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da Silva MDV, Martelossi-Cebinelli G, Yaekashi KM, Carvalho TT, Borghi SM, Casagrande R, Verri WA. A Narrative Review of the Dorsal Root Ganglia and Spinal Cord Mechanisms of Action of Neuromodulation Therapies in Neuropathic Pain. Brain Sci 2024; 14:589. [PMID: 38928589 PMCID: PMC11202229 DOI: 10.3390/brainsci14060589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 06/05/2024] [Accepted: 06/07/2024] [Indexed: 06/28/2024] Open
Abstract
Neuropathic pain arises from injuries to the nervous system in diseases such as diabetes, infections, toxicity, and traumas. The underlying mechanism of neuropathic pain involves peripheral and central pathological modifications. Peripheral mechanisms entail nerve damage, leading to neuronal hypersensitivity and ectopic action potentials. Central sensitization involves a neuropathological process with increased responsiveness of the nociceptive neurons in the central nervous system (CNS) to their normal or subthreshold input due to persistent stimuli, leading to sustained electrical discharge, synaptic plasticity, and aberrant processing in the CNS. Current treatments, both pharmacological and non-pharmacological, aim to alleviate symptoms but often face challenges due to the complexity of neuropathic pain. Neuromodulation is emerging as an important therapeutic approach for the treatment of neuropathic pain in patients unresponsive to common therapies, by promoting the normalization of neuronal and/or glial activity and by targeting cerebral cortical regions, spinal cord, dorsal root ganglia, and nerve endings. Having a better understanding of the efficacy, adverse events and applicability of neuromodulation through pre-clinical studies is of great importance. Unveiling the mechanisms and characteristics of neuromodulation to manage neuropathic pain is essential to understand how to use it. In the present article, we review the current understanding supporting dorsal root ganglia and spinal cord neuromodulation as a therapeutic approach for neuropathic pain.
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Affiliation(s)
- Matheus Deroco Veloso da Silva
- Laboratory of Pain, Inflammation, Neuropathy and Cancer, Department of Immunology, Parasitology and General Pathology, Londrina State University, Londrina 86057-970, PR, Brazil; (M.D.V.d.S.); (G.M.-C.); (K.M.Y.); (S.M.B.)
| | - Geovana Martelossi-Cebinelli
- Laboratory of Pain, Inflammation, Neuropathy and Cancer, Department of Immunology, Parasitology and General Pathology, Londrina State University, Londrina 86057-970, PR, Brazil; (M.D.V.d.S.); (G.M.-C.); (K.M.Y.); (S.M.B.)
| | - Kelly Megumi Yaekashi
- Laboratory of Pain, Inflammation, Neuropathy and Cancer, Department of Immunology, Parasitology and General Pathology, Londrina State University, Londrina 86057-970, PR, Brazil; (M.D.V.d.S.); (G.M.-C.); (K.M.Y.); (S.M.B.)
| | - Thacyana T. Carvalho
- Department of Pediatrics, Division of Infectious Diseases and Immunology, Guerin Children’s at Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA;
| | - Sergio M. Borghi
- Laboratory of Pain, Inflammation, Neuropathy and Cancer, Department of Immunology, Parasitology and General Pathology, Londrina State University, Londrina 86057-970, PR, Brazil; (M.D.V.d.S.); (G.M.-C.); (K.M.Y.); (S.M.B.)
- Center for Research in Health Sciences, University of Northern Paraná, Londrina 86041-140, PR, Brazil
| | - Rubia Casagrande
- Department of Pharmaceutical Sciences, Center of Health Science, Londrina State University, Londrina 86038-440, PR, Brazil;
| | - Waldiceu A. Verri
- Laboratory of Pain, Inflammation, Neuropathy and Cancer, Department of Immunology, Parasitology and General Pathology, Londrina State University, Londrina 86057-970, PR, Brazil; (M.D.V.d.S.); (G.M.-C.); (K.M.Y.); (S.M.B.)
- Biological Sciences Center, State University of Londrina, Rod. Celso Garcia Cid Pr 445, KM 380, P.O. Box 10.011, Londrina 86057-970, PR, Brazil
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Wu S, Su Y, Wang Y, Wang J, Xu D, Liu Y, Yang K, Gao J, Cui J, Bai W. Region-specific response of central microglial cells to sciatic nerve demyelination through sensory and motor pathways. Histol Histopathol 2024; 39:771-781. [PMID: 38051019 DOI: 10.14670/hh-18-681] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/07/2023]
Abstract
Peripheral nerve injury can cause changes in microglial cells on the spinal dorsal and ventral horns. This region-specific response implies that central microglial cells could be activated through both sensory and motor pathways. In order to further determine how peripheral nerve injury activates central microglial cells through neural pathways, the sciatic nerve was selected as the target for neural tract tracing and demyelination. Firstly, we used cholera toxin subunit B (CTB) to map the central sensory and motor territories of the sciatic nerve. Secondly, we applied lysophosphatidylcholine to establish the model of sciatic nerve demyelination and examined the distribution of activated microglial cells via immunofluorescence with ionized calcium-binding adapter molecule 1. It was shown that CTB labeling included the transganglionically labeled sensory afferents and retrogradely labeled somata of motor neurons along the sensory and motor pathways of the sciatic nerve ipsilateral to the injection, in which sensory afferents terminated on the gracile nucleus, Clarke's nucleus, and spinal dorsal horn, while motor neurons located on the spinal ventral horn. Consistently, after sciatic nerve demyelination, the activated microglial cells were observed in the same territories as CTB-labeling, showing shortened processes and enlarged cell bodies. These results support the idea that central microglia might be activated by signals from the demyelinated sciatic nerve through both sensory and motor pathways.
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Affiliation(s)
- Shuang Wu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Yuxin Su
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Yuqing Wang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Jia Wang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Dongsheng Xu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Yihan Liu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Kunwu Yang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Junhong Gao
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China
| | - Jingjing Cui
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China.
| | - Wanzhu Bai
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, PR China.
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Florence TJ, Bari A, Vivas AC. Functional Stimulation and Imaging to Predict Neuromodulation of Chronic Low Back Pain. Neurosurg Clin N Am 2024; 35:191-197. [PMID: 38423734 DOI: 10.1016/j.nec.2023.11.004] [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] [Indexed: 03/02/2024]
Abstract
Back pain is one of the most common aversive sensations in human experience. Pain is not limited to the sensory transduction of tissue damage; rather, it encompasses a range of nervous system activities including lateral modulation, long-distance transmission, encoding, and decoding. Although spine surgery may address peripheral pain generators directly, aberrant signals along canonical aversive pathways and maladaptive influence of affective and cognitive states can result in persistent subjective pain refractory to classical surgical intervention. The clinical identification of who will benefit from surgery-and who will not-is increasingly grounded in neurophysiology.
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Affiliation(s)
- Timothy J Florence
- UCLA Neurosurgery, 300 Stein Plaza Driveway, Suite 562, Los Angeles, CA 90095, USA
| | - Ausaf Bari
- UCLA Neurosurgery, 300 Stein Plaza Driveway, Suite 562, Los Angeles, CA 90095, USA
| | - Andrew C Vivas
- UCLA Neurosurgery, 300 Stein Plaza Driveway, Suite 562, Los Angeles, CA 90095, USA.
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4
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Wolf-Johnston A, Ikeda Y, Zabbarova I, Kanai AJ, Bastacky S, Moldwin R, Stern JN, Jackson EK, Birder LA. Purine nucleoside phosphorylase inhibition is an effective approach for the treatment of chemical hemorrhagic cystitis. JCI Insight 2024; 9:e176103. [PMID: 38271096 PMCID: PMC10972598 DOI: 10.1172/jci.insight.176103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Accepted: 01/22/2024] [Indexed: 01/27/2024] Open
Abstract
Hemorrhagic cystitis may be induced by infection, radiation therapy, or medications or may be idiopathic. Along with hemorrhagic features, symptoms include urinary urgency and frequency, dysuria (painful urination), and visceral pain. Cystitis-induced visceral pain is one of the most challenging types of pain to treat, and an effective treatment would address a major unmet medical need. We assessed the efficacy of a purine nucleoside phosphorylase inhibitor, 8-aminoguanine (8-AG), for the treatment of hemorrhagic/ulcerative cystitis. Lower urinary tract (LUT) function and structure were assessed in adult Sprague-Dawley rats, treated chronically with cyclophosphamide (CYP; sacrificed day 8) and randomized to daily oral treatment with 8-AG (begun 14 days prior to CYP induction) or its vehicle. CYP-treated rats exhibited multiple abnormalities, including increased urinary frequency and neural mechanosensitivity, reduced bladder levels of inosine, urothelial inflammation/damage, and activation of spinal cord microglia, which is associated with pain hypersensitivity. 8-AG treatment of CYP-treated rats normalized all observed histological, structural, biochemical, and physiological abnormalities. In cystitis 8-AG improved function and reduced both pain and inflammation likely by increasing inosine, a tissue-protective purine metabolite. These findings demonstrate that 8-AG has translational potential for reducing pain and preventing bladder damage in cystitis-associated LUT dysfunctions.
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Affiliation(s)
| | - Youko Ikeda
- Renal-Electrolyte Division, Department of Medicine
| | | | - Anthony J Kanai
- Renal-Electrolyte Division, Department of Medicine
- Department of Pharmacology and Chemical Biology; and
| | - Sheldon Bastacky
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Robert Moldwin
- Arthur Smith Institute for Urology, Northwell Health, Zucker School of Medicine at Hofstra/Northwell, Lake Success, New York, USA
| | - Joel Nh Stern
- Arthur Smith Institute for Urology, Northwell Health, Zucker School of Medicine at Hofstra/Northwell, Lake Success, New York, USA
| | | | - Lori A Birder
- Renal-Electrolyte Division, Department of Medicine
- Department of Pharmacology and Chemical Biology; and
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Chen S, Wang H, Du J, Ding Z, Wang T, Zhang L, Yang J, Guan Y, Chen C, Li M, Hei Z, Tao Y, Yao W. Near-infrared light-activatable, analgesic nanocomposite delivery system for comprehensive therapy of diabetic wounds in rats. Biomaterials 2024; 305:122467. [PMID: 38224643 DOI: 10.1016/j.biomaterials.2024.122467] [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: 10/19/2023] [Revised: 12/31/2023] [Accepted: 01/03/2024] [Indexed: 01/17/2024]
Abstract
Impaired angiogenesis, bacterial infection, persistent severe pain, exacerbated inflammation, and oxidative stress injury are intractable problems in the treatment of chronic diabetic ulcer wounds. A strategy that effectively targets all these issues has proven challenging. Herein, an in-situ sprayable nanoparticle-gel composite comprising platinum clusters (Pt) loaded-mesoporous polydopamine (MPDA) nanoparticle and QX-314-loaded fibrin gel (Pt@MPDA/QX314@Fibrin) was developed for diabetic wound analgesia and therapy. The composite shows good local analgesic effect of QX-314 mediated by near-infrared light (NIR) activation of transient receptor potential vanilloid 1 (TRPV1) channel, as well as multifunctional therapeutic effects of rapid hemostasis, anti-inflammation, antioxidation, and antibacterial properties that benefit the fast-healing of diabetic wounds. Furthermore, it demonstrates that the composite, with good biodegradability and biosafety, significantly relieved wound pain by inhibiting the expression of c-Fos in the dorsal root ganglion and the activation of glial cells in the spinal cord dorsal horn. Consequently, our designed sprayable Pt@MPDA/QX314@Fibrin composite with good biocompatibility, NIR activation of TRPV1 channel-mediated QX-314 local wound analgesia and comprehensive treatments, is promising for chronic diabetic wound therapy.
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Affiliation(s)
- Sufang Chen
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China; Laboratory of Biomaterials and Translational Medicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Haixia Wang
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China; Laboratory of Biomaterials and Translational Medicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China; Guangdong Provincial Key Laboratory of Liver Disease Research, Guangzhou, 510630, China
| | - Jingyi Du
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Zhendong Ding
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Tienan Wang
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Linan Zhang
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Jing Yang
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Yu Guan
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Chaojin Chen
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China
| | - Mingqiang Li
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China; Laboratory of Biomaterials and Translational Medicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China; Guangdong Provincial Key Laboratory of Liver Disease Research, Guangzhou, 510630, China
| | - Ziqing Hei
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China.
| | - Yu Tao
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China; Laboratory of Biomaterials and Translational Medicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China; Guangdong Provincial Key Laboratory of Liver Disease Research, Guangzhou, 510630, China.
| | - Weifeng Yao
- Department of Anesthesiology and Center for Nanomedicine, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, 510630, China.
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Ummadisetty O, Akhilesh, Gadepalli A, Chouhan D, Tiwari V. Development and validation of clinically Mimicable model of frostbite injury-induced chronic pain. Cell Signal 2024; 115:111028. [PMID: 38176530 DOI: 10.1016/j.cellsig.2023.111028] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 12/17/2023] [Accepted: 12/28/2023] [Indexed: 01/06/2024]
Abstract
Frostbite, a debilitating condition, significantly affects the well-being of military veterans and high-altitude residents, causing severe clinical complications such as chronic pain that markedly impacts overall quality of life. There has been a notable increase in the development of pre-clinical models for studying frostbite injury, but their suitability for pain evaluation remains limited. The major hurdle in the development of novel therapeutics for the treatment of frostbite-induced chronic pain is the unavailability of well-established preclinical models. In this study, we employed deep-frozen magnets to induce frostbite injury and conducted validation for chronic pain through assessments of face, predictive, and mechanistic validity. Behavioral assays demonstrated that frostbite injury exhibited significant mechanical, thermal & cold hypersensitivity in rats. Further, molecular analysis indicated that frostbite injury triggered the activation of TRP channels (TRPA1, TRPV1 and TRPM8), microgliosis, and neuroinflammation in the dorsal root ganglion (DRG) and spinal cord of rats. Notably, NR2B protein expressions were significantly upregulated in the DRG of injured rats, while no changes were observed in spinal NR2B expressions. Furthermore, the administration of ibuprofen (25, 50, and 100 mg/kg, i.p.) resulted in a significant improvement in behavioral, biochemical, and molecular alterations in frostbite-injured rats. Overall, results suggested that established frostbite model effectively recapitulates face, pharmacological, and mechanistic validity, highlighting its potential for screening future treatment modalities and exploring the intricate mechanisms associated with frostbite-induced chronic pain.
