Increased plasma nitric oxide, L-arginine, and arginase-1 in cirrhotic patients with progressive renal dysfunction

Endothelin-1/Nitric Oxide Ratio as a Predictive Factor of Response to Therapy With Terlipressin and Albumin in Patients With Type-1 Hepatorenal Syndrome

Background and Purpose

Predictors of response to type-1 hepatorenal syndrome (HRS) therapy are urgently needed. This study's purpose is to evaluate the proposed predictors in these patients.

Methods

Forty-two type-1 HRS patients with cirrhosis were treated with albumin and terlipressin. Clinical, biochemical, and demographic parameters taken at the onset of therapy and changes in endothelin-1/nitric oxide (ET-1/NO) ratio during therapy were analyzed to check their predictive value.

Results

Response to treatment (serum creatinine level <1.5 mg/dL at the end of therapy) was shown in 20 patients (48%). Independent predictive variables of response to therapy were early reduction of ET-1/NO ratio ≥0.15 at day 3 of therapy and serum bilirubin baseline <8 mg/dL (area under the receiver operating characteristic curve, 0.751; P < 0.001; specificity, 55%; sensitivity, 85%). Response rates in patients with serum bilirubin level <8 and ≥8 mg/dL were 63% and 20%, respectively (P = 0.008). The corresponding values in patients with an early reduction of ET-1/NO ratio ≥0.15 and <0.15 on day 3 were 85% and 13.6%, respectively (P < 0.001).

Conclusions

Early reduction of ET-1/NO ratio and lower serum bilirubin baseline can predict response to type-1 HRS therapy with albumin and terlipressin. Alternative therapy should be investigated for nonresponder type-1 HRS patients.

Endotoxemia-enhanced renal vascular reactivity to endothelin-1 in cirrhotic rats

Hepatorenal syndrome (HRS), a severe complication of advanced cirrhosis, is defined as hypoperfusion of kidneys resulting from intense renal vasoconstriction in response to generalized systemic arterial vasodilatation. Nevertheless, the mechanisms have been barely investigated. Cumulative studies demonstrated renal vasodilatation in portal hypertensive and compensated cirrhotic rats. Previously, we identified that blunted renal vascular reactivity of portal hypertensive rats was reversed after lipopolysaccharide (LPS). This study was therefore conducted to delineate the sequence of renal vascular alternation and underlying mechanisms in LPS-treated cirrhotic rats. Sprague-Dawley rats were randomly allocated to receive sham surgery (Sham) or common bile duct ligation (CBDL). LPS was induced on the 28th day after surgery. Kidney perfusion was performed at 0.5 or 3 h after LPS to evaluate renal vascular response to endothelin-1 (ET-1). Endotoxemia increased serum ET-1 levels ( P < 0.0001) and renal arterial blood flow ( P < 0.05) in both Sham and CBDL rats. CBDL rats showed enhanced renal vascular reactivity to ET-1 at 3 h after LPS ( P = 0.026). Pretreatment with endothelin receptor type A (ET_A) antagonist abrogated the LPS-enhanced renal vascular response in CBDL rats ( P < 0.001). There were significantly lower inducible nitric oxide synthase (iNOS) expression but higher ET_A and phosphorylated extracellular signal-regulated kinase (p-ERK) expressions in renal medulla of endotoxemic CBDL rats ( P < 0.05). We concluded that LPS-induced renal iNOS inhibition, ET_A upregulation, and subsequent ERK signaling activation may participate in renal vascular hyperreactivity in cirrhosis. ET-1-targeted therapy may be feasible in the control of HRS. NEW & NOTEWORTHY Hepatorenal syndrome (HRS) occurred in advanced cirrhosis after large-volume paracentesis or bacterial peritonitis. We demonstrated that intraperitoneal lipopolysaccharide (LPS) enhanced renal vascular reactivity to endothelin-1 (ET-1) in cirrhotic rats, accompanied by inducible nitric oxide synthase inhibition, endothelin receptor type A (ET_A) upregulation, and subsequent extracellular signal-regulated kinase activation in renal medulla. Pretreatment with ET_A antagonist abrogated the LPS-enhanced renal vascular response in common bile duct ligation rats. These findings suggest that further clinical investigation of ET-1-targeted therapy may be feasible in the control of HRS.

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.

Protective Effects of the Third Generation Vasodilatory Βeta - Blocker Nebivolol against D-Galactosamine - Induced Hepatorenal Syndrome in Rats

BACKGROUND:

Renal dysfunction is very common in patients with advanced liver cirrhosis and portal hypertension. The development of renal failure in the absence of clinical, anatomical or pathological causes renal of failure is termed hepatorenal syndrome (HRS).

AIM:

The present study was constructed to investigate the possible protective effects of nebivolol (Nebi) against D-galactosamine (Gal)-induced HRS in rats.

