51
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Spencer NJ, Magnúsdóttir EI, Jakobsson JET, Kestell G, Chen BN, Morris D, Brookes SJ, Lagerström MC. CGRPα within the Trpv1-Cre population contributes to visceral nociception. Am J Physiol Gastrointest Liver Physiol 2018; 314:G188-G200. [PMID: 28971837 DOI: 10.1152/ajpgi.00188.2017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The role of calcitonin gene-related peptide (CGRP) in visceral and somatic nociception is incompletely understood. CGRPα is highly expressed in sensory neurons of dorsal root ganglia and particularly in neurons that also express the transient receptor potential cation channel subfamily V member 1 (Trpv1). Therefore, we investigated changes in visceral and somatic nociception following deletion of CGRPα from the Trpv1-Cre population using the Cre/lox system. In control mice, acetic acid injection (0.6%, ip) caused significant immobility (time stationary), an established indicator of visceral pain. In CGRPα-mCherrylx/lx;Trpv1-Cre mice, the duration of immobility was significantly less than controls, and the distance CGRPα-mCherrylx/lx;Trpv1-Cre mice traveled over 20 min following acetic acid was significantly greater than controls. However, following acetic acid injection, there was no difference between genotypes in the writhing reflex, number of abdominal licks, or forepaw wipes of the cheek. CGRPα-mCherrylx/lx;Trpv1-Cre mice developed more pronounced inflammation-induced heat hypersensitivity above baseline values compared with controls. However, analyses of noxious acute heat or cold transmission revealed no difference between genotypes. Also, odor avoidance test, odor preference test, and buried food test for olfaction revealed no differences between genotypes. Our findings suggest that CGRPα-mediated transmission within the Trpv1-Cre population plays a significant role in visceral nociceptive pathways underlying voluntary movement. Monitoring changes in movement over time is a sensitive parameter to identify differences in visceral nociception, compared with writhing reflexes, abdominal licks, or forepaw wipes of the cheek that were unaffected by deletion of CGRPα- from Trpv1-Cre population and likely utilize different mechanisms. NEW & NOTEWORTHY The neuropeptide calcitonin gene-related peptide (CGRP) is highly colocalized with transient receptor potential cation channel subfamily V member 1 (TRPV1)-expressing primary afferent neurons, but the functional role of CGRPα specifically in these neurons is unknown in pain processing from visceral and somatic afferents. We used cre-lox recombination to conditionally delete CGRPα from TRPV1-expressing neurons in mice. We show that CGRPα from within TRPV1-cre population plays an important role in visceral nociception but less so in somatic nociception.
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Affiliation(s)
- Nick J Spencer
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia , Adelaide , Australia
| | | | | | - Garreth Kestell
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia , Adelaide , Australia
| | - Bao Nan Chen
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia , Adelaide , Australia
| | - David Morris
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia , Adelaide , Australia
| | - Simon J Brookes
- Discipline of Human Physiology and Centre for Neuroscience, School of Medicine, Flinders University of South Australia , Adelaide , Australia
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52
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Wan L, Jin H, Liu XY, Jeffry J, Barry DM, Shen KF, Peng JH, Liu XT, Jin JH, Sun Y, Kim R, Meng QT, Mo P, Yin J, Tao A, Bardoni R, Chen ZF. Distinct roles of NMB and GRP in itch transmission. Sci Rep 2017; 7:15466. [PMID: 29133874 PMCID: PMC5684337 DOI: 10.1038/s41598-017-15756-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 11/01/2017] [Indexed: 01/12/2023] Open
Abstract
A key question in our understanding of itch coding mechanisms is whether itch is relayed by dedicated molecular and neuronal pathways. Previous studies suggested that gastrin-releasing peptide (GRP) is an itch-specific neurotransmitter. Neuromedin B (NMB) is a mammalian member of the bombesin family of peptides closely related to GRP, but its role in itch is unclear. Here, we show that itch deficits in mice lacking NMB or GRP are non-redundant and Nmb/Grp double KO (DKO) mice displayed additive deficits. Furthermore, both Nmb/Grp and Nmbr/Grpr DKO mice responded normally to a wide array of noxious stimuli. Ablation of NMBR neurons partially attenuated peripherally induced itch without compromising nociceptive processing. Importantly, electrophysiological studies suggested that GRPR neurons receive glutamatergic input from NMBR neurons. Thus, we propose that NMB and GRP may transmit discrete itch information and NMBR neurons are an integral part of neural circuits for itch in the spinal cord.
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Affiliation(s)
- Li Wan
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Pain Medicine, The State Key Clinical Specialty in Pain Medicine, The Second Affiliated Hospital, Guangzhou Medical University, Guangdong, 510260, P.R. China
| | - Hua Jin
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, The First Hospital of Yunnan Province, Kunming, Yunnan, 650031, P.R. China
| | - Xian-Yu Liu
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Joseph Jeffry
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Devin M Barry
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Kai-Feng Shen
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, 400037, P.R. China
| | - Jia-Hang Peng
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Xue-Ting Liu
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, The State Key Laboratory of Respiratory Disease, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong, 510260, P.R. China
| | - Jin-Hua Jin
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, 100144, P.R. China
| | - Yu Sun
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200011, P.R. China
| | - Ray Kim
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Qing-Tao Meng
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, Hubei, 430060, P.R. China
| | - Ping Mo
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, the Affiliated Nanhai Hospital of Southern Medical University, Foshan, Guangdong, 528000, P.R. China
| | - Jun Yin
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Ailin Tao
- Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, The State Key Laboratory of Respiratory Disease, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong, 510260, P.R. China
| | - Rita Bardoni
- Department of Biomedical, Metabolic and Neural Sciences, University of Modena and Reggio Emilia, Modena, 41125, Italy
| | - Zhou-Feng Chen
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA.
- Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
- Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, 63110, USA.
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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53
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Roeckel LA, Utard V, Reiss D, Mouheiche J, Maurin H, Robé A, Audouard E, Wood JN, Goumon Y, Simonin F, Gaveriaux-Ruff C. Morphine-induced hyperalgesia involves mu opioid receptors and the metabolite morphine-3-glucuronide. Sci Rep 2017; 7:10406. [PMID: 28871199 PMCID: PMC5583172 DOI: 10.1038/s41598-017-11120-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Accepted: 08/21/2017] [Indexed: 12/14/2022] Open
Abstract
Opiates are potent analgesics but their clinical use is limited by side effects including analgesic tolerance and opioid-induced hyperalgesia (OIH). The Opiates produce analgesia and other adverse effects through activation of the mu opioid receptor (MOR) encoded by the Oprm1 gene. However, MOR and morphine metabolism involvement in OIH have been little explored. Hence, we examined MOR contribution to OIH by comparing morphine-induced hyperalgesia in wild type (WT) and MOR knockout (KO) mice. We found that repeated morphine administration led to analgesic tolerance and hyperalgesia in WT mice but not in MOR KO mice. The absence of OIH in MOR KO mice was found in both sexes, in two KO global mutant lines, and for mechanical, heat and cold pain modalities. In addition, the morphine metabolite morphine-3beta-D-glucuronide (M3G) elicited hyperalgesia in WT but not in MOR KO animals, as well as in both MOR flox and MOR-Nav1.8 sensory neuron conditional KO mice. M3G displayed significant binding to MOR and G-protein activation when using membranes from MOR-transfected cells or WT mice but not from MOR KO mice. Collectively our results show that MOR is involved in hyperalgesia induced by chronic morphine and its metabolite M3G.
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Affiliation(s)
- Laurie-Anne Roeckel
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Université de Strasbourg, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France
| | - Valérie Utard
- Université de Strasbourg, Illkirch, France.,Biotechnologie et Signalisation Cellulaire, UMR 7242 CNRS, Illkirch, France
| | - David Reiss
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Université de Strasbourg, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France
| | - Jinane Mouheiche
- CNRS UPR3212, Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, Strasbourg, France
| | - Hervé Maurin
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Université de Strasbourg, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France
| | - Anne Robé
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Université de Strasbourg, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France
| | - Emilie Audouard
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.,Université de Strasbourg, Illkirch, France.,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France
| | - John N Wood
- Molecular Nociception group, Wolson Institute for Biomedical Research, University College London, WCIE 6BT, London, UK
| | - Yannick Goumon
- CNRS UPR3212, Institut des Neurosciences Cellulaires et Intégratives, Centre National de la Recherche Scientifique, Strasbourg, France
| | - Frédéric Simonin
- Université de Strasbourg, Illkirch, France.,Biotechnologie et Signalisation Cellulaire, UMR 7242 CNRS, Illkirch, France
| | - Claire Gaveriaux-Ruff
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France. .,Université de Strasbourg, Illkirch, France. .,Centre National de la Recherche Scientifique, UMR7104, Illkirch, France. .,Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.
