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Huang R, Han S, Qiu Y, Zhou T, Wu Y, Du H, Xu J, Wei X. Glucocorticoid regulation of lactate release from spinal astrocytes contributes to the induction of spinal LTP of C-fiber-evoked field potentials and the development of mechanical allodynia. Neuropharmacology 2022; 219:109253. [PMID: 36108796 DOI: 10.1016/j.neuropharm.2022.109253] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 08/28/2022] [Accepted: 09/06/2022] [Indexed: 10/31/2022]
Abstract
High-frequency stimulation (HFS) of the sciatic nerve leads to long-term potentiation (LTP) at C-fiber synapse and long-lasting pain hypersensitivity. The underlying mechanisms, however, are still unclear. In the present study, we investigated the involvement of astrocytes derived l-lactate in the spinal dorsal horn subsequent to glucocorticoid (GC) secretion into the plasma in this process using Sprague-Dawley rats and Aldh1L1-CreERT2 mice of either sex. We found that HFS increased l-lactate and monocarboxylate transporters 1/2 (MCT1/2) in the spinal dorsal horn. Inhibition of glycogenolysis or blocking lactate transport prevented the induction of spinal LTP following HFS. Furthermore, Chemogenetical inhibition of dorsal horn astrocytes, which were activated by HFS, prevented spinal LTP, alleviated the mechanical allodynia and the decreased the level l-lactate and GFAP expression in the dorsal horn following HFS. In contrast, Chemogenetics activation of dorsal horn astrocytes in naïve rats induced spinal LTP as well as mechanical allodynia, and increased GFAP expression and l-lactate. Application of l-lactate directly to the spinal cord of naïve rats induced spinal LTP, mechanical allodynia, and increased spinal expression of p-ERK. Importantly, HFS increased GC in the plasma and glucocorticoid receptor (GR) expression in spinal astrocytes, adrenalectomy or knocking down of GR in astrocytes by using Cre-Loxp system blocked the mechanical allodynia, prevented the spinal LTP and the enhancement of lactate after HFS. These results show that lactate released from spinal astrocytes following glucocorticoid release into the plasma enhance synaptic transmission at the C-fiber synapse and underlie pain chronicity.
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Affiliation(s)
- Ruizhen Huang
- Department of Physiology and Pain Research Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Shuang Han
- Department of Physiology and Pain Research Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Yuxin Qiu
- Department of Anesthesiology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, China
| | - Taihe Zhou
- Department of Physiology and Pain Research Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Yuning Wu
- Department of Physiology and Pain Research Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Hongchun Du
- Department of Pulmonary and Critical Care Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510080, China.
| | - Jing Xu
- Department of Physiology and Pain Research Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China; Center for Laboratory Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
| | - Xuhong Wei
- Department of Physiology and Pain Research Center, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, Guangdong, China; Guangdong Provincial Key Laboratory of Brain Function and Disease, Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China.
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Role of Na V1.6 and Na Vβ4 Sodium Channel Subunits in a Rat Model of Low Back Pain Induced by Compression of the Dorsal Root Ganglia. Neuroscience 2019; 402:51-65. [PMID: 30699332 DOI: 10.1016/j.neuroscience.2019.01.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Revised: 01/08/2019] [Accepted: 01/11/2019] [Indexed: 01/18/2023]
Abstract
Low back pain is a common cause of chronic pain and disability. It is modeled in rodents by chronically compressing the lumbar dorsal root ganglia (DRG) with small metal rods, resulting in ipsilateral mechanical and cold hypersensitivity, and hyperexcitability of sensory neurons. Sodium channels are implicated in this hyperexcitability, but the responsible isoforms are unknown. In this study, we used siRNA-mediated knockdown of the pore-forming NaV1.6 and regulatory NaVβ4 sodium channel isoforms that have been previously implicated in a different model of low back pain caused by locally inflaming the L5 DRG. Knockdown of either subunit markedly reduced spontaneous pain and mechanical and cold hypersensitivity induced by DRG compression, and reduced spontaneous activity and hyperexcitability of sensory neurons with action potentials <1.5 msec (predominately cells with myelinated axons, based on conduction velocities measured in a subset of cells) 4 days after DRG compression. These results were similar to those previously obtained in the DRG inflammation model and some neuropathic pain models, in which sensory neurons other than nociceptors seem to play key roles. The cytokine profiles induced by DRG compression and DRG inflammation were also very similar, with upregulation of several type 1 pro-inflammatory cytokines and downregulation of type 2 anti-inflammatory cytokines. Surprisingly, the cytokine profile was largely unaffected by NaVβ4 knockdown in either model. The NaV1.6 channel, and the NaVβ4 subunit that can regulate NaV1.6 to enhance repetitive firing, play key roles in both models of low back pain; targeting the abnormal spontaneous activity they generate may have therapeutic value.
