Journal Club 2016.1.29.

The expression of Toll-like receptor 4, 7 and co-receptors in neurochemical sub-populations of rat trigeminal ganglion sensory neurons.

Helley MP1, Abate W2, Jackson SK2, Bennett JH1, Thompson SW3.

Abstract

The recent discovery that mammalian nociceptors express Toll-like receptors (TLRs) has raised the possibility that these cells directly detect and respond to pathogens with implications for either direct nociceptor activation or sensitization. A range of neuronal TLRs have been identified, however a detailed description regarding the distribution of expression of these receptors within sub-populations of sensory neurons is lacking. There is also some debate as to the composition of the TLR4 receptor complex on sensory neurons. Here we use a range of techniques to quantify the expression of TLR4, TLR7 and some associated molecules within neurochemically-identified sub-populations of trigeminal (TG) and dorsal root (DRG) ganglion sensory neurons. We also detail the pattern of expression and co-expression of two isoforms of lysophosphatidylcholine acyltransferase (LPCAT), a phospholipid remodeling enzyme previously shown to be involved in the lipopolysaccharide-dependent TLR4 response in monocytes, within sensory ganglia. Immunohistochemistry shows that both TLR4 and TLR7 preferentially co-localize with transient receptor potential vallinoid 1 (TRPV1) and purinergic receptor P2X ligand-gated ion channel 3 (P2X3), markers of nociceptor populations, within both TG and DRG. A gene expression profile shows that TG sensory neurons express a range of TLR-associated molecules. LPCAT1 is expressed by a proportion of both nociceptors and non-nociceptive neurons. LPCAT2 immunostaining is absent from neuronal profiles within both TG and DRG and is confined to non-neuronal cell types under naïve conditions. Together, our results show that nociceptors express the molecular machinery required to directly respond to pathogenic challenge independently from the innate immune system.

The expression of Toll-like receptor 4, 7 and co-receptors in neurochemical sub-populations of rat trigeminal ganglion sensory neurons

Journal Club 2016.1.29. Read More »

journal club 2016-01-08

3-iodothyroacetic acid, a metabolite of thyroid hormone, induces itch and reduces threshold to noxious and to painful heat stimuli in mice.

Laurino A1, De Siena G, Resta F, Masi A, Musilli C, Zucchi R, Raimondi L.

Abstract

BACKGROUND AND PURPOSE:

Itch is associated with increased sensitization to nociceptive stimuli. We investigated whether 3-iodothyroacetic acid (TA1), by releasing histamine, induces itch and increases sensitization to noxious and painful heat stimuli.

EXPERIMENTAL APPROACH:

Itch was evaluated after s.c. administration of TA1 (0.4, 1.32 and 4 μg·kg(-1) ). Mice threshold to noxious (NHT) and to painful heat stimuli were evaluated by the increasing-temperature hot plate (from 45.5 to 49.5°C) or by the hot plate (51.5°C) test, respectively, 15 min after i.p. injection of TA1 (0.4, 1.32 and 4 μg·kg(-1) ). Itch, NHT and pain threshold evaluation were repeated in mice pretreated with pyrilamine. Itch and NHT were also measured in HDC(+/+) and HDC(-/-) following injection of saline or TA1 (1.32, 4 and 11 μg·kg(-1) ; s.c. and i.p.). pERK1/2 levels were determined by Western blot in dorsal root ganglia (DRG) isolated from CD1 mice 15 min after they received (i.p.): saline, saline and noxious heat stimulus (46.5°C), TA1 (0.1, 0.4, 1.32, 4 μg·kg(-1) ) or TA1 1.32 μg·kg(-1) and noxious heat stimulus.

KEY RESULTS:

TA1 0.4 and 1.32 μg·kg(-1) induced itch and reduced NHT; pyrilamine pretreatment prevented both of these effects. TA1 4 μg·kg(-1) (i.p.) reduced pain threshold without inducing itch or modifying NHT. In HDC(-/-) mice, TA1 failed to induce itch and to reduce NHT. In DRG, pERK1/2 levels were significantly increased by noxious heat stimuli and by TA1 0.1, 0.4 and 1.32 μg·kg(-1) ; i.p.

