101
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The pathophysiological role of astrocytic endothelin-1. Prog Neurobiol 2016; 144:88-102. [DOI: 10.1016/j.pneurobio.2016.04.009] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Revised: 03/23/2016] [Accepted: 04/25/2016] [Indexed: 12/13/2022]
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103
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Kay CWP, Ursu D, Sher E, King AE. The role of Cx36 and Cx43 in 4-aminopyridine-induced rhythmic activity in the spinal nociceptive dorsal horn: an electrophysiological study in vitro. Physiol Rep 2016; 4:e12852. [PMID: 27462070 PMCID: PMC4962069 DOI: 10.14814/phy2.12852] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 06/10/2016] [Accepted: 06/13/2016] [Indexed: 01/09/2023] Open
Abstract
Connexin (Cx) proteins and gap junctions support the formation of neuronal and glial syncytia that are linked to different forms of rhythmic firing and oscillatory activity in the CNS. In this study, quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to profile developmental expression of two specific Cx proteins, namely glial Cx43 and neuronal Cx36, in postnatal lumbar spinal cord aged 4, 7, and 14 days. Extracellular electrophysiology was used to determine the contribution of Cx36 and Cx43 to a previously described form of 4-aminopyridine (4-AP)-induced 4-12 Hz rhythmic activity within substantia gelatinosa (SG) of rat neonatal dorsal horn (DH) in vitro. The involvement of Cx36 and Cx43 was probed pharmacologically using quinine, a specific uncoupler of Cx36 and the mimetic peptide blocker Gap 26 which targets Cx43. After establishment of 4-12 Hz rhythmic activity by 4-AP (25 μmol/L), coapplication of quinine (250 μmol/L) reduced 4-AP-induced 4-12 Hz rhythmic activity (P < 0.05). Preincubation of spinal cord slices with Gap 26 (100 μmol/L), compromised the level of 4-AP-induced 4-12 Hz rhythmic activity in comparison with control slices preincubated in ACSF alone (P < 0.05). Conversely, the nonselective gap junction "opener" trimethylamine (TMA) enhanced 4-12 Hz rhythmic behavior (P < 0.05), further supporting a role for Cx proteins and gap junctions. These data have defined a physiological role for Cx36 and Cx43 in rhythmic firing in SG, a key nociceptive processing area of DH. The significance of these data in the context of pain and Cx proteins as a future analgesic drug target requires further study.
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Affiliation(s)
- Christopher W P Kay
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - Daniel Ursu
- Eli Lilly & Co., Lilly Research Centre Erl Wood Manor, Windlesham, Surrey, GU20 6PH, United Kingdom
| | - Emanuele Sher
- Eli Lilly & Co., Lilly Research Centre Erl Wood Manor, Windlesham, Surrey, GU20 6PH, United Kingdom
| | - Anne E King
- School of Biomedical Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom
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104
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Taves S, Berta T, Liu DL, Gan S, Chen G, Kim YH, Van de Ven T, Laufer S, Ji RR. Spinal inhibition of p38 MAP kinase reduces inflammatory and neuropathic pain in male but not female mice: Sex-dependent microglial signaling in the spinal cord. Brain Behav Immun 2016; 55:70-81. [PMID: 26472019 PMCID: PMC5502100 DOI: 10.1016/j.bbi.2015.10.006] [Citation(s) in RCA: 213] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Revised: 10/04/2015] [Accepted: 10/10/2015] [Indexed: 12/23/2022] Open
Abstract
Previous studies have shown that activation of p38 mitogen-activating kinase (MAPK) in spinal microglia participates in the generation of inflammatory and neuropathic pain in various rodent models. However, these studies focused on male mice to avoid confounding effects of the estrous cycle of females. Recent studies have shown that some spinal pro-inflammatory signaling such as Toll-like receptor 4-mediated signaling contributes to pain hypersensitivity only in male mice. In this study we investigated the distinct role of spinal p38 in inflammatory and neuropathic pain using a highly selective p38 inhibitor skepinone. Intrathecal injection of skepinone prevented formalin induced inflammatory pain in male but not female mice. Furthermore, intrathecal skepinone reduced chronic constriction injury (CCI) induced neuropathic pain (mechanical allodynia) in male mice on CCI-day 7 but not CCI-day 21. This male-dependent inhibition of neuropathic pain also occurred in rats following intrathecal skepinone. Nerve injury induced spinal p38 activation (phosphorylation) in CX3CR1-GFP(+) microglia on CCI-day 7, and this activation was more prominent in male mice. In contrast, CCI induced comparable microgliosis and expression of the microglial markers CX3CR1 and IBA-1 in both sexes. Notably, intraperitoneal or local perineural administration of skepinone inhibited CCI-induced mechanical allodynia in both sexes of mice. Finally, skepinone only reduced the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) in lamina IIo neurons of spinal cord slices of males 7days post CCI. Therefore, the sex-specific p38 activation and signaling is confined to the spinal cord in inflammatory and neuropathic pain conditions.
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Affiliation(s)
- Sarah Taves
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA; Department of Neurobiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA.
| | - Temugin Berta
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA
| | - Da-Lu Liu
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA
| | - Sophie Gan
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA
| | - Gang Chen
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA
| | - Yong Ho Kim
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA
| | - Thomas Van de Ven
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA
| | - Stefan Laufer
- Departments Pharmacy and Biochemistry, University of Tuebingen, Auf der Morgenstelle 8, 72076 Tuebingen, Germany
| | - Ru-Rong Ji
- Department of Anesthesiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA; Department of Neurobiology, Duke University Medical Center, 595 LaSalle Street, Durham, NC 27710, USA.
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105
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Neumann E, Brandenburger T, Santana-Varela S, Deenen R, Köhrer K, Bauer I, Hermanns H, Wood JN, Zhao J, Werdehausen R. MicroRNA-1-associated effects of neuron-specific brain-derived neurotrophic factor gene deletion in dorsal root ganglia. Mol Cell Neurosci 2016; 75:36-43. [PMID: 27346077 DOI: 10.1016/j.mcn.2016.06.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 06/08/2016] [Accepted: 06/20/2016] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND MicroRNAs (miRNAs) regulate gene expression in physiological as well as in pathological processes, including chronic pain. Whether deletion of a gene can affect expression of the miRNAs that associate with the deleted gene mRNA remains elusive. We investigated the effects of brain-derived neurotrophic factor (Bdnf) gene deletion on the expression of miR-1 in dorsal root ganglion (DRG) neurons and its pain-associated downstream targets heat shock protein 60 (Hsp60) and connexin 43 (Cx43) in tamoxifen-inducible conditional knockout mice, Bdnf(fl/fl); Advillin-CreER(T2) (Bdnf cKO). RESULTS Efficient Bdnf gene deletion was confirmed in DRG of Bdnf cKO mice by Real-Time qRT-PCR and ELISA 10days after completed tamoxifen treatment. In DRG, miR-1 expression was reduced 0.44-fold (p<0.05; Real-time qRT-PCR) in Bdnf cKO compared to floxed wildtype littermate control Bdnf(fl/fl) mice (WT). While Hsp60 protein expression was increased 1.85-fold (p<0.05; Western blot analysis), expression levels of Cx43 and the miR-1-associated transcription factors MEF2a and SRF remained unchanged. When analyzing Bdnf cKO mice 32days after complete tamoxifen treatment to investigate whether observed expression alterations remain permanently, we found no significant differences between Bdnf cKO and WT mice. However, miRNA microarray analysis revealed that 167 miRNAs altered (p<0.05) in DRG of these mice following Bdnf gene deletion. CONCLUSIONS Our results indicate that deletion of Bdnf in DRG neurons leads to a temporary dysregulation of miR-1, suggesting an impairment of a presumable feedback loop between BDNF protein and its targeting miR-1. This appears to affect its downstream protein Hsp60 and as a consequence might influence the phenotype after inducible Bdnf gene deletion. While this appears to be a MEF2a-/SRF-independent and transient effect, expression levels of various other miRNAs may remain permanently altered.
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Affiliation(s)
- Elena Neumann
- Department of Anesthesiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Moorenstr. 5, Düsseldorf 40225, Germany.
| | - Timo Brandenburger
- Department of Anesthesiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Moorenstr. 5, Düsseldorf 40225, Germany.
| | - Sonia Santana-Varela
- Molecular Nociception Group, Wolfson Institute for Biomedical Research (WIBR), Cruciform Building, University College London (UCL), London WC1E 6BT, UK.
| | - René Deenen
- Biological and Medical Research Center (BMFZ), Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, Düsseldorf 40225, Germany.
| | - Karl Köhrer
- Biological and Medical Research Center (BMFZ), Medical Faculty, Heinrich-Heine-University Düsseldorf, Universitätsstrasse 1, Düsseldorf 40225, Germany.
| | - Inge Bauer
- Department of Anesthesiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Moorenstr. 5, Düsseldorf 40225, Germany.
| | - Henning Hermanns
- Department of Anesthesiology, Academic Medical Center, Meibergdreef 9, Amsterdam 1100 DD, The Netherlands.
| | - John N Wood
- Molecular Nociception Group, Wolfson Institute for Biomedical Research (WIBR), Cruciform Building, University College London (UCL), London WC1E 6BT, UK.
| | - Jing Zhao
- Molecular Nociception Group, Wolfson Institute for Biomedical Research (WIBR), Cruciform Building, University College London (UCL), London WC1E 6BT, UK.
| | - Robert Werdehausen
- Department of Anesthesiology, Medical Faculty, Heinrich-Heine-University Düsseldorf, Moorenstr. 5, Düsseldorf 40225, Germany.
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Connexin 50 modulates Sox2 expression in spinal-cord-derived ependymal stem/progenitor cells. Cell Tissue Res 2016; 365:295-307. [PMID: 27221278 DOI: 10.1007/s00441-016-2421-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 05/01/2016] [Indexed: 12/23/2022]
Abstract
Ion channels included in the family of Connexins (Cx) have been reported to influence the secondary expansion of traumatic spinal cord injury (SCI) and neuropathic pain following SCI. However, Cxs also contribute to spinal cord neurogenesis during the remyelinating process and functional recovery after SCI. Certain Cxs have been recently related to the control of cell proliferation and the differentiation of neuronal progenitors. Adult spinal-cord-derived ependymal stem progenitor cells (epSPC) show high expression levels of Cx50 in non-pathological conditions and lower expression when they actively proliferate after injury (epSPCi). We explore the role of Cx50 in the ependymal population in the modulation of Sox2, a crucial factor of neural progenitor self-renewal and a promising target for promoting neuronal-cell-fate induction for neuronal tissue repair. Short-interfering-RNA ablation or over-expression of Cx50 regulates the expression of Sox2 in both epSPC and epSPCi. Interestingly, Cx50 and Sox2 co-localize at the nucleus indicating a potential role for this ion channel beyond cell-to-cell communication in the spinal cord. In vivo and in vitro experiments with Clotrimazole, a specific pharmacological modulator of Cx50, show the convergent higher expression of Cx50 and Sox2 in the isolated epSPC/epSPCi and in spinal cord tissue. Therefore, the pharmacological modulation of Cx50 might constitute an interesting mechanism for Sox2 induction to modulate the endogenous regenerative potential of neuronal tissue with a potential application in regenerative therapies.
