An overt increased liver lipid peroxidation associated with Liver lipid peroxidation, nonheme iron, antioxidants, alcohol-dependent liver disease 4,5 had been described in the and protein oxidation were investigated in experimental intragastric rat feeding model. The high blood alcohol levels alcohol-induced liver disease in the rat. Wistar male rats achieved in this model as well as the rich unsaturated fat were intragastrically and continuously infused for 4 diet appear important in determining the susceptibility to weeks with a high-fat diet plus an ethanol or an isocafree-radical-related reactions and to alcohol-dependent liver loric amount of dextrose, maintaining a high blood alcodisease. [6][7][8] However, membranous lipids are not the sole tarhol level (200-300 mg%). This model induced fatty liver, gets of an ethanol-induced oxidative stress in the liver. It is spotty necrosis, and focal inflammation. This pathology well documented that cellular proteins may also be disturbed was associated with an enhanced lipid peroxidation and by free radicals. Remmer et al. 9 reported that the primary a decrease in the major antioxidant factors. Hepatic atarget of the oxygen-radical attack promoted by ethanol is tocopherol and glutathione concentrations were signifirepresented by cellular proteins and not by lipids. Key metacantly decreased in ethanol-fed rats. Glutathione peroxibolic enzymes may be involved among the proteins damaged dase (GPx) was also decreased, whereas glutathione by free-radical attack. Fucci et al. 10 showed that microsomal S-transferase (GST) was unaffected. The nonheme iron mixed function oxidation reactions involving cytochrome level was significantly decreased. Protein oxidation was P450 inactivate 10 enzymes playing a key role in metabolism. assessed through three parameters: protein thiols, pro-Among these enzymes, glutamine synthetase (GS) is a key tein carbonyl groups, and the activity of glutamine synenzyme in nitrogen metabolism and is highly sensitive to thetase (GS), a centrilobular enzyme particularly susfree-radical attack. Its exclusive localization in the periveceptible to free-radical-mediated damage. Ethanol-fed nous area of the liver lobule 11 could favor its oxidative modifirats had decreased protein thiol concentrations and recation through reactive oxygen species generated by CYP duced GS activity, together with increased protein car-2E1, which is markedly induced in the perivenous cells by bonyls. A significant correlation between GS activity ethanol treatment in the intragastric feeding model. 12 and the pathological score was observed. This study con-
The present study was undertaken to determine the ethafirms the ethanol-related increase in lipid peroxidation nol effects on lipid peroxidation and on some cellular antioxiand shows that ethanol impairs the hepatic antioxidant dants represented by a-tocopherol, a main chain-breaking potential. Furthermore, evidence of oxidative protein membranous antioxidant, as well as by glutathione and gludamage is given, including decreased activity of a key tathione-related enzymes. For the assessment of oxidative enzyme of ammonia metabolism. These protein disturprotein damage, the levels of protein thiol and protein carbances may contribute to the pathogenesis of the obbonyl, as well as GS activities, were measured. served liver damage. (HEPATOLOGY 1997;25:351-355.)
MATERIALS AND METHODS
Among the mechanisms implicated in alcohol-dependent
Chemicals. All chemicals (analytical grade) were purchased from liver disease, free-radical generation and lipid peroxidation Sigma Chemical Co. (St. Louis, MO), except high-performance liquid appear to play an important role. chromatography solvents (high-performance liquid chromatography
The voluntary ingestion of a liquid ethanol diet by rats grade), which were from Interchim (Paris, France). fails to induce progressive alcoholic liver injury beyond the Animals and Diet. Male Wistar rats (230-250 g body weight) were fatty liver stage, 1 although ethanol administration induces purchased from Charles River (Hollister, CA). The permanent intra- cytochrome P450 (CYP) 2E1 and favors microsomal free-radigastric cannula was implanted under sodium thiopental ketamine cal generation. However, enhanced liver lipid peroxidation is anesthesia as previously reported. 12 The rats were maintained ac- cording to the Guidelines of Animal Care described by the National not a constant feature after long-term alcohol consumption. 2,3 Academy of Sciences and published by the National Institutes of This may be due to adaptative processes that result in an Health. Rats were intragastrically infused with a high-fat diet plus enhanced antioxidant defense.
an ethanol or isocaloric amount of dextrose as previously described. 13,14 In these diets, corn oil contributed to 30% to 40% of the total calories. Infusion of the diet and ethanol was continued for 4 weeks. The amount of ethanol was initially started at 8 g/kg per day and gradually increased as tolerance developed. Blood alcohol levels Abbreviations: CYP, cytochrome P450; GS, glutamine synthetase; GPx, glutathione perwere maintained between 200 and 300 mg/dL as monitored by the oxidase; GST, glutathione S-transferase.