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54
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Itch induces conditioned place aversion in mice. Neurosci Lett 2017; 658:91-96. [DOI: 10.1016/j.neulet.2017.08.046] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2017] [Revised: 08/16/2017] [Accepted: 08/17/2017] [Indexed: 11/23/2022]
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55
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Martinelli-Boneschi F, Colombi M, Castori M, Devigili G, Eleopra R, Malik RA, Ritelli M, Zoppi N, Dordoni C, Sorosina M, Grammatico P, Fadavi H, Gerrits MM, Almomani R, Faber CG, Merkies ISJ, Toniolo D, Cocca M, Doglioni C, Waxman SG, Dib-Hajj SD, Taiana MM, Sassone J, Lombardi R, Cazzato D, Zauli A, Santoro S, Marchi M, Lauria G. COL6A5 variants in familial neuropathic chronic itch. Brain 2017; 140:555-567. [PMID: 28073787 DOI: 10.1093/brain/aww343] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 11/22/2016] [Indexed: 11/14/2022] Open
Abstract
Itch is thought to represent the peculiar response to stimuli conveyed by somatosensory pathways shared with pain through the activation of specific neurons and receptors. It can occur in association with dermatological, systemic and neurological diseases, or be the side effect of certain drugs. However, some patients suffer from chronic idiopathic itch that is frequently ascribed to psychological distress and for which no biomarker is available to date. We investigated three multigenerational families, one of which diagnosed with joint hypermobility syndrome/Ehlers-Danlos syndrome hypermobility type (JHS/EDS-HT), characterized by idiopathic chronic itch with predominantly proximal distribution. Skin biopsy was performed in all eight affected members and revealed in six of them reduced intraepidermal nerve fibre density consistent with small fibre neuropathy. Whole exome sequencing identified two COL6A5 rare variants co-segregating with chronic itch in eight affected members and absent in non-affected members, and in one unrelated sporadic patient with type 1 painless diabetic neuropathy and chronic itch. Two families and the diabetic patient carried the nonsense c.6814G>T (p.Glu2272*) variant and another family carried the missense c.6486G>C (p.Arg2162Ser) variant. Both variants were predicted as likely pathogenic by in silico analyses. The two variants were rare (minor allele frequency < 0.1%) in 6271 healthy controls and absent in 77 small fibre neuropathy and 167 JHS/EDS-HT patients without itch. Null-allele test on cDNA from patients' fibroblasts of both families carrying the nonsense variant demonstrated functional haploinsufficiency due to activation of nonsense mediated RNA decay. Immunofluorescence microscopy and western blotting revealed marked disorganization and reduced COL6A5 synthesis, respectively. Indirect immunofluorescence showed reduced COL6A5 expression in the skin of patients carrying the nonsense variant. Treatment with gabapentinoids provided satisfactory itch relief in the patients carrying the mutations. Our findings first revealed an association between COL6A5 gene and familiar chronic itch, suggesting a new contributor to the pathogenesis of neuropathic itch and identifying a new candidate therapeutic target.
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Affiliation(s)
- Filippo Martinelli-Boneschi
- Laboratory of Human Genetics of Neurological Disorders and Department of Neurology, Institute of Experimental Neurology (INSPE), Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Marina Colombi
- Division of Biology and Genetics, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Marco Castori
- Unit of Medical Genetics, Department of Molecular Medicine, Sapienza University, San Camillo-Forlanini Hospital, Rome, Italy
| | - Grazia Devigili
- Neurological Unit, University-Hospital "S. Maria della Misericordia", Udine, Italy
| | - Roberto Eleopra
- Neurological Unit, University-Hospital "S. Maria della Misericordia", Udine, Italy
| | - Rayaz A Malik
- Institute of Human Development, Centre for Endocrinology and Diabetes, University of Manchester and Central Manchester NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - Marco Ritelli
- Division of Biology and Genetics, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Nicoletta Zoppi
- Division of Biology and Genetics, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Chiara Dordoni
- Division of Biology and Genetics, Department of Molecular and Translational Medicine, University of Brescia, Brescia, Italy
| | - Melissa Sorosina
- Laboratory of Human Genetics of Neurological Disorders and Department of Neurology, Institute of Experimental Neurology (INSPE), Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Paola Grammatico
- Unit of Medical Genetics, Department of Molecular Medicine, Sapienza University, San Camillo-Forlanini Hospital, Rome, Italy
| | - Hassan Fadavi
- Institute of Human Development, Centre for Endocrinology and Diabetes, University of Manchester and Central Manchester NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK
| | - Monique M Gerrits
- Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Rowida Almomani
- Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Catharina G Faber
- Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Ingemar S J Merkies
- Clinical Genetics, Maastricht University Medical Center, Maastricht, The Netherlands.,Department of Neurology, Maastricht University Medical Center, Maastricht, The Netherlands
| | | | | | - Massimiliano Cocca
- Department of Medical, Surgical and Health Sciences, University of Trieste, 34100 Trieste, Italy
| | - Claudio Doglioni
- Department of Pathology, IRCCS San Raffaele Scientific Institute and Vita-Salute San Raffaele University, Milan, Italy
| | - Stephen G Waxman
- Department of Neurology and Center for Neuroscience and regeneration Research, Yale University School of Medicine, New Haven, CT 06515, USA.,Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06515, USA
| | - Sulayman D Dib-Hajj
- Department of Neurology and Center for Neuroscience and regeneration Research, Yale University School of Medicine, New Haven, CT 06515, USA.,Center for Neuroscience and Regeneration Research, Veterans Affairs Medical Center, West Haven, CT 06515, USA
| | - Michela M Taiana
- Neuroalgology Unit and Skin Biopsy, Peripheral Neuropathy and Neuropathic Pain Center, IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy
| | - Jenny Sassone
- Neuroalgology Unit and Skin Biopsy, Peripheral Neuropathy and Neuropathic Pain Center, IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy
| | - Raffaella Lombardi
- Neuroalgology Unit and Skin Biopsy, Peripheral Neuropathy and Neuropathic Pain Center, IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy
| | - Daniele Cazzato
- Neuroalgology Unit and Skin Biopsy, Peripheral Neuropathy and Neuropathic Pain Center, IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy
| | - Andrea Zauli
- Laboratory of Human Genetics of Neurological Disorders and Department of Neurology, Institute of Experimental Neurology (INSPE), Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Silvia Santoro
- Laboratory of Human Genetics of Neurological Disorders and Department of Neurology, Institute of Experimental Neurology (INSPE), Division of Neuroscience, San Raffaele Scientific Institute, Milan, Italy
| | - Margherita Marchi
- Neuroalgology Unit and Skin Biopsy, Peripheral Neuropathy and Neuropathic Pain Center, IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy
| | - Giuseppe Lauria
- Neuroalgology Unit and Skin Biopsy, Peripheral Neuropathy and Neuropathic Pain Center, IRCCS Foundation "Carlo Besta" Neurological Institute, Milan, Italy
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56
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Tajiri K, Shimizu Y. Recent advances in the management of pruritus in chronic liver diseases. World J Gastroenterol 2017; 23:3418-3426. [PMID: 28596678 PMCID: PMC5442078 DOI: 10.3748/wjg.v23.i19.3418] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2017] [Revised: 03/13/2017] [Accepted: 05/04/2017] [Indexed: 02/06/2023] Open
Abstract
Pruritus is a symptom found in patients with chronic liver diseases, especially cholestatic liver diseases such as primary biliary cholangitis. This symptom impairs patient quality of life by disturbing sleep and may lead to consideration of liver transplantation. Mechanisms implicated in pruritus have been associated with the peripheral and central nervous systems, leading to the development of various therapeutic options. Little evidence for the efficacy of most of these treatments is currently available, indicating a need for further investigations.
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57
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Green D, Dong X. The cell biology of acute itch. J Cell Biol 2017; 213:155-61. [PMID: 27114499 PMCID: PMC4862869 DOI: 10.1083/jcb.201603042] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 04/05/2016] [Indexed: 01/22/2023] Open
Abstract
Itch, the irritation we feel and the relief that comes from scratching, is an evolutionary warning system and defense against harmful environmental agents. Although once considered a subtype of pain, itch is now recognized as a unique sense, with its own distinct physiology and cell receptors. Here, we discuss recent advances in our understanding of itch and the molecular players that mediate this sensory modality.
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Affiliation(s)
- Dustin Green
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205 Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, MD 21205
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58
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Duan B, Cheng L, Ma Q. Spinal Circuits Transmitting Mechanical Pain and Itch. Neurosci Bull 2017; 34:186-193. [PMID: 28484964 PMCID: PMC5799122 DOI: 10.1007/s12264-017-0136-z] [Citation(s) in RCA: 83] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Accepted: 04/01/2017] [Indexed: 12/11/2022] Open
Abstract
In 1905, Henry Head first suggested that transmission of pain-related protopathic information can be negatively modulated by inputs from afferents sensing innocuous touch and temperature. In 1965, Melzak and Wall proposed a more concrete gate control theory of pain that highlights the interaction between unmyelinated C fibers and myelinated A fibers in pain transmission. Here we review the current understanding of the spinal microcircuits transmitting and gating mechanical pain or itch. We also discuss how disruption of the gate control could cause pain or itch evoked by innocuous mechanical stimuli, a hallmark symptom for many chronic pain or itch patients.
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Affiliation(s)
- Bo Duan
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, 830 North University Ave, Ann Arbor, MI, 48109, USA.
| | - Longzhen Cheng
- Institute of Brain Science, the State Key Laboratory of Medical Neurobiology and the Collaborative Innovation Center for Brain Science, Fudan University, Shanghai, 200032, China.
| | - Qiufu Ma
- Dana-Farber Cancer Institute and Department of Neurobiology, Harvard Medical School, 1 Jimmy Fund Way, Boston, MA, 02115, USA.
