Urotensin II and urantide exert opposite effects on the cellular components of atherosclerotic plaque in hypercholesterolemic rabbits.

Increasing levels of plasma urotensin II (UII) are positively associated with atherosclerosis. In this study we investigated the role of macrophage-secreted UII in atherosclerosis progression, and evaluated the therapeutic value of urantide, a potent competitive UII receptor antagonist, in atherosclerosis treatment. Macrophage-specific human UII-transgenic rabbits and their nontransgenic littermates were fed a high cholesterol diet for 16 weeks to induce atherosclerosis. Immunohistochemical staining of the cellular components (macrophages and smooth muscle cells) of aortic atherosclerotic lesions revealed a significant increase (52%) in the macrophage-positive area in only male transgenic rabbits compared with that in the nontransgenic littermates. However, both male and female transgenic rabbits showed a significant decrease (45% in males and 31% in females) in the smooth muscle cell-positive area compared with that of their control littermates. The effects of macrophage-secreted UII on the plaque cellular components were independent of plasma lipid level. Meanwhile the wild-type rabbits were continuously subcutaneously infused with urantide (5.4 µg· kg-1· h-1) using osmotic mini-pumps. Infusion of urantide exerted effects opposite to those caused by UII, as it significantly decreased the macrophage-positive area in male wild-type rabbits compared with that of control rabbits. In cultured human umbilical vein endothelial cells, treatment with UII dose-dependently increased the expression of the adhesion molecules VCAM-1 and ICAM-1, and this effect was partially reversed by urantide. The current study provides direct evidence that macrophage-secreted UII plays a key role in atherogenesis. Targeting UII with urantide may promote plaque stability by decreasing macrophage-derived foam cell formation, which is an indicator of unstable plaque.

Potent cardiovascular effects of homologous urotensin II (UII)-related peptide and UII in unanesthetized eels after peripheral and central injections.

We cloned cDNAs encoding urotensin II (UII)-related peptide (URP) and UII in Japanese eel, Anguilla japonica, the former being the first such cloning in teleost fishes. Unlike the exclusive expression of UII in the urophysis, the URP gene was expressed most abundantly in the brain (medulla oblongata) followed by the urophysis. Peripheral injections of URP into eels increased blood pressure by 16.1 ± 0.8 mmHg at 0.1 nmol/kg in ventral aortic blood pressure (P(VA)) and with similar potency and efficacy to that of UII (relative potency of URP to UII = 0.83). URP/UII and ANG II preferentially acted on the branchial and systemic circulations, respectively, and the duration of effect was distinct among the three peptides in the order of UII (60 min) >URP (30 min) >ANG II (14 min) in P(VA). Urantide, a mammalian UII receptor antagonist, inhibited the URP effect (-63.6 ± 5.2%) to a greater extent than for UII (-39.9 ± 5.0%). URP and UII constricted isolated eel branchial and systemic arteries, showing their direct actions on the vascular smooth muscle. Central injection of URP increased blood pressure by 12.3 ± 0.8 mmHg at 50 pmol/eel in P(VA) and with similar efficacy but less potency (relative potency = 0.47) and shorter duration compared with UII. The central actions of URP/UII were more potent on the branchial circulation than on the systemic circulation, again opposite the effects of ANG II. The similar responses to peripheral and central injections suggest that peripheral hormones may act on the brain. Taken together, in eels, URP and UII are potent cardiovascular hormones like ANG II, acting directly on the peripheral vasculature, as well as a central vasomotor site, and their actions are mediated to different degrees by the UII receptor.

Chronic urotensin-II infusion induces diastolic dysfunction and enhances collagen production in rats.

