Identification of urotensin II as the endogenous ligand for the orphan G-protein-coupled receptor GPR14

Urotensin II-related peptides, Urp1 and Urp2, control zebrafish spine morphology

The spine provides structure and support to the body, yet how it develops its characteristic morphology as the organism grows is little understood. This is underscored by the commonality of conditions in which the spine curves abnormally such as scoliosis, kyphosis, and lordosis. Understanding the origin of these spinal curves has been challenging in part due to the lack of appropriate animal models. Recently, zebrafish have emerged as promising tools with which to understand the origin of spinal curves. Using zebrafish, we demonstrate that the urotensin II-related peptides (URPs), Urp1 and Urp2, are essential for maintaining spine morphology. Urp1 and Urp2 are 10-amino acid cyclic peptides expressed by neurons lining the central canal of the spinal cord. Upon combined genetic loss of Urp1 and Urp2, adolescent-onset planar curves manifested in the caudal region of the spine. Highly similar curves were caused by mutation of Uts2r3, an URP receptor. Quantitative comparisons revealed that urotensin-associated curves were distinct from other zebrafish spinal curve mutants in curve position and direction. Last, we found that the Reissner fiber, a proteinaceous thread that sits in the central canal and has been implicated in the control of spine morphology, breaks down prior to curve formation in mutants with perturbed cilia motility but was unaffected by loss of Uts2r3. This suggests a Reissner fiber-independent mechanism of curvature in urotensin-deficient mutants. Overall, our results show that Urp1 and Urp2 control zebrafish spine morphology and establish new animal models of spine deformity.

Inhibition of U-II/UT signaling ameliorates cystitis-associated bladder hyperactivity by targeting the RhoA/Rho-kinase pathway

Urotensin II (U-II) and its receptor (UT) are involved in the pathogenesis of various diseases; however, their association with the development of cystitis has not been elucidated. The present study was designed to investigate the functional role of U-II/UT signaling in cyclophosphamide (CYP)-induced cystitis. A total of 60 female rats were randomly divided into the control and CYP-treated groups. Intraperitoneal injection of CYP successfully induced cystitis in rats of the CYP-treated group. The protein and mRNA expression levels of U-II and UT were significantly enhanced in rat bladder tissues of the CYP-treated group. Furthermore, the results of the immunofluorescence staining analysis demonstrated that CYP treatment apparently increased the expression levels of UT in the urothelium layer, detrusor smooth muscle, and bladder interstitial Cajal-like cells. The selective antagonist of UT, SB657510 (10 μm), significantly suppressed the CYP-induced increase in the spontaneous contractions of muscle strips and ameliorated the bladder hyperactivity of CYP-treated rats. Moreover, CYP treatment significantly increased the protein expression levels of Ras homolog family member (Rho) A and Rho-associated protein kinase 2 in rat bladder tissues. Following pretreatment with the Rho-kinase inhibitor Y-27632 (10 μm), the inhibitory effects of SB657510 (10 μm) on the spontaneous contractions of muscle strips were eliminated. In conclusion, the results of the present study suggested that activation of U-II/UT signaling promoted the development of cystitis-associated-bladder hyperactivity by targeting the RhoA/Rho-kinase pathway, indicating that the U-II/UT signaling could serve as a novel target for the treatment of interstitial cystitis/bladder pain syndrome.

Urotensin II-related peptide (Urp) is expressed in motoneurons in zebrafish, but is dispensable for locomotion in larva

The urotensin 2 (uts2) gene family consists of four paralogs called uts2, uts2-related peptide (urp), urp1 and urp2. uts2 is known to exert a large array of biological effects, including osmoregulation, control of cardiovascular functions and regulation of endocrine activities. Lately, urp1 and urp2 have been shown to regulate axial straightening during embryogenesis. In contrast, much less is known about the roles of urp. The aim of the present study was to investigate the expression and the functions of urp by using the zebrafish as a model. For this purpose, we determined the expression pattern of the urp gene. We found that urp is expressed in motoneurons of the brainstem and the spinal cord, as in tetrapods. This was confirmed with a new Tg(urp:gfp) fluorescent reporter line. We also generated a urp knockout mutant by using CRISPR/Cas9-mediated genome editing and analysed its locomotor activity in larvae. urp mutant did not exhibit any apparent defect of spontaneous swimming when compared to wild-type. We also tested the idea that urp may represent an intermediary of urp1 and urp2 in their role on axial straightening. We found that the upward bending of the tail induced by the overexpression of urp2 in 24-hpf embryos was not altered in urp mutants. Our results indicate that urp does probably not act as a relay downstream of urp2. In conclusion, the present study showed that zebrafish urp gene is primarily expressed in motoneurons but is apparently dispensable for locomotor activity in the early larval stages.

Conserved role of the urotensin II receptor 4 signalling pathway to control body straightness in a tetrapod

Urp1 and Urp2 are two neuropeptides of the urotensin II family identified in teleost fish and mainly expressed in cerebrospinal fluid (CSF)-contacting neurons. It has been recently proposed that Urp1 and Urp2 are required for correct axis formation and maintenance. Their action is thought to be mediated by the receptor Uts2r3, which is specifically expressed in dorsal somites. In support of this view, it has been demonstrated that the loss of uts2r3 results in severe scoliosis in adult zebrafish. In the present study, we report for the first time the occurrence of urp2, but not of urp1, in two tetrapod species of the Xenopus genus. In X. laevis, we show that urp2 mRNA-containing cells are CSF-contacting neurons. Furthermore, we identified utr4, the X. laevis counterparts of zebrafish uts2r3, and we demonstrate that, as in zebrafish, it is expressed in the dorsal somatic musculature. Finally, we reveal that, in X. laevis, the disruption of utr4 results in an abnormal curvature of the antero-posterior axis of the tadpoles. Taken together, our results suggest that the role of the Utr4 signalling pathway in the control of body straightness is an ancestral feature of bony vertebrates and not just a peculiarity of ray-finned fishes.

Identification and signaling characterization of four urotensin II receptor subtypes in the western clawed frog, Xenopus tropicalis

Urotensin II (UII) is involved, via the UII receptor (UTR), in many physiological and pathological processes, including vasoconstriction, locomotion, osmoregulation, immune response, and metabolic syndrome. In silico studies have revealed the presence of four or five distinct UTR (UTR1-UTR5) gene sequences in nonmammalian vertebrates. However, the functionality of these receptor subtypes and their associations to signaling pathways are unclear. In this study, full-length cDNAs encoding four distinct UTR subtypes (UTR1, UTR3, UTR4, and UTR5) were isolated from the western clawed frog (Xenopus tropicalis). In functional analyses, homologous Xenopus UII stimulation of cells expressing UTR1 or UTR5 induced intracellular calcoum mobilization and phosphorylation of extracellular signal-regulated kinase 1/2. Cells expressing UTR3 or UTR4 did not show this response. Furthermore, UII induced the phosphorylation of cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) through the UII-UTR1/5 system. However, intracellular cAMP accumulation was not observed, suggesting that UII-induced CREB phosphorylation is caused by a signaling pathway different from that involving Gs protein. In contrast, the administration of UII to cells increased the phosphorylation of guanine nucleotide exchange factor-H1 (GEF-H1) and myosin light chain 2 (MLC2) in all UTR subtypes. These results define four distinct UTR functional subtypes and are consistent with the molecular evolution of UTR subtypes in vertebrates. Further understanding of signaling properties associated with UTR subtypes may help in clarifying the functional roles associated with UII-UTR interactions in nonmammalian vertebrates.

