Urocortin

KCNN4 as a genomic determinant of cytosolic delivery by the attenuated cationic lytic peptide L17E

The development of a cytosolic delivery strategy for biopharmaceuticals is one of the central issues in drug development. Knowledge of the mechanisms underlying these processes may also pave the way for the discovery of novel delivery systems. L17E is an attenuated cationic amphiphilic lytic (ACAL) peptide developed by our research group that shows promise for cytosolic antibody delivery. In this study, given the high efficacy of L17E in cytosolic delivery, we investigated the mechanism of action of L17E in detail. L17E was found to achieve cytosolic delivery predominantly by transient disruption of the plasma membrane without the need for endocytosis. Importantly, the cell-line selectivity studies of L17E revealed a strong correlation between the efficiency of L17E-mediated delivery and the expression level of KCNN4, the gene encoding the calcium-activated potassium channel KCa3.1. Genetic and pharmacological regulation of KCNN4 expression and KCa3.1 activity, respectively, correlate closely with the efficiency of L17E-mediated cytosolic delivery, suggesting the importance of membrane-potential regulation by extracellular Ca2+ influx. Therefore, the activity of the L17E is relevant to the calcium-activated potassium channel.

The peripheral corticotropin releasing factor family's role in vasculitis

Corticotropin releasing factor family peptides (CRF peptides) include 4 members, corticotropin releasing hormone (CRH), Urocortin (UCN1), UCN2 and UCN3. CRF peptides function via the two distinct receptors, CRF1 and CRF2. Among them, CRH/CRF1 has been recognized to influence immunity/inflammation peripherally. Both pro- and anti-inflammatory effects of CRH are reported. Likewise, UCNs, peripherally in cardiovascular system have been documented to have both potent protective and harmful effects, with UCN1 acting on both CRF1 & CRF2 and UCN2 & UCN3 on CRF2. We and others also observe protective and detrimental effects of CRF peptides/receptors on vasculature, with the latter of predominantly higher incidence, i.e., they play an important role in the development of vasculitis while in some cases they are found to counteract vascular inflammation. The pro-vasculitis effects of CRH & UCNs include increasing vascular endothelial permeability, interrupting endothelial adherens & tight junctions leading to hyperpermeability, stimulating immune/inflammatory cells to release inflammatory factors, and promoting angiogenesis by VEGF release while the anti-vasculitis effects may be just the opposite, depending on many factors such as different CRF receptor types, species and systemic conditions. Furthermore, CRF peptides' pro-vasculitis effects are found to be likely related to cPLA2 and S1P receptor signal pathway. This minireview will focus on summarizing the peripheral effects of CRF peptides on vasculature participating in the processes of vasculitis.

Differentially Expressed Genes and Molecular Susceptibility to Human Age-Related Diseases

Mainstream transcriptome profiling of susceptibility versus resistance to age-related diseases (ARDs) is focused on differentially expressed genes (DEGs) specific to gender, age, and pathogeneses. This approach fits in well with predictive, preventive, personalized, participatory medicine and helps understand how, why, when, and what ARDs one can develop depending on their genetic background. Within this mainstream paradigm, we wanted to find out whether the known ARD-linked DEGs available in PubMed can reveal a molecular marker that will serve the purpose in anyone's any tissue at any time. We sequenced the periaqueductal gray (PAG) transcriptome of tame versus aggressive rats, identified rat-behavior-related DEGs, and compared them with their known homologous animal ARD-linked DEGs. This analysis yielded statistically significant correlations between behavior-related and ARD-susceptibility-related fold changes (log₂ values) in the expression of these DEG homologs. We found principal components, PC1 and PC2, corresponding to the half-sum and the half-difference of these log₂ values, respectively. With the DEGs linked to ARD susceptibility and ARD resistance in humans used as controls, we verified these principal components. This yielded only one statistically significant common molecular marker for ARDs: an excess of Fcγ receptor IIb suppressing immune cell hyperactivation.

The hypoxia response and nutritional peptides

Hypoxia controls metabolism at several levels, e.g., via mitochondrial ATP production, glucose uptake and glycolysis. Hence it is likely that hypoxia also affects the action and/or production of many peptide hormones linked to food intake and appetite control. Many of those are produced in the gastrointestinal tract, endocrine pancreas, adipose tissue, and selective areas in the brain which modulate and concert their actions. However, the complexity of the hypoxia response and the links to peptides/hormones involved in food intake and appetite control in the different organs are not well known. This review summarizes the role of the hypoxia response and its effects on major peptides linked to appetite regulation, nutrition and metabolism.