The vasoactive peptide urotensin-II (U-II) is likely to play a key causal role in cardiac remodeling that ultimately leads to heart failure. Its contribution, specifically to the development of diastolic dysfunction and the downstream intracellular signaling, however, remains unresolved. This study interrogates the effect of chronic U-II infusion in normal rats on cardiac structure and function. The contribution of Rho kinase (ROCK) signaling to these pathophysiological changes is evaluated in cell culture studies. Chronic high-dose U-II infusion over 4 wk significantly impaired diastolic function in rats on echocardiography-derived Doppler indexes, including E-wave deceleration time (vehicle 56.7 +/- 3.3 ms, U-II 118.0 +/- 21.5 ms; P < 0.01) and mitral valve annulus peak early/late diastolic tissue velocity (vehicle 2.01 +/- 0.19 ms, U-II 1.04 +/- 0.25 ms; P < 0.01). A lower dose of U-II infusion (1 nmol.kg(-1).h(-1)) yielded comparable changes. Diastolic dysfunction was accompanied by molecular [significant increases in procollagen-alpha(1)(I) gene expression on real-time PCR] and morphological (increases in total collagen, P < 0.05, and collagen type-I protein deposition, P < 0.001) evidence of left ventricular (LV) fibrosis following high-dose U-II infusion. The ROCK inhibitor GSK-576371 (10(-7) to 10(-5) M) elicited concentration-dependent inhibition of U-II (10(-7) M)-stimulated cardiac fibroblast collagen synthesis and cardiac myocyte protein synthesis. Chronic U-II infusion causes diastolic dysfunction, caused by fibrosis of the LV. The in vitro data suggest that this may be in part occurring via a ROCK-dependent pathway.

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.

Effects of exogenous urotensin II on vascular remodelling after balloon injury.

1. Urotensin II (U-II) is a powerful vasoconstrictor peptide that stimulates cell proliferation. However, the systemic effects of U-II on cellular and extracellular matrix responses of vessel walls have not been investigated. The aim of the present study was to determine the effect of exogenous U-II on arterial neointimal hyperplasia after balloon injury. 2. A stenosis model of the thoracic aorta after balloon injury was established in male Wistar rats. Rats were divided into three groups (n = 5 in each): (i) uninjured; (ii) injured for 21 days; and (iii) injured and then treated with U-II (1 nmol/kg per h) via an osmotic minipump for 21 days. Another group of rats were killed on Days 7 and 14 after balloon injury for the analysis of in vitro collagen synthesis and secretion with U-II treated by [(3)H]-proline incorporation and determination of [(3)H]-hydroxyproline radioactivity, respectively. 3. Urotensin II immunoreactivity was 1.74-fold higher in vessels injured for 21 days than in uninjured vessels and mRNA levels of the urotensin UT receptor were upregulated by 55% following injury. After U-II treatment, the mRNA levels of the UT receptor were further upregulated (by 40%). In addition, U-II treatment increased the intimal area of injured aortas (13 +/- 5 vs 7 +/- 2% in group iii and ii, respectively), as well as increasing collagen content and cell proliferation. Protein levels of matrix metalloproteinase 1 were decreased in U-II-treated rats. In vitro, U-II treatment increased collagen synthesis and secretion in uninjured vessels in a concentration-dependent manner (10(-10), 10(-9) and 10(-8) mol/L U-II), especially in injured aortas on Day 7 after injury. 4. In conclusion, exogenous U-II may upregulate mRNA levels of the UT receptor, as well as increase collagen and cell proliferation, all of which would contribute to intimal hyperplasia after angioplasty.

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.

Microinjection of urotensin II into the pedunculopontine tegmentum leads to an increase in the consumption of sweet tastants.

The pedunculopontine tegmentum (PPTg) plays a role in processing multiple sensory inputs and innervates brain regions associated with reward-related behaviors. The urotensin II receptor, activated by the urotensin II peptide (UII), is selectively expressed by the cholinergic neurons of the PPTg. Although the exact function of cholinergic neurons of the PPTg is unknown, they are thought to contribute to the perception of reward magnitude or salience detection. We hypothesized that the activation of PPTg cholinergic neurons would alter sensory processing across multiple modalities (ex. taste and hearing). Here we had three aims: first, determine if cholinergic activation is involved in consumption behavior of palatable solutions (sucrose). Second, if so, distinguish the impact of the caloric value by using saccharin, a zero calorie sweetener. Lastly, we tested the UII-mediated effects on perception of acoustic stimuli by measuring acoustic startle reflex (ASR). Male Sprague-Dawley rats were bilaterally cannulated into the PPTg, then placed under food restriction lasting the entire consumption experiment (water ad lib.). Treatment consisted of a microinjection of either 1 µL of aCSF or 1 µL of 10 µM UII into the PPTg, and the rats were immediately given access to either sucrose or saccharin. For the remaining five days, rats were allowed one hour access per day to the same sweet solution without any further treatments. During the saccharin experiment rats were tested in a contact lickometer which recorded each individual lick to give insight into the microstructure of the consumption behavior. ASR testing consisted of a baseline (no treatment), treatment day, and two additional days (no treatment). Immediately following the microinjection of UII, consumption of both saccharin and sucrose increased compared to controls. This significant increase persisted for days after the single administration of UII, but there was no generalized arousal or increase in water consumption between testing sessions. The effects on ASR were not significant. Activating cholinergic PPTg neurons may lead to a miscalculation of the salience of external stimuli, implicating the importance of cholinergic input in modulating a variety of behaviors. The long-lasting effects seen after UII treatment support further research into the role of sensory processing on reward related-behaviors at the level of the PPTg cholinergic neurons.

