| With the aging of population increases,the incidence of cerebrovascular disease increased significantly,and the population incidence showed younger trend in recent years.Ischemic brain injury has become one of the major causes of death and disability around the world.However,there are still lack of effective preventive measures and therapies.Different from other tissues,neuronals cells are more susceptible to harmful stimuli.In the spatial learning and memory-related brain regions,pyramidal neurons in the hippocampal CA1 region are very vulnerable to cerebral ischemia.Furthermore,the regeneration ability of adult hippocampus CA1 region is very low.Therefore,how to prevent and protect the ischemic neuron damage has become the main strategy for the treatment of stroke,brain trauma and other diseases.Resveratrol(3,4,5-trihydroxy-trans-stilbene,Res)is a phenolic compound enriched in many plants,such as polygonum cuspidatum,veratrum nigrum,grapes,peanuts and cassiatora.Previous studies have demonstrated that resveratrol inhibits N-methylD-aspartic acid receptor mediated Ca2+ influx,promotes synaptic growth and synapase formation.It is generally considered that excessive activation of NMDA receptor leads to excitotoxic neuronal death in stroke.We speculated that resveratrol may be involved in the regulation of NMDA receptor mediated Ca2+ overload,and thus block the apoptosis signal transduction pathways.ERK1/2 signal transduction pathway is a classical MAPK pathway.Previous studies had showed that the activation of ERK1/2 inhibited NMDA receptor-mediated Ca2+ influx and protected neurons from ischemic brain injury.CREB is a transcription factor and downstream target of ERK pathway,plays an important role in the central nervous system.Activation of CREB plays a crucial role in promoting neuronal survival.However,inhibition of CREB transcriptional activity promotes neuronal apoptosis after ischemia/reperfusion.Many evidences in laboratory have showed that the PI3K-Akt pathway plays an important role in inhibition of apoptosis.A variety of neurotrophic factors and traditional Chinese medicine exert neuroprotective effects via activating PI3K-Akt signaling pathway.Apoptosis associated genes Bcl-2 and Bax were associated with ischemic brain injury.The ratio of Bcl-2 to Bax plays an important role in regulating apoptotic cell death.Although there have reported that resveratrol exerts neuroprotective effective on ischemic brain injury,little is known about the efficacious time-window and mechanisms underlying the resveratrol neuroprotection.The present study is divided into two parts to illustrate the effect of resveratrol on ischemic brain injury:(1)The role of NMDA receptor mediated ERK-CREB pathway in the neuroprotective effect of resveratrol preconditioning on ischemic neuronal injury.(2)The effects of chronic resveratrol treatment on the expression of pAkt,apoptosis associated proteins Bcl-2 and Bax of ischemic hippocampal.The aim of the present study was to evaluate the effects of resveratrol on focal cerebral ischemia induced brain injury and explore the underlying molecular mechanisms in order to provide theoretical bassis for clinical treatment.1.Resveratrol pretreatment protects CA1 neurons against focal cerebral ischemic reperfusion-induced damage via the ERK-CREB signaling pathway in rats.In this study,we found that(1)compared with sham group rats,focal cerebral ischemia caused extensive hippocampal CA1 pyramidal neuronal death on the fifth day after MCAO,and the volume of cerebral infarction was also significantly increased.Surprising,a single injection of resveratrol(30 mg/kg)at 1 h or 4 h before ischemia significantly attenuated neuronal loss and the volume of cerebral infarction.(2)Escape latency to the hidden platform was significantly elongated in MCAO rats when compared with the sham rats.However,a single administration of Res at 1 or 4 h before ischemia markedly attenuated the prolongation of the escape latency to the platform on the fifth day after training.(3)To determine whether the NMDA receptor was involved in the neuroprotective effects of Res,an NMDA receptor blocker MK801 was given(30 min prior to cerebral ischemia)or at 30 min before Res administration.The results showed that MK801 alone significantly prevented ischemia-induced neuronal death when compared with MCAO group rats.In rats treated with MK801,the administration of Res at 1 h before ischemia decreased the surviving neurons.However,there was no obvious change when resveratrol was administrated at 24 h before ischemia.(4)To determine whether ERK signaling pathway was involved in the neuroprotective effects of Res,an ERK kinase inhibitor U0126 was given 30 min prior to cerebral ischemia or at 30 min before Res administration.The results showed that U0126 alone further increased ischemia induced neuronal death,and pretreatment with U0126 prevented the neuroprotective action of Res when administrated at 1 h before ischemia.In contrast,pretreatment with U0126 had no effect on ischemia-induced neuronal injury to the rats treated with Res at 24 h before ischemia.(5)At 5 d after reperfusion,compared with MCAO rats,administration of resveratrol at 1 h before ischemia significantly increased the expression of phosphorylated ERK1/2 and CREB,which could be blocked by U0126.2.Resveratrol chronic administration after reperfusion attenuates ischemic brain damage via up-regulation of hippocampal Bcl-2 and pAkt,down-regulation of Bax.In the present study,we found that for the focal cerebral ischemia rat model,when resveratrol was administrated at a dose of 30mg/kg i.p.starting at 3 h after reperfusion and lasting for 4 days:(1)The results of HE staining showed that a 90 min MCAO approach caused approximately 82% pyramidal neuronal death of hippocampal CA1 area on the fifth day after reperfusion.However,chronic administration of resveratrol significantly reduced cerebral ischemia-induced pyramidal neuronal damage.The results of TUNEL staining showed that compared with sham group,the number of TUNEL-positive cells in the hippocampal CA1 region of MCAO rats was increased significantly.Interestingly,compared to MCAO group rats,chronic resveratrol treatment significantly reduced the number of TUNEL-positive cells in the hippocampal CA1 region.(2)On the fifth day after reperfusion,high-frequency stimulation cannot evoke a stable potentiation of EPSP slope in slices of MCAO rats,indicating that MCAO impairs the induction of LTP.However,chronic resveratrol administration rescued LTP induction.(3)The basal properties of Schaffer collateral-CA1 synaptic transmission of MCAO rats was affected by focal cerebral ischemia,but did not change the capacity for presynaptic glutamate release.(4)The results of Western blot revealed that resveratrol administration up-regulated the expression of pAkt of Res + MCAO group rats,but had no effect on Res + Sham group rats.(5)Compared with sham group rats,the Bcl-2 levels of MCAO rats were significantly decreased,and the Bax levels of MCAO rats were increased.Chronic resveratrol administration prevented cerebral ischemia induced decrease in Bcl-2 and increase in Bax.Moreover,compared to Sham group rats,the ratio of Bcl-2/Bax of MCAO rats was down-regulated.The ratio of Bcl-2/Bax was up-regulated by chronic resveratrol treatment.Conclusions: A single injection of resveratrol at 1 hefore ischemia protects CA1 neurons against focal cerebral ischemic reperfusion-induced damage via NMDA receptor mediated ERK-CREB signaling pathway.Chronic resveratrol administration after cerebral attenuates ischemic brain damage via up-regulation of hippocampal Bcl-2 and pAkt,down-regulation of Bax. |
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