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Alterations in expression of genes coding for key astrocytic proteins in acute liver failure

Neuroscience Research Unit, Hôpital Saint-Luc du CHUM (University of Montreal), 1058 St-Denis Street, Montreal, Quebec H2X 3J4, Canada.
Journal of Neuroscience Research (Impact Factor: 2.73). 01/2002; 66(5):967-71. DOI: 10.1002/jnr.10045
Source: PubMed

ABSTRACT Cerebral edema and hepatic encephalopathy are major complications of acute liver failure. Brain herniation caused by increased intracranial pressure as a result of cell swelling is the major cause of death in this condition. Evidence available currently suggests that the rapid accumulation of ammonia by the brain is the major cause of the central nervous system complications of acute liver failure. Increased brain ammonia may cause cell swelling via the osmotic effects of an increase in astrocytic glutamine concentrations or by inhibition of glutamate removal from brain extracellular space. Acute liver failure results in altered expression of several genes in brain, some of which code for important proteins involved in CNS function such as the glucose (GLUT-1) and glutamate (GLT-1) transporters, the astrocytic structural protein glial fibrillary acidic protein (GFAP) the "peripheral-type" benzodiazepine receptor (PTBR) and the water channel protein, aquaporin IV. Loss of expression of GLT-1 results in increased extracellular brain glutamate in acute liver failure. Experimental acute liver failure also results in post-translational modifications of the serotonin and noradrenaline transporters resulting in increased extracellular concentrations of these monoamines. Therapeutic measures currently used to prevent and treat brain edema and encephalopathy in patients with acute liver failure include mild hypothermia and the ammonia-lowering agent L-ornithine-L-aspartate.

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    • "The transport across the endothelial cell includes passive diffusion for lipid soluble and non-polar molecules; solute carriers including glucose, amino acids, and nucleosides; and receptor and adsorptive mediated transcytosis (Abbott et al., 2010). Glutamate and glucose transporters are significantly altered in brains of ALF animals (Belanger et al., 2006; Desjardins et al., 2001; Knecht et al., 1997). Increased vesicles have been observed in brain endothelial cells of animals and patients with ALF (Gove et al., 1997; Kato et al., 1992; Traber et al., 1987). "
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    • "To date, there are limited data on changes in the composition of brain endothelial cells in FHF. Certain astrocyte genes have been shown to be significantly altered in FHF [10]. Both endothelial and astrocytic glucose transporter proteins are selectively altered in brains of FHF animals [11]. "
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    • "Acute hyperammonemia causes astrocytic swelling leading to intracranial hypertension which can potentially cause brain herniation and death in severe cases. A growing number of studies have demonstrated that hyperammonemia causes changes in cerebral and, in particular, astrocytic gene expression (see Desjardins et al., 2001 for review). In contrast to the wealth of information available on astrocytes, little is known about the effects of ammonia on the function and gene expression of brain capillary endothelial cells constituting the BBB. "
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