Fetal Hypothalamic-pituitary-adrenal Axis Research Articles

Early establishment of chloride homeostasis in CRH neurons is altered by prenatal stress leading to fetal HPA axis dysregulation.

Corticotropin-releasing hormone (CRH) neurons play an important role in the regulation of neuroendocrine responses to stress. The excitability of CRH neurons is regulated by inhibitory GABAergic inputs. However, it is unclear when GABAergic regulation of CRH neurons is established during fetal brain development. Furthermore, the exact progression of the developmental shift of GABA action from depolarization to hyperpolarization remains unelucidated. Considering the importance of CRH neuron function in subsequent hypothalamic-pituitary-adrenal (HPA) axis regulation during this critical phase of development, we investigated the ontogeny of GABAergic inputs to CRH neurons and consequent development of chloride homeostasis. Both CRH neuron soma in the paraventricular nucleus (PVN) and axons projecting to the median eminence could be identified at embryonic day 15 (E15). Using acute slices containing the PVN of CRF-VenusΔNeo mice, gramicidin perforated-patch clamp-recordings of CRH neurons at E15, postnatal day 0 (P0), and P7 were performed to evaluate the developmental shift of GABA action. The equilibrium potential of GABA (EGABA) was similar between E15 and P0 and showed a further hyperpolarizing shift between P0 and P7 that was comparable to EGABA values in adult CRH neurons. GABA primarily acted as an inhibitory signal at E15 and KCC2 expression was detected in CRH neurons at this age. Activation of the HPA axis has been proposed as the primary mechanism through which prenatal maternal stress shapes fetal development and subsequent long-term disease risk. We therefore examined the impact of maternal food restriction stress on the development of chloride homeostasis in CRH neurons. We observed a depolarization shift of EGABA in CRH neurons of pups exposed to maternal food restriction stress. These results suggest that Cl- homeostasis in early developmental CRH neurons attains mature intracellular Cl- levels, GABA acts primarily as inhibitory, and CRH neurons mature and function early compared with neurons in other brain regions, such as the cortex and hippocampus. Maternal food restriction stress alters chloride homeostasis in CRH neurons of pups, reducing their inhibitory control by GABA. This may contribute to increased CRH neuron activity and cause activation of the HPA axis in pups.

Independent and Combined Effects of Prenatal Alcohol Exposure and Prenatal Stress on Fetal HPA Axis Development.

Prenatal alcohol exposure (PAE) and prenatal stress (PS) are highly prevalent conditions known to affect fetal programming of the hypothalamic-pituitary-adrenal (HPA) axis. The objectives of this study were to assess the effect of light PAE, PS, and PAE-PS interaction on fetal HPA axis activity assessed via placental and umbilical cord blood biomarkers. Participants of the ENRICH-2 cohort were recruited during the second trimester and classified into the PAE and unexposed control groups. PS was assessed by the Perceived Stress Scale. Placental tissue was collected promptly after delivery; gene and protein analysis for 11β-HSD1, 11β-HSD2, and pCRH were conducted by qPCR and ELISA, respectively. Umbilical cord blood was analyzed for cortisone and cortisol. Pearson correlation and multivariable linear regression examined the association of PAE and PS with HPA axis biomarkers. Mean alcohol consumption in the PAE group was ~2 drinks/week. Higher PS was observed in the PAE group (p < 0.01). In multivariable modeling, PS was associated with pCRH gene expression (β = 0.006, p < 0.01), while PAE was associated with 11β-HSD2 protein expression (β = 0.56, p < 0.01). A significant alcohol-by-stress interaction was observed with respect to 11β-HSD2 protein expression (p < 0.01). Results indicate that PAE and PS may independently and in combination affect fetal programming of the HPA axis.

Initiation and endocrine control of parturition in domestic mammals - Part 1

Endocrine regulation of parturition is based on an intense exchange of signals between the fetus, placenta and mother. Apart from sheep, our knowledge of the endocrine control of parturition is still very incomplete. However, current observations suggest significant differences between the species. For the maintenance of pregnancy, progesterone (P4) is the crucial superordinate regulatory factor, although in some species, such as the horse, functions of P4 are at least partially fulfilled by other progestogens. In general, prepartum P4 withdrawal is considered a prerequisite for the onset of physiological birth. In species with exclusive (dog) or predominant (e. g., cattle, goat, pig) luteal P4 at the end of gestation, luteolysis is the crucial event. In sheep, where P4 is of placental origin prior to parturition, the prepartum P4 decline is due to a switch in placental steroid metabolism. The mechanism of prepartum progestogen withdrawal in the mare is still largely unclear. In sheep, initiation of parturition proceeds from maturation of the fetal hypothalamic-pituitary-adrenal (HPA) axis, which leads to a steep prepartum rise in fetal cortisol concentrations stimulating the collapse of placental P4 production. In cattle, fetal cortisol probably triggers luteolysis via stimulation of placental prostaglandin secretion. In several other domestic mammalian species, there is also evidence that the initiation of parturition proceeds from maturation of the fetal HPA axis. However, the functional relationships between fetal cortisol and prepartum P4 withdrawal are largely unknown in nonruminant species.

