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Yi B, Wang S, Li W, Xu X, Yu L. Potential applications of P2X3 receptor antagonists in the treatment of refractory cough. Respir Med 2023; 217:107336. [PMID: 37364722 DOI: 10.1016/j.rmed.2023.107336] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2023] [Revised: 05/24/2023] [Accepted: 06/20/2023] [Indexed: 06/28/2023]
Abstract
Refractory chronic cough is defined as a clinical condition in which the cause of the cough remains unclear after comprehensive examination and treatment, or the cause is clear but symptomatic treatment is ineffective. Patients with refractory chronic cough experience a variety of physiological and psychological issues that significantly lower their quality of life and place a significant socio-economic burden on society. As a result, research both domestically and internationally has turned heavily toward these patients. Recently, several studies have identified P2X3 receptor antagonists for the treatment of refractory chronic cough, and this paper reviews the background, mechanism of action, evidence-based proof and application prospects of this class of drugs. KEY MESSAGE: There were plenty of studies about P2X3 receptor antagonists in the past, and in recent years this series of drugs are effective in refractory chronic cough. Although review articles summarizing have been published previously, most have focused on their chemical properties rather than their clinical aspects, with some omitting drugs that have been in clinical studies for nearly two years such as Eliapixant and Sivopixant. Focusing on four P2X3 receptor antagonists with proven efficacy in clinical studies, we analyzed the characteristics and disadvantages of each drug by comparing their clinical results of them and theoretically explained the common side effects of these drugs, as well as their potential for treating refractory chronic cough. This article can be used as a reference for the follow-up studies of P2X3 receptor antagonists in chronic cough. Additionally, it also has implications for the clinical focus of the drug and the approaches to relieve some side effects.
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Affiliation(s)
- Baiyi Yi
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, School of Medicine, Tongji University, No. 389 Xincun Road, Shanghai, 200065, China
| | - Shengyuan Wang
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, School of Medicine, Tongji University, No. 389 Xincun Road, Shanghai, 200065, China
| | - Wanzhen Li
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, School of Medicine, Tongji University, No. 389 Xincun Road, Shanghai, 200065, China
| | - Xianghuai Xu
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, School of Medicine, Tongji University, No. 389 Xincun Road, Shanghai, 200065, China.
| | - Li Yu
- Department of Pulmonary and Critical Care Medicine, Tongji Hospital, School of Medicine, Tongji University, No. 389 Xincun Road, Shanghai, 200065, China.
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Pelleg A, Sirtori E, Rolland JF, Mahadevan A. DT-0111: a novel P2X3 receptor antagonist. Purinergic Signal 2023; 19:467-479. [PMID: 36944825 PMCID: PMC10539268 DOI: 10.1007/s11302-023-09930-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 03/06/2023] [Indexed: 03/23/2023] Open
Abstract
Extracellular adenosine 5'-triphosphate (ATP) acts as an autocrine and paracrine agent, the actions of which on affected cells are mediated by P2 receptors (P2R), which include trans cell-membrane cationic channels (P2XRs), and G protein coupled receptors (P2YRs). The mammalian P2X receptors form homotrimeric or heterotrimeric cationic channels, each of which contains three ATP-binding sites. There are seven homotrimeric P2X receptors (P2X1-7) and three heteromeric (P2X2/P2X3, P2X4/P2X6, P2X1/P2X5). In the lungs and airways, ATP activates P2X3 and P2X2/3 receptors (P2X3R, P2X2/3R, respectively) localized on vagal sensory nerve terminals resulting in bronchoconstriction, and cough, and probably also localized release of pro-inflammatory neuropeptides via the axon reflex. Currently, several P2X3R and P2X2/3R antagonists are being developed as drug-candidates for the treatment of chronic cough. This report presents the receptor affinity data of a novel water-soluble small molecule, DT-0111, that acts as a selective P2X3R antagonist.
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Affiliation(s)
- Amir Pelleg
- Danmir Therapeutics LLC, 24 Dartmouth Lane, Haverford, PA, 19041-1020, USA.
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3
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Dong G, Kogan S, Venugopal N, Chang E, He L, Faal F, Shi Y, Phillips McCluskey L. Interleukin (IL)-1 Receptor Signaling Is Required for Complete Taste Bud Regeneration and the Recovery of Neural Taste Responses following Axotomy. J Neurosci 2023; 43:3439-3455. [PMID: 37015809 PMCID: PMC10184746 DOI: 10.1523/jneurosci.1355-22.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 03/03/2023] [Accepted: 03/07/2023] [Indexed: 04/06/2023] Open
Abstract
Experimental or traumatic nerve injury causes the degeneration of associated taste buds. Unlike most sensory systems, the sectioned nerve and associated taste buds can then regenerate, restoring neural responses to tastants. It was previously unknown whether injury-induced immune factors mediate this process. The proinflammatory cytokines, interleukin (IL)-1α and IL-1β, and their requisite receptor are strongly expressed by anterior taste buds innervated by the chorda tympani nerve. We tested taste bud regeneration and functional recovery in mice lacking the IL-1 receptor. After axotomy, the chorda tympani nerve regenerated but was initially unresponsive to tastants in both WT and Il1r KO mice. In the absence of Il1r signaling, however, neural taste responses remained minimal even >8 weeks after injury in both male and female mice, whereas normal taste function recovered by 3 weeks in WT mice. Failed recovery was because of a 57.8% decrease in regenerated taste buds in Il1r KO compared with WT axotomized mice. Il1a gene expression was chronically dysregulated, and the subset of regenerated taste buds were reinnervated more slowly and never reached full volume as progenitor cell proliferation lagged in KO mice. Il1r signaling is thus required for complete taste bud regeneration and the recovery of normal taste transmission, likely by impairing taste progenitor cell proliferation. This is the first identification of a cytokine response that promotes taste recovery. The remarkable plasticity of the taste system makes it ideal for identifying injury-induced mechanisms mediating successful regeneration and recovery.SIGNIFICANCE STATEMENT Taste plays a critical role in nutrition and quality of life. The adult taste system is highly plastic and able to regenerate following the disappearance of most taste buds after experimental nerve injury. Several growth factors needed for taste bud regeneration have been identified, but we demonstrate the first cytokine pathway required for the recovery of taste function. In the absence of IL-1 cytokine signaling, taste bud regeneration is incomplete, preventing the transmission of taste activity to the brain. These results open a new direction in revealing injury-specific mechanisms that could be harnessed to promote the recovery of taste perception after trauma or disease.
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Affiliation(s)
- Guangkuo Dong
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
| | - Schuyler Kogan
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
| | - Natasha Venugopal
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
| | - Eddy Chang
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
| | - Lianying He
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
| | - Fama Faal
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
| | - Yang Shi
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
- Division of Biostatistics and Data Science, Department of Population Health Sciences, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
| | - Lynnette Phillips McCluskey
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Georgia 30912
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4
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Jaime-Lara RB, Brooks BE, Vizioli C, Chiles M, Nawal N, Ortiz-Figueroa RSE, Livinski AA, Agarwal K, Colina-Prisco C, Iannarino N, Hilmi A, Tejeda HA, Joseph PV. A systematic review of the biological mediators of fat taste and smell. Physiol Rev 2023; 103:855-918. [PMID: 36409650 PMCID: PMC9678415 DOI: 10.1152/physrev.00061.2021] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Taste and smell play a key role in our ability to perceive foods. Overconsumption of highly palatable energy-dense foods can lead to increased caloric intake and obesity. Thus there is growing interest in the study of the biological mediators of fat taste and associated olfaction as potential targets for pharmacologic and nutritional interventions in the context of obesity and health. The number of studies examining mechanisms underlying fat taste and smell has grown rapidly in the last 5 years. Therefore, the purpose of this systematic review is to summarize emerging evidence examining the biological mechanisms of fat taste and smell. A literature search was conducted of studies published in English between 2014 and 2021 in adult humans and animal models. Database searches were conducted using PubMed, EMBASE, Scopus, and Web of Science for key terms including fat/lipid, taste, and olfaction. Initially, 4,062 articles were identified through database searches, and a total of 84 relevant articles met inclusion and exclusion criteria and are included in this review. Existing literature suggests that there are several proteins integral to fat chemosensation, including cluster of differentiation 36 (CD36) and G protein-coupled receptor 120 (GPR120). This systematic review will discuss these proteins and the signal transduction pathways involved in fat detection. We also review neural circuits, key brain regions, ingestive cues, postingestive signals, and genetic polymorphism that play a role in fat perception and consumption. Finally, we discuss the role of fat taste and smell in the context of eating behavior and obesity.
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Affiliation(s)
- Rosario B. Jaime-Lara
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Brianna E. Brooks
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Carlotta Vizioli
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Mari Chiles
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland,4Section of Neuromodulation and Synaptic Integration, Division of Intramural Research, National Institute of Mental Health, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Nafisa Nawal
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Rodrigo S. E. Ortiz-Figueroa
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Alicia A. Livinski
- 3NIH Library, Office of Research Services, Office of the Director, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Khushbu Agarwal
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Claudia Colina-Prisco
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Natalia Iannarino
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Aliya Hilmi
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Hugo A. Tejeda
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland
| | - Paule V. Joseph
- 1Section of Sensory Science and Metabolism Unit, Division of Intramural Research, National Institutes of Health, National Institute of Alcohol Abuse and Alcoholism, U.S. Department of Health and Human Services, Bethesda, Maryland,2Section of Sensory Science and Metabolism, Division of Intramural Research, National Institute of Nursing Research, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland
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5
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Bae J, Mook Kang K, Kim YC. Discovery of 5-methyl-1H-benzo[d]imidazole derivatives as novel P2X3 Receptor antagonists. Bioorg Med Chem Lett 2022; 72:128820. [PMID: 35644300 DOI: 10.1016/j.bmcl.2022.128820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 05/17/2022] [Accepted: 05/22/2022] [Indexed: 11/02/2022]
Abstract
Drug discovery programs targeting P2X3 receptors (P2X3R), an extracellular adenosine 5'-triphosphate (ATP) gated cation channel family, have been actively investigated for several CNS-related diseases. The current unmet need in the field of P2X3R targeted drugs is to avoid a side effect, the loss of taste, that could be reduced by increase of the P2X3R selectivity vs P2X2/3R. In this study, 5-methyl-1H-benzo[d]imidazole derivatives were designed and synthesized from the analysis of key pharmacophores of current antagonists. In the structure-activity relationship study, the most potent compounds 17a-b was discovered as potent P2X3R antagonists with IC50 values of 145 and 206 nM, and selectivity index of 60 and 41, respectively. In addition, 17a-b showed the not-competitive antagonism, but poor binding score in the docking study at the known allosteric binding site of Gefapixant binding site, indicating that another allosteric binding site might be existing for the novel P2X3R antagonists.
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Affiliation(s)
- Jinsu Bae
- Department of Biomedical Science and Engineering, Gwangju Institute of Science and Technology (GIST) 61005, Republic of Korea
| | - Koon Mook Kang
- School of Life Sciences, Gwangju Institute of Science and Technology (GIST) 61005, Republic of Korea
| | - Yong-Chul Kim
- Department of Biomedical Science and Engineering, Gwangju Institute of Science and Technology (GIST) 61005, Republic of Korea; School of Life Sciences, Gwangju Institute of Science and Technology (GIST) 61005, Republic of Korea.
