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Kashlan OB, Wang XP, Sheng S, Kleyman TR. Epithelial Na + Channels Function as Extracellular Sensors. Compr Physiol 2024; 14:1-41. [PMID: 39109974 PMCID: PMC11309579 DOI: 10.1002/cphy.c230015] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/10/2024]
Abstract
The epithelial Na + channel (ENaC) resides on the apical surfaces of specific epithelia in vertebrates and plays a critical role in extracellular fluid homeostasis. Evidence that ENaC senses the external environment emerged well before the molecular identity of the channel was reported three decades ago. This article discusses progress toward elucidating the mechanisms through which specific external factors regulate ENaC function, highlighting insights gained from structural studies of ENaC and related family members. It also reviews our understanding of the role of ENaC regulation by the extracellular environment in physiology and disease. After familiarizing the reader with the channel's physiological roles and structure, we describe the central role protein allostery plays in ENaC's sensitivity to the external environment. We then discuss each of the extracellular factors that directly regulate the channel: proteases, cations and anions, shear stress, and other regulators specific to particular extracellular compartments. For each regulator, we discuss the initial observations that led to discovery, studies investigating molecular mechanism, and the physiological and pathophysiological implications of regulation. © 2024 American Physiological Society. Compr Physiol 14:5407-5447, 2024.
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Affiliation(s)
- Ossama B. Kashlan
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Computational and Systems Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania
| | - Xue-Ping Wang
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Shaohu Sheng
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Thomas R. Kleyman
- Department of Medicine, Renal-Electrolyte Division,
University of Pittsburgh, Pittsburgh, Pennsylvania
- Department of Cell Biology, University of Pittsburgh,
Pittsburgh, Pennsylvania
- Department of Pharmacology and Chemical Biology, University
of Pittsburgh, Pittsburgh, Pennsylvania
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2
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Chen R, Liu XC, Xiang J, Sun W, Tomasevic I. Prospects and challenges for the application of salty and saltiness-enhancing peptides in low-sodium meat products. Meat Sci 2023; 204:109261. [PMID: 37384955 DOI: 10.1016/j.meatsci.2023.109261] [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: 04/28/2023] [Revised: 06/09/2023] [Accepted: 06/19/2023] [Indexed: 07/01/2023]
Abstract
A long-term high-sodium diet has been reported to increase the incidence of cardiovascular diseases and other diseases, including osteoporosis, gastric cancer, stomach cancer, and kidney stones. Meat products contain high NaCl content and contribute to approximately 20% of the total sodium intake, so reducing its sodium content has always been the critical focus of industries and researchers. Salty and saltiness-enhancing peptides (SSEP) are a potential salt substitute that exhibits a salt taste or saltiness-enhancing activity. The partial replacement of NaCl by SSEP in low-sodium meat products has been a technological challenge. This review discussed the salt taste transduction mechanism of SSEP. The current studies about preparing SSEP based on different protein sources were summarized. Further, the effects of SSEP combined with other chloride salts, such as KCl and CaCl2, on the sensory properties of meat products were summarized. Finally, the challenges associated with applying the peptide to low-sodium meat products were discussed, focusing on the efficient preparation method and the effect of meat product processing methods and matrices on the efficacy of SSEP.
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Affiliation(s)
- Ruixia Chen
- School of Food Science and Engineering, South China University of Technology, Guangzhou 510641, China
| | - Xiao-Chen Liu
- School of Food Science and Engineering, South China University of Technology, Guangzhou 510641, China
| | - Junyi Xiang
- School of Food Science and Engineering, South China University of Technology, Guangzhou 510641, China; Qingyuan Food Inspection Center, Qingyuan 511538, China
| | - Weizheng Sun
- School of Food Science and Engineering, South China University of Technology, Guangzhou 510641, China; Overseas Expertise Introduction Center for Discipline Innovation of Food Nutrition and Human Health (111 Center), Guangzhou 510641, China.
| | - Igor Tomasevic
- Faculty of Agriculture, University of Belgrade, Nemanjina 6, 11080 Belgrade, Serbia; DIL German Institute of Food Technologies, Prof.-v.-Klitzing-Str. 7, Quakenbrueck 49610, Germany.
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3
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Langhans W, Watts AG, Spector AC. The elusive cephalic phase insulin response: triggers, mechanisms, and functions. Physiol Rev 2023; 103:1423-1485. [PMID: 36422994 PMCID: PMC9942918 DOI: 10.1152/physrev.00025.2022] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 11/04/2022] [Accepted: 11/20/2022] [Indexed: 11/25/2022] Open
Abstract
The cephalic phase insulin response (CPIR) is classically defined as a head receptor-induced early release of insulin during eating that precedes a postabsorptive rise in blood glucose. Here we discuss, first, the various stimuli that elicit the CPIR and the sensory signaling pathways (sensory limb) involved; second, the efferent pathways that control the various endocrine events associated with eating (motor limb); and third, what is known about the central integrative processes linking the sensory and motor limbs. Fourth, in doing so, we identify open questions and problems with respect to the CPIR in general. Specifically, we consider test conditions that allow, or may not allow, the stimulus to reach the potentially relevant taste receptors and to trigger a CPIR. The possible significance of sweetness and palatability as crucial stimulus features and whether conditioning plays a role in the CPIR are also discussed. Moreover, we ponder the utility of the strict classical CPIR definition based on what is known about the effects of vagal motor neuron activation and thereby acetylcholine on the β-cells, together with the difficulties of the accurate assessment of insulin release. Finally, we weigh the evidence of the physiological and clinical relevance of the cephalic contribution to the release of insulin that occurs during and after a meal. These points are critical for the interpretation of the existing data, and they support a sharper focus on the role of head receptors in the overall insulin response to eating rather than relying solely on the classical CPIR definition.
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Affiliation(s)
- Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zürich, Schwerzenbach, Switzerland
| | - Alan G Watts
- Department of Biological Sciences, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Alan C Spector
- Department of Psychology and Program in Neuroscience, Florida State University, Tallahassee, Florida
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4
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Kumari A, Mistretta CM. Anterior and Posterior Tongue Regions and Taste Papillae: Distinct Roles and Regulatory Mechanisms with an Emphasis on Hedgehog Signaling and Antagonism. Int J Mol Sci 2023; 24:ijms24054833. [PMID: 36902260 PMCID: PMC10002505 DOI: 10.3390/ijms24054833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/21/2023] [Accepted: 02/25/2023] [Indexed: 03/06/2023] Open
Abstract
Sensory receptors across the entire tongue are engaged during eating. However, the tongue has distinctive regions with taste (fungiform and circumvallate) and non-taste (filiform) organs that are composed of specialized epithelia, connective tissues, and innervation. The tissue regions and papillae are adapted in form and function for taste and somatosensation associated with eating. It follows that homeostasis and regeneration of distinctive papillae and taste buds with particular functional roles require tailored molecular pathways. Nonetheless, in the chemosensory field, generalizations are often made between mechanisms that regulate anterior tongue fungiform and posterior circumvallate taste papillae, without a clear distinction that highlights the singular taste cell types and receptors in the papillae. We compare and contrast signaling regulation in the tongue and emphasize the Hedgehog pathway and antagonists as prime examples of signaling differences in anterior and posterior taste and non-taste papillae. Only with more attention to the roles and regulatory signals for different taste cells in distinct tongue regions can optimal treatments for taste dysfunctions be designed. In summary, if tissues are studied from one tongue region only, with associated specialized gustatory and non-gustatory organs, an incomplete and potentially misleading picture will emerge of how lingual sensory systems are involved in eating and altered in disease.
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Affiliation(s)
- Archana Kumari
- Cell Biology and Neuroscience, Rowan University School of Osteopathic Medicine, Stratford, NJ 08084, USA
- Correspondence:
| | - Charlotte M. Mistretta
- Department of Biologic and Materials Sciences & Prosthodontics, School of Dentistry, University of Michigan, Ann Arbor, MI 48109, USA
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5
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Bigiani A, Rhyu M. Effect of kokumi taste-active γ-glutamyl peptides on amiloride-sensitive epithelial Na+ channels in rat fungiform taste cells. Biochem Biophys Rep 2023; 33:101400. [DOI: 10.1016/j.bbrep.2022.101400] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 11/17/2022] [Accepted: 11/27/2022] [Indexed: 12/03/2022] Open
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6
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Bradshaw C. The effect of adulteration with a bitter tastant, denatonium benzoate, on the reinforcing value of sucrose. Behav Processes 2022; 203:104771. [DOI: 10.1016/j.beproc.2022.104771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 10/17/2022] [Accepted: 10/21/2022] [Indexed: 11/02/2022]
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7
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NODA M, MATSUDA T. Central regulation of body fluid homeostasis. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2022; 98:283-324. [PMID: 35908954 PMCID: PMC9363595 DOI: 10.2183/pjab.98.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Extracellular fluids, including blood, lymphatic fluid, and cerebrospinal fluid, are collectively called body fluids. The Na+ concentration ([Na+]) in body fluids is maintained at 135-145 mM and is broadly conserved among terrestrial animals. Homeostatic osmoregulation by Na+ is vital for life because severe hyper- or hypotonicity elicits irreversible organ damage and lethal neurological trauma. To achieve "body fluid homeostasis" or "Na homeostasis", the brain continuously monitors [Na+] in body fluids and controls water/salt intake and water/salt excretion by the kidneys. These physiological functions are primarily regulated based on information on [Na+] and relevant circulating hormones, such as angiotensin II, aldosterone, and vasopressin. In this review, we discuss sensing mechanisms for [Na+] and hormones in the brain that control water/salt intake behaviors, together with the responsible sensors (receptors) and relevant neural pathways. We also describe mechanisms in the brain by which [Na+] increases in body fluids activate the sympathetic neural activity leading to hypertension.
