Urocortins as cardiovascular peptides

Urocortin-positive nerve fibres and cells are present in the human choroid

BACKGROUND

Choroidal vascular regulation is mediated by the autonomic nervous system in order to gain proper blood flow control. While the mechanisms behind this control are unknown, neuroregulatory peptides are involved in this process. To better understand choroidal function, we investigate the presence of urocortin-1 (UCN), a neuroregulatory peptide with vascular effects, in the human choroid and its possible intrinsic and extrinsic origin.

METHODS

Human choroid and eye-related cranial ganglia (superior cervical ganglion- SCG, ciliary ganglion-CIL, pterygopalatine ganglion-PPG, trigeminal ganglion-TRI) were prepared for immunohistochemistry against UCN, protein-gene product 9.5 (PGP9.5), substance P (SP), tyrosine hydroxylase (TH) and vesicular acetylcholine transporter (VAChT). For documentation, confocal laser scanning microscopy was used.

RESULTS

In choroidal stroma, UCN-immunoreactivity was present in nerve fibres, small cells and intrinsic choroidal neurons (ICN). Some UCN+ nerve fibres colocalised for VAChT, while others were VAChT. A similar situation was found with SP: some UCN+ nerve fibres showed colocalisation for SP, while others lacked SP. Colocalisation for UCN and TH was not observed. In eye-related cranial ganglia, only few cells in the SCG, PPG and TRI were UCN+, while many cells of the CIL displayed weak UCN immunoreactivity.

CONCLUSION

UCN is part of the choroidal innervation. UCN+/VAChT+ fibres could derive from the few cells of the PPG or cells of the CIL, if these indeed supply the choroid. UCN+/SP+ fibres might originate from ICN, or the few UCN+ cells detected in the TRI. Further studies are necessary to establish UCN function in the choroid and its implication for choroidal autonomic control.

Exploring the Role of Urocortin in Osteoporosis

Osteoporosis is a debilitating disease that affects over 200 million people worldwide. Overactive osteoclast activity leads to micro-architectural defects and low bone mass. This culminates in fragility fractures, such as femoral neck fractures. Treatments currently available either are not completely effective or have considerable side effects; thus, there is a need for more effective treatments. The urocortin (Ucn) family, composed of urocortin 1 (Ucn1), urocortin 2 (Ucn2), urocortin 3 (Ucn3), corticotropin-releasing factor (CRF) and corticotropin-releasing factor-binding protein (CRF-BP), exerts a wide range of effects throughout the body. Ucn1 has been shown to inhibit murine osteoclast activity. This review article will aim to bridge the gap between existing knowledge of Ucn and whether it can affect human osteoclasts.

Urocortin3: Local inducer of somatostatin release and bellwether of beta cell maturity

Urocortin 3 (UCN3) is a peptide hormone expressed in pancreatic islets of Langerhans of both human alpha and human beta cells and solely in murine beta cells. UCN3 signaling acts locally within the islet to activate its cognate receptor, corticotropin releasing hormone receptor 2 (CRHR2), which is expressed by delta cells, to potentiate somatostatin (SST) negative feedback to reduce islet cell hormone output. The functional importance of UCN3 signaling in the islet is to modulate the amount of SST tone allowing for finely tuned regulation of insulin and glucagon secretion. UCN3 signaling is a hallmark of functional beta cell maturation, increasing the beta cell glucose threshold for insulin secretion. In doing so, UCN3 plays a relevant functional role in accurately maintaining blood glucose homeostasis. Additionally, UCN3 acts as an indicator of beta cell maturation and health, as UCN3 is not expressed in immature beta cells and is downregulated in dedifferentiated and dysfunctional beta cell states. Here, we review the mechanistic underpinnings of UCN3 signaling, its net effect on islet cell hormone output, as well as its value as a marker for beta cell maturation and functional status.

Transcriptome Analysis Reveals Downregulation of Urocortin Expression in the Hypothalamo-Neurohypophysial System of Spontaneously Hypertensive Rats

The chronically increased blood pressure characteristic of essential hypertension represents an insidious and cumulative risk for cardiovascular disease. Essential hypertension is a multifactorial condition, with no known specific aetiology but a strong genetic component. The Spontaneously Hypertensive rat (SHR) shares many characteristics of human essential hypertension, and as such is a commonly used experimental model. The mammalian hypothalamo-neurohypophyseal system (HNS) plays a pivotal role in the regulation of blood pressure, volume and osmolality. In order to better understand the possible role of the HNS in hypertension, we have used microarray analysis to reveal differential regulation of genes in the HNS of the SHR compared to a control normotensive strain, the Wistar Kyoto rat (WKY). These results were validated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). One of the genes identified and validated as being downregulated in SHR compared to WKY was that encoding the neuropeptide urocortin (Ucn). Immunohistochemical analyses revealed Ucn to be highly expressed within magnocellular neurons of the PVN and SON, with pronounced localisation in dendritic projections containing oxytocin and vasopressin. When Ucn was overexpressed in the PVN of the SHR by in vivo lentiviral mediated gene transfer, blood pressure was unaffected but there were significant, transient reductions in the VLF spectra of systolic blood pressure consistent with an action on autonomic balance. We suggest that Ucn may act, possibly via dendritic release, to subtly regulate neurohumoral aspects of arterial pressure control.