Association between Plasma Urotensin II and Risk of Hypertension: Findings from a Prospective Study

Up to date, human urotensin II (UII) is the most potent vasoconstrictor in mammalian animals. To explore whether UII played an important role in the development of hypertension, we conducted a prospective study in Changshu city, China. The baseline investigation was carried out in 2007, and the first follow-up investigation was conducted in 2013. From the participants, we randomly obtained 2000 normotensive subjects aged 40 years and older without any severe disease at baseline and examined plasma UII and endothelin-1 (ET-1) with their blood samples at baseline. Logistic models were used to analyze the association between baseline UII, baseline ET-1, and newly occurring hypertension. In 1,819 subjects with complete data, 723 subjects developed into hypertensive in about five years. After adjusting some potential confounders, the odds ratio (95% confidence interval) for risk of hypertension comparing the highest with the lowest quartile of baseline UII was 0.888 (0.689–1.144). The role of UII in the development of hypertension was not found in the current study; therefore, further research studies should be conducted to explore the relationship between UII and hypertension.

Urotensin II, urotensin-related peptide, and their receptor in aortic valve stenosis

OBJECTIVES

Aortic valve stenosis (AVS) is the most common cause of surgical valve replacement worldwide. The vasoactive peptide urotensin II (UII) is upregulated in atherosclerosis and several other cardiovascular diseases; however, its role in the pathogenesis of AVS remains to be determined. Here, we investigated the expression of UII, urotensin-related peptide (URP), and the urotensin receptor (UT) and the role this system plays in AVS.

METHODS

Immunohistochemistry and reverse-transcriptase polymerase chain reaction were used to examine the cellular localization and mRNA expression, of UII, URP, and UT in calcified and noncalcified aortic valves. Human aortic valve interstitial cells were isolated from normal valves and treated with UII or URP, and changes in cell proliferation, cholesterol efflux, calcium deposition, and β-catenin translocation were assessed.

RESULTS

The mRNA expression of UII, URP, and UT was significantly greater in patients with AVS. There was abundant presence of UII, URP, and UT immunostaining in diseased compared with nondiseased valves and correlated significantly with presence of calcification (P < .0001) and fibrosis (P < .0001). Treating human aortic valve interstitial cells with UII or URP significantly increased cell proliferation (P < .0001) and decreased cholesterol efflux (P = .0011 and P = .0002, respectively). UII also significantly reduced ABCA1 protein expression (P = .0457) and increased β-catenin nuclear translocation (P < .0001) and mineral deposition (P < .0001).

CONCLUSIONS

Together, these data suggest that the urotensin system plays a role in the pathogenesis of AVS and warrants further investigation.

Urotensin II receptor expression in patients with ulcerative colitis: a pilot study

BACKGROUND

Urotensin II (U-II) is a vasoactive peptide that interacts with a specific receptor named UTR. Recently, our group has demonstrated increased UTR expression in both human colon adenocarcinoma cell lines and adenomatous polyps, as well as in colon carcinoma samples if compared to healthy colon samples of the same patients. We also showed that an UTR agonist induced an increase in colon adenocarcinoma cell growth in vitro, whereas the UTR block with a specific antagonist caused an inhibition of their growth and an inhibition of about 50% of both motility and cell invasion. Ulcerative colitis (UC) is an inflammatory bowel disease (IBD) associated with an increased baseline risk for colon cancer compared with the general population, and this risk is mostly attributed to chronic inflammation and immune dysregulation. This risk increases along with the duration of the disease, as demonstrated by many studies. There are no UTR expression data related to UC, and we therefore evaluated UTR expression in ill colon biopsies and in healthy colon ones of patients with UC and colon biopsies of healthy patients.

METHODS

We enrolled, prior to informed consent, 11 patients (5 males and 6 females, age range 29-75 years, median age 52 years) with first UC diagnosis compared to 11 healthy controls (6 males and 5 females, age range 30-78 years, median age 55 years). We have therefore sampled inflammatory and healthy tissue in UC patients. We have also taken colic tissue samples in healthy subjects. Evaluation of receptor expression was performed by reverse transcription-polymerase chain reaction (RT-PCR), Western Blot analysis. The ANOVA Test (P<0.05) was used for statistical analysis.

RESULTS

We found: 1) increased expression of UTR in 11/11 UC patients with ill mucosa biopsies compared to healthy controls in RT-PCR and in Western Blot analysis; 2) increased UTR expression in 11/11 UC patients with ill colon biopsies compared to the results obtained from healthy colon biopsies of the same patients both in RT-PCR and in Western Blot analysis; 3) increased UTR expression in 9/11 UC patients healthy colon biopsy specimens compared to healthy controls.

CONCLUSIONS

UTR could be considered as an inflammatory UC disease marker because its expression is greater in the mucosa of ill colon than in the healthy colon of the same patients and compared to healthy controls.

Urotensin II Induces Mice Skeletal Muscle Atrophy Associated with Enhanced Autophagy and Inhibited Irisin Precursor (Fibronectin Type III Domain Containing 5) Expression in Chronic Renal Failure

BACKGROUND/AIMS

Skeletal muscle atrophy is one of the main manifestations of protein energy wasting. We hypothesized that urotensin II (UII) can lead to skeletal muscle atrophy through upregulating autophagy and affecting Irisin precursor fibronectin type III domain containing 5 (FNDC5) expressions.

METHODS

Three animal models (the sham operation, wild-type C57BL/6 mice with 5/6 nephrectomy, UII receptor (UT) gene knockout (UTKO) mice with 5/6 nephrectomy) were designed. Skeletal muscle weight, cross-sectional area (CSA) along with UII, FNDC5, LC3, and p62 expression were investigated. C2C12 cells were differentiated for up to 4 days into myotubes. These cells were then exposed to different UII concentrations (10-5 to 10-7 M) for 6-12 h and analyzed for the expressions of autophagic markers. These cells were also exposed to the same predetermined UII concentrations for 48-72 h and analyzed for the FNDC5 expression. Myotube diameter was measured.

RESULTS

Upregulation of UII expression in skeletal muscle tissue was accompanied by reduced muscle weight and skeletal muscle CSA in the 2 posterior limbs, upregulated autophagy markers expression, and downregulated FNDC5 expression in 5/6 nephrectomy mice. The decrease of skeletal muscle weight, skeletal muscle CSA, downregulation of FNDC5 expression, and the upregulation of autophagy markers were inhibited in UTKO with 5/6 nephrectomy mice. Our in vitrostudy showed that UII could directly decrease myotube diameter, induce autophagy markers upregulation, and inhibit expression of FNDC5. When UII receptor gene was interfered by UT-specific siRNA, UII induced autophagy markers upregulation and FNDC5 downregulation were inhibited.

CONCLUSION

We are the first to verify UII induces mice skeletal muscle atrophy associated with enhanced skeletal muscle autophagy and inhibited FNDC5 expression in chronic renal failure.

Urotensin-II gene rs228648 polymorphism associated with the risk of diabetes mellitus

Background: Urotensin-II (UII) rs228648 polymorphism has been reported to be associated with the risk of diabetes mellitus (DM) with inconsistent results. The present study sought to reassess the relationship between this polymorphism and susceptibility to DM by meta-analysis.

Methods: Relevant eligible studies and whole genome association study (GWAS) data electronically searched were pooled to evaluate the strength of the association with odds ratios (ORs) and 95% confidence intervals (CIs).

Results: Seven case–control studies involving 894 cases and 1186 controls were finally included in the meta-analysis. Overall analyses indicated that UII gene rs228648 variant was significantly associated with reduced risk of DM (allele, A vs. G: OR = 0.68, 95%CI = 0.56–0.82; dominant, AA+GA vs. GG: OR = 0.70, 95%CI = 0.53–0.91; homozygote, AA vs. GG: OR = 0.41, 95%CI = 0.28–0.61; recessive, AA vs. GA+GG: OR = 0.36, 95%CI = 0.19–0.71). In subgroup analyses based on ethnicity, the results showed a significant association of rs228648 polymorphism with decreased risk of DM in Chinese population under all five genetic models as well as in non-Chinese population under heterozygote and recessive models. Stratified analyses by specific type of DM also presented a significant association for common diabetes mellitus (CDM) under allele and homozygote as well as gestational diabetes mellitus (GDM) under all genetic models except for homozygote model. However, the synthetic analysis with GWAS data suggested an increased risk of DM with rs228648 effect allele in European population (OR = 1.01, 95%CI = 1.00–1.02).

