Journal Club 2014.03.05

By

Enhanced excitability of MRGPRA3- and MRGPRD-positive nociceptors in a model ofinflammatory itch and pain

Lintao Qu,1,* Ni Fan,1,2,* Chao Ma,1,3 Tao Wang,1,3 Liang Han,4 Kai Fu,1 Yingdi Wang,5 Steven G. Shimada,1 Xinzhong Dong4 and Robert H. LaMotte1

  1. 1  Department of Anaesthesiology, Yale University School of Medicine, New Haven, CT, 06520, USA
  2. 2  Guangzhou Brain Hospital, the Affiliated Hospital of Guangzhou Medical University, Guangzhou, Guangdong, China 510370
  3. 3 InstituteofBasicMedicalSciences,Chinese Academy of Medical Sciences, School of Basic Medicine, Peking Union Medical College, Department of Anatomy, Histology and Embryology, Beijing, China
  4. 4  Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, USA
  5. 5  Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06511, USA

*These authors contributed equally to this work.

Correspondence to: Robert H. LaMotte, Ph.D.,
Department of Anaesthesiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
E-mail: robert.lamotte@yale.edu

Brain-2014-Qu-brain_awu007

Itch is a common symptom of diseases of the skin but can also accompany diseases of other tissues including the nervous system. Acute itch from chemicals experimentally applied to the skin is initiated and maintained by action potential activity in a subset of nociceptive neurons. But whether these pruriceptive neurons are active or might become intrinsically more excitable under the pathological conditions that produce persistent itch and nociceptive sensations in humans is largely unexplored. Recently, two distinct types of cutaneous nociceptive dorsal root ganglion neurons were identified as responding to pruritic chemicals and playing a role in itch sensation. One expressed the mas-related G-coupled protein receptor MRGPRA3 and the other MRGPRD (MRGPRA3+ and MRGPRD+ neurons, respectively). Here we tested whether these two distinct pruriceptive nociceptors exhibited an enhanced excitability after the development of contact hypersensitivity, an animal model of allergic contact dermatitis, a common pruritic disorder in humans. The characteristics of increased excitability of pruriceptive neurons during this disorder may also pertain to the same types of neurons active in other pruritic diseases or pathologies that affect the nervous system and other tissues or organs. We found that challenging the skin of the calf of the hind paw or the cheek of previously sensitized mice with the hapten, squaric acid dibutyl ester, produced symptoms of contact hypersensitivity including an increase in skin thickness and site-directed spontaneous pain-like (licking or wiping) and itch-like (biting or scratching) behaviours. Ablation of MRGPRA3+ neurons led to a significant reduction in spontaneous scratching of the hapten-challenged nape of the neck of previously sensitized mice. In vivo, electrophysiological recordings revealed that MRGPRA3+ and MRGPRD+ neurons innervating the hapten-challenged skin exhibited a greater incidence of spontaneous activity and/or abnor- mal after-discharges in response to mechanical and heat stimuli applied to their receptive fields compared with neurons from the vehicle-treated control animals. Whole-cell recordings in vitro showed that both MRGPRA3+ and MRGPRD+ neurons from hapten-challenged mice displayed a significantly more depolarized resting membrane potential, decreased rheobase, and greater number of action potentials at twice rheobase compared with neurons from vehicle controls. These signs of neuronal hyper- excitability were associated with a significant increase in the peak amplitude of tetrodotoxin-sensitive and resistant sodium currents. Thus, the hyperexcitability of MRGPRA3+ and MRGPRD+ neurons, brought about in part by enhanced sodium currents, may contribute to the spontaneous itch- and pain-related behaviours accompanying contact hypersensitivity and/or other inflammatory diseases in humans.

Keywords: itch; pain; MRGPRA3; MRGPRD; allergic contact dermatitis
Abbreviations: CHS = contact hypersensitivity; GFP = green fluorescent protein; SADBE = squaric acid dibutyl ester;

TTX = tetrodotoxin

Journal club 2014.02.13.

