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Dvornikova KA, Platonova ON, Bystrova EY. The Role of TRP Channels in Sepsis and Colitis. Int J Mol Sci 2024; 25:4784. [PMID: 38731999 PMCID: PMC11084600 DOI: 10.3390/ijms25094784] [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: 03/31/2024] [Revised: 04/20/2024] [Accepted: 04/24/2024] [Indexed: 05/13/2024] Open
Abstract
To date, several members of the transient receptor potential (TRP) channels which provide a wide array of roles have been found in the gastrointestinal tract (GI). The goal of earlier research was to comprehend the intricate signaling cascades that contribute to TRP channel activation as well as how these receptors' activity affects other systems. Moreover, there is a large volume of published studies describing the role of TRP channels in a number of pathological disorders, including inflammatory bowel disease (IBD) and sepsis. Nevertheless, the generalizability of these results is subject to certain limitations. For instance, the study of IBD relies on various animal models and experimental methods, which are unable to precisely imitate the multifactorial chronic disease. The diverse pathophysiological mechanisms and unique susceptibility of animals may account for the inconsistency of the experimental data collected. The main purpose of this study was to conduct a comprehensive review and analysis of existing studies on transient receptor potential (TRP) channels implicating specific models of colitis and sepsis, with particular emphasis on their involvement in pathological disorders such as IBD and sepsis. Furthermore, the text endeavors to evaluate the generalizability of experimental findings, taking into consideration the limitations posed by animal models and experimental methodologies. Finally, we also provide an updated schematic of the most important and possible molecular signaling pathways associated with TRP channels in IBD and sepsis.
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Affiliation(s)
| | | | - Elena Y. Bystrova
- I.P. Pavlov Institute of Physiology RAS, 199034 St. Petersburg, Russia; (K.A.D.); (O.N.P.)
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Zhang M, Ma Y, Ye X, Zhang N, Pan L, Wang B. TRP (transient receptor potential) ion channel family: structures, biological functions and therapeutic interventions for diseases. Signal Transduct Target Ther 2023; 8:261. [PMID: 37402746 DOI: 10.1038/s41392-023-01464-x] [Citation(s) in RCA: 36] [Impact Index Per Article: 36.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 03/26/2023] [Accepted: 04/25/2023] [Indexed: 07/06/2023] Open
Abstract
Transient receptor potential (TRP) channels are sensors for a variety of cellular and environmental signals. Mammals express a total of 28 different TRP channel proteins, which can be divided into seven subfamilies based on amino acid sequence homology: TRPA (Ankyrin), TRPC (Canonical), TRPM (Melastatin), TRPML (Mucolipin), TRPN (NO-mechano-potential, NOMP), TRPP (Polycystin), TRPV (Vanilloid). They are a class of ion channels found in numerous tissues and cell types and are permeable to a wide range of cations such as Ca2+, Mg2+, Na+, K+, and others. TRP channels are responsible for various sensory responses including heat, cold, pain, stress, vision and taste and can be activated by a number of stimuli. Their predominantly location on the cell surface, their interaction with numerous physiological signaling pathways, and the unique crystal structure of TRP channels make TRPs attractive drug targets and implicate them in the treatment of a wide range of diseases. Here, we review the history of TRP channel discovery, summarize the structures and functions of the TRP ion channel family, and highlight the current understanding of the role of TRP channels in the pathogenesis of human disease. Most importantly, we describe TRP channel-related drug discovery, therapeutic interventions for diseases and the limitations of targeting TRP channels in potential clinical applications.
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Affiliation(s)
- Miao Zhang
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
- Experiment Center for Science and Technology, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
- The Center for Microbes, Development and Health; Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200031, China
| | - Yueming Ma
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
| | - Xianglu Ye
- Institute of Interdisciplinary Integrative Medicine Research, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
| | - Ning Zhang
- Experiment Center for Science and Technology, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China.
| | - Lei Pan
- The Center for Microbes, Development and Health; Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, Shanghai, 200031, China.
- CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Bing Wang
- School of Pharmacy, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China.
- Center for Pharmaceutics Research, Shanghai Institute of Materia Medica Chinese Academy of Sciences, Shanghai, 201203, China.
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Psychosocial Stress Induces Orofacial Mechanical Allodynia Due to the Enhancement of Transient Receptor Potential Ankyrin 1 Expression in Trigeminal Ganglion Neurons via the Increment of the Trace Amine-Associated Receptor 7f Expression. STRESSES 2022. [DOI: 10.3390/stresses3010006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
(1) Background: Chronic psychosocial stress can lead to oral dysesthesia with tongue pain. We examined whether psychosocial stress causes orofacial pain, and analyzed the comprehensive gene expression patterns of circulating cells and transient receptor potential ankyrin 1 (TRPA1) expression in trigeminal ganglion (TG) neurons in a mouse model of psychosocial stress. (2) Methods: Mice were divided into two groups: one group was kept in confrontational housing, and the other group was kept in single housing. Blood, adrenal gland, and tongue were collected. The head withdrawal threshold (HWT) of mechanical stimulation to the whisker pad skin was measured. TRPA1-positive TG neurons were immunohistochemically examined. DNA microarray analysis and quantitative reverse transcription polymerase chain reaction analysis were performed. (3) Results: The HWT was significantly lower in mice under the psychosocial stress condition compared to non-stressed mice. In stress-loaded mice, the number of TRPA1-positive TG neurons was significantly increased. Moreover, we showed that trace amine-associated receptor 7f expression was upregulated in circulating cells in blood and downregulated in the tongue. (4) Conclusions: Our results indicated that chronic psychosocial stress induced the orofacial mechanical allodynia through enhancement of TRPA1 expression in TG neurons with changes in the levels of trace amine-associated receptor 7f.
