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Pecze L, Winter Z, Jósvay K, Ötvös F, Kolozsi C, Vizler C, Budai D, Letoha T, Dombi G, Szakonyi G, Oláh Z. Divalent heavy metal cations block the TRPV1 Ca(2+) channel. Biol Trace Elem Res 2013; 151:451-61. [PMID: 23264033 PMCID: PMC3566393 DOI: 10.1007/s12011-012-9570-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2012] [Accepted: 12/03/2012] [Indexed: 01/17/2023]
Abstract
Transient receptor potential vanilloid 1 (TRPV1) is a non-selective cation channel involved in pain sensation and in a wide range of non-pain-related physiological and pathological conditions. The aim of the present study was to explore the effects of selected heavy metal cations on the function of TRPV1. The cations ranked in the following sequence of pore-blocking activity: Co(2+) [half-maximal inhibitory concentration (IC(50)) = 13 μM] > Cd(2+) (I (50) = 38 μM) > Ni(2+) (IC(50) = 62 μM) > Cu(2+) (IC(50) = 200 μM). Zn(2+) proved to be a weak (IC(50) = 27 μM) and only partial inhibitor of the channel function, whereas Mg(2+), Mn(2+) and La(3+) did not exhibit any substantial effect. Co(2+), the most potent channel blocker, was able not only to compete with Ca(2+) but also to pass with it through the open channel of TRPV1. In response to heat activation or vanilloid treatment, Co(2+) accumulation was verified in TRPV1-transfected cell lines and in the TRPV1+ dorsal root ganglion neurons. The inhibitory effect was also demonstrated in vivo. Co(2+) applied together with vanilloid agonists attenuated the nocifensive eye wipe response in mice. Different rat TRPV1 pore point mutants (Y627W, N628W, D646N and E651W) were created that can validate the binding site of previously used channel blockers in agonist-evoked (45)Ca(2+) influx assays in cells expressing TRPV1. The IC(50) of Co(2+) on these point mutants were determined to be reasonably comparable to those on the wild type, which suggests that divalent cations passing through the TRPV1 channel use the same negatively charged amino acids as Ca(2+).
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Affiliation(s)
- László Pecze
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
- Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Zoltán Winter
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
| | - Katalin Jósvay
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
- Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Ferenc Ötvös
- Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
- Greenformatix Nonprofit Ltd., Szeged, Hungary
| | - Csongor Kolozsi
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
- Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | - Csaba Vizler
- Institute of Biochemistry, Biological Research Centre of the Hungarian Academy of Sciences, Szeged, Hungary
| | | | - Tamás Letoha
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
- Pharmacoidea Ltd., Szeged, Hungary
| | - György Dombi
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
| | - Gerda Szakonyi
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
| | - Zoltán Oláh
- Institute of Pharmaceutical Analysis, Faculty of Pharmacy, University of Szeged, Szeged, Hungary
- Acheuron Hungary Ltd., Szeged, Hungary
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102
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Szolcsányi J, Pintér E. Transient receptor potential vanilloid 1 as a therapeutic target in analgesia. Expert Opin Ther Targets 2013; 17:641-57. [PMID: 23421411 DOI: 10.1517/14728222.2013.772580] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION The selective excitatory action of capsaicin followed by long-term chemoanalgesia due to an action on the 'capsaicin receptor' of C-polymodal nociceptors, cloned 15 years ago, opened up fascinating perspectives for a class of nociceptor blocking analgesics. AREAS COVERED The TRPV1/capsaicin receptor is an integrative, chemoceptive, noxious heat-gated cation channel also gated by several endogenous ligands and sensitized by phosphorylation through intracellular cascades triggered from receptors of bradykinin, prostanoids, NGF and interactions with TRPA1. In this review, types of sensory receptors and unique mechanisms for blocking nociceptor action, e.g., 'pore dilation' intracellular acidosis and the long-term function-related mitochondrial swelling at the nerve terminals and sensory neurons are summarized. In humans the 8% capsaicin dermal patch is already in usage for nondiabetic neuropathic pain and two topical preparations of civamide have also been approved recently for cluster headache and osteoarthritis. Evidence for epidermal nerve terminal loss in humans after topical applications and misleading results on sensory neuron death evoked by TRPV1 agonism in animals are discussed. EXPERT OPINION The unique 'multisteric' gating of TRPV1 channel which is opened and modulated in various conformational changes to natural stimuli differs from the operation of canonical ligand-gated channels and makes it suitable to initiate development of second generation of TRPV1 antagonists without on-target side effects of hyperthermia and risk of burn injury.
