(2A) receptor agonist CGS21680 (3 nM). Our data suggest that the direct mechanical inhibition of nodose C-fibers in the esophagus is unlikely to contribute to beneficial effects of GABA(B) agonists in patients with esophageal diseases.
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Affiliation(s)
- M Brozmanová
- Department of Pathophysiology, Jessenius Faculty of Medicine, Comenius University, Martin, Slovakia.
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Canning BJ, Mori N, Lehmann A. Antitussive effects of the peripherally restricted GABAB receptor agonist lesogaberan in guinea pigs: comparison to baclofen and other GABAB receptor-selective agonists. COUGH 2012; 8:7. [PMID: 23025757 PMCID: PMC3520872 DOI: 10.1186/1745-9974-8-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 09/07/2012] [Indexed: 12/17/2022]
Abstract
UNLABELLED BACKGROUND Gastroesophageal reflux disease (GERD) is a common cause of chronic cough. Both acid and nonacid reflux is thought to play a role in the initiation of coughing and cough hypersensitivity. The GABAB receptor agonist lesogaberan was developed as a peripherally restricted anti-reflux therapy that reduces the frequency of transient lower esophageal sphincter relaxations (TLESR; the major cause of reflux) in animals and in patients with GERD. GABAB receptor agonists have also been shown to possess antitussive effects in patients and in animals independent of their effects on TLESR, suggesting that lesogaberan may be a promising treatment for chronic cough. METHODS We have assessed the direct antitussive effects of lesogaberan (AZD3355). The effects of other GABAB receptor agonists were also determined. Coughing was evoked in awake guinea pigs using aerosol challenges with citric acid. RESULTS Lesogaberan dose-dependently inhibited citric acid evoked coughing in guinea pigs. Comparable effects of the GABAB receptor agonists baclofen and 3-aminopropylphosphinic acid (3-APPiA) on cough were also observed. Baclofen produced obvious signs of sedation and respiratory depression. By contrast, both lesogaberan and 3-APPiA (both inactivated centrally by GABA transporters) were devoid of sedative effects and did not alter respiratory rate. CONCLUSIONS Together, the data suggest that lesogaberan and related GABAB receptor agonists may hold promise as safe and effective antitussive agents largely devoid of CNS side effects.
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Affiliation(s)
- Brendan J Canning
- Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, Maryland, 21224, USA.
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Altan E, Blondeau K, Pauwels A, Farré R, Tack J. Evolving pharmacological approaches in gastroesophageal reflux disease. Expert Opin Emerg Drugs 2012; 17:347-59. [PMID: 22834684 DOI: 10.1517/14728214.2012.702753] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
INTRODUCTION Proton pump inhibitors (PPIs) have considerably improved quality of life in patients with gastroesophageal reflux disease (GERD). However, many patients remain symptomatic despite standard PPI therapy. AREAS COVERED This review focuses on evolving therapeutic strategies related to the pathophysiological processes of GERD and insufficient response to PPIs. Several clinical trials evaluated new PPI formulations and newer types of acid-suppressive drugs. These studies have evaluated traditional end points in GERD, but have not shown clinical superiority to current PPIs. Novel therapeutic strategies targeting underlying mechanisms of GERD, such as transient lower esophageal sphincter relaxations (TLESRs) and esophageal hypersensitivity, are being developed for add-on therapy to PPIs. Prokinetic drugs may also have some potential in the add-on treatment of GERD with insufficient response to PPIs. Add-on studies are hampered by insufficient information on optimal patient selection and lack of established end points. EXPERT OPINION Newer drugs for symptomatic control in GERD have largely focused on improved acid suppression, without evidence of clinical superiority. Drugs targeting esophageal motility and sensitivity to be used as add-onc therapy in PPI insufficient responders have not reached Phase III trials to date, due to difficulties with patient selection, tolerability and end points.
