Publications by authors named "Admire Munanairi"

7 Publications

  • Page 1 of 1

PAR2 Mediates Itch via TRPV3 Signaling in Keratinocytes.

J Invest Dermatol 2020 08 29;140(8):1524-1532. Epub 2020 Jan 29.

Center for the Study of Itch and Sensory Disorders, Washington University School of Medicine, St. Louis, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, USA; Department of Psychiatry, Washington University School of Medicine, St. Louis, USA; Department of Developmental Biology, Washington University School of Medicine, St. Louis, USA. Electronic address:

Animal studies have suggested that transient receptor potential ion channels and G-protein coupled receptors play important roles in itch transmission. TRPV3 gain-of-function mutations have been identified in patients with Olmsted syndrome, which is associated with severe pruritus. However, the mechanisms causing itch remain poorly understood. Here, we show that keratinocytes lacking TRPV3 impair the function of protease-activated receptor 2 (PAR2), resulting in reduced neuronal activation and scratching behavior in response to PAR2 agonists. Moreover, we show that TRPV3 and PAR2 were upregulated in skin biopsies from patients and mice with atopic dermatitis, whereas their inhibition attenuated scratching and inflammatory responses in mouse atopic dermatitis models. These results reveal a previously unrecognized link between TRPV3 and PAR2 in keratinocytes to convey itch information and suggest that a blockade of PAR2 or TRPV3 individually or both may serve as a potential approach for antipruritic therapy in atopic dermatitis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jid.2020.01.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7387154PMC
August 2020

Non-canonical Opioid Signaling Inhibits Itch Transmission in the Spinal Cord of Mice.

Cell Rep 2018 Apr;23(3):866-877

Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address:

Chronic itch or pruritus is a debilitating disorder that is refractory to conventional anti-histamine treatment. Kappa opioid receptor (KOR) agonists have been used to treat chronic itch, but the underlying mechanism remains elusive. Here, we find that KOR and gastrin-releasing peptide receptor (GRPR) overlap in the spinal cord, and KOR activation attenuated GRPR-mediated histamine-independent acute and chronic itch in mice. Notably, canonical KOR-mediated G signaling is not required for desensitizing GRPR function. In vivo and in vitro studies suggest that KOR activation results in the translocation of Ca-independent protein kinase C (PKC)δ from the cytosol to the plasma membrane, which in turn phosphorylates and inhibits GRPR activity. A blockade of phospholipase C (PLC) in HEK293 cells prevented KOR-agonist-induced PKCδ translocation and GRPR phosphorylation, suggesting a role of PLC signaling in KOR-mediated GRPR desensitization. These data suggest that a KOR-PLC-PKCδ-GRPR signaling pathway in the spinal cord may underlie KOR-agonists-induced anti-pruritus therapies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2018.03.087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5937707PMC
April 2018

Spinal Mechanisms of Itch Transmission.

Neurosci Bull 2018 Feb 1;34(1):156-164. Epub 2017 Apr 1.

Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, 63110, USA.

Peripheral itch stimuli are transmitted by sensory neurons to the spinal cord dorsal horn, which then transmits the information to the brain. The molecular and cellular mechanisms within the dorsal horn for itch transmission have only been investigated and identified during the past ten years. This review covers the progress that has been made in identifying the peptide families in sensory neurons and the receptor families in dorsal horn neurons as putative itch transmitters, with a focus on gastrin-releasing peptide (GRP)-GRP receptor signaling. Also discussed are the signaling mechanisms, including opioids, by which various types of itch are transmitted and modulated, as well as the many conflicting results arising from recent studies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12264-017-0125-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5799115PMC
February 2018

Facilitation of TRPV4 by TRPV1 is required for itch transmission in some sensory neuron populations.

Sci Signal 2016 07 19;9(437):ra71. Epub 2016 Jul 19.

Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO 63110, USA. Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA. Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA. Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA.

The transient receptor potential channels (TRPs) respond to chemical irritants and temperature. TRPV1 responds to the itch-inducing endogenous signal histamine, and TRPA1 responds to the itch-inducing chemical chloroquine. We showed that, in sensory neurons, TRPV4 is important for both chloroquine- and histamine-induced itch and that TRPV1 has a role in chloroquine-induced itch. Chloroquine-induced scratching was reduced in mice in which TRPV1 was knocked down or pharmacologically inhibited. Both TRPV4 and TRPV1 were present in some sensory neurons. Pharmacological blockade of either TRPV4 or TRPV1 significantly attenuated the Ca(2+) response of sensory neurons exposed to histamine or chloroquine. Knockout of Trpv1 impaired Ca(2+) responses and reduced scratching behavior evoked by a TRPV4 agonist, whereas knockout of Trpv4 did not alter TRPV1-mediated capsaicin responses. Electrophysiological analysis of human embryonic kidney (HEK) 293 cells coexpressing TRPV4 and TRPV1 revealed that the presence of both channels enhanced the activation kinetics of TRPV4 but not of TRPV1. Biochemical and biophysical studies suggested a close proximity between TRPV4 and TRPV1 in dorsal root ganglion neurons and in cultured cells. Thus, our studies identified TRPV4 as a channel that contributes to both histamine- and chloroquine-induced itch and indicated that the function of TRPV4 in itch signaling involves TRPV1-mediated facilitation. TRP facilitation through the formation of heteromeric complexes could be a prevalent mechanism by which the vast array of somatosensory information is encoded in sensory neurons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/scisignal.aaf1047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5310287PMC
July 2016

Critical evaluation of the expression of gastrin-releasing peptide in dorsal root ganglia and spinal cord.

