Sex-specific and lasting effects of a single course of antenatal betamethasone treatment on human placental 11ß-HSD2.

INTRODUCTION: We have previously shown that even a single course of antenatal betamethasone (BET) as an inductor for lung maturity reduces birth weight and head circumference. Moreover, animal studies link BET administration to alterations of the hypothalamic-pituitary-adrenal-gland-axis (HPA). The unhindered development of the fetal HPA axis is dependent on the function and activity of 11ß-hydroxysteroiddehydrogenase type 2 (11ß-HSD2), a transplacental cortisol barrier. Therefore, we investigated the effects of BET on this transplacental barrier and fetal growth. METHODS: Pregnant women treated with a single course of BET between 23 + 5 to 34 + 0 weeks of gestation were compared to gestational-age-matched controls. Placental size and neonatal anthropometrics were taken. Cortisol and ACTH levels were measured in maternal and umbilical cord blood samples. Placental 11ß-hydroxysteroiddehydrogenase type 1 (11ß-HSD1) protein levels and 11ß-HSD2 protein and activity levels were determined. Parameters were analyzed independent of sex, and in subgroups divided by gender and gestational age. RESULTS: In term born females, BET administration was associated with reduced head circumference and decreased 11ß-HSD2 protein levels and enzyme activity. Males treated with BET, especially those born prematurely, showed increased 11ß-HSD2 protein levels. CONCLUSION: A single course of BET alters placental glucocorticoid metabolism in a sex-specific manner. Decreased 11ß-HSD2 levels in term born females may lead to an increased placental transfer of maternal cortisol and therefore result in a reduced head circumference and a higher risk for altered stress response in adulthood. Further research is needed to conclude the significance of increased 11ß-HSD2 levels in males.

Expression of natural antimicrobials by human placenta and fetal membranes.

Preterm birth associated with infection is a major clinical problem. We hypothesized that this condition is associated with altered expression of natural antimicrobial molecules (beta-defensins (HBD), elafin). Therefore, we examined expression of these molecules and their regulation by proinflammatory cytokines in placentae and fetal membranes from term pregnancy. HBD1-3 and elafin were localized by immunohistochemistry in fetal membranes and placenta. Real-time quantitative PCR was used to examine mRNA expression in primary trophoblast cells treated with inflammatory molecules. HBD1-3 and elafin were immunolocalized to placental and chorion trophoblast layers of fetal membranes and placenta. Immunoreactivity was also observed in amnion epithelium and decidua. No differences were noted between samples from women who were not in labour compared to those in active labour. In in vitro cultures of primary trophoblast cells, HBD2 and elafin mRNA expression was upregulated by the proinflammatory cytokine, IL-1beta. These results suggest that the chorion and placental trophoblast layers may be key barriers to the progression of infection in the pregnant uterus. Natural antimicrobial expression may be altered in response to inflammatory mediator expression associated with the onset of labour and/or uterine infection, providing increased protection when the uterus may be particularly susceptible to infection.

Innate immune defences in the human uterus during pregnancy.

The prevention of uterine infection is critical to appropriate fetal development and term delivery. The innate immune system is one component of the uterine environment and has a role in prevention of uterine infection. Natural antimicrobials are innate immune molecules with anti-bacterial, anti-viral and anti-fungal activity. We discuss two groups of natural antimicrobials in relation to pregnancy: (i) the defensins; and (ii) the whey acidic protein motif containing proteins, secretory leukocyte protease inhibitor (SLPI) and elafin. Human beta-defensins (HBD) 1-3 are expressed by placental and chorion trophoblast, amnion epithelium and decidua in term and preterm pregnancy. Elafin shows a similar pattern of localisation while SLPI is produced only by amnion epithelium and decidua. Evidence suggests that there is aberrant production of some natural antimicrobials in pathologic conditions of pregnancy. In preterm premature rupture of membranes (PPROM) levels of SLPI and elafin are reduced in amniotic fluid and fetal membranes, respectively. Elafin and HBD3 increase in chorioamnionitis and levels of the alpha-defensins, HNP1-3, increase in maternal plasma and amniotic fluid in women affected by microbial invasion of the uterus. In vitro culture studies have suggested a mechanism for increased production of natural antimicrobials in chorioamnionitis. Elafin, SLPI, HBD2 and 3 are all upregulated by inflammatory molecules in cells derived from gestational tissues. In summary, production of natural antimicrobials at key sites within the pregnant uterus suggests an important role in prevention of uterine infection during pregnancy and labour. Aberrant production of these molecules in PPROM and chorioamnionitis suggests that they also have a role in pathologic conditions. In particular, upregulation of these molecules by inflammatory molecules present in chorioamnionitis will ensure a robust response to infection.

