水通道蛋白-4 在肝衰竭性脑水肿发展中的作用。

Role of aquaporin-4 in the development of brain oedema in liver failure.

机构信息

Institute of Hepatology, University College London, London, UK.

出版信息

J Hepatol. 2010 Jul;53(1):91-7. doi: 10.1016/j.jhep.2010.02.020. Epub 2010 Apr 1.

DOI:10.1016/j.jhep.2010.02.020

PMID:20451280

Abstract

BACKGROUND & AIMS: Liver failure is associated with progressive cytotoxic brain oedema (astrocyte swelling), which underlies hepatic encephalopathy (HE). Ammonia and superimposed inflammation are key synergistic factors in HE, but the mechanism(s) involved remain unknown. We aimed to determine whether aquaporin-4 (AQP4), an astrocyte endfeet bi-directional water channel, is associated with the brain oedema of HE.

METHOD

Rats (n=60) received sham-operation (sham), 5 days hyperammonaemia-inducing diet (HD), galactosamine (GALN) induced acute liver failure (ALF), 4 weeks bile duct-ligation (BDL) induced cirrhosis, or caecal ligation and puncture (CLP), a 24h model of bacterial peritonitis. Rats from every group (except CLP) were randomised to receive intraperitoneal injections of lipopolysaccharide (LPS; 1mg/kg) or saline, prior to termination 3h later. Brain water, AQP4 protein expression (western blot) and AQP4 localisation by immunogold electron microscopy were investigated.

RESULTS

Significant hyperammonaemia was observed in saline-injected BDL (p<0.05), GALN (p<0.01), and HD (p<0.01), compared to sham rats. LPS injection did not affect arterial ammonia or plasma biochemistry in any of the treatment groups. Increased brain water was observed in saline-injected GALN (p<0.05), HD (p<0.01), and CLP (p<0.001) compared to sham rats. Brain water was numerically increased in BDL rats, but this failed to reach significance (p=0.09). LPS treatment further increased oedema significantly in all treatment groups (p<0.05, respectively). AQP4 expression was significantly increased in saline-injected BDL (p<0.05), but not other treatment groups, compared to sham rats. Membrane polarisation was maintained in BDL rats.

CONCLUSION

The results suggest that AQP4 is not directly associated with the development of brain oedema in liver failure, hyperammonaemia, or sepsis. In cirrhosis, there is increased AQP4 protein expression, but membrane polarisation, is maintained, possibly in a compensatory attempt to limit severe brain oedema.

摘要

背景与目的

肝衰竭与进行性细胞毒性脑水肿（星形胶质细胞肿胀）有关，后者是肝性脑病（HE）的基础。氨和叠加的炎症是 HE 的关键协同因素，但其中涉及的机制仍不清楚。我们旨在确定水通道蛋白-4（AQP4），一种星形胶质细胞足突双向水通道，是否与 HE 的脑水肿有关。

方法

将大鼠（n=60）分为假手术（sham）组、5 天高氨血症诱导饮食（HD）组、半乳糖胺（GALN）诱导的急性肝衰竭（ALF）组、4 周胆管结扎（BDL）诱导的肝硬化组或盲肠结扎和穿刺（CLP）组，CLP 组为细菌腹膜炎 24 小时模型。除 CLP 组外，每组大鼠（n=60）随机接受腹腔内注射脂多糖（LPS；1mg/kg）或生理盐水，然后在 3 小时后终止实验。通过 Western blot 检测脑水、AQP4 蛋白表达和免疫金电子显微镜检测 AQP4 定位。

结果

与 sham 大鼠相比，生理盐水注射 BDL（p<0.05）、GALN（p<0.01）和 HD（p<0.01）大鼠出现明显的高氨血症。LPS 注射未影响任何治疗组的动脉氨或血浆生化。与 sham 大鼠相比，生理盐水注射 GALN（p<0.05）、HD（p<0.01）和 CLP（p<0.001）大鼠的脑水增加。BDL 大鼠的脑水增加，但未达到统计学意义（p=0.09）。LPS 治疗进一步显著增加了所有治疗组的脑水肿（p<0.05，分别）。与 sham 大鼠相比，生理盐水注射 BDL 大鼠的 AQP4 表达显著增加（p<0.05），但其他治疗组则不然。BDL 大鼠的膜极化得到维持。