Dilinoleoylphosphatidylcholine protects human low density lipoproteins against oxidation

LDL oxidation may promote atherosclerosis. We found that polyenyphosphatidy lcholine (PPC), a mixture of polyunsaturated phospholipids extracted from s oybeans, has antioxidant effects in in vivo models of oxidative stress. To assess whether components of PPC affect the in vitro oxidizability of LDL, plasma from 15 healthy volunteers was incubated with 10 mu M of either dili noleoyl-, palmitoyl-linoleoyl-, linoleoyl-palmitoyl- or distearoyl-phosphat idylcholine as well as 10 mu M and 1 mM alpha-tocopherol. LDL oxidation was initiated with 5 mu M Cu2+ sulfate and monitored by conjugated diene produ ction, or with 2,2'-azobis (2-amidinopropane) dihydrochloride. a free radic al generator, and monitored by O-2 consumption. After addition of Cu2+, the lag phase (indicative of resistance of LDL to oxidation) was longer (140% of controls; P < 0.001) for LDL incubated with dilinoleoyl-. but not with t he other phosphatidylcholine species. This effect was similar to that of 1 mM alpha-tocopherol (135%,). After addition of 2,2'-azobis (2-amidinopropan e) dihydrochloride, the inhibition time (also reflecting the antioxidant co ntent of LDL) was prolonged (P<0.001) for alpha-tocopherol (206%) and dilin oleoyl-( 188%), but not for distearoyl-phosphatidyl-choline. Thus, dilinole oyl-phosphatidylcholine (the main component of PPC) protects against LDL ox idation, a possible mechanism for its reported anti-atherosclerosis effects . (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.