Conclusion: The present meta-analysis preliminarily suggested a potentially opposite role of rs228648 polymorphism associated with DM risk in the Chinese and European population. Further studies are in great request to verify the results.

Natural and synthetic peptides in the cardiovascular diseases: An update on diagnostic and therapeutic potentials

Several peptides play an important role in physiological and pathological conditions into the cardiovascular system. In addition to well-known vasoactive agents such as angiotensin II, endothelin, serotonin or natriuretic peptides, the vasoconstrictor Urotensin-II (Uro-II) and the vasodilators Urocortins (UCNs) and Adrenomedullin (AM) have been implicated in the control of vascular tone and blood pressure as well as in cardiovascular disease states including congestive heart failure, atherosclerosis, coronary artery disease, and pulmonary and systemic hypertension. Therefore these peptides, together with their receptors, become important therapeutic targets in cardiovascular diseases (CVDs). Circulating levels of these agents in the blood are markedly modified in patients with specific CVDs compared with those in healthy patients, becoming also potential biomarkers for these pathologies. This review will provide an overview of current knowledge about the physiological roles of Uro-II, UCN and AM in the cardiovascular system and their implications in cardiovascular diseases. It will further focus on the structural modifications carried out on original peptide sequences in the search of analogues with improved physiochemical properties as well as in the delivery methods. Finally, we have overviewed the possible application of these peptides and/or their precursors as biomarkers of CVDs.

Discovery of New Allosteric Modulators of the Urotensinergic System through Substitution of the Urotensin II-Related Peptide (URP) Phenylalanine Residue

Urotensin II (UII) and urotensin II-related peptide (URP) are functionally selective, suggesting that these two hormones might play distinct physiological role through different interactions with their cognate receptor UT. Hypothesizing that the Phe³ residue of URP, which is also present in UII, is a key-element of its specific UT activation, we evaluated the impact of its replacement by non-natural amino acids in URP. Each compound was evaluated for its ability to bind UT, induce rat aortic ring contraction, and activate G_q, G₁₂, and β-arrestin 1 signaling pathways. Such modifications impaired contractile efficacy, reflected by a reduced aptitude to activate G₁₂ in URP but not in the truncated but equipotent UII_4-11. Moreover, we have identified two structurally different UT modulators: [d-Phe(pI)³]URP and [Bip³]URP, which exert a probe-dependent action against UII and URP. These compounds should help us understand the specific roles of these hormones as well as guide further therapeutic development.

Urotensin II inhibitor eases neuropathic pain by suppressing the JNK/NF-κB pathway

Urotensin II (U-II), a cyclic peptide originally isolated from the caudal neurosecretory system of fishes, can produce proinflammatory effects through its specific G protein-coupled receptor, GPR14. Neuropathic pain, a devastating disease, is related to excessive inflammation in the spinal dorsal horn. However, the relationship between U-II and neuropathic pain has not been reported. This study was designed to investigate the effect of U-II antagonist on neuropathic pain and to understand the associated mechanisms. We reported that U-II and its receptor GPR14 were persistently upregulated and activated in the dorsal horn of L4-6 spinal cord segments after chronic constriction injury (CCI) in rats. Intrathecal injection of SB657510, a specific antagonist against U-II, reversed CCI-induced thermal hyperalgesia and mechanical allodynia. Furthermore, we found that SB657510 reduced the expression of phosphorylated c-Jun N-terminal kinase (p-JNK) and nuclear factor-κB (NF-κB) p65 as well as subsequent secretion of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α). It was also showed that both the JNK inhibitor SP600125 and the NF-κB inhibitor PDTC significantly attenuated thermal hyperalgesia and mechanical allodynia in CCI rats. Our present research showed that U-II receptor antagonist alleviated neuropathic pain possibly through the suppression of the JNK/NF-κB pathway in CCI rats, which will contribute to the better understanding of function of U-II and pathogenesis of neuropathic pain.

The G Protein-Coupled Receptor UT of the Neuropeptide Urotensin II Displays Structural and Functional Chemokine Features

The urotensinergic system was previously considered as being linked to numerous physiopathological states, including atherosclerosis, heart failure, hypertension, pre-eclampsia, diabetes, renal disease, as well as brain vascular lesions. Thus, it turns out that the actions of the urotensin II (UII)/G protein-coupled receptor UT system in animal models are currently not predictive enough in regard to their effects in human clinical trials and that UII analogs, established to target UT, were not as beneficial as expected in pathological situations. Thus, many questions remain regarding the overall signaling profiles of UT leading to complex involvement in cardiovascular and inflammatory responses as well as cancer. We address the potential UT chemotactic structural and functional definition under an evolutionary angle, by the existence of a common conserved structural feature among chemokine receptorsopioïdergic receptors and UT, i.e., a specific proline position in the transmembrane domain-2 TM2 (P2.58) likely responsible for a kink helical structure that would play a key role in chemokine functions. Even if the last decade was devoted to the elucidation of the cardiovascular control by the urotensinergic system, we also attempt here to discuss the role of UII on inflammation and migration, likely providing a peptide chemokine status for UII. Indeed, our recent work established that activation of UT by a gradient concentration of UII recruits Gαi/o and Gα13 couplings in a spatiotemporal way, controlling key signaling events leading to chemotaxis. We think that this new vision of the urotensinergic system should help considering UT as a chemotactic therapeutic target in pathological situations involving cell chemoattraction.

Blocking of urotensin receptors as new target for treatment of carrageenan induced inflammation in rats

This study investigated possible role of U-II and its receptor expression in inflammation by using UTR agonist and antagonist in carrageenan induced acute inflammation. Rats were divided into 5 groups as (1) Healthy control, (2) Carrageenan control, (3) Carrageenan +Indomethacin 20mg/kg, orally, (4) Carrageenan +AC7954 (U-II receptor agonist, intraperitoneally) 30mg/kg and (5) Carrageenan +SB657510 (UTR antagonist, intraperitoneally) 30mg/kg. 1h after drug administration, carrageenan was injected. At the 3rd hour after carrageenan injection, agonist produced no effect while antagonist 63% anti-inflammatory effect respectively. UTR and UT-II expression increased in carrageenan induced paw tissue. Antagonist administration prevented the decrease in an antioxidant system and also capable to decrease TNF-α and IL-6 mRNA expressions. This study showed the role of urotensin II receptors in the physiopathogenesis of acute inflammatory response that underlying many diseases accompanied by inflammation.

International Union of Basic and Clinical Pharmacology. XCII. Urotensin II, urotensin II-related peptide, and their receptor: from structure to function

Urotensin II (UII) is a cyclic neuropeptide that was first isolated from the urophysis of teleost fish on the basis of its ability to contract the hindgut. Subsequently, UII was characterized in tetrapods including humans. Phylogenetic studies and synteny analysis indicate that UII and its paralogous peptide urotensin II-related peptide (URP) belong to the somatostatin/cortistatin superfamily. In mammals, the UII and URP genes are primarily expressed in cholinergic neurons of the brainstem and spinal cord. UII and URP mRNAs are also present in various organs notably in the cardiovascular, renal, and endocrine systems. UII and URP activate a common G protein-coupled receptor, called UT, that exhibits relatively high sequence identity with somatostatin, opioid, and galanin receptors. The UT gene is widely expressed in the central nervous system (CNS) and in peripheral tissues including the retina, heart, vascular bed, lung, kidney, adrenal medulla, and skeletal muscle. Structure-activity relationship studies and NMR conformational analysis have led to the rational design of a number of peptidic and nonpeptidic UT agonists and antagonists. Consistent with the wide distribution of UT, UII has now been shown to exert a large array of biologic activities, in particular in the CNS, the cardiovascular system, and the kidney. Here, we review the current knowledge concerning the pleiotropic actions of UII and discusses the possible use of antagonists for future therapeutic applications.