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Affiliation(s)
- János Szolcsányi
- University of Pécs Medical School, Department of Pharmacology and Pharmacotherapy , H-7624 Pécs, Szigeti u. 12 , Hungary.
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103
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Kono T, Kaneko A, Omiya Y, Ohbuchi K, Ohno N, Yamamoto M. Epithelial transient receptor potential ankyrin 1 (TRPA1)-dependent adrenomedullin upregulates blood flow in rat small intestine. Am J Physiol Gastrointest Liver Physiol 2013; 304:G428-36. [PMID: 23275609 PMCID: PMC3566615 DOI: 10.1152/ajpgi.00356.2012] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The functional roles of transient receptor potential (TRP) channels in the gastrointestinal tract have garnered considerable attention in recent years. We previously reported that daikenchuto (TU-100), a traditional Japanese herbal medicine, increased intestinal blood flow (IBF) via adrenomedullin (ADM) release from intestinal epithelial (IE) cells (Kono T et al. J Crohns Colitis 4: 161-170, 2010). TU-100 contains multiple TRP activators. In the present study, therefore, we examined the involvement of TRP channels in the ADM-mediated vasodilatatory effect of TU-100. Rats were treated intraduodenally with the TRP vanilloid type 1 (TRPV1) agonist capsaicin (CAP), the TRP ankyrin 1 (TRPA1) agonist allyl-isothiocyanate (AITC), or TU-100, and jejunum IBF was evaluated using laser-Doppler blood flowmetry. All three compounds resulted in vasodilatation, and the vasodilatory effect of TU-100 was abolished by a TRPA1 antagonist but not by a TRPV1 antagonist. Vasodilatation induced by AITC and TU-100 was abrogated by anti-ADM antibody treatment. RT-PCR and flow cytometry revealed that an IEC-6 cell line originated from the small intestine and purified IE cells expressed ADM and TRPA1 but not TRPV1. AITC increased ADM release in IEC cells remarkably, while CAP had no effect. TU-100 and its ingredient 6-shogaol (6SG) increased ADM release dose-dependently, and the effects were abrogated by a TRPA1 antagonist. 6SG showed similar TRPA1-dependent vasodilatation in vivo. These results indicate that TRPA1 in IE cells may play an important role in controlling bowel microcirculation via ADM release. Epithelial TRPA1 appears to be a promising target for the development of novel strategies for the treatment of various gastrointestinal disorders.
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Affiliation(s)
- Toru Kono
- Center for Clinical and Biomedical Research, Sapporo Hisgashi Tokushukai Hospital, Hokkaido, Japan.
| | - Atsushi Kaneko
- 2Division of Gastroenterologic and General Surgery, Department of Surgery, Asahikawa Medical University, Hokkaido, Japan; and ,3Tsumura Research Laboratories, Tsumura and Co., Ibaraki, Japan
| | - Yuji Omiya
- 2Division of Gastroenterologic and General Surgery, Department of Surgery, Asahikawa Medical University, Hokkaido, Japan; and ,3Tsumura Research Laboratories, Tsumura and Co., Ibaraki, Japan
| | - Katsuya Ohbuchi
- 3Tsumura Research Laboratories, Tsumura and Co., Ibaraki, Japan
| | - Nagisa Ohno
- 3Tsumura Research Laboratories, Tsumura and Co., Ibaraki, Japan
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104
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Ugarte GD, Diaz E, Biscaia M, Stehberg J, Montecino M, van Zundert B. Transcription of the pain-related TRPV1 gene requires Runx1 and C/EBPβ factors. J Cell Physiol 2012; 228:860-70. [DOI: 10.1002/jcp.24236] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 09/21/2012] [Indexed: 11/08/2022]
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105
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Jardí F, Martínez V, Vergara P. NGF is involved in oral ovalbumin-induced altered colonic contractility in rats: evidence from the blockade of TrkA receptors with K252a. Neurogastroenterol Motil 2012; 24:e580-90. [PMID: 23072452 DOI: 10.1111/nmo.12027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Nerve growth factor (NGF)-mucosal mast cell (MMC) interaction has been implicated in the remodeling of enteric circuitries and associated functional changes. We investigated the involvement of NGF and its receptor TrkA in the altered colonic contractile activity observed in the model of oral ovalbumin (OVA)-induced MMC hyperactivity in rats. We also studied the role of colonic MMCs as a source of NGF. METHODS Rats received oral OVA, alone or with the TrkA antagonist K252a. Colonic co-expression of NGF/TrkA and rat