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59
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Spinal cord interneurons expressing the gastrin-releasing peptide receptor convey itch through VGLUT2-mediated signaling. Pain 2017; 158:945-961. [PMID: 28157737 PMCID: PMC5402714 DOI: 10.1097/j.pain.0000000000000861] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Supplemental Digital Content is Available in the Text. Gastrin-releasing peptide receptor–expressing cells are interneurons that use glutamate to transmit the perception of chemical itch to the next step in the labeled line of itch in the spinal cord. Itch is a sensation that promotes the desire to scratch, which can be evoked by mechanical and chemical stimuli. In the spinal cord, neurons expressing the gastrin-releasing peptide receptor (GRPR) have been identified as specific mediators of itch. However, our understanding of the GRPR population in the spinal cord, and thus how these neurons exercise their functions, is limited. For this purpose, we constructed a Cre line designed to target the GRPR population of neurons (Grpr-Cre). Our analysis revealed that Grpr-Cre cells in the spinal cord are predominantly excitatory interneurons that are found in the dorsal lamina, especially in laminae II-IV. Application of the specific agonist gastrin-releasing peptide induced spike responses in 43.3% of the patched Grpr-Cre neurons, where the majority of the cells displayed a tonic firing property. Additionally, our analysis showed that the Grpr-Cre population expresses Vglut2 mRNA, and mice ablated of Vglut2 in Grpr-Cre cells (Vglut2-lox;Grpr-Cre mice) displayed less spontaneous itch and attenuated responses to both histaminergic and nonhistaminergic agents. We could also show that application of the itch-inducing peptide, natriuretic polypeptide B, induces calcium influx in a subpopulation of Grpr-Cre neurons. To summarize, our data indicate that the Grpr-Cre spinal cord neural population is composed of interneurons that use VGLUT2-mediated signaling for transmitting chemical and spontaneous itch stimuli to the next, currently unknown, neurons in the labeled line of itch.
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60
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Abstract
Peripheral itch stimuli are transmitted by sensory neurons to the spinal cord dorsal horn, which then transmits the information to the brain. The molecular and cellular mechanisms within the dorsal horn for itch transmission have only been investigated and identified during the past ten years. This review covers the progress that has been made in identifying the peptide families in sensory neurons and the receptor families in dorsal horn neurons as putative itch transmitters, with a focus on gastrin-releasing peptide (GRP)-GRP receptor signaling. Also discussed are the signaling mechanisms, including opioids, by which various types of itch are transmitted and modulated, as well as the many conflicting results arising from recent studies.
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Andersen H, Elberling J, Sharma N, Hauberg L, Gazerani P, Arendt-Nielsen L. Histaminergic and non-histaminergic elicited itch is attenuated in capsaicin-evoked areas of allodynia and hyperalgesia: A healthy volunteer study. Eur J Pain 2017; 21:1098-1109. [DOI: 10.1002/ejp.1013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/22/2016] [Indexed: 01/08/2023]
Affiliation(s)
- H.H. Andersen
- Laboratory for Experimental Cutaneous Pain Research; SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Denmark
| | - J. Elberling
- Department of Dermato-Allergology; Copenhagen University Hospital; Herlev-Gentofte Hospital; Copenhagen Denmark
| | - N. Sharma
- Laboratory for Experimental Cutaneous Pain Research; SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Denmark
| | - L.E. Hauberg
- Laboratory for Experimental Cutaneous Pain Research; SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Denmark
| | - P. Gazerani
- Laboratory for Experimental Cutaneous Pain Research; SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Denmark
| | - L. Arendt-Nielsen
- Laboratory for Experimental Cutaneous Pain Research; SMI; Department of Health Science and Technology; Faculty of Medicine; Aalborg University; Denmark
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62
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Lee JS, Han JS, Lee K, Bang J, Lee H. The peripheral and central mechanisms underlying itch. BMB Rep 2017; 49:474-87. [PMID: 27418284 PMCID: PMC5227140 DOI: 10.5483/bmbrep.2016.49.9.108] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Indexed: 12/20/2022] Open
Abstract
Itch is one of the most distressing sensations that substantially impair quality of life. It is a cardinal symptom of many skin diseases and is also caused by a variety of systemic disorders. Unfortunately, currently available itch medications are ineffective in many chronic itch conditions, and they often cause undesirable side effects. To develop novel therapeutic strategies, it is essential to identify primary afferent neurons that selectively respond to itch mediators as well as the central nervous system components that process the sensation of itch and initiate behavioral responses. This review summarizes recent progress in the study of itch, focusing on itch-selective receptors, signaling molecules, neuronal pathways from the primary sensory neurons to the brain, and potential decoding mechanisms based on which itch is distinguished from pain. [BMB Reports 2016; 49(9): 474-487]
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Affiliation(s)
- Jae Seung Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | | | - Kyeongho Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Juwon Bang
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
| | - Hyosang Lee
- Department of Brain and Cognitive Sciences, DGIST, Daegu 42988, Korea
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63
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The molecular and cellular mechanisms of itch and the involvement of TRP channels in the peripheral sensory nervous system and skin. Allergol Int 2017; 66:22-30. [PMID: 28012781 DOI: 10.1016/j.alit.2016.10.003] [Citation(s) in RCA: 74] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 10/14/2016] [Indexed: 12/24/2022] Open
Abstract
Itch is an unpleasant cutaneous sensation that can arise following insect bites, exposure to plant ingredients, and some diseases. Itch can also have idiopathic causes. Itch sensations are thought to protect against external insults and toxic substances. Although itch is not directly lethal, chronic and long lasting itch in certain diseases can worsen quality of life. Therefore, the mechanisms responsible for chronic itch require careful investigation. There is a significant amount of basic research concerning itch, and the effect of various itch mediators on primary sensory neurons have been studied. Interestingly, many mediators of itch involve signaling related to transient receptor potential (TRP) channels. TRP channels, especially thermosensitive TRP channels, are expressed by primary sensory neurons and skin keratinocytes, which receive multimodal stimuli, including those that cause itch sensations. Here we review the molecular and cellular mechanisms of itch and the involvement of TRP channels in mediating itch sensations.
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64
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Takanami K, Inoue K, Mukai H, Tamura K, Jogahara T, Oda SI, Kawata M, Sakamoto T, Sakamoto H. Comparative Anatomy of Gastrin-releasing Peptide Pathways in the Trigeminal Sensory System of Mouse and the Asian House Musk Shrew Suncus murinus. Acta Histochem Cytochem 2016; 49:181-190. [PMID: 28127106 PMCID: PMC5263228 DOI: 10.1267/ahc.16030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 10/09/2016] [Indexed: 01/02/2023] Open
Abstract
Gastrin-releasing peptide (GRP) has recently been identified as an itch-signaling molecule in the primary afferents and spinal cord of rodents. However, little information exists on the expression and localization of GRP in the trigeminal somatosensory system other than in rats. We examined the generality of the trigeminal GRP system in mammals using two distinct species, suncus as a model of specialized placental mammals known to have a well-developed trigeminal sensory system and mice as a representative small laboratory animal. We first analyzed the gross morphology of the trigeminal somatosensory system in suncus to provide a brainstem atlas on which to map GRP distribution. Immunohistochemical analyses showed that 8% of trigeminal ganglion neurons in suncus and 6% in mice expressed GRP. Expression was restricted to cells with smaller somata. The GRP-containing fibers were densely distributed in the superficial layers of the caudal part of the trigeminal spinal nucleus (Vc) but rare in the rostral parts, both in suncus and mice. Expression of GRP receptor mRNA and protein was also detected in the Vc of suncus. Taken together, these results suggest that the trigeminal GRP system mediating itch sensation is conserved in mammals.
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Affiliation(s)
- Keiko Takanami
- Ushimado Marine Institute (UMI), Graduate School of Natural Science and Technology, Okayama University
- Anatomy and Neurobiology, Kyoto Prefectural University of Medicine
| | - Kaihei Inoue
- Anatomy and Neurobiology, Kyoto Prefectural University of Medicine
| | - Hiroki Mukai
- Anatomy and Neurobiology, Kyoto Prefectural University of Medicine
| | - Kei Tamura
- Ushimado Marine Institute (UMI), Graduate School of Natural Science and Technology, Okayama University
| | - Takamichi Jogahara
- Laboratory of Animal Management and Resources, Department of Zoology, Okayama University of Science
- Division of Bio-resources, Department of Biotechnology, Frontier Science Research Center, University of Miyazaki
| | - Sen-ichi Oda
- Laboratory of Animal Management and Resources, Department of Zoology, Okayama University of Science
| | - Mitsuhiro Kawata
- Anatomy and Neurobiology, Kyoto Prefectural University of Medicine
- School of Health Science, Bukkyo University
| | - Tatsuya Sakamoto
- Ushimado Marine Institute (UMI), Graduate School of Natural Science and Technology, Okayama University
| | - Hirotaka Sakamoto
- Ushimado Marine Institute (UMI), Graduate School of Natural Science and Technology, Okayama University
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65
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Bui TV, Stifani N, Akay T, Brownstone RM. Spinal microcircuits comprising dI3 interneurons are necessary for motor functional recovery following spinal cord transection. eLife 2016; 5. [PMID: 27977000 PMCID: PMC5218533 DOI: 10.7554/elife.21715] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 12/12/2016] [Indexed: 01/09/2023] Open
Abstract
The spinal cord has the capacity to coordinate motor activities such as locomotion. Following spinal transection, functional activity can be regained, to a degree, following motor training. To identify microcircuits involved in this recovery, we studied a population of mouse spinal interneurons known to receive direct afferent inputs and project to intermediate and ventral regions of the spinal cord. We demonstrate that while dI3 interneurons are not necessary for normal locomotor activity, locomotor circuits rhythmically inhibit them and dI3 interneurons can activate these circuits. Removing dI3 interneurons from spinal microcircuits by eliminating their synaptic transmission left locomotion more or less unchanged, but abolished functional recovery, indicating that dI3 interneurons are a necessary cellular substrate for motor system plasticity following transection. We suggest that dI3 interneurons compare inputs from locomotor circuits with sensory afferent inputs to compute sensory prediction errors that then modify locomotor circuits to effect motor recovery.
