Significance of increased plasma adrenomedullin concentration in patients with cirrhosis

Upregulated expression of hypoxia reactive genes in peripheral blood mononuclear cells from chronic liver disease patients

Liver fibrosis induces intrahepatic microcirculation disorder and hypoxic stress. Hypoxic stress has the potential for an increase in the possibility of more liver fibrosis and carcinogenesis. Liver biopsy is a standard method that evaluates of intrahepatic hypoxia, however, is invasive and has a risk of bleeding as a complication. Here, we investigated the hypoxia reactive gene expressions in peripheral blood mononuclear cells (PBMC) from chronic liver disease patients to evaluate intrahepatic hypoxia in a non-invasive manner. The subjects enrolled for this study were composed of 20 healthy volunteers (HV) and 48 patients with chronic liver disease (CLD). CLD patients contained 24 patients with chronic hepatitis（CH）and 24 patients with liver cirrhosis (LC). PBMC were isolated from heparinized peripheral blood samples. We measured the transcriptional expression of hypoxia reactive genes and inflammatory cytokines by quantitative RT-PCR. mRNA expression of adrenomedullin (AM), vascular endothelial growth factor A (VEGFA) superoxide dismutase (SOD), glutathione peroxidase (GPx) (p < 0.05), Interleukin-6 (IL-6), transforming growth factor-beta (TGF-β) and heme oxygenase-1 (HO-1) in CLD group were significantly higher than HV. AM mRNA expression is correlated with serum lactate dehydrogenase (LDH), serum albumin (Alb), IL6, and SOD mRNA expression. The hypoxia reactive gene expression in PBMCs from CLD patients was more upregulated than HV. Especially, angiogenic genes were notably upregulated and correlated with liver fibrosis. Here, we suggest that mRNA expression of AM in PBMCs could be the biomarker of intrahepatic hypoxia.

•

The hypoxia reactive genes in PBMC were elevated in patients with chronic liver disease.

^•Angiogenic genes were upregulated and correlated with liver fibrosis in patients with chronic liver disease.

^•Adrenomedullin mRNA expression in PBMC was correlated with liver function.

^•mRNA expression of adrenomedullin in PBMC could be the biomarker of intrahepatic hypoxia.

Evaluation of the relationship between central serous chorioretinopathy and liver cirrhosis: A nationwide, population-based study

BACKGROUND

Central serous chorioretinopathy (CSCR) and liver cirrhosis share numerous risk factors and may have possible connections. We aimed to investigate whether patients with liver cirrhosis and the severity of cirrhosis have an increased incidence of CSCR.

METHODS

This population-based retrospective cohort study was conducted by collecting data from the Taiwan National Health Insurance Research Database from January 1, 2000, to December 31, 2015. We included patients who were newly diagnosed with cirrhosis and selected an equal number of sex- and age-matched control subjects. The effect of cirrhosis on the risk of CSCR was examined via a Cox proportional hazard regression analysis. The cumulative incidence of CSCR was assessed with the Kaplan-Meier method and the log-rank test.

RESULTS

Both groups in this study comprised a total of 25 925 individuals. The cirrhotic patients had a significantly higher cumulative risk of developing CSCR in following years than patients without cirrhosis (log-rank test < 0.001). Furthermore, compared with noncirrhotic patients, the risk of CSCR was increased 3.59-fold (95% confidence interval [CI], 2.31-5.28) in cirrhotic patients with complications, and 2.34-fold (95% CI, 1.27-3.24) in cirrhotic patients without complications. Additionally, male sex, springtime, diabetes mellitus, hepatitis B virus, and hepatitis C virus statistical significantly increased the incidence of CSCR.

CONCLUSION

Cirrhosis is an independent indicator of CSCR. Among the cirrhotic population, patients with ascites and other complications have a higher incidence of CSCR than those with uncomplicated cirrhosis. Physicians should be observant when managing cirrhotic patients with visual disturbances.

Pro-adrenomedullin in acute decompensation of liver cirrhosis: relationship with acute-on-chronic liver failure and short-term survival

Background and aim: Acute-on-chronic liver failure (ACLF) is characterized by the presence of acute decompensation (AD) of cirrhosis, organ failures, and high short-term mortality rates. In present study, we explored whether Pro-adrenomedullin (Pro-ADM), a biomarker of sepsis, is a potential marker of outcome in patients admitted for AD or ACLF and whether it might be of additional value to conventional prognostic scoring systems in these patients.Methods: 332 consecutive patients with AD of cirrhosis were prospectively enrolled. Pro-ADM was measured for all patients at baseline. Cox regression analysis was used to evaluate the impact of pro-ADM on short-term survival and developing ACLF during hospital stay.Results: Serum pro-ADM levels were significantly high in non-survivors (p < .001) and showed significant correlation with ALT (r = 0.181, p = .001), INR (r = 0.144, p = .009), TB (r = 0.368, p < .001), Creatinine (r = 0.145, p = .004), MELD score (r = 0.334, p = <.001) and CLI-C OF score (r = 0.375, p= <.001). Serum pro-ADM at admission was shown to be a predictor of 28-day mortality independently of MELD and CLIF-C OF scores. Prognostic models incorporating pro-ADM achieved high C index for predicting 28-day mortality in AD patients of cirrhosis. Moreover, baseline pro-ADM was found to be predictive of ACLF development during hospital stay.Conclusions: Serum pro-ADM levels correlate with multiorgan failure and are independently associated with short-term survival and ACLF development in patients admitted for AD or ACLF.

