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Zhao C, Zhou X, Shi X. The influence of Nav1.9 channels on intestinal hyperpathia and dysmotility. Channels (Austin) 2023; 17:2212350. [PMID: 37186898 DOI: 10.1080/19336950.2023.2212350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023] Open
Abstract
The Nav1.9 channel is a voltage-gated sodium channel. It plays a vital role in the generation of pain and the formation of neuronal hyperexcitability after inflammation. It is highly expressed in small diameter neurons of dorsal root ganglions and Dogiel II neurons in enteric nervous system. The small diameter neurons in dorsal root ganglions are the primary sensory neurons of pain conduction. Nav1.9 channels also participate in regulating intestinal motility. Functional enhancements of Nav1.9 channels to a certain extent lead to hyperexcitability of small diameter dorsal root ganglion neurons. The hyperexcitability of the neurons can cause visceral hyperalgesia. Intestinofugal afferent neurons and intrinsic primary afferent neurons in enteric nervous system belong to Dogiel type II neurons. Their excitability can also be regulated by Nav1.9 channels. The hyperexcitability of intestinofugal afferent neurons abnormally activate entero-enteric inhibitory reflexes. The hyperexcitability of intrinsic primary afferent neurons disturb peristaltic waves by abnormally activating peristaltic reflexes. This review discusses the role of Nav1.9 channels in intestinal hyperpathia and dysmotility.
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Affiliation(s)
- Chenyu Zhao
- Department of Gastroenterology, Henan Provincial People's Hospital, Zhengzhou University People's Hospital, Zhengzhou, China
- Department of Gastroenterology, The Second Xiangya Hospital, Central South University, Changsha, China
- Department of Medical Genetics, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Xi Zhou
- The National & Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha, Hunan, China
| | - Xiaoliu Shi
- Department of Medical Genetics, The Second Xiangya Hospital, Central South University, Changsha, China
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2
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Dos Santos NL, Lenert ME, Castillo ZW, Mody PH, Thompson LT, Burton MD. Age and sex drive differential behavioral and neuroimmune phenotypes during postoperative pain. Neurobiol Aging 2023; 123:129-144. [PMID: 36577640 PMCID: PMC9892227 DOI: 10.1016/j.neurobiolaging.2022.09.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2022] [Revised: 09/08/2022] [Accepted: 09/14/2022] [Indexed: 11/24/2022]
Abstract
Surgical procedures in the geriatric population are steadily increasing, driven by improved healthcare technologies and longer lifespans. However, effective postoperative pain treatments are lacking, and this diminishes quality of life and recovery. Here we present one of the first preclinical studies to pursue sex- and age-specific differences in postoperative neuroimmune phenotypes and pain. We found that aged males, but not females, had a delayed onset of mechanical hypersensitivity post-surgery and faster resolution than young counterparts. This sex-specific age effect was accompanied by decreased paw innervation and increased local inflammation. Additionally, we find evidence of an age-dependent decrease in hyperalgesic priming and perioperative changes in nociceptor populations and spinal microglia in the aged. These findings suggest that impaired neuronal function and maladaptive inflammatory mechanisms influence postoperative pain development in advanced age. Elucidation of these neuroimmune phenotypes across age and sex enables the development of novel therapies that can be tailored for improved pain relief.
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Affiliation(s)
- Natalia L Dos Santos
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, School of Behavioral and Brain Sciences, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX, USA
| | - Melissa E Lenert
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, School of Behavioral and Brain Sciences, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX, USA
| | - Zachary W Castillo
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, School of Behavioral and Brain Sciences, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX, USA
| | - Prapti H Mody
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, School of Behavioral and Brain Sciences, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX, USA
| | - Lucien T Thompson
- Aging and Memory Research Laboratory, Department of Neuroscience, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson TX, USA
| | - Michael D Burton
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, School of Behavioral and Brain Sciences, Center for Advanced Pain Studies, University of Texas at Dallas, Richardson TX, USA.
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3
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Menezes LFS, Maranhão MM, Tibery DV, de Souza ACB, da Mata DO, Campos LA, Souza AA, Freitas SMD, Schwartz EF. Ts17, a Tityus serrulatus β-toxin structurally related to α-scorpion toxins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184057. [PMID: 36240866 DOI: 10.1016/j.bbamem.2022.184057] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 09/18/2022] [Accepted: 09/26/2022] [Indexed: 11/13/2022]
Abstract
Ts17 was purified from the venom of the scorpion Tityus serrulatus, the most dangerous scorpion species in Brazil. The activity on Nav1.1-Nav1.7 channels was electrophysiologically characterized by patch-clamp technique. Ts17 amino acid sequence indicated high similarity to alpha-scorpion toxins; however, it presented beta-toxin activity, altering the kinetics of the Na+-channels. The most affected subtypes during activation (with and without prepulse) and inactivation phases were Nav1.2 and Nav1.5, respectively. For recovery from inactivation, the most affected voltage-gated sodium channel was Nav1.5. Circular dichroism spectra showed that Ts17 presents mainly β-sheet and unordered structures at all analyzed pHs, and the maximum value of α-helix was found at pH 4.0 (13.3 %). Based on the results, Ts17 might be used as a template to develop a new cardiac drug. Key contribution Purification of Ts17 from Tityus serrulatus, electrophysiological characterization of Ts17 on voltage-gated sodium channel subtypes, β-toxin classification.
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Affiliation(s)
- Luis Felipe Santos Menezes
- Laboratório de Neurofarmacologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil
| | - Mariza Mendanha Maranhão
- Laboratório de Neurofarmacologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil
| | - Diogo Vieira Tibery
- Laboratório de Neurofarmacologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil
| | - Adolfo Carlos Barros de Souza
- Laboratório de Neurofarmacologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil
| | - Daniel Oliveira da Mata
- Laboratório de Neurofarmacologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil
| | - Leandro Ambrósio Campos
- Laboratório de Neurofarmacologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil; Instituto de Ciências da Saúde, Universidade Paulista, Brasília 70390-130, Distrito Federal, Brazil
| | - Amanda Araújo Souza
- Brazilian Biosciences National Laboratory (LNBio), National Center for Research in Energy and Materials (CNPEM), Campinas 13083-970, São Paulo, Brazil
| | - Sonia Maria de Freitas
- Laboratório de Biofísica Molecular, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil
| | - Elisabeth Ferroni Schwartz
- Laboratório de Neurofarmacologia, Departamento de Biologia Celular, Universidade de Brasília, Brasília 70910-900, Distrito Federal, Brazil.
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4
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Role of Omics in Migraine Research and Management: A Narrative Review. Mol Neurobiol 2022; 59:5809-5834. [PMID: 35796901 DOI: 10.1007/s12035-022-02930-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 06/14/2022] [Indexed: 10/17/2022]
Abstract
Migraine is a neurological disorder defined by episodic attacks of chronic pain associated with nausea, photophobia, and phonophobia. It is known to be a complex disease with several environmental and genetic factors contributing to its susceptibility. Risk factors for migraine include head or neck injury (Arnold, Cephalalgia 38(1):1-211, 2018). Stress and high temperature are known to trigger migraine, while sleep disorders and anxiety are considered to be the comorbid conditions with migraine. Studies have reported various biomarkers, including genetic variants, proteins, and metabolites implicated in migraine's pathophysiology. Using the "omics" approach, which deals with genetics, transcriptomics, proteomics, and metabolomics, more specific biomarkers for various migraine can be identified. On account of its multifactorial nature, migraine is an ideal study model focusing on integrated omics approaches, including genomics, transcriptomics, proteomics, and metabolomics. The current review has been compiled with an aim to focus on the genomic alterations especially involved in the regulation of glutamatergic neurotransmission, cortical excitability, ion channels, solute carrier proteins, or receptors; their expression in migraine patients and also specific proteins and metabolites, including some inflammatory biomarkers that might represent the migraine phenotype at the molecular level. The systems biology approach holds the promise to understand the pathophysiology of the disease at length and also to identify the specific therapeutic targets for novel interventions.
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5
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Xiao Y, Theile JW, Zybura A, Pan Y, Lin Z, Cummins TR. A-type FHFs mediate resurgent currents through TTX-resistant voltage-gated sodium channels. eLife 2022; 11:77558. [PMID: 35441593 PMCID: PMC9071269 DOI: 10.7554/elife.77558] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
Resurgent currents (INaR) produced by voltage-gated sodium channels are required for many neurons to maintain high-frequency firing, and contribute to neuronal hyperexcitability and disease pathophysiology. Here we show, for the first time, that INaR can be reconstituted in a heterologous system by co-expression of sodium channel α-subunits and A-type fibroblast growth factor homologous factors (FHFs). Specifically, A-type FHFs induces INaR from Nav1.8, Nav1.9 tetrodotoxin-resistant neuronal channels and, to a lesser extent, neuronal Nav1.7 and cardiac Nav1.5 channels. Moreover, we identified the N-terminus of FHF as the critical molecule responsible for A-type FHFs-mediated INaR. Among the FHFs, FHF4A is the most important isoform for mediating Nav1.8 and Nav1.9 INaR. In nociceptive sensory neurons, FHF4A knockdown significantly reduces INaR amplitude and the percentage of neurons that generate INaR, substantially suppressing excitability. Thus, our work reveals a novel molecular mechanism underlying TTX-resistant INaR generation and provides important potential targets for pain treatment.
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Affiliation(s)
- Yucheng Xiao
- Biology Department, Indiana University - Purdue University Indianapolis, Indianapolis, United States
| | | | - Agnes Zybura
- Paul and Carole Stark Neurosciences Research Institute, Indiana University, Indianapolis, United States
| | - Yanling Pan
- Biology Department, Indiana University - Purdue University Indianapolis, Indianapolis, United States
| | | | - Theodore R Cummins
- Biology Department, Indiana University - Purdue University Indianapolis, Indianapolis, United States
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6
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Kwon M, Jung IY, Cha M, Lee BH. Inhibition of the Nav1.7 Channel in the Trigeminal Ganglion Relieves Pulpitis Inflammatory Pain. Front Pharmacol 2021; 12:759730. [PMID: 34955831 PMCID: PMC8694709 DOI: 10.3389/fphar.2021.759730] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 11/15/2021] [Indexed: 11/29/2022] Open
Abstract
Pulpitis causes significant changes in the peripheral nervous system, which induce hyperalgesia. However, the relationship between neuronal activity and Nav1.7 expression following pulpal noxious pain has not yet been investigated in the trigeminal ganglion (TG). The aim of our study was to verify whether experimentally induced pulpitis activates the expression of Nav1.7 peripherally and the neuronal activities of the TGs can be affected by Nav1.7 channel inhibition. Acute pulpitis was induced through allyl isothiocyanate (AITC) application to the rat maxillary molar tooth pulp. Three days after AITC application, abnormal pain behaviors were recorded, and the rats were euthanized to allow for immunohistochemical, optical imaging, and western blot analyses of the Nav1.7 expression in the TG. A significant increase in AITC-induced pain-like behaviors and histological evidence of pulpitis were observed. In addition, histological and western blot data showed that Nav1.7 expressions in the TGs were significantly higher in the AITC group than in the naive and saline group rats. Optical imaging showed that the AITC group showed higher neuronal activity after electrical stimulation of the TGs. Additionally, treatment of ProTxII, selective Nav1.7 blocker, on to the TGs in the AITC group effectively suppressed the hyperpolarized activity after electrical stimulation. These findings indicate that the inhibition of the Nav1.7 channel could modulate nociceptive signal processing in the TG following pulp inflammation.
