Progesterone receptors A and B differentially modulate corticotropin-releasing hormone gene expression through a cAMP regulatory element

Preterm Birth and Corticotrophin-Releasing Hormone as a Placental Clock

Preterm birth worldwide remains a significant cause of neonatal morbidity and mortality, yet the exact mechanisms of preterm parturition remain unclear. Preterm birth is not a single condition, but rather a syndrome with a multifactorial etiology. This multifactorial nature explains why individual predictive measures for preterm birth have had limited sensitivity and specificity. One proposed pathway for preterm birth is via placentally synthesized corticotrophin-releasing hormone (CRH). CRH is a peptide hormone that increases exponentially in pregnancy and has been implicated in preterm birth because of its endocrine, autocrine, and paracrine roles. CRH has actions that increase placental production of estriol and of the transcription factor nuclear factor-κB, that likely play a key role in activating the myometrium. CRH has been proposed as part of a placental clock, with early activation of placental production resulting in preterm birth. This article will review the current understanding of preterm birth, CRH as an initiator of human parturition, and the evidence regarding the use of CRH in the prediction of preterm birth.

Chronic psychosocial stress during pregnancy affects maternal behavior and neuroendocrine function and modulates hypothalamic CRH and nuclear steroid receptor expression

Postpartum depression (PPD) affects up to 20% of mothers and has negative consequences for both mother and child. Although exposure to psychosocial stress during pregnancy and abnormalities in the hypothalamic pituitary adrenal (HPA) axis have been linked to PPD, molecular changes in the brain that contribute to this disease remain unknown. This study utilized a novel chronic psychosocial stress paradigm during pregnancy (CGS) to investigate the effects of psychosocial stress on maternal behavior, neuroendocrine function, and gene expression changes in molecular regulators of the HPA axis in the early postpartum period. Postpartum female mice exposed to CGS display abnormalities in maternal behavior, including fragmented and erratic maternal care patterns, and the emergence of depression and anxiety-like phenotypes. Dysregulation in postpartum HPA axis function, evidenced by blunted circadian peak and elevation of stress-induced corticosterone levels, was accompanied by increased CRH mRNA expression and a reduction in CRH receptor 1 in the paraventricular nucleus of the hypothalamus (PVN). We further observed decreased PVN expression of nuclear steroid hormone receptors associated with CRH transcription, suggesting these molecular changes could underlie abnormalities in postpartum HPA axis and behavior observed. Overall, our study demonstrates that psychosocial stress during pregnancy induces changes in neuroendocrine function and maternal behavior in the early postpartum period and introduces our CGS paradigm as a viable model that can be used to further dissect the molecular defects that lead to PPD.

Physiology and Pathophysiology of Steroid Biosynthesis, Transport and Metabolism in the Human Placenta

The steroid hormones progestagens, estrogens, androgens, and glucocorticoids as well as their precursor cholesterol are required for successful establishment and maintenance of pregnancy and proper development of the fetus. The human placenta forms at the interface of maternal and fetal circulation. It participates in biosynthesis and metabolism of steroids as well as their regulated exchange between maternal and fetal compartment. This review outlines the mechanisms of human placental handling of steroid compounds. Cholesterol is transported from mother to offspring involving lipoprotein receptors such as low-density lipoprotein receptor (LDLR) and scavenger receptor class B type I (SRB1) as well as ATP-binding cassette (ABC)-transporters, ABCA1 and ABCG1. Additionally, cholesterol is also a precursor for placental progesterone and estrogen synthesis. Hormone synthesis is predominantly performed by members of the cytochrome P-450 (CYP) enzyme family including CYP11A1 or CYP19A1 and hydroxysteroid dehydrogenases (HSDs) such as 3β-HSD and 17β-HSD. Placental estrogen synthesis requires delivery of sulfate-conjugated precursor molecules from fetal and maternal serum. Placental uptake of these precursors is mediated by members of the solute carrier (SLC) family including sodium-dependent organic anion transporter (SOAT), organic anion transporter 4 (OAT4), and organic anion transporting polypeptide 2B1 (OATP2B1). Maternal-fetal glucocorticoid transport has to be tightly regulated in order to ensure healthy fetal growth and development. For that purpose, the placenta expresses the enzymes 11β-HSD 1 and 2 as well as the transporter ABCB1. This article also summarizes the impact of diverse compounds and diseases on the expression level and activity of the involved transporters, receptors, and metabolizing enzymes and concludes that the regulatory mechanisms changing the physiological to a pathophysiological state are barely explored. The structure and the cellular composition of the human placental barrier are introduced. While steroid production, metabolism and transport in the placental syncytiotrophoblast have been explored for decades, few information is available for the role of placental-fetal endothelial cells in these processes. With regard to placental structure and function, significant differences exist between species. To further decipher physiologic pathways and their pathologic alterations in placental steroid handling, proper model systems are mandatory.

