Cardiovascular actions of CRH and urocortin: an update

Structural and Functional Insights into CRF Peptides and Their Receptors

Corticotropin-releasing factor or hormone (CRF or CRH) and the urocortins regulate a plethora of physiological functions and are involved in many pathophysiological processes. CRF and urocortins belong to the family of CRF peptides (CRF family), which includes sauvagine, urotensin, and many synthetic peptide and non-peptide CRF analogs. Several of the CRF analogs have shown considerable therapeutic potential in the treatment of various diseases. The CRF peptide family act by interacting with two types of plasma membrane proteins, type 1 (CRF1R) and type 2 (CRF2R), which belong to subfamily B1 of the family B G-protein-coupled receptors (GPCRs). This work describes the structure of CRF peptides and their receptors and the activation mechanism of the latter, which is compared with that of other GPCRs. It also discusses recent structural information that rationalizes the selective binding of various ligands to the two CRF receptor types and the activation of receptors by different agonists.

Design, synthesis, structural optimization, SAR, in silico prediction of physicochemical properties and pharmacological evaluation of novel & potent thiazolo[4,5-d]pyrimidine corticotropin releasing factor (CRF) receptor antagonists

Corticotropin-releasing factor (CRF) is a 41-amino-acid neuropeptide secreted from the hypothalamus and is the main regulator of the hypothalamus-pituitary-adrenocortical (HPA) axis. CRF is the master hormone which modulates physiological and behavioral responses to stress. Many disorders including anxiety, depression, addictive disorders and others are related to over activation of the CRF system. This suggests that new molecules which can interfere with CRF binding to its receptors may be potential candidates for neuropsychiatric drugs to treat stress-related disorders. Previously, three series of pyrimidine and fused pyrimidine CRF₁ receptor antagonists were synthesized by our group and specific binding assays, competitive binding studies and determination of the ability to antagonize the agonist-stimulated accumulation of cAMP (the second messenger for CRF receptors) were reported. In continuation of our efforts in this direction, in the current manuscript, we report the synthesis & biological evaluation of a new series of CRF₁ receptor antagonists. Seven compounds showed promising binding affinity with the best two compounds (compounds 6 & 43) displaying a superior binding affinity to all of our previous compounds. Compounds 6 & 43 have only 4 times and 2 times less binding affinity than the standard CRF antagonist antalarmin, respectively. Thus, our two best lead compounds (compound 6 & 43) can be considered potent CRF receptor antagonists with binding affinity of 41.0 & 19.2 nM versus 9.7 nM for antalarmin.

The PKA-p38MAPK-NFAT5-Organic Osmolytes Pathway in Duchenne Muscular Dystrophy: From Essential Player in Osmotic Homeostasis, Inflammation and Skeletal Muscle Regeneration to Therapeutic Target

In Duchenne muscular dystrophy (DMD), the absence of dystrophin from the dystrophin-associated protein complex (DAPC) causes muscle membrane instability, which leads to myofiber necrosis, hampered regeneration, and chronic inflammation. The resulting disabled DAPC-associated cellular pathways have been described both at the molecular and the therapeutical level, with the Toll-like receptor nuclear factor kappa-light-chain-enhancer of activated B cells pathway (NF-ƘB), Janus kinase/signal transducer and activator of transcription proteins, and the transforming growth factor-β pathways receiving the most attention. In this review, we specifically focus on the protein kinase A/ mitogen-activated protein kinase/nuclear factor of activated T-cells 5/organic osmolytes (PKA-p38MAPK-NFAT5-organic osmolytes) pathway. This pathway plays an important role in osmotic homeostasis essential to normal cell physiology via its regulation of the influx/efflux of organic osmolytes. Besides, NFAT5 plays an essential role in cell survival under hyperosmolar conditions, in skeletal muscle regeneration, and in tissue inflammation, closely interacting with the master regulator of inflammation NF-ƘB. We describe the involvement of the PKA-p38MAPK-NFAT5-organic osmolytes pathway in DMD pathophysiology and provide a clear overview of which therapeutic molecules could be of potential benefit to DMD patients. We conclude that modulation of the PKA-p38MAPK-NFAT5-organic osmolytes pathway could be developed as supportive treatment for DMD in conjunction with genetic therapy.

The Modulation of Cardiac Contractile Function by the Pharmacological and Toxicological Effects of Urocortin2

Urocortin2 (Ucn2) has been revealed to enhance cardiac function in heart failure. However, the pharmacological and toxicological effects of Ucn2 on cardiomyocytes are incompletely understood. In this study, we investigated the possible mechanisms of Ucn2 on mediating the contractility of cardiomyocytes. Mechanical properties and intracellular Ca(2+) properties were measured in isolated cardiomyocytes from different treatment groups. The stress signaling was evaluated using Western blot. The results demonstrated that Ucn2 induced maximal velocity of shortening (+dL/dt), peak height, peak shortening (PS) amplitude, maximal velocity of relengthening (-dL/dt), accompanied by a significant rise in intracellular Ca(2+) level and a fall of the mean time constant of Ca(2+) transient decay (Tau) in WT cardiomyocytes. However, these effects were abolished by preincubation of type 2 CRF receptors (CRFR2) antagonist anti-sauvagine 30 (a-SVG-30). We also found that Ucn2 treatment activated the AMPK pathway in isolated cardiomyocytes via CRFR2. Furthermore, Ucn2 induced protein kinase A (PKA) and phospholamban (PLN) phosphorylation. Pretreatment of PKA inhibitor H89 reduced the inotropic and lusitropic effects of Ucn2 as well as decreased the intracellular Ca(2+) load and slowed down the Ca(2+) transient decay. We also showed that preincubation of Compound C, an inhibitor of AMPK, inhibited the phosphorylation of PKA and the intracellular Ca(2+) level in cardiomyocytes without affecting the contractile function and the Tau of cardiomyocytes. Taken together, it suggests that Ucn2 facilitate the contractility of cardiomyocytes via activating both AMPK and PKA.

Therapeutic effects of human urocortin-1, -2 and -3 in intracerebral hemorrhage of rats

Urocortin exerts neuroprotective effects in intracerebral hemorrhage (ICH) of rats. For pre-clinical trial, we intended to study the neuroprotective efficacy of human UCN (hUCN)-1, -2 and -3 in treating ICH rats. ICH was induced by infusing bacterial collagenase VII (0.23 U in sterile saline) to the striatum. The hUCN-1, -2, and -3 were administrated (2.5μg/kg, i.p.) at 1h after ICH insult, respectively. Neurological deficits were evaluated by modified Neurological Severity Scores. Brain edema and hematoma expansion was evaluated by coronal T2-WI and DWI magnetic resonance imaging on 1, 3, 6, 24, and 56h after ICH insult. Blood-brain barrier permeability was evaluated by Evans blue assay on day 3 after ICH. Brain lesion volume was evaluated by morphormetric measurement on day 7 after ICH. Our results demonstrated that the hUCN-1 significantly reduced hematoma, blood-brain barrier disruption and neurological deficits on day 3, and brain lesion volume on day 7 after ICH insult. The prediction of secondary structure of the hUCNs clarifies that the percentage of alpha-helix, random coil and extended strand between rat-UCN (rUCN)-1 and hUCN-1 are the same. The structure similarity between human- and rat-UCN-1 may be one of the reasons that both can exert similar therapeutic potential in ICH rats.

