Apo-Lipoprotein Localization in Human Atherosclerotic Arteries

Abstract

A study documenting the localization in human arteries of apoproteins from human plasma high density (HDL), low density (LDL), and very low density (VLDL) lipoproteins was undertaken in light of their possible roles in the pathogenesis and regression of the atherosclerotic process in man. Apo A-I from HDL, apo B from LDL, apo C-III from VLDL were all localized by immunohistochemical techniques to generally the same areas of atherosclerotic lesions. These consisted of certain bands of collagen and elastic fibers in fatty streaks and fibrous plaques, and extracellular pools of neutral lipid in fibrous plaques. Apoproteins were also occasionally present in areas of diffuse intimal thickening in coronary arteries. Extensiveness and frequency of appearance of apo B in atherosclerotic lesions was greatest in type II hyperlipoproteinemics, thus correlating with the plasma apo B levels. Employing an immuno-peroxidase procedure, apo B was localized ultra-structurally in atherosclerotic lesions to the outer surface of spheres ranging in diameter between 250 and 700 A. These spheres, localized predominantly in lipid cores and between collagen bands, were also seen in negatively-stained preparations of arterial extracts which also reacted positively against anti-apo B, suggesting that the spheres may represent native LDL and VLDL. The superimposed localization of apo A-I, apo B, and apo C-III in atherosclerotic lesions suggests that a specific interaction exists between certain lesion components and these apoproteins.