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Affiliation(s)
- Masaharu NODA
- Homeostatic Mechanism Research Unit, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
- Correspondence should be addressed to: Homeostatic Mechanism Research Unit, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho 4259, Midori-ku, Yokohama, Kanagawa 226-8503, Japan (e-mail: )
| | - Takashi MATSUDA
- Homeostatic Mechanism Research Unit, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
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8
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D'Urso O, Drago F. Pharmacological significance of extra-oral taste receptors. Eur J Pharmacol 2021; 910:174480. [PMID: 34496302 DOI: 10.1016/j.ejphar.2021.174480] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 08/23/2021] [Accepted: 09/01/2021] [Indexed: 01/17/2023]
Abstract
It has recently been shown that taste receptors, in addition to being present in the oral cavity, exist in various extra-oral organs and tissues such as the thyroid, lungs, skin, stomach, intestines, and pancreas. Although their physiological function is not yet fully understood, it appears that they can help regulate the body's homeostasis and provide an additional defense function against pathogens. Since the vast majority of drugs are bitter, the greatest pharmacological interest is in the bitter taste receptors. In this review, we describe how bitter taste 2 receptors (TAS2Rs) induce bronchodilation and mucociliary clearance in the airways, muscle relaxation in various tissues, inhibition of thyroid stimulating hormone (TSH) in thyrocytes, and release of glucagon-like peptide-1 (GLP-1) and ghrelin in the digestive system. In fact, substances such as dextromethorphan, chloroquine, methimazole and probably glimepiride, being agonists of TAS2Rs, lead to these effects. TAS2Rs and taste 1 receptors (TAS1R2/3) are G protein-coupled receptors (GPCR). TAS1R2/3 are responsible for sweet taste perception and may induce GLP-1 release and insulin secretion. Umami taste receptors, belonging to the same superfamily of receptors, perform a similar function with regard to insulin. The sour and salty taste receptors work in a similar way, both being channel receptors sensitive to amiloride. Finally, gene-protein coupled receptor 40 (GPR40) and GPR120 for fatty taste perception are also protein-coupled receptors and may induce GLP-1 secretion and insulin release, similar to those of other receptors belonging to the same superfamily.
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Affiliation(s)
- Ottavio D'Urso
- Department of Biomedical and Biotechnological Sciences, University of Catania, Via S. Sofia, 97, 95125 Catania, Italy
| | - Filippo Drago
- Department of Biomedical and Biotechnological Sciences, University of Catania, Via S. Sofia, 97, 95125 Catania, Italy.
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9
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Lossow K, Hermans-Borgmeyer I, Meyerhof W, Behrens M. Segregated Expression of ENaC Subunits in Taste Cells. Chem Senses 2021; 45:235-248. [PMID: 32006019 DOI: 10.1093/chemse/bjaa004] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Salt taste is one of the 5 basic taste qualities. Depending on the concentration, table salt is perceived either as appetitive or aversive, suggesting the contribution of several mechanisms to salt taste, distinguishable by their sensitivity to the epithelial sodium channel (ENaC) blocker amiloride. A taste-specific knockout of the α-subunit of the ENaC revealed the relevance of this polypeptide for low-salt transduction, whereas the response to other taste qualities remained normal. The fully functional ENaC is composed of α-, β-, and γ-subunits. In taste tissue, however, the precise constitution of the channel and the cell population responsible for detecting table salt remain uncertain. In order to examine the cells and subunits building the ENaC, we generated mice carrying modified alleles allowing the synthesis of green and red fluorescent proteins in cells expressing the α- and β-subunit, respectively. Fluorescence signals were detected in all types of taste papillae and in taste buds of the soft palate and naso-incisor duct. However, the lingual expression patterns of the reporters differed depending on tongue topography. Additionally, immunohistochemistry for the γ-subunit of the ENaC revealed a lack of overlap between all potential subunits. The data suggest that amiloride-sensitive recognition of table salt is unlikely to depend on the classical ENaCs formed by α-, β-, and γ-subunits and ask for a careful investigation of the channel composition.
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Affiliation(s)
- Kristina Lossow
- Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee, Nuthetal, Germany
| | - Irm Hermans-Borgmeyer
- Transgenic Animal Unit, University Medical Center Hamburg-Eppendorf (ZMNH), Hamburg, Germany
| | - Wolfgang Meyerhof
- Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee, Nuthetal, Germany
| | - Maik Behrens
- Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee, Nuthetal, Germany
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10
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Abstract
Among the 5 taste qualities, salt is the least understood. The receptors, their expression pattern in taste cells, and the transduction mechanisms for salt taste are still unclear. Previous studies have suggested that low concentrations of NaCl are detected by the amiloride-sensitive epithelial Na+ channel (ENaC), which in other systems requires assembly of 3 homologous subunits (α, β, and γ) to form a functional channel. However, a new study from Lossow and colleagues, published in this issue of Chemical Senses, challenges that hypothesis by examining expression levels of the 3 ENaC subunits in individual taste cells using gene-targeted mice in combination with immunohistochemistry and in situ hybridization. Results show a lack of colocalization of ENaC subunits in taste cells as well as expression of subunits in taste cells that show no amiloride sensitivity. These new results question the molecular identity of the amiloride-sensitive Na+ conductance in taste cells.
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Affiliation(s)
- Aurelie Vandenbeuch
- Department of Otolaryngology and Rocky Mountain Taste and Smell Center, University of Colorado-Anschutz Medical Campus, Aurora, USA
| | - Sue C Kinnamon
- Department of Otolaryngology and Rocky Mountain Taste and Smell Center, University of Colorado-Anschutz Medical Campus, Aurora, USA
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11
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Association of single nucleotide polymorphisms with taste and food preferences of the Hungarian general and Roma populations. Appetite 2021; 164:105270. [PMID: 33930497 DOI: 10.1016/j.appet.2021.105270] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 04/14/2021] [Accepted: 04/15/2021] [Indexed: 11/20/2022]
Abstract
It is reasonable to suppose that poor diet underlies the unfavorable health status of the Roma population of Europe. Previously in the framework of a complex health survey, fruit and vegetable consumption, quantity of sugar added, salting frequency; bitter, salty, sweet and fat taste preferences were evaluated of Hungarian (HG, n = 410) and Roma (HR, n = 387) populations. In the present study the associations of taste and food preferences with TAS1R3, CD36, SCNN1B, TRPV1, TAS2R38, TAS2R19 and CA6 polymorphisms were tested in the same samples. Genotype frequencies did not differ significantly between the two populations. Although we initially observed associations between certain genetic polymorphisms and taste and food preferences in our study samples, none of the p values remained significant after the multiple test correction. However, some of our results could be considered promising (0.05<corrected p < 0.20), which showed potential ethnicity-specific effects (CA6 rs2274333 with salty taste and raw kohlrabi preference, CD36 rs1527483 with fat taste preference, TAS2R19 rs10772420 with grapefruit preference, and TAS2R38 rs713598 with quantity of sugar added). Our results may suggest that genetics may mediate food preferences, and individuals with different ethnic background may require personalized interventions to modify diet. Further investigations with greater sample sizes are essential to explore the effect of these genetic variants on taste and food preferences.
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12
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Melis M, Haehner A, Mastinu M, Hummel T, Tomassini Barbarossa I. Molecular and Genetic Factors Involved in Olfactory and Gustatory Deficits and Associations with Microbiota in Parkinson's Disease. Int J Mol Sci 2021; 22:ijms22084286. [PMID: 33924222 PMCID: PMC8074606 DOI: 10.3390/ijms22084286] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 04/14/2021] [Accepted: 04/17/2021] [Indexed: 12/11/2022] Open
Abstract
Deficits in olfaction and taste are among the most frequent non-motor manifestations in Parkinson’s disease (PD) that start very early and frequently precede the PD motor symptoms. The limited data available suggest that the basis of the olfactory and gustatory dysfunction related to PD are likely multifactorial and may include the same determinants responsible for other non-motor symptoms of PD. This review describes the most relevant molecular and genetic factors involved in the PD-related smell and taste impairments, and their associations with the microbiota, which also may represent risk factors associated with the disease.
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Affiliation(s)
- Melania Melis
- Department of Biomedical Sciences, University of Cagliari, Monserrato, 09042 Cagliari, Italy; (M.M.); (M.M.)
| | - Antje Haehner
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technical University of Dresden, 01307 Dresden, Germany; (A.H.); (T.H.)
| | - Mariano Mastinu
- Department of Biomedical Sciences, University of Cagliari, Monserrato, 09042 Cagliari, Italy; (M.M.); (M.M.)
| | - Thomas Hummel
- Smell and Taste Clinic, Department of Otorhinolaryngology, Technical University of Dresden, 01307 Dresden, Germany; (A.H.); (T.H.)
| | - Iole Tomassini Barbarossa
- Department of Biomedical Sciences, University of Cagliari, Monserrato, 09042 Cagliari, Italy; (M.M.); (M.M.)
- Correspondence: ; Tel.: +39-070-675-4144
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13
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Liu G, Fu D, Tian H, Dai A. The mechanism of ions in pulmonary hypertension. Pulm Circ 2021; 11:2045894020987948. [PMID: 33614016 PMCID: PMC7869166 DOI: 10.1177/2045894020987948] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 12/23/2020] [Indexed: 12/15/2022] Open
Abstract
Pulmonary hypertension(PH)is a kind of hemodynamic and pathophysiological state, in which the pulmonary artery pressure (PAP) rises above a certain threshold. The main pathological manifestation is pulmonary vasoconstriction and remodelling progressively. More and more studies have found that ions play a major role in the pathogenesis of PH. Many vasoactive substances, inflammatory mediators, transcription-inducing factors, apoptosis mediators, redox substances and translation modifiers can control the concentration of ions inside and outside the cell by regulating the activity of ion channels, which can regulate vascular contraction, cell proliferation, migration, apoptosis, inflammation and other functions. We all know that there are no effective drugs to treat PH. Ions are involved in the occurrence and development of PH, so it is necessary to clarify the mechanism of ions in PH as a therapeutic target for PH. The main ions involved in PH are calcium ion (Ca2+), potassium ion (K+), sodium ion (Na+) and chloride ion (Cl-). Here, we mainly discuss the distribution of these ions and their channels in pulmonary arteries and their role in the pathogenesis of PH.
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Affiliation(s)
- Guogu Liu
- Department of Graduate School, University of South China,
Hengyang, China
- Department of Respiratory Medicine, Hunan Provincial People’s
Hospital, Changsha, China
| | - Daiyan Fu
- Department of Respiratory Medicine, Hunan Provincial People’s
Hospital, Changsha, China
| | - Heshen Tian
- Department of Graduate School, University of South China,
Hengyang, China
- Department of Respiratory Medicine, Hunan Provincial People’s
Hospital, Changsha, China
| | - Aiguo Dai
- Department of Respiratory Diseases, Hunan University of Chinese
Medicine, Changsha, China
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14
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Abstract
All organisms have the ability to detect chemicals in the environment, which likely evolved out of organisms' needs to detect food sources and avoid potentially harmful compounds. The taste system detects chemicals and is used to determine whether potential food items will be ingested or rejected. The sense of taste detects five known taste qualities: bitter, sweet, salty, sour, and umami, which is the detection of amino acids, specifically glutamate. These different taste qualities encompass a wide variety of chemicals that differ in their structure and as a result, the peripheral taste utilizes numerous and diverse mechanisms to detect these stimuli. In this chapter, we will summarize what is currently known about the signaling mechanisms used by taste cells to transduce stimulus signals.
