1
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Mena S, Cruikshank A, Best J, Nijhout HF, Reed MC, Hashemi P. Modulation of serotonin transporter expression by escitalopram under inflammation. Commun Biol 2024; 7:710. [PMID: 38851804 DOI: 10.1038/s42003-024-06240-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 04/24/2024] [Indexed: 06/10/2024] Open
Abstract
Selective serotonin reuptake inhibitors (SSRIs) are widely used for depression based on the monoamine deficiency hypothesis. However, the clinical use of these agents is controversial, in part because of their variable clinical efficacy and in part because of their delayed onset of action. Because of the complexities involved in replicating human disease and clinical dosing in animal models, the scientific community has not reached a consensus on the reasons for these phenomena. In this work, we create a theoretical hippocampal model incorporating escitalopram's pharmacokinetics, pharmacodynamics (competitive and non-competitive inhibition, and serotonin transporter (SERT) internalization), inflammation, and receptor dynamics. With this model, we simulate chronic oral escitalopram in mice showing that days to weeks are needed for serotonin levels to reach steady-state. We show escitalopram's chemical efficacy is diminished under inflammation. Our model thus offers mechanisms for how chronic escitalopram affects brain serotonin, emphasizing the importance of optimized dose and time for future antidepressant discoveries.
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Affiliation(s)
- Sergio Mena
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK
| | | | - Janet Best
- Department of Mathematics, The Ohio State University, Columbus, OH, USA
| | - H F Nijhout
- Department of Biology, Duke University, Durham, NC, USA
| | - Michael C Reed
- Department of Mathematics, Duke University, Durham, NC, USA
| | - Parastoo Hashemi
- Department of Bioengineering, Imperial College London, London, SW7 2AZ, UK.
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2
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Witt CE, Mena S, Holmes J, Hersey M, Buchanan AM, Parke B, Saylor R, Honan LE, Berger SN, Lumbreras S, Nijhout FH, Reed MC, Best J, Fadel J, Schloss P, Lau T, Hashemi P. Serotonin is a common thread linking different classes of antidepressants. Cell Chem Biol 2023; 30:1557-1570.e6. [PMID: 37992715 DOI: 10.1016/j.chembiol.2023.10.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 09/07/2023] [Accepted: 10/12/2023] [Indexed: 11/24/2023]
Abstract
Depression pathology remains elusive. The monoamine hypothesis has placed much focus on serotonin, but due to the variable clinical efficacy of monoamine reuptake inhibitors, the community is looking for alternative therapies such as ketamine (neurogenesis theory of antidepressant action). There is evidence that different classes of antidepressants may affect serotonin levels; a notion we test here. We measure hippocampal serotonin in mice with voltammetry and study the effects of acute challenges of escitalopram, fluoxetine, reboxetine, and ketamine. We find that pseudo-equivalent doses of these drugs similarly raise ambient serotonin levels, despite their differing pharmacodynamics because of differences in Uptake 1 and 2, rapid SERT trafficking, and modulation of serotonin by histamine. These antidepressants have different pharmacodynamics but have strikingly similar effects on extracellular serotonin. Our findings suggest that serotonin is a common thread that links clinically effective antidepressants, synergizing different theories of depression (synaptic plasticity, neurogenesis, and the monoamine hypothesis).
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Affiliation(s)
- Colby E Witt
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA
| | - Sergio Mena
- Department of Bioengineering, Imperial College London, London, UK
| | - Jordan Holmes
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA
| | - Melinda Hersey
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA; Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, USA
| | - Anna Marie Buchanan
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA; Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, USA
| | - Brenna Parke
- Department of Bioengineering, Imperial College London, London, UK
| | - Rachel Saylor
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA
| | - Lauren E Honan
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA
| | - Shane N Berger
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA
| | - Sara Lumbreras
- Department of Psychiatry and Psychotherapy, Biochemical Laboratory, Central Institute of Mental Health, Medical Faculty, Mannheim, Heidelberg University, Mannheim, Germany
| | | | - Michael C Reed
- Department of Mathematics, Duke University, Durham, NC, USA
| | - Janet Best
- Department of Mathematics, The Ohio State University, Columbus, OH, USA
| | - James Fadel
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, Columbia, SC, USA
| | - Patrick Schloss
- Department of Psychiatry and Psychotherapy, Biochemical Laboratory, Central Institute of Mental Health, Medical Faculty, Mannheim, Heidelberg University, Mannheim, Germany
| | - Thorsten Lau
- Department of Psychiatry and Psychotherapy, Biochemical Laboratory, Central Institute of Mental Health, Medical Faculty, Mannheim, Heidelberg University, Mannheim, Germany; Department of Neuroanatomy, Mannheim Centre for Translational Neuroscience, Medical Faculty Mannheim, Heidelberg University, Mannheim, Germany
| | - Parastoo Hashemi
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, USA; Department of Bioengineering, Imperial College London, London, UK.
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3
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Xue W, Fu T, Deng S, Yang F, Yang J, Zhu F. Molecular Mechanism for the Allosteric Inhibition of the Human Serotonin Transporter by Antidepressant Escitalopram. ACS Chem Neurosci 2022; 13:340-351. [PMID: 35041375 DOI: 10.1021/acschemneuro.1c00694] [Citation(s) in RCA: 67] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Human serotine transporter (hSERT) is one of the most influential drug targets, and its allosteric modulators (e.g., escitalopram) have emerged to be the next-generation medication for psychiatric disorders. However, the molecular mechanism underlying the allosteric modulation of hSERT is still elusive. Here, the simulation strategies of conventional (cMD) and steered (SMD) molecular dynamics were applied to investigate this molecular mechanism from distinct perspectives. First, cMD simulations revealed that escitalopram's binding to hSERT's allosteric site simultaneously enhanced its binding to the orthosteric site. Then, SMD simulation identified that the occupation of hSERT's allosteric site by escitalopram could also block its dissociation from the orthosteric site. Finally, by comparing the simulated structures of two hSERT-escitalopram complexes with and without allosteric modulation, a new conformational coupling between an extracellular (Arg104-Glu494) and an intracellular (Lys490-Glu494) salt bridge was identified. In summary, this study explored the mechanism underlying the allosteric modulation of hSERT by collectively applying two MD simulation strategies, which could facilitate our understanding of the allosteric modulations of not only hSERT but also other clinically important therapeutic targets.
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Affiliation(s)
- Weiwei Xue
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Innovative Drug Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
- Central Nervous System Drug Key Laboratory of Sichuan Province, Luzhou 646000, China
| | - Tingting Fu
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Innovative Drug Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
| | - Shengzhe Deng
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Innovative Drug Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
| | - Fengyuan Yang
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Innovative Drug Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
| | - Jingyi Yang
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Innovative Drug Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
| | - Feng Zhu
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, Innovative Drug Research Center, School of Pharmaceutical Sciences, Chongqing University, Chongqing 401331, China
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou 310058, China
- Innovation Institute for Artificial Intelligence in Medicine of Zhejiang University, Alibaba-Zhejiang University Joint Research Center of Future Digital Healthcare, Hangzhou 330110, China
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4
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Silva S, Bicker J, Fonseca C, Ferreira NR, Vitorino C, Alves G, Falcão A, Fortuna A. Encapsulated Escitalopram and Paroxetine Intranasal Co-Administration: In Vitro/In Vivo Evaluation. Front Pharmacol 2021; 12:751321. [PMID: 34925013 PMCID: PMC8675330 DOI: 10.3389/fphar.2021.751321] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Accepted: 11/05/2021] [Indexed: 01/16/2023] Open
Abstract
Depression is a common mental disorder. Its treatment with selective serotonin reuptake inhibitors (SSRIs) is effective only in a fraction of patients, and pharmacoresistance is increasing steadily. Intranasal (IN) drug delivery to the brain stands out as a promising strategy to improve current therapeutic approaches by operating as a shuttle to overcome the blood–brain barrier. This work aimed to simultaneously administer escitalopram and paroxetine by IN route to mice. For this purpose, three nanostructured lipid carriers (NLC1, NLC2, and BorNLC) and one nanoemulsion (NE) were tested for drug loading. After their characterization, investigation of their impact on nasal cell viability and SSRI permeability assays were performed, using a human nasal RPMI 2650 cell line in air–liquid interface. In vitro assays demonstrated that NLCs, including borneol (BorNLC), significantly increased escitalopram permeability (p < 0.01) and paroxetine recovery values (p < 0.05) in relation to the other formulations and non-encapsulated drugs. IN and intravenous (IV) pharmacokinetic studies performed in vivo with a single dose of 2.38 mg/kg demonstrated similar results for escitalopram brain-to-plasma ratios. IN administrations delayed escitalopram peak concentrations in the brain for 15–60 min and no direct nose-to-brain delivery was detected. However, encapsulation with BorNLC considerably decreased escitalopram exposure in the lungs (124 μg min/g) compared with free escitalopram by IN (168 μg min/g) and IV (321 μg min/g) routes. Surprisingly, BorNLC IN instillation increased concentration levels of paroxetine in the brain by five times and accelerated brain drug delivery. Once again, lung exposure was considerably lower with BorNLC (AUCt = 0.433 μg min/g) than that with IV administration (AUCt = 1.01 μg min/g) and non-encapsulated IN formulation (AUCt = 2.82 μg min/g). Direct nose-to-brain delivery was observed for paroxetine IN administration with a direct transport percentage (DTP) of 56.9%. If encapsulated, it increases to 74.2%. These results clearly emphasize that nose-to-brain delivery and lung exposure depend on the formulation and on the characteristics of the drug under investigation. NLCs seem to be an advantageous strategy for nose-to-brain delivery of lipophilic molecules, since they reduce systemic and lung exposure, thereby decreasing adverse effects. For hydrophilic compounds, NLCs are particularly important to decrease lung exposure after IN administration.
