Distinct temporal and spatial activities of RU486 on progesterone receptor function in reproductive organs of ovariectomized mice

Discovery of Vilaprisan (BAY 1002670): A Highly Potent and Selective Progesterone Receptor Modulator Optimized for Gynecologic Therapies

Progesterone plays an important role in the female reproductive system. However, there is also evidence that gynecologic disorders/diseases such as uterine fibroids and endometriosis are progesterone-dependent. Steroidal and non-steroidal selective progesterone receptor modulators (SPRMs) have shown potential for the treatment of such diseases. Steroidal SPRMs, including mifepristone and ulipristal acetate, have proven effective in clinical trials. However, several steroidal SPRMs containing a dimethylamino substituent have been associated with elevated liver enzymes in patients. An earlier drug discovery program identified lonaprisan as a highly selective SPRM that did not show drug-related change in liver enzyme activity. Building on data obtained from that work, here we describe the research program that culminated in the discovery of a novel steroidal SPRM, vilaprisan, which combines an extremely high potency with very favorable drug metabolism and pharmacokinetic properties. Vilaprisan has entered clinical development and is currently undergoing phase 3 clinical trials.

Rethinking progesterone regulation of female reproductive cyclicity

The progesterone receptor (PGR) is a ligand-activated transcription factor with key roles in the regulation of female fertility. Much has been learned of the actions of PGR signaling through the use of pharmacologic inhibitors and genetic manipulation, using mouse mutagenesis. Characterization of rats with a null mutation at the Pgr locus has forced a reexamination of the role of progesterone in the regulation of the female reproductive cycle. We generated two Pgr mutant rat models, using genome editing. In both cases, deletions yielded a null mutation resulting from a nonsense frame-shift and the emergence of a stop codon. Similar to Pgr null mice, Pgr null rats were infertile because of deficits in sexual behavior, ovulation, and uterine endometrial differentiation. However, in contrast to the reported phenotype of female mice with disruptions in Pgr signaling, Pgr null female rats exhibit robust estrous cycles. Cyclic changes in vaginal cytology, uterine histology, serum hormone levels, and wheel running activity were evident in Pgr null female rats, similar to wild-type controls. Furthermore, exogenous progesterone treatment inhibited estrous cycles in wild-type female rats but not in Pgr-null female rats. As previously reported, pharmacologic antagonism supports a role for PGR signaling in the regulation of the ovulatory gonadotropin surge, a result at variance with experimentation using genetic ablation of PGR signaling. To conclude, our findings in the Pgr null rat challenge current assumptions and prompt a reevaluation of the hormonal control of reproductive cyclicity.

Progesterone action in breast, uterine, and ovarian cancers

Progesterone and progesterone receptors (PRs) are essential for the development and cyclical regulation of hormone-responsive tissues including the breast and reproductive tract. Altered functions of PR isoforms contribute to the pathogenesis of tumors that arise in these tissues. In the breast, progesterone acts in concert with estrogen to promote proliferative and pro-survival gene programs. In sharp contrast, progesterone inhibits estrogen-driven growth in the uterus and protects the ovary from neoplastic transformation. Progesterone-dependent actions and associated biology in diverse tissues and tumors are mediated by two PR isoforms, PR-A and PR-B. These isoforms are subject to altered transcriptional activity or expression levels, differential crosstalk with growth factor signaling pathways, and distinct post-translational modifications and cofactor-binding partners. Herein, we summarize and discuss the recent literature focused on progesterone and PR isoform-specific actions in breast, uterine, and ovarian cancers. Understanding the complexity of context-dependent PR actions in these tissues is critical to developing new models that will allow us to advance our knowledge base with the goal of revealing novel and efficacious therapeutic regimens for these hormone-responsive diseases.

