Estrogen Sulfatase

Study of anti-tumorigenic actions of essential fatty acids in a murine mammary gland adenocarcinoma by micro-XRF

In the present work, a statistical experiment based on the microscopy X-ray fluorescence technique was developed to evaluate the effect of diets rich in ω-3 and ω-6 polyunsaturated fatty acids on tumour tissues. Relative variations on the local content of P, S, Ca, Fe, Cu and Zn were analysed in the experiment. Neoplastic tissues were obtained from mammary gland adenocarcinomas inoculated in mice belonging to three different dietary groups: normal, rich in ω-3 and in ω-6 polyunsaturated fatty acids. Slices of 30 microns thick sections of these samples were scanned in the air atmosphere in areas of 5 mm × 5 mm with a spatial resolution of 50 microns using synchrotron radiation. Principal component analysis was employed to analyse the correlation between the X-ray fluorescence signals of P, S, Ca, Fe, Cu and Zn. The subsequent application of the K-means clustering was used for the automatic segmentation of the image scans. By comparison with conventional histological analysis, the clusters were positively identified as tumour parenchyma, transition and necrotic region. The calculation of the mean content of P, S, Ca, Fe, Cu, and Zn in these regions showed that dietary polyunsaturated fatty acids modify elemental content of tumour parenchyma, suggesting its involvement in the antitumour effects of chia oil and protumour effects of safflower oil.

Rapid and simultaneous determination of multiple endocrine-disrupting chemicals and their metabolites in human serum and urine samples

Bisphenols, parabens, and their metabolites are a group of chemical compounds with a wide range of polarities but similar chemical structures, which presents a challenge for the simultaneous determination of these compounds in complex biological samples. In this study, a rapid and sensitive method for simultaneous quantification of free bisphenol A (BPA), conjugated BPA, bisphenols, and parabens analogs was developed using solid-phase extraction (SPE) tandem liquid-liquid extraction (LLE). We compared the effects of different types of SPE cartridges, diluents, and LLE solvents on the analyte recovery. Utilizing the direct and indirect determination methods (enzyme hydrolysis), we confirmed the accuracy of the direct method for measuring BPA glucuronide and BPA disulfate. The method enabled the analysis of 24 endocrine-disrupting chemicals (EDCs) in one injection through UHPLC-MSMS measurements, with satisfactory recovery (mean: 91.8-98.6% for urine, 80.2%-96.8% for serum) and precision (RSD <15%). The LOD and LOQ values were 0.003 and 0.01 ng/mL for serum, and 0.002 and 0.006 ng/mL for urine samples, respectively. For real sample analysis, the median concentration of analytes in serum and urine samples ranged from 0.04 ng/mL (BPS) to 56.4 ng/mL (4-HB) and 0.11 ng/mL (BPA) to 136 ng/mL (4-HB), respectively. This method provides a new strategy to simultaneously identify compounds with a wide range of polarities from complicated biological matrices.

SLCO1B1 polymorphisms and plasma estrone conjugates in postmenopausal women with ER+ breast cancer: genome-wide association studies of the estrone pathway

BACKGROUND

Estrone (E1), the major circulating estrogen in postmenopausal women, promotes estrogen-receptor positive (ER+) breast tumor growth and proliferation. Two major reactions contribute to E1 plasma concentrations, aromatase (CYP19A1) catalyzed E1 synthesis from androstenedione and steroid sulfatase (STS) catalyzed hydrolysis of estrone conjugates (E1Cs). E1Cs have been associated with breast cancer risk and may contribute to tumor progression since STS is expressed in breast cancer where its activity exceeds that of aromatase.

METHODS

We performed genome-wide association studies (GWAS) to identify SNPs associated with variation in plasma concentrations of E1Cs, E1, and androstenedione in 774 postmenopausal women with resected early-stage ER+ breast cancer. Hormone concentrations were measured prior to aromatase inhibitor therapy.