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Affiliation(s)
- Obulapathi Ummadisetty
- Neuroscience and Pain Research Laboratory, Department of Pharmaceutical Engineering & Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pradesh, India
| | - Akhilesh
- Neuroscience and Pain Research Laboratory, Department of Pharmaceutical Engineering & Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pradesh, India
| | - Anagha Gadepalli
- Neuroscience and Pain Research Laboratory, Department of Pharmaceutical Engineering & Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pradesh, India
| | - Deepak Chouhan
- Neuroscience and Pain Research Laboratory, Department of Pharmaceutical Engineering & Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pradesh, India
| | - Vinod Tiwari
- Neuroscience and Pain Research Laboratory, Department of Pharmaceutical Engineering & Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi, Uttar Pradesh, India.
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Chen X, Tang SJ. Neural Circuitry Polarization in the Spinal Dorsal Horn (SDH): A Novel Form of Dysregulated Circuitry Plasticity during Pain Pathogenesis. Cells 2024; 13:398. [PMID: 38474361 PMCID: PMC10930392 DOI: 10.3390/cells13050398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2024] [Revised: 02/20/2024] [Accepted: 02/23/2024] [Indexed: 03/14/2024] Open
Abstract
Pathological pain emerges from nociceptive system dysfunction, resulting in heightened pain circuit activity. Various forms of circuitry plasticity, such as central sensitization, synaptic plasticity, homeostatic plasticity, and excitation/inhibition balance, contribute to the malfunction of neural circuits during pain pathogenesis. Recently, a new form of plasticity in the spinal dorsal horn (SDH), named neural circuit polarization (NCP), was discovered in pain models induced by HIV-1 gp120 and chronic morphine administration. NCP manifests as an increase in excitatory postsynaptic currents (EPSCs) in excitatory neurons and a decrease in EPSCs in inhibitory neurons, presumably facilitating hyperactivation of pain circuits. The expression of NCP is associated with astrogliosis. Ablation of reactive astrocytes or suppression of astrogliosis blocks NCP and, concomitantly, the development of gp120- or morphine-induced pain. In this review, we aim to compare and integrate NCP with other forms of plasticity in pain circuits to improve the understanding of the pathogenic contribution of NCP and its cooperation with other forms of circuitry plasticity during the development of pathological pain.
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Affiliation(s)
| | - Shao-Jun Tang
- Stony Brook University Pain and Anesthesia Research Center (SPARC), Department of Anesthesiology, Stony Brook University, Stony Brook, NY 11794, USA;
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Chen O, Luo X, Ji RR. Macrophages and microglia in inflammation and neuroinflammation underlying different pain states. MEDICAL REVIEW (2021) 2023; 3:381-407. [PMID: 38283253 PMCID: PMC10811354 DOI: 10.1515/mr-2023-0034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 09/26/2023] [Indexed: 01/30/2024]
Abstract
Pain is a main symptom in inflammation, and inflammation induces pain via inflammatory mediators acting on nociceptive neurons. Macrophages and microglia are distinct cell types, representing immune cells and glial cells, respectively, but they share similar roles in pain regulation. Macrophages are key regulators of inflammation and pain. Macrophage polarization plays different roles in inducing and resolving pain. Notably, macrophage polarization and phagocytosis can be induced by specialized pro-resolution mediators (SPMs). SPMs also potently inhibit inflammatory and neuropathic pain via immunomodulation and neuromodulation. In this review, we discuss macrophage signaling involved in pain induction and resolution, as well as in maintaining physiological pain. Microglia are macrophage-like cells in the central nervous system (CNS) and drive neuroinflammation and pathological pain in various inflammatory and neurological disorders. Microglia-produced inflammatory cytokines can potently regulate excitatory and inhibitory synaptic transmission as neuromodulators. We also highlight sex differences in macrophage and microglial signaling in inflammatory and neuropathic pain. Thus, targeting macrophage and microglial signaling in distinct locations via pharmacological approaches, including immunotherapies, and non-pharmacological approaches will help to control chronic inflammation and chronic pain.
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Affiliation(s)
- Ouyang Chen
- Department of Anesthesiology, Center for Translational Pain Medicine, Duke University Medical Center, Durham, NC, USA
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
| | - Xin Luo
- Department of Anesthesiology, Center for Translational Pain Medicine, Duke University Medical Center, Durham, NC, USA
- Guangdong-Hong Kong-Macao Greater Bay Area Center for Brain Science and Brain-Inspired Intelligence, Southern Medical University, Guangzhou, Guangdong Province, China
| | - Ru-Rong Ji
- Department of Anesthesiology, Center for Translational Pain Medicine, Duke University Medical Center, Durham, NC, USA
- Department of Cell Biology, Duke University Medical Center, Durham, NC, USA
- Department of Neurobiology, Duke University Medical Center, Durham, NC, USA
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Cui JJ, Wang J, Xu DS, Wu S, Guo YT, Su YX, Liu YH, Wang YQ, Jing XH, Bai WZ. Alexa Fluor 488-conjugated cholera toxin subunit B optimally labels neurons 3-7 days after injection into the rat gastrocnemius muscle. Neural Regen Res 2022; 17:2316-2320. [PMID: 35259856 PMCID: PMC9083145 DOI: 10.4103/1673-5374.337055] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Neural tract tracing is used to study neural pathways and evaluate neuronal regeneration following nerve injuries. However, it is not always clear which tracer should be used to yield optimal results. In this study, we examined the use of Alexa Fluor 488-conjugated cholera toxin subunit B (AF488-CTB). This was injected into the gastrocnemius muscle of rats, and it was found that motor, sensory, and sympathetic neurons were labeled in the spinal ventral horn, dorsal root ganglia, and sympathetic chain, respectively. Similar results were obtained when we injected AF594-CTB into the tibialis anterior muscle. The morphology and number of neurons were evaluated at different time points following the AF488-CTB injection. It was found that labeled motor and sensory neurons could be observed 12 hours post-injection. The intensity was found to increase over time, and the morphology appeared clear and complete 3-7 days post-injection, with clearly distinguishable motor neuron axons and dendrites. However, 14 days after the injection, the quality of the images decreased and the neurons appeared blurred and incomplete. Nissl and immunohistochemical staining showed that the AF488-CTB-labeled neurons retained normal neurochemical and morphological features, and the surrounding microglia were also found to be unaltered. Overall, these results imply that the cholera toxin subunit B, whether unconjugated or conjugated with Alexa Fluor, is effective for retrograde tracing in muscular tissues and that it would also be suitable for evaluating the regeneration or degeneration of injured nerves.
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Affiliation(s)
- Jing-Jing Cui
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Jia Wang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Dong-Sheng Xu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Shuang Wu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Ya-Ting Guo
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yu-Xin Su
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yi-Han Liu
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yu-Qing Wang
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Xiang-Hong Jing
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
| | - Wan-Zhu Bai
- Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences, Beijing, China
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10
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Pike CK, Kim M, Schnitzer K, Mercaldo N, Edwards R, Napadow V, Zhang Y, Morrissey EJ, Alshelh Z, Evins AE, Loggia ML, Gilman JM. Study protocol for a phase II, double-blind, randomised controlled trial of cannabidiol (CBD) compared with placebo for reduction of brain neuroinflammation in adults with chronic low back pain. BMJ Open 2022; 12:e063613. [PMID: 36123113 PMCID: PMC9486315 DOI: 10.1136/bmjopen-2022-063613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
INTRODUCTION Chronic pain is a debilitating medical problem that is difficult to treat. Neuroinflammatory pathways have emerged as a potential therapeutic target, as preclinical studies have demonstrated that glial cells and neuroglial interactions play a role in the establishment and maintenance of pain. Recently, we used positron emission tomography (PET) to demonstrate increased levels of 18 kDa translocator protein (TSPO) binding, a marker of glial activation, in patients with chronic low back pain (cLBP). Cannabidiol (CBD) is a glial inhibitor in animal models, but studies have not assessed whether CBD reduces neuroinflammation in humans. The principal aim of this trial is to evaluate whether CBD, compared with placebo, affects neuroinflammation, as measured by TSPO levels. METHODS AND ANALYSIS This is a double-blind, randomised, placebo-controlled, phase II clinical trial. Eighty adults (aged 18-75) with cLBP for >6 months will be randomised to either an FDA-approved CBD medication (Epidiolex) or matching placebo for 4 weeks using a dose-escalation design. All participants will undergo integrated PET/MRI at baseline and after 4 weeks of treatment to evaluate neuroinflammation using [11C]PBR28, a second-generation radioligand for TSPO. Our primary hypothesis is that participants randomised to CBD will demonstrate larger reductions in thalamic [11C]PBR28 signal compared with those receiving placebo. We will also assess the effect of CBD on (1) [11C]PBR28 signal from limbic regions, which our prior work has linked to depressive symptoms and (2) striatal activation in response to a reward task. Additionally, we will evaluate self-report measures of cLBP intensity and bothersomeness, depression and quality of life at baseline and 4 weeks. ETHICS AND DISSEMINATION This protocol is approved by the Massachusetts General Brigham Human Research Committee (protocol number: 2021P002617) and FDA (IND number: 143861) and registered with ClinicalTrials.gov. Results will be published in peer-reviewed journals and presented at conferences. TRIAL REGISTRATION NUMBER NCT05066308; ClinicalTrials.gov.
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Affiliation(s)
- Chelsea K Pike
- Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA
- Massachusetts General Hospital Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
| | - Minhae Kim
- Massachusetts General Hospital Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
| | - Kristina Schnitzer
- Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA
| | - Nathaniel Mercaldo
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Robert Edwards
- Department of Anesthesiology, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Vitaly Napadow
- Massachusetts General Hospital Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
- Department of Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Charlestown, Massachusetts, USA
| | - Yi Zhang
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Erin Janas Morrissey
- Massachusetts General Hospital Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
| | - Zeynab Alshelh
- Massachusetts General Hospital Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
| | - A Eden Evins
- Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA
| | - Marco L Loggia
- Massachusetts General Hospital Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
- Department of Radiology, Harvard Medical School, Boston, Massachusetts, USA
- Department of Anesthesia, Critical Care and Pain Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA
| | - Jodi M Gilman
- Department of Psychiatry, Massachusetts General Hospital, Boston, Massachusetts, USA
- Massachusetts General Hospital Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, Massachusetts, USA
- Department of Psychiatry, Harvard Medical School, Boston, Massachusetts, USA
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11
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Neuroimmune Mechanisms Underlying Neuropathic Pain: The Potential Role of TNF-α-Necroptosis Pathway. Int J Mol Sci 2022; 23:ijms23137191. [PMID: 35806192 PMCID: PMC9266916 DOI: 10.3390/ijms23137191] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 06/24/2022] [Accepted: 06/27/2022] [Indexed: 02/05/2023] Open
Abstract
The neuroimmune mechanism underlying neuropathic pain has been extensively studied. Tumor necrosis factor-alpha (TNF-α), a key pro-inflammatory cytokine that drives cytokine storm and stimulates a cascade of other cytokines in pain-related pathways, induces and modulates neuropathic pain by facilitating peripheral (primary afferents) and central (spinal cord) sensitization. Functionally, TNF-α controls the balance between cell survival and death by inducing an inflammatory response and two programmed cell death mechanisms (apoptosis and necroptosis). Necroptosis, a novel form of programmed cell death, is receiving increasing attraction and may trigger neuroinflammation to promote neuropathic pain. Chronic pain is often accompanied by adverse pain-associated emotional reactions and cognitive disorders. Overproduction of TNF-α in supraspinal structures such as the anterior cingulate cortex (ACC) and hippocampus plays an important role in pain-associated emotional disorders and memory deficits and also participates in the modulation of pain transduction. At present, studies reporting on the role of the TNF-α–necroptosis pathway in pain-related disorders are lacking. This review indicates the important research prospects of this pathway in pain modulation based on its role in anxiety, depression and memory deficits associated with other neurodegenerative diseases. In addition, we have summarized studies related to the underlying mechanisms of neuropathic pain mediated by TNF-α and discussed the role of the TNF-α–necroptosis pathway in detail, which may represent an avenue for future therapeutic intervention.
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12
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Silva R, Malcangio M. Fractalkine/CX 3CR 1 Pathway in Neuropathic Pain: An Update. FRONTIERS IN PAIN RESEARCH 2022; 2:684684. [PMID: 35295489 PMCID: PMC8915718 DOI: 10.3389/fpain.2021.684684] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 06/30/2021] [Indexed: 01/23/2023] Open
Abstract
Injuries to the nervous system can result in a debilitating neuropathic pain state that is often resistant to treatment with available analgesics, which are commonly associated with several side-effects. Growing pre-clinical and clinical evidence over the last two decades indicates that immune cell-mediated mechanisms both in the periphery and in the Central Nervous System (CNS) play significant roles in the establishment and maintenance of neuropathic pain. Specifically, following peripheral nerve injury, microglia, which are CNS resident immune cells, respond to the activity of the first pain synapse in the dorsal horn of spinal cord and also to neuronal activity in higher centres in the brain. This microglial response leads to the production and release of several proinflammatory mediators which contribute to neuronal sensitisation under neuropathic pain states. In this review, we collect evidence demonstrating the critical role played by the Fractalkine/CX3CR1 signalling pathway in neuron-to-microglia communication in neuropathic pain states and explore how strategies that include components of this pathway offer opportunities for innovative targets for neuropathic pain.
