In vitro low-density lipoprotein oxidation by copper or OH/O2−: new features on carbonylation and fragmentation of apolipoprotein B during the lag phase

The aim of our study was to evaluate the carbonylation and the carbonylated fragmentation of apolipoprotein B upon low-density lipoprotein (LDL) oxidation induced in vitro by copper and OH/O2− free radicals generated by γ-radiolysis. Therefore, we developed a very sensitive Western blot immunoassay using 2,4-dinitrophenylhydrazine which allows the revelation of the apolipoprotein B carbonylation and its carbonylated fragmentation. The main results of this study show that (i) apolipoprotein B carboylation is present during the lag phase of LDL oxidation in the two oxidative processes and (ii) apolipoprotein B carbonylated fragmentation was not detected during the lag phase of copper-oxidized LDL but was detected during the propagation phase. By contrast, apolipoprotein B carbonylated fragmentation was detected in the lag phase of OH/O2− oxidized LDL.