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Brito R, Sheth S, Mukherjea D, Rybak LP, Ramkumar V. TRPV1: A Potential Drug Target for Treating Various Diseases. Cells 2014; 3:517-45. [PMID: 24861977 PMCID: PMC4092862 DOI: 10.3390/cells3020517] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 05/14/2014] [Accepted: 05/15/2014] [Indexed: 12/11/2022] Open
Abstract
Transient receptor potential vanilloid 1 (TRPV1) is an ion channel present on sensory neurons which is activated by heat, protons, capsaicin and a variety of endogenous lipids termed endovanilloids. As such, TRPV1 serves as a multimodal sensor of noxious stimuli which could trigger counteractive measures to avoid pain and injury. Activation of TRPV1 has been linked to chronic inflammatory pain conditions and peripheral neuropathy, as observed in diabetes. Expression of TRPV1 is also observed in non-neuronal sites such as the epithelium of bladder and lungs and in hair cells of the cochlea. At these sites, activation of TRPV1 has been implicated in the pathophysiology of diseases such as cystitis, asthma and hearing loss. Therefore, drugs which could modulate TRPV1 channel activity could be useful for the treatment of conditions ranging from chronic pain to hearing loss. This review describes the roles of TRPV1 in the normal physiology and pathophysiology of selected organs of the body and highlights how drugs targeting this channel could be important clinically.
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Affiliation(s)
- Rafael Brito
- Department of Pharmacology and Neuroscience, Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
| | - Sandeep Sheth
- Department of Pharmacology and Neuroscience, Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
| | - Debashree Mukherjea
- Department of Surgery (Otoloryngalogy), Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
| | - Leonard P Rybak
- Department of Pharmacology and Neuroscience, Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
| | - Vickram Ramkumar
- Department of Pharmacology and Neuroscience, Southern Illinois University School of Medicine, Springfield, IL 62702, USA.
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2
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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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3
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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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4
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Mao J. Translational pain research: achievements and challenges. THE JOURNAL OF PAIN 2009; 10:1001-11. [PMID: 19628433 DOI: 10.1016/j.jpain.2009.06.002] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Revised: 05/29/2009] [Accepted: 05/29/2009] [Indexed: 10/20/2022]
Abstract
UNLABELLED The achievements in both preclinical and clinical pain research over the past 4 decades have led to significant progress in clinical pain management. However, pain research still faces enormous challenges and there remain many obstacles in the treatment of clinical pain, particularly chronic pain. Translational pain research needs to involve a number of important areas including: 1) bridging the gap between pain research and clinical pain management; 2) developing objective pain-assessment tools; 3) analyzing current theories of pain mechanisms and their relevance to clinical pain; 4) exploring new tools for both preclinical and clinical pain research; and 5) coordinating research efforts among basic scientists, clinical investigators, and pain-medicine practitioners. These issues are discussed in this article in light of the achievements and challenges of translational pain research. PERSPECTIVE The subjective nature of clinical pain calls for innovative research approaches. As translational pain research emerges as an important field in pain medicine, it will play a unique role in improving clinical pain management through coordinated bidirectional research approaches between bedside and bench.
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Affiliation(s)
- Jianren Mao
- MGH Center for Translational Pain Research, Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA.
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5
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Peripheral Nociceptors. Mol Pain 2009. [DOI: 10.1007/978-0-387-75269-3_19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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6
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Abstract
Pain is initiated when noxious stimuli excite the peripheral terminals of specialized primary afferent neurons called nociceptors. Many molecules are involved in conversion of the noxious stimuli to the electrical signals in the nociceptor endings. Among them, TRP channels play important roles in detecting noxious stimuli.
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Affiliation(s)
- M Tominaga
- Section of Cell Signaling, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, 444-8787 Okazaki, Japan.
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7
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Hudgens DP, Taylor C, Batts TW, Patel MK, Brown ML. Discovery of diphenyl amine based sodium channel blockers, effective against hNav1.2. Bioorg Med Chem 2006; 14:8366-78. [PMID: 17035036 PMCID: PMC2756728 DOI: 10.1016/j.bmc.2006.09.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 08/31/2006] [Accepted: 09/07/2006] [Indexed: 11/26/2022]
Abstract
The development of new therapies for chronic pain is an area of unmet medical need. Central to pathways of chronic pain is the upregulation of voltage-gated sodium channels. The use of tricyclic antidepressants, which also have sodium channel activity, in chronic pain therapy prompted us to develop novel compounds from this scaffold. Herein, we show that the tricyclic moiety is not needed for effective inhibition of the [(3)H]-BTX binding site and sodium currents of hNa(v)1.2. Our lead compound 6, containing a diphenyl amine motif, demonstrated a 53% inhibitory block of Na(v)1.2 currents at 10microM, which is greater than 50% increase in current block in comparison to the amitriptyline standard. Altogether our study establishes that the tricyclic motif is unnecessary for hNa(v)1.2 activity and modification of the amine portion is detrimental to sodium channel block.
