Rat Uterine Cytosol Estrogen Receptors Research Articles

2-Morpholinoisoflav-3-enes as flexible intermediates in the synthesis of phenoxodiol, isophenoxodiol, equol and analogues: Vasorelaxant properties, estrogen receptor binding and Rho/RhoA kinase pathway inhibition

Isoflavone consumption correlates with reduced rates of cardiovascular disease. Epidemiological studies and clinical data provide evidence that isoflavone metabolites, such as the isoflavan equol, contribute to these beneficial effects. In this study we developed a new route to isoflavans and isoflavenes via 2-morpholinoisoflavenes derived from a condensation reaction of phenylacetaldehydes, salicylaldehydes and morpholine. We report the synthesis of the isoflavans equol and deoxygenated analogues, and the isoflavenes 7,4′-dihydroxyisoflav-3-ene (phenoxodiol, haganin E) and 7,4′-dihydroxyisoflav-2-ene (isophenoxodiol). Vascular pharmacology studies reveal that all oxygenated isoflavans and isoflavenes can attenuate phenylephrine-induced vasoconstriction, which was unaffected by the estrogen receptor antagonist ICI 182,780. Furthermore, the compounds inhibited U46619 (a thromboxane A2 analogue) induced vasoconstriction in endothelium-denuded rat aortae, and reduced the formation of GTP RhoA, with the effects being greatest for equol and phenoxodiol. Ligand displacement studies of rat uterine cytosol estrogen receptor revealed the compounds to be generally weak binders. These data are consistent with the vasorelaxation activity of equol and phenoxodiol deriving at least in part by inhibition of the RhoA/Rho-kinase pathway, and along with the limited estrogen receptor affinity supports a role for equol and phenoxodiol as useful agents for maintaining cardiovascular function with limited estrogenic effects.

Resolution, molecular structure and biological activities of the d- and l-enantiomers of potent anti-implantation agent, dl-2-[4-(2-Piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran

Compound 1 (dl-2-[4-(2-piperidinoethoxy)phenyl]-3-phenyl-2H-1-benzopyran, CDRI 85/287) a potent anti-estrogen and anti-implantation agent has been successfully resolved into its pure d- and l-enantiomers. Biological studies showed l-enantiomer to be the active form, exhibiting a fivefold higher receptor affinity for the rat uterine cytosolic estrogen receptor, 100% contraceptive efficacy at 1.3 mg/kg dose in single day schedule and 89% inhibition of estradiol induced increase of uterine weight at its contraceptive dose. The absolute stereochemistry determined by X-ray crystallographic analysis showed that the l-enantiomer has 2R configuration at its asymmetric centre.

Antiestrogenic Activity of Hydroxylated Polychlorinated Biphenyl Congeners Identified in Human Serum

Several hydroxylated polychlorinated biphenyls (PCBs) identified in human serum have been synthesized and these include 2,2′,3,4′,5,5′-hexachloro-4-biphenylol; 2,3,3′,4′,5-pentachloro-4-biphenylol; 2′,3,3′,4′,5-pentachloro-4-biphenylol; 2,2′,3,3′,4′,5-hexachloro-4-biphenylol; 2,2′,3,3′,4′,5,5′-heptachloro-4-biphenylol; 2,2′,3,4′,5,5′,6-heptachloro-4-biphenylol; and 2,2′,3′,4,4′,5,5′-heptachloro-3-biphenylol. The hydroxy-PCBs exhibited minimal binding to the rat uterine cytosolic estrogen receptor (ER) and did not induce proliferation of estrogen-responsive MCF-7 human breast cancer cells at concentrations ranging from 10−5to 10−8m. The estrogenic activity of these compounds was further investigated utilizing two estrogen-responsivein vitrobioassays, namely, (i) HeLa cells stably transfected with a Gal4:human ER chimera and a 17-mer-regulated luciferase reporter gene, and (ii) MCF-7 cells transiently transfected with a full-length human ER expression plasmid and a plasmid containing an estrogen-responsive vitellogenin A2 promoter linked to a chloramphenicol acetyl transferase (CAT) reporter gene. None of the hydroxy-PCBs significantly induced luciferase activity in the stably transfected HeLa cells or CAT activity in MCF-7 cells at concentrations as high as 10−5m. The antiestrogenic effects of the hydroxy-PCBs were also investigated using the same bioassays in which the cells were cotreated with 17β-estradiol plus the hydroxy-PCBs. All of the hydroxy-PCB congeners inhibited one or more estrogenic response, and one congener, 2,2′,3,4′,5,5′,6-heptachloro-4-biphenylol, inhibited 17β-estradiol-induced cell proliferation and CAT activity in MCF-7 cells and luciferase activity in HeLa cells.

