Molecular action of progesterone

Regulation of uterine function during estrous cycle, anestrus phase and pregnancy by steroids in red deer (Cervus elaphus L.)

Steroid synthesis and production in ruminant uterus is not obvious, especially in seasonally reproduced. We compared steroid production by investigating enzymes involved in red deer uterine steroid metabolism in reproductive seasons. Blood and uteri (endometrium and myometrium) were collected post mortem from hinds on 4th day (N = 8), 13th day of the cycle (N = 8), anestrus (N = 8) and pregnancy (N = 8). The expression of cytochrome P450 aromatase (P450), 3 -beta-hydroxysteroid dehydrogenase (3β-HSD), 17 -beta-hydroxysteroid dehydrogenase (17β-HSD), aldo-keto reductase family 1 C1 (AKR1C1), estrogen receptor alpha (ERα), and progesterone receptors (PRs), were analyzed using real-time-PCR and Western Blotting. Plasma samples were assayed for 17-beta-estradiol (E2), progesterone (P4), luteinizing hormone (LH), follicle-stimulating hormone (FSH), and testosterone (T4) concentrations by EIA. Hinds at the beginning of the estrous cycle, mainly in endometrium, were characterized by a high mRNA expression of 3β-HSD, AKR1C1, PRs and ERα, contrary to the expression in myometrium during pregnancy (P < 0.05). For P4, E2, and FSH, concentration was the highest during the 13th day of the estrous cycle (P < 0.05). Uterine steroid production and output in hinds as a representative seasonally reproduced ruminant occurred mainly during the estrous cycle and sustained in anestrus.

Decidual cell FKBP51-progesterone receptor binding mediates maternal stress-induced preterm birth

Depression and posttraumatic stress disorder increase the risk of idiopathic preterm birth (iPTB); however, the exact molecular mechanism is unknown. Depression and stress-related disorders are linked to increased FK506-binding protein 51 (FKBP51) expression levels in the brain and/or FKBP5 gene polymorphisms. Fkbp5-deficient (Fkbp5 ^-/-) mice resist stress-induced depressive and anxiety-like behaviors. FKBP51 binding to progesterone (P4) receptors (PRs) inhibits PR function. Moreover, reduced PR activity and/or expression stimulates human labor. We report enhanced in situ FKBP51 expression and increased nuclear FKBP51-PR binding in decidual cells of women with iPTB versus gestational age-matched controls. In Fkbp5 ^+/+ mice, maternal restraint stress did not accelerate systemic P4 withdrawal but increased Fkbp5, decreased PR, and elevated AKR1C18 expression in uteri at E17.25 followed by reduced P4 levels and increased oxytocin receptor (Oxtr) expression at 18.25 in uteri resulting in PTB. These changes correlate with inhibition of uterine PR function by maternal stress-induced FKBP51. In contrast, Fkbp5 ^-/- mice exhibit prolonged gestation and are completely resistant to maternal stress-induced PTB and labor-inducing uterine changes detected in stressed Fkbp5 ^+/+ mice. Collectively, these results uncover a functional P4 withdrawal mechanism mediated by maternal stress-induced enhanced uterine FKBP51 expression and FKPB51-PR binding, resulting in iPTB.

2D Electrophoretic pattern of bovine placental proteins during early-mid pregnancy

The Placenta, like every tissue, possesses its own characteristic protein profile, which may change within the course of pregnancy. These changes can be used for the elucidation of the mechanisms related to both physiology of pregnancy and pathological events. The aim of the study was to describe proteinergic profiles of maternal and fetal parts of bovine placenta during early-mid pregnancy by the use of 2D electrophoresis and MALDI TOF/TOF MS identification to evaluate dynamics of the possible changes necessary for placentation. Placental samples were collected from six pregnant cows (3-5 months) in the local abattoir. Placentomes were separated, and proteins were extracted and subjected to 2D electrophoresis and MALDI TOF/TOF identification. Out of 907 spots identified by the statistical analysis of gels, 54 were identified. Out of this number, 36 spots were significantly different between examined samples. Moreover, the obtained patterns differed between maternal and fetal parts of the placenta with regard to the intensity of staining, suggesting quantitative differences in protein content. These preliminary results are unique for this period of pregnancy. Such data are important for further experiments to obtain full protein profiles necessary to understand biochemical mechanisms underlying the attachment between fetal and maternal parts of the placenta during placentation. Moreover, the outcomes may help in elucidating pregnancy biomarkers in the future.

Progesterone Receptor (PGR) Gene Variants Associated with Breast Cancer and Associated Features: a Case-Control Study

Insofar as altered estrogen receptor-progesterone receptor (PR) expression contribute to breast cancer pathogenesis, previous studies examined the association of genetic variation in PR gene (PGR) with breast cancer, but with mixed outcome. We evaluated the association between PGR variants, and breast cancer and associated features. A retrospective case-control study involving 183 female breast cancer patients, and 222 control women. PGR genotyping was done by real-time PCR. Minor allele frequencies of rs1042838, rs590688, and rs10895068 PGR gene polymorphisms were significantly higher in breast cancer patients compared to controls. Patients carrying rs1042838 G/T, rs590688 C/C, and rs10895068 G/A genotypes had higher risk of breast cancer, while carriage of rs3740753 G/G genotype was associated with marginal reduction in breast cancer risk. In addition, carriage of rs1042839, rs3740753, and rs10895068 minor allele was associated with Her2 status, while rs3740753 and rs10895068 were associated with effective hormone replacement therapy. Furthermore, carriage of rs10895068 minor allele in breast cancer women were also associated with age at first pregnancy, hormone receptor (RH) status, and previous use of oral contraceptives. PGR haploview analysis documented moderate-strong linkage disequilibrium (non-random association of alleles at different loci) between 7 of the 8 tested PGR SNPs, thus allowing construction of 7-locus PGR haplotypes. Two haplotypes, ATGCCGA and GTGCCGA, both containing rs590688, were positively associated with breast cancer, thus assigning a breast cancer-susceptible nature to these haplotypes. PGR rs1042838, rs590688, and rs10895068, and ATGCCGA and GTGCCGA haplotypes are related with increased breast cancer susceptibility in Tunisian women.

