Urantide alleviates the symptoms of atherosclerotic rats in vivo and in vitro models through the JAK2/STAT3 signaling pathway

Atherosclerosis is the leading cause of human death, and its occurrence and development are related to the urotensin II (UII) and UII receptor (UT) system and the biological function of vascular smooth muscle cells (VSMCs). During atherosclerosis, impaired biological function VSMCs may promote atherosclerotic plaque formation. The Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) pathway is an important mediator of signal transduction; however, the role of this signaling pathway in atherosclerosis and VSMCs remains unknown. This study aimed to investigate the effects of urantide on the JAK2/STAT3 signaling pathway in atherosclerosis. We examined the effect of urantide on the UII/UT system and the JAK2/STAT3 signaling pathway in a high fat diet induced atherosclerosis rat model and studied the effect and mechanism of urantide on the phenotypic transformation of VSMCs. We found that the UII/UT system and JAK2/STAT3 signaling pathway were highly activated in the thoracic aorta in atherosclerotic rats and in ox-LDL- and UII-induced VSMCs. After urantide treatment, the pathological changes in atherosclerotic rats were effectively improved, and the activities of the UII/UT system and JAK2/STAT3 signaling pathway were inhibited. Moreover, urantide effectively inhibited proliferation and migration and reversed the phenotypic transformation of VSMCs. These results demonstrated that urantide may control the JAK2/STAT3 signaling pathway by antagonizing the UII/UT system, thereby maintaining the biological function of VSMCs and potentially preventing and curing atherosclerosis.

Urantide attenuates myocardial damage in atherosclerotic rats by regulating the MAPK signalling pathway

OBJECTIVE

To explore the effect of urantide on atherosclerotic myocardial injury by antagonizing the urotensin II/urotensin II receptor (UII/UT) system and regulating the mitogen-activated protein kinase (MAPK) signalling pathway.

METHODS

Atherosclerosis (AS) was established in rats by administering a high-fat diet and an intraperitoneal injection of vitamin D₃. The effect of treatment with urantide (30 μg/kg), a UII receptor antagonist, for 3, 7, or 14 days on AS-induced myocardial damage was evaluated.

RESULTS

The heart of rats with AS exhibited pathological changes suggestive of myocardial injury, and the serum levels of creatine kinase (CK) and lactate dehydrogenase (LDH) were significantly increased. Additionally, significant increases in the levels of UII, its receptor (G protein-coupled receptor 14, GPR14), p-P38, p-extracellular signal-regulated kinase (ERK) and p-c-Jun N-terminal kinase (JNK) were observed in the heart. Urantide improved pathological changes in the heart of rats with AS and reduced the serum CK and LDH levels. Additionally, the UII antagonist decreased the increased levels of UII, GPR14, p-P38, p-ERK and p-JNK in the heart.

CONCLUSIONS

Urantide alleviates atherosclerotic myocardial injury by inhibiting the UII-GPR14 interaction and regulating the MAPK signalling pathway. We hypothesized that myocardial injury may be associated with the regulation of the MAPK signalling pathway.

Urotensin receptor antagonist palosuran attenuates cyclosporine-a-induced nephrotoxicity in rats

BACKGROUND

Cyclosporine-A (CsA) is widely used for immunosuppressive therapy in renal transplantation. Nephrotoxicity is the main dose-limiting undesirable consequence of CsA. Urotensin II (U-II), a novel peptide with a powerful influence on vascular biology, has been added to the list of potential renal vascular regulators. Upregulation of the urotensin receptors and elevation of plasma U-II levels are thought to possibly play a role in the etiology of renal failure.

OBJECTIVES

The present study examines this hypothesis by evaluating renal function and histology with regard to the potential role of U-II and its antagonist, palosuran, in the pathogenesis of CsA-induced nephrotoxicity in rats.

MATERIAL AND METHODS

Male Sprague-Dawley rats were treated with CsA (15 mg/kg, for 21 days, intraperitoneally) or CsA + palosuran (300 mg/kg, for 21 days). Renal function was measured and histopathology, U-II immunostaining and protein detection with western blotting of the kidneys were performed.

