Modifications of Vimentin Filament Architecture and Vimentin–Nuclear Interactions by Cholesterol Oxides in 73/73 Endothelial Cells

Abstract

Among the different targets of the cytodamaging effects of cholesterol oxides in endothelial cells, cytoskeleton is one of the most relevant, due to the large variety of biological events controlled by this subcellular structure. The modifications of the intermediate filament network caused by three cholesterol oxides (cholestane-3β,5α,6β-triol, CH, 7-keto-cholesterol, KC, and 25-OH-cholesterol, COH) was investigated in the endothelial cell line 73/73 using immunofluorescence and laser scanner confocal microscopy. All three cholesterol oxides promoted a redistribution of vimentin filaments that took place well before cell detachment and the occurrence of any detectable sign of cell death. CH-induced alterations were characterized by the polarization of vimentin to the edges of the cell and a concomitant destruction of its interaction with the nucleus. In KC-treated cells, vimentin filaments appeared cross-linked and formed a sort of circular network ring between the nucleus and the cell periphery. COH promoted the aggregation of vimentin filaments in thick and irregular bundles that delimited apparently empty regions. All these changes occurred independently of gross modifications in microtubule organization, which was generally retained except for the appearance of immunoreactive tubulin spots throughout the cytoplasm. These results indicate that the organization of the intermediate-size filament protein vimentin is markedly affected by cholesterol oxides. The different rearrangements caused by CH, KC, and COH may derive from different pathobiochemical processes triggered by these compounds.