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Mandadi S, Armati PJ, Roufogalis BD. Protein kinase C modulation of thermo-sensitive transient receptor potential channels: Implications for pain signaling. J Nat Sci Biol Med 2012; 2:13-25. [PMID: 22470230 PMCID: PMC3312694 DOI: 10.4103/0976-9668.82311] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
A variety of molecules are reported to be involved in chronic pain. This review outlines the specifics of protein kinase C (PKC), its isoforms and their role in modulating thermo-sensitive transient receptor potential (TRP) channels TRPV1-4, TRPM8, and TRPA1. Anatomically, PKC and thermo-sensitive TRPs are co-expressed in cell bodies of nociceptive dorsal root ganglion (DRG) neurons, which are used as physiological correlates of peripheral and central projections involved in pain transmission. In the past decade, modulation of painful heat-sensitive TRPV1 by PKC has received the most attention. Recently, PKC modulation of other newly discovered thermo-sensitive pain-mediating TRPs has come into focus. Such modulation may occur under conditions of chronic pain resulting from nerve damage or inflammation. Since thermo-TRPs are primary detectors of acute pain stimuli, their modulation by PKC can severely alter their function, resulting in chronic pain. Comprehensive knowledge of pain signaling involving interaction of specific isoforms of PKC with specific thermo-sensitive TRP channels is incomplete. Such information is necessary to dissect out modality specific mechanisms to better manage the complex polymodal nature of chronic pain. This review is an attempt to update the readers on current knowledge of PKC modulation of thermo-sensitive TRPs and highlight implications of such modulation for pain signaling
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Affiliation(s)
- Sravan Mandadi
- Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
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52
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Vay L, Gu C, McNaughton PA. Current perspectives on the modulation of thermo-TRP channels: new advances and therapeutic implications. Expert Rev Clin Pharmacol 2012; 3:687-704. [PMID: 22111750 DOI: 10.1586/ecp.10.41] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The thermo transient receptor potential (TRP) ion channels, a recently discovered family of ion channels activated by temperature, are expressed in primary sensory nerve terminals, where they provide information regarding thermal changes in the environment. Six thermo-TRPs have been characterized to date: TRPV1-4, which respond to different levels of warmth and heat, and TRPM8 and TRPA1, which respond to cool temperatures. We review the current state of knowledge of thermo-TRPs, and of the modulation of their thermal thresholds by a range of inflammatory mediators. Blockers of these channels are likely to have therapeutic uses as novel analgesics but may also cause unacceptable side effects. Controlling the modulation of thermo-TRPs by inflammatory mediators may be a useful alternative strategy in developing novel analgesics.
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Affiliation(s)
- Laura Vay
- Deptartment of Pharmacology, University of Cambridge, Tennis Court Rd, Cambridge, CB2 1PD, UK
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53
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Zhang X, Mak S, Li L, Parra A, Denlinger B, Belmonte C, McNaughton PA. Direct inhibition of the cold-activated TRPM8 ion channel by Gαq. Nat Cell Biol 2012; 14:851-8. [PMID: 22750945 PMCID: PMC3428855 DOI: 10.1038/ncb2529] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2012] [Accepted: 05/22/2012] [Indexed: 12/03/2022]
Abstract
Activation of the TRPM8 ion channel in sensory nerve endings produces a sensation of pleasant coolness. Here we show that inflammatory mediators such as bradykinin and histamine inhibit TRPM8 in intact sensory nerves, but do not do so via conventional signalling pathways. The G-protein subunit Gaq instead binds to TRPM8 and when activated by a Gq-coupled receptor directly inhibits ion channel activity. Deletion of Gaq largely abolished inhibition of TRPM8, and inhibition was rescued by a Gaq chimera whose ability to activate downstream signalling pathways was completely ablated. Activated Gaq protein, but not Gβγ, potently inhibits TRPM8 in excised patches. We conclude that Gaq pre-forms a complex with TRPM8 and inhibits activation of TRPM8, following activation of G-protein coupled receptors, by a direct action. This signalling mechanism may underlie the abnormal cold sensation caused by inflammation.
