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Liu L, Liang Z, Zhang L, Feng Z, Cao F, Zhang Y, Yang X, Zhang L, Wang J, Zhu Q. Corticothalamic input derived from corticospinal neurons contributes to chronic neuropathic pain after spinal cord injury. Exp Neurol 2024; 381:114923. [PMID: 39142366 DOI: 10.1016/j.expneurol.2024.114923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 08/01/2024] [Accepted: 08/12/2024] [Indexed: 08/16/2024]
Abstract
Neuropathic pain is a significant and persistent issue for individuals with spinal cord injuries (SCI), severely impacting their quality of life. While changes at the peripheral and spinal levels are known to contribute to SCI-related pain, whether and how supraspinal centers contribute to post SCI chronic neuropathic pain is poorly understood. Here, we first validated delayed development of chronic neuropathic pain in mice with moderate contusion SCI. To identify supraspinal regions involved in the pathology of neuropathic pain after SCI, we next performed an activity dependent genetic screening and identified multiple cortical and subcortical regions that were activated by innocuous tactile stimuli at a late stage following contusion SCI. Notably, chemogenetic inactivation of pain trapped neurons in the lateral thalamus alleviated neuropathic pain and reduced tactile stimuli evoked cortical overactivation. Retrograde tracing showed that contusion SCI led to enhanced corticothalamic axonal sprouting and over-activation of corticospinal neurons. Mechanistically, ablation or silencing of corticospinal neurons prevented the establishment or maintenance of chronic neuropathic pain following contusion SCI. These results highlighted a corticospinal-lateral thalamic feed-forward loop whose activation is required for the development and maintenance of chronic neuropathic pain after SCI. Our data thus shed lights into the central mechanisms underlying chronic neuropathic pain associated with SCI and the development of novel therapeutic avenues to treat refractory pain caused by traumatic brain or spinal cord injuries.
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Affiliation(s)
- Ling Liu
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhihou Liang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lei Zhang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Zhou Feng
- Department of Rehabilitation, Southwest Hospital, Army Medical University, Chongqing, China
| | - Fei Cao
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yunjian Zhang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Xiaoman Yang
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Lijie Zhang
- Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Jing Wang
- Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
| | - Qing Zhu
- Department of Neurology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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Sankaranarayanan I, Kume M, Mohammed A, Mwirigi JM, Inturi NN, Munro G, Petersen KA, Tavares-Ferreira D, Price TJ. Persistent changes in nociceptor translatomes govern hyperalgesic priming in mouse models. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.08.07.606891. [PMID: 39149295 PMCID: PMC11326310 DOI: 10.1101/2024.08.07.606891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/17/2024]
Abstract
Hyperalgesic priming is a model system that has been widely used to understand plasticity in painful stimulus-detecting sensory neurons, called nociceptors. A key feature of this model system is that following priming, stimuli that do not normally cause hyperalgesia now readily provoke this state. We hypothesized that hyperalgesic priming occurs due to reorganization of translation of mRNA in nociceptors. To test this hypothesis, we used paclitaxel treatment as the priming stimulus and translating ribosome affinity purification (TRAP) to measure persistent changes in mRNA translation in Nav1.8+ nociceptors. TRAP sequencing revealed 161 genes with persistently altered mRNA translation in the primed state. We identified Gpr88 as upregulated and Metrn as downregulated. We confirmed a functional role for these genes, wherein a GPR88 agonist causes pain only in primed mice and established hyperalgesic priming is reversed by Meteorin. Our work demonstrates that altered nociceptor translatomes are causative in producing hyperalgesic priming.
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Affiliation(s)
- Ishwarya Sankaranarayanan
- Pain Neurobiology Research Group, Department of Neuroscience, Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
| | - Moeno Kume
- Pain Neurobiology Research Group, Department of Neuroscience, Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
| | - Ayaan Mohammed
- Pain Neurobiology Research Group, Department of Neuroscience, Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
| | - Juliet M Mwirigi
- Pain Neurobiology Research Group, Department of Neuroscience, Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
| | - Nikhil Nageswar Inturi
- Pain Neurobiology Research Group, Department of Neuroscience, Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
| | | | | | - Diana Tavares-Ferreira
- Pain Neurobiology Research Group, Department of Neuroscience, Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
| | - Theodore J Price
- Pain Neurobiology Research Group, Department of Neuroscience, Center for Advanced Pain Studies, School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas
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Bryson M, Kloefkorn H, Idlett-Ali S, Carrasco DI, Noble DJ, Martin K, Sawchuk MA, Au Yong N, Garraway SM, Hochman S. Emergent epileptiform activity in spinal sensory circuits drives ectopic bursting in afferent axons and sensory dysfunction after cord injury. Pain 2024:00006396-990000000-00676. [PMID: 39106457 DOI: 10.1097/j.pain.0000000000003364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 06/25/2024] [Indexed: 08/09/2024]
Abstract
ABSTRACT Spinal cord injury leads to hyperexcitability and dysfunction in spinal sensory processing. As hyperexcitable circuits can become epileptiform, we explored whether such activity emerges in a thoracic spinal cord injury (SCI) contusion model of neuropathic pain. Recordings from spinal sensory axons in multiple below-lesion segmental dorsal roots demonstrated that SCI facilitated the emergence of spontaneous ectopic burst spiking in afferent axons, which were correlated across multiple adjacent dorsal roots. Burst frequency correlated with behavioral mechanosensitivity. The same bursting events were recruited by afferent stimulation, and timing interactions with ongoing spontaneous bursts revealed that recruitment was limited by a prolonged post-burst refractory period. Ectopic bursting in afferent axons was driven by GABAA receptor activation, presumably by conversion of subthreshold GABAergic interneuronal presynaptic axoaxonic inhibitory actions to suprathreshold spiking. Collectively, the emergence of stereotyped bursting circuitry with hypersynchrony, sensory input activation, post-burst refractory period, and reorganization of connectivity represent defining features of an epileptiform network. Indeed, these same features were reproduced in naive animals with the convulsant 4-aminopyridine (fampridine). We conclude that spinal cord injury promotes the emergence of epileptiform activity in spinal sensory networks that promote profound corruption of sensory signaling. This includes hyperexcitability and bursting by ectopic spiking in afferent axons that propagate bidirectionally by reentrant central and peripheral projections as well as sensory circuit hypoexcitability during the burst refractory period. More broadly, the work links circuit hyperexcitability to epileptiform circuit emergence, further strengthening it as a conceptual basis to understand features of sensory dysfunction and neuropathic pain.
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Affiliation(s)
- Matthew Bryson
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Heidi Kloefkorn
- Department of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR, United States
| | | | - Dario I Carrasco
- Department of Neurosurgery, Emory University School of Medicine, Atlanta, GA, United States
| | - Donald James Noble
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Karmarcha Martin
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Michael A Sawchuk
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Nicholas Au Yong
- Department of Neurosurgery, Emory University School of Medicine, Atlanta, GA, United States
| | - Sandra M Garraway
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
| | - Shawn Hochman
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA, United States
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Xu GY, Maskey M, Wu Z, Yang Q. Timed sulfonylurea modulation improves locomotor and sensory dysfunction following spinal cord injury. Front Pharmacol 2024; 15:1440198. [PMID: 39148545 PMCID: PMC11324438 DOI: 10.3389/fphar.2024.1440198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Accepted: 07/02/2024] [Indexed: 08/17/2024] Open
Abstract
Traumatic spinal cord injury (SCI) results in immediate tissue necrosis and delayed secondary expansion of neurological damage, often resulting in lifelong paralysis, neurosensory dysfunction, and chronic pain. Progressive hemorrhagic necrosis (PHN) and excessive excitation are the main sources of secondary neural injury. Recent approaches to attenuate PHN by glibenclamide can improve locomotor function after SCI. However, use of glibenclamide can exacerbate development of SCI-induced chronic pain by inhibiting KATP channels to increase neuronal excitation and glial activation. In this study, we explored a treatment strategy involving administration of glibenclamide, which suppresses PHN, and diazoxide, which protects against neuronal excitation and inflammation, at different time intervals following spinal cord contusion. Our goal was to determine whether this combined approach enhances both sensory and motor function. Contusive SCI was induced at spinal segment T10 in adult rats. We found that KATP channels opener, diazoxide, decreased the hyperexcitability of primary sensory neurons after SCI by electrophysiology. Timed application of glibenclamide and diazoxide following contusion significantly improved locomotor function and mitigated development of SCI-induced chronic pain, as shown by behavioral evidence. Finally, we found that timed application of glibenclamide and diazoxide attenuates the inflammatory activity in the spinal cord and increases the survival of spinal matters following SCI. These preclinical studies introduce a promising potential treatment strategy to address SCI-induced dysfunction.
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Affiliation(s)
- Guo-Ying Xu
- Department of Neurobiology, University of Texas Medical Branch, Galveston, TX, United States
| | - Manjit Maskey
- Department of Neurobiology, University of Texas Medical Branch, Galveston, TX, United States
| | - Zizhen Wu
- Department of Neurobiology, University of Texas Medical Branch, Galveston, TX, United States
| | - Qing Yang
- Department of Neurobiology, University of Texas Medical Branch, Galveston, TX, United States
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Türk Börü Ü, Kadir Sarıtaş Z, Görücü Özbek F, Bölük C, Acar H, Koç Y, Zeytin Demiral G. Alterations in the spinal cord, trigeminal nerve ganglion, and infraorbital nerve through inducing compression of the dorsal horn region at the upper cervical cord in trigeminal neuralgia. Brain Res 2024; 1832:148842. [PMID: 38447599 DOI: 10.1016/j.brainres.2024.148842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 02/25/2024] [Accepted: 02/27/2024] [Indexed: 03/08/2024]
Abstract
BACKGROUND Idiopathic trigeminal neuralgia (TN) cases encountered frequently in daily practice indicate significant gaps that still need to be illuminated in the etiopathogenesis. In this study, a novel TN animal model was developed by compressing the dorsal horn (DH) of the upper cervical spinal cord. METHODS Eighteen rabbits were equally divided into three groups, namely control (CG), sham (SG), and spinal cord compression (SCC) groups. External pressure was applied to the left side at the C3 level in the SCC group. Dorsal hemilaminectomy was performed in the SG, and the operative side was closed without compression. No procedure was implemented in the control group. Samples from the SC, TG, and ION were taken after seven days. For the histochemical staining, damage and axons with myelin were scored using Hematoxylin and Eosin and Toluidine Blue, respectively. Immunohistochemistry, nuclei, apoptotic index, astrocyte activity, microglial labeling, and CD11b were evaluated. RESULTS Mechanical allodynia was observed on the ipsilateral side in the SCC group. In addition, both the TG and ION were partially damaged from SC compression, which resulted in significant histopathological changes and increased the expression of all markers in both the SG and SCC groups compared to that in the CG. There was a notable increase in tissue damage, an increase in the number of apoptotic nuclei, an increase in the apoptotic index, an indication of astrocytic gliosis, and an upsurge in microglial cells. Significant increases were noted in the SG group, whereas more pronounced significant increases were observed in the SCC group. Transmission electron microscopy revealed myelin damage, mitochondrial disruption, and increased anchoring particles. Similar changes were observed to a lesser extent in the contralateral spinal cord. CONCLUSION Ipsilateral trigeminal neuropathic pain was developed due to upper cervical SCC. The clinical finding is supported by immunohistochemical and ultrastructural changes. Thus, alterations in the DH due to compression of the upper cervical region should be considered as a potential cause of idiopathic TN.
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Affiliation(s)
- Ülkü Türk Börü
- Department of Neurology University of Afyonkarahisar Health Sciences, Afyonkarahisar, Turkey
| | - Zülfükar Kadir Sarıtaş
- Department of Surgery, Faculty of Veterinary Medicine, University of Afyon Kocatepe, Afyonkarahisar, Turkey
| | - Fatma Görücü Özbek
- Department of Surgery, Faculty of Veterinary Medicine, University of Afyon Kocatepe, Afyonkarahisar, Turkey
| | - Cem Bölük
- Department of Neurology and Clinical Neurophysiology, Sanliurfa Training and Research Hospital, Sanliurfa, Turkey.
| | - Hakan Acar
- Department of Neurology University of Afyonkarahisar Health Sciences, Afyonkarahisar, Turkey
| | - Yusuf Koç
- Department of Surgery, Faculty of Veterinary Medicine, University of Afyon Kocatepe, Afyonkarahisar, Turkey
| | - Gökçe Zeytin Demiral
- Department of Neurology University of Afyonkarahisar Health Sciences, Afyonkarahisar, Turkey
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Sliwinski C, Heutehaus L, Taberner FJ, Weiss L, Kampanis V, Tolou-Dabbaghian B, Cheng X, Motsch M, Heppenstall PA, Kuner R, Franz S, Lechner SG, Weidner N, Puttagunta R. Contribution of mechanoreceptors to spinal cord injury-induced mechanical allodynia. Pain 2024; 165:1336-1347. [PMID: 38739766 PMCID: PMC11090032 DOI: 10.1097/j.pain.0000000000003139] [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: 06/01/2023] [Revised: 09/29/2023] [Accepted: 10/27/2023] [Indexed: 05/16/2024]
Abstract
ABSTRACT Evidence from previous studies supports the concept that spinal cord injury (SCI)-induced neuropathic pain (NP) has its neural roots in the peripheral nervous system. There is uncertainty about how and to which degree mechanoreceptors contribute. Sensorimotor activation-based interventions (eg, treadmill training) have been shown to reduce NP after experimental SCI, suggesting transmission of pain-alleviating signals through mechanoreceptors. The aim of the present study was to understand the contribution of mechanoreceptors with respect to mechanical allodynia in a moderate mouse contusion SCI model. After genetic ablation of tropomyosin receptor kinase B expressing mechanoreceptors before SCI, mechanical allodynia was reduced. The identical genetic ablation after SCI did not yield any change in pain behavior. Peptidergic nociceptor sprouting into lamina III/IV below injury level as a consequence of SCI was not altered by either mechanoreceptor ablation. However, skin-nerve preparations of contusion SCI mice 7 days after injury yielded hyperexcitability in nociceptors, not in mechanoreceptors, which makes a substantial direct contribution of mechanoreceptors to NP maintenance unlikely. Complementing animal data, quantitative sensory testing in human SCI subjects indicated reduced mechanical pain thresholds, whereas the mechanical detection threshold was not altered. Taken together, early mechanoreceptor ablation modulates pain behavior, most likely through indirect mechanisms. Hyperexcitable nociceptors seem to be the main drivers of SCI-induced NP. Future studies need to focus on injury-derived factors triggering early-onset nociceptor hyperexcitability, which could serve as targets for more effective therapeutic interventions.