RESULTS

Multiple SNPs in SLCO1B1, a gene encoding a hepatic influx transporter, displayed genome-wide significant associations with E1C plasma concentrations and with the E1C/E1 ratio. The top SNP for E1C concentrations, rs4149056 (p = 3.74E-11), was a missense variant that results in reduced transporter activity. Patients homozygous for the variant allele had significantly higher average E1C plasma concentrations than did other patients. Furthermore, three other SLCO1B1 SNPs, not in LD with rs4149056, were associated with both E1C concentrations and the E1C/E1 ratio and were cis-eQTLs for SLCO1B3. GWAS signals of suggestive significance were also observed for E1, androstenedione, and the E1/androstenedione ratio.

CONCLUSION

These results suggest a mechanism for genetic variation in E1C plasma concentrations as well as possible SNP biomarkers to identify ER+ breast cancer patients for whom STS inhibitors might be of clinical value.

Uterine and placental expression of HPGD in cows during pregnancy and release of fetal membranes

15-Hydroxyprostaglandin dehydrogenase (HPGD) plays a key role in prostaglandins (PGs) catabolism. Its expression and activity appear to be regulated by progesterone (P4). We investigated the HPGD mRNA-expression and protein localization in placentomes and interplacental uterine sites throughout gestation (Study I), and after fetal membranes retention (RFM) compared with normally delivered fetal membranes (DFM) (Study II). Furthermore, we analyzed the influence of aglepristone (AP), dexamethasone (GC) or cloprostenol (CP), on HPGD expression in bovine placentomes (Study III). Tissues from late gestation (D272) and at normal term (NT) served as controls. HPGD was highest in all sites at the beginning of pregnancy and at (NT). Following induced parturition HPGD was lower after (AP) and (GC) compared with (NT), and was similar in RFM and DFM. Placentomes stained primarily in fetal compartments; interplacentomal signals were observed in endometrial glandular and luminal epithelium. Results indicate that HPGD may play a role during establishment and termination of gestation.

Critical evaluation of key evidence on the human health hazards of exposure to bisphenol A

Despite the fact that more than 5000 safety-related studies have been published on bisphenol A (BPA), there seems to be no resolution of the apparently deadlocked controversy as to whether exposure of the general population to BPA causes adverse effects due to its estrogenicity. Therefore, the Advisory Committee of the German Society of Toxicology reviewed the background and cutting-edge topics of this BPA controversy. The current tolerable daily intake value (TDI) of 0.05 mg/kg body weight [bw]/day, derived by the European Food Safety Authority (EFSA), is mainly based on body weight changes in two- and three-generation studies in mice and rats. Recently, these studies and the derivation of the TDI have been criticized. After having carefully considered all arguments, the Committee had to conclude that the criticism was scientifically not justified; moreover, recently published additional data further support the reliability of the two- and three-generation studies demonstrating a lack of estrogen-dependent effects at and below doses on which the current TDI is based. A frequently discussed topic is whether doses below 5 mg/kg bw/day may cause adverse health effects in laboratory animals. Meanwhile, it has become clear that positive results from some explorative studies have not been confirmed in subsequent studies with higher numbers of animals or a priori defined hypotheses. Particularly relevant are some recent studies with negative outcomes that addressed effects of BPA on the brain, behavior, and the prostate in rodents for extrapolation to the human situation. The Committee came to the conclusion that rodent data can well be used as a basis for human risk evaluation. Currently published conjectures that rats are insensitive to estrogens compared to humans can be refuted. Data from toxicokinetics studies show that the half-life of BPA in adult human subjects is less than 2 hours and BPA is completely recovered in urine as BPA-conjugates. Tissue deconjugation of BPA-glucuronide and -sulfate may occur. Because of the extremely low quantities, it is only of minor relevance for BPA toxicity. Biomonitoring studies have been used to estimate human BPA exposure and show that the daily intake of BPA is far below the TDI for the general population. Further topics addressed in this article include reasons why some studies on BPA are not reproducible; the relevance of oral versus non-oral exposure routes; the degree to which newborns are at higher systemic BPA exposure; increased BPA exposure by infusions in intensive care units; mechanisms of action other than estrogen receptor activation; and the current regulatory status in Europe, as well as in the USA, Canada, Japan, New Zealand, and Australia. Overall, the Committee concluded that the current TDI for BPA is adequately justified and that the available evidence indicates that BPA exposure represents no noteworthy risk to the health of the human population, including newborns and babies.