Urocortin ameliorates diabetic cardiomyopathy in rats via the Akt/GSK-3β signaling pathway

Urocortin has been shown to exert powerful protective effects on various cardiovascular disease models. However, the role and mechanism of urocortin in protecting against diabetic cardiomyopathy (DCM) has not yet been elucidated. In the present study, the effects of urocortin on cardiac dysfunction, fibrosis, inflammation and the interrelated signaling pathways were investigated in a diabetic rat model. Diabetes mellitus (DM) was induced in the rats by intraperitoneal injection of streptozotocin. The diabetic rats were randomly divided into four groups: Diabetic control, urocortin, urocortin + astressin treatment and urocortin + triciribine treatment groups. All the experiments were conducted at 16 weeks following the induction of DM. The levels of glycosylated hemoglobin (HbA1c), creatine phosphokinase isoenzyme (CK-MB) and plasma brain natriuretic peptide (BNP), as well as the myocardial collagen volume fraction (CVF) and left ventricular mass index (LVWI), were measured. In addition, levels of inflammatory factors, including transforming growth factor (TGF)-β1, connective tissue growth factor (CTGF) and interrelated proteins, such as Akt and glycogen synthase kinase (GSK)-3β, were detected by biochemical analyses. In the diabetic group, the levels of BNP and CK-MB, as well as the mRNA and protein expression levels of TGF-β1 and CTGF, and the LVWI and CVF, were higher compared with the rats in the control group (P<0.05). This was accompanied by decreased Akt and GSK-3β phosphorylation (P<0.05). Notably, urocortin attenuated myocardial dysfunction, cardiac fibrosis and inflammation in the hearts of the diabetic rats. However, urocortin exhibited no effect on the level of HbA1c. In addition, the inhibited phosphorylation of Akt and GSK-3β was restored with urocortin administration. However, all the effects of urocortin were eliminated with treatment of the corticotropin releasing factor receptor 2 antagonist, astressin. Triciribine, an Akt inhibitor, partially eliminated the effects of urocortin on myocardial dysfunction, inflammation and cardiac fibrosis in the hearts of the diabetic rats. These results indicated that urocortin may exhibit great therapeutic potential in the treatment of DCM by attenuating fibrosis and inflammation. Furthermore, the Akt/GSK-3β signaling pathway may be partially involved in mediating these effects.

NFAT transcription factor regulation by urocortin II in cardiac myocytes and heart failure

Urocortin II (UcnII), a cardioactive peptide with beneficial effects in normal and failing hearts, is also arrhythmogenic and prohypertrophic. We demonstrated that cardiac effects are mediated by a phosphatidylinositol-3 kinase (PI3K)/Akt kinase (Akt)/endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) signaling pathways. Nuclear factor of activated T-cells (NFAT) transcription factors play a key role in the regulation of gene expression in cardiac development, maintenance of an adult differentiated cardiac phenotype, and remodeling processes in cardiac hypertrophy and heart failure (HF). We tested the hypothesis that UcnII differentially regulates NFAT activity in cardiac myocytes from both normal and failing hearts through the PI3K/Akt/eNOS/NO pathway. Isoforms NFATc1 and NFATc3 revealed different basal subcellular distribution in normal and HF rabbit ventricular myocytes with a nuclear NFATc1 and a cytosolic localization of NFATc3. However, in HF, the nuclear localization of NFATc1 was less pronounced, whereas the nuclear occupancy of NFATc3 was increased. In normal myocytes, UcnII induced nuclear export of NFATc1 and attenuated NFAT-dependent transcriptional activity but did not affect the distribution of NFATc3. In HF UcnII facilitated nuclear export of both isoforms and reduced transcriptional activity. NFAT regulation was mediated by a PI3K/Akt/eNOS/NO signaling cascade that converged on the activation of several kinases, including glycogen synthase kinase-3β (GSK3β), c-Jun NH2-terminal kinase (JNK), p38 mitogen-activated kinase (p38), and PKG, resulting in phosphorylation, deactivation, and nuclear export of NFAT. In conclusion, while NFATc1 and NFATc3 reveal distinct subcellular distribution patterns, both are regulated by the UcnII-PI3K/Akt/eNOS/NO pathway that converges on the activation of NFAT kinases and NFAT inactivation. The data reconcile cardioprotective and prohypertrophic UcnII effects mediated by different NFAT isoforms.

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.

Systemic administration of urocortin after intracerebral hemorrhage reduces neurological deficits and neuroinflammation in rats

Background

Intracerebral hemorrhage (ICH) remains a serious clinical problem lacking effective treatment. Urocortin (UCN), a novel anti-inflammatory neuropeptide, protects injured cardiomyocytes and dopaminergic neurons. Our preliminary studies indicate UCN alleviates ICH-induced brain injury when administered intracerebroventricularly (ICV). The present study examines the therapeutic effect of UCN on ICH-induced neurological deficits and neuroinflammation when administered by the more convenient intraperitoneal (i.p.) route.

Methods

ICH was induced in male Sprague-Dawley rats by intrastriatal infusion of bacterial collagenase VII-S or autologous blood. UCN (2.5 or 25 μg/kg) was administered i.p. at 60 minutes post-ICH. Penetration of i.p. administered fluorescently labeled UCN into the striatum was examined by fluorescence microscopy. Neurological deficits were evaluated by modified neurological severity score (mNSS). Brain edema was assessed using the dry/wet method. Blood-brain barrier (BBB) disruption was assessed using the Evans blue assay. Hemorrhagic volume and lesion volume were assessed by Drabkin's method and morphometric assay, respectively. Pro-inflammatory cytokine (TNF-α, IL-1β, and IL-6) expression was evaluated by enzyme-linked immunosorbent assay (ELISA). Microglial activation and neuronal loss were evaluated by immunohistochemistry.

Results

Administration of UCN reduced neurological deficits from 1 to 7 days post-ICH. Surprisingly, although a higher dose (25 μg/kg, i.p.) also reduced the functional deficits associated with ICH, it is significantly less effective than the lower dose (2.5 μg/kg, i.p.). Beneficial results with the low dose of UCN included a reduction in neurological deficits from 1 to 7 days post-ICH, as well as a reduction in brain edema, BBB disruption, lesion volume, microglial activation and neuronal loss 3 days post-ICH, and suppression of TNF-α, IL-1β, and IL-6 production 1, 3 and 7 days post-ICH.

