Page 1 of 1

Chronic Itch: Moving away from Neurons

PostPosted: Fri Sep 18, 2015 7:32 pm
by CFH
Figure 1 pour DH.png
Figure 1 pour DH.png (89.79 KiB) Viewed 4500 times
STAT3-dependent reactive astrogliosis in the spinal dorsal horn underlies chronic itch.
Shiratori-Hayashi M, Koga K, Tozaki-Saitoh H, Kohro Y, Toyonaga H, Yamaguchi C, Hasegawa A, Nakahara T, Hachisuka J, Akira S, Okano H, Furue M, Inoue K, Tsuda M.
Nat Med. 2015 Aug;21(8):927-31. doi: 10.1038/nm.3912. Epub 2015 Jul 20.

Chronic itch is defined by itch persisting for more than 6 weeks. It is a therapeutic challenge and this study provides new clues to the understanding of its phenomenon. Hopefully, this can translate into future treatment tools.

Introduction
-Itch is a complex sensation and for many it is an interplay between afferent and efferent neurons in the Central Nervous System (CNS)
-The CNS is made up of two types of cells, neurons and the supportive glial cells (Astrocytes and Oligodendrocytes)
Neurons are less numerous, diminish in number and are not normally able to multiply. On the other hand astrocytes have replicative potential and are already known to play a role in neurological diseases including Alzheimer’s disease, amyotrophic lateral sclerosis, Parkinson’s disease, and various forms of dementia.
-This last observation is crucial because acquired diseases often stem from cells with ability to undergo mitosis (neoplasia, inflammation, autoimmune)

Study
This study from Japan done was done in mice (atopic dermatitis model):
-When deprived from a germ-free environment, the mice developed itch
-Upon examination of the spinal cord astrocytes were found to be increased in number in the sections corresponding to the innervation of the itch areas (dermatomes). (Conversely, the density of astrocytes was normal when there was no itching)
-Molecular studies then revealed activation of signal transducer and activator of transcription 3 (STAT3).
–Disruption of astrocytic STAT3 suppressed chronic itch, and pharmacological inhibition of spinal STAT3 improved he fully developed chronic itch.
-Mice with atopic dermatitis exhibited an increase in scratching elicited by intrathecal administration of the itch-inducer gastrin-releasing peptide (GRP)4, and this enhancement was normalized by suppressing STAT3-mediated reactive astrogliosis.
-Authors also identified that in chronic itch lipocalin-2 (LCN2) was upregulated through STAT3. In this context and intrathecal administration of LCN2 to normal mice was shown to increase spinal GRP-evoked scratching

Comment
The involvement of astrocytes in chronic itch constitutes a Paradigm Shift away from the “Classical” neuron one.


CFH

JC-2015-DH8 (October)

PostPosted: Wed Oct 14, 2015 8:18 am
by CFH
http://www.dermatologicahelvetica.com/e ... clesID=118 (Page 4)

1-Arrhythmia in patients with psoriasis

2-Is Human Papillomavirus Vaccination also a Therapy ?

3-Astrogliosis in the spinal dorsal horn underlies chronic itch

4-Adhesive Strips are useless onto sutures

5-Comorbidities in Rosacea ?

6-Imiquimod for lentigo maligna: 76% clearance rate