Urotensin II causes fatal circulatory collapse in anesthesized monkeys in vivo: a “vasoconstrictor” with a unique hemodynamic profile

Urotensin II system in chronic kidney disease

Chronic kidney disease (CKD) is a progressive and long-term condition marked by a gradual decline in kidney function. CKD is prevalent among those with conditions such as diabetes mellitus, hypertension, and glomerulonephritis. Affecting over 10% of the global population, CKD stands as a significant cause of morbidity and mortality. Despite substantial advances in understanding CKD pathophysiology and management, there is still a need to explore novel mechanisms and potential therapeutic targets. Urotensin II (UII), a potent vasoactive peptide, has garnered attention for its possible role in the development and progression of CKD. The UII system consists of endogenous ligands UII and UII-related peptide (URP) and their receptor, UT. URP pathophysiology is understudied, but alterations in tissue expression levels of UII and UT and blood or urinary UII concentrations have been linked to cardiovascular and kidney dysfunctions, including systemic hypertension, chronic heart failure, glomerulonephritis, and diabetes. UII gene polymorphisms are associated with increased risk of diabetes. Pharmacological inhibition or genetic ablation of UT mitigated kidney and cardiovascular disease in rodents, making the UII system a potential target for slowing CKD progression. However, a deeper understanding of the UII system's cellular mechanisms in renal and extrarenal organs is essential for comprehending its role in CKD pathophysiology. This review explores the evolving connections between the UII system and CKD, addressing potential mechanisms, therapeutic implications, controversies, and unexplored concepts.

Potential Therapeutic Value of Urotensin II Receptor Antagonist in Chronic Kidney Disease and Associated Comorbidities

Chronic kidney disease (CKD) remains a common disorder, leading to growing health and economic burden without curative treatment. In diabetic patients, CKD may result from a combination of metabolic and nonmetabolic-related factors, with mortality mainly driven by cardiovascular events. The marked overactivity of the urotensinergic system in diabetic patients implicates this vasoactive peptide as a possible contributor to the pathogenesis of renal as well as heart failure. Previous preclinical studies with urotensin II (UII) antagonists in chronic kidney disease were based on simple end points that did not reflect the complex etiology of the disease. Given this, our studies revisited the therapeutic value of UII antagonism in CKD and extensively characterized 1-({[6-{4-chloro-3-[3-(dimethylamino)propoxy]phenyl}-5-(2-methylphenyl)pyridin-2-yl]carbonyl}amino) cyclohexanecarboxylic acid hydrochloride (SAR101099), a potent, selective, and orally long-acting UII receptor competitive antagonist, inhibiting not only UII but also urotensin-related peptide activities. SR101099 treatment more than halved proteinurea and albumin/creatinine ratio in spontaneously hypertensive stroke-prone (SHR-SP) rats fed with salt/fat diet and Dahl-salt-sensitive rats, respectively, and it halved albuminuria in streptozotocin-induced diabetes rats. Importantly, these effects were accompanied by a decrease in mortality of 50% in SHR-SP and of 35% in the Dahl salt-sensitive rats. SAR101099 was also active on CKD-related cardiovascular pathologies and partly preserved contractile reserve in models of heart failure induced by myocardial infarction or ischemia/reperfusion in rats and pigs, respectively. SAR101099 exhibited a good safety/tolerability profile at all tested doses in clinical phase-I studies. Together, these data suggest that CKD patient selection considering comorbidities together with new stratification modalities should unveil the urotensin antagonists' therapeutic potential. SIGNIFICANCE STATEMENT: Chronic kidney disease (CKD) is a pathology with growing health and economic burden, without curative treatment. For years, the impact of urotensin II receptor (UT) antagonism to treat CKD may have been compromised by available tools or models to deeper characterize the urotensinergic system. New potent, selective, orally long-acting cross-species UT antagonist such as SAR101099 exerting reno- and cardioprotective effects could offer novel therapeutic opportunities. Its preclinical and clinical results suggest that UT antagonism remains an attractive target in CKD on top of current standard of care.