Characterization of estrogen-binding sites associated with the endoplasmic reticulum of rat uterus

Microsomes prepared from rat uterine homogenates harbor high-affinity (Ka = 10 10 m −1), low-capacity binding sites for estrogens. Previous work from our laboratory has demonstrated that these estrophiles are located on endoplasmic reticulum and are not cytosolic contaminants of the membrane preparation. Subfractionation of microsomes into granular and agranular membranes and polysomes revealed approximately equal distribution of estrogen-binding activity among each of these constituents. These binding sites were fully extractable with 0.6 m KCl. Microsomal estrophiles solubilized under conditions of low ionic strength and complexed with estradiol migrated as 8S forms on continuous sucrose gradients. In the presence of 0.4 m KCl, the solubilized binding sites exhibit a sedimentation coefficient of 4S. Extracted binding sites do not undergo heat-induced transformation from a 4S to 5S species. The monoclonal antibody JS34/32 interacted with the endoplasmic reticulum-associated estrogen-binding sites when present in 50-fold molar excess, but not at lower antibody to binding site ratios. In comparison, the rat uterine cytosolic estrogen receptor formed complexes with JS34/32 at antibody to receptor ratios as low as 2:1. These results suggest that the endoplasmic reticulum possesses estrogen-binding sites with biochemical properties that differ from those of the classically described cytosolic (loosely associated nuclear) estrogen receptor.

Binding of estradiol-peroxidase conjugate to estrogen receptor

The binding of estradiol-horseradish peroxidase conjugate to rat uterine cytosolic estrogen receptor was studied. The conjugate having a steroid to enzyme ratio of 2.8 : 1 was allowed to bind to protamine precipitated receptor in presence or absence of 100-fold excess of free estradiol. The bound enzyme activity was measured and the data subjected to Scatchard analysis to obtain the dissociation constant and the number of binding sites. Although the binding parameter so obtained differed from values obtained using radiolabelled estradiol, the method may be used for comparative studies.

Estrogen receptor binding to a DNA response element in vitro is not dependent upon estradiol

Gel shift assays were employed to distinguish between the contribution of 17 beta-estradiol (E2) and a short heating step to the ability of the rat uterine cytosolic estrogen receptor (ER) to bind to the estrogen response element (ERE) from the vitellogenin A2 gene (vitERE). Despite the popularity of models in which the ER is a ligand-activated DNA-binding protein, these studies find that estrogen does not significantly contribute to receptor-DNA complex formation. An avidin-biotin complex with DNA (ABCD) assay was utilized to obtain quantitative measurement of the affinities of the ER for the vitERE and a mutant sequence. Scatchard analysis gave a dissociation constant of 390 +/- 40 pM for the E2-occupied, heated ER to the vitERE. The data fit a one-site model and evidence for cooperatively was not observed. A dissociation constant of 450 +/- 170 pM was obtained for the unoccupied, heated ER, leading to the conclusion that estrogen was not necessary for specific binding to DNA. The percentage of ER capable of binding vitERE varied with each cytosol preparation, ranging from 60 to 100% and estrogen did not appear to affect this variation. Competition against the vitERE with a 2-bp mutant sequence showed a 250-fold lower relative binding affinity of the receptor for the mutant over the vitERE sequence. This ability of the ER to discriminate between target and nonspecific DNA sequences was also not dependent on the presence of estrogen.

