Characterization and gestational regulation of corticotropin-releasing hormone messenger RNA in human placenta

Human placenta releases extracellular vesicles carrying corticotrophin releasing hormone mRNA into the maternal blood

The human placenta releases diverse extracellular vesicles (EVs), including microvesicles (100-1000 nm) and exosomes (30-150 nm), into the maternal blood for feto-maternal communication. Exosomes and microvesicles contribute to normal pregnancy physiology and major pregnancy pathologies. Differences in miRNA expressions and protein content in placental exosomes have been reported in complicated pregnancies. During human pregnancy, Corticotropin-Releasing Hormone (CRH) is produced and released by the placenta into the maternal blood. CRH is involved in regulating gestational length and the initiation of labour. CRH mRNA levels in the maternal plasma rise with gestation. High levels of CRH mRNA are reported to be associated with preeclamptic and preterm pregnancies. However, the underlying mechanism of placental CRH mRNA secretion remains to be elucidated. We hypothesise that the placenta releases CRH mRNA packaged within extracellular vesicles (EVs) into the maternal blood. In this study, placental EVs (microvesicles and exosomes) were isolated from human term healthy placentas via villus washes and from explant culture media by differential centrifugation and purified by density gradient ultracentrifugation using a continuous sucrose gradient (0.25-2.5 M). Western blotting using placenta- and exosome-specific markers and electron microscopy confirmed exosomes and microvesicles in the placental wash and explant media samples. Real-time quantitative RT-PCR data detected CRH mRNA in placenta-derived EVs from placental washes and explants. We also sorted placenta-secreted EVs in maternal plasma samples (≥37 weeks) by high-resolution flow cytometry using a fluorescent-labelled PLAP antibody. CRH mRNA was demonstrated in placental EVs obtained from maternal blood plasma. We therefore show that human placental EVs carry CRH mRNA into the maternal blood. Our study implies that measuring CRH mRNA in placental EVs in the maternal plasma could beused for monitoring pregnancy.

A framework for testing pathways from prenatal stress-responsive hormones to cardiovascular disease risk

Cardiovascular disease (CVD) is a leading cause of death globally, with the prevalence projected to keep rising. Risk factors for adult CVD emerge at least as early as the prenatal period. Alterations in stress-responsive hormones in the prenatal period are hypothesized to contribute to CVD in adulthood, but little is known about relations between prenatal stress-responsive hormones and early precursors of CVD, such as cardiometabolic risk and health behaviors. The current review presents a theoretical model of the relation between prenatal stress-responsive hormones and adult CVD through cardiometabolic risk markers (e.g., rapid catch-up growth, high BMI/adiposity, high blood pressure, and altered blood glucose, lipids, and metabolic hormones) and health behaviors (e.g., substance use, poor sleep, poor diet and eating behaviors, and low physical activity levels). Emerging evidence in human and non-human animal literatures suggest that altered stress-responsive hormones during gestation predict higher cardiometabolic risk and poorer health behaviors in offspring. This review additionally highlights limitations of the current literature (e.g., lack of racial/ethnic diversity, lack of examination of sex differences), and discusses future directions for this promising area of research.

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.

Prenatal phthalate exposure in relation to placental corticotropin releasing hormone (pCRH) in the CANDLE cohort

CONTEXT

Phthalates may disrupt maternal-fetal-placental endocrine pathways, affecting pregnancy outcomes and child development. Placental corticotropin releasing hormone (pCRH) is critical for healthy pregnancy and child development, but understudied as a target of endocrine disruption.

OBJECTIVE

To examine phthalate metabolite concentrations (as mixtures and individually) in relation to pCRH.

DESIGN

Secondary data analysis from a prospective cohort study.

SETTING

Prenatal clinics in Tennessee, USA.

PATIENTS

1018 pregnant women (61.4% non-Hispanic Black, 32% non-Hispanic White, 6.6% other) participated in the CANDLE study and provided data. Inclusion criteria included: low-medical-risk singleton pregnancy, age 16-40, and gestational weeks 16-29.

INTERVENTION

None.

MAIN OUTCOME MEASURES

Plasma pCRH at two visits (mean gestational ages 23.0 and 31.8 weeks) and change in pCRH between visits (ΔpCRH).

RESULTS

In weighted quantile sums (WQS) regression models, phthalate mixtures were associated with higher pCRH at Visit 1 (β = 0.07, 95 %CI: 0.02, 0.11) but lower pCRH at Visit 2 (β = -0.08, 95 %CI: -0.14, -0.02). In stratified analyses, among women with gestational diabetes (n = 59), phthalate mixtures were associated with lower pCRH at Visit 1 (β = -0.17, 95 %CI: -0.35, 0.0006) and Visit 2 (β = -0.35, 95 %CI: -0.50, -0.19), as well as greater ΔpCRH (β = 0.16, 95 %CI: 0.07, 0.25). Among women with gestational hypertension (n = 102), phthalate mixtures were associated with higher pCRH at Visit 1 (β = 0.20, 95 %CI: 0.03, 0.36) and Visit 2 (β = 0.42; 95 %CI: 0.19, 0.64) and lower ΔpCRH (β = -0.17, 95 %CI: -0.29, -0.06). Significant interactions between individual phthalate metabolites and pregnancy complications were observed.

CONCLUSIONS

Phthalates may impact placental CRH secretion, with differing effects across pregnancy. Differences in results between women with and without gestational diabetes and gestational hypertension suggest a need for further research examining whether women with pregnancy complications may be more vulnerable to endocrine-disrupting effects of phthalates.

Molecular Mechanism and Pathways of Normal Human Parturition in Different Gestational Tissues: A Systematic Review of Transcriptome Studies

Objective: Genome-wide transcriptomic studies on gestational tissues in labor provide molecular insights in mechanism of normal parturition. This systematic review aimed to summarize the important genes in various gestational tissues around labor onset, and to dissect the underlying molecular regulations and pathways that trigger the labor in term pregnancies.

Data sources: PubMed and Web of Science were searched from inception to January 2021.

Study Eligibility Criteria: Untargeted genome-wide transcriptomic studies comparing the gene expression of various gestational tissues in normal term pregnant women with and without labor were included.

Methods: Every differentially expressed gene was retrieved. Consistently expressed genes with same direction in different studies were identified, then gene ontology and KEGG analysis were conducted to understand molecular pathways and functions. Gene-gene association analysis was performed to determine the key regulatory gene(s) in labor onset.

Results: A total of 15 studies, including 266 subjects, were included. 136, 26, 15, 7, and 3 genes were significantly changed during labor in the myometrium (seven studies, n = 108), uterine cervix (four studies, n = 64), decidua (two studies, n = 42), amnion (two studies, n = 44) and placenta (two studies, n = 41), respectively. These genes were overrepresented in annotation terms related to inflammatory and immune responses. TNF and NOD-like receptor signaling pathways were overrepresented in all mentioned tissues, except the placenta. IL6 was the only gene included in both pathways, the most common reported gene in all included studies, and also the gene in the central hub of molecular regulatory network.

