Identification of Eight Different Isoforms of the Glucocorticoid Receptor in Guinea Pig Placenta: Relationship to Preterm Delivery, Sex and Betamethasone Exposure

The Glucocorticoid Receptor: Isoforms, Functions, and Contribution to Glucocorticoid Sensitivity

Glucocorticoids exert pleiotropic effects on all tissues to regulate cellular and metabolic homeostasis. Synthetic forms are used therapeutically in a wide range of conditions for their anti-inflammatory benefits, at the cost of dose and duration-dependent side effects. Significant variability occurs between tissues, disease states, and individuals with regard to both the beneficial and deleterious effects. The glucocorticoid receptor (GR) is the site of action for these hormones and a vast body of work has been conducted understanding its function. Traditionally, it was thought that the anti-inflammatory benefits of glucocorticoids were mediated by transrepression of pro-inflammatory transcription factors, while the adverse metabolic effects resulted from direct transactivation. This canonical understanding of the GR function has been brought into question over the past 2 decades with advances in the resolution of scientific techniques, and the discovery of multiple isoforms of the receptor present in most tissues. Here we review the structure and function of the GR, the nature of the receptor isoforms, and the contribution of the receptor to glucocorticoid sensitivity, or resistance in health and disease.

Prenatal ethanol exposure and changes in fetal neuroendocrine metabolic programming

Prenatal ethanol exposure (PEE) (mainly through maternal alcohol consumption) has become widespread. However, studies suggest that it can cause intrauterine growth retardation (IUGR) and multi-organ developmental toxicity in offspring, and susceptibility to various chronic diseases (such as neuropsychiatric diseases, metabolic syndrome, and related diseases) in adults. Through ethanol's direct effects and its indirect effects mediated by maternal-derived glucocorticoids, PEE alters epigenetic modifications and organ developmental programming during fetal development, which damages the offspring health and increases susceptibility to various chronic diseases after birth. Ethanol directly leads to the developmental toxicity of multiple tissues and organs in many ways. Regarding maternal-derived glucocorticoid-mediated IUGR, developmental programming, and susceptibility to multiple conditions after birth, ethanol induces programmed changes in the neuroendocrine axes of offspring, such as the hypothalamus-pituitary-adrenal (HPA) and glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axes. In addition, the differences in ethanol metabolic enzymes, placental glucocorticoid barrier function, and the sensitivity to glucocorticoids in various tissues and organs mediate the severity and sex differences in the developmental toxicity of ethanol exposure during pregnancy. Offspring exposed to ethanol during pregnancy have a "thrifty phenotype" in the fetal period, and show "catch-up growth" in the case of abundant nutrition after birth; when encountering adverse environments, these offspring are more likely to develop diseases. Here, we review the developmental toxicity, functional alterations in multiple organs, and neuroendocrine metabolic programming mechanisms induced by PEE based on our research and that of other investigators. This should provide new perspectives for the effective prevention and treatment of ethanol developmental toxicity and the early prevention of related fetal-originated diseases.

Transgenerational inheritance of adrenal steroidogenesis inhibition induced by prenatal dexamethasone exposure and its intrauterine mechanism

BACKGROUND

Adrenal gland is the synthesis and secretion organ of glucocorticoid, which is crucial to fetal development and postnatal fate. Recently, we found that prenatal dexamethasone exposure (PDE) could cause adrenal dysfunction in offspring rats, but its multigenerational genetic effects and related mechanisms have not been reported.

METHODS

The PDE rat model was established, and female filial generation 1 (F1) rats mate with wild males to produce the F2, the same way for the F3. Three generation rats were sacrificed for the related detection. SW-13 cells were used to clarify the epigenetic molecular mechanism.

RESULTS

This study confirmed that PDE could activate fetal adrenal glucocorticoid receptor (GR). The activated GR, on the one hand, up-regulated Let-7b (in human cells) to inhibit steroidogenic acute regulatory protein (StAR) expression directly; on the other hand, down-regulated CCCTC binding factor (CTCF) and up-regulated DNA methyltransferase 3a/3b (Dnmt3a/3b), resulting in H19 hypermethylation and low expression. The decreased interaction of H19 and let-7 can further inhibit adrenal steroidogenesis. Additionally, oocytes transmitted the expression change of H19/let-7c axis to the next generation rats. Due to its genetic stability, F2 generation oocytes indirectly exposed to dexamethasone also inhibited H19 expression, which could be inherited to the F3 generation.