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107
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Almad AA, Doreswamy A, Gross SK, Richard JP, Huo Y, Haughey N, Maragakis NJ. Connexin 43 in astrocytes contributes to motor neuron toxicity in amyotrophic lateral sclerosis. Glia 2016; 64:1154-69. [PMID: 27083773 DOI: 10.1002/glia.22989] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 03/09/2016] [Accepted: 03/30/2016] [Indexed: 11/09/2022]
Abstract
Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of motor neurons in the CNS. Astrocytes play a critical role in disease progression of ALS. Astrocytes are interconnected through a family of gap junction proteins known as connexins (Cx). Cx43 is a major astrocyte connexin conducting crucial homeostatic functions in the CNS. Under pathological conditions, connexin expression and functions are altered. Here we report that an abnormal increase in Cx43 expression serves as one of the mechanisms for astrocyte-mediated toxicity in ALS. We observed a progressive increase in Cx43 expression in the SOD1(G93A) mouse model of ALS during the disease course. Notably, this increase in Cx43 was also detected in the motor cortex and spinal cord of ALS patients. Astrocytes isolated from SOD1(G93A) mice as well as human induced pluripotent stem cell (iPSC)-derived astrocytes showed an increase in Cx43 protein, which was found to be an endogenous phenomenon independent of neuronal co-culture. Increased Cx43 expression led to important functional consequences when tested in SOD1(G93A) astrocytes when compared to control astrocytes over-expressing wild-type SOD1 (SOD1(WT) ). We observed SOD1(G93A) astrocytes exhibited enhanced gap junction coupling, increased hemichannel-mediated activity, and elevated intracellular calcium levels. Finally, we tested the impact of increased expression of Cx43 on MN survival and observed that use of both a pan Cx43 blocker and Cx43 hemichannel blocker conferred neuroprotection to MNs cultured with SOD1(G93A) astrocytes. These novel findings show a previously unrecognized role of Cx43 in ALS-related motor neuron loss. GLIA 2016;64:1154-1169.
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Affiliation(s)
- Akshata A Almad
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland
| | - Arpitha Doreswamy
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland
| | - Sarah K Gross
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland
| | - Jean-Philippe Richard
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland
| | - Yuqing Huo
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland
| | - Norman Haughey
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland
| | - Nicholas J Maragakis
- Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, Maryland
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108
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Lavrov I, Fox L, Shen J, Han Y, Cheng J. Gap Junctions Contribute to the Regulation of Walking-Like Activity in the Adult Mudpuppy (Necturus Maculatus). PLoS One 2016; 11:e0152650. [PMID: 27023006 PMCID: PMC4811563 DOI: 10.1371/journal.pone.0152650] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2015] [Accepted: 03/17/2016] [Indexed: 12/03/2022] Open
Abstract
Although gap junctions are widely expressed in the developing central nervous system, the role of electrical coupling of neurons and glial cells via gap junctions in the spinal cord in adults is largely unknown. We investigated whether gap junctions are expressed in the mature spinal cord of the mudpuppy and tested the effects of applying gap junction blocker on the walking-like activity induced by NMDA or glutamate in an in vitro mudpuppy preparation. We found that glial and neural cells in the mudpuppy spinal cord expressed different types of connexins that include connexin 32 (Cx32), connexin 36 (Cx36), connexin 37 (Cx37), and connexin 43 (Cx43). Application of a battery of gap junction blockers from three different structural classes (carbenexolone, flufenamic acid, and long chain alcohols) substantially and consistently altered the locomotor-like activity in a dose-dependent manner. In contrast, these blockers did not significantly change the amplitude of the dorsal root reflex, indicating that gap junction blockers did not inhibit neuronal excitability nonselectively in the spinal cord. Taken together, these results suggest that gap junctions play a significant modulatory role in the spinal neural networks responsible for the generation of walking-like activity in the adult mudpuppy.
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Affiliation(s)
- Igor Lavrov
- Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, Russia
| | - Lyle Fox
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jun Shen
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Yingchun Han
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
| | - Jianguo Cheng
- Departments of Pain Management and Neurosciences, Anesthesiology Institute, Cleveland Clinic, Cleveland, Ohio, United States of America
- * E-mail:
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109
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Kaji K, Shinoda M, Honda K, Unno S, Shimizu N, Iwata K. Connexin 43 contributes to ectopic orofacial pain following inferior alveolar nerve injury. Mol Pain 2016; 12:12/0/1744806916633704. [PMID: 27030716 PMCID: PMC4955997 DOI: 10.1177/1744806916633704] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2015] [Accepted: 12/29/2015] [Indexed: 12/22/2022] Open
Abstract
Background Clinically, it is well known that injury of mandibular nerve fiber induces persistent ectopic pain which can spread to a wide area of the orofacial region innervated by the uninjured trigeminal nerve branches. However, the exact mechanism of such persistent ectopic orofacial pain is not still known. The present study was undertaken to determine the role of connexin 43 in the trigeminal ganglion on mechanical hypersensitivity in rat whisker pad skin induced by inferior alveolar nerve injury. Here, we examined changes in orofacial mechanical sensitivity following inferior alveolar nerve injury. Furthermore, changes in connexin 43 expression in the trigeminal ganglion and its localization in the trigeminal ganglion were also examined. In addition, we investigated the functional significance of connexin 43 in relation to mechanical allodynia by using a selective gap junction blocker (Gap27). Results Long-lasting mechanical allodynia in the whisker pad skin and the upper eyelid skin, and activation of satellite glial cells in the trigeminal ganglion, were induced after inferior alveolar nerve injury. Connexin 43 was expressed in the activated satellite glial cells encircling trigeminal ganglion neurons innervating the whisker pad skin, and the connexin 43 protein expression was significantly increased after inferior alveolar nerve injury. Administration of Gap27 in the trigeminal ganglion significantly reduced satellite glial cell activation and mechanical hypersensitivity in the whisker pad skin. Moreover, the marked activation of satellite glial cells encircling trigeminal ganglion neurons innervating the whisker pad skin following inferior alveolar nerve injury implies that the satellite glial cell activation exerts a major influence on the excitability of nociceptive trigeminal ganglion neurons. Conclusions These findings indicate that the propagation of satellite glial cell activation throughout the trigeminal ganglion via gap junctions, which are composed of connexin 43, plays a pivotal role in ectopic mechanical hypersensitivity in whisker pad skin following inferior alveolar nerve injury.
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Affiliation(s)
- Kaori Kaji
- Department of Orthodontics, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
| | - Masamichi Shinoda
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
| | - Kuniya Honda
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
| | - Syumpei Unno
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
| | - Noriyoshi Shimizu
- Department of Orthodontics, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
| | - Koichi Iwata
- Department of Physiology, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan
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110
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Analysis of the behavioral, cellular and molecular characteristics of pain in severe rodent spinal cord injury. Exp Neurol 2016; 278:91-104. [PMID: 26808661 DOI: 10.1016/j.expneurol.2016.01.009] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2015] [Revised: 01/07/2016] [Accepted: 01/12/2016] [Indexed: 12/31/2022]
Abstract
Human SCI is frequently associated with chronic pain that is severe and refractory to medical therapy. Most rodent models used to assess pain outcomes in SCI apply moderate injuries to lower thoracic spinal levels, whereas the majority of human lesions are severe in degree and occur at cervical or upper thoracic levels. To better model and understand mechanisms associated with chronic pain after SCI, we subjected adult rats to T3 severe compression or complete transection lesions, and examined pain-related behaviors for three months. Within one week after injury, rats developed consistent forepaw pain-related behaviors including increased spontaneous lifts, tactile allodynia and cold sensitivity that persisted for three months. Place escape avoidance testing confirmed that withdrawal of the forepaws from a von Frey stimulus represented active pain-related aversion. Spontaneous and evoked pain-related measures were attenuated by gabapentin, further indicating that these behaviors reflect development of pain. Spinal level of injury was relevant: rats with T11 severe SCI did not exhibit forepaw pain-related behaviors. Immunoblotting and immunofluorescence of C6-C8 spinal dorsal horn, reflecting sensory innervation of the forepaw, revealed: 1) expansion of CGRP immunoreactivity in lamina I/II; 2) increased GAP-43 expression; and 3) increased IBA1, GFAP and connexin-43 expression. These findings indicate that aberrant pain fiber sprouting and gliopathy occur after severe SCI. Notably, satellite glial cells (SGCs) in C6-C8 DRGs exhibited increases in GFAP and connexin-43, suggesting ongoing peripheral sensitization. Carbenoxolone, a gap junction inhibitor, and specific peptide inhibitors of connexin-43, ameliorated established tactile allodynia after severe SCI. Collectively, severe T3 SCI successfully models persistent pain states and could constitute a useful model system for examining candidate translational pain therapies after SCI.
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111
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Chen ZY, Shen FY, Jiang L, Zhao X, Shen XL, Zhong W, Liu S, Wang ZR, Wang YW. Attenuation of Neuropathic Pain by Inhibiting Electrical Synapses in the Anterior Cingulate Cortex. Anesthesiology 2016; 124:169-83. [PMID: 26566282 DOI: 10.1097/aln.0000000000000942] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
BACKGROUND Synaptic mechanisms and neuronal oscillations have been proposed to be responsible for neuropathic pain formation. Many studies have also highlighted the important role of electrical synapses in synaptic plasticity and in neuronal oscillations. Thus, electrical synapses may contribute to neuropathic pain generation. However, previous studies have primarily focused on the role of chemical synapses, while ignoring the role of electrical synapses, in neuropathic pain generation. METHODS The authors adopted microinjection, RNA interference techniques, and behavioral tests to verify the link between connexin 36 (Cx36) and neuropathic pain. They also studied the selective Cx36 blocker mefloquine in rat chronic constriction injury and spared nerve injury model of neuropathic pain. Electrophysiologic recordings were used to further confirm the behavioral data. RESULTS The authors found that Cx36, which constitutes the neuron-neuron electrical synapses, was up-regulated in the anterior cingulate cortex after nerve injury (n = 5). Meanwhile, Cx36-mediated neuronal oscillations in the gamma frequency range (30 to 80 Hz) (n = 7 to 8) and the neuronal synaptic transmission (n = 13 to 19) were also enhanced. Neuropathic pain was relieved by disrupting Cx36 function or expression in the anterior cingulate cortex. They also found that mefloquine, which are clinically used for treating malaria, affected gamma oscillations and synaptic plasticity, leading to a sustained pain relief in chronic constriction injury and spared nerve injury models (n = 7 to 12). CONCLUSION The electrical synapses blocker mefloquine could affect gamma oscillations and synaptic plasticity in the anterior cingulate cortex and relieve neuropathic pain. Cx36 may be a new therapeutic target for treating chronic pain.
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Affiliation(s)
- Zhi-Yu Chen
- From the Department of Anesthesiology and Intensive Care Medicine, Xinhua Hospital, College of Medicine, Shanghai Jiaotong University, Shanghai, China (Z.-Y.C., F.-Y.S., L.J., X.Z., X.-L.S., Y.-W.W.); and Laboratory of Neural Circuit Plasticity & Memory, Institute of Brain Functional Genomics, East China Normal University, Shanghai, China (W.Z., S.L., Z.-R.W.)
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Block L. Glial dysfunction and persistent neuropathic postsurgical pain. Scand J Pain 2016; 10:74-81. [PMID: 28361776 DOI: 10.1016/j.sjpain.2015.10.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 10/10/2015] [Accepted: 10/13/2015] [Indexed: 12/30/2022]
Abstract
BACKGROUND Acute pain in response to injury is an important mechanism that serves to protect living beings from harm. However, persistent pain remaining long after the injury has healed serves no useful purpose and is a disabling condition. Persistent postsurgical pain, which is pain that lasts more than 3 months after surgery, affects 10-50% of patients undergoing elective surgery. Many of these patients are affected by neuropathic pain which is characterised as a pain caused by lesion or disease in the somatosensory nervous system. When established, this type of pain is difficult to treat and new approaches for prevention and treatment are needed. A possible contributing mechanism for the transition from acute physiological pain to persistent pain involves low-grade inflammation in the central nervous system (CNS), glial dysfunction and subsequently an imbalance in the neuron-glial interaction that causes enhanced and prolonged pain transmission. AIM This topical review aims to highlight the contribution that inflammatory activated glial cell dysfunction may have for the development of persistent pain. METHOD Relevant literature was searched for in PubMed. RESULTS Immediately after an injury to a nerve ending in the periphery such as in surgery, the inflammatory cascade is activated and immunocompetent cells migrate to the site of injury. Macrophages infiltrate the injured nerve and cause an inflammatory reaction in the nerve cell. This reaction leads to microglia activation in the central nervous system and the release of pro-inflammatory cytokines that activate and alter astrocyte function. Once the astrocytes and microglia have become activated, they participate in the development, spread, and potentiation of low-grade neuroinflammation. The inflammatory activated glial cells exhibit cellular changes, and their communication to each other and to neurons is altered. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocyte dysfunction can be experimentally restored using the combined actions of a μ-opioid receptor agonist, a μ-opioid receptor antagonist, and an anti-epileptic agent. To find these agents we searched the literature for substances with possible anti-inflammatory properties that are usually used for other purposes in medicine. Inflammatory induced glial cell dysfunction is restorable in vitro by a combination of endomorphine-1, ultralow doses of naloxone and levetiracetam. Restoring inflammatory-activated glial cells, thereby restoring astrocyte-neuron interaction has the potential to affect pain transmission in neurons. CONCLUSION Surgery causes inflammation at the site of injury. Peripheral nerve injury can cause low-grade inflammation in the CNS known as neuroinflammation. Low-grade neuroinflammation can cause an imbalance in the glial-neuron interaction and communication. This renders neurons more excitable and pain transmission is enhanced and prolonged. Astrocytic dysfunction can be restored in vitro by a combination of endomorphin-1, ultralow doses of naloxone and levetiracetam. This restoration is essential for the interaction between astrocytes and neurons and hence also for modulation of synaptic pain transmission. IMPLICATIONS Larger studies in clinical settings are needed before these findings can be applied in a clinical context. Potentially, by targeting inflammatory activated glial cells and not only neurons, a new arena for development of pharmacological agents for persistent pain is opened.
