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Willemen HL, Eijkelkamp N, Wang H, Dantzer R, Dorn GW, Kelley KW, Heijnen CJ, Kavelaars A. Microglial/macrophage GRK2 determines duration of peripheral IL-1beta-induced hyperalgesia: contribution of spinal cord CX3CR1, p38 and IL-1 signaling. Pain 2010; 150:550-560. [PMID: 20609517 PMCID: PMC3099597 DOI: 10.1016/j.pain.2010.06.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2010] [Revised: 05/17/2010] [Accepted: 06/15/2010] [Indexed: 12/27/2022]
Abstract
Chronic pain associated with inflammation is a major clinical problem, but the underlying mechanisms are incompletely understood. Recently, we reported that GRK2(+/-) mice with a approximately 50% reduction of GRK2 develop prolonged hyperalgesia following a single intraplantar injection of the pro-inflammatory cytokine interleukin-1beta (IL-1beta). Here we show that spinal microglia/macrophage GRK2 is reduced during chronic inflammation-induced hyperalgesia. Next, we applied CRE-Lox technology to create mice with low GRK2 in microglia/macrophages/granulocytes (LysM-GRK2(f/+)), or sensory neurons or astrocytes. Only mice deficient in microglial/macrophage/granulocyte GRK2 display prolonged IL-1beta-induced hyperalgesia that lasts up to 8days. Two days after intraplantar IL-1beta, increased microglial/macrophage activity occurs in the lumbar but not thoracic spinal cord of GRK2-deficient mice. Intrathecal pre-treatment with minocycline, an inhibitor of microglia/macrophage activation, accelerates resolution of hyperalgesia independent of genotype and prevents transition to chronic hyperalgesia in GRK2(+/-) mice. Ongoing hyperalgesia in GRK2(+/-) mice is reversed by minocycline administration at days 1 and 2 after IL-1beta injection. Similarly, IL-1beta-induced hyperalgesia in LysM-GRK2(f/+) mice is attenuated by intrathecal administration of anti-CX3CR1 to abrogate fractalkine signaling, the p38 inhibitor SB239063 and the IL-1 antagonist IL-1ra. These data establish that chronic inflammatory hyperalgesia is associated with reduced GRK2 in microglia/macrophages and that low GRK2 in these cells is sufficient to markedly prolong hyperalgesia after a single intraplantar injection of IL-1beta. Ongoing hyperalgesia is maintained by spinal microglial/macrophage activity, fractalkine signaling, p38 activation and IL-1 signaling. We propose that chronic inflammation decreases spinal microglial/macrophage GRK2, which prevents silencing of microglia/macrophage activity and thereby contributes to prolonged hyperalgesia.
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Affiliation(s)
- Hanneke L.D.M. Willemen
- Laboratory of Neuroimmunology and Developmental Origins of Disease (NIDOD), University Medical Center Utrecht, 3584 EA Utrecht, The Netherlands
| | - Niels Eijkelkamp
- Laboratory of Neuroimmunology and Developmental Origins of Disease (NIDOD), University Medical Center Utrecht, 3584 EA Utrecht, The Netherlands
- Integrative Immunology and Behavior Program, College of ACES and College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Huijing Wang
- Laboratory of Neuroimmunology and Developmental Origins of Disease (NIDOD), University Medical Center Utrecht, 3584 EA Utrecht, The Netherlands
| | - Robert Dantzer
- Integrative Immunology and Behavior Program, College of ACES and College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Gerald W. Dorn
- Center for Pharmacogenomics, Washington University, St. Louis, MI 63110, USA
| | - Keith W. Kelley
- Integrative Immunology and Behavior Program, College of ACES and College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Cobi J. Heijnen
- Laboratory of Neuroimmunology and Developmental Origins of Disease (NIDOD), University Medical Center Utrecht, 3584 EA Utrecht, The Netherlands
- Integrative Immunology and Behavior Program, College of ACES and College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Annemieke Kavelaars
- Laboratory of Neuroimmunology and Developmental Origins of Disease (NIDOD), University Medical Center Utrecht, 3584 EA Utrecht, The Netherlands
- Integrative Immunology and Behavior Program, College of ACES and College of Medicine, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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152
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Fan W, Huang F, Zhu X, Dong W, Gao Z, Li D, He H. Involvement of microglial activation in the brainstem in experimental dental injury and inflammation. Arch Oral Biol 2010; 55:706-11. [DOI: 10.1016/j.archoralbio.2010.06.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 06/02/2010] [Accepted: 06/14/2010] [Indexed: 12/18/2022]
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153
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Gao YJ, Ji RR. Light touch induces ERK activation in superficial dorsal horn neurons after inflammation: involvement of spinal astrocytes and JNK signaling in touch-evoked central sensitization and mechanical allodynia. J Neurochem 2010; 115:505-14. [PMID: 20722971 DOI: 10.1111/j.1471-4159.2010.06946.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Activation of extracellular signal-regulated kinase (ERK) in spinal cord neurons could serve as a marker for sensitization of dorsal horn neurons in persistent pain. ERK is normally activated by high-threshold noxious stimuli. We investigated how low-threshold mechanical stimuli could activate ERK after complete Freund's adjuvant (CFA)-induced inflammation. Unilateral injection of CFA induced ipsilateral heat hyperalgesia and bilateral mechanical allodynia. CFA-induced ERK activation in ipsilateral dorsal horn neurons declined after 2 days. Interestingly, low-threshold mechanical stimulation given by light touch either on the inflamed paw or the contralateral non-inflamed paw dramatically increased ERK phosphorylation in the dorsal horn ipsilateral to touch stimulation. Notably, light touch induced ERK phosphorylation mainly in superficial neurons in laminae I-IIo. Intrathecal administration of the astroglial toxin L-α-aminoadipate on post-CFA day 2 reversed CFA-induced bilateral mechanical allodynia but not heat hyperalgesia. Furthermore, L-α-aminoadipate, the glial inhibitor fluorocitrate, and a peptide inhibitor of c-Jun N-terminal Kinase all reduced light touch-evoked ERK activation ipsilateral to touch. Collectively, these data suggest that (i) ERK can be activated in superficial dorsal horn neurons by low-threshold mechanical stimulation under pathological condition and (ii) ERK activation by light touch is associated with mechanical allodynia and requires an astrocyte network.
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Affiliation(s)
- Yong-Jing Gao
- Department of Anesthesiology, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
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154
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Biggs JE, Lu VB, Stebbing MJ, Balasubramanyan S, Smith PA. Is BDNF sufficient for information transfer between microglia and dorsal horn neurons during the onset of central sensitization? Mol Pain 2010; 6:44. [PMID: 20653959 PMCID: PMC2918544 DOI: 10.1186/1744-8069-6-44] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 07/23/2010] [Indexed: 12/12/2022] Open
Abstract
Peripheral nerve injury activates spinal microglia. This leads to enduring changes in the properties of dorsal horn neurons that initiate central sensitization and the onset of neuropathic pain. Although a variety of neuropeptides, cytokines, chemokines and neurotransmitters have been implicated at various points in this process, it is possible that much of the information transfer between activated microglia and neurons, at least in this context, may be explicable in terms of the actions of brain derived neurotrophic factor (BDNF). Microglial-derived BDNF mediates central sensitization in lamina I by attenuating inhibitory synaptic transmission. This involves an alteration in the chloride equilibrium potential as a result of down regulation of the potassium-chloride exporter, KCC2. In lamina II, BDNF duplicates many aspects of the effects of chronic constriction injury (CCI) of the sciatic nerve on excitatory transmission. It mediates an increase in synaptic drive to putative excitatory neurons whilst reducing that to inhibitory neurons. CCI produces a specific pattern of changes in excitatory synaptic transmission to tonic, delay, phasic, transient and irregular neurons. A very similar 'injury footprint' is seen following long-term exposure to BDNF. This review presents new information on the action of BDNF and CCI on lamina II neurons, including the similarity of their actions on the kinetics and distributions of subpopulations of miniature excitatory postsynaptic currents (mEPSC). These findings raise the possibility that BDNF functions as a final common path for a convergence of perturbations that culminate in the generation of neuropathic pain.
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Affiliation(s)
- James E Biggs
- Department of Pharmacology and Centre for Neuroscience University of Alberta, Edmonton, Alberta, Canada
| | - Van B Lu
- Laboratory of MolecularPhysiology, NIH/NIAAA, Rockville, MD, USA
| | - Martin J Stebbing
- School of Medical Sciences, RMIT University, Bundoora, Victoria, Australia
| | | | - Peter A Smith
- Department of Pharmacology and Centre for Neuroscience University of Alberta, Edmonton, Alberta, Canada
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155
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Clark AK, Wodarski R, Guida F, Sasso O, Malcangio M. Cathepsin S release from primary cultured microglia is regulated by the P2X7 receptor. Glia 2010; 58:1710-26. [DOI: 10.1002/glia.21042] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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156
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Xu B, Zhang WS, Yang JL, Lû N, Deng XM, Xu H, Zhang YQ. Evidence for suppression of spinal glial activation by dexmedetomidine in a rat model of monoarthritis. Clin Exp Pharmacol Physiol 2010; 37:e158-66. [DOI: 10.1111/j.1440-1681.2010.05426.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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157
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Staniland AA, Clark AK, Wodarski R, Sasso O, Maione F, D'Acquisto F, Malcangio M. Reduced inflammatory and neuropathic pain and decreased spinal microglial response in fractalkine receptor (CX3CR1) knockout mice. J Neurochem 2010; 114:1143-57. [PMID: 20524966 DOI: 10.1111/j.1471-4159.2010.06837.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The chemokine fractalkine (FKN) is a critical mediator of spinal neuronal-microglial communication in chronic pain. Mature FKN is enzymatically cleaved from neuronal membranes and activation of its receptor, CX3CR1, which is expressed by microglia, induces phosphorylation of p38 MAPK. We used CX3CR1 knockout (KO) mice to examine pain behaviour in the absence of FKN signalling. Naive CX3CR1 KO mice had normal responses to acute noxious stimuli. However, KO mice showed deficits in inflammatory and neuropathic nociceptive responses. After intraplantar zymosan, KO mice did not display thermal hyperalgesia, whereas mechanical allodynia developed fully. In the partial sciatic nerve ligation model of neuropathic pain, both mechanical allodynia and thermal hyperalgesia were less severe in KO mice than in wild-types (WT). Dorsal horn Iba1 immunostaining and phosphorylation of p38 MAPK increased after injury in WT controls but not in KO animals. In WT mice, inflammation and nerve injury increased spinal cord CX3CR1 and FKN expression. FKN protein was also increased in KO mice following inflammation but not after neuropathy, suggesting the FKN/CX3CR1 system is differently affected in the two pain models. Loss of FKN/CX3CR1 neuroimmune communication attenuates hyperalgesia and allodynia in a modality-dependent fashion highlighting the complex nature of microglial response in pathological pain models.