CONCLUSIONS

This cascade effect of CTCF/H19/Let-7c ultimately resulted in the transgenerational inheritance of adrenal steroidogenesis inhibition of PDE offspring. This study deepens the understanding of the intrauterine origin of adrenal developmental toxicity, and it will provide evidence for the systematic analysis of the transgenerational inheritance effect of acquired traits induced by PDE. Video Abstract.

Glucocorticoids and Their Receptor Isoforms: Roles in Female Reproduction, Pregnancy, and Foetal Development

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis and associated changes in circulating levels of glucocorticoids are integral to an organism's response to stressful stimuli. Glucocorticoids acting via glucocorticoid receptors (GRs) play a role in fertility, reproduction, placental function, and foetal development. GRs are ubiquitously expressed throughout the female reproductive system and regulate normal reproductive function. Stress-induced glucocorticoids have been shown to inhibit reproduction and affect female gonadal function by suppressing the hypothalamic-pituitary-gonadal (HPG) axis at each level. Furthermore, during pregnancy, a mother's exposure to prenatal stress or external glucocorticoids can result in long-lasting alterations to the foetal HPA and neuroendocrine function. Several GR isoforms generated via alternative splicing or translation initiation from the GR gene have been identified in the mammalian ovary and uterus. The GR isoforms identified include the splice variants, GRα and GRβ, and GRγ and GR-P. Glucocorticoids can exert both stimulatory and inhibitory effects and both pro- and anti-inflammatory functions in the ovary, in vitro. In the placenta, thirteen GR isoforms have been identified in humans, guinea pigs, sheep, rats, and mice, indicating they are conserved across species and may be important in mediating a differential response to stress. Distinctive responses to glucocorticoids, differential birth outcomes in pregnancy complications, and sex-based variations in the response to stress could all potentially be dependent on a particular GR expression pattern. This comprehensive review provides an overview of the structure and function of the GR in relation to female fertility and reproduction and discusses the changes in the GR and glucocorticoid signalling during pregnancy. To generate this overview, an extensive non-systematic literature search was conducted across multiple databases, including PubMed, Web of Science, and Google Scholar, with a focus on original research articles, meta-analyses, and previous review papers addressing the subject. This review integrates the current understanding of GR variants and their roles in glucocorticoid signalling, reproduction, placental function, and foetal growth.

Neuronal and Astroglial Localization of Glucocorticoid Receptor GRα in Adult Zebrafish Brain (Danio rerio)

Glucocorticoid receptor α (GRα), a ligand-regulated transcription factor, mainly activated by cortisol in humans and fish, mediates neural allostatic and homeostatic functions induced by different types of acute and chronic stress, and systemic inflammation. Zebrafish GRα is suggested to have multiple transcriptional effects essential for normal development and survival, similarly to mammals. While sequence alignments of human, monkey, rat, and mouse GRs have shown many GRα isoforms, we questioned the protein expression profile of GRα in the adult zebrafish (Danio rerio) brain using an alternative model for stress-related neuropsychiatric research, by means of Western blot, immunohistochemistry and double immunofluorescence. Our results identified four main GRα-like immunoreactive bands (95 kDa, 60 kDa, 45 kDa and 35 kDa), with the 95 kDa protein showing highest expression in forebrain compared to midbrain and hindbrain. GRα showed a wide distribution throughout the antero-posterior zebrafish brain axis, with the most prominent labeling within the telencephalon, preoptic, hypothalamus, midbrain, brain stem, central grey, locus coeruleus and cerebellum. Double immunofluorescence revealed that GRα is coexpressed in TH+, β₂-AR+ and vGLUT+ neurons, suggesting the potential of GRα influences on adrenergic and glutamatergic transmission. Moreover, GRα was co-localized in midline astroglial cells (GFAP+) within the telencephalon, hypothalamus and hindbrain. Interestingly, GRα expression was evident in the brain regions involved in adaptive stress responses, social behavior, and sensory and motor integration, supporting the evolutionarily conserved features of glucocorticoid receptors in the zebrafish brain.

