phalloidine and Arteriosclerosis

Endothelial cell dysfunction has been implicated in the development of atherosclerosis. Of vital importance to the maintenance of endothelial cell integrity is the preservation of membrane functional and structural properties, such as membrane fluidity. The aim of this study was to develop a model for studying the relationship between endothelial cell integrity and membrane fluidity alterations in a well-defined cell culture setting. Alterations in membrane fluidity were assessed using electron spin resonance after labeling endothelial cells with the lipid-specific spin labels, CAT-16 and 12-nitroxide stearic acid. Endothelial cells were exposed to various 18-carbon fatty acids, i.e. stearic (18:0), oleic (18:1), linoleic (18:2), or linolenic (18:3), in addition to lipolyzed HDL (L-HDL) and benzyl alcohol. Membrane phospholipid fatty acid composition of endothelial cells supplemented with these fatty acids was analyzed using gas chromatography. All fatty acids, except 18:0, decreased membrane fluidity. A relationship between membrane fluidity and fatty acid compositional alterations in cellular phospholipids was observed. In particular, the arachidonic acid content decreased following exposure to 18:1, 18:2, or 18:3. Exposure of endothelial cells to L-HDL, lipoprotein particles which contain high levels of 18:1 and 18:2, also decreased membrane fluidity. The stabilization of cytoskeletal actin filaments by phalloidin partially prevented 18:2-induced increases in albumin transfer, thus implicating a cytoskeletal involvement in the 18:2-induced membrane fluidity changes involved in endothelial cell dysfunction. The present study shows that the exposure of endothelial cells to various lipids causes membrane fluidity alterations which may contribute to endothelial cell dysfunction and atherosclerosis.

Topics: Animals; Arteriosclerosis; Benzyl Alcohol; Benzyl Alcohols; Cell Membrane; Cells, Cultured; Electron Spin Resonance Spectroscopy; Endothelium, Vascular; Fatty Acids; Lipoproteins, HDL; Membrane Fluidity; Molecular Structure; Phalloidine; Phospholipids; Pulmonary Artery; Spin Labels; Swine; Vitamin E

Endothelial injury or dysfunction has long been postulated to promote atherogenesis, but structural alterations of endothelium in atherosclerosis have remained obscure. We report the common occurrence of actin-containing stress fibers, stainable by rhodamine-phalloidin, in endothelium overlying atherosclerotic lesions in cholesterol-fed rabbits. Nonlesioned areas in the same aortas showed normal endothelium with minimal development of stress fibers, which was no different from the appearance of endothelium in chow-fed rabbits. Microtubule organization revealed by immunofluorescence appeared normal in all areas. The development of stress fibers may be related to an altered substratum for endothelial attachment. This study provided no evidence to relate stress fiber formation with lesion initiation, but an association with well-developed foam cell lesions was evident.

Topics: Animals; Aorta, Thoracic; Aortic Diseases; Arteriosclerosis; Cytoskeleton; Diet, Atherogenic; Endothelium, Vascular; Fluorescent Dyes; Foam Cells; Phalloidine; Rabbits; Stress, Physiological