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Microglia activation and temporal changes in rat model of trigeminal neuralgia. HUA XI KOU QIANG YI XUE ZA ZHI = HUAXI KOUQIANG YIXUE ZAZHI = WEST CHINA JOURNAL OF STOMATOLOGY 2022; 40:638-644. [PMID: 36416315 PMCID: PMC9763952 DOI: 10.7518/hxkq.2022.06.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVES This study aimed to investigate whether the microglia in the spinal trigeminal nucleus caudal part (Sp5C) were activated in a rat model of trigeminal neuralgia and to explore whether the activation level of microglia is consistent with maxillofacial pain level. METHODS Chronic constriction injury of trigeminal nerve (CCI) was induced by partial ligation of infraorbital nerve (IoN) in rats. The behavioral change of rats observed at D1, D5, D10, D15, and D30 days post-surgery and the change of pain threshold were detected with electronic Von Frey filaments served as an evaluation index of maxillofacial pain. Weight change was measured by weighing. Ionized calcium binding adaptor molecule-1 (Iba-1) expression level of Sp5C at each time point was detected, and three microglia morphological categories were analyzed by immunohistochemical staining. RESULTS The changes of behavioral and pain threshold suggested the maxillofacial pain level first increased and then decreased post-surgery in the IoN-CCI group. Both the expressions of Iba-1 and proportion of ameboid morphology in ipsilateral Sp5C increased from D1 and reached their peaks in D10 and D5, respectively. Then, they recovered nearly to the same level with contralateral Sp5C on D30. This trend was consistent with the maxillofacial change. CONCLUSIONS The model of trigeminal neuralgia in rats constructed by partial ligation of infraorbital nerve can induce the activation of microglia in Sp5C, and the activation level is consistent with maxillofacial pain, which reached its peak at around D10 post-surgery.
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Li Z, Zhang H, Wang Y, Li Y, Li Q, Zhang L. The distinctive role of menthol in pain and analgesia: Mechanisms, practices, and advances. Front Mol Neurosci 2022; 15:1006908. [PMID: 36277488 PMCID: PMC9580369 DOI: 10.3389/fnmol.2022.1006908] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 09/13/2022] [Indexed: 11/13/2022] Open
Abstract
Menthol is an important flavoring additive that triggers a cooling sensation. Under physiological condition, low to moderate concentrations of menthol activate transient receptor potential cation channel subfamily M member 8 (TRPM8) in the primary nociceptors, such as dorsal root ganglion (DRG) and trigeminal ganglion, generating a cooling sensation, whereas menthol at higher concentration could induce cold allodynia, and cold hyperalgesia mediated by TRPM8 sensitization. In addition, the paradoxical irritating properties of high concentrations of menthol is associated with its activation of transient receptor potential cation channel subfamily A member 1 (TRPA1). Under pathological situation, menthol activates TRPM8 to attenuate mechanical allodynia and thermal hyperalgesia following nerve injury or chemical stimuli. Recent reports have recapitulated the requirement of central group II/III metabotropic glutamate receptors (mGluR) with endogenous κ-opioid signaling pathways for menthol analgesia. Additionally, blockage of sodium channels and calcium influx is a determinant step after menthol exposure, suggesting the possibility of menthol for pain management. In this review, we will also discuss and summarize the advances in menthol-related drugs for pathological pain treatment in clinical trials, especially in neuropathic pain, musculoskeletal pain, cancer pain and postoperative pain, with the aim to find the promising therapeutic candidates for the resolution of pain to better manage patients with pain in clinics.
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Affiliation(s)
- Ziping Li
- The Graduate School, Tianjin Medical University, Tianjin, China
| | - Haoyue Zhang
- The Graduate School, Tianjin Medical University, Tianjin, China
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, China
| | - Yigang Wang
- The Graduate School, Tianjin Medical University, Tianjin, China
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, China
| | - Yize Li
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, China
| | - Qing Li
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, China
- Qing Li,
| | - Linlin Zhang
- Department of Anesthesiology, Tianjin Medical University General Hospital, Tianjin, China
- *Correspondence: Linlin Zhang,
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Ness TJ, DeWitte C, DeBerry JJ, Hart MP, Clodfelder-Miller B, Gu JG, Ling J, Randich A. A Model in Female Rats With Phenotypic Features Similar to Interstitial Cystitis/Bladder Pain Syndrome. FRONTIERS IN PAIN RESEARCH 2021; 2:791045. [PMID: 35295535 PMCID: PMC8915626 DOI: 10.3389/fpain.2021.791045] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 11/03/2021] [Indexed: 12/16/2022] Open
Abstract
This report describes methodological and exploratory investigations of the zymosan-induced neonatal bladder inflammation (NBI) model of interstitial cystitis/bladder pain syndrome (IC/BPS) in female rats. These results validate and extend the currently employed model by evaluating critical timepoints for obtaining treatment effects and identified that a second insult as an adult including repeat intravesical zymosan, intravesical lipopolysaccharide, acute footshock stress, neuropathic nociception (facial) or somatic inflammation (hindpaw) all resulted in magnified visceromotor responses to urinary bladder distension (UBD) in rats which had experienced NBI when compared with their controls. NBI also resulted in increased tone and reactivity of pelvic floor musculature to UBD, as well as increased responsiveness to intravesical potassium chloride solutions, abnormal anxiety measures (elevated plus maze) and an increased number of submucosal petechial hemorrhages following 30 min of hydrodistension of the bladder. These phenotypic findings have correlates to the clinical features of IC/BPS in humans and so support use of this model system to examine mechanisms of and treatments for IC/BPS.