Developmental toxicity and programming alterations of multiple organs in offspring induced by medication during pregnancy

Medication during pregnancy is widespread, but there are few reports on its fetal safety. Recent studies suggest that medication during pregnancy can affect fetal morphological and functional development through multiple pathways, multiple organs, and multiple targets. Its mechanisms involve direct ways such as oxidative stress, epigenetic modification, and metabolic activation, and it may also be indirectly caused by placental dysfunction. Further studies have found that medication during pregnancy may also indirectly lead to multi-organ developmental programming, functional homeostasis changes, and susceptibility to related diseases in offspring by inducing fetal intrauterine exposure to too high or too low levels of maternal-derived glucocorticoids. The organ developmental toxicity and programming alterations caused by medication during pregnancy may also have gender differences and multi-generational genetic effects mediated by abnormal epigenetic modification. Combined with the latest research results of our laboratory, this paper reviews the latest research progress on the developmental toxicity and functional programming alterations of multiple organs in offspring induced by medication during pregnancy, which can provide a theoretical and experimental basis for rational medication during pregnancy and effective prevention and treatment of drug-related multiple fetal-originated diseases.

Maternal Dexamethasone Exposure Induces Sex-Specific Changes in Histomorphology and Redox Homeostasis of Rat Placenta

As the mediator between the mother and fetus, the placenta allows the most appropriate environment and optimal fetal growth. The placenta of one sex sometimes has a greater ability over the other to respond to and protect against possible maternal insults. Here, we characterized sex differences in the placenta’s morphological features and antioxidant status following dexamethasone (Dx) exposure. Pregnant rats were exposed to Dx or saline. The placenta was histologically and stereologically analyzed. The activity of the antioxidant enzymes, lipid peroxides (TBARS), superoxide anion and nitric oxide (NO) was measured. The decrease in placental zone volumes was more pronounced (p < 0.05) in female placentas. The volume density of PCNA-immunopositive nuclei was reduced (p < 0.05) in both sexes. The reduced (p < 0.05) antioxidant enzyme activities, enhanced TBARS and NO concentration indicate that Dx exposure triggered oxidative stress in the placenta of both fetal sexes, albeit stronger in the placenta of female fetuses. In conclusion, maternal Dx treatment reduced the size and volume of placental zones, altered placental histomorphology, decreased cell proliferation and triggered oxidative stress; however, the placentas of female fetuses exerted more significant responses to the treatment effects. The reduced placental size most probably reduced the transport of nutrients and oxygen, thus resulting in the reduced weight of fetuses, similar in both sexes. The lesser ability of the male placenta to detect and react to maternal exposure to environmental challenges may lead to long-standing health effects.

In utero exposure to glucocorticoids and risk of anxiety and depression in childhood or adolescence

Glucocorticoid use is prevalent in pregnant women, but whether in utero exposure impacts mental health in the offspring has not been fully explored. The aim of this study was to investigate if in utero exposure to synthetic glucocorticoids increases the risk of anxiety and depression in childhood or adolescence. The study was conducted as a nationwide cohort study, including negative control exposure analyses and a sibling design to optimize control of confounding. The study population comprised 1,275,909 children born in 1996-2015 in Denmark (median follow-up of 13 years). Exposure was divided into systemic and local glucocorticoid exposure, levels of cumulative dose, generic type and according to trimester of exposure. The comparison cohort was children without exposure born to maternal never-users. Negative control exposures included children without glucocorticoid exposure born to: maternal users of non-steroidal anti-inflammatory drugs or immunotherapy during pregnancy, maternal former users of systemic glucocorticoids, maternal users of systemic glucocorticoids in the postnatal period, and fathers who were prescribed glucocorticoids. The sibling design compared siblings with and without exposure. 9307 (0.7%) children were exposed to systemic glucocorticoids and 116,389 (9.1%) children were exposed to local glucocorticoids. High-dose systemic glucocorticoids (≥500 mg prednisolone equivalents) increased the risk of anxiety compared to the comparison cohort [aIRR 1.79 (95% CI: 1.36-2.37), cumulative risk 16% vs. 7.8% by age 20]. A similar result was found for depression [aIRR 1.45 (95% CI: 0.80-2.63), cumulative risk 3.6% vs. 2.6% by age 20]. The association with anxiety was consistent in the sibling design [aIRR 1.83 (95% CI: 1.03-3.66), exposed siblings (≥ 500 mg) vs. unexposed]. Sex did not modify the associations. Negative control exposure analyses indicated robustness towards confounding from genetics and family environment. No association was found with low doses of systemic exposure or local use. In conclusion, potential adverse mental health effects of in utero exposure to high-dose glucocorticoids merit clinical attention.