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Affiliation(s)
- Debarghya Dutta Banik
- Department of Biological Sciences, University at Buffalo, State University of New York at Buffalo, Buffalo, NY, USA
- Department of Anatomy, Cell Biology and Physiology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Kathryn F Medler
- Department of Biological Sciences, University at Buffalo, State University of New York at Buffalo, Buffalo, NY, USA.
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15
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Optogenetic Stimulation of Type I GAD65 + Cells in Taste Buds Activates Gustatory Neurons and Drives Appetitive Licking Behavior in Sodium-Depleted Mice. J Neurosci 2020. [PMID: 32878902 DOI: 10.1523/jneurosci.0597‐20.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Mammalian taste buds are comprised of specialized neuroepithelial cells that act as sensors for molecules that provide nutrition (e.g., carbohydrates, amino acids, and salts) and those that are potentially harmful (e.g., certain plant compounds and strong acids). Type II and III taste bud cells (TBCs) detect molecules described by humans as "sweet," "bitter," "umami," and "sour." TBCs that detect metallic ions, described by humans as "salty," are undefined. Historically, type I glial-like TBCs have been thought to play a supportive role in the taste bud, but little research has been done to explore their role in taste transduction. Some evidence implies that type I cells may detect sodium (Na+) via an amiloride-sensitive mechanism, suggesting they play a role in Na+ taste transduction. We used an optogenetic approach to study type I TBCs by driving the expression of the light-sensitive channelrhodopsin-2 (ChR2) in type I GAD65+ TBCs of male and female mice. Optogenetic stimulation of GAD65+ TBCs increased chorda tympani nerve activity and activated gustatory neurons in the rostral nucleus tractus solitarius. "N neurons," whose NaCl responses were blocked by the amiloride analog benzamil, responded robustly to light stimulation of GAD65+ TBCs on the anterior tongue. Two-bottle preference tests were conducted under Na+-replete and Na+-deplete conditions to assess the behavioral impact of optogenetic stimulation of GAD65+ TBCs. Under Na+-deplete conditions GAD65-ChR2-EYFP mice displayed a robust preference for H2O illuminated with 470 nm light versus nonilluminated H2O, suggesting that type I glial-like TBCs are sufficient for driving a behavior that resembles Na+ appetite.SIGNIFICANCE STATEMENT This is the first investigation on the role of type I GAD65+ taste bud cells (TBCs) in taste-mediated physiology and behavior via optogenetics. It details the first definitive evidence that selective optogenetic stimulation of glial-like GAD65+ TBCs evokes neural activity and modulates behavior. Optogenetic stimulation of GAD65+ TBCs on the anterior tongue had the strongest effect on gustatory neurons that responded best to NaCl stimulation through a benzamil-sensitive mechanism. Na+-depleted mice showed robust preferences to "light taste" (H2O illuminated with 470 nm light vs nonilluminated H2O), suggesting that the activation of GAD65+ cells may generate a salt-taste sensation in the brain. Together, our results shed new light on the role of GAD65+ TBCs in gustatory transduction and taste-mediated behavior.
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16
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Optogenetic Stimulation of Type I GAD65 + Cells in Taste Buds Activates Gustatory Neurons and Drives Appetitive Licking Behavior in Sodium-Depleted Mice. J Neurosci 2020; 40:7795-7810. [PMID: 32878902 DOI: 10.1523/jneurosci.0597-20.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 08/17/2020] [Accepted: 08/23/2020] [Indexed: 01/27/2023] Open
Abstract
Mammalian taste buds are comprised of specialized neuroepithelial cells that act as sensors for molecules that provide nutrition (e.g., carbohydrates, amino acids, and salts) and those that are potentially harmful (e.g., certain plant compounds and strong acids). Type II and III taste bud cells (TBCs) detect molecules described by humans as "sweet," "bitter," "umami," and "sour." TBCs that detect metallic ions, described by humans as "salty," are undefined. Historically, type I glial-like TBCs have been thought to play a supportive role in the taste bud, but little research has been done to explore their role in taste transduction. Some evidence implies that type I cells may detect sodium (Na+) via an amiloride-sensitive mechanism, suggesting they play a role in Na+ taste transduction. We used an optogenetic approach to study type I TBCs by driving the expression of the light-sensitive channelrhodopsin-2 (ChR2) in type I GAD65+ TBCs of male and female mice. Optogenetic stimulation of GAD65+ TBCs increased chorda tympani nerve activity and activated gustatory neurons in the rostral nucleus tractus solitarius. "N neurons," whose NaCl responses were blocked by the amiloride analog benzamil, responded robustly to light stimulation of GAD65+ TBCs on the anterior tongue. Two-bottle preference tests were conducted under Na+-replete and Na+-deplete conditions to assess the behavioral impact of optogenetic stimulation of GAD65+ TBCs. Under Na+-deplete conditions GAD65-ChR2-EYFP mice displayed a robust preference for H2O illuminated with 470 nm light versus nonilluminated H2O, suggesting that type I glial-like TBCs are sufficient for driving a behavior that resembles Na+ appetite.SIGNIFICANCE STATEMENT This is the first investigation on the role of type I GAD65+ taste bud cells (TBCs) in taste-mediated physiology and behavior via optogenetics. It details the first definitive evidence that selective optogenetic stimulation of glial-like GAD65+ TBCs evokes neural activity and modulates behavior. Optogenetic stimulation of GAD65+ TBCs on the anterior tongue had the strongest effect on gustatory neurons that responded best to NaCl stimulation through a benzamil-sensitive mechanism. Na+-depleted mice showed robust preferences to "light taste" (H2O illuminated with 470 nm light vs nonilluminated H2O), suggesting that the activation of GAD65+ cells may generate a salt-taste sensation in the brain. Together, our results shed new light on the role of GAD65+ TBCs in gustatory transduction and taste-mediated behavior.
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Does ENaC Work as Sodium Taste Receptor in Humans? Nutrients 2020; 12:nu12041195. [PMID: 32344597 PMCID: PMC7230849 DOI: 10.3390/nu12041195] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2020] [Revised: 04/14/2020] [Accepted: 04/21/2020] [Indexed: 12/17/2022] Open
Abstract
Taste reception is fundamental for the proper selection of food and beverages. Among the several chemicals recognized by the human taste system, sodium ions (Na+) are of particular relevance. Na+ represents the main extracellular cation and is a key factor in many physiological processes. Na+ elicits a specific sensation, called salty taste, and low-medium concentrations of table salt (NaCl, the common sodium-containing chemical we use to season foods) are perceived as pleasant and appetitive. How we detect this cation in foodstuffs is scarcely understood. In animal models, such as the mouse and the rat, the epithelial sodium channel (ENaC) has been proposed as a key protein for recognizing Na+ and for mediating preference responses to low-medium salt concentrations. Here, I will review our current understanding regarding the possible involvement of ENaC in the detection of food Na+ by the human taste system.
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Rhyu MR, Song AY, Kim EY, Son HJ, Kim Y, Mummalaneni S, Qian J, Grider JR, Lyall V. Kokumi Taste Active Peptides Modulate Salt and Umami Taste. Nutrients 2020; 12:nu12041198. [PMID: 32344605 PMCID: PMC7254231 DOI: 10.3390/nu12041198] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 04/21/2020] [Accepted: 04/22/2020] [Indexed: 12/27/2022] Open
Abstract
Kokumi taste substances exemplified by γ-glutamyl peptides and Maillard Peptides modulate salt and umami tastes. However, the underlying mechanism for their action has not been delineated. Here, we investigated the effects of a kokumi taste active and inactive peptide fraction (500-10,000 Da) isolated from mature (FIIm) and immature (FIIim) Ganjang, a typical Korean soy sauce, on salt and umami taste responses in humans and rodents. Only FIIm (0.1-1.0%) produced a biphasic effect in rat chorda tympani (CT) taste nerve responses to lingual stimulation with 100 mM NaCl + 5 μM benzamil, a specific epithelial Na+ channel blocker. Both elevated temperature (42 °C) and FIIm produced synergistic effects on the NaCl + benzamil CT response. At 0.5% FIIm produced the maximum increase in rat CT response to NaCl + benzamil, and enhanced salt taste intensity in human subjects. At 2.5% FIIm enhanced rat CT response to glutamate that was equivalent to the enhancement observed with 1 mM IMP. In human subjects, 0.3% FIIm produced enhancement of umami taste. These results suggest that FIIm modulates amiloride-insensitive salt taste and umami taste at different concentration ranges in rats and humans.
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Affiliation(s)
- Mee-Ra Rhyu
- Korea Food Research Institute, Wanju-gun, Jeollabuk-do 55365, Korea; (A.-Y.S.); (E.-Y.K.); (H.-J.S.); (Y.K.)
- Correspondence: (M.-R.R.); (V.L.); Tel.: +82-63-219-9268 (M.-R.R.); +1-(804)-828-9759 (V.L.); Fax: +82-63-219-9876 (M.-R.R.); +1-(804)-827-0947 (V.L.)
| | - Ah-Young Song
- Korea Food Research Institute, Wanju-gun, Jeollabuk-do 55365, Korea; (A.-Y.S.); (E.-Y.K.); (H.-J.S.); (Y.K.)
| | - Eun-Young Kim
- Korea Food Research Institute, Wanju-gun, Jeollabuk-do 55365, Korea; (A.-Y.S.); (E.-Y.K.); (H.-J.S.); (Y.K.)
| | - Hee-Jin Son
- Korea Food Research Institute, Wanju-gun, Jeollabuk-do 55365, Korea; (A.-Y.S.); (E.-Y.K.); (H.-J.S.); (Y.K.)
| | - Yiseul Kim
- Korea Food Research Institute, Wanju-gun, Jeollabuk-do 55365, Korea; (A.-Y.S.); (E.-Y.K.); (H.-J.S.); (Y.K.)
| | - Shobha Mummalaneni
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA; (S.M.); (J.Q.); (J.R.G.)
| | - Jie Qian
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA; (S.M.); (J.Q.); (J.R.G.)
| | - John R. Grider
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA; (S.M.); (J.Q.); (J.R.G.)
| | - Vijay Lyall
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298, USA; (S.M.); (J.Q.); (J.R.G.)