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Affiliation(s)
- Debjani P Hudgens
- Department of Chemistry, University of Virginia, Charlottesville, VA 22904, USA
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8
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Tominaga M. The Role of TRP Channels in Thermosensation. TRP ION CHANNEL FUNCTION IN SENSORY TRANSDUCTION AND CELLULAR SIGNALING CASCADES 2006. [DOI: 10.1201/9781420005844.ch20] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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9
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Abstract
We feel a wide range of temperatures spanning from cold to heat. Within this range, temperatures over about 43 degrees C and below about 15 degrees C evoke not only a thermal sensation, but also a feeling of pain. In mammals, six thermosensitive ion channels have been reported, all of which belong to the TRP (transient receptor potential) superfamily. These include TRPV1 (VR1), TRPV2 (VRL-1), TRPV3, TRPV4, TRPM8 (CMR1), and TRPA1 (ANKTM1). These channels exhibit distinct thermal activation thresholds (>43 degrees C for TRPV1, >52 degrees C for TRPV2, > approximately 34-38 degrees C for TRPV3, > approximately 27-35 degrees C for TRPV4, < approximately 25-28 degrees C for TRPM8 and <17 degrees C for TRPA1), and are expressed in primary sensory neurons as well as other tissues. The involvement of TRPV1 in thermal nociception has been demonstrated by multiple methods, including the analysis of TRPV1-deficient mice. TRPV2, TRPM8, and TRPA1 are also very likely to be involved in thermal nociception, because their activation thresholds are within the noxious range of temperatures.
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Affiliation(s)
- Makoto Tominaga
- Section of Cell Signaling, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan.
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10
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Dai Y, Moriyama T, Higashi T, Togashi K, Kobayashi K, Yamanaka H, Tominaga M, Noguchi K. Proteinase-activated receptor 2-mediated potentiation of transient receptor potential vanilloid subfamily 1 activity reveals a mechanism for proteinase-induced inflammatory pain. J Neurosci 2004; 24:4293-9. [PMID: 15128843 PMCID: PMC6729433 DOI: 10.1523/jneurosci.0454-04.2004] [Citation(s) in RCA: 237] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Proteinase-activated receptor (PAR) 2 is expressed on a subset of primary afferent neurons and involved in inflammatory nociception. Transient receptor potential vanilloid subfamily 1 (TRPV1) is a sensory neuron-specific cation channel that responds to capsaicin, protons, or heat stimulus. Here, we show that TRPV1 is coexpressed with PAR2 but not with PAR1 or PAR3, and that TRPV1 can functionally interact with PAR2. In human embryonic kidney 293 cells expressing TRPV1 and PAR2, PAR2 agonists increased capsaicin- or proton-evoked TRPV1 currents through a PKC-dependent pathway. After application of PAR2 agonists, temperature threshold for TRPV1 activation was reduced from 42 degrees C to well below the body temperature. PAR2-mediated Fos expression in spinal cord was decreased in TRPV1-deficient mice. The functional interaction was also observed in mouse DRG neurons and proved at a behavioral level. These represent a novel mechanism through which trypsin or tryptase released in response to tissue inflammation might trigger the sensation of pain by PAR2 activation.