Conclusion

Systemic post-ICH treatment with UCN reduces striatal injury and neurological deficits, likely via suppression of microglial activation and inflammatory cytokine production. The low dose of UCN necessary and the clinically amenable peripheral route make UCN a potential candidate for development into a clinical treatment regimen.

Brain neuropeptides in central ventilatory and cardiovascular regulation in trout

Many neuropeptides and their G-protein coupled receptors (GPCRs) are present within the brain area involved in ventilatory and cardiovascular regulation but only a few mammalian studies have focused on the integrative physiological actions of neuropeptides on these vital cardio-respiratory regulations. Because both the central neuroanatomical substrates that govern motor ventilatory and cardiovascular output and the primary sequence of regulatory peptides and their receptors have been mostly conserved through evolution, we have developed a trout model to study the central action of native neuropeptides on cardio-ventilatory regulation. In the present review, we summarize the most recent results obtained using this non-mammalian model with a focus on PACAP, VIP, tachykinins, CRF, urotensin-1, CGRP, angiotensin-related peptides, urotensin-II, NPY, and PYY. We propose hypotheses regarding the physiological relevance of the results obtained.

cAMP- and Ca²(+) /calmodulin-dependent protein kinases mediate inotropic, lusitropic and arrhythmogenic effects of urocortin 2 in mouse ventricular myocytes

BACKGROUND AND PURPOSE

Urocortin 2 is beneficial in heart failure, but the underlying cellular mechanisms are not completely understood. Here we have characterized the functional effects of urocortin 2 on mouse cardiomyocytes and elucidated the underlying signalling pathways and mechanisms.

EXPERIMENTAL APPROACH

Mouse ventricular myocytes were field-stimulated at 0.5 Hz at room temperature. Fractional shortening and [Ca²(+)](i) transients were measured by an edge detection and epifluorescence system respectively. Western blots were carried out on myocyte extracts with antibodies against total phospholamban (PLN) and PLN phosphorylated at serine-16.

KEY RESULTS

Urocortin 2 elicited time- and concentration-dependent positive inotropic and lusitropic effects (EC₅₀ : 19 nM) that were abolished by antisauvagine-30 (10 nM, n= 6), a specific antagonist of corticotrophin releasing factor (CRF) CRF₂ receptors. Urocortin 2 (100 nM) increased the amplitude and decreased the time constant of decay of the underlying [Ca²(+)](i) transients. Urocortin 2 also increased PLN phosphorylation at serine-16. H89 (2 µM) or KT5720 (1 µM), two inhibitors of protein kinase A (PKA), as well as KN93 (1 µM), an inhibitor of Ca²(+)/calmodulin-dependent protein kinase II (CaMKII), suppressed the urocortin 2 effects on shortening and [Ca²(+)](i) transients. In addition, urocortin 2 also elicited arrhythmogenic events consisting of extra cell shortenings and extra [Ca²(+)](i) increases in diastole. Urocortin 2-induced arrhythmogenic events were significantly reduced in cells pretreated with KT5720 or KN93.

CONCLUSIONS AND IMPLICATIONS

Urocortin 2 enhanced contractility in mouse ventricular myocytes via activation of CRF₂ receptors in a cAMP/PKA- and Ca²(+)/CaMKII-dependent manner. This enhancement was accompanied by Ca²(+)-dependent arrhythmogenic effects mediated by PKA and CaMKII.

The impact of stress on tumor growth: peripheral CRF mediates tumor-promoting effects of stress

Introduction

Stress has been shown to be a tumor promoting factor. Both clinical and laboratory studies have shown that chronic stress is associated with tumor growth in several types of cancer. Corticotropin Releasing Factor (CRF) is the major hypothalamic mediator of stress, but is also expressed in peripheral tissues. Earlier studies have shown that peripheral CRF affects breast cancer cell proliferation and motility. The aim of the present study was to assess the significance of peripheral CRF on tumor growth as a mediator of the response to stress in vivo.

Methods

For this purpose we used the 4T1 breast cancer cell line in cell culture and in vivo. Cells were treated with CRF in culture and gene specific arrays were performed to identify genes directly affected by CRF and involved in breast cancer cell growth. To assess the impact of peripheral CRF as a stress mediator in tumor growth, Balb/c mice were orthotopically injected with 4T1 cells in the mammary fat pad to induce breast tumors. Mice were subjected to repetitive immobilization stress as a model of chronic stress. To inhibit the action of CRF, the CRF antagonist antalarmin was injected intraperitoneally. Breast tissue samples were histologically analyzed and assessed for neoangiogenesis.

Results

Array analysis revealed among other genes that CRF induced the expression of SMAD2 and β-catenin, genes involved in breast cancer cell proliferation and cytoskeletal changes associated with metastasis. Cell transfection and luciferase assays confirmed the role of CRF in WNT- β-catenin signaling. CRF induced 4T1 cell proliferation and augmented the TGF-β action on proliferation confirming its impact on TGFβ/SMAD2 signaling. In addition, CRF promoted actin reorganization and cell migration, suggesting a direct tumor-promoting action. Chronic stress augmented tumor growth in 4T1 breast tumor bearing mice and peripheral administration of the CRF antagonist antalarmin suppressed this effect. Moreover, antalarmin suppressed neoangiogenesis in 4T1 tumors in vivo.

Conclusion

This is the first report demonstrating that peripheral CRF, at least in part, mediates the tumor-promoting effects of stress and implicates CRF in SMAD2 and β-catenin expression.

Synthesis and Biological Evaluation of New CRH Analogues

A series of 7 new human/rat Corticotropin Releasing Hormone (h/r-CRH) analogues were synthesized. The induced alterations include substitution of Phe at position 12 with D-Phe, Leu at positions 14 and 15 with Aib and Met at positions 21 and 38 with Cys(Et) and Cys(Pr). The analogues were tested regarding their binding affinity to the CRH-1 receptor and their activity which is represented by means of percentage of maximum response in comparison to the native molecule. The results indicated that the introduction of Aib, or Cys derivatives although altering the secondary structure of the molecule, did not hinder receptor recognition and binding.

Evaluation of anti-obesity activity of duloxetine in comparison with sibutramine along with its anti-depressant activity: an experimental study in obese rats

5-HT and noradrenaline are important neurotransmitters that control increase in body mass and are involved in the pathophysiology of obesity and depression. Sibutramine, an established anti-obesity agent, and duloxetine, an anti-depressant agent, are serotonin noradrenaline reuptake inhibitors (SNRIs). The objective of the present study was to compare the anti-obesity effect of duloxetine with sibutramine along with its effect on blood pressure and depression in obese rats. The secondary objective of the study was to determine if a relationship exists between obesity and depression. Obesity was induced by high-fat diet (HFD) in healthy male Sprague-Dawley rats. After 5 weeks of feeding HFD, animals were overweight (17.57%) with high food intake (57.15%) in comparison with normal animals. These obese animals were treated with duloxetine (30 mg x kg(-1), p.o.) and sibutramine (5 mg x kg(-1), p.o.) for 4 weeks. Control animals were treated with duloxetine alone (30 mg x kg(-1), p.o.). Our results depict that duloxetine was as effective as sibutramine in reducing food intake, body mass, and relative adiposity, and increasing rectal temperature with an added advantage of decreasing blood pressure, which sibutramine failed to do. Besides reduction in body mass, unlike sibutramine, duloxetine improved depressive state as evaluated by despair swimming test, tail suspension test, and open field test, speculating its use as an anti-obesity agent in obese-depressive animals. Since obese control animals reflected decreased locomotor activity, a positive relationship can be speculated to exist between obesity and depression. Further studies on various antidepressant models are required to confirm this relationship.

