Detection of serum nitrite and nitrate in primary biliary cirrhosis: possible role of nitric oxide in bile duct injury

Peroxisome Proliferator-Activated Receptors Regulate Hepatic Immunity and Assist in the Treatment of Primary Biliary Cholangitis

Fibrates, which are agonists of peroxisome proliferator-activated receptor alpha, have received increasing attention in the treatment of primary biliary cholangitis. Reduced alkaline phosphatase levels and improved clinical outcomes were observed in patients with primary biliary cholangitis with an inadequate response to ursodeoxycholic acid (UDCA) monotherapy4 when treated with bezafibrate or fenofibrate combined with UDCA. In contrast to obeticholic acid, which exacerbates pruritus in patients, fibrates have been shown to relieve pruritus. Clinical trial outcomes show potential for the treatment of primary biliary cholangitis by targeting peroxisome proliferator-activated receptors. It is currently agreed that primary biliary cholangitis is an autoimmune-mediated cholestatic liver disease, and peroxisome proliferator-activated receptor is a nuclear receptor that regulates the functions of multiple immune cells, thus playing an important role in regulating innate and adaptive immunity. Therefore, this review focuses on the immune disorder of primary biliary cholangitis and summarizes the regulation of hepatic immunity when peroxisome proliferator-activated receptors are targeted for treating primary biliary cholangitis.

Hepatoprotective effect of the hydroalcoholic extract of Cichorium intybus in a rat model of obstructive cholestasis

BACKGROUND AND STUDY AIMS

Obstructive cholestasis increases the levels of oxidants and inflammatory mediators, leading to liver damage. Previous studies have found that Cichorium intybus possesses anti-inflammatory effects. In the present study, the effects of the hydroalcoholic extract of C. intybus leaves were assessed in a rat model of obstructive cholestasis.

MATERIAL AND METHODS

Male Wistar rats were randomly divided into five groups (n = 6 rats per group): sham-operated, control [bile duct ligation (BDL) + vehicle)] and BDL + extract treatment (100, 200 and 400 mg/kg/day, i.p.) groups. Rats received treatments for 7 consecutive days. On the eighth day, prothrombin time (PT); serum albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase and total and direct bilirubin levels and total antioxidant and paraoxonase activities were measured using colorimetric methods. In addition, tumour necrosis factor-α and nitric oxide (NO) levels were measured using enzyme-linked immunosorbent assay.

RESULTS

The hydroalcoholic extract of C. intybus significantly decreased PT and the serum levels of AST, ALT, TNF-α and NO compared with the control group (p < 0.05). On the other hand, the serum albumin levels were increased in the extract-treated groups compared with the control group (p < 0.05).

CONCLUSION

The hydroalcoholic extract of C. intybus protects the liver against injury induced by obstructive cholestasis.

Can Chronic Nitric Oxide Inhibition Improve Liver and Renal Dysfunction in Bile Duct Ligated Rats?

The aims of the present work were to study the effects of chronic NO inhibition on liver cirrhosis and to analyze its relationship with liver and kidney damage markers. Two inhibitors of NO synthesis (inducible NO synthase (iNOS) inhibitor, aminoguanidine (AG), and nonselective NOS inhibitor, L-nitroarginine methyl ester (L-NAME)) were administered for 6 weeks to bile duct ligated (BDL) rats 3 days after surgery. The present study showed that BDL was associated with liver injury and renal impairment. BDL increased liver NO content and myeloperoxidase (MPO) activity. This was corroborated by increased oxidative stress, TNF-α, TGF-1β, and MMP-13 genes overexpression. Although both drugs reduced NO synthesis and TNF-α gene overexpression, only AG improved renal dysfunction and liver damage and reduced liver oxidative stress. However, L-NAME exacerbated liver and renal dysfunction. Both drugs failed to modulate TGF-1β and MMP-13 genes overexpression. In conclusion, inhibition of NO production by constitutive nitric oxide synthase (cNOS) plays a crucial role in liver injury and renal dysfunction while inhibition of iNOS by AG has beneficial effect. TNF-α is not the main cytokine responsible for liver injury in BDL model. Nitric oxide inhibition did not stop the progression of cholestatic liver damage.

