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Rodríguez-Palma EJ, Huerta de la Cruz S, Islas-Espinoza AM, Castañeda-Corral G, Granados-Soto V, Khanna R. Nociplastic pain mechanisms and toll-like receptors as promising targets for its management. Pain 2024; 165:2150-2164. [PMID: 38595206 DOI: 10.1097/j.pain.0000000000003238] [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: 11/06/2023] [Accepted: 02/29/2024] [Indexed: 04/11/2024]
Abstract
ABSTRACT Nociplastic pain, characterized by abnormal pain processing without an identifiable organic cause, affects a significant portion of the global population. Unfortunately, current pharmacological treatments for this condition often prove ineffective, prompting the need to explore new potential targets for inducing analgesic effects in patients with nociplastic pain. In this context, toll-like receptors (TLRs), known for their role in the immune response to infections, represent promising opportunities for pharmacological intervention because they play a relevant role in both the development and maintenance of pain. Although TLRs have been extensively studied in neuropathic and inflammatory pain, their specific contributions to nociplastic pain remain less clear, demanding further investigation. This review consolidates current evidence on the connection between TLRs and nociplastic pain, with a specific focus on prevalent conditions like fibromyalgia, stress-induced pain, sleep deprivation-related pain, and irritable bowel syndrome. In addition, we explore the association between nociplastic pain and psychiatric comorbidities, proposing that modulating TLRs can potentially alleviate both pain syndromes and related psychiatric disorders. Finally, we discuss the potential sex differences in TLR signaling, considering the higher prevalence of nociplastic pain among women. Altogether, this review aims to shed light on nociplastic pain, its underlying mechanisms, and its intriguing relationship with TLR signaling pathways, ultimately framing the potential therapeutic role of TLRs in addressing this challenging condition.
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Affiliation(s)
- Erick J Rodríguez-Palma
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, United States
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Cinvestav, South Campus, Mexico City, Mexico
| | | | - Ana M Islas-Espinoza
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Cinvestav, South Campus, Mexico City, Mexico
| | | | - Vinicio Granados-Soto
- Neurobiology of Pain Laboratory, Departamento de Farmacobiología, Cinvestav, South Campus, Mexico City, Mexico
| | - Rajesh Khanna
- Department of Pharmacology and Therapeutics, College of Medicine, University of Florida, Gainesville, FL, United States
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Li J, Zhang L, Xu C, Lin YH, Zhang Y, Wu HY, Chang L, Zhang YD, Luo CX, Li F, Zhu DY. Prolonged Use of NMDAR Antagonist Develops Analgesic Tolerance in Neuropathic Pain via Nitric Oxide Reduction-Induced GABAergic Disinhibition. Neurotherapeutics 2020; 17:1016-1030. [PMID: 32632774 PMCID: PMC7609518 DOI: 10.1007/s13311-020-00883-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Neuropathic pain is usually persistent due to maladaptive neuroplasticity-induced central sensitization and, therefore, necessitates long-term treatment. N-methyl-D-aspartate receptor (NMDAR)-mediated hypersensitivity in the spinal dorsal horn represents key mechanisms of central sensitization. Short-term use of NMDAR antagonists produces antinociceptive efficacy in animal pain models and in clinical practice by reducing central sensitization. However, how prolonged use of NMDAR antagonists affects central sensitization remains unknown. Surprisingly, we find that prolonged blockage of NMDARs does not prevent but aggravate nerve injury-induced central sensitization and produce analgesic tolerance, mainly due to reduced synaptic inhibition. The disinhibition that results from the continuous decrease in the production of nitric oxide from neuronal nitric oxide synthase, downstream signal of NMDARs, leads to the reduction of GABAergic inhibitory synaptic transmission by upregulating brain-derived neurotrophic factor expression and inhibiting the expression and function of potassium-chloride cotransporter. Together, our findings suggest that chronic blockage of NMDARs develops analgesic tolerance through the neuronal nitric oxide synthase-brain-derived neurotrophic factor-potassium-chloride cotransporter pathway. Thus, preventing the GABAergic disinhibition induced by nitric oxide reduction may be necessary for the long-term maintenance of the analgesic effect of NMDAR antagonists.
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Affiliation(s)
- Jun Li
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
- Department of Pharmacy, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006, China
| | - Lin Zhang
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Chu Xu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Yu-Hui Lin
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Yu Zhang
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Hai-Yin Wu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Lei Chang
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Ying-Dong Zhang
- Department of Neurology, Nanjing First Hospital, Nanjing Medical University, Nanjing, 210006, China
| | - Chun-Xia Luo
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Fei Li
- Department of Medicinal Chemistry, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China
| | - Dong-Ya Zhu
- Department of Pharmacology, School of Pharmacy, Nanjing Medical University, Nanjing, 211166, China.
- Institution of Stem Cells and Neuroregeneration, Nanjing Medical University, Nanjing, 211166, China.
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Guangzhou, 510000, China.
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Liu X, Zhu M, Ju Y, Li A, Sun X. Autophagy dysfunction in neuropathic pain. Neuropeptides 2019; 75:41-48. [PMID: 30910234 DOI: 10.1016/j.npep.2019.03.005] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Revised: 02/28/2019] [Accepted: 03/18/2019] [Indexed: 01/13/2023]
Abstract
Autophagy is a lysosomal degradation pathway that maintains tissue homeostasis by recycling damaged and aged cellular components, which plays important roles in development of the nervous system, as well as in neuronal function and survival. In addition, autophagy dysfunction underlies neuropathic pain. Thus, the modulation of autophagy can alleviate neuropathic pain. Here, we describe the definition, mechanisms of autophagy and neuropathic pain. On this basis, we further discuss the role of autophagy dysfunction in neuropathic pain. This review updates our knowledge on autophagy mechanisms which propose potential therapeutic targets for the treatment of neuropathic pain.
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Affiliation(s)
- Xiaojuan Liu
- Department of Pathogen Biology, Medical College, Nantong University, Nantong 226001, Jiangsu, China
| | - Manhui Zhu
- Department of Ophthalmology, Affiliated Lixiang Eye Hospital of Soochow University, Suzhou 210005, Jiangsu, China
| | - Yuanyuan Ju
- Medical College, Nantong University, Nantong 2266001, Jiangsu, China
| | - Aihong Li
- Department of Neurology, Affiliated Hospital of Nantong University, Nantong 226001, Jiangsu, China.
| | - Xiaolei Sun
- Department of Pathogen Biology, Medical College, Nantong University, Nantong 226001, Jiangsu, China.
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Safieh-Garabedian B, Nomikos M, Saadé N. Targeting inflammatory components in neuropathic pain: The analgesic effect of thymulin related peptide. Neurosci Lett 2018; 702:61-65. [PMID: 30503917 DOI: 10.1016/j.neulet.2018.11.041] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Neuropathic pain is considered to be pathological in nature and has been shown to involve, at least partially, dysregulated inflammatory processes. It is a severe chronic disease that can develop following lesions to the central nervous system or to peripheral nerves. The peripheral nerve damage can be caused by either diseases such as diabetes, or by trauma. A common underlying mechanism of neuropathic pain is the presence of inflammation at the site of the damaged or affected nerve(s). This inflammatory response, especially when unresolved, initiates and maintains a cascade of events resulting in the activation of innate immune cells at the site of tissue injury. The release of inflammatory mediators such as cytokines, neurotrophic factors, and chemokines initiates local actions and can result in a more generalized immune response. The resultant neuroinflammatory environment can cause activation of glial cells, which can release, in an uncontrolled manner, more of these mediators and exasperate the situation, thus having a prominent role in nociception. The neuropathic pain pathophysiology is complex and includes peripheral and central neuronal alterations as well as neuro-immune interactions, which become more prominent during inflammatory reactions. This report focuses on how targeting inflammatory mediators may result in novel therapeutic approaches to neuropathic pain management.
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Affiliation(s)
| | - Michail Nomikos
- College of Medicine, Member of QU Health, Qatar University, Doha, Qatar
| | - Nayef Saadé
- Department of Cell Biology, Anatomy and Physiology, Faculty of Medicine, American University of Beirut, Beirut, Lebanon
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5
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Rosen S, Ham B, Mogil JS. Sex differences in neuroimmunity and pain. J Neurosci Res 2017; 95:500-508. [PMID: 27870397 DOI: 10.1002/jnr.23831] [Citation(s) in RCA: 214] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Revised: 06/14/2016] [Accepted: 06/20/2016] [Indexed: 12/12/2022]
Abstract
Differences in the prevalence of chronic pain in women vs. men are well known, and decades of laboratory experimentation have demonstrated that women are more sensitive to pain than are men. Attention has thus shifted to investigating mechanisms underlying such differences. Recent evidence suggests that neuroimmune modulation of pain may represent an important cause of sex differences. The current Review examines the evidence for gonadal hormone modulation of the immune system, immune system modulation of pain, and interactions that might help to explain sex differences in pain. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Sarah Rosen
- Department of Psychology and Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, Canada
| | - Boram Ham
- Department of Psychology and Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, Canada
| | - Jeffrey S Mogil
- Department of Psychology and Alan Edwards Centre for Research on Pain, McGill University, Montreal, Quebec, Canada
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Shah M, Choi S. Toll-like Receptor-Dependent Negative Effects of Opioids: A Battle between Analgesia and Hyperalgesia. Front Immunol 2017; 8:642. [PMID: 28620391 PMCID: PMC5450035 DOI: 10.3389/fimmu.2017.00642] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 05/17/2017] [Indexed: 11/28/2022] Open
Abstract
Our understanding of the pathophysiology of the pathological pain and the pharmacology of analgesic treatments has progressed tremendously over the past two decades. Among the well-documented pro-algesic factors, glia and other toll-like receptors (TLRs)-expressing cells in the neuroimmune interface have been recognized for their role in the development of neuropathic pain and for compromising the analgesic effects of opioids. Here, we comprehensively review the molecular mechanisms of pain initiation and progression, the role of TLRs in these processes, and the molecular mechanisms of morphine and morphine-3-glucuronide in TLR-dependent central immune signaling. The data reviewed here suggest that, while targeting glia to treat neuropathic pain, both analgesic and analgesia-opposing effects of opioids must be considered by acknowledging their role in TLR-mediated signaling.