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Affiliation(s)
- Linda Block
- Institute of Clinical Sciences at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
- Department of Anesthesiology and Intensive Care, Sahlgrenska University Hospital, Gothenburg, Sweden
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113
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Connexin 43 Mediates CXCL12 Production from Spinal Dorsal Horn to Maintain Bone Cancer Pain in Rats. Neurochem Res 2015; 41:1200-8. [DOI: 10.1007/s11064-015-1815-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 12/11/2015] [Accepted: 12/21/2015] [Indexed: 01/28/2023]
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Quesseveur G, Portal B, Basile JA, Ezan P, Mathou A, Halley H, Leloup C, Fioramonti X, Déglon N, Giaume C, Rampon C, Guiard BP. Attenuated Levels of Hippocampal Connexin 43 and its Phosphorylation Correlate with Antidepressant- and Anxiolytic-Like Activities in Mice. Front Cell Neurosci 2015; 9:490. [PMID: 26733815 PMCID: PMC4686612 DOI: 10.3389/fncel.2015.00490] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 12/03/2015] [Indexed: 11/13/2022] Open
Abstract
Clinical and preclinical studies have implicated glial anomalies in major depression. Conversely, evidence suggests that the activity of antidepressant drugs is based, at least in part, on their ability to stimulate density and/or activity of astrocytes, a major glial cell population. Despite this recent evidence, little is known about the mechanism(s) by which astrocytes regulate emotionality. Glial cells communicate with each other through gap junction channels (GJCs), while they can also directly interact with neurons by releasing gliotransmitters in the extracellular compartment via an hemichannels (HCs)-dependent process. Both GJCs and HCs are formed by two main protein subunits: connexins (Cx) 30 and 43 (Cx30 and Cx43). Here we investigate the role of hippocampal Cx43 in the regulation of depression-like symptoms using genetic and pharmacological approaches. The first aim of this study was to evaluate the impact of the constitutive knock-down of Cx43 on a set of behaviors known to be affected in depression. Conversely, the expression of Cx43 was assessed in the hippocampus of mice subjected to prolonged corticosterone (CORT) exposure, given either alone or in combination with an antidepressant drug, the selective serotonin reuptake inhibitor fluoxetine. Our results indicate that the constitutive deficiency of Cx43 resulted in the expression of some characteristic hallmarks of antidepressant-/anxiolytic-like behavioral activities along with an improvement of cognitive performances. Moreover, in a new cohort of wild-type mice, we showed that CORT exposure elicited anxiety and depression-like abnormalities that were reversed by chronic administration of fluoxetine. Remarkably, CORT also increased hippocampal amounts of phosphorylated form of Cx43 whereas fluoxetine treatment normalized this parameter. From these results, we envision that antidepressant drugs may exert their therapeutic activity by decreasing the expression and/or activity of Cx43 resulting from a lower level of phosphorylation in the hippocampus.
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Affiliation(s)
- Gaël Quesseveur
- Institut National de la Santé et de la Recherche Médicale UMR-S 1178 - Dépression, Plasticité and Résistance Aux Antidépresseurs, Laboratoire de Neuropharmacologie EA 3544, Faculté de Pharmacie, Université Paris-Sud Châtenay-Malabry, France
| | - Benjamin Portal
- Centre National de la Recherche Scientifique, Centre de Recherches sur la Cognition Animale UMR 5169, Centre de Biologie Intégrative, Université Toulouse III- Paul Sabatier Toulouse, France
| | - Jean-Arnaud Basile
- Centre National de la Recherche Scientifique, Centre de Recherches sur la Cognition Animale UMR 5169, Centre de Biologie Intégrative, Université Toulouse III- Paul Sabatier Toulouse, France
| | - Pascal Ezan
- Center for Interdisciplinary Research in Biology, Centre National de la Recherche Scientifique UMR 7241, Collège de France Paris, France
| | - Alexia Mathou
- Centre des Sciences du Goût et de l'Alimentation - Centre National de la Recherche Scientifique UMR 6265 - Institut National de la Recherche Agronomique UMR 1324, Université de Bourgogne Dijon, France
| | - Hélène Halley
- Centre National de la Recherche Scientifique, Centre de Recherches sur la Cognition Animale UMR 5169, Centre de Biologie Intégrative, Université Toulouse III- Paul Sabatier Toulouse, France
| | - Corinne Leloup
- Centre des Sciences du Goût et de l'Alimentation - Centre National de la Recherche Scientifique UMR 6265 - Institut National de la Recherche Agronomique UMR 1324, Université de Bourgogne Dijon, France
| | - Xavier Fioramonti
- Centre des Sciences du Goût et de l'Alimentation - Centre National de la Recherche Scientifique UMR 6265 - Institut National de la Recherche Agronomique UMR 1324, Université de Bourgogne Dijon, France
| | - Nicole Déglon
- Laboratory of Cellular and Molecular Neurotherapies, Department of Clinical Neurosciences, Centre Hospitalier Universitaire Vaudois Lausanne, Switzerland
| | - Christian Giaume
- Center for Interdisciplinary Research in Biology, Centre National de la Recherche Scientifique UMR 7241, Collège de France Paris, France
| | - Claire Rampon
- Centre National de la Recherche Scientifique, Centre de Recherches sur la Cognition Animale UMR 5169, Centre de Biologie Intégrative, Université Toulouse III- Paul Sabatier Toulouse, France
| | - Bruno P Guiard
- Institut National de la Santé et de la Recherche Médicale UMR-S 1178 - Dépression, Plasticité and Résistance Aux Antidépresseurs, Laboratoire de Neuropharmacologie EA 3544, Faculté de Pharmacie, Université Paris-SudChâtenay-Malabry, France; Centre National de la Recherche Scientifique, Centre de Recherches sur la Cognition Animale UMR 5169, Centre de Biologie Intégrative, Université Toulouse III- Paul SabatierToulouse, France
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115
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Jeon YH, Youn DH. Spinal Gap Junction Channels in Neuropathic Pain. Korean J Pain 2015; 28:231-5. [PMID: 26495077 PMCID: PMC4610936 DOI: 10.3344/kjp.2015.28.4.231] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 06/17/2015] [Accepted: 06/25/2015] [Indexed: 11/26/2022] Open
Abstract
Damage to peripheral nerves or the spinal cord is often accompanied by neuropathic pain, which is a complex, chronic pain state. Increasing evidence indicates that alterations in the expression and activity of gap junction channels in the spinal cord are involved in the development of neuropathic pain. Thus, this review briefly summarizes evidence that regulation of the expression, coupling, and activity of spinal gap junction channels modulates pain signals in neuropathic pain states induced by peripheral nerve or spinal cord injury. We particularly focus on connexin 43 and pannexin 1 because their regulation vastly attenuates symptoms of neuropathic pain. We hope that the study of gap junction channels eventually leads to the development of a suitable treatment tool for patients with neuropathic pain.
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Affiliation(s)
- Young Hoon Jeon
- Department of Anesthesiology and Pain Medicine, School of Dentistry, Kyungpook National University, Daegu, Korea
| | - Dong Ho Youn
- Department of Oral Physiology, School of Dentistry, Kyungpook National University, Daegu, Korea
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Brown IA, McClain JL, Watson RE, Patel BA, Gulbransen BD. Enteric glia mediate neuron death in colitis through purinergic pathways that require connexin-43 and nitric oxide. Cell Mol Gastroenterol Hepatol 2015; 2:77-91. [PMID: 26771001 PMCID: PMC4707972 DOI: 10.1016/j.jcmgh.2015.08.007] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND AND AIMS The concept of enteric glia as regulators of intestinal homeostasis is slowly gaining acceptance as a central concept in neurogastroenterology. Yet how glia contribute to intestinal disease is still poorly understood. Purines generated during inflammation drive enteric neuron death by activating neuronal P2X7 purine receptors (P2X7R), triggering ATP release via neuronal pannexin-1 channels that subsequently recruits intracellular calcium ([Ca2+]i) responses in the surrounding enteric glia. We tested the hypothesis that the activation of enteric glia contributes to neuron death during inflammation. METHODS We studied neuroinflammation in vivo using the 2,4-dinitrobenzenesulfonic acid model of colitis and in situ using whole-mount preparations of human and mouse intestine. Transgenic mice with a targeted deletion of glial connexin-43 (Cx43) [GFAP∷CreERT2+/-/Cx43f/f ] were used to specifically disrupt glial signaling pathways. Mice deficient in inducible nitric oxide (NO) synthase (iNOS-/-) were used to study NO production. Protein expression and oxidative stress were measured using immunohistochemistry and in situ Ca2+ and NO imaging were used to monitor glial [Ca2+]i and [NO]i. RESULTS Purinergic activation of enteric glia drove [Ca2+]i responses and enteric neuron death through a Cx43-dependent mechanism. Neurotoxic Cx43 activity, driven by NO production from glial iNOS, was required for neuron death. Glial Cx43 opening liberated ATP and Cx43-dependent ATP release was potentiated by NO. CONCLUSIONS Our results show that the activation of glial cells in the context of neuroinflammation kills enteric neurons. Mediators of inflammation that include ATP and NO activate neurotoxic pathways that converge on glial Cx43 hemichannels. The glial response to inflammatory mediators might contribute to the development of motility disorders.
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Affiliation(s)
- Isola A.M. Brown
- Department of Physiology, Michigan State University, East Lansing, Michigan
- Pharmacology and Toxicology Program, Michigan State University, East Lansing, Michigan
| | | | - Ralph E. Watson
- Department of Medicine, Michigan State University, East Lansing, Michigan
| | - Bhavik A. Patel
- School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, United Kingdom
| | - Brian D. Gulbransen
- Department of Physiology, Michigan State University, East Lansing, Michigan
- Neuroscience Program, Michigan State University, East Lansing, Michigan
- Correspondence Address correspondence to: Brian D. Gulbransen, PhD, Department of Physiology, Michigan State University, 567 Wilson Road, East Lansing, Michigan 48824. fax: (517) 355-5125.Department of PhysiologyMichigan State University567 Wilson RoadEast LansingMichigan 48824
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117
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Do stars govern our actions? Astrocyte involvement in rodent behavior. Trends Neurosci 2015; 38:535-49. [DOI: 10.1016/j.tins.2015.07.006] [Citation(s) in RCA: 123] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Revised: 07/24/2015] [Accepted: 07/28/2015] [Indexed: 12/20/2022]
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Abstract
Neuroglia, the "glue" that fills the space between neurons in the central nervous system, takes active part in nerve cell signaling. Neuroglial cells, astroglia, oligodendroglia, and microglia, are together about as numerous as neurons in the brain as a whole, and in the cerebral cortex grey matter, but the proportion varies widely among brain regions. Glial volume, however, is less than one-fifth of the tissue volume in grey matter. When stimulated by neurons or other cells, neuroglial cells release gliotransmitters by exocytosis, similar to neurotransmitter release from nerve endings, or by carrier-mediated transport or channel flux through the plasma membrane. Gliotransmitters include the common neurotransmitters glutamate and GABA, the nonstandard amino acid d-serine, the high-energy phosphate ATP, and l-lactate. The latter molecule is a "buffer" between glycolytic and oxidative metabolism as well as a signaling substance recently shown to act on specific lactate receptors in the brain. Complementing neurotransmission at a synapse, neuroglial transmission often implies diffusion of the transmitter over a longer distance and concurs with the concept of volume transmission. Transmission from glia modulates synaptic neurotransmission based on energetic and other local conditions in a volume of tissue surrounding the individual synapse. Neuroglial transmission appears to contribute significantly to brain functions such as memory, as well as to prevalent neuropathologies.
