Docosahexaenoic and eicosapentaenoic acids increase prion formation in neuronal cells

Clive Bate, Mourad Tayebi, Luisa Diomede, Mario Salmona, Alun Williams

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Background: The transmissible spongiform encephalopathies, otherwise known as prion diseases, occur following the conversion of the cellular prion protein (PrPC) to an alternatively folded, disease-associated isoform (PrPSc). Recent studies suggest that this conversion occurs via a cholesterol-sensitive process, as cholesterol synthesis inhibitors reduced the formation of PrPSc and delayed the clinical phase of scrapie infection. Since polyunsaturated fatty acids also reduced cellular cholesterol levels we tested their effects on PrPSc formation in three prion-infected neuronal cell lines (ScGT1, ScN2a and SMB cells). Results: We report that treatment with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) or the cholesterol synthesis inhibitor simvastatin reduced the amounts of free cholesterol in membrane extracts from prion-infected neuronal cells. Simvastatin reduced cholesterol production while DHA and EPA promoted the conversion of free cholesterol to cholesterol esters. Crucially, while simvastatin reduced PrPSc formation, both DHA and EPA significantly increased the amounts of PrPSc in these cells. Unlike simvastatin, the effects of DHA and EPA on PrPSc content were not reversed by stimulation of cholesterol synthesis with mevalonate. Treatment of ScGT1 cells with DHA and EPA also increased activation of cytoplasmic phospholipase A2 and prostaglandin E2 production. Finally, treatment of neuronal cells with DHA and EPA increased the amounts of PrPC expressed at the cell surface and significantly increased the half-life of biotinylated PrPC. Conclusion: We report that although treatment with DHA or EPA significantly reduced the free cholesterol content of prion-infected cells they significantly increased PrPSc formation in three neuronal cell lines. DHA or EPA treatment of infected cells increased activation of phospholipase A2, a key enzyme in PrPSc formation, and altered the trafficking of PrPC. PrPC expression at the cell surface, a putative site for the PrPSc formation, was significantly increased, and the rate at which PrPC was degraded was reduced. Cholesterol depletion is seen as a potential therapeutic strategy for prion diseases. However, these results indicate that a greater understanding of the precise relationship between membrane cholesterol distribution, PrPC trafficking, cell activation and PrPSc formation is required before cholesterol manipulation can be considered as a prion therapeutic.

Original languageEnglish
Article number39
JournalBMC Biology
Volume6
DOIs
Publication statusPublished - Sep 12 2008

Fingerprint

Eicosapentaenoic Acid
Docosahexaenoic Acids
Prions
prions
PrPSc proteins
eicosapentaenoic acid
docosahexaenoic acid
neurons
Cholesterol
cholesterol
acid
Simvastatin
Prion Diseases
prion diseases
Anticholesteremic Agents
cells
Phospholipases A2
phospholipase A2
prion disease
Chemical activation

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Ecology, Evolution, Behavior and Systematics
  • Plant Science
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biotechnology
  • Cell Biology
  • Developmental Biology
  • Physiology
  • Structural Biology

Cite this

Docosahexaenoic and eicosapentaenoic acids increase prion formation in neuronal cells. / Bate, Clive; Tayebi, Mourad; Diomede, Luisa; Salmona, Mario; Williams, Alun.

In: BMC Biology, Vol. 6, 39, 12.09.2008.

Research output: Contribution to journalArticle

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AU - Williams, Alun

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AB - Background: The transmissible spongiform encephalopathies, otherwise known as prion diseases, occur following the conversion of the cellular prion protein (PrPC) to an alternatively folded, disease-associated isoform (PrPSc). Recent studies suggest that this conversion occurs via a cholesterol-sensitive process, as cholesterol synthesis inhibitors reduced the formation of PrPSc and delayed the clinical phase of scrapie infection. Since polyunsaturated fatty acids also reduced cellular cholesterol levels we tested their effects on PrPSc formation in three prion-infected neuronal cell lines (ScGT1, ScN2a and SMB cells). Results: We report that treatment with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) or the cholesterol synthesis inhibitor simvastatin reduced the amounts of free cholesterol in membrane extracts from prion-infected neuronal cells. Simvastatin reduced cholesterol production while DHA and EPA promoted the conversion of free cholesterol to cholesterol esters. Crucially, while simvastatin reduced PrPSc formation, both DHA and EPA significantly increased the amounts of PrPSc in these cells. Unlike simvastatin, the effects of DHA and EPA on PrPSc content were not reversed by stimulation of cholesterol synthesis with mevalonate. Treatment of ScGT1 cells with DHA and EPA also increased activation of cytoplasmic phospholipase A2 and prostaglandin E2 production. Finally, treatment of neuronal cells with DHA and EPA increased the amounts of PrPC expressed at the cell surface and significantly increased the half-life of biotinylated PrPC. Conclusion: We report that although treatment with DHA or EPA significantly reduced the free cholesterol content of prion-infected cells they significantly increased PrPSc formation in three neuronal cell lines. DHA or EPA treatment of infected cells increased activation of phospholipase A2, a key enzyme in PrPSc formation, and altered the trafficking of PrPC. PrPC expression at the cell surface, a putative site for the PrPSc formation, was significantly increased, and the rate at which PrPC was degraded was reduced. Cholesterol depletion is seen as a potential therapeutic strategy for prion diseases. However, these results indicate that a greater understanding of the precise relationship between membrane cholesterol distribution, PrPC trafficking, cell activation and PrPSc formation is required before cholesterol manipulation can be considered as a prion therapeutic.

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