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The peripheral corticotropin-releasing factor (CRF)-induced analgesic effect on somatic pain sensitivity in conscious rats: involving CRF, opioid and glucocorticoid receptors. Inflammopharmacology 2018; 26:305-318. [DOI: 10.1007/s10787-018-0445-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 01/23/2018] [Indexed: 12/30/2022]
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Greenwood-Van Meerveld B, Johnson AC. Stress-Induced Chronic Visceral Pain of Gastrointestinal Origin. Front Syst Neurosci 2017; 11:86. [PMID: 29213232 PMCID: PMC5702626 DOI: 10.3389/fnsys.2017.00086] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Accepted: 11/10/2017] [Indexed: 12/12/2022] Open
Abstract
Visceral pain is generally poorly localized and characterized by hypersensitivity to a stimulus such as organ distension. In concert with chronic visceral pain, there is a high comorbidity with stress-related psychiatric disorders including anxiety and depression. The mechanisms linking visceral pain with these overlapping comorbidities remain to be elucidated. Evidence suggests that long term stress facilitates pain perception and sensitizes pain pathways, leading to a feed-forward cycle promoting chronic visceral pain disorders such as irritable bowel syndrome (IBS). Early life stress (ELS) is a risk-factor for the development of IBS, however the mechanisms responsible for the persistent effects of ELS on visceral perception in adulthood remain incompletely understood. In rodent models, stress in adult animals induced by restraint and water avoidance has been employed to investigate the mechanisms of stress-induce pain. ELS models such as maternal separation, limited nesting, or odor-shock conditioning, which attempt to model early childhood experiences such as neglect, poverty, or an abusive caregiver, can produce chronic, sexually dimorphic increases in visceral sensitivity in adulthood. Chronic visceral pain is a classic example of gene × environment interaction which results from maladaptive changes in neuronal circuitry leading to neuroplasticity and aberrant neuronal activity-induced signaling. One potential mechanism underlying the persistent effects of stress on visceral sensitivity could be epigenetic modulation of gene expression. While there are relatively few studies examining epigenetically mediated mechanisms involved in visceral nociception, stress-induced visceral pain has been linked to alterations in DNA methylation and histone acetylation patterns within the brain, leading to increased expression of pro-nociceptive neurotransmitters. This review will discuss the potential neuronal pathways and mechanisms responsible for stress-induced exacerbation of chronic visceral pain. Additionally, we will review the importance of specific experimental models of adult stress and ELS in enhancing our understanding of the basic molecular mechanisms of pain processing.
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Affiliation(s)
- Beverley Greenwood-Van Meerveld
- Oklahoma Center for Neuroscience, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
- Department of Physiology, University of Oklahoma Health Science Center, Oklahoma City, OK, United States
- VA Medical Center, Oklahoma City, OK, United States
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Ibrahim SIA, Strong JA, Zhang JM. Mineralocorticoid Receptor, A Promising Target for Improving Management of Low Back Pain by Epidural Steroid Injections. ACTA ACUST UNITED AC 2016; 3:177-184. [PMID: 28956026 PMCID: PMC5611848 DOI: 10.24015/japm.2016.0023] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
AIM OF REVIEW Low back pain is a major health problem in United States and worldwide. In this review, we aim to show that mineralocorticoid receptor (MR) activation has a critical role in the initiation of immune and inflammatory responses, which in turn can impact the effectiveness of the currently used steroids for epidural injections in low back pain management since most steroids activate MR in addition to the primary target, glucocorticoid receptor (GR). Moreover, we would like to determine some of the benefits of blocking the MR-induced negative effects. Overall, we propose a novel therapeutic approach for low back pain management by using a combination of a MR antagonist and a GR agonist in the epidural injections. METHOD We will first introduce the societal cost of low back pain and discuss how epidural steroid injections became a popular treatment for this condition. We will then describe several preclinical models used for the study of low back pain conditions and the findings with respect to the role of MR in the development of inflammatory low back pain. RECENT FINDINGS MR has pro-inflammatory effects in many tissues which can counteract the anti-inflammatory effects induced by GR activation. Blocking MR using the selective MR antagonist eplerenone can reduce pain and sensory neuron excitability in experimental models of low back pain. Moreover, combining the MR antagonist with clinically used steroids is more effective in reducing pain behaviors than using the steroids alone. SUMMARY MR antagonists are promising candidates to increase the effectiveness of currently used steroids. Since the activation of the MR is evident in preclinical models of low back pain, blocking its deleterious effects can be beneficial in managing inflammatory pain conditions.