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MESH Headings
- Animals
- Cells, Cultured
- Endopeptidases/metabolism
- Enzyme Inhibitors/pharmacology
- Ganglia, Spinal/metabolism
- Ganglia, Spinal/pathology
- Humans
- Hyperalgesia/genetics
- Hyperalgesia/physiopathology
- Inflammation/enzymology
- Inflammation/physiopathology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Pain/enzymology
- Pain/physiopathology
- Patch-Clamp Techniques
- Protein Kinase C/antagonists & inhibitors
- Protein Kinase C/metabolism
- Proto-Oncogene Proteins c-fos/metabolism
- Receptor, PAR-1/genetics
- Receptor, PAR-1/metabolism
- Receptor, PAR-2/agonists
- Receptor, PAR-2/genetics
- Receptor, PAR-2/metabolism
- Receptors, Drug/deficiency
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Receptors, Thrombin/genetics
- Receptors, Thrombin/metabolism
- Signal Transduction/physiology
- Spinal Cord/metabolism
- Spinal Cord/pathology
- Temperature
- Transfection
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Affiliation(s)
- Yi Dai
- Department of Anatomy and Neuroscience, Hyogo College of Medicine, Hyogo 663-8501, Japan
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11
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Abstract
A reciprocal relationship exists between persistent pain and negative affective states such as fear, anxiety, and depression. Accumulating evidence points to the amygdala as an important site of such interaction. Whereas a key role of the amygdala in the neuronal mechanisms of emotionality and affective disorders has been well established, the concept of the amygdala as an important contributor to pain and its emotional component is still emerging. This article will review and discuss evidence from anatomical, neuroimaging, behavioral, electrophysiological, pharmacological, and biochemical data that implicate the amygdala in pain modulation and emotional responses to pain. The latero-capsular division of the central nucleus of the amygdala is now defined as the "nociceptive amygdala" and integrates nociceptive information with poly-modal information about the internal and external bodily environment. Dependent on environmental conditions and affective states, the amygdala appears to play a dual facilitatory and inhibitory role in the modulation of pain behavior and nociceptive processing at different levels of the pain neuraxis. Only recently, electrophysiological, pharmacological, and biochemical neuroplastic changes were shown in the nociceptive amygdala in persistent pain. It is conceivable, however, that amygdala plasticity plays an important role in emotional pain behavior and its modulation by affective state.
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Affiliation(s)
- Volker Neugebauer
- Department of Anatomy & Neurosciences, University of Texas Medical Branch, Galveston, 77555-1069, USA.
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12
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Wood JN, Heath MJ. Molecules that specify modality: mechanisms of nociception. THE JOURNAL OF PAIN 2003; 1:19-25. [PMID: 14622839 DOI: 10.1054/jpai.2000.9807a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Damage-sensing neurons express a unique cohort of genes encoding channels and receptors that play a role in nociception. However, there are redundant pathways involved in, for example, inflammatory pain and many channels and receptors have additional physiologic roles unrelated to nociception. Thus, it is impossible to ascribe a particular sensory modality to the expressions of a single molecular entity. Despite this, the relatively selective expression of a number of channels and receptors in nociceptive neurons provide potentially interesting analgesic drug targets that can be examined through the generation of knockout mice.
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Affiliation(s)
- J N Wood
- Department of Biology, University College, London, England, United Kingsdom.
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13
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Possible involvement of P2Y2 metabotropic receptors in ATP-induced transient receptor potential vanilloid receptor 1-mediated thermal hypersensitivity. J Neurosci 2003. [PMID: 12853424 DOI: 10.1523/jneurosci.23-14-06058.2003] [Citation(s) in RCA: 175] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The capsaicin receptor transient receptor potential V1 (TRPV1; also known as vanilloid receptor 1) is a sensory neuron-specific ion channel that serves as a polymodal detector of pain-producing chemical and physical stimuli. It has been reported that extracellular ATP potentiates the TRPV1 currents evoked by capsaicin or protons and reduces the temperature threshold for its activation through metabotropic P2Y receptors in a PKC-dependent pathway, suggesting that TRPV1 activation could trigger the sensation of pain at normal body temperature in the presence of ATP. Here, we show that ATP-induced thermal hyperalgesia was abolished in mice lacking TRPV1, suggesting the functional interaction between ATP and TRPV1 at a behavioral level. However, thermal hyperalgesia was preserved in P2Y1 receptor-deficient mice. Patch-clamp analyses using mouse dorsal root ganglion neurons indicated the involvement of P2Y2 rather than P2Y1 receptors. Coexpression of TRPV1 mRNA with P2Y2 mRNA, but not P2Y1 mRNA, was determined in the rat lumbar DRG using in situ hybridization histochemistry. These data indicate the importance of metabotropic P2Y2 receptors in nociception through TRPV1.