Nitric oxide is a potential mediator of hepatic inflammation and fibrogenesis in autoimmune hepatitis

BACKGROUND

Despite advances in the understanding of the pathophysiological basis of autoimmune hepatitis (AIH), it is still difficult to delineate the mechanisms involved in progression from hepatic inflammation toward fibrosis. Our aim was to study serum concentrations of NO in AIH of different histological severity and possible effects of immunosuppressive therapy on NO production.

MATERIALS AND METHODS

We studied serum NO metabolites (NOx) in 47 consecutive patients with AIH and in 28 age- and sex-matched controls.

RESULTS

Serum NOx concentrations were higher in AIH patients than in controls (10.3 (4.5-27.3 µmol/L) vs. 4.3 (1.6-14.3 µmol/L), p < 0.001). According to liver histology, median NOx concentrations were significantly higher in patients with severe interface hepatitis compared to patients with mild-moderate interface hepatitis (12.3 (4.5-27.3 µmol/L) vs. 9.3 (4.6-20.3 µmol/L), p = 0.029). Similarly, serum NOx concentrations were significantly higher in patients with advanced fibrosis than in those with early fibrosis (12.2 (4.6-27.3 µmol/L) vs. 9.3 (6.6-12.8 µmol/L), p = 0.018). NOx concentrations decreased in 16 AIH patients who were tested also after biochemical remission was achieved (12.6 (4.5-22.8 µmol/L) at baseline and 5.9 (2.8-10.5 µmol/L) after remission, p = 0.001).

CONCLUSION

This study shows that serum NOx levels are associated with the histological severity of AIH. Hepatocyte inflammation and injury may activate hepatic stellate cells and kupffer cells, and the consequences may include release of NO, which ultimately promotes hepatic fibrosis. Immunosuppressive therapy inhibits this process and the production of NO.

Nitric oxide mediates the beneficial effect of chronic naltrexone on cholestasis-induced memory impairment in male rats

Recent studies suggest an augmentation of endogenous opioids following bile duct ligation (BDL) and their pivotal role in the pathophysiology of cholestasis. In this study, the effect of naltrexone, an opioid receptor antagonist, was determined on cholestasis-induced memory impairment and the possible involvement of nitric oxide (NO) in this effect. Male Albino-Wistar rats were randomized to sham-operated and BDL-operated groups. In each group, animals were treated for up to 28 days with saline; naltrexone (10 mg/kg); naltrexone and N(G)-nitro-L-arginine methyl ester (L-NAME), a nonselective nitric oxide synthase (NOS) inhibitor (3, 10 mg/kg); naltrexone and aminoguanidine, an inducible NOS inhibitor (100 mg/kg); or methylnaltrexone, a peripherally acting opioid receptor antagonist (3 mg/kg, intraperitoneal). Spatial recognition memory was determined in a Y-maze task on the day before surgery and days 7, 14, 21, and 28 after surgery. Memory performance was impaired 14 days after BDL in cholestatic rats and was significantly reversed by chronic treatment with naltrexone at days 14, 21, and 28 after BDL. On day 21 after BDL, chronic L-NAME produced only a nonsignificant decrease in the beneficial effect of naltrexone, whereas on day 28, chronic administration of both L-NAME and aminoguanidine significantly reversed this effect of naltrexone. It is therefore shown in this study that naltrexone improves BDL-induced memory deficit in rats. We conclude that the memory impairment in cholestatic rats might be because of an increase in the level of endogenous opioids and that naltrexone improved the spatial recognition memory by antagonizing opioid receptors. The observation that the procognitive effect of naltrexone is counteracted either by general inhibition of NOS enzymes or by selective inhibition of inducible NOS suggests the nitrergic pathway as a probable mechanism involved in the amelioration of spatial recognition memory by naltrexone in BDL rats.