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Affiliation(s)
- Minjee Kwon
- Department of Nursing, Kyungil University, Gyeongsan, South Korea
| | - Il Young Jung
- Department of Conservative Dentistry and Oral Science Research Center, Yonsei University College of Dentistry, Seoul, South Korea
| | - Myeounghoon Cha
- Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea
| | - Bae Hwan Lee
- Department of Physiology, Yonsei University College of Medicine, Seoul, South Korea.,Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, South Korea
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7
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Chao D, Mecca CM, Yu G, Segel I, Gold MS, Hogan QH, Pan B. Dorsal root ganglion stimulation of injured sensory neurons in rats rapidly eliminates their spontaneous activity and relieves spontaneous pain. Pain 2021; 162:2917-2932. [PMID: 33990112 PMCID: PMC8486885 DOI: 10.1097/j.pain.0000000000002284] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 03/23/2021] [Indexed: 11/26/2022]
Abstract
ABSTRACT Dorsal root ganglion field stimulation (GFS) relieves evoked and spontaneous neuropathic pain by use-dependent blockade of impulse trains through the sensory neuron T-junction, which becomes complete within less than 1 minute for C-type units, also with partial blockade of Aδ units. We used this tool in the spinal nerve ligation (SNL) rat model to selectively block sensory neuron spontaneous activity (SA) of axotomized neurons at the fifth lumbar (L5) level vs blockade of units at the L4 level that remain uninjured but exposed to inflammation. In vivo dorsal root single-unit recordings after SNL showed increased SA in L5 units but not L4 units. Ganglion field stimulation blocked this SA. Ganglion field stimulation delivered at the L5 dorsal root ganglion blocked mechanical hyperalgesia behavior, mechanical allodynia, and ongoing spontaneous pain indicated by conditioned place preference, whereas GFS at L4 blocked evoked pain behavior but not spontaneous pain. In vivo single-unit recordings of spinal cord dorsal horn (DH) wide-dynamic-range neurons showed elevated SA after SNL, which was reduced by GFS at the L5 level but not by GFS at the L4 level. In addition, L5 GFS, but not L4 GFS, increased mechanical threshold of DH units during cutaneous mechanical stimulation, while L5 GFS exceeded L4 GFS in reducing evoked firing rates. Our results indicate that SA in injured neurons supports increased firing of DH wide-dynamic-range neurons, contributing to hyperalgesia, allodynia, and ongoing pain. Ganglion field stimulation analgesic effects after nerve injury are at least partly attributable to blocking propagation of this SA.
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Affiliation(s)
- Dongman Chao
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Christina M. Mecca
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Guoliang Yu
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Ian Segel
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Michael S. Gold
- Department of Neurobiology, University of Pittsburgh, 3500 Terrace Street Rm E1440 BST, Pittsburgh, PA 15213
| | - Quinn H. Hogan
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
| | - Bin Pan
- Department of Anesthesiology, Medical College of Wisconsin, 8701 W Watertown Plank Rd, Milwaukee, WI 53226
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8
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Stucky CL, Mikesell AR. Cutaneous pain in disorders affecting peripheral nerves. Neurosci Lett 2021; 765:136233. [PMID: 34506882 PMCID: PMC8579816 DOI: 10.1016/j.neulet.2021.136233] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 08/16/2021] [Accepted: 09/02/2021] [Indexed: 02/08/2023]
Abstract
Our ability to quickly detect and respond to harmful environmental stimuli is vital for our safety and survival. This inherent acute pain detection is a "gift" because it both protects our body from harm and allows healing of damaged tissues [1]. Damage to tissues from trauma or disease can result in distorted or amplified nociceptor signaling and sensitization of the spinal cord and brain (Central Nervous System; CNS) pathways to normal input from light touch mechanoreceptors. Together, these processes can result in nagging to unbearable chronic pain and extreme sensitivity to light skin touch (allodynia). Unlike acute protective pain, chronic pain and allodynia serve no useful purpose and can severely reduce the quality of life of an affected person. Chronic pain can arise from impairment to peripheral neurons, a phenomenon called "peripheral neuropathic pain." Peripheral neuropathic pain can be caused by many insults that directly affect peripheral sensory neurons, including mechanical trauma, metabolic imbalance (e.g., diabetes), autoimmune diseases, chemotherapeutic agents, viral infections (e.g., shingles). These insults cause "acquired" neuropathies such as small-fiber neuropathies, diabetic neuropathy, chemotherapy-induced peripheral neuropathy, and post herpetic neuralgia. Peripheral neuropathic pain can also be caused by genetic factors and result in hereditary neuropathies that include Charcot-Marie-Tooth disease, rare channelopathies and Fabry disease. Many acquired and hereditary neuropathies affect the skin, our largest organ and protector of nearly our entire body. Here we review how cutaneous nociception (pain perceived from the skin) is altered following diseases that affect peripheral nerves that innervate the skin. We provide an overview of how noxious stimuli are detected and encoded by molecular transducers on subtypes of cutaneous afferent endings and conveyed to the CNS. Next, we discuss several acquired and hereditary diseases and disorders that cause painful or insensate (lack of sensation) cutaneous peripheral neuropathies, the symptoms and percepts patients experience, and how cutaneous afferents and other peripheral cell types are altered in function in these disorders. We highlight exciting new research areas that implicate non-neuronal skin cells, particularly keratinocytes, in cutaneous nociception and peripheral neuropathies. Finally, we conclude with ideas for innovative new directions, areas of unmet need, and potential opportunities for novel cutaneous therapeutics that may avoid CNS side effects, as well as ideas for improved translation of mechanisms identified in preclinical models to patients.
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Affiliation(s)
- Cheryl L Stucky
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, United States.
| | - Alexander R Mikesell
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, United States
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9
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Gemignani F, Bellanova MF, Saccani E, Pavesi G. Non-length-dependent small fiber neuropathy: Not a matter of stockings and gloves. Muscle Nerve 2021; 65:10-28. [PMID: 34374103 DOI: 10.1002/mus.27379] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 07/11/2021] [Accepted: 07/18/2021] [Indexed: 12/17/2022]
Abstract
The clinical spectrum of small fiber neuropathy (SFN) encompasses manifestations related to the involvement of thinly myelinated A-delta and unmyelinated C fibers, including not only the classical distal phenotype, but also a non-length-dependent (NLD) presentation that can be patchy, asymmetrical, upper limb-predominant, or diffuse. This narrative review is focused on NLD-SFN. The diagnosis of NLD-SFN can be problematic, due to its varied and often atypical presentation, and diagnostic criteria developed for distal SFN are not suitable for NLD-SFN. The topographic pattern of NLD-SFN is likely related to ganglionopathy restricted to the small neurons of dorsal root ganglia. It is often associated with systemic diseases, but about half the time is idiopathic. In comparison with distal SFN, immune-mediated diseases are more common than dysmetabolic conditions. Treatment is usually based on the management of neuropathic pain. Disease-modifying therapy, including immunotherapy, may be effective in patients with identified causes. Future research on NLD-SFN is expected to further clarify the interconnected aspects of phenotypic characterization, diagnostic criteria, and pathophysiology.
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Affiliation(s)
- Franco Gemignani
- Neurology Unit, Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Maria F Bellanova
- Laboratory of Neuromuscular Histopathology, Department of Medicine and Surgery, University of Parma, Parma, Italy
| | - Elena Saccani
- Neurology Unit, Department of Specialized Medicine, University Hospital of Parma, Parma, Italy
| | - Giovanni Pavesi
- Neurology Unit, Department of Medicine and Surgery, University of Parma, Parma, Italy
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10
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Llewellyn SH, Faroni A, Iliut M, Bartlam C, Vijayaraghavan A, Reid AJ. Graphene Oxide Substrate Promotes Neurotrophic Factor Secretion and Survival of Human Schwann-Like Adipose Mesenchymal Stromal Cells. Adv Biol (Weinh) 2021; 5:e2000271. [PMID: 33852181 DOI: 10.1002/adbi.202000271] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 02/04/2021] [Indexed: 11/11/2022]
Abstract
Mesenchymal stromal cells from adipose tissue (AD-MSCs) exhibit favorable clinical traits for autologous transplantation and can develop 'Schwann-like' phenotypes (sAD-MSCs) to improve peripheral nerve regeneration, where severe injuries yield insufficient recovery. However, sAD-MSCs regress without biochemical stimulation and detach from conduits under unfavorable transplant conditions, negating their paracrine effects. Graphene-derived materials support AD-MSC attachment, regulating cell adhesion and function through physiochemistry and topography. Graphene oxide (GO) is a suitable substrate for human sAD-MSCs incubation toward severe peripheral nerve injuries by evaluating transcriptome changes, neurotrophic factor expression over a 7-days period, and cell viability in apoptotic conditions is reported. Transcriptome changes from GO incubation across four patients are minor compared to biological variance. Nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and glial-derived neurotrophic factor (GDNF) gene expression is unchanged from sAD-MSCs on GO substrates, but NGF and GDNF protein secretion increase at day 3 and 7. Secretome changes do not improve dorsal root ganglia neuron axon regeneration in conditioned media culture models. Fewer sAD-MSCs detach from GO substrates compared to glass following phosphate buffer saline exposure, which simulates apoptotic conditions. Overall, GO substrates are compatible with sAD-MSC primed for peripheral nerve regeneration strategies and protect the cell population in harsh environments.
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Affiliation(s)
- Steffan H Llewellyn
- Blond McIndoe Laboratories, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, M13 9PL, UK.,Department of Materials and National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - Alessandro Faroni
- Blond McIndoe Laboratories, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, M13 9PL, UK
| | - Maria Iliut
- Department of Materials and National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - Cian Bartlam
- Department of Materials and National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK.,Institute of Physics, EIT 2, Bundeswehr University Munich, Neubiberg, 85577, Germany
| | - Aravind Vijayaraghavan
- Department of Materials and National Graphene Institute, The University of Manchester, Manchester, M13 9PL, UK
| | - Adam J Reid
- Blond McIndoe Laboratories, Division of Cell Matrix Biology and Regenerative Medicine, School of Biological Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester, M13 9PL, UK.,Department of Plastic Surgery & Burns, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, M23 9LT, UK
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11
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Raasing LR, Vogels OJ, Veltkamp M, van Swol CF, Grutters JC. Current View of Diagnosing Small Fiber Neuropathy. J Neuromuscul Dis 2021; 8:185-207. [PMID: 33337383 PMCID: PMC8075405 DOI: 10.3233/jnd-200490] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Small fiber neuropathy (SFN) is a disorder of the small myelinated Aδ-fibers and unmyelinated C-fibers [5, 6]. SFN might affect small sensory fibers, autonomic fibers or both, resulting in sensory changes, autonomic dysfunction or combined symptoms [7]. As a consequence, the symptoms are potentially numerous and have a large impact on quality of life [8]. Since diagnostic methods for SFN are numerous and its pathophysiology complex, this extensive review focusses on categorizing all aspects of SFN as disease and its diagnosis. In this review, sensitivity in combination with specificity of different diagnostic methods are described using the areas under the curve. In the end, a diagnostic work-flow is suggested based on different phenotypes of SFN.
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Affiliation(s)
- Lisette R.M. Raasing
- ILD Center of Excellence, Department of Pulmonology,St Antonius Hospital, CM, Nieuwegein, The Netherlands
| | - Oscar J.M. Vogels
- Department of Neurology, St Antonius Hospital, CM, Nieuwegein, The Netherlands
| | - Marcel Veltkamp
- ILD Center of Excellence, Department of Pulmonology,St Antonius Hospital, CM, Nieuwegein, The Netherlands
- Division of Heart and Lungs, University Medical Center Utrecht, CX, Utrecht, The Netherlands
| | | | - Jan C. Grutters
- ILD Center of Excellence, Department of Pulmonology,St Antonius Hospital, CM, Nieuwegein, The Netherlands
- Division of Heart and Lungs, University Medical Center Utrecht, CX, Utrecht, The Netherlands
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12
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Djouhri L, Zeidan A, Alzoghaibi M, Al Otaibi MF, Abd El-Aleem SA. L5 Spinal Nerve Axotomy Induces Distinct Electrophysiological Changes in Axotomized L5- and Adjacent L4-Dorsal Root Ganglion Neurons in Rats In Vivo. J Neurotrauma 2020; 38:330-341. [PMID: 32993425 DOI: 10.1089/neu.2020.7264] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Peripheral neuropathic pain (PNP) is a major health problem for which effective drug treatment is lacking. Its underlying neuronal mechanisms are still illusive, but pre-clinical studies using animal models of PNP including the L5-spinal nerve axotomy (L5-SNA) model, suggest that it is partly caused by excitability changes in dorsal root ganglion (DRG) neurons. L5-SNA results in two DRG neuronal groups: (1) axotomized/damaged neurons in L5- plus some in L4-DRGs, and (2) ipsilateral L4-neurons with intact/uninjured fibers intermingling with degenerating L5-fibers. The axotomized neurons are deprived of peripherally derived trophic factors and degenerate causing neuroinflammation, whereas the uninjured L4-neuorns are subject to increased trophic factors and neuroinflammation associated with Wallerian degeneration of axotomized L5-nerve fibers. Whether these two groups of DRG neurons exhibit similar or distinct electrophysiological changes after L5-SNA remains unresolved. Conflicting evidence for this may result from some studies assuming that all L4-fibers are undamaged. Here, we recorded somatic action potentials (APs) intracellularly from C- and A-fiber L4/L5 DRG neurons in vivo, to examine our hypothesis that L5-SNA would induce distinct electrophysiological changes in the two populations of DRG neurons. Consistent with this hypothesis, we found (7 days post-SNA), in SNA rats with established pain hypersensitivity, slower AP kinetics in axotomized L5-neurons and faster AP kinetics in L4-nociceptive neurons including decreased rise time in Aδ-and Aβ-fiber nociceptors, and after-hyperpolarization duration in Aβ-fiber nociceptors. We also found several changes in axotomized L5-neurons but not in L4-nociceptive neurons, and some changes in L4-nociceptive but not L5-neurons. The faster AP kinetics (decreased refractory period) in L4-nociceptive neurons that are consistent with their reported hyperexcitability may lead to repetitive firing and thus provide enhanced afferent input necessary for initiating and/or maintaining PNP development. The changes in axotomized L5-neurons may contribute to the central mechanisms of PNP via enhanced neurotransmitter release in the central nervous system (CNS).
