Antioxidant BO-653 and human macrophage-mediated LDL oxidation

Oxidation of LDL is now widely accepted to be involved in atherogenesis. Th e aim of this study was to examine the effect of BO-653, a strong radical s cavenger and antioxidant, on oxidation of LDL by human macrophages in vitro . Fifty mu g/ml LDL protein was incubated with macrophages in Ham's F10 med ium, supplemented with additional Fe2+, for up to 48 h. Then the medium was analysed by LDL agarose gel electrophoresis, the thiobarbituric acid assay and gas chromatography. In the absence of added exogenous antioxidants, af ter 24 h LDL oxidation produced 30.48 nmoles MDA equivalents/mg LDL protein and a relative electrophoretic mobility of 4.74. Linoleic acid (18 : 2), a rachidonic acid (20 : 4) and cholesterol were depleted and 7 beta-hydroxych olesterol was generated. BO-653 completely inhibited this cell-mediated oxi dation of LDL in concentrations as low as 5 mu M, being more effective than either alpha-tocopherol or probucol, which completely inhibited oxidation at 200 and 80 mu M and only partially at 80 and 8 mu M, respectively. This inhibition of cell-mediated LDL oxidation was not due to toxicity, as alpha -tocopherol, probucol and BO-653 were not toxic for the macrophages at the concentrations tested. Eighty mu M alpha-tocopherol, 8 mu M probucol and 5 mu M BO-653 significantly reduced the toxicity to the oxidising culture cau sed by LDL oxidation. The results show that in this system BO-653 is a more effective antioxidant than alpha-tocopherol or probucol.