Urotensin II modulates hepatic fibrosis and portal hemodynamic alterations in rats

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.

Portal hypertension in cirrhosis: Pathophysiological mechanisms and therapy

Portal hypertension, defined as increased pressure in the portal vein, develops as a consequence of increased intrahepatic vascular resistance due to the dysregulation of liver sinusoidal endothelial cells (LSECs) and hepatic stellate cells (HSCs), frequently arising from chronic liver diseases. Extrahepatic haemodynamic changes contribute to the aggravation of portal hypertension. The pathogenic complexity of portal hypertension and the unsuccessful translation of preclinical studies have impeded the development of effective therapeutics for patients with cirrhosis, while counteracting hepatic and extrahepatic mechanisms also pose a major obstacle to effective treatment. In this review article, we will discuss the following topics: i) cellular and molecular mechanisms of portal hypertension, focusing on dysregulation of LSECs, HSCs and hepatic microvascular thrombosis, as well as changes in the extrahepatic vasculature, since these are the major contributors to portal hypertension; ii) translational/clinical advances in our knowledge of portal hypertension; and iii) future directions.

Urotensin II in the development and progression of chronic kidney disease following ⅚ nephrectomy in the rat

NEW FINDINGS

What is the central question of this study? Urotensin II is upregulated in patients in the later stages of chronic kidney disease (CKD), particularly in individuals requiring dialysis. Could treatment with a urotensin II receptor antagonist slow progression of renal disease? What is the main finding and its importance? In the rat, expression of urotensin II and its receptor increased, extending into cortical structures as CKD progressed towards end-stage renal failure. Subchronic treatment with a urotensin receptor antagonist slowed but did not prevent progression of CKD. This suggests that urotensin II contributes to the decline in renal function in CKD.

ABSTRACT

Elevated serum and urine urotensin II (UII) concentrations have been reported in patients with end-stage chronic kidney disease (CKD). Similar increases in UII and its receptor, UT, have been reported in animal models of CKD, but only at much earlier stages of renal dysfunction. The aim of this study was to characterize urotensin system expression as renal disease progresses to end-stage failure in a ⅚ subtotal nephrectomy (SNx) rat model. Male Sprague-Dawley rats underwent SNx or sham surgery and were killed at 8 weeks postsurgery [early (E)] or immediately before end-stage renal failure [30 ± 3 weeks postsurgery; late (L)]. Systolic blood pressure, urinary albumin:creatinine ratio and glomerulosclerosis index were all increased in SNx-E rats compared with sham-E by 8 weeks postsurgery. These changes were associated with an increase in renal immunoreactive UII staining but little change in UT expression. As CKD progressed to end-stage disease in the SNx-L group, markers of renal function deteriorated further, in association with a marked increase in immunoreactive UII and UT staining. Subchronic administration of a UT antagonist, SB-611812, at 30 mg kg^-1  day^-1 for 13 weeks, in a separate group of SNx rats resulted in a 2 week delay in the increase in both systolic blood pressure and urinary albumin:creatinine ratio observed in vehicle-treated SNx but did not prevent the progression of renal dysfunction. The urotensin system is upregulated as renal function deteriorates in the rat; UT antagonism can slow but not prevent disease progression, suggesting that UII plays a role in CKD.

Partial Portal Vein Arterialization Attenuates Acute Bile Duct Injury Induced by Hepatic Dearterialization in a Rat Model

Hepatic infarcts or abscesses occur after hepatic artery interruption. We explored the mechanisms of hepatic deprivation-induced acute liver injury and determine whether partial portal vein arterialization attenuated this injury in rats. Male Sprague-Dawley rats underwent either complete hepatic arterial deprivation or partial portal vein arterialization, or both. Hepatic ischemia was evaluated using biochemical analysis, light microscopy, and transmission electron microscopy. Hepatic ATP levels, the expression of hypoxia- and inflammation-associated genes and proteins, and the expression of bile transporter genes were assessed. Complete dearterialization of the liver induced acute liver injury, as evidenced by the histological changes, significantly increased serum biochemical markers, decreased ATP content, increased expression of hypoxia- and inflammation-associated genes and proteins, and decreased expression of bile transporter genes. These detrimental changes were extenuated but not fully reversed by partial portal vein arterialization, which also attenuated ductular reaction and fibrosis in completely dearterialized rat livers. Collectively, complete hepatic deprivation causes severe liver injury, including bile infarcts and biloma formation. Partial portal vein arterialization seems to protect against acute ischemia-hypoxia-induced liver injury.

