Inhibition of cholesteryl ester formation in macrophages by azole antimycotics

Cultured macrophages take up and metabolize cholesterol-containing liposome s, resulting in massive accumulation of cholesteryl esters in the cells. Us ing this system, the effects of azole antimycotics on cholesteryl ester for mation were studied. Incubation of mouse peritoneal macrophages with ketoco nazole, miconazole, or econazole (0.1-10 mu M) resulted in concentration de pendent inhibition of cholesteryl ester synthesis from endocytosed choleste rol. IC50 values (concentration resulting in 50% inhibition) were 1.4 +/- 0 .1 mu M, 4.1 + 0.2 mu M, and 3.6 +/- 0.2 mu M for ketoconazole, miconazole, and econazole, respectively. Complete inhibition was observed with 10 mu M ketoconazole, and miconazole and econazole, each at 10 mu M, caused 70 and 75% inhibition, respectively, of cholesteryl ester synthesis. The mechanis m underlying the inhibition by ketoconazole was further studied. Ketoconazo le did not appreciably block the uptake of liposomes or formation of triacy lglycerol up to 10 mu M. Interestingly, ketoconazole suppressed only 30% of 25-hydroxycholesterol-induced endogenous cholesterol esterification under conditions where esterification of endocytosed cholesterol was completely i nhibited. Cytochemical studies with filipin-cholesterol staining revealed t hat ketoconazole induced massive accumulation of endocytosed cholesterol in macrophage phagolysosomes. These results indicate that ketoconazole inhibi ts cholesteryl ester formation in macrophages by blocking the intracellular transport of endocytosed cholesterol from lysosomes to the endoplasmic ret iculum. (C) 1999 Elsevier Science Inc.