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Affiliation(s)
- Ege Altan
- University of Leuven, Translational Research Center for Gastrointestinal Disorders, Herestraat 49, B-3000, Leuven, Belgium
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Jirholt J, Åsling B, Hammond P, Davidson G, Knutsson M, Walentinsson A, Jensen JM, Lehmann A, Agreus L, Lagerström-Fermer M. 4-aminobutyrate aminotransferase (ABAT): genetic and pharmacological evidence for an involvement in gastro esophageal reflux disease. PLoS One 2011; 6:e19095. [PMID: 21552517 PMCID: PMC3084265 DOI: 10.1371/journal.pone.0019095] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 03/28/2011] [Indexed: 01/06/2023] Open
Abstract
Gastro-esophageal reflux disease (GERD) is partly caused by genetic factors. The underlying susceptibility genes are currently unknown, with the exception of COL3A1. We used three independent GERD patient cohorts to identify GERD susceptibility genes. Thirty-six families, demonstrating dominant transmission of GERD were subjected to whole genome microsatellite genotyping and linkage analysis. Five linked regions were identified. Two families shared a linked region (LOD 3.9 and 2.0) on chromosome 16. We used two additional independent GERD patient cohorts, one consisting of 219 trios (affected child with parents) and the other an adult GERD case control cohort consisting of 256 cases and 485 controls, to validate individual genes in the linked region through association analysis. Sixty six single nucleotide polymorphism (SNP) markers distributed over the nine genes present in the linked region were genotyped in the independent GERD trio cohort. Transmission disequilibrium test analysis followed by multiple testing adjustments revealed a significant genetic association for one SNP located in an intron of the gene 4-aminobutyrate aminotransferase (ABAT) (P(adj) = 0.027). This association did not replicate in the adult case-control cohort, possibly due to the differences in ethnicity between the cohorts. Finally, using the selective ABAT inhibitor vigabatrin (γ-vinyl GABA) in a dog study, we were able to show a reduction of transient lower esophageal sphincter relaxations (TLESRs) by 57.3 ± 11.4 % (p = 0.007) and the reflux events from 3.1 ± 0.4 to 0.8 ± 0.4 (p = 0.007). Our results demonstrate the direct involvement of ABAT in pathways affecting lower esophageal sphincter (LES) control and identifies ABAT as a genetic risk factor for GERD.
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Affiliation(s)
| | | | - Paul Hammond
- Gastroenterology Unit, Women's & Children's Hospital, North Adelaide, Australia
| | - Geoffrey Davidson
- Gastroenterology Unit, Women's & Children's Hospital, North Adelaide, Australia
| | | | | | | | | | - Lars Agreus
- Center for Family and Community Medicine, Karolinska Institutet, Huddinge, Sweden
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Padgett CL, Slesinger PA. GABAB receptor coupling to G-proteins and ion channels. ADVANCES IN PHARMACOLOGY 2010; 58:123-47. [PMID: 20655481 DOI: 10.1016/s1054-3589(10)58006-2] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
GABA(B) receptors have been found to play a key role in regulating membrane excitability and synaptic transmission in the brain. The GABA(B) receptor is a G-protein coupled receptor (GPCR) that associates with a subset of G-proteins (pertussis toxin sensitive Gi/o family), that in turn regulate specific ion channels and trigger cAMP cascades. In this review, we describe the relationships between the GABA(B) receptor, its effectors and associated proteins that mediate GABA(B) receptor function within the brain. We discuss a unique feature of the GABA(B) receptor, the requirement for heterodimerization to produce functional receptors, as well as an increasing body of evidence that suggests GABA(B) receptors comprise a macromolecular signaling heterocomplex, critical for efficient targeting and function of the receptors. Within this complex, GABA(B) receptors associate specifically with Gi/o G-proteins that regulate voltage-gated Ca(2+) (Ca(V)) channels, G-protein activated inwardly rectifying K(+) (GIRK) channels, and adenylyl cyclase. Numerous studies have revealed that lipid rafts, scaffold proteins, targeting motifs in the receptor, and regulators of G-protein signaling (RGS) proteins also contribute to the function of GABA(B) receptors and affect cellular processes such as receptor trafficking and activity-dependent desensitization. This complex regulation of GABA(B) receptors in the brain may provide opportunities for new ways to regulate GABA-dependent inhibition in normal and diseased states of the nervous system.
