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Avau B, Depoortere I. The bitter truth about bitter taste receptors: beyond sensing bitter in the oral cavity. Acta Physiol (Oxf) 2016; 216:407-20. [PMID: 26493384 DOI: 10.1111/apha.12621] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/28/2015] [Accepted: 10/14/2015] [Indexed: 11/26/2022]
Abstract
The bitter taste receptor (TAS2R)-family of G-protein-coupled receptors has been identified on the tongue as detectors of bitter taste over a decade ago. In the last few years, they have been discovered in an ever growing number of extra-oral tissues, including the airways, the gut, the brain and even the testis. In tissues that contact the exterior, protective functions for TAS2Rs have been proposed, in analogy to their function on the tongue as toxicity detector. However, TAS2Rs have also been found in internal organs, suggesting other roles for these receptors, perhaps involving as yet unidentified endogenous ligands. The current review gives an overview of the different proposed functions for TAS2Rs in tissues other than the oral cavity; from appetite regulation to the treatment of asthma, regulation of gastrointestinal motility and control of airway innate immunity.
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Affiliation(s)
- B. Avau
- Translational Research Center for Gastrointestinal Disorders (TARGID); Gut Peptide Research Lab; University of Leuven; Leuven Belgium
| | - I. Depoortere
- Translational Research Center for Gastrointestinal Disorders (TARGID); Gut Peptide Research Lab; University of Leuven; Leuven Belgium
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102
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Shaik FA, Singh N, Arakawa M, Duan K, Bhullar RP, Chelikani P. Bitter taste receptors: Extraoral roles in pathophysiology. Int J Biochem Cell Biol 2016; 77:197-204. [PMID: 27032752 DOI: 10.1016/j.biocel.2016.03.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2016] [Revised: 03/16/2016] [Accepted: 03/22/2016] [Indexed: 11/17/2022]
Abstract
Over the past decade tremendous progress has been made in understanding the functional role of bitter taste receptors (T2Rs) and bitter taste perception. This review will cover the recent advances made in identifying the role of T2Rs in pathophysiological states. T2Rs are widely expressed in various parts of human anatomy and have been shown to be involved in physiology of respiratory system, gastrointestinal tract and endocrine system. Empirical evidence has shown T2Rs to be an integral component of antimicrobial immune responses in upper respiratory tract infections. The studies on human airway smooth muscle cells have shown that a potent bitter tastant induced bronchodilatory effects mediated by bitter taste receptors. Clinical data suggests a role for T2R38 polymorphism in predisposition of individuals to chronic rhinosinusitis. The role of genetic variation in T2Rs and its impact on disease susceptibility have been investigated in various other disease risk factors such as alcohol dependence, head and neck cancers. Preliminary reports have demonstrated differential expression of functional T2Rs in breast cancer cell lines. Studies on the role of T2Rs in pathophysiology of diseases including chronic rhinosinusitis, asthma, cystic fibrosis, and cancer have been promising. However, research in this field is in its nascent stages, and more confirmatory studies on animal models and in clinical settings are required.
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Affiliation(s)
- Feroz Ahmed Shaik
- Manitoba Chemosensory Biology (MCSB) Research Group and Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada; Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
| | - Nisha Singh
- Manitoba Chemosensory Biology (MCSB) Research Group and Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada; Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
| | - Makoto Arakawa
- Manitoba Chemosensory Biology (MCSB) Research Group and Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada
| | - Kangmin Duan
- Manitoba Chemosensory Biology (MCSB) Research Group and Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada; Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
| | - Rajinder P Bhullar
- Manitoba Chemosensory Biology (MCSB) Research Group and Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada
| | - Prashen Chelikani
- Manitoba Chemosensory Biology (MCSB) Research Group and Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada; Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada; Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB R3E 0W2, Canada.
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103
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Workman AD, Palmer JN, Adappa ND, Cohen NA. The Role of Bitter and Sweet Taste Receptors in Upper Airway Immunity. Curr Allergy Asthma Rep 2016; 15:72. [PMID: 26492878 DOI: 10.1007/s11882-015-0571-8] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Over the past several years, taste receptors have emerged as key players in the regulation of innate immune defenses in the mammalian respiratory tract. Several cell types in the airway, including ciliated epithelial cells, solitary chemosensory cells, and bronchial smooth muscle cells, all display chemoresponsive properties that utilize taste receptors. A variety of bitter products secreted by microbes are detected with resultant downstream inflammation, increased mucous clearance, antimicrobial peptide secretion, and direct bacterial killing. Genetic variation of bitter taste receptors also appears to play a role in the susceptibility to infection in respiratory disease states, including that of chronic rhinosinusitis. Ongoing taste receptor research may yield new therapeutics that harness innate immune defenses in the respiratory tract and may offer alternatives to antibiotic treatment. The present review discusses taste receptor-protective responses and analyzes the role these receptors play in mediating airway immune function.
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Affiliation(s)
- Alan D Workman
- Department of Otorhinolaryngology: Head and Neck Surgery, University of Pennsylvania Medical Center, 5th Floor Ravdin Building, 3400 Spruce Street, Philadelphia, PA, 19104, USA.,Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - James N Palmer
- Department of Otorhinolaryngology: Head and Neck Surgery, University of Pennsylvania Medical Center, 5th Floor Ravdin Building, 3400 Spruce Street, Philadelphia, PA, 19104, USA.,Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Nithin D Adappa
- Department of Otorhinolaryngology: Head and Neck Surgery, University of Pennsylvania Medical Center, 5th Floor Ravdin Building, 3400 Spruce Street, Philadelphia, PA, 19104, USA.,Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA
| | - Noam A Cohen
- Department of Otorhinolaryngology: Head and Neck Surgery, University of Pennsylvania Medical Center, 5th Floor Ravdin Building, 3400 Spruce Street, Philadelphia, PA, 19104, USA. .,Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, USA. .,Monell Smell and Taste Center, Philadelphia, PA, USA. .,Philadelphia Veterans Affairs Medical Center, Philadelphia, PA, USA.
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104
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Tomás J, Santos CRA, Quintela T, Gonçalves I. "Tasting" the cerebrospinal fluid: Another function of the choroid plexus? Neuroscience 2016; 320:160-71. [PMID: 26850994 DOI: 10.1016/j.neuroscience.2016.01.057] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 12/29/2015] [Accepted: 01/27/2016] [Indexed: 01/10/2023]
Abstract
The choroid plexus (CP) located in brain ventricles, by forming the interface between the blood and the cerebrospinal fluid (CSF) is in a privileged position to monitor the composition of these body fluids. Yet, the mechanisms involved in this surveillance system remain to be identified. The taste transduction pathway senses some types of molecules, thereby evaluating the chemical content of fluids, not only in the oral cavity but also in other tissues throughout the body, such as some cell types of the airways, the gastrointestinal tract, testis and skin. Therefore, we hypothesized that the taste transduction pathway could also be operating in the CP to assess the composition of the CSF. We found transcripts for some taste receptors (Tas1r1, Tas1r2, Tas1r3, Tas2r109 and Tas2r144) and for downstream signaling molecules (α-Gustducin, Plcβ2, ItpR3 and TrpM5) that encode this pathway, and confirmed the expression of the corresponding proteins in Wistar rat CP explants and in the CP epithelial cells (CPEC). The functionality of the T2R receptor expressed in CP cells was assessed by calcium imaging, of CPEC stimulated with the bitter compound D-Salicin, which elicited a rise in the intracellular Ca(2+). This effect was diminished in the presence of the bitter receptor blocker Probenecid. In summary, we described the expression of the taste-related components involved in the transduction signaling cascade in CP. Taken together, our results suggest that the taste transduction pathway in CPEC makes use of T2R receptors in the chemical surveillance of the CSF composition, in particular to sense bitter noxious compounds.
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Affiliation(s)
- J Tomás
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - C R A Santos
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - T Quintela
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal
| | - I Gonçalves
- CICS-UBI - Health Sciences Research Centre, University of Beira Interior, Avenida Infante D. Henrique, 6200-506 Covilhã, Portugal.
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105
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Douglas JE, Saunders CJ, Reed DR, Cohen NA. A role for airway taste receptor modulation in the treatment of upper respiratory infections. Expert Rev Respir Med 2016; 10:157-70. [PMID: 26731661 DOI: 10.1586/17476348.2016.1135742] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Taste receptors, initially identified in the oral epithelium, have since been shown to be widely distributed, being found in the upper and lower respiratory tracts, gastrointestinal epithelium, thyroid, and brain. The presence of taste receptors in the nasal epithelium has led to the discovery of their role in innate immunity, defending the paranasal sinuses against pathogens. This article addresses the current paradigm for understanding the role of extraoral taste receptors, specifically the T2R38 bitter taste receptor and the T1R2+3 sweet taste receptor, in respiratory innate defenses and presents evidence for the use of these and other taste receptors as therapeutic targets in the management of chronic rhinosinusitis. Future studies should focus on understanding the polymorphisms of taste receptors beyond T2R38 to fully elucidate their potential therapeutic use and lay the groundwork for their modulation in a clinical setting to decrease the health impact and economic burden of upper respiratory disease.
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Affiliation(s)
- Jennifer E Douglas
- a Perelman School of Medicine , University of Pennsylvania , Philadelphia , PA , USA.,b Department of Otorhinolaryngology-Head and Neck Surgery , University of Pennsylvania Health System , Philadelphia , PA , USA.,c Monell Chemical Senses Center , Philadelphia , PA , USA
| | - Cecil J Saunders
- b Department of Otorhinolaryngology-Head and Neck Surgery , University of Pennsylvania Health System , Philadelphia , PA , USA
| | | | - Noam A Cohen
- a Perelman School of Medicine , University of Pennsylvania , Philadelphia , PA , USA.,b Department of Otorhinolaryngology-Head and Neck Surgery , University of Pennsylvania Health System , Philadelphia , PA , USA.,c Monell Chemical Senses Center , Philadelphia , PA , USA.,d Philadelphia Veterans Affairs Medical Center Surgical Services , Philadelphia , PA , USA
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106
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Otake M, Kurose M, Uchida Y, Hasegawa M, Yamada Y, Saito I, Yamamura K. The interactions between different tastes on initiation of reflex swallow elicited by electrical stimulation in humans. Odontology 2015; 104:282-90. [PMID: 26702624 DOI: 10.1007/s10266-015-0226-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2015] [Accepted: 07/23/2015] [Indexed: 11/29/2022]
Abstract
The act of eating is a source of pleasure for people and is a major factor in maintaining a good quality of life. Several types of products for dysphagia patients are available to decrease aspiration of food that often accompanies daily food intake. The final goal of these products is to improve the ease of forming a food bolus and/or the safety of the swallowing process; however, tastes of products are not a major concern with initiation of swallowing. In the present study, we investigated the effect of bitter taste stimuli (quinine) and the combination of quinine and umami (monosodium glutamate: MSG) applied to the oropharynx on reflex swallows evoked by electrical stimulation to the oropharyngeal mucosa. Each of the distilled water (DW), quinine and quinine-MSG mixture solution (volume of each solutions, 100 µl) was applied 1 s prior to electrical stimulation. No swallow was evoked when each of the solutions was applied without electrical stimulation. The application of DW and lower concentration of quinine (<100 µM) did not affect the latency of reflex swallow, but 100 µM quinine application increased the latency of the reflex swallow. In addition, application of quinine-MSG mixture solution counteracted the increase in latency induced by quinine application alone. These findings suggest that MSG enhances the initiation of swallowing along with its well-known increase in appetite stimulation. Adding MSG might be effective when creating food to promote swallowing.