Mol Pain 2016 11;12. Epub 2016 Apr 11.

Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA Departments of Psychiatry, Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA Departments of Developmental Biology, Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO, USA

There are substantial disagreements about the expression of gastrin-releasing peptide (GRP) in sensory neurons and whether GRP antibody cross-reacts with substance P (SP). These concerns necessitate a critical revaluation of GRP expression using additional approaches. Here, we show that a widely used GRP antibody specifically recognizes GRP but not SP. In the spinal cord of mice lacking SP (Tac1KO), the expression of not only GRP but also other peptides, notably neuropeptide Y (NPY), is significantly diminished. We detectedGrpmRNA in dorsal root ganglias using reverse transcription polymerase chain reaction, in situ hybridization and RNA-seq. We demonstrated thatGrpmRNA and protein are upregulated in dorsal root ganglias, but not in the spinal cord, of mice with chronic itch. Few GRP(+)immunostaining signals were detected in spinal sections following dorsal rhizotomy and GRP(+)cell bodies were not detected in dissociated dorsal horn neurons. Ultrastructural analysis further shows that substantially more GRPergic fibers form synaptic contacts with gastrin releasing peptide receptor-positive (GRPR(+)) neurons than SPergic fibers. Our comprehensive study demonstrates that a majority of GRPergic fibers are of primary afferent origin. A number of factors such as low copy number ofGrptranscripts, small percentage of cells expressingGrp, and the use of an eGFP GENSAT transgenic as a surrogate for GRP protein have contributed to the controversy. Optimization of experimental procedures facilitates the specific detection of GRP expression in dorsal root ganglia neurons.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/1744806916643724DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4972254PMC
December 2016

Descending control of itch transmission by the serotonergic system via 5-HT1A-facilitated GRP-GRPR signaling.

Neuron 2014 Nov 30;84(4):821-34. Epub 2014 Oct 30.

Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address:

Unlabelled: Central serotonin (5-hydroxytryptophan, 5-HT) modulates somatosensory transduction, but how it achieves sensory modality-specific modulation remains unclear. Here we report that enhancing serotonergic tone via administration of 5-HT potentiates itch sensation, whereas mice lacking 5-HT or serotonergic neurons in the brainstem exhibit markedly reduced scratching behavior. Through pharmacological and behavioral screening, we identified 5-HT1A as a key receptor in facilitating gastrin-releasing peptide (GRP)-dependent scratching behavior. Coactivation of 5-HT1A and GRP receptors (GRPR) greatly potentiates subthreshold, GRP-induced Ca(2+) transients, and action potential firing of GRPR(+) neurons. Immunostaining, biochemical, and biophysical studies suggest that 5-HT1A and GRPR may function as receptor heteromeric complexes. Furthermore, 5-HT1A blockade significantly attenuates, whereas its activation contributes to, long-lasting itch transmission. Thus, our studies demonstrate that the descending 5-HT system facilitates GRP-GRPR signaling via 5-HT1A to augment itch-specific outputs, and a disruption of crosstalk between 5-HT1A and GRPR may be a useful antipruritic strategy.

Video Abstract:
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.neuron.2014.10.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4254557PMC
November 2014

The multiple Maillard reactions of ribose and deoxyribose sugars and sugar phosphates.

Carbohydr Res 2007 Dec 19;342(17):2575-92. Epub 2007 Aug 19.

Department of Chemistry and Biochemistry, Middlebury College, Middlebury, VT 05753, United States.

Ribose 5-phosphate (R5P) undergoes the Maillard reaction with amines at significantly higher rates than most other sugars and sugar phosphates. The presence of an intramolecular phosphate group, which catalyzes the early stages of the Maillard reaction, provides the opportunity for the R5P molecule to undergo novel reaction paths creating unique Maillard products. The initial set of reactions leading to an Amadori product (phosphorylated) and to an alpha-dicarbonyl phosphate compound follows a typical Maillard reaction sequence, but an observed phosphate hydrolysis accompanying the reaction adds to the complexity of the products formed. The reaction rate for the loss of R5P is partially dependent on the pK(a) of the amine but also is correlated to the protonation of an early intermediate of the reaction sequence. In the presence of oxygen, a carboxymethyl group conjugated to the amine is a major product of the reaction of R5P with N-acetyllysine while little of this product is generated in the absence of oxygen. Despite lacking a critical hydroxyl group necessary for the Maillard reaction, 2-deoxyribose 5-phosphate (dR5P) still generates an Amadori-like product (with a carbonyl on the C-3 carbon) and undergoes phosphate cleavage. Two highly UV-absorbing products of dR5P were amine derivatives of 5-methylene-2-pyrrolone and 2-formylpyrrole. The reaction of dR5P with certain amines generates a set of products that exhibit an interesting absorbance at 340nm and a high fluorescence.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.carres.2007.08.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2141680PMC
December 2007