Steroid hormone metabolizing enzymes in benign and malignant human bone tumors

IMPORTANCE IN THE FIELD: Primary bone tumors are considered as (sex steroid) hormone-dependent tumors. Osteosarcoma, osteoblastoma and bone cysts are preferentially found in males, while giant cell tumors are more common in females. Indeed, bone tumor development and progression are influenced by sex steroid hormones derived from in situ synthesis in bone cells.

AREAS COVERED IN THIS REVIEW

This review describes intracrine mechanisms for local formation of the biologically most active estrogen, 17beta-estradiol (E2), from circulating steroid precursors through the 'aromatase' (aromatization of androgens) and the 'sulfatase' (conversion of inactive estrone-sulfate) pathway.

WHAT THE READER WILL GAIN

The reader gains knowledge on both pathways and the enzymes, which contribute to the in situ availability of active hormones, namely 3beta-hydroxysteroid dehydrogenases, 17beta-hydroxysteroid dehydrogenases, aromatase, steroid sulfatases and sulfotransferases. An overview is given and the expression and function of these enzymes in bone tumors are discussed.

TAKE HOME MESSAGE

Knowledge on pathways for the in situ formation of E2 in bone cells may allow the identification of potential targets for i) novel endocrine therapeutic options in primary bone tumors and ii) future preventive interventions.

The human estrogen sulfotransferase: a half-site reactive enzyme

The affinity of 17beta-estradiol (E(2)) for the estrogen receptor is weakened beyond the point of physiological relevance by the transfer of the sulfuryl moiety (-SO(3)) from PAPS (3'-phosphoadenosine 5'-phosphosulfate) to the 3'-hydroxyl of E(2). The mechanism of this transfer reaction, catalyzed by estrogen sulfotransferase (EST), is investigated here in detail. The enzyme (a dimer of identical protomers) presents a clear example of half-sites reactivity--only one of the subunits of the dimer produces product during the catalytic cycle. This is the first example of half-sites reactivity in the sulfotransferase family. A burst of product, with an amplitude that corresponds to one-half of the available active sites, reveals that the mechanism is rate-limited by product release. The equilibrium constant governing interconversion of the substrate (E.PAPS.E(2)) and product (E.PAP.E(2)S) central complexes was determined and is strongly biased toward product (K(eq int) approximately 49). Slow product release allows the interconversion of the central complexes to approach equilibrium, with the result that K(eq int) becomes nearly linearly coupled to K(m) and contributes a factor of approximately 30 to the steady-state affinity of the enzyme for substrate. Typical of its family, estrogen sulfotransferase is partially k(cat)-inhibited by its acceptor substrate, E(2). This inhibition does not influence the burst kinetics and thus occurs after formation of the product central complex, a finding consistent with the slow escape of PAP from the nonreactive E.PAP.E(2) complex.

Does rapid metabolism ensure negligible risk from bisphenol A?

BACKGROUND

Bisphenol A (BPA) risks are being evaluated by many regulatory bodies because exposure is widespread and the potential exists for toxicity at low doses.

OBJECTIVE

We evaluated evidence that BPA is cleared more rapidly in humans than in rats in relation to BPA risk assessment.

