The question of "increased lipid peroxidation" in plasma from hyperlipidaemic patients was investigated using an improved HPLC-based assay for thiobarbituric acid-reactive material. Levels of TBARS in healthy human controls were at or close to zero, provided that butylated hydroxytoluene was added to the sample with the TBA reagents. Levels of plasma TBARS in hyperlipidaemic patients were elevated, although the absolute levels were much lower than those reported previously in the literature.

Human monocyte-macrophages were incubated for 24 h with low-density Hpoprotein (LDL) which had been previously oxidized for varying periods up to 24 h with copper ions, in the presence or absence of DL-ot-tocopberol or probucol. The release of radioactivity from cells preloaded with tritiated adenine was used as an assay of toxicity. Toxicity of oxidized LDL increased with duration of copper oxidation and with increasing evidence of lipid oxidation, measured by assay of thiobarbituric acid-reactive substances and by gas chromatography. Oxidation and toxicity were inhibited by DL-a-tocopherol (200/tM) and probucol (50 riM).

We have investigated the cytotoxic and chemotactic potencies of malondialdehyde (MDA), hexanal, 4-hydroxyhexenal (HHE), 4-hydroxynonenal (HNE) and 4-hydroxyoctenal (HOE), which are aldehydes found in oxidised low density lipoprotein (LDL), for human monocyte-macrophages. They were toxic in the following order: hexanal

No abstract

Human monocyte-macrophage cultures were exposed to native low density lipoprotein (LDL) for up to 24 h in Ham's F10 medium and the extent of cell-mediated LDL oxidation was determined by measurement of electrophoretic mobility on agarose gels and measurement of lipids and oxidised lipids (including 7 beta-hydroxycholesterol) by GC. After an initial lag phase, which varied from 2-8 h, there was a steady increase in oxidation over 24 h. No-cell control incubations showed minimal increases in oxidation over 24 h. Significant toxicity, measured as release of radioactivity from macrophages pre-loaded with tritiated adenine, was observed in the cells when they oxidised LDL and the extent of radioactivity release correlated closely with the extent of LDL oxidation. Inhibition of oxidation using alpha-tocopherol or probucol reduced toxicity within the oxidising culture. This self-inflicted toxicity may help to explain the origin and enlargement of the lipid core of advanced atherosclerotic lesions.

No abstract