Estradiol esters can replace 17 beta-estradiol in the stimulation of DNA and esterase synthesis by MCF-7 cells: a possible role for the estrogen-sensitive MCF-7 cell esterase

Design and synthesis of novel flexible ester-containing analogs of tamoxifen and their evaluation as anticancer agents

Background: Tamoxifen (TAM) is metabolized to the more active 4-hydroxytamoxifen by CYP2D6 enzyme. Due to the genetic polymorphisms in CYP2D6, clinical outcomes of TAM treatment vary. Novel flexible TAM analogs with altered activation pathway were synthesized and were tested for their antiproliferative action on MCF-7 cell lines and their binding affinity for ERα and ERβ. Results: All compounds showed better antiproliferative activity than TAM. Compound 3 showed 80-times more ERα binding than TAM, 900-times more selectivity toward ERα. Compound 3 was tested on the entire National Cancer Institute cancerous cell lines; results indicated a broad spectrum anticancer activity. Conclusion: The novel analogs were more potent than TAM with higher selectivity toward ERα and with potential metabolic stability toward CYP2D6.

A specific molecular beacon probe for the detection of human prostate cancer cells

The small-molecule, water-soluble molecular beacon probe 1 is hydrolyzed by the lysate and living cells of human prostate cancer cell lines (LNCaP), resulting in strong green fluorescence. In contrast, probe 1 does not undergo significant hydrolysis in either the lysate or living cells of human nontumorigenic prostate cells (RWPE-1). These results, corroborated by UV-Vis spectroscopy and fluorescent microscopy, reveal that probe 1 is a sensitive and specific fluorogenic and chromogenic sensor for the detection of human prostate cancer cells among nontumorigenic prostate cells and that carboxylesterase activity is a specific biomarker for human prostate cancer cells.

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.

Electrochemical sensor highly selective for estradiol valerate determination based on a modified carbon paste with iron tetrapyridinoporphyrazine

This work reports the use of iron tetrapyridinoporphyrazine (FeTPyPz) as a highly selective catalyst in the construction of an electrochemical sensor for estradiol valerate (EV) determination. The sensor was prepared by modifying a carbon paste with FeTPyPz. The best results were obtained in a mixture of acetonitrile (MeCN) and 0.1 mol L(-1) phosphate buffer solution (pH 6.0) in a volume ratio of 47 : 53. A linear response range was observed between 45 and 450 micromol L(-1) with a sensitivity of 12160 +/- 306 microA L mol(-1) and quantification and detection limits of 45 and 13 micromol L(-1), respectively. The repeatability, expressed as the relative standard deviation (RSD) for n = 10, was 5.9% ([EV] = 50 micromol L(-1)). The reproducibility (RSD) for the sensor construction was better than 4% and the operational stability (RSD) over 50 measurements was 1.8%. A detailed investigation regarding the selectivity and electrochemical characteristics was carried out. Finally, in a first step to evaluate the application potential of the sensor, it was successfully applied to determine EV in a commercial formulation.

Estradiol fatty acid esters in adipose tissue and serum of pregnant and pre- and postmenopausal women

CONTEXT

The 17beta-estradiol fatty acid esters are hormone derivatives with long-lasting estrogenic effect. They are transported in serum lipoproteins and thought to be sequestered in adipose tissue.

OBJECTIVE

Our objective was to determine the 17beta-estradiol fatty acid ester concentrations in serum and adipose tissue in women of various hormonal states.

DESIGN

After several chromatographic steps separating esterified from free estradiol, time-resolved fluoroimmunoassay was used as a quantifying tool.

PARTICIPANTS

Samples were obtained from pregnant women undergoing cesarean section (n = 13), or premenopausal (n = 8) and postmenopausal women (n = 6) during gynecological surgery.

MAIN OUTCOME MEASURES

17beta-Estradiol and 17beta-estradiol fatty acid ester concentrations in serum, and visceral and sc adipose tissue were examined.

RESULTS

The ratio of esterified to free estradiol in plasma increased with decreasing estradiol level from 0.5% in pregnant, to 15% in premenopausal and 110% in postmenopausal women. Estradiol esters constituted about 10% of the free estradiol present in adipose tissue in pregnancy. In nonpregnant women, most of the adipose tissue estradiol was in esterified form, the median ester to free ratio being elevated to 150-490%. After menopause, the overwhelming majority of estradiol in both free and esterified form was present in adipose tissue.

CONCLUSIONS

The overall higher ester to free estradiol ratio in adipose tissue than in serum indicates active esterification capacity in adipose tissue. The predominance of esterified and free estradiol in postmenopausal adipose tissue compared with serum suggests in situ production and storage. Whether the estradiol esters have an independent physiological role in adipose tissue remains to be clarified.

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.

Esterification of vertebrate-type steroids in the Eastern oyster (Crassostrea virginica)

Characteristics of acyl-coenzyme A (acyl-CoA):steroid acyltransferase from the digestive gland of the oyster Crassostrea virginica were determined by using estradiol (E2) and dehydroepiandrosterone (DHEA) as substrates. The apparent Km and Vmax values for esterification of E2 with the six fatty acid acyl-CoAs tested (C20:4, C18:2, C18:1, C16:1, C18:0, and C16:0) were in the range of 9-17 microM E2 and 35-74 pmol/min/mg protein, respectively. Kinetic parameters for esterification of DHEA (Km: 45-120 microM; Vmax: 30-182 pmol/min/mg protein) showed a lower affinity of the enzyme for this steroid. Formation of endogenous fatty acid esters of steroids by microsomes of digestive gland and gonads incubated in the presence of ATP and CoA was assessed, and at least seven E2 fatty acid esters and five DHEA fatty acid esters were observed. Some peaks eluted at the same retention times as palmitoleoyl-, linoleoyl-, oleoyl/palmitoyl-, and stearoyl-E2; and palmitoleoyl-, oleoyl/palmitoyl-, and stearoyl-DHEA. The same endogenous esters, although in different proportions, were produced by gonadal microsomes. The kinetic parameters for both E2 (Km: 10 microM; Vmax: 38 pmol/min/mg protein) and DHEA (Km: 61 microM; Vmax: 60 pmol/min/mg protein) were similar to those obtained in the digestive gland. Kinetic parameters obtained are similar to those observed in mammals; thus, fatty acid esterification of sex steroids appears to be a well-conserved conjugation pathway during evolution.

