Effects of LDL and HDL on morphology of and prostacyclin synthesis in cultured vascular endothelial cells

Abstract

Serum low-density lipoprotein (LDL) and high-density lipoprotein (HDL) were prepared by gradient ultracentrifugation. Cholesterol and lipid peroxide of the two lipoproteins wers determined. Human umbilical vein endothelial cells were cultured in lipoprotein-deficient serum media with LDL or HDL added. The release of 6-keto-PGF₁α in the media was measured by radioimmunoassay. The morphological changes were observed under phase-contrast and electron microscope. Endothelial cells injured by LDL (100–600 cholesterol ug/ml) showed contraction (reversible), rounding-up, lysis and detachment from the surface of culture bottle (irreversible) respectively. The cellular ultrastructure was also damaged. The severity of cell injury was correlated with the concentration of LDL-cholesterol and the time of action. The synthesis of prostacyclin (PGI₂) was stimulated by HDL, and inhibited by LDL, in culture (P< 0.01). A close relationship between morphological injury and decrease in PGI₂ synthesis induced by LDL was demonstrated. The injury of endothelial cells induced by LDL was supposed to be due to the increase in lipid peroxide. The results of this study showed that the noxious effect of LDL on morphology and PGI₂ synthesis may play an important role in thrombogenesis and atherosclerosis.

Keywords

endothelial cell / LDL / HDL / prostacyclin

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