Expression of CPPED1 in human trophoblasts is associated with timing of term birth

Understanding of timing of human parturition is incomplete. Therefore, we carried out proteomic analyses of full-term placentas from uncomplicated pregnancies to identify protein signatures associated with the onset of spontaneous delivery. We found quantitative associations of 10 proteins with spontaneous term birth, evident either in the basal or in the chorionic plates or in both. Additional 18 proteins were associated according to the location within placenta indicating local variations in protein amounts. Calcineurin-like phosphoesterase domain-containing 1 (CPPED1), a phosphatase previously suggested dephosphorylating AKT1/PKB, was one of the identified proteins. qRT-PCR revealed the mRNA level of CPPED1 was higher in elective caesarean deliveries than in spontaneous births, while immunohistochemistry showed CPPED1 in cytotrophoblasts, syncytiotrophoblasts and extravillous trophoblasts. Noteworthy, phosphorylation status of AKT1 did not differ between placentas from elective caesarean and spontaneous deliveries. Additionally, analyses of samples from infants indicated that single-nucleotide polymorphisms rs11643593 and rs8048866 of CPPED1 were associated with duration of term pregnancy. Finally, post-transcriptional silencing of CPPED1 in cultured HTR8/SVneo cells by siRNAs affected gene expression in pathways associated with inflammation and blood vessel development. We postulate that functions regulated by CPPED1 in trophoblasts at choriodecidual interphase have a role in the induction of term labour, but it may be independent of AKT1.

Exposure to aflatoxin B1 in late gestation alters protein kinase C and apoptotic protein expression in murine placenta

Mycotoxins are chemicals with diverse toxicities that are produced by fungi. Aflatoxin B1 is commonly found in plant food, and is generally regarded as one of the most toxic mycotoxins. In the present study, pregnant ICR mice were given p.o. daily doses of aflatoxin B1 at 0, 0.05, 0.5, 5mg/kg for 4days (from E13.5 to E16.5). Compared to the control group, time of delivery was shortened and low birth weight was induced in mice treated with 0.5 and 5mg aflatoxin B1/kg, respectively. Placental tissue isolated from pregnant mice at E17.5 showed that the mRNA expression of crh was increased in aflatoxin-treated groups. This upregulation might signify premature delivery. Further analysis indicated that Pkc proteins were activated and Bcl-2 was reduced in the placental tissue of the aflatoxin-treated groups. Reduction of the anti-apoptotic proteins, on the other hand, might affect the morphorgenesis and maintenance of the placenta.

Decreased maternal hypothalamic-pituitary-adrenal axis activity in very severely obese pregnancy: Associations with birthweight and gestation at delivery

BACKGROUND

The maternal hypothalamic-pituitary-adrenal-axis (HPAA) undergoes dramatic activation during pregnancy. Increased cortisol and corticotrophin-releasing-hormone (CRH) associate with low birthweight and preterm labor. In non-pregnant obesity, the HPAA is activated but circulating cortisol levels are normal or lower than in lean women. We hypothesized that maternal cortisol levels would be lower in obese pregnancy, and would associate with increased fetal size and length of gestation.

METHOD

Fasting serum cortisol was measured at 16, 28 and 36 weeks gestation and at 3-6 months postpartum in 276 severely obese and 135 lean women. In a subset of obese (n=20) and lean (n=20) we measured CRH, hormones that regulate bioavailable cortisol (corticosteroid-binding-globulin, estradiol, estriol, and progesterone). Urinary glucocorticoid metabolites were measured in pregnant (obese n=6, lean n=5) and non-pregnant (obese n=7, lean n=7) subjects.

RESULTS

Maternal cortisol and HPAA hormones were lower in obese pregnancy. Total urinary glucocorticoid metabolites increased significantly in lean pregnancy, but not in obese. Lower maternal cortisol in obese tended to be associated with increased birthweight (r=-0.13, p=0.066). In obese, CRH at 28 weeks correlated inversely with gestational length (r=-0.49, p=0.04), and independently predicted gestational length after adjustment for confounding factors (mean decrease in CRH of -0.25 pmol/L (95% CI -0.45 to -0.043 pmol/L) per/day increase in gestation).

CONCLUSION

In obese pregnancy, lower maternal cortisol without an increase in urinary glucocorticoid clearance may indicate a lesser activation of the HPAA than in lean pregnancy. This may offer a novel mechanism underlying increased birthweight and longer gestation in obese pregnancy.

