Modulation of aromatase activity in human endometrial stromal cells by steroids, tamoxifen and RU 486

Scaffold-Free Endometrial Organoids Respond to Excess Androgens Associated With Polycystic Ovarian Syndrome

CONTEXT

Polycystic ovary syndrome (PCOS) is a prevalent disorder in reproductive aged women associated with a number of endocrine and metabolic complications, including increased risk of endometrial cancer.

OBJECTIVE

To study the effect of the characteristic increased androgen levels in PCOS on the endometrium, a novel scaffold-free multicellular endometrial organoid was established.

DESIGN

Human endometrial organoids were constructed using primary endometrial epithelial and stromal cells from endometrial tissues. Organoids were treated for 14 days with physiologic levels of estradiol and testosterone to mimic a normal follicular phase or PCOS hormone profiles. Organoids were harvested for immunostaining and ribonucleic acid sequencing.

SETTING

Academic institution.

PATIENTS

Endometrial tissues from 10 premenopausal women undergoing hysterectomy for benign pathologies were obtained following written consent.

MAIN OUTCOME MEASURES

Organoid architecture, cell specific markers, functional markers, proliferation, and gene expression were measured.

RESULTS

A method to generate scaffold-free endometrial organoids containing epithelial and stromal cells was established. These organoids exhibited distinct organization with epithelial cells lining the outer surface and stromal cells in the center of the organoids. Epithelial cells were polarized, organoids expressed cell type specific and functional markers, as well as androgen, estrogen, and progesterone receptors. Treatment with PCOS hormones increased cell proliferation and dysregulated genes in endometrial organoids.

CONCLUSIONS

A new multicellular, scaffold-free endometrial organoid system was established that resembled physiology of the native endometrium. Excess androgens in PCOS promoted cell proliferation in endometrial organoids, revealing new mechanisms of PCOS-associated with risk of endometrial neoplasia.

Detection and functional portrayal of a novel class of dihydrotestosterone derived selective progesterone receptor modulators (SPRM)

In early pregnancy, abortion can be induced by blocking the actions of progesterone receptors (PR). However, the PR antagonist, mifepristone (RU38486), is rather unselective in clinical use because it also cross-reacts with other nuclear receptors. Since the ligand-binding domain of human progesterone receptor (hPR) and androgen receptor (hAR) share 54% identity, we hypothesized that derivatives of dihydrotestosterone (DHT), the cognate ligand for hAR, might also regulate the hPR. Compounds designed and synthesized in our laboratory were investigated for their affinities for hPRB, hAR, glucocorticoid receptor (hGRα) and mineralocorticoid receptor (hMR), using whole cell receptor competitive binding assays. Agonistic and antagonistic activities were characterized by reporter assays. Nuclear translocation was monitored using cherry-hPRB and GFP-hAR chimeric receptors. Cytostatic properties and apoptosis were tested on breast cancer cells (MCF7, T-47D). One compound presented a favorable profile with an apparent neutral hPRB antagonistic function, a selective cherry-hPRB nuclear translocation and a cytostatic effect. 3D models of human PR and AR with this ligand were constructed to investigate the molecular basis of selectivity. Our data suggest that these novel DHT-derivatives provide suitable templates for the development of new selective steroidal hPR antagonists.

Endometrial Intracrinology--generation of an estrogen-dominated microenvironment in the secretory phase of women

CONTEXT

The human endometrium is a complex multicellular tissue subject to cyclical fluctuations in ovarian-derived steroid hormones. Fertile cycles are characterized by differentiation (decidualization) of endometrial stromal cells (ESC).

OBJECTIVE

To determine the impact of human stromal cell decidualization on biosynthesis and secretion of estrogens.

DESIGN

Primary cell culture was used. Cells were decidualized in vitro. Some cultures were treated with an aromatase inhibitor.

SETTING

A University Research Institute.

PATIENTS

Primary ESC were derived from women with normal menstrual cycles (n = 12). None of the women were receiving hormonal therapy or suffering from endometriosis.

MAIN OUTCOME MEASUREMENTS

Expression of mRNA and protein encoded by the aromatase (CYP19A1) and 3-β-hydroxysteroid dehydrogenase (HSD3B1) genes was assessed. Aromatase activity was measured using a tritiated water assay; steroid metabolism was determined using thin layer chromatography. Estrone (E1) and estradiol (E2) in cell culture media were measured by ELISA.

RESULTS

Decidualization induced a two-fold increase in aromatase mRNA. Aromatase protein was only detected in decidualized ESC. 3-β-Hydroxysteroid dehydrogenase protein was present in ESC both before and after decidualization; concentrations appeared unchanged. The existence of functional aromatase in decidualized ESC was confirmed; E1 and E2 were secreted into culture media in decidualized ESC and concentrations were reduced when cells were incubated with an aromatase inhibitor. Decidualization resulted in reduced metabolism of E2 and an increase in the ratio of E2:E1.