Differential expression of placental 11β-HSD2 induced by high maternal glucocorticoid exposure mediates sex differences in placental and fetal development

A variety of adverse environmental factors during pregnancy cause maternal chronic stress. Caffeine is a common stressor, and its consumption during pregnancy is widespread. Our previous study showed that prenatal caffeine exposure (PCE) increased maternal blood glucocorticoid levels and caused abnormal development of offspring. However, the placental mechanism for fetal development inhibition caused by PCE-induced high maternal glucocorticoid has not been reported. This study investigated the effects of PCE-induced high maternal glucocorticoid level on placental and fetal development by regulating placental 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) expression and its underlying mechanism. First, human placenta and umbilical cord blood samples were collected from women without prenatal use of synthetic glucocorticoids. We found that placental 11β-HSD2 expression was significantly correlated with umbilical cord blood cortisol level and birth weight in male newborns but not in females. Furthermore, we established a rat model of high maternal glucocorticoids induced by PCE (caffeine, 60 mg/kg·d, ig), and found that the expression of 11β-HSD2 in male PCE placenta was decreased and negatively correlated with the maternal/fetal/placental corticosterone levels. Meanwhile, we found abnormal placental structure and nutrient transporter expression. In vitro, BeWo cells were used and confirm that 11β-HSD2 mediated inhibition of placental nutrient transporter expression induced by high levels of glucocorticoid. Finally, combined with the animal and cell experiments, we further confirmed that high maternal glucocorticoid could activate the GR-C/EBPα-Egr1 signaling pathway, leading to decreased expression of 11β-HSD2 in males. However, there was no significant inhibition of placental 11β-HSD2 expression, placental and fetal development in females. In summary, we confirmed that high maternal glucocorticoids could regulate placental 11β-HSD2 expression in a sex-specific manner, leading to differences in placental and fetal development. This study provides the theoretical and experimental basis for analyzing the inhibition of fetoplacental development and its sex difference caused by maternal stress.

Identification of multiple isoforms of glucocorticoid receptor in nasal polyps of patients with chronic rhinosinusitis

Background

The conventional belief that glucocorticosteroid (GC) acts through a single brand glucocorticoid receptor (GR)α protein has changed dramatically with the discovery of multiple GR isoforms. We aimed to evaluate whether multiple GR protein isoforms are expressed in chronic rhinosinusitis with nasal polyps (CRSwNP) and whether GR protein isoform expression profiles differ between different endotypes of CRSwNP.

Methods

Thirty-eight patients with CRSwNP and ten healthy volunteers were included. The protein expression of multiple GR isoforms in nasal polyps (NPs) tissue and control mucosae was examined by western blot analysis with different GR antibodies.

Results

Five bands, including three bands for known proteins (GRα-A/B, GRα-C, and GRα-D) and two bands for unidentified proteins at 67 kilodaltons (kDa) and 60 kDa, were identified with both total GR antibody (PA1-511A) and GRα-specific antibody (PA1-516). GRα-D intensity, which was abundant in nasal mucosa, was significantly increased in the CRSwNP group and was especially elevated in the noneosinophilic CRSwNP (NE-CRSwNP) group (PA1-511A: P < 0.001 and P = 0.0018; PA1-516: P < 0.003 and P = 0.006, respectively). Additionally, the intensities of the newly recognized 67 kDa and 60 kDa bands were much greater in the NE-CRSwNP subgroup than in the eosinophilic CRSwNP (E-CRSwNP) subgroup; in the E-CRSwNP subgroup, the median intensities were even lower than those in the control group.

