Effects of onapristone on postmenopausal endometrium

The progesterone antagonist mifepristone (RU486, Exelgyn) has been shown to exert a paradoxical agonist effect on postmenopausal endometrium. We conducted a study to investigate the effects of the 'pure' antiprogestin onapristone (ZK 98 299, Schering AG) on postmenopausal endometrium. Seventeen postmenopausal subjects (45-62 years), took 2 mg of oestradiol and either placebo, 1 mg onapristone or 10 mg of onapristone, daily for 56 days. An endometrial biopsy was performed during the final week of treatment and assessed for histology and immunohistochemistry for oestrogen receptors (ER), progesterone (PR), androgen receptors (AR) and the cell proliferation marker Ki 67. FSH fell in all 14 subjects who completed the study, consistent with the effect of oestradiol treatment. There was a dose-dependent additive effect of onapristone on suppression of gonadotrophins. All endometrial biopsies showed proliferative endometrium. A similar pattern and intensity of immunostaining of ER, PR and Ki 67 was observed in all groups, with positive immunoreactivity in both glands and stroma. AR immunostaining was observed in both glands and stroma from all subjects, but there was an increase in intensity of immunostaining within the glandular epithelium of women receiving 10 mg onapristone. The antiprogestin onapristone, in contrast to mifepristone, is not agonistic on postmenopausal endometrium and does not exert obvious antiproliferative effects. It does however cause a dose dependent suppression of FSH and LH release.

Glucocorticoid agonistic and antagonistic effects of mifepristone and onapristone on thymocyte subset composition and CD26/dipeptidyl peptidase IV activity in infant male rats

Antiglucocorticoid activities of two antigestagens-antiglucocorticoids (AGs)-mifepristone and onapristone-were tested in hydrocortisone-treated suckling male rats. Hydrocortisone (HC) treatment in vivo resulted in (1) reduction of the relative thymus weight and absolute thymocyte counts; (2) relative decrease of the CD4(+)CD8(+) thymocyte proportion accompanied by an increase of single-positive and double negative thymocyte populations, the latter of which contained large CD3-negative cells expressing a high level of CD26 on their surface; (3) increase of specific dipeptidyl peptidase IV (DPP IV) activity in thymocyte homogenates. Both AGs suppressed the systems (1) and (2) to a comparable extent. When administered alone, mifepristone and onapristone at higher doses exhibited a slight thymolytic effect as revealed by the reduction of the relative thymus weight and thymocyte counts, accompanied by some reduction of the numbers of cycling thymocytes. These effects were limited to the early postnatal period (days 12-17). A comparable agonistic effect of AGs was not observed in systems (2) and (3). Neither HC nor AGs influenced the sialylation pattern of thymocyte membrane bound CD26/DPP IV, which was exclusively of alpha2,6-type, as demonstrated by analytical isoelectric focusing (IEF) and PAGE analysis in combination with the application of neuraminidases, specific lectins and histochemical staining for DPP IV activity in the gels.

Ovarian steroids reduce apoptosis induced by trophic insufficiency in nerve growth factor-differentiated PC12 cells and axotomized rat facial motoneurons

Previous studies have demonstrated that ovarian steroids exert neuroprotective effects in a variety of in vitro and in vivo systems. The mechanisms underlying these effects remain poorly understood. In the present study, the neuroprotective effects of estradiol (E(2)) and progesterone (P) were examined in two models of apoptosis induced by growth factor insufficiency: partially nerve growth factor (NGF)-differentiated PC12 cells, after serum and NGF withdrawal; and axotomized immature rat facial motor motoneurons. E(2) and P both increased the survival of trophically withdrawn NGF-differentiated PC12 cells, at physiologically relevant concentrations. However, neither steroid had a significant effect on the survival of PC12 cells that had not been NGF treated. Exposure to NGF had no effect on the expression of estrogen receptor (ER)beta, but markedly increased the levels of ERalpha and altered the expression of the progesterone receptor (PR) from predominantly PR-B in NGF naive cells, to predominantly PR-A after NGF. The survival promoting effects of E(2) and P were blocked by the specific steroid receptor antagonists Faslodex (ICI 182780) and onapristone (ZK98299), respectively. Inhibitors of RNA (actinomycin D) or protein (cycloheximide) synthesis also abrogated the protective effects of both steroids. In immature rats, E(2) and P both significantly increased the numbers of surviving facial motor neurons at 21 days after axotomy. These data demonstrate significant protective effects of E(2) and P in two well-characterized models of apoptosis induced by trophic withdrawal and suggest that, at least in PC12 cells, the effects of the steroids are mediated via interaction with nuclear steroid receptor systems. The lack of steroid responsiveness in NGF-naive PC12 cells despite the presence of abundant ERbeta and PR-B are consistent with the view that ERalpha and PR-A may be particularly important as mediators of the neuroprotective effects of their corresponding hormonal ligands.