CONCLUSIONS

Decidualization is characterized by an increase in aromatase expression/activity favoring the generation of an E2-dominated estrogen microenvironment within the endometrial stroma.

Mifepristone for treatment of uterine leiomyoma. A prospective randomized placebo controlled trial

BACKGROUND

Uterine leiomyomas are widely prevalent and frequently cause menorrhagia. The major therapeutic option today is hysterectomy. Medical options are of highest interest.

METHODS

A total of 30 women with uterine leiomyomas scheduled for surgical intervention were randomized to receive either 50 mg mifepristone or placebo every other day during 3 months prior to surgery. Uterine blood flow and leiomyoma volume were evaluated once a month until surgery. Endometrial biopsies were obtained prior to and at end of treatment. Relevant biochemistry, symptoms and bleeding were recorded. Primary outcome was reduction in uterine leiomyoma size.

RESULTS

There was a significant percentual decrease (P = 0.021) in the total leiomyoma volume in the mifepristone-treated group, -28 (-48, -8) % (mean +/- 0, 95 confidence interval), compared with the control group values 6 (-13, 25) %. Mifepristone treatment significantly reduced the bleeding days (P = 0.001) and increased serum haemoglobin values (P = 0.046). Serum cortisol levels remained unchanged, while a mild increase in serum androgens was noted. Endometrial biopsies showed no premalignant changes or changes in mitotic indices.

CONCLUSION

Mifepristone may offer an effective treatment option for women with uterine leiomyoma and the associated pronounced uterovaginal bleeding. Clinical Trials identifier: www.clinicaltrials.gov: NCT00579475.

Membrane ERalpha-dependent activation of PKCalpha in endometrial cancer cells by estradiol

The purpose of this study was to investigate the role of the oestrogen receptor subtypes ERalpha and ERbeta in mediating the non-genomic effects of 17-beta-estradiol (E(2)) in two human endometrial cancer cell lines (RL95-2 and HEC-1A) expressing different levels of these receptor subtypes. Western blotting analysis using phosphorylation site-specific antibodies showed that physiological concentrations of E(2) rapidly (<20 min) activated PKCalpha, but not PKCdelta in the RL95-2 cell line. E(2) had no effect on PKCalpha or PKCdelta activity in the HEC-1A cell line and suppressed basal levels of PKA activity in both cell lines. PKCalpha activation coincided with its membrane translocation. ERalpha was detected in the RL95-2 cell line by Western blotting and RT-PCR but not in the HEC-1A cells, which did express ERbeta. A selective ERalpha agonist PPT had the same effect as E(2) on PKCalpha activation in the RL95-2 cells, but the selective ERbeta agonist DPN had no such effect. A 46kDa variant of ERalpha increased in abundance in the cell membrane within 20 min of E(2) treatment suggesting that ERalpha mediated the E(2) non-genomic effects on PKCalpha through the formation of a membrane associated signalling complex.

Selective progesterone receptor modulators and progesterone antagonists: mechanisms of action and clinical applications

Since the discovery of the antiprogestin mifepristone, hundreds of similar compounds have been synthesized, which can be grouped in a large family of progesterone receptor ligands. This family includes pure agonists such as progesterone itself or progestins and, at the other end of the biological spectrum, pure progesterone receptor antagonists (PA). Selective progesterone receptor modulators (SPRM) have mixed agonist-antagonist properties, and occupy an intermediate position of the spectrum. These compounds have numerous applications in female health care. Mifepristone is used to terminate pregnancy, and as such is commercially available in many countries. The negative abortion-related image of mifepristone has clearly limited the involvement of the major pharmaceutical companies in the development of PA and SPRM. Many PA and SPRM display direct antiproliferative effects in the endometrium, although with variable actions which seem product- and dose-dependent. This property justifies their use in the treatment of myomas and endometriosis. PA also suppress late follicular development, block the LH surge and retard endometrial maturation, which renders them potential estrogen-free contraceptive drugs. SPRM such as asoprisnil are not as effective in blocking the LH surge and appear to target the endometrium directly and produce amenorrhoea. Interestingly, clinical data show that treatment with these compounds is not associated with hypo-estrogenism and bone loss. The potential clinical applications of these compounds cover a broad field and are very promising in major public health areas. These include emergency contraception, long-term estrogen-free contraception (administered alone, or in association with a progestin-only pill to improve bleeding patterns), myomas (where they induce a marked reduction in tumour volume and produce amenorrhoea) and endometriosis. Further developments might also include hormone replacement therapy in post-menopausal women, as well as the treatment of hormone-dependent tumours.

