Partially reassembled high density lipoproteins. Effects on cholesterol flux, synthesis, and esterification in normal human skin fibroblasts.
The effects of a partially reassembled high density lipoprotein (PR-HDL) prepared by a detergent removal method on the cholesterol metabolism of fibroblasts has been tested under conditions of lipid depletion. The PR-HDL were composed of apolipoprotein A-I (1 mol) from human plasma HDL, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) 100 mol, and varying amounts of cholesterol. Below 15 mol%, the PR-HDL effected a net efflux of cholesterol from the fibroblasts; as a consequence, the activities of 3-hydroxy-3-methylglutaryl coenzyme A reductase and acyl coenzyme A acyltransferase, respectively, were increased and decreased. Above 15 mol% cholesterol in the PR-HDL, net influx of cholesterol was observed and 3-hydroxy-3-methyl-glutaryl coenzyme A reductase activity was decreased, while acyl coenzyme A acyltransferase activity was increased. The uptake of several phosphatidylcholines, apo A-I, and cholesterol were measured as a function of time. The rates of lipid transfer to the cells decreased with increasing hydrophobicity of the transferring lipid. By contrast, in parallel experiments a relatively small quantity of 125I apo A-I was associated with the cells. Our results suggest that a component of lipid transfer from PR-HDL to fibroblasts occurs via monomeric transfer through the aqueous phase that is independent of apo A-I binding.
D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D004951:Esterification; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007231:Infant, Newborn; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D012867:Skin / Q000187:drug effects / Q000378:metabolism*; D002785:Sterol O-Acyltransferase / Q000378:metabolism
D008075:Lipoproteins, HDL; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D002785:Sterol O-Acyltransferase