Conclusions

This study provides evidence that nasal tissues express multiple GR protein isoforms. GR protein isoforms presented disease and tissue-specific expression profiles that differed between the CRSwNP and control groups and between the E-CRSwNP and NE-CRSwNP subgroups.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s40463-022-00561-1.

Sexual dimorphism in placental development and its contribution to health and diseases

According to the Developmental Origin of Health and Disease (DOHaD), intrauterine exposure to adverse environments can affect fetus and birth outcomes and lead to long-term disease susceptibility. Evidence has shown that neonatal outcomes and the timing and severity of adult diseases are sexually dimorphic. As the link between mother and fetus, the placenta is an essential regulator of fetal development programming. It is found that the physiological development trajectory of the placenta has sexual dimorphism. Furthermore, under pathological conditions, the placental function undergoes sex-specific adaptation to ensure fetal survival. Therefore, the placenta may be an important mediator of sexual dimorphism in neonatal outcomes and adult disease susceptibility. Few systematic reviews have been conducted on sexual dimorphism in placental development and its underlying mechanisms. In this review, sex chromosomes and sex hormones, as the main reasons for sexual differentiation of the placenta, will be discussed. Besides, in the etiology of fetal-originated adult diseases, overexposure to glucocorticoids is closely related to adverse neonatal outcomes and long-term disease susceptibility. Studies have found that prenatal glucocorticoid overexposure leads to sexually dimorphic expression of placental glucocorticoid receptor isoforms, resulting in different sensitivity of the placenta to glucocorticoids, and may further affect fetal development. The present review examines what is currently known about sex differences in placental development and the underlying regulatory mechanisms of this sex bias. This review highlights the importance of placental contributions to the origins of sexual dimorphism in health and diseases. It may help develop personalized diagnosis and treatment strategies for fetal development in pathological pregnancies.

A preferential switch between placental GR exon 1 promoter variants in the presence of maternal asthma or inflammation upregulates GRα D isoforms

INTRODUCTION

The human placenta expresses multiple glucocorticoid receptor (GR) isoforms that may be partially regulated by the untranslated 5' exon 1 GR gene promoter region which consists of 9 different promoters and 13 splice variants. The objective of this study was to determine which GR exon 1 variants are expressed in the human placenta and relate these findings to GR mRNA and protein expression.

METHODS

Placental extracts from pregnancies with or without the complication of maternal asthma and trophoblast cells exposed to an inflammatory challenge in vitro were examined using PCR and Western blot to measure GR exon 1 variants, GR splice variant mRNA and GR protein isoforms, respectively.

RESULTS

All 9 GR exon 1 variants were detectable in the human placenta and included GR exons 1A, 1B, 1C, 1D, 1E, 1F, 1H, 1I and 1J. In the presence of maternal asthma and a male fetus there was preferential expression of GR exon 1B, 1C, IF and 1J (KW-ANOVA, P < 0.05) which were positively correlated with GRα D3 protein isoform. In female placentae from pregnancies complicated by asthma there was no upregulation of any exon 1 variant (KW-ANOVA, P < 0.05). Exposure of BeWo trophoblast cell line to an inflammatory challenge, lipopolysaccharide, in vitro, resulted in preferential expression of GR exon 1B, 1D, 1E and 1H and associated with GRα-D1 protein upregulation.

DISCUSSION

The preferential expression of different GR exon 1 promoters drive the upregulation of GRα D isoforms and contribute to glucocorticoid resistance observed in male placentae of pregnancies complicated by asthma.

Dexamethasone-induced intrauterine growth restriction modulates expression of placental vascular growth factors and fetal and placental growth