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Affiliation(s)
- Amelia A Staniland
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
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158
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Peripheral formalin injury induces 2 stages of microglial activation in the spinal cord. THE JOURNAL OF PAIN 2010; 11:1056-65. [PMID: 20488758 DOI: 10.1016/j.jpain.2010.01.268] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Revised: 01/15/2010] [Accepted: 01/26/2010] [Indexed: 12/30/2022]
Abstract
UNLABELLED The formalin test produces 2 well-known acute phases of nociceptive behavior. Recently, we have shown that this same formalin test produces a third phase of nociceptive behavior consisting of prolonged thermal and mechanical hyperalgesia beginning days after formalin injection and lasting for at least 3 weeks. Here we investigated the activity of 3 MAPKs (p38, ERK and JNK) in the spinal dorsal horn following 5% formalin injection into rat hind paw. The p38 MAPK was rapidly activated in the spinal microglia minutes after injection and the activation persisted for 1 hour. In addition, this same injury induced a secondary increase of phospho-p38 expression in spinal microglia that was maximal 3 to 7 days postinjection. Intrathecal administration of p38 inhibitor SB203580 not only inhibited the early acute spontaneous nociceptive behaviors, but also inhibited the long-term formalin injury-induced mechanical hyperalgesia. Our results suggest that peripheral formalin injection induces 2 stages of microglial activation, and p38 activation in spinal microglia plays key roles in central pain modulation in formalin test respectively for the early acute phases and the late secondary long-term pain state as well. PERSPECTIVE This article presents unique properties of spinal microglial activation in a pain animal model. This finding could potentially help clinicians to further understand the contributions of spinal microglia to acute and chronic pain state.
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159
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Dexmedetomidine blocks thermal hyperalgesia and spinal glial activation in rat model of monoarthritis. Acta Pharmacol Sin 2010; 31:523-30. [PMID: 20364156 DOI: 10.1038/aps.2010.32] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
AIM To investigate the effect of systemic administration dexmedetomidine, a selective alpha 2 adrenergic receptor (alpha(2)AR) agonist, on thermal hyperalgesia and spinal glial activation evoked by monoarthritis (MA). METHODS MA was induced by an intra-articular injection of complete Freund's adjuvant (CFA). Thermal hyperalgesia was measured by Hargreaves' test. The spinal glial activation status was analyzed by GFAP (an astrocytic marker) and Iba-1 (a microglial marker) immunohistochemistry or immunoblotting. RESULTS Unilateral intra-articular injection of CFA produced a robust glial activation of astrocytes and microglia in the spinal cord, which was associated with the development and maintenance of thermal hyperalgesia. Intraperitoneal (ip) injection of dexmedetomidine (2.5 and 10 microg/kg) was repeatedly given once daily for 5 days with the first injection 60 min before intra-articular CFA. At the dose of 10 microg/kg, dexmedetomidine significantly attenuated MA-induced ipsilateral hyperalgesia from day 2 to day 5. MA-induced up-regulation of GFAP expression on both sides of the spinal dorsal horn was significantly suppressed by day 5 post-MA following dexmedetomidine application, whereas MA-induced Iba-1 up-regulation was only partially suppressed. CONCLUSION Systemic dexmedetomidine inhibits the activation of spinal glia, which is possibly associated with its antihyperalgesia in monoarthritic rats.
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160
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Increased spontaneous electrical activity at a latent myofascial trigger point after nociceptive stimulation of another latent trigger point. Clin J Pain 2010; 26:138-43. [PMID: 20090441 DOI: 10.1097/ajp.0b013e3181bad736] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate the changes in surface and intramuscular electromyographic (EMG) activity at latent trigger points (TrPs) in the extensor carpi radialis brevis muscle after injection of either glutamate or isotonic saline into latent TrPs in the infraspinatus muscle. METHOD Nociceptive muscle stimulation was obtained by a bolus injection of glutamate (0.2 mL, 0.5 M) into a latent TrP located in the right infraspinatus muscle in 12 healthy volunteers. A bolus of isotonic saline (0.9%, 0.2 mL) injection served as control. Injections were guided by intramuscular EMG showing resting spontaneous electrical activity at the latent myofascial TrP in the infraspinatus muscle. Intramuscular (at the TrP) and surface EMG activities of both infraspinatus and extensor carpi radialis brevis muscles were recorded before, during, and after injection for a period of 6 minutes to monitor changes produced in EMG activity. RESULTS Glutamate injection into latent TrPs induced higher pain intensity than isotonic saline injection (P<0.001). The analysis of variance showed a significant increase in root mean square score of intramuscular EMG activity at TrP in the extensor carpi radialis brevis after glutamate (mean+/-SD: 212.0+/-215.6 microV) but not isotonic saline (mean+/-SD: 74.2+/-72.2 microV) injections (P<0.001). No changes in surface EMG activity were found. No significant changes in root mean square of intramuscular and surface EMG activity in the infraspinatus muscle were found. CONCLUSIONS Our results show that an increased nociceptive activity at latent TrPs in the infraspinatus muscle may increase motor activity and sensitivity of a TrP in distant muscles at a same segmental level.
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161
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P2X7-dependent release of interleukin-1beta and nociception in the spinal cord following lipopolysaccharide. J Neurosci 2010; 30:573-82. [PMID: 20071520 DOI: 10.1523/jneurosci.3295-09.2010] [Citation(s) in RCA: 245] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The cytokine interleukin-1beta (IL-1beta) released by spinal microglia in enhanced response states contributes significantly to neuronal mechanisms of chronic pain. Here we examine the involvement of the purinergic P2X7 receptor in the release of IL-1beta following activation of Toll-like receptor-4 (TLR4) in the dorsal horn, which is associated with nociceptive behavior and microglial activation. We observed that lipopolysaccharide (LPS)-induced release of IL-1beta was prevented by pharmacological inhibition of the P2X7 receptor with A-438079, and was absent in spinal cord slices taken from P2X7 knock-out mice. Application of ATP did not evoke release of IL-1beta from the dorsal horn unless preceded by an LPS priming stimulus, and this release was dependent on P2X7 receptor activation. Extensive phosphorylation of p38 MAPK in microglial cells in the dorsal horn was found to correlate with IL-1beta secretion following both LPS and ATP. In behavioral studies, intrathecal injection of LPS in the lumbar spinal cord produced mechanical hyperalgesia in rat hindpaws, which was attenuated by concomitant injections of either a nonspecific (oxidized ATP) or a specific (A-438079) P2X7 antagonist. In addition, LPS-induced hypersensitivity was observed in wild-type but not P2X7 knock-out mice. These data suggest a critical role for the P2X7 receptor in the enhanced nociceptive transmission associated with microglial activation and secretion of IL-1beta in the dorsal horn. We suggest that CNS-penetrant P2X7 receptor antagonists, by targeting microglia in pain-enhanced response states, may be beneficial for the treatment of persistent pain.
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162
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Gao YJ, Ji RR. Chemokines, neuronal-glial interactions, and central processing of neuropathic pain. Pharmacol Ther 2010; 126:56-68. [PMID: 20117131 DOI: 10.1016/j.pharmthera.2010.01.002] [Citation(s) in RCA: 469] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2010] [Accepted: 01/15/2010] [Indexed: 12/23/2022]
Abstract
Millions of people worldwide suffer from neuropathic pain as a result of damage to or dysfunction of the nervous system under various disease conditions. Development of effective therapeutic strategies requires a better understanding of molecular and cellular mechanisms underlying the pathogenesis of neuropathic pain. It has been increasingly recognized that spinal cord glial cells such as microglia and astrocytes play a critical role in the induction and maintenance of neuropathic pain by releasing powerful neuromodulators such as proinflammatory cytokines and chemokines. Recent evidence reveals chemokines as new players in pain control. In this article, we review evidence for chemokine modulation of pain via neuronal-glial interactions by focusing on the central role of two chemokines, CX3CL1 (fractalkine) and CCL2 (MCP-1), because they differentially regulate neuronal-glial interactions. Release of CX3CL1 from neurons is ideal to mediate neuronal-to-microglial signaling, since the sole receptor of this chemokine, CX3CR1, is expressed in spinal microglia and activation of the receptor leads to phosphorylation of p38 MAP kinase in microglia. Although CCL2 was implicated in neuronal-to-microglial signaling, a recent study shows a novel role of CCL2 in astroglial-to-neuronal signaling after nerve injury. In particular, CCL2 rapidly induces central sensitization by increasing the activity of NMDA receptors in dorsal horn neurons. Insights into the role of chemokines in neuronal-glial interactions after nerve injury will identify new targets for therapeutic intervention of neuropathic pain.
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Affiliation(s)
- Yong-Jing Gao
- Pain Research Center, Department of Anesthesiology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, United States.
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163
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Bardoni R, Ghirri A, Zonta M, Betelli C, Vitale G, Ruggieri V, Sandrini M, Carmignoto G. Glutamate-mediated astrocyte-to-neuron signalling in the rat dorsal horn. J Physiol 2010; 588:831-46. [PMID: 20083514 DOI: 10.1113/jphysiol.2009.180570] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
By releasing neuroactive agents, including proinflammatory cytokines, prostaglandins and neurotrophins, microglia and astrocytes are proposed to be involved in nociceptive transmission, especially in conditions of persistent, pathological pain. The specific action on dorsal horn neurons of agents released from astrocytes, such as glutamate, has been, however, poorly investigated. By using patch-clamp and confocal microscope calcium imaging techniques in rat spinal cord slices, we monitored the activity of dorsal horn lamina II neurons following astrocyte activation. Results obtained revealed that stimuli that triggered Ca(2+) elevations in astrocytes, such as the purinergic receptor agonist BzATP and low extracellular Ca(2+), induce in lamina II neurons slow inward currents (SICs). Similarly to SICs triggered by astrocytic glutamate in neurons from other central nervous system regions, these currents (i) are insensitive to tetrodotoxin (TTX), (ii) are blocked by the NMDA receptor (NMDAR) antagonist d-AP5, (iii) lack an AMPA component, and (iv) have slow rise and decay times. Ca(2+) imaging also revealed that astrocytic glutamate evokes NMDAR-mediated episodes of synchronous activity in groups of substantia gelatinosa neurons. Importantly, in a model of peripheral inflammation, the development of thermal hyperalgesia and mechanical allodynia was accompanied by a significant increase of spontaneous SICs in dorsal horn neurons. The NMDAR-mediated astrocyte-to-neuron signalling thus represents a novel pathway that may contribute to the control of central sensitization in pathological pain.
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Affiliation(s)
- Rita Bardoni
- Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41100 Modena, Italy.