Urotensin II Exerts Pressor Effects By Stimulating Renin And Aldosterone Synthase Gene Expression

We investigated the in vivo pressor effects of the potent vasoconstrictor Urotensin II (UII). We randomized normotensive Sprague-Dawley rats into 4 groups that received a 7-day UII infusion (cases) or vehicle (controls). Group 1 received normal sodium intake; Group 2 underwent unilateral nephrectomy and salt loading; Group 3 received spironolactone, besides unilateral nephrectomy and salt loading; Group 4 only received spironolactone. UII raised BP transiently after a lag phase of 12-36 hours in Group 1, and progressively over the week in Group 2. Spironolactone did not affect blood pressure, but abolished both pressor effects of UII in Group 3, and left blood pressure unaffected in Group 4. UII increased by 7-fold the renal expression of renin in Group 2, increased aldosterone synthase expression in the adrenocortical zona glomerulosa, and prevented the blunting of renin expression induced by high salt. UII raises BP transiently when sodium intake and renal function are normal, but progressively in salt-loaded uninephrectomized rats. Moreover, it increases aldosterone synthase and counteracts the suppression of renin induced by salt loading. This novel action of UII in the regulation of renin and aldosterone synthesis could play a role in several clinical conditions where UII levels are up-regulated.

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.

Knockout of p21-activated kinase-1 attenuates exercise-induced cardiac remodelling through altered calcineurin signalling

AIMS

Despite its known cardiovascular benefits, the intracellular signalling mechanisms underlying physiological cardiac growth remain poorly understood. Therefore, the purpose of this study was to investigate a novel role of p21-activated kinase-1 (Pak1) in the regulation of exercise-induced cardiac hypertrophy.

METHODS AND RESULTS

Wild-type (WT) and Pak1 KO mice were subjected to 6 weeks of treadmill endurance exercise training (ex-training). Cardiac function was assessed via echocardiography, in situ haemodynamics, and the pCa-force relations in skinned fibre preparations at baseline and at the end of the training regimen. Post-translational modifications to the sarcomeric proteins and expression levels of calcium-regulating proteins were also assessed following ex-training. Heart weight/tibia length and echocardiography data revealed that there was marked hypertrophy following ex-training in the WT mice, which was not evident in the KO mice. Additionally, following ex-training, WT mice demonstrated an increase in cardiac contractility, myofilament calcium sensitivity, and phosphorylation of cardiac myosin-binding protein C, cardiac TnT, and tropomyosin compared with KO mice. With ex-training in WT mice, there were also increased protein levels of calcineurin and increased phosphorylation of phospholamban.

CONCLUSIONS

Our data suggest that Pak1 is essential for adaptive physiological cardiac remodelling and support previous evidence that demonstrates Pak1 signalling is important for cardiac growth and survival.

Pregnancy as a cardiac stress model

Cardiac hypertrophy occurs during pregnancy as a consequence of both volume overload and hormonal changes. Both pregnancy- and exercise-induced cardiac hypertrophy are generally thought to be similar and physiological. Despite the fact that there are shared transcriptional responses in both forms of cardiac adaptation, pregnancy results in a distinct signature of gene expression in the heart. In some cases, however, pregnancy can induce adverse cardiac events in previously healthy women without any known cardiovascular disease. Peripartum cardiomyopathy is the leading cause of non-obstetric mortality during pregnancy. To understand how pregnancy can cause heart disease, it is first important to understand cardiac adaptation during normal pregnancy. This review provides an overview of the cardiac consequences of pregnancy, including haemodynamic, functional, structural, and morphological adaptations, as well as molecular phenotypes. In addition, this review describes the signalling pathways responsible for pregnancy-induced cardiac hypertrophy and angiogenesis. We also compare and contrast cardiac adaptation in response to disease, exercise, and pregnancy. The comparisons of these settings of cardiac hypertrophy provide insight into pregnancy-associated cardiac adaptation.

