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Layunta E, Buey B, Mesonero JE, Latorre E. Crosstalk Between Intestinal Serotonergic System and Pattern Recognition Receptors on the Microbiota-Gut-Brain Axis. Front Endocrinol (Lausanne) 2021; 12:748254. [PMID: 34819919 PMCID: PMC8607755 DOI: 10.3389/fendo.2021.748254] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 10/05/2021] [Indexed: 12/12/2022] Open
Abstract
Disruption of the microbiota-gut-brain axis results in a wide range of pathologies that are affected, from the brain to the intestine. Gut hormones released by enteroendocrine cells to the gastrointestinal (GI) tract are important signaling molecules within this axis. In the search for the language that allows microbiota to communicate with the gut and the brain, serotonin seems to be the most important mediator. In recent years, serotonin has emerged as a key neurotransmitter in the gut-brain axis because it largely contributes to both GI and brain physiology. In addition, intestinal microbiota are crucial in serotonin signaling, which gives more relevance to the role of the serotonin as an important mediator in microbiota-host interactions. Despite the numerous investigations focused on the gut-brain axis and the pathologies associated, little is known regarding how serotonin can mediate in the microbiota-gut-brain axis. In this review, we will mainly discuss serotonergic system modulation by microbiota as a pathway of communication between intestinal microbes and the body on the microbiota-gut-brain axis, and we explore novel therapeutic approaches for GI diseases and mental disorders.
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Affiliation(s)
- Elena Layunta
- Institute of Biomedicine, Department of Medical Biochemistry and Cell Biology, University of Gothenburg, Gothenburg, Sweden
- Instituto de Investigación Sanitaria de Aragón (IIS Aragón), Zaragoza, Spain
| | - Berta Buey
- Departamento de Farmacología, Fisiología y Medicina Legal y Forense, Universidad de Zaragoza, Zaragoza, Spain
| | - Jose Emilio Mesonero
- Instituto de Investigación Sanitaria de Aragón (IIS Aragón), Zaragoza, Spain
- Departamento de Farmacología, Fisiología y Medicina Legal y Forense, Universidad de Zaragoza, Zaragoza, Spain
- Instituto Agroalimentario de Aragón—IA2 (Universidad de Zaragoza–CITA), Zaragoza, Spain
| | - Eva Latorre
- Instituto de Investigación Sanitaria de Aragón (IIS Aragón), Zaragoza, Spain
- Instituto Agroalimentario de Aragón—IA2 (Universidad de Zaragoza–CITA), Zaragoza, Spain
- Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
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2
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Martin AM, Jones LA, Jessup CF, Sun EW, Keating DJ. Diet differentially regulates enterochromaffin cell serotonin content, density and nutrient sensitivity in the mouse small and large intestine. Neurogastroenterol Motil 2020; 32:e13869. [PMID: 32378785 DOI: 10.1111/nmo.13869] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 04/03/2020] [Accepted: 04/09/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND Enterochromaffin (EC) cells are specialized enteroendocrine cells lining the gastrointestinal (GI) tract and the source of almost all serotonin (5-hydroxytryptamine; 5-HT) in the body. Gut-derived 5-HT has a plethora of physiological roles, including regulation of gastrointestinal motility, and has been implicated as a driver of obesity and metabolic disease. This is due to 5-HT influencing key metabolic processes, such as hepatic gluconeogenesis, adipose tissue lipolysis and hindering thermogenic capacity. Increased circulating 5-HT occurs in humans with obesity and type 2 diabetes. However, despite the known metabolic roles of gut-derived 5-HT, the mechanisms underlying the cellular-level change in EC cells under obesogenic conditions remains unknown. METHODS We use a mouse model of diet-induced obesity (DIO) to identify the regional changes that occur in primary EC cells from the duodenum and colon. Transcriptional changes in the nutrient sensing profile of primary EC cells were assessed, and responses to nutrient stimuli in culture were determined by 5-HT ELISA. KEY RESULTS We find that obesogenic conditions affect EC cells in a region-dependent manner. Duodenal EC cells from DIO mice have impaired sugar sensing even in the presence of increased 5-HT content per cell, while colonic EC cell numbers are significantly increased, but have unaltered nutrient sensing capacity. CONCLUSIONS & INFERENCES Our findings from this study add novel insights into the mechanisms by which functional changes to EC cells occur at a cellular level, which may contribute to the altered circulating 5-HT seen with obesity and metabolic disease, and associated gastrointestinal disorders.