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Affiliation(s)
- Soraia Silva
- Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.,CIBIT-Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, Coimbra, Portugal
| | - Joana Bicker
- Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.,CIBIT-Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, Coimbra, Portugal
| | - Carla Fonseca
- Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.,CIBIT-Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, Coimbra, Portugal
| | - Nuno R Ferreira
- Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.,CIBIT-Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, Coimbra, Portugal
| | - Carla Vitorino
- Laboratory of Technology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.,Coimbra Chemistry Center, Department of Chemistry, University of Coimbra, Coimbra, Portugal
| | - Gilberto Alves
- CICS-UBI-Health Sciences Research Centre, University of Beira Interior, Covilhã, Portugal
| | - Amílcar Falcão
- Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.,CIBIT-Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, Coimbra, Portugal
| | - Ana Fortuna
- Laboratory of Pharmacology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.,CIBIT-Coimbra Institute for Biomedical Imaging and Translational Research, University of Coimbra, Coimbra, Portugal
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5
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Perez-Caballero L, Soto-Montenegro ML, Desco M, Mico JA, Berrocoso E. Sustained escitalopram administration affects glucose metabolism in the rat brain. Eur Neuropsychopharmacol 2021; 51:1-6. [PMID: 34022746 DOI: 10.1016/j.euroneuro.2021.04.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 04/12/2021] [Accepted: 04/20/2021] [Indexed: 11/18/2022]
Abstract
Escitalopram is a selective serotonin reuptake inhibitor (SSRIs) antidepressant, drug that is currently used as first-line agents for the treatment of depression and it is also used in the treatment of other psychiatric disorders. The main goal of this study was to identify which brain areas are affected by escitalopram administration. This study was carried out on male Wistar rats that received escitalopram daily over 14 days and that were studied by 2-deoxy-2[18F]fluoro-D-glucose ([18F]FDG)-PET on the last day of treatment. Computed tomography (CT) images were acquired immediately before each PET scan and the main effects of drug administration were elucidated by Statistical Parametric Mapping. The results obtained indicated that repeated exposure to escitalopram increased metabolic activity in the retrosplenial and posterior cingulate cortices, while it decreased such activity in the ventral hippocampus, cerebellum, brainstem and midbrain regions, including the raphe nuclei and ventral tegmental area. Therefore, repeated exposure to escitalopram alters the activity of several brain areas closely related to the serotonergic system, and previously identified as key regions in the antidepressant effect induced by SSRIs. Furthermore, some of the changes found, such as the dampened metabolism in the ventral tegmental area, are similar to changes that have been described after treating with other fast-acting antidepressant approaches.
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Affiliation(s)
- L Perez-Caballero
- Neuropsychopharmacology & Psychobiology Research Group, Area of Psychobiology, Department of Psychology, University of Cádiz, Cádiz, Spain; CIBER for Mental Health (CIBERSAM), Madrid, Spain
| | - M L Soto-Montenegro
- CIBER for Mental Health (CIBERSAM), Madrid, Spain; Unidad de Medicina y Cirugía Experimental, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain
| | - M Desco
- CIBER for Mental Health (CIBERSAM), Madrid, Spain; Unidad de Medicina y Cirugía Experimental, Instituto de Investigación Sanitaria Gregorio Marañón, Madrid, Spain; Department of Bioengineering and Aerospace Engineering, Universidad Carlos III de Madrid, Leganés, Spain; Centro Nacional de Investigaciones Cardiovasculares, CNIC, Madrid, Spain
| | - J A Mico
- CIBER for Mental Health (CIBERSAM), Madrid, Spain; Neuropsychopharmacology & Psychobiology Research Group, Department of Neuroscience, Pharmacology and Psychiatry, University of Cádiz, Cádiz, Spain
| | - E Berrocoso
- Neuropsychopharmacology & Psychobiology Research Group, Area of Psychobiology, Department of Psychology, University of Cádiz, Cádiz, Spain; CIBER for Mental Health (CIBERSAM), Madrid, Spain.
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6
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Eap CB, Gründer G, Baumann P, Ansermot N, Conca A, Corruble E, Crettol S, Dahl ML, de Leon J, Greiner C, Howes O, Kim E, Lanzenberger R, Meyer JH, Moessner R, Mulder H, Müller DJ, Reis M, Riederer P, Ruhe HG, Spigset O, Spina E, Stegman B, Steimer W, Stingl J, Suzen S, Uchida H, Unterecker S, Vandenberghe F, Hiemke C. Tools for optimising pharmacotherapy in psychiatry (therapeutic drug monitoring, molecular brain imaging and pharmacogenetic tests): focus on antidepressants. World J Biol Psychiatry 2021; 22:561-628. [PMID: 33977870 DOI: 10.1080/15622975.2021.1878427] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Objectives: More than 40 drugs are available to treat affective disorders. Individual selection of the optimal drug and dose is required to attain the highest possible efficacy and acceptable tolerability for every patient.Methods: This review, which includes more than 500 articles selected by 30 experts, combines relevant knowledge on studies investigating the pharmacokinetics, pharmacodynamics and pharmacogenetics of 33 antidepressant drugs and of 4 drugs approved for augmentation in cases of insufficient response to antidepressant monotherapy. Such studies typically measure drug concentrations in blood (i.e. therapeutic drug monitoring) and genotype relevant genetic polymorphisms of enzymes, transporters or receptors involved in drug metabolism or mechanism of action. Imaging studies, primarily positron emission tomography that relates drug concentrations in blood and radioligand binding, are considered to quantify target structure occupancy by the antidepressant drugs in vivo. Results: Evidence is given that in vivo imaging, therapeutic drug monitoring and genotyping and/or phenotyping of drug metabolising enzymes should be an integral part in the development of any new antidepressant drug.Conclusions: To guide antidepressant drug therapy in everyday practice, there are multiple indications such as uncertain adherence, polypharmacy, nonresponse and/or adverse reactions under therapeutically recommended doses, where therapeutic drug monitoring and cytochrome P450 genotyping and/or phenotyping should be applied as valid tools of precision medicine.
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Affiliation(s)
- C B Eap
- Unit of Pharmacogenetics and Clinical Psychopharmacology, Center for Psychiatric Neurosciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,Center for Research and Innovation in Clinical Pharmaceutical Sciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,School of Pharmaceutical Sciences, University of Geneva, Geneva, Switzerland.,Institute of Pharmaceutical Sciences of Western Switzerland, University of Geneva, Geneva, Switzerland.,Institute of Pharmaceutical Sciences of Western Switzerland, University of Lausanne, Switzerland, Geneva, Switzerland
| | - G Gründer
- Department of Molecular Neuroimaging, Central Institute of Mental Health, Medical Faculty Mannheim, University of Heidelberg, Mannheim, Germany
| | - P Baumann
- Department of Psychiatry, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - N Ansermot
- Unit of Pharmacogenetics and Clinical Psychopharmacology, Center for Psychiatric Neurosciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - A Conca
- Department of Psychiatry, Health Service District Bolzano, Bolzano, Italy.,Department of Child and Adolescent Psychiatry, South Tyrolean Regional Health Service, Bolzano, Italy
| | - E Corruble
- INSERM CESP, Team ≪MOODS≫, Service Hospitalo-Universitaire de Psychiatrie, Universite Paris Saclay, Le Kremlin Bicetre, France.,Service Hospitalo-Universitaire de Psychiatrie, Hôpital Bicêtre, Assistance Publique Hôpitaux de Paris, Le Kremlin Bicêtre, France
| | - S Crettol
- Unit of Pharmacogenetics and Clinical Psychopharmacology, Center for Psychiatric Neurosciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - M L Dahl
- Division of Clinical Pharmacology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - J de Leon
- Eastern State Hospital, University of Kentucky Mental Health Research Center, Lexington, KY, USA
| | - C Greiner
- Bundesinstitut für Arzneimittel und Medizinprodukte, Bonn, Germany
| | - O Howes
- King's College London and MRC London Institute of Medical Sciences (LMS)-Imperial College, London, UK
| | - E Kim
- Department of Brain and Cognitive Sciences, Seoul National University College of Natural Sciences, Seoul, South Korea.,Department of Psychiatry, Seoul National University College of Medicine, Seoul, South Korea
| | - R Lanzenberger
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Vienna, Austria
| | - J H Meyer
- Campbell Family Mental Health Research Institute, CAMH and Department of Psychiatry, University of Toronto, Toronto, Canada
| | - R Moessner
- Department of Psychiatry and Psychotherapy, University of Tübingen, Tübingen, Germany
| | - H Mulder
- Department of Clinical Pharmacy, Wilhelmina Hospital Assen, Assen, The Netherlands.,GGZ Drenthe Mental Health Services Drenthe, Assen, The Netherlands.,Department of Pharmacotherapy, Epidemiology and Economics, Department of Pharmacy and Pharmaceutical Sciences, University of Groningen, Groningen, The Netherlands.,Department of Psychiatry, Interdisciplinary Centre for Psychopathology and Emotion Regulation, University of Groningen, Groningen, The Netherlands
| | - D J Müller
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, ON, Canada.,Department of Psychiatry, University of Toronto, Toronto, ON, Canada.,Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada
| | - M Reis
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden.,Clinical Chemistry and Pharmacology, Skåne University Hospital, Lund, Sweden
| | - P Riederer
- Center of Mental Health, Clinic and Policlinic for Psychiatry, Psychosomatics and Psychotherapy, University Hospital Würzburg, Würzburg, Germany.,Department of Psychiatry, University of Southern Denmark Odense, Odense, Denmark
| | - H G Ruhe
- Department of Psychiatry, Radboudumc, Nijmegen, the Netherlands.,Donders Institute for Brain, Cognition and Behavior, Radboud University, Nijmegen, Netherlands
| | - O Spigset
- Department of Clinical Pharmacology, St. Olav University Hospital, Trondheim, Norway.,Department of Clinical and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - E Spina
- Department of Clinical and Experimental Medicine, University of Messina, Messina, Italy
| | - B Stegman
- Institut für Pharmazie der Universität Regensburg, Regensburg, Germany
| | - W Steimer
- Institute for Clinical Chemistry and Pathobiochemistry, Technical University of Munich, Munich, Germany
| | - J Stingl
- Institute for Clinical Pharmacology, University Hospital of RWTH Aachen, Germany
| | - S Suzen
- Department of Toxicology, Faculty of Pharmacy, Ankara University, Ankara, Turkey
| | - H Uchida
- Department of Neuropsychiatry, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
| | - S Unterecker
- Department of Psychiatry, Psychosomatics and Psychotherapy, University Hospital of Würzburg, Würzburg, Germany
| | - F Vandenberghe
- Unit of Pharmacogenetics and Clinical Psychopharmacology, Center for Psychiatric Neurosciences, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - C Hiemke
- Department of Psychiatry and Psychotherapy, University Medical Center Mainz, Mainz, Germany
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7
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The mechanism of a high-affinity allosteric inhibitor of the serotonin transporter. Nat Commun 2020; 11:1491. [PMID: 32198394 PMCID: PMC7083837 DOI: 10.1038/s41467-020-15292-y] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 02/24/2020] [Indexed: 11/08/2022] Open
Abstract
The serotonin transporter (SERT) terminates serotonin signaling by rapid presynaptic reuptake. SERT activity is modulated by antidepressants, e.g., S-citalopram and imipramine, to alleviate symptoms of depression and anxiety. SERT crystal structures reveal two S-citalopram binding pockets in the central binding (S1) site and the extracellular vestibule (S2 site). In this study, our combined in vitro and in silico analysis indicates that the bound S-citalopram or imipramine in S1 is allosterically coupled to the ligand binding to S2 through altering protein conformations. Remarkably, SERT inhibitor Lu AF60097, the first high-affinity S2-ligand reported and characterized here, allosterically couples the ligand binding to S1 through a similar mechanism. The SERT inhibition by Lu AF60097 is demonstrated by the potentiated imipramine binding and increased hippocampal serotonin level in rats. Together, we reveal a S1-S2 coupling mechanism that will facilitate rational design of high-affinity SERT allosteric inhibitors.