Moderate intensity, but not high intensity, treadmill exercise training alters power output properties in myocardium from aged rats

Aging is characterized by a progressive decline in cardiac function, but endurance exercise training has been shown to retard a number of deleterious effects of aging. However, underlying mechanisms by which exercise training improves age-related decrements in myocardial contractile function are not well understood. The purpose of this study was to determine the effects of exercise training on power output properties in permeablized (skinned) myocytes of old rats. Thirty-month-old rats were divided into sedentary control (C) and groups undergoing 11 weeks of treadmill exercise training at moderate intensity (MI) and at high intensity (HI). Peak power output normalized to maximal force was significantly increased in MI but not in HI compared to C with significant increases in atrial myosin light chain 1 in ventricle. These results suggest that MI exercise training is beneficial as a significant increase was seen in the ability of the myocardium to do work, but this effect was not seen with HI training.

Role of urotensin II in health and disease

Urotensin II (UII) is an 11 amino acid cyclic peptide originally isolated from the goby fish. The amino acid sequence of UII is exceptionally conserved across most vertebrate taxa, sharing structural similarity to somatostatin. UII binds to a class of G protein-coupled receptor known as GPR14 or the urotensin receptor (UT). UII and its receptor, UT, are widely expressed throughout the cardiovascular, pulmonary, central nervous, renal, and metabolic systems. UII is generally agreed to be the most potent endogenous vasoconstrictor discovered to date. Its physiological mechanisms are similar in some ways to other potent mediators, such as endothelin-1. For example, both compounds elicit a strong vascular smooth muscle-dependent vasoconstriction via Ca2+ release. UII also exerts a wide range of actions in other systems, such as proliferation of vascular smooth muscle cells, fibroblasts, and cancer cells. It also 1) enhances foam cell formation, chemotaxis of inflammatory cells, and inotropic and hypertrophic effects on heart muscle; 2) inhibits insulin release, modulates glomerular filtration, and release of catecholamines; and 3) may help regulate food intake and the sleep cycle. Elevated plasma levels of UII and increased levels of UII and UT expression have been demonstrated in numerous diseased conditions, including hypertension, atherosclerosis, heart failure, pulmonary hypertension, diabetes, renal failure, and the metabolic syndrome. Indeed, some of these reports suggest that UII is a marker of disease activity. As such, the UT receptor is emerging as a promising target for therapeutic intervention. Here, a concise review is given on the vast physiologic and pathologic roles of UII.

NaCl plus chitosan as a dietary salt to prevent the development of hypertension in spontaneously hypertensive rats

The effect of NaCl plus 3% chitosan on the systolic blood pressure of spontaneously hypertensive rats (SHR) were evaluated and compared with NaCl plus KCl (NaCl, 49.36% + KCl 49.36%) and chitosan or NaCl treatment alone. In SHR, administration of NaCl plus chitosan (44 mM Na/day) for two months significantly decreased the systolic blood pressure greater than of NaCl plus KCl and NaCl alone. NaCl plus chitosan resulted, though not statistically significant, in decreased urinary Na⁺ excretion and decreased blood urea nitrogen levels. Urinary creatinine of NaCl plus chitosan was slightly decreased compared to 3 treated groups. Serum electrolytes levels, however, remained unchanged. The combination of NaCl and chitosan may be superior to the conventional use of NaCl plus KCl or NaCl alone in the prevention of hypertension. Even though these supplementary diets have demonstrated potential anti-hypertensive effects in the experimental animal model, further research is needed before any recommendations can be made.

Urotensin II: a new pharmacologic target in the treatment of cardiovascular disease

Urotensin II was first identified over 30 years ago as a potent vasoconstrictor, and the identification of its receptor in the heart, lungs, blood vessels, and brain have made it a potential target for human pharmacotherapy. Current research would suggest that urotensin II plays a major role in the pathophysiology of various cardiovascular disease entities. This article discusses the biologic effects of urotensin under normal and pathophysiologic conditions, and reviews the research experiences with synthetic urotensin blockers in the treatment of various cardiovascular illnesses.