mast cell protease II (RMCPII) (double immunofluorescence), RMCPII content (ELISA) and expression of NGF, Brain-derived neurotrophic factor (BDNF) and TrkA/B (QT-PCR) were assessed. Colonic contractile activity was determined in vivo and in vitro. KEY RESULTS TrkA, but not NGF, was localized in colonic MMCs (RMCPII-positive). Oral ovalbumin exposure increased colonic RMCPII levels but did not change the percentage of TrkA-positive MMCs. Neither OVA nor K252a, alone or combined, altered NGF, BDNF or TrkA/B expression. Spontaneous colonic activity in vivo and in vitro was altered by OVA, an effect prevented by K252a. Electrical stimulation-induced contractile responses in vivo and carbachol responses in vitro were increased by OVA in a K252a-independent manner. In OVA-treated animals, inhibition of NO synthesis with l-NNA significantly enhanced spontaneous colonic activity in vitro, a response completely prevented by K252a. CONCLUSIONS & INFERENCES These results suggest that NGF-TrkA-dependent pathways are implicated in colonic contractile alterations observed during OVA exposure in rats. NGF-TrkA system might represent a potential target for treatment of gastrointestinal disorders characterized by colonic motor alterations.
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Affiliation(s)
- F Jardí
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
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106
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Abstract
Tissue damage evokes an inflammatory response that promotes the removal of harmful stimuli, tissue repair, and protective behaviors to prevent further damage and encourage healing. However, inflammation may outlive its usefulness and become chronic. Chronic inflammation can lead to a host of diseases, including asthma, itch, rheumatoid arthritis, and colitis. Primary afferent sensory neurons that innervate target organs release inflammatory neuropeptides in the local area of tissue damage to promote vascular leakage, the recruitment of immune cells, and hypersensitivity to mechanical and thermal stimuli. TRPA1 channels are required for neuronal excitation, the release of inflammatory neuropeptides, and subsequent pain hypersensitivity. TRPA1 is also activated by the release of inflammatory agents from nonneuronal cells in the area of tissue injury or disease. This dual function of TRPA1 as a detector and instigator of inflammatory agents makes TRPA1 a gatekeeper of chronic inflammatory disorders of the skin, airways, and gastrointestinal tract.
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Affiliation(s)
- Diana M Bautista
- Department of Molecular & Cell Biology, University of California, Berkeley, California 94720, USA.
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107
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Srinath AI, Walter C, Newara MC, Szigethy EM. Pain management in patients with inflammatory bowel disease: insights for the clinician. Therap Adv Gastroenterol 2012; 5:339-57. [PMID: 22973418 PMCID: PMC3437534 DOI: 10.1177/1756283x12446158] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Abdominal pain is a common symptom in patients with inflammatory bowel disease (IBD) and has a profound negative impact on patients' lives. There are growing data suggesting that pain is variably related to the degree of active inflammation. Given the multifactorial etiologies underlying the pain, the treatment of abdominal pain in the IBD population is best accomplished by individualized plans. This review covers four clinically relevant categories of abdominal pain in patients with IBD, namely, inflammation, surgical complications, bacterial overgrowth, and neurobiological processes and how pain management can be addressed in each of these cases. The role of genetic factors, psychological factors, and psychosocial stress in pain perception and treatment will also be addressed. Lastly, psychosocial, pharmacological, and procedural pain management techniques will be discussed. An extensive review of the existing literature reveals a paucity of data regarding pain management specific to IBD. In addition, there is growing consensus suggesting a spectrum between IBD and irritable bowel syndrome (IBS) symptoms. Thus, this review for adult and pediatric clinicians also incorporates the literature for the treatment of functional abdominal pain and the clinical consensus from IBD and IBS experts on pharmacological, behavioral, and procedural methods to treat abdominal pain in this population.
