Synergistic neuroprotective effect of saikosaponin A and albiflorin on corticosterone-induced apoptosis in PC12 cells via regulation of metabolic disorders and neuroinflammation

Background Saikosaponin A (SSA) and albiflorin (AF) are major bioactive compounds of Radix Bupleuri and Radix Paeoniae alba respectively, which possess antidepressant effects in pharmacological experiments. However, whether SSA and AF have synergistic neuroprotective effects and the synergistic mechanisms are still unknown. Methods and Results The corticosterone-induced PC12 cells apoptosis model was employed to assess the neuroprotective effects of SSA and AF, and the synergistic effect was analyzed using three mathematical models. Meanwhile, cell metabolomics was used to detect the effects on metabolite regulation of SSA and AF. Furthermore, the key metabolites, metabolic enzymes, and cellular markers were verified by ELISA and Western blotting. The results showed that the combination of SSA and AF has a synergistic neuroprotective effect. Besides, the combination could regulate more metabolites than a single agent and possessed a stronger adjustment effect on metabolites. The TCA cycle was regulated by SSA and AF via improving mitochondrial function. The purine metabolism was regulated by SSA via inhibition xanthine oxidase activity and the glutamate metabolism was regulated by AF via inhibition glutaminase activity. Moreover, the oxidative stress induced by the purine metabolism was attenuated by SSA via a reduction in the ROS level. Additionally, the inflammation induced by the oxidative stress was attenuated by the SSA and AF via inhibition of the NLRP3 protein expression. Conclusions This study for the first time demonstrated the synergistic neuroprotective effects of SSA and AF, and the synergistic mechanisms were involved in metabolic disorders regulation and neuroinflammation inhibition.