7-ketocholesterol inhibits Na,K-ATPase activity by decreasing expression of its α1-subunit and membrane fluidity in human endothelial cells.

Abstract

As cholesterol, oxysterols, can insert the cell membrane and thereby modify the functions of membrane-bound proteins. The Na,K-ATPase is very sensitive to its lipid environment, seems to be involved in important endothelial functions as the regulation of nitric oxide (NO) release. The effects of 7-ketocholesterol , an oxysterol present in oxidized LDL, was investigated on Na,K-ATPase in isolated human endothelial cells. Cells were incubated 24h with lecithin-, cholesterol- or 7-ketocholesterol liposomes (6 μg/ml). K+-stimulated paranitrophenyl phosphatase activity, reflecting Na,K-ATPase activity, was evaluated as well as cell viability and lipoperoxidation. The expression of Na,K-ATPase subunits mRNAs and membrane fluidity were also investigated. As Na,K-ATPase and nitric oxide seem to be related, we determined the production of NO and the expression of endothelial NO synthase mRNAs. Na,K-ATPase activity was strongly decreased by 7-ketocholesterol. This decrease, not related to lipoperoxidation, was correlated with a decreased expression of the Na,K-ATPase α1-subunit messengers and with rigidity of plasma membranes. Cholesterol induced similar effects but was less potent than 7-ketocholesterol. Basal NO production and expression of endothelial NO synthase mRNAs were not modified by 7-ketocholesterol. Our new findings demonstrate that 7-ketocholesterol, used at non toxic doses, was very potent to disrupt the transport of ions by Na,K-ATPase and perturb membrane structure. These data demonstrate that 7-ketocholesterol induces endothelial dysfunction without cell death that may contribute to early events in atherosclerosis.

• Authors: M J Duran, S V Pierre, P Lesnik, G Pieroni, M Bourdeaux, F Dignat-Georges, J Sampol, J M Maixent
• Journal: Cellular and molecular biology (Noisy-le-Grand, France) (Cell Mol Biol (Noisy-le-grand)) Vol. 56 Suppl Pg. OL1434-41 (Nov 09 2010) ISSN: 1165-158X [Electronic] France
• PMID: 21062577 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Ketocholesterols
• Lecithins
• Protein Subunits
• RNA, Messenger
• Nitric Oxide
• Cholesterol
• Nitric Oxide Synthase Type III
• Sodium-Potassium-Exchanging ATPase
• 7-ketocholesterol

Topics

• Cell Survival (drug effects)
• Cholesterol (pharmacology)
• Endothelial Cells (drug effects, enzymology)
• Endothelium, Vascular (cytology)
• Humans
• Ketocholesterols (pharmacology)
• Lecithins (pharmacology)
• Lipid Peroxidation (drug effects)
• Membrane Fluidity (drug effects)
• Nitric Oxide (metabolism)
• Nitric Oxide Synthase Type III (genetics, metabolism)
• Protein Subunits (genetics, metabolism)
• RNA, Messenger (metabolism)
• Sodium-Potassium-Exchanging ATPase (antagonists & inhibitors, genetics, metabolism)