Progesterone antagonists and progesterone receptor modulators

Since the discovery of the antiprogestin RU 486 (mifepristone), other compounds have been synthesised that function as pure progesterone antagonists or progesterone receptor modulators. The latter are mixed agonists-antagonists. Mifepristone is usually used to terminate pregnancy but these compounds have numerous other applications in female healthcare. Mifepristone is an excellent agent for emergency contraception. Many progesterone antagonists and progesterone receptor modulators display antiproliferative effects on the endometrium and thus have application in the treatment of endometriosis and uterine myoma without being associated with hypoestrogenism and bone loss. They also have contraceptive potential by suppressing follicular development, blocking the luteinising hormone surge and retarding endometrial maturation. Finally, they have clinical application in GeneSwitch system, a plasmid-based method enabling controlled expression of specific genes (e.g., erythropoietin) using a progesterone antagonist as the inducer.

Mouse Bioassay to Assess Oestrogenic and Anti-oestrogenic Compounds: Hydroxytamoxifen, Diethylstilbestrol and Genistein

Young intact and adult gonadectomized C3H male and female mice were utilized as bioassay models to detect endocrine disruption chemicals. Animals treated with oestradiol (E) or progesterone (Prog) or E plus Prog were used to assess steroid hormone agonist and antagonist activities of 4-OH-tamoxifen (TAM), diethylstilbestrol (DES) and genistein (GEN) by bioassay. The stimulation or inhibition of mammary growth by TAM depended on sex, the state of animal (intact or gonadectomized), hormonal treatment (Prog, E, E plus Prog) and dose of TAM. TAM stimulated mammary growth in untreated ovariectomized (OV-X) females and in Prog-treated intact males and OV-X females. In intact males, mammary growth was increased by TAM at dose 0.1-1 microg day(-1) and decreased at dose 10 microg day(-1). Mammary growth was inhibited by TAM in Prog-treated intact females and in E or E plus Prog-treated intact and gonadectomized males and females. Uterine weights were increased by TAM in both untreated and treated (E, Prog, E plus Prog) intact and OV-X females; however, seminal vesicle weights were decreased by TAM in both untreated and treated (E, Prog, E plus Prog) intact males. DES alone affected mammary growth (an inverted-U-shaped dose-response curve) both in male and female mice. DES increased uterine weights; however, seminal vesicle weights were decreased. GEN increased mammary and uterine growth in OV-X females, GEN plus Prog stimulated mammary growth in intact males. The results obtained in these studies show clearly that only a bioassay consisting of several endpoints reflective to the mechanism of oestrogen and anti-oestrogen action has the ability to evaluate activities of a molecule.

Progesterone antagonists and progesterone receptor modulators: an overview

Since the original description of the structure of the antiprogestin, mifepristone, was published, numerous related compounds have been synthesized which may function as progesterone antagonists (PAs) or progesterone receptor modulators (PRMs). The latter are mixed agonists-antagonists. Both PAs and PRMs have therapeutic applications in female health care. Mifepristone is predominantly a PA and displays only minimum agonist activity in certain systems. Together with a prostaglandin, mifepristone can terminate pregnancies of less than 9 weeks duration, and it may also be used at later gestational ages. Mifepristone causes expulsion of the uterine contents following intrauterine fetal death. A mifepristone-prostaglandin combination has been shown to be very effective treatment in women with menses delay of 11 days or less. Many PAs and PRMs display antiproliferative effects in the endometrium. Serum estradiol levels however remain in the early to mid-follicular phase range. For this reason, they have application in the treatment of endometriosis and myoma without being associated with bone loss and hypoestrogenism. PRMs may also find application in the treatment of dysfunctional bleeding as well as an adjunct to estrogens in hormone replacement therapy in postmenopausal women. Many PAs have contraceptive potential by suppressing follicular development and blocking the LH surge. Low doses may also be potential contraceptives by retarding endometrial maturation without affecting ovulation or inducing bleeding. Mifepristone is an excellent agent for use as an emergency "postcoital" contraceptive. PAs may also be useful in IVF programs to prevent a premature LH surge and to delay the emergence of the implantation window. In addition to their use in women's health care, mifepristone and several other PAs are potent antiglucocorticoid agents and may be used to treat ACTH-independent Cushing's syndrome. They may also be used in the treatment of tumors containing steroid receptors and in other situations which require suppression of the ACTH-cortisol axis.

Quantitative evaluation of the influence of ovarian steroids on plasminogen activators and inhibitors in human endometrial cells and trophoblasts

INTRODUCTION

Plasminogen activators and inhibitors were quantitated in cultured human endometrial and trophoblast cells under the influence of ovarian steroids in order to investigate the role of the fibrinolytic system for trophoblast invasion and anchorage.

MATERIALS AND METHODS

Plasminogen activators (t-PA and u-PA) and their inhibitors (PAI-1 and PAI-2) secretions were assayed in cultures of epithelial, stromal, and trophoblast cells. These cells were also cultured on a fibrin substrate for microscopic examination of the fibrinolytic degradation.