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Affiliation(s)
- Xuming Zhang
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
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54
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Yudin Y, Rohacs T. Regulation of TRPM8 channel activity. Mol Cell Endocrinol 2012; 353:68-74. [PMID: 22061619 PMCID: PMC3295897 DOI: 10.1016/j.mce.2011.10.023] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Revised: 10/21/2011] [Accepted: 10/22/2011] [Indexed: 11/28/2022]
Abstract
Transient Receptor Potential Melastatin 8 (TRPM8) is a Ca(2+) permeable non-selective cation channel directly activated by cold temperatures and chemical agonists such as menthol. It is a well established sensor of environmental cold temperatures, found in peripheral sensory neurons, where its activation evokes depolarization and action potentials. The activity of TRPM8 is regulated by a number of cellular signaling pathways, most notably by phosphoinositides and the activation of phospholipase C. This review will summarize current knowledge on the physiological and pathophysiological roles of TRPM8 and its regulation by various intracellular messenger molecules and signaling pathways.
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Affiliation(s)
- Yevgen Yudin
- Department of Pharmacology and Physiology, UMDNJ - New Jersey Medical School, Newark, NJ 07103, USA
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55
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Vay L, Gu C, McNaughton PA. The thermo-TRP ion channel family: properties and therapeutic implications. Br J Pharmacol 2012; 165:787-801. [PMID: 21797839 PMCID: PMC3312478 DOI: 10.1111/j.1476-5381.2011.01601.x] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 04/13/2011] [Accepted: 05/01/2011] [Indexed: 01/09/2023] Open
Abstract
The thermo-transient receptor potentials (TRPs), a recently discovered family of ion channels activated by temperature, are expressed in primary sensory nerve terminals where they provide information about thermal changes in the environment. Six thermo-TRPs have been characterised to date: TRP vanilloid (TRPV) 1 and 2 are activated by painful levels of heat, TRPV3 and 4 respond to non-painful warmth, TRP melastatin 8 is activated by non-painful cool temperatures, while TRP ankyrin (TRPA) 1 is activated by painful cold. The thermal thresholds of many thermo-TRPs are known to be modulated by extracellular mediators, released by tissue damage or inflammation, such as bradykinin, PG and growth factors. There have been intensive efforts recently to develop antagonists of thermo-TRP channels, particularly of the noxious thermal sensors TRPV1 and TRPA1. Blockers of these channels are likely to have therapeutic uses as novel analgesics, but may also cause unacceptable side effects. Controlling the modulation of thermo-TRPs by inflammatory mediators may be a useful alternative strategy in developing novel analgesics.
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Affiliation(s)
- Laura Vay
- Department of Pharmacology, University of Cambridge, Cambridge, UK
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56
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Latorre R, Brauchi S, Madrid R, Orio P. A cool channel in cold transduction. Physiology (Bethesda) 2012; 26:273-85. [PMID: 21841075 DOI: 10.1152/physiol.00004.2011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Transient receptor potential melastatin 8 (TRPM8), a calcium-permeable cation channel activated by cold, cooling compounds and voltage, is the main molecular entity responsible for detection of cold temperatures in the somatosensory system. Here, we review the biophysical properties, physiological role, and near-membrane trafficking of this exciting polymodal ion channel.
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Affiliation(s)
- Ramón Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso, Chile
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57
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McCoy DD, Knowlton WM, McKemy DD. Scraping through the ice: uncovering the role of TRPM8 in cold transduction. Am J Physiol Regul Integr Comp Physiol 2011; 300:R1278-87. [PMID: 21411765 DOI: 10.1152/ajpregu.00631.2010] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The proper detection of environmental temperatures is essential for the optimal growth and survival of organisms of all shapes and phyla, yet only recently have the molecular mechanisms for temperature sensing been elucidated. The discovery of temperature-sensitive ion channels of the transient receptor potential (TRP) superfamily has been pivotal in explaining how temperatures are sensed in vivo, and here we will focus on the lone member of this cohort, TRPM8, which has been unequivocally shown to be cold sensitive. TRPM8 is expressed in somatosensory neurons that innervate peripheral tissues such as the skin and oral cavity, and recent genetic evidence has shown it to be the principal transducer of cool and cold stimuli. It is remarkable that this one channel, unlike other thermosensitive TRP channels, is associated with both innocuous and noxious temperature transduction, as well as cold hypersensitivity during injury and, paradoxically, cold-mediated analgesia. With ongoing research, the field is getting closer to answering a number of fundamental questions regarding this channel, including the cellular mechanisms of TRPM8 modulation, the molecular context of TRPM8 expression, as well as the full extent of the role of TRPM8 in cold signaling in vivo. These findings will further our understanding of basic thermotransduction and sensory coding, and may have important implications for treatments for acute and chronic pain.