Conclusions: This systematic review identified that genes involved in immunological and inflammatory regulations are expressed in specific gestational tissues in labor. We put forward the hypothesis that IL6 might be the key gene triggering specific mechanism in different gestational tissues, eventually leading to labor onset through inducing uterine contraction, wakening fetal membranes and stimulating cervical ripening.

Systematic Review Registration: Identifier [CRD42020187975].

Placental Corticotrophin-Releasing Hormone is a Modulator of Fetal Liver Blood Perfusion

CONTEXT

Variation in fetal liver blood flow influences fetal growth and postnatal body composition. Placental corticotrophin-releasing hormone has been implicated as a key mediator of placental-fetal perfusion.

OBJECTIVE

To determine whether circulating levels of placental corticotrophin-releasing hormone across gestation are associated with variations in fetal liver blood flow.

DESIGN

Prospective cohort study.

METHODS

Fetal ultrasonography was performed at 30 weeks' gestation to characterize fetal liver blood flow (quantified by subtracting ductus venosus flow from umbilical vein flow). Placental corticotrophin-releasing hormone was measured in maternal circulation at approximately 12, 20, and 30 weeks' gestation. Multiple regression analysis was used to determine the proportion of variation in fetal liver blood flow explained by placental corticotrophin-releasing hormone. Covariates included maternal age, parity, pre-pregnancy body mass index, gestational weight gain, and fetal sex.

RESULTS

A total of 79 uncomplicated singleton pregnancies were analyzed. Fetal liver blood flow was 68.4 ± 36.0 mL/min (mean ± SD). Placental corticotrophin-releasing hormone concentrations at 12, 20, and 30 weeks were 12.5 ± 8.1, 35.7 ± 24.5, and 247.9 ± 167.8 pg/mL, respectively. Placental corticotrophin-releasing hormone at 30 weeks, but not at 12 and 20 weeks, was significantly and positively associated with fetal liver blood flow at 30 weeks (r = 0.319; P = 0.004) and explained 10.4% of the variance in fetal liver blood flow.

CONCLUSIONS

Placental corticotrophin-releasing hormone in late gestation is a possible modulator of fetal liver blood flow and may constitute a biochemical marker in clinical investigations of fetal growth and body composition.

Cortisol and estriol responses to awakening in the first pregnancy trimester: Associations with maternal stress and resilience factors

BACKGROUND

Little is known about the maternal cortisol awakening response (CAR) in the first pregnancy trimester. Similarly unknown is how the CAR in early gestation relates to other steroid hormones, such as estriol. Maternal estriol in blood and urine is used to monitor fetal well-being since it is produced by the fetoplacental unit from fetal precursors. Low levels have been associated with maternal-fetal complications. We were recently able to show that estriol is measurable in maternal saliva from 6 weeks' gestation onwards. However, its pattern following morning awakening and potential links with salivary cortisol in early gestation is relatively unknown. In this prospective study, we explored the cortisol and estriol responses to morning awakening in first-trimester pregnant women, the potential association of these endocrine variables with maternal stress and resilience factors, and their predictive value for the further pregnancy course.

METHODS

Fifty-one women with an uncomplicated, singleton pregnancy responded to questionnaires measuring chronic and pregnancy-specific stress, emotional support, and daily uplifts at 6 weeks' gestation. At 8 and 10 weeks, the women collected saliva samples immediately, 30, and 60 min after morning awakening. After 12 weeks, 40 women reported on the further pregnancy course, of whom 6 had developed complications.

RESULTS

In response to morning awakening, cortisol levels increased significantly at 10 weeks (p = .04), while estriol levels decreased significantly at both 8 and 10 weeks (p < .001). A stronger cortisol increase was linked to a stronger estriol decrease at 8 (p = .03), but not at 10 weeks. Then, perceived emotional support at 6 weeks was negatively associated with cortisol baseline at 8 (p = .01) and positively with estriol baseline at 10 weeks (p = .03). Moreover, higher pregnancy-specific stress was related to a lower estriol baseline at 8 weeks (p = .047). Furthermore, compared to healthy women, those with complications at follow-up had already reported less emotional support (p = .03) and fewer daily uplifts (p = .03) at 6 weeks. These women also seemed to lack a significant estriol response to morning awakening at 8 weeks (p > .10).

DISCUSSION

These findings advance our knowledge of cortisol and estriol secretion following morning awakening and encourage the investigation of E3 in addition to cortisol when researching prenatal stress and its consequences for maternal and fetal health.

Placental 11β-HSD2 downregulated in HIV associated preeclampsia

Preeclampsia (PE) and human immunodeficiency virus (HIV) have been linked with marked increases in maternal stress, resulting in a significant change in placental function ranging from alterations in placental structure to the precise and delicate transformations in placental gene expression. Such changes may lead to altered transport of essential signals to the fetus, which can have long-term impacts on offspring health and consequently affect fetal neurodevelopment. Therefore, this work investigated the role of placental 11β-hydroxysteroid dehydrogenase types 2 (11β-HSD2) in HIV associated preeclampsia. The placenta were obtained from 76 pregnant women, which were stratified based on pregnancy type and HIV status into; Normotensive HIV negative, normotensive HIV positive, PE HIV negative and PE HIV positive. The placental tissue was processed for immunocytochemistry and stained with rabbit polyclonal to 11β-HSD2 Our results showed significant downregulation in the placental expression of 11β-HSD2 in both the conducting and exchange villi of PE and HIV-positive patients when compared with Normotensive and HIV-negative individuals, respectively. Our results provide inferential evidence for comorbidity of PE and HIV in the downregulation of placental 11β-HSD2 enzyme function, which mediates the programmed outcomes of an adverse maternal environment during pregnancy and long-term impacts on offspring health and consequently affects fetal neurodevelopment.

UCN2: a new candidate influencing pancreatic β-cell adaptations in pregnancy

The corticotropin-releasing hormone (CRH) family of peptides, including urocortin (UCN) 1, 2 and 3, are established hypothalamic neuroendocrine peptides, regulating the physiological and behaviour responses to stress indirectly, via the hypothalamic-pituitary-adrenal (HPA) axis. More recently, these peptides have been implicated in diverse roles in peripheral organs through direct signalling, including in placental and pancreatic islet physiology. CRH has been shown to stimulate insulin release through activation of its cognate receptors, CRH receptor 1 (CRHR1) and 2. However, the physiological significance of this is unknown. We have previously reported that during mouse pregnancy, expression of CRH peptides increase in mouse placenta suggesting that these peptides may play a role in various biological functions associated with pregnancy, particularly the pancreatic islet adaptations that occur in the pregnant state to compensate for the physiological increase in maternal insulin resistance. In the current study, we show that mouse pregnancy is associated with increased circulating levels of UCN2 and that when we pharmacologically block endogenous CRHR signalling in pregnant mice, impairment of glucose tolerance is observed. This effect on glucose tolerance was comparable to that displayed with specific CRHR2 blockade and not with specific CRHR1 blockade. No effects on insulin sensitivity or the proliferative capacity of β-cells were detected. Thus, CRHR2 signalling appears to be involved in β-cell adaptive responses to pregnancy in the mouse, with endogenous placental UCN2 being the likely signal mediating this.