Effect of maternal periconceptional undernutrition in sheep on cortisol regulation in offspring from mid-late gestation, through to adulthood.

Maternal periconceptional undernutrition (PCUN) alters fetal hypothalamic-pituitary-adrenal axis (HPAA) function and placental glucocorticoid metabolism in sheep. The effects of PCUN on HPAA function in adult life are not known. We investigated the effects of PCUN on fetal adrenal development across gestation and on cortisol regulation in adult offspring. Ewes were undernourished from 61 days before to 30 days after conception ('PCUN') or fed ad libitum ('N'). mRNA expression in the fetal adrenal gland of ACTH receptor (ACTHR), steroidogenic acute regulatory protein (STAR), cytochrome P450 17A1 (CYP17A1), 11beta-hydroxysteroid-dehydrogenase type 2 (11βHSD2), insulin-like growth factor-2 (IGF2), and in the fetal hippocampus of 11βHSD1, 11βHSD2, mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) was determined at 50 (adrenal only), 85, 120 and 131 days of gestation (term=148 days). In adult offspring (≥ 3 years, N; 10 female, 5 male, PCUN; 10 female, 10 male) a combined arginine vasopressin (AVP, 0.1 μg/kg) and corticotropin-releasing hormone (CRH, 0.5 μg/kg) challenge and a metyrapone (40 mg/kg) challenge were undertaken. mRNA expression of ACTHR, STAR and CYP17A1 were determined in adult adrenals. Fetal adrenal STAR, CYP17A1 and IGF2 mRNA expression were not different between groups in early gestation but were higher in PCUN than N at 131 days' gestation (all p<0.01). PCUN reduced fetal hippocampal MR and GR mRNA expression by 50% at 85 day, but not in later gestation. Adult offspring plasma cortisol responses to AVP+CRH or metyrapone were not different between groups. Plasma ACTH response to AVP+CRH was lower in PCUN males but ACTH response to metyrapone was not different between groups. Adult adrenal ACTHR, STAR, and CYP17A1 mRNA expression were not affected by PCUN. We conclude that the effects of PCUN on fetal HPAA function that became apparent in late gestation, are not reflected in adrenal cortisol secretion in mid-adulthood.

Hair cortisol and dehydroepiandrosterone sulfate concentrations in healthy beef calves from birth to 6 months of age

Cortisol (C) and dehydroepiandrosterone (DHEA) are recognized as the main fetal steroids, and they are likely to influence fetal development and have long-term effects on newborn hypothalamic-pituitary-adrenal axis (HPA) function. DHEA is often measured as its sulfates and expressed as DHEA-S. Hair analysis represents a promising methodological approach for the non-invasive measurement of steroids, allowing for a retrospective analysis of the total exposure to steroids over time, and avoiding the influence of acute events or circadian fluctuations. Hair cortisol and DHEA concentrations have been investigated in cows, but no studies have been performed on calves. The object of this study was to evaluate hair cortisol (HC) and hair DHEA-S (HDHEA-S) concentrations in beef calves from birth to six months of age. Hair samples of 12 beef calves (seven males, five females) were firstly collected at birth (T1) and then every three weeks up to six months of age (T2-T10), collecting only the re-grown hair. HC and HDHEA-S were analyzed by radioimmunoassay (RIA). Calves sex, weight and APGAR score were registered immediately after birth. Statistical analysis revealed that both HC and HDHEA-S were influenced by sampling time (P < 0.001). HC concentrations were higher at T1 compared to all subsequent samplings (T2-T10, P < 0.01); HC concentrations were higher at T2 compared to T4-T10 (P < 0.01), while no further changes were detected from T3 onward. Higher HDHEA-S concentrations were registered at T1, T2 and T3 compared to all the other samplings (P < 0.01). No correlation was found between hair concentrations of both steroids and calf sex or birthweight. APGAR score was negatively correlated only with HC at birth (P < 0.05). These data demonstrate that C and DHEA-S are quantifiable in the hair of calves and are influenced by their age. The higher HC detected at birth (T1) probably reflects the high serum C concentrations present late in pregnancy and increased by the fetal HPA axis, by which parturition is initiated in cows. The highest HDHEA-S at birth (T1) in calves indicates that the largest amounts of DHEA and its sulfates are produced during fetal development. Moreover, the findings of higher HC at three weeks after birth and of higher HDHEA-S until six weeks after birth, suggest that C and DHEA secretion continues also beyond birth, and that these steroids could be involved in the events occurring during the challenging first weeks of age in the calf.