Comparative distribution and in vitro activities of the urotensin II-related peptides URP1 and URP2 in zebrafish: evidence for their colocalization in spinal cerebrospinal fluid-contacting neurons

Urotensin II (UII) is an evolutionarily conserved neuropeptide initially isolated from teleost fish on the basis of its smooth muscle-contracting activity. Subsequent studies have demonstrated the occurrence of several UII-related peptides (URPs), such that the UII family is now known to include four paralogue genes called UII, URP, URP1 and URP2. These genes probably arose through the two rounds of whole genome duplication that occurred during early vertebrate evolution. URP has been identified both in tetrapods and teleosts. In contrast, URP1 and URP2 have only been observed in ray-finned and cartilaginous fishes, suggesting that both genes were lost in the tetrapod lineage. In the present study, the distribution of urp1 mRNA compared to urp2 mRNA is reported in the central nervous system of zebrafish. In the spinal cord, urp1 and urp2 mRNAs were mainly colocalized in the same cells. These cells were also shown to be GABAergic and express the gene encoding the polycystic kidney disease 2-like 1 (pkd2l1) channel, indicating that they likely correspond to cerebrospinal fluid-contacting neurons. In the hindbrain, urp1-expressing cells were found in the intermediate reticular formation and the glossopharyngeal-vagal motor nerve nuclei. We also showed that synthetic URP1 and URP2 were able to induce intracellular calcium mobilization in human UII receptor (hUT)-transfected CHO cells with similar potencies (pEC50=7.99 and 7.52, respectively) albeit at slightly lower potencies than human UII and mammalian URP (pEC50=9.44 and 8.61, respectively). The functional redundancy of URP1 and URP2 as well as the colocalization of their mRNAs in the spinal cord suggest the robustness of this peptidic system and its physiological importance in zebrafish.

The relationship between urotensin II and its receptor and the clinicopathological parameters of breast cancer

BACKGROUND

Urotensin II is a vasoactive polypeptide. It is known that some vasoactive polypeptides are produced and secreted by tumor cells, and act as a paracrine growth stimulant. The aim of this study was to examine the relationship between urotensin II and its receptor's messenger RNA expression in breast cancer.

MATERIAL/METHODS

Fifty-nine women with breast cancer were included in this study. The median age was 48 years. The relationships between urotensin II and urotensin II receptor mRNA expressions, which were derived from fresh breast cancer tissues and adjacent normal breast tissues, and clinical and pathological parameters, were assessed.

RESULTS

We found expressions of urotensin II mRNA and its receptor in 55 of 59 breast cancer tissues and in 55 of 59 normal breast tissues. We found a positive significant correlation between urotensin II and its receptor (p=0.001, r=0.632), and found a negative, but insignificant, correlation between urotensin II and age (p=0.038, r=-0.281). Urotensin II levels were higher in the premenopausal group compared to the postmenopausal group (p<0.05). The mean urotensin II receptor expression was higher in the premenopausal group (p<0.05) compared to the postmenopausal group, and its expression was also higher in the group without extra-nodal invasion compared to that of the group with extra-nodal invasion (p=0.001). Urotensin II levels were higher in the group without lymphatic invasion compared to the group with lymphatic invasion (p=0.048).

CONCLUSIONS

This study is the first in the English medical literature to determine the urotensin II and its receptor mRNA expressions in breast cancer tissues. Consequently, urotensin II seems be associated with menopausal status, and extra-nodal and lymphatic invasion.

Molecular evolution of GPCRs: Somatostatin/urotensin II receptors

Somatostatin (SS) and urotensin II (UII) are members of two families of structurally related neuropeptides present in all vertebrates. They exert a large array of biological activities that are mediated by two families of G-protein-coupled receptors called SSTR and UTS2R respectively. It is proposed that the two families of peptides as well as those of their receptors probably derive from a single ancestral ligand-receptor pair. This pair had already been duplicated before the emergence of vertebrates to generate one SS peptide with two receptors and one UII peptide with one receptor. Thereafter, each family expanded in the three whole-genome duplications (1R, 2R, and 3R) that occurred during the evolution of vertebrates, whereupon some local duplications and gene losses occurred. Following the 2R event, the vertebrate ancestor is deduced to have possessed three SS (SS1, SS2, and SS5) and six SSTR (SSTR1-6) genes, on the one hand, and four UII (UII, URP, URP1, and URP2) and five UTS2R (UTS2R1-5) genes, on the other hand. In the teleost lineage, all these have been preserved with the exception of SSTR4. Moreover, several additional genes have been gained through the 3R event, such as SS4 and a second copy of the UII, SSTR2, SSTR3, and SSTR5 genes, and through local duplications, such as SS3. In mammals, all the genes of the SSTR family have been preserved, with the exception of SSTR6. In contrast, for the other families, extensive gene losses occurred, as only the SS1, SS2, UII, and URP genes and one UTS2R gene are still present.

Therapeutic implications of peptide interactions with G-protein-coupled receptors in diabetic vasculopathy

The dramatic worldwide increase in the prevalence of diabetes has generated an attempt by the scientific community to identify strategies for its treatment and prevention. Vascular dysfunction is a hallmark of diabetes and frequently leads to the development of atherosclerosis, coronary disease-derived myocardial infarction, stroke, peripheral arterial disease and diabetic 'triopathy' (retinopathy, nephropathy and neuropathy). These vascular complications, developing in an increasingly younger cohort of patients with diabetes, contribute to morbidity and mortality. Despite the development of new anti-diabetic or anti-hyperglycaemic drugs, vascular complications remain to be a problem. This warrants a need for new therapeutic strategies to tackle diabetic vasculopathy. There is a growing body of evidence showing that peptide-binding G-protein-coupled receptors (peptide-binding GPCRs) play an important role in the pathophysiology of vascular dysfunction during diabetes. Thus, in this review, we discuss some of the peptide-binding GPCRs involved in the regulation of vascular function that have potential to be a therapeutic target in the treatment of diabetic vasculopathy.

RGS2 regulates urotensin II-induced intracellular Ca2+ elevation and contraction in glomerular mesangial cells

Urotensin II (UII), a vasoactive peptide modulates renal hemodynamics. However, the physiological functions of UII in glomerular cells are unclear. In particular, whether UII alters mesangial tone remains largely unknown. The present study investigates the physiological effects of UII on glomerular mesangial cells (GMCs). This study also tested the hypothesis that the regulator of G-protein signaling (RGS) controls UII receptor (UTR) activity in GMCs. RT-PCR, Western immunoblotting, and immunofluorescence revealed UTR expression in cultured murine GMCs. Mouse UII (mUII) stimulated Ca(2+) release from intracellular stores and activated store-operated Ca(2+) entry (SOCE) in the cells. mUII also caused a reduction in planar GMC surface area. mUII-induced [Ca(2+)]i elevation and contraction were attenuated by SB 657510, a UTR antagonist, araguspongin B, an inositol 1,4,5-trisphosphate receptor antagonist, thapsigargin, a sarco/endoplasmic reticulum Ca(2+)-ATPase inhibitor, and La(3+), a store-operated Ca(2+) channel blocker, but not nimodipine, an L-type Ca(2+) channel blocker. In situ proximity ligation assay indicated molecular proximity between endogenous RGS2 and UTR in the cells. Treatment of GMCs with mUII elevated plasma membrane expression of RGS2 by ∼2-fold. mUII also increased the interaction between RGS2 and UTR in the cells. siRNA-mediated knockdown of RGS2 in murine GMCs increased mUII-induced [Ca(2+)]i elevation and contraction by ∼35 and 31%, respectively. These findings indicate that mUII-induced SOCE results in murine GMC contraction. These data also suggest that UTR activation stimulates RGS2 recruitment to GMC plasma membrane as a negative feedback mechanism to regulate UTR signaling.