Tracking progesterone receptor-mediated actions in breast cancer

Ovarian steroid hormones contribute to breast cancer initiation and progression primarily through the actions of their nuclear transcription factors, the estrogen receptor alpha (ERα) and progesterone receptors (PRs). These receptors are important drivers of the luminal A and B subtypes of breast cancer, where estrogen-blocking drugs have been effective endocrine therapies for patients with these tumors. However, many patients do not respond, or become resistant to treatment. When endocrine therapies fail, the luminal subtypes of breast cancer are more difficult to treat because these subtypes are among the most heterogeneous in terms of mutation diversity and gene expression profiles. Recent evidence suggests that progestin and PR actions may be important drivers of luminal breast cancers. Clinical trial data has demonstrated that hormone replacement therapy with progestins drives invasive breast cancer and results in greater mortality. PR transcriptional activity is dependent upon cross-talk with growth factor signaling pathways that alter PR phosphorylation, acetylation, or SUMOylation as mechanisms for regulating PR target gene selection required for increased cell proliferation and survival. Site-specific PR phosphorylation is the primary driver of gene-selective PR transcriptional activity. However, PR phosphorylation and heightened transcriptional activity is coupled to rapid PR protein degradation; the range of active PR detected in tumors is likely to be dynamic. Thus, PR target gene signatures may provide a more accurate means of tracking PR's contribution to tumor progression rather than standard clinical protein-based (IHC) assays. Further development of antiprogestin therapies should be considered alongside antiestrogens and aromatase inhibitors.

Recent advances in structure of progestins and their binding to progesterone receptors

The role of progesterone in women's cancers as well as the knowledge of the progesterone receptor (PR) structure has prompted the design of different therapies. The aim of this review is to describe the basic structure of PR agonists and antagonists as well as the recent treatments for illness associated with the progesterone receptor. The rational design for potent and effective drugs for the treatment of female cancer must consider the structural changes of the androgen and progestogen skeleton which are an indicator of their activity as progestins or antiprogestins. The presence of a hydroxyl group at C-17 in the progesterone skeleton brings about a loss of progestational activity whereas acetylation induces a progestational effect. The incorporation of an ethynyl functional group to the testosterone framework results in a loss of androgenic activity with a concomitant enhancement of the progestational effect. On the other hand, an ester function at C-3 of dehydroepiandrosterone skeleton induces partial antagonism to the PR.

BAY 1002670: a novel, highly potent and selective progesterone receptor modulator for gynaecological therapies

STUDY QUESTION

Does the novel progesterone receptor (PR) modulator BAY 1002670, based on its preclinical pharmacological profile, offer a potential novel treatment option for uterine fibroids?

SUMMARY ANSWER

The newly synthesized BAY1002670 has proved to be a very potent, highly selective PR modulator in all in vitro and in vivo pharmacodynamics assays performed: it exhibits marked efficacy in an innovative humanized fibroid disease model, suggesting BAY 1002670 to be a very promising treatment option for uterine fibroids.

WHAT IS KNOWN ALREADY

PR inhibiting ligands have shown clinical utility in a range of potential indications and applications. Despite the emergence of the first PR antagonist >30 years ago, no agent of this compound class has been authorized in any indication for long-term application. Among other reasons, suboptimal selectivity and safety profiles of previous candidates have led to discontinuation and modification of development programmes.

STUDY, DESIGN, SIZE, DURATION

The preclinical studies include relevant in vitro and in vivo assays to clarify the properties of the PR modulator BAY 1002670 as well as a fibroid xenograft study to show directly the efficacy of BAY 1002670 on the human target tissue.

PARTICIPANTS/MATERIAL, SETTING, METHODS

BAY 1002670 was tested for binding and transactivational activity towards different human steroid receptors. Activity of the compound in the corresponding in vivo models (rat, rabbit) was assessed. Furthermore, BAY 1002670 was tested in a disease model for uterine fibroids utilizing primary human tumour tissues as xenograft in immunodeficient mice treated with estradiol (E2) and progesterone (P).

MAIN RESULT AND THE ROLE OF CHANCE

BAY1002670 in subnanomolar concentrations exhibits a highly selective binding profile and antagonistic activity for the PR. These properties are also reflected in its action in two progesterone-dependent animal models that assess the termination of pregnancy and endometrial transformation. Favourable selectivity towards other nuclear hormone receptors was demonstrated. No in vivo activity was found at the glucocorticoid, estrogenic and mineralocorticoid receptors with only weak anti-androgenic activity. In a human fibroid xenograft model BAY 1002670 showed a marked dose-dependent reduction of fibroid tumour weight gain of 95% at a dose of 3 mg/kg/day (P < 0.005).

LIMITATIONS AND REASON FOR CAUTION

Selectivity and potency of BAY 1002670 have only been determined in vitro and in animal models so far.