Prenatal exposure to glucocorticoids (GC) is a central topic of interest in medicine since GCs are essential for the maturation of fetal organs and intrauterine growth. Synthetic glucocorticoids, which are used in obstetric practice, exert beneficial effects on the fetus, but have also been reported to lead to intrauterine growth retardation (IUGR). In this study, a model of growth restriction in mice was established through maternal administration of dexamethasone during late gestation. We hypothesised that GC overexposure may adversely affect placental angiogenesis and fetal and placental growth. Female BALB/c mice were randomly assigned to control or dexamethasone treatment, either left to give birth or euthanised on days 15, 16, 17 and 18 of gestation followed by collection of maternal and fetal tissue. The IUGR rate increased to 100% in the dexamethasone group (8 mg/kg body weight on gestational days 14 and 15) and pups had clinical features of symmetrical IUGR at birth. Dexamethasone administration significantly decreased maternal body weight gain and serum corticosterone levels. Moreover, prenatal dexamethasone treatment not only induced fetal growth retardation but also decreased placental weight. In IUGR placentas, VEGFA protein levels and mRNA expression of VEGF receptors were reduced and NOS activity was lower. Maternal dexamethasone administration also reduced placental expression of the GC receptor, αGR. We demonstrated that maternal dexamethasone administration causes fetal and placental growth restriction. Furthermore, we propose that the growth retardation induced by prenatal GC overexposure may be caused, at least partially, by an altered placental angiogenic profile.

Steroid receptors and their regulation in avian extraembryonic membranes provide a novel substrate for hormone mediated maternal effects

Exposure of the vertebrate embryo to maternal hormones can have long-lasting effects on its phenotype, which has been studied extensively by experimentally manipulating maternal steroids, mostly androgens, in bird eggs. Yet, there is a severe lack of understanding of how and when these effects are actually mediated, hampering both underlying proximate and ultimate explanations. Here we report a novel finding that the embryo expresses androgen receptor (AR) and estrogen receptor (ERα) mRNA in its extraembryonic membranes (EMs) as early as before its own hormone production starts, suggesting a novel substrate for action of maternal hormones on the offspring. We also report the first experimental evidence for steroid receptor regulation in the avian embryo in response to yolk steroid levels: the level of AR is dependent on yolk androgen levels only in the EMs but not in body tissues, suggesting embryonic adaptation to maternal hormones. The results also solve the problem of uptake of lipophilic steroids from the yolk, why they affect multiple traits, and how they could mediate maternal effects without affecting embryonic sexual differentiation.

Placental glucocorticoid receptor isoforms in a sheep model of maternal allergic asthma

Maternal asthma increases the risk of adverse pregnancy outcomes and may affect fetal growth and placental function by differential effects on the expression of glucocorticoid receptor (GR) isoforms, leading to altered glucocorticoid signalling. Our aim was to examine the effect of maternal asthma on placental GR profiles using a pregnant sheep model of asthma. Nine known GR isoforms were detected. There was a significant increase in the expression of placental GR isoforms that are known to have low trans-activational activity in other species including GR A, GR P and GRγ which may result in a pro-inflammatory environment in the presence of allergic asthma.

Guinea pig models for translation of the developmental origins of health and disease hypothesis into the clinic

Over 30 years ago Professor David Barker first proposed the theory that events in early life could explain an individual's risk of non-communicable disease in later life: the developmental origins of health and disease (DOHaD) hypothesis. During the 1990s the validity of the DOHaD hypothesis was extensively tested in a number of human populations and the mechanisms underpinning it characterised in a range of experimental animal models. Over the past decade, researchers have sought to use this mechanistic understanding of DOHaD to develop therapeutic interventions during pregnancy and early life to improve adult health. A variety of animal models have been used to develop and evaluate interventions, each with strengths and limitations. It is becoming apparent that effective translational research requires that the animal paradigm selected mirrors the tempo of human fetal growth and development as closely as possible so that the effect of a perinatal insult and/or therapeutic intervention can be fully assessed. The guinea pig is one such animal model that over the past two decades has demonstrated itself to be a very useful platform for these important reproductive studies. This review highlights similarities in the in utero development between humans and guinea pigs, the strengths and limitations of the guinea pig as an experimental model of DOHaD and the guinea pig's potential to enhance clinical therapeutic innovation to improve human health.