Thyroid Hormone Deficiency Suppresses Fetal Pituitary-Adrenal Function Near Term: Implications for the Control of Fetal Maturation and Parturition.

Background: The fetal hypothalamic-pituitary-adrenal (HPA) axis plays a key role in the control of parturition and maturation of organ systems in preparation for birth. In hypothyroid fetuses, gestational length may be prolonged and maturational processes delayed. The extent to which the effects of thyroid hormone deficiency in utero on the timing of fetal maturation and parturition are mediated by changes to the structure and function of the fetal HPA axis is unknown. Methods: In twin sheep pregnancies where one fetus was thyroidectomized and the other sham-operated, this study investigated the effect of hypothyroidism on circulating concentrations of adrenocorticotrophic hormone (ACTH) and cortisol, and the structure and secretory capacity of the anterior pituitary and adrenal glands. The relative population of pituitary corticotrophs and the masses of the adrenal zones were assessed by immunohistochemical and stereological techniques. Adrenal mRNA abundances of key steroidogenic enzymes and growth factors were examined by quantitative polymerase chain reaction. Results: Hypothyroidism in utero reduced plasma concentrations of ACTH and cortisol. In thyroid-deficient fetuses, the mass of corticotrophs in the anterior pituitary gland was unexpectedly increased, while the mass of the zona fasciculata and its proportion of the adrenal gland were decreased. These structural changes were associated with lower adrenocortical mRNA abundances of insulin-like growth factor (IGF)-I and its receptor, and key steroidogenic enzymes responsible for glucocorticoid synthesis. The relative mass of the adrenal medulla and its proportion of the adrenal gland were increased by thyroid hormone deficiency in utero, without any change in expression of phenylethanolamine N-methyltransferase or the IGF system. Conclusions: Thyroid hormones are important regulators of the structure and secretory capacity of the pituitary-adrenal axis before birth. In hypothyroid fetuses, low plasma cortisol may be due to impaired adrenocortical growth and steroidogenic enzyme expression, secondary to low circulating ACTH concentration. Greater corticotroph population in the anterior pituitary gland of the hypothyroid fetus indicates compensatory cell proliferation and that there may be abnormal corticotroph capacity for ACTH synthesis and/or impaired hypothalamic input. Suppression of the development of the fetal HPA axis by thyroid hormone deficiency may contribute to the delay in fetal maturation and delivery observed in hypothyroid offspring.

Association between Maternal Serum Hormones along the Maternal–Fetal Hypothalamic–Pituitary–Adrenal Axis and Successful Vaginal Delivery Measured Prior to Labor Induction

This study aimed to evaluate if maternal serum hormones along the maternal-fetal hypothalamic-pituitary-adrenal (HPA) axis, when drawn prior to labor induction, differed between women who delivered vaginally and those who underwent cesarean. This was a prospective observational study at a single perinatal center performed from August 2017 to May 2018. Nulliparous women with uncomplicated singleton pregnancies ≥39 weeks had maternal serum collected prior to induction. Corticotrophin-releasing hormone (CRH) was measured by ELISA; dehydroepiandrosterone sulfate (DHEA-S), cortisol, estriol (E3) estradiol (E2), and progesterone (P4) were measured by chemiluminescent reaction. Mean analyte concentrations as well as three ratios (E2/P4, E3/P4, and E2/E3) were compared between women who had a vaginal versus cesarean delivery. Logistic regression was used to model the relationship between CRH and the odds of vaginal birth. We estimated that a sample size of 66 would have 90% power to detect a 25% difference in mean CRH levels assuming a vaginal:cesarean ratio of 2:1 with a baseline CRH concentration of 140 (standard deviation = 36) pg/mL. Of the 88 women who had their serum analyzed, 27 (31%) underwent cesarean. Mean maternal serum CRH levels were similar between the vaginal delivery and cesarean groups (122.6 ± 95.2 vs. 112.3 ± 142.4, p = 0.73). Similarly, there were no significant differences in any other maternal serum analytes or ratios. Logistic regression showed a nonsignificant odds ratio for successful vaginal birth (p = 0.69) even when evaluating only the 16 women who had a cesarean for an arrest disorder (p = 0.08). In low-risk nulliparous women undergoing full-term labor induction, there were no differences noted in a broad array of other maternal-fetal HPA-axis hormones between women who had a vaginal or cesarean delivery.

