Cholesterol stimulation of HDL binding to human endothelial cells EAhy 926 and skin fibroblasts: evidence for a mechanism independent of cellular metabolism

The properties of the HDL binding site on the permanent human cell line EAhy 926 were studied. This cell line presents with highly differentiated functions of vascular endothelium. EAhy 926 cells possess HDL3 saturable binding sites with a Kd of about 20 micrograms/ml, which were up-regulated by cholesterol and were pronase- and EDTA-insensitive. Furthermore, HDL3 promoted cholesterol efflux from EAhy 926 cells in a dose-dependent manner. Thus, the HDL-binding site in EAhy 926 cells is similar to that present in fibroblasts, smooth muscle cells and endothelial cells. Up-regulation of HDL binding by cholesterol did not require de novo synthesis of HDL 'receptor' protein, as shown by the lack of effect of cycloheximide and alpha-amanitin and also occurred in fixed, non-living cells. Similar results were obtained using human skin fibroblasts. From these data we conclude that: (a) EAhy 926 cells are a good model for studying the HDL interaction with endothelial cells; (b) a mechanism independent of cellular metabolism is involved in the cholesterol-mediated up-regulation of HDL binding sites in EAhy 926 cells and human skin fibroblasts