Expression and localization of cellular prion and COMMD1 proteins in human placenta throughout pregnancy.

Copper is an essential trace element for successful pregnancy. However, the mechanisms by which copper is transported from maternal circulation to the fetus have not been clearly elucidated. Two proteins, cellular prion (PrP(C)) and COMMD1, are known to be responsible for prion diseases and canine copper toxicosis, respectively, and are thought to play a role in copper homeostasis. However, their placental expression and localization throughout human gestation are still unknown. In this study, we used quantitative RT-PCR, western blotting and immunohistochemistry to investigate in detail the expression and localization of PrP(C) and COMMD1 proteins in human placenta throughout pregnancy. Our results show that both proteins are expressed in human placenta. PrP(C) showed the highest mRNA and protein expression levels during the first trimester of pregnancy. PrP(C) and COMMD1 proteins are similarly localized within the placental villi. Both proteins are present in the syncytiotrophoblast, the cytotrophoblast, vascular endothelial cells and Hofbauer cells. These data offer some insights into possible roles for PrP(C) and COMMD1 within the placenta.

IL-1beta treatment does not co-ordinately up-regulate mPGES-1 and COX-2 mRNA expression, but results in higher degree of cellular and intracellular co-localization of their immunoreactive proteins in human placenta trophoblast cells.

PGE2 is involved in initiation and progression of labor in many species. Biosynthesis of PGE2 is mediated by cyclooxygenases (COX) and prostaglandin E synthases (PGES). mPGES-1 and COX-2 form an inducible pathway for PGE2 production in many cell systems. In this study we investigated whether mPGES-1 is involved in cytokine induced PGE2 biosynthesis in human trophoblast cells. We have evaluated the cellular and intracellular co-localization of mPGES-1 and COX-2, as well as cPGES and COX-1 in human trophoblast cells by dual immunofluorescent staining. The effect of IL-1beta on mPGES-1 and COX-2 co-localization, such as would occur with infection, and the regulatory effects of pro-inflammatory cytokines IL-1beta and TNF-alpha on transcriptional activity of mPGES-1 and COX-2 in these cells were also studied. We found that in cultured unstimulated trophoblasts, some cells expressed predominantly either mPGES-1 or COX-2, though there were cells co-expressing both enzymes. With IL-1beta treatment, mPGES-1 and COX-2 became more consistently co-localized. mPGES-1 was not transcriptionally co-induced with COX-2 by the cytokine treatment. We conclude that mPGES-1 is not involved in the inducible COX-2 mediated pathway for PGE2 biosynthesis at the transcriptional level, however, the treatment with IL-1beta results in a higher degree of co-ordination of the mPGES-1 and COX-2 protein immunolocalization, eliciting PGE2 synthesis.

Synthetic glucocorticoids: antenatal administration and long-term implications.

