Reduced maternal plasma urocortin concentrations and impaired uterine artery blood flow at human mid pregnancy

Urocortins as biomarkers in cardiovascular disease

The urocortins (Ucns) belong to the corticotropin-releasing factor (CRF) family of peptides and have multiple effects within the central nervous and the cardiovascular systems. With growing evidence indicating significant cardioprotective properties and cardiovascular actions of these peptides, the question arises as to whether the plasma profiles of the Ucns are altered in pathologic settings. While reports have shown conflicting results and findings have not been corroborated in multiple independent cohorts, it seems likely that plasma Ucn concentrations are elevated in multiple cardiovascular conditions. The degree of increase and accurate determination of circulating values of the Ucns requires further validation.

Corticotropin-Releasing Factor Family: A Stress Hormone-Receptor System's Emerging Role in Mediating Sex-Specific Signaling

No organ in the body is impervious to the effects of stress, and a coordinated response from all organs is essential to deal with stressors. A dysregulated stress response that fails to bring systems back to homeostasis leads to compromised function and ultimately a diseased state. The components of the corticotropin-releasing factor (CRF) family, an ancient and evolutionarily conserved stress hormone-receptor system, helps both initiate stress responses and bring systems back to homeostasis once the stressors are removed. The mammalian CRF family comprises of four known agonists, CRF and urocortins (UCN1–3), and two known G protein-coupled receptors (GPCRs), CRF₁ and CRF₂. Evolutionarily, precursors of CRF- and urocortin-like peptides and their receptors were involved in osmoregulation/diuretic functions, in addition to nutrient sensing. Both CRF and UCN1 peptide hormones as well as their receptors appeared after a duplication event nearly 400 million years ago. All four agonists and both CRF receptors show sex-specific changes in expression and/or function, and single nucleotide polymorphisms are associated with a plethora of human diseases. CRF receptors harbor N-terminal cleavable peptide sequences, conferring biased ligand properties. CRF receptors have the ability to heteromerize with each other as well as with other GPCRs. Taken together, CRF receptors and their agonists due to their versatile functional adaptability mediate nuanced responses and are uniquely positioned to orchestrate sex-specific signaling and function in several tissues.

Role of urocortin in pregnancy: An update and future perspectives

The activities of corticotropin-releasing factor (CRF) and related peptides are mediated a number of receptors with seven transmembrane domains that are coupled to the Gs and Gq proteins. These receptors are known as CRF-Rs. In vitro studies have evidenced that urocortin (UCN) and CRF provoke an increase in the contractility of the uterus which is induced by endometrial prostaglandin F2a. Furthermore, through trophoblasts, it stimulates the secretion of adrenocorticotropic hormone (ACTH) and prostaglandin PGE2 and has a vasodilatory effect on the placenta. While it is well known that the placenta produces considerable quantities of CRF, several studies have, however, excluded that the placenta can generate significant quantities of UCN. In the short term, the human fetal adrenal gland produces more cortisol and dehydroepiandrosterone sulfate. The gestational tissues express UCN3 and UCN2 mRNA in cytotrophoblast and syncytiotrophoblast cells, while UCN2 is only to be found in the maternal and fetal vessels and amniotic cells. Nevertheless, gestational tissues express UCN2 and UCN3 differentially and do not stimulate placental ACTH secretion. In term pregnancies, maternal plasma levels of CRF and UCN are lower than at the beginning of pregnancy and are correlated to labor onset. Conversely, they do not decrease in post-term pregnancies. This evidence would seem to indicate that the fine-regulated expression of these neuropeptides is important in determining the duration of human gestation. In this scenario, low concentrations of UCN in the amniotic fluid at mid-term may be considered a sign of predisposition to preterm birth.

