Saikosaponins from Bupleurum scorzonerifolium Willd. alleviates microglial pyroptosis in depression by binding and inhibiting P2X7 expression

•Fifty-seven saikosaponins from water extract of Bupleurum scorzonerifolium Willd. were identified.•Saikosaponins were verified alleviate depression behavior and restore nerve cell function in mice.•Saikosaponin can inhibit pyroptosis of nerve cells in MDD mice and N9 cells.•Saikosaponins can bind P2X7 and reduce its stability. The major depressive disorder (MDD) is a heterogeneous condition and characterized by a high recurrence rate, with neuroinflammation playing a significant role in its various potential pathologies. In recent years, neuronal pyroptosis induced by neuroinflammation has garnered increasing attention in depression research. Bupleurum scorzonerifolium Willd. is depression research in traditional Chinese medicine prescriptions to treat depression and exhibits notable anti-inflammatory properties. Saikosaponins (SSs) are the primary active components of Bupleurum scorzonerifolium Willd., although their mechanism of action in relation to anti-depressive effects remains unclear. The purpose is to evaluate the efficacy of Chinese herbal medicine in treating depression through the lens of modern pharmacology. Additionally, it aims to explore the potential value of new mechanisms in the treatment of depression. An in vivo model of depression was established by intraperitoneal injection of LPS. HE staining, Nissl staining, and Golgi staining were used to evaluate the effectiveness of depression treatments in each group of mice. The activation of microglia was analyzed using immunofluorescence to evaluate the anti-inflammatory effects of drugs. In vitro models, N9 cells induced by LPS and ATP used CCK-8 assay, and lactate dehydrogenase assay were conducted to explore the therapeutic effect of the SSs. Western blot and immunohistochemical methods were employed to investigate the expression of P2X7 and apoptosis-related proteins. BzATP was introduced as a P2X7 agonist, and CETSA and CHX pulse-chase assay were utilized to verify the combined action and stability of the SSs with P2X7. 57 triterpenoid saponin compounds were identified by Unifi in Bupleurum scorzonerifolium Willd. In both in vivo and in vitro models, the SSs has been shown to significantly improve depression-like behavior, reduce central inflammation, and significantly inhibit neuronal pyroptosis in mice. The SSs can significantly decrease the expression of P2X7 in the brains of depressed mice and enhance the stability of P2X7 protein in N9 cells. SSs in Bupleurum scorzonerifolium Will