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Affiliation(s)
- Vidar Gundersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Jon Storm-Mathisen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
| | - Linda Hildegard Bergersen
- SN-Lab, Division of Anatomy, Department of Molecular Medicine, Institute of Basic Medical Sciences, and CMBN/SERTA/Healthy Brain Ageing Centre, University of Oslo, Oslo, Norway; Department of Neurology, Oslo University Hospital-Rikshospitalet, Oslo, Norway; Center for Healthy Aging, Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark; and Brain and Muscle Energy Group, Department of Oral Biology and Division of Anatomy, Department of Molecular Medicine, University of Oslo, Oslo, Norway
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Hansson E, Skiöldebrand E. Coupled cell networks are target cells of inflammation, which can spread between different body organs and develop into systemic chronic inflammation. JOURNAL OF INFLAMMATION-LONDON 2015. [PMID: 26213498 PMCID: PMC4514450 DOI: 10.1186/s12950-015-0091-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Several organs in the body comprise cells coupled into networks. These cells have in common that they are excitable but do not express action potentials. Furthermore, they are equipped with Ca2+ signaling systems, which can be intercellular and/or extracellular. The transport of small molecules between the cells occurs through gap junctions comprising connexin 43. Examples of cells coupled into networks include astrocytes, keratinocytes, chondrocytes, synovial fibroblasts, osteoblasts, connective tissue cells, cardiac and corneal fibroblasts, myofibroblasts, hepatocytes, and different types of glandular cells. These cells are targets for inflammation, which can be initiated after injury or in disease. If the inflammation reaches the CNS, it develops into neuroinflammation and can be of importance in the development of systemic chronic inflammation, which can manifest as pain and result in changes in the expression and structure of cellular components. Biochemical parameters of importance for cellular functions are described in this review.
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Affiliation(s)
- Elisabeth Hansson
- Department of Clinical Neuroscience and Rehabilitation, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Per Dubbsgatan 14, 1tr, , SE 413 45 Gothenburg, Sweden
| | - Eva Skiöldebrand
- Section of Pathology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Uppsala, Sweden ; Department of Clinical Chemistry and Transfusion Medicine, Institute of Biomedicine, Sahlgrenska University Hospital, Gothenburg University, Gothenburg, Sweden
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120
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Kékesi O, Ioja E, Szabó Z, Kardos J, Héja L. Recurrent seizure-like events are associated with coupled astroglial synchronization. Front Cell Neurosci 2015; 9:215. [PMID: 26150770 PMCID: PMC4471369 DOI: 10.3389/fncel.2015.00215] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 05/20/2015] [Indexed: 01/22/2023] Open
Abstract
Increasing evidence suggest that astrocytes significantly modulate neuronal function at the level of the tripartite synapse both in physiological and pathophysiological conditions. The global control of the astrocytic syncytium over neuronal networks, however, is still less recognized. Here we examined astrocytic signaling during epileptiform activity which is generally attributed to large-scale neuronal synchronization. We show that seizure-like events in the low-[Mg(2+)] in vitro epilepsy model initiate massive, long-range astrocytic synchronization which is spatiotemporally coupled to the synchronized neuronal activity reaching its maximum at the electrographic tonic/clonic transition. Cross-correlation analysis of neuronal and astrocytic Ca(2+) signaling demonstrates that high degree of synchronization arises not only among astrocytes, but also between neuronal and astrocyte populations, manifesting in astrocytic seizure-like events. We further show that astrocytic gap junction proteins contribute to astrocytic synchronization since their inhibition by carbenoxolone (CBX) or Cx43 antibody increased the interictal interval and in 41% of slices completely prevented recurrent seizure-like activity. In addition, CBX also induced unsynchronized Ca(2+) transients associated with decreasing incidence of epileptiform discharges afterwards. We propose therefore that local, unsynchronized astrocytic Ca(2+) transients inhibit, while long-range, synchronized Ca(2+) signaling contributes to the propagation of recurrent seizure-like events.
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Affiliation(s)
- Orsolya Kékesi
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - Enikö Ioja
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - Zsolt Szabó
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - Julianna Kardos
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
| | - László Héja
- Research Centre for Natural Sciences, Hungarian Academy of Sciences, Institute of Organic Chemistry, Functional Pharmacology Group Budapest, Hungary
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121
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Kulkarni PM, Barton E, Savelonas M, Padmanabhan R, Lu Y, Trett K, Shain W, Leasure JL, Roysam B. Quantitative 3-D analysis of GFAP labeled astrocytes from fluorescence confocal images. J Neurosci Methods 2015; 246:38-51. [DOI: 10.1016/j.jneumeth.2015.02.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2014] [Revised: 02/13/2015] [Accepted: 02/14/2015] [Indexed: 12/31/2022]
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122
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Liu WJ, Yang J. Preferentially regulated expression of connexin 43 in the developing spiral ganglion neurons and afferent terminals in post-natal rat cochlea. Eur J Histochem 2015; 59:2464. [PMID: 25820563 PMCID: PMC4378217 DOI: 10.4081/ejh.2015.2464] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 02/02/2015] [Accepted: 02/03/2015] [Indexed: 11/23/2022] Open
Abstract
The expression pattern of connexin 43 (Cx43) in the cochlea is not determined and is controversial. Since the presence of Cx43 is essential for hearing, we re-examined its distribution during post-natal development of rat cochlea. Cx43 protein was expressed in spiral ganglion neurons (SGNs) and their neurite terminals innervating the inner and outer hair cells (IHCs and OHCs) as early as birth (postnatal day 0, P0), and persisted until P14. Double immunofluorescence staining, using two antibodies against Cx43 and TUJ1, a marker for all SGNs and afferent terminals, showed that immunoreactivity for Cx43 and TUJ1 was perfectly colocalized in SGNs and afferent terminals associated with the IHCs and OHCs. However, beyond P14, Cx43 immunostaining could no longer be detected in the region of the synaptic terminals at the bases of IHCs and OHCs (P17, adult). In contrast, Cx43 maintained its expression in SGNs into adulthood. We further performed quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR) to identify the presence of Cx43 mRNA in the modiolus (mainly containing SGNs). Cx43 mRNA was higher at P8, compared with P1, and subsequently decreased at P14. These results indicated that Cx43 correlated with cochlear synaptogenesis and establishment of auditory neurotransmission.
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Affiliation(s)
- W J Liu
- Xinhua Hospital, Shanghai Jiaotong University, Shanghai Jiaotong University Ear Institute.
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123
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Tonkin RS, Mao Y, O'Carroll SJ, Nicholson LFB, Green CR, Gorrie CA, Moalem-Taylor G. Gap junction proteins and their role in spinal cord injury. Front Mol Neurosci 2015; 7:102. [PMID: 25610368 PMCID: PMC4285056 DOI: 10.3389/fnmol.2014.00102] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Accepted: 12/12/2014] [Indexed: 12/25/2022] Open
Abstract
Gap junctions are specialized intercellular communication channels that are formed by two hexameric connexin hemichannels, one provided by each of the two adjacent cells. Gap junctions and hemichannels play an important role in regulating cellular metabolism, signaling, and functions in both normal and pathological conditions. Following spinal cord injury (SCI), there is damage and disturbance to the neuronal elements of the spinal cord including severing of axon tracts and rapid cell death. The initial mechanical disruption is followed by multiple secondary cascades that cause further tissue loss and dysfunction. Recent studies have implicated connexin proteins as playing a critical role in the secondary phase of SCI by propagating death signals through extensive glial networks. In this review, we bring together past and current studies to outline the distribution, changes and roles of various connexins found in neurons and glial cells, before and in response to SCI. We discuss the contribution of pathologically activated connexin proteins, in particular connexin 43, to functional recovery and neuropathic pain, as well as providing an update on potential connexin specific pharmacological agents to treat SCI.
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Affiliation(s)
- Ryan S Tonkin
- School of Medical Sciences, Faculty of Medicine, University of New South Wales Sydney, NSW, Australia
| | - Yilin Mao
- School of Medical and Molecular Bioscience, Faculty of Science, University of Technology Sydney, NSW, Australia
| | - Simon J O'Carroll
- Department of Anatomy with Radiology and Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland Auckland, New Zealand
| | - Louise F B Nicholson
- Department of Anatomy with Radiology and Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland Auckland, New Zealand
| | - Colin R Green
- Department of Ophthalmology, Faculty of Medical and Health Sciences, University of Auckland Auckland, New Zealand
| | - Catherine A Gorrie
- School of Medical and Molecular Bioscience, Faculty of Science, University of Technology Sydney, NSW, Australia
| | - Gila Moalem-Taylor
- School of Medical Sciences, Faculty of Medicine, University of New South Wales Sydney, NSW, Australia
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124
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Liu TT, He ZG, Tian XB, Liu C, Xiang HB, Zhang JG. Hypothesis: Astrocytes in the central medial amygdala may be implicated in sudden unexpected death in epilepsy by melanocortinergic signaling. Epilepsy Behav 2015; 42:41-3. [PMID: 25499161 DOI: 10.1016/j.yebeh.2014.10.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 10/24/2014] [Indexed: 01/06/2023]
Affiliation(s)
- Tao-Tao Liu
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, People's Republic of China
| | - Zhi-Gang He
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, People's Republic of China
| | - Xue-Bi Tian
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, People's Republic of China
| | - Cheng Liu
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, People's Republic of China
| | - Hong-Bing Xiang
- Department of Anesthesiology and Pain Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, People's Republic of China.
| | - Jian-Guo Zhang
- Department of Functional Neurosurgery, Beijing Neurosurgical Institute, Capital Medical University, Beijing, People's Republic of China; Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University, Beijing 100050, People's Republic of China; Beijing Key Laboratory of Neurostimulation, Beijing 100050, China.
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125
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Robinson CR, Dougherty PM. Spinal astrocyte gap junction and glutamate transporter expression contributes to a rat model of bortezomib-induced peripheral neuropathy. Neuroscience 2014; 285:1-10. [PMID: 25446343 DOI: 10.1016/j.neuroscience.2014.11.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Revised: 11/04/2014] [Accepted: 11/05/2014] [Indexed: 01/01/2023]
Abstract
There is increasing evidence implicating astrocytes in multiple forms of chronic pain, as well as in the specific context of chemotherapy-induced peripheral neuropathy (CIPN). However, it is still unclear what the exact role of astrocytes may be in the context of CIPN. Findings in oxaliplatin and paclitaxel models have displayed altered expression of astrocytic gap junctions and glutamate transporters as means by which astrocytes may contribute to observed behavioral changes. The current study investigated whether these changes were also generalizable to the bortezomib CIPN. Changes in mechanical sensitivity were verified in bortezomib-treated animals, and these changes were prevented by co-treatment with a glial activation inhibitor (minocycline), a gap junction decoupler (carbenoxolone), and by a glutamate transporter upregulator (ceftriaxone). Immunohistochemistry data at day 30 in bortezomib-treated animals showed increases in expression of glial fibrillary acidic protein (GFAP) and connexin 43 but a decrease in GLAST expression. These changes were prevented by co-treatment with minocycline. Follow-up Western blotting data showed a shift in connexin 43 from a non-phosphorylated state to a phosphorylated state, indicating increased trafficking of expressed connexin 43 to the cell membrane. These data suggest that increases in behavioral sensitivity to cutaneous stimuli may be tied to persistent synaptic glutamate resulting from increased calcium flow between spinal astrocytes.
