Saikosaponin A

The herbal combination of Bupleurum chinense DC (Chaihu) and Paeonia lactiflora Pall (Baishao), collectively referred to as Chaihu-Baishao (CB), has been historically utilized in traditional Chinese medicine for the treatment of depression. However, the mechanisms underlying its therapeutic benefits have not been clearly defined.

This study investigated whether CB alleviates depressive symptoms by modulating the interaction between the voltage-gated calcium channel subunit α2δ-1 and the N-methyl-D-aspartate receptor (NMDAR) subunit NMDAR2B (NR2B), thereby restoring hippocampal synaptic plasticity.

In vivo, the chronic social defeat stress (CSDS) mouse model was employed to assess the impact of CB on depression-like behaviors, hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, impairments in hippocampal neuronal and synaptic plasticity, as well as the expression and interaction of α2δ-1 and NR2B. In vitro, corticosterone (CORT) was utilized to induce cellular injury. In PC12 cells, the therapeutic effects of CB-containing serum and the α2δ-1 inhibitor gabapentin (GBP) were assessed, focusing on the interaction between α2δ-1 and NR2B, as well as the expression levels of synaptic proteins postsynaptic density protein 95 (PSD95) and synaptophysin (SYN). The role of CB was further corroborated using Cacna2d1 gene knockout cells. Molecular docking techniques were employed to predict the key active components within CB that target α2δ-1 and NR2B, hereby exerting antidepressant effects.

In vivo studies demonstrated that CB significantly alleviated depression-like behaviors in mice, decreased levels of adrenocorticotropic hormone (ACTH) and CORT. Furthermore, CB relieved structural damage to hippocampal neurons and synapses, downregulated the expression of α2δ-1 and NR2B, inhibited their interaction and restored synaptic protein expression. In vitro experiments revealed that CB mitigated CORT-induced cellular damage, suppressed the α2δ-1-NR2B interaction, and enhanced synaptic proteins expression. Additionally, studies involving GBP treatment and Cacna2d1-knockout confirmed that α2δ-1 plays a regulatory role in NR2B expression and synaptic plasticity. Molecular docking analyses identified Saikosaponin C, Saikosaponin B4, and Bupleuroside I as potential key components.

The findings of this study elucidate a novel mechanism through which CB exerts its antidepressant effects, specifically by modulating the α2δ-1-NR2B interaction and restoring of synaptic plasticity within the hippocampus.

Xin-Jia-Tong-Xie-Yao-Fang (XJTXYF) is a proven prescription for managing diarrhea-predominant irritable bowel syndrome (IBS-D), which is a prevalent functional gastrointestinal disorder. However, the underlying mechanism of XJTXYF remains unclear. This study aims to explore the material basis and potential mechanisms of XJTXYF against IBS-D.

The constituents of XJTXYF were identified by UPLC-Q-TOF-MS/MS, and potential targets and pathways were screened by network pharmacology. Changes in the intestinal microbiome and fecal butyric acid levels after XJTXYF administration were analyzed through 16S rRNA sequencing and HPLC respectively. The abdominal withdrawal reflex score, serum levels of FITC-D and the expression of intestinal epithelial tight junction proteins, as well as the activity of the PI3K/Akt pathway were assessed. In-vitro experiments involved silencing GPR109A using small interfering RNA and inducing barrier damage with LPS pre-treatment in the Caco-2 cell line. Barrier function was evaluated by FITC-D permeability and tight junction protein expressions. The activity of the PI3K/Akt pathway was determined through Western blotting analysis.

The major active compounds of XJTXYF identified by UPLC-Q-TOF-MS/MS include Saikosaponin C, Hesperetin, Neohesperidin, Albiflorin, Quercetin and so on. The PI3K/Akt signaling pathway was predicted by network pharmacology as a potential target of XJTXYF in treating IBS-D. Animal experiments demonstrated that XJTXYF could increase body weight, improve visceral hypersensitivity, rebalance gut flora dysbiosis and upregulate fecal butyric acid content in IBS mice. The XJTXYF also showed the abilities of intestinal barrier repairment and PI3K/Akt pathway suppression. Fecal microbiota transplantation and the positive controls (NaB and Clostridium Butyricum) verified that a causal relationship existed between gut microbiome changes and IBS-D improvement after XJTXYF treatment. In-vitro experiments revealed the role of butyrate in barrier protection via PI3K/Akt inhibition.

Overall, in this study, we revealed that XJTXYF could restore intestinal barrier function through microbial butyrate mediated PI3K/Akt inhibition and improve IBS-D symptoms.