Moderate Grade Hyperammonemia Induced Concordant Activation of Antioxidant Enzymes is Associated with Prevention of Oxidative Stress in the Brain Slices

• Published in: Neurochemical research Vol. 37; no. 1; pp. 171 - 181
• Main Authors: Mehrotra, Aditi, Trigun, Surendra Kumar
• Format: Journal Article
• Language: English
• Published: Boston Springer US 2012; Springer Nature B.V
• Subjects: Ammonia; Animals; Antioxidants; Biochemistry; Biomedical and Life Sciences; Biomedicine; Brain - enzymology; Brain - metabolism; Brain injury; Brain slice preparation; Catalase; Cell Biology; Electrophoresis, Polyacrylamide Gel; Enzyme Activation; Enzymes; Female; Glutathione peroxidase; glutathione reductase; Hepatic encephalopathy; hyperammonemia; Hyperammonemia - enzymology; In Vitro Techniques; Lipid Peroxidation; Liver diseases; Neurochemistry; Neurology; Neuropathology; Neurosciences; Original Paper; Oxidative Stress; oxygen free radicals; Rats; Reactive oxygen species; Reactive Oxygen Species - metabolism; Superoxide dismutase; Thiols; Moderate grade hyperammonemia; Lipid peroxidation; Oxidative stress; GSH; Antioxidant enzymes
• ISSN: 0364-3190; 1573-6903
• DOI: 10.1007/s11064-011-0596-x

Acute hyperammonemia (HA) induced oxidative stress in the brain is considered to play critical roles in the neuropathology of end stage hepatic encephalopathy (HE). Moderate grade HA led minimal/moderate type HE is more common in the patients with chronic liver failure. However, implication of oxygen free radical (
) based oxidative mechanisms remain to be defined during moderate grade HA. This article describes profiles of all the antioxidant enzymes Vis a Vis status of oxidative stress/damage in the brain slices exposed to 0.1–1 mM ammonia, reported to exist in the brain of animals with chronic liver failure and in liver cirrhotic patients. Superoxide dismutase catalyzes the first step of antioxidant mechanism and, with concerted activity of catalase, neutralizes
produced in the cells. Both these enzymes remained unchanged up to 0.2–0.3 mM ammonia, however, with significant increments (
P
 < 0.01–0.001) in the brain slices exposed to 0.5–1 mM ammonia. This was consistent with the similar pattern of production of reactive oxygen species in the brain slices. However, level of lipid peroxidation remained unchanged throughout the ammonia treatment. Synchronized activities of glutathione peroxidase and glutathione reductase regulate the level of glutathione to maintain reducing equivalents in the cells. The activities of both these enzymes also increased significantly in the brain slices exposed to 0.5–1 mM ammonia with concomitant increments in GSH/GSSG ratio and in the levels of total and protein bound thiol. The findings suggest resistance of brain cells from ammonia induced oxidative damage during moderate grade HA due to concordant activations of antioxidant enzymes.