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Ito M, Yokoyama T, Hirakawa M, Yamamoto Y, Sakanoue W, Sato K, Saino T. Morphology and chemical characteristics of taste buds associated with P2X3-immunoreactive afferent nerve endings in the rat incisive papilla. J Anat 2022; 240:688-699. [PMID: 34719779 PMCID: PMC8930809 DOI: 10.1111/joa.13583] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 10/16/2021] [Accepted: 10/22/2021] [Indexed: 11/30/2022] Open
Abstract
The present study investigated the cellular components and afferent innervations of taste buds in the rat incisive papilla by immunohistochemistry using confocal scanning laser microscopy. Taste buds containing guanine nucleotide-binding protein G(t), subunit α3 (GNAT3)-imunoreactive cells were densely distributed in the lateral wall of incisive papilla forming the opening of nasoincisor ducts. GNAT3-immunoreactive cells in the taste buds were slender in shape and the tips of apical processes gathered at one point at the surface of the epithelium. The number of taste buds was 56.8 ± 4.5 in the incisive papilla. The incisive taste buds also contained ectonucleoside triphosphate diphosphohydrolase 2-immunoreactive cells and synaptotagmin-1-immunoreactive cells in addition to GNAT3-immunoreactive cells. Furthermore, GNAT3-immunoreactive cells were immunoreactive to taste transduction molecules such as phospholipase C, β2-subunit, and inositol 1,4,5-trisphosphate receptor, type 3. P2X3-immunoreactive subepithelial nerve fibers intruded into the taste buds and terminated with hederiform or calix-like nerve endings attached to GNAT3-immunoreactive cells and synaptosomal-associated protein, 25 kDa-immunoreactive cells. Some P2X3-immunoreactive endings were also weakly immunoreactive for P2X2. Furthermore, a retrograde tracing method using fast blue dye indicated that most of the P2X3-immunoreactive nerve endings originated from the geniculate ganglia (GG) of the facial nerve. These results suggest that incisive taste buds are morphologically and cellularly homologous to lingual taste buds and are innervated by P2X3-immunoreactive nerve endings derived from the GG. The incisive papilla may be the palatal taste papilla that transmits chemosensory information in the oral cavity to the GG via P2X3-immunoreactive afferent nerve endings.
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Affiliation(s)
- Motoi Ito
- Division of Dental AnesthesiologyDepartment of Reconstructive Oral and Maxillofacial SurgerySchool of DentistryIwate Medical UniversityYahabaJapan
| | - Takuya Yokoyama
- Department of Anatomy (Cell Biology)Iwate Medical UniversityYahabaJapan
| | - Masato Hirakawa
- Department of Anatomy (Cell Biology)Iwate Medical UniversityYahabaJapan
| | - Yoshio Yamamoto
- Laboratory of Veterinary Anatomy and Cell BiologyFaculty of AgricultureIwate UniversityMoriokaJapan
| | - Wakana Sakanoue
- Division of Dental AnesthesiologyDepartment of Reconstructive Oral and Maxillofacial SurgerySchool of DentistryIwate Medical UniversityYahabaJapan
| | - Kenichi Sato
- Division of Dental AnesthesiologyDepartment of Reconstructive Oral and Maxillofacial SurgerySchool of DentistryIwate Medical UniversityYahabaJapan
| | - Tomoyuki Saino
- Department of Anatomy (Cell Biology)Iwate Medical UniversityYahabaJapan
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7
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Donnelly CR, Kumari A, Li L, Vesela I, Bradley RM, Mistretta CM, Pierchala BA. Probing the multimodal fungiform papilla: complex peripheral nerve endings of chorda tympani taste and mechanosensitive fibers before and after Hedgehog pathway inhibition. Cell Tissue Res 2021; 387:225-247. [PMID: 34859291 PMCID: PMC8821500 DOI: 10.1007/s00441-021-03561-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 11/16/2021] [Indexed: 11/28/2022]
Abstract
The fungiform papilla (FP) is a gustatory and somatosensory structure incorporating chorda tympani (CT) nerve fibers that innervate taste buds (TB) and also contain somatosensory endings for touch and temperature. Hedgehog (HH) pathway inhibition eliminates TB, but CT innervation remains in the FP. Importantly, after HH inhibition, CT neurophysiological responses to taste stimuli are eliminated, but tactile responses remain. To examine CT fibers that respond to tactile stimuli in the absence of TB, we used Phox2b-Cre; Rosa26LSL−TdTomato reporter mice to selectively label CT fibers with TdTomato. Normally CT fibers project in a compact bundle directly into TB, but after HH pathway inhibition, CT fibers reorganize and expand just under the FP epithelium where TB were. This widened expanse of CT fibers coexpresses Synapsin-1, β-tubulin, S100, and neurofilaments. Further, GAP43 expression in these fibers suggests they are actively remodeling. Interestingly, CT fibers have complex terminals within the apical FP epithelium and in perigemmal locations in the FP apex. These extragemmal fibers remain after HH pathway inhibition. To identify tactile end organs in FP, we used a K20 antibody to label Merkel cells. In control mice, K20 was expressed in TB cells and at the base of epithelial ridges outside of FP. After HH pathway inhibition, K20 + cells remained in epithelial ridges but were eliminated in the apical FP without TB. These data suggest that the complex, extragemmal nerve endings within and disbursed under the apical FP are the mechanosensitive nerve endings of the CT that remain after HH pathway inhibition.
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Affiliation(s)
- Christopher R Donnelly
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA.,Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC, USA.,Duke Cancer Institute, Duke University Medical Center, Durham, NC, USA
| | - Archana Kumari
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA.,Rowan University School of Osteopathic Medicine, Stratford, NJ, USA
| | - Libo Li
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Iva Vesela
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Robert M Bradley
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA
| | - Charlotte M Mistretta
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA.
| | - Brian A Pierchala
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, MI, USA. .,Department of Anatomy, Cell Biology & Physiology, Stark Neurosciences Research Institute, Indiana University School of Medicine, IN, Indianapolis, USA.
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8
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Hirakawa M, Yokoyama T, Yamamoto Y, Saino T. Distribution and morphology of P2X3-immunoreactive subserosal afferent nerve endings in the rat gastric antrum. J Comp Neurol 2020; 529:2014-2028. [PMID: 33190284 DOI: 10.1002/cne.25069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 10/27/2020] [Accepted: 11/09/2020] [Indexed: 12/15/2022]
Abstract
The present study investigated the morphological characteristics of subserosal afferent nerve endings with immunoreactivity for the P2X3 purinoceptor (P2X3) in the rat stomach by immunohistochemistry of whole-mount preparations using confocal scanning laser microscopy. P2X3 immunoreactivity was observed in subserosal nerve endings proximal and lateral to the gastric sling muscles in the distal antrum of the lesser curvature. Parent axons ramified into several lamellar processes to form net-like complex structures that extended two-dimensionally in every direction on the surface of the longitudinal smooth muscle layer. The axon terminals in the periphery of P2X3-immunoreactive net-like structures were flat and looped or leaf-like in shape. Some net-like lamellar structures and their axon terminals with P2X3 immunoreactivity were also immunoreactive for P2X2. P2X3-immunoreactive nerve fibers forming net-like terminal structures were closely surrounded by S100B-immunoreactive terminal Schwann cells, whereas axon terminals twined around these cells and extended club-, knob-, or thread-like protrusions in the surrounding tissues. Furthermore, a retrograde tracing method using fast blue dye indicated that most of these nerve endings originated from the nodose ganglia of the vagus nerve. These results suggest that P2X3-immunoreactive subserosal nerve endings have morphological characteristics of mechanoreceptors and contribute to sensation of a mechanical deformation of the distal antral wall associated with antral peristalsis.
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Affiliation(s)
- Masato Hirakawa
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba-cho, Japan
| | - Takuya Yokoyama
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba-cho, Japan
| | - Yoshio Yamamoto
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Tomoyuki Saino
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba-cho, Japan
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9
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Function, Innervation, and Neurotransmitter Signaling in Mice Lacking Type-II Taste Cells. eNeuro 2020; 7:ENEURO.0339-19.2020. [PMID: 31988217 PMCID: PMC7004487 DOI: 10.1523/eneuro.0339-19.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Revised: 01/14/2020] [Accepted: 01/15/2020] [Indexed: 01/08/2023] Open
Abstract
The Skn-1a transcription factor (Pou2f3) is required for Type II taste cell differentiation in taste buds. Taste buds in Skn-1a-/- mice lack Type II taste cells but have a concomitant expansion of Type III cells, providing an ideal model to determine the relative role of taste cell types in response specificity. We confirmed that chorda tympani responses to sweet, bitter, and umami stimuli were greatly reduced in the knock-outs (KOs) compared with wild-type (WT) littermates. Skn-1a-/- mice also had reductions to NaCl that were partially amiloride-insensitive, suggesting that both Type II and Type III cells contribute to amiloride-insensitive salt detection in anterior tongue. We also confirmed that responses to sour stimuli are equivalent in the KOs, despite the large increase in the number of Type III taste cells. To examine their innervation, we crossed the Htr3a-GFP (5-HT3A-GFP) reporter mouse with the Skn-1a-/- mice and examined geniculate ganglion neurons for GFP expression and responses to 5-HT. We found no change in the number of 5-HT3A-expressing neurons with KO of Skn-1a. Calcium imaging showed that only 5-HT3A-expressing neurons respond to exogenous 5-HT, while most neurons respond to ATP, similar to WT mice. Interestingly, despite loss of all Type II cells, the P2X3 antagonist AF353 blocked all chorda tympani responses. These data collectively raise questions pertaining the source of ATP signaling in the absence of Type II taste cells and whether the additional Type III cells are innervated by fibers that would have normally innervated Type II cells.
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10
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Abstract
The Skn-1a transcription factor (Pou2f3) is required for Type II taste cell differentiation in taste buds. Taste buds in Skn-1a -/- mice lack Type II taste cells but have a concomitant expansion of Type III cells, providing an ideal model to determine the relative role of taste cell types in response specificity. We confirmed that chorda tympani responses to sweet, bitter, and umami stimuli were greatly reduced in the knock-outs (KOs) compared with wild-type (WT) littermates. Skn-1a -/- mice also had reductions to NaCl that were partially amiloride-insensitive, suggesting that both Type II and Type III cells contribute to amiloride-insensitive salt detection in anterior tongue. We also confirmed that responses to sour stimuli are equivalent in the KOs, despite the large increase in the number of Type III taste cells. To examine their innervation, we crossed the Htr3a-GFP (5-HT3A-GFP) reporter mouse with the Skn-1a -/- mice and examined geniculate ganglion neurons for GFP expression and responses to 5-HT. We found no change in the number of 5-HT3A-expressing neurons with KO of Skn-1a Calcium imaging showed that only 5-HT3A-expressing neurons respond to exogenous 5-HT, while most neurons respond to ATP, similar to WT mice. Interestingly, despite loss of all Type II cells, the P2X3 antagonist AF353 blocked all chorda tympani responses. These data collectively raise questions pertaining the source of ATP signaling in the absence of Type II taste cells and whether the additional Type III cells are innervated by fibers that would have normally innervated Type II cells.
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11
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Yokoyama T, Yamamoto Y, Hirakawa M, Kato K, Saino T. Vesicular nucleotide transporter-immunoreactive type I cells associated with P2X3-immunoreactive nerve endings in the rat carotid body. J Comp Neurol 2019; 528:1486-1501. [PMID: 31808543 DOI: 10.1002/cne.24837] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Revised: 11/21/2019] [Accepted: 12/02/2019] [Indexed: 12/23/2022]
Abstract
ATP is the major excitatory transmitter from chemoreceptor type I cells to sensory nerve endings in the carotid body, and has been suggested to be released by exocytosis from these cells. We investigated the mRNA expression and immunohistochemical localization of vesicular nucleotide transporter (VNUT) in the rat carotid body. RT-PCR detected mRNA expression of VNUT in extracts of the tissue. Immunoreactivity for VNUT was localized in a part of type I cells immunoreactive for synaptophysin (SYN), but not in glial-like type II cells immunoreactive for S100 and S100B. Among SYN-immunoreactive type I cells, VNUT immunoreactivity was selectively localized in the sub-population of tyrosine hydroxylase (TH)-immunorective type I cells associated with nerve endings immunoreactive for the P2X3 purinoceptor; however, it was not detected in the sub-population of type I cells immunoreactive for dopamine beta-hydroxylase. Multi-immunolabeling for VNUT, P2X3, and Bassoon revealed that Bassoon-immunoreactive products were localized in type I cells with VNUT immunoreactivity, and accumulated on the contact side of P2X3-immunoreactive nerve endings. These results revealed the selective localization of VNUT in the subpopulation of TH-immunoreactive type I cells attached to sensory nerve endings and suggested that these cells release ATP by exocytosis for chemosensory transmission in the carotid body.