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8
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Fitzgerald PJ, Watson BO. In vivo electrophysiological recordings of the effects of antidepressant drugs. Exp Brain Res 2019; 237:1593-1614. [PMID: 31079238 PMCID: PMC6584243 DOI: 10.1007/s00221-019-05556-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Accepted: 05/06/2019] [Indexed: 12/11/2022]
Abstract
Antidepressant drugs are a standard biological treatment for various neuropsychiatric disorders, yet relatively little is known about their electrophysiologic and synaptic effects on mood systems that set moment-to-moment emotional tone. In vivo electrical recording of local field potentials (LFPs) and single neuron spiking has been crucial for elucidating important details of neural processing and control in many other systems, and yet electrical approaches have not been broadly applied to the actions of antidepressants on mood-related circuits. Here we review the literature encompassing electrophysiologic effects of antidepressants in animals, including studies that examine older drugs, and extending to more recently synthesized novel compounds, as well as rapidly acting antidepressants. The existing studies on neuromodulator-based drugs have focused on recording in the brainstem nuclei, with much less known about their effects on prefrontal or sensory cortex. Studies on neuromodulatory drugs have moreover focused on single unit firing patterns with less emphasis on LFPs, whereas the rapidly acting antidepressant literature shows the opposite trend. In a synthesis of this information, we hypothesize that all classes of antidepressants could have common final effects on limbic circuitry. Whereas NMDA receptor blockade may induce a high powered gamma oscillatory state via direct and fast alteration of glutamatergic systems in mood-related circuits, neuromodulatory antidepressants may induce similar effects over slower timescales, corresponding with the timecourse of response in patients, while resetting synaptic excitatory versus inhibitory signaling to a normal level. Thus, gamma signaling may provide a biomarker (or “neural readout”) of the therapeutic effects of all classes of antidepressants.
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Affiliation(s)
- Paul J Fitzgerald
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, 48109-5720, USA.
| | - Brendon O Watson
- Department of Psychiatry, University of Michigan, Ann Arbor, MI, 48109-5720, USA.
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9
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Abstract
This study retrospectively investigated the effectiveness of paroxetine for the treatment of poststroke depression (PSD).Seventy patient cases with PSD were included in this study, and were assigned to an intervention group and a control group equally. All patients received routine treatment in both groups. Additionally, patients in the intervention group underwent paroxetine, while patients in the control group received psychotherapy for a total of 8 weeks intervention. The primary outcomes included depression, measured by Hamilton depression rating scale (HAMD); and anxiety, measured by Hamilton Anxiety Rating Scale (HAMA). The secondary outcomes consisted of neurological impairment, measured by Scandinavian Stroke Scale (SSS), and activities of daily living, measured by Barthel index (BI), as well as the adverse events. All outcomes were assessed before and after 8-week treatment.After 8-week treatments, patients in the intervention group did not show greater effectiveness in depression, measured by HAMD (P = .11), and anxiety, assessed by HAMA (P = .13), as well as the neurological impairment, evaluated by SSS (P = .24), and activities of daily, performed by BI (P = .19), compared with patients in the control group. In addition, no significant differences regarding adverse events were found between the 2 groups.The results of this study indicated that paroxetine may not bring promising effectiveness for patients with PSD. Future studies are still needed to warrant the results of this study.
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Affiliation(s)
- Chen Ma
- Department of Cerebrovascular Treatment Center, Fifth Center Hospital of Tianjin
| | - Ping Li
- Department of Neurology, Affiliated Hospital of Logistics University of People's Armed Police Force, Tianjin, China
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10
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Behavioural Phenotyping of APPswe/PS1δE9 Mice: Age-Rrelated Changes and Effect of Long-Term Paroxetine Treatment. PLoS One 2016; 11:e0165144. [PMID: 27814403 PMCID: PMC5096719 DOI: 10.1371/journal.pone.0165144] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 10/09/2016] [Indexed: 12/20/2022] Open
Abstract
Alzheimer’s disease (AD) is a devastating illness characterized by a progressive loss of cognitive, social, and emotional functions, including memory impairments and more global cognitive deficits. Clinical-epidemiological evidence suggests that neuropsychiatric symptoms precede the onset of cognitive symptoms both in humans with early and late onset AD. The behavioural profile promoted by the AD pathology is believed to associate with degeneration of the serotonergic system. Using the APPswe/PS1δE9 model of AD-like pathology starting with 9 months old mice, we characterised long term non-cognitive behavioural changes measured at 9, 12, 15, and 18 months of age and applied principal component analysis on data obtained from open field, elevated plus maze, and social interaction tests. Long-term treatment with the selective serotonin reuptake inhibitor (SSRI) paroxetine was applied to assess the role of 5-HT on the behavioural profile; duration of treatment was 9 months, initiated when mice were 9 months of age. Treatment with paroxetine delays the decline in locomotion, in exploration and risk assessment behaviour, found in the APP/PS1 mice. APP/PS1 mice also exhibit low social activity and less aggressiveness, both of which are not affected by treatment with paroxetine. The APP/PS1 behavioural phenotype, demonstrated in this study, only begins to manifest itself from 12 months of age. Our results indicate that treatment with SSRI might ameliorate some of the behavioural deficits found in aged APP/PS1 mice.
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Matthäus F, Haddjeri N, Sánchez C, Martí Y, Bahri S, Rovera R, Schloss P, Lau T. The allosteric citalopram binding site differentially interferes with neuronal firing rate and SERT trafficking in serotonergic neurons. Eur Neuropsychopharmacol 2016; 26:1806-1817. [PMID: 27665061 DOI: 10.1016/j.euroneuro.2016.09.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 07/10/2016] [Accepted: 09/01/2016] [Indexed: 10/21/2022]
Abstract
Citalopram is a clinically applied selective serotonin re-uptake inhibitor for antidepressant pharmacotherapy. It consists of two enantiomers, S-citalopram (escitalopram) and R-citalopram, of which escitalopram exerts the antidepressant therapeutic effect and has been shown to be one of the most efficient antidepressants, while R-citalopram antagonizes escitalopram via an unknown molecular mechanism that may depend on binding to a low-affinity allosteric binding site of the serotonin transporter. However, the precise mechanism of antidepressant regulation of the serotonin transporter by citalopram enantiomers still remains elusive. Here we investigate escitalopram׳s acute effect on (1) serotonergic neuronal firing in transgenic mice that express the human serotonin transporter without and with a mutation that disables the allosteric binding site, and (2) regulation of the serotonin transporter׳s cell surface localization in stem cell-derived serotonergic neurons. Our results demonstrate that escitalopram inhibited neuronal firing less potently in the mouse line featuring a mutation that abolishes the function of the allosteric binding site and induced serotonin transporter internalization independently of the allosteric binding site mechanism. Furthermore, citalopram enantiomers dose-dependently induced serotonin transporter internalization. In conclusion, this study provides new insight into antidepressant effects exerted by citalopram enantiomers in presence and absence of a functional allosteric binding site.
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Affiliation(s)
- Friederike Matthäus
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Department Psychiatry and Psychotherapy, Biochemical Laboratory, Mannheim, Germany
| | - Nasser Haddjeri
- Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, 69500 Bron, France
| | - Connie Sánchez
- Sourcing and Scientific Excellence at Lundbeck Research USA, Inc., Paramus, NJ, USA
| | - Yasmina Martí
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Department Psychiatry and Psychotherapy, Biochemical Laboratory, Mannheim, Germany
| | - Senda Bahri
- Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, 69500 Bron, France
| | - Renaud Rovera
- Univ Lyon, Université Claude Bernard Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, 69500 Bron, France
| | - Patrick Schloss
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Department Psychiatry and Psychotherapy, Biochemical Laboratory, Mannheim, Germany
| | - Thorsten Lau
- Central Institute of Mental Health, Medical Faculty Mannheim, Heidelberg University, Department Psychiatry and Psychotherapy, Biochemical Laboratory, Mannheim, Germany.
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Capillary electrophoresis hyphenated with UV-native-laser induced fluorescence detection (CE/UV-native-LIF). Electrophoresis 2016; 38:135-149. [DOI: 10.1002/elps.201600248] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 07/11/2016] [Accepted: 07/12/2016] [Indexed: 01/01/2023]
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Mnie-Filali O, Lau T, Matthaeus F, Abrial E, Delcourte S, El Mansari M, Pershon A, Schloss P, Sánchez C, Haddjeri N. Protein Kinases Alter the Allosteric Modulation of the Serotonin Transporter In Vivo and In Vitro. CNS Neurosci Ther 2016; 22:691-9. [PMID: 27171685 DOI: 10.1111/cns.12562] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 04/14/2016] [Accepted: 04/17/2016] [Indexed: 01/17/2023] Open
Abstract
AIM Studies using S- and R-enantiomers of the SSRI citalopram have shown that R-citalopram exerts an antagonistic effect on the efficacy of the antidepressant S-citalopram (escitalopram) through an interaction at an allosteric modulator site on the serotonin transporter (SERT). Here, we show that protein kinase signaling systems are involved in the allosteric modulation of the SERT in vivo and in vitro. METHODS We assessed the effects of nonspecific protein kinase inhibitor staurosporine in the action of escitalopram and/or R-citalopram using electrophysiological and behavioral assays in rats and cell surface SERT expression measures in serotoninergic cells. RESULTS Acute administration of R-citalopram counteracted the escitalopram-induced suppression of the serotonin (5-HT) neuronal firing activity and increase of the head twitches number following L-5-hydroxytryptophan injection. Importantly, these counteracting effects of R-citalopram were abolished by prior systemic administration of staurosporine. Interestingly, the preventing effect of staurosporine on 5-HT neuronal firing activity was abolished by direct activation of protein kinase C with phorbol 12-myristate 13-acetate. Finally, in vitro, quantification of the amount of cell surface-expressed SERT molecules revealed that R-citalopram prevented escitalopram-induced SERT internalization that was completely altered by staurosporine. CONCLUSION Taken together, these results highlight for the first time an involvement of protein kinases in the allosteric modulation of SERT function.
