Anti-leakage mechanism and effect of sodium aescinate on the permeability of blood-brain barrier in rats exposed to hypoxia / 解放军医学杂志

ABSTRACT

Objective To study the anti-leakage mechanism and protective effect of sodium aescinate on the blood-brain barrier of rats acutely exposed to hypoxia. Methods Seventy-five healthy SD rats were randomly divided into 3 groups (25 each) normoxic control (NC), simple hypoxic (SH) and drug treated (DT) group. Acute hypoxia brain edema rat model was established by a simulation of acute high-altitude hypoxia for 5 days. The cerebral water content was determined by dry-wet method. The permeability of the blood-brain barrier (BBB) was evaluated by Evans blue (EB) method. The pathological change of the brain was detected by HE staining. The state of BBB tight junction (TJ) and ultrastructures of the brain tissues were observed by lanthanum nitrate tracer method under transmission electron microscope (TEM). 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 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 the expressions of rat's 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 playing a profitable role of anti-leakage and BBB protection.