Sex differences in neurosteroid and hormonal responses to metyrapone in posttraumatic stress disorder

RATIONALE

Mechanisms contributing to sex differences in the regulation of acute stress responsivity and their effect on the increased incidence of posttraumatic stress disorder (PTSD) in women are poorly understood. The reproductive hormone, progesterone, through conversion to allopregnanolone (ALLO), suppresses the hypothalamic pituitary adrenal (HPA) axis and has potent anxiolytic effects. The potential that progesterone and allopregnanolone reactivity modulate HPA axis responses and account for sex differences in PTSD has not been previously examined.

OBJECTIVE

The present study examined the effects of sex and PTSD on adrenocorticotropic hormone (ACTH), progesterone, and allopregnanolone responses to metyrapone and whether progesterone and allopregnanolone reactivity could affect the ACTH response in PTSD.

METHODS

Healthy medication-free male and premenopausal follicular phase female participants with chronic PTSD (n = 43; 49 % female) and controls (n = 42; 50 % female) completed an overnight metyrapone challenge and ACTH, progesterone, and allopregnanolone were obtained by repeated blood sampling.

RESULTS

The increase in ACTH response to metyrapone was higher in PTSD subjects compared to controls and in women compared to men. Contrary to our initial prediction of an inverse relationship, progesterone and allopregnanolone were positively associated with ACTH. Progesterone and allopregnanolone partially mediated the relationship between PTSD and ACTH.

CONCLUSIONS

Our findings of increased ACTH to metyrapone in PTSD and in women may reflect heightened hypothalamic CRF hypersecretion. Progesterone and allopregnanolone partially mediated the ACTH response in PTSD. Further characterizing sex differences in these processes will advance our understanding of the pathophysiology of PTSD, and may ultimately lead to better-targeted, more effective treatment.

Negative effects of progesterone receptor isoform-A on human placental activity of the noncanonical NF-κB signaling

CONTEXT

Progesterone (P4)contributes to the maintenance of human pregnancy, in part by inhibiting activity of the human pro-labor genes CRH and cyclooxygenase-2 (COX-2). However, the molecular mechanisms underlying the action of P4 remain poorly defined. We have shown that in human placenta, the constitutively activated noncanonical nuclear factor (NF)-κB pathway positively regulates CRH and COX-2, which is further stimulated by glucocorticoid receptor signaling.

OBJECTIVE

We investigated the role of P4 receptor (PR) in the regulation of nuclear activity of v-rel avian reticuloendotheliosis viral oncogene homolog B (RelB)/NF-κB2 and, in turn, expression of placental CRH and COX-2.

METHODS

We used a variety of techniques including gene silencing, ectopic expression, chromatin immunoprecipitation, Western blot, quantitative RT-PCR, and immunohistochemical staining assays in human placental tissues and primary culture of human cytotrophoblast.

RESULTS

We identified PR isoform-A (PR-A) as the only isoform of PR produced in human placenta. PR-A levels were lower in term placenta than in midterm placenta. Depletion of PR-A by short interfering RNA derepressed inhibition of CRH and COX-2 by P4 and the synthetic progestin 17α-hydroxyprogesterone caproate. Overexpression of PR-A inhibited transcription of CRH and COX-2, which was further downregulated by treatment with P4 or 17α-hydroxyprogesterone caproate. Such an inhibition was mediated by a negative functional interaction of PR-A with the activity of RelB/NF-κB2.

CONCLUSION

P4 inhibits the pro-labor genes CRH and COX-2 via PR-A repression of the noncanonical NF-κB signaling in human placenta. Characterization of these pathways may identify potential drug targets for prevention of preterm birth.

Revisiting the roles of progesterone and allopregnanolone in the nervous system: resurgence of the progesterone receptors

Progesterone is commonly considered as a female reproductive hormone and is well-known for its role in pregnancy. It is less well appreciated that progesterone and its metabolite allopregnanolone are also male hormones, as they are produced in both sexes by the adrenal glands. In addition, they are synthesized within the nervous system. Progesterone and allopregnanolone are associated with adaptation to stress, and increased production of progesterone within the brain may be part of the response of neural cells to injury. Progesterone receptors (PR) are widely distributed throughout the brain, but their study has been mainly limited to the hypothalamus and reproductive functions, and the extra-hypothalamic receptors have been neglected. This lack of information about brain functions of PR is unexpected, as the protective and trophic effects of progesterone are much investigated, and as the therapeutic potential of progesterone as a neuroprotective and promyelinating agent is currently being assessed in clinical trials. The little attention devoted to the brain functions of PR may relate to the widely accepted assumption that non-reproductive actions of progesterone may be mainly mediated by allopregnanolone, which does not bind to PR, but acts as a potent positive modulator of γ-aminobutyric acid type A (GABA(A) receptors. The aim of this review is to critically discuss effects of progesterone on the nervous system via PR, and of allopregnanolone via its modulation of GABA(A) receptors, with main focus on the brain.

