Cell and molecular biological approaches to atherosclerosis in an animal model for familial hypercholesterolemia.

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We have reported that mouse peritoneal macrophages have three of receptors for modified LDL(acetyl and oxidized LDL)(BBRC 1989 159p.1375 Arai et al). In current study,the characteristics of modified LDL receptors in rabbit peritoneal macrophages and Kupffer cells were examined. Cross competition analysis of the degradation assay between acetyl and oxidized LDL indicated that rabbit macrophages have two kinds of modified LDL receptors;one is specific for acetyl LDL,and the other recognizes both oxidized and acetyl LDL.On the other hand,rabbit Kupffer cells have receptor which recognizes oxidized LDL specifically. However,specific receptor for acetyl-LDL does not exist in rabbit Kupffer cellsIn addition to LDL,we performed oxidative modification of HDL in vitro. This modification resulted in denaturation of apo A-1 on SDS/PAGE and increased the negative charge on agarose gel electrophoresis. When incubated with macrophages-derived foam cells,native HDL caused a marked efflux of cholesteryl ester in the cells. However oxidized HDL showed a lessened effect on the decrease of cholesteryl ester in foam cells. Nevertheless it was shown that HDL from patients treated by probucol,an antioxidant,is hardly oxidized by Cu^<++>. These results indicated that apo A-1 in HDL particles is essential for efflux of cholesteryl ester in the foam cells.Finally we found that one of the components of oxidized LDL,lyso-phosphatidylcholine,induced the expression of MCP-1 mRNA in endothelial cells. We are now investigating the detail mechanism of this expression.