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Affiliation(s)
- Rita Silva
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
| | - Marzia Malcangio
- Wolfson Centre for Age-Related Diseases, King's College London, London, United Kingdom
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13
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Wang TF, Wu SY, Pan BS, Tsai SF, Kuo YM. Inhibition of Nigral Microglial Activation Reduces Age-Related Loss of Dopaminergic Neurons and Motor Deficits. Cells 2022; 11:cells11030481. [PMID: 35159290 PMCID: PMC8834087 DOI: 10.3390/cells11030481] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 12/17/2022] Open
Abstract
Parkinson's disease (PD) is an age-related neurodegenerative disease caused by a selective loss of dopaminergic (DA) neurons in the substantia nigra (SN). Microglial activation is implicated in the pathogenesis of PD. This study aimed to characterize the role of microglial activation in aging-related nigral DA neuron loss and motor deficits in mice. We showed that, compared to 3-month-old mice, the number of DA neurons in the SN and the expression of dopamine transporter (DAT) in the striatum decreased during the period of 9 to 12 months of age. Motor deficits and microglial activation in the SN were also evident during these months. The number of DA neurons was negatively correlated with the degrees of microglial activation. The inhibition of age-related microglial activation by ibuprofen during these 3 months decreased DA neuron loss in the SN. Eliminating the microglia prevented systemic inflammation-induced DA neuron death. Forcing mice to run during these 3 months inhibited microglial activation and DA neuron loss. Blocking the brain-derived neurotrophic factor (BDNF) signaling eliminated the exercise-induced protective effects. In conclusion, nigral DA neurons were susceptible to local microglial activation. Running exercise upregulated BDNF-TrkB signaling and inhibited microglial activation during aging. Long-term exercise can be considered as a non-pharmacological strategy to ameliorate microglial activation and related neurodegeneration.
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Affiliation(s)
- Tzu-Feng Wang
- Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Cheng Kung University and Academia Sinica, Taipei 11529, Taiwan;
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
| | - Shih-Ying Wu
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
- Department of Cancer Biology, Wake Forest Baptist Medical Center, Wake Forest University, Winston Salem, NC 27157, USA
| | - Bo-Syong Pan
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
- Department of Cancer Biology, Wake Forest Baptist Medical Center, Wake Forest University, Winston Salem, NC 27157, USA
| | - Sheng-Feng Tsai
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
| | - Yu-Min Kuo
- Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Cheng Kung University and Academia Sinica, Taipei 11529, Taiwan;
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
- Correspondence: ; Tel.: +886-6-2353535 (ext. 5294); Fax: +886-6-2093007
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14
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Dworsky-Fried Z, Faig CA, Vogel HA, Kerr BJ, Taylor AMW. Central amygdala inflammation drives pain hypersensitivity and attenuates morphine analgesia in experimental autoimmune encephalomyelitis. Pain 2022; 163:e49-e61. [PMID: 33863858 DOI: 10.1097/j.pain.0000000000002307] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 03/23/2021] [Indexed: 11/25/2022]
Abstract
ABSTRACT Chronic pain is a highly prevalent symptom associated with the autoimmune disorder multiple sclerosis (MS). The central nucleus of the amygdala plays a critical role in pain processing and modulation. Neuropathic pain alters nociceptive signaling in the central amygdala, contributing to pain chronicity and opioid tolerance. Here, we demonstrate that activated microglia within the central amygdala disrupt nociceptive sensory processing and contribute to pain hypersensitivity in experimental autoimmune encephalomyelitis (EAE), the most frequently used animal model of MS. Male and female mice with EAE exhibited differences in microglial morphology in the central amygdala, which was associated with heat hyperalgesia, impaired morphine reward, and reduced morphine antinociception in females. Animals with EAE displayed a lack of morphine-evoked activity in cells expressing somatostatin within the central amygdala, which drive antinociception. Induction of focal microglial activation in naïve mice via injection of lipopolysaccharide into the central amygdala produced a loss of morphine analgesia in females, similar to as observed in EAE animals. Our data indicate that activated microglia within the central amygdala may contribute to the sexually dimorphic effects of morphine and may drive neuronal adaptations that lead to pain hypersensitivity in EAE. Our results provide a possible mechanism underlying the decreased efficacy of opioid analgesics in the management of MS-related pain, identifying microglial activation as a potential therapeutic target for pain symptoms in this patient population.
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Affiliation(s)
- Zoë Dworsky-Fried
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Christian A Faig
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Holly A Vogel
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
| | - Bradley J Kerr
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
- Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, AB, Canada
| | - Anna M W Taylor
- Department of Pharmacology, University of Alberta, Edmonton, AB, Canada
- Neuroscience and Mental Health Institute, University of Alberta, Edmonton, AB, Canada
- Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, AB, Canada
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15
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Yeo JH, Kim SJ, Roh DH. Rapamycin reduces orofacial nociceptive responses and microglial p38 mitogen-activated protein kinase phosphorylation in trigeminal nucleus caudalis in mouse orofacial formalin model. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2021; 25:365-374. [PMID: 34187953 PMCID: PMC8255123 DOI: 10.4196/kjpp.2021.25.4.365] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 05/07/2021] [Accepted: 05/21/2021] [Indexed: 12/30/2022]
Abstract
The mammalian target of rapamycin (mTOR) plays a role in various cellular phenomena, including autophagy, cell proliferation, and differentiation. Although recent studies have reported its involvement in nociceptive responses in several pain models, whether mTOR is involved in orofacial pain processing is currently unexplored. This study determined whether rapamycin, an mTOR inhibitor, reduces nociceptive responses and the number of Fos-immunoreactive (Fos-ir) cells in the trigeminal nucleus caudalis (TNC) in a mouse orofacial formalin model. We also examined whether the glial cell expression and phosphorylated p38 (p-p38) mitogen-activated protein kinases (MAPKs) in the TNC are affected by rapamycin. Mice were intraperitoneally given rapamycin (0.1, 0.3, or 1.0 mg/kg); then, 30 min after, 5% formalin (10 µl) was subcutaneously injected into the right upper lip. The rubbing responses with the ipsilateral forepaw or hindpaw were counted for 45 min. High-dose rapamycin (1.0 mg/kg) produced significant antinociceptive effects in both the first and second phases of formalin test. The number of Fos-ir cells in the ipsilateral TNC was also reduced by high-dose rapamycin compared with vehicle-treated animals. Furthermore, the number of p-p38-ir cells the in ipsilateral TNC was significantly decreased in animals treated with high-dose rapamycin; p-p38 expression was co-localized in microglia, but not neurons and astrocytes. Therefore, the mTOR inhibitor, rapamycin, reduces orofacial nociception and Fos expression in the TNC, and its antinociceptive action on orofacial pain may be associated with the inhibition of p-p38 MAPK in the microglia.
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Affiliation(s)
- Ji-Hee Yeo
- Department of Oral Physiology, School of Dentistry, Kyung Hee University, Seoul 02447, Korea
| | - Sol-Ji Kim
- Department of Oral Physiology, School of Dentistry, Kyung Hee University, Seoul 02447, Korea
| | - Dae-Hyun Roh
- Department of Oral Physiology, School of Dentistry, Kyung Hee University, Seoul 02447, Korea
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16
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Szeredi ID, Jancsó G, Oszlács O, Sántha P. Prior perineural or neonatal treatment with capsaicin does not alter the development of spinal microgliosis induced by peripheral nerve injury. Cell Tissue Res 2021; 383:677-692. [PMID: 32960358 PMCID: PMC7904541 DOI: 10.1007/s00441-020-03285-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2020] [Accepted: 08/14/2020] [Indexed: 11/28/2022]
Abstract
Peripheral nerve injury is associated with spinal microgliosis which plays a pivotal role in the development of neuropathic pain behavior. Several agents of primary afferent origin causing the microglial reaction have been identified, but the type(s) of primary afferents that release these mediators are still unclear. In this study, specific labeling of C-fiber spinal afferents by lectin histochemistry and selective chemodenervation by capsaicin were applied to identify the type(s) of primary afferents involved in the microglial response. Comparative quantitative morphometric evaluation of the microglial reaction in central projection territories of intact and injured peripheral nerves in the superficial (laminae I and II) and deep (laminae III and IV) spinal dorsal horn revealed a significant, about three-fold increase in microglial density after transection of the sciatic or the saphenous nerve. Prior perineural treatment of these nerves with capsaicin, resulting in a selective defunctionalization of C-fiber afferent fibers failed to affect spinal microgliosis. Similarly, peripheral nerve injury-induced increase in microglial density was unaffected in rats treated neonatally with capsaicin known to result in a near-total loss of C-fiber dorsal root fibers. Perineural treatment with capsaicin per se did not evoke a significant increase in microglial density. These observations indicate that injury-induced spinal microgliosis may be attributed to phenotypic changes in injured myelinated primary afferent neurons, whereas the contribution of C-fiber primary sensory neurons to this neuroimmune response is negligible. Spinal myelinated primary afferents may play a hitherto unrecognized role in regulation of neuroimmune and perisynaptic microenvironments of the spinal dorsal horn.
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Affiliation(s)
- Ivett Dorina Szeredi
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary
| | - Gábor Jancsó
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary
| | - Orsolya Oszlács
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary
| | - Péter Sántha
- Department of Physiology, University of Szeged, Dóm tér 10, Szeged, H-6720, Hungary.
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17
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Hu X, Liu Y, Wu J, Liu Y, Liu W, Chen J, Yang F. Inhibition of P2X7R in the amygdala ameliorates symptoms of neuropathic pain after spared nerve injury in rats. Brain Behav Immun 2020; 88:507-514. [PMID: 32311494 DOI: 10.1016/j.bbi.2020.04.030] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 03/23/2020] [Accepted: 04/11/2020] [Indexed: 12/26/2022] Open
Abstract
The amygdala circuitry and P2X7 receptor (P2X7R) have both been shown to play important roles in the modulation of neuropathic pain (NP). However, little is known about the functional role of P2X7R in the amygdala for the regulation of NP. This study aims to evaluate the alleviative effect of intra-amygdala microinfusion of a pharmacological antagonist of P2X7R (A-438079) on NP and explore its possible mechanism of action. Male Sprague-Dawley rats were used to construct the animal model of NP through spared nerve injury (SNI). The SNI rats randomly received chronic bilateral microinjection of A-438079 (100 pmol/side) or saline into the amygdalae via cannulas. Mechanical paw withdrawal threshold (MWT) and thermal withdrawal duration (TWD) were measured by von Frey monofilaments. Besides, tail suspension test (TST), forced swimming test (FST), open field test (OFT) and sucrose preference test (SPT) were performed to assess depression- and anxiety-like behaviors. Immunofluorescence assay was employed to determine the levels of glial fibrillary acidic protein (GFAP), ionized calcium binding adaptor molecule 1 (IBA-1) and connexin 43 (Cx43) in the spinal cord. In addition, the change of growth associated protein 43 (GAP43) level in the spinal cord was assessed by Western blot. Our data showed that chronic treatment with A-438079 increased MWT and decreased TWD on days 11-21 post-SNI while decreased depression-like and anxiety-like behaviors. A-438079 administration significantly attenuated the elevated immunoreactivities of IBA-1 and GFAP in microglia and astrocytes after SNI. Furthermore, the decreased expression of GAP-43 in the spinal cord due to SNI was significantly attenuated by A-438079. However, when A-438079 and a pharmacological agonist (BzATP) of P2X7R were given simultaneously, all the effects caused by A-438079 alone were reversed. In brief, our study revealed the protective role of inhibiting P2X7R in the amygdala against symptoms associated with NP, possibly attributing to its inhibitory effects on spinal microglia and astrocytes.
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Affiliation(s)
- Xiaoling Hu
- Department of Anesthesiology, The First Affiliated Hospital of University of South China, Hunan Province 421001, China
| | - Yiming Liu
- Department of Anesthesiology, Affiliated Nanhua Hospital, University of South China, Hunan Province 421001, China
| | - Junting Wu
- Department of Anesthesiology, The First Affiliated Hospital of University of South China, Hunan Province 421001, China
| | - Yu Liu
- Department of Anesthesiology, The First Affiliated Hospital of University of South China, Hunan Province 421001, China
| | - Wenjie Liu
- Department of Anesthesiology, The First Affiliated Hospital of University of South China, Hunan Province 421001, China
| | - Ji Chen
- Department of Endocrinology, The First Affiliated Hospital of University of South China, Hunan Province 421001, China
| | - Fengrui Yang
- Department of Anesthesiology, The First Affiliated Hospital of University of South China, Hunan Province 421001, China; Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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18
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Arman A, Deng F, Goldys EM, Liu G, Hutchinson MR. In vivo intrathecal IL-1β quantification in rats: Monitoring the molecular signals of neuropathic pain. Brain Behav Immun 2020; 88:442-450. [PMID: 32272226 DOI: 10.1016/j.bbi.2020.04.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 04/03/2020] [Accepted: 04/04/2020] [Indexed: 10/24/2022] Open
Abstract
BACKGROUND Neuropathic pain, or pain after nerve injury, is a disorder with a significant reliance on the signalling of cytokines such as IL-1β. However, quantifying the cytokine release repeatedly over time in vivo is technically challenging. AIM To evaluate if changes in IL-1β are correlated with the presentation of mechanical allodynia over time, by repeatedly quantifying intrathecal IL-1β concentrations following chronic constriction injury of the sciatic nerve in rats. Also, to establish any possible correlation between biochemical spinal marker expression and the in vivo quantification of IL-1β. Finally, to assess the expression of the mature IL-1β in lumbar spinal cord samples. METHOD The Chronic Constriction Injury model (CCI) was used to initiate nerve injury in male Sprague Dawley rats and the generation of behavioural mechanical allodynia was quantified. Using an indwelling intrathecal catheter, a stainless steel (SS) wire biosensing device was repeatedly introduced to quantify intrathecal IL-1β concentrations at three timepoints of 0, 7, and 14 days post CCI. Fixed spinal cord samples (L4-L5), collected on day 14, were imaged for the expression of glial fibrillary acidic protein (GFAP, astrocytes) and ionized calcium binding adaptor molecule 1 (IBA1, microglia). Snap frozen spinal cord tissues (L4-L5) were also processed for western blot analysis. RESULTS Using the novel SS based biosensing device we established that CCI caused a significant increase in intrathecal IL-1β concentrations from day 0 to day 7 (p = 0.001) and to day 14 (p < 0.0001), while the sham group did not show any significant increase. We also further showed that the degree of mechanical allodynia correlated positively with the increase in the intrathecal concentration of IL-1β in the active CCI animals (p = 0.0007). While there was a significant increase in the ipsilateral GFAP expression in injured animals compared to sham animals (p = 0.03), we did not find any significant correlation between in vivo IL-1β concentration on days 7 and 14 and the area of dorsal horn GFAP or IBA1 positive structures on day 14. The result of western blot analysis of whole lumbar spinal cord revealed that there was no significant change (p = 0.7579) in IL-1β expression on day 14 in the CCI group compared to the sham group. CONCLUSION For the first time we have established that the SS based immunosensing platform technology can repeatedly sample the intrathecal space for bioactive peptides, such as IL-1β. Using this novel approach, we have been able to establish the correlation of the intrathecal concentration of IL-1β with the extent of mechanical allodynia, providing a molecular biomarker of the degree of the exaggerated pain state.
