Peptides (v.29, #5)
Editorial Board (CO2).
Editorial by Hubert Vaudry (647-648).
From fish tail to human brain by Howard A. Bern (649-650).
“Liberation” of urotensin II from the teleost urophysis: An historical overview by J. Michael Conlon (651-657).
During the past 20 years, urotensin II (UII) has progressed from being a peptide synthesized only in the urophysis of the caudal neurosecretory system of teleost fish to being considered an important physiological regulator in mammals with implications for the pathogenesis of a range of human cardiovascular and renal diseases. The “liberation” of UII from the urophysis was a gradual process and involved the sequential realization that (a) UII is present not only in the urophysis but also in the central nervous systems (CNS) of teleosts, (b) UII peptides, similar in structure to the urophysial peptides, are present in the diffuse caudal neurosecretory systems and/or CNS of species less evolutionarily advanced than teleosts, including Agnatha, thereby showing that UII is a phylogenetically ancient peptide, (c) UII is present in the brain and spinal cord of a tetrapod, the green frog Rana ridibunda, and (d) the UII gene and its specific receptor (GPR14/UT) are expressed in the CNS and certain peripheral tissues of mammals, including the human. The discovery that the genomes of mammals contain an additional gene encoding a UII-related peptide (URP) and the availability of highly effective peptide and non-peptide antagonists to investigate the role of UII in human physiology and pathophysiology ensure that the peptide will remain “center stage” for several years to come.
Keywords: Urophysis; Caudal neurosecretory system; Neurohormone evolution;
Structure–activity relationships of urotensin II and URP by Jérôme Leprince; David Chatenet; Christophe Dubessy; Alain Fournier; Bruno Pfeiffer; Elizabeth Scalbert; Pierre Renard; Pierre Pacaud; Hassan Oulyadi; Isabelle Ségalas-Milazzo; Laure Guilhaudis; Daniel Davoust; Marie-Christine Tonon; Hubert Vaudry (658-673).
Urotensin II (U-II) and urotensin II-related peptide (URP) are the endogenous ligands for the orphan G-protein-coupled receptor GPR14 now renamed UT. At the periphery, U-II and/or URP exert a wide range of biological effects on cardiovascular tissues, airway smooth muscles, kidney and endocrine glands, while central administration of U-II elicits various behavioral and cardiovascular responses. There is also evidence that U-II and/or URP may be involved in a number of pathological conditions including heart failure, atherosclerosis, renal dysfunction and diabetes. Because of the potential involvement of the urotensinergic system in various physiopathological processes, there is need for the rational design of potent and selective ligands for the UT receptor. Structure–activity relationship studies have shown that the minimal sequence required to retain full biological activity is the conserved U-II(4–11) domain, in particular the Cys5 and Cys10 residues involved in the disulfide bridge, and the Phe6, Lys8 and Tyr9 residues. Free α-amino group and C-terminal COOH group are not necessary for the biological activity, and modifications of these radicals may even increase the stability of the analogs. Punctual substitution of native amino acids, notably Phe6 and Trp7, by particular residues generates analogs with antagonistic properties. These studies, which provide crucial information regarding the structural and conformational requirements for ligand–receptor interactions, will be of considerable importance for the design of novel UT ligands with increased selectivity, potency and stability, that may eventually lead to the development of innovative drugs.
Keywords: Urotensin II; Urotensin II-related peptide; Structure–activity relationship;
Structure–activity relationship study of position 4 in the urotensin-II receptor ligand U-II(4-11) by Erika Marzola; Valeria Camarda; Madura Batuwangala; David G. Lambert; Girolamo Calo’; Remo Guerrini; Claudio Trapella; Domenico Regoli; Roberto Tomatis; Severo Salvadori (674-679).
In the present study we describe the synthesis and biological evaluation of 24 analogues of the urotensin II (U-II) fragment U-II(4-11) substituted in position 4 with coded and non-coded aromatic amino acids. All of the new analogues behaved as full U-II receptor (UT) agonists. Our results indicated that aromaticity is well tolerated, size, length and chirality of the side chain are not important, while substituents with a nitrogen atom are preferred. Thus acylation of U-II(5-11) with small groups bearing nitrogen atoms could be instrumental in future studies for the identification of novel potent UT receptor ligands.
Keywords: Urotensin II; UT receptor; Structure–activity study; HEK293rUT; Rat aorta;
Nonpeptide Urotensin-II receptor agonists and antagonists: Review and structure–activity relationships by Elodie Lescot; Ronan Bureau; Sylvain Rault (680-690).