Antioxidant and antigenotoxic effects of lycopene in obstructive jaundice

BACKGROUND

Obstructive jaundice, a frequently observed condition caused by obstruction of the common bile duct or its flow and seen in many clinical situations, may end up with serious complications like sepsis, immune depression, coagulopathy, wound breakdown, gastrointestinal hemorrhage, and hepatic and renal failures. Intrahepatic accumulation of reactive oxygen species is thought to be an important cause for the possible mechanisms of the pathogenesis of cholestatic tissue injury from jaundice. Carotenoids have been well described that are able to scavenge reactive oxygen species. Lycopene, a carotenoid present in tomatoes, tomato products, and several fruits and vegetables, have been suggested to have antioxidant activity, so may play a role in certain diseases related to the oxidative stress. The aim of the present study was to determine the effects of lycopene on oxidative stress and DNA damage induced by experimental biliary obstruction in Wistar albino rats.

MATERIALS AND METHODS

Daily doses of 100 mg/kg lycopene were given to the bile duct-ligation (BDL) rats orally for 14 days. DNA damage was evaluated by an alkaline comet assay. The levels of aspartate transferase, amino alanine transferase, gamma glutamyl transferase, alkaline phosphatase, and direct bilirubin were analyzed in plasma for the determination of liver functions. The levels of malondialdehyde, reduced glutathione, nitric oxide, catalase, superoxide dismutase, and glutathione S transferase were determined in the liver and kidney tissues. Pro-inflammatory cytokine tumor necrosis factor-alpha level was determined in the liver tissues. Histologic examinations of the liver and kidney tissues were also performed.

RESULTS

According to this study, lycopene significantly recovered the parameters of liver functions in plasma, reduced malondialdehyde and nitric oxide levels, enhanced reduced glutathione levels, as well as enhancing all antioxidant enzyme activity in all tissues obtained from the BDL group. Moreover, the parameters of DNA damage in the liver and kidney tissue cells, whole blood cells, and lymphocytes were significantly lower in the lycopene-treated BDL group, compared with the BDL group.

CONCLUSIONS

Lycopene significantly reduced the DNA damage, and markedly recovered the liver and kidney tissue injuries seen in rats with obstructive jaundice.

Long-term ursodeoxycholate improves circulating redox changes in primary biliary cirrhotic patients

BACKGROUND AND AIMS

Cholestasis is associated with systemic and hepatic oxidative and nitrosative stress; in this scenario, the conjugated hydrophilic bile salt ursodeoxycholate (UDCA) might play a protective role.

METHODS

Circulating oxidative and nitrosative stress markers were assessed in patients with primary biliary cirrhosis (PBC) before and during UDCA (15-20mg/kg/day) therapy.

RESULTS

In patients with stage I-II PBC, UDCA improved ALT and alkaline phosphatase levels and near normalized serum thioredoxin (1.97 ± 0.37 vs 2.41 ± 0.39 nmol/L), nitrotyrosine (15 ± 4 vs 22 ± 7 nmol/L), nitrosothiols (144 ± 28 vs 205 ± 84 nmol/L) and K-18 levels (162 ± 21 vs 228 ± 33 U/L). Conversely, less marked changes were noted in patients with stages III-IV who showed lower thioredoxin (1.01 ± 0.31 nmol/L), higher nitrosothiols (605 ± 64 nmol/L), nitrotyrosine (62 ± 13 nmol/L) and K-18 levels (521 ± 57 U/L). Overall, thioredoxin was inversely related with nitrotyrosine (r=-0.838, P<0.001) and K-18 (r=-0.838, P<0.001) levels. Nitrosothiols and K-18 were linearly and significantly related with nitrotyrosine (r=0.862, P<0.001; r=0.894, P<0.001, respectively).

CONCLUSIONS

Oxidative and nitrosative changes in patients with PBC are effectively counteracted by UDCA. The protective effect of UDCA, however, are limited to early disease stages and progressively diminishes with ongoing cholestasis.