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Affiliation(s)
- C R Robinson
- The Department of Anesthesiology and Pain Medicine Research, The University of Texas M.D. Anderson Cancer Center, 1400 Holcombe, Unit 409, Houston, TX 77030, Unites States
| | - P M Dougherty
- The Department of Anesthesiology and Pain Medicine Research, The University of Texas M.D. Anderson Cancer Center, 1400 Holcombe, Unit 409, Houston, TX 77030, Unites States.
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Toll-like receptors 2, -3 and -4 prime microglia but not astrocytes across central nervous system regions for ATP-dependent interleukin-1β release. Sci Rep 2014; 4:6824. [PMID: 25351234 PMCID: PMC5381369 DOI: 10.1038/srep06824] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 09/09/2014] [Indexed: 12/13/2022] Open
Abstract
Interleukin-1β (IL-1β) is a crucial mediator in the pathogenesis of inflammatory diseases at the periphery and in the central nervous system (CNS). Produced as an unprocessed and inactive pro-form which accumulates intracellularly, release of the processed cytokine is strongly promoted by ATP acting at the purinergic P2X7 receptor (P2X7R) in cells primed with lipopolysaccharide (LPS), a Toll-like receptor (TLR) 4 ligand. Microglia are central to the inflammatory process and a major source of IL-1β when activated. Here we show that purified (>99%) microglia cultured from rat cortex, spinal cord and cerebellum respond robustly to ATP-dependent IL-1β release, upon priming with a number of TLR isoform ligands (zymosan and Pam3CSK4 for TLR2, poly(I:C) for TLR3). Cytokine release was prevented by a P2X7R antagonist and inhibitors of stress-activated protein kinases. Enriched astrocytes (≤5% microglia) from these CNS regions displayed responses qualitatively similar to microglia but became unresponsive upon eradication of residual microglia with the lysosomotropic agent Leu-Leu-OMe. Activation of multiple TLR isoforms in nervous system pathology, coupled with elevated extracellular ATP levels and subsequent P2X7R activation may represent an important route for microglia-derived IL-1β. This phenomenon may have important consequences for neuroinflammation and its position to the common pathology of CNS diseases.
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127
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DosSantos MF, Holanda-Afonso RC, Lima RL, DaSilva AF, Moura-Neto V. The role of the blood-brain barrier in the development and treatment of migraine and other pain disorders. Front Cell Neurosci 2014; 8:302. [PMID: 25339863 PMCID: PMC4189386 DOI: 10.3389/fncel.2014.00302] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 09/08/2014] [Indexed: 12/23/2022] Open
Abstract
The function of the blood-brain barrier (BBB) related to chronic pain has been explored for its classical role in regulating the transcellular and paracellular transport, thus controlling the flow of drugs that act at the central nervous system, such as opioid analgesics (e.g., morphine) and non-steroidal anti-inflammatory drugs. Nonetheless, recent studies have raised the possibility that changes in the BBB permeability might be associated with chronic pain. For instance, changes in the relative amounts of occludin isoforms, resulting in significant increases in the BBB permeability, have been demonstrated after inflammatory hyperalgesia. Furthermore, inflammatory pain produces structural changes in the P-glycoprotein, the major efflux transporter at the BBB. One possible explanation for these findings is the action of substances typically released at the site of peripheral injuries that could lead to changes in the brain endothelial permeability, including substance P, calcitonin gene-related peptide, and interleukin-1 beta. Interestingly, inflammatory pain also results in microglial activation, which potentiates the BBB damage. In fact, astrocytes and microglia play a critical role in maintaining the BBB integrity and the activation of those cells is considered a key mechanism underlying chronic pain. Despite the recent advances in the understanding of BBB function in pain development as well as its interference in the efficacy of analgesic drugs, there remain unknowns regarding the molecular mechanisms involved in this process. In this review, we explore the connection between the BBB as well as the blood-spinal cord barrier and blood-nerve barrier, and pain, focusing on cellular and molecular mechanisms of BBB permeabilization induced by inflammatory or neuropathic pain and migraine.
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Affiliation(s)
- Marcos F. DosSantos
- Universidade Federal do Rio de Janeiro – Campus MacaéRio de Janeiro, Brazil
- Laboratório de Morfogênese Celular, Instituto de Ciências Biomédicas, Universidade Federal do Rio de JaneiroRio de Janeiro, Brazil
- Headache and Orofacial Pain Effort, Department of Biologic and Materials Sciences and Michigan Center for Oral Health Research, School of Dentistry, University of MichiganAnn Arbor, MI, USA
| | - Rosenilde C. Holanda-Afonso
- Laboratório de Morfogênese Celular, Instituto de Ciências Biomédicas, Universidade Federal do Rio de JaneiroRio de Janeiro, Brazil
| | - Rodrigo L. Lima
- Departamento de Ortodontia e Odontopediatria, Faculdade de Odontologia, Universidade Federal do Rio de Janeiro, Rio de JaneiroBrazil
| | - Alexandre F. DaSilva
- Headache and Orofacial Pain Effort, Department of Biologic and Materials Sciences and Michigan Center for Oral Health Research, School of Dentistry, University of MichiganAnn Arbor, MI, USA
| | - Vivaldo Moura-Neto
- Laboratório de Morfogênese Celular, Instituto de Ciências Biomédicas, Universidade Federal do Rio de JaneiroRio de Janeiro, Brazil
- Instituto Estadual do Cérebro Paulo NiemeyerRio de Janeiro, Brazil
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128
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Walters ET. Neuroinflammatory contributions to pain after SCI: roles for central glial mechanisms and nociceptor-mediated host defense. Exp Neurol 2014; 258:48-61. [PMID: 25017887 DOI: 10.1016/j.expneurol.2014.02.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 01/23/2014] [Accepted: 02/02/2014] [Indexed: 12/30/2022]
Abstract
Neuropathic pain after spinal cord injury (SCI) is common, often intractable, and can be severely debilitating. A number of mechanisms have been proposed for this pain, which are discussed briefly, along with methods for revealing SCI pain in animal models, such as the recently applied conditioned place preference test. During the last decade, studies of animal models have shown that both central neuroinflammation and behavioral hypersensitivity (indirect reflex measures of pain) persist chronically after SCI. Interventions that reduce neuroinflammation have been found to ameliorate pain-related behavior, such as treatment with agents that inhibit the activation states of microglia and/or astroglia (including IL-10, minocycline, etanercept, propentofylline, ibudilast, licofelone, SP600125, carbenoxolone). Reversal of pain-related behavior has also been shown with disruption by an inhibitor (CR8) and/or genetic deletion of cell cycle-related proteins, deletion of a truncated receptor (trkB.T1) for brain-derived neurotrophic factor (BDNF), or reduction by antisense knockdown or an inhibitor (AMG9810) of the activity of channels (TRPV1 or Nav1.8) important for electrical activity in primary nociceptors. Nociceptor activity is known to drive central neuroinflammation in peripheral injury models, and nociceptors appear to be an integral component of host defense. Thus, emerging results suggest that spinal and systemic effects of SCI can activate nociceptor-mediated host defense responses that interact via neuroinflammatory signaling with complex central consequences of SCI to drive chronic pain. This broader view of SCI-induced neuroinflammation suggests new targets, and additional complications, for efforts to develop effective treatments for neuropathic SCI pain.
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Affiliation(s)
- Edgar T Walters
- Department of Integrative Biology and Pharmacology, University of Texas Medical School at Houston, TX, USA.
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129
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Actin filament reorganization in astrocyte networks is a key functional step in neuroinflammation resulting in persistent pain: novel findings on network restoration. Neurochem Res 2014; 40:372-9. [PMID: 24952067 DOI: 10.1007/s11064-014-1363-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 06/09/2014] [Accepted: 06/13/2014] [Indexed: 10/25/2022]
Abstract
In recent years, the importance of glial cell activation in the generation and maintenance of long-term pain has been investigated. One novel mechanism underlying long-lasting pain is injury-induced inflammation in the periphery, followed by microglial activation in the dorsal horn of the spinal cord, which results in local neuroinflammation. An increase in neuronal excitability may follow, with intense signaling along the pain tracts to the thalamus and the parietal cortex along with other cortical regions for the identification and recognition of the injury. If the local neuroinflammation develops into a pathological state, then the astrocytes become activated. Previous studies in which lipopolysaccharide (LPS) was used to induce inflammation have shown that in a dysfunctional astrocyte network, the actin cytoskeleton is reorganized from the normally occurring F-actin stress fibers into the more diffusible, disorganized, ring-form globular G-actin. In addition, Ca(2+) signaling systems are altered, Na(+)- and glutamate transporters are downregulated, and pro-inflammatory cytokines, particularly IL-1β, are released in dysfunctional astrocyte networks. In a series of experiments, we have demonstrated that these LPS-induced changes in astrocyte function can be restored by stimulation of Gi/o and inhibition of Gs with a combination of a μ-receptor agonist and ultralow concentrations of a μ-receptor antagonist and by inhibition of cytokine release, particularly IL-1β, by the antiepileptic drug levetiracetam. These findings could be of clinical significance and indicate a novel treatment for long-term pain.
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130
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Retamal MA, Alcayaga J, Verdugo CA, Bultynck G, Leybaert L, Sáez PJ, Fernández R, León LE, Sáez JC. Opening of pannexin- and connexin-based channels increases the excitability of nodose ganglion sensory neurons. Front Cell Neurosci 2014; 8:158. [PMID: 24999316 PMCID: PMC4064533 DOI: 10.3389/fncel.2014.00158] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Accepted: 05/19/2014] [Indexed: 11/23/2022] Open
Abstract
Satellite glial cells (SGCs) are the main glia in sensory ganglia. They surround neuronal bodies and form a cap that prevents the formation of chemical or electrical synapses between neighboring neurons. SGCs have been suggested to establish bidirectional paracrine communication with sensory neurons. However, the molecular mechanism involved in this cellular communication is unknown. In the central nervous system (CNS), astrocytes present connexin43 (Cx43) hemichannels and pannexin1 (Panx1) channels, and the opening of these channels allows the release of signal molecules, such as ATP and glutamate. We propose that these channels could play a role in glia-neuron communication in sensory ganglia. Therefore, we studied the expression and function of Cx43 and Panx1 in rat and mouse nodose-petrosal-jugular complexes (NPJcs) using confocal immunofluorescence, molecular and electrophysiological techniques. Cx43 and Panx1 were detected in SGCs and in sensory neurons, respectively. In the rat and mouse, the electrical activity of vagal nerve increased significantly after nodose neurons were exposed to a Ca2+/Mg2+-free solution, a condition that increases the open probability of Cx hemichannels. This response was partially mimicked by a cell-permeable peptide corresponding to the last 10 amino acids of Cx43 (TAT-Cx43CT). Enhanced neuronal activity was reduced by Cx hemichannel, Panx1 channel and P2X7 receptor blockers. Moreover, the role of Panx1 was confirmed in NPJc, because in those from Panx1 knockout mice showed a reduced increase of neuronal activity induced by Ca2+/Mg2+-free extracellular conditions. The data suggest that Cx hemichannels and Panx channels serve as paracrine communication pathways between SGCs and neurons by modulating the excitability of sensory neurons.