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Transient Receptor Potential (TRP) Ion Channels in Orofacial Pain. Mol Neurobiol 2021; 58:2836-2850. [PMID: 33515176 DOI: 10.1007/s12035-021-02284-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Accepted: 01/05/2021] [Indexed: 02/07/2023]
Abstract
Orofacial pain, including temporomandibular joint disorders pain, trigeminal neuralgia, dental pain, and debilitating headaches, affects millions of Americans each year with significant population health impact. Despite the existence of a large body of information on the subject, the molecular underpinnings of orofacial pain remain elusive. Two decades of research has identified that transient receptor potential (TRP) ion channels play a crucial role in pathological pain. A number of TRP ion channels are clearly expressed in the trigeminal sensory system and have critical functions in the transduction and pathogenesis of orofacial pain. Although there are many similarities, the orofacial sensory system shows some distinct peripheral and central pain processing and different sensitivities from the spinal sensory system. Relative to the extensive review on TRPs in spinally-mediated pain, the summary of TRPs in trigeminally-mediated pain has not been well-documented. This review focuses on the current experimental evidence involving TRP ion channels, particularly TRPV1, TRPA1, TRPV4, and TRPM8 in orofacial pain, and discusses their possible cellular and molecular mechanisms.
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Kv4.3 Channel Dysfunction Contributes to Trigeminal Neuropathic Pain Manifested with Orofacial Cold Hypersensitivity in Rats. J Neurosci 2021; 41:2091-2105. [PMID: 33472822 DOI: 10.1523/jneurosci.2036-20.2021] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2020] [Revised: 01/08/2021] [Accepted: 01/11/2021] [Indexed: 02/06/2023] Open
Abstract
Trigeminal neuropathic pain is the most debilitating pain disorder but current treatments including opiates are not effective. A common symptom of trigeminal neuropathic pain is cold allodynia/hyperalgesia or cold hypersensitivity in orofacial area, a region where exposure to cooling temperatures are inevitable in daily life. Mechanisms underlying trigeminal neuropathic pain manifested with cold hypersensitivity are not fully understood. In this study, we investigated trigeminal neuropathic pain in male rats following infraorbital nerve chronic constrictive injury (ION-CCI). Assessed by the orofacial operant behavioral test, ION-CCI animals displayed orofacial cold hypersensitivity. The cold hypersensitivity was associated with the hyperexcitability of small-sized trigeminal ganglion (TG) neurons that innervated orofacial regions. Furthermore, ION-CCI resulted in a reduction of A-type voltage-gated K+ currents (IA currents) in these TG neurons. We further showed that these small-sized TG neurons expressed Kv4.3 voltage-gated K+ channels, and Kv4.3 expression in these cells was significantly downregulated following ION-CCI. Pharmacological inhibition of Kv4.3 channels with phrixotoxin-2 inhibited IA-currents in these TG neurons and induced orofacial cold hypersensitivity. On the other hand, pharmacological potentiation of Kv4.3 channels amplified IA currents in these TG neurons and alleviated orofacial cold hypersensitivity in ION-CCI rats. Collectively, Kv4.3 downregulation in nociceptive trigeminal afferent fibers may contribute to peripheral cold hypersensitivity following trigeminal nerve injury, and Kv4.3 activators may be clinically useful to alleviate trigeminal neuropathic pain.SIGNIFICANCE STATEMENT Trigeminal neuropathic pain, the most debilitating pain disorder, is often triggered and exacerbated by cooling temperatures. Here, we created infraorbital nerve chronic constrictive injury (ION-CCI) in rats, an animal model of trigeminal neuropathic pain to show that dysfunction of Kv4.3 voltage-gated K+ channels in nociceptive-like trigeminal ganglion (TG) neurons underlies the trigeminal neuropathic pain manifested with cold hypersensitivity in orofacial regions. Furthermore, we demonstrate that pharmacological potentiation of Kv4.3 channels can alleviate orofacial cold hypersensitivity in ION-CCI rats. Our results may have clinical implications in trigeminal neuropathic pain in human patients, and Kv4.3 channels may be an effective therapeutic target for this devastating pain disorder.