Effects of an antiprogestin onapristone on the endometrium of bonnet monkeys: morphometric and ultrastructural studies

Our previous studies demonstrated the ability of low doses of antiprogestin ZK 98.299 (onapristone) to inhibit fertility in bonnet monkeys. In the present study cumulative effects of low doses of ZK 98.299 on the endometrial cytoarchitecture of bonnet monkeys were analyzed. Treatment with either the vehicle (n = 3) or onapristone at 2.5 mg (n = 4) or 5.0 mg (n = 3) was initiated on Day 5 of the first menstrual cycle and thereafter repeated every third day for four to seven consecutive cycles. The last treatment cycles were anovulatory in two animals treated with 2.5 mg and all animals treated with 5.0 mg. Endometrial biopsies were collected on Day 8 after the midcycle estradiol peak in ovulatory menstrual cycles and on Day 20 in anovulatory menstrual cycles during the last treatment cycle. Ultrathin sections of the fixed endometrium were stained with toluidine blue for morphometric analysis and uranyl acetate and lead citrate for ultrastructural analysis. The ZK 98.299-treated animals showed a dose-dependent endometrial atrophy as evident by a decrease in the height and diameter of the glands and early signs of compaction in the stroma. Ultrastructural analysis also revealed dose-dependent degenerative changes in the subcellular organelles such as the nucleus, mitochondria, endoplasmic reticulum, lysosomes, and Golgi apparatus. This suggests that long-term treatment with low doses of ZK 98.299 leads to the suppression of estrogen-dependent endometrial proliferation. However, this blockade operates independent of estradiol receptor (ER) and progesterone receptor (PR) concentrations as the expressions of these steroid receptors did not show any significant changes even after prolonged treatment. The study demonstrated an antiestrogenic effect of ZK 98.299 on endometrium after prolonged treatment in bonnet monkeys.

Expression of regulator of G protein signaling-2 in rat myometrium during pregnancy and parturition

OBJECTIVE

The purpose of this study was to determine the potential physiologic roles of myometrial regulator of G protein signaling-2 (RGS2), a G protein-associated GTPase, by the analysis of the changes in RGS2 messenger RNA expression during pregnancy and parturition and to examine factors that regulate these changes.

STUDY DESIGN

Myometrial RGS2 messenger RNA levels were analyzed by Northern blotting in rats (1). during pregnancy, parturition, and in the postpartum period; (2). with preterm-induced and delayed, postterm delivery; (3). that were ovariectomized and treated with either estradiol, progesterone, or both; and (4). with unilateral uterine pregnancies.

RESULTS

RGS2 messenger RNA was almost undetectable until day 5 of pregnancy, when it rose sharply and remained elevated up to and including day 19, at the time that progesterone withdrawal occurs. The expression of myometrial RGS2 messenger RNA on day 22 did not differ between rats either before or during delivery. Onapristone caused preterm delivery and a premature fall in RGS2 messenger RNA levels. In contrast, progesterone treatment prolonged pregnancy beyond day 25 and attenuated the decline in RGS2 messenger RNA levels. Simulation of the first 5 days of pregnancy resulted in a 3-fold rise in RGS2 messenger RNA expression. The levels of RGS2 in nonimplanted horns were approximately one half that of pregnant horns.

CONCLUSION

Sex steroids, in particular progesterone, and the presence of the conceptus play a role in the regulation of myometrial RGS2 messenger RNA expression. Although the elevated myometrial RGS2 messenger RNA expression corresponds to the period during pregnancy when the uterus is relatively quiescent and the down-regulation of RGS2 messenger RNA at the end of pregnancy may be related to the timing of parturition, the specific role of myometrial RGS2 remains unknown.

Molecular determinants of glucocorticoid receptor mobility in living cells: the importance of ligand affinity

The actions of glucocorticoids are mediated by the glucocorticoid receptor (GR), which is activated upon ligand binding, and can alter the expression of target genes either by transrepression or transactivation. We have applied FRAP (fluorescence recovery after photobleaching) to quantitatively assess the mobility of the yellow fluorescent protein (YFP)-tagged human GR alpha-isoform (hGRalpha) in the nucleus of transiently transfected COS-1 cells and to elucidate determinants of its mobility. Addition of the high-affinity agonist dexamethasone markedly decreases the mobility of the receptor in a concentration-dependent manner, whereas low-affinity ligands like corticosterone decrease the mobility to a much lesser extent. Analysis of other hGRalpha ligands differing in affinity suggests that it is the affinity of the ligand that is a major determinant of the decrease in mobility. Similar results were observed for two hGRalpha antagonists, the low-affinity antagonist ZK98299 and the high-affinity antagonist RU486. The effect of ligand affinity on mobility was confirmed with the hGRalpha mutant Q642V, which has an altered affinity for triamcinolone acetonide, dexamethasone, and corticosterone. Analysis of hGRalpha deletion mutants indicates that both the DNA-binding domain and the ligand-binding domain of the receptor are required for a maximal ligand-induced decrease in receptor mobility. Interestingly, the mobility of transfected hGRalpha differs among cell types. Finally, the proteasome inhibitor MG132 immobilizes a subpopulation of unliganded receptors, via a mechanism requiring the DNA-binding domain and the N-terminal part of the ligand-binding domain. Ligand binding makes the GR resistant to the immobilizing effect of MG132, and this effect depends on the affinity of the ligand. Our data suggest that ligand binding induces a conformational change of the receptor which is dependent on the affinity of the ligand. This altered conformation decreases the mobility of the receptor, probably by targeting the receptor to relatively immobile nuclear domains with which it transiently associates. In addition, this conformational change blocks immobilization of the receptor by MG132.