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Affiliation(s)
- Shaimaa I A Ibrahim
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, USA.,Graduate Program in Molecular, Cellular, and Biochemical Pharmacology, University of Cincinnati, Cincinnati, USA
| | - Judith A Strong
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, USA
| | - Jun-Ming Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, USA
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A Novel Nitronyl Nitroxide with Salicylic Acid Framework Attenuates Pain Hypersensitivity and Ectopic Neuronal Discharges in Radicular Low Back Pain. Neural Plast 2015; 2015:752782. [PMID: 26609438 PMCID: PMC4644553 DOI: 10.1155/2015/752782] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 03/31/2015] [Accepted: 04/07/2015] [Indexed: 01/04/2023] Open
Abstract
Evidence has accumulated that reactive oxygen species and inflammation play crucial roles in the development of chronic pain, including radicular low back pain. Nonsteroid anti-inflammatory drugs (NSAIDs), for example, salicylic acid, aspirin, provided analgesic effects in various types of pain. However, long-term use of these drugs causes unwanted side effects, which limits their implication. Stable nitronyl (NIT) nitroxide radicals have been extensively studied as a unique and interesting class of new antioxidants for protection against oxidative damage. The present study synthesized a novel NIT nitroxide radical with salicylic acid framework (SANR) to provide synergistic effect of both antioxidation and antiinflammation. We demonstrated for the first time that both acute and repeated SANR treatment exerted dramatic analgesic effect in radicular low back pain mimicked by chronic compression of dorsal root ganglion in rats. This analgesic potency was more potent than that produced by classical NSAIDs aspirin and traditional nitroxide radical Tempol alone. Furthermore, SANR-induced behavioral analgesia is found to be mediated, at least in partial, by a reduction of ectopic spontaneous discharges in injured DRG neurons. Therefore, the synthesized NIT nitroxide radical coupling with salicylic acid framework may represent a novel potential therapeutic candidate for treatment of chronic pain, including radicular low back pain.
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Zuo ZF, Liao YH, Ding T, Dong YL, Qu J, Wang J, Wei YY, Lu YC, Liu XZ, Li YQ. Astrocytic NDRG2 is involved in glucocorticoid-mediated diabetic mechanical allodynia. Diabetes Res Clin Pract 2015; 108:128-36. [PMID: 25656762 DOI: 10.1016/j.diabres.2015.01.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 11/14/2014] [Accepted: 01/03/2015] [Indexed: 12/29/2022]
Abstract
AIMS The present study aims to test whether astrocytes contribute to glucocorticoid-mediated diabetic mechanical allodynia. METHODS Streptozotocin (STZ)-induced diabetic rats were used in our study. The intrathecal operation was performed 21 days after the onset of diabetes. Diabetic mechanical allodynia was present 28 d after the onset of diabetes, and the mechanical threshold was tested using von Frey filaments. Immunohistochemistry, including immunofluorescent histochemical staining, was performed to observe the morphology of the spinal dorsal horn (SDH). Western blot analysis was employed as a semi-quantitative assay of the expression levels of GFAP and NDRG2 associated with diabetic mechanical allodynia. RESULTS Diabetic rats displayed mechanical allodynia and activated astrocytes in the SDH 28 days after the onset of diabetes. This allodynia was attenuated by intrathecal administration of the astrocyte-specific inhibitor l-α-aminoadipate. In parallel, intrathecal injection of RU486, a glucocorticoid receptor antagonist, inhibited the activation of astrocytes in the SDH, alleviating the diabetes-induced mechanical allodynia. Furthermore, we found that dorsal horn astrocytes express abundant N-myc downstream-regulated gene 2 (NDRG2), which contributes to astrocyte reactivity. NDRG2 was over-expressed in activated astrocytes in diabetic rats with mechanical allodynia. Intrathecal injection of RU486 prevented the over-expression of NDRG2, which reversed the astrocyte reactivity and diabetic tactile allodynia. CONCLUSIONS These results suggest that glucocorticoid-mediated over-expression of NDRG2 may contribute to the activation of dorsal horn astrocytes, which play a crucial role in diabetic mechanical allodynia. Thus, inhibiting glucocorticoid receptors and/or astrocyte reactivity in the SDH may be a therapeutic strategy for treating diabetic tactile allodynia.