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Affiliation(s)
- Masanori Otake
- Division of Oral Physiology, Niigata University, Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata, 951-8514, Japan.,Division of Orthodontics, Niigata University, Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Masayuki Kurose
- Division of Oral Physiology, Niigata University, Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata, 951-8514, Japan.
| | | | - Mana Hasegawa
- Division of Oral Physiology, Niigata University, Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata, 951-8514, Japan
| | | | - Isao Saito
- Division of Orthodontics, Niigata University, Graduate School of Medical and Dental Sciences, Niigata, Japan
| | - Kensuke Yamamura
- Division of Oral Physiology, Niigata University, Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata, 951-8514, Japan
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107
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Takahashi N, Nakamuta N, Yamamoto Y. Morphology of P2X3-immunoreactive nerve endings in the rat laryngeal mucosa. Histochem Cell Biol 2015; 145:131-46. [DOI: 10.1007/s00418-015-1371-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/05/2015] [Indexed: 11/25/2022]
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108
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Ablation of TRPM5 in Mice Results in Reduced Body Weight Gain and Improved Glucose Tolerance and Protects from Excessive Consumption of Sweet Palatable Food when Fed High Caloric Diets. PLoS One 2015; 10:e0138373. [PMID: 26397098 PMCID: PMC4580452 DOI: 10.1371/journal.pone.0138373] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 08/27/2015] [Indexed: 01/09/2023] Open
Abstract
The calcium activated cation channel transient receptor potential channel type M5 (TRPM5) is part of the downstream machinery of the taste receptors and have been shown to play a central role in taste signalling. In addition it is also found in other types of chemosensory cells in various parts of the body as well as in pancreatic β-cells. The aim of this study was to investigate the effects of TRPM5 gene ablation on body weight, insulin sensitivity and other metabolic parameters in long-term high caloric diet induced obesity. Trpm5-/- mice gained significantly less body weight and fat mass on both palatable carbohydrate and fat rich cafeteria diet and 60% high fat diet (HFD) and developed less insulin resistance compared to wild type mice. A main finding was the clearly improved glucose tolerance in Trpm5-/- mice compared to wild type mice on cafeteria diet, which was independent of body weight. In addition, it was shown that Trpm5-/- mice consumed the same amount of calories when fed a HFD only or a HFD in combination with a palatable chocolate ball, which is in contrast to wild type mice that increased their caloric intake when fed the combination, mainly due to excessive consumption of the chocolate ball. Thus the palatable sugar containing diet induced overeating was prevented in Trpm5-/- mice. This indicates that sweet taste induced overeating may be a cause for the increased energy intake and glucose intolerance development seen for wild type mice on a sugar and high fat rich cafeteria diet compared to when on a high fat diet. This study point to an important role for the taste signalling system and TRPM5 in diet induced glucose intolerance.
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109
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Voigt A, Hübner S, Döring L, Perlach N, Hermans-Borgmeyer I, Boehm U, Meyerhof W. Cre-Mediated Recombination in Tas2r131 Cells-A Unique Way to Explore Bitter Taste Receptor Function Inside and Outside of the Taste System. Chem Senses 2015; 40:627-39. [PMID: 26377344 DOI: 10.1093/chemse/bjv049] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The type 2 taste receptors (Tas2rs) comprise a large family of G protein-coupled receptors that recognize compounds bitter to humans and aversive to vertebrates. Tas2rs are expressed in both gustatory and nongustatory tissues, however, identification and functional analyses of T2R-expressing cells have been difficult in most tissues. To overcome these limitations and to be able to manipulate Tas2r-expressing cells in vivo, we used gene-targeting to generate a Tas2r131-specific Cre knock-in mouse strain. We then employed a binary genetic approach to characterize Cre-mediated recombination in these animals and to investigate Tas2r131 expression during postnatal development. We demonstrate that a Cre-activated fluorescent reporter reliably visualizes Tas2r131-cells in gustatory tissue. We show that the onset of Tas2r131 as well as of α-Gustducin expression is initiated at different developmental stages depending on the type of taste bud. Furthermore, the number of Tas2r131- and α-Gustducin-expressing cells increased during postnatal development. Our results demonstrate that the Tas2r131-expressing cells constitute a subpopulation of α-Gustducin positive cells at all stages. We detected Tas2r131-expressing cells in several nongustatory tissues including lung, trachea, ovary, ganglia, and brain. Thus, the Tas2r131-Cre strain will help to dissect the functional role of Tas2r131 cells in both gustatory and nongustatory tissues in the future.
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Affiliation(s)
- Anja Voigt
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany, Institute for Neural Signal Transduction, Center for Molecular Neurobiology Hamburg, Falkenried 94, 20251 Hamburg, Germany and
| | - Sandra Hübner
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Linda Döring
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Nathalie Perlach
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Irm Hermans-Borgmeyer
- Transgenic Animals Service Group, Center for Molecular Neurobiology Hamburg, UKE, Martinistraße 52, 20246 Hamburg, Germany
| | - Ulrich Boehm
- Institute for Neural Signal Transduction, Center for Molecular Neurobiology Hamburg, Falkenried 94, 20251 Hamburg, Germany and Present address: Department of Pharmacology and Toxicology, University of Saarland, School of Medicine, 66421 Homburg, Germany
| | - Wolfgang Meyerhof
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany,
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110
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Role of the bitter taste receptor T2R38 in upper respiratory infection and chronic rhinosinusitis. Curr Opin Allergy Clin Immunol 2015; 15:14-20. [PMID: 25304231 DOI: 10.1097/aci.0000000000000120] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE OF REVIEW Taste receptor family 2 (T2R) bitter taste receptors were originally identified and named on the basis of their role in type 2 taste cells of the tongue, in which they serve to detect the presence of potentially harmful ingested chemicals. In 2009, researchers demonstrated that airway epithelial cells also express T2R receptors, but their role in airway physiology and human disease has only recently begun to be identified. RECENT FINDINGS Recent research has demonstrated that at least one airway T2R receptor, taste receptor family 2 isoform 38 protein (T2R38) is activated by secreted bacterial products. Activation of T2R38 in sinonasal epithelial cells stimulates nitric oxide production, increasing ciliary beating and directly killing bacteria. Clinical studies have also found correlations of TAS2R38 genotype with susceptibility to gram-negative upper respiratory infection and established T2R38 as an independent risk factor for chronic rhinosinusitis requiring sinus surgery. SUMMARY These recent studies identify a role for T2R38 in sinonasal innate immunity and chronic rhinosinusitis. Clinical implications include the potential development of T2R38-directed topical therapies, as well as using taste testing and/or genotyping to predict susceptibility to infection. Further studies are needed to more clearly determine how TAS2R38 genotype affects patient outcomes in chronic rhinosinusitis and other upper airway diseases.
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111
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Ciullo DL, Dotson CD. Using Animal Models to Determine the Role of Gustatory Neural Input in the Control of Ingestive Behavior and the Maintenance of Body Weight. CHEMOSENS PERCEPT 2015; 8:61-77. [PMID: 26557212 PMCID: PMC4636125 DOI: 10.1007/s12078-015-9190-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
INTRODUCTION Decades of research have suggested that nutritional intake contributes to the development of human disease, mainly by influencing the development of obesity and obesity-related conditions. A relatively large body of research indicates that functional variation in human taste perception can influence nutritional intake as well as body mass accumulation. However, there are a considerable number of studies that suggest that no link between these variables actually exists. These discrepancies in the literature likely result from the confounding influence of a variety of other, uncontrolled, factors that can influence ingestive behavior. STRATEGY In this review, the use of controlled animal experimentation to alleviate at least some of these issues related to the lack of control of experimental variables is discussed. Specific examples of the use of some of these techniques are examined. DISCUSSION AND CONCLUSIONS The review will close with some specific suggestions aimed at strengthening the link between gustatory neural input and its putative influence on ingestive behaviors and the maintenance of body weight.
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Affiliation(s)
- Dana L Ciullo
- Departments of Neuroscience and Psychiatry, Division of Addiction Medicine, University of Florida College of Medicine, and Center for Smell and Taste, University of Florida, Gainesville, FL 32611, USA,
| | - Cedrick D Dotson
- Departments of Neuroscience and Psychiatry, Division of Addiction Medicine, University of Florida College of Medicine, and Center for Smell and Taste, University of Florida, Gainesville, FL 32611, USA,
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112
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Lee N, Jung YS, Lee HY, Kang N, Park YJ, Hwang JS, Bahk YY, Koo J, Bae YS. Mouse neutrophils express functional umami taste receptor T1R1/T1R3. BMB Rep 2015; 47:649-54. [PMID: 25301019 PMCID: PMC4281345 DOI: 10.5483/bmbrep.2014.47.11.185] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Indexed: 02/04/2023] Open
Abstract
Neutrophils play an important role in the initiation of innate immunity against infection and injury. Although many different types of G-protein coupled receptors are functionally expressed in neutrophils, no reports have demonstrated functional expression of umami taste receptor in these cells. We observed that mouse neutrophils express the umami taste receptor T1R1/T1R3 through RNA sequencing and quantitative RT-PCR analysis. Stimulation of mouse neutrophils with L-alanine or L-serine, which are ligands for the umami taste receptor, elicited not only ERK or p38 MAPK phosphorylation but also chemotactic migration. Moreover, addition of L-alanine or L-serine markedly reduced the production of several cytokines including TNF-α induced by lipopolysaccharide (LPS) through inhibition of NF-κB activity or STAT3 phosphorylation in neutrophils. Our findings demonstrate that neutrophils express the umami taste receptor, through which tastants stimulate neutrophils, resulting in chemotactic migration, and attenuation of LPS-induced inflammatory response.
