Involvement of TRPV4 in serotonin-evoked scratching

Tasuku Akiyama^1,2, Margaret Ivanov¹, Masaki Nagamine¹, Auva Davoodi¹, Mirela Iodi Carstens¹, Akihiko Ikoma³, Ferda Cevikbas³, Cordula Kempkes³, Joerg Buddenkotte^3,4, Martin Steinhoff^3,4 and E Carstens¹

Involvement of TRPV4 in serotonin-evoked scratching

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

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

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

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

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.

ASIC3 Mediates Itch Sensation in Response to Coincident Stimulation by Acid and Nonproton Ligand.

Oral supplementation with fish oil reduces dryness and pruritus in the acetone-induced dry skin rat model

1-s2.0-S0923181115300207-main

Raquel C.S. Barcelosa,b,c,d,f, Cristina de Mello-Sampayob,c,f,*, Caren T.D. Antoniazzia, Hecson J. Segata, Henrique Silvad, Juliana C. Veite, Jaqueline Piccoloe,
Tatiana Emanuellia,e, Marilise E. Bürgera, Beatriz Silva- Limab,c, Luis M. Rodriguesb,d
a Universidade Federal de Santa Maria (UFSM), Programa de Pós-Graduação em Farmacologia, Santa Maria, RS, Brazil
b Pharmacological Sciences Department, Faculty of Pharmacy, Universidade de Lisboa, 1649-003 Lisbon, Portugal
c Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, 1649-003 Lisbon, Portugal
d CBIOS, Research Center for Bioscience and Health Technologies, Universidade Lusófona, Lisboa, Portugal
e Departamento de Tecnologia dos Alimentos, Programa de Pós-Graduação em Ciência Tecnologia dos Alimentos, Universidade Federal de Santa Maria, Av. Roraima, 1000, 97105-900 Santa Maria, RS, Brazil
f Both authors have contributed equally to this work.

Background: Pruritus and discomfort are often present in patients with xerosis and atopic dermatitis. Several studies suggest an important role of diet in skin pathophysiology.
Objective: This study evaluated the effect of dietary fatty acids in the skin physiology via an itch-related animal model with and without supplementation with fish oil (FO), a source of polyunsaturated fatty acids (PUFA), especially omega 3 (n-3).
Methods: Male Wistar rats were divided into two groups—non-supplemented (control) and supplemented with FO (3g/kg/day) by gavage for 90 days. Every 30 days, scratching and skin parameters (transepidermal water loss (TEWL), hydration, and local blood flow) were evaluated before and after dorsal skin exposure to acetone to induce the itch-related dry skin. At the end of the study, animals were sacrificed, and skin samples collected for fatty acids composition analysis by GC–FID. Results: FO supplementation reduced the TEWL and increased the skin hydration, with significant changes from day 60 on, while skin microcirculation registered no changes. It also alleviated the acetone induced skin barrier alteration, revealed by a faster resolution of TEWL and hydration, and elimination of itch-related scratching induced by dry skin. These changes were associated with the shift in the skin fatty acids incorporation pattern (richer in n-3 with n-6/n-3 < 5) resulting from the FO supplementation. Conclusion: Skin barrier dynamics seem to be influenced by FO n-3 PUFA, with suppressive effects on the scratching behaviour induced by dry skin. Hence, long-term supplementation with n-3 PUFA rich nutrients might reinforce and restore cutaneous integrity and function.
ã 2015 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.

Histamine Released from Epidermal Keratinocytes Plays a Role in a-MelanocyteeStimulating Hormone-Induced Itching in Mice

Histamine Released from Epidermal Keratinocytes Plays a Role in α-Melanocyte–Stimulating Hormone-Induced Itching in Mice

Kyoko Shimizu,* Tsugunobu Andoh,y Yoko Yoshihisa,* and Tadamichi Shimizu*
From the Departments of Dermatology* and Applied Pharmacology,y Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama, Japan
Accepted for publication July 14, 2015.
Address correspondence to Tadamichi Shimizu, Depart- ment of Dermatology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama, Japan. E-mail: shimizut@med.u- toyama.ac.jp.

