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Poulaki S, Rassouli O, Liapakis G, Gravanis A, Venihaki M. Analgesic and Anti-Inflammatory Effects of the Synthetic Neurosteroid Analogue BNN27 during CFA-Induced Hyperalgesia. Biomedicines 2021; 9:biomedicines9091185. [PMID: 34572370 PMCID: PMC8469064 DOI: 10.3390/biomedicines9091185] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 09/01/2021] [Accepted: 09/07/2021] [Indexed: 01/02/2023] Open
Abstract
Dehydroepiandrosterone (DHEA), an adrenal and neurosteroid hormone with strong neuroprotective and immunomodulatory properties, and ligand for all high-affinity neurotrophin tyrosine kinase receptors (Trk), also exerts important effects on hyperalgesia. Its synthetic, 17-spiro-epoxy analogue, BNN27, cannot be converted to estrogen or androgen as DHEA; it is a specific agonist of TrkA, the receptor of pain regulator Nerve Growth Factor (NGF), and it conserves the immunomodulatory properties of DHEA. Our study aimed to evaluate the anti-nociceptive and anti-inflammatory properties of BNN27 during Complete Freund’s Adjuvant (CFA)-induced inflammatory hyperalgesia in mice. Hyperalgesia was evaluated using the Hargreaves test. Inflammatory markers such as cytokines, NGF and opioids were measured, additionally to corticosterone and the protein kinase B (AKT) signaling pathway. We showed for the first time that treatment with BNN27 reversed hyperalgesia produced by CFA. The effect of BNN27 involved the inhibition of NGF in the dorsal root ganglia (DRG) and the increased synthesis of opioid peptides and their receptors in the inflamed paw. We also found alterations in the cytokine levels as well as in the phosphorylation of AKT2. Our findings strongly support that BNN27 represents a lead molecule for the development of analgesic and anti-inflammatory compounds with potential therapeutic applications in inflammatory hyperalgesia.
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Affiliation(s)
- Smaragda Poulaki
- Department of Clinical Chemistry, Medical School, University of Crete, Voutes, 71110 Heraklion, Greece; (S.P.); (O.R.)
| | - Olga Rassouli
- Department of Clinical Chemistry, Medical School, University of Crete, Voutes, 71110 Heraklion, Greece; (S.P.); (O.R.)
| | - George Liapakis
- Department of Pharmacology, Medical School, University of Crete, Voutes, 71110 Heraklion, Greece; (G.L.); (A.G.)
| | - Achille Gravanis
- Department of Pharmacology, Medical School, University of Crete, Voutes, 71110 Heraklion, Greece; (G.L.); (A.G.)
- Institute of Molecular Biology & Biotechnology, Foundation of Research & Technology-Hellas, 71110 Heraklion, Greece
| | - Maria Venihaki
- Department of Clinical Chemistry, Medical School, University of Crete, Voutes, 71110 Heraklion, Greece; (S.P.); (O.R.)
- Correspondence: ; Tel.: +30-2810-394583
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Luo J, Walters ET, Carlton SM, Hu H. Targeting Pain-evoking Transient Receptor Potential Channels for the Treatment of Pain. Curr Neuropharmacol 2014; 11:652-63. [PMID: 24396340 PMCID: PMC3849790 DOI: 10.2174/1570159x113119990040] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Revised: 06/19/2013] [Accepted: 06/19/2013] [Indexed: 02/06/2023] Open
Abstract
Chronic pain affects billions of lives globally and is a major public health problem in the United States. However, pain management is still a challenging task due to a lack of understanding of the fundamental mechanisms of pain. In the past decades transient receptor potential (TRP) channels have been identified as molecular sensors of tissue damage and inflammation. Activation/sensitization of TRP channels in peripheral nociceptors produces neurogenic inflammation and contributes to both somatic and visceral pain. Pharmacological and genetic studies have affirmed the role of TRP channels in multiple forms of inflammatory and neuropathic pain. Thus pain-evoking TRP channels emerge as promising therapeutic targets for a wide variety of pain and inflammatory conditions.