RESULTS

Cyclosporine-A administration caused a marked decline in creatinine clearance (Ccr). Fractional sodium excretion (FENa) tended to increase in the CsA-treated rats. Plasma U-II levels decreased in the CsA-treated rats. Cyclosporine-A treatment resulted in a marked deterioration in renal histology and an increase in the expression of U-II protein in the kidneys. Palosuran's improvement of renal function manifested as a significant decrease in serum creatinine levels and a significant increase in urine creatinine levels, resulting in a marked increase in Ccr. Palosuran produced a significant normalization of kidney histology and prevented an increase in U-II expression.

CONCLUSIONS

Cyclosporine-A-induced renal impairment was accompanied by an increase in U-II expression in kidneys and a contrary decrease in systemic U-II levels. Palosuran improved the condition of rats suffering from renal dysfunction by preventing the decrease in renal U-II expression without affecting the systemic levels of U-II. The protective effect of palosuran in CsA nephrotoxicity is possibly independent of its U-II receptor antagonism.

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.

Effects of peripherally administered urotensin II and arginine vasotocin on the QT interval of the electrocardiogram in trout

The QT interval of the electrocardiogram (ECG) is a measure of the duration of the ventricular depolarization and repolarization. In fish as in human, the QT interval is positively correlated with the RR interval of the ECG, a measure of the cardiac cycle length. Urotensin II (UII) is a neuropeptide that has been highly conserved from fish to human, and UII and its receptor (UT) are expressed in cardiovascular tissues including the heart. Although UII exerts potent cardiovascular actions, its possible effects on the QT interval have never been investigated. The goal of the present study was to provide insight into the potential effect of UII on the QT interval in an established in vivo trout model. To this end, the effects of UII on dorsal aortic blood pressure (PDA), RR, QT intervals and corrected QT (QTc) for RR interval, were investigated after intra-arterial (IA) injection of 5, 50 and 100 pmol UII. The effects of UII were compared to those of two structurally UII-related peptides (URPs), URP1 and URP2, and to those of arginine vasotocin (AVT), homolog of the mammalian arginine vasopressin. IA injection of vehicle or 5 pmol UII had no effect on the various parameters. At the 50-pmol dose, UII evoked its usual increase in PDA with a peak value observed 15 min after the injection (+22% from baseline, P<0.001). This hypertensive effect of UII was accompanied by a significant increase in the RR interval (+18%, P<0.001), i.e. a bradycardia, and these effects remained constant until the end of the recording. The highest dose of UII evoked similar hypertensive and bradycardic effects. Of interest, the QT interval did not change during the bradycardic action of UII (50 and 100 pmol) but the QTc interval significantly decreased. In trout pre-treated with urantide, a peptidic antagonist of UT, the hypertensive and bradycardic actions of 50 pmol UII were reduced 3-fold and no change occurred in the QT and QTc intervals. In trout pre-treated with blockers of the autonomic nervous system, the hypertensive effect of UII was maintained but no change appeared in RR, QT and QTc intervals. IA injections of 50 pmol URPs were without action on the preceding parameters. IA administration of 50 pmol AVT provoked quite similar increase in PDA, and elevation of the RR interval to those evoked by IA injection of UII but, in contrast to UII, AVT injection induced a highly significant and sustained prolongation of the QT interval compared to baseline (+7%, P<0.001) without change in QTc. Our results are indicative of a lack of QT interval change during UII-evoked bradycardia but not after AVT-induced bradycardia and suggest for the first time that some compensatory mechanism specific for the UII peptide is working to stabilize the QT interval. Further research is needed to elucidate the mechanism involved in this action of UII. The potential for UII to prevent detrimental prolongation of cardiac ventricular repolarization might be questioned.

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.

