U-101033E (2,4-diaminopyrrolopyrimidine), a potent inhibitor of membrane lipid peroxidation as assessed by the production of 4-hydroxynonenal, malondialdehyde, and 4-hydroxynonenal- protein adducts

4-Hydroxy-2-nonenal (4-HNE) and malondialdehyde (MDA) are major lipid peroxidation products generated by free radical attack on membranes and appear to contribute to the cytotoxic effects of oxidative stress by a mechanism involving adduct formation with cellular proteins. In the present studies, we investigated the relationship between lipid peroxidation and eventual inactivation of plasma membrane proteins using a model system consisting of purified red blood cell membranes and Fe²⁺/EDTA. Using this system, we also analyzed the ability of a novel antioxidant, U-101033E (2,4-diaminopyrrolopyrimidine), to inhibit lipid peroxidation and associated protein damage. Our results demonstrated that significant levels of MDA and 4-HNE are generated in this model system, and that both aldehydes are capable of cross-linking membrane proteins. In addition, we used a monoclonal antibody to demonstrate the presence of 4-HNE-protein adducts in this system. The generation of 4-HNE-protein adducts closely paralleled the time course of lipid peroxidation and membrane protein cross-linking, suggesting that 4-HNE may contribute to membrane protein cross-linking. Analysis of U-101033E in this system showed that this antioxidant inhibited lipid peroxidation, prevented the appearance of 4-HNE-protein adducts, and strongly reduced membrane protein cross-linking, with an ec₅₀ of 0.5 μM. We also show that these antioxidant effects were not due to the scavenging of superoxide anion. Thus, these studies demonstrate the potential usefulness of U-101033E for treating certain disease processes where lipid peroxidation plays a role in disease pathogenesis. Copyright (C) 1998 Elsevier Science Inc.