Transient Receptor Potential Vanilloid 4 Ion Channel Functions as a Pruriceptor in Epidermal Keratinocytes to Evoke Histaminergic Itch.

Abstract

TRPV4 ion channels function in epidermal keratinocytes and in innervating sensory neurons; however, the contribution of the channel in either cell to neurosensory function remains to be elucidated. We recently reported TRPV4 as a critical component of the keratinocyte machinery that responds to ultraviolet B (UVB) and functions critically to convert the keratinocyte into a pain-generator cell after excess UVB exposure. One key mechanism in keratinocytes was increased expression and secretion of endothelin-1, which is also a known pruritogen. Here we address the question of whether TRPV4 in skin keratinocytes functions in itch, as a particular form of "forefront" signaling in non-neural cells. Our results support this novel concept based on attenuated scratching behavior in response to histaminergic (histamine, compound 48/80, endothelin-1), not non-histaminergic (chloroquine) pruritogens in Trpv4 keratinocyte-specific and inducible knock-out mice. We demonstrate that keratinocytes rely on TRPV4 for calcium influx in response to histaminergic pruritogens. TRPV4 activation in keratinocytes evokes phosphorylation of mitogen-activated protein kinase, ERK, for histaminergic pruritogens. This finding is relevant because we observed robust anti-pruritic effects with topical applications of selective inhibitors for TRPV4 and also for MEK, the kinase upstream of ERK, suggesting that calcium influx via TRPV4 in keratinocytes leads to ERK-phosphorylation, which in turn rapidly converts the keratinocyte into an organismal itch-generator cell. In support of this concept we found that scratching behavior, evoked by direct intradermal activation of TRPV4, was critically dependent on TRPV4 expression in keratinocytes. Thus, TRPV4 functions as a pruriceptor-TRP in skin keratinocytes in histaminergic itch, a novel basic concept with translational-medical relevance.

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Citation

Published Version (Please cite this version)

10.1074/jbc.M116.716464

Publication Info

Chen, Yong, Quan Fang, Zilong Wang, Jennifer Y Zhang, Amanda S MacLeod, Russell P Hall and Wolfgang B Liedtke (2016). Transient Receptor Potential Vanilloid 4 Ion Channel Functions as a Pruriceptor in Epidermal Keratinocytes to Evoke Histaminergic Itch. J Biol Chem, 291(19). pp. 10252–10262. 10.1074/jbc.M116.716464 Retrieved from https://hdl.handle.net/10161/12969.

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Scholars@Duke

Chen

Yong Chen

Associate Professor in Neurology

Dr. Yong Chen is an Associate Professor of Neurology at the Duke University School of Medicine.  He is also affiliated with Duke Anesthesiology-Center for Translational Pain Medicine (CTPM) and Duke-Pathology.

The Chen lab mainly studies sensory neurobiology of pain and itch, with a focus on TRP ion channels and neural circuits. The main objective of our lab is to identify molecular and cellular mechanisms underlying chronic pain and chronic-disease associated itch, using a combination of animal behavioral, genetic, molecular and cellular, advanced imaging, viral, and optogenetic approaches.  There are three major research areas in the lab: craniofacial pain, arthritis pain and joint function, and systemic-disease associated itch.

Zhang

Jennifer Yunyan Zhang

Professor in Dermatology

Epidermis of the skin constitutes the largest organ and the outer most barrier of the body. It is one of the few organs that undergo lifelong self-renewal through a tight balance of cell growth, differentiation, and programmed cell death. Deregulation of this balance is manifested in many diseases, including various immune diseases and cancer. 

Our lab is focused on 3 interrelated topics:

1. Gene regulation of epithelial cell proliferation and differentiation

Using regenerated human skin tissues and murine genetic models, we have demonstrated important functions NF-kB and AP-1 gene regulators in epidermal cell growth and differentiation. Currently, our efforts are focused on understating how loss-of-function of CYLD, a deubiquitinase and tumor suppressor, leads to the development of hair follicle defects, skin inflammation, and cancer. Specifically, we want to determine how CYLD integrates NF-kB, AP1, Myc, and other transcription factors to control epidermal cell growth and lineage differentiation.

De novo skin regeneration is life-saving procedure for severely burned patients and lethal genetic skin diseases such as epidermal bullosa. An additional aspect of our study is to improve new skin regeneration techniques and to create experimental skin disease models with gene transduced keratinocytes, as illustrated below.

2. Keratinocytes as instigators of inflammatory responses

Keratinocytes are constantly challenged by external insults, as well as immune cells. Disarray of the crosstalk between keratinocytes and immune cells underlies various immune diseases, including dermatitis, psoriasis, and cutaneous graft-versus-host disease (GVHD). GVHD is a common complication and the leading cause of non-relapse mortality among patients after receiving allogenic hematopoietic stem cell transplantation.  The skin is the most commonly affected organ in both the acute and chronic forms of this disease.  Treatment options for GVHD are limited and the current standard therapy is high dose systemic corticosteroid which is itself associated with significant morbidity. Our goal is to understand how keratinocytes contribute to the progression of GVHD, and may therefore be targeted to mitigate the disease.