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Affiliation(s)
- Christopher Sliwinski
- Laboratory of Experimental Neuroregeneration, Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Laura Heutehaus
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | | | - Lisa Weiss
- Laboratory of Experimental Neuroregeneration, Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Vasileios Kampanis
- Laboratory of Experimental Neuroregeneration, Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Bahardokht Tolou-Dabbaghian
- Laboratory of Experimental Neuroregeneration, Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Xing Cheng
- Laboratory of Experimental Neuroregeneration, Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Melanie Motsch
- Laboratory of Experimental Neuroregeneration, Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | | | - Rohini Kuner
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Steffen Franz
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Stefan G. Lechner
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
- Department of Anesthesiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Norbert Weidner
- Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
| | - Radhika Puttagunta
- Laboratory of Experimental Neuroregeneration, Spinal Cord Injury Center, Heidelberg University Hospital, Heidelberg, Germany
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Zhao Q, Zhao L, Fan P, Zhu Y, Zhu R, Cheng L, Xie N. Positive Correlation Between Motor Function and Neuropathic Pain-Like Behaviors After Spinal Cord Injury: A Longitudinal Study of Mice. J Neurotrauma 2024; 41:1077-1088. [PMID: 38185845 DOI: 10.1089/neu.2023.0422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2024] Open
Abstract
Abstract With the recovery of motor function, some spinal cord injury (SCI) patients still suffer from severe pain-like behaviors symptoms. Whether motor function correlates with neuropathic pain-like behaviors remain unclear. In this study, a longitudinal cohort study of mice with moderate thoracic 10 contusion was performed to explore the characteristics of neuropathic pain-like behaviors and its correlation with motor function in different sexes. Pain-like behaviors data up to 42 days post-injury (dpi) were collected and compared. Mice of both sexes were divided into three groups based on their Basso Mouse Scale at 42 dpi. There was no significant difference in motor function recovery between the sexes. Female mice showed more significant mechanical allodynia than males at 14 dpi, which was sustained until 42 dpi without significant dynamic changes. However, males showed a gradually worsening state and more severe mechanical allodynia than females at 28 dpi, and then the differences disappeared. Interestingly, male mice obtained more severe cold hyperalgesia symptoms than females. Additionally, we found that there was a correlation between the occurrence of mechanical allodynia and cold and thermal hyperalgesia. Importantly, motor function recovery was positively associated with the outcomes of neuropathic pain-like behaviors after SCI, which was more obvious in female mice. Our data not only revealed the characteristics of neuropathic pain-like behaviors but also clarified the correlations between motor function recovery and neuropathic pain-like behaviors after SCI. These findings may provide new opinions and suggestions for promoting the clinical diagnosis and treatment of neuropathic pain-like behaviors after SCI.
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Affiliation(s)
- Qing Zhao
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, School of Medicine, School of Life Sciences and Technology, Tongji University, Shanghai, China
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Tongji University, Shanghai, China
| | - Lijuan Zhao
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, School of Medicine, School of Life Sciences and Technology, Tongji University, Shanghai, China
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Tongji University, Shanghai, China
| | - Pianpian Fan
- Department of Pediatrics, West China Second Hospital, Sichuan University, Sichuan, China
| | - Yanjing Zhu
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, School of Medicine, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Rongrong Zhu
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, School of Medicine, School of Life Sciences and Technology, Tongji University, Shanghai, China
| | - Liming Cheng
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, School of Medicine, School of Life Sciences and Technology, Tongji University, Shanghai, China
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Tongji University, Shanghai, China
- Clinical Center for Brain and Spinal Cord Research, Tongji University, Shanghai, China
| | - Ning Xie
- Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, School of Medicine, School of Life Sciences and Technology, Tongji University, Shanghai, China
- Division of Spine, Department of Orthopedics, Tongji Hospital, Tongji University School of Medicine, Tongji University, Shanghai, China
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Kumar PA, Stallman J, Kharbat Y, Hoppe J, Leonards A, Kerim E, Nguyen B, Adkins RL, Baltazar A, Milligan S, Letchuman S, Hook MA, Dulin JN. Chemogenetic Attenuation of Acute Nociceptive Signaling Enhances Functional Outcomes Following Spinal Cord Injury. J Neurotrauma 2024; 41:1060-1076. [PMID: 37905504 DOI: 10.1089/neu.2023.0141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023] Open
Abstract
Identifying novel therapeutic approaches to promote recovery of neurological functions following spinal cord injury (SCI) remains a great unmet need. Nociceptive signaling in the acute phase of SCI has been shown to inhibit recovery of locomotor function and promote the development of chronic neuropathic pain. We therefore hypothesized that inhibition of nociceptive signaling in the acute phase of SCI might improve long-term functional outcomes in the chronic phase of injury. To test this hypothesis, we took advantage of a selective strategy utilizing AAV6 to deliver inhibitory (hM4Di) Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) to nociceptors of the L4-L6 dorsal root ganglia to evaluate the effects of transient nociceptor silencing on long-term sensory and motor functional outcomes in a rat thoracic contusion SCI model. Following hM4Di-mediated nociceptor inhibition from 0-14 days post-SCI, we conducted behavioral assessments until 70 days post-SCI, then performed histological assessments of lesion severity and axon plasticity. Our results show highly selective expression of hM4Di within small diameter nociceptors including calcitonin gene-related peptide (CGRP)+ and IB4-binding neurons. Expression of hM4Di in less than 25% of nociceptors was sufficient to increase hindlimb thermal withdrawal latency in naïve rats. Compared with subjects who received AAV-yellow fluorescent protein (YFP; control), subjects who received AAV-hM4Di exhibited attenuated thermal hyperalgesia, greater coordination, and improved hindlimb locomotor function. However, treatment did not impact the development of cold allodynia or mechanical hyperalgesia. Histological assessments of spinal cord tissue suggested trends toward reduced lesion volume, increased neuronal sparing and increased CGRP+ axon sprouting in hM4Di-treated animals. Together, these findings suggest that nociceptor silencing early after SCI may promote beneficial plasticity in the acute phase of injury that can impact long-term functional outcomes, and support previous work highlighting primary nociceptors as possible therapeutic targets for pain management after SCI.
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Affiliation(s)
| | - Jacob Stallman
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Yahya Kharbat
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Joseph Hoppe
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Amy Leonards
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Ethan Kerim
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Britney Nguyen
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Robert L Adkins
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Angelina Baltazar
- Department of Biology, Texas A&M University, College Station, Texas, USA
- Department of Biomedical Engineering, Texas A&M University, College Station, Texas, USA
| | - Sara Milligan
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Sunjay Letchuman
- Mays Business School, Texas A&M University, College Station, Texas, USA
| | - Michelle A Hook
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas, USA
- Department of Neuroscience and Experimental Therapeutics, School of Medicine, Texas A&M Health Science Center, Bryan, Texas, USA
| | - Jennifer N Dulin
- Department of Biology, Texas A&M University, College Station, Texas, USA
- Texas A&M Institute for Neuroscience, Texas A&M University, College Station, Texas, USA
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9
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Tian J, Bavencoffe AG, Zhu MX, Walters ET. Readiness of nociceptor cell bodies to generate spontaneous activity results from background activity of diverse ion channels and high input resistance. Pain 2024; 165:893-907. [PMID: 37862056 PMCID: PMC10950548 DOI: 10.1097/j.pain.0000000000003091] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 08/09/2023] [Indexed: 10/21/2023]
Abstract
ABSTRACT Nociceptor cell bodies generate "spontaneous" discharge that can promote ongoing pain in persistent pain conditions. Little is known about the underlying mechanisms. Recordings from nociceptor cell bodies (somata) dissociated from rodent and human dorsal root ganglia have shown that previous pain in vivo is associated with low-frequency discharge controlled by irregular depolarizing spontaneous fluctuations of membrane potential (DSFs), likely produced by transient inward currents across the somal input resistance. Using mouse nociceptors, we show that DSFs are associated with high somal input resistance over a wide range of membrane potentials, including depolarized levels where DSFs approach action potential (AP) threshold. Input resistance and both the amplitude and frequency of DSFs were increased in neurons exhibiting spontaneous activity. Ion substitution experiments indicated that the depolarizing phase of DSFs is generated by spontaneous opening of channels permeable to Na + or Ca 2+ and that Ca 2+ -permeable channels are especially important for larger DSFs. Partial reduction of the amplitude or frequency of DSFs by perfusion of pharmacological inhibitors indicated small but significant contributions from Nav1.7, Nav1.8, TRPV1, TRPA1, TRPM4, and N-type Ca 2+ channels. Less specific blockers suggested a contribution from NALCN channels, and global knockout suggested a role for Nav1.9. The combination of high somal input resistance plus background activity of diverse ion channels permeable to Na + or Ca 2+ produces DSFs that are poised to reach AP threshold if resting membrane potential depolarizes, AP threshold decreases, or DSFs become enhanced-all of which can occur under painful neuropathic and inflammatory conditions.
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Affiliation(s)
- Jinbin Tian
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Alexis G. Bavencoffe
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Michael X. Zhu
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Edgar T. Walters
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
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10
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Grau JW, Hudson KE, Johnston DT, Partipilo SR. Updating perspectives on spinal cord function: motor coordination, timing, relational processing, and memory below the brain. Front Syst Neurosci 2024; 18:1184597. [PMID: 38444825 PMCID: PMC10912355 DOI: 10.3389/fnsys.2024.1184597] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Accepted: 01/29/2024] [Indexed: 03/07/2024] Open
Abstract
Those studying neural systems within the brain have historically assumed that lower-level processes in the spinal cord act in a mechanical manner, to relay afferent signals and execute motor commands. From this view, abstracting temporal and environmental relations is the province of the brain. Here we review work conducted over the last 50 years that challenges this perspective, demonstrating that mechanisms within the spinal cord can organize coordinated behavior (stepping), induce a lasting change in how pain (nociceptive) signals are processed, abstract stimulus-stimulus (Pavlovian) and response-outcome (instrumental) relations, and infer whether stimuli occur in a random or regular manner. The mechanisms that underlie these processes depend upon signal pathways (e.g., NMDA receptor mediated plasticity) analogous to those implicated in brain-dependent learning and memory. New data show that spinal cord injury (SCI) can enable plasticity within the spinal cord by reducing the inhibitory effect of GABA. It is suggested that the signals relayed to the brain may contain information about environmental relations and that spinal cord systems can coordinate action in response to descending signals from the brain. We further suggest that the study of stimulus processing, learning, memory, and cognitive-like processing in the spinal cord can inform our views of brain function, providing an attractive model system. Most importantly, the work has revealed new avenues of treatment for those that have suffered a SCI.
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Affiliation(s)
- James W. Grau
- Lab of Dr. James Grau, Department of Psychological and Brain Sciences, Cellular and Behavioral Neuroscience, Texas A&M University, College Station, TX, United States
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Bavencoffe AG, Lopez ER, Johnson KN, Tian J, Gorgun FM, Shen BQ, Zhu MX, Dessauer CW, Walters ET. Widespread latent hyperactivity of nociceptors outlasts enhanced avoidance behavior following incision injury. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.30.578108. [PMID: 38352319 PMCID: PMC10862851 DOI: 10.1101/2024.01.30.578108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
Nociceptors with somata in dorsal root ganglia (DRGs) exhibit an unusual readiness to switch from an electrically silent state to a hyperactive state of tonic, nonaccommodating, low-frequency, irregular discharge of action potentials (APs). Ongoing activity (OA) during this state is present in vivo in rats months after spinal cord injury (SCI), and has been causally linked to SCI pain. OA induced by various neuropathic conditions in rats, mice, and humans is retained in nociceptor somata after dissociation and culturing, providing a powerful tool for investigating its mechanisms and functions. An important question is whether similar nociceptor OA is induced by painful conditions other than neuropathy. The present study shows that probable nociceptors dissociated from DRGs of rats subjected to postsurgical pain (induced by plantar incision) exhibit OA. The OA was most apparent when the soma was artificially depolarized to a level within the normal range of membrane potentials where large, transient depolarizing spontaneous fluctuations (DSFs) can approach AP threshold. This latent hyperactivity persisted for at least 3 weeks, whereas behavioral indicators of affective pain - hindpaw guarding and increased avoidance of a noxious substrate in an operant conflict test - persisted for 1 week or less. An unexpected discovery was latent OA in neurons from thoracic DRGs that innervate dermatomes distant from the injured tissue. The most consistent electrophysiological alteration associated with OA was enhancement of DSFs. Potential in vivo functions of widespread, low-frequency nociceptor OA consistent with these and other findings are to amplify hyperalgesic priming and to drive anxiety-related hypervigilance.
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Affiliation(s)
- Alexis G. Bavencoffe
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Elia R. Lopez
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Kayla N. Johnson
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Jinbin Tian
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Falih M. Gorgun
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Breanna Q. Shen
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Michael X. Zhu
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Carmen W. Dessauer
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
| | - Edgar T. Walters
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston
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12
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Saunders MN, Griffin KV, Kalashnikova I, Kolpek D, Smith DR, Saito E, Cummings BJ, Anderson AJ, Shea LD, Park J. Biodegradable nanoparticles targeting circulating immune cells reduce central and peripheral sensitization to alleviate neuropathic pain following spinal cord injury. Pain 2024; 165:92-101. [PMID: 37463227 PMCID: PMC10787809 DOI: 10.1097/j.pain.0000000000002989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2022] [Accepted: 05/26/2023] [Indexed: 07/20/2023]
Abstract
ABSTRACT Neuropathic pain is a critical source of comorbidity following spinal cord injury (SCI) that can be exacerbated by immune-mediated pathologies in the central and peripheral nervous systems. In this article, we investigate whether drug-free, biodegradable, poly(lactide- co -glycolide) (PLG) nanoparticle treatment mitigates the development of post-SCI neuropathic pain in female mice. Our results show that acute treatment with PLG nanoparticles following thoracic SCI significantly reduces tactile and cold hypersensitivity scores in a durable fashion. Nanoparticles primarily reduce peripheral immune-mediated mechanisms of neuropathic pain, including neuropathic pain-associated gene transcript frequency, transient receptor potential ankyrin 1 nociceptor expression, and MCP-1 (CCL2) chemokine production in the subacute period after injury. Altered central neuropathic pain mechanisms during this period are limited to reduced innate immune cell cytokine expression. However, in the chronic phase of SCI, nanoparticle treatment induces changes in both central and peripheral neuropathic pain signaling, driving reductions in cytokine production and other immune-relevant markers. This research suggests that drug-free PLG nanoparticles reprogram peripheral proalgesic pathways subacutely after SCI to reduce neuropathic pain outcomes and improve chronic central pain signaling.