Acute kidney injury spectrum in patients with chronic liver disease: Where do we stand?

Acute kidney injury (AKI) is a common complication of liver cirrhosis and is of the utmost clinical and prognostic relevance. Patients with cirrhosis, especially decompensated cirrhosis, are more prone to develop AKI than those without cirrhosis. The hepatorenal syndrome type of AKI (HRS–AKI), a spectrum of disorders in prerenal chronic liver disease, and acute tubular necrosis (ATN) are the two most common causes of AKI in patients with chronic liver disease and cirrhosis. Differentiating these conditions is essential due to the differences in treatment. Prerenal AKI, a more benign disorder, responds well to plasma volume expansion, while ATN requires more specific renal support and is associated with substantial mortality. HRS–AKI is a facet of these two conditions, which are characterized by a dysregulation of the immune response. Recently, there has been progress in better defining this clinical entity, and studies have begun to address optimal care. The present review synopsizes the current diagnostic criteria, pathophysiology, and treatment modalities of HRS–AKI and as well as AKI in other chronic liver diseases (non-HRS–AKI) so that early recognition of HRS–AKI and the appropriate management can be established.

Plasma levels of mid-regional pro-adrenomedullin in sepsis are associated with risk of death

BACKGROUND

Identifying Intensive Care Unit (ICU) patients with sepsis and predicting the risk of death are unmet clinical needs.

METHODS

Prospective observational single-center study of 120 consecutive ICU patients with suspected severe sepsis at Jerez Hospital. Epidemiological, clinical, laboratory data and MR-proADM, Procalcitonin (PCT) and C-reactive protein (CRP) levels were recorded at ICU admission and follow-up.

RESULTS

At ICU discharge, 104 patients were diagnosed with severe sepsis and 39 died. Plasma MR-proADM was highly indicative of sepsis: 4.05 nmol/L vs. of 0.309 nmol/L (P<0.001), with area under the ROC curve (AUC-ROC) was 0.947. At 48 hours following admission, the median MR-proADM levels in surviving sepsis patients fell to 1.65 nmol/L but remained higher in the non-survivors (2.475 nmol/L) (P=0.04). On day 5 the levels fell to 1.36 nmol/L in surviving sepsis patients vs. 3.42 nmol/L in the non-survivors (P<0.001). On day 5 the survivors showed greater MR-proADM clearance (62.7% vs. 21.2%). The AUC-ROC on day 5 was 0.825, PCT 0.725 and CRP 0.700. The AUC-ROC to MR-proADM clearance on day 5 was 0.734. In a multivariable model, MR-proADM levels at 48 hours and on day 5 and clearance on day 5 following admission were statistically significant predictive factors of mortality.

CONCLUSIONS

In clinical practice, in ICU patients admitted with SIRS and organ dysfunction, an MR-proADM cut-off point of 1.425 nmol/L helps to identify those with sepsis. An MR-proADM value above 5.626 nmol/L 48 hours after admission was associated with a high risk of death.

Serum adrenomedullin and urinary thromboxane B2 help early categorizing of acute kidney injury in decompensated cirrhotic patients: A prospective cohort study

AIMS

Increases in the systemic vasodilator adrenomedullin and the renal vasoconstrictors thromboxane A₂ in cirrhotic patients are pathogenic factors for the development of functional acute kidney injury (AKI), including pre-renal azotemia (PRA) and hepatorenal syndrome (HRS), which is associated with high mortality. This study aims to find biomarkers that can diagnose HRS at an early stage, to enable treatment as soon as possible.

METHODS

Acute decompensated cirrhotic patients who had been admitted to hospital were enrolled in this prospective cohort study. Blood and urinary samples were collected immediately after admission. In addition to initially categorizing AKI cases into PRA, acute tubular necrosis (ATN), and HRS groups, their final diagnosis was adjudicated by a nephrologist and a hepatologist who checked the corrected and misclassification rates for significant biomarkers.

RESULTS

The cut-off values for serum adrenomedullin and urinary thromboxane B₂ (TXB₂ ), when used as predictors for functional AKI (adrenomedullin >283 pg/mL, urinary TXB₂ >978 [pg/mg urinary creatinine]), for HRS (adrenomedullin >428, urinary TXB₂  >1604), and for good terlipressin plus albumin treatment responders (adrenomedullin >490, urinary TXB₂  >1863), were observed. Patients with HRS who could be treated, due to high mortality, had significantly higher serum adrenomedullin and urinary TXB₂ levels compared to HRS patients receiving standard treatment. In addition to predicting 60-day mortality, a combination of these two markers further increased diagnostic accuracy for HRS among functional AKI.

CONCLUSIONS

Prompt diagnosis of HRS by differentiating it from PRA and ATN can be achieved by using serum adrenomedullin and urinary TXB₂ in acute decompensated cirrhotic patients. In combination with severe clinical courses, these two markers are useful to select HRS patients who cannot be treated.

