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

Urotensin II upregulates migration and cytokine gene expression in leukocytes of the African clawed frog, Xenopus laevis

Urotensin II (UII) exhibits diverse physiological actions including vasoconstriction, locomotor activity, osmoregulation, and immune response via the UII receptor (UTR) in mammals. However, in amphibians the function of the UII-UTR system remains unknown. In the present study, we investigated the potential immune function of UII using leukocytes isolated from the African clawed frog, Xenopus laevis. Stimulation of male frogs with lipopolysaccharide increased mRNA expression of UII and UTR in leukocytes, suggesting that inflammatory stimuli induce activation of the UII-UTR system. Migration assays showed that both UII and UII-related peptide enhanced migration of leukocytes in a dose-dependent manner, and that UII effect was inhibited by the UTR antagonist urantide. Inhibition of Rho kinase with Y-27632 abolished UII-induced migration, suggesting that it depends on the activation of RhoA/Rho kinase. Treatment of isolated leukocytes with UII increased the expression of several cytokine genes including tumor necrosis factor-α, interleukin-1β, and macrophage migration inhibitory factor, and the effects were abolished by urantide. These results suggest that in amphibian leukocytes the UII-UTR system is involved in the activation of leukocyte migration and cytokine gene expression in response to inflammatory stimuli.

Progress in understanding role of urotensin Ⅱ in hepatic cirrhosis

Urotensin Ⅱ (UⅡ) is a potent vasoactive substance that can result in vasoactive response through interaction with its specific orphan G-protein-coupled receptor GPR-14. In addition to the role of vasoactivity, UⅡ can promote mitosis and fibrosis. The vascular role of UⅡ is to some degree both species- and disease-specific. Studies have found that plasma levels of UⅡ are elevated in patients with cirrhosis, but the relationship between plasma levels of UⅡ and the development of chronic liver disease and portal hypertension has yet to be fully elucidated. This review focuses on the potential relevance of UⅡ as vasoactive substance in chronic liver disease and the site where UⅡ is overproduced.

Inhibition of UII/UTR system relieves acute inflammation of liver through preventing activation of NF-κB pathway in ALF mice

Urotensin II (UII) is implicated in immune inflammatory diseases through its specific high-affinity UT receptor (UTR). Enhanced expression of UII/UTR was recently demonstrated in the liver with acute liver failure (ALF). Here, we analysed the relationship between UII/UTR expression and ALF in lipopolysaccharide (LPS)/D-galactosamine (GalN)-challenged mice. Thereafter, we investigated the effects produced by the inhibition of UII/UTR system using urantide, a special antagonist of UTR, and the potential molecular mechanisms involved in ALF. Urantide was administered to mice treated with LPS/GalN. Expression of UII/UTR, releases of proinflammatory cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and interferon-γ (IFN-γ), and activation of nuclear factor κB (NF-κB) signaling pathway were assessed in the lethal ALF with or without urantide pretreatment. We found that LPS/GalN-challenged mice showed high mortality and marked hepatic inflammatory infiltration and cell apoptosis as well as a significant increase of UII/UTR expression. Urantide pretreatment protected against the injury in liver following downregulation of UII/UTR expression. A close relationship between the acutely flamed hepatic injury and UII/UTR expression was observed. In addition, urantide prevented the increases of proinflammatory cytokines such as TNF-α, IL-1β and IFN-γ, and activation of NF-κB signaling pathway induced by LPS/GalN in mice. Thus, we conclude that UII/UTR system plays a role in LPS/GalN-induced ALF. Urantide has a protective effect on the acutely inflamed injury of liver in part through preventing releases of proinflammatory cytokines and activation of NF-κB pathway.

Expression and role of Urotensin Ⅱ in lipopolysaccharide/D-galactosamine-induced acute liver failure in mice

AIM: To investigate the expression and role of Urotensin Ⅱ (UⅡ) in lipopolysaccharide (LPS)/D-galactosamine (D-GalN)-induced acute liver failure (ALF) in mice.

METHODS: Male Balb/c mice were randomly and equally divided into four groups: normal control group (group A), pre-treatment control group (group B), ALF model group (group C), and pre-treatment model group (group D). ALF were induced in mice by intraperitoneal injection of LPS (50 μg/kg body weight)/D-GalN (800 mg/kg body weight). The pre-treatment mice were intravenously injected with Urantide (0.6 mg/kg body weight) 30 min before model induction. Serum and liver tissues were sampled 12 h after LPS/D-GalN injection. Mortality was calculated 24 h after attack. Serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected using the Reitman-Frankel method. Histopathological changes were observed by hematoxylin and eosin (HE) staining. Serum UⅡ levels were assessed by ELISA, and the expression of UⅡ and UT was detected by RT-PCR and immunohistochemistry.

RESULTS: A mortality of 66.7% was observed in group C, while all mice of groups A, B and D survived. Serum ALT and AST levels had a dramatic increase in groups C and D, but were significantly lower in group D than in group C (2 271.09 U/L ± 102.24 U/L vs 1 160.67 U/L ± 258.32 U/L, 1 569.42 U/L ± 204.04 U/L vs 1 030.31 U/L ± 108.09 U/L, both P < 0.01). Widespread destruction of liver architecture, hemorrhagic necrosis, and neutrophil infiltration were noted in group C, whereas liver architecture was completely preserved, and focal necrosis and fewer neutrophil infiltrates were observed in group D. After LPS/D-GalN challenge, serum UⅡ levels increased sharply in groups C and D, but were lower in group D than in group C (3.73 μg/L ± 0.52 μg/L vs 1.90 μg/L ± 0.27 μg/L, both P < 0.01). Overexpression of liver UⅡ and UT mRNAs and proteins was induced by the injection of LPS/D-GalN in groups C and D. Compared to group C, group D had lower levels of UⅡ and UT in the liver.

CONCLUSION: UⅡ expression and secretion can be induced by LPS/D-GalN challenge in the liver tissue of ALF mice via a positive feedback mechanism associated with promoting the expression of its receptor UT. UⅡ/UT receptor may be a vital mediator of LPS/D-GalN-induced ALF.

Noninvasive evaluation of portal hypertension: emerging tools and techniques

Portal hypertension is the main cause of complications in patients with cirrhosis. However, evaluating the development and progression of portal hypertension represents a challenge for clinicians. There has been considerable focus on the potential role of noninvasive markers of portal hypertension that could be used to stratify patients with respect to the stage of portal hypertension and to monitor disease progression or treatment response in a longitudinal manner without having to undertake repeated invasive assessment. The pathogenesis of portal hypertension is increasingly understood and emerging knowledge of the vascular processes that underpin portal hypertension has paved the way for exploring novel biomarkers of vascular injury, angiogenesis, and endothelial dysfunction. In this paper we focus on the pathogenesis of portal hypertension and potential non-invasive biomarkers with particular emphasis on serum analytes.