Biomarkers in the Hypothalamus-pituitary-adrenal Axis Were Associated with Maternal Psychosocial Stress and Choline Intake and Status During Pregnancy (P11-011-19)

ObjectivesMaternal psychosocial stress during pregnancy can lead to heightened activity of the hypothalamus-pituitary-adrenal (HPA) axis, increasing the risk of pre-term birth, intrauterine restriction, and preeclampsia. Maternal dietary intakes and nutrition status modify epigenetic marks in the placental and fetal HPA axis, which may then counter the negative influence of maternal stress. This study aims to determine the correlation of maternal psychosocial stress and nutrient intakes with biomarkers of HPA axis activity in human pregnancies. MethodsPregnant women (n = 60) were recruited to this observational study. Psychosocial stress survey, dietary recalls and blood samples were obtained in the 3rd trimester. Placentas and cord blood were retrieved at delivery. ResultsMaternal financial stress, neighborhood stress, and anxiety were positively or tended to be positively associated with maternal blood cortisol levels (P = 0.01-0.08), although none of the psychosocial stress measurements were correlated with placental corticotropin-releasing hormone (CRH), glucocorticoid receptor (NR3C1), or 11β-hydroxysteroid dehydrogenase (11BHSD) expression. Placental NR3C1 expression was positively associated with birth weight (r = 0.42, P = 0.02) while placental CRH was negatively associated with gestational length (r = –0.45, P = 0.01). Overall dietary quality as measured by the Healthy Eating Index (HEI) was not associated with psychosocial stress or related biomarkers, while intakes of the methyl donor choline (r = 0.46, P = 0.04) and omega-3 fatty acids (r = 0.47, P = 0.03) were positively associated with placental NR3C1 expression. Placental choline content was also positively associated with NR3C1 expression (r = 0.39, P = 0.04) and negatively associated with maternal neighborhood stress (r = –0.72, P = 0.02). ConclusionsIn summary, these data suggest that maternal psychosocial stress may adversely affect HPA axis functioning during pregnancy, whereas choline and other nutrients have the potential to counteract some of the impacts of psychosocial stress. Funding SourcesCUNY Interdisciplinary Research Grant.

Control of parturition in ruminants

Parturition is a process which, when set into motion, occurs to completion. This review concerns the control of parturition in ruminants. Parturition is an endocrine event, dependent upon the activation of the fetal hypothalamus-pituitary-adrenal (HPA) axis. In sheep and other ruminants, increases in plasma concentrations of cortisol induce the activity of 17-hydroxylase and 17,20 lyase in the placenta, increasing the biosynthesis of oestrogen relative to progesterone. The increase in the so-called E:P ratio increases myometrial activity and culminates in labour and delivery. Much work has been done to identify the mechanism of the endogenous activation of the fetal HPA axis. Recent work suggests that production of prostanoids within the fetal brain influences fetal ACTH secretion, and that induction of prostanoid biosynthesis at the end of gestation might be important in the process of parturition. Oestrogen and androgens, secreted by the placenta at the end of gestation, augment activity of the fetal HPA axis by increasing fetal ACTH secretion and by decreasing negative feedback sensitivity to cortisol. Although significant progress has been made concerning the neuroendocrinology of parturition, many significant questions remain. Is parturition regulated or simply programmed? Is parturition the ultimate result of neuronal maturation within the fetal hypothalamus, or is there a complex interplay between the placenta and fetal hypothalamus? Answers to these and other important questions await further research, but may provide key information which will prove useful in understanding general principles of parturition in many mammalian species.

ВЛИЯНИЕ ПРЕНАТАЛЬНОГО СТРЕССА НА ОКИСЛИТЕЛЬНЫЕ МОДИФИКАЦИИ БЕЛКОВ И АКТИВНОСТЬ СУПЕРОКСИДДИСМУТАЗЫ В МОЗГЕ И ПЛАЗМЕ КРОВИ САМЦОВ КРЫС В МОДЕЛИ ПОСТТРАВМАТИЧЕСКОГО СТРЕССОВОГО РАССТРОЙСТВА

Biochemical changes during development of posttraumatic stress disorder (PTSD) after prenatal stress were investigated in prenatally stressed male rats. Stress factors activate hypothalamus-pituitary-adrenal (HPA) axis thus increasing penetration of stress hormones into the fetus. It can disturb fetal HPA axis and lead to increased risk of stress-related disorders like PTSD. Our previous works showed that prenatally stressed male rats have longer anxious-depressive state in PTSD «stress-restress» model with more severe neuroendocrine disturbances. In this work, oxidative modifications of proteins and superoxide dismutase activity were estimated in the hypothalamus, hippocampus and neocortex of male rats 1, 10 and 20 days after PTSD with and without prenatal stress. Prenatal stress was modeled by 60-min immobilization of females in days 15—19 of pregnancy, and PTSD was modeled with «stress-restress» model consisted of 2-h immobilization, 20-min forced swimming and ether anesthesia with restress in 7 days as 30-min immobilization. Oxidative modification of proteins was measured by amount of products of spontaneous and induced by Fenton's reactive modifications. Prenatally stressed rats without PTSD had increased spontaneous and induced modifications in the hypothalamus — key structure for stress response, and bi-directional changes in superoxide dismutase in neocortex and blood. In prenatally stressed rats, protein oxidation started next day after PTSD induction, but it was found only in the hippocampus. In rats without prenatal stress, protein oxidation started later and was found in all investigated brain structures 10 days after PTSD.