Extracellular matrix proteins in healthy and retained placentas, comparing hemochorial and synepitheliochorial placentas

The placenta expresses structural and biologically active proteins. Their synthesis is mainly regulated by genomic or nongenomic signals and modulated by hormones. These protein profiles are altered during different stages of pregnancy. The biological properties of extracellular matrix (ECM) proteins were defined and described in a number of tissues including placenta. These properties enable them to be the main players in the processes of attachment or invasion into the endometrium during initial placenta formation and its timely separation after delivery and detachment. In this review, we focused on the role of ECM proteins during attachment of the placenta to the uterine wall, its timely separation, and the implications of this process on retained or pathologically attached placenta. Although the amount of published information in this area is relatively scant, some of the key proteins and processes are well defined. We focused on the available data detailing the ECM protein profiles of human (histologically thin; hemochorial) and bovine (histologically thick; epitheliochorial) placentas and compared the shared and unique ECM proteins that are relevant to placental attachment and separation.

The Deep Correlation between Energy Metabolism and Reproduction: A View on the Effects of Nutrition for Women Fertility

In female mammals, mechanisms have been developed, throughout evolution, to integrate environmental, nutritional and hormonal cues in order to guarantee reproduction in favorable energetic conditions and to inhibit it in case of food scarcity. This metabolic strategy could be an advantage in nutritionally poor environments, but nowadays is affecting women's health. The unlimited availability of nutrients, in association with reduced energy expenditure, leads to alterations in many metabolic pathways and to impairments in the finely tuned inter-relation between energy metabolism and reproduction, thereby affecting female fertility. Many energetic states could influence female reproductive health being under- and over-weight, obesity and strenuous physical activity are all conditions that alter the profiles of specific hormones, such as insulin and adipokines, thus impairing women fertility. Furthermore, specific classes of nutrients might affect female fertility by acting on particular signaling pathways. Dietary fatty acids, carbohydrates, proteins and food-associated components (such as endocrine disruptors) have per se physiological activities and their unbalanced intake, both in quantitative and qualitative terms, might impair metabolic homeostasis and fertility in premenopausal women. Even though we are far from identifying a "fertility diet", lifestyle and dietary interventions might represent a promising and invaluable strategy to manage infertility in premenopausal women.

Progesterone receptor transcriptome and cistrome in decidualized human endometrial stromal cells

Decidualization is a complex process involving cellular proliferation and differentiation of the endometrial stroma that is required to establish and support pregnancy. Progesterone acting via its nuclear receptor, the progesterone receptor (PGR), is a critical regulator of decidualization and is known to interact with certain members of the activator protein-1 (AP-1) family in the regulation of transcription. In this study, we identified the cistrome and transcriptome of PGR and identified the AP-1 factors FOSL2 and JUN to be regulated by PGR and important in the decidualization process. Direct targets of PGR were identified by integrating gene expression data from RNA sequencing with the whole-genome binding profile of PGR determined by chromatin immunoprecipitation followed by deep sequencing (ChIP-seq) in primary human endometrial stromal cells exposed to 17β-estradiol, medroxyprogesterone acetate, and cAMP to promote in vitro decidualization. Ablation of FOSL2 and JUN attenuates the induction of 2 decidual marker genes, IGFBP1 and PRL. ChIP-seq analysis of genomic binding revealed that FOSL2 is bound in proximity to 8586 distinct genes, including nearly 80% of genes bound by PGR. A comprehensive assessment of the PGR-dependent decidual transcriptome integrated with the genomic binding of PGR identified FOSL2 as a potentially important transcriptional coregulator of PGR via direct interaction with regulatory regions of genes actively regulated during decidualization.

Role of nuclear progesterone receptor isoforms in uterine pathophysiology

BACKGROUND

Progesterone is a key hormonal regulator of the female reproductive system. It plays a major role to prepare the uterus for implantation and in the establishment and maintenance of pregnancy. Actions of progesterone on the uterine tissues (endometrium, myometrium and cervix) are mediated by the combined effects of two progesterone receptor (PR) isoforms, designated PR-A and PR-B. Both receptors function primarily as ligand-activated transcription factors. Progesterone action on the uterine tissues is qualitatively and quantitatively determined by the relative levels and transcriptional activities of PR-A and PR-B. The transcriptional activity of the PR isoforms is affected by specific transcriptional coregulators and by PR post-translational modifications that affect gene promoter targeting. In this context, appropriate temporal and cell-specific expression and function of PR-A and PR-B are critical for normal uterine function.

METHODS

Relevant studies describing the role of PRs in uterine physiology and pathology (endometriosis, uterine leiomyoma, endometrial cancer, cervical cancer and recurrent pregnancy loss) were comprehensively searched using PubMed, Cochrane Library, Web of Science, and Google Scholar and critically reviewed.

RESULTS

Progesterone, acting through PR-A and PR-B, regulates the development and function of the endometrium and induces changes in cells essential for implantation and the establishment and maintenance of pregnancy. During pregnancy, progesterone via the PRs promotes myometrial relaxation and cervical closure. Withdrawal of PR-mediated progesterone signaling triggers menstruation and parturition. PR-mediated progesterone signaling is anti-mitogenic in endometrial epithelial cells, and as such, mitigates the tropic effects of estrogen on eutopic normal endometrium, and on ectopic implants in endometriosis. Similarly, ligand-activated PRs function as tumor suppressors in endometrial cancer cells through inhibition of key cellular signaling pathways required for growth. In contrast, progesterone via PR activation appears to increase leiomyoma growth. The exact role of PRs in cervical cancer is unclear. PRs regulate implantation and therefore aberrant PR function may be implicated in recurrent pregnancy loss (RPL). PRs likely regulate key immunogenic factors involved in RPL. However, the exact role of PRs in the pathophysiology of RPL and the use of progesterone for therapeutic benefit remains uncertain.

CONCLUSIONS

PRs are key mediators of progesterone action in uterine tissues and are essential for normal uterine function. Aberrant PR function (due to abnormal expression and/or function) is a major cause of uterine pathophysiology. Further investigation of the underlying mechanisms of PR isoform action in the uterus is required, as this knowledge will afford the opportunity to create progestin/PR-based therapeutics to treat various uterine pathologies.

