Total Saponins of Panax Notoginseng Exhibit Neuroprotection by The Activation of Akt/mTOR Pathway in Vitro and in Vivo

Abstract Background: Panax notoginseng (Burkill) F.H.Chen is a traditional Chinese medicine. The present study reports the potential therapeutic effect of total saponins of Panax notoginseng (Burkill) F.H.Chen (TSPN) on ischemic stroke and investigates the underlying mechanisms. To reveal the neuroprotective effect of TSPN on cerebral ischemia-reperfusion injury and the underlying mechanisms.Methods: Oxygen-glucose deprivation/reoxygenation (OGD/R) of cultured cortical neurons was used as a model of neuronal injury. The neuroprotective effect of TSPN was evaluated by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, flow cytometry and Live/Dead cell assay. The morphology of dendrites was detected by immunofluorescence. Rat middle cerebral artery occlusion (MCAO) was used as a model of cerebral ischemia-reperfusion. The neuroprotective effect of TSPN was evaluated by neurological score, tail hang test, TTC staining, and Nissl staining. Western blot analysis, immunohistochemistry or immunofluorescence was used to measure the changes in Akt/mTOR signaling pathway.Results: MTT showed that TSPN had a rescue effect on cortical neurons after OGD/R-treated. Flow cytometry and Live/Dead cell assay indicated that TSPN decreased neuronal apoptosis, and immunofluorescence showed that TSPN restored dendrite morphology of the damaged neurons. Moreover, TSPN down-regulated the expressions of cleaved-Caspase-3 and LC3B-II/LC3B-I, whereas up-regulated the levels of phosphorylated (p)- Akt and p-mTOR. In MCAO model, TSPN rescued defective neurological behavior and reduced infarct volume. Moreover, the expressions of Beclin-1 and LC3B in cerebral ischemic penumbra were down-regulated after the treatment of TSPN, whereas p-mTOR level was up-regulated.Conclusion: TSPN show neuroprotective effects against OGD/R-induced cortical neuronal damage and exhibit potential therapeutic effects on cerebral ischemia in rat MCAO model. Up-regulation of mTOR pathway and inhibition of the autophagic pathway could be the mechanisms that underlie the action of TSPN.