Chemical speciation and enzymatic impact of silver in antimicrobial fabric buried in soil

This study investigated the impact of Ag in antibacterial fabric on soil enzymes in relation to solubility and speciation of Ag. Sections of Ag-containing sock fabric (1.0-1.5cm(2)) were incubated in soils with aerobic and anaerobic conditions and periodically determined activity of arylsulfatase, dehydrogenase and urease. Microscale distribution and speciation of Ag at the interface between socks and soil particles were investigated using micro-focused X-ray fluorescence (μ-XRF), and Ag speciation was determined using micro-focused X-ray absorption near edge structure (μ-XANES) spectroscopy. Results showed that the sock fabric consisted of elemental Ag and Ag2S. After 60-day exposure to soil, majority (50-90%) of Ag in sock did not undergo phase transformation and present as elemental Ag and Ag2S in aerobic and anaerobic conditions. A part of Ag in sock fabric was bound with soil colloids (<15%), depending on the distance from the edge of sock fabric. Soil enzyme activities were overall unaffected by Ag in sock textile after 60days of incubation, although a significant decrease in arylsulfatase activity was found only in the initial stage of soil incubation. Silver in the sock fabric is relatively stable and has little detrimental impacts on enzyme activity in ordinary soil conditions.

Synthesis and evaluation of general mechanism-based inhibitors of sulfatases based on (difluoro)methyl phenyl sulfate and cyclic phenyl sulfamate motifs

Several model mechanism-based inhibitors (MbIs) were designed and evaluated for their ability to inhibit sulfatases. The MbI motifs were based on simple aromatic sulfates, which are known to be commonly accepted substrates across this highly conserved enzyme class, so that they might be generally useful for sulfatase labeling studies. (Difluoro)methyl phenol sulfate analogs, constructed to release a reactive quinone methide trap, were not capable of irreversibly inactivating the sulfatase active site. On the other hand, the cyclic sulfamates (CySAs) demonstrated inhibition profiles consistent with an active site-directed mode of action. These molecules represent a novel scaffold for labeling sulfatases and for probing their catalytic mechanism.

Sensitivity of lysosomal enzymes to the plant alkaloid sanguinarine: comparison with other SH-specific agents

The influence of the benzo[c]phenanthridine alkaloid sanguinarine on some lysosomal enzyme activities was investigated. Sanguinarine inhibits lysosomal hydrolases in homogenates of cultured mouse fibroblasts. After incubation of mouse fibroblasts in culture with 100 microM sanguinarine an approximately 50% decrease in the activities of N-acetyl-beta,D-glucosaminidase (NAGA), beta-galactosidase (GAL), arylsulfatase and acid lipase was observed. Because the biological activity of sanguinarine might arise from the interaction of its iminium cation with enzyme thiol groups, we compared its effect on NAGA, GAL and acid phosphatase (AcP) activities with the effects of SH-specific reagents p-chloromercuribenzoic acid (CPMA) and N-ethylmaleimide (NEM). Treatment of lysosomal fractions with millimolar concentrations of sanguinarine induces a dose-dependent inhibition of the enzymes; for example, 0.6 mM sanguinarine causes approximately a 40% decrease in AcP and NAGA activities. NEM has similar effects, and increasing the preincubation temperature from 0 degrees C to 37 degrees C intensifies the inhibition due to both agents. CPMA also inhibits the activity of GAL (IC50 0.7 microM), AcP (IC50 12.5 microM) and NAGA (IC50 6.8 microM) in a dose-dependent manner but is more potent than sanguinarine or NEM. Comparative analysis of the primary structures of these enzymes using the program BLAST reveals the presence of highly conserved cysteine residues, which confirms the importance of thiol-groups for their activities. Thus, both the experimental observations obtained in this study and the literature data imply a significant role of redox-based mechanisms in regulating lysosomal functional activity.

Aryl sulfatase from Naja nigricolis venom: characterization and possible contribution in the pathology of snake poisoning

The venom of Naja nigricolis was found to contain a high level of the enzyme aryl sulfatase. The enzyme was isolated from the venom of N. nigriclois and purified to electrophoretic homogeneity by gel chromatography on Sephadex G-100, DEAE-cellulose, and phenyl-sepharose columns. The enzyme was optimally active at pH 5 and 40 degrees C. Arrhenius plot for the determination of the activation energy (E(a)) gave the value 25 kJ/mol with a half-life (t(1/2)) of 5 min at 50 degrees C. It was highly activated by Fe(2+) and Ca(2+) and inhibited by Co(2+) and Mn(2+). The enzyme catalyzed the hydrolysis of the fluorescent compound methylumbelliferyl-sulfate (MU-SO(4)). Double reciprocal plots of initial velocity data, using MU-SO(4) as substrate, gave a K(M) value of 110 microM and V(max) of 225 micromol min(-1) x mg(-1). N. nigricolis Aryl sulphatase also hydrolyzed chondroitin-4-sulphate. It was inhibited competitively by N-acetyl glucosamine sulfate (GlcNAc-SO(4)), glucose-6-sulfate (Glc-6-SO(4)), and glucose 1-sulfate (Glc-1-SO(4)). Extrapolated inhibition binding constants (K(i)) gave the values of 3, 25, and 315 microM for GlcNAc-SO(4), Glc-6-SO(4), and Glc-1-SO(4) respectively.

First dual aromatase-steroid sulfatase inhibitors

Aromatase inhibitors in clinical use block the biosynthesis of estrogens. Hydrolysis of estrone 3-sulfate by steroid sulfatase is an important additional source of tumor estrogen, and blockade of both enzymes should provide a more effective endocrine therapy. Sulfamoylated derivatives of the aromatase inhibitor YM511 inhibited sulfatase and aromatase in JEG-3 cells with respective IC(50) values of 20-227 and 0.82-100 nM (cf. letrozole, 0.89 nM). One dual inhibitor was potent against both enzymes in vivo, validating the concept.

Solid-phase parallel synthesis of 17alpha-substituted estradiol sulfamate and phenol libraries using the multidetachable sulfamate linker

We report an application of the multidetachable sulfamate linker in the synthesis of two model libraries of N-derivatized 17alpha-piperazinomethyl estradiols (phenols and sulfamates) by solid-phase parallel chemistry. The solid-phase precursor, a 3-sulfamoyl-17alpha-(N-trifluoroacetyl-piperazinomethyl) estradiol, was synthesized in solution from estrone and loaded efficiently onto trityl chloride resin as polymeric support. After cleavage of the trifluoroacetyl protecting group, sequential acylation reactions with five Fmoc-protected amino acids and five carboxylic acids were performed to introduce two levels of molecular diversity. Finally, the resins were split into two parts, and acidic (5% trifluoroacetic acid in dichloromethane) and nucleophilic (piperazine in tetrahydrofuran) cleavages were used to generate libraries A (5 x 5 sulfamates) and B (5 x 5 phenols) members in overall yields of 18-66% and high HPLC purities (87-96%) without purification steps. A preliminary screening test for inhibition of steroid sulfatase showed that the phenols were clearly weaker inhibitors, as compared to their sulfamate analogues. The most potent inhibitors were those with suitable hydrophobic amino acid and carboxylic acid substituents. Thus, compounds with a phenylalanine residue as the first element of diversity inhibited over 90% of steroid sulfatase activity at a concentration of 1 nM in homogenates of HEK-293 transfected cells, being as potent as the leading inhibitor 17alpha-tert-butylbenzyl estradiol 3-O-sulfamate previously reported. These results suggest that the steroid sulfatase inhibitory potency of estradiol derivatives, sulfamoylated or not, can be increased by the hydrophobic effect of a suitable substituent introduced in the proximity of the D ring of the steroid. The present work also demonstrated the efficiency and the cleavage versatility of the sulfamate linker to generate libraries of compounds with relevant biological importance, phenols and sulfamates.