NF-kappaB related abnormal hyper-expression of iNOS and NO correlates with the inflammation procedure in biliary atresia livers

OBJECTIVE

To study the expression of inducible nitric oxide synthase (iNOS) and its related regulators in biliary atresia (BA) livers and exlpore their relationships with the inflammation pathway in BA livers.

METHOD

The iNOS expression in livers of 38 cases of BA children, 15 cases of neonatal cholestasis (NC) children, and 18 cases of normal control were, respectively, examined and total nitric oxide (NO) metabolites concentration of all samples were calculated by a colorimetric method based on Griess reaction. The TdT-mediated dupt biotin nick end labeling (TUNEL) method was used to label the apoptotic bile duct epithelial cells and hepatocytes. The western blotting and immunohistochemistry methods to semi-quantitatively analyze the nuclear factor-kappaB (NF-kappaB) expression of each group were also used.

RESULTS

The iNOS expression intensity and total NO metabolites concentration of BA group (0.30 +/- 0.08, 90.40 +/- 12.46 micromol/L) were significantly higher than those of NC and normal control groups, P < 0.01. Correlation analysis showed a strong positive correlation between the serum AST level (152.76 +/- 29.59 U/L) and total NO metabolites concentration in BA group. Compared with the NC (32.47 +/- 5.55) and normal control (20.72 +/- 5.63) groups, a significantly higher apoptosis rate of intrahepatic bile duct epithelial cells was found in BA group (54.00 +/- 11.67) that tightly correlated with the iNOS intensity (r = 0.99, P < 0.01). The NF-kappaB intensity of BA group was also significantly higher than that of NC and normal control groups and had a strong positive correlation with the iNOS intensity (r = 0.97, P < 0.01).

CONCLUSION

The abnormal hyper-expression of iNOS may play an important role in mediating the inflammation procedure in BA livers. This change perhaps has some relationship with the high expression of NF-kappaB and NO. These regulators can up-regulate the apoptosis of bile duct epithelial cells in BA livers and cause the damage to liver tissues.

Inhibition of nitric oxide synthesis during induced cholestasis ameliorates hepatocellular injury by facilitating S-nitrosothiol homeostasis

Cholestatic liver injury following extra- or intrahepatic bile duct obstruction causes nonparenchymal cell proliferation and matrix deposition leading to end-stage liver disease and cirrhosis. In cholestatic conditions, nitric oxide (NO) is mainly produced by a hepatocyte-inducible NO synthase (iNOS) as a result of enhanced inflow of endotoxins to the liver and also by accumulation of bile salts in hepatocytes and subsequent hepatocellular injury. This study was aimed to investigate the role of NO and S-nitrosothiol (SNO) homeostasis in the development of hepatocellular injury during cholestasis induced by bile duct ligation (BDL) in rats. Male Wistar rats (200-250 g) were divided into four groups (n=10 each), including sham-operated (SO), bile duct-ligated (BDL), tauroursodeoxycholic acid (TUDCA, 50 mg/kg) and S-methylisothiourea (SMT, 25 mg/kg) treated. After 7 days, BDL rats showed elevated serum levels of gamma-glutamiltranspeptidase, aspartate aminotransferase, alanine aminotransferase, LDH, and bilirubin, bile duct proliferation and fibrosis, compared with the SO group. TUDCA treatment did not significantly alter these parameters, but the iNOS inhibitor SMT ameliorated hepatocellular injury, as shown by lower levels of circulating hepatic enzymes and bilirubin, and a decreased grade of bile duct proliferation and fibrosis. Both TUDCA and SMT treatments reversed Mrp2 canalicular pump expression to control levels. However, only SMT treatment significantly lowered the increased levels of plasma NO and S-nitrosation (S-nitrosylation) of liver proteins in BDL rats. Moreover, BDL resulted in a reduction of the S-nitrosoglutathione reductase (GSNOR/Adh5) enzymatic activity and a downregulation of the GSNOR/Adh5 mRNA expression that was reverted by SMT, but not TUDCA, treatment. A total of 25 liver proteins, including S-adenosyl methionine synthetase, betaine-homocysteine S-methyltransferase, Hsp90 and protein disulfide isomerase, were found to be S-nitrosated in BDL rats. In conclusion, the inhibition of NO production during induced cholestasis ameliorates hepatocellular injury. This effect is in part mediated by the improvement of cell proficiency in maintaining SNO homeostasis.