RESULTS

The u-PA from epithelial cells was predominant among PAs and PAI-1 in endometrial cells. Estradiol (E2) enhanced t-PA production in stromal cells and PAI-1 production in epithelial cells. Progesterone (P4) suppressed u-PA production in epithelial cells and enhanced PAI-1 production in both epithelial and stromal cells. Trophoblasts produced PAI-1, PAI-2, and small quantities of t-PA and u-PA, none of which were notably influenced by E2 or P4. The PAI-1 production in trophoblasts was more than four-fold greater than the u-PA production in epithelial cells. Epithelial and stromal cells initially grew on fibrin substrate but were gradually detached from the substrate with fibrinolytic degradation, with the exception of the stromal cells grown in the presence of P4 (or E2+P4). Trophoblasts grew well on fibrin substrate without fibrinolytic degradation both in the presence and absence of the steroids tested.

CONCLUSIONS

Fibrinolytic balance seemed to be basically maintained between the endometrial PAs and the relative excess of trophoblasts-derived PAI-1. This balance might be regulated principally by P4 and focally by E2 in the endometrial tissue for placental implantation.

Immunohistochemical localization of receptors for progesterone and oestradiol-17 beta in the implantation site of the rhesus monkey

The aim of the present study was to examine the cellular basis of the involvement of oestradiol and progesterone in blastocyst implantation in the primate. To this end, the cellular distribution of receptors for oestradiol (ER) and progesterone (PR) in fetal trophoblast cells and in endometrial compartments of timed lacunar (pre-villous) and villous stages of placentation in primary implantation sites collected on days 13-22 of gestation were investigated in rhesus monkeys. Both in pre-villous stage tissue and in villous stage tissue, cytotrophoblast cells and syncytiotrophoblast cells and other trophoblast derived cells were PR positive, while they were generally ER negative. Maternal endometrial cells were ER negative, while epithelial cells, stromal cells and vascular endothelial cells in maternal endometrium showed heterogeneous staining patterns for PR depending on their relative location; these patterns, however, correlated well with glandular hyperplasia and differentiation, stromal-decidual transformation and vascular response seen during blastocyst implantation.

Mechanisms of action of endocrine treatment in breast cancer

Endocrine treatment plays an important role in the therapy of breast cancer. While the basic mechanisms are understood, additional mechanisms may be of importance to their action and they may also contribute to the mechanism(s) of acquired resistance. Currently, several novel drugs are entering into clinical trials. Observations of the absence or presence of cross resistance to novel 'pure' steroidal antiestrogens and the non-steroidal tamoxifen may add important information to our understanding of the mechanisms of action of both classes of drugs. Similarly, exploration of different aromatase inhibitors in sequence or concert, as well as the combining of different endocrine treatment options may be warranted. Additionally, alterations in different biochemical parameters such as growth factors should not only be carefully explored in relation to treatment options but should also be followed during the course of treatment to asess alterations over time and in relation to the development of drug resistance.

Inhibition of aromatase activity in human placental microsomes by 13-retro-antiprogestins

Mifepristone (RU 486), used clinically for the termination of early pregnancy, and its acetyl and 13-retro (13 alpha) analogs show potent antiproliferative effects against estrogen-dependent human breast tumors and endometriosis. However, there has been no report on direct inhibition of aromatase by antiprogesterones. Aromatase inhibitors have been shown to be effective against estrogen-dependent breast cancer. We evaluated the inhibition of aromatase by various antiprogestins (ZK 112.993, ZK 98.734, ZK 114.043, ZK 98.299, and ZK 114.863). Human placental microsomes were incubated with [1 beta-3H,4-14C] androstenedione (3-114 nM) in the presence of NADPH, with or without putative inhibitors (10-200 microM). Aromatase activity was assessed by tritium release to water from the 1 beta-position of the substrate. ZK 112.993 and ZK 98.734 did not show any inhibitory effect. The statistical analysis of the data using standard errors was obtained from replicate experiments. ZK 114.043 showed slight inhibition with a Ki of 54.8 +/- 6.4 microM (m +/- SE, n = 6) against androstenedione aromatization. The two 13-retro-steroids, ZK 98.299 and ZK 114.863, showed aromatase inhibition with Ki values of 19.0 +/- 1.5 microM (n = 7) and 12.7 +/- 0.94 microM (n = 7), respectively, which is weak with respect to some known potent inhibitors, but significant when compared with the other antiprogestins which were tested. The results suggest that the unnatural 13-retro-antiprogestin conformation may have a better fit to the aromatase active site than the natural 13 beta-antiprogestin conformation. (Steroids 60:234-238, 1995).

Evidence for estrogen synthesis in adenomyotic tissues

OBJECTIVE

To investigate steroidogenesis in eutopic and ectopic endometrial tissues in adenomyosis.

STUDY DESIGN

Aromatase and estrone sulfatase activities were determined by anion-exchange resin column chromatography, thin-layer chromatography, and cocrystallization. The effects of danazol on the activity of these enzymes were also examined. Moreover, localization of aromatase in eutopic and ectopic endometrial tissues was immunohistochemically examined with antihuman placental aromatase cytochrome P-450 antibody.