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Affiliation(s)
- Ouissame Mnie-Filali
- Univ Lyon, Université Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, 69500 Bron, France.,Department of Integrative Neurophysiology, CNCR, Vrije Universiteit, Amsterdam, The Netherlands
| | - Thorsten Lau
- Biochemical Laboratory, Central Institute of Mental Health, Mannheim, Germany
| | | | - Erika Abrial
- Univ Lyon, Université Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, 69500 Bron, France
| | - Sarah Delcourte
- Univ Lyon, Université Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, 69500 Bron, France
| | - Mostafa El Mansari
- Institute of Mental Health Research, University of Ottawa, Ottawa, ON, Canada
| | - Alan Pershon
- Neuropharmacology, Lundbeck Research USA, Paramus, NJ, USA
| | - Patrick Schloss
- Biochemical Laboratory, Central Institute of Mental Health, Mannheim, Germany
| | - Connie Sánchez
- Neuropharmacology, Lundbeck Research USA, Paramus, NJ, USA
| | - Nasser Haddjeri
- Univ Lyon, Université Lyon 1, Inserm, Stem Cell and Brain Research Institute U1208, 69500 Bron, France
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Wang Y, Zhang S, Breitbach ZS, Petersen H, Ellegaard P, Armstrong DW. Enantioseparation of citalopram analogues with sulfated β-cyclodextrin by capillary electrophoresis. Electrophoresis 2016; 37:841-8. [DOI: 10.1002/elps.201500541] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2015] [Revised: 12/22/2015] [Accepted: 12/22/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Yadi Wang
- Department of Chemistry and Biochemistry; University of Texas at Arlington; Arlington TX USA
| | - Shusheng Zhang
- Department of Chemistry and Biochemistry; University of Texas at Arlington; Arlington TX USA
- College of Chemistry & Molecular Engineering; Zhengzhou University; Zhengzhou P. R. China
| | - Zachary S. Breitbach
- Department of Chemistry and Biochemistry; University of Texas at Arlington; Arlington TX USA
| | - Hans Petersen
- H. Lundbeck A/S, Chemical Process Research; Valby Denmark
| | | | - Daniel W. Armstrong
- Department of Chemistry and Biochemistry; University of Texas at Arlington; Arlington TX USA
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Larsen MAB, Plenge P, Andersen J, Eildal JNN, Kristensen AS, Bøgesø KP, Gether U, Strømgaard K, Bang-Andersen B, Loland CJ. Structure-activity relationship studies of citalopram derivatives: examining substituents conferring selectivity for the allosteric site in the 5-HT transporter. Br J Pharmacol 2016; 173:925-36. [PMID: 26699847 DOI: 10.1111/bph.13411] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 12/10/2015] [Accepted: 12/14/2015] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE The 5-HT transporter (SERT) is a target for antidepressant drugs. SERT possesses two binding sites: the orthosteric (S1) binding site, which is the presumed target for current SERT inhibitors, and an allosteric (S2) site for which potential therapeutic effects are unknown. The antidepressant drug citalopram displays high-affinity S1 binding and low-affinity S2 binding. To elucidate a possible therapeutic role of allosteric inhibition of SERT, a drug that specifically targets the allosteric site is required. The purpose of this study was to find a compound having higher selectivity towards the S2 site. EXPERIMENTAL APPROACH We performed a systematic structure-activity relationship study based on the scaffold of citalopram and the structurally closely related congener, talopram, which shows low-affinity S1 binding in SERT. The role of the four chemical substituents, which distinguish citalopram from talopram in conferring selectivity towards the S1 and S2 site, respectively, was assessed by determining the binding of 14 citalopram/talopram analogous to the S1 and S2 binding sites in SERT using membranes of COS7 cells transiently expressing SERT. KEY RESULTS The structure-activity relationship study revealed that dimethyl citalopram possesses the highest affinity for the allosteric site relative to the S1 site in SERT and has approximately twofold selectivity for the allosteric site relative to the S1 site in SERT. CONCLUSIONS AND IMPLICATIONS The compound could be a useful lead for future synthesis of drugs with high affinity and high selectivity towards the allosteric binding site.
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Affiliation(s)
- M Andreas B Larsen
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Per Plenge
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jacob Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jonas N N Eildal
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Anders S Kristensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Klaus P Bøgesø
- Neuroscience Drug Discovery, H. Lundbeck A/S, Valby, Denmark
| | - Ulrik Gether
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Kristian Strømgaard
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Benny Bang-Andersen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Neuroscience Drug Discovery, H. Lundbeck A/S, Valby, Denmark
| | - Claus J Loland
- Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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16
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Bétry C, Overstreet D, Haddjeri N, Pehrson A, Bundgaard C, Sanchez C, Mørk A. A 5-HT3 receptor antagonist potentiates the behavioral, neurochemical and electrophysiological actions of an SSRI antidepressant. Pharmacol Biochem Behav 2015; 131:136-42. [DOI: 10.1016/j.pbb.2015.02.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/07/2015] [Accepted: 02/10/2015] [Indexed: 12/29/2022]
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17
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Jacobsen JP, Plenge P, Sachs BD, Pehrson AL, Cajina M, Du Y, Roberts W, Rudder ML, Dalvi P, Robinson TJ, O’Neill SP, Khoo KS, Morillo CS, Zhang X, Caron MG. The interaction of escitalopram and R-citalopram at the human serotonin transporter investigated in the mouse. Psychopharmacology (Berl) 2014; 231:4527-40. [PMID: 24810106 PMCID: PMC4346315 DOI: 10.1007/s00213-014-3595-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Accepted: 04/18/2014] [Indexed: 12/12/2022]
Abstract
RATIONALE Escitalopram appears to be a superior antidepressant to racemic citalopram. It has been hypothesized that binding of R-citalopram to the serotonin transporter (SERT) antagonizes escitalopram binding to and inhibition of the SERT, there by curtailing the elevation of extracellular 5-hydroxytryptamine (5-HTExt), and hence anti-depressant efficacy. Further, it has been suggested that a putative allosteric binding site is important for binding of escitalopram to the primary, orthosteric, site, and for R-citalopram's inhibition here of. OBJECTIVES Primary: Investigate at the human (h)SERT, at clinical relevant doses, whether R-citalopram antagonizes escitalopram-induced 5-HTExt elevation. Secondary: Investigate whether abolishing the putative allosteric site affects escitalopram-induced 5-HTExt elevation and/or modulates the effect of R-citalopram. METHODS Recombinant generation of hSERT transgenic mice; in vivo microdialysis; SERT binding; pharmacokinetics; 5-HT sensitive behaviors (tail suspension, marble burying). RESULTS We generated mice expressing either the wild-type human SERT (hSERT(WT)) or hSERT carrying amino acid substitutions (A505V, L506F, I507L, S574T and I575T) collectively abolishing the putative allosteric site (hSERT(ALI/VFL+SI/TT)). One mg/kg escitalopram yielded clinical relevant plasma levels and brain levels consistent with therapeutic SERT occupancy. The hSERT mice showed normal basal 5-HTExt levels. Escitalopram-induced 5-HTExt elevation was not decreased by R-citalopram co-treatment and was unaffected by loss of the allosteric site. The behavioral effects of the clinically relevant escitalopram dose were small and tended to be enhanced by R-citalopram co-administration. CONCLUSIONS We find no evidence that R-citalopram directly antagonizes escitalopram or that the putative allosteric site is important for hSERT inhibition by escitalopram.
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Affiliation(s)
| | - Per Plenge
- Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Benjamin D. Sachs
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | | | | | - Yunzhi Du
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Wendy Roberts
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Meghan L. Rudder
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Prachiti Dalvi
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Taylor J. Robinson
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Sharon P. O’Neill
- Neuroscience and Behavioral Disorders Program, Duke-NUS Graduate Medical School Singapore, Singapore
| | - King S. Khoo
- Neuroscience and Behavioral Disorders Program, Duke-NUS Graduate Medical School Singapore, Singapore
| | | | - Xiaodong Zhang
- Neuroscience and Behavioral Disorders Program, Duke-NUS Graduate Medical School Singapore, Singapore
| | - Marc G. Caron
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
- Corresponding Author: Dr. Marc G. Caron, James B. Duke Professor, Department of Cell Biology, Duke University Medical Center, PO Box 3287, Durham, NC 27710, USA., Tel: +1 919 684 5433, Fax: +1 919 681 8641,
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Sanchez C, Reines EH, Montgomery SA. A comparative review of escitalopram, paroxetine, and sertraline: Are they all alike? Int Clin Psychopharmacol 2014; 29:185-96. [PMID: 24424469 PMCID: PMC4047306 DOI: 10.1097/yic.0000000000000023] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Accepted: 10/25/2013] [Indexed: 10/25/2022]
Abstract
It is known that newer antidepressants, such as the selective serotonin reuptake inhibitors (SSRIs), provide advantages in tolerability over antidepressants such as the tricyclics. However, even within the SSRI class, differences in efficacy or tolerability exist between the individual drugs. Among the three most widely prescribed SSRIs are paroxetine, sertraline, and escitalopram. Escitalopram is commonly referred to as an SSRI, but also has well-documented allosteric properties, and thus can be further classed as an allosteric serotonin reuptake inhibitor. All three antidepressants are efficacious compared with placebo, but there is evidence that escitalopram is more effective than a range of other antidepressants. There are no direct data to regard either paroxetine or sertraline as a superior antidepressant. Escitalopram is superior compared with paroxetine, which has a less favorable tolerability profile. Paroxetine is associated with cholinergic muscarinic antagonism and potent inhibition of CYP2D6, and sertraline has moderate drug interaction issues in comparison with escitalopram. Overall, as an allosteric serotonin reuptake inhibitor that is somewhat different from classical SSRIs, escitalopram is the first choice judged by combined efficacy and tolerability, and nonclinical data have offered possible mechanisms through which escitalopram could be more efficacious, based on its interaction with orthosteric and allosteric binding sites at the serotonin transporter.
