急性肝性脑病大鼠脑水肿与脑水通道蛋白－4的相关性

Expression of aquaporin-4 during brain edema in rats with thioacetamide-induced acute encephalopathy

目的探讨水通道蛋白－4（AQP4）在急性肝衰竭肝性脑病与脑水肿的相关性。方法采用硫代乙酰胺（rrAA）腹腔注射制备急性肝衰竭肝性脑病大鼠模型。将健康雄性SD大鼠随机分为对照组8只和模型组24只，其中模型组根据造模后处死大鼠时间不同，分为24、48、60h组。观察大鼠一般情况，评估HE等级，测定血浆丙氨酸转氨酶、天冬氨酸转氨酶、总胆红素和血氨，观察肝组织病理学，检测脑含水量和脑组织AQP4（包括蛋白和mRNA）表达水平。结果模型组大鼠表现出典型肝性脑病症状，随着造模后观察时间延长，HE等级进行性升高，肝脏生化和血氨水平较对照组显著升高（P〈0．05），肝组织病理变化与对照组差异有统计学意义。脑含水量和AQP4表达水平（包括蛋白和mRNA）明显高于对照组（P〈0．05），并且AQP4蛋白和mRNA表达水平分别与脑含水量呈正相关（r：0．536，P〈0．01；r=0．566，P=0．01）。结论急性肝衰竭肝性脑病大鼠脑水通道蛋白－4（AQP4）表达与脑水肿密切相关，因此AQP4是急性肝衰竭肝性脑病脑水肿发生发展的重要分子机制之一。

Objective To investigate the expression of aquaporin-4 （AQP4） during brain edema in rats with thioaeetamide-induced acute liver failure and encephalopathy. Methods The rat model of acute hepatic failure and encephalopathy was induced by intraperitoneal injection of thioacetamide （TAA） at a 24-hour interval for ：2 consecutive days. Thirty-two SD rats were randomly divided into the model group （ n = 24） and the control group （normal saline, n = 8 ）. And then the model group was further divided into 3 subgroups by the timepoint of decapitation ： 24 h （ n = 8 ）, 48 h （ n = 8 ） and 60 h （ n = 8 ）. Then we observed their clinical symptoms and stages of HE, indices of liver function and ammonia, liver histology and brain water content. The expression of AQP4 protein in brain tissues was measured with Western blot and the expression of AQP4mRNA with RT-PCR （reverse transeription-polymerase chain reaction ）. Results Typical clinical manifestations of hepatic eneephalopathy occurred in all TAA-administrated rats. The model rats showed the higher indices of ALT （alanine aminotransferase）, AST （aspartate aminotransferase）, TBIL （total bilirubin） and ammonia than the control rats （P 〈 0. 05 ）. The brain water content was significantly elevated in TAA-administrated rats compared with the control （ P 〈 0. 05 ）. The expressions of AQP4 protein and mRNA in brain tissues significantly increased in TAA-administrated rats （ P 〈 0. 05 ）. In addition, the expressions of AQP4 protein and mRNA were positively correlated with brain water content（ r = 0. 536, P 〈 0. 01 ; r = 0. 566, P = 0. 01 ）. Conclusions The high expression of AQP4 in rats with TAA-indueed acute liver failure and encephalopathy plays a significant role during brain edema. AQP4 is one of the molecular mechanisms for the occurrence of brain edema in hepatic encephalopathy.