Urotensin II and urotensin II-related peptide (URP) in cardiac ischemia-reperfusion injury

Circulating urotensin II (UII) concentrations and the tissue expression of its cognate receptor (UT) are elevated in patients with cardiovascular disease (CVD). The functional significance of elevated plasma UII levels in CVD is unclear. Urotensin-related peptide (URP) is a paralog of UII in that it contains the six amino acid ring structures found in UII. Although both peptides are implicated as bioactive factors capable of modulating cardiovascular status, the role of both UII and URP in ischemic injury is unknown. Accordingly, we provide here the first report describing the direct cardiac effects of UII and URP in ischemia-reperfusion injury. Isolated perfused rat hearts were subjected to no-flow global ischemia for 45 min after 30min preconditioning with either 1nM rUII or 10nM URP. Both rUII- and URP-induced significant vasodilation of coronary arteries before (both P<0.05) and after ischemia (both P<0.05). Rat UII alone lowered contractility prior to ischemia (P=0.053). Specific assay of perfusate revealed rUII and URP both significantly inhibited reperfusion myocardial creatine kinase (CK) release (P=0.012 and 0.036, respectively) and atrial natriuretic peptide (ANP) secretion (P=0.025). Antagonism of the UT receptor with 1muM palosuran caused a significant increase in perfusion pressure (PP) prior to and post-ischemia. Furthermore, palosuran significantly inhibited reductions in both PP and myocardial damage marker release induced by both rUII and URP. In conclusion, our data suggests rUII and URP reduce cardiac ischemia-reperfusion injury by increasing flow through the coronary circulation, reducing contractility and therefore myocardial energy demand, and inhibiting reperfusion myocardial damage. Thus, UII and URP present as novel peptides with potential cardioprotective actions.

Cardiorenovascular effects of urotensin II and the relevance of the UT receptor

Urotensin II (U-II) is a vasoactive peptide with many potent effects in the cardiorenovascular system. U-II activates a G-protein-coupled receptor termed UT. UT and U-II are highly expressed in the cardiovascular and renal system. Patients with various cardiovascular diseases show high U-II plasma levels. It was demonstrated that elevated U-II plasma levels and increased UT expression seem to play a role in heart failure, end-stage renal disease and atherosclerosis. U-II induces potent changes in vascular tone regulation. In addition, U-II stimulates vascular smooth muscle cell proliferation and cardiomyocyte hypertrophy. Currently several pharmaceutical companies are developing compounds to control the U-II/UT system. There are preclinical and some clinical studies showing potential benefits of inhibiting U-II function in renal disease, heart failure, and diabetes. This article will review both pre- and clinical data concerning cardiorenovascular effects of U-II.

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.

The peptidic urotensin-II receptor ligand GSK248451 possesses less intrinsic activity than the low-efficacy partial agonists SB-710411 and urantide in native mammalian tissues and recombinant cell systems

