Brain-derived Neurotrophic Factor Reduce Injury Induced By Cerebral Ischemia/reperfusion

Background and Objective: The establishment of stroke unit and emergency green channel in recent years has provided venous thrombolysis and endovascular treatment for more patients with ischemic stroke.Reperfusion can not only improve the blood supply to ischemic area,but also cause ischemia/reperfusion(I/R)injury.I/R injury and thrombolytic drugs increase the damage of the blood-brain barrier(BBB),then it causes brain edema and cerebral hemorrhage.At present,the protection of BBB is an important therapeutic target of ischemic stroke.In recent years,more and more studies have shown that brain-derived neurotrophic factor(BDNF)is an important factor in the protection of neurovascular units,and has a protective effect on BBB,but the exact mechanism is still not clear.Pentraxin 3(PTX3)can support BBB integrity and reduce the brain edema under acute phase of stroke by protecting the vascular endothelial cells.In the human gastric cancer and porcine oocytes,BDNF activates its receptor,tropomyosin receptor kinase B(TrkB)that has been shown to increas the levels of PTX3.In this study,BDNF intervention in cerebral I/R rats to observe its BBB and brain edema,explore whether it reduce blood-brain barrier injury induced by cerebral I/R via upregulating pentraxin 3.Methods:(1)Animals were randomly divided into sham-operated group(Sham group),model group(I/R group),solvent group(DMSO group),drug group(BDNF group)and inhibitor group(BDNF+K252a group).(2)I/R model was established by rats undergoing 90-minute transient middle cerebral artery occlusion(MCAO)by intraluminal filament.The rats of Sham groupunderwent the filament entering the internal carotid artery 5mm depth,the rest of the surgical procedure the same as I/R group.(3)After cerebral ischemia we immediately inject the drug to the lateral ventricle.The rats of Sham group and I/R group were not received intraventricular infusion.The rats of DMSO group were received intraventricular infusion of 1% DMSO 5?l volume,1%DMSO is the solvent of K252 a.The rats of BDNF group were received intraventricular infusion of BDNF 2?g/5?l.The rats of BDNF+K252a group first were received intraventricular infusion of K252 a 2?g/2.5?l,and then they were received intraventricular infusion of BDNF 2?g/2.5?l after 15 min.(4)After cerebral I/R 24 hours and 72 hours,rats were neurologically assessed and the number of surviving rats were recorded.(5)After cerebral I/R 72 hours,Evan's blue(EB)extravasation and brain water content in the rats were detected.(6)After cerebral I/R 72 hours,the expressions of PTX3 and p-TrkB were detected by immunohistochemical staining,the levels of p-TrkB and PTX3 in penumbra were detected by Western Blot.Results:(1)Results of neurological scores and survival rate: After reperfusion 24 hous,the neurological scores of I/R group were significantly worse than Sham group(P <0.05).The neurological scores were no difference between I/R group and DMSO group(P >0.05).Compared with I/R group,the neurological scores of BDNF group were significantly improved and the survival rate was significantly increased.The survival rate of BDNF+K252a group were significantly decreased(P <0.05).(2)Results of the leakage of EB and brain water content: Compared with Sham group,the leakage of EB and brain water content of I/R group were increased significantly(P <0.05).The leakage of EB and brain water content were no difference between I/R group and DMSO group(P >0.05).Compared with I/R group,the leakage of EB andbrain water content of BNDF group were decreased(P <0.05),the leakage of EB and brain water content of BDNF+K252a group were increased(P <0.05).(3)Results of immunohistochemistry: In the Sham group,p-TrkB was widely expressed in the whole brain,mainly in the cortex and hippocampus.No PTX3 expression was observed in the Sham group.Compared with Sham group,in the I/R group and DMSO group,p-TrkB and PTX3 in cerebral ischemia penumbra were increased(P <0.05).PTX3 was mainly expressed in the neurons,glial cells of the penumbra.Compared with the I/R group,the expression of p-TrkB and PTX3 in the penumbra in BDNF group were increased significantly(P <0.05),the expression PTX3 in the vascular endothelial cells were increased significantly.However,the expressions of p-TrkB and PTX3 in penumbra in BDNF+K252a group were significantly decreased(P <0.05).(4)Results of WB: Compared with Sham group,the content of p-TrkB and PTX3 in I/R group and DMSO group were no difference(P <0.05).Compared with I/R group,the content of p-TrkB and PTX3 in BDNF group were increased(P <0.05)and the contents of p-TrkB and PTX3 in BDNF+K252a group were decreased significantly(P <0.05).Conclusion:(1)BDNF treatment improve the survival rate and improve the neurological deficits in the rats subjected to acute cerebral ischemia/reperfusion injury.(2)BDNF can attenuate injury of BBB and brain edema induced by cerebral ischemia/reperfusion.(3)BDNF may maintain the integrity of BBB through upregrating PTX3 expression in cerebral ischemia penumbra by binding to TrkB.