Integrin ?5?1-Ang1/Tie2 Receptor Cross-talk Regulates Brain Endothelial Cell Responses Following Cerebral Ischemia

Objective We have Previously demonstrated that in response to cerebral ischemia,the growth factor Angiopoietin-1(Ang1)and ?5?1 integrin are both induced in cerebral vessels,which is involved in the endogenous angiogenic response and vascular protection after cerebral ischemic stroke.However,the precise relation ship between endothelial Ang1 and ?5?1 integrin after cerebral ischemia remains poorly understood.Here,we investigated the interaction between the Ang1/Tie2 system and ?5?1integrin on brain endothelial cells(BECs)under cerebral ischemic.Methods BEC cultures were subjected ischemia-reperfusion injury through Oxygen glucose deprivation/restoration(OGD/R).Mouse models of focal cerebral ischemic stroke were induced by reverserble right middle cerebral artery occlusion(MCAO)surgery.BECs were knockdown target genes by transfecting with small hair-pin RNA(shRNA),then stimulated with or without Ang1,the changes of downstream signaling molecules were observed in BECs after cerebral ischemia.To investigate cell migration and tube formation,scratch wound migration assay and tube formation assay were employed in vitro.Results Immunofluorescent study demonstrated integrin?5?1 colocalized with Tie2/phosphorylated Tie2 on cerebral vessles in the ischemic penumbra.The in vitro study showed that in vitro oxygen-glucose deprivation/restoration(OGD/R)induced the expression of the Ang1 receptor Tie2 on BEC in a manner similar to that of integrin ?5 and Ang1 in response to OGD/R,accompanied by increased activation of Tie2 and its downstreameffectors FAK and Akt.Knockdown of ?5 integrin markedly Suppressed OGD/R-induced Tie2 receptoractivation in BECs,while in contrast,priming BECs with Ang1 promoted the expression of ?5 integrin as well as the Tie2 down stream transcription factor Ets-1in OGD treated BECs.In keeping with this,Ets-1 knock down significantly attenuated Ang1-mediated upregulation of ?5 integrin.Functionally,Ang1 induced cell migration and tube.Conclusion Taken together,our data indicate that the Ang-1/Tie2 system crosstalks with integrin ?5?1 in BECs after cerebral ischemia,which may contribute to the endogenous angiogenic vascular protective response following cerebral ischemia.