[Research progress of urotensin Ⅱ and urotensin Ⅱ receptor]

Urotensin II (UII) is the most potent vasoconstrictor among the identified vasoactive peptides. UII and its receptor (UT), which play varies of physiological roles, are widely expressed in central nerve system and peripheral organs. The change on the expressional level of UII/UT system has been proved to be closely correlated with pathological conditions. Therefore, UII/UT system was considered to be a potential target for treating many diseases. This review article is devoted to the latest research progress of UII/UT system in several aspects including ligand and receptor distribution, physiological activity, characteristics under pathological conditions and antagonist classification.

Urotensin II inhibits doxorubicin-induced human umbilical vein endothelial cell death by modulating ATF expression and via the ERK and Akt pathway

Background and Purpose

Regulation of the homeostasis of vascular endothelium is critical for the processes of vascular remodeling and angiogenesis under physiological and pathological conditions. Urotensin II (U-II), a potent vasoactive peptide, participates in vascular and myocardial remodeling after injury. We investigated the protective effect of U-II on doxorubicin (DOX)-induced apoptosis in cultured human umbilical vein endothelial cells (HUVECs) and the potential mechanisms involved in this process.

Experimental Approach

Cultured HUVECs were treated with vehicle, DOX (1 µM), U-II, or U-II plus DOX. Apoptosis was evaluated by DNA strand break level with TdT-mediated dUTP nick-end labeling (TUNEL) staining. Western blot analysis was employed to determine the related protein expression and flow cytometry assay was used to determine the TUNEL positive cells.

Key Results

U-II reduced the quantity of cleaved caspase-3 and cytosol cytochrome c and increased Bcl-2 expression, which results in protecting HUVECs from DOX-induced apoptosis. U-II induced Activating transcription factor 3 (ATF3) at both mRNA and protein levels in U-II-treated cells. Knockdown of ATF3 with ATF3 siRNA significantly reduced ATF3 protein levels and U-II protective effect under DOX-treated condition. U-II downregulated p53 expression in DOX-induced HUVECs apoptosis, and it rapidly activated extracellular signal-regulated protein kinase (ERK) and Akt. The DOX induced change of p53 was not affected by U-II antagonist (urantide) under ATF-3 knockdown. The inhibitory effect of U-II on DOX-increased apoptosis was attenuated by inhibitors of ERK (U0126) and PI3K/Akt (LY294002).

Conclusion and Implications

Our observations provide evidence that U-II protects HUVECs from DOX-induced apoptosis. ERK-Akt phosphorylation, ATF3 activation, and p53 downregulation may play a signal-transduction role in this process.

Urotensin II induces interleukin 8 expression in human umbilical vein endothelial cells

Background

Urotensin II (U-II), an 11-amino acid peptide, exerts a wide range of actions in cardiovascular systems. Interleukin-8 (IL-8) is secreted by endothelial cells, thereby enhancing endothelial cell survival, proliferation, and angiogenesis. However, the interrelationship between U-II and IL-8 as well as the detailed intracellular mechanism of U-II in vascular endothelial cells remain unclear. The aim of this study was to investigate the effect of U-II on IL-8 expression and to explore its intracellular mechanism in human umbilical vein endothelial cells.

Methods/Principal Findings

Primary human umbilical vein endothelial cells were used. Expression of IL-8 was determined by real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and luciferase reporter assay. Western blot analyses and experiments with specific inhibitors were performed to reveal the downstream signaling pathways as concerned. U-II increased the mRNA/protein levels of IL-8 in human umbilical vein endothelial cells. The U-II effects were significantly inhibited by its receptor antagonist [Orn⁵]-URP. Western blot analyses and experiments with specific inhibitors indicated the involvement of phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinase in U-II-induced IL-8 expression. Luciferase reporter assay further revealed that U-II induces the transcriptional activity of IL-8. The site-directed mutagenesis indicated that the mutation of AP-1 and NF-kB binding sites reduced U-II-increased IL-8 promoter activities. Proliferation of human umbilical vein endothelial cells induced by U-II could be inhibited significantly by IL-8 RNA interference.

Conclusion/Significance

The results show that U-II induces IL-8 expression in human umbilical vein endothelial cells via p38 mitogen-activated protein kinase and extracellular signal-regulated kinase signaling pathways and IL-8 is involved in the U-II-induced proliferation of human umbilical vein endothelial cells.

Urotensin-II system in genetic control of blood pressure and renal function

Urotensin-II controls ion/water homeostasis in fish and vascular tone in rodents. We hypothesised that common genetic variants in urotensin-II pathway genes are associated with human blood pressure or renal function. We performed family-based analysis of association between blood pressure, glomerular filtration and genes of the urotensin-II pathway (urotensin-II, urotensin-II related peptide, urotensin-II receptor) saturated with 28 tagging single nucleotide polymorphisms in 2024 individuals from 520 families; followed by an independent replication in 420 families and 7545 unrelated subjects. The expression studies of the urotensin-II pathway were carried out in 97 human kidneys. Phylogenetic evolutionary analysis was conducted in 17 vertebrate species. One single nucleotide polymorphism (rs531485 in urotensin-II gene) was associated with adjusted estimated glomerular filtration rate in the discovery cohort (p = 0.0005). It showed no association with estimated glomerular filtration rate in the combined replication resource of 8724 subjects from 6 populations. Expression of urotensin-II and its receptor showed strong linear correlation (r = 0.86, p<0.0001). There was no difference in renal expression of urotensin-II system between hypertensive and normotensive subjects. Evolutionary analysis revealed accumulation of mutations in urotensin-II since the divergence of primates and weaker conservation of urotensin-II receptor in primates than in lower vertebrates. Our data suggest that urotensin-II system genes are unlikely to play a major role in genetic control of human blood pressure or renal function. The signatures of evolutionary forces acting on urotensin-II system indicate that it may have evolved towards loss of function since the divergence of primates.

