Journal club 2015.07.24.

Polysulfide evokes acute pain through the activation of nociceptive TRPA1 in mouse sensory neurons
Yukari Hatakeyama1, Kenji Takahashi1, Makoto Tominaga2, Hideo Kimura3 and Toshio Ohta1*

s12990-015-0023-4

Abstract
Background: Hydrogen sulfide (H2S) is oxidized to polysulfide. Recent reports show that this sulfur compound modulates various biological functions. We have reported that H2S is involved in inflammatory pain in mice. On the other hand, little is known about the functional role of polysulfide in sensory neurons. Here we show that polysulfide selectively stimulates nociceptive TRPA1 and evokes acute pain, using TRPA1-gene deficient mice (TRPA1(−/−)), a heterologous expression system and a TRPA1-expressing cell line.
Results: In wild-type mouse sensory neurons, polysulfide elevated the intracellular Ca concentration ([Ca2+]i) in a dose-dependent manner. The half maximal effective concentration (EC50) of polysulfide was less than one-tenth that of H2S. The [Ca2+]i responses to polysulfide were observed in neurons responsive to TRPA1 agonist and were inhibited by blockers of TRPA1 but not of TRPV1. Polysulfide failed to evoke [Ca2+]i increases in neurons from TRPA1(−/−) mice. In RIN-14B cells, constitutively expressing rat TRPA1, polysulfide evoked [Ca2+]i increases with the same EC50 value as in sensory neurons. Heterologously expressed mouse TRPA1 was activated by polysulfide and that was suppressed by dithiothreitol. Analyses of the TRPA1 mutant channel revealed that cysteine residues located in the internal domain were related to the sensitivity to polysulfide. Intraplantar injection of polysulfide into the mouse hind paw induced acute pain and edema which were significantly less than in TRPA1(−/−) mice.
Conclusions: The present data suggest that polysulfide functions as pronociceptive substance through the activation of TRPA1 in sensory neurons. Since the potency of polysulfide is higher than parental H2S and this sulfur compound is generated under pathophysiological conditions, it is suggested that polysulfide acts as endogenous ligand for TRPA1. Therefore, TRPA1 may be a promising therapeutic target for endogenous sulfur compound-related algesic action.
Keywords: Transient Receptor Potential Channels (TRP Channels), Calcium imaging, Dorsal root ganglia, Heterologous expression

Journal club 2015.07.17.

A Sensory Neuron-expressed Interleukin-31 Receptor Mediates T helper Cell-dependent Itch: Involvement of TRPV1 and TRPA1

nihms540721

Ferda Cevikbas, PhD1,5,*, Xidao Wang, PhD2,*, Tasuku Akiyama, PhD3, Cordula Kempkes, PhD1, Terhi Savinko, PhD4, Attila Antal, MD5, Gabriela Kukova, MD5, Timo Buhl, MD1, Akihiko Ikoma, MD, PhD1, Joerg Buddenkotte, PhD6, Vassili Soumelis, MD7, Micha Feld, PhD5, Harri Alenius, PhD4, Stacey R. Dillon, PhD8, Earl Carstens, PhD3, Bernhard Homey, MD5,#,§, Allan Basbaum, PhD2,#,§, and Martin Steinhoff, MD, PhD1,5,#,§
1Depts. of Dermatology and Surgery, University of California San Francisco, San Francisco, CA, USA 2Depts. of Anatomy and W.M. Keck Foundation Center for Integrative Neuroscience, University California San Francisco, San Francisco, CA, USA 3Dept. of Neurobiology, University California Davis, CA, USA 4Unit of Toxicology, Finnish Institute of Occupational Health, Helsinki, Finland 5Dept. of Dermatology, University Hospital Duesseldorf, Duesseldorf, Germany 6Dept. of Dermatology, University Hospital Muenster, Muenster Germany 7Dep. of Immunology, Institut Curie, Paris, France 8ZymoGenetics, Inc. (a Bristol-Myers Squibb Company) Seattle, WA, USA

Abstract
Background—Although the cytokine, interleukin-31 (IL-31), has been implicated in
inflammatory and lymphoma-associated itch, the cellular basis for its pruritic action is yet unclear.
Objective—To determine whether immune cell-derived IL-31 directly stimulates sensory neurons, and to identify the molecular basis of IL-31-induced itch.
Methods—We used immunohistochemistry and qRTPCR to determine IL-31 expression levels in mice and humans. Immunohistochemistry, immunofluorescence, qRTPCR, in vivo pharmacology, western blotting, single cell calcium and electrophysiology were used to examine the distribution, functionality and cellular basis of the neuronal IL-31 receptor (IL-31RA) in mice and humans.
Results—Among all immune and resident skin cells examined, IL-31 was predominantly produced by TH2 and to a significantly lesser extend by mature dendritic cells. Cutaneous and intrathecal injections of IL-31 evoked intense itch, and its concentration increased significantly in murine atopic-like dermatitis skin. Both human and mouse DRG neurons express IL-31RA, largely in neurons that co-express TRPV1. IL-31-induced itch was significantly reduced in TRPV1- and TRPA1-deficient mice, not c-kit or PAR-2 mice. In cultured primary sensory neurons, IL-31 triggered Ca2+-release and ERK1/2 phosphorylation, Inhibition of which blocked IL-31 signaling in vitro and reduced IL-31-induced scratching in vivo.
Conclusion—IL-31RA is a functional receptor expressed by a small subpopulation of IL-31RA+/TRPV1+/TRPA1+ neurons, and is a critical neuro-immune link between TH2 cells and sensory nerves for the generation of T cell-mediated itch. Thus, targeting neuronal IL-31RA may be effective in the management of TH2-mediated itch, including atopic dermatitis and cutaneous T cell lymphoma.
Keywords
cytokine; atopic dermatitis; sensory nerve; skin; TRP channel