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Affiliation(s)
- Tuan V Bui
- Department of Biology, Brain and Mind Research Institute, University of Ottawa, Ottawa, Canada
| | - Nicolas Stifani
- Department of Medical Neuroscience, Dalhousie University, Halifax, Canada
| | - Turgay Akay
- Department of Medical Neuroscience, Dalhousie University, Halifax, Canada
| | - Robert M Brownstone
- Department of Medical Neuroscience, Dalhousie University, Halifax, Canada.,Division of Neurosurgery, Department of Surgery, Dalhousie University, Halifax, Canada.,Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, London, United Kingdom
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66
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Midbrain Gene Screening Identifies a New Mesoaccumbal Glutamatergic Pathway and a Marker for Dopamine Cells Neuroprotected in Parkinson's Disease. Sci Rep 2016; 6:35203. [PMID: 27762319 PMCID: PMC5071886 DOI: 10.1038/srep35203] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 09/26/2016] [Indexed: 11/08/2022] Open
Abstract
The ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) of the midbrain are associated with Parkinson’s disease (PD), schizophrenia, mood disorders and addiction. Based on the recently unraveled heterogeneity within the VTA and SNc, where glutamate, GABA and co-releasing neurons have been found to co-exist with the classical dopamine neurons, there is a compelling need for identification of gene expression patterns that represent this heterogeneity and that are of value for development of human therapies. Here, several unique gene expression patterns were identified in the mouse midbrain of which NeuroD6 and Grp were expressed within different dopaminergic subpopulations of the VTA, and TrpV1 within a small heterogeneous population. Optogenetics-coupled in vivo amperometry revealed a previously unknown glutamatergic mesoaccumbal pathway characterized by TrpV1-Cre-expression. Human GRP was strongly detected in non-melanized dopaminergic neurons within the SNc of both control and PD brains, suggesting GRP as a marker for neuroprotected neurons in PD. This study thus unravels markers for distinct subpopulations of neurons within the mouse and human midbrain, defines unique anatomical subregions within the VTA and exposes an entirely new glutamatergic pathway. Finally, both TRPV1 and GRP are implied in midbrain physiology of importance to neurological and neuropsychiatric disorders.
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67
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Dorsal root ganglion neurons and tyrosine hydroxylase--an intriguing association with implications for sensation and pain. Pain 2016; 157:314-320. [PMID: 26447702 DOI: 10.1097/j.pain.0000000000000381] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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68
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Seal RP. Do the distinct synaptic properties of VGLUTs shape pain? Neurochem Int 2016; 98:82-8. [PMID: 27180049 DOI: 10.1016/j.neuint.2016.04.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2016] [Revised: 04/26/2016] [Accepted: 04/28/2016] [Indexed: 11/25/2022]
Abstract
The somatosensory system transmits touch, temperature, itch and pain. Three vesicular glutamate transporter isoforms mediate the release of glutamate throughout the mammalian nervous system with largely non-overlapping distributions and unique roles at the synapse. This review discusses the contribution of each of these essential transporters to circuits underlying pain and other somatosensory behaviors throughout postnatal development and in the adult. A better understanding of the individual contributions of the VGLUT isoforms could provide new avenues for therapeutic intervention.
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Affiliation(s)
- Rebecca P Seal
- Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA; Pittsburgh Center for Pain Research, University of Pittsburgh School of Medicine, Pittsburgh, PA, 15213, USA.
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69
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Inhibition of the mammalian target of rapamycin complex 1 signaling pathway reduces itch behaviour in mice. Pain 2016; 156:1519-1529. [PMID: 25906350 DOI: 10.1097/j.pain.0000000000000197] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Activated mammalian target of rapamycin (P-mTOR) has been shown to maintain the sensitivity of subsets of small-diameter primary afferent A-nociceptors. Local or systemic inhibition of the mTOR complex 1 (mTORC1) pathway reduced punctate mechanical and cold sensitivity in neuropathic pain and therefore offered a new approach to chronic pain control. In this study, we have investigated the effects of the rapamycin analog temsirolimus (CCI-779) on itch. Bouts of scratching induced by the histamine-dependent pruritogenic compound 48/80 and histamine-independent pruritogens, chloroquine and SLIGRL-NH2, injected intradermally were significantly reduced by local (intradermal) or systemic (intraperitoneal, i.p.) pretreatment with CCI-779. We also investigated the action of metformin, a drug taken to control type 2 diabetes and recently shown to inhibit mTORC1 in vivo. Although the response to nonhistaminergic stimuli was reduced at all of the time points tested, scratching to compound 48/80 was modified by metformin only when the drug was injected 24 hours before this pruritogen. We also examined the colocalization of P-mTOR with gastrin-releasing peptide, a putative marker for some itch-sensitive primary afferents, and found that P-mTOR was coexpressed in less than 5% of gastrin-releasing peptide-positive fibers in the mouse skin. Taken together, the data highlight the role that P-mTOR-positive A-fibers play in itch signaling and underline the importance of the mTORC1 pathway in the regulation of homeostatic primary afferent functions such as pain and itch. The actions of the antidiabetic drug metformin in ameliorating nonhistamine-mediated itch also suggest a new therapeutic route for the control of this category of pruritus.
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70
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Abstract
Itch is a unique sensation associated with the scratch reflex. Although the scratch reflex plays a protective role in daily life by removing irritants, chronic itch remains a clinical challenge. Despite urgent clinical need, itch has received relatively little research attention and its mechanisms have remained poorly understood until recently. The goal of the present review is to summarize our current understanding of the mechanisms of acute as well as chronic itch and classifications of the primary itch populations in relationship to transient receptor potential (Trp) channels, which play pivotal roles in multiple somatosensations. The convergent involvement of Trp channels in diverse itch signaling pathways suggests that Trp channels may serve as promising targets for chronic itch treatments.
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Affiliation(s)
- Shuohao Sun
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA
| | - Xinzhong Dong
- The Solomon H. Snyder Department of Neuroscience, Center for Sensory Biology, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA.
- Howard Hughes Medical Institute, Johns Hopkins University, School of Medicine, Baltimore, MD, 21205, USA.
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71
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Barry DM, Li H, Liu XY, Shen KF, Liu XT, Wu ZY, Munanairi A, Chen XJ, Yin J, Sun YG, Li YQ, Chen ZF. Critical evaluation of the expression of gastrin-releasing peptide in dorsal root ganglia and spinal cord. Mol Pain 2016; 12:12/0/1744806916643724. [PMID: 27068287 PMCID: PMC4972254 DOI: 10.1177/1744806916643724] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 02/18/2016] [Indexed: 01/29/2023] Open
Abstract
There are substantial disagreements about the expression of gastrin-releasing peptide (GRP) in sensory neurons and whether GRP antibody cross-reacts with substance P (SP). These concerns necessitate a critical revaluation of GRP expression using additional approaches. Here, we show that a widely used GRP antibody specifically recognizes GRP but not SP. In the spinal cord of mice lacking SP (Tac1 KO), the expression of not only GRP but also other peptides, notably neuropeptide Y (NPY), is significantly diminished. We detected Grp mRNA in dorsal root ganglias using reverse transcription polymerase chain reaction, in situ hybridization and RNA-seq. We demonstrated that Grp mRNA and protein are upregulated in dorsal root ganglias, but not in the spinal cord, of mice with chronic itch. Few GRP+ immunostaining signals were detected in spinal sections following dorsal rhizotomy and GRP+ cell bodies were not detected in dissociated dorsal horn neurons. Ultrastructural analysis further shows that substantially more GRPergic fibers form synaptic contacts with gastrin releasing peptide receptor-positive (GRPR+) neurons than SPergic fibers. Our comprehensive study demonstrates that a majority of GRPergic fibers are of primary afferent origin. A number of factors such as low copy number of Grp transcripts, small percentage of cells expressing Grp, and the use of an eGFP GENSAT transgenic as a surrogate for GRP protein have contributed to the controversy. Optimization of experimental procedures facilitates the specific detection of GRP expression in dorsal root ganglia neurons.
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Affiliation(s)
- Devin M Barry
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Hui Li
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Department of Anatomy, K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, PR China
| | - Xian-Yu Liu
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Kai-Feng Shen
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing, PR China
| | - Xue-Ting Liu
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, The State Key Laboratory of Respiratory Disease, The Second Affiliated Hospital, Guangzhou Medical University, Guangdong, PR China
| | - Zhen-Yu Wu
- Department of Anatomy, K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, PR China
| | - Admire Munanairi
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Xiao-Jun Chen
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Jun Yin
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Yan-Gang Sun
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Yun-Qing Li
- Department of Anatomy, K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, PR China
| | - Zhou-Feng Chen
- Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA Departments of Psychiatry, Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Developmental Biology, Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA
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72
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Zhang MD, Barde S, Szodorai E, Josephson A, Mitsios N, Watanabe M, Attems J, Lubec G, Kovács GG, Uhlén M, Mulder J, Harkany T, Hökfelt T. Comparative anatomical distribution of neuronal calcium-binding protein (NECAB) 1 and -2 in rodent and human spinal cord. Brain Struct Funct 2016; 221:3803-23. [DOI: 10.1007/s00429-016-1191-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Accepted: 01/18/2016] [Indexed: 12/21/2022]
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73
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Rogoz K, Aresh B, Freitag FB, Pettersson H, Magnúsdóttir EI, Larsson Ingwall L, Haddadi Andersen H, Franck MCM, Nagaraja C, Kullander K, Lagerström MC. Identification of a Neuronal Receptor Controlling Anaphylaxis. Cell Rep 2016; 14:370-9. [DOI: 10.1016/j.celrep.2015.12.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Revised: 10/20/2015] [Accepted: 12/03/2015] [Indexed: 12/31/2022] Open
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74
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Malet M, Brumovsky PR. VGLUTs and Glutamate Synthesis-Focus on DRG Neurons and Pain. Biomolecules 2015; 5:3416-37. [PMID: 26633536 PMCID: PMC4693284 DOI: 10.3390/biom5043416] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 11/13/2015] [Accepted: 11/17/2015] [Indexed: 12/14/2022] Open
Abstract
The amino acid glutamate is the principal excitatory transmitter in the nervous system, including in sensory neurons that convey pain sensation from the periphery to the brain. It is now well established that a family of membrane proteins, termed vesicular glutamate transporters (VGLUTs), serve a critical function in these neurons: they incorporate glutamate into synaptic vesicles. VGLUTs have a central role both under normal neurotransmission and pathological conditions, such as neuropathic or inflammatory pain. In the present short review, we will address VGLUTs in the context of primary afferent neurons. We will focus on the role of VGLUTs in pain triggered by noxious stimuli, peripheral nerve injury, and tissue inflammation, as mostly explored in transgenic mice. The possible interplay between glutamate biosynthesis and VGLUT-dependent packaging in synaptic vesicles, and its potential impact in various pain states will be presented.