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Affiliation(s)
- Zhong-Fu Zuo
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China; Department of Anatomy, Histology and Embryology, Liaoning Medical University, No. 3-40 Songpo Road, Jinzhou, Liaoning 121000, PR China
| | - Yong-Hui Liao
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Tan Ding
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Yu-Lin Dong
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Juan Qu
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Jian Wang
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Yan-Yan Wei
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Ya-Cheng Lu
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China
| | - Xue-Zheng Liu
- Department of Anatomy, Histology and Embryology, Liaoning Medical University, No. 3-40 Songpo Road, Jinzhou, Liaoning 121000, PR China.
| | - Yun-Qing Li
- Department of Anatomy, Histology and Embryology & K.K. Leung Brain Research Centre, Preclinical School of Medicine, The Fourth Military Medical University, Xi'an 710032, PR China.
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Johnson AC, Greenwood-Van Meerveld B. Stress-induced pain: a target for the development of novel therapeutics. J Pharmacol Exp Ther 2014; 351:327-35. [PMID: 25194019 PMCID: PMC4201269 DOI: 10.1124/jpet.114.218065] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 09/04/2014] [Indexed: 12/12/2022] Open
Abstract
Although current therapeutics provide relief from acute pain, drugs used for treatment of chronic pain are typically less efficacious and limited by adverse side effects, including tolerance, addiction, and gastrointestinal upset. Thus, there is a significant need for novel therapies for the treatment of chronic pain. In concert with chronic pain, persistent stress facilitates pain perception and sensitizes pain pathways, leading to a feed-forward cycle promoting chronic pain disorders. Stress exacerbation of chronic pain suggests that centrally acting drugs targeting the pain- and stress-responsive brain regions represent a valid target for the development of novel therapeutics. This review provides an overview of how stress modulates spinal and central pain pathways, identifies key neurotransmitters and receptors within these pathways, and highlights their potential as novel targets for therapeutics to treat chronic pain.
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Affiliation(s)
- Anthony C Johnson
- Veterans Affairs Medical Center (B.G.-V.M.), Department of Physiology (B.G.-V.M.), and Oklahoma Center for Neuroscience (A.C.J., B.G.-V.M.), University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Beverley Greenwood-Van Meerveld
- Veterans Affairs Medical Center (B.G.-V.M.), Department of Physiology (B.G.-V.M.), and Oklahoma Center for Neuroscience (A.C.J., B.G.-V.M.), University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
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Chen YJ, Wang YH, Wang CZ, Ho ML, Kuo PL, Huang MH, Chen CH. Effect of low level laser therapy on chronic compression of the dorsal root ganglion. PLoS One 2014; 9:e89894. [PMID: 24594641 PMCID: PMC3942382 DOI: 10.1371/journal.pone.0089894] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2013] [Accepted: 01/28/2014] [Indexed: 11/18/2022] Open
Abstract
Dorsal root ganglia (DRG) are vulnerable to physical injury of the intervertebral foramen, and chronic compression of the DRG (CCD) an result in nerve root damage with persistent morbidity. The purpose of this study was to evaluate the effects of low level laser therapy (LLLT) on the DRG in a CCD model and to determine the mechanisms underlying these effects. CCD rats had L-shaped stainless-steel rods inserted into the fourth and fifth lumbar intervertebral foramen, and the rats were then subjected to 0 or 8 J/cm2 LLLT for 8 consecutive days following CCD surgery. Pain and heat stimuli were applied to test for hyperalgesia following CCD. The levels of TNF-α, IL-1β and growth-associated protein-43 (GAP-43) messenger RNA (mRNA) expression were measured via real-time PCR, and protein expression levels were analyzed through immunohistochemical analyses. Our data indicate that LLLT significantly decreased the tolerable sensitivity to pain and heat stimuli in the CCD groups. The expression levels of the pro-inflammatory cytokines TNF-α and IL-1β were increased following CCD, and we found that these increases could be reduced by the application of LLLT. Furthermore, the expression of GAP-43 was enhanced by LLLT. In conclusion, LLLT was able to enhance neural regeneration in rats following CCD and improve rat ambulatory behavior. The therapeutic effects of LLLT on the DRG during CCD may be exerted through suppression of the inflammatory response and induction of neuronal repair genes. These results suggest potential clinical applications for LLLT in the treatment of compression-induced neuronal disorders.