- Correspondence: (M.-R.R.); (V.L.); Tel.: +82-63-219-9268 (M.-R.R.); +1-(804)-828-9759 (V.L.); Fax: +82-63-219-9876 (M.-R.R.); +1-(804)-827-0947 (V.L.)
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19
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Sodium Imbalance in Mice Results Primarily in Compensatory Gene Regulatory Responses in Kidney and Colon, but Not in Taste Tissue. Nutrients 2020; 12:nu12040995. [PMID: 32260115 PMCID: PMC7230584 DOI: 10.3390/nu12040995] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 03/27/2020] [Accepted: 03/30/2020] [Indexed: 12/12/2022] Open
Abstract
Renal excretion and sodium appetite provide the basis for sodium homeostasis. In both the kidney and tongue, the epithelial sodium channel (ENaC) is involved in sodium uptake and sensing. The diuretic drug amiloride is known to block ENaC, producing a mild natriuresis. However, amiloride is further reported to induce salt appetite in rodents after prolonged exposure as well as bitter taste impressions in humans. To examine how dietary sodium content and amiloride impact on sodium appetite, mice were subjected to dietary salt and amiloride intervention and subsequently analyzed for ENaC expression and taste reactivity. We observed substantial changes of ENaC expression in the colon and kidney confirming the role of these tissues for sodium homeostasis, whereas effects on lingual ENaC expression and taste preferences were negligible. In comparison, prolonged exposure to amiloride-containing drinking water affected β- and αENaC expression in fungiform and posterior taste papillae, respectively, next to changes in salt taste. However, amiloride did not only change salt taste sensation but also perception of sucrose, glutamate, and citric acid, which might be explained by the fact that amiloride itself activates bitter taste receptors in mice. Accordingly, exposure to amiloride generally affects taste impression and should be evaluated with care.
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20
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Kleyman TR, Eaton DC. Regulating ENaC's gate. Am J Physiol Cell Physiol 2020; 318:C150-C162. [PMID: 31721612 PMCID: PMC6985836 DOI: 10.1152/ajpcell.00418.2019] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2019] [Revised: 10/24/2019] [Accepted: 10/24/2019] [Indexed: 02/07/2023]
Abstract
Epithelial Na+ channels (ENaCs) are members of a family of cation channels that function as sensors of the extracellular environment. ENaCs are activated by specific proteases in the biosynthetic pathway and at the cell surface and remove embedded inhibitory tracts, which allows channels to transition to higher open-probability states. Resolved structures of ENaC and an acid-sensing ion channel revealed highly organized extracellular regions. Within the periphery of ENaC subunits are unique domains formed by antiparallel β-strands containing the inhibitory tracts and protease cleavage sites. ENaCs are inhibited by Na+ binding to specific extracellular site(s), which promotes channel transition to a lower open-probability state. Specific inositol phospholipids and channel modification by Cys-palmitoylation enhance channel open probability. How these regulatory factors interact in a concerted manner to influence channel open probability is an important question that has not been resolved. These various factors are reviewed, and the impact of specific factors on human disorders is discussed.
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Affiliation(s)
- Thomas R Kleyman
- Renal-Electrolyte Division, Department of Medicine, and Departments of Cell Biology and of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Douglas C Eaton
- Division of Nephrology, Department of Medicine, Emory University, Atlanta, Georgia
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21
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Diószegi J, Llanaj E, Ádány R. Genetic Background of Taste Perception, Taste Preferences, and Its Nutritional Implications: A Systematic Review. Front Genet 2019; 10:1272. [PMID: 31921309 PMCID: PMC6930899 DOI: 10.3389/fgene.2019.01272] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 11/19/2019] [Indexed: 01/01/2023] Open
Abstract
Background: The rise in nutrition-related morbidity and mortality requires public health intervention programs targeting nutritional behavior. In addition to socio-economical, socio-cultural, psychological determinants, taste is one of the main factors that influence food choices. Differences in taste perception and sensitivity may be explained by genetic variations, therefore the knowledge of the extent to which genetic factors influence the development of individual taste preferences and eating patterns is important for public policy actions addressing nutritional behaviors. Our aim was to review genetic polymorphisms accounting for variability in taste and food preferences to contribute to an improved understanding of development of taste and food preferences. Methods: The electronic databases PubMed, Scopus, and Web of Science were searched using MeSH in PubMed and free text terms for articles published between January 1, 2000 and April 13, 2018. The search strategy was conducted following the PRISMA statement. The quality of the included studies was assessed by the validated Q-Genie tool. Results: Following the PRISMA flowchart, finally 103 articles were included in the review. Among the reviewed studies, 43 were rated to have good quality, 47 were rated to have moderate quality, and 13 were rated to have low quality. The majority of the studies assessed the association of genetic variants with the bitter taste modality, followed by articles analyzing the impact of polymorphisms on sweet and fat preferences. The number of studies investigating the association between umami, salty, and sour taste qualities and genetic polymorphisms was limited. Conclusions: Our findings suggest that a significant association exists between TAS2R38 variants (rs713598, rs1726866, rs10246939) and bitter and sweet taste preference. Other confirmed results are related to rs1761667 (CD36) and fat taste responsiveness. Otherwise further research is essential to confirm results of studies related to genetic variants and individual taste sensitivity. This knowledge may enhance our understanding of the development of individual taste and related food preferences and food choices that will aid the development of tailored public health strategy to reduce nutrition-related disease and morbidity.
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Affiliation(s)
- Judit Diószegi
- MTA-DE Public Health Research Group, Public Health Research Institute, University of Debrecen, Debrecen, Hungary
| | - Erand Llanaj
- Doctoral School of Health Sciences, University of Debrecen, Debrecen, Hungary
| | - Róza Ádány
- MTA-DE Public Health Research Group, Public Health Research Institute, University of Debrecen, Debrecen, Hungary.,Doctoral School of Health Sciences, University of Debrecen, Debrecen, Hungary.,WHO Collaborating Centre on Vulnerability and Health, University of Debrecen, Debrecen, Hungary
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22
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Li Q, Fung E. Multifaceted Functions of Epithelial Na + Channel in Modulating Blood Pressure. Hypertension 2019; 73:273-281. [PMID: 30580685 DOI: 10.1161/hypertensionaha.118.12330] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Qi Li
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
| | - Erik Fung
- From the Division of Cardiology, Department of Medicine and Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong (Q.L., E.F.).,Gerald Choa Cardiac Research Centre, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Lui Che Woo Institute of Innovative Medicine, Faculty of Medicine, The Chinese University of Hong Kong (E.F.).,Laboratory for Heart Failure and Circulation Research, Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, Hong Kong SAR (Q.L., E.F.)
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23
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Schier LA, Spector AC. The Functional and Neurobiological Properties of Bad Taste. Physiol Rev 2019; 99:605-663. [PMID: 30475657 PMCID: PMC6442928 DOI: 10.1152/physrev.00044.2017] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 05/18/2018] [Accepted: 06/30/2018] [Indexed: 12/12/2022] Open
Abstract
The gustatory system serves as a critical line of defense against ingesting harmful substances. Technological advances have fostered the characterization of peripheral receptors and have created opportunities for more selective manipulations of the nervous system, yet the neurobiological mechanisms underlying taste-based avoidance and aversion remain poorly understood. One conceptual obstacle stems from a lack of recognition that taste signals subserve several behavioral and physiological functions which likely engage partially segregated neural circuits. Moreover, although the gustatory system evolved to respond expediently to broad classes of biologically relevant chemicals, innate repertoires are often not in register with the actual consequences of a food. The mammalian brain exhibits tremendous flexibility; responses to taste can be modified in a specific manner according to bodily needs and the learned consequences of ingestion. Therefore, experimental strategies that distinguish between the functional properties of various taste-guided behaviors and link them to specific neural circuits need to be applied. Given the close relationship between the gustatory and visceroceptive systems, a full reckoning of the neural architecture of bad taste requires an understanding of how these respective sensory signals are integrated in the brain.
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Affiliation(s)
- Lindsey A Schier
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
| | - Alan C Spector
- Department of Biological Sciences, University of Southern California , Los Angeles, California ; and Department of Psychology and Program in Neuroscience, Florida State University , Tallahassee, Florida
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24
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Kaushik S, Kumar R, Kain P. Salt an Essential Nutrient: Advances in Understanding Salt Taste Detection Using Drosophila as a Model System. J Exp Neurosci 2018; 12:1179069518806894. [PMID: 30479487 PMCID: PMC6249657 DOI: 10.1177/1179069518806894] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 09/19/2018] [Indexed: 11/16/2022] Open
Abstract
Taste modalities are conserved in insects and mammals. Sweet gustatory signals evoke attractive behaviors while bitter gustatory information drive aversive behaviors. Salt (NaCl) is an essential nutrient required for various physiological processes, including electrolyte homeostasis, neuronal activity, nutrient absorption, and muscle contraction. Not only mammals, even in Drosophila melanogaster, the detection of NaCl induces two different behaviors: Low concentrations of NaCl act as an attractant, whereas high concentrations act as repellant. The fruit fly is an excellent model system for studying the underlying mechanisms of salt taste due to its relatively simple neuroanatomical organization of the brain and peripheral taste system, the availability of powerful genetic tools and transgenic strains. In this review, we have revisited the literature and the information provided by various laboratories using invertebrate model system Drosophila that has helped us to understand NaCl salt taste so far. We hope that this compiled information from Drosophila will be of general significance and interest for forthcoming studies of the structure, function, and behavioral role of NaCl-sensitive (low and high concentrations) gustatory circuitry for understanding NaCl salt taste in all animals.