RESULTS

Aromatase and estrone sulfatase activities were detected in ectopic endometrium. The activity of these enzymes was significantly suppressed by danazol. In addition, aromatase was immunohistochemically detected in glandular cells of eutopic and ectopic endometrial tissues.

CONCLUSIONS

The results suggest that estrogen is synthesized in the eutopic and ectopic endometrial tissues of women with uterine adenomyosis and that it may affect the growth of adenomyosis. Danazol suppressed synthesis of estrogen in vitro.

Effects of progestin antagonists, glucocorticoids and estrogen on progesterone-induced protein secreted by rabbit endometrial stromal cells in culture

Progesterone enhances the synthesis of a 42 kDa protein secreted by rabbit endometrial stromal cells in primary culture. The duration of that response, the effects of estrogen and the inhibitory ability of antiprogestin steroid analogs, RU486, ZK98.299 and ZK98.734, were tested. Although there was a progressive decrease in the amount of the 42 kDa protein synthesized during a 6-day culture period, progesterone stimulated its rate of synthesis greater than 2-fold throughout that period. The addition of estrogen did not prevent the progressive decrease in the amount of the protein synthesized, nor did it enhance the progesterone effect when the culture medium contained phenol red. Estrogen alone did slightly induce 42 kDa protein synthesis by cells grown in phenol red-free medium, and the progesterone response was accentuated to the same degree. When present in a concentration that was 100-fold that of the progesterone, RU486, ZK98.299 and ZK98.734 each abolished stimulation. This antagonistic effect was overcome by addition of an equimolar concentration of progesterone. Deoxycorticosterone (DOC) also stimulated 42 kDa protein synthesis. The antiprogestins blocked this stimulatory effect, even when both steroids were in equimolar concentrations. There was no difference in the ability of ZK98.299 or ZK98.734 to block DOC stimulation, even though ZK98.734 exhibits no antiglucocorticoid activity [J. Steroid Biochem. 25 (1986) 835]. Therefore, it is likely that the DOC effect is mediated by the progesterone receptor system. These studies indicate that enhanced synthesis of the 42 kDa protein represents a progesterone receptor mediated event and that the cell culture system described can be used as a bioassay for determination of antiprogestin activity.

Comparison of norethindrone and medroxyprogesterone acetate with natural progesterone and estradiol in stimulating prolactin production from cultured endometrial stromal cells

Progestins stimulate prolactin production from endometrial stromal cells in culture. We compared the potencies of the synthetic progestins norethindrone and medroxyprogesterone acetate to natural progesterone in inducing stromal prolactin production. Modifications of the culture system provided an increase in stromal cell yield, thus permitting multiple comparisons from the treatment of cells from a common endometrial sample. The effects of high-dose estradiol also were evaluated in this system. The findings suggest relative potencies of 50:1 for medroxyprogesterone acetate and progesterone. Norethindrone gave intermediate and more variable responses. Estradiol potentiated prolactin production from only submaximal progestins doses. The differences between the progestin effects, in large measure, were due to differential culture growth as reflected by culture mass. Compared to controls and estradiol alone, all the progestins induced much greater prolactin production. Thus during decidualization, progestins probably promote both stromal growth and intracellular prolactin production. High-dose estradiol may not interfere with these events.

Progestins and Antiprogestins: A Review of Their Role in Medicine and Bioassays Used in Their Development

The physiological role of ovarian progesterone in reproduction and the medical uses of synthetic progestins and antiprogestins are briefly reviewed. Although a number of progestins are in wide use, the search continues for better analogues that display fewer of the unwanted effects of the present compounds. The one antiprogestin approved for human use to date, RU486, exhibits considerable antiglucocortoid activity

The classical bioassays currently in use for the development of these steroid analogues depend upon in vivo progestin effects. However, progestins induce measurable responses in several cell culture systems that could be used as alternative bioassays. Rabbit uterine stromal cells in primary culture are especially suitable for such use. Addition of progesterone to these cultures stimulates synthesis of a 42 kilodalton (42kD) protein that appears in the medium. The 42kD protein response is specific for a progesterone receptor-mediated event and it can be blocked by known progestins. Using this culture system as a bioassay, one rabbit yields enough cells to measure the effect of 30 test doses in triplicate. Thus, a culture system is described that could substitute for current in vivo bioassays. This culture bioassay would allow large scale screening for potential progestin or antiprogestin activity.