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Affiliation(s)
- Alyce M Martin
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Lauren A Jones
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Claire F Jessup
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Emily W Sun
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
| | - Damien J Keating
- Flinders Health and Medical Research Institute, College of Medicine and Public Health, Flinders University, Adelaide, Australia
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3
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Martin AM, Lumsden AL, Young RL, Jessup CF, Spencer NJ, Keating DJ. Regional differences in nutrient-induced secretion of gut serotonin. Physiol Rep 2017; 5:5/6/e13199. [PMID: 28320893 PMCID: PMC5371566 DOI: 10.14814/phy2.13199] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 02/15/2017] [Accepted: 02/16/2017] [Indexed: 12/17/2022] Open
Abstract
Enterochromaffin (EC) cells located in the gastrointestinal (GI) tract provide the vast majority of serotonin (5-HT) in the body and constitute half of all enteroendocrine cells. EC cells respond to an array of stimuli, including various ingested nutrients. Ensuing 5-HT release from these cells plays a diverse role in regulating gut motility as well as other important responses to nutrient ingestion such as glucose absorption and fluid balance. Recent data also highlight the role of peripheral 5-HT in various pathways related to metabolic control. Details related to the manner by which EC cells respond to ingested nutrients are scarce and as that the nutrient environment changes along the length of the gut, it is unknown whether the response of EC cells to nutrients is dependent on their GI location. The aim of the present study was to identify whether regional differences in nutrient sensing capability exist in mouse EC cells. We isolated mouse EC cells from duodenum and colon to demonstrate differential responses to sugars depending on location. Measurements of intracellular calcium concentration and 5-HT secretion demonstrated that colonic EC cells are more sensitive to glucose, while duodenal EC cells are more sensitive to fructose and sucrose. Short-chain fatty acids (SCFAs), which are predominantly synthesized by intestinal bacteria, have been previously associated with an increase in circulating 5-HT; however, we find that SCFAs do not acutely stimulate EC cell 5-HT release. Thus, we highlight that EC cell physiology is dictated by regional location within the GI tract, and identify differences in the regional responsiveness of EC cells to dietary sugars.
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Affiliation(s)
- Alyce M Martin
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Amanda L Lumsden
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Richard L Young
- South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, Australia
| | - Claire F Jessup
- Department of Anatomy and Histology and Centre for Neuroscience, Flinders University, Adelaide, Australia.,Adelaide Medical School, University of Adelaide, Adelaide, Australia
| | - Nick J Spencer
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia
| | - Damien J Keating
- Department of Human Physiology and Centre for Neuroscience, Flinders University, Adelaide, Australia .,South Australian Health and Medical Research Institute (SAHMRI), Adelaide, Australia
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4
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Martin AM, Young RL, Leong L, Rogers GB, Spencer NJ, Jessup CF, Keating DJ. The Diverse Metabolic Roles of Peripheral Serotonin. Endocrinology 2017; 158:1049-1063. [PMID: 28323941 DOI: 10.1210/en.2016-1839] [Citation(s) in RCA: 139] [Impact Index Per Article: 19.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Accepted: 02/23/2017] [Indexed: 02/07/2023]
Abstract
Serotonin (5-hydroxytryptamine or 5-HT) is a multifunctional bioamine with important signaling roles in a range of physiological pathways. Almost all of the 5-HT in our bodies is synthesized in specialized enteroendocrine cells within the gastrointestinal (GI) mucosa called enterochromaffin (EC) cells. These cells provide all of our circulating 5-HT. We have long appreciated the important contributions of 5-HT within the gut, including its role in modulating GI motility. However, evidence of the physiological and clinical significance of gut-derived 5-HT outside of the gut has recently emerged, implicating 5-HT in regulation of glucose homeostasis, lipid metabolism, bone density, and diseases associated with metabolic syndrome, such as obesity and type 2 diabetes. Although a new picture has developed in the last decade regarding the various metabolic roles of peripheral serotonin, so too has our understanding of the physiology of EC cells. Given that they are scattered throughout the lining of the GI tract within the epithelial cell layer, these cells are typically difficult to study. Advances in isolation procedures now allow the study of pure EC-cell cultures and single cells, enabling studies of EC-cell physiology to occur. EC cells are sensory cells that are capable of integrating cues from ingested nutrients, the enteric nervous system, and the gut microbiome. Thus, levels of peripheral 5-HT can be modulated by a multitude of factors, resulting in both local and systemic effects for the regulation of a raft of physiological pathways related to metabolism and obesity.