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Affiliation(s)
- Mariana Malet
- Institute of Research on Translational Medicine, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Austral University, Avenida Juan D. Perón 1500, Pilar, Buenos Aires 1629AHJ, Argentina.
| | - Pablo R Brumovsky
- Institute of Research on Translational Medicine, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Austral University, Avenida Juan D. Perón 1500, Pilar, Buenos Aires 1629AHJ, Argentina.
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75
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Luo J, Feng J, Liu S, Walters ET, Hu H. Molecular and cellular mechanisms that initiate pain and itch. Cell Mol Life Sci 2015; 72:3201-23. [PMID: 25894692 PMCID: PMC4534341 DOI: 10.1007/s00018-015-1904-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 03/20/2015] [Accepted: 04/07/2015] [Indexed: 12/17/2022]
Abstract
Somatosensory neurons mediate our sense of touch. They are critically involved in transducing pain and itch sensations under physiological and pathological conditions, along with other skin-resident cells. Tissue damage and inflammation can produce a localized or systemic sensitization of our senses of pain and itch, which can facilitate our detection of threats in the environment. Although acute pain and itch protect us from further damage, persistent pain and itch are debilitating. Recent exciting discoveries have significantly advanced our knowledge of the roles of membrane-bound G protein-coupled receptors and ion channels in the encoding of information leading to pain and itch sensations. This review focuses on molecular and cellular events that are important in early stages of the biological processing that culminates in our senses of pain and itch.
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Affiliation(s)
- Jialie Luo
- Department of Anesthesiology, The Center for the Study of Itch, Washington University School of Medicine, 660 S. Euclid Ave., St. Louis, MO, 63110, USA
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76
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Kim YS, Kim TH, McKemy DD, Bae YC. Expression of vesicular glutamate transporters in transient receptor potential melastatin 8 (TRPM8)-positive dental afferents in the mouse. Neuroscience 2015; 303:378-88. [PMID: 26166724 DOI: 10.1016/j.neuroscience.2015.07.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 07/01/2015] [Accepted: 07/02/2015] [Indexed: 01/31/2023]
Abstract
Transient receptor potential melastatin 8 (TRPM8) is activated by innocuous cool and noxious cold and plays a crucial role in cold-induced acute pain and pain hypersensitivity. To help understand the mechanism of TRPM8-mediated cold perception under normal and pathologic conditions, we used light microscopic immunohistochemistry and Western blot analysis in mice expressing a genetically encoded axonal tracer in TRPM8-positive (+) neurons. We investigated the coexpression of TRPM8 and vesicular glutamate transporter 1 (VGLUT1) and VGLUT2 in the trigeminal ganglion (TG) and the dental pulp before and after inducing pulpal inflammation. Many TRPM8+ neurons in the TG and axons in the dental pulp expressed VGLUT2, while none expressed VGLUT1. TRPM8+ axons were dense in the pulp horn and peripheral pulp and also frequently observed in the dentinal tubules. Following pulpal inflammation, the proportion of VGLUT2+ and of VGLUT2+/TRPM8+ neurons increased significantly, whereas that of TRPM8+ neurons remained unchanged. Our findings suggest the existence of VGLUT2 (but not VGLUT1)-mediated glutamate signaling in TRPM8+ neurons possibly underlying the cold-induced acute pain and hypersensitivity to cold following pulpal inflammation.
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Affiliation(s)
- Y S Kim
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 700-412, South Korea
| | - T H Kim
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 700-412, South Korea
| | - D D McKemy
- Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089, USA
| | - Y C Bae
- Department of Anatomy and Neurobiology, School of Dentistry, Kyungpook National University, Daegu 700-412, South Korea.
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77
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The anti-inflammatory alkaloid aloperine in Chinese herbal medicine is potentially useful for management of pain and itch. Scand J Pain 2015; 8:25-26. [DOI: 10.1016/j.sjpain.2015.04.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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78
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Incoherent feed-forward regulatory loops control segregation of C-mechanoreceptors, nociceptors, and pruriceptors. J Neurosci 2015; 35:5317-29. [PMID: 25834056 DOI: 10.1523/jneurosci.0122-15.2015] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mammalian skin is innervated by diverse, unmyelinated C fibers that are associated with senses of pain, itch, temperature, or touch. A key developmental question is how this neuronal cell diversity is generated during development. We reported previously that the runt domain transcription factor Runx1 is required to coordinate the development of these unmyelinated cutaneous sensory neurons, including VGLUT3(+) low-threshold c-mechanoreceptors (CLTMs), MrgprD(+) polymodal nociceptors, MrgprA3(+) pruriceptors, MrgprB4(+) c-mechanoreceptors, and others. However, how these Runx1-dependent cutaneous sensory neurons are further segregated is poorly illustrated. Here, we find that the Runx1-dependent transcription factor gene Zfp521 is expressed in, and required for establishing molecular features that define, VGLUT3(+) CLTMs. Furthermore, Runx1 and Zfp521 form a classic incoherent feedforward loop (I-FFL) in controlling molecular identities that normally belong to MrgprD(+) neurons, with Runx1 and Zfp51 playing activator and repressor roles, respectively (in genetic terms). A knock-out of Zfp521 allows prospective VGLUT3 lineage neurons to acquire MrgprD(+) neuron identities. Furthermore, Runx1 might form other I-FFLs to regulate the expression of MrgprA3 and MrgprB4, a mechanism preventing these genes from being expressed in Runx1-persistent VGLUT3(+) and MrgprD(+) neurons. The evolvement of these I-FFLs provides an explanation for how modality-selective sensory subtypes are formed during development and may also have intriguing implications for sensory neuron evolution and sensory coding.
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79
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Aida T, Yoshida J, Nomura M, Tanimura A, Iino Y, Soma M, Bai N, Ito Y, Cui W, Aizawa H, Yanagisawa M, Nagai T, Takata N, Tanaka KF, Takayanagi R, Kano M, Götz M, Hirase H, Tanaka K. Astroglial glutamate transporter deficiency increases synaptic excitability and leads to pathological repetitive behaviors in mice. Neuropsychopharmacology 2015; 40:1569-79. [PMID: 25662838 PMCID: PMC4915262 DOI: 10.1038/npp.2015.26] [Citation(s) in RCA: 109] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Revised: 01/10/2015] [Accepted: 01/10/2015] [Indexed: 02/04/2023]
Abstract
An increase in the ratio of cellular excitation to inhibition (E/I ratio) has been proposed to underlie the pathogenesis of neuropsychiatric disorders, such as autism spectrum disorders (ASD), obsessive-compulsive disorder (OCD), and Tourette's syndrome (TS). A proper E/I ratio is achieved via factors expressed in neuron and glia. In astrocytes, the glutamate transporter GLT1 is critical for regulating an E/I ratio. However, the role of GLT1 dysfunction in the pathogenesis of neuropsychiatric disorders remains unknown because mice with a complete deficiency of GLT1 exhibited seizures and premature death. Here, we show that astrocyte-specific GLT1 inducible knockout (GLAST(CreERT2/+)/GLT1(flox/flox), iKO) mice exhibit pathological repetitive behaviors including excessive and injurious levels of self-grooming and tic-like head shakes. Electrophysiological studies reveal that excitatory transmission at corticostriatal synapse is normal in a basal state but is increased after repetitive stimulation. Furthermore, treatment with an N-methyl-D-aspartate (NMDA) receptor antagonist memantine ameliorated the pathological repetitive behaviors in iKO mice. These results suggest that astroglial GLT1 has a critical role in controlling the synaptic efficacy at corticostriatal synapses and its dysfunction causes pathological repetitive behaviors.