Osteopontin is involved in urotensin II-induced migration of rat aortic adventitial fibroblasts

Recent studies suggest that both osteopontin and urotensin II (UII) play critical roles in vascular remodeling. We previously showed that UII could stimulate the migration of aortic adventitial fibroblasts. In this study, we examined whether osteopontin is involved in UII-induced migration of rat aortic adventitial fibroblasts and examined the effects and mechanisms of UII on osteopontin expression in adventitial fibroblasts. Migration of adventitial fibroblasts induced by UII could be inhibited significantly by osteopontin antisense oligonucleotide (P<0.01) but not sense or mismatch oligonucleotides (P>0.05). Moreover, UII dose- and time-dependently promoted osteopontin mRNA expression and protein secretion in the cells, with maximal effect at 10(-8)mol/l at 3h for mRNA expression or at 12h for protein secretion (both P<0.01). Furthermore, the UII effects were significantly inhibited by its receptor antagonist SB710411 (10(-6)mol/l), and Ca(2+) channel blocker nicardipine (10(-5)mol/l), protein kinase C (PKC) inhibitor H7 (10(-5)mol/l), calcineurin inhibitor cyclosporine A (10(-5)mol/l), mitogen-activated protein kinase (MAPK) inhibitor PD98059 (10(-5)mol/l) and Rho kinase inhibitor Y-27632 (10(-5)mol/l). Thus, osteopontin is involved in the UII-induced migration of adventitial fibroblasts, and UII could upregulate osteopontin gene expression and protein synthesis in rat aortic adventitial fibroblasts by activating its receptor and the Ca(2+) channel, PKC, calcineurin, MAPK and Rho kinase signal transduction pathways.

Transforming growth factor-β1 involved in urotensin II-induced phenotypic differentiation of adventitial fibroblasts from rat aorta

BACKGROUND

Urotensin II (UII) is a new vasoconstrictive peptide that may activate the adventitial fibroblasts. Transforming growth factor-β1 (TGF-β1) is an important factor that could induce the phenotypical transdifferentiation of adventitial fibroblasts. This study aimed to explore whether TGF-β1 is involved in UII-induced phenotypic differentiation of adventitial fibroblasts from rat aorta.

METHODS

Adventitial fibroblasts were prepared by the explant culture method. TGF-β1 protein secretion from the cells was determined by enzyme-linked immunosorbent assay (ELISA). The mRNA and protein expression of α-smooth nuscle actin (α-SM-actin), the marker of phenotypic differentiation from fibroblasts to myofibroblasts, were determined using real-time quantitative RT-PCR (real-time RT-PCR) and Western blotting, respectively.

RESULTS

UII stimulated the secretion of TGF-β1 in cultured adventitial fibroblasts in a time-dependent manner. The secretion reached a peak at 24 hours, was higher by 69.8% (P < 0.01), than the control group. This effect was also concentration dependent. Maximal stimulation was reached at 10(-8) mol/L of UII (P < 0.01), which was increased by 59.9%, compared with in the control group (P < 0.01). The secretion of TGF-β1 induced by UII was significantly blocked by SB-710411 (10(-7) mol/L), a specific antagonist of UII receptor. In addition, both UII (10(-8) mol/L) and TGF-β1 significantly stimulated α-SM-actin mRNA and protein expression. Moreover, the α-SM-actin induced by UII was inhibited by the specific neutralizing antibody (20 µg/ml) of TGF-β1, while the α-SM-actin expression stimulated by TGF-β1 (20 ng/ml) was inhibited by SB-710411 (10(-7) mol/L), the UII receptor antagonist.

CONCLUSION

This study suggests that UII could induce TGF-β1 secretion in adventitial fibroblasts via UT activation, and TGF-β1 might be involved in phenotypic differentiation from adventitial fibroblasts into myofibroblasts induced by UII, and TGF-β1 signaling might be one of the important pathways by which UII is involved in vascular fibrosis.