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14
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Zhou Y, Li GD, Zhao ZQ. State-dependent phosphorylation of epsilon-isozyme of protein kinase C in adult rat dorsal root ganglia after inflammation and nerve injury. J Neurochem 2003; 85:571-80. [PMID: 12694383 DOI: 10.1046/j.1471-4159.2003.01675.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The epsilon-isozyme of protein kinase C (PKCepsilon) and the vanilloid receptor 1 (VR1) are both expressed in dorsal root ganglion (DRG) neurons and are reported to be predominantly and specifically involved in nociceptive function. Using phosphospecific antibody against the C-terminal hydrophobic site Ser729 of PKCepsilon as a marker of enzyme activation, the state-dependent activation of PKCepsilon, as well as the expression of VR1 in rat DRG neurons, was evaluated in different experimental pain models in vivo. Quantitative analysis showed that phosphorylation of PKCepsilon in DRG neurons was significantly up-regulated after carrageen- and Complete Freund's Adjuvant-induced inflammation, while it was markedly down-regulated after chronic constriction injury. A double-labeling study showed that phosphorylation of PKCepsilon was expressed predominantly in VR1 immunoreactivity positive small diameter DRG neurons mediating the nociceptive information from peripheral tissue to spinal cord. The VR1 protein expression showed no significant changes after either inflammation or chronic constriction injury. These data indicate that functional activation of PKCepsilon has a close relationship with the production of inflammatory hyperalgesia and the sensitization of the nociceptors. Inflammatory mediator-induced activation of PKCepsilon and subsequent sensitization of VR1 to noxious stimuli by PKCepsilon may be involved in nociceptor sensitization.
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Affiliation(s)
- Yu Zhou
- Institute of Neurobiology, Fu-Dan University, Shanghai, China
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15
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PRICE TJ, HELESIC G, PARGHI D, HARGREAVES KM, FLORES CM. The neuronal distribution of cannabinoid receptor type 1 in the trigeminal ganglion of the rat. Neuroscience 2003; 120:155-62. [PMID: 12849749 PMCID: PMC1899155 DOI: 10.1016/s0306-4522(03)00333-6] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Cannabinoid compounds have been shown to produce antinociception and antihyperalgesia by acting upon cannabinoid receptors located in both the CNS and the periphery. A potential mechanism by which cannabinoids could inhibit nociception in the periphery is the activation of cannabinoid receptors located on one or more classes of primary nociceptive neurons. To address this hypothesis, we evaluated the neuronal distribution of cannabinoid receptor type 1 (CB1) in the trigeminal ganglion (TG) of the adult rat through combined in situ hybridization (ISH) and immunohistochemistry (IHC). CB1 receptor mRNA was localized mainly to medium and large diameter neurons of the maxillary and mandibular branches of the TG. Consistent with this distribution, in a de facto nociceptive sensory neuron population that exhibited vanilloid receptor type 1 immunoreactivity, colocalization with CB1 mRNA was also sparse (<5%). Furthermore, very few neurons (approximately 5%) in the peptidergic (defined as calcitonin gene-related peptide- or substance P-immunoreactive) or the isolectin B4-binding sensory neuron populations contained CB1 mRNA. In contrast, and consistent with the neuron-size distribution for CB1, nearly 75% of CB1-positive neurons exhibited N52-immunoreactivity, a marker of myelinated axons. These results indicate that in the rat TG, CB1 receptors are expressed predominantly in neurons that are not thought to subserve nociceptive neurotransmission in the noninjured animal. Taken together with the absence of an above background in situ signal for CB2 mRNA in TG neurons, these findings suggest that the peripherally mediated antinociceptive effects of cannabinoids may involve either as yet unidentified receptors or interaction with afferent neuron populations that normally subserve non-nociceptive functions.
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Affiliation(s)
- T. J. PRICE
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - G. HELESIC
- Department of Endodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - D. PARGHI
- Department of Endodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - K. M. HARGREAVES
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
- Department of Endodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - C. M. FLORES
- Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
- Department of Endodontics, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
- *Correspondence to: C. M. Flores, Johnson and Johnson Pharmaceutical Research and Development, L.L.C., Welsh and McKean Roads, Spring House, PA 19477-0776, USA. Tel: +1-215-628-5457; fax: +1-215-628-3297. E-mail address: (C. M. Flores)
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16
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Neugebauer V, Carlton SM. Peripheral metabotropic glutamate receptors as drug targets for pain relief. Expert Opin Ther Targets 2002; 6:349-61. [PMID: 12223072 DOI: 10.1517/14728222.6.3.349] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The relatively new family of G-protein-coupled metabotropic glutamate receptors (mGluRs) is comprised of eight cloned subtypes, which are classified into three groups based on their sequence homology, signal transduction mechanisms and receptor pharmacology. It is now well-established that mGluRs in the central nervous system are essential for neuroplasticity associated with normal brain functions but are also critically involved in various neurological and psychiatric disorders. Recent anatomical and behavioural evidence suggests an important role of mGluRs in peripheral tissues in animal models of inflammatory and neuropathic pain. Once the cellular effects of peripheral mGluR activation and inhibition are better understood, certain peripheral mGluR subtypes may become important novel therapeutic targets for the relief of pain associated with peripheral tissue injury. Peripherally acting drugs that modulate nociceptive processing through mGluRs should have the advantage of lacking the central side effects commonly observed with drugs interfering with glutamatergic transmission in the central nervous system.