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164
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1-(2′,4′-dichlorophenyl)-6-methyl-N-cyclohexylamine-1,4-dihydroindeno[1,2-c]pyrazole-3-carboxamide, a novel CB2 agonist, alleviates neuropathic pain through functional microglial changes in mice. Neurobiol Dis 2010; 37:177-85. [DOI: 10.1016/j.nbd.2009.09.021] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 09/18/2009] [Accepted: 09/27/2009] [Indexed: 12/14/2022] Open
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165
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Shimizu K, Guo W, Wang H, Zou S, LaGraize SC, Iwata K, Wei F, Dubner R, Ren K. Differential involvement of trigeminal transition zone and laminated subnucleus caudalis in orofacial deep and cutaneous hyperalgesia: the effects of interleukin-10 and glial inhibitors. Mol Pain 2009; 5:75. [PMID: 20025765 PMCID: PMC2806354 DOI: 10.1186/1744-8069-5-75] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2009] [Accepted: 12/21/2009] [Indexed: 01/11/2023] Open
Abstract
Background In addition to caudal subnucleus caudalis (Vc) of the spinal trigeminal complex, recent studies indicate that the subnuclei interpolaris/caudalis (Vi/Vc) transition zone plays a unique role in processing deep orofacial nociceptive input. Studies also suggest that glia and inflammatory cytokines contribute to the development of persistent pain. By systematically comparing the effects of microinjection of the antiinflammatory cytokine interleukin (IL)-10 and two glial inhibitors, fluorocitrate and minocycline, we tested the hypothesis that there was a differential involvement of Vi/Vc and caudal Vc structures in deep and cutaneous orofacial pain. Results Deep or cutaneous inflammatory hyperalgesia, assessed with von Frey filaments, was induced in rats by injecting complete Freund's adjuvant (CFA) into the masseter muscle or skin overlying the masseter, respectively. A unilateral injection of CFA into the masseter or skin induced ipsilateral hyperalgesia that started at 30 min, peaked at 1 d and lasted for 1-2 weeks. Secondary hyperalgesia on the contralateral site also developed in masseter-, but not skin-inflamed rats. Focal microinjection of IL-10 (0.006-1 ng), fluorocitrate (1 μg), and minocycline (0.1-1 μg) into the ventral Vi/Vc significantly attenuated masseter hyperalgesia bilaterally but without an effect on hyperalgesia after cutaneous inflammation. Injection of the same doses of these agents into the caudal Vc attenuated ipsilateral hyperalgesia after masseter and skin inflammation, but had no effect on contralateral hyperalgesia after masseter inflammation. Injection of CFA into the masseter produced significant increases in N-methyl-D-aspartate (NMDA) receptor NR1 serine 896 phosphorylation and glial fibrillary acidic protein (GFAP) levels, a marker of reactive astrocytes, in Vi/Vc and caudal Vc. In contrast, cutaneous inflammation only produced similar increases in the Vc. Conclusion These results support the hypothesis that the Vi/Vc transition zone is involved in deep orofacial injury and suggest that glial inhibition and interruption of the cytokine cascade after inflammation may provide pain relief.
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Affiliation(s)
- Kohei Shimizu
- Department of Neural and Pain Sciences, Dental School, University of Maryland, Baltimore, MD 21201, USA.
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166
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Baloui H, Stettler O, Weiss S, Nothias F, von Boxberg Y. Upregulation in rat spinal cord microglia of the nonintegrin laminin receptor 37 kDa-LRP following activation by a traumatic lesion or peripheral injury. J Neurotrauma 2009; 26:195-207. [PMID: 19196078 DOI: 10.1089/neu.2008.0677] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The molecular mechanisms triggering microglial activation after injury to the central nervous system, involving cell-extracellular matrix interactions and cytokine signaling, are not yet fully understood. Here, we report that resident microglia in spinal cord express low levels of the non-integrin laminin receptor precursor (LRP), also found on certain neurons and glial cells in the peripheral nervous system. 37LRP/p40 and its 67-kDa isoform laminin receptor (LR) were the first high-affinity laminin binding proteins identified. While the role of laminin receptor was later attributed to integrins, LRP/LR gained new interest as receptors for prions, and their interaction with laminin seems important for migration of metastatic cancer cells. Using immunohistochemistry and Western blotting, we demonstrate that traumatic spinal cord injury leads to a strong and rapid increase in LRP levels in relation to activated microglia/macrophages. Associated with laminin re-expression in the lesion epicenter, LRP-positive microglia/macrophages exhibit a rounded, ameboid-like shape characteristic of phagocytic cells, whereas in more distant loci they reveal a hypertrophied cell body and short ramifications. The same morphological difference is observed in vitro for purified microglia cultured with or without laminin. Strong, transient upregulation of LRP by activated spinal cord microglia is also induced by transection of the sciatic nerve that affects the spinal cord circuitry without blood-brain barrier dysruption. LRP expression is maximal by 1 week post-lesion, before becoming restricted to dorsal and ventral horns, sites of major structural reorganization. Our findings strongly suggest the involvement of LRP in lesion-induced activation and migration of microglia.
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Affiliation(s)
- Hasna Baloui
- Université Pierre et Marie Curie-Paris6, UMR7101 NSI; and CNRS, UMR7101 IFR-83, Paris, France
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167
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Weyerbacher AR, Xu Q, Tamasdan C, Shin SJ, Inturrisi CE. N-Methyl-D-aspartate receptor (NMDAR) independent maintenance of inflammatory pain. Pain 2009; 148:237-246. [PMID: 20005044 DOI: 10.1016/j.pain.2009.11.003] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Revised: 09/24/2009] [Accepted: 11/04/2009] [Indexed: 10/20/2022]
Abstract
Following peripheral inflammation, NMDA receptor (NMDAR) activation in spinal cord dorsal horn neurons facilitates the generation of pain in response to low threshold inputs (allodynia) and signals the phosphorylation of protein kinase C (pPKC) and extracellular signal-regulated kinase 2 (pERK2). Intraplantar complete Freund's adjuvant (CFA) induces inflammatory nociception (allodynic pain) at 24 hours (h) with a concurrent increase in neuronal pPKCgamma and pERK2 but not glial pERK2. These effects are attenuated in a spatial knockout of the NMDAR (NR1 KO) confined to SCDH neurons. Although glia and proinflammatory cytokines are implicated in the maintenance of inflammatory pain and neuronal activation, the role of NMDARs and neuronal-glial-cytokine interactions that initiate and maintain inflammatory pain are not well defined. In the maintenance phase of inflammatory pain at 96h after CFA the NR1 KO mice are no longer protected from allodynia and the SCDH expression of pPKCgamma and pERK2 are increased. At 96h the expression of the proinflammatory cytokine, IL-1beta, and pERK2 are increased in astrocytes. Intrathecal IL-1 receptor antagonist (IL-1ra), acting on neuronal IL-1 receptors, completely reverses the allodynia at 96h after CFA. Deletion of NMDAR-dependent signaling in neurons protects against early CFA-induced allodynia. Subsequent NMDAR-independent signaling that involves neuronal expression of pPKCgamma and the induction of pERK2 and IL-1beta in activated astrocytes contributes to the emergence of NMDAR-independent inflammatory pain behavior at 96h after CFA. Effective reduction of the initiation and maintenance of inflammatory pain requires targeting the neuron-astrocyte-cytokine interactions revealed in these studies.
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Affiliation(s)
- Amanda R Weyerbacher
- Department of Pharmacology, Weill Cornell Medical College, New York, NY 10065, USA Department of Neurology and the Pain and Palliative Care Service, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA
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168
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Pain and purinergic signaling. ACTA ACUST UNITED AC 2009; 63:222-32. [PMID: 19931560 DOI: 10.1016/j.brainresrev.2009.11.003] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2009] [Revised: 11/10/2009] [Accepted: 11/11/2009] [Indexed: 01/12/2023]
Abstract
A growing body of evidence indicates that extracellular nucleotides play important roles in the regulation of neuronal and glial functions in the nervous system through P2 purinoceptors. P2 purinoceptors are divided into two families, ionotropic receptors (P2X) and metabotropic receptors (P2Y). P2X receptors (seven types; P2X1-P2X7) contain intrinsic pores that open by binding with ATP, and P2Y receptors (eight types; P2Y1, 2, 4, 6, 11, 12, 13 and 14) are activated by nucleotides and couple to intracellular second-messenger systems through heterotrimeric G-proteins. Nucleotides are released or leaked from non-excitable cells as well as neurons in physiological and pathophysiological conditions. Studies have shown that microglia, a type of glial cells known as resident macrophages in the CNS, express several subtypes of P2X and P2Y receptors, and these receptors play a key role in pain signaling in the spinal cord under pathological conditions such as by peripheral nerve injury (called neuropathic pain). Within the spinal dorsal horn, peripheral nerve injury leads to a progressive series of changes in microglia including morphological hypertrophy of the cell body and proliferation, which are considered indicative of activation. These activated microglia upregulate expression of P2X/Y receptors (e.g., P2X4 and P2Y12). Importantly, pharmacological, molecular and genetic manipulations of the function or expression of these microglial molecules strongly suppress neuropathic pain. We expect that further investigation to determine how ATP signaling via P2X receptors participates in the pathogenesis of chronic pain will lead to a better understanding of the molecular mechanisms of pathological pain and provide clues for the development of new therapeutic drugs.
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169
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170
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Watkins LR, Hutchinson MR, Rice KC, Maier SF. The "toll" of opioid-induced glial activation: improving the clinical efficacy of opioids by targeting glia. Trends Pharmacol Sci 2009; 30:581-91. [PMID: 19762094 DOI: 10.1016/j.tips.2009.08.002] [Citation(s) in RCA: 291] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 07/27/2009] [Accepted: 08/03/2009] [Indexed: 12/24/2022]
Abstract
Glial activation participates in the mediation of pain including neuropathic pain, due to release of neuroexcitatory, proinflammatory products. Glial activation is now known to occur in response to opioids as well. Opioid-induced glial activation opposes opioid analgesia and enhances opioid tolerance, dependence, reward and respiratory depression. Such effects can occur, not via classical opioid receptors, but rather via non-stereoselective activation of toll-like receptor 4 (TLR4), a recently recognized key glial receptor participating in neuropathic pain as well. This discovery identifies a means for separating the beneficial actions of opioids (opioid receptor mediated) from the unwanted side-effects (TLR4/glial mediated) by pharmacologically targeting TLR4. Such a drug should be a stand-alone therapeutic for treating neuropathic pain as well. Excitingly, with newly-established clinical trials of two glial modulators for treating neuropathic pain and improving the utility of opioids, translation from rats-to-humans now begins with the promise of improved clinical pain control.
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Affiliation(s)
- Linda R Watkins
- Department of Psychology & Neuroscience and The Center for Neuroscience, University of Colorado at Boulder, Boulder, Colorado USA.
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171
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Rothman SM, Guarino BB, Winkelstein BA. Spinal microglial proliferation is evident in a rat model of painful disc herniation both in the presence of behavioral hypersensitivity and following minocycline treatment sufficient to attenuate allodynia. J Neurosci Res 2009; 87:2709-17. [DOI: 10.1002/jnr.22090] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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172
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Hernstadt H, Wang S, Lim G, Mao J. Spinal translocator protein (TSPO) modulates pain behavior in rats with CFA-induced monoarthritis. Brain Res 2009; 1286:42-52. [PMID: 19555675 PMCID: PMC2749299 DOI: 10.1016/j.brainres.2009.06.043] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2009] [Revised: 06/12/2009] [Accepted: 06/15/2009] [Indexed: 12/20/2022]
Abstract
Translocator protein 18 kDa (TSPO), previously known as the peripheral benzodiazepine receptor (PBR), is predominantly located in the mitochondrial outer membrane and plays an important role in steroidogenesis, immunomodulation, cell survival and proliferation. Previous studies have shown an increased expression of TSPO centrally in neuropathology, as well as in injured nerves. TSPO has also been implicated in modulation of nociception. In the present study, we examined the hypothesis that TSPO is involved in the initiation and maintenance of inflammatory pain using a rat model of Complete Freund's Adjuvant (CFA)-induced monoarthritis of the tibio-tarsal joint. Immunohistochemistry was performed using Iba-1 (microglia), NeuN (neurons), anti-Glial Fibrillary Acidic Protein, GFAP (astrocytes) and anti-PBR (TSPO) on Days 1, 7 and 14 after CFA-induced arthritis. Rats with CFA-induced monoarthritis showed mechanical allodynia and thermal hyperalgesia on the ipsilateral hindpaw, which correlated with the increased TSPO expression in ipsilateral laminae I-II on all experimental days. Iba-1 expression in the ipsilateral dorsal horn was also increased on Days 7 and 14. Moreover, TSPO was colocalized with Iba-1, GFAP and NeuN within the spinal cord dorsal horn. The TSPO agonist Ro5-4864, given intrathecally, dose-dependently retarded or prevented the development of mechanical allodynia and thermal hyperalgesia in rats with CFA-induced monoarthritis. These findings provide evidence that spinal TSPO is involved in the development and maintenance of inflammatory pain behaviors in rats. Thus, spinal TSPO may present a central target as a complementary therapy to reduce inflammatory pain.