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De Caro C, Cristiano C, Avagliano C, Bertamino A, Ostacolo C, Campiglia P, Gomez-Monterrey I, La Rana G, Gualillo O, Calignano A, Russo R. Characterization of New TRPM8 Modulators in Pain Perception. Int J Mol Sci 2019; 20:ijms20225544. [PMID: 31703254 PMCID: PMC6888553 DOI: 10.3390/ijms20225544] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 10/25/2019] [Accepted: 11/06/2019] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND Transient Receptor Potential Melastatin-8 (TRPM8) is a non-selective cation channel activated by cold temperature and by cooling agents. Several studies have proved that this channel is involved in pain perception. Although some studies indicate that TRPM8 inhibition is necessary to reduce acute and chronic pain, it is also reported that TRPM8 activation produces analgesia. These conflicting results could be explained by extracellular Ca2+-dependent desensitization that is induced by an excessive activation. Likely, this effect is due to phosphatidylinositol 4,5-bisphosphate (PIP2) depletion that leads to modification of TRPM8 channel activity, shifting voltage dependence towards more positive potentials. This phenomenon needs further evaluation and confirmation that would allow us to understand better the role of this channel and to develop new therapeutic strategies for controlling pain. EXPERIMENTAL APPROACH To understand the role of TRPM8 in pain perception, we tested two specific TRPM8-modulating compounds, an antagonist (IGM-18) and an agonist (IGM-5), in either acute or chronic animal pain models using male Sprague-Dawley rats or CD1 mice, after systemic or topical routes of administration. RESULTS IGM-18 and IGM-5 were fully characterized in vivo. The wet-dog shake test and the body temperature measurements highlighted the antagonist activity of IGM-18 on TRPM8 channels. Moreover, IGM-18 exerted an analgesic effect on formalin-induced orofacial pain and chronic constriction injury-induced neuropathic pain, demonstrating the involvement of TRPM8 channels in these two pain models. Finally, the results were consistent with TRPM8 downregulation by agonist IGM-5, due to its excessive activation. CONCLUSIONS TRPM8 channels are strongly involved in pain modulation, and their selective antagonist is able to reduce both acute and chronic pain.
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Affiliation(s)
- Carmen De Caro
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
- Department of Science of Health, School of Medicine and Surgery, University of Catanzaro, 88100 Catanzaro, Italy
| | - Claudia Cristiano
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
| | - Carmen Avagliano
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
| | - Alessia Bertamino
- Department of Pharmacy, University of Salerno, 84084 Fisciano, Italy; (A.B.); (P.C.)
| | - Carmine Ostacolo
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
| | - Pietro Campiglia
- Department of Pharmacy, University of Salerno, 84084 Fisciano, Italy; (A.B.); (P.C.)
| | - Isabel Gomez-Monterrey
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
| | - Giovanna La Rana
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
| | - Oreste Gualillo
- SERGAS (Servizo Galego de Saude) and IDIS (Instituto de Investigación Sanitaria de Santiago), The NEIRID Group (Neuroendocrine Interactions in Rheumatology and inflammatory Diseases), Santiago University Clinical Hospital, 15706 Santiago de Compostela, Spain;
| | - Antonio Calignano
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
| | - Roberto Russo
- Department of Pharmacy, University of Naples Federico II, 80131 Naples, Italy; (C.D.C.); (C.C.); (C.A.); (C.O.); (I.G.-M.); (G.L.R.); (A.C.)
- Correspondence:
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Araújo-Filho HG, Pereira EWM, Campos AR, Quintans-Júnior LJ, Quintans JSS. Chronic orofacial pain animal models - progress and challenges. Expert Opin Drug Discov 2018; 13:949-964. [PMID: 30220225 DOI: 10.1080/17460441.2018.1524458] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
INTRODUCTION Chronic orofacial pain is one of the most common pain conditions experienced by adults. Animal models are often selected as the most useful scientific methodology to explore the pathophysiology of the disorders that cause this disabling pain to facilitate the development of new treatments. The creation of new models or the improvement of existing ones is essential for finding new ways to approach the complex neurobiology of this type of pain. Areas covered: The authors describe and discuss a variety of animal models used in chronic orofacial pain (COFP). Furthermore, they examine in detail the mechanisms of action involved in orofacial neuropathic pain and orofacial inflammatory pain. Expert opinion: The use of animal models has several advantages in chronic orofacial pain drug discovery. Choosing an animal model that most closely represents the human disease helps to increase the chances of finding effective new therapies and is key to the successful translation of preclinical research to clinical practice. Models using genetically modified animals seem promising but have not yet been fully developed for use in chronic orofacial pain research. Although animal models have provided significant advances in the pharmacological treatment of orofacial pain, several barriers still need to be overcome for better treatment options.
