Diphenylhexatriene as a fluorescent probe for monitoring low density lipoprotein peroxidation.

The use of the fluorescent probe diphenylhexatriene (DPH) for monitoring low density lipoprotein (LDL) peroxidation has been investigated. The DPH incorporation into LDL results in a high fluorescence signal which decreases with time after addition of cupric ions. A strong correlation was found between the decay of the DPH fluorescence signal and the appearance of the thiobarbituric reactive substances (TBARS). HPLC and spectrofluorometric analyses demonstrated that DPH is destroyed during the time course of the copper-induced LDL peroxidation. The decrease in DPH fluorescent signal is prevented by addition of EDTA, vitamin E and drugs which protect LDL against peroxidation such as probucol or calcium antagonists. The high fluorescence of DPH allows the use of very small quantities of LDL (less than 5 micrograms/ml LDL protein). We thus suggest that DPH could be of use for continuous monitoring of LDL autooxidation, especially for the in vitro testing of the protective effect of antioxidant compounds.

Glucose-enriched medium enhances cell-mediated low density lipoprotein peroxidation.

A 1 week preculture of endothelial or smooth muscle cells in glucose-enriched (11.2 to 44.8 mM) media resulted in a marked enhancement of the subsequent ability of cells to oxidize low density lipoprotein, as assessed by the lipid peroxidation end product and conjugated diene content of the particle, its relative electrophoretic mobility and its degradation by macrophages. This phenomenon is correlated to a marked stimulation of superoxide anion secretion by cells. Such an effect of elevated glucose concentration on cell-induced LDL oxidative modification could be involved in the increased occurrence of atherosclerotic lesions in diabetes mellitus.