Abstract
Oxidative stress induced by a high ammonia concentration could modify protein expression in the brain. This study was undertaken in order to investigate the impact of hyperammonemia, caused by thioacetmide (TAA) in rats, on brain cortex protein expression using 2D-DIGE, and analyzing its role in the pathogenesis of HE. Hyperammonemia was induced with TAA. Ammonia and active oxidants were measured by L-glutamate dehydrogenase and dichlorodihydrofluorescein diacetate methods, respectively. Lipid peroxidation and protein oxidation biomarkers were also studied. Differential protein expression in the cortex of TAA- and control-rats was studied by 2D-DIGE. Image analysis was performed using the DeCyder? Software. Ammonia concentration in plasma and brain tissue was higher in TAA-rats compared to control-rats, 3.12 and 2.43 fold higher, respectively. Active oxidants production in TAA-rats was increased by 2.7 fold compared to control-rats. Measurements of MDA, HNE and carbonyl groups, biomarkers of lipid peroxidation and protein oxidation respectively, were found to be statistically significantly increased in TAA-rats compared to control-rats (3.16-, 2.44- and 1.95-fold, respectively), reflecting the presence of oxidative stress in the brain of TAA-rats. 2D-DIGE analysis of brain cortex protein allowed the detection of 2896 spots, however, image analysis showed no statistically significant differential protein expression between the proteins expressed in TAA- and control-rats. No statistical significant differential protein expression in the cortex of TAA-rats was observed, although oxidative stress biomarkers for lipid and proteins were higher in the brain of TAA-rats than in control-rats. These results support the idea that oxidative post-translational modifications are implicated in HE physiopathology.
Highlights
Hepatic encephalopathy (HE) is the major neurologic disorder occurring in patients with severe liver disease which presents in chronic and acute forms
Ammonia concentration in plasma and brain tissue was higher in TAA-rats compared to control-rats, 3.12 and 2.43 fold higher, respectively
Measurements of MDA, HNE and carbonyl groups, biomarkers of lipid peroxidation and protein oxidation respectively, were found to be statistically significantly increased in TAA-rats compared to control-rats (3.16, 2.44and 1.95-fold, respectively), reflecting the presence of oxidative stress in the brain of TAA-rats. 2D-differential in gel electrophoresis (2D-differential in gel electrophoresis (DIGE)) analysis of brain cortex protein allowed the detection of 2896 spots, image analysis showed no statistically significant differential protein expression between the proteins expressed in TAA- and control-rats
Summary
Hepatic encephalopathy (HE) is the major neurologic disorder occurring in patients with severe liver disease which presents in chronic and acute forms. Acute HE (acute liver failure) has a high mortality rate (80% 90%) due to the development of brain edema and increased intracranial pressure, and often presents with the abrupt onset of delirium, seizures and coma [1]. Ammonia accumulates in the brain in both acute and chronic liver failure, leading to a series of metabolic, energetic and signal transduction-related alterations [4]. It appears that other factors may contribute. Increased expression of the endothelial and inducible isoforms of nitric oxide synthase as well as heme oxygenase-1 [6] and direct oxidative biomarkers [7,8] have been reported in animal models, suggesting that oxidative/nitrosative stress plays a significant role in the pathogenesis of brain complications observed in liver failure, and in HE
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