Phospholipid composition of reconstituted high density lipoproteins influences their ability to inhibit endothelial cell adhesion molecule expression

The ability of different phosphatidylcholine (PC) species to inhibit cytoki ne-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in huma n umbilical vein endothelial cells (](HUVECs) was investigated. PC species con taining palmitoyl- in the sn-1 position and palmitoyl- (DPPC), arachido nyl- (PAPC), linoleoyl- (PLPC) or oleoyl- (POPC) in the sn-2 position were compared. These PC species were studied as components of reconstituted high density lipoproteins (rHDL) (containing apolipoprotein A-I [apoA-I] as the sole protein) or as small unilamellar vesicles (SUVs), The rHDL containing PLPC and PAPC inhibited VCAM-1 expression in activated HUVECs by 95 and 70 %, respectively, at an apoA-I concentration of 16 mu M. At this concentrati on of apoA-I, POPC rHDL inhibited by only 16% and DPPC rHDL did not inhibit at all. These differences could not be explained by differential binding o f the rHDL to HUVECs. The same hierarchy of inhibitory activity was observe d when these PC species were presented to the cells as SUVs but only when t he SUVs also contained an;antioxidant.jlr It was concluded that rHDL PC is responsible for their inhibitory activity and that this varies widely with different PC species.