Non-genomic effects of progestins--inhibition of cell growth and increased intracellular levels of cyclic nucleotides

The anti-proliferative effect of progestins was studied in human transformed cell lines from the uterine cervix (C-4I, C33A and Me-180). Progestins caused a concentration-dependent inhibition of proliferation. The maximum tested concentration (2.6-3.2 microM) inhibited C-4I cell growth by the following order of potency: progesterone (56%) > medroxyprogesterone (38%) > megestrol acetate (25%). The sensitivity, expressed as I(25) (the concentration that caused 25% inhibition of growth), showed the same order: progesterone (7.7 nM) > medroxyprogesterone (78 nM) > megestrol acetate (570 nM). The intracellular levels of cGMP and cAMP were elevated and the cellular export of these cyclic nucleotides was inhibited by a similar order of potency. The C-4I cell line was devoid of progesterone-, estrogen-, androgen- and glucocorticoid-receptors. In addition, the antiprogestins mifepristone, onapristone and ZK-112993 did not block the anti-proliferative effect of progesterone. On the other hand, antiprogestins (2.3 nM) appeared to have some progesterone-like ("mimetic") activity with inhibition of C-4I cell growth; mifepristone (11%), onapristone (12%) and ZK-112993 (16%). The observed effects of progestins and antiprogestins on C-4I cells were also presented in C33A cells (16% androgen receptor positive) and Me-180 cells (22% progesterone receptor positive, 9% androgen receptor positive and 17% glucocorticoid receptor positive). This study suggests that a non-genomic mechanism contributes to the anti-proliferative effect of progestins.

A nonsteroidal glucocorticoid receptor antagonist

Selective intracellular receptor antagonists are used clinically to ameliorate hormone-dependent disease states. Patients with Cushing's syndrome have high levels of the glucocorticoid, cortisol, and suffer significant consequences from this overexposure. High levels of this hormone are also implicated in exacerbating diabetes and the stress response. Selectively inhibiting this hormone may have clinical benefit in these disease states. To this end, we have identified the first selective, nonsteroidal glucocorticoid receptor (GR) antagonist. This compound is characterized by a tri-aryl methane core chemical structure. This GR-specific antagonist binds with nanomolar affinity to the GR and has no detectable binding affinity for the highly related receptors for mineralocorticoids, androgens, estrogens, and progestins. We demonstrate that this antagonist inhibits glucocorticoid-mediated transcriptional regulation. This compound binds competitively with steroids, likely occupying a similar site within the ligand-binding domain. Once bound, however, the compound fails to induce critical conformational changes in the receptor necessary for agonist activity.

Effects of GnRH analogues, 'add-back' steroid therapy, antiestrogen and antiprogestins on leiomyoma and myometrial smooth muscle cell growth and transforming growth factor-beta expression

The objective of this study was to elucidate the biological significance of GnRH and antiprogestins and antiestrogen in leiomyoma and their interactions with ovarian steroid 'add-back' therapy. Leiomyoma and myometrial smooth muscle cells (LSMC and MSMC) were isolated and exposed to GnRH agonist (leuprolide acetate, LA), 17beta-estradiol (E2), medroxyprogesterone acetate (MPA), GnRH antagonist (Antide), estrogen antagonist, ICI182780 (Fulvestrant) and progesterone antagonists RU486 (Mifepristone) and ZK98299 (Onapristone) and combinations thereof. The rate of DNA synthesis, cell proliferation and transforming growth factor-beta (TGF-beta) expression were then determined. In both cell types, we found that in a dose-dependent manner, LA inhibited, whereas E2, MPA and the combination of E2 + MPA stimulated, the rate of DNA synthesis in these cells. Antide reversed the inhibitory effect of LA, while LA partly inhibited the stimulatory effect of the steroids. In addition, RU486, ICI182780 and ZK98299 at 0.1 micro mol/l or higher doses inhibited the rate of DNA synthesis and partly reversed the effects of E2 and/or MPA. We also found that LSMC expressed elevated levels of TGF-beta1 compared with MSMC. In both cell types, the effects of LA, E2, MPA, RU, ZK and ICI and combinations thereof on TGF-beta1 production were reflective of their effects on DNA synthesis. In line with this, TGF-beta1 was found to stimulate DNA synthesis and the E2-, TGF-beta1- or E2 + TGF-beta1-induced DNA synthesis was found to be inhibited by TGF-beta1 neutralizing antibodies and/or LA. In conclusion, the results provide further evidence that GnRH agonist- and RU486-induced leiomyoma regression is mediated in part through an interactive mechanism that results in altered cell growth and suppression of TGF-beta production.