A clear relationship between intrauterine development and later life predisposition to long-term disease is well established. Weight at birth provides a surrogate measure for fetal development and low birth weight predicts changes in most endocrine axes in adulthood. The exposure of the fetus to elevated levels of either endogenous or synthetic glucocorticoids, pre and periconceptional nutritional status and immediate postnatal development including catch-up growth all contribute substantially to the development of adult onset disease. Fetal exposure to high levels of glucocorticoids has direct clinical relevance. Synthetic glucocorticoids (betamethasone/ dexamethasone) are administered to women at risk of preterm delivery to advance fetal maturation and reduce neonatal morbidity and mortality. However, in human pregnancy, evidence suggests that fetal exposure to synthetic glucocorticoids has detrimental effects on birth outcome, childhood cognition and long-term behavior. Studies in animals have established a link between prenatal exposure to synthetic glucocorticoids and alterations in fetal development as well as changes in placental function. These developmental alterations appear to be permanent. Whether this is the case in humans awaits long-term follow-up of children enrolled in randomized controlled trials of prenatal glucocorticoid therapy. The research challenges in this field are now centered on uncovering the mechanisms by which glucocorticoids are involved in programming the fetus for its future life, and discovering ways in which the effectiveness and safety of antenatal glucocorticoids can be enhanced. The purpose of this mini-review is to provide a background into the use of antenatal synthetic corticosteroids and to highlight and summarize recently published clinical and animal-based studies.

Localization of prostaglandin H synthase, prostaglandin dehydrogenase, corticotropin releasing hormone and glucocorticoid receptor in rhesus monkey fetal membranes with labor and in the presence of infection.

Prostaglandins (PGs) play a central role in primate parturition by their actions on uterine contractility and on cervical ripening. Rhesus monkey placentation is hemochorial and the endocrine events surrounding parturition are qualitatively similar to human pregnancy. Although there is an increase in PG production before the onset of labor, little is known about the cellular localization of the PGH synthase (PGHS) or the 15-hydroxy PG dehydrogenase (PGDH) in the fetal membranes of nonhuman primates and whether it changes at term in spontaneous labor or during preterm labor associated with infection. Placental corticotropin releasing hormone (CRH) and the glucocorticoid receptor (GR) have also been implicated as mediators in parturition by virtue of their roles in PG production. We utilized immunohistochemical methods to localize the inducible isoform PGHS-2, PGDH, GR and CRH in rhesus monkey amnion, chorion and attached decidua. Tissues were obtained at cesarean section during late pregnancy, in spontaneous labor at term and in premature labor induced by Group B streptococcal intraamniotic infection. Specific staining for immunoreactive (ir)-PGHS-2 was observed in amnion epithelial and mesenchymal cells and to a lesser extent in chorion and decidua. In contrast, ir-PGDH was localized primarily to the extravillous trophoblast layer of chorion. GR was localized to both the cytoplasm and nucleus of amnion epithelial cells, subepithelial fibroblasts, chorion trophoblasts and in decidua. Immunostaining for CRH was found in amnion and in scattered decidual cells but was most intense in the chorion trophoblast layer. There was no demonstrable change in this overall pattern of immunostaining in association with the onset of labor at term except for a decrease in staining for ir-PGDH in chorion. Experimental Group B streptococcal chorioamnionitis resulted in preterm labor and extensive necrosis of extravillous trophoblast cells with subsequent loss of chorionic ir-PGDH and relative sparing of ir-PGHS-2 in amnion epithelium which favors the net production of PGs. The expression pattern of these effectors in the rhesus monkey fetal membranes points to a functional role of PGs and glucocorticoids in the process of term and preterm parturition which is similar to that in human pregnancy.

Effects of maternal dexamethasone treatment early in pregnancy on glucocorticoid receptors in the ovine placenta.

The effects of endogenous cortisol on binucleate cells (BNCs), which promote fetal growth, may be mediated by glucocorticoid receptors (GRs), and exposure to dexamethasone (DEX) in early pregnancy stages of placental development might modify this response. In this article, we have investigated the expression of GR as a determinant of these responses. Pregnant ewes carrying singleton fetuses (n = 119) were randomized to control (2 mL saline/ewe) or DEX-treated groups (intramuscular injections of 0.14 mg/kg ewe weight per 12 hours) at 40 to 41 days of gestation (dG). Placental tissue was collected at 50, 100, 125, and 140 dG. Total glucocorticoid receptor protein (GRt) was increased significantly by DEX at 50 and 125 dG in females only, but decreased in males at 125 dG as compared to controls. Glucocorticoid receptor α (GRα) protein was not changed after DEX treatment. Three BNC phenotypes were detected regarding GRα expression (++, +-, --), DEX increased the proportion of (++) and decreased (--) BNC at 140 dG. Effects were sex- and cell type dependent, modifying the responsiveness of the placenta to endogenous cortisol. We speculate that 3 maturational stages of BNCs exist and that the overall activity of BNCs is determined by the distribution of these 3 cell types, which may become altered through early pregnancy exposure to elevated glucocorticoids.