Effect of urotensin II on apolipoprotein B100 and apolipoprotein A-I expression in HepG2 cell line

BACKGROUND

Increased apolipoprotein B100 (apo B) and decreased apolipoprotein A-I (apo A-I) production are important risk factors in atherosclerosis. Urotensin II (UII), as the most potent vasoconstrictor in human, is related with hypertension and probably atherosclerosis. Because of the relationship between the hypertension and lipoprotein metabolism in atherosclerosis, the aim of this study was to test the effect of urotensin II on apo B and apo A-I expression in hepatic (HepG2) cell line.

MATERIALS AND METHODS

HepG2 cells were treated with 10, 50, 100, and 200 nmol/L of urotensin II (n = 6). Relative apo B and apo A-I messenger RNA (mRNA) levels in conditioned media, normalized to glyceraldehyde-3-phosphate dehydrogenase, were measured with quantitative real-time polymerase chain reaction method. In addition, apo B and apo A-I levels were also estimated and compared with the controls using the western blotting method. Data were analyzed statistically by ANOVA and non-parametric tests.

RESULTS

The apo B mRNA levels were not increased significantly following the treatment with UII. However, apo B protein levels were increased significantly after the treatment with urotensin II, especially at 100 and 200 nmol/L. The apo A-I mRNA and protein levels in conditioned media also were not significantly changed. However, there was a significant decrease in apo A-I mRNA and protein levels at 200 nM UII.

CONCLUSIONS

UII might increase apo B at protein level probably through participating factors in its synthesis and/ or stability/degradation. In addition, UII may have decreasing effect at more than 200 nM concentrations on apo A-I.

UII and UT in grouper: cloning and effects on the transcription of hormones related to growth control

Urotensin II (UII) is a cyclic peptide that was originally extracted from the caudal neurosecretory system (CNSS) of fish. UII is well known to exhibit cardiovascular, ventilatory, and motor effects in vertebrates. Studies have reported that UII exerts mitogenic effects and can act as an autocrine/paracrine growth factor in mammals. However, similar information in fish is limited. In this study, the full-length cDNAs of UII and its receptor (UT) were cloned and characterized in the orange-spotted grouper. UII and UT were expressed ubiquitously in various tissues in grouper, and particularly high levels were observed in the CNSS, CNS, and ovary. A functional study showed that UT was coupled with intracellular Ca2+ mobilization in HEK293 cells. Studies carried out using i.p. injections of UII in grouper showed the following: i) in the hypothalamus, UII can significantly stimulate the mRNA expression of ghrh and simultaneously inhibit the mRNA expression of somatostatin 1 (ss1) and ss2 3 h after injection; ii) in the pituitary, UII also significantly induced the mRNA expression of gh 6 and 12  h after injection; and iii) in the liver, the mRNA expression levels of ghr1/ghr2 and igf1/igf2 were markedly increased 12 and 3  h after the i.p. injection of UII respectively. These results collectively indicate that the UII/UT system may play a role in the promotion of the growth of the orange-spotted grouper.

The Concise Guide to PHARMACOLOGY 2013/14: G protein-coupled receptors

The Concise Guide to PHARMACOLOGY 2013/14 provides concise overviews of the key properties of over 2000 human drug targets with their pharmacology, plus links to an open access knowledgebase of drug targets and their ligands (www.guidetopharmacology.org), which provides more detailed views of target and ligand properties. The full contents can be found at http://onlinelibrary.wiley.com/doi/10.1111/bph.12444/full. G protein-coupled receptors are one of the seven major pharmacological targets into which the Guide is divided, with the others being G protein-coupled receptors, ligand-gated ion channels, ion channels, catalytic receptors, nuclear hormone receptors, transporters and enzymes. These are presented with nomenclature guidance and summary information on the best available pharmacological tools, alongside key references and suggestions for further reading. A new landscape format has easy to use tables comparing related targets. It is a condensed version of material contemporary to late 2013, which is presented in greater detail and constantly updated on the website www.guidetopharmacology.org, superseding data presented in previous Guides to Receptors and Channels. It is produced in conjunction with NC-IUPHAR and provides the official IUPHAR classification and nomenclature for human drug targets, where appropriate. It consolidates information previously curated and displayed separately in IUPHAR-DB and the Guide to Receptors and Channels, providing a permanent, citable, point-in-time record that will survive database updates.

Progress in understanding role of urotensin Ⅱ in hepatic cirrhosis

Urotensin Ⅱ (UⅡ) is a potent vasoactive substance that can result in vasoactive response through interaction with its specific orphan G-protein-coupled receptor GPR-14. In addition to the role of vasoactivity, UⅡ can promote mitosis and fibrosis. The vascular role of UⅡ is to some degree both species- and disease-specific. Studies have found that plasma levels of UⅡ are elevated in patients with cirrhosis, but the relationship between plasma levels of UⅡ and the development of chronic liver disease and portal hypertension has yet to be fully elucidated. This review focuses on the potential relevance of UⅡ as vasoactive substance in chronic liver disease and the site where UⅡ is overproduced.

Impact of gene/genome duplications on the evolution of the urotensin II and somatostatin families

The present review describes the molecular evolution of two phylogenetically related families of neuropeptides, the urotensin II (UII) and somatatostatin (SS) families. The UII family consists of four paralogous genes called UII, URP, URP1 and URP2 and the SS family is composed of six paralogous genes named SS1, SS2, SS3, SS4, SS5 and SS6. All these paralogs are present in teleosts, while only four of them, UII, URP, SS1 and SS2 are detected in tetrapods. Comparative genomics showed that most of these genes, namely UII, URP, URP1 and URP2 on the one hand and SS1, SS2 and SS5 on the other hand arose through the 2R. In contrast, the teleost-specific 3R had a much more moderate impact since it only concerned the UII and SS1 genes, which once duplicated, generated a second UII copy and SS4, respectively. The two remaining genes, SS3 and SS6, arose through tandem duplications of the SS1 and SS2 genes respectively, probably in the stem lineage of actinopterygians, before the emergence of teleosts. The history of the UII and SS families has also been marked by massive gene lost, both in tetrapods and in teleosts, but only after the 3R in this latter lineage. Finally, ancestral UII and SS genes are thought to have arisen through tandem duplication of a single ancestral gene, largely before the 1R. An important challenge for the future will be to understand the physiological significance of the molecular diversity of these two families.

Urotensin II and the kidney

PURPOSE OF REVIEW

Urotensin II (UTS2), the most potent vasoconstrictor identified thus far, is an undecapeptide hormone with a structure that is highly conserved through mammalian phylogeny. In spite of its broad expression across the invertebrate and vertebrate world, the precise role of UTS2 in physiology and disease is still unknown. The first description of human UTS2 and its receptor brought initial promise of a potential therapeutic target for progressive renal disease, with vasoconstrictive and profibrotic actions within an autocrine and paracrine system and local renal generation that was upregulated with renal pathology.

RECENT FINDINGS

However, the last decade has not brought the successful development of new treatments first hoped for, with one small human clinical trial bearing negative results. What has become apparent is that the spectrum of actions of UTS2 is broad and often paradoxical. This ancient hormone has both vasoconstrictor and vasodilatory actions, has both profibrotic and antiapoptotic activity, as well as actions which are highly contextual on the particular vascular bed studied and on the presence or absence of superimposed disease state.

SUMMARY

With current development of newer UTS2 antagonists attempting to more closely replicate the ligand-receptor kinetics of UTS2 and its receptor, the focus on potential clinical applications of UTS2 inhibition has moved away from the kidney to the treatment of chronic lung and cardiovascular diseases.