Molecular Mechanisms Leading to Splanchnic Vasodilation in Liver Cirrhosis

In liver cirrhosis, portal hypertension is a consequence of enhanced intrahepatic vascular resistance and portal blood flow. Significant vasodilation in the arterial splanchnic district is crucial for an increase in portal flow. In this pathological condition, increased levels of circulating endogenous vasodilators, including nitric oxide, prostacyclin, carbon monoxide, epoxyeicosatrienoic acids, glucagon, endogenous cannabinoids, and adrenomedullin, and a decreased vascular response to vasoconstrictors are the main mechanisms underlying splanchnic vasodilation. In this review, the molecular pathways leading to splanchnic vasodilation will be discussed in detail.

New role of biomarkers: mid-regional pro-adrenomedullin, the biomarker of organ failure

Mid-regional pro-adrenomedullin (MR-proADM) has a good biomarker profile: its half-life is several hours, and its plasma concentrations can be determined in clinical practice, it is essentially irrelevant, but proportionally represents the levels and activity of adrenomedullin (ADM). ADM synthesis is widely distributed in tissues, including bone, adrenal cortex, kidney, lung, blood vessels and heart. Its fundamental biological effects include vasodilator, positive inotropic, diuretic, natriuretic and bronchodilator. It has been described high levels in septic patients, interacting directly with the relaxation of vascular tone, triggering hypotension of these patients. It is also found high levels in other diseases such as hypertension, heart failure, respiratory failure, renal failure, cirrhosis and cancer. MR-proADM has been identified as a prognostic marker, stratifying the mortality risk in patients with sepsis in emergency department (ED) and ICU. Evolutionary MR-proADM levels and clearance marker to the 2nd-5th days of admission help to determine the poor performance and the risk of mortality in patients with severe sepsis admitted to the ICU. The MR-proADM levels are more effective than procalcitonin (PCT) and C-reactive protein (CRP) levels to determine an unfavorable outcome and the risk of mortality in patients with sepsis admitted to the ICU. It has also proved useful in patients diagnosed with organ dysfunction of infectious etiology. MR-proADM levels are independent of the germ conversely it is related to the magnitude of organ failure and therefore severity. We consider advisable incorporating the MR-proADM the panel of biomarkers necessary for the diagnosis and treatment of critically ill patients admitted to the ICU with severe sepsis. The combined PCT and MR-proADM levels could represent a valid tool in the clinical practice to timely identify patients with bacterial infections and guide the diagnosis and treatment of sepsis and septic shock.

Genomic profiles and predictors of early allograft dysfunction after human liver transplantation

Early hepatic allograft dysfunction (EAD) manifests posttransplantation with high serum transaminases, persistent cholestasis, and coagulopathy. The biological mechanisms are poorly understood. This study investigates the molecular mechanisms involved in EAD and defines a gene expression signature revealing different biological pathways in subjects with EAD from those without EAD, a potential first step in developing a molecular classifier as a potential clinical diagnostic. Global gene expression profiles of 30 liver transplant recipients of deceased donor grafts with EAD and 26 recipients without graft dysfunction were investigated using microarrays of liver biopsies performed at the end of cold storage and after graft reperfusion prior to closure. Results reveal a shift in inflammatory and metabolic responses between the two time points and differences between EAD and non-EAD. We identified relevant pathways (PPARα and NF-κB) and targets (such as CXCL1, IL1, TRAF6, TIPARP, and TNFRSF1B) associated with the phenotype of EAD. Preliminary proof of concept gene expression classifiers that distinguish EAD from non-EAD patients, with Area Under the Curve (AUC) >0.80 were also identified. This data may have mechanistic and diagnostic implications for EAD.

Regulation of RAMP expression in diseases

Receptor-activity modifying proteins (RAMPs) belong to a single family of transmembrane proteins. RAMPs determine ligand specificity of G-protein coupled receptors; calcitonin receptor and the calcitonin-receptor like receptor (CLR). To date, three members of RAMP family (RAMP-1, -2, -3) have been identified. The co-expression of RAMP-1 with CLR constitutes the calcitonin gene related peptide receptor whereas the association of the RAMP-2 or RAMP-3 with CLR forms the adrenomedullin (AM) receptor. Alterations in signaling and subcellular distribution of G-protein coupled receptors can be responsible for the regulation of many disease conditions. These changes may be mediated by the different isoforms of RAMPs associated with such receptors. In this chapter, we describe the differential responses associated with upregulation of RAMPs in disease conditions. For instance, the upregulation of all three RAMP isoforms contributes to the cardioprotective effects of the CLR/RAMP ligands. On the other hand, strong evidence exists for the involvement of AM in various cancers and that its action is mediated by the upregulation of RAMP isoforms, RAMP-2 and -3. Though limited, a few studies have been reported on the differential response associated with the upregulation of RAMP in other disease conditions such as sepsis, liver cirrhosis, glomerulonephritis, Type 1 diabetes and Parkinson's disease. Thus, the regulation of RAMP expression is involved in the pathophysiology associated with various diseases.