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Affiliation(s)
- Arvind Iyengar Srinath
- Department of Pediatric Gastroenterology, Children's Hospital of Pittsburgh, Pittsburgh, PA, USA
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108
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Lennertz RC, Kossyreva EA, Smith AK, Stucky CL. TRPA1 mediates mechanical sensitization in nociceptors during inflammation. PLoS One 2012; 7:e43597. [PMID: 22927999 PMCID: PMC3426543 DOI: 10.1371/journal.pone.0043597] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 07/23/2012] [Indexed: 12/18/2022] Open
Abstract
Inflammation is a part of the body's natural response to tissue injury which initiates the healing process. Unfortunately, inflammation is frequently painful and leads to hypersensitivity to mechanical stimuli, which is difficult to treat clinically. While it is well established that altered sensory processing in the spinal cord contributes to mechanical hypersensitivity (central sensitization), it is still debated whether primary afferent neurons become sensitized to mechanical stimuli after tissue inflammation. We induced inflammation in C57BL/6 mice via intraplantar injection of Complete Freund's Adjuvant. Cutaneous C fibers exhibited increased action potential firing to suprathreshold mechanical stimuli. We found that abnormal responses to intense mechanical stimuli were completely suppressed by acute incubation of the receptive terminals with the TRPA1 inhibitor, HC-030031. Further, elevated responses were predominantly exhibited by a specific subgroup of C fibers, which we determined to be C-Mechano Cold sensitive fibers. Thus, in the presence of HC-030031, C fiber mechanical responses in inflamed mice were not different than responses in saline-injected controls. We also demonstrate that injection of the HC-030031 compound into the hind paw of inflamed mice alleviates behavioral mechanical hyperalgesia without affecting heat hyperalgesia. Further, we pharmacologically anesthetized the TRPA1-expressing fibers in vivo by co-injecting the membrane-impermeable sodium channel inhibitor QX-314 and the TRPA1 agonist cinnamaldehyde into the hind paw. This approach also alleviated behavioral mechanical hyperalgesia in inflamed mice but left heat hypersensitivity intact. Our findings indicate that C-Mechano Cold sensitive fibers exhibit enhanced firing to suprathreshold mechanical stimuli in a TRPA1-dependent manner during inflammation, and that input from these fibers drives mechanical hyperalgesia in inflamed mice.
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Affiliation(s)
- Richard C Lennertz
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin, United States of America
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109
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Alvarez P, Chen X, Bogen O, Green PG, Levine JD. IB4(+) nociceptors mediate persistent muscle pain induced by GDNF. J Neurophysiol 2012; 108:2545-53. [PMID: 22914655 DOI: 10.1152/jn.00576.2012] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Skeletal muscle is a well-known source of glial cell line-derived neurotrophic factor (GDNF), which can produce mechanical hyperalgesia. Since some neuromuscular diseases are associated with both increased release of GDNF and intense muscle pain, we explored the role of GDNF as an endogenous mediator in muscle pain. Intramuscularly injected GDNF induced a dose-dependent (0.1-10 ng/20 μl) persistent (up to 3 wk) mechanical hyperalgesia in the rat. Once hyperalgesia subsided, injection of prostaglandin E(2) at the site induced a prolonged mechanical hyperalgesia (>72 h) compared with naïve rats (<4 h; hyperalgesic priming). Selective neurotoxic destruction of IB4(+) nociceptors attenuated both GDNF hyperalgesia and hyperalgesic priming. Ergonomic muscular injury induced by eccentric exercise or mechanical vibration increased muscle GDNF levels at 24 h, a time point where rats also exhibited marked muscle hyperalgesia. Intrathecal antisense oligodeoxynucleotides to mRNA encoding GFRα1, the canonical binding receptor for GDNF, reversibly inhibited eccentric exercise- and mechanical vibration-induced muscle hyperalgesia. Finally, electrophysiological recordings from nociceptors innervating the gastrocnemius muscle in anesthetized rats, revealed significant increase in response to sustained mechanical stimulation after local GDNF injection. In conclusion, these data indicate that GDNF plays a role as an endogenous mediator in acute and induction of chronic muscle pain, an effect likely to be produced by GDNF action at GFRα1 receptors located in IB4(+) nociceptors.