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.

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.

Role of urocortin in pregnancy: An update and future perspectives

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

Effect of Urocortin on strength and microarchitecture of osteopenic rat femur

As yet there is no evidence of the potential antiosteoporotic effect of Urocortin-1 (UCN), a corticotropin releasing factor related peptide, in vivo. In this study, and for the first time, we investigated the effect of UCN in a rat osteopenia model. Sixty female Sprague-Dawley rats were divided into 5 groups: (1) sham-operated, (2) untreated ovariectomized (OVX) rats, (3) and (4) OVX animals treated for 5 weeks with daily subcutaneous low-dose UCN (3 μg/kg of BW) or high-dose UCN (30 μg/kg of BW) 8 weeks after ovariectomy, and (5) OVX rats treated with daily estrogen (0.2 mg/kg of BW p.o) 8 weeks after ovariectomy for 5 weeks (E). After sacrifice, the femurs were reserved for biomechanical, histomorphometric and ash testing. In the biomechanical test, the high-dose UCN rats showed significantly improved mechanical stiffness (341.6 N/mm) compared with the untreated OVX animals (275.9 N/mm). In the histomorphometric evaluation, the high-dose UCN rats demonstrated an improved trabecular microarchitecture especially and significantly at the distal femur (distal femur Tb.Ar = 41.4% and N.Nd/mm(2) = 26.8, proximal femur Tb.Ar = 71.8% and N.Nd/mm(2) = 28.7) compared with untreated OVX rats (distal femur Tb.Ar = 23.3% and N.Nd/mm(2) = 11.7, proximal femur Tb.Ar = 60.2% and N.Nd/mm(2) = 25.2). Our results show that short-term treatment with UCN seems to have a positive effect on the metaphyseal bone structure and strength of the femur in ovariectomized rats.

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.

Urocortin I inhibits the effects of ghrelin and neuropeptide Y on feeding and energy substrate utilization

The corticotropin releasing hormone-related ligand, urocortin-I (UcnI), suppresses food intake when injected into multiple hypothalamic and extrahypothalamic areas. UcnI also alters energy substrate utilization, specifically via enhanced fat oxidation as reflected in reductions in respiratory quotient (RQ). In the present study we compared the feeding and metabolic effects of ghrelin and NPY following pretreatment with UcnI. Direct PVN injections of NPY (50 pmol) and ghrelin (50 pmol) were orexigenic while UcnI (10-40 pmol) reliably suppressed food intake. Both ghrelin and NPY increased RQ, indicating enhanced utilization of carbohydrates and the preservation of fat stores. UcnI alone suppressed RQ responses. PVN UcnI attenuated the effects of both ghrelin and NPY on food intake and energy substrate utilization. While ghrelin (5 pmol) potentiated the effect of NPY (25 pmol) on RQ and food intake, these responses were inhibited by pretreatment with UcnI (10 pmol). In conclusion, PVN NPY and ghrelin stimulate eating and promote carbohydrate oxidation while inhibiting fat utilization. These effects are blocked by UcnI which alone suppresses appetite and promotes fat oxidation. Overall these findings are consistent with a possible interactive role of PVN NPY, ghrelin and urocortin in the modulation of appetite and energy metabolism.

Central urocortin 3 and type 2 corticotropin-releasing factor receptor in the regulation of energy homeostasis: critical involvement of the ventromedial hypothalamus

The vital role of the corticotropin-releasing factor (CRF) peptide family in the brain in coordinating response to stress has been extensively documented. The effects of CRF are mediated by two G-protein-coupled receptors, type 1 and type 2 CRF receptors (CRF(1) and CRF(2)). While the functional role of CRF(1) in hormonal and behavioral adaptation to stress is well-known, the physiological significance of CRF(2) remains to be fully appreciated. Accumulating evidence has indicated that CRF(2) and its selective ligands including urocortin 3 (Ucn 3) are important molecular mediators in regulating energy balance. Ucn 3 is the latest addition of the CRF family of peptides and is highly selective for CRF(2). Recent studies have shown that central Ucn 3 is important in a number of homeostatic functions including suppression of feeding, regulation of blood glucose levels, and thermoregulation, thus reinforcing the functional role of central CRF(2) in metabolic regulation. The brain loci that mediate the central effects of Ucn 3 remain to be fully determined. Anatomical and functional evidence has suggested that the ventromedial hypothalamus (VMH), where CRF(2) is prominently expressed, appears to be instrumental in mediating the effects of Ucn 3 on energy balance, permitting Ucn 3-mediated modulation of feeding and glycemic control. Thus, the Ucn 3-VMH CRF(2) system is an important neural pathway in the regulation of energy homeostasis and potentially plays a critical role in energy adaptation in response to metabolic perturbations and stress to maintain energy balance.