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Affiliation(s)
- Yi-Jen Chen
- Department of Physical Medicine and Rehabilitation, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yan-Hsiung Wang
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; School of Dentistry, College of Dental Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Chau-Zen Wang
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Physiology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Mei-Ling Ho
- Orthopaedic Research Center, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Physiology, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Graduate Institute of Medicine, School of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Po-Lin Kuo
- Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Medical Research, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Mao-Hsiung Huang
- Department of Physical Medicine and Rehabilitation, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; Department of Physical Medicine and Rehabilitation, Faculty of Medicine, School of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Chia-Hsin Chen
- Department of Physical Medicine and Rehabilitation, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; Department of Physical Medicine and Rehabilitation, Faculty of Medicine, School of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; Department of Physical Medicine and Rehabilitation, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung, Taiwan
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Activation of GRs-Akt-nNOs-NR2B signaling pathway by second dose GR agonist contributes to exacerbated hyperalgesia in a rat model of radicular pain. Mol Biol Rep 2014; 41:4053-61. [PMID: 24562683 DOI: 10.1007/s11033-014-3274-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 02/13/2014] [Indexed: 10/25/2022]
Abstract
Central Akt, neuronal nitric oxide synthase (nNOS) and N-methyl-D-aspartate receptor subunit 2B (NR2B) play key roles in the development of neuropathic pain. Here we investigate the effects of glucocorticoid receptors (GRs) on the expression and activation of spinal Akt, nNOS and NR2B after chronic compression of dorsal root ganglia (CCD). Thermal hyperalgesia test and mechanical allodynia test were used to measure rats after intrathecal injection of GR antagonist mifepristone or GR agonist dexamethasone for 21 days postoperatively. Expression of spinal Akt, nNOS, NR2B and their phosphorylation state after CCD was examined by western blot. The effects of intrathecal treatment with dexamethasone or mifepristone on nociceptive behaviors and the corresponding expression of Akt, nNOS and NR2B in spinal cord were also investigated. Intrathecal injection of mifepristone or dexamethasone inhibited PWMT and PWTL in CCD rats. However, hyperalgesia was induced by intrathecal injection of dexamethasone on days 12 to 14 after surgery. Treatment of dexamethasone increased the expression and phosphorylation levels of spinal Akt, nNOS, GR and NR2B time dependently, whereas administration of mifepristone downregulated the expression of these proteins significantly. GRs activated spinal Akt-nNOS/NR2B pathway play important roles in the development of neuropathic pain in a time-dependent manner.
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Strong JA, Xie W, Bataille FJ, Zhang JM. Preclinical studies of low back pain. Mol Pain 2013; 9:17. [PMID: 23537369 PMCID: PMC3617092 DOI: 10.1186/1744-8069-9-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 03/18/2013] [Indexed: 12/12/2022] Open
Abstract
Chronic low back pain is a major cause of disability and health care costs. Current treatments are inadequate for many patients. A number of preclinical models have been developed that attempt to mimic aspects of clinical conditions that contribute to low back pain. These involve application of nucleus pulposus material near the lumbar dorsal root ganglia (DRG), chronic compression of the DRG, or localized inflammation of the DRG. These models, which are primarily implemented in rats, have many common features including behavioral hypersensitivity of the hindpaw, enhanced excitability and spontaneous activity of sensory neurons, and locally elevated levels of inflammatory mediators including cytokines. Clinically, epidural injection of steroids (glucocorticoids) is commonly used when more conservative treatments fail, but clinical trials evaluating these treatments have yielded mixed results. There are relatively few preclinical studies of steroid effects in low back pain models. One preclinical study suggests that the mineralocorticoid receptor, also present in the DRG, may have pro-inflammatory effects that oppose the activation of the glucocorticoid receptor. Although the glucocorticoid receptor is the target of anti-inflammatory steroids, many clinically used steroids activate both receptors. This could be one explanation for the limited effects of epidural steroids in some patients. Additional preclinical research is needed to address other possible reasons for limited efficacy of steroids, such as central sensitization or presence of an ongoing inflammatory stimulus in some forms of low back pain.