3. Ubiquitination enzymes in melanoma

Melanoma most lethal and difficult to treat skin cancer. In the recent years, BRAF/MEK-targeted therapies have produced exciting results, but they suffer from short duration. Our goal is to uncover novel mechanisms crucial for melanoma malignancy. Specifically, we want to understand how ubiquitination enzymes contribute to melanoma growth. Previously, we have demonstrated that CYLD inhibits melanoma growth through suppression of JNK/AP1 and b1-integrin signaling pathways. In contrast, UBE2N, a K63-Ubiquitin conjusage, promotes melanoma growth in part through activation of the MEK/FRA/SOX10 signaling cascade. Currently, our efforts are focused on understanding how UBE2N and other ubiquitin enzymes regulate the MAPK signaling pathway and whether they can be targeted for melanoma therapy.

MacLeod

Amanda S MacLeod

Adjunct Associate Professor in the Department of Dermatology

The MacLeod Lab investigates the dynamic regulation of innate immunity, with specific focus on host-microbial interactions, antimicrobial host defense, antiviral proteins, and repair functions.

Skin is an active immune organ and comprises not only epithelial keratinocytes, but also harbors dendritic cells, macrophages, nerve cells, and other immune cells. Furthermore, the skin is inhabited by a multitude of microbes, including bacteria, viruses and fungi and even parasites. The healthy and controlled immune interactions of the skin barrier cells with microbes and environmental factors are critical to maintain homeostasis and to prevent overt immune responses resulting in disease. The dynamic regulation of innate host defense factors allows for critical protection against microbial pathogens in situations of barrier defects and injury.

We use interdisciplinary approaches, combining various disease mouse models, human skin tissues and cells, and techniques from immunology, stem cell biology, microbiology and pharmacology to ultimately reveal strategies that coordinate, regulate or co-opt innate immunity in the skin. This allows us to identify mechanisms that fundamentally control skin immunity and will help in the development of new immune-modulatory therapeutics and a better understanding of health and disease.

 

We study the interplay of innate  immune cells with microbial and additional environmental factors. Our interest is to decipher the mechanisms that facilitate antimicrobial immune surveillance and repair functions in the skin under homeostatic and challenged conditions.

I. Innate immune regulation and modulation during skin injury and microbial infection

Damage to the skin through physical injury and microbes initiates release of multiple pro-inflammatory cytokines and mediators including IL-27, IL-17, extracellular ATP, nucleic acids, NO, as well as antimicrobial peptides and proteins. Upon skin injury, inflammatory immune responses are aimed at clearing microbial contamination before a repair program can subsequently facilitate wound closure. However, prolonged inflammation is detrimental and mediates tissue damage and is considered a major pathogenic factor for the development of chronic non-healing wounds and may be a trigger for auto-inflammatory skin diseases such as psoriasis. The focus of our laboratory is on identifying and characterizing such key factors that regulate innate  immunity in the skin. Fine regulation of the cutaneous innate immune response is critical to maintain skin barrier function and protection upon injury and infection.  Our studies on innate antimicrobial peptides and proteins (AMPs), including antiviral proteins, have fundamentally advanced our knowledge of how the innate immune system works in the skin.  We further aim to understand the dynamic regulation of innate antimicrobial host immunity during aging and in early life, in response to diverse microbial stimuli, and in various complex dermatological diseases, including eczema, psoriasis, hidradenitis suppurativa, wounds etc. Decoding the microbial-epithelial-immune dialogue in the skin  may offer insights into novel strategies of treatment.

 

II. Role of IL-27 in cutaneous immunity

IL-27, a member of the IL-12 family of heterodimeric cytokines, consists of p28 and Epstein-Barr virus gene 3 (EBI3) and signals through its receptor composed of IL-27RA and gp130. Previous studies indicated that IL-27 can play pro-inflammatory and anti-inflammatory roles depending on the cell type and context. In the context of infectious inflammation, a recent study reported that IL-27 is produced by CD103+ dermal dendritic cells (DC) in the skin , whereas other studies identified that IL-27 is produced by mesenteric lymph node CD103- DC, splenic CD4+ DC and macrophages. Our work identified IL-27 production in dermal CD301b+ monocyte-derived DC following injury. Here, IL-27 promotes the wound healing response by promoting keratinocyte proliferation. Furthermore, we have identified multiple new and unprecedented roles for IL-27 in cutaneous immunity in response to contact allergens, microbes and in psoriasis. Our lab recently described and published that IL-27 signaling provides a novel path of antiviral protein activation in the skin and that IL-27 signaling is critical in activating host defenses against cutaneous Zika virus infections.

 

III. Antiviral Proteins

A large part of our laboratory's efforts are  focused to better understanding the constitutive and inducible antiviral proteins and their mode of regulation in the skin. Antiviral proteins comprise Oligoadenylate Synthases (OAS), Protein Kinase R (PKR), Interferon-stimulated Gene (ISG) 15 and 20, and multiple Interferon Induced proteins with Tetratricopeptide repeats (IFIT) and Interferon-induced transmembrane proteins (IFITM) and others. Antiviral proteins provide a natural defense mechanism against viruses. Their expression and regulation in the skin are still poorly understood and our lab is providing some new and exciting insights into cutaneous innate antiviral immunity and the regulation of expression of antiviral proteins.


 

Complete List of Published Work can be found here:

http://www.ncbi.nlm.nih.gov/myncbi/browse/collection/47851812/?sort=date&direction=descending
Her maiden name Büchau was used prior to MacLeod.

Our lab website can be found here: https://sites.duke.edu/macleodlab/



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