The Role of Urocortins in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) causes an accumulation of blood in the brain parenchyma that disrupts the normal neurological function of the brain. Despite extensive clinical trials, no medical or surgical therapy has shown to be effective in managing ICH, resulting in a poor prognosis for the patients. Urocortin (UCN) is a 40-amino-acid endogenous neuropeptide that belongs to the corticotropin-releasing hormone (CRH) family. The effect of UCN is activated by binding to two G-protein coupled receptors, CRH-R1 and CRH-R2, which are expressed in brain neurons and glial cells in various brain regions. Current research has shown that UCN exerts neuroprotective effects in ICH models via anti-inflammatory effects, which generally reduced brain edema and reduced blood-brain barrier disruption. These effects gradually help in the improvement of the neurological outcome, and thus, UCN may be a potential therapeutic target in the treatment of ICH. This review summarizes the data published to date on the role of UCN in ICH and the possible protective mechanisms underlined.

Current Evidence for a Role of Neuropeptides in the Regulation of Autophagy

Neuropeptides drive a wide diversity of biological actions and mediate multiple regulatory functions involving all organ systems. They modulate intercellular signalling in the central and peripheral nervous systems as well as the cross talk among nervous and endocrine systems. Indeed, neuropeptides can function as peptide hormones regulating physiological homeostasis (e.g., cognition, blood pressure, feeding behaviour, water balance, glucose metabolism, pain, and response to stress), neuroprotection, and immunomodulation. We aim here to describe the recent advances on the role exerted by neuropeptides in the control of autophagy and its molecular mechanisms since increasing evidence indicates that dysregulation of autophagic process is related to different pathological conditions, including neurodegeneration, metabolic disorders, and cancer.

The effects of CRF and urocortins on the sociability of mice

The aim of our study was to determine the role of corticotropin-releasing factor (CRF), the urocortins (Ucn1, Ucn2 and Ucn3) and their receptors (CRF₁ and CRF₂) in the sociability of mice. Male CFLP mice were administered intracerebroventricularly (icv) with CRF and urocortins alone or in combination with antalarmin (specific CRF₁ antagonist) and astressin_2B (specific CRF₂ antagonist) and then investigated in a Crawley social interaction test arena, that consists of three chambers. An unknown male in a cage was put in the first chamber and an empty cage was put in the opposite chamber. The tested male was habituated with the middle chamber for 5min and then allowed to explore the remaining chambers for 5min, during which the number of entries and the time of interaction were measured. Intracerebroventricular administration of CRF decreased significantly the number of entries and the time of interaction with the unknown male and these effects were blocked by antalarmin, but not astressin_2B. In contrast, central administration of Ucn1 increased significantly the number of entries into the chamber of the unknown male, without changing the time of interaction and this effect was blocked by astressin_2B, but not antalarmin. Central administration of Ucn2 and Ucn3 didn't influence remarkably the number of entries, but it reduced the time of interaction between the male mice. Our study suggests that CRF and Ucn1 may play important, but different roles in sociability, and that Ucn2 and Ucn3, playing similar roles, must be also involved in social interactions.

Urocortins and CRF receptor type 2 variants in the male rat colon: gene expression and regulation by endotoxin and anti-inflammatory effect

Urocortins (Ucns) 1, 2, and 3 and corticotropin-releasing factor receptor 2 (CRF2) mRNA are prominently expressed in various layers of the upper gut. We tested whether Ucns and CRF2 variants are also expressed in the different layers of the rat colon, regulated by LPS (100 μg/kg ip) and play a modulatory role in the colonic immune response to LPS. Transcripts of Ucns and CRF2b, the most common isoform in the periphery, were detected in all laser microdissected layers, including myenteric neurons. LPS increased the mRNA level of Ucn 1, Ucn 2, and Ucn 3 and decreased that of CRF2b in both the colonic mucosa and submucosa + muscle (S+M) layers at 2, 6, and 9 h after injection with a return to basal at 24 h. In addition, CRF2a, another variant more prominent in the brain, and a novel truncated splice variant CRF2a-3 mRNA were detected in all segments of the large intestine. LPS reciprocally regulated the colonic expression of these CRF2 variants by decreasing both CRF2a and CRF2b, while increasing CRF2a-3 in the mucosa and S+M. The CRF2 antagonist astressin2-B further enhanced LPS-induced increase of mRNA level of interleukin (IL)-1β, TNF-α, and inducible nitric oxide synthase in S+M layers and IL-1β in the mucosa and evoked TNF-α expression in the mucosa. These data indicate that Ucns/CRF2 variants are widely expressed in all colonic layers and reciprocally regulated by LPS. CRF2 signaling dampens the CD14/TLR4-mediated acute inflammatory response to Gram-negative bacteria in the colon.