The critical importance of the fetal hypothalamus-pituitary-adrenal axis.

The fetal hypothalamus-pituitary-adrenal (HPA) axis is at the center of mechanisms controlling fetal readiness for birth, survival after birth and, in several species, determination of the timing of birth. Stereotypical increases in fetal HPA axis activity at the end of gestation are critical for preparing the fetus for successful transition to postnatal life. The fundamental importance in fetal development of the endogenous activation of this endocrine axis at the end of gestation has led to the use of glucocorticoids for reducing neonatal morbidity in premature infants. However, the choice of dose and repetition of treatments has been controversial, raising the possibility that excess glucocorticoid might program an increased incidence of adult disease (e.g., coronary artery disease and diabetes). We make the argument that because of the critical importance of the fetal HPA axis and its interaction with the maternal HPA axis, dysregulation of cortisol plasma concentrations or inappropriate manipulation pharmacologically can have negative consequences at the beginning of extrauterine life and for decades thereafter.

Antenatal Treatment with Glucocorticoids and the Hypotalamic-Pituitary-Adrenal Axis

Summary Fetal development is a critical period in the life cycle which is why the placenta provides a structural and physiological barrier that protects the fetus from the outer fluctuations and inner disturbances. A variety of influences from the environment, however, might induce fetal overexposure to glucocorticoids that target the fetal hypothalamic-pituitary-adrenal (HPA) axis and influence the fetal growth trajecto-r y. Development of the HPA axis starts in the early stages of pregnancy, but the timing of HPA axis maturation and the glucocorticoid receptor (GR) expression in relation to birth is highly species-specific. The functional state of the fetal HPA axis plays a key role in the maturation of many organs necessary for intrauterine development and existence after birth. A functional HPA axis in near-term fetuses provides an adequate response to stress and also affects the timing of parturition. Due to their potent effect on the maturation of fetal tissues, synthetic glucocorticoids are used in human pregnancy at risk of preterm delivery. Dexamethasone and betamethasone, as the ones most commonly used, cross the placental enzymatic barrier (11b-hydroxysteroid dehydrogenase type 2 – 11b-HSD2) and have 25-fold higher affinity to the GR than endogenous glucocorticoids, stimulating many aspects of fetal maturation. Despite the numerous positive effects, exposure to synthetic glucocorticoids during fetal development may result in intrauterine growth retardation and fetal programming of the HPA axis function which is associated with cardiovascular, metabolic and psychiatric disorders manifested later in life. Long-term consequences indicate the need for the implementation of new studies that will provide a better understanding of the link between glucocorti-coid overexposure during fetal development and adverse outcomes in adulthood.

Prenatal xenobiotic exposure and intrauterine hypothalamus-pituitary-adrenal axis programming alteration.

The hypothalamic-pituitary-adrenal (HPA) axis is one of the most important neuroendocrine axes and plays an important role in stress defense responses before and after birth. Prenatal exposure to xenobiotics, including environmental toxins (such as smoke, sulfur dioxide and carbon monoxide), drugs (such as synthetic glucocorticoids), and foods and beverage categories (such as ethanol and caffeine), affects fetal development indirectly by changing the maternal status or damaging the placenta. Certain xenobiotics (such as caffeine, ethanol and dexamethasone) may also affect the fetus directly by crossing the placenta into the fetus due to their lipophilic properties and lower molecular weights. All of these factors probably result in intrauterine programming alteration of the HPA axis, which showed a low basal activity but hypersensitivity to chronic stress. These alterations will, therefore, increase the susceptibility to adult neuropsychiatric (such as depression and schizophrenia) and metabolic diseases (such as hypertension, diabetes and non-alcoholic fatty liver disease). The "over-exposure of fetuses to maternal glucocorticoids" may be the main initiation factor by which the fetal HPA axis programming is altered. Meantime, xenobiotics can directly induce abnormal epigenetic modifications and expression on the important fetal genes (such as hippocampal glucocorticoid receptor, adrenal steroidogenic acute regulatory protein, et al) or damage by in situ oxidative metabolism of fetal adrenals, which may also be contributed to the programming alteration of fetal HPA axis.

