Ischemia postconditioning induces tight junction protein expression and inhibits brain edema after thrombotic cerebral ischemia in tree shrews / 中国病理生理杂志

ABSTRACT

AIM:To assess whether the expression of tight junction (TJ) proteins, occludin/zonula occludins (ZO)-1, and regional cerebral blood flow (rCBF) link to brain edema in tree shrews during thrombotic cerebral ischemia and ischemic postconditioning (PC), and to explore how TJ affects brain edema and cerebral infarction .METHODS:Tree shrews were randomly grouped into control , ischemia and cerebral ischemia +PC (n=23), and the remaining 3 ani-mals were used for magnetic resonance imaging ( MRI) .The local cerebral thrombosis were induced by photochemical reac-tion in the tree shrews , and ischemic PC was established at 4 h after induction of cerebral ischemia followed by clipped ipsi-lateral common carotid artery (5 min ×3).The changes of the neural ultrastructure were observed under electron micro-scope.The neuronal apoptosis was analyzed by the method of TUNEL .Laser Doppler brain flowmetry was used to monitor the rCBF.The protein levels of occludin/ZO-1 were determined by immunochemistry and Western blot .The cerebral in-farction volume was detected by MRI .The brain water content was measured by dry-wet weight method .RESULTS: In-duction of cerebral ischemia led to a significant reduction of the normal neuron numbers in the hippocampal CA 1 area, and conversely, the number of neurons with abnormal ultrastructure was increased .The TUNEL positive cells were increased significantly (P<0.01) in ischemia group.Moreover, the rCBF decreased significantly (P<0.01), and occludin/ZO-1 protein expression decreased ( P<0.01 ) .The brain water content and cerebral infarction volume were significantly in-creased (P<0.01).Ischemic PC increased the rCBF and the occludin/ZO-1 expression, but reduced the brain water con-tent, the TUNEL positive cells, and the infarction volume (P<0.01).CONCLUSION:Ischemic PC increases the rCBF but not the local water content , suggesting that reduced cerebral infarction volume after ischemia PC is associated with the attenuation of cerebral edema by the enhancement of occludin /ZO-1 protein expression .