Plasma endothelin-1 levels in liver cirrhosis

Biological basis of child health 9: development of the liver and clinical features of childhood liver disease

This article is the ninth in a series on the biological basis of child health and follows on from the previous article, which discussed the gastrointestinal system. The liver is the largest solid organ in the body and has more than 500 functions. These functions include: producing bile, which serves as a vehicle for waste products and as an aid for the digestion of dietary fat; synthesising most coagulation factors, needed in the clotting cascade; and transforming glycogen into glucose for use as energy in cell metabolism. While most liver conditions seen in children are rare, it is important that children's nurses can identify the clinical features of childhood liver disease. This article provides an overview of the embryological development of the liver, its anatomy and functions, liver function tests in children, and the clinical features and pathophysiology of childhood liver disease.

Endothelin 1 and transforming growth factor-β1 correlate with liver function and portal pressure in cirrhotic patients

OBJECTIVE

The invasive measurement of hepatic venous pressure gradient is the recommended method for the assessment of portal hypertension. We assessed if the mediators that regulate portal hypertension may be used as noninvasive markers of portal hypertension and liver insufficiency.

MATERIALS AND METHODS

We explored in prospective, observational study the concentration of endothelin-1, nitric oxide, and transforming growth factor-β1/2 in peripheral and hepatic venous blood; their relationship with the values of portal hypertension and liver insufficiency; and their level changes 4-6 months after non-selective beta-blocker therapy in cirrhotic patients with non-bleeding esophageal varices.

RESULTS

(1) Cirrhotics have significantly increased peripheral endothelin 1 and decreased transforming growth factor-β1 levels; (2) peripheral levels of all factors correlated significantly with their hepatic levels; (3) after therapy, peripheral endothelin-1 levels significantly increased, but transforming growth factor-β2 levels decreased and were lower in patients with pressure gradient value normalization; (4) before and after therapy, peripheral and hepatic endothelin-1, transforming growth factor-β1/2 levels correlated significantly with liver failure indicators (laboratory parameters, Child-Pough and MELD scores) and pressure gradient values.

CONCLUSIONS

Peripheral endothelin-1 and transforming growth factor-β1 levels, which strongly correlate with their hepatic levels, reflect the stage of portal hypertension and liver insufficiency in cirrhosis.

Hepatosplanchnic circulation in cirrhosis and sepsis

Hepatosplanchnic circulation receives almost half of cardiac output and is essential to physiologic homeostasis. Liver cirrhosis is estimated to affect up to 1% of populations worldwide, including 1.5% to 3.3% of intensive care unit patients. Cirrhosis leads to hepatosplanchnic circulatory abnormalities and end-organ damage. Sepsis and cirrhosis result in similar circulatory changes and resultant multi-organ dysfunction. This review provides an overview of the hepatosplanchnic circulation in the healthy state and in cirrhosis, examines the signaling pathways that may play a role in the physiology of cirrhosis, discusses the physiology common to cirrhosis and sepsis, and reviews important issues in management.

Epoxyeicosatrienoic Acids Contribute With Altered Nitric Oxide and Endothelin-1 Pathways to Conduit Artery Endothelial Dysfunction in Essential Hypertension

Background—

We sought to clarify, using functional and biological approaches, the role of epoxyeicosatrienoic acids, nitric oxide (NO)/reactive oxygen species balance, and endothelin-1 in conduit artery endothelial dysfunction during essential hypertension.

