| Stroke is one of the leading causes of death and disability worldwide.It is the leading cause of death in China.Ischemic stroke is the major subtype of stroke,accounting for 87% of stroke cases.However,current treatments for ischemic stroke are only limited to thrombolytic therapy within an extremely narrow time window.Thus,developing novel therapeutic approaches for ischemic stroke is urgent.Histone deacetylases(HDACs)along with histone acetyltransferases(HATs)regulate chromatin remodeling and subsequent gene transcription by controlling the status of histone acetylation.Compared with histone acetylation,histone deacetylation induces a condensed chromatin conformation,contributing to the repression of gene transcription which is involved in diverse physiological processes.Recent evidence suggests that HDACs are dysregulated in a number of brain disorders,which is implicated the pathogenesis of these diseases,e.g.,ischemic stroke,autism,Alzheimer’s disease,and depressive disorders.However,there are about 15 subtypes of HDACs family.The effects of different subtypes are different or even opposite.Therefore,it is necessary to study the role of different subtypes of HDACs in central system diseases.Growing evidence indicates that histone deacetylase 9(HDAC9)is closely related to stroke,but its mechanism in cerebral ischaemia/reperfusion injury(CIRI)is not clear.After the occurrence of cerebral ischemia,a large number of neuronal cell death is an important factor leading to cerebral ischemia injury.However,the role of excitatory neurons and inhibitory neurons in CIRI is not the same.Therefore,it is urgent to explore the mechanism of HDAC9 in different neurosubtypes in CIRI to find more effective interventions and drug targests.In this study,we use Cre / lox P technology to specifically regulate HDAC9 in excitatory neurons,clarify the role of HDAC9 in cerebral CIRI.Furthermore,we use the genechip analysis to explore the underlying mechanism of HDAC9 in CIRI.First,we found that the expression of HDAC9 gradually increased within 24 hours after reperfusion,and its high expression was mainly in excitatory neurons.The same phenotype was also found in the primary neurons cultured in vitro after glucose deprivation hypoxia reperfusion injury.To further explore the role of HDAC9 in excitatory neurons in CIRI.We used Cre / lox P technique to specifically knock out HDAC9 in excitatory neurons,and found that HDAC9 deficient mice(HDAC9 c KO)showed decreased infarct volume,neurological score and apoptosis in penumbra after24 hours of cerebral ischemia-reperfusion.Then,we recovered HDAC9 expression in HDAC9 c KO mice by virus infection.Through up-regulation and down-regulation of HDAC9,we confirmed that HDAC9 in excitatory neurons can promote neuronal apoptosis and aggravate CIRI.In addition,we analyzed the cerebral cortex of HDAC9 c KO mice with expression profile chip,and identified up-regulated as a candidate molecule downstream of HDAC9.Using Western bolt,immunohistochemistry and fluorescence quantitative PCR,it was showed that the expression of cGK Ⅱ in HDAC9 c KO mice after ischemia was higher than that in the control group.Inhibiting the activity of cGK Ⅱ reversed the decrease of infarct volume and higher neurological score in HDAC9 c KO mice.Above results indicated that upregulation of cGK Ⅱ is the key element for the protective effect of c KO mice in cerebral ischemia injury.Then,we used database prediction and chromatin immunoprecipitation to explain the molecular mechanism of HDAC9’s down-regulation of cGK Ⅱ,that is,HDAC9 directly down regulates the expression of cGK Ⅱ by interacting with MEF2 during cerebral ischemia-reperfusion.In conclusion,our results firstly suggested that the up regulation of HDAC9 in excitatory neurons aggravates CIRI,and its mechanism is to directly down regulate the CGK II expression through interaction with MEF2,thereby affecting the apoptosis of neurons.From this study,the role and mechanism of HDAC9 in excitatory neurons in CIRI were preliminarily clarified,and it was also suggested that he specific inhibitors of HDAC9 and the agonists of CGK II may be the potential direction of developing CIRI drugs in the future. |