Can Placental Corticotropin-Releasing Hormone Inform Timing of Antenatal Corticosteroid Administration?

CONTEXT

Antenatal corticosteroids are commonly administered to pregnant women at risk for delivering between 23 and 34 gestational weeks; they provide crucial benefits to fetal lung maturation and reduce risk for neonatal morbidity and mortality. Corticosteroids are maximally efficacious for lung maturation when administered within 2 to 7 days of delivery. Accurately identifying the timing of preterm delivery is thus critical to ensure that antenatal corticosteroids are administered within a week of delivery and to avoid unnecessary administration to women who will deliver at term. A plausible biomarker for predicting time of delivery is placental corticotropin-releasing hormone (pCRH).

OBJECTIVE

To assess whether pCRH concentrations predict time to delivery and specifically which women will deliver within a week of treatment.

DESIGN

pCRH concentrations were evaluated before administration of the corticosteroid betamethasone, and timing of delivery was recorded.

PARTICIPANTS

A total of 121 women with singleton pregnancies who were prescribed betamethasone.

RESULTS

Elevated pCRH concentrations were associated with a shorter time from treatment to delivery. Receiver-operating characteristic curves revealed that pCRH may improve the precision of predicting preterm delivery.

CONCLUSIONS

In the current sample, pCRH concentrations predicted the likelihood of delivering within 1 week of corticosteroid treatment. Current findings suggest that pCRH may be a diagnostic indicator of impending preterm delivery. Increasing the precision in predicting time to delivery could inform when to administer antenatal corticosteroids, thus maximizing benefits and reducing the likelihood of exposing fetuses who will be delivered at term.

The relationship between maternal anxiety and cortisol during pregnancy and birth weight of chinese neonates

BACKGROUND

To determine the relationship between maternal anxiety and cortisol values and birth weight at various stages of pregnancy.

METHODS

Two hundred sixteen pregnant Chinese women were assessed for anxiety and depression and had measurement of morning fasting serum cortisol. Women were assessed either in the first (71), second (72) or third (73) trimester. Birth weights of all children were recorded.

RESULTS

There were significant negative correlations between anxiety level and birth weight of - 0.507 (p < 0.01) and - 0.275 (p < 0.05) in trimesters 1and 2. In trimester 3 the negative relation between anxiety and birth weight of -.209 failed to reach significance (p = 0.070). There was no relation between depression and birth weight in any trimester (p > 0.5 for all). Maternal cortisol was significantly inversely related to birth weight in trimester 1 (r = - 0.322) and with borderline significance in trimester 2 (r = - 0.229). Anxiety score and maternal cortisol were significantly correlated in each trimester (r = 0.551, 0.650, 0.537). When both anxiety score and maternal cortisol were simultaneously included in multiple regression analyses only anxiety score remained significant.

CONCLUSION

Whilst both maternal anxiety score and maternal cortisol are inversely related to birth weight the associations with anxiety score were more robust perhaps indicating the importance of mechanisms other than, or in addition to, maternal cortisol in mediating the effects of anxiety. The findings indicate the importance of measures to reduce maternal anxiety, particularly of a severe degree, at all stages of pregnancy.

TRIAL REGISTRATION

The study was approved by the Ethics Committee of the 1st Affiliated Hospital of Xi'an Jiaotong University.

Developmental origins of the human hypothalamic-pituitary-adrenal axis

INTRODUCTION

The developmental origins of disease or fetal programming model predicts that intrauterine exposures have life long consequences for physical and psychological health. Prenatal programming of the fetal hypothalamic-pituitary-adrenal (HPA) axis is proposed as a primary mechanism by which early experiences are linked to later disease risk. Areas covered: This review describes the development of the fetal HPA axis, which is determined by an intricately timed cascade of endocrine events during gestation and is regulated by an integrated maternal-placental-fetal steroidogenic unit. Mechanisms by which stress-induced elevations in hormones of maternal, fetal, or placental origin influence the structure and function of the emerging fetal HPA axis are discussed. Recent prospective studies documenting persisting associations between prenatal stress exposures and altered postnatal HPA axis function are summarized, with effects observed beginning in infancy into adulthood. Expert commentary: The results of these studies are synthesized, and potential moderating factors are discussed. Promising areas of further research highlighted include epigenetic mechanisms and interactions between pre and postnatal influences.

Abnormal dendritic maturation of developing cortical neurons exposed to corticotropin releasing hormone (CRH): Insights into effects of prenatal adversity?

Corticotropin releasing hormone (CRH) produced by the hypothalamus initiates the hypothalamic-pituitary-adrenal (HPA) axis, which regulates the body's stress response. CRH levels typically are undetectable in human plasma, but during pregnancy the primate placenta synthesizes and releases large amounts of CRH into both maternal and fetal circulations. Notably, placental CRH synthesis increases in response to maternal stress signals. There is evidence that human fetal exposure to high concentrations of placental CRH is associated with behavioral consequences during infancy and into childhood, however the direct effects on of the peptide on the human brain are unknown. In this study, we used a rodent model to test the plausibility that CRH has direct effects on the developing cortex. Because chronic exposure to CRH reduces dendritic branching in hippocampal neurons, we tested the hypothesis that exposure to CRH would provoke impoverishment of dendritic trees in cortical neurons. This might be reflected in humans as cortical thinning. We grew developing cortical neurons in primary cultures in the presence of graded concentrations of CRH. We then employed Sholl analyses to measure dendritic branching and total dendritic length of treated cells. A seven-day exposure to increasing levels of CRH led to a significant, dose-dependent impoverishment of the branching of pyramidal-like cortical neurons. These results are consistent with the hypothesis that, rather than merely being a marker of prenatal stress, CRH directly decreases dendritic branching. Because dendrites comprise a large portion of cortical volume these findings might underlie reduced cortical thickness and could contribute to the behavioral consequences observed in children exposed to high levels of CRH in utero.

Cell-Mediated Delivery of Brain-Derived Neurotrophic Factor Enhances Dopamine Levels in an Mpp+ Rat Model of Substantia Nigra Degeneration

Brain-derived neurotrophic factor (BDNF) promotes the survival of fetal mesencephalic dopaminergic cells and protects dopaminergic neurons against the toxicity of MPP+ in vitro. Supranigral implantation of fibroblasts genetically engineered to secrete BDNF attenuates the loss of substantia nigra pars compacta (SNc) dopaminergic neurons associated with striatal infusion of MPP+ in the adult rat. Using this MPP+ rat model of nigral degeneration, we evaluated the neurochemical effects of supranigral, cell-mediated delivery of BDNF on substantia nigra (SN) dopamine (DA) content and turnover. Genetically engineered BDNF-secreting fibroblasts (~12 ng BDNF/24 h) were implanted dorsal to the SN 7 days prior to striatal MPP+ administration. The present results demonstrate that BDNF-secreting fibroblasts, as compared to control fibroblasts, enhance SN DA levels ipsilateral as well as contralateral to the graft without altering DA turnover. This augmentation of DA levels suggests that local neurotrophic factor delivery by genetically engineered cells may provide a therapeutic strategy for preventing neuronal death or enhancing neuronal function in neurodegenerative diseases characterized by dopaminergic neuronal dysfunction, such as Parkinson's disease.

