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Boakye PA, Tang SJ, Smith PA. Mediators of Neuropathic Pain; Focus on Spinal Microglia, CSF-1, BDNF, CCL21, TNF-α, Wnt Ligands, and Interleukin 1β. FRONTIERS IN PAIN RESEARCH 2022; 2:698157. [PMID: 35295524 PMCID: PMC8915739 DOI: 10.3389/fpain.2021.698157] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 07/14/2021] [Indexed: 01/04/2023] Open
Abstract
Intractable neuropathic pain is a frequent consequence of nerve injury or disease. When peripheral nerves are injured, damaged axons undergo Wallerian degeneration. Schwann cells, mast cells, fibroblasts, keratinocytes and epithelial cells are activated leading to the generation of an “inflammatory soup” containing cytokines, chemokines and growth factors. These primary mediators sensitize sensory nerve endings, attract macrophages, neutrophils and lymphocytes, alter gene expression, promote post-translational modification of proteins, and alter ion channel function in primary afferent neurons. This leads to increased excitability and spontaneous activity and the generation of secondary mediators including colony stimulating factor 1 (CSF-1), chemokine C-C motif ligand 21 (CCL-21), Wnt3a, and Wnt5a. Release of these mediators from primary afferent neurons alters the properties of spinal microglial cells causing them to release tertiary mediators, in many situations via ATP-dependent mechanisms. Tertiary mediators such as BDNF, tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and other Wnt ligands facilitate the generation and transmission of nociceptive information by increasing excitatory glutamatergic transmission and attenuating inhibitory GABA and glycinergic transmission in the spinal dorsal horn. This review focusses on activation of microglia by secondary mediators, release of tertiary mediators from microglia and a description of their actions in the spinal dorsal horn. Attention is drawn to the substantial differences in the precise roles of various mediators in males compared to females. At least 25 different mediators have been identified but the similarity of their actions at sensory nerve endings, in the dorsal root ganglia and in the spinal cord means there is considerable redundancy in the available mechanisms. Despite this, behavioral studies show that interruption of the actions of any single mediator can relieve signs of pain in experimental animals. We draw attention this paradox. It is difficult to explain how inactivation of one mediator can relieve pain when so many parallel pathways are available.
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Affiliation(s)
- Paul A Boakye
- Department of Anesthesiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, United States
| | - Shao-Jun Tang
- Department of Anesthesiology, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, United States
| | - Peter A Smith
- Neuroscience and Mental Health Institute and Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
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Roza C, Bernal L. Electrophysiological characterization of ectopic spontaneous discharge in axotomized and intact fibers upon nerve transection: a role in spontaneous pain? Pflugers Arch 2022; 474:387-396. [PMID: 35088129 DOI: 10.1007/s00424-021-02655-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 12/14/2022]
Abstract
Many patients experience positive symptoms after traumatic nerve injury. Despite the increasing number of experimental studies in models of peripheral neuropathy and the knowledge acquired, most of these patients lack an effective treatment for their chronic pain. One possible explanation might be that most of the preclinical studies focused on the development of mechanical or thermal allodynia/hyperalgesia, neglecting that most of the patients with peripheral neuropathies complain mostly about spontaneous forms of pains. Here, we summarize the aberrant electrophysiological behavior of peripheral nerve fibers recorded in experimental models, the underlying pathophysiological mechanisms, and their relationship with the symptoms reported by patients. Upon nerve section, axotomized but also intact fibers develop ectopic spontaneous activity. Most interestingly, a proportion of axotomized fibers might present receptive fields in the skin far beyond the site of damage, indicative of a functional cross talk between neuromatose and intact fibers. All these features can be linked with some of the symptoms that neuropathic patients experience. Furthermore, we spotlight the consequence of primary afferents with different patterns of spontaneous discharge on the neural code and its relationship with chronic pain states. With this article, readers will be able to understand the pathophysiological mechanisms that might underlie some of the symptoms that experience neuropathic patients, with a special focus on spontaneous pain.
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Affiliation(s)
- Carolina Roza
- Dpto. Biología de Sistemas, Edificio de Medicina Universidad de Alcalá, 28871, Alcalá de Henares, Madrid, Spain.