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Affiliation(s)
- Michael N Saunders
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA
| | - Kate V Griffin
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA
| | - Irina Kalashnikova
- Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY USA
| | - Daniel Kolpek
- Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY USA
| | - Dominique R Smith
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA
| | - Eiji Saito
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA
| | - Brian J Cummings
- Department of Anatomy and Neurobiology, University of California, Irvine, CA USA
- Department of Physical Medicine and Rehabilitation, University of California, Irvine, CA USA
| | - Aileen J Anderson
- Department of Anatomy and Neurobiology, University of California, Irvine, CA USA
- Department of Physical Medicine and Rehabilitation, University of California, Irvine, CA USA
| | - Lonnie D Shea
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI USA
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI USA
| | - Jonghyuck Park
- Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, KY USA
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, KY USA
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Jang K, Garraway SM. A review of dorsal root ganglia and primary sensory neuron plasticity mediating inflammatory and chronic neuropathic pain. NEUROBIOLOGY OF PAIN (CAMBRIDGE, MASS.) 2024; 15:100151. [PMID: 38314104 PMCID: PMC10837099 DOI: 10.1016/j.ynpai.2024.100151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/04/2024] [Accepted: 01/19/2024] [Indexed: 02/06/2024]
Abstract
Pain is a sensory state resulting from complex integration of peripheral nociceptive inputs and central processing. Pain consists of adaptive pain that is acute and beneficial for healing and maladaptive pain that is often persistent and pathological. Pain is indeed heterogeneous, and can be expressed as nociceptive, inflammatory, or neuropathic in nature. Neuropathic pain is an example of maladaptive pain that occurs after spinal cord injury (SCI), which triggers a wide range of neural plasticity. The nociceptive processing that underlies pain hypersensitivity is well-studied in the spinal cord. However, recent investigations show maladaptive plasticity that leads to pain, including neuropathic pain after SCI, also exists at peripheral sites, such as the dorsal root ganglia (DRG), which contains the cell bodies of sensory neurons. This review discusses the important role DRGs play in nociceptive processing that underlies inflammatory and neuropathic pain. Specifically, it highlights nociceptor hyperexcitability as critical to increased pain states. Furthermore, it reviews prior literature on glutamate and glutamate receptors, voltage-gated sodium channels (VGSC), and brain-derived neurotrophic factor (BDNF) signaling in the DRG as important contributors to inflammatory and neuropathic pain. We previously reviewed BDNF's role as a bidirectional neuromodulator of spinal plasticity. Here, we shift focus to the periphery and discuss BDNF-TrkB expression on nociceptors, non-nociceptor sensory neurons, and non-neuronal cells in the periphery as a potential contributor to induction and persistence of pain after SCI. Overall, this review presents a comprehensive evaluation of large bodies of work that individually focus on pain, DRG, BDNF, and SCI, to understand their interaction in nociceptive processing.
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Affiliation(s)
- Kyeongran Jang
- Department of Cell Biology, Emory University, School of Medicine, Atlanta, GA, 30322, USA
| | - Sandra M. Garraway
- Department of Cell Biology, Emory University, School of Medicine, Atlanta, GA, 30322, USA
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Willits AB, Kader L, Eller O, Roberts E, Bye B, Strope T, Freudenthal BD, Umar S, Chintapalli S, Shankar K, Pei D, Christianson J, Baumbauer KM, Young EE. Spinal cord injury-induced neurogenic bowel: A role for host-microbiome interactions in bowel pain and dysfunction. NEUROBIOLOGY OF PAIN (CAMBRIDGE, MASS.) 2024; 15:100156. [PMID: 38601267 PMCID: PMC11004406 DOI: 10.1016/j.ynpai.2024.100156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Revised: 04/04/2024] [Accepted: 04/04/2024] [Indexed: 04/12/2024]
Abstract
Background and aims Spinal cord injury (SCI) affects roughly 300,000 Americans with 17,000 new cases added annually. In addition to paralysis, 60% of people with SCI develop neurogenic bowel (NB), a syndrome characterized by slow colonic transit, constipation, and chronic abdominal pain. The knowledge gap surrounding NB mechanisms after SCI means that interventions are primarily symptom-focused and largely ineffective. The goal of the present studies was to identify mechanism(s) that initiate and maintain NB after SCI as a critical first step in the development of evidence-based, novel therapeutic treatment options. Methods Following spinal contusion injury at T9, we observed alterations in bowel structure and function reflecting key clinical features of NB. We then leveraged tissue-specific whole transcriptome analyses (RNAseq) and fecal 16S rRNA amplicon sequencing in combination with histological, molecular, and functional (Ca2+ imaging) approaches to identify potential mechanism(s) underlying the generation of the NB phenotype. Results In agreement with prior reports focused on SCI-induced changes in the skin, we observed a rapid and persistent increase in expression of calcitonin gene-related peptide (CGRP) expression in the colon. This is suggestive of a neurogenic inflammation-like process engaged by antidromic activity of below-level primary afferents following SCI. CGRP has been shown to disrupt colon homeostasis and negatively affect peristalsis and colon function. As predicted, contusion SCI resulted in increased colonic transit time, expansion of lymphatic nodules, colonic structural and genomic damage, and disruption of the inner, sterile intestinal mucus layer corresponding to increased CGRP expression in the colon. Gut microbiome colonization significantly shifted over 28 days leading to the increase in Anaeroplasma, a pathogenic, gram-negative microbe. Moreover, colon specific vagal afferents and enteric neurons were hyperresponsive after SCI to different agonists including fecal supernatants. Conclusions Our data suggest that SCI results in overexpression of colonic CGRP which could alter colon structure and function. Neurogenic inflammatory-like processes and gut microbiome dysbiosis can also sensitize vagal afferents, providing a mechanism for visceral pain despite the loss of normal sensation post-SCI. These data may shed light on novel therapeutic interventions targeting this process to prevent NB development in patients.
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Affiliation(s)
- Adam B. Willits
- Department of Anesthesiology, Pain and Perioperative Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Leena Kader
- Department of Anesthesiology, Pain and Perioperative Medicine, University of Kansas Medical Center, Kansas City, KS, United States
| | - Olivia Eller
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Emily Roberts
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Bailey Bye
- Department of Cancer Biology, University of Kansas Medical Center, Kansas City, KS
| | - Taylor Strope
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Bret D. Freudenthal
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Shahid Umar
- Department of Surgery, University of Kansas Medical Center, Kansas City, KS, United States
| | - Sree Chintapalli
- Department of Pediatrics, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Kartik Shankar
- Department of Pediatrics, Section of Nutrition, University of Colorado Anschutz Medical Campus, Aurora, CO, United States
| | - Dong Pei
- Department of Biostatistics & Data Science, University of Kansas Medical Center, Kansas City, KS, United States
| | - Julie Christianson
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Kyle M. Baumbauer
- Department of Cell Biology and Physiology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Erin E. Young
- Department of Anesthesiology, Pain and Perioperative Medicine, University of Kansas Medical Center, Kansas City, KS, United States
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Idlett-Ali S, Kloefkorn H, Goolsby W, Hochman S. Relating Spinal Injury-Induced Neuropathic Pain and Spontaneous Afferent Activity to Sleep and Respiratory Dysfunction. J Neurotrauma 2023; 40:2654-2666. [PMID: 37212274 PMCID: PMC11093096 DOI: 10.1089/neu.2022.0305] [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] [Indexed: 05/23/2023] Open
Abstract
Abstract Spinal cord injury (SCI) can induce dysfunction in a multitude of neural circuits including those that lead to impaired sleep, respiratory dysfunction, and neuropathic pain. We used a lower thoracic rodent contusion SCI model of neuropathic pain that has been shown to associate with increased spontaneous activity in primary afferents and hindlimb mechanosensory stimulus hypersensitivity. Here we paired capture of these variables with chronic capture of three state sleep and respiration to more broadly understand SCI-induced physiological dysfunction and to assess possible interrelations. Noncontact electric field sensors were embedded into home cages to non-invasively capture the temporal evolution of sleep and respiration changes for six weeks after SCI in naturally behaving mice. Hindlimb mechanosensitivity was assessed weekly, and terminal experiments measured primary afferent spontaneous activity in situ from intact lumbar dorsal root ganglia (DRG). We observed that SCI led to increased spontaneous primary afferent activity (both firing rate and the number of spontaneously active DRGs) that correlated with increased respiratory rate variability and measures of sleep fragmentation. This is the first study to measure and link sleep dysfunction and variability in respiratory rate in a SCI model of neuropathic pain, and thereby provide broader insight into the magnitude of overall stress burden initiated by neural circuit dysfunction after SCI.
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Affiliation(s)
- Shaquia Idlett-Ali
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
- Department of Physiology, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Heidi Kloefkorn
- Department of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, Oregon, USA
| | - William Goolsby
- Department of Physiology, School of Medicine, Emory University, Atlanta, Georgia, USA
| | - Shawn Hochman
- Department of Physiology, School of Medicine, Emory University, Atlanta, Georgia, USA
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Walters ET. Exaptation and Evolutionary Adaptation in Nociceptor Mechanisms Driving Persistent Pain. BRAIN, BEHAVIOR AND EVOLUTION 2023; 98:314-330. [PMID: 38035556 PMCID: PMC10922759 DOI: 10.1159/000535552] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 11/23/2023] [Indexed: 12/02/2023]
Abstract
BACKGROUND Several evolutionary explanations have been proposed for why chronic pain is a major clinical problem. One is that some mechanisms important for driving chronic pain, while maladaptive for modern humans, were adaptive because they enhanced survival. Evidence is reviewed for persistent nociceptor hyperactivity (PNH), known to promote chronic pain in rodents and humans, being an evolutionarily adaptive response to significant bodily injury, and primitive molecular mechanisms related to cellular injury and stress being exapted (co-opted or repurposed) to drive PNH and consequent pain. SUMMARY PNH in a snail (Aplysia californica), squid (Doryteuthis pealeii), fruit fly (Drosophila melanogaster), mice, rats, and humans has been documented as long-lasting enhancement of action potential discharge evoked by peripheral stimuli, and in some of these species as persistent extrinsically driven ongoing activity and/or intrinsic spontaneous activity (OA and SA, respectively). In mammals, OA and SA are often initiated within the protected nociceptor soma long after an inducing injury. Generation of OA or SA in nociceptor somata may be very rare in invertebrates, but prolonged afterdischarge in nociceptor somata readily occurs in sensitized Aplysia. Evidence for the adaptiveness of injury-induced PNH has come from observations of decreased survival of injured squid exposed to predators when PNH is blocked, from plausible survival benefits of chronic sensitization after severe injuries such as amputation, and from the functional coherence and intricacy of mammalian PNH mechanisms. Major contributions of cAMP-PKA signaling (with associated calcium signaling) to the maintenance of PNH both in mammals and molluscs suggest that this ancient stress signaling system was exapted early during the evolution of nociceptors to drive hyperactivity following bodily injury. Vertebrates have retained core cAMP-PKA signaling modules for PNH while adding new extracellular modulators (e.g., opioids) and cAMP-regulated ion channels (e.g., TRPV1 and Nav1.8 channels). KEY MESSAGES Evidence from multiple phyla indicates that PNH is a physiological adaptation that decreases the risk of attacks on injured animals. Core cAMP-PKA signaling modules make major contributions to the maintenance of PNH in molluscs and mammals. This conserved signaling has been linked to ancient cellular responses to stress, which may have been exapted in early nociceptors to drive protective hyperactivity that can persist while bodily functions recover after significant injury.
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Affiliation(s)
- Edgar T Walters
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center at Houston, Houston, Texas, USA
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17
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Párraga JP, Castellanos A. A Manifesto in Defense of Pain Complexity: A Critical Review of Essential Insights in Pain Neuroscience. J Clin Med 2023; 12:7080. [PMID: 38002692 PMCID: PMC10672144 DOI: 10.3390/jcm12227080] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 11/10/2023] [Accepted: 11/10/2023] [Indexed: 11/26/2023] Open
Abstract
Chronic pain has increasingly become a significant health challenge, not just as a symptomatic manifestation but also as a pathological condition with profound socioeconomic implications. Despite the expansion of medical interventions, the prevalence of chronic pain remains remarkably persistent, prompting a turn towards non-pharmacological treatments, such as therapeutic education, exercise, and cognitive-behavioral therapy. With the advent of cognitive neuroscience, pain is often presented as a primary output derived from the brain, aligning with Engel's Biopsychosocial Model that views disease not solely from a biological perspective but also considering psychological and social factors. This paradigm shift brings forward potential misconceptions and over-simplifications. The current review delves into the intricacies of nociception and pain perception. It questions long-standing beliefs like the cerebral-centric view of pain, the forgotten role of the peripheral nervous system in pain chronification, misconceptions around central sensitization syndromes, the controversy about the existence of a dedicated pain neuromatrix, the consciousness of the pain experience, and the possible oversight of factors beyond the nervous system. In re-evaluating these aspects, the review emphasizes the critical need for understanding the complexity of pain, urging the scientific and clinical community to move beyond reductionist perspectives and consider the multifaceted nature of this phenomenon.
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Affiliation(s)
- Javier Picañol Párraga
- Laboratory of Neurophysiology, Biomedicine Department, Faculty of Medicine and Health Sciences, Institute of Neurosciences, University of Barcelona, 08036 Barcelona, Spain
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Son GY, Tu NH, Santi MD, Lopez SL, Souza Bomfim GH, Vinu M, Zhou F, Chaloemtoem A, Alhariri R, Idaghdour Y, Khanna R, Ye Y, Lacruz RS. The Ca 2+ channel ORAI1 is a regulator of oral cancer growth and nociceptive pain. Sci Signal 2023; 16:eadf9535. [PMID: 37669398 PMCID: PMC10747475 DOI: 10.1126/scisignal.adf9535] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Accepted: 08/15/2023] [Indexed: 09/07/2023]
Abstract
Oral cancer causes pain associated with cancer progression. We report here that the function of the Ca2+ channel ORAI1 is an important regulator of oral cancer pain. ORAI1 was highly expressed in tumor samples from patients with oral cancer, and ORAI1 activation caused sustained Ca2+ influx in human oral cancer cells. RNA-seq analysis showed that ORAI1 regulated many genes encoding oral cancer markers such as metalloproteases (MMPs) and pain modulators. Compared with control cells, oral cancer cells lacking ORAI1 formed smaller tumors that elicited decreased allodynia when inoculated into mouse paws. Exposure of trigeminal ganglia neurons to MMP1 evoked an increase in action potentials. These data demonstrate an important role of ORAI1 in oral cancer progression and pain, potentially by controlling MMP1 abundance.