By

Cortical GluK1 kainate receptors modulate scratching in adult mice

Journal of Neurochemistry | 2013 | 126 | 636-650

Kaori Yamada and Min Zhuo

jnc12351

Abstract

Recent investigations into the mechanisms mediating itch transmission have focused on spinal mechanisms, whereas few studies have investigated the role of the cerebral cortex in itch-related behaviors. Human imaging studies show that several cortical regions are active in correspondence with itch, including the anterior cingulate cortex (ACC). We present here evidence of cortical modulation of pruritogen-induced scratch- ing behavior. We combine pharmacological, genetic, and electrophysiological approaches to show that cortical GluK1- containing kainate (KA) receptors are involved in scratching

induced by histamine and non-histamine-dependent itching stimuli. We further show that scratching corresponds with enhanced excitatory transmission in the ACC through KA receptor modulation of inhibitory circuitry. In addition, we found that inhibiting GluK1-containing KA receptors in the ACC also reduced behavioral nociceptive responses induced by forma- lin. Our results reveal a new role of the cortex in pruritogen- induced scratching.

Keywords: cortex, glutamatergic transmission, inhibitory trans- mission, itch, kainate receptors, scratching.
J. Neurochem. (2013) 126, 636–650.

Journal club 2014.01.29.

By

Distinct Expression of Mas1-Related G-Protein-Coupled Receptor B4 in Dorsal Root and Trigeminal Ganglia—Implications for Altered Behaviors in Acid-Sensing Ion Channel 3-Deficient Mice

Ya-Han Huang & Chin-Yu Chang & Chih-Cheng Chen & Chih-Dong Yang & Wei-Hsin Sun

Received: 26 February 2013 / Accepted: 8 July 2013 / Published online: 31 July 2013 # Springer Science+Business Media New York 2013

art%3A10.1007%2Fs12031-013-0070-0

Abstract

Mas1-related G-protein-coupled receptors (Mrgprs), comprising more than 50 distinct members, are specifically expressed in primary sensory neurons. Reflecting the diversity and specificity of stimuli they detect, Mrgprs are involved in pain, touch, and itch-related behaviors. Sensory–neuron-specif- ic acid-sensing ion channel 3 (ASIC3) is essential for touch and inflammatory pain, but mice lacking ASIC3 have complex behavioral alterations in various modalities of pain and touch. To understand whether Mrgprs are involved in complex behav- ioral alterations found in ASIC3-deficient mice, we examined Mrgpr gene expression in ASIC3−/− mice. Only MrgprB4 expression has shown significant change. MrgprB4 expression was increased in ASIC3−/− dorsal root ganglia (DRG) but decreased in ASIC3−/− trigeminal ganglia. The distinct alter- ations in DRG and trigeminal ganglia imply that MrgprB4 could have multiple functions. Given that MrgprB4 is expressed in neurons that may detect gentle touch and that ASIC3−/− mice have altered sensitivity of mechanoreceptors for light touch, the expression change of MrgprB4 is more likely related to the altered touch behaviors of ASIC3−/− mice.

Keywords

Dorsal root ganglion . Trigeminal ganglion . Mas1-related G-protein-coupled receptor B4 . ASIC3 . Nociceptors

Journal Club 2014.01.16

By

Roles of glutamate, substance P, and gastrin-releasing peptide as spinal neurotransmitters of histaminergic and nonhistaminergic itch

Tasuku Akiyama a, Mitsutoshi Tominaga b, Kenji Takamori b, Mirela Iodi Carstens a, E. Carstens a,⇑ a Department of Neurobiology, Physiology & Behavior, University of California, Davis, CA, USA

b Institute for Environmental and Gender Specific Medicine, Juntendo University Graduate School of Medicine, Urayasu, Chiba 279-0021, Japan

1-s2.0-S0304395913005083-main

abstract

We investigated roles for substance P (SP), gastrin-releasing peptide (GRP), and glutamate in the spinal neurotransmission of histamine-dependent and -independent itch. In anesthetized mice, responses of single superficial dorsal horn neurons to intradermal (i.d.) injection of chloroquine were partially reduced by spinal application of the a-amino-3-hydroxy-5-methyl-4-isoxazole proprionate acid (AMPA)/kainate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Co-application of CNQX plus a neurokinin-1 (NK-1) antagonist produced stronger inhibition, while co-application of CNQX, NK-1, and GRP receptor (GRPR) antagonists completely inhibited firing. Nociceptive-specific and wide dynamic range-type neu- rons exhibited differential suppression by CNQX plus either the GRPR or NK-1 antagonist, respectively. Neuronal responses elicited by i.d. histamine were abolished by CNQX alone. In behavioral studies, indi- vidual intrathecal administration of a GRPR, NK-1, or AMPA antagonist each significantly attenuated chlo- roquine-evoked scratching behavior. Co-administration of the NK-1 and AMPA antagonists was more effective, and administration of all 3 antagonists abolished scratching. Intrathecal CNQX alone prevented histamine-evoked scratching behavior. We additionally employed a double-label strategy to investigate molecular markers of pruritogen-sensitive dorsal root ganglion (DRG) cells. DRG cells responsive to his- tamine and/or chloroquine, identified by calcium imaging, were then processed for co-expression of SP, GRP, or vesicular glutamate transporter type 2 (VGLUT2) immunofluorescence. Subpopulations of chloro- quine- and/or histamine-sensitive DRG cells were immunopositive for SP and/or GRP, with >80% immu- nopositive for VGLUT2. These results indicate that SP, GRP, and glutamate each partially contribute to histamine-independent itch. Histamine-evoked itch is mediated primarily by glutamate, with GRP play- ing a lesser role. Co-application of NK-1, GRP, and AMPA receptor antagonists may prove beneficial in treating chronic itch.