Overexpression of hepatic inducible nitric oxide synthase in biliary atresia

AIMS

Biliary atresia (BA) is a rare and serious liver disease in infants characterized by progressive inflammatory cholangiopathy. The aims of this study were to investigate hepatic expression of inducible nitric oxide synthase (iNOS) in BA and to associate the iNOS expression with their early therapeutic outcome.

METHODS

Hepatic iNOS expression was determined using immunohistochemistry from liver biopsies of 24 BA patients, and 16 non-BA patients whose liver tissues were needed in the treatment process. Six months after surgery, the BA patients were categorized into two groups;good and poor outcome. The iNOS expression of hepatocyte areas was evaluated based on its intensity using ImageJ software. Unpaired t-tests were used for the comparisons of iNOS expression between groups.

RESULTS

Hepatic iNOS expression of BA patients was significantly stronger than that of non-BA patients (P < 0.0001). The largest area of hepatic iNOS expression was the area of hepatocytes. Subgroup analysis of BA patients at 6 months post-op revealed that there was no difference in iNOS expression between the patients with good outcome and those with poor outcome (P = 0.732).

CONCLUSIONS

Overexpression of hepatic iNOS in BA patients was demonstrated. Within liver tissues, hepatocytes were the major source of hepatic iNOS production. However, the expression was not associated with the early therapeutic outcome. These results suggest that iNOS plays a role in the liver pathology of BA but its expression cannot be used as a predictor for therapeutic outcome.

Mutual changes of thioredoxin and nitrosothiols during biliary cirrhosis: results from humans and cholestatic rats

Cholestasis is associated with changes in NO metabolism and thiol oxidation. Thioredoxin contributes to regulate vascular tone and intracellular redox status by cleaving nitrosothiols and maintaining -SH groups. This study investigated the changes in circulating thioredoxin and nitrosothiols and the relationship with protein sulfhydryls (PSH), hepatic concentrations, hyaluronate, and histology in patients with primary biliary cirrhosis (PBC) and in rats with bile duct ligation (BDL). PSH in erythrocytes were significantly decreased in stage III and IV PBC and at day 10 after BDL. Compared with controls, erythrocyte thioredoxin levels were higher in stage I through III PBC and lower in stage IV patients. Serum thioredoxin levels were significantly higher in PBC stages I and II and lower in stages III and IV. Serum nitrosothiols were higher in all PBC patients and inversely related to thioredoxin and hyaluronate. In rats, serum, hepatic, and mitochondrial thioredoxin had initially increased after BDL (day 1-3) and then decreased. After day 7 BDL, nitrosothiols were 10-fold increased in serum and liver, and even higher in mitochondria. In the liver, thioredoxin was inversely related to both nitrosothiols and PSH. In rats, the difference in time average changes from baseline among serum, hepatic, and erythrocyte thioredoxin suggests that most of circulating thioredoxin originates from the liver.

CONCLUSION

Our findings indicate that cholestasis is associated with significant mutual and interrelated changes between circulating and hepatic thioredoxin and nitrosothiols. The increase of hepatic, mitochondrial, and circulating nitrosothiols with ongoing cholestasis suggests an active participation of NO in both liver injury and extrahepatic changes.

Is there a link between hyperbilirubinemia and elevated urine nitrite

OBJECTIVE

The aim of this study was to determine whether hyperbilirubinemia affects the association between a positive urine nitrite test and a positive urine culture.

