Role of apolipoproteins A-I, A-II and C-I in cholesterol efflux from endothelial and smooth muscle cells.
The role of purified apolipoproteins A-I, A-II and C-I in the process of cholesterol efflux from cultured vascular endothelial and smooth muscle cells was studied. [3H]Cholesterol pre-labelled cultures were exposed to serum-free medium supplemented with free apolipoproteins or with apolipoproteins and phosphatidylcholine liposomes and the cholesterol efflux from the cells was determined. Free apolipoproteins A-I and A-II supported cholesterol efflux from vascular endothelial and smooth muscle cells to a higher extent than apolipoprotein C-I. The ability of free apolipoproteins A-I and A-II to support cholesterol efflux was in correlation with their specific binding to the cultures, while no specific binding of apolipoprotein C-I was detected. The association of apolipoprotein A-I with phosphatidylcholine liposomes resulted in a more than two-fold increase in cholesterol efflux compared to free apolipoprotein A-I, while association of apolipoproteins A-II and C-I with phosphatidylcholine liposomes resulted in a very limited increase in cholesterol efflux above that achieved by the free apolipoproteins. These results suggest that apolipoprotein A-I is involved in cholesterol efflux performed by high density lipoprotein. Furthermore, free apolipoproteins A-I and A-II, but not apolipoprotein C-I may take an active part in cholesterol efflux from endothelial and smooth muscle cells.
Savion
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Maurice and Gabriela Goldschleger Eye Research Institute, Sackler Faculty of Medicine, Tel-Aviv University, Israel.
Kotev-Emeth
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S
D000818:Animals; D016632:Apolipoprotein A-I / Q000502:physiology; D016633:Apolipoprotein A-II / Q000502:physiology; D053302:Apolipoprotein C-I; D001053:Apolipoproteins / Q000378:metabolism / Q000502:physiology*; D001056:Apolipoproteins C / Q000502:physiology; D002417:Cattle; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology
D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D053302:Apolipoprotein C-I; D001053:Apolipoproteins; D001056:Apolipoproteins C; D002784:Cholesterol