Endometrial function in vervet monkeys (Cercopithecus aethiops): morphology, beta3 integrin and insulin-like growth factor binding protein-1 expression during the menstrual cycle and pregnancy in the normal and disrupted endometrium

The expression of endometrial beta3 integrin and insulin-like growth factor binding protein-1 (IGFBP-1) was studied in cycling and pregnant vervet monkeys. There were clear changes of beta3 integrin expression during the menstrual cycle, with the strongest immunostaining observed on day 26. Moderate to strong expression was observed during pregnancy. The expression of IGFBP-1 during the menstrual cycle was weak but upregulated during pregnancy with moderate to strong staining. The administration of a single dose of onapristone at 10 mg/kg on days 17, 21 and 22 of the menstrual cycle, followed by a biopsy on days 22, 22 and 26, respectively, and during pregnancy (34-44 days menstrual age) 24 h before the biopsy, disrupted and desynchronized the endometrium. However, no effect on beta3 integrin expression could be observed and staining reflected the untreated patterns. The same applied to IGFBP-1 except that during pregnancy the expression of this protein was reduced or abolished. The results suggest that beta3 integrin is associated with endometrial receptivity in vervet monkeys and that IGFBP-1 plays an important role during pregnancy in this species. The administration of onapristone appeared to only influence IGFBP-1 expression. To our knowledge, this is the first time that these endometrial proteins have been investigated in vervet monkeys. This study should therefore contribute to improving our understanding of the reproductive function of this species.

An antiprogesterone, onapristone, enhances the gene expression of promatrix metalloproteinase 3/prostromelysin-1 in the uterine cervix of pregnant rabbit

Using a progesterone receptor antagonist, onapristone/ZK 98.299, we examined the in-vivo effects of progesterone on the function of uterine cervix during pregnancy. Onapristone was intravenously administered to pregnant rabbits on day 20 post coitum. After 24 h, the antiprogesterone increased the wet weight of the uterine cervix and decreased the DNA concentration in the cervix. In-situ hybridization also indicated that antiprogesterone augmented the expression of matrix metalloproteinase (MMP)-3/stromelysin-1 mRNA in the uterine cervix. These changes are very similar to those observed and reported thus far in ripened and dilated uterine cervix. These results suggest that during pregnancy, progesterone closely participates in the maintenance of the function of uterine cervix by preventing the production of MMPs and thereby destruction of extracellular matrix, and thus add support to the theory that antiprogesterone has the potential to accelerate for the uterine cervical ripening and dilatation.

Coactivator/corepressor ratios modulate PR-mediated transcription by the selective receptor modulator RU486

Selective receptor modulators, such as the antiprogestin RU486, are known to exhibit partial agonist activities in a cell-type-dependent manner. Employing an in vitro chromatin transcription system that recapitulates progesterone receptor (PR)-mediated transcription in vivo, we have investigated the molecular basis by which the antiprogestin RU486 regulates transcription in a cell-type-specific manner. We have compared the effects of RU486 on PR-dependent transcription in vitro using T47D and HeLa cell nuclear extracts. RU486 exhibits a differential ability to activate transcription within these two cell types. The differential effect on transcription correlates with different ratios of endogenous coactivators/corepressors in these cells. Unlike agonist-bound PR that interacts only with coactivators such as steroid receptor coactivator-1 (SRC-1), RU486-bound PR binds to both coactivator SRC-1 and corepressor silencing mediator for retinoid and thyroid hormone receptor (SMRT) in vitro. Both SRC-1 and SMRT have the capacity to modulate RU486-dependent activity. Moreover, a change in the relative levels of SRC-1 and SMRT contained in our chromatin transcription system modulates agonist/antagonist effects of RU486 on transcription by PR. Our data indicate that the ability of RU486 to activate transcription is modulated by the ratio of coactivators to corepressors and substantiate the important roles of coregulators in the regulation of steroid receptor mediated transactivation in response to selective receptor modulators.

Expression of MAPkinases (Erk1/2) during decidualization in the rat: regulation by progesterone and nitric oxide

The interaction between nitric oxide (NO), progesterone and the MAPkinase signalling pathway involved in decidualization was studied using immunohistochemistry during implantation in the rat. Early pregnant rats were treated with the inhibitor of nitric oxide synthesizing enzyme iNOS, aminoguanidine, either alone or in combination with the low dose antiprogestin, onapristone. The combined treatment was most effective on days 7 and 9 post coitum leading to a complete loss of embryos. The expression pattern of activated MAPkinases, Erk1/2 and iNOS appeared to be associated with the differentiation process of decidualization. A maximum staining of both enzymes was observed on day 9 post coitum in the mesometrial decidua. In addition, Erk1/2 and iNOS were highly coexpressed around the mesometrial sinusoids. Combined treatment with aminoguanidine and onapristone for 3 days led to a transient suppression of Erk1/2 and abolished Cox2 expression. Concomitantly, angiogenesis was reduced and dilated sinusoids were missing in the mesometrial decidua. In conclusion, our study suggests that (i) the member of the mitogen-activated protein kinase (MAPK) family, Erk1/2, is activated during implantation and may play an important role during the decidualization process, and (ii) this enzyme may be regulated by both progesterone and NO.