Peptides: Basic determinants of reproductive functions

Mammalian reproduction is a costly process in terms of energy consumption. The critical information regarding metabolic status is signaled to the hypothalamus mainly through peripheral peptides from the adipose tissue and gastrointestinal tract. Changes in energy stores produce fluctuations in leptin, insulin, ghrelin and glucose signals that feedback mainly to the hypothalamus to regulate metabolism and fertility. In near future, possible effects of the nutritional status on GnRH regulation can be evaluated by measuring serum or tissue levels of leptin and ghrelin in patiens suffering from infertility. The fact that leptin and ghrelin are antagonistic in their effects on GnRH neurons, their respective agonistic and antagonistic roles make them ideal candidates to use instead of GnRH agonist and antagonist. Similarly, kisspeptin expressing neurons are likely to mediate the well-established link between energy balance and reproductive functions. Exogenous kisspeptin can be used for physiological ovarian hyperstimulation for in-vitro fertilization. Moreover, kisspeptin antagonist therapy can be used for the treatment of postmenapousal women, precocious puberty, PCOS, endometriosis and uterine fibroids. In this review, we will analyze the central mechanisms involved in the integration of metabolic information and their contribution to the control of the reproductive function. Particular attention will be paid to summarize the participation of leptin, kisspeptin, ghrelin, NPY, orexin, urocortin, VIP, insulin, galanin, galanin like peptide, oxytocin, agouti gene-related peptide, and POMC neurons in this process and their possible interactions to contribute to the metabolic control of reproduction.

Peripheral corticotropin-releasing factor receptor type 2 activation increases colonic blood flow through nitric oxide pathway in rats

BACKGROUND

Corticotropin-releasing factor (CRF) peptides exert profound effects on the secretomotor function of the gastrointestinal tract. Nevertheless, despite the presence of CRF peptides and receptors in colonic tissue, their influence on colonic blood flow (CBF) is unknown.

AIM

To determine the effect and mechanism of members of the CRF peptide family on CBF in isoflurane-anesthetized rats.

METHODS

Proximal CBF was measured with laser-Doppler flowmetry simultaneously with mean arterial blood pressure (MABP) measurement. Rats were injected with intravenous human/rat CRF (CRF1 > CRF2 affinity), mouse urocortin 2 (mUcn2, selective CRF2 agonist), or sauvagine (SVG, CRF2 > CRF1 affinity) at 1-30 µg/kg. The nitric oxide (NO) synthase inhibitor, L-NAME (3 mg/kg, iv), the cyclooxygenase inhibitor, indomethacin (Indo, 5 mg/kg, ip), or selective CRF2 antagonist, astressin2-B (Ast2B, 50 µg/kg, iv) was given before SVG injection (10 µg/kg, iv).

RESULTS

SVG and mUcn2 dose-dependently increased CBF while decreasing MABP and colonic vascular resistance (CVR). CRF had no effect on CBF, but increased CVR. The hyperemic effect of SVG was inhibited by L-NAME but not by Indo, whereas hypotension was partially reduced by L-NAME. Sensory denervation had no effect on SVG-induced changes. Ast2B inhibited SVG-induced hyperemia and decreased CVR, and partially reduced the hypotension.

CONCLUSIONS

Peripheral CRF2 activation induces colonic hyperemia through NO synthesis, without involving prostaglandin synthesis or sensory nerve activation, suggesting a direct action on the endothelium and myenteric neurons. Members of the CRF peptide family may protect the colonic mucosa via the activation of the CRF2 receptor.

Differential stress response in rats subjected to chronic mild stress is accompanied by changes in CRH-family gene expression at the pituitary level

The purpose of this study was to examine molecular markers of the stress response at the pituitary and peripheral levels in animals that responded differently to chronic mild stress (CMS). Rats were subjected to 2-weeks CMS and symptoms of anhedonia was measured by the consumption of 1% sucrose solution. mRNA levels of CRH-family neuropeptides (Crh-corticotropin-releasing hormone, Ucn1-urocortin 1, Ucn2-urocortin 2, Ucn3-urocortin 3), CRH receptors (Crhr1-corticotropin-releasing hormone receptor 1, Crhr2-corticotropin-releasing hormone receptor 2) and Crhbp (corticotropin-releasing factor binding protein) in the pituitaries of rats were determined with real-time PCR. Plasma levels of ACTH (adrenocorticotropin), CRH and urocortins were measured with ELISA assays. CMS procedure led to the development of anhedonia manifested by the decreased sucrose consumption (stress-reactive, SR, stress-susceptible group). Additionally, the group of animals not exhibiting any signs of anhedonia (stress non-reactive, SNR, stress-resilient group) and the group characterized by the increased sucrose consumption (stress invert-reactive group SIR) were selected. The significant increases in ACTH plasma level accompanied by the decreases in the pituitary gene expression of the Crh, Ucn2 and Ucn3 in both stress non-reactive and stress invert-reactive groups were observed. The only molecular change observed in stress-reactive group was the increase in UCN2 plasma level. The differentiated behavioral stress responses were reflected by gene expression changes in the pituitary. Alterations in the mRNA levels of Crh, Ucn2 and Ucn3 in the pituitary might confirm the paracrine and/or autocrine effects of these peptides in stress response. The opposite behavioral effect between SNR vs. SIR groups and the surprising similarity at gene expression and plasma ACTH levels in these two groups may suggest the discrepancy between molecular and behavioral stress responses; however, there results might indicate to similarity underlying different ways to cope with stress conditions.