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Affiliation(s)
- Jialie Luo
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin Street, Houston, TX 77030
| | - Edgar T Walters
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin Street, Houston, TX 77030
| | - Susan M Carlton
- Department of Neuroscience and Cell Biology, University of Texas Medical Branch, 301 University Boulevard, Galveston, TX 77555-1069
| | - Hongzhen Hu
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, 6431 Fannin Street, Houston, TX 77030
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Regulation of avoidant behaviors and pain by the anti-inflammatory tyrosine phosphatase SHP-1. ACTA ACUST UNITED AC 2012; 2:235-46. [PMID: 18250891 DOI: 10.1017/s1740925x07000476] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The protein tyrosine phosphatase SHP-1 is a critical regulator of cytokine signaling and inflammation. Mice homozygous for a null allele at the SHP-1 locus have a phenotype of severe inflammation and are hyper-responsive to the TLR4 ligand LPS. TLR4 stimulation in the CNS has been linked to both neuropathic pain and sickness behaviors. To determine if reduction in SHP-1 expression affects LPS-induced behaviors, responses of heterozygous SHP-1-deficient (me/+) and wild-type (+/+) mice to LPS were measured. Chronic (4-week) treatment with LPS induced avoidant behaviors indicative of fear/anxiety in me/+, but not +/+, mice. These behaviors were correlated with a LPS-induced type 2 cytokine, cytokine receptor, and immune effector arginase profile in the brains of me/+ mice not found in +/+ mice. Me/+ mice also had a constitutively greater level of TLR4 in the CNS than +/+ mice. Additionally, me/+ mice displayed constitutively increased thermal sensitivity compared to +/+ mice, measured by the tail-flick test. Moreover, me/+ glial cultures were more responsive to LPS than +/+ glia. Therefore, the reduced expression of SHP-1 in me/+ imparts haploinsufficiency with respect to the control of CNS TLR4 and pain signaling. Furthermore, type 2 cytokines become prevalent during chronic TLR4 hyperstimulation in the CNS and are associated positively with behaviors that are usually linked to type 1 pro-inflammatory cytokines. These findings question the notion that type 2 immunity is solely anti-inflammatory in the CNS and indicate that type 2 immunity induces/potentiates CNS inflammatory processes.
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Turabi A, Plunkett AR. The application of genomic and molecular data in the treatment of chronic cancer pain. J Surg Oncol 2012; 105:494-501. [DOI: 10.1002/jso.21707] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Dolan S, Hastie P, Crossan C, Nolan AM. Co-induction of cyclooxygenase-2 [correction of cyclooxyenase-2] and early growth response gene (Egr-1) in spinal cord in a clinical model of persistent inflammation and hyperalgesia. Mol Pain 2011; 7:91. [PMID: 22112635 PMCID: PMC3256114 DOI: 10.1186/1744-8069-7-91] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 11/23/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND This study characterised the effects of persistent peripheral inflammation of the foot on pain and spinal cord expression of cyclooxygenase-1 and -2 (COX-1 and COX-2) and early growth response gene 1 (Egr-1), known markers of neuronal plasticity, in a clinical model of naturally-occurring inflammatory disease and hyperalgesia in sheep ('footrot'), before and after routine treatment (parenteral treatment with antibiotics and antiseptic footbathing). The temporal pattern of expression of COX-1, COX-2 and Egr-1 mRNA and protein were analysed using real-time PCR and Western blotting. RESULTS Animals affected with persistent peripheral inflammation displayed significant hyperalgesia and lameness (a proxy indicator of spontaneous pain) restricted to the inflamed limb. Hyperalgesia and lameness were significantly attenuated 1 day after treatment, and resolved further by day 7 and day 3, respectively. COX-2 but not COX-1, protein expression was up-regulated in spinal cord from lame animals on day 0, before treatment. Following treatment and attenuation of pain behaviours, levels of COX-2 returned to control levels. Significant induction of Egr-1 mRNA and protein were observed in spinal cord from lame animals. Three days after treatment, levels of Egr-1 mRNA returned to control levels, however, Egr-1 protein remained elevated. CONCLUSION Elevated levels of spinal COX-2 and Egr-1 protein correlate with the presence of pain and hyperalgesia, and may underlie persistent pain, although a direct causal link has still to be established. Understanding the temporal pattern of expression of key mediators in clinical pain states may lead to better strategies to manage pain.
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Affiliation(s)
- Sharron Dolan
- Department of Biological and Biomedical Sciences, Glasgow Caledonian University, Cowcaddens Road, Glasgow, G4 0BA, UK.
