Phenothiazines inhibit cholesteryl ester formation in J 774 monocyte-like cells

The effect of phenothiazines (trifluoperazine and chlorpromazine) on cholesteryl ester metabolism has been investigated in J 774 mouse monocyte-macrophages. The incorporation of oleic acid into cholesteryl ester and the activity of acylcoenzyme A: cholesterol-O-acyltransferase were strongly decreased in cells pretreated for 24 h with trifluoperazine or chlorpromazine. Furthermore, trifluoperazine or chlorpromazine decreased the degradation of acetylated low density lipoprotein by J 774 cells. When cell homogenates were preincubated in vitro with trifluoperazine or chlorpromazine, a marked inhibition of acylcoenzyme A: cholesterol-O-acyltransferase activity was observed. In cells incubated with acetylated low density lipoprotein loaded with radiolabeled cholesteryl-linoleate, trifluoperazine and chlorpromazine dramatically reduced the radioactivity recovered in cholesteryl esters. The radioactivity recovered in free cholesterol was also decreased, but to a lesser extent. These results suggest that phenothiazines could efficiently antagonize cholesteryl ester accumulation in macrophages by at least two different mechanisms: a reduction of modified LDL catabolism, and a direct inhibition of the enzyme acylcoenzyme A: cholesterol-O-acyltransferase.