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Affiliation(s)
- Hayley Hernstadt
- Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Victoria 3010, Australia
- MGH Center for Translational Pain Research, Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114
| | - Shuxing Wang
- MGH Center for Translational Pain Research, Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114
| | - Grewo Lim
- MGH Center for Translational Pain Research, Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114
| | - Jianren Mao
- MGH Center for Translational Pain Research, Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114
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173
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Rapid isolation and culture of primary microglia from adult mouse spinal cord. J Neurosci Methods 2009; 183:223-37. [PMID: 19596375 DOI: 10.1016/j.jneumeth.2009.07.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 06/30/2009] [Accepted: 07/01/2009] [Indexed: 12/13/2022]
Abstract
Microglia are important in homeostasis and widely considered to have roles in the pathogenesis of conditions such as neuropathic pain and multiple sclerosis. The need to study microglia from the adult spinal cord is essential to further understand the role of these cells in disease pathology. Primary microglia are often prepared from brain tissues obtained from embryonic or perinatal age rodents and the process can take over a week to complete. The protocol in this study provides rapid isolation of microglia from adult spinal cord, allowing immediate availability for experimentation of both ex vivo and in vitro within a few hours. A purity of 99% with little or no neuronal or astrocytic contamination can be achieved. Between 70% and 85% of these adult microglia were in a relatively non-activated state. Functionally, these microglia respond to lipopolysaccharide incubation with increases in both phospho-p38 MAPK and OX42 immunostaining, as well as release of ATP, as compared to un-stimulated microglia. This technique provides a protocol to achieve rapid and efficient extraction of high purity, quiescent and functionally active microglia from adult mouse spinal cord, allowing greater study of adult spinal microglia in physiological and pathophysiological states.
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174
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Guasti L, Richardson D, Jhaveri M, Eldeeb K, Barrett D, Elphick MR, Alexander SPH, Kendall D, Michael GJ, Chapman V. Minocycline treatment inhibits microglial activation and alters spinal levels of endocannabinoids in a rat model of neuropathic pain. Mol Pain 2009; 5:35. [PMID: 19570201 PMCID: PMC2719614 DOI: 10.1186/1744-8069-5-35] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2008] [Accepted: 07/01/2009] [Indexed: 01/19/2023] Open
Abstract
Activation of spinal microglia contributes to aberrant pain responses associated with neuropathic pain states. Endocannabinoids (ECs) are present in the spinal cord, and inhibit nociceptive processing; levels of ECs may be altered by microglia which modulate the turnover of endocannabinoids in vitro. Here, we investigate the effect of minocycline, an inhibitor of activated microglia, on levels of the endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG), and the related compound N-palmitoylethanolamine (PEA), in neuropathic spinal cord. Selective spinal nerve ligation (SNL) in rats resulted in mechanical allodynia and the presence of activated microglia in the ipsilateral spinal cord. Chronic daily treatment with minocycline (30 mg/kg, ip for 14 days) significantly reduced the development of mechanical allodynia at days 5, 10 and 14 post-SNL surgery, compared to vehicle-treated SNL rats (P < 0.001). Minocycline treatment also significantly attenuated OX-42 immunoreactivity, a marker of activated microglia, in the ipsilateral (P < 0.001) and contralateral (P < 0.01) spinal cord of SNL rats, compared to vehicle controls. Minocycline treatment significantly (P < 0.01) decreased levels of 2-AG and significantly (P < 0.01) increased levels of PEA in the ipsilateral spinal cord of SNL rats, compared to the contralateral spinal cord. Thus, activation of microglia affects spinal levels of endocannabinoids and related compounds in neuropathic pain states.
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Affiliation(s)
- Leonardo Guasti
- School of Biological and Chemical Sciences, Queen Mary University of London, UK.
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175
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Tsuda M, Masuda T, Kitano J, Shimoyama H, Tozaki-Saitoh H, Inoue K. IFN-gamma receptor signaling mediates spinal microglia activation driving neuropathic pain. Proc Natl Acad Sci U S A 2009; 106:8032-7. [PMID: 19380717 PMCID: PMC2683100 DOI: 10.1073/pnas.0810420106] [Citation(s) in RCA: 225] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2008] [Indexed: 01/23/2023] Open
Abstract
Neuropathic pain, a highly debilitating pain condition that commonly occurs after nerve damage, is a reflection of the aberrant excitability of dorsal horn neurons. This pathologically altered neurotransmission requires a communication with spinal microglia activated by nerve injury. However, how normal resting microglia become activated remains unknown. Here we show that in naive animals spinal microglia express a receptor for the cytokine IFN-gamma (IFN-gammaR) in a cell-type-specific manner and that stimulating this receptor converts microglia into activated cells and produces a long-lasting pain hypersensitivity evoked by innocuous stimuli (tactile allodynia, a hallmark symptom of neuropathic pain). Conversely, ablating IFN-gammaR severely impairs nerve injury-evoked microglia activation and tactile allodynia without affecting microglia in the contralateral dorsal horn or basal pain sensitivity. We also find that IFN-gamma-stimulated spinal microglia show up-regulation of Lyn tyrosine kinase and purinergic P2X(4) receptor, crucial events for neuropathic pain, and genetic approaches provide evidence linking these events to IFN-gammaR-dependent microglial and behavioral alterations. These results suggest that IFN-gammaR is a key element in the molecular machinery through which resting spinal microglia transform into an activated state that drives neuropathic pain.
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Affiliation(s)
- Makoto Tsuda
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan
| | - Takahiro Masuda
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan
| | - Junko Kitano
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan
| | - Hiroshi Shimoyama
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan
| | - Hidetoshi Tozaki-Saitoh
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan
| | - Kazuhide Inoue
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan
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176
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Abbadie C, Bhangoo S, De Koninck Y, Malcangio M, Melik-Parsadaniantz S, White FA. Chemokines and pain mechanisms. BRAIN RESEARCH REVIEWS 2009; 60:125-34. [PMID: 19146875 PMCID: PMC2691997 DOI: 10.1016/j.brainresrev.2008.12.002] [Citation(s) in RCA: 210] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Accepted: 12/29/2008] [Indexed: 11/15/2022]
Abstract
The development of new therapeutic approaches to the treatment of painful neuropathies requires a better understanding of the mechanisms that underlie the development of these chronic pain syndromes. It is now well established that astrocytic and microglial cells modulate the neuronal mechanisms of chronic pain in spinal cord and possibly in the brain. In animal models of neuropathic pain following peripheral nerve injury, several changes occur at the level of the first pain synapse between the central terminals of sensory neurons and second order neurons. These neuronal mechanisms can be modulated by pro-nociceptive mediators released by non neuronal cells such as microglia and astrocytes which become activated in the spinal cord following PNS injury. However, the signals that mediate the spread of nociceptive signaling from neurons to glial cells in the dorsal horn remain to be established. Herein we provide evidence for two emerging signaling pathways between injured sensory neurons and spinal microglia: chemotactic cytokine ligand 2 (CCL2)/CCR2 and cathepsin S/CX3CL1 (fractalkine)/CX3CR1. We discuss the plasticity of these two chemokine systems at the level of the dorsal root ganglia and spinal cord demonstrating that modulation of chemokines using selective antagonists decrease nociceptive behavior in rodent chronic pain models. Since up-regulation of chemokines and their receptors may be a mechanism that directly and/or indirectly contributes to the development and maintenance of chronic pain, these molecular molecules may represent novel targets for therapeutic intervention in sustained pain states.
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Affiliation(s)
- Catherine Abbadie
- Department of Immunology, Merck Research Laboratories, PO Box 2000, Rahway, NJ 07065, USA.
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177
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Mitchell K, Yang HYT, Berk JD, Tran JH, Iadarola MJ. Monocyte chemoattractant protein-1 in the choroid plexus: a potential link between vascular pro-inflammatory mediators and the CNS during peripheral tissue inflammation. Neuroscience 2009; 158:885-95. [PMID: 19032979 PMCID: PMC2668531 DOI: 10.1016/j.neuroscience.2008.10.047] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Revised: 10/17/2008] [Accepted: 10/28/2008] [Indexed: 12/22/2022]
Abstract
During peripheral tissue inflammation, inflammatory processes in the CNS can be initiated by blood-borne pro-inflammatory mediators. The choroid plexus, the site of cerebrospinal fluid (CSF) production, is a highly specialized interface between the vascular system and CNS, and thus, this structure may be an important element in communication between the vascular compartment and the CNS during peripheral tissue inflammation. We investigated the potential participation of the choroid plexus in this process during peripheral tissue inflammation by examining expression of the small inducible cytokine A2 (SCYA2) gene which codes for monocyte chemoattractant protein-1 (MCP-1). MCP-1 protein was previously reported to be induced in a variety of cells during peripheral tissue inflammation. In the basal state, SCYA2 is highly expressed in the choroid plexus as compared with other rat CNS tissues. During hind paw inflammation, SCYA2 expression was significantly elevated in choroid plexus, whereas it remained unchanged in a variety of brain regions. The SCYA2-expressing cells were strongly associated with the choroid plexus as vascular depletion of blood cells by whole-body saline flush did not significantly alter SCYA2 expression in the choroid plexus. In situ hybridization suggested that the SCYA2-expressing cells were localized to the choroid plexus stroma. To elucidate potential molecular mechanisms of SCYA2 increase, we examined genes in the nuclear factor-kappa B (NF-kappaB) signaling cascade including tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and inhibitor of kappa B alpha (IkappaBalpha) in choroid tissue. Given that we also detected increased levels of MCP-1 protein by ELISA, we sought to identify potential downstream targets of MCP-1 and observed altered expression levels of mRNAs encoding tight junction proteins TJP2 and claudin 5. Finally, we detected a substantial up-regulation of the transcript encoding endothelial leukocyte adhesion molecule 1 (E-selectin), a molecule which could participate in leukocyte recruitment to the choroid plexus along with MCP-1. Together, these results suggest that profound changes occur in the choroid plexus during peripheral tissue inflammation, likely initiated by blood-borne inflammatory mediators, which may modify events in CNS.