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Gomez R, Por ED, Berg KA, Clarke WP, Glucksman MJ, Jeske NA. Metallopeptidase inhibition potentiates bradykinin-induced hyperalgesia. Pain 2011; 152:1548-1554. [PMID: 21458920 DOI: 10.1016/j.pain.2011.02.044] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 01/10/2011] [Accepted: 02/18/2011] [Indexed: 10/18/2022]
Abstract
The neuropeptide bradykinin (BK) sensitizes nociceptor activation following its release in response to inflammatory injury. Thereafter, the bioactivity of bradykinin is controlled by the enzymatic activities of circulating peptidases. One such enzyme, the metalloendopeptidase EC3.4.24.15 (EP24.15), is co-expressed with bradykinin receptors in primary afferent neurons. In this study, using approaches encompassing pharmacology, biochemistry, cell biology, and behavioral animal models, we identified a crucial role for EP24.15 and the closely related EP24.16 in modulating bradykinin-mediated hyperalgesia. Pharmacological analyses indicated that EP24.15 and EP24.16 inhibition significantly enhances bradykinin type-2 receptor activation by bradykinin in primary trigeminal ganglia cultures. In addition, bradykinin-induced sensitization of TRPV1 activation was increased in the presence of the EP24.15/16 inhibitor JA-2. Furthermore, behavioral analyses illustrated a significant dose-response relationship between JA-2 and bradykinin-mediated thermal hyperalgesia. These results indicate an important physiological role for the metallopeptidases EP24.15 and EP24.16 in regulating bradykinin-mediated sensitization of primary afferent nociceptors.
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Affiliation(s)
- Ruben Gomez
- Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center of San Antonio, TX, USA Department of Pharmacology, University of Texas Health Science Center of San Antonio, TX, USA Center for Biomedical Neuroscience, University of Texas Health Science Center of San Antonio, TX, USA Department of Biochemistry and Molecular Biology and Midwest Proteome Center, Rosalind Franklin University of Medicine and Science/Chicago Medical School, North Chicago, IL, USA
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Bai ZT, Liu T, Jiang F, Cheng M, Pang XY, Hua LM, Shi J, Zhou JJ, Shu XQ, Zhang JW, Ji YH. Phenotypes and peripheral mechanisms underlying inflammatory pain-related behaviors induced by BmK I, a modulator of sodium channels. Exp Neurol 2010; 226:159-72. [DOI: 10.1016/j.expneurol.2010.08.018] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 08/05/2010] [Accepted: 08/12/2010] [Indexed: 10/19/2022]
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Jiang F, Liu T, Cheng M, Pang XY, Bai ZT, Zhou JJ, Ji YH. Spinal astrocyte and microglial activation contributes to rat pain-related behaviors induced by the venom of scorpion Buthus martensi Karch. Eur J Pharmacol 2009; 623:52-64. [PMID: 19782067 DOI: 10.1016/j.ejphar.2009.09.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 08/18/2009] [Accepted: 09/08/2009] [Indexed: 12/30/2022]
Abstract
The present study investigated whether spinal astrocyte and microglia were activated in Buthus martensi Karch (BmK) venom-induced rat pain-related behaviors. The results showed that glial fibrillary acidic protein (GFAP) immunoreactivity indicative astrocyte activation in bilateral spinal cord started to increase by day 3, peaked at day 7 and gradually reversed at day 14 following intraplantar injection of BmK venom. Western blotting analysis confirmed GFAP expression was up-regulated by BmK venom. In contrast, bilateral spinal increase of OX-42 immunoreactivity indicative of microglial activation began at 4h peaked at day 1 and gradually reversed by days 3 to 7 after the administration of BmK venom. Pretreatment with either intrathecal injection of fluorocitrate or intraperitonial injection of minocycline, and two glial activation inhibitors, suppressed the spontaneous nociceptive responses, and prevented the primary thermal and bilateral mechanical hyperalgesia induced by BmK venom. The post-treatment with fluorocitrate or minocycline could not affect the mechanical hyperalgesia. Moreover, minocycline partially inhibited BmK venom-induced spinal c-Fos expression but lack of effects on BmK venom-induced paw edema. Taken together, the current study demonstrated that spinal astrocyte and microglial activation may contribute to BmK venom-induced rat pain-related behaviors. Thus, spinal glia may represent novel targets for effective treatment of pain syndrome associated with scorpion envenomation.