The cannabinoid receptor CB₁ inverse agonist AM251 potentiates the anxiogenic activity of urocortin I in the basolateral amygdala

The basolateral amygdala is reported to play an important role in the neural bases of emotional processing. Previous studies have shown that injections of urocortin I (UcnI) into the basolateral amygdala (BLA) elicit anxiety-like behaviors in animal models. The present study examined the anxiogenic effects of UcnI administered directly into the BLA of male Sprague-Dawley rats. UcnI was administered at doses of 0.1-10.0 pmol and rats were then placed in an elevated plus maze for 10 min. UcnI reliably decreased the percent time spent in the open arms of the elevated plus maze (EPM) as well as open arm entries. This effect was observed across all doses tested, indicating the induction of anxiety-like behavior. In separate groups of rats, the CB(1) inverse agonist AM251 was administered systemically (0.03-3.0 mg/kg IP) or directly into the BLA (0.25-25.0 pmol) and EPM performance assessed. Both routes of AM251 administration produced a reduction in open arm entries and in time spent in the open arms. Moreover, when rats were pretreated with AM251 either systemically or directly into the BLA, the anxiogenic effect of UcnI was potentiated. That is, co-administration of AM251 and UcnI produced a greater suppression of percent time spent in the open arms and open arm entries as compared to UcnI alone. Based on these findings, we propose that urocortin and endocannabinoid signaling are part of an integrated neural axis modulating anxiety states within the basolateral amygdala. This article is part of a Special Issue entitled 'Anxiety and Depression'.

Novel neuroprotective strategies in ischemic retinal lesions

Retinal ischemia can be effectively modeled by permanent bilateral common carotid artery occlusion, which leads to chronic hypoperfusion-induced degeneration in the entire rat retina. The complex pathways leading to retinal cell death offer a complex approach of neuroprotective strategies. In the present review we summarize recent findings with different neuroprotective candidate molecules. We describe the protective effects of intravitreal treatment with: (i) urocortin 2; (ii) a mitochondrial ATP-sensitive K⁺ channel opener, diazoxide; (iii) a neurotrophic factor, pituitary adenylate cyclase activating polypeptide; and (iv) a novel poly(ADP-ribose) polymerase inhibitor (HO3089). The retinoprotective effects are demonstrated with morphological description and effects on apoptotic pathways using molecular biological techniques.

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.

Differentiation dependent expression of urocortin's mRNA and peptide in human osteoprogenitor cells: influence of BMP-2, TGF-beta-1 and dexamethasone

Urocortin-1 (UCN) a corticotropin releasing-factor (CRF) related peptide, has been found to be expressed in many different tissues like the central nervous system, the cardiovascular system, adipose tissue, and skeletal muscle. The effects of UCN are mediated via stimulation of CRF-receptors 1 and 2 (CRFR1 and 2, CRFR’s) with a high affinity for CRFR2. It has been shown that the CRF-related peptides and CRFR’s are involved in the regulation of stress-related endocrine, autonomic and behavioural responses. Using immunocytochemistry, immunohistochemistry and RT–PCR, we now can show the differentiation dependent expression of UCN mRNA and peptide in human mesenchymal progenitor cells (MSCs) directed to the osteoblastic phenotype for the first time. UCN expression was down regulated by TGF-beta and BMP-2 in the early proliferation phase of osteoblast development, whereas dexamethasone (dex) minimally induced UCN gene expression during matrix maturation after 24 h stimulation. Stimulation of MSCs for 28 days with ascorbate/beta-glycerophosphate (asc/bGp) induced UCN gene expression at day 14. This effect was prevented when using 1,25-vitamin D3 or dex in addition. There was no obvious correlation to osteocalcin (OCN) gene expression in these experiments. In MSCs from patients with metabolic bone disease (n = 9) UCN gene expression was significantly higher compared to MSCs from normal controls (n = 6). Human MSCs did not express any of the CRFR’s during differentiation to osteoblasts. Our results indicate that UCN is produced during the development of MSCs to osteoblasts and differentially regulated during culture as well as by differentiation factors. The expression is maximal between proliferation and matrix maturation phase. However, UCN does not seem to act on the osteoblast itself as shown by the missing CRFR’s. Our results suggest new perspectives on the role of urocortin in human skeletal tissue in health and disease.