The urotensin system is up-regulated in the pre-hypertensive spontaneously hypertensive rat

Urotensin II (UII) concentrations are raised both in humans with hypertension and in spontaneously hypertensive rats (SHR). Since the urotensin system acts to regulate glomerular filtration in the kidney it may play a greater role in the pre-hypertensive SHR in which renal dysfunction is known to precede the onset of severe hypertension. This study aimed to determine the renal actions and expression of the urotensin system in the young SHR. Intravenous rat UII (6 pmol. min^-1. 100 g body weight^-1) had no significant effect on GFR; however urotensin-related peptide (URP) reduced GFR (P<0.05) in 4-5 week old SHR. Administration of the UT antagonist SB-706375 evoked marked increases in GFR (baseline 0.38 ± 0.07 vs antagonist 0.76 ± 0.05 ml. min^-1. 100 g body weight^-1, P<0.05), urine flow and sodium excretion (baseline 2.5 ± 0.4 vs antagonist 9.1 ± 2.1 µmol. min^-1. 100 g body weight^-1, P<0.05) in the SHR. Normotensive Wistar-Kyoto rats showed little response to UT antagonism. Quantitative RT-PCR showed that neither UII nor UT mRNA expression differed between the kidneys of young SHR and WKY rats; however expression of URP was 4-fold higher in the SHR kidney. Renal transcriptional up-regulation indicates that URP is the major UT ligand in young SHR and WKY rats. Enhanced tonic UT activation may contribute to known renal dysfunction in pre-hypertensive SHR.

Urotensin II exerts antiapoptotic effect on NRK-52E cells through prostacyclin-mediated peroxisome proliferator-activated receptor alpha and Akt activation

Urotensin II (UII) is a cyclic vasoactive peptide which is mainly expressed in kidneys. Although elevated plasma UII levels are associated with renal impairment, the influence of UII on renal injury is unclear. In this study, we monitored the influence of UII on gentamicin-induced apoptosis in rat tubular cells (NRK-52E). We found that UII significantly reduced gentamicin-induced apoptosis and apoptotic signals. Blocking endogenous UII secretion caused cells to be more susceptible to gentamicin. In gentamicin-treated mice, UII also expressed protective effect on renal tubular cells. UII was also found to induce prostacyclin (PGI2) production, which caused peroxisomal proliferator-activated receptor α (PPARα) activation as revealed by both PGI2 synthase siRNA transfection and piroxicam treatment. Blockage of PPARα by siRNA transfection inhibited UII-induced Akt phosphorylation and the antiapoptotic effect of UII. Our results suggest that UII can protect renal tubular cells from gentamicin-induced apoptosis through PGI2-mediated PPARα and Akt activation.

[Urotensin II--a newly discovered modulator of cardiovascular functions in vertebrates]

Peptide urotensin II was originally isolated from the urophysis of teleost fishes; later it was identified also in higher vertebrates in various organs and tissues, including cardiovascular structures. Since its discovery it has been considered as a highly potent vasoconstrictor inducing contraction of smooth muscle in subnanomolar concentrations. Its wide distribution as well as its high interspecies homology indicates that this peptide is involved in regulation of many important physiological functions in vertebrates. An effort to discover other possible functions of urotensin II was intensified by the identification of its G-protein coupled receptor and its identification in humans. Furthermore, altered levels of expression of urotensin II and its receptor were found in various disease states including hypertension, diabetes, heart and renal failure, in experimental animal models as well as in humans. Therefore, there is widely discussed question regarding the possible role of urotensin II in etiopathogeneses of these diseases, however the exact mechanisms are still unknown. The aim of this review is to summarize the current knowledge about urotensin II with emphasis to its direct and undirect effects in cardiovascular system.

Urotensin II in invertebrates: from structure to function in Aplysia californica

Neuropeptides are ancient signaling molecules that are involved in many aspects of organism homeostasis and function. Urotensin II (UII), a peptide with a range of hormonal functions, previously has been reported exclusively in vertebrates. Here, we provide the first direct evidence that UII-like peptides are also present in an invertebrate, specifically, the marine mollusk Aplysia californica. The presence of UII in the central nervous system (CNS) of Aplysia implies a more ancient gene lineage than vertebrates. Using representational difference analysis, we identified an mRNA of a protein precursor that encodes a predicted neuropeptide, we named Aplysia urotensin II (apUII), with a sequence and structural similarity to vertebrate UII. With in-situ hybridization and immunohistochemistry, we mapped the expression of apUII mRNA and its prohormone in the CNS and localized apUII-like immunoreactivity to buccal sensory neurons and cerebral A-cluster neurons. Mass spectrometry performed on individual isolated neurons, and tandem mass spectrometry on fractionated peptide extracts, allowed us to define the posttranslational processing of the apUII neuropeptide precursor and confirm the highly conserved cyclic nature of the mature neuropeptide apUII. Electrophysiological analysis of the central effects of a synthetic apUII suggests it plays a role in satiety and/or aversive signaling in feeding behaviors. Finding the homologue of vertebrate UII in the numerically small CNS of an invertebrate animal model is important for gaining insights into the molecular mechanisms and pathways mediating the bioactivity of UII in the higher metazoan.

Endogenous urotensin II selectively modulates erectile function through eNOS

Background

Urotensin II (U-II) is a cyclic peptide originally isolated from the neurosecretory system of the teleost fish and subsequently found in other species, including man. U-II was identified as the natural ligand of a G-protein coupled receptor, namely UT receptor. U-II and UT receptor are expressed in a variety of peripheral organs and especially in cardiovascular tissue. Recent evidence indicates the involvement of U-II/UT pathway in penile function in human, but the molecular mechanism is still unclear. On these bases the aim of this study is to investigate the mechanism(s) of U-II-induced relaxation in human corpus cavernosum and its relationship with L-arginine/Nitric oxide (NO) pathway.

Methodology/Principal Findings

Human corpus cavernosum tissue was obtained following in male-to-female transsexuals undergoing surgical procedure for sex reassignment. Quantitative RT-PCR clearly demonstrated the U-II expression in human corpus cavernosum. U-II (0.1 nM–10 µM) challenge in human corpus cavernosum induced a significant increase in NO production as revealed by fluorometric analysis. NO generation was coupled to a marked increase in the ratio eNOS phosphorilated/eNOS as determined by western blot analysis. A functional study in human corpus cavernosum strips was performed to asses eNOS involvement in U-II-induced relaxation by using a pharmacological modulation. Pre-treatment with both wortmannin or geldanamycinin (inhibitors of eNOS phosphorylation and heath shock protein 90 recruitment, respectively) significantly reduced U-II-induced relaxation (0.1 nM–10 µM) in human corpus cavernosum strips. Finally, a co-immunoprecipitation study demonstrated that UT receptor and eNOS co-immunoprecipitate following U-II challenge of human corpus cavernosum tissue.

Conclusion/Significance

U-II is endogenously synthesized and locally released in human corpus cavernosum. U-II elicited penile erection through eNOS activation. Thus, U-II/UT pathway may represent a novel therapeutical target in erectile dysfunction.