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Affiliation(s)
- Laiche Djouhri
- Department of Basic Medical Sciences, College of Medicine (QU Health), Qatar University, Doha, Qatar
| | - Asad Zeidan
- Department of Basic Medical Sciences, College of Medicine (QU Health), Qatar University, Doha, Qatar
| | - Mohammad Alzoghaibi
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad F Al Otaibi
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Seham A Abd El-Aleem
- Department of Histology and Cell Biology, University of Manchester, Manchester, United Kingdom.,Department of Pathology, Faculty of Medicine, Minia University, Minia, Egypt
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13
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McMahon KL, Tay B, Deuis JR, Tanaka BS, Peigneur S, Jin AH, Tytgat J, Waxman SG, Dib-Hajj SD, Vetter I, Schroeder CI. Pharmacological activity and NMR solution structure of the leech peptide HSTX-I. Biochem Pharmacol 2020; 181:114082. [PMID: 32524995 DOI: 10.1016/j.bcp.2020.114082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Revised: 06/03/2020] [Accepted: 06/04/2020] [Indexed: 10/24/2022]
Abstract
The role of voltage-gated sodium (NaV) channels in pain perception is indisputable. Of particular interest as targets for the development of pain therapeutics are the tetrodotoxin-resistant isoforms NaV1.8 and NaV1.9, based on animal as well as human genetic studies linking these ion channel subtypes to the pathogenesis of pain. However, only a limited number of inhibitors selectively targeting these channels have been reported. HSTX-I is a peptide toxin identified from saliva of the leech Haemadipsa sylvestris. The native 23-residue peptide, stabilised by two disulfide bonds, has been reported to inhibit rat NaV1.8 and mouse NaV1.9 with low micromolar activity, and may therefore represent a scaffold for development of novel modulators with activity at human tetrodotoxin-resistant NaV isoforms. We synthetically produced this hydrophobic peptide in high yield using a one-pot oxidation and single step purification and determined the three-dimensional solution structure of HSTX-I using NMR solution spectroscopy. However, in our hands, the synthetic HSTX-I displayed only very modest activity at human NaV1.8 and NaV1.9, and lacked analgesic efficacy in a murine model of inflammatory pain.
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Affiliation(s)
- Kirsten L McMahon
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Bryan Tay
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jennifer R Deuis
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Brian S Tanaka
- Center for Neuroscience and Regeneration Research, New Haven, CT, United States; Department of Neurology, Yale University School of Medicine, New Haven, CT, United States; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Steve Peigneur
- Toxicology and Pharmacology, Katholieke Universiteit (KU) Leuven, Campus Gasthuisberg, Leuven, Belgium
| | - Ai-Hua Jin
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia
| | - Jan Tytgat
- Toxicology and Pharmacology, Katholieke Universiteit (KU) Leuven, Campus Gasthuisberg, Leuven, Belgium
| | - Stephen G Waxman
- Center for Neuroscience and Regeneration Research, New Haven, CT, United States; Department of Neurology, Yale University School of Medicine, New Haven, CT, United States; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Sulayman D Dib-Hajj
- Center for Neuroscience and Regeneration Research, New Haven, CT, United States; Department of Neurology, Yale University School of Medicine, New Haven, CT, United States; Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, CT, United States
| | - Irina Vetter
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia; School of Pharmacy, The University of Queensland, Woolloongabba, Queensland 4103, Australia.
| | - Christina I Schroeder
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland 4072, Australia; National Cancer Institute, National Institutes of Health, Frederick, MD 21702, United States.
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14
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Djouhri L, Zeidan A, Abd El-Aleem SA, Smith T. Cutaneous Aβ-Non-nociceptive, but Not C-Nociceptive, Dorsal Root Ganglion Neurons Exhibit Spontaneous Activity in the Streptozotocin Rat Model of Painful Diabetic Neuropathy in vivo. Front Neurosci 2020; 14:530. [PMID: 32528247 PMCID: PMC7263321 DOI: 10.3389/fnins.2020.00530] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 04/29/2020] [Indexed: 12/30/2022] Open
Abstract
Diabetic peripheral neuropathic pain (DPNP) is the most devastating complication of diabetes mellitus. Unfortunately, successful therapy for DPNP remains a challenge because its pathogenesis is still elusive. However, DPNP is believed to be due partly to abnormal hyperexcitability of dorsal root ganglion (DRG) neurons, but the relative contributions of specific functional subtypes remain largely unknown. Here, using the strepotozotocin (STZ) rat model of DPNP induced by a STZ injection (60 mg/kg, i.p), and intracellular recordings of action potentials (APs) from DRG neurons in anesthetized rats, we examined electrophysiological changes in C-and Aβ-nociceptive and Aβ-low threshold mechanoreceptive (LTM) neurons that may contribute to DPNP. Compared with control, we found in STZ-rats with established pain hypersensitivity (5 weeks post-STZ) several significant changes including: (a) A 23% increase in the incidence of spontaneous activity (SA) in Aβ-LTMs (but not C-mechanosensitive nociceptors) that may cause dysesthesias/paresthesia suffered by DPNP patients, (b) membrane hyperpolarization and a ∼85% reduction in SA rate in Aβ-LTMs by Kv7 channel activation with retigabine (6 mg/kg, i.v.) suggesting that Kv7/M channels may be involved in mechanisms of SA generation in Aβ-LTMs, (c) decreases in AP duration and in duration and amplitude of afterhyperpolarization (AHP) in C-and/or Aβ-nociceptors. These faster AP and AHP kinetics may lead to repetitive firing and an increase in afferent input to the CNS and thereby contribute to DPNP development, and (d) a decrease in the electrical thresholds of Aβ-nociceptors that may contribute to their sensitization, and thus to the resulting hypersensitivity associated with DPNP.
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Affiliation(s)
- Laiche Djouhri
- Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar
| | - Asad Zeidan
- Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar
| | - Seham A. Abd El-Aleem
- Department of Histology and Cell Biology, University of Manchester, Manchester, United Kingdom
- Department of Pathology, Faculty of Medicine, Minia University, Minya, Egypt
| | - Trevor Smith
- Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
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15
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Lee SJ, Krieger JP, Vergara M, Quinn D, McDougle M, de Araujo A, Darling R, Zollinger B, Anderson S, Pan A, Simonnet EJ, Pignalosa A, Arnold M, Singh A, Langhans W, Raybould HE, de Lartigue G. Blunted Vagal Cocaine- and Amphetamine-Regulated Transcript Promotes Hyperphagia and Weight Gain. Cell Rep 2020; 30:2028-2039.e4. [PMID: 32049029 PMCID: PMC7063787 DOI: 10.1016/j.celrep.2020.01.045] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 12/06/2019] [Accepted: 01/15/2020] [Indexed: 12/31/2022] Open
Abstract
The vagus nerve conveys gastrointestinal cues to the brain to control eating behavior. In obesity, vagally mediated gut-brain signaling is disrupted. Here, we show that the cocaine- and amphetamine-regulated transcript (CART) is a neuropeptide synthesized proportional to the food consumed in vagal afferent neurons (VANs) of chow-fed rats. CART injection into the nucleus tractus solitarii (NTS), the site of vagal afferent central termination, reduces food intake. Conversely, blocking endogenous CART action in the NTS increases food intake in chow-fed rats, and this requires intact VANs. Viral-mediated Cartpt knockdown in VANs increases weight gain and daily food intake via larger meals and faster ingestion rate. In obese rats fed a high-fat, high-sugar diet, meal-induced CART synthesis in VANs is blunted and CART antibody fails to increase food intake. However, CART injection into the NTS retains its anorexigenic effect in obese rats. Restoring disrupted VAN CART signaling in obesity could be a promising therapeutic approach.
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Affiliation(s)
- Shin J Lee
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - Jean-Philippe Krieger
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland; Department of Metabolic Physiology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Macarena Vergara
- Department of Pharmacodynamics, Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL, USA
| | | | - Molly McDougle
- Department of Pharmacodynamics, Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL, USA; The John B. Pierce Laboratory, New Haven, CT, USA
| | - Alan de Araujo
- Department of Pharmacodynamics, Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL, USA; The John B. Pierce Laboratory, New Haven, CT, USA; Yale University, New Haven, CT, USA
| | - Rebecca Darling
- Anatomy, Physiology and Cell Biology Department School of Veterinary Medicine, University of California Davis, Davis, CA, USA
| | - Benjamin Zollinger
- The John B. Pierce Laboratory, New Haven, CT, USA; Yale University, New Haven, CT, USA
| | - Seth Anderson
- The John B. Pierce Laboratory, New Haven, CT, USA; Yale University, New Haven, CT, USA
| | - Annabeth Pan
- The John B. Pierce Laboratory, New Haven, CT, USA; Yale University, New Haven, CT, USA
| | - Emilie J Simonnet
- Anatomy, Physiology and Cell Biology Department School of Veterinary Medicine, University of California Davis, Davis, CA, USA
| | - Angelica Pignalosa
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - Myrtha Arnold
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - Arashdeep Singh
- Department of Pharmacodynamics, Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL, USA
| | - Wolfgang Langhans
- Physiology and Behavior Laboratory, ETH Zurich, Schwerzenbach, Switzerland
| | - Helen E Raybould
- Anatomy, Physiology and Cell Biology Department School of Veterinary Medicine, University of California Davis, Davis, CA, USA
| | - Guillaume de Lartigue
- Department of Pharmacodynamics, Center for Integrative Cardiovascular and Metabolic Disease, University of Florida, Gainesville, FL, USA; The John B. Pierce Laboratory, New Haven, CT, USA; Yale University, New Haven, CT, USA.
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16
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Taylor TS, Konda P, John SS, Bulmer DC, Hockley JRF, Smith ESJ. Galanin suppresses visceral afferent responses to noxious mechanical and inflammatory stimuli. Physiol Rep 2020; 8:e14326. [PMID: 31960596 PMCID: PMC6971316 DOI: 10.14814/phy2.14326] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Galanin is a neuropeptide expressed by sensory neurones innervating the gastrointestinal (GI) tract. Galanin displays inhibitory effects on vagal afferent signaling within the upper GI tract, and the goal of this study was to determine the actions of galanin on colonic spinal afferent function. Specifically, we sought to evaluate the effect of galanin on lumbar splanchnic nerve (LSN) mechanosensitivity to noxious distending pressures and the development of hypersensitivity in the presence of inflammatory stimuli and colitis. Using ex vivo electrophysiological recordings we show that galanin produces a dose-dependent suppression of colonic LSN responses to mechanical stimuli and prevents the development of hypersensitivity to acutely administered inflammatory mediators. Using galanin receptor (GalR) agonists, we show that GalR1 activation, but not GalR2/3 activation, suppresses mechanosensitivity. The effect of galanin on colonic afferent activity was not observed in tissue from mice with dextran sodium sulfate-induced colitis. We conclude that galanin has a marked suppressive effect on colonic mechanosensitivity at noxious distending pressures and prevents the acute development of mechanical hypersensitivity to inflammatory mediators, an effect not seen in the inflamed colon. These actions highlight a potential role for galanin in the regulation of mechanical nociception in the bowel and the therapeutic potential of targeting galaninergic signaling to treat visceral hypersensitivity.
