P695Anti-leakage mechanism and effect of sodium aescinate on the permeability of blood-brain barrier exposed to hypoxia rat

Abstract

Objective: To study the anti-leakage mechanism and protective effect of sodium aescinate on the blood-brain barrier of rat exposed to hypoxia. Methods 75 SD rats were randomly divided into normoxic control (NC),simple hypoxic (SH) and drug treated (DT) group. Acute brain edema rat model was established by a simulation of plateau acute hypoxia for 5 days. Dry-wet method to determine cerebral water content, evans blue (EB) method to evaluate the permeability of blood-brain barrier (BBB). HE staining to detect pathological changes of brain. Lanthanum nitrate tracer method with transmission electron microscopy (TEM) to observe the state of BBB tight junction (TJ) and ultrastructure of brain tissue. Protein and mRNA expression of Occludin, Zo-1 and Claudin-5 were investigated by immunohistochemistry, western-blotting and real-time PCR respectively. Results After exposure to acute hypoxia for 5 days, compared with NC group, the water content of brain in SH group increased obviously (P<0.01) while that in DT group decreased significantly (P<0.05), and EB content analysis revealed a similar result. It was observed by microscopy that hippocampus neurons were lost and edemas occurred heavily in SH group while slightly in DT group. It was detected by TEM that lanthanum nitrate infiltrated and deposited into cerebral interstitium through widened TJ gap of the brain microvascular endothelial cells (BMVECs), and the perivascular edema was obvious in SH group, while these changes were lessened in DT group. The lowest expression levels of Occludin mRNA and protein were found in SH group (P<0.01), and the highest levels were in DT group (P<0.05). Meanwhile, to compare with SH group, the expression of zo-1 and Claudin-5 mRNA increased remarkably in both NC and DT group (P<0.05), while no significant difference existed between the latter two groups. Conclusion Acute hypoxia exposure may lead to a remarkable decline of brain occludin protein and the Occludin, Zo-1 and Claudin-5 mRNA, and an obvious increase of BBB permeability. Sodium aescinate can up-regulate the expression level of these molecules and decrease BBB permeability,thus play a role of anti-leakage and BBB protection.