Urocortin 2 autocrine/paracrine and pharmacologic effects to activate AMP-activated protein kinase in the heart

Urocortin 2 (Ucn2), a peptide of the corticotropin-releasing factor (CRF) family, binds with high affinity to type 2 CRF receptors (CRFR2) on cardiomyocytes and confers protection against ischemia/reperfusion. The mechanisms by which the Ucn2-CRFR2 axis mitigates against ischemia/reperfusion injury remain incompletely delineated. Activation of AMP-activated protein kinase (AMPK) also limits cardiac damage during ischemia/reperfusion. AMPK is classically activated by alterations in cellular energetics; however, hormones, cytokines, and additional autocrine/paracrine factors also modulate its activity. We examined the effects of both the endogenous cardiac Ucn2 autocrine/paracrine pathway and Ucn2 treatment on AMPK regulation. Ucn2 treatment increased AMPK activation and downstream acetyl-CoA carboxylase phosphorylation and glucose uptake in isolated heart muscles. These actions were blocked by the CRFR2 antagonist anti-sauvagine-30 and by a PKCε translocation-inhibitor peptide (εV1-2). Hypoxia-induced AMPK activation was also blunted in heart muscles by preincubation with either anti-sauvagine-30, a neutralizing anti-Ucn2 antibody, or εV1-2. Treatment with Ucn2 in vivo augmented ischemic AMPK activation and reduced myocardial injury and cardiac contractile dysfunction after regional ischemia/reperfusion in mice. Ucn2 also directly activated AMPK in ex vivo-perfused mouse hearts and diminished injury and contractile dysfunction during ischemia/reperfusion. Thus, both Ucn2 treatment and the endogenous cardiac Ucn2 autocrine/paracrine pathway activate AMPK signaling pathway, via a PKCε-dependent mechanism, defining a Ucn2-CRFR2-PKCε-AMPK pathway that mitigates against ischemia/reperfusion injury.

Urocortins and CRF type 2 receptor isoforms expression in the rat stomach are regulated by endotoxin: role in the modulation of delayed gastric emptying

Peripheral activation of corticotropin-releasing factor receptor type 2 (CRF(2)) by urocortin 1, 2, or 3 (Ucns) exerts powerful effects on gastric function; however, little is known about their expression and regulation in the stomach. We investigated the expression of Ucns and CRF(2) isoforms by RT-PCR in the gastric corpus (GC) mucosa and submucosa plus muscle (S+M) or laser captured layers in naive rats, their regulations by lipopolysaccharide (LPS, 100 μg/kg ip) over 24 h, and the effect of the CRF(2) antagonist astresssin(2)-B (100 μg/kg sc) on LPS-induced delayed gastric emptying (GE) 2-h postinjection. Transcripts of Ucns and CRF(2b,) the most common wild-type CRF(2) isoform in the periphery, were expressed in all layers, including myenteric neurons. LPS increased Ucn mRNA levels significantly in both mucosa and S+M, reaching a maximal response at 6 h postinjection and returning to basal levels at 24 h except for Ucn 1 in S+M. By contrast, CRF(2b) mRNA level was significantly decreased in the mucosa and M+S with a nadir at 6 h. In addition, CRF(2a), reportedly only found in the brain, and the novel splice variant CRF(2a-3) were also detected in the GC, antrum, and pylorus. LPS reciprocally regulated these variants with a decrease of CRF(2a) and an increase of CRF(2a-3) in the GC 6 h postinjection. Astressin(2)-B exacerbated LPS-delayed GE (42-73%, P < 0.001). These data indicate that Ucn and CRF(2) isoforms are widely distributed throughout the rat stomach and inversely regulated by immune stress. The CRF(2) signaling system may act to counteract the early gastric motor alterations to endotoxemia.

The corticotropin releasing factor system in the kidney: perspectives for novel therapeutic intervention in nephrology

The adaptation to endogenous and exogenous stress stimuli is crucial for survival but also for the onset of various diseases in humans. Corticotropin releasing factor (CRF) system is the major regulator of stress response and homeostasis. The members of this family of peptides extend their actions also outside CNS to the periphery where they may affect various body systems independently, acting via vagal and/or autocrine/paracrine pathways. In search for peripheral targets, kidney has rarely been studied separately, regarding expression and action of CRF and CRF-related peptides. We reviewed the existing literature concerning expression and action of the CRF system in normal and pathological renal tissue and explored possible clinical implications in nephrology. CRF system components are expressed in the kidney of experimental animals and in humans. The intrarenal distribution is reported to be equally extensive, suggesting a physiological or pathophysiological role in renal function and in the occurrence of renal disease. Urocortins have given multiple interesting observations in experimental models of renal disease and clinical studies, showing robust effects in renal regulation mechanisms. We summarize the relevant data and put them in context, proposing applications with clinical significance in the field of hypertension, diabetic nephropathy, chronic kidney disease, cardiorenal syndrome, and peritoneal dialysis.

