Antidepressant Advantage of Chaihushugan San in Female Mice: a Novel Signaling Mechanism in Hippocampus

Ethnopharmacological relevancy: Chaihushugan san (CSS), a classic formula for soothing the liver and relieving depression, has been identified to produce rapid antidepressant-like effects in female mice. However, the gender predominance and underlying mechanisms of CSS's antidepressant remain unclear. Aim of the study: In this study, we focused on unraveling the gender predominance of CSS in antidepressant and the specific neuronal mechanisms that mediate this predominance. Methods and materials: Tail suspension test (TST), forced swimming test (FST) and sucrose preference test (SPT) were used to evaluate depressive phenotypes or antidepressant-like effects of CSS in female and male chronic unpredictable mild stress (CUMS) mice model. RNA-sequencing was used to screen specific target for CSS antidepressant gender dominance. RT-PCR and elisa were used to detect the expressions of specific molecule, hormones, and inflammatory factors in the hippocampus. hippocampal viral overactivation and pharmacological blockade were used to detect the correlation between CSS antidepressant gender dominance and related targets. Results: In the present study, both female and male mice displayed depressive phenotypes including significant increasing immobility time in TST and reducing sucrose preference ratio in SPT after exposing CUMS for 3 weeks. However, acute administration of CSS (2,4 g/kg) improved the depressive phenotypes only in female mice or not male mice at 2 h later. Moreover, the expressions of TC2N were increased only in female mice after exposing CUMS for 3 weeks, which were also reversed by CSS after a single administration 2 h later, but no alterations in male mice. The hippocampal expressions of estrogen receptor (3 (Er(3), pro-inflammatory factors (IL-1(3 and TNF alpha) and anti-inflammatory factors (IL-10, TGF-(3 and IL-1R alpha) were all abnormal in female CUMS mice model, which were all normalized by CSS. Furthermore, overactivation of hippocampal TC2N by AAV-TC2N+/+ blocked the antidepressant-like effects of CSS and the up-regulation of hippocampal Er(3 in female mice. However, inhibition of Er(3 blunted the antidepressant-like effects of CSS and CSS's suppression of pro-inflammatory factors (IL-1(3 and TNF-alpha), which had no any effect on hippocampal TC2N and anti-inflammatory factors (IL-10 and TGF(3). Conclusions: The study revealed that CSS had antidepressant superiority in female mice depending on inhibiting hippocampal TC2N and then activating Er(3, further inhibiting the release of pro-inflammatory factors to produce antidepressant effects, which provided a basis for the guidance of CSS in clinical application, new ideas and targets for the development of drugs for depression with gender differences.