alpha- and beta-Carotenes in low density lipoprotein are the preferred target for nitric oxide-induced oxidation

Whereas low plasma levels of carotenes are strongly associated with the ele vated risk of atherosclerosis, the reason for this is still unknown. We hyp othesized that lipoprotein oxidation in the arterial wall might selectively deplete carotenes, thus explaining the observed effects. In order to asses s this hypothesis, we incubated plasma low density lipoprotein (LDL) with d ifferent oxidants and measured the consumption of carotenes and tocopherols . We found that when LDL oxidation was induced by nitric oxide, both alpha- and beta-carotene were consumed at a significantly higher relative rate th an alpha- or gamma-tocopherol. In contrast, superoxide: peroxynitrite, hypo chlorite or transition metal ions were unable to induce selective consumpti on of carotenes in LDL. These data suggest that the decreased plasma levels of alpha- and beta-carotene frequently measured in atherosclerosis may be related to their preferred consumption by reactive nitrogen species in the arterial wall. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.