Glial Cells and Chronic Pain

Pain Research Unit, Department of Anesthesiology, University Hospital Center, University of Lausanne, Lausanne, Switzerland.
The Neuroscientist (Impact Factor: 6.84). 10/2010; 16(5):519-31. DOI: 10.1177/1073858409360822
Source: PubMed


Over the past few years, the control of pain exerted by glial cells has emerged as a promising target against pathological pain. Indeed, changes in glial phenotypes have been reported throughout the entire nociceptive pathway, from peripheral nerves to higher integrative brain regions, and pharmacological inhibition of such glial reactions reduces the manifestation of pain in animal models. This complex interplay between glia and neurons relies on various mechanisms depending both on glial cell types considered (astrocytes, microglia, satellite cells, or Schwann cells), the anatomical location of the regulatory process (peripheral nerve, spinal cord, or brain), and the nature of the chronic pain paradigm. Intracellularly, recent advances have pointed to the activation of specific cascades, such as mitogen-associated protein kinases (MAPKs) in the underlying processes behind glial activation. In addition, given the large number of functions accomplished by glial cells, various mechanisms might sensitize nociceptive neurons including a release of pronociceptive cytokines and neurotrophins or changes in neurotransmitter-scavenging capacity. The authors review the conceptual advances made in the recent years about the implication of central and peripheral glia in animal models of chronic pain and discuss the possibility to translate it into human therapies in the future.