Caffeine-Induced Activated Glucocorticoid Metabolism in the Hippocampus Causes Hypothalamic-Pituitary-Adrenal Axis Inhibition in Fetal Rats

Epidemiological investigations have shown that fetuses with intrauterine growth retardation (IUGR) are susceptible to adult metabolic syndrome. Clinical investigations and experiments have demonstrated that caffeine is a definite inducer of IUGR, as children who ingest caffeine-containing food or drinks are highly susceptible to adult obesity and hypertension. Our goals for this study were to investigate the effect of prenatal caffeine ingestion on the functional development of the fetal hippocampus and the hypothalamic-pituitary-adrenal (HPA) axis and to clarify an intrauterine HPA axis-associated neuroendocrine alteration induced by caffeine. Pregnant Wistar rats were intragastrically administered 20, 60, and 180 mg/kg·d caffeine from gestational days 11–20. The results show that prenatal caffeine ingestion significantly decreased the expression of fetal hypothalamus corticotrophin-releasing hormone. The fetal adrenal cortex changed into slight and the expression of fetal adrenal steroid acute regulatory protein (StAR) and cholesterol side-chain cleavage enzyme (P450scc), as well as the level of fetal adrenal endogenous corticosterone (CORT), were all significantly decreased after caffeine treatment. Moreover, caffeine ingestion significantly increased the levels of maternal and fetal blood CORT and decreased the expression of placental 11β-hydroxysteroid dehydrogenase-2 (11β-HSD-2). Additionally, both in vivo and in vitro studies show that caffeine can downregulate the expression of fetal hippocampal 11β-HSD-2, promote the expression of 11β-hydroxysteroid dehydrogenase 1 and glucocorticoid receptor (GR), and enhance DNA methylation within the hippocampal 11β-HSD-2 promoter. These results suggest that prenatal caffeine ingestion inhibits the development of the fetal HPA axis, which may be associated with the fetal overexposure to maternal glucocorticoid and activated glucocorticoid metabolism in the fetal hippocampus. These results will be beneficial in elucidating the developmental toxicity of caffeine and in exploring the fetal origin of adult HPA axis dysfunction and metabolic syndrome susceptibility for offspring with IUGR induced by caffeine.

Effects of early- and late-gestational maternal stress and synthetic glucocorticoid on development of the fetal hypothalamus–pituitary–adrenal axis in sheep

Prenatal maternal stress (PMS) programs dysregulation of the hypothalamus–pituitary–adrenal axis (HPAA) in postnatal life, though time periods vulnerable to PMS, are still unclear. We evaluated in pregnant sheep the effect of PMS during early gestation [30–100 days of gestation (dGA); term is 150 dGA] or late gestation (100–120 dGA) on development of fetal HPAA function. We compared the effects of endogenous cortisol with synthetic glucocorticoid (GC) exposure, as used clinically to enhance fetal lung maturation. Pregnant sheep were exposed to repeated isolation stress twice per week for 3 h in a separate box with no visual, tactile, or auditory contact with their flock-mates either during early (n = 7) or late (n = 7) gestation. Additional groups received two courses of betamethasone (BM; n = 7; 2 × 110 μg kg− 1 body weight, 24 h apart) during late gestation (106/107 and 112/113 dGA, n = 7) or acted as controls (n = 7). Fetal cortisol responses to hypotensive challenge, a physiological fetal stressor, were measured at 112 and 129 dGA, i.e. before and during maturation of the HPAA. Hypotension was induced by fetal infusion of sodium nitroprusside, a potent vasodilator. At 112 dGA, neither PMS nor BM altered fetal cortisol responses. PMS, during early or late gestation, and BM treatment increased fetal cortisol responses at 129 dGA with the greatest increase achieved in stressed early pregnant sheep. Thus, development of the HPAA is vulnerable to inappropriate levels of GCs during long periods of fetal life, whereas early gestation is most vulnerable to PMS.

Maternal choline intake alters the epigenetic state of fetal cortisol‐regulating genes in humans

The in utero availability of methyl donors, such as choline, may modify fetal epigenetic marks and lead to sustainable functional alterations throughout the life course. The hypothalamic-pituitary-adrenal (HPA) axis regulates cortisol production and is sensitive to perinatal epigenetic programming. As an extension of a 12-wk dose-response choline feeding study conducted in third-trimester pregnant women, we investigated the effect of maternal choline intake (930 vs. 480 mg/d) on the epigenetic state of cortisol-regulating genes, and their expression, in placenta and cord venous blood. The higher maternal choline intake yielded higher placental promoter methylation of the cortisol-regulating genes, corticotropin releasing hormone (CRH; P=0.05) and glucocorticoid receptor (NR3C1; P=0.002); lower placental CRH transcript abundance (P=0.04); lower cord blood leukocyte promoter methylation of CRH (P=0.05) and NR3C1 (P=0.04); and 33% lower (P=0.07) cord plasma cortisol. In addition, placental global DNA methylation and dimethylated histone H3 at lysine 9 (H3K9me2) were higher (P=0.02) in the 930 mg choline/d group, as was the expression of select placental methyltransferases. These data collectively suggest that maternal choline intake in humans modulates the epigenetic state of genes that regulate fetal HPA axis reactivity as well as the epigenomic status of fetal derived tissues.