CONCLUSIONS AND IMPLICATIONS:

Increased TA1 levels induce itch and an enhanced sensitivity to noxious heat stimuli suggesting that TA1 might represent a potential cause of itch in thyroid diseases.

journal club 2016-01-08 Read More »

journal club 2015.12.31

Sensory Neuron-Specific GPCR Mrgprs Are Itch Receptors Mediating Chloroquine-Induced Pruritus

Qin Liu,1 Zongxiang Tang,1 Lenka Surdenikova,2,4 Seungil Kim,5 Kush N. Patel,1 Andrew Kim,1 Fei Ru,2 Yun Guan,3
Hao-Jui Weng,1 Yixun Geng,1 Bradley J. Undem,2 Marian Kollarik,2 Zhou-Feng Chen,5 David J. Anderson,6,7
and Xinzhong Dong1,7,*

The cellular and molecular mechanisms mediating
histamine-independent itch in primary sensory
neurons are largely unknown. Itch induced by chloroquine
(CQ) is a common side effect of this widely
used antimalarial drug. Here, we show that Mrgprs,
a family of G protein-coupled receptors expressed
exclusively in peripheral sensory neurons, function
as itch receptors. Mice lacking a cluster of Mrgpr
genes display significant deficits in itch induced by
CQ but not histamine. CQ directly excites sensory
neurons in an Mrgpr-dependent manner. CQ specifically
activates mouse MrgprA3 and human MrgprX1.
Loss- and gain-of-function studies demonstrate
that MrgprA3 is required for CQ responsiveness in
mice. Furthermore, MrgprA3-expressing neurons
respond to histamine and coexpress gastrin-releasing
peptide, a peptide involved in itch sensation,
and MrgprC11. Activation of these neurons with the
MrgprC11-specific agonist BAM8-22 induces itch in
wild-type but not mutant mice. Therefore, Mrgprs
may provide molecular access to itch-selective
neurons and constitute novel targets for itch therapeutics.

2.Sensory Neuron-Specific GPCR Mrgprs

journal club 2015.12.31 Read More »

Journal Club 2015.12.18.

Toll-like receptor 4 contributes to chronic itch, alloknesis and spinal astrocyte activation in male mice
Tong Liu , Qingjian Han , Gang Chen , Ya Huang , Lin-Xia Zhao , Temugin Berta ,Yong-Jing Gao , and Ru-Rong Ji

Running title: TLR4 and glial signaling in acute and chronic itch

00006396-900000000-99651

Abstract
Increasing evidence suggests that Toll-like receptor 4 (TLR4) contributes importantly to spinal cord glial activation and chronic pain sensitization; however, its unique role in acute and chronic itch is unclear. In this study, we investigated the involvement of TLR4 in acute and chronic itch models in male mice using both transgenic and pharmacological approaches. Tlr4−/− mice exhibited normal acute itch induced by compound 48/80 and chloroquine, but these mice showed substantial reductions in scratching in chronic itch models of dry skin, induced by acetone and diethyether followed by water (AEW), contact dermatitis, and allergic contact dermatitis on the neck. Intrathecal (spinal) inhibition of TLR4 with lipopolysaccharide Rhodobacter sphaeroides (LPS-RS) did not affect acute itch but suppressed AEW-induced chronic itch. Compound 48/80 and AEW also produced robust alloknesis, a touch-elicited itch in wild-type mice, which was suppressed by intrathecal LPS-RS and Tlr4−/− deletion. AEW induced persistent upregulation of Tlr4 mRNA and increased TLR4 expression in GFAP-expressing astrocytes in spinal cord dorsal horn. AEW also induced TLR4-dependent astrogliosis (GFAP upregulation) in spinal cord. Intrathecal injection of astroglial inhibitor L-α- aminoadipate reduced AEW-induced chronic itch and alloknesis without affecting acute itch. Spinal TLR4 was also necessary for AEW-induced chronic itch in the cheek model. Interestingly, scratching plays an essential role in spinal astrogliosis, since AEW-induced astrogliosis was abrogated by putting Elizabethan Collars on the neck to prevent scratching the itchy skin. Our findings suggest that spinal TLR4 signaling is important for spinal astrocyte activation and astrogliosis that may underlie alloknesis and chronic itch.
Key words: Alloknesis (touch-evoked itch), astrogliosis, dry skin, innate immunity, lipopolysaccharide (LPS), Toll-like receptor 4 (TLR4)

Journal Club 2015.12.18. Read More »