WIDER IMPLICATIONS OF THE FINDING

The PR modulator BAY 1002670 might offer a treatment option not only for uterine fibroids but also for other gynaecological indications.

STUDY FUNDING/COMPETING INTEREST

The studies took place at Bayer Pharma AG. All authors are employees of Bayer Pharma AG. No external funding declared.

Antiprogestins in breast cancer treatment: are we ready?

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death in females worldwide. It is accepted that breast cancer is not a single disease, but instead constitutes a spectrum of tumor subtypes with distinct cellular origins, somatic changes, and etiologies. Molecular gene expression studies have divided breast cancer into several categories, i.e. basal-like, ErbB2 enriched, normal breast-like (adipose tissue gene signature), luminal subtype A, luminal subtype B, and claudin-low. Chances are that as our knowledge increases, each of these types will also be subclassified. More than 66% of breast carcinomas express estrogen receptor alpha (ERα) and respond to antiestrogen therapies. Most of these ER+ tumors also express progesterone receptors (PRs), the expression of which has been considered as a reliable marker of a functional ER. In this paper we will review the evidence suggesting that PRs are valid targets for breast cancer therapy. Experimental data suggest that both PR isoforms (A and B) have different roles in breast cancer cell growth, and antiprogestins have already been clinically used in patients who have failed to other therapies. We hypothesize that antiprogestin therapy may be suitable for patients with high levels of PR-A. This paper will go over the experimental evidence of our laboratory and others supporting the use of antiprogestins in selected breast cancer patients.

Research resource: Transcriptional profiling in a cellular model of breast cancer reveals functional and mechanistic differences between clinically relevant SERM and between SERM/estrogen complexes

Exploitation of the relationship between estrogen receptor (ER) structure and activity has led to the development of 1) selective ER modulators (SERM), compounds whose relative agonist/antagonist activities differ between target tissues; 2) selective ER degraders (SERD), compounds that induce a conformational change in the receptor that targets it for proteasomal degradation; and 3) tissue-selective estrogen complexes (TSEC), drugs in which a SERM and an ER agonist are combined to yield a blended activity that results in distinct clinical profiles. In this study, we have performed a comprehensive head-to-head analysis of the transcriptional activity of these different classes of ERM in a cellular model of breast cancer. Not surprisingly, these studies highlighted important functional differences and similarities among the existing SERM, selective ER degraders, and TSEC. Of particular importance was the identification of genes that were regulated by various TSEC combinations but not by an estrogen or SERM alone. Cumulatively, the findings of this analysis are informative with respect to the mechanisms by which ER is engaged by different enhancers/promoters and highlights how promoter context influences the pharmacological activity of ER ligands.

Ligand-dependent degradation of SRC-1 is pivotal for progesterone receptor transcriptional activity

The progesterone receptor (PR), a ligand-activated transcription factor, recruits the primary coactivator steroid receptor coactivator-1 (SRC-1) gene promoters. It is known that PR transcriptional activity is paradoxically coupled to its ligand-dependent down-regulation. However, despite its importance in PR function, the regulation of SRC-1 expression level during hormonal exposure is poorly understood. Here we report that SRC-1 expression level (but not other p160 family members) is down-regulated by the agonist ligand R5020 in a PR-dependent manner. In contrast, the antagonist RU486 fails to induce down-regulation of the coactivator and impairs PR agonist-dependent degradation of SRC-1. We show that SRC-1 proteolysis is a proteasome- and ubiquitin-mediated process that, predominantly but not exclusively, occurs in the cytoplasmic compartment in which SRC-1 colocalizes with proteasome antigens as demonstrated by confocal imaging. Moreover, SRC-1 was stabilized in the presence of leptomycin B or several proteasomal inhibitors. Two degradation motifs, amino-acids 2-16 corresponding to a PEST motif and amino acids 41-136 located in the basic helix loop helix domain of the coactivator, were identified and shown to control the stability as well as the hormone-dependent down-regulation of the coactivator. SRC-1 degradation is of physiological importance because the two nondegradable mutants that still interacted with PR as demonstrated by coimmunoprecipitation failed to stimulate transcription of exogenous and endogenous target genes, suggesting that concomitant PR/SRC-1 ligand-dependent degradation is a necessary step for PR transactivation activity. Collectively our findings are consistent with the emerging role of proteasome-mediated proteolysis in the gene-regulating process and indicate that the ligand-dependent down-regulation of SRC-1 is critical for PR transcriptional activity.