Microinjection of urotensin II into the rostral ventrolateral medulla increases sympathetic vasomotor tone via the GPR14/ERK pathway in rats.

The present study aimed to reveal the effects of urotensin II (UII) on sympathetic vasomotor tone in the rostral ventrolateral medulla (RVLM). UII (0.3, 3, and 30 nmol/L, 50 nL) was microinjected into the RVLM. Blood pressure (BP), heart rate (HR), and renal sympathetic nerve activity (RSNA) were measured to determine the sympathetic vasomotor tone. BP, HR, and RSNA were simultaneously recorded after drugs had been microinjected into the RVLM. Microinjection of UII (0.3, 3, and 30 nmol/L, 50 nL) into the RVLM significantly increased BP, HR, and RSNA. Pretreatment with BIM23127 (300 nmol/L, 50 nL), a potent antagonist of the UII receptor GPR14, abolished the effect of UII. Previous microinjection of PD98059 (25 µmol/L, 50 nL), an inhibitor of ERK, significantly suppressed the effects of UII. Preinjection of an inhibitor of the N-type Ca2+ channel, ω-conotoxin GVIA (50 nmol/L, 50 nL), inhibited the effects of UII. The present study demonstrated that microinjection of UII into the RVLM significantly increased sympathetic vasomotor tone, which was mediated by the GPR14/ERK/N-type Ca2+ channel pathway. UII may become a novel therapeutic target for autonomic nervous system regulation, especially in hypertension.

Urotensin II modulates hepatic fibrosis and portal hemodynamic alterations in rats.

The influence of circulating urotensin II (UII) on liver disease and portal hypertension is unknown. We aimed to evaluate whether UII executes a pathogenetic role in the development of hepatic fibrosis and portal hypertension. UII was administered by continuous infusion over 4 wk in 20 healthy rats divided into three treatment groups, controls (saline, n = 7), low dose (UII, 1 nmol x kg(-1) x h(-1), n = 8), and high dose (UII, 3 nmol x kg(-1) x h(-1), n = 5). Hemodynamic parameters and morphometric quantification of fibrosis were assessed, and profibrotic cytokines and fibrosis markers were assayed in hepatic tissue. UII induced a significant dose-dependent increase in portal venous pressure (5.8 +/- 0.4, 6.4 +/- 0.3, and 7.6 +/- 0.7, respectively, P = 0.03). High-dose UII infusion was associated with an increase in hepatic transcript for transforming growth factor-beta (P < 0.05) and platelet-derived growth factor-beta (P = 0.06). Liver tissue hydroxyproline was elevated in the high-dose group (P < 0.05). No systemic hemodynamic alterations were noted. We concluded that UII infusion elevates portal pressure and induces hepatic fibrosis in normal rats. This response may be mediated via induction of fibrogenic cytokines. These findings have pathophysiological implications in human liver disease where increased plasma UII levels have been observed.

The effects of urotensin II and urantide on forearm blood flow and systemic haemodynamics in humans.

AIMS: (i) To compare the effects of intra-arterial administration of urotensin II in patients with CVD with healthy volunteers, and (ii) to study the haemodynamic effects of intra-arterial infusion of the urotensin II receptor antagonist, urantide. METHODS: Ten healthy volunteers and 10 patients with CVD received a dose-ramped brachial artery infusion of urotensin II. A further six healthy male volunteers received a prolonged urotensin II infusion and 11 healthy male volunteers received a dose-ramped infusion of urantide. Forearm blood flow (FBF) was measured every 20 min and blood pressure and heart rate were assessed every 20 min. RESULTS: In healthy volunteers and patients with CVD, intra-arterial infusion of urotensin II had no effect on FBF ratio. A dose-ramped infusion of urantide similarly had no effect on FBF ratio. During dose-ramped infusions of urotensin II and urantide, systolic and mean arterial blood pressure increased significantly. In healthy volunteers, urotensin II and urantide, respectively, increased systolic blood pressure from 133 +/- 6 to 137 +/- 5 mmHg (P < 0.01) and from 113 +/- 4 to 120 +/- 4 mmHg (P < 0.01). In patients with CVD, heart rate also significantly increased during dose-ramped infusion of urotensin II from 59 +/- 3 to 62 +/- 4 bpm (P < 0.05). CONCLUSIONS: We have shown no in vivo effect of urotensin II or urantide on human forearm resistance vessels. Previous discrepancies do not seem to relate to either the age or CVD status of subjects. Changes in systemic cardiovascular haemodynamics during the dose-ramped infusion studies are unlikely to be caused by urotensin II receptor modulation.

