[49] Fluorescence analysis of lipoprotein peroxidation

Publisher Summary Low-density lipoproteins (LDL) can be oxidized by transition metals, by cells including endothelial cells, smooth muscle cells, monocytes, macrophages, and fibroblasts, and also by irradiation. Low-density lipoproteins oxidatively modified by metal ions are characterized by alterations in biochemical composition because of the hydrolysis of phospholipids, a decrease in unsaturated fatty acids, and the generation of aldehydes with a concomitant increase in thiobarbituric acid-reactive substances. The compositional changes observed in ox-LDL and the role of antioxidants in the process is also presented in the chapter. The compositional changes of ox-LDL are associated with modifications in properties, for example, density, electrophoretic mobility, and fluidity, and in functions. Ultraviolet radiation also induces a strong peroxidation of the lipid content of LDL without changing the apolipoprotein moiety. Beside the biochemical modifications, ox-LDL are toxic for cultured cells. The abnormal receptor-mediated interactions between ox-LDL and cells are mainly related to the modifications of apoB structure, as the apoprotein plays a key role in receptor recognition; ox-LDL are cleared through the scavenger receptor pathway in macrophages and can induce the formation of foam cells involved in the atherogenesis pathway.