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Affiliation(s)
- Tomomi Aida
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Junichi Yoshida
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Masatoshi Nomura
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Asami Tanimura
- Department of Neurophysiology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Yusuke Iino
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Miho Soma
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Ning Bai
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Yukiko Ito
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Wanpeng Cui
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Hidenori Aizawa
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Michiko Yanagisawa
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan
| | - Terumi Nagai
- Laboratory for Neuron-Glia Circuitry, Brain Science Institute, RIKEN, Saitama, Japan
| | - Norio Takata
- Laboratory for Neuron-Glia Circuitry, Brain Science Institute, RIKEN, Saitama, Japan
| | - Kenji F Tanaka
- Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan
| | - Ryoichi Takayanagi
- Department of Medicine and Bioregulatory Science, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Masanobu Kano
- Department of Neurophysiology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan
| | - Magdalena Götz
- Physiological Genomics, Institute of Physiology, Ludwig-Maximilians University Munich, Munich, Germany
| | - Hajime Hirase
- Department of Neuropsychiatry, Keio University School of Medicine, Tokyo, Japan
| | - Kohichi Tanaka
- Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan,JST, CREST, Saitama, Japan,The Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan,Laboratory of Molecular Neuroscience, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-Ku, Tokyo 113-8510, Japan, Tel: +81 3 5803 5846, Fax: +81 3 5803 5843, E-mail:
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80
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Gunduz O, Topuz RD, Todurga ZG, Duvan K, Karadag CH, Ulugol A. Effect of Activation of the GLT-1 Transporter by a Beta-Lactam Antibiotic on Serotonin-Induced Scratching Behavior in Mice. NEUROPHYSIOLOGY+ 2015. [DOI: 10.1007/s11062-015-9494-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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81
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Altered nociception in mice with genetically induced hypoglutamatergic tone. Neuroscience 2015; 293:80-91. [PMID: 25743253 DOI: 10.1016/j.neuroscience.2015.02.044] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 02/23/2015] [Accepted: 02/24/2015] [Indexed: 12/11/2022]
Abstract
Extensive pharmacological evidence supports the idea that glutamate plays a key role in both acute and chronic pain. In the present study, we investigated the implication of the excitatory amino acid in physiological nociception by using mutant mice deficient in phosphate-activated glutaminase type 1 (GLS1), the enzyme that synthesizes glutamate in central glutamatergic neurons. Because homozygous GLS1-/- mutants die shortly after birth, assays for assessing mechanical, thermal and chemical (formalin) nociception were performed on heterozygous GLS1+/- mutants, which present a clear-cut decrease in glutamate synthesis in central neurons. As compared to paired wild-type mice, adult male GLS1+/- mutants showed decreased responsiveness to mechanical (von Frey filament and tail-pressure, but not tail-clip, tests) and thermal (Hargreaves' plantar, tail-immersion and hot-plate tests) nociceptive stimuli. Genotype-related differences were also found in the formalin test for which GLS1+/- mice exhibited marked decreases in the nociceptive responses (hindlimb lift, lick and flinch) during both phase 1 (0-5 min) and phase 2 (16-45 min) after formalin injection. On the other hand, acute treatment with memantine (1mg/kg i.p.), an uncompetitive antagonist at NMDA glutamate receptors, reduced nociception responses in wild-type but not GLS1+/- mice. Conversely, antinociceptive response to acute administration of a low dose (1mg/kg s.c.) of morphine was significantly larger in GLS1+/- mutants versus wild-type mice. Our findings indicate that genetically driven hypoactivity of central glutamatergic neurotransmission renders mice hyposensitive to nociceptive stimulations, and promotes morphine antinociception, further emphasizing the critical role of glutamate in physiological nociception and its opioid-mediated control.
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82
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Molecular dissection of itch. Curr Opin Neurobiol 2015; 34:61-6. [PMID: 25700248 DOI: 10.1016/j.conb.2015.01.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 01/26/2015] [Accepted: 01/28/2015] [Indexed: 01/17/2023]
Abstract
There have been many exciting recent advances in our understanding of the molecular and cellular basis of itch. These discoveries cover diverse aspects of itch sensation, from the identification of new receptors to the characterization of spinal cord itch circuits. A common thread of these studies is that they demonstrate that itch sensory signals are segregated from input for other somatosensory modalities, such as pain, touch, and thermosensation. This specificity is achieved by the expression of dedicated receptors and transmitters in a select population of sensory neurons which detect pruritogens. Further, recent studies show that itch specificity is maintained in a spinal cord circuit by the utilization of specific neurotransmitters and cognate receptors to convey input along a distinct cellular pathway.
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83
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Multimodal use of calcitonin gene-related peptide and substance P in itch and acute pain uncovered by the elimination of vesicular glutamate transporter 2 from transient receptor potential cation channel subfamily V member 1 neurons. J Neurosci 2015; 34:14055-68. [PMID: 25319702 DOI: 10.1523/jneurosci.1722-14.2014] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Primary afferents are known to use glutamate as their principal fast neurotransmitter. However, it has become increasingly clear that peptides have an influential role in both mediating and modulating sensory transmission. Here we describe the transmission accounting for different acute pain states and itch transmitted via the transient receptor potential cation channel subfamily V member 1 (TRPV1) population by either ablating Trpv1-Cre-expressing neurons or inducing vesicular glutamate transporter 2 (VGLUT2) deficiency in Trpv1-Cre-expressing neurons. Furthermore, by pharmacological inhibition of substance P or calcitonin gene-related peptide (CGRP) signaling in Vglut2-deficient mice, we evaluated the contribution of substance P or CGRP to these sensory modulations, with or without the presence of VGLUT2-mediated glutamatergic transmission in Trpv1-Cre neurons. This examination, together with c-Fos analyses, showed that glutamate via VGLUT2 in the Trpv1-Cre population together with substance P mediate acute cold pain, whereas glutamate together with CGRP mediate noxious heat. Moreover, we demonstrate that glutamate together with both substance P and CGRP mediate tissue-injury associated pain. We further show that itch, regulated by the VGLUT2-mediated transmission via the Trpv1-Cre population, depends on CGRP and gastrin-releasing peptide receptor (GRPR) transmission because pharmacological blockade of the CGRP or GRPR pathway, or genetic ablation of Grpr, led to a drastically attenuated itch. Our study reveals how different neurotransmitters combined can cooperate with each other to transmit or regulate various acute sensations, including itch.
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84
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Palkar R, Lippoldt EK, McKemy DD. The molecular and cellular basis of thermosensation in mammals. Curr Opin Neurobiol 2015; 34:14-9. [PMID: 25622298 DOI: 10.1016/j.conb.2015.01.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 01/10/2015] [Indexed: 12/01/2022]
Abstract
Over a decade and a half of intensive study has shown that the Transient Receptor Potential family ion channels TRPV1 and TRPM8 are the primary sensors of heat and cold temperatures in the peripheral nervous system. TRPV homologues and TRPA1 are also implicated, but recent genetic evidence has diminished their significance in thermosensation and suggests that a number of newly identified thermosensitive channels, including TRPM3, two-pore potassium channels, and the chloride channel Ano1, require further consideration. In addition to novel thermostransducers, recent genetic and pharmacological approaches have begun to elucidate the afferent neurocircuits underlying temperature sensation, continuing the rapid expansion in our understanding of the cellular and molecular basis of thermosensation that began with the discovery of TRPV1 and TRPM8.
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Affiliation(s)
- Radhika Palkar
- Neuroscience Graduate Program, University of Southern California, United States
| | - Erika K Lippoldt
- Neurobiology Graduate Program, University of Southern California, United States
| | - David D McKemy
- Neuroscience Graduate Program, University of Southern California, United States; Neurobiology Graduate Program, University of Southern California, United States; Department of Biological Sciences, University of Southern California, United States.
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85
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Rogoz K, Stjärne L, Kullander K, Lagerström MC. VGLUT2 controls heat and punctuate hyperalgesia associated with nerve injury via TRPV1-Cre primary afferents. PLoS One 2015; 10:e0116568. [PMID: 25615623 PMCID: PMC4304805 DOI: 10.1371/journal.pone.0116568] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 12/11/2014] [Indexed: 12/04/2022] Open
Abstract
Nerve injury induces a state of prolonged thermal and mechanical hypersensitivity in the innervated area, causing distress in affected individuals. Nerve injury-induced hypersensitivity is partially due to increased activity and thereby sustained release of neurotransmitters from the injured fibers. Glutamate, a prominent neurotransmitter in primary afferents, plays a major role in development of hypersensitivity. Glutamate is packed in vesicles by vesicular glutamate transporters (VGLUTs) to enable controlled release upon depolarization. While a role for peripheral VGLUTs in nerve injury-induced pain is established, their contribution in specific peripheral neuronal populations is unresolved. We investigated the role of VGLUT2, expressed by transient receptor potential vanilloid (TRPV1) fibers, in nerve injury-induced hypersensitivity. Our data shows that removal of Vglut2 from Trpv1-Cre neurons using transgenic mice abolished both heat and punctuate hyperalgesia associated with nerve injury. In contrast, the development of cold hypersensitivity after nerve injury was unaltered. Here, we show that, VGLUT2-mediated glutamatergic transmission from Trpv1-Cre neurons selectively mediates heat and mechanical hypersensitivity associated with nerve injury. Our data clarifies the role of the Trpv1-Cre population and the dependence of VGLUT2-mediated glutamatergic transmission in nerve injury-induced hyperalgesia.
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Affiliation(s)
- Katarzyna Rogoz
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Ludvig Stjärne
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Klas Kullander
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
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86
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Abstract
Pain and itch are generally regarded antagonistic as painful stimuli such as scratching suppresses itch. Moreover, inhibition of pain processing by opioids generates itch further supporting their opposing role. Separate specific pathways for itch and pain processing have been uncovered, and several molecular markers have been established in mice that identify neurons involved in the processing of histaminergic and non-histaminergic itch on primary afferent and spinal level. These results are in agreement with the specificity theory for itch and might suggest that pain and itch should be investigated separately on the level of neurons, mediators, and mechanisms. However, in addition to broadly overlapping mediators of itch and pain, there is also evidence for overlapping functions in primary afferents: nociceptive primary afferents can provoke itch when activated very locally in the epidermis, and sensitization of both nociceptors and pruriceptors has been found following local nerve growth factor application in volunteers. Thus, also mechanisms that underlie the development of chronic itch and pain including spontaneous activity and sensitization of primary afferents as well as spinal cord sensitization may well overlap to a great extent. Rather than separating itch and pain, research concepts should therefore address the common mechanisms. Such an approach appears most appropriate for clinical conditions of neuropathic itch and pain and also chronic inflammatory conditions. While itch researchers can benefit from the large body of information of the pain field, pain researchers will find behavioral readouts of spontaneous itch much simpler than those for spontaneous pain in animals and the skin as source of the pruritic activity much more accessible even in patients.