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Affiliation(s)
- Toni S. Taylor
- Department of PharmacologyUniversity of CambridgeCambridgeUK
| | - Parvesh Konda
- Department of PharmacologyUniversity of CambridgeCambridgeUK
| | - Sarah S. John
- Department of PharmacologyUniversity of CambridgeCambridgeUK
| | - David C. Bulmer
- Department of PharmacologyUniversity of CambridgeCambridgeUK
| | - James R. F. Hockley
- Department of PharmacologyUniversity of CambridgeCambridgeUK
- GSKGSK Medicines Research CentreStevenageHertfordshireUK
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17
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Hugosdottir R, Mørch CD, Andersen OK, Arendt-Nielsen L. Investigating stimulation parameters for preferential small-fiber activation using exponentially rising electrical currents. J Neurophysiol 2019; 122:1745-1752. [PMID: 31461369 DOI: 10.1152/jn.00390.2019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Electrical stimulation is widely used in pain research and profiling, but current technologies lack selectivity toward small sensory fibers. Pin electrodes deliver high current density in upper skin layers, and it has been proposed that slowly rising exponential pulses can elevate large-fiber activation threshold and thereby increase preferential small-fiber activation. Optimal stimulation parameters for the combined pin electrode and exponential pulse stimulation have so far not been established, which is the aim of this study. Perception thresholds were compared between pin and patch electrodes using single 1- to 100-ms exponential and rectangular pulses. Stimulus-response functions were evaluated for both pulse shapes delivered as single pulses and pulse trains of 10 Hz using intensities from 0.1 to 20 times perception threshold. Perception thresholds (mA) decreased when duration was increased for both electrodes with rectangular pulses and the pin electrode with exponential pulses. For the patch electrode, perception thresholds for exponential pulses decreased for durations ≤10 ms but increased for durations ≥15 ms, indicating accommodation of large fibers. Stimulus-response curves for single pulses were similar for the two pulse shapes. For pulse trains, the slope of the curve was higher for rectangular pulses. Maximal large-fiber accommodation to exponential pulses was observed for 100-ms pulses, indicating that 100-ms exponential pulses should be applied for preferential small-fiber activation. Intensity of 10 times perception threshold was sufficient to cause maximal pain ratings. The developed methodology may open new opportunities for using electrical stimulation paradigms for small-fiber stimulation and diagnostics.NEW & NOTEWORTHY Selective activation of small cutaneous nerve fibers is pivotal for investigations of the pain system. The present study demonstrated that patch electrode perception thresholds increase with increased duration of exponential currents from 20 to 100 ms. This is likely caused by large-fiber accommodation, which can be utilized to activate small fibers preferentially through small-diameter pin electrodes. This finding may be utilized in studies of fundamental pain mechanisms and, for example, in small-fiber neuropathy.
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Affiliation(s)
- Rosa Hugosdottir
- Center of Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Carsten Dahl Mørch
- Center of Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Ole Kæseler Andersen
- Center of Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
| | - Lars Arendt-Nielsen
- Center of Neuroplasticity and Pain, SMI, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark
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18
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Lawson SN, Fang X, Djouhri L. Nociceptor subtypes and their incidence in rat lumbar dorsal root ganglia (DRGs): focussing on C-polymodal nociceptors, Aβ-nociceptors, moderate pressure receptors and their receptive field depths. CURRENT OPINION IN PHYSIOLOGY 2019; 11:125-146. [PMID: 31956744 PMCID: PMC6959836 DOI: 10.1016/j.cophys.2019.10.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
A recent study with Ca++-sensitive-dyes in neurons in whole DRGs (Table 5) found that much lower percentages of nociceptors were polymodal-nociceptors (PMNs) (Emery et al., 2016), than the 50-80% values in many electrophysiological fiber studies. This conflict highlighted the lack of knowledge about percentages of nociceptor-subtypes in the DRG. This was analysed from intracellularly-recorded neurons in rat lumbar DRGs stimulated from outside the skin. Polymodal nociceptors (PMNs) were 11% of all neurons and 19% of all nociceptors. Most PMNs had C-fibers (CPMNs). Percentages of C-nociceptors that were CPMNs varied with receptive field (RF) depths, whether superficial (∼80%), dermal (25%), deep (0%) or cutaneous (superficial + dermal) (40%). This explains CPMN percentages 40-90%, being highest, in electrophysiological studies using cutaneous nerves, and lowest in studies that also include deep RFs, including ours, and the recent Ca++-imaging studies in whole DRGs. Despite having been originally described in 1967 (Burgess and Perl), both Aβ-nociceptors and Aβ-moderate pressure receptors (MPRs) remain overlooked. Most A-fiber nociceptors in rodents have Aβ-fibers. Of rat lumbar Aβ-nociceptors with superficial RFs, 50% were MPRs with variable medium-low trkA-expression. Despite having conduction velocities at the two extremes for nociceptors, both CPMNs and MPRs have relatively low thresholds, superficial/epidermal RFs and low trkA-expression. For abbreviations used see Table 5.
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Affiliation(s)
- Sally N Lawson
- The Physiology Department, University of Bristol, Bristol BS8 1TD, UK
| | - Xin Fang
- Qihan BioTech Co. Ltd, Hangzhou, China
| | - Laiche Djouhri
- Department of Basic Medical Sciences, College of Medicine, QU Health, Qatar University, Doha, Qatar
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19
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Hugosdottir R, Mørch CD, Andersen OK, Helgason T, Arendt-Nielsen L. Preferential activation of small cutaneous fibers through small pin electrode also depends on the shape of a long duration electrical current. BMC Neurosci 2019; 20:48. [PMID: 31521103 PMCID: PMC6744690 DOI: 10.1186/s12868-019-0530-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Accepted: 09/04/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Electrical stimulation is widely used in experimental pain research but it lacks selectivity towards small nociceptive fibers. When using standard surface patch electrodes and rectangular pulses, large fibers are activated at a lower threshold than small fibers. Pin electrodes have been designed for overcoming this problem by providing a higher current density in the upper epidermis where the small nociceptive fibers mainly terminate. At perception threshold level, pin electrode stimuli are rather selectively activating small nerve fibers and are perceived as painful, but for high current intensity, which is usually needed to evoke sufficient pain levels, large fibers are likely co-activated. Long duration current has been shown to elevate the threshold of large fibers by the mechanism of accommodation. However, it remains unclear whether the mechanism of accommodation in large fibers can be utilized to activate small fibers even more selectively by combining pin electrode stimulation with a long duration pulse. RESULTS In this study, perception thresholds were determined for a patch- and a pin electrode for different pulse shapes of long duration. The perception threshold ratio between the two different electrodes was calculated to estimate the ability of the pulse shapes to preferentially activate small fibers. The perception threshold ratios were compared between stimulation pulses of 5- and 50 ms durations and shapes of: exponential increase, linear increase, bounded exponential, and rectangular. Qualitative pain perception was evaluated for all pulse shapes delivered at 10 times perception threshold. The results showed a higher perception threshold ratio for long duration 50 ms pulses than for 5 ms pulses. The highest perception threshold ratio was found for the 50 ms, bounded exponential pulse shape. Results furthermore revealed different strength-duration relation between the bounded exponential- and rectangular pulse shapes. Pin electrode stimulation at high intensity was mainly described as "stabbing", "shooting", and "sharp". CONCLUSION These results indicate that long duration pulses with a bounded exponential increase preferentially activate the small nociceptive fibers with a pin electrode and concurrently cause elevated threshold of large non-nociceptive fibers with patch electrodes.
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Affiliation(s)
- Rosa Hugosdottir
- Center of Neuroplasticity and Pain, SMI®, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D3, 9220, Aalborg, Denmark.
| | - Carsten Dahl Mørch
- Center of Neuroplasticity and Pain, SMI®, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D3, 9220, Aalborg, Denmark.
| | - Ole Kæseler Andersen
- Center of Neuroplasticity and Pain, SMI®, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D3, 9220, Aalborg, Denmark
| | - Thordur Helgason
- Institute of Biomedical and Neural Engineering, Health Technology Center, School of Engineering and Science, Reykjavik University, Menntavegur 1, 101, Reykjavik, Iceland
| | - Lars Arendt-Nielsen
- Center of Neuroplasticity and Pain, SMI®, Department of Health Science and Technology, Aalborg University, Fredrik Bajers Vej 7D3, 9220, Aalborg, Denmark
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20
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Lee K, Lee BM, Park CK, Kim YH, Chung G. Ion Channels Involved in Tooth Pain. Int J Mol Sci 2019; 20:ijms20092266. [PMID: 31071917 PMCID: PMC6539952 DOI: 10.3390/ijms20092266] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2019] [Revised: 05/03/2019] [Accepted: 05/03/2019] [Indexed: 01/05/2023] Open
Abstract
The tooth has an unusual sensory system that converts external stimuli predominantly into pain, yet its sensory afferents in teeth demonstrate cytochemical properties of non-nociceptive neurons. This review summarizes the recent knowledge underlying this paradoxical nociception, with a focus on the ion channels involved in tooth pain. The expression of temperature-sensitive ion channels has been extensively investigated because thermal stimulation often evokes tooth pain. However, temperature-sensitive ion channels cannot explain the sudden intense tooth pain evoked by innocuous temperatures or light air puffs, leading to the hydrodynamic theory emphasizing the microfluidic movement within the dentinal tubules for detection by mechanosensitive ion channels. Several mechanosensitive ion channels expressed in dental sensory systems have been suggested as key players in the hydrodynamic theory, and TRPM7, which is abundant in the odontoblasts, and recently discovered PIEZO receptors are promising candidates. Several ligand-gated ion channels and voltage-gated ion channels expressed in dental primary afferent neurons have been discussed in relation to their potential contribution to tooth pain. In addition, in recent years, there has been growing interest in the potential sensory role of odontoblasts; thus, the expression of ion channels in odontoblasts and their potential relation to tooth pain is also reviewed.
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Affiliation(s)
- Kihwan Lee
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 406-799, Korea.
| | - Byeong-Min Lee
- Department of Oral Physiology and Program in Neurobiology, School of Dentistry, Seoul National University, Seoul 08826, Korea.
| | - Chul-Kyu Park
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 406-799, Korea.
| | - Yong Ho Kim
- Gachon Pain Center and Department of Physiology, College of Medicine, Gachon University, Incheon 406-799, Korea.
| | - Gehoon Chung
- Department of Oral Physiology and Program in Neurobiology, School of Dentistry, Seoul National University, Seoul 08826, Korea.
- Dental Research Institute, Seoul National University, Seoul 03080, Korea.
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21
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Bennett DL, Clark AJ, Huang J, Waxman SG, Dib-Hajj SD. The Role of Voltage-Gated Sodium Channels in Pain Signaling. Physiol Rev 2019; 99:1079-1151. [DOI: 10.1152/physrev.00052.2017] [Citation(s) in RCA: 256] [Impact Index Per Article: 51.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Acute pain signaling has a key protective role and is highly evolutionarily conserved. Chronic pain, however, is maladaptive, occurring as a consequence of injury and disease, and is associated with sensitization of the somatosensory nervous system. Primary sensory neurons are involved in both of these processes, and the recent advances in understanding sensory transduction and human genetics are the focus of this review. Voltage-gated sodium channels (VGSCs) are important determinants of sensory neuron excitability: they are essential for the initial transduction of sensory stimuli, the electrogenesis of the action potential, and neurotransmitter release from sensory neuron terminals. Nav1.1, Nav1.6, Nav1.7, Nav1.8, and Nav1.9 are all expressed by adult sensory neurons. The biophysical characteristics of these channels, as well as their unique expression patterns within subtypes of sensory neurons, define their functional role in pain signaling. Changes in the expression of VGSCs, as well as posttranslational modifications, contribute to the sensitization of sensory neurons in chronic pain states. Furthermore, gene variants in Nav1.7, Nav1.8, and Nav1.9 have now been linked to human Mendelian pain disorders and more recently to common pain disorders such as small-fiber neuropathy. Chronic pain affects one in five of the general population. Given the poor efficacy of current analgesics, the selective expression of particular VGSCs in sensory neurons makes these attractive targets for drug discovery. The increasing availability of gene sequencing, combined with structural modeling and electrophysiological analysis of gene variants, also provides the opportunity to better target existing therapies in a personalized manner.
