Invited Speaker

Pharmacologic-Induced Cholesterol Homeostasis Affects Prion Generation in a Synergistic Manner
C.D. Orru, M.D. Cannas, S. Vascellari, C. Abete, F. Angius, P.L. Cocco1, C. Norfo, A. Mandas, P. La Colla, S. Dessi, A. Pani.
Italy

Background: In our previous work we reported abnormal accumulation of cholesterol esters in brain biopsies and ex vivo skin fibroblasts from sheep susceptible-to or suffering-from scrapie, as well as in prion-infected N2a cells, which showed reduced prion generation following drug treatments with cholesterol ester modulators, altogether indicating a direct relationship between susceptibility to prion infection/replication and altered cholesterol homeostasis.

Methods: Expression of genes and gene products in sheep samples was determined by RT-PCR and Western blotting. Lipid analysis in N2a cells was performed by lipid staining with Oil Red-O, Nile Red and filipin, and by lipid separation in TLC and HPLC. Prion detection was performed by Western and dot blot procedure.

Results: Accumulation of cholesterol esters in brains and skin fibroblasts from susceptible/infected sheep was accompanied by altered expression levels of ACAT1 (up-regulated) and Cav-1 (down-regulated), and of cellular PrP itself (up-regulated). Lipid analysis in N2a cells revealed a general derangement of content and distribution of most intracellular lipids in the prion-infected cells; i.e. cholesterol esters, free cholesterol, phospholipids, and triglycerides. Drug combinations of cholesterol/cholesterol ester modulators capable of restoring lipid profile similar to uninfected-untreated N2a cells, showed strong synergistic anti-prion effect.

Conclusions: We conclude that prion-infected cells display alteration of all lipid classes and that pharmacologic induced homeostasis can represent a more successful way to hamper prion generation than drug treatments lowering free cholesterol per se (i.e. statins). Notably, these data further support our hypothesis that a systemic alteration of cholesterol homeostasis -involving central and peripheral cells- accompany prion infection, and point to cholesterol ester accumulation in peripheral cells as an easy-to-detect lipid hallmark indicative of increased susceptibility to develop prion disease, and to cholesterol/cholesterol ester metabolism as successful targets in combinatorial therapies.