Carbonic anhydrase inhibitors. Inhibition of cytosolic isozymes I and II and transmembrane, tumor-associated isozyme IX with sulfamates including EMATE also acting as steroid sulfatase inhibitors

A series of sulfamates or bis-sulfamates incorporating aliphatic, aromatic, polycyclic (steroidal), and sugar moieties in their molecules has been synthesized and assayed as inhibitors of the zinc enzyme carbonic anhydrase (CA), and more precisely of the cytosolic isozymes CA I andII, and the transmembrane, tumor-associated isozymes CA IX. Some of these compounds were previously reported to act as inhibitors of steroid sulfatases, among which estrone sulfatase (ES) and dehydroepiandrosterone sulfatase (DHEAS) are the key therapeutic targets for estrogen-dependent tumors. Very potent (nanomolar) inhibitors were detected against the three investigated CA isozymes. Best CA I inhibitors were phenylsulfamate and some of its 4-halogeno derivatives, as well as the aliphatic compound n-octyl sulfamate. Against CA II, low nanomolar inhibitors (1.1-5 nM) were phenylsulfamate and some of its 4-halogeno/nitro derivatives, n-octyl sulfamate, and estradiol 3,17beta-disulfamate among others. All the investigated sulfamates showed efficient CA IX inhibitory properties, with inhibition constants in the range of 18-63 nM. The best CA IX inhibitor detected so far was 4-chlorophenylsulfamate. These data are critical for the design of novel antitumor properties, mainly for hypoxic tumors that overexpress CA IX, which are nonresponsive to radiation or chemotherapy. The antitumor properties of the ES/DHEAS inhibitors in clinical trials may on the other hand also be due to their potent inhibitory properties of CA isozymes involved in tumorigenicity, such as CA II and CA IX.

3Beta-sulfamate derivatives of C19 and C21 steroids bearing a t-butylbenzyl or a benzyl group: synthesis and evaluation as non-estrogenic and non-androgenic steroid sulfatase inhibitors

A series of C19 and C21 steroids bearing one or two inhibiting groups (3beta-sulfamate and 17alpha- or 20(S)-t-butylbenzyl or benzyl) were synthesized and tested for inhibition of steroid sulfatase activity. When only a sulfamate group was added to dehydroepiandrosterone, androst-5-ene-3beta,17beta-diol, pregnenolone and 20-hydroxy-pregnenolone, no significant inhibition of steroid sulfatase occurred at concentrations of 0.3 and 3 microM. With only a t-butylbenzyl or a benzyl group, a stronger steroid sulfatase inhibition was obtained in the androst-5-ene than in the pregn-5-ene series. Comparative results from the screening tests and the IC50 values have shown that the effect of a sulfamate moiety as a second inhibiting group can be combined to the t-butylbenzyl or benzyl effect in the C19 and C21 steroid series. The 3beta-sulfamoyloxy-17alpha-t-butylbenzyl-5-androsten-17beta-ol (10) was thus found to be the most active compound with IC50 values of 46 +/- 8 and 14 +/- 1 nM, respectively for the transformations of E1S to E1 and DHEAS to DHEA. The IC50 values of compound 10 are similar to that of 17alpha-t-butylbenzyl-estradiol, which was previously reported by our group as a good steroid sulfatase reversible inhibitor, but remains higher than that of the potent inactivators estrone-3-O-sulfamate (EMATE) and 17alpha-t-butylbenzyl-EMATE. However, contrary to these two latter inhibitors, compound 10 did not induce any proliferative effect on estrogen-sensitive ZR-75-1 cells nor on androgen-sensitive Shionogi cells at concentrations tested, suggesting that this steroid sulfatase inhibitor is non estrogenic and non androgenic.

In vitro and in vivo models for the evaluation of new inhibitors of human steroid sulfatase, devoid of residual estrogenic activity

The goal of our research project is to develop a new class of orally active drugs, estrone sulfatase inhibitors, for the treatment of estrogen-dependent (receptor positive) breast cancer. Several compounds were synthesized and their pharmacological potencies explored. Based on encouraging preliminary results, three of them, TX 1299, TX 1492 and TX 1506 were further studied in vitro as well as in vivo. They proved to be strong inhibitors of estrone sulfatase when measured on the whole human JEG-3 choriocarcinoma and MCF-7 breast cancer cells and their IC(50)s found to be in the range of known standard inhibitors. Their residual estrogenic activity was checked as negative in the test of induction of alkaline phosphatase (APase) activity in whole human endometrial adenocarcinoma Ishikawa cells. In addition, their effect on aromatase activity in JEG-3 cells was also examined, since the goal of inhibiting both sulfatase and aromatase activities appears very attractive. However, it has been unsuccessful so far. Then, in vivo potencies of TX 1299, the lead compound in our chemical series, were evaluated in comparison with 6,6,7-COUMATE, a non-steroidal standard, in two different rat models and by oral route. First, the absence of any residual estrogenic activity for these compounds was checked in the uterotrophic model in prepubescent female rats. Second, antiuterotrophic activity in adult ovariectomized rat supplemented with estrone sulfate (E(1)S), showed that both compounds were potent inhibitors, the power of TX 1299 relative to 6,6,7-COUMATE being around 80%. This assay was combined with uterine sulfatase level determination and confirmed the complete inhibition of this enzyme within the target organ. Preliminary studies indicated that other non-steroid compounds in the Théramex series were potent in vitro and in vivo inhibitors of estrone sulfatase in rats and further studies are in progress.

Novel D-ring modified steroid derivatives as potent, non-estrogenic, steroid sulfatase inhibitors with in vivo activity

In pursuit of novel steroid sulfatase (STS) inhibitors devoid of estrogenicity, several D-ring modified steroid derivatives were synthesised. In vitro evaluation of the compounds identified two highly potent inhibitors, 4a and 4b, which were 18 times more active than estrone-3-O-sulfamate (EMATE), both having IC(50) values of ca. 1nM. These 16,17-seco-estra-1,3,5(10)-triene-16,17-imide derivatives were synthesised from estrone, via the intermediate 1, which was easily alkylated, deprotected and sulfamoylated affording the final compounds in high yields. In order to assess their biological profile, the selected inhibitors were tested for their in vivo inhibitory potency and estrogenicity in ovariectomised rats. After an oral dose of 10mg/kg per day for 5 days, 4a and 4b were found to inhibit rat liver steroid sulfatase by 99%. They were also devoid of estrogenic activity in the uterine weight gain assay, indicating that these two leads have therapeutic potential for the treatment of hormone-dependent breast cancer.

Sulfamoyloxy-substituted 2-phenylindoles: antiestrogen-based inhibitors of the steroid sulfatase in human breast cancer cells

Estrone sulfate (E1S) is an endogenous prodrug that delivers estrone and, subsequently, estradiol to the target cells following the hydrolysis by the enzyme estrone sulfatase which is active in various tissues including hormone dependent breast cancer cells. Blockade of this enzyme should reduce the estrogen level in breast cancer cells and prevent hormonal growth stimulation. Sulfamates of a variety of phenolic compounds have been shown to be inhibitors of estrone sulfatase. Our rational is based on findings that these inhibitors can undergo hydrolysis and the pharmacological effects of the free hydroxy compounds contribute to the bioactivity of the sulfamates. A desirable action of the metabolites would be an estrogen antagonism to block stimulatory effects of residual amounts of estrogens. Thus, we synthesized a number of sulfamoyloxy-substituted 2-phenylindoles with side chains at the indole nitrogen that guarantee antiestrogenic activity. All of the new sulfamates were studied for their inhibitory effects on the enzyme estrone sulfatase from human breast cancer cells and their (anti)hormonal activities in stably transfected human MCF-7/2a mammary carcinoma cells. The hormonal profile of the sulfamates was partly reflected by the properties of the corresponding hydroxy precursors. Some of the sulfamoylated antiestrogens strongly inhibited estrone sulfatase activity with IC(50) values in the submicromolar range. They were devoid of agonist activity and suppressed estrone sulfate-stimulated gene expression mainly by blocking the enzyme. Examples are the disulfamates of the indoles ZK 119, 010 and ZK 164, 015. Their IC(50)s for sulfatase inhibition were 0.3 and 0.2 microM, respectively, and 50 and 80 nM, respectively, for the inhibition of E1S-stimulated luciferase expression in transfected MCF-7 cells. With some of the new sulfamates an additional direct antiestrogenic effect was noticed which might be due to a partial hydrolysis during incubation and would improve the growth inhibitory effect on estrogen-sensitive breast cancer cells.

2-Substituted 4-(thio)chromenone 6-O-sulfamates: potent inhibitors of human steroid sulfatase

Steroid sulfatase (STS) has emerged as a highly attractive target for the therapy of a number of disorders. Starting with the known inhibitor estrone sulfamate (1) as lead compound and with the finding that steroid sulfamates containing a nonaromatic A-ring are inactive, chromen-4-one sulfamates were designed, prepared, and tested for their ability to block human STS. This new class of nonsteroidal inhibitors shows high potency when the sulfamate group and the side chain are situated in diagonally opposite positions (i.e., 2,6- and 3,7-substitution pattern). The highest activity is achieved with fully branched, bulky aliphatic side chains and with thiochromen-4-one as the core element. 2-(1-Adamantyl)-4H-thiochromen-4-on-6-O-sulfamate (6c) is the most potent STS inhibitor discovered so far, and it is about 170-fold superior to 1. As with 1, all chromenone sulfamates are irreversible inhibitors of STS with a biphasic time course of inactivation.