MATERIAL AND METHODS:

Rats were treated with Nebi for ten successive days. On the 8th day of the experiment, they received a single dose of Gal. Serum levels of Cr, BUN, Na+ and K+ as well as AST, ALT, total bilirubin (TB), NH3 and endothelin-1 (ET-1) were determined following Gal administration. Moreover, renal and liver contents of MDA, GSH, F2-isoprostanes (F2-IPs), tumor necrosis factor-alpha (TNF-α), nuclear factor kappa-B (NF-κB), total nitric oxide (NO), in addition to activities of caspase-3 (Cas-3), heme oxygenase-1 (HO-1), inducible and endothelial NO synthase (iNOS and eNOS) enzymes were also assessed. Finally, histopathological examination was performed.

RESULTS:

Nebi attenuated Gal-induced renal and hepatic dysfunction. It also decreased the Gal-induced oxidative stress and inflammatory recruitment.

CONCLUSION:

Results demonstrated both nephroprotective and hepatoprotective effects of Nebi against HRS and suggested a role of its antioxidant, anti-inflammatory, anti-apoptotic and NO-releasing properties.

Electrolyte and Acid-Base Disturbances in End-Stage Liver Disease: A Physiopathological Approach

Electrolyte and acid-base disturbances are frequent in patients with end-stage liver disease; the underlying physiopathological mechanisms are often complex and represent a diagnostic and therapeutic challenge to the physician. Usually, these disorders do not develop in compensated cirrhotic patients, but with the onset of the classic complications of cirrhosis such as ascites, renal failure, spontaneous bacterial peritonitis and variceal bleeding, multiple electrolyte, and acid-base disturbances emerge. Hyponatremia parallels ascites formation and is a well-known trigger of hepatic encephalopathy; its management in this particular population poses a risky challenge due to the high susceptibility of cirrhotic patients to osmotic demyelination. Hypokalemia is common in the setting of cirrhosis: multiple potassium wasting mechanisms both inherent to the disease and resulting from its management make these patients particularly susceptible to potassium depletion even in the setting of normokalemia. Acid-base disturbances range from classical respiratory alkalosis to high anion gap metabolic acidosis, almost comprising the full acid-base spectrum. Because most electrolyte and acid-base disturbances are managed in terms of their underlying trigger factors, a systematic physiopathological approach to their diagnosis and treatment is required.

Association of eNOS Gene Polymorphisms G894T and T-786C with Risk of Hepatorenal Syndrome

Background. There are no studies investigating the relationship between endothelial nitric oxide synthase (eNOS) gene polymorphisms and hepatorenal syndrome (HRS). Aim. The purpose of this study is to elucidate whether eNOS gene polymorphisms (G894T and T-786C) play a role in the development of type-2 HRS. Methods. This study was carried out in a group of 92 patients with cirrhosis (44 patients with type-2 HRS and 48 without HRS) and 50 healthy controls. Polymorphisms were determined by polymerase chain reaction (PCR) and melting curve analysis. Results. We did not find any significant difference in allele and genotype distributions of the eNOS -T-786C polymorphism among the groups (p = 0.440). However, the frequency of GT (40.9%) and TT (13.6%) genotypes and mutant allele T (34.1%) for the eNOS G894T polymorphism were significantly higher (p < 0.001 and p < 0.001, resp.) in the HRS group than in both the stable cirrhosis (14.6%, 4.2%, and 11.5%, resp.) and the control (22.0%, 2.0%, and 13.0%, resp.) groups. Conclusion. The occurrence of mutant genotypes (GT/TT) and mutant allele T in eNOS -G894T polymorphisms should be considered as a potential risk factor in cirrhotic patients with HRS.

Effect of nitric oxide pathway regulation on water/sodium balance and renal function in a rodent model of acute liver and renal failure

BACKGROUND

The pathomechanism of acute hepatorenal syndrome (HRS), a particular form of acute renal failure that occurs in the course of acute liver injury, is still poorly understood. The aim of our study was to estimate the influence of the activation and inhibition of the nitric oxide pathway on the water/sodium balance and development of acute renal failure in the course of HRS.

MATERIAL AND METHODS

We used male Sprague-Dawley rats in the acute galactosamine (Ga1N) model of HRS. The nitric oxide synthase (NOS) inhibitors L-NAME and L-arginine were administered intraperitoneally before and after liver damage.

RESULTS

HRS developed in all tested groups. L-NAME increased osmotic clearance and urine volume more effectively before liver injury. Furthermore, administration of L-NAME increased creatinine clearance both before and after Ga1N injection. A double dose of L-NAME did not yield further improvement before Ga1N injection, but improved creatinine clearance after Ga1N intoxication. Injection of L-arginine increased sodium excretion and urine volume, but only after liver injury. Moreover, L-arginine injected after Ga1N caused significant improvement of the creatinine clearance in a dose-dependent manner.