Stromal PRs mediate induction of 17beta-hydroxysteroid dehydrogenase type 2 expression in human endometrial epithelium: a paracrine mechanism for inactivation of E2

Progesterone stimulates the expression of 17beta-hydroxysteroid dehydrogenase (HSD) type 2, which catalyzes the conversion of the potent estrogen, E2, to an inactive form, estrone, in epithelial cells of human endometrial tissue. Various effects of progesterone on uterine epithelium have recently been shown to be mediated by stromal PRs in mice. We describe herein a critical paracrine mechanism whereby progesterone induction of 17beta-HSD type 2 enzyme activity, transcript levels, and promoter activity in human endometrial epithelial cells are mediated primarily by PR in endometrial stromal cells. Medium conditioned with progestin-pretreated human endometrial stromal cells robustly increased 17beta-HSD type 2 enzyme activity (2-fold) and mRNA levels (13.2-fold) in Ishikawa malignant endometrial epithelial cells. In contrast, direct progestin treatment of Ishikawa epithelial cells gave rise to much smaller increases in enzyme activity (1.2-fold) and mRNA levels (4-fold). These results suggest that progesterone- dependent paracrine factors arising from stromal cells are primarily responsible for the induction of epithelial 17beta-HSD type 2 expression in the endometrium. We transfected serial deletion mutants of the -1,244 bp 5'-flanking region of the 17beta-HSD type 2 gene into Ishikawa cells. No progesterone response elements could be identified upstream of the 17beta-HSD type 2 promoter. Stromal PR-dependent induction of the 17beta-HSD type 2 promoter was mediated by a critical regulatory region mapped to the -200/-100 bp sequence. Direct treatment of Ishikawa cells with progestin gave rise to a maximal increase in the activity of -200 bp/Luciferase construct only by 1.2-fold, whereas medium conditioned by progestin-pretreated endometrial stromal cells increased promoter activity up to 2.4-fold in a time- and concentration-dependent manner. The stimulatory effect of medium conditioned by progestin-pretreated stromal cells was enhanced strikingly by increasing stromal cell PR levels with the addition of estrogen. This epithelial-stromal interaction was specific for endometrial epithelial cells, since 17beta-HSD type 2 could not be induced in malignant breast epithelial cells by media conditioned with progestin-treated breast or endometrial stromal cells. In conclusion, progesterone regulates the conversion of biologically active E2 to estrone by inducing the 17beta-HSD type 2 enzyme in human endometrial epithelium primarily via PR in stromal cells, which secrete factors that induce transcription mediated primarily by the -200/-100 bp 5'-regulatory region of the 17beta-HSD type 2 promoter.

Demonstration of mixed properties of RU486 in progesterone receptor (PR)-transfected MDA-MB-231 cells: a model for studying the functions of progesterone analogues

Progesterone antagonist RU486 (mifepristone) has been implicated for many anti-neoplastic and obstetrical applications. But the compound has demonstrated undesired agonist-like effect depending on cell, tissue and species studied. Using PR-transfected breast cancer cells MDA-MB-231, this report describes the similarities and differences between progesterone- and RU486-mediated effects on cell growth, cell differentiation and, at the molecular level, on the activation of p44/p42 MAP kinases (MAPK). Like progesterone, RU486 inhibited cells growth by arresting the cells in G0/G1 phase of the cell cycle. In contrast to progesterone that induced cell spreading, RU486 induced a multipolar, stellate morphology. RU486-treated cells showed no increase of stress fibers, nor was there any increase of focal adhesions as progesterone-treated cells did. Furthermore, despite of the fact that both compounds inhibited cell growth, RU486 significantly stimulated the activation of p44/p42 MAP kinases whereas progesterone markedly inhibited the activation. Nonetheless, the effects of RU486 were PR-mediated and RU486 was able to antagonize the effect of progesterone on cell growth and focal adhesion. In conclusion, RU486 can act not only as a progesterone antagonist, a progesterone agonist but also induced morphological and molecular changes that were distinct from progesterone-mediated effects in PR-transfected MDA-MB-231 cells. The non-progesterone-like effect of RU486 may be mediated through a pathway that is different from the progesterone-mediated pathway, or it is the result of a blockade of certain critical step(s) in the progesterone-mediated pathway. In any case, undesired side effects of antiprogestin may create clinical complications. PR-transfected MDA-MB-231 breast cancer cells provide a model for studying the functions of progesterone analogues.

Expression profiles of endometrial leukemia inhibitory factor, transforming growth factor beta2 (TGFbeta2), and TGFbeta2 receptor in infertile bonnet monkeys

