Effect Of The Extract Of Ginkgo Biloba(EGb761) On Traumatic Brain Edema In Rats And Its Potential Mechanism

ObjectiveThe increase of intracranial pressure is a common symptom after traumatic brain injury(TBI),which mainly caused by brain edema.Relieving brain edema is helpful to improve the prognosis of traumatic brain injury.Extract of Ginkgo biloba can scavenge free radicals,inhibit apoptosis,protect neurons and improve brain capillary endothelial cell function.The aim of this study was to investigate the therapeutic effect and potential mechanism of the Extract of Ginkgo biloba(EGb761)on traumatic brain edema in rats,and to provide theoretical basis for clinical treatment of traumatic brain edema.MethodsSixty-four adult SD rats(male and female unlimited)were randomly divided into four groups:Sham group,TBI+saline group(TBI group),TBI+low dose group(TBI+25mg/kg EGb761 group),TBI+high dose group(TBI+50mg/kg EGb761 group).The model of focal cortical contusion in the rats was established by Feeney's free fall injury method.TBI+25mg/kg and TBI+50mg/kg groups were administered with EGb761 in a dosage of 25mg/kg and 50mg/kg after 1h of trauma.The degree of brain edema was determined by wet-dry weights method.The morphological changes of the injured lateral brain tissue were observed by H&E staining.DHE staining analysis was used to detect the expression of oxygen free radicals in the injured lateral brain tissue.Western blot analysis was used to detect the protein levels of VEGFR2,PI3K,Akt,p-Akt,SRC,MMP-9,occludin and claudin-5.Results1.The results of brain edema measured by wet-dry weights method showed that compared with Sham group(77.06±0.22)%,the water content in injured lateral brain of TBI group(81.34±0.35)%,TBI+25mg/kg group(79.62±0.15)%and TBI+50mg/kg group(78.53±0.12)%were significantly increased(n=6,P<0.05).Compared with TBI group,TBI+25mg/kg group and TBI+50mg/kg group had significantly lower water content in injured lateral brain(P<0.05).And the decrease level was much lower in TBI+50mg/kg group than that in TBI+25mg/kg group(P<0.05).2.H&E staining results showed that there was lateral cerebral injury and microvascular edema accompanying with a large number of neurons lost in the TBI group.The edema degree was significantly reduced after treated with EGb761 1h after surgery(n=4).3.DHE staining results showed that compared with Sham group,the relative intensity of fluorescence in TBI,TBI+25mg/kg and TBI+50mg/kg groups were significantly increased(n=4,P<0.05),exhibiting that the expression of oxygen free radicals were increased.Compared with TBI group,the relative intensity of fluorescence in TBI+25mg/kg and TBI+50mg/kg groups were significantly decreased(P<0.05),and the relative intensity of fluorescence was decreased more significantly in TBI+50mg/kg group(P<0.05),which representes the decrease of oxygen free radicals.4.Western blot results showed that the expression levels of VEGFR2,PI3K,p-Akt,SRC,and MMP-9 protein in TBI,TBI+25mg/kg and TBI+50mg/kg groups were up-regulated compared with Sham group,the expression levels of occludin and claudin-5 were down-regulated.(n=6,P<0.05).Compared with TBI group,the expression levels of VEGFR2,PI3K,p-Akt,SRC,and MMP-9 in TBI+25mg/kg and TBI+50mg/kg groups were decreased and the expression levels of occludin and claudin-5 were increased after EGb761 pre-treatment(P<0.05).All protein changes metioned above were more significant in TBI+50mg/kg group than that in TBI+25mg/kg group(P<0.05).ConclusionsEGb761 is effective in relieving traumatic cerebral edema by up-regulation the expression of tight junction proteins occludin and claudin-5 with a dosage-dependent manner,and its mechanism is related to scavenging oxygen free radicals,inhibit the signaling pathway of VEGF/PI3K/Akt and down-regulation MMP-9.