Intralysosomal hydrolysis of cholesterol esters of varying fatty acid composition in cultured human skin fibroblasts

Abstract

Intralysosomal accumulation of low density lipoprotein-cholesterol ester was achieved during incubation of cultured human skin fibroblasts in the presence of chloroquine and the subsequent hydrolysis of the cholesterol ester was studied after removal of chloroquine. The fall in the ratio of cholesterol linoleate to cholesterol oleate during recovery from chloroquine inhibition suggested preferential hydrolysis of cholesterol linoleate. To verify this assumption, low density lipoprotein (labeled with [ 3H]cholesterol linoleate, oleate, palmitate or stearate) was sequestered in the lysosomes as described above. The rate of hydrolysis of the different cholesterol esters was determined 24 and 48 h after removal of chloroquine from the medium and was found to be similar for the four cholesterol esters studied. These findings indicate that enrichment in cholesterol oleate in atheromatous lesions does not result from preferential hydrolysis of intralysosomal cholesterol linoleate, but rather could be due to preferential utilization of oleic acid for the esterification in the cytoplasm of free cholesterol released from the lysosomal compartment.