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Affiliation(s)
- Feng Jiang
- Lab of Neuropharmacology and Toxicology, Shanghai University, Shanghai, 200444, PR China
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Wang N, Wang JY, Luo F. Corticofugal outputs facilitate acute, but inhibit chronic pain in rats. Pain 2009; 142:108-15. [PMID: 19167812 DOI: 10.1016/j.pain.2008.12.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Revised: 11/10/2008] [Accepted: 12/08/2008] [Indexed: 11/29/2022]
Abstract
It has been widely accepted that the primary somatosensory cortex (SI) plays an essential role in the sensory-discriminative aspect of pain perception. However, it remains unclear whether the SI has a role in the descending modulation of pain. Although there are abundant fibers projecting back from sensory cortex to thalamic nuclei, and the influence of cortical modulation from SI on the thalamic nociceptive relay neurons has been addressed, little is known about how the cortical outputs modulate the nociceptive behaviors resulting from tissue injury or evoked by painful stimulation. The present study was designed to test whether the cortical outputs influenced the nociceptive behaviors using rat models of noxious thermal-induced acute pain, formalin-induced acute and CFA-evoked chronic inflammatory pain. The results showed that intracortical microinjection of GABAA agonist muscimol significantly reduced the first and second phase behaviors in formalin tests and elevated the nociceptive thresholds in the thermal stimulus-elicited acute pain, suggesting a facilitatory influence of SI on the acute pain sensation. By contrast, microinjection of GABAA antagonist bicuculline remarkably reduced the thermal hyperalgesia of the CFA-inflamed hindpaws, indicating an inhibitory effect of SI output in the chronic pain state. The opposite modulatory effects in acute and chronic pain states suggest that there exists a functional switch for the SI cortex at different stages of pain disease, which is of great significance for the biological adaptation.
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Affiliation(s)
- Ning Wang
- Neuroscience Research Institute and Department of Neurobiology, Peking University, Beijing, PR China
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Bai ZT, Liu T, Pang XY, Jiang F, Cheng M, Ji YH. Functional depletion of capsaicin-sensitive primary afferent fibers attenuates rat pain-related behaviors and paw edema induced by the venom of scorpion Buthus martensi Karch. Neurosci Res 2008; 62:78-85. [PMID: 18619501 DOI: 10.1016/j.neures.2008.06.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Revised: 06/09/2008] [Accepted: 06/10/2008] [Indexed: 11/25/2022]
Abstract
The role of capsaicin-sensitive primary afferent fibers in rat pain-related behaviors and paw edema induced by scorpion Buthus martensi Karch (BmK) venom was investigated in this study. It was found that functional depletion of capsaicin-sensitive primary afferent fibers with a single systemic injection of resiniferatoxin (RTX) dramatically decreased spontaneous nociceptive behaviors, prevented the development of primary mechanical and thermal hyperalgesia as well as mirror-image mechanical hyperalgesia. RTX treatment significantly attenuated BmK venom-induced c-Fos expression in all laminaes of bilateral L4-L5 lumbar spinal cord, especially in superficial laminaes. Moreover, RTX treatment markedly reduced the early paw edema induced by BmK venom. Thus, the results indicate that capsaicin-sensitive primary afferent fibers play a critical role in various pain-related behaviors and paw edema induced by BmK venom in rats.
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Affiliation(s)
- Zhan-Tao Bai
- College of Life Sciences, Yanan University, Yanan 716000, PR China
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Liu T, Bai ZT, Pang XY, Chai ZF, Jiang F, Ji YH. Degranulation of mast cells and histamine release involved in rat pain-related behaviors and edema induced by scorpion Buthus martensi Karch venom. Eur J Pharmacol 2007; 575:46-56. [PMID: 17716653 DOI: 10.1016/j.ejphar.2007.07.057] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2007] [Revised: 07/20/2007] [Accepted: 07/23/2007] [Indexed: 10/23/2022]
Abstract
In the present study, it was investigated whether the degranulation of mast cells and histamine release were involved in rat pain-related behaviors and edema induced by the venom of scorpion Buthus martensi Karch (BmK) or not. It was found that the obvious degranulation of mast cells could be triggered in rat hindpaw skin by BmK venom. The chronic degranulation of mast cells using compound 48/80 relieved the spontaneous nociceptive responses, the primary thermal and bilateral mechanical hyperalgesia and the rat paw edema, as well as partially reduced c-Fos expression in superficial layers (laminae I-II) of bilateral spinal cord induced by BmK venom. In addition, individual peripheral co-administration of either 100 nmol chlorpheniramine or 100 nmol pyrilamine (histamine H(1) receptor antagonist) or 500 nmol cimetidine (histamine H(2) receptor antagonist) and BmK venom suppressed the spontaneous nociceptive responses, partially the primary thermal and bilateral mechanical hyperalgesia and rat paw edema induced by BmK venom. Thus, these results suggest that the peripheral cellular incidents of mast cells degranulation and histamine release are involved in BmK venom-induced pain-related behaviors and inflammation.