Placental glucocorticoid receptor and 11β-hydroxysteroid dehydrogenase-2 recruitment indicates impact of prenatal adversity upon postnatal development in mice

Prenatal stress may increase concentrations of maternal glucocorticoids, which restrict fetal growth, with variable impact upon postnatal development. Among key regulators of stress hormone effects are the glucocorticoid receptor (GR) and 11β-hydroxysteroid dehydrogenase-2 (11βHSD2), the enzyme that inactivates glucocorticoid. This study utilized mice selectively bred for social dominance (Dom) or submissiveness (Sub), respectively exhibiting resilience or sensitivity to stress, to test whether stress-induced alterations in placental GR and 11βHSD2 protein expression may mediate divergent effects of prenatal adversity upon postnatal development. Pregnant Dom and Sub dams underwent prenatal restraint stress (PRS) for 45 min on gestational days (GD) 15-17. PRS induced a similar spike in serum corticosterone concentrations of dams from each strain on GD15 (p < .001, n = 8), and impaired fetal growth (p < .01, n = 5 litters), although Dom placentae were larger than Sub placentae (p < .01). Among placentae from Dom dams, PRS elevated protein contents of both GR (p < .05, n = 5 litters) and 11βHSD2 (p < .01) on GD19. In contrast, GR contents were reduced among placentae from PRS-exposed Sub mice (p < .01), without changes in 11βHSD2 content. Correspondingly, Dom PRS pup growth recovered by PND14, yet Sub PRS pups remained underweight into adolescence (p < .0001, n = 40 pups). Thus, prenatal stress more strongly increased placental GR and 11βHSD2 levels among Dom mice than in Subs. Increased GR may improve placental function and up-regulate 11βHSD2 expression, protecting fetuses from effects of prenatal stress upon postnatal development. Placental recruitment of GR and 11βHSD2 are potential markers of stress-induced developmental disorders, in accordance with maternal resilience or sensitivity to stress.

Microvascular circulatory dysregulation driven in part by cystathionine gamma-lyase: A new paradigm for cardiovascular compromise in the preterm newborn

OBJECTIVE

H₂ S may explain the dysregulation of microvascular tone associated with poor outcome following preterm birth. In adult vasculature, H₂ S is predominantly produced by CSE. We hypothesized that vascular CSE activity contributes to microvascular tone regulation during circulatory transition.

METHODS

Preterm (GA62) and full-term (GA69) guinea pig fetuses and neonates were studied. Microvascular blood flow was assessed by laser Doppler flowmetry. Thiosulfate, primary urinary metabolite of H₂ S, was determined by high-performance liquid chromatography. Real-time H₂ S production was assessed using a microrespiration system in fetal and postnatal (10, 24 hours) skin and heart samples. CSE contribution was investigated by inhibition via propargylglycine.

RESULTS

In preterm animals, postnatal H₂ S production capacity in peripheral vasculature increased significantly and was significantly reduced by the inhibition of CSE. Urinary thiosulfate correlated with both microvascular blood flow and capacity of the vasculature to produce H₂ S. H₂ S produced via CSE did not correlate directly with microvascular blood flow.

CONCLUSIONS

In preterm neonates, H₂ S production increases during fetal-to-neonatal transition and CSE contribution to total H₂ S increases postnatally. CSE-dependent mechanisms may therefore underpin the increase in H₂ S production over the first 72 hours of life in preterm human neonates, associated with both central and peripheral cardiovascular instability.

Prenatal Maternal Cortisol Has Sex-Specific Associations with Child Brain Network Properties

Elevated maternal cortisol concentrations have the potential to alter fetal development in a sex-specific manner. Female brains are known to show adaptive behavioral and anatomical flexibility in response to early-life exposure to cortisol, but it is not known how these sex-specific effects manifest at the whole-brain structural networks. A prospective longitudinal study of 49 mother child dyads was conducted with serial assessments of maternal cortisol levels from 15 to 37 gestational weeks. We modeled the structural network of typically developing children (aged 6-9 years) and examined its global connectome properties, rich-club organization, and modular architecture. Network segregation was susceptible only for girls to variations in exposure to maternal cortisol during pregnancy. Girls generated more connections than boys to maintain topologically capable and efficient neural circuits, and this increase in neural cost was associated with higher levels of internalizing problems. Maternal cortisol concentrations at 31 gestational weeks gestation were most strongly associated with altered neural connectivity in girls, suggesting a sensitive period for the maternal cortisol-offspring brain associations. Our data suggest that girls exhibit an adaptive response by increasing the neural network connectivity necessary for maintaining homeostasis and efficient brain function across the lifespan.