The effect of progesterone replacement on gene expression in the corpus luteum during induced regression and late luteal phase in the bonnet monkey (Macaca radiata)

BACKGROUND

In higher primates, although LH/CG play a critical role in the control of corpus luteum (CL) function, the direct effects of progesterone (P4) in the maintenance of CL structure and function are unclear. Several experiments were conducted in the bonnet monkey to examine direct effects of P4 on gene expression changes in the CL, during induced luteolysis and the late luteal phase of natural cycles.

METHODS

To identify differentially expressed genes encoding PR, PR binding factors, cofactors and PR downstream signaling target genes, the genome-wide analysis data generated in CL of monkeys after LH/P4 depletion and LH replacement were mined and validated by real-time RT-PCR analysis. Initially, expression of these P4 related genes were determined in CL during different stages of luteal phase. The recently reported model system of induced luteolysis, yet capable of responsive to tropic support, afforded an ideal situation to examine direct effects of P4 on structure and function of CL. For this purpose, P4 was infused via ALZET pumps into monkeys 24 h after LH/P4 depletion to maintain mid luteal phase circulating P4 concentration (P4 replacement). In another experiment, exogenous P4 was supplemented during late luteal phase to mimic early pregnancy.

RESULTS

Based on the published microarray data, 45 genes were identified to be commonly regulated by LH and P4. From these 19 genes belonging to PR signaling were selected to determine their expression in LH/P4 depletion and P4 replacement experiments. These 19 genes when analyzed revealed 8 genes to be directly responsive to P4, whereas the other genes to be regulated by both LH and P4. Progesterone supplementation for 24 h during the late luteal phase also showed changes in expression of 17 out of 19 genes examined.

CONCLUSION

These results taken together suggest that P4 regulates, directly or indirectly, expression of a number of genes involved in the CL structure and function.

Steroid receptor coactivator-2 expression in brain and physical associations with steroid receptors

Estradiol and progesterone bind to their respective receptors in the hypothalamus and hippocampus to influence a variety of behavioral and physiological functions, including reproduction and cognition. Work from our lab and others has shown that the nuclear receptor coactivators, steroid receptor coactivator-1 (SRC-1) and SRC-2, are essential for efficient estrogen receptor (ER) and progestin receptor (PR) transcriptional activity in brain and for hormone-dependent behaviors. While the expression of SRC-1 in brain has been studied extensively, little is known about the expression of SRC-2 in brain. In the present studies, we found that SRC-2 was highly expressed throughout the hippocampus, amygdala and hypothalamus, including the medial preoptic area (MPOA), ventral medial nucleus (VMN), arcuate nucleus (ARC), bed nucleus of the stria terminalis, supraoptic nucleus and suprachiasmatic nucleus. In order for coactivators to function with steroid receptors, they must be expressed in the same cells. Indeed, SRC-2 and ER(alpha) were coexpressed in many cells in the MPOA, VMN and ARC, all brain regions known to be involved in female reproductive behavior and physiology. While in vitro studies indicate that SRC-2 physically associates with ER and PR, very little is known about receptor-coactivator interactions in brain. Therefore, we used pull-down assays to test the hypotheses that SRC-2 from hypothalamic and hippocampal tissue physically associate with ER and PR subtypes in a ligand-dependent manner. SRC-2 from both brain regions interacted with ER(alpha) bound to agonist, but not in the absence of ligand or in the presence of the selective ER modulator, tamoxifen. Analysis by mass spectrometry confirmed these ligand-dependent interactions between ER(alpha) and SRC-2 from brain. In dramatic contrast, SRC-2 from brain showed little to no interaction with ERbeta. Interestingly, SRC-2 from both brain regions interacted with PR-B, but not PR-A, in a ligand-dependent manner. Taken together, these findings reveal that SRC-2 is expressed in brain regions known to mediate a variety of steroid-dependent functions. Furthermore, SRC-2 is expressed in many ER(alpha) containing cells in the hypothalamus. Finally, SRC-2 from brain interacts with ER and PR in a subtype-specific manner, which may contribute to the functional differences of these steroid receptor subtypes in brain.