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Affiliation(s)
- Masaud Shah
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea
| | - Sangdun Choi
- Department of Molecular Science and Technology, Ajou University, Suwon, South Korea
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Thakur KK, Saini J, Mahajan K, Singh D, Jayswal DP, Mishra S, Bishayee A, Sethi G, Kunnumakkara AB. Therapeutic implications of toll-like receptors in peripheral neuropathic pain. Pharmacol Res 2017; 115:224-232. [DOI: 10.1016/j.phrs.2016.11.019] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2016] [Revised: 10/28/2016] [Accepted: 11/20/2016] [Indexed: 12/13/2022]
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Upregulated TLR3 Promotes Neuropathic Pain by Regulating Autophagy in Rat With L5 Spinal Nerve Ligation Model. Neurochem Res 2016; 42:634-643. [DOI: 10.1007/s11064-016-2119-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 10/20/2016] [Accepted: 11/21/2016] [Indexed: 12/18/2022]
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Guan Z, Hellman J, Schumacher M. Contemporary views on inflammatory pain mechanisms: TRPing over innate and microglial pathways. F1000Res 2016; 5. [PMID: 27781082 PMCID: PMC5054801 DOI: 10.12688/f1000research.8710.1] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/27/2016] [Indexed: 12/14/2022] Open
Abstract
Tissue injury, whether by trauma, surgical intervention, metabolic dysfunction, ischemia, or infection, evokes a complex cellular response (inflammation) that is associated with painful hyperalgesic states. Although in the acute stages it is necessary for protective reflexes and wound healing, inflammation may persist well beyond the need for tissue repair or survival. Prolonged inflammation may well represent the greatest challenge mammalian organisms face, as it can lead to chronic painful conditions, organ dysfunction, morbidity, and death. The complexity of the inflammatory response reflects not only the inciting event (infection, trauma, surgery, cancer, or autoimmune) but also the involvement of heterogeneous cell types including neuronal (primary afferents, sensory ganglion, and spinal cord), non-neuronal (endothelial, keratinocytes, epithelial, and fibroblasts), and immune cells. In this commentary, we will examine 1.) the expression and regulation of two members of the transient receptor potential family in primary afferent nociceptors and their activation/regulation by products of inflammation, 2.) the role of innate immune pathways that drive inflammation, and 3.) the central nervous system’s response to injury with a focus on the activation of spinal microglia driving painful hyperalgesic states.
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Affiliation(s)
- Zhonghui Guan
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA, USA
| | - Judith Hellman
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA, USA
| | - Mark Schumacher
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA, USA
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10
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Kato J, Agalave NM, Svensson CI. Pattern recognition receptors in chronic pain: Mechanisms and therapeutic implications. Eur J Pharmacol 2016; 788:261-273. [PMID: 27343378 DOI: 10.1016/j.ejphar.2016.06.039] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2016] [Revised: 06/22/2016] [Accepted: 06/22/2016] [Indexed: 12/13/2022]
Abstract
For the individual, it is vital to promptly detect and recognize a danger that threatens the integrity of the body. Pattern recognition receptors (PRRs) are several classes of protein families originally classified as receptors detecting exogenous pathogens. PRRs are also capable of recognizing molecules released from damaged tissues (damage-associated molecular pattern molecules; DAMPs) and thereby contribute to danger recognition. Importantly, it is now evident that PRRs, such as toll-like receptors (TLRs) and receptors for advanced glycation end products (RAGE), are not only expressed in peripheral immune cells but also present in neurons and glial cells in the nervous system. These PRR-expressing cells work in concert, enabling highly sensitive danger recognition. However, this sensitiveness can act as a double-edged sword. Accumulated evidence has led to the hypothesis that aberrant activation of PRRs may play a crucial role in the pathogenesis of pathological pain. Indeed, numerous studies employing gene deletion or pharmacological inhibition of PRRs successfully reversed or prevented pathological pain in experimental animal models. Furthermore, a number of preclinical studies have shown the therapeutic potential of targeting PRRs for chronic pain. Here, we review the current knowledge regarding the role of PRRs in chronic pain and discuss the promise and challenges of targeting PRRs as a novel therapeutic approach for chronic pain.
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Affiliation(s)
- Jungo Kato
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
| | - Nilesh M Agalave
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Camilla I Svensson
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
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11
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García Bueno B, Caso JR, Madrigal JLM, Leza JC. Innate immune receptor Toll-like receptor 4 signalling in neuropsychiatric diseases. Neurosci Biobehav Rev 2016; 64:134-47. [PMID: 26905767 DOI: 10.1016/j.neubiorev.2016.02.013] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/27/2015] [Accepted: 02/12/2016] [Indexed: 02/08/2023]
Abstract
The innate immunity is a stereotyped first line of defense against pathogens and unspecified damage signals. One of main actors of innate immunity are the Toll-like receptors (TLRs), and one of the better characterized members of this family is TLR-4, that it is mainly activated by Gram-negative bacteria lipopolysaccharide. In brain, TLR-4 organizes innate immune responses against infections or cellular damage, but also possesses other physiological functions. In the last years, some evidences suggest a role of TLR-4 in stress and stress-related neuropsychiatric diseases. Peripheral and brain TLR-4 activation triggers sickness behavior, and its expression is a risk factor of depression. Some elements of the TLR-4 signaling pathway are up-regulated in peripheral samples and brain post-mortem tissue from depressed and suicidal patients. The "leaky gut" hypothesis of neuropsychiatric diseases is based on the existence of an increase of the intestinal permeability which results in bacterial translocation able to activate TLR-4. Enhanced peripheral TLR-4 expression/activity has been described in subjects diagnosed with schizophrenia, bipolar disorder and in autistic children. A role for TLR-4 in drugs abuse has been also proposed. The therapeutic potential of pharmacological/genetic modulation of TLRs signaling pathways in neuropsychiatry is promising, but a great preclinical/clinical scientific effort is still needed.
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Affiliation(s)
- B García Bueno
- Department of Pharmacology, School of Medicine, Complutense University, CIBERSAM, Instituto de Investigación Hospital 12 de Octubre (Imas12), 28040 Madrid, Spain.
| | - J R Caso
- Department of Pharmacology, School of Medicine, Complutense University, CIBERSAM, Instituto de Investigación Hospital 12 de Octubre (Imas12), 28040 Madrid, Spain.
| | - J L M Madrigal
- Department of Pharmacology, School of Medicine, Complutense University, CIBERSAM, Instituto de Investigación Hospital 12 de Octubre (Imas12), 28040 Madrid, Spain.
| | - J C Leza
- Department of Pharmacology, School of Medicine, Complutense University, CIBERSAM, Instituto de Investigación Hospital 12 de Octubre (Imas12), 28040 Madrid, Spain.
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Marinelli C, Di Liddo R, Facci L, Bertalot T, Conconi MT, Zusso M, Skaper SD, Giusti P. Ligand engagement of Toll-like receptors regulates their expression in cortical microglia and astrocytes. J Neuroinflammation 2015; 12:244. [PMID: 26714634 PMCID: PMC4696218 DOI: 10.1186/s12974-015-0458-6] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Accepted: 12/15/2015] [Indexed: 12/13/2022] Open
Abstract
Background Toll-like receptor (TLR) activation on microglia and astrocytes are key elements in neuroinflammation which accompanies a number of neurological disorders. While TLR activation on glia is well-established to up-regulate pro-inflammatory mediator expression, much less is known about how ligand engagement of one TLR may affect expression of other TLRs on microglia and astrocytes. Methods In the present study, we evaluated the effects of agonists for TLR2 (zymosan), TLR3 (polyinosinic-polycytidylic acid (poly(I:C)), a synthetic analogue of double-stranded RNA) and TLR4 (lipopolysaccaride (LPS)) in influencing expression of their cognate receptor as well as that of the other TLRs in cultures of rat cortical purified microglia (>99.5 %) and nominally microglia-free astrocytes. Elimination of residual microglia (a common contaminant of astrocyte cultures) was achieved by incubation with the lysosomotropic agent l-leucyl-l-leucine methyl ester (L-LME). Results Flow cytometric analysis confirmed the purity (essentially 100 %) of the obtained microglia, and up to 5 % microglia contamination of astrocytes. L-LME treatment effectively removed microglia from the latter (real-time polymerase chain reaction). The three TLR ligands robustly up-regulated gene expression for pro-inflammatory markers (interleukin-1 and interleukin-6, tumor necrosis factor) in microglia and enriched, but not purified, astrocytes, confirming cellular functionality. LPS, zymosan and poly(I:C) all down-regulated TLR4 messenger RNA (mRNA) and up-regulated TLR2 mRNA at 6 and 24 h. In spite of their inability to elaborate pro-inflammatory mediator output, the nominally microglia-free astrocytes (>99 % purity) also showed similar behaviours to those of microglia, as well as changes in TLR3 gene expression. LPS interaction with TLR4 activates downstream mitogen-activated protein kinase and nuclear factor-κB signalling pathways and subsequently causes inflammatory mediator production. The effects of LPS on TLR2 mRNA in both cell populations were antagonized by a nuclear factor-κB inhibitor. Conclusions TLR2 and TLR4 activation in particular, in concert with microglia and astrocytes, comprise key elements in the initiation and maintenance of neuropathic pain. The finding that both homologous (zymosan) and heterologous (LPS, poly(I:C)) TLR ligands are capable of regulating TLR2 gene expression, in particular, may have important implications in understanding the relative contributions of different TLRs in neurological disorders associated with neuroinflammation. Electronic supplementary material The online version of this article (doi:10.1186/s12974-015-0458-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Carla Marinelli
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
| | - Rosa Di Liddo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
| | - Laura Facci
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
| | - Thomas Bertalot
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
| | - Maria Teresa Conconi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
| | - Morena Zusso
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
| | - Stephen D Skaper
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
| | - Pietro Giusti
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Largo "E. Meneghetti" 2, 35131, Padua, Italy.