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Affiliation(s)
- David L. Bennett
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Alex J. Clark
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Jianying Huang
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Stephen G. Waxman
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
| | - Sulayman D. Dib-Hajj
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom; Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut; and Rehabilitation Research Center, Veterans Affairs Connecticut Healthcare System, West Haven, Connecticut
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Zhang XL, Cao XY, Lai RC, Xie MX, Zeng WA. Puerarin Relieves Paclitaxel-Induced Neuropathic Pain: The Role of Na v1.8 β1 Subunit of Sensory Neurons. Front Pharmacol 2019; 9:1510. [PMID: 30666203 PMCID: PMC6330330 DOI: 10.3389/fphar.2018.01510] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 12/10/2018] [Indexed: 12/18/2022] Open
Abstract
Currently there is no effective treatment available for clinical patients suffering from neuropathic pain induced by chemotherapy paclitaxel. Puerarin is a major isoflavonoid extracted from the Chinese medical herb kudzu root, which has been used for treatment of cardiovascular disorders and brain injury. Here, we found that puerarin dose-dependently alleviated paclitaxel-induced neuropathic pain. At the same time, puerarin preferentially reduced the excitability and blocked the voltage-gated sodium (Nav) channels of dorsal root ganglion (DRG) neurons from paclitaxel-induced neuropathic pain rats. Furthermore, puerarin was a more potent blocker of tetrodotoxin-resistant (TTX-R) Nav channels than of tetrodotoxin-sensitive (TTX-S) Nav channels in chronic pain rats’ DRG neurons. In addition, puerarin had a stronger blocking effect on Nav1.8 channels in DRG neurons of neuropathic pain rats and β1 subunit siRNA can abolish this selective blocking effect on Nav1.8. Together, these results suggested that puerarin may preferentially block β1 subunit of Nav1.8 in sensory neurons contributed to its anti-paclitaxel induced neuropathic pain effect.
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Affiliation(s)
- Xiao-Long Zhang
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Anesthesiology, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Xian-Ying Cao
- College of Food Science and Technology, Hainan University, Haikou, China.,State Key Laboratory of Marine Resources Utilization in South China Sea, Hainan University, Haikou, China
| | - Ren-Chun Lai
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Anesthesiology, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Man-Xiu Xie
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Anesthesiology, Sun Yat-sen University Cancer Center, Guangzhou, China
| | - Wei-An Zeng
- State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Department of Anesthesiology, Sun Yat-sen University Cancer Center, Guangzhou, China
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Nunes D, Kuner T. Axonal sodium channel NaV1.2 drives granule cell dendritic GABA release and rapid odor discrimination. PLoS Biol 2018; 16:e2003816. [PMID: 30125271 PMCID: PMC6117082 DOI: 10.1371/journal.pbio.2003816] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 08/30/2018] [Accepted: 08/06/2018] [Indexed: 12/19/2022] Open
Abstract
Dendrodendritic synaptic interactions between olfactory bulb mitral and granule cells represent a key neuronal mechanism of odor discrimination. Dendritic release of gamma-aminobutyric acid (GABA) from granule cells contributes to stimulus-dependent, rapid, and accurate odor discrimination, yet the physiological mechanisms governing this release and its behavioral relevance are unknown. Here, we show that granule cells express the voltage-gated sodium channel α-subunit NaV1.2 in clusters distributed throughout the cell surface including dendritic spines. Deletion of NaV1.2 in granule cells abolished spiking and GABA release as well as inhibition of synaptically connected mitral cells (MCs). As a consequence, mice required more time to discriminate highly similar odorant mixtures, while odor discrimination learning remained unaffected. In conclusion, we show that expression of NaV1.2 in granule cells is crucial for physiological dendritic GABA release and rapid discrimination of similar odorants with high accuracy. Hence, our data indicate that neurotransmitter-releasing dendritic spines function just like axon terminals. In axonal nerve terminals, neurotransmitter release is triggered by a localized Ca2+ nanodomain generated by voltage-gated calcium channels in response to an action potential, which in turn is mediated by voltage-gated sodium channels. Dendritic neurotransmitter release has been thought to work differently, mainly depending on Ca2+ entering directly through N-methyl-D-aspartate (NMDA) receptors, a subtype of ligand-gated ion channel. To further investigate how dendritic neurotransmitter is released, we studied granule cells in the olfactory bulb of mice, which establish inhibitory dendrodendritic synapses with mitral cells. We show that granule cells express voltage-gated sodium channels predominantly localized in dendrites and spines. Down-regulation of these channels precludes action potential firing in granule cells and strongly reduces mitral cell inhibition. Behaviorally, these mice require more time to discriminate highly similar odorants at maximal accuracy. Therefore, the inhibition of mitral cells relies on neurotransmitter released from the dendrites of granule cells by a mechanism that resembles axonal neurotransmitter release much more than previously thought.
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Affiliation(s)
- Daniel Nunes
- Champalimaud Research, Champalimaud Centre for the Unknown, Lisbon, Portugal
- Functional Neuroanatomy Department, Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
- * E-mail: (DN); (TK)
| | - Thomas Kuner
- Functional Neuroanatomy Department, Institute for Anatomy and Cell Biology, Heidelberg University, Heidelberg, Germany
- * E-mail: (DN); (TK)
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Djouhri L, Smith T, Ahmeda A, Alotaibi M, Weng X. Hyperpolarization-activated cyclic nucleotide-gated channels contribute to spontaneous activity in L4 C-fiber nociceptors, but not Aβ-non-nociceptors, after axotomy of L5-spinal nerve in the rat in vivo. Pain 2018; 159:1392-1402. [PMID: 29578948 DOI: 10.1097/j.pain.0000000000001224] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Peripheral neuropathic pain associated with partial nerve injury is believed to be driven partly by aberrant spontaneous activity (SA) in both injured and uninjured dorsal root ganglion (DRG) neurons. The underlying ionic mechanisms are not fully understood, but hyperpolarization-activated cyclic nucleotide-gated (HCN) channels which underlie the excitatory Ih current have been implicated in SA generation in axotomized A-fiber neurons after L5-spinal nerve ligation/axotomy (SNL/SNA). Here, using a modified model of SNA (mSNA) which involves, in addition to L5-SNA, loose ligation of the L4-spinal nerve with neuroinflammation-inducing chromic gut, we examined whether HCN channels also contribute to SA in the adjacent L4-neurons. Intracellular recordings from L4-DRG neurons in control rats, and L4-DRG neurons in mSNA rats were made using in vivo voltage- and current-clamp techniques. Compared with control, L4 C-nociceptors and Aβ-low-threshold mechanoreceptors (LTMs) exhibited SA 7 days after mSNA. This was accompanied, in C-nociceptors, by a significant increase in Ih amplitude, the percentage of Ih-expressing neurons, and Ih activation rate. Hyperpolarization-activated cyclic nucleotide-gated channel blockade with ZD7288 (10 mg/kg, intravenously) suppressed SA in C-nociceptors, but not Aβ-LTMs, and caused in C-nociceptors, membrane hyperpolarization and a decrease in Ih activation rate. Furthermore, intraplantar injection of ZD7288 (100 μM) was found to be as effective as gabapentin (positive control) in attenuating cold hypersensitivity in mSNA rats. These findings suggest that HCN channels contribute to nerve injury-induced SA in L4 C-nociceptors, but not Aβ-LTMs, and that ZD7288 exerts its analgesic effects by altering Ih activation properties and/or causing membrane hyperpolarization in L4 C-nociceptors.
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Affiliation(s)
- Laiche Djouhri
- Department of Physiology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia
- Department of Clinical and Molecular Pharmacology, Institute of Translational Medicine, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, United Kingdom
| | - Trevor Smith
- Wolfson CARD, Neurorestoration Group, King's College London, London, United Kingdom
| | - Ahmad Ahmeda
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Mohammad Alotaibi
- Department of Physiology, College of Medicine, King Saud University, Riyadh, Saudi Arabia
| | - Xiechuan Weng
- State Key Laboratory of Proteomics, Department of Neurobiology, Beijing Institute of Basic Medical Sciences, Beijing, China
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Djouhri L, Smith T, Alotaibi M, Weng X. Membrane potential oscillations are not essential for spontaneous firing generation in L4 Aβ-afferent neurons after L5 spinal nerve axotomy and are not mediated by HCN channels. Exp Physiol 2018; 103:1145-1156. [PMID: 29860719 DOI: 10.1113/ep087013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/23/2018] [Indexed: 01/01/2023]
Abstract
NEW FINDINGS What is the central question of this study? Is spontaneous activity (SA) in L4 dorsal root ganglion (DRG) neurons induced by L5 spinal nerve axotomy associated with membrane potential oscillations in these neurons, and if so, are these membrane oscillations mediated by HCN channels? What is the main finding and its importance? Unlike injured L5 DRG neurons, which have been shown to be incapable of firing spontaneously without membrane potential oscillations, membrane potential oscillations are not essential for SA generation in conducting 'uninjured' L4 neurons, and they are not mediated by HCN channels. These findings suggest that the underlying cellular mechanisms of SA in injured and 'uninjured' DRG neurons induced by spinal nerve injury are distinct. ABSTRACT The underlying cellular and molecular mechanisms of peripheral neuropathic pain are not fully understood. However, preclinical studies using animal models suggest that this debilitating condition is driven partly by aberrant spontaneous activity (SA) in injured and uninjured dorsal root ganglion (DRG) neurons, and that SA in injured DRG neurons is triggered by subthreshold membrane potential oscillations (SMPOs). Here, using in vivo intracellular recording from control L4-DRG neurons, and ipsilateral L4-DRG neurons in female Wistar rats that had previously undergone L5 spinal nerve axotomy (SNA), we examined whether conducting 'uninjured' L4-DRG neurons in SNA rats exhibit SMPOs, and if so, whether such SMPOs are associated with SA in those L4 neurons, and whether they are mediated by hyperpolarization-activated cyclic nucleotide gated (HCN) channels. We found that 7 days after SNA: (a) none of the control A- or C-fibre DRG neurons showed SMPOs or SA, but 50%, 43% and 0% of spontaneously active cutaneous L4 Aβ-low threshold mechanoreceptors, Aβ-nociceptors and C-nociceptors exhibited SMPOs, respectively, in SNA rats with established neuropathic pain behaviors; (b) neither SMPOs nor SA in L4 Aβ-neurons was suppressed by blocking HCN channels with ZD7288 (10 mg kg-1 , i.v.); and (c) there is a tendency for female rats to show greater pain hypersensitivity than male rats. These results suggest that SMPOs are linked to SA only in some of the conducting L4 Aβ-neurons, that such oscillations are not a prerequisite for SA generation in those L4 A- or C-fibre neurons, and that HCN channels are not involved in their electrogenesis.
