1
|
Qualls KA, Xie W, Zhang J, Lückemeyer DD, Lackey SV, Strong JA, Zhang JM. Mineralocorticoid Receptor Antagonism Reduces Inflammatory Pain Measures in Mice Independent of the Receptors on Sensory Neurons. Neuroscience 2024; 541:64-76. [PMID: 38307407 DOI: 10.1016/j.neuroscience.2024.01.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/24/2024] [Accepted: 01/29/2024] [Indexed: 02/04/2024]
Abstract
Corticosteroids are commonly used in the treatment of inflammatory low back pain, and their nominal target is the glucocorticoid receptor (GR) to relieve inflammation. They can also have similar potency at the mineralocorticoid receptor (MR). The MR has been shown to be widespread in rodent and human dorsal root ganglia (DRG) neurons and non-neuronal cells, and when MR antagonists are administered during a variety of inflammatory pain models in rats, pain measures are reduced. In this study we selectively knockout (KO) the MR in sensory neurons to determine the role of MR in sensory neurons of the mouse DRG in pain measures as MR antagonism during the local inflammation of the DRG (LID) pain model. We found that MR antagonism using eplerenone reduced evoked mechanical hypersensitivity during LID, but MR KO in paw-innervating sensory neurons only did not. This could be a result of differences between prolonged (MR KO) versus acute (drug) MR block or an indicator that non-neuronal cells in the DRG are driving the effect of MR antagonists. MR KO unmyelinated C neurons are more excitable under normal and inflamed conditions, while MR KO does not affect excitability of myelinated A cells. MR KO in sensory neurons causes a reduction in overall GR mRNA but is protective against reduction of the anti-inflammatory GRα isoform during LID. These effects of MR KO in sensory neurons expanded our understanding of MR's functional role in different neuronal subtypes (A and C neurons), and its interactions with the GR.
Collapse
Affiliation(s)
- Katherine A Qualls
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Wenrui Xie
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Jietong Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Debora Denardin Lückemeyer
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Sierra V Lackey
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Judith A Strong
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA
| | - Jun-Ming Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
| |
Collapse
|
2
|
Li X, Prudente AS, Prato V, Guo X, Hao H, Jones F, Figoli S, Mullen P, Wang Y, Tonnello R, Lee SH, Shah S, Maffei B, Berta T, Du X, Gamper N. Peripheral gating of pain by glial endozepine. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.20.567848. [PMID: 38045227 PMCID: PMC10690183 DOI: 10.1101/2023.11.20.567848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
We report that diazepam binding inhibitor (DBI) is a glial messenger mediating satellite glia-sensory neuron crosstalk in the dorsal root ganglion (DRG). DBI is highly and specifically expressed in satellite glia cells (SGCs) of mice, rat and human, but not in sensory neurons or other DRG-resident cells. Knockdown of DBI results in a robust mechanical hypersensitivity without significant effects on other sensory modalities. In vivo overexpression of DBI in SGCs reduces sensitivity to mechanical stimulation and alleviates mechanical allodynia in neuropathic and inflammatory pain models. We further show that DBI acts as a partial agonist and positive allosteric modulator at the neuronal GABAA receptors, particularly strongly effecting those with a high-affinity benzodiazepine binding site. Such receptors are selectively expressed by a subpopulation of mechanosensitive DRG neurons and these are also more enwrapped with DBI-expressing glia, as compared to other DRG neurons, suggesting a mechanism for specific effect of DBI on mechanosensation. These findings identified a new, peripheral neuron-glia communication mechanism modulating pain signalling, which can be targeted therapeutically.