Ethanol-induced inhibition of fetal hypothalamic–pituitary–adrenal axis due to prenatal overexposure to maternal glucocorticoid in mice

Prenatal ethanol exposure has been well documented to be one of the etiological factors responsible for intrauterine growth retardation (IUGR). Previous studies have shown that chronic ethanol exposure during pregnancy elevated the basic level of corticosterone in fetus. However, the potential mechanisms behind them are still unclear. The aim of the present study was to investigate the effects of prenatal ethanol exposure on maternal and fetal hypothalamic–pituitary–adrenal (HPA) axis as well as placental 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD-2), and to clarify the mechanism of ethanol-induced IUGR. Pregnant mice were intragastricly administrated with ethanol at a dose of 6.4 g kg −1 d −1 from day 11 to 17 of gestation and parameters representing fetal growth and development were recorded either. The level of corticosterone in maternal serum was determined by ELISA kit. The mRNA expressions of steroidogenic acute regulatory protein (StAR) and cytochrome P450 cholesterol side chain cleavage (P450scc) both in maternal and fetal adrenal, and placental 11β-HSD-2 were detected by real-time quantitative PCR, respectively. The results showed that fetal body weight significantly decreased, and the incidence of IUGR was obviously increased after prenatal ethanol exposure. Maternal serum corticosterone level was elevated, and the expressions of StAR and P450scc were increased in maternal adrenal while decreased in fetal adrenal. The expression of placental 11β-HSD-2 was significantly reduced. These results suggest that prenatal ethanol exposure induces an inhibition of fetal HPA axis activity and IUGR occurs. The mechanism may be associated with ethanol-induced maternal HPA axis activation and high glucocorticoid condition, which impair the placental barrier, and lead to an overexposure of elevated maternal glucocorticoid to fetus, and eventually result in the inhibition of the fetal HPA axis.

Interaction of PGHS-2 and glutamatergic mechanisms controlling the ovine fetal hypothalamus-pituitary-adrenal axis

Prostaglandins, generated within the fetal brain, are integral components of the mechanism controlling the fetal hypothalamus-pituitary-adrenal (HPA) axis. Previous studies in this laboratory demonstrated that prostaglandin G/H synthase isozyme 2 (PGHS-2) inhibition reduces the fetal HPA axis response to cerebral hypoperfusion, blocks the preparturient rise in fetal plasma ACTH concentration, and delays parturition. We also discovered that blockade of N-methyl-d-aspartate (NMDA) receptors reduces the fetal ACTH response to cerebral hypoperfusion. The present study was designed to test the hypothesis that PGHS-2 action and the downstream effect of HPA axis stimulation are stimulated by NMDA-mediated glutamatergic neurotransmission. Chronically catheterized late-gestation fetal sheep (n = 8) were injected with NMDA (1 mg iv). All responded with increases in fetal plasma ACTH and cortisol concentrations. Pretreatment with resveratrol (100 mg iv, n = 5), a specific inhibitor of PGHS-1, did not alter the magnitude of the HPA axis response to NMDA. Pretreatment with nimesulide (10 mg iv, n = 6), a specific inhibitor of PGHS-2, significantly reduced the HPA axis response to NMDA. To further explore this interaction, we injected NMDA in six chronically catheterized fetal sheep that were chronically infused with nimesulide (n = 6) at a rate of 1 mg/day into the lateral cerebral ventricle for 5-7 days. In this group, there was no significant ACTH response to NMDA. Finally, we tested whether the HPA axis response to prostaglandin E(2) (PGE(2)) is mediated by NMDA receptors. Seven chronically catheterized late-gestation fetal sheep were injected with 100 ng of PGE(2), which significantly increased fetal plasma ACTH and cortisol concentrations. Pretreatment with ketamine (10 mg iv), an NMDA antagonist, did not alter the ACTH or cortisol response to PGE(2). We conclude that generation of prostanoids via the action of PGHS-2 in the fetal brain augments the fetal HPA axis response to NMDA-mediated glutamatergic stimulation.

Do Alterations in Placental 11β-Hydroxysteroid Dehydrogenase (11βHSD) Activities Explain Differences in Fetal Hypothalamic-Pituitary-Adrenal (HPA) Function Following Periconceptional Undernutrition or Twinning in Sheep?

