Expression of nitric oxide synthase isoforms in human liver cirrhosis

Nitric oxide and peroxynitrite as new biomarkers for early diagnosis of autism

Autism spectrum disorder, or autism, is a neurodevelopmental disorder of the developing child's brain with a genetic causality. It can be diagnosed at about three years after birth when it begins to present itself via a range of neuropsychiatric symptoms. Nitric oxide is a crucial small molecule of life synthesized within cells of our body systems, including cells of our brain. Peroxynitrite is the product of reaction between superoxide anion and nitric oxide. It normally isomerizes into harmless nitrates or nitrites. However, when excessive superoxide anion is present, the cellular concentration of peroxynitrite can increase to a toxic level. Autism has been suggested to cause oxidative damage to brain cells. Until now, it is impossible to sample tissue from a live brain. Instead, stem cells can be derived (from an autism patient's somatic cells) which can then be differentiated and chemically directed to grow into miniature 3-dimensional tissue masses resembling specific brain regions (e.g., the cortex) called brain organoids. This review discusses utilizing nitric oxide and peroxynitrite as biomarkers and comparing their relative concentrations in stem cells and stem cell derived brain organoids of healthy and autistic individuals to develop a bioanalytical process for early diagnosis of autism.

Role of Nitric Oxide in the Altered Calcium Homeostasis of Platelets from Rats with Biliary Cirrhosis

INTRODUCTION

Previously, we found that intracellular calcium (Ca²⁺) homeostasis is altered in platelets from an experimental model of liver cirrhosis, namely the bile-duct-ligated (BDL) rat. These alterations are compatible with the existence of a hypercoagulable state.

OBJECTIVE

In the present study, we analyzed the role of nitric oxide in the abnormal calcium signaling responses of an experimental cirrhosis model, the bile duct-ligated rat.

METHODS

Chronic treatment with L-NAME was used to inhibit NO production in a group of control and BDL animals, and the responses compared to those obtained in a control and BDL untreated group (n = 6 each). The experiments were conducted on isolated platelets loaded with fura-2, using fluorescence spectrometry.

RESULTS

Chronic treatment with L-NAME increased thrombin-induced Ca²⁺ release from internal stores in both control and BDL rats. However, the effect was significantly greater in the BDL rats (p < 0.05). Thrombin-induced calcium entry from the extracellular space was also elevated but at lower doses and, similarly in both control and BDL platelets, treated with the NO synthesis inhibitor. Capacitative calcium entry was also enhanced in the control platelets but not in platelets from BDL rats treated with L-NAME. Total calcium in intracellular stores was elevated in untreated platelets from BDL rats, and L-NAME pretreatment significantly (p < 0.05) elevated these values both in controls and in BDL but significantly more in the BDL rats (p < 0.05).

CONCLUSIONS

Our results suggest that nitric oxide plays a role in the abnormal calcium signaling responses observed in platelets from BDL rats by interfering with the mechanism that releases calcium from the internal stores.

Royal Jelly and Chlorella vulgaris Mitigate Gibberellic Acid-Induced Cytogenotoxicity and Hepatotoxicity in Rats via Modulation of the PPARα/AP-1 Signaling Pathway and Suppression of Oxidative Stress and Inflammation

Gibberellic acid (GA3) is a well-known plant growth regulator used in several countries, but its widespread use has negative effects on both animal and human health. The current study assesses the protective effect of royal jelly (RJ) and Chlorella vulgaris (CV) on the genotoxicity and hepatic injury induced by GA3 in rats. Daily oral administration of 55 mg/kg GA3 to rats for 6 constitutive weeks induced biochemical and histopathological changes in the liver via oxidative stress and inflammation. Co-administration of 300 mg/kg RJ or 500 mg/kg CV with GA3 considerably ameliorated the serum levels of AST (aspartate aminotransferase), ALT (alanine aminotransferase), ALP (alkaline phosphatase), γGT (gamma-glutamyl transferase), total bilirubin, and albumin. Lowered malondialdehyde, tumor necrosis factor α (TNF-α), and nuclear factor κB (NF-κB) levels along with elevated SOD (superoxide dismutase), CAT (catalase), and GPx (glutathione peroxidase) enzyme activities indicated the antioxidant and anti-inflammatory properties of both RJ and CV. Also, they improved the histological structure and reduced cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expressions along with up-regulating peroxisome proliferator activated receptor α (PPARα) and down-regulating activator protein 1 (AP-1) gene expression. Additionally, chromosomal abnormalities and mitotic index were nearly normalized after treatment with RJ and CV. In conclusion, RJ and CV can protect against GA3-induced genotoxicity and liver toxicity by diminishing oxidative stress and inflammation, and modulating the PPARα/AP-1 signaling pathway.