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Affiliation(s)
- Martin Schmelz
- Department of Anesthesiology and Intensive Care Medicine, Faculty of Medicine Mannheim, University of Heidelberg, Theodor-Kutzer Ufer 1-3, Mannheim, 68167, Germany,
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87
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Abstract
As we all can easily differentiate the sensations of itch and pain, the most straightforward neurophysiologic concept would consist of two specific pathways that independently encode itch and pain. Indeed, a neuronal pathway for histamine-induced itch in the peripheral and central nervous system has been described in animals and humans, and recently several non-histaminergic pathways for itch have been discovered in rodents that support a dichotomous concept differentiated into a pain and an itch pathway, with both pathways being composed of different "flavors." Numerous markers and mediators have been found that are linked to itch processing pathways. Thus, the delineation of neuronal pathways for itch from pain pathways seemingly proves that all sensory aspects of itch are based on an itch-specific neuronal pathway. However, such a concept is incomplete as itch can also be induced by the activation of the pain pathway in particular when the stimulus is applied in a highly localized spatial pattern. These opposite views reflect the old dispute between specificity and pattern theories of itch. Rather than only being of theoretic interest, this conceptual problem has key implication for the strategy to treat chronic itch as key therapeutic targets would be either itch-specific pathways or unspecific nociceptive pathways.
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Affiliation(s)
- Martin Schmelz
- Faculty of Medicine Mannheim, Department of Anesthesiology and Intensive Care Medicine, University of Heidelberg, Theodor-Kutzer Ufer 1-3, 68167, Mannheim, Germany,
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88
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Abstract
In this chapter we discuss the many recent discoveries of the mechanisms by which itch is transmitted: the neurotransmitters and the responses they trigger, the mechanisms by which specific neuronal targets are activated, and the specificity of the pathways. Current data reveal that DRG neurons and spinal cord cells use a remarkably selective set of transmitters to convey pruritic information from the periphery to the brain: glutamate and Nppb are released from primary itch-sensory cells; these molecules activate secondary spinal cord pruriceptive-specific neurons, which in turn utilize Grp to activate tertiary pruriceptive-selective neurons. Intersecting this basic linear excitatory pathway, inhibitory input from dynorphin and neurons that express the somatostatin receptor modify itch sensation. Cumulatively, these studies paint an elegantly simple picture of how itch signals are transformed and integrated in the spinal cord and open new avenues for research efforts aimed at understanding and better treating itch.
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89
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Tóth BI, Szallasi A, Bíró T. Transient receptor potential channels and itch: how deep should we scratch? Handb Exp Pharmacol 2015; 226:89-133. [PMID: 25861776 DOI: 10.1007/978-3-662-44605-8_6] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Over the past 30 years, transient receptor potential (TRP) channels have evolved from a somewhat obscure observation on how fruit flies detect light to become the center of drug discovery efforts, triggering a heated debate about their potential as targets for therapeutic applications in humans. In this review, we describe our current understanding of the diverse mechanism of action of TRP channels in the itch pathway from the skin to the brain with focus on the peripheral detection of stimuli that elicit the desire to scratch and spinal itch processing and sensitization. We predict that the compelling basic research findings on TRP channels and pruritus will be translated into the development of novel, clinically useful itch medications.
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Affiliation(s)
- Balázs I Tóth
- DE-MTA "Lendület" Cellular Physiology Research Group, Department of Physiology, University of Debrecen, Debrecen, 4032, Hungary
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90
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Abstract
Pruritus is defined as "an unpleasant sensation that causes the need to scratch". This is not a small pain. It seems that pruriceptors exist but their level of separation from nociceptive receptors is still debated. Pathways of pruritus were identified from the skin (around the dermo-epidermal junction) to the brain. Many mediators are involved in pruritus but there are at least a histaminergic and a non-histaminergic pathway (PAR-2dependent). Similarly to pain, gate control or peripheral and central sensitization mechanisms have been highlighted in pruritus. These pathophysiological advances are important and anticipate therapeutic advances, that will be very useful for the symptomatic treatment of pruritus (poorly efficient at present).
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Affiliation(s)
- Laurent Misery
- Laboratoire des neurosciences de Brest (EA4685), université de Bretagne occidentale, faculté de médecine, rue Camille Desmoulins, 29200 Brest, France service de dermatologie, CHU de Brest, 2, avenue Foch, 29200 Brest, France
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91
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Takanami K, Sakamoto H, Matsuda KI, Satoh K, Tanida T, Yamada S, Inoue K, Oti T, Sakamoto T, Kawata M. Distribution of gastrin-releasing peptide in the rat trigeminal and spinal somatosensory systems. J Comp Neurol 2014; 522:1858-73. [PMID: 24254931 DOI: 10.1002/cne.23506] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 08/30/2013] [Accepted: 11/15/2013] [Indexed: 12/12/2022]
Abstract
Gastrin-releasing peptide (GRP) has recently been identified as an itch-specific neuropeptide in the spinal sensory system in mice, but there are no reports of the expression and distribution of GRP in the trigeminal sensory system in mammals. We characterized and compared GRP-immunoreactive (ir) neurons in the trigeminal ganglion (TG) with those in the rat spinal dorsal root ganglion (DRG). GRP immunoreactivity was expressed in 12% of TG and 6% of DRG neurons and was restricted to the small- and medium-sized type cells. In both the TG and DRG, many GRP-ir neurons also expressed substance P and calcitonin gene-related peptide, but not isolectin B4 . The different proportions of GRP and transient receptor potential vanilloid 1 double-positive neurons in the TG and DRG imply that itch sensations via the TG and DRG pathways are transmitted through distinct mechanisms. The distribution of the axon terminals of GRP-ir primary afferents and their synaptic connectivity with the rat trigeminal sensory nuclei and spinal dorsal horn were investigated by using light and electron microscopic histochemistry. Although GRP-ir fibers were rarely observed in the trigeminal sensory nucleus principalis, oralis, and interpolaris, they were predominant in the superficial layers of the trigeminal sensory nucleus caudalis (Vc), similar to the spinal dorsal horn. Ultrastructural analysis revealed that GRP-ir terminals contained clear microvesicles and large dense-cored vesicles, and formed asymmetric synaptic contacts with a few dendrites in the Vc and spinal dorsal horn. These results suggest that GRP-dependent orofacial and spinal pruriceptive inputs are processed mainly in the superficial laminae of the Vc and spinal dorsal horn.
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Affiliation(s)
- Keiko Takanami
- Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, 602-8566, Japan
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92
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Takanami K, Sakamoto H. The Gastrin-Releasing Peptide Receptor (GRPR) in the Spinal Cord as a Novel Pharmacological Target. Curr Neuropharmacol 2014; 12:434-43. [PMID: 25426011 PMCID: PMC4243033 DOI: 10.2174/1570159x12666140923201432] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/28/2014] [Accepted: 09/10/2014] [Indexed: 12/02/2022] Open
Abstract
Gastrin-releasing peptide (GRP) is a mammalian neuropeptide that acts through the G protein-coupled receptor, GRP receptor (GRPR). Increasing evidence indicates that GRPR-mediated signaling in the central nervous system plays an important role in many physiological processes in mammals. Additionally, we have recently reported that the GRP system within the lumbosacral spinal cord not only controls erection but also triggers ejaculation in male rats. This system of GRP neurons is sexually dimorphic, being prominent in male rats but vestigial or absent in females. It is suggested that the sexually dimorphic GRP/GRPR system in the lumbosacral spinal cord plays a critical role in the regulation of male sexual function. In parallel, it has been reported that the somatosensory GRP/GRPR system in the spinal cord contributes to the regulation of itch specific transmission independently of the pain transmission. Interestingly, these two distinct functions in the same spinal region are both regulated by the neuropeptide, GRP. In this report, we review findings on recently identified GRP/GRPR systems in the spinal cord. These GRP/GRPR systems in the spinal cord provide new insights into pharmacological treatments for psychogenic erectile dysfunction as well as for chronic pruritus.
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Affiliation(s)
- Keiko Takanami
- Department of Anatomy and Neurobiology, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto 602-8566, Japan
| | - Hirotaka Sakamoto
- Ushimado Marine Institute (UMI), Graduate School of Natural Science and Technology, Okayama University, Ushimado, Setouchi, Okayama 701-4303, Japan
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93
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Zhang X. Targeting TRP ion channels for itch relief. Naunyn Schmiedebergs Arch Pharmacol 2014; 388:389-99. [PMID: 25418889 DOI: 10.1007/s00210-014-1068-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 11/11/2014] [Indexed: 12/13/2022]
Abstract
Acute itch (pruritus) is unpleasant and acts as an alerting mechanism for removing irritants. However, severe chronic itch is debilitating and impairs the quality of life. Rapid progress has been made in recent years in our understanding of the fundamental neurobiology of itch. Notably, several temperature-sensitive transient receptor potential (thermo-TRP) ion channels have emerged as critical players in many types of itch, in addition to pain. They serve as markers that define the itch neural pathway. Thermo-TRP ion channels are thus becoming attractive targets for developing effective anti-pruritic therapies.