Distribution of urocortins and corticotropin-releasing factor receptors in the cardiovascular system

Urocortins are human homologues of urotensin I, a fish corticotropin-releasing-factor- (CRF-) like peptide secreted from the urophysis. There are three urocortins: urocortin 1, urocortin 2, and urocortin 3 in mammals. We have shown that urocortin 1 and urocortin 3 are endogenously synthesized in the myocardial cells of human heart and may act on CRF type 2 receptor (CRFR2) expressed in the heart. Expression levels of urocortin 1 in the heart and plasma urocortin 1 levels are elevated in patients with heart failure. Recent studies have shown that urocortins have various biological actions in the cardiovascular system, such as a vasodilator action, a positive inotropic action, a cardioprotective action against ischemia/reperfusion injury, and suppressive actions against the renin angiotensin system and the sympathetic nervous system. Urocortins and CRFR2 may therefore be a potential therapeutic target for cardiovascular diseases, such as congestive heart failure, hypertension, and myocardial infarction.

PD-sauvagine: a novel sauvagine/corticotropin releasing factor analogue from the skin secretion of the Mexican giant leaf frog, Pachymedusa dacnicolor

Sauvagine is a potent and broad-spectrum biologically active peptide of 40 amino acid residues originally isolated from the skin of the South American frog, Phyllomedusa sauvagei. Since its discovery, no additional sauvagine structures have been reported. Following the discovery of sauvagine, peptides with similar primary structures/activities were identified in mammalian brain [corticotropin-releasing factor (CRF) and urocortin]. Here, we report the identification of a second sauvagine from the Mexican giant leaf frog, Pachymedusa dacnicolor, which displays primary structural features of both sauvagine and CRF. A cDNA encoding the peptide precursor was "shotgun" cloned from a cDNA library constructed from lyophilised skin secretion by 3'- and 5'-RACE reactions. From this, the primary structure of a 38-mer peptide was deduced and this was located in reverse phase HPLC fractions of skin secretion and both its mass and structure were confirmed by mass spectrometry. The biological activities of synthetic replicates of PD-sauvagine and sauvagine were compared using two different mammalian smooth muscle preparations and the novel peptide was found to be more potent in both. Bioinformatic analyses of PD-sauvagine revealed that it shared different regional sequence identities with both sauvagine and CRF.

Relevance of urocortins to cardiovascular disease

Acquired cardiovascular diseases such as coronary heart disease, peripheral artery disease and related vascular problems contribute to more than one-third of worldwide morbidity and mortality. In many instances, particularly in the under developed world, cardiovascular diseases are diagnosed at a late stage limiting the scope for improving outcomes. A range of therapies already exist for established cardiovascular disease, although there is significant interest in further understanding disease pathogenesis in order to improve diagnosis and achieve primary and secondary therapeutic goals. The urocortins are a group of recently defined peptide members of the corticotrophin-releasing factor family. Previous pre-clinical work and human association studies suggest that urocortins have potential to exert some beneficial and other detrimental effects on the heart and major blood vessels. More current evidence however favours beneficial effects of urocortins, for example these peptides have been shown to inhibit production of reactive oxygen species and vascular cell apoptosis, and thus may have potential to antagonise the progression of cardiovascular disease. This review summarises published data on the potential role of urocortins in cardiovascular disease.

Urocortins are present in the rat testis

The synthesis and release of testosterone (T) depends both on circulating luteinizing hormone (LH) and on an array of testicular factors whose role remains incompletely understood. Corticotropin-releasing factor (CRF) had been reported in the rat testes, where it was thought to inhibit T secretion. However, the discovery that the CRF-related peptides urocortins (Ucns), of which there are currently three subtypes (Ucn 1, 2 and 3), cross-react with many reagents previously used to detect CRF, has cast doubt on this concept. Here we show that while CRF was readily measurable in rat hypothalami (which served as controls), signals for this peptide were barely detectable in total RNA extracted from the testes. On the other hand, microarray, RT-PCR and real-time quantitative RT-PCR (qRT-PCR) analyses all indicated strong signals for Ucn 1 in the male gonads, with weaker levels of Ucn 2 and 3 mRNA gene expression. Results obtained for Ucn 1 gene expression were corroborated by immunohistochemical detection, which appeared restricted to Leydig cells. Finally, to investigate possible changes in testicular Ucn 1 levels induced by homeostatic challenges, we measured them in rats exposed to alcohol. We observed that indeed, the intragastric injection of this drug significantly increased testicular Ucn 1, but not Ucn 2, Ucn 3, CRF, CRFR1 or CRFR2 mRNA levels. Collectively, these results provide novel information regarding the presence of CRF-like peptides in the adult male rat testis.

Corticotropin-releasing factor signaling and visceral response to stress

Stress may cause behavioral and/or psychiatric manifestations such as anxiety and depression and also impact on the function of different visceral organs, namely the gastrointestinal and cardiovascular systems. During the past years substantial progress has been made in the understanding of the underlying mechanisms recruited by stressors. Activation of the corticotropin-releasing factor (CRF) signaling system is recognized to be involved in a large number of stress-related behavioral and somatic disorders. This review will outline the present knowledge on the distribution of the CRF system (ligands and receptors) expressed in the brain and peripheral viscera and its relevance in stress-induced alterations of gastrointestinal and cardiovascular functions and the therapeutic potential of CRF(1) receptor antagonists.