Inhibition of steryl sulfatase activity in LNCaP human prostate cancer cells

The enzyme steryl sulfatase may help support the growth of hormone-dependent tumors, including prostate cancers, by facilitating the conversion of circulating precursor steroids to active hormones. We sought to determine the presence of steryl sulfatase activity in the androgen-dependent human prostate cancer cell line LNCaP, and to determine if this activity was inhibited by known steryl sulfatase inhibitors. Intact LNCaP cultures had steryl sulfatase activity, as determined by conversion of [3H]estrone sulfate (E(1)S) to unconjugated steroids. The level of steryl sulfatase activity was relatively low (4.6 pmol/18 h/million cells) compared to MDA-MB-231 breast cancer cells (284.0 pmol/18 h/million cells). The observed activity in both cell lines was blocked by addition of 1 microM estrone sulfamate (EMATE), an active-site-directed, steroidal inhibitor of steryl sulfatase. Steryl sulfatase activity was also inhibited by Danazol, and by (p-O-sulfamoyl)-tetradecanoyl tyramine (C2-14), a non-steroidal inhibitor. Microsomes prepared from LNCaP cultures also showed steryl sulfatase activity, as determined by hydrolysis of [3H]E(1)S and [3H]dehydroepiandrosterone sulfate (DHEAS) to unconjugated forms. LNCaP and MDA-MB-231 microsomes both hydrolyzed E(1)S about two times faster than DHEAS. Hydrolysis of E(1)S in LNCaP and MDA-MB-231 microsomes was blocked by steryl sulfatase inhibitors with the following relative potencies: EMATE>C2-14>Danazol. These data demonstrate that LNCaP prostate cancer cells contain a steryl sulfatase with properties similar to that found in human breast cancer cells, and that the activity of this enzyme can be blocked by known steryl sulfatase inhibitors. Steryl sulfatase inhibitors may be useful as an adjuvant to androgen deprivation therapy for prostate cancer.

4,4'-Benzophenone-O,O'-disulfamate: a potent inhibitor of steroid sulfatase

We investigated whether the benzophenone moiety can be used as core element of steroid sulfatase (STS) inhibitors. While 4- and 3-benzophenone-O-sulfamates inhibit STS with IC(50) values between 5 and 7 microM irrespective of additional hydroxy and methoxy substituents at the second phenyl ring, benzophenone-O,O'-disulfamates show increased activity. With an IC(50) value of 190 nM the 4,4'-derivative is the first small monocyclic STS inhibitor coming close to the potency of the steroidal standard estrone sulfamate.

Nonsteroidal compounds designed to mimic potent steroid sulfatase inhibitors

Chemical synthesis and enzyme inhibition results are reported for a series of nonsteroidal sulfatase inhibitors, 1-(p-sulfamoyloxyphenyl)-5-(p-t-butylbenzyl)-5-alkanols and the lower active phenolic analogues. These compounds conserve some structural elements from the previously reported potent steroidal inhibitor 3-O-sulfamate-17alpha-(p-t-butylbenzyl)-17beta-hydroxy-estra-1,3,5(10)-triene, while the C18-methyl group and the hydrocarbon backbone represented by the steroid rings B, C, and D were replaced with a free conformational chain. Using estrone sulfate (100 microM) as substrate and homogenate of transfected HEK-293 cells as source of steroid sulfatase activity, the IC(50) values of the best inhibitors, the undecanol derivatives, were 0.4+/-0.1 and >300 nM, respectively, in the sulfamate and phenolic series. Although these sulfamoylated nonsteroidal inhibitors appear a bit less active than their steroidal analogues, they are however more potent than known inhibitors estrone-3-O-sulfamate and p-(O-sulfamoyl)-N-tetradecanoyl tyramine. The optimal side-chain length for the inhibition of steroid sulfatase activity was found to be six carbons, which corresponds to the number of carbons that mimic the B, C and D steroid rings, between C6 and C17. Furthermore, compounds with only the t-butylbenzyl group or the alkyl chain of six carbons are less potent inhibitors compared to the one that include both of these hydrophobic substituents. Such results suggest that compound from this later category better mimic the steroidal inhibitor.

Aggressive behavior induced by the steroid sulfatase inhibitor COUMATE and by DHEAS in CBA/H mice

The steroid sulfatase enzyme (STS) regulates the formation of dehydroepiandrosterone (DHEA) from dehydroepiandrosterone-sulfate (DHEAS). DHEAS is a well-known negative allosteric modulator of the GABA(A) receptor-gated chloride channels. It is classified as an excitatory neurosteroid. The implication of GABA(A) receptor activity in aggressive behavior in rodents is well-documented. In addition a genetic correlation between STS level in the liver and aggressive behavior across 12 strains of mice suggest that STS activity could be involved in aggression in mice. We assessed herein whether COUMATE (an STS inhibitor) and DHEAS modulate aggression in CBA/H mice. We hypothesized that inhibiting STS activity in vivo followed by DHEAS injections which increase the level of sulfated steroid that cross the blood-brain barrier and then modulate neurotransmitter receptors could modify the attack behavior in mice. COUMATE (10 mg/kg) was administrated p.o. alone or in combination with the neurosteroid DHEAS (0-50 mg/kg) i.p. Animals were thereafter tested for aggression. A single dose of COUMATE significantly inhibited STS activity both in the brain (70.57%) and in the liver (87%) 24 h following administration. Behavioral tests showed that the inhibitor and DHEAS enhanced aggressive behavior when animals were simultaneously subjected to both molecules. These results confirm the correlation between aggressive behavior and STS concentration in mice. In addition, we confirm that the steroid metabolism can modulate the behavior in rodents.

Automated synthesis of 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate

After 16alpha-[15F]fluoroestradiol ([18F]FES) has been successfully prepared in an automated module, the synthesis of 16alpha-[18F]fluoroestradiol-3,17beta-disulphamate ([18F]FESDS) is described as a module-assisted one-pot procedure which can provide 10GBq [18F]FESDS with a radiochemical purity better than 99%. The procedure is reliable and reproducible and requires a time of about 90 min. Because of its high sulphatase-inhibitory effect [15F]FESDS is thought to be a new PET tracer to image sites of high sulphatase activity.

Do dietary phytoestrogens influence susceptibility to hormone-dependent cancer by disrupting the metabolism of endogenous oestrogens?

Phytoestrogens are natural constituents of our diets that have been suggested to protect against hormone-dependent breast cancer. Some of the diverse effects of these compounds may be attributed to ligand-dependent differences in their interaction with oestrogen receptor sub-classes. However, phytoestrogens can also inhibit enzymes that are involved in the generation and removal of endogenous steroid hormones. Among the most potent effects of dietary phytoestrogens is their ability to inhibit the sulphotransferases that sulphate both oestrogenic steroids and a variety of environmental chemicals, including dietary pro-carcinogens. Circulating steroid sulphates are thought to be the major source of oestradiol in post-menopausal breast tumours and sulphation is a key step in the activation of some dietary pro-carcinogens. Hence the inhibition of sulphotransferases by dietary phytoestrogens may have complex effects upon human susceptibility to breast cancer.

