Relationship of aquaporin-4 expression with edema formation after brain contusion in rats / 中华创伤杂志

ABSTRACT

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.