Effects Of Ginsenoside Rd On The Phosphorylation Of NMDA Receptor After Cerebral Ischemia Injury

Ginseng(Panax ginseng C.A.Meyer) as a traditional Chinese herbal medicine, havemany effects in central neuron system, such as balance the excitation and inhibition ofthe brain, antioxidation, improve brain function, anti-fatigue, enhance brain functionssuch as learning and memory, etc.. The modern pharmacology proves that Ginsenosidesare the main active ingredients. Ginsenosides (the Ginsenosides GS) is the main activeingredient of ginseng, although the content is meager but play the major role in itspharmacological effects. From ginseng genus extracted40GS monomer. The ginsengsaponins Rd (Ginsenoside Rd, GSRD) is one of the important components frome GS. Bya large number of clinical and basic researches, GSRd shows unique pharmacologicaleffects in the nervous system, cardiovascular system and renal system. In recent years,studies have shown that the GSRD has significant neuroprotective effects, such as toprotect neurons against peroxides and oxygen-glucose deprivation (oxygen-glucosedeprivation, OGD) injury, reduce animal cerebral ischemic infarct volume and promote the recovery of neurological function. Our latest research revealed that GSRD is able toinhibit the high concentration of glutamate (Glu) and N-methyl-D-aspartate receptor(NMDA receptor, NMDAR)-mediated large amounts of calcium flow[1], which indicateGSRd may play a neuroprotective effect by acting on NMDAR, but the exact mechanismis not yet clear. There also others reported that GSRd and similar material monomers canadjusted a variety of protein phosphorylations and affect their functions[2-5]. So, wepropose the hypothesis: GSRd may thus play its neuroprotective effects by influencingthe phosphorylation of NMDAR. Therefore, middle cerebral artery occlusion (middlecerebral artery occlusion, MCAO) model and OGD model are used to investigate theeffects of GSRd on NMDA receptor and its phosphorylation, in order to reveal thepossible mechanisms of GSRd in brain protection.Experiment1The effects of GSRd on neurological deficits scores andvolume of cerebral infraction in rats in MCAO modelOBJECTIVE: To test the effects of GSRd on neurological deficits scores andvolume of cerebral infraction in rats with cerebral ischemia. METHOD: A middlecerebral artery occlusion model (MCAO) was used in this study. Different doses ofGSRd (10、50mg/kg) were administrated intraperitoneally1h before and immediatelyafter the MCAO surgery; Neurological deficits scores were used for evaluation of ratmotor functions and TTC staining for cerebral infraction volume; RESULTS: Comparedwith sham group (rats with surgery but not under occlusion), GSRd amelioratedneurological deficits scores and decreased the volume of cerebral infraction significantly;CONCLUSION: GSRd protects against cerebral ischemia in rat.Experiment2The effects of GSRd on NR2B subunit and itsphosphorylation point in MCAO modelOBJECTIVE: To investigate the effects of GSRd on NR2B subunit and itsphosphorylation points in MCAO model. METHOD: Western blot is used to measurethe expression of NR2B subunit and its phosphorylation points at Ser1303, Tyr1472and Ser1480in rat MCAO model at different time points. RESULTS:(1) Western blotanalysis indicated that the expression of NR2B subunit and its phosphorylation pointsincreased remarkably in MCAO group, compared with sham operation group；(2) Givendifferent doses of GSRd (10、50mg/kg) to rat1hour before and immediately after MCAOoperation can effectively decrease the expression of NR2B subunit and itsphosphorylation points at Ser1303, Tyr1472and Ser1480remarkably. CONCLUSION:GSRd can reduce the expression of NR2B subunit and its phosphorylation leveleffectively in rat MCAO model, which suggested that GSRd plays a regular role in thesepoints.Experiment3The effects of GSRd on NR2B subunit and itsphosphorylation point in OGD modelOBJECTIVE: To study the effects of GSRd on NR2B subunit and itsphosphorylation in OGD model. METHOD: Western blot is used to test the effects ofGSRd on NR2B subunit and its phosphorylation in cultured neurons with OGD (oxygenglucose deprivation) injury. RESULTS: GSRd (10μM) added into OGD model coulddown regulate the expression of NR2B subunit and its phosphorylation at Ser1303,Tyr1472and Ser1480points. CONCLUSION: GSRd can reduce the expression ofNR2B subunit and its phosphorylation level effectively in OGD model, which suggestedthat decreasing the level of NR2B subunit and its phosphorylation level after ischemiain ju r y ma y c o nt r ibu t e t o t he ne ur o p r ot e ct ive me c ha n is ms o f G SR d.