Electronegative LDL from normolipemic subjects induces IL-8 and monocyte chemotactic protein secretion by human endothelial cells

The presence in plasma of an electronegative LDL subfraction [LDL(-)] cytot oxic for endothelial cells (ECs) has been reported. We studied the effect o f LDL(-) on the release by ECs of molecules implicated in leukocyte recruit ment [interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1)] and in the plasminogen activator inhibitor-1 (PAI-1), LDL(-), isolated by anion -exchange chromatography, differed from nonelectronegative LDL [LDL(+)] in its higher triglyceride, nonesterified fatty acid, apoprotein E and apoprot ein C-III, and sialic acid contents. No evidence of extensive oxidation was found in LDL(-); its antioxidant and thiobarbituric acid-reactive substanc es contents were similar to those of LDL(+) However, conjugated dienes were increased in LDL(-), which suggests that mild oxidation might affect these particles. LDL(-) increased, in a concentration-dependent manner, the rele ase of IL-8 and MCP-1 by ECs and was a stronger inductor of both chemokines than oxidized LDL (oxLDL) or LDL(+), PAI-1 release increased slightly in E Cs incubated with both LDL(-) and oxLDL but not with LDL(+). However, no cy totoxic effects of LDL(-) were observed on ECs, Actinomycin D inhibited the release of IL-8 and MCP-1 induced by LDL(-) and oxLDL by up to 80%, indica ting that their production is mediated by protein synthesis. Incubation of ECs with N-acetyl cysteine inhibited production of IL-8 and MCP-1 induced b y LDL(-) and oxLDL by >50%. The free radical scavenger butylated hydroxytol uene slightly inhibited the effect of oxLDL but did not modify the effect o f LDL(-). An antagonist (BN-50730) of the platelet-activating factor recept or inhibited production of both chemokines by LDL(-) and oxLDL in a concent ration-dependent manner. Our results indicate that LDL(-) shows proinflamma tory activity on ECs and may contribute to early atherosclerotic events.