Combined quantification of corticotropin-releasing hormone, cortisol-to-cortisone ratio and progesterone by liquid chromatography-Tandem mass spectrometry in placental tissue

With mid-gestation the production of placental corticotropin-releasing hormone (CRH) starts to steadily increase. The fetal peptide CRH excerts direct functions at the feto-maternal interface (vasodilatation, timing of birth) via its interaction with progesterone and indirectly ensures maturation and growth of fetal organ systems for delivery by driving fetal cortisol production via its induction of adrenocorticotropic hormone release. This feedback loop is tightly controlled by the amount of enzymatic cortisol/cortisone turnover in the placental syncytiotrophoblast by 11β-hydroxy-steroid dehydrogenase type 2 (11β-HSD2). Traditionally, placental tissue hormones have been quantified by immunological methods (e.g. RIA or ELISA), which have the drawback of possible cross-reactivity and tissue perturbations. Most importantly, it is not possible to quantify CRH and steroid hormones, such as cortisol, cortisone and progesterone together in the same sample with these methods. Hence, we aimed to develop and validate a quantitative mass spectrometry (MS) method for multi-modal quantification of these placental hormones: While CRH was readily detectable throughout the placenta, the placental levels of progesterone and especially cortisol and cortisone were higher at the placental base facing the maternal side. The HPLC-MS/MS procedure showed excellent selectivity and sufficient limit of quantification in placental tissue homogenates to allow for simultaneous detection of CRH, cortisol and cortisone, and progesterone.

Recent advances in understanding the endocrinology of human birth

The timing of human birth has a crucial impact upon the survival of the fetus. New knowledge on the regulation of human birth includes the role of endogenous retroviruses in the formation of the syncytiotrophoblast cells and consequently the secretion of corticotrophin releasing hormone, a hormone linked to gestational length determination. miRNAs have been identified that mediate progesterone withdrawal at labor by suppressing progesterone-induced transcription factors. Progress has also been made in understanding how the contractile machinery of the uterine myocytes is activated at labor and the role of small heat-shock proteins in this process. From this work, new therapeutic targets have been identified that may be used to regulate the onset of labor and improve neonatal mortality.

Progesterone receptors, their isoforms and progesterone regulated transcription

This review discusses mechanisms by which progesterone receptors (PR) regulate transcription. We examine available data in different species and tissues regarding: (1) regulation of PR levels; and (2) expression profiling of progestin-regulated genes by total PRs, or their PRA and PRB isoforms. (3) We address current views about the composition of progesterone response elements, and postulate that PR monomers acting through "half-site" elements are common, entailing cooperativity with neighboring DNA-bound transcription factors. (4) We summarize transcription data for multiple progestin-regulated promoters as directed by total PR, or PRA vs. PRB. We conclude that current models and methods used to study PR function are problematical, and recommend that future work employ cells and receptors appropriate to the species, focusing on analyses of the effects of endogenous receptors targeting endogenous genes in native chromatin.

ACTH and cortisol response to Dex/CRH testing in women with and without premenstrual dysphoria during GnRH agonist-induced hypogonadism and ovarian steroid replacement

CONTEXT

During conditions of ovarian suppression, women with premenstrual dysphoria (PMD) experience abnormal behavioral responses to physiological levels of ovarian steroids. Although hypothalamic-pituitary-adrenal (HPA) axis dysregulation frequently accompanies depression, and ovarian steroids regulate HPA axis responsivity, the role of HPA axis dysregulation in PMD is not known. We hypothesized that women with PMD would show abnormalities of HPA axis function analogous to those reported in depressive illness, and that ovarian steroids would differentially regulate HPA axis function in women with PMD compared with asymptomatic controls (AC).

OBJECTIVE

Our objective was to characterize the HPA axis response to physiological levels of estradiol and progesterone in women with PMD and AC.

DESIGN AND SETTING

We conducted an open-label trial of the GnRH agonist depot Lupron with ovarian steroid replacement administered in a double-blind crossover design in an outpatient clinic.

PARTICIPANTS

Forty-three women (18 with prospectively confirmed PMD and 25 AC) participated.

INTERVENTIONS

Women received Lupron for 6 months. After 3 months of hypogonadism, women received 5 wk each of estradiol (100-μg patch daily) or progesterone (suppositories 200 mg twice daily). During each condition, combined dexamethasone-suppression/CRH-stimulation tests and 24-h urinary free cortisol levels were performed.

MAIN OUTCOME MEASURES

Plasma cortisol and ACTH levels were evaluated.

RESULTS

HPA axis function was similar in PMD compared with AC. In all, progesterone significantly increased the secretion of cortisol compared with estradiol [area under the curve (t(74) = 3.1; P < 0.01)] and urinary free cortisol (t(74) = 3.2; P < 0.01) and ACTH compared with hypogonadism [area under the curve (t(74) = 2.4; P < 0.05)].