Chronic urotensin II receptor antagonist treatment does not alter hypertrophy or fibrosis in a rat model of pressure-overload hypertrophy

Urotensin II (UII) is a potential mediator in the pathogenesis of cardiovascular disease, and inhibition of its actions at the urotensin receptor (UT) has been shown to improve cardiac function and structural changes of the myocardium in a model of myocardial infarction. In this study we utilized a model of pressure-overload hypertrophy induced by abdominal aortic constriction (AAC) which resulted in hypertrophy, increased fibrosis and impaired diastolic and systolic function. These changes were associated with a 4-fold increase in UII protein expression in the myocardium. Treatment of animals with a selective UT (SB-657510) antagonist for 20 weeks at a dose of 1500 ppm did not improve cardiac function as assessed by echocardiography and pressure-volume loop analysis, nor did it inhibit left ventricular hypertrophy or fibrosis. We hypothesize that other neurohumoral pathways may have a greater involvement in the pathogenesis of this model. Targeting the UII system appears to be insufficient to observe a beneficial outcome.

Potent and selective small-molecule human urotensin-II antagonists with improved pharmacokinetic profiles

Lead compound 1 was successfully redesigned to provide compounds with improved pharmacokinetic profiles for this series of human urotensin-II antagonists. Replacement of the 2-pyrrolidinylmethyl-3-phenyl-piperidine core of 1 with a substituted N-methyl-2-(1-pyrrolidinyl)ethanamine core as in compound 7 resulted in compounds with improved oral bioavailability in rats. The relationship between stereochemistry and selectivity for hUT over the kappa-opioid receptor was also explored.

Urotensin-II and cardiovascular remodeling

Urotensin-II (U-II), a cyclic undecapeptide, and its receptor, UT, have been linked to vascular and cardiac remodeling. In patients with coronary artery disease (CAD), it has been shown that U-II plasma levels are significantly greater than in normal patients and the severity of the disease is increased proportionally to the U-II plasma levels. We showed that U-II protein and mRNA levels were significantly elevated in the arteries of patients with coronary atherosclerosis in comparison to healthy arteries. We observed U-II expression in endothelial cells, foam cells, and myointimal and medial vSMCs of atherosclerotic human coronary arteries. Recent studies have demonstrated that U-II acts in synergy with mildly oxidized LDL inducing vascular smooth muscle cell (vSMC) proliferation. Additionally, U-II has been shown to induce cardiac fibrosis and cardiomyocyte hypertrophy leading to cardiac remodeling. When using a selective U-II antagonist, SB-611812, we demonstrated a decrease in cardiac dysfunction including a reduction in cardiomyocyte hypertrophy and cardiac fibrosis. These findings suggest that U-II is undoubtedly a potential therapeutic target in treating cardiovascular remodeling.

[The role of urotensin II in human pathophysiology]

Human urotensin II (U-II) is a cyclic peptide generated by proteolytic cleavage from a precursor prohormone. It was first isolated from the fish spinal cord and has been recognized as a hormone in the neurosecretory system of teleost fish. It is expressed in the human 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 caliber of the vessel. The net effect on vascular tone is a balance between endothelium-independent vasoconstriction and endothelium-dependent vasodilatation. Urotensin II is also a neuropeptide and may play a role in tumor development. The development of U-II receptor antagonists may provide a useful research tool as well as a novel treatment not only for cardiovascular diseases.

Structure-activity relationships of a novel series of urotensin II analogues: identification of a urotensin II antagonist

Urotensin II (U-II) is a potent vasoconstrictor peptide which has been identified as the endogenous ligand for the orphan G protein-coupled receptor GPR14 now renamed UT receptor. As the C-terminal cyclic hexapeptide of U-II (U-II(4-11), H-Asp-Cys-Phe-Trp-Lys-Tyr-Cys-Val-OH) possesses full biological activity, we have synthesized a series of U-II(4-11) analogues and measured their binding affinity on hGPR14-transfected CHO cells and their contractile activity on de-endothelialized rat aortic rings. The data indicate that a free amino group and a functionalized side-chain at the N-terminal extremity of the peptide are not required for biological activity. In addition, the minimal chemical requirement at position 9 of U-II(4-11) is the presence of an aromatic moiety. Most importantly, replacement of the Phe6 residue by cyclohexyl-Ala (Cha) led to an analogue, [Cha6]U-II(4-11), that was devoid of agonistic activity but was able to dose-dependently suppress the vasoconstrictor effect of U-II on rat aortic rings. These new pharmacological data, by providing further information regarding the structure-activity relationships of U-II analogues, should prove useful for the rational design of potent and nonpeptidic UT receptor agonists and antagonists.

