Background and aims: Dehydroepiandrosterone (DHEA) is an important prohormone and precursor of all sex steroids. DHEA fatty acid esters (DHEA-FAEs) belong to a unique family of naturally occurring hydrophobic steroid hormone derivatives with long-lasting hormonal activity, which are exclusively transported in lipoproteins. In the circulation, DHEA is esterified in a reaction catalyzed by lecithin-cholesterol acyltransferase associated with HDL particles. The physiological role of DHEA-FAEs remains to be clarified. This study aims to study the metabolic fate of lipoprotein-transported DHEA-FAEs in cultured HeLa cells, derived from epithelium of reproductive tract.
Methods: We incubated 3H-DHEA with VLDL-free plasma which resulted in formation of 3H -DHEA -FAEs contained in LDL. We then incubated the labelled LDL particles with cultured HeLa cells in the presence of the ACAT inhibitor, PKF 58-035. After different time points, cells and medium were harvested and immediately extracted with organic solvents. Unesterified 3H-DHEA was separated from 3H-DHEA-FAE by hydrophobic chromatography on Sephadex LH-20, and two-dimensional TLC was used to identify labelled steroid metabolites.
Results: Increased accumulation of 3H-DHEA -FAEs in the cellular fractions were discovered with incubation time up to 24 hours. In the medium fractions, minimal amounts of 3H-DHEA-FAE were observed but increasing amounts of free 3H-DHEA and two metabolites, androstanedione and androstenedione, appeared after 48 hours. Conversely, the cellular fractions only had 3H-DHEA-FAE.
Conclusions: Our preliminary studies suggest that 1.3H-DHEA-FAEs transported by LDL entered HeLa cells via LDL-receptor-mediated intake, 2.3H-DHAE-FAEs were hydrolyzed inside the HeLa cells, 3. The free 3H-DHEA was metabolised into androstanedione and androstenedione, which were secreted into the medium.
03 - 07 May 2008
European Society of Endocrinology