CONCLUSIONS

HPA axis regulation is normal in PMD, suggesting that the pathophysiology of PMD differs from major depression. As observed previously, progesterone but not estradiol up-regulates HPA axis function in women.

Immune aspects and myometrial actions of progesterone and CRH in labor

Progesterone and corticotropin-releasing hormone (CRH) have a critical role in pregnancy and labor, as changes related to these hormones are crucial for the transition from myometrial quiescence to contractility. The mechanisms related to their effect differ between humans and other species, thus, despite extensive research, many questions remain to be answered regarding their mediation in human labor. Immune responses to progesterone and CRH are important for labor. Progesterone acts as an immunomodulator which controls many immune actions during pregnancy, and its withdrawal releases the inhibitory action on inflammatory pathways. In humans, a "functional" progesterone withdrawal occurs with onset of labor through changes in progesterone metabolism, progesterone receptors, and other molecules that either facilitate or antagonize progesterone function. Placental CRH acts on the fetal pituitary-adrenal axis to stimulate adrenal production of androgens and cortisol and also acts directly on myometrial cells via its receptors. CRH also affects inflammatory signals and vice versa. Interactions between progesterone and CRH additionally occur during labor. We describe the role of these two hormones in human myometrium and their interactions with the immune system during labor.

Development and function of the human fetal adrenal cortex: a key component in the feto-placental unit

Continuous efforts have been devoted to unraveling the biophysiology and development of the human fetal adrenal cortex, which is structurally and functionally unique from other species. It plays a pivotal role, mainly through steroidogenesis, in the regulation of intrauterine homeostasis and in fetal development and maturation. The steroidogenic activity is characterized by early transient cortisol biosynthesis, followed by its suppressed synthesis until late gestation, and extensive production of dehydroepiandrosterone and its sulfate, precursors of placental estrogen, during most of gestation. The gland rapidly grows through processes including cell proliferation and angiogenesis at the gland periphery, cellular migration, hypertrophy, and apoptosis. Recent studies employing modern technologies such as gene expression profiling and laser capture microdissection have revealed that development and/or function of the fetal adrenal cortex may be regulated by a panoply of molecules, including transcription factors, extracellular matrix components, locally produced growth factors, and placenta-derived CRH, in addition to the primary regulator, fetal pituitary ACTH. The role of the fetal adrenal cortex in human pregnancy and parturition appears highly complex, probably due to redundant and compensatory mechanisms regulating these events. Mounting evidence indicates that actions of hormones operating in the human feto-placental unit are likely mediated by mechanisms including target tissue responsiveness, local metabolism, and bioavailability, rather than changes only in circulating levels. Comprehensive study of such molecular mechanisms and the newly identified factors implicated in adrenal development should help crystallize our understanding of the development and physiology of the human fetal adrenal cortex.

Neuroendocrine mechanisms in pregnancy and parturition

The complex mechanisms controlling human parturition involves mother, fetus, and placenta, and stress is a key element activating a series of physiological adaptive responses. Preterm birth is a clinical syndrome that shares several characteristics with term birth. A major role for the neuroendocrine mechanisms has been proposed, and placenta/membranes are sources for neurohormones and peptides. Oxytocin (OT) is the neurohormone whose major target is uterine contractility and placenta represents a novel source that contributes to the mechanisms of parturition. The CRH/urocortin (Ucn) family is another important neuroendocrine pathway involved in term and preterm birth. The CRH/Ucn family consists of four ligands: CRH, Ucn, Ucn2, and Ucn3. These peptides have a pleyotropic function and are expressed by human placenta and fetal membranes. Uterine contractility, blood vessel tone, and immune function are influenced by CRH/Ucns during pregnancy and undergo major changes at parturition. Among the others, neurohormones, relaxin, parathyroid hormone-related protein, opioids, neurosteroids, and monoamines are expressed and secreted from placental tissues at parturition. Preterm birth is the consequence of a premature and sustained activation of endocrine and immune responses. A preterm birth evidence for a premature activation of OT secretion as well as increased maternal plasma CRH levels suggests a pathogenic role of these neurohormones. A decrease of maternal serum CRH-binding protein is a concurrent event. At midgestation, placental hypersecretion of CRH or Ucn has been proposed as a predictive marker of subsequent preterm delivery. While placenta represents the major source for CRH, fetus abundantly secretes Ucn and adrenal dehydroepiandrosterone in women with preterm birth. The relevant role of neuroendocrine mechanisms in preterm birth is sustained by basic and clinic implications.

Effect of primary human endometrial stromal cells on epithelial cell receptivity and protein expression is dependent on menstrual cycle stage

BACKGROUND

Successful implantation requires a receptive endometrium. We hypothesized that effects of endometrial stromal cells (ESC) on epithelial cell receptivity and trophoblast-endometrium interaction are menstrual cycle dependent.