CONCLUSIONS

Our study shows that inhibition of the nitric oxide pathway improves parameters of water and sodium balance and prevents development of acute renal failure in the course of acute liver injury and liver failure. Activation of the nitric oxide system also has a favorable influence on water/sodium balance and renal failure, but only after liver injury.

Nitric oxide in the normal kidney and in patients with diabetic nephropathy

Nitric oxide (NO) is a gas with biological and regulatory properties, produced from arginine by the way of nitric oxide synthases (NOS), and with a very short half-life (few seconds). A "coupled" NOS activity leads to NO generation, whereas its uncoupling produces the reactive oxygen species peroxynitrite (ONOO(-)). Uncoupling is usually due to inflammation, oxidative stress, decreased cofactor availability, or excessive NO production. Competitive inhibitors of NO production are post-translationally methylated arginine residues in proteins, which are constantly released into the circulation. NO availability is altered in many clinical conditions associated with vascular dysfunction, such as diabetes mellitus. The kidney plays an important role in body NO homeostasis. This article provides an overview of current literature, on NO production/availability, with a focus on diabetic nephropathy. In diabetes, NO availability is usually decreased (with exception of the early, hyper filtration phase of nephropathy in Type 1 diabetes), and it could constitute a factor of the generalized vasculopathy present in diabetic nephropathy. NO generation in Type 2 diabetes with nephropathy is inversely associated with the dimethyl-arginine concentrations, which are therefore important modulators of NO synthesis independently from the classic stimulatory pathways (such as the insulin effect). A disturbed NO metabolism is present in diabetes associated with nephropathy. Although modulation of NO production is not yet a common therapeutical strategy, a number of yet experimental compounds need to be tested as potential interventions to treat the vascular dysfunction and nephropathy in diabetes, as well as in other diseased states. Finally, in diabetic nephropathy NO deficiency may be associated to that of hydrogen sulfide, another interesting gaseous mediator which is increasingly investigated.

Could serum nitrate and nitrite levels possibly predict hepatorenal syndrome in hepatitis C virus-related liver cirrhosis?

PURPOSE

This study aimed to determine whether serum levels of nitric oxide metabolites (nitrates and nitrites) correlate with renal dysfunction in patients with liver cirrhosis and, moreover, to assess nitric oxide metabolite (NOx) power for predicting hepatorenal syndrome (HRS) in such patients.

METHODS

Among patients admitted to the Tropical Medicine Department, Ain Shams University Hospital, a total of 60 patients with chronic hepatitis C-related liver cirrhosis were included in this study. Patients were divided into three groups. Group I included 20 patients with compensated liver cirrhosis (CLC). Group II included 20 patients with decompensated liver cirrhosis (DLC). Group III included 20 patients with decompensated liver cirrhosis and HRS. Twenty healthy subjects with no clinical or laboratory evidence of liver disease were enrolled as a control group (group IV).

RESULTS

Patients with HRS had a higher mean nitrite levels followed by DLC, then CLC, and then controls. The sensitivity and specificity of NO metabolites (nitrites) were 100 % and 93.3 %, respectively, with accuracy of 95 % at cutoff value of 387 μmol/L for diagnosing patients with HRS. There was a highly significant statistical difference between patients positive and negative for nitrites as regards renal profile (p = 0.000).

CONCLUSION

A strong relation between nitrite cutoff value and renal dysfunction in liver cirrhosis has been found. Also, patients with HRS had higher mean serum nitrite levels than decompensated liver cirrhosis or compensated liver cirrhosis, raising the possibility of using nitrate and nitrite levels as a predictor for HRS in HCV-related liver cirrhosis.

Strain of experimental animals and modulation of nitric oxide pathway: their influence on development of renal failure in an experimental model of hepatorenal syndrome

INTRODUCTION

Pathomechanism of HRS is still poorly understood. The aim of our study was: (1) to test whether different strains of rats could develop typical HRS, and (2) to estimate the influence of activation and inhibition of nitric oxide for development of renal failure in course of HRS.

MATERIAL AND METHODS

First, we used 16 of Wistar and 16 of Sprague-Dawley rats in galactosamine model of HRS. Next, we used 48 of SDR rats, which received saline, N-nitro-L-arginine or L-arginine before and after liver damage. Twenty four hours urine and blood samples were collected 48 h after saline or Ga1N injection. Biochemical parameters were determined in serum or urine and then creatinine clearance and osmolality clearance were calculated. Liver and kidney tissues were collected for histopathological examination.