Urotensin II and urocortin trigger the expression of myostatin, a negative regulator of cardiac growth, in cardiomyocytes

Urotensin II (UII) and urocortin (UCN) are potent contributors to the physiopathology of heart failure. Our study investigated the effects of UII and UCN on the expression of myostatin (Mstn) in primary culture of adult cardiomyocytes. Adult rat cardiomyocytes were stimulated for 48 h with UII and UCN. Cell size and protein content were determined. Mstn gene expression was determined by real time quantitative polymerase chain reaction. Treatment with UII and UCN stimulates hypertrophy of adult cardiomyocytes. This effect was associated with a twofold increase of Mstn gene expression. We have established for the first time that the two hypertrophic peptides UII and UCN stimulate the expression of Mstn.

Immunomodulatory role of urotensins in teleost Channa punctatus

The present study, for the first time in ectothermic vertebrates, reports the immunoregulatory role of urotensins I and II (UI and UII). Urotensins decreased the phagocytosis and nitrite production by splenic phagocytes. On superoxide production, UI had stimulatory while UII showed inhibitory effect. UI exerted its effect on phagocytes through corticotrophin-releasing factor (CRF) receptor as its non-specific antagonist astressin completely blocked the effect of UI on phagocytosis, nitrite release and superoxide production. Among the antagonists for specific CRF receptor 1 and 2, only CRF receptor 1 antagonist NBI 27914 abolished the effect of urotensin I. On the other hand, UII mediated its effect through urotensin receptor (UT receptor) since its antagonist urantide antagonized the effect of UII on phagocytosis, superoxide and nitrite release. These findings provide the direct evidence on physiological role of UI and UII through CRF receptor 1 and UT receptor, respectively in control of fish immune responses.

Urotensin-II as an angiogenic factor

Angiogenesis, the process through which new blood vessels arise from pre-existing ones, is regulated by numerous "classic" factors and other "nonclassic" regulators of angiogenesis. Among these latter urotensin-II is a cyclic 11-amino acid (human) or 15-amino acid (rodent) peptide, originally isolated from the fish urophysis, which exerts a potent systemic vasoconstrictor and hypertensive effect. This review article summarizes the literature data concerning the involvement of urotensin-II in angiogenesis.

Ontogeny of the corticotropin-releasing factor system in zebrafish

The corticotropin-releasing factor (CRF) system in fish functions to maintain homeostasis during stress in part by regulating cortisol production via the hypothalamus-pituitary-interrenal (HPI) axis. Towards understanding the role of the CRF system in vertebrate development, we describe the ontogeny of the CRF system, cortisol, and the stress response in the zebrafish, Danio rerio. Early embryonic expression of mRNA encoding CRF, urotensin I (UI), CRF-binding protein (CRF-BP), and two CRF receptors (CRF-R1 and CRF-R2) suggest a function in the early organization of the developing embryo. The expression patterns of CRF, UI, and CRF-BP in the larval brain are consistent with the adult distribution patterns for these genes and support HPI-axis independent functions. The relative amounts of CRF and UI mRNA in the heads and tails of developing and adult zebrafish suggest that CRF functions primarily in the brain while UI also plays an important role in the caudal neurosecretory system. The amount of cortisol in developing zebrafish is low and relatively constant through the first 6 days of development. The commencement of feeding after 4 dpf, however, significantly increases basal cortisol production. Finally, we show that zebrafish larvae are able to respond to an osmotic stressor as early as 3 dpf. Overall, results from this study establish the zebrafish as a model species for research on stress during ontogeny and offer new insights into an HPI-axis independent function for the CRF system during embryogenesis.

Urotensin II induces transactivation of the epidermal growth factor receptor via transient oxidation of SHP-2 in the rat renal tubular cell line NRK-52E

Urotensin-II (UII) is a potent vasoactive peptide that has been implicated in cardiac fibrosis and renal diseases. However, the role played by UII in renal tissues is largely unknown. In this study, we investigated the effects of human UII (hUII) on rat renal proximal tubular cells of the NRK-52E line and the role of Src homology 2-containing phosphotyrosine phosphatase (SHP-2) in the hUII-induced transactivation of the epidermal growth factor receptor (EGFR). Exposure to hUII at low concentrations significantly induced proliferation in NRK-52E cells; this effect was inhibited by treatment with an ERK1/2 inhibitor (PD98059). UII treatment increased the phosphorylation of EGFR and induced the generation of reactive oxygen species (ROS). Treatment of the ROS scavenger N-acetyl-cysteine (NAC) inhibited EGFR transactivation and ERK phosphorylation induced by hUII. SHP-2 was found to interact with EGFR and be transiently oxidized following the hUII treatment. In SHP-2 knockdown cells, UII-induced phosphorylation of EGFR was less influenced by NAC, and significantly suppressed by heparin binding (HB)-EGF neutralizing antibody. Our data suggest that the ROS-mediated oxidation of SHP-2 is essential for the hUII-induced mitogenic pathway in NRK-52E cells.

Expression and functional role of urotensin-II and its receptor in the adrenal cortex and medulla: novel insights for the pathophysiology of primary aldosteronism

CONTEXT

The involvement of urotensin II, a vasoactive peptide acting via the G protein-coupled urotensin II receptor, in arterial hypertension remains contentious.

OBJECTIVE

We investigated the expression of urotensin II and urotensin II receptor in adrenocortical and adrenomedullary tumors and the functional effects of urotensin II receptor activation.

DESIGN

The expression of urotensin II and urotensin II receptor was measured by real time RT-PCR in aldosterone-producing adenoma (n = 22) and pheochromocytoma (n = 10), using histologically normal adrenocortical (n = 6) and normal adrenomedullary (n = 5) tissue as control. Urotensin II peptide and urotensin II receptor protein were investigated with immunohistochemistry and immunoblotting. To identify urotensin II-related and urotensin II receptor-related pathways, a whole transcriptome analysis was used. The adrenocortical effects of urotensin II receptor activation were also assessed by urotensin II infusion with/without the urotensin II receptor antagonist palosuran in rats.

RESULTS

Urotensin II was more expressed in pheochromocytoma than in aldosterone-producing adenoma tissue; the opposite was seen for the urotensin II receptor expression. Urotensin II receptor activation in vivo in rats enhanced (by 182 +/- 9%; P < 0.007) the adrenocortical expression of immunoreactive aldosterone synthase.

CONCLUSIONS

Urotensin II is a putative mediator of the effects of the adrenal medulla and pheochromocytoma on the adrenocortical zona glomerulosa. This pathophysiological link might account for the reported causal relationship between pheochromocytoma and primary aldosteronism.