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Affiliation(s)
- Azim Arman
- ARC Centre of Excellence for Nanoscale Biophotonics, The University of Adelaide, SA 5005, Australia; Institute for Photonics and Advanced Sensing (IPAS) and Adelaide Medical School, The University of Adelaide, Adelaide, SA 5005, Australia
| | - Fei Deng
- Graduate School of Biomedical Engineering, ARC Centre of Excellence in Nanoscale Biophotonics, Faculty of Engineering, University of New South Wales, Sydney, NSW 2052, Australia; Australian Centre for NanoMedicine, University of New South Wales, Sydney, NSW 2052, Australia
| | - Ewa M Goldys
- Graduate School of Biomedical Engineering, ARC Centre of Excellence in Nanoscale Biophotonics, Faculty of Engineering, University of New South Wales, Sydney, NSW 2052, Australia; Australian Centre for NanoMedicine, University of New South Wales, Sydney, NSW 2052, Australia
| | - Guozhen Liu
- Graduate School of Biomedical Engineering, ARC Centre of Excellence in Nanoscale Biophotonics, Faculty of Engineering, University of New South Wales, Sydney, NSW 2052, Australia; Australian Centre for NanoMedicine, University of New South Wales, Sydney, NSW 2052, Australia.
| | - Mark R Hutchinson
- ARC Centre of Excellence for Nanoscale Biophotonics, The University of Adelaide, SA 5005, Australia; Institute for Photonics and Advanced Sensing (IPAS) and Adelaide Medical School, The University of Adelaide, Adelaide, SA 5005, Australia.
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19
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Orofacial skin inflammation increases the number of macrophages in the maxillary subregion of the rat trigeminal ganglion in a corticosteroid-reversible manner. Cell Tissue Res 2020; 382:551-561. [PMID: 32696216 PMCID: PMC7683439 DOI: 10.1007/s00441-020-03244-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 06/15/2020] [Indexed: 10/25/2022]
Abstract
Inflammation of the cutaneous orofacial tissue can lead to a prolonged alteration of neuronal and nonneuronal cellular functions in trigeminal nociceptive pathways. In this study, we investigated the effects of experimentally induced skin inflammation by dithranol (anthralin) on macrophage activation in the rat trigeminal ganglion. Tissue localization and protein expression levels of ionized calcium-binding adaptor molecule 1 (Iba1), a macrophage/microglia-specific marker, and proliferation/mitotic marker antigen identified by the monoclonal antibody Ki67 (Ki67), were quantitatively analyzed using immunohistochemistry and western blots in control, dithranol-treated, dithranol- and corticosteroid-treated, and corticosteroid-treated trigeminal ganglia. Chronic orofacial dithranol treatment elicited a strong pro-inflammatory effect in the ipsilateral trigeminal ganglion. Indeed, daily dithranol treatment of the orofacial skin for 3-5 days increased the number of macrophages and Iba1 protein expression in the maxillary subregion of the ipsilateral ganglion. In the affected ganglia, none of the Iba1-positive cells expressed Ki67. This absence of mitotically active cells suggested that the accumulation of macrophages in the ganglion was not the result of resident microglia proliferation but rather the extravasation of hematogenous monocytes from the periphery. Subsequently, when a 5-day-long anti-inflammatory corticosteroid therapy was employed on the previously dithranol-treated orofacial skin, Iba1 immunoreactivity was substantially reduced in the ipsilateral ganglion. Collectively, our findings indicate that both peripheral inflammation and subsequent anti-inflammatory therapy affect macrophage activity and thus interfere with the functioning of the affected sensory ganglion neurons.
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20
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Litvin DG, Denstaedt SJ, Borkowski LF, Nichols NL, Dick TE, Smith CB, Jacono FJ. Peripheral-to-central immune communication at the area postrema glial-barrier following bleomycin-induced sterile lung injury in adult rats. Brain Behav Immun 2020; 87:610-633. [PMID: 32097765 PMCID: PMC8895345 DOI: 10.1016/j.bbi.2020.02.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 02/02/2020] [Accepted: 02/13/2020] [Indexed: 02/07/2023] Open
Abstract
The pathways for peripheral-to-central immune communication (P → C I-comm) following sterile lung injury (SLI) are unknown. SLI evokes systemic and central inflammation, which alters central respiratory control and viscerosensory transmission in the nucleus tractus solitarii (nTS). These functional changes coincide with increased interleukin-1 beta (IL-1β) in the area postrema, a sensory circumventricular organ that connects P → C I-comm to brainstem circuits that control homeostasis. We hypothesize that IL-1β and its downstream transcriptional target, cyclooxygenase-2 (COX-2), mediate P → C I-comm in the nTS. In a rodent model of SLI induced by intratracheal bleomycin (Bleo), the sigh frequency and duration of post-sigh apnea increased in Bleo- compared to saline- treated rats one week after injury. This SLI-dependent change in respiratory control occurred concurrently with augmented IL-1β and COX-2 immunoreactivity (IR) in the funiculus separans (FS), a barrier between the AP and the brainstem. At this barrier, increases in IL-1β and COX-2 IR were confined to processes that stained for glial fibrillary acidic protein (GFAP) and that projected basolaterally to the nTS. Further, FS radial-glia did not express TNF-α or IL-6 following SLI. To test our hypothesis, we blocked central COX-1/2 activity by intracerebroventricular (ICV) infusion of Indomethacin (Ind). Continuous ICV Ind treatment prevented Bleo-dependent increases in GFAP + and IL-1β + IR, and restored characteristics of sighs that reset the rhythm. These data indicate that changes in sighs following SLI depend partially on activation of a central COX-dependent P → C I-comm via radial-glia of the FS.
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Affiliation(s)
- David G Litvin
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Department of Fundamental Neuroscience, University of Lausanne, 1005 Lausanne, Switzerland
| | - Scott J Denstaedt
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, MI 48109, United States
| | - Lauren F Borkowski
- Department of Biomedical Sciences, University of Missouri College of Veterinary Medicine, Columbia, MO 65212, United States
| | - Nicole L Nichols
- Department of Biomedical Sciences, University of Missouri College of Veterinary Medicine, Columbia, MO 65212, United States
| | - Thomas E Dick
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States
| | - Corey B Smith
- Department of Physiology & Biophysics, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States
| | - Frank J Jacono
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, OH 44106, United States; Division of Pulmonary, Critical Care and Sleep Medicine, Louis Stokes VA Medical Center, Cleveland, OH 44106, United States.
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21
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Ward H, West SJ. Microglia: sculptors of neuropathic pain? ROYAL SOCIETY OPEN SCIENCE 2020; 7:200260. [PMID: 32742693 PMCID: PMC7353970 DOI: 10.1098/rsos.200260] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 06/01/2020] [Indexed: 05/02/2023]
Abstract
Neuropathic pain presents a huge societal and individual burden. The limited efficacy of current analgesics, diagnostic markers and clinical trial outcome measures arises from an incomplete understanding of the underlying mechanisms. A large and growing body of evidence has established the important role of microglia in the onset and possible maintenance of neuropathic pain, and these cells may represent an important target for future therapy. Microglial research has further revealed their important role in structural remodelling of the nervous system. In this review, we aim to explore the evidence for microglia in sculpting nervous system structure and function, as well as their important role in neuropathic pain, and finally integrate these studies to synthesize a new model for microglia in somatosensory circuit remodelling, composed of six key and inter-related mechanisms. Summarizing the mechanisms through which microglia modulate nervous system structure and function helps to frame a better understanding of neuropathic pain, and provide a clear roadmap for future research.
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Affiliation(s)
- Harry Ward
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Steven J. West
- Sainsbury Wellcome Centre, University College London, 25 Howland St, London WC1E 6BT, UK
- Author for correspondence: Steven J. West e-mail:
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22
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Martinez NW, Sánchez A, Diaz P, Broekhuizen R, Godoy J, Mondaca S, Catenaccio A, Macanas P, Nervi B, Calvo M, Court FA. Metformin protects from oxaliplatin induced peripheral neuropathy in rats. NEUROBIOLOGY OF PAIN 2020; 8:100048. [PMID: 32490289 PMCID: PMC7260677 DOI: 10.1016/j.ynpai.2020.100048] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 04/20/2020] [Accepted: 05/12/2020] [Indexed: 12/14/2022]
Abstract
After oxaliplatin treatment rats developed mechanical and cold hyperalgesia. We observed intraepidermal nerve fiber degeneration, and mild spinal cord gliosis. Co treatment with Metformin could prevent all these pathological outcomes. This suggests metformin as a candidate drug to prevent oxaliplatin-induced neuropathy.
Oxaliplatin is a commonly used drug to treat cancer, extending the rate of disease-free survival by 20% in colorectal cancer. However, oxaliplatin induces a disabling form of neuropathy resulting in more than 60% of patients having to reduce or discontinue oxaliplatin, negatively impacting their chance of survival. Oxaliplatin-induced neuropathies are accompanied by degeneration of sensory fibers in the epidermis and hyperexcitability of sensory neurons. These morphological and functional changes have been associated with sensory symptoms such as dysesthesia, paresthesia and mechanical and cold allodynia. Various strategies have been proposed to prevent or treat oxaliplatin-induced neuropathies without success. The anti-diabetic drug metformin has been recently shown to exert neuroprotection in other chemotherapy-induced neuropathies, so here we aimed to test if metformin can prevent the development of oxaliplatin-induced neuropathy in a rat model of this condition. Animals treated with oxaliplatin developed significant intraepidermal fiber degeneration, a mild gliosis in the spinal cord, and mechanical and cold hyperalgesia. The concomitant use of metformin prevented degeneration of intraepidermal fibers, gliosis, and the altered sensitivity. Our evidence further supports metformin as a new approach to prevent oxaliplatin-induced neuropathy with a potential important clinical impact.
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Affiliation(s)
- N W Martinez
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor de Chile, Santiago 8580745, Chile.,Department of Physiology, Faculty of Biology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - A Sánchez
- Department of Physiology, Faculty of Biology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - P Diaz
- Department of Physiology, Faculty of Biology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - R Broekhuizen
- Department of Hematology and Oncology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - J Godoy
- Department of Neurology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - S Mondaca
- Department of Hematology and Oncology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - A Catenaccio
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor de Chile, Santiago 8580745, Chile
| | - P Macanas
- Department of Hematology and Oncology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - B Nervi
- Department of Hematology and Oncology, Pontificia Universidad Católica de Chile, Santiago, Chile.,Millennium Institute on Immunology and Immunotherapy, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - M Calvo
- Department of Physiology, Faculty of Biology, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - F A Court
- Center for Integrative Biology, Faculty of Sciences, Universidad Mayor de Chile, Santiago 8580745, Chile.,FONDAP Center for Geroscience, Brain Health and Metabolism, Santiago 8580745, Chile.,Buck Institute for Research on Ageing, Novato, San Francisco, CA 94945, USA
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23
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Rosenberger DC, Blechschmidt V, Timmerman H, Wolff A, Treede RD. Challenges of neuropathic pain: focus on diabetic neuropathy. J Neural Transm (Vienna) 2020; 127:589-624. [PMID: 32036431 PMCID: PMC7148276 DOI: 10.1007/s00702-020-02145-7] [Citation(s) in RCA: 112] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 01/19/2020] [Indexed: 02/07/2023]
Abstract
Neuropathic pain is a frequent condition caused by a lesion or disease of the central or peripheral somatosensory nervous system. A frequent cause of peripheral neuropathic pain is diabetic neuropathy. Its complex pathophysiology is not yet fully elucidated, which contributes to underassessment and undertreatment. A mechanism-based treatment of painful diabetic neuropathy is challenging but phenotype-based stratification might be a way to develop individualized therapeutic concepts. Our goal is to review current knowledge of the pathophysiology of peripheral neuropathic pain, particularly painful diabetic neuropathy. We discuss state-of-the-art clinical assessment, validity of diagnostic and screening tools, and recommendations for the management of diabetic neuropathic pain including approaches towards personalized pain management. We also propose a research agenda for translational research including patient stratification for clinical trials and improved preclinical models in relation to current knowledge of underlying mechanisms.
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Affiliation(s)
- Daniela C Rosenberger
- Department of Neurophysiology, Mannheim Center for Translational Neuroscience (MCTN), Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Vivian Blechschmidt
- Department of Neurophysiology, Mannheim Center for Translational Neuroscience (MCTN), Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany
| | - Hans Timmerman
- Department of Anesthesiology, Pain Center, University Medical Center of Groningen (UMCG), University of Groningen, Groningen, The Netherlands
| | - André Wolff
- Department of Anesthesiology, Pain Center, University Medical Center of Groningen (UMCG), University of Groningen, Groningen, The Netherlands
| | - Rolf-Detlef Treede
- Department of Neurophysiology, Mannheim Center for Translational Neuroscience (MCTN), Medical Faculty Mannheim, University of Heidelberg, Heidelberg, Germany.
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24
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Ullah F, Liang H, Niedermayer G, Münch G, Gyengesi E. Evaluation of Phytosomal Curcumin as an Anti-inflammatory Agent for Chronic Glial Activation in the GFAP-IL6 Mouse Model. Front Neurosci 2020; 14:170. [PMID: 32226360 PMCID: PMC7081170 DOI: 10.3389/fnins.2020.00170] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Accepted: 02/14/2020] [Indexed: 01/13/2023] Open
Abstract
Chronic glial activation is characterized by an increased number of activated microglia and astroglia; these secrete free radicals and cytotoxic cytokines, subsequently causing neuronal damage. This study investigated the hypothesis that a soy-lecithin based phytosomal curcumin formulation can decrease glial activation in the brains of GFAP-IL6 mice, a model of chronic glial activation, which exhibits gliosis in various regions of the brain. Three doses of Meriva curcumin (MC) (874, 436, and 218 PPM) were fed to 3-month-old GFAP-IL6 and wild-type (WT) mice for 4 weeks. As markers of glial activation, the total numbers of Iba-1+ and TSPO+ microglia and macrophages, and GFAP+ astrocytes, were determined in the cerebellum and hippocampus by immunohistochemistry and unbiased stereology. Furthermore, the morphology of the glial cells was assessed by confocal microscopy and Sholl analysis. Administration of phytosomal curcumin led to a dose-dependent reduction in neuroinflammatory markers. Phytosomal curcumin (874 PPM) decreased the number of microglia by 26.2% in the hippocampus and by 48% in the cerebellum of the GFAP-IL6 mice compared with the GFAP-IL6 mice on normal food. Additionally, GFAP+ astrocyte numbers in the hippocampus of the GFAP-IL6 mice were decreased by 42%. The GFAP-IL6 mice exhibited a different microglial morphology to the WT mice, showing an increased soma size and perimeter. This difference was significantly reduced by the 874 PPM phytosomal curcumin dose. Our findings demonstrate that phytosomal curcumin is able to attenuate the inflammatory pathology, and potentially reverse the detrimental effects of chronic glial activation.