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Affiliation(s)
- NaHye Lee
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, Korea
| | - Young Su Jung
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Korea
| | - Ha Young Lee
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746; Mitochondria Hub Regulation Center, Dong-A University, Busan 602-714, Korea
| | - NaNa Kang
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, Korea
| | - Yoo Jung Park
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Korea
| | - Jae Sam Hwang
- Department of Agricultural Biology, National Academy of Agricultural Science, RDA, Wanju 565-851, Korea
| | - Young Yil Bahk
- Department of Biotechnology, Konkuk University, Chungju 380-701, Korea
| | - JaeHyung Koo
- Department of Brain Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873, Korea
| | - Yoe-Sik Bae
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746; Mitochondria Hub Regulation Center, Dong-A University, Busan 602-714; Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul 135-710, Korea
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113
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Wiederhold S, Papadakis T, Chubanov V, Gudermann T, Krasteva-Christ G, Kummer W. A novel cholinergic epithelial cell with chemosensory traits in the murine conjunctiva. Int Immunopharmacol 2015; 29:45-50. [PMID: 26119492 DOI: 10.1016/j.intimp.2015.06.027] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Revised: 06/12/2015] [Accepted: 06/22/2015] [Indexed: 12/27/2022]
Abstract
We recently identified a specialized cholinergic cell type in tracheal and urethral epithelium that utilizes molecules of the canonical taste transduction signaling cascade to sense potentially harmful substances in the luminal content. Upon stimulation, this cell initiates protective reflexes. Assuming a sentinel role of such cells at mucosal surfaces exposed to bacteria, we hypothesized their occurrence also in ocular mucosal surfaces. Utilizing a mouse strain expressing eGFP under the promoter of the acetylcholine synthesizing enzyme, choline acetyltransferase (ChAT-eGFP), we observed a cholinergic cell in the murine conjunctiva. Singular cholinergic cells reaching the epithelial surface with slender processes were detected in fornical, but neither in bulbar nor palpebral epithelia. These cells were found neither in the lacrimal canaliculi, nor in the lacrimal sac and the nasolacrimal duct. Cholinergic conjunctival epithelial cells were immunoreactive for components of the canonical taste transduction signaling cascade, i.e. α-gustducin, phospholipase Cβ2 and the monovalent cation channel TRPM5. Calcitonin gene-related peptide- and substance P-immunoreactive sensory nerve fibers were observed extending into the conjunctival epithelium approaching slender ChAT-eGFP-positive cells. In addition, we noted both ChAT-eGFP expression and α-gustducin-immunoreactivity, albeit in different cell populations, in occasionally occurring lymphoid follicles of the nictitating membrane. The data show a previously unidentified cholinergic cell in murine conjunctiva with chemosensory traits that presumably utilizes acetylcholine for signaling. In analogy to similar cells described in the respiratory and urethral epithelium, it might serve to detect bacterial products and to initiate protective reflexes.
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Affiliation(s)
- Stephanie Wiederhold
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, 35385, Giessen, Germany
| | - Tamara Papadakis
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, 35385, Giessen, Germany
| | - Vladimir Chubanov
- Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilians-University, Munich, Germany
| | - Thomas Gudermann
- Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilians-University, Munich, Germany
| | - Gabriela Krasteva-Christ
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, 35385, Giessen, Germany; Institute for Anatomy and Cell Biology, Julius-Maximilians-Universität Würzburg, Koellikerstraße 6, 97070 Würzburg, Germany
| | - Wolfgang Kummer
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, 35385, Giessen, Germany.
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Soultanova A, Voigt A, Chubanov V, Gudermann T, Meyerhof W, Boehm U, Kummer W. Cholinergic chemosensory cells of the thymic medulla express the bitter receptor Tas2r131. Int Immunopharmacol 2015; 29:143-7. [PMID: 26102274 DOI: 10.1016/j.intimp.2015.06.005] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 06/02/2015] [Indexed: 12/14/2022]
Abstract
The thymus is the site of T cell maturation which includes positive selection in the cortex and negative selection in the medulla. Acetylcholine is locally produced in the thymus and cholinergic signaling influences the T cell development. We recently described a distinct subset of medullary epithelial cells in the murine thymus which express the acetylcholine-synthesizing enzyme choline acetyltransferase (ChAT) and components of the canonical taste transduction cascade, i.e. transient receptor potential melastatin-like subtype 5 channel (TRPM5), phospholipase Cβ(2), and Gα-gustducin. Such a chemical phenotype is characteristic for chemosensory cells of mucosal surfaces which utilize bitter receptors for detection of potentially hazardous compounds and cholinergic signaling to initiate avoidance reflexes. We here demonstrate mRNA expression of bitter receptors Tas2r105, Tas2r108, and Tas2r131 in the murine thymus. Using a Tas2r131-tauGFP reporter mouse we localized the expression of this receptor to cholinergic cells expressing the downstream elements of the taste transduction pathway. These cells are distinct from the medullary thymic epithelial cells which promiscuously express tissue-restricted self-antigens during the process of negative selection, since double-labeling immunofluorescence showed no colocalization of autoimmune regulator (AIRE), the key mediator of negative selection, and TRPM5. These data demonstrate the presence of bitter taste-sensing signaling in cholinergic epithelial cells in the thymic medulla and opens a discussion as to what is the physiological role of this pathway.
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Affiliation(s)
- Aichurek Soultanova
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, German Center for Lung Research, Giessen, Germany.
| | - Anja Voigt
- Department of Molecular Genetics, German Institute of Human Nutrition, Potsdam Rehbruecke, Nuthetal, Germany
| | - Vladimir Chubanov
- Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilian-University, Munich, Germany
| | - Thomas Gudermann
- Walter-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilian-University, Munich, Germany
| | - Wolfgang Meyerhof
- Department of Molecular Genetics, German Institute of Human Nutrition, Potsdam Rehbruecke, Nuthetal, Germany
| | - Ulrich Boehm
- Department of Pharmacology and Toxicology, University of Saarland School of Medicine, Homburg, Germany
| | - Wolfgang Kummer
- Institute for Anatomy and Cell Biology, Justus-Liebig-University Giessen, German Center for Lung Research, Giessen, Germany
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115
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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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Cardiac gene expression data and in silico analysis provide novel insights into human and mouse taste receptor gene regulation. Naunyn Schmiedebergs Arch Pharmacol 2015; 388:1009-27. [PMID: 25986534 DOI: 10.1007/s00210-015-1118-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 03/24/2015] [Indexed: 12/21/2022]
Abstract
G protein-coupled receptors are the principal mediators of the sweet, umami, bitter, and fat taste qualities in mammals. Intriguingly, the taste receptors are also expressed outside of the oral cavity, including in the gut, airways, brain, and heart, where they have additional functions and contribute to disease. However, there is little known about the mechanisms governing the transcriptional regulation of taste receptor genes. Following our recent delineation of taste receptors in the heart, we investigated the genomic loci encoding for taste receptors to gain insight into the regulatory mechanisms that drive their expression in the heart. Gene expression analyses of healthy and diseased human and mouse hearts showed coordinated expression for a subset of chromosomally clustered taste receptors. This chromosomal clustering mirrored the cardiac expression profile, suggesting that a common gene regulatory block may control the taste receptor locus. We identified unique domains with strong regulatory potential in the vicinity of taste receptor genes. We also performed de novo motif enrichment in the proximal promoter regions and found several overrepresented DNA motifs in cardiac taste receptor gene promoters corresponding to ubiquitous and cardiac-specific transcription factor binding sites. Thus, combining cardiac gene expression data with bioinformatic analyses, this study has provided insights into the noncoding regulatory landscape for taste GPCRs. These findings also have broader relevance for the study of taste GPCRs outside of the classical gustatory system, where understanding the mechanisms controlling the expression of these receptors may have implications for future therapeutic development.
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117
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Kusumakshi S, Voigt A, Hübner S, Hermans-Borgmeyer I, Ortalli A, Pyrski M, Dörr J, Zufall F, Flockerzi V, Meyerhof W, Montmayeur JP, Boehm U. A Binary Genetic Approach to Characterize TRPM5 Cells in Mice. Chem Senses 2015; 40:413-25. [PMID: 25940069 DOI: 10.1093/chemse/bjv023] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Transient receptor potential channel subfamily M member 5 (TRPM5) is an important downstream signaling component in a subset of taste receptor cells making it a potential target for taste modulation. Interestingly, TRPM5 has been detected in extra-oral tissues; however, the function of extra-gustatory TRPM5-expressing cells is less well understood. To facilitate visualization and manipulation of TRPM5-expressing cells in mice, we generated a Cre knock-in TRPM5 allele by homologous recombination. We then used the novel TRPM5-IRES-Cre mouse strain to report TRPM5 expression by activating a τGFP transgene. To confirm faithful coexpression of τGFP and TRPM5 we generated and validated a new anti-TRPM5 antiserum enabling us to analyze acute TRPM5 protein expression. τGFP cells were found in taste bud cells of the vallate, foliate, and fungiform papillae as well as in the palate. We also detected TRPM5 expression in several other tissues such as in the septal organ of Masera. Interestingly, in the olfactory epithelium of adult mice acute TRPM5 expression was detected in only one (short microvillar cells) of two cell populations previously reported to express TRPM5. The TRPM5-IC mouse strain described here represents a novel genetic tool and will facilitate the study and tissue-specific manipulation of TRPM5-expressing cells in vivo.