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Affiliation(s)
- Daniel D McCoy
- Neurobiology, University of Southern California, Los Angeles, California 90089, USA
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58
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Liu Y, Qin N. TRPM8 in health and disease: cold sensing and beyond. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 704:185-208. [PMID: 21290296 DOI: 10.1007/978-94-007-0265-3_10] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
This review focuses on TRPM8, one of the approximately 30 members of the diverse family of transient receptor potential (TRP) ion channels. Initially identified from the prostate, TRPM8 has been studied more extensively in the sensory system and is best established as a major transducer of environmental cold temperatures. An increasing body of evidence suggests that it may also be an important player in various chronic conditions, such as inflammatory/neuropathic pain and prostate cancer. Small molecule compounds that selectively modulate TRPM8 are beginning to emerge and will be critically valuable for better understanding the role of this channel in both physiological and pathological states, on which the prospects of TRPM8 as a viable therapeutic target rest.
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Affiliation(s)
- Yi Liu
- Johnson & Johnson Pharmaceutical Research and Development, LLC, San Diego, CA 92121, USA.
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59
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Schmid D, Messlinger K, Belmonte C, Fischer MJM. Altered thermal sensitivity in neurons injured by infraorbital nerve lesion. Neurosci Lett 2010; 488:168-72. [PMID: 21078368 DOI: 10.1016/j.neulet.2010.11.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2010] [Revised: 10/28/2010] [Accepted: 11/04/2010] [Indexed: 10/18/2022]
Abstract
Nerve lesions are common injuries. While peripheral sensitivity is lost, the partially regenerating nerve undergoes a complex transformation, occasionally leading to persistent pain syndromes. Changes of thermal perception following nerve injury have received little attention. This study investigates the sensitivity of trigeminal neurons after infraorbital nerve lesion in guinea-pigs. Cultured trigeminal neurons innervating the area of denervation were identified by retrograde transport of DiI deposited at the site of the lesion. The standardized protocol consisted of cold and heat stimulation starting from body temperature as well as application of menthol and capsaicin, while activation was quantified by Fura-2-based calcium microfluorimetry. Compared to neurons from control animals, DiI-positive neurons were similar in the percentage and extend of the responses to menthol and capsaicin. However, DiI-positive neurons were less responsive to cold stimulation and had a lower cold threshold when compared to DiI-negative or control neurons. At the same time, DiI-positive neurons were more responsive to heat stimulation and had a lower heat threshold compared to control neurons. In summary, the percentage of trigeminal neurons responsive to thermal or chemical stimulation did not change after axotomy. However, thermal sensitivity of these neurons was altered.