Journal Club 2013/12/26

By

Modulation of Transient Receptor Vanilloid 1 Activity by Transient Receptor Potential Ankyrin 1
Viola Spahn, Christoph Stein and Christian Zöllner

Transient Receptor Potential Vanilloid 1 (TRPV1) is a nonselective ligand-gated cation channel responding to noxious heat, protons, and chemicals like capsaicin. TRPV1 is expressed in sensory neurons and plays a critical role in pain associated with tissue injury, inflammation or nerve lesions. Transient Receptor Potential Ankyrin 1 (TRPA1) is co- expressed with TRPV1. It is activated by compounds that cause a burning sensation (e.g. mustard oil) and, indirectly, by components of the inflammatory milieu eliciting nociceptor excitation and pain hypersensitivity. Previous studies indicate an interaction of TRPV1 and TRP A1 signaling pathways. Here we sought to examine the molecular mechanisms underlying such interactions in nociceptive neurons. We first excluded physical interactions of both channels using radioligand binding studies. By microfluorimetry, electrophysiological experiments, cAMP measurements, and site-directed mutagenesis we found a sensitization of TRPV1 after TRPA1 stimulation with mustard oil in a calcium- and cAMP/PKA-dependent manner. TRPA1 stimulation enhanced TRPV1 phosphorylation via the putative PKA phosphorylation site serine 116. We also detected calcium-sensitive increased TRPV1 activity after TRPA1 activation in dorsal root ganglion (DRG) neurons. The inhibition of TRPA1 by HC-030031 after its initial stimulation and the calcium-insensitive TRPA1 mutant D477A still showed increased capsaicin-induced TRPV1 activity excluding an additive TRPA1 current after TRPV1 stimulation. Our study shows sensitization of TRPV1 via activation of TRPA1, which involves adenylyl cyclase, increased cAMP, subsequent translocation and activation of PKA, and phosphorylation of TRPV1 at PKA phosphorylation residues. This suggests that cross-sensitization of TRP channels contributes to enhanced pain sensitivity in inflamed tissues.

Journal club 2013-11-29

By

Chronic itch development in sensory neurons requires BRAF signaling pathways

JCI70528

Zhong-Qiu Zhao,1,2 Fu-Quan Huo,1,2 Joseph Jeffry,1,2 Lori Hampton,3 Shadmehr Demehri,4,5 Seungil Kim,1 Xian-Yu Liu,1,2 Devin M. Barry,1,5 Li Wan,1,6 Zhong-Chun Liu,1,2 Hui Li,1,7 Ahu Turkoz,4 Kaijie Ma,8 Lynn A. Cornelius,1,5 Raphael Kopan,4 James F. Battey Jr.,9
Jian Zhong,8,10 and Zhou-Feng Chen1,2,4

1Center for the Study of Itch and 2Departments of Anesthesiology and Psychiatry, Washington University School of Medicine Pain Center,
St. Louis, Missouri, USA. 3Office of Laboratory Animal Welfare, NIH, Bethesda, Maryland, USA. 4Department of Developmental Biology and 5Division of Dermatology, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, USA. 6Department of Anesthesiology, The Second Affiliated Hospital, Guangzhou Medical University, Guangzhou, China.
7Department of Anatomy, Histology, and Embryology and K.K. Leung Brain Research Centre, The Fourth Military Medical University, Xi’an, China. 8Burke Medical Research Institute, Weill Medical College of Cornell University, White Plains, New York, USA.
9National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, Maryland, USA.
10Brain and Mind Research Institute, Weill Medical College of Cornell University, New York, New York, USA.

