In vitro synergistic anti-prion effect of cholesterol ester modulators in combination with chlorpromazine and quinacrine

Background. Our studies on the role of cholesterol in prion infection/replication showed that brains and peripheral cells of sheep susceptible to or suffering from Scrapie were characterized by an altered cholesterol homeostasis compared to animals with a scrapie resistant genotype, and that drugs influencing cholesterol esterification were endowed with selective antiprion activity in N2a cell lines infected with the 22L and RML prion strains. Results. In prioninfected N2a cell lines we now report increased antiprion activity of dual drug combinations consisting of cholesterol ester modulators associated with prion inhibitors Synergism was obtained with the cholesterol ester modulators everolimus, pioglitazone, progesterone, and verapamil associated with the antiprion chlorpromazine, and with everolimus and pioglitazone associated with the antiprion quinacrine. Comparative lipid analyses in prioninfected and noninfected N2a cells by colorimetric, enzymatic, and chemical means, clearly demonstrated a derangement of type and distribution of cholesterol esters, free cholesterol, and triglycerides in the infected N2a cells. Although singledrug treatments influenced lipid syntheses, only the combineddrug treatments appeared to restore a lipid profile similar to that of untreateduninfected cells. Conclusions. We conclude that the antiprion synergistic effect of cholesterol ester modulators with the cholesterol metabolism interfering antiprion drugs chlorpromazine and quinacrine may arise from the ability of combined drugs to reestablish the intracellular lipid profile of untreateduninfected cells. Overall, these data suggest that inhibition of prion replication can be readily potentiated by combinatorial drug treatments, and that steps of cholesterol/cholesterol ester metabolism may represent suitable targets.