Journal Club – 23.07.21

The G protein-coupled estrogen receptor of the trigeminal ganglion regulates acute and chronic itch in mice

Jun Li1,2,3 | Po Gao2,3 | Siyu Zhang2,3,4 | Xiaoqi Lin2,3 | Junhui Chen2,3 | Song Zhang2,3 | Yingfu Jiao2,3 | Weifeng Yu2,3 | Xiaoqiong Xia1 | Liqun Yang2,3

Abstract
Aims: Itch is an unpleasant sensation that severely impacts the patient’s quality of life. Recent studies revealed that the G protein-coupled estrogen receptor (GPER) may play a crucial role in the regulation of pain and itch perception. However, the contribution of the GPER in primary sensory neurons to the regulation of itch perception remains elusive. This study aimed to investigate whether and how the GPER participates in the regulation of itch perception in the trigeminal ganglion (TG).
Methods and Results: Immunofluorescence staining results showed that GPERpositive (GPER+) neurons of the TG were activated in both acute and chronic itch. Behavioral data indicated that the chemogenetic activation of GPER+ neurons of the TG of Gper-Cre mice abrogated scratching behaviors evoked by acute and chronic itch. Conversely, the chemogenetic inhibition of GPER+ neurons resulted in increased itch
responses. Furthermore, the GPER expression and function were both upregulated in the TG of the dry skin-induced chronic itch mouse model. Pharmacological inhibition of GPER (or Gper deficiency) markedly increased acute and chronic itch-related scratching behaviors in mouse. Calcium imaging assays further revealed that Gper deficiency in TG neurons led to a marked increase in the calcium responses evoked by agonists of the transient receptor potential ankyrin A1 (TRPA1) and transient receptor potential vanilloid V1 (TRPV1).
Conclusion: Our findings demonstrated that the GPER of TG neurons is involved in the regulation of acute and chronic itch perception, by modulating the function of TRPA1 and TRPV1. This study provides new insights into peripheral itch sensory signal processing mechanisms and offers new targets for future clinical antipruritic therapy.

Presenter: Ji Eun Cha