Definition of New Pharmacophores for Nonpeptide Antagonists of Human Urotensin-II. Comparison with the 3D-structure of Human Urotensin-II and URP

Starting from nonpeptide agonists and antagonists of human urotensin-II (hU-II), several pharmacophores were designed and compared to the structure of hU-II. NMR and dynamic studies were realized on hU-II and urotensin-II-related peptide to check the conformation flexibilities of these peptides and the relationships between their potential 3D structures and the pharmacophores. In parallel, a virtual screening was carried out, leading to the discovery of six new derivatives with micromolar affinities. This last result shows the interest of these pharmacophores for the discovery of new ligands.

Urotensin-II induces ear flushing in rats

BACKGROUND AND PURPOSE

While investigating the effects of systemic urotensin II (U-II), a potent vasoactive peptide acting at the UT receptor, we observed ear pinna flushing after systemic administration to conscious rats. In the present study, U-II-induced ear flushing was quantified in terms of ear pinna temperature change and potential mechanisms were explored.

EXPERIMENTAL APPROACH

U-II-induced ear flushing was quantified by measuring lateral ear pinna temperature changes and compared to that of calcitonin gene-related peptide (CGRP), a known cutaneous vasodilator. Further, the effects of a variety of pharmacological agents on U-II-induced ear flushing were explored.

KEY RESULTS

Subcutaneous injection of U-II (9 microg kg(-1))produced localized ear pinna flushing with an onset of approximately 15 min, a duration of approximately 30 min and a maximal temperature change of 9 degrees C. In contrast, CGRP caused cutaneous flushing within multiple cutaneous beds including the ear pinna with a shorter onset and greater duration than U-II. A potent UT receptor antagonist, urantide, blocked U-II-induced ear flushing but did not affect CGRP-induced ear flushing. Pretreatment with indomethacin or L-Nomega-nitroarginine methylester (L-NAME) abolished U-II-induced ear flushing. Mecamylamine or propranolol did not affect this response to U-II. Direct intracerebroventricular injection studies suggested that the ear flushing response to U-II was not mediated directly by the CNS.

CONCLUSION AND IMPLICATIONS

Our results suggest that U-II-induced ear flushing and temperature increase is mediated by peripheral activation of the UT receptor and involves prostaglandin- and nitric oxide-mediated vasodilation of small capillary beds in the rat ear pinna.

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 blockade with SB-611812 attenuates cardiac dysfunction in a rat model of coronary artery ligation

Expression of urotensin II (UII) is significantly elevated in the hearts of patients with congestive heart failure (CHF). Recent reports have also shown increased plasma levels of UII in patients with CHF, and these levels correlated with the severity of disease. We therefore hypothesized that blockade of UII signaling would improve cardiac function in a rat model of CHF. CHF was induced in rats by ligating the left coronary artery. Animals were randomized to either treatment with a specific UT receptor antagonist, SB-611812 (30 mg/kg/day, UID by gavage), or vehicle, starting either 30 min prior to coronary ligation (early treatment) or 10 days after ligation (delayed treatment). Treatment drug or vehicle was administered daily thereafter for 8 weeks. We measured cardiac function and evaluated the levels of mRNA expression for mediators of CHF. In addition, we evaluated UII and UT protein levels using immunohistochemistry and Western blotting. Cardiomyocyte hypertrophy was evaluated by measuring cardiomyocyte cross-sectional area. Animals with CHF showed increased UII and UT expression as evidenced by immunohistochemistry and Western blotting. Treatment with the SB-611812 significantly reduced overall mortality, left ventricular end-diastolic pressure by 72%, lung edema by 71%, right ventricular systolic pressure by 92%, central venous pressure by 59%, cardiomyocyte hypertrophy by 54%, and ventricular dilatation by 79% (P < 0.05). Therefore, blockade of the UT receptor reduced mortality and improved cardiac function in this model of myocardial infarction and CHF, suggesting an important role for UII in the pathogenesis of this condition.

