Absence of correlation between oxysterol accumulation in lipid raft microdomains, calcium increase, and apoptosis induction on 158N murine oligodendrocytes

• Published in: Biochemical pharmacology Vol. 86; no. 1; pp. 67 - 79
• Main Authors: Ragot, Kévin, Mackrill, John J., Zarrouk, Amira, Nury, Thomas, Aires, Virginie, Jacquin, Agnès, Athias, Anne, Barros, Jean-Paul Pais de, Véjux, Anne, Riedinger, Jean-Marc, Delmas, Dominique, Lizard, Gérard
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 01.07.2013
• Subjects: 27-Hydroxycholesterol; 7-Ketocholesterol; 7β-Hydroxycholesterol; alpha-Tocopherol - pharmacology; Animals; Apoptosis; Calcium; Calcium - metabolism; caspase-3; Cell Line; Cell Proliferation; Cell Survival; central nervous system; cholesterol; condensation; cytotoxicity; dephosphorylation; ellagic acid; Glycogen Synthase Kinase 3 - metabolism; Hydroxycholesterols - metabolism; Hydroxycholesterols - pharmacology; Ketocholesterols - metabolism; Ketocholesterols - pharmacology; Lipid rafts; Membrane Microdomains - drug effects; Membrane Microdomains - metabolism; Mice; Myeloid Cell Leukemia Sequence 1 Protein; neurodegenerative diseases; Oligodendrocytes; Oligodendroglia - cytology; Oligodendroglia - drug effects; Oligodendroglia - metabolism; patients; pharmacology; Proto-Oncogene Proteins c-akt - metabolism; Proto-Oncogene Proteins c-bcl-2 - metabolism; resveratrol; Sterols - metabolism; α-Tocopherol; 7β-Hydroxycholesterol; Calcium; Oligodendrocytes; 27-Hydroxycholesterol; α-Tocopherol; Lipid rafts; 7-Ketocholesterol; Apoptosis
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2013.02.028

The ability of oxysterols (7-ketocholesterol, 7β-hydroxycholesterol) to trigger a mode of cell death by apoptosis involving GSK-3 and caspase-3 activation is independent of the increase in the Ca2+ level and of their accumulation in lipid raft microdomains. Noteworthy, oxysterol-induced apoptosis was counteracted by α-tocopherol but not by ellagic acid and resveratrol. 27-hydroxycholesterol, which does not induce cell death, accumulates in lipid rafts. There is some evidence that oxidized derivatives of cholesterol, 7-ketocholesterol (7KC) and 7β-hydroxycholesterol (7βOHC), are increased in the plasma of patients with neurodegenerative diseases associated with demyelinization of the central nervous system (CNS). It was therefore of interest to investigate the effects of these oxysterols on oligodendrocytes, the myelin-forming cells in the CNS. To this end, 158N murine oligodendrocytes were treated with 7KC or 7βOHC inducing an apoptotic mode of cell death characterized by condensation/fragmentation of the nuclei, dephosphorylation of Akt and GSK3, mitochondrial depolarization involving Mcl-1, and caspase-3 activation. In contrast, under treatment with 27-hydroxycholesterol (27OHC), no cell death was observed. When the cells were stained with Fura-2, no significant Ca2+ rise was found with the different oxysterols, whereas strong signals were detected with ionomycin used as positive control. At concentrations which induced apoptosis, 7KC but not 7βOHC accumulated in lipid rafts. Although not cytotoxic, 27OHC was mainly detected in lipid rafts. It is noteworthy that α-tocopherol (but not ellagic acid and resveratrol) was able to counteract 7KC- and 7βOHC-induced apoptosis and to decrease the accumulation of 7KC and 27OHC in lipid rafts. Thus, in 158N cells, the ability of oxysterols to trigger a mode of cell death by apoptosis involving GSK-3 and caspase-3 activation is independent of the increase in the Ca2+ level and of their accumulation in lipid raft microdomains.