DISCUSSION

The European Food Safety Authority (EFSA) relied on pharmacokinetic evidence to conclude that rodent toxicity data are not directly relevant to human risk assessment. Further, the EFSA argues that rapid metabolism will result in negligible exposure during the perinatal period because of BPA glucuronidation in pregnant women or sulfation in newborns. These arguments fail to consider the deconjugation of BPA glucuronide in utero by beta-glucuronidase, an enzyme that is present in high concentrations in placenta and various other tissues. Further, arylsulfatase C, which reactivates endogenous sulfated estrogens, develops early in life and so may deconjugate BPA sulfate in newborns. Biomonitoring studies and laboratory experiments document free BPA in rat and human maternal, placental, and fetal tissues, indicating that human BPA exposure is not negligible. The pattern of these detections is consistent with deconjugation in the placenta, resulting in fetal exposure. The tolerable daily intake set by the EFSA (0.05 mg/kg/day) is well above effect levels reported in some animal studies.

CONCLUSION

This potential risk should not be dismissed on the basis of an uncertain pharmacokinetic argument. Rather, risk assessors need to decipher the BPA dose response and apply it to humans with comprehensive pharmacokinetic models that account for metabolite deconjugation.

Phosphoconjugation and dephosphorylation reactions of steroid hormone in insects

In insects, the major products of phase II metabolism of ecdysteroids, which include the molting hormone, are phosphate esters. The phosphoconjugation pathway is a reversible process, comprising two enzyme systems: ecdysteroid 22-kinase (EcKinase) and ecdysteroid-phosphate phosphatase (EPPase). We report here that: (1) the biochemical characteristics of EcKinase and EPPase, (2) the physiological significance of the reciprocal conversion of ecdysteroids and ecdysteroid phosphates in the ovary-egg system in insects, (3) the biochemical mechanism by which ecdysteroid phosphates are synthesized in the ovary, transferred to eggs, and finally dephosphorylated in eggs, and (4) the possible catalytic steps of EcKinase and EPPase on the basis of the data obtained by an in silico study. From these studies, it is obvious that ecdysteroid phosphates as well as steroid sulfates, which are major products of phase II metabolism in mammals, function as precursors for the formation of biologically active hormones.

24-hydroxycholesterol sulfation by human cytosolic sulfotransferases: formation of monosulfates and disulfates, molecular modeling, sulfatase sensitivity, and inhibition of liver x receptor activation

24-Hydroxycholesterol (24-OHChol) is a major cholesterol metabolite and the form in which cholesterol is secreted from the brain. 24-OHChol is transported by apolipoprotein E to the liver and converted into bile acids or excreted. In both brain and liver, 24-OHChol is a liver X receptor (LXR) agonist and has an important role in cholesterol homeostasis. 24-OHChol sulfation was examined to understand its role in 24-OHChol metabolism and its effect on LXR activation. 24-OHChol was conjugated by three isoforms of human cytosolic sulfotransferase (SULT). SULT2A1 and SULT1E1 sulfated both the 3- and 24-hydroxyls to form the 24-OHChol-3, 24-disulfate. SULT2B1b formed only 24-OHChol-3-sulfate. The 3-sulfate as a monosulfate or as the disulfate was hydrolyzed by human placental steroid sulfatase, whereas the 24-sulfate was resistant. At physiological 24-OHChol concentrations, SULT2A1 formed the 3-monosulfate and the 3, 24-disulfate as a result of a high affinity for sulfation of the 3-OH in 24-OHChol-24-sulfate. Molecular docking simulations indicate that 24-OHChol-24-sulfate binds in an active configuration in the SULT2A1 substrate binding site with high affinity only when the SULT2A1 homodimer structure was used. 24-OHChol is an LXR activator. In contrast, the 24-OHChol monosulfates were not LXR agonists in a fluorescence resonance energy transfer coactivator recruitment assay. However, both the 24-OHChol-3-sulfate and 24-sulfate were antagonists of LXR activation by N-(2,2,2-trifluoroethyl)-N-[4-[2,2,2-trif-luoro-1-hydroxy-1-(trifluoromethyl)ethyl]phenyl]-benzenesulfonamide (T0901317) with an IC(50) of 0.15 and 0.31 muM, respectively. Inhibition of LXR activation by the 24-OHChol monosulfates at low nanomolar concentrations indicates that sulfation has a role in LXR regulation by oxysterols.