Urotensin II and renal function in the rat

Urotensin II (UII) is a potent vasoactive hormone in mammals. However, despite its well-known effects on epithelial sodium transport in fish, little is known about its actions on the mammalian kidney. The aim of this study was to determine the effects of UII on renal function in the rat. Using standard clearance methods, the effects of rUII and the rat UII receptor (UT) antagonist, urantide, were studied. UII was measured in plasma and urine by radioimmunoassay. UII and UT were localized in the kidney by immunohistochemistry and mRNA expression quantified. Rat urinary [UII] was 1,650-fold higher than that in plasma. Immunoreactive-UII was localized to the proximal tubules, outer and inner medullary collecting ducts (IMCD); UT receptor was identified in glomerular arterioles, thin ascending limbs, and IMCD. UII and UT mRNA expression was greater in the medulla; expression was higher still in spontaneously hypertensive rats (SHRs) associated with raised plasma (UII). Injection of rUII induced reductions in glomerular filtration rate (GFR), urine flow, and sodium excretion. Urantide infusion resulted in increases in these variables. Endogenous UII appears to contribute to the regulation of GFR and renal sodium and water handling in the rat. While hemodynamic changes predominate, we cannot rule out the possibility of a direct tubular action of UII. Increased expression of UII and UT in the SHR suggests that UII plays a role in the pathophysiology of cardiovascular disease.

A role for urotensin II in restenosis following balloon angioplasty: use of a selective UT receptor blocker

Recent studies have postulated that the vasoactive peptide urotensin II (UII) plays a role in the control of vascular remodeling by inducing smooth muscle proliferation and fibroblast-mediated collagen deposition. The present study examined the expression of UII mRNA and immunoreactivity in rat carotid arteries before and after balloon angioplasty. In addition, the effect of UT receptor blockade was assessed in this model using a selective non-peptidic UT receptor antagonist, SB-611812. In carotid arteries of uninjured rats (naïve group), there was weak expression of UII in endothelial cells and little to no expression in vascular smooth muscle cells. At day 7, there was intimal proliferation associated with pronounced expression of UII in myointimal cells. By day 14, there was extensive intimal thickening exhibiting strong expression of UII. The contralateral arteries of all groups exhibited similar UII expression to that of naïve arteries. Animals treated with methylcellulose (vehicle) for 28 days showed a significant increase in intimal thickening compared to sham operated animals. Treatment with the SB-611812 resulted in a significant 60% reduction in intima-to-media area ratio when compared to vehicle treatment (P<0.005). These findings demonstrate upregulation of UII following balloon angioplasty, and a significant reduction in intimal lesion in response to UT receptor blockade. The present study suggests an important role for UII in the pathogenesis of restenosis following balloon angioplasty.

Cardiac actions of central but not peripheral urotensin II are prevented by beta-adrenoceptor blockade

