α-Tocopherol Enrichment of High-Density Lipoproteins: Stabilization of Hydroperoxides Produced During Copper Oxidation

In the aim to study the effect of an in vitro enrichment of high-density lipoprotein (HDL) with α-tocopherol in alcoholic solution on a copper-induced peroxidation, we monitored several markers of lipid peroxidation (α-tocopherol consumption, formation of conjugated dienes and of fatty acid hydroperoxides, production of thiobarbituric acid-reactive substances) and the integrity of apolipoprotein A-I. High-density lipoproteins (1.063 < d < 1.21) with a mean of 0.58 α-tocopherol molecules per HDL particle were enriched whith α-tocopherol in alcoholic solution to obtain an average of 3.7 and 21 α-tocopherol molecules per HDL particle. HDL oxidation with 5 μM CuSO4 at 37°C resulted in the total disappearance of endogenous α-tocopherol after 2 h, but after 24 h about 19% of α-tocopherol remained in the most enriched HDL. In agreement with the tocopherol-mediated peroxidation, the formation of conjugated dienes and of fatty acid hydroperoxides was very fast and increased with α-tocopherol concentration, whereas TBARS production decreased. These results showed that α-tocopherol enrichment stabilized the production of hydroperoxides in HDL and decreased the formation of secondary oxidation products. These latter products are known for deleterious effects towards apolipoproteins. This could explain why we observed that the apolipoprotein A-I of the most enriched HDL was only slightly altered after incubation with CuSO4.Copyright © 1996 Elsevier Science Inc.