Methods and Results—

Radial artery diameter and mean wall shear stress were determined in 28 untreated patients with essential hypertension and 30 normotensive control subjects during endothelium-dependent flow-mediated dilatation induced by hand skin heating. The role of epoxyeicosatrienoic acids and NO was assessed with the brachial infusion of inhibitors of cytochrome P450 epoxygenases (fluconazole) and NO synthase ( N G -monomethyl- l -arginine [L-NMMA]). Compared with controls, hypertensive patients exhibited a decreased flow-mediated dilatation in response to postischemic hyperemia as well as to heating, as shown by the lesser slope of their diameter–shear stress relationship. In controls, heating-induced flow-mediated dilatation was reduced by fluconazole, L-NMMA, and, to a larger extent, by L-NMMA+fluconazole. In patients, flow-mediated dilatation was not affected by fluconazole and was reduced by L-NMMA and L-NMMA+fluconazole to a lesser extent than in controls. Furthermore, local plasma epoxyeicosatrienoic acids increased during heating in controls (an effect diminished by fluconazole) but not in patients. Plasma nitrite, an indicator of NO availability, increased during heating in controls (an effect abolished by L-NMMA) and, to a lesser extent, in patients, whereas, inversely, reactive oxygen species increased more in patients (an effect diminished by L-NMMA). Plasma endothelin-1 decreased during heating in controls but not in patients.

Conclusions—

These results show that an impaired role of epoxyeicosatrienoic acids contributes, together with an alteration in NO/reactive oxygen species balance and endothelin-1 pathway, to conduit artery endothelial dysfunction in essential hypertension.

Clinical Trial Registration—

https://www.eudract.ema.europa.eu . Unique identifier: RCB2007-A001–10-53.

Plasma Cytokines and Portopulmonary Hypertension in Patients With Cirrhosis Waiting for Orthotopic Liver Transplantation

Portopulmonary hypertension (PPHTN) is a rare complication in patients with portal hypertension. A role of endothelin 1 (ET-1) and other cytokines was demonstrated in primary pulmonary hypertension but not in PPHTN. We evaluated the possible role of ET-1, interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor alpha (TNF-α) in the pathogenesis of PPHTN. Plasmatic concentrations of ET-1, IL-6, IL-1β, and TNF-α were measured in patients with pulmonary systolic arterial pressure (PAPs) >30 mm Hg and in patients with cirrhosis. In all, Six out of 11 patients with PAPs >30 mm Hg had PPHTN on right heart catheterization. The remaining 10 patients had an hyperdynamic circulation (HC). In PPHTN patients, ET-1 and IL-6 were significantly higher compared with HC and patients with cirrhosis. Endothelin 1 and IL-6 could be implicated in the pathogenesis of PPHTN. On the basis of these results, ET-1 receptor antagonists or anti-IL-6 could have a rationale in the treatment of PPHTN.

Endothelial nitric oxide synthase is not essential for the development of fibrosis and portal hypertension in bile duct ligated mice

BACKGROUND/AIMS

It is postulated that nitric oxide (NO) is responsible for the hyperdynamic circulation of portal hypertension. Therefore, we investigated induction of fibrosis and hyperdynamic circulation in endothelial NO synthase knock-out (KO) mice.

METHODS

Fibrosis was induced by bile duct ligation. Hemodynamic studies were performed after portal vein ligation. All studies were performed in wild-type (WT) and KO mice.

RESULTS

Three to 4 weeks after bile duct ligation (BDL), both WT and KO groups had similar degrees of portal hypertension, 12 (9-14) and 11(8-15) mmHg, median (range), and liver function. Fibrosis increased from 0.0% in sham operated to 1.0 and 1.1% in WT and KO mice, respectively. Cardiac output was similar after portal vein ligation (20 and 17 ml/min in WT and KO mice, respectively). There was no difference in liver of mRNA for endothelin 1, inducible NO synthase (iNOS) and hem-oxygenase 1 (HO1); proteins of iNOS, HO1 and HO2; nor in endothelin A and B (EtA and EtB) receptor density between WT and KO mice after BDL.

CONCLUSIONS

These results suggest that endothelial NO synthase is neither essential for the development of fibrosis and portal hypertension in bile duct ligated mice, nor for the hyperdynamic circulation associated with portal hypertension in the portal vein ligated mice.