Journal Club 2015.12.11

Involvement of TRPV4 in serotonin-evoked scratching

Tasuku Akiyama1,2, Margaret Ivanov1, Masaki Nagamine1, Auva Davoodi1, Mirela Iodi Carstens1, Akihiko Ikoma3, Ferda Cevikbas3, Cordula Kempkes3, Joerg Buddenkotte3,4, Martin Steinhoff3,4 and E Carstens1

Abstract

Several thermo-sensitive TRP channels (TRPV1, -3; TRPA1) have been implicated in itch. In contrast, the role of transient receptor potential vanilloid type-4 (TRPV4) in itch is unknown. Therefore, we investigated if TRPV4, a temperature-sensitive cation channel, plays an important role in acute itch in mice. Four different pruritogens including serotonin (5-hydroxytrytamine, 5-HT), histamine, SLIGRL (PAR2/MrgprC11 agonist) and chloroquine (MrgprA3 agonist) were intradermally injected and itch-related scratching behavior was assessed. TRPV4 knockout (TRPV4KO) mice exhibited significantly fewer 5-HT-evoked scratching bouts compared to wild-type (WT) mice. Notably, no differences between TRPV4KO and WT mice were observed in the number of scratch bouts elicited by SLIGRL and histamine. Pretreatment with a TRPV4 antagonist significantly attenuated 5-HT-evoked scratching in vivo. Using calcium imaging in cultured primary murine dorsal root ganglion (DRG) neurons, the response of neurons after 5-HT application, but not other pruritogens, was significantly lower in TRPV4KO compared to WT mice. A TRPV4 antagonist significantly suppressed 5-HT-evoked responses in DRG cells from WT mice. Approximately 90% of 5-HT-sensitive DRG neurons were immunoreactive for an antibody to TRPV4, as assessed by calcium imaging. These results indicate that serotonin-induced itch is linked to TRPV4.

Involvement of TRPV4 in serotonin-evoked scratching

Journal Club 2015.12.11 Read More »

Journal club 2015-12-04

Incoherent feed-forward regulatory loops control segregation of C-mechanoreceptors, nociceptors, and pruriceptors.

Lou S1, Pan X2, Huang T1, Duan B1, Yang FC1, Yang J2, Xiong M3, Liu Y4, Ma Q5.

Abstract

Mammalian skin is innervated by diverse, unmyelinated C fibers that are associated with senses of pain, itch, temperature, or touch. A key developmental question is how this neuronal cell diversity is generated during development. We reported previously that the runt domain transcription factor Runx1 is required to coordinate the development of these unmyelinated cutaneous sensory neurons, including VGLUT3(+) low-threshold c-mechanoreceptors (CLTMs), MrgprD(+) polymodal nociceptors, MrgprA3(+) pruriceptors, MrgprB4(+) c-mechanoreceptors, and others. However, how these Runx1-dependent cutaneous sensory neurons are further segregated is poorly illustrated. Here, we find that the Runx1-dependent transcription factor gene Zfp521 is expressed in, and required for establishing molecular features that define, VGLUT3(+) CLTMs. Furthermore, Runx1 and Zfp521 form a classic incoherent feedforward loop (I-FFL) in controlling molecular identities that normally belong to MrgprD(+) neurons, with Runx1 and Zfp51 playing activator and repressor roles, respectively (in genetic terms). A knock-out of Zfp521 allows prospective VGLUT3 lineage neurons to acquire MrgprD(+) neuron identities. Furthermore, Runx1 might form other I-FFLs to regulate the expression of MrgprA3 and MrgprB4, a mechanism preventing these genes from being expressed in Runx1-persistent VGLUT3(+) and MrgprD(+) neurons. The evolvement of these I-FFLs provides an explanation for how modality-selective sensory subtypes are formed during development and may also have intriguing implications for sensory neuron evolution and sensory coding

KEYWORDS:

Runx1; Zfp521; low-threshold c-mechanoreceptors; nociceptors; pruriceptors; sensory subtype specification

 

5317.full

Journal club 2015-12-04 Read More »

Journal Club 2015.11.26

Gate control of mechanical itch by a subpopulation of spinal cord interneurons

Light mechanical stimulation of hairy skin can induce a form of itch known as mechanical itch. This itch sensation is normally suppressed by inputs from mechanoreceptors; however, in many forms of chronic itch, including alloknesis, this gating mechanism is lost. Here we demonstrate that a population of spinal inhibitory interneurons that are defined by the expression of neuropeptide Y::Cre (NPY::Cre) act to gate mechanical itch. Mice in which dorsal NPY::Cre-derived neurons are selectively ablated or silenced develop mechanical itch without an increase in sensitivity to chemical itch or pain. This chronic itch state is histamine-independent and is transmitted independently of neurons that express the gastrin-releasing peptide receptor. Thus, our studies reveal a dedicated spinal cord inhibitory pathway that gates the transmission of mechanical itch.