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Affiliation(s)
- Soumya Kusumakshi
- Department of Pharmacology and Toxicology, University of Saarland, School of Medicine, 66421 Homburg, Germany
| | - Anja Voigt
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Sandra Hübner
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Irm Hermans-Borgmeyer
- Transgenic Animals Service Group, UKE, Center for Molecular Neurobiology Hamburg (ZMNH), Falkenried 94, 20251 Hamburg, Germany
| | - Ana Ortalli
- Department of Pharmacology and Toxicology, University of Saarland, School of Medicine, 66421 Homburg, Germany, Centre des Sciences du Goût et de l'Alimentation, UMR6265 CNRS, UMR1324 INRA, Université de Bourgogne, 9E Boulevard Jeanne D'Arc, 21000 Dijon, France and
| | - Martina Pyrski
- Department of Physiology, University of Saarland, School of Medicine, 66421 Homburg, Germany
| | - Janka Dörr
- Department of Pharmacology and Toxicology, University of Saarland, School of Medicine, 66421 Homburg, Germany
| | - Frank Zufall
- Department of Physiology, University of Saarland, School of Medicine, 66421 Homburg, Germany
| | - Veit Flockerzi
- Department of Pharmacology and Toxicology, University of Saarland, School of Medicine, 66421 Homburg, Germany
| | - Wolfgang Meyerhof
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
| | - Jean-Pierre Montmayeur
- Centre des Sciences du Goût et de l'Alimentation, UMR6265 CNRS, UMR1324 INRA, Université de Bourgogne, 9E Boulevard Jeanne D'Arc, 21000 Dijon, France and
| | - Ulrich Boehm
- Department of Pharmacology and Toxicology, University of Saarland, School of Medicine, 66421 Homburg, Germany,
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Hatten KM, Palmer JN, Lee RJ, Adappa ND, Kennedy DW, Cohen NA. Corticosteroid use does not alter nasal mucus glucose in chronic rhinosinusitis. Otolaryngol Head Neck Surg 2015; 152:1140-4. [PMID: 25820586 DOI: 10.1177/0194599815577567] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2014] [Accepted: 02/24/2015] [Indexed: 01/09/2023]
Abstract
OBJECTIVES To evaluate nasal mucus glucose concentrations in patients with and without chronic rhinosinusitis and determine if corticosteroid therapy alters mucus glucose. STUDY DESIGN Prospective observational study. SETTING Single tertiary care center. SUBJECTS Ninety-five patients presenting to an otolaryngology clinic. METHODS Participants completed questionnaires that included a history of medical and surgical therapies as well as sinusitis-specific quality-of-life measurements. Nasal mucus was collected in an outpatient clinic using an open cell foam technique. The nasal mucus glucose concentrations of patients with and without chronic rhinosinusitis were compared to the use of systemic and topical glucocorticoid treatment. RESULTS A statistically significant difference was measured between mean nasal glucose secretions of control patients, 10.2 mg/dL, compared with patients diagnosed with chronic rhinosinusitis, 18.4 mg/dL (P < .0001). Use of corticosteroids, both topical and systemic, did not correlate with nasal glucose concentrations. CONCLUSION Patients diagnosed with chronic rhinosinusitis have elevated nasal glucose concentrations compared with control patients, and this elevated nasal glucose level was independent of corticosteroid use. Nasal glucose may independently contribute to the pathophysiology of chronic rhinosinusitis.
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Affiliation(s)
- Kyle M Hatten
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA
| | - James N Palmer
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA
| | - Robert J Lee
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA
| | - Nithin D Adappa
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA
| | - David W Kennedy
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA
| | - Noam A Cohen
- Department of Otorhinolaryngology-Head & Neck Surgery, University of Pennsylvania Health System, Philadelphia, Pennsylvania, USA Philadelphia Veterans Affairs Medical Center Surgical Services, Philadelphia, Pennsylvania, USA
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119
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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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Farquhar DR, Kovatch KJ, Palmer JN, Shofer FS, Adappa ND, Cohen NA. Phenylthiocarbamide taste sensitivity is associated with sinonasal symptoms in healthy adults. Int Forum Allergy Rhinol 2014; 5:111-8. [PMID: 25532854 DOI: 10.1002/alr.21437] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2014] [Accepted: 09/10/2014] [Indexed: 12/29/2022]
Abstract
BACKGROUND The bitter taste receptor T2R38, expressed in the tongue and nasal epithelium, has been shown to trigger sinonasal innate immunity contributing to the prevention of gram-negative upper airway bacterial infections. Common polymorphisms of the T2R38 gene, correlating with bitter taste sensitivity to phenylthiocarbamide (PTC), have been linked to differences in sinonasal innate immune response, with specific genotypes significantly more common in medically recalcitrant chronic rhinosinusitis patients. The purpose of this study was to examine this association between T2R38 function and sinonasal infection or symptoms in a healthy population. METHODS A survey of the frequency of sinus infections, as well as other nasal symptoms such as colds, allergies, and overall nasal quality of life (nQOL), was administered to healthy adult participants. nQOL was measured using a 0 to 3 scale of worsening symptoms. A PTC compound taste strip was administered with T2R38 taste sensitivity classified as extremely, somewhat, or not sensitive. RESULTS Among 217 participants (55% female, 70% Caucasian, 42% age 21 to 25 years), 30% did not detect bitterness (nontasters), 34% were moderate tasters, and 36% were "supertasters," experiencing a strong, unpalatable bitterness. Supertasters were associated with less frequent sinus infections (p = 0.04), and PTC sensitivity was predictive of nasal symptoms: Supertasters had the best nQOL scores, followed by moderate tasters and nontasters (means: 0.65, 0.81, 1.00, respectively; p = 0.014 for trend). There were no significant associations with other variables. CONCLUSION This study provides evidence that T2R38 functionality in the tongue correlates with nasal symptoms in healthy individuals.
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Affiliation(s)
- Douglas R Farquhar
- Department of Otorhinolaryngology-Head and Neck Surgery, The University of Pennsylvania, Philadelphia, PA
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121
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Bitter and sweet taste receptors in the respiratory epithelium in health and disease. J Mol Med (Berl) 2014; 92:1235-44. [PMID: 25391251 DOI: 10.1007/s00109-014-1222-6] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 11/01/2014] [Accepted: 11/04/2014] [Indexed: 11/27/2022]
Abstract
Taste receptors on the tongue communicate information to the brain about the nutrient content or potential toxicity of ingested foods. However, recent research has now shown that taste receptors are also expressed far beyond the tongue, from the airway and gastrointestinal epithelia to the pancreas and brain. The functions of many of these so-called extraoral taste receptors remain unknown, but emerging basic science and clinical evidence suggests that bitter and sweet taste receptors in the airway are important in sensing bacteria and regulating innate immunity. This review focuses on the role of bitter and sweet taste receptors in human airway innate immunity and the potential clinical relevance to airway infections. The T2R38 bitter taste receptor in sinonasal cilia detects bitter bacterial quorum-sensing molecules and activates nitric oxide-dependent innate immune responses. Polymorphisms that underlie T2R38 functionality also appear to be involved in susceptibility to upper respiratory infection and chronic rhinosinusitis (CRS). Bitter and sweet receptors in specialized sinonasal solitary chemosensory cells control antimicrobial peptide secretion, which may have important implications for airway infections in CRS patients as well as patients with diabetes mellitus. Future research on taste receptors in the airway has tremendous potential to identify immune mechanisms involved in host-pathogen interactions and thus reveal novel therapeutic targets.
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122
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Clark AA, Dotson CD, Elson AET, Voigt A, Boehm U, Meyerhof W, Steinle NI, Munger SD. TAS2R bitter taste receptors regulate thyroid function. FASEB J 2014; 29:164-72. [PMID: 25342133 DOI: 10.1096/fj.14-262246] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Dysregulation of thyroid hormones triiodothyronine and thyroxine (T3/T4) can impact metabolism, body composition, and development. Thus, it is critical to identify novel mechanisms that impact T3/T4 production. We found that type 2 taste receptors (TAS2Rs), which are activated by bitter-tasting compounds such as those found in many foods and pharmaceuticals, negatively regulate thyroid-stimulating hormone (TSH)-dependent Ca(2+) increases and TSH-dependent iodide efflux in thyrocytes. Immunohistochemical Tas2r-dependent reporter expression and real-time PCR analyses reveal that human and mouse thyrocytes and the Nthy-Ori 3-1 human thyrocyte line express several TAS2Rs. Five different agonists for thyrocyte-expressed TAS2Rs reduced TSH-dependent Ca(2+) release in Nthy-Ori 3-1 cells, but not basal Ca(2+) levels, in a dose-dependent manner. Ca(2+) responses were unaffected by 6-n-propylthiouracil, consistent with the expression of an unresponsive variant of its cognate receptor, TAS2R38, in these cells. TAS2R agonists also inhibited basal and TSH-dependent iodide efflux. Furthermore, a common TAS2R42 polymorphism is associated with increased serum T4 levels in a human cohort. Our findings indicate that TAS2Rs couple the detection of bitter-tasting compounds to changes in thyrocyte function and T3/T4 production. Thus, TAS2Rs may mediate a protective response to overingestion of toxic materials and could serve as new druggable targets for therapeutic treatment of hypo- or hyperthyroidism.
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Affiliation(s)
- Adam A Clark
- Department of Anatomy and Neurobiology, Program in Toxicology
| | | | - Amanda E T Elson
- Department of Anatomy and Neurobiology, Program in Neuroscience, and
| | - Anja Voigt
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam Rehbruecke, Nuthetal, Germany; and
| | - Ulrich Boehm
- Department of Pharmacology and Toxicology, University of Saarland School of Medicine, Homburg, Germany
| | - Wolfgang Meyerhof
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam Rehbruecke, Nuthetal, Germany; and
| | - Nanette I Steinle
- Department of Medicine, Division of Endocrinology, Diabetes and Nutrition, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Steven D Munger
- Department of Anatomy and Neurobiology, Program in Toxicology, Program in Neuroscience, and Department of Medicine, Division of Endocrinology, Diabetes and Nutrition, University of Maryland School of Medicine, Baltimore, Maryland, USA;
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Mantella NM, Youngentob SL. Prenatal alcohol exposure increases postnatal acceptability of nicotine odor and taste in adolescent rats. PLoS One 2014; 9:e102255. [PMID: 25029285 PMCID: PMC4100884 DOI: 10.1371/journal.pone.0102255] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2014] [Accepted: 06/12/2014] [Indexed: 01/18/2023] Open
Abstract
Human studies indicate that alcohol exposure during gestation not only increases the chance for later alcohol abuse, but also nicotine dependence. The flavor attributes of both alcohol and nicotine can be important determinants of their initial acceptance and they both share the component chemosensory qualities of an aversive odor, bitter taste and oral irritation. There is a growing body of evidence demonstrating epigenetic chemosensory mechanisms through which fetal alcohol exposure increases adolescent alcohol acceptance, in part, by decreasing the aversion to alcohol's bitter and oral irritation qualities, as well as its odor. Given that alcohol and nicotine have noteworthy chemosensory qualities in common, we investigated whether fetal exposure to alcohol increased the acceptability of nicotine's odor and taste in adolescent rats. Study rats were alcohol-exposed during fetal development via the dams' liquid diet. Control animals received ad lib access to an iso-caloric, iso-nutritive diet throughout gestation. Odorant-induced innate behavioral responses to nicotine odor (Experiment 1) or orosensory-mediated responses to nicotine solutions (Experiment 2) were obtained, using whole-body plethysmography and brief access lick tests, respectively. Compared to controls, rats exposed to fetal alcohol showed an enhanced nicotine odor response that was paralleled by increased oral acceptability of nicotine. Given the common aversive component qualities imbued in the flavor profiles of both drugs, our findings demonstrate that like postnatal alcohol avidity, fetal alcohol exposure also influences nicotine acceptance, at a minimum, by decreasing the aversion of both its smell and taste. Moreover, they highlight potential chemosensory-based mechanism(s) by which fetal alcohol exposure increases the later initial risk for nicotine use, thereby contributing to the co-morbid expression with enhanced alcohol avidity. Where common chemosensory mechanisms are at play, our results suggest broader implications related to the consequence of fetal exposure with one substance of abuse and initial acceptability of others.