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Affiliation(s)
- Alyce M Martin
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
| | - Richard L Young
- Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide 5001, Australia
- Adelaide Medical School, University of Adelaide, Adelaide 5005, Australia
| | - Lex Leong
- Infection and Immunity, SAHMRI, Adelaide 5001, Australia
- SAHMRI Microbiome Research Laboratory, School of Medicine, Flinders University of South Australia, Adelaide 5042, Australia
| | - Geraint B Rogers
- Infection and Immunity, SAHMRI, Adelaide 5001, Australia
- SAHMRI Microbiome Research Laboratory, School of Medicine, Flinders University of South Australia, Adelaide 5042, Australia
| | - Nick J Spencer
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
| | - Claire F Jessup
- Adelaide Medical School, University of Adelaide, Adelaide 5005, Australia
- Discipline of Anatomy and Histology, Flinders University of South Australia, Adelaide 5042, Australia
| | - Damien J Keating
- Discipline of Human Physiology and Centre for Neuroscience, Flinders University of South Australia, Adelaide 5042, Australia
- Nutrition and Metabolism, South Australian Health and Medical Research Institute (SAHMRI), Adelaide 5001, Australia
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5
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The effect of folate status on the uptake of physiologically relevant compounds by Caco-2 cells. Eur J Pharmacol 2010; 640:29-37. [DOI: 10.1016/j.ejphar.2010.04.056] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2010] [Revised: 03/19/2010] [Accepted: 04/23/2010] [Indexed: 12/25/2022]
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Serotonin pharmacology in the gastrointestinal tract: a review. Naunyn Schmiedebergs Arch Pharmacol 2008; 377:181-203. [PMID: 18398601 DOI: 10.1007/s00210-008-0276-9] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Accepted: 02/15/2008] [Indexed: 12/17/2022]
Abstract
Serotonin (5-hydroxytryptamine or 5-HT) plays a critical physiological role in the regulation of gastrointestinal (GI) function. 5-HT dysfunction may also be involved in the pathophysiology of a number of functional GI disorders, such as chronic constipation, irritable bowel syndrome and functional dyspepsia. This article describes the role of 5-HT in the enteric nervous system (ENS) of the mammalian GI tract and the receptors with which it interacts. Existing serotonergic therapies that have proven effective in the treatment of GI functional disorders and the potential of drugs currently in development are also highlighted. Advances in our understanding of the physiological and pathophysiological roles of 5-HT in the ENS and the identification of selective receptor ligands bodes well for the future development of more efficacious therapies for patients with functional GI disorders.
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Kuramoto H, Kadowaki M, Sakamoto H, Yuasa K, Todo A, Shirai R. Distinct morphology of serotonin-containing enterochromaffin (EC) cells in the rat distal colon. ACTA ACUST UNITED AC 2008; 70:235-41. [PMID: 18296824 DOI: 10.1679/aohc.70.235] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The present study was performed to examine the distribution and distinct morphology of the serotonin-containing enterochromaffin (EC) cells in the rat distal colon by immunohistochemical and electron microscopic methods. Serotonin-immunohistochemistry revealed that most of the serotonin-immunoreactive EC cells possessed extended cytoplasmic processes. In particular, the immunoreactive EC cells with long processes located along the body of the crypt were characterized by their bipolar processes comprising one with the terminal swellings extending vertically down to the basal crypt and the other running up along the luminal side - in many cases, with the apical ends reaching the glandular lumen. Moreover, a few EC cells had long processes which resembled neuronal processes with varicosities. Electron microscopic observations revealed rod-like, tortuous, oval, or round small pleomorphic granules in the long processbearing EC cells. The cell bodies and processes directly faced the crypt epithelial cells - including the enterocytes and goblet cells on one side and the basement membrane on the opposite side. The accumulation of the granules sometimes appeared within the cytoplasm on the side of the epithelial cells. These findings suggest that serotonin is released from the long processes of the EC cells and directly acts in a paracrine fashion on the crypt epithelial cells to secrete electrolytes and fluids into the colonic lumen. The long cytoplasmic processes of the EC cells may be a major contributor to the serotonininduced secretory events in the rat distal colon.