In vitro induction of prolactin production and aromatase activity by gonadal steroids exclusively in the stroma of separated proliferative human endometrium

Prolactin production by decidualized human endometrium has been demonstrated in organ explant cultures and presumed to be of stromal origin by immunocytochemistry and the presence of simultaneous stromal histologic changes. To test the hypothesis that endometrial prolactin production is exclusively of stromal origin, late proliferative human endometrium was separated into glands and stroma and cultured for 3 days. Confluent cultures were incubated with progesterone, 50 ng/ml; estradiol, 5 ng/ml; or both progesterone and estradiol for 4, 8, and 15 days. Prolactin concentration was measured at 2-day intervals by specific radioimmunoassay throughout a 15-day culture in all samples. Aromatase activity at 15 days was assayed by the production of tritiated water from 1 beta 3H-androstenedione. Possible contamination of gland cultures by stromal cells was controlled by the substitution of D-valine in the culture media. No prolactin was detected in the D-valine-treated gland cultures. Stromal cell cultures demonstrated increasing prolactin with continuous incubation with progesterone (15-day control: 11.28 +/- 0.91 ng/100 micrograms deoxyribonucleic acid versus 15-day progesterone: 245.8 +/- 4.24 ng/100 micrograms). Prolactin levels increased after progesterone was removed at day 4 and 8, reaching peak production 4 days later, followed by a steady decline. Estradiol induced a sustained increase in prolactin production even after withdrawal of steroids. Aromatase activity in gland cells exposed to steroids exhibited no change with time. Steroid-treated stromal cell cultures showed an increase in aromatase activity in all 15-day (controls: 21.6 +/- 0.7 pmol substrate converted per mg of deoxyribonucleic acid per 24 hours versus progesterone: 43.4 +/- 4.2 versus estradiol: 34.2 +/- 3.5 versus progesterone and estradiol: 47.5 +/- 2.4) but not in 4- or 8-day incubations. These studies support these conclusions: (1) nongestational endometrial prolactin is of stromal, not glandular origin; (2) stromal prolactin production is induced and maintained by progesterone: (3) stromal prolactin production is induced by estradiol but does not require continued exposure for maintenance; (4) aromatase activity is increased by long-term exposure to progesterone and estradiol in stroma but not in glands.

Testosterone lowers aromatase activity in cultured human genital skin fibroblasts

The cytochrome P-450-dependent aromatase pathway utilizes the androgens testosterone (T) and androstenedione, as substrates for estrogen formation. In addition, androgens have been shown to influence the level of aromatase activity in various tissues. In cultured human skin fibroblasts, incubation with T for 14 h resulted in a dose-dependent decline in aromatase activity, the concentration of T producing a half-maximal decline being 6 nM. In the presence of T (50 nM), aromatase activity declined in a time-dependent fashion with maximal reduction occurring by 9 h. When aromatase kinetics were determined after preincubation of cells with T, there was a significant decline in the calculated Vmax with no significant change in the apparent Km, suggesting that incubation of cells with T reduced the number of active enzyme sites. Aromatase activity was unaffected by preincubation of cells with the synthetic androgen methyltrienolone. In addition, the decline in aromatase activity following preincubation with T was observed in cells derived from patients with complete androgen insensitivity demonstrating that the effect of T was not mediated by androgen receptors. Furthermore, new protein synthesis was not necessary for the T-mediated effect as the presence of cycloheximide (50 micrograms/ml) did not prevent it. When cells were incubated at low oxygen tension, the inhibition of aromatase activity by T was diminished. Testosterone is rapidly metabolized in genital skin fibroblasts to dihydrotestosterone, androstanedione, androsterone, 3 alpha-androstanediol, 3 beta-androstanediol and estradiol. To determine if a metabolite of T might be responsible for the repression of aromatase activity, aromatase activity was determined in cells following preincubation with various metabolites of T. Preincubation of cells with androstenedione, androstanedione or 3 alpha-androstanediol produced a small but significant decline in aromatase activity, whereas preincubation of cells with dihydrotestosterone, androsterone, or 3 beta-androstanediol did not have a significant effect. Aromatase activity was also unaffected by preincubation of cells with estradiol or diethylstilbestrol. When aromatase activity was assayed in microsomal preparations from cells preincubated with T, activity was reduced. Although cells preincubated with 50 nM [3H]T contained between 0.25 and 0.51 pmol of residual steroid/mg microsomal protein, the amount of [1-3H]androstenedione and T was insufficient to account for the observed decline in aromatase activity on the basis of competitive inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunologic identification of the aromatase enzyme system in human endometrium

Confluent human endometrial stromal cells were cultured in medium with no hormone or supplemented with medroxyprogesterone acetate (MPA), estradiol (E2), and porcine relaxin (RLX) for 5 days. These stromal cells were then labeled with [35S]methionine for 3 h. The radioactive proteins in the particulate fraction of cell homogenate were extracted by detergent and incubated with antisera to purified placental aromatase cytochrome P-450 (P-450arom) and NADPH-cytochrome P-450 reductase to isolate the radio-labeled aromatase enzyme components. Analysis of the radio-labeled protein, isolated by antibody to the cytochrome P-450arom from different preparations (P45FBIII or R-8-2) showed a major band at molecular weight 54k on SDS polyacrylamide gel electrophoresis (SDS-PAGE). The intensity of 54k band was stronger in hormone treated stromal cells than that of control in parallel with the increase of aromatase activity. The radio-labeled protein isolated by anti-NADPH cytochrome P-450 reductase, REDFBIV, showed a major band at the molecular weight 73k on SDS-PAGE with comparable intensity in control and hormone treated samples. Thus, the apparent molecular weights of endometrial cytochrome P-450arom and cytochrome P-450 reductase were identical to placental aromatase enzyme system. When a secretory endometrium and a decidua were labeled with [35S]methionine, the cytochrome P-450arom was detected only in the decidua. NADPH cytochrome P-450 reductase was detected both in the endometrium and the decidua. These results show that antisera to placental aromatase enzyme system cross reacts with the endometrial aromatase enzyme components. The synthesis of cytochrome P-450arom was stimulated by MPA, E2 and RLX while the synthesis of the NADPH-cytochrome P-450 reductase aromatase component was not affected by the hormone.