Adrenomedullin Function in Vascular Endothelial Cells: Insights from Genetic Mouse Models

Adrenomedullin is a highly conserved peptide implicated in a variety of physiological processes ranging from pregnancy and embryonic development to tumor progression. This review highlights past and present studies that have contributed to our current appreciation of the important roles adrenomedullin plays in both normal and disease conditions. We provide a particular emphasis on the functions of adrenomedullin in vascular endothelial cells and how experimental approaches in genetic mouse models have helped to drive the field forward.

Physiology of Kidney Renin

The protease renin is the key enzyme of the renin-angiotensin-aldosterone cascade, which is relevant under both physiological and pathophysiological settings. The kidney is the only organ capable of releasing enzymatically active renin. Although the characteristic juxtaglomerular position is the best known site of renin generation, renin-producing cells in the kidney can vary in number and localization. (Pro)renin gene transcription in these cells is controlled by a number of transcription factors, among which CREB is the best characterized. Pro-renin is stored in vesicles, activated to renin, and then released upon demand. The release of renin is under the control of the cAMP (stimulatory) and Ca2+(inhibitory) signaling pathways. Meanwhile, a great number of intrarenally generated or systemically acting factors have been identified that control the renin secretion directly at the level of renin-producing cells, by activating either of the signaling pathways mentioned above. The broad spectrum of biological actions of (pro)renin is mediated by receptors for (pro)renin, angiotensin II and angiotensin-( 1 – 7 ).

The effects of isoflurane on adrenomedullin-induced haemodynamic responses in pithed rats

BACKGROUND AND OBJECTIVES

Adrenomedullin is a potent vasodilatory peptide. The mechanisms of adrenomedullin-induced responses are via guanine nucleotide guanosine 5'-triphosphate-binding protein (G-protein)-coupled receptor activation and are similar to those of calcitonin gene-related peptide (CGRP). Previously, we reported that sevoflurane and isoflurane inhibit CGRP-induced haemodynamic responses. The effects of volatile anaesthetics on adrenomedullin-induced haemodynamic responses, however, are unclear. We hypothesized that the volatile anaesthetic isoflurane inhibits adrenomedullin-induced haemodynamic responses. We studied the effects of isoflurane on adrenomedullin-induced haemodynamic responses in pithed rats, which enables us to evaluate the direct cardiovascular effects of drugs without interference from centrally mediated circulatory reflexes.

METHODS

Male Wistar rats were pithed by inserting a stainless-steel rod into the spinal cord. Following median sternotomy, a flow probe was placed around the ascending aorta to measure aortic blood flow. Mean arterial pressure and cardiac output were maintained at approximately 100 mmHg and 50 mL min-1, respectively, with continuous infusion of norepinephrine. After 30 min inhalation of isoflurane (1%, or 2%) in oxygen, or only oxygen, adrenomedullin (1, 3, 10 or 30 microg kg-1) was administered intravenously.

RESULTS

Adrenomedullin administration induced a transient increase followed by a persistent decrease in mean arterial pressure and cardiac output. Isoflurane (2%) significantly inhibited the initial increase in mean arterial pressure and the later decrease in mean arterial pressure and systemic vascular resistance.

CONCLUSION

Isoflurane inhibits adrenomedullin-induced vasodilation and positive inotropic effect in pithed rats. Isoflurane might inhibit the adrenomedullin receptor-mediated response, which is a common pathway for both actions.

Liver fibrosis: a balance of ACEs?

There is an increasing body of evidence to suggest that the RAS (renin–angiotensin system) contributes to tissue injury and fibrosis in chronic liver disease. A number of studies have shown that components of a local hepatic RAS are up-regulated in fibrotic livers of humans and in experimental animal models. Angiotensin II, the main physiological effector molecule of this system, mediates liver fibrosis by stimulating fibroblast proliferation (myofibroblast and hepatic stellate cells), infiltration of inflammatory cells, and the release of inflammatory cytokines and growth factors such as TGF (transforming growth factor)-β1, IL (interleukin)-1β, MCP (monocyte chemoattractant protein)-1 and connective tissue growth factor. Furthermore, blockade of the RAS by ACE (angiotensin-converting enzyme) inhibitors and angiotensin type 1 receptor antagonists significantly attenuate liver fibrosis in experimental models of chronic liver injury. In 2000 ACE2 (angiotensin-converting enzyme 2), a human homologue of ACE, was identified. ACE2 efficiently degrades angiotensin II to angiotensin-(1–7), a peptide which has recently been shown to have both vasodilatory and tissue protective effects. This suggests that ACE2 and its products may be part of an alternate enzymatic pathway in the RAS, which counterbalances the generation and actions of angiotensin II, the ACE2–angiotensin-(1–7)–Mas axis. This review focuses on the potential roles of the RAS, angiotensin II and ACE2 in chronic liver injury and fibrogenesis.