Several peptidic urotensin-II (UT) receptor antagonists exert 'paradoxical' agonist activity in recombinant cell- and tissue-based bioassay systems, likely the result of differential urotensin-II receptor (UT receptor) signal transduction/coupling efficiency between assays. The present study has examined this phenomenon in mammalian arteries and recombinant UT-HEK (human embryonic kidney) cells.BacMam-mediated recombinant UT receptor upregulation in HEK cells augmented agonist activity for all four peptidic UT ligands studied. The nominal rank order of relative intrinsic efficacy was U-II>urantide ([Pen(5)-DTrp(7)-Orn(8)]hU-II(4-11))>SB-710411 (Cpa-c[DCys-Pal-DTrp-Lys-Val-Cys]-Cpa-amide)>>GSK248451 (Cin-c[DCys-Pal-DTrp-Orn-Val-Cys]-His-amide) (the relative coupling efficiency of recombinant HEK cells was cat>human>>rat UT receptor). The present study further demonstrated that the use of high signal transduction/coupling efficiency isolated blood vessel assays (primate>cat arteries) is required in order to characterize UT receptor antagonism thoroughly. This cannot be attained simply by using the rat isolated aorta, an artery with low signal transduction/coupling efficiency in which low-efficacy agonists appear to function as antagonists. In contrast to the 'low-efficacy agonists' urantide and SB-710411, GSK248451 functioned as a potent UT receptor antagonist in all native isolated tissues studied (UT receptor selectivity was confirmed in the rat aorta). Further, GSK248451 exhibited an extremely low level of relative intrinsic activity in recombinant HEK cells (4-5-fold less than seen with urantide). Since GSK248451 (1 mg kg(-1), i.v.) blocked the systemic pressor actions of exogenous U-II in the anaesthetized cat, it represents a suitable peptidic tool antagonist for delineating the role of U-II in the aetiology of mammalian cardiometabolic diseases.

Hydrogen sulfide and its possible roles in myocardial ischemia in experimental rats

The role of hydrogen sulfide (H(2)S) in myocardial infarction (MI) has not been previously studied. We therefore investigated the effect of H(2)S in a rat model of MI in vivo. Animals were randomly divided into three groups (n = 80) and received either vehicle, 14 micromol/kg of sodium hydrosulfide (NaHS), or 50 mg/kg propargylglycine (PAG) everyday for 1 wk before surgery, and the treatment was continued for a further 2 days after MI when the animals were killed. The mortality was 35% in vehicle-treated, 40% in PAG-treated, and 27.5% in NaHS-treated (P < 0.05 vs. vehicle) groups. Infarct size was 52.9 +/- 3.5% in vehicle-treated, 62.9 +/- 7.6% in PAG-treated, and 43.4 +/- 2.8% in NaHS-treated (P < 0.05 vs. vehicle) groups. Plasma H(2)S concentration was significantly increased after MI (59.2 +/- 7.16 microM) compared with the baseline concentration (i.e., 38.2 +/- 2.07 microM before MI; P < 0.05). Elevated plasma H(2)S after MI was abolished by treatment of animals with PAG (39.2 +/- 5.02 microM). We further showed for the first time cystathionine-gamma-lyase protein localization in the myocardium of the infarct area by using immunohistochemical staining. In the hypoxic vascular smooth muscle cells, we found that cell death was increased under the stimuli of hypoxia but that the increased cell death was attenuated by the pretreatment of NaHS (71 +/- 1.2% cell viability in hypoxic vehicle vs. 95 +/- 2.3% in nonhypoxic control; P < 0.05). In conclusion, endogenous H(2)S was cardioprotective in the rat model of MI. PAG reduced endogenous H(2)S production after MI by inhibiting cystathionine-gamma-lyase. The results suggest that H(2)S might provide a novel approach to the treatment of MI.

Proliferation and anti-apoptotic effects of human urotensin II on human endothelial cells

BACKGROUND

Human urotensin II (hU-II) is a potent vasoconstrictor, highly expressed in cardiac tissues and blood vessels. Recent studies indicate that hU-II participates in vascular and myocardial remodeling after injury. This study was designed to study the role of hU-II in cell DNA synthesis and apoptosis in human umbilical vein endothelial cells (HUVECs) and underlying intracellular signaling mechanisms.