Expression of estrogen-metabolizing enzymes and estrogen receptors in cholelithiasis gallbladder

BACKGROUND

Estrogen exposure is a risk factor for gallstone disease (cholelithiasis), which often leads to chronic inflammation (cholecystitis). Studies in various estrogen-sensitive tissues showed that key enzymes involved in the inactivation and activation of estrogens as well as expression of estrogen receptors alpha and beta determine the amount of active estrogen. In estrogen-sensitive tissues, e.g. the female breast, estrone sulfate (E1S), present at high concentrations in the circulation, is converted into the biologically active estrone (E1) by steroid sulfatase (STS) and again reverted into E1S by estrogen sulfotransferase (SULT1E1) providing a local estrogen storage.

AIMS

To assess whether this might also apply for gallbladder epithelia, we determined expression of these two enzymes and of ERalpha and ERbeta in 15 cholelithiasis specimens from tissues with/or without inflammation.

METHODS

Quantitative (Real-time) PCR and immunofluorescence were used as methods.

RESULTS

We demonstrate mRNA expression of SULT1E1, STS, and ERalpha in all specimens with mean enrichment of 3.53- vs. 1.72-fold (n.s.), 3.5- vs. 0.91-fold (n.s.), and 3.04- vs. 1.6-fold (n.s.) in the inflammatory and non-inflammatory groups, respectively. Although high expression levels were seen in many specimens (means 4.88-fold vs. 5.77-fold), ERbeta mRNA was below the detection limit in two specimens from cholecystitis patients. To further investigate this varying expression pattern of ERbeta, immunohistological studies were performed, which indeed showed low expression levels of ERbeta in the damaged mucosa, while in specimens with well preserved mucosa, high ERbeta levels were seen in the cytosol and in the nucleus.

CONCLUSION

The data show expression of an estrogen network of activating STS and inactivating SULT1E1. Together with ERalpha and ERbeta, these enzymes could regulate estrogen concentrations in human gallbladder.

Pregnenolone sulfate in the brain: a controversial neurosteroid

Pregnenolone sulfate (PREGS) has been shown, either at high nanomolar or at micromolar concentrations, to increase neuronal activity by inhibiting GABAergic and by stimulating glutamatergic neurotransmission. PREGS is also a potent modulator of sigma type 1 (sigma1) receptors. It has been proposed that these actions of PREGS underlie its neuropharmacological effects, and in particular its influence on memory processes. On the other hand, the PREGS-mediated increase in neuronal excitability may become dangerous under particular conditions, for example in the case of excitotoxic stress or convulsions. However, the physiopathological significance of these observations has recently been put into question by the failure to detect significant levels of PREGS within the brain and plasma of rats and mice, either by direct analytical methods based on liquid chromatography/mass spectrometry (LC/MS) or enzyme linked immunosorbent assay (ELISA) with specific antibodies against PREGS, or by indirect gas chromatography/mass spectrometry (GC/MS) analysis with improved sample workup. These recent results have not come to the attention of a large number of neurobiologists interested in steroid sulfates. However, although available direct analytical methods have failed to detect levels of PREGS above 0.1-0.3 ng/g in brain tissue, it may be premature to completely exclude the local formation of biologically active PREGS within specific and limited compartments of the nervous system. In contrast to the situation in rodents, significant levels of sulfated 3beta-hydroxysteroids have been measured in human plasma and brain. Previous indirect measures of steroid sulfates by radioimmunoassays (RIA) or GC/MS had detected elevated levels of PREGS in rodent brain. The discrepancies between the results of different assay procedures have revealed the danger of indirect analysis of steroid sulfates. Indeed, PREGS must be solvolyzed/hydrolyzed prior to RIA or GC/MS analysis, and it is the released, unconjugated PREG which is then quantified. Extreme caution needs to be exercised during the preparation of samples for RIA or GC/MS analysis, because the fraction presumed to contain only steroid sulfates can be contaminated by nonpolar components from which PREG is generated by the solvolysis/hydrolysis/derivatization reactions.