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Affiliation(s)
- Xuming Zhang
- Rowett Institute of Nutrition and Health & Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK,
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94
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Descending control of itch transmission by the serotonergic system via 5-HT1A-facilitated GRP-GRPR signaling. Neuron 2014; 84:821-34. [PMID: 25453842 DOI: 10.1016/j.neuron.2014.10.003] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/26/2014] [Indexed: 12/26/2022]
Abstract
UNLABELLED Central serotonin (5-hydroxytryptophan, 5-HT) modulates somatosensory transduction, but how it achieves sensory modality-specific modulation remains unclear. Here we report that enhancing serotonergic tone via administration of 5-HT potentiates itch sensation, whereas mice lacking 5-HT or serotonergic neurons in the brainstem exhibit markedly reduced scratching behavior. Through pharmacological and behavioral screening, we identified 5-HT1A as a key receptor in facilitating gastrin-releasing peptide (GRP)-dependent scratching behavior. Coactivation of 5-HT1A and GRP receptors (GRPR) greatly potentiates subthreshold, GRP-induced Ca(2+) transients, and action potential firing of GRPR(+) neurons. Immunostaining, biochemical, and biophysical studies suggest that 5-HT1A and GRPR may function as receptor heteromeric complexes. Furthermore, 5-HT1A blockade significantly attenuates, whereas its activation contributes to, long-lasting itch transmission. Thus, our studies demonstrate that the descending 5-HT system facilitates GRP-GRPR signaling via 5-HT1A to augment itch-specific outputs, and a disruption of crosstalk between 5-HT1A and GRPR may be a useful antipruritic strategy. VIDEO ABSTRACT
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95
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Zhao ZQ, Wan L, Liu XY, Huo FQ, Li H, Barry DM, Krieger S, Kim S, Liu ZC, Xu J, Rogers BE, Li YQ, Chen ZF. Cross-inhibition of NMBR and GRPR signaling maintains normal histaminergic itch transmission. J Neurosci 2014; 34:12402-14. [PMID: 25209280 PMCID: PMC4160775 DOI: 10.1523/jneurosci.1709-14.2014] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 08/04/2014] [Accepted: 08/05/2014] [Indexed: 12/11/2022] Open
Abstract
We previously showed that gastrin-releasing peptide receptor (GRPR) in the spinal cord is important for mediating nonhistaminergic itch. Neuromedin B receptor (NMBR), the second member of the mammalian bombesin receptor family, is expressed in a largely nonoverlapping pattern with GRPR in the superficial spinal cord, and its role in itch transmission remains unclear. Here, we report that Nmbr knock-out (KO) mice exhibited normal scratching behavior in response to intradermal injection of pruritogens. However, mice lacking both Nmbr and Grpr (DKO mice) showed significant deficits in histaminergic itch. In contrast, the chloroquine (CQ)-evoked scratching behavior of DKO mice is not further reduced compared with Grpr KO mice. These results suggest that NMBR and GRPR could compensate for the loss of each other to maintain normal histamine-evoked itch, whereas GRPR is exclusively required for CQ-evoked scratching behavior. Interestingly, GRPR activity is enhanced in Nmbr KO mice despite the lack of upregulation of Grpr expression; so is NMBR in Grpr KO mice. We found that NMB acts exclusively through NMBR for itch transmission, whereas GRP can signal through both receptors, albeit to NMBR to a much lesser extent. Although NMBR and NMBR(+) neurons are dispensable for histaminergic itch, GRPR(+) neurons are likely to act downstream of NMBR(+) neurons to integrate NMB-NMBR-encoded histaminergic itch information in normal physiological conditions. Together, we define the respective function of NMBR and GRPR in itch transmission, and reveal an unexpected relationship not only between the two receptors but also between the two populations of interneurons in itch signaling.
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Affiliation(s)
- Zhong-Qiu Zhao
- Center for the Study of Itch, and Departments of Anesthesiology
| | - Li Wan
- Center for the Study of Itch, and Departments of Anesthesiology, Department of Anesthesiology, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong 510260, People's Republic of China, and
| | - Xian-Yu Liu
- Center for the Study of Itch, and Departments of Anesthesiology
| | - Fu-Quan Huo
- Center for the Study of Itch, and Departments of Anesthesiology
| | - Hui Li
- Center for the Study of Itch, and Departments of Anesthesiology, Department of Anatomy, Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, Shaanxi 710032, People's Republic of China
| | - Devin M Barry
- Center for the Study of Itch, and Departments of Anesthesiology
| | | | - Seungil Kim
- Center for the Study of Itch, and Departments of Anesthesiology
| | - Zhong-Chun Liu
- Center for the Study of Itch, and Departments of Anesthesiology
| | - Jinbin Xu
- Radiology, Washington University School of Medicine, St. Louis, Missouri 63110
| | | | - Yun-Qing Li
- Department of Anatomy, Histology and Embryology, and K. K. Leung Brain Research Centre, The Fourth Military Medical University, Xi'an, Shaanxi 710032, People's Republic of China
| | - Zhou-Feng Chen
- Center for the Study of Itch, and Departments of Anesthesiology, Psychiatry, Developmental Biology,
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96
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Kremer AE, Bolier R, van Dijk R, Oude Elferink RPJ, Beuers U. Advances in pathogenesis and management of pruritus in cholestasis. Dig Dis 2014; 32:637-45. [PMID: 25034299 DOI: 10.1159/000360518] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Chronic pruritus is a burdensome feature of numerous hepatobiliary disorders such as primary biliary cirrhosis, primary sclerosing cholangitis, cholangiocarcinoma, inherited forms of cholestasis and intrahepatic cholestasis of pregnancy. Bile salts, μ-opioids, serotonin, histamine and steroids have been controversially discussed in the pathogenesis of cholestatic pruritus. However, for these substances neither a correlation with itch severity nor a causative link has ever been established. Recent findings indicate that the potent neuronal activator lysophosphatidic acid and autotaxin, the enzyme forming lysophosphatidic acid, may play a key element in the pathogenesis of cholestatic pruritus. Serum activity of autotaxin correlated with itch intensity and response to antipruritic treatment in patients with cholestatic pruritus, but not other forms of pruritus. Autotaxin activity thereby represents the first biomarker for pruritus and had a positive predictive value of 70% in differentiating cholestatic pruritus from other forms of pruritus. Treatment options for patients with cholestatic pruritus include the anion exchange resin colestyramine, the PXR agonist rifampicin, the μ-opioid antagonist naltrexone, and the serotonin reuptake inhibitor sertraline. These drugs are recommended by evidence-based guidelines as a stepwise therapeutic approach. Patients unresponsive to these drugs should be referred to specialized centers to receive experimental approaches such as UVB phototherapy, albumin dialysis, plasmapheresis or nasobiliary drainage. This review discusses pruritogen candidates in cholestasis, gives novel insights into the neuronal signaling pathway of pruritus and summarizes evidence-based treatment options for patients suffering from pruritus in cholestasis.
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Affiliation(s)
- Andreas E Kremer
- Department of Medicine 1, Friedrich Alexander University of Erlangen-Nuremberg, Erlangen, Germany
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97
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Receptors, cells and circuits involved in pruritus of systemic disorders. Biochim Biophys Acta Mol Basis Dis 2014; 1842:869-92. [DOI: 10.1016/j.bbadis.2014.02.007] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Revised: 02/16/2014] [Accepted: 02/18/2014] [Indexed: 12/12/2022]
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98
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Braz J, Solorzano C, Wang X, Basbaum AI. Transmitting pain and itch messages: a contemporary view of the spinal cord circuits that generate gate control. Neuron 2014; 82:522-36. [PMID: 24811377 DOI: 10.1016/j.neuron.2014.01.018] [Citation(s) in RCA: 296] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The original formulation of Gate Control Theory (GCT) proposed that the perception of pain produced by spinal cord signaling to the brain depends on a balance of activity generated in large (nonnociceptive)- and small (nociceptive)-diameter primary afferent fibers. The theory proposed that activation of the large-diameter afferent "closes" the gate by engaging a superficial dorsal horn interneuron that inhibits the firing of projection neurons. Activation of the nociceptors "opens" the gate through concomitant excitation of projection neurons and inhibition of the inhibitory interneurons. Sixty years after publication of the GCT, we are faced with an ever-growing list of morphologically and neurochemically distinct spinal cord interneurons. The present Review highlights the complexity of superficial dorsal horn circuitry and addresses the question whether the premises outlined in GCT still have relevance today. By examining the dorsal horn circuits that underlie the transmission of "pain" and "itch" messages, we also address the extent to which labeled lines can be incorporated into a contemporary view of GCT.
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Affiliation(s)
- João Braz
- Department of Anatomy, University California, San Francisco, San Francisco, CA 94158, USA
| | - Carlos Solorzano
- Department of Anatomy, University California, San Francisco, San Francisco, CA 94158, USA
| | - Xidao Wang
- Department of Anatomy, University California, San Francisco, San Francisco, CA 94158, USA
| | - Allan I Basbaum
- Department of Anatomy, University California, San Francisco, San Francisco, CA 94158, USA.
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99
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Nilius B, Szallasi A. Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine. Pharmacol Rev 2014; 66:676-814. [DOI: 10.1124/pr.113.008268] [Citation(s) in RCA: 348] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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100
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Abstract
Itch is immensely frustrating. Most studies focus on the cause of itch. In this issue of Neuron, Kardon et al. (2014) find that itch can be modulated by inhibitory neurons that produce dynorphin, an endogenous agonist of κ-opioid receptors.
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Affiliation(s)
- Paula Juliana Seadi Pereira
- Cutaneous Biology Research Center, Department of Dermatology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA; Postgraduate Program in Cellular and Molecular Biology, Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS 90619-900, Brazil
| | - Ethan A Lerner
- Cutaneous Biology Research Center, Department of Dermatology, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
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