Central hyperventilatory action of the stress-related neurohormonal peptides, corticotropin-releasing factor and urotensin-I in the trout Oncorhynchus mykiss

The stress-related neurohormonal peptides corticotropin-releasing factor (CRF) and urotensin-I (U-I), an ortholog of mammalian urocortin 1, are widely distributed in the central nervous systems of teleost fish but little is known about their possible central neurotropic actions. In the present study, we investigated the effect of intracerebroventricular (ICV) injection of CRF and U-I (1-10pmol) on ventilatory and cardiovascular variables in our established unanaesthetized trout model. CRF and U-I produced a significant dose-dependent and long-lasting increase in the ventilatory frequency (VF) and the ventilatory amplitude (VA). Consequently the net effect of these peptides was a hyperventilatory response since the total ventilation (VTOT) was significantly elevated. However, CRF evoked a significant hyperventilatory response 5-10min sooner than that observed after ICV administration of U-I and the hyperventilatory effect of 10pmol CRF was twofold higher than that of equimolar dose of U-I. Pre-treatment of the trout with the antagonist, alpha-helical CRF(9-41), significantly reduced by about threefold the CRF-induced increase in VF, VA and VTOT. The most significant cardiovascular action of central CRF and U-I was to evoke a hypertensive response without changing the heart rate. Peripheral injection of CRF and U-I at doses of 5 and 50pmol produced no change in VF, VA or VTOT. Only a transient hypertensive response without change in heart rate was observed after the injection of the highest dose of U-I. Our results demonstrate that in a teleost fish, CRF and U-I produce a potent hyperventilatory response only when injected centrally. The two endogenous stress-related neuropeptides may play an important stimulatory role acting as neurotransmitters and/or neuromodulators in the central control of ventilatory apparatus during stress.

Urocortin: a protective peptide that targets both the myocardium and vasculature

The urocortins are a family of endogenously produced peptide hormones that show great promise as potential drugs for the treatment of heart disease. They can increase contractility and cardiac output without causing changes in mean arterial blood pressure. As expected, the receptor for these peptides is present in cardiomyocytes, and they can bind and protect these cells from simulated ischemia and reperfusion in vitro. The receptor is present, however, in much higher density in the endothelial cells that form a continuous lining of the coronary vasculature. Functionally, the urocortin peptides have been shown to have potent local vasodilatory effects, and may affect other aspects of vascular function. In this review, we will attempt to distinguish the "cardio" from the "vascular" effects of urocortin and its homologues, including the archetypal family member, corticotrophin releasing hormone.

Water deprivation increases Fos expression in hypothalamic corticotropin-releasing factor neurons induced by right atrial distension in awake rats

Atrial mechanoreceptors, sensitive to stretch, contribute in regulating heart rate and intravascular volume. The information from those receptors reaches the nucleus tractus solitarius and then the paraventricular nucleus (PVN), known to have a crucial role in the regulation of cardiovascular function. Neurons in the PVN synthesize CRF, AVP, and oxytocin (OT). Stimulation of atrial mechanoreceptors was performed in awake rats implanted with a balloon at the junction of the superior vena cava and right atrium. Plasma ACTH, AVP, and OT concentrations and Fos, CRF, AVP, and OT immunolabeling in the PVN were determined after balloon inflation in hydrated and water-deprived rats. The distension of the balloon increased the plasma ACTH concentrations, which were higher in water-deprived than in hydrated rats ( P < 0.05). In addition, the distension in the water-deprived group decreased plasma AVP concentrations ( P < 0.05), compared with the respective control group. The distension increased the number of Fos- and double-labeled Fos/CRF neurons in the parvocellular PVN, which was higher in the water-deprived than in the hydrated group ( P < 0.01). There was no difference in the Fos expression in magnocellular PVN neurons after distension in hydrated and water-deprived groups, compared with respective controls. In conclusion, parvocellular CRF neurons showed an increase of Fos expression induced by stimulation of right atrial mechanoreceptors, suggesting that CRF participates in the cardiovascular reflex adjustments elicited by volume loading. Activation of CRF neurons in the PVN by cardiovascular reflex is affected by osmotic stimulation.

Urocortin 1 exhibits potent inhibition of cardiac sympathetic nerve activity in conscious sheep

OBJECTIVES

Urocortin 1 (Ucn1) and the sympathetic nervous system both participate in cardiac and circulatory regulation, but little is known about their possible interactions.

METHODS

We report the effects of Ucn1 on the cardiac sympathetic nerve activity (CSNA), haemodynamics and plasma catecholamines in normal sheep.

RESULTS

Bolus intravenous administration of Ucn1 at 2.5 and 10 microg in seven sheep had no significant effect on haemodynamic parameters, including heart rate, mean arterial pressure (MAP) and cardiac output. At these doses, however, Ucn1 administration reduced CSNA, with burst frequency (P = 0.011), burst incidence (P = 0.015) and burst area (P = 0.012) all significantly reduced in a dose-related manner compared with a time-matched control. At higher doses (25 and 100 microg; n = 5 sheep), Ucn1 induced significant rises in heart rate (P < 0.001) and cardiac output (P = 0.03) and reduced peripheral resistance (P = 0.03), but had no effect on MAP. Ucn1 administration at the higher doses reduced CSNA, with burst incidence (P < 0.001), burst area/min (P = 0.001) and burst area/100 beats (P < 0.001) all significantly reduced in a dose-related manner compared with a time-matched control. There was no change in plasma catecholamines at any dose.

CONCLUSION

The present study shows that Ucn1 induces potent inhibition of sympathetic traffic to the heart at doses both above and below the threshold for direct actions of Ucn1 on the myocardium. These findings suggest an important role for Ucn1 in cardiovascular homeostasis and warrant further investigation for potential therapeutic applications in acute myocardial injury and heart disease.

Peripheral and central administration of exogenous urocortin 1 disrupts the fasted motility pattern of the small intestine in rats via the corticotrophin releasing factor receptor 2 and a cholinergic mechanism

BACKGROUND AND AIM

The action of the corticotrophin releasing factor (CRF) receptor on the small intestinal motility has been rarely investigated. The present study aimed to determine the effects of urocortin 1 on small intestinal motility in rats and the CRF receptor subtypes and autonomic pathways mediating the effects.