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Affiliation(s)
- Takuya Yokoyama
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba, Japan
| | - Yoshio Yamamoto
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Masato Hirakawa
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba, Japan
| | - Kouki Kato
- Center for Laboratory Animal Science, National Defense Medical College, Tokorozawa, Japan
| | - Tomoyuki Saino
- Department of Anatomy (Cell Biology), Iwate Medical University, Yahaba, Japan
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12
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Garceau D, Chauret N. BLU-5937: A selective P2X3 antagonist with potent anti-tussive effect and no taste alteration. Pulm Pharmacol Ther 2019; 56:56-62. [DOI: 10.1016/j.pupt.2019.03.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 01/17/2019] [Accepted: 03/17/2019] [Indexed: 12/21/2022]
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13
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Ishida Y, Sugiura Y, Magome T, Kamakura T, Takimoto Y, Hanada Y, Kitayama K, Nakamura Y, Shimada S, Ohta N, Naono-Nakayama R, Kamijo K. Expression Analysis of Serotonin Receptors, Serotonin Transporter and l-Amino Acid Decarboxylase in the Mouse Sphenopalatine Ganglion by RT-PCR, Northern Blot Analysis and In Situ Hybridization. Neuroscience 2019; 411:23-36. [PMID: 31128160 DOI: 10.1016/j.neuroscience.2019.05.028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 05/03/2019] [Accepted: 05/14/2019] [Indexed: 11/26/2022]
Abstract
The sphenopalatine ganglion (SPG) is a gathering of the cell bodies of parasympathetic fibers that dominate the nasal gland, lacrimal gland and cerebral blood vessels. The SPG controls nasal secretions, tears, and the dilation of cerebral blood vessels. However, it is unclear how serotonin regulates SPG functions. In this study, we investigated the expression of genes involved in the serotonergic system in the mouse SPG. We examined the mRNA expression levels of 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3A, 5-HT3B, 5-HT4, 5-HT5A, 5-HT5B, 5-HT6 and 5-HT7 receptors, as well as serotonin transporter, tryptophan hydroxylases 1 and 2, and L-amino acid decarboxylase (AADC) by RT-PCR. It revealed that the 5-HT3A and 5-HT3B ionotropic receptors and AADC were likely to be highly expressed in the SPG, as measured by RT-PCR. We next performed in situ hybridization on the SPG to examine the expression of these three genes at the cellular level after validating the specificity of each cRNA probe by northern blotting. The 5-HT3A receptor, 5-HT3B receptor, and AADC were expressed in 96.5% ± 1.0%, 29.7% ± 10.7%, and 57.4% ± 2.9% of neuronal cell bodies in the SPG, respectively, indicating that the 5-HT3A receptor was virtually expressed in all SPG neurons. Our results on the expression of these critical serotonin system genes in the parasympathetic SPG provide insight into the pathogenetics of rhinitis, conjunctivitis and headache. Furthermore, our findings suggest that targeting the 5-HT3A receptor might have therapeutic potential in the treatment of these ailments.
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Affiliation(s)
- Yusuke Ishida
- Division of Anatomy and Cell Biology, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-ku, Sendai 983-8536, Japan; Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; Division of Otorhinolaryngology, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-ku, Sendai 983-8536, Japan.
| | - Yusuke Sugiura
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Takuya Magome
- Department of medicine for Sports and Performing Arts, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Takefumi Kamakura
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Yasumitsu Takimoto
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Yukiko Hanada
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan; Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Kazuki Kitayama
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Yukiko Nakamura
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Shoichi Shimada
- Department of Neuroscience and Cell Biology, Graduate School of Medicine, Osaka University, Osaka 565-0871, Japan
| | - Nobuo Ohta
- Division of Otorhinolaryngology, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-ku, Sendai 983-8536, Japan
| | - Rumi Naono-Nakayama
- Division of Anatomy and Cell Biology, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-ku, Sendai 983-8536, Japan
| | - Keiju Kamijo
- Division of Anatomy and Cell Biology, Tohoku Medical and Pharmaceutical University, 1-15-1 Fukumuro, Miyagino-ku, Sendai 983-8536, Japan
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14
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Imamura Y, Shinozaki T, Okada-Ogawa A, Noma N, Shinoda M, Iwata K, Wada A, Abe O, Wang K, Svensson P. An updated review on pathophysiology and management of burning mouth syndrome with endocrinological, psychological and neuropathic perspectives. J Oral Rehabil 2019; 46:574-587. [PMID: 30892737 DOI: 10.1111/joor.12795] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Revised: 01/19/2019] [Accepted: 03/12/2019] [Indexed: 12/17/2022]
Abstract
Burning mouth syndrome (BMS) is a chronic oro-facial pain disorder of unknown cause. It is more common in peri- and post-menopausal women, and sex hormone dysregulation is believed to be an important causative factor. Psychosocial events often trigger or exacerbate symptoms, and persons with BMS appear to be predisposed towards anxiety and depression. Atrophy of small nerve fibres in the tongue epithelium has been reported, and potential neuropathic mechanisms for BMS are now widely investigated. Historically, BMS was thought to comprise endocrinological, psychosocial and neuropathic components. Neuroprotective steroids and glial cell line-derived neurotrophic factor family ligands may have pivotal roles in the peripheral mechanisms associated with atrophy of small nerve fibres. Denervation of chorda tympani nerve fibres that innervate fungiform buds leads to alternative trigeminal innervation, which results in dysgeusia and burning pain when eating hot foods. With regard to the central mechanism of BMS, depletion of neuroprotective steroids alters the brain network-related mood and pain modulation. Peripheral mechanistic studies support the use of topical clonazepam and capsaicin for the management of BMS, and some evidence supports the use of cognitive behavioural therapy. Hormone replacement therapy may address the causes of BMS, although adverse effects prevent its use as a first-line treatment. Selective serotonin reuptake inhibitors (SSRIs) and serotonin and noradrenaline reuptake inhibitors (SNRIs) may have important benefits, and well-designed controlled studies are expected. Other treatment options to be investigated include brain stimulation and TSPO (translocator protein 18 kDa) ligands.
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Affiliation(s)
- Yoshiki Imamura
- Department of Oral Diagnostic Sciences, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan.,Nihon University School of Dentistry Dental Research Center, Chiyoda-ku, Tokyo, Japan
| | - Takahiro Shinozaki
- Department of Oral Diagnostic Sciences, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan.,Nihon University School of Dentistry Dental Research Center, Chiyoda-ku, Tokyo, Japan
| | - Akiko Okada-Ogawa
- Department of Oral Diagnostic Sciences, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan.,Nihon University School of Dentistry Dental Research Center, Chiyoda-ku, Tokyo, Japan
| | - Noboru Noma
- Department of Oral Diagnostic Sciences, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan.,Nihon University School of Dentistry Dental Research Center, Chiyoda-ku, Tokyo, Japan
| | - Masahiro Shinoda
- Nihon University School of Dentistry Dental Research Center, Chiyoda-ku, Tokyo, Japan.,Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
| | - Koichi Iwata
- Nihon University School of Dentistry Dental Research Center, Chiyoda-ku, Tokyo, Japan.,Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
| | - Akihiko Wada
- Department of Radiology, Faculty of Medicine, Juntendo University, Bunkyo-ku, Tokyo, Japan
| | - Osamu Abe
- Department of Radiology, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Kelun Wang
- Department of Health Science and Technology, Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark
| | - Peter Svensson
- Department of Dentistry and Oral Health, Section for Orofacial Pain and Jaw Function, Aarhus University, Aarhus, Denmark
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15
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Rios-Pilier J, Krimm RF. TrkB expression and dependence divides gustatory neurons into three subpopulations. Neural Dev 2019; 14:3. [PMID: 30691513 PMCID: PMC6350382 DOI: 10.1186/s13064-019-0127-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 01/07/2019] [Indexed: 01/01/2023] Open
Abstract
Background During development, gustatory (taste) neurons likely undergo numerous changes in morphology and expression prior to differentiation into maturity, but little is known this process or the factors that regulate it. Neuron differentiation is likely regulated by a combination of transcription and growth factors. Embryonically, most geniculate neuron development is regulated by the growth factor brain derived neurotrophic factor (BDNF). Postnatally, however, BDNF expression becomes restricted to subpopulations of taste receptor cells with specific functions. We hypothesized that during development, the receptor for BDNF, tropomyosin kinase B receptor (TrkB), may also become developmentally restricted to a subset of taste neurons and could be one factor that is differentially expressed across taste neuron subsets. Methods We used transgenic mouse models to label both geniculate neurons innervating the oral cavity (Phox2b+), which are primarily taste, from those projecting to the outer ear (auricular neurons) to label TrkB expressing neurons (TrkBGFP). We also compared neuron number, taste bud number, and taste receptor cell types in wild-type animals and conditional TrkB knockouts. Results Between E15.5-E17.5, TrkB receptor expression becomes restricted to half of the Phox2b + neurons. This TrkB downregulation was specific to oral cavity projecting neurons, since TrkB expression remained constant throughout development in the auricular geniculate neurons (Phox2b-). Conditional TrkB removal from oral sensory neurons (Phox2b+) reduced this population to 92% of control levels, indicating that only 8% of these neurons do not depend on TrkB for survival during development. The remaining neurons failed to innervate any remaining taste buds, 14% of which remained despite the complete loss of innervation. Finally, some types of taste receptor cells (Car4+) were more dependent on innervation than others (PLCβ2+). Conclusions Together, these findings indicate that TrkB expression and dependence divides gustatory neurons into three subpopulations: 1) neurons that always express TrkB and are TrkB-dependent during development (50%), 2) neurons dependent on TrkB during development but that downregulate TrkB expression between E15.5 and E17.5 (41%), and 3) neurons that never express or depend on TrkB (9%). These TrkB-independent neurons are likely non-gustatory, as they do not innervate taste buds.
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Affiliation(s)
- Jennifer Rios-Pilier
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, 511 S. Floyd St., MDR Building Room 111, Louisville, KY, 40202, USA
| | - Robin F Krimm
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, 511 S. Floyd St., MDR Building Room 111, Louisville, KY, 40202, USA.
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16
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Masuda H, Nakamuta N, Yamamoto Y. Morphology of GNAT3-immunoreactive chemosensory cells in the rat larynx. J Anat 2018; 234:149-164. [PMID: 30467855 DOI: 10.1111/joa.12914] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/24/2018] [Indexed: 01/07/2023] Open
Abstract
The upper airways play important roles in respiratory defensive reflexes. Although solitary chemosensory cells and chemosensory cell clusters have been reported in the laryngeal mucosa of mammalian species, the distribution and cellular morphology of chemosensory cells remain unclear. In the present study, the distribution and morphology of solitary chemosensory cells and chemosensory cell clusters were examined by immunofluorescence for GNAT3 on whole-mount preparations of the rat laryngeal mucosa. Electrophysiological experiments were performed to analyze the respiratory reflexes evoked by bitter stimuli to the laryngeal cavity. In the whole area of the laryngeal mucosa, the numbers of GNAT3-immunoreactive solitary chemosensory cells and chemosensory clusters were 421.0 ± 20.3 and 62.7 ± 6.9, respectively. GNAT3-immunoreactive solitary chemosensory cells were mainly distributed in the mucosa overlying epiglottic and arytenoid cartilage, and chemosensory clusters were mainly distributed on the edge of the epiglottis and aryepiglottic fold. GNAT3-immunoreactive solitary chemosensory cells were slender with elongated processes or had a flask-like/columnar shape. The number of GNAT3-immunoreactive cells in chemosensory clusters was 6.1 ± 0.4, ranging between 2 and 14 cells. GNAT3-immunoreactive cells in the cluster were variform and the tips of apical processes gathered at one point at the surface of the epithelium. The tips of apical cytoplasmic processes in solitary chemosensory cells and cells in the cluster were immunoreactive for espin, and faced the laryngeal cavity. Physiological experiments showed that the application of 10 mm quinine hydrochloride to the laryngeal cavity decreased respiratory frequency. The present results revealed the chemosensory field of the larynx and the morphological characteristics of the laryngeal chemosensory system for respiratory depression.