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Affiliation(s)
- Pedro Alvarez
- Departments of Oral and Maxillofacial Surgery, University of California, San Francisco, California 94143-0440, USA
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110
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Merrill L, Girard BM, May V, Vizzard MA. Transcriptional and translational plasticity in rodent urinary bladder TRP channels with urinary bladder inflammation, bladder dysfunction, or postnatal maturation. J Mol Neurosci 2012; 48:744-56. [PMID: 22865090 DOI: 10.1007/s12031-012-9867-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 07/25/2012] [Indexed: 10/28/2022]
Abstract
These studies examined the transcriptional and translational plasticity of three transient receptor potential (TRP) channels (TRPA1, TRPV1, TRPV4) with established neuronal and non-neuronal expression and functional roles in the lower urinary tract. Mechanosensor and nociceptor roles in either physiological or pathological lower urinary tract states have been suggested for TRPA1, TRPV1, and TRPV4. We have previously demonstrated the neurochemical, organizational, and functional plasticity in micturition reflex pathways following induction of urinary bladder inflammation using the antineoplastic agent, cyclophosphamide. More recently, we have characterized similar plasticity in micturition reflex pathways in a transgenic mouse model with chronic urothelial overexpression (OE) of nerve growth factor (NGF) and in a transgenic mouse model with deletion of vasoactive intestinal polypeptide (VIP). In addition, the micturition reflex undergoes postnatal maturation that may also reflect plasticity in urinary bladder TRP channel expression. Thus, we examined plasticity in urinary bladder TRP channel expression in diverse contexts using a combination of quantitative, real-time PCR and western blotting approaches. We demonstrate transcriptional and translational plasticity of urinary bladder TRPA1, TRPV1, and TRVP4 expression. Although the functional significance of urinary bladder TRP channel plasticity awaits further investigation, these studies demonstrate context- (inflammation, postnatal development, NGF-OE, VIP deletion) and tissue-dependent (urothelium + suburothelium, detrusor) plasticity.
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Affiliation(s)
- Liana Merrill
- Department of Anatomy and Neurobiology, University of Vermont, Burlington, VT 05405, USA
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111
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Ji Y, Tang B, Cao DY, Wang G, Traub RJ. Sex differences in spinal processing of transient and inflammatory colorectal stimuli in the rat. Pain 2012; 153:1965-1973. [PMID: 22819535 DOI: 10.1016/j.pain.2012.06.019] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/14/2012] [Accepted: 06/19/2012] [Indexed: 02/06/2023]
Abstract
Sex differences in the spinal processing of somatic and visceral stimuli contribute to greater female sensitivity in many pain disorders. The present study examined spinal mechanisms that contribute to sex differences in visceral sensitivity. The visceromotor response to colorectal distention (CRD) was more robust in normal female rats and after intracolonic mustard oil compared with that in male rats. No sex difference was observed in the CRD-evoked response of lumbosacral (LS) and thoracolumbar (TL) colonic afferents in normal and mustard oil-treated rats, but there was a sex difference in spontaneous activity that was exacerbated by intracolonic mustard oil. The response of visceroceptive dorsal horn neurons to CRD was greater in normal female rats in the LS and TL spinal segments. The effect of intracolonic mustard oil on the CRD-evoked response of different phenotypes of visceroceptive dorsal horn neurons was dependent on sex and segment. The NMDA receptor antagonist 2-amino-5-phosphonopentanoic acid (APV) dose-dependently attenuated the visceromotor response in normal rats with greater effect in male rats. Correspondingly, there was greater cell membrane expression of the GluN1 subunit in dorsal horn extracts in female rats. After intracolonic mustard oil, there was no longer a sex difference in the effect of APV nor GluN1 expression in LS segments, but greater female expression in TL segments. These data document a sex difference in spinal processing of nociceptive visceral stimuli from the normal and inflamed colon. Differences in dorsal horn neuronal activity and NMDA receptor expression contribute to the sex differences in the visceral sensitivity observed in awake rats.