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Affiliation(s)
- Nicole M. Mantella
- Department of Psychiatry and Behavioral Sciences, State University of New York Upstate Medical University, Syracuse, New York, United States of America
| | - Steven L. Youngentob
- Department of Psychiatry and Behavioral Sciences, State University of New York Upstate Medical University, Syracuse, New York, United States of America
- State University of New York Developmental Exposure Alcohol Research Center, Syracuse & Binghamton, New York, United States of America
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Kummer W, Krasteva-Christ G. Non-neuronal cholinergic airway epithelium biology. Curr Opin Pharmacol 2014; 16:43-9. [DOI: 10.1016/j.coph.2014.03.001] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 02/26/2014] [Accepted: 03/03/2014] [Indexed: 01/06/2023]
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Parlee SD, Simon BR, Scheller EL, Alejandro EU, Learman BS, Krishnan V, Bernal-Mizrachi E, MacDougald OA. Administration of saccharin to neonatal mice influences body composition of adult males and reduces body weight of females. Endocrinology 2014; 155:1313-26. [PMID: 24456165 PMCID: PMC3959603 DOI: 10.1210/en.2013-1995] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Nutritional or pharmacological perturbations during perinatal growth can cause persistent effects on the function of white adipose tissue, altering susceptibility to obesity later in life. Previous studies have established that saccharin, a nonnutritive sweetener, inhibits lipolysis in mature adipocytes and stimulates adipogenesis. Thus, the current study tested whether neonatal exposure to saccharin via maternal lactation increased susceptibility of mice to diet-induced obesity. Saccharin decreased body weight of female mice beginning postnatal week 3. Decreased liver weights on week 14 corroborated this diminished body weight. Initially, saccharin also reduced male mouse body weight. By week 5, weights transiently rebounded above controls, and by week 14, male body weights did not differ. Body composition analysis revealed that saccharin increased lean and decreased fat mass of male mice, the latter due to decreased adipocyte size and epididymal, perirenal, and sc adipose weights. A mild improvement in glucose tolerance without a change in insulin sensitivity or secretion aligned with this leaner phenotype. Interestingly, microcomputed tomography analysis indicated that saccharin also increased cortical and trabecular bone mass of male mice and modified cortical bone alone in female mice. A modest increase in circulating testosterone may contribute to the leaner phenotype in male mice. Accordingly, the current study established a developmental period in which saccharin at high concentrations reduces adiposity and increases lean and bone mass in male mice while decreasing generalized growth in female mice.
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Affiliation(s)
- Sebastian D Parlee
- Departments of Molecular and Integrative Physiology and Internal Medicine (S.D.P., B.R.S., E.L.S., B.S.L., O.A.M.), and Division of Metabolism, Endocrinology and Diabetes (E.U.A., E.B.-M., O.A.M.), School of Medicine, University of Michigan, Ann Arbor, Michigan 48105; and Musculoskeletal Research (V.K.), Lilly Research Laboratories, Indianapolis, Indiana 46285
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Gu X, Karp PH, Brody SL, Pierce RA, Welsh MJ, Holtzman MJ, Ben-Shahar Y. Chemosensory functions for pulmonary neuroendocrine cells. Am J Respir Cell Mol Biol 2014; 50:637-46. [PMID: 24134460 PMCID: PMC4068934 DOI: 10.1165/rcmb.2013-0199oc] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 10/04/2013] [Indexed: 12/28/2022] Open
Abstract
The mammalian airways are sensitive to inhaled stimuli, and airway diseases are characterized by hypersensitivity to volatile stimuli, such as perfumes, industrial solvents, and others. However, the identity and function of the cells in the airway that can sense volatile chemicals remain uncertain, particularly in humans. Here, we show that solitary pulmonary neuroendocrine cells (PNECs), which are morphologically distinct and physiologically undefined, might serve as chemosensory cells in human airways. This conclusion is based on our finding that some human PNECs expressed members of the olfactory receptor (OR) family in vivo and in primary cell culture, and are anatomically positioned in the airway epithelium to respond to inhaled volatile chemicals. Furthermore, apical exposure of primary-culture human airway epithelial cells to volatile chemicals decreased levels of serotonin in PNECs, and the led to the release of the neuropeptide calcitonin gene-related peptide (CGRP) to the basal medium. These data suggest that volatile stimulation of PNECs can lead to the secretion of factors that are capable of stimulating the corresponding receptors in the lung epithelium. We also found that the distribution of serotonin and neuropeptide receptors may change in chronic obstructive pulmonary disease, suggesting that increased PNEC-dependent chemoresponsiveness might contribute to the altered sensitivity to volatile stimuli in this disease. Together, these data indicate that human airway epithelia harbor specialized cells that respond to volatile chemical stimuli, and may help to explain clinical observations of odorant-induced airway reactions.
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Affiliation(s)
- Xiaoling Gu
- Department of Biology, Washington University in St. Louis, Missouri
| | - Philip H. Karp
- Howard Hughes Medical Institute, Departments of Internal Medicine, and Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Steven L. Brody
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri; and
| | - Richard A. Pierce
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri; and
| | - Michael J. Welsh
- Howard Hughes Medical Institute, Departments of Internal Medicine, and Molecular Physiology and Biophysics, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa
| | - Michael J. Holtzman
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri; and
| | - Yehuda Ben-Shahar
- Department of Biology, Washington University in St. Louis, Missouri
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri; and
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Kojima I, Nakagawa Y, Ohtsu Y, Medina A, Nagasawa M. Sweet Taste-Sensing Receptors Expressed in Pancreatic β-Cells: Sweet Molecules Act as Biased Agonists. Endocrinol Metab (Seoul) 2014; 29:12-9. [PMID: 24741449 PMCID: PMC3970274 DOI: 10.3803/enm.2014.29.1.12] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The sweet taste receptors present in the taste buds are heterodimers comprised of T1R2 and T1R3. This receptor is also expressed in pancreatic β-cells. When the expression of receptor subunits is determined in β-cells by quantitative reverse transcription polymerase chain reaction, the mRNA expression level of T1R2 is extremely low compared to that of T1R3. In fact, the expression of T1R2 is undetectable at the protein level. Furthermore, knockdown of T1R2 does not affect the effect of sweet molecules, whereas knockdown of T1R3 markedly attenuates the effect of sweet molecules. Consequently, a homodimer of T1R3 functions as a receptor sensing sweet molecules in β-cells, which we designate as sweet taste-sensing receptors (STSRs). Various sweet molecules activate STSR in β-cells and augment insulin secretion. With regard to intracellular signals, sweet molecules act on STSRs and increase cytoplasmic Ca(2+) and/or cyclic AMP (cAMP). Specifically, when an STSR is stimulated by one of four different sweet molecules (sucralose, acesulfame potassium, sodium saccharin, or glycyrrhizin), distinct signaling pathways are activated. Patterns of changes in cytoplasmic Ca(2+) and/or cAMP induced by these sweet molecules are all different from each other. Hence, sweet molecules activate STSRs by acting as biased agonists.
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Affiliation(s)
- Itaru Kojima
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Yuko Nakagawa
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Yoshiaki Ohtsu
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Anya Medina
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
| | - Masahiro Nagasawa
- Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan
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Lee RJ, Kofonow JM, Rosen PL, Siebert AP, Chen B, Doghramji L, Xiong G, Adappa ND, Palmer JN, Kennedy DW, Kreindler JL, Margolskee RF, Cohen NA. Bitter and sweet taste receptors regulate human upper respiratory innate immunity. J Clin Invest 2014; 124:1393-405. [PMID: 24531552 DOI: 10.1172/jci72094] [Citation(s) in RCA: 294] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 12/11/2013] [Indexed: 12/11/2022] Open
Abstract
Bitter taste receptors (T2Rs) in the human airway detect harmful compounds, including secreted bacterial products. Here, using human primary sinonasal air-liquid interface cultures and tissue explants, we determined that activation of a subset of airway T2Rs expressed in nasal solitary chemosensory cells activates a calcium wave that propagates through gap junctions to the surrounding respiratory epithelial cells. The T2R-dependent calcium wave stimulated robust secretion of antimicrobial peptides into the mucus that was capable of killing a variety of respiratory pathogens. Furthermore, sweet taste receptor (T1R2/3) activation suppressed T2R-mediated antimicrobial peptide secretion, suggesting that T1R2/3-mediated inhibition of T2Rs prevents full antimicrobial peptide release during times of relative health. In contrast, during acute bacterial infection, T1R2/3 is likely deactivated in response to bacterial consumption of airway surface liquid glucose, alleviating T2R inhibition and resulting in antimicrobial peptide secretion. We found that patients with chronic rhinosinusitis have elevated glucose concentrations in their nasal secretions, and other reports have shown that patients with hyperglycemia likewise have elevated nasal glucose levels. These data suggest that increased glucose in respiratory secretions in pathologic states, such as chronic rhinosinusitis or hyperglycemia, promotes tonic activation of T1R2/3 and suppresses T2R-mediated innate defense. Furthermore, targeting T1R2/3-dependent suppression of T2Rs may have therapeutic potential for upper respiratory tract infections.