Second-trimester amniotic fluid corticotropin-releasing hormone and urocortin in relation to maternal stress and fetal growth in human pregnancy

This study explored the association between the acute psychobiological stress response, chronic social overload and amniotic fluid corticotropin-releasing hormone (CRH) and urocortin (UCN) in 34 healthy, second-trimester pregnant women undergoing amniocentesis. The study further examined the predictive value of second-trimester amniotic fluid CRH and UCN for fetal growth and neonatal birth outcome. The amniocentesis served as a naturalistic stressor, during which maternal state anxiety and salivary cortisol was measured repeatedly and an aliquot of amniotic fluid was collected. The pregnant women additionally completed a questionnaire on chronic social overload. Fetal growth parameters were obtained at amniocentesis using fetal ultrasound biometry and at birth from medical records. The statistical analyzes revealed that the acute maternal psychobiological stress response was unassociated with the amniotic fluid peptides, but that maternal chronic overload and amniotic CRH were positively correlated. Moreover, amniotic CRH was negatively associated with fetal size at amniocentesis and positively with growth in size from amniocentesis to birth. Hardly any studies have previously explored whether acute maternal psychological stress influences fetoplacental CRH or UCN levels significantly. Our findings suggest that (i) chronic, but not acute maternal stress may affect fetoplacental CRH secretion and that (ii) CRH is complexly involved in fetal growth processes as previously shown in animals.

Long-term consequences of prenatal stress and neurotoxicants exposure on neurodevelopment

There is a large consensus that the prenatal environment determines the susceptibility to pathological conditions later in life. The hypothesis most widely accepted is that exposure to insults inducing adverse conditions in-utero may have negative effects on the development of target organs, disrupting homeostasis and increasing the risk of diseases at adulthood. Several models have been proposed to investigate the fetal origins of adult diseases, but although these approaches hold true for almost all diseases, particular attention has been focused on disorders related to the central nervous system, since the brain is particularly sensitive to alterations of the microenvironment during early development. Neurobiological disorders can be broadly divided into developmental, neurodegenerative and neuropsychiatric disorders. Even though most of these diseases share genetic risk factors, the onset of the disorders cannot be explained solely by inheritance. Therefore, current understanding presumes that the interactions of environmental input, may lead to different disorders. Among the insults that can play a direct or indirect role in the development of neurobiological disorders are stress, infections, drug abuse, and environmental contaminants. Our laboratories have been involved in the study of the neurobiological impact of gestational stress on the offspring (Dr. Antonelli's lab) and on the effect of gestational exposure to toxicants, mainly methyl mercury (MeHg) and perfluorinated compounds (PFCs) (Dr. Ceccatelli's lab). In this focused review, we will review the specialized literature but we will concentrate mostly on our own work on the long term neurodevelopmental consequences of gestational exposure to stress and neurotoxicants.

Corticotropin-releasing hormone: Mediator of vertebrate life stage transitions?

Hormones, particularly thyroid hormones and corticosteroids, play critical roles in vertebrate life stage transitions such as amphibian metamorphosis, hatching in precocial birds, and smoltification in salmonids. Since they synergistically regulate several metabolic and developmental processes that accompany vertebrate life stage transitions, the existence of extensive cross-communication between the adrenal/interrenal and thyroidal axes is not surprising. Synergies of corticosteroids and thyroid hormones are based on effects at the level of tissue hormone sensitivity and gene regulation. In addition, in representative nonmammalian vertebrates, corticotropin-releasing hormone (CRH) stimulates hypophyseal thyrotropin secretion, and thus functions as a common regulator of both the adrenal/interrenal and thyroidal axes to release corticosteroids and thyroid hormones. The dual function of CRH has been speculated to control or affect the timing of vertebrate life history transitions across taxa. After a brief overview of recent insights in the molecular mechanisms behind the synergic actions of thyroid hormones and corticosteroids during life stage transitions, this review examines the evidence for a possible role of CRH in controlling vertebrate life stage transitions.

Fetal and Neonatal HPA Axis

Stress is an integral part of life. Activation of the hypothalamus-pituitary-adrenal (HPA) axis in the adult can be viewed as mostly adaptive to restore homeostasis in the short term. When stress occurs during development, and specifically during periods of vulnerability in maturing systems, it can significantly reprogram function, leading to pathologies in the adult. Thus, it is critical to understand how the HPA axis is regulated during developmental periods and what are the factors contributing to shape its activity and reactivity to environmental stressors. The HPA axis is not a passive system. It can actively participate in critical physiological regulation, inducing parturition in the sheep for instance or being a center stage actor in the preparation of the fetus to aerobic life (lung maturation). It is also a major player in orchestrating mental function, metabolic, and cardiovascular function often reprogrammed by stressors even prior to conception through epigenetic modifications of gametes. In this review, we review the ontogeny of the HPA axis with an emphasis on two species that have been widely studied-sheep and rodents-because they each share many similar regulatory mechanism applicable to our understanding of the human HPA axis. The studies discussed in this review should ultimately inform us about windows of susceptibility in the developing brain and the crucial importance of early preconception, prenatal, and postnatal interventions designed to improve parental competence and offspring outcome. Only through informed studies will our public health system be able to curb the expansion of many stress-related or stress-induced pathologies and forge a better future for upcoming generations.

Immunoglobulin isotype isolated from human placental extract does not interfere in complement-mediated bacterial opsonization within the wound milieu

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Human placental extract has many applications as a wound healer.

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Immunoglobulin G is a key glycoprotein present in human placental extract.

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Placental IgG (25.2 ± 3.97 μg/ml) did not exert anti-complementary effects.

The wound healing potency of an aqueous extract of placenta can be evaluated through the presence of numerous regulatory components. The presence of glycans was detected by thin layer chromatography and fluorophore-assisted carbohydrate electrophoresis. Mass spectrometric analysis revealed the existence of multiple fragments of immunoglobulin G (IgG). IgG was present in the extract at a concentration of 25.2 ± 3.97 μg/ml. IgG possesses anti-complementary activity by diverting the complement activation from target surface. Thus, effect of placental IgG on complement–bacteria interaction was investigated through classical and alternative pathway and the preparation was ascertained to be safe with respect to their interference in the process of bacterial opsonization.