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Affiliation(s)
- Haruka Masuda
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Nobuaki Nakamuta
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan
| | - Yoshio Yamamoto
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Japan
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17
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Zhang Y, Shi S, Xu Q, Zhang Q, Shanti RM, Le AD. SIS-ECM Laden with GMSC-Derived Exosomes Promote Taste Bud Regeneration. J Dent Res 2018; 98:225-233. [PMID: 30335555 DOI: 10.1177/0022034518804531] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Oral cancer has a high annual incidence rate all over the world, and the tongue is the most frequently affected anatomic structure. The current standard care is ablative surgery of malignant neoplasm, followed by tongue reconstruction with free flap. However, such reconstructive modalities with postsurgery radiotherapy or chemotherapy can hardly support the functional recovery of the tongue-particularly, functional taste bud regeneration-in reconstructed areas, thus seriously affecting patients' prognosis and life quality. Using a critical-sized tongue defect model in rats, we show that combinatory transplantation of small intestinal submucosa-extracellular matrix (SIS-ECM) with gingival mesenchymal stem cells (GMSCs) or their derivative exosomes promoted tongue lingual papillae recovery and taste bud regeneration as evidenced by increased expression of CK14, CK8, and markers for type I, II, and III taste bud cells (NTPdase 2, PLC-β2, and AADC, respectively). In addition, our results indicate that GMSCs or their derivative exosomes could increase BDNF expression, a growth factor that plays an important role in the proliferation and differentiation of epithelial basal progenitor cells into taste bud cells. Meanwhile, we showed an elevated expression level of Shh-which is essential for development, homeostasis, and maintenance of the taste bud organ-in wounded areas of the tongue among animals treated with GMSC/SIS-ECM or exosome/SIS-ECM as compared with SIS-ECM control. Moreover, our data show that GMSCs or their derivative exosomes promoted innervation of regenerated taste buds, as evidenced by elevated expressions of neurofilament and P2X3 at the injury areas. Together, our findings indicate that GMSC/SIS-ECM and exosome/SIS-ECM constructs can facilitate taste bud regeneration and reinnervation with promising potential application in postsurgery tongue reconstruction of patients with tongue cancer.
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Affiliation(s)
- Y Zhang
- 1 Department of Oral and Maxillofacial Surgery and Pharmacology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.,2 Department of Orthodontics, West China School of Stomatology, Sichuan University, Chengdu, China
| | - S Shi
- 1 Department of Oral and Maxillofacial Surgery and Pharmacology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Q Xu
- 1 Department of Oral and Maxillofacial Surgery and Pharmacology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Q Zhang
- 1 Department of Oral and Maxillofacial Surgery and Pharmacology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - R M Shanti
- 1 Department of Oral and Maxillofacial Surgery and Pharmacology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.,3 Department of Otorhinolaryngology-Head and Neck Surgery, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.,4 Department of Oral and Maxillofacial Surgery, Penn Medicine Hospital of the University of Pennsylvania, Philadelphia, PA, USA
| | - A D Le
- 1 Department of Oral and Maxillofacial Surgery and Pharmacology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA.,4 Department of Oral and Maxillofacial Surgery, Penn Medicine Hospital of the University of Pennsylvania, Philadelphia, PA, USA
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18
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Distribution and morphology of baroreceptors in the rat carotid sinus as revealed by immunohistochemistry for P2X3 purinoceptors. Histochem Cell Biol 2018; 151:161-173. [PMID: 30244428 DOI: 10.1007/s00418-018-1734-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/18/2018] [Indexed: 01/08/2023]
Abstract
The morphological characteristics of baroreceptors in the rat carotid sinus were reevaluated by whole-mount preparations with immunohistochemistry for P2X3 purinoceptors using confocal scanning laser microscopy. Immunoreactive nerve endings for P2X3 were distributed in the internal carotid artery proximal to the carotid bifurcation, particularly in the region opposite the carotid body. Some pre-terminal axons in nerve endings were ensheathed by myelin sheaths immunoreactive for myelin basic protein. Pre-terminal axons ramified into several branches that extended two-dimensionally in every direction. The axon terminals of P2X3-immunoreactive nerve endings were flat and leaf-like in shape, and extended hederiform- or knob-like protrusions in the adventitial layer. Some axons and axon terminals with P2X3 immunoreactivity were also immunoreactive for P2X2, and axon terminals were closely surrounded by terminal Schwann cells with S100 or S100B immunoreactivity. These results revealed the detailed morphology of P2X3-immunoreactive nerve endings and suggested that these endings respond to a mechanical deformation of the carotid sinus wall with their flat leaf-like terminals.
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19
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P2X 2 Receptor Deficiency in Mouse Vestibular End Organs Attenuates Vestibular Function. Neuroscience 2018; 386:41-50. [PMID: 29944897 DOI: 10.1016/j.neuroscience.2018.06.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 06/13/2018] [Accepted: 06/18/2018] [Indexed: 02/02/2023]
Abstract
P2X2 receptors are ligand-gated cation channels activated by extracellular ATP that modulate neural transmission in various neuronal systems. Although the function and distribution of P2X2 receptors in the cochlea portion of the inner ear are well established, their physiological role in the vestibular portion is still not understood. Therefore, we investigated P2X2 receptor localization in the peripheral vestibular portion, and assessed their physiological function in vivo using P2X2 receptor knock out (P2X2-KO) mice. Histological analysis revealed that P2X2 receptors were localized on the epithelial surface of supporting and transitional cells of the vestibular end organs. To examine vestibular function in P2X2-KO mice, we conducted behavioral tests and tested the vestibulo-ocular reflex (VOR) during sinusoidal rotations. P2X2-KO mice exhibited significant motor balance impairment in the balance beam test. VOR gain in P2X2-KO mice was significantly reduced, with no decrease in the optokinetic response. In conclusion, we showed that P2X2 receptors are mainly localized in the supporting cells of the vestibular inner ear, and the loss of P2X2 receptors causes mild vestibular dysfunction. Taken together, our findings suggest that the P2X2 receptor plays a modulatory role in vestibular function.
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20
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Romanov RA, Lasher RS, High B, Savidge LE, Lawson A, Rogachevskaja OA, Zhao H, Rogachevsky VV, Bystrova MF, Churbanov GD, Adameyko I, Harkany T, Yang R, Kidd GJ, Marambaud P, Kinnamon JC, Kolesnikov SS, Finger TE. Chemical synapses without synaptic vesicles: Purinergic neurotransmission through a CALHM1 channel-mitochondrial signaling complex. Sci Signal 2018; 11:11/529/eaao1815. [PMID: 29739879 DOI: 10.1126/scisignal.aao1815] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Conventional chemical synapses in the nervous system involve a presynaptic accumulation of neurotransmitter-containing vesicles, which fuse with the plasma membrane to release neurotransmitters that activate postsynaptic receptors. In taste buds, type II receptor cells do not have conventional synaptic features but nonetheless show regulated release of their afferent neurotransmitter, ATP, through a large-pore, voltage-gated channel, CALHM1. Immunohistochemistry revealed that CALHM1 was localized to points of contact between the receptor cells and sensory nerve fibers. Ultrastructural and super-resolution light microscopy showed that the CALHM1 channels were consistently associated with distinctive, large (1- to 2-μm) mitochondria spaced 20 to 40 nm from the presynaptic membrane. Pharmacological disruption of the mitochondrial respiratory chain limited the ability of taste cells to release ATP, suggesting that the immediate source of released ATP was the mitochondrion rather than a cytoplasmic pool of ATP. These large mitochondria may serve as both a reservoir of releasable ATP and the site of synthesis. The juxtaposition of the large mitochondria to areas of membrane displaying CALHM1 also defines a restricted compartment that limits the influx of Ca2+ upon opening of the nonselective CALHM1 channels. These findings reveal a distinctive organelle signature and functional organization for regulated, focal release of purinergic signals in the absence of synaptic vesicles.
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Affiliation(s)
- Roman A Romanov
- Institute of Cell Biophysics, Russian Academy of Science, Pushchino, Moscow Region 142290, Russia.,Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria.,Immanuel Kant Baltic Federal University, Kaliningrad 236041, Russia
| | - Robert S Lasher
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University Colorado School of Medicine, Aurora, CO 80045, USA
| | - Brigit High
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University Colorado School of Medicine, Aurora, CO 80045, USA
| | - Logan E Savidge
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University Colorado School of Medicine, Aurora, CO 80045, USA
| | - Adam Lawson
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University Colorado School of Medicine, Aurora, CO 80045, USA
| | - Olga A Rogachevskaja
- Institute of Cell Biophysics, Russian Academy of Science, Pushchino, Moscow Region 142290, Russia
| | - Haitian Zhao
- Litwin-Zucker Research Center for the Study of Alzheimer's Disease, The Feinstein Institute for Medical Research, Manhasset, NY 11030, USA
| | - Vadim V Rogachevsky
- Institute of Cell Biophysics, Russian Academy of Science, Pushchino, Moscow Region 142290, Russia.,United Pushchino Center for Electron Microscopy, Pushchino, Moscow Region 142290, Russia
| | - Marina F Bystrova
- Institute of Cell Biophysics, Russian Academy of Science, Pushchino, Moscow Region 142290, Russia
| | - Gleb D Churbanov
- Institute of Cell Biophysics, Russian Academy of Science, Pushchino, Moscow Region 142290, Russia
| | - Igor Adameyko
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria.,Department of Physiology and Pharmacology, Karolinska Institutet, SE-17177 Stockholm, Sweden
| | - Tibor Harkany
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, A-1090 Vienna, Austria.,Department of Neuroscience, Karolinska Institutet, SE-17177 Stockholm, Sweden
| | - Ruibiao Yang
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University Colorado School of Medicine, Aurora, CO 80045, USA
| | - Grahame J Kidd
- Department of Neuroscience, Lerner Research Institute, Cleveland Clinic, and 3D-Electron Microscopy, Renovo Neural Inc., Cleveland, OH 44195, USA
| | - Philippe Marambaud
- Litwin-Zucker Research Center for the Study of Alzheimer's Disease, The Feinstein Institute for Medical Research, Manhasset, NY 11030, USA
| | - John C Kinnamon
- Rocky Mountain Taste and Smell Center, Department of Biological Sciences, University of Denver, Denver, CO 80210, USA
| | - Stanislav S Kolesnikov
- Institute of Cell Biophysics, Russian Academy of Science, Pushchino, Moscow Region 142290, Russia.
| | - Thomas E Finger
- Rocky Mountain Taste and Smell Center, Department of Cell and Developmental Biology, University Colorado School of Medicine, Aurora, CO 80045, USA.
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21
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Biphasic functions for the GDNF-Ret signaling pathway in chemosensory neuron development and diversification. Proc Natl Acad Sci U S A 2017; 115:E516-E525. [PMID: 29282324 PMCID: PMC5776963 DOI: 10.1073/pnas.1708838115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
While knowledge of signaling mechanisms orchestrating the development and diversification of peripheral somatosensory neurons is extensive, our understanding of the mechanisms controlling chemosensory neuron specification remains rudimentary. Lingually projecting sensory neurons of the geniculate ganglion are receptive to the five taste qualities, as well as temperature and tactile stimuli, but the mechanisms responsible for the diversification of the unique subpopulations that respond to one, or several, of these stimuli remain unknown. Here we demonstrate that the GDNF-Ret signaling pathway exerts a unique, dual function in peripheral taste system development and postnatal function. Ret acts embryonically to regulate the expression of the chemosensory master regulator Phox2b, thus inducing chemosensory differentiation, while postnatally acting to specify a molecularly unique subpopulation of lingual mechanoreceptors. The development of the taste system relies on the coordinated regulation of cues that direct the simultaneous development of both peripheral taste organs and innervating sensory ganglia, but the underlying mechanisms remain poorly understood. In this study, we describe a novel, biphasic function for glial cell line-derived neurotrophic factor (GDNF) in the development and subsequent diversification of chemosensory neurons within the geniculate ganglion (GG). GDNF, acting through the receptor tyrosine kinase Ret, regulates the expression of the chemosensory fate determinant Phox2b early in GG development. Ret−/− mice, but not Retfx/fx; Phox2b-Cre mice, display a profound loss of Phox2b expression with subsequent chemosensory innervation deficits, indicating that Ret is required for the initial amplification of Phox2b expression but not its maintenance. Ret expression is extinguished perinatally but reemerges postnatally in a subpopulation of large-diameter GG neurons expressing the mechanoreceptor marker NF200 and the GDNF coreceptor GFRα1. Intriguingly, we observed that ablation of these neurons in adult Ret-Cre/ERT2; Rosa26LSL-DTA mice caused a specific loss of tactile, but not chemical or thermal, electrophysiological responses. Overall, the GDNF-Ret pathway exerts two critical and distinct functions in the peripheral taste system: embryonic chemosensory cell fate determination and the specification of lingual mechanoreceptors.
