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Role of aquaporin-4 in the development of brain oedema in liver failure.
91 - 97.
Background 8: 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 24 h model of bacterial peritonitis. Rats from every group (except CLP) were randomised to receive intraperitoneal injections of lipopolysaccharide (LPS; 1 mg/kg) or saline, prior to termination 3 h 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). U'S 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. (C) 2010 Published by Elsevier B.V. on behalf of the European Association for the Study of the Liver.
|Title:||Role of aquaporin-4 in the development of brain oedema in liver failure|
|Keywords:||Liver failure, Aquaporin, Hepatic encephalopathy, Ammonia, Inflammation, Cerebral oedema and astrocyte, FULMINANT HEPATIC-FAILURE, GRADE CEREBRAL EDEMA, MAGNETIC-RESONANCE, INTRACRANIAL HYPERTENSION, PATHOPHYSIOLOGICAL BASIS, INDUCED HYPERAMMONEMIA, WATER TRANSPORT, TRANSGENIC MICE, RAT ASTROCYTES, GLIAL-CELLS|
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