Central hyperventilatory action of the stress-related neurohormonal peptides, corticotropin-releasing factor and urotensin-I in the trout Oncorhynchus mykiss.

The stress-related neurohormonal peptides corticotropin-releasing factor (CRF) and urotensin-I (U-I), an ortholog of mammalian urocortin 1, are widely distributed in the central nervous systems of teleost fish but little is known about their possible central neurotropic actions. In the present study, we investigated the effect of intracerebroventricular (ICV) injection of CRF and U-I (1-10pmol) on ventilatory and cardiovascular variables in our established unanaesthetized trout model. CRF and U-I produced a significant dose-dependent and long-lasting increase in the ventilatory frequency (VF) and the ventilatory amplitude (VA). Consequently the net effect of these peptides was a hyperventilatory response since the total ventilation (VTOT) was significantly elevated. However, CRF evoked a significant hyperventilatory response 5-10min sooner than that observed after ICV administration of U-I and the hyperventilatory effect of 10pmol CRF was twofold higher than that of equimolar dose of U-I. Pre-treatment of the trout with the antagonist, alpha-helical CRF(9-41), significantly reduced by about threefold the CRF-induced increase in VF, VA and VTOT. The most significant cardiovascular action of central CRF and U-I was to evoke a hypertensive response without changing the heart rate. Peripheral injection of CRF and U-I at doses of 5 and 50pmol produced no change in VF, VA or VTOT. Only a transient hypertensive response without change in heart rate was observed after the injection of the highest dose of U-I. Our results demonstrate that in a teleost fish, CRF and U-I produce a potent hyperventilatory response only when injected centrally. The two endogenous stress-related neuropeptides may play an important stimulatory role acting as neurotransmitters and/or neuromodulators in the central control of ventilatory apparatus during stress.

Effect of central urotensin II on heart rate, blood pressure and brain Fos immunoreactivity in conscious rats.

Central administration of urotensin II (UII) increases heart rate (HR), cardiac contractility, and plasma levels of epinephrine and glucose. To investigate the mechanisms causing these responses we examined the effects of i.c.v. administration of rat UII (10 microg) on the sympatho-adrenal and pituitary-adrenal axes in conscious rats, and we mapped the brain sites activated by UII by immunohistochemically detecting Fos expression. In six conscious rats i.c.v. UII, but not vehicle, increased HR significantly 60-90 min after treatment and increased plasma glucose at 60 and 90 min, both indicators of increased epinephrine release. Plasma corticosterone levels were significantly elevated 90 min after i.c.v. UII. Conscious rats, given i.c.v. UII (n=12) and killed after 100 or 160 min, showed increased Fos-immunoreactivity (Fos-IR) in the nucleus of the solitary tract and the central nucleus of the amygdala (CeA) at both time points, compared with vehicle (n=11). In UII-treated rats, Fos-IR in the paraventricular nucleus of the hypothalamus (PVN) was significantly elevated at 160 min, but not 100 min, compared with vehicle. There were no increases in Fos-IR in the rostral ventrolateral medulla or the A5 cell group, areas associated with sympathetic outflow to the adrenal gland. In summary, i.c.v. UII increased HR and plasma glucose and corticosterone in conscious rats. UII increased Fos-IR in the CeA and PVN, but over a longer time course in the latter. These findings indicate that UII acts on specific brain nuclei to stimulate the hypothalamo-pituitary-adrenal axis and to stimulate adrenal sympathetic nerve activity.

PPAR-gamma expression in animals subjected to volume overload and chronic Urotensin II administration.