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Affiliation(s)
- Mauricio A Retamal
- Facultad de Medicina, Centro de Fisiología Celular e Integrativa, Clínica Alemana Universidad del Desarrollo Santiago, Chile ; Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Julio Alcayaga
- Laboratorio de Fisiología Celular, Departamento de Biología, Facultad de Ciencias, Universidad de Chile Santiago, Chile
| | - Christian A Verdugo
- Facultad de Medicina, Centro de Fisiología Celular e Integrativa, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Geert Bultynck
- KU Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine Leuven, Belgium
| | - Luc Leybaert
- Physiology Group, Department of Basic Medical Sciences, Faculty of Medicine and Health Sciences, Ghent University Ghent, Belgium
| | - Pablo J Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Ricardo Fernández
- Facultad de Ciencias Biológicas y Facultad de Medicina, Universidad Andrés Bello Santiago, Chile
| | - Luis E León
- Facultad de Medicina, Centro de Genética Humana, Clínica Alemana Universidad del Desarrollo Santiago, Chile
| | - Juan C Sáez
- Departamento de Fisiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile Santiago, Chile ; Centro Interdisciplinario de Neurociencias de Valparaíso, Instituto Milenio Valparaíso, Chile
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131
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Abstract
Current analgesics predominately modulate pain transduction and transmission in neurons and have limited success in controlling disease progression. Accumulating evidence suggests that neuroinflammation, which is characterized by infiltration of immune cells, activation of glial cells and production of inflammatory mediators in the peripheral and central nervous system, has an important role in the induction and maintenance of chronic pain. This Review focuses on emerging targets - such as chemokines, proteases and the WNT pathway - that promote spinal cord neuroinflammation and chronic pain. It also highlights the anti-inflammatory and pro-resolution lipid mediators that act on immune cells, glial cells and neurons to resolve neuroinflammation, synaptic plasticity and pain. Targeting excessive neuroinflammation could offer new therapeutic opportunities for chronic pain and related neurological and psychiatric disorders.
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132
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Orellana JA, Stehberg J. Hemichannels: new roles in astroglial function. Front Physiol 2014; 5:193. [PMID: 24987373 PMCID: PMC4060415 DOI: 10.3389/fphys.2014.00193] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Accepted: 05/07/2014] [Indexed: 01/16/2023] Open
Abstract
The role of astrocytes in brain function has evolved over the last decade, from support cells to active participants in the neuronal synapse through the release of "gliotransmitters."Astrocytes express receptors for most neurotransmitters and respond to them through Ca(2+) intracellular oscillations and propagation of intercellular Ca(2+) waves. While such waves are able to propagate among neighboring astrocytes through gap junctions, thereby activating several astrocytes simultaneously, they can also trigger the release of gliotransmitters, including glutamate, d-serine, glycine, ATP, adenosine, or GABA. There are several mechanisms by which gliotransmitter release occurs, including functional hemichannels. These gliotransmitters can activate neighboring astrocytes and participate in the propagation of intercellular Ca(2+) waves, or activate pre- and post-synaptic receptors, including NMDA, AMPA, and purinergic receptors. In consequence, hemichannels could play a pivotal role in astrocyte-to-astrocyte communication and astrocyte-to-neuron cross-talk. Recent evidence suggests that astroglial hemichannels are involved in higher brain functions including memory and glucose sensing. The present review will focus on the role of hemichannels in astrocyte-to-astrocyte and astrocyte-to neuron communication and in brain physiology.
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Affiliation(s)
- Juan A Orellana
- Departamento de Neurología, Escuela de Medicina, Pontificia Universidad Católica de Chile Santiago, Chile
| | - Jimmy Stehberg
- Laboratorio de Neurobiología, Centro de Investigaciones Médicas, Facultad de Ciencias Biológicas and Facultad de Medicina, Universidad Andrés Bello Santiago, Chile
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Chen G, Park CK, Xie RG, Berta T, Nedergaard M, Ji RR. Connexin-43 induces chemokine release from spinal cord astrocytes to maintain late-phase neuropathic pain in mice. ACTA ACUST UNITED AC 2014; 137:2193-209. [PMID: 24919967 DOI: 10.1093/brain/awu140] [Citation(s) in RCA: 212] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Accumulating evidence suggests that spinal cord astrocytes play an important role in neuropathic pain sensitization by releasing astrocytic mediators (e.g. cytokines, chemokines and growth factors). However, it remains unclear how astrocytes control the release of astrocytic mediators and sustain late-phase neuropathic pain. Astrocytic connexin-43 (now known as GJ1) has been implicated in gap junction and hemichannel communication of cytosolic contents through the glial syncytia and to the extracellular space, respectively. Connexin-43 also plays an essential role in facilitating the development of neuropathic pain, yet the mechanism for this contribution remains unknown. In this study, we investigated whether nerve injury could upregulate connexin-43 to sustain late-phase neuropathic pain by releasing chemokine from spinal astrocytes. Chronic constriction injury elicited a persistent upregulation of connexin-43 in spinal astrocytes for >3 weeks. Spinal (intrathecal) injection of carbenoxolone (a non-selective hemichannel blocker) and selective connexin-43 blockers (connexin-43 mimetic peptides (43)Gap26 and (37,43)Gap27), as well as astroglial toxin but not microglial inhibitors, given 3 weeks after nerve injury, effectively reduced mechanical allodynia, a cardinal feature of late-phase neuropathic pain. In cultured astrocytes, TNF-α elicited marked release of the chemokine CXCL1, and the release was blocked by carbenoxolone, Gap26/Gap27, and connexin-43 small interfering RNA. TNF-α also increased connexin-43 expression and hemichannel activity, but not gap junction communication in astrocyte cultures prepared from cortices and spinal cords. Spinal injection of TNF-α-activated astrocytes was sufficient to induce persistent mechanical allodynia, and this allodynia was suppressed by CXCL1 neutralization, CXCL1 receptor (CXCR2) antagonist, and pretreatment of astrocytes with connexin-43 small interfering RNA. Furthermore, nerve injury persistently increased excitatory synaptic transmission (spontaneous excitatory postsynaptic currents) in spinal lamina IIo nociceptive synapses in the late phase, and this increase was suppressed by carbenoxolone and Gap27, and recapitulated by CXCL1. Together, our findings demonstrate a novel mechanism of astrocytic connexin-43 to enhance spinal cord synaptic transmission and maintain neuropathic pain in the late-phase via releasing chemokines.
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Affiliation(s)
- Gang Chen
- 1 Departments of Anaesthesiology and Neurobiology, Duke University Medical Centre, Durham, NC, 27710, USA
| | - Chul-Kyu Park
- 1 Departments of Anaesthesiology and Neurobiology, Duke University Medical Centre, Durham, NC, 27710, USA
| | - Rou-Gang Xie
- 1 Departments of Anaesthesiology and Neurobiology, Duke University Medical Centre, Durham, NC, 27710, USA
| | - Temugin Berta
- 1 Departments of Anaesthesiology and Neurobiology, Duke University Medical Centre, Durham, NC, 27710, USA
| | - Maiken Nedergaard
- 2 Centre for Translational Neuromedicine, University of Rochester Medical Centre, Rochester, NY, 14642, USA
| | - Ru-Rong Ji
- 1 Departments of Anaesthesiology and Neurobiology, Duke University Medical Centre, Durham, NC, 27710, USA
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134
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Xu Q, Cheong YK, He SQ, Tiwari V, Liu J, Wang Y, Raja SN, Li J, Guan Y, Li W. Suppression of spinal connexin 43 expression attenuates mechanical hypersensitivity in rats after an L5 spinal nerve injury. Neurosci Lett 2014; 566:194-199. [PMID: 24631560 PMCID: PMC4007756 DOI: 10.1016/j.neulet.2014.03.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 02/27/2014] [Accepted: 03/01/2014] [Indexed: 02/07/2023]
Abstract
Activation of spinal astrocytes may contribute to neuropathic pain. Adjacent astrocytes can make direct communication through gap junctions formed by connexin 43 (Cx43) in the central nervous system. Yet, the role of spinal astroglial gap junctions in neuropathic pain is not fully understood. Since Cx43 is the connexin isoform expressed preferentially in astrocytes in the spinal cord, we used a small interfering RNA (siRNA) approach to examine whether suppression of spinal Cx43 expression inhibits mechanical hypersensitivity in rats after an L5 spinal nerve ligation (SNL). SNL rats were administered intrathecal Cx43 siRNA (3μg/15μl, twice/day) or an equal amount of mismatch siRNA (control) on days 14-17 post-SNL. Cx43 siRNA, but not mismatch siRNA, alleviated mechanical hypersensitivity in SNL rats. Furthermore, Western blot analysis showed that the pain inhibition induced by Cx43 siRNA correlated with downregulation of Cx43 expression, but not that of Cx36 (the neuronal gap junction protein) or glial fibrillary acidic protein (GFAP, a marker for reactive astrocytes) in the spinal cord of SNL rats. Western blot analysis and immunohistochemistry also showed that SNL increased GFAP expression, but decreased Cx43 expression, in spinal cord. Our results provide direct evidence that selective suppression of spinal Cx43 after nerve injury alleviates neuropathic mechanical hypersensitivity. These findings suggest that in the spinal cord, the enhanced function of astroglial gap junctions, especially those formed by Cx43, may be important to neuropathic pain in SNL rats.
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Affiliation(s)
- Qian Xu
- Department of Clinical Pharmacology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, Jiangsu, China
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA
| | - Yong-Kwan Cheong
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA
- Department of Anesthesiology and Pain Medicine, School of Medicine, Wonkwang University, Iksan, Korea
| | - Shao-Qiu He
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA
| | - Vinod Tiwari
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA
| | - Jian Liu
- Department of Anesthesiology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, Jiangsu, China
| | - Yun Wang
- Department of Anesthesiology, Beijing Chaoyang Hospital, Capital Medical University, Beijing 100020, China
| | - Srinivasa N. Raja
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA
| | - Jinheng Li
- Department of Clinical Pharmacology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, Jiangsu, China
| | - Yun Guan
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, School of Medicine, Baltimore, Maryland, USA
| | - Weiyan Li
- Department of Anesthesiology, Jinling Hospital, School of Medicine, Nanjing University, Nanjing, Jiangsu, China
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135
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De Bock M, Decrock E, Wang N, Bol M, Vinken M, Bultynck G, Leybaert L. The dual face of connexin-based astroglial Ca(2+) communication: a key player in brain physiology and a prime target in pathology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2211-32. [PMID: 24768716 DOI: 10.1016/j.bbamcr.2014.04.016] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 12/21/2022]
Abstract
For decades, studies have been focusing on the neuronal abnormalities that accompany neurodegenerative disorders. Yet, glial cells are emerging as important players in numerous neurological diseases. Astrocytes, the main type of glia in the central nervous system , form extensive networks that physically and functionally connect neuronal synapses with cerebral blood vessels. Normal brain functioning strictly depends on highly specialized cellular cross-talk between these different partners to which Ca(2+), as a signaling ion, largely contributes. Altered intracellular Ca(2+) levels are associated with neurodegenerative disorders and play a crucial role in the glial responses to injury. Intracellular Ca(2+) increases in single astrocytes can be propagated toward neighboring cells as intercellular Ca(2+) waves, thereby recruiting a larger group of cells. Intercellular Ca(2+) wave propagation depends on two, parallel, connexin (Cx) channel-based mechanisms: i) the diffusion of inositol 1,4,5-trisphosphate through gap junction channels that directly connect the cytoplasm of neighboring cells, and ii) the release of paracrine messengers such as glutamate and ATP through hemichannels ('half of a gap junction channel'). This review gives an overview of the current knowledge on Cx-mediated Ca(2+) communication among astrocytes as well as between astrocytes and other brain cell types in physiology and pathology, with a focus on the processes of neurodegeneration and reactive gliosis. Research on Cx-mediated astroglial Ca(2+) communication may ultimately shed light on the development of targeted therapies for neurodegenerative disorders in which astrocytes participate. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Marijke De Bock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Elke Decrock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium.