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Affiliation(s)
- K. Mitchell
- Neurobiology and Pain Therapeutics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Building 49, Room 1C20, 49 Convent Drive, MSC 4410, Bethesda, MD 20892-4410, USA
| | - H.-Y. T. Yang
- Neurobiology and Pain Therapeutics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Building 49, Room 1C20, 49 Convent Drive, MSC 4410, Bethesda, MD 20892-4410, USA
| | - J. D. Berk
- Neurobiology and Pain Therapeutics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Building 49, Room 1C20, 49 Convent Drive, MSC 4410, Bethesda, MD 20892-4410, USA
| | - J. H. Tran
- Neurobiology and Pain Therapeutics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Building 49, Room 1C20, 49 Convent Drive, MSC 4410, Bethesda, MD 20892-4410, USA
| | - M. J. Iadarola
- Neurobiology and Pain Therapeutics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, Building 49, Room 1C20, 49 Convent Drive, MSC 4410, Bethesda, MD 20892-4410, USA
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178
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Fu KY, Tan YH, Sung B, Mao J. Peripheral formalin injection induces unique spinal cord microglial phenotypic changes. Neurosci Lett 2009; 449:234-9. [PMID: 19015000 PMCID: PMC4082795 DOI: 10.1016/j.neulet.2008.11.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Revised: 11/05/2008] [Accepted: 11/05/2008] [Indexed: 12/25/2022]
Abstract
Microglia are resident immune cells of brain and activated by peripheral tissue injury. In the present study, we investigated the possible induction of several microglial surface immunomolecules in the spinal cord, including leukocyte common antigen (LCA/CD45), MHC class I antigen, MHC class II antigen, Fc receptor, and CD11c following formalin injection into the rat's hind paw. CD45 and MHC class I were upregulated in the activated microglia, which was evident on day 3 with the peak expression on day 7 following peripheral formalin injection. There was a very low basal expression of MHC class II, CD11c, and the Fc receptor, which did not change after the formalin injection. These results, for the first time, indicate that peripheral formalin injection can induce phenotypic changes of microglia with distinct upregulation of CD45 and MHC class I antigen. The data suggest that phenotypic changes of the activated microglia may be a unique pattern of central changes following peripheral tissue injury.
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Affiliation(s)
- Kai-Yuan Fu
- Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing 100081, People's Republic of China.
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179
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Rothman SM, Huang Z, Lee KE, Weisshaar CL, Winkelstein BA. Cytokine mRNA expression in painful radiculopathy. THE JOURNAL OF PAIN 2009; 10:90-9. [PMID: 18848809 PMCID: PMC2630380 DOI: 10.1016/j.jpain.2008.07.008] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Revised: 07/18/2008] [Accepted: 07/29/2008] [Indexed: 01/01/2023]
Abstract
UNLABELLED Inflammatory cytokines contribute to lumbar radiculopathy. Regulation of cytokines for transient cervical injuries, with or without longer-lasting inflammation, remains to be defined. The C7 root in the rat underwent compression (10gf), chromic gut suture exposure (chr), or their combination (10gf+chr). Ipsilateral C7 spinal cord and dorsal root ganglia (DRG) were harvested at 1 hour after injury for real-time PCR analysis of IL-1beta, IL-6, and TNF-alpha. Cytokine mRNA increased after all 3 injuries. TNF-alpha mRNA in the DRG was significantly increased over sham after 10gf+chr (P = .026). Spinal IL-1beta was significantly increased over sham after 10gf and 10gf+chr (P < .024); IL-6 was significantly increased after 10gf+chr (P < .024). In separate studies, the soluble TNF-alpha receptor was administered at injury and again at 6 hours in all injury paradigms. Allodynia was assessed and tissue samples were harvested for cytokine PCR. Allodynia significantly decreased with receptor administration for 10gf and 10gf+chr (P < .005). Treatment also significantly decreased IL-1beta and TNF-alpha mRNA in the DRG for 10gf+chr (P < .028) at day 1. Results indicate an acute, robust cytokine response in cervical nerve root injury with varying patterns, dependent on injury type, and that early increases in TNF-alpha mRNA in the DRG may drive pain-related signaling for transient cervical injuries. PERSPECTIVE Inflammatory cytokine mRNA in the DRG and spinal cord are defined after painful cervical nerve root injury. Studies describe a role for TNF-alpha in mediating behavioral sensitivity and inflammatory cytokines in transient painful radiculopathy. Results outline an early response of inflammatory cytokine upregulation in cervical pain.
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Affiliation(s)
- Sarah M. Rothman
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Zhong Huang
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Kathryn E. Lee
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | | | - Beth A. Winkelstein
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA 19104, USA
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180
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Galvan MD, Luchetti S, Burgos AM, Nguyen HX, Hooshmand MJ, Hamers FPT, Anderson AJ. Deficiency in complement C1q improves histological and functional locomotor outcome after spinal cord injury. J Neurosci 2008; 28:13876-88. [PMID: 19091977 PMCID: PMC2680920 DOI: 10.1523/jneurosci.2823-08.2008] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Revised: 09/29/2008] [Accepted: 10/24/2008] [Indexed: 02/08/2023] Open
Abstract
Although studies have suggested a role for the complement system in the pathophysiology of spinal cord injury (SCI), that role remains poorly defined. Additionally, the relative contribution of individual complement pathways in SCI is unknown. Our initial studies revealed that systemic complement activation was strongly influenced by genetic background and gender. Thus, to investigate the role of the classical complement pathway in contusion-induced SCI, male C1q knock-out (KO) and wild-type (WT) mice on a complement sufficient background (BUB) received a mild-moderate T9 contusion injury with the Infinite Horizon impactor. BUB C1q KO mice exhibited greater locomotor recovery compared with BUB WT mice (p<0.05). Improved recovery observed in BUB C1q KO mice was also associated with decreased threshold for withdrawal from a mild stimulus using von Frey filament testing. Surprisingly, quantification of microglia/macrophages (F4/80) by FACS analysis showed that BUB C1q KO mice exhibited a significantly greater percentage of macrophages in the spinal cord compared with BUB WT mice 3 d post-injury (p<0.05). However, this increased macrophage response appeared to be transient as stereological assessment of spinal cord tissue obtained 28 d post-injury revealed no difference in F4/80-positive cells between groups. Stereological assessment of spinal cord tissue showed that BUB C1q KO mice had reduced lesion volume and an increase in tissue sparing compared with BUB WT mice (p<0.05). Together, these data suggest that initiation of the classical complement pathway via C1q is detrimental to recovery after SCI.
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Affiliation(s)
- Manuel D. Galvan
- Departments of Physical Medicine & Rehabilitation and
- Anatomy & Neurobiology, Reeve-Irvine Research Center, University of California, Irvine, Irvine, California 92697-4292, and
| | - Sabina Luchetti
- Departments of Physical Medicine & Rehabilitation and
- Anatomy & Neurobiology, Reeve-Irvine Research Center, University of California, Irvine, Irvine, California 92697-4292, and
| | - Adrian M. Burgos
- Departments of Physical Medicine & Rehabilitation and
- Anatomy & Neurobiology, Reeve-Irvine Research Center, University of California, Irvine, Irvine, California 92697-4292, and
| | - Hal X. Nguyen
- Departments of Physical Medicine & Rehabilitation and
- Anatomy & Neurobiology, Reeve-Irvine Research Center, University of California, Irvine, Irvine, California 92697-4292, and
| | - Mitra J. Hooshmand
- Departments of Physical Medicine & Rehabilitation and
- Anatomy & Neurobiology, Reeve-Irvine Research Center, University of California, Irvine, Irvine, California 92697-4292, and
| | - Frank P. T. Hamers
- Rehabilitation Hospital “DE Hoogstraat,” Rudolf Magnus Institute of Neuroscience, 3583 TM Utrecht, The Netherlands
| | - Aileen J. Anderson
- Departments of Physical Medicine & Rehabilitation and
- Anatomy & Neurobiology, Reeve-Irvine Research Center, University of California, Irvine, Irvine, California 92697-4292, and
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181
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Wei F, Guo W, Zou S, Ren K, Dubner R. Supraspinal glial-neuronal interactions contribute to descending pain facilitation. J Neurosci 2008; 28:10482-95. [PMID: 18923025 PMCID: PMC2660868 DOI: 10.1523/jneurosci.3593-08.2008] [Citation(s) in RCA: 244] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Accepted: 09/02/2008] [Indexed: 01/13/2023] Open
Abstract
Spinal glial reaction and proinflammatory cytokine induction play an important role in the development of chronic pain states after tissue and nerve injury. The present study investigated the cellular and molecular mechanisms underlying descending facilitation of neuropathic pain with an emphasis on supraspinal glial-neuronal relationships. An early and transient reaction of microglia and prolonged reaction of astrocytes were found after chronic constriction injury (CCI) of the rat infraorbital nerve in the rostral ventromedial medulla (RVM), a major component of brainstem descending pain modulatory circuitry. There were prolonged elevations of cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) after CCI, and they were expressed in RVM astrocytes at 14 d after injury. Intra-RVM injection of microglial and astrocytic inhibitors attenuated mechanical hyperalgesia and allodynia at 3 and 14 d after CCI, respectively. Moreover, TNFR1 and IL-1R, receptors for TNF-alpha and IL-1beta, respectively, were expressed primarily in RVM neurons exhibiting immunoreactivity to the NMDA receptor (NMDAR) subunit NR1. CCI increased TNFR1 and IL-1R levels and NR1 phosphorylation in the RVM. Neutralization of endogenous TNF-alpha and IL-1beta in the RVM significantly reduced CCI-induced behavioral hypersensitivity and attenuated NR1 phosphorylation. Finally, intra-RVM administration of recombinant TNF-alpha or IL-1beta upregulated NR1 phosphorylation and caused a reversible and NMDAR-dependent allodynia in normal rats, further suggesting that TNF-alpha and IL-1beta couple glial hyperactivation with NMDAR function. These studies have addressed a novel contribution of supraspinal astrocytes and associated cytokines as well as central glial-neuronal interactions to the enhancement of descending facilitation of neuropathic pain.
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Affiliation(s)
- Feng Wei
- Department of Neural and Pain Sciences, Dental School, Program in Neuroscience, University of Maryland, Baltimore, Maryland 21201, USA.
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182
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Scholz J, Abele A, Marian C, Häussler A, Herbert TA, Woolf CJ, Tegeder I. Low-dose methotrexate reduces peripheral nerve injury-evoked spinal microglial activation and neuropathic pain behavior in rats. Pain 2008; 138:130-142. [PMID: 18215468 PMCID: PMC2536692 DOI: 10.1016/j.pain.2007.11.019] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2007] [Revised: 10/30/2007] [Accepted: 11/26/2007] [Indexed: 01/23/2023]
Abstract
Peripheral nerve injuries that provoke neuropathic pain are associated with microglial activation in the spinal cord. We have investigated the characteristics of spinal microglial activation in three distinct models of peripheral neuropathic pain in the rat: spared nerve injury (SNI), chronic constriction injury, and spinal nerve ligation. In all models, dense clusters of cells immunoreactive for the microglial marker CD11b formed in the ipsilateral dorsal horn 7 days after injury. Microglial expression of ionised calcium binding adapter molecule 1 (Iba1) increased by up to 40% and phosphorylation of p38 mitogen-activated protein kinase, a marker of microglial activity, by 45%. Expression of the lysosomal ED1-antigen indicated phagocytic activity of the cells. Unlike the peripheral nerve lesions, rhizotomy produced only a weak microglial reaction within the spinal gray matter but a strong activation of microglia and phagocytes in the dorsal funiculus at lumbar and thoracic spinal cord levels. This suggests that although degeneration of central terminals is sufficient to elicit microglial activation, it does not account for the inflammatory response in the dorsal horn after peripheral nerve injury. Early intrathecal treatment with low-dose methotrexate, beginning at the time of injury, decreased microglial activation, reduced p38 phosphorylation, and attenuated pain-like behavior after SNI. In contrast, systemic or intrathecal delivery of the glucocorticoid dexamethasone did not inhibit the activation of microglia or reduce pain-like behavior. We confirm that microglial activation is crucial for the development of pain after nerve injury, and demonstrates that suppression of this cellular immune response is a promising approach for preventing neuropathic pain.