Ursodeoxycholic acid inhibits endothelin-1 production in human vascular endothelial cells

Endothelin-1 is known to be implicated in the pathogenesis of hepatobiliary diseases such as cirrhosis, especially in portal hypertension. This study aimed to investigate the effects of ursodeoxycholic acid on endothelin-1 production in human endothelial cells. The effects of ursodeoxycholic acid and its conjugates (tauroursodeoxycholic and glycoursodeoxycholic acids) on endothelin-1 production as well as nitric oxide (NO) in human umbilical vein endothelial cells (HUVECs) were examined. The production of endothelin-1 and nitric oxide in culture medium was measured using enzyme-linked immunosorbent assay (ELISA) and the Griess method, respectively. Endothelin-1 and endothelial nitric oxide synthase (eNOS) mRNA expression were investigated by real-time quantitative reverse transcriptase/polymerase chain reaction (RT-PCR). Ursodeoxycholic acid (30-1000 microM) inhibited endothelin-1 production in a concentration-dependent manner, and ursodeoxycholic acid at concentrations higher than 300 microM increased nitric oxide production in culture medium. The conjugates of ursodeoxycholic acid also increased nitric oxide production and decreased endothelin-1 production, which was less effective than ursodeoxycholic acid. N-nitro-L-arginine-mythel-ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, suppressed the ursodeoxycholic acid-induced nitric oxide production, but it did not antagonize the inhibitory effects of ursodeoxycholic acid on endothelin-1 production. Ursodeoxycholic acid also induced a concentration-dependent decrease in endothelin-1 mRNA expression without significant changes in eNOS mRNA expression. These results provide novel evidence that ursodeoxycholic acid inhibits endothelin-1 production in human endothelial cells, but nitric oxide is not responsible for the inhibitory effect of ursodeoxycholic acid on endothelin-1. Thus, ursodeoxycholic acid therapy may prevent the development of several pathogenesis such as portal hypertension observed in patients with cirrhosis due to the improvement of endothelial function.

Nitric oxide synthase 1 is partly compensating for nitric oxide synthase 3 deficiency in nitric oxide synthase 3 knock-out mice and is elevated in murine and human cirrhosis

BACKGROUND

The role of endothelial nitric oxide synthase 3 (NOS-3) in the hyperdynamic circulation associated with cirrhosis is established but not that of the neuronal (NOS-1) isoform. We therefore investigated aortic NOS-1 levels in NOS-3 knock-out (KO) and wildtype (WT) mice and in hepatic arteries of patients.

METHODS

Mice rendered cirrhotic by bile duct ligation (BDL) were compared with sham-operated controls. Hepatic arteries of cirrhotic patients were collected during liver transplantation; donor vessels served as controls. mRNA levels were quantified by real-time PCR, protein levels by Western blotting and NO production by Nomega-nitro-L-arginine methyl ester inhibitable arginine-citrulline assay.

RESULTS

Aortae of NOS-3 KO mice exhibited higher NOS-1mRNA (5.6-fold, P < 0.004) and protein levels (8.8-fold) compared with WT. NO production in aortae of NOS-3 KO mice was 52% compared with WT (P = 0.002). BDL increased NOS-1 mRNA (2.4-fold, P = 0.01) and protein (7.1-fold) levels in aortae of WT, but no further in the NOS-3 KO mice. Hepatic artery NOS-1 mRNA levels in cirrhotic patients were markedly increased compared with controls (24.5-fold, P = 0.0007).

CONCLUSIONS

Increased NOS-1 mRNA and protein levels and partially maintained in vitro NO-production in aortae of NOS-3 KO mice suggest that NOS-1 may partially compensate for NOS-3 deficiency. BDL-induced increase in aortic NOS-1 mRNA and protein levels hint that not only NOS-3, but also NOS-1 may be involved in the regulation of systemic hyperdynamic circulation and portal hypertension. Upregulation of NOS-1 mRNA levels in hepatic arteries of portal hypertensive patients suggests possible clinical significance for these experimental findings.