Sunburn, wound repair, and chronic renal failure with hemodialysis are usually accompanied by both pigmentation and itching. Proopiomelanocortin-derived a-melanocyteestimulating hormone (a-MSH) is produced in response to external stimuli, such as UV irradiation, and is involved in cutaneous pigmen- tation. However, it is unclear whether a-MSH is also involved in the itching. We therefore investigated whether a-MSH elicited itch-related responses in mice. We found that an intradermal injection of a-MSH induced hind-paw scratching, an itch-related response, in mice. The a-MSHeinduced scratching was inhibited by the m-opioid receptor antagonist naltrexone and the H1 histamine receptor antagonist terfenadine. In mast cell-deficient mice, a-MSH also elicited scratching, which was inhibited by terfe- nadine. The immunoreactivity for L-histidine decarboxylase, a key enzyme required for the production of histamine, histamine, and the melanocortin 1 and 5 receptors were shown in not only mast cells but also keratinocytes in murine skin. In addition to the expression of L-histidine decarboxylase and melanocortin 1 and 5 receptors, the mouse keratinocyte cell lines (Pam212) also showed immunoreactivity for L-his- tidine decarboxylase, histamine, and melanocortin 1 and 5 receptors. The application of a-MSH induced the release of histamine from Pam212 cells. These findings indicate that a-MSH may play an important role in the itching associated with pigmented cutaneous lesions and that the histamine released from keratinocytes is involved in this a-MSHeinduced itching. (Am J Pathol 2015, -: 1e8; http://dx.doi.org/ 10.1016/j.ajpath.2015.07.015)

Antipruritic mechanisms of topical E6005, a phosphodiesterase
4 inhibitor: Inhibition of responses to proteinase-activated receptor 2 stimulation mediated by increase in intracellular cyclic AMP
Tsugunobu Andoh, Yasushi Kuraishi *
Department of Applied Pharmacology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, Toyama 930-0194, Japan

1-s2.0-S0923181114002497-main

ABSTRACT
Background: Phosphodiesterase 4 (PDE4), which catalyses the conversion of cyclic adenosine 30,50- monophosphate (cAMP) to 50-AMP, plays a critical role in the pathogenesis of inflammatory disorders. Pruritus is the main symptom of dermatitides, such as atopic dermatitis, and is very difficult to control. Recent studies have shown that the activation of proteinase-activated receptor 2 (PAR2) is involved in pruritus in dermatoses in humans and rodents.
Objective: To investigate the inhibitory effect of E6005, a topically effective PDE4 inhibitor, on PAR2-associated itching in mice.
Methods: Mice were given an intradermal injection of SLIGRL-NH2 (100 nmol/site), a PAR2 agonist peptide, into the rostral part of the back. E6005 and 8-bromo-cAMP were applied topically and injected intradermally, respectively, to the same site. Scratching bouts were observed as an itch-related behavior, and firing activity of the cutaneous nerve was electrophysiologically recorded. Keratinocytes were isolated from the skin of neonatal mice and cultured for in vitro experiments. The concentrations of cAMP and leukotriene B4 (LTB4) were measured by enzyme immunoassay. The distribution of PDE4 subtypes in the skin was investigated by immunostaining.
Results: Topical E6005 and intradermal 8-bromo-cAMP significantly inhibited SLIGRL-NH2-induced scratching and cutaneous nerve firing. Topical E6005 increased cutaneous cAMP content. Topical E6005 and intradermal 8-bromo-cAMP inhibited cutaneous LTB4 production induced by SLIGRL-NH2, which has been shown to elicit LTB4-mediated scratching. E6005 and 8-bromo-cAMP inhibited SLIGRL-NH2- induced LTB4 production in the cultured murine keratinocytes also. PDE4 subtypes were mainly expressed in keratinocytes and mast cells in the skin.
Conclusions: The results suggest that topical E6005 treatment inhibits PAR2-associated itching. Inhibition of LTB4 production mediated by an increase in cAMP may be partly involved in the antipruritic action of E6005.
ß 2014 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.