Pressor and renal regional hemodynamic effects of urotensin II in neonatal pigs

Renal expression of the peptide hormone urotensin II (UII) and its receptor (UTR) are dependent on kidney maturation and anatomical regions. However, renal regional hemodynamic effects of UII in neonates are unclear. Here, we investigated regional hemodynamic responses to acute intrarenal arterial administration of UII in newborn pigs. Western immunoblotting and immunofluorescence confirmed UTR expression and membrane localization in newborn pig renal afferent arterioles and afferent arteriolar smooth muscle cells respectively. Intrarenal arterial bolus injections of human UII (hUII; 1-100  ng/kg) resulted in a dose-dependent decrease in total renal blood flow (RBF) and an increase in mean arterial pressure (MAP) and renal vascular resistance (RVR) in newborn pigs. Moreover, hUII dose dependently reduced cortical blood flow (CBF) but increased medullary blood flow (MBF) in the piglets. hUII-induced MAP elevation and hemodynamic changes were inhibited by urantide, a UTR antagonist, but not losartan, a type 1 angiotensin II receptor antagonist. U-73122, a phospholipase C (PLC) inhibitor, and 2-aminoethoxydiphenyl borate, an inositol 1,4,5 trisphosphate (IP₃) receptor antagonist, attenuated hUII-induced MAP and RVR elevations, RBF and CBF reductions, but not MBF increase. These findings indicate that intrarenal arterial administration of hUII elevates blood pressure and induces region-selective renal hemodynamic changes in newborn pigs. Our data also suggest that the PLC/IP₃ signaling pathway contributes to hUII-induced alterations in MAP, RBF, RVR, and CBF but not MBF in newborn pigs.

Urotensin II receptor antagonism confers vasoprotective effects in diabetes associated atherosclerosis: studies in humans and in a mouse model of diabetes

AIMS/HYPOTHESIS

The small, highly conserved vasoactive peptide urotensin II (UII) is upregulated in atherosclerosis. However, its effects in diabetes-associated atherosclerosis have not been assessed.

METHODS

Endothelial cells were grown in normal- and high-glucose (5 and 25 mmol/l) media with and without UII (10⁻⁸ mol/l) and/or the UII receptor antagonist, SB-657510 (10⁻⁸ mol/l). Apoe knockout (KO) mice with or without streptozotocin-induced diabetes were treated with or without SB-657510 (30 mg kg⁻¹ day⁻¹; n = 20 per group) and followed for 20 weeks. Carotid endarterectomy specimens from diabetic and non-diabetic humans were also evaluated.

RESULTS

In high (but not normal) glucose medium, UII significantly increased CCL2 (encodes macrophage chemoattractant protein 1 [MCP-1]) gene expression (human aortic endothelial cells) and increased monocyte adhesion (HUVECs). UII receptor antagonism in diabetic Apoe KO mice significantly attenuated diabetes-associated atherosclerosis and aortic staining for MCP-1, F4/80 (macrophage marker), cyclooxygenase-2, nitrotyrosine and UII. UII staining was significantly increased in carotid endarterectomies from diabetic compared with non-diabetic individuals, as was staining for MCP-1.

CONCLUSIONS/INTERPRETATION

This is the first report to demonstrate that UII is increased in diabetes-associated atherosclerosis in humans and rodents. Diabetes-associated plaque development was attenuated by UII receptor antagonism in the experimental setting. Thus UII may represent a novel therapeutic target in the treatment of diabetes-associated atherosclerosis.

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.

Urotensin-II: More Than a Mediator for Kidney

Human urotensin-II (hU-II) is one of the most potent vasoconstrictors in mammals. Although both hU-II and its receptor, GPR14, are detected in several tissues, kidney is a major source of U-II in humans. Recent studies suggest that U-II may have a possible autocrine/paracrine functions in kidney and may be an important target molecule in studying renal pathophysiology. It has several effects on tubular transport and probably has active role in renal hemodynamics. Although it is an important peptide in renal physiology, certain diseases, such as hypertension and glomerulonephritis, may alter the expression of U-II. As might be expected, oxidative stress, mediators, and inflammation are like a devil's triangle in kidney diseases, mostly they induce each other. Since there is a complex relationship between U-II and oxidative stress, and other mediators, such as transforming growth factor β1 and angiotensin II, U-II is more than a mediator in glomerular diseases. Although it is an ancient peptide, known for 31 years, it looks like that U-II will continue to give new messages as well as raising more questions as research on it increases. In this paper, we mainly discuss the possible role of U-II on renal physiology and its effect on kidney diseases.

Urotensin II protects ischemic reperfusion injury of hearts through ROS and antioxidant pathway

Urotensin II (UII) is a vasoactive peptide which is bound to a G protein-coupled receptor. UII and its receptor are upregulated in ischemic and chronic hypoxic myocardium, but the effect of UII on ischemic reperfusion (I/R) injury is still controversial. The aim of the present study was to investigate whether UII protects heart function against I/R injury. Global ischemia was performed using isolated perfused Langendorff hearts of Sprague-Dawley rats. Hearts were perfused with Krebs-Henseleit buffer for 20min pre-ischemic period followed by a 20min global ischemia and 50min reperfusion. Pretreatment with UII (10nM) for 10min increased recovery percentage of the post-ischemic left ventricular developed pressure and ±dp/dt, and decreased post-ischemic left ventricular end-diastolic pressure as compared with I/R group. UII decreased infarct size and an increased lactate dehydrogenase level during reperfusion. Cardioprotective effects of UII were attenuated by pretreatment with UII receptor antagonist. The hydrogen peroxide activity was increased in UII-treated heart before ischemia. The Mn-SOD, catalase, heme oxygenase-1 and Bcl-2 levels were increased, and the Bax and caspase-9 levels were decreased in UII-treated hearts. These results suggest that UII has cardioprotective effects against I/R injury partly through activating antioxidant enzymes and reactive oxygen species.

Genetic and pharmacological manipulation of urotensin II ameliorate the metabolic and atherosclerosis sequalae in mice

OBJECTIVE

Urotensin II (UII) is a potent vasoactive peptide that binds to the urotensin receptor-coupled receptor-14 (known as UT) and exerts a wide range of actions in humans and experimental animals. We tested the hypothesis that UII gene deletion or UT blockade ameliorate experimental atherosclerosis.

METHODS AND RESULTS

We observed a significant reduction in weight gain, visceral fat, blood pressure, circulating plasma lipids, and proatherogenic cytokines and improvement of glucose tolerance in UII knockout mice compared with wild type (P<0.05). Deletion of UII after an apolipoprotein E knockout resulted in a significant reduction in serum cytokines, adipokines, and aortic atherosclerosis compared with apolipoprotein E knockout mice. Similarly, treatment of apolipoprotein E knockout mice fed on high-fat diet with the UT antagonist SB657510A reduced weight gain, visceral fat, and hyperlipidemia and improved glucose tolerance (P<0.05) and attenuated the initiation and progression of atherosclerosis. The UT antagonist also decreased aortic extracellular signal-regulated kinase 1/2 phosphorylation and oxidant formation and serum level of cytokines (P<0.05).

CONCLUSIONS

These findings demonstrate for the first time the role of UII gene deletion in atherosclerosis and suggest that the use of pharmaceutical agents aimed at blocking the UII pathway may provide a novel approach in the treatment of atherosclerosis and its associated precursors such as obesity, hyperlipidemia, diabetes mellitus, and hypertension.

Characterization of the true ortholog of the urotensin II-related peptide (URP) gene in teleosts

It has been recently established that the urotensin II (UII) family consists of four distinct paralogs in bony vertebrates, namely UII, and the three UII-related peptides (URPs) called URP, URP1 and URP2. These four peptides are encoded by genes which arose from the two rounds of tetraploidization (2R) which took place early during vertebrate evolution. Up to now, three of them, UII, URP1 and URP2, have been identified in teleosts, while only two, UII and URP, have been reported in tetrapods. The fact that fish URP has not been found in previous studies led to the suggestion that the corresponding gene had been lost in the teleost lineage. In the present study, we show that this view is not correct. A search of the most recent release of the Ensembl genome database led us to identify a novel UII/URP-like gene in teleosts. Using synteny analysis, we demonstrate that this gene corresponds to the true ortholog of the tetrapod URP gene. Molecular cloning of the corresponding cDNA in medaka revealed that URP gene encodes a putative peptide, with the primary structure GEPCFWKYCV. In stickleback, tilapia and takifugu, URP exhibited the same sequence while, in tetraodon, it differed by only one amino acid substitution Gly ↔ Ser. In zebrafish, URP appeared totally divergent at its N-terminus with the structure DDTCFWKYCV. In conclusion, the occurrence of a true URP in teleosts shows that the quartet of UII-related genes which arose from 2R has been integrally preserved in this lineage.