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.

Urocortin 2 protects against retinal degeneration following bilateral common carotid artery occlusion in the rat

Urocortin 2 (Ucn 2) is corticotropin-releasing factor (CRF) paralog that preferentially activates CRF(2) receptors. Ucns exert CRF(2)-mediated cytoprotective effects against ischemia-reperfusion injury in cardiomyocytes. However, little is known regarding potential retinoprotective effects of Ucns despite the known presence of CRF family peptides and their receptors (predominantly CRF(2 alpha)) in retina. Therefore, the present study investigated the effects of post-ischemic intravitreal Ucn 2 (2 nmol) administration on ischemia-induced retinal degeneration. Two-month-old rats were subjected to permanent bilateral common carotid artery occlusion, and their retinas were processed histologically after two weeks survival to determine the density of viable cells in the ganglion cell layer and the thickness of all retinal layers. In vehicle-treated subjects, carotid occlusion reduced retina thickness by approximately 60% as compared to sham-operated animals. In contrast, intraocular Ucn 2 treatment led to a marked amelioration of the retinal layers, and the thickness of all layers was significantly increased by 40% compared to ischemic vehicle-treated subjects. Ucn 2 treatment also increased the number of cells by 55% in the ganglion cell layer as compared to those from carotid-occluded retinas of vehicle-treated subjects. These findings suggest that intraocular Ucn 2 treatment may protect against ischemia-induced retinal degeneration, results with potential therapeutic implications for ophthalmic diseases.

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.

Presence of and stress-related changes in urocortin-like molecules in neurons and immune cells from the mussel Mytilus galloprovincialis

The distribution of urocortin (UCN)-like material is investigated in the bivalve mollusc Mytilus galloprovincialis. Immunocytochemical data demonstrate that UCN-like molecules are present in ganglionic neurons, microglial cells and immunocytes. Moreover, a co-localization of UCN- and corticotrophin-releasing hormone (CRH)-like molecules is found in microglial cells and in immunocytes, but not in neurons. Following high salinity-stress experiments, immunoreactivity for UCN and CRH increased in ganglionic neurons and immunocytes. Our findings extend the number of molecules potentially used by molluscan immunocytes to confront stress situations and strengthen the idea of functional conservation of stress-related molecules during evolution.

Urocortin prevents mitochondrial permeability transition in response to reperfusion injury indirectly by reducing oxidative stress

Urocortin (UCN) protects hearts against ischemia and reperfusion injury whether given before ischemia or at reperfusion. Here we investigate the roles of PKC, reactive oxygen species, and the mitochondrial permeability transition pore (MPTP) in mediating these effects. In Langendorff-perfused rat hearts, acute UCN treatment improved hemodynamic recovery during reperfusion after 30 min of global ischemia; this was accompanied by less necrosis (lactate dehydrogenase release) and MPTP opening (mitochondrial entrapment of 2-[(3)H]deoxyglucose). UCN pretreatment protected mitochondria against calcium-induced MPTP opening, but only if the mitochondria had been isolated from hearts after reperfusion. These mitochondria also exhibited less protein carbonylation, suggesting that UCN decreases levels of oxidative stress. In isolated adult and neonatal rat cardiac myocytes, both acute (60 min) and chronic (16 h) treatment with UCN reduced cell death following simulated ischemia and re-oxygenation. This was accompanied by less MPTP opening as measured using tetramethylrhodamine methyl ester. The level of oxidative stress during reperfusion was reduced in cells that had been pretreated with UCN, suggesting that this is the mechanism by which UCN desensitizes the MPTP to reperfusion injury. Despite the fact that we could find no evidence that either PKC-epsilon or PKC-alpha translocate to the mitochondria following acute UCN treatment, inhibition of PKC with chelerythrine eliminated the effect of UCN on oxidative stress. Our data suggest that acute UCN treatment protects the heart by inhibiting MPTP opening. However, the mechanism appears to be indirect, involving a PKC-mediated reduction in oxidative stress.

