High-density lipoprotein-associated 17beta-estradiol fatty acyl ester uptake by Fu5AH hepatoma cells: implications of the roles of scavenger receptor class B, type I and the low-density lipoprotein receptor.

Abstract	17beta-estradiol (E2) fatty acyl esters naturally incorporate into high-density lipoprotein (HDL). The objective was to elucidate mechanisms involved in HDL-associated E2 cellular uptake and to determine the intracellular distribution of E2 and its fatty acyl esters (E2-FAE) after uptake. [3H]E2 or [3H] cholesterol was incubated with human serum for 24 h to allow for fatty acyl esterification. Total-HDL containing [3H]E2-FAE or [3H]cholesterol esters was isolated by sequential density ultracentrifugation and then incubated with Fu5AH rat hepatoma cells for various time points. Cellular uptake was determined by intracellular radioactivity as a percentage of total radioactivity. Chemical inhibition of scavenger receptor class B, type I and low-density lipoprotein (LDL) receptor competition assays were performed to determine cellular uptake mechanisms. Compared to HDL-[3H]cholesterol, cellular uptake of HDL-[3H]E2 occurred at an initially rapid rate. SR-BI inhibition resulted in a decrease in HDL-E2 uptake and LDL impaired this uptake in a concentration-dependent manner. Accordingly, pretreatment of cells with BLT-1 combined with LDL addition significantly attenuated HDL-E2 uptake. HDL-E2-FAE was hydrolyzed into free E2 with the maximum at 24 h. Fu5AH cells facilitate HDL-E2 uptake by at least SR-BI and LDL receptor pathways and intracellular hydrolysis of E2-FAE into free E2 ensues.
Authors	Robert M Badeau, Jari Metso, Matti J Tikkanen, Matti Jauhiainen
Journal	Biochimica et biophysica acta (Biochim Biophys Acta) Vol. 1771 Issue 10 Pg. 1329-34 (Oct 2007) ISSN: 0006-3002 [Print] Netherlands
PMID	17905649 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	CD36 Antigens Esters Lipoproteins, HDL Receptors, LDL Estradiol Cholesterol
Topics	Animals CD36 Antigens (chemistry, metabolism) Carcinoma, Hepatocellular (metabolism) Cell Line Cell Line, Tumor Cholesterol (metabolism) Esters (chemistry) Estradiol (metabolism) Humans Lipoproteins, HDL (metabolism) Models, Biological Rats Receptors, LDL (metabolism) Ultracentrifugation

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