Regulation of 15-hydroxy prostaglandin dehydrogenase by corticotrophin-releasing hormone through a calcium-dependent pathway in human chorion trophoblast cells.

Prostaglandins (PGs) play a crucial role in mediating parturition events, and their synthesis and metabolism are regulated by PG H synthase and 15-hydroxy-PG dehydrogenase (PGDH), respectively. Within the chorion tissue, it is the actions of PGDH that predominate. Throughout gestation, the fetal membranes secrete increasing amounts of CRH. We hypothesized that CRH, produced locally in the chorion, could act to modulate PGDH activity throughout gestation. To investigate this, we obtained Percoll-purified human chorion and placental trophoblast cells from uncomplicated term pregnancies and cultured them for 72 h. Activity of PGDH was assessed by incubation (4 h) with PGF(2alpha) (282 nM) and measurement of conversion to 13,14-dihydro-15-keto PG F(2alpha). Dose-response curves were constructed for the chorion cell cultures with CRH or 8-bromo-cAMP. To investigate the role of CRH and calcium, cells were treated with either astressin, a CRH antibody, BAPTA, or EGTA. CRH (0-1 micro M) had no effect on PGDH activity; however, cells treated with astressin (10 micro M), with or without exogenous CRH (1 micro M), and cells treated with a CRH antibody showed a significant decrease in PGDH activity. 8-Bromo-cAMP (0-1 mM) had no effect on 13,14-dihydro-15-keto PG F(2alpha) output in chorion trophoblast cells but significantly decreased output from placental trophoblast cells. Cells treated with either BAPTA-AM or EGTA had significantly reduced PGDH activity; and, at intermediate concentrations of chelator, exogenous CRH restored PGDH activity. We suggest that, in chorion trophoblast cells, endogenously produced CRH exerts a tonic stimulatory effect on PGDH activity and may help maintain a metabolic barrier, preventing the transfer of bioactive PGs from the chorioamnion to the myometrium.

Oxygen regulation of placental 11 beta-hydroxysteroid dehydrogenase 2: physiological and pathological implications.

Preeclampsia (PE) is a major cause of maternal and perinatal morbidity and mortality. The genesis of PE is related to deficient trophoblast invasion of maternal spiral arteries, which might result in a reduction of placental (PL) oxygen (O(2)). An absence of increased O(2) that normally occurs around the 10-12th wk of gestation results in aberrant expression of genes that might contribute to the pathophysiology of PE. We examined the expression and regulation of PL 11 beta-hydroxysteroid dehydrogenase 2 (11 beta-HSD) in normal pregnancies and in PE. Two types of 11 beta-HSD exist in the placenta, 11 beta-HSD1 and 11 beta-HSD2. 11 beta-HSD2 is thought to protect the fetus from cortisol excess. In PE, both the expression and activity of PL 11 beta-HSD2 were reduced significantly compared with those in age-matched controls. As PE is associated with a reduction of PL O(2), we next investigated whether in normal pregnancy 11 beta-HSD2 expression changes at the time of the increase in O(2). 11 beta-HSD2 was detected as early as 5 wk, with expression limited to the syncytiotrophoblast (ST). At 10-12 wk, this expression increased and was also found in the cytotrophoblast and extravillous trophoblast. These results were substantiated by Western blot. The ability of O(2) to regulate 11 beta-HSD2 was determined both in cultures of villous explant from early gestation and in term trophoblast cells after incubation under 3% or 20% O(2). Villous explants cultured under 20% O(2) showed higher enzyme activity and expression compared with 3% O(2). Term trophoblast cells also exhibited higher enzyme activity at 20% vs. 3% O(2). No change in 11 beta-HSD1 expression was observed in early pregnancy or in PE. This is the first report to suggest that 11 beta-HSD2 is O(2) dependent in first and third trimester placenta during human gestation.