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Yamamoto Y, Nakamuta N. Morphology of P2X3-immunoreactive nerve endings in the rat tracheal mucosa. J Comp Neurol 2017; 526:550-566. [PMID: 29124772 DOI: 10.1002/cne.24351] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 10/24/2017] [Accepted: 10/30/2017] [Indexed: 01/28/2023]
Abstract
Nerve endings with immunoreactivity for the P2X3 purinoreceptor (P2X3) in the rat tracheal mucosa were examined by immunohistochemistry of whole-mount preparations with confocal scanning laser microscopy. P2X3 immunoreactivity was observed in ramified endings distributed in the whole length of the trachea. The myelinated parent axons of P2X3-immunoreactive nerve endings ramified into several branches that extended two-dimensionally in every direction at the interface between the epithelial layer and lamina propria. The axonal branches of P2X3-immunoreactive endings branched off many twigs located just beneath the epithelium, and continued to intraepithelial axon terminals. The axon terminals of P2X3-immunoreactive endings were beaded, rounded, or club-like in shape and terminated between tracheal epithelial cells. Flat axon terminals sometimes partly ensheathed neuroendocrine cells with immunoreactivity for SNAP25 or CGRP. Some axons and axon terminals with P2X3 immunoreactivity were immunoreactive for P2X2, while some terminals were immunoreactive for vGLUT2. Furthermore, a retrograde tracing method using fast blue (FB) revealed that 88.4% of FB-labeled cells with P2X3 immunoreactivity originated from the nodose ganglion. In conclusion, P2X3-immunoreactive nerve endings in the rat tracheal mucosa have unique morphological characteristics, and these endings may be rapidly adapting receptors and/or irritant receptors that are activated by mucosal irritant stimuli.
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Affiliation(s)
- Yoshio Yamamoto
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
| | - Nobuaki Nakamuta
- Laboratory of Veterinary Anatomy and Cell Biology, Faculty of Agriculture, Iwate University, Morioka, Iwate, Japan
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23
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Ohman-Gault L, Huang T, Krimm R. The transcription factor Phox2b distinguishes between oral and non-oral sensory neurons in the geniculate ganglion. J Comp Neurol 2017; 525:3935-3950. [PMID: 28856690 DOI: 10.1002/cne.24312] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Revised: 08/04/2017] [Accepted: 08/08/2017] [Indexed: 02/01/2023]
Abstract
Many basic characteristics of gustatory neurons remain unknown, partly due to the absence of specific markers. Some neurons in the geniculate ganglion project to taste regions in the oral cavity, whereas others innervate the outer ear. We hypothesized that the transcription factor Phox2b would identify oral cavity-projecting neurons in the geniculate ganglion. To test this possibility, we characterized mice in which Phox2b-Cre mediated gene recombination labeled neurons with tdTomato. Nerve labeling revealed that all taste neurons projecting through the chorda tympani (27%) and greater superficial petrosal nerves (15%) expressed Phox2b during development, whereas non-oral somatosensory neurons (58%) in the geniculate ganglion did not. We found tdTomato-positive innervation within all taste buds. Most (57%) of the fungiform papillae had labeled innervation only in taste buds, whereas 43% of the fungiform papillae also had additional labeled innervation to the papilla epithelium. Chorda tympani nerve transection eliminated all labeled innervation to taste buds, but most of the additional innervation in the fungiform papillae remained. Some of these additional fibers also expressed tyrosine hydroxylase, suggesting a sympathetic origin. Consistent with this, both sympathetic and parasympathetic fibers innervating blood vessels and salivary glands contained tdTomato labeling. Phox2b-tdTomato labels nerve fascicles in the tongue of the developing embryo and demonstrates a similar stereotyped branching pattern DiI-labeling.
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Affiliation(s)
- Lisa Ohman-Gault
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky
| | - Tao Huang
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky
| | - Robin Krimm
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, Kentucky
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Trigemino-gustatory interactions: a randomized controlled clinical trial assessing the effects of selective anesthesia of dental afferents on taste thresholds. Clin Oral Investig 2017; 22:1093-1102. [DOI: 10.1007/s00784-017-2193-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 08/21/2017] [Indexed: 12/18/2022]
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25
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Stratford JM, Larson ED, Yang R, Salcedo E, Finger TE. 5-HT 3A -driven green fluorescent protein delineates gustatory fibers innervating sour-responsive taste cells: A labeled line for sour taste? J Comp Neurol 2017; 525:2358-2375. [PMID: 28316078 DOI: 10.1002/cne.24209] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2017] [Revised: 03/03/2017] [Accepted: 03/10/2017] [Indexed: 12/29/2022]
Abstract
Taste buds contain multiple cell types with each type expressing receptors and transduction components for a subset of taste qualities. The sour sensing cells, Type III cells, release serotonin (5-HT) in response to the presence of sour (acidic) tastants and this released 5-HT activates 5-HT3 receptors on the gustatory nerves. We show here, using 5-HT3A GFP mice, that 5-HT3 -expressing nerve fibers preferentially contact and receive synaptic contact from Type III taste cells. Further, these 5-HT3 -expressing nerve fibers terminate in a restricted central-lateral portion of the nucleus of the solitary tract (nTS)-the same area that shows increased c-Fos expression upon presentation of a sour tastant (30 mM citric acid). This acid stimulation also evokes c-Fos in the laterally adjacent mediodorsal spinal trigeminal nucleus (DMSp5), but this trigeminal activation is not associated with the presence of 5-HT3 -expressing nerve fibers as it is in the nTS. Rather, the neuronal activation in the trigeminal complex likely is attributable to direct depolarization of acid-sensitive trigeminal nerve fibers, for example, polymodal nociceptors, rather than through taste buds. Taken together, these findings suggest that transmission of sour taste information involves communication between Type III taste cells and 5-HT3 -expressing afferent nerve fibers that project to a restricted portion of the nTS consistent with a crude mapping of taste quality information in the primary gustatory nucleus.
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Affiliation(s)
- J M Stratford
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado.,Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado
| | - E D Larson
- Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado.,Department of Otolaryngology, University of Colorado School of Medicine, Aurora, Colorado
| | - R Yang
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado.,Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado
| | - E Salcedo
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado.,Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado
| | - T E Finger
- Department of Cell and Developmental Biology, University of Colorado School of Medicine, Aurora, Colorado.,Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, Colorado
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Meng L, Huang T, Sun C, Hill DL, Krimm R. BDNF is required for taste axon regeneration following unilateral chorda tympani nerve section. Exp Neurol 2017; 293:27-42. [PMID: 28347764 DOI: 10.1016/j.expneurol.2017.03.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 03/22/2017] [Accepted: 03/23/2017] [Indexed: 12/18/2022]
Abstract
Taste nerves readily regenerate to reinnervate denervated taste buds; however, factors required for regeneration have not yet been identified. When the chorda tympani nerve is sectioned, expression of brain-derived neurotrophic factor (BDNF) remains high in the geniculate ganglion and lingual epithelium, despite the loss of taste buds. These observations suggest that BDNF is present in the taste system after nerve section and may support taste nerve regeneration. To test this hypothesis, we inducibly deleted Bdnf during adulthood in mice. Shortly after Bdnf gene recombination, the chorda tympani nerve was unilaterally sectioned causing a loss of both taste buds and neurons, irrespective of BDNF levels. Eight weeks after nerve section, however, regeneration was differentially affected by Bdnf deletion. In control mice, there was regeneration of the chorda tympani nerve and taste buds reappeared with innervation. In contrast, few taste buds were reinnervated in mice lacking normal Bdnf expression such that taste bud number remained low. In all genotypes, taste buds that were reinnervated were normal-sized, but non-innervated taste buds remained small and atrophic. On the side of the tongue contralateral to the nerve section, taste buds for some genotypes became larger and all taste buds remained innervated. Our findings suggest that BDNF is required for nerve regeneration following gustatory nerve section.
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Affiliation(s)
- Lingbin Meng
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA
| | - Tao Huang
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA
| | - Chengsan Sun
- Department of Psychology, University of Virginia, Charlottesville, VA 22904, USA
| | - David L Hill
- Department of Psychology, University of Virginia, Charlottesville, VA 22904, USA
| | - Robin Krimm
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA.
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Ermilov AN, Kumari A, Li L, Joiner AM, Grachtchouk MA, Allen BL, Dlugosz AA, Mistretta CM. Maintenance of Taste Organs Is Strictly Dependent on Epithelial Hedgehog/GLI Signaling. PLoS Genet 2016; 12:e1006442. [PMID: 27893742 PMCID: PMC5125561 DOI: 10.1371/journal.pgen.1006442] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 10/21/2016] [Indexed: 12/12/2022] Open
Abstract
For homeostasis, lingual taste papilla organs require regulation of epithelial cell survival and renewal, with sustained innervation and stromal interactions. To investigate a role for Hedgehog/GLI signaling in adult taste organs we used a panel of conditional mouse models to manipulate GLI activity within epithelial cells of the fungiform and circumvallate papillae. Hedgehog signaling suppression rapidly led to taste bud loss, papilla disruption, and decreased proliferation in domains of papilla epithelium that contribute to taste cells. Hedgehog responding cells were eliminated from the epithelium but retained in the papilla stromal core. Despite papilla disruption and loss of taste buds that are a major source of Hedgehog ligand, innervation to taste papillae was maintained, and not misdirected, even after prolonged GLI blockade. Further, vimentin-positive fibroblasts remained in the papilla core. However, retained innervation and stromal cells were not sufficient to maintain taste bud cells in the context of compromised epithelial Hedgehog signaling. Importantly taste organ disruption after GLI blockade was reversible in papillae that retained some taste bud cell remnants where reactivation of Hedgehog signaling led to regeneration of papilla epithelium and taste buds. Therefore, taste bud progenitors were either retained during epithelial GLI blockade or readily repopulated during recovery, and were poised to regenerate taste buds once Hedgehog signaling was restored, with innervation and papilla connective tissue elements in place. Our data argue that Hedgehog signaling is essential for adult tongue tissue maintenance and that taste papilla epithelial cells represent the key targets for physiologic Hedgehog-dependent regulation of taste organ homeostasis. Because disruption of GLI transcriptional activity in taste papilla epithelium is sufficient to drive taste organ loss, similar to pharmacologic Hedgehog pathway inhibition, the findings suggest that taste alterations in cancer patients using systemic Hedgehog pathway inhibitors result principally from interruption of signaling activity in taste papillae.
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Affiliation(s)
- Alexandre N Ermilov
- Department of Dermatology, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Archana Kumari
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Libo Li
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Ariell M Joiner
- Department of Cell and Developmental Biology, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Marina A Grachtchouk
- Department of Dermatology, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Benjamin L Allen
- Department of Cell and Developmental Biology, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Andrzej A Dlugosz
- Department of Dermatology, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America.,Department of Cell and Developmental Biology, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Charlotte M Mistretta
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan, United States of America
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Abstract
Activation of taste buds triggers the release of several neurotransmitters, including ATP and serotonin (5-hydroxytryptamine; 5-HT). Type III taste cells release 5-HT directly in response to acidic (sour) stimuli and indirectly in response to bitter and sweet tasting stimuli. Although ATP is necessary for activation of nerve fibers for all taste stimuli, the role of 5-HT is unclear. We investigated whether gustatory afferents express functional 5-HT3 receptors and, if so, whether these receptors play a role in transmission of taste information from taste buds to nerves. In mice expressing GFP under the control of the 5-HT(3A) promoter, a subset of cells in the geniculate ganglion and nerve fibers in taste buds are GFP-positive. RT-PCR and in situ hybridization confirmed the presence of 5-HT(3A) mRNA in the geniculate ganglion. Functional studies show that only those geniculate ganglion cells expressing 5-HT3A-driven GFP respond to 10 μM 5-HT and this response is blocked by 1 μM ondansetron, a 5-HT3 antagonist, and mimicked by application of 10 μM m-chlorophenylbiguanide, a 5-HT3 agonist. Pharmacological blockade of 5-HT3 receptors in vivo or genetic deletion of the 5-HT3 receptors reduces taste nerve responses to acids and other taste stimuli compared with controls, but only when urethane was used as the anesthetic. We find that anesthetic levels of pentobarbital reduce taste nerve responses apparently by blocking the 5-HT3 receptors. Our results suggest that 5-HT released from type III cells activates gustatory nerve fibers via 5-HT3 receptors, accounting for a significant proportion of the neural taste response.