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Affiliation(s)
- Hirofumi Kuramoto
- Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo, Kyoto, Japan.
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Kim MK, Shim CK. The transport of organic cations in the small intestine: current knowledge and emerging concepts. Arch Pharm Res 2006; 29:605-16. [PMID: 16903083 DOI: 10.1007/bf02969273] [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: 10/21/2022]
Abstract
A wide variety of drugs and endogenous bioactive amines are organic cations (OCs). Approximately 40% of all conventional drugs on the market are OCs. Thus, the transport of xenobiotics or endogenous OCs in the body has been a subject of considerable interest, since the discovery and cloning of a family of OC transporters, referred to as organic cation transporter (OCTs), and a new subfamily of OCTs, OCTNs, leading to the functional characterization of these transporters in various systems including oocytes and some cell lines. Organic cation transporters are critical in drug absorption, targeting, and disposition of a drug. In this review, the recent advances in the characterization of organic cation transporters and their distribution in the small intestine are discussed. The results of the in vitro transport studies of various OCs in the small intestine using techniques such as isolated brush-border membrane vesicles, Ussing chamber systems and Caco-2 cells are discussed, and in vivo knock-out animal studies are summarized. Such information is essential for predicting pharmacokinetics and pharmacodynamics and in the design and development of new cationic drugs. An understanding of the mechanisms that control the intestinal transport of OCs will clearly aid achieving desirable clinical outcomes.
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Affiliation(s)
- Moon Kyoung Kim
- Laboratory of Transporters Targeted Drug Design, College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 151-742, Korea
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9
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Abstract
1. 5-Hydroxytryptamine (5-HT) modulates the motility and secretion of the gastrointestinal tract. To examine the direct effect of 5-HT on the secretions of colonic epithelial cells, a short-circuit current was used to measure electrolyte transport in the rat stripped distal colon. A neuronal Na+ channel blocker and a cyclo-oxygenase inhibitor were routinely added in experiments to abolish the effects of the enteric nervous system and endogenous prostaglandin, respectively. 2. Basolateral application of 5-HT (10 micromol/L) induced an increase in the short circuit current (ISC). Removal of extracellular Cl-, HCO3- or both resulted in a 59.6, 76.4 and 90% reduction of 5-HT-elicited responses, respectively. The Ca(2+)-dependent Cl- channel blocker 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) had no effect on the 5-HT-induced increase in ISC, but the selective cystic fibrosis transmembrane conductance regulator (CFTR) channel blocker glibenclamide (1 mmol/L) inhibited 5-HT-induced increases in ISC by approximately 92.9%. Removal of apical Na+ reduced the 5-HT-induced increase in ISC by 33.3%. 3. Basolateral pretreatment with 100 micromol/L bumetanide (an inhibitor of the Na(+)-K(+)-2Cl- cotransporter), 200 micromol/L DIDS (an inhibitor of the Na(+)-HCO3- transporter or the Cl-/HCO3- exchanger) or both decreased the DeltaISC induced by 5-HT by approximately 75.5, 59.0 and 86.3%, respectively. Removal of basolateral Na+ also reduced the current evoked by 5-HT. 4. The selective 5-HT4 antagonist GR113808 (1 micromol/L) totally abolished the 5-HT-induced increase in ISC, whereas 2-methyl-5-HT (100 micromol/L) induced a weak ISC response. 5. In conclusion, the present study has demonstrated that 5-HT can elicit Cl(-)- and HCO3- anion secretion and Na+ absorption by acting directly on colonic epithelial cells via 5-HT4 receptors.