Inhibin alpha gene expression in human trophoblasts is regulated by interactions between TFAP2 and cAMP signaling pathways

Inhibin α (Inha) gene expression is regulated, in rat granulosa cells, via a cyclic 3',5'-adenosine monophosphate (AMP)-response element (CRE) found in a region of the promoter that is homologous to the human INHA promoter. We previously found that during in vitro cytotrophoblast differentiation, human INHA gene expression was regulated by TFAP2A via association with an AP-2 site located upstream of this CRE. The aim of this study was to evaluate if the human INHA gene was also regulated by cAMP in trophoblasts, and to investigate the possible crosstalk between TFAP2 and cAMP signaling pathways in the regulation of INHA gene expression. Treatment with cAMP or forskolin increased INHA mRNA expression by 7- and 2-fold in primary cytotrophoblasts and choriocarcinoma-derived BeWo cells, respectively. Treatment with the protein kinase A inhibitor H-89 reduced forskolin-induced luciferase activity by ∼40% in BeWo cells transfected with an INHA promoter-driven luciferase reporter vector. TFAP2 overexpression increased basal luciferase activity, whereas the dominant repressor KCREB abolished it. Surprisingly, mutation of the CRE also eliminated the TFAP2-induced transcription, although TFAP2 overexpression was still able to increase forskolin-induced luciferase activity when the AP-2 binding site, but not the CRE site, was mutated. Thus, INHA gene expression is upregulated by cAMP via CRE in human trophoblasts, and TFAP2 regulates this expression by interacting with CRE.

Disruption of fetal hormonal programming (prenatal stress) implicates shared risk for sex differences in depression and cardiovascular disease

Comorbidity of major depressive disorder (MDD) and cardiovascular disease (CVD) represents the fourth leading cause of morbidity and mortality worldwide, and women have a two times greater risk than men. Thus understanding the pathophysiology has widespread implications for attenuation and prevention of disease burden. We suggest that sex-dependent MDD-CVD comorbidity may result from alterations in fetal programming consequent to the prenatal maternal environments that produce excess glucocorticoids, which then drive sex-dependent developmental alterations of the fetal hypothalamic-pituitary-adrenal (HPA) axis circuitry impacting mood, stress regulation, autonomic nervous system (ANS), and the vasculature in adulthood. Evidence is consistent with the hypothesis that disruptions of pathways associated with gamma aminobutyric acid (GABA) in neuronal and vascular development and growth factors have critical roles in key developmental periods and adult responses to injury in heart and brain. Understanding the potential fetal origins of these sex differences will contribute to development of novel sex-dependent therapeutics.

New insights into the role of perinatal HPA-axis dysregulation in postpartum depression

Postpartum depression affects 10-20% of women following birth and exerts persisting adverse consequences on both mother and child. An incomplete understanding of its etiology constitutes a barrier to early identification and treatment. It is likely that prenatal hormone trajectories represent both markers of risk and also causal factors in the development of postpartum depression. During pregnancy the maternal hypothalamic-pituitary-adrenal axis undergoes dramatic alterations, due in large part, to the introduction of the placenta, a transient endocrine organ of fetal origin. We suggest that prenatal placental and hypothalamic-pituitary-adrenal axis dysregulation is predictive of risk for postpartum depression. In this model the positive feedback loop involving the systems regulating the products of the HPA axis results in higher prenatal levels of cortisol and placental corticotropin-releasing hormone. Greater elevations in placental corticotropin-releasing hormone are related to a disturbance in the sensitivity of the anterior pituitary to cortisol and also perhaps to decreased central corticotropin-releasing hormone secretion. Secondary or tertiary adrenal insufficiencies of a more extreme nature, which emerge during the prenatal period, may be predictive of an extended or more pronounced postpartum hypothalamic-pituitary-adrenal refractory period, which in turn represents a risk factor for development of postpartum depression. In addition to reviewing the relevant existing literature, new data are presented in support of this model which link elevated placental corticotropin-releasing hormone with low levels of ACTH at 3-months postpartum. Future research will further elucidate the role of hypothalamic-pituitary-adrenal axis dysregulation in postpartum depression and also whether prenatal placental and hypothalamic-pituitary-adrenal profiles might prove useful in the early identification of mothers at risk for postpartum mood dysregulation.

Gene expression analysis of the microdissected trophoblast layer of human placenta after the spontaneous onset of labor

Background

Despite increasing evidence that human parturition is associated with alteration in gene expression in the uteroplacental unit, the precise mechanisms that elicit spontaneous term labor in humans remain unknown. Our goal in this study was to compare the mRNA expression pattern of the trophoblast layer of normal term placenta between women who had given natural birth (labor group) and those who had undergone an elective cesarean section without labor (non-labor group).

Methods

We collected placental tissue samples from six pregnant women after term vaginal deliveries (labor group) and from six pregnant women after scheduled Cesarean sections (non-labor group). Frozen sections were made immediately after placental delivery. Because the placenta is a heterogeneous tissue composed of several cell types, we used laser capture microdissection to separate the trophoblast layer from the rest of the placental tissues.

Results

A number of genes were differentially expressed in the trophoblast layer when the labor and non-labor groups were compared. The expression of SIRT1, KAP1, and CRH was significantly lower in the trophoblast layer of the labor group than of the non-labor group. The expression of IL-1b, NF-kB1 and TLR 8 in the labor group was significantly higher than that in the non-labor group.

Conclusions

Human term labor may be closely associated with inflammatory response. We suggest that downregulation of SIRT1, KAP1, and CRH gene expression in the trophoblast may play a key role in parturition and initiation of labor in pregnant human females.

Neurobehavioral risk is associated with gestational exposure to stress hormones

The developmental origins of disease or fetal programming model predict that early exposures to threat or adverse conditions have lifelong consequences that result in harmful outcomes for health. The maternal endocrine 'fight or flight' system is a source of programming information for the human fetus to detect threats and adjust their developmental trajectory for survival. Fetal exposures to intrauterine conditions including elevated stress hormones increase the risk for a spectrum of health outcomes depending on the timing of exposure, the timetable of organogenesis and the developmental milestones assessed. Recent prospective studies, reviewed here, have documented the neurodevelopmental consequences of fetal exposures to the trajectory of stress hormones over the course of gestation. These studies have shown that fetal exposures to biological markers of adversity have significant and largely negative consequences for fetal, infant and child emotional and cognitive regulation and reduced volume in specific brain structures.

On the function of placental corticotropin-releasing hormone: a role in maternal-fetal conflicts over blood glucose concentrations

Throughout the second and third trimesters, the human placenta (and the placenta in other anthropoid primates) produces substantial quantities of corticotropin-releasing hormone (placental CRH), most of which is secreted into the maternal bloodstream. During pregnancy, CRH concentrations rise over 1000-fold. The advantages that led selection to favour placental CRH production and secretion are not yet fully understood. Placental CRH stimulates the production of maternal adrenocorticotropin hormone (ACTH) and cortisol, leading to substantial increases in maternal serum cortisol levels during the third trimester. These effects are puzzling in light of widespread theory that cortisol has harmful effects on the fetus. The maternal hypothalamic-pituitary-adrenal (HPA) axis becomes less sensitive to cortisol during pregnancy, purportedly to protect the fetus from cortisol exposure. Researchers, then, have often looked for beneficial effects of placental CRH that involve receptors outside the HPA system, such as the uterine myometrium (e.g. the placental clock hypothesis). An alternative view is proposed here: the beneficial effect of placental CRH to the fetus lies in the fact that it does stimulate the production of cortisol, which, in turn, leads to greater concentrations of glucose in the maternal bloodstream available for fetal consumption. In this view, maternal HPA insensitivity to placental CRH likely reflects counter-adaptation, as the optimal rate of cortisol production for the fetus exceeds that for the mother. Evidence pertaining to this proposal is reviewed.