Urotensin II is an autocrine/paracrine growth factor for aortic adventitia of rat

Urotensin II (UII) is a potent vasoconstrictive peptide; however, its significance in vascular adventitia has not been clearly elucidated. In this study, rat aortic adventitia showed mRNA expression and immunoreactivity of UII and its receptor (UT). Moreover, radioligand-binding assay showed that maximum binding capacity (Bmax) of [(125)I]-UII was higher in adventitia than in media (28.60+/-1.94 vs. 20.21+/-1.11 fmol/mg, P<0.01), with no difference in binding affinity (dissociation constant [Kd] 4.27+/-0.49 vs. 4.60+/-0.40 nM, P>0.05). Furthermore, in cultured adventitial fibroblasts, UII stimulated DNA synthesis, collagen synthesis and secretion in a concentration-dependent manner. These effects were inhibited by the UII receptor antagonist urantide (10(-6) mol/l), Ca(2+) channel blocker nicardipine (10(-5) mol/l), protein kinase C inhibitor H7 (10(-6) mol/l), and mitogen-activated protein kinase inhibitor PD98059 (10(-6) mol/l) but not the phosphatidyl inositol-3 kinase inhibitor wortmannin (10(-7) mol/l). UII may act as an autocrine/paracrine factor through its receptor and the Ca(2+) channel, protein kinase C, and mitogen-activated protein kinase signal transduction pathways, in the pathogenesis of vascular remodeling by activating vascular adventitia.

Diabetes-induced upregulation of urotensin II and its receptor plays an important role in TGF-beta1-mediated renal fibrosis and dysfunction

Urotensin II (UII) was identified as the ligand for a novel G protein-coupled receptor, GPR14. UII was found not only to have a potent vasoconstrictive action but also to have profibrotic effects in the heart. The present study was to define whether UII and GPR14 also play important roles in diabetes-induced renal fibrosis and dysfunction. Diabetic rats were induced using streptozotocin, and the rat proximal tubular epithelial cells (NRK-52E) were used for the in vitro mechanism study. Results showed that expression of UII and GPR14 was significantly upregulated at both mRNA and protein levels in the diabetic kidneys compared with controls. The upregulated expressions of UII and GPR14 in the kidney were accompanied by significant increases in the renal profibrotic factor transforming growth factor (TGF)-beta1 expression, the renal extracellular matrix (fibronectin and collagen IV) accumulation, and the renal dysfunction (increases in urinal N-acetyl-beta-d-glucosaminidase content, 24-h urinary retinol-binding protein excretion rate, and decrease in creatinine clearance rate). Exposure of NRK-52E cells to 10(-8) mol/l UII for 48 h caused a significant increase of TGF-beta1, but not ANG II, production that was GPR14- and calcium-dependent, since GPR14 small-interfering RNA and calcium channel blocker nimodipine or calcium chelator EDTA all could abolish the induction of TGF- beta1 by UII. Furthermore, exposure of NRK-52E cells to TGF-beta1 or ANG II also increased UII and GPR14 mRNA expressions. These results suggested that diabetes-induced upregulation of UII and GPR14, most likely through autocrine and/or paracrine mechanisms, plays an important role in TGF-beta1-mediated renal fibrosis and dysfunction.

Urotensin II induces phenotypic differentiation, migration, and collagen synthesis of adventitial fibroblasts from rat aorta

BACKGROUND

Urotensin II is a new potent vasoconstrictor. Nevertheless, little is known about its effects on the activation of adventitial fibroblasts.

OBJECTIVE

To explore the effects of urotensin II on phenotypic differentiation, migration, and collagen I synthesis of rat aortic adventitial fibroblasts.

METHODS

Growth-arrested adventitial fibroblasts were incubated in serum-free medium with urotensin II and some inhibitors of signal transduction pathways. The alpha-smooth muscle-actin expression, collagen I synthesis and migration of adventitial fibroblasts induced by urotensin II were evaluated by western blot, enzyme-linked immunosorbant assay, and the transwell technique, respectively.

RESULTS

Urotensin II induced the [alpha]-smooth muscle-actin expression in a dose-dependent and time-dependent manner, with maximal effect at a concentration of 10(-8) mol/l at 24 h (79.9%); it also caused a dose-dependent increase in collagen I synthesis, with maximal effect at a concentration of 10(-7) mol/l (42.6%). The Ca2+ channel blocker nicardipine (10(-5) mol/l), protein kinase C inhibitor H7 (10(-5) mol/l), Rho protein kinase inhibitor Y-27632 (10(-5) mol/l), calcineurin inhibitor cyclosporine A (10(-5) mol/l), and mitogen-activated protein kinase inhibitor PD98059 (10(-5) mol/l) inhibited urotensin II-induced increases in [alpha]-smooth muscle-actin expression and collagen synthesis. Meanwhile, urotensin II stimulated the migration of adventitial fibroblasts dose dependently, with maximal effect at a concentration of 10(-8) mol/l, which was 5.7-fold greater than that of the control. This effect could also be inhibited by PD98059, H7, cyclosporine A, and Y-27632 but not nicardipine.

CONCLUSION

Urotensin II may stimulate adventitial fibroblasts phenotypic conversion, migration, and collagen I synthesis through the protein kinase C, mitogen-activated protein kinase, calcineurin, Rho kinase, and/or Ca2+ signal transduction pathways, contributing to the development of vascular remodeling through adventitial fibroblasts activation.

Urotensin II: lessons from comparative studies for general endocrinology

The importance of combining studies across vertebrates to provide insights into the functionality of hormone systems is considered, using recent advances in Urotensin II (UII) biology to illustrate this. The impact of genome analyses on understanding ligand and UII receptor (UT) structures is reviewed, noting their high conservation from fish to mammals. The early linkage of UII with fish osmoregulatory physiology drove our investigation of possible renal actions of UII in mammals. The kidney is a potential major source of UII in mammals and endogenous peptide appears to have tonal influence over renal excretion of water and electrolytes. Blockade of UII actions by administration of UT receptor antagonist, urantide, in anaesthetised rats, indicates that endogenous UII lowers renal filtration rates and excretion of water and ions. These effects are considered in relation to apparent association of UII with a number of human cardiovascular and renal disorders. Following up the sequencing of UT in mammals here we contrast the first fish UT sequences with those in other species. It is now evident that UT expression in fish osmoregulatory tissues, such as the gill and kidney, exhibits considerable plasticity in response to physiological challenge, providing an important component of the adaptive organismal responses. A number of areas of UII research, which will continue to benefit from moving questions between appropriate vertebrate groups, have been highlighted. These comparative approaches will yield improved understanding and further novel actions of this intriguing endocrine and paracrine system, so highly conserved across the vertebrate series.

Urotensin-II in the lung: a matter for vascular remodelling and pulmonary hypertension?