Steroid hormone receptor expression in ovarian cancer: progesterone receptor B as prognostic marker for patient survival

BACKGROUND

There is partially conflicting evidence on the influence of the steroid hormones estrogen (E) and progesterone (P) on the development of ovarian cancer (OC). The aim of this study was to assess the expression of the receptor isoforms ER-α/-β and PR-A/-B in OC tissue and to analyze its impact on clinical and pathological features and patient outcome.

METHODS

155 OC patients were included who had been diagnosed and treated between 1990 and 2002. Patient characteristics, histology and follow-up data were available. ER-α/-β and PR-A/-B expression were determined by immunohistochemistry.

RESULTS

OC tissue was positive for ER-α/-β in 31.4% and 60.1% and PR-A/-B in 36.2% and 33.8%, respectively. We identified significant differences in ER-β expression related to the histological subtype (p=0.041), stage (p=0.002) and grade (p=0.011) as well as PR-A and tumor stage (p=0.03). Interestingly, median receptor expression for ER-α and PR-A/-B was significantly higher in G1 vs. G2 OC. Kaplan Meier analysis revealed a good prognosis for ER-α positive (p=0.039) and PR-B positive (p<0.001) OC. In contrast, ER-β negative OC had a favorable outcome (p=0.049). Besides tumor grade and stage, Cox-regression analysis showed PR-B to be an independent prognostic marker for patient survival (p=0.009, 95% CI 0.251-0.823, HR 0.455).

CONCLUSION

ER-α/-β and PR-A/-B are frequently expressed in OC with a certain variability relating to histological subtype, grade and stage. Univariate analysis indicated a favorable outcome for ER-α positive and PR-B positive OC, while multivariate analysis showed PR-B to be the only independent prognostic marker for patient survival. In conclusion, ER and PR receptors may be useful targets for a more individualized OC therapy.

Oviductal, endometrial and embryonic gene expression patterns as molecular clues for pregnancy establishment

In higher animals, the beginning of new life and transfer of genetic material to the next generation occurs in the oviduct when two distinct gametes cells unite resulting in the formation of a zygote. The zygote then undergoes serial developmental processes in the oviduct and enters into the uterus where it faces challenges and scrutiny from the endometrial ecosystem. Thus, embryos that are able to establish an appropriate embryo-maternal dialogue are capable of developing to term whereas the incompetent ones can perish any time during the gestation period. Although several lines of evidences indicated that pregnancy loss is a multi-factorial phenomenon, the biochemical composition of the embryo and maternal environment are the main players to determine pregnancy outcome. Indeed, expression patterns of the genes are the driving forces that induce biochemical composition changes in embryo, oviduct and uterine environment. Thus, examining the molecular signals that are associated with oviductal or endometrial receptivity and embryo implantation is essential for establishing strategies to improve pregnancy success. Therefore, this review focuses on the contribution of oviduct and its transcriptome profile on early stage embryo development and the impact of endometrium and its transcriptome changes on peri and post embryo implantation. In addition, this paper integrates established facts about hormonal and molecular signatures associated with endometrial receptivity. Finally, the blastocyst and pre-conception endometrial gene expression profiles have been discussed in relation to the pregnancy outcome to highlight the potentials of blastocyst and pre-transfer endometrial transcriptome profile approach for selecting appropriate recipient and developmentally competent embryo.

Estrogen and progesterone-related gene variants and colorectal cancer risk in women

Background

Observational studies and randomized trials have suggested that estrogens and/or progesterone may lower the risk for colorectal cancer. Inherited variation in the sex-hormone genes may be one mechanism by which sex hormones affect colorectal cancer, although data are limited.

Method

We conducted a comprehensive evaluation of single nucleotide polymorphisms (SNPs) in genes encoding 3 hormone receptors (ESR1, ESR2, PGR) and 5 hormone synthesizers (CYP19A1 and CYP17A1, HSD17B1, HSD17B2, HSD17B4) among 427 women with incident colorectal cancer and 871 matched controls who were Caucasians of European ancestry from 93676 postmenopausal women enrolled in the Women's Health Initiative Observational cohort. A total of 242 haplotype-tagging and functional SNPs in the 8 genes were included for analysis. Unconditional logistic regression with adjustment for age and hysterectomy status was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

Results

We observed a weak association between the CYP17A1 rs17724534 SNP and colorectal cancer risk (OR per risk allele (A) = 1.39, 95% CI = 1.09-1.78, corrected p-value = 0.07). In addition, a suggestive interaction between rs17724534 and rs10883782 in 2 discrete LD blocks of CYP17A1 was observed in relation to colorectal cancer (empirical p value = 0.04). Moreover, one haplotype block of CYP19A1 was associated with colorectal cancer (corrected global p value = 0.02), which likely reflected the association with the tagging SNP, rs1902584, in the block.

Conclusion

Our findings offer some support for a suggestive association of CYP17A1 and CYP19A1 variants with colorectal cancer risk.

Human labor is associated with reduced decidual cell expression of progesterone, but not glucocorticoid, receptors

CONTEXT

Unchanging plasma progesterone (P4) levels suggest that human labor is initiated by reduced P4 receptor (PR) expression, which elicits functional P4 withdrawal. The glucocorticoid receptor (GR) is also implicated in this process.

OBJECTIVE

Our objective was to compare PR and GR staining in human decidual cells (DCs) and interstitial trophoblasts (ITs) of gestational age-matched pre- and postcontraction specimens and to evaluate steroid effects on PR and GR expression in human DC cultures.

INTERVENTIONS AND MAIN OUTCOME MEASURES

Decidua basalis and parietalis sections were immunostained for PR or GR and then for the cytoplasmic DC and IT markers vimentin and cytokeratin. Western blotting measured PR and GR levels in nuclear extracts of cultured leukocyte-free term DCs after incubation with estradiol-17beta (E2) with or without medroxyprogesterone acetate (MPA).

RESULTS

PR histological scores (HSCOREs) were significantly higher in DC nuclei from pre- vs. post-uterine-contraction decidua basalis and parietalis sections with PR immunostaining absent from ITs. In contrast, immunoreactive GR was localized in IT and DC nuclei. GR HSCORES were significantly higher in ITs than DCs but similar in pre- vs. post-uterine-contraction specimens. In term DC monolayers, PR-A and PR-B were enhanced by E2 and inhibited by MPA, whereas E2 plus MPA produced intermediate PR expression. The GR was constitutively expressed.