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Available from: Ru-Rong Ji
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    • "Identification of the cell type expressing the σ1 receptors would provide an important clue to understanding the role of σ1 receptors and p-p38 in relation to development of chronic MA. It is increasingly recognized that glial cells (astrocytes and microglia) play an important role in chronic pain processing (Gosselin et al., 2010). In particular, astrocytes represent the most abundant cells in the CNS and dynamically modulate neuronal function under both physiological and "
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    ABSTRACT: Background and purpose: Spinal astrocytes have emerged as important mechanistic contributors to the genesis of mechanical allodynia (MA) in neuropathic pain. We recently demonstrated that the spinal sigma non-opioid intracellular receptor 1 (σ1 receptor) modulates p38 MAPK phosphorylation (p-p38), which plays a critical role in the induction of MA in neuropathic rats. However, the histological and physiological relationships among σ1, p-p38 and astrocyte activation is unclear. Experimental approach: We investigated: (i) the precise location of σ1 receptors and p-p38 in spinal dorsal horn; (ii) whether the inhibition of σ1 receptors or p38 modulates chronic constriction injury (CCI)-induced astrocyte activation; and (iii) whether this modulation of astrocyte activity is associated with MA development in CCI mice. Key results: The expression of σ1 receptors was significantly increased in astrocytes on day 3 following CCI surgery. Sustained intrathecal treatment with the σ1 antagonist, BD-1047, attenuated CCI-induced increase in GFAP-immunoreactive astrocytes, and the treatment combined with fluorocitrate, an astrocyte metabolic inhibitor, synergistically reduced the development of MA, but not thermal hyperalgesia. The number of p-p38-ir astrocytes and neurons, but not microglia was significantly increased. Interestingly, intrathecal BD-1047 attenuated the expression of p-p38 selectively in astrocytes but not in neurons. Moreover, intrathecal treatment with a p38 inhibitor attenuated the GFAP expression, and this treatment combined with fluorocitrate synergistically blocked the induction of MA. Conclusions and implications: Spinal σ1 receptors are localized in astrocytes and blockade of σ1 receptors inhibits the pathological activation of astrocytes via modulation of p-p38, which ultimately prevents the development of MA in neuropathic mice.
    Full-text · Article · Aug 2014 · British Journal of Pharmacology
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    • "The pronociceptive role of ATP in nociception is well characterized [3-8]. This effect has been associated with the activation of the P2X family receptors expressed in dorsal root ganglion [9-12], satellite glial cells [13,14], spinal dorsal horn [15-17] and microglia/astrocytes [16,18,19]. Following nerve damage, spinal microglia and astrocytes proliferate and up-regulate specific protein markers like ionized calcium-binding adapter molecule-1 (Iba-1) and glial fibrillary acidic protein (GFAP), respectively [20,21]. "
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    ABSTRACT: Background The participation of spinal P2X receptors in neuropathic pain is well recognized. However, the role of P2Y receptors has been less studied. The purpose of this study was to investigate the contribution of spinal P2Y6,11 receptors following peripheral nerve damage induced by spinal nerve ligation. In addition, we determined the expression of P2Y6,11 receptors in the dorsal spinal cord in presence of the selective P2Y6,11 receptors antagonists. Furthermore, we evaluated the participation of spinal microglia and astrocytes in the pronociceptive role of P2Y6,11 receptors. Results Spinal administration of the selective P2Y6 (MRS2578, 10–100 μM) and P2Y11 (NF340, 0.3–30 μM) receptor antagonists reduced tactile allodynia in spinal nerve ligated rats. Nerve injury increased the expression of P2Y6,11 receptors at 7, 14 and 21 days after injury. Furthermore, intrathecal administration of MRS2578 (100 μM/day) and NF340 (30 μM/day) for 3 days significantly reduced spinal nerve injury-induced increase in P2Y6,11 receptors expression, respectively. Spinal treatment (on day 14 after injury) with minocycline (100 μg/day) or fluorocitrate (1 nmol/day) for 7 days reduced tactile allodynia and spinal nerve injury-induced up-regulation in Iba-1 and GFAP, respectively. In addition, minocycline reduced nerve injury-induced up-regulation in P2Y6,11 receptors whereas that fluorocitrate diminished P2Y11, but not P2Y6, receptors up-regulation. Intrathecal treatment (on day 21 after injury) with the selective P2Y6 (PSB0474, 3–30 μM) and P2Y11 (NF546, 1–10 μM) receptor agonists produced remarkable tactile allodynia in nerve ligated rats previously treated with minocycline or fluorocitrate for 7 days. Conclusions Our data suggest that spinal P2Y6 is present in spinal microglia while P2Y11 receptors are present in both spinal microglia and astrocytes, and both receptors are up-regulated in rats subjected to spinal nerve injury. In addition, our data suggest that the spinal P2Y6 and P2Y11 receptors participate in the maintenance of neuropathic pain.
    Full-text · Article · May 2014 · Molecular Pain
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    • "Other presumptions made by the Gate Control Theory, such as spinal dorsal horn termination of primary afferents, have not been borne out by experimental data. In addition, the theory did not foresee a role of glial cells, which vastly outnumber neurons, in modulating pain perception and there is no accounting for potential plasticity of the nervous system following injury or disease [3]. Even after acknowledging flaws of the Gate Control Theory, it is still characterized as having led to " significant advancement " of our understanding of pain [1]. "
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    ABSTRACT: Neuropathic pain is a chronic disability associated with a dysfunction of the nervous system, initiated by a primary lesion or disease. Even after resolution of the initiating pathology, neuropathic pain often persists, leading to a significantly diminished quality of life. A vast literature has documented alterations in the expression and distribution of various pain-related proteins in the peripheral nervous system following injury or disease. The current review examines pain-related molecules in the pathogenesis of peripheral nerve injury-induced pain and discusses potentially useful therapeutic targets on the basis of preclinical findings in rodent neuropathic pain models. There are indeed a number of cellular processes that are involved in maintaining the neuropathic pain state, but the current review will focus on transmembrane proteins, particularly the voltage-gated and ligand-gated ion channels, which modulate peripheral nerve function. Given the complexity of the process involved in peripheral nerves, clinical efficacy could be greatly enhanced if several of these targets are engaged at once. A key advantage of therapy directed peripherally is that penetration of the therapeutic into the CNS is not entirely necessary, thereby reducing the risk of adverse psychomotor effects. While a number of fascinating targets have been identified in preclinical rodent models, there is a need to confirm that they are in fact relevant to clinical neuropathic pain. Thus, the current review will also discuss the extent to which clinical data confirms the findings of preclinical studies.
    Full-text · Article · May 2014 · CNS & neurological disorders drug targets
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