The Role And Mechanism Of Histone Deacetylase 3 In Blood-Brain Barrier Injury

Objectives:The blood-brain barrier(BBB)is a complex structure consisting of cells such as endothelial cells,pericytes and astrocytes as is located between the brain parenchyma and the vascular system.The main purpose of the existence of the BBB is to separate the central nervous system(CNS)from the peripheral tissues.In order to maintain homeostasis in the CNS,the BBB controls material,nutrients and cell transfer from the blood to the brain and from the brain to the blood.The permeability of the BBB is altered in many CNS pathologies,including brain injury,ischemic stroke,multiple sclerosis,epilepsy,Parkinson's disease,Alzheimer's disease and major depression.Loss of BBB integrity allows for the entrance of cytokines and immune cells into the CNS,which activates glial cells and causes the alterations in the extracellular environment,then induces very serious damage to the function of the nervous system.Therefore,it is necessary to develop an effective way to protect against BBB injury in neurological diseases,which will provide new ideas for clinical treatment and improve the outcomes of patients thus reducing the huge social burden.The roles of Histone deacetylases(HDAC)and Histone deacetylases 3(HDAC3)have been well defined and applied to the treatment in a variety of neurological diseases.However,we still lack understandings about the roles of different HDAC isoforms,especially for HDAC3,in BBB regulation.It is well described that inhibition of HDAC3 plays a role in neuroprotection and anti-neuroinflammation.But whether the regulation of HDAC3 could function as a protective manner in BBB damage in various neurological diseases remains unknown.Methods:In each sections of this study,we explored the role and mechanism of HDAC3 inhibition in different neurological BBB injury models separately.In first section,Human Brain Microvascular Endothelial cells(HBMEC)Oxygen glucose deprivation/reoxygenation(OGD/R)model was used to represent ischemic stroke BBB injury.In second section,we used HBMEC treated with High glucose and interleukin1?(HG-IL1?)for in vitro part and db/db genetic mice for the in vivo part to mimic type 2 diabetes induced BBB injury.In the last section,photoischemic stroke model was performed on db/db mice to mimic ischemic stroke in type 2 diabetes patient.HDAC3 specific inhibitor RGFP966 and Small interfering RNA(siRNA)were used as intervention tools in this study.Through Fluorescein isothiocyanate(FITC)leakage test,transendothelial electrical resistance(TEER)measurement,sodium flourescein(NaFl)leakage test,Evans-Blue leakage measurement and immunostaining,the BBB injury were observed in both of in vivo and in vitro models.By using Western-blots,Quantitative Polymerase chain reaction(PCR),immunostaining and activity kit,the alterations of HDAC3 activity and expression were clarified.With performing Western-blots,Quantitative PCR,immunostaining and Co-Immunoprecipitation,the underlying mechanisms were then investigated.Meanwhile,foot-fault test,grip test and Y-maze test were performed accordingly to evaluate the protective effects of HDAC3 inhibition in stroke model with type 2 diabetes.Results:(1)In HBMEC OGD/R model,HDAC3 translocated into nuclear and its activity increased accompanied by the reduction of Peroxisome proliferator-activated receptor gamma(PPARy)activity.HDAC3 inhibition significantly attenuated OGD/R-induced endothelial cell permeability,which was partly associated with the increased PPARy activity through acetylation as well as Claudin-5 up-regulation.(2)In in vivo and in vitro models of type 2 diabetes,inhibition of HDAC3 protected against the BBB injury induced by type 2 diabetes.The underlying mechanism was related to microRNA-200a(miR-200a)/Keleh-like ECH-associated protein 1(Keapl)/Nuclear factor E2-related factor 2(Nrf2)pathway activation.(3)In stroke model with type 2 diabetes,HDAC3 inhibition reduced the infarction volume and improved their performance in behavior test such as foot fault test and Y-maze test,which was partly related to its protection effects on BBB injury.Conclusions:HDAC3 inhibition exerted protective effects in many neurological BBB injury models.Besides to its anti-neuroinflammation role and neuroprotection role we already known,it could serve as a novel protective mechanism in neurological disease as well as a new target for clinical treatment on BBB injury.