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Affiliation(s)
- L Djouhri
- Department of Physiology, College of Medicine, Alfaisal University, PO Box 50927, Riyadh, 11533, Saudi Arabia
| | - T Smith
- Wolfson CARD, Neurorestoration Group, Hodgkin Building, King's College London, Guy's Campus, London, SE1 1UL, UK
| | - M Alotaibi
- Department of Physiology, College of Medicine, King Saud University, PO Box 7805, Riyadh, 11472, Saudi Arabia
| | - X Weng
- Department of Neurobiology and State Key Laboratory of Proteomics, Beijing Institute of Basic Medical Sciences, Beijing, 100850, China
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26
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Marler TL, Wright AB, Elmslie KL, Heier AK, Remily E, Kim-Han JS, Ramachandra R, Elmslie KS. Na V1.9 channels in muscle afferent neurons and axons. J Neurophysiol 2018; 120:1032-1044. [PMID: 29847236 DOI: 10.1152/jn.00573.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The exercise pressor reflex (EPR) is activated by muscle contractions to increase heart rate and blood pressure during exercise. While this reflex is beneficial in healthy individuals, the reflex activity is exaggerated in patients with cardiovascular disease, which is associated with increased mortality. Group III and IV afferents mediate the EPR and have been shown to express both tetrodotoxin-sensitive (TTX-S, NaV1.6, and NaV1.7) and -resistant (TTX-R, NaV1.8, and NaV1.9) voltage-gated sodium (NaV) channels, but NaV1.9 current has not yet been demonstrated. Using a F--containing internal solution, we found a NaV current in muscle afferent neurons that activates at around -70 mV with slow activation and inactivation kinetics, as expected from NaV1.9 current. However, this current ran down with time, which resulted, at least in part, from increased steady-state inactivation since it was slowed by both holding potential hyperpolarization and a depolarized shift of the gating properties. We further show that, following NaV1.9 current rundown (internal F-), application of the NaV1.8 channel blocker A803467 inhibited significantly more TTX-R current than we had previously observed (internal Cl-), which suggests that NaV1.9 current did not rundown with that internal solution. Using immunohistochemistry, we found that the majority of group IV somata and axons were NaV1.9 positive. The majority of small diameter myelinated afferent somata (putative group III) were also NaV1.9 positive, but myelinated muscle afferent axons were rarely labeled. The presence of NaV1.9 channels in muscle afferents supports a role for these channels in activation and maintenance of the EPR. NEW & NOTEWORTHY Small diameter muscle afferents signal pain and muscle activity levels. The muscle activity signals drive the cardiovascular system to increase muscle blood flow, but these signals can become exaggerated in cardiovascular disease to exacerbate cardiac damage. The voltage-dependent sodium channel NaV1.9 plays a unique role in controlling afferent excitability. We show that NaV1.9 channels are expressed in muscle afferents, which supports these channels as a target for drug development to control hyperactivity of these neurons.
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Affiliation(s)
- Tyler L Marler
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Andrew B Wright
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Kristina L Elmslie
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Ankeeta K Heier
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Ethan Remily
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Jeong Sook Kim-Han
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Renuka Ramachandra
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
| | - Keith S Elmslie
- The Baker Laboratory of Pharmacology, Department of Pharmacology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, Missouri
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Behavioral, cellular and molecular maladaptations covary with exposure to pyridostigmine bromide in a rat model of gulf war illness pain. Toxicol Appl Pharmacol 2018; 352:119-131. [PMID: 29803855 DOI: 10.1016/j.taap.2018.05.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 05/16/2018] [Accepted: 05/20/2018] [Indexed: 12/12/2022]
Abstract
Many veterans of Operation Desert Storm (ODS) struggle with the chronic pain of Gulf War Illness (GWI). Exposure to insecticides and pyridostigmine bromide (PB) have been implicated in the etiology of this multisymptom disease. We examined the influence of 3 (DEET (N,N-diethyl-meta-toluamide), permethrin, chlorpyrifos) or 4 GW agents (DEET, permethrin, chlorpyrifos, pyridostigmine bromide (PB)) on the post-exposure ambulatory and resting behaviors of rats. In three independent studies, rats that were exposed to all 4 agents consistently developed both immediate and delayed ambulatory deficits that persisted at least 16 weeks after exposures had ceased. Rats exposed to a 3 agent protocol (PB excluded) did not develop any ambulatory deficits. Cellular and molecular studies on nociceptors harvested from 16WP (weeks post-exposure) rats indicated that vascular nociceptor Nav1.9 mediated currents were chronically potentiated following the 4 agent protocol but not following the 3 agent protocol. Muscarinic linkages to muscle nociceptor TRPA1 were also potentiated in the 4 agent but not the 3 agent, PB excluded, protocol. Although Kv7 activity changes diverged from the behavioral data, a Kv7 opener, retigabine, transiently reversed ambulation deficits. We concluded that PB played a critical role in the development of pain-like signs in a GWI rat model and that shifts in Nav1.9 and TRPA1 activity were critical to the expression of these pain behaviors.
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28
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Wang G, Long C, Liu W, Xu C, Zhang M, Li Q, Lu Q, Meng P, Li D, Rong M, Sun Z, Luo X, Lai R. Novel Sodium Channel Inhibitor From Leeches. Front Pharmacol 2018; 9:186. [PMID: 29559913 PMCID: PMC5845541 DOI: 10.3389/fphar.2018.00186] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 02/19/2018] [Indexed: 12/16/2022] Open
Abstract
Considering blood-sucking habits of leeches from surviving strategy of view, it can be hypothesized that leech saliva has analgesia or anesthesia functions for leeches to stay undetected by the host. However, no specific substance with analgesic function has been reported from leech saliva although clinical applications strongly indicated that leech therapy produces a strong and long lasting pain-reducing effect. Herein, a novel family of small peptides (HSTXs) including 11 members which show low similarity with known peptides was identified from salivary glands of the leech Haemadipsa sylvestris. A typical HSTX is composed of 22-25 amino acid residues including four half-cysteines, forming two intra-molecular disulfide bridges, and an amidated C-terminus. HSTX-I exerts significant analgesic function by specifically inhibiting voltage-gated sodium (NaV) channels (NaV1.8 and NaV1.9) which contribute to action potential electrogenesis in neurons and potential targets to develop analgesics. This study reveals that sodium channel inhibitors are analgesic substances in the leech. HSTXs are excellent candidates or templates for development of analgesics.
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Affiliation(s)
- Gan Wang
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China
| | - Chengbo Long
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China
| | - Weihui Liu
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China
| | - Cheng Xu
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China
| | - Min Zhang
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China.,Graduate School of University of Chinese Academy of Sciences, Beijing, China
| | - Qiong Li
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
| | - Qiumin Lu
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China.,Sino-African Joint Research Center, Chinese Academy of Sciences, Wuhan, China
| | - Ping Meng
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China
| | - Dongsheng Li
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China
| | - Mingqiang Rong
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China.,Sino-African Joint Research Center, Chinese Academy of Sciences, Wuhan, China
| | - Zhaohui Sun
- Department of Clinical Laboratory, Guangzhou General Hospital of Guangzhou Military Command of PLA, Guangzhou, China
| | - Xiaodong Luo
- State Key Laboratory of Phytochemistry and Plant Resources in West China, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, China
| | - Ren Lai
- Key Laboratory of Bioactive Peptides of Yunnan Province/Key Laboratory of Animal Models and Human Disease Mechanisms of Chinese Academy of Sciences, Kunming Institute of Zoology, Kunming, China.,Life Sciences College of Nanjing Agricultural University, Nanjing, China
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30
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Song Y, Gao L. The effect of acute dissociation on the electrophysiological properties of rat dorsal root ganglion neurons. Somatosens Mot Res 2018; 35:11-17. [PMID: 29471715 DOI: 10.1080/08990220.2018.1439000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The acutely dissociated neurons from the dorsal root ganglia (DRGs) are extensively used. The effects of acute dissociation on the properties of these neurons are, however, not clear. In this study, the action potentials (APs) were recorded from both acutely dissociated and in vivo identified DRG neurons with patch clamp and sharp electrode recording techniques, respectively. We found that acute dissociation slowed both the depolarizing and repolarizing rate of APs, and elongated the AP duration (APD). The lower recording temperature presented in the acutely dissociated neurons contributed to about 10% of these differences. The major contributor of these differences was possibly modulation of the mRNA expression especially those of the ion channels, as suggested by our observation that acute dissociation significantly reduced the mRNA abundance of Nav1.6-1.9. In conclusion, acute dissociation altered the electrophysiological properties of the DRG neurons; the disrupted gene-expression pattern may contribute to this effect.
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Affiliation(s)
- Yuanlong Song
- a Department of Physiology , School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.,b Institutes of Brain Research , Huazhong University of Science and Technology , Wuhan , China
| | - Linlin Gao
- a Department of Physiology , School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology , Wuhan , China.,b Institutes of Brain Research , Huazhong University of Science and Technology , Wuhan , China
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Wu Y, Ma H, Zhang F, Zhang C, Zou X, Cao Z. Selective Voltage-Gated Sodium Channel Peptide Toxins from Animal Venom: Pharmacological Probes and Analgesic Drug Development. ACS Chem Neurosci 2018; 9:187-197. [PMID: 29161016 DOI: 10.1021/acschemneuro.7b00406] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Voltage-gated sodium channels (Navs) play critical roles in action potential generation and propagation. Nav channelopathy as well as pathological sensitization contribute to allodynia and hyperalgesia. Recent evidence has demonstrated the significant roles of Nav subtypes (Nav1.3, 1.7, 1.8, and 1.9) in nociceptive transduction, and therefore these Navs may represent attractive targets for analgesic drug discovery. Animal toxins are structurally diverse peptides that are highly potent yet selective on ion channel subtypes and therefore represent valuable probes to elucidate the structures, gating properties, and cellular functions of ion channels. In this review, we summarize recent advances on peptide toxins from animal venom that selectively target Nav1.3, 1.7, 1.8, and 1.9, along with their potential in analgesic drug discovery.
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Affiliation(s)
- Ying Wu
- Jiangsu Provincial Key Laboratory for TCM Evaluation
and Translational Development, China Pharmaceutical University, Nanjing 211198, China
| | - Hui Ma
- Jiangsu Provincial Key Laboratory for TCM Evaluation
and Translational Development, China Pharmaceutical University, Nanjing 211198, China
| | - Fan Zhang
- Jiangsu Provincial Key Laboratory for TCM Evaluation
and Translational Development, China Pharmaceutical University, Nanjing 211198, China
| | - Chunlei Zhang
- Jiangsu Provincial Key Laboratory for TCM Evaluation
and Translational Development, China Pharmaceutical University, Nanjing 211198, China
| | - Xiaohan Zou
- Jiangsu Provincial Key Laboratory for TCM Evaluation
and Translational Development, China Pharmaceutical University, Nanjing 211198, China
| | - Zhengyu Cao
- Jiangsu Provincial Key Laboratory for TCM Evaluation
and Translational Development, China Pharmaceutical University, Nanjing 211198, China
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32
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Difference of acute dissociation and 1-day culture on the electrophysiological properties of rat dorsal root ganglion neurons. J Physiol Biochem 2018; 74:207-221. [DOI: 10.1007/s13105-017-0606-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 12/29/2017] [Indexed: 10/24/2022]
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33
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Gawlak M, Szulczyk B, Berłowski A, Grzelka K, Stachurska A, Pełka J, Czarzasta K, Małecki M, Kurowski P, Nurowska E, Szulczyk P. Age-dependent expression of Nav1.9 channels in medial prefrontal cortex pyramidal neurons in rats. Dev Neurobiol 2017; 77:1371-1384. [PMID: 28913981 DOI: 10.1002/dneu.22537] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 09/08/2017] [Accepted: 09/10/2017] [Indexed: 12/19/2022]
Abstract
Developmental changes that occur in the prefrontal cortex during adolescence alter behavior. These behavioral alterations likely stem from changes in prefrontal cortex neuronal activity, which may depend on the properties and expression of ion channels. Nav1.9 sodium channels conduct a Na+ current that is TTX resistant with a low threshold and noninactivating over time. The purpose of this study was to assess the presence of Nav1.9 channels in medial prefrontal cortex (mPFC) layer II and V pyramidal neurons in young (20-day old), late adolescent (60-day old), and adult (6- to 7-month old) rats. First, we demonstrated that layer II and V mPFC pyramidal neurons in slices obtained from young rats exhibited a TTX-resistant, low-threshold, noninactivating, and voltage-dependent Na+ current. The mRNA expression of the SCN11a gene (which encodes the Nav1.9 channel) in mPFC tissue was significantly higher in young rats than in late adolescent and adult rats. Nav1.9 protein was immunofluorescently labeled in mPFC cells in slices and analyzed via confocal microscopy. Nav1.9 immunolabeling was present in layer II and V mPFC pyramidal neurons and was more prominent in the neurons of young rats than in the neurons of late adolescent and adult rats. We conclude that Nav1.9 channels are expressed in layer II and V mPFC pyramidal neurons and that Nav1.9 protein expression in the mPFC pyramidal neurons of late adolescent and adult rats is lower than that in the neurons of young rats. © 2017 Wiley Periodicals, Inc. Develop Neurobiol 77: 1371-1384, 2017.