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Affiliation(s)
- Judith A Strong
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0531, USA
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12
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Gu X, Peng L, Yang D, Ma Q, Zheng Y, Liu C, Zhu B, Song L, Sun X, Ma Z. The respective and interaction effects of spinal GRs and MRs on radicular pain induced by chronic compression of the dorsal root ganglion in the rat. Brain Res 2011; 1396:88-95. [PMID: 21550593 DOI: 10.1016/j.brainres.2011.04.012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 04/05/2011] [Accepted: 04/07/2011] [Indexed: 01/02/2023]
Abstract
High levels of glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) are colocalized in the substantia gelatinosa. This indicates that the pain pathways appear to be under a strong regulation of these receptors. However, their respective effects on pain behaviors and their interaction remain unclear. Here we show that the nociceptive behaviors induced by chronic compression of the lumbar dorsal root ganglion (CCD) are attenuated by either GR agonist dexamethasone (4=2 μg>vehicle) or MR antagonist spironolactone (3 μg) administered intrathecally twice daily for postoperative days 2-4, whereas the GR antagonist mifepristone (2 μg) significantly exacerbated both mechanical hyperalgesia and thermal allodynia. Co-administration of spironolactone (3 μg) with dexamethasone (2 μg or 4 μg) twice daily on days 2-4 after CCD surgery produced positive synergistic effects. Moreover, different from intrathecally administered dexamethasone alone [no difference was found between two dose levels of dexamethasone (4 μg=2 μg)], dexamethasone suppresses mechanical allodynia and thermal hyperalgesia in a dose-dependent manner (4 μg>2 μg>vehicle) when combined with spironolactone (3 μg). These findings indicate that both central GRs and MRs play an important role in the regulation of pain behaviors and they have a perplexing interaction with each other. Spironolactone can enhance the analgesic effects of dexamethasone via complex mechanisms.
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Affiliation(s)
- XiaoPing Gu
- Department of Anaesthesiology, Affiliated Drum-Tower Hospital of Medical College of Nanjing University, Jiangsu Province, China
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Devor M. Ectopic discharge in Abeta afferents as a source of neuropathic pain. Exp Brain Res 2009; 196:115-28. [PMID: 19242687 DOI: 10.1007/s00221-009-1724-6] [Citation(s) in RCA: 273] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Accepted: 01/22/2009] [Indexed: 12/25/2022]
Abstract
Ectopic discharge in axotomized dorsal root ganglion neurons is a key driver of neuropathic pain. However, the bulk of this activity is generated and carried centrally in large diameter myelinated Abeta afferents, a cell type that normally signals touch and vibration sense. Evidence is considered suggesting that following axotomy, Abeta afferents undergo a change in their electrical characteristics and also in the neurotransmitter complement that they express. This dual phenotypic switching renders them capable of (1) directly driving postsynaptic pain signaling pathways in the spinal cord, and (2) triggering and maintaining central sensitization.
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Affiliation(s)
- Marshall Devor
- Department of Cell and Developmental Biology, Institute of Life Sciences and Center for Research on Pain, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
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Shin YH, Kim TH, Lee SJ, Lee CJ, Sim WS, Gwak MS, Kim CS, Hahm TS, Kim MH, Cho HS, Chung IS, Lee BD. The Effective Steroid Dose of Caudal Epidural Injection with Unilateral Epidural Catheter Position in Patients with Symptomatic Herniated Nucleus Purposus. Korean J Anesthesiol 2008. [DOI: 10.4097/kjae.2008.54.4.427] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Young Hee Shin
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Tae Hyeong Kim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Seok Jin Lee
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Chul Joong Lee
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Woo Seok Sim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Mi Sook Gwak
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Chung Soo Kim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Tae Soo Hahm
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Myung Hee Kim
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Hyun Sung Cho
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Ik Soo Chung
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Byung Dal Lee
- Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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