In vitro liver tissue model established from transgenic mice: role of HIF-1alpha on hypoxic gene expression

The instability of the hepatocyte phenotype in vitro has limited the ability to quantitatively investigate regulation of stress responses of the liver. Here, we adopt a tissue-engineering approach to form stable liver tissue in vitro by forming collagen "sandwich" cultures of transgenic murine hepatocytes harboring a regulatory gene of interest flanked by loxP sites. The floxed gene is excised in a subset of cultures by transfection with adenovirus carrying the gene for Cre-recombinase, thereby generating wild-type and null liver tissues from a single animal. In this study, we specifically investigated the role of hypoxia inducible factor 1 alpha (HIF-1alpha) in the hepatocellular response to hypoxia. Using high-density oligonucleotide arrays, we examined genome-wide gene expression after 8 h of hypoxia in wild-type and HIF- 1alpha null hepatocyte cultures. We identified more than 130 genes differentially expressed under hypoxia involved in metabolic adaptation, angiogenic signaling, immediate early response, and cell cycle regulation. Real-time polymerase chain reaction analysis verified that known hypoxia-responsive genes such as glucose transporter-1 and vascular endothelial growth factor were induced in a HIF-1alpha-dependent manner under hypoxia. Our results demonstrate the potential to integrate in vitro tissue models with transgenic and microarray technologies for the study of physiologic stress responses.

The gene expression of adrenomedullin, calcitonin-receptor-like receptor and receptor activity modifying proteins (RAMPs) in CCl4-induced rat liver cirrhosis

This study was undertaken to determine AM expression in carbon tetrachloride (CCl4)-induced liver cirrhosis developed with peritoneal ascites. Sprague-Dawley rats received subcutaneous injections of CCl4 twice weekly in olive oil (1:1, 0.3 ml per kg body weight) for 6 or 12 weeks until ascites developed, or saline in olive oil as control. At 6 weeks, fibrosis developed and at 12 weeks cirrhosis developed with ascites formation. At both 6 and 12 weeks, increases in plasma renin and AM were evident, as was the gene expression of AM. At 12 weeks after CCl4 injection, the gene expression of calcitonin-like-receptor (CRLR) and receptor activity modifying proteins (RAMP1, RAMP2 and RAMP3) were all elevated when compared to the control. The results suggest that liver cirrhosis increases mRNA expressions of AM, CRLR and RAMP1, RAMP2 and RAMP3 and that the increase in AM gene expression precedes the development of cirrhosis. The increase in AM synthesis as reflected by an increase in AM gene expression, together with a lack of increase in AM peptide at both 6 and 12 weeks may suggest an elevation of AM release. Given the potent vasodilatory action of AM, the increase in the synthesis and release of AM in the cirrhotic liver may also contribute to peripheral vasodilatation in liver cirrhosis.

Local regulator adrenomedullin contributes to the circulatory disturbance in cirrhotic rats

AIM: To investigate whether adrenomedullin, a potent vasodilator peptide, plays a role in the circulatory disturbance in cirrhosis.

METHODS: Cirrhosis was induced in rats by weekly gavage of carbon tetrachloride. Hemodynamic studies were performed in vivo using radioactive microspheres and in vitro using isolated aortic rings. The adrenomedullin concentrations were measured by radioimmunoassay.

RESULTS: Acute administration of adrenomedullin to the control rats reduced the systemic arterial pressure along with an increase of serum levels of the stable metabolite of nitric oxide (NOx), in a dose-dependent manner. Chronic infusion of adrenomedullin reduced the vascular resistance and increased the blood flow in the systemic and splanchnic circulation. Intravenous administration of anti-adrenomedullin antibody did not affect any hemodynamic parameters in the cirrhotic rats, whereas this antibody ameliorated the blunted contractile response to phenylephrine, α-adrenergic receptor agonist, in the aortic rings of the cirrhotic rats. The adrenomedullin concentrations in the aorta were higher in the cirrhotic rats than in the controls, and correlated with the mean arterial pressure in the cirrhotic rats. Moreover, adrenomedullin blunted the contractile response to phenylephrine in both of the control aorta and cirrhotic aorta, but not in the presence of NG-nitro-L-arginine methyl ester, an NO synthase inhibitor.

CONCLUSION: Adrenomedullin overproduced in the vascular wall may contribute to the circulatory disturbance in cirrhosis as a local regulator of the vascular tonus rather than a circulating hormone.

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.

Natriuretic Peptides and the Dialysis Patient

The natriuretic peptide family consists of four structurally similar, but genetically distinct molecules with pronounced cardiovascular and renal actions. They are counterregulatory hormones playing an important role in fluid volume homeostasis. Atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) cause diuresis, natriuresis, and vasodilatation. C-type natriuretic peptide (CNP) has antimitogenic effects and causes vascular smooth muscle relaxation. Dendroaspis natriuretic peptide (DNP) shares many of the actions of ANP and BNP, but its function in humans is not yet fully understood. Natriuretic peptides have been extensively investigated as biochemical markers of the fluid state. Levels are elevated in disease conditions characterized by fluid overload and are closely related to survival in various cardiac disease states. In the dialysis population, BNP correlates significantly with cardiac function, whereas ANP is sensitive to volume changes during dialysis. However, changes in concentration do not predict achievement of euvolemia, and short half-life, combined with complicated assay techniques, make ANP a less than satisfactory tool for assessing hydration. BNP is a superior prognosticator for risk stratification in dialysis patients, and serial estimations will help in the identification of occult cardiac disease.