Urotensin II (UII) is a highly conserved peptide that has potent cardiovascular actions following central and systemic administration. To determine whether the cardiovascular actions of UII are mediated via beta-adrenoceptors, we examined the effect of intravenous (IV) propranolol on the responses to intracerebroventricular (ICV) and IV administration of UII in conscious sheep. Sheep were surgically instrumented with ICV guide tubes and flow probes or cardiac sympathetic nerve recording electrodes. ICV UII (0.2 nmol/kg over 1 h) caused prolonged increases in heart rate (HR; 33 +/- 11 beats/min; P < 0.01), dF/dt (581 +/- 83 L/min/s; P < 0.001) and cardiac output (2.3 +/- 0.4 L/min; P < 0.001), accompanied by increases in coronary (19.8 +/- 5.4 mL/min; P < 0.01), mesenteric (211 +/- 50 mL/min; P < 0.05) and iliac (162 +/- 31 mL/min; P < 0.001) blood flows and plasma glucose (7.0 +/- 2.6 mmol/L; P < 0.05). Propranolol (30 mg bolus followed by 0.5 mg/kg/h IV) prevented the cardiac responses to ICV UII and inhibited the mesenteric vasodilatation. At 2 h after ICV UII, when HR and mean arterial pressure (MAP) were increased, cardiac sympathetic nerve activity (CSNA) was unchanged and the relation between CSNA and diastolic pressure was shifted to the right (P < 0.05). The hyperglycemia following ICV UII was abolished by ganglion blockade but not propranolol. IV UII (20 nmol/kg) caused a transient increase in HR and fall in stroke volume; these effects were not blocked by propranolol. These results demonstrate that the cardiac actions of central UII depend on beta-adrenoreceptor stimulation, secondary to increased CSNA and epinephrine release, whereas the cardiac actions of systemic UII are not mediated by beta-adrenoreceptors and probably depend on a direct action of UII on the heart.

Facile preparation of disulfide-bridged peptides using the polymer-supported oxidant CLEAR-OX

Formation of disulfide bonds in synthetic peptides is one of the more challenging transformations to achieve in peptide chemistry, in view of the possible formation of oligomeric by-products and other side reactions, as well as occasional solubility problems in aqueous oxidizing media. It was shown previously that 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB identical with Ellman's reagent), when attached to polyethylene glycol-polystyrene (PEG-PS), controlled-pore glass (CPG), or modified Sephadex supports, was an effective oxidizing agent that promoted disulfide formation under mild conditions. More recently, this work was extended to Cross-Linked Ethoxylate Acrylate Resin (CLEAR) supports, because of their compatibility with both organic and aqueous solvent mixtures. The resultant new tool, termed CLEAR-OX, was used to conveniently produce several model cyclic disulfides with improved purities and yields, when compared with solution oxidations. A particularly striking example was the gram-scale oxidation of a urotensin II antagonist peptide containing a hindered penicillamine unit.

Clinically validated peptides as templates for de novo peptidomimetic drug design at G-protein-coupled receptors

Recent advances in the development of potent and selective peptide and non-peptide ligands for peptidergic receptors are anticipated to help further unravel the roles of class I and II G-protein-coupled receptors in the pathogenesis of human diseases and to accelerate the clinical utility of small molecule peptidomimetics. Peptidomimetic drug discovery directed towards somatostatin agonists, urotensin II antagonists, gonadotropin-releasing hormone antagonists, neurotensin and complement C5a modulators, melanocortin-4 agonists and vasopressin V(2) agonists has achieved success through integration of conformational-based drug design, site-directed mutagenesis, screening, combinatorial chemistry and classical medicinal chemistry. Acceptance that discreet ensembles of secondary structural motifs underpin the interactions of peptides with their cognate receptors has enabled the development of molecules which mimic or stabilize such pharmacophores.

Human urotensin-II as a novel cardiovascular target: 'heart' of the matter or simply a fishy 'tail'?

Urotensin-II (U-II), originally identified as a fish neuropeptide, exerts a broad spectrum of biological actions in mammals: responses that influence cardiorenal, pulmonary (bronchoconstriction), central nervous system (locomotion) and endocrine (thyroid-stimulating hormone, prolactin and insulin secretion) function. Because the U-II isopeptide family is highly conserved across species, both amongst invertebrates and vertebrates, it has been inferred that U-II and its G-protein-coupled receptor, UT, play a seminal role in the physiological regulation of major mammalian organ systems, most notably within the cardiovasculature. However, despite the evolutionary conservation of U-II, the (patho)physiological significance of this 'somatostatin-like' peptide remains ambiguous. Can the identification of a fish peptide as a ligand for an 'orphan' mammalian G-protein-coupled receptor really tell us something about human physiology? Emerging preclinical and clinical data suggest that it might.