Human Urotensin-II (hU-II) is a cyclic 11-amino acid peptide that plays a role in cardiovascular homeostasis. Its receptor is a member of the class A of G-protein-coupled receptors, called GPR14. In recent years, several nonpeptide ligands have been reported in the literature. Most were identified by high-throughput screening and optimized by medicinal chemistry methods. Other nonpeptide ligands were discovered starting from the 3D structure of hU-II or other ligands. They were identified by a virtual screening approach based on a 3D pharmacophore or by structural similarity with others cyclic peptides. In this review, nonpeptide agonists and antagonists are presented in relation to structure–activity relationships.
Keywords: Urotensin-II; GPR14; Nonpeptide agonists and antagonists; GPCR; SAR; Pharmacophore;
Biological properties and functional determinants of the urotensin II receptor by Christophe D. Proulx; Brian J. Holleran; Pierre Lavigne; Emanuel Escher; Gaétan Guillemette; Richard Leduc (691-699).
The urotensin II receptor (UT) is a member of the G protein-coupled receptor (GPCR) family and binds the cyclic undecapeptide urotensin II (U-II) as well as the octapeptide urotensin II-related peptide (URP). The active UT mediates pleiotropic effects through various signal transduction pathways, including coupling to G proteins and activating the mitogen-activated protein kinase pathway. Several highly conserved residues and motifs of class A GPCRs that are important for activity are found in UT. This review highlights some of the putative roles of these motifs in the binding, activation and desensitization of UT.
Keywords: Urotensin II; Urotensin II receptor; GPCR; Structure; Signal transduction;
Solution structure of urotensin-II receptor extracellular loop III and characterization of its interaction with urotensin-II by Stéphane Boivin; Isabelle Ségalas-Milazzo; Laure Guilhaudis; Hassan Oulyadi; Alain Fournier; Daniel Davoust (700-710).
Urotensin-II (U-II) is a vasoactive hormone that acts through a G-protein-coupled receptor named UT. Recently, we have shown, using the surface plasmon resonance technology that human U-II (hU-II) interacts with the hUT(281–300) fragment, a segment containing the extracellular loop III (EC-III) and short extensions of the transmembrane domains VI and VII (TM-VI and TM-VII). To further investigate the interaction of UT receptor with U-II, we have determined the solution structure of hUT(281–300) by high-resolution NMR and molecular modeling and we have examined, also using NMR, the binding with hU-II at residue level. In the presence of dodecylphosphocholine micelles, hUT(281–300) exhibited a type III β-turn (Q285–L288), followed by an α-helical structure (A289–L299), the latter including a stretch of transmembrane helix VII. Upon addition of hU-II, significant chemical shift perturbations were observed for residues located just on the N-terminal side of the β-turn (end of TM-VI/beginning of EC-III) and on one face of the α-helix (end of EC-III/beginning of TM-VII). These data, in conjunction with intermolecular NOEs, suggest that the initiation site of EC-III, as well as the upstream portion of helix VII, would be involved in agonist binding and allow to propose points of interaction in the ligand–receptor complex.
Keywords: UT receptor; Urotensin-II; Chemical shift perturbation; Interaction; NMR spectroscopy;
Urotensin II and urotensin II-related peptide activate somatostatin receptor subtypes 2 and 5 by Maria M. Malagon; Marcelo Molina; Manuel D. Gahete; Mario Duran-Prado; Antonio J. Martinez-Fuentes; Francisco J. Alcain; Marie-Christine Tonon; Jérôme Leprince; Hubert Vaudry; Justo P. Castaño; Rafael Vazquez-Martinez (711-720).
The UII and urotensin II-related peptide (URP) genes belong to the same superfamily as the somatostatin gene. It has been previously shown that somatostatin activates the UII-receptor (UTR). In contrast, the possible interaction between UII and URP and somatostatin receptors has remained scarcely analyzed. Herein, we have investigated the effects of UII and URP on cell proliferation and free cytosolic Ca2+ concentration ([Ca2+]i) in CHO-K1 cells stably expressing the porcine somatostatin receptor subtypes sst2 and sst5. Results show that both UII and URP induce stimulation of cell proliferation mediated by sst2 receptors and UII provokes inhibition of cell proliferation mediated by sst5 receptors. UII and URP also provoked an increase of [Ca2+]i in both sst2- and sst5-transfected cells. Together, our present data demonstrate that UII and URP directly activate sst2 and sst5 and thus mimic the effect of somatostatin on its cognate receptors.
