Naslov
The impacts of LXR ligand TO901317 on amyloid-β levels and cholesterol metabolism in Niemann-Pick type C (NPC) model cells

Autori
Štefulj, Jasminka ; Malnar, Martina ; Schweinzer, Cornelia ; Košiček, Marko ; Živković, Jelena ; Panzenboeck, Ute ; Hećimović Katušić, Silva

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Alzheimer's and Dementia / - New York (NY) : Elsevier, 2011, E72-e72

Skup
Alzheimer's Association International Conference on Alzheimer's Disease

Mjesto i datum
Pariz, Francuska, 16.07.2011. - 21.07.2011

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Alzheimer's disease ; Abeta ; APP ; cholesterol efflux ; LXR ; NPC1

Sažetak
Background: Niemann-Pick type C (NPC) disease is a rare genetic disorder caused by dysfunctional mutation within NPC1 gene, leading to accumulation of unesterified cholesterol in the lysosomal compartment. Similarly to Alzheimer's disease (AD), NPC disease is characterised by progressive neurodegeneration and abnormal accumulation of amyloid-ß (Aß) peptides in the brain tissue. LXRs are transcriptional factors, activated by cholesterol derivates, that control the expression of an array of genes involved in lipid and glucose metabolism and inflammation. Administration of the synthetic LXR agonist TO901317 (TO90) to a murine model of NPC disease was shown to enhance cholesterol loss from the brain, decrease neuroinflammation and increase survival of the affected animals. Here we have investigated the effects of TO901317 on amyloid-ß (Aß) levels as well as on cholesterol pathways in NPC disease model cells. Methods: The experiments were performed on mutant Chinese hamster ovary (CHO) cells lacking NPC1 gene (NPC cells) and, in parallel, on wild-type CHO cells. For the analysis of Aß levels, cells were, prior to treatment with TO90, transiently transfected with APPsw-6myc construct. Secreted as well as soluble and insoluble intracellular Aß40 levels were measured by ELISA (Invitrogen). Total Aß40 levels were calculated as the sum of secreted and cell-associated levels and expressed as pg of Aß40 per mg of cellular protein. For measuring cholesterol efflux, cells were labelled with [3H]-cholesterol prior to treatment with TO90. Time-dependant cholesterol efflux to apolipoprotein A-I (apoA-I) or high density lipoproteins (HDL) was determined as the percentage of the radioactivity in the media relative to the total radioactivity in media and cell lysates. Cholesterol biosynthesis and esterification were analysed by labelling cells with [14C]-acetate during incubation with TO90, followed by lipid extraction, separation of lipid classes by thin layer chromatography and quantification of radioactivity by ß-counting. Results: TO90 dose-dependently reduced total Aß40 levels in both wild-type and NPC cells to similar degrees. Cholesterol efflux to apoA-I and HDL was strongly up-regulated by TO90 treatment in wild-type cells, but only marginally in NPC cells, despite the fact that the levels of cholesterol efflux protein ABCA1 were similarly up-regulated in both cell types. Furthermore, there were no differences in total levels of Aß40 between cells incubated with TO90 in the presence or the absence of cholesterol acceptor apoA-I in medium. In addition, the increase in cholesterol synthesis and decrease in cholesterol esterification in NPC as compared to wild type cells could not be corrected by treatment of the cells with TO90. Conclusions: The results indicate that TO90 may decrease accumulation of Aß40 in NPC disease and that the underlying mechanism of this action dose not relate to its effects on cholesterol homeostasis.

Izvorni jezik
Engleski

Znanstvena područja
Biologija, Temeljne medicinske znanosti

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