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Affiliation(s)
- Claire L Padgett
- Peptide Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA, USA
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Hyland NP, Cryan JF. A Gut Feeling about GABA: Focus on GABA(B) Receptors. Front Pharmacol 2010; 1:124. [PMID: 21833169 PMCID: PMC3153004 DOI: 10.3389/fphar.2010.00124] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2010] [Accepted: 09/07/2010] [Indexed: 12/15/2022] Open
Abstract
γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the body and hence GABA-mediated neurotransmission regulates many physiological functions, including those in the gastrointestinal (GI) tract. GABA is located throughout the GI tract and is found in enteric nerves as well as in endocrine-like cells, implicating GABA as both a neurotransmitter and an endocrine mediator influencing GI function. GABA mediates its effects via GABA receptors which are either ionotropic GABA(A) or metabotropic GABA(B). The latter which respond to the agonist baclofen have been least characterized, however accumulating data suggest that they play a key role in GI function in health and disease. Like GABA, GABA(B) receptors have been detected throughout the gut of several species in the enteric nervous system, muscle, epithelial layers as well as on endocrine-like cells. Such widespread distribution of this metabotropic GABA receptor is consistent with its significant modulatory role over intestinal motility, gastric emptying, gastric acid secretion, transient lower esophageal sphincter relaxation and visceral sensation of painful colonic stimuli. More intriguing findings, the mechanisms underlying which have yet to be determined, suggest GABA(B) receptors inhibit GI carcinogenesis and tumor growth. Therefore, the diversity of GI functions regulated by GABA(B) receptors makes it a potentially useful target in the treatment of several GI disorders. In light of the development of novel compounds such as peripherally acting GABA(B) receptor agonists, positive allosteric modulators of the GABA(B) receptor and GABA producing enteric bacteria, we review and summarize current knowledge on the function of GABA(B) receptors within the GI tract.
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Affiliation(s)
- Niall P Hyland
- Alimentary Pharmabiotic Centre and Department of Pharmacology and Therapeutics, University College Cork Cork, Ireland
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Brändén L, Fredriksson A, Harring E, Jensen J, Lehmann A. The novel, peripherally restricted GABAB receptor agonist lesogaberan (AZD3355) inhibits acid reflux and reduces esophageal acid exposure as measured with 24-h pHmetry in dogs. Eur J Pharmacol 2010; 634:138-41. [PMID: 20176012 DOI: 10.1016/j.ejphar.2010.02.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 02/03/2010] [Accepted: 02/12/2010] [Indexed: 01/01/2023]
Abstract
While patients with symptoms of gastroesophageal reflux disease generally respond well to proton pump inhibitors, 20-30% continue to experience troublesome symptoms. In such cases, agents that target transient lower esophageal sphincter (LES) relaxation may be useful as add-on therapy to proton pump inhibitors. The GABAB receptor agonist baclofen inhibits transient LES relaxation but it is not an ideal agent due to central nervous system activity. Lesogaberan (AZD3355) is a peripherally restricted GABAB receptor agonist with limited central nervous system activity that inhibits transient LES relaxation in dogs. In the present study, the comparative effects of lesogaberan (7 micromol/kg) and baclofen (2.8 micromol/kg) on reflux were studied in dogs using 24-h pHmetry. Drugs (or vehicle control) were administered orally prior to the first meal of the day, and the number of reflux episodes (pH<4 for > or = 5 s) and acid exposure time were computed for the 24-h monitoring period. The mean (S.E.M.) number of reflux episodes/24 h was 4.6 (0.4) and 6.4 (0.6) for lesogaberan and baclofen, respectively, versus 10.7 (0.5) for control (P<0.0001 for both). Acid exposure time was 51.2 (4.5) min for control versus 23.6 (3.8) min for lesogaberan (P<0.0001) and 35.4 (6.5) min with baclofen (P=0.05). It is concluded that lesogaberan significantly reduces acid reflux in dogs, with comparable efficacy to baclofen.