An investigation into the expression and mechanism of action of urotensin II in chronic pressure-overloaded rat hearts

The present study aimed to investigate the role and mode of action of urotensin II (U II) in the occurrence and progression of cardiac fibrosis in a pressure-overload rat model. Coarctation of the abdominal aorta was used to establish an animal model, and postoperative echocardiography, hemodynamic detection, hematoxylin and eosin staining, Masson staining and immunohistochemistry were performed to assess the changes in cardiac function and pathology. The expression levels of U II, G-protein-coupled receptor 14 and collagen (Col) I and Col III in the myocardial tissues were also analyzed. Neonatal rat fibroblasts were isolated, cultured and subsequently, generations 3–5 were randomly divided into different groups for the detection of Col I and Col III levels by enzyme-linked immunosorbent assay and western blotting. The protein expression levels were markedly increased in the model group, and this increase correlated with an increase in myocardial fibrosis. In cultured neonatal rat fibroblast cells, 10⁻⁸ mol/l U II significantly stimulated the synthesis of Col I and Col III (P<0.01) compared with the control group. Compared with the U II group, the administration of KT5720 (1 mol/l) or SB-611812 (1 mol/l) significantly reduced the synthesis and expression levels of Col I and Col III (P<0.05). U II may exert an important role in the process of myocardial fibrosis in chronic pressure-overload rats, and the cyclic adenosine monophosphate-protein kinase A signaling pathway may be partly involved in this process.

Unravelling osteoarthritis-related synovial fibrosis: a step closer to solving joint stiffness

Synovial fibrosis is often found in OA, contributing heavily to joint pain and joint stiffness, the main symptoms of OA. At this moment the underlying mechanism of OA-related synovial fibrosis is not known and there is no cure available. In this review we discuss factors that have been reported to be involved in synovial fibrosis. The aim of the study was to gain insight into how these factors contribute to the fibrotic process and to determine the best targets for therapy in synovial fibrosis. In this regard, the following factors are discussed: TGF-β, connective tissue growth factor, procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2, tissue inhibitor of metalloproteinase 1, A disintegrin and metalloproteinase domain 12, urotensin-II, prostaglandin F2α and hyaluronan.

H2 S inhibits the activation of hepatic stellate cells and downregulates the expression of urotensin II

AIM

H2 S, a newly discovered signaling gasotransmitter, has been found involved in the pathogenesis of portal hypertension through the H2 S/CSE system. Studies also showed that urotensin II (UII), a recently discovered most potent vasoconstrictor, played an important role in cirrhotic portal hypertension. Therefore, studies were conducted to explore the relationship between H2 S and UII in cirrhosis.

METHODS

In the present study, the changes in the expression levels of cystathionine-γ-lyase (CSE), UII, urotensin II receptor (UT), collagen I, collagen III, tissue inhibitor of metalloproteinase-1 (TIMP-1) and α-smooth muscle actin (α-SMA) were determined by fluorescence quantitative polymerase chain reaction after exposure of hepatic stellate cells to H2 S. The influence of H2 S on UII was examined by western blotting, and the relationship between H2 S and UII was further confirmed by detection of cell proliferation and apoptosis.

RESULTS

Studies have shown that increase in H2 S concentration could reduce the expression of UII, UT, collagen I, collagen III, TIMP-1 and α-SMA without involvement of CSE. Moreover, the results of western blotting further proved that H2 S inhibited the expression of UII. The examination of cell proliferation by 5-ethynyl-2'-deoxyuridine assay suggests that H2 S significantly inhibited the proliferation of LX-2 cells and the proliferation-promoting effect of UII. Similarly, the examination of cell apoptosis revealed that H2 S could promote LX-2 cell apoptosis and inhibit the apoptosis-inhibiting effect of UII.

CONCLUSION

H2 S suppresses fibrosis by inhibiting the activation of hepatic stellate cells and reducing the expression of UII.

Role of urotensin-Ⅱ in the pathogenesis of liver cirrhosis and portal hypertension and collateral circulation

Urotensin-Ⅱ (U-Ⅱ) is a somatostatin-like cyclic peptide which has a potent vasoactive effect and can promote vascular reconstruction and hyperplasia. Research shows that UⅡ plays an important role in the development of liver cirrhosis and portal hypertension. UⅡ influences intrahepatic resistance and splanchnic hemodynamics through a variety of pathways, causing portal hypertension and participating in the formation of esophageal and gastric varices. UⅡ receptor antagonists can reduce portal pressure in cirrhotic rats, but this finding need to be confirmed clinically.