METHODS

Fasted or fed rats were used to investigate the effect of intravenous or intracerebroventricular urocortin 1 on duodenum and jejunum motility. NBI-27914 and astressin(2)-B (CRF receptor 1 and 2 antagonists, respectively), atropine (an M-receptor antagonist), phentolamine (an alpha-receptor antagonist), propranolol (a beta-receptor antagonist) and N(omega)-Nitro-L-arginine (a nitric oxide synthase [NOS] inhibitor) were applied to determine the involved CRF receptor subtypes and autonomic pathways.

RESULTS

In fasted rats, intravenous or intracerebroventricular injection of urocortin 1 disrupted duodenal and jejunal migrating myoelectric complex pattern, leading to an irregular spiking activity similar to the fed motility pattern. When urocortin 1 was given in the fed state, the fed motility pattern remained unchanged. In addition, urocortin 1 also inhibited small intestinal transit function. Astressin(2)-B injected intraperitoneally or intracerebroventricularly blocked urocortin 1-induced change, while NBI-27914 had no effect. The disruption of migrating myoelectric complex induced by urocortin 1 was abolished by atropine, but not affected by phentolamine, propranolol and N(omega)-Nitro-L-arginine.

CONCLUSION

Intravenous or intracerebroventricular injection of urocortin 1 acts, respectively, on peripheral and central CRF receptor 2 to disrupt the intestinal migrating myoelectric complex through an M-receptor-dependent mechanism, and such change has an inhibitory effect as proved by measuring the small intestinal transit function.

Cortagine: behavioral and autonomic function of the selective CRF receptor subtype 1 agonist

Corticotropin-releasing factor (CRF) is a neuropeptide and mediating component of neuroendocrine, autonomic, and behavioral processes associated with the stress response. The two receptor subtypes identified in the mammalian brain, CRF receptor subtype 1 (CRF1) and CRF2, are suggested to differentially modulate these processes. Manipulation of these receptors with selective CRF compounds and transgenic models has revealed, in most studies, a clear potentiation of the stress response through central activation of CRF1. However, pharmacological activation of CRF restricted to CRF1 has been limited by the availability of selective peptidic compounds. Recently, a highly selective CRF1 agonist, cortagine, has been developed. It was synthesized from chimeric intermediate sequences of ovine CRF, sauvagine, and human/rat CRF into a highly soluble peptide with strong affinity for CRF1 (IC(50) < 5 nM) and a very low binding preference for CRF2 (IC(50) > 500 nM). Affinity for the CRF binding protein (IC(50) > 1,000 nM) can be abolished by the addition of a glutamate residue on position 21 of the cortagine peptide sequence. Cortagine has recently been tested in a variety of preclinical models of behavior including the elevated-plus-maze (EPM), forced swim test (FST), homecage, and rat exposure test (RET). Preliminary characterization in the EPM and FST suggested that this compound elicits anxiogenic and antidepressant-like effects, respectively. Additional testing in the homecage and RET, which targets various elements of behavior, directs to a more potent anxiogenic profile of cortagine. In this review, we discuss the behavioral findings and the tests used to measure these effects. Finally, we also discuss preliminary findings of autonomic activation obtained by central injection of cortagine that support CRF1 involvement in the modulation of heart rate and heart rate variability.

Expression profiling identifies the CRH/CRH-R1 system as a modulator of neurovascular gene activity

Corticotropin-releasing hormone receptor type 1 (CRH-R1)-deficient mice display reduced anxiety-like behavior, a chronic corticosterone deficit, and an impaired neuroendocrine stress response caused by disruption of the hypothalamic-pituitary-adrenocortical (HPA) axis. The molecular substrates and pathways of CRH/CRH-R1-dependent signaling mechanisms underlying the behavioral phenotype as well as the consequences of lifelong glucocorticoid deficit remain largely obscure. To dissect involved neuronal circuitries, we performed comparative expression profiling of brains of CRH-R1 mutant and wild-type mice using our custom made MPIP (Max Planck Institute of Psychiatry) 17k cDNA microarray. Microarray analysis yielded 107 genes showing altered expression levels when comparing CRH-R1 knockout mice with wild-type littermates. A significant proportion of differentially expressed genes was related to control of HPA and hypothalamic-pituitary-thyroid (HPT) axes reflecting not only the disturbance of the HPA axis in CRH-R1 mutant mice but also the interplay of both neuroendocrine systems. The spatial analysis of regulated genes revealed a prevalence for genes expressed in the cerebral microvasculature. This phenotype was confirmed by the successful cross-validation of regulated genes in CRH overexpressing mice. Analysis of the cerebral vasculature of CRH-R1 mutant and CRH overexpressing mice revealed alterations of functional rather than structural properties. A direct role of the CRH/CRH-R1 system was supported by demonstrating Crhr1 expression in the adult murine cerebral vasculature. In conclusion, these data suggest a novel, previously unknown role of the CRH/CRH-R1 system in modulating neurovascular gene expression and function.

Urocortin 1 modulates the neurohumoral response to acute nitroprusside-induced hypotension in sheep

In addition to haemodynamic actions, Ucn1 (urocortin 1) has been reported to affect a number of hormonal systems; however, it remains unclear whether Ucn1 modulates circulating hormones under physiological conditions. Accordingly, in the present study, we have examined the effects of Ucn1 on haemodynamics, hormones and renal indices in normal conscious sheep subjected to a nitroprusside-induced hypotensive stimulus designed to alter hormonal levels within the physiological range. Ucn1 administration did not alter the haemodynamic response to nitroprusside-induced hypotension. However, compared with the rise observed on the control day, plasma ANP (atrial natriuretic peptide; P=0.043), BNP (brain natriuretic peptide; P=0.038) and endothelin-1 (P=0.011) levels were reduced following Ucn1 administration. Associated with this significant reduction in natriuretic peptides, the increase in urinary sodium output associated with rising pressures post-nitroprusside was abolished following Ucn1 administration (P=0.048). Ucn1 had no significant effect on the response of hormones of the renin-angiotensin-aldosterone system or the hypothalamo-pituitary-adrenal axis. In conclusion, Ucn1, administered at physiologically relevant levels during nitroprusside-induced hypotension, attenuates the secretion/release of endothelin-1 and the cardiac natriuretic peptides ANP and BNP. Suppression of ANP and BNP probably led to an attenuated natriuretic response to recovery from acute hypotension. The threshold for the action of Ucn1 on the natriuretic peptides and endothelin-1 appears to be below that of other actions of Ucn1.

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.