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Affiliation(s)
- Joachim Scholz
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Andrea Abele
- Pharmazentrum frankfurt, Institut für Klinische Pharmakologie/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
| | - Claudiu Marian
- Pharmazentrum frankfurt, Institut für Klinische Pharmakologie/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
| | - Annett Häussler
- Pharmazentrum frankfurt, Institut für Klinische Pharmakologie/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
| | - Teri A. Herbert
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Clifford J. Woolf
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
| | - Irmgard Tegeder
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA
- Pharmazentrum frankfurt, Institut für Klinische Pharmakologie/ZAFES, Klinikum der Johann Wolfgang Goethe-Universität, Frankfurt am Main, Germany
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183
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Schreiber KL, Beitz AJ, Wilcox GL. Activation of spinal microglia in a murine model of peripheral inflammation-induced, long-lasting contralateral allodynia. Neurosci Lett 2008; 440:63-7. [PMID: 18541374 PMCID: PMC2519608 DOI: 10.1016/j.neulet.2008.05.044] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2008] [Revised: 05/02/2008] [Accepted: 05/07/2008] [Indexed: 12/26/2022]
Abstract
Increased sensitivity contralateral to an injury has been described in humans and in various models of neuropathic pain in rats. The mechanism underlying contralateral hypersensitivity is as yet unclear, although previous studies have implicated involvement of both spinal neurons and glia. We describe the development of a temporally delayed, robust and long-lasting contralateral allodynia in mice after hindpaw injection with 4% carrageenan. Both ipsilateral and contralateral allodynia could be inhibited temporarily by intrathecally administered morphine, clonidine, or neostigmine. The delayed development of contralateral allodynia correlated with an increase in OX-42, but not GFAP immunoreactivity in the contralateral dorsal horn. Furthermore, intrathecal treatment with minocycline inhibited the development of contralateral allodynia, suggesting that microglial activation plays a key role in contralateralization, and may be a potential target for clinical intervention after injury or inflammation has occurred, to eliminate the subsequent development of extraterritorial pain.
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Affiliation(s)
- Kristin L Schreiber
- Department of Anesthesiology, University of Minnesota, 321 Church Street, Minneapolis, MN 55455, United States.
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184
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Cao H, Zhang YQ. Spinal glial activation contributes to pathological pain states. Neurosci Biobehav Rev 2008; 32:972-983. [PMID: 18471878 DOI: 10.1016/j.neubiorev.2008.03.009] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2007] [Revised: 02/28/2008] [Accepted: 03/13/2008] [Indexed: 12/21/2022]
Abstract
Chronic pain, a pathological state, affects millions of people worldwide. Despite decades of study on the neuronal processing of pain, mechanisms underlying the creation and maintenance of enhanced pain states after injury or inflammation remain far from clear. In the last decade, however, the discovery that glial activation amplifies pain has challenged classic neuronal views of "pain". This review focuses on recent developments in understanding that spinal cord glia are involved in pathological pain. We overview the action of spinal glia (both microglia and astrocytes) in several persistent pain models, and provide new evidence that spinal glia activation contributes to the development and maintenance of arthritic pain facilitation. We also attempt to discuss some critical questions, such as how signals are conveyed from primary afferents to spinal glia following peripheral nerve injury and inflammation. What causes glia to become activated after peripheral/central injury/inflammation? And how the activated glia alter neuronal sensitivity and pain processing? Answers to these questions might open a new approach for treatment of pathological pain.
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Affiliation(s)
- Hong Cao
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China
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185
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P2Y12 receptors in spinal microglia are required for neuropathic pain after peripheral nerve injury. J Neurosci 2008; 28:4949-56. [PMID: 18463248 DOI: 10.1523/jneurosci.0323-08.2008] [Citation(s) in RCA: 226] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Extracellular nucleotides have been implicated as signaling molecules used by microglia to sense adverse physiological conditions, such as neuronal damage. They act through purinoceptors, especially the G-protein-coupled P2Y receptor P2Y(12)R. Emerging evidence has indicated that activated spinal microglia responding to nerve injury are key cellular intermediaries in the resulting highly debilitating chronic pain state, namely neuropathic pain. However, the role of microglial P2Y(12)Rs in neuropathic pain remains unknown. Here, we show that the level of P2Y(12)R mRNA expression was markedly increased in the spinal cord ipsilateral to the nerve injury and that this expression was highly restricted to ionized binding calcium adapter molecule 1-positive microglia. An increase in the immunofluorescence of P2Y(12)R protein in the ipsilateral spinal cord was also observed after nerve injury, and P2Y(12)R-positive cells were double labeled with the microglial marker OX-42. Blocking spinal P2Y(12)R by the intrathecal administration of its antagonist AR-C69931MX prevented the development of tactile allodynia (pain hypersensitivity to innocuous stimuli), a hallmark of neuropathic pain syndrome. Furthermore, mice lacking P2ry(12) (P2ry(12)(-/-)) displayed impaired tactile allodynia after nerve injury without any change in basal mechanical sensitivity. Moreover, a single intrathecal administration of AR-C69931MX or oral administration of clopidogrel (a P2Y(12)R blocker clinically in use) to nerve-injured rats produced a striking alleviation of existing tactile allodynia. Together, our findings indicate that activation of P2Y(12)Rs in spinal microglia may be a critical event in the pathogenesis of neuropathic pain and suggest that blocking microglial P2Y(12)R might be a viable therapeutic strategy for treating neuropathic pain.
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186
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Luongo L, Sajic M, Grist J, Clark AK, Maione S, Malcangio M. Spinal changes associated with mechanical hypersensitivity in a model of Guillain-Barré syndrome. Neurosci Lett 2008; 437:98-102. [PMID: 18448252 DOI: 10.1016/j.neulet.2008.04.019] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Revised: 03/31/2008] [Accepted: 04/06/2008] [Indexed: 12/30/2022]
Abstract
Guillain-Barré syndrome (GBS) is an inflammatory disease of the peripheral nervous system which can cause pain via mechanisms that are poorly understood. Here, we show that in rat experimental autoimmune neuritis (EAN) mechanical allodynia developed up to 9 days before the onset of detectable neurological deficits. Allodynia was associated with an increase in the number of microglial cells in the dorsal horn of the spinal cord. The expression of the chemokine CX3CL1 (fractalkine) and its receptor CX3CR1 were also higher in EAN than in control dorsal horns suggesting spinal microglia and CX3CL1/CX3CR1 may play a role in the pain-like behaviour.
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Affiliation(s)
- Livio Luongo
- Neurorestoration group, Wolfson Centre for Age Related Diseases, King's College London, London, UK
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187
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Scholz J, Woolf CJ. The neuropathic pain triad: neurons, immune cells and glia. Nat Neurosci 2008; 10:1361-8. [PMID: 17965656 DOI: 10.1038/nn1992] [Citation(s) in RCA: 1334] [Impact Index Per Article: 78.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Nociceptive pain results from the detection of intense or noxious stimuli by specialized high-threshold sensory neurons (nociceptors), a transfer of action potentials to the spinal cord, and onward transmission of the warning signal to the brain. In contrast, clinical pain such as pain after nerve injury (neuropathic pain) is characterized by pain in the absence of a stimulus and reduced nociceptive thresholds so that normally innocuous stimuli produce pain. The development of neuropathic pain involves not only neuronal pathways, but also Schwann cells, satellite cells in the dorsal root ganglia, components of the peripheral immune system, spinal microglia and astrocytes. As we increasingly appreciate that neuropathic pain has many features of a neuroimmune disorder, immunosuppression and blockade of the reciprocal signaling pathways between neuronal and non-neuronal cells offer new opportunities for disease modification and more successful management of pain.
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Affiliation(s)
- Joachim Scholz
- Neural Plasticity Research Group, Department of Anesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
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188
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Topographical mapping and mechanical pain sensitivity of myofascial trigger points in the infraspinatus muscle. Eur J Pain 2008; 12:859-65. [PMID: 18203637 DOI: 10.1016/j.ejpain.2007.12.005] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Revised: 12/07/2007] [Accepted: 12/07/2007] [Indexed: 10/22/2022]
Abstract
OBJECTIVES To screen for the presence of latent and active myofascial trigger points (MTrPs) in patients with unilateral shoulder and arm pain and perform topographical mapping of mechanical pain sensitivity bilaterally in the infraspinatus muscles. METHODS Nineteen patients with unilateral musculoskeletal shoulder pain participated in the study. The area overlying the infraspinatus on each side was divided into 10 adjacent sub-areas of 1cm(2), corresponding to the area of a pressure algometer probe. Pressure pain threshold (PPT) was measured in each sub-area bilaterally in the infraspinatus muscles. Following PPT measurement, an acupuncture needle was inserted into each sub-area five times in different directions in order to induce local twitch response and/or referred pain. RESULTS A significantly lower PPT level in the infraspinatus muscle was detected on the painful side compared with the non-painful side (P=0.001). PPT at midfiber region of the infraspinatus muscles was lower than that at other muscle parts (P<0.05). Multiple, but not single, active MTrPs were found in the infraspinatus muscle on the painful side and there were also multiple latent MTrPs bilaterally in the infraspinatus muscles. PPT at active MTrPs was much lower than the latent MTrPs and again lower than the non-MTrPs. CONCLUSIONS There exists bilateral mechanical hyperalgesia in patients with unilateral shoulder pain. Further, the association of multiple active MTrPs with unilateral shoulder pain and the heterogeneity of mechanical pain sensitivity distribution suggest a crucial role of peripheral sensitization in chronic myofascial pain conditions. Additionally, the locations of MTrPs identified with dry needling correspond well to PPT topographical mapping, suggesting that dry needling and PPT topographical mapping are sensitive techniques in the identification of MTrPs.
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189
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Mitchell K, Yang HYT, Tessier PA, Muhly WT, Swaim WD, Szalayova I, Keller JM, Mezey E, Iadarola MJ. Localization of S100A8 and S100A9 expressing neutrophils to spinal cord during peripheral tissue inflammation. Pain 2007; 134:216-31. [PMID: 18063312 DOI: 10.1016/j.pain.2007.10.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2007] [Revised: 09/24/2007] [Accepted: 10/22/2007] [Indexed: 11/28/2022]
Abstract
Investigation of hyperalgesia at the spinal transcriptome level indicated that carrageenan-induced inflammation of rat hind paws leads to a rapid but sustained increase in S100A8 and S100A9 expression, two genes implicated in the pathology of numerous inflammatory diseases including rheumatoid arthritis and gout. In situ hybridization revealed that the elevation occurred in neutrophils that migrate to the spinal cord vasculature during peripheral inflammation, not in spinal neurons or glial cells. Immunohistochemical analysis suggests, but does not prove, that these neutrophils abundantly release S100A8 and S100A9. Consistent with this, we detected an increase in ICAM and VCAM, both indicators of endothelial activation, a known trigger for secretion of S100A8 and S100A9. Migration of S100A8- and S100A9-expressing neutrophils to spinal cord is selective, since MCP-1- and CD68-expressing leukocytes do not increase in spinal cord vasculature during hind paw inflammation. Examination of many neutrophil granule mediators in spinal cord indicated that they are not regulated to the same degree as S100A8 and S100A9. Neutrophil migration also occurs in the vasculature of brain and pituitary gland during peripheral inflammation. Together, these findings suggest an interaction between a subpopulation of leukocytes and the CNS during peripheral tissue inflammation, as implied by an apparent release and possible diffusion of S100A8 and S100A9 through the endothelial blood-brain barrier. Although the present findings do not establish the neurophysiological or behavioral relevance of these observations to nociceptive processing, the data raise the possibility that selective populations of leukocytes may communicate the presence of disease or tissue damage from the periphery to cells in the central nervous system.