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Affiliation(s)
- Shivam Kaushik
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
| | - Rahul Kumar
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India.,Department of Biotechnology, Maharshi Dayanand University, Rohtak, India
| | - Pinky Kain
- Department of Neurobiology and Genetics, Regional Centre for Biotechnology, NCR Biotech Science Cluster, Faridabad, India
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25
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Kasahara Y, Sakurai T, Matsuda R, Narukawa M, Yasuoka A, Mori N, Watanabe H, Okabe T, Kojima H, Abe K, Misaka T, Asakura T. Novel indole and benzothiophene ring derivatives showing differential modulatory activity against human epithelial sodium channel subunits, ENaC β and γ. Biosci Biotechnol Biochem 2018; 83:243-250. [PMID: 30343635 DOI: 10.1080/09168451.2018.1533802] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The epithelial sodium channel (ENaC) plays a pivotal role in sodium homeostasis, and the development of drugs that modulate ENaC activity is of great potential therapeutic relevance. We screened 6100 chemicals for their ability to activate sodium permeability of ENaC. We used a two-step strategy: a high throughput cell-based assay and an electrophysiological assay. Five compounds were identified showing common structural features including an indole or benzothiophene ring. ENaC consists of three subunits: α, β, and γ. Changing the heteromeric combination of human and mouse ENaC αβγ subunits, we found that all five compounds activated the human β subunit but not the mouse subunit. However, four of them exhibited lower activity when the human γ subunit was substituted by the mouse γ subunit. Our findings provide a structural basis for designing human ENaC activity modulators. Abbreviations: ENaC: Epithelial sodium channel; ΔRFU: delta relative fluorescence units; EC50: Half-maximal effective concentration; Emax: maximum effect value.
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Affiliation(s)
- Yoichi Kasahara
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Takanobu Sakurai
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Ryusei Matsuda
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Masataka Narukawa
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Akihito Yasuoka
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Naoki Mori
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Hidenori Watanabe
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Takayoshi Okabe
- b Drug Discovery Initiative (DDI) , The University of Tokyo , Tokyo , Japan
| | - Hirotatsu Kojima
- b Drug Discovery Initiative (DDI) , The University of Tokyo , Tokyo , Japan
| | - Keiko Abe
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan.,c Kanagawa Institute of Industrial Science and Technology (KISTEC) , Kanagawa , Japan
| | - Takumi Misaka
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
| | - Tomiko Asakura
- a Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences , The University of Tokyo , Tokyo , Japan
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Kandel C, Schmidt P, Perniss A, Keshavarz M, Scholz P, Osterloh S, Althaus M, Kummer W, Deckmann K. ENaC in Cholinergic Brush Cells. Front Cell Dev Biol 2018; 6:89. [PMID: 30159312 PMCID: PMC6103785 DOI: 10.3389/fcell.2018.00089] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 07/25/2018] [Indexed: 12/17/2022] Open
Abstract
Cholinergic polymodal chemosensory cells in the mammalian urethra (urethral brush cells = UBC) functionally express the canonical bitter and umami taste transduction signaling cascade. Here, we aimed to determine whether UBC are functionally equipped for the perception of salt through ENaC (epithelial sodium channel). Cholinergic UBC were isolated from ChAT-eGFP reporter mice (ChAT = choline acetyltransferase). RT-PCR showed mRNA expression of ENaC subunits Scnn1a, Scnn1b, and Scnn1g in urethral epithelium and isolated UBC. Scnn1a could also be detected by next generation sequencing in 4/6 (66%) single UBC, two of them also expressed the bitter receptor Tas2R108. Strong expression of Scnn1a was seen in some urothelial umbrella cells and in 65% of UBC (30/46 cells) in a Scnn1a reporter mouse strain. Intracellular [Ca2+] was recorded in isolated UBC stimulated with the bitter substance denatonium benzoate (25 mM), ATP (0.5 mM) and NaCl (50 mM, on top of 145 mM Na+ and 153 mM Cl− baseline in buffer); mannitol (150 mM) served as osmolarity control. NaCl, but not mannitol, evoked an increase in intracellular [Ca2+] in 70% of the tested UBC. The NaCl-induced effect was blocked by the ENaC inhibitor amiloride (IC50 = 0.47 μM). When responses to both NaCl and denatonium were tested, all three possible positive response patterns occurred in a balanced distribution: 42% NaCl only, 33% denatonium only, 25% to both stimuli. A similar reaction pattern was observed with ATP and NaCl as test stimuli. About 22% of the UBC reacted to all three stimuli. Thus, NaCl evokes calcium responses in several UBC, likely involving an amiloride-sensitive channel containing α-ENaC. This feature does not define a new subpopulation of UBC, but rather emphasizes their polymodal character. The actual function of α-ENaC in cholinergic UBC—salt perception, homeostatic ion transport, mechanoreception—remains to be determined.
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Affiliation(s)
- Chrissy Kandel
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Patricia Schmidt
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Alexander Perniss
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Maryam Keshavarz
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Paul Scholz
- Department of Cell Physiology, Ruhr-University Bochum, Bochum, Germany
| | - Sabrina Osterloh
- Department of Cell Physiology, Ruhr-University Bochum, Bochum, Germany
| | - Mike Althaus
- School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Wolfgang Kummer
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
| | - Klaus Deckmann
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Giessen, Germany
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27
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Xu JJ, Elkaddi N, Garcia-Blanco A, Spielman AI, Bachmanov AA, Chung HY, Ozdener MH. Arginyl dipeptides increase the frequency of NaCl-elicited responses via epithelial sodium channel alpha and delta subunits in cultured human fungiform taste papillae cells. Sci Rep 2017; 7:7483. [PMID: 28790369 PMCID: PMC5548727 DOI: 10.1038/s41598-017-07756-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Accepted: 06/12/2017] [Indexed: 12/19/2022] Open
Abstract
Salty taste is one of the five basic tastes and is often elicited by NaCl. Because excess sodium intake is associated with many health problems, it could be useful to have salt taste enhancers that are not sodium based. In this study, the regulation of NaCl-induced responses was investigated in cultured human fungiform taste papillae (HBO) cells with five arginyl dipeptides: Ala-Arg (AR), Arg-Ala (RA), Arg-Pro (RP), Arg-Glu (RE), and Glu-Arg (ER); and two non-arginyl dipeptides: Asp-Asp (DD) and Glu-Asp (ED). AR, RA, and RP significantly increased the number of cell responses to NaCl, whereas no effect was observed with RE, ER, DD, or ED. We also found no effects with alanine, arginine, or a mixture of both amino acids. Pharmacological studies showed that AR significantly increased responses of amiloride-sensitive but not amiloride-insensitive cells. In studies using small interfering RNAs (siRNAs), responses to AR were significantly decreased in cells transfected with siRNAs against epithelial sodium channel ENaCα or ENaCδ compared to untransfected cells. AR dramatically increased NaCl-elicited responses in cells transfected with NHE1 siRNA but not in those transfected with ENaCα or ENaCδ siRNAs. Altogether, AR increased responses of amiloride-sensitive cells required ENaCα and ENaCδ.
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Affiliation(s)
- Jiao-Jiao Xu
- Food and Nutritional Sciences Programme, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China
| | - Nadia Elkaddi
- Monell Chemical Senses Center, Philadelphia, PA, 19104, USA
| | | | | | | | - Hau Yin Chung
- Food and Nutritional Sciences Programme, School of Life Sciences, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong SAR, China.
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28
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Sharma K, Haque M, Guidry R, Ueta Y, Teruyama R. Effect of dietary salt intake on epithelial Na + channels (ENaC) in vasopressin magnocellular neurosecretory neurons in the rat supraoptic nucleus. J Physiol 2017; 595:5857-5874. [PMID: 28714095 PMCID: PMC5577521 DOI: 10.1113/jp274856] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Accepted: 07/11/2017] [Indexed: 01/18/2023] Open
Abstract
KEY POINTS A growing body of evidence suggests that epithelial Na+ channels (ENaCs) in the brain play a significant role in the regulation of blood pressure; however, the brain structures that mediate the effect are not well understood. Because vasopressin (VP) neurons play a pivotal role in coordinating neuroendocrine and autonomic responses to maintain cardiovascular homeostasis, a basic understanding of the regulation and activity of ENaC in VP neurons is of great interest. We show that high dietary salt intake caused an increase in the expression and activity of ENaC which resulted in the steady state depolarization of VP neurons. The results help us understand one of the mechanisms underlying how dietary salt intake affects the activity of VP neurons via ENaC activity. ABSTRACT All three epithelial Na+ channel (ENaC) subunits (α, β and γ) are located in vasopressin (VP) magnocellular neurons in the hypothalamic supraoptic (SON) and paraventricular nuclei. Our previous study demonstrated that ENaC mediates a Na+ leak current that affects the steady state membrane potential in VP neurons. In the present study, we evaluated the effect of dietary salt intake on ENaC regulation and activity in VP neurons. High dietary salt intake for 7 days caused an increase in expression of β- and γENaC subunits in the SON and the translocation of αENaC immunoreactivity towards the plasma membrane. Patch clamp experiments on hypothalamic slices showed that the mean amplitude of the putative ENaC currents was significantly greater in VP neurons from animals that were fed a high salt diet compared with controls. The enhanced ENaC current contributed to the more depolarized basal membrane potential observed in VP neurons in the high salt diet group. These findings indicate that high dietary NaCl intake enhances the expression and activity of ENaCs, which augments synaptic drive by depolarizing the basal membrane potential close to the action potential threshold during hormonal demand. However, ENaCs appear to have only a minor role in the regulation of the firing activity of VP neurons in the absence of synaptic inputs as neither the mean intraburst frequency, burst duration, nor interspike interval variability of phasic bursting activity was affected. Moreover, ENaC activity did not affect the initiation, sustention, or termination of the phasic bursting generated in an intrinsic manner without synaptic inputs.
