7-ketocholesterol inhibits Na,K-ATPase activity by decreasing expression of its α1-subunit and membrane fluidity in human endothelial cells.
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.
INSERM U603, Marseille, France.
M J
MJ
Duran
S V
SV
Pierre
P
P
Lesnik
G
G
Pieroni
M
M
Bourdeaux
F
F
Dignat-Georges
J
J
Sampol
J M
JM
Maixent
D002470:Cell Survival / Q000187:drug effects; D002784:Cholesterol / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology*; D004730:Endothelium, Vascular / Q000166:cytology; D006801:Humans; D007653:Ketocholesterols / Q000494:pharmacology*; D054709:Lecithins / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects; D008560:Membrane Fluidity / Q000187:drug effects*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
D007653:Ketocholesterols; D054709:Lecithins; D021122:Protein Subunits; D012333:RNA, Messenger; D009569:Nitric Oxide; D002784:Cholesterol; D052250:Nitric Oxide Synthase Type III; D000254:Sodium-Potassium-Exchanging ATPase; C003001:7-ketocholesterol