In vitro characterization of ZK 230211--A type III progesterone receptor antagonist with enhanced antiproliferative properties

The progesterone receptor (PR) is a key regulator of female reproductive functions. Compounds with progesterone inhibiting effects (PR antagonists) have found numerous utilities in female reproductive health, ranging from contraception to potential treatment of progesterone-dependent diseases like uterine leiomyomas. Based on in vitro characteristics such as DNA binding activity and partial agonistic transcriptional behavior in the presence of protein kinase A activators (cyclic-AMP), three types of PR modulators with antagonistic properties have been defined. In this study, we analyzed the in vitro characteristics of the PR antagonist ZK 230211 in comparison to the classical antagonists onapristone and mifepristone. We focused on PR actions in genomic signaling pathways, including DNA binding activity, nuclear localization and association with the nuclear receptor corepressor (NCoR) as well as actions in non-genomic signaling, such as the activation of c-Src kinase signaling and cyclin D1 gene promoter activity. ZK 230211 represents a type of PR antagonist with increased inhibitory properties in comparison to mifepristone and onapristone. When liganded to the progesterone receptor, ZK 230211 induces a strong and persistent binding to its target response element (PRE) and increases NCoR recruitment in CV-1 cells. Furthermore, ZK 230211 displays less agonistic properties with regard to the association of PR isoform B and the cytoplasmic c-Src kinase in HeLa cells. It represses T47D cell cycle progression, in particular estradiol-induced S phase entry. In summary, our studies demonstrate ZK 230211 to be a type III progesterone receptor antagonist which is characterized by very strong DNA binding activity and strong antiproliferative effects in the cancer cell lines HeLa and T47D.

Up-regulation of circadian clock gene Period 2 in the prostate mesenchymal cells during flutamide-induced apoptosis

Androgen regulates the proper development and physiological function of the prostate. Here, we investigated the modulation of androgen and androgen receptor (AR) antagonist on circadian oscillations of a clock core gene Period 2 (Per2) in rat prostate mesenchymal cells (PMCs). Circadian oscillations were analyzed with the real-time monitoring system of gene expression using transgenic rats introduced with mouse Per2 promoter fused to a destabilized luciferase (Per2-dLuc) reporter gene. Analyses of circadian oscillations, immunofluorescence, and androgen response element (ARE)-luciferase reporter assay revealed that circadian clocks are operative and the AR protein is functional in PMCs in vitro. Androgen such as testosterone (T) and dihydrotestosterone (DHT) did not cause any changes in circadian Per2-dLuc oscillations of confluent cells. Conversely, flutamide (FL) up-regulated the amplitude of circadian Per2-dLuc oscillations in a dose-dependent manner, whereas T antagonized the action of FL. The PER2 protein was markedly accumulated by FL treatment and localized in both the nucleus and cytoplasm during the first peak period of circadian Per2-dLuc oscillations. Simultaneously, FL treatment increased apoptotic cell death. Collectively, the present study demonstrates that a clock gene Per2 is up-regulated in PMCs during FL-induced apoptotic cell death. Thus, circadian oscillations of Per2 gene expression may be closely linked to the cellular states of PMCs such as apoptotic cell death.

Global gene expression profiling of progesterone receptor modulators in T47D cells provides a new classification system

