Journal of Lipid Research, Vol 30, 885-891, Copyright © 1989 by Lipid Research, Inc.
An immunochemical marker of low density lipoprotein oxidation
Z Zawadzki, RW Milne and YL Marcel
Laboratory of Lipoprotein Metabolism, Clinical Research Institute, Montreal, Canada.
Using monoclonal antibodies against apolipoprotein B (apoB) we studied
changes in apoB immunoreactivity during copper ion-mediated oxidation of
human low density lipoprotein (LDL). The radioimmunoassay experiments
demonstrated the decrease of immunoreactivity of three different epitopes
of apoB located in different parts of the protein; at the same time the
immunoreactivity of another epitope, previously mapped to the C-terminal 20
amino acids of apoB increased markedly during the first 6 h of LDL
oxidation and diminished gradually upon prolonged incubation with copper
ions. The fate of LDL during oxidation was also monitored using
electrophoretic techniques combined with immunodetection. These experiments
showed a rapid fragmentation and disappearance of immunoreactive apoB. They
also indicated that the diminishing LDL immunoreactivity detectable during
oxidation is associated with apoB fragments still attached to the lipid
core. The changes in apoB immunoreactivity during Cu2+ treatment of LDL are
similar to those observed upon LDL aging. Therefore, it appears that the
enhancement of immunoreactivity of the C-terminus of apoB is a general
phenomenon associated with various kinds of oxidative modifications of LDL.