Urinary proteins for the diagnosis of obstructive sleep apnea syndrome

Approximately 2-3% of all children in the United States suffer from obstructive sleep apnea (OSA). This condition is characterized by repeated events of partial or complete obstruction of the upper airways during sleep leading to recurring episodes of hypercapnia, hypoxemia, and arousal throughout the night as well as snoring, which afflicts 7-10% of all children. Since clinical history and physical examination are unreliable in the differentiation between children with OSA and children with primary snoring (PS) who have no apparent alteration in sleep architecture, current diagnostic approaches for OSA require an overnight sleep study (ONP). ONP is onerous, relatively unavailable, labor intensive, and inconvenient, leading to long waiting periods and unnecessary delays in diagnosis and treatment. Development of noninvasive biomarker(s) capable of reliably distinguishing children with PS from those with OSA would greatly facilitate timely screening and diagnosis of OSA in children. Therefore, we hypothesized that proteomic strategies in the urine may permit the identification of biomarker(s) that reliably screen for OSA. In this study, time-of-flight mass spectrometry was used to profile proteins in the first morning void urines from children. We discovered that urocortins are increased in OSA and provide a noninvasive approach for quick and convenient diagnosis otf OSA in snoring children.

Urocortin in second trimester amniotic fluid: its role as predictor of preterm labor

Backgound. The existence of a “placental clock” which determines the duration of gestation has been previously proposed. It is related to placental CRH secretion and is active from an early phase in human pregnancy. Urocortin is a specific ligand for the corticotropin-releasing factor (CRF) receptor expressed by human trophoblast and fetal membranes. The purpose of this study was to evaluate whether urocortin concentrations in the early second trimester amniotic fluid might serve to predict preterm delivery. Method. The urocortin concentrations in early second trimester amniotic fluid were measured in 41 pregnancies with term delivery and in 41 pregnancies with preterm delivery by using an immunoradiometric assay. Conditional logistic regression analysis was used for statistical analysis. Results. Mean amniotic fluid urocortin concentrations in women with preterm labor were 1.55 ± 0.63 ng/mL while those in women with term labor were 1.6 ± 0.49 ng/mL (p: NS). No statistical significant results were found when comparing amniotic fluid urocortin concentrations in women with preterm premature rupture of membranes leading to preterm labor (n = 19) to women with term delivery without premature rupture of membranes. Conclusion. These results suggest that urocortin concentrations in the amniotic fluid of genetic amniocentesis are not predictive of preterm labor and birth.

A case of multiple endocrine neoplasia type II accompanied by thyroid medullary carcinoma and pheochromocytomas expressing corticotropin-releasing factor and urocortins

A 38-year-old woman with RET gene mutation presented with tumors in her thyroid and bilateral adrenal glands. I-metaiodobenzylguanidine scintigraphy revealed accumulation of the radioisotope in both adrenal glands. Both plasma adrenaline and noradrenaline levels were elevated. The circadian rhythms for plasma adrenocorticotropic hormone (ACTH) and cortisol levels were disturbed. Plasma ACTH and cortisol levels failed to be suppressed by an overnight dexamethasone test, suggesting autonomic secretion of ACTH and cortisol, although the patient had no typical Cushingoid features, hypertension, or impaired glucose tolerance. Pathological examination showed that these tumors were pheochromocytoma and thyroid medullary carcinoma, respectively, both of which highly expressed corticotropin-releasing factor, urocortin1, and urocortin3. Together with the endocrinological and pathological observations, the patient was diagnosed as multiple endocrine neoplasia type II with corticotropin-releasing factor- and urocortin-producing tumors that stimulated ACTH and glucocorticoid secretion.

Urocortin and the brain

Urocortin is a member of the corticotropin-releasing hormone (CRH) family of peptides. In the brain, its potent suppression of food intake is mediated by CRH receptors (CRHR). Urocortin also participates in the regulation of anxiety, learning, memory, and body temperature, and it shows neuroprotection. This review will summarize the location of urocortin-producing neurons and their projections, the pharmacological evidence of its actions in the CNS, and information acquired from knockout mice. Urocortin interacts with leptin, neuropeptide Y, orexin, and corticotropin in the brain. Also produced by the GI tract, heart, and immune cells, urocortin has blood concentrations ranging from 13 to 152 pg/ml. Blood-borne urocortin stimulates the cerebral endothelial cells composing the blood-brain barrier and crosses the blood-brain barrier by a unique transport system. Overall, urocortin acts on a broad neuronal substrate as a neuromodulator important for basic survival.

Cardioprotective actions of peptide hormones in myocardial ischemia

The myocardium represents a major source of several families of peptide hormones under normal physiological conditions and the plasma concentrations of many of these "cardiac peptides" (or related pro-peptide fragments) are substantially augmented in many cardiac disease states. In addition to well-characterised endocrine functions of several of the cardiac peptides, pleiotropic functions within the myocardium and the coronary vasculature represent a significant aspect of their actions in health and disease. Here, we focus specifically on the cardioprotective roles of four major peptide families in myocardial ischemia and reperfusion: adrenomedullin, kinins, natriuretic peptides and the urocortins. The patterns of early release of all these peptides are consistent with roles as autacoid cardioprotective mediators. Clinical and experimental research indicates the early release and upregulation of many of these peptides by acute ischemia and there is a convincing body of evidence showing that exogenously administered adrenomedullin, bradykinin, ANP, BNP, CNP and urocortins are all markedly protective against experimental myocardial ischemia-reperfusion injury through a conserved series of cytoprotective signal transduction pathways. Intriguingly, all the peptides examined so far have the potential to salvage against infarction when administered specifically during early reperfusion. Thus, the myocardial secretion of peptide hormones likely represents an early protective response to ischemia. Further work is required to explore the potential therapeutic manipulation of these peptides in acute coronary syndromes and their promise as biomarkers of acute myocardial ischemia.