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Abstract
The G-protein-coupled receptor molecules and downstream effectors that are used by taste buds to detect sweet, bitter, and savory tastes are also utilized by chemoresponsive cells of the airways to detect irritants. Here, we describe the different cell types in the airways that utilize taste-receptor signaling to trigger protective epithelial and neural responses to potentially dangerous toxins and bacterial infection.
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Affiliation(s)
- Marco Tizzano
- Department of Cell & Developmental Biology, Rocky Mountain Taste & Smell Center, University of Colorado School of Medicine, Aurora, Colorado, USA
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130
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Taste Receptor Gene Expression Outside the Gustatory System. TOPICS IN MEDICINAL CHEMISTRY 2014. [DOI: 10.1007/7355_2014_79] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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131
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Pydi SP, Bhullar RP, Chelikani P. Constitutive Activity of Bitter Taste Receptors (T2Rs). ADVANCES IN PHARMACOLOGY 2014; 70:303-26. [DOI: 10.1016/b978-0-12-417197-8.00010-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Liggett SB. Bitter taste receptors in the wrong place: novel airway smooth muscle targets for treating asthma. TRANSACTIONS OF THE AMERICAN CLINICAL AND CLIMATOLOGICAL ASSOCIATION 2014; 125:64-75. [PMID: 25125719 PMCID: PMC4112707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
There is a need to expand the classes of drugs used to treat obstructive lung diseases to achieve better outcomes. With only one class of direct bronchodilators (β-agonists), we sought to find receptors on human airway smooth muscle (ASM) that act via a unique mechanism to relax the muscle, have a diverse agonist binding profile to enhance the probability of finding new therapeutics, and relax ASM with equal or greater efficacy than β-agonists. We have found that human and mouse ASM express six bitter taste receptor (TAS2R) subtypes, previously thought only to exist in taste buds of the tongue. Agonists acting at TAS2Rs evoke profound bronchodilation via a Ca(2+)-dependent mechanism. TAS2R function is not altered in asthma models, undergoes minimal tachyphylaxis upon repetitive dosing, and relaxes even under extreme desensitization of relaxation by β-agonists. Taken together, TAS2Rs on ASM represent a novel pathway to consider for development of agonists in the treatment of asthma and chronic obstructive lung disease.
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MESH Headings
- Adrenergic beta-2 Receptor Agonists/pharmacology
- Animals
- Anti-Asthmatic Agents/pharmacology
- Asthma/drug therapy
- Asthma/metabolism
- Asthma/physiopathology
- Bronchoconstriction/drug effects
- Bronchodilator Agents/pharmacology
- Calcium Signaling/drug effects
- Cells, Cultured
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Drug Design
- Humans
- Mice, Inbred BALB C
- Molecular Targeted Therapy
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Muscle, Smooth/physiopathology
- Receptors, G-Protein-Coupled/agonists
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Respiratory System/drug effects
- Respiratory System/metabolism
- Respiratory System/physiopathology
- Time Factors
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Affiliation(s)
- Stephen B. Liggett
- Correspondence and reprint requests: Stephen B. Liggett, MD,
Departments of Internal Medicine and Molecular Pharmacology and Physiology, University of South Florida, Morsani College of Medicine, 12901 Bruce B. Downs Blvd., MDC02, Tampa, FL 33612813-974-7715813-974-3886
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133
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Adappa ND, Zhang Z, Palmer JN, Kennedy DW, Doghramji L, Lysenko A, Reed DR, Scott T, Zhao NW, Owens D, Lee RJ, Cohen NA. The bitter taste receptor T2R38 is an independent risk factor for chronic rhinosinusitis requiring sinus surgery. Int Forum Allergy Rhinol 2013; 4:3-7. [PMID: 24302675 DOI: 10.1002/alr.21253] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2013] [Revised: 10/08/2013] [Accepted: 10/10/2013] [Indexed: 01/11/2023]
Abstract
BACKGROUND The bitter taste receptor T2R38 was recently described to play a role in upper airway innate mucosal defense. When activated by bacterial quorum-sensing molecules, T2R38 stimulates the ciliated epithelial cells to produce nitric oxide (NO), resulting in bactericidal activity and an increase in mucociliary clearance (MCC). Polymorphisms within the T2R38 gene (TAS2R38) confer variability in activation of the receptor yielding dramatic differences in upper airway defensive responses (NO production and accelerated MCC) to microbial stimulation based on genotype. Our objective was to determine whether the nonprotective TAS2R38 polymorphisms, which render the receptor inactive, correlate with medically recalcitrant chronic rhinosinusitis (CRS) necessitating surgical intervention in the context of known risk factors, and thus identify whether the TAS2R38 genotype is an independent risk factor for patients undergoing functional endoscopic sinus surgery (FESS). METHODS CRS patients undergoing primary FESS were prospectively genotyped for TAS2R38. Chi-square analysis was performed on the genotype distribution with respect to other risk factors, including allergies, asthma, nasal polyposis, aspirin sensitivity, diabetes, and smoking exposure. RESULTS Seventy primary FESS patients were genotyped demonstrating a statistically significant skewing from the expected distribution of the general population (p < 0.0383). CRS patients with a particular polymorphism seemed less likely to have allergies, asthma, nasal polyposis, aspirin sensitivity, and diabetes, but this did not demonstrate statistical significance. CONCLUSION Our investigation suggests that TAS2R38 genotype is an independent risk factor for patients failing medical therapy, necessitating surgical intervention.
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Affiliation(s)
- Nithin D Adappa
- Department of Otorhinolaryngology-Head and Neck Surgery, University of Pennsylvania, Philadelphia, PA
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134
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Extrasensory perception: odorant and taste receptors beyond the nose and mouth. Pharmacol Ther 2013; 142:41-61. [PMID: 24280065 DOI: 10.1016/j.pharmthera.2013.11.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 11/04/2013] [Indexed: 12/22/2022]
Abstract
G protein-coupled receptors (GPCRs) represent the largest family of transmembrane receptors and are prime therapeutic targets. The odorant and taste receptors account for over half of the GPCR repertoire, yet they are generally excluded from large-scale, drug candidate analyses. Accumulating molecular evidence indicates that the odorant and taste receptors are widely expressed throughout the body and functional beyond the oronasal cavity - with roles including nutrient sensing, autophagy, muscle regeneration, regulation of gut motility, protective airway reflexes, bronchodilation, and respiratory disease. Given this expanding array of actions, the restricted perception of these GPCRs as mere mediators of smell and taste is outdated. Moreover, delineation of the precise actions of odorant and taste GPCRs continues to be hampered by the relative paucity of selective and specific experimental tools, as well as the lack of defined receptor pharmacology. In this review, we summarize the evidence for expression and function of odorant and taste receptors in tissues beyond the nose and mouth, and we highlight their broad potential in physiology and pathophysiology.
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135
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Saunders CJ, Reynolds SD, Finger TE. Chemosensory brush cells of the trachea. A stable population in a dynamic epithelium. Am J Respir Cell Mol Biol 2013; 49:190-6. [PMID: 23526223 DOI: 10.1165/rcmb.2012-0485oc] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Tracheal brush cells (BCs) are specialized epithelial chemosensors that use the canonical taste transduction cascade to detect irritants. To test whether BCs are replaced at the same rate as other cells in the surrounding epithelium of adult mice, we used 5-bromo-2'-deoxyuridine (BrdU) to label dividing cells. Although scattered BrdU-labeled epithelial cells are present 5-20 days after BrdU, no BCs are labeled. These data indicate that BCs comprise a relatively static population. To determine how BCs are generated during development, we injected 5-day-old mice with BrdU and found labeled BCs and non-BC epithelial cells 5 days after BrdU. During the next 60 days, the percentage of labeled BCs increased, whereas the percentage of other labeled cell types decreased. These data suggest that BCs are generated from non-BC progenitor cells during postnatal tracheal growth. To test whether the adult epithelium retains the capacity to generate BCs, tracheal epithelial cells were recovered from adult mice and grown in an air-liquid interface (ALI) culture. After transition to differentiation conditions, BCs are detected, and comprise 1% of the total cell population by Day 14. BrdU added to cultures before the differentiation of BCs was chased into BCs, indicating that the increase in BC density is attributable to the proliferation of a non-BC progenitor. We conclude that: (1) BCs are normally a static population in adult mice; (2) BC progenitors proliferate and differentiate during neonatal development; and (3) BCs can be regenerated from a proliferative population resident in adult epithelium.
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Affiliation(s)
- Cecil J Saunders
- Rocky Mountain Taste and Smell Center, Neuroscience Program, Department of Cellular and Developmental Biology, University of Colorado School of Medicine and Anschutz Medical Center, Aurora, CO 80045, USA.
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136
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Lee RJ, Chen B, Redding KM, Margolskee RF, Cohen NA. Mouse nasal epithelial innate immune responses to Pseudomonas aeruginosa quorum-sensing molecules require taste signaling components. Innate Immun 2013; 20:606-17. [PMID: 24045336 DOI: 10.1177/1753425913503386] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 08/02/2013] [Indexed: 11/17/2022] Open
Abstract
We previously observed that the human bitter taste receptor T2R38 is an important component of upper respiratory innate defense because it detects acyl homoserine lactone (AHL) quorum-sensing molecules secreted by Gram-negative bacteria. T2R38 activation in human sinonasal epithelial cells stimulates calcium and NO signals that increase mucociliary clearance, the major physical respiratory defense against inhaled pathogens. While mice do not have a clear T2R38 ortholog, they do have bitter taste receptors capable of responding to T2R38 agonists, suggesting that T2R-mediated innate immune mechanisms may be conserved in mice. We examined whether AHLs activate calcium and NO signaling in mouse nasal epithelial cells, and utilized pharmacology, as well as cells from knockout mice lacking important components of canonical taste signal transduction pathways, to determine if AHL-stimulated responses require taste signaling molecules. We found that AHLs stimulate calcium-dependent NO production that increases mucociliary clearance and thus likely serves an innate immune role against Gram-negative bacteria. These responses require PLCβ2 and TRPM5 taste signaling components, but not α-gustducin. These data suggest the mouse may be a useful model for further studies of T2R-mediated innate immunity.