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Affiliation(s)
- Ga-Yeon Son
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, NY 10010
| | - Nguyen Huu Tu
- NYU Dentistry Translational Research Center, Department of Oral and Maxillofacial Surgery, New York University College of Dentistry, New York, NY 10010
| | - Maria Daniela Santi
- NYU Dentistry Translational Research Center, Department of Oral and Maxillofacial Surgery, New York University College of Dentistry, New York, NY 10010
| | - Santiago Loya Lopez
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, NY 10010
- New York University Pain Research Center, New York University, New York, NY 10010
| | | | - Manikandan Vinu
- Program in Biology, Division of Science and Mathematics, New York University Abu Dhabi, 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates
| | - Fang Zhou
- Department of Pathology, New York University Langone Health, New York, NY 10010
| | - Ariya Chaloemtoem
- Program in Biology, Division of Science and Mathematics, New York University Abu Dhabi, 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates
| | - Rama Alhariri
- Program in Biology, Division of Science and Mathematics, New York University Abu Dhabi, 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates
| | - Youssef Idaghdour
- Program in Biology, Division of Science and Mathematics, New York University Abu Dhabi, 129188, Saadiyat Island, Abu Dhabi, United Arab Emirates
| | - Rajesh Khanna
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, NY 10010
- New York University Pain Research Center, New York University, New York, NY 10010
| | - Yi Ye
- NYU Dentistry Translational Research Center, Department of Oral and Maxillofacial Surgery, New York University College of Dentistry, New York, NY 10010
- New York University Pain Research Center, New York University, New York, NY 10010
| | - Rodrigo S. Lacruz
- Department of Molecular Pathobiology, New York University College of Dentistry, New York, NY 10010
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Ma D, Huang Q, Gao X, Ford NC, Guo R, Zhang C, Liu S, He SQ, Raja SN, Guan Y. The Utility of Peripherally Restricted Kappa-Opioid Receptor Agonists for Inhibiting Below-Level Pain After Spinal Cord Injury in Mice. Neuroscience 2023; 527:92-102. [PMID: 37516437 PMCID: PMC10530135 DOI: 10.1016/j.neuroscience.2023.07.017] [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: 04/14/2023] [Revised: 07/10/2023] [Accepted: 07/15/2023] [Indexed: 07/31/2023]
Abstract
Pain after spinal cord injury (SCI) can be difficult to treat. Drugs that target the opioid receptor (OR) outside the central nervous system (CNS) have gained increasing interest in pain control owing to their low risk of central side effects. Asimadoline and ICI-204448 are believed to be peripherally restricted KOR agonists withlimited access to the CNS. This study examined whether they can attenuate pain hypersensitivity in mice subjected to a contusive T10 SCI. Subcutaneous (s.c.) injection of asimadoline (5, 20 mg/kg) and ICI-204448 (1, 10 mg/kg) inhibited heat hypersensitivity at both doses, but only attenuated mechanical hypersensitivity at the high dose. However, the high-dose asimadoline adversely affected animals' exploratory performance in SCI mice and caused aversion, suggesting CNS drug penetration. In contrast, high-dose ICI-204448 did not impair exploration and remained effective in reducing both mechanical and heat hypersensitivities after SCI. Accordingly, we chose to examine the potential peripheral neuronal mechanism for ICI-204448-induced pain inhibition by conducting in vivo calcium imaging of dorsal root ganglion (DRG) in Pirt-GCaMP6s+/- mice. High-dose ICI-204448 (10 mg/kg, s.c.) attenuated the increased fluorescence intensity of lumbar DRG neurons activated by a noxious pinch (400 g) stimulation in SCI mice. In conclusion, systemic administration of ICI-204448 achieved SCI pain inhibition at doses that did not induce notable side effects and attenuated DRG neuronal excitability which may partly contribute to its pain inhibition. These findings suggest that peripherally restricted KOR agonists may be useful for treating SCI pain, but the therapeutic window must be carefully examined.
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Affiliation(s)
- Danxu Ma
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Qian Huang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Xinyan Gao
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Neil C Ford
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Ruijuan Guo
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Chi Zhang
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Shuguang Liu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Shao-Qiu He
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Srinivasa N Raja
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA; Department of Neurological Surgery, Johns Hopkins University, School of Medicine, Baltimore, MD 21205, USA.
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Liu H, Lauzadis J, Gunaratna K, Sipple E, Kaczocha M, Puopolo M. Inhibition of T-Type Calcium Channels With TTA-P2 Reduces Chronic Neuropathic Pain Following Spinal Cord Injury in Rats. THE JOURNAL OF PAIN 2023; 24:1681-1695. [PMID: 37169156 DOI: 10.1016/j.jpain.2023.05.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Revised: 04/03/2023] [Accepted: 05/02/2023] [Indexed: 05/13/2023]
Abstract
Spinal cord injury (SCI)-induced neuropathic pain (SCI-NP) develops in up to 60 to 70% of people affected by traumatic SCI, leading to a major decline in quality of life and increased risk for depression, anxiety, and addiction. Gabapentin and pregabalin, together with antidepressant drugs, are commonly prescribed to treat SCI-NP, but their efficacy is unsatisfactory. The limited efficacy of current pharmacological treatments for SCI-NP likely reflects our limited knowledge of the underlying mechanism(s) responsible for driving the maintenance of SCI-NP. The leading hypothesis in the field supports a major role for spontaneously active injured nociceptors in driving the maintenance of SCI-NP. Recent data from our laboratory provided additional support for this hypothesis and identified the T-type calcium channels as key players in driving the spontaneous activity of SCI-nociceptors, thus providing a rational pharmacological target to treat SCI-NP. To test whether T-type calcium channels contribute to the maintenance of SCI-NP, male and female SCI and sham rats were treated with TTA-P2 (a blocker of T-type calcium channels) to determine its effects on mechanical hypersensitivity (as measured with the von Frey filaments) and spontaneous ongoing pain (as measured with the conditioned place preference paradigm), and compared them to the effects of gabapentin, a blocker of high voltage-activated calcium channels. We found that both TTA-P2 and gabapentin reduced mechanical hypersensitivity in male and females SCI rats, but surprisingly only TTA-P2 reduced spontaneous ongoing pain in male SCI rats. PERSPECTIVES: SCI-induced neuropathic pain, and in particular the spontaneous ongoing pain component, is notoriously very difficult to treat. Our data provide evidence that inhibition of T-type calcium channels reduces spontaneous ongoing pain in SCI rats, supporting a clinically relevant role for T-type channels in the maintenance of SCI-induced neuropathic pain.
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Affiliation(s)
- Huilin Liu
- Department of Anesthesiology, Stony Brook Pain and Analgesia Research Center (SPARC), Health Sciences Center L4-072, Stony Brook Renaissance School of Medicine, Stony Brook, New York
| | - Justas Lauzadis
- Department of Anesthesiology, Stony Brook Pain and Analgesia Research Center (SPARC), Health Sciences Center L4-072, Stony Brook Renaissance School of Medicine, Stony Brook, New York
| | - Kavindu Gunaratna
- Department of Anesthesiology, Stony Brook Pain and Analgesia Research Center (SPARC), Health Sciences Center L4-072, Stony Brook Renaissance School of Medicine, Stony Brook, New York
| | - Erin Sipple
- Department of Anesthesiology, Stony Brook Pain and Analgesia Research Center (SPARC), Health Sciences Center L4-072, Stony Brook Renaissance School of Medicine, Stony Brook, New York
| | - Martin Kaczocha
- Department of Anesthesiology, Stony Brook Pain and Analgesia Research Center (SPARC), Health Sciences Center L4-072, Stony Brook Renaissance School of Medicine, Stony Brook, New York
| | - Michelino Puopolo
- Department of Anesthesiology, Stony Brook Pain and Analgesia Research Center (SPARC), Health Sciences Center L4-072, Stony Brook Renaissance School of Medicine, Stony Brook, New York.
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21
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Lee SE, Greenough EK, Fonken LK, Gaudet AD. Spinal cord injury in mice amplifies anxiety: A novel light-heat conflict test exposes increased salience of anxiety over heat. Exp Neurol 2023; 364:114382. [PMID: 36924982 PMCID: PMC10874685 DOI: 10.1016/j.expneurol.2023.114382] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/24/2023] [Accepted: 03/11/2023] [Indexed: 03/17/2023]
Abstract
Spinal cord injury (SCI) predisposes individuals to anxiety and chronic pain. Anxiety- and pain-like behavior after SCI can be tested in rodents, yet commonly used tests assess one variable and may not replicate effects of SCI or sex differences seen in humans. Thus, novel preclinical tests should be optimized to better evaluate behaviors relating to anxiety and pain. Here, we use our newly developed conflict test - the Thermal Increments Dark-Light (TIDAL) test - to explore how SCI affects anxiety- vs. pain-like behavior, and whether sex affects post-SCI behavior. The TIDAL conflict test consists of two plates connected by a walkway; one plate remains illuminated and at an isothermic temperature, whereas the other plate is dark but is heated incrementally to aversive temperatures. A control mice thermal place preference test was also performed in which both plates are illuminated. Female and male mice received moderate T9 contusion SCI or remained uninjured. At 7 days post-operative (dpo), mice with SCI increased dark plate preference throughout the TIDAL conflict test compared to uninjured mice. SCI increased dark plate preference for both sexes, although female (vs. male) mice remained on the heated-dark plate to higher temperatures. Mice with SCI that repeated TIDAL at 7 and 21 dpo showed reduced preference for the dark-heated plate at 21 dpo. Overall, in female and male mice, SCI enhances the salience of anxiety (vs. heat sensitivity). The TIDAL conflict test meets a need for preclinical anxiety- and pain-related tests that recapitulate the human condition; thus, future rodent behavioral studies should incorporate TIDAL or other conflict tests to help understand and treat neurologic disorders.
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Affiliation(s)
- Sydney E Lee
- Department of Psychology, College of Liberal Arts, The University of Texas at Austin, 108 E. Dean Keeton St, Mail Stop A800, Austin, TX 78712, USA; Department of Neurology, Dell Medical School, The University of Texas at Austin, Austin, TX, USA.
| | - Emily K Greenough
- Department of Psychology, College of Liberal Arts, The University of Texas at Austin, 108 E. Dean Keeton St, Mail Stop A800, Austin, TX 78712, USA; Department of Neurology, Dell Medical School, The University of Texas at Austin, Austin, TX, USA
| | - Laura K Fonken
- Division of Pharmacology and Toxicology, College of Pharmacy, The University of Texas at Austin, 107 W. Dean Keeton St, Stop C0875 BME 3.510, Austin, TX 78712, USA.
| | - Andrew D Gaudet
- Department of Psychology, College of Liberal Arts, The University of Texas at Austin, 108 E. Dean Keeton St, Mail Stop A800, Austin, TX 78712, USA; Department of Neurology, Dell Medical School, The University of Texas at Austin, Austin, TX, USA.
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22
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Cuevas-Diaz Duran R, Li Y, Garza Carbajal A, You Y, Dessauer CW, Wu J, Walters ET. Major Differences in Transcriptional Alterations in Dorsal Root Ganglia Between Spinal Cord Injury and Peripheral Neuropathic Pain Models. J Neurotrauma 2023; 40:883-900. [PMID: 36178348 PMCID: PMC10150729 DOI: 10.1089/neu.2022.0238] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Chronic, often intractable, pain is caused by neuropathic conditions such as traumatic peripheral nerve injury (PNI) and spinal cord injury (SCI). These conditions are associated with alterations in gene and protein expression correlated with functional changes in somatosensory neurons having cell bodies in dorsal root ganglia (DRGs). Most studies of DRG transcriptional alterations have utilized PNI models where axotomy-induced changes important for neural regeneration may overshadow changes that drive neuropathic pain. Both PNI and SCI produce DRG neuron hyperexcitability linked to pain, but contusive SCI produces little peripheral axotomy or peripheral nerve inflammation. Thus, comparison of transcriptional signatures of DRGs across PNI and SCI models may highlight pain-associated transcriptional alterations in sensory ganglia that do not depend on peripheral axotomy or associated effects such as peripheral Wallerian degeneration. Data from our rat thoracic SCI experiments were combined with meta-analysis of published whole-DRG RNA-seq datasets from prominent rat PNI models. Striking differences were found between transcriptional responses to PNI and SCI, especially in regeneration-associated genes (RAGs) and long noncoding RNAs (lncRNAs). Many transcriptomic changes after SCI also were found after corresponding sham surgery, indicating they were caused by injury to surrounding tissue, including bone and muscle, rather than to the spinal cord itself. Another unexpected finding was of few transcriptomic similarities between rat neuropathic pain models and the only reported transcriptional analysis of human DRGs linked to neuropathic pain. These findings show that DRGs exhibit complex transcriptional responses to central and peripheral neural injury and associated tissue damage. Although only a few genes in DRG cells exhibited similar changes in expression across all the painful conditions examined here, these genes may represent a core set whose transcription in various DRG cell types is sensitive to significant bodily injury, and which may play a fundamental role in promoting neuropathic pain.
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Affiliation(s)
- Raquel Cuevas-Diaz Duran
- Tecnologico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Monterrey, Nuevo Leon, Mexico
| | - Yong Li
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Anibal Garza Carbajal
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Yanan You
- Department of Neurosurgery, The University of Texas Health Science Center at Houston, Houston, Texas, USA
- Center for Stem Cell and Regenerative Medicine, UT Brown Foundation Institute of Molecular Medicine, Houston, Texas, USA
| | - Carmen W. Dessauer
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas, USA
| | - Jiaqian Wu
- Department of Neurosurgery, The University of Texas Health Science Center at Houston, Houston, Texas, USA
- Center for Stem Cell and Regenerative Medicine, UT Brown Foundation Institute of Molecular Medicine, Houston, Texas, USA
| | - Edgar T. Walters
- Department of Integrative Biology and Pharmacology, The University of Texas Health Science Center at Houston, Houston, Texas, USA
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23
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Hamlet C, Fauci L, Morgan JR, Tytell ED. Proprioceptive feedback amplification restores effective locomotion in a neuromechanical model of lampreys with spinal injuries. Proc Natl Acad Sci U S A 2023; 120:e2213302120. [PMID: 36897980 PMCID: PMC10089168 DOI: 10.1073/pnas.2213302120] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 01/19/2023] [Indexed: 03/12/2023] Open
Abstract
Spinal injuries in many vertebrates can result in partial or complete loss of locomotor ability. While mammals often experience permanent loss, some nonmammals, such as lampreys, can regain swimming function, though the exact mechanism is not well understood. One hypothesis is that amplified proprioceptive (body-sensing) feedback can allow an injured lamprey to regain functional swimming even if the descending signal is lost. This study employs a multiscale, integrative, computational model of an anguilliform swimmer fully coupled to a viscous, incompressible fluid and examines the effects of amplified feedback on swimming behavior. This represents a model that analyzes spinal injury recovery by combining a closed-loop neuromechanical model with sensory feedback coupled to a full Navier-Stokes model. Our results show that in some cases, feedback amplification below a spinal lesion is sufficient to partially or entirely restore effective swimming behavior.
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Affiliation(s)
- Christina Hamlet
- Department of Mathematics, Bucknell University, Lewisburg, PA17837
| | - Lisa Fauci
- Department of Mathematics, Tulane University, New Orleans, LA70118
| | - Jennifer R. Morgan
- The Eugene Bell Center for Regenerative Biology, Marine Biological Laboratory (MBL), Woods Hole, MA02543
| | - Eric D. Tytell
- Department of Biology, Tufts University, Medford, MA02155
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24
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Lee SE, Greenough EK, Oancea P, Scheinfeld AR, Douglas AM, Gaudet AD. Sex Differences in Pain: Spinal Cord Injury in Female and Male Mice Elicits Behaviors Related to Neuropathic Pain. J Neurotrauma 2023; 40:833-844. [PMID: 36719772 DOI: 10.1089/neu.2022.0482] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Spinal cord injury (SCI) in humans frequently causes intractable chronic pain. Females are susceptible to worse pain than males, and females may show higher pain prevalence after SCI. Despite this difference in the clinical prevalence of SCI pain, few pre-clinical studies have systematically studied sex differences in SCI-elicited pain-related behaviors in rodents. Here, we leverage data from a large cohort of mice to test whether contusion SCI consistently causes pain symptoms in mice, and to establish whether female (vs. male) mice display heightened hypersensitivity after SCI. Mechanical and heat sensory thresholds were assessed using the von Frey and Hargreaves tests, respectively. In an initial experiment, female mice receiving moderate 60 kDyn SCI or moderate-to-severe 75 kDyn SCI at T9 both exhibited mechanical and heat pain symptoms compared with sham controls. A 75 kDyn SCI caused excess motor deficits that confounded defining pain sensitivity at acute times; therefore, the moderate SCI force was used for subsequent experiments. Next, adult female and male C57BL6/J mice received sham surgery or T9 moderate contusion SCI. Comparing female to male mice after SCI, we reveal that mice of both sexes displayed mechanical and heat hypersensitivity compared with sham controls, from acute-to-chronic post-injury times. Females had amplified SCI-elicited hypersensitivity compared with males. Our data suggest that thoracic contusion SCI elicits consistent and persistent pain-associated symptoms, which are more intense in female than in male mice. These results have important implications for uncovering sex-specific mechanisms and therapeutic targets to ameliorate neuropathic pain after SCI.
