The Effects Of Ischemic Postconditioning On Cerebral Edema And Brain Blood Barrier Disruption Caused By Relief Of Carotid Stenosis In A Rat Model

Cerebrovascular disease is a kind of serious diseases endangering human health,and has become one of the three major causes of global human death. The stroke causedby carotid artery stenosis disease accounts for1/4~1/2of all strokes. In USA, almost1/3strokes come from carotid artery stenosis, but in our country, the annual rate ofischemic stroke from extracranial carotid stenosis is120~180/10million. The annualfatality rate is up to80~120/10million. Buy now, the treatments of carotid arterystenosis include drug treatment, operation treatment and interventional therapy. Theearly revascularization of severe carotid artery stenosis can effectively reduce strokerecurrence and mortality. But complications such as neurocognitive dysfunction, severebrain edema, persistent headache,intracranial hemorrhage, seriously threat patients afterrevascularization. Thus, finding an effective method to solve the complications afterrevascularization has becomed an urgent problem to be solved.The blood brain barrier (BBB) is composed of vascular endothelial cell, pericyte,glial cells and the extracellular space. It is a complex system between blood and braintissue, and is an unique structure of the nervous system. When the structure and functionof blood brain barrier is integrity,blood brain barrier can block some macromolecularsubstances and strictly screen the substances exchange between blood and brain tissue.When the structure and function of blood brain barrier is abnormal, the permeability ofblood brain barrier is elevated and the brain edema is induced. The TJ (Tight junction,TJ) between the vascular endothelial cells is the key factor to maintain the normalpermeability of blood brain barrier. Tight junctions is mainly composed of tight junctionproteins ZO, occludin, transmembrane protein, Claudins etc. And occludin and Claudin-5are the ctitical proteins to the formation of the tight junction. Changes in theexpression and distribution of them can lead to the integrity of the blood-brain barrierdamaged. Futhermore, the increased expression of claudin-5and occludin can reducethe permeability of the blood brain barrier. In addition, the function of blood brainbarrier is closely related to matrix meta-llproteinases family (MMPs). Hydrolysising IVcollagen the main component of cell matrix and basement membrane is the mainfunction of gelatinase (MMP-2, MMP-9). Studies have demonstrated that MMP-2andMMP-9are closely related with the changes of blood brain barrier structure andfunction.Especially MMP-9could moderate the BBB permeability via the degradationof claudin-5and occludin. Therefore, we focus on the research about the relationshipMMP-9, occluding, claudin-5and the functional changes of blood brain barrier.Recently, ischemic postconditioning is an effective method as a protection fromischemia and reperfusion injury. In the ealy stage of reperfusion,Ischemicpostconditioning changes the dynamics of blood flow by blocking blood flowintermittently and fastly. In previous experiments we demonstrate that ischemicpostconditioning can prevent neuronal death in the early stage of carotid stenosis relief,but The relationship between ischemic postconditioning and the functional changs ofBBB after carotid artery stenosis relief is still unclear.Purpose:we investigated the effects of ischemic postconditioning on brain edema anddisruption of blood brain barrier Caused by Relief of Carotid Stenosis via establishingrat model of severe carotid stenosis.Methods:Wistar rat model of hypoperfusion due to severe carotid stenosis was establishedby binding a stainless microtube to both carotid arteries. Ischemic postconditioningprocedure consisted of three cycles of30seconds ischemia and30seconds reperfusion.Brain edema was evaluated by measuring cerebral water content, and blood brainbarrier permeability was assayed by examining cerebral concentration of Evans’ Blue(EB) and fluorescein sodium (NaF). ELISA was used to analyze the expression of MMP-9, claudin-5and occludin. The activity and location of MMP-9was analyzed bygelatin zymography and in situ zymography, respectively. The distribution of tightjunction proteins claudin-5and occluding was observed by immunohistochemistry.Results:The increased brain water content and cerebral concentration of EB and NaF weresuppressed by administration of ischemic postconditioning prior to relief of carotidstenosis. Zymographic studies showed that MMP-9was mainly located in the cortexand its activity was significantly improved by relief of carotid stenosis and, but theelevated MMP-9activity was inhibited markedly by ischemic postconditioning.Immunohistochemistry revealed that ischemic postconditioning improved thediscontinuous distribution of claudin-5and occludin. ELISA detected that theexpression of up-regulated MMP-9and down-regulated claudin-5and occludin causedby carotid relief were all attenuated by ischemic postconditioning.Conclusions:Ischemic postconditioning is an effective method to prevent brain edema andimprove BBB permeability and could be used during relief of severe carotid stenosis.