© 2013 American Academy of Allergy, Asthma and Immunology. Published by Mosby, Inc. All rights reserved.
#Addresses for correspondence: Martin Steinhoff, M.D., Ph.D., Departments of Dermatology and Surgery, University of California, San Francisco, 513 Parnassus Ave, Room S-1268, San Francisco, CA, 94143 USA, Phone: +1 415 476 6978, FAX: +1 415 476 0936, SteinhoffM@derm.ucsf.edu. Allan. I. Basbaum, Ph.D., Department of Anatomy, University of California, San Francisco, 1550 4th Street, San Francisco, CA, USA, Phone: +1 415 476 5270, FAX: +1 415 476 1974, Allan.Basbaum@ucsf.edu. Bernhard Homey, M.D.. Department of Dermatology. University Hospital Duesseldorf, Duesseldorf, Germany, Phone: +49 211 811 7600, FAX: +49 211 811 7316, bernhard.homey@uni-duesseldorf.de.
*contributed equally to this work; §Co-senior authors;
Author contribution:
F. C.: conducted most of the experiments, designed the study, wrote manuscript. X. W.: conducted in vivo and morphological experiments with F.C. T.A: performed single cell calcium measurement and electrophysiology recordings under supervision of E.C; T. S.: designed the study for the in vivo mouse models of AD under supervision of H.A; A.A, M.F.: performed human staining experiments of skin tissue and qPCR of cells under supervision of B.H.; C. K.: performed western blotting and wrote part of the manuscript; G. K.: performed human staining experiments of skin tissue and qPCR of cells; A. I.: assisted in cheek model assay; T. B.: stained human DRG for IL-31RA; H. A.: supervised the murine AD study; S. D.: supervised vivo mouse studies; E. C.: supervised electrophysiology study; B. H.: designed, supervised human IL-31 studies and mouse atopy models, and wrote manuscript; A.I.B.: designed, supervised the neuronal experiments, and wrote manuscript; M.S.: designed, supervised all experiments, analyzed data, and wrote manuscript.
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Journal club 2015.07.10.

HTR7 Mediates Serotonergic Acute and Chronic Itch

HTR7 Mediates Serotonergic Acute and Chronic Itch

Takeshi Morita,1,2,7 Shannan P. McClain,1,7 Lyn M. Batia,1 Maurizio Pellegrino,1 Sarah R. Wilson,1,2 Michael A. Kienzler,3 Kyle Lyman,3 Anne Sofie Braun Olsen,3 Justin F. Wong,1 Cheryl L. Stucky,4 Rachel B. Brem,5,6,* and Diana M. Bautista1,2,* 1Department of Molecular & Cell Biology, 142 Life Sciences Addition, University of California, Berkeley, Berkeley, CA 94720-3200, USA 2Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
3Neurobiology Course, Marine Biological Laboratory, Woods Hole, MA 02543, USA
4Departments of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI 53226, USA 5Buck Institute for Research on Aging, 8001 Redwood Boulevard, Novato, CA 94945, USA
6Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA
7Co-first author
*Correspondence: rbrem@buckinstitute.org (R.B.B.), dbautista@berkeley.edu (D.M.B.) http://dx.doi.org/10.1016/j.neuron.2015.05.044

SUMMARY
Chronic itch is a prevalent and debilitating condition for which few effective therapies are available. We harnessed the natural variation across genetically distinct mouse strains to identify transcripts co-re- gulated with itch behavior. This survey led to the discovery of the serotonin receptor HTR7 as a key mediator of serotonergic itch. Activation of HTR7 promoted opening of the ion channel TRPA1, which in turn triggered itch behaviors. In addition, acute itch triggered by serotonin or a selective serotonin reuptake inhibitor required both HTR7 and TRPA1. Aberrant serotonin signaling has long been linked to a variety of human chronic itch conditions, in- cluding atopic dermatitis. In a mouse model of atopic dermatitis, mice lacking HTR7 or TRPA1 dis- played reduced scratching and skin lesion severity. These data highlight a role for HTR7 in acute and chronic itch and suggest that HTR7 antagonists may be useful for treating a variety of pathological itch conditions.

Journal club 2015.7.3

Unbiased classification of sensory neuron types by large-scale single-cell RNA sequencing

Abstract

The primary sensory system requires the integrated function of multiple cell types, although its full complexity remains unclear. We used comprehensive transcriptome analysis of 622 single mouse neurons to classify them in an unbiased manner, independent of any a priori knowledge of sensory subtypes. Our results reveal eleven types: three distinct low-threshold mechanoreceptive neurons, two proprioceptive, and six principal types of thermosensitive, itch sensitive, type C low-threshold mechanosensitive and nociceptive neurons with markedly different molecular and operational properties. Confirming previously anticipated major neuronal types, our results also classify and provide markers for new, functionally distinct subtypes. For example, our results suggest that itching during inflammatory skin diseases such as atopic dermatitis is linked to a distinct itch-generating type. We demonstrate single-cell RNA-seq as an effective strategy for dissecting sensory responsive cells into distinct neuronal types. The resulting catalog illustrates the diversity of sensory types and the cellular complexity underlying somatic sensation.

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