Investigating the Mechanisms of Sini San in Alleviating Inflammatory Responses via Multi-Omics and the BDNF/TrkB/PI3K/AKT Signaling Pathway in Depressive Model Rats

Jiawei Zeng¹Zhen-Jie Han¹Xiutang He²Xue-Jiao Liu¹Hui-Yue Wang¹Shu-Sheng Yang³Jing Bai^1*Yan-Jun Duan^1*Li Lin^1*

• ¹Hubei University of Chinese Medicine, Wuhan, China
• ²Jingchu university of technology, Wuhan, China
• ³Wuhan Red Cross Hospital, Wuhan, China

Background: Sini San, from the traditional Chinese medicine classic Treatise on Exogenous Febrile Disease, can improve anxiety and depressive symptoms in the clinic, and has certain anti-inflammatory effects. Studies have demonstrated that inflammatory response is not merely a concomitant feature of depression, but actively contributes to its pathogenesis via neuroimmune mechanisms. However, the underlying mechanism remains unclear. Aim: The aim of this study was evaluated the antidepressant effect and inflammatory profile of Sini San on the treatment of CUMS (chronic unpredictable mild stress) -induced rats and explore its potential mechanism. Methods: The primary active ingredients, targets and pathways with Sini San in treating depression were determined through network pharmacology. The improvement of depression-like behaviors by Sini San was defined by behavioral experiments. Tissue inflammatory responses were comprehensively evaluated through histopathological analysis (HE staining, Nissl staining), and quantitative measurement of inflammatory cytokines (ELISA). Western blot (WB) was employed to quantify protein expression levels, while RT-qPCR was utilized to assess mRNA transcription levels. Gut microbial composition was analyzed by 16S rRNA gene amplicon sequencing with taxonomic classification performed using the Greengenes database. Results: The data indicated that Sini San reduced inflammation related to the NLRP3 inflammatory pathway by inhibiting the expression levels of NLRP3, ASC, Caspase-1, along with downstream pro-inflammatory cytokines IL-18, IL-1β, and TNF-α. According to the network pharmacology studies, Sini San mitigated depression via modulation of the PI3K/AKT signaling pathway, and their upstream and downstream proteins, BDNF (Brain-Derived Neurotrophic Factor), TrkB (Tropomyosin receptor kinase B), and p-CREB (phosphorylated cAMP response element-binding protein) were decreased after CUMS-inducing. Furthermore, Sini San enhanced the expression of colonic tight junction protein/adhesion junction protein ZO-1, Claudin-1, Occludin-1 mRNA, while simultaneously restoring balance of intestinal microbiota—indicating that it can ameliorate CUMS-induced disruptions in intestinal barrier function and microbial composition. Conclusion: Sini San modulates the gut-brain axis by inhibiting the NLRP3 inflammasome, thereby alleviating CUMS-induced inflammation and gut microbiota dysbiosis in rats. This effect may further contribute to the improvement of depressive symptoms via the regulation of the BDNF/TrkB/PI3K/AKT signaling pathway.