Down-regulation of GABA(A) receptor via promiscuity with the vasoactive peptide urotensin II receptor. Potential involvement in astrocyte plasticity

GABA_A receptor (GABA_AR) expression level is inversely correlated with the proliferation rate of astrocytes after stroke or during malignancy of astrocytoma, leading to the hypothesis that GABA_AR expression/activation may work as a cell proliferation repressor. A number of vasoactive peptides exhibit the potential to modulate astrocyte proliferation, and the question whether these mechanisms may imply alteration in GABA_AR-mediated functions and/or plasma membrane densities is open. The peptide urotensin II (UII) activates a G protein-coupled receptor named UT, and mediates potent vasoconstriction or vasodilation in mammalian vasculature. We have previously demonstrated that UII activates a PLC/PIPs/Ca²⁺ transduction pathway, via both G_q and G_i/o proteins and stimulates astrocyte proliferation in culture. It was also shown that UT/G_q/IP₃ coupling is regulated by the GABA_AR in rat cultured astrocytes. Here we report that UT and GABA_AR are co-expressed in cerebellar glial cells from rat brain slices, in human native astrocytes and in glioma cell line, and that UII inhibited the GABAergic activity in rat cultured astrocytes. In CHO cell line co-expressing human UT and combinations of GABA_AR subunits, UII markedly depressed the GABA current (β₃γ₂>α₂β₃γ₂>α₂β₁γ₂). This effect, characterized by a fast short-term inhibition followed by drastic and irreversible run-down, is not relayed by G proteins. The run-down partially involves Ca²⁺ and phosphorylation processes, requires dynamin, and results from GABA_AR internalization. Thus, activation of the vasoactive G protein-coupled receptor UT triggers functional inhibition and endocytosis of GABA_AR in CHO and human astrocytes, via its receptor C-terminus. This UII-induced disappearance of the repressor activity of GABA_AR, may play a key role in the initiation of astrocyte proliferation.

Urotensin-II signaling mechanism in rat coronary artery: role of STIM1 and Orai1-dependent store operated calcium influx in vasoconstriction

OBJECTIVE

Human urotensin-II (UII) is considered the most potentendogenous vasoconstrictor discovered to date, although the precise mechanism activated downstream of its receptor UTS2R in blood vessels remains elusive. The aim of this study was to determine the role of the store operated Ca(2+) entry (SOCE) signaling pathway in UII-induced coronary artery vasoconstriction.

METHODS AND RESULTS

We used a combination of isometric tension measurement, Ca(2+) imaging, pharmacology, and molecular approaches to study UII-mediated rat coronary artery vasoconstriction and intracellular Ca(2+) mobilization in coronary smooth muscle cells. We found that UII promoted dose-dependent vasoconstriction and elicited Ca(2+) and Mn(2+) influx, which were sensitive to classical SOCE inhibitors. In addition, knockdown of either STIM1 or Orai1 essentially inhibited UII-mediated SOCE and prevented UII but not high-KCL evoked contraction in transfected coronary artery. Moreover, we found that Ca(2+)-independent phospholipase A(2)β was involved in UII effects and that is colocalized with STIM1 in different submembrane compartments. Importantly, STIM1 but not Orai1 downregulation inhibits significantly independent phospholipase A(2) activation. Furthermore, lysophosphatidylcholine, an independent phospholipase A(2) product, activated Orai1 but not STIM1-dependent contraction and SOCE.

CONCLUSIONS

Here, we demonstrated that different critical players of SOCE signaling pathway are required for UII-induced vasoconstriction of rat coronary artery.

Update on the urotensinergic system: new trends in receptor localization, activation, and drug design

The urotensinergic system plays central roles in the physiological regulation of major mammalian organ systems, including the cardiovascular system. As a matter of fact, this system has been linked to numerous pathophysiological states including atherosclerosis, heart failure, hypertension, diabetes as well as psychological, and neurological disorders. The delineation of the (patho)physiological roles of the urotensinergic system has been hampered by the absence of potent and selective antagonists for the urotensin II-receptor (UT). Thus, a more precise definition of the molecular functioning of the urotensinergic system, in normal conditions as well as in a pathological state is still critically needed. The recent discovery of nuclear UT within cardiomyocytes has highlighted the cellular complexity of this system and suggested that UT-associated biological responses are not only initiated at the cell surface but may result from the integration of extracellular and intracellular signaling pathways. Thus, such nuclear-localized receptors, regulating distinct signaling pathways, may represent new therapeutic targets. With the recent observation that urotensin II (UII) and urotensin II-related peptide (URP) exert different biological effects and the postulate that they could also have distinct pathophysiological roles in hypertension, it appears crucial to reassess the recognition process involving UII and URP with UT, and to push forward the development of new analogs of the UT system aimed at discriminating UII- and URP-mediated biological activities. The recent development of such compounds, i.e. urocontrin A and rUII(1-7), is certainly useful to decipher the specific roles of UII and URP in vitro and in vivo. Altogether, these studies, which provide important information regarding the pharmacology of the urotensinergic system and the conformational requirements for binding and activation, will ultimately lead to the development of potent and selective drugs.

Effects of urotensin II on functional activity of late endothelial progenitor cells

Urotensin II (UII) is a potent vasoactive cyclic peptide which has multiple effects on the cardiovascular system. However, the effects of UII on late endothelial progenitor cells (EPCs) are still unclear. The aim of the present study is to investigate whether UII influences the functional activity of late EPCs. Late EPCs were isolated from human umbilical cord blood by Ficoll density gradient centrifugation and treated with UII (10(-10), 10(-9), 10(-8), 10(-7) and 10(-6)M), or vehicle control. Expression of urotensin II receptor (UT) in late EPCs was confirmed by indirect immunofluorescence staining. Late EPCs proliferation, migration and in vitro vasculogenesis activity were assayed with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, transwell chamber assay, and matrigel tube formation assay. Late EPCs adhesive assay was performed by replating cells on fibronectin-coated dishes, and then adherent cells were counted. Incubation with UII increased the migratory, adhesive and in vitro vasculogenesis capacity and inhibited the proliferative activity of late EPCs. Furthermore, these UII-mediated effects on late EPCs were attenuated by pretreatment with the UT antagonist urantide. These findings indicate that UII may exert multiple effects on functional activity of late EPCs through UT.

A closer look at the role of urotensin II in the metabolic syndrome

Urotensin II (UII) is a vasoactive peptide that was first discovered in the teleost fish, and later in mammals and humans. UII binds to the G protein coupled receptor GPR14 (now known as UT). UII mediates important physiological and pathological actions by interacting with its receptor. The metabolic syndrome (MetS) is described as cluster of factors such as obesity, dyslipidemia, hypertension, and insulin resistance (IR), further leading to development of type 2 diabetes mellitus and cardiovascular diseases. UII levels are upregulated in patients with the MetS. Evidence directly implicating UII in every risk factor of the MetS has been accumulated. The mechanism that links the different aspects of the MetS relies primarily on IR and inflammation. By directly modulating both of these factors, UII is thought to play a central role in the pathogenesis of the MetS. Moreover, UII also plays an important role in hypertension and hyperlipidemia thereby contributing to cardiovascular complications associated with the MetS.