The dynamic developmental localization of the full-length corticotropin-releasing factor receptor type 2 in rat cerebellum

Corticotropin releasing factor receptor 2 (CRF-R2) is strongly expressed in the cerebellum and plays an important role in the development of the cerebellar circuitry, particularly in the development of the dendritic trees and afferent input to Purkinje cells. However, the mechanisms responsible for the distribution and stabilization of CRF-R2 in the cerebellum are not well understood. Here, we provide the first detailed analysis of the cellular localization of the full-length form of CRF-R2 in rat cerebellum during early postnatal development. We document unique and developmentally regulated subcellular distributions of CRF-R2 in cerebellar cell types, e.g. granule cells after postnatal day 15. The presence of one or both receptor isoforms in the same cell may provide a molecular basis for distinct developmental processes. The full-length form of CRF-R2 may be involved in the regulation of the first stage of dendritic growth and at later stages in the controlling of the structural arrangement of immature cerebellar circuits and in the autoregulatory pathway of the cerebellum.

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.

Chronic disruption of body weight but not of stress peptides or receptors in rats exposed to repeated restraint stress

Rats exposed to restraint stress for 3 h on each of 3 days lose weight and do not return to the weight of their non-stressed controls for extended periods of time. Studies described here demonstrate that the initial weight loss is associated with increased energy expenditure and reduced food intake on the days of restraint but that there is no difference between stressed and control rats once stress ends. The failure to compensate for this energy deficit accounts for the sustained reduction in weight which lasts for up to 80 days after the end of restraint. In an additional experiment, in situ hybridization was used to measure mRNA expression of corticotrophin releasing factor (CRF) and CRF receptors in hypothalamic nuclei, of urocortin (UCN) in the Edinger Westphal nucleus and of UCN III in the rostral perifornical area and medial amygdaloidal nucleus. Immediately after the second 3 h bout of restraint stress, there was a significant increase in expression of UCN in the Edinger Westphal nucleus and of CRF-R1 in the paraventricular nucleus of the hypothalamus and a less pronounced decrease in CRF-R2 expression in the ventromedial nucleus of the hypothalamus. There were no differences in expression of stress-related peptides or their receptors 40 days after the end of repeated restraint. These results suggest that the sustained reduction in body weight and increased responsiveness to subsequent stressors in rats that have been exposed to repeated restraint are not associated with prolonged changes in mRNA expression of CRF receptors or their ligands.

Distribution and expression of CRF receptor 1 and 2 mRNAs in the CRF over-expressing mouse brain

Corticotropin-releasing factor (CRF) acts through CRF 1 and CRF 2 receptors (CRF1, CRF2). To test the hypothesis that CRF controls the expression of these receptors in a brain site- and receptor-type specific manner, we studied CRF1 mRNA and CRF2 mRNA expressions in mice with central CRF over-expression (CRF-OE) and using in situ hybridization. CRF1 and CRF2 mRNAs appear to be differentially distributed across the brain. The brain structures expressing the receptors are the same in wild-type (WT) and in CRF-OE mice. We therefore conclude that chronically elevated CRF does not induce or inhibit expression of these receptors in structures that normally do not or do, respectively, show these receptors. However, from counting cell body profiles positive for CRF1 and CRF2 mRNAs, clear differences appear in receptor expression between CRF-OE and WT mice, in a brain-structure-specific fashion. Whereas some structures do not differ, CRF-OE mice exhibit remarkably lower numbers of CRF1 mRNA-positive profiles in the subthalamic nucleus (-38.6%), globus pallidus (-31.5%), dorsal part of the lateral septum (-23.5%), substantia nigra (-22,8%), primary somatosensory cortex (-18.9%) and principal sensory nucleus V (-18.4%). Furthermore, a higher number of CRF2 mRNA-positive profiles are observed in the dorsal raphe nucleus (+32.2%). These data strongly indicate that central CRF over-expression in the mouse brain is associated with down-regulation of CRF1 mRNA and up-regulation of CRF2 mRNA in a brain-structure-specific way. On the basis of these results and the fact that CRF-OE mice reveal a number of physiological and autonomic symptoms that may be related to chronic stress, we suggest that CRF1 in the basal nuclei may be involved in disturbed information processing and that CRF2 in the dorsal raphe nucleus may play a role in mediating stress-induced release of serotonin by CRF.