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Affiliation(s)
- Yaping Ji
- Department of Neural and Pain Sciences, School of Dentistry, University of Maryland, Baltimore, MD, USA Center for Pain Studies, University of Maryland, Baltimore, MD, USA Program in Neuroscience, University of Maryland, Baltimore, MD, USA
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112
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Ramer LM, van Stolk AP, Inskip JA, Ramer MS, Krassioukov AV. Plasticity of TRPV1-Expressing Sensory Neurons Mediating Autonomic Dysreflexia Following Spinal Cord Injury. Front Physiol 2012; 3:257. [PMID: 22934013 PMCID: PMC3429033 DOI: 10.3389/fphys.2012.00257] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2012] [Accepted: 06/20/2012] [Indexed: 01/22/2023] Open
Abstract
Spinal cord injury (SCI) triggers profound changes in visceral and somatic targets of sensory neurons below the level of injury. Despite this, little is known about the influence of injury to the spinal cord on sensory ganglia. One of the defining characteristics of sensory neurons is the size of their cell body: for example, nociceptors are smaller in size than mechanoreceptors or proprioceptors. In these experiments, we first used a comprehensive immunohistochemical approach to characterize the size distribution of sensory neurons after high- and low-thoracic SCI. Male Wistar rats (300 g) received a spinal cord transection (T3 or T10) or sham-injury. At 30 days post-injury, dorsal root ganglia (DRGs) and spinal cords were harvested and analyzed immunohistochemically. In a wide survey of primary afferents, only those expressing the capsaicin receptor (TRPV1) exhibited somal hypertrophy after T3 SCI. Hypertrophy only occurred caudal to SCI and was pronounced in ganglia far distal to SCI (i.e., in L4-S1 DRGs). Injury-induced hypertrophy was accompanied by a small expansion of central territory in the lumbar spinal dorsal horn and by evidence of TRPV1 upregulation. Importantly, hypertrophy of TRPV1-positive neurons was modest after T10 SCI. Given the specific effects of T3 SCI on TRPV1-positive afferents, we hypothesized that these afferents contribute to autonomic dysreflexia (AD). Rats with T3 SCI received vehicle or capsaicin via intrathecal injection at 2 or 28 days post-SCI; at 30 days, AD was assessed by recording intra-arterial blood pressure during colo-rectal distension (CRD). In both groups of capsaicin-treated animals, the severity of AD was dramatically reduced. While AD is multi-factorial in origin, TRPV1-positive afferents are clearly involved in AD elicited by CRD. These findings implicate TRPV1-positive afferents in the initiation of AD and suggest that TRPV1 may be a therapeutic target for amelioration or prevention of AD after high SCI.
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Affiliation(s)
- Leanne M Ramer
- International Collaboration On Repair Discoveries, University of British Columbia Vancouver, BC, Canada
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113
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Tanaka T, Shinoda M, Feng B, Albers KM, Gebhart GF. Modulation of visceral hypersensitivity by glial cell line-derived neurotrophic factor family receptor α-3 in colorectal afferents. Am J Physiol Gastrointest Liver Physiol 2011; 300:G418-24. [PMID: 21193524 PMCID: PMC3064124 DOI: 10.1152/ajpgi.00456.2010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Irritable bowel syndrome is characterized by colorectal hypersensitivity and contributed to by sensitized mechanosensitive primary afferents and recruitment of mechanoinsensitive (silent) afferents. Neurotrophic factors are well known to orchestrate dynamic changes in the properties of sensory neurons. Although pain modulation by proteins in the glial cell line-derived neurotrophic factor (GDNF) family has been documented in various pathophysiological states, their role in colorectal hypersensitivity remains unexplored. Therefore, we investigated the involvement of the GDNF family receptor α-3 (GFRα3) signaling in visceral hypersensitivity by quantifying visceromotor responses (VMR) to colorectal distension before and after intracolonic treatment with 2,4,6-trinitrobenzene sulfonic acid (TNBS). Baseline responses to colorectal distension did not differ between C57BL/6 and GFRα3 knockout (KO) mice. Relative to intracolonic saline treatment, TNBS significantly enhanced the VMR to colorectal distension in C57BL/6 mice 2, 7, 10, and 14 days posttreatment, whereas TNBS-induced visceral hypersensitivity was significantly suppressed in GFRα3 KO mice. The proportion of GFRα3 immunopositive thoracolumbar and lumbosacral colorectal dorsal root ganglion neurons was significantly elevated 2 days after TNBS treatment. In single fiber recordings, responses to circumferential stretch of colorectal afferent endings in C57BL/6 mice were significantly increased (sensitized) after exposure to an inflammatory soup, whereas responses to stretch did not sensitize in GFRα3 KO mice. These findings suggest that enhanced GFRα3 signaling in visceral afferents may contribute to development of colorectal hypersensitivity.
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Affiliation(s)
- T. Tanaka
- 1Center for Pain Research, Departments of Anesthesiology and
| | - M. Shinoda
- 1Center for Pain Research, Departments of Anesthesiology and
| | - B. Feng
- 1Center for Pain Research, Departments of Anesthesiology and
| | - K. M. Albers
- 2Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - G. F. Gebhart
- 1Center for Pain Research, Departments of Anesthesiology and
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