Urotensin-II (UII) is an evolutionary conserved peptide which has been initially discovered in the urophysis of the fish goby regulating body fluid composition and vascular tone. Mammalian UII has gained increasing interest since it has been considered as an even more potent vasoconstrictor than endothelin-1, although its efficiency is greatly variable throughout species and vascular beds. More recently, it has been shown that UII, which mediates its action via binding to the G-protein coupled urotensin-II receptor, is not only involved in the regulation of the vascular tone but can also stimulate a variety of signaling cascades in different cells and organs in the body including generation of reactive oxygen species and nitric oxide, activation of MAP kinases, and modulation of gene expression. Indeed, UII can stimulate proliferative processes, affect the extracellular matrix and may even add to a prothrombotic state. Such vascular remodelling processes are, in conjunction with enhanced vasoconstriction, involved in the pathogenesis of pulmonary hypertension, suggesting that UII may play a novel role in the pathogenesis of this disorder.

Urotensin II acutely increases myocardial length and distensibility: potential implications for diastolic function and ventricular remodeling

Urotensin II (U-II) is a cyclic peptide that may be involved in cardiovascular dysfunction. In the present study, the acute effects of U-II on diastolic properties of the myocardium were investigated. Increasing concentrations of U-II (10(-8) to 10(-6) M) were added to rabbit papillary muscles in the absence (n = 15) or presence of: (1) damaged endocardial endothelium (EE; n = 9); (2) U-II receptor antagonist, urantide (10(-5) M; n = 7); (3) nitric oxide (NO) synthase inhibitor, N(G)-Nitro-L-Arginine (10(-5) M; n = 9); (4) cyclooxygenase inhibitor, indomethacin (10(-5) M; n = 8); (5) NO synthase and cyclooxygenase inhibitors, N(G)-Nitro-L-Arginine (10(-5) M) and indomethacin (10(-5) M), respectively, (n = 8); or (6) protein kinase C (PKC) inhibitor, chelerythrine (10(-5) M; n = 9). Passive length-tension relations were constructed before and after a single concentration of U-II (10(-6) M; n = 3). U-II concentration dependently decreased inotropy and increased resting muscle length (RL). At 10(-6) M, active tension decreased 13.8 +/- 5.4%, and RL increased to 1.007 +/- 0.001 L/L (max). Correcting RL to its initial value resulted in an 18.1 +/- 3.0% decrease in resting tension, indicating decreased muscle stiffness, which was also suggested by the down and rightward shift of the passive length-tension relation. This effect remained unaffected by EE damage and PKC inhibition. In contrast, the presence of urantide and NO inhibition abolished the effects of U-II on myocardial stiffness, while cyclooxygenase inhibition significantly attenuated them. U-II decreases myocardial stiffness, an effect that is mediated by the urotensin-II receptor, NO, and prostaglandins. This represents a novel mechanism of acute neurohumoral modulation of diastolic function, suggesting that U-II is an important regulator of cardiac filling.

Role of urotensin II and its receptor in health and disease

Urotensin II (U-II) is currently the most potent vasoconstrictor identified. This action is brought about via activation of a G(q/11)-protein coupled receptor (UT receptor). U-II activation of the UT receptor increases inositol phosphate turnover and intracellular Ca(2+). In addition to producing vasoconstriction, dilation and ionotropic effects have also been described. There is considerable variation in the responsiveness of particular vascular beds from the same and different species, including humans. Receptors for U-II are located peripherally on vascular smooth muscle (contractile responses) and endothelial cells (dilatory responses via nitric oxide). In humans, plasma U-II is elevated in heart failure, renal failure, liver disease, and diabetes. Iontophoresis of U-II in healthy volunteers produces vasodilation (of the forearm) while in patients with heart failure or hypertension a constriction is observed. To date there is only one clinical study using a UT receptor antagonist (palosuran) in diabetic patients with macroalbuminuria. This antagonist reduced albumin excretion, probably by increasing renal blood flow. Studies in other disease conditions are eagerly awaited. In summary, the U-II / UT receptor system has clinical potential, and for the anesthesiologist, this novel peptide-receptor system may be of use in the intensive care unit.

Hemodynamic effects of chronic urotensin II administration in animals with and without aorto-caval fistula

Urotensin II (UTII) is a potent vasoactive peptide. Recent studies have demonstrated increased expression of both UTII and its receptor (UTR) expression in end-stage congestive heart failure (CHF), but it is unclear whether UTII and UTR are late stage markers of decompensation, or earlier adaptive responses. The purpose of this study was to measure the effects of chronic UTII administration in normal and volume overloaded animals. Chronic 4 weeks administration of UTII produced decreases in hemodynamic function in animals not subjected to volume overload while returning function to control levels in animals with overload. Expression levels of calcium regulatory proteins phospholamban (PLN), sarcoplasmic reticulum Ca(2+) ATPase (SERCA2), and Na(+)/Ca(2+) exchanger (NCX) were measured to determine if administration of UTII resulted in aberrant Ca(2+) handling. Changes in protein expression revealed that UTII influenced Ca(2+) handling proteins in normal animals although these changes are not seen in the volume overload.

Cardiovascular effects of native and non-native urotensin II and urotensin II-related peptide on rat and salmon hearts

Urotensin II (UII) was first discovered in the urophyses of goby fish and later identified in mammals, while urotensin II-related peptide (URP) was recently isolated from rat brain. We studied the effects of UII on isolated heart preparations of Chinook salmon and Sprague-Dawley rats. Native rat UII caused potent and sustained, dose-dependent dilation of the coronary arteries in the rat, whereas non-native UII (human and trout UII) showed attenuated vasodilation. Rat URP dilated rat coronary arteries, with 10-fold less potency compared with rUII. In salmon, native trout UII caused sustained dilation of the coronary arteries, while rat UII and URP caused significant constriction. Nomega-nitro-(l)-arginine methyl (l-NAME) and indomethacin significantly attenuated the URP and rat UII-induced vasodilation in the rat heart. We conclude that UII is a coronary vasodilator, an action that is species form specific. We also provide the first evidence for cardiac actions of URP, possibly via mechanisms common with UII.

Urotensin-II and cardiovascular diseases

Urotensin-II (U-II) is a vasoactive factor with pleiotropic effects. U-II exerts its activity by binding to a G-protein-coupled receptor termed UT. U-II and its receptor are highly expressed in the cardiovascular system. Increased U-II plasma levels have been reported in patients with cardiovascular disease of varying etiologies. We and others have shown that U-II and UT expression is elevated in both clinical and experimental heart failure and atherosclerosis. U-II induces cardiac fibrosis by increasing fibroblast collagen synthesis. In addition, U-II induces cardiomyocyte hypertrophy and increased vascular smooth muscle cell proliferation. We have shown that U-II antagonism using a selective U-II blocker, SB-611812 reduces neointimal thickening and increases lumen diameter in a rat restenosis model of carotid artery angioplasty. These findings suggest an important role for U-II in cardiovascular dysfunction and remodeling.