Activation of PPAR-gamma through the administration of glitazones has shown promise in preserving function following cardiac injury, although recent evidence has suggested their use may be contraindicated in the case of severe heart failure. This study tested the hypothesis that PPAR-gamma expression increases in a time dependent manner in response to chronic volume overload (VO) induced heart failure. Additionally, we attempted to determine what effect 4 week administration of Urotensin II (UTII) may have on PPAR-gamma expression. VO induced heart failure was produced in Sprague-Dawley rats (n=32) by aorta-caval fistula. Animals were sacrificed at 1, 4, and 14 weeks following shunt creation. In a separate set of experiments, animals were administered 300 pmol/kg/h of UTII for 4 weeks, subjected to 4 weeks of volume overload, or given UTII+VO. Densitometric analysis of left ventricular (LV) protein demonstrated PPAR-gamma expression was significantly ((*)p<0.05) upregulated at 4 and 14 weeks (31.5% and 37%, respectively) post-fistula formation compared to control values. PPAR-gamma activation was decreased in the 4 and 14 week (39.16% and 42.4%, respectively), but not in the 1-week animals, and these changes did not correlate with NF-kappaB activity. Animals given UTII either with or without VO demonstrated increased expression of PPAR-gamma as did animals subjected to 4 week VO alone. Animals given UTII either with or without VO had decreased activity vs. control. These data suggest PPAR-gamma may play a role in the progression of heart failure, however, the exact nature has yet to be determined.

Hemodynamic-independent anti-natriuretic effect of urotensin II in spontaneously hypertensive rats.

The present study aims to test the hypothesis that U-II might have a direct anti-natriuretic action in spontaneously hypertensive rats (SHR). Bolus U-II injection (15 nmol kg(-1)) caused a transient decrease in glomerular filtration rate (GFR), urine flow rate (UV), urinary sodium (UNaV) and potassium excretion (U(K)V) that corresponded with a committed decrease in mean arterial pressure (MAP) and renal blood flow (RBF) during the first 30 min. Continuous U-II infusion (0.2 nmol kg(-1)h(-1)) following a bolus U-II injection (0.3 nmol kg(-1)) caused an anti-natriuretic effect without any significant change in MAP, RBF, GFR, UV and UKV during the entire 1.5-h perfusion period in SHR. The levels of aldosterone and angiotensin II were not altered in the plasma and kidney, while plasma antidiuretic hormone decreased in response to U-II injection (15 nmol kg(-1)). Protein levels of U-II receptors (UT) were significantly increased in the kidney of 17-week-old SHR when compared with the age-matched WKY rats, while mRNA transcripts of both U-II and UT were increased in the kidney, left ventricle and thoracic aorta. In conclusion, U-II exerts a hemodynamic-independent anti-natriuretic action in adult SHR. The anti-natriuretic action of U-II in SHR is probably associated with an increased expression of the U-II-UT system in the kidney, suggesting a potential renal role of U-II in the pathogenesis of hypertension.

Effect of urotensin II on skin microvessel tone in diabetic patients without heart failure or essential hypertension.

Urotensin II (UII) is a potent vasoconstrictor peptide. Increased plasma levels and kidney expression of UII and its receptor have been observed in diabetes mellitus (DM). The aim of the present study was to evaluate the direct effect of exogenous UII on microvascular tone in DM patients compared with healthy controls. Vasoactive effect of UII (10(-12), 10(-9) and 10(-7) mol/L) on skin microvascular tone was evaluated in 12 controls and 12 DM patients (Type 1 or Type 2) without concomitant heart failure or essential hypertension using the non-invasive technique of iontophoresis and laser Doppler velocimetry. In addition, responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were evaluated. Urotensin II dose-dependently dilated skin microvasculature in control subjects (-51.8 +/- 59.4, 138.6 +/- 101.5, 204.2 +/- 115.7 and 207.5 +/- 81.6 arbitrary flux units (AFUs) for MilliQ and 10(-12), 10(-9) and 10(-7) mol/L UII, respectively) and dose-dependently vasoconstricted the microvasculature in DM patients (100.8 +/- 81.2, 46.2 +/- 85.1, 35.4 +/- 81.4 and 26.6 +/- 79.6 AFUs for MilliQ and 10(-12), 10(-9) and 10(-7) mol/L UII, respectively). Blood flow in control subjects and DM patients was differed significantly, with pair-wise comparisons indicating differences for 10(-9) and 10(-7) mol/L UII (P = 0.04 and P = 0.003). Results of blood flow in diet-controlled DM patients (204.7 +/- 193.6, 261.2 +/- 212.8, 256.1 +/- 202.9 and 233.7 +/- 115.9 AFUs for MilliQ and 10(-12), 10(-9) and 10(-7) mol/L UII, respectively) were similar to those in control subjects compared with results for DM patients receiving antidiabetic medication (48.8 + 80.0, -61.4 +/- 49.1, -75.0 +/- 40.0, -91.7 +/- 80.0 AFUs for MilliQ and 10(-12), 10(-9) and 10(-7) mol/L UII, respectively). Between-group significance remained after adjustment for baseline blood pressure values. Acetylcholine vasodilator responses were attenuated in DM patients compared with those in control subjects (1309.5 +/- 488.6 vs 3498.0 +/- 912.5 AFUs, respectively), whereas SNP responses were similar in the two groups (1467.9 +/- 411.3 vs 1984.4 +/- 410.7 AFUs, respectively). In conclusion, UII causes net vasoconstriction in DM. The UII-induced increases in peripheral vascular tone may contribute to DM-related cardiovascular complications.