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Affiliation(s)
- Yang Ning
- Epithelial Cell Biology Research Center, Department of Physiology, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong
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10
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Martel F, Monteiro R, Lemos C, Vieira-Coelho MA. In vitro and in vivo effect of fluoxetine on the permeability of3H-serotonin across rat intestine. Can J Physiol Pharmacol 2004; 82:940-50. [PMID: 15644933 DOI: 10.1139/y04-083] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The aim of this work was to characterize the mucosal-to-serosal (apical to basolateral; AP-BL) and serosal-to-mucosal (basolateral to apical; BL-AP) transport of serotonin (5-HT) across rat jejunum, ileum, and colon, and to determine the influence of serotonin neuronal transporter inhibitors on this transport. The AP-BL apparent permeability (Papp) of3H-5-HT increased in the order colon = jejunum < ileum, and the BL-AP Pappof3H-5-HT increased in the order colon < jejunum = ileum. In vitro, neither fluoxetine (0.02 or 0.2 µmol/L) nor desipramine (0.4 or 4 µmol/L) had a significant effect upon the AP-BL or BL-AP Pappof3H-5-HT in any of the intestinal regions. However, fluoxetine (0.2 µmol/L) decreased the accumulation of3H-5-HT in the ileum (to 65% of control) in the BL-AP experiments. In vivo, chronic fluoxetine (10 mg/kg daily administered orally for 15 days), as assessed in the ileum, significantly increased (to ±180% of control levels) the BL-AP Pappof3H-5-HT and tended to increase the AP-BL Pappof3H-5-HT. In conclusion, the increase in the Pappof3H-5-HT after chronic administration of fluoxetine suggests that this treatment is able to increase the extracellular concentration of3H-5-HT at the intestinal level.Key words: fluoxetine, serotonin, rat intestine, permeability.
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Affiliation(s)
- Fátima Martel
- Department of Biochemistry, Faculty of Medicine, University of Porto, Portugal.
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11
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Martel F, Monteiro R, Lemos C. Uptake of serotonin at the apical and basolateral membranes of human intestinal epithelial (Caco-2) cells occurs through the neuronal serotonin transporter (SERT). J Pharmacol Exp Ther 2003; 306:355-62. [PMID: 12682218 DOI: 10.1124/jpet.103.049668] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Serotonin plays important physiological functions at the intestinal level. However, nothing is known concerning its inactivation mechanisms in the human intestine. So, the aim of this work was to characterize the uptake of serotonin at the apical and basolateral membranes of human intestinal epithelial (Caco-2) cells. Uptake of [3H]serotonin at the apical membrane of Caco-2 cells was specific and Na+-, Cl--, and potential-dependent. It was concentration dependently inhibited by several monoamines (with the following rank order of potency: serotonin >> dopamine > or = noradrenaline) and tricyclic and nontricyclic antidepressants (with the following rank order of potency: fluoxetine > desipramine > cocaine > GBR 12909). In contrast, it was not affected by corticosterone (0.01-100 micro M) and was only partially inhibited by decynium-22 (0.001-10 micro M). Transepithelial apparent permeability (Papp) to [3H]serotonin in the apical-to-basolateral direction was reduced by desipramine (0.4 micro M) and fluoxetine (0.02 micro M), and it was not Na+-dependent nor affected by corticosterone (100 micro M). Uptake of [3H]serotonin at the basolateral membrane of Caco-2 cells was Na+-dependent and reduced by desipramine (0.4 micro M) and fluoxetine (0.02 micro M), and it was not affected by corticosterone (100 micro M). The Papp to [3H]serotonin in the basolateral-to-apical direction was reduced by desipramine (0.4 micro M) and fluoxetine (0.02 micro M), and it was not affected by Na+ omission or by corticosterone (100 micro M). Reverse transcriptase-polymerase chain reaction indicates that mRNA of the neuronal serotonin transporter (SERT) is present in Caco-2 cells and in human small intestine. In conclusion, these results suggest that human intestinal epithelial Caco-2 cells functionally express SERT, both at their apical and basolateral cell membranes.