Chronic itch, or pruritus, is associated with a wide range of skin abnormalities. The mechanisms responsible for chronic itch induction and persistence remain unclear. We developed a mouse model in which a constitutively active form of the serine/threonine kinase BRAF was expressed in neurons gated by the sodium channel Nav1.8 (BRAFNav1.8 mice). We found that constitutive BRAF pathway activation in BRAFNav1.8 mice results in ectopic and enhanced expression of a cohort of itch-sensing genes, including gastrin-releasing peptide (GRP) and MAS-related GPCR member A3 (MRGPRA3), in nociceptors expressing transient receptor potential vanilloid 1 (TRPV1). BRAFNav1.8 mice showed de novo neuronal responsiveness to pruritogens, enhanced pruriceptor excit- ability, and heightened evoked and spontaneous scratching behavior. GRP receptor expression was increased in the spinal cord, indicating augmented coding capacity for itch subsequent to amplified pruriceptive inputs. Enhanced GRP expression and sustained ERK phosphorylation were observed in sensory neurons of mice with allergic contact dermatitis– or dry skin–elicited itch; however, spinal ERK activation was not required for main- taining central sensitization of itch. Inhibition of either BRAF or GRP signaling attenuated itch sensation in chronic itch mouse models. These data uncover RAF/MEK/ERK signaling as a key regulator that confers a subset of nociceptors with pruriceptive properties to initiate and maintain long-lasting itch sensation.

Journal Club 2013-10-11

By

The Epithelial Cell-Derived Atopic Dermatitis Cytokine TSLP Activates Neurons to Induce Itch

Sarah R. Wilson,1,2,3 Lydia The ́ ,1,3 Lyn M. Batia,1 Katherine Beattie,1 George E. Katibah,1 Shannan P. McClain,1 Maurizio Pellegrino,1 Daniel M. Estandian,1 and Diana M. Bautista1,2,*
1Department of Molecular and Cell Biology
2Helen Wills Neuroscience Institute

University of California, Berkeley, Berkeley, CA 94720, USA 3These authors contributed equally to this work *Correspondence: dbautista@berkeley.edu

http://dx.doi.org/10.1016/j.cell.2013.08.057

1-s2.0-S009286741301088X-main

SUMMARY

Atopic dermatitis (AD) is a chronic itch and inflamma- tory disorder of the skin that affects one in ten peo- ple. Patients suffering from severe AD eventually progress to develop asthma and allergic rhinitis, in a process known as the ‘‘atopic march.’’ Signaling between epithelial cells and innate immune cells via the cytokine thymic stromal lymphopoietin (TSLP) is thought to drive AD and the atopic march. Here, we report that epithelial cells directly communicate to cutaneous sensory neurons via TSLP to promote itch. We identify the ORAI1/NFAT calcium signaling pathway as an essential regulator of TSLP release from keratinocytes, the primary epithelial cells of the skin. TSLP then acts directly on a subset of TRPA1-positive sensory neurons to trigger robust itch behaviors. Our results support a model whereby calcium-dependent TSLP release by keratinocytes activates both primary afferent neurons and immune cells to promote inflammatory responses in the skin and airways.

Journal club 2013-09-06

By

Essential Role for TRPC5 in Amygdala Function
and Fear-Related Behavior

1-s2.0-S0092867409003766-main PIIS0092867409003766.mmc1

Antonio Riccio,1,2 Yan Li,3 Jisook Moon,3,5 Kwang-Soo Kim,3 Kiersten S. Smith,3 Uwe Rudolph,3 Svetlana Gapon,1 Gui Lan Yao,2 Evgeny Tsvetkov,3 Scott J. Rodig,4 Ashlee Van’t Veer,3 Edward G. Meloni,3 William A. Carlezon Jr.,3 Vadim Y. Bolshakov,3,* and David E. Clapham1,2,*
1Department of Cardiology, Howard Hughes Medical Institute, Manton Center for Orphan Disease, Children’s Hospital Boston, Boston, MA 02115, USA

2Department of Neurobiology, Harvard Medical School, Boston, MA 02115, USA
3Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA 02478, USA
4Department of Pathology, Brigham and Women’s Hospital, Boston, MA 02115, USA
5Present address: College of Medicine, Pochon CHA University, 606-5 Yeoksam-dong, Gangnam-gu, Seoul 135-081, Republic of Korea *Correspondence: vadimb@mclean.harvard.edu (V.Y.B.), dclapham@enders.tch.harvard.edu (D.E.C.)
DOI 10.1016/j.cell.2009.03.039