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Affiliation(s)
- Tong Liu
- Graduate School of the Chinese Academy of Sciences, Institute of Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, PR China
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Chen WL, Zhang YQ, Zhao ZQ. Neurokinin-1 receptor in peripheral nerve terminals mediates thermal hyperalgesia. Biochem Biophys Res Commun 2005; 339:132-6. [PMID: 16300741 DOI: 10.1016/j.bbrc.2005.11.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2005] [Accepted: 11/07/2005] [Indexed: 10/25/2022]
Abstract
Neurokinin-1 receptor (NK-1) plays an important role in nociception. The present study was to explore whether activation of peripheral NK-1 receptor, especially expressed on primary sensory afferents, could induce hyperalgesia and sensitize C-type sensory afferents. (1) Intraplantar administration of NK-1 agonist [Sar9, Met(O2)11]SP (Sar-SP, 0.2, 1 nmol, 20 microl) produced significant thermal hyperalgesia and edema, which was blocked by co-injection of NK-1 antagonist WIN51,708 (10 nmol). But in the rats with compound 48/80 treatment for mast cell depletion, the Sar-SP-induced edema, but not hyperalgesia, was attenuated. (2) Close-arterial injection of Sar-SP (1 nmol, 0.1 ml) excited and sensitized sensory C afferents of the sural nerve to heat stimuli. The results suggest involvement of NK-1 receptors expressed on the peripheral afferent terminals in thermal hyperalgesia mediated by directly sensitizing C-type sensory afferents.
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Affiliation(s)
- Wen-Ling Chen
- Institute of Neurobiology, Fudan University, Shanghai 200433, China
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Menéndez L, Juárez L, García E, García-Suárez O, Hidalgo A, Baamonde A. Analgesic effects of capsazepine and resiniferatoxin on bone cancer pain in mice. Neurosci Lett 2005; 393:70-3. [PMID: 16243435 DOI: 10.1016/j.neulet.2005.09.046] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 09/16/2005] [Accepted: 09/19/2005] [Indexed: 10/25/2022]
Abstract
In the present paper, we describe the analgesic effects induced by the transient receptor potential vanilloid type 1 (TRPV1) antagonist, capsazepine, and the TRPV1 agonist, resiniferatoxin, on the thermal hyperalgesia induced by the presence of a tibial osteosarcoma or an inflammatory process in mice. The administration of capsazepine abolished the osteosarcoma-induced hyperalgesia at a dose range (3-10 mg/kg; s.c.) ineffective to inhibit the hyperalgesia elicited by the intraplantar administration of complete Freund's adjuvant (CFA). In contrast, the administration of resiniferatoxin (0.01-0.1 mg/kg; s.c.) inhibited both the osteosarcoma- and the CFA-induced hyperalgesia. Remarkably, a single dose of resiniferatoxin abolished the osteosarcoma-induced hyperalgesia for several days and completely prevented the instauration of thermal hyperalgesia when administered at the initial stages of osteosarcoma development. The potential of drugs acting through TRPV1 for the management of some types of bone cancer pain is proposed.
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Affiliation(s)
- Luis Menéndez
- Laboratorio de Farmacología, Facultad de Medicina, Instituto Universitario de Oncología del Principado de Asturias, IUOPA, Universidad de Oviedo, C/ Julián Clavería 6, 33006 Oviedo, Spain.