A Comparison between the Cardiovascular Actions of Urocortin 1 and Urocortin 2 (Stresscopin-Related Peptide) in Conscious Rats

The aims of the study were, in conscious Sprague-Dawley rats, to compare the effects of stresscopin-related peptide (SRP) and urocortin (UCN) 1 on blood pressure, heart rate, and regional hemodynamics; to determine whether or not there were residual tachycardic effects of SRP or UCN1 after cardiac autonomic blockade; and to investigate a possible involvement of corticotropin releasing factor type 1 (CRF1) receptor-mediated histamine release in the vasodilator actions of UCN1. SRP and UCN1 (both at 3 nmol/kg i.v.) caused hypotension, tachycardia, and mesenteric and hindquarters vasodilatation, but the magnitude and/or duration of the effects of UCN1 were generally greater than those of SRP. Pretreatment with atropine plus propranolol abolished the tachycardic effects of SRP and UCN1, and, under those conditions, the hypotensive effect of SRP, but not that of UCN1, was enhanced, probably because the hindquarters vasodilator effect of the latter was also reduced. Pretreatment with mepyramine plus cimetidine had no effect on the hemodynamic actions of either SRP or UCN1. It is concluded that, in conscious rats, the tachycardic effects of SRP and UCN1 are due to autonomic nervous activation mainly through baroreflex mechanisms. There is no evidence for an involvement of CRF1 receptor-mediated histamine release in the vasodilator actions of UCN1, but a propranolol-sensitive hindquarters vasodilator action of UCN, but not of SRP, was identified.

Localization of corticotropin-releasing factor, urotensin I, and CRF-binding protein gene expression in the brain of the zebrafish,Danio rerio

Our current understanding of the corticotropin-releasing factor (CRF) system distribution in the teleost brain is restricted by limited immunohistochemical studies and a lack of complete transcriptional distribution maps. The present study used in situ hybridization to localize and compare CRF, urotensin I (UI), and CRF-binding protein (CRF-BP) expression in the brain of adult zebrafish (Danio rerio). All three peptides were localized in the preoptic area, periventricular hypothalamic and tectal regions, and dorsal part of the trigeminal motor nucleus. CRF and UI were both expressed in several nuclei of the dorsal telencephalon, whereas CRF and CRF-BP were both expressed in the ventral nucleus of the ventral telencephalon. Sole expression of CRF and CRF-BP was apparent in the olfactory bulbs and superior raphe nucleus, respectively, whereas only UI was observed in the corpus mamillare, nucleus of the medial longitudinal fascicle, dorsal tegmental nucleus, nucleus lateralis valvulae, and nucleus interpeduncularis. A major finding of this study was the general regional overlapping of CRF-BP with its ligands and a tendency to be expressed in tandem with CRF rather than UI. Overall, the mRNA expression patterns outlined in this study support the stress-related neuroendocrine, autonomic, and behavioral functions generally ascribed to the vertebrate CRF system and suggest some unique functional roles for CRF and UI in the teleost brain.

Vasodilation of Retinal Arteriole Mediated by Corticotropin-Releasing Factor Receptor is Impaired in Streptozotocin-Induced Diabetic Rats

We investigated the vasodilator responses of retinal arterioles induced by stimulating corticotropin-releasing factor receptors in non-diabetic and diabetic rats. Male Wistar rats were treated with streptozotocin (65 mg/kg, i.v.) and experiments were performed 6-8 weeks later. Rats were treated with tetrodotoxin (50 mug/kg, i.v.) to eliminate any nerve activity and prevent movement of the eye and infused with a mixture of norepinephrine and epinephrine to maintain adequate systemic circulation under artificial ventilation. Fundus images were captured with an original high-resolution digital fundus camera system. The vasodilator responses of retinal arterioles were assessed by measuring changes in diameters of retinal arterioles in response to urocortin and urocortin 2. Both urocortin (0.03-1.0 micromol/kg, i.v.) and urocortin 2 (0.1-3.0 micromol/kg, i.v.) increased diameters of retinal arterioles and decreased systemic blood pressure in a dose-dependent manner. The responses to urocortins were reduced in diabetic rats. These results suggest that urocortin and urocortin 2 play as vasodilators in retinal and peripheral resistance arterioles. The impairment of vasodilation mediated by the corticotropin-releasing factor receptors may contribute to the alteration of retinal and systemic circulation in the diabetic state.

Corticotropin-releasing factor, urocortin 1, and their receptors in the mouse spinal cord

Corticotropin-releasing factor (CRF) and urocortin 1 (Ucn1) are involved in stress adaptation. CRF receptor 1 (CRF1) binds CRF and Ucn1 with similar high affinity, but CRF receptor 2 (CRF2) binds Ucn1 with higher affinity than CRF. We tested the hypothesis that in the spinal cord CRF and Ucn1 control peripheral components of the stress response, by assessing the distribution of CRF- and Ucn1-containing fibers, CRF1 and CRF2 mRNAs, and CRF receptor protein (CRFR) in the mouse spinal cord, by using immunofluorescence and in situ hybridization. CRF, Ucn1, and CRFR occurred throughout the spinal cord. CRF fibers predominated in laminae I, V-VII, and X of Rexed. Ucn1 fibers occurred mainly in laminae VII and X and occasionally in lamina IX. Both CRFR mRNAs occurred in all laminae except the superficial laminae of the dorsal horn, but they exhibited different distributions, CRF2 mRNA having a wider occurrence (laminae III-X) than CRF1 mRNA (laminae III-VIII). Double immunofluorescence indicated that CRF and Ucn1 fibers contacted CRFR-containing neurons, mainly in laminae VII and X. The strongest co-distribution of CRF1 and CRF2 mRNAs with CRF and Ucn1 fibers appeared in lamina VII. CRF2 mRNA predominated in lamina IX together with Ucn1, whereas CRF2 mRNA predominated in lamina X, where it had similar distributions with each ligand. In view of the lamina-specific and similar distributions of the two CRF receptor mRNAs with their ligands, we suggest that CRF1 and CRF2 are involved in peripheral stress adaptation processes, such as modulation of stress-induced analgesia and the mediation of visceral nociceptive information by CRF2.

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.

CRF receptors in the rodent and human cardiovascular systems: species differences

CRF has powerful receptor-mediated cardiovascular actions. To evaluate the precise distribution of CRF receptors, in vitro CRF receptor autoradiography with (125)I-[Tyr(0), Glu(1), Nle(17)]-sauvagine or [(125)I]-antisauvagine-30 was performed in the rodent and human cardiovascular system. An extremely high density of CRF(2) receptors was detected with both tracers in vessels of rodent lung, intestine, pancreas, mesenterium, kidney, urinary bladder, testis, heart, brain, and in heart muscle. In humans, CRF(2) receptors were detected with (125)I- antisauvagine-30 at low levels in vessels of kidneys, intestine, urinary bladder, testis, heart and in heart muscle, while only heart vessels were detected with (125)I-[Tyr(0), Glu(1), Nle(17)]-sauvagine. This is the first extensive morphological study reporting the extremely wide distribution of CRF(2) receptors in the rodent cardiovascular system and a more limited expression in man, suggesting a species-selective CRF receptor expression.