METHODS

An endometrial in vitro 3D co-culture model of primary human ESC with the endometrial epithelial cell line (RL95-2) was constructed. Co-cultures were prepared using primary ESC from biopsies taken before the window of implantation (ESCbw) and during the window of implantation (ESCw), on cycle days 10-17 and 19-23, respectively. RL95-2 served as a constant parameter upon which the influence of ESC from different phases of the cycle was investigated. proMMP-2 (MMP, matrix metalloproteinase) and proMMP-9 secretion was tested in response to progesterone. Progesterone receptor B (PR-B) and plexin B1 protein expression and mRNA levels were investigated using immunofluorescence and RT-PCR, respectively.

RESULTS

Progesterone increased proMMP-2 secretion in primary ESCbw (P = 0.0046) but decreased proMMP-2 and proMMP-9 secretion in ESCw (P < 0.0005). In the presence of ESCbw, JAR spheroid attachment rate to overlying RL95-2 cells was decreased (P < 0.0001), whereas in the presence of ESCw, attachment rate was unchanged. Progesterone treatment restored epithelial cell receptivity in co-culture with ESCbw (P = 0.00004). A correlation between spheroid attachment rate and plexin B1 mRNA level was observed (P = 0.01). PR-B protein and mRNA level were influenced by the interplay between RL95-2 and stromal cells.

CONCLUSION

The effects of human primary ESC on epithelial cell receptivity and trophoblast-endometrium interaction depended upon whether the ESC were taken before or during the window of implantation.

Levels of maternal serum corticotropin-releasing hormone (CRH) at midpregnancy in relation to maternal characteristics

BACKGROUND

Corticotropin-releasing hormone (CRH) in maternal blood originates primarily from gestational tissues and elevated levels in midpregnancy have been linked to adverse pregnancy outcomes. Investigators have hypothesized that high levels of maternal stress might lead to elevated CRH levels in pregnancy. Yet a few studies have measured maternal CRH levels among subgroups of women who experience disproportionate socioeconomic disadvantage, such as African-American and Hispanic women, and found that these groups have lower CRH levels in pregnancy. Our goal was to identify maternal characteristics related to CRH levels in midpregnancy and examine which if any of these factors help to explain race differences in CRH levels.

METHODS

The Pregnancy Outcomes and Community Health (POUCH) Study prospectively enrolled women at 15-27 weeks' gestation from 52 clinics in five Michigan communities (1998-2004). Data from the POUCH Study were used to examine maternal demographics, anthropometrics, health behaviors, and psychosocial factors (independent variables) in relation to midpregnancy blood CRH levels modeled as logCRHpg/ml (dependent variable). Analyses were conducted within a sub-cohort from the POUCH Study (671 non-Hispanic Whites, 545 African-Americans) and repeated in the sub-cohort subset with uncomplicated pregnancies (n=746). Blood levels of CRH and independent variables were ascertained at the time of enrollment. All regression models included week of enrollment as a covariate. In addition, final multivariate regression models alternately incorporated different psychosocial measures along with maternal demographics and weight. Psychosocial variables included measures of current depressive symptoms, perceived stress, coping style, hostility, mastery, anomie, and a chronic stressor (history of abuse as a child and adult).

RESULTS

In sub-cohort models, the adjusted mean log CRH level was significantly lower in African-Americans vs. non-Hispanic Whites; the difference was -0.48pg/ml (P<0.01). This difference was reduced by 21% (-0.38pg/ml, P<0.01) after inclusion of other relevant covariates. Adjusted mean log CRH levels were also lower among women with <12 years vs. >or=12 years of education (minimal difference=-0.19pg/ml, P<0.05), and among women with high levels of depressive symptoms who did not use antidepressants vs. women with lower levels of depressive symptoms and no antidepressant use (minimal difference=-0.13pg/ml, P<0.01). Log CRH levels were inversely associated with maternal weight (-0.03pg/ml per 10 pound increase, P<.05) but unrelated to smoking and all other psychosocial measures. Results were similar in the subset of women with uncomplicated pregnancies, except that lower CRH levels were also linked to higher perceived stress.

CONCLUSION

African-American women have lower blood CRH levels at midpregnancy and the race difference in CRH levels is reduced modestly after adjustment for other maternal characteristics. CRH levels were not elevated among women with high levels of perceived stress or more chronic stressors. The inverse association between CRH levels and maternal weight is likely due to a hemodilution effect. Relations among maternal CRH levels and maternal race, educational level, and depressive symptoms are difficult to explain and invite further investigation. Our results highlight a group of covariates that merit consideration in studies that address CRH in the context of pregnancy and/or post-partum complications.

