Effects of Ginsenoside Rb1 on Expressions of Phosphorylation Akt/Phosphorylation mTOR/Phosphorylation PTEN in Artificial Abnormal Hippocampal Microenvironment in Rats.

Artificial abnormal microenvironment caused by microperfusion of L-glutamate (Glu) and Ca2+ in the hippocampus results in neuron damage, which is closely related to cerebral ischemia. Ginsenoside Rb1, a compound from Panax notoginseng, was previously used to counter the artificial abnormal hippocampal environment in a microperfusion model. In addition, while the Akt/mTOR/PTEN signaling pathway has been shown to mediate neuronprotection in cerebral ischemia, whether this pathway is involved in the neuroprotection of ginsenoside Rb1 is unknown. Here SH-SY5Y cells exposed to OGD/R injury in treated with LY294002, ginsenoside Rb1, ginsenoside Rb1+ LY294002. Expressions of phosphorylation (P-)Akt/P-mTOR/P-PTEN (24 h after OGD/R) were detected by Western blotting. Effects were examined via the memory function of rats (by Morris water maze test), morphological changes in pyramidal cell (by histology), and mRNA expression (by qRT-PCR) and phosphorylation (P-) (by Western blotting and immunohistochemical staining) of Akt, P-mTOR, and P-PTEN in the hippocampus. The memory deficit of rats and pyramidal cellular necrosis and apoptosis in the CA1 region of hippocampus after microperfusion of Glu and Ca2+ were dose dependently alleviated by ginsenoside Rb1.Moreover,Western blot showed that ginsenoside Rb1 increased the expressions of P-Akt, P-mTOR and reduced P-PTEN in vivo and vitro. Thus, the potent neuroprotection of ginsenoside Rb1 in artificial abnormal microenvironment is, at least partially, related to the activation of P-AKT/P-mTOR signaling pathway and inhibition of P-PTEN protein.

Panax notoginsenoside saponins Rb1 regulates the expressions of Akt/ mTOR/PTEN signals in the hippocampus after focal cerebral ischemia in rats.

Panax notoginsenoside saponins Rb1 (PNS-Rb1) is an important active ingredient of panax notoginseng for effective treatment of cerebrovascular diseases. However, the mechanism underlying its actions in the state of cerebral ischemia is still unclear. We asked whether the potential neuroprotection of PNS-Rb1 on the brain is due to, at least partially, its modulation of AkT/mTOR/PTEN signalling pathway along with down-regulation of caspase-3 in rats subjected to phototrombic stroke. To test this hypothesis, rats with induced photothrombotic stroke were treated with PNS-Rb1 (applied in three different doses, 25 mg/kg, 50 mg/kg,100 mg/kg, respectively) or saline, while sham operated rats injected with saline were used as the control. Our results indicate that PNS-Rb1 significantly alleviated the morphological lesion concomitant with improvement of cognitive and sensorimotor deficits induced by ischemic stroke. Moreover, immunohistochemistry and Western blot analyses showed that PNS Rb1 in a dose dependent manner increased the expressions of P-Akt, P-mTOR and reduced P-PTEN and caspase-3. The present study suggests that the improvement of cognitive and sensorimotor deficits by PNS-Rb1 is made, at least partially, by the modulation of the Akt/mTOR/PTEN signalling pathway.