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MESH Headings
- Analgesics, Non-Narcotic/pharmacology
- Analgesics, Non-Narcotic/therapeutic use
- Animals
- Anti-Inflammatory Agents, Non-Steroidal/pharmacology
- Anti-Inflammatory Agents, Non-Steroidal/therapeutic use
- Axons/drug effects
- Axons/metabolism
- Drug Design
- Drug Evaluation, Preclinical
- Humans
- Inflammation/drug therapy
- Inflammation/physiopathology
- Ion Channels/drug effects
- Mice
- Neuralgia/drug therapy
- Neuralgia/physiopathology
- Pain/drug therapy
- Pain/physiopathology
- Rats
- Receptors, Glutamate/drug effects
- Receptors, Glutamate/physiology
- Receptors, Metabotropic Glutamate/antagonists & inhibitors
- Receptors, Metabotropic Glutamate/classification
- Receptors, Metabotropic Glutamate/physiology
- Receptors, Opioid/drug effects
- Receptors, Opioid/physiology
- Signal Transduction/drug effects
- Synaptic Transmission/drug effects
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Affiliation(s)
- Volker Neugebauer
- Department of Anatomy & Neurosciences and Marine Biomedical Institute, University of Texas, Medical Branch, Galveston, TX 77555-1069, USA.
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17
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Numazaki M, Tominaga T, Toyooka H, Tominaga M. Direct phosphorylation of capsaicin receptor VR1 by protein kinase Cepsilon and identification of two target serine residues. J Biol Chem 2002; 277:13375-8. [PMID: 11884385 DOI: 10.1074/jbc.c200104200] [Citation(s) in RCA: 375] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The capsaicin receptor, VR1, is a sensory neuron-specific ion channel that serves as a polymodal detector of pain-producing chemical and physical stimuli. It has been reported that ATP, one of the inflammatory mediators, potentiates the VR1 currents evoked by capsaicin or protons and reduces the temperature threshold for activation of VR1 through metabotropic P2Y(1) receptors in a protein Kinase C (PKC)-dependent pathway, suggesting the phosphorylation of VR1 by PKC. In this study, direct phosphorylation of VR1 upon application of phorbol 12-myristate 13-acetate (PMA) was proven biochemically in cells expressing VR1. An in vitro kinase assay using glutathione S-transferase fusion proteins with cytoplasmic segments of VR1 showed that both the first intracellular loop and carboxyl terminus of VR1 were phosphorylated by PKCepsilon. Patch clamp analysis of the point mutants where Ser or Thr residues were replaced with Ala in the total 16 putative phosphorylation sites showed that two Ser residues, Ser(502) and Ser(800) were involved in the potentiation of the capsaicin-evoked currents by either PMA or ATP. In the cells expressing S502A/S800A double mutant, the temperature threshold for activation was not reduced upon PMA treatment. The two sites would be promising targets for the development of substance modulating VR1 function, thereby reducing pain.
