大鼠脑挫伤后脑组织水通道蛋白4表达及其与脑水肿的关系

Relationship of aquaporin-4 expression with edema formation after brain contusion in rats

目的 探讨脑挫伤后水通道蛋白4（AQP4）脑组织中的表达及其与脑水肿的关系.方法 健康成年SD大鼠70只,制作脑挫伤模型,按随机数字表法分为假手术组（A组）和挫伤侧组（B组）和非挫伤侧组（C组）,分为1,6,24,48,72和7d6个时相点,每组10只.观察各组脑组织病理变化,并采用免疫组织化学及免疫印迹检测AQP4表达. 结果 A组双侧脑组织结构正常,AQP4主要分布于胶质细胞、血管内皮细胞.B组挫伤后的病理表现为血管源性水肿和细胞内水肿参与的混合性水肿,并可见组织坏死、大量炎性细胞浸润、胶质瘢痕样改变.B组胶质细胞、血管内皮细胞的AQP4表达丰富,在1h表达下调,6h最低,之后升高至24h达峰值,48 h缓慢下调,72 h出现第二个高峰值,随后下降至7d.除1h外各时相点与A组比较差异有统计学意义（P＜0.01）.C组挫伤后1h未见异常,6h出现细胞水肿,24 h为细胞水肿为主的混合性脑水肿,至48 h细胞水肿持续存在,血管源性水肿缓解,72 h仍有明显的细胞水肿,7d细胞水肿减轻.C组胶质细胞、血管内皮细胞AQP4表达上调,在1h为1.313 ±0.010,6h开始缓慢上升,72 h达高峰2.662±0.020,之后下降至7d,接近正常;C组6,24,48,72 h与A组比较差异有统计学意义（P＜0.01）,1h及7d与A组比较差异无统计学意义（P＞0.05）. 结论 脑挫伤后挫伤侧首先出现血管源性水肿,继后出现细胞水肿.非挫伤侧病理改变晚于挫伤侧,先出现细胞水肿,后发生血管源性水肿.AQP4的表达水平与挫伤性脑水肿的形成密切相关.

Objective To investigate the expression of aquaporin-4 （AQP4） in contused brain and contralateral side and correlation of AQP4 level with brain edema.Methods A total of 70 health adult SD rats were divided into sham operation group （n =10） and brain contusion group （n =60） according to the random number table.Except for no impact in sham operation group,the remaining operations were the same in both groups.Ten rats in brain contusion group were separately sacrificed at 1,6,24,48 and 72 hours,and 7 days.Pathological changes in brain tissues of rats were detected and immunohistochemistry staining and Western-blot were used to measure AQP-4 expression.Results There were no abnormalities of brain tissue structure in sham operation group with AQP4 expressed mainly in glial cells and vascular endothelial cells.With respect to the injured side in brain contusion group,mixed brain edema that consisted of angioedema and cellular edema occurred along with tissue necrosis,massive inflammatory cell infiltration,and microgial proliferation.AQP4 was apparently expressed in gliocytes and vascular endothelial cells,which showed a fall at 1 hour,the lowest at 6 hours,the peak at 24 hours,slow fall at 48 hours,a second peak at 72 hours,and then a fall until 7 days.Level of AQP4 other than that at 1 hour had significant difference compared with sham operation group （P 〈 0.01）.Whereas the contralateral side in brain contusion group showed no pathological abnormalities at 1 hour,but cellular edema emerged at 6 hours followed by mixed brain edema mainly characterized as cellular edema at 24 hours,continued cellular edema but alleviated angioedema at 48 and 72 hours,and alleviated cellular edema at day 7.AQP4 was up-regulated in gliocytes and vascular endothelial cells,which decreased at 1 hour （1.313 ± 0.01）,minimized at 6 hours （0.922 ± 0.03）,peaked at 24 hours （2.848 ± 0.020）,fell at 48 hours,peaked again at 72 hours （2.662 ± 0.02） and fell to almost normal level at day 7.By contrast with sham operation group,level of AQP4 had significant difference other than that at 1 hour and 7 days （P 〈 0.01）.Conclusions After brain contusion,angioedema and subsequent cellular edema emerge in the contused side.Pathological changes are delayed in non-contused side with cellular edema ahead of angioedema.Level of AQP4 is closely related with traumatic brain edema.