In vitro and in vivo binding of toremifene and its metabolites in rat uterus

The in vitro binding affinities of toremifene (TOR), 4-hydroxy toremifene (4-OH-TOR) and several other metabolites for the rat uterine cytosolic estrogen receptor were compared with those of tamoxifen (TAM) and 4-hydroxy tamoxifen (4-OH-TAM). Only small differences were observed and the binding affinities of both 4-hydroxy metabolites were similar to that of estradiol (E2). Uterine uptake and subcellular distribution of [ 3H]TOR and [ 3H]TAM were then compared at 1, 8 and 72 h after administration to castrated rats. The uptake and retention of both antiestrogens were similar at all times. In each case the amount of nuclear bound radioactivity declined to low levels at 8 and 72 h but the ratios of 4-OH-TAM/TAM and 4-OH-TOR/TOR determined by HPLC analysis increased dramatically at 72 h. The level of radioactivity in both plasma and uterine cytsol at 72 h was significantly higher following [ 3H]TAM administration. However, most of the radioactivity appeared to be in a conjugated form since it was not extractable with solvent. Finally, the ability of prior administration of each antiestrogen (100 mg/kg) to block uterine [ 3H]estradiol uptake was examined at 3 and 7 days. It was found that uterine wet weights were higher than control one week after administration of both compounds. Prior administration of TOR increased nuclear uptake of [ 3H]E2 whereas TAM had no effect. The results of these experiments suggest that toremifene and tamoxifen have very similar in vitro and in vivo binding properties but differences in metabolism exist that may be important.

Identification of phytoestrogens in the urine of male dogs

It is becoming increasingly apparent that dietary factors may play a role in the etiology of hormone dependent neoplasias. It has been hypothesized that estrogens play some role in the etiology of benign prostatic hyperplasia (BPH) in the canine. The presence of estrogen receptor binding activity in a fraction of canine urine purified by high performance liquid chromatography (HPLC) that did not correspond to estriol, estradiol, estrone or any of their primary metabolites was observed in the present study. We used thermospray-mass spectrometry and GC-MS to identify the phytoestrogens daidzein, equol, formononetin and genistein in HPLC purified fractions of urine obtained from male beagles. Using the same techniques we also confirmed the presence of daidzein and genistein in the commercial diet fed to these same dogs. Using the immature rat uterine cytosol estrogen receptor assay, relative binding affinities of 0.08, 1.1, < 0.01 and 3.9% were obtained for daidzein, equol, formononetin and genistein, respectively when compared to estradiol (100%). In conclusion, phytoestrogens are present in urine of male beagles. Moreover, the commercial diet fed to these dogs contains isoflavones which can be converted to equol by intestinal microflora. These results suggest the need for investigations of phytoestrogens (e.g. equol) excreted into the urine daily and its relationship to the incidence and severity of BPH in the dog.

Saccharomyces cerevisiae produces a yeast substance that exhibits estrogenic activity in mammalian systems.

Partially purified lipid extracts of Saccharomyces cerevisiae contain a substance that displaces tritiated estradiol from rat uterine cytosol estrogen receptors. The yeast product induces estrogenic bioresponses in mammalian systems as measured by induction of progesterone receptors in cultured MCF-7 human breast cancer cells and by a uterotrophic response and progesterone receptor induction after administration to ovariectomized mice. The findings raise the possibility that bakers' yeast may be a source of environmental estrogens.

ChemInform Abstract: ESTROGEN RECEPTOR BINDING AND ESTROGENIC/ANTIESTROGENIC EFFECTS OF TWO NEW METABOLITES OF NITROMIPHENE, 2‐(P‐(2‐NITRO‐1‐(4‐METHOXYPHENYL)‐2‐PHENYLVINYL)PHENOXY)‐N‐ETHYLPYRROLIDINE

AbstractDurch Reduktion des Antiöstrogens (I) erhält man das Desoxybenzoin (II), das auch aus (I) auf biologischem Weg entsteht.