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Affiliation(s)
- Sydney E Lee
- Department of Psychology, College of Liberal Arts, and Dell Medical School, University of Texas at Austin, Austin, Texas, USA.,Department of Neurology, Dell Medical School, University of Texas at Austin, Austin, Texas, USA
| | - Emily K Greenough
- Department of Psychology, College of Liberal Arts, and Dell Medical School, University of Texas at Austin, Austin, Texas, USA.,Department of Neurology, Dell Medical School, University of Texas at Austin, Austin, Texas, USA
| | - Paul Oancea
- Department of Psychology, College of Liberal Arts, and Dell Medical School, University of Texas at Austin, Austin, Texas, USA.,Department of Neurology, Dell Medical School, University of Texas at Austin, Austin, Texas, USA
| | - Ashley R Scheinfeld
- Department of Psychology, College of Liberal Arts, and Dell Medical School, University of Texas at Austin, Austin, Texas, USA.,Department of Neurology, Dell Medical School, University of Texas at Austin, Austin, Texas, USA
| | - Apsaline M Douglas
- Department of Psychology, College of Liberal Arts, and Dell Medical School, University of Texas at Austin, Austin, Texas, USA.,Department of Neurology, Dell Medical School, University of Texas at Austin, Austin, Texas, USA
| | - Andrew D Gaudet
- Department of Psychology, College of Liberal Arts, and Dell Medical School, University of Texas at Austin, Austin, Texas, USA.,Department of Neurology, Dell Medical School, University of Texas at Austin, Austin, Texas, USA
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25
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Walters ET, Crook RJ, Neely GG, Price TJ, Smith ESJ. Persistent nociceptor hyperactivity as a painful evolutionary adaptation. Trends Neurosci 2023; 46:211-227. [PMID: 36610893 PMCID: PMC9974896 DOI: 10.1016/j.tins.2022.12.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 12/05/2022] [Accepted: 12/16/2022] [Indexed: 01/07/2023]
Abstract
Chronic pain caused by injury or disease of the nervous system (neuropathic pain) has been linked to persistent electrical hyperactivity of the sensory neurons (nociceptors) specialized to detect damaging stimuli and/or inflammation. This pain and hyperactivity are considered maladaptive because both can persist long after injured tissues have healed and inflammation has resolved. While the assumption of maladaptiveness is appropriate in many diseases, accumulating evidence from diverse species, including humans, challenges the assumption that neuropathic pain and persistent nociceptor hyperactivity are always maladaptive. We review studies indicating that persistent nociceptor hyperactivity has undergone evolutionary selection in widespread, albeit selected, animal groups as a physiological response that can increase survival long after bodily injury, using both highly conserved and divergent underlying mechanisms.
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Affiliation(s)
- Edgar T Walters
- Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USA.
| | - Robyn J Crook
- Department of Biology, San Francisco State University, San Francisco, CA 94132, USA
| | - G Gregory Neely
- Charles Perkins Centre and School of Life and Environmental Sciences, The University of Sydney, NSW 2006, Australia
| | - Theodore J Price
- Department of Neuroscience and Center for Advanced Pain Studies, University of Texas at Dallas, Richardson, TX 75080, USA
| | - Ewan St John Smith
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK
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26
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Ji RR. Specialized Pro-Resolving Mediators as Resolution Pharmacology for the Control of Pain and Itch. Annu Rev Pharmacol Toxicol 2023; 63:273-293. [PMID: 36100219 DOI: 10.1146/annurev-pharmtox-051921-084047] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Specialized pro-resolving mediators (SPMs), including resolvins, protectins, and maresins, are endogenous lipid mediators that are synthesized from omega-3 polyunsaturated fatty acids during the acute phase or resolution phase of inflammation. Synthetic SPMs possess broad safety profiles and exhibit potent actions in resolving inflammation in preclinical models. Accumulating evidence in the past decade has demonstrated powerful analgesia of exogenous SPMs in rodent models of inflammatory, neuropathic, and cancer pain. Furthermore, endogenous SPMs are produced by sham surgery and neuromodulation (e.g., vagus nerve stimulation). SPMs produce their beneficial actions through multiple G protein-coupled receptors, expressed by immune cells, glial cells, and neurons. Notably, loss of SPM receptors impairs the resolution of pain. I also highlight the emerging role of SPMs in the control of itch. Pharmacological targeting of SPMs or SPM receptors has the potential to lead to novel therapeutics for pain and itch as emerging approaches in resolution pharmacology.
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Affiliation(s)
- Ru-Rong Ji
- Center for Translational Pain Medicine, Department of Anesthesiology, and Departments of Neurobiology and Cell Biology, Duke University Medical Center, Durham, North Carolina, USA;
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27
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Noble DJ, Dongmo R, Parvin S, Martin KK, Garraway SM. C-low threshold mechanoreceptor activation becomes sufficient to trigger affective pain in spinal cord-injured mice in association with increased respiratory rates. Front Integr Neurosci 2022; 16:1081172. [PMID: 36619238 PMCID: PMC9811591 DOI: 10.3389/fnint.2022.1081172] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2022] [Accepted: 11/25/2022] [Indexed: 12/24/2022] Open
Abstract
The mechanisms of neuropathic pain after spinal cord injury (SCI) are not fully understood. In addition to the plasticity that occurs within the injured spinal cord, peripheral processes, such as hyperactivity of primary nociceptors, are critical to the expression of pain after SCI. In adult rats, truncal stimulation within the tuning range of C-low threshold mechanoreceptors (C-LTMRs) contributes to pain hypersensitivity and elevates respiratory rates (RRs) after SCI. This suggests that C-LTMRs, which normally encode pleasant, affiliative touch, undergo plasticity to transmit pain sensation following injury. Because tyrosine hydroxylase (TH) expression is a specific marker of C-LTMRs, in the periphery, here we used TH-Cre adult mice to investigate more specifically the involvement of C-LTMRs in at-level pain after thoracic contusion SCI. Using a modified light-dark chamber conditioned place aversion (CPA) paradigm, we assessed chamber preferences and transitions between chambers at baseline, and in response to mechanical and optogenetic stimulation of C-LTMRs. In parallel, at baseline and select post-surgical timepoints, mice underwent non-contact RR recordings and von Frey assessment of mechanical hypersensitivity. The results showed that SCI mice avoided the chamber associated with C-LTMR stimulation, an effect that was more pronounced with optical stimulation. They also displayed elevated RRs at rest and during CPA training sessions. Importantly, these changes were restricted to chronic post-surgery timepoints, when hindpaw mechanical hypersensitivity was also evident. Together, these results suggest that C-LTMR afferent plasticity, coexisting with potentially facilitatory changes in breathing, drives at-level affective pain following SCI in adult mice.
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28
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Paclitaxel Inhibits KCNQ Channels in Primary Sensory Neurons to Initiate the Development of Painful Peripheral Neuropathy. Cells 2022; 11:cells11244067. [PMID: 36552832 PMCID: PMC9776748 DOI: 10.3390/cells11244067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 12/11/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
Cancer patients undergoing paclitaxel infusion usually experience peripheral nerve degeneration and serious neuropathic pain termed paclitaxel-induced peripheral neuropathy (PIPN). However, alterations in the dose or treatment schedule for paclitaxel do not eliminate PIPN, and no therapies are available for PIPN, despite numerous studies to uncover the mechanisms underlying the development/maintenance of this condition. Therefore, we aimed to uncover a novel mechanism underlying the pathogenesis of PIPN. Clinical studies suggest that acute over excitation of primary sensory neurons is linked to the pathogenesis of PIPN. We found that paclitaxel-induced acute hyperexcitability of primary sensory neurons results from the paclitaxel-induced inhibition of KCNQ potassium channels (mainly KCNQ2), found abundantly in sensory neurons and axons. We found that repeated application of XE-991, a specific KCNQ channel blocker, induced PIPN-like alterations in rats, including mechanical hypersensitivity and degeneration of peripheral nerves, as detected by both morphological and behavioral assays. In contrast, genetic deletion of KCNQ2 from peripheral sensory neurons in mice significantly attenuated the development of paclitaxel-induced peripheral sensory fiber degeneration and chronic pain. These findings may lead to a better understanding of the causes of PIPN and provide an impetus for developing new classes of KCNQ activators for its therapeutic treatment.
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29
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Zhu YF, Kan P, Singh G. Differences and Similarities in Spontaneous Activity Between Animal Models of Cancer-Induced Pain and Neuropathic Pain. J Pain Res 2022; 15:3179-3187. [PMID: 36258759 PMCID: PMC9572504 DOI: 10.2147/jpr.s383373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/29/2022] [Indexed: 11/07/2022] Open
Abstract
Background Clinical data on cancer-induced pain (CIP) demonstrate widespread changes in sensory function. It is characterized in humans not only by stimulus-invoked pain, but also by spontaneous pain. In our previous studies in an animal model of CIP, we observed changes in intrinsic membrane properties and excitability of dorsal root ganglion (DRG) sensory neurons corresponding to mechanical allodynia and hyperalgesia, of which abnormal activities of Aβ-fiber sensory neurons are consistent in a rat model of peripheral neuropathic pain (NEP). Objective To investigate whether there are related peripheral neural mechanisms between the CIP and NEP models of spontaneous pain, we compared the electrophysiological properties of DRG sensory neurons at 2–3 weeks after CIP and NEP model induction. Methods CIP models were induced with metastasis tumour-1 rat breast cancer cells implanted into the distal epiphysis of the femur. NEP models were induced with a polyethylene cuff implanted around the sciatic nerve. Spontaneous pain in animals is measured by spontaneous foot lifting (SFL). After measurement of SFL, the animals were prepared for electrophysiological recordings of spontaneous activity (SA) in DRG neurons in vivo. Results Our data showed that SFL and SA occurred in both models. The proportion of SFL and SA of C-fiber sensory neurons in CIP was more significantly increased than in NEP models. There was no difference in duration of SFL and the rate of SA between the two models. The duration of SFL is related to the rate of SA in C-fiber in both models. Conclusion Thus, SFL may result from SA activity in C-fiber neurons in CIP and NEP rats. The differences and similarities in spontaneous pain between CIP and NEP rats is related to the proportion and rate of SA in C-fibers, respectively.
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Affiliation(s)
- Yong Fang Zhu
- Michael G. DeGroote Institute for Pain Research and Care, McMaster University, Hamilton, ON, Canada,Department of Pathology & Molecular Medicine, McMaster University, Hamilton, ON, Canada
| | - Peter Kan
- Health Sciences, McMaster University, Hamilton, ON, Canada
| | - Gurmit Singh
- Michael G. DeGroote Institute for Pain Research and Care, McMaster University, Hamilton, ON, Canada,Department of Pathology & Molecular Medicine, McMaster University, Hamilton, ON, Canada,Correspondence: Gurmit Singh, Email
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30
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Lenert ME, Gomez R, Lane BT, Dailey DL, Vance CGT, Rakel BA, Crofford LJ, Sluka KA, Merriwether EN, Burton MD. Translating Outcomes from the Clinical Setting to Preclinical Models: Chronic Pain and Functionality in Chronic Musculoskeletal Pain. PAIN MEDICINE (MALDEN, MASS.) 2022; 23:1690-1707. [PMID: 35325207 PMCID: PMC9527603 DOI: 10.1093/pm/pnac047] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Revised: 03/11/2022] [Accepted: 03/15/2022] [Indexed: 11/13/2022]
Abstract
Fibromyalgia (FM) is a chronic pain disorder characterized by chronic widespread musculoskeletal pain (CWP), resting pain, movement-evoked pain (MEP), and other somatic symptoms that interfere with daily functioning and quality of life. In clinical studies, this symptomology is assessed, while preclinical models of CWP are limited to nociceptive assays. The aim of the study was to investigate the human-to-model translatability of clinical behavioral assessments for spontaneous (or resting) pain and MEP in a preclinical model of CWP. For preclinical measures, the acidic saline model of FM was used to induce widespread muscle pain in adult female mice. Two intramuscular injections of acidic or neutral pH saline were administered following baseline measures, 5 days apart. An array of adapted evoked and spontaneous pain measures and functional assays were assessed for 3 weeks. A novel paradigm for MEP assessment showed increased spontaneous pain following activity. For clinical measures, resting and movement-evoked pain and function were assessed in adult women with FM. Moreover, we assessed correlations between the preclinical model of CWP and in women with fibromyalgia to examine whether similar relationships between pain assays that comprise resting and MEP existed in both settings. For both preclinical and clinical outcomes, MEP was significantly associated with mechanical pain sensitivity. Preclinically, it is imperative to expand how the field assesses spontaneous pain and MEP when studying multi-symptom disorders like FM. Targeted pain assessments to match those performed clinically is an important aspect of improving preclinical to clinical translatability of animal models.