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Helley M, Abate W, Jackson S, Bennett J, Thompson S. The expression of Toll-like receptor 4, 7 and co-receptors in neurochemical sub-populations of rat trigeminal ganglion sensory neurons. Neuroscience 2015; 310:686-98. [DOI: 10.1016/j.neuroscience.2015.09.069] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/03/2015] [Accepted: 09/25/2015] [Indexed: 12/12/2022]
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14
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Tsuda M. Microglia in the spinal cord and neuropathic pain. J Diabetes Investig 2015; 7:17-26. [PMID: 26813032 PMCID: PMC4718109 DOI: 10.1111/jdi.12379] [Citation(s) in RCA: 172] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 05/13/2015] [Accepted: 05/16/2015] [Indexed: 12/13/2022] Open
Abstract
In contrast to physiological pain, pathological pain is not dependent on the presence of tissue‐damaging stimuli. One type of pathological pain – neuropathic pain – is often a consequence of nerve injury or of diseases such as diabetes. Neuropathic pain can be agonizing, can persist over long periods and is often resistant to known painkillers. A growing body of evidence shows that many pathological processes within the central nervous system are mediated by complex interactions between neurons and glial cells. In the case of painful peripheral neuropathy, spinal microglia react and undergo a series of changes that directly influence the establishment of neuropathic pain states. After nerve damage, purinergic P2X4 receptors (non‐selective cation channels activated by extracellular adenosine triphosphate) are upregulated in spinal microglia in a manner that depends on the transcription factors interferon regulatory factor 8 and 5, both of which are expressed in microglia after peripheral nerve injury. P2X4 receptor expression on the cell surface of microglia is also regulated at the post‐translational level by signaling from CC chemokine receptor chemotactic cytokine receptor 2. Furthermore, spinal microglia in response to extracellular stimuli results in signal transduction through intracellular signaling cascades, such as mitogen‐activated protein kinases, p38 and extracellular signal‐regulated protein kinase. Importantly, inhibiting the function or expression of these microglial molecules suppresses the aberrant excitability of dorsal horn neurons and neuropathic pain. These findings show that spinal microglia are a central player in mechanisms for neuropathic pain, and might be a potential target for treating the chronic pain state.
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Affiliation(s)
- Makoto Tsuda
- Department of Life Innovation Graduate School of Pharmaceutical Sciences Kyushu University Fukuoka Japan
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15
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Wardill HR, Van Sebille YZ, Mander KA, Gibson RJ, Logan RM, Bowen JM, Sonis ST. Toll-like receptor 4 signaling: A common biological mechanism of regimen-related toxicities. Cancer Treat Rev 2015; 41:122-8. [DOI: 10.1016/j.ctrv.2014.11.005] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 11/24/2014] [Accepted: 11/27/2014] [Indexed: 01/02/2023]
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Toll-like receptors 2, -3 and -4 prime microglia but not astrocytes across central nervous system regions for ATP-dependent interleukin-1β release. Sci Rep 2014; 4:6824. [PMID: 25351234 PMCID: PMC5381369 DOI: 10.1038/srep06824] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 09/09/2014] [Indexed: 12/13/2022] Open
Abstract
Interleukin-1β (IL-1β) is a crucial mediator in the pathogenesis of inflammatory diseases at the periphery and in the central nervous system (CNS). Produced as an unprocessed and inactive pro-form which accumulates intracellularly, release of the processed cytokine is strongly promoted by ATP acting at the purinergic P2X7 receptor (P2X7R) in cells primed with lipopolysaccharide (LPS), a Toll-like receptor (TLR) 4 ligand. Microglia are central to the inflammatory process and a major source of IL-1β when activated. Here we show that purified (>99%) microglia cultured from rat cortex, spinal cord and cerebellum respond robustly to ATP-dependent IL-1β release, upon priming with a number of TLR isoform ligands (zymosan and Pam3CSK4 for TLR2, poly(I:C) for TLR3). Cytokine release was prevented by a P2X7R antagonist and inhibitors of stress-activated protein kinases. Enriched astrocytes (≤5% microglia) from these CNS regions displayed responses qualitatively similar to microglia but became unresponsive upon eradication of residual microglia with the lysosomotropic agent Leu-Leu-OMe. Activation of multiple TLR isoforms in nervous system pathology, coupled with elevated extracellular ATP levels and subsequent P2X7R activation may represent an important route for microglia-derived IL-1β. This phenomenon may have important consequences for neuroinflammation and its position to the common pathology of CNS diseases.
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Sung J, Morales W, Kim G, Pokkunuri V, Weitsman S, Rooks E, Marsh Z, Barlow GM, Chang C, Pimentel M. Effect of repeated Campylobacter jejuni infection on gut flora and mucosal defense in a rat model of post infectious functional and microbial bowel changes. Neurogastroenterol Motil 2013; 25:529-37. [PMID: 23521493 DOI: 10.1111/nmo.12118] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Accepted: 02/15/2013] [Indexed: 12/24/2022]
Abstract
BACKGROUND Campylobacter jejuni infection is a leading cause of gastroenteritis and post infectious irritable bowel syndrome (PI-IBS). Unanswered questions include the role of cytokines, effects on gut flora, and why IBS is not more prevalent in countries with higher gastroenteritis rates. Therefore, we determined the effects of early and repeat C. jejuni infections on post infectious phenotypes, gut flora, and cytokine levels in a rat model of functional bowel and microbial changes. METHODS Sprague-Dawley rats were gavaged with 10(8) cfu C. jejuni as juveniles and again as adults (J+/A+), as adults only (J-/A+), or vehicle (controls). Stool consistency during acute colonization, post infectious stool wet weight, total bacteria and Methanobrevibacter smithii levels in bowel segments, and ileal cytokines were evaluated. KEY RESULTS C. jejuni colonization was longer for first exposures as juveniles (43.4 ± 1.7 days) vs. adults (30.4 ± 3.5 days) (P < 0.01) and shortest for second exposures (10.5 ± 1.7 days, P < 0.05). Small intestinal bacterial overgrowth (SIBO) was more prevalent in J+/A+ (47%) than J-/A+ rats (26%) (P = 0.019), but J-/A+ rats had greater stool consistency alterations (P < 0.01). Ileal β-defensin 2, TLR-4, IL-8, and β-defensin 6 levels were increased in J-/A+ rats and further increased in J+/A+ rats; TNF-α was highest and IL6 lowest in J-/A+ rats. Total bacteria increased, and M. smithii decreased, with successive infections. CONCLUSIONS & INFERENCES We conclude that C. jejuni infection results in long-term alterations in small bowel flora, including methanogens. Mucosal defense mediators appear related to the number of infections, but not to SIBO development or the development of functional bowel phenotypes.
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Affiliation(s)
- J Sung
- GI Motility Program, Division of Gastroenterology, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA
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David BT, Ratnayake A, Amarante MA, Reddy NP, Dong W, Sampath S, Heary RF, Elkabes S. A toll-like receptor 9 antagonist reduces pain hypersensitivity and the inflammatory response in spinal cord injury. Neurobiol Dis 2013; 54:194-205. [PMID: 23313320 DOI: 10.1016/j.nbd.2012.12.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 11/11/2012] [Accepted: 12/28/2012] [Indexed: 12/20/2022] Open
Abstract
Toll-like receptors (TLRs) are mediators of the innate immune response to exogenous pathogens. They have also been implicated in sterile inflammation associated with systemic injury and non-infectious diseases via binding of endogenous ligands, possibly released by damaged cells. Emerging evidence indicates that some TLRs play a role in nervous system injury and especially in injury-elicited pain and sterile inflammation. However, no information is available about the contribution of TLR9, a member of the TLR family, to traumatic spinal cord injury (SCI). Moreover, the therapeutic potential of TLR9 ligands in the functional outcomes of SCI, including pain, has not been explored. We report, for the first time, that the intrathecal administration of a TLR9 antagonist, cytidine-phosphate-guanosine oligodeoxynucleotide 2088 (CpG ODN 2088), to mice sustaining a severe contusion SCI, diminishes injury-induced heat hypersensitivity. Investigations on the potential mechanisms underlying the reduction in pain sensitivity indicated an attenuation of the inflammatory reaction manifested by a decrease in the number of CD11b-, CD45- and CD3-immunoreactive cells and a reduction in tumor necrosis factor-α (TNF-α) expression at the epicenter. Conversely, intrathecal delivery of a TLR9 agonist, CpG ODN 1826, increased inflammatory cell numbers and TNF-α expression in the epicenter. The CpG ODN 2088 treatment did not appear to induce systemic adverse effects as shown by spleen histology and serum cytokine levels. We propose that CpG ODN 2088 dampens injury-induced heat hypersensitivity by suppressing the inflammatory response and TNF-α expression. This investigation defines a previously unreported therapeutic role for CpG ODN 2088 in SCI-induced pain.