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Affiliation(s)
- Fatima Martel
- Department of Biochemistry, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal.
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12
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Noda M, Yasuda S, Okada M, Higashida H, Shimada A, Iwata N, Ozaki N, Nishikawa K, Shirasawa S, Uchida M, Aoki S, Wada K. Recombinant human serotonin 5A receptors stably expressed in C6 glioma cells couple to multiple signal transduction pathways. J Neurochem 2003; 84:222-32. [PMID: 12558985 DOI: 10.1046/j.1471-4159.2003.01518.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Human serotonin 5A (5-HT5A) receptors were stably expressed in undifferentiated C6 glioma. In 5-HT5A receptors-expressing cells, accumulation of cAMP by forskolin was inhibited by 5-HT as reported previously. Pertussis toxin-sensitive inhibition of ADP-ribosyl cyclase was also observed, indicating a decrease of cyclic ADP ribose, a potential intracellular second messenger mediating ryanodine-sensitive Ca2+ mobilization. On the other hand, 5-HT-induced outward currents were observed using the patch-clamp technique in whole-cell configuration. The 5-HT-induced outward current was observed in 84% of the patched 5-HT5A receptor-expressing cells and was concentration-dependent. The 5-HT-induced current was inhibited when intracellular K+ was replaced with Cs+ but was not significantly inhibited by typical K+ channel blockers. The 5-HT-induced current was significantly attenuated by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) in the patch pipette. Depleting intracellular Ca2+ stores by application of caffeine or thapsigargin also blocked the 5-HT-induced current. Blocking G protein, the inositol triphosphate (IP3) receptor, or pretreatment with pertussis toxin, all inhibited the 5-HT-induced current. IP3 showed a transient increase after application of 5-HT in 5-HT5A receptor-expressing cells. It was concluded that in addition to the inhibition of cAMP accumulation and ADP-ribosyl cyclase activity, 5-HT5A receptors regulate intracellular Ca2+ mobilization which is probably a result of the IP3-sensitive Ca2+ store. These multiple signal transduction systems may induce complex changes in the serotonergic system in brain function.
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Affiliation(s)
- Mami Noda
- Laboratory of Pathophysiology, Kyushu University Graduate School of Pharmaceutical Sciences, Fukuoka, Japan.
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13
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Fiorica-Howells E, Hen R, Gingrich J, Li Z, Gershon MD. 5-HT(2A) receptors: location and functional analysis in intestines of wild-type and 5-HT(2A) knockout mice. Am J Physiol Gastrointest Liver Physiol 2002; 282:G877-93. [PMID: 11960784 DOI: 10.1152/ajpgi.00435.2001] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The distribution and function of the 5-hydroxytryptamine (5-HT(2A)) receptor were investigated in the intestines of wild-type (5-HT(2A) +/+) and knockout (5-HT(2A) -/-) mice. In 5-HT(2A) +/+ mice, rats, and guinea pigs, 5-HT(2A) receptor immunoreactivity was found on circular and longitudinal smooth muscle cells, neurons, enterocytes, and Paneth cells. Muscular 5-HT(2A) receptors were concentrated in caveolae; neuronal 5-HT(2A) receptors were found intracellularly and on the plasma membranes of nerve cell bodies and axons. Neuronal 5-HT(2A) immunoreactivity was detected as early as E14 in ganglia, intravillus nerves, and the deep muscle plexus. The 5-HT(2A) -/- colon did not express 5-HT(2A) receptors and did not contract in response to exogenous 5-HT. 5-HT(2A) -/- enterocytes were smaller, Paneth cells fewer, and muscle layers thinner (and showed degeneration) compared with those of 5-HT(2A) +/+ littermates. The 5-HT(2A) receptor may thus be required for the maintenance and/or development of enteric neuroeffectors and other enteric functions, although gastrointestinal and colonic transit times in 5-HT(2A) -/- and +/+ mice did not differ significantly.
