Role of lysosomal acid lipase in the intracellular metabolism of LDL-transported dehydroepiandrosterone-fatty acyl esters.
Dehydroepiandrosterone-fatty acyl esters (DHEA-FAE) belong to a unique family of naturally occurring hydrophobic steroid hormone derivatives that are transported in circulating lipoproteins and may act as a source of dehydroepiendrosterone (DHEA) and other biologically active steroid hormones in cells. Here, we studied the metabolic fate of low-density lipoprotein-associated [(3)H]DHEA-FAE ([(3)H]DHEA-FAE-LDL) and the possible role of lysosomal acid lipase (LAL) in the hydrolysis of DHEA-FAE in cultured human cells. When HeLa cells were incubated with [(3)H]DHEA-FAE-LDL, the accumulation of label in the cellular fraction increased with incubation time and could be inhibited by excess unlabeled LDL, suggesting LDL receptor or LDL receptor-related receptor-dependent uptake. During 48 h of chase, decreasing amounts of [(3)H]DHEA-FAE were found in the cellular fraction, while in the medium increasing amounts of unesterified [(3)H]DHEA and its two metabolites, [(3)H]-5alpha-androstanedione (5alpha-adione) and [(3)H]androstenedione (4-adione), appeared. As LDL-cholesteryl ester hydrolysis is dependent on LAL activity, we depleted LAL from HeLa cells using small interfering RNAs and compared the hydrolysis of [(3)H]DHEA-FAE-LDL and [(3)H]cholesteryl-FAE-LDL. The results demonstrated a more modest but significant reducing effect on the hydrolysis of [(3)H]DHEA-FAE compared with [(3)H]cholesteryl-FAE. Moreover, experiments in LAL-deficient human fibroblasts (Wolman disease patient cells) showed that [(3)H]DHEA-FAE hydrolysis was not completely dependent on LAL activity. In summary, LDL-transported [(3)H]DHEA-FAE entered cells via LDL receptor or LDL receptor-related receptor-mediated uptake, followed by intracellular hydrolysis and further metabolism into 5alpha-adione and 4-adione that were excreted from cells. Although LAL contributed to the deesterification of DHEA-FAE, it was not solely responsible for the hydrolysis.
Wang
Feng
F
Dept. of Medicine, Helsinki Univ. Central Hospital, Haartmaninkatu 4, 00290 Helsinki, Finland.
Wang
Wei
W
Wähälä
Kristiina
K
Adlercreutz
Herman
H
Ikonen
Elina
E
Tikkanen
Matti J
MJ
D002478:Cells, Cultured; D002788:Cholesterol Esters / Q000378:metabolism; D003687:Dehydroepiandrosterone / Q000737:chemistry / Q000378:metabolism*; D004952:Esters / Q000378:metabolism; D005227:Fatty Acids / Q000737:chemistry / Q000378:metabolism*; D005260:Female; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D002787:Sterol Esterase / Q000378:metabolism / Q000502:physiology*
D002788:Cholesterol Esters; D004952:Esters; D005227:Fatty Acids; D008077:Lipoproteins, LDL; D003687:Dehydroepiandrosterone; D002787:Sterol Esterase