Expression of prostaglandin I(2) synthase, but not prostaglandin E synthase, changes in myometrium of women at term pregnancy.

Prostaglandins (PGs) act as potent uterotonins at the time of labor. Prostaglandin E synthase (PGES) is responsible for the formation of PGE(2), a uterotonin. PGI(2) is synthesized by the prostaglandin I synthase enzyme (PGIS) and contributes to relaxation in the lower uterine segment. We examined the expression of membrane-bound PGES and PGIS in myometrium from pregnant women during preterm and term labor. Tissues were collected from the lower uterine segment from preterm no labor, preterm labor, term no labor, and term labor patients and used for immunohistochemistry and Western blot analysis using specific antibodies. Immunoreactive (ir-) PGES and PGIS proteins were localized to the cytoplasm of myocytes of the myometrium and vascular smooth muscle cells. Ir-PGES was also detected in vascular endothelial cells. Western blot analyses revealed a predominant protein band of 180 kDa, and a second 16-kDa band for ir-PGES and 56-kDa band for ir-PGIS. There was no significant change in ir-PGES protein (180 or 16 kDa) or mRNA levels with preterm or term labor or gestational age. There was a significant decrease in PGIS mRNA and protein with advancing gestational age. We conclude that the gestational age decrease in the inhibitory PGIS is consistent with lessening of its influence in myometrium at the time of labor. The lack of change in PGES indicates that alterations at other points along the pathway of arachidonic acid metabolism may be of greater importance in affecting local changes in PGE(2).

Differential changes in 15-hydroxyprostaglandin dehydrogenase and prostaglandin H synthase (types I and II) in human pregnant myometrium.

Prostaglandins (PGs) play a key role in the onset of labor in many species and regulate uterine contractility and cervical dilatation. Therefore, the regulation of prostaglandin output by PG synthesizing (PGHS-I and PGHS-II) and metabolizing (PGDH) enzymes in the human myometrium may determine uterine activity patterns in human labor both at preterm and at term. We hypothesized that expression of PGHS isozymes and PGDH in myometrium from women at preterm and term labor would change to favor increased uterotonin (PG) production. Myometrial samples were obtained from the lower uterine segment during cesarean section deliveries from women presenting in preterm, no labor; preterm, labor; term, no labor; term, labor. Immunoreactive (ir-) PGHS and PGDH protein was localized using immunohistochemistry, and changes in protein levels were determined by Western blotting. Ir-PGHS-I and PGHS-II proteins were localized only to myocytes. Ir-PGDH was localized to myocytes in all samples of myometrium examined, but using dual immunofluorescence and immunohistochemistry, ir-PGDH was also detected in cells of the connective tissue. Levels of ir-PGHS-I and PGHS-II protein were not significantly different between no labor and labor tissues, either at preterm or at term. There was no significant effect of gestational age on levels of PGDH, PGHS-I, and PGHS-II protein, but there was a significant decrease in ir-PGDH protein levels in myometrium with labor both at preterm and at term. In addition, there was a decrease in PGDH activity in myometrium from women in labor, both at preterm and at term. Therefore, we conclude that PGDH, PGHS-I, and PGHS-II protein localize within the myocytes of the human pregnant myometrium. A decrease in PGDH protein and activity occurs in association with active labor and may contribute to the amount of bioactive PGs available to act within the human pregnant myometrium at that time.

Intramolecular interactions between the AF3 domain and the C-terminus of the human progesterone receptor are mediated through two LXXLL motifs.

The human progesterone receptor (PR) exists in two major forms, PRA and PRB, which differentially regulate gene transcription in a cell- and promoter-specific manner. The molecular mechanisms underlying this differential transcriptional activity have been attributed to the presence of a unique AF3 domain within PRB that may result in the two isoforms adopting different protein conformations. We demonstrate here that in myometrial cells, PRB exhibits strong progesterone-dependent transcriptional activity that is dependent on the presence of two LXXLL motifs within the AF3 domain. In vitro and in vivo protein interaction assays indicate that these motifs mediate the direct interaction between the AF3 domain and C-PR in a progesterone-dependent manner. Mutation of either of the LXXLL motifs or deletion of the last 30 amino acids within the C-terminus disrupts this interaction and progesterone-dependent transcriptional activity of PRB. Members of the p160 family of co-activators (such as GRIP-1) also interact with C-PR through their LXXLL motifs. However, GRIP-1 does not compete with AF3 but rather acts to synergize these two transactivation domains. Our data suggest that a failure to form an appropriate AF3-C-terminus interaction results in an inability of co-activators to induce maximal PR-dependent transactivation. The absence of an AF3 domain within PRA may account for its inability to activate progesterone-responsive genes, as well as its actions as a dominant trans-repressor.