Effects of corticotropin-releasing hormone (CRH) on endothelin-1 and NO release, mediated by CRH receptor subtype R2: a potential link between stress and endothelial dysfunction?

OBJECTIVE

Psychosocial factors, associated with elevated corticotropin releasing hormone (CRH) concentrations, have been reported to be independently associated with coronary heart disease.

METHODS

Endothelin-1 and NO release of human endothelial cells were quantified via ELISA or fluorometrically after treatment with CRH. CRH-receptor subtype 2 (CRH-R2) was visualized on endothelial cells by immunohistochemistry and confirmed by polymerase chain reaction using CRH-R2 primers.

RESULTS

CRH induced a significant increase of ET-1 release, and the effect was abolished by the CRH-receptor antagonist astressin. The effect was mediated by CRH-R2. In contrast, NO release was not affected.

CONCLUSION

CRH-R2 is expressed on human endothelial cells, mediating the CRH-induced stimulation of ET-1 release, whereas NO release is not affected. Thus, peripherally circulating CRH may offset the balance between endothelial vasoconstrictor and vasodilator release with unopposed vasoconstriction. Our data may provide a new concept on how CRH-receptor antagonists may prevent CRH-induced disorders of vascular biology.

Localisation and physiological regulation of corticotrophin-releasing factor receptor 1 mRNA in the Xenopus laevis brain and pituitary gland

In Xenopus laevis, corticotrophin-releasing factor (CRF) and urocortin 1 are present in the brain and they both are potent stimulators of alpha-melanophore stimulating hormone (MSH) secretion by melanotroph cells in the pituitary gland. Because both CRF and urocortin 1 bind with high affinity to CRF receptor type 1 (CRF1) in mammals and Xenopus laevis, one of the purposes of the present study was to identify the sites of action of CRF and urocortin 1 in the Xenopus brain and pituitary gland. Moreover, we raised the hypothesis that the external light intensity is a physiological condition controlling CRF1 expression in the pituitary melanotroph cells. By in situ hybridisation, the presence of CRF1 mRNA is demonstrated in the olfactory bulb, amygdala, nucleus accumbens, preoptic area, ventral habenular nuclei, ventromedial thalamic area, suprachiasmatic nucleus, ventral hypothalamic area, posterior tuberculum, tectum mesencephali and cerebellum. In the pituitary gland, CRF1 mRNA occurs in the intermediate and distal lobe. The optical density of the CRF1 mRNA hybridisation signal in the intermediate lobe of the pituitary gland is 59.4% stronger in white-adapted animals than in black-adapted ones, supporting the hypothesis that the environmental light condition controls CRF1 mRNA expression in melanotroph cells of X. laevis, a mechanism likely to be responsible for CRF- and/or urocortin 1-stimulated secretion of alpha-MSH.

Effect of starvation on Fos and neuropeptide immunoreactivities in the brain and pituitary gland of Xenopus laevis

In mammals complex interactions between various brain structures and neuropeptides such as corticotropin-releasing factor (CRF) and urocortin 1 (Ucn1) underlay the control of feeding by the brain. Recently, in the amphibian Xenopus laevis, CRF- and Ucn1-immunoreactivities were shown in the hypothalamic magnocellular nucleus (Mg) and evidence was obtained for their involvement in food intake. To gain a better understanding of the brain structures controlling feeding in X. laevis, the effects of 16 weeks starvation on neurones immunoreactive (ir) to Fos and neuropeptides in various brain structures were quantified. In the Mg, compared to controls, starved animals showed fewer neurones immunopositive for Fos (-55.9%), Ucn1 (-44.0%), cocaine and amphetamine-regulated transcript (CART) (-94.3%) and metenkephalin (ENK) (-65.0%), whereas CRF-ir neurones were 2.1 times more numerous. These differences were mainly apparent in the ventral part of the Mg, followed by the medial and dorsal part of the nucleus. In the neural lobe of the pituitary gland a 22.5% lower optical density of CART-ir was observed. In the four other brain structures investigated, starvation had different effects. The dorsomedial part of the suprachiasmatic nucleus showed 5.9 times more NPY-ir cells and in the ventromedial thalamic area a lower number of NPY-ir cells (-33.6%) was found, whereas the Edinger-Westphal nucleus contained fewer CART-ir cells (-42.2%); no effect of starvation was seen in the ventral hypothalamic nucleus. Our results support the hypothesis that in X. laevis, the Mg plays a pivotal role in feeding-related processes and, moreover, that starvation also has neuropeptide- and brain structure-specific effects in other parts of the brain and in the pituitary gland, suggesting particular roles of these structures and their neuropeptides in physiological adaptation to starvation.

Expression of urocortin in the extravillous human trophoblast at the implantation site

Urocortin (UCN) is a 40 amino acid peptide which is closely related to corticotropin-releasing hormone and binds with high affinity to both CRH type 1 and type 2 receptors. UCN is expressed in human reproductive tissues including endometrium, ovary, and placenta. This study was designed to investigate the cellular localization of UCN at the implantation site of the human blastocyst, as well as the regulation of the UCN promoter by two major intracellular signaling pathways, the cAMP/PKA and diacylglycerol/PKC pathways, in cells of placental origin. For this reason, immunohistochemistry was performed on tissue sections from paraffin-embedded human first trimester placentas and freshly isolated human invasive extravillous trophoblast cells (EVT) were analyzed for UCN expression using RT-PCR and immunofluorescence. Finally, UCN promoter activity was analyzed in the JEG3 human choriocarcinoma cell line. Immunohistochemistry revealed expression of UCN in the cytotrophoblast, the EVT and decidual cells. Both UCN mRNA and peptide were detectable in freshly isolated EVT. Finally, a human UCN promoter luciferase reporter construct transfected into JEG3 cells was significantly inducible by phorbol ester plus ionomycin, but not by phorbol ester alone or by forskolin. Collectively, the present study reports the expression of UCN in EVT and the activation of the UCN gene promoter by the diacylglycerol/PKC pathway. The functional significance of urocortin for the physiology of EVT requires further investigation.

Fractal rigidity by enhanced sympatho-vagal antagonism in heartbeat interval dynamics elicited by central application of corticotropin-releasing factor in mice

The dynamics of heartbeat interval fluctuations were studied in awake unrestrained mice following intracerebroventricular application of the neuropeptide corticotropin-releasing factor (CRF). The cardiac time series derived from telemetric ECG monitoring were analyzed by non-parametric techniques of nonlinear signal processing: delay-vector variance (DVV) analysis, higher-order variability (HOV) analysis, empirical mode decomposition (EMD), multiscale embedding-space decomposition (MESD), multiexponent multifractal (MEMF) analysis. The analyses support the conjecture that cardiac dynamics of normal control mice has both deterministic and stochastic elements, is nonstationary, nonlinear, and exerts multifractal properties. Central application of CRF results in bradycardia and increased variability of the beat-to-beat fluctuations. The altered dynamical properties elicited by CRF reflect a significant loss of intrinsic structural complexity of cardiac control which is due to central neuroautonomic hyperexcitation, i.e., enhanced sympatho-vagal antagonism. The change in dynamical complexity is characterized by an effect referred to as fractal rigidity, leading to a significant impairment of adaptability to extrinsic challenges in a fluctuating environment. The impact of dynamical neurocardiopathy as a major precipiting factor for the propensity of cardiac arrhythmias or sudden cardiac death by unchecked central CRF release in significant acute life events in man is critically discussed.