METHODS AND RESULTS

Cultured HUVECs were incubated with hU-II (10(-10)-10(-8)M) for 24h. Cell DNA synthesis was examined by 3H thymidine incorporation. Apoptosis was detected by flow cytometry and TUNEL. hU-II increased the 3H thymidine incorporation into DNA in a concentration-dependent manner. hU-II inhibited endothelial apoptosis induced by serum withdrawal (5.74+/-0.64% versus 13.20+/-1.96%, P<0.01) and TNFalpha (6.76+/-0.70% versus 13.80+/-1.02%, P<0.01). The data from flow cytometry and TUNEL are consistent. Further studies showed that hU-II caused the phosphorylation of mitogen-activated protein kinasep42/44 (MAPKp42/44) in a concentration-dependent manner and this effect of hU-II was inhibited by pretreatment of cells with the MEK inhibitor (PD98059, 10muM). In addition, the use of PD98059 also attenuated 3H thymidine incorporation and anti-apoptotic effect elicited by hU-II (both P<0.01 versus hU-II alone).

CONCLUSIONS

Our observations provide evidence that hU-II promotes cell proliferation and inhibits apoptosis in HUVECs, and MAPKp42/44 activation may play a signal transduction role in this process.

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.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The in vivo effects of human urotensin II in the rabbit and rat pulmonary circulation: Effects of experimental pulmonary hypertension

In vivo haemodynamic responses to human urotensin-II were determined in two models of pulmonary hypertension: rabbits with left ventricular dysfunction following coronary artery ligation and the hypoxic rat. Effects were also examined in the presence of the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME). Human urotensin-II increased pulmonary arterial pressure to a greater extent in ligated rabbits than their controls and L-NAME increased pulmonary pressure without significantly affecting these responses to human urotensin-II. Human urotensin-II raised right ventricular pressure slightly in control rats but not in hypoxic rats. Human urotensin-II did not constrict control rat isolated small pulmonary arteries and only induced a small constriction of these vessels in hypoxic rats. In conclusion, exogenous human urotensin-II exerts pulmonary pressor responses in vivo in rabbits and also induced small pulmonary pressor responses in control rats. Pulmonary pressor responses to urotensin-II were increased by pulmonary hypertension in rabbits but not in rats.

Cell and tissue responses of a range of Urotensin II analogs at cloned and native urotensin II receptors. Evidence for coupling promiscuity

Urotensin II (U-II) is the peptide ligand for the G-protein-coupled U-II receptor (UT). U-II has been dubbed "the most potent vasoconstrictor identified to date". However, in vivo studies with this system are hampered by the paucity of available ligands. Here, we characterise Chinese hamster ovary (CHO) cells expressing the human UT receptor in the following assays; (1) [(125)I]U-II binding, (2) GTPgamma[(35)S] binding, (3) cAMP formation, and (4) intracellular Ca(2+). We assess activity of 9 U-II analogues using these paradigms and examine their ability to contract isolated rat aorta. CHO(hUT) cells bound [(125)I]U-II with a B (max) and K (d) of 1,110+/-70 fmol/mg protein and 742 pM, respectively. hU-II stimulated GTPgamma[(35)S] binding (pEC(50) 8.38), optimal at low (0.1 muM) GDP concentrations. The hU-II GTPgamma[(35)S] response was partially PTx sensitive and there was a potent (pEC(50) 9.23) low efficacy ( approximately 20% inhibition) coupling to adenylyl cyclase. In CHO(hUT) cells hU-II stimulates calcium release from intracellular stores (pEC(50) 8.80) and calcium influx in a PTx-insensitive manner. In our structure-activity relationship study most ligands acted as full agonists. However, urantide behaved as a partial agonist (pEC(50) 7.67/pK(B) 7.55) in GTPgamma[(35)S] binding, a full agonist (pEC(50) 8.11) for increases in intracellular Ca(2+) and a competitive antagonist in the rat aorta bioassay (pK(B) 8.59). Collectively, these data show promiscuity at high expression and indicate the need for careful multi-assay evaluation of novel U-II analogues. Further modification of urantide, in order to eliminate residual agonist activity and to identify novel ligands for in vivo cardiovascular studies are clearly warranted.