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Calcitonin Gene-Related Peptide Reduces Taste-Evoked ATP Secretion from Mouse Taste Buds. J Neurosci 2016; 35:12714-24. [PMID: 26377461 DOI: 10.1523/jneurosci.0100-15.2015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
UNLABELLED Immunoelectron microscopy revealed that peripheral afferent nerve fibers innervating taste buds contain calcitonin gene-related peptide (CGRP), which may be as an efferent transmitter released from peripheral axon terminals. In this report, we determined the targets of CGRP within taste buds and studied what effect CGRP exerts on taste bud function. We isolated mouse taste buds and taste cells, conducted functional imaging using Fura-2, and used cellular biosensors to monitor taste-evoked transmitter release. The findings showed that a subset of Presynaptic (Type III) taste cells (53%) responded to 0.1 μm CGRP with an increase in intracellular Ca(2+). In contrast, Receptor (Type II) taste cells rarely (4%) responded to 0.1 μm CGRP. Using pharmacological tools, the actions of CGRP were probed and elucidated by the CGRP receptor antagonist CGRP(8-37). We demonstrated that this effect of CGRP was dependent on phospholipase C activation and was prevented by the inhibitor U73122. Moreover, applying CGRP caused taste buds to secrete serotonin (5-HT), a Presynaptic (Type III) cell transmitter, but not ATP, a Receptor (Type II) cell transmitter. Further, our previous studies showed that 5-HT released from Presynaptic (Type III) cells provides negative paracrine feedback onto Receptor (Type II) cells by activating 5-HT1A receptors, and reducing ATP secretion. Our data showed that CGRP-evoked 5-HT release reduced taste-evoked ATP secretion. The findings are consistent with a role for CGRP as an inhibitory transmitter that shapes peripheral taste signals via serotonergic signaling during processing gustatory information in taste buds. SIGNIFICANCE STATEMENT The taste sensation is initiated with a highly complex set of interactions between a variety of cells located within the taste buds before signal propagation to the brain. Afferent signals from the oral cavity are carried to the brain in chemosensory fibers that contribute to chemesthesis, the general chemical sensitivity of the mucus membranes in the oronasal cavities and being perceived as pungency, irritation, or heat. This is a study of a fundamental question in neurobiology: how are signals processed in sensory end organs, taste buds? More specifically, taste-modifying interactions, via transmitters, between gustatory and chemosensory afferents inside taste buds will help explain how a coherent output is formed before being transmitted to the brain.
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Taste Bud-Derived BDNF Is Required to Maintain Normal Amounts of Innervation to Adult Taste Buds. eNeuro 2015; 2:eN-NWR-0097-15. [PMID: 26730405 PMCID: PMC4697083 DOI: 10.1523/eneuro.0097-15.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 11/29/2015] [Accepted: 11/30/2015] [Indexed: 11/26/2022] Open
Abstract
Gustatory neurons transmit chemical information from taste receptor cells, which reside in taste buds in the oral cavity, to the brain. As adult taste receptor cells are renewed at a constant rate, nerve fibers must reconnect with new taste receptor cells as they arise. Therefore, the maintenance of gustatory innervation to the taste bud is an active process. Understanding how this process is regulated is a fundamental concern of gustatory system biology. We speculated that because brain-derived neurotrophic factor (BDNF) is required for taste bud innervation during development, it might function to maintain innervation during adulthood. If so, taste buds should lose innervation when Bdnf is deleted in adult mice. To test this idea, we first removed Bdnf from all cells in adulthood using transgenic mice with inducible CreERT2 under the control of the Ubiquitin promoter. When Bdnf was removed, approximately one-half of the innervation to taste buds was lost, and taste buds became smaller because of the loss of taste bud cells. Individual taste buds varied in the amount of innervation each lost, and those that lost the most innervation also lost the most taste bud cells. We then tested the idea that that the taste bud was the source of this BDNF by reducing Bdnf levels specifically in the lingual epithelium and taste buds. Taste buds were confirmed as the source of BDNF regulating innervation. We conclude that BDNF expressed in taste receptor cells is required to maintain normal levels of innervation in adulthood.
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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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Meng L, Jiang X, Ji R. Role of neurotrophin in the taste system following gustatory nerve injury. Metab Brain Dis 2015; 30:605-13. [PMID: 25381474 DOI: 10.1007/s11011-014-9626-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Accepted: 10/30/2014] [Indexed: 12/12/2022]
Abstract
Taste system is a perfect system to study degeneration and regeneration after nerve injury because the taste system is highly plastic and the regeneration is robust. Besides, degeneration and regeneration can be easily measured since taste buds arise in discrete locations, and nerves that innervate them can be accurately quantified. Neurotrophins are a family of proteins that regulate neural survival, function, and plasticity after nerve injury. Recent studies have shown that neurotrophins play an important role in the developmental and mature taste system, indicating neurtrophin might also regulate taste system following gustatory nerve injury. This review will summarize how taste system degenerates and regenerates after gustatory nerve cut and conclude potential roles of neurotrophin in regulating the process.
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Affiliation(s)
- Lingbin Meng
- Department of Anatomical Sciences and Neurobiology, University of Louisville, School of Medicine, Louisville, KY, 40202, USA
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Takai S, Yasumatsu K, Inoue M, Iwata S, Yoshida R, Shigemura N, Yanagawa Y, Drucker DJ, Margolskee RF, Ninomiya Y. Glucagon-like peptide-1 is specifically involved in sweet taste transmission. FASEB J 2015; 29:2268-80. [PMID: 25678625 DOI: 10.1096/fj.14-265355] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 01/22/2015] [Indexed: 11/11/2022]
Abstract
Five fundamental taste qualities (sweet, bitter, salty, sour, umami) are sensed by dedicated taste cells (TCs) that relay quality information to gustatory nerve fibers. In peripheral taste signaling pathways, ATP has been identified as a functional neurotransmitter, but it remains to be determined how specificity of different taste qualities is maintained across synapses. Recent studies demonstrated that some gut peptides are released from taste buds by prolonged application of particular taste stimuli, suggesting their potential involvement in taste information coding. In this study, we focused on the function of glucagon-like peptide-1 (GLP-1) in initial responses to taste stimulation. GLP-1 receptor (GLP-1R) null mice had reduced neural and behavioral responses specifically to sweet compounds compared to wild-type (WT) mice. Some sweet responsive TCs expressed GLP-1 and its receptors were expressed in gustatory neurons. GLP-1 was released immediately from taste bud cells in response to sweet compounds but not to other taste stimuli. Intravenous administration of GLP-1 elicited transient responses in a subset of sweet-sensitive gustatory nerve fibers but did not affect other types of fibers, and this response was suppressed by pre-administration of the GLP-1R antagonist Exendin-4(3-39). Thus GLP-1 may be involved in normal sweet taste signal transmission in mice.
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Affiliation(s)
- Shingo Takai
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Keiko Yasumatsu
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Mayuko Inoue
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Shusuke Iwata
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Ryusuke Yoshida
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Noriatsu Shigemura
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Yuchio Yanagawa
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Daniel J Drucker
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Robert F Margolskee
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
| | - Yuzo Ninomiya
- *Section of Oral Neuroscience, Graduate School of Dental Sciences, Kyushu University, Fukuoka, Japan; Division of Sensory Physiology, Research and Development Center for Taste and Odor Sensing, Kyushu University, Fukuoka, Japan; Department of Genetic and Behavioral Neuroscience, Gunma University Graduate School of Medicine, and JST, CREST, Maebashi, Japan; The Lunenfeld Tanenbaum Research Institute, Mt. Sinai Hospital, University of Toronto, Toronto, Ontario, Canada; and Monell Chemical Senses Center, Philadelphia, Pennsylvania, USA
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Vandenbeuch A, Larson ED, Anderson CB, Smith SA, Ford AP, Finger TE, Kinnamon SC. Postsynaptic P2X3-containing receptors in gustatory nerve fibres mediate responses to all taste qualities in mice. J Physiol 2015; 593:1113-25. [PMID: 25524179 DOI: 10.1113/jphysiol.2014.281014] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Accepted: 12/12/2014] [Indexed: 12/15/2022] Open
Abstract
Taste buds release ATP to activate ionotropic purinoceptors composed of P2X2 and P2X3 subunits, present on the taste nerves. Mice with genetic deletion of P2X2 and P2X3 receptors (double knockout mice) lack responses to all taste stimuli presumably due to the absence of ATP-gated receptors on the afferent nerves. Recent experiments on the double knockout mice showed, however, that their taste buds fail to release ATP, suggesting the possibility of pleiotropic deficits in these global knockouts. To test further the role of postsynaptic P2X receptors in afferent signalling, we used AF-353, a selective antagonist of P2X3-containing receptors to inhibit the receptors acutely during taste nerve recording and behaviour. The specificity of AF-353 for P2X3-containing receptors was tested by recording Ca(2+) transients to exogenously applied ATP in fura-2 loaded isolated geniculate ganglion neurons from wild-type and P2X3 knockout mice. ATP responses were completely inhibited by 10 μm or 100 μm AF-353, but neither concentration blocked responses in P2X3 single knockout mice wherein the ganglion cells express only P2X2-containing receptors. Furthermore, AF-353 had no effect on taste-evoked ATP release from taste buds. In wild-type mice, i.p. injection of AF-353 or simple application of the drug directly to the tongue, inhibited taste nerve responses to all taste qualities in a dose-dependent fashion. A brief access behavioural assay confirmed the electrophysiological results and showed that preference for a synthetic sweetener, SC-45647, was abolished following i.p. injection of AF-353. These data indicate that activation of P2X3-containing receptors is required for transmission of all taste qualities.
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Affiliation(s)
- Aurelie Vandenbeuch
- Department of Otolaryngology, University of Colorado School of Medicine, Aurora, CO, USA; Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine, Aurora, CO, USA
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Ganchrow D, Ganchrow JR, Cicchini V, Bartel DL, Kaufman D, Girard D, Whitehead MC. Nucleus of the solitary tract in the C57BL/6J mouse: Subnuclear parcellation, chorda tympani nerve projections, and brainstem connections. J Comp Neurol 2014; 522:1565-96. [PMID: 24151133 PMCID: PMC4090073 DOI: 10.1002/cne.23484] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Accepted: 10/08/2013] [Indexed: 01/28/2023]
Abstract
The nucleus of the solitary tract (NST) processes gustatory and related somatosensory information rostrally and general viscerosensory information caudally. To compare its connections with those of other rodents, this study in the C57BL/6J mouse provides a subnuclear cytoarchitectonic parcellation (Nissl stain) of the NST into rostral, intermediate, and caudal divisions. Subnuclei are further characterized by NADPH staining and P2X2 immunoreactivity (IR). Cholera toxin subunit B (CTb) labeling revealed those NST subnuclei receiving chorda tympani nerve (CT) afferents, those connecting with the parabrachial nucleus (PBN) and reticular formation (RF), and those interconnecting NST subnuclei. CT terminals are densest in the rostral central (RC) and medial (M) subnuclei; less dense in the rostral lateral (RL) subnucleus; and sparse in the ventral (V), ventral lateral (VL), and central lateral (CL) subnuclei. CTb injection into the PBN retrogradely labels cells in the aforementioned subnuclei; RC and M providing the largest source of PBN projection neurons. Pontine efferent axons terminate mainly in V and rostral medial (RM) subnuclei. CTb injection into the medullary RF labels cells and axonal endings predominantly in V at rostral and intermediate NST levels. Small CTb injections within the NST label extensive projections from the rostral division to caudal subnuclei. Projections from the caudal division primarily interconnect subnuclei confined to the caudal division of the NST; they also connect with the area postrema. P2X2-IR identifies probable vagal nerve terminals in the central (Ce) subnucleus in the intermediate/caudal NST. Ce also shows intense NADPH staining and does not project to the PBN. J. Comp. Neurol. 522:1565–1596, 2014.