Synthesis and steroid sulphatase inhibitory activity of C19- and C21-steroidal derivatives bearing a benzyl-inhibiting group

Two series of compounds, benzyl alkylated at position 17alpha and 20 of androstane and pregnane, respectively, were synthesised and tested for steroid sulphatase inhibition. We compared the ability of the compounds to inhibit steroid sulphatase obtained from two different sources (homogenates of transfected HEK-293 cells and Jeg-3 cells) and with two types of substrate (DHEAS or E(1)S). The inhibitory activity of 17alpha-benzyl-5alpha-androstane-3beta,17beta-diol (7), 17alpha-benzyl-5-androstene-3beta,17beta-diol (9), 17alpha-benzyl-4,17beta-dihydroxy-4-androsten-3-one (15) and 20-benzyl-5-pregnene-3beta,20alpha-diol (16) has proven to be superior to that of danazol, the first steroid sulphatase inhibitor to be reported, but still lower than that of the potent inhibitor estrone-3-O-sulphamate. The inhibitory activity of compound 7 was as potent as that of its previously reported estrane analogue, 17alpha-benzyl estradiol. Benzyl alkylated compounds with no OH group on the A-ring (with a 4-OCH(3), 4-Cl, or 4-H and their precursor epoxides), as well as a series of basic steroids without a benzyl group (ADT, epi-ADT, 3alpha-diol, 3beta-diol, DHEA, Delta(5)-diol, DHT, T, Preg and Prog), did not show steroid sulphatase inhibition. We have thus demonstrated that the steroid sulphatase inhibitory effect of a benzyl group, previously observed for an estrane nucleus, can be extended to certain androstane and pregnane nuclei bearing a 3beta-OH or a 4-OH group. Inhibitors 7, 9, 15 and 16 did not induce any proliferative effect on androgen-sensitive Shionogi cells. However, when tested on oestrogen-sensitive ZR-75-1 cells, a proliferative effect was observed for 7 and 9, but not for 15 and 16.

Inhibition of steroid sulphatase activity by tricyclic coumarin sulphamates

The identification of the active pharmacophore required for potent inhibition of steroid sulphatase activity, i.e. an aryl-O-sulphamate structure, has led to the synthesis and testing of a large number of 1-4 ring-based inhibitors. 4-Methylcoumarin-7-O-sulphamate (COUMATE) was one of the first non-steroid based inhibitors identified. In an attempt to increase the potency of this class of inhibitor a series of tricyclic COUMATEs (665-6615 COUMATEs) have been synthesised and evaluated. Using placental microsomes as a source of oestrone sulphatase (E1-STS) the size of the third ring of the tricyclic COUMATEs was found to have a marked effect on inhibitor potency. Whereas 665- and 6615-COUMATEs had IC(50)s of 200 and 370 nM, respectively, the most potent inhibitor in vitro in this series was 6610 COUMATE with an IC(50) of 1 nM. Selected inhibitors were tested for their in vivo potency by administration of a single dose (0.1 or 1 mg/kg, p.o.) to female rats. Surprisingly, in vivo 6615 COUMATE proved to be the most active drug, inhibiting rat liver E1-STS activity by 23 and 94% when assayed 24 h after administration of the 0.1 and 1 mg/kg doses. E1-STS activity in brain tissue and white blood cells was also found to be inhibited when selected drugs were tested. These studies have identified a number of tricyclic COUMATEs with therapeutic potential.

Structure-activity relationships of 17alpha-derivatives of estradiol as inhibitors of steroid sulfatase

The steroid sulfatase or steryl sulfatase is a microsomal enzyme widely distributed in human tissues that catalyzes the hydrolysis of sulfated 3-hydroxy steroids to the corresponding free active 3-hydroxy steroids. Since androgens and estrogens may be synthesized inside the cancerous cells starting from dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E(1)S) available in blood circulation, the use of therapeutic agents that inhibit steroid sulfatase activity may be a rewarding approach to the treatment of androgeno-sensitive and estrogeno-sensitive diseases. In the present study, we report the chemical synthesis and biological evaluation of a new family of steroid sulfatase inhibitors. The inhibitors were designed by adding an alkyl, a phenyl, a benzyl, or a benzyl substituted at position 17alpha of estradiol (E(2)), a C18-steroid, and enzymatic assays were performed using the steroid sulfatase of homogenized JEG-3 cells or transfected in HEK-293 cells. We observed that a hydrophobic substituent induces powerful inhibition of steroid sulfatase while a hydrophilic one was weak. Although a hydrophobic group at the 17alpha-position increased the inhibitory activity, the steric factors contribute to the opposite effect. As exemplified by 17alpha-decyl-E(2) and 17alpha-dodecyl-E(2), a long flexible side chain prevents adequate fitting into the enzyme catalytic site, thus decreasing capacity to inhibit the steroid sulfatase activity. In the alkyl series, the best compromise between hydrophobicity and steric hindrance was obtained with the octyl group (IC(50) = 440 nM), but judicious branching of side chain could improve this further. Benzyl substituted derivatives of estradiol were better inhibitors than alkyl analogues. Among the series of 17alpha-(benzyl substituted)-E(2) derivatives studied, the 3'-bromobenzyl, 4'-tert-butylbenzyl, 4'-butylbenzyl, and 4'-benzyloxybenzyl groups provided the most potent inhibition of steroid sulfatase transformation of E(1)S into E(1) (IC(50) = 24, 28, 25, and 22 nM, respectively). As an example, the tert-butylbenzyl group increases the ability of the E(2) nucleus to inhibit the steroid sulfatase by 3000-fold, and it also inhibits similarly the steroid sulfatase transformations of both natural substrates, E(1)S and DHEAS. Interestingly, the newly reported family of steroid sulfatase inhibitors acts by a reversible mechanism of action that is different from the irreversible mechanism of the known inhibitor estrone sulfamate (EMATE).

Potent active site-directed inhibition of steroid sulphatase by tricyclic coumarin-based sulphamates

BACKGROUND

There is now abundant evidence that inhibition of steroid sulphatase alone or in conjunction with inhibition of aromatase may enhance the response of postmenopausal patients with hormone-dependent breast cancer to this type of endocrine therapy. Additionally, sulphatase inhibition has been proposed to be of potential therapeutic benefit in the immune system and for neuro-degenerative diseases. After the finding that our first highly potent active site-directed steroid sulphatase inhibitor, oestrone-3-O-sulphamate (EMATE), was highly oestrogenic, we proposed non-steroidal coumarin sulphamates such as 4-methylcoumarin-7-O-sulphamate (COUMATE) as alternative non-steroidal steroid sulphatase inhibitors. In this work, we describe how tricyclic coumarin-based sulphamates have been developed which are even more potent than COUMATE, are non-oestrogenic and orally active. We also discuss potential mechanisms of action.

RESULTS

4-Ethyl- (4), 4-(n-propyl)- (6), 3-ethyl-4-methyl- (8), 4-methyl-3-(n-propyl)coumarin-7-O-sulphamate (11); the tricyclic derivatives 665COUMATE (13), 666COUMATE (15), 667COUMATE (17), 668COUMATE (20) and the tricyclic oxepin sulphamate (22) were synthesised. In a placental microsome preparation, all of these analogues were found to be more active than COUMATE in the inhibition of oestrone sulphatase, with the most potent inhibitor being 667COUMATE which has an IC(50) of 8 nM, some 3-fold lower than that for EMATE (25 nM). In addition, 667COUMATE was also found to inhibit DHEA-sulphatase some 25-fold more potently than EMATE in a placental microsome preparation. Like EMATE, 667COUMATE acts in a time- and concentration-dependent manner, suggesting that it is an active site-directed inhibitor. However, in contrast to EMATE, 667COUMATE has the important advantage of not being oestrogenic. In addition, we propose several diverse mechanisms of action for this active site-directed steroid sulphatase inhibitor in the light of recent publications on the crystal structures of human arylsulphatases A and B and the catalytic site topology for the hydrolysis of a sulphate ester.

CONCLUSIONS

A highly potent non-steroidal, non-oestrogenic and irreversible steroid sulphatase inhibitor has been developed. Several mechanisms of action for an active site-directed steroid sulphatase inhibitor are proposed. With 667COUMATE now in pre-clinical development for clinical trial, this should allow the biological and/or clinical significance of steroid sulphatase inhibitors in the treatment of postmenopausal women with hormone-dependent breast cancer and other therapeutic indications to be fully evaluated.

Stimulation of MCF-7 breast cancer cell proliferation by estrone sulfate and dehydroepiandrosterone sulfate: inhibition by novel non-steroidal steroid sulfatase inhibitors

Steroid sulfatase (STS) regulates the formation of active steroids from systemic precursors, such as estrone sulfate and dehydroepiandrosterone sulfate (DHEAS). In breast tissues, this pathway is a source for local production of estrogens, which support the growth of endocrine-dependent tumours. Therefore, inhibitors of STS could have therapeutic potential. In this study, we report on substituted chromenone sulfamates as a novel class of non-steroidal irreversible inhibitors of STS. The compounds are substantially more potent (6- to 80-fold) than previously described types of non-steroidal inhibitors when tested against purified STS. In MCF-7 breast cancer cells, they inhibit STS activity with IC(50) below 100 pM. Importantly, the compounds also potently block estrone sulfate-stimulated growth of MCF-7 cells, again with IC(50) below 100 pM. For one compound, we also observed a lack of any estrogenic effect at high concentrations (1 microM). We also demonstrate for the first time that STS inhibitors can block the DHEAS-stimulated growth of MCF-7 cells. Interestingly, this cannot be achieved with specific inhibitors of the aromatase, suggesting that stimulation of MCF-7 cell growth by DHEAS follows an aromatase-independent pathway. This gives further justification to consider steroid sulfatase inhibitors as potential drugs in the therapy of breast cancer.