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Affiliation(s)
- Connie Sanchez
- External Sourcing, Lundbeck Research USA Inc., Paramus, New Jersey, USA
| | - Elin H. Reines
- International Clinical Research, H. Lundbeck A/S, Copenhagen, Denmark
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Loland CJ. The use of LeuT as a model in elucidating binding sites for substrates and inhibitors in neurotransmitter transporters. Biochim Biophys Acta Gen Subj 2014; 1850:500-10. [PMID: 24769398 DOI: 10.1016/j.bbagen.2014.04.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Revised: 04/09/2014] [Accepted: 04/11/2014] [Indexed: 01/24/2023]
Abstract
BACKGROUND The mammalian neurotransmitter transporters are complex proteins playing a central role in synaptic transmission between neurons by rapid reuptake of neurotransmitters. The proteins which transport dopamine, noradrenaline and serotonin belong to the Neurotransmitter:Sodium Symporters (NSS). Due to their important role, dysfunctions are associated with several psychiatric and neurological diseases and they also serve as targets for a wide range of therapeutic and illicit drugs. Despite the central physiological and pharmacological importance, direct evidence on structure-function relationships on mammalian NSS proteins has so far been unsuccessful. The crystal structure of the bacterial NSS protein, LeuT, has been a turning point in structural investigations. SCOPE OF REVIEW To provide an update on what is known about the binding sites for substrates and inhibitors in the LeuT. The different binding modes and binding sites will be discussed with special emphasis on the possible existence of a second substrate binding site. It is the goal to give an insight into how investigations on ligand binding in LeuT have provided basic knowledge about transporter conformations and translocation mechanism which can pave the road for a deeper understanding of drug binding and function of the mammalian transporters. MAJOR CONCLUSIONS The LeuT is a suitable model for the structural investigation of NSS proteins including the possible location of drug binding sites. It is still debated whether the LeuT is a suitable model for the molecular mechanisms behind substrate translocation. GENERAL SIGNIFICANCE Structure and functional aspects of NSS proteins are central for understanding synaptic transmission. With the purification and crystallization of LeuT as well as the dopamine transporter from Drosophila melanogaster, the application of biophysical methods such as fluorescence spectroscopy, neutron- or x-ray scattering and NMR for understanding its function becomes increasingly available. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins.
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Affiliation(s)
- Claus J Loland
- Molecular Neuropharmacology Laboratory, Department of Neuroscience and Pharmacology, The Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen N, Denmark.
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Karlsson L, Carlsson B, Hiemke C, Ahlner J, Bengtsson F, Schmitt U, Kugelberg FC. Altered brain concentrations of citalopram and escitalopram in P-glycoprotein deficient mice after acute and chronic treatment. Eur Neuropsychopharmacol 2013; 23:1636-44. [PMID: 23428338 DOI: 10.1016/j.euroneuro.2013.01.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 01/13/2013] [Accepted: 01/15/2013] [Indexed: 12/26/2022]
Abstract
According to both in vitro and in vivo data P-glycoprotein (P-gp) may restrict the uptake of several antidepressants into the brain, thus contributing to the poor success rate of current antidepressant therapies. The therapeutic activity of citalopram resides in the S-enantiomer, whereas the R-enantiomer is practically devoid of serotonin reuptake potency. To date, no in vivo data are available that address whether the enantiomers of citalopram and its metabolites are substrates of P-gp. P-gp knockout (abcb1ab (-/-)) and wild-type (abcb1ab (+/+)) mice underwent acute (single-dose) and chronic (two daily doses for 10 days) treatment with citalopram (10mg/kg) or escitalopram (5mg/kg) Serum and brain samples were collected 1-6h after the first or last i.p. injection for subsequent drug analysis by an enantioselective HPLC method. In brain, 3-fold higher concentrations of S- and R-citalopram, and its metabolites, were found in abcb1ab (-/-) mice than in abcb1ab (+/+) mice after both acute and chronic citalopram treatments. After escitalopram treatment, the S-citalopram brain concentration was 3-5 times higher in the knockout mice than in controls. The results provide novel evidence that the enantiomers of citalopram are substrates of P-gp. Possible clinical and toxicological implications of this finding need to be further elucidated.
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Affiliation(s)
- Louise Karlsson
- Department of Medical and Health Sciences, Division of Drug Research, Clinical Pharmacology, Linköping University, Linköping, Sweden
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The rapid recovery of 5-HT cell firing induced by the antidepressant vortioxetine involves 5-HT(3) receptor antagonism. Int J Neuropsychopharmacol 2013; 16:1115-27. [PMID: 23089374 DOI: 10.1017/s1461145712001058] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The therapeutic effect of current antidepressant drugs appears after several weeks of treatment and a significant number of patients do not respond to treatment. Here, we report the effects of the multi-modal antidepressant vortioxetine (Lu AA21004), a 5-HT(3) and 5-HT(7) receptor antagonist, 5-HT(1B) receptor partial agonist, 5-HT(1A) receptor agonist and 5-HT transporter (SERT) inhibitor, on rat 5-HT neurotransmission. Using in vivo electrophysiological recordings in the dorsal raphe nucleus of anaesthetized rats, we assessed the acute and subchronic effects of vortioxetine and/or the selective 5-HT(3) receptor agonist, SR57227 or the selective 5-HT(1A) receptor agonist flesinoxan, on 5-HT neuronal firing activity. Using ex-vivo autoradiography, we correlated SERT occupancy and presumed 5-HT firing activity. The selective serotonin reuptake inhibitor, fluoxetine, was used as comparator. Importantly, the recovery of 5-HT neuronal firing was achieved after 1 d with vortioxetine and 14 d with fluoxetine. SR57227 delayed this recovery. In contrast, vortioxetine failed to alter the reducing action of 3 d treatment of flesinoxan. Acute dosing of vortioxetine inhibited neuronal firing activity more potently than fluoxetine. SR57227 prevented the suppressant effect of vortioxetine, but not of fluoxetine. In contrast, flesinoxan failed to modify the suppressant effect of vortioxetine acutely administered. Differently to fluoxetine, vortioxetine suppressed neuronal firing without saturating occupancy at the SERT. Vortioxetine produced a markedly faster recovery of 5-HT neuronal firing than fluoxetine. This is at least partly due to 5-HT(3) receptor antagonism of vortioxetine in association with its reduced SERT occupancy.
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Quesseveur G, Repérant C, David DJ, Gardier AM, Sanchez C, Guiard BP. 5-HT2A receptor inactivation potentiates the acute antidepressant-like activity of escitalopram: involvement of the noradrenergic system. Exp Brain Res 2013; 226:285-95. [DOI: 10.1007/s00221-013-3434-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 01/25/2013] [Indexed: 11/30/2022]
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Plenge P, Shi L, Beuming T, Te J, Newman AH, Weinstein H, Gether U, Loland CJ. Steric hindrance mutagenesis in the conserved extracellular vestibule impedes allosteric binding of antidepressants to the serotonin transporter. J Biol Chem 2012; 287:39316-26. [PMID: 23007398 DOI: 10.1074/jbc.m112.371765] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The serotonin transporter (SERT) controls synaptic serotonin levels and is the primary target for antidepressants, including selective serotonin reuptake inhibitors (e.g. (S)-citalopram) and tricyclic antidepressants (e.g. clomipramine). In addition to a high affinity binding site, SERT possesses a low affinity allosteric site for antidepressants. Binding to the allosteric site impedes dissociation of antidepressants from the high affinity site, which may enhance antidepressant efficacy. Here we employ an induced fit docking/molecular dynamics protocol to identify the residues that may be involved in the allosteric binding in the extracellular vestibule located above the central substrate binding (S1) site. Indeed, mutagenesis of selected residues in the vestibule reduces the allosteric potency of (S)-citalopram and clomipramine. The identified site is further supported by the inhibitory effects of Zn(2+) binding in an engineered site and the covalent attachment of benzocaine-methanethiosulfonate to a cysteine introduced in the extracellular vestibule. The data provide a mechanistic explanation for the allosteric action of antidepressants at SERT and suggest that the role of the vestibule is evolutionarily conserved among neurotransmitter:sodium symporter proteins as a binding pocket for small molecule ligands.
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Affiliation(s)
- Per Plenge
- Molecular Neuropharmacology Laboratory, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, DK-2200 Copenhagen, Denmark
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Trueta C, De-Miguel FF. Extrasynaptic exocytosis and its mechanisms: a source of molecules mediating volume transmission in the nervous system. Front Physiol 2012; 3:319. [PMID: 22969726 PMCID: PMC3432928 DOI: 10.3389/fphys.2012.00319] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2012] [Accepted: 07/21/2012] [Indexed: 11/14/2022] Open
Abstract
We review the evidence of exocytosis from extrasynaptic sites in the soma, dendrites, and axonal varicosities of central and peripheral neurons of vertebrates and invertebrates, with emphasis on somatic exocytosis, and how it contributes to signaling in the nervous system. The finding of secretory vesicles in extrasynaptic sites of neurons, the presence of signaling molecules (namely transmitters or peptides) in the extracellular space outside synaptic clefts, and the mismatch between exocytosis sites and the location of receptors for these molecules in neurons and glial cells, have long suggested that in addition to synaptic communication, transmitters are released, and act extrasynaptically. The catalog of these molecules includes low molecular weight transmitters such as monoamines, acetylcholine, glutamate, gama-aminobutiric acid (GABA), adenosine-5-triphosphate (ATP), and a list of peptides including substance P, brain-derived neurotrophic factor (BDNF), and oxytocin. By comparing the mechanisms of extrasynaptic exocytosis of different signaling molecules by various neuron types we show that it is a widespread mechanism for communication in the nervous system that uses certain common mechanisms, which are different from those of synaptic exocytosis but similar to those of exocytosis from excitable endocrine cells. Somatic exocytosis has been measured directly in different neuron types. It starts after high-frequency electrical activity or long experimental depolarizations and may continue for several minutes after the end of stimulation. Activation of L-type calcium channels, calcium release from intracellular stores and vesicle transport towards the plasma membrane couple excitation and exocytosis from small clear or large dense core vesicles in release sites lacking postsynaptic counterparts. The presence of synaptic and extrasynaptic exocytosis endows individual neurons with a wide variety of time- and space-dependent communication possibilities. Extrasynaptic exocytosis may be the major source of signaling molecules producing volume transmission and by doing so may be part of a long duration signaling mode in the nervous system.