NO, CO and H2S: A Trinacrium of Bioactive Gases in the Brain

Oxygen and carbon dioxide are time honored gases that have direct bearing on almost all life forms, but over the past thirty years, and in large part due to the Nobel Prize Award in Medicine for the elucidation of nitric oxide (NO) as a bioactive gas, the research and medical communities now recognize other gases as critical for survival. In addition to NO, hydrogen sulfide (H₂S) and carbon monoxide (CO) have emerged as a triumvirate or Trinacrium of gases with analogous importance and that serve important homeostatic functions. Perhaps, one of the most intriguing aspects of these gases is the functional interaction between them, which is intimately linked by the enzyme systems that produce them. Despite the need to better understand NO, H₂S and CO biology, the notion that these are environmental pollutants remains ever present. For this reason, incorporating the concept of hormesis becomes imperative and must be included in discussions when considering developing new therapeutics that involve these gases. While there is now an enormous literature base for each of these gasotransmitters, we provide here an overview of their respective physiologic roles in the brain.

Nitrogenous compounds in the saliva and blood of cirrhotic patients: a cross-sectional study

OBJECTIVES

Serum increase of nitrogenous compounds (NC) in cirrhotic patients has been associated with the development of hepatic encephalopathy (HE). However, the relation between NC in saliva and HE is unclear. The objective of this study is to measure the levels of nitric oxide and urea in the blood and saliva in 38 cirrhotic patients and correlate them with clinical characteristics and presence and grades of HE.

MATERIAL AND METHODS

Automated enzymatic colourimetric assays were performed to determine the levels of NC. Diagnosis and severity of HE were determined based on the West Haven criteria and by using the inhibitory control test.

RESULTS

HE was diagnosed in 89.47% of the patients, with the majority (60.50%) presenting covert HE. With regard to the measurement of NC, although nitric oxide is moderately correlated with its amount in blood and saliva (r = 0.630; P < 0.001), only salivary levels were associated with the presence of ascites and ecchymosis (P = 0.013 and P = 0.030, respectively). In patients with HE, the serum levels of urea were higher (P = 0.013) than those in patients without HE or minimal HE.

CONCLUSIONS

Nitrogenous compounds in the saliva were correlated with neither the presence nor grades of HE, whereas in the blood, only urea was positively correlated with the severity and presence of HE.

CLINICAL RELEVANCE

Saliva is an excellent fluid for diagnosing several diseases, but it does not seem to be able to collaborate with the identification of HE.

Mutual inter-regulation between iNOS and TGF-β1: Possible molecular and cellular mechanisms of iNOS in wound healing

Abnormal wound healing with excessive scarring is a major health problem with socioeconomic and psychological impacts. In human, chronic wounds and scarring are associated with upregulation of the inducible nitric oxide synthase (iNOS). Recently, we have shown physiological regulation of iNOS in wound healing. Here, we sought to investigate the possible mechanistic role of iNOS in wound healing using biochemical and immunohistochemical assays. We found: (a) iNOS is the main source of wound nitric oxide (NO), (b) NOS inhibition in the wound, downregulated iNOS protein, mRNA and enzymatic activity, and reduced wound NO, and (c) iNOS inhibition resulted in delayed healing at early time points, and excessive scarring at late time points. Furthermore, molecular and cellular analysis of the wound showed that iNOS inhibition significantly (P < 0.05) increased TGF-β1 mRNA and protein levels, fibroblasts and collagen deposition. These latter findings suggest that iNOS might be exerting its action in the wound by signaling through TGF-β1 that activates wound fibroblasts to produce excessive collagen. Our current findings provide further support that iNOS is crucial for physiological wound healing, and suggest that dysregulation of iNOS during the inflammatory phase impairs healing, and results in disfiguring post-healing scarring. Thus, the mutual feedback regulation between iNOS and TGF-β1 at the gene, protein and functional levels might be the mechanism through which iNOS regulates the healing. Monitoring and maintenance of wound NO levels might be important for healing and avoiding long-term complications in susceptible people including patients with diabetic wounds, venous ulcers or keloid prone.

