Panax notoginseng Saponins Protect Cerebral Microvascular Endothelial Cells against Oxygen-Glucose Deprivation/Reperfusion-Induced Barrier Dysfunction via Activation of PI3K/Akt/Nrf2 Antioxidant Signaling Pathway

Abstract

Oxidative stress plays a critical role in cerebral ischemia/reperfusion (I/R)-induced blood-brain barrier (BBB) disruption. Panax notoginseng saponins (PNS) possess efficient antioxidant activity and have been used in the treatment of cerebral ischemic stroke in China. In this study, we determined the protective effects of PNS on BBB integrity and investigated the underlying mechanism in cerebral microvascular endothelial cells (bEnd.3) exposed to oxygen-glucose deprivation/reperfusion (OGD/R). MTT and LDH release assays revealed that PNS mitigated the OGD/R-induced cell injury in a dose-dependent manner. TEER and paracellular permeability assays demonstrated that PNS alleviated the OGD/R-caused disruption of BBB integrity. Fluorescence probe DCFH-DA showed that PNS suppressed ROS generation in OGD/R-treated cells. Immunofluorescence and western blot analysis indicated that PNS inhibited the degradation of tight junction proteins triggered by OGD/R. Moreover, mechanism investigations suggested that PNS increased the phosphorylation of Akt, the activity of nuclear Nrf2, and the expression of downstream antioxidant enzyme HO-1. All the effects of PNS could be reversed by co-treatment with PI3K inhibitor LY294002. Taken together, these observations suggest that PNS may act as an extrinsic regulator that activates Nrf2 antioxidant signaling depending on PI3K/Akt pathway and protects against OGD/R-induced BBB disruption in vitro.

Panax notoginseng saponins suppress lipopolysaccharide‐induced barrier disruption and monocyte adhesion on bEnd.3 cells via the opposite modulation of Nrf2 antioxidant and NF‐κB inflammatory pathways

“…Fortunately, both of them were notably upregulated with PNS intervention in spite of LPS challenge. Our previous investigation reveals that PNS promote the phosphorylation of Akt, which subsequently strengthen the nuclear Nrf2 activation and suppress the OGD/R-induced oxidative injury (Hu et al, 2018).…”

“…Nevertheless, PNS treatment significantly upregulated Nrf2 activation, HO‐1 expression, and downregulated NF‐κB activation, regardless of LPS stimulation. Our prior study demonstrated that PNS acted as an efficient regulator that activated Nrf2/HO‐1 signaling depending on the PI3K/Akt pathway in OGD/R injured endothelial cells (Hu et al, ). Consequently, we likewise detected the level of Akt phosphorylation in this study.…”

“…Fortunately, both of them were notably upregulated with PNS intervention in spite of LPS challenge. Our previous investigation reveals that PNS promote the phosphorylation of Akt, which subsequently strengthen the nuclear Nrf2 activation and suppress the OGD/R‐induced oxidative injury (Hu et al, ). Not surprisingly, as expected, the phosphorylation of Akt was also remarkably augmented with PNS treatment, but not significantly influenced by LPS insult.…”

“…LPS has been widely used as a potent inducer of BBB disruption under inflammatory condition (Li et al, ). Although we recently demonstrated that PNS could protect against OGD/R‐induced oxidative stress injury of BBB in vitro (Hu et al, ), whether PNS could also protect against LPS‐induced BBB dysfunction under inflammatory condition has not been known. In addition, potential mechanisms have not been illustrated yet.…”

“…What is more, previous report demonstrated that early BBB disruption might be a cause rather than a consequence of brain neuron injury in several cerebral disease (Shi et al, ). We recently demonstrated that PNS could protect cerebral microvascular endothelial cells against oxygen‐glucose deprivation/reperfusion (OGD/R) induced oxidative stress injury of BBB barrier function, relating to the activation of Akt/Nrf2 antioxidant pathway (Hu et al, ). Meanwhile, it is reported that PNS or the active compounds could inhibit the inflammatory responses and adhesion events by suppression of the NF‐κB activation (Dou et al, ; Lee, Hyam, Jang, Han, & Kim, ; Zheng et al, ).…”