Urotensin II and its receptor in the killifish gill: regulators of NaCl extrusion

The peptide urotensin II (UII) and its receptor (UT) mediate cardiovascular and renal effects in both mammals and fishes. In both groups, vasopressor and diuretic responses predominate, although, in mammals, some secondary vasodilatation is found, mediated by secondary release of nitric oxide or prostacyclin. In fishes, gill extrusion of NaCl is inhibited by UII, but a single study has determined that UT is expressed in gill vasculature, not on the epithelium that mediates the transport. To begin to clarify the pathways involved in UII inhibition of gill transport, we have cloned the cDNA encoding UII and UT from the euryhaline killifish (Fundulus heteroclitus L.) gill and spinal cord, quantified UT mRNA expression in various tissues and measured relative expression in gill tissue from fish acclimated to seawater (SW) vs fresh water (FW). We have also localized UT in the gill epithelium, and measured the effect of UII on ion transport across the opercular epithelium. We found that both UII and UT are synthesized in the gill of F. heteroclitus and that gill UT mRNA levels are ∼80% higher in SW- vs FW-acclimated individuals. In addition, UII inhibits NaCl transport across the opercular epithelium in a concentration-dependent manner, and this inhibition is at least partially mediated by both nitric oxide and a prostanoid.

Potential Clinical Implications of the Urotensin II Receptor Antagonists

Urotensin II (UII) binds to its receptor, UT, playing an important role in the heart, kidneys, pancreas, adrenal gland, and central nervous system. In the vasculature, it acts as a potent endothelium-independent vasoconstrictor and endothelium-dependent vasodilator. In disease states, however, this constriction–dilation equilibrium is disrupted. There is an upregulation of the UII system in heart disease, metabolic syndrome, and kidney failure. The increase in UII release and UT expression suggest that UII system may be implicated in the pathology and pathogenesis of these diseases by causing an increase in acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) activity leading to smooth muscle cell proliferation and foam cell infiltration, insulin resistance (DMII), as well as inflammation, high blood pressure, and plaque formation. Recently, UT antagonists such as SB-611812, palosuran, and most recently a piperazino-isoindolinone based antagonist have been developed in the hope of better understanding the UII system and treating its associated diseases.

Urotensin II levels are an important marker for the severity of portal hypertension in children

BACKGROUND AND AIM

Urotensin II (U-II), a somatostatin-like cyclic peptide, was recently identified as the most potent human vasoconstrictor peptide; however, the contribution of U-II-mediated alterations in peripheral vascular tone in disease states such as chronic liver disease and portal hypertension is poorly characterised. There are no data examining U-II in chronic liver disease in children. In this study, we aimed to determine whether U-II levels in healthy children are ontogenically regulated and we explored the effect of chronic liver disease on peripheral circulating U-II levels.

MATERIALS AND METHODS

U-II levels from healthy controls (n = 129) were compared with a healthy adult population (n = 80) in addition to a well-characterised cohort of children with chronic liver disease (n = 20). U-II was measured by radioimmunoassay.

RESULTS

There was no correlation between U-II and age in healthy children (r2 = 0, P = 0.8). U-II levels were similar between the paediatric and the adult control populations (1.35 ± 0.96 vs 1.25 ± 0.78, P = 0.8). U-II was significantly elevated in children with liver disease compared with controls (1.35 ± 0.96 pmol/L vs 3.56 ± 2.21 pmol/L; P < 0.001). In addition, U-II levels positively correlated with severity of liver disease as determined by Child-Pugh score (P < 0.05) and paediatric end-stage liver disease score (P < 0.001). Levels of U-II also correlated with long-term clinical outcome.

CONCLUSIONS

These data suggest that U-II is an important marker of severity of portal hypertension in children. It is independent of age and may be a potential therapeutic target in the chronic liver disease population.

Suppression of ANP secretion by somatostatin through somatostatin receptor type 2

Somatostatin is a cyclic-14 amino acid peptide which mainly distributed in digestive system and brain. Somatostatin receptor (SSTR) is a G-protein coupled receptor and all five SSTR subtypes are expressed in cardiomyocytes. The aim of this study was to investigate the effect of somatostatin on atrial natriuretic peptide (ANP) secretion and its signaling pathway. Somatostatin (0.01 and 0.1nM) decreased ANP secretion in isolated beating rat atrium in a dose-dependent manner. But atrial contractility and translocation of extracellular fluid were not changed. Somatostatin-induced decrease in ANP secretion was significantly attenuated by the pretreatment with CYN 154806 (SSTR type 2 antagonist; 0.1μM), but not by BIM 23056 (SSTR type 5 antagonist; 0.1μM) and urantide (urotensin II receptor antagonist; 0.1μM). When pretreated with an agonist for SSTR type 2 (Seglitide, 0.1nM) and SSTR type 5 (L 817818, 0.1nM), only Seglitide reduced ANP secretion similar to that of somatostatin. The suppressive effect of somatostatin on ANP secretion was attenuated by the pretreatment with an inhibitor for adenylyl cyclase (MDL-12330A, 5μM) or protein kinase A (KT 5720, 0.1μM). In diabetic rat atria, the suppressive effect of somatostatin on ANP secretion and concentration was attenuated. Real time-PCR and western blot shows the decreased level of SSTR type 2 mRNA and protein in diabetic rat atria. These data suggest that somatostatin decreased ANP secretion through SSTR type 2 and an attenuation of suppressive effect of somatostatin on ANP secretion in diabetic rat atria is due to a down-regulation of SSTR type 2.

Occurrence of two distinct urotensin II-related peptides in zebrafish provides new insight into the evolutionary history of the urotensin II gene family

The urotensin II (UII) family is currently known to consist of two paralogous peptides, namely UII and UII-related peptide (URP). In contrast to UII, which has been identified in all vertebrate classes so far, URP has only been characterized in tetrapods. We report here the occurrence of two distinct URP genes in teleosts, which we have named URP1 and URP2. Synteny analysis revealed that teleost URP1 and URP2 genes and tetrapod URP genes represent three distinct paralog genes that, together with the UII gene, probably arose from the two rounds of tetraploidization, which took place early in vertebrate evolution. The absence of URP in fish indicates that the corresponding gene has been lost in the teleost lineage, whereas it is likely that both the URP1 and URP2 genes have been lost in the tetrapod lineage. Quantitative RT-PCR analysis revealed that the URP2 gene is mainly expressed in the spinal cord and the brain in adult zebrafish. In situ hybridization experiments showed that in zebrafish embryos, URP2 mRNA-containing cells are located in the floor plate of the neural tube. In adult, URP2-expressing cells occur in close contact with the ventral side of the ependymal canal along the whole spinal cord, whereas in the brain, they are located below the fourth ventricle. These URP-expressing cells may correspond to cerebrospinal fluid-contacting neurons. In conclusion, our study reveals the occurrence of four distinct UII paralogous systems in vertebrates that may exert distinct functions, both in tetrapods and teleosts.

Urotensin II receptor antagonist attenuates monocrotaline-induced cardiac hypertrophy in rats

Urotensin II (UII) is a vasoactive peptide with potent cardiovascular effects through a G protein-coupled receptor. Hypoxia stimulates the secretion of UII and atrial natriuretic peptide (ANP). However, the effect of UII on hypoxia-induced cardiac hypertrophy is still controversial. The present study was conducted to determine whether human UII (hUII)-mediated ANP secretion influences hypoxia-induced cardiac hypertrophy using in vitro and in vivo models. Hypoxia caused an increase in ANP secretion and a decrease in atrial contractility in isolated perfused beating rat atria. hUII (0.01 and 0.1 nM) attenuated hypoxia-induced ANP secretion without changing the atrial contractility, and the hUII effect was mediated by the UII receptor signaling involving phospholipase C, inositol 1,3,4 trisphosphate receptor, and protein kinase C. Rats treated with monocrotaline (MCT, 60 mg/kg) showed right ventricular hypertrophy with increases in pulmonary arterial pressure and its diameter and plasma levels of UII and ANP that were attenuated by the pretreatment with an UII receptor antagonist, urantide. An acute administration of hUII (5 μM injection plus 2.5 μM infusion for 15 min) decreased the plasma ANP level in MCT-treated rats but increased the plasma ANP level in MCT plus urantide-treated and sham-operated rats. These results suggest that hUII may deteriorate MCT-induced cardiac hypertrophy mainly through a vasoconstriction of the pulmonary artery and partly through the suppression of ANP secretion.