METHODS

We conducted an institutional review board-approved, retrospective review of 12 months of patient data, compiling information for patients having urinalysis, urine culture, and total serum bilirubin. Patients were divided into 3 groups according to total serum bilirubin: less than 1.5 mg/dL, 1.5 to 3.0 mg/dL, and greater than 3.0 mg/dL. The point estimates and 95% confidence intervals of the sensitivity, specificity, false-positive proportion (proportion of false positive to all positive tests), and other test characteristics of urine nitrite as an indicator of urinary tract infection were calculated and tested for trend as a function of the 3 total serum bilirubin ranges.

RESULTS

Three thousand one hundred seventy-four patients met our study criteria. Specificity of the nitrite test decreased as a function of increasing total serum bilirubin (0.974, 0.966, and 0.855 for the 3 total bilirubin levels, respectively) with a significant trend (P < .0001). There was no significant trend in comparable sensitivity values (0.380, 0.417, and 0.241, respectively) with P = .55. The false-positive proportion also increased as a function of total serum bilirubin (17.5%, 17.3%, and 72.0%) with P < .0001. Thus, if a patient's total serum bilirubin was elevated to the point of jaundice (>3.0 mg/dL), it was approximately 4 times more likely that a positive urine nitrite test would be a "false positive" (ie, nitrite-positive/culture-negative) compared with those with normal serum bilirubin levels.

CONCLUSIONS

Specificity of the urine nitrite test for urinary tract infection decreases as a function of increasing serum bilirubin. Most patients with hyperbilirubinemia and a positive nitrite test in our sample did not have an associated urinary tract infection.

Concept on the pathogenesis and treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an organ-specific autoimmune disease that predominantly affects women and is characterized by chronic, progressive destruction of small intrahepatic bile ducts with portal inflammation and ultimately fibrosis, leading to liver failure in the absence of treatment. Little is known about the etiology of PBC. PBC is characterized by anti-mitochondrial antibodies and destruction of intra-hepatic bile ducts. The serologic hallmark of PBC is the presence of auto-antibodies to mitochondria, especially to the E2 component of the pyruvate dehydrogenase complex (PDC). Current theories on the pathogenesis of PBC favor the hypothesis that the disease develops as a result of an inappropriate immune response following stimulation by an environmental or infectious agent. Some reports suggest that xenobiotics and viral infections may induce PBC. The pathogenetic mechanism is believed to be caused by a defect in immunologic tolerance, resulting in the activation and expansion of self-antigen specific T and B lymphocyte clones and the production of circulating autoantibodies in addition to a myriad of cytokines and other inflammatory mediators. This leads to ductulopenia and persistent cholestasis, by developing end-stage hepatic-cell failure. In this review are given our own and literary data about mechanisms of development of intrahepatic cholestasis and possible ways of its correction.

Elevated serum nitric oxide metabolites in biliary atresia

Biliary atresia (BA) remains one of the most intractable liver diseases in children. The aim of this study was to investigate the possible roles of nitric oxide (NO) in BA. Serum levels of nitrite and nitrate (NO production) were determined using a colorimetric method from 65 post-operative BA patients and 12 healthy children. The patients were categorized into two groups according to their jaundice status, and serum alanine aminotransferase (ALT, a marker for liver injury). Unpaired t tests were used. Data are expressed as mean and SD in terms of mumol/l. Age and gender between BA patients and controls were comparable. Serum NO metabolites of BA patients was higher than the controls (79.77+/-21.22 vs. 65.75+/-9.44, P=0.001). Subgroup analysis revealed that there was no difference in serum nitrate/nitrite levels of BA patients without jaundice compared to those with jaundice (78.85+/-23.23 vs. 80.90+/-18.76, P=0.70). However, patients with serum ALT> or =100 IU/l had higher levels of serum NO metabolites compared to those with serum ALT<100 IU/l. In conclusion, NO production was elevated in BA patients compared to normal controls. Serum NO was associated with serum ALT levels, but not with jaundice status, in BA patients. These suggest that NO plays a role in the pathophysiology of liver injury in post-operative BA.

