The removal of cholesterol from aortic smooth muscle cells in culture and landschutz ascites cells by fractions of human high-density apolipoprotein

Y. Stein*, M. C. Glangeaud, M. Fainaru, O. Stein

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Ascites cells were labeled by intraperitoneal injection of [3H] cholesterol and aortic smooth muscle cells by addition of [3H] cholesterol to the serum component of the culture medium. The release of cholesterol from cells into a serum-free medium supplemented with the various "acceptors" was studied using ascites cells in suspension and aortic smooth muscle cells in a multilayer culture. Unfractionated human high-density apolipoprotein was somewhat more effective in the removal of labeled cellular free cholesterol, in both cell types, than apolipoprotein derived from rat high-density lipoprotein. Following separation of human high-density apolipoprotein into four fractions by Sephadex chromatography, the effect of each fraction on the removal of cellular cholesterol from ascites cells was studied. The individual fractions had a lower capacity for cholesterol removal than the original unfractionated high-density apolipoprotein and the lowest activity was detected in Fraction II which comprised 75% of the total apolipoprotein. The effectiveness to remove cholesterol could be restored to all the fractions, as well as enhanced, by addition of sonicated suspensions of lecithin or sphingomyelin, which by themselves promoted a more limited removal of cellular cholesterol. Negatively stained preparations of mixtures of the four fractions and sonicated dispersion of lecithin were shown to consist of vesicles and discs of various sizes. Addition of the apolipoprotein fractions (especially Fractions II and IV) to sonicated dispersion of sphingomyelin resulted in a pronounced formation of discs which showed a high tendency towards stack formation. Mixtures of Fraction II and lecithin or sphingomyelin were effective in the release of cellular cholesterol from multilayers of aortic smooth muscle cells in culture. These results show the feasibility of net removal of cholesterol from cells which grow in a form resembling a tissue and thus provide a model to study the role of apolipoprotein-phospholipid mixtures in cholesterol removal from cells and tissues in vivo.

Original languageEnglish
Pages (from-to)106-118
Number of pages13
JournalBiochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
Volume380
Issue number1
DOIs
StatePublished - 24 Jan 1975
Externally publishedYes

Funding

FundersFunder number
Government of Israel
United States-Israel Binational Science Foundation
Centre National pour la Recherche Scientifique et Technique
Ministeriet Sundhed Forebyggelse

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