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Affiliation(s)
- Donald Ganchrow
- Department of Anatomy and Anthropology, Sackler Faculty of Medicine, Tel-Aviv University, 69978, Ramat Aviv, Tel-Aviv, Israel
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Kumari A, Ermilov AN, Allen BL, Bradley RM, Dlugosz AA, Mistretta CM. Hedgehog pathway blockade with the cancer drug LDE225 disrupts taste organs and taste sensation. J Neurophysiol 2014; 113:1034-40. [PMID: 25392175 DOI: 10.1152/jn.00822.2014] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Taste sensation on the anterior tongue requires chorda tympani nerve function and connections with continuously renewing taste receptor cells. However, it is unclear which signaling pathways regulate the receptor cells to maintain chorda tympani sensation. Hedgehog (HH) signaling controls cell proliferation and differentiation in numerous tissues and is active in taste papillae and taste buds. In contrast, uncontrolled HH signaling drives tumorigenesis, including the common skin cancer, basal cell carcinoma. Systemic HH pathway inhibitors (HPIs) lead to basal cell carcinoma regression, but these drugs cause severe taste disturbances. We tested the hypothesis that taste disruption by HPIs reflects a direct requirement for HH signaling in maintaining taste organs and gustatory sensation. In mice treated with the HPI LDE225 up to 28 days, HH-responding cells were lost in fungiform papilla epithelium, and papillae acquired a conical apex. Taste buds were either absent or severely reduced in size in more than 90% of aberrant papillae. Taste bud remnants expressed the taste cell marker keratin 8, and papillae retained expression of nerve markers, neurofilament and P2X3. Chorda tympani nerve responses to taste stimuli were markedly reduced or absent in LDE225-treated mice. Responses to touch were retained, however, whereas cold responses were retained after 16 days of treatment but lost after 28 days. These data identify a critical, modality-specific requirement for HH signaling in maintaining taste papillae, taste buds and neurophysiological taste function, supporting the proposition that taste disturbances in HPI-treated patients are an on-target response to HH pathway blockade in taste organs.
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Affiliation(s)
- Archana Kumari
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan
| | - Alexandre N Ermilov
- Department of Dermatology, Medical School, University of Michigan, Ann Arbor, Michigan
| | - Benjamin L Allen
- Department of Cell and Developmental Biology, Medical School, University of Michigan, Ann Arbor, Michigan
| | - Robert M Bradley
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan; Department of Molecular and Integrative Physiology, Medical School, University of Michigan, Ann Arbor, Michigan; and
| | - Andrzej A Dlugosz
- Department of Dermatology, Medical School, University of Michigan, Ann Arbor, Michigan; Department of Cell and Developmental Biology, Medical School, University of Michigan, Ann Arbor, Michigan
| | - Charlotte M Mistretta
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, Ann Arbor, Michigan;
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Koudelka J, Horn JM, Vatanashevanopakorn C, Minichiello L. Genetic dissection of TrkB activated signalling pathways required for specific aspects of the taste system. Neural Dev 2014; 9:21. [PMID: 25256039 PMCID: PMC4178162 DOI: 10.1186/1749-8104-9-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 09/18/2014] [Indexed: 01/26/2023] Open
Abstract
Background Neurotrophin-4 (NT-4) and brain derived neurotrophic factor (BDNF) bind to the same receptor, Ntrk2/TrkB, but play distinct roles in the development of the rodent gustatory system. However, the mechanisms underlying these processes are lacking. Results Here, we demonstrate, in vivo, that single or combined point mutations in major adaptor protein docking sites on TrkB receptor affect specific aspects of the mouse gustatory development, known to be dependent on BDNF or NT-4. In particular, mice with a mutation in the TrkB-SHC docking site had reduced gustatory neuron survival at both early and later stages of development, when survival is dependent on NT-4 and BDNF, respectively. In addition, lingual innervation and taste bud morphology, both BDNF-dependent functions, were altered in these mutants. In contrast, mutation of the TrkB-PLCγ docking site alone did not affect gustatory neuron survival. Moreover, innervation to the tongue was delayed in these mutants and taste receptor expression was altered. Conclusions We have genetically dissected pathways activated downstream of the TrkB receptor that are required for specific aspects of the taste system controlled by the two neurotrophins NT-4 and BDNF. In addition, our results indicate that TrkB also regulate the expression of specific taste receptors by distinct signalling pathways. These results advance our knowledge of the biology of the taste system, one of the fundamental sensory systems crucial for an organism to relate to the environment.
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Affiliation(s)
| | | | | | - Liliana Minichiello
- Centre for Neuroregeneration, University of Edinburgh, EH16 4SB Edinburgh, UK.
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Fei D, Huang T, Krimm RF. The neurotrophin receptor p75 regulates gustatory axon branching and promotes innervation of the tongue during development. Neural Dev 2014; 9:15. [PMID: 24961238 PMCID: PMC4083039 DOI: 10.1186/1749-8104-9-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 05/28/2014] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT4) regulate the survival of gustatory neurons, axon growth and branching, and innervation of taste buds during development. These actions are largely, but not completely, mediated through the tyrosine kinase receptor, TrkB. Here, we investigated the role of p75, the other major receptor for BDNF and NT4, in the development of the taste system. RESULTS We found that p75-/-mice showed delayed axon outgrowth and reduced branching of gustatory axons at embryonic day (E)13.5. From E14.5 to E18.5, gustatory neurons innervated fewer papillae and completely failed to innervate the mid-region of the tongue in p75-/-mice. These early effects of the p75 mutation on gustatory axons preceded the loss of geniculate ganglion neurons starting at E14.5 and also contributed to a loss of taste buds at and after birth. Because knockouts for the TrkB receptor (TrkB-/-) do not lose as many taste buds as hybrid knockouts for its two ligands (BDNF and NT4), we asked if p75 maintains those additional taste buds in the absence of TrkB. It does not; hybrid TrkB-/-/p75-/-mice had more taste buds than TrkB-/-mice; these additional taste buds were not due to an increase in neurons or innervation. CONCLUSIONS p75 regulates gustatory neuron axon branching and tongue innervation patterns during taste system development. This function is likely accomplished independently of BDNF, NT4, and TrkB. In addition, p75 does not support the remaining neurons or taste buds in TrkB-/-mice.
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Affiliation(s)
| | | | - Robin F Krimm
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA.
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Kim YS, Park JH, Choi SJ, Bae JY, Ahn DK, McKemy DD, Bae YC. Central connectivity of transient receptor potential melastatin 8-expressing axons in the brain stem and spinal dorsal horn. PLoS One 2014; 9:e94080. [PMID: 24710558 PMCID: PMC3977991 DOI: 10.1371/journal.pone.0094080] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Accepted: 03/11/2014] [Indexed: 12/12/2022] Open
Abstract
Transient receptor potential melastatin 8 (TRPM8) ion channels mediate the detection of noxious and innocuous cold and are expressed by primary sensory neurons, but little is known about the processing of the TRPM8-mediated cold information within the trigeminal sensory nuclei (TSN) and the spinal dorsal horn (DH). To address this issue, we characterized TRPM8-positive (+) neurons in the trigeminal ganglion and investigated the distribution of TRPM8+ axons and terminals, and their synaptic organization in the TSN and in the DH using light and electron microscopic immunohistochemistry in transgenic mice expressing a genetically encoded axonal tracer in TRPM8+ neurons. TRPM8 was expressed in a fraction of small myelinated primary afferent fibers (23.7%) and unmyelinated fibers (76.3%), suggesting that TRPM8-mediated cold is conveyed via C and Aδ afferents. TRPM8+ axons were observed in all TSN, but at different densities in the dorsal and ventral areas of the rostral TSN, which dominantly receive sensory afferents from intra- and peri-oral structures and from the face, respectively. While synaptic boutons arising from Aδ and non-peptidergic C afferents usually receive many axoaxonic contacts and form complex synaptic arrangements, TRPM8+ boutons arising from afferents of the same classes of fibers showed a unique synaptic connectivity; simple synapses with one or two dendrites and sparse axoaxonic contacts. These findings suggest that TRPM8-mediated cold is conveyed via a specific subset of C and Aδ afferent neurons and is processed in a unique manner and differently in the TSN and DH.
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Affiliation(s)
- Yun Sook Kim
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Jun Hong Park
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Su Jung Choi
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Jin Young Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Dong Kuk Ahn
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - David D McKemy
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California, United States of America
| | - Yong Chul Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu, Korea
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BDNF and NT4 play interchangeable roles in gustatory development. Dev Biol 2013; 386:308-20. [PMID: 24378336 DOI: 10.1016/j.ydbio.2013.12.031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Revised: 12/17/2013] [Accepted: 12/20/2013] [Indexed: 01/10/2023]
Abstract
A limited number of growth factors are capable of regulating numerous developmental processes, but how they accomplish this is unclear. The gustatory system is ideal for examining this issue because the neurotrophins brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT4) have different developmental roles although both of them activate the same receptors, TrkB and p75. Here we first investigated whether the different roles of BDNF and NT4 are due to their differences in temporal and spatial expression patterns. Then, we asked whether or not these two neurotrophins exert their unique roles on the gustatory system by regulating different sets of downstream genes. By using Bdnf(Nt4/Nt4) mice, in which the coding region for BDNF is replaced with NT4, we examined whether the different functions of BDNF and NT4 are interchangeable during taste development. Our results demonstrated that NT4 could mediate most of the unique roles of BDNF during taste development. Specifically, caspase-3-mediated cell death, which was increased in the geniculate ganglion in Bdnf(-/-) mice, was rescued in Bdnf(Nt4/Nt4) mice. In BDNF knockout mice, tongue innervation was disrupted, and gustatory axons failed to reach their targets. However, disrupted innervation was rescued and target innervation is normal when NT4 replaced BDNF. Genome wide expression analyses revealed that BDNF and NT4 mutant mice exhibited different gene expression profiles in the gustatory (geniculate) ganglion. Compared to wild type, the expression of differentiation-, apoptosis- and axon guidance-related genes was changed in BDNF mutant mice, which is consistent with their different roles during taste development. However, replacement of BDNF by NT4 rescued these gene expression changes. These findings indicate that the functions of BDNF and NT4 in taste development are interchangeable. Spatial and temporal differences in BDNF and NT4 expression can regulate differential gene expression in vivo and determine their specific roles during development.
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Taste neurons consist of both a large TrkB-receptor-dependent and a small TrkB-receptor-independent subpopulation. PLoS One 2013; 8:e83460. [PMID: 24386206 PMCID: PMC3873951 DOI: 10.1371/journal.pone.0083460] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 11/04/2013] [Indexed: 12/17/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) are two neurotrophins that play distinct roles in geniculate (taste) neuron survival, target innervation, and taste bud formation. These two neurotrophins both activate the tropomyosin-related kinase B (TrkB) receptor and the pan-neurotrophin receptor p75. Although the roles of these neurotrophins have been well studied, the degree to which BDNF and NT-4 act via TrkB to regulate taste development in vivo remains unclear. In this study, we compared taste development in TrkB−/− and Bdnf−/−/Ntf4−/− mice to determine if these deficits were similar. If so, this would indicate that the functions of both BDNF and NT-4 can be accounted for by TrkB-signaling. We found that TrkB−/− and Bdnf−/−/Ntf4−/− mice lose a similar number of geniculate neurons by E13.5, which indicates that both BDNF and NT-4 act primarily via TrkB to regulate geniculate neuron survival. Surprisingly, the few geniculate neurons that remain in TrkB−/− mice are more successful at innervating the tongue and taste buds compared with those neurons that remain in Bdnf−/−/Ntf4−/− mice. The remaining neurons in TrkB−/− mice support a significant number of taste buds. In addition, these remaining neurons do not express the TrkB receptor, which indicates that either BDNF or NT-4 must act via additional receptors to influence tongue innervation and/or targeting.
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Kinnamon SC, Finger TE. A taste for ATP: neurotransmission in taste buds. Front Cell Neurosci 2013; 7:264. [PMID: 24385952 PMCID: PMC3866518 DOI: 10.3389/fncel.2013.00264] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 12/03/2013] [Indexed: 11/13/2022] Open
Abstract
Not only is ATP a ubiquitous source of energy but it is also used widely as an intercellular signal. For example, keratinocytes release ATP in response to numerous external stimuli including pressure, heat, and chemical insult. The released ATP activates purinergic receptors on nerve fibers to generate nociceptive signals. The importance of an ATP signal in epithelial-to-neuronal signaling is nowhere more evident than in the taste system. The receptor cells of taste buds release ATP in response to appropriate stimulation by tastants and the released ATP then activates P2X2 and P2X3 receptors on the taste nerves. Genetic ablation of the relevant P2X receptors leaves an animal without the ability to taste any primary taste quality. Of interest is that release of ATP by taste receptor cells occurs in a non-vesicular fashion, apparently via gated membrane channels. Further, in keeping with the crucial role of ATP as a neurotransmitter in this system, a subset of taste cells expresses a specific ectoATPase, NTPDase2, necessary to clear extracellular ATP which otherwise will desensitize the P2X receptors on the taste nerves. The unique utilization of ATP as a key neurotransmitter in the taste system may reflect the epithelial rather than neuronal origins of the receptor cells.
