Vasoconstrictive effects of endothelin-1, endothelin-3, and urotensin II in isolated perfused human lungs and isolated human pulmonary arteries

Identifying Circulating Urotensin II and Urotensin II-Related Peptide-Generating Enzymes in the Human Plasma Fraction Cohn IV-4

Urotensin II (UII) and UII-related peptide (URP) are vasoactive peptide hormones causing strong vasoconstriction or vasodilation, depending on the type of blood vessel. In humans, the active forms are resulting from proteolytic cleavage of their inactive precursor protein. In blood plasma, a defined protease converting the inactive UII and URP precursors into their active forms has not been identified yet. Using mass spectrometry-based enzyme screening for detecting UII- and URP-converting enzymes, the human plasma fraction Cohn IV-4 was chromatographed, and the resulting fractions were screened for UII- or URP-generating activity. Plasma kallikrein (PK) as a UII- and URP-generating protease was identified. URP generation was also found for the serine protease factor XIa, plasmin, thrombin, and, to a smaller extent, factor XIIa. It was demonstrated that in the Cohn IV-4 fraction, PK accounts for a significant amount of UII- and URP-generating activity.

The ratio of circulating endothelin-1 to endothelin-3 associated with TIMI risk and dynamic TIMI risk score in ST elevation acute myocardial infarction

In ST segment elevation acute myocardial infarction (STEMI), the endothelin (ET) system imbalance, reflected by the circulating ET-1:ET-3 ratio has not been investigated. This study's primary objective was to measure the circulating ET-1:ET-3 ratio and correlate it with the risk stratification for 1 year mortality of STEMI based on TIMI score. On admission, the TIMI risk score and at discharge, the dynamic TIMI risk score were calculated in 68 consecutive subjects with STEMI. Subjects with high TIMI risk score were associated with higher mean ET-1 level and ET-1:ET-3 ratio. The ET-1:ET-3 ratio more accurately predicted the high on admission TIMI risk score than the ET-1 level. Subjects with high dynamic TIMI risk score were associated with higher mean ET-1 level and ET-1:ET-3 ratio. The ET-1:ET-3 ratio more accurately predicted the high at discharge dynamic TIMI risk score than ET-1 level. From multivariable analysis, the ET-1:ET-3 ratio was not independently associated with high on admission TIMI risk score but independently predicted high at discharge dynamic TIMI risk score (odds ratio = 9.186, p = 0.018). In conclusion, combining the ET-1 and ET-3 levels into the ET-1:ET-3 ratio provided a prognostic value by independently predicting the increased risk to 1 year mortality as indicated by at discharge dynamic TIMI risk score in patients with STEMI.

The ex vivo human lung: research value for translational science

Respiratory diseases are among the leading causes of death and disability worldwide. However, the pathogenesis of both acute and chronic lung diseases remains incompletely understood. As a result, therapeutic options for important clinical problems, including acute respiratory distress syndrome and chronic obstructive pulmonary disease, are limited. Research efforts have been held back in part by the difficulty of modeling lung injury in animals. Donor human lungs that have been rejected for transplantation offer a valuable alternative for understanding these diseases. In 2007, our group developed a simple preparation of an ex vivo-perfused single human lung. In this Review, we discuss the availability of donor human lungs for research, describe the ex vivo-perfused lung preparation, and highlight how this preparation can be used to study the mechanisms of lung injury, to isolate primary cells, and to test novel therapeutics.

Evaluation of Endothelial Dysfunction in Bipolar Affective Disorders: Serum Endocan and Urotensin-II Levels

Objective

This study investigated changes in urotensin-II (U-II) and endocan levels which can be used as an early biological marker of endothelial injury in the episode and remission phases of bipolar affective disorder (BAD).

Methods

We compared endocan and U-II levels, which has been shown to be closely associated with neurotransmitter systems in addition to continuity of endothelial structure and inflammatory response, in patients with BAD in remission for at least one year (n=42) and in patients still in manic or depressive episodes (n=16) with healthy controls (n=30).