Keywords: Urotensin II; Urotensin II-related peptide; Somatostatin; Somatostatin receptors; Proliferation; Intracellular Ca2+;
State-dependent calcium mobilization by urotensin-II in cultured human endothelial cells by Eugen Brailoiu; Xiaohua Jiang; G. Cristina Brailoiu; Jun Yang; Jaw Kang Chang; Hong Wang; Nae J. Dun (721-726).
Human endothelial cells express urotensin-II (U-II) as well as its receptor GPR14. Using microfluorimetric techniques, the effect of human U-II on cytosolic Ca2+ concentrations [Ca2+] i in cultured human aortic endothelial cells (HAECs) loaded with Fura-2 was evaluated in static or flow conditions. Under the static state, U-II (100 nM) abolished spontaneous Ca2+ oscillations, which occurred in a population of cultured HAEC. Similarly, U-II reduced thrombin-, but not ATP-induced calcium responses, suggesting that the peptide does not alter the Gq/11/IP3 pathway; rather, it modifies the coupling between protease-activated receptors and Gq/11/IP3. Under the flow condition, U-II (1, 10 and 100 nM) produced a dose-dependent increase in [Ca2+] i , which was subjected to desensitization. The result demonstrates a state-dependent effect of U-II in cultured HAEC, which may explain the variable responses to U-II under different experimental conditions.
Keywords: Calcium mobilization; Human endothelial cells; G-protein coupled receptor;
Effect of GABAA receptor activation on UT-coupled signaling pathways in rat cortical astrocytes by Laurence Desrues; Thomas Lefebvre; Mickaël Diallo; Pierrick Gandolfo; Jérôme Leprince; David Chatenet; Hubert Vaudry; Marie-Christine Tonon; Hélène Castel (727-734).
Cultured rat cortical astrocytes express two types of urotensin II (UII) binding sites: a high affinity site corresponding to the UT (GPR14) receptor and a low affinity site that has not been fully characterized. Activation of the high affinity site in astroglial cells stimulates polyphosphoinositide (PIP) turnover and provokes an increase in intracellular calcium concentration. We have hypothesized that the existence of distinct affinity sites for UII in rat cortical astrocytes could be accounted for by a possible cross-talk between UT and the ligand-gated ion channel GABAA receptor (GABAAR). Exposure of cultured astrocytes to UII provoked a bell-shaped increase in cAMP production, with an EC50 stimulating value of 0.83 ± 0.04 pM, that was totally blocked in the presence of the adenylyl cyclase inhibitor SQ 22,536. In contrast, UII was found to inhibit forskolin-induced cAMP formation. In the presence of the specific PKA inhibitor H89, UII provoked a sustained stimulation of cAMP formation. Inhibition of PKA by H89 strongly reduced the stimulatory effect of UII on PIP metabolism. GABA and the GABAAR agonist isoguvacine provoked a marked inhibition of UII-induced cAMP synthesis and a significant reduction of UII-evoked PIP turnover. These data suggest that functional interaction between UT and GABAAR negatively regulates coupling of UT to the classical PLC/IP3 signaling cascade as well as to the adenylyl cyclase/PKA pathway.
Keywords: Astrocytes; Urotensin II; UT; GABAAR; cAMP; Polyphosphoinositide;
Immunocytochemical localization of the urotensin-II receptor, UT, to rat and human tissues: Relevance to function by Janet J. Maguire; Rhoda E. Kuc; Matthias J. Kleinz; Anthony P. Davenport (735-742).
We have examined whether differential expression of UT receptors in cardiovascular tissues from rats and humans may account for the diverse vascular actions reported for urotensin-II. We found UT immunoreactivity ubiquitously expressed in arterial and venous smooth muscle and cardiomyocytes in both species, however, compared to human, levels of UT immunoreactivity in rat vascular endothelial cells was below the level for detection. In rat skeletal muscle cells UT receptor localized to the sarcolemma, a pattern comparable to that for isoforms of nitric oxide synthase suggesting that urotensin-II mediated hindquarter vasodilatation may involve release of nitric oxide from skeletal muscle fibers.
Keywords: Urotensin-II; UT receptor; Human cardiovascular system; Immunocytochemistry; Endothelial cells; Rat skeletal muscle;
Cardiorenovascular effects of urotensin II and the relevance of the UT receptor by Markus Tölle; Markus van der Giet (743-763).