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mélissa Bol
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mathieu Vinken
- Department of Toxicology, Center for Pharmaceutical Research, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, B-1090 Brussels, Belgium
| | - Geert Bultynck
- Department of Cellular and Molecular Medicine, Laboratory of Molecular and Cellular Signalling, KULeuven, Campus Gasthuisberg O/N-I bus 802, B-3000 Leuven, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
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136
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Harris AL, Contreras JE. Motifs in the permeation pathway of connexin channels mediate voltage and Ca (2+) sensing. Front Physiol 2014; 5:113. [PMID: 24744733 PMCID: PMC3978323 DOI: 10.3389/fphys.2014.00113] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 03/06/2014] [Indexed: 11/13/2022] Open
Abstract
Connexin channels mediate electrical coupling, intercellular molecular signaling, and extracellular release of signaling molecules. Connexin proteins assemble intracellularly as hexamers to form plasma membrane hemichannels. The docking of two hemichannels in apposed cells forms a gap junction channel that allows direct electrical and selective cytoplasmic communication between adjacent cells. Hemichannels and junctional channels are gated by voltage, but extracellular Ca (2+) also gates unpaired plasma membrane hemichannels. Unlike other ion channels, connexin channels do not contain discrete voltage- or Ca (2+)-sensing modules linked to a separate pore-forming module. All studies to date indicate that voltage and Ca (2+) sensing are predominantly mediated by motifs that lie within or are exposed to the pore lumen. The sensors appear to be integral components of the gates, imposing an obligatory structural linkage between sensing and gating not commonly present in other ion channels, in which the sensors are semi-independent domains distinct from the pore. Because of this, the structural and electrostatic features that define connexin channel gating also define pore permeability properties, and vice versa; analysis/mutagenesis of gating and of permeability properties are linked. This offers unique challenges and opportunities for elucidating mechanisms of ligand and voltage-driven gating.
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Affiliation(s)
- Andrew L Harris
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Jorge E Contreras
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA
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137
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Yan X, Yadav R, Gao M, Weng HR. Interleukin-1 beta enhances endocytosis of glial glutamate transporters in the spinal dorsal horn through activating protein kinase C. Glia 2014; 62:1093-109. [PMID: 24677092 DOI: 10.1002/glia.22665] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 03/12/2014] [Accepted: 03/12/2014] [Indexed: 01/01/2023]
Abstract
Excessive activation of glutamate receptors in spinal dorsal horn neurons is a key mechanism leading to abnormal neuronal activation in pathological pain conditions. Previous studies have shown that activation of glutamate receptors in the spinal dorsal horn is enhanced by impaired glial glutamate transporter functions and proinflammatory cytokines including interleukin-1 beta (IL-1β). In this study, we for the first time revealed that spinal glial glutamate transporter activities in the neuropathic animals are attenuated by endogenous IL-1β. Specifically, we demonstrated that nerve injury results in an increased expression of IL-1β and activation of PKC in the spinal dorsal horn as well as suppression of glial glutamate uptake activities. We provided evidence that the nerve-injury induced suppression of glial glutamate uptake is at least in part ascribed to endogenous IL-1β and activation of PKC in the spinal dorsal horn. IL-1β reduces glial glutamate transporter activities through enhancing the endocytosis of both GLT-1 and GLAST glial glutamate transporters. The IL-1β induced trafficking of glial glutamate transporters is through the calcium/PKC signaling pathway, and the dynamin-dependent endocytosis, which is dependent on the integrity of actin filaments. The signaling pathway regulating glial glutamate transporters revealed in this study provides novel targets to attenuate aberrant activation of glutamate receptors in the spinal dorsal horn, which could ultimately help the development of analgesics.
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Affiliation(s)
- Xisheng Yan
- Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia; Department of Cardiovascular Medicine, The Third Hospital of Wuhan, Wuhan, Hubei Province, China
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138
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Grek CL, Rhett JM, Ghatnekar GS. Cardiac to cancer: connecting connexins to clinical opportunity. FEBS Lett 2014; 588:1349-64. [PMID: 24607540 DOI: 10.1016/j.febslet.2014.02.047] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 02/25/2014] [Accepted: 02/26/2014] [Indexed: 12/26/2022]
Abstract
Gap junctions and their connexin components are indispensable in mediating the cellular coordination required for tissue and organ homeostasis. The critical nature of their existence mandates a connection to disease while at the same time offering therapeutic potential. Therapeutic intervention may be offered through the pharmacological and molecular disruption of the pathways involved in connexin biosynthesis, gap junction assembly, stabilization, or degradation. Chemical inhibitors aimed at closing connexin channels, peptide mimetics corresponding to short connexin sequences, and gene therapy approaches have been incredibly useful molecular tools in deciphering the complexities associated with connexin biology. Recently, therapeutic potential in targeting connexins has evolved from basic research in cell-based models to clinical opportunity in the form of human trials. Clinical promise is particularly evident with regards to targeting connexin43 in the context of wound healing. The following review is aimed at highlighting novel advances where the pharmacological manipulation of connexin biology has proven beneficial in animals or humans.
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Affiliation(s)
- Christina L Grek
- FirstString Research, Inc., 300 W. Coleman Blvd., Suite 203, Mount Pleasant, SC, United States
| | - J Matthew Rhett
- Department of Surgery, Division of General Surgery, Medical University of South Carolina, Charleston, SC, United States
| | - Gautam S Ghatnekar
- FirstString Research, Inc., 300 W. Coleman Blvd., Suite 203, Mount Pleasant, SC, United States.
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139
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Zhao BS, Meng LX, Ding YY, Cao YY. Hyperbaric oxygen treatment produces an antinociceptive response phase and inhibits astrocyte activation and inflammatory response in a rat model of neuropathic pain. J Mol Neurosci 2014; 53:251-61. [PMID: 24390961 DOI: 10.1007/s12031-013-0213-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Accepted: 12/15/2013] [Indexed: 10/25/2022]
Abstract
Hyperbaric oxygen (HBO) treatment has been proven to be a promising candidate for protection of the nervous system after acute injury in animal models of neuropathic pain. The purposes of this study were to examine the antinociceptive response phase induced by HBO treatment in a model of neuropathic pain and to determine the dependence of the treatment's mechanism of alleviating neuropathic pain on the inhibition of spinal astrocyte activation. Neuropathic pain was induced in rats by chronic constriction injury of the sciatic nerve. Mechanical threshold and thermal latency were tested preoperatively and for 1 week postoperatively, four times daily at fixed time points. Methane dicarboxylic aldehyde (MDA) and superoxide dismutase (SOD) parameters were used as indices of oxidative stress response and tested before and after the treatment. The inflammatory cytokines interleukin (IL)-1β and IL-10 were assayed in the sciatic nerve were with enzyme-linked immunoassay. Glial fibrillary acidic protein activation in the spinal cord was evaluated immunohistochemically. The rats exhibited temporary allodynia immediately after HBO treatment completion. This transient allodynia was closely associated with changes in MDA and SOD levels. A single HBO treatment caused a short-acting antinociceptive response phase. Repetitive HBO treatment led to a long-acting antinociceptive response phase and inhibited astrocyte activation. These results indicated that HBO treatment played a dual role in the aggravation and alleviation of neuropathic pain, though the aggravated pain effect (transient allodynia) was far less pronounced than the antinociceptive phase. Astrocyte inhibition and anti-inflammation may contribute to the antinociceptive effect of HBO treatment after nerve injury.
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Affiliation(s)
- Bai-Song Zhao
- Department of Anesthesiology, China Medical University, Shengjing Hospital, 110004, Shenyang, China,
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140
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Ji RR, Berta T, Nedergaard M. Glia and pain: is chronic pain a gliopathy? Pain 2013; 154 Suppl 1:S10-S28. [PMID: 23792284 PMCID: PMC3858488 DOI: 10.1016/j.pain.2013.06.022] [Citation(s) in RCA: 808] [Impact Index Per Article: 73.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 05/23/2013] [Accepted: 06/12/2013] [Indexed: 12/22/2022]
Abstract
Activation of glial cells and neuro-glial interactions are emerging as key mechanisms underlying chronic pain. Accumulating evidence has implicated 3 types of glial cells in the development and maintenance of chronic pain: microglia and astrocytes of the central nervous system (CNS), and satellite glial cells of the dorsal root and trigeminal ganglia. Painful syndromes are associated with different glial activation states: (1) glial reaction (ie, upregulation of glial markers such as IBA1 and glial fibrillary acidic protein (GFAP) and/or morphological changes, including hypertrophy, proliferation, and modifications of glial networks); (2) phosphorylation of mitogen-activated protein kinase signaling pathways; (3) upregulation of adenosine triphosphate and chemokine receptors and hemichannels and downregulation of glutamate transporters; and (4) synthesis and release of glial mediators (eg, cytokines, chemokines, growth factors, and proteases) to the extracellular space. Although widely detected in chronic pain resulting from nerve trauma, inflammation, cancer, and chemotherapy in rodents, and more recently, human immunodeficiency virus-associated neuropathy in human beings, glial reaction (activation state 1) is not thought to mediate pain sensitivity directly. Instead, activation states 2 to 4 have been demonstrated to enhance pain sensitivity via a number of synergistic neuro-glial interactions. Glial mediators have been shown to powerfully modulate excitatory and inhibitory synaptic transmission at presynaptic, postsynaptic, and extrasynaptic sites. Glial activation also occurs in acute pain conditions, and acute opioid treatment activates peripheral glia to mask opioid analgesia. Thus, chronic pain could be a result of "gliopathy," that is, dysregulation of glial functions in the central and peripheral nervous system. In this review, we provide an update on recent advances and discuss remaining questions.
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Affiliation(s)
- Ru-Rong Ji
- Department of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC, USA
| | - Temugin Berta
- Department of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC, USA
| | - Maiken Nedergaard
- Division of Glial Disease and Therapeutics, Center for Translational Neuromedicine, University of Rochester, Rochester, NY, USA
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141
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Wang H, Cao Y, Chiang CY, Dostrovsky JO, Sessle BJ. The gap junction blocker carbenoxolone attenuates nociceptive behavior and medullary dorsal horn central sensitization induced by partial infraorbital nerve transection in rats. Pain 2013; 155:429-435. [PMID: 24239671 DOI: 10.1016/j.pain.2013.11.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Revised: 11/01/2013] [Accepted: 11/06/2013] [Indexed: 12/15/2022]
Abstract
Glial cells are being increasingly implicated in mechanisms underlying pathological pain, and recent studies suggest glial gap junctions involving astrocytes may contribute. The aim of this study was to examine the effect of a gap junction blocker, carbenoxolone (CBX), on medullary dorsal horn (MDH) nociceptive neuronal properties and facial mechanical nociceptive behavior in a rat trigeminal neuropathic pain model involving partial transection of the infraorbital nerve (p-IONX). p-IONX produced facial mechanical hypersensitivity reflected in significantly reduced head withdrawal thresholds that lasted for more than 3weeks. p-IONX also produced central sensitization in MDH nociceptive neurons that was reflected in significantly increased receptive field size, reduction of mechanical activation threshold, and increases in noxious stimulation-evoked responses. Intrathecal CBX treatment significantly attenuated the p-IONX-induced mechanical hypersensitivity and the MDH central sensitization parameters, compared to intrathecal vehicle treatment. These results provide the first documentation that gap junctions may be critically involved in orofacial neuropathic pain mechanisms.
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Affiliation(s)
- Hua Wang
- Department of Oral Physiology, Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
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142
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Han Y, Yu HX, Sun ML, Wang Y, Xi W, Yu YQ. Astrocyte-restricted disruption of connexin-43 impairs neuronal plasticity in mouse barrel cortex. Eur J Neurosci 2013; 39:35-45. [PMID: 24148096 DOI: 10.1111/ejn.12394] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2013] [Revised: 09/17/2013] [Accepted: 09/18/2013] [Indexed: 11/29/2022]
Abstract
There is intensive gap-junctional coupling between glial processes, but their significance in sensory functions remains unknown. Connexin-43 (Cx43), a major component of astrocytic gap-junction channels, is abundantly expressed in astrocytes. To investigate the role of Cx43-mediated gap junctions between astrocytes in sensory functions, we generated Cx43 knockout (KO) mice with a mouse line carrying loxP sites flanking exon 2 of the Cx43 gene and the transgenic line expressing Cre recombinase under control of the glial fibrillary acidic protein promoter, which exhibited a significant loss of Cx43 in astrocytes in the barrel cortex. Although Cx43 expression between the astrocytes measured by immunohistochemistry was virtually abolished in Cx43 KO mice, they had normal architecture in the barrel cortex but the intensity of cytochrome oxide histochemistry decreased significantly. In vivo electrophysiological analysis revealed that the long-term potentiation of the vibrissal evoked responses in the barrel cortex evoked by high-frequency rhythmic vibrissal stimuli (100 Hz, 1 s) was abolished in Cx43 KO mice. Current source density analysis also revealed that astrocytic Cx43 was important to the flow of excitation within the laminar connections in barrel cortex. Behavioral tests showed that the ability of Cx43 KO mice to sense the environment with their whiskers decreased. Even so, the jump-stand experiment showed that they could still discriminate rough from smooth surfaces. Our findings suggest that Cx43-mediated gap-junctional coupling between astrocytes is important in the neuron-glia interactions required for whisker-related sensory functions and plasticity.
