alpha-(4-pyridyl-1-oxide)-n-tert-butylnitrone and Reperfusion-Injury

These experiments were designed to determine whether green tea extract (GTE), which contains polyphenolic free radical scavengers, prevents ischemia-reperfusion injury to the liver. Rats were fed a powdered diet containing 0-0.3% GTE starting 5 days before hepatic warm ischemia and reperfusion. Free radicals in bile were trapped with the spin-trapping reagent alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) and measured using electron spin resonance spectroscopy. Hepatic ischemia-reperfusion increased transaminase release and caused pathological changes including focal necrosis and hepatic leukocyte infiltration in the liver. Transaminase release was diminished by over 85% and pathological changes were almost totally blocked by 0.1% dietary GTE. Ischemia-reperfusion increased 4-POBN/radical adducts in bile nearly twofold, an effect largely blocked by GTE. Epicatechin, one of the major green tea polyphenols, gave similar protection as GTE. In addition, hepatic ischemia-reperfusion activated NF-kappa B and increased TNF-alpha mRNA and protein expression. These effects were all blocked by GTE. Taken together, these results demonstrate that GTE scavenges free radicals in the liver after ischemiareoxygenation, thus preventing formation of toxic cytokines. Therefore, GTE could prove to be effective in decreasing hepatic injury in disease states where ischemia-reperfusion occurs.

Topics: Animals; Aspartate Aminotransferases; Bile; Catechin; Electron Spin Resonance Spectroscopy; Flavonoids; Free Radical Scavengers; Free Radicals; Leukocytes; Liver; Male; Necrosis; NF-kappa B; Nitrogen Oxides; Oxidative Stress; Peroxidase; Phenols; Plant Extracts; Polymers; Pyridines; Rats; Rats, Sprague-Dawley; Reperfusion Injury; RNA, Messenger; Tea; Tumor Necrosis Factor-alpha

Free radical generation and release from the cerebral hemispheres of rats subjected to four vessel occlusion followed by reperfusion was monitored using a cortical cup technique in conjunction with the spin-trapping agent alpha(4-pyridyl-1-oxide)-N-tert-butylnitrone (POBN). Electron spin resonance (ESR) was used to detect the presence of free radical adducts of POBN in the cortical superfusates. 30 min of ischemia plus reperfusion resulted in the release of .OH radical adducts during the period of ischemia and, especially, during the initial phases of reperfusion. No radical adducts were detectable 90 min after the onset of reperfusion. Pretreatment with the xanthine oxidase inhibitor, oxypurinol (40 mg/kg i.p.), virtually abolished free radical formation and release. The results of this study are consistent with earlier evidence of free radical formation during ischemia/reperfusion and suggest that the cerebroprotective actions of oxypurinol may be related to its ability to prevent the cascade of free radical generation.

Topics: Animals; Cerebral Cortex; Electron Spin Resonance Spectroscopy; Hydroxyl Radical; Male; Nitrogen Oxides; Oxypurinol; Pyridines; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Spin Labels