Urotensin II (U-II) is a vasoactive peptide with many potent effects in the cardiorenovascular system. U-II activates a G-protein-coupled receptor termed UT. UT and U-II are highly expressed in the cardiovascular and renal system. Patients with various cardiovascular diseases show high U-II plasma levels. It was demonstrated that elevated U-II plasma levels and increased UT expression seem to play a role in heart failure, end-stage renal disease and atherosclerosis. U-II induces potent changes in vascular tone regulation. In addition, U-II stimulates vascular smooth muscle cell proliferation and cardiomyocyte hypertrophy. Currently several pharmaceutical companies are developing compounds to control the U-II/UT system. There are preclinical and some clinical studies showing potential benefits of inhibiting U-II function in renal disease, heart failure, and diabetes. This article will review both pre- and clinical data concerning cardiorenovascular effects of U-II.
Keywords: Urotensin; Urotensin receptor; Cardiovascular disease; Renal disease; Blood pressure;
Urotensin-II and cardiovascular remodeling by Panayiota Papadopoulos; Nicolas Bousette; Adel Giaid (764-769).
Urotensin-II (U-II), a cyclic undecapeptide, and its receptor, UT, have been linked to vascular and cardiac remodeling. In patients with coronary artery disease (CAD), it has been shown that U-II plasma levels are significantly greater than in normal patients and the severity of the disease is increased proportionally to the U-II plasma levels. We showed that U-II protein and mRNA levels were significantly elevated in the arteries of patients with coronary atherosclerosis in comparison to healthy arteries. We observed U-II expression in endothelial cells, foam cells, and myointimal and medial vSMCs of atherosclerotic human coronary arteries. Recent studies have demonstrated that U-II acts in synergy with mildly oxidized LDL inducing vascular smooth muscle cell (vSMC) proliferation. Additionally, U-II has been shown to induce cardiac fibrosis and cardiomyocyte hypertrophy leading to cardiac remodeling. When using a selective U-II antagonist, SB-611812, we demonstrated a decrease in cardiac dysfunction including a reduction in cardiomyocyte hypertrophy and cardiac fibrosis. These findings suggest that U-II is undoubtedly a potential therapeutic target in treating cardiovascular remodeling.
Keywords: Atherosclerosis; Congestive heart failure; Human; Heart; Animals; Blood vessels;
Urotensin II and urotensin II-related peptide (URP) in cardiac ischemia-reperfusion injury by H.C.G. Prosser; M.E. Forster; A.M. Richards; C.J. Pemberton (770-777).
Circulating urotensin II (UII) concentrations and the tissue expression of its cognate receptor (UT) are elevated in patients with cardiovascular disease (CVD). The functional significance of elevated plasma UII levels in CVD is unclear. Urotensin-related peptide (URP) is a paralog of UII in that it contains the six amino acid ring structures found in UII. Although both peptides are implicated as bioactive factors capable of modulating cardiovascular status, the role of both UII and URP in ischemic injury is unknown. Accordingly, we provide here the first report describing the direct cardiac effects of UII and URP in ischemia-reperfusion injury. Isolated perfused rat hearts were subjected to no-flow global ischemia for 45 min after 30 min preconditioning with either 1 nM rUII or 10 nM URP. Both rUII- and URP-induced significant vasodilation of coronary arteries before (both P < 0.05) and after ischemia (both P < 0.05). Rat UII alone lowered contractility prior to ischemia (P = 0.053). Specific assay of perfusate revealed rUII and URP both significantly inhibited reperfusion myocardial creatine kinase (CK) release (P = 0.012 and 0.036, respectively) and atrial natriuretic peptide (ANP) secretion (P = 0.025). Antagonism of the UT receptor with 1 μM palosuran caused a significant increase in perfusion pressure (PP) prior to and post-ischemia. Furthermore, palosuran significantly inhibited reductions in both PP and myocardial damage marker release induced by both rUII and URP. In conclusion, our data suggests rUII and URP reduce cardiac ischemia-reperfusion injury by increasing flow through the coronary circulation, reducing contractility and therefore myocardial energy demand, and inhibiting reperfusion myocardial damage. Thus, UII and URP present as novel peptides with potential cardioprotective actions.
Keywords: Isolated heart; Ischemia-reperfusion injury; Urotensin II; URP; Palosuran;
Urotensin II and atherosclerosis by Gervaise Loirand; Malvyne Rolli-Derkinderen; Pierre Pacaud (778-782).
Urotensin II, through its interaction with its UT receptor, is a potent vasoactive peptide in humans and in several animal models. Recent studies have demonstrated elevated plasma U-II levels in patients with atherosclerosis and coronary artery disease. U-II is expressed in endothelial cells, smooth muscle cells and infiltrating macrophages of atherosclerotic human coronary arteries. UT receptor expression is up-regulated by inflammatory stimuli. Activation of UT receptor by U-II stimulates endothelial and smooth muscle cell proliferation and monocytes chemotaxis. Therefore, in addition to its primary vasoactive effect, these observations suggest a role of U-II and UT receptor in the initiation and/or progression of atherosclerosis.