CONCLUSIONS

In post- vs. pre-uterine-contraction specimens, significantly lower HSCOREs in DC nuclei, but not IT, and unchanging GR levels in DCs and ITs suggest that functional P4 withdrawal may occur in DCs and is unlikely to involve the GR. Nuclear extracts from DC monolayer cultures express steroid-regulated PR-A and PR-B and constitutive GR.

Effects of menstrual cycle phase on metabolomic profiles in premenopausal women

BACKGROUND

Characterization of the normal degree of physiological variation in the metabolomic profiles of healthy humans is a necessary step in the development of metabolomics as both a clinical research and diagnostic tool. This study investigated the effects of the menstrual cycle on (1)H nuclear magnetic resonance (NMR) derived metabolomic profiles of urine and plasma from healthy women.

METHODS

In this study, 34 healthy women were recruited and a first void urine and fasting blood sample were collected from each woman at four different time points during one menstrual cycle. Serum hormone levels were used in combination with the menstrual calendar to classify the urine and plasma samples into five different phases i.e. menstrual, follicular, periovulatory, luteal and premenstrual. The urine and plasma samples were analysed using (1)H NMR spectroscopy and subsequent data were analysed using principal component analysis (PCA) and partial least squares discriminant analysis.

RESULTS

PCA of the urine spectra showed no separation of samples based on the phases of the menstrual cycle. Multivariate analysis of the plasma spectra showed a separation of the menstrual phase and the luteal phase samples (R(2) = 0.61, Q(2) = 0.41). Subsequent analysis revealed a significant decrease in levels of glutamine, glycine, alanine, lysine, serine and creatinine and a significant increase in levels of acetoacetate and very low density lipoprotein (VLDL CH(2)) during the luteal phase.

CONCLUSIONS

These results establish a need to control for metabolic changes that occur in plasma due to the menstrual cycle in the design of future metabolomic studies involving premenopausal women.

Attenuated sex steroid receptor expression in fallopian tube of women with ectopic pregnancy

CONTEXT

Sex steroid hormone receptor (SHR) dynamics are well-documented in human endometrium but have not been comprehensively studied in Fallopian tube (FT).

OBJECTIVE

The aim of the study was to compare expression patterns and hormonal regulation of SHR in FT with that described in endometrium and to determine whether SHR expression is altered in FT of women with ectopic pregnancy (EP).

DESIGN

Tissue was analyzed and cultured.

PATIENTS OR OTHER PARTICIPANTS

Women undergoing surgery for benign gynecological conditions (n = 14) and EP (n = 6) participated in the study.

INTERVENTIONS

Quantitative RT-PCR and immunohistochemistry were used to determine SHR mRNA expression and protein localization, respectively. SHR levels were measured in tubal explant cultures stimulated with estrogen and progestogen.

RESULTS

ERalpha and ERbeta mRNAs were constitutively expressed in FT during the menstrual cycle. PR-AB and PR-B mRNAs were decreased in midluteal phase compared to follicular phase. ERalpha, PR-AB, and PR-B mRNAs were down-regulated in human FT in vitro by treatment with progestogen. ERalpha, ERbeta1, ERbeta2, PR, and AR proteins localized to cell nuclei of epithelium, stroma, and smooth muscle of nonpregnant FT. In FT from women with EP, PR-B mRNA was decreased when compared to midluteal FT, and ERalpha protein was not detected.

CONCLUSIONS

SHR expression in FT is different from that observed in endometrium recovered at similar stages of the menstrual cycle, and expression in FT from women with EP is also altered compared with normal FT. These data are an important benchmark for furthering the understanding of normal human FT physiology, changes in expression of SHR in FT in response to progesterone, and disorders of FT function, such as EP.

The cytoplasmic 60 kDa progesterone receptor isoform predominates in the human amniochorion and placenta at term

BACKGROUND

The mechanism that initiates human parturition has been proposed to be 'functional progesterone withdrawal' whereby the 116 kDa B-isoform of the progesterone receptor (PR-B) switches in favour of the 94 kDa A-isoform (PR-A) in reproductive tissues. Recently, other PR isoforms, PR-S, PR-C and PR-M generated from the same gene have been identified and partially characterised.

METHODS AND RESULTS

Using immunohistochemical, western blotting and RT-PCR techniques, evidence is provided that indicates the major PR isoform present in human term fetal membranes (amnion and chorion) and syncytiotrophoblast of the placenta is neither of the classical nuclear PR-B or PR-A isoforms but is the N-terminally truncated 60 kDa PR-C isoform. Evidence is also provided that this 60 kDa isoform resides in the cytoplasm of the expressing cell types. Data are also presented to show that PR-B, PR-A and PR-S isoforms are essentially absent from the amnion and chorion, whereas PR isoforms A, B, C and S are all present in the decidua, with PR-A being the major isoform. The syncytiotrophoblast of the placenta contains the cytoplasmic 60 kDa isoform, but not isoforms PR-A, PR-B or PR-S.

CONCLUSION

The major PR isoform in the amnion, chorion and placenta is a 60 kDa protein that could be PR-C, suggesting that the cytoplasmic isoform has a specific role in extra-embryonic tissues and may be involved in the regulation of human parturition.

The progesterone receptor in human term amniochorion and placenta is isoform C

The mechanism that initiates human parturition has been proposed to be functional progesterone withdrawal whereby the 116-kDa B isoform of the progesterone receptor (PR-B) switches in favor of the 94-kDa A isoform (PR-A) in reproductive tissues. Recently other PR isoforms, PR-S, PR-C, and PR-M generated from the same gene have been identified and partially characterized. Using immunohistochemical, Western blotting, and RT-PCR techniques, evidence is provided that the major PR isoform present in human term fetal membranes (amnion and chorion) and syncytiotrophoblast of the placenta is neither of the classical nuclear PR-B or PR-A isoforms but is the N terminally truncated 60-kDa PR-C isoform. Evidence is also provided that the PR-C isoform resides in the cytoplasm of the expressing cell types. Data are also presented to show that PR-B, PR-A, and PR-S isoforms are essentially absent from the amnion and chorion, whereas PR isoforms A, B, C, and S are all present in the decidua, with PR-A being the major isoform. The syncytiotrophoblast of the placenta contains the cytoplasmic PR-C isoform but not PR-A, PR-B, or PR-S. The major PR isoform in the amnion, chorion, and placenta is PR-C, suggesting that the cytoplasmic PR-C isoform has a specific role in extraembryonic tissues and may be involved in the regulation of human parturition.