Fetal-placental inflammation, but not adrenal activation, is associated with extreme preterm delivery

OBJECTIVE

Spontaneous labor at term involves the activation of placental corticotropin-releasing hormone and the fetal adrenal axis, but the basis for extreme preterm labor is unknown. Our objective was to determine whether placental corticotropin-releasing hormone is activated in extreme preterm labor.

STUDY DESIGN

One thousand five hundred six mothers delivering at less than 28 weeks' gestation were enrolled. Each mother/infant pair was assigned to the category that described the primary reason for hospitalization. Observers who had no knowledge of patient categorization assessed placenta microbiology, histology, and corticotropin-releasing hormone expression. These were correlated with the primary reason for hospitalization.

RESULTS

Among infants delivered at less than 28 weeks' gestation, spontaneous (vs induced) delivery was associated with less placental corticotropin-releasing hormone expression and more frequent signs of placental inflammation and infection.

CONCLUSION

Inflammation and infection, rather than premature activation of the fetal adrenal axis, should be the major focus of research to prevent extremely preterm human birth.

Expression of Nuclear Receptor Coactivators in the Human Fetal Membranes at Term before and after Labor

Human fetal membranes play an important role in term and preterm labor and are responsive to steroids. We examined the expression of steroid receptor coactivators in fetal membranes obtained prior to and following labor at term. Proteins were localized by immunohistochemistry, Western analysis was carried out in nuclear extracts, and mRNA levels were determined by real-time RT-PCR. SRC-1, SRC-2, p300, and PCAF proteins were present in all nuclear extracts. The amnion nuclei expressed higher levels of SRC-1, p300, and PCAF than nuclei from the chorion-decidua, whereas the reverse was true for SRC-2. Chorion-decidua from patients before labor expressed higher levels of SRC-1 than those from patients after labor. Also, the PCAF level was higher in the amnion obtained before labor than the same tissue obtained after labor. In contrast to the protein expression, mRNA levels of SRC-1 and p300 were higher in the chorion-decidua compared to the amnion, whereas there was no difference in levels of SRC-2 and PCAF mRNAs between these two tissues. These data underline that the regulation of the expression of the coactivators in these tissues occurs during labor and is complex and tissue specific.

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.

Pattern of maternal circulating CRH in laboratory-housed squirrel and owl monkeys

The anthropoid primate placenta appears to be unique in producing corticotropin-releasing hormone (CRH). Placental CRH is involved in an endocrine circuit key to the production of estrogens during pregnancy. CRH induces cortisol production by the maternal and fetal adrenal glands, leading to further placental CRH production. CRH also stimulates the fetal adrenal glands to produce dehydroepiandrostendione sulfate (DHEAS), which the placenta converts into estrogens. There are at least two patterns of maternal circulating CRH across gestation among anthropoids. Monkeys examined to date (Papio and Callithrix) have an early-to-mid gestational peak of circulating CRH, followed by a steady decline to a plateau level, with a possible rise near parturition. In contrast, humans and great apes have an exponential rise in circulating CRH peaking at parturition. To further document and compare patterns of maternal circulating CRH in anthropoid primates, we collected monthly blood samples from 14 squirrel monkeys (Saimiri boliviensis) and ten owl monkeys (Aotus nancymaae) during pregnancy. CRH immunoreactivity was measured from extracted plasma by using solid-phase radioimmunoassay. Both squirrel and owl monkeys displayed a mid-gestational peak in circulating CRH: days 45-65 of the 152-day gestation for squirrel monkeys (mean±SEM CRH=2,694±276 pg/ml) and days 60-80 of the 133-day gestation for owl monkeys (9,871±974 pg/ml). In squirrel monkeys, circulating CRH declined to 36% of mean peak value by 2 weeks before parturition and then appeared to increase; the best model for circulating CRH over gestation in squirrel monkeys was a cubic function, similar to previous results for baboons and marmosets. In owl monkeys, circulating CRH appeared to reach plateau with no subsequent significant decline approaching parturition, although a cubic function was the best fit. This study provides additional evidence for a mid-gestational peak of maternal circulating CRH in ancestral anthropoids that has been lost in the hominoid lineage.

The role of stress in female reproduction and pregnancy: an update

Life exists by establishing a balanced equilibrium, called homeostasis, constantly challenged by adverse stimuli, called stressors. In response to these stimuli, a complex neurohormonal reaction exerted by the activation of the so-called stress system is initiated. The latter is activated in a coordinated fashion, leading to behavioral and peripheral changes that improve the ability of the organism to adjust homeostasis and increase its chance for survival. The stress system suppressive effects on female reproduction involve suppression of the hypothalamic-pituitary-ovarian axis at the hypothalamic, pituitary, ovarian, and uterine levels. Experimental and human data suggest that adverse prenatal stimuli, of either maternal or fetal origin, acting in the developing embryo in utero, can lead to the development of short- and long-term health disorders. These include preterm birth of the offspring, low birth weight, and the development of adult diseases ranging from the metabolic syndrome to several neurodevelopmental disorders.

Terbutaline inhibits corticotropin-releasing hormone (CRH) expression in human trophoblast cells

OBJECTIVE

To evaluate the effect of beta-adrenergic agonists on the regulation of the expression of the placental corticotropin-releasing hormone (CRH) gene.

STUDY DESIGN

Term placentae were collected at the time of elective cesarean section, and trophoblast cells were harvested, isolated, and cultured. The isolated trophoblasts were plated, cultured and subsequently treated with cortisol, terbutaline, RU486, or vehicle control. CRH expression, mRNA abundance of CRH, and the housekeeping gene beta-actin were evaluated by Northern blot analysis.

RESULTS

Exposure of the trophoblasts to terbutaline (10(-8) M) inhibited the expression of the CRH gene as depicted by Northern blot analysis. Co-addition of terbutaline (10(-8) M) and RU486 (10(-6) M) did not block the stimulatory effects of RU486 on placental trophoblast cells.

CONCLUSION

The beta-adrenergic agonist terbutaline inhibits the expression of CRH in human trophoblasts. This finding may provide insight into the mechanism of action of terbutaline as a tocolytic agent.

Maternal levels of corticotropin-releasing hormone during pregnancy in relation to adiponectin and leptin in early childhood

BACKGROUND

Fetal glucocorticoid exposure is associated with later development of features of the metabolic syndrome such as central obesity and insulin resistance. Fat tissue, especially visceral fat, produces adiponectin, which is inversely associated with insulin resistance in older children and adults. Adipocytes also produce leptin, directly related to measures of adiposity. It is unknown how the secretion of these hormones in early childhood is related to pregnancy levels of CRH, a proxy of fetal glucocorticoid exposure.

AIM

Our aim was to study the relationship of maternal midpregnancy CRH levels with offspring levels of adiponectin and leptin in early childhood.

METHODS

The study population consisted of 349 mother-children pairs from Project Viva, a prospective prebirth cohort study from eastern Massachusetts. We created a general linear model with log CRH levels in midpregnancy maternal blood as the predictor and adiponectin and leptin measured in the 3-yr-old offspring as outcomes, adjusting for covariates.