Hepatopulmonary syndrome: role of nitric oxide and clinical aspects

Hepatopulmonary syndrome is defined by oxygenation impairment due to abnormal intrapulmonary vascular dilatations in patients with liver disease. The implication of enhanced pulmonary production of nitric oxide in the pathogenesis of intrapulmonary vascular dilatations has been demonstrated both in murine models and in human hepatopulmonary syndrome. The diagnosis of hepatopulmonary syndrome in chronic liver disease is of paramount importance, considering the fact that severe hypoxemia related to hepatopulmonary syndrome may occur in patients with well compensated liver disease and that survival is reduced in patients with hepatopulmonary syndrome relative to non hepatopulmonary syndrome patients. Priority for liver transplantation, which is presently the only cure, has been recently increased in patients with advanced hepatopulmonary syndrome.

Endogenous endothelin increases gallbladder tone and leads to acute cholecystitis in the Australian possum

Endothelins are bioactive peptides produced by gallbladder epithelial cells. We aimed to determine the role of endothelins in acute cholecystitis. Escherichia coli lipopolysaccharide vs saline (sham) was instilled into the gallbladder lumen of Australian possums. Some animals received the non-selective endothelin antagonist, tezosentan. At 4 or 24 h, plasma and gallbladder endothelins and white blood cell count (WBCC) were determined. Acute cholecystitis was assessed using a histopathology score. In other animals gallbladder tone was determined. At 4h, a dose-dependent 60-fold increase in gallbladder endothelin level occurred (P = 0.001) but other parameters remained comparable with sham animals. Epithelial cells were endothelin-immunoreactive. At 24 h, the WBCC rose (P < 0.007), and severe cholecystitis developed. Gallbladder but not plasma endothelin levels remained elevated. Tezosentan pre-treatment resulted in a histologically normal gallbladder, but the WBCC and gallbladder endothelin levels were elevated. Lipopolysaccharide or saline instillation also caused a time-dependent increase in gallbladder tone over 4 h (P < 0.001), but not in control animals. This increase was reduced by tezosentan treatment. Gallbladder endothelin production is an early event in acute cholecystitis, increases gallbladder tone and plays a crucial role in the inflammatory process.

Effects of ET-1 and NO on hepatic hemodynamics at various stages of isolated perfused cirrhotic liver in rats

AIM

To investigate the effects of ET-1, NO on hepatic hemodynamics in isolated perfused rat liver at various stages of liver cirrhosis (LC).

METHODS

LC was induced by an intraperitoneal injection of CCL₄ combined with ethanol as drinking water. According to time points of CCL₄ injection, and combined with histopathological changes of liver and ascites, the isolated perfusion of liver was performed at a constant flow rate to determine the modulating effects of ET-1 and NO in the ends of 9th week (E-LC) and 14^th week (L-LC) after injected CCL₄.

RESULTS

After perfusion of L-NAME into the portal vein, there were no significant changes in the perfused pressure of portal vein (PP) and the hepatic venous pressure (Phv) of the L-LC group, the E-LC group and control group (P>0.05). After perfusion of ET-1, the PP of each group increased significantly (P<0.01). The elevated ranges of PP of the L-LC group was more than that of the E-LC group (P<0.01), both of which were higher than that of the control group (P<0.01). Compared with the ET-1 groups, the PP of the control group, the E-LC group and the L-LC group increased significantly (P<0.05) after perfusion of ET-1+L-NAME. There were no significant differences between the elevated ranges of PP of the L-LC and that of the E-LC group (P>0.05), both of which were more than that of the control group (P<0.01).

CONCLUSION

ET-1 plays a key role in elevating intra-hepatic resistance, facilitating synthesis of NO, which grow stronger in LC. With the development of LC, the compensation of NO decreases further. It is considered that antagonist of ET receptor and NO provider can increase synthesis of NO and be thus used in treatment of the high pressure of portal vein.