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Affiliation(s)
- Melissa E Lenert
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, Center for Advanced Pain Studies (CAPS), School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Rachelle Gomez
- Inclusive and Translational Research in Pain Lab, Department of Physical Therapy, Steinhardt School of Culture, Education, and Human Development, New York University, New York, New York, USA
| | - Brandon T Lane
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, Center for Advanced Pain Studies (CAPS), School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
| | - Dana L Dailey
- Neurobiology of Pain Lab, Department of Physical Therapy and Rehabilitation Science, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
- Department of Physical Therapy, Center for Health Sciences, St. Ambrose University, Davenport, Iowa, USA
| | - Carol G T Vance
- Neurobiology of Pain Lab, Department of Physical Therapy and Rehabilitation Science, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Barbara A Rakel
- College of Nursing, University of Iowa, Iowa City, Iowa, USA
| | - Leslie J Crofford
- Division of Rheumatology and Immunology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Kathleen A Sluka
- Neurobiology of Pain Lab, Department of Physical Therapy and Rehabilitation Science, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
| | - Ericka N Merriwether
- Inclusive and Translational Research in Pain Lab, Department of Physical Therapy, Steinhardt School of Culture, Education, and Human Development, New York University, New York, New York, USA
| | - Michael D Burton
- Neuroimmunology and Behavior Laboratory, Department of Neuroscience, Center for Advanced Pain Studies (CAPS), School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, Texas, USA
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31
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Martin KK, Noble DJ, Parvin S, Jang K, Garraway SM. Pharmacogenetic inhibition of TrkB signaling in adult mice attenuates mechanical hypersensitivity and improves locomotor function after spinal cord injury. Front Cell Neurosci 2022; 16:987236. [PMID: 36226073 PMCID: PMC9548551 DOI: 10.3389/fncel.2022.987236] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2022] [Accepted: 09/01/2022] [Indexed: 11/24/2022] Open
Abstract
Brain-derived neurotrophic factor (BDNF) signals through tropomyosin receptor kinase B (TrkB), to exert various types of plasticity. The exact involvement of BDNF and TrkB in neuropathic pain states after spinal cord injury (SCI) remains unresolved. This study utilized transgenic TrkBF616 mice to examine the effect of pharmacogenetic inhibition of TrkB signaling, induced by treatment with 1NM-PP1 (1NMP) in drinking water for 5 days, on formalin-induced inflammatory pain, pain hypersensitivity, and locomotor dysfunction after thoracic spinal contusion. We also examined TrkB, ERK1/2, and pERK1/2 expression in the lumbar spinal cord and trunk skin. The results showed that formalin-induced pain responses were robustly attenuated in 1NMP-treated mice. Weekly assessment of tactile sensitivity with the von Frey test showed that treatment with 1NMP immediately after SCI blocked the development of mechanical hypersensitivity up to 4 weeks post-SCI. Contrastingly, when treatment started 2 weeks after SCI, 1NMP reversibly and partially attenuated hind-paw hypersensitivity. Locomotor scores were significantly improved in the early-treated 1NMP mice compared to late-treated or vehicle-treated SCI mice. 1NMP treatment attenuated SCI-induced increases in TrkB and pERK1/2 levels in the lumbar cord but failed to exert similar effects in the trunk skin. These results suggest that early onset TrkB signaling after SCI contributes to maladaptive plasticity that leads to spinal pain hypersensitivity and impaired locomotor function.
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Eller OC, Stair RN, Neal C, Rowe PS, Nelson-Brantley J, Young EE, Baumbauer KM. Comprehensive phenotyping of cutaneous afferents reveals early-onset alterations in nociceptor response properties, release of CGRP, and hindpaw edema following spinal cord injury. NEUROBIOLOGY OF PAIN (CAMBRIDGE, MASS.) 2022; 12:100097. [PMID: 35756343 PMCID: PMC9218836 DOI: 10.1016/j.ynpai.2022.100097] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 06/09/2022] [Accepted: 06/10/2022] [Indexed: 11/30/2022]
Abstract
Spinal cord injury (SCI) is a complex syndrome that has profound effects on patient well-being, including the development of medically-resistant chronic pain. The mechanisms underlying SCI pain have been the subject of thorough investigation but remain poorly understood. While the majority of the research has focused on changes occurring within and surrounding the site of injury in the spinal cord, there is now a consensus that alterations within the peripheral nervous system, namely sensitization of nociceptors, contribute to the development and maintenance of chronic SCI pain. Using an ex vivo skin/nerve/DRG/spinal cord preparation to characterize afferent response properties following SCI, we found that SCI increased mechanical and thermal responding, as well as the incidence of spontaneous activity (SA) and afterdischarge (AD), in below-level C-fiber nociceptors 24 hr following injury relative to naïve controls. Interestingly, the distribution of nociceptors that exhibit SA and AD are not identical, and the development of SA was observed more frequently in nociceptors with low heat thresholds, while AD was found more frequently in nociceptors with high heat thresholds. We also found that SCI resulted in hindpaw edema and elevated cutaneous calcitonin gene-related peptide (CGRP) concentration that were not observed in naïve mice. These results suggest that SCI causes a rapidly developing nociceptor sensitization and peripheral inflammation that may contribute to the early emergence and persistence of chronic SCI pain.
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Affiliation(s)
- Olivia C. Eller
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Rena N. Stair
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Christopher Neal
- Kansas Intellectual and Developmental Disabilities Research Center, University of Kansas Medical Center, Kansas City, KS, United States
| | - Peter S.N. Rowe
- Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS, United States
- The Kidney Institute & Division of Nephrology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Jennifer Nelson-Brantley
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Erin E. Young
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, United States
- Department of Anesthesiology, University of Kansas Medical Center, Kansas City, KS, United States
- Center for Advancement in Managing Pain, School of Nursing, University of Connecticut, Storrs, CT, United States
- Department of Genetics and Genome Sciences, UConn Health, Farmington, CT, United States
- Department of Neuroscience, UConn Health, Farmington, CT, United States
| | - Kyle M. Baumbauer
- Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, KS, United States
- Department of Anesthesiology, University of Kansas Medical Center, Kansas City, KS, United States
- Center for Advancement in Managing Pain, School of Nursing, University of Connecticut, Storrs, CT, United States
- Department of Neuroscience, UConn Health, Farmington, CT, United States
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North RY, Odem MA, Li Y, Tatsui CE, Cassidy RM, Dougherty PM, Walters ET. Electrophysiological Alterations Driving Pain-Associated Spontaneous Activity in Human Sensory Neuron Somata Parallel Alterations Described in Spontaneously Active Rodent Nociceptors. THE JOURNAL OF PAIN 2022; 23:1343-1357. [PMID: 35292377 PMCID: PMC9357108 DOI: 10.1016/j.jpain.2022.02.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 02/21/2022] [Accepted: 02/24/2022] [Indexed: 06/10/2023]
Abstract
Neuropathic pain in rodents can be driven by ectopic spontaneous activity (SA) generated by sensory neurons in dorsal root ganglia (DRG). The recent demonstration that SA in dissociated human DRG neurons is associated with reported neuropathic pain in patients enables a detailed comparison of pain-linked electrophysiological alterations driving SA in human DRG neurons to alterations that distinguish SA in nociceptors from SA in low-threshold mechanoreceptors (LTMRs) in rodent neuropathy models. Analysis of recordings from dissociated somata of patient-derived DRG neurons showed that SA and corresponding pain in both sexes were significantly associated with the three functional electrophysiological alterations sufficient to generate SA in the absence of extrinsic depolarizing inputs. These include enhancement of depolarizing spontaneous fluctuations of membrane potential (DSFs), which were analyzed quantitatively for the first time in human DRG neurons. The functional alterations were indistinguishable from SA-driving alterations reported for nociceptors in rodent chronic pain models. Irregular, low-frequency DSFs in human DRG neurons closely resemble DSFs described in rodent nociceptors while differing substantially from the high-frequency sinusoidal oscillations described in rodent LTMRs. These findings suggest that conserved physiological mechanisms of SA in human nociceptor somata can drive neuropathic pain despite documented cellular differences between human and rodent DRG neurons. PERSPECTIVE: Electrophysiological alterations in human sensory neurons associated with patient-reported neuropathic pain include all three of the functional alterations that logically can promote spontaneous activity. The similarity of distinctively altered spontaneous depolarizations in human DRG neurons and rodent nociceptors suggests that spontaneously active human nociceptors can persistently promote neuropathic pain in patients.
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Affiliation(s)
- Robert Y North
- Department of Neurosurgery, The University of Texas M.D. Anderson Cancer Center, Houston, Texas
| | - Max A Odem
- Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, Texas
| | - Yan Li
- Department of Anesthesia and Pain Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas
| | - Claudio Esteves Tatsui
- Department of Neurosurgery, The University of Texas M.D. Anderson Cancer Center, Houston, Texas
| | - Ryan M Cassidy
- M.D. Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, Texas
| | - Patrick M Dougherty
- Department of Anesthesia and Pain Medicine, The University of Texas M.D. Anderson Cancer Center, Houston, Texas
| | - Edgar T Walters
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas..
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Bavencoffe A, Spence EA, Zhu MY, Garza-Carbajal A, Chu KE, Bloom OE, Dessauer CW, Walters ET. Macrophage Migration Inhibitory Factor (MIF) Makes Complex Contributions to Pain-Related Hyperactivity of Nociceptors after Spinal Cord Injury. J Neurosci 2022; 42:5463-5480. [PMID: 35610050 PMCID: PMC9270921 DOI: 10.1523/jneurosci.1133-21.2022] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 05/12/2022] [Accepted: 05/19/2022] [Indexed: 02/08/2023] Open
Abstract
Neuropathic pain is a major, inadequately treated challenge for people with spinal cord injury (SCI). While SCI pain mechanisms are often assumed to be in the CNS, rodent studies have revealed mechanistic contributions from primary nociceptors. These neurons become chronically hyperexcitable after SCI, generating ongoing electrical activity that promotes ongoing pain. A major question is whether extrinsic chemical signals help to drive ongoing electrical activity after SCI. People living with SCI exhibit acute and chronic elevation of circulating levels of macrophage migration inhibitory factor (MIF), a cytokine implicated in preclinical pain models. Probable nociceptors isolated from male rats and exposed to an MIF concentration reported in human plasma (1 ng/ml) showed hyperactivity similar to that induced by SCI, although, surprisingly, a 10-fold higher concentration failed to increase excitability. Conditioned behavioral aversion to a chamber associated with peripheral MIF injection suggested that MIF stimulates affective pain. A MIF inhibitor, Iso-1, reversed SCI-induced hyperexcitability. Unlike chronic SCI-induced hyperexcitability, acute MIF-induced hyperexcitability was only partially abrogated by inhibiting ERK signaling. Unexpectedly, MIF concentrations that induced hyperactivity in nociceptors from naive animals, after SCI induced a long-lasting conversion from a highly excitable nonaccommodating type to a rapidly accommodating, hypoexcitable type, possibly as a homeostatic response to prolonged depolarization. Treatment with conditioned medium from cultures of DRG cells obtained after SCI was sufficient to induce MIF-dependent hyperactivity in neurons from naive rats. Thus, changes in systemic and DRG levels of MIF may help to maintain SCI-induced nociceptor hyperactivity that persistently promotes pain.SIGNIFICANCE STATEMENT Chronic neuropathic pain is a major challenge for people with spinal cord injury (SCI). Pain can drastically impair quality of life, and produces substantial economic and social burdens. Available treatments, including opioids, remain inadequate. This study shows that the cytokine macrophage migration inhibitory factor (MIF) can induce pain-like behavior and plays an important role in driving persistent ongoing electrical activity in injury-detecting sensory neurons (nociceptors) in a rat SCI model. The results indicate that SCI produces an increase in MIF release within sensory ganglia. Low MIF levels potently excite nociceptors, but higher levels trigger a long-lasting hypoexcitable state. These findings suggest that therapeutic targeting of MIF in neuropathic pain states may reduce pain and sensory dysfunction by curbing nociceptor hyperactivity.
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Affiliation(s)
- Alexis Bavencoffe
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas 77030
| | - Emily A Spence
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas 77030
| | - Michael Y Zhu
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas 77030
| | - Anibal Garza-Carbajal
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas 77030
| | - Kerry E Chu
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas 77030
| | - Ona E Bloom
- Laboratory of Spinal Cord Injury Research, Feinstein Institutes for Medical Research, Manhasset, New York 11030
| | - Carmen W Dessauer
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas 77030
| | - Edgar T Walters
- Department of Integrative Biology and Pharmacology, McGovern Medical School at UTHealth, Houston, Texas 77030
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Central Neuropathic Pain Syndromes: Current and Emerging Pharmacological Strategies. CNS Drugs 2022; 36:483-516. [PMID: 35513603 DOI: 10.1007/s40263-022-00914-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 03/10/2022] [Indexed: 12/31/2022]
Abstract
Central neuropathic pain is caused by a disease or lesion of the brain or spinal cord. It is difficult to predict which patients will develop central pain syndromes after a central nervous system injury, but depending on the etiology, lifetime prevalence may be greater than 50%. The resulting pain is often highly distressing and difficult to treat, with no specific treatment guidelines currently available. This narrative review discusses mechanisms contributing to central neuropathic pain, and focuses on pharmacological approaches for managing common central neuropathic pain conditions such as central post-stroke pain, spinal cord injury-related pain, and multiple sclerosis-related neuropathic pain. Tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors, and gabapentinoids have some evidence for efficacy in central neuropathic pain. Medications from other pharmacologic classes may also provide pain relief, but current evidence is limited. Certain non-pharmacologic approaches, neuromodulation in particular, may be helpful in refractory cases. Emerging data suggest that modulating the primary afferent input may open new horizons for the treatment of central neuropathic pain. For most patients, effective treatment will likely require a multimodal therapy approach.
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Dietz V, Knox K, Moore S, Roberts N, Corona KK, Dulin JN. Dorsal horn neuronal sparing predicts the development of at-level mechanical allodynia following cervical spinal cord injury in mice. Exp Neurol 2022; 352:114048. [PMID: 35304102 DOI: 10.1016/j.expneurol.2022.114048] [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: 12/13/2021] [Revised: 03/03/2022] [Accepted: 03/13/2022] [Indexed: 11/04/2022]
Abstract
Spinal cord injury (SCI) frequently results in immediate and sustained neurological dysfunction, including intractable neuropathic pain in approximately 60-80% of individuals. SCI induces immediate mechanical damage to spinal cord tissue followed by a period of secondary injury in which tissue damage is further propagated, contributing to the development of anatomically unique lesions. Variability in lesion size and location influences the degree of motor and sensory dysfunction incurred by an individual. We predicted that variability in lesion parameters may also explain why some, but not all, experimental animals develop mechanical sensitivity after SCI. To characterize the relationship of lesion anatomy to mechanical allodynia, we utilized a mouse cervical hemicontusion model of SCI that has been shown to lead to the development and persistence of mechanical allodynia in the ipsilateral forelimb after injury. At four weeks post-SCI, the numbers and locations of surviving neurons were quantified along with total lesion volume and nociceptive fiber sprouting. We found that the subset of animals exhibiting mechanical allodynia had significantly increased neuronal sparing in the ipsilateral dorsal horn around the lesion epicenter compared to animals that did not exhibit mechanical allodynia. Additionally, we failed to observe significant differences between groups in nociceptive fiber density in the dorsal horn around the lesion epicenter. Notably, we found that impactor probe displacement upon administration of the SCI surgery was significantly lower in sensitive animals compared with not-sensitive animals. Together, our data indicate that lesion severity negatively correlates with the manifestation of at-level mechanical hypersensitivity and suggests that sparing of dorsal horn neurons may be required for the development of neuropathic pain.
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Affiliation(s)
- Valerie Dietz
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | - Katelyn Knox
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | - Sherilynne Moore
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | - Nolan Roberts
- Department of Biology, Texas A&M University, College Station, TX 77843, USA
| | | | - Jennifer N Dulin
- Department of Biology, Texas A&M University, College Station, TX 77843, USA; Texas A&M Institute for Neuroscience, Texas A&M University, College Station, TX 77843, USA.