Homogeneous cell-based fluorescence polarization assay for the direct detection of cAMP

A fluorescence polarization-based functional assay for cyclic AMP (cAMP) production in cells has been proven effective for the detection of agonist-stimulated cAMP production in a HEK 293 recombinant cell line expressing the corticotropin-releasing factor subtype 2alpha (CRF2alpha) receptor. Assays were completed in a single well of a 384-well microplate with no transfer, separation, or wash steps incurred. The assay performance is excellent for adaptation to the high throughput screening environment in terms of speed of analysis, magnitude of displaced signal, precision, and detection limits for cAMP quantitation. Relative potencies of agonists and antagonists are maintained with respect to radiometric assays. The assay withstands up to 5% DMSO and up to 10 microM concentrations of highly colored compound. These attributes suggest that accurate assessment of drug binding can be measured using this assay.

Vasodilator effect of urotensin II, one of the most potent vasoconstricting factors, on rat coronary arteries

The effects of human urotensin II on coronary flow were studied in the perfused rat heart. Urotensin II transiently decreased coronary flow, then induced sustained vasodilatation. In the presence of a cyclooxygenase inhibitor, diclofenac, coronary vasodilatation was significantly inhibited. A nitric oxide synthase inhibitor, N(G)-nitro-L-arginine (L-NNA), attenuated the urotensin-induced vasodilatation. These data suggest that urotensin II modulates coronary flow through factors such as cyclooxygenase products and nitric oxide to elicit coronary vasodilatation.

Central CRF inhibits gastric emptying of a nutrient solid meal in rats: the role of CRF2 receptors

Corticotropin-releasing factor (CRF)-related peptides exhibit different affinity for the receptor subtypes 1 and 2 cloned in the rat brain. We investigated, in conscious rats, the effects of intracisternal (i.c.) injection of CRF (rat/human) on the 5-h rate of gastric emptying of a solid nutrient meal (Purina chow and water ad libitum for 3 h) and the CRF receptor subtype involved. CRF, urotensin I (suckerfish), and sauvagine (frog) injected i.c. inhibited gastric emptying in a dose-dependent manner, with ED50 values of 0.31, 0.13, and 0.08 microgram/rat, respectively. Rat CRF-(6-33) (0.1-10 micrograms i.c.) had no effect. The nonselective CRF1 and CRF2 receptor antagonist, astressin, injected i.c. completely blocked the inhibitory effect of i.c. CRF, urotensin I, and sauvagine with antagonist-to-agonist ratios of 3:1, 10:1, and 16:1, respectively. The CRF1-selective receptor antagonist NBI-27914 injected i.c. at a ratio of 170:1 had no effect. These data show that central CRF and CRF-related peptides are potent inhibitors of gastric emptying of a solid meal with a rank order of potency characteristic of the CRF2 receptor subtype affinity (sauvagine > urotensin I > CRF). In addition, the reversal by astressin but not by the CRF1-selective receptor antagonist further supports the view that the CRF2 receptor subtype is primarily involved in central CRF-induced delayed gastric emptying.

Inhibition of CRF- and urotensin I-stimulated ACTH release from goldfish pituitary cell columns by the CRF analogue alpha-helical CRF-(9-41)

alpha-Helical CRF-(9-41) is an analogue of corticotropin-releasing factor (CRF) that antagonizes CRF-stimulated ACTH release in rats. In the present study, alpha-helical CRF-(9-41) was tested to determine whether it would antagonize the ACTH-releasing activity of CRF or urotensin I (UI) observed with superfused, dispersed goldfish anterior pituitary cells. At a concentration of 4 microM, alpha-helical CRF-(9-41) completely blocked the ACTH-releasing activity of 100 nM CRF or 100 nM UI. The inhibitor by itself showed little intrinsic ACTH-releasing activity. This investigation reveals similarities in the CRF-antagonism of alpha-helical CRF-(9-41) in the teleost and mammalian pituitary in vitro. It also provides are similar and suggests that alpha-helical CRF-(9-41) may be useful as a tool to investigate the effects of CRF-like and UI-like peptides in teleost fishes.

Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis

The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.

Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis

The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.