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Affiliation(s)
- Robert J Lee
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Bei Chen
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Kevin M Redding
- Monell Chemical Senses Center and Philadelphia VA Medical Center Surgical Services, Philadelphia, PA, USA
| | - Robert F Margolskee
- Monell Chemical Senses Center and Philadelphia VA Medical Center Surgical Services, Philadelphia, PA, USA
| | - Noam A Cohen
- Department of Otorhinolaryngology - Head and Neck Surgery, University of Pennsylvania, Philadelphia, PA, USA Surgical Services, Philadelphia Veterans Administration Medical Center, Philadelphia, PA, USA
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Abstract
INTRODUCTION There is an unmet need for a new class of direct bronchodilators for the treatment of asthma and chronic obstructive lung disease. Unexpectedly, bitter taste receptors (TAS2Rs) have been localized on airway smooth muscle and when activated cause marked smooth muscle relaxation through a mechanism that is distinct from β2-adrenegic receptors. Thus TAS2R agonists have emerged as a novel class of bronchodilator. AREAS COVERED A synopsis of the TAS2R family and its biology for bitter taste perception on the tongue is provided, followed by a review of the identification and molecular and physiological characterization of TAS2R subtypes on human and mouse airway smooth muscle. The proposed molecular mechanisms leading to the relaxation response are provided, along with gaps in our understanding at certain points in the signaling cascade. Unresolved issues that may need to be considered for drug development are discussed. EXPERT OPINION TAS2R agonists show promise as a new class of highly efficacious bronchodilators for treatment of obstructive lung disease. With tens of thousands of known natural and synthetic bitter compounds, there is substantial diversity within the known agonists, and, a ready source of agents for screening and further development of an inhaled TAS2R agonist for therapeutic purposes.
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Affiliation(s)
- Stephen B Liggett
- University of South Florida Morsani College of Medicine, Departments of Internal Medicine and Molecular Pharmacology and Physiology , 12901 Bruce B. Downs Blvd, MDC02 Tampa, FL 33612 , USA.
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138
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Expression, regulation and putative nutrient-sensing function of taste GPCRs in the heart. PLoS One 2013; 8:e64579. [PMID: 23696900 PMCID: PMC3655793 DOI: 10.1371/journal.pone.0064579] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 04/15/2013] [Indexed: 01/07/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are critical for cardiovascular physiology. Cardiac cells express >100 nonchemosensory GPCRs, indicating that important physiological and potential therapeutic targets remain to be discovered. Moreover, there is a growing appreciation that members of the large, distinct taste and odorant GPCR families have specific functions in tissues beyond the oronasal cavity, including in the brain, gastrointestinal tract and respiratory system. To date, these chemosensory GPCRs have not been systematically studied in the heart. We performed RT-qPCR taste receptor screens in rodent and human heart tissues that revealed discrete subsets of type 2 taste receptors (TAS2/Tas2) as well as Tas1r1 and Tas1r3 (comprising the umami receptor) are expressed. These taste GPCRs are present in cultured cardiac myocytes and fibroblasts, and by in situ hybridization can be visualized across the myocardium in isolated cardiac cells. Tas1r1 gene-targeted mice (Tas1r1(Cre)/Rosa26(tdRFP)) strikingly recapitulated these data. In vivo taste receptor expression levels were developmentally regulated in the postnatal period. Intriguingly, several Tas2rs were upregulated in cultured rat myocytes and in mouse heart in vivo following starvation. The discovery of taste GPCRs in the heart opens an exciting new field of cardiac research. We predict that these taste receptors may function as nutrient sensors in the heart.
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139
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Ieki T, Okada S, Aihara Y, Ohmoto M, Abe K, Yasuoka A, Misaka T. Transgenic labeling of higher order neuronal circuits linked to phospholipase C-β2-expressing taste bud cells in medaka fish. J Comp Neurol 2013; 521:1781-802. [DOI: 10.1002/cne.23256] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2012] [Revised: 07/22/2012] [Accepted: 10/25/2012] [Indexed: 11/12/2022]
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141
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Barham HP, Cooper SE, Anderson CB, Tizzano M, Kingdom TT, Finger TE, Kinnamon SC, Ramakrishnan VR. Solitary chemosensory cells and bitter taste receptor signaling in human sinonasal mucosa. Int Forum Allergy Rhinol 2013; 3:450-7. [PMID: 23404938 DOI: 10.1002/alr.21149] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2012] [Revised: 11/29/2012] [Accepted: 12/07/2012] [Indexed: 01/18/2023]
Abstract
BACKGROUND Solitary chemosensory cells (SCCs) are specialized cells in the respiratory epithelium that respond to noxious chemicals including bacterial signaling molecules. SCCs express components of bitter taste transduction including the taste receptor type 2 (TAS2R) bitter taste receptors and downstream signaling effectors: α-Gustducin, phospholipase Cβ2 (PLCβ2), and transient receptor potential cation channel subfamily M member 5 (TRPM5). When activated, SCCs evoke neurogenic reflexes, resulting in local inflammation. The purpose of this study was to test for the presence SCCs in human sinonasal epithelium, and to test for a correlation with inflammatory disease processes such as allergic rhinitis and chronic rhinosinusitis. METHODS Patient demographics and biopsies of human sinonasal mucosa were obtained from control patients (n = 7) and those with allergic rhinitis and/or chronic rhinosinusitis (n = 15). Reverse transcription polymerase chain reaction (RT-PCR), quantitative PCR (qPCR), and immunohistochemistry were used to determine whether expression of signaling effectors was altered in diseased patients. RESULTS RT-PCR demonstrated that bitter taste receptors TAS2R4, TAS2R14, and TAS2R46, and downstream signaling effectors α-Gustducin, PLCβ2, and TRPM5 are expressed in the inferior turbinate, middle turbinate, septum, and uncinate of both control and diseased patients. PLCβ2/TRPM5-immunoreactive SCCs were identified in the sinonasal mucosa of both control and diseased patients. qPCR showed similar expression of α-Gustducin and TRPM5 in the uncinate process of control and diseased groups, and there was no correlation between level of expression and 22-item Sino-Nasal Outcomes Test (SNOT-22) or pain scores. CONCLUSION SCCs are present in human sinonasal mucosa in functionally relevant areas. Expression level of signaling effectors was similar in control and diseased patients and did not correlate with measures of pain and inflammation. Further study into these pathways may provide insight into nasal inflammatory diseases and may offer potential therapeutic targets.
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Affiliation(s)
- Henry P Barham
- Department of Otolaryngology-Head and Neck Surgery, University of Colorado Denver, Aurora, CO 80045, USA
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142
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Adappa ND, Howland TJ, Palmer JN, Kennedy DW, Doghramji L, Lysenko A, Reed DR, Lee RJ, Cohen NA. Genetics of the taste receptor T2R38 correlates with chronic rhinosinusitis necessitating surgical intervention. Int Forum Allergy Rhinol 2013; 3:184-7. [PMID: 23322450 DOI: 10.1002/alr.21140] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 11/15/2012] [Accepted: 11/29/2012] [Indexed: 12/17/2022]
Abstract
BACKGROUND We recently demonstrated the bitter taste receptor T2R38 upregulates sinonasal mucosal innate defense in response to gram-negative quorum-sensing molecules through increased nitric oxide production and mucociliary clearance. T2R38 was initially identified in the quest to understand the variability in bitter taste perception to the compound phenylthiocarbamide (PTC) and demonstrated to have polymorphisms generating diplotypes dividing people into PTC supertasters, heterozygotes (with variable PTC detection), and nontasters. We have further demonstrated that sinonasal epithelial cultures derived from supertasters significantly increase innate defenses in response to gram-negative quorum-sensing molecules compared with sinonasal cultures derived from heterozygotes and nontaster individuals. Based on this data, we hypothesize that supertasters are less likely to require sinus surgery compared with heterozygous or nontasters and that supertasters have improved surgical outcomes. METHODS Banked sinonasal tissue samples from patients who had undergone primary functional endoscopic sinus surgery at the University of Pennsylvania or the Philadelphia Veterans Affairs Medical Center were genotyped for T2R38 and compared to the expected population distribution. Necessity for additional antibiotic therapy following the postoperative healing time frame was evaluated. RESULTS A total of 28 patients were included in the study. Only 1 supertaster was identified (expected 5.6, p < 0.043). Additionally, 14 heterozygous and 13 nontaster patients were identified. CONCLUSION This pilot study investigating the genetics of the bitter taste receptor T2R38 in the context of primary sinonasal surgery demonstrates supertaster patients are less likely to need surgical intervention for chronic rhinosinusitis. Additional study is necessary to ascertain postsurgical outcomes.
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Affiliation(s)
- Nithin D Adappa
- Department of Otorhinolaryngology, Head and Neck Surgery, University of Pennsylvania, Philadelphia, PA 19104, USA
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143
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Nilius B, Appendino G. Spices: the savory and beneficial science of pungency. Rev Physiol Biochem Pharmacol 2013; 164:1-76. [PMID: 23605179 DOI: 10.1007/112_2013_11] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Spicy food does not only provide an important hedonic input in daily life, but has also been anedoctically associated to beneficial effects on our health. In this context, the discovery of chemesthetic trigeminal receptors and their spicy ligands has provided the mechanistic basis and the pharmacological means to investigate this enticing possibility. This review discusses in molecular terms the connection between the neurophysiology of pungent spices and the "systemic" effects associated to their trigeminality. It commences with a cultural and historical overview on the Western fascination for spices, and, after analysing in detail the mechanisms underlying the trigeminality of food, the main dietary players from the transient receptor potential (TRP) family of cation channels are introduced, also discussing the "alien" distribution of taste receptors outside the oro-pharingeal cavity. The modulation of TRPV1 and TRPA1 by spices is next described, discussing how spicy sensations can be turned into hedonic pungency, and analyzing the mechanistic bases for the health benefits that have been associated to the consumption of spices. These include, in addition to a beneficial modulation of gastro-intestinal and cardio-vascular function, slimming, the optimization of skeletal muscle performance, the reduction of chronic inflammation, and the prevention of metabolic syndrome and diabetes. We conclude by reviewing the role of electrophilic spice constituents on cancer prevention in the light of their action on pro-inflammatory and pro-cancerogenic nuclear factors like NFκB, and on their interaction with the electrophile sensor protein Keap1 and the ensuing Nrf2-mediated transcriptional activity. Spicy compounds have a complex polypharmacology, and just like any other bioactive agent, show a balance of beneficial and bad actions. However, at least for moderate consumption, the balance seems definitely in favour of the positive side, suggesting that a spicy diet, a caveman-era technology, could be seriously considered in addition to caloric control and exercise as a measurement to prevent and control many chronic diseases associate to malnutrition from a Western diet.