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Affiliation(s)
- Brian T David
- Department of Neurological Surgery, New Jersey Medical School, Newark, NJ 07103, USA
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19
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Abstract
Toll-like receptors (TLRs) are germline-encoded pattern-recognition receptors that initiate innate immune responses by recognizing molecular structures shared by a wide range of pathogens, known as pathogen-associated molecular patterns (PAMPs). After tissue injury or cellular stress, TLRs also detect endogenous ligands known as danger-associated molecular patterns (DAMPs). TLRs are expressed in both non-neuronal and neuronal cell types in the central nervous system (CNS) and contribute to both infectious and non-infectious disorders in the CNS. Following tissue insult and nerve injury, TLRs (such as TLR2, TLR3, and TLR4) induce the activation of microglia and astrocytes and the production of the proinflammatory cytokines in the spinal cord, leading to the development and maintenance of inflammatory pain and neuropathic pain. In particular, primary sensory neurons, such as nociceptors, express TLRs (e.g., TLR4 and TLR7) to sense exogenous PAMPs and endogenous DAMPs released after tissue injury and cellular stress. These neuronal TLRs are new players in the processing of pain and itch by increasing the excitability of primary sensory neurons. Given the prevalence of chronic pain and itch and the suffering of affected people, insights into TLR signaling in the nervous system will open a new avenue for the management of clinical pain and itch.
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20
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Calvo M, Dawes JM, Bennett DLH. The role of the immune system in the generation of neuropathic pain. Lancet Neurol 2012; 11:629-42. [PMID: 22710756 DOI: 10.1016/s1474-4422(12)70134-5] [Citation(s) in RCA: 317] [Impact Index Per Article: 26.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Persistent pain is a sequela of several neurological conditions with a primary immune basis, such as Guillain-Barré syndrome and multiple sclerosis. Additionally, diverse forms of injury to the peripheral or the central nervous systems--whether traumatic, metabolic, or toxic--result in substantial recruitment and activation of immune cells. This response involves the innate immune system, but evidence also exists of T-lymphocyte recruitment, and in some patient cohorts antibodies to neuronal antigens have been reported. Mediators released by immune cells, such as cytokines, sensitise nociceptive signalling in the peripheral and central nervous systems. Preclinical data suggest an immune pathogenesis of neuropathic pain, but clinical evidence of a central role of the immune system is less clear. An important challenge for the future is to establish to what extent this immune response initiates or maintains neuropathic pain in patients and thus whether it is amenable to therapy.
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Affiliation(s)
- Margarita Calvo
- Department of Neurorestoration, Wolfson CARD, King's College London, London, UK
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21
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Yan JE, Yuan W, Lou X, Zhu T. Streptozotocin-induced diabetic hyperalgesia in rats is associated with upregulation of Toll-like receptor 4 expression. Neurosci Lett 2012; 526:54-8. [PMID: 22910613 DOI: 10.1016/j.neulet.2012.08.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 07/24/2012] [Accepted: 08/08/2012] [Indexed: 10/28/2022]
Abstract
Neuropathic pain is one of the common complications of diabetes mellitus, and current treatments often do not meet medical needs. Toll-like receptor 4 (TLR4) has been implicated as a potential therapeutic target in neuropathic and other pain models. In this study, we investigated whether TLR4 expression in spinal cord would be altered in streptozotocin-induced diabetic rat model, which had persistent mechanical and thermal hypersensitivity. The results showed that the mRNA expression of TLR4 was upregulated in streptozotocin-treated animals. Furthermore, TLR4 expression was associated with both paw-pressure withdrawal threshold toward mechanical stimulus and paw withdrawal latency toward thermal stimulus. The protein levels of TNF-α and IL-1β, two downstream proinflammatory cytokines of TLR4 signaling pathway, were also significantly raised and correlated with mechanical/thermal hypersensitivity in diabetic rats. Together, these data have demonstrated that TLR4 and its signaling pathway are associated with neuropathic pain in a diabetic model. It may imply that TLR4 could be a novel target for treating diabetic neuropathy.
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Affiliation(s)
- Jian-E Yan
- Department of Anesthesia, Guiyang Medical College, Guiyang, China
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22
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Ito G, Suekawa Y, Watanabe M, Takahashi K, Inubushi T, Murasaki K, Hirose N, Hiyama S, Uchida T, Tanne K. P2X7receptor in the trigeminal sensory nuclear complex contributes to tactile allodynia/hyperalgesia following trigeminal nerve injury. Eur J Pain 2012; 17:185-99. [DOI: 10.1002/j.1532-2149.2012.00174.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/01/2012] [Indexed: 12/29/2022]
Affiliation(s)
- G. Ito
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - Y. Suekawa
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - M. Watanabe
- Department of Oral Biology; Division of Molecular Medical Science; Hiroshima University Graduate School of Biomedical Science; Japan
| | - K. Takahashi
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - T. Inubushi
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - K. Murasaki
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - N. Hirose
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
| | - S. Hiyama
- Department of Oral Biology; Division of Molecular Medical Science; Hiroshima University Graduate School of Biomedical Science; Japan
| | - T. Uchida
- Department of Oral Biology; Division of Molecular Medical Science; Hiroshima University Graduate School of Biomedical Science; Japan
| | - K. Tanne
- Department of Orthodontics and Craniofacial Developmental Biology; Hiroshima University Graduate School of Biomedical Sciences; Japan
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Mao-Ying QL, Wang XW, Yang CJ, Li X, Mi WL, Wu GC, Wang YQ. Robust spinal neuroinflammation mediates mechanical allodynia in Walker 256 induced bone cancer rats. Mol Brain 2012; 5:16. [PMID: 22607655 PMCID: PMC3443428 DOI: 10.1186/1756-6606-5-16] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Accepted: 05/02/2012] [Indexed: 12/31/2022] Open
Abstract
It has been reported that remarkable and sustained activation of astrocytes and/or microglia occurs in cancer induced pain (CIP), which is different from neuropathic and inflammatory pain. The present study was designed to investigate the role of spinal Toll-like receptor 4 (TLR4) induced glial neuroinflammation in cancer induced pain using a modified rat model of bone cancer. The rat model of CIP consisted of unilateral intra-tibial injection with Walker 256 mammary gland carcinoma. Nine days after Walker 256 inoculation, a robust activation of both astrocytes and microglia in bilateral spinal dorsal horn was observed together with significant bilateral mechanical allodynia. This neuroinflammation was characterized by enhanced immunostaining of both glial fibrillary acidic protein (GFAP, astrocyte marker) and OX-42 (microglia marker), and an elevated level of IL-1β, IL-6 and TNF-α mRNA. I.t. administration of fluorocitrate (an inhibitor of glial metabolism, 1 nmol) or minocycline (an inhibitor of microglia, 100 μg) has significant anti-allodynic effects on day 12 after Walker 256 inoculation. Naloxone (a nonstereoselective TLR4 signaling blocker, 60 μg, i.t.) also significantly alleviated mechanical allodynia and simultaneously blocked the increased inflammatory cytokine mRNA. The results suggested that spinal TLR4 might play an important role in the sustained glial activation that critically contributed to the robust and sustained spinal neuroinflammation in CIP. This result could potentially help clinicians and researchers to better understand the mechanism of complicated cancer pain.
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Affiliation(s)
- Qi-Liang Mao-Ying
- Department of Integrative Medicine and Neurobiology, Shanghai Medical College, Institute of Acupuncture Research, Institutes of Brain Science, State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
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24
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Liu T, Berta T, Xu ZZ, Park CK, Zhang L, Lü N, Liu Q, Liu Y, Gao YJ, Liu YC, Ma Q, Dong X, Ji RR. TLR3 deficiency impairs spinal cord synaptic transmission, central sensitization, and pruritus in mice. J Clin Invest 2012; 122:2195-207. [PMID: 22565312 DOI: 10.1172/jci45414] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2011] [Accepted: 03/21/2012] [Indexed: 12/11/2022] Open
Abstract
Itch, also known as pruritus, is a common, intractable symptom of several skin diseases, such as atopic dermatitis and xerosis. TLRs mediate innate immunity and regulate neuropathic pain, but their roles in pruritus are elusive. Here, we report that scratching behaviors induced by histamine-dependent and -independent pruritogens are markedly reduced in mice lacking the Tlr3 gene. TLR3 is expressed mainly by small-sized primary sensory neurons in dorsal root ganglions (DRGs) that coexpress the itch signaling pathway components transient receptor potential subtype V1 and gastrin-releasing peptide. Notably, we found that treatment with a TLR3 agonist induces inward currents and action potentials in DRG neurons and elicited scratching in WT mice but not Tlr3(-/-) mice. Furthermore, excitatory synaptic transmission in spinal cord slices and long-term potentiation in the intact spinal cord were impaired in Tlr3(-/-) mice but not Tlr7(-/-) mice. Consequently, central sensitization-driven pain hypersensitivity, but not acute pain, was impaired in Tlr3(-/-) mice. In addition, TLR3 knockdown in DRGs also attenuated pruritus in WT mice. Finally, chronic itch in a dry skin condition was substantially reduced in Tlr3(-/-) mice. Our findings demonstrate a critical role of TLR3 in regulating sensory neuronal excitability, spinal cord synaptic transmission, and central sensitization. TLR3 may serve as a new target for developing anti-itch treatment.