Progesterone suppresses the fetal inflammatory response ex vivo

OBJECTIVE

Progesterone supplementation has been shown to be efficacious in preventing preterm birth. We sought to investigate the effects of progesterone on fetal inflammatory responses.

STUDY DESIGN

Fetal mononuclear cells were isolated from umbilical cord blood and exposed to vehicle or progesterone (P4) for 1 hour prior to lipopolysaccharide (LPS) stimulation. Supernatants were assayed for tumor necrosis factor-alpha. Similar experiments were performed using cyclic adenosine monophosphate (cAMP) and progesterone modulators. The effect of P4 treatment on intracellular cAMP levels was also determined.

RESULTS

LPS treatment led to a significant increase in cytokine production by fetal mononuclear cells. Despite the lack of detectable nuclear progesterone receptors, P4 suppressed this inflammatory response. R5020 (progesterone agonist), forskolin (cAMP inducer), and dibutyryl cAMP (cAMP agonist) all achieved immunosuppression. The cAMP antagonist, Rp-cAMP, blocked the inhibitory effect of progesterone. P4 significantly increased intracellular cAMP levels.

CONCLUSION

Progesterone rapidly suppresses the fetal inflammatory response, possibly via nongenomic activation of the cAMP cascade.

Pathological interactions with the timing of birth and uterine activation

The physiological processes that regulate the onset of parturition and birth are slowly being elucidated, and the points at which pathology can intervene are becoming more apparent. The data support the view that multiple pathways lead to myometrial activation. The clinical corollary is that combinations of tocolytics that operate via different mechanisms may be more effective than single agents. It may also be necessary to divide preterm labour into groups based on underlying mechanisms and to tailor therapy accordingly.

Progesterone regulates catechol-O-methyl transferase gene expression in breast cancer cells: distinct effect of progesterone receptor isoforms

There is strong evidence that catechol-O-methyl transferase (COMT) protects breast cells against estrogen-induced cancer by detoxifying catecholestrogens, the carcinogenic estrogen metabolites. COMT gene expression is controlled by two promoters - a proximal promoter (COMTP1) and a distal promoter (COMTP2) - that regulate the expression of soluble (S-COMT) and membrane-bound (MB-COMT) isoforms, respectively. We investigated the transcriptional regulation of the COMT gene by progesterone/progesterone receptors in breast cancer cells. Our results indicated that progesterone (P4) downregulates COMT gene expression in breast cancer cell lines. In addition, the COMTP1 and COMTP2 harbor several progesterone response elements (PREs). Electrophoretic mobility shift assay (EMSA) indicated that nuclear extracts of T47D cells bind to the identified PREs in COMTP1. Site-directed mutagenesis of PREs in COMTP1 not only reversed the P4-induced inhibition of COMTP1, but also increased its basal activity. The two progesterone receptor isoforms, PR-A and PR-B, were found to have opposite effects on the regulation of P4 in COMT expression; PR-A is associated with P4-induced upregulation of COMT, while PR-B is associated with P4-induced downregulation of COMT. In summary, our data demonstrated that P4 downregulates the COMT gene expression through multiple PREs in the COMT promoters and that different progesterone receptor isoforms have distinctive effects on COMT gene expression.

The cyclic AMP-dependent protein kinase A pathway is involved in progesterone effects on calcitonin secretion from TT cells

It is well known that gonadal steroid hormones influence the level of plasma calcitonin (CT), but the mechanism by which progesterone affects CT secretion is not clear. Immortalized TT cells are a reliable model system for studying the endocrine function of human parafollicular cells. In the present study, the effects of progesterone on CT secretion were examined in TT cells. TT cells were incubated in medium containing vehicle (DMSO), progesterone or BSA-progesterone for 60 or 150 min, and then the levels of CT in the medium, progesterone receptors, cAMP accumulation and CT mRNA expression were measured. To study the correlation between progesterone effects and the cAMP-dependent protein kinase A (PKA) pathway, cell lysates or cells in 24-well plates were treated with either vehicle or progesterone plus RU486, SQ22536, KT5720, or 3-isobutyl-1-methylxanthine. Then, adenylyl cyclase and protein kinase A (PKA) activities were measured in the cell lysates, and the CT levels were measured in the medium from the 24-well plate. The activated cAMP response element binding protein (P-CREB) was also measured by immunofluorescence. Administration of 1 microM progesterone or 500 nM BSA-progesterone increased the secretion of CT by 381% and 100%, respectively. Progesterone receptors A and B were downregulated by progesterone treatment. The cAMP concentration, adenylyl cyclase and PKA activity, CT mRNA expression, and nuclear P-CREB concentrations all showed an increase after progesterone treatment. RU486, SQ22536 and KT5720 inhibited the progesterone-stimulated effects. These results suggest that a cAMP-dependent PKA pathway is involved in progesterone-stimulated effects on CT secretion from TT cells.

