EXPOSURE TO HYPERCHOLESTEROLEMIC SERUM MODIFIES THE EXPRESSION OF CYTOSKELETAL PROTEINS IN CULTURED ENDOTHELIA

Arterial endothelial layer dysfunction is considered to be one of the most important events which initiate the development of the atheroscle rotic plaque and the cell cytoskeleton plays an essential role in main taining the integrity of the endothelium exposed continuously to haemo dynamic forces. The aim of this work was to study the modifications of the cytoskeletal proteins in the vascular endothelium exposed to athe rogenic conditions. A hamster aortic endothelial cell line (HAEC) grow n on glass coverslips was exposed for 24 h to hypercholesterolemic or normal homologous serum. Upon staining with Oil Red O and examination by phase contrast and fluorescence microscopy, HAEC incubated with hyp ercholesterolemic serum appeared heavily loaded with lipid droplets th at showed a yellow autofluorescence in UV light and the general aspect of a foam cell. HAEC were incubated with: a) anti-actin serum; b) ant i-vinculin monoclonal antibody (MoAb); c) anti-or actinin MoAb, and d) anti-talin MoAb, followed by appropriate secondary antibodies coupled with FITC or rhodamine. As compared to normal HAEC, the cells exposed to hypercholesterolemic serum showed a modified pattern for actin and vinculin localization. Actin appeared as a weakly stained network aro und the nuclear zone whereas vinculin was distributed as small granule s throughout the cell cytoplasm. These experimental data suggest that in advanced atherosclerosis, some of the endothelial cytoskeletal prot eins undergo modifications which could represent one of the important factors involved in further development of the atheromatous plaque. In addition they indicate that HAEC exposed to hyper-cholesterolemic ser um could represent an in vitro working model for studying the events o ccurring in the endothelium at advanced stages of atherosclerosis.