EFFECT OF E5324, A NOVEL INHIBITOR OF ACYL-COA-CHOLESTEROL ACYLTRANSFERASE, ON CHOLESTERYL ESTER SYNTHESIS AND ACCUMULATION IN MACROPHAGES

The in vitro potencies of a novel inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), E5324 (n-butyl-N'-[2-[3-(5-ethyl-4-phenyl-1H--imidazol-1-yl)propoxy]-6-methylphenyl]urea), were studied. E5324 was found to be a potent ACAT inhibitor in microsomes from a various tissues and in cultured cell homogenate, with IC,, values in the range of 0.044 to 0.19 mu M. The kinetic study on E5324 showed that the inhibition of rat intestine ACAT was competitive with respect to oleoyl CoA. E5324 inhibited [H-3]oleate incorporation into cholesteryl [3H]oleate in phorbol ester-treated THP-1 cell lines (IC50=0.44 mu M). The rate of [H-3]oleate incorporation into phospholipids and triglycerides was not affected by E5324. In an experiment with [H-3]cholesterol as the substrate for ACAT, E5324 also inhibited [H-3]cholesteryl ester synthesis (IC50=0.41 mu M). Furthermore, E5324 prevented accumulation of both esterified and total cholesterol in acetyl low density lipoprotein-loaded THE-I cells. These results indicate that E5324 is a potent and selective ACAT inhibitor and prevents cholesteryl ester accumulation in macrophages.