Structure-activity relationships of estrogens: Effects of esterification of the 11β-hydroxyl group

Fourteen esters (formate, acetate, propionate, butyrate, hexanoate, heptanoate, and benzoate) located at C-11 of 11β-hydroxyestrone and 11β-hydroxyestradiol-17β were synthesized and evaluated for uterotropic and gonadotropin release inhibition in rats, as well as their ability to displace ( 3H) estradiol-17β from the rat uterine cytosolic estrogen receptor. The most potent uterotropic agent was 11β-formoxyesterone which was 1,625 or 2,500 times as active as 11β-hydroxyestrone in the uterotropic or gonadotropin release inhibition assay, respectively. 11β-Formoxyesterone was 7.5 times as uterotropic as estradiol-17β and equal to estradiol-17β in inhibiting gonadotropin release. However, the most potent inhibitor of gonadotropin release was 11β-acetoxy-estradiol-17β which had 133% of the activity of estradiol-17β, although it had only 38% of the activity of estradiol-17β in the uterotropic assay. Esters larger than the acetoxy group showed sharply decreased activities in either assay. Despite the high estrogenic potency of the 11-formates or 11-acetates, they were rather weak (6% to 35% as active as estradiol-17β) in displacing ( 3H) estradiol-17β from the rat uterine cytosolic estrogen receptor.

Estrogen receptor binding and estrogenic/antiestrogenic effects of two new metabolites of nitromiphene, 2-[p-[2-nitro-1-(4-methoxyphenyl)-2-phenylvinyl]phenoxy]-N-ethylpyrrolidine.

Reduction of the triarylethylene antiestrogen 2-[p-[2-nitro-1-(4-methoxphenyl)-2-phenylvinyl]phenoxy]-N-ethylpyrrolidine (1) with sodium borohydride-stannous chloride afforded 2-(p-methoxyphenyl)-p'-(2-pyrrolidin-1-ylethoxy)deoxybenzoin (2). Incubation of 1 with rat cecal content suspension under aerobic or anaerobic conditions also resulted in the generation of 2. The lactam analogue of 1 (6) was prepared by condensation of 4-(2-bromoethoxy)-4'-methoxybenzophenone (3) with benzylmagnesium chloride, followed by dehydration, amidation with 2-pyrrolidinone, and nitration. A metabolite with chromatographic and spectral properties identical with those of 6 was found in extracts from incubation mixtures of 1 with phenobarbital-induced rat liver 9000g supernatant. Compound 2 did not exhibit appreciable binding to the rat uterine cytosol estrogen receptor at concentrations of up to 1 X 10(-6) M and had no estrogenic or antiestrogenic activity in the 3-day rat uterotropic assay. By contrast, 6 had estrogen receptor affinity somewhat greater than that of 1 and slightly greater estrogenic activity accompanied by reduced antiestrogenic activity in comparison with those of 1.

Structure-activity relationships of 9β-estrogens

The 9β isomers of estradiol-17β, estradiol-17α, estrone and 17-ethinylestradiol-17β were synthesized and compared with their 9α-counterparts in the rat uterine cytosol estrogen receptor, utero-tropic, and gonadotropin release inhibition assays. Except for 17-ethinyl-9β-estradiol-17β which was as active as its 9α isomer in the uterotropic assay, none of the 9β estrogens exhibited any biological activity which was equal to or greater than their 9α counterparts. For examples, 9β-estradiol-17β was 1 10 as active as estradiol-17β, and 9β-estrone was 1 4 as active as estrone in the uterotropic assay.

Antagonism of estrogen action with a new benzothiophene derived antiestrogen

A new benzothiophene derived antiestrogen, LY139481, inhibited the uterotropic action of estradiol in a dose related fashion, and at 1 mg per day suppressed more than 90 percent of estradiol's activity in immature rats. LY139481 induced minimal uterotropic activity, and that activity declined in relation to dose. The relative binding affinity of LY139481 for rat uterine cytosol estrogen receptors was greater than that of estradiol in competitive assays and increased in relation to temperature (2.9 ± 0.5 × estradiol at 30° C). LY139481 caused estradiol-induced uterine hypertrophy to regress in a manner similar to that which resulted from withdrawal of estradiol treatment. Three successive daily injections of LY139481 slightly increased uterine weight, and blocked additional uterotropic action in response to estradiol and LY139481 administration on subsequent days. Furthermore, ten daily injections of estradiol alone did not increase uterine weight in animals pretreated with LY139481 for three days. In contrast, LY139481 did not prevent the partial uterotropic action of tamoxifen administration.