Role of nitric oxide (NO) in interferon-alpha therapy for hepatitis C

BACKGROUND AND AIM

The role of nitric oxide in infectious disease is gaining increased attention because antiviral effects of nitric oxide. In addition, there is evidence that nitric oxide synthase-2 expression was noted in chronic hepatitis C found within mononuclear cells.

METHODS

We studied serum levels of nitrite and nitrate before and during interferon alpha therapy in 66 patients with chronic hepatitis C.

RESULTS

There was no significant difference of their levels between the healthy control subjects and the patients before the treatment with interferon (55.9+/-21.8 microM vs. 60.9+/-30.0 microM). Their levels were determined at 2 weeks after the initiation of treatment with interferon and compared with those before the treatment in the patients with chronic hepatitis C. In the total patients treated, there was no significant difference between their levels before and at 2 weeks after the treatment (60.9+/-30.0 microM vs. 65.5+/-30.0 microM, P=0.14). However, when the levels were compared between sustained responders, in whom hepatitis C virus was eradicated, and non-responders, in whom the virus was not eradicated, the former had significantly higher levels of nitrite and nitrate than the latter at 2 weeks after the initiation of treatment (83.7+/-40.9 microM vs. 57.6+/-19.5 microM, P<0.01). The multivariate logistic regression analysis showed that the rise of nitrite and nitrate was an independent predictive factor for efficacy of interferon treatment.

CONCLUSIONS

Nitric oxide may be an important factor for antiviral therapy by interferon treatment for chronic hepatitis C, which suggests an additional therapeutic pathway for further study.

Ursodeoxycholic acid reduces increased circulating endothelin 2 in primary biliary cirrhosis

BACKGROUND

Endothelins and nitric oxide regulate sinusoidal blood flow and the perfusion of the peribiliary vascular plexus.

AIMS

To study the serum and hepatic vein concentration of ET-1, ET-2, ET-3 and nitric oxide in patients with primary biliary cirrhosis and the effect of ursodeoxycholic acid treatment.

METHODS

Endothelins and nitrites/nitrates were measured in serum and hepatic vein blood in primary biliary cirrhosis and viral cirrhotic patients prior and after ursodeoxycholic acid therapy and in serum in controls. Endothelins were measured with commercial enzyme-linked immunosorbent assays and nitrites/nitrates with a modification of Griess reaction.

RESULTS

The ET-1 and ET-3 levels were similar in patients and controls. Primary biliary cirrhosis patients had the highest serum ET-2 (P < 0.001) compared with other groups. Nitrites/nitrates was increased in primary biliary cirrhosis (P < 0.05) compared with normal. ET-2 and nitric oxide were similar in all primary biliary cirrhosis stages. Ursodeoxycholic acid significantly decreased ET-2 in all stages (I and II: P < 0.05 and III and IV: P < 0.01) and increased nitric oxide (P < 0.05) in early primary biliary cirrhosis. Hepatic vein ET-1 and ET-3 were higher in viral cirrhosis patients, but only in primary biliary cirrhosis a significant difference for ET-1 and ET-3 between hepatic and peripheral veins was found.

CONCLUSIONS

Increased ET-2 is an early defect in primary biliary cirrhosis that is significantly reduced by the ursodeoxycholic acid treatment. The possibility of a more generalized endothelial cell dysfunction in primary biliary cirrhosis requires further investigation.

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.

Genetic variants of endothelial nitric oxide synthase in patients with primary biliary cirrhosis: association with disease severity

BACKGROUND AND AIMS

Primary biliary cirrhosis (PBC) presents a wide spectrum of clinical manifestations. In experimental models of liver cirrhosis and cholestasis it has been suggested that altered nitric oxide production is involved in liver injury and portal hypertension development. The present study investigated endothelial nitric oxide synthase (eNOS) genetic polymorphisms (894G/T, -786T/C) in patients with PBC and in controls to verify whether disease susceptibility and progression are associated with a particular genotype.