Periconceptional undernutrition (UN) in sheep accelerates fetal hypothalamic-pituitary-adrenal (HPA) axis activation, resulting in preterm birth. In contrast, twin conception suppresses fetal HPA function and delays prepartum HPA activation. We hypothesized that these dissimilar effects on fetal HPA activity result from different influences of maternal glucocorticoid (GC) on maturation of the fetal HPA axis, mediated via different activities of placental 11beta-hydroxysteroid dehydrogenase (11betaHSD) isozymes. We examined the effects of twinning and maternal periconceptional UN from 60 days before until 30 days after mating on the ontogeny of placental 11betaHSD-1 and -2 enzyme activities. At day 85 of gestation, placental 11betaHSD-2 activity was lower in UN than in normally nourished (N) fetuses (P < .05) and was higher in twins than in singletons (P < .05). Furthermore, placental 11betaHSD-1 activity was not different between nutritional groups but was higher in twins than in singletons (P = .01). At day 85, fetal plasma cortisol (P < .001) and cortisone (P < .001) concentrations were lower in UN than in N fetuses, but the cortisol to cortisone ratio was higher in UN than in N fetuses (P = .01). There was no effect of fetus number on plasma cortisol or cortisone concentrations or on the ratio of cortisol to cortisone at day 85. Therefore, periconceptional UN and twinning may result in the alterations of placental 11betaHSD isozyme activities at particular times during gestation. Changes in these activities during critical periods of fetal development could affect transplacental transfer or placental generation of GCs that reach the fetus, potentially influencing the timing of activation of the fetal HPA axis, fetal maturation, and hence the development and health later in life.

A Blood Test to Predict Preterm Birth: Don’t Mess with Maternal-Fetal Stress

The timely onset of labor and birth is a critical determinant of perinatal outcome. The mean duration of human pregnancy is 40 wk (280 d) from the first day of the last normal menstrual period. Both preterm birth (PTB; defined as delivery before 37 wk gestation) and postterm pregnancy (delivery after 42 wk) are associated with adverse perinatal outcome. In developed countries, PTB complicates 7–12% of all deliveries but accounts for over 70% of perinatal morbidity and mortality (1). Although the incidence of PTB has continued to rise every year for the past three decades, perinatal survival and intact survival have increased steadily during this same time period due in large part to the appropriate and timely use of antenatal corticosteroids and to improvements in neonatal resuscitation and infant care. For these reasons, early and accurate identification of women at risk of PTB is critical to optimize perinatal outcome. Early identification of women at risk will become even more important if recent reports on the use of progesterone supplementation to prevent PTB can be replicated (2–4). Obstetric care providers have traditionally relied on clinical symptoms (regular uterine contractions, pelvic pressure) to identify women at risk of spontaneous PTB. Numerous studies have now shown that reliance on clinical symptoms alone is inaccurate and unreliable. Such an approach will fail to identify the majority of womenwhodeliverpreterm(5), and, contrary topopularbelief, the presence of symptoms is not associated with an increased risk of spontaneous PTB (6, 7). For these reasons, extensive efforts have been made to develop objective tests to identify women at risk of PTB. Two such tests are currently recommended by the American College of Obstetricians and Gynecologists (ACOG) for the prediction of PTB, namely cervicovaginal fetal fibronectin (fFN) and measurement of cervical length by transvaginal ultrasound (8). A number of other predictive tests are under investigation, the most promising of which are measurements of steroid and stress hormones in the maternal circulation. The biological plausibility behind the use of maternal serum stress and sex steroid hormone levels to predict PTB is well established. Considerable evidence suggests that the hormonal milieu of the fetoplacental unit is in control of the timing of labor, although maternal and genetic factors are also involved (9–11). It is likely that a “parturition cascade” exists at term that is responsible for the removal of mechanisms maintaining uterine quiescence and the recruitment of factors acting to promote uterine activity. Although a detailed review of the proposed cascade is beyond the scope of this editorial, it is clear that endocrine factors are involved. As in other mammalian viviparous species, the final common pathway toward parturition in the human appears to be maturation and activation of the fetal hypothalamic-pituitary-adrenal (HPA) axis, with an increase in the major adrenal glucocorticoid product in the fetal circulation in late gestation (cortisol in the sheep and human; corticosterone in the rat and mouse). The cellular and molecular factors responsible for the maturation of the fetal HPA axis are incompletely understood, but are associated with the gestational age-dependent up-regulation of a number of critical genes, most importantly fetoplacental CRH. Levels of CRH in the maternal circulation increase from 10–100 pg/ml in nonpregnant women to 500–3,000 pg/ml in the third trimester of pregnancy (12). The source of this excess CRH is the placenta. Shortly before the onset of labor, both at term and preterm, CRH levels increase and hepatic-derived CRH-binding protein levels decrease, resulting in a marked increase in free (biologically active) CRH (13). CRH, in turn, acts via specific nuclear receptors in the myometrium, placenta, and fetal membranes to differentially regulate target genes. Among its effects on term uterine tissues, CRH promotes myometrial contractility by stimulating prostaglandin production from the decidua and fetal membranes (14) and potentiates the contractile effects of oxytocin and prostaglandins on the myometrium (15). At term, CRH also directly stimulates the production of the C-19 steroid, dehydroepiandrostenedione sulfate, from the intermediate (fetal) zone of the fetal adrenal glands (16, 17). Dehydroepiandrostenedione sulfate is then 16-hydroxylated in the fetal liver and converted to estriol