Effect of a new acyl-coenzyme A:cholesterol acyltransferase inhibitor, HL-004, on cholesterol esterification and lipid metabolism in hep G2 cells

Abstract

We studied the effect of a new acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibitor, HL-004, on intracellular cholesterol metabolism in the human hepatoma cell line Hep G2. Culture of Hep G2 cells in the presence of HL-004 at the concentrations of 10 −4 mol/L and 10 −6 mol/L resulted in pronounced inhibition of the incorporation of radio-labeled [ 3H]cholesterol (20% decrease at 10 −7 mol/L and 80% decrease at 10 −6 mol/L) and [ 14C]oleate into intracellular cholesterol ester (CE). This inhibition was dose dependent and became evident at ⩾3 hours of culture. The intracellular CE mass also began to decline at 3 hours. The secretion of radioactive CE in the non-high-density lipoprotein (HDL) fraction, but not the HDL fraction, of the culture medium was inhibited in proportion to the decrease in CE production. The free cholesterol level, however, remained unchanged both in the cells and in the medium. In contrast, the effect of the drug on the incorporation of radioactivity from [ 14C]sodium acetate into free cholesterol and from [ 3H]glycerol into triglycerides or phospholipids was not marked, suggesting no potential to exert any other significant effect on hepatic lipid metabolism. In conclusion, the present study demonstrated that HL-004 was incorporated into liver cells, specifically inhibited ACAT, and suppressed the secretion of lipoprotein CE from the liver.