Repeated maternal glucocorticoid administration and the developing liver in fetal sheep.

Prenatal glucocorticoid exposure has been associated with a reduction in birth weight and postnatal alterations in glucose homeostasis and hypothalamic-pituitary-adrenal (HPA) axis function. The mechanisms underlying these responses are unknown, although changes in fetal hepatic development may play an important role. The fetal liver produces key regulators of fuel metabolism and of the developing HPA axis that are altered by glucocorticoids. The local availability of glucocorticoids is regulated, in part, by corticosteroid-binding protein (CBG), glucocorticoid receptors (GR) and by the enzyme 11beta-hydroxysteroid dehydrogenase (11betaHSD), but the effects of maternal glucocorticoid administration on the expression of these genes in the fetal liver are unknown. 11betaHSD1 is the predominant form of this enzyme present in the liver and is responsible for the conversion of cortisone to cortisol. To determine if prenatal glucocorticoid exposure alters fetal hepatic regulation of CBG, 11betaHSD1 and GRs, we treated pregnant ewes with betamethasone (0.5 mg/kg) intramuscularly at 104, 111 and 118 days of gestation (term 150 days). Animals were killed at 125 or 146 days of gestation. Maternal betamethasone administration did not alter mean cord plasma glucose but significantly decreased cord plasma insulin levels (P<0.05) at 125 days of gestation. At 146 days of gestation, cord plasma glucose levels were significantly increased without alterations in insulin levels following maternal betamethasone treatment (P<0.05). Maternal betamethasone administration resulted in a significant increase in fetal hepatic 11betaHSD1 mRNA and protein levels at 125 days of gestation (P<0.05). CBG mRNA levels were significantly elevated over control at 125 days although levels of CBG protein were not significantly different. GR protein levels were not statistically different at either 125 or 146 days of gestation following glucocorticoid administration. These data suggest that prenatal betamethasone exposure in the ovine fetus results in alterations in cord glucose and insulin levels as well as alterations in hepatic 11betaHSD1 mRNA and protein expression. These changes in 11betaHSD1 increase the potential to generate local cortisol from circulating cortisone. We speculate that this could affect expression of glucocorticoid-dependent hepatic enzymes involved with the regulation of glucose production and HPA responsiveness.

The late gestation increase in circulating ACTH and cortisol in the fetal sheep is suppressed by intracerebroventricular infusion of recombinant ovine leptin.

The obese gene product leptin, originally characterised as an adipocyte hormone coordinating the behavioural and neuroendocrine responses to starvation, is expressed in fetal adipocytes and placental trophoblast cells and is present in the fetal circulation. Concentrations of leptin in fetal blood correlate with fetal bodyweight and fat mass. In post-natal life, leptin conveys information about calorie intake and the state of adipose tissue energy stores, and plasma leptin levels are generally inversely correlated with hypothalamo-pituitary adrenal (HPA) activity. Late fetal life is characterised by increasing HPA activity that prepares the fetus for extrauterine life and initiates the endocrine cascade leading to parturition. We have investigated the hypothesis that leptin in the fetal circulation can inhibit the fetal HPA axis, thereby providing a mechanism by which the fetus can determine the fine timing of parturition as long as it is adequately nourished and growing appropriately. Here we show that a 5-day intracerebroventricular infusion of leptin to the sheep fetus in late gestation inhibits the pre-parturient rise in ACTH and cortisol concentrations, and that this seems to be a centrally mediated effect.