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.

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

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

The effects of urotensin II on migration and invasion are mediated by NADPH oxidase-derived reactive oxygen species through the c-Jun N-terminal kinase pathway in human hepatoma cells.

AIMS: Urotensin II (UII) is a vasoactive neuropeptide involved in migration and invasion in various cell types. However, the effects of UII on human hepatoma cells still remain unclear. The aim of this study was to investigate the role and mechanism of UII on migration and invasion in human hepatoma cells. METHODS: Migration was measured by wound healing assays and a Transwell® methodology, and invasion was analyzed using Matrigel® invasion chambers. Reactive oxygen species (ROS) levels were detected using a 2', 7'-dichlorofluorescein diacetate probe, and flow cytometry, and protein expression levels were evaluated by western blotting. Cell proliferation and actin polymerization were examined using cell proliferation reagent WST-1 and F-actin immunohistochemistry staining. RESULTS: Exposure to UII promoted migration and invasion in hepatoma cells compared with that in cells without UII. UII also increased matrix metalloproteinase-2 (MMP2) expression in a time-independent manner. Furthermore, UII markedly enhanced ROS generation and NADPH oxidase subunit expression, and consequently facilitated the phosphorylation of c-Jun N-terminal kinase (JNK). The UT antagonist urantide or the antioxidant/NADPH oxidase inhibitor apocynin decreased UII-induced ROS production. JNK phosphorylation, migration, invasion, and MMP9/2 expression were also reversed by pretreatment with apocynin. Urantide and JNK inhibitor SP600125 abrogated migration, invasion, or MMP9/2 expression in response to UII. UII induced actin polymerization and fascin protein expression, and could be reversed by apocynin and SP600125. CONCLUSIONS: Exogenous UII induced migration and invasion in hepatoma cells that mainly involved NADPH oxidase-derived ROS through JNK activation. UT played an additional role in regulating hepatoma cells migration and invasion. Thus, our data suggested an important effect of UII in hepatocellular carcinoma metastasis.

Regional heterogeneity in the haemodynamic responses to urotensin II infusion in relation to UT receptor localisation.

The aim of the study was to measure regional haemodynamic responses to 6 h infusions of human urotensin II (hUII), to identify possible mediators of the effects observed, and to relate the findings to the distribution of urotensin II receptors (UT receptors). Male, Sprague-Dawley rats had pulsed Doppler flow probes and intravascular catheters implanted for measurement of regional haemodynamics in the conscious, freely moving state. Infusions of saline (0.4 ml h(-1)) or hUII (30, 300 and 3,000 pmol kg(-1) h(-1)) were given i.v. for 6 h, and the effects of pretreatment with indomethacin (5 mg kg(-1) h(-1)), N(G)-nitro-L-arginine methyl ester (L-NAME, 3 mg kg(-1) h(-1)) or propranolol (1 mg kg(-1); 0.5 mg kg(-1) h(-1)) on responses to hUII (300 pmol kg(-1) h(-1) for 6 h) were assessed. Cellular localisation of UT receptor-like immunoreactivity was determined in relevant tissues. hUII caused dose-dependent tachycardia and hindquarters vasodilatation, accompanied by a slowly developing rise in blood pressure. Haemodynamic effects of hUII were attenuated by propranolol or L-NAME and abolished by indomethacin. UT receptor-like immunoreactivity was detected in skeletal and vascular smooth muscle. The findings indicate that in conscious rats, infusions of hUII cause vasodilatation, which, of the vascular beds monitored, is selective for the hindquarters and dependent on cyclooxygenase products and nitric oxide. The pressor effect of hUII under these conditions is likely to be due to an increase in cardiac output, possibly due to a positive inotropic effect. UT receptor-like immunoreactivity present in skeletal muscle is consistent with the haemodynamic pattern.

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.