Inhibitory effects of glucocorticoids on urocortin-mediated increases in interleukin-6 gene expression in rat aortic smooth muscle cells

Urocortin (Ucn) 1, Ucn2, and Ucn3 have potent effects on appetite and the cardiovascular system. Endogenous Ucns in combination with CRF receptor type 2beta may have a physiological role in the cardiovascular system. We previously demonstrated that both Ucn1 and Ucn2 increased IL-6 output levels in A7r5 aortic smooth muscle cells. In the present study, we extended observations on stress or hormone-induced changes in IL-6 gene expression in the cardiovascular system, and determined the effects of glucocorticoids on Ucn-mediated increases in IL-6 mRNA levels, protein levels, and gene transcription activity in A7r5 cells. Ucn1, Ucn2, and Ucn3 all increased IL-6 mRNA levels via CRF receptor type 2. Dexamethasone blocked the ability of Ucn1 to increase IL-6 mRNA and protein levels, while it failed to attenuate the Ucns-mediated changes in cyclic AMP (cAMP)-response element binding protein or extracellular signal-related kinases phosphorylation. Dexamethasone also suppressed Ucn1- or cAMP-stimulated IL-6 gene transcription via a glucocorticoid receptor. Together, these findings demonstrate that glucocorticoids suppress IL-6 gene transcription via Ucn-induced cAMP-dependent pathways in A7r5 cells.

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.

Expression of urocortin 2 and its inhibitory effects on intracellular ca2+ via L-type voltage-gated calcium channels in rat pheochromocytoma (PC12) cells

Urocortin 2, a new member of the corticotrophin-releasing factor (CRF) neuropeptide family, was reported to be widely expressed in the central nervous system and peripheral tissues. Here, we detected urocortin 2 mRNA in PC12 cells using reverse transcription-polymerase chain reaction (RT-PCR). Furthermore, we observed its effects on intracellular Ca(2+) concentration ([Ca(2+)](i)) using confocal microscopy and flow cytometry and on voltage-gated calcium channel (VGCC) currents using whole-cell patch clamp. Our results showed that urocortin 2 mRNA was coexpressed with CRF, and CRF receptor (CRFR) 2beta in undifferentiated PC12 cells, but not CRFR1 or CRFR2alpha. KCl (40 mM) or Bay K8644 (1 microM), an L-type VGCC activator, increased [Ca(2+)](i). Pretreatment of the cells with urocortin 2 significantly diminished the effect of Bay K8644 or KCl. Urocortin 2 showed no influence on [Ca(2+)](i) in tyrode's solution containing EGTA or Ca(2+)-free tyrode's solution. It reversibly inhibited the VGCC currents in a concentration-dependent manner, but had no apparent effects on the cells treated with nifedipine (1 microM), an L-type VGCC blocker. Urocortin 2 up-shifted the current-voltage curves. No frequency-dependence of urocortin 2 effects on I(Ba) was observed. The inhibitory effects of urocortin 2 on VGCC currents or [Ca(2+)](i) were not affected by astressin 2B, an antagonist of CRFR2. As calcium overload play a key role in some neuronal degenerative diseases such as Alzheimer's and Parkinson's diseases, our results suggest that urocortin 2 may be a potentially interesting agent for the treatment of these diseases.

Widespread tissue distribution and diverse functions of corticotropin-releasing factor and related peptides

Peptides of the corticotropin-releasing factor (CRF) family are expressed throughout the central nervous system (CNS) and in peripheral tissues where they play diverse roles in physiology, behavior, and development. Current data supports the existence of four paralogous genes in vertebrates that encode CRF, urocortin/urotensin 1, urocortin 2 or urocortin 3. Corticotropin-releasing factor is the major hypophysiotropin for adrenocorticotropin, and also functions as a thyrotropin-releasing factor in non-mammalian species. In the CNS, CRF peptides function as neurotransmitters/neuromodulators. Recent work shows that CRF peptides are also expressed at diverse sites outside of the CNS in mammals, and we found widespread expression of CRF and urocortins, CRF receptors and CRF binding protein (CRF-BP) genes in the frog Xenopus laevis. The functions of CRF peptides expressed in the periphery in non-mammalian species are largely unexplored. We recently found that CRF acts as a cytoprotective agent in the X. laevis tadpole tail, and that the CRF-BP can block CRF action and hasten tail muscle cell death. The expression of the CRF-BP is strongly upregulated in the tadpole tail at metamorphic climax where it may neutralize CRF bioactivity, thus promoting tail resorption. Corticotropin-releasing factor and urocortins are also known to be cytoprotective in mammalian cells. Thus, CRF peptides may play diverse roles in physiology and development, and these functions likely arose early in vertebrate evolution.

