Chylomicrons induce E-selectin and VCAM-1 expression in endothelial cells.

An increased adherence of leukocytes to the vascular endothelium appears to be a crucial event in the development of atherosclerosis. The role of endothelial cell adhesion molecules is gaining increasingly interest in this context. Several studies show an influence of lipoproteins, especially low-density-lipoproteins on adhesion molecule stimulation. The aim of our study was to analyze the atherogenic potential of postprandially elevated serum triglyceride levels by investigating the impact of postprandial lipoproteins (chylomicrons (CH, isolated 4 h after a standard oral lipid load)) on the expression of E-selectin (endothelial leukocyte adhesion molecule-1, ELAM-1) and VCAM-1 (vascular cell adhesion molecule-1). In addition we used chylomicrons that had been incubated with lipoprotein lipase (50 U/ml) for 3 h (CH-LPL). The endotoxin lipopolysaccharide (LPS) served as positive control for adhesion molecule stimulation. Human umbilical vein endothelial cells (HUVEC) were incubated with the samples for 4 h and expression of E-Selectin and VCAM-1 was determined by ELISA. The expression of E-selectin was induced by LPS (530 +/- 64% compared to the basal activity (= 100%)) and by CH (342 +/- 94%); CH-LPL had no effect on E-Selectin expression. VCAM-1 expression was stimulated by LPS (395 +/- 221%) and similarly by CH-LPL (322 +/- 136%) but considerably stronger by CH (1245 +/- 324). In summary, chylomicrons induced an enhancement of the expression of both adhesion molecules, which closely resembled or even exceeded the endotoxin-induced stimulation. Interestingly, this effect was diminished or even reversed after incubation with LPL.