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Affiliation(s)
- Heitor G Araújo-Filho
- a Laboratory of Neuroscience and Pharmacological Assays (LANEF), Department of Physiology , Federal University of Sergipe , São Cristóvão , Brazil
| | - Erik W M Pereira
- a Laboratory of Neuroscience and Pharmacological Assays (LANEF), Department of Physiology , Federal University of Sergipe , São Cristóvão , Brazil
| | - Adriana Rolim Campos
- b Experimental Biology Centre (NUBEX) , University of Fortaleza (UNIFOR) , Fortaleza , Brazil
| | - Lucindo J Quintans-Júnior
- a Laboratory of Neuroscience and Pharmacological Assays (LANEF), Department of Physiology , Federal University of Sergipe , São Cristóvão , Brazil
| | - Jullyana S S Quintans
- a Laboratory of Neuroscience and Pharmacological Assays (LANEF), Department of Physiology , Federal University of Sergipe , São Cristóvão , Brazil
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Ling J, Erol F, Viatchenko-Karpinski V, Kanda H, Gu JG. Orofacial neuropathic pain induced by oxaliplatin: downregulation of KCNQ2 channels in V2 trigeminal ganglion neurons and treatment by the KCNQ2 channel potentiator retigabine. Mol Pain 2018; 13:1744806917724715. [PMID: 28741430 PMCID: PMC5549876 DOI: 10.1177/1744806917724715] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Neuropathic pain induced by chemotherapy drugs such as oxaliplatin is a dose-limiting side effect in cancer treatment. The mechanisms underlying chemotherapy-induced neuropathic pain are not fully understood. KCNQ2 channels are low-threshold voltage-gated K+ channels that play a role in controlling neuronal excitability. Downregulation of KCNQ2 channels has been proposed to be an underlying mechanism of sensory hypersensitivity that leads to neuropathic pain. However, it is currently unknown whether KCNQ channels may be downregulated by chemotherapy drugs in trigeminal ganglion neurons to contribute to the pathogenesis of chemotherapy-induced orofacial neuropathic pain. In the present study, mechanical sensitivity in orofacial regions is measured using the operant behavioral test in rats treated with oxaliplatin. Operant behaviors in these animals show the gradual development of orofacial neuropathic pain that manifests with orofacial mechanical allodynia. Immunostaining shows strong KCNQ2 immunoreactivity in small-sized V2 trigeminal ganglion neurons in controls, and the numbers of KCNQ2 immunoreactivity positive V2 trigeminal ganglion neurons are significantly reduced in oxaliplatin-treated animals. Immunostaining is also performed in brainstem and shows strong KCNQ2 immunoreactivity at the trigeminal afferent central terminals innervating the caudal spinal trigeminal nucleus (Vc) in controls, but the KCNQ2 immunoreactivity intensity is significantly reduced in oxaliplatin-treated animals. We further show with the operant behavioral test that oxaliplatin-induced orofacial mechanical allodynia can be alleviated by the KCNQ2 potentiator retigabine. Taken together, these findings suggest that KCNQ2 downregulation may be a cause of oxaliplatin-induced orofacial neuropathic pain and KCNQ2 potentiators may be useful for alleviating the neuropathic pain.
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Affiliation(s)
- Jennifer Ling
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Ferhat Erol
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | | | - Hirosato Kanda
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
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De Caro C, Russo R, Avagliano C, Cristiano C, Calignano A, Aramini A, Bianchini G, Allegretti M, Brandolini L. Antinociceptive effect of two novel transient receptor potential melastatin 8 antagonists in acute and chronic pain models in rat. Br J Pharmacol 2018; 175:1691-1706. [PMID: 29485712 DOI: 10.1111/bph.14177] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 01/23/2018] [Accepted: 02/05/2018] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND AND PURPOSE Transient receptor potential (TRP) channels are a superfamily of non-selective cation permeable channels involved in peripheral sensory signalling. Animal studies have shown that several TRPs are important players in pain modulation. Among them, the TRP melastatin 8 (TRPM8) has elicited more interest for its controversial role in nociception. This channel, expressed by a subpopulation of sensory neurons in dorsal root ganglia (DRG) and trigeminal ganglia (TG), is activated by cold temperatures and cooling agents. In experimental neuropathic pain models, an up-regulation of this receptor in DRG and TG has been observed, suggesting a key role for TRPM8 in the development and maintenance of pain. Consistent with this hypothesis, TRPM8 knockout mice are less responsive to pain stimuli. EXPERIMENTAL APPROACH In this study, the therapeutic potential and efficacy of two novel TRPM8 antagonists, DFL23693 and DFL23448, were tested. KEY RESULTS Two potent and selective TRPM8 antagonists with distinct pharmacokinetic profiles, DFL23693 and DFL23448, have been fully characterized in vitro. In vivo studies in well-established models, namely, the wet-dog shaking test and changes in body temperature, confirmed their ability to block the TRPM8 channel. Finally, TRPM8 blockage resulted in a significant antinociceptive effect in formalin-induced orofacial pain and in chronic constriction injury-induced neuropathic pain, confirming an important role for this channel in pain perception. CONCLUSION AND IMPLICATIONS Our findings, in agreement with previous literature, encourage further studies for a better comprehension of the therapeutic potential of TRPM8 blockers as novel agents for pain management.
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Affiliation(s)
- Carmen De Caro
- Department of Pharmacy, University of Naples Federico II, Naples, Italy.,Department of Science of Health, School of Medicine and Surgery, University of Catanzaro, Catanzaro, Italy
| | - Roberto Russo
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Carmen Avagliano
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Claudia Cristiano
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
| | - Antonio Calignano
- Department of Pharmacy, University of Naples Federico II, Naples, Italy
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Ling J, Erol F, Gu JG. Role of KCNQ2 channels in orofacial cold sensitivity: KCNQ2 upregulation in trigeminal ganglion neurons after infraorbital nerve chronic constrictive injury. Neurosci Lett 2018; 664:84-90. [PMID: 29133175 PMCID: PMC5817018 DOI: 10.1016/j.neulet.2017.11.026] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 11/08/2017] [Accepted: 11/09/2017] [Indexed: 11/17/2022]
Abstract
Sensitivity to cooling temperatures often becomes heightened in orofacial regions leading to orofacial cold allodynia/hyperalgesia after chronic trigeminal nerve injury. KCNQ2 channels are involved in controlling excitability of primary afferent neurons and thereby regulate sensory functions under both physiological and pathological conditions. In the present study, we sought to determine whether KCNQ2 channels in trigeminal nerves are involved in regulating orofacial operant behavioral responses to cooling stimulation. We also sought to examine whether chronic trigeminal nerve injury may alter KCNQ2 channel expression in trigeminal ganglions. Using the orofacial operant tests, animals show cold allodynia/hyperalgesia in orofacial regions following infraorbital nerve chronic constrictive injury (ION-CCI), which could be alleviated by subcutaneous administration of retigabine, a KCNQ2 activator. In contrast, subcutaneous administration of the KCNQ2 inhibitor XE991 directly elicits cold allodynia/hyperalgesia in sham animals. Using immunostaining, we show that KCNQ2 channels are primarily expressed in small-sized TG neurons. Interestingly, KCNQ2 channel expression becomes significantly upregulated in TG neurons following the ION-CCI. Our results suggest that KCNQ2 channels are involved in regulating orofacial cold sensitivity. Upregulation of KCNQ2 channels may be a compensatory change in attempting to limit injury-induced trigeminal hyperexcitability.