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Affiliation(s)
- Citlali Trueta
- Departamento de Neurofisiología, Instituto Nacional de Psiquiatría Ramón de la Fuente Muñiz México, D.F., México
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Zhong H, Haddjeri N, Sánchez C. Escitalopram, an antidepressant with an allosteric effect at the serotonin transporter--a review of current understanding of its mechanism of action. Psychopharmacology (Berl) 2012; 219:1-13. [PMID: 21901317 DOI: 10.1007/s00213-011-2463-5] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Accepted: 08/19/2011] [Indexed: 02/08/2023]
Abstract
RATIONALE Escitalopram is a widely used antidepressant for the treatment of patients with major depression. It is the pure S-enantiomer of racemic citalopram. Several clinical trials and meta-analyses indicate that escitalopram is quantitatively more efficacious than many other antidepressants with a faster onset of action. OBJECTIVE This paper reviews current knowledge about the mechanism of action of escitalopram. RESULTS The primary target for escitalopram is the serotonin transporter (SERT), which is responsible for serotonin (or 5-hydroxytryptamine [5-HT]) reuptake at the terminals and cell bodies of serotonergic neurons. Escitalopram and selective serotonin reuptake inhibitors bind with high affinity to the 5-HT binding site (orthosteric site) on the transporter. This leads to antidepressant effects by increasing extracellular 5-HT levels which enhance 5-HT neurotransmission. SERT also has one or more allosteric sites, binding to which modulates activity at the orthosteric binding site but does not directly affect 5-HT reuptake by the transporter. In vitro studies have shown that through allosteric binding, escitalopram decreases its own dissociation rate from the orthosteric site on the SERT. R-citalopram, the nontherapeutic enantiomer in citalopram, is also an allosteric modulator of SERT but can inhibit the actions of escitalopram by interfering negatively with its binding. Both nonclinical studies and some clinical investigations have demonstrated the cellular, neurochemical, neuroadaptive, and neuroplastic changes induced by escitalopram with acute and chronic administration. CONCLUSIONS The findings from binding, neurochemical, and neurophysiological studies may provide a mechanistic rationale for the clinical difference observed with escitalopram compared to other antidepressant therapies.
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Affiliation(s)
- Huailing Zhong
- U-Pharm Laboratories LLC, 239 New Road, Suite A-107, Parsippany, NJ 07054, USA.
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Marcus MM, Jardemark K, Malmerfelt A, Gertow J, Konradsson-Geuken Å, Svensson TH. Augmentation by escitalopram, but not citalopram or R-citalopram, of the effects of low-dose risperidone: Behavioral, biochemical, and electrophysiological evidence. Synapse 2011; 66:277-90. [DOI: 10.1002/syn.21510] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Accepted: 11/05/2011] [Indexed: 12/21/2022]
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Favré P. [Clinical efficacy and achievement of a complete remission in depression: increasing interest in treatment with escitalopram]. Encephale 2011; 38:86-96. [PMID: 22381728 DOI: 10.1016/j.encep.2011.11.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Accepted: 09/12/2011] [Indexed: 10/14/2022]
Abstract
Such a prevalent disease as Major Depressive Disorder (MDD), associated with prominent impairment in physical and social functioning, implies as well an increased morbidity and mortality. Long-term treatments are required due to the frequent occurrence of relapses. Patient compliance is a core factor in both acute and continuation treatment, closely related to tolerability issues. We have partially reviewed the literature published on PubMed since 2004 which assess the relative antidepressant efficacy of escitalopram and comparator antidepressants in adult patients who met DSM-IV criteria for major depressive disorder (MDD). Clinically important differences exist between commonly prescribed antidepressants. These analyses are in favor of a superior efficacy and tolerability of long-term escitalopram treatment (10 to 20mg/day) compared with active controls, including selective serotonin re-uptake inhibitors (SSRIs) (paroxetine, citalopram, bupropion, fluoxetine, fluvoxamine, sertraline), serotonin/noradrenaline reuptake inhibitors (SNRIs) (venlafaxine, milnacipran and duloxetine) and noradrenergic and specific serotonergic antidepressants (NaSSAs) (mirtazapine). Cipriani et al. (2009) have performed a network meta-analysis of 12 new generation antidepressants. They have shown that clinically important differences exist between commonly prescribed antidepressants for both efficacy and acceptability in favor of escitalopram and sertraline in acute treatment, defined as 8-week treatment. Kasper et al. (2009) conducted a post-hoc pooled analysis of data from two 6-month randomized controlled trials that revealed superior efficacy and tolerability of escitalopram when compared with paroxetine. The pooled analysis of four randomized, double-blind, active comparator, 6-month trials in MDD, by Wade et al. (2009), showed that short-term outcomes may predict long-term treatment compliance and outcomes. A higher probability of achieving remission was associated with responding after 8 weeks and with completing 6 months of treatment. Furthermore, Week 24 complete remission (MADRS≤5) was significantly (P<0,01) higher for escitalopram (51.7%) than for the pooled comparators (45.6%). And after 6 months, fewer patients discontinued treatment with escitalopram (15.9%) than with the pooled comparators (23.9%) (P<0.001). This fragmentary review of the literature shows that it is necessary to adopt a stringent definition of remission in depression, especially in clinical trials; a MADRS total score less or equal to 10 to define remission, a MADRS total score less or equal to 5 to define complete remission, and moreover no MADRS single item greater than 1 to define symptom-free remission. In all these meta-analyses, the superiority of escitalopram compared with other antidepressants was confirmed for both acute and long-term treatment of MDD, especially in harshly depressed patients.
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Affiliation(s)
- P Favré
- EPS Ville-Evrard, secrétariat 93G16, 202, avenue J.-Jaurès, 93332 Neuilly-sur-Marne cedex, France.
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Zhong H, Sánchez C, Caron MG. Consideration of allosterism and interacting proteins in the physiological functions of the serotonin transporter. Biochem Pharmacol 2011; 83:435-42. [PMID: 21983034 DOI: 10.1016/j.bcp.2011.09.020] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Accepted: 09/19/2011] [Indexed: 11/25/2022]
Abstract
The serotonin transporter (SERT) functions to transport serotonin (5-HT) from the extracellular space into neurons to maintain homeostatic control of 5-HT. It is the molecular target for selective serotonin reuptake inhibitor (SSRI) antidepressants. Preclinical research has shown that some SERT inhibitors can bind to two distinct binding sites on the SERT, a primary high affinity binding site and a low affinity allosteric binding site. Mutational studies of the SERT and computational modeling methods with escitalopram resulted in the identification of key amino acid residues important for the function of the allosteric binding site. While this allosteric binding site appears to influence the clinical efficacy of escitalopram under physiological conditions, the molecular mechanism of this effect is still poorly understood and may involve a large network of protein-protein interactions with the SERT. Dynamic interfaces between the SERT and the SERT interacting proteins (SIPs) potentially influence not only the SERT on its uptake function, its regulation, and trafficking, but also on known as well as yet to be identified non-canonical signaling pathways through SIPs. In this commentary, we outline approaches in the areas of selective small-molecule allosteric compound discovery, biochemistry, in vivo genetic knock-in mouse models, as well as computational and structural biology. These studies of the intra-molecular allosteric modulation of the SERT in the context of the myriad of potential inter-molecular signaling interactions with SIPs may help uncover unknown physiological functions of the SERT.
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Affiliation(s)
- Huailing Zhong
- U-Pharm Laboratories LLC, 239 New Road, Suite A-107, Parsippany, NJ 07054, USA.
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Schilström B, Konradsson-Geuken Å, Ivanov V, Gertow J, Feltmann K, Marcus MM, Jardemark K, Svensson TH. Effects of S-citalopram, citalopram, and R-citalopram on the firing patterns of dopamine neurons in the ventral tegmental area, N-methyl-D-aspartate receptor-mediated transmission in the medial prefrontal cortex and cognitive function in the rat. Synapse 2010; 65:357-67. [DOI: 10.1002/syn.20853] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2010] [Accepted: 07/27/2010] [Indexed: 11/10/2022]
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Nutt DJ, Feetam CL. What one hand giveth the other taketh away: some unpredicted effects of enantiomers in psychopharmacology. J Psychopharmacol 2010; 24:1137-41. [PMID: 20663810 DOI: 10.1177/0269881110374782] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
It is well known that many medicines are a mixture of two enantiomers, or mirror-image molecules. Two enantiomers occur when a molecule has a single chiral centre and the two mirror images, called S or L (left handed) and R or D (right handed), are usually found in equal amounts in the parent (racemic) mixture. While for many compounds used in clinical practice the active moiety is found in one of the two enantiomers with the other being seen as an unnecessary and redundant component of the racemic mixture, the difference between enantiomers can mean a difference between therapeutic and adverse effects, as well as in beneficial pharmacological effect and potency.
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Affiliation(s)
- David J Nutt
- Neuropsychopharmacology Unit, Centre for Pharmacology and Therapeutics, Imperial College London, Hammersmith Hospital, London, UK.