Steroid sulfatase inhibitor alters blood pressure and steroid profiles in hypertensive rats

Our hypothesis is that the steroid sulfatase gene (Sts) may indirectly contribute to the modulation of blood pressure (BP) in rats with genetic hypertension. The steroid sulfatase enzyme (STS) catalyzes the conversion of estrone sulfate, dehydroepiandrosterone sulfate, cholesterol sulfate and glucocorticoid sulfates to their active nonconjugated forms. This causes the elevation of biologically active steroids, such as glucocorticoids, mineralcorticoids as well as testosterone, which may lead to increased BP. The main objective was to examine the effects of a steroid sulfatase inhibitor on blood pressure and steroid levels in rats with hypertensive genetic backgrounds. Three treatment groups, 5-15 weeks of age were used: controls, estrone and STS inhibitor (estrone-3-O-sulfamate), (n=8 per group). BP was taken weekly by tail cuff, and serum testosterone (T), estrogens (E), and plasma corticosterone (C) levels were measured by radioimmunoassay. BP was significantly reduced by the STS inhibitor in the strains with genetically elevated BP. Also the inhibitor alone significantly reduced plasma corticosterone in all strains compared to estrone treatment with a concomitant as well as significant rise in estrogens and reduction in testosterone and body weight.

New fluorogenic substrate for the first continuous steroid sulfatase assay

The screening for new inhibitors of steroid sulfatase requires an efficient test system. To overcome the shortcomings of the available discontinuous fluorimetric assay, several coumarin-type compounds were investigated as potential new substrates. 3,4-Benzocoumarin 7-O-sulfate was found to have appropriate substrate properties for the establishment of the first direct continuous assay of steroid sulfatase.

17Alpha-alkan (or alkyn) amide derivatives of estradiol as inhibitors of steroid-sulfatase activity

To develop inhibitors of steroid sulfatase without residual estrogenic activity, we have designed a series of estradiol (E2) derivatives bearing an alkan (or alkyn) amide side chain at position 17alpha. A hydrophobic alkyl group was selected from our previous study where 17alpha-octyl-E2 was found to inhibit strongly the steroid-sulfatase activity. Furthermore, it is known that an alkylamide side chain blocks the estrogen-receptor activation. Starting from ethynylestradiol, the chemical synthesis of target compounds was short and efficient with overall yields of 22-42% (3 or 4 steps). Among these compounds, N-octyl,N-methyl-3-(3',17'beta-dihydroxy-1',3',5'(10')-estratrien- 17'alpha-yl)-propanamide (15) was the most potent inhibitor, with an IC50 value of 0.08 microM for the transformation of estrone sulfate (E1S) to estrone (E1) by homogenated JEG-3 cells. N-butyl, N-hexyl, and N,N-dioctyl propanamide derivatives of E2 (IC50 values of 6.4, 2.8, and >20 microM, respectively) were less potent inhibitors than N-octyl analog 15. Furthermore, the unsaturated propynamide analog of 15 gave lower inhibition (four times) than the saturated compound. Compound 15 is also about 100-fold more effective in interacting with the enzyme than substrate E1S itself. The ability of target compounds to bind the estrogen receptor, to stimulate the proliferation of estrogen-sensitive ZR-75-1 cells, or to inhibit the E2-stimulation of ZR-75-1 cells was also evaluated. Although a mixed estrogenic/anti-estrogenic activity was obtained for tested compounds at 1 microM, no estrogenic activity was observed at 0.03 microM for 15. In conclusion, a promising inhibitor of steroid-sulfatase activity was obtained by introducing a hydrophobic octyl group in a 17alpha-propanamide side chain of E2, but further structure-activity relationships (SAR) studies are necessary to minimize the residual estrogenic activity.

Peripheral steroid sulfatase inhibition potentiates improvement of memory retention for hippocampally administered dehydroepiandrosterone sulfate but not pregnenolone sulfate

Dehydroepiandrosterone sulfate (DHEAS) improves memory retention when administered peripherally. Estrone-3-O-sulfamate (EMATE), a steroid sulfatase inhibitor, potentiates the effect of DHEAS on memory retention such that lower doses of DHEAS improve memory retention. It is not clear if this effect is mediated by both compounds entering the central nervous system. In the current studies, mice were trained to avoid footshock in a T-maze and memory retention was tested 1 week later. DHEAS, injected into the hippocampus after training, improved memory retention in a dose-dependent manner. In previous studies, pregnenolone sulfate (PREGS) improved memory retention when injected into the hippocampus. EMATE, administered peripherally, potentiated the effect of centrally administered DHEAS on memory retention. However, EMATE did not potentiate the effect of centrally administered PREGS. It was concluded that EMATE, acting peripherally, increased plasma levels of DHEAS which entered the brain and added to the effect of centrally administered DHEAS. The failure of EMATE to potentiate PREGS is discussed.

Synthesis and biological activity of the superestrogen (E)-17-oximino-3-O-sulfamoyl-1,3,5(10)-estratriene: x-ray crystal structure of (E)-17-oximino-3-hydroxy-1,3,5(10)-estratriene

Steroid sulfatases regulate the formation of estrogenic steroids which can support the growth of endocrine-dependent breast tumors. Therefore, the development of potent steroid sulfatase inhibitors could have considerable therapeutic potential. Several such inhibitors have now been developed including estrone 3-O-sulfamate (EMATE, 1), which shows potent active site-directed inhibition. However, EMATE was subsequently shown to be also a potent estrogen. In an attempt to reduce the estrogenicity while retaining the potent sulfatase inhibitory properties associated with this type of molecule, (E)-17-oximino-3-O-sulfamoyl-1,3,5(10)-estratriene (5) (estrone oxime 3-O-sulfamate, OMATE) was synthesized. The X-ray crystal structure of (E)-17-oximino-3-hydroxy-1,3,5(10)-estratriene (4) (estrone oxime) demonstrated the presence of only one geometrical isomer [anti-isomer, (E)]. OMATE potently inhibited estrone sulfatase (E1-STS) activity and was similar to EMATE (>99% inhibition at 0.1 microM in MCF-7 breast cancer cells). It was also evaluated in vivo for its estrogenicity and ability to inhibit sulfatase activity. While it was equipotent with EMATE in vivo as a sulfatase inhibitor, it surprisingly had a stimulatory effect on uterine growth in ovariectomized rats about 1.5-fold greater than that of EMATE. Thus, OMATE possesses potential as a superestrogen and modification at C-17 is identified as a useful route for enhancement of estrogenicity in sulfamate-based estrogens.

Potent inhibition of steroid sulfatase activity by 3-O-sulfamate 17alpha-benzyl(or 4'-tert-butylbenzyl)estra-1,3,5(10)-trienes: combination of two substituents at positions C3 and c17alpha of estradiol

Steroid sulfates are precursors of hormones that stimulate androgen- and estrogen-dependent cancers. Thus, steroid sulfatase, the enzyme that catalyzes conversion of DHEAS and E1S to the corresponding unconjugated steroids DHEA and E1, appears to be one of the key enzymes regulating the level of active androgenic and estrogenic steroids. Since 17alpha-substituted benzylestradiols and 3-O-sulfamate estrone (EMATE) represent two families of steroid sulfatase inhibitors that probably act through different mechanisms, we synthesized compounds 3-O-sulfamate 17alpha-benzylestradiol (4) and 3-O-sulfamate 17alpha-(tert-butylbenzyl)estradiol (5) that contain two kinds of substituents on the same molecule. In our enzymatic assay using a homogenate of human embryonal (293) cells transfected with steroid sulfatase, compounds 4 and 5 were found to be more potent inhibitors than already known steroid sulfatase inhibitors that have only a C17alpha-substituent or only a C3-sulfamate group (EMATE). The IC50 values of 4 and 5 were, respectively, 0.39 and 0.15 nM for the transformation of E1S to E1 and 4.1 and 1.4 nM for the transformation of DHEAS to DHEA. Compound 5 inhibited the steroid sulfatase activity in intact transfected (293) cell culture assays by inactivating the enzyme activity. Compound 5 also inactivates the steroid sulfatase activity at lower concentration than EMATE in microsomes of transfected (293) cells. In this assay, an excess of natural substrate E1S protects enzyme against inactivation by 5 or EMATE. Furthermore, the unsulfamoylated analogue of 5, compound 3, did not inactivate the steroid sulfatase.

