7-Ketocholesterol Incorporation into Sphingolipid/Cholesterol-enriched (Lipid Raft) Domains Is Impaired by Vitamin E: a specific role for alpha-tocopherol with consequences on cell death

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Royer, Marie-Charlotte | Lemaire-Ewing, Stéphanie | Desrumaux, Catherine, M | Monier, Serge | Pais de Barros, Jean-Paul | Athias, Anne | Néel, Dominique | Lagrost, Laurent

Edité par CCSD ; American Society for Biochemistry and Molecular Biology -

International audience. Cholesterol oxides, in particular 7-ketocholesterol, are proatherogenic compounds that induce cell death in the vascular wall when localized in lipid raft domains of the cell membrane. Deleterious effects of 7-ketocholesterol can be prevented by vitamin E, but the molecular mechanism involved is unclear. In this study, unlike gamma-tocopherol, the alpha-tocopherol vitamin E form was found to prevent 7-ketocholesterol-mediated apoptosis of A7R5 smooth muscle cells. To be operative, alpha-tocopherol needed to be added to the cells before 7-ketocholesterol, and its anti-apoptotic effect was reduced and even suppressed when added together or after 7-ketocholesterol, respectively. Both pre- and co-treatment of the cells with alpha-tocopherol resulted in the redistribution of 7-ketocholesterol out of the sphingolipid/cholesterol-enriched (lipid raft) domains. In turn, fewer amounts of alpha-tocopherol associated with lipid rafts on 7-ketocholesterol-pretreated cells compared with untreated cells, with no prevention of cell death in this case. In further support of the implication of lipid raft domains, the dephosphorylation/inactivation of Akt-PKB was involved in the 7-ketocholesterol-induced apoptosis. Akt-PKB dephosphorylation was prevented by alpha-tocopherol, but not gamma-tocopherol pretreatment.

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