Progesterone receptor modulators (PRMs) play an important role in women's health. They are widely used in oral contraception or hormone therapy, and provide an attractive treatment approach for gynecological disorders such as uterine leiomyomas, endometriosis or breast cancer. Due to the broad range of activities, various studies were conducted to assess progesterone receptor antagonists (PAs) and selective progesterone receptor modulators (SPRMs) with respect to progesterone receptor (PR) agonistic and antagonistic activities in vivo. These properties are not always adequately reflected in classical in vitro models, especially differences in the agonistic potential of SPRMs, such as asoprisnil, J1042, and J912, and mixed antagonists, such as mifepristone, are not sufficiently substantiated. The effects of PRMs upon gene expression in progesterone target tissues such as breast epithelium and uterus are poorly understood. This study compares the properties of PR ligands using mammalian two-hybrid assays and gene expression profiling. The protein-protein interaction analyses in HeLa cells provide for specific ligand-induced PR conformations, whereas Affymetrix GeneChip HG-U133Plus2.0 analyses in T47D breast cancer cells indicate the transcriptional activity on the level of target genes. The analyses comprise the pure agonist R5020, the non-steroidal PR modulator PRA-910, SPRMs (J1042, asoprisnil, J912), the mixed antagonist mifepristone, classical antagonists (onapristone, ZK 137316) and the pure antagonist lonaprisan to consider all types of ligands described before. Marginal differences were identified in coactivator interaction profiles at all, but significant differences between SPRMs and PR antagonists (PAs) were observed in recruiting the LXXLL-motif containing peptide (LX-H10), very similar to in vivo activities in endometrial transformation in the rabbit (McPhail test). Global gene expression profiles demonstrated progesterone-independent effects for all PR modulators examined and emphasised similarities of asoprisnil and J1042 compared to J912 and all types of PR antagonists. In summary, the data support the popular concept of PR modulator classification in agonists, selective progesterone receptor modulators, mixed and pure antagonists. It further refines previous classification models and accentuates unique effects for each PR modulator.

Endometrial angiogenesis, vascular maturation, and lymphangiogenesis

Angiogenesis, arteriogenesis or vessel maturation, and lymphangiogenesis comprise a continuum of vascular development, with overlap and interaction between the mechanisms by which they are controlled. These processes are of clinical interest because they play roles in endometrial repair, placental development, and in gynecological disorders including endometrial cancer, endometriosis and abnormal uterine bleeding. Using mouse models we have shown that estrogen can be either proangiogenic or antiangiogenic in endometrium. Progesterone alone is proangiogenic, although this can be moderated by pretreatment with estrogen. Arteriogenesis also increases in response to progesterone, and this effect is not inhibited by estrogen. Lymphatics account for 13% of all vessels in the human functionalis compared to 57% in the basalis. Many of the basalis lymphatic vessels are closely associated with spiral arterioles and this intimate connection may provide a mechanism for paracrine communication between the functionalis and the arteries supplying the endometrium.

Steroid receptor coactivator-1 from brain physically interacts differentially with steroid receptor subtypes

In vitro studies reveal that nuclear receptor coactivators enhance the transcriptional activity of steroid receptors, including estrogen (ER) and progestin receptors (PR), through ligand-dependent interactions. Whereas work from our laboratory and others shows that steroid receptor coactivator-1 (SRC-1) is essential for efficient ER and PR action in brain, very little is known about receptor-coactivator interactions in brain. In the present studies, pull-down assays were used to test the hypotheses that SRC-1 from hypothalamic and hippocampal tissue physically associate with recombinant PR or ER in a ligand-dependent manner. SRC-1, from hypothalamus or hippocampus, interacted with PR-A and PR-B in the presence of an agonist, but not in the absence of ligand or in the presence of a selective PR modulator, RU486. Interestingly, SRC-1 from brain associated more with PR-B, the stronger transcriptional activator, than with PR-A. In addition, SRC-1 from brain, which was confirmed by mass spectrometry, interacted with ERalpha and ERbeta in the presence of agonist but not when unliganded or in the presence of the selective ER modulator, tamoxifen. Furthermore, SRC-1 from hypothalamus, but not hippocampus, interacted more with ERalpha than ERbeta, suggesting distinct expression patterns of other cofactors in these brain regions. These findings suggest that interactions of SRC-1 from brain with PR and ER are dependent on ligand, receptor subtype, and brain region to manifest the pleiotropic functional consequences that underlie steroid-regulated behaviors. The present findings reveal distinct contrasts with previous cell culture studies and emphasize the importance of studying receptor-coactivator interactions using biologically relevant tissue.

Influence of progesterone on endometrial nitric oxide synthase expression

OBJECTIVE

To determine the effect of P on nitric oxide synthase (NOS) expression in human endometrial epithelial cells.

DESIGN

Laboratory-based study.

SETTING

University-based research institute.

PATIENT(S)

None.

INTERVENTION(S)

The effect of P on the expression of NOS protein isoforms was examined in an in vitro preparation.

MAIN OUTCOME MEASURE(S)

The expression of NOS and phosphorylated endothelial NOS (peNOS) protein in human endometrial-derived epithelial cells (HES cells) and messenger RNA (mRNA) in human primary endometrial cell culture.