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Froestl W. Chemistry and Pharmacology of GABAB Receptor Ligands. GABABRECEPTOR PHARMACOLOGY - A TRIBUTE TO NORMAN BOWERY 2010; 58:19-62. [DOI: 10.1016/s1054-3589(10)58002-5] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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GABAB receptor agonism as a novel therapeutic modality in the treatment of gastroesophageal reflux disease. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2010; 58:287-313. [PMID: 20655487 DOI: 10.1016/s1054-3589(10)58012-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Defined pharmacologically by its insensitivity to the GABA(A) antagonist bicuculline and sensitivity to the GABA analogue baclofen, the G protein-linked gamma-aminobutyric acid type B (GABA(B)) receptor couples to adenylyl cyclase, voltage-gated calcium channels, and inwardly-rectifying potassium channels. On the basis of a wealth of preclinical data in conjunction with early clinical observations that baclofen improves symptoms of gastroesophageal reflux disease (GERD), the GABA(B) receptor has been proposed as a therapeutic target for a number of diseases including GERD. Subsequently, there has been a significant effort to develop a peripherally-restricted GABA(B) agonist that is devoid of the central nervous system side effects that are observed with baclofen. In this article we review the in vitro and in vivo pharmacology of the peripherally-restricted GABA(B) receptor agonists and the preclinical and clinical development of lesogaberan (AZD3355, (R)-(3-amino-2-fluoropropyl) phosphinic acid), a potent and predominately peripherally-restricted GABA(B) receptor agonist with a preclinical therapeutic window superior to baclofen.
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Gastroesophageal reflux disease: medical or surgical treatment? Gastroenterol Res Pract 2009; 2009:371580. [PMID: 20069112 PMCID: PMC2804043 DOI: 10.1155/2009/371580] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2009] [Revised: 10/14/2009] [Accepted: 10/26/2009] [Indexed: 12/14/2022] Open
Abstract
Background. Gastroesophageal reflux disease is a common condition with increasing prevalence worldwide. The disease encompasses a broad spectrum of clinical symptoms and disorders from simple heartburn without esophagitis to erosive esophagitis with severe complications, such as esophageal strictures and intestinal metaplasia. Diagnosis is based mainly on ambulatory esophageal pH testing and endoscopy. There has been a long-standing debate about the best treatment approach for this troublesome disease. Methods and Results. Medical treatment with PPIs has an excellent efficacy in reversing the symptoms of GERD, but they should be taken for life, and long-term side effects do exist. However, patients who desire a permanent cure and have severe complications or cannot tolerate long-term treatment with PPIs are candidates for surgical treatment. Laparoscopic antireflux surgery achieves a significant symptom control, increased patient satisfaction, and complete withdrawal of antireflux medications, in the majority of patients. Conclusion. Surgical treatment should be reserved mainly for young patients seeking permanent results. However, the choice of the treatment schedule should be individualized for every patient. It is up to the patient, the physician and the surgeon to decide the best treatment option for individual cases.
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Both GABAA and GABAB receptors mediate vagal inhibition in nucleus tractus solitarii neurones in anaesthetized rats. Auton Neurosci 2009; 152:75-83. [PMID: 19926533 DOI: 10.1016/j.autneu.2009.10.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2009] [Revised: 10/22/2009] [Accepted: 10/23/2009] [Indexed: 01/31/2023]
Abstract
GABA receptors in the nucleus tractus solitarius (NTS) are known to play an important role in the mediation/modulation of various cardiovascular/respiratory functions. Vagal afferent activation of these neurones usually evokes an initial excitation followed by a long lasting inhibition. The present study examines the role of GABA(B) as well as GABA(A) receptors in the mediation of this inhibition in anaesthetized rats, using CGP 35348 and bicuculline, respective antagonists at these receptors, applied topically or by ionophoresis. Bicuculline delayed the onset and reduced the duration of this inhibition. The duration of this inhibition was further and significantly decreased when CGP 35348 was administered along with bicuculline but the delay in onset was unaffected. CGP 35348 application alone, had no effect on the vagal afferent-evoked inhibition. From intracellular recordings the early and late components of this inhibition were found to have reversal potentials close to E(Cl) and E(K), respectively. Therefore it is concluded that this inhibition is mediated by both GABA(A) and GABA(B) receptors, although GABA(B) mediated inhibition can only be unmasked when GABA(A) receptors are blocked.