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Affiliation(s)
- Tong Liu
- Sensory Plasticity Laboratory, Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts, USA
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25
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Skaper SD, Giusti P, Facci L. Microglia and mast cells: two tracks on the road to neuroinflammation. FASEB J 2012; 26:3103-17. [PMID: 22516295 DOI: 10.1096/fj.11-197194] [Citation(s) in RCA: 176] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
One of the more important recent advances in neuroscience research is the understanding that there is extensive communication between the immune system and the central nervous system (CNS). Proinflammatory cytokines play a key role in this communication. The emerging realization is that glia and microglia, in particular, (which are the brain's resident macrophages), constitute an important source of inflammatory mediators and may have fundamental roles in CNS disorders from neuropathic pain and epilepsy to neurodegenerative diseases. Microglia respond also to proinflammatory signals released from other non-neuronal cells, principally those of immune origin. Mast cells are of particular relevance in this context. These immunity-related cells, while resident in the CNS, are capable of migrating across the blood-spinal cord and blood-brain barriers in situations where the barrier is compromised as a result of CNS pathology. Emerging evidence suggests the possibility of mast cell-glia communications and opens exciting new perspectives for designing therapies to target neuroinflammation by differentially modulating the activation of non-neuronal cells normally controlling neuronal sensitization, both peripherally and centrally. This review aims to provide an overview of recent progress relating to the pathobiology of neuroinflammation, the role of microglia, neuroimmune interactions involving mast cells, in particular, and the possibility that mast cell-microglia crosstalk may contribute to the exacerbation of acute symptoms of chronic neurodegenerative disease and accelerate disease progression, as well as promote pain transmission pathways. We conclude by considering the therapeutic potential of treating systemic inflammation or blockade of signaling pathways from the periphery to the brain in such settings.
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Affiliation(s)
- Stephen D Skaper
- Dipartimento di Scienze del Farmaco, University of Padova, Largo E. Meneghetti 2, 35131 Padova, Italy.
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26
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Schomberg D, Olson JK. Immune responses of microglia in the spinal cord: Contribution to pain states. Exp Neurol 2012; 234:262-70. [DOI: 10.1016/j.expneurol.2011.12.021] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 12/05/2011] [Accepted: 12/13/2011] [Indexed: 01/24/2023]
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27
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28
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Landry RP, Jacobs VL, Romero-Sandoval EA, DeLeo JA. Propentofylline, a CNS glial modulator does not decrease pain in post-herpetic neuralgia patients: in vitro evidence for differential responses in human and rodent microglia and macrophages. Exp Neurol 2011; 234:340-50. [PMID: 22119425 DOI: 10.1016/j.expneurol.2011.11.006] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Revised: 10/20/2011] [Accepted: 11/07/2011] [Indexed: 12/13/2022]
Abstract
There is a growing body of preclinical evidence for the potential involvement of glial cells in neuropathic pain conditions. Several glial-targeted agents are in development for the treatment of pain conditions. Here we report the failure of a glial modulating agent, propentofylline, to decrease pain reported in association with post-herpetic neuralgia. We offer new evidence to help explain why propentofylline failed in patients by describing in vitro functional differences between rodent and human microglia and macrophages. We directly compared the proinflammatory response induced by lipopolysaccharide (LPS) with or without propentofylline using rat postnatal microglia, rat peritoneal macrophages, human fetal microglia, human peripheral macrophages and human immortalized THP-1 cells. We measured tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and nitrite release (as an indicator of nitric oxide (NO)) as downstream indicators. We found that LPS treatment did not induce nitrite in human microglia, macrophages or THP-1 cells; however LPS treatment did induce nitrite release in rat microglia and macrophages. Following LPS exposure, propentofylline blocked TNF-α release in rodent microglia with all the doses tested (1-100 μM), and dose-dependently decreased TNF-α release in rodent macrophages. Propentofylline partially decreased TNF-α (35%) at 100 μM in human microglia, macrophages and THP-1 macrophages. Propentofylline blocked nitrite release from LPS stimulated rat microglia and inhibited nitrite in LPS-stimulated rat macrophages. IL-1β was decreased in LPS-stimulated human microglia following propentofylline at 100 μM. Overall, human microglia were less responsive to LPS stimulation and propentofylline treatment than the other cell types. Our data demonstrate significant functional differences between cell types and species following propentofylline treatment and LPS stimulation. These results may help explain the differential behavioral effects of propentofylline observed between rodent models of pain and the human clinical trial.
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Affiliation(s)
- Russell P Landry
- Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, NH 03755, USA
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29
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Nicotra L, Loram LC, Watkins LR, Hutchinson MR. Toll-like receptors in chronic pain. Exp Neurol 2011; 234:316-29. [PMID: 22001158 DOI: 10.1016/j.expneurol.2011.09.038] [Citation(s) in RCA: 190] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 09/26/2011] [Accepted: 09/30/2011] [Indexed: 12/16/2022]
Abstract
Proinflammatory central immune signaling contributes significantly to the initiation and maintenance of heightened pain states. Recent discoveries have implicated the innate immune system, pattern recognition Toll-like receptors in triggering these proinflammatory central immune signaling events. These exciting developments have been complemented by the discovery of neuronal expression of Toll-like receptors, suggesting pain pathways can be activated directly by the detection of pathogen associated molecular patterns or danger associated molecular patterns. This review will examine the evidence to date implicating Toll-like receptors and their associated signaling components in heightened pain states. In addition, insights into the impact Toll-like receptors have on priming central immune signaling systems for heightened pain states will be discussed. The influence possible sex differences in Toll-like receptor signaling have for female pain and the recognition of small molecule xenobiotics by Toll-like receptors will also be reviewed.
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Affiliation(s)
- Lauren Nicotra
- Discipline of Pharmacology, School of Medical Sciences, University of Adelaide, South Australia, 5005, Australia
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30
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Grace PM, Rolan PE, Hutchinson MR. Peripheral immune contributions to the maintenance of central glial activation underlying neuropathic pain. Brain Behav Immun 2011; 25:1322-32. [PMID: 21496480 DOI: 10.1016/j.bbi.2011.04.003] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 04/04/2011] [Accepted: 04/04/2011] [Indexed: 10/18/2022] Open
Abstract
Recent evidence implicates an adaptive immune response in the central nervous system (CNS) mechanisms of neuropathic pain. This review identifies how neuropathic pain alters CNS immune privilege to facilitate T cell infiltration. Once in the CNS, T cells may interact with the local antigen presenting cells, microglia, via the major histocompatibility complex and the costimulatory molecules CD40 and B7. In this way, T cells may contribute to the maintenance of neuropathic pain through pro-inflammatory interactions with microglia and by facilitating the activation of astrocytes in the spinal dorsal horn. Based on the evidence presented in this review, we suggest that this bidirectional, pro-inflammatory system of neurons, glia and T cells in neuropathic pain should be renamed the pentapartite synapse, and identifies the latest member as a potential disease-modifying therapeutic target.
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Affiliation(s)
- Peter M Grace
- Discipline of Pharmacology, School of Medical Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
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31
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Kim D, You B, Lim H, Lee SJ. Toll-like receptor 2 contributes to chemokine gene expression and macrophage infiltration in the dorsal root ganglia after peripheral nerve injury. Mol Pain 2011; 7:74. [PMID: 21951975 PMCID: PMC3192680 DOI: 10.1186/1744-8069-7-74] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2011] [Accepted: 09/28/2011] [Indexed: 12/19/2022] Open
Abstract
Background We have previously reported that nerve injury-induced neuropathic pain is attenuated in toll-like receptor 2 (TLR2) knock-out mice. In these mice, inflammatory gene expression and spinal cord microglia actvation is compromised, whereas the effects in the dorsal root ganglia (DRG) have not been tested. In this study, we investigated the role of TLR2 in inflammatory responses in the DRG after peripheral nerve injury. Results L5 spinal nerve transection injury induced the expression of macrophage-attracting chemokines such as CCL2/MCP-1 and CCL3/MIP-1 and subsequent macrophage infiltration in the DRG of wild-type mice. In TLR2 knock-out mice, however, the induction of chemokine expression and macrophage infiltration following nerve injury were markedly reduced. Similarly, the induction of IL-1β and TNF-α expression in the DRG by spinal nerve injury was ameliorated in TLR2 knock-out mice. The reduced inflammatory response in the DRG was accompanied by attenuation of nerve injury-induced spontaneous pain hypersensitivity in TLR2 knock-out mice. Conclusions Our data show that TLR2 contributes to nerve injury-induced proinflammatory chemokine/cytokine gene expression and macrophage infiltration in the DRG, which may have relevance in the reduced pain hypersensitivity in TLR2 knock-out mice after spinal nerve injury.
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Affiliation(s)
- Donghoon Kim
- Department of Neuroscience and Oral Physiology, and Dental Research Institute, School of Dentistry, Seoul National University, 28 Yeongun-dong Jongno-gu, Seoul, 110-749, Republic of Korea
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Stokes JA, Corr M, Yaksh TL. Transient tactile allodynia following intrathecal puncture in mouse: contributions of Toll-like receptor signaling. Neurosci Lett 2011; 504:215-8. [PMID: 21964382 DOI: 10.1016/j.neulet.2011.09.025] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2011] [Revised: 09/12/2011] [Accepted: 09/13/2011] [Indexed: 12/11/2022]
Abstract
Studies of spinal drug action in mice often involve percutaneous intrathecal drug administration delivered in a lightly anesthetized animal. A successful lumbar intrathecal (IT) needle stick of a lightly anesthetized (isoflurane) mouse evokes a tail flick, which is an indication of local spinal nerve stimulation. Immediately upon arousal, a hind paw tactile allodynia, as measured with von Frey hairs (pre 1.55±0.11 g vs. injected 0.66±0.08 g) lasts 3-4 h. In a similarly anesthetized mouse without the needle stick, a 1-h allodynia was noted. In studies on spinal Toll-like receptor (TLR) signaling, we observed that following intrathecal puncture and mechanical stimulation of the nerve roots mice deficient in TLR down-stream signaling (Myd88(-/-)/Trif(lps2)), displayed only the transient (1-h) allodynia otherwise observed following isoflurane alone. These data suggest that the extended period of hyperalgesia observed with needle penetration of the dura and mechanical stimulation of the nerve roots requires signaling through the MyD88/TRIF pathways and supports the intrinsic role of Toll-like receptors in the allodynia secondary to the minor nerve activation occurring during the intradural puncture.
