Selective inhibition of acyl coenzyme A:Cholesterol acyltransferase by compound 58-035

Compound 58-035 (3-[decyldimethylsily]-N-[2-(4-methylphenyl)-1-phenylethyl]propanamide) has been found to inhibit the accumulation of cholesteryl esters in both rat hepatoma (Fu5AH) cells and arterial smooth muscle cells in culture. To explore the specificity of 58-035, we have studied the esterification of cholesterol, retinol, and glycerides by the Fu5AH cell and by isolated membranes. Exposure of Fu5AH to cholesterol/phospholipid dispersions and 58-035 (> 100 ng/ml) for 24 h resulted in greater than 95% inhibition of cholesterol esterification while cellular free cholesterol increased slightly. Inhibition was also rapid; incorporation of [³H]oleate into cholesteryl [³H]oleate equaled only 12% of control value after 30 min with 58-035 at 5 μg/ml. In contrast, there was no decrease in [³H]oleate incorporation into phospholipids or diglycerides, nor was the esterification of [³H]retinol inhibited by 58-035. In microsomal fractions acyl-CoA:cholesterol acyltransferase could be inhibited completely by 58-035, while activities of acyl-CoA: retinol acyltransferase and triglyceride synthesis proceeded at 75-100% of control values. These observations that 58-035 is highly selective allow the inference that acyl-CoA:cholesterol acyltransferase is a separate microsomal enzyme whose activity can be modulated independently from acyl-CoA:retinol acyltransferase and other cellular acyltransferases.