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Fu B, Zhu R. Analgesia effect of lentivirus-siSCN9A infected neurons in vincristine induced neuropathic pain rats. Bioengineered 2021; 12:12498-12508. [PMID: 34927536 PMCID: PMC8810170 DOI: 10.1080/21655979.2021.2008696] [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] [Indexed: 10/26/2022] Open
Abstract
At present, the mechanism of siSCN9A in Vincristine (VCR)-induced neuropathic pain (NP) is still unclear. This study aimed to explore the analgesic mechanism of lentivirus-siSCN9A (LV-siSCN9A) infected neurons against NP. 40 male Sprague-Dawley (SD) rats were divided into a control group (injected with normal saline), a model group (VCR-induced NP model), a LV-SC group (NP model mice were injected with LV-SC-infected dorsal root ganglia (DRG) neuron cells under the microscope), and a LV-siSCN9A group (NP model mice were injected with LV-siSCN9A-infected DRG neuron cells under the microscope, with 10 rats in each group. The changes of mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) of rats in different groups were detected by behavior testing, the Nav1.7 changes in each group were detected by immunofluorescence double standard and Western-blot method. It was found that compared with the control group, the MWT and TWL of the rats in model group were significantly decreased (P < 0.05), and the expression levels of Nav1.7 messenger ribonucleic acid (mRNA) and proteins were significantly increased (P < 0.05). Compared with LV-SC group, the MWT and TWL of rats in LV-siSCN9A group were significantly increased (P < 0.05), the expression levels of Nav1.7 mRNA and proteins were significantly decreased (P < 0.05), and the CGRP expression of spinal dorsal horn was significantly decreased. It was concluded that the LV-siSCN9A infected neurons could play an analgesic role by down-regulating Nav1.7 expression induced by VCR in NP model.
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Affiliation(s)
- Baojun Fu
- Department of Anesthesiology, The Sixth Affiliated Hospital of Guangzhou Medical University Qingyuan People Hospital, Qingyuan, Guangdong, China
| | - Rong Zhu
- Department of Anesthesiology, The Second Xiangya Hospital,Central South University, Changsha, Hunan, China
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Shi P, Li Z, He T, Li N, Xu X, Yu P, Lu X, Nie J, Liu D, Cai Q, Guan Y, Ge F, Wang J, Guan X. Astrocyte-selective STAT3 knockdown rescues methamphetamine withdrawal-disrupted spatial memory in mice via restoring the astrocytic capacity of glutamate clearance in dCA1. Glia 2021; 69:2404-2418. [PMID: 34110044 DOI: 10.1002/glia.24046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 05/29/2021] [Accepted: 06/01/2021] [Indexed: 01/07/2023]
Abstract
Methamphetamine (METH) is a common abused drug. METH-triggered glutamate (Glu) levels in dorsal CA1 (dCA1) could partially explain the etiology of METH-caused abnormal memory, but the synaptic mechanism remains unclear. Here, we found that METH withdrawal disrupted spatial memory in mice, accompanied by the increases in Glu levels and postsynaptic neuronal activities at dCA1 synapses. METH withdrawal weakened the capacity of Glu clearance in astrocytes, as indicated by increasing the A1-like astrocytes and phosphorylated signal transducer and activator of transcription 3 (p-STAT3), decreasing the Glu transporter 1(GLT-1, also known as EAAT2 or SLC1A2), Glu-aspartate-transporter (GLAST also known as EAAT1 or SLC1A3) and astrocytic glutamine synthase (GS), but failed to affect the presynaptic Glu release from dCA3 within dCA1. Moreover, we identified that in vitro A1-like astrocytes exhibited an increased STAT3 activation and the impaired capacity of Glu clearance. Most importantly, selective knockdown of astrocytic STAT3 in vivo in dCA1 restored the astrocytic capacity of Glu clearance, normalized Glu levels at dCA1 synapses, and finally rescued METH withdrawal-disrupted spatial memory in mice. Thus, astrocytic Glu clearance system, especially STAT3, serves as a novel target for future therapies against METH neurotoxicity.
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Affiliation(s)
- Pengbo Shi
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China.,Department of Orthopedics, The First Affiliated Hospital of Henan University of Chinese Medicine, Zhengzhou, Henan, China
| | - Zhaosu Li
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Teng He
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Nanqin Li
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Xing Xu
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Peiyao Yu
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Xue Lu
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Jiaxun Nie
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Dekang Liu
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Qinglong Cai
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Feifei Ge
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
| | - Jun Wang
- Department of Toxicology, School of Public Health, Nanjing Medical University, Nanjing, China
| | - Xiaowei Guan
- Department of Human Anatomy and Histoembryology, Nanjing University of Chinese Medicine, Nanjing, China
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