The role of cellular oxidases and catalytic iron in the pathogenesis of ethanol-induced liver injury

Free radical generation and catalytic iron have been implicated in the pathogenesis of alcohol-induced liver injury but the source of free radicals is a subject of controversy. The mechanism of ethanol-induced liver injury was investigated in isolated hepatocytes from a rodent model of iron loading in which free radical generation was measured by the determination of alkane production (ethane and pentane). Iron loading (125mg/kg i.p.) increased hepatic non-heme iron 3-fold, increased the prooxidant activity of cytosolic ultrafiltrates 2-fold and doubled ethanol-induced alkane production. The addition of desferrioxamine (20μM), a tight chelator of iron, completely abolished alkane production indicating the importance of catalytic iron. The role of cellular oxidases as a source of ethanol induced free radicals was studied through the use of selective inhibitors. In both the presence and absence of iron loading, selective inhibition of xanthine oxidase with oxipurinol(20μM) diminished ethanol-induced alkane production 0-40%, inhibition of aldehyde oxidase with menadione (20μM) diminished alkane production 36-75%, while the inhibition of aldehyde and xanthine oxidase by feeding tungstate (100mg/kg/day) virtually abolished alkane production. Addition of acetaldehyde(50μM) to hepatocytes generated alkanes at rates comparable to those achieved with ethanol indicating the importance of acetaldehyde metabolism in free radical generation. The cellular oxidases (aldehyde and xanthine oxidase) along with catalytic iron play a fundamental role in the pathogenesis of free radical injury due to ethanol.