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Spinal cord injury-mediated changes in electrophysiological properties of rat gastric nodose ganglion neurons. Exp Neurol 2022; 348:113927. [PMID: 34798136 PMCID: PMC8727501 DOI: 10.1016/j.expneurol.2021.113927] [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: 05/12/2021] [Revised: 10/30/2021] [Accepted: 11/11/2021] [Indexed: 02/03/2023]
Abstract
In preclinical rodent models, spinal cord injury (SCI) manifests as gastric vagal afferent dysfunction both acutely and chronically. However, the mechanism that underlies this dysfunction remains unknown. In the current study, we examined the effect of SCI on gastric nodose ganglia (NG) neuron excitability and on voltage-gated Na+ (NaV) channels expression and function in rats after an acute (i.e. 3-days) and chronic (i.e. 3-weeks) period. Rats randomly received either T3-SCI or sham control surgery 3-days or 3-weeks prior to experimentation as well as injections of 3% DiI solution into the stomach to identify gastric NG neurons. Single cell qRT-PCR was performed on acutely dissociated DiI-labeled NG neurons to measure NaV1.7, NaV1.8 and NaV1.9 expression levels. The results indicate that all 3 channel subtypes decreased. Current- and voltage-clamp whole-cell patch-clamp recordings were performed on acutely dissociated DiI-labeled NG neurons to measure active and passive properties of C- and A-fibers as well as the biophysical characteristics of NaV1.8 channels in gastric NG neurons. Acute and chronic SCI did not demonstrate deleterious effects on either passive properties of dissociated gastric NG neurons or biophysical properties of NaV1.8. These findings suggest that although NaV gene expression levels change following SCI, NaV1.8 function is not altered. The disruption throughout the entirety of the vagal afferent neuron has yet to be investigated.
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Velasco E, Alvarez JL, Meseguer VM, Gallar J, Talavera K. Membrane potential instabilities in sensory neurons: mechanisms and pathophysiological relevance. Pain 2022; 163:64-74. [PMID: 34086629 DOI: 10.1097/j.pain.0000000000002289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 03/29/2021] [Indexed: 11/25/2022]
Abstract
ABSTRACT Peripheral sensory neurons transduce physicochemical stimuli affecting somatic tissues into the firing of action potentials that are conveyed to the central nervous system. This results in conscious perception, adaptation, and survival, but alterations of the firing patterns can result in pain and hypersensitivity conditions. Thus, understanding the molecular mechanisms underlying action potential firing in peripheral sensory neurons is essential in sensory biology and pathophysiology. Over the past 30 years, it has been consistently reported that these cells can display membrane potential instabilities (MPIs), in the form of subthreshold membrane potential oscillations or depolarizing spontaneous fluctuations. However, research on this subject remains sparse, without a clear conductive thread to be followed. To address this, we here provide a synthesis of the description, molecular bases, mathematical models, physiological roles, and pathophysiological implications of MPIs in peripheral sensory neurons. Membrane potential instabilities have been reported in trigeminal, dorsal root, and Mes-V ganglia, where they are believed to support repetitive firing. They are proposed to have roles also in intercellular communication, ectopic firing, and responses to tonic and slow natural stimuli. We highlight how MPIs are of great interest for the study of sensory transduction physiology and how they may represent therapeutic targets for many pathological conditions, such as acute and chronic pain, itch, and altered sensory perceptions. We identify future research directions, including the elucidation of the underlying molecular determinants and modulation mechanisms, their relation to the encoding of natural stimuli and their implication in pain and hypersensitivity conditions.
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Affiliation(s)
- Enrique Velasco
- Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain
| | - Julio L Alvarez
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Leuven, Belgium
| | - Victor M Meseguer
- Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain
| | - Juana Gallar
- Instituto de Neurociencias, Universidad Miguel Hernández-CSIC, San Juan de Alicante, Spain
- Instituto de Investigación Sanitaria y Biomédica de Alicante, San Juan de Alicante, Spain
| | - Karel Talavera
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, KU Leuven, VIB Center for Brain & Disease Research, Leuven, Belgium
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Nociceptor-localized cGMP-dependent protein kinase I is a critical generator for central sensitization and neuropathic pain. Pain 2021; 162:135-151. [PMID: 32773598 DOI: 10.1097/j.pain.0000000000002013] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Patients with neuropathic pain often experience exaggerated pain and anxiety. Central sensitization has been linked with the maintenance of neuropathic pain and may become an autonomous pain generator. Conversely, emerging evidence accumulated that central sensitization is initiated and maintained by ongoing nociceptive primary afferent inputs. However, it remains elusive what mechanisms underlie this phenomenon and which peripheral candidate contributes to central sensitization that accounts for pain hypersensitivity and pain-related anxiety. Previous studies have implicated peripherally localized cGMP-dependent protein kinase I (PKG-I) in plasticity of nociceptors and spinal synaptic transmission as well as inflammatory hyperalgesia. However, whether peripheral PKG-I contributes to cortical plasticity and hence maintains nerve injury-induced pain hypersensitivity and anxiety is unknown. Here, we demonstrated significant upregulation of PKG-I in ipsilateral L3 dorsal root ganglia (DRG), no change in L4 DRG, and downregulation in L5 DRG upon spared nerve injury. Genetic ablation of PKG-I specifically in nociceptors or post-treatment with intervertebral foramen injection of PKG-I antagonist, KT5823, attenuated the development and maintenance of spared nerve injury-induced bilateral pain hypersensitivity and anxiety. Mechanistic analysis revealed that activation of PKG-I in nociceptors is responsible for synaptic potentiation in the anterior cingulate cortex upon peripheral neuropathy through presynaptic mechanisms involving brain-derived neurotropic factor signaling. Our results revealed that PKG-I expressed in nociceptors is a key determinant for cingulate synaptic plasticity after nerve injury, which contributes to the maintenance of pain hypersensitivity and anxiety. Thereby, this study presents a strong basis for opening up a novel therapeutic target, PKG-I, in nociceptors for treatment of comorbidity of neuropathic pain and anxiety with least side effects.
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Kong F, Sun K, Zhu J, Li F, Lin F, Sun X, Luo X, Ren C, Lu L, Zhao S, Sun J, Wang Y, Shi J. PD-L1 Improves Motor Function and Alleviates Neuropathic Pain in Male Mice After Spinal Cord Injury by Inhibiting MAPK Pathway. Front Immunol 2021; 12:670646. [PMID: 33936116 PMCID: PMC8081847 DOI: 10.3389/fimmu.2021.670646] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Accepted: 03/29/2021] [Indexed: 12/17/2022] Open
Abstract
Background Traumatic spinal cord injury (SCI) causes severe motor dysfunction and persistent central neuropathic pain (Nep), which has not yet been effectively cured. Programmed cell death ligand-1 (PD-L1) is typically produced by cancer cells and contributes to the immune-suppressive in tumor microenvironment. However, the role of PD-L1 in regulating inflammatory response and Nep after SCI remains unclear. A growing amount of researches have begun to investigate the effect of PD-L1 on macrophages and microglia in recent years. Considering the pivotal role of macrophages/microglia in the inflammatory response after SCI, we proposed the hypothesis that PD-L1 improved the recovery of locomotor and sensory functions after SCI through regulating macrophages and microglia. Methods The mice SCI model was established to determine the changes in expression patterns of PD-L1. Meanwhile, we constructed PD-L1 knockout mice to observe differences in functional recovery and phenotypes of macrophages/microglia post-SCI. Results In present study, PD-L1 was significantly upregulated after SCI and highly expressed on macrophages/microglia at the injury epicenter. PD-L1 knockout (KO) mice showed worse locomotor recovery and more serious pathological pain compared with wild-type (WT) mice. Furthermore, deletion of PD-L1 significantly increased the polarization of M1-like macrophages/microglia. Mechanistic analysis revealed that PD-L1 may improve functional outcomes following SCI by inhibiting phosphorylation of p38 and ERK1/2. Conclusions Our observations implicate the involvement of PD-L1 in recovery of SCI and provide a new treatment strategy for the prevention and treatment of this traumatic condition.
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Affiliation(s)
- Fanqi Kong
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Kaiqiang Sun
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Jian Zhu
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Fudong Li
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Feng Lin
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Xiaofei Sun
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Xi Luo
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Changzhen Ren
- Department of Cardiology, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Lantao Lu
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - ShuJie Zhao
- Department of Orthopedics, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China
| | - Jingchuan Sun
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Yuan Wang
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
| | - Jiangang Shi
- Department of Orthopedic Surgery, Spine Center, Changzheng Hospital, Naval Medical University, Shanghai, China
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Interleukin-10 resolves pain hypersensitivity induced by cisplatin by reversing sensory neuron hyperexcitability. Pain 2021; 161:2344-2352. [PMID: 32427749 DOI: 10.1097/j.pain.0000000000001921] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Understanding the mechanisms that drive transition from acute to chronic pain is essential to identify new therapeutic targets. The importance of endogenous resolution pathways acting as a "brake" to prevent development of chronic pain has been largely ignored. We examined the role of interleukin-10 (IL-10) in resolution of neuropathic pain induced by cisplatin. In search of an underlying mechanism, we studied the effect of cisplatin and IL-10 on spontaneous activity (SA) in dorsal root ganglia neurons. Cisplatin (2 mg/kg daily for 3 days) induced mechanical hypersensitivity that resolved within 3 weeks. In both sexes, resolution of mechanical hypersensitivity was delayed in Il10 mice, in WT mice treated intrathecally with neutralizing anti-IL-10 antibody, and in mice with cell-targeted deletion of IL-10R1 on advillin-positive sensory neurons. Electrophysiologically, small- to medium-sized dorsal root ganglia neurons from cisplatin-treated mice displayed an increase in the incidence of SA. Cisplatin treatment also depolarized the resting membrane potential, and decreased action potential voltage threshold and rheobase, while increasing ongoing activity at -45 mV and the amplitude of depolarizing spontaneous fluctuations. In vitro addition of IL-10 (10 ng/mL) reversed the effect of cisplatin on SA and on the depolarizing spontaneous fluctuation amplitudes, but unexpectedly had little effect on the other electrophysiological parameters affected by cisplatin. Collectively, our findings challenge the prevailing concept that IL-10 resolves pain solely by dampening neuroinflammation and demonstrate in a model of chemotherapy-induced neuropathic pain that endogenous IL-10 prevents transition to chronic pain by binding to IL-10 receptors on sensory neurons to regulate their activity.
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Blumenthal GH, Nandakumar B, Schnider AK, Detloff MR, Ricard J, Bethea JR, Moxon KA. Modelling at-level allodynia after mid-thoracic contusion in the rat. Eur J Pain 2021; 25:801-816. [PMID: 33296535 DOI: 10.1002/ejp.1711] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND The rat mid-thoracic contusion model has been used to study at-level tactile allodynia, a common type of pain that develops after spinal cord injury (SCI). An important advantage of this model is that not all animals develop hypersensitivity. Therefore, it can be used to examine mechanisms that are strictly related to the development of pain-like behaviour separately from mechanisms related to the injury itself. However, how to separate animals that develop hypersensitivity from those that do not is unclear. METHODS The aims of the current study were to identify where hypersensitivity and spasticity develop and use this information to identify metrics to separate animals that develop hypersensitivity from those that do not to study differences in their behaviour. To accomplish these aims, a grid was used to localize hypersensitivity on the dorsal trunk relative to thoracic dermatomes and supraspinal responses to tactile stimulation were tallied. These supraspinal responses were used to develop a hypersensitivity score to separate animals that develop hypersensitivity, or pain-like response to nonpainful stimuli. RESULTS Similar to humans, the development of hypersensitivity could occur with the development of spasticity or hyperreflexia. Moreover, the time course and prevalence of hypersensitivity phenotypes (at-, above-, or below level) produced by this model were similar to that observed in humans with SCI. CONCLUSION However, the amount of spared spinal matter in the cord did not explain the development of hypersensitivity, as previously reported. This approach can be used to study the mechanisms underlying the development of hypersensitivity separately from mechanisms related to injury alone.
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Affiliation(s)
- Gary H Blumenthal
- Department of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, PA, USA.,Department of Biomedical Engineering, University of California-Davis, Davis, CA, USA
| | - Bharadwaj Nandakumar
- Department of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, PA, USA.,Department of Biomedical Engineering, University of California-Davis, Davis, CA, USA
| | - Ashley K Schnider
- Department of Biomedical Engineering, University of California-Davis, Davis, CA, USA
| | - Megan R Detloff
- Department of Neurobiology and Anatomy, Spinal Cord Research Center, College of Medicine, Drexel University, Philadelphia, PA, USA
| | - Jerome Ricard
- Department of Biology, Drexel University, Philadelphia, PA, USA
| | - John R Bethea
- Department of Biology, Drexel University, Philadelphia, PA, USA
| | - Karen A Moxon
- Department of Biomedical Engineering, Science, and Health Systems, Drexel University, Philadelphia, PA, USA.,Department of Biomedical Engineering, University of California-Davis, Davis, CA, USA.,Center for Neuroscience, Davis, CA, USA
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43
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Blanke EN, Holmes GM, Besecker EM. Altered physiology of gastrointestinal vagal afferents following neurotrauma. Neural Regen Res 2021; 16:254-263. [PMID: 32859772 PMCID: PMC7896240 DOI: 10.4103/1673-5374.290883] [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] [Indexed: 12/13/2022] Open
Abstract
The adaptability of the central nervous system has been revealed in several model systems. Of particular interest to central nervous system-injured individuals is the ability for neural components to be modified for regain of function. In both types of neurotrauma, traumatic brain injury and spinal cord injury, the primary parasympathetic control to the gastrointestinal tract, the vagus nerve, remains anatomically intact. However, individuals with traumatic brain injury or spinal cord injury are highly susceptible to gastrointestinal dysfunctions. Such gastrointestinal dysfunctions attribute to higher morbidity and mortality following traumatic brain injury and spinal cord injury. While the vagal efferent output remains capable of eliciting motor responses following injury, evidence suggests impairment of the vagal afferents. Since sensory input drives motor output, this review will discuss the normal and altered anatomy and physiology of the gastrointestinal vagal afferents to better understand the contributions of vagal afferent plasticity following neurotrauma.
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Affiliation(s)
- Emily N Blanke
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, USA
| | - Gregory M Holmes
- Department of Neural and Behavioral Sciences, Penn State University College of Medicine, Hershey, PA, USA
| | - Emily M Besecker
- Department of Health Sciences, Gettysburg College, Gettysburg, PA, USA
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Smith PA. K + Channels in Primary Afferents and Their Role in Nerve Injury-Induced Pain. Front Cell Neurosci 2020; 14:566418. [PMID: 33093824 PMCID: PMC7528628 DOI: 10.3389/fncel.2020.566418] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 08/21/2020] [Indexed: 12/12/2022] Open
Abstract
Sensory abnormalities generated by nerve injury, peripheral neuropathy or disease are often expressed as neuropathic pain. This type of pain is frequently resistant to therapeutic intervention and may be intractable. Numerous studies have revealed the importance of enduring increases in primary afferent excitability and persistent spontaneous activity in the onset and maintenance of peripherally induced neuropathic pain. Some of this activity results from modulation, increased activity and /or expression of voltage-gated Na+ channels and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. K+ channels expressed in dorsal root ganglia (DRG) include delayed rectifiers (Kv1.1, 1.2), A-channels (Kv1.4, 3.3, 3.4, 4.1, 4.2, and 4.3), KCNQ or M-channels (Kv7.2, 7.3, 7.4, and 7.5), ATP-sensitive channels (KIR6.2), Ca2+-activated K+ channels (KCa1.1, 2.1, 2.2, 2.3, and 3.1), Na+-activated K+ channels (KCa4.1 and 4.2) and two pore domain leak channels (K2p; TWIK related channels). Function of all K+ channel types is reduced via a multiplicity of processes leading to altered expression and/or post-translational modification. This also increases excitability of DRG cell bodies and nociceptive free nerve endings, alters axonal conduction and increases neurotransmitter release from primary afferent terminals in the spinal dorsal horn. Correlation of these cellular changes with behavioral studies provides almost indisputable evidence for K+ channel dysfunction in the onset and maintenance of neuropathic pain. This idea is underlined by the observation that selective impairment of just one subtype of DRG K+ channel can produce signs of pain in vivo. Whilst it is established that various mediators, including cytokines and growth factors bring about injury-induced changes in DRG function and excitability, evidence presently available points to a seminal role for interleukin 1β (IL-1β) in control of K+ channel function. Despite the current state of knowledge, attempts to target K+ channels for therapeutic pain management have met with limited success. This situation may change with the advent of personalized medicine. Identification of specific sensory abnormalities and genetic profiling of individual patients may predict therapeutic benefit of K+ channel activators.
