低氧脑水肿大鼠脑组织VEGF和AQPs基因及蛋白表达的变化

目的：探讨低氧脑水肿时血管内皮细胞生长因子（VEGF）、水通道蛋白（AQP1和AQP4）基因和蛋白表达变化,为阐明急性低氧对脑组织的损伤及低氧脑水肿的发病机制提供实验依据。方法：Wistar大鼠随机分为4个组：常氧对照组（Control）、低氧暴露4 000 m组（4 000 m）、低氧暴露6 000 m组（6 000 m）和低氧暴露8 000 m组（8 000 m）,低氧组于低压舱中模拟相应海拔高度持续暴露8 h建立低氧脑水肿模型。用干-湿重法测定脑组织水含量,常规光镜观察脑组织形态学的改变;用RT-PCR法和免疫组化法检测低氧脑水肿时大鼠脑组织VEGF、AQP1和AQP4mRNA和蛋白表达的变化。结果：①干-湿重法测定表明,低氧（≥6 000 m）暴露后,大鼠脑组织水含量明显增加（P〈0.01）。②常规光镜检测结果表明,低氧暴露4 000 m时大鼠脑神经细胞、血管内皮细胞和星形胶质细胞足突轻度肿胀,组织中出现漏出液;低氧暴露6 000 m时脑血管内皮细胞和星形胶质细胞足突肿胀加重,血管与组织间隙扩大,组织中漏出液增多;低氧暴露8 000m时脑血管内皮细胞和星形胶质细胞足突重度肿胀,血管与组织间隙进一步扩大,组织中漏出液明显增多。③低氧脑水肿时,VEGF、AQP1、AQP4mRNA表达水平增高,AQP1在内皮细胞异常表达,内皮细胞VEGF和AQP1、星形胶质细胞足突AQP4蛋白质表达水平增高。结论：低氧脑水肿时,VEGF、AQP1和AQP4表达和分布的变化可能是引起血脑屏障损伤、导致低氧脑水肿的发病机制之一。

Changes of VEGF and AQPs gene and protein expression in rat brain tissue during hypoxic encephaledema

Objective： To explore the changes of vascular endothelial growth factor（VEGF）,aquaporin（AQP） gene and protein expression during hypoxic encephaledema so as to provide the basis for elucidating the brain injury caused by acute hypoxic exposure and pathogenesis of the encephaledema.Methods： Wistar rats were randomly divided into 4 groups,i.e.control group,hypoxia 4 000 m group,hypoxia 6 000 m group and hypoxia 8 000 m group.Rats in hypoxic groups were exposed to hypoxia at simulated altitude of 4 000 m,6 000 m and 8 000 m above sea level for 8 hours respectively in order to establish hypoxic encephaledema model.The water content in brain was determined by dry-weight method.The changes in morphology of brains were observed under optical microscope.The changes in expression of VEGF,AQP1 and AQP4 genes and protein were determined by RT-PCR and immunohistochemistry.Results： ①The results determined by dry-weight method indicated that water content of rats brain increased markedly after rats were exposed to a simulated altitude at 6 000 m, 8 000 m.②The results determined by microscopy indicated that during the rats exposed to hypoxia,nerve cells,vascular endothelial cells and astrocyte foot processes swelled lightly,transudate occurred in tissues at 4 000 m.The swelling of vascular endothelial cell（VEC） and astrocyte foot processes aggravated,interspace between vessels and tissues enlarged,and transudate in tissue increased at 6 000 m.The swelling of VEC and astrocyte foot processes went from bad to worse,interspace between vessels and tissues enlarged further,and transudate in tissue increased evidently at 8 000 m.③During hypoxic encephaledema,the expression of VEGF,AQP1 and AQP4 mRNA increased,AQP1 was abnormally expressed on the surface of VEC,and the expressive level of VEGF and AQP1 on VEC and AQP4 on astrocyte foot processes increased.Conclusion： The changes in expression and distribution of VEGF,AQP1 and AQP4 during encephaledema caused by hypoxic exposure may induce blood-brain barrier injury,and may be one of the pathogenesis of hypoxic encephaledema.