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Affiliation(s)
- Sue C Kinnamon
- Department of Otolaryngology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine Aurora, CO, USA
| | - Thomas E Finger
- Department Cell and Developmental Biology, Rocky Mountain Taste and Smell Center, University of Colorado School of Medicine Aurora, CO, USA
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Abstract
Taste buds are unusual in requiring ATP as a transmitter to activate sensory nerve fibers. In response to taste stimuli, taste cells release ATP, activating purinergic receptors containing the P2X2 and P2X3 subunits on taste nerves. In turn, the released ATP is hydrolyzed to ADP by a plasma membrane nucleoside triphosphate previously identified as nucleoside triphosphate diphosphohydrolase-2 (NTPDase2). In this paper we investigate the role of this ectonucleotidase in the function of taste buds by examining gene-targeted Entpd2-null mice globally lacking NTPDase2. RT-PCR confirmed the absence of NTPDase2, and ATPase enzyme histochemistry reveals no reaction product in taste buds of knockout mice, suggesting that NTPDase2 is the dominant form in taste buds. RT-PCR and immunocytochemistry demonstrated that in knockout mice all cell types are present in taste buds, even those cells normally expressing NTPDase2. In addition, the overall number and size of taste buds are normal in Entpd2-null mice. Luciferin/luciferase assays of circumvallate tissue of knockout mice detected elevated levels of extracellular ATP. Electrophysiological recordings from two taste nerves, the chorda tympani and glossopharyngeal, revealed depressed responses to all taste stimuli in Entpd2-null mice. Responses were more depressed in the glossopharyngeal nerve than in the chorda tympani nerve and involved all taste qualities; responses in the chorda tympani were more depressed to sweet and umami stimuli than to other qualities. We suggest that the excessive levels of extracellular ATP in the Entpd2-knockout animals desensitize the P2X receptors associated with nerve fibers, thereby depressing taste responses.
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Boucher Y, Felizardo R, Klein AH, Carstens MI, Carstens E. Gustatory modulation of the responses of trigeminal subnucleus caudalis neurons to noxious stimulation of the tongue in rats. Eur J Neurosci 2013; 38:2812-22. [PMID: 23802589 DOI: 10.1111/ejn.12282] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Revised: 05/15/2013] [Accepted: 05/22/2013] [Indexed: 11/30/2022]
Abstract
Certain tastants inhibit oral irritation by capsaicin, whereas anesthesia of the chorda tympani (CT) enhances oral capsaicin burn. We tested the hypothesis that tastants activate the CT to suppress responses of trigeminal subnucleus caudalis (Vc) neurons to noxious oral stimuli. In anesthetized rats, we recorded Vc unit responses to noxious electrical, chemical (pentanoic acid, 200 μm) and thermal (55 °C) stimulation of the tongue. Electrically evoked responses were significantly reduced by a tastant mix and individually applied NaCl, monosodium glutamate (MSG), and monopotassium glutamate. Sucrose, citric acid, quinine and water (control) had no effect. Pentanoic acid-evoked responses were similarly attenuated by NaCl and MSG, but not by other tastants. Responses to noxious heat were not affected by any tastant. Transection and/or anesthesia of the CT bilaterally affected neither Vc neuronal responses to electrical or pentanoic acid stimulation, nor the depressant effect of NaCl and MSG on electrically evoked responses. Calcium imaging showed that neither NaCl nor MSG directly excited any trigeminal ganglion cells or affected their responses to pentanoic acid. GABA also had no effect, arguing against peripheral effects of GABA, NaCl or MSG on lingual nocicepive nerve endings. The data also rule out a central mechanism, as the effects of NaCl and MSG were intact following CT transection. We speculate that the effect is mediated peripherally by the release from taste receptor cells (type III) of some mediator(s) other than GABA to indirectly inhibit trigeminal nociceptors. The results also indicate that the CT does not exert a tonic inhibitory effect on nociceptive Vc neurons.
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Affiliation(s)
- Yves Boucher
- UFR Odontologie, Université Diderot Paris, Paris, France
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Immunocytochemical analysis of P2X2 in rat circumvallate taste buds. BMC Neurosci 2012; 13:51. [PMID: 22621423 PMCID: PMC3507709 DOI: 10.1186/1471-2202-13-51] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2012] [Accepted: 04/20/2012] [Indexed: 11/23/2022] Open
Abstract
Background Our laboratory has shown that classical synapses and synaptic proteins are associated with Type III cells. Yet it is generally accepted that Type II cells transduce bitter, sweet and umami stimuli. No classical synapses, however, have been found associated with Type II cells. Recent studies indicate that the ionotropic purinergic receptors P2X2/P2X3 are present in rodent taste buds. Taste nerve processes express the ionotropic purinergic receptors (P2X2/P2X3). P2X2/P2X3Dbl−/− mice are not responsive to sweet, umami and bitter stimuli, and it has been proposed that ATP acts as a neurotransmitter in taste buds. The goal of the present study is to learn more about the nature of purinergic contacts in rat circumvallate taste buds by examining immunoreactivity to antisera directed against the purinergic receptor P2X2. Results P2X2-like immunoreactivity is present in intragemmal nerve processes in rat circumvallate taste buds. Intense immunoreactivity can also be seen in the subgemmal nerve plexuses located below the basal lamina. The P2X2 immunoreactive nerve processes also display syntaxin-1-LIR. The immunoreactive nerves are in close contact with the IP3R3-LIR Type II cells and syntaxin-1-LIR and/or 5-HT-LIR Type III cells. Taste cell synapses are observed only from Type III taste cells onto P2X2-LIR nerve processes. Unusually large, “atypical” mitochondria in the Type II taste cells are found only at close appositions with P2X2-LIR nerve processes. P2X2 immunogold particles are concentrated at the membranes of nerve processes at close appositions with taste cells. Conclusions Based on our immunofluorescence and immunoelectron microscopical studies we believe that both perigemmal and most all intragemmal nerve processes display P2X2-LIR. Moreover, colloidal gold immunoelectron microscopy indicates that P2X2-LIR in nerve processes is concentrated at sites of close apposition with Type II cells. This supports the hypothesis that ATP may be a key neurotransmitter in taste transduction and that Type II cells release ATP, activating P2X2 receptors in nerve processes.
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Nosrat IV, Margolskee RF, Nosrat CA. Targeted taste cell-specific overexpression of brain-derived neurotrophic factor in adult taste buds elevates phosphorylated TrkB protein levels in taste cells, increases taste bud size, and promotes gustatory innervation. J Biol Chem 2012; 287:16791-800. [PMID: 22442142 DOI: 10.1074/jbc.m111.328476] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) is the most potent neurotrophic factor in the peripheral taste system during embryonic development. It is also expressed in adult taste buds. There is a lack of understanding of the role of BDNF in the adult taste system. To address this, we generated novel transgenic mice in which transgene expression was driven by an α-gustducin promoter coupling BDNF expression to the postnatal expression of gustducin in taste cells. Immunohistochemistry revealed significantly stronger BDNF labeling in taste cells of high BDNF-expressing mouse lines compared with controls. We show that taste buds in these mice are significantly larger and have a larger number of taste cells compared with controls. To examine whether innervation was affected in Gust-BDNF mice, we used antibodies to neural cell adhesion molecule (NCAM) and ATP receptor P2X3. The total density of general innervation and specifically the gustatory innervation was markedly increased in high BDNF-expressing mice compared with controls. TrkB and NCAM gene expression in laser capture microdissected taste epithelia were significantly up-regulated in these mice. Up-regulation of TrkB transcripts in taste buds and elevated taste cell-specific TrkB phosphorylation in response to increased BDNF levels indicate that BDNF controls the expression and activation of its high affinity receptor in taste cells. This demonstrates a direct taste cell function for BDNF. BDNF also orchestrates and maintains taste bud innervation. We propose that the Gust-BDNF transgenic mouse models can be employed to further dissect the specific roles of BDNF in the adult taste system.
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Affiliation(s)
- Irina V Nosrat
- University of Tennessee Health Science Center, College of Medicine, Memphis, Tennessee 38163, USA
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Brandao KE, Dell'Acqua ML, Levinson SR. A-kinase anchoring protein 150 expression in a specific subset of TRPV1- and CaV 1.2-positive nociceptive rat dorsal root ganglion neurons. J Comp Neurol 2012; 520:81-99. [PMID: 21674494 PMCID: PMC4807902 DOI: 10.1002/cne.22692] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Modulation of phosphorylation states of ion channels is a critical step in the development of hyperalgesia during inflammation. Modulatory enhancement of channel activity may increase neuronal excitability and affect downstream targets such as gene transcription. The specificity required for such regulation of ion channels quickly occurs via targeting of protein kinases and phosphatases by the scaffolding A-kinase anchoring protein 79/150 (AKAP79/150). AKAP79/150 has been implicated in inflammatory pain by targeting protein kinase A (PKA) and protein kinase C (PKC) to the transient receptor potential vanilloid 1 (TRPV1) channel in peripheral sensory neurons, thus lowering threshold for activation of the channel by multiple inflammatory reagents. However, the expression pattern of AKAP150 in peripheral sensory neurons is unknown. Here we identify the peripheral neuron subtypes that express AKAP150, the subcellular distribution of AKAP150, and the potential target ion channels in rat dorsal root ganglion (DRG) slices. We found that AKAP150 is expressed predominantly in a subset of small DRG sensory neurons, where it is localized at the plasma membrane of the soma, axon initial segment, and small fibers. Most of these neurons are peripherin positive and produce C fibers, although a small portion produce Aδ fibers. Furthermore, we demonstrate that AKAP79/150 colocalizes with TRPV1 and Ca(V) 1.2 in the soma and axon initial segment. Thus AKAP150 is expressed in small, nociceptive DRG neurons, where it is targeted to membrane regions and where it may play a role in the modulation of ion channel phosphorylation states required for hyperalgesia.
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Affiliation(s)
- Katherine E Brandao
- Program in Neuroscience, University of Colorado School of Medicine, Anschutz Medical Campus, Aurora, CO 80045, USA
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Shikano M, Ueda T, Kamiya T, Ishida Y, Yamada T, Mizushima T, Shimura T, Mizoshita T, Tanida S, Kataoka H, Shimada S, Ugawa S, Joh T. Acid inhibits TRPV4-mediated Ca²⁺ influx in mouse esophageal epithelial cells. Neurogastroenterol Motil 2011; 23:1020-8, e497. [PMID: 21883699 DOI: 10.1111/j.1365-2982.2011.01767.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
BACKGROUND The transient receptor potential vanilloid 4 (TRPV4), a thermo-sensitive stretch-activated cation channel, is expressed in the skin stratified squamous epithelium, contributing to the acquisition of barrier function. Similarly, functional TRPV4 may be located in the stratified squamous epithelial lining of the esophagus, being involved in the pathogenesis of gastroesophageal reflux disease (GERD). Here we investigated the expression of TRPV4 in the mouse esophageal epithelium. METHODS TRPV4 expression at the mRNA and protein levels was examined by reverse transcription-polymerase chain reaction (RT-PCR), in situ hybridization, and immunohistochemistry. A calcium imaging technique and ATP assay were used to evaluate the functionality of TRPV4 in freshly isolated esophageal epithelial cells. KEY RESULTS Transcripts and proteins encoding TRPV4 were colocalized in the basal and intermediate layers of the esophageal epithelium. Both 4α-phorbol 12,13- didecanoate (4α-PDD), a selective agonist for TRPV4, and hypo-osmolar solution (160 mOsm) elevated the intracellular calcium concentration ([Ca(2+) ](i) ) in a subset of the isolated cells (70%). These [Ca(2+) ](i) increases were potently inhibited by ruthenium red (RuR), a TRPV4 channel antagonist, and were suppressed by extracellular protons (pH 5.0). Finally, application of 4α-PDD evoked ATP release in primary esophageal epithelial cells. CONCLUSIONS & INFERENCES Acid-sensitive TRPV4 channels were mainly expressed in the esophageal epithelial cells of the basal and intermediate layers. Direct exposure of TRPV4-expressing cells to gastric acid, as would occur in cases of GERD, could influence their cellular functions, possibly aggravating the disease state.
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Affiliation(s)
- M Shikano
- Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
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