Photoaffinity Cross-Linking of the Corticotropin-Releasing Factor Receptor Type 1 with Photoreactive Urocortin Analogues

Interaction of natural peptide ligands with class 2 GPCRs, which are targets of biologically important hormones such as glucagon, secretin, and corticotropin-releasing factor (CRF), occurs with a common orientation, in that the ligand C-terminus binds to the extracellular receptor N-terminus, whereas the ligand N-terminus binds to the receptor juxtamembrane domain. N-Terminal truncation, by eight amino acids in the case of CRF, leads to antagonists, suggesting those residues constitute the receptor activating sequence. Here, we identified by photoaffinity cross-linking using p-benzoyl-l-phenylalanine (Bpa) analogues of urocortin (Ucn) the most affine CRF receptor agonist, interaction domains of CRF(1) receptor with Bpa residues at exclusive positions. Specific cleavage patterns of the corresponding ligand-receptor complexes, obtained using several cleavage methods in combination with SDS-PAGE for fragment size determination, showed that a Bpa group located N-terminally or in position 12 binds at the second and such in position 17 or 22 at the first extracellular receptor loop. Our results indicate that the very N-terminal ligand residues (1-11), which are responsible for receptor activation, are oriented to the juxtamembrane domain by interaction of amino acid residues 12, 17, and 22. Our findings contradict a recently proposed interaction model derived from ligand interaction with a soluble receptor N-terminus, indicating that conclusions drawn from such a reduced system may be of limited value to understand the interaction with the full-length receptor.

CRF and urocortin differentially modulate GluRdelta2 expression and distribution in parallel fiber-Purkinje cell synapses

Corticotropin-releasing factor (CRF) and urocortin (UCN) are closely related multifunctional regulators, governing, among other processes, Purkinje cell development. Here, we investigate the effects of CRF and UCN on Purkinje cells in organotypic slices. We show that both peptides upregulate delta2 ionotropic glutamate receptor gene expression, and increase the abundance of the receptor in the postsynaptic density. However, only UCN treatment results in increased delta2 protein level per Purkinje cell, implying the existence of posttranscriptional regulation of GluRdelta2 mRNA. CRF, in contrast, reduces the number of delta2-positive dendritic shafts per cell, implying that the increase of GluRdelta2 in remaining synapses may be mainly due to its retargeting. We further observed different patterns of GluRdelta2 distribution in the zone of postsynaptic density upon CRF and UCN treatment. CRF treatment results in a clustered distribution of GluRdelta2 along the postsynaptic density, whereas UCN treatment provides a linear distribution.

The transcriptional coactivator p300 plays a critical role in the hypertrophic and protective pathways induced by phenylephrine in cardiac cells but is specific to the hypertrophic effect of urocortin

Anacardic acid is an alkylsalicylic acid obtained from cashew-nut-shell liquid, and is a potent inhibitor of p300 histone acetyl-transferase (HAT) activity. We have used anacardic acid to prevent the induction of hypertrophy in isolated neonatal rat cardiomyocytes. Hypertrophy was detected as an increase in cell size, the rearrangement of sarcomeres into a striated pattern, and the induction of embryonic genes beta-MHC and ANF. p300 inhibition was equally effective at preventing hypertrophy whether it was induced by treatment with the alpha1-adrenergic agonist, phenylephrine, or by treatment with urocortin, a member of the corticotrophin-releasing-factor family, which stimulates specific G protein-coupled receptors. Spiruchostatin A is a natural-product inhibitor of histone deacetylases (HDAC) similar to the depsipeptide FK228 molecule. We have recently synthesized spiruchostatin A and now show that, although HDACs act in opposition to HATs, spiruchostatin A has the same effect as anacardic acid, that is, it prevents the induction of hypertrophy in response to phenylephrine or urocortin. Pretreatment with either phenylephrine or urocortin reduced the extent of death observed after the exposure of isolated cardiomyocytes to simulated ischaemia and reoxygenation. Inhibition of p300 or HDAC activity eliminated the protection conferred by phenylephrine; however, it did not affect the protection conferred by urocortin. Therefore, it might eventually be possible to use chemical inhibitors such as these in a therapeutic setting to dissociate the protective effect and hypertrophic effect of urocortin, enhancing the survival of cardiomyocytes exposed to transient ischemia, while inhibiting the hypertrophic pathway that would otherwise be induced concurrently.