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Affiliation(s)
- Maciej Gawlak
- Laboratory of Physiology and Pathophysiology, Centre for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
| | - Bartłomiej Szulczyk
- Department of Drug Technology and Pharmaceutical Biotechnology, The Medical University of Warsaw, Warsaw, Poland
| | - Adam Berłowski
- Department of Physiology and Pathophysiology, The Medical University of Warsaw, Warsaw, Poland
| | - Katarzyna Grzelka
- Laboratory of Physiology and Pathophysiology, Centre for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
| | - Anna Stachurska
- Department of Molecular Biology, The Medical University of Warsaw, Warsaw, Poland
| | - Justyna Pełka
- Department of Physiology and Pathophysiology, The Medical University of Warsaw, Warsaw, Poland
| | - Katarzyna Czarzasta
- Laboratory of Experimental and Clinical Physiology, Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Maciej Małecki
- Department of Molecular Biology, The Medical University of Warsaw, Warsaw, Poland
| | - Przemysław Kurowski
- Laboratory of Physiology and Pathophysiology, Centre for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
| | - Ewa Nurowska
- Laboratory of Physiology and Pathophysiology, Centre for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
| | - Paweł Szulczyk
- Laboratory of Physiology and Pathophysiology, Centre for Preclinical Research and Technology, The Medical University of Warsaw, Warsaw, Poland
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Bulleyaconitine A preferably reduces tetrodotoxin-sensitive sodium current in uninjured dorsal root ganglion neurons of neuropathic rats probably via inhibition of protein kinase C. Pain 2017; 158:2169-2180. [DOI: 10.1097/j.pain.0000000000001018] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Huang J, Vanoye CG, Cutts A, Goldberg YP, Dib-Hajj SD, Cohen CJ, Waxman SG, George AL. Sodium channel NaV1.9 mutations associated with insensitivity to pain dampen neuronal excitability. J Clin Invest 2017; 127:2805-2814. [PMID: 28530638 DOI: 10.1172/jci92373] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2016] [Accepted: 03/23/2017] [Indexed: 02/05/2023] Open
Abstract
Voltage-gated sodium channel (NaV) mutations cause genetic pain disorders that range from severe paroxysmal pain to a congenital inability to sense pain. Previous studies on NaV1.7 and NaV1.8 established clear relationships between perturbations in channel function and divergent clinical phenotypes. By contrast, studies of NaV1.9 mutations have not revealed a clear relationship of channel dysfunction with the associated and contrasting clinical phenotypes. Here, we have elucidated the functional consequences of a NaV1.9 mutation (L1302F) that is associated with insensitivity to pain. We investigated the effects of L1302F and a previously reported mutation (L811P) on neuronal excitability. In transfected heterologous cells, the L1302F mutation caused a large hyperpolarizing shift in the voltage-dependence of activation, leading to substantially enhanced overlap between activation and steady-state inactivation relationships. In transfected small rat dorsal root ganglion neurons, expression of L1302F and L811P evoked large depolarizations of the resting membrane potential and impaired action potential generation. Therefore, our findings implicate a cellular loss of function as the basis for impaired pain sensation. We further demonstrated that a U-shaped relationship between the resting potential and the neuronal action potential threshold explains why NaV1.9 mutations that evoke small degrees of membrane depolarization cause hyperexcitability and familial episodic pain disorder or painful neuropathy, while mutations evoking larger membrane depolarizations cause hypoexcitability and insensitivity to pain.
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Affiliation(s)
- Jianying Huang
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine; and Rehabilitation Research Center, Veterans Administration Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Carlos G Vanoye
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Alison Cutts
- Xenon Pharmaceuticals, Burnaby, British Columbia, Canada
| | | | - Sulayman D Dib-Hajj
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine; and Rehabilitation Research Center, Veterans Administration Connecticut Healthcare System, West Haven, Connecticut, USA
| | | | - Stephen G Waxman
- Department of Neurology and Center for Neuroscience and Regeneration Research, Yale University School of Medicine; and Rehabilitation Research Center, Veterans Administration Connecticut Healthcare System, West Haven, Connecticut, USA
| | - Alfred L George
- Department of Pharmacology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
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Li K, Zhong X, Yang S, Luo Z, Li K, Liu Y, Cai S, Gu H, Lu S, Zhang H, Wei Y, Zhuang J, Zhuo Y, Fan Z, Ge J. HiPSC-derived retinal ganglion cells grow dendritic arbors and functional axons on a tissue-engineered scaffold. Acta Biomater 2017; 54:117-127. [PMID: 28216299 DOI: 10.1016/j.actbio.2017.02.032] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Revised: 02/08/2017] [Accepted: 02/15/2017] [Indexed: 12/21/2022]
Abstract
Numerous therapeutic procedures in modern medical research rely on the use of tissue engineering for the treatment of retinal diseases. However, the cell source and the transplantation method are still a limitation. Previously, it was reported that a self-organizing three-dimensional neural retina can be induced from human-induced pluripotent stem cells (hiPSCs). In this study, we disclose the generation of retinal ganglion cells (RGCs) from the neural retina and their seeding on a biodegradable poly (lactic-co-glycolic acid) (PLGA) scaffold to create an engineered RGC-scaffold biomaterial. Moreover, we explored the dendritic arbor, branching point, functional axon and action potential of the biomaterial. Finally, the cell-scaffold was transplanted into the intraocular environment of rabbits and rhesus monkeys. STATEMENT OF SIGNIFICANCE As a part of the mammalian central nervous system (CNS), the retinal ganglion cell (RGC) shows little regenerative capacity. With the use of medical biomaterial for cells seeding and deliver, a new domain is now emerging that uses tissue engineering therapy for retinal disease. However, previous studies utilized RGCs from rodent model, which has limitations for human disease treatment. In the present study, we generated RGCs from hiPSCs-3D neural retina and then seeded these RGCs on PLGA scaffold to create an engineered RGC-scaffold biomaterial. Moreover, we assessed the transplantation method for biomaterial in vivo. Our study provides a technique to produce the engineered human RGC-scaffold biomaterial.
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Affiliation(s)
- Kangjun Li
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Xiufeng Zhong
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Sijing Yang
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Ziming Luo
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Kang Li
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Ying Liu
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Song Cai
- Department of Anatomy and Neurobiology, Zhongshan School of Medicine, Yet-Sen University, Guangzhou, Guangdong, China
| | - Huaiyu Gu
- Department of Anatomy and Neurobiology, Zhongshan School of Medicine, Yet-Sen University, Guangzhou, Guangdong, China
| | - Shoutao Lu
- Bai Duoan Medical Equipment Company, Qihe, Shandong, China
| | - Haijun Zhang
- Bai Duoan Medical Equipment Company, Qihe, Shandong, China
| | - Yantao Wei
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Jing Zhuang
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Yehong Zhuo
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Zhigang Fan
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China
| | - Jian Ge
- State Key Laboratory of Ophthalmology, Key Lab of Ophthalmology and Visual Science, Zhongshan Ophthalmic Center, Sun Yet-Sen University, Guangzhou, Guangdong, China.
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Han C, Yang Y, Te Morsche RH, Drenth JPH, Politei JM, Waxman SG, Dib-Hajj SD. Familial gain-of-function Na v1.9 mutation in a painful channelopathy. J Neurol Neurosurg Psychiatry 2017; 88:233-240. [PMID: 27503742 DOI: 10.1136/jnnp-2016-313804] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 06/23/2016] [Accepted: 07/19/2016] [Indexed: 11/04/2022]
Abstract
OBJECTIVE Gain-of-function mutations in Nav1.9 have been identified in three families with rare heritable pain disorders, and in patients with painful small-fibre neuropathy. Identification and functional assessment of new Nav1.9 mutations will help to elucidate the phenotypic spectrum of Nav1.9 channelopathies. METHODS Patients from a large family with early-onset pain symptoms were evaluated by clinical examination and genomic screening for mutations in SCN9A and SCN11A. Electrophysiological recordings and multistate modelling analysis were implemented for functional analyses. RESULTS A novel Nav1.9 mutation, p.Arg222His, was identified in patients with early-onset pain in distal extremities including joints and gastrointestinal disturbances, but was absent from an asymptomatic blood relative. This mutation alters channel structure by substituting the highly conserved first arginine residue in transmembrane segment 4 (domain 1), the voltage sensor, with histidine. Voltage-clamp recordings demonstrate a hyperpolarising shift and acceleration of activation of the p.Arg222His mutant channel, which make it easier to open the channel. When expressed in dorsal root ganglion neurons, mutant p.Arg222His channels increase excitability via a depolarisation of resting potential and increased evoked firing. CONCLUSIONS This study expands the spectrum of heritable pain disorders linked to gain-of-function mutations in Nav1.9, strengthening human validation of this channel as a potential therapeutic target for pain.
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Affiliation(s)
- Chongyang Han
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut, USA
| | - Yang Yang
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut, USA
| | - Rene H Te Morsche
- Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Joost P H Drenth
- Department of Gastroenterology and Hepatology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | - Juan M Politei
- Department of Neurology, Fundación para el Estudio de las Enfermedades Neurometabólicas, Buenos Aires, Argentina
| | - Stephen G Waxman
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut, USA
| | - Sulayman D Dib-Hajj
- Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Neuroscience and Regeneration Research, Yale University School of Medicine, New Haven, Connecticut, USA.,Center for Restoration of Nervous System Function, Veterans Affairs Medical Center, West Haven, Connecticut, USA
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Flunker LK, Nutter TJ, Johnson RD, Cooper BY. DEET potentiates the development and persistence of anticholinesterase dependent chronic pain signs in a rat model of Gulf War Illness pain. Toxicol Appl Pharmacol 2016; 316:48-62. [PMID: 28025109 DOI: 10.1016/j.taap.2016.12.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 12/16/2016] [Accepted: 12/20/2016] [Indexed: 12/18/2022]
Abstract
Exposure to DEET (N,N-diethyl-meta-toluamide) may have influenced the pattern of symptoms observed in soldiers with GWI (Gulf War Illness; Haley and Kurt, 1997). We examined how the addition of DEET (400mg/kg; 50% topical) to an exposure protocol of permethrin (2.6mg/kg; topical), chlorpyrifos (CP; 120mg/kg), and pyridostigmine bromide (PB;13mg/kg) altered the emergence and pattern of pain signs in an animal model of GWI pain (Nutter et al., 2015). Rats underwent behavioral testing before, during and after a 4week exposure: 1) hindlimb pressure withdrawal threshold; 2) ambulation (movement distance and rate); and 3) resting duration. Additional studies were conducted to assess the influence of acute DEET (10-100μM) on muscle and vascular nociceptor Kv7, KDR, Nav1.8 and Nav1.9. We report that a 50% concentration of DEET enhanced the development and persistence of pain-signs. Rats exposed to all 4 compounds exhibited ambulation deficits that appeared 5-12weeks post-exposure and persisted through weeks 21-24. Rats exposed to only three agents (CP or PB excluded), did not fully develop ambulation deficits. When PB was excluded, rats also developed rest duration pain signs, in addition to ambulation deficits. There was no evidence that physiological doses of DEET acutely modified nociceptor Kv7, KDR, Nav1.8 or Nav1.9 activities. Nevertheless, DEET augmented protocols decreased the conductance of Kv7 expressed in vascular nociceptors harvested from chronically exposed rats. We concluded that DEET enhanced the development and persistence of pain behaviors, but the anticholinesterases CP and PB played a determinant role.
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Affiliation(s)
- L K Flunker
- Division of Neuroscience, Dept. of Oral and Maxillofacial Surgery, Box 100416, JHMHC, University of Florida College of Dentistry, Gainesville, FL 32610, USA.
| | - T J Nutter
- Division of Neuroscience, Dept. of Oral and Maxillofacial Surgery, Box 100416, JHMHC, University of Florida College of Dentistry, Gainesville, FL 32610, USA.
| | - R D Johnson
- Dept. of Physiological Sciences, University of Florida College of Veterinary Science, Gainesville, FL 32610, USA.
| | - B Y Cooper
- Division of Neuroscience, Dept. of Oral and Maxillofacial Surgery, Box 100416, JHMHC, University of Florida College of Dentistry, Gainesville, FL 32610, USA.