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MESH Headings
- Animals
- Enterocytes/chemistry
- Enterocytes/pathology
- Enterocytes/ultrastructure
- Female
- Fetus/cytology
- Gastric Emptying/physiology
- Gastrointestinal Motility/physiology
- Immunohistochemistry
- Intestines/chemistry
- Intestines/innervation
- Intestines/pathology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microscopy, Immunoelectron
- Muscle, Smooth/chemistry
- Muscle, Smooth/innervation
- Muscle, Smooth/pathology
- Myenteric Plexus/chemistry
- Myenteric Plexus/ultrastructure
- Paneth Cells/chemistry
- Paneth Cells/pathology
- Rats
- Rats, Sprague-Dawley
- Receptor, Serotonin, 5-HT2A
- Receptors, Serotonin/analysis
- Receptors, Serotonin/genetics
- Receptors, Serotonin/metabolism
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Affiliation(s)
- Elena Fiorica-Howells
- Department of Anatomy and Cell Biology, Columbia University, College of Physicians and Surgeons, New York, New York 10032, USA.
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Engelmann BE, Bindslev N, Poulsen SS, Hansen MB. Effects of cyclooxygenase and lipoxygenase inhibition on basal- and serotonin-induced ion transport in rat colon. Comp Biochem Physiol C Toxicol Pharmacol 2002; 132:37-52. [PMID: 12039683 DOI: 10.1016/s1532-0456(02)00042-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The purpose of this study was to determine the effect of a selective cyclooxygenase (COX)-2 inhibitor as compared to non-selective COX and lipoxygenase (LOX) inhibitors in rat colon. Basal- and serotonin (5-hydroxytryptamine, 5-HT)-induced electrogenic ion transport (short circuit current, SCC), prostaglandin E2 (PGE2) release and histological characteristics were measured. Muscle-stripped mucosal sheets of the proximal and distal segment of rat colon were investigated by employing the Ussing chamber technique, radioimmunoassays for PGE2 and light microscopy examinations for control of tissue integrity. 5-HT and PGE2 both induced a concentration-dependent increase in SCC by activation of multiple receptors. The response to 5-HT was bumetanide-sensitive. Neither the non-selective COX inhibitor piroxicam, nor the selective COX-2 inhibitor SC-'236, altered basal- SCC or 5-HT-induced SCC. Indomethacin reduced both basal- and 5-HT-induced SCC in both segments. Nordihydroguaiaretic acid reduced the 5-HT-induced increase in SCC, but did not change basal SCC. 5-HT-induced a concentration-dependent release of PGE2. Only high concentrations of piroxicam and indomethacin reduced basal PGE2 release and 5-HT-induced PGE2 release. Histological examination of the specimens demonstrated only minor changes following mounting in chambers. There were no apparent differences in the morphology following treatment with COX or LOX inhibitors. These results suggest that in rat colon only the COX-1 enzyme is expressed under basal conditions. Furthermore, data suggest neither the COX-1 nor the COX-2 enzyme to be of major importance for 5-HT-induced ion transport in rat colon in vitro. In conclusion, this study supports 5-HT as a mediator of chloride secretion by activating several receptor subtypes and the LOX enzyme, releasing mediators such as leucotrienes.
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Affiliation(s)
- Bodil Elisabeth Engelmann
- Department of Medical Physiology, The Panum Institute, 12/4, University of Copenhagen, 3 Blegdamsvej, Copenhagen, Denmark
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15
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Alcalde AI, Sorribas V, Rodriguez-Yoldi MJ, Lahuerta A. Study of serotonin interactions with brush border membrane of rabbit jejunum enterocytes. Eur J Pharmacol 2000; 403:9-15. [PMID: 10969138 DOI: 10.1016/s0014-2999(00)00484-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Recent studies have demonstrated that serotonin (5-hydroxytryptamine, 5-HT) may interact with either specific receptors or with a specific transporter that takes up 5-HT in the gastrointestinal tract. The purpose of the present work was to study the 5-HT interactions with brush border membrane from rabbit jejunum enterocytes. The results obtained showed that 5-HT did not seem to be transported by any specific system of transport in brush border membrane vesicles. Nevertheless, [3H]5-HT seemed to bind specifically to this membrane. The kinetic analysis indicated a saturable and dissociable specific binding with a dissociation constant K(D)=14x10(-9) M. The saturation studies with [3H]5-HT indicated the presence of one specific site in the brush border membrane. The results of displacement of [3H]5-HT specific binding from the brush border membrane showed that both unlabelled 5-HT and unlabelled GR113080 ([1-[(2-methyl sulphonyl) amino] ethyl-4-piperidinyl] methyl-1-methyl-1H-indole-3-carboxylate), a specific competitive antagonist of 5-HT(4) receptors, inhibited the specific binding of [3H]5-HT to this membrane.