Carcinogenesis on the background of liver fibrosis: Implications for the management of hepatocellular cancer

Hepatocellular carcinoma (HCC) is now the second leading cause of cancer-related deaths globally and many patients have incurable disease. HCC predominantly occurs in the setting of liver cirrhosis and is a paradigm for inflammation-induced cancer. The causes of chronic liver disease promote the development of transformed or premalignant hepatocytes and predisposes to the development of HCC. For HCC to grow and progress it is now clear that it requires an immunosuppressive niche within the fibrogenic microenvironment of cirrhosis. The rationale for targeting this immunosuppression is supported by responses seen in recent trials with checkpoint inhibitors. With the impact of immunotherapy, HCC progression may be delayed and long term durable responses may be seen. This makes the management of the underlying liver cirrhosis in HCC even more crucial as studies demonstrate that measures of liver function are a major prognostic factor in HCC. In this review, we discuss the development of cancer in the setting of liver inflammation and fibrosis, reviewing the microenvironment that leads to this tumourigenic climate and the implications this has for patient management.

Role and regulation of autophagy and apoptosis by nitric oxide in hepatic stellate cells during acute liver failure

BACKGROUND & AIMS

We previously found that hepatic stellate cell activation induced by autophagy maintains the liver architecture to prevent collapse during acute liver failure. Nitric oxide has shown to induce hepatic stellate cell apoptosis. Whether and how nitric oxide is involved in acute liver failure and autophagy remains unclear.

METHODS

Acute liver failure patients were recruited to investigate the correlation between plasma nitric oxide levels and clinical features. Liver tissues were collected from chronic hepatitis patients by biopsy and from acute liver failure patients who had undergone liver transplantation. The expression of nitric oxide synthases and hepatic stellate cell activation (alpha-SMA), and autophagic activity (LC3) were investigated by immunohistochemistry. Autophagy and apoptosis were investigated by immunoblot analysis, confocal microscopy, and flow cytometry in hepatic stellate cells treated with nitric oxide donors.

RESULTS

Plasma nitric oxide level was significantly increased in patients with acute liver failure compared to those with cirrhosis (53.60±19.74 μM vs 19.40±9.03 μM, Z=-7.384, P<.001) and positively correlated with MELD-Na score (r=.539, P<.001), implicating nitric oxide in acute liver failure. At least some Nitric oxide was produced by overexpression of inducible nitric oxide synthases and endothelial nitric oxide synthases, but not neuronal nitric oxide synthases in the liver tissue. In vivo observation revealed that autophagy was inhibited in hepatic stellate cells based on decreased LC3 immunostaining, and in vitro experiments demonstrated that Nitric oxide can inhibit autophagy. Moreover, nitric oxide promoted hepatic stellate cell apoptosis, which was rescued by an autophagy inducer.

CONCLUSIONS

Increased nitric oxide synthases/ nitric oxide promotes apoptosis through autophagy inhibition in hepatic stellate cells during acute liver failure, providing a novel strategy for the treatment of patients with acute liver failure.

Diosmin attenuates radiation-induced hepatic fibrosis by boosting PPAR-γ expression and hampering miR-17-5p-activated canonical Wnt-β-catenin signaling

BACKGROUND

Liver fibrosis is one of the major complications from upper right quadrant radiotherapy. MicroRNA-17-5p (miR-17-5p) is hypothesized to act as a regulator of hepatic stellate cell (HSCs) activation by activation of the canonical Wnt-β-catenin pathway. Diosmin (Dios), a citrus bioflavonoid, is known to possess potent antioxidant, anti-inflammatory, and anti-apoptotic properties.

PURPOSE

To explore the molecular mechanisms that underlie radiation-induced liver fibrosis, and to evaluate the possible influence of Dios on the miR-17-5p-Wnt-β-catenin signaling axis during fibrogenesis provoked by irradiation (IRR) in rats. Also, the effect of Dios on hepatic peroxisome proliferator activated receptor-γ (PPAR-γ) expression as a regulator for HSC activation was considered.

METHODS

We administered 100 mg·(kg body mass)^-1·day^-1 (per oral) of Dios were administered to IRR-exposed rats (overall dose of 12 Gy on 6 fractions of 2 Gy each) for 6 successive weeks.

RESULTS

Data analysis revealed that Dios treatment mitigated oxidative stress, enhanced antioxidant defenses, alleviated hepatic inflammatory responses, abrogated pro-fibrogenic cytokines, and stimulated PPAR-γ expression. Dios treatment repressed the miR-17-5p activated Wnt-β-catenin signaling induced by IRR. Moreover, Dios treatment restored the normal hepatic architecture and reversed pathological alterations induced by IRR.

CONCLUSION

We hypothesize that the stimulation of PPAR-γ expression and interference with miR-17-5p activated Wnt-β-catenin signaling mediates the antifibrotic properties of Dios.