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Affiliation(s)
- Kendall Mitchell
- Neurobiology and Pain Therapeutics Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Department of Health and Human Services, 49 Convent Drive, Bethesda, MD 20892, United States
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190
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Lin T, Li K, Zhang FY, Zhang ZK, Light AR, Fu KY. Dissociation of spinal microglia morphological activation and peripheral inflammation in inflammatory pain models. J Neuroimmunol 2007; 192:40-8. [PMID: 17919739 PMCID: PMC2198900 DOI: 10.1016/j.jneuroim.2007.09.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2007] [Revised: 09/01/2007] [Accepted: 09/04/2007] [Indexed: 01/07/2023]
Abstract
We compared the effects of peripheral Freund's Complete Adjuvant (CFA) and formalin injection on spinal microglia activation. Both qualitative and quantitative analyses showed signs of microglia activation on the ipsilateral side of the lumbar dorsal horn on day 3, day 7 and day 14 after formalin injection. However, significant microglia morphological alteration was not found in the CFA model. At the injection site in the paw, CFA injection induced considerably more inflammation than formalin injection. Although spinal microglia might be activated in inflammatory pain models, morphologically, spinal microglia activation was not closely correlated with peripheral inflammation.
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Affiliation(s)
- Ting Lin
- Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing 100081
| | - Kai Li
- Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing 100081
| | - Fei-Yu Zhang
- Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing 100081
| | - Zhen-Kang Zhang
- Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing 100081
| | - Alan R Light
- Dept. of Anesthesiology, University of Utah, Salt Lake City, Utah 84132-2304
| | - Kai-Yuan Fu
- Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing 100081
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191
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Rothman SM, Winkelstein BA. Chemical and mechanical nerve root insults induce differential behavioral sensitivity and glial activation that are enhanced in combination. Brain Res 2007; 1181:30-43. [PMID: 17920051 PMCID: PMC2174426 DOI: 10.1016/j.brainres.2007.08.064] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Revised: 07/19/2007] [Accepted: 08/28/2007] [Indexed: 12/24/2022]
Abstract
Both chemical irritation and mechanical compression affect radicular pain from disc herniation. However, relative effects of these insults on pain symptoms are unclear. This study investigated chemical and mechanical contributions for painful cervical nerve root injury. Accordingly, the C7 nerve root separately underwent chromic gut exposure, 10gf compression, or their combination. Mechanical allodynia was assessed, and glial reactivity in the C7 spinal cord tissue was assayed at days 1 and 7 by immunohistochemistry using GFAP and OX-42 as markers of astrocytes and microglia, respectively. Both chromic gut irritation and 10gf compression produced ipsilateral increases in allodynia over sham (p<0.048); combining the two insults significantly (p<0.027) increased ipsilateral allodynia compared to either insult alone. Behavioral hypersensitivity was also produced in the contralateral forepaw for all injuries, but only the combined insult was significantly increased over sham (p<0.031). Astrocytic activation was significantly increased over normal (p<0.001) in the ipsilateral dorsal horn at 1 day after either compression or the combined injury. By day 7, GFAP-reactivity was further increased for the combined injury compared to day 1 (p<0.001). In contrast, spinal OX-42 staining was generally variable, with only mild activation at day 1. By day 7 after the combined injury, there were significant (p<0.003) bilateral increases in OX-42 staining over normal. Spinal astrocytic and microglial reactivity follow different patterns after chemical root irritation, compression, and a combined insult. The combination of transient compression and chemical irritation produces sustained bilateral hypersensitivity, sustained ipsilateral spinal astrocytic activation and late onset bilateral spinal microglial activation.
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Affiliation(s)
- Sarah M. Rothman
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Beth A. Winkelstein
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA 19104, USA
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192
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Inoue K, Koizumi S, Tsuda M. The role of nucleotides in the neuron--glia communication responsible for the brain functions. J Neurochem 2007; 102:1447-1458. [PMID: 17697046 DOI: 10.1111/j.1471-4159.2007.04824.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Accumulating findings indicate that nucleotides play an important role in cell-to-cell communication through P2 purinoceptors, even though ATP is recognized primarily to be a source of free energy and nucleotides are key molecules in cells. P2 purinoceptors are divided into two families, ionotropic receptors (P2X) and metabotropic receptors (P2Y). P2X receptors (7 types; P2X(1)-P2X(7)) contain intrinsic pores that open by binding with ATP. P2Y (8 types; P2Y(1, 2, 4, 6, 11, 12, 13,) and (14)) are activated by nucleotides and couple to intracellular second-messenger systems through heteromeric G-proteins. Nucleotides are released or leaked from non-excitable cells as well as neurons in physiological and pathophysiological conditions. One of the most exciting cells in non-excitable cells is the glia cells, which are classified into astrocytes, oligodendrocytes, and microglia. Astrocytes express many types of P2 purinoceptors and release the 'gliotransmitter' ATP to communicate with neurons, microglia and the vascular walls of capillaries. Microglia also express many types of P2 purinoceptors and are known as resident macrophages in the CNS. ATP and other nucleotides work as 'warning molecules' especially through activating microglia in pathophysiological conditions. Microglia play a key role in neuropathic pain and show phagocytosis through nucleotide-evoked activation of P2X(4) and P2Y(6) receptors, respectively. Such strong molecular, cellular and system-level evidence for extracellular nucleotide signaling places nucleotides in the central stage of cell communications in glia/CNS.
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Affiliation(s)
- Kazuhide Inoue
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Maidashi, Higashi, Fukuoka, JapanDepartment of Pharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Shimokato, Chuo, Yamanashi, Japan
| | - Schuichi Koizumi
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Maidashi, Higashi, Fukuoka, JapanDepartment of Pharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Shimokato, Chuo, Yamanashi, Japan
| | - Makoto Tsuda
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Maidashi, Higashi, Fukuoka, JapanDepartment of Pharmacology, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Shimokato, Chuo, Yamanashi, Japan
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193
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Abstract
Management of chronic pain is a real challenge, and current treatments that focus on blocking neurotransmission in the pain pathway have resulted in limited success. Activation of glial cells has been widely implicated in neuroinflammation in the CNS, leading to neurodegeneration in conditions such as Alzheimer's disease and multiple sclerosis. The inflammatory mediators released by activated glial cells, such as tumor necrosis factor-a and interleukin-1b not only cause neurodegeneration in these disease conditions, but also cause abnormal pain by acting on spinal cord dorsal horn neurons in injury conditions. Pain can also be potentiated by growth factors such as brain-derived growth factor and basic fibroblast growth factor, which are produced by glia to protect neurons. Thus, glial cells can powerfully control pain when they are activated to produce various pain mediators. We review accumulating evidence that supports an important role for microglial cells in the spinal cord for pain control under injury conditions (e.g. nerve injury). We also discuss possible signaling mechanisms, in particular mitogen-activated protein kinase pathways that are crucial for glial-mediated control of pain.Investigating signaling mechanisms in microglia might lead to more effective management of devastating chronic pain.
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Affiliation(s)
- Marc R Suter
- Pain Research Center, Department of Anesthesiology, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Yeong-Ray Wen
- Department of Anesthesiology, Shin-Kong Wu Ho-Su Memorial Hospital, Taipei, Taiwan
| | - Isabelle Decosterd
- Anesthesiology Pain Research Group, Anesthesiology Department, University Hospital Center and University of Lausanne CH-1011 Lausanne, Switzerland
- Department of Cell Biology and Morphology, University of Lausanne, CH-1005 Lausanne, Switzerland
| | - Ru-Rong Ji
- Pain Research Center, Department of Anesthesiology, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts 02115
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194
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Tawfik VL, Nutile-McMenemy N, LaCroix-Fralish ML, DeLeo JA. Reprint of "efficacy of propentofylline, a glial modulating agent, on existing mechanical allodynia following peripheral nerve injury" [Brain Behav. Immun. 21 (2007) 238-246]. Brain Behav Immun 2007; 21:677-85. [PMID: 17544848 DOI: 10.1016/s0889-1591(07)00095-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 07/06/2006] [Accepted: 07/07/2006] [Indexed: 10/23/2022] Open
Abstract
Increasing evidence points to a role for spinal neuroimmune dysregulation (glial cell activation and cytokine expression) in the pathogenesis of chronic pain. Suppression of astrocytic and microglial activation with the methylxanthine derivative, propentofylline, pre-emptively attenuates the development of nerve injury-induced allodynia. Currently, we investigated the ability of systemic propentofylline to reverse existing, long-term allodynia after nerve injury-a clinically relevant paradigm. Rats received L5 spinal nerve transection or sham surgery and the development of mechanical allodynia was assessed daily for 2 weeks, at which time injured rats exhibited robust responses to non-noxious von Frey filaments. On days 14-27, rats received either saline or 101 mg/kg propentofylline by intraperitoneal (i.p.) injection. On day 28 or 42 (after a 14-day drug washout period), lumbar spinal cord sections were processed for assessment of astrocytic glial fibrillary acidic protein (GFAP) and microglial OX-42 (antibody against CR3/CD11b). Propentofylline treatment to nerve injured rats resulted in significant reversal of allodynia that lasted throughout the 14-day washout period. Spinal microglial activation was observed at days 28 and 42 post-injury at the protein level, in the absence of mRNA level changes. Less robust increases in GFAP immunoreactivity were observed at days 28 and 42 post-transection. Interestingly, propentofylline treatment suppressed microglial activation at both time points in this paradigm. Taken together, our results highlight the clinical potential of the glial modulating agent, propentofylline, for the treatment of neuropathic pain as well as a role for microglia in the long-term maintenance of allodynia.