Dexamethasone and sex regulate placental glucocorticoid receptor isoforms in mice

Maternal dexamethasone exposure in the mouse impairs placental development and programs adult disease in a sexually dimorphic manner. Glucocorticoids bind to different glucocorticoid receptor (GR) isoforms to regulate gene transcription and cellular signaling. We hypothesized that sexually dimorphic placental responses to glucocorticoids are due to differences in GR isoforms present in the placenta. Pregnant C57Bl6 mice were exposed to saline or dexamethasone from E12.5 until E14.5 (1 µg/kg/h) before the collection of placentae. Cytoplasmic and nuclear protein fractions were extracted from placentae of male and female fetuses for Western blot analysis of GR isoforms. Eight known isoforms of the GR were detected in the mouse placenta including the translational isoforms GRα-A, B, C and D1-3 and the splice variants GRA and GRP. The expression of GRA, GRP and each of the GRα isoforms were altered by dexamethasone in relation to fetal sex and cellular location. Placentae of female fetuses had higher GRα-A and GRP expression in the cytoplasm than males, and GRα-C was more highly expressed in the nucleus of females than that in males. Dexamethasone significantly increased the cytoplasmic expression of GRα-A, but reduced the expression of GRα-C in placentae of males. Dexamethasone increased the expression of the GRα-C-regulated genes Sgk1 and Bcl2l11, particularly in females. The cleaved caspase-3 staining in placental sections indicated GRα-C may mediate sex differences in dexamethasone-induced apoptosis. These findings may underlie the sex-specific placental adaptations that regulate different growth profiles in males and females and different risks for programmed disease outcomes in offspring.

Molecular analysis of sequence and splice variants of the human SLC13A4 sulfate transporter

The solute linked carrier 13A4 gene (SLC13A4) is abundantly expressed in the human and mouse placenta where it is proposed to transport nutrient sulfate to the fetus. In mice, targeted disruption of placental Slc13a4 leads to severe and lethal fetal phenotypes, however the involvement of SLC13A4 in human development is unknown. A search of the NCBI and Ensembl gene databases identified two alternatively spliced SLC13A4 mRNA transcripts and 98 SLC13A4 gene variants, including 85 missense, 4 splice site, 5 frameshift and 2 nonsense variants, as well as 2 in-frame deletions. We examined the relative abundance of the two SLC13A4 mRNA transcripts and then compared the sulfate transport function and plasma membrane expression of both isoforms as well as 6 sequence variants that predict disrupted SLC13A4 protein structure and function. SLC13A4 mRNA variant 1 has three additional nucleotides CAG compared to SLC13A4 mRNA variant 2 as a result of alternative splicing at the 5'-end of exon 6. Using qRT-PCR, we show a 4-fold higher abundance of SLC13A4 mRNA variant 1 compared to variant 2 in term human placentas and cultured BeWo and JEG-3 cell lines. The corresponding SLC13A4 protein isoforms 1 and 2 were found to have similar sulfate uptake activity and apical membrane expression in cultured MDCK cells. In addition, sulfate uptake into MDCK cells was similar between SLC13A4 isoform 1 and four missense variants N300S, F310C, E360Q and I570V, whereas V513M and frameshift variant L72Sfs led to partial (≈75% decrease) and complete loss-of-function, respectively. Localisation of these variants in MDCK cells showed N300S, E360Q, V513M and I570V expression on the apical plasma membrane, L72Sfs intracellularly and F310C on both apical and basolateral membranes. Our finding of partial and complete loss-of-function variants warrants further studies of the potential involvement of SLC13A4 in fetal pathophysiology.

Mechanisms of Glucocorticoid Action During Development

Glucocorticoids are primary stress hormones produced by the adrenal cortex. The concentration of serum glucocorticoids in the fetus is low throughout most of gestation but surge in the weeks prior to birth. While their most well-known function is to stimulate differentiation and functional development of the lungs, glucocorticoids also play crucial roles in the development of several other organ systems. Mothers at risk of preterm delivery are administered glucocorticoids to accelerate fetal lung development and prevent respiratory distress. Conversely, excessive glucocorticoid signaling is detrimental for fetal development; slowing fetal and placental growth and programming the individual for disease later in adult life. This review explores the mechanisms that control glucocorticoid signaling during pregnancy and provides an overview of the impact of glucocorticoid signaling on fetal development.