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Leonard B, Taylor D. Escitalopram--translating molecular properties into clinical benefit: reviewing the evidence in major depression. J Psychopharmacol 2010; 24:1143-52. [PMID: 20147575 PMCID: PMC2923415 DOI: 10.1177/0269881109349835] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The majority of currently marketed drugs contain a mixture of enantiomers; however, recent evidence suggests that individual enantiomers can have pharmacological properties that differ importantly from enantiomer mixtures. Escitalopram, the S-enantiomer of citalopram, displays markedly different pharmacological activity to the R-enantiomer. This review aims to evaluate whether these differences confer any significant clinical advantage for escitalopram over either citalopram or other frequently used antidepressants. Searches were conducted using PubMed and EMBASE (up to January 2009). Abstracts of the retrieved studies were reviewed independently by both authors for inclusion. Only those studies relating to depression or major depressive disorder were included. The search identified over 250 citations, of which 21 studies and 18 pooled or meta-analyses studies were deemed suitable for inclusion. These studies reveal that escitalopram has some efficacy advantage over citalopram and paroxetine, but no consistent advantage over other selective serotonin reuptake inhibitors. Escitalopram has at least comparable efficacy to available serotonin-norepinephrine reuptake inhibitors, venlafaxine XR and duloxetine, and may offer some tolerability advantages over these agents. This review suggests that the mechanistic advantages of escitalopram over citalopram translate into clinical efficacy advantages. Escitalopram may have a favourable benefit-risk ratio compared with citalopram and possibly with several other antidepressant agents.
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Affiliation(s)
- Brian Leonard
- Department of Pharmacology, National University of Ireland, Galway, Ireland.,Department of Psychiatry and Psychotherapy, Ludwig Maximilians University, Munich, Germany
| | - David Taylor
- Division of Pharmaceutical Sciences, King’s College, London, UK.,Maudsley Hospital, London, UK.,David Taylor, Maudsley Hospital, Denmark Hill, London SE5 8AZ, UK.
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Matheus N, Mendoza C, Iceta R, Mesonero JE, Alcalde AI. Melatonin inhibits serotonin transporter activity in intestinal epithelial cells. J Pineal Res 2010; 48:332-9. [PMID: 20210852 DOI: 10.1111/j.1600-079x.2010.00757.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Gastrointestinal serotonin (5-HT) and melatonin are two closely related neuromodulators which are synthesised in the enterochromaffin cells of the intestinal epithelium and which have been shown to be involved in the physiopathology of the gastrointestinal tract. The effects of 5-HT depend on 5-HT availability which is, in part, modulated by the serotonin transporter (SERT). This transporter provides an efficient 5-HT uptake after release and is expressed in the membrane of the enterocytes. Although the origin and effects of 5-HT and melatonin are similar, the interrelationship between them in the gastrointestinal tract is unknown. The main aim of this study was to determine whether melatonin affects SERT activity and expression, and, if so, to elucidate the mechanisms involved. Caco-2 cell line was used to carry out the study as these cells have been shown to endogenously express SERT. The results showed that melatonin inhibits SERT activity by affecting both V(max) and kt kinetic constants although SERT synthesis or intracellular trafficking did not appear to be affected. The melatonin effect seemed to be independent of melatonin receptors MT(1) and MT(2) and protein kinase C and cAMP intracellular pathways. Our results suggest that the inhibition of SERT might be due to a catalytic effect of melatonin on the allosteric citalopram-sensitive site in SERT. This study shows, for the first time, that melatonin modulates SERT activity, thus demonstrating the feedback system between melatonin and the serotoninergic system in the gastrointestinal tract.
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Affiliation(s)
- Nyurky Matheus
- Departamento de Farmacología y Fisiología, Universidad de Zaragoza, Spain
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33
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Hawken ER, Owen JA, Hudson RW, Delva NJ. Specific effects of escitalopram on neuroendocrine response. Psychopharmacology (Berl) 2009; 207:27-34. [PMID: 19662384 DOI: 10.1007/s00213-009-1633-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Accepted: 07/20/2009] [Indexed: 11/30/2022]
Abstract
PURPOSE Citalopram, a selective serotonin reuptake inhibitor, is used as a neuroendocrine probe in human subjects to assess serotonin function as reflected in prolactin and plasma cortisol release. Citalopram is a racemic mixture of equal proportions of the S(+) and R(-) enantiomers. Inhibition of serotonin reuptake and, consequently, antidepressant activity is associated, almost exclusively, with the S(+) enantiomer ("escitalopram"). Studies in animal models indicate that the presence of the R(-) isomer may interfere with the serotonin reuptake activity of escitalopram. The current study compared the neuroendocrine effects of citalopram and escitalopram in healthy human volunteers. METHODS Plasma cortisol and prolactin levels following a single oral dose of citalopram (40 mg) or escitalopram (20 mg) were compared in samples taken every 15-30 min over a period of 240 min. Plasma citalopram concentration was determined at the same intervals. RESULTS Escitalopram and citalopram caused equivalent increases in plasma cortisol and prolactin. The administration of dexamethasone prior to the escitalopram challenge blocked the evoked increase in cortisol. CONCLUSION This is the first study to prove that a single dose of escitalopram acts centrally and not peripherally, providing further support of the use of oral escitalopram as a probe for brain serotonergic function.
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Affiliation(s)
- Emily R Hawken
- Providence Care Centre-Mental Health Services, Kingston, ON, Canada
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Zhong H, Hansen KB, Boyle NJ, Han K, Muske G, Huang X, Egebjerg J, Sánchez C. An allosteric binding site at the human serotonin transporter mediates the inhibition of escitalopram by R-citalopram: Kinetic binding studies with the ALI/VFL–SI/TT mutant. Neurosci Lett 2009; 462:207-12. [DOI: 10.1016/j.neulet.2009.07.030] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2009] [Revised: 06/29/2009] [Accepted: 07/11/2009] [Indexed: 11/28/2022]
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Andersen J, Kristensen AS, Bang-Andersen B, Strømgaard K. Recent advances in the understanding of the interaction of antidepressant drugs with serotonin and norepinephrine transporters. Chem Commun (Camb) 2009:3677-92. [PMID: 19557250 DOI: 10.1039/b903035m] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The biogenic monoamine transporters are integral membrane proteins that perform active transport of extracellular dopamine, serotonin and norepinephrine into cells. These transporters are targets for therapeutic agents such as antidepressants, as well as addictive substances such as cocaine and amphetamine. Seminal advances in the understanding of the structure and function of this transporter family have recently been accomplished by structural studies of a bacterial transporter, as well as medicinal chemistry and pharmacological studies of mammalian transporters. This feature article focuses on antidepressant drugs that act on the serotonin and/or the norepinephrine transporters. Specifically, we focus on structure-activity relationships of these drugs with emphasis on relationships between their molecular properties and the current knowledge of transporter structure.
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Affiliation(s)
- Jacob Andersen
- Department of Medicinal Chemistry, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen, Denmark.
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Differences in the dynamics of serotonin reuptake transporter occupancy may explain superior clinical efficacy of escitalopram versus citalopram. Int Clin Psychopharmacol 2009; 24:119-25. [PMID: 19367152 DOI: 10.1097/yic.0b013e32832a8ec8] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Escitalopram the S-enantiomer of the racemate citalopram, is clinically more effective than citalopram in the treatment of major depressive disorder. However, the precise mechanism by which escitalopram achieves superiority over citalopram is yet to be determined. It has been hypothesized that the therapeutically inactive R-enantiomer competes with the serotonin-enhancing S-enantiomer at a low-affinity allosteric site on serotonin reuptake transporters (SERTs), and reduces the effectiveness of the S-enantiomer at the primary, high-affinity serotonin-binding site. This study summarizes the results of two recent single-photon emission computerized tomography studies measuring SERT occupancy in citalopram-treated and escitalopram-treated healthy volunteers, after a single dose and multiple doses (i.e. under steady-state conditions). The single-dose study showed no attenuating effect of R-citalopram. After multiple dosing, however, SERT occupancy was significantly reduced in the presence of R-citalopram. Under steady-state conditions, R-enantiomer concentrations were greater than for the S-enantiomer because of slower clearance of R-citalopram. A pooled analysis suggests that build-up of the R-enantiomer after repeated citalopram dosing may lead to increased inhibition of S-enantiomer occupancy of SERT. This review adds to the growing body of evidence regarding differences in the dynamics of SERT occupancy, that is, molecular mechanisms underlying the often-observed superior clinical efficacy of escitalopram compared with citalopram in major depressive disorder.
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Kasper S, Baldwin DS, Larsson Lönn S, Boulenger JP. Superiority of escitalopram to paroxetine in the treatment of depression. Eur Neuropsychopharmacol 2009; 19:229-37. [PMID: 19185467 DOI: 10.1016/j.euroneuro.2008.12.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Revised: 12/01/2008] [Accepted: 12/09/2008] [Indexed: 01/01/2023]
Abstract
Post-hoc pooled analysis of data from two 6-month randomised controlled trials in patients with major depressive disorder (MDD) revealed superior efficacy and tolerability of escitalopram when compared with paroxetine. Escitalopram (n=394) produced a significantly (p<0.01) greater mean treatment difference of 2.0 points in primary endpoints, judged using the Montgomery-Asberg Depression Rating Scale (MADRS) total score, compared with paroxetine (n=383). Significant differences were also observed in Clinical Global Impression (CGI)--severity (escitalopram, 2.1; paroxetine, 2.4; p<0.01) and CGI--improvement (escitalopram, 1.8; paroxetine, 2.0: p<0.01). In the sub-group of severely depressed patients (baseline MADRS> or = 30), escitalopram showed further improved efficacy compared with paroxetine in all scores. This analysis supports previous observations of superior efficacy and tolerability of long-term escitalopram treatment (10 to 20 mg/day) compared with paroxetine (20 to 40 mg/day). Escitalopram is a good therapeutic option for the long-term treatment of MDD, particularly in severely depressed patients.
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Affiliation(s)
- Siegfried Kasper
- Department of Psychiatry and Psychotherapy, Medical University of Vienna, Austria.