Recent advances in the development of steroid sulphatase inhibitors

Inhibition of steroid sulphatase is now an important target for the development of new drugs for the treatment of women with endocrine-dependent breast tumours. The first potent sulphatase inhibitor identified, oestrone-3-O-sulphamate (EMATE) proved. unexpectedly, to be oestrogenic. A number of strategies have therefore been adopted to design and synthesize a non-oestrogenic inhibitor. For this, a number of modifications have been made to the A and D rings of the oestrone nucleus. 2 Methoxyoestrone-3-O-sulphamate, while having similar in vitro and in vivo sulphatase inhibitory potency to that of EMATE, was devoid of oestrogenic activity when tested at 2 mg/kg in an ovariectomised rat uterine weight gain assay. 17-Deoxyoestrone-3-O-sulphamate was also a potent steroid sulphatase inhibitor and while it was devoid of oestrogenic activity when tested at 0.1 mg/kg, did stimulate uterine growth at 1.0 mg/kg. As an alternative approach to the use of steroid-based inhibitors a number of single ring, bicyclic non-fused ring, and two fused ring sulphamate analogues were designed, synthesized and tested for their ability to inhibit steroid sulphatase activity. In general, although the single ring and bicyclic non-fused ring sulphamate analogues could inhibit sulphatase activity, they were considerably less potent than EMATE. The mono- and bis-sulphamate derivatives of 5,7-dihydroxyisoflavone were relatively potent, inhibiting in vivo steroid sulphatase activity by 62 and 81% respectively at a single oral dose of 10 mg/kg. A study of the structure-activity relationship of a series of coumarin-based sulphamates has led to the development of a number of potent non-steroidal inhibitors, one of which has a similar potency to that of EMATE. The identification of potent steroid- and non-steroid-based sulphatase inhibitors will enable the therapeutic value of this therapy to be examined in the near future.

A two-component affinity chromatography purification of Helix pomatia arylsulfatase by tyrosine vanadate

The inhibition of Helix pomatia arylsulfatase by the synergistic combination of N-acetyl-l-tyrosine ethyl ester and vanadate has been extended to affinity chromatography for purification. In the presence of vanadate, l-tyrosine ethyl ester (TEE), immobilized on CH-Sepharose 4B retained arylsulfatase from the digestive juice or lyophilized powder of H. pomatia. No enzyme was retained without vanadate or with arsenate or phosphate. Arylsulfatase was eluted from the column matrix by removing the vanadate to less than 50 microM with buffer containing EDTA to chelate the vanadate. Escherichia coli alkaline phosphatase and potato acid phosphatase, two enzymes which are inhibited by vanadate but not by the vanadate-TEE complex, were not retained by the immobilized TEE under any conditions used. The sulfatase activity was completely separated from contaminating glucuronidase activity present in the crude enzyme extracts. The Ki for the immobilized vanadate-TEE system was found to be 5.0 x 10(-7) M with a capacity of 25 mg/ml swollen gel. A purification of greater than 40-fold from the lyophilized powder of H. pomatia (Sigma Type H-5) was achieved using this technique. The Ki/Keq of other phenols with vanadate were determined in a 96-well plate format as an example of a rapid screening technique that could be extended to other phosphoryl and sulfuryl-transfer enzyme classes.

Steroidal and nonsteroidal sulfamates as potent inhibitors of steroid sulfatase

Synthetic routes to potent steroidal and nonsteroidal sulfamate-based active site-directed inhibitors of the enzyme steroid sulfatase, a topical target in the treatment of postmenopausal women with hormone-dependent breast cancer, are described. Novel compounds were examined for estrone sulfatase (E1-STS) inhibition in intact MCF-7 breast cancer cells and placental microsomes. Reaction of the sodium salt of estrone with sulfamoyl chloride gave estrone 3-O-sulfamate (EMATE, 2) which inhibits E1-STS activity potently (> 99% at 0.1 microM in intact MCF-7 cells, IC50 = 65 pM) in a time- and concentration-dependent manner, suggesting that EMATE is an active site-directed inhibitor. EMATE is also active in vivo orally. 5,6,7,8-Tetrahydronaphthalene 2-O-sulfamate (7) and its N-methylated derivatives (8 and 9) were synthesized, and 7 inhibits the E1-STS activity in intact MCF-7 cells by 79% at 10 microM. 4-Methylcoumarin 7-O-sulfamate (COUMATE) and its derivatives (14, 16, and 18) were prepared to extend this series of nonsteroidal inhibitors, and COUMATE reduces the E1-STS activity in placental microsomes by > 90% at 10 microM. Although the orally active COUMATE is less potent than EMATE as an active site-directed inhibitor, it has the important advantage of being nonestrogenic. Analogues (20, 22, 24, 26, 27, 31, 33, 39, and 44) of COUMATE were synthesized to study its structure-activity relationships, and sulfamates of tetralones (46 and 48) and indanones (49, 51, and 53) were also prepared. While most of these compounds were found to inhibit E1-STS activity less effectively than COUMATE, one analogue, 3,4-dimethylcoumarin 3-O-sulfamate (24), was found to be some 12-fold more potent than COUMATE as an E1-STS inhibitor in intact MCF-7 cells (IC50 = 30 nM for 24, cf. 380 nM for COUMATE). Hence, highly potent sulfamate-based inhibitors of steroid sulfatase, such as EMATE, COUMATE, and 24, possess therapeutic potential and will allow the importance of estrogen formation in breast tumors via the E1-STS pathway to be assessed. A pharmacophore for active site-directed sulfatase inhibition is proposed.

The development of A-ring modified analogues of oestrone-3-O-sulphamate as potent steroid sulphatase inhibitors with reduced oestrogenicity

Steroid sulphatases regulate the formation of oestrogenic steroids which can support the growth of endocrine-dependent breast tumours. The development of potent steroid sulphatase inhibitors could therefore have considerable therapeutic potential. Several such inhibitors have now been developed of which the most potent to date is oestrone-3-O-sulphamate (EMATE). Unexpectedly, this inhibitor proved to be a potent oestrogen. In an attempt to reduce the oestrogenicity, whilst retaining the potent sulphatase inhibitory properties associated with this type of molecule, a number of A-ring modified derivatives were designed and synthesized. A-ring modified compounds included the 2-methoxy, 2/4-nitro, 2/4-n-propyl and 2/4-allyl EMATE analogues. The ability of these derivatives to inhibit oestrone sulphatase activity was examined using placental microsomes. The allyl-substituted EMATE derivatives were more potent inhibitors than the propyl analogues but were all considerably less potent than EMATE. In contrast, the 2-methoxy and 2/4-nitro analogues were potent sulphatase inhibitors with 4-nitro EMATE being 5 times more active than EMATE. The 4-nitro, 2-methoxy, 4-n-propyl and 4-allyl derivatives were also tested in vivo for their oestrogenicity and ability to inhibit sulphatase activity. While both 4-nitro and 2-methoxy EMATE were potent inhibitors in vivo, 2-methoxy EMATE had no stimulatory effect on uterine growth in ovariectomized rats. The identification of a potent steroid sulphatase inhibitor lacking any oestrogenicity, such as 2-methoxy EMATE, should be of considerable value in evaluating the potential of steroid sulphatase inhibition for breast cancer therapy.

Steroid sulphatase: expression, isolation and inhibition for active-site identification studies

Steroid sulphatase, which can hydrolyse 3-hydroxysteroid sulphates, has important roles in several physiological and pathological processes. A number of steroid sulphatase inhibitors have now been developed, of which the most potent to date is oestrone-3-O-sulphamate (EMATE). This inhibitor inactivates steroid sulphatase in an irreversible, time- and concentration-dependent manner. In order to be able to use a radiolabelled derivative of EMATE to study the active site, it will be essential to prepare the steroid sulphatase in a pure form. For this, attempts have been made to express the protein, using the steroid sulphatase cDNA, in the pGEX2T expression system and also to express a mutant form of the protein, in which the putative membrane-spanning domain was deleted, in CHO cells. In addition, a soluble steroid sulphatase has been identified from the snail Helix pomatia. This steroid sulphatase is inhibited by EMATE in an irreversible manner, similar to the human steroid sulphatase and appears to possess a histidine residue at its active site. The expression and/or isolation of a steroid sulphatase, in conjunction with the use of a radiolabelled derivative of EMATE should allow important new information about the active site of this enzyme and the mechanism of its inactivation to be obtained.