Keywords: Urotensin II; Urotensin receptor; Artery; Atherosclerosis;
Hemodynamic-independent anti-natriuretic effect of urotensin II in spontaneously hypertensive rats by Ying Shi; Yin-Xiang Cao; Ning Lu; Tai Yao; Yi-Chun Zhu (783-794).
The present study aims to test the hypothesis that U-II might have a direct anti-natriuretic action in spontaneously hypertensive rats (SHR). Bolus U-II injection (15 nmol kg−1) caused a transient decrease in glomerular filtration rate (GFR), urine flow rate (UV), urinary sodium (UNaV) and potassium excretion (UKV) that corresponded with a committed decrease in mean arterial pressure (MAP) and renal blood flow (RBF) during the first 30 min. Continuous U-II infusion (0.2 nmol kg−1 h−1) following a bolus U-II injection (0.3 nmol kg−1) caused an anti-natriuretic effect without any significant change in MAP, RBF, GFR, UV and UKV during the entire 1.5-h perfusion period in SHR. The levels of aldosterone and angiotensin II were not altered in the plasma and kidney, while plasma antidiuretic hormone decreased in response to U-II injection (15 nmol kg−1). Protein levels of U-II receptors (UT) were significantly increased in the kidney of 17-week-old SHR when compared with the age-matched WKY rats, while mRNA transcripts of both U-II and UT were increased in the kidney, left ventricle and thoracic aorta. In conclusion, U-II exerts a hemodynamic-independent anti-natriuretic action in adult SHR. The anti-natriuretic action of U-II in SHR is probably associated with an increased expression of the U-II–UT system in the kidney, suggesting a potential renal role of U-II in the pathogenesis of hypertension.
Keywords: Urotensin II; Hypertension; Renal function;
PPAR-γ expression in animals subjected to volume overload and chronic Urotensin II administration by Gregory S. Harris; Robert M. Lust; Jonathan H. DeAntonio; Laxmansa C. Katwa (795-800).
Activation of PPAR-γ through the administration of glitazones has shown promise in preserving function following cardiac injury, although recent evidence has suggested their use may be contraindicated in the case of severe heart failure. This study tested the hypothesis that PPAR-γ expression increases in a time dependent manner in response to chronic volume overload (VO) induced heart failure. Additionally, we attempted to determine what effect 4 week administration of Urotensin II (UTII) may have on PPAR-γ expression. VO induced heart failure was produced in Sprague–Dawley rats (n = 32) by aorta-caval fistula. Animals were sacrificed at 1, 4, and 14 weeks following shunt creation. In a separate set of experiments, animals were administered 300 pmol/kg/h of UTII for 4 weeks, subjected to 4 weeks of volume overload, or given UTII + VO. Densitometric analysis of left ventricular (LV) protein demonstrated PPAR-γ expression was significantly (* p < 0.05) upregulated at 4 and 14 weeks (31.5% and 37%, respectively) post-fistula formation compared to control values. PPAR-γ activation was decreased in the 4 and 14 week (39.16% and 42.4%, respectively), but not in the 1-week animals, and these changes did not correlate with NF-κB activity. Animals given UTII either with or without VO demonstrated increased expression of PPAR-γ as did animals subjected to 4 week VO alone. Animals given UTII either with or without VO had decreased activity vs. control. These data suggest PPAR-γ may play a role in the progression of heart failure, however, the exact nature has yet to be determined.
Keywords: Urotensin II infusion; PPAR-γ activity; NF-κB; Progressive heart failure;
Increased gene expression of urotensin II-related peptide in the hearts of rats with congestive heart failure by Takashi Nakayama; Takuo Hirose; Kazuhito Totsune; Nobuyoshi Mori; Yutaka Maruyama; Takahiro Maejima; Kana Minagawa; Ryo Morimoto; Kei Asayama; Masahiro Kikuya; Takayoshi Ohkubo; Junichiro Hashimoto; Masahiro Kohzuki; Kazuhiro Takahashi; Yutaka Imai (801-808).