Urocortin 1 expression and secretion by human umbilical vein endothelial cells: In vitro effects of interleukin 8, interferon γ, lipopolysaccharide, endothelin 1, prostaglandin F-2α, estradiol, progesterone and dexamethasone

Urocortin 1 (Ucn1) is a 40-amino-acid peptide that has vasodilatory activity and displays immunomodulatory and antioxidant properties. Maternal and cord plasma Ucn1 levels are increased in preeclampsia and preterm labor, but the mechanisms of such increase are poorly known. Thus, we investigated Ucn1 localization in human umbilical cord and assessed some potential stimuli to Ucn1 release by human umbilical vein endothelial cells (HUVEC). Human umbilical cords were obtained at uncomplicated term pregnancy (n=11). Ucn1 localization was assessed by immunohistochemistry and quantified. HUVEC were grown in vitro to confluence, then incubated with serial concentrations of interleukin (IL)-8, interferon (INF)-γ, lipopolysaccharide (LPS), endothelin (ET)-1, prostaglandin (PG)F-2α, estradiol, progesterone and dexamethasone and Ucn1 concentrations were measured in the supernatants. Ucn1 was immunolocalized with similar intensity in umbilical cord arteries, vein and Wharton's jelly. Ucn1 mRNA was detected in all HUVEC cultures and Ucn1 peptide was detectable in culture medium from untreated cells at different time points. Incubation with IFN-γ increased Ucn1 secretion in a dose-dependent manner. Treatments with IL-8, LPS, ET-1 and dexamethasone were able to increase three to fourfold Ucn1 release from cultured endothelial cells. In conclusion, umbilical vessels express Ucn1 and may be a contributive source of Ucn1 release into fetal-placental circulation. IL-8, IFN-γ, LPS, ET-1 and dexamethasone promote Ucn1 secretion from cultured HUVEC.

Expression of urocortin and corticotrophin-releasing hormone receptor-2 in patients with intrahepatic cholestasis of pregnancy

INTRODUCTION

Intrahepatic cholestasis of pregnancy (ICP) is associated with an increased risk of adverse pregnancy outcomes. Fetal distress in ICP is an acute process, and the abnormal expression of placental local vasodilatory factors play an essential role. Urocortin (UCN) exhibits a powerful concentration-dependent vasodilatation effect in the utero-placental-fetal unit. Our study aimed to investigate placental and serum UCN expression in ICP patients.

METHODS

Blood and placenta samples were obtained from the ICP patients and controls. UCN and corticotrophin-releasing hormone receptor-2 (CRH-R2) expression were detected by ELISA, immunohistochemistry, Western Blotting and real-time PCR.

RESULTS

Placental UCN expression of ICP was lower compare to the controls (0.27 ± 0.11 vs. 0.85 ± 0.21) (P < 0.05). Placental CRH-R2 (0.97 ± 0.09 vs. 0.86 ± 0.09) showed no difference between the ICP and controls (P > 0.05). Placental UCN mRNA (1.45 ± 0.31 vs. 0.72 ± 0.29) and CRH-R2 mRNA expression (1.11 ± 0.10 vs. 0.84 ± 0.24) were higher compared to the controls (all P < 0.05). Maternal serum UCN levels demonstrated no difference from 34 (79.47 ± 11.35 pg/ml) to 37 (84.24 ± 13.62 pg/ml) weeks of gestation in controls (P > 0.05). Maternal serum UCN levels of ICP were decreased from 34 (68.53 ± 16.95 pg/ml) to 37 (47.91 ± 15.65 pg/ml) weeks of gestation (P < 0.05) and were lower than controls at 35 (64.19 ± 22.50 pg/ml), 36 (50.06 ± 13.98 pg/ml) and 37 weeks of gestation (all P < 0.05).

DISCUSSION

The down-regulated UCN expression in the placenta and maternal serum during ICP may impair the blood flow regulation of the utero-placental-fetal unit and contribute to fetal distress. Maternal serum UCN levels might represent a potential clinical predictor of adverse fetal outcomes and optimize the clinical management.