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Affiliation(s)
- Faheem Ullah
- Department of Pharmacology, School of Medicine, Western Sydney University, Campbelltown, NSW, Australia
| | - Huazheng Liang
- Department of Pharmacology, School of Medicine, Western Sydney University, Campbelltown, NSW, Australia.,Department of Neurology, Translational Research Institute of Brain and Brain-like Intelligence, Shanghai Fourth People's Hospital Affiliated to Tongji University School of Medicine, Shanghai, China
| | - Garry Niedermayer
- School of Science, Western Sydney University, Campbelltown, NSW, Australia
| | - Gerald Münch
- Department of Pharmacology, School of Medicine, Western Sydney University, Campbelltown, NSW, Australia.,NICM Health Research Institute, Western Sydney University, Campbelltown, NSW, Australia
| | - Erika Gyengesi
- Department of Pharmacology, School of Medicine, Western Sydney University, Campbelltown, NSW, Australia
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25
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Lorenzo LE, Godin AG, Ferrini F, Bachand K, Plasencia-Fernandez I, Labrecque S, Girard AA, Boudreau D, Kianicka I, Gagnon M, Doyon N, Ribeiro-da-Silva A, De Koninck Y. Enhancing neuronal chloride extrusion rescues α2/α3 GABA A-mediated analgesia in neuropathic pain. Nat Commun 2020; 11:869. [PMID: 32054836 PMCID: PMC7018745 DOI: 10.1038/s41467-019-14154-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 12/16/2019] [Indexed: 02/06/2023] Open
Abstract
Spinal disinhibition has been hypothesized to underlie pain hypersensitivity in neuropathic pain. Apparently contradictory mechanisms have been reported, raising questions on the best target to produce analgesia. Here, we show that nerve injury is associated with a reduction in the number of inhibitory synapses in the spinal dorsal horn. Paradoxically, this is accompanied by a BDNF-TrkB-mediated upregulation of synaptic GABAARs and by an α1-to-α2GABAAR subunit switch, providing a mechanistic rationale for the analgesic action of the α2,3GABAAR benzodiazepine-site ligand L838,417 after nerve injury. Yet, we demonstrate that impaired Cl- extrusion underlies the failure of L838,417 to induce analgesia at high doses due to a resulting collapse in Cl- gradient, dramatically limiting the benzodiazepine therapeutic window. In turn, enhancing KCC2 activity not only potentiated L838,417-induced analgesia, it rescued its analgesic potential at high doses, revealing a novel strategy for analgesia in pathological pain, by combined targeting of the appropriate GABAAR-subtypes and restoring Cl- homeostasis.
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Affiliation(s)
- Louis-Etienne Lorenzo
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
| | - Antoine G Godin
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Department of Psychiatry & Neuroscience, Université Laval, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Francesco Ferrini
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Department of Psychiatry & Neuroscience, Université Laval, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
- Department of Veterinary Sciences, University of Turin, Turin, Italy
| | - Karine Bachand
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
| | - Isabel Plasencia-Fernandez
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Simon Labrecque
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
| | - Alexandre A Girard
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Ecole Polytechnique, IP Paris, Palaiseau, France
| | - Dominic Boudreau
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada
| | - Irenej Kianicka
- Chlorion Pharma, Laval, Québec, QC, Canada
- Laurent Pharmaceuticals Inc., Montreal, QC, Canada
| | - Martin Gagnon
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Centre for Innovation, University of Otago, Dunedin, New Zealand
| | - Nicolas Doyon
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada
- Finite Element Interdisciplinary Research Group (GIREF), Université Laval, Québec, QC, Canada
| | - Alfredo Ribeiro-da-Silva
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada
- Department of Anatomy & Cell Biology, McGill University, Montreal, QC, Canada
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
| | - Yves De Koninck
- CERVO Brain Research Centre, Quebec Mental Health Institute, Québec, QC, Canada.
- Department of Pharmacology & Therapeutics, McGill University, Montreal, QC, Canada.
- Department of Psychiatry & Neuroscience, Université Laval, Québec, QC, Canada.
- Graduate program in Neuroscience, Université Laval, Québec, QC, Canada.
- Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada.
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26
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García-Magro N, Martin YB, Palomino-Antolin A, Egea J, Negredo P, Avendaño C. Multiple Morphometric Assessment of Microglial Cells in Deafferented Spinal Trigeminal Nucleus. Front Neuroanat 2020; 13:103. [PMID: 32038181 PMCID: PMC6987390 DOI: 10.3389/fnana.2019.00103] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 12/16/2019] [Indexed: 12/11/2022] Open
Abstract
Microglia (MG) are the first cells to react to the abnormal incoming signals that follow an injury of sensory nerves and play a critical role in the development and maintenance of neuropathic pain, a common sequel of nerve injuries. Here we present population data on cell number, soma size, and length of processes of MG in the caudal division of the spinal trigeminal nucleus (Sp5C) in control mice and at the peak of microgliosis (7 days) following unilateral transection of the infraorbital nerve (IoN). The study is performed combining several bias- and assumption-free imaging and stereological approaches with different immunolabeling procedures, with the objective of tackling some hard problems that often hinder proper execution of MG morphometric studies. Our approach may easily be applied to low-density MG populations, but also works, with limited biases, in territories where MG cell bodies and processes form dense meshworks. In controls, and contralaterally to the deafferented side, MG cell body size and shape and branching pattern matched well the descriptions of “resting” or “surveillant” MG described elsewhere, with only moderate intersubject variability. On the superficial laminae of the deafferented side, however, MG displayed on average larger somata and remarkable diversity in shape. The number of cells and the length of MG processes per mm3 increased 5 and 2.5 times, respectively, indicating a net 50% decrease in the mean length of processes per cell. By using specific immunolabeling and cell sorting of vascular macrophages, we found only a negligible fraction of these cells in Sp5C, with no differences between controls and deafferented animals, suggesting that blood-borne monocytes play at most a very limited role in the microgliosis occurring following sensory nerve deafferentation. In sum, here we present reliable morphometric data on MG in control and deafferented trigeminal nuclei using efficient methods that we propose may equally be applied to any morphometric population analysis of these cells under different physiological or pathological conditions.
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Affiliation(s)
- Nuria García-Magro
- Department of Anatomy, Histology and Neuroscience, Medical School, Autonomous University of Madrid, Madrid, Spain.,Ph.D. Programme in Neuroscience, Doctoral School, Autonomous University of Madrid, Madrid, Spain
| | - Yasmina B Martin
- Department of Anatomy, Faculty of Medicine, Francisco de Vitoria University, Madrid, Spain
| | - Alejandra Palomino-Antolin
- Research Unit, Hospital Universitario Santa Cristina, Instituto de Investigación Sanitaria Hospital Universitario de La Princesa, Madrid, Spain
| | - Javier Egea
- Research Unit, Hospital Universitario Santa Cristina, Instituto de Investigación Sanitaria Hospital Universitario de La Princesa, Madrid, Spain
| | - Pilar Negredo
- Department of Anatomy, Histology and Neuroscience, Medical School, Autonomous University of Madrid, Madrid, Spain
| | - Carlos Avendaño
- Department of Anatomy, Histology and Neuroscience, Medical School, Autonomous University of Madrid, Madrid, Spain
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27
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Bureta C, Setoguchi T, Saitoh Y, Tominaga H, Maeda S, Nagano S, Komiya S, Yamamoto T, Taniguchi N. TGF-β Promotes the Proliferation of Microglia In Vitro. Brain Sci 2019; 10:brainsci10010020. [PMID: 31905898 PMCID: PMC7016844 DOI: 10.3390/brainsci10010020] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Revised: 12/21/2019] [Accepted: 12/27/2019] [Indexed: 12/17/2022] Open
Abstract
The activation and proliferation of microglia is characteristic of the early stages of brain pathologies. In this study, we aimed to identify a factor that promotes microglial activation and proliferation and examined the in vitro effects on these processes. We cultured microglial cell lines, EOC 2 and SIM-A9, with various growth factors and evaluated cell proliferation, death, and viability. The results showed that only transforming growth factor beta (TGF-β) caused an increase in the in vitro proliferation of both microglial cell lines. It has been reported that colony-stimulating factor 1 promotes the proliferation of microglia, while TGF-β promotes both proliferation and inhibition of cell death of microglia. However, upon comparing the most effective doses of both (assessed from the proliferation assay), we identified no statistically significant difference between the two factors in terms of cell death; thus, both have a proliferative effect on microglial cells. In addition, a TGF-β receptor 1 inhibitor, galunisertib, caused marked inhibition of proliferation in a dose-dependent manner, indicating that inhibition of TGF-β signalling reduces the proliferation of microglia. Therefore, galunisertib may represent a promising therapeutic agent for the treatment of neurodegenerative diseases via inhibition of nerve injury-induced microglial proliferation, which may result in reduced inflammatory and neuropathic and cancer pain.
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Affiliation(s)
- Costansia Bureta
- Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan
| | - Takao Setoguchi
- Department of Orthopaedic Surgery, Japanese Red Cross Kagoshima Hospital, Kagoshima 891-0133, Japan
- Correspondence: ; Tel.: +81-992-612-111; Fax: +81-992-610-491
| | - Yoshinobu Saitoh
- Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan
| | - Hiroyuki Tominaga
- Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan
| | - Shingo Maeda
- Department of Medical Joint Materials, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima 890-8520, Japan
| | - Satoshi Nagano
- Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan
| | - Setsuro Komiya
- Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan
| | - Takuya Yamamoto
- Department of Orthopaedic Surgery, Japanese Red Cross Kagoshima Hospital, Kagoshima 891-0133, Japan
| | - Noboru Taniguchi
- Department of Orthopaedic Surgery, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan
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28
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Chen G, Zhang YQ, Qadri YJ, Serhan CN, Ji RR. Microglia in Pain: Detrimental and Protective Roles in Pathogenesis and Resolution of Pain. Neuron 2019; 100:1292-1311. [PMID: 30571942 DOI: 10.1016/j.neuron.2018.11.009] [Citation(s) in RCA: 463] [Impact Index Per Article: 92.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2018] [Revised: 10/22/2018] [Accepted: 11/02/2018] [Indexed: 12/18/2022]
Abstract
The previous decade has seen a rapid increase in microglial studies on pain, with a unique focus on microgliosis in the spinal cord after nerve injury and neuropathic pain. Numerous signaling molecules are altered in microglia and contribute to the pathogenesis of pain. Here, we discuss how microglial signaling regulates spinal cord synaptic plasticity in acute and chronic pain conditions with different degrees and variations of microgliosis. We highlight that microglial mediators such as pro- and anti-inflammatory cytokines are powerful neuromodulators that regulate synaptic transmission and pain via neuron-glial interactions. We also reveal an emerging role of microglia in the resolution of pain, in part via specialized pro-resolving mediators including resolvins, protectins, and maresins. We also discuss a possible role of microglia in chronic itch.
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Affiliation(s)
- Gang Chen
- Key Laboratory of Neuroregeneration of Jiangsu and Ministry of Education, Co-Innovation Center of Neuroregeneration, Nantong University, Nantong, Jiangsu 226001, China
| | - Yu-Qiu Zhang
- Institute of Neurobiology, Institutes of Brain Science and State Key Laboratory of Medical Neurobiology, Collaborative Innovation Center for Brain Science, Fudan University, Shanghai 200032, China
| | - Yawar J Qadri
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA
| | - Charles N Serhan
- Center for Experimental Therapeutics and Reperfusion Injury, Hale Transformative Medicine, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Ru-Rong Ji
- Center for Translational Pain Medicine, Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA; Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA.
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29
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Krøigård T, Metaxas A, Wirenfeldt M, Finsen B. Protective effect of ibuprofen in a rat model of chronic oxaliplatin-induced peripheral neuropathy. Exp Brain Res 2019; 237:2645-2651. [PMID: 31388734 DOI: 10.1007/s00221-019-05615-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 07/26/2019] [Indexed: 12/31/2022]
Abstract
Despite extensive preclinical and clinical investigations, a clinically relevant neuroprotective agent against oxaliplatin-induced peripheral neuropathy, which affects the quality of life following chemotherapy, has not been identified. Epidemiological data suggest that ibuprofen may reduce the risk of neuropathy. Male rats were treated with oxaliplatin (n = 6), oxaliplatin and ibuprofen (n = 5) or vehicle (n = 5) every second day for 15 days. Neuropathy was evaluated using mechanical detection thresholds (MDT) at the hind paw and sensory nerve conduction velocity (SNCV) in the tail nerve at baseline, right after and 3 weeks after the end of treatment. Intraepidermal nerve fibre density (IENFD) was evaluated in the hind paw and inflammation in the dorsal root ganglia 3 weeks after treatment. Inflammation in the dorsal root ganglia was assessed using quantitative real-time RT-PCR (qPCR) of the mRNA levels for the pro-inflammatory cytokines, TNF-α and IL-1β, and by immunohistochemical staining for Iba1+ macrophages. SNCV was reduced in rats treated with oxaliplatin and with oxaliplatin and ibuprofen compared to control rats 3 weeks after treatment. No differences were found for MDT 3 weeks after treatment. IENFD was reduced in rats treated with oxaliplatin. There was a trend towards up-regulation of TNF-α mRNA levels in rats treated with oxaliplatin and with oxaliplatin and ibuprofen. Morphological changes of Iba1+ macrophages suggested activation, but no differences were found in area fraction or size of macrophage cell bodies. The results did not support a neuroprotective effect of ibuprofen but indicated that inflammation may play a role in oxaliplatin-induced peripheral neuropathy.