Chronic steroid sulfatase inhibition by (p-O-sulfamoyl)-N-tetradecanoyl tyramine increases dehydroepiandrosterone sulfate in whole brain

Dehydroepiandrosterone sulfate (DHEAS) is a neurosteroid which functions as a negative allosteric modulator of the GABA(A) receptor-gated chloride channel. Steroid sulfatase inhibitors including (p-O-sulfamoyl)-N-tetradecanoyl tyramine (DU-14), can potentiate the blockade of the amnestic effects of scopolamine by exogenously administered DHEAS. Moreover, when administered over a 15 day period, DU-14 can block scopolamine amnesia without the concurrent administration of DHEAS. Since the enzyme, steroid sulfatase, facilitates the hydrolysis of the sulfate moiety from DHEAS, the intent of this study was to determine whether chronic administration of DU-14 could increase whole brain concentrations of endogenous DHEAS. Rats were administered DU-14 or corn oil vehicle for 15 days. Following the last day the animals were sacrificed and the brains were removed and analyzed for DHEAS content. DU-14 increased the whole brain concentration of DHEAS 77.6%, from 0.65 +/- 0.06 to 1.15 +/- 0.12 microg/g (mean +/- SEM). This result suggests that steroid sulfatase inhibitors may enhance cognitive function following chronic treatment by increasing the concentration of excitatory neurosteroids such as DHEAS in the brain. Steroid sulfatase inhibitors, therefore, may provide a novel mechanism for facilitating central nervous system function.

Enhanced plasma DHEAS, brain acetylcholine and memory mediated by steroid sulfatase inhibition

Steroid sulfatase inhibitors can alter the metabolism of neurosteroids which modulate brain function. Administration of the non-steroidal steroid sulfatase inhibitor (p-O-sulfamoyl)-N-tetradecanoyl tyramine (DU-14) to rats for 15 days increased plasma dehydroepiandrosterone sulfate (DHEAS) concentrations by 88.2%, decreased plasma dehydroepiandrosterone (DHEA) concentrations by 84.6%, increased hippocampal acetylcholine (ACh) release determined via in vivo microdialysis by almost 3-fold, and produced a significant blockade of scopolamine-induced amnesia as measured by a passive avoidance test. These results suggest DHEAS rather than DHEA enhances brain cholinergic function and that steroid sulfatase inhibition may become an important tool for enhancing neuronal functions, such as memory, mediated by excitatory neurosteroids.

Distribution and characterization of neurosteroid sulfatase from the bovine brain

We investigated the regional and subcellular distribution of neurosteroid sulfatase (NSS) in the bovine brain and its enzymatic properties by using dehydroepiandrosterone sulfate (DHEA-S) as a substrate. Bovine NSS was highly concentrated in the region of the midbrain and in the hypothalamus. The enzyme was found to be a microsomal enzyme. The optimal temperature of the enzyme was 50 degrees C, which was slightly lower than that of other steroid sulfatases. The optimal pH of bovine NSS was 7.4 with a second optimum at pH 4.0. The second optimal pH of 4.0 was the most characteristic property of bovine NSS. Employing DHEA-S as the substrate, apparent Km and Vmax values were 113 +/- 21 microM and 4.1 +/- 0.4 nmol/mg protein/h, respectively, whereas Km and Vmax values were found to be 1.6 +/- 0.2 M and 1.9 +/- 0.3 micromol/mg protein/h with p-nitrophenyl sulfate (NP-S) as the substrate. NSS has thus been shown to have a higher affinity for the steroid sulfate than the phenolic compound. When DHEA-S was used as the substrate, pregnenolone sulfate (Preg-S) was a competitive inhibitor with an apparent Ki value of 46 microM, and NP-S was a non-competitive inhibitor (apparent Ki=12 mM).

Immune enhancing effects of dehydroepiandrosterone and dehydroepiandrosterone sulphate and the role of steroid sulphatase

Steroid hormones, such as glucocorticoids (GC), influence immune and inflammatory responses through their suppressive actions. Recent evidence suggests that another steroid hormone, dehydroepiandrosterone (DHEA), provides an immunostimulatory influence opposing the effect of GC. DHEA circulates in its inactive sulphated form, DHEAS, requiring conversion to DHEA by a steroid sulphatase (SS) enzyme for biological activity. Therefore, inhibition of SS activity may affect immune responses, allowing endogenous GC effects to predominate. We have shown that administration of DHEA and DHEAS in contact sensitization (CS) augments ear swelling by 39 and 46% respectively (P < 0.001). DHEAS at doses of 0.5, 5 and 50 mg/kg reverses the inhibitory effect of corticosterone (5 mg/kg) (P < 0.01). In CS, CT2251 (SS inhibitor) at 10 and 0.1 mg/kg inhibited ear swelling by 61 and 38% (P < 0.05) respectively. In addition, it inhibited DHEAS-augmented responses by 49 and 35% respectively (P < 0.05), with no effect on DHEA-augmented responses. DHEAS reversed CT2251 inhibition of the CS response with complete reversal at 50 mg/kg (P < 0.05). DHEAS and CT2251 appear to affect cellular infiltration into the ear, since DHEAS increased the number of lymphocytes by 63.8% and macrophages by 107% (P < 0.001), whereas CT2251 at 0.1 mg/kg decreased the number of lymphocytes by 65% (P < 0.001) and macrophages by 80% (P < 0.001). DHEAS, CT2251 and dexamethasone had no effect on oedema in the ear. From our data we have shown that steroid hormones, such as DHEA, have the potential to act as immunostimulatory factors in vivo. Inhibiting the conversion of DHEAS to DHEA by SS enzyme leads to an anti-inflammatory effect.

Daidzein sulfoconjugates are potent inhibitors of sterol sulfatase (EC 3.1.6.2)

Recent studies have associated high dietary isoflavone intake with low incidence of breast cancer. Since estrogenic steroids are important factors in the evolution of breast cancer, and in breast tumors they are derived mainly from the sterol sulfatase pathway, we have therefore investigated effects of the isoflavone daidzein and its sulfoconjugates, daidzein-4'-O-sulfate and daidzein-7,4'-di-O-sulfate, on sterol sulfatase acitivity using dehydroepiandrosterone sulfate as substrate. While daidzein does not affect sterol sulfatase, its sulfoconjugates are potent inhibitors of this enzyme. Kinetic analyses reveal that daidzein-4'-O-sulfate and daidzein-7,4'-di-O-sulfate inhibit sterol sulfatase competitively with respect to the steroid substrate and with Ki values of 5.9 and 1 microM, respectively. Daidzein sulfo-conjugates also inhibit hydroxysteroid and phenol sulfotransferases but at much higher concentrations. These results provide a biochemical basis for the putative chemopreventive role of dietary isoflavones against breast cancer.

Memory enhancement mediated by the steroid sulfatase inhibitor (p-O-sulfamoyl)-N-tetradecanoyl tyramine

The intent of this study was to determine whether altering the metabolism of neurosteroids via blockade of the enzyme, steroid sulfatase, could enhance memory retention in rats. The steroid sulfatase inhibitor p-O-(sulfamoyl)-N-tetradecanoyl tyramine (DU-14) was administered alone and in combination with the neurosteroid dehydroepiandrosterone sulfate (DHEAS) to rats which were then tested for the reversal of scopolamine-induced amnesia. A single 30 mg/kg IP dose of DU-14 produced a significant inhibition of steroid sulfatase activity in both brain (14.8%), and liver (85.2%) tissues, 24 hours following administration. In a passive avoidance test, DU-14 enhanced the reversal of amnesia by DHEAS. These results suggest that steroid sulfatase inhibition can potentiate the memory enhancing properties of DHEAS.