550.full supple dat

Journal Club 2015.11.26 Read More »

Journal Club 2015.11.19

J Allergy Clin Immunol. 2012 Sep;130(3):671-682.e4. doi: 10.1016/j.jaci.2012.05.027. Epub 2012 Jul 4.

Artemin causes hypersensitivity to warm sensation, mimicking warmth-provoked pruritus in atopic dermatitis.

Murota H1, Izumi M, Abd El-Latif MI, Nishioka M, Terao M, Tani M, Matsui S, Sano S, Katayama I.

1-s2.0-S0091674912008664-main
Filename : 1-s2-0-s0091674912008664-main.pdf (3 MB)
Caption :

Abstract

BACKGROUND:

Itch impairs the quality of life for many patients with dermatoses, especially atopic dermatitis (AD), and is frequently induced by a warm environment.

OBJECTIVE:

To determine the mechanism underlying itch induction by warmth, we focused on artemin, a member of glial cell line-derived neurotrophic factors (GDNFs).

METHODS:

A gene array assay revealed that artemin was expressed in substance P-treated dermal fibroblasts. The expression of artemin in healthy and AD-lesional skin was evaluated with immunohistochemistry and in situ hybridization. The impact of fibroblast-derived artemin on the proliferation and morphology of neural cell was investigated in vitro. To confirm the involvement of artemin in skin sensibility, wild-type and GDNF family receptor α3 knockout mice were employed for sensory examination.

RESULTS:

Artemin-expressing fibroblasts accumulated in skin lesions of patients with AD. Artemin induced cell proliferation of a neuroblastoma cell line in vitro, and intradermal injection of artemin in mice resulted in peripheral nerve sprouting and thermal hyperalgesia. Artemin-treated mice demonstrated scratching behavior in a warm environment, but mice deficient for GDNF family receptor α3, a potent artemin receptor, did not show this behavior. Furthermore, the escaping response to heat stimulus was attenuated in GDNF family receptor α3 knockout mice, suggesting that artemin may contribute to sensitivity to heat.

CONCLUSION:

These data suggest that dermal fibroblasts secrete artemin in response to substance P, leading to abnormal peripheral innvervation and thermal hyperalgesia. We hypothesize that artemin lowers the threshold of temperature-dependent itch sensation and might therefore be a novel therapeutic target for treating pruritic skin disorders, including AD.

Copyright © 2012 American Academy of Allergy, Asthma & Immunology. Published by Mosby, Inc. All rights reserved.

Journal Club 2015.11.19 Read More »

Journal Club 2015.10.30

J Neurosci. 2011 May 18;31(20):7563-7. doi: 10.1523/JNEUROSCI.1192-11.2011.

BAM8-22 peptide produces itch and nociceptive sensations in humans independent of histamine release.

Sikand P1, Dong X, LaMotte RH.

Author information

presentation
Filename : presentation.pdf (864 KB)
Caption :

Abstract

Chronic itch accompanying many dermatological, neurological, and systemic diseases is unresponsive to antihistamines. Our knowledge of endogenous chemicals that evoke histamine-independent itch and their molecular targets is very limited. Recently it was demonstrated in behavioral and cellular experiments that bovine adrenal medulla 8-22 peptide (BAM8-22), a proteolytically cleaved product of proenkephalin A, is a potent activator of Mas-related G-protein-coupled receptors (Mrgprs), MrgprC11 and hMrgprX1, and induces scratching in mice in an Mrgpr-dependent manner. To study the sensory qualities that BAM8-22 evokes in humans, we tested the volar forearm of 15 healthy volunteers with heat-inactivated cowhage spicules previously soaked in the peptide. BAM8-22 produced itch in each subject, usually accompanied by sensations of pricking/stinging and burning. The sensations were occasionally accompanied by one or more mechanically evoked dysesthesias, namely alloknesis, hyperknesis, and/or hyperalgesia, but no wheal or neurogenic flare in the skin surrounding the application site. The inactive truncated peptide BAM8-18 produced weak or no sensations. Pretreatment of the tested skin with an antihistamine cream (doxepin) inhibited histamine-induced sensations, dysesthesias, and skin reactions but not the sensations and dysesthesias evoked by BAM8-22. We show that BAM8-22 produces itch and nociceptive sensations in humans in a histamine-independent manner. Thus, BAM8-22 may be an endogenous itch mediator that activates, in humans, MrgprX1, a novel target for potential anti-itch treatments.