Urotensin II-related peptide (URP) is a novel endogenous ligand for urotensin II receptor (UT-R). To investigate the pathophysiological role of URP in heart failure, we examined URP, UII and UT-R expression in hearts and kidneys of rats with congestive heart failure due to coronary ligation by quantitative RT-PCR and immunocytochemistry. Significantly increased expression levels of URP mRNA were found in the atrium, the right ventricle and the infarcted part of left ventricle of heart failure rats, when compared with sham-operated rats (about 2.2-fold, 2.7-fold and 3.9-fold, respectively). Expression levels of UII mRNA in the heart were about 10% of URP mRNA, and were slightly increased only in the infarcted part of left ventricle of heart failure rats, when compared with sham-operated rats. The expression levels of UT-R mRNA were increased in the atrium of heart failure rats. There was no significant change of URP, UII and UT-R mRNA expression levels in the kidney between heart failure and sham-operated rats. The myocardium was diffusely immunostained with URP in both rats. The blood vessels in the heart were positively immunostained with URP in heart failure rats, but not in sham-operated rats, whereas they were positively immunostained with UT-R in both rats. These findings suggest that the expression of URP, UII and UT-R is enhanced in failing heart, and the UII/URP/UT-R system has important pathophysiological roles in the progression of heart failure.
Keywords: Urotensin II; Urotensin II-related peptide; GPR14; Heart failure; RT-PCR; Immunocytochemistry;
Another ligand fishing for G protein-coupled receptor 14 by Tsukasa Sugo; Masaaki Mori (809-812).
Urotensin II (UII), which was originally isolated from the teleost urophysis, was identified as an endogenous ligand for orphan G protein-coupled receptor 14 (GPR14). The structure of mammalian UII was confirmed by isolation from spinal cord in porcine, or was easily predicted from the sequence of prepro-UII in human. For rat and mouse, however, only the tentative sequences of UII peptides have been demonstrated because the typical processing sites are absent from the amino-terminal region of the mature peptides. Isolation of UII-like immunoreactivity in rat brain revealed the presence of a novel peptide, designated urotensin II-related peptide (URP). URP binds and activates the human and rat urotensin II receptors (GPR14) and has a hypotensive effect when administrated to anesthetized rats. Based on the DNA sequences of the cloned prepro-URP gene, the amino acid sequences of mature URP for mouse and human are identical to that for rat URP. These results suggest that URP is the endogenous and functional ligand for urotensin II receptor in the rat and mouse, and possibly in the human.
Keywords: Urotensin II; Urotensin II-related peptide; URP; GPR14; SENR; UTR;
[Orn5]URP acts as a pure antagonist of urotensinergic receptors in rat cortical astrocytes by Mickaël Diallo; Marie Jarry; Laurence Desrues; Hélène Castel; David Chatenet; Jérôme Leprince; Hubert Vaudry; Marie-Christine Tonon; Pierrick Gandolfo (813-819).
Cultured rat astrocytes, which express functional urotensin II (UII)/UII-related peptide (URP) receptors (UT), represent a very suitable model to investigate the pharmacological profile of UII and URP analogs towards native UT. We have recently designed three URP analogs [d-Trp4]URP, [Orn5]URP and [d-Tyr6]URP, that act as UT antagonists in the rat aortic ring bioassay. However, it has been previously reported that UII/URP analogs capable of inhibiting the contractile activity of UII possess agonistic activity on UT-transfected cells. In the present study, we have compared the ability of URP analogs to compete for [125I]URP binding and to modulate cytosolic calcium concentration ([Ca2+]c) in cultured rat astrocytes. All three analogs displaced radioligand binding: [d-Trp4]URP and [d-Tyr6]URP interacted with high- and low-affinity sites whereas [Orn5]URP only bound high-affinity sites. [d-Trp4]URP and [d-Tyr6]URP both induced a robust increase in [Ca2+]c in astrocytes while [Orn5]URP was totally devoid of activity. [Orn5]URP provoked a concentration-dependent inhibition of URP- and UII-evoked [Ca2+]c increase and a rightward shift of the URP and UII dose–response curves. The present data indicate that [d-Trp4]URP and [d-Tyr6]URP, which act as UII antagonists in the rat aortic ring assay, behave as agonists in the [Ca2+]c mobilization assay in cultured astrocytes, whereas [Orn5]URP is a pure selective antagonist in both rat aortic ring contraction and astrocyte [Ca2+]c mobilization assays.
Keywords: Urotensin II; Urotensin II-related peptide (URP); UT antagonists; Cytosolic calcium; Binding; Astrocytes;
Comparative distribution of the mRNAs encoding urotensin I and urotensin II in zebrafish by Caroline Parmentier; Emilie Hameury; Isabelle Lihrmann; Jacques Taxi; Hélène Hardin-Pouzet; Hubert Vaudry; André Calas; Hervé Tostivint (820-829).