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Affiliation(s)
- Jennifer Ling
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Ferhat Erol
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States
| | - Jianguo G Gu
- Department of Anesthesiology and Perioperative Medicine, University of Alabama at Birmingham, Birmingham, AL, 35294, United States.
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Dussor G, Cao YQ. TRPM8 and Migraine. Headache 2016; 56:1406-1417. [PMID: 27634619 PMCID: PMC5335856 DOI: 10.1111/head.12948] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 05/31/2016] [Accepted: 06/19/2016] [Indexed: 12/27/2022]
Abstract
Migraine is among the most common diseases on earth and one of the most disabling, the latter due in large part to poor treatment efficacy. Development of new therapeutics is dependent on the identification of mechanisms contributing to migraine and discovery of targets for new drugs. Numerous genome-wide association studies (GWAS) have implicated the transient receptor-potential M8 (TRPM8) channel in migraine. This channel is predominantly expressed on peripheral sensory neurons and is known as the sensor for cold temperature in cutaneous tissue but is also expressed on deep visceral afferents where cold is not likely a stimulus. Consequently, a number of alternative endogenous agonists have been proposed. Apart from its role in cold sensation, TRPM8 also contributes to cold allodynia after nerve injury or inflammation, and it is necessary for cooling/menthol-based analgesia. How it might contribute to migraine is less clear. The purpose of this review is to discuss the anatomical and physiological mechanisms by which meningeal TRPM8 may play a role in migraine as well as the potential of TRPM8 as a therapeutic target. TRPM8 is expressed on sensory afferents innervating the meninges, and these neurons are subject to developmental changes that may influence their contribution to migraine. As in viscera, meningeal TRPM8 channels are unlikely to be activated by temperature fluctuations and their endogenous ligands remain unknown. Preclinical migraine studies show that activation of meningeal TRPM8 by exogenous agonists can both cause and alleviate headache behaviors, depending on whether other meningeal afferents concurrently receive noxious stimuli. This is reminiscent of the fact that cold can trigger migraine in humans but menthol can also alleviate headache. We propose that both TRPM8 agonists and antagonists may be potential therapeutics, depending on how migraine is triggered in individual patients. In this regard, TRPM8 may be a novel target for personalized medicine in migraine treatment.
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Affiliation(s)
- Greg Dussor
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Richardson, TX, USA.
| | - Yu-Qing Cao
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA
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Pérez de Vega MJ, Gómez-Monterrey I, Ferrer-Montiel A, González-Muñiz R. Transient Receptor Potential Melastatin 8 Channel (TRPM8) Modulation: Cool Entryway for Treating Pain and Cancer. J Med Chem 2016; 59:10006-10029. [PMID: 27437828 DOI: 10.1021/acs.jmedchem.6b00305] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
TRPM8 ion channels, the primary cold sensors in humans, are activated by innocuous cooling (<28 °C) and cooling compounds (menthol, icilin) and are implicated in sensing unpleasant cold stimuli as well as in mammalian thermoregulation. Overexpression of these thermoregulators in prostate cancer and in other life-threatening tumors, along with their contribution to an increasing number of pathological conditions, opens a plethora of medicinal chemistry opportunities to develop receptor modulators. This Perspective seeks to describe current known modulators for this ion channel because both agonists and antagonists may be useful for the treatment of most TRPM8-mediated pathologies. We primarily focus on SAR data for the different families of compounds and the pharmacological properties of the most promising ligands. Furthermore, we also address the knowledge about the channel structure, although still in its infancy, and the role of the TRPM8 protein signalplex to channel function and dysfunction. We finally outline the potential future prospects of the challenging TRPM8 drug discovery field.
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Affiliation(s)
| | - Isabel Gómez-Monterrey
- Dipartimento di Farmacia, Università "Federico II" de Napoli , Via D. Montesano 49, 80131, Naples, Italy
| | - Antonio Ferrer-Montiel
- Instituto de Biología Molecular y Celular. Universitas Miguel Hernández . 03202 Alicante, Spain
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Frutalin reduces acute and neuropathic nociceptive behaviours in rodent models of orofacial pain. Chem Biol Interact 2016; 256:9-15. [DOI: 10.1016/j.cbi.2016.06.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 06/01/2016] [Accepted: 06/10/2016] [Indexed: 02/07/2023]
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Systemic desensitization through TRPA1 channels by capsazepine and mustard oil - a novel strategy against inflammation and pain. Sci Rep 2016; 6:28621. [PMID: 27356469 PMCID: PMC4928060 DOI: 10.1038/srep28621] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2016] [Accepted: 06/01/2016] [Indexed: 01/27/2023] Open
Abstract
We demonstrate a novel dual strategy against inflammation and pain through body-wide desensitization of nociceptors via TRPA1. Attenuation of experimental colitis by capsazepine (CPZ) has long been attributed to its antagonistic action on TRPV1 and associated inhibition of neurogenic inflammation. In contrast, we found that CPZ exerts its anti-inflammatory effects via profound desensitization of TRPA1. Micromolar CPZ induced calcium influx in isolated dorsal root ganglion (DRG) neurons from wild-type (WT) but not TRPA1-deficient mice. CPZ-induced calcium transients in human TRPA1-expressing HEK293t cells were blocked by the selective TRPA1 antagonists HC 030031 and A967079 and involved three cysteine residues in the N-terminal domain. Intriguingly, both colonic enemas and drinking water with CPZ led to profound systemic hypoalgesia in WT and TRPV1−/− but not TRPA1−/− mice. These findings may guide the development of a novel class of disease-modifying drugs with anti-inflammatory and anti-nociceptive effects.