Journal Club 2015.10.30 Read More »

Journal Club 2015.10.23

Lysophosphatidic Acid Is a Potential Mediator of Cholestatic Pruritus

1-s2.0-S0016508510007377-main

ANDREAS E. KREMER,* JOB J. W. W. MARTENS,* WIM KULIK,‡ FRANZISKA RUËFF,§ EDITH M. M. KUIPER,? HENK R. VAN BUUREN,? KAREL J. VAN ERPECUM,¶ JURATE KONDRACKIENE,# JESUS PRIETO,** CHRISTIAN RUST,‡‡ VICTORIA L. GEENES,§§ CATHERINE WILLIAMSON,§§ WOUTER H. MOOLENAAR,?? ULRICH BEUERS,* and RONALD P. J. OUDE ELFERINK* *Tytgat Institute for Liver and Intestinal Research and ‡Laboratory Genetic Metabolic Diseases, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; §Departments of Dermatology and Allergology, University of Munich, Munich, Germany; ‡‡Internal Medicine II – Grosshadern, University of Munich, Munich, Germany; ?Department of Gastroenterology & Hepatology, Erasmus MC University Medical Center, Rotterdam, The Netherlands; ¶Department of Gastroenterology and Hepatology, University Medical Center, Utrecht, The Netherlands; #Department of Gastroenterology, Kaunas University of Medicine, Kaunas, Lithuania; **Department of Medicine and Liver Unit, Clinica Universitaria, Medical School and Center for Applied Medical Research (CIMA), University of Navarra, Pamplona, Spain; §§Maternal and Fetal Disease Group, Institute of Reproductive and Developmental Biology, Imperial College London, London, England; and ?Division of Cell Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands

BACKGROUND & AIMS: Pruritus is a common and disabling symptom in cholestatic disorders. However, its causes remain unknown. We hypothesized that potential pruritogens accumulate in the circulation of cholestatic patients and activate sensory neurons.
METHODS: Cytosolic free calcium ([Ca2?]i) was measured in neuronal cell lines by ratiometric fluorometry upon exposure to serum samples from pruritic patients with intrahepatic cholestasis of pregnancy (ICP), primary biliary cirrhosis (PBC), other cholestatic disorders, and pregnant, healthy, and nonpruritic disease controls. Putative [Ca2?]i-induc- ing factors in pruritic serum were explored by analytical techniques, including quantification by high-performance liquid chromatography/mass spectroscopy. In mice, scratch activity after intradermal pruritogen injection was quantified using a magnetic device.
RESULTS: Transient increases in neuronal [Ca2?]i induced by pruritic PBC and ICP sera were higher than corresponding controls. Lysophosphatidic acid (LPA) could be identified as a major [Ca2?]i agonist in pruritic sera, and LPA concentrations were increased in cholestatic patients with pruritus. LPA injected intradermally into mice induced scratch responses. Autotaxin, the serum enzyme converting lysophosphatidylcholine into LPA, was markedly increased in patients with ICP versus pregnant controls (P ?<.0001) and cholestatic patients with versus without pruritus (P <? .0001). Autotaxin activity correlated with intensity of pruritus (P ?<.0001), which was not the case for serum bile salts, histamine, tryptase, substance P, or ?-opioids. In patients with PBC who underwent temporary nasobiliary drainage, both itch intensity and autotaxin activity markedly decreased during drainage and returned to preexistent levels after drain removal.
CONCLUSIONS: We suggest that LPA and autotaxin play a critical role in cholestatic pruritus and may serve as potential targets for future thera- peutic interventions.
Keywords: Autotaxin; Bile Salts; Cholestasis; Itch.

Journal Club 2015.10.23 Read More »

Scroll to Top