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 cytokine-induced expression of vascular cell adhesion molecule 1 (VCAM-1) in human umbilical vein endothelial cells (HUVECs) was investigated. PC species containing palmitoyl- in the sn-1 position and palmitoyl- (DPPC), arachidonyl- (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 micrometer. At this concentration 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 of the rHDL to HUVECs. The same hierarchy of inhibitory activity was observed when these PC species were presented to the cells as SUVs but only when the SUVs also contained an antioxidant. It was concluded that rHDL PC is responsible for their inhibitory activity and that this varies widely with different PC species.