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Affiliation(s)
- Damaris Schmid
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Spain
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60
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Sarria I, Gu J. Menthol response and adaptation in nociceptive-like and nonnociceptive-like neurons: role of protein kinases. Mol Pain 2010; 6:47. [PMID: 20727164 PMCID: PMC2936373 DOI: 10.1186/1744-8069-6-47] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2010] [Accepted: 08/20/2010] [Indexed: 02/07/2023] Open
Abstract
Menthol-sensitive/capsaicin-insensitive neurons (MS/CI) and menthol-sensitive/capsaicin-sensitive neurons (MS/CS) are thought to represent two functionally distinct populations of cold-sensing neurons that use TRPM8 receptors to convey innocuous and noxious cold information respectively. However, TRPM8-mediated responses have not been well characterized in these two neuron populations. Using rat dorsal root ganglion neurons, here we show that MS/CI neurons had larger menthol responses with greater adaptation. In contrast, MS/CS neurons had smaller menthol responses with less adaptation. All menthol-sensitive neurons showed significant reduction of menthol responses following the treatment of cells with the protein kinase C (PKC) activator PDBu (Phorbol 12,13-dibutyrate). PDBu-induced reduction of menthol responses was completely abolished in the presence of PKC inhibitors BIM (bisindolylmaleimide) or staurosporine. When menthol responses were examined in the presence of protein kinase inhibitors, it was found that the adaptation was significantly attenuated by either BIM or staurosporine and also by the Ca2+/calmodulin-dependent protein kinase (CamKII) inhibitor KN62 (N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine) in MS/CI neurons. In contrast, in MS/CS neurons menthol response was not affected significantly by BIM, staurosporine or KN62. In both MS/CI and MS/CS neurons, the menthol responses were not affected by PKA activators forskolin and 8-Br-cAMP (8-Bromoadenosine-3', 5'-cyclic monophosphate) or by protein kinase A (PKA) inhibitor Rp-cAMPs (Rp-Adenosine-3',5'-cyclic monophosphorothioate). Taken together, these results suggest that TRPM8-mediated responses are significantly different between non-nociceptive-like and nociceptive-like neurons.
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Affiliation(s)
- Ignacio Sarria
- Department of Anesthesiology, University of Cincinnati College of Medicine, PO Box 670531, 231 Albert Sabin Way, Cincinnati, OH 45267-0531, USA
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61
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Kounalakis SN, Botonis PG, Koskolou MD, Geladas ND. The effect of menthol application to the skin on sweating rate response during exercise in swimmers and controls. Eur J Appl Physiol 2010; 109:183-9. [DOI: 10.1007/s00421-009-1345-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/21/2009] [Indexed: 10/20/2022]
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62
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Babes A. Ion channels involved in cold detection in mammals: TRP and non-TRP mechanisms. Biophys Rev 2009; 1:193-200. [PMID: 28510025 DOI: 10.1007/s12551-009-0020-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Accepted: 10/20/2009] [Indexed: 12/30/2022] Open
Abstract
Substantial progress in understanding thermal transduction in peripheral sensory nerve endings was achieved with the recent cloning of six thermally gated ion channels from the TRP (transient receptor potential) super-family. Two of these channels, TRP melastatin 8 (TRPM8) and TRP ankyrin 1 (TRPA1), are expressed in dorsal root ganglion (DRG) and trigeminal ganglion (TG) neurons, are activated by various degrees of cooling, and are candidates for mediating gentle cooling and noxious cold, respectively. However, accumulating evidence suggests that more than just these two channels are involved in cold sensing in mammals. A recent report described a critical role of the voltage-gated tetrodotoxin-resistant sodium channel Nav1.8 in perceiving intense cold and noxious stimuli at cold temperatures. Other ion channels, such as two-pore domain background potassium channels (K2P), are known to be expressed in peripheral nerves, have pronounced temperature dependence, and may contribute to cold sensing and/or cold hypersensitivity in pain states. This article reviews the evidence supporting a role for each of these channels in cold transduction, focusing on their biophysical properties, expression pattern, and modulation by pro-inflammatory mediators.
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Affiliation(s)
- Alexandru Babes
- Department of Animal Physiology and Biophysics, Faculty of Biology, University of Bucharest, Splaiul Independentei 91-95, 050095, Bucharest, Romania.