Collapse
Affiliation(s)
- Xinmeng Li
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Arthur Silveira Prudente
- Pain Research Center, Department of Anesthesiology, University of Cincinnati Medical Center, Cincinnati, OH, USA
| | - Vincenzo Prato
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Xianchuan Guo
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Han Hao
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Frederick Jones
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
- Department of Life Sciences, Manchester Metropolitan University, Manchester, UK
| | - Sofia Figoli
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Pierce Mullen
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Yujin Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Raquel Tonnello
- Pain Research Center, Department of Anesthesiology, University of Cincinnati Medical Center, Cincinnati, OH, USA
| | - Sang Hoon Lee
- Pain Research Center, Department of Anesthesiology, University of Cincinnati Medical Center, Cincinnati, OH, USA
| | - Shihab Shah
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Benito Maffei
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Temugin Berta
- Pain Research Center, Department of Anesthesiology, University of Cincinnati Medical Center, Cincinnati, OH, USA
| | - Xiaona Du
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Nikita Gamper
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
- Faculty of Biological Sciences, School of Biomedical Sciences, University of Leeds, Leeds, UK
| |
Collapse
|
3
|
Verdoorn TA, Parry TJ, Pinna G, Lifshitz J. Neurosteroid Receptor Modulators for Treating Traumatic Brain Injury. Neurotherapeutics 2023; 20:1603-1615. [PMID: 37653253 PMCID: PMC10684848 DOI: 10.1007/s13311-023-01428-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2023] [Indexed: 09/02/2023] Open
Abstract
Traumatic brain injury (TBI) triggers wide-ranging pathology that impacts multiple biochemical and physiological systems, both inside and outside the brain. Functional recovery in patients is impeded by early onset brain edema, acute and chronic inflammation, delayed cell death, and neurovascular disruption. Drug treatments that target these deficits are under active development, but it seems likely that fully effective therapy may require interruption of the multiplicity of TBI-induced pathological processes either by a cocktail of drug treatments or a single pleiotropic drug. The complex and highly interconnected biochemical network embodied by the neurosteroid system offers multiple options for the research and development of pleiotropic drug treatments that may provide benefit for those who have suffered a TBI. This narrative review examines the neurosteroids and their signaling systems and proposes directions for their utility in the next stage of TBI drug research and development.
Collapse
Affiliation(s)
- Todd A Verdoorn
- NeuroTrauma Sciences, LLC, 2655 Northwinds Parkway, Alpharetta, GA 30009, USA.
| | - Tom J Parry
- NeuroTrauma Sciences, LLC, 2655 Northwinds Parkway, Alpharetta, GA 30009, USA
| | - Graziano Pinna
- Psychiatric Institute, Department of Psychiatry, University of Illinois at Chicago College of Medicine, 1601 W. Taylor Street, Chicago, IL 60612, USA
| | - Jonathan Lifshitz
- Department of Psychiatry, University of Arizona College of Medicine - Phoenix, 475 N. 5th Street, Phoenix, AZ 85004, USA
| |
Collapse
|
4
|
Liu J, Xie X, Qin K, Xu L, Peng J, Li X, Li X, Liu Z. Dexamethasone and potassium canrenoate alleviate hyperalgesia by competitively regulating IL-6/JAK2/STAT3 signaling pathway during inflammatory pain in vivo and in vitro. Immun Inflamm Dis 2022; 10:e721. [PMID: 36301041 PMCID: PMC9597488 DOI: 10.1002/iid3.721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 09/18/2022] [Accepted: 09/22/2022] [Indexed: 11/07/2022] Open
Abstract
Background Dexamethasone (Dexa) and potassium canrenoate (Cane) modulate nociceptive behavior via glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) by two mechanisms (genomic and nongenomic pathways). This study was designed to investigate the Dexa‐ or Cane‐mediated nongenomic and genomic effects on mechanical nociception and inflammation‐induced changes in interleukin‐6 (IL‐6) mediated signaling pathway in rats. Methods Freund's complete adjuvant (FCA) was used to trigger an inflammation of the right hind paw in male Sprague–Dawley rats. First, the mechanical nociceptive behavioral changes were examined following intraplantar administration of GR agonist Dexa and/or MR antagonist Cane in vivo. Subsequently, the protein levels of IL‐6, IL‐6Rα, JAK2, pJAK2, STAT3, pSTAT3Ser727, migration inhibitory factor, and cyclooxygenase‐2 were assessed by Western blot following intraplantar injection of Dexa or Cane or the combination. Moreover, the molecular docking studies determined the interaction between Dexa, Cane, and IL‐6. The competition binding assay was carried out using enzyme‐linked immunosorbent assays (ELISA). Results Administration of Dexa and Cane dose‐dependently attenuated FCA‐induced inflammatory pain. The sub‐additive effect of Dexa/Cane combination was elucidated by isobologram analysis, accompanied by decrease in the spinal levels of IL‐6, pJAK2, and pSTAT3Ser727. The molecular docking study demonstrated that both Dexa and Cane displayed a firm interaction with THR138 binding site of IL‐6 via a strong hydrogen bond. ELISA revealed that Dexa has a higher affinity to IL‐6 than Cane. Conclusions There was no additive or negative effect of Dexa and Cane, and they modulate the IL‐6/JAK2/STAT3 signaling pathway through competitive binding with IL‐6 and relieves hypersensitivity during inflammatory pain.