Effect of systemic progesterone concentration on the expression of progesterone-responsive genes in the bovine endometrium during the early luteal phase

Increasing evidence indicates an association between the concentration of systemic progesterone during the early luteal phase of the oestrous cycle and embryo survival rate in cattle. We examined the relationship between the concentration of systemic progesterone on Days 4 to 8 post-ovulation and expression of progesterone receptor (PGR), oestrogen receptor α (ESR1) and retinol-binding protein (RBP) mRNA in the bovine endometrium. Heifers were blood sampled from the day of ovulation (Day 0) to Day 8 post-ovulation. On Day 4, animals were divided into low progesterone control (LC) and high progesterone control (HC) groups based on their plasma progesterone concentrations. Half of each group was supplemented with exogenous progesterone resulting in two further groups, low progesterone supplemented (LS) and high progesterone supplemented (HS). Endometrial tissues were recovered from all groups on Day 6 or Day 8 and gene expression was analysed following Northern blotting. Increasing progesterone concentrations were associated with decreased PGR and ESR1 expression. Duration-dependent effects of progesterone supplementation on ESR1 were evident and there was an effect of systemic progesterone concentrations between Day 0 and Day 4 on the expression of RBP at Days 6 and 8. Such progesterone-responsive changes in uterine gene expression are likely to affect embryo development.

Fine tuning of the specificity of an anti-progesterone antibody by first and second sphere residue engineering

The specificity of anti-progesterone P15G12C12G11 antibody was improved by combination of in vitro scanning saturation mutagenesis and error-prone PCR. The most evolved mutant is able to discriminate against 5beta- or 5alpha-dihydroprogesterone, 23 and 15 times better than the starting antibody, while maintaining the affinity for progesterone that remains in the picomolar range. The high level of homology with anti-progesterone monoclonal antibody DB3 allowed the construction of three-dimensional models of P15G12C12G11 based on the structures of DB3 in complex with various steroids. These models together with binding data, derived from site-directed mutagenesis, were used to build a phage library in which five first sphere positions in complementarity-determining regions 2H and 3L were varied. Variants selected by an initial screening in competition against a large excess of 5beta- or 5alpha-dihydroprogesterone were characterized by a convergent amino acid signature different from that of the wild-type antibody and had lower cross-reactivity. Binding properties of this first set of mutants were further improved by the addition of second sphere mutations selected independently from an error-prone library. The three-dimensional models of the best variant show changes in the antigen binding site that explain well the increase in selectivity. The improvements are partly linked to a change in the canonical class of the light chain third hypervariable loop.

SEX STEROID HORMONE RECEPTORS IN THE DEVELOPING FEMALE REPRODUCTIVE TRACT OF LABORATORY RODENTS

Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans. Some of these chemicals exhibit estrogenic activity by binding to the estrogen receptors. The developing organism is particularly sensitive to estrogenic chemicals during the critical period in which the induction of long-term changes and persistent molecular alterations in female reproductive tracts occur. Perinatal mouse and rat models can be utilized as indicators for determining the consequences of exposure to exogenous estrogenic agents, including possible xenoestrogens or environmental endocrine disruptors. Estrogen receptors (ER) and estrogen responsive genes, therefore, need to be identified in order to understand the molecular basis of estrogenic actions. Recent identifications of ER subtypes and isoforms make understanding target organ responses to these estrogenic chemicals even more difficult. Indeed, many reports suggest that these chemicals do affect the reproductive and developmental processes of female laboratory rodents that had been perinatally exposed, and that interactions between sex steroid hormone receptors occur. Much information concerning the expression of sex steroid receptors in rodents has been reported concerning the normal development of the Müllerian duct. Thus, accumulated information on the expression of ER subtypes and isoforms as well as that of progesterone and androgen receptors in laboratory rodents is herein reviewed, in addition to the presentation of our own data.

Expression of progesterone receptors A and B in the mouse ovary during the estrous cycle

Progesterone plays a central role in the regulation of ovarian function. The progesterone receptor (PR) has been shown to be essential for ovulation because mice lacking PR fail to ovulate and are infertile. PR is expressed as two isoforms, PRA and PRB, which have been shown to have different functional activities. In this study, we investigated the cellular distribution of PRA and PRB in the ovaries and oviducts of cycling mice using immunohistochemistry with isoform-specific monoclonal antibodies. In the ovary, on the evening of proestrus before ovulation, both the granulosa and theca cells of the preovulatory follicles expressed both PR isoforms. PRA and PRB staining was also observed in the theca cells of preantral and antral follicles, whereas only PRB was observed in the granulosa cells of primary, preantral, and antral follicles and in the corpus luteum. In the oviduct, PRA was the predominant isoform observed, expressed in both the epithelial and stromal cells, whereas PRB was only detected in the epithelial cells. The differences in PRA and PRB localization in the ovary and oviduct may reflect diverse functions for PRA and PRB in reproductive tissues and may have important implications in understanding the mechanisms of progesterone action.

The correlation between the response to progestogen treatment and the expression of progesterone receptor B and 17beta-hydroxysteroid dehydrogenase type 2 in human endometrial carcinoma

OBJECTIVE

In situ metabolism and synthesis of oestrogens are considered to play important roles in the pathogenesis and development of human endometrial endometrioid adenocarcinoma. Approximately 3-5% of patients with these neoplasms are under age 40, some of whom have been treated with progestogen alone as a primary therapy for both atypical endometrial hyperplasia and adenocarcinoma in order to preserve their fertility. Medroxyprogesterone acetate (MPA) has been used extensively in the treatment of both breast and endometrial disorders as an endocrine therapy. However, details of the alterations of in situ oestrogen metabolism following progestogen treatment have yet to be fully elucidated.