Attenuated tubal and endometrial urocortin 1 and corticotropin-releasing hormone receptor expression in ectopic pregnancy

Fallopian tube (FT) and endometrial urocortin 1 (Ucn1) and corticotropin-releasing hormone (CRH)-receptor (CRH-R1/CRH-R2) expression were examined using quantitative real-time polymerase chain reaction (RT-PCR) and immunohistochemistry in nonpregnant and pregnant women (intrauterine, IUP; ectopic pregnancy, EP). Tubal Ucn1 messenger RNA (mRNA) expression was higher in luteal compared to follicular phase (P < .01) and equivalent to follicular phase in FT from EP. Tubal CRH-R1/CRH-R2 mRNA was lower in luteal phase (P < .05) and in FT from EP compared to follicular phase (P < .01). Ucn1 mRNA was lower in endometrium from EP compared to IUP (P < .05). Corticotropin-releasing hormone-R1 mRNA was higher in endometrium from EP compared to viable IUP (P < .05). No differences were observed in CRH-R2 expression. Corticotropin-releasing hormone-R1 protein was primarily localized to epithelium of FT and endometrium. Quantitative analysis of tubal CRH-R1 protein expression reflected that seen at the mRNA level but endometrial expression was equivocal. The demonstration of attenuated tubal/endometrial Ucn1/CRH-R expression in EP further supports a role of the CRH-family in embryo implantation.

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.

Baby on board: do responses to stress in the maternal brain mediate adverse pregnancy outcome?

Stress and adverse environmental surroundings result in suboptimal conditions in a pregnant mother such that she may experience poor pregnancy outcome including complete pregnancy failure and preterm labor. Furthermore her developing baby is at risk of adverse programming, which confers susceptibility to long term ill health. While some mechanisms at the feto-maternal interface underlying these conditions are understood, the underlying cause for their adverse adaptation is often not clear. Progesterone plays a key role at many levels, including control of neuroendocrine responses to stress, procuring the required immune balance and controlling placental and decidual function, and lack of progesterone can explain many of the unwanted consequences of stress. How stress that is perceived by the mother inhibits progesterone secretion and action is beginning to be investigated. This overview of maternal neuroendocrine responses to stress throughout pregnancy analyses how they interact to compromise progesterone secretion and precipitate undesirable effects in mother and offspring.

Urocortin increases IL-4 and IL-10 secretion and reverses LPS-induced TNF-alpha release from human trophoblast primary cells

PROBLEM

As urocortin (Ucn) is a placental peptide belonging to the corticotrophin-releasing hormone (CRH) family that modulates immune function in other biological models, this study evaluated Ucn effects on cytokines secretion from cultured human trophoblast cells.

METHOD OF STUDY

Placentas were collected from normal term pregnancies after elective caesarean section, and primary trophoblast culture was prepared followed by the treatment of Ucn and/or CRH selective antagonists, antalarmin and astressin 2b. The anti-inflammatory cytokines IL-4 and IL-10 and the pro-inflammatory cytokine TNF-alpha were measured by ELISA.

RESULTS

Urocortin treatment induced a significant and dose-dependent increase of IL-4 and IL-10, whereas it did not affect TNF-alpha secretion. When incubated in the presence of LPS, Ucn reversed LPS-induced TNF-alpha release from cultured trophoblast cells, an effect that was blocked by the CRH-R2 selective antagonist, astressin 2b.

CONCLUSION

Urocortin stimulates IL-4 and IL-10 secretion and reverses LPS-induced TNF-alpha release from trophoblast cells through action on CRH-R2 receptors, suggesting that this peptide may play a possible role as an anti-inflammatory agent.

Physiology, pharmacology, and therapeutic relevance of urocortins in mammals: ancient CRF paralogs

Urocortins, three paralogs of the stress-related peptide corticotropin-releasing factor (CRF) found in bony fish, amphibians, birds, and mammals, have unique phylogenies, pharmacologies, and tissue distributions. As a result and despite a structural family resemblance, the natural functions of urocortins and CRF in mammalian homeostatic responses differ substantially. Endogenous urocortins are neither simply counterpoints nor mimics of endogenous CRF action. In their own right, urocortins may be clinically relevant molecules in the pathogenesis or management of many conditions, including congestive heart failure, hypertension, gastrointestinal and inflammatory disorders (irritable bowel syndrome, active gastritis, gastroparesis, and rheumatoid arthritis), atopic/allergic disorders (dermatitis, urticaria, and asthma), pregnancy and parturition (preeclampsia, spontaneous abortion, onset, and maintenance of effective labor), major depression and obesity. Safety trials for intravenous urocortin treatment have already begun for the treatment of congestive heart failure. Further understanding the unique functions of urocortin 1, urocortin 2, and urocortin 3 action may uncover other therapeutic opportunities.