The expression profiles of leukemia inhibitory factor (LIF), transforming growth factor beta2 (TGFbeta2), and transforming growth factor beta2 receptor (TGFbeta2R) were analyzed during the peri-implantation period in regularly menstruating, fertile bonnet monkeys and in animals in which endometrial nonreceptivity was induced by administering an antiprogestin, onapristone. Based on our previous experiences, a dose of 2.5 or 5 mg of onapristone was administered s.c. every third day during the menstrual cycle, because these dosages impair endometrial development without upsetting the normal gonadal endocrine profiles. Endometrial biopsy specimens were collected during the proliferative phase (estradiol levels about 200 pg/ml, n = 5) and peri-implantation period (Day 8 after midcycle peak in estradiol levels, n = 5) from normal ovulatory animals and during the peri-implantation period from onapristone-treated animals (n = 10). The biopsy specimens were processed to determine the expression patterns of LIF, TGFbeta2, and TGFbeta2R by immunohistochemical and reverse transcription-polymerase chain reaction (RT-PCR) methods. Levels of both protein and mRNA for LIF, TGFbeta2, and TGFbeta2R (analyzed by immunohistochemistry and RT-PCR, respectively) were greater in the endometrial samples collected during the peri-implantation period compared to samples collected during the proliferative phase in control animals. Treatment with either of the two doses (2.5 or 5 mg) of onapristone caused a significant (P < 0.05) down-regulation in the expression of LIF in the peri-implantation endometria. The endometrial expressions of TGFbeta2 and TGFbeta2R mRNAs were reduced significantly in animals treated with 5 mg of onapristone, but not in those treated with the lower dose. However, immunoreactive TGFbeta2 and TGFbeta2R proteins were significantly (P < 0.05) down-regulated in the endometrial samples from both the 2.5- and 5-mg-treated groups. The alterations observed in the expression patterns of LIF, TGFbeta2, and TGFbeta2R were specific, because the expression levels of epidermal growth factor receptor remained unaffected in the endometria from the treated groups. The present study demonstrates derangement in the expression profiles of LIF, TGFbeta2, and TGFbeta2R during the peri-implantation period in infertile bonnet monkeys. It may be hypothesized that TGFbeta2 function is one of the early steps in the regulation of the progesterone-driven cascade of events leading to endometrial receptivity, and that any aberration in this step may adversely affect the subsequent molecular events (i.e., expression of LIF). These data also suggest that potential aberrations in the functional network of locally produced cytokines and growth factors even may occur in an endometrium exposed to the optimal peripheral hormonal levels.

Dexamethasone blocks antioestrogen- and oxidant-induced death of pituitary tumour cells

The oestrogen receptor is fundamental to the growth and survival of the rat pituitary tumour cell line, GH(3). Our previous studies have shown that antioestrogens such as RU 58668 and ZM 182780 will reduce the rate of cell division and also induce cell death. Death of these cells in response to antioestrogen treatment appears to be due to a heightened sensitivity to reactive oxygen species (ROS). As part of a study to determine the cross-talk between steroid receptor systems in these cells, we have observed that the glucocorticoid, dexamethasone (Dex), inhibits antioestrogen-induced cell death. Cell death induced by H(2)O(2) is enhanced by ZM 182780 and this effect is also blocked by Dex. As apoptotic cell death in a number of systems involves an early loss of mitochondrial membrane potential (DeltaPsi(m)), we have performed detailed studies on the time-course of DeltaPsi(m) loss in relation to the loss in cell membrane function. These studies have indicated that a loss of DeltaPsi(m) parallels a loss of cell membrane function - this is more characteristic of necrosis than of apoptosis. From microscopic observations of these cells in response to H(2)O(2), it has been noted that early cell membrane blebbing, induced by H(2)O(2), is blocked in the presence of ZM 182780. Cell membrane blebbing can precede necrosis as well as apoptosis and it is thought to involve cytoskeletal changes, for which localised glycolytic reactions provide ATP. These observations, together with those showing that removal of glucose, but not inhibition of mitochondrial function, enhances ROS-induced cell death, prompted studies on the glycolytic pathway. As a strong candidate mechanism, it would appear that, via an effect on one of the rate-limiting glycolytic enzymes, glyceraldehyde-3-phosphate dehydrogenase, Dex is able to overcome the antioestrogen-enhanced loss of glycolytic function following exposure of cells to ROS. This report contributes to the growing body of evidence showing that glucocorticoids provide a survival advantage to both normal and tumour cell types.

Differential regulation of retinoblastoma protein by hormonal and antihormonal agents in T47D breast cancer cells

Phosphorylation of the tumor suppressor protein, retinoblastoma (pRb), regulates the progression of the cell cycle. Previous work from this laboratory had shown that estradiol (E(2)) regulates tumor suppressor proteins, p53 and retinoblastoma in breast cancer cells. In the present study, we have examined the phosphorylation of pRB in T47D breast cancer cells following treatments with R5020 and antiprogestins. In growth medium containing serum depleted of endogenous steroids by charcoal treatment, pRb appeared mainly in its hypophosphorylated form. Addition of 10 nM R5020 to the culture medium caused hyperphosphorylation of pRb within 24 h, but the hypophosphorylated form of pRb began to accumulate after 72 h. Upon prolonged R5020 treatment (72-96 h), pRb was detected exclusively in its hypophosphorylated form. While treatment of cells with R5020 caused a transient increase in the level of cyclin D1, E(2) addition caused a sustained increase in the level of cyclin D1 consistent with its role in stimulating pRb phosphorylation. Antagonists of both estrogen receptor (ER) and progesterone receptor (PR) blocked the E(2) and R5020-induced pRb phosphorylation, respectively. These results suggest that R5020 induces pRb phosphorylation via a transient increased expression of cyclin D1, whereas E(2) treatment results in sustained expression of cyclin D1 and increased pRb phosphorylation. Furthermore, R5020 effects on pRb phosphorylation appear PR-mediated as no cross-antagonism of pRb phosphorylation was observed: the R5020 effects were blocked by RU486 and ZK98299, but not by the pure ER antagonist, ICI 182, 780 (ICI).