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Abstract
The last 50 years have seen a transformation in the understanding and treatment of reflux disease. The development and wide use of flexible endoscopy and progressively more sophisticated approaches to measurement of pathophysiological factors have been major drivers of advances. The recognition and progressive elucidation of the mechanical events that comprise the transient lower esophageal sphincter relaxation and how they lead to reflux provide a novel and firm foundation for tailoring therapies that act directly to reduce occurrence of reflux episodes, either surgically or pharmacologically. Novel GABA(B) agonist drugs have been shown to inhibit transient relaxations and are currently being evaluated in clinical trials on patients with reflux disease. Better understanding has extended to recognition of the extraordinarily high prevalence of reflux disease and of the ability of proton pump inhibitor drugs to deliver major benefits to a high proportion of patients with reflux disease. The life of the Gastroenterological Society of Australia has spanned the period of these major advances. A large number of the members of the Society and their associates have contributed substantially to these advances.
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Affiliation(s)
- John Dent
- Department of Gastroenterology & Hepatology, Royal Adelaide Hospital & University of Adelaide, Adelaide, South Australia, Australia.
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Lehmann A, Antonsson M, Holmberg AA, Blackshaw LA, Brändén L, Bräuner-Osborne H, Christiansen B, Dent J, Elebring T, Jacobson BM, Jensen J, Mattsson JP, Nilsson K, Oja SS, Page AJ, Saransaari P, von Unge S. (R)-(3-amino-2-fluoropropyl) phosphinic acid (AZD3355), a novel GABAB receptor agonist, inhibits transient lower esophageal sphincter relaxation through a peripheral mode of action. J Pharmacol Exp Ther 2009; 331:504-12. [PMID: 19648470 DOI: 10.1124/jpet.109.153593] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Gastroesophageal reflux disease (GERD) affects >10% of the Western population. Conventionally, GERD is treated by reducing gastric acid secretion, which is effective in most patients but inadequate in a significant minority. We describe a new therapeutic approach for GERD, based on inhibition of transient lower esophageal sphincter relaxation (TLESR) with a proposed peripherally acting GABA(B) receptor agonist, (R)-(3-amino-2-fluoropropyl)phosphinic acid (AZD3355). AZD3355 potently stimulated recombinant human GABA(B) receptors and inhibited TLESR in dogs, with a biphasic dose-response curve. In mice, AZD3355 produced considerably less central side effects than the prototypical GABA(B) receptor agonist baclofen but evoked hypothermia at very high doses (blocked by a GABA(B) receptor antagonist and absent in GABA(B)-/- mice). AZD3355 and baclofen differed markedly in their distribution in rat brain; AZD3355, but not baclofen, was concentrated in circumventricular organs as a result of active uptake (shown by avid intracellular sequestration) and related to binding of AZD3355 to native GABA transporters in rat cerebrocortical membranes. AZD3355 was also shown to be transported by all four recombinant human GABA transporters. AR-H061719 [(R/S)-(3-amino-2-fluoropropyl)phosphinic acid], (the racemate of AZD3355) inhibited the response of ferret mechanoreceptors to gastric distension, further supporting its peripheral site of action on TLESR. In summary, AZD3355 probably inhibits TLESR through stimulation of peripheral GABA(B) receptors and may offer a potential new approach to treatment of GERD.
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