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

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

Cardioprotective effects of nitroparacetamol and paracetamol in acute phase of myocardial infarction in experimental rats

We aimed to determine whether nitroparacetamol (NO-paracetamol) and paracetamol exhibit cardioprotective effects. Myocardial infarction (MI) was induced in rats, and drug treatment was started 1 wk before surgery. Mortality rate and infarct size at 2 days after MI were compared. Treatment groups included vehicle (saline), paracetamol (5 mg x kg(-1) x day(-1)) and NO-paracetamol (15 mg x kg(-1) x day(-1)). Mortality rates for vehicle (n = 80), paracetamol (n = 79), and NO-paracetamol (n = 76) groups were 37.5%, 21.5%, and 26.3%, respectively. Infarct size for the vehicle group was 44.8% (+/-6.1%) of the left ventricle (LV). For the paracetamol and NO-paracetamol groups, infarct size was 31.3% (+/-5.6%) and 30.7% (+/-8.1%) of the LV, respectively. Both paracetamol- and NO-paracetamol-treated groups showed increased activities of catalase and SOD compared with the vehicle group. They could attenuate endothelial, inducible, and neuronal nitric oxide synthase and cyclooxygenase-1 and -2 gene expression after MI. The observation indicates the potential clinical significance of the cardioprotective effects of these drugs.

Myocardial Heat Shock Protein 70 Expression in Young and Old Rats After Identical Exercise Programs

Synthesis of inducible heat shock protein 70 (HSP70) is impaired in aged animals following acute stresses including exercise. In this study we determined whether aging affects expression of this cytoprotective protein following chronic exercise participation. Male Fischer 344 rats, final ages 6 and 24 months, exercised identically for 10 weeks on a treadmill (15 degrees incline, 15 m/min for up to 60 minutes, 5 days/week). In 6-month-old animals, exercise increased HSP70 in heart (44%), liver (216%), and skeletal muscle (126%) (p <.05 vs sedentary). In 24-month-old animals, exercise increased HSP70 in muscle (69%), but not in heart or liver. In heart, antioxidant enzyme activities and HSP70 messenger RNA were measured and found to be unaffected by exercise at both ages. Our results indicate an age-related decrease in HSP70 production in heart and liver following chronic exercise. Furthermore, the aged heart does not increase its antioxidant enzyme defenses to compensate for the HSP70 deficit.

Cellular distribution of GPR14 and the positive inotropic role of urotensin II in the myocardium in adult rat

Urotensin II is a cyclic neuropeptide recently shown to play a role via its receptor GPR14 in regulating vascular tone in the mammalian cardiovascular system. The existence of GPR14 in rat heart has been validated by ligand binding assay and RT-PCR. In the present study, we investigated the cellular distribution of GPR14 protein in rat heart by using immunohistochemistry and confocal microscopic immunofluorescence double staining with antipeptide polyclonal antibodies against GPR14 and cell type markers for myocytes and endothelial cells. The direct effect of urotensin II on left ventricular contractility was further evaluated in isolated left ventricular papillary muscles of the rat. In paraffin-embedded heart sections, positive immunohistochemical staining was observed in the left ventricle but not in the right ventricle and atria. Immunofluorescence double staining revealed the cardiac myocyte as the only cell type expressing GPR14 protein in frozen heart sections as well as in isolated cardiac myocytes. There was no visible signal for GPR14 in intramyocardial coronary arteries and capillaries. The existence of GPR14 protein in rat heart was further validated by immunoprecipitation and Western blot analysis. In isolated rat left ventricular papillary muscle preparations, urotensin II induced an increase in active contractile force. GPR14 mRNA was also detected in rat heart by RT-PCR. These data provide the first direct evidence for the cellular localization of GPR14 receptor protein and a positive inotropic effect of urotensin II in normal rat heart.

Human Urotensin II Modulates Collagen Synthesis and the Expression of MMP-1 in Human Endothelial Cells

OBJECTIVES

Human urotensin II (hU-II) is a cyclic peptide highly expressed in cardiac tissues and blood vessels. hU-II is a potent vasoconstrictor. Recent studies indicate that urotensin II participates in myocardial remodeling after injury. This study was designed to study the role of hU-II in the expression of matrix metalloproteinase-1 (MMP-1) and collagen-1 in human umbilical vein endothelial cells (HUVECs) and underlying intracellular signaling mechanisms.