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Kilts CD, Wade AG, Andersen HF, Schlaepfer TE. Baseline severity of depression predicts antidepressant drug response relative to escitalopram. Expert Opin Pharmacother 2009; 10:927-36. [DOI: 10.1517/14656560902849258] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Iceta R, Aramayona JJ, Mesonero JE, Alcalde AI. Regulation of the human serotonin transporter mediated by long-term action of serotonin in Caco-2 cells. Acta Physiol (Oxf) 2008; 193:57-65. [PMID: 18081886 DOI: 10.1111/j.1748-1716.2007.01793.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIM The aim of this study was to determine the effect of long-term serotonin (5-hydroxytryptamine, 5-HT) treatment on the human serotonin transporter (hSERT) function and its expression. METHODS This study was carried out in the enterocyte-like cell line Caco-2. These cells constitutively express the hSERT and have been shown to be an excellent model for the study of this protein. We measured serotonin transport, levels of mRNA expression and of the SERT protein after treating the cells with serotonin. RESULTS Serotonin treatment diminished hSERT activity in a concentration and period-dependent way by increasing the K(t) value and reducing V(max). This inhibition was reversible and was not mediated by either the action of 5-HT(2), 5-HT(3) or 5-HT(4) receptors, or by the intracellular second messengers, protein kinase C and cAMP. 5-HT did not seem to affect either the mRNA level of the SERT or the protein transporter measured in either the membrane or the cell lysate. The 5-HT treatment effect was additive to the inhibitory effect of treatment with a low concentration of citalopram and fluoxetine. Nevertheless, 5-HT did not increase the inhibition yielded by treatment with high concentration citalopram. CONCLUSION The chronic increase in serotonin in the extracellular medium diminishes the function of the SERT. This effect seems to be due to an effect on the transporter molecule itself in the membrane, without altering protein synthesis, intracellular traffic, or its availability.
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Affiliation(s)
- R Iceta
- Division of Physiology, Department of Pharmacology and Physiology, Faculty of Veterinary Sciences, Zaragoza University, Zaragoza, Spain
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Sit DK, Perel JM, Helsel JC, Wisner KL. Changes in antidepressant metabolism and dosing across pregnancy and early postpartum. J Clin Psychiatry 2008; 69:652-8. [PMID: 18426260 PMCID: PMC2408825 DOI: 10.4088/jcp.v69n0419] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
OBJECTIVE Little information about the disposition of individual antidepressant drugs during pregnancy has been published. We examined the dose requirements and level-to-dose (L/D) ratios of citalopram, escitalopram, and sertraline during pregnancy and after birth. METHOD Women aged from 32 to 43 years with major depressive disorder according to the Structured Clinical Interview for DSM-IV Axis I Disorders participated in the study. Doses were charted across each week of gestation and post-partum. Samples were collected at 20, 30, and 36 weeks' gestation; delivery; and at 2 and 12 weeks postpartum. Plasma trough levels were obtained 8 to 15 hours after dose intake. Across pregnancy and postpartum, the mean dose-corrected plasma concentrations (L/D ratios) of S- and R-citalopram and S-sertraline, and the corresponding primary chiral metabolites S- and R-desmethylcitalopram and N-desmethylsertra-line were assessed. The samples were analyzed for concentrations of stereospecific parent drug and metabolites. The study was conducted from 2003 to 2006. RESULTS Three women received citalopram, 2 women were treated with escitalopram, and 6 women received sertraline. In 4 of 5 subjects who received citalopram or escitalopram and 5 of 6 subjects who received sertraline, the L/D ratios for the stereoisomers of the parent compound and primary metabolite decreased between 20 weeks gestation and delivery, which reflects increased drug metabolism. By 12 weeks postpartum the L/D ratios were similar to those detected at 20 weeks gestation. CONCLUSIONS Our cases illustrate that dose requirements frequently increase during the second half of pregnancy to offset increased drug turnover and maintain optimal pharmacotherapy. These findings replicate and extend earlier published data with other antidepressants. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00279370.
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Mnie-Filali O, El Mansari M, Scarna H, Zimmer L, Sánchez C, Haddjeri N. [Escitalopram: a selective inhibitor and allosteric modulator of the serotonin transporter]. Encephale 2007; 33:965-72. [PMID: 18789789 DOI: 10.1016/j.encep.2007.11.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2007] [Accepted: 11/06/2007] [Indexed: 02/02/2023]
Abstract
Citalopram (Séropram) is an antidepressant of the selective serotonin (5-HT) reuptake inhibitor (SSRI) class, composed of equal amounts of S-enantiomer, escitalopram, and R-enantiomer, R-citalopram. Both clinical and preclinical studies have reported that escitalopram is a potent SSRI that possesses a faster onset of antidepressant activity in comparison with citalopram. Conversely, R-citalopram, although devoid of 5-HT reuptake inhibition property, was reported to counteract the effect of the S-enantiomer in several in vitro and in vivo experiments. For instance, microdialysis studies have shown that escitalopram increased the extracellular 5-HT levels in the frontal cortex and the ventral hippocampus, and this effect was prevented by concomitant injection of R-citalopram. The in vivo relevance of the antagonistic effect of R-citalopram on escitalopram efficacy was confirmed in dorsal raphe nucleus, a brain region known to be a target for SSRIs. In the later region, escitalopram was four times more potent than citalopram in suppressing the firing activity of 5-HT neurons and this effect of escitalopram was significantly prevented by R-citalopram. The antagonizing effect of R-citalopram on escitalopram efficacy was also observed in behavioural tests predictive of anxiolytic or antidepressant properties. In adult rats, R-citalopram reduced the anxiolytic-like effect of escitalopram obtained in the footshock-induced ultrasonic vocalization model, the conditioned fear model or the Vogel conflict and elevated plus maze tests. In validated chronic models with high predictive value for antidepressant activity, when escitalopram was administered for five weeks, either alone or with twice as much R-citalopram, the effect of the treatment regimens on reversal of hedonic deficit was significantly different. Importantly, chronic treatment with escitalopram reversed the decrease in cytogenesis in the rat dentate gyrus, induced by chronic mild stress. However, in naïve rats, while chronic treatment with R-citalopram did not modify the basal proliferation rate in the dentate gyrus, it blocked the increase induced by escitalopram when coadministered. This suggests that neuronal adaptive changes, which are essential for antidepressant response, are rapidly induced by escitalopram but prevented by R-citalopram coadministration. The attenuating effect of R-citalopram was suggested to underlie the delayed recovery of 5-HT neuronal activity following long-term treatment with citalopram versus escitalopram. This is confirmed since a treatment with R-citalopram antagonized the recovery of firing observed in escitalopram-treated rats. The exact mechanism by which R-citalopram exerts its action is not yet fully defined; however, an allosteric interaction between the enantiomers and the 5-HT transporter (SERT) has been proposed. In this context, in vitro studies have revealed the existence of at least two binding sites on SERT: (1) a primary high-affinity binding site or orthosteric site that mediates the inhibition of 5-HT reuptake and (2) an allosteric low-affinity binding site that modulates the binding of ligands at the primary site. In presence of escitalopram alone, both the primary and the allosteric sites are occupied. Thus, escitalopram exerts a stabilizing effect on this association to SERT, resulting in an effective inhibition of 5-HT reuptake activity. On the other hand, in the presence of the two enantiomers, R-citalopram binds to the allosteric site and decreases the escitalopram action on SERT. Such an innovative mechanism of action can constitute a basis for development of new allosteric antidepressants that demonstrate higher efficacy and earlier onset of therapeutic effect.
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Affiliation(s)
- O Mnie-Filali
- Laboratoire de neuropharmacologie, faculté de pharmacie, université de Lyon-1, 8, avenue Rockefeller, 69373 Lyon cedex 08, France
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Townsend MH, Conrad EJ. The therapeutic potential of escitalopram in the treatment of panic disorder. Neuropsychiatr Dis Treat 2007; 3:835-8. [PMID: 19300618 PMCID: PMC2656325 DOI: 10.2147/ndt.s965] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Panic disorder is a chronic and disabling condition that is often accompanied by other psychiatric and medical conditions. The serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) have been used effectively with panic disorder (PD) and conditions in which panic attacks frequently occur. Escitalopram is the most selective SSRI and a variety of evidence suggests it is of great value in the treatment of panic disorder. In this paper, we review the theoretical and practical implications of its use.
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Affiliation(s)
- Mark H Townsend
- Department of Psychiatry, Louisiana State University Health Sciences Center New Orleans, New Orleans, Louisiana, USA
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Mnie-Filali O, Faure C, Mansari ME, Lambás-Señas L, Bérod A, Zimmer L, Sánchez C, Haddjeri N. R-citalopram prevents the neuronal adaptive changes induced by escitalopram. Neuroreport 2007; 18:1553-6. [PMID: 17885600 DOI: 10.1097/wnr.0b013e3282f04047] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study examined the long-term effects of the antidepressant escitalopram on rat serotonin (5-HT) neuronal activity and hippocampal neuroplasticity. In the dorsal raphe nucleus, a 2-week treatment with escitalopram (10 mg/kg/day, subcutaneous) did not modify the firing activity of 5-HT neurons, whereas a cotreatment with R-citalopram (20 mg/kg/day, subcutaneous) decreased it. In the dentate gyrus of dorsal hippocampus, escitalopram increased significantly (57%) the number of de novo cells and this was prevented by a cotreatment with R-citalopram. The present results support the role of the allosteric modulation of the 5-HT transporter in the regulation of the recovery of 5-HT neuronal activity and long-lasting hippocampal cellular plasticity induced by escitalopram, two adaptive changes presumably associated with the antidepressant response.
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Affiliation(s)
- Ouissame Mnie-Filali
- Laboratory of Neuropharmacology, Faculty of Pharmacy, University Lyon 1, Lyon Cedex, France
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Jørgensen AM, Tagmose L, Jørgensen AMM, Topiol S, Sabio M, Gundertofte K, Bøgesø KP, Peters GH. Homology Modeling of the Serotonin Transporter: Insights into the Primary Escitalopram-binding Site. ChemMedChem 2007; 2:815-26. [PMID: 17405130 DOI: 10.1002/cmdc.200600242] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The serotonin transporter (SERT) is one of the neurotransmitter transporters that plays a critical role in the regulation of endogenous amine concentrations and therefore is an important target for therapeutic agents affecting the central nervous system. The recently published, high resolution X-ray structure of the closely related amino acid transporter, Aquifex aeolicus leucine transporter (LeuT), provides an opportunity to develop a three-dimensional model of the structure of SERT. We present herein a homology model of SERT using LeuT as the template and containing escitalopram as a bound ligand. Our model explains selectivities known from mutational studies and varying ligand data, which are discussed and illustrated in the paper.
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Affiliation(s)
- Anne Marie Jørgensen
- MEMPHYS-Center for Biomembrane Physics, Department of Chemistry, Technical University of Denmark, Building 206, 2800 Kgs. Lyngby, Denmark
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