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Affiliation(s)
- Peter A. Smith
- Department of Pharmacology and Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
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Sham surgeries for central and peripheral neural injuries persistently enhance pain-avoidance behavior as revealed by an operant conflict test. Pain 2020; 160:2440-2455. [PMID: 31323014 DOI: 10.1097/j.pain.0000000000001642] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Studies using rodent models of neuropathic pain use sham surgery control procedures that cause deep tissue damage. Sham surgeries would thus be expected to induce potentially long-lasting postsurgical pain, but little evidence for such pain has been reported. Operant tests of voluntary behavior can reveal negative motivational and cognitive aspects of pain that may provide sensitive tools for detecting pain-related alterations. In a previously described operant mechanical conflict test involving lengthy familiarization and training, rodents freely choose to either escape from a brightly lit chamber by crossing sharp probes or refuse to cross. Here, we describe a brief (2-day) mechanical conflict protocol that exploits rats' innate exploratory response to a novel environment to detect persistently enhanced pain-avoidance behavior after sham surgeries for 2 neural injury models: thoracic spinal cord injury and chronic constriction injury of the sciatic nerve. Pitting the combined motivations to avoid the bright light and to explore the novel device against pain from crossing noxious probes disclosed a conflicting, hyperalgesia-related reluctance to repeatedly cross the probes after injury. Rats receiving standard sham surgeries demonstrated enhanced pain-like avoidance behavior compared with naive controls, and this behavior was similar to that of corresponding chronic constriction injury or spinal cord injury rats weeks or months after injury. In the case of sham surgery for spinal cord injury, video analysis of voluntary exploratory behavior directed at the probes revealed enhanced forepaw withdrawal responses. These findings have important implications for preclinical investigations into behavioral alterations and physiological mechanisms associated with postsurgical and neuropathic pain.
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Contribution of T-Type Calcium Channels to Spinal Cord Injury-Induced Hyperexcitability of Nociceptors. J Neurosci 2020; 40:7229-7240. [PMID: 32839232 DOI: 10.1523/jneurosci.0517-20.2020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 07/22/2020] [Accepted: 07/30/2020] [Indexed: 01/24/2023] Open
Abstract
A hyperexcitable state and spontaneous activity of nociceptors have been suggested to play a critical role in the development of chronic neuropathic pain following spinal cord injury (SCI). In male rats, we employed the action potential-clamp technique to determine the underlying ionic mechanisms responsible for driving SCI-nociceptors to a hyperexcitable state and for triggering their spontaneous activity. We found that the increased activity of low voltage activated T-type calcium channels induced by the injury sustains the bulk (∼60-70%) of the inward current active at subthreshold voltages during the interspike interval in SCI-nociceptors, with a modest contribution (∼10-15%) from tetrodotoxin (TTX)-sensitive and TTX-resistant sodium channels and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. In current-clamp recordings, inhibition of T-type calcium channels with 1 μm TTA-P2 reduced both the spontaneous and the evoked firing in response to current injections in SCI-nociceptors to a level similar to sham-nociceptors. Electrophysiology in vitro was then combined with the conditioned place preference (CPP) paradigm to determine the relationship between the increased activity of T-type channels in SCI-nociceptors and chronic neuropathic pain following SCI. The size of the interspike T-type calcium current recorded from nociceptors isolated from SCI rats showing TTA-P2-induced CPP (responders) was ∼6 fold greater than the interspike T-type calcium current recorded from nociceptors isolated from SCI rats without TTA-P2-induced CPP (non-responders). Taken together, our data suggest that the increased activity of T-type calcium channels induced by the injury plays a primary role in driving SCI-nociceptors to a hyperexcitable state and contributes to chronic neuropathic pain following SCI.SIGNIFICANCE STATEMENT Chronic neuropathic pain is a major comorbidity of spinal cord injury (SCI), affecting up to 70-80% of patients. Anticonvulsant and tricyclic antidepressant drugs are first line analgesics used to treat SCI-induced neuropathic pain, but their efficacy is very limited. A hyperexcitable state and spontaneous activity of SCI-nociceptors have been proposed as a possible underlying cause for the development of chronic neuropathic pain following SCI. Here, we show that the increased activity of T-type calcium channels induced by the injury plays a major role in driving SCI-nociceptors to a hyperexcitable state and for promoting their spontaneous activity, suggesting that T-type calcium channels may represent a pharmacological target to treat SCI-induced neuropathic pain.
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47
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Depolarization-Dependent C-Raf Signaling Promotes Hyperexcitability and Reduces Opioid Sensitivity of Isolated Nociceptors after Spinal Cord Injury. J Neurosci 2020; 40:6522-6535. [PMID: 32690613 DOI: 10.1523/jneurosci.0810-20.2020] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 06/16/2020] [Accepted: 07/13/2020] [Indexed: 12/22/2022] Open
Abstract
Chronic pain caused by spinal cord injury (SCI) is notoriously resistant to treatment, particularly by opioids. After SCI, DRG neurons show hyperactivity and chronic depolarization of resting membrane potential (RMP) that is maintained by cAMP signaling through PKA and EPAC. Importantly, SCI also reduces the negative regulation by Gαi of adenylyl cyclase and its production of cAMP, independent of alterations in G protein-coupled receptors and/or G proteins. Opioid reduction of pain depends on coupling of opioid receptors to Gαi/o family members. Combining high-content imaging and cluster analysis, we show that in male rats SCI decreases opioid responsiveness in vitro within a specific subset of small-diameter nociceptors that bind isolectin B4. This SCI effect is mimicked in nociceptors from naive animals by a modest 5 min depolarization of RMP (15 mm K+; -45 mV), reducing inhibition of cAMP signaling by μ-opioid receptor agonists DAMGO and morphine. Disinhibition and activation of C-Raf by depolarization-dependent phosphorylation are central to these effects. Expression of an activated C-Raf reduces sensitivity of adenylyl cyclase to opioids in nonexcitable HEK293 cells, whereas inhibition of C-Raf or treatment with the hyperpolarizing drug retigabine restores opioid responsiveness and blocks spontaneous activity of nociceptors after SCI. Inhibition of ERK downstream of C-Raf also blocks SCI-induced hyperexcitability and depolarization, without direct effects on opioid responsiveness. Thus, depolarization-dependent C-Raf and downstream ERK activity maintain a depolarized RMP and nociceptor hyperactivity after SCI, providing a self-reinforcing mechanism to persistently promote nociceptor hyperexcitability and limit the therapeutic effectiveness of opioids.SIGNIFICANCE STATEMENT Chronic pain induced by spinal cord injury (SCI) is often permanent and debilitating, and usually refractory to treatment with analgesics, including opioids. SCI-induced pain in a rat model has been shown to depend on persistent hyperactivity in primary nociceptors (injury-detecting sensory neurons), associated with a decrease in the sensitivity of adenylyl cyclase production of cAMP to inhibitory Gαi proteins in DRGs. This study shows that SCI and one consequence of SCI (chronic depolarization of resting membrane potential) decrease sensitivity to opioid-mediated inhibition of cAMP and promote hyperactivity of nociceptors by enhancing C-Raf activity. ERK activation downstream of C-Raf is necessary for maintaining ongoing depolarization and hyperactivity, demonstrating an unexpected positive feedback loop to persistently promote pain.
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Chambel SS, Tavares I, Cruz CD. Chronic Pain After Spinal Cord Injury: Is There a Role for Neuron-Immune Dysregulation? Front Physiol 2020; 11:748. [PMID: 32733271 PMCID: PMC7359877 DOI: 10.3389/fphys.2020.00748] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 06/08/2020] [Indexed: 12/14/2022] Open
Abstract
Spinal cord injury (SCI) is a devastating event with a tremendous impact in the life of the affected individual and family. Traumatic injuries related to motor vehicle accidents, falls, sports, and violence are the most common causes. The majority of spinal lesions is incomplete and occurs at cervical levels of the cord, causing a disruption of several ascending and descending neuronal pathways. Additionally, many patients develop chronic pain and describe it as burning, stabbing, shooting, or shocking and often arising with no stimulus. Less frequently, people with SCI also experience pain out of context with the stimulus (e.g., light touch). While abolishment of the endogenous descending inhibitory circuits is a recognized cause for chronic pain, an increasing number of studies suggest that uncontrolled release of pro- and anti-inflammatory mediators by neurons, glial, and immune cells is also important in the emergence and maintenance of SCI-induced chronic pain. This constitutes the topic of the present mini-review, which will focus on the importance of neuro-immune dysregulation for pain after SCI.
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Affiliation(s)
- Sílvia S Chambel
- Department of Biomedicine, Experimental Biology Unit, Faculty of Medicine, University of Porto, Porto, Portugal.,Translational NeuroUrology Group, Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, Porto, Portugal
| | - Isaura Tavares
- Department of Biomedicine, Experimental Biology Unit, Faculty of Medicine, University of Porto, Porto, Portugal.,Pain Research Group, Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, Porto, Portugal
| | - Célia D Cruz
- Department of Biomedicine, Experimental Biology Unit, Faculty of Medicine, University of Porto, Porto, Portugal.,Translational NeuroUrology Group, Instituto de Investigação e Inovação em Saúde - i3S, Universidade do Porto, Porto, Portugal
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Wangzhou A, McIlvried LA, Paige C, Barragan-Iglesias P, Shiers S, Ahmad A, Guzman CA, Dussor G, Ray PR, Gereau RW, Price TJ. Pharmacological target-focused transcriptomic analysis of native vs cultured human and mouse dorsal root ganglia. Pain 2020; 161:1497-1517. [PMID: 32197039 PMCID: PMC7305999 DOI: 10.1097/j.pain.0000000000001866] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Dorsal root ganglion (DRG) neurons detect sensory inputs and are crucial for pain processing. They are often studied in vitro as dissociated cell cultures with the assumption that this reasonably represents in vivo conditions. However, to the best of our knowledge, no study has directly compared genome-wide transcriptomes of DRG tissue in vivo versus in vitro or between laboratories and culturing protocols. Comparing RNA sequencing-based transcriptomes of native to cultured (4 days in vitro) human or mouse DRG, we found that the overall expression levels of many ion channels and G-protein-coupled receptors specifically expressed in neurons are markedly lower although still expressed in culture. This suggests that most pharmacological targets expressed in vivo are present under the condition of dissociated cell culture, but with changes in expression levels. The reduced relative expression for neuronal genes in human DRG cultures is likely accounted for by increased expression of genes in fibroblast-like and other proliferating cells, consistent with their mitotic status in these cultures. We found that the expression of a subset of genes typically expressed in neurons increased in human and mouse DRG cultures relative to the intact ganglion, including genes associated with nerve injury or inflammation in preclinical models such as BDNF, MMP9, GAL, and ATF3. We also found a striking upregulation of a number of inflammation-associated genes in DRG cultures, although many were different between mouse and human. Our findings suggest an injury-like phenotype in DRG cultures that has important implications for the use of this model system for pain drug discovery.
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Affiliation(s)
- Andi Wangzhou
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Lisa A. McIlvried
- Washington University Pain Center and Department of
Anesthesiology, Washington University School of Medicine
| | - Candler Paige
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Paulino Barragan-Iglesias
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Stephanie Shiers
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Ayesha Ahmad
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Carolyn A. Guzman
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Gregory Dussor
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Pradipta R. Ray
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
| | - Robert W. Gereau
- Washington University Pain Center and Department of
Anesthesiology, Washington University School of Medicine
| | - Theodore J. Price
- The University of Texas at Dallas, School of Behavioral and
Brain Sciences and Center for Advanced Pain Studies, 800 W Campbell Rd. Richardson,
TX, 75080, USA
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50
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Tao X, Lee MS, Donnelly CR, Ji RR. Neuromodulation, Specialized Proresolving Mediators, and Resolution of Pain. Neurotherapeutics 2020; 17:886-899. [PMID: 32696274 PMCID: PMC7609770 DOI: 10.1007/s13311-020-00892-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The current crises in opioid abuse and chronic pain call for the development of nonopioid and nonpharmacological therapeutics for pain relief. Neuromodulation-based approaches, such as spinal cord stimulation, dorsal root ganglion simulation, and nerve stimulation including vagus nerve stimulation, have shown efficacy in achieving pain control in preclinical and clinical studies. However, the mechanisms by which neuromodulation alleviates pain are not fully understood. Accumulating evidence suggests that neuromodulation regulates inflammation and neuroinflammation-a localized inflammation in peripheral nerves, dorsal root ganglia/trigeminal ganglia, and spinal cord/brain-through neuro-immune interactions. Specialized proresolving mediators (SPMs) such as resolvins, protectins, maresins, and lipoxins are lipid molecules produced during the resolution phase of inflammation and exhibit multiple beneficial effects in resolving inflammation in various animal models. Recent studies suggest that SPMs inhibit inflammatory pain, postoperative pain, neuropathic pain, and cancer pain in rodent models via immune, glial, and neuronal modulations. It is noteworthy that sham surgery is sufficient to elevate resolvin levels and may serve as a model of resolution. Interestingly, it has been shown that the vagus nerve produces SPMs and vagus nerve stimulation (VNS) induces SPM production in vitro. In this review, we discuss how neuromodulation such as VNS controls pain via immunomodulation and neuro-immune interactions and highlight possible involvement of SPMs. In particular, we demonstrate that VNS via auricular electroacupuncture effectively attenuates chemotherapy-induced neuropathic pain. Furthermore, auricular stimulation is able to increase resolvin levels in mice. Thus, we propose that neuromodulation may control pain and inflammation/neuroinflammatioin via SPMs. Finally, we discuss key questions that remain unanswered in our understanding of how neuromodulation-based therapies provide short-term and long-term pain relief.
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Affiliation(s)
- Xueshu Tao
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Michael S Lee
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Christopher R Donnelly
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Ru-Rong Ji
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC, 27710, USA.
- Department of Neurobiology, Duke University Medical Center, Durham, NC, 27710, USA.
- Department of Cell Biology, Duke University Medical Center, Durham, NC, 27710, USA.
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