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63
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Acute and chronic effects of neurotrophic factors BDNF and GDNF on responses mediated by thermo-sensitive TRP channels in cultured rat dorsal root ganglion neurons. Brain Res 2009; 1284:54-67. [DOI: 10.1016/j.brainres.2009.06.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Revised: 06/05/2009] [Accepted: 06/06/2009] [Indexed: 11/22/2022]
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64
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Grossmann L, Gorodetskaya N, Baron R, Jänig W. Enhancement of Ectopic Discharge in Regenerating A- and C-Fibers by Inflammatory Mediators. J Neurophysiol 2009; 101:2762-74. [DOI: 10.1152/jn.91091.2008] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Afferent A- and C-fibers regenerating into a nerve following peripheral nerve injury are exposed to inflammatory mediators released by Schwann cells, resident and invading macrophages, and other inflammatory cells. Here we tested the hypothesis that ongoing and evoked activity in these afferent fibers are enhanced by a mixture of inflammatory mediators [inflammatory soup (IS)] applied to the injured nerve. Using in vivo electrophysiology, regenerating afferent nerve fibers were studied 7–14 days after sural nerve crush lesion. The ectopic activity was studied before and ≤1.5 h after topical application of IS to the nerve in 73 C-fibers and 22 A-fibers that were either ectopically active before application of IS (61 C-fibers, 17 A-fibers) or recruited by IS (12 C-fibers, 5 A-fibers). More than one half of the C-fibers were activated by IS for ≤90 min after its removal. The majority of mechano- (23/38) and heat-sensitive (29/35) C-fibers as well as mechano-sensitive A-fibers (12/17) decreased their activation thresholds and/or increased the response magnitude to mechanical and/or heat stimulation of the nerve. Noxious cold sensitivity, but not nonnoxious cold sensitivity, was weakly influenced by IS. Some initially nonresponsive C- and A-fibers developed new ectopic properties, i.e., were recruited, and exhibited ongoing activity and/or could be activated by physiological stimuli after application of IS. The results suggest that inflammatory mediators may be critical to enhance ectopic excitability of regenerating afferent nerve fibers. These peripheral mechanisms may be important triggering and maintaining neuropathic pain.
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65
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Pethő G, Reeh PW. Effects of Bradykinin on Nociceptors. NEUROGENIC INFLAMMATION IN HEALTH AND DISEASE 2009. [DOI: 10.1016/s1567-7443(08)10407-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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66
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Broad LM, Mogg AJ, Beattie RE, Ogden AM, Blanco MJ, Bleakman D. TRP channels as emerging targets for pain therapeutics. Expert Opin Ther Targets 2008; 13:69-81. [DOI: 10.1517/14728220802616620] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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67
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Daniels RL, Takashima Y, McKemy DD. Activity of the neuronal cold sensor TRPM8 is regulated by phospholipase C via the phospholipid phosphoinositol 4,5-bisphosphate. J Biol Chem 2008; 284:1570-82. [PMID: 19019830 DOI: 10.1074/jbc.m807270200] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Cold temperatures robustly activate a small cohort of somatosensory nerves, yet during a prolonged cold stimulus their activity will decrease, or adapt, over time. This process allows for the discrimination of subtle changes in temperature. At the molecular level, cold is detected by transient receptor potential melastatin 8 (TRPM8), a nonselective cation channel expressed on a subset of peripheral afferent fibers. We and others have reported that TRPM8 channels also adapt in a calcium-dependent manner when activated by the cooling compound menthol. Additionally, TRPM8 activity is sensitive to the phospholipid phosphoinositol 4,5-bisphosphate (PIP2), a substrate for the enzyme phospholipase C (PLC). These results suggest an adaptation model whereby TRPM8-mediated Ca2+ influx activates PLC, thereby decreasing PIP2 levels and resulting in reduced TRPM8 activity. Here we tested this model using pharmacological activation of PLC and by manipulating PIP2 levels independent of both PLC and Ca2+. PLC activation leads to adaptation-like reductions in cold- or menthol-evoked TRPM8 currents in both heterologous and native cells. Moreover, PLC-independent reductions in PIP2 had a similar effect on cold- and menthol-evoked currents. Mechanistically, either form of adaptation does not alter temperature sensitivity of TRPM8 but does lead to a change in channel gating. Our results show that adaptation is a shift in voltage dependence toward more positive potentials, reversing the trend toward negative potentials caused by agonist. These data suggest that PLC activity not only mediates adaptation to thermal stimuli, but likely underlies a more general mechanism that establishes the temperature sensitivity of somatosensory neurons.