Urocortin 2 induces tyrosine hydroxylase phosphorylation in PC12 cells

Urocotins (Ucns) are newly discovered members of the corticotropin-releasing factor (CRF) neuropeptide family. Ucn 2 is expressed in the adrenal medulla, and its receptor, CRF2 receptor, is also expressed in the adrenal gland. To predict the physiological significance of Ucn 2 expression in the adrenal medulla, we examined the effects of Ucn 2 on catecholamine secretion and intracellular signaling using PC12 cells, a rat pheochromocytoma cell line. PC12 cells were found to express CRF2 receptor, but not CRF1 receptor. Treatment with Ucn 2 increased noradrenaline secretion and induced phosphorylation of PKA and Erk1/2. Tyrosine hydroxylase (TH), a rate-limiting enzyme for catecholamine synthesis, was also phosphorylated by Ucn 2. Pretreatment with a PKA inhibitor blocked Ucn 2-induced NA secretion, and Erk1/2 and TH phosphorylation. Pretreatment with a MEK inhibitor did not block Ucn 2-induced noradrenaline secretion or PKA phosphorylation, although TH phosphorylation was blocked. Thus, Ucn 2 induces noradrenaline secretion and TH phosphorylation through the PKA pathway and the PKA-Erk1/2 pathway, respectively. These results suggest Ucn 2 in the adrenal gland may be involved in the regulation of catecholamine release and synthesis.

Corticotropin-releasing factor: effect on cerebral blood flow in physiologic and ischaemic conditions

The expression of corticotrophin-releasing factor (CRF) receptors in cerebral arteries and arterioles suggests that CRF may modulate cerebral blood flow (CBF). In the present study, the effects of CRF, CRF-like peptides and the CRF broad spectrum antagonist DPhe-CRF on CBF have been investigated under normal physiologic conditions and in the margins of focal ischaemic insult. The experiments were carried out in anaesthetised and ventilated rats. Changes in CBF after subarachnoid microapplication of CRF and related peptides were assessed with a laser-Doppler flowmetry (LDF) probe. In the ischaemic animals, agents were injected approximately 60 minutes after permanent middle cerebral artery occlusion (MCAo). Microapplication of CRF and related peptides in normal rats into the subarachnoid space produced sustained concentration-dependent increases in CBF. This effect was attenuated by co-application with DPhe-CRF, which did not alter CBF itself. A second microapplication of CRF 30 min after the first failed to produce increases in CBF in normal animals. Microapplication of CRF in the subarachnoid space overlying the ischaemic cortex effected minor increases in CBF whereas D-Phe-CRF had no significant effect on CBF. Activation of the CRF peptidergic system increases CBF in the rat. Repeated activation of CRF receptors results in tachyphylaxis of the vasodilator response. CRF vasodilator response is still present after MCAo in the ischaemic penumbra, suggesting that the CRF peptidergic system may modulate CBF in ischaemic stroke.

Cardioprotection mediated by urocortin is dependent upon PKCε activation

Urocortin (Ucn) is an endogenous cardioprotective agent that protects against the damaging effects of ischemia and reperfusion injury in vitro and in vivo. We have found that the mechanism of action of Ucn involves both acute activation of specific target molecules, and using Affymetrix (Santa Clara, CA) gene chip technology, altered gene expression of different end effector molecules. Here, from our gene chip data, we show that after a 24 h exposure to Ucn, there was a specific increase in mRNA and protein levels of the protein kinase C epsilon (PKCepsilon) isozyme in primary rat cardiomyocytes compared with untreated cells and in the Langendorff perfused ex vivo heart. Furthermore, a short 10 min exposure of these cells to Ucn caused a specific translocation/activation of PKCepsilon in vitro and in the Langendorff perfused ex vivo heart. The importance of the PKCepsilon isozyme in cardioprotection and its relationship to cardioprotection produced by Ucn was assessed using PKCepsilon-specific inhibitor peptides. The inhibitor peptide, when introduced into cardiomyocytes, caused an increase in apoptotic cell death compared with control peptide after ischemia and reperfusion. When the inhibitor peptide was present with Ucn, the cardioprotective effect of Ucn was lost. This loss of cardioprotection by Ucn was also seen in whole hearts from PKCepsilon knockout mice. These findings indicate that the cardioprotective effect of Ucn is dependent upon PKCepsilon.

Urocortin does not reduce the renal injury and dysfunction caused by experimental ischaemia/reperfusion

Recent evidence indicates that activators of the serine/threonine kinase pathway protect against ischaemia/reperfusion. Here, we investigate the effects of renal ischaemia/reperfusion on the degree of renal dysfunction and injury with urocortin in rats. Rats treated with urocortin or its vehicle (saline) were subjected to bilateral renal artery occlusion (45 min) and reperfusion (6 h). At the end of experiments, the following indicators and markers of renal injury and dysfunction were measured: plasma urea, creatinine and aspartate aminotransferase, urine flow and creatinine clearance. Urocortin (1 or 15 microg/kg i.v.), administered 5 min prior to reperfusion, was not able to significantly reduce plasma urea, creatinine and aspartate aminotransferase indicating a non-protective effect on the renal dysfunction and reperfusion-injury caused by ischaemia/reperfusion. In addition, 15 microg/kg urocortin significantly depressed urine flow and creatinine clearance, which was associated with a significant depression in mean arterial pressure, indicating reduced renal perfusion. Thus, we propose that the pharmacological application of urocortin does not reduce the renal injury caused by bilateral renal ischaemia/reperfusion.