RESULT(S)

Progesterone induced a concentration- and time-dependent stimulation of endothelial NOS (eNOS), inducible NOS (iNOS), and peNOS protein in HES cells. Progesterone also stimulated eNOS and iNOS mRNA in human primary endometrial cells. The effect of P on eNOS and iNOS was completely blocked by RU486 but was partially blocked in case of phosphorylated eNOS. RU486 alone had an inhibitory effect on expression of eNOS but not iNOS protein at a concentration of 10(-5) mol/L. Progesterone stimulated phosphorylation of eNOS within 30 minutes, and this effect was completely blocked by an inhibitor of PI3/Akt pathway, wortmannin, and by the extracellular signal-regulated kinase 1,2 pathway blocker UO126.

CONCLUSION(S)

Progesterone has both genomic and nongenomic effects to stimulate the expression of NOS in HES cells. The nongenomic action of P on NOS phosphorylation is mediated by the PI3/Akt and extracellular signal-regulated kinase 1,2 pathways.

Delayed parturition and altered myometrial progesterone receptor isoform A expression in mice null for Krüppel-like factor 9

Preterm and delayed labor conditions are devastating health problems with currently unknown etiologies. We previously showed that the transcription factor Krüppel-like factor 9 (KLF9) influences the expression and/or transcriptional activity of receptors for estrogen and progesterone in endometrial cells in vivo and in vitro. Given that estrogen and progesterone differentially regulate uterine myometrial contractility during gestation, we hypothesized that lack of KLF9 could compromise myometrial function, leading to defects in parturition. To test this, we used mice null for Klf9 to evaluate gestation length, response to the progesterone receptor (PGR) antagonist RU486, expression levels of steroid receptor proteins, nuclear receptor coactivator and contractility-associated genes, and nuclear factor-kappaB (NF-kappaB) DNA binding activity in myometrium near term. Klf9 knockout (KO) mice exhibited delayed parturition by 1-2 days relative to wild-type (WT) counterparts, in the absence of fetal genotype contribution and differences in serum estrogen and progesterone levels. Knockout mice near term were refractory to the abortive action of RU486, and they displayed aberrant myometrial expression patterns of nuclear PGR-A and NF-kappaB p65/RELA relative to WT mice. Myometrial expression levels of nuclear estrogen receptor-alpha did not differ, whereas those for Oxtr and Crebbp mRNAs were lower, in KO versus WT mice. Results indicate that KLF9 contributes to the regulation of PGR-associated components in the myometrium necessary for timely onset of parturition in mice. The present study highlights the potential utility of Klf9 null mice to investigate the pathophysiology of parturition defects involving PGR signaling.

Progesterone, but not estrogen, stimulates vessel maturation in the mouse endometrium

The human endometrium undergoes regular periods of growth and regression, including concomitant changes in the vasculature, and is one of the few adult tissues where significant angiogenesis and vascular maturation occurs on a routine, physiological basis. The aim of this study was to investigate the effects of estrogen and progesterone on endometrial vascular maturation in mice. Endometrial tissues were collected from early pregnant mice (d 1-4) and ovariectomized mice given a single 17beta-estradiol (100 ng) injection 24 h before dissection (short-term estrogen regime) or three consecutive daily injections of progesterone (1 mg) with/without estrogen priming (progesterone regime). Experiments were then repeated with the inclusion of mice treated concurrently with progesterone and either RU486 or a vascular endothelial growth factor-A antiserum. Proliferating vascular mural cells (PVMC) were observed on d 3-4 of pregnancy, corresponding with an increase in circulating progesterone. A significant increase in PVMC and alpha-smooth muscle actin (labels mural cells) coverage of vessel profiles were observed in mice treated with progesterone in comparison to controls; no significant change was noted in mice treated with estrogen or with vascular endothelial growth factor antiserum. RU486 treatment did not inhibit the progesterone-induced increases in PVMC and mural cell coverage, although progesterone-induced changes in endothelial and epithelial cell proliferation were inhibited. These results show that progesterone, but not estrogen, stimulates vessel maturation in the mouse endometrium. The work illustrates the relevancy of the mouse model for understanding endometrial vascular remodeling during the menstrual cycle and in response to the clinically important progesterone receptor antagonist RU486.