The neural neurosecretory system of fishes produces two biologically active neuropeptides, i.e. the corticotropin-releasing hormone paralog urotensin I (UI) and the somatostatin-related peptide urotensin II (UII). In zebrafish, we have recently characterized two UII variants termed UIIα and UIIβ. In the present study, we have investigated the distribution of UI, UIIα and UIIβ mRNAs in different organs by quantitative RT-PCR analysis and the cellular localization of the three mRNAs in the spinal cord by in situ hybridization (ISH) histochemistry. The data show that the UI gene is mainly expressed in the caudal portion of the spinal cord and, to a lesser extent, in the brain, while the UIIα and the UIIβ genes are exclusively expressed throughout the spinal cord. Single-ISH labeling revealed that UI, UIIα and UIIβ mRNAs occur in large cells, called Dahlgren cells, located in the ventral part of the caudal spinal cord. Double-ISH staining showed that UI, UIIα and UIIβ mRNAs occur mainly in distinct cells, even though a few cells were found to co-express the UI and UII genes. The differential expression of UI, UIIα and UIIβ genes may contribute to the adaptation of Dahlgren cell activity during development and/or in various physiological conditions.
Keywords: Caudal neurosecretory system; Urotensins; In situ hybridization;
Central and peripheral cardiovascular, ventilatory, and motor effects of trout urotensin-II in the trout by Jean-Claude Le Mével; Frédéric Lancien; Nagi Mimassi; Jérôme Leprince; J. Michael Conlon; Hubert Vaudry (830-837).
Urotensin-II (U-II) was originally considered to be exclusively the product of the caudal neurosecretory system (CNSS) of teleost fish, but it has now been demonstrated that U-II is widely expressed in peripheral tissues and nervous structures of species from lampreys to mammals. However, very little is known regarding the physiological effects of this peptide in its species of origin. In the present review, we summarize the most significant results relating to the cardiovascular, ventilatory, and motor effects of centrally and peripherally administered synthetic trout U-II in our experimental animal model, the unanesthetized trout Oncorhynchus mykiss. In addition, we compare the actions of U-II with those of other neurohormonal peptides, particularly with the actions of urotensin-I, a 41-amino acid residue peptide paralogous to corticotropin-releasing hormone that is co-localized with U-II within neurons of the CNSS.
Keywords: Neuropeptides; Brain; Intracerebroventricular injection; Intra-arterial injection; Blood pressure; Heart rate; Ventilation; Locomotion;
Behavioral actions of urotensin-II by Jean-Claude do Rego; Jérôme Leprince; Elizabeth Scalbert; Hubert Vaudry; Jean Costentin (838-844).
Urotensin-II (U-II) and urotensin-II-related peptide (URP) have been identified as the endogenous ligands of the orphan G-protein-coupled receptor GPR14 now renamed UT. The occurrence of U-II and URP in the central nervous system, and the widespread distribution of UT in the brain suggest that U-II and URP may play various behavioral activities. Studies conducted in rodents have shown that central administration of U-II stimulates locomotion, provokes anxiety- and depressive-like states, enhances feeding activity and increases the duration of paradoxical sleep episodes. These observations indicate that, besides the endocrine/paracrine activities of U-II and URP on cardiovascular and kidney functions, these peptides may act as neurotransmitters and/or neuromodulators to regulate various neurobiological activities.
Keywords: Urotensin-II; GPR14; UT; Locomotor activity; Psychiatric disorders; Feeding behavior; Sleep;
Neuropeptide interactions and REM sleep: A role for Urotensin II? by Luis de Lecea; Patrice Bourgin (845-851).
Urotensin II (UII) is a peptide with structural similarity to the somatostatin family with potent vasoconstrictor activity. UII receptor is expressed broadly in the periphery, and most notably in the heart and microvessels. In the brain, the UII receptor can be detected in the spinal cord and in cholinergic nuclei in the brainstem known to be involved in REM sleep regulation. Recent data suggest that, in addition to their vasoactive properties, UII receptor ligands may have excitatory activity on a selective group of neurons that modulate REM sleep. This review focuses on the implications of these findings for the neurobiology of REM sleep regulation and discusses the possible impact of UII and other neuropeptides on the balance of the alternation between sleep states.
Keywords: Urotensin-related peptide; Sleep; Wakefulness; Laterodorsal tegmentum; Pedunculopontine nucleus; Acetylcholine; Vasoactive; Blood flow;
Evidence for endogenous urotensin-II as an inhibitor of insulin secretion by José Marco; Eva M. Egido; Raquel Hernández; Ramona A. Silvestre (852-858).
