beta-Carotene inhibits the oxidative modification of low-density lipoprotein
1991
Jialal, I. | Norkus, E.P. | Cristol, L. | Grundy, S.M.
Several lines of evidence indicate that oxidized LDL (Ox-LDL) may promote atherogenesis. Hence, the role of antioxidants in the prevention of LDL oxidation needs to be determined. beta-Carotene, in addition to being an efficient quencher of singlet oxygen, can also function as a radical-trapping antioxidant. Since previous studies have failed to show that beta-carotene inhibits LDL oxidation, we re-examined its effect on the oxidative modification of LDL. For these studies, LDL was oxidized in both a cell-free (2.5 micromolar Cu2+ in PBS) and a cellular system (human monocyte macrophages in Ham's F-10 medium). beta-carotene inhibited the oxidative modification of LDL in both systems as evidenced by a decrease in the lipid peroxide content (thiobarbituric-acid-reacting substances activity), the negative charge of LDL electrophoretic mobility) and the formation of conjugated dienes. By inhibiting LDL oxidation, beta-carotene substantially decreased its degradation by macrophages. beta-carotene (2 micromolar) was more potent than alpha-tocopherol (40 micromolar) in inhibiting LDL oxidation. Thus, beta-carotene, like ascorbate and alpha-tocopherol, inhibits LDL oxidation and might have an important role in the prevention of atherosclerosis.
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