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Affiliation(s)
- Mitsuko Numazaki
- Department of Physiology, Mie University School of Medicine, Edobashi 2-174, Tsu, Mie 514-8507, Japan
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18
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A sensory neuron subpopulation with unique sequential survival dependence on nerve growth factor and basic fibroblast growth factor during development. J Neurosci 2001. [PMID: 11698599 DOI: 10.1523/jneurosci.21-22-08873.2001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We characterized a subpopulation of dorsal root ganglion (DRG) sensory neurons that were previously identified as preferential targets of enkephalins. This group, termed P-neurons after their "pear" shape, sequentially required nerve growth factor (NGF) and basic fibroblast growth factor (bFGF) for survival in vitro during different developmental stages. Embryonic P-neurons required NGF, but not bFGF. NGF continued to promote their survival, although less potently, up to postnatal day 2 (P2). Conversely, at P5, they needed bFGF but not NGF, with either factor having similar effects at P2. This trophic switch was unique to that DRG neuronal group. In addition, neither neurotrophin-3 (NT-3) nor brain-derived neurotrophic factor influenced their survival during embryonic and postnatal stages, respectively. The expression of NGF (Trk-A) and bFGF (flg) receptors paralleled the switch in trophic requirement. No single P-neuron appeared to coexpress both Trk-A and flg. In contrast, all of them coexpressed flg and substance P, providing a specific marker of these cells. Immunosuppression of bFGF in newborn animals greatly reduced their number, suggesting that the factor was required in vivo. bFGF was present in the DRG and spinal cord, as well as in skeletal muscle, the peripheral projection site of P-neurons, as revealed by tracer DiIC(18)3. The lack of requirement of NT-3 for survival and immunoreactivity for the neurofilament of 200 kDa distinguished them from muscle proprioceptors, suggesting that they are likely to be unmyelinated muscle fibers. Collectively, their properties indicate that P-neurons constitute a distinct subpopulation of sensory neurons for which the function may be modulated by enkephalins.
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19
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Affiliation(s)
- S G Waxman
- Department of Neurology LCI 707, Yale University School of Medicine, P.O. Box 208018, 333 Cedar Street, New Haven, Connecticut 06520-8018, USA.
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Tominaga M, Wada M, Masu M. Potentiation of capsaicin receptor activity by metabotropic ATP receptors as a possible mechanism for ATP-evoked pain and hyperalgesia. Proc Natl Acad Sci U S A 2001; 98:6951-6. [PMID: 11371611 PMCID: PMC34459 DOI: 10.1073/pnas.111025298] [Citation(s) in RCA: 394] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The capsaicin (vanilloid) receptor, VR1, is a sensory neuron-specific ion channel that serves as a polymodal detector of pain-producing chemical and physical stimuli. It has been proposed that ATP, released from different cell types, initiates the sensation of pain by acting predominantly on nociceptive ionotropic purinoceptors located on sensory nerve terminals. In this study, we examined the effects of extracellular ATP on VR1. In cells expressing VR1, ATP increased the currents evoked by capsaicin or protons through activation of metabotropic P2Y(1) receptors in a protein kinase C-dependent pathway. The involvement of G(q/11)-coupled metabotropic receptors in the potentiation of VR1 response was confirmed in cells expressing both VR1 and M1 muscarinic acetylcholine receptors. In the presence of ATP, the temperature threshold for VR1 activation was reduced from 42 degrees C to 35 degrees C, such that normally nonpainful thermal stimuli (i.e., normal body temperature) were capable of activating VR1. This represents a novel mechanism through which the large amounts of ATP released from damaged cells in response to tissue trauma might trigger the sensation of pain.
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Affiliation(s)
- M Tominaga
- Department of Molecular Neurobiology, Institute of Basic Medical Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8575, Japan.
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Wood JN. Pathobiology of visceral pain: molecular mechanisms and therapeutic implications. II. Genetic approaches to pain therapy. Am J Physiol Gastrointest Liver Physiol 2000; 278:G507-12. [PMID: 10762603 DOI: 10.1152/ajpgi.2000.278.4.g507] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
New analgesic drugs are necessary because a number of pain states are untreatable. Genetic approaches to the identification of analgesic drug targets include mapping genes involved in human pain perception (e.g., trkA involved in hereditary neuropathies), identifying regulators of sensory neuron function in simple multicellular organisms and then investigating the activity of their mammalian homologs (e.g., POU domain transcription factors that specify sensory cell fate), as well as difference, expression, and homology cloning of receptors, ion channels, and transcription factors present in sensory neurons. After target validation through the construction of null mutant mice, high-throughput cell-based screens can be used to identify potential drug candidates. As a result of these approaches, a number of receptors and ion channels present in sensory neurons such as voltage-gated sodium channels [sensory neuron specific (SNS) and Na channel novel] and ATP-gated (P2X3), capsaicin-gated [vanilloid receptor 1(VR1)], and proton-gated [acid-sensing ion channel (ASIC)] channels are now under investigation as potential new analgesic drug targets.
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Affiliation(s)
- J N Wood
- Department of Biology, University College, London WC1E 6BT, United Kingdom.
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