Reduced cholesterol efflux to mildly oxidized high density lipoprotein

Mild oxidation (< 6h) of human high density lipoprotein (HDL) induced by incubation with copper ions increased its thiobarbituric acid reactivity, decreased its phospholipid content, increased its free cholesterol to phospholipid ratio and reduced its ability to mediate cholesterol efflux from cells. While protein modification did occur with further oxidation (> 12h), diminished efflux of cell cholesterol was apparent for HDL samples without increased electrophoretic mobility or altered apolipoproteins. Thus, reduced cholesterol efflux to mildly oxidized HDL may reflect changes in its lipids rather than its apoproteins. By limiting cholesterol removal from cells, any mild oxidation of HDL which might occur in vivo could contribute to cellular cholesterol accumulation.