Anti-depressant mechanism of Bupleuri Radix in regulating hippocampal FGFR1-5-HT_(1A)R heterodimer formation. - GreenMedInfo Summary

Based on the"gut-brain" axis, this study investigated the molecular mechanism of the antidepressant effect of Bupleuri Radix. The effect of Bupleuri Radix on human intestinal flora cultured in vitro was analyzed by 16S rRNA sequencing. Differential bacteria were identified by real-time quantitative PCR(qPCR). Short-chain fatty acid(SCFA) content was determined by the GC-FID method. A depression-like mouse model was established using the"triple-one" compound stress method. Mice were administered the aqueous extract of Bupleuri Radix by gavage, transplanted with Bacteroides acidifaciens or spore-forming bacteria, or gavaged with SCFAs. Behavioral changes were assessed. SCFA content in feces was measured by GC-FID. Hippocampal(fibroblast growth factor 21, FGF21) protein expression was detected by Western blot. The formation of fibroblast growth factor receptor 1-5-hydroxytryptamine receptor 1A(FGFR1-5-HT_(1A)R) heterodimers was examined using the Duolink PLA method. The results showed that Bupleuri Radix significantly increased the abundance of the three spore-forming bacterial genera Ruminococcus, Dorea, and Blautia(P<0.05), as well as B. acidifaciens(P<0.001). Administration of Bupleuri Radix(P<0.001 or P<0.05) and transplantation of B. acidifaciens(P<0.01) both increased the levels of SCFAs such as acetic acid and butyric acid in bacterial metabolites. Treatment with Bupleuri Radix, transplantation of B. acidifaciens, or high doses of SCFAs significantly improved depression-like behaviors in mice, increased hippocampal FGF21 expression(P<0.05, P<0.01, or P<0.001), and promoted FGFR1-5-HT_(1A)R heterodimer formation(P<0.05 or P<0.01), whereas transplantation of spore-forming bacteria showed no obvious antidepressant effect. In conclusion, the antidepressant effect of Bupleuri Radix is mediated by intestinal bacteria such as B. acidifaciens, which regulate the synthesis and metabolism of SCFAs, thereby modulating hippocampal FGF21 expression and activating FGFR1-5-HT_(1A)R heterodimers.