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.

Adrenomedullin contributes to vascular hyporeactivity in cirrhotic rats with ascites via a release of nitric oxide

BACKGROUND

Plasma levels of adrenomedullin, a potent vasodilator peptide, are increased in cirrhotic patients, whereas its role in vascular hyporeactivity in cirrhosis has not been clarified.

METHODS

Adrenomedullin expression was evaluated by radioimmunoassay and reverse-transcription polymerase chain reaction. Vascular reactivity to phenylephrine, alpha-adrenoceptor agonist, was investigated in the aortic rings from control rats and CCl-induced cirrhotic rats with ascites in the presence of the neutralizing antibody against adrenomedullin, human adrenomedullin and/or N-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor.

RESULTS

Plasma adrenomedullin levels were significantly higher in cirrhotic rats than in controls (16.3 +/- 2.9 versus 7.4 +/- 1.7 fmol/mL, P < 0.05) and correlated negatively with systemic arterial pressure (r = -0.62, P < 0.05). Gene expression of adrenomedullin in various organs (liver, kidney, lung) and vessels (portal vein, aorta) was enhanced in cirrhotic rats compared with controls. Neutralizing antibody against adrenomedullin ameliorated the blunted contractile response to phenylephrine in cirrhotic aorta (Rmax: 1.5 +/- 0.1 versus 1.0 +/- 0.1 g/mg tissue, P < 0.05), whereas contraction remained unchanged in control aorta (Rmax: 1.9 +/- 0.2 versus 1.9 +/- 0.2 g/mg tissue). Intravenous infusion of human adrenomedullin induced a reduction of mean arterial pressure together with an increase of serum nitrate levels, which was abolished by neutralizing antibody against adrenomedullin. Human adrenomedullin caused a blunted contractile response to phenylephrine in both control and cirrhotic aortas, which was not observed in the presence of N-nitro-L-arginine methyl ester.

CONCLUSIONS

These findings indicate that the overproduction of adrenomedullin may contribute to vascular hyporeactivity in cirrhosis via a release of nitric oxide.

Role of cyclooxygenase in ventricular effects of adrenomedullin: is adrenomedullin a double-edged sword in sepsis?

Adrenomedullin (ADM) is upregulated in cardiac tissue under various pathophysiological conditions. However, the direct inotropic effect of ADM on normal and compromised cardiomyocytes is not clear. In rat ventricular myocytes, ADM produced an initial (<30 min) increase in cell shortening and Ca2+ transient and, on prolonged incubation (>1 h), a marked decrease in cell shortening and Ca2+ transient. Both effects were sensitive to inhibition by the ADM antagonist ADM-(22–52). The increase and decrease in cell shortening and Ca2+ transient were attenuated by pretreatment with indomethacin [a nonspecific cyclooxygenase (COX) inhibitor], nimesulide and SC-236 (specific COX-2 inhibitors), and tranylcypromine (a prostacyclin synthase inhibitor); SQ-29548 (a thromboxane receptor antagonist) was without effect. Cells isolated from LPS-treated rats that were in the late, hypodynamic phase of septic shock also showed a marked decrease in cell shortening and Ca2+ transient. Because ADM is overexpressed in sepsis, we repeated the above protocol in cells isolated from LPS-treated rats. At 4 h after LPS injection, ADM levels markedly increased in plasma, ventricles, and freshly isolated ventricular myocytes. Decreases in cell shortening and Ca2+ transient in LPS-treated cells were reversed by pretreatment with ADM-(22–52). Anti-ADM (rat) IgG also reversed the decrease in cell shortening and other parameters of cell kinetics. Indomethacin, SC-236, and tranylcypromine restored cell contractility and the decrease in Ca2+ transient, whereas SQ-29548 had no effect, implying that prostacyclin played a role in both effects. However, with regard to cell-shortening kinetics, indomethacin and SQ-29548 decreased the amount of time taken by the cells to return to baseline, whereas SC-236 and tranylcypromine did not, implying that not only prostacyclin, but also thromboxane, is involved. The results indicate that ADM interacts with COX to yield prostanoids, which mediate its negative inotropic effect in LPS-treated rat ventricular myocytes.

Adrenomedullin in cirrhotic and non-cirrhotic portal hypertension

AIM: Adrenomedullin (ADM) is a potent vasodilator peptide. ADM and nitric oxide (NO) are produced in vascular endothelial cells. Increased ADM level has been linked to hyperdynamic circulation and arterial vasodilatation in cirrhotic portal hypertension (CPH). The role of ADM in non-cirrhotic portal hypertension (NCPH) is unknown. plasma ADM levels were studied in patients with NCPH, compensated and decompensated cirrhosis in order to determine its contribution to portal hypertension (PH) in these groups.

