Different apolipoprotein B breakdown patterns in models of oxidized low density lipoprotein

Low density lipoprotein (LDL) oxidation is characterized by alterations in biological properties and structure of the lipoprotein particles, including breakdown and modification of apolipoprotein B (apoB). We compared apoB br eakdown patterns in different models of minimally and extensively oxidized LDL using Western blotting techniques and several monoclonal and polyclonal antibodies. It was found that copper and endothelial cell-mediated oxidati on produced a relatively similar apoB banding pattern with progressive frag mentation of apoB during LDL oxidation, whereas malondialdehyde (MDA)- and hydroxynonenal (HNE)-modified LDL produced an aggregated apoB. It is concei vable that apoB fragments present in copper and endothelial cell oxidized L DL lead to the exposure on the lipoprotein surface of different protein epi topes than in aggregated MDA-LDL and HNE-LDL. Although all models of extens ively oxidized LDL led to increased lipid uptake in macrophages, mild degre es of oxidation interfered with LDL uptake in fibroblasts and extensively o xidized LDL impaired degradation of native LDL in fibroblasts. We suggest t hat in order to improve interpretation and comparison of results, data obta ined with various models of oxidized LDL should be compared to the simplies t and most reproducible models of 3 h and 18 h copper-oxidized LDL (apoB br eakdown) and MDA-LDL (apoB aggregation) since different models of oxidized LDL have significant differences in apoB breakdown and aggregation patterns which may affect immunological and biological properties of oxidized LDL.