RESULTS

The means (sd) of log CRH, adiponectin, and leptin were 4.97 (0.65) log pg/ml, 22.4 (5.8) microg/ml, and 1.9 (1.8) ng/ml. For each unit increment in log CRH, mean value of offspring adiponectin was 1.10 microg/ml (95% confidence interval = 0.06-2.14) higher. We found no association with leptin (-0.08 ng/ml; 95% confidence interval = -0.40-0.24).

CONCLUSIONS

Higher maternal blood levels of CRH were associated with higher levels of adiponectin but unchanged levels of leptin at age 3 yr. The increased adiponectin levels might represent secretion from organs other than fat or reflect a compensatory mechanism to increase insulin sensitivity.

Effects of maternal prenatal stress on offspring development: a commentary

Pregnancy is associated with major physiological changes and adaptation to these changes is crucial for normal fetal development. Heightened emotional stress during pregnancy may interfere with the necessary adaptation and lead to dysregulation of the two major stress response systems: the Hypothalamic-Pituitary-Adrenal (HPA) Axis and the Autonomic Nervous System (ANS). Negative effects on the fetus of such maladaptation have been documented in both animals and humans and range from poor birth outcomes to negative impacts on neurodevelopment, as well as long term emotional and behavioural disturbances. Conversely, it has been hypothesized that low levels of maternal prenatal stress may actually have an adaptive value for the offspring. Investigation of these associations employing physiological markers and repeated measures throughout pregnancy and postpartum of both the mother and the offspring, is required in order to understand the various effects of prenatal stress on the development of the offspring. It is also crucial to explore the possibility of variable periods of vulnerability throughout gestation. The aim of this commentary is to reexamine the current literature on the ill-effects of maternal stress during pregnancy on the offspring and to explore avenues for future treatment and prevention.

Mechanism(s) of in utero meconium passage

To use sheep and rat models and demonstrate that stressors activate fetal glucocorticoid (GC) system, corticotrophin-releasing factor (CRF) system and cholinergic neurotransmitter system (ChNS) leading to propulsive colonic motility and in utero meconium passage. Immunohistochemical studies (IHS) were performed to localize GC-Receptors, CRF-receptors and key molecules of ChNS in sheep fetal distal colon. CRF expression in placenta and enteric endocrine cells in fetal rat system were examined and the effects of acute hypoxia on in utero meconium passage was tested. IHS confirmed localization and gestation dependent changes in GC-Rs, CRF-Rs and cholinergic markers in sheep fetal colon. Rat placenta and enteric endocrine cells express CRF and gastrointestinal tract express CRF-Rs. Hypoxia is a potent inducer of meconium passage in term fetal rats. Stress is a risk factor for in utero meconium passage and laboratory animal models can be used to develop pharmacotherapy to prevent stress-induced in utero meconium passage.

Endocrinology of labour

Preterm labour, defined as delivery before 37 weeks of completed pregnancy, continues to present a major problem in clinical obstetrics and remains the major contributory factor to the perinatal mortality and morbidity statistics. While it is now possible, with recent advances in neonatal care, to take infants delivered very prematurely and provide them with the lifelines that will ensure their ultimate discharge from the neonatal intensive care nursery, the cost of this form of management – in terms both of health care funds and of emotion – is extraordinarily high. Hence there remains a strong rationale for attempting to understand the underlying biochemistry and physiology of labour in order to develop methods of recognizing the patient in true preterm labour, and of developing better strategies to prevent or to manage this condition. In the best of our neonatal intensive care settings, survival of the infant born at 28–30 weeks’ gestation, or greater than 1500 grams, may be greater than 90%. Thus, the clinical management strategy may be directed more towards sustaining intrauterine life for 4–6 weeks in those patients presenting in preterm labour before this time in order to gain time for intrauterine maturation of these fetuses before they are delivered to the tertiary care NICU setting.

Immune function in pregnancy: the role of corticotropin-releasing hormone

Pregnancy represents a major challenge to the maternal immune system since it has to tolerate the semi-allograft fetus. Indeed, the success of pregnancy requires an appropriate immunological interaction between the mother and the fetus. Furthermore, evidence suggests that some pregnancy complications, such as spontaneous abortions, preeclampsia and intrauterine growth restriction, are associated with abnormal maternal-fetal immune responses. Corticotropin-releasing hormone (CRH), a 41-amino acid peptide originally found in the hypothalamus, appears to have a fundamental role in the mechanisms responsible for the implantation and maintenance of human pregnancy. Reproductive CRH is a form of tissue CRH (CRH found in peripheral tissues), analogous to the immune CRH detected in peripheral inflammatory sites. Reproductive CRH has been identified in the endometrial glands, the decidualized endometrial stroma and the placental trophoblast, synctiotrophoblast and decidua. Reproductive CRH participates in various reproductive functions with an inflammatory component, where it serves as an autocrine/paracrine modulator. The immunological mechanisms contributing to the establishment and maintenance of pregnancy are not fully understood. The present article focuses on the potential roles of CRH on the physiology and pathophysiology of pregnancy and highlights its participation in implantation, early fetal immunotolerance and parturition.

Genetic contributions to preterm birth: implications from epidemiological and genetic association studies

Infants born before term (<37 weeks) have an increased risk of neonatal mortality as well as other health problems. The increasing rate of preterm birth in recent decades, despite improvements in health care, creates an impetus to better understand and prevent this disorder. Preterm birth likely depends on a number of interacting factors, including genetic, epigenetic, and environmental risk factors. Genetic studies may identify markers, which more accurately predict preterm birth than currently known risk factors, or novel proteins and/or pathways involved in the disorder. This review summarizes epidemiological and genetic studies to date, emphasizing the complexity of genetic influences on birth timing. While several candidate genes have been reportedly associated with the disorder, inconsistency across studies has been problematic. More systematic and unbiased genetic approaches are needed for future studies to examine the genetic etiology of human birth timing thoroughly.

The regulation of adrenocorticotrophic hormone receptor by corticotropin-releasing hormone in human fetal adrenal definitive/transitional zone cells

As gestation progresses, human fetal adrenals (HFA) initiate the production of cortisol, which increases placental corticotropin-releasing hormone (CRH) biosynthesis. While adrenocorticotrophic hormone (ACTH) is important for the onset of cortisol production, the late gestational surge in cortisol production occurs despite falling ACTH levels in the fetal circulation. The authors determine if CRH directly regulates the expression of the ACTH receptor (ACTHR) in HFA definitive/transitional zone (DZ/TZ) cells. DZ/TZ cells isolated from midgestation HFA were cultured before treatment with 0.01 nM to 100 nM CRH or ACTH. Cortisol was measured by radioimmunoassay. Real-time reverse-transcriptase polymerase chain reaction was used to measure ACTHR mRNA. Whole-cell ACTH binding studies were performed using I(125) (Tyr-23) ACTH. CRH produced a dose-dependent rise in cortisol production and caused a time-dependent increase in ACTHR mRNA levels between 12 and 24 hours. As little as 0.1 nM CRH induced ACTHR transcript by 12-fold at 24 hours. Together with ACTH 0.01 nM, 0.03 or 0.1 nM CRH increased ACTHR expression more than ACTH alone. Binding assays demonstrated a 3.5-fold increase in ACTHR protein at 48 hours with combined CRH and ACTH treatment. Physiologic levels of CRH seen in the late-gestation fetus stimulate DZ/TZ ACTHR expression. Since placental CRH production increases strikingly near the end of gestation, the authors suggest that CRH-induced ACTH receptor expression may increase TZ responsiveness to circulating ACTH and contribute to the late gestational rise in cortisol secretion by the HFA, participating in an endocrine cascade that is involved in fetal organ maturation and potentially in the timing of human parturition.