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Affiliation(s)
- Kaustubh Sharma
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Masudul Haque
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Richard Guidry
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Yoichi Ueta
- Department of Physiology, University of Occupational and Environmental Health, Kitakyushu, 807-8555, Japan
| | - Ryoichi Teruyama
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA
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Affiliation(s)
- Jian Yang
- Department of Nutrition, Daping Hospital, The Third Military Medical University, Chongqing, China.,Department of Cardiology, Daping Hospital, The Third Military Medical University, Chongqing, China
| | - Pedro A Jose
- Division of Renal Disease & Hypertension, The George Washington University School of Medicine and Health Sciences, Washington, DC
| | - Chunyu Zeng
- Department of Cardiology, Daping Hospital, The Third Military Medical University, Chongqing, China
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Qian J, Mummalaneni S, Phan THT, Heck GL, DeSimone JA, West D, Mahavadi S, Hojati D, Murthy KS, Rhyu MR, Spielman AI, Özdener MH, Lyall V. Cyclic-AMP regulates postnatal development of neural and behavioral responses to NaCl in rats. PLoS One 2017; 12:e0171335. [PMID: 28192441 PMCID: PMC5305205 DOI: 10.1371/journal.pone.0171335] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2016] [Accepted: 01/18/2017] [Indexed: 02/07/2023] Open
Abstract
During postnatal development rats demonstrate an age-dependent increase in NaCl chorda tympani (CT) responses and the number of functional apical amiloride-sensitive epithelial Na+ channels (ENaCs) in salt sensing fungiform (FF) taste receptor cells (TRCs). Currently, the intracellular signals that regulate the postnatal development of salt taste have not been identified. We investigated the effect of cAMP, a downstream signal for arginine vasopressin (AVP) action, on the postnatal development of NaCl responses in 19-23 day old rats. ENaC-dependent NaCl CT responses were monitored after lingual application of 8-chlorophenylthio-cAMP (8-CPT-cAMP) under open-circuit conditions and under ±60 mV lingual voltage clamp. Behavioral responses were tested using 2 bottle/24h NaCl preference tests. The effect of [deamino-Cys1, D-Arg8]-vasopressin (dDAVP, a specific V2R agonist) was investigated on ENaC subunit trafficking in rat FF TRCs and on cAMP generation in cultured adult human FF taste cells (HBO cells). Our results show that in 19-23 day old rats, the ENaC-dependent maximum NaCl CT response was a saturating sigmoidal function of 8-CPT-cAMP concentration. 8-CPT-cAMP increased the voltage-sensitivity of the NaCl CT response and the apical Na+ response conductance. Intravenous injections of dDAVP increased ENaC expression and γ-ENaC trafficking from cytosolic compartment to the apical compartment in rat FF TRCs. In HBO cells dDAVP increased intracellular cAMP and cAMP increased trafficking of γ- and δ-ENaC from cytosolic compartment to the apical compartment 10 min post-cAMP treatment. Control 19-23 day old rats were indifferent to NaCl, but showed clear preference for appetitive NaCl concentrations after 8-CPT-cAMP treatment. Relative to adult rats, 14 day old rats demonstrated significantly less V2R antibody binding in circumvallate TRCs. We conclude that an age-dependent increase in V2R expression produces an AVP-induced incremental increase in cAMP that modulates the postnatal increase in TRC ENaC and the neural and behavioral responses to NaCl.
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Affiliation(s)
- Jie Qian
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Shobha Mummalaneni
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Tam-Hao T. Phan
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Gerard L. Heck
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - John A. DeSimone
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - David West
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Sunila Mahavadi
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Deanna Hojati
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Karnam S. Murthy
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Mee-Ra Rhyu
- Korea Food Research Institute, Bundang-gu, Sungnam-si, Gyeonggi-do, Korea
| | | | - Mehmet Hakan Özdener
- Monell Chemical Senses Center, Philadelphia, Pennsylvania, United States of America
| | - Vijay Lyall
- Departments of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
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Lapis TJ, Penner MH, Lim J. Humans Can Taste Glucose Oligomers Independent of the hT1R2/hT1R3 Sweet Taste Receptor. Chem Senses 2016; 41:755-762. [PMID: 27553043 DOI: 10.1093/chemse/bjw088] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
It is widely accepted that humans can taste mono- and disaccharides as sweet substances, but they cannot taste longer chain oligo- and polysaccharides. From the evolutionary standpoint, the ability to taste starch or its oligomeric hydrolysis products would be highly adaptive, given their nutritional value. Here, we report that humans can taste glucose oligomer preparations (average degree of polymerization 7 and 14) without any other sensorial cues. The same human subjects could not taste the corresponding glucose polymer preparation (average degree of polymerization 44). When the sweet taste receptor was blocked by lactisole, a known sweet inhibitor, subjects could not detect sweet substances (glucose, maltose, and sucralose), but they could still detect the glucose oligomers. This suggests that glucose oligomer detection is independent of the hT1R2/hT1R3 sweet taste receptor. Human subjects described the taste of glucose oligomers as "starchy," while they describe sugars as "sweet." The dose-response function of glucose oligomer was also found to be indistinguishable from that of glucose on a molar basis.
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Affiliation(s)
- Trina J Lapis
- Department of Food Science and Technology, Oregon State University , Corvallis, OR 97331 , USA
| | - Michael H Penner
- Department of Food Science and Technology, Oregon State University , Corvallis, OR 97331 , USA
| | - Juyun Lim
- Department of Food Science and Technology, Oregon State University , Corvallis, OR 97331 , USA
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Kumarhia D, He L, McCluskey LP. Inflammatory stimuli acutely modulate peripheral taste function. J Neurophysiol 2016; 115:2964-75. [PMID: 27009163 DOI: 10.1152/jn.01104.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 03/23/2016] [Indexed: 12/30/2022] Open
Abstract
Inflammation-mediated changes in taste perception can affect health outcomes in patients, but little is known about the underlying mechanisms. In the present work, we hypothesized that proinflammatory cytokines directly modulate Na(+) transport in taste buds. To test this, we measured acute changes in Na(+) flux in polarized fungiform taste buds loaded with a Na(+) indicator dye. IL-1β elicited an amiloride-sensitive increase in Na(+) transport in taste buds. In contrast, TNF-α dramatically and reversibly decreased Na(+) flux in polarized taste buds via amiloride-sensitive and amiloride-insensitive Na(+) transport systems. The speed and partial amiloride sensitivity of these changes in Na(+) flux indicate that IL-1β and TNF-α modulate epithelial Na(+) channel (ENaC) function. A portion of the TNF-mediated decrease in Na(+) flux is also blocked by the TRPV1 antagonist capsazepine, although TNF-α further reduced Na(+) transport independently of both amiloride and capsazepine. We also assessed taste function in vivo in a model of infection and inflammation that elevates these and additional cytokines. In rats administered systemic lipopolysaccharide (LPS), CT responses to Na(+) were significantly elevated between 1 and 2 h after LPS treatment. Low, normally preferred concentrations of NaCl and sodium acetate elicited high response magnitudes. Consistent with this outcome, codelivery of IL-1β and TNF-α enhanced Na(+) flux in polarized taste buds. These results demonstrate that inflammation elicits swift changes in Na(+) taste function, which may limit salt consumption during illness.
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Affiliation(s)
- Devaki Kumarhia
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia; and Graduate Program in Molecular Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia
| | - Lianying He
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia; and
| | - Lynnette Phillips McCluskey
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, Georgia; and
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Recent Advances in Molecular Mechanisms of Taste Signaling and Modifying. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2016; 323:71-106. [PMID: 26944619 DOI: 10.1016/bs.ircmb.2015.12.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The sense of taste conveys crucial information about the quality and nutritional value of foods before it is ingested. Taste signaling begins with taste cells via taste receptors in oral cavity. Activation of these receptors drives the transduction systems in taste receptor cells. Then particular transmitters are released from the taste cells and activate corresponding afferent gustatory nerve fibers. Recent studies have revealed that taste sensitivities are defined by distinct taste receptors and modulated by endogenous humoral factors in a specific group of taste cells. Such peripheral taste generations and modifications would directly influence intake of nutritive substances. This review will highlight current understanding of molecular mechanisms for taste reception, signal transduction in taste bud cells, transmission between taste cells and nerves, regeneration from taste stem cells, and modification by humoral factors at peripheral taste organs.
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Sakamoto T, Fujii A, Saito N, Kondo H, Ohuchi A. Alteration of amiloride-sensitive salt taste nerve responses in aldosterone/NaCl-induced hypertensive rats. Neurosci Res 2016; 108:60-6. [PMID: 26828852 DOI: 10.1016/j.neures.2016.01.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Revised: 01/21/2016] [Accepted: 01/21/2016] [Indexed: 01/23/2023]
Abstract
Salt taste sensitivity is related to physiological condition, and declined in hypertensive patients. However, little is known about the mechanism underlying changes in salt taste sensitivity during the development of hypertension. This is largely due to lack of an appropriate animal model which shows the decline of salt taste sensitivity caused by hypertension. Previous studies have suggested that one of main causes of salt-sensitive hypertension is dysfunction of the renin-angiotensin-aldosterone system (RAAS). To examine the involvement of RAAS in modulation of salt taste sensitivity, we utilized aldosterone/NaCl-treated rats as a well-established model of salt-sensitive hypertension caused by RAAS dysfunction. Amount of sodium intake in aldosterone/NaCl-treated rats was higher than that in control rats. In addition to behavioral changes, the amiloride-sensitive salt taste nerve responses in aldosterone/NaCl-treated rats were remarkably lower by approximately 90% than those in the other groups. Moreover, αENaC mRNA expression in the epithelium of circumvallate papillae was significantly low in aldosterone/NaCl-treated rats. Thus, RAAS modulates salt taste system as is case in hypertensive patients. This report is to our knowledge the first to describe an animal model with decline of amiloride-sensitive salt taste nerve responses by RAAS dysfunction-mediated salt-sensitive hypertension.
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Affiliation(s)
- Takashi Sakamoto
- Kansei Science Laboratories, Kao Corporation, 2606 Akabane, Ichikaimachi, Haga, Tochigi 321-3497, Japan
| | - Akihiko Fujii
- Biological Science Laboratories, Kao Corporation, 2606 Akabane, Ichikaimachi, Haga, Tochigi 321-3497, Japan
| | - Naoko Saito
- Kansei Science Laboratories, Kao Corporation, 2606 Akabane, Ichikaimachi, Haga, Tochigi 321-3497, Japan
| | - Hidehiko Kondo
- Kansei Science Laboratories, Kao Corporation, 2606 Akabane, Ichikaimachi, Haga, Tochigi 321-3497, Japan
| | - Atsushi Ohuchi
- Kansei Science Laboratories, Kao Corporation, 2606 Akabane, Ichikaimachi, Haga, Tochigi 321-3497, Japan.