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Affiliation(s)
- Vivianne L Tawfik
- Department of Pharmacology, Dartmouth Medical School, Hanover, NH 03755, USA
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195
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Clark AK, Yip PK, Grist J, Gentry C, Staniland AA, Marchand F, Dehvari M, Wotherspoon G, Winter J, Ullah J, Bevan S, Malcangio M. Inhibition of spinal microglial cathepsin S for the reversal of neuropathic pain. Proc Natl Acad Sci U S A 2007; 104:10655-60. [PMID: 17551020 PMCID: PMC1965568 DOI: 10.1073/pnas.0610811104] [Citation(s) in RCA: 365] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2006] [Indexed: 02/06/2023] Open
Abstract
A recent major conceptual advance has been the recognition of the importance of immune system-neuronal interactions in the modulation of brain function, one example of which is spinal pain processing in neuropathic states. Here, we report that in peripheral nerve-injured rats, the lysosomal cysteine protease cathepsin S (CatS) is critical for the maintenance of neuropathic pain and spinal microglia activation. After injury, CatS was exclusively expressed by activated microglia in the ipsilateral dorsal horn, where expression peaked at day 7, remaining high on day 14. Intrathecal delivery of an irreversible CatS inhibitor, morpholinurea-leucine-homophenylalanine-vinyl phenyl sulfone (LHVS), was antihyperalgesic and antiallodynic in neuropathic rats and attenuated spinal microglia activation. Consistent with a pronociceptive role of endogenous CatS, spinal intrathecal delivery of rat recombinant CatS (rrCatS) induced hyperalgesia and allodynia in naïve rats and activated p38 mitogen-activated protein kinase (MAPK) in spinal cord microglia. A bioinformatics approach revealed that the transmembrane chemokine fractalkine (FKN) is a potential substrate for CatS cleavage. We show that rrCatS incubation reduced the levels of cell-associated FKN in cultured sensory neurons and that a neutralizing antibody against FKN prevented both FKN- and CatS-induced allodynia, hyperalgesia, and p38 MAPK activation. Furthermore, rrCatS induced allodynia in wild-type but not CX3CR1-knockout mice. We suggest that under conditions of increased nociception, microglial CatS is responsible for the liberation of neuronal FKN, which stimulates p38 MAPK phosphorylation in microglia, thereby activating neurons via the release of pronociceptive mediators.
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Affiliation(s)
- Anna K. Clark
- *Novartis Institutes for Biomedical Research, 5 Gower Place, London WC1E 6BS, United Kingdom; and
- Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
| | - Ping K. Yip
- Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
| | - John Grist
- Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
| | - Clive Gentry
- *Novartis Institutes for Biomedical Research, 5 Gower Place, London WC1E 6BS, United Kingdom; and
| | - Amelia A. Staniland
- Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
| | - Fabien Marchand
- Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
| | - Maliheh Dehvari
- Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
| | - Glen Wotherspoon
- *Novartis Institutes for Biomedical Research, 5 Gower Place, London WC1E 6BS, United Kingdom; and
| | - Janet Winter
- *Novartis Institutes for Biomedical Research, 5 Gower Place, London WC1E 6BS, United Kingdom; and
| | - Jakir Ullah
- *Novartis Institutes for Biomedical Research, 5 Gower Place, London WC1E 6BS, United Kingdom; and
| | - Stuart Bevan
- *Novartis Institutes for Biomedical Research, 5 Gower Place, London WC1E 6BS, United Kingdom; and
| | - Marzia Malcangio
- *Novartis Institutes for Biomedical Research, 5 Gower Place, London WC1E 6BS, United Kingdom; and
- Wolfson Centre for Age Related Diseases, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
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196
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Nakagawa T, Wakamatsu K, Zhang N, Maeda S, Minami M, Satoh M, Kaneko S. Intrathecal administration of ATP produces long-lasting allodynia in rats: differential mechanisms in the phase of the induction and maintenance. Neuroscience 2007; 147:445-55. [PMID: 17543465 DOI: 10.1016/j.neuroscience.2007.03.045] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 03/22/2007] [Accepted: 03/23/2007] [Indexed: 01/18/2023]
Abstract
Several lines of evidence suggest that extracellular ATP plays a role in pain signaling through the activation of ionotropic P2X-receptors, especially homomeric P2X3- and heteromeric P2X2/3-receptors on capsaicin-sensitive and -insensitive primary afferent neurons, respectively, at peripheral and spinal sites. We investigated the mechanisms of the induction and maintenance of mechanical allodynia produced by a single intrathecal (i.t.) administration of ATP in rats. We found that i.t. administration of ATP and the P2X-receptor agonist alpha,beta-methylene-ATP produced tactile allodynia which lasted more than 1 week. The i.t. ATP- and alpha,beta-methylene-ATP-produced long-lasting allodynia remained in neonatal capsaicin-treated adult rats. I.t. administration of a P2X3/P2X2/3-receptor selective antagonist completely prevented the induction (co-administration on day 0) and partially attenuated the early phase (day 1 post-ATP administration), but not the late phase (day 7 post-ATP administration) of maintenance of allodynia. The N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 completely prevented the induction phase, but not the early and late phases of maintenance of allodynia. Immunohistochemical and immunoblotting studies for microglial and astrocytic markers revealed that i.t. ATP administration caused spinal microglial activation within 1 day, and astrocytic activation which peaked at 1-3 days after ATP administration. Furthermore, minocycline, a microglial inhibitor, attenuated the induction but not the early and late phases of maintenance, while fluorocitrate, a glial metabolic inhibitor, attenuated the induction and the early phase but not the late phase of maintenance. Taken together, these results suggest that the activation of P2X-receptors, most likely spinal P2X2/3-receptors on capsaicin-insensitive primary afferent neurons, triggers the induction of long-lasting allodynia through NMDA receptors, and the induction and early maintenance phase, but not the late phase, is mediated through the functions of spinal glial cells.
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Affiliation(s)
- T Nakagawa
- Department of Molecular Pharmacology, Graduate School of Pharmaceutical Sciences, Kyoto University, Kyoto 606-8501, Japan.
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197
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Blackbeard J, O'Dea KP, Wallace VCJ, Segerdahl A, Pheby T, Takata M, Field MJ, Rice ASC. Quantification of the rat spinal microglial response to peripheral nerve injury as revealed by immunohistochemical image analysis and flow cytometry. J Neurosci Methods 2007; 164:207-17. [PMID: 17553569 PMCID: PMC2726922 DOI: 10.1016/j.jneumeth.2007.04.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 04/17/2007] [Accepted: 04/22/2007] [Indexed: 12/29/2022]
Abstract
Microgliosis is implicated in the pathophysiology of several neurological disorders, including neuropathic pain. Consequently, perturbation of microgliosis is a mechanistic and drug development target in neuropathic pain, which highlights the requirement for specific, sensitive and reproducible methods of microgliosis measurement. In this study, we used the spinal microgliosis associated with L5 spinal nerve transection and minocycline-induced attenuation thereof to: (1) evaluate novel software based semi-quantitative image analysis paradigms for the assessment of immunohistochemical images. Microgliosis was revealed by immunoreactivity to OX42. Several image analysis paradigms were assessed and compared to a previously validated subjective categorical rating scale. This comparison revealed that grey scale measurement of the proportion of a defined area of spinal cord occupied by OX42 immunoreactive cells is a robust image analysis paradigm. (2) Develop and validate a flow cytometric approach for quantification of spinal microgliosis. The flow cytometric technique reliably quantified microgliosis in spinal cord cell suspensions, using OX42 and ED9 immunoreactivity to identify microglia. The results suggest that image analysis of immunohistochemical revelation of microgliosis reliably detects the spinal microgliosis in response to peripheral nerve injury and pharmacological attenuation thereof. In addition, flow cytometry provides an alternative approach for quantitative analysis of spinal microgliosis elicited by nerve injury.
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Affiliation(s)
- J Blackbeard
- Department of Anaesthetics, Pain Medicine and Intensive Care, Faculty of Medicine, Imperial College London, Chelsea and Westminster Hospital Campus, 369 Fulham Road, London SW10 9NH, UK.
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198
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Brett K, Parker R, Wittenauer S, Hayashida KI, Young T, Vincler M. Impact of chronic nicotine on sciatic nerve injury in the rat. J Neuroimmunol 2007; 186:37-44. [PMID: 17382409 PMCID: PMC1948068 DOI: 10.1016/j.jneuroim.2007.02.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 02/19/2007] [Accepted: 02/20/2007] [Indexed: 01/29/2023]
Abstract
Chronic nicotine exposure and the immune response to peripheral nerve injury has not been investigated thoroughly. Rats were exposed to chronic nicotine or saline followed by chronic constriction injury (CCI) of the sciatic nerve. Mechanical sensitivity was measured at various time points and the immune response was investigated at 21 days post-CCI. Chronic nicotine increased mechanical hypersensitivity, microglia activation, and the production of IL-1beta, but not the number of immune cells at the site of injury. These results suggest that chronic nicotine increases mechanical hypersensitivity following peripheral nerve injury through a mechanism that may involve an increased production and release of central and peripheral cytokines.
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Affiliation(s)
- Kyle Brett
- Department of Anesthesiology, and Center for the Study of Pharmacological Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Renée Parker
- Department of Anesthesiology, and Center for the Study of Pharmacological Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Shannon Wittenauer
- Department of Anesthesiology, and Center for the Study of Pharmacological Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Ken-ichiro Hayashida
- Department of Anesthesiology, and Center for the Study of Pharmacological Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Tracey Young
- Department of Anesthesiology, and Center for the Study of Pharmacological Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
| | - Michelle Vincler
- Department of Anesthesiology, and Center for the Study of Pharmacological Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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199
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Steffens H, Schomburg ED, Maznychenko AV, Maisky VA, Kostyukov AI, Pilyavskii AI. Monosynaptic reflexes, c-fos expression, and NADPH-diaphorase activity in the cat spinal cord: Changes induced by chronic muscle inflammation. NEUROPHYSIOLOGY+ 2007. [DOI: 10.1007/s11062-007-0026-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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200
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Tawfik VL, Nutile-McMenemy N, Lacroix-Fralish ML, Deleo JA. Efficacy of propentofylline, a glial modulating agent, on existing mechanical allodynia following peripheral nerve injury. Brain Behav Immun 2007; 21:238-46. [PMID: 16949251 DOI: 10.1016/j.bbi.2006.07.001] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 07/06/2006] [Accepted: 07/07/2006] [Indexed: 10/24/2022] Open
Abstract
Increasing evidence points to a role for spinal neuroimmune dysregulation (glial cell activation and cytokine expression) in the pathogenesis of chronic pain. Suppression of astrocytic and microglial activation with the methylxanthine derivative, propentofylline, pre-emptively attenuates the development of nerve injury-induced allodynia. Currently, we investigated the ability of systemic propentofylline to reverse existing, long-term allodynia after nerve injury--a clinically relevant paradigm. Rats received L5 spinal nerve transection or sham surgery and the development of mechanical allodynia was assessed daily for 2 weeks, at which time injured rats exhibited robust responses to non-noxious von Frey filaments. On days 14-27, rats received either saline or 101 mg/kg propentofylline by intraperitoneal (i.p.) injection. On day 28 or 42 (after a 14-day drug washout period), lumbar spinal cord sections were processed for assessment of astrocytic glial fibrillary acidic protein (GFAP) and microglial OX-42 (antibody against CR3/CD11b). Propentofylline treatment to nerve injured rats resulted in significant reversal of allodynia that lasted throughout the 14-day washout period. Spinal microglial activation was observed at days 28 and 42 post-injury at the protein level, in the absence of mRNA level changes. Less robust increases in GFAP immunoreactivity were observed at days 28 and 42 post-transection. Interestingly, propentofylline treatment suppressed microglial activation at both time points in this paradigm. Taken together, our results highlight the clinical potential of the glial modulating agent, propentofylline, for the treatment of neuropathic pain as well as a role for microglia in the long-term maintenance of allodynia.
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Affiliation(s)
- Vivianne L Tawfik
- Department of Pharmacology, Dartmouth Medical School, Hanover, NH 03755, USA
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