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Calcium Entry Through Thermosensory Channels. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 898:265-304. [PMID: 27161233 DOI: 10.1007/978-3-319-26974-0_12] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
ThermoTRPs are unique channels that mediate Na(+) and Ca(2+) currents in response to changes in ambient temperature. In combination with their activation by other physical and chemical stimuli, they are considered key integrators of environmental cues into neuronal excitability. Furthermore, roles of thermoTRPs in non-neuronal tissues are currently emerging such as insulin secretion in pancreatic β-cells, and links to cancer. Calcium permeability through thermoTRPs appears a central hallmark for their physiological and pathological activities. Moreover, it is currently being proposed that beyond working as a second messenger, Ca(2+) can function locally by acting on protein complexes near the membrane. Interestingly, thermoTRPs can enhance and expand the inherent plasticity of signalplexes by conferring them temperature, pH and lipid regulation through Ca(2+) signalling. Thus, unveiling the local role of Ca(2+) fluxes induced by thermoTRPs on the dynamics of membrane-attached signalling complexes as well as their significance in cellular processes, are central issues that will expand the opportunities for therapeutic intervention in disorders involving dysfunction of thermoTRP channels.
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Abd-Elsayed AA, Ikeda R, Jia Z, Ling J, Zuo X, Li M, Gu JG. KCNQ channels in nociceptive cold-sensing trigeminal ganglion neurons as therapeutic targets for treating orofacial cold hyperalgesia. Mol Pain 2015; 11:45. [PMID: 26227020 PMCID: PMC4521366 DOI: 10.1186/s12990-015-0048-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 07/22/2015] [Indexed: 12/03/2022] Open
Abstract
Background Hyperexcitability of nociceptive afferent fibers is an underlying mechanism of neuropathic pain and ion channels involved in neuronal excitability are potentially therapeutic targets. KCNQ channels, a subfamily of voltage-gated K+ channels mediating M-currents, play a key role in neuronal excitability. It is unknown whether KCNQ channels are involved in the excitability of nociceptive cold-sensing trigeminal afferent fibers and if so, whether they are therapeutic targets for orofacial cold hyperalgesia, an intractable trigeminal neuropathic pain. Methods Patch-clamp recording technique was used to study M-currents and neuronal excitability of cold-sensing trigeminal ganglion neurons. Orofacial operant behavioral assessment was performed in animals with trigeminal neuropathic pain induced by oxaliplatin or by infraorbital nerve chronic constrictive injury. Results We showed that KCNQ channels were expressed on and mediated M-currents in rat nociceptive cold-sensing trigeminal ganglion (TG) neurons. The channels were involved in setting both resting membrane potentials and rheobase for firing action potentials in these cold-sensing TG neurons. Inhibition of KCNQ channels by linopirdine significantly decreased resting membrane potentials and the rheobase of these TG neurons. Linopirdine directly induced orofacial cold hyperalgesia when the KCNQ inhibitor was subcutaneously injected into rat orofacial regions. On the other hand, retigabine, a KCNQ channel potentiator, suppressed the excitability of nociceptive cold-sensing TG neurons. We further determined whether KCNQ channel could be a therapeutic target for orofacial cold hyperalgesia. Orofacial cold hyperalgesia was induced in rats either by the administration of oxaliplatin or by infraorbital nerve chronic constrictive injury. Using the orofacial operant test, we showed that retigabine dose-dependently alleviated orofacial cold hyperalgesia in both animal models. Conclusion Taken together, these findings indicate that KCNQ channel plays a significant role in controlling cold sensitivity and is a therapeutic target for alleviating trigeminal neuropathic pain that manifests orofacial cold hyperalgesia.
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Affiliation(s)
- Alaa A Abd-Elsayed
- Department of Anesthesiology and the Graduate Program in Neuroscience, The University of Cincinnati College of Medicine, PO Box 670531, 231 Albert Sabin Way, Cincinnati, OH, 45267-0531, USA. .,Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA.
| | - Ryo Ikeda
- Department of Anesthesiology and the Graduate Program in Neuroscience, The University of Cincinnati College of Medicine, PO Box 670531, 231 Albert Sabin Way, Cincinnati, OH, 45267-0531, USA. .,Department of Orthopedic Surgery, Jikei University School of Medicine, 3-25-8 Nishi-Shinbashi, Minato-ku, Tokyo, 105-8461, Japan.
| | - Zhanfeng Jia
- Department of Anesthesiology and the Graduate Program in Neuroscience, The University of Cincinnati College of Medicine, PO Box 670531, 231 Albert Sabin Way, Cincinnati, OH, 45267-0531, USA. .,Department of Pharmacology, Hebei Medical University, 361 East Zhongshan Road, Shijiazhuang, 050017, Hebei, China.