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Affiliation(s)
- Jennifer A Stokes
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0818, USA
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The mechanisms of microgliosis and pain following peripheral nerve injury. Exp Neurol 2011; 234:271-82. [PMID: 21893056 DOI: 10.1016/j.expneurol.2011.08.018] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 08/10/2011] [Accepted: 08/18/2011] [Indexed: 12/23/2022]
Abstract
Microglia are the resident macrophages in the central nervous system (CNS). Any insult to the CNS homeostasis will induce a rapid change in microglia morphology, gene expression profile and functional behaviour. These responses of microglia have been collectively known as 'microgliosis'. Interestingly, damage to the nervous system outside the CNS, such as axotomy of a peripheral nerve, can lead to microgliosis in the spinal cord. There is a variation in the degree of microgliosis depending on the model of nerve injury employed for instance this response is more marked following traumatic nerve injury than in models of chemotherapy induced neuropathy. Following peripheral nerve injury nociceptive inputs from sensory neurons appear to be critical in triggering the development of spinal microgliosis. A number of signalling pathways including growth factors such as Neuregulin-1, matrix metalloproteases such as MMP-9 and multiple chemokines enable direct communication between injured primary afferents and microglia. In addition, we describe a group of mediators which although not demonstrably shown to be released from neurons are known to modulate microglial phenotype. There is a great functional diversity of the microglial response to peripheral nerve injury which includes: Cellular migration, proliferation, cytokine release, phagocytosis, antigen presentation and recruitment of T cells. It should also be noted that in certain contexts microglia may have a role in the resolution of neuro-inflammation. Although there is still no direct evidence demonstrating that spinal microglia have a role in neuropathic pain in humans, these patients present a pro-inflammatory cytokine profile and it is a reasonable hypothesis that these cells may contribute to this inflammatory response. Modulating microglial functions offers a novel therapeutic opportunity following nerve injury which ideally would involve reducing the pro-inflammatory nature of these cells whilst retaining their potential beneficial functions.
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Hutchinson MR, Shavit Y, Grace PM, Rice KC, Maier SF, Watkins LR. Exploring the neuroimmunopharmacology of opioids: an integrative review of mechanisms of central immune signaling and their implications for opioid analgesia. Pharmacol Rev 2011; 63:772-810. [PMID: 21752874 DOI: 10.1124/pr.110.004135] [Citation(s) in RCA: 291] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Vastly stimulated by the discovery of opioid receptors in the early 1970s, preclinical and clinical research was directed at the study of stereoselective neuronal actions of opioids, especially those played in their crucial analgesic role. However, during the past decade, a new appreciation of the non-neuronal actions of opioids has emerged from preclinical research, with specific appreciation for the nonclassic and nonstereoselective sites of action. Opioid activity at Toll-like receptors, newly recognized innate immune pattern recognition receptors, adds substantially to this unfolding story. It is now apparent from molecular and rodent data that these newly identified signaling events significantly modify the pharmacodynamics of opioids by eliciting proinflammatory reactivity from glia, the immunocompetent cells of the central nervous system. These central immune signaling events, including the release of cytokines and chemokines and the associated disruption of glutamate homeostasis, cause elevated neuronal excitability, which subsequently decreases opioid analgesic efficacy and leads to heightened pain states. This review will examine the current preclinical literature of opioid-induced central immune signaling mediated by classic and nonclassic opioid receptors. A unification of the preclinical pharmacology, neuroscience, and immunology of opioids now provides new insights into common mechanisms of chronic pain, naive tolerance, analgesic tolerance, opioid-induced hyperalgesia, and allodynia. Novel pharmacological targets for future drug development are discussed in the hope that disease-modifying chronic pain treatments arising from the appreciation of opioid-induced central immune signaling may become practical.
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Affiliation(s)
- Mark R Hutchinson
- Discipline of Pharmacology, School of Medical Science, University of Adelaide, South Australia, Australia, 5005.
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Abstract
Microglial cells are the resident macrophages in the central nervous system. These cells of mesodermal/mesenchymal origin migrate into all regions of the central nervous system, disseminate through the brain parenchyma, and acquire a specific ramified morphological phenotype termed "resting microglia." Recent studies indicate that even in the normal brain, microglia have highly motile processes by which they scan their territorial domains. By a large number of signaling pathways they can communicate with macroglial cells and neurons and with cells of the immune system. Likewise, microglial cells express receptors classically described for brain-specific communication such as neurotransmitter receptors and those first discovered as immune cell-specific such as for cytokines. Microglial cells are considered the most susceptible sensors of brain pathology. Upon any detection of signs for brain lesions or nervous system dysfunction, microglial cells undergo a complex, multistage activation process that converts them into the "activated microglial cell." This cell form has the capacity to release a large number of substances that can act detrimental or beneficial for the surrounding cells. Activated microglial cells can migrate to the site of injury, proliferate, and phagocytose cells and cellular compartments.
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Qi J, Buzas K, Fan H, Cohen JI, Wang K, Mont E, Klinman D, Oppenheim JJ, Howard OMZ. Painful pathways induced by TLR stimulation of dorsal root ganglion neurons. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2011; 186:6417-26. [PMID: 21515789 PMCID: PMC3098909 DOI: 10.4049/jimmunol.1001241] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We hypothesize that innate immune signals from infectious organisms and/or injured tissues may activate peripheral neuronal pain signals. In this study, we demonstrated that TLRs 3, 7, and 9 are expressed by human dorsal root ganglion neurons (DRGNs) and in cultures of primary mouse DRGNs. Stimulation of murine DRGNs with TLR ligands induced expression and production of proinflammatory chemokines and cytokines CCL5 (RANTES), CXCL10 (IP-10), IL-1α, IL-1β, and PGE(2), which have previously been shown to augment pain. Further, TLR ligands upregulated the expression of a nociceptive receptor, transient receptor potential vanilloid type 1 (TRPV1), and enhanced calcium flux by TRPV1-expressing DRGNs. Using a tumor-induced temperature sensitivity model, we showed that in vivo administration of a TLR9 antagonist, known as a suppressive oligodeoxynucleotide, blocked tumor-induced temperature sensitivity. Taken together, these data indicate that stimulation of peripheral neurons by TLR ligands can induce nerve pain.
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Affiliation(s)
- Jia Qi
- Laboratory of Molecular Immunoregulation, Cancer and Inflammatory Program, Center for Cancer Research, National Cancer Institute-Frederick, Frederick, MD 21702, USA
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Berger JV, Knaepen L, Janssen SPM, Jaken RJP, Marcus MAE, Joosten EAJ, Deumens R. Cellular and molecular insights into neuropathy-induced pain hypersensitivity for mechanism-based treatment approaches. ACTA ACUST UNITED AC 2011; 67:282-310. [PMID: 21440003 DOI: 10.1016/j.brainresrev.2011.03.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2010] [Revised: 02/16/2011] [Accepted: 03/18/2011] [Indexed: 12/15/2022]
Abstract
Neuropathic pain is currently being treated by a range of therapeutic interventions that above all act to lower neuronal activity in the somatosensory system (e.g. using local anesthetics, calcium channel blockers, and opioids). The present review highlights novel and often still largely experimental treatment approaches based on insights into pathological mechanisms, which impact on the spinal nociceptive network, thereby opening the 'gate' to higher brain centers involved in the perception of pain. Cellular and molecular mechanisms such as ectopia, sensitization of nociceptors, phenotypic switching, structural plasticity, disinhibition, and neuroinflammation are discussed in relation to their involvement in pain hypersensitivity following either peripheral neuropathies or spinal cord injury. A mechanism-based treatment approach may prove to be successful in effective treatment of neuropathic pain, but requires more detailed insights into the persistence of cellular and molecular pain mechanisms which renders neuropathic pain unremitting. Subsequently, identification of the therapeutic window-of-opportunities for each specific intervention in the particular peripheral and/or central neuropathy is essential for successful clinical trials. Most of the cellular and molecular pain mechanisms described in the present review suggest pharmacological interference for neuropathic pain management. However, also more invasive treatment approaches belong to current and/or future options such as neuromodulatory interventions (including spinal cord stimulation) and cell or gene therapies, respectively.