SUMMARY

The transient receptor potential channel 5 (TRPC5) is predominantly expressed in the brain where it can form heterotetrameric complexes with TRPC1 and TRPC4 channel subunits. These excitatory, nonse- lective cationic channels are regulated by G protein, phospholipase C-coupled receptors. Here, we show that TRPC5

Journal club 2013-07-26

By

Human Mas-Related G Protein-Coupled Receptors-X1 Induce Chemokine Receptor 2 Expression in Rat Dorsal Root Ganglia Neurons and Release of Chemokine Ligand 2 from the Human LAD-2 Mast Cell Line

pone.0058756

Hans Ju ̈rgen Solinski1, Franziska Petermann2, Kathrin Rothe1, Ingrid Boekhoff1, Thomas Gudermann1, Andreas Breit1*

1Walther-Straub-Institut fu ̈r Pharmakologie und Toxikologie, Ludwig-Maximilians-Universita ̈t Mu ̈nchen, Munich, Germany, 2Department of Neurology, Klinikum rechts der Isar, Technical University Munich, Munich, Germany

Abstract

Primate-specific Mas-related G protein-coupled receptors-X1 (MRGPR-X1) are highly enriched in dorsal root ganglia (DRG) neurons and induce acute pain. Herein, we analyzed effects of MRGPR-X1 on serum response factors (SRF) or nuclear factors of activated T cells (NFAT), which control expression of various markers of chronic pain. Using HEK293, DRG neuron-derived F11 cells and cultured rat DRG neurons recombinantly expressing human MRGPR-X1, we found activation of a SRF reporter gene construct and induction of the early growth response protein-1 via extracellular signal-regulated kinases-1/2 known to play a significant role in the development of inflammatory pain. Furthermore, we observed MRGPR-X1-induced up- regulation of the chemokine receptor 2 (CCR2) via NFAT, which is considered as a key event in the onset of neuropathic pain and, so far, has not yet been described for any endogenous neuropeptide. Up-regulation of CCR2 is often associated with increased release of its endogenous agonist chemokine ligand 2 (CCL2). We also found MRGPR-X1-promoted release of CCL2 in a human connective tissue mast cell line endogenously expressing MRGPR-X1. Thus, we provide first evidence to suggest that MRGPR-X1 induce expression of chronic pain markers in DRG neurons and propose a so far unidentified signaling circuit that enhances chemokine signaling by acting on two distinct yet functionally co-operating cell types. Given the important role of chemokine signaling in pain chronification, we propose that interruption of this signaling circuit might be a promising new strategy to alleviate chemokine-promoted pain.
Citation: Solinski HJ, Petermann F, Rothe K, Boekhoff I, Gudermann T, et al. (2013) Human Mas-Related G Protein-Coupled Receptors-X1 Induce Chemokine Receptor 2 Expression in Rat Dorsal Root Ganglia Neurons and Release of Chemokine Ligand 2 from the Human LAD-2 Mast Cell Line. PLoS ONE 8(3): e58756. doi:10.1371/journal.pone.0058756

Editor: Roland Seifert, Medical School of Hannover, United States of America Received January 18, 2013; Accepted February 6, 2013; Published March 7, 2013

Copyright: ß 2013 Solinski et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This work was supported by a grant from the ‘‘Deutsche Forschungsgemeinschaft’’ [grant BR 3346/3–1]. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.*

E-mail: andreas.breit@lrz.uni-muenchen.de

Journal club 2013-07-12

By

Lysophosphatidic acid directly activates TRPV1 through a C-terminal binding site

Andrés Nieto-Posadas1, Giovanni Picazo-Juárez1, Itzel Llorente1, Andrés Jara-Oseguera2,
Sara Morales-Lázaro1, Diana Escalante-Alcalde1*, León D Islas2* & Tamara Rosenbaum1*

Since 1992, there has been growing evidence that the bioactive phospholipid lysophosphatidic acid (LPA), whose amounts are
increased upon tissue injury, activates primary nociceptors resulting in neuropathic pain. The TRPV1 ion channel is expressed in
primary afferent nociceptors and is activated by physical and chemical stimuli. Here we show that in control mice LPA produces
acute pain-like behaviors, which are substantially reduced in Trpv1-null animals. Our data also demonstrate that LPA activates
TRPV1 through a unique mechanism that is independent of G protein–coupled receptors, contrary to what has been widely
shown for other ion channels, by directly interacting with the C terminus of the channel. We conclude that TRPV1 is a direct
molecular target of the pain-producing molecule LPA and that this constitutes, to our knowledge, the first example of LPA
binding directly to an ion channel to acutely regulate its function.

nchembio.712

Scroll to Top