Advanced glycation is a major pathway for the posttranslational modification of plasma and tissue proteins. The initiating reaction is the nonenzymatic addition of sugars such as glucose to the primary amino groups of proteins, i.e., mainly to lysine residues. These "early" Schiff base and Amadori products then undergo a series of inter- and intramolecular rearrangements to produce the "late" products termed advanced glycation end products (AGEs). Incubation of LDL with glucose or glucose-6-phosphate produces AGE moieties on both the lipid and apolipoprotein B components. In addition, we tried to generate AGE-LDL by reaction with AGE-peptides (< 10 kD) obtained by enzymatic digestion of long-term glycated fibronectin as a model for connective tissue AGE-peptides. AGE-formation can be assessed by monitoring of fluorescence (370/440 nm) which is easily differentiated from the much lower autofluorescence of oxidized low density lipoproteins (oxLDL). Alternatively, AGE formation was detected by an AGE-specific ELISA using antibodies elicited in rabbits against bovine AGE-RNAse. In the present study we investigated the influence of oxidative stress on the long-term glycation of LDL and the modulation of LDL-oxidation by AGE-modification. We observed (a) that the rate of AGE formation is reduced by BHT/EDTA both on LDL and serum albumin (glycation vs. glycoxidation), (b) long-term glycated LDL is more readily oxidized than unglycated LDL, (c) oxLDL is more prone to AGE-modification, (d) AGE-modification of LDL strongly alters its epitope spectrum and (e) that aminoguanidine at higher concentrations (1-10 mM) inhibits copper-catalyzed LDL oxidation in the way of a classical antioxidant.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.