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Affiliation(s)
- Richard L Daniels
- Neuroscience Graduate Program, Neurobiology Section, Department of Biological Sciences, University of Southern California, Los Angeles, California 90089, USA
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68
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Cold hyposensitivity after topical application of capsaicin in humans. Exp Brain Res 2008; 191:447-52. [DOI: 10.1007/s00221-008-1535-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Accepted: 08/03/2008] [Indexed: 10/21/2022]
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69
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Lashinger ESR, Steiginga MS, Hieble JP, Leon LA, Gardner SD, Nagilla R, Davenport EA, Hoffman BE, Laping NJ, Su X. AMTB, a TRPM8 channel blocker: evidence in rats for activity in overactive bladder and painful bladder syndrome. Am J Physiol Renal Physiol 2008; 295:F803-10. [PMID: 18562636 DOI: 10.1152/ajprenal.90269.2008] [Citation(s) in RCA: 137] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The activation of the TRPM8 channel, a member of the large class of TRP ion channels, has been reported to be involved in overactive bladder and painful bladder syndrome, although an endogenous activator has not been identified. In this study, N-(3-aminopropyl)-2-{[(3-methylphenyl) methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride salt (AMTB) was evaluated as a TRPM8 channel blocker and used as a tool to evaluate the effects of this class of ion channel blocker on volume-induced bladder contraction and nociceptive reflex responses to noxious bladder distension in the rat. AMTB inhibits icilin-induced TRPM8 channel activation as measured in a Ca(2+) influx assay, with a pIC(50) of 6.23. In the anesthetized rat, intravenous administration of AMTB (3 mg/kg) decreased the frequency of volume-induced bladder contractions, without reducing the amplitude of contraction. The nociceptive response was measured by analyzing both visceromotor reflex (VMR) and cardiovascular (pressor) responses to urinary bladder distension (UBD) under 1% isoflurane. AMTB (10 mg/kg) significantly attenuated reflex responses to noxious UBD to 5.42 and 56.51% of the maximal VMR response and pressor response, respectively. The ID50 value on VMR response was 2.42 +/- 0.46 mg/kg. These results demonstrate that TRPM8 channel blocker can act on the bladder afferent pathway to attenuate the bladder micturition reflex and nociceptive reflex responses in the rat. Targeting TRPM8 channel may provide a new therapeutic opportunity for overactive bladder and painful bladder syndrome.
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Affiliation(s)
- Erin S R Lashinger
- GlaxoSmithKline Pharmaceuticals, Department of Urology, 709 Swedeland Road, King of Prussia, PA 19406-0939, USA
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70
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Abstract
The cold- and menthol-sensitive receptor TRPM8 (transient receptor potential melastatin 8) has been suggested to play a role in cold allodynia, an intractable pain seen clinically. We studied how TRPM8 is involved in cold allodynia using rats with chronic constrictive nerve injury (CCI), a neuropathic pain model manifesting cold allodynia in hindlimbs. We found that cold allodynic response in the CCI animals was significantly attenuated by capsazepine, a blocker for both TRPM8 and TRPV1 (transient receptor potential vanilloid 1) receptors, but not by the selective TRPV1 antagonist I-RTX (5-iodoresiniferatoxin). In L5 dorsal root ganglion (DRG) sections of the CCI rats, immunostaining showed an increase in the percentage of TRPM8-immunoreactive neurons when compared with the sham group. Using the Ca2+-imaging technique and neurons acutely dissociated from the L5 DRGs, we found that CCI resulted in a significant increase in the percentage of menthol- and cold-sensitive neurons and also a substantial enhancement in the responsiveness of these neurons to both menthol and innocuous cold. These changes occurred in capsaicin-sensitive neurons, a subpopulation of nociceptive-like neurons. Using patch-clamp recordings, we found that membrane currents evoked by both menthol and innocuous cold were significantly enhanced in the CCI group compared with the sham group. By retrograde labeling afferent neurons that target hindlimb skin, we showed that the skin neurons expressed TRPM8 receptors, that the percentage of menthol-sensitive/cold-sensitive/capsaicin-sensitive neurons increased, and that the menthol- and cold-evoked responses were significantly enhanced in capsaicin-sensitive neurons after CCI. Together, the gain of TRPM8-mediated cold sensitivity on nociceptive afferent neurons provides a mechanism of cold allodynia.