DESIGN, PATIENTS AND MEASUREMENTS

In this study we examined the immunolocalization of 17beta-hydroxysteroid dehydrogenase (17beta-HSD) types 1 and 2, oestrogen receptor (ER), progesterone receptor (PR)A + PRB, PRB, and Ki67 in progestogen-treated endometrial endometrioid adenocarcinoma (16 cases). We compared our findings both prior to and following treatment. These findings were then correlated with the treatment outcome of individual patients in order to elucidate factors associated with the response to treatment.

RESULTS

17beta-HSD type 2 immunoreactivity was detected in 8/16 cases examined, whereas 17beta-HSD type 1 immunoreactivity was undetected in all cases examined. 17beta-HSD type 2 positive immunostaining, PRA + PRB labelling index (LI), and PRB/PRA + PRB ratio were all significantly higher in cases responding to the treatment than in those not responding. There were no significant correlations between responsive and nonresponsive cases for positive 17beta-HSD type 1 immunostaining, Ki67 LI, ER LI and age. There were no significant differences in the positive immunostaining for 17beta-HSD types 1 and 2, Ki67 LI, ER LI, PRA + PRB LI, age and PRB/PRA + PRB ratio between specimens taken prior to and following progestogen treatment.

CONCLUSION

These results suggest that in situ abundance of 17beta-HSD type 2 and PR, especially PRB, can predict the possible response of patients with endometrial carcinoma to progestogen treatment.

Progesterone receptor isoform B in the human fallopian tube and endometrium following mifepristone

The distribution of progesterone receptor isoform B may have important clinical significance. The aim of this study was to compare the expression, localization and regulation of progesterone receptor isoform B in the human Fallopian tube and endometrium following mifepristone in a dose effective for contraception. Fertile women were treated with a single dose of 200 mg mifepristone on day luteinizing hormone (LH)+2. Biopsies were obtained from the Fallopian tube on day LH+4 to LH+6 and from the endometrium on day LH+6 to LH+8. Progesterone receptor isoform B expression was analyzed by immunohistochemistry and reverse transcriptase polymerase chain reaction. Treatment with mifepristone increased progesterone receptor isoform B concentration in epithelial and stromal cells in the Fallopian tube and also increased progesterone receptor isoform B concentration in the glandular cells of the endometrium. These results further support the hypothesis that the contraceptive effect of mifepristone when given postovulatory is primarily due to alteration of the peri-implantation milieu influencing endometrial receptivity.

Differential expression of progesterone receptor isoforms A and B in the normal ovary, and in benign, borderline, and malignant ovarian tumors

Human epithelial ovarian neoplasm is well-known to be sex steroid-related, but the possible biological significance of progesterone actions in these tumors remains controversial. In this study, we examined the differential expression patterns of the two progesterone receptor (PR) isoforms, PRA and PRB, using immunohistochemistry and real-time quantitative RT-PCR in normal and neoplastic ovarian tissues, and in cell lines derived from a normal ovarian surface epithelium and an ovarian epithelial carcinoma in order to further elucidate the possible involvement of progesterone in the development of ovarian neoplasms. The median H scores for PR isoforms in normal (n = 8), benign (n = 10), borderline (n = 8) and malignant (n = 24) ovarian tissues were as follows; PRA: 194.0, 171.0, 49.5, 0 (P < 0.05), and PRB: 175.0, 180.5, 251.5, 168.5, respectively. In ovarian cancer cell lines (OVCAR-3 and Caov-3), the PRB / PRAB mRNA ratio was increased by 17beta-estradiol, both time- and dose-dependently. However, this ratio was unaltered following the addition of 17beta-estradiol in a normal ovarian epithelial cell line (NOV-31). Immunoblotting analysis demonstrated that PRB protein expression was markedly up-regulated in OVCAR-3, whereas the PRA and PRB isoforms both appeared to be increased in NOV-31. These results suggest that down-regulation of PRA is associated with the development of ovarian epithelial carcinoma.

Endocrine disrupters--testing strategies to assess human hazard

During the last decade an hypothesis has been developed linking certain chemicals (natural and synthetic) to observed and suspected adverse effects on reproduction in both wildlife and humans. The issue of 'endocrine disruption' originally focused on chemicals that mimic the action of the natural hormone oestrogen. However, the concern is now encompassing effects on the whole endocrine system. In response to public awareness, regulatory agencies (including the US EPA) and the OECD are formulating potential testing strategies and have begun the process of validating defined tests to systematically assess chemicals for their endocrine-disrupting activities. In order to investigate chemicals that have the potential to cause endocrine disruption, a large number of in vitro and in vivo assays have been identified. In vitro test systems (particularly when used in combination) offer the possibility of providing an early screen for large numbers of chemicals and can be useful in characterising the mechanism of action and potency. In vitro assays in widespread use for the screening/characterisation of endocrine disrupting potential include hormone receptor ligand binding assays (determination of the ability of a chemical to bind to the hormone receptor), cell proliferation assays (analysis of the ability of a chemical to stimulate growth of oestrogen sensitive cells), reporter gene assays in yeast or mammalian cells (analysis of the ability of a chemical to stimulate the transcription of a reporter gene construct in cell culture), and the analysis of the regulation of endogenous oestrogen sensitive genes in cell lines. However, in vitro assays do not always reliably predict the outcome in vivo due to differences in metabolic capabilities of the test systems used and the diverse range of mechanisms by which endocrine disrupting chemicals may act. Therefore a complementary battery of short- and long-term in vitro and in vivo assays (that assess both receptor and non-receptor mediated mechanisms of action) seems the most appropriate way at present of assessing the potential endocrine disrupting activities of chemicals. At Unilever we have used a combination of in vitro assays (receptor binding, reporter gene and cell proliferation assays) together with short-term in vivo tests (uterotrophic assay in immature rodents) to examine the oestrogenic potential of a large number of chemicals. An evaluation of the advantages and limitations of these methods is provided. Finally, any potential test system needs to be validated and standardized before the information generated can be for the identification of hazard, and possibly for risk assessment purposes.