METHODS AND RESULTS

Cultured HUVECs were incubated with hU-II (10 to 80 nM) for 3 to 24 hours. hU-II increased the expression (mRNA and protein) of collagen-1 in a concentration- and time-dependent manner. In contrast, hU-II decreased the expression and activity of MMP-1. Further, hU-II caused the phosphorylation of mitogen-activated protein kinase p42/44 (MAPKp42/44). This effect of hU-II was inhibited by pretreatment of cells with the MEK inhibitor (PD98059, 10 microM). In addition, treatment of cells with PD98059 attenuated protein expression of collagen-1 and MMP-1 elicited by hU-II (P < 0.01 versus hU-II alone).

CONCLUSIONS

Our observations provide evidence that hU-II modulates the expression of MMP-1 and collagen-1 in HUVECs, and MAPKp42/44 activation may play a signal transduction role in this process.

Cardiovascular role of urotensin II: effect of chronic infusion in the rat

Urotensin II (UII) is a potent vaso-active peptide thought to have multiple roles in the regulation of cardiovascular physiology and pathophysiology. The actions of UII are complex and difficult to interpret given its systemic hemodynamic effects and variable action on different vascular beds and isolated vessels. Direct effects of UII on the myocardium, include myocyte hypertrophy, extracellular matrix deposition and contractility. These observations, together with elevated plasma levels found in disease, are common traits reported in other pathophysiologically implicated neurohormonal systems. In this review, we include original data obtained from chronic infusion of UII in rats. We report a reduction in first derivative of left ventricular pressure (+dP/dt), as well as an increase in the ratio of left ventricular collagen I:III, that may contribute to the reduced myocardial contractility observed in these animals.

Emerging roles of urotensin-II in cardiovascular disease

Urotensin-II (UII) is a highly potent endogenous peptide within the cardiovascular system. Through stimulation of Galphaq-coupled UT receptors, UII mediates contraction of vascular smooth muscle and endothelial-dependent vasorelaxation, and positive inotropy in human right atrium and ventricle. A pathogenic role of the UT receptor system is emerging in cardiovascular disease states, with evidence for up-regulation of the UT receptor system in patients with congestive heart failure (CHF), pulmonary hypertension, cirrhosis and portal hypertension, and chronic renal failure. In vitro and in vivo studies show that under pathophysiological conditions, UII might contribute to cardiomyocyte hypertrophy, extracellular matrix production, enhanced vasoconstriction, vascular smooth muscle cell hyperplasia, and endothelial cell hyper-permeability. Single nucleotide polymorphisms of the UII gene may also impart a genetic predisposition of patients to diabetes. Therefore, the UT receptor system is a potential therapeutic target in the treatment of cardiac, pulmonary, and renal diseases. UT receptor antagonists are currently being developed to prevent and/or reverse the effects of over-activated UT receptors by the endogenous ligand. This review describes UII peptide and converting enzymes, and UT receptors in the cardiovascular system, focusing on pathophysiological roles of UII in the heart and blood vessels.

Urotensin II: the old kid in town

Urotensin II (U-II) is a vasoactive hormone that acts through a recently described seven transmembrane-spanning G-protein-coupled receptor called GPR14. Although touted as the most potent vasoconstrictor peptide yet identified, the responses elicited by U-II are species-, tissue- and endothelium-dependent. Available data question the contribution of U-II to resting cardiovascular homeostasis in humans; instead they point to a role for this hormone in disease (heart failure and cardiac cell growth, renal function, diabetes, and mitogenesis in vascular and tumour cells). Key features of these diseases are increased expression and activity of U-II receptors. In this review, we focus on recent evidence that supports a role of U-II and its receptor in cardiovascular disease.

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.