The effect of prenatal betamethasone administration on postnatal ovine hypothalamic-pituitary-adrenal function.

Prenatal exposure to glucocorticoids is associated with alterations in fetal growth and endocrine function. However, few studies have examined the effects of clinically relevant doses of glucocorticoids on postnatal hypothalamic-pituitary-adrenal (HPA) function. To determine the effects of maternal or fetal betamethasone administration (0.5 mg/kg maternal or estimated fetal weight) on postnatal HPA function at 6 months and 1 year postnatal age, pregnant ewes were randomized into the following treatment groups: no treatment (n=6); maternal saline (n=6); single maternal betamethasone (M1) (n=6); repeated maternal betamethasone (M4) (n=6); fetal saline (n=5); single fetal betamethasone (n=6) and repeated fetal betamethasone (F4) (n=6). Single injections were given at 104 days of gestation and repeated injections at 104, 111, 118 and 125 days. Lambs were born spontaneously and the ACTH and cortisol responses to i.v. corticotropin-releasing hormone (CRH) (0.5 microg/kg) plus arginine vasopressin (AVP) (0.1 microg/kg) were measured at 6 months and 1 year postnatally. At 6 months postnatal age, neither maternal nor fetal prenatal betamethasone administration altered significantly the ACTH and cortisol responses to CRH+AVP. However, in animals at 1 year postnatal age, a previous single injection of betamethasone to the mother (M1) resulted in significantly elevated basal and stimulated cortisol levels (P<0.05), without significant change in the ACTH response. In contrast, betamethasone administration to the fetus resulted in significantly attenuated ACTH responses to CRH+AVP at 1 year compared with control animals (P<0.05), but these were not associated with any significant changes in basal or stimulated cortisol levels. All control animals exhibited a significant increase in peak ACTH responses to CRH+AVP between 6 months and 1 year postnatal age (P<0.05). After prenatal betamethasone (F4, M4) the difference in peak ACTH response between animals at 6 months and 1 year postnatal age was abolished. We conclude that in sheep between 6 months and 1 year postnatal age, HPA function undergoes developmental changes that are influenced by prenatal glucocorticoid exposure. Furthermore, the effects of glucocorticoid on postnatal HPA responses may vary according to the time in gestation that the steroid was administered, and whether it was given directly into the fetal or maternal compartment.

Effects of cortisol and oestradiol on hepatic 11beta-hydroxysteroid dehydrogenase type 1 and glucocorticoid receptor proteins in late-gestation sheep fetus.

In the late-gestation sheep, increased fetal plasma cortisol concentration and placental oestradiol (E(2)) output contribute to fetal organ maturation, in addition to the onset of parturition. Both cortisol and E(2) are believed to regulate the enzyme 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1), which interconverts bioactive 11-hydroxy glucocorticoids and their inactive 11-keto metabolites. 11beta-HSD1, abundantly expressed in fetal liver, operates primarily as a reductase enzyme to produce bioactive cortisol and thus regulates local hepatic glucocorticoid concentrations. Cortisol acts through the glucocorticoid receptor (GR) present in the liver. In this study, we examined the effects of cortisol and E(2) on hepatic 11beta-HSD1 and GR in the liver of chronically catheterized sheep fetuses treated with saline (n=5), cortisol (1.35 mg/h; n=5), saline+4-hydroxyandrostendione, a P450 aromatase inhibitor (4-OHA; 1.44 mg/h; n=5), or cortisol+4-OHA (n=5). Cortisol infusion resulted in increased plasma concentrations of fetal cortisol and E(2); concurrent administration of 4-OHA attenuated the increase in plasma E(2) concentrations. Using immunohistochemistry, we showed that fetal hepatocytes expressed both 11beta-HSD1 and GR proteins. Cortisol treatment increased GR in both cytosol and nuclei of hepatocytes; concurrent administration of 4-OHA was associated with distinct nuclear GR staining. Western blot revealed that cortisol, in the absence of increased E(2) concentrations, significantly increased concentrations of 11beta-HSD1 (34 kDa) and GR (95 kDa) proteins. 11beta-HSD1 enzyme activity was measured in the liver microsomal fraction in the presence of [(3)H]cortisone (10(-)(6) M) or [(3)H]cortisol (10(-)(6) M) and NADPH (reductase activity) or NADP(+) (dehydrogenase activity) respectively. 11beta-HSD1 reductase activity was significantly greater in the presence of cortisol. In summary, we found that, in sheep during late gestation, cortisol increased both 11beta-HSD1 and GR in the fetal liver, and these effects were accentuated in the absence of increased E(2).