Immunohistochemical analysis of steroid sulfatase in human tissues

Steroid sulfatase (EC 3.1.6.2) is an enzyme that removes the sulfate group from 3beta-hydroxysteroid sulfates. This enzyme is best known for its role in estrogen production via the fetal adrenal-placental pathway during pregnancy; however, it also has important functions in other physiological and pathological steroid pathways. The objective of this study was to examine the distribution of steroid sulfatase in normal human tissues and in breast cancers using immunohistochemistry, employing a newly developed steroid sulfatase antibody. A rabbit polyclonal antiserum was generated against a peptide representing a conserved region of the steroid sulfatase protein. In Western blotting experiments using human placental microsomes, this antiserum crossreacted with a 65 kDa protein, the reported size of steroid sulfatase. The antiserum also crossreacted with single protein bands in Western blots of microsomes from two human breast cancer cell lines (MDA-MB-231 and MCF-7) and from rat liver; however, there were some size differences in the immunoreactive bands among tissues. The steroid sulfatase antibody was used in immunohistochemical analyses of individual human tissue slides as well as a human tissue microarray. For single tissues, human placenta and liver showed strong positive staining against the steroid sulfatase antibody. ER+/PR+ breast cancers also showed relatively strong levels of steroid sulfatase immunoreactivity. Normal human breast showed moderate levels of steroid sulfatase immunoreactivity, while ER-/PR- breast cancer showed weak immunoreactivity. This confirms previous reports that steroid sulfatase is higher in hormone-dependent breast cancers. For the tissue microarray, most tissues showed some detectable level of steroid sulfatase immunoreactivity, but there were considerable differences among tissues, with skin, liver and lymph nodes having the highest immunoreactivity and brain tissues having the lowest. These data reveal the utility of immunohistochemistry in evaluation of steroid sulfatase activity among tissues. The newly developed antibody should be useful in studies of both humans and rats.

Redox regulation of human estrogen sulfotransferase (hSULT1E1)

Sulfotransferases (SULTs) are enzymes that catalyze the sulfation of hydroxyl-containing compounds. Sulfation regulates hormone activities and detoxifies xenobiotics. Human estrogen sulfotransferase (hSULT1E1) catalyzes the sulfation of estrogens and regulates estrogen bioactivities. Oxidative regulation provides a biological mechanism for regulating enzyme activities in vivo. The oxidative regulation of human SULTs has not been reported. In this study, we used amino acid modification, manipulation of intracellular redox state, and site-directed mutagenesis to study the redox regulation of human SULTs and specifically the mechanism of hSULT1E1 inhibitory regulation by oxidized glutathione (GSSG). Of the four major human SULTs, hSULT1A1, hSULT1A3, and hSULT2A1 do not undergo redox regulation; hSULT1E1, on the other hand, can be redox regulated. GSSG inactivated hSULT1E1 activity in an efficient, time- and concentration-dependant manner. The co-enzyme adenosine 3'-phosphate 5'-phosphosulfate protected hSULT1E1 from GSSG-associated inactivation. A reduced glutathione (GSH) inducer (N-acetyl cysteine) significantly increased while a GSH depletor (buthionine sulfoxamine) significantly decreased hSULT1E1 activity, but both failed to affect the amount of hSULT1E1 protein in human hepatocyte carcinoma Hep G2 cells. Crystal structure suggested that no Cys residues exist near the active sites of hSULT1A1, hSULT1A3, and hSULT2A1, but Cys residues do exist within the active site of hSULT1E1. Site-directed mutagenesis demonstrated that Cys83 is critical for the redox regulation of hSULT1E1. This first report on the redox regulation of human SULTs suggests that the redox regulation of hSULT1E1 may interrupt the regulation and function of estrogens under various physiological and pathological conditions.