The thermolability of rat uterine cytosol estrogen receptors: Basis for a novel cytosol exchange-denaturation assay

Thermal denaturation of the rat uterine cytosol estrogen receptor obeys simple first-order reaction kinetics in the temperature range from 0–48°C, whether 17β-estradiol is present or not. The rate of inactivation is five times faster in the absence of 17β-estradiol than in its presence, and was shown to be independent of protein concentration over a wide range. Analysis of denaturation data as a function of variable temperature by Arrhenius plots showed that: (1) the stability of the receptor to heat effects is enhanced dramatically by the presence of 17β-estradiol; (2) 5α-dihydrotestosterone exerts a protective effect on the receptor, whereas progesterone does not; and (3) inactivation of binding at temperatures below 30°C is much more rapid than would be predicted from its behavior above 30°C. A cytosol receptor assay has been developed which exploits the fact that denaturation of the estrogen receptor does occur during thermally-accelerated isotope exchange procedures. When receptor site exchange is performed at 40°C, bound radio-labeled steroid achieves a maximal level within 3 min, at which point bound and unbound pools of steroid are at equilibrium, with the same specific activity. For the remainder of a 10-min incubation period at 40°C, binding decreases linearly as the receptor undergoes denaturation. By extrapolation of the receptor denaturation curve to zero time and correction for dilution of specific activity, an accurate determination of total specific estrogen receptor binding site concentration is realized.

Synthesis and antiestrogenic activity of [3,4-dihydro-2-(4-methoxyphenyl)-1-naphthalenyl][4-[2-(1-pyrrolidinyl)ethoxy]-phenyl]methanone, methanesulfonic acid salt.

Acylation of the sodio anion of beta-tetralone with phenyl anisoate, followed by a Grignard reaction of the resultant 4 with 4-methoxyphenylmagnesium bromide, gave rise to two novel dihydronaphthalene isomers 5 and 6. Regioselective demethylation of either 5 or 6 by NaSEt produced [3,4-dihydro-2-(4-methoxyphenyl)-1-naphthalenyl](4-hydroxyphenyl)methanone (7). Etherification of the phenolic group of 7 by N-(2-chloroethyl)pyrrolidine and subsequent methanesulfonate salt formation provided [3,4-dihydro-2-(4-methoxyphenyl)-1-maphthalenyl]]4-]2-(1-pyrrolidinyl)ethoxy]phenyl]methanone, methane sulfonic acid salt (3). Potent antiestrogenic activity of 3 was demonstrated by both oral and subcutaneous administration to rats and mice. In vitro binding studies with rat uterine cytosol estrogen receptors indicate compound 3 has a very high binding affinity which exceeds that of estradiol.

Competition of delta 9-tetrahydrocannabinol with estrogen in rat uterine estrogen receptor binding.

Direct competition experiments with delta 9 -tetrahydrocannibinol (delta 9-THC) and estradiol in binding assays with rat uterine cytosol estrogen receptors showed that delta 9-THC was a weak, but nevertheless significant, competitor for binding to cytoplasmic estrogen receptors. These data support, at the molecular level, the observations that delta 9-THC has a weak estrogenic activity (at least the ability to bind to estrogen receptors). Moreover, estrogen-like binding suggests that delta 9-THC, acting at the level of estrogen receptor, causes a primary estrogenic effect rather than an indirect or secondary phenomenon.

Uterine estrogen receptor binding of catecholestrogens and of estetrol (1,3,5(10)-estratriene-3,15α,16α,17β-tetrol)

The binding affinities for the catecholestrogen metabolites of estradiol and of their methyl ethers for the rat uterine cytosol estrogen receptors were examined. Similarly the binding of the fetal estradiol metabolite, 15α-hydroxyestriol (estetrol) was also measured. All of the catecholestrogens showed binding affinities far in excess of their uterotrophic potency. This is different from estriol, the product of the alternative metabolic pathways and suggests that the direction of estradiol metabolism may have an important role in the modulation of estrogenic activity of the female sex hormone.