The alpha-subunit of the epithelial sodium channel is an aldosterone-induced transcript in mammalian collecting ducts, and this transcriptional response is mediated via distinct cis-elements in the 5'-flanking region of the gene

Aldosterone stimulates Na(+) reabsorption in the collecting ducts by increasing the activity of the epithelial sodium channel, ENaC. Systemic administration of aldosterone increases alpha ENaC mRNA expression in mammalian kidney, suggesting that the alpha ENaC gene is a target for aldosterone action in the distal nephron. To determine whether aldosterone increases alpha ENaC gene transcription, a portion of the alpha ENaC 5'- flanking region coupled to luciferase was transfected into MDCK-C7 cells, a collecting duct cell line with aldosterone-stimulated Na(+) transport. Both dexamethasone and aldosterone stimulated alpha ENaC-coupled reporter gene activity via the glucocorticoid receptor (GR), and this response correlated with the effect of these hormones on endogenous alpha ENaC expression. The aldosterone-stimulated alpha ENaC expression was blocked by actinomycin D, and aldosterone had no effect on alpha ENaC mRNA decay, confirming a transcriptional effect. In HT-29 cells, a GR/mineralocorticoid receptor (MR)-deficient colonic cell line with constitutive alpha ENaC expression, cotransfection with GR or MR restored aldosterone-stimulated alpha ENaC gene transcription, although aldosterone had a functional preference for MR. Analysis of deletion constructs confirmed that a single imperfect glucocorticoid response element (GRE) is necessary and sufficient to confer the aldosterone responsiveness to the alpha ENaC gene promoter in MDCK-C7 and HT-29 cells. These results confirm that alpha ENaC is an aldosterone-induced transcript in the collecting duct and delineates the molecular mechanism for this effect.

Synthesis and biological activity of a novel, highly potent progesterone receptor antagonist

Herein we describe the chemical synthesis and pharmacological characterization of a novel, highly potent progesterone receptor (PR) antagonist, ZK 230211. The introduction of a 17alpha-pentafluorethyl side chain in the D-ring of the steroid skeleton allowed the combination of high antiprogestagenic activity with little or no other endocrinological effects. In contrast to many other antiprogestins, ZK 230211 did not convert to an agonist in the presence of protein kinase A (PKA) activators and showed high antiprogestagenic activity on both PR isoforms PR-A and PR-B. This high antiprogestagenic activity could also be demonstrated in several in vivo models. Furthermore, this compound displayed only marginal antiglucocorticoid effects. In tumor models ZK 230211 exhibited strong antiproliferative action. The pharmacological properties of ZK 230211 may prove useful in the treatment of endometriosis, leiomyomas, breast cancer, and in hormone replacement therapy.

The rationale for a wider range of progestogens

Progestogens are commonly used in hormone replacement therapy, normally as opponents of estrogen to protect the endometrium from hyperplasia and cancer. While these benefits of endometrial protection are well recognized, the data related to the effect of progestogens on breast tissue and the cardiovascular system are conflicting. It has been demonstrated that, according to the type of progestogen used, and the dose and duration of its application, a predominant proliferative effect may be observed in human breast cells. As far as breast cancer is concerned, most epidemiological studies suggest no difference in risk between therapy with estrogens alone or estrogens combined with progestogens, but recent data do indicate an increased risk with combined therapy. When the cardiovascular risk factors are considered, some progestogen molecules with a higher androgenic potency than others attenuate the beneficial effects of estrogens on both the lipid profile and vasomotion. On the other hand, the epidemiological data on primary prevention do not suggest any negative effect of the progestogens administered together with estrogens on cardiovascular morbidity or mortality. Recent results have questioned the cardioprotective effect of hormone replacement therapy in women with established coronary heart disease. It has been suggested that the lack of a secondary preventive effect by hormone replacement therapy may be due to the progestogens selected. The effect on osteoporosis is also the subject of debate, with some progestogens having a neutral effect on bone mineral density and others producing a marked improvement. Awareness of the classic contraindications of hormone replacement therapy and selection of molecules devoid of estrogenic, androgenic or glucocorticoid effect should allow greater use of the progestogens without any major drawback.

Progesterone receptor activation mediates LH-induced type-I pituitary adenylate cyclase activating polypeptide receptor (PAC(1)) gene expression in rat granulosa cells