Collapse
Affiliation(s)
- Jie Liu
- Department of AnesthesiologyThe Second Affiliated Hospital of Guangzhou University of Chinese MedicineGuangzhouGuangdongChina
| | - Xiaolan Xie
- Department of AnesthesiologyThe Second Affiliated Hospital of Guangzhou University of Chinese MedicineGuangzhouGuangdongChina
| | - Kai Qin
- Department of AnesthesiologyThe Second Affiliated Hospital of Guangzhou University of Chinese MedicineGuangzhouGuangdongChina
| | - Le Xu
- Department of AnesthesiologyThe Second Affiliated Hospital of Guangzhou University of Chinese MedicineGuangzhouGuangdongChina
| | - Juxiang Peng
- Department of AnesthesiologyThe Second Affiliated Hospital of Guangzhou University of Chinese MedicineGuangzhouGuangdongChina
| | - Xiangyu Li
- Department of AnesthesiologyThe Second Affiliated Hospital of Guangzhou University of Chinese MedicineGuangzhouGuangdongChina
| | - Xiongjuan Li
- Department of Anesthesiology, Shenzhen Second People's HospitalThe First Affiliated Hospital of Shenzhen University, Health Science CenterShenzhenGuangdongChina
| | - Zhiheng Liu
- Department of Anesthesiology, Shenzhen Second People's HospitalThe First Affiliated Hospital of Shenzhen University, Health Science CenterShenzhenGuangdongChina
| |
Collapse
|
5
|
Su PYP, Zhang L, He L, Zhao N, Guan Z. The Role of Neuro-Immune Interactions in Chronic Pain: Implications for Clinical Practice. J Pain Res 2022; 15:2223-2248. [PMID: 35957964 PMCID: PMC9359791 DOI: 10.2147/jpr.s246883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Accepted: 07/19/2022] [Indexed: 11/23/2022] Open
Affiliation(s)
- Po-Yi Paul Su
- Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, CA, USA
| | - Lingyi Zhang
- Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, CA, USA
- Department of Anesthesiology, the First Affiliated Hospital, Sun Yat-Sen University, Guangzhou, People’s Republic of China
| | - Liangliang He
- Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, CA, USA
- Department of Pain Management, Xuanwu Hospital, Capital Medical University, Beijing, People’s Republic of China
| | - Na Zhao
- Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, CA, USA
| | - Zhonghui Guan
- Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, CA, USA
- Correspondence: Zhonghui Guan, Department of Anesthesia and Perioperative Care, University of California San Francisco, San Francisco, CA, USA, Tel +415.885.7246, Fax +415.885.7575, Email
| |
Collapse
|
6
|
Zhang L, Xie W, Zhang J, Shanahan H, Tonello R, Lee SH, Strong JA, Berta T, Zhang JM. Key role of CCR2-expressing macrophages in a mouse model of low back pain and radiculopathy. Brain Behav Immun 2021; 91:556-567. [PMID: 33197543 PMCID: PMC7758110 DOI: 10.1016/j.bbi.2020.11.015] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 10/12/2020] [Accepted: 11/11/2020] [Indexed: 12/12/2022] Open
Abstract
Chronic low back pain is a common condition, with high societal costs and often ineffectual treatments. Communication between macrophages/monocytes (MØ) and sensory neurons has been implicated in various preclinical pain models. However, few studies have examined specific MØ subsets, although distinct subtypes may play opposing roles. This study used a model of low back pain/radiculopathy involving direct local inflammation of the dorsal root ganglia (DRG). Reporter mice were employed that had distinct fluorescent labels for two key MØ subsets: CCR2-expressing (infiltrating pro-inflammatory) MØ, and CX3CR1-expressing (resident) macrophages. We observed that local DRG inflammation induced pain behaviors in mice, including guarding behavior and mechanical