Mechanisms of term and preterm birth.

Labour at term and preterm results from activation and then stimulation of the myometrium. Activation can occur through mechanical stretch of the uterus, and by endocrine pathways resulting from increased activity of the fetal hypothalamic-pituitary-adrenal axis. In women and in experimental animals, cortisol likely contributes to increased prostaglandin production in fetal tissues through up-regulation of the type 2 prostaglandin H2, synthase-2 (PGHS-2) and down-regulation of 15-OH prostaglandin dehydrogenase. Cortisol increases expression of prostaglandin dehydrogenase in the chorion by reversing the stimulatory effect of progesterone, and may represent "progesterone withdrawal" in the primate. By competing with progesterone inhibition, cortisol also increases expression of placental corticotropin-releasing hormone. Other agents, such as pro-inflammatory cytokines, similarly up-regulate PGHS-2 and decrease expression of prostaglandin dehydrogenase. Oxytocin, produced locally within the intrauterine tissues, is also thought to be involved in parturition, and there is a marked increase in oxytocin receptor expression at term. There are thus several mechanisms by which labour at term or preterm may be initiated. These different mechanisms need to be considered in the development of strategies for the detection and management of women in preterm labour. Ongoing studies are investigating the use of oxytocin receptor antagonists, PGHS-2 inhibitors, and nitric oxide to prevent or regulate preterm labour. The presence of fibronectin in vaginal secretions, and elevated maternal serum levels of corticotropin-releasing hormone, estrogens, and cytokines have been examined as possible markers of preterm labour. However, at the present time, we do not have the ability to accurately predict or diagnose preterm labour, nor do we have specific or efficient methods to inhibit labour once it has started.

Growth restricting effects of a single course of antenatal betamethasone treatment and the role of human placental lactogen.

UNLABELLED: Betamethasone (BET) is a widely used treatment for women who are at high risk of preterm delivery. In sheep, BET-induced growth restriction was found to be associated with reduced placenta lactogen (PL), a key regulator of fetal growth. We therefore hypothesized that also in humans a single course of BET administration is associated with a reduction of PL, associated with a deceleration in fetal growth. OBJECTIVE: To investigate effects of a single course of antenatal BET in humans on birth weight and PL. METHODS: Women exposed to BET (2 × 12 mg; n = 44) with normally grown fetuses between 23 + 5 and 34 + 0 wks (weeks + days of gestation) who delivered between 23 + 5 to 42 + 0 wks were compared to gestational age-matched controls (n = 49). Maternal gestational blood samples were obtained before, during and after BET treatment and at the time of birth. MAIN OUTCOME MEASURES: BET effects on fetal anthropometrics, placental morphometry and placental PL-protein and maternal plasma levels. RESULTS: The mean duration of days between BET administration and birth was 52 days. BET treatment was associated with decreased birth weight (-18.2%), head circumference (-8.6%), body length (-6.0%), and placental width (-5.5%), as compared to controls. These changes were irrespective of possible maternal confounders (gestational age at birth, maternal age, maternal BMI gain during pregnancy, smoking etc.). However, neither PL-plasma levels within 48 h after BET treatment nor placental PL-protein levels and maternal plasma levels at birth were changed after BET treatment. In central regions of the placenta, BET treatment increased the circumference of syncytiotrophoblast nuclei by +4.7% and nucleus surface area by +9.4% compared to controls, but these changes were not related to placental PL-protein or maternal PL-plasma levels at birth. CONCLUSION: A single course of BET treatment was accompanied with reduced fetal growth, but this growth restricting effect was not associated with altered placental or maternal plasma PL levels. Altered expression of PL appears not to be causal for BET-induced fetal growth restriction in the human.