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Affiliation(s)
- Julie V Berger
- Department of Anesthesiology, Maastricht University Medical Centre, Maastricht, The Netherlands
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Mei XP, Zhou Y, Wang W, Tang J, Wang W, Zhang H, Xu LX, Li YQ. Ketamine depresses toll-like receptor 3 signaling in spinal microglia in a rat model of neuropathic pain. Neurosignals 2011; 19:44-53. [PMID: 21389680 DOI: 10.1159/000324293] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 01/14/2011] [Indexed: 12/30/2022] Open
Abstract
Reports suggest that microglia play a key role in spinal nerve ligation (SNL)-induced neuropathic pain, and toll-like receptor 3 (TLR3) has a substantial role in the activation of spinal microglia and the development of tactile allodynia after nerve injury. In addition, ketamine application could suppress microglial activation in vitro, and ketamine could inhibit proinflammatory gene expression possibly by suppressing TLR-mediated signal transduction. Therefore, the present study was designed to disclose whether intrathecal ketamine could suppress SNL-induced spinal microglial activation and exert some antiallodynic effects on neuropathic pain by suppressing TLR3 activation. Behavioral results showed that intrathecal ketamine attenuated SNL-induced mechanical allodynia, as well as spinal microglial activation, in a dose-dependent manner. Furthermore, Western blot analysis displayed that ketamine application downregulated SNL-induced phosphorylated-p38 (p-p38) expression, which was specifically expressed in spinal microglia but not in astrocytes or neurons. Besides, ketamine could reverse TLR3 agonist (polyinosine-polycytidylic acid)-induced mechanical allodynia and spinal microglia activation. It was concluded that intrathecal ketamine depresses TLR3-induced spinal microglial p-p38 mitogen-activated protein kinase pathway activation after SNL, probably contributing to the antiallodynic effect of ketamine on SNL-induced neuropathic pain.
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Affiliation(s)
- Xiao-Peng Mei
- Department of Anesthesiology, School of Stomatology, Fourth Military Medical University, Xi'an, PR China
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Qian NS, Liao YH, Feng QX, Tang Y, Dou KF, Tao KS. Spinal toll like receptor 3 is involved in chronic pancreatitis-induced mechanical allodynia of rat. Mol Pain 2011; 7:15. [PMID: 21342497 PMCID: PMC3048572 DOI: 10.1186/1744-8069-7-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 02/22/2011] [Indexed: 12/25/2022] Open
Abstract
Background Mechanisms underlying pain in chronic pancreatitis (CP) are incompletely understood. Our previous data showed that astrocytes were actively involved. However, it was unclear how astrocytic activation was induced in CP conditions. In the present study, we hypothesized that toll-like receptors (TLRs) were involved in astrocytic activation and pain behavior in CP-induced pain. Results To test our hypothesis, we first investigated the changes of TLR2-4 in the rat CP model induced by intrapancreatic infusion of trinitrobenzene sulfonic acid (TNBS). Western blot showed that after TNBS infusion, TLR3, but not TLR2 or TLR4, was increased gradually and maintained at a very high level for up to 5 w, which correlated with the changing course of mechanical allodynia. Double immunostaining suggested that TLR3 was highly expressed on astrocytes. Infusion with TLR3 antisense oligodeoxynucleotide (ASO) dose-dependently attenuated CP-induced allodynia. CP-induced astrocytic activation in the spinal cord was also significantly suppressed by TLR3 ASO. Furthermore, real-time PCR showed that IL-1β, TNF-α, IL-6 and monocyte chemotactic protein-1 (MCP-1) were significantly increased in spinal cord of pancreatic rats. In addition, TLR3 ASO significantly attenuated CP-induced up-regulation of IL-1β and MCP-1. Conclusions These results suggest a probable "TLR3-astrocytes-IL-1β/MCP-1" pathway as a positive feedback loop in the spinal dorsal horn in CP conditions. TLR3-mediated neuroimmune interactions could be new targets for treating persistent pain in CP patients.
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Affiliation(s)
- Nian-Song Qian
- Department of Hepatobiliary Surgery, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, PR China
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Mei XP, Zhang H, Wang W, Wei YY, Zhai MZ, Wang W, Xu LX, Li YQ. Inhibition of spinal astrocytic c-Jun N-terminal kinase (JNK) activation correlates with the analgesic effects of ketamine in neuropathic pain. J Neuroinflammation 2011; 8:6. [PMID: 21255465 PMCID: PMC3033337 DOI: 10.1186/1742-2094-8-6] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 01/24/2011] [Indexed: 01/08/2023] Open
Abstract
Background We have previously reported that inhibition of astrocytic activation contributes to the analgesic effects of intrathecal ketamine on spinal nerve ligation (SNL)-induced neuropathic pain. However, the underlying mechanisms are still unclear. c-Jun N-terminal kinase (JNK), a member of mitogen-activated protein kinase (MAPK) family, has been reported to be critical for spinal astrocytic activation and neuropathic pain development after SNL. Ketamine can decrease lipopolysaccharide (LPS)-induced phosphorylated JNK (pJNK) expression and could thus exert its anti-inflammatory effect. We hypothesized that inhibition of astrocytic JNK activation might be involved in the suppressive effect of ketamine on SNL-induced spinal astrocytic activation. Methods Immunofluorescence histochemical staining was used to detect SNL-induced spinal pJNK expression and localization. The effects of ketamine on SNL-induced mechanical allodynia were confirmed by behavioral testing. Immunofluorescence histochemistry and Western blot were used to quantify the SNL-induced spinal pJNK expression after ketamine administration. Results The present study showed that SNL induced ipsilateral pJNK up-regulation in astrocytes but not microglia or neurons within the spinal dorsal horn. Intrathecal ketamine relieved SNL-induced mechanical allodynia without interfering with motor performance. Additionally, intrathecal administration of ketamine attenuated SNL-induced spinal astrocytic JNK activation in a dose-dependent manner, but not JNK protein expression. Conclusions The present results suggest that inhibition of JNK activation may be involved in the suppressive effects of ketamine on SNL-induced spinal astrocyte activation. Therefore, inhibition of spinal JNK activation may be involved in the analgesic effects of ketamine on SNL-induced neuropathic pain.
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Affiliation(s)
- Xiao-Peng Mei
- Department of Anesthesiology, School of Stomatology, Fourth Military Medical University, Xi'an, PR China
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Carty M, Bowie AG. Evaluating the role of Toll-like receptors in diseases of the central nervous system. Biochem Pharmacol 2011; 81:825-37. [PMID: 21241665 DOI: 10.1016/j.bcp.2011.01.003] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 01/04/2011] [Accepted: 01/06/2011] [Indexed: 02/06/2023]
Abstract
A key part of the innate immune system is a network of pattern recognition receptors (PRRs) and their associated intracellular signalling pathways. Toll-like receptors (TLRs) are one such group of PRRs that detect pathogen associated molecular patterns (PAMPs). Activation of the TLRs with their respective agonists results in the activation of intracellular signalling pathways leading to the expression of proinflammatory mediators and anti-microbial effector molecules. Activation of the innate immune system through TLRs also triggers the adaptive immune response, resulting in a comprehensive immune program to eradicate invading pathogens. It is now known that immune surveillance and inflammatory responses occur in the central nervous system (CNS). Furthermore it is becoming increasingly clear that TLRs have a role in such CNS responses and are also implicated in the pathogenesis of a number of conditions in the CNS, such as Alzheimer's, stroke and multiple sclerosis. This is likely due to the generation of endogenous TLR agonists in these conditions which amplifies a detrimental neurotoxic inflammatory response. However TLRs in some situations can be neuroprotective, if triggered in a favourable context. This review aims to examine the recent literature on TLRs in the CNS thus demonstrating their importance in a range of infectious and non-infectious diseases of the brain.
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Affiliation(s)
- Michael Carty
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
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Kooij G, Mizee MR, van Horssen J, Reijerkerk A, Witte ME, Drexhage JAR, van der Pol SMA, van Het Hof B, Scheffer G, Scheper R, Dijkstra CD, van der Valk P, de Vries HE. Adenosine triphosphate-binding cassette transporters mediate chemokine (C-C motif) ligand 2 secretion from reactive astrocytes: relevance to multiple sclerosis pathogenesis. ACTA ACUST UNITED AC 2010; 134:555-70. [PMID: 21183485 DOI: 10.1093/brain/awq330] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Adenosine triphosphate-binding cassette efflux transporters are highly expressed at the blood-brain barrier and actively hinder passage of harmful compounds, thereby maintaining brain homoeostasis. Since, adenosine triphosphate-binding cassette transporters drive cellular exclusion of potential neurotoxic compounds or inflammatory molecules, alterations in their expression and function at the blood-brain barrier may contribute to the pathogenesis of neuroinflammatory disorders, such as multiple sclerosis. Therefore, we investigated the expression pattern of different adenosine triphosphate-binding cassette efflux transporters, including P-glycoprotein, multidrug resistance-associated proteins-1 and -2 and breast cancer resistance protein in various well-characterized human multiple sclerosis lesions. Cerebrovascular expression of P-glycoprotein was decreased in both active and chronic inactive multiple sclerosis lesions. Interestingly, foamy macrophages in active multiple sclerosis lesions showed enhanced expression of multidrug resistance-associated protein-1 and breast cancer resistance protein, which coincided with their increased function of cultured foamy macrophages. Strikingly, reactive astrocytes display an increased expression of P-glycoprotein and multidrug resistance-associated protein-1 in both active and inactive multiple sclerosis lesions, which correlated with their enhanced in vitro activity on astrocytes derived from multiple sclerosis lesions. To investigate whether adenosine triphosphate-binding cassette transporters on reactive astrocytes can contribute to the inflammatory process, primary cultures of reactive human astrocytes were generated through activation of Toll-like receptor-3 to mimic the astrocytic phenotype as observed in multiple sclerosis lesions. Notably, blocking adenosine triphosphate-binding cassette transporter activity on reactive astrocytes inhibited immune cell migration across a blood-brain barrier model in vitro, which was due to the reduction of astrocytic release of the chemokine (C-C motif) ligand 2. Our data point towards a novel (patho)physiological role for adenosine triphosphate-binding cassette transporters, suggesting that limiting their activity by dampening astrocyte activation may open therapeutic avenues to diminish tissue damage during multiple sclerosis pathogenesis.