Mechanisms of progesterone action in inhibiting prematurity

Progesterone is a steroid hormone that plays an integral role in each step of human pregnancy. In early pregnancy, progesterone produced by the corpus luteum is critical to the maintenance of early pregnancy until the placenta takes over this function at 7 to 9 weeks of gestation, hence its name (pro-gestational steroid hormone). The role of progesterone in later pregnancy, however, is less clear. It has been proposed that progesterone may be important in maintaining uterine quiescence in the latter half of pregnancy by limiting the production of stimulatory prostaglandins and inhabiting the expression of contraction-associated protein genes within the myometrium. Although systemic progesterone withdrawl may not correlate directly with the onset of labour in humans, there is increasing evidence to suggest that progesterone exerts its influence indirectly via a 'functional' withdrawl at the level of the uterus. The molecular mechanisms by which progesterone is able to maintain uterine quiescence and prevent preterm birth in some high-risk women are not clear. Six putative mechanisms have been proposed in the literature by both US and other investigators and are explored in this review.

Identification of a family of DNA-binding proteins with homology to RNA splicing factors

We describe a unique family of human proteins that are capable of binding to the cAMP regulatory element (CRE) and that are homologous to RNA splicing proteins. A human cDNA was isolated that encodes a protein with a distinctive combination of modular domain structures: 2 leucine-zipper-like domains, a DNA-binding zinc-finger-like domain, an RNA-binding zinc-finger-like domain, and 2 coiled-coil protein-protein interaction domains. It also has a serine-arginine-rich domain, commonly found in proteins involved in RNA splicing. The protein was discovered using the CRE as bait in a yeast 1-hybrid assay. It was then shown to bind specifically to the CRE in vitro using gel shift assays. We have named the protein CRE-associated protein (CREAP). We show that it is widely expressed in human tissues but is highly expressed in several fetal tissues and in several regions of the adult brain. CREAP is closely related to 2 human proteins of unknown function. CREAP shows significant homology with a small nuclear ribonucleoprotein of yeast, Luc7p, involved in 5' splice site recognition. The 3 human CREAP proteins form a unique family with the potential to act as transcription factors that link to RNA processing.

Identification of transcription factors at the site of implantation in the later stages of murine pregnancy

Despite medical advances, preterm delivery continues to complicate 12% of all births in the United States and is a major cause of neonatal deaths. One of the reasons that preterm labor continues to be a significant problem is that very little is understood about the factors involved in normal labor. Many investigators have studied parturition in the mouse and defined essential pathways for normal labor. Prostaglandins play an essential role in mouse labor and are important in human labor as well. We examined the 23 transcription factors from pregnant mouse uterus that change expression after the induction of cyclooxygenase-1, the enzyme that catalyzes the first committed step in prostaglandin synthesis. Usingin situhybridization, we have identified three of these transcription factors, Hoxa10, Hoxa11 and GILZ as being expressed in the decidua and regulated at the end of pregnancy. Both Hoxa10 and Hoxa11 are known to be critical for implantation, but very little is known about their roles in late gestation. GILZ has not previously been identified in the gravid uterus. In summary, we have identified three transcription factors that are regulated in the decidua at the end of pregnancy, suggesting a role in detachment of the fetus and placenta.

Difference in progesterone-receptor isoforms ratio between early and late first-trimester human trophoblast is associated with differential cell invasion and matrix metalloproteinase 2 expression

The expression profile of the progesterone-receptor isoforms and progesterone regulation of matrix metalloproteinase 2 (MMP2) were investigated in early and late first-trimester trophoblast cells. Human trophoblast cells were obtained from legal abortions (6-12 wk of gestation). Purity of 95-98% was verified using immunohistochemistry with specific antibodies. Evaluation of cell count was performed with XTT Reagent kit, and invasion was tested using Matrigel invasion assay. Zymography was used to detect proteolytic activity, and Western blot immunoassay was used to study protein concentration. Gene expression of PGRB, PGR, and MMP2 was studied using reverse transcription-polymerase chain reaction with the housekeeping gene GAPDH used for normalization. Promoter activity was determined using luciferase reporter assay. Differential progesterone-receptor profile was documented with the dominance of PGRB in early trophoblast and the dominance of PGRA in late trophoblast. This differential profile is compatible with the inverse effect of progesterone on the two cell populations, decreasing invasion and gelatinase expression in the early first-trimester trophoblast and increasing invasion and gelatinase expression in the late first-trimester trophoblast. A decrease in MMP2 promoter activity in early trophoblast cells exposed to progesterone suggests that MMP2 expression is regulated by progesterone at the transcriptional level as well. Early trophoblast cells transfected with expressing vector for PGR encoding PGRA revealed less MMP2 activity and reversal of its response to progesterone similar to the effect observed in late trophoblast cells.