Results

Both endocan and U-II levels were significantly higher in the bipolar patients than in the controls. Endocan and U-II levels were also significantly correlated with one another (p=0.000, r=0.833). Both endocan (p=0.000) and U-II levels (p=0.000) were significantly higher in the bipolar attack group compared to the subjects in remission, and in the remission group compared to the controls.

Conclusion

In this study we determined significantly higher endocan and U-II levels in BAD compared to the controls, while serum endocan and U-II levels of patients undergoing attacks were also significantly higher than those of the controls and also those of patients in remission.

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

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

Modelling the Human Respiratory System: Approaches for in Vitro Safety Testing and Drug Discovery

Respiratory research can be broken down into two main areas: (i) exposure to airborne substances (basic toxicology assessment); and (ii) respiratory diseases (understanding disease mechanisms and development of new therapeutics, including toxicological assessment). Both have suffered from inadequate and inaccurate models used to predict human toxicological end points. A growing need therefore exists for accurate in vitro models of the respiratory system, which accurately reflect the human lung situation in vivo. Advances in cell culture techniques and accessibility of human cells/tissues have resulted in the development of increasingly in vivo-like respiratory models. This chapter will focus on the development, advantages and disadvantages of these models and what the future holds for in vitro lung toxicology.

The effect of deep hypothermia on the human pulmonary circulation

OBJECTIVE

Acute rises in pulmonary artery pressures following complex cardiac surgery are associated with high morbidity and mortality. We hypothesised that periods of deep hypothermia predispose to elevated pulmonary pressures upon rewarming. We investigated the effect of this hypothermic preconditioning on isolated human pulmonary arteries and isolated perfused lungs.

METHODS

Isometric tension was measured in human pulmonary artery rings (n=24). We assessed the constriction and dilation of these arteries at 37 °C and 17 °C. Isolated perfused human lung models consisted of lobes ventilated via a bronchial cannula and perfused with Krebs via a pulmonary artery cannula. Bronchial and pulmonary artery pressures were recorded. We investigated the effect of temperature using a heat exchanger.

RESULTS

Rewarming from 17 °C to 37 °C caused a 1.3 fold increase in resting tension (p<0.05). Arteries constricted 8.6 times greater to 30 nM KCl, constricted 17 times greater to 1 nM Endothelin-1 and dilated 30.3 times greater to 100 μM SNP at 37 °C than at 17 °C (p<0.005). No difference was observed in the responses of arteries originally maintained at 37 °C compared to those arteries maintained at 17 °C and rewarmed to 37 °C. Hypothermia blunted the increase in pulmonary artery pressures to stimulants such as potassium chloride as well as to H-R but did not precondition arteries to higher pulmonary artery pressures upon re-warming.

CONCLUSIONS

Deep hypothermia reduces the responsiveness of human pulmonary arteries but does not, however, precondition an exaggerated response to vasoactive agents upon re-warming.

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.

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.

State-dependent calcium mobilization by urotensin-II in cultured human endothelial cells

Human endothelial cells express urotensin-II (U-II) as well as its receptor GPR14. Using microfluorimetric techniques, the effect of human U-II on cytosolic Ca2+ concentrations [Ca2+]i in cultured human aortic endothelial cells (HAECs) loaded with Fura-2 was evaluated in static or flow conditions. Under the static state, U-II (100 nM) abolished spontaneous Ca2+ oscillations, which occurred in a population of cultured HAEC. Similarly, U-II reduced thrombin-, but not ATP-induced calcium responses, suggesting that the peptide does not alter the Gq/11/IP3 pathway; rather, it modifies the coupling between protease-activated receptors and Gq/11/IP3. Under the flow condition, U-II (1, 10 and 100 nM) produced a dose-dependent increase in [Ca2+]i, which was subjected to desensitization. The result demonstrates a state-dependent effect of U-II in cultured HAEC, which may explain the variable responses to U-II under different experimental conditions.

Characterization of the vasodilatory action of testosterone in the human pulmonary circulation

AIM

To assess for the first time the vasodilatory effect of testosterone in the human pulmonary circulation utilizing both isolated human pulmonary arteries and isolated perfused human lungs. In addition, a secondary aim was to determine whether there was any difference in the response to testosterone dependent upon gender.