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Epstein JB, Smutzer G, Doty RL. Understanding the impact of taste changes in oncology care. Support Care Cancer 2016; 24:1917-31. [DOI: 10.1007/s00520-016-3083-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Accepted: 01/07/2016] [Indexed: 12/22/2022]
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Lee RJ, Cohen NA. Sinonasal solitary chemosensory cells "taste" the upper respiratory environment to regulate innate immunity. Am J Rhinol Allergy 2015; 28:366-73. [PMID: 25198020 DOI: 10.2500/ajra.2014.28.4077] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND It is not fully understood how sinonasal epithelial cells detect the presence of pathogens and activate innate defense responses necessary for protecting the upper airway from infection. One mechanism is through bitter taste receptors (T2Rs), which are expressed in the sinonasal cavity. One T2R isoform, T2R38, is expressed in ciliated cells and detects quorum-sensing molecules from gram-negative bacteria, activating antimicrobial nitric oxide production. More recent studies have examined the role of T2Rs expressed in a sinonasal cell type that has only recently been identified in humans, the solitary chemosensory cell (SCC). We sought to provide an overview of SCCs and taste receptor function in human sinonasal defense as well as implications for chronic rhinosinusitis (CRS). METHODS A literature review of the current knowledge of SCCs and taste receptors in sinonasal physiology and CRS was conducted. RESULTS Human sinonasal SCCs express both bitter T2R and sweet T1R2/3 receptors. Activation of SCC T2Rs activates a calcium signal that propagates to the surrounding epithelial cells and causes secretion of antimicrobial peptides. T1R2/3 sweet receptor activation by physiological airway surface liquid (ASL) glucose concentrations attenuates the T2R response, likely as a mechanism to prevent full activation of the T2R pathway except during times of infection, when pathogens may consume ASL glucose and reduce its concentration. CONCLUSION SCCs appear to be important mediators of upper airway innate immunity, as the SCC T2Rs regulate antimicrobial peptide secretion, but further study is needed to determine the specific T2R isoforms involved as well as whether polymorphisms in these isoforms affect susceptibility to infection or patient outcomes in CRS. The inhibitory role of T1R2/3 sweet receptor suggests that T1R2/3 blockers may have therapeutic potential in some CRS patients, particularly those with diabetes mellitus. However, further clinical study of the relationship between infection and T1R2/3 genotype is required.
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Affiliation(s)
- Robert J Lee
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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38
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DeSimone JA, Phan THT, Mummalaneni S, Rhyu MR, Heck GL, Lyall V. Regulatory Effects of Ca2+ and H+ on the Rat Chorda Tympani Response to NaCl and KCl. Chem Senses 2015; 40:401-12. [PMID: 25953775 DOI: 10.1093/chemse/bjv022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Modulatory effects of pHi and [Ca(2+)]i on taste receptor cell (TRC) epithelial sodium channel (ENaC) were investigated by monitoring chorda tympani (CT) responses to NaCl and KCl at various lingual voltages, before and after lingual application of ionomycin and with 0-10mM CaCl2 in the stimulus and rinse solutions adjusted to pHo 2.0-9.7. 0.1 and 0.5M KCl responses varied continuously with voltage and were fitted to an apical ion channel kinetic model using the same parameters. ENaC-dependent NaCl CT response was fitted to the same channel model but with parameters characteristic of ENaC. A graded increase in TRC [Ca(2+)]i decreased the ENaC-dependent NaCl CT response, and inhibited and ultimately eliminated its pH sensitivity. CT responses to KCl were pHi- and [Ca(2+)]i-independent. Between ±60 mV applied lingual potential, the data were well described by a linear approximation to the nonlinear channel equation and yielded 2 parameters, the open-circuit response and the negative of the slope of the line in the CT response versus voltage plot, designated the response conductance. The ENaC-dependent NaCl CT response conductance was a linear function of the open-circuit response for all pHi-[Ca(2+)]i combinations examined. Analysis of these data shows that pHi and [Ca(2+)]i regulate TRC ENaC exclusively through modulation of the maximum CT response.
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Affiliation(s)
- John A DeSimone
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298-0551, USA and
| | - Tam-Hao T Phan
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298-0551, USA and
| | - Shobha Mummalaneni
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298-0551, USA and
| | - Mee-Ra Rhyu
- Korea Food Research Institute, Bundang-gu, Sungnam-si, Gyeonggi-do 463-746, Korea
| | - Gerard L Heck
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298-0551, USA and
| | - Vijay Lyall
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, VA 23298-0551, USA and
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40
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Roper SD. The taste of table salt. Pflugers Arch 2015; 467:457-63. [PMID: 25559847 DOI: 10.1007/s00424-014-1683-z] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Revised: 12/18/2014] [Accepted: 12/19/2014] [Indexed: 12/14/2022]
Abstract
Solutions of table salt (NaCl) elicit several tastes, including of course saltiness but also sweet, sour, and bitter. This brief review touches on some of the mileposts concerning what is known about taste transduction for the Na(+) ion, the main contributor to saltiness. Electrophysiological recordings, initially from single gustatory nerve fibers, and later, integrated impulse activity from gustatory nerves led researchers to predict that Na(+) ions interacted with a surface molecule. Subsequent studies have resolved that this molecule is likely to be an epithelial sodium channel, ENaC. Other Na(+) transduction mechanisms are also present in taste buds but have not yet been identified. The specific type(s) of taste cells responsible for salt taste also remains unknown.
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Affiliation(s)
- Stephen D Roper
- Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL, 33146, USA,
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41
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Shigemura N. Modulation of Taste Responsiveness by Angiotensin II. FOOD SCIENCE AND TECHNOLOGY RESEARCH 2015. [DOI: 10.3136/fstr.21.757] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Affiliation(s)
- Noriatsu Shigemura
- Section of Oral Neuroscience, Graduate School of Dental Science, Kyushu University
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Lee RJ, Cohen NA. Taste receptors in innate immunity. Cell Mol Life Sci 2015; 72:217-36. [PMID: 25323130 PMCID: PMC4286424 DOI: 10.1007/s00018-014-1736-7] [Citation(s) in RCA: 91] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/11/2014] [Accepted: 09/16/2014] [Indexed: 02/07/2023]
Abstract
Taste receptors were first identified on the tongue, where they initiate a signaling pathway that communicates information to the brain about the nutrient content or potential toxicity of ingested foods. However, recent research has shown that taste receptors are also expressed in a myriad of other tissues, from the airway and gastrointestinal epithelia to the pancreas and brain. The functions of many of these extraoral taste receptors remain unknown, but emerging evidence suggests that bitter and sweet taste receptors in the airway are important sentinels of innate immunity. This review discusses taste receptor signaling, focusing on the G-protein-coupled receptors that detect bitter, sweet, and savory tastes, followed by an overview of extraoral taste receptors and in-depth discussion of studies demonstrating the roles of taste receptors in airway innate immunity. Future research on extraoral taste receptors has significant potential for identification of novel immune mechanisms and insights into host-pathogen interactions.
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Affiliation(s)
- Robert J. Lee
- Department of Otorhinolaryngology, Perelman School of Medicine, University of Pennsylvania, Ravdin Building, 5th floor, Philadelphia, PA 19104 USA
| | - Noam A. Cohen
- Department of Otorhinolaryngology, Perelman School of Medicine, University of Pennsylvania, Ravdin Building, 5th floor, Philadelphia, PA 19104 USA
- Philadelphia Veterans Affairs Medical Center Surgical Services, 3900 Woodland Ave, Philadelphia, PA 19104 USA
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Bigiani A. Amiloride-sensitive sodium currents in fungiform taste cells of rats chronically exposed to nicotine. Neuroscience 2014; 284:180-191. [PMID: 25305667 DOI: 10.1016/j.neuroscience.2014.09.077] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Revised: 09/17/2014] [Accepted: 09/30/2014] [Indexed: 01/18/2023]
Abstract
Many studies have demonstrated that chronic exposure to nicotine, one of the main components of tobacco smoke, has profound effects on the functionality of the mammalian taste system. However, the mechanisms underlying nicotine action are poorly understood. In particular no information is available on the chronic effect of nicotine on the functioning of taste cells, the peripheral detectors which transduce food chemicals into electrical signals to the brain. To address this issue, I studied the membrane properties of rat fungiform taste cells and evaluated the effect of long-term exposure to nicotine on the amiloride-sensitive sodium currents (ASSCs). These currents are mediated by the epithelial sodium channels (ENaC) thought to be important, at least in part, in the transduction of salty stimuli. Patch-clamp recording data indicated that ASSCs in taste cells from rats chronically treated with nicotine had a reduced amplitude compared to controls. The pharmacological and biophysical analysis of ASSCs revealed that amplitude reduction was not dependent on changes in amiloride sensitivity or channel ionic permeability, but likely derived from a decrease in the activity of ENaCs. Since these channels are considered to be sodium receptors in taste cells, my results suggest that chronic exposure to nicotine hampers the capability of these cells to respond to sodium ions. This might represent a possible cellular mechanism underlying the reduced taste sensitivity to salt typically found in smokers.
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Affiliation(s)
- A Bigiani
- Dipartimento di Scienze Biomediche, Metaboliche e Neuroscienze, Sezione di Fisiologia e Neuroscienze, Università di Modena e Reggio Emilia, via G. Campi 287, 41125 Modena, Italy.
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Kuo WY, Lee Y. Effect of Food Matrix on Saltiness Perception-Implications for Sodium Reduction. Compr Rev Food Sci Food Saf 2014. [DOI: 10.1111/1541-4337.12094] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Wan-Yuan Kuo
- Dept. of Food Science and Human Nutrition; Univ. of Illinois at Urbana-Champaign, 382K; Agricultural Engineering and Sciences Building; 1304 W. Pennsylvania Ave Urbana IL 61801 USA
| | - Youngsoo Lee
- Dept. of Food Science and Human Nutrition; Univ. of Illinois at Urbana-Champaign, 382K; Agricultural Engineering and Sciences Building; 1304 W. Pennsylvania Ave Urbana IL 61801 USA
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Mummalaneni S, Qian J, Phan THT, Rhyu MR, Heck GL, DeSimone JA, Lyall V. Effect of ENaC modulators on rat neural responses to NaCl. PLoS One 2014; 9:e98049. [PMID: 24839965 PMCID: PMC4026388 DOI: 10.1371/journal.pone.0098049] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2014] [Accepted: 04/28/2014] [Indexed: 01/31/2023] Open
Abstract
The effects of small molecule ENaC activators N,N,N-trimethyl-2-((4-methyl-2-((4-methyl-1H-indol-3-yl)thio)pentanoyl)oxy)ethanaminium iodide (Compound 1) and N-(2-hydroxyethyl)-4-methyl-2-((4-methyl-1H-indol-3-yl)thio)pentanamide (Compound 2), were tested on the benzamil (Bz)-sensitive NaCl chorda tympani (CT) taste nerve response under open-circuit conditions and under ±60 mV applied lingual voltage-clamp, and compared with the effects of known physiological activators (8-CPT-cAMP, BAPTA-AM, and alkaline pH), and an inhibitor (ionomycin+Ca2+) of ENaC. The NaCl CT response was enhanced at −60 mV and suppressed at +60 mV. In every case the CT response (r) versus voltage (V) curve was linear. All ENaC activators increased the open-circuit response (ro) and the voltage sensitivity (κ, negative of the slope of the r versus V curve) and ionomycin+Ca2+ decreased ro and κ to zero. Compound 1 and Compound 2 expressed a sigmoidal-saturating function of concentration (0.25–1 mM) with a half-maximal response concentration (k) of 0.49 and 1.05 mM, respectively. Following treatment with 1 mM Compound 1, 8-CPT-cAMP, BAPTA-AM and pH 10.3, the Bz-sensitive NaCl CT response to 100 mM NaCl was enhanced and was equivalent to the Bz-sensitive CT response to 300 mM NaCl. Plots of κ versus ro in the absence and presence of the activators or the inhibitor were linear, suggesting that changes in the affinity of Na+ for ENaC under different conditions are fully compensated by changes in the apical membrane potential difference, and that the observed changes in the Bz-sensitive NaCl CT response arise exclusively from changes in the maximum CT response (rm). The results further suggest that the agonists enhance and ionomycin+Ca2+ decreases ENaC function by increasing or decreasing the rate of release of Na+ from its ENaC binding site to the receptor cell cytosol, respectively. Irrespective of agonist type, the Bz-sensitive NaCl CT response demonstrated a maximum response enhancement limit of about 75% over control value.