RESULTS

Liver failure developed in all tested groups with significant increase of bilirubin (p < 0.001), ALT (p < 0.001) and ammonia (p < 0.001). Nevertheless we did not achieve any evidence of renal failure in Wistar, but we found typical renal failure in Sprague-Dawley group with significant decrease in creatinine clearance (p < 0.0012) and increase in concentration of creatinine and urea (p < 0.001) and (p < 0.001) respectively. Inhibition of NOS prevented development of renal failure with significant improvement of GFR both before (p < 0.0017) and after (p < 0.003) Ga1N injection. Injection of L-arginine after Ga1N injection did not caused significant improvement of GFR.

CONCLUSIONS

Our study showed, that genetic factors might be responsible for development of renal failure in course of HRS and nitric oxide play important role in acute model of this syndrome.

Inhaled nitric oxide therapy increases blood nitrite, nitrate, and s-nitrosohemoglobin concentrations in infants with pulmonary hypertension

OBJECTIVE

To measure the circulating concentrations of nitric oxide (NO) adducts with NO bioactivity after inhaled NO (iNO) therapy in infants with pulmonary hypertension.

STUDY DESIGN

In this single center study, 5 sequential blood samples were collected from infants with pulmonary hypertension before, during, and after therapy with iNO (n = 17). Samples were collected from a control group of hospitalized infants without pulmonary hypertension (n = 16) and from healthy adults for comparison (n = 12).

RESULTS

After beginning iNO (20 ppm) whole blood nitrite levels increased approximately two-fold within 2 hours (P<.01). Whole blood nitrate levels increased to 4-fold higher than baseline during treatment with 20 ppm iNO (P<.01). S-nitrosohemoglobin increased measurably after beginning iNO (P<.01), whereas iron nitrosyl hemoglobin and total hemoglobin-bound NO-species compounds did not change.

CONCLUSION

Treatment of pulmonary hypertensive infants with iNO results in increases in levels of nitrite, nitrate, and S-nitrosohemoglobin in circulating blood. We speculate that these compounds may be carriers of NO bioactivity throughout the body and account for peripheral effects of iNO in the brain, heart, and other organs.

Arginases and arginine deficiency syndromes

PURPOSE OF REVIEW

Many physiologic and pathophysiologic processes are modulated by arginine availability, which can be regulated by arginase. An understanding of the conditions that result in elevated arginase activity as well as the consequences of arginine deficiency is essential for design of effective nutritional support for disease. This review will emphasize recent findings regarding effects of plasma arginase and arginine deficiencies in disease.

RECENT FINDINGS

Elevations in plasma arginase, derived primarily from hemolysis of red blood cells or liver damage, that are associated with arginine deficiency have been identified in an increasing number of diseases and conditions. Arginine insufficiency not only can activate a stress kinase pathway that impairs function of T lymphocytes but it also can inhibit the mitogen-activated protein kinase signaling pathway required for macrophage production of cytokines in response to bacterial endotoxin/lipopolysaccharide.

SUMMARY

There are at least two broad categories of arginine deficiency syndromes, involving either T-cell dysfunction or endothelial dysfunction, depending on the disease context in which arginine deficiency occurs. There is limited information regarding the safety and efficacy of supplementation with arginine or its precursor citrulline in ameliorating arginine deficiency in specific diseases, indicating the need for further studies.

Inhaled nitrite reverses hemolysis-induced pulmonary vasoconstriction in newborn lambs without blood participation

BACKGROUND

Nitrite can be converted to nitric oxide (NO) by a number of different biochemical pathways. In newborn lambs, an aerosol of inhaled nitrite has been found to reduce pulmonary blood pressure, possibly acting via conversion to NO by reaction with intraerythrocytic deoxyhemoglobin. If so, the vasodilating effects of nitrite would be attenuated by free hemoglobin in plasma that would rapidly scavenge NO.

METHODS AND RESULTS

Pulmonary vascular pressures and resistances to flow were measured in anesthetized newborn lambs. Plasma hemoglobin concentrations were then elevated, resulting in marked pulmonary hypertension. This effect was attenuated if infused hemoglobin was first oxidized to methemoglobin, which does not scavenge NO. These results further implicate NO as a tonic pulmonary vasodilator. Next, while free hemoglobin continued to be infused, the lambs were given inhaled NO gas (20 ppm), inhaled sodium nitrite aerosol (0.87 mol/L), or an intravascular nitrite infusion (3 mg/h bolus, 5 mg · kg⁻¹ · h⁻¹ infusion). Inhaled NO and inhaled nitrite aerosol both resulted in pulmonary vasodilation. Intravascular infusion of nitrite, however, did not. Increases in exhaled NO gas were observed in lambs while breathing the nitrite aerosol (≈ 20 ppb NO) but not during intravascular infusion of nitrite.

CONCLUSIONS

We conclude that the pulmonary vasodilating effect of inhaled nitrite results from its conversion to NO in airway and parenchymal lung tissue and is not dependent on reactions with deoxyhemoglobin in the pulmonary circulation. Inhaled nitrite aerosol remains a promising candidate to reduce pulmonary hypertension in clinical application.