In vivo activity of 4-methylcoumarin-7-O-sulfamate, a nonsteroidal, nonestrogenic steroid sulfatase inhibitor

Steroid sulfatase regulates the formation of estrone from estrone sulfate (E1S) and dehydroepiandrosterone (DHA) from DHA sulfate. DHA can be converted to androstenediol, a steroid with potent estrogenic properties, and inhibition of steroid sulfatase activity is therefore an important therapeutic target. Because nonsteroidal steroid sulfatase inhibitors may offer some advantage for use in the treatment of breast cancer, 4-methylcoumarin-7-O-sulfamate (COUMATE) was synthesized and shown to be active in vitro. In this study, in vitro and in vivo techniques have been used to confirm that COUMATE, in contrast to the steroidal steroid sulfatase inhibitor estrone-3-O-sulfamate, is devoid of estrogenic activity. COUMATE did not stimulate the growth of MCF-7 breast cancer cells or uteri of ovariectomized rats, in contrast to estrone-3-O-sulfamate. COUMATE was orally active in vivo and after multiple dosing (10 mg/kg/day for 7 days) inhibited liver estrone sulfatase activity by 85%. Seven days after single or multiple dosing with COUMATE, liver estrone sulfatase activity was almost fully restored. Measurement of estrone sulfatase activity in WBCs revealed a degree of inhibition similar to that detected in liver samples. COUMATE was able to completely block the ability of E1S to stimulate uterine growth in ovariectomized rats. The development of a potent nonsteroidal, nonestrogenic steroid sulfatase inhibitor should allow the therapeutic potential of this type of therapy to be evaluated.

Effect of breast cyst fluid on oestrone sulphatase activity in MCF-7 breast cancer cells

Breast cyst fluid is a rich source of growth factors and sex hormones but the pathophysiology of cystic breast disease is largely unknown. In this study the net effects of breast cyst fluid on growth of, and oestrone sulphatase activity (oestrone sulphate --> oestrone) in the hormone-dependent MCF-7 and hormone-independent MDA-MB-231 breast cancer cell lines were assessed. Using a final breast cyst fluid dilution of 16.7% (v/v) MCF-7 cell growth was significantly inhibited by 7 of 21 samples (16% - 54%) while MDA-MB-231 cell growth was significantly inhibited by 17 of 20 samples (15% - 45%). Oestrone sulphatase activity was significantly inhibited in the MCF-7 cell line by 19 of 21 samples (22% - 81%) while significant stimulation of oestrone sulphatase activity was observed in MDA-MB-231 cells in 11 of 20 samples (17% - 149%). The presence of endogenous substances in breast cyst fluid which inhibit oestrone sulphatase activity in the MCF-7 cell line is exciting because of the therapeutic potential of oestrone sulphatase inhibition in hormone-dependent breast cancers.

Reversal of scopolamine induced amnesia in rats by the steroid sulfatase inhibitor estrone-3-O-sulfamate

The intent of the study was to determine whether altering the metabolism of neurosteroids via blockade of the enzyme, steroid sulfatase, could enhance retention test performance in rats. The steroid sulfatase inhibitor estrone-3-O-sulfamate (EMATE) was administered alone and in combination with the neurosteroid dehydroepiandrosterone sulfate (DHEAS) to rats which were then tested for the reversal of scopolamine induced amnesia. EMATE enhanced the reversal of amnesia by DHEAS as measured by a passive avoidance test. When administered without DHEAS, as a single acute dose, EMATE had no effect. When administered without DHEAS over 10 consecutive days, however, EMATE significantly improved retention. These results suggest that steroid sulfatase inhibition can potentiate the memory enhancing properties of DHEAS. The study also suggests that increasing the levels of endogenous sulfated neurosteroids via the inhibition of steroid sulfatase activity may enhance learning and/or memory function.

In vivo inhibition of oestrone sulphatase and dehydroepiandrosterone sulphatase by oestrone-3-O-sulphamate

Many tumours in endocrine-sensitive tissues, such as the breast and endometrium, are hormone-dependent and the hydrolysis of oestrone sulphate (EIS) to oestrone by oestrone sulphatase (EI-STS) is a major source of oestrogen in such tumours. Oestrone-3-O-sulphamate (EMATE) has been shown to be a potent EI-STS inhibitor in vitro, and in this study its ability to inhibit enzyme activity in vivo was examined. EMATE was initially administered to female rats for 7 days, after which liver EI-STS activity was measured. As EMATE also inhibits a related sulphatase in vitro, dehydroepiandrosterone sulphatase (DHA-STS), its effect on the activity of this enzyme in vivo was also investigated. DHA-STS has a pivotal role in regulating the synthesis of another steroid with potent oestrogenic properties, androstenediol. Administration of EMATE almost completely inhibited liver EI-STS (99%) and DHA-STS (99%) activities and was active when given by the oral or subcutaneous routes. After a single dose of EMATE or following the cessation of multiple doses for 10 days, liver EI-STS activity remained inhibited ( > 95%) for up to 7 and 10 days, respectively. Other compounds, such as 4-hydroxytamoxifen and the "pure" antioestrogen ICI 182,780, which are reported to inhibit EI-STS activity in vitro, did not inhibit activity in vivo. In a preliminary study, EMATE, when injected over a 12-day period, effectively reduced the growth of EIS-stimulated nitrosomethyl-urea-induced mammary tumours in ovariectomised rats and inhibited tumour sulphatase activity in treated animals.

Inactivation of steroid sulfatase by an active site-directed inhibitor, estrone-3-O-sulfamate

Steroid sulfatases are responsible for the hydrolysis of 3beta-hydroxy steroid sulfates, such as cholesterol and pregnenolone sulfate, and have an important role in regulating the synthesis of estrogenic steroids, from estrone sulfate and dehydroepiandrosterone sulfate, in endocrine-dependent tumors. Although little is known about the mechanism by which the sulfate group is removed from a steroid nucleus, an active site-directed sulfatase inhibitor has been developed. This inhibitor, estrone-3-O-sulfamate (EMATE), was synthesized by treating the sodium salt of estrone with sulfamoyl chloride. This compound inhibited not only estrone sulfatase but also dehydroepiandrosterone sulfatase activity in placental microsomes and in intact MCF-7 breast cancer cells. Pretreatment of MCF-7 cells or placental microsomes with EMATE, followed by extensive washing or dialysis indicated irreversible inhibition. This was confirmed by showing that EMATE inhibited estrone sulfatase activity in placental microsomes in a time-, concentration-, and pH-dependent manner. The enzyme is protected from inactivation by estrone sulfate, which is also consistent with active site-directed inhibition. EMATE is proposed to inactivate estrone sulfatase by irreversible sulfamoylation of the enzyme. Maximum enzyme activity was detected at pH 8.6, and the maximum rate of enzyme inactivation by EMATE also occurred at this pH. The pKa values of the enzymatic reaction and pKa of inactivation were 7.2 and 9.8, providing evidence that two active site residues are being modified by EMATE. As the phenolic pKa of tyrosine (9.7) and the pKa of histidine will allow the roles that (6.8) are similar to the pKa values of inactivation, these amino acid residues may play a role in the catalytic mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Arylsulfatase from Streptomyces griseorubiginosus S980-14

A new arylsulfatase designated Es-1, which desulfated etoposide 4'-sulfate and p-nitrophenyl sulfate, was isolated from Streptomyces griseorubiginosus S980-14 and purified to protein homogeneity by ammonium sulfate fractionation, ion exchange column chromatography, and chromatofocusing. The enzyme was active in monomeric form with an approximate molecular weight of 45,000, had a pI value of 4.95, and required calcium for full activity. At an optimum reaction pH of 8.5, iodoacetate, mercurous chloride, and EDTA severely inhibited the activity of Es-1 arylsulfatase.

Effect of Decapeptyl (a GnRH analogue) and of transforming growth factor-alpha (TGF-alpha), in the presence of heparin, on the sulfatase activity of human breast cancer cells

The effects of the polypeptide Decapeptyl (a gonadotropin-releasing hormone (GnRH) agonist analogue) and of transforming growth factor-alpha (TGF-alpha), on estrone sulfate-sulfatase activities in the homogenates of various breast cancer cell lines were studied in the presence of heparin. In hormone-dependent MCF-7 breast cancer cells, Decapeptyl can inhibit sulfatase activity, and this effect is significantly augmented in the presence of heparin. In the other hormone-dependent T-47D breast cancer cell line, the decrease of sulfatase activity was only significant when Decapeptyl was associated with heparin. No significant effect on sulfatase activity elicited by heparin, Decapeptyl or a mixture of both was found in the hormone-independent MDA-MB-231 breast cancer cells. TGF-alpha stimulates sulfatase activity in the MDA-MB-231 cells but has no effect in the MCF-7 cells; in contrast, TGF-alpha combined with heparin provokes a decrease of the sulfatase activity in both cell lines. It is concluded that the sulfatase activity in some types of breast cancer cell can be inhibited by heparin combined with the polypeptides Decapeptyl or TGF-alpha.