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Affiliation(s)
- Gijs Kooij
- Blood-Brain Barrier Research Group, Department of Molecular Cell Biology and Immunology, VU University Medical Centre, Amsterdam, The Netherlands
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Shi XQ, Zekki H, Zhang J. The role of TLR2 in nerve injury-induced neuropathic pain is essentially mediated through macrophages in peripheral inflammatory response. Glia 2010; 59:231-41. [DOI: 10.1002/glia.21093] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Corrigendum. J Neurochem 2010. [DOI: 10.1111/j.1471-4159.2010.06959.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Mei XP, Wang W, Wang W, Zhu C, Chen L, Zhang T, Xu LX, Wu SX, Li YQ. Combining ketamine with astrocytic inhibitor as a potential analgesic strategy for neuropathic pain ketamine, astrocytic inhibitor and pain. Mol Pain 2010; 6:50. [PMID: 20815929 PMCID: PMC2942826 DOI: 10.1186/1744-8069-6-50] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 09/06/2010] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Neuropathic pain is an intractable clinical problem. Intrathecal ketamine, a noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, is reported to be useful for treating neuropathic pain in clinic by inhibiting the activity of spinal neurons. Nevertheless, emerging studies have disclosed that spinal astrocytes played a critical role in the initiation and maintenance of neuropathic pain. However, the present clinical therapeutics is still just concerning about neuronal participation. Therefore, the present study is to validate the coadministration effects of a neuronal noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine and astrocytic cytotoxin L-α-aminoadipate (LAA) on spinal nerve ligation (SNL)-induced neuropathic pain. RESULTS Intrathecal ketamine (10, 100, 1000 μg/kg) or LAA (10, 50, 100 nmol) alleviated SNL-induced mechanical allodynia in a dose-dependent manner respectively. Phosphorylated NR1 (pNR1) or glial fibrillary acidic protein (GFAP) expression was down-regulated by intrathecal ketamine (100, 1000 μg/kg) or LAA (50, 100 nmol) respectively. The combination of ketamine (100 μg/kg) with LAA (50 nmol) showed superadditive effects on neuropathic pain compared with that of intrathecal administration of either ketamine or LAA alone. Combined administration obviously relieved mechanical allodynia in a quick and stable manner. Moreover, down-regulation of pNR1 and GFAP expression were also enhanced by drugs coadministration. CONCLUSIONS These results suggest that combining NMDAR antagonist ketamine with an astrocytic inhibitor or cytotoxin, which is suitable for clinical use once synthesized, might be a potential strategy for clinical management of neuropathic pain.
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Affiliation(s)
- Xiao-Peng Mei
- Department of Anesthesiology, School of Stomatology, Fourth Military Medical University, Xi'an, China
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Harano N, Ono K, Hidaka K, Kai A, Nakanishi O, Inenaga K. Differences between Orofacial Inflammation and Cancer Pain. J Dent Res 2010; 89:615-20. [DOI: 10.1177/0022034510363095] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rat models of orofacial cancer exhibit both allodynia and hyperalgesia; however, it is unclear whether cancer-induced pain is secondary to cancer-induced inflammation. To address this question, we compared the effects of an anti-inflammatory drug, indomethacin, on pain and neurochemical changes in the medullary dorsal horn in orofacial inflammation and cancer models. Daily peripheral administration of indomethacin largely suppressed mechanical allodynia and thermal hyperalgesia in the inflammation model. The same procedure suppressed allodynia and hyperalgesia in the cancer model, but the suppression was weak when compared with that in the inflammation model. In the medullary dorsal horn, calcitonin gene-related peptide and substance P levels were significantly increased in the inflammation model, but did not change in the cancer model. These results suggest that pain in the orofacial cancer model is not significantly mediated by cancer-induced peripheral inflammation, although it may have some involvement.
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Affiliation(s)
- N. Harano
- Department of Control of Physical Functions, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka, 803-8580, Japan
| | - K. Ono
- Department of Biosciences, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka, 803-8580, Japan
| | - K. Hidaka
- Department of Control of Physical Functions, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka, 803-8580, Japan
- Department of Biosciences, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka, 803-8580, Japan
| | - A. Kai
- Department of Control of Physical Functions, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka, 803-8580, Japan
| | - O. Nakanishi
- Department of Control of Physical Functions, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka, 803-8580, Japan
| | - K. Inenaga
- Department of Biosciences, Kyushu Dental College, 2-6-1 Manazuru, Kokurakitaku, Kitakyushu, Fukuoka, 803-8580, Japan
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McKernan DP, Nolan A, Brint EK, O'Mahony SM, Hyland NP, Cryan JF, Dinan TG. Toll-like receptor mRNA expression is selectively increased in the colonic mucosa of two animal models relevant to irritable bowel syndrome. PLoS One 2009; 4:e8226. [PMID: 20011045 PMCID: PMC2785428 DOI: 10.1371/journal.pone.0008226] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Accepted: 11/11/2009] [Indexed: 02/06/2023] Open
Abstract
Background Irritable bowel syndrome (IBS) is largely viewed as a stress-related disorder caused by aberrant brain-gut–immune communication and altered gastrointestinal (GI) homeostasis. Accumulating evidence demonstrates that stress modulates innate immune responses; however, very little is known on the immunological effects of stress on the GI tract. Toll-like receptors (TLRs) are critical pattern recognition molecules of the innate immune system. Activation of TLRs by bacterial and viral molecules leads to activation of NF-kB and an increase in inflammatory cytokine expression. It was our hypothesis that innate immune receptor expression may be changed in the gastrointestinal tract of animals with stress-induced IBS-like symptoms. Methodology/Principal Findings In this study, our objective was to evaluate the TLR expression profile in the colonic mucosa of two rat strains that display colonic visceral hypersensivity; the stress-sensitive Wistar-Kyoto (WKY) rat and the maternally separated (MS) rat. Quantitative PCR of TLR2-10 mRNA in both the proximal and distal colonic mucosae was carried out in adulthood. Significant increases are seen in the mRNA levels of TLR3, 4 & 5 in both the distal and proximal colonic mucosa of MS rats compared with controls. No significant differences were noted for TLR 2, 7, 9 & 10 while TLR 6 could not be detected in any samples in both rat strains. The WKY strain have increased levels of mRNA expression of TLR3, 4, 5, 7, 8, 9 & 10 in both the distal and proximal colonic mucosa compared to the control Sprague-Dawley strain. No significant differences in expression were found for TLR2 while as before TLR6 could not be detected in all samples in both strains. Conclusions These data suggest that both early life stress (MS) and a genetic predisposition (WKY) to stress affect the expression of key sentinels of the innate immune system which may have direct relevance for the molecular pathophysiology of IBS.
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Affiliation(s)
- Declan P. McKernan
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
| | - Aoife Nolan
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
| | - Elizabeth K. Brint
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- Department of Pathology, University College Cork, Cork, Ireland
| | - Siobhain M. O'Mahony
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- Department of Anatomy, University College Cork, Cork, Ireland
| | - Niall P. Hyland
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- Department of Pharmacology and Therapeutics, University College Cork, Cork, Ireland
| | - John F. Cryan
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- School of Pharmacy, University College Cork, Cork, Ireland
- Department of Pharmacology and Therapeutics, University College Cork, Cork, Ireland
- * E-mail: (JFC); (TGD)
| | - Timothy G. Dinan
- Laboratory of Neurogastroenterology, Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland
- Department of Psychiatry, University College Cork, Cork, Ireland
- * E-mail: (JFC); (TGD)
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A Critical Role of Src-Suppressed C Kinase Substrate in Rat Astrocytes After Chronic Constriction Injury. Neuromolecular Med 2009; 12:205-16. [PMID: 19937403 DOI: 10.1007/s12017-009-8093-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Accepted: 09/25/2009] [Indexed: 01/03/2023]
Abstract
Src-suppressed C kinase substrate (SSeCKS), is an in vivo and in vitro protein kinase C substrate that may have a role in both mitogenic regulation and cytoskeletal arrangement. In this study, we mainly investigated the mRNA and protein expression and cellular localization of SSeCKS during chronic constriction injury (CCI). Reverse transcriptase-mediated PCR and western blot analysis revealed that SSeCKS was present in normal whole spinal cord. It gradually increased, and reached a peak at 2 weeks for its mRNA level and 7 days for its protein level after CCI. The protein expression of SSeCKS was further analyzed by immunohistochemistry. The positively stained areas for SSeCKS changed with the similar pattern to that of protein expression detected by immunoblotting analysis. Double immunofluorescence staining showed SSeCKS immunoreactivity was mostly co-localized with neurons, partly with activated astrocytes and rarely with microglia in the superficial laminar of spinal dorsal horn. In cell culture, the expression of pro-inflammation cytokines, p-ERK, and SSeCKS was increased in the spinal astrocytes after stimulated by damaged sensory neurons. However, SSeCKS gene silencing by siRNA inhibited the up-regulation of p-ERK and the pro-inflammation cytokines. Taken together, activated astrocytes released cytokines and iNOS after neuropathic pain via SSeCKS-ERK signaling. SSeCKS might be critical for the activation of astrocytes in the neuropathic pain.
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Abstract
The nervous system detects and interprets a wide range of thermal and mechanical stimuli, as well as environmental and endogenous chemical irritants. When intense, these stimuli generate acute pain, and in the setting of persistent injury, both peripheral and central nervous system components of the pain transmission pathway exhibit tremendous plasticity, enhancing pain signals and producing hypersensitivity. When plasticity facilitates protective reflexes, it can be beneficial, but when the changes persist, a chronic pain condition may result. Genetic, electrophysiological, and pharmacological studies are elucidating the molecular mechanisms that underlie detection, coding, and modulation of noxious stimuli that generate pain.
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Affiliation(s)
- Allan I Basbaum
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158, USA.
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