The inductive effects of progestogens on aromatase activity in stromal cells of human uterine endometrium

Aromatase activity for androstenedione was measured in stromal cells of human uterine endometrium throughout the menstrual cycle. The effect of progestogen on aromatase activity was also examined in the endometrial stromal cells. Aromatase activity tended to be high in the proliferative cells compared to the secretory cells. Moreover, its enzyme activity was enhanced at the concentration of 0.1 or 1.0 microM of medroxyprogesterone acetate (MPA) and norethindrone (ENT) in all phases of menstrual cycle. MPA stimulated aromatase activity in the stromal cells more strongly than did ENT. These results may suggest that although aromatase in uterine endometrium is not regarded to be so much influenced by endogenous progesterone during menstruation, the increase of aromatase activity by progestogen added lead to the more differentiated endometrium.

Steroid metabolism by epidermal keratinocytes

The metabolism of various radiolabeled steroids by cultured human epidermal keratinocytes was studied in an attempt to identify the steroid-metabolizing enzymes present in these cells. Sulfatase activity was demonstrated in keratinocytes with either E1S or DS as substrates. The products of sulfatase action were E1 and DHEA, respectively. The specific activity of the enzyme was approximately 5- to 14-fold greater with E1S as the substrate compared with DS, and the rates of hydrolysis were linear with incubation time up to 3 h. The metabolism of DHEA by the keratinocyte 17 beta-HSOR-catalyzed reaction resulted in the predominant formation of 5-androstene-3 beta,17 beta-diol. The rate of formation of 5-androstene-3 beta,17 beta-diol was linear with time of incubation up to 18 h, and the specific activity of 17 beta-HSOR, with DHEA as the substrate, was greater in keratinocytes maintained in culture for 4 weeks compared with keratinocytes kept in culture for 1 week. Androstenedione was a minor product of DHEA metabolism. The metabolism of DHT by epidermal keratinocytes resulted in the formation of 5 alpha-androstanedione, 5 alpha-androstane-3 alpha,17 beta-diol, 5 alpha-androstane-3 beta,17 beta-diol, androsterone, and isoandrosterone: the rates of formation of 5 alpha-androstane-3 alpha,17 beta-diol and 5 alpha-androstane-3 beta,17 beta-diol were linear with incubation time up to 24 h, and the specific activities of 3 alpha-HSOR and 3 beta-HSOR did not appear to change with keratinocyte time in culture up to 3 weeks. The metabolism of DOC by epidermal keratinocytes resulted in 5 alpha-dihydrodeoxycorticosterone production: the rate of formation of this metabolite was linear with incubation time up to 4 h. The metabolism of E1 by epidermal keratinocytes yielded E2, and that of E2 resulted in the formation of E1. The rate of E1 formation from E2, was approximately 10-fold greater than the rate of formation of E2 from E1; these rates were linear with incubation time up to 4 h. Epidermal keratinocytes maintained in culture did not metabolize androstenedione to either E1 or E2, and pregnenolone was not metabolized by these cells. This study serves to ascertain that epidermal keratinocytes express steroid 5 alpha-reductase, 17 beta-HSOR, 3 beta-HSOR, 3 alpha-HSOR, 3 beta-hydroxysteroid oxidoreductase-delta 5----4-isomerase, and sulfatase activities.

Transformation of human progesterone receptor in the presence of the progestin (R5020) and the antiprogestin (RU486)