METHODS: There were 4 groups of subjects. Group 1 consisted of 27 patients (F/M: 12/15) with NCPH due to portal and/or splenic vein thrombosis (mean age: 41 ± 12 years), group 2 consisted of 14 patients (F/M: 6/8) with compensated (Child-Pugh A) cirrhosis (mean age: 46 ± 4), group 3 consisted of 16 patients (F/M: 6/10) with decompensated (Child-Pugh C) cirrhosis (mean age: 47 ± 12). Fourteen healthy subjects (F/M: 6/8) (mean age: 44 ± 8) were used as controls in Group 4. ADM level was measured by ELISA. NO was determined as nitrite/nitrate level by chemoluminescence.

RESULTS: ADM level in Group 1 (236 ± 61.4 pg/mL) was significantly higher than that in group 2 (108.4 ± 28.3 pg/mL) and group 4 (84.1 ± 31.5 pg/mL) (both P < 0.0001) but was lower than that in Group3 (324 ± 93.7 pg/mL) (P = 0.002). NO level in group 1 (27 ± 1.4 μmol/L) was significantly higher than that in group 2 (19.8 ± 2.8 μmol/L) and group 4 (16.9 ± 1.6 μmol/L) but was lower than that in Group 3 (39 ± 3.6 μmol/L) (for all three P < 0.0001). A strong correlation was observed between ADM and NO levels (r = 0.827, P < 0.0001).

CONCLUSION: Adrenomedullin and NO levels were high in both non-cirrhotic and cirrhotic portal hypertension and were closely correlated, Adrenomedullin and NO levels increased proportionally with the severity of cirrhosis, and were significantly higher than those in patients with NCPH. Portal hypertension plays an important role in the increase of ADM and NO. Parenchymal damage in cirrhosis may contribute to the increase in these parameters.

Circulating adrenomedullin is increased in relation with increased creatinine and atrial natriuretic peptide in liver-transplant recipients

OBJECTIVES

Circulating adrenomedullin (ADM), a potent vasorelaxing and natriuretic peptide involved in cardiovascular homeostasis, is increased after cardiac and renal transplantation. ADM is also implicated in hemodynamic abnormalities during liver cirrhosis, but whether ADM is increased late after liver transplantation is unknown.

PATIENTS

A total of 18 subjects--10 liver-transplant patients (Ltx) and 8 healthy subjects--were enrolled in the study.

DESIGN AND MEASUREMENTS

After a 15-min rest period in supine position, heart rate and systemic blood pressure were determined in all subjects. Then, venous blood samples were obtained in order to simultaneously determine the cyclosporine through levels, the biological (cyclosporine, renal and hepatic functions) and hormonal (ADM and atrial natriuretic peptide (ANP)) characteristics of the Ltx.

RESULTS

ADM (27.2+/-4.1 vs. 53.8+/-6.9 pmol/l, P=0.02), and ANP (5.9+/-0.9 vs. 12.8+/-1.4 pmol/l, P=0.001) were significantly increased in late, stable Ltx (35.4+/-9.6 months after transplantation). Furthermore, increased ADM correlated positively with elevated creatinine (r=0.76, P=0.01) and ANP (r=0.64, P=0.04) after liver transplantation.

CONCLUSIONS

Liver-transplant patients exhibit a sustained increase in circulating ADM. Such an increase likely results from renal impairment associated with volume regulation abnormalities, suggesting a potential role for ADM in volume regulation after liver transplantation.

Cell and molecular biology of the multifunctional peptide, adrenomedullin

Adrenomedullin (AM) is a recently discovered regulatory peptide involved in many functions including vasodilatation, electrolyte balance, neurotransmission, growth, and hormone secretion regulation, among others. This 52-amino acid peptide is expressed by specific cell types in many organs throughout the body. A complex receptor system has been described for AM; it requires at least the presence of a seven-transmembrane-domain G-protein-coupled receptor, a single-transmembrane-domain receptor activity modifying protein, and a receptor component protein needed to establish the connection with the downstream signal transduction pathway, which usually involves cyclicAMP. In addition, a serum-binding protein regulates the biological actions of AM, frequently by increasing AM functional attributes. Changes in levels of circulating AM correlate with several critical diseases, including cardiovascular and renal disorders, sepsis, cancer, and diabetes. Whether AM is a causal agent, a protective reaction, or just a marker for these diseases is currently under investigation. New technologies seeking to elevate and/or reduce AM levels are being investigated as potential therapeutic avenues.

Mature form of adrenomedullin is a useful marker to evaluate blood volume in hemodialysis patients

We investigated the pathophysiological significance of the mature form of adrenomedullin (AM) in hemodialysis (HD) patients. Thirty-nine HD patients were enrolled and divided into two groups: those undergoing ultrafiltration (UF) during an HD session, group I; and those not undergoing UF, group II. We measured mature AM, atrial natriuretic peptide (ANP), endothelin-1, nitric oxide, cyclic guanosine 3',5'-monophosphate, and catecholamine levels at 1-hour intervals during HD sessions. On-line optical measurement of hematocrit was used to estimate change in blood volume during HD. In group II, blood volume did not change significantly during HD, nor did plasma mature AM concentrations estimated at the beginning and end of the HD treatment (3.0 +/- 0.3 and 2.8 +/- 0.2 fmol/mL, respectively). However, blood volume decreased significantly in group I patients (-7.3% +/- 0.6%), as did plasma mature AM concentrations (from 4.4 +/- 0.3 to 3.1 +/- 0.3 fmol/mL; P < 0.01). In contrast to mature AM, plasma ANP concentrations declined in both groups (from 193 +/- 32 to 87 +/- 14 pg/mL in group I and 67 +/- 12 to 46 +/- 8 pg/mL in group II). We conclude that mature AM is a useful marker to evaluate circulating blood volume in HD patients. Circulating blood volume may regulate the conversion of AM from the inactive to the mature form.