Cardiovascular actions of the stress-related neurohormonal peptides, corticotropin-releasing factor and urotensin-I in the trout Oncorhynchus mykiss

In this review, we summarize the most significant data concerning the cardiovascular effects of centrally and peripherally administered synthetic trout corticotropin-releasing factor (CRF) and urotensin-I (U-I) in our animal model, the unanesthetized trout Oncorhynchus mykiss. Although there is more than 60% sequence identity between these two stress-related neurohormonal peptides, CRF and U-I-induced differential actions upon the mean dorsal aortic blood pressure (Pda) and the heart rate (HR) in trout maintained under similar experimental situations. After intracerebroventricular injections, only U-I induced an increase in Pda while in non-cannulated trout, CRF only decreased the HR and elevated the heart rate variability by a presumed activation of the parasympathetic nervous system activity to the heart. The CRF antagonist, the alpha-helical CRF(9-41) blocked these central actions of CRF. After intra-arterial (IA) injections, U-I induced a direct hypotensive action and an elevation in HR. This hypotensive phase was reversed to hypertension by the release of catecholamines. IA injection of CRF caused no change in Pda or HR. These cardiovascular effects are compared with the much better established actions of CRF and the orthologous urocortins in mammals.

Urocortin reduces the viability of adult rat vascular smooth muscle cells via inhibiting L-type calcium channels

The newly isolated peptide, urocortin (UCN), is a member of the corticotropin-releasing factor (CRF)-related peptides that has been found to have potent cardiovascular protective effects. In order to investigate the effect of UCN on the viability of adult rat vascular smooth muscle cells (VSMC) and the relevant mechanisms, we exposed the VSMC to UCN to observe the change in cell viability using MTT assay and intracellular calcium concentration using confocal laser scanning microscope methods. Our results showed that UCN (10(-7)M) inhibited the viability of VSMC by about 26% (P<0.05, compared to control). The effect was concentration-dependent, but it was not dependent on the affecting time. Glybenclamide (Gly, 10(-5)M), the ATP-sensitive potassium channel (K(ATP) channel) blocker, and astressin (10(-6)M), a competitive antagonist of CRF receptors, had no influence on this inhibition. Bay K8644 (10(-6)M), a special L-type calcium channel activator, increased the viability of VSMC. Pre-treatment of the cells with UCN diminished the effect of Bay K8644 (n=6, P<0.05). UCN was also observed to reduce the intracellular Ca2+ increase induced by KCl and Bay K8644. There was no significant difference in nitrite accumulation between UCN groups and the control. In conclusion, UCN reduced the viability of VSMC through L-type calcium channels. These interesting results might suggest that UCN may be a new vasoactive agent involved in hindering vascular remodeling in combination with previous reports about UCN's hypotensive effects.

Influence of urocortin and corticotropin releasing factor on venous tone in conscious rats

The corticotropin releasing factor (CRF) family includes CRF and urocortin. The effects of urocortin and CRF (0.3, 1, 3 and 10 nmol/kg, i.v.) relative to those of vehicle (0.9% NaCl) on mean arterial pressure and mean circulatory filling pressure (index of venous tone) were examined in conscious, unrestrained rats that were either intact (unblocked) or ganglion-blocked by treatment with mecamylamine (10 mg/kg, i.v.) followed by noradrenaline (4 microg/kg/min, i.v.) to increase vasomotor tone. Both urocortin and CRF dose-dependently decreased mean arterial pressure in intact rats and ganglion-blocked rats. The depressor action of urocortin was greater than that of CRF at all doses. In intact rats, neither compound reduced mean circulatory filling pressure. In ganglion-blocked rats, urocortin and the highest dose of CRF decreased mean circulatory filling pressure. In conclusion, both urocortin and CRF are vasodepressor agents with venodilator action.

In vivo protective effects of urocortin on ischemia-reperfusion injury in rat heart via free radical mechanisms

The aim of this study was to investigate the effects of urocortin (UCN) on oxidative stress and the mechanisms of urocortin on ischemia–reperfusion injury in vivo in the rat model. Thirty-six Sprague–Dawley rats were divided into 6 groups, including sham, control (normal saline solution), UCN1, UCN2, UCN3, and verapamil groups. The left anterior descending coronary artery of all rats except those in the sham group was treated with a 30-min occlusion followed by a 60-min reperfusion. Just before the occlusion, normal saline solution, UCN (5, 10, and 20 µg/kg body mass), or verapamil (1 mg/kg body mass) was administered. Heart rates, beating rhythm, and S-T segments were constantly monitored using an ECG. At the completion of the drug adminstration, blood samples were taken to measure the activity of superoxide dismutase (SOD), malonaldehyde (MDA), glutathione peroxidase (GSH-PX), and nitric oxide (NO) to evaluate the effects of UCN on oxidative stress. Finally, the size of infarction was measured. Arrhythmia rates were significantly lower, and the infarction size was significantly smaller (p < 0.01), in the UCN groups vs. the control group. Verapamil also significantly reduced arrhythmia rates and infarction size. The MDA activities were remarkably diminished, whereas the SOD, GSH-PX, and NO activities were significantly higher in the UCN and VER groups (p < 0.01). MDA, SOD, and NO activities were strongly correlated with UCN doses. These results suggest that UCN may play a protective role in ischemia–reperfusion injury in rat hearts against the oxidative stress by inhibiting free radicals' activities. Key words: urocortin, ischemia–reperfusion injury, arrhythmias, free radical anti-oxidative enzymes, oxidative stress.

Hypertrophic effects of urocortin homologous peptides are mediated via activation of the Akt pathway

The UCN homologues SCP and SRP bind specifically to the CRFR2 receptor, whereas UCN binds to both CRFR1 and CRFR2. We have previously demonstrated that all three peptides are cardioprotective, and both the Akt and MAPK p42/44 pathways are essential for this effect. Here we tested the hypertrophic effects of these peptides. We examined the effects of the peptides on cell area, protein synthesis, and induction of the natriuretic peptides ANP and BNP. All three peptides were able to increase all the markers of hypertrophy examined, with SCP being the most potent of the three, followed by UCN and SRP last. In addition, we provide a mechanism of action for the three peptides and show that Akt phosphorylation is important for their hypertrophic action, whereas MAPK p42/44 is not involved in this effect.