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39
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Reduced excitability and impaired nociception in peripheral unmyelinated fibers from Nav1.9-null mice. Pain 2016; 158:58-67. [DOI: 10.1097/j.pain.0000000000000723] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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40
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Lin Z, Santos S, Padilla K, Printzenhoff D, Castle NA. Biophysical and Pharmacological Characterization of Nav1.9 Voltage Dependent Sodium Channels Stably Expressed in HEK-293 Cells. PLoS One 2016; 11:e0161450. [PMID: 27556810 PMCID: PMC4996523 DOI: 10.1371/journal.pone.0161450] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Accepted: 08/07/2016] [Indexed: 11/19/2022] Open
Abstract
The voltage dependent sodium channel Nav1.9, is expressed preferentially in peripheral sensory neurons and has been linked to human genetic pain disorders, which makes it target of interest for the development of new pain therapeutics. However, characterization of Nav1.9 pharmacology has been limited due in part to the historical difficulty of functionally expressing recombinant channels. Here we report the successful generation and characterization of human, mouse and rat Nav1.9 stably expressed in human HEK-293 cells. These cells exhibit slowly activating and inactivating inward sodium channel currents that have characteristics of native Nav1.9. Optimal functional expression was achieved by coexpression of Nav1.9 with β1/β2 subunits. While recombinantly expressed Nav1.9 was found to be sensitive to sodium channel inhibitors TC-N 1752 and tetracaine, potency was up to 100-fold less than reported for other Nav channel subtypes despite evidence to support an interaction with the canonical local anesthetic (LA) binding region on Domain 4 S6. Nav1.9 Domain 2 S6 pore domain contains a unique lysine residue (K799) which is predicted to be spatially near the local anesthetic interaction site. Mutation of this residue to the consensus asparagine (K799N) resulted in an increase in potency for tetracaine, but a decrease for TC-N 1752, suggesting that this residue can influence interaction of inhibitors with the Nav1.9 pore. In summary, we have shown that stable functional expression of Nav1.9 in the widely used HEK-293 cells is possible, which opens up opportunities to better understand channel properties and may potentially aid identification of novel Nav1.9 based pharmacotherapies.
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Affiliation(s)
- Zhixin Lin
- Neuroscience and Pain Research Unit, Pfizer Inc., Durham, North Carolina, United States of America
- * E-mail:
| | - Sonia Santos
- Neuroscience and Pain Research Unit, Pfizer Inc., Durham, North Carolina, United States of America
| | - Karen Padilla
- Neuroscience and Pain Research Unit, Pfizer Inc., Durham, North Carolina, United States of America
| | - David Printzenhoff
- Neuroscience and Pain Research Unit, Pfizer Inc., Durham, North Carolina, United States of America
| | - Neil A. Castle
- Neuroscience and Pain Research Unit, Pfizer Inc., Durham, North Carolina, United States of America
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41
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Song Y, Zhang M, Tao X, Xu Z, Zhang L, Zheng Y, Zhu M, Gao L. A Single-Cell-Type Real-Time PCR Method Based on a Modified Patch-Pipette Cell Harvesting System. Mol Biotechnol 2016; 58:558-65. [DOI: 10.1007/s12033-016-9953-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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42
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L5 spinal nerve axotomy induces sensitization of cutaneous L4 Aβ-nociceptive dorsal root ganglion neurons in the rat in vivo. Neurosci Lett 2016; 624:72-7. [DOI: 10.1016/j.neulet.2016.05.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 05/06/2016] [Accepted: 05/07/2016] [Indexed: 12/21/2022]
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43
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Sodium Channels, Mitochondria, and Axonal Degeneration in Peripheral Neuropathy. Trends Mol Med 2016; 22:377-390. [DOI: 10.1016/j.molmed.2016.03.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 03/21/2016] [Accepted: 03/22/2016] [Indexed: 12/19/2022]
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44
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Kuga N, Tanioka A, Hagihara K, Kawai T. Modulation of afferent nerve activity by prostaglandin E2 upon urinary bladder distension in rats. Exp Physiol 2016; 101:577-87. [PMID: 26841236 DOI: 10.1113/ep085418] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Accepted: 01/29/2016] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? It has been widely assumed that C fibres innervating the bladder are mainly excited in overactive bladder syndrome. However, it remains unclear whether Aδ fibres are also activated in pathological conditions. What is the main finding and its importance? We found that a certain population of Aδ fibres, which become active specifically at a bladder pressure of more than 15 cmH2 O in normal conditions, showed increased excitability in conditions of prostaglandin E2 -induced overactive bladder. This result suggests that a certain population of Aδ fibres, together with C fibres, triggers pathophysiological activity. In overactive bladder syndrome, afferent C fibres innervating the bladder show an increased activity level. However, it remains unclear whether all C fibres are highly activated and whether Aδ fibres, the other type of bladder afferent fibre, are also involved in pathological conditions. To address these questions, we analysed the relationship between bladder pressure and single-unit firing patterns of afferent nerves in the left L6 dorsal roots in living rats. The recorded fibres were classified as Aδ fibres or C fibres based on the response to 0.3 μm tetrodotoxin. Certain populations of both Aδ fibres and C fibres were activated at bladder pressures below 15 cmH2 O (classified as low-threshold fibres), indicating their potential contribution to detection of normal bladder filling. Intravesical administration of prostaglandin E2 (PGE2 ) induced hyperexcitation in approximately half of such C fibres, whereas the activity patterns of low-threshold Aδ fibres were unchanged. All fibres, regardless of type, which were almost silent in control conditions (classified as high-threshold fibres), were activated by application of PGE2 . Notably, the firing patterns of Aδ fibres, rather than C fibres, were highly time locked to PGE2 -induced micro-oscillation of bladder pressure. These modulatory effects of PGE2 on Aδ fibres and C fibres might trigger pathophysiological activity together in overactive bladder syndrome.
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Affiliation(s)
- Nahoko Kuga
- Watarase Research Center, Kyorin Pharmaceutical Co., Ltd, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, Japan
| | - Asao Tanioka
- Watarase Research Center, Kyorin Pharmaceutical Co., Ltd, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, Japan
| | - Koichiro Hagihara
- Watarase Research Center, Kyorin Pharmaceutical Co., Ltd, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, Japan
| | - Tomoyuki Kawai
- Watarase Research Center, Kyorin Pharmaceutical Co., Ltd, Nogi, Nogi-machi, Shimotsuga-gun, Tochigi, Japan
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Hockley JRF, Winchester WJ, Bulmer DC. The voltage-gated sodium channel NaV 1.9 in visceral pain. Neurogastroenterol Motil 2016; 28:316-26. [PMID: 26462871 DOI: 10.1111/nmo.12698] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 09/06/2015] [Indexed: 12/16/2022]
Abstract
BACKGROUND Visceral pain is a common symptom for patients with gastrointestinal (GI) disease. It is unpleasant, debilitating, and represents a large unmet medical need for effective clinical treatments. Recent studies have identified NaV 1.9 as an important regulator of afferent sensitivity in visceral pain pathways to mechanical and inflammatory stimuli, suggesting that NaV 1.9 could represent an important therapeutic target for the treatment of visceral pain. This potential has been highlighted by the identification of patients who have an insensitivity to pain or painful neuropathies associated with mutations in SCN11A, the gene encoding voltage-gated sodium channel subtype 1.9 (NaV 1.9). PURPOSE Here, we address the role of NaV 1.9 in visceral pain and what known human NaV 1.9 mutants can tell us about NaV 1.9 function in gut physiology and pathophysiology.
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Affiliation(s)
- J R F Hockley
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | | | - D C Bulmer
- Wingate Institute of Neurogastroenterology, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK.,National Centre for Bowel Research and Surgical Innovation, Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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46
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Djouhri L. Electrophysiological evidence for the existence of a rare population of C-fiber low threshold mechanoreceptive (C-LTM) neurons in glabrous skin of the rat hindpaw. Neurosci Lett 2016; 613:25-9. [DOI: 10.1016/j.neulet.2015.12.040] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2015] [Revised: 12/17/2015] [Accepted: 12/18/2015] [Indexed: 12/31/2022]
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47
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Djouhri L. Aδ-fiber low threshold mechanoreceptors innervating mammalian hairy skin: A review of their receptive, electrophysiological and cytochemical properties in relation to Aδ-fiber high threshold mechanoreceptors. Neurosci Biobehav Rev 2016; 61:225-38. [DOI: 10.1016/j.neubiorev.2015.12.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Revised: 12/10/2015] [Accepted: 12/18/2015] [Indexed: 01/06/2023]
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48
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Upregulation of Ih expressed in IB4-negative Aδ nociceptive DRG neurons contributes to mechanical hypersensitivity associated with cervical radiculopathic pain. Sci Rep 2015; 5:16713. [PMID: 26577374 PMCID: PMC4649360 DOI: 10.1038/srep16713] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 10/19/2015] [Indexed: 11/30/2022] Open
Abstract
Cervical radiculopathy represents aberrant mechanical hypersensitivity. Primary sensory neuron’s ability to sense mechanical force forms mechanotransduction. However, whether this property undergoes activity-dependent plastic changes and underlies mechanical hypersensitivity associated with cervical radiculopathic pain (CRP) is not clear. Here we show a new CRP model producing stable mechanical compression of dorsal root ganglion (DRG), which induces dramatic behavioral mechanical hypersensitivity. Amongst nociceptive DRG neurons, a mechanically sensitive neuron, isolectin B4 negative Aδ-type (IB4− Aδ) DRG neuron displays spontaneous activity with hyperexcitability after chronic compression of cervical DRGs. Focal mechanical stimulation on somata of IB4- Aδ neuron induces abnormal hypersensitivity. Upregulated HCN1 and HCN3 channels and increased Ih current on this subset of primary nociceptors underlies the spontaneous activity together with neuronal mechanical hypersensitivity, which further contributes to the behavioral mechanical hypersensitivity associated with CRP. This study sheds new light on the functional plasticity of a specific subset of nociceptive DRG neurons to mechanical stimulation and reveals a novel mechanism that could underlie the mechanical hypersensitivity associated with cervical radiculopathy.
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Assessment of TTX-s and TTX-r Action Potential Conduction along Neurites of NGF and GDNF Cultured Porcine DRG Somata. PLoS One 2015; 10:e0139107. [PMID: 26407014 PMCID: PMC4583387 DOI: 10.1371/journal.pone.0139107] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 09/09/2015] [Indexed: 12/19/2022] Open
Abstract
Nine isoforms of voltage-gated sodium channels (NaV) have been characterized and in excitable tissues they are responsible for the initiation and conduction of action potentials. For primary afferent neurons residing in dorsal root ganglia (DRG), individual neurons may express multiple NaV isoforms extending the neuron’s functional capabilities. Since expression of NaV isoforms can be differentially regulated by neurotrophic factors we have examined the functional consequences of exposure to either nerve growth factor (NGF) or glial cell line-derived neurotrophic factor (GDNF) on action potential conduction in outgrowing cultured porcine neurites of DRG neurons. Calcium signals were recorded using the exogenous intensity based calcium indicator Fluo-8®, AM. In 94 neurons, calcium signals were conducted along neurites in response to electrical stimulation of the soma. At an image acquisition rate of 25 Hz it was possible to discern calcium transients in response to individual electrical stimuli. The peak amplitude of electrically-evoked calcium signals was limited by the ability of the neuron to follow the stimulus frequency. The stimulus frequency required to evoke a half-maximal calcium response was approximately 3 Hz at room temperature. In 13 of 14 (93%) NGF-responsive neurites, TTX-r NaV isoforms alone were sufficient to support propagated signals. In contrast, calcium signals mediated by TTX-r NaVs were evident in only 4 of 11 (36%) neurites from somata cultured in GDNF. This establishes a basis for assessing action potential signaling using calcium imaging techniques in individual cultured neurites and suggests that, in the pig, afferent nociceptor classes relying on the functional properties of TTX-r NaV isoforms, such as cold-nociceptors, most probably derive from NGF-responsive DRG neurons.
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