Increased 4–Hydroxynonenal Levels in Experimental Alcoholic Liver Disease: Association of Lipid Peroxidation With Liver Fibrogenesis

Abstract

The precise role of lipid peroxidation in the pathogenesis of alcoholic liver disease is still being debated. To explore the issue, this study was undertaken to investigate the status of lipid peroxidation, antioxidants and prooxidants at two discrete stages of experimental alcoholic liver disease. Male Wistar rats were intragastrically fed a high-fat diet plus ethanol for 5 or 16 wk (the duration that resulted in initiation of centrilobular liver necrosis or liver fibrosis, respectively). Lipid peroxidation was assessed in isolated microsomes and mitochondria with three parameters: malondialdehyde equivalents as determined by thiobarbituric acid assay, conjugated diene formation and 4-hydroxynonenal as a 2,4-dinitrophenylhydrazone derivative. To assess antioxidant systems, hepatic concentrations of glutathione, methionine and alpha-tocopherol were determined. The concentration of nonheme iron, a known prooxidant, was also measured. At wk 5, centrilobular liver necrosis was already evident in the ethanol-fed animals, with two- or threefold increases in plasma AST and ALT levels. At this stage, neither malondialdehyde equivalents nor conjugated diene values were elevated, and the 4-hydroxynonemal level was below 0.2 nmol/mg protein. Hepatic concentrations of methionine and alpha-tocopherol in these animals were increased two- and threefold, respectively, whereas the reduced glutathione level remained unchanged. When alcoholic liver disease had progressed to perivenular or bridging fibrosis at wk 16, all three parameters of lipid peroxidation showed consistent increases that were accompanied by significant reductions in the hepatic glutathione and methionine levels. Interestingly, the control animals pair-fed with the high-fat diet also had significantly elevated 4-hydroxynonenal levels at wk 16 compared to the wk 5 level.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ethanol and high-fat feeding on hepatic γ-glutamylcysteine synthetase subunit expression in the rat

“…1,10,11 Ethanol-induced liver damage is believed to be mediated at least in part by increased oxidative stress. 26 A decreased hepatic GSH level is a well-recognized complication of alcoholic liver disease in both humans and animals. [18][19][20][21][22]26 Our study also demonstrated this.…”

“…26 A decreased hepatic GSH level is a well-recognized complication of alcoholic liver disease in both humans and animals. [18][19][20][21][22]26 Our study also demonstrated this. The steady-state liver GSH level is determined by the rates of its synthesis, utilization (conjugation), and loss (export).…”

“…23 None of these studies examined changes in GCS subunit gene expression. Chronic ethanol administration causes oxidative stress 18,23,24,26 …”

“…23 None of these studies examined changes in GCS subunit gene expression. Chronic ethanol administration causes oxidative stress 18,23,24,26 and enhances AP-1 expression, 27 both of which up-regulate GCS subunit gene expression. In the current study, we examined the effect of intragastric ethanol and a high-fat diet feeding for 9 weeks on GCS expression and activity of important cis-acting elements.…”

“…This model was chosen because of its reproducibility in causing liver injury. 26,28 At the 9-week time point, the liver begins to exhibit centrilobular necrosis and mononuclear inflammation, and Kupffer cell cytokine expression is induced. 28,29 …”