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Affiliation(s)
- Thomas Krøigård
- Department of Neurology, Odense University Hospital, Odense, Denmark. .,Institute of Clinical Research, University of Southern Denmark, J. B. Winsløws Vej 4, 5000, Odense C, Denmark.
| | - Athanasios Metaxas
- Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
| | - Martin Wirenfeldt
- Department of Pathology, Odense University Hospital, Odense, Denmark.,Institute of Clinical Research, University of Southern Denmark, J. B. Winsløws Vej 4, 5000, Odense C, Denmark
| | - Bente Finsen
- Department of Neurobiology Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark
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30
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Diverse Role of Biological Plasticity in Low Back Pain and Its Impact on Sensorimotor Control of the Spine. J Orthop Sports Phys Ther 2019; 49:389-401. [PMID: 31151376 DOI: 10.2519/jospt.2019.8716] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Pain is complex. It is no longer acceptable to consider pain solely as a peripheral phenomenon involving activation of nociceptive neurons. The contemporary understanding of pain involves consideration of different underlying pain mechanisms and an increasing awareness of plasticity in all of the biological systems. Of note, recent advances in technology and understanding have highlighted the critical importance of neuroimmune interactions, both in the peripheral and central nervous systems, and the interaction between the nervous system and body tissues in the development and maintenance of pain, including low back pain (LBP). Further, the biology of many tissues changes when challenged by pain and injury, as reported in a growing body of literature on the biology of muscle, fat, and connective tissue. These advances in understanding of the complexity of LBP have implications for our understanding of pain and its interaction with the motor system, and may change how we consider motor control in the rehabilitation of LBP. This commentary provides a state-of-the-art overview of plasticity of biology in LBP. The paper is divided into 4 parts that address (1) biology of pain mechanisms, (2) neuroimmune interaction in the central nervous system, (3) neuroimmune interaction in the periphery, and (4) brain and peripheral tissue interaction. Each section considers the implications for clinical management of LBP. J Orthop Sports Phys Ther 2019;49(6):389-401. doi:10.2519/jospt.2019.8716.
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31
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Alterations in evoked and spontaneous activity of dorsal horn wide dynamic range neurons in pathological pain: a systematic review and analysis. Pain 2019; 160:2199-2209. [DOI: 10.1097/j.pain.0000000000001632] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Blaszczyk L, Maître M, Lesté-Lasserre T, Clark S, Cota D, Oliet SHR, Fénelon VS. Sequential alteration of microglia and astrocytes in the rat thalamus following spinal nerve ligation. J Neuroinflammation 2018; 15:349. [PMID: 30572902 PMCID: PMC6302506 DOI: 10.1186/s12974-018-1378-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 11/26/2018] [Indexed: 12/28/2022] Open
Abstract
Background Spinal reactive astrocytes and microglia are known to participate to the initiation and maintenance of neuropathic pain. However, whether reactive astrocytes and microglia in thalamic nuclei that process sensory-discriminative aspects of pain play a role in pain behavior remains poorly investigated. Therefore, the present study evaluated whether the presence of reactive glia (hypertrophy, increased number and upregulation of glial markers) in the ventral posterolateral thalamic nucleus (VPL) correlates with pain symptoms, 14 and 28 days after unilateral L5/L6 spinal nerve ligation (SNL) in rats. Methods Mechanical allodynia and hyperalgesia (von Frey filament stimulation) as well as ambulatory pain (dynamic weight bearing apparatus) were assessed. Levels of nine glial transcripts were determined by quantitative real-time PCR on laser microdissected thalamic nuclei, and levels of proteins were assessed by Western blot. We also studied by immunohistofluorescence the expression of glial markers that label processes (GFAP for astrocytes and iba-1 for microglia) and cell body (S100β for astrocytes and iba-1 for microglia) and quantified the immunostained surface and the number of astrocytes and microglia (conventional counts and optical dissector method of stereological counting). Results Differential, time-dependent responses were observed concerning microglia and astrocytes. Specifically, at day 14, iba-1 immunostained area and number of iba-1 immunopositive cells were decreased in the VPL of SNL as compared to naïve rats. By contrast, at day 28, GFAP-immunostained area was increased in the VPL of SNL as compared to naïve rats while number of GFAP/S100β immunopositive cells remained unchanged. Using quantitative real-time PCR of laser microdissected VPL, we found a sequential increase in mRNA expression of cathepsin S (day 14), fractalkine (day 28), and fractalkine receptor (day 14), three well-known markers of microglial reactivity. Using Western blot, we confirmed an increase in protein expression of fractalkine receptor at day 14. Conclusions Our results demonstrate a sequential alteration of microglia and astrocytes in the thalamus of animals with lesioned peripheral nerves. Furthermore, our data report unprecedented concomitant molecular signs of microglial activation and morphological signs of microglial decline in the thalamus of these animals.
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Affiliation(s)
- Lucie Blaszczyk
- Bordeaux University, Bordeaux, France.,Neurocentre Magendie, INSERM U1215, Bordeaux, France
| | - Marlène Maître
- Bordeaux University, Bordeaux, France.,Neurocentre Magendie, INSERM U1215, Bordeaux, France
| | - Thierry Lesté-Lasserre
- Bordeaux University, Bordeaux, France.,Neurocentre Magendie, INSERM U1215, Bordeaux, France
| | - Samantha Clark
- Bordeaux University, Bordeaux, France.,Neurocentre Magendie, INSERM U1215, Bordeaux, France
| | - Daniela Cota
- Bordeaux University, Bordeaux, France.,Neurocentre Magendie, INSERM U1215, Bordeaux, France
| | - Stéphane H R Oliet
- Bordeaux University, Bordeaux, France.,Neurocentre Magendie, INSERM U1215, Bordeaux, France
| | - Valérie S Fénelon
- Bordeaux University, Bordeaux, France. .,Neurocentre Magendie, INSERM U1215, Bordeaux, France.
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Contribution of CD137L to Sensory Hypersensitivity in a Murine Model of Neuropathic Pain. eNeuro 2018; 5:eN-NWR-0218-18. [PMID: 30417077 PMCID: PMC6223109 DOI: 10.1523/eneuro.0218-18.2018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 10/02/2018] [Accepted: 10/07/2018] [Indexed: 01/21/2023] Open
Abstract
CD137L (4-1BBL) is a costimulatory molecule whose signaling can promote monocyte/macrophage functions; however, CD137L-mediated microglial response and its role in neuropathic pain remain unknown. We investigated CD137L following peripheral nerve injury-induced neuropathic pain using a spinal nerve L5 transection (L5Tx) murine model in both sexes. First, C57BL/6_CD137L knock-out (KO) mice displayed decreased mechanical and diminished heat hypersensitivity compared to wild-type (WT) controls, beginning on day 3 to up to day 35 post-L5Tx. Purified anti-mouse CD137L neutralizing monoclonal antibody (0.1 or 0.5 µg) was also used to identify CD137L’s window of action in BALB/c mice. Anti-CD137L antibody was intrathecally administered either from day 0 (before surgery) to day 7 (early treatment), or from day 6 to 13 post-L5Tx (late treatment), and nociceptive thresholds were assessed before surgery to up to day 35 post-surgery. Early treatment with anti-CD137L reduced L5Tx-induced mechanical but not heat hypersensitivity, while later treatment did not alter either sensitivity. Pro- versus anti-inflammatory responses within the lumbar spinal cord following L5Tx were further evaluated via quantitative real-time PCR (qRT-PCR) and immunohistochemistry (IHC) in time-course studies. Following L5Tx, female CD137L KO mice did not show increased iNOS mRNA and had reduced numbers of IL-1β+ cells compared to WT. At 21 d post-surgery, CD137L KO mice had higher total numbers of arginase (Arg)-1+ cells and Arg-1+ microglia. Altogether, results indicate that spinal cord CD137L contributes to the development of peripheral nerve injury-induced neuropathic pain, which may be in part mediated through CD137L’s modulation of the pro- and anti-inflammatory balance within the spinal cord.
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Palmisano M, Caputi FF, Mercatelli D, Romualdi P, Candeletti S. Dynorphinergic system alterations in the corticostriatal circuitry of neuropathic mice support its role in the negative affective component of pain. GENES BRAIN AND BEHAVIOR 2018; 18:e12467. [PMID: 29430855 PMCID: PMC7379183 DOI: 10.1111/gbb.12467] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 01/19/2018] [Accepted: 02/07/2018] [Indexed: 01/01/2023]
Abstract
The dynorphinergic system is involved in pain transmission at spinal level, where dynorphin exerts antinociceptive or pronociceptive effects, based on its opioid or non‐opioid actions. Surprisingly, little evidence is currently available concerning the supraspinal role of the dynorphinergic system in pain conditions. The present study aimed to investigate whether neuropathic pain is accompanied by prodynorphin (Pdyn) and κ‐opioid receptor (Oprk1) gene expression alterations in selected mouse brain areas. To this end, mice were subjected to chronic constriction injury of the right sciatic nerve and neuropathic pain behavioral signs were ascertained after 14 days. At this interval, a marked increase in Pdyn mRNA in the anterior cingulate cortex (ACC) and prefrontal cortex (PFC) was observed. Oprk1 gene expression was increased in the PFC, and decreased in the ACC and nucleus accumbens (NAc). No changes were observed in the other investigated regions. Because of the relationship between dynorphin and the brain‐derived neurotrophic factor, and the role of this neurotrophin in chronic pain‐related neuroplasticity, we investigated brain‐derived neurotrophic factor gene (Bdnf) expression in the areas showing Pdyn or Oprk1 mRNAs changes. Bdnf mRNA levels were increased in both the ACC and PFC, whereas no changes were assessed in the NAc. Present data indicate that the dynorphinergic system undergoes quite selective alterations involving the corticostriatal circuitry during neuropathic pain, suggesting a contribution to the negative affective component of pain. Moreover, parallel increases in Pdyn and Bdnf mRNA at cortical level suggest the occurrence of likely interactions between these systems in neuropathic pain maladaptive neuroplasticity.
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Affiliation(s)
- M Palmisano
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | - F F Caputi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | - D Mercatelli
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | - P Romualdi
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Bologna, Italy
| | - S Candeletti
- Department of Pharmacy and Biotechnology, Alma Mater Studiorum - University of Bologna, Bologna, Italy
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Kobiela Ketz A, Byrnes KR, Grunberg NE, Kasper CE, Osborne L, Pryor B, Tosini NL, Wu X, Anders JJ. Characterization of Macrophage/Microglial Activation and Effect of Photobiomodulation in the Spared Nerve Injury Model of Neuropathic Pain. PAIN MEDICINE 2018; 18:932-946. [PMID: 27497321 DOI: 10.1093/pm/pnw144] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Objective Neuropathic pain is common and debilitating with limited effective treatments. Macrophage/microglial activation along ascending somatosensory pathways following peripheral nerve injury facilitates neuropathic pain. However, polarization of macrophages/microglia in neuropathic pain is not well understood. Photobiomodulation treatment has been used to decrease neuropathic pain, has anti-inflammatory effects in spinal injury and wound healing models, and modulates microglial polarization in vitro. Our aim was to characterize macrophage/microglia response after peripheral nerve injury and modulate the response with photobiomodulation. Methods Adult male Sprague-Dawley rats were randomly assigned to sham (N = 13), spared nerve injury (N = 13), or injury + photobiomodulation treatment groups (N = 7). Mechanical hypersensitivity was assessed with electronic von Frey. Photobiomodulation (980 nm) was applied to affected hind paw (output power 1 W, 20 s, 41cm above skin, power density 43.25 mW/cm 2 , dose 20 J), dorsal root ganglia (output power 4.5W, 19s, in skin contact, power density 43.25 mW/cm 2 , dose 85.5 J), and spinal cord regions (output power 1.5 W, 19s, in skin contact, power density 43.25 mW/cm 2 , dose 28.5 J) every other day from day 7-30 post-operatively. Immunohistochemistry characterized macrophage/microglial activation. Results Injured groups demonstrated mechanical hypersensitivity 1-30 days post-operatively. Photobiomodulation-treated animals began to recover after two treatments; at day 26, mechanical sensitivity reached baseline. Peripheral nerve injury caused region-specific macrophages/microglia activation along spinothalamic and dorsal-column medial lemniscus pathways. A pro-inflammatory microglial marker was expressed in the spinal cord of injured rats compared to photobiomodulation-treated and sham group. Photobiomodulation-treated dorsal root ganglion macrophages expressed anti-inflammatory markers. Conclusion Photobiomodulation effectively reduced mechanical hypersensitivity, potentially through modulating macrophage/microglial activation to an anti-inflammatory phenotype.
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Affiliation(s)
- Ann Kobiela Ketz
- Center for Nursing Science and Clinical Inquiry, Landstuhl Regional Medical Center, Landstuhl, Germany
| | - Kimberly R Byrnes
- Anatomy, Physiology & Genetics, The Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Neil E Grunberg
- Departments of Neuroscience, Uniformed Services University, Bethesda, MD, USA.,Department of Medical and Clinical Psychology, Uniformed Services University of the Health Sciences , Bethesda, MD , USA
| | - Christine E Kasper
- Daniel K. Inouye Graduate School of Nursing, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Lisa Osborne
- Daniel K. Inouye Graduate School of Nursing, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | | | | | - Xingjia Wu
- Anatomy, Physiology & Genetics, The Uniformed Services University of the Health Sciences, Bethesda, MD, USA
| | - Juanita J Anders
- Anatomy, Physiology & Genetics, The Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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Abstract
PURPOSE OF REVIEW The review aims to present the latest research into microglia and their role in pain. RECENT FINDINGS Microglia affect sex and age-dependent differences in pain. The various microglial phenotypes make their involvement in pain more complex but provide more potential as pain modulators. SUMMARY Glial cells, composed of microglia, astrocytes, and oligodendrocytes, outnumber neurons in the central nervous system. The crosstalk between these cells and neurons is now established as participating in the development of chronic pain. There has been a great advance in the description of microglia reactivity from pro to anti-inflammatory phenotypes. The modulation of these phenotypes could be a potential target for pain therapy. Recently, different microglial reactivity between man and woman and between neonates and adults, in response to nerve injury were described, which could explain some of the sex differences in pain sensitivity and the absence of neuropathic pain development in neonates. Clinical trials using microglia as a target have been carried out in various neurological diseases and pain, with limited efficacy in the latter, but there are nonetheless, indications that with some improvement in study strategies microglia could be a future target for pain control.