The role of adrenomedullin in producing differential hemodynamic responses during sepsis

Although the hemodynamic response to polymicrobial sepsis is characterized by an early, hyperdynamic phase followed by a late, hypodynamic phase, the factors responsible for producing the transition from the hyperdynamic to the hypodynamic stage are not fully understood. The failure to recognize or prevent this transition may lead to progressive deteriorations in cell and organ functions and ultimately result in multiple organ failure. Despite the fact that several vasoactive mediators (i.e., nitric oxide, prostacyclin, calcitonin gene-related peptide) have been implicated in producing cardiovascular alterations during sepsis, recent studies have indicated that adrenomedullin (AM), a novel vasodilatory peptide, plays an important role in initiating the hyperdynamic response during the early stage of polymicrobial sepsis. In addition, the reduced vascular responsiveness appears to be responsible for producing the transition from the early, hyperdynamic phase to the late, hypodynamic phase of sepsis. Moreover, modulation of AM vascular responsiveness reduces sepsis-induced mortality. In this review the physiological effects of AM, mechanisms of its action, and regulation of its production under various pathophysiological conditions will be discussed. Furthermore, the role of AM in producing the biphasic hemodynamic responses observed during polymicrobial sepsis and approaches for pharmacologically modulating vascular responsiveness and hemodynamic stability under such conditions will be described.

Adrenomedullin, a multifunctional regulatory peptide

Since the discovery of adrenomedullin in 1993 several hundred papers have been published regarding the regulation of its secretion and the multiplicity of its actions. It has been shown to be an almost ubiquitous peptide, with the number of tissues and cell types synthesizing adrenomedullin far exceeding those that do not. In Section II of this paper we give a comprehensive review both of tissues and cell lines secreting adrenomedullin and of the mechanisms regulating gene expression. The data on circulating adrenomedullin, obtained with the various assays available, are also reviewed, and the disease states in which plasma adrenomedullin is elevated are listed. In Section III the pharmacology and biochemistry of adrenomedullin binding sites, both specific sites and calcitonin gene-related peptide (CGRP) receptors, are discussed. In particular, the putative adrenomedullin receptor clones and signal transduction pathways are described. In Section IV the various actions of adrenomedullin are discussed: its actions on cellular growth, the cardiovascular system, the central nervous system, and the endocrine system are all considered. Finally, in Section V, we consider some unresolved issues and propose future areas for research.

Adrenomedullin in liver transplantation and its relationship with vascular complications

Adrenomedullin (AM) is a potent vasodilating peptide that increases rat platelet cyclic adenosine monophosphate levels and acts on endothelial cells to stimulate nitric oxide release. Both mechanisms inhibit platelet function. Considering these effects, AM may have a role in cardiovascular regulation after orthotopic liver transplantation (OLT) and could have an antithrombotic effect. The aim of the present study is to investigate plasma AM levels in the early postoperative period after OLT and their relationship with vascular complications in OLT. We measured plasma AM levels in 35 patients with cirrhosis who underwent OLT at baseline and 1, 7, and 15 days postoperatively. We found that AM levels were significantly greater in patients with cirrhosis compared with healthy subjects. Of the 35 patients, 10 had vascular complications. In these 10 patients, AM concentrations were significantly greater than those observed in the nonthrombotic group in the early postoperative period. In addition, we also noticed in the nonthrombotic group a significant increase in AM levels from baseline to day 1, then a decrease to baseline levels in the early postoperative period. Our study shows that AM might act as a new humoral factor involved in the response to surgery in OLT and is significantly associated with vascular thrombosis in OLT.

Portal hypertension

Cirrhosis represents the end stage of any chronic liver disease. Two major syndromes result from cirrhosis: portal hypertension and hepatic insufficiency. Additionally, vasodilatation and the hyperdynamic circulation are hemodynamic abnormalities typical of cirrhosis and portal hypertension. Complications of cirrhosis occur as a consequence of a combination of these factors. Gastroesophageal varices result almost solely from portal hypertension, although the hyperdynamic circulation contributes to variceal growth and hemorrhage. Ascites results from sinusoidal hypertension and sodium retention, which is, in turn, secondary to vasodilatation and activation of neurohumoral systems. Hyponatremia and the hepatorenal syndrome result from water retention and renal vasoconstriction, respectively, both of which are also consequences of peripheral vasodilatation. Vasodilatation that occurs in the pulmonary circulation leads to the hepatopulmonary syndrome. Another complication of cirrhosis, portosystemic encephalopathy, is a consequence of both portal hypertension (shunting of blood through portosystemic collaterals) and hepatic insufficiency. This paper reviews the recent advances in the pathophysiology and management of the complications of cirrhosis and portal hypertension.