Panax notoginseng Saponins Protect Brain Microvascular Endothelial Cells against Oxygen-Glucose Deprivation/Resupply-Induced Necroptosis via Suppression of RIP1-RIP3-MLKL Signaling Pathway

Recently, necroptosis has emerged as one of the important mechanisms of ischemia stroke. Necroptosis can be rapidly activated in endothelial cells to cause vascular damage and neuroinflammation. Panax notoginseng saponins (PNS), an ingredient extracted from the root of Panax notoginseng (Burk.) F.H. Chen, was commonly used for ischemic stroke, while its molecular mechanism and targets have not been fully clarified. Our study aimed to clarify the anti-necroptosis effect of PNS by regulating RIP1-RIP3-MLKL signaling pathway in brain microvascular endothelial cells (BMECs) subjected to transient oxygen-glucose deprivation (OGD/resupply [R]). In vitro, the necroptosis model of rat BMECs was established by testing the effect of OGD/R in the presence of the pan-caspase inhibitor z-VAD-FMK. After administration of PNS and Nec-1, cell viability, cell death modality, the expression of RIP1-RIP3-MLKL pathway and mitochondrial membrane potential (Delta psi m) level were investigated in BMECs upon OGD/R injury. The results showed that PNS significantly enhanced cell viability of BMECs determined by CCK-8 analysis, and protected BMECs from necroptosis by Flow cytometry and TEM. In addition, PNS inhibited the phosphorylation of RIP1, RIP3, MLKL and the downstream expression of PGAM5 and Drp1, while similar results were observed in Nec-1 intervention. We further investigated whether PNS prevented the Delta psi m depolarization. Our current findings showed that PNS effectively reduced the occurrence of necroptosis in BMECs exposed to OGD/R by inhibition of the RIP1-RIP3-MLK signaling pathway and mitigation of mitochondrial damage. This study provided a novel insight of PNS application in clinics.