hypersensitivity, similar to the previously described rat model. The increase in MØ in the inflamed DRG was dominated by increases in CCR2+ MØ, which persisted for at least 14 days. The primary endogenous ligand for CCR2, CCL2, was upregulated in inflamed DRG. Three different experimental manipulations that reduced the CCR2+ MØ influx also reduced pain behaviors: global CCR2 knockout; systemic injection of INCB3344 (specific CCR2 blocker); and intravenous injection of liposomal clodronate. The latter two treatments when applied around the time of DRG inflammation reduced CCR2+ but not CX3CR1+ MØ in the DRG. Together these experiments suggest a key role for the CCR2/CCL2 system in establishing the pain state in this model of inflammatory low back pain and radiculopathy. Intravenous clodronate given after pain was established had the opposite effect on pain behaviors, suggesting the role of macrophages or their susceptibility to clodronate may change with time.
Collapse
Affiliation(s)
- Li Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA; Department of Anesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing 100050, China
| | - Wenrui Xie
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA
| | - Jingdong Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA
| | - Hailey Shanahan
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA
| | - Raquel Tonello
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA
| | - Sang Hoon Lee
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA
| | - Judith A Strong
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA
| | - Temugin Berta
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA
| | - Jun-Ming Zhang
- Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, OH 45040, USA.
| |
Collapse
|
7
|
Gong Q, Yin J, Wang M, He L, Lei F, Luo Y, Yang S, Feng Y, Li J, Du L. Comprehensive study of dexamethasone on albumin biogenesis during normal and pathological renal conditions. PHARMACEUTICAL BIOLOGY 2020; 58:1252-1262. [PMID: 33332210 PMCID: PMC7751422 DOI: 10.1080/13880209.2020.1855214] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Accepted: 11/19/2020] [Indexed: 06/12/2023]
Abstract
CONTEXT Dexamethasone (DXM) has an anti-immunoinflammatory effect, and is often used in acute kidney injury (AKI). However, the effects of DXM on albumin (ALB) have not been fully studied. OBJECTIVE To investigate the effects of DXM on ALB production and renal function. MATERIALS AND METHODS Male Wistar rats were divided into normal and DXM groups (0.25, 0.5, 1 mg/kg for 5 days) (n = 15) for a dose-dependent study. Rats were divided into normal group and DXM groups (0.5 mg/kg for 3, 5, 7 days) (n = 9) for a time-dependent study. In AKI experiment, rats were divided into normal (saline), cisplatin (CP, 5 mg/kg, i.v.), CP + DXM groups (0.25, 0.5 and 1 mg/kg, i.m.) (n = 16). The blood and the organs were isolated for analysis. RESULTS In normal, serum ALB (sALB) and serum total protein (sTP) increased in DXM group with sALB increased 19.8-32.2% (from small to large dosages); and 30.2-32.5.6% (from 3 to 7 days of DXM); sTP 15.7-22.6% and 14.2-24.3%; urine ALB (uALB) 31.5-392.3%, and 1047.2-1390.8%; urine TP (uTP) 0.68-173.1% and 98.0-504.9%, compared with normal groups. DXM increased the mRNA expression of Cebp and Hnf, suppressing podocin. In AKI, DXM decreased serum BUN (53.7%), serum Cre (73.4%), sALB (30.0%), sTP (18.7%), uALB (74.5%), uTP (449.3%), rescuing the suppressed podocin in kidney. CONCLUSIONS DXM acts on Cebp and Hnf and promotes ALB production. This finding helps to evaluate the rationale of DXM for kidney injury.