We have previously reported that the pituitary adenylate cyclase activating polypeptide (PACAP) gene is regulated in ovarian granulosa cells by the autocrine and/or paracrine interaction between progesterone and its nuclear receptor progesterone receptor (PR). To initiate studies on the functional significance of the progesterone-induced PACAP production in luteinizing granulosa cells, we sought to determine the expression and hormonal regulation of PACAP receptors in the rat ovary. The relative mRNA levels of three known PACAP receptor subtypes (PAC(1), VPAC(1), and VPAC(2)) were determined in ovaries of immature rats treated with gonadotropins, by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) assays. Results show that all PAC(1), VPAC(1), and VPAC(2) transcripts are expressed at a detectable level in immature rat ovaries. Importantly, the ovarian level of PAC(1), but not VPAC(1) or VPAC(2), mRNA notably changes during gonadotropin challenges. Ovarian PAC(1) mRNA expression decreases during the pregnant mare's serum gonadotropin (PMSG)-induced follicular phase but substantially increases during the human chorionic gonadotropin (hCG)-induced periovulatory period. Because the hCG-induced increase in ovarian PAC(1) mRNA expression is attributable to the hormone-induced PAC(1) mRNA expression in granulosa cells of the preovulatory follicles, we next examined whether hCG regulates PAC(1) mRNA expression by directly acting on granulosa cells. When granulosa cells isolated from PMSG (40 h)-primed immature rats were challenged with hCG (or forskolin), PAC(1), but not VPAC(1) or VPAC(2), mRNA expression significantly increased within 6 h. Because the LH-induced PAC(1) mRNA expression (6 h) proceeds PR activation (3 h) in granulosa cells as the LH-induced PACAP mRNA expression (6 h) does, we further determined the cause-effect relationship among LH, PR activation and PAC(1) receptor gene expression, by examining the effect of PR antagonist, ZK98299, on the ability of LH to increase PAC(1) mRNA levels in luteinizing granulosa cells. Results show that ZK98299 inhibited the stimulatory effect of hCG (or forskolin) on PAC(1) mRNA expression, at the level of all known splice variants of PAC(1) mRNA in granulosa cells. In summary, our results demonstrating that PR activation is critical for the LH-induced PAC(1) gene expression in luteinizing granulosa cells suggest that PR activation regulates the finely tuned expression of the PACAP/PACAP receptor genes in luteinizing granulosa cells and thus dictates the timing of the autocrine and/or paracrine function of PACAP in preovulatory follicles.

Cervical dilatation: induction by antigestagens via adhesion molecules. An in vitro examination in endothelial cell cultures

Cervical ripening at term resembles an inflammatory reaction with invasion of activated granulocytes into the cervical stroma. Our objective was to investigate the influence of the antigestagen onapristone alone and in combination with other substances associated with cervical ripening on the expression of the inflammation-associated adhesion molecules ELAM-1, ICAM-1 and VCAM-1. Human endothelial cell cultures were stimulated with onapristone (200 ng/ml), TNF-alpha (100 U/ml), IL-8 (20 ng/ml) and PGE2 (3 ng/ml) separately and in combination (n = 6). The expression of adhesion molecules was determined qualitatively and quantitatively by immunofluorescence staining and flow cytometry with statistical evaluation by Kolmogorov-Smirnov analysis. Onapristone upregulated slightly the expression of ELAM-1 (19%). The costimulation of onapristone and TNF-alpha provoked an additive expression of VCAM-1 (64%) beyond the effect of TNF-alpha alone, while the costimulation of onapristone and PGE2 as well as the combination with IL-8 did not result in an additional stimulatory effect. All results were statistically significant (p < 0.001). This result supports our hypothesis that onapristone may lead to an increased adhesion of granulocytes to the capillary endothelium thereby initiating cervical ripening.

Endometrial contraception: modulation of molecular determinants of uterine receptivity

Modulation of endometrial receptivity is a promising approach for fertility regulation since it allows a contraceptive to act specifically at the endometrium. This was corroborated by our previous observations that treatment with low doses of a pure progesterone antagonist (PA, antiprogestin), onapristone (ZK 98299), in bonnet monkeys inhibited fertility by selectively retarding endometrial development, without affecting the hypophyseal-hypothalamic function. In the present study, further investigations, undertaken to analyze the molecular repertoire of a nonreceptive primate endometrium, determined expression of: steroid hormone receptors, i.e. progesterone receptor (PR) and estrogen receptor (ER); cytokines, i.e. leukemia inhibitory factor (LIF): transforming growth factor beta (TGFbeta) and its receptor (TGFbetaR); and cell adhesion molecules, i.e. integrins (alpha(v)beta(3), alpha(1)beta(1)). These studies were conducted during the different phases of the normal menstrual cycle and following treatment with different doses of onapristone (2.5 mg, 5 mg, or 10 mg every third day for one cycle) in bonnet monkeys. The molecules were analysed collectively to explore the possibility of a correlation between expression of these markers and endometrial receptivity and to investigate whether there exists a regulatory link between expression of these molecules under in vivo conditions. Three types of expression patterns of endometrial factors were observed during the peri-implantation period following onapristone treatment: 1) LIF, alpha(v)beta(3), and alpha(1)beta(1) showed significant (P < 0.02) down regulation in glandular epithelium of endometria in animals treated with all three doses of onapristone as compared to the control group. This was indicative of their critical role in the progesterone-driven cascade leading to implantation. 2) PR, TGFbeta, and TGFbetaR remained unaffected in the endometria from 2.5 mg treated animals and showed down regulation in animals treated with 5 and 10 mg onapristone as compared to the control group, thereby suggesting that the expression of these markers may not truely reflect endometrial receptivity per se. However, their facilitatory role in preparing the endometrium for implantation can not be ruled out since continued perturbation in the expression of these molecules may affect endometrial growth, remodelling, and differentiation, which in turn may render the endometrium nonreceptive; 3) ER remained unaltered in endometria of animals rendered infertile with 2.5, 5, and 10 mg onapristone. This observation indirectly suggests that onapristone-induced endometrial changes are mediated via some specific mechanisms. The present study clearly demonstrates that endometrial non-receptivity induced at low doses of onapristone is associated with changes in the expression pattern of specific molecular markers. However, no direct correlation was observed between in vivo expression of TGFbeta, LIF, and integrins, thereby lending support to the concept that there exists redundancy or multiple pathways which regulate implantation events.