Strong synergistic anti-peroxidative effects of HDL3 and ascorbic acid against copper-catalyzed LDL peroxidation

The aim of this study was to investigate the effects of high density lipoprotein 3 (HDL3) and ascorbic acid (AsA) in combination on copper-catalyzed low density lipoprotein (LDL) peroxidation. LDL and HDL3 were isolated from sera of healthy volunteers. LDL protein, 200 microg/ml, was incubated in phosphate-buffered saline (PBS) containing 2.5 microM CuSO4 in the absence or presence of AsA, with HDL3 protein alone, or with coincubation of HDL3, 200 microg/ml, and AsA, 20 microg/ml, at 37 degrees C for up to 24 h. As a control, the same amount of control LDL protein was added to PBS. The protective effects of the HDL3 and AsA were examined by both electrophoresis and determination of the lipid hydroperoxide (LPO) level in each sample. The concentration of AsA was also measured in samples containing AsA. The coincubation of HDL3 and AsA exerts more powerful anti-peroxidative effects against copper-catalyzed LDL peroxidation, than either of these agents alone. In addition, AsA was retained in the media by the addition of HDL3. The findings suggest that there are strong synergistic anti-peroxidative effects of HDL3 and AsA and these two may act in concert in vivo to inhibit LDL peroxidation and thus exert an anti-atherosclerotic effect.