Non-specific steroidal esterase activity and distribution in human and other mammalian tissues

An NADPH dependent arylamine carcinogen and fatty acid steroid ester metabolizing esterase activity belonging to the B- or carboxylesterase class of non-specific esterase (EC 3.1.1.1) was measured by two different methods: (i) a spectrophotometric assay using alpha naphthyl acetate (ANA) as substrate and (ii) a radiometric method using the conversion of beclomethasone-17,21-dipropionate to beclomethasone-17-monopropionate as the endpoint. The two methods were strongly correlated when assayed in human mononuclear leukocytes (r = 0.89, P < 0.0001) and human mammary tissue (r = 0.91, P < 0.0001). Hence it was concluded that the two substrates are metabolized at least in part by the same enzyme. This esterase activity was abundant in human monocytes, present in T-lymphocytes and equally divided between CD4 and CD8 T-lymphocyte subsets. The same activity was expressed in human liver, colon, stomach, breast and brain tissues. The distribution of this esterase in human tissues showed high activity in liver, intermediate activity in colon, stomach and breast and low activity in brain tissue. The interorgan distribution observed in human tissues was closely mimicked when the esterase activity was assessed in liver, colon and brain tissues from three mouse strains and three rat strains. The non-specific steroidal esterase activity determined by ANA metabolism in human mammary tissue was shown to be reproducible when assayed as triplicate samples from each of 16 different women (intraclass correlation coefficient 67.3%, P < 0.03). The interindividual variation in mammary tissue was high (18.4-fold) and there was a positive correlation between the esterase activity and age (r = 0.58, P < 0.01), as well as a tendency toward bimodal distribution. To our knowledge, these data represent the first systematic study of interorgan and interspecies comparisons of a non-specific steroidal esterase activity.

Aromatase and testosterone fatty acid esters: the search for a cryptic biosynthetic pathway to estradiol esters

The estradiol fatty acid esters (lipoidal derivatives, LE2) are extremely potent estrogens that accumulate in fat, including fat of menopausal women. These steroidal esters are protected from metabolism and are converted to the free, biologically active steroid through the action of esterases. Previous studies have shown that biosynthetic pathways in the adrenal gland exist in which steroid fatty acid esters are substrates. This led us to determine whether a cryptic aromatase pathway exists in which testosterone esters could be converted directly into LE2. We tested a representative fatty acid ester, testosterone stearate, both as an inhibitor and as a substrate for the aromatase enzyme from human placental microsomes. This ester had neither activity. In addition, we tested [1 beta-3H]testosterone acetate as a substrate for this enzyme complex, measuring the production of 3H2O as evidence of aromatization. Although the rate of reaction was considerably slower than that of testosterone, 3H2O was produced. However, when [2, 4, 6, 7-3H]testosterone acetate was incubated and the steroidal products isolated, we found that hydrolysis of the substrate had occurred. Both [3H]-labeled testosterone and estradiol were found, and very little if any [3H]estradiol acetate was formed. Thus, we conclude that an aromatase pathway involving testosterone esters does not exist and that the sole source of LE2 is through direct esterification of estradiol.

Esterase-1: developmental expression in the mouse and distribution of related proteins in other species

Esterase 1 (Es-1) is a sexually dimorphic 65-kDa glycoprotein present in plasma and other murine tissues able to hydrolyze a variety of esters including fatty acid esters of estradiol. Like most other carboxylesterases, its function is unknown. To gain insight into the function of Es-1 and by analogy other carboxylesterases, we have examined the developmental regulation of Es-1 in the mouse and have looked for the presence of related proteins in the plasma of other species. Northern blot analysis of total RNA from the livers of mice of various ages using a 32P-labeled 470-bp Es-1 cDNA probe showed clear postpartum induction with no detectable Es-1 mRNA in fetal liver. Similarly, immunoblotting after sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an affinity-purified rabbit antibody to Es-1 showed no cross-reacting proteins in the plasma until after birth. Northern blot analysis of total RNA from a variety of adult mouse tissues showed the presence of substantial levels of Es-1 mRNA only in liver with lower levels in kidney, testes, and ovaries. Liver mRNA and plasma protein levels rose in parallel attaining full adult levels between 15 and 20 days of age. When plasma proteins were electrophoresed on 7% polyacrylamide gels under nondenaturing conditions, the antibody to Es-1 recognized a low mobility protein in mouse, rat, human, baboon, guinea pig, bovine, horse, and canine but not in chicken plasma. Consistent with the immunoblotting results, the Es-1 cDNA probe hybridized to restriction fragments from human, monkey, rat, and rabbit as well as mouse genomic DNA but not from chicken DNA indicating conservation of the esterase (or esterase-like) gene in mammalian species. The low mobility antigens in mouse and human plasma appeared also to cross-react with antibodies to human thyroglobulin, although antibodies to human thyroglobulin did not appear to recognize Es-1 under these conditions.