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.
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.
Badeau
Robert M
RM
Department of Molecular Medicine, National Public Health Institute, and Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland. robert.badeau@helsinki.fi
Metso
Jari
J
Tikkanen
Matti J
MJ
Jauhiainen
Matti
M
D000818:Animals; D018955:CD36 Antigens / Q000737:chemistry / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D002784:Cholesterol / Q000378:metabolism; D004952:Esters / Q000737:chemistry*; D004958:Estradiol / Q000378:metabolism*; D006801:Humans; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008954:Models, Biological; D051381:Rats; D011973:Receptors, LDL / Q000378:metabolism*; D014461:Ultracentrifugation
D018955:CD36 Antigens; D004952:Esters; D008075:Lipoproteins, HDL; D011973:Receptors, LDL; D004958:Estradiol; D002784:Cholesterol