Urotensin upregulates transforming growth factor-β1 expression of asthma airway through ERK-dependent pathway

Airway smooth muscle cells (ASMCs) play a key role in the process of asthma airway remodeling. Urotensin II (UII) and transforming growth factor (TGF)-β are potent mitogens for ASMCs proliferation. The study was aimed to determine whether UII-upregulated TGF-β-mediated ASMCs proliferation and extracellular signal-regulated kinase (ERK) was required for such an effect. OVA-sensitized rats were challenged to induce asthma. Lung morphology and airway dynamic parameters were monitored. ASMCs from control and asthma rats were purified for the measurement of UII and TGF-β1 expression. In vitro experiments were conducted to determine the direct effect of UII on TGF-β1 expression by ASMCs. Finally, U0126, an ERK inhibitor was used to examine the role of ERK pathway in UII mediated TGF-β1 upregulation. We found that both UII and TGF-β1 were upregulated in asthma lung tissues. In vitro study on ASMCs further revealed that UII may render its effect on ASMCs cells through the upregulation of TGF-β1. Data also supported the conclusion that ERK pathway was required, but not sufficient in UII-induced TGF-β1 upregulation. The current study provides new evidence that UII is involved in the TGF-β mediated mitogenic effect on ASMCs. UII, at least partially, uses ERK pathway to render such effect.

Association Between Thr21Met and Ser89Asn Polymorphisms of the Urotensin II Gene and Systemic Sclerosis

Objective.

Systemic sclerosis (SSc) is an autoimmune chronic fibrotic disorder. Urotensin II (U-II) is predominantly a vasoactive peptide with fibrotic and prothrombotic features. Like endothelin-1 (ET-1), U-II could play an important role in SSc pathogenesis. We evaluated the possible role of the U-II gene polymorphisms (Thr21Met and Ser89Asn) in the genetic susceptibility to SSc in a Turkish population.

Methods.

A total of 189 patients with SSc and 205 healthy controls were enrolled in our study. We analyzed the genotype and allele frequencies of the U-II (UTS2) gene polymorphisms Thr21Met and Ser89Asn in patients with SSc and in controls.

Results.

We found that the Thr21Met polymorphism of the UTS2 gene was markedly associated with the risk of developing SSc (p < 0.0001), but there was no relationship between the Ser89Asn polymorphism and SSc (p > 0.05). Two haplotypes (MS and TS) were markedly associated with SSc (p < 0.05). There were significant associations between the genotype and allele frequencies of UTS2 gene Thr21Met polymorphism and cases with diffuse or limited SSc, systemic or lung involvement, finger flexion deformity, pitting scars at the fingertips, positive anticentromere, or positive antitopoisomerase 1 antibody groups.

Conclusion.

Our study shows the association between Thr21Met, but not Ser89Asn, in the UTS2 gene and SSc. The results strongly suggest that this single-nucleotide polymorphism may be an important risk factor in the development of SSc, and a powerful indicator of severe skin and lung involvement in patients with SSc.

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

BACKGROUND AND AIM

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Elevated plasma levels of urotensin II do not correlate with systemic haemodynamics in patients with cirrhosis

BACKGROUND

The hyperdynamic circulation of hepatic cirrhosis is related to decreased systemic vascular resistance due to arterial vasodilation. Urotensin II plasma levels are increased in cirrhotic patients, and have been suggested to play a role in the pathogenesis of systemic haemodynamic alterations.

AIM

To evaluate the relationships between systemic haemodynamics and urotensin II plasma levels.

METHODS

Thirty-six consecutive in-patients with cirrhosis and no alteration of plasma creatinine, and 20 age- and gender-matched healthy volunteers underwent noninvasive assessment of systemic haemodynamics and measurement of urotensin II plasma levels.

RESULTS

In comparison to healthy controls, cirrhotic patients had signs of hyperdynamic circulation and higher plasma urotensin II levels. Plasma urotensin II was neither significantly different amongst patients with different severity of cirrhosis nor between patients with or without ascites. Both in controls and cirrhotic patients no significant correlations were found between parameters of systemic haemodynamics and plasma urotensin II levels.

CONCLUSIONS

In patients with cirrhosis and hyperdynamic circulation, but with normal serum creatinine, urotensin II is higher than in healthy subjects. However, no correlation with cardiac index or other haemodynamic parameters was observed, indicating that other mechanisms prevail.

Advances in understanding the role of the UII/UT system in the pathogenesis of portal hypertension

Urotensin II (UII), a vasoactive peptide with structural similarity to somatostatin, is the most potent vasoconstrictor known in systemic resistance vessels and has multiple biological effects related to a variety of human diseases. Numerous studies have found that UII and its receptor (UT) play an important role in the pathogenesis of portal hypertension. This paper reviews the recent advances in understanding the role of the UII/UT system in the pathogenesis of portal hypertension.

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.