Human urotensin II as a link between hypertension and coronary artery disease

Hypertension is a well-known risk factor for atherosclerosis, but the molecular mechanisms that link elevated blood pressure to the progression of atherosclerosis remain unclear. Human urotensin II (U-II), the most potent endogenous vasoconstrictor peptide identified to date, and its receptor (UT receptor) are involved in the etiology of essential hypertension. In patients with essential hypertension, U-II infused into the forearm brachial artery has been shown to induce vasoconstriction. Recent studies have demonstrated elevated plasma U-II concentrations in patients with essential hypertension, diabetes mellitus, atherosclerosis, and coronary artery disease. U-II is expressed in endothelial cells, macrophages, macrophage-derived foam cells, and myointimal and medial vascular smooth muscle cells (VSMCs) of atherosclerotic human coronary arteries. UT receptors are present in VSMCs of human coronary arteries, the thoracic aorta and cardiac myocytes. Lymphocytes are the most active producers of U-II, whereas monocytes and macrophages are the major cell types expressing UT receptors, with relatively little receptor expression in foam cells, lymphocytes, and platelets. U-II accelerates foam cell formation by up-regulation of acyl-coenzyme A:cholesterol acyltransferase-1 in human monocyte-derived macrophages. In human endothelial cells, U-II promotes cell proliferation and up-regulates type 1 collagen expression. U-II also activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and plasminogen activator inhibitor-1 in human VSMCs, and stimulates VSMC proliferation with synergistic effects observed when combined with oxidized low-density lipoprotein, lysophosphatidylcholine, reactive oxygen species or serotonin. These findings suggest that U-II plays key roles in accelerating the development of atherosclerosis, thereby leading to coronary artery disease.

Enhancement of vascular smooth muscle cell migration by urotensin II

The effects of urotensin II (UII) on migration of human aortic smooth muscle cells (HASMCs) were investigated. UII (1-100 nM) significantly increased velocity of HASMC motility in a concentration-dependent manner. Stress-fiber formation and ERK (p44/p42) activity were also increased by UII. U0126 and PD 98059, MEK inhibitors, abolished the effects of UII on motility velocity and stress-fiber formation. These results suggest that UII enhances HASMC migration through activation of an ERK-dependent pathway.

Renal and vascular actions of urotensin II

The peptide hormone urotensin II (UII) has been highly conserved through the vertebrates from fish to humans. As it was shown to be the endogenous ligand for the mammalian orphan G-protein-coupled receptor GPR14, now renamed the UT receptor, interest in UII physiology has grown. Initial observations of a potent vasoconstrictor effect have been tempered with the subsequent revelation of an endothelium-dependent vasodilator action. These complex and contrasting vascular actions are both species- and vascular bed-specific. UII also plays a role in body fluid regulation in lower vertebrates, and it now appears that this extends to mammals. The kidney is a major source of both circulating and urinary UII. UII is found in both the proximal tubules and collecting ducts; the UT receptor is localized primarily to the renal medulla, with greatest expression in the inner medullary collecting ducts. Infusion in rats produced conflicting results: exogenous UII has been shown to increase glomerular filtration rate (GFR) and excretion of water and sodium, but also to reduce the same variables. Inhibition of UT receptor activity with the antagonist urantide resulted in an increase in GFR, diuresis, and natriuresis, suggesting that endogenous UII exerts a tonic influence on basal renal function. UII may also play a role in renal disease, being elevated in the circulation or urine of patients with renal failure and in experimental models of cardiovascular disease such as the spontaneously hypertensive rat. It remains to be established whether these changes represent an underlying primary cause or a compensatory response.

Exercise urotensin II dynamics in myocardial infarction survivors with and without hypertension

BACKGROUND

Hypertension is diagnosed in approximately 50% of patients with acute myocardial infarction. Urotensin II (U-II) - a potent vasoactive peptide shown to be elevated in hypertensive subjects, can contribute to negative myocardial remodelling and development of left ventricular failure. Data concerning U-II activity under exercise conditions and its influence on blood pressure in patients after myocardial infarction is scant. Therefore we sought to determine U-II dynamics during exercise in myocardial infarction survivors with and without hypertension.

METHODS

Forty patients with acute myocardial infarction treated with successful primary coronary angioplasty, after four weeks of uneventful and symptom-free period following initial hospitalization underwent treadmill exercise test. U-II plasma concentration was measured before and shortly after the exercise.

RESULTS

Hypertension was diagnosed in 17 (42.5%) patients. We found no significant differences between normotensive and hypertensive subjects except higher smoking rate and lower calcium channel blockers prescription in normotensive patients. Both systolic and diastolic blood pressure were comparable between study groups before exercise. After exercise we observed higher systolic blood pressure in hypertensive subjects (169.06 +/- 30.23 vs. 150.0 +/- 18.97 mm Hg; p < 0.05). U-II concentration showed no significant difference in pretest sampling (54.93 +/- 38.11 vs. 73.97 +/- 48.52 ng/ml; p = NS). After exercise we noted significantly higher peptide level in hypertensive patients (63.32 +/- 36.11 vs. 98.03 +/- 40.47 ng/ml; p = 0.01).

CONCLUSIONS

The present study is the first one to show differences in U-II concentration exercise dynamics in hypertensive and normotensive myocardial infarction survivors. It sheds additional light on hypertension pathophysiology in myocardial infarction patients, and thus identifies a novel, potentially relevant, target for future therapeutic interventions.

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

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

Urotensin II modulates rapid eye movement sleep through activation of brainstem cholinergic neurons

Urotensin II (UII) is a cyclic neuropeptide with strong vasoconstrictive activity in the peripheral vasculature. UII receptor mRNA is also expressed in the CNS, in particular in cholinergic neurons located in the mesopontine tegmental area, including the pedunculopontine tegmental (PPT) and lateral dorsal tegmental nuclei. This distribution suggests that the UII system is involved in functions regulated by acetylcholine, such as the sleep-wake cycle. Here, we tested the hypothesis that UII influences cholinergic PPT neuron activity and alters rapid eye movement (REM) sleep patterns in rats. Local administration of UII into the PPT nucleus increases REM sleep without inducing changes in the cortical blood flow. Intracerebroventricular injection of UII enhances both REM sleep and wakefulness and reduces slow-wave sleep 2. Intracerebroventricular, but not local, administration of UII increases cortical blood flow. Moreover, whole-cell recordings from rat-brain slices show that UII selectively excites cholinergic PPT neurons via an inward current and membrane depolarization that were accompanied by membrane conductance decreases. This effect does not depend on action potential generation or fast synaptic transmission because it persisted in the presence of TTX and antagonists of ionotropic glutamate, GABA, and glycine receptors. Collectively, these results suggest that UII plays a role in the regulation of REM sleep independently of its cerebrovascular actions by directly activating cholinergic brainstem neurons.