The cardioprotective effect of urocortin during ischaemia/reperfusion involves the prevention of mitochondrial damage

We have previously shown, using Affymetrix gene chip technology, that urocortin induces the expression of several diverse genes in cardiac myocytes. An ATP sensitive inwardly rectifying potassium channel, Katp (Kir6.1), the enzyme calcium independent phospholipase A2 (iPLA2), and protein kinase C epsilon (PKCepsilon) and that these genes are involved in the cardioprotective mechanism of action of urocortin. Here we demonstrate that these gene products are localized to cardiac myocyte mitochondria and for the first time show that urocortin protects cardiac myocytes from ischaemia/reperfusion induced cell death by preventing mitochondrial damage. Using pharmacological agents to Katp channels and iPLA2 and synthetic peptide inhibitors of PKCepsilon, we go on to demonstrate that these three gene products are involved in the urocortin induced protection of cardiac myocyte mitochondria. These proteins may interact at the mitochondria to produce the protective effect.

Ancient evolution of stress-regulating peptides in vertebrates

Recent studies on genomic sequences have led to the discovery of novel corticotropin-releasing factor (CRF) type 2 receptor-selective agonists, stresscopin (SCP)/urocortin III (UcnIII), and stresscopin-related peptide (SRP)/urocortin II (UcnII). In addition, analyses of vertebrate genomes showed that the CRF peptide family includes four distinct genes, CRF, urocortin/urotensin I, SCP/UcnIII, and SRP/UcnII. Each of these four genes is highly conserved during evolution and the identity between mammalian and teleost orthologs ranges from >96% for CRF to >55% for SCP. Phylogenetic studies showed that the origin of each of these peptides predates the evolution of tetrapods and teleosts, and that this family of peptide hormones evolved from an ancestor gene that developed the CRF/urocortin and SCP/SRP branches through an early gene duplication event. These two ancestral branches then gave rise to additional paralogs through a second round of gene duplication. Consequently, each of these peptides participates in the regulation of stress responses over the 550 million years of vertebrate evolution. The study also suggested that the fight-or-flight and stress-coping responses mediated mainly by CRF types 1 and 2 receptors evolved early in chordate evolution. In addition, we hypothesize that the CRF/CRF receptor signaling evolved from the same ancestors that also gave rise to the diuretic hormone/diuretic hormone receptors in insects. Thus, a complete inventory of CRF family ligands and their receptors in the genomes of different organisms provides an opportunity to reveal an integrated view of the physiology and pathophysiology of the CRF/SCP family peptides, and offers new insights into the evolution of stress regulation in vertebrates.

Urocortin protects cardiac myocytes from ischemia/reperfusion injury by attenuating calcium insensitive phospholipase A2gene expression

We have used Affymetrix gene chip technology to look for changes in gene expression caused by a 24 h exposure of rat primary neonatal cardiac myocytes to the cardioprotective agent urocortin. We observed a 2.5-fold down-regulation at both the mRNA and protein levels of a specific calcium-insensitive phospholipase A2 enzyme. Levels of lysophosphatidylcholine, a toxic metabolite of phospholipase A2, were lowered by 30% in myocytes treated with urocortin for 24 h and by 50% with the irreversible iPLA2 inhibitor bromoenol lactone compared with controls. Both 4 h ischemia and ischemia followed by 24 h reperfusion caused a significant increase in lysophosphatidylcholine concentration compared with controls. When these myocytes were pretreated with urocortin, the ischemia-induced increase in lysophosphatidylcholine concentration was significantly lowered. Moreover, co-incubation of cardiac myocytes with urocortin, or the specific phospholipase A2 inhibitor bromoenol lactone, reduces the cytotoxicity produced by lysophosphatidylcholine or ischemia/reperfusion. Similarly, in the intact heart ex vivo we found that cardiac damage measured by infarct size was significantly increased when lysophoshatidylcholine was applied during ischemia, compared with ischemia alone, and that pre-treatment with both urocortin and bromoenol lactone reversed the increase in infarct size. This, to our knowledge, is the first study linking the cardioprotective effect of urocortin to a decrease in a specific enzyme protein and a subsequent decrease in the concentration of its cardiotoxic metabolite.