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Shinoda M, Ozaki N, Asai H, Nagamine K, Sugiura Y. Changes in P2X3 receptor expression in the trigeminal ganglion following monoarthritis of the temporomandibular joint in rats. Pain 2005; 116:42-51. [PMID: 15936887 DOI: 10.1016/j.pain.2005.03.042] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2004] [Revised: 03/08/2005] [Accepted: 03/29/2005] [Indexed: 11/22/2022]
Abstract
The pathophysiological mechanisms of orofacial deep-tissue pain is still unclear. Previously, P2X receptors (P2XR) in sensory neurons have been shown to play a role in the signal transduction of cutaneous pain. We investigated the functional significance of P2X3R in relation to orofacial deep-tissue pain caused by monoarthritis of the temporomandibular joint (TMJ). Monoarthritis was induced by the injection of complete Freund's adjuvant (CFA) into the unilateral TMJ of the rat. The pain associated with monoarthritis was assessed by the pressure pain threshold (PPT), which was defined as the amount of pressure required to induce vocalization. Fifteen days after CFA-treatment, changes in PPT were examined after injection of P2XR agonists or antagonists into the TMJ. The number of cells expressing P2X3R in trigeminal ganglia (TG) was investigated by immunohistochemistry. Inflamed TMJ showed a continuous decline in PPT during the experimental period (P<0.001). Injection of alpha,beta-meATP, an agonist of P2X1,3,2/3R, dramatically reduced the bilateral PPTs of both inflamed and non-inflamed TMJs (P<0.01) although beta,gamma-me-l-ATP, a selective agonist of P2X1R, did not. The decreased PPTs of inflamed TMJ were reversed either by PPADS, an antagonist of P2X1,2,3,5,1/5,4/5R, or by TNP-ATP, an antagonist of P2X1,3,2/3,1/5R. Immunohistochemically, the number of P2X3R-positive cells increased in the small cell group in TG (P<0.01), whereas there was no change in medium or large cell groups after the CFA-injection. Retrograde tracing confirmed that TMJ neurons in the TG exhibited P2X3R immunoreactivity. Our results suggested that P2X3R plays an important role in orofacial pressure pain caused by monoarthritis of TMJ.
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Affiliation(s)
- Masamichi Shinoda
- Department of Functional Anatomy and Neuroscience, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho Showa-ku, Nagoya 466-8550, Japan
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Baamonde A, Lastra A, Juarez L, Hidalgo A, Menéndez L. TRPV1 desensitisation and endogenous vanilloid involvement in the enhanced analgesia induced by capsaicin in inflamed tissues. Brain Res Bull 2005; 67:476-81. [PMID: 16216696 DOI: 10.1016/j.brainresbull.2005.07.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2005] [Accepted: 07/05/2005] [Indexed: 11/17/2022]
Abstract
The intra-plantar acute administration of 10 microg of capsaicin to mice which had received complete Freund's adjuvant (CFA) 1 week before inhibits the thermal inflammatory hyperalgesia it induces and even produces a long-lasting analgesia for at least 2 weeks. In this study, we show that the administration of capsaicin (10 microg) also reduces the immediate licking behavior evoked by the intra-plantar administration of a lower dose of capsaicin (0.1 microg), the duration of this inhibitory effect being greater in CFA-inflamed mice (at least 2 weeks) than in non-inflamed animals (less than 4 days). Since this reduction of capsaicin-induced licking behavior may be interpreted as a consequence of the transient receptor potential vanilloid 1 receptor (TRPV1) unresponsiveness, we conclude that the administration of 10 microg of capsaicin into inflamed tissues can render the TRPV1 desensitised. We next explored whether endogenous vanilloids released during inflammation contribute to maintain the analgesia triggered by exogenous capsaicin. The acute administration of capsazepine (10 microg; intra-plantarly (i.pl.)) abolished the analgesic effect induced by the injection of capsaicin 1 week before in inflamed mice. From these results, it may be proposed that the maintenance by endovanilloids of the TRPV1 desensitisation induced by capsaicin could contribute to prolonging the analgesic effect induced by this agonist in inflamed tissues.
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Affiliation(s)
- Ana Baamonde
- Laboratorio de Farmacología, Facultad de Medicina, Instituto Universitario de Oncología del Principado de Asturias (IUOPA), Universidad de Oviedo, C/Julián Clavería 6, 33006 Oviedo, Asturias, Spain.
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