Progesterone receptor isoforms A and B in human epithelial ovarian carcinoma: immunohistochemical and RT-PCR studies

Human epithelial ovarian carcinoma is well-known as a sex steroid-dependent neoplasm, but the possible biological significance of progesterone receptor (PR) in this cancer remains controversial. Recently, two isoforms of human PR, PRA and PRB, have been characterized and different functional characteristics have been reported for these two isoforms. We therefore examined immunohistochemistry (107 cases) and reverse transcription-polymerase chain reaction (RT-PCR) (16 cases) for PRA, PRB, and oestrogen receptor-a (ER-a). Labeling indices (LI) for PRA and PRB were 2.4 and 43.6, respectively, and the difference was statistically significant. PRB LI, but not PRA LI, as well as performance status, stage, and residual tumour turned out to be independent prognostic factors following multivariate analysis. There was also a significant correlation between ER-a LI and PRB LI (r = 0.595, P < 0.0001), suggestive of a possible interaction between these two receptors. RT-PCR also detected the expression of PR isoform transcripts in the same pattern as was observed with immunohistochemistry. Results of these studies indicate that PRA and PRB both mediate distinct pathways of progesterone action in ovarian carcinoma. Moreover, it is important to examine PRB LI as a prognostic factor in the cases of human epithelial ovarian carcinoma.

Colocalization of progesterone receptors A and B by dual immunofluorescent histochemistry in human endometrium during the menstrual cycle

The human progesterone receptor (PR) is expressed as two isoforms, PRA and PRB, that function as ligand-activated transcription factors. In vitro studies suggest that the isoforms differ functionally and that the relative levels in a target cell may determine the nature and magnitude of response to progesterone. However, it is not known whether the two isoforms are normally coexpressed in vivo. To understand the functional significance of relative PR isoform expression in normal physiology, it is essential to determine whether PRA and PRB are coexpressed in the same cell. This study reports the development of a dual immunofluorescent staining technique to demonstrate PRA and PRB proteins by single cell analysis in the same tissue section of human endometrium during the menstrual cycle. PRA and PRB are coexpressed in target cells of the human uterus. In the glands, PRA and PRB were expressed before subnuclear vacuole formation and glycogenolysis, implicating both isoforms in this process, whereas persistence of PRB during the midsecretory phase suggested its significance in glandular secretion. In the stroma, the predominance of PRA throughout the cycle implicates this isoform in post-ovulatory progesterone-mediated events. These results support the view that PRA and PRB mediate distinct pathways of progesterone action in the glandular epithelium and stroma of the human uterus throughout the menstrual cycle.

Progesterone receptor A and B protein expression in human breast cancer

The human progesterone receptor (PR) is a ligand-activated nuclear transcription factor which mediates progesterone action in target tissues. Two PR proteins, PR A (81-83 kDa) and PR B (116-120 kDa), have been described and different physiological activities ascribed to each on the basis of in vitro studies, suggesting that their ratio of expression may control progesterone responsiveness in target cells. Presence of PR in breast tumors is an important indicator of likely responsiveness to endocrine agents. However, the relative expression of PR A and B in breast cancer has not been described and its clinical significance has not been addressed. We have examined the expression of PR A and B in PR-positive breast tumors and found that while in most tumors PR A and B were expressed in similar amounts there was a broad overall distribution of PR A:B ratio which deviated significantly from a normal log distribution with tumors containing a PR A:B ration greater than 4 being over-represented in the group. Linear regression analysis revealed that high PR A:B ratios, in general, derived from a low concentration of PR B rather than high expression of PR A. PR A:B protein ratios were not correlated with the age of the patient or with total PR concentration. A third PR protein band (PR 78 kDa) was detected which comprised greater than 20% of total PR protein in a quarter of the tumor samples examined. The characteristics of tumors containing PR 78 kDa were not different from the overall group. In summary, in PR-positive breast tumors the ratio of expression of PR A and B proteins is close to unity as is seen in a number of other progestin target tissues. However, a significant proportion of tumors expressed very low levels of PR B and a consequently high PR A:B ration. Although the clinical consequence of this observation is not known, the in vitro findings that PR A may act as a repressor for PR B suggests that tumors containing primarily PR A may identify a subset of patients with low or aberrant response to endocrine agents.

Preferential stimulation of human progesterone receptor B expression by estrogen in T-47D human breast cancer cells

Human progesterone receptor (PR) expression is controlled by two promoter regions giving rise to transcripts encoding PR A and B proteins. It is unknown whether estrogen and progesterone, the major physiological modulators of PR expression, exert their effects equally on the PR promoters. The aim of this study was to analyze estrogen and progestin effects on PR promoters, PR-encoding transcripts, and PR A and B proteins in T-47D human breast cancer cells. The progestin ORG 2058 caused a prolonged decrease in transcription of the PR gene and also abrogated estrogen stimulation of PR transcription. Estradiol (E2) treatment increased the activity of the B but not the A promoter transfected into T-47D cells. ORG 2058 had no effect on the basal or E2-stimulated activity of either promoter. E2 caused a preferential increase in transcripts derived from promoter B, whereas progestins decreased the levels of all PR transcripts. E2 preferentially increased the concentration of the PR B protein and caused a decrease in the PR A/B ratio. This demonstration that estrogen and progestin independently control the synthesis of transcripts arising from the PR promoters and that estrogen alters the cellular PR A/B ratio provides possible mechanisms underlying the cell and tissue specificity of PR regulation.

Receptors for sex steroids in the primate corpus luteum New insight into gonadotropin and steroid action

The evidence is compelling for progesterone receptor (PR) expression in the primate corpus luteum during the menstrual cycle, based on three experimental approaches: (a) immunocytochemistry, (b) radioligand binding to steroid-depleted tissue, and (c) reverse transcription-polymerase chain reaction or ribonuclease protection assay. This information is providing the impetus for studies on possible receptormediated roles for progesterone to control periovulatory events (including follicle rupture and luteal development) and the functional lifespan of the corpus luteum. Similar experiments suggest that estrogen receptors are nondetectable in the corpus luteum. Thus, "classic" receptor-mediated actions of estrogen, such as promoting PR expression, are not apparent; rather, the midcycle surge of LH assumes the role of stimulating PR expression in luteinizing granulosa cells. The recent discovery of androgen receptor expression in primate luteal tissue should lead to studies on the heretofore unsuspected actions of androgens in the corpus luteum.

