FORMATION OF LIVER MICROSOMAL MDA-PROTEIN ADDUCTS IN MICE WITH CHRONIC DIETARY IRON OVERLOAD

Lipid peroxidation has been proposed to be a major mechanism involved in the pathophysiology of hepatic iron overload. Hepatic microsomal li pid peroxidation has been demonstrated in animals with dietary iron ov erload, and major products of lipid peroxidation with known cytotoxici ty, such as malondialdehyde (MDA): may be involved in iron-induced hep atocellular injury by covalent binding to microsomal proteins. This in vestigation examined whether DB4/2Ibg mice fed a diet enriched with fe rrocene-iron for 16 weeks, results in hepatic lipid peroxidation, and if liver microsomes contain proteins adducted by MDA. Chronic iron fee ding to mice resulted in a severe hepatic iron overload with hepatic s tores of iron 12-fold greater than those measured in control mice and a three-fold increase in hepatic concentrations of MDA, indicating the occurrence of iron-induced lipid peroxidation in vivo. Hepatic collag en content was increased by over three-fold (p <0.05) in iron-fed mice as compared to control animals, suggesting increased fibrogenesis. Us ing rabbit antiserum specific for MDA-amine protein adducts and immuno precipitation-western blotting, we documented formation of 10 liver mi crosomal proteins adducted by MDA in iron overload mice (approximate m olecular weights; 214, 140, 129, 121. 103, 83, 62, 60, 48, and 43-kD). Control mice did not exhibit positive immunostaining for these protei n adducts. The incubation of synthetic MDA with liver microsomes isola ted from untreated mice demonstrated formation of MDA-adducted protein s with molecular weights comparable to those detected following in viv o iron overload. The data from this animal study are the first to demo nstrate that lipid-derived aldehydes produced from hepatic iron overlo ad in vivo, covalently bind and hence, chemically modify numerous prot eins in microsomes. These data suggest that MDA modified proteins in m icrosomes may play a role in a sequence of events that lead to cell in jury during metal-induced liver damage. (C) 1998 Elsevier Science irel and Ltd. All rights reserved.