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Abstract
HIV-associated sensory neuropathy (HIV-SN) is the most frequent manifestation of HIV disease. It often presents with significant neuropathic pain and is associated with previous exposure to neurotoxic nucleoside reverse transcriptase inhibitors. However, HIV-SN prevalence remains high even in resource-rich settings where these drugs are no longer used. Previous evidence suggests that exposure to indinavir, a protease inhibitor commonly used in antiretroviral therapy, may link to elevated HIV-SN risk. Here, we investigated whether indinavir treatment was associated with the development of a "dying back" axonal neuropathy and changes in pain-relevant limb withdrawal and thigmotactic behaviours. After 2 intravenous injections of indinavir (50 mg/kg, 4 days apart), adult rats developed hind paw mechanical hypersensitivity, which peaked around 2 weeks post first injection (44% reduction from baseline). At this time, animals also had (1) significantly changed thigmotactic behaviour (62% reduction in central zone entries) comparing with the controls and (2) a significant reduction (45%) in hind paw intraepidermal nerve fibre density. Treatment with gabapentin, but not amitriptyline, was associated with a complete attenuation of hind paw mechanical hypersensitivity observed with indinavir treatment. Furthermore, we found a small but significant increase in microglia with the effector morphology in the lumbar spinal dorsal horn in indinavir-treated animals, coupled with significantly increased expression of phospho-p38 in microglia. In summary, we have reported neuropathic pain-related sensory and behavioural changes accompanied by a significant loss of hind paw skin sensory innervation in a rat model of indinavir-induced peripheral neuropathy that is suitable for further pathophysiological investigation and preclinical evaluation of novel analgesics.
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Wang B, Fan B, Dai Q, Xu X, Jiang P, Zhu L, Dai H, Yao Z, Xu Z, Liu X. Fascin-1 Contributes to Neuropathic Pain by Promoting Inflammation in Rat Spinal Cord. Neurochem Res 2017; 43:287-296. [PMID: 29052088 DOI: 10.1007/s11064-017-2420-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 09/17/2017] [Accepted: 10/13/2017] [Indexed: 12/27/2022]
Abstract
Neuropathic pain is a complicated clinical syndrome caused by heterogeneous etiology. Despite the fact that the underlying mechanisms remain elusive, it is well accepted that neuroinflammation plays a critical role in the development of neuropathic pain. Fascin-1, an actin-bundling protein, has been proved to be involved in the processing of diverse biological events including cellular development, immunity, and tumor invasion etc. Recent studies have shown that Fascin-1 participates in antigen presentation and the regulation of pro-inflammatory agents. However, whether Fascin-1 is involved in neuropathic pain has not been reported. In the present study we examined the potential role of Fascin-1 by using a rodent model of chronic constriction injury (CCI). Our results showed that Fascin-1 increased rapidly in dorsal root ganglions (DRG) and spinal cord (SC) after CCI. The increased Fascin-1 widely expressed in DRG, however, it localized predominantly in microglia, seldom in neuron, and hardly in astrocyte in the SC. Intrathecal injection of Fascin-1 siRNA not only suppressed the activation of microglia and the release of pro-inflammatory mediators, but also attenuated the mechanical allodynia and thermal hyperalgesia induced by CCI.
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Affiliation(s)
- Binbin Wang
- Department of Anesthesiology, Affiliated Hospital of Nantong University, Nantong, 226001, Jiangsu, China
| | - Bingbing Fan
- Department of Radiology, Zhongshan Hospital and Shanghai Institute of Medical Imaging, Department of Medical Imaging, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Qijun Dai
- Nanjing University of Traditional Chinese Medicine Hanlin College Affiliated Hai'an Chinese Medicine Hospital, Nanjing University of Traditional Chinese Medicine, Haian, Jiangsu, China
| | - Xingguo Xu
- Department of Anesthesiology, Affiliated Hospital of Nantong University, Nantong, 226001, Jiangsu, China
| | - Peipei Jiang
- Nanjing University of Traditional Chinese Medicine Hanlin College Affiliated Hai'an Chinese Medicine Hospital, Nanjing University of Traditional Chinese Medicine, Haian, Jiangsu, China
| | - Lin Zhu
- Nanjing University of Traditional Chinese Medicine Hanlin College Affiliated Hai'an Chinese Medicine Hospital, Nanjing University of Traditional Chinese Medicine, Haian, Jiangsu, China
| | - Haifeng Dai
- Nanjing University of Traditional Chinese Medicine Hanlin College Affiliated Hai'an Chinese Medicine Hospital, Nanjing University of Traditional Chinese Medicine, Haian, Jiangsu, China
| | - Zhigang Yao
- Nanjing University of Traditional Chinese Medicine Hanlin College Affiliated Hai'an Chinese Medicine Hospital, Nanjing University of Traditional Chinese Medicine, Haian, Jiangsu, China
| | - Zhongling Xu
- Department of Anesthesiology, Affiliated Hospital of Nantong University, Nantong, 226001, Jiangsu, China.
| | - Xiaojuan Liu
- Department of Pathogen Biology, Medical College, Nantong University, Nantong, 2266001, Jiangsu, China.
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Xiao X, Feng YP, Du B, Sun HR, Ding YQ, Qi JG. Antibody incubation at 37°C improves fluorescent immunolabeling in free-floating thick tissue sections. Biotechniques 2017; 62:115-122. [PMID: 28298178 DOI: 10.2144/000114524] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2016] [Accepted: 01/04/2017] [Indexed: 11/23/2022] Open
Abstract
Fluorescent immunolabeling and imaging in free-floating thick (50-60 μm) tissue sections is relatively simple in practice and enables design-based non-biased stereology, or 3-D reconstruction and analysis. This method is widely used for 3-D in situ quantitative biology in many areas of biological research. However, the labeling quality and efficiency of standard protocols for fluorescent immunolabeling of these tissue sections are not always satisfactory. Here, we systematically evaluate the effects of raising the conventional antibody incubation temperatures (4°C or 21°C) to mammalian body temperature (37°C) in these protocols. Our modification significantly enhances the quality (labeling sensitivity, specificity, and homogeneity) and efficiency (antibody concentration and antibody incubation duration) of fluorescent immunolabeling of free-floating thick tissue sections.
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Affiliation(s)
- Xia Xiao
- Department of Histology, Embryology and Neurobiology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chngdu, Sichuan, China
| | - Ya-Ping Feng
- Department of Histology, Embryology and Neurobiology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chngdu, Sichuan, China
| | - Bin Du
- Department of Histology, Embryology and Neurobiology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chngdu, Sichuan, China
| | - Han-Ru Sun
- Department of Histology, Embryology and Neurobiology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chngdu, Sichuan, China
| | - You-Quan Ding
- Department of Histology, Embryology and Neurobiology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chngdu, Sichuan, China
| | - Jian-Guo Qi
- Department of Histology, Embryology and Neurobiology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chngdu, Sichuan, China
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Li J, Li X, Jiang X, Yang M, Yang R, Burnstock G, Xiang Z, Yuan H. Microvesicles shed from microglia activated by the P2X7-p38 pathway are involved in neuropathic pain induced by spinal nerve ligation in rats. Purinergic Signal 2016; 13:13-26. [PMID: 27683228 DOI: 10.1007/s11302-016-9537-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 09/12/2016] [Indexed: 12/30/2022] Open
Abstract
Microglia are critical in the pathogenesis of neuropathic pain. In this study, we investigated the role of microvesicles (MVs) in neuropathic pain induced by spinal nerve ligation (SNL) in rats. First, we found that MVs shed from microglia were increased in the cerebrospinal fluid and dorsal horn of the spinal cord after SNL. Next, MVs significantly reduced paw withdrawal threshold (PWT) and paw withdrawal latency (PWL). In addition, the P2X7-p38 pathway was related to the bleb of MVs after SNL. Interleukin (IL)-1β was found to be significantly upregulated in the package of MVs, and PWT and PWL increased following inhibition with shRNA-IL-1β. Finally, the amplitude and frequency of spontaneous excitatory postsynaptic currents increased following stimulation with MVs. Our results indicate that the P2X7-p38 pathway is closely correlated with the shedding of MVs from microglia in neuropathic pain, and MVs had a significant effect on neuropathic pain by participating in the interaction between microglia and neurons.
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Affiliation(s)
- Jian Li
- Department of Anesthesiology, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai, 200003, China
| | - Xiangnan Li
- Department of Anesthesiology, The Third People's Hospital of Yancheng, Yancheng, 224001, China
| | - Xin Jiang
- Department of Anesthesiology, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai, 200003, China
| | - Mei Yang
- Department of Anesthesiology, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai, 200003, China
| | - Rui Yang
- Department of Anesthesiology, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai, 200003, China
| | - Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, London, UK.,Department of Pharmacology and Therapeutics, The University of Melbourne, Melbourne, Australia
| | - Zhenghua Xiang
- Department of Neurobiology, MOE Key Laboratory of Molecular Neurobiology, Ministry of Education, Second Military Medical University, Shanghai, 200433, China.
| | - Hongbin Yuan
- Department of Anesthesiology, Changzheng Hospital, Second Military Medical University, 415 Fengyang Road, Shanghai, 200003, China.
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Targeting the innate repair receptor to treat neuropathy. Pain Rep 2016; 1:e566. [PMID: 29392190 PMCID: PMC5741312 DOI: 10.1097/pr9.0000000000000566] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 06/13/2016] [Accepted: 06/13/2016] [Indexed: 11/26/2022] Open
Abstract
The innate repair receptor (IRR) is a heteromer of the erythropoietin receptor and the β-common (CD131) receptor, which simultaneously activates anti-inflammatory and tissue repair pathways. Experimental data suggest that after peripheral nerve injury, the IRR is upregulated in the spinal cord and modulates the neurogenic inflammatory response. The recently introduced selective IRR agonist ARA290 is an 11-amino acid peptide initially tested in animal models of neuropathy. After sciatic nerve injury, ARA290 produced a rapid and long-term relief of mechanical and cold allodynia in normal mice, but not in animals with a β-common receptor knockout phenotype. In humans, ARA290 has been evaluated in patients with small fiber neuropathy associated with sarcoidosis or type 2 diabetes (T2D) mellitus. In patients with sarcoidosis, ARA290 significantly improved neuropathic and autonomic symptoms, as well as quality of life as assessed by the small fiber neuropathy screening list questionnaire. In addition, ARA290 treatment for 28 days initiated a regrowth of small nerve fibers in the cornea, but not in the epidermis. In patients with T2D, the results were similar to those observed in patients with sarcoidosis along with an improved metabolic profile. In both populations, ARA290 lacked significant adverse effects. These experimental and clinical studies show that ARA290 effectively reprograms a proinflammatory, tissue-damaging milieu into one of healing and tissue repair. Further clinical trials with long-term treatment and follow-up are needed to assess the full potential of IRR activation by ARA290 as a disease-modifying therapy in neuropathy of various etiologies.
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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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Tashima R, Mikuriya S, Tomiyama D, Shiratori-Hayashi M, Yamashita T, Kohro Y, Tozaki-Saitoh H, Inoue K, Tsuda M. Bone marrow-derived cells in the population of spinal microglia after peripheral nerve injury. Sci Rep 2016; 6:23701. [PMID: 27005516 PMCID: PMC4804310 DOI: 10.1038/srep23701] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 03/09/2016] [Indexed: 12/18/2022] Open
Abstract
Accumulating evidence indicates that peripheral nerve injury (PNI) activates spinal microglia that are necessary for neuropathic pain. Recent studies using bone marrow (BM) chimeric mice have reported that after PNI, circulating BM-derived cells infiltrate into the spinal cord and differentiate into microglia-like cells. This raises the possibility that the population of spinal microglia after PNI may be heterogeneous. However, the infiltration of BM cells in the spinal cord remains controversial because of experimental adverse effects of strong irradiation used for generating BM chimeric mice. In this study, we evaluated the PNI-induced spinal infiltration of BM-derived cells not only by irradiation-induced myeloablation with various conditioning regimens, but also by parabiosis and mice with genetically labelled microglia, models without irradiation and BM transplantation. Results obtained from these independent approaches provide compelling evidence indicating little contribution of circulating BM-derived cells to the population of spinal microglia after PNI.
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Affiliation(s)
- Ryoichi Tashima
- Department of Life Innovation, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.,Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Satsuki Mikuriya
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Daisuke Tomiyama
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Miho Shiratori-Hayashi
- Department of Life Innovation, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.,Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Tomohiro Yamashita
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Yuta Kohro
- Department of Life Innovation, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.,Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Hidetoshi Tozaki-Saitoh
- Department of Life Innovation, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.,Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Kazuhide Inoue
- Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
| | - Makoto Tsuda
- Department of Life Innovation, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan.,Department of Molecular and System Pharmacology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan
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Spinal Cord T-Cell Infiltration in the Rat Spared Nerve Injury Model: A Time Course Study. Int J Mol Sci 2016; 17:352. [PMID: 27005622 PMCID: PMC4813213 DOI: 10.3390/ijms17030352] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Revised: 02/26/2016] [Accepted: 02/29/2016] [Indexed: 12/31/2022] Open
Abstract
The immune system is involved in the development of neuropathic pain. In particular, the infiltration of T-lymphocytes into the spinal cord following peripheral nerve injury has been described as a contributor to sensory hypersensitivity. We used the spared nerve injury (SNI) model of neuropathic pain in Sprague Dawley adult male rats to assess proliferation, and/or protein/gene expression levels for microglia (Iba1), T-lymphocytes (CD2) and cytotoxic T-lymphocytes (CD8). In the dorsal horn ipsilateral to SNI, Iba1 and BrdU stainings revealed microglial reactivity and proliferation, respectively, with different durations. Iba1 expression peaked at D4 and D7 at the mRNA and protein level, respectively, and was long-lasting. Proliferation occurred almost exclusively in Iba1 positive cells and peaked at D2. Gene expression observation by RT-qPCR array suggested that T-lymphocytes attracting chemokines were upregulated after SNI in rat spinal cord but only a few CD2/CD8 positive cells were found. A pronounced infiltration of CD2/CD8 positive T-cells was seen in the spinal cord injury (SCI) model used as a positive control for lymphocyte infiltration. Under these experimental conditions, we show early and long-lasting microglia reactivity in the spinal cord after SNI, but no lymphocyte infiltration was found.