"Reproductive" corticotropin-releasing hormone

Corticotropin-releasing hormone (CRH), a 41 amino acid peptide, is an important regulatory molecule synthesized by neurons of the parvocellular and magnocellular hypothalamic paraventricular nuclei. It acts as the major physiologic corticotropin (ACTH) secretagogue. The CRH gene is located in humans on chromosome 8. The CRH hormone family has at least four ligands, two receptors (CRH-R1 and CRH-R2), and a binding protein (CRHbp). CRH is the principal regulator of the hypothalamic-pituitary-adrenal axis. Furthermore, CRH has been identified in most female reproductive tissues including the uterus, the placenta, and the ovary. CRH produced in the endometrium may participate in decidualization, implantation, and early maternal tolerance to semiallograft embryo. Placental CRH may participate in the physiology of pregnancy, in late pregnancy complications such as preterm labor and preeclampsia, and also in the onset of parturition. Ovarian CRH is involved in follicular maturation, ovulation, and luteolysis. Increased levels of unbound placental CRH may be responsible for the hypercortisolism of the second half of pregnancy. This hypercortisolism is followed by a transient suppression of hypothalamic CRH secretion in the postpartum period. This may explain the depressive states frequently observed in the postpartum period.

Maternal serum corticotropin-releasing hormone and ACTH levels as predictive markers of premature labor

OBJECTIVE

To investigate whether corticotropin-releasing hormone (CRH) and corticotropin (ACTH) plasma concentrations in women diagnosed with preterm labor are of potential clinical value in the assessment of the risk of preterm birth.

METHOD

Plasma samples of 79 women diagnosed with preterm labor were used in this study. Samples were divided into three groups based on the week of gestation (24th-28th, 29th-32nd, 33rd-37th). CRH and ACTH values were determined by ELISA.

RESULT

Mean maternal peripheral plasma values of CRH and ACTH were significantly higher (p<0.001) in women who were initially diagnosed with preterm labor and finally delivered a preterm birth, compared to women with the same diagnosis but with term birth.

CONCLUSION

CRH and ACTH serum levels in women diagnosed with preterm labor could be used as predictors for the timing of parturition.

Elevated plasma corticotrophin release factor levels and in utero meconium passage

Intrauterine meconium (MEC) passage and aspiration may result in significant newborn morbidity, though there is little understanding of the physiologic mechanisms for MEC passage. We hypothesized that stress induces fetal MEC passage via corticotrophin releasing factor (CRF), a known mediator of colonic motility in adult rats. Pregnant rats at e22 were subjected to acute hypoxia or normoxia for 35 min, after which rats were anesthetized and fetuses operatively delivered. Amniotic fluid bilirubin and intestinal alkaline phosphatase were measured as markers for MEC passage, and fetal and maternal plasma CRF and corticosterone levels determined. Hypoxic stress induced defecation in all dams and provoked visible MEC passage in all fetuses. Amniotic fluid bilirubin content was significantly higher in hypoxic fetuses versus controls (1.064 +/- 0.101 versus 0.103 +/- 0.003 O.D. at 410 nm) and intestinal alkaline phosphatase was consistently elevated in MEC stained amniotic fluid. Hypoxia significantly increased plasma CRF (maternal, 82 +/- 5 to 196 +/- 14 pg/mL; fetal, 284 +/- 15 to 1523 +/- 185 pg/mL) and corticosterone (maternal, 417 +/- 50 to 1150 +/- 50 ng/mL; fetal, 96 +/- 5 to 182 +/- 10 ng/mL) compared with controls. In view of the known action of CRF in adult colonic motility, these results suggest that hypoxic stress-mediated MEC passage in term fetal rats is mediated by a CRF dependent pathway.

The HPA axis and perinatal depression: a hypothesis

Episodes of depression and anxiety are as common during pregnancy as postpartum. Some start in pregnancy and resolve postpartum, others are triggered by parturition and some are maintained throughout. In order to determine any biological basis it is important to delineate these different subtypes. During pregnancy, as well as the rise in plasma oestrogen and progesterone there is a very large increase in plasma corticotropin releasing hormone (CRH), and an increase in cortisol. The latter reaches levels found in Cushing's syndrome and major melancholic depression. Levels of all these hormones drop rapidly on parturition.We here suggest that the symptoms of antenatal and postnatal depression may be different, and linked in part with differences in the function of the hypothalamic pituitary adrenal (HPA) axis. There are two subtypes of major depression, melancholic and atypical, with some differences in symptom profile, and these subtypes are associated with opposite changes in the HPA axis. Antenatal depression may be more melancholic and associated with the raised cortisol of pregnancy, whereas postnatal depression may be more atypical, triggered by cortisol withdrawal and associated with reduced cortisol levels. There is evidence that after delivery some women experience mild bipolar II depression, and others experience post traumatic stress disorder. Both of these are associated with atypical depression. It may also be that some women are genetically predisposed to depression of the melancholic type and some to depression of the atypical type. These women may be more or less vulnerable to depression at the different stages of the perinatal period.

Elevated maternal cortisol early in pregnancy predicts third trimester levels of placental corticotropin releasing hormone (CRH): priming the placental clock

The purposes of this study were to determine the intervals when placental corticotrophic-releasing hormone (CRH) was most responsive to maternal cortisol. A sample of 203 women each were evaluated at 15, 19, 25 and 31 weeks gestation and followed to term. Placental CRH and maternal adrenocorticotropin hormone (ACTH), B-endorphin and cortisol were determined from plasma. CRH levels increased faster and were higher in women who delivered preterm compared with women who delivered at term (F3,603 = 5.73, p < .001). Simple effects indicated that CRH levels only at 31 weeks predicted preterm birth (F1,201 = 5.53, p = .02). Levels of cortisol were higher in women who delivered preterm at 15 weeks gestation (F1,201 = 4.45, p = .03) with a similar trend at 19 weeks gestation. Hierarchical regression suggested that the influence on birth outcome of maternal cortisol early in pregnancy was mediated by its influence on placental CRH at 31 weeks. Elevated cortisol at 15 weeks predicted the surge in placental CRH at 31 weeks (R = .49, d.f. = 1,199, Fchange = 61.78, p < .0001). Every unit of change in cortisol (microg/dl) at 15 weeks was associated with a 34 unit change of CRH (pg/ml) at 31 weeks. These findings suggested that early detection of stress signals by the placenta stimulated the subsequent release of CRH and resulted in increased risk for preterm delivery.