Urocortin II Inhibits the Apoptosis of Mesenteric Arterial Smooth Muscle Cells Via L-type Calcium Channels in Spontaneously Hypertensive Rats

Urocortin (UCN) II, a newly isolated corticotropinreleasing- factor (CRF) related peptide, has been found to have potent cardiovascular protective effects. To investigate the mechanisms of its vascular protective effects, we exposed mesenteric arterial smooth muscle cells (MASMC) from spontaneously hypertensive rats (SHR) to UCN II to observe the change in cell apoptosis using TUNEL assay and measured intracellular calcium concentration ([Ca2+]i) using confocal laser scanning microscope. In addition, effects of UCN II on L-type calcium currents (ICa,L) were also measured using whole-cell patch clamp. Our results showed that UCN II concentration-dependently, but time-independently inhibited cell apoptosis. Astressin 2B, a special CRF 2 receptor antagonist, had no influence on this inhibition. Hypoxia or Bay K8644, the L-type calcium channel activator, induced the apoptosis of MASMC from SHR. Pretreatment of the cells with UCN II diminished the effects of hypoxia or Bay K8644. UCN II was also observed to reduce [Ca2+]i increase induced by KCl or Bay K8644. UCN II concentration-dependently inhibited ICa,L, which was not affected by astressin 2B. It did not affect the activation of ICa,L, but markedly shifted the inactivation curve to the left. In conclusion, UCN II inhibits the apoptosis of MASMC from SHR via inhibiting L-type calcium channels.

Expression of urocortin 3/stresscopin in human adrenal glands and adrenal tumors

Urocortin 3 (Ucn 3)/stresscopin (SCP) is a novel peptide of the corticotropin-releasing factor (CRF) family and is a specific ligand for the CRF type 2 receptor. In the present study, we studied expression of Ucn3/SCP in the normal adrenal and adrenal tumors by radioimmunoassay and reverse transcriptase-polymerase chain reaction (RT-PCR). High concentrations of immunoreactive (IR)-Ucn3 were present in the normal portions of adrenal glands (4.2+/-0.51 pmol/g wet weight, mean+/-S.E.M., n = 14), and the levels were higher than those in the brain. IR-Ucn3 was also detected in the tumor tissues of aldosterone-secreting adenomas (6.2+/-0.6 pmol/g wet weight, n = 10), cortisol-secreting adenomas (5.0+/-1.2 pmol/g wet weight, n = 4), and pheochromocytomas (1.9+/-0.4 pmol/g wet weight, n = 7). Reverse phase high performance liquid chromatography showed that IR-Ucn3 in normal portions of adrenal glands and aldosterone-secreting adenomas was eluted mainly in the positions of Ucn3 and SCP with several minor peaks eluting earlier. The RT-PCR showed expression of Ucn3 mRNA in normal portions of adrenal gland (positive ratio; 4/4), aldosterone-secreting adenomas (3/4), cortisol-secreting adenomas (1/3) and pheochromocytomas (6/7). These findings indicate that Ucn3 is produced in normal adrenal and adrenal tumors (both adrenocortical tumors and pheochromocytomas), and suggest that Ucn3 acts as an autocrine or paracrine regulator in normal adrenal and adrenal tumors.

Urocortin 1, urocortin 3/stresscopin, and corticotropin-releasing factor receptors in human adrenal and its disorders

CONTEXT

Urocortin 1 (Ucn1) and urocortin 3 (Ucn3)/stresscopin are new members of the corticotropin-releasing factor (CRF) neuropeptide family. Ucn1 binds to both CRF type 1 (CRF1) and type 2 receptors (CRF2), whereas Ucn3 is a specific agonist for CRF2. Recently, direct involvement of the locally synthesized CRF family in adrenocortical function has been proposed.

OBJECTIVE, DESIGN, AND SETTING

We examined in situ expression of Ucn and CRF receptors in nonpathological human adrenal gland and its disorders using immunohistochemistry and mRNA in situ hybridization.

RESULTS

Ucn immunoreactivity was localized in the cortex and medulla of nonpathological adrenal glands. Ucn1 immunoreactivity was marked in the medulla, whereas Ucn3 was immunostained mostly in the cortex. Both CRF type 1 and CRF2 were expressed in the cortex, particularly in the zonae fasciculata and reticularis but very weakly or undetectably in the medulla. Immunohistochemistry in serial tissue sections with mirror images revealed that both Ucn3 and CRF2 were colocalized in more than 85% of the adrenocortical cells. mRNA in situ hybridization confirmed these findings above. In fetal adrenals, Ucn and CRF receptors were expressed in both fetal and definitive zones of the cortex. Ucn and CRF receptors were all expressed in the tumor cells of pheochromocytomas, adrenocortical adenomas, and carcinomas, but its positivity was less than that in nonpathological adrenal glands, suggesting that Ucn1, Ucn3, and CRF receptors were down-regulated in these adrenal neoplasms.

CONCLUSIONS

Ucn1, Ucn3, and CRF receptors are all expressed in human adrenal cortex and medulla and may play important roles in physiological adrenal functions.