We have examined and compared the binding characteristics and transformation in vitro of human uterine cytosolic progesterone receptor (PR) bound to either the progestin agonist, R5020 or the antiprogestin, RU486. Incubation of cytosol with 5-20 nM [3H]R5020 and [3H]RU486 yielded macromolecular complexes that sedimented in the 4S and 8S regions in 10-35% glycerol gradients. The 8S peaks of radioactivity due to macromolecular-bound [3H]R5020 or [3H]RU486 could be eliminated by a preincubation of the uterine cytosol with 1-2 microM progesterone or RU486. The [3H]R5020 binding in the 4S peak was not competable with either steroid. In contrast, the binding of [3H]RU486 in the 4S peak could be abolished by a pretreatment of uterine cytosol with excess RU486, but not progesterone. Selective fractionation of the cytosol with ammonium sulfate, in the presence of sodium molybdate, eliminated the non-specific 4S [3H]R5020 binder. The thermal (23 degrees C) transformation of the [3H]RU486-receptor complex, as a function of the loss of the area under the 8S peak, appeared to be comparable to that achieved with [3H]R5020-receptor complex. The 8S [3H]RU486 peak was reduced by only 46% compared to the [3H]R5020 peak, which was reduced by 60%. These results demonstrate that in human uterine cytosol, R5020 and RU486 bind in a specific and saturable manner to an 8S PR, which is susceptible to thermal 8S to 4S transformation. In addition, [3H]R5020 also interacts with a nonsaturable 4S macromolecule, whereas the 4S [3H]RU486 binder is saturable and specific for RU486. The above observations indicate the heterogeneity of the steroid binding components present in the human uterine cytosol, and suggest that caution should be taken when interpreting data which shows the presence of different molecular forms of the steroid receptors.

The effect of progestin on rabbit endometrial aromatase activity

The ability of rabbit endometrium to synthesize estrogen was investigated. Aromatase activity was measured by incubating the viable tissue fragments with [3H] testosterone at 37 degrees C and quantitated the [3H]estrogens at the end of 6 h incubation. The activity was not detectable in endometrium and myometrium of non-pregnant rabbits. In pregnant rabbit, the activity increased from 2 to 12 fmol/h/g of tissue in endometrium obtained from both gravid and nongravid uterine horns 4-8 days after mating. Aromatase activity in endometrium at implanted sites on the 8th day after mating reached up to 550 fmol/h/g of tissue. Hormonal regulation of the aromatase activity was studied directly in cultured rabbit endometrial stromal cells. Both progesterone and medroxyprogesterone acetate stimulated the activity with 2- to 25-fold increase over the control values (0.2-1 fmol/h/mg protein). The stimulation of aromatase activity by progestin was found to be both time- and dose-dependent. Estrogen, Bu2cAMP, forskolin, HCG or relaxin had no effect on the activity. Aromatase activity in glandular epithelial cells was neither detectable nor affected by progestin. These results indicate that aromatase activity in rabbit endometrium is concentrated in stromal cells and progestin stimulates the activity. However, estrogen, forskolin and relaxin which enhanced the stimulation of the activity by progestin in human endometrium had no effect on aromatase in rabbit endometrium. The increase of aromatase activity observed after the onset of conception may be physiologically important to increase the local estrogen content for decidualization of the endometrium.

The effect of insulin on aromatase activity in isolated human endometrial glands and stroma

Hyperinsulinemic states have been associated with an increased incidence of estrogen-dependent endometrial neoplasia. To study the effect of insulin on the ability of endometrium to aromatize androgens to estrogens, late proliferative endometrium was obtained from normally cycling women at the time of indicated surgery, separated into component glands and stroma, and grown to confluence. Separated gland and stromal cultures were incubated in triplicate with increasing insulin concentrations and epidermal growth factor. Aromatase activity was assayed by the production of tritiated water from tritium-labeled androstenedione. The activity was noted to increase proportionally with increasing concentrations of insulin greater than 10 U/ml, and the effect was specific. These data suggest the following conclusions: (1) Insulin stimulates aromatase activity in both endometrial glands and stroma; (2) hyperinsulinemia may predispose to endometrial neoplasia by enhancing endogenous endometrial estrogen production.

Antisera against estrogen synthetase from human placental microsomes. Antibody characterization and cross-reactivity studies in other organs

Antibodies were obtained against both protein components of the cytochrome P-450 enzyme system responsible for estrogen biosynthesis, estrogen synthetase (aromatase), from human placental microsomes. The antiserum against the NADPH-cytochrome P-450 reductase component (antiserum denoted RE-DFBIV) gave a single major band at the Mr of the authentic enzyme by immunoblotting after electrophoretic separation of SDS-solubilized microsomes and inhibited both the reductase and aromatase activities in human placental and endometrial microsomes (Tseng, L. and Bellino, F.L. (1985) J. Steroid Biochem. 22, 555-557) and in homogenates of cultured aromatase-stimulated human endometrial stromal cells and human ovarian microsomes. The antiserum against the cytochrome P-450 component of aromatase (antiserum denoted P45FBIII) also gave a single band at the Mr of the authentic protein by immunoblotting after electrophoresis, and inhibited aromatase activity in homogenates of human placental microsomes, ovarian and decidual particulate fractions and cultured aromatase-stimulated endometrial stromal cells. This antiserum had no effect on NADPH-cytochrome c reductase activity in any of the systems studied. We conclude that these antiserum preparations separately recognize the NADPH-cytochrome P-450 reductase and cytochrome P-450 components of aromatase in human placenta, ovary, decidua and endometrium. Epitopes on these aromatase component proteins involved in enzyme activity are shared among these various human tissue sources.