Angiotensin-converting enzyme inhibitor prevents oxidative stress, inflammation, and fibrosis in carbon tetrachloride-treated rat liver

Hepatic fibrosis is a common feature of chronic liver injury, and the involvement of angiotensin II in such process has been studied earlier. We hypothesized that anti-angiotensin II agents may be effective in preventing hepatic fibrosis. In this study, Long Evans female rats were used and divided into four groups such as Group-I, Control; Group-II, Control + ramipril; Group-III, CCl4; and Group-IV, CCl4 + ramipril. Group II and IV are treated with ramipril for 14 d. At the end of treatment, the livers were removed, and the level of hepatic marker enzymes (aspartate aminotransferase, Alanine aminotransferase, and alkaline phosphatase), nitric oxide, advanced protein oxidation product , catalase activity, and lipid peroxidation were determined. The degree of fibrosis was evaluated through histopathological staining with Sirius red and trichrome milligan staining. Carbon-tetrachloride (CCl4) administration in rats developed hepatic dysfunction and raised the hepatic marker enzymes activities significantly. CCl4 administration in rats also produced oxidative stress, inflammation, and fibrosis in liver. Furthermore, angiotensinogen-inhibitor ramipril normalized the hepatic enzymes activities and improved the antioxidant enzyme catalase activity. Moreover, ramipril treatment ameliorated lipid peroxidation and hepatic inflammation in CCl4-treated rats. Ramipril treatment also significantly reduced hepatic fibrosis in CCl4-administered rats. In conclusion, our investigation suggests that the antifibrotic effect of ramipril may be attributed to inhibition of angiotensin-II mediated oxidative stress and inflammation in liver CCl4-administered rats.

Association between lymphocyte-to-monocyte ratio (LMR) and the mortality of HBV-related liver cirrhosis: a retrospective cohort study

OBJECTIVE

Infection with hepatitis B virus (HBV) remains a major cause of liver cirrhosis (LC) in China. Recent reports suggest that the lymphocyte-to-monocyte ratio (LMR) is a potential biomarker for predicting clinical outcomes. In our study, we investigated if LMR can be used as a prognostic marker of mortality in patients with HBV-related LC.

DESIGN

A retrospective cohort study.

SETTING

HBV-infected patients with LC and patients with chronic hepatitis B infection (CHB) from the Department of Infectious Disease were enrolled and 240 healthy individuals were recruited from the healthcare centre at the First Affiliated Hospital of Zhejiang University.

PARTICIPANTS

479 HBV-infected patients with LC, 134 patients with CHB and 240 healthy individuals were enrolled.

PRIMARY AND SECONDARY OUTCOME MEASURES

The receiver operating characteristic (ROC) curve and multivariable logistic regression analysis after adjusting for total protein, albumin, total bilirubin and the model for end-stage liver disease (MELD) score were used to evaluate the power of LMR for predicting 1 year mortality in patients with LC.

RESULTS

The LMR was statistically lower in patients with LC. The MELD score and mortality were statistically higher in patients with LC compared with the CHB and control groups. The area under the ROC curve, cut-off values, sensitivity and specificity of LMR for predicting mortality LC in the training cohort were 0.817 (95% CI 0.746 to 0.888; p<0.001), 2.10, 82.6 and 78.8%, and these data were confirmed in the validation cohort. The multivariate logistic regression analysis showed that LMR was an independent predictive factor of mortality in LC (OR 2.370, 95% CI (1.070 to 5.249); p=0.033).

CONCLUSIONS

Our results strongly suggest that low LMR can be considered as an independent biomarker for predicting mortality in patients with LC.

Novel aspects of the liver microenvironment in hepatocellular carcinoma pathogenesis and development

Hepatocellular carcinoma (HCC) is a prevalent primary liver cancer that is derived from hepatocytes and is characterised by high mortality rate and poor prognosis. While HCC is driven by cumulative changes in the hepatocyte genome, it is increasingly recognised that the liver microenvironment plays a pivotal role in HCC propensity, progression and treatment response. The microenvironmental stimuli that have been recognised as being involved in HCC pathogenesis are diverse and include intrahepatic cell subpopulations, such as immune and stellate cells, pathogens, such as hepatitis viruses, and non-cellular factors, such as abnormal extracellular matrix (ECM) and tissue hypoxia. Recently, a number of novel environmental influences have been shown to have an equally dramatic, but previously unrecognized, role in HCC progression. Novel aspects, including diet, gastrointestinal tract (GIT) microflora and