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71
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Daniels RL, McKemy DD. Mice left out in the cold: commentary on the phenotype of TRPM8-nulls. Mol Pain 2007; 3:23. [PMID: 17705869 PMCID: PMC1988789 DOI: 10.1186/1744-8069-3-23] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2007] [Accepted: 08/17/2007] [Indexed: 12/17/2022] Open
Abstract
Detection of innocuous temperatures allows an organism to select an appropriate environmental climate, while the ability to recognize noxious temperature extremes warns of impending tissue damage. For temperatures considered cold, the menthol receptor TRPM8 is activated when temperatures drop below ~26°C, thus making it an intriguing candidate as the molecular mediator of cold perception. However, confirmation of this hypothesis in vivo has eluded researchers until recently. Three independent research groups have reported that mice lacking this single gene are severely impaired in their ability to detect cold temperatures. Remarkably, these animals are deficient in many diverse aspects of cold signaling, including cool and noxious cold perception, injury-evoked sensitization to cold, and cooling-induced analgesia. These animals provide a great deal of insight into the molecular signaling pathways that participate in the detection of cold and painful stimuli.
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Affiliation(s)
- Richard L Daniels
- Neuroscience Graduate Program, Department of Biological Sciences, University of Southern California, Los Angeles, CA90089-0641, USA
| | - David D McKemy
- Neuroscience Graduate Program, Department of Biological Sciences, and School of Dentistry, University of Southern California, Los Angeles, CA90089-0641, USA
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De Petrocellis L, Starowicz K, Moriello AS, Vivese M, Orlando P, Di Marzo V. Regulation of transient receptor potential channels of melastatin type 8 (TRPM8): effect of cAMP, cannabinoid CB(1) receptors and endovanilloids. Exp Cell Res 2007; 313:1911-20. [PMID: 17428469 DOI: 10.1016/j.yexcr.2007.01.008] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Revised: 01/09/2007] [Accepted: 01/10/2007] [Indexed: 11/17/2022]
Abstract
The transient receptor potential channel of melastatin type 8 (TRPM8), which is gated by low (<25 degrees C) temperature and chemical compounds, is regulated by protein kinase C-mediated phosphorylation in a way opposite to that observed with the transient receptor potential channel of vanilloid type 1 (TRPV1), i.e. by being desensitized and not sensitized. As TRPV1 is sensitized also by protein kinase A (PKA)-mediated phosphorylation, we investigated the effect of two activators of the PKA pathway, 8-Br-cAMP and forskolin, on the activity of menthol and icilin at TRPM8 in HEK-293 cells stably overexpressing the channel (TRPM8-HEK-293 cells). We also studied the effect on TRPM8 of: (1) a series of compounds previously shown to activate or antagonize TRPV1, and (2) co-stimulation of transiently co-expressed cannabinoid CB(1) receptors. Both 8-Br-cAMP (100 microM) and forskolin (10 microM) right-shifted the dose-response curves for the TRPM8-mediated effect of icilin and menthol on intracellular Ca(2+). The inhibitory effects of 8-Br-cAMP and forskolin were attenuated by the selective PKA inhibitor Rp-cAMP-S. Stimulation of human CB(1) receptors transiently co-expressed in TRPM8-HEK-293 cells also inhibited TRPM8 response to icilin. Finally, some TRPV1 agonists and antagonists, but not iodinated antagonists, antagonized icilin- and much less so menthol-, induced TRPM8 activation. Importantly, the endovanilloids/endocannabinoids, anandamide and NADA, also antagonized TRPM8 at submicromolar concentrations. Although these findings need to be confirmed by experiments directly measuring TRPM8 activity in natively TRPM8-expressing cells, they support the notion that the same regulatory events have opposing actions on TRPM8 and TRPV1 receptors and identify anandamide and NADA as the first potential endogenous functional antagonists of TRPM8 channels.
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Affiliation(s)
- Luciano De Petrocellis
- Endocannabinoid Research Group, Institute of Cybernetics, National Research Council, Via Campi Flegrei 34, Comprensorio Olivetti, 80078 Pozzuoli, Naples, Italy
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