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Affiliation(s)
- Yong Han
- Key Laboratory of Medical Neurobiology of the Ministry of Health of China, Zhejiang Province Key Laboratory of Neurobiology, Department of Physiology and Neurobiology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
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143
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Schmitz K, Pickert G, Wijnvoord N, Häussler A, Tegeder I. Dichotomy of CCL21 and CXCR3 in nerve injury-evoked and autoimmunity-evoked hyperalgesia. Brain Behav Immun 2013; 32:186-200. [PMID: 23643685 DOI: 10.1016/j.bbi.2013.04.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/17/2013] [Revised: 04/20/2013] [Accepted: 04/22/2013] [Indexed: 02/07/2023] Open
Abstract
The chemokine CCL21 is released from injured neurons and acts as a ligand of the chemokine receptor, CXCR3, which likely contributes to pro-inflammatory adaptations and secondary neuronal damage. CCL21-CXCR3 signalling may therefore impact on the development of neuropathic pain. By using the respective knockout mice we show that deficiency of CCL19/21 in plt/plt mice attenuates nerve injury evoked pain but not the hyperalgesia evoked by autoimmune encephalomyelitis (EAE). Oppositely, CXCR3-deficiency had no protective effect after traumatic nerve injury but reduced EAE-evoked hyperalgesia and was associated with reduced clinical EAE scores, a reduction of the pro-inflammatory cell infiltration and reduced upregulation of interferon gamma and interleukin-17 in the spinal cord. In contrast, microglia activation in the spinal cord after traumatic sciatic nerve injury was neither attenuated in CXCR3(-/-) nor plt/plt mice, nor in double knockouts. However, the severity of EAE, but not the hyperalgesia, was also reduced in plt/plt mice, which was associated with reduced infiltration of the spinal cord with CCR7+ T-cells, an increase of CD25+ T-cells and reduced upregulation of CXCL9 and 10, CCL11 and 12. The data show that CCL21 and CXCR3 have dichotomous functions in traumatic and EAE-evoked neuropathic pain suggesting diverse mechanisms likely requiring diverse treatments although both types of neuropathic pain are mediated in part through the immune activation.
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Affiliation(s)
- Katja Schmitz
- Pharmazentrum Frankfurt, Institute of Clinical Pharmacology, Goethe-University Hospital, Frankfurt, Germany
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144
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Wu F, Miao X, Chen J, Liu Z, Tao Y, Yu W, Sun Y. Inhibition of GAP-43 by propentofylline in a rat model of neuropathic pain. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2013; 6:1516-1522. [PMID: 23923069 PMCID: PMC3726966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 07/11/2013] [Indexed: 06/02/2023]
Abstract
Neural plasticity within the spinal nociceptive network may be fundamental to the chronic nature of neuropathic pain. The relation of growth-associated protein-43 (GAP-43), a protein involved in the nerve fiber growth and sprouting, to pain hypersensitivity has been investigated. Glial activation and inflammatory cytokines released by microglia and astrocytes are considered to be involved in the neural sprouting and plasticity. In the present study, the anti-nociception effect of propentofylline, a glial modulating agent, was investigated in a rat chronic constriction injury (CCI) model aiming to explore the role of GAP-43 expression. Our results demonstrated that propentofylline could attenuate the CCI-induced mechanical allodynia and thermal hyperalgesia and inhibit the astrocyte activation and production of IL-1β. GAP-43 expression was also down-regulated by intrathecal propentofylline. These findings suggest that astrocyte activation is involved in the regulation of GAP-43 expression and propentofylline might be used in the treatment of neuropathic pain.
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Affiliation(s)
- Feixiang Wu
- Department of Anesthesiology, Eastern Hepatobiliary Hospital, the Second Military Medical UniversityNo. 225 Changhai Road, Shanghai 200433, China
| | - Xuerong Miao
- Department of Anesthesiology, Eastern Hepatobiliary Hospital, the Second Military Medical UniversityNo. 225 Changhai Road, Shanghai 200433, China
| | - Jiaying Chen
- Department of Anesthesiology, Eastern Hepatobiliary Hospital, the Second Military Medical UniversityNo. 225 Changhai Road, Shanghai 200433, China
| | - Zhiqiang Liu
- Department of Anesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of MedicineNo. 536 Changle Road, Shanghai 200126, China
| | - Yong Tao
- Department of Anesthesiology, Eastern Hepatobiliary Hospital, the Second Military Medical UniversityNo. 225 Changhai Road, Shanghai 200433, China
| | - Weifeng Yu
- Department of Anesthesiology, Eastern Hepatobiliary Hospital, the Second Military Medical UniversityNo. 225 Changhai Road, Shanghai 200433, China
| | - Yuming Sun
- Department of Anesthesiology, Eastern Hepatobiliary Hospital, the Second Military Medical UniversityNo. 225 Changhai Road, Shanghai 200433, China
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145
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Cerebral ischemic injury is enhanced in a model of oculodentodigital dysplasia. Neuropharmacology 2013; 75:549-56. [PMID: 23727526 DOI: 10.1016/j.neuropharm.2013.05.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Revised: 05/01/2013] [Accepted: 05/04/2013] [Indexed: 11/20/2022]
Abstract
Oculodentodigital dysplasia (ODDD) is a rare autosomal dominant disease that results in visible developmental anomalies of the limbs, face, eyes and teeth. Recently analysis of human connexin43 (Cx43) DNA sequences has revealed a number of different missense, duplication and frame shift mutations resulting in this phenotype. A mouse model of this disorder has been created with a missense point mutation of the glycine amino acid at position 60 to serine (G60S). Heterozygote +/G60S mice exhibit a similar ODDD phenotype as observed in humans. In addition to the malformations listed above, ODDD patients often have neurological findings. In the brain, Cx43 is highly expressed in astrocytes and has been shown to play a role in neuroprotection. We were interested in determining the effect of the +/G60S mutation following stroke. Four days after middle cerebral artery occlusion the volume of infarct was larger in mice with the +/G60S mutation. In astrocyte-neuron co-cultures, exposure to glutamate also resulted in greater cellular death in the +/G60S mutants. Protein levels of Cx43 in the mutant mouse were found to be reduced when compared to the normal tissue. Cx43 protein was observed as a continual line of small punctate aggregates in the plasma membrane with increased intracellular localization, which is distinct from the larger plaques seen in the normal mouse astrocytes. Functionally, primary +/G60S astrocytes exhibited reduced gap junctional coupling and increased hemichannel activity, which may underlie the mechanism of increased damage during stroke. This article is part of the Special Issue Section entitled 'Current Pharmacology of Gap Junction Channels and Hemichannels'.
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146
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Pannasch U, Rouach N. Emerging role for astroglial networks in information processing: from synapse to behavior. Trends Neurosci 2013; 36:405-17. [PMID: 23659852 DOI: 10.1016/j.tins.2013.04.004] [Citation(s) in RCA: 179] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 04/01/2013] [Accepted: 04/01/2013] [Indexed: 01/05/2023]
Abstract
Astrocytes contribute to neurotransmission through a variety of mechanisms ranging from synapse isolation to active signaling. Astroglial involvement in neurophysiology has been mostly investigated at the single-cell level. However, a unique feature of astrocytes is their high level of intercellular connectivity mediated by connexins, the proteins forming gap junction (GJ) channels. These astroglial GJ circuits enable the rapid intercellular exchange of ions, metabolites, and neuroactive substances. Recent findings have suggested that, despite their extensity, astroglial networks are also selective, preferential as well as plastic, and can regulate synapses, neuronal circuits, and behavior. The present review critically discusses the impact of astroglial networks on normal and pathological neuronal information processing as well as the underlying mechanisms.
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Affiliation(s)
- Ulrike Pannasch
- Neuroglial Interactions in Cerebral Physiopathology, Center for Interdisciplinary Research in Biology, Centre Nationale de la Recherche Scientifique (CNRS) Unité Mixte de Recherche 7241, Institut National de la Santé et de la Recherche Médicale (INSERM) Unité 1050, Collège de France, 75005 Paris, France
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147
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Gao Z, Zhu Q, Zhang Y, Zhao Y, Cai L, Shields CB, Cai J. Reciprocal modulation between microglia and astrocyte in reactive gliosis following the CNS injury. Mol Neurobiol 2013; 48:690-701. [PMID: 23613214 DOI: 10.1007/s12035-013-8460-4] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 04/09/2013] [Indexed: 12/16/2022]
Abstract
Reactive gliosis, also known as glial scar formation, is an inflammatory response characterized by the proliferation of microglia and astrocytes as well as astrocytic hypertrophy following injury in the central nervous system (CNS). The glial scar forms a physical and molecular barrier to isolate the injured area from adjacent normal nervous tissue for re-establishing the integrity of the CNS. It prevents the further spread of cellular damage but represents an obstacle to regrowing axons. In this review, we integrated the current findings to elucidate the tightly reciprocal modulation between activated microglia and astrocytes in reactive gliosis and proposed that modification of cellular response to the injury or cellular reprogramming in the glial scar could lead advances in axon regeneration and functional recovery after the CNS injury.
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Affiliation(s)
- Zhongwen Gao
- Department of Spine Surgery, the First Hospital of Jilin University, 71 Xinmin Street, Changchun, Jilin, 130021, China
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148
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Ren Z, Chen X, Yang J, Kress BT, Tong J, Liu H, Takano T, Zhao Y, Nedergaard M. Improved axonal regeneration after spinal cord injury in mice with conditional deletion of ephrin B2 under the GFAP promoter. Neuroscience 2013; 241:89-99. [PMID: 23518227 DOI: 10.1016/j.neuroscience.2013.03.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Revised: 03/03/2013] [Accepted: 03/12/2013] [Indexed: 12/13/2022]
Abstract
Spinal cord injury (SCI) initiates a cascade of processes that ultimately form a nonpermissive environment for axonal regeneration. Emerging evidence suggests that regenerative failure may be due in part to inhibitory factors expressed by reactive spinal cord glial cells and meningeal fibroblasts, such as the Eph receptor protein-tyrosine kinases and their corresponding ligands (ephrins). Here we sought to assess the role of ephrin B2, an inhibitory axonal guidance molecule, as an inhibitor of the recovery process following SCI. To determine the extent of ephrin B2 involvement in axonal regenerative failure, a SCI model was performed on a conditional ephrin B2 knockout mouse strain (ephrin B2(-/-)), in which the ephrin B2 gene was deleted under the GFAP promoter . The expression of ephrin B2 was significantly decreased in astrocytes of injured and uninjured ephrin B2(-/-) mice compared to wild-type mice. Notably, in the ephrin B2(-/-) mice, the deletion of ephrin B2 reduced astrogliosis, and accelerated motor function recovery after SCI. Anterograde axonal tracing on a hemisection model of SCI further showed that ephrin B2(-/-) mice exhibited increased regeneration of injured corticospinal axons and a reduced glial scar, when compared to littermate controls exposed to similar injury. These results were confirmed by an in vitro neurite outgrowth assay and ephrin B2 functional blockage, which showed that ephrin B2 expressed on astrocytes inhibited axonal growth. Combined these findings suggest that ephrin B2 ligands expressed by reactive astrocytes impede the recovery process following SCI.
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Affiliation(s)
- Z Ren
- Department of Neurosurgery, University of Rochester, Rochester, NY 14642, USA.
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