METHODS

Genomic DNA from 109 Italian PBC patients (65 with advanced disease, i.e. liver transplantation or histological stage III-IV) was obtained and polymorphisms determined by fluorescent probe analysis. Healthy subjects (n = 242) were used as a control group.

RESULTS

The allelic frequencies of both polymorphisms did not differ significantly between PBC patients and controls. When the association between genotypes and disease severity was addressed, both the 894T and the -786T alleles were more frequently found in the 22 patients with progressing disease (894T, frequency 0.455 compared with 0.240; P = 0.032; -786T, frequency 0.682 compared with 0.460; P = 0.038). Patients with 894TT presented higher Mayo score values (6.1 +/- 1.2 compared with 5.4 +/- 1.3 in 894G/G patients; P = 0.030) but similar age and disease duration values.

CONCLUSIONS

The authors suggest that genetic variants of eNOS are not associated with susceptibility to PBC, although the genotypes may lead to differences in disease severity and progression.

Cholestatic syndromes

Further insights into the cellular and molecular mechanisms underlying hepatobiliary transport function and its regulation now permit a better understanding of the pathogenesis and treatment options of cholestatic liver diseases. Identification of the molecular basis of hereditary cholestatic syndromes will result in an improved diagnosis and management of these conditions. New insights into the pathogenesis of extrahepatic manifestations of cholestasis (eg, pruritus) have facilitated new treatment strategies. Important new studies have been published about the pathogenesis, clinical features, diagnosis, and treatment of primary biliary cirrhosis, primary sclerosing cholangitis, cholestasis of pregnancy, total parenteral nutrition-induced cholestasis, drug-induced cholestasis, and viral cholestatic syndromes.

Ribavirin in cancer immunotherapies: controlling nitric oxide augments cytotoxic lymphocyte function

Either ribavirin (RBV) or cyclophosphamide (CY) can shift an immune response from Th2 toward a Th1 cytokine profile. CY is used in this role in various current cancer immunotherapy attempts but with mixed success. More potent and reliable immunoadjuvants and Th1 response biasing methods are needed. RBV is used today mainly to augment interferon-alpha treatment of hepatitis C. RBV shifts an immune response from Th2 toward Th1 more effectively than CY and may be a safe and useful adjuvant for current cancer immunotherapeutic efforts. RBV is thought to act by inhibition of tetrahydrobiopterin synthesis. Tetrahydrobiopterin is an essential cofactor for all known isoforms of nitric oxide synthase. Lowered nitric oxide favors Th1 development as high levels favor Th2 weighting.

Enhanced intrahepatic inducible nitric oxide synthase expression and nitrotyrosine accumulation in primary biliary cirrhosis and autoimmune hepatitis

BACKGROUND/AIMS

Nitrosative stress resulting from increased nitric oxide (NO) synthesis contributes to the pathogenesis of chronic inflammatory diseases, including chronic viral hepatitis. Our goal was to assess the expression of inducible nitric oxide synthase (iNOS) and the formation of nitrotyrosine (NTY), as a marker of nitrosative stress, in liver biopsies from primary biliary cirrhosis (PBC) and autoimmune hepatitis (AIH) patients.

METHODS

Intrahepatic expression of iNOS and NTY was measured immunohistochemically and compared to histological scores of the severity of liver disease.

RESULTS

Hepatocellular iNOS expression was observed in liver sections from PBC patients (with a diffuse lobular distribution) and from AIH patients (marked staining in areas of pronounced inflammation and necrosis), but not in control liver sections, including non-autoimmune cholestatic liver disease. Liver samples from PBC and AIH patients, but not from controls, showed NTY accumulation in clusters of hepatocytes and Kupffer cells. Increased iNOS expression and NTY accumulation correlated with the histological severity of PBC or AIH, especially with the degree of inflammation.

CONCLUSIONS

Patients with PBC and AIH showed an enhanced intrahepatic iNOS expression and NTY accumulation, related to the histological severity of liver disease, consistent with NO-mediated nitration of hepatocellular proteins contributing to liver damage in both diseases.