| | - Jennifer Ling
- Department of Anesthesiology and Perioperative Medicine, College of Medicine, University of Alabama at Birmingham, 901 19th Street South, BMR II 210, Birmingham, AL, 35294, USA. .,Department of Anesthesiology and the Graduate Program in Neuroscience, The University of Cincinnati College of Medicine, PO Box 670531, 231 Albert Sabin Way, Cincinnati, OH, 45267-0531, USA.
| | - Xiaozhuo Zuo
- Department of Anesthesiology and the Graduate Program in Neuroscience, The University of Cincinnati College of Medicine, PO Box 670531, 231 Albert Sabin Way, Cincinnati, OH, 45267-0531, USA.
| | - Min Li
- Department of Neuroscience and High Throughput Biology Center, Johns Hopkins University School of Medicine, 733 N. Broadway 311 BRB, Baltimore, MD, 21205, USA. .,GlaxoSmithKline, New York, NY, USA.
| | - Jianguo G Gu
- Department of Anesthesiology and Perioperative Medicine, College of Medicine, University of Alabama at Birmingham, 901 19th Street South, BMR II 210, Birmingham, AL, 35294, USA. .,Department of Anesthesiology and the Graduate Program in Neuroscience, The University of Cincinnati College of Medicine, PO Box 670531, 231 Albert Sabin Way, Cincinnati, OH, 45267-0531, USA.
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Henry MA, Fairchild DD, Patil MJ, Hanania T, Hain HS, Davis SF, Malekiani SA, Hu A, Sucholeiki R, Nix D, Sucholeiki I. Effect of a Novel, Orally Active Matrix Metalloproteinase-2 and -9 Inhibitor in Spinal and Trigeminal Rat Models of Neuropathic Pain. J Oral Facial Pain Headache 2015; 29:286-96. [PMID: 26244437 PMCID: PMC6757329 DOI: 10.11607/ofph.1350] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
AIMS To study the effects of a novel matrix metalloproteinase-2 (MMP-2) and MMP-9 inhibitor, AQU-118, on mechanical allodynia in the spinal nerve ligation (SNL) model of neuropathic pain and the chronic constriction injury of the infraorbital nerve (CCI-IoN) model of neuropathic orofacial pain. METHODS Five groups of SNL rats were given daily oral doses of AQU-118 (5, 10, 20 mg/kg), gabapentin (100 mg/kg), or vehicle (0.5% methylcellulose) and then paw withdrawal threshold was measured with von Frey filaments (VF). Three groups of CCI-IoN rats were given daily oral doses of either AQU-118 (40 mg/kg), gabapentin (100 mg/kg), or vehicle (0.5% methylcellulose) and then mechanical allodynia was measured with facial VF and non-reflex-based orofacial stimulation test (OFST) assay. Naïve rats were also tested for the effect of AQU-118 (40 mg/kg) on basal sensitivity to mechanical stimulation/locomotive activity. RESULTS Mechanical allodynia in SNL rats was attenuated by gabapentin (100 mg/kg) and AQU-118 (in a dose-dependent manner). Mechanical allodynia in CCI-IoN rats was also attenuated (in an equipotent manner) by both AQU-118 (40 mg/ kg) and gabapentin (100 mg/kg) as measured by both facial VF and OFST assay. Upon cessation of either AQU-118 or gabapentin, VF-related responses in both models and OFST assay times reverted to levels observed in vehicle-treated rats. No statistically significant change was observed in locomotive activity/paw withdrawal threshold by AQU-118 (40 mg/kg) in naïve rats. CONCLUSION The results demonstrated that oral AQU-118 attenuates mechanical allodynia in both neuropathic pain models and with efficacies that mirror gabapentin at the 40 mg/kg dose used in the CCI-IoN model but without effect on basal sensitivity to mechanical stimulation/locomotive activity. These findings support a possible role for MMP-2/-9 in the etiology of neuropathic pain and also suggest that inhibition strategies represent a viable treatment option.
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Murphy NP, Mills RH, Caudle RM, Neubert JK. Operant assays for assessing pain in preclinical rodent models: highlights from an orofacial assay. Curr Top Behav Neurosci 2014; 20:121-45. [PMID: 25103871 DOI: 10.1007/7854_2014_332] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Despite an immense investment of resources, pain remains at epidemic proportions. Given this, there has been an increased effort toward appraising the process by which new painkillers are developed, focusing specifically on why so few analgesics make it from the benchside to the bedside. The use of behavioral assays and animal modeling for the preclinical stages of analgesic development is being reexamined to determine whether they are truly relevant, meaningful, and predictive. Consequently, there is a strengthening consensus that the traditional reflex-based assays upon which several decades of preclinical pain research has been based are inadequate. Thus, investigators have recently turned to the development of new preclinical assays with improved face, content, and predictive validity. In this regard, operant pain assays show considerable promise, as they are more sensitive, present better validity, and, importantly, better encompass the psychological and affective dimensions of pain that trouble human pain sufferers. Here, we briefly compare and contrast reflex assays with operant assays, and we introduce a particular operant orofacial pain assay used in a variety of experiments to emphasize how operant pain assays can be applied to preclinical studies of pain.
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Affiliation(s)
- Niall P Murphy
- Department of Psychiatry and Biobehavioral Sciences, University of California, Los Angeles, USA,
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