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Affiliation(s)
- Shobha Mummalaneni
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Jie Qian
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Tam-Hao T. Phan
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Mee-Ra Rhyu
- Korea Food Research Institute, Bundang-gu, Sungnam-si, Gyeonggi-do, Korea
| | - Gerard L. Heck
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - John A. DeSimone
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Vijay Lyall
- Department of Physiology and Biophysics, Virginia Commonwealth University, Richmond, Virginia, United States of America
- * E-mail:
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46
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Rossier BC. Epithelial sodium channel (ENaC) and the control of blood pressure. Curr Opin Pharmacol 2014; 15:33-46. [DOI: 10.1016/j.coph.2013.11.010] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 11/18/2013] [Accepted: 11/18/2013] [Indexed: 11/29/2022]
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47
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Bachmanov AA, Bosak NP, Lin C, Matsumoto I, Ohmoto M, Reed DR, Nelson TM. Genetics of taste receptors. Curr Pharm Des 2014; 20:2669-83. [PMID: 23886383 PMCID: PMC4764331 DOI: 10.2174/13816128113199990566] [Citation(s) in RCA: 110] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 07/24/2013] [Indexed: 12/19/2022]
Abstract
Taste receptors function as one of the interfaces between internal and external milieus. Taste receptors for sweet and umami (T1R [taste receptor, type 1]), bitter (T2R [taste receptor, type 2]), and salty (ENaC [epithelial sodium channel]) have been discovered in the recent years, but transduction mechanisms of sour taste and ENaC-independent salt taste are still poorly understood. In addition to these five main taste qualities, the taste system detects such noncanonical "tastes" as water, fat, and complex carbohydrates, but their reception mechanisms require further research. Variations in taste receptor genes between and within vertebrate species contribute to individual and species differences in taste-related behaviors. These variations are shaped by evolutionary forces and reflect species adaptations to their chemical environments and feeding ecology. Principles of drug discovery can be applied to taste receptors as targets in order to develop novel taste compounds to satisfy demand in better artificial sweeteners, enhancers of sugar and sodium taste, and blockers of bitterness of food ingredients and oral medications.
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Noh H, Paik HY, Kim J, Chung J. Salty taste acuity is affected by the joint action of αENaC A663T gene polymorphism and available zinc intake in young women. Nutrients 2013; 5:4950-63. [PMID: 24317554 PMCID: PMC3875918 DOI: 10.3390/nu5124950] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 11/21/2013] [Accepted: 11/26/2013] [Indexed: 12/29/2022] Open
Abstract
Salty taste perception affects salt intake, of which excess amounts is a major public health concern. Gene polymorphisms in salty taste receptors, zinc status and their interaction may affect salty taste perception. In this study, we examined the relationships among the α-epithelial sodium channel (αENaC) A663T genotype, zinc intake, and salty taste perception including salty taste acuity and preference in healthy young adults. The αENaC A663T genotype was determined by the PCR-restriction fragment length polymorphism in 207 adults. Zinc intake was examined by one 24-h recall and a two-day dietary record. Salty taste acuity and preference were determined by measuring the salty taste recognition threshold and the preferred salinity of beansprout soup, respectively. Men had significantly higher thresholds and preferences for salty taste than women did (p < 0.05). In women, the salty taste threshold was significantly lower in the highest tertile of available zinc intake than in the lowest tertile (12.2 mM and 17.6 mM, respectively, p = 0.02). Interestingly, a significant inverse association between available zinc intake and salty taste threshold was found only in women with αENaC AA homozygotes (β = −0.833, p = 0.02), and no such association was found in T663 allele carriers. The salty taste preference was not associated with the αENaC A663T genotype or available zinc intake in either sex. In conclusion, our data suggest that gene-nutrient interactions between the αENaC A663T genotype and available zinc intake play a role in determining the salty taste acuity in young women.
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Affiliation(s)
- Hwayoung Noh
- Department of Food and Nutrition, College of Human Ecology, Seoul National University, Seoul 151-742, Korea; E-Mails: (H.N.); (H.-Y.P.)
| | - Hee-Young Paik
- Department of Food and Nutrition, College of Human Ecology, Seoul National University, Seoul 151-742, Korea; E-Mails: (H.N.); (H.-Y.P.)
- Research Institute of Human Ecology, College of Human Ecology, Seoul National University, Seoul 151-742, Korea
| | - Jihye Kim
- Department of Medical Nutrition, Graduate School of East-West Medical Science, Kyung Hee University, Yongin 446-701, Korea; E-Mail:
| | - Jayong Chung
- Department of Food and Nutrition, College of Human Ecology, Kyung Hee University, Seoul 130-701, Korea
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +82-2961-0977; Fax: +82-2968-0260
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Cai H, Cong WN, Daimon CM, Wang R, Tschöp MH, Sévigny J, Martin B, Maudsley S. Altered lipid and salt taste responsivity in ghrelin and GOAT null mice. PLoS One 2013; 8:e76553. [PMID: 24124572 PMCID: PMC3790684 DOI: 10.1371/journal.pone.0076553] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 08/26/2013] [Indexed: 02/06/2023] Open
Abstract
Taste perception plays an important role in regulating food preference, eating behavior and energy homeostasis. Taste perception is modulated by a variety of factors, including gastric hormones such as ghrelin. Ghrelin can regulate growth hormone release, food intake, adiposity, and energy metabolism. Octanoylation of ghrelin by ghrelin O-acyltransferase (GOAT) is a specific post-translational modification which is essential for many biological activities of ghrelin. Ghrelin and GOAT are both widely expressed in many organs including the gustatory system. In the current study, overall metabolic profiles were assessed in wild-type (WT), ghrelin knockout (ghrelin−/−), and GOAT knockout (GOAT−/−) mice. Ghrelin−/− mice exhibited decreased food intake, increased plasma triglycerides and increased ketone bodies compared to WT mice while demonstrating WT-like body weight, fat composition and glucose control. In contrast GOAT−/− mice exhibited reduced body weight, adiposity, resting glucose and insulin levels compared to WT mice. Brief access taste behavioral tests were performed to determine taste responsivity in WT, ghrelin−/− and GOAT−/− mice. Ghrelin and GOAT null mice possessed reduced lipid taste responsivity. Furthermore, we found that salty taste responsivity was attenuated in ghrelin−/− mice, yet potentiated in GOAT−/− mice compared to WT mice. Expression of the potential lipid taste regulators Cd36 and Gpr120 were reduced in the taste buds of ghrelin and GOAT null mice, while the salt-sensitive ENaC subunit was increased in GOAT−/− mice compared with WT mice. The altered expression of Cd36, Gpr120 and ENaC may be responsible for the altered lipid and salt taste perception in ghrelin−/− and GOAT−/− mice. The data presented in the current study potentially implicates ghrelin signaling activity in the modulation of both lipid and salt taste modalities.
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Affiliation(s)
- Huan Cai
- Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Wei-na Cong
- Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Caitlin M. Daimon
- Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Rui Wang
- Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Matthias H. Tschöp
- Institute for Diabetes and Obesity, Helmholtz Centre Munich, Munich, Germany
| | - Jean Sévigny
- Centre de recherche en Rhumatologie et Immunologie, Centre de recherche du CHU de Québec, QC and Département de microbiologie-infectiologie et d′immunologie, Faculté de médecine, Université Laval, Québec, Quebec City, Canada
| | - Bronwen Martin
- Metabolism Unit, Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
| | - Stuart Maudsley
- Receptor Pharmacology Unit, Laboratory of Neuroscience, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
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Miller RL, Wang MH, Gray PA, Salkoff LB, Loewy AD. ENaC-expressing neurons in the sensory circumventricular organs become c-Fos activated following systemic sodium changes. Am J Physiol Regul Integr Comp Physiol 2013; 305:R1141-52. [PMID: 24049115 DOI: 10.1152/ajpregu.00242.2013] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The sensory circumventricular organs (CVOs) are specialized collections of neurons and glia that lie in the midline of the third and fourth ventricles of the brain, lack a blood-brain barrier, and function as chemosensors, sampling both the cerebrospinal fluid and plasma. These structures, which include the organum vasculosum of the lamina terminalis (OVLT), subfornical organ (SFO), and area postrema (AP), are sensitive to changes in sodium concentration but the cellular mechanisms involved remain unknown. Epithelial sodium channel (ENaC)-expressing neurons of the CVOs may be involved in this process. Here we demonstrate with immunohistochemical and in situ hybridization methods that ENaC-expressing neurons are densely concentrated in the sensory CVOs. These neurons become c-Fos activated, a marker for neuronal activity, after various manipulations of peripheral levels of sodium including systemic injections with hypertonic saline, dietary sodium deprivation, and sodium repletion after prolonged sodium deprivation. The increases seen c-Fos activity in the CVOs were correlated with parallel increases in plasma sodium levels. Since ENaCs play a central role in sodium reabsorption in kidney and other epithelia, we present a hypothesis here suggesting that these channels may also serve a related function in the CVOs. ENaCs could be a significant factor in modulating CVO neuronal activity by controlling the magnitude of sodium permeability in neurons. Hence, some of the same circulating hormones controlling ENaC expression in kidney, such as angiotensin II and atrial natriuretic peptide, may coordinate ENaC expression in sensory CVO neurons and could potentially orchestrate sodium appetite, osmoregulation, and vasomotor sympathetic drive.
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Affiliation(s)
- Rebecca L Miller
- Department of Anatomy and Neurobiology, Washington University School of Medicine, St. Louis, Missouri
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