title: 7β-Hydroxycholesterol-induced energy stress leads to sequential opposing signaling responses and to death of C6 glioblastoma cells.
abstract: 7β-Hydroxycholesterol cytotoxicity has been shown in vivo and in vitro to be dependent on the accumulation of its esters. We show in our study, using a detergent-free raft preparation and LC/MS lipid content analysis, that membrane microdomains isolated from 7β-hydroxycholesterol-treated C6 cells have a reduced cholesterol: cholesterol ester ratio and accumulate 7keto-hydroxycholesterol, 7β-hydroxycholesterol and 7β-hydroxycholesterol esters. These modifications in lipid content are accompanied by a redistribution of flotillin-1 in the lipid rafts. Transient increases of AMPK phosphorylation and mitochondrial activity during the first 12 h of 7β-hydroxycholesterol treatment indicate that C6 cells undergo energy stress and increase oxidative phosphorylation. Even so, ATP levels are maintained during 15 h until glucose uptake decreases. The cell's answers to raft modifications and energy stress are sequential activations of different signaling pathways such as ERK, AMPK and PI3K/Akt. These pathways, known to be activated under energy stress conditions, are transiently activated at 6 h (ERK, AMPK) and 12 h (Akt) of treatment respectively suggesting a shift from cell survival to cell proliferation. The persistence of 7β-hydroxycholesterol-induced stress led after 24 h to P38 activation, loss of GSK3β activation and to cell death. Finally we demonstrate that the observed signaling responses depend on 7β-hydroxycholesterol esterification, confirming that esterification of 7β-hydroxycholesterol is essential for cytotoxicity.
authors: Institut des Neurosciences de Montpellier INSERM U, France.
authors: Ludovic
authors: L
authors: Clarion
authors: Mathilde
authors: M
authors: Schindler
authors: Jan
authors: J
authors: de Weille
authors: Karine
authors: K
authors: Lolmède
authors: Audrey
authors: A
authors: Laroche-Clary
authors: Emmanuelle
authors: E
authors: Uro-Coste
authors: Jacques
authors: J
authors: Robert
authors: Marcel
authors: M
authors: Mersel
authors: Norbert
authors: N
authors: Bakalara
mesh_terms: D000818:Animals; D002417:Cattle; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology*; D005909:Glioblastoma / Q000378:metabolism*; D006801:Humans; D006888:Hydroxycholesterols / Q000378:metabolism* / Q000633:toxicity; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
chemical_list: D006888:Hydroxycholesterols; C011724:cholest-5-en-3 beta,7 alpha-diol