METHODS

Isolated human pulmonary arteries were studied by wire myography. Vessels were preconstricted with U46619 (1 nM-1 microM) prior to exposing them to either testosterone (1 nM-100 microM) or ethanol vehicle (<0.1%). Isolated lungs were studied in a ventilated and perfused model. They were exposed to KCl (100 mM), prior to the addition of either testosterone (1 nM-100 microM) or ethanol vehicle (<0.1%).

RESULTS

Testosterone caused significant vasodilatation in all preparations, but a greater response to testosterone was observed in the isolated perfused lungs, 24.9 +/- 2.2% at the 100 microM dose of testosterone in the isolated pulmonary arteries compared to 100 +/- 13.6% at the 100 microM dose in the isolated perfused lungs. No significant differences in the response to testosterone were observed between sexes.

CONCLUSION

Testosterone is an efficacious vasodilator in the human pulmonary vasculature and this is not modulated by patient sex. This vasodilator action suggests that testosterone therapy may be beneficial to male patients with pulmonary arterial hypertension.

Endothelin-1/Endothelin-3 Ratio

BACKGROUND

Pulmonary arterial hypertension (PAH) is a rare condition characterized by elevated pulmonary artery pressure leading to right-heart failure and death. Endothelin (ET)-1 has been shown to play a significant pathogenic role in PAH. ET-3 has not yet been investigated in PAH.

METHODS

ET-1 and ET-3 plasma concentrations were measured in 33 PAH patients prior to any specific PAH therapy and in 9 control subjects. In PAH patients, hemodynamic parameters measured by right-heart catheterization, 6-min walk distance (6MWD), New York Heart Association (NYHA) functional class, and time until lung transplantation or death were recorded.

RESULTS

In patients with PAH, levels of ET-1 were increased while those of ET-3 were decreased, as compared to control subjects (p < 0.005 for both comparisons). ET-1/ET-3 ratio varied little in control subjects, while it increased threefold in PAH patients (p < 0.0001). ET-1 correlated positively with right atrial pressure (RAP), indexed total pulmonary resistance, and negatively with cardiac index and venous saturation of oxygen (Svo(2)). ET-3 correlated positively with 6MWD. ET-1/ET-3 ratio correlated positively with RAP, negatively with Svo(2) and 6MWD, and was also associated with NYHA functional class. ET-1/ET-3 ratio was associated with prognosis in this sample of PAH patients treated with specific therapies.

CONCLUSIONS

PAH is characterized by elevated ET-1 and ET-1/ET-3 ratio and decreased ET-3 plasma concentrations. All of them correlate with hemodynamic and clinical markers of disease severity. ET-1/ET-3 ratio might be a novel prognostic factor in PAH. These preliminary data should be validated in a large prospective multicenter cohort of PAH patients.

The effects of urotensin-II on proliferation of pheochromocytoma cells and mRNA expression of urotensin-II and its receptor in pheochromocytoma tissues

This study was conducted to investigate the effects of urotensin-II (UII) on the proliferation of pheochromocytoma cells and the mRNA expression of UII and its receptor G protein-coupled receptor 14 (GPR14) in normal adrenal and human pheochromocytoma tissues. The effects on the cell proliferation by different UII concentrations and at different time were observed with the MTT method in both rat pheochromocytoma cell line (PC12 cell) and human pheochromocytoma cells. The mRNA expression of UII and GPR14 was evaluated by RT-PCR. UII had no significant effect on the proliferation in PC12 cells, but promoted the proliferation of human pheochromocytoma cells. The mRNA expression of UII and GPR14 in pheochromocytoma was lower than that in normal adrenal tissues. But mRNA expression of UII and GPR14 in adrenal pheochromocytomas was lower than that in extra-adrenal pheochromocytomas. Thus, UII and its receptor GPR14 exert a possible effect in the pathogenesis of pheochromocytoma.

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

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

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.

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.

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.

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.