Effect of estradiol and progesterone on c-myc expression in the sea star testis and the seasonal regulation of spermatogenesis

Analysis of the expression of cell cycle control genes provides a sensitive assay for mitotic and meiotic progression under experimental conditions. Transcription of the c-myc proto-oncogene and thymidine incorporation into DNA were both used to assay the mitogenic effects of estradiol and progesterone on the testicular germinal epithelium of the starfish Asterias vulgaris. Experimental in vitro studies during the annual spermatogenic cycle show that testes are not sensitive to mitotic stimulation by estradiol alone, whereas progesterone alone is mitotically inhibitory. The germinal epithelium can only be mitotically stimulated by estradiol after pretreatment with progesterone. The net increase in mitotic activity following a progesterone to estradiol transfer is dependent on the length of progesterone pretreatment. Overall, the seasonal pattern of testicular estradiol and progesterone levels evident in field populations of A. vulgaris (Hines et al., 1992a: Endocrinology 100:1468-1471) do not appear to be responsible for initiating spermatogonial mitosis at the onset of the annual spermatogenic cycle. Expression rates of the c-myc proto-oncogene are substantially more sensitive than thymidine incorporation in quantifying mitotic activity. Measuring proto-oncogene expression provides an ideal experimental approach to investigations of the regulatory mechanisms that control growth and reproduction in marine organisms.

Abstinent alcoholics exhibit an exaggerated stress response to 2-deoxy-D-glucose challenge

Chronic excessive alcohol consumption can significantly disturb the hypothalamic control of glucose metabolism; however, the mechanism and clinical significance of this disturbance are poorly understood. We used 2-deoxy-D-glucose (2-DG), which produces intracellular glucoprivation, to compare neurochemical, physiological, and behavioral responses to glucoprivic stress between alcoholics abstinent for 3 weeks and healthy volunteers. Twenty-six male alcoholics and 15 male healthy volunteers received intravenous infusions of placebo, 12.5 mg/kg, and 25.0 mg/kg of body weight of 2-DG over 30 min on three separate days, following a random-ordered, double-blind procedure. Minimal effects were observed following administration of the 12.5 mg/kg of body weight dose of 2-DG. Following 25.0 mg/kg, alcoholics showed both exaggerated ACTH and cortisol responses and greater increases in caloric intake when compared with controls. Although anxiety, desire to consume alcohol, plasma progesterone, and sympathetic and adrenal medullary activity all increased following 2-DG, these responses did not differ between alcoholics and controls. The present findings suggest certain specificity for the exaggerated hypothalamic and adrenocortical responses to mild glucoprivic stress in 3-week-abstinent alcoholics.

Structure of the human progesterone receptor gene

The complete organization of the human progesterone receptor (hPR) gene has been determined. It spans over 90 kbp and contains eight exons. The first exon encodes the N-terminal part of the receptor. The DNA binding domain is encoded by two exons, each exon corresponding to one zinc finger. The steroid binding domain is encoded by five exons. The nucleotide sequence of 1144 bp of the 5' flanking region has been determined.

Endometrial expression of progesterone receptor and uteroglobin genes during early pregnancy in the rabbit

The progesterone receptor (PR) plays a pivotal role in the maturation process of the secretory endometrium, implantation and maintenance of pregnancy in rabbits. To determine the dynamics of PR gene expression and its physiological significance, the endometrial expression of PR and PR mRNA were evaluated and compared with the expression of the progesterone-regulated uteroglobin (UG) gene during 0-5 days post-coitus in rabbits. The results of immunoblot experiments indicated the presence of PR in endometrial cell extracts from days 1-4 of pregnancy with maximum PR immunostaining on day 2, followed by a marked diminution until its complete disappearance on day 5. When endometrial PR mRNA content was assessed by Northern blots, the results were similar to those of PR immunostaining, with maximal concentrations on the second day after mating. However, PR mRNA levels were still high on day 3, despite the concomitant decrease in immunostainable PR. Endometrial UG gene expression, on the other hand, exhibited a different time sequence. Thus, the UG content in uterine flushings progressively increased from day 3 after mating, reaching maximal levels on the fifth day. The endometrial UG mRNA content presented a similar profile, as its maximum concentration occurred on days 4-5. The overall results indicate that endometrial PR is down-regulated at both the mRNA and protein levels, possibly by endogenous progesterone during early pregnancy. The striking observation that maximal expression of endometrial UG gene products occurred when PR and its mRNA are no longer detectable suggests an important role for this progesterone-binding uterine protein during the preimplantation period.

Progesterone stimulates sulfate uptake in subcultured endometrial epithelial cells

The effect of progesterone was studied on the sulfate entry in glandular epithelial cells of guinea-pig endometrium subcultured in bicameral chambers on matrix-coated filters in a chemically defined medium. At post-confluency (8 days of subculture), cells were treated with 10 nM estradiol alone or in association with various concentrations of progesterone. Optimal progesterone action was at a 16 h incubation time and a 10 nM hormonal concentration. Progesterone increased in a dose-dependent fashion the sulfate uptake specifically in glandular epithelial cells, preferentially from the basal surface. Progesterone effect on the sulfate uptake occurred only in estradiol-primed epithelial cells and was inhibited by the antiprogestin steroid RU-486. The progesterone-dependent increase in sulfate uptake was inhibited by the inhibitor of anion exchange, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). At physiological sulfate concentrations, progesterone essentially induces a high-affinity DIDS-sensitive transport system.

The effects of metabolic stress on plasma progesterone in healthy volunteers and schizophrenic patients

A number of preclinical studies suggest that progesterone may play an important role in the stress response, however, the effects of stress on progesterone in humans has not been established. Also, several lines of evidence indicate that schizophrenia may be associated with abnormal neurobiological responses to stress, but the effects of stress on progesterone in schizophrenia has not been investigated. The purpose of the present study was to examine the effects of stress on plasma progesterone and cortisol in healthy subjects and to determine if schizophrenic patients have altered stress-induced plasma progesterone levels compared to normal controls. Stress was induced through administration of 2-deoxyglucose (2DG), a glucose analog that impairs glucose metabolism resulting in a clinical state comparable to hypoglycemia. There were significant increases in plasma progesterone and cortisol levels following 2DG-induced glucoprivic stress in healthy controls. There was no relationship between stress related progesterone and cortisol elevations. Schizophrenic patients, in comparison to controls, had significantly greater 2DG-induced elevations in progesterone levels but no differences in stress-related cortisol levels. There was evidence that basal progesterone and cortisol levels were elevated in the schizophrenic patients. The implications of these data are discussed.