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Shaikh S, Shortland P, Lauto A, Barton M, Morley JW, Mahns DA. Sensory perturbations using suture and sutureless repair of transected median nerve in rats. Somatosens Mot Res 2016; 33:20-8. [PMID: 26899181 DOI: 10.3109/08990220.2016.1142438] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The effects of changes to cold, mechanical, and heat thresholds following median nerve transection with repair by sutures (Su) or Rose Bengal adhesion (RA) were compared to sham-operated animals. Both nerve-injured groups showed a transient, ipsilateral hyposensitivity to mechanical and heat stimuli followed by a robust and long-lasting hypersensitivity (6-7 weeks) with gradual recovery towards pre-injury levels by 90 days post-repair. Both tactile and thermal hypersensitivity were seen in the contralateral limb that was similar in onset but differed in magnitude and resolved more rapidly compared to the injured limb. Prior to injury, no animals showed any signs of aversion to cold plate temperatures of 4-16 °C. After injury, animals showed cold allodynia, lasting for 7 weeks in RA-repaired rats before recovering towards pre-injury levels, but were still present at 12 weeks in Su-repaired rats. Additionally, sensory recovery in the RA group was faster compared to the Su group in all behavioural tests. Surprisingly, sham-operated rats showed similar bilateral behavioural changes to all sensory stimuli that were comparable in onset and magnitude to the nerve-injured groups but resolved more quickly compared to nerve-injured rats. These results suggest that nerve repair using a sutureless approach produces an accelerated recovery with reduced sensorimotor disturbances compared to direct suturing. They also describe, for the first time, that unilateral forelimb nerve injury produces mirror-image-like sensory perturbations in the contralateral limb, suggesting that the contralateral side is not a true control for sensory testing. The potential mechanisms involved in this altered behaviour are discussed.
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Affiliation(s)
- Sumaiya Shaikh
- a School of Medicine, Western Sydney University , NSW , Australia
| | - Peter Shortland
- b School of Science and Health, Western Sydney University , NSW , Australia
| | - Antonio Lauto
- b School of Science and Health, Western Sydney University , NSW , Australia
| | - Matthew Barton
- a School of Medicine, Western Sydney University , NSW , Australia
| | - John W Morley
- a School of Medicine, Western Sydney University , NSW , Australia
| | - David A Mahns
- a School of Medicine, Western Sydney University , NSW , Australia
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Hernangómez M, Klusáková I, Joukal M, Hradilová-Svíženská I, Guaza C, Dubový P. CD200R1 agonist attenuates glial activation, inflammatory reactions, and hypersensitivity immediately after its intrathecal application in a rat neuropathic pain model. J Neuroinflammation 2016; 13:43. [PMID: 26891688 PMCID: PMC4759712 DOI: 10.1186/s12974-016-0508-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Accepted: 02/10/2016] [Indexed: 12/15/2022] Open
Abstract
Background Interaction of CD200 with its receptor CD200R has an immunoregulatory role and attenuates various types of neuroinflammatory diseases. Methods Immunofluorescence staining, western blot analysis, and RT-PCR were used to investigate the modulatory effects of CD200 fusion protein (CD200Fc) on activation of microglia and astrocytes as well as synthesis of pro- (TNF, IL-1β, IL-6) and anti-inflammatory (IL-4, IL-10) cytokines in the L4–L5 spinal cord segments in relation to behavioral signs of neuropathic pain after unilateral sterile chronic constriction injury (sCCI) of the sciatic nerve. Withdrawal thresholds for mechanical hypersensitivity and latencies for thermal hypersensitivity were measured in hind paws 1 day before operation; 1, 3, and 7 days after sCCI operation; and then 5 and 24 h after intrathecal application of artificial cerebrospinal fluid or CD200Fc. Results Seven days from sCCI operation and 5 h from intrathecal application, CD200Fc reduced mechanical and thermal hypersensitivity when compared with control animals. Simultaneously, CD200Fc attenuated activation of glial cells and decreased proinflammatory and increased anti-inflammatory cytokine messenger RNA (mRNA) levels. Administration of CD200Fc also diminished elevation of CD200 and CD200R proteins as a concomitant reaction of the modulatory system to increased neuroinflammatory reactions after nerve injury. The anti-inflammatory effect of CD200Fc dropped at 24 h after intrathecal application. Conclusions Intrathecal administration of the CD200R1 agonist CD200Fc induces very rapid suppression of neuroinflammatory reactions associated with glial activation and neuropathic pain development. This may constitute a promising and novel therapeutic approach for the treatment of neuropathic pain.
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Affiliation(s)
- Miriam Hernangómez
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 3, 62500, Brno, Czech Republic.
| | - Ilona Klusáková
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 3, 62500, Brno, Czech Republic. .,Department of Anatomy, Division of Neuroanatomy, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic.
| | - Marek Joukal
- Department of Anatomy, Division of Neuroanatomy, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic.
| | - Ivana Hradilová-Svíženská
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 3, 62500, Brno, Czech Republic. .,Department of Anatomy, Division of Neuroanatomy, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic.
| | - Carmen Guaza
- Department of Functional and Systems Neurobiology, Neuroimmunology Group, Cajal Institute, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain.
| | - Petr Dubový
- Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 3, 62500, Brno, Czech Republic. .,Department of Anatomy, Division of Neuroanatomy, Faculty of Medicine, Masaryk University, Kamenice 3, 62500, Brno, Czech Republic.
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Xu F, Huang J, He Z, Chen J, Tang X, Song Z, Guo Q, Huang C. Microglial polarization dynamics in dorsal spinal cord in the early stages following chronic sciatic nerve damage. Neurosci Lett 2016; 617:6-13. [PMID: 26820376 DOI: 10.1016/j.neulet.2016.01.038] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2015] [Revised: 01/14/2016] [Accepted: 01/21/2016] [Indexed: 11/19/2022]
Abstract
Peripheral nerve injury can lead to activation of spinal microglia, which can mediate neuroinflammation and contribute to neuropathic pain following nerve injury. Activated microglia may manifest with either pro-inflammatory M1 phenotype or anti-inflammatory M2 phenotype, which may lead to detrimental or beneficial roles in the nervous system. In this study, microglia numbers, morphology and gene profiles were examined in the dorsal spinal cord of rats over 14 days following sciatic nerve chronic constriction injury (CCI). The morphology of some microglia changed from a surveying to an activated state within 1 day of CCI. Neuropathic pain developed within seven to 14 days following injury and microglia numbers were increased, with almost all in the dorsal spinal cord morphologically defined as activated. At day one after CCI, both M1 and M2 microglia-related genes were increased but only M1 microglia-related genes remained elevated at day seven and 14 thereafter. These results indicate that both M1 and M2 microglia were activated in the dorsal spinal cord one day after CCI but the microglia skewed towards M1 phenotype during the following seven and 14 days.
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Affiliation(s)
- Fangting Xu
- Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha 410008, China
| | - Juan Huang
- Department of Breast Surgery, Xiangya Hospital of Central South University, Changsha 410008, China
| | - Zhenghua He
- Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha 410008, China
| | - Jia Chen
- Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha 410008, China
| | - Xiaoting Tang
- Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha 410008, China
| | - Zongbin Song
- Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha 410008, China
| | - Qulian Guo
- Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha 410008, China
| | - Changsheng Huang
- Department of Anesthesiology, Xiangya Hospital of Central South University, Changsha 410008, China.
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48
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Abstract
Repeated administration of peroxisome proliferator-activated receptor gamma (PPARγ) agonists reduces neuropathic pain-like behavior and associated changes in glial activation in the spinal cord dorsal horn. As PPARγ is a nuclear receptor, sustained changes in gene expression are widely believed to be the mechanism of pain reduction. However, we recently reported that a single intrathecal (i.t.) injection of pioglitazone, a PPARγ agonist, reduced hyperalgesia within 30 minutes, a time frame that is typically less than that required for genomic mechanisms. To determine the very rapid antihyperalgesic actions of PPARγ activation, we administered pioglitazone to rats with spared nerve injury and evaluated hyperalgesia. Pioglitazone inhibited hyperalgesia within 5 minutes of injection, consistent with a nongenomic mechanism. Systemic or i.t. administration of GW9662, a PPARγ antagonist, inhibited the antihyperalgesic actions of intraperitoneal or i.t. pioglitazone, suggesting a spinal PPARγ-dependent mechanism. To further address the contribution of nongenomic mechanisms, we blocked new protein synthesis in the spinal cord with anisomycin. When coadministered intrathecally, anisomycin did not change pioglitazone antihyperalgesia at an early 7.5-minute time point, further supporting a rapid nongenomic mechanism. At later time points, anisomycin reduced pioglitazone antihyperalgesia, suggesting delayed recruitment of genomic mechanisms. Pioglitazone reduction of spared nerve injury-induced increases in GFAP expression occurred more rapidly than expected, within 60 minutes. We are the first to show that activation of spinal PPARγ rapidly reduces neuropathic pain independent of canonical genomic activity. We conclude that acute pioglitazone inhibits neuropathic pain in part by reducing astrocyte activation and through both genomic and nongenomic PPARγ mechanisms.
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49
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Loggia ML, Chonde DB, Akeju O, Arabasz G, Catana C, Edwards RR, Hill E, Hsu S, Izquierdo-Garcia D, Ji RR, Riley M, Wasan AD, Zürcher NR, Albrecht DS, Vangel MG, Rosen BR, Napadow V, Hooker JM. Evidence for brain glial activation in chronic pain patients. ACTA ACUST UNITED AC 2015; 138:604-15. [PMID: 25582579 DOI: 10.1093/brain/awu377] [Citation(s) in RCA: 337] [Impact Index Per Article: 37.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Although substantial evidence has established that microglia and astrocytes play a key role in the establishment and maintenance of persistent pain in animal models, the role of glial cells in human pain disorders remains unknown. Here, using the novel technology of integrated positron emission tomography-magnetic resonance imaging and the recently developed radioligand (11)C-PBR28, we show increased brain levels of the translocator protein (TSPO), a marker of glial activation, in patients with chronic low back pain. As the Ala147Thr polymorphism in the TSPO gene affects binding affinity for (11)C-PBR28, nine patient-control pairs were identified from a larger sample of subjects screened and genotyped, and compared in a matched-pairs design, in which each patient was matched to a TSPO polymorphism-, age- and sex-matched control subject (seven Ala/Ala and two Ala/Thr, five males and four females in each group; median age difference: 1 year; age range: 29-63 for patients and 28-65 for controls). Standardized uptake values normalized to whole brain were significantly higher in patients than controls in multiple brain regions, including thalamus and the putative somatosensory representations of the lumbar spine and leg. The thalamic levels of TSPO were negatively correlated with clinical pain and circulating levels of the proinflammatory citokine interleukin-6, suggesting that TSPO expression exerts pain-protective/anti-inflammatory effects in humans, as predicted by animal studies. Given the putative role of activated glia in the establishment and or maintenance of persistent pain, the present findings offer clinical implications that may serve to guide future studies of the pathophysiology and management of a variety of persistent pain conditions.
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Affiliation(s)
- Marco L Loggia
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA 2 Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02155, USA
| | - Daniel B Chonde
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Oluwaseun Akeju
- 3 Department of Anesthesia, Critical Care and Pain Medicine, MGH/HMS, Boston, MA 02114, USA
| | - Grae Arabasz
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Ciprian Catana
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Robert R Edwards
- 2 Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02155, USA 4 Department of Psychiatry, Brigham and Women's Hospital, HMS, Boston, MA 02155, USA
| | - Elena Hill
- 5 Tufts University School of Medicine, Boston, MA 02111, USA
| | - Shirley Hsu
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - David Izquierdo-Garcia
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Ru-Rong Ji
- 2 Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02155, USA 6 Departments of Anesthesiology and Neurobiology, Duke University Medical Center, Durham, NC 27705, USA
| | - Misha Riley
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Ajay D Wasan
- 2 Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02155, USA 4 Department of Psychiatry, Brigham and Women's Hospital, HMS, Boston, MA 02155, USA 7 Departments of Anesthesiology and Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15206, USA
| | - Nicole R Zürcher
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Daniel S Albrecht
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Mark G Vangel
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Bruce R Rosen
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA 8 Division of Health Sciences and Technology, Harvard-Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Vitaly Napadow
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA 2 Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02155, USA 9 Department of Biomedical Engineering, Kyung Hee University, Seoul 130-872, Republic of Korea
| | - Jacob M Hooker
- 1 MGH/MIT/HMS Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
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MCP-1 stimulates spinal microglia via PI3K/Akt pathway in bone cancer pain. Brain Res 2014; 1599:158-67. [PMID: 25555372 DOI: 10.1016/j.brainres.2014.12.043] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 12/19/2014] [Accepted: 12/21/2014] [Indexed: 01/25/2023]
Abstract
Accumulating evidence suggests that chemokine monocyte chemoattractant protein-1 (MCP-1) is significantly involved in the activation of spinal microglia associated with pathological pain, at the same time that the phosphatidylinositol 3-kinase/Protein Kinase B (PI3K/Akt) pathway localized in spinal microglia is involved in both neuropathic and inflammatory pain. However, whether there is a connection between MCP-1 and the PI3K/Akt pathway and in their underlying mechanisms in bone cancer pain (BCP) has not yet been elucidated. In the current study, we investigated the expression changes of p-Akt in microglia and OX-42 (microglia marker) after being stimulated with MCP-1 in vitro, as well as in a BCP model that was established by an intramedullary injection of mammary gland carcinoma cells(Walker 256 cells) into the tibia of rats. We observed a significant increase in expression levels of p-Akt and OX-42 in microglia as well as in spinal dorsal horns of BCP rats. Furthermore, the intrathecal administration of an anti-MCP-1 neutralizing antibody or PI3K inhibitor LY294002 reduced the expression of p-Akt or OX-42, and LY294002 attenuated the mechanical allodynia of BCP rats. These results suggest that MCP-1 may stimulate spinal microglia via the PI3K/Akt pathway in BCP.
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