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Affiliation(s)
- A I Alcalde
- Department of Physiology, Veterinary Faculty, University of Zaragoza, Miguel Servet 177, 50013, Zaragoza, Spain.
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16
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Hardcastle J, Hardcastle PT, Klaren PH, Taylor CJ, White SJ. The action of 5-hydroxytryptamine on normal and cystic fibrosis mouse colon: effects on secretion and intracellular calcium. J Pharm Pharmacol 1999; 51:449-56. [PMID: 10385218 DOI: 10.1211/0022357991772501] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The ability of mouse colon to generate a secretory response to stimulation by 5-hydroxytryptamine (5-HT) was investigated in intact colonic sheets mounted in Ussing chambers. A preparation of intact isolated crypts was used to determine whether 5-HT action was associated with an elevation of cytosolic calcium levels, measured using the calcium-sensitive fluorescent dye, fura-2. 5-HT increased the short-circuit current, an effect that was inhibited by 55% in the absence of chloride and by 83% in the presence of serosal frusemide, consistent with the stimulation of electrogenic chloride secretion. This was confirmed by the observation that colonic tissue from transgenic cystic fibrosis mice (n = 4) failed to respond to 5-HT, although wild-type tissues generated an increased short-circuit current of 52.4+/-1.1 microAcm(-2) (n = 9). The electrical response to 5-HT was calcium-dependent. 5-HT action was unaffected by tetrodotoxin and was not mimicked by the 5-HT3 agonist 1-phenylbiguanide, indicating that neural mechanisms are not involved. The cyclooxygenase inhibitor indomethacin, however, reduced the 5-HT-induced rise in short-circuit current by 73%, suggesting that prostaglandin production contributes to the response. Stimulation of crypts with acetylcholine elicited an increase in cytosolic calcium levels, but no such response was detected on application of 5-HT (10(-6) to 10(-4) M), suggesting that 5-HT does not directly modulate intracellular calcium in colonic crypt cells. It is concluded that mouse colon responds to 5-HT challenge with a stimulation of electrogenic chloride secretion and that this effect is mediated by indirect mechanisms that might involve immune elements within the colonic wall.
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Affiliation(s)
- J Hardcastle
- Department of Biomedical Science, University of Sheffield, UK
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Nakagawa K, Ueda S, Kida H, Sawamura M, Ikeda K, Yamori Y. Effects of cytosolic Ca2+ on membrane voltage and conductance of cultured mesangial cells from stroke-prone spontaneously hypertensive rats and WKY rats. Biochem Biophys Res Commun 1999; 256:273-7. [PMID: 10079175 DOI: 10.1006/bbrc.1998.0219] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mesangial cells (MC) are considered to play an important role in the development of hypertension. The purpose of this study was to characterize the effects of cytosolic Ca2+ on membrane voltage and conductance of MC using stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar Kyoto rats (WKY). We applied the patch-clamp technique in the whole-cell configuration to measure membrane potential (Vm) and ion currents. There was no significant difference in resting Vm values between MC from WKY and SHRSP. The cytosolic Ca2+ increase induced membrane depolarization and the increase of Cl- currents in MC from WKY but not in MC from SHRSP. On the other hand, the Ca2+ increase induced membrane hyperpolarization and the increase of K+ currents in MC from SHRSP but not in MC from WKY. Such differences between MC from two rat strains may play an important role in the alterations in renal hemodynamics observed in hypertension.
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Affiliation(s)
- K Nakagawa
- Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, 606-8507, Japan
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