In vitro synergistic anti-prion effect of cholesterol ester modulators

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 anti-prion activity in N2a cell lines infected with the 22L and RML prion strains. Results. In prion-infected N2a cell lines we now report increased anti-prion 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 anti-prion chlorpromazine, and with everolimus and pioglitazone associated with the anti-prion quinacrine. Comparative lipid analyses in prion-infected and non-infected 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 single-drug treatments influenced lipid syntheses, only the combined-drug treatments appeared to restore a lipid profile similar to that of untreated-uninfected cells. Conclusions. We conclude that the anti-prion synergistic effect of cholesterol ester modulators with the cholesterol metabolism interfering anti-prion drugs chlorpromazine and quinacrine may arise from the ability of combined drugs to re-establish the intracellular lipid profile of untreated-uninfected 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