In the perfused rat pancreas, infusion of urotensin-II (UII), a somatostatin-like peptide, inhibits glucose-induced insulin secretion. We have resorted to specific antagonists of the UII receptor (UT), palosuran and urantide, to investigate whether endogenous UII also behaves as an inhibitor of beta-cell secretion. The insulinostatic effect of UII was counteracted by palosuran and by urantide but not by a somatostatin-receptor antagonist (cyclo-somatostatin). Furthermore, the insulinostatic effect of somatostatin was not reversed by palosuran. These results suggest that UII and somatostatin blocked beta-cell secretion via distinct receptors. Finally, in the absence of exogenous UII, both palosuran and urantide potentiated glucose-induced insulin release, thus supporting the concept that endogenous UII is an insulinostatic peptide. By virtue of their insulinotropic effect, UT antagonists may be considered potential drugs for treating the impaired insulin secretion characteristic of type 2 diabetic patients.
Keywords: Urotensin-II; UT antagonists; Palosuran; Urantide; Insulin secretion; Rat pancreas;
The role of urotensin II in the metabolic syndrome by Kwok Leung Ong; Louisa Y.F. Wong; Bernard M.Y. Cheung (859-867).
Urotensin II is a potent vasoconstrictive peptide that mediates both endothelium-independent vasoconstriction and endothelium-dependent vasodilatation. Its plasma level correlates positively with body weight and is raised in diabetes, renal failure, hypertension, and other cardiovascular diseases including congestive heart failure and carotid atherosclerosis. It can inhibit glucose-induced insulin secretion, and genetic variants in urotensin II gene are associated with insulin resistance and type 2 diabetes. Urotensin II also affects lipid metabolism in fish and food intake in mice. Recent studies have also demonstrated a role of urotensin II in inflammation and endothelial dysfunction. These findings suggest a close relationship between urotensin II and at least some components of the metabolic syndrome, including hypertension, insulin resistance, hyperglycemia, and inflammation.
Keywords: Diabetes; Hypertension; Inflammation; Metabolic syndrome; Urotensin II; Vasoactive peptide;
Increased circulating urotensin II in cirrhosis: Potential implications in liver disease by William Kemp; Stuart Roberts; Henry Krum (868-872).
Urotensin II (UII) is a potent vasoactive mediator which, through interaction with a specific G-protein coupled receptor, can result in either a vasoconstrictive or vasodilatory response. In addition to its effect upon vascular tone, UII possess mitogenic and fibrogenic potential. The influence of UII on vascular tone is to some degree both species-specific and disease-specific. Increased circulating UII levels have been documented in subjects with liver cirrhosis although the significance of this finding with regards to the development of chronic liver disease and portal hypertension has yet to be fully elucidated. In this review we focus on the potential relevance of UII as a vasoactive mediator in the chronic liver disease population and postulate as to the site of overproduction of UII.
Keywords: Urotensin II; Cirrhosis; Liver disease; Portal hypertension;
Immunolocalization of urotensin II and its receptor in human adrenal tumors and attached non-neoplastic adrenal tissues by Ryo Morimoto; Fumitoshi Satoh; Osamu Murakami; Kazuhito Totsune; Yoichi Arai; Takashi Suzuki; Hironobu Sasano; Sadayoshi Ito; Kazuhiro Takahashi (873-880).
Urotensin II (UII), first identified from goby urophysis, is a potent vasoactive peptide hormone and an endogenous ligand for an orphan G protein-coupled receptor GPR14, now named urotensin II receptor (UT-R). In addition to its vascular actions, UII has been shown to have mitogenic effects on tumor growth and some regulatory effects on adrenal steroidogenesis. In the present study, we examined expression of UII and UT-R in human adrenal tumors and attached non-neoplastic adrenal tissues by immunohistochemistry. Both UII and UT-R were immunolocalized in tumor cells of all adrenal tumors examined: 8 cases of cortisol-producing adenomas, 8 cases of aldosterone-producing adenomas, 2 cases of non-functioning adenomas, 17 cases of adrenocortical carcinomas, and 8 cases of pheochromocytomas. In attached adrenals, immunoreactivity for UII was detected in medulla, but much weaker in the cortex than in cortical tumors, suggesting that expression of UII was up-regulated in neoplastic adrenocortical tissues. No significant differences were found in the degree of immunoreactivity for UT-R between the tumors and the attached adrenal tissues. The present study showed that both UII and UT-R were expressed in the adrenal tumors and attached non-neoplastic adrenal tissues, and suggests possible roles of UII and UT-R in tumor growth and/or secretory activities of these tumors.
Keywords: Urotensin II; Urotensin II receptor; Adrenal tumor; Immunohistochemistry;