Collapse
Affiliation(s)
- Qin Gong
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Jilei Yin
- Department of Traditional Chinese Medicine, Jiangsu Union Technical Institute Lianyungang Branch Institute of Traditional Chinese Medicine, Lianyungang, China
| | - Mulan Wang
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Luling He
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Fan Lei
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Yingying Luo
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Shilin Yang
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Yulin Feng
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Jun Li
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
| | - Lijun Du
- School of Pharmacy, Jiangxi University of Traditional Chinese Medicine, Nanchang, China
- Pharmacology Laboratory, State Key Laboratory of Innovative Drugs and Efficient Energy-Saving Pharmaceutical Equipment, Nanchang, China
- School of Life Sciences, Tsinghua University, Beijing, China
| |
Collapse
|
8
|
Ibrahim SIA, Strong JA, Qualls KA, Ulrich-Lai YM, Zhang JM. Differential Regulation of the Glucocorticoid Receptor in a Rat Model of Inflammatory Pain. Anesth Analg 2020; 131:298-306. [PMID: 31990732 DOI: 10.1213/ane.0000000000004652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Anti-inflammatory corticosteroids are a common treatment for different conditions involving chronic pain and inflammation. Clinically used steroids target the glucocorticoid receptor (GR) for its anti-inflammatory effects. We previously reported that GR in sensory neurons may play central roles in some pain models and that GR immunoreactivity signal in dorsal root ganglia (DRG) decreased after local inflammation of the DRG (a model of low back pain). In the current study, we aimed to determine if similar changes in GR signal also exist in a skin inflammation model, the complete Freund's adjuvant (CFA) model (a model of peripheral inflammatory pain), in which the terminals of the sensory neurons rather than the somata are inflamed. METHODS A low dose of CFA was injected into the hind paw to establish the peripheral inflammation model in Sprague-Dawley rats of both sexes, as confirmed by measurements of behavior and paw swelling. Immunohistochemical and western blotting techniques were used to determine the expression pattern of the GR in the inflamed hind paw and the DRGs. Plasma corticosterone levels were measured with radioimmunoassay. RESULTS The immunohistochemical staining revealed that GR is widely expressed in the normal DRG and skin tissues. Paw injection with CFA caused upregulation of the GR in the skin tissue on postinjection day 1, mostly detected in the dermis area. However, paw inflammation significantly reduced the GR signal in the L5 DRG 1 day after the injection. The GR downregulation was still evident 14 days after CFA inflammation. On day 1, western blotting confirmed this downregulation and showed that it could also be observed in the contralateral L5 DRG, as well as in the L2 DRG (a level which does not innervate the paw). Plasma corticosterone levels were elevated in both sexes on day 14 after CFA compared to day 1, suggesting autologous downregulation of the GR by corticosterone may have contributed to the downregulation observed on day 14 but not day 1. CONCLUSIONS There are distinctive patterns of GR activation under different pain conditions, depending on the anatomical location. The observed downregulation of the GR in sensory neurons may have a significant impact on the use of steroids as treatment in these conditions and on the regulatory effects of endogenous glucocorticoids.
Collapse
Affiliation(s)
- Shaimaa I A Ibrahim
- From the Department of Anesthesiology, Pain Research Center.,Graduate Program in Molecular, Cellular, and Biochemical Pharmacology
| | | | - Katherine A Qualls
- From the Department of Anesthesiology, Pain Research Center.,Graduate Program in Molecular, Cellular, and Biochemical Pharmacology
| | - Yvonne M Ulrich-Lai
- Department of Pharmacology and Systems Physiology, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Jun-Ming Zhang
- From the Department of Anesthesiology, Pain Research Center
| |
Collapse
|