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Affiliation(s)
- Bernd Nilius
- KU Leuven Department of Cellular and Molecular Medicine, Laboratory of Ion Channel Research, Leuven, Belgium,
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Voigt A, Hübner S, Lossow K, Hermans-Borgmeyer I, Boehm U, Meyerhof W. Genetic labeling of Tas1r1 and Tas2r131 taste receptor cells in mice. Chem Senses 2012; 37:897-911. [PMID: 23010799 DOI: 10.1093/chemse/bjs082] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Characterization of the peripheral taste system relies on the identification and visualization of the different taste bud cell types. So far, genetic strategies to label taste receptor cells are limited to sweet, sour, and salty detecting cells. To visualize Tas1r1 umami and Tas2r131 bitter sensing cells, we generated animals in which the Tas1r1 and Tas2r131 open reading frames are replaced by expression cassettes containing the fluorescent proteins mCherry or hrGFP, respectively. These animals enabled us to visualize and quantify the entire oral Tas1r1 and Tas2r131 cell populations. Tas1r1-mCherry cells were predominantly detected in fungiform papillae, whereas Tas2r131-hrGFP cells, which are ~4-fold more abundant, were mainly present in foliate and vallate papillae. In the palate, both cell types were similarly distributed. Mice carrying both recombinant alleles demonstrated completely segregated Tas1r1 and Tas2r131 cell populations. Only ~50% of the entire bitter cell population expressed hrGFP, indicating that bitter taste receptor cells express a subset of the bitter receptor repertoire. In extragustatory tissues, mCherry fluorescence was observed in testis and hrGFP fluorescence in testis, thymus, vomeronasal organ, and respiratory epithelium, suggesting that only few extraoral sites express Tas2r131 and Tas1r1 receptors at levels comparable to taste tissue.
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Affiliation(s)
- Anja Voigt
- Department of Molecular Genetics, German Institute of Human Nutrition Potsdam-Rehbruecke (DIfE), Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
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Xu J, Cao J, Iguchi N, Riethmacher D, Huang L. Functional characterization of bitter-taste receptors expressed in mammalian testis. Mol Hum Reprod 2012; 19:17-28. [PMID: 22983952 DOI: 10.1093/molehr/gas040] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Mammalian spermatogenesis and sperm maturation are susceptible to the effects of internal and external factors. However, how male germ cells interact with and respond to these elements including those potentially toxic substances is poorly understood. Here, we show that many bitter-taste receptors (T2rs), which are believed to function as gatekeepers in the oral cavity to detect and innately prevent the ingestion of poisonous bitter-tasting compounds, are expressed in mouse seminiferous tubules. Our in situ hybridization results indicate that Tas2r transcripts are expressed postmeiotically. Functional analysis showed that mouse spermatids and spermatozoa responded to both naturally occurring and synthetic bitter-tasting compounds by increasing intracellular free calcium concentrations, and individual male germ cells exhibited different ligand-activation profiles, indicating that each cell may express a unique subset of T2r receptors. These calcium responses could be suppressed by a specific bitter-tastant blocker or abolished by the knockout of the gene for the G protein subunit α-gustducin. Taken together, our data strongly suggest that male germ cells, like taste bud cells in the oral cavity and solitary chemosensory cells in the airway, utilize T2r receptors to sense chemicals in the milieu that may affect sperm behavior and fertilization.
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Affiliation(s)
- Jiang Xu
- Monell Chemical Senses Center, 3500 Market Street, Philadelphia, PA 19104, USA
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Abstract
Airway epithelial healing is defined as restoration of health or soundness; to cure. Our research indicates that two types of progenitor cells participate in this process: the tissue-specific stem cell (TSC) and the facultative basal progenitor (FBP). The TSC restores the epithelium to its normal structure and function. Thus, the TSC regenerates the epithelium. In contrast, the FBP-derived epithelium is characterized by regions of cellular hyperplasia and hypoplasia. Since the FBP-derived epithelium deviates from normal, we term the FBP-mediated process repair. Our work indicates that the TSC responds to signals from other epithelial cells, including the FBP. These signals instruct the TSC to proliferate or to select one of several differentiation pathways. We interpret these data in the context of Stephen Padget's "seed and soil" paradigm. Therein, Padget explained that metastasis of a tumor, the seed, to a specific site, the soil, was determined by the growth and differentiation requirements of the tumor cell. By extending the seed and soil paradigm to airway epithelial healing, we suggest that proliferation and differentiation of the TSC, the seed, is determined by its interactions with other cell types, the soil. Based on this concept, we provide a set of suggestions for development of cell-based therapies that are directed toward chronic airways disease.
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Clark AA, Liggett SB, Munger SD. Extraoral bitter taste receptors as mediators of off-target drug effects. FASEB J 2012; 26:4827-31. [PMID: 22964302 DOI: 10.1096/fj.12-215087] [Citation(s) in RCA: 92] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We present a novel hypothesis that could explain many off-target effects of diverse pharmaceuticals. Specifically, we propose that any drug with a bitter taste could have unintended actions in the body through stimulation of extraoral type 2 taste receptors (T2Rs). T2Rs were first identified in the oral cavity, where they function as bitter taste receptors. However, recent findings indicate that they are also expressed outside the gustatory system, including in the gastrointestinal and respiratory systems. T2R ligands include a diverse array of natural and synthetic compounds, many of which are toxins. Notably, many pharmaceuticals taste bitter, with compounds such as chloroquine, haloperidol, erythromycin, procainamide, and ofloxacin known to activate T2Rs. Bitter-tasting compounds can have specific physiological effects in T2R-expressing cells. For example, T2Rs are found in some gastrointestinal endocrine cells, including those that secrete the peptide hormones (e.g., ghrelin and glucagon-like peptide-1) in response to stimulation by bitter-tasting compounds. In the respiratory system, stimulation of T2Rs expressed in respiratory epithelia and smooth muscle has been implicated in protective airway reflexes, ciliary beating, and bronchodilation. If our hypothesis is confirmed, it would offer a new paradigm for understanding the off-target actions of diverse drugs and could reveal potential new therapeutic targets.
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Affiliation(s)
- Adam A Clark
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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Pulkkinen V, Manson ML, Säfholm J, Adner M, Dahlén SE. The bitter taste receptor (TAS2R) agonists denatonium and chloroquine display distinct patterns of relaxation of the guinea pig trachea. Am J Physiol Lung Cell Mol Physiol 2012; 303:L956-66. [PMID: 22962016 DOI: 10.1152/ajplung.00205.2012] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Activation of taste receptors (TAS2Rs) by bitter taste agonists has been reported to cause bronchodilation. The aim of this study was to extend the information on the effects of bitter taste agonists on responses induced by different contractile mediators in a standard airway physiology preparation. Isometric responses were assessed in guinea pig trachea (GPT). TAS2R agonists were administered either to segments precontracted with different agonists for contraction or given before challenge with the different contractile stimuli, including antigen in tissues from ovalbumin-sensitized animals. TAS2R mRNA expression on GPT epithelium and smooth muscle was measured with real-time PCR. Denatonium, chloroquine, thiamine, and noscapine induced concentration-dependent relaxations (R(max): 98.3 ± 1.6, 100.0 ± 0.0, 100.0 ± 0.0, and 52.3 ± 1.1% of maximum, respectively, in the presence of indomethacin) in segments precontracted with carbachol. The receptors for denatonium (TAS2R4, TAS2R10) and chloroquine (TAS2R3, TAS2R10) were expressed in GPT. Whereas denatonium selectively inhibited contractions induced by carbachol, chloroquine uniformly inhibited contractions evoked by prostaglandin E(2), the thromboxane receptor agonist U-46619, leukotriene D(4), histamine, and antigen. The effects of denatonium, but not those of chloroquine, were partly inhibited by blockers of the large Ca(2+)-activated K(+) channels and decreased by an increase of the level of precontraction. In conclusion, TAS2R agonists mediated strong relaxations and substantial inhibition of contractions in GPT. Chloroquine and denatonium had distinct patterns of activity, indicating different signaling mechanisms. The findings reinforce the hypothesis that TAS2Rs are potential targets for the development of a new class of more efficacious agonists for bronchodilation.
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Affiliation(s)
- Ville Pulkkinen
- The Unit for Asthma and Allergy Research, the National Institute of Environmental Medicine and the Centre for Allergy Research, Karolinska Institutet, Stockholm, Sweden
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Geraedts MCP, Takahashi T, Vigues S, Markwardt ML, Nkobena A, Cockerham RE, Hajnal A, Dotson CD, Rizzo MA, Munger SD. Transformation of postingestive glucose responses after deletion of sweet taste receptor subunits or gastric bypass surgery. Am J Physiol Endocrinol Metab 2012; 303:E464-74. [PMID: 22669246 PMCID: PMC3423100 DOI: 10.1152/ajpendo.00163.2012] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The glucose-dependent secretion of the insulinotropic hormone glucagon-like peptide-1 (GLP-1) is a critical step in the regulation of glucose homeostasis. Two molecular mechanisms have separately been suggested as the primary mediator of intestinal glucose-stimulated GLP-1 secretion (GSGS): one is a metabotropic mechanism requiring the sweet taste receptor type 2 (T1R2) + type 3 (T1R3) while the second is a metabolic mechanism requiring ATP-sensitive K(+) (K(ATP)) channels. By quantifying sugar-stimulated hormone secretion in receptor knockout mice and in rats receiving Roux-en-Y gastric bypass (RYGB), we found that both of these mechanisms contribute to GSGS; however, the mechanisms exhibit different selectivity, regulation, and localization. T1R3(-/-) mice showed impaired glucose and insulin homeostasis during an oral glucose challenge as well as slowed insulin granule exocytosis from isolated pancreatic islets. Glucose, fructose, and sucralose evoked GLP-1 secretion from T1R3(+/+), but not T1R3(-/-), ileum explants; this secretion was not mimicked by the K(ATP) channel blocker glibenclamide. T1R2(-/-) mice showed normal glycemic control and partial small intestine GSGS, suggesting that T1R3 can mediate GSGS without T1R2. Robust GSGS that was K(ATP) channel-dependent and glucose-specific emerged in the large intestine of T1R3(-/-) mice and RYGB rats in association with elevated fecal carbohydrate throughout the distal gut. Our results demonstrate that the small and large intestines utilize distinct mechanisms for GSGS and suggest novel large intestine targets that could mimic the improved glycemic control seen after RYGB.
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Affiliation(s)
- Maartje C P Geraedts
- Division of Endocrinology, Diabetes, and Nutrition, Department of Anatomy & Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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