低灌注时水通道蛋白-4在血脑屏障通透性升高中的作用

目的 探讨慢性低灌注时,水通道蛋白-4(aquaporin-4, AQP4)的表达与构型变化在血脑屏障(blood-brain barrier, BBB)通透性增高中的作用。方法 Wistar大鼠采用双侧颈总动脉结扎术(2-vessel occlusion, 2VO)建立慢性低灌注模型,测定2VO术后不同时间点脑组织伊文思蓝(evans blue, EB)含量,评价BBB通透性,RT-PCR和Western印迹法测定不同时间点AQP4 mRNA及蛋白水平表达,免疫荧光双标法观察AQP4的构型变化。结果 2VO术后早期,BBB通透性迅速升高,AQP4 mRNA和蛋白表达水平与BBB通透性变化趋势一致,均在术后3d时达到高峰,1、2周时仍显著升高(P<0.01),随着慢性缺血时间的延长,无论是BBB通透性还是AQP4 mRNA和蛋白表达水平均逐渐降低,至3个月时与假手术组相比,差异无统计学意义。而AQP4的功能构型OAPs与BBB通透性变化趋势呈负相关,2VO术后早期AQP4与GFAP共定位明显减少,随后逐渐增多,术后3个月时恢复至正常水平。结论 慢性低灌注状态可引起BBB通透性升高,AQP4的表达与构型改变与BBB通透性密切相关。
Objective To investigate the effect of the expression and configuration of aquaporin-4(AQP4) on permeability increasing of blood-brain barrier(BBB) during chronic hypoperfusion in rats. Methods Rat models of chronic hypoperfusion were established by bilateral common carotid artery occlusion(2-vessel occlusion, 2VO). BBB permeability was verified by evans blue(EB) content, the mRNA and protein expression of AQP4 was evaluated. OAPs was assessed by visualising the distribution and expression of AQP4 on astrocyte end-feet membranes. Results At early phase of postoperation, the permeability of BBB significantly increased compared with that in sham group(P<0.01),and the changing trends of mRNA and protein expression of AQP4 were consistent with the EB concentration. They were significantly increased to reach its maximal value compared with the sham rats and then gradually decreased at 1 week, 2 weeks and 1 month after 2VO, and returned to the control levels after 3 months. Double labelling with GFAP and AQP4 demonstrated that AQP4 was correctly anchored on astrocyte end-feet membranes, and was redistributed on membranes in the 3-day, 1-week and 2-week groups, and the GFAP and AQP4 were co-localized on astrocyte end-feet membranes after 3 months. Conclusion The permeability of BBB was increased in hypoperfusion rats, the expression and configuration change of AQP4 are closely related to the BBB permeability