Urotensin II: Ancient Hormone with New Functions in Vertebrate Body Fluid Regulation

Urotensin II (UII), described in many fish species, is secreted by the caudal neurosecretory system, a unique fish neuroendocrine structure. We have examined UII secretion and its control in euryhaline fish, supporting a proposed role in osmoregulation. However, it is now apparent that UII is present in other vertebrates, including mammals. The 12-amino-acid peptide has been highly conserved and the key cyclic region is common from fish to humans. Our UII radioimmunoassay for flounder, directed to this cyclic region, has shown circulating UII levels in humans and rats comparable with those in fish. In mammals, UII cardiovascular effects vary between species, with vasoconstriction only evident in specific vascular beds. The kidney expresses UII receptors and responds to UII administration by a reduction in glomerular filtration rate, urine flow, and excretion of the major ions. Interestingly, plasma levels of UII are chronically elevated in rat models of hypertension. These observations imply an unforeseen role for this ancient fish hormone in the physiological and perhaps pathophysiological regulation of body fluids in higher vertebrates, including humans.

Time-Course Effects of Centrally Administered Native Urotensin-II on Motor and Cardioventilatory Activity in Trout

Although in most vertebrate species urotensin-II (UII) is synthesized in neurons of the central nervous system, little is known regarding the physiological actions of UII in the brain. We have investigated the effects of intracerebroventricular (ICV) administration of synthetic trout UII (1, 5, and 50 pmol) on total motor activity (ACT), ventilatory frequency (VF), ventilatory amplitude (VA), and heart rate (HR) in the unanesthetized trout. ICV injection of UII increased ACT in a dose-dependent manner, and the maximal effect was observed at a dose of 5 pmol. At doses of 1 and 5 pmol, UII did not affect VF, VA, or HR. At the highest dose tested (50 pmol), UII not only increased ACT, but also significantly activated VF, VA, and HR. In contrast, ICV injection of synthetic trout angiotensin-II (5 pmol) did not produce any effect on ACT, VF, or VA, but sharply increased HR. These data provide the first evidence that UII can act centrally to induce motor activity in a nonmammalian vertebrate species.

Vascular contractile effect of urotensin II in young and aged rats: influence of aging and contribution of endothelial nitric oxide

To elucidate whether aging influences the vascular contractile effect of urotensin II in rat thoracic aorta, and to evaluate the contribution of endothelial vasodilating substances in mediating the effect of urotensin II, the effect of urotensin II was examined in the vessels of young (2-3-month-old) and aged rat. Isolated rat aortic rings incubated in Krebs-Henseleit solution gassed with 95% O2/5% CO2 were stimulated with urotensin II, and the developed tension was measured. Urotensin II increased the developed tension, which was decreased by aging. In 2-3-months-old young aorta without endothelium, urotensin II (10(-10) to 10(-7)) elicited a concentration-dependent aortic contraction to the maximal response almost equivalent to high KCl-induced contraction (79.4+/-11.3% of KCl(max)). In the presence of endothelium, the urotensin II-induced vasoconstriction in young aorta was significantly attenuated to 33.3+/-4.6% of KCl(max). However, the contractile response was greater in the pretreatment with N(G)-nitro-L-arginine (L-NNA) (100 microM) (50.3+/-8.4% of KCl(max) in endothelial denuded aorta), suggesting the vasorelaxing role of endothelial nitric oxide. In 25-27-months-old aged rat aorta, the urotensin II-mediated contraction was remarkably decreased, both in the presence (6.3+/-2.0% of KCl(max)) and absence (11.7+/-3.0% of KCl(max)) of endothelium. A cyclooxygenase inhibitor, diclofenac (10 microM), did not have any effect on the urotensin II-induced contraction. These results suggest that urotensin II can induce vascular smooth muscle contraction in rat aorta, and there was an aging-related decline in the urotensin II-induced contraction. Endothelial production of nitric oxide in response to urotensin II but not cyclooxygenase metabolites such as prostacyclin may play a role in reducing the vascular constriction especially in young aorta.

From heart to mind

The discovery of novel biologically active peptides has led to an explosion in our understanding of the molecular mechanisms that underlie the regulation of sleep and wakefulness. Urotensin II (UII), a peptide originally isolated from fish and known for its strong cardiovascular effects in mammals, is another surprising candidate in the regulatory network of sleep. The UII receptor was found to be expressed by cholinergic neurons of laterodorsal and pedunculopontine tegmental nuclei, an area known to be of utmost importance for the on- and offset of rapid eye movement (REM) sleep. Recently, physiological data have provided further evidence that UII is indeed a modulator of REM sleep. The peptide directly excites cholinergic mesopontine neurons and increases the rate of REM sleep episodes. These new results and its emerging behavioral effects establish UII as a neurotransmitter/neuromodulator in mammals and should spark further interest into the neurobiological role of the peptide.

Urotensin II acts as a modulator of mesopontine cholinergic neurons

Urotensin II (UII) is a vasomodulatory peptide that was not predicted to elicit CNS activity. However, because we have recently shown that the urotensin II receptor (UII-R) is selectively expressed in rat mesopontine cholinergic (MPCh) neurons, we hypothesize that UII may have a central function. The present study demonstrates that the UII system is able to modulate MPCh neuron activity. Brain slice experiments demonstrate that UII excites MPCh neurons of the mouse laterodorsal tegmentum (LDTg) by activating a slow inward current. Furthermore, microinfusion of UII into the ventral tegmental area produces a sustained increase in dopamine efflux in the nucleus accumbens, as measured by in vivo chronoamperometry. In agreement with UII activation of MPCh neurons, intracerebroventricular injections of UII significantly modulate ambulatory movements in both rats and mice but do not significantly affect startle habituation or prepulse inhibition. The present study establishes that UII is a neuromodulator that may be exploited to target disorders involving MPCh dysfunction.

Urotensin II: its function in health and its role in disease

Urotensin II (U-II) is the most potent vasoconstrictor known, even more potent than endothelin-1. It was first isolated from the fish spinal cord and has been recognized as a hormone in the neurosecretory system of teleost fish for over 30 years. After the identification of U-II in humans and the orphan human G-protein-coupled receptor 14 as the urotensin II receptor, UT, many studies have shown that U-II may play an important role in cardiovascular regulation. Human urotensin II (hU-II) is an 11 amino acid cyclic peptide, generated by proteolytic cleavage from a precursor prohormone. It is expressed in the central nervous system as well as other tissues, such as kidney, spleen, small intestine, thymus, prostate, pituitary, and adrenal gland and circulates in human plasma. The plasma U-II level is elevated in renal failure, congestive heart failure, diabetes mellitus, systemic hypertension and portal hypertension caused by liver cirrhosis. The effect of U-II on the vascular system is variable, depending on species, vascular bed and calibre of the vessel. The net effect on vascular tone is a balance between endothelium-independent vasoconstriction and endothelium-dependent vasodilatation. U-II is also a neuropeptide and may play a role in tumour development. The development of UT receptor antagonists may provide a useful research tool as well as a novel treatment for cardiorenal diseases.

[A vasoactive peptide: urotensin II]

Urotensin II (U II ) is currently the most potent vasoconstrictor. G-protein coupled receptor 14 ( GPR-14) is its specific receptor. This review mainly discribes the structure and distribution of U II and GPR14, the activities that U II and GPR14 stimulates proliferation of vascular smooth muscle cells and vasoconstriction, as well as its mechanism.

Structure-activity relationship study on human urotensin II

The vasoactive cyclic undecapeptide urotensin-II (U-II) has been identified as an endogenous ligand for the G-protein coupled receptor now referred to as the UT receptor. The U-II/UT receptor system might be relevant for cardiovascular functions. A structure-activity study of human U-II investigating 31 peptides in the rat aorta bioassay is reported. Ala- and D-scan investigations indicated that the sequence Phe6-Trp7-Lys8-Tyr9 is essential for biological activity and that Lys8 and Tyr9 are particularly important. These two residues were substituted with a series of coded and non-coded amino acids. These studies demonstrated that the positive charge of the primary aliphatic amine at position 8 and its relative spatial orientation is crucial for both receptor occupation and activation, while the only chemical requirement at position 9 is the presence of an aromatic moiety. Moreover, this study led to the identification of UT receptor partial agonists (compounds 23 and 24) which can be used as chemical templates for further investigations aimed at the identification of selective antagonists.

Increased plasma levels of Urotensin-II in preeclampsia–eclampsia: a new mediator in pathogenesis?

OBJECTIVE

To assess the possible role of human Urotensin-II (hU-II), a vasoactive peptide, in the pathophysiology of preeclampsia-eclampsia prospectively.

STUDY DESIGN

Sixty subjects, 30 with a diagnosis of preeclampsia-eclampsia (group I) and 30 control subjects (group II), who had been admitted between January, 2002 and December, 2002, were taken into the study. Patients in group I had an increase in blood pressure after 28th week of gestation, without any history of hypertensive disease and/or preeclampsia or eclampsia. hU-II levels were assessed using a radioimmunoassay method.

RESULTS

No statistically significant difference in terms of age, gestational age, gravidity, abortion and parity was detected among groups (P > 0.05). Plasma hU-II levels in the preeclampsia-eclampsia and control groups were 10.11 +/- 5.94 pg/mL and 3.93 +/- 1.73 pg/mL, respectively. Difference between plasma hU-II levels of the two groups was found to be statistically significant (P < 0.00001). Also there was correlation between hU-II levels and mean arterial pressures in both groups (r = 0.73, P < 0.0001 and r = 0.72, P < 0.0001 for groups I and II, respectively).

CONCLUSION

Results of our study strongly suggest an important role for hU-II in the pathophysiology of preeclampsia-eclampsia. Further studies concerning placenta and cord blood samples will more clearly elucidate the role of Urotensin-II in the pathogenesis of preeclampsia-eclampsia, and its feto-maternal effects.

Urotensin II in the cardiovascular system

Urotensin II is a peptide present, together with its receptor, in the central nervous system and many peripheral tissues (including heart, blood vessels, kidneys and endocrine organs) of many species. The bioactive, mature form contains a cyclic heptapeptide perfectly preserved across species spanning 550 million years of evolution Its biological activity has been explored in cultured cells, in isolated vessels from several species, in the isolated perfused heart and in intact animals and man. Initial demonstration of potent vasoconstriction and cardiac depression by the human isoform in non-human primates has been followed by a series of reports indicating potent but highly variable and generally modest vascular responses dependent on species and vascular region. In man short term cardiovascular responses to administered urotensin II are small or absent. The place of urotensin II in the chronic trophic responses to cardiac and vascular injury and its possible roles as a neurotransmitter and/or regulator of renal and endocrine function remain largely unexplored.

Role of urotensin II in peripheral tissue as an autocrine/paracrine growth factor

Urotensin II (UII), originally isolated from goby urophysis, has been shown to be an endogenous ligand for an orphan G-protein-coupled receptor, GPR14. Recent development of PCR quantitative method revealed that UII and UT receptor (GPR14) were expressed in a broad range of tissues and organs, including cardiovascular and renal system, and assumed to function as an autocrine/paracrine factor. UII is a potent vasoconstrictor peptide, whose potency is greater than any other vasoconstrictors thus far known. However, its physiological roles have been found to extend far beyond the regulation of vascular tone. In this review, we focused on the mitogenic action of UII and discuss its underlying cellular mechanisms and potential physiological/pathophysiological role in various human diseases.

Physiological roles of urocortins, human homologues of fish urotensin I, and their receptors

Urocortin 1, a human homologue of fish urotensin I, together with its related-compounds (urocortins 2 and 3), comprises a distinct family of stress peptides. Urocortin 1 has a high affinity for both corticotropin-releasing factor (CRF) type 1 receptor (CRF1) and CRF type 2 receptor (CRF2), and urocortins 2 and 3 have a high affinity for CRF2, while CRF has a low affinity for CRF2 and a high affinity for CRF1. These differences of the binding affinity with receptors make the biological actions of these peptides. Besides the binding affinity with receptors, the limited overlap of the distribution of CRF and urocortins may also contribute to the differences of physiological roles of each peptide. Urocortins show 'stress-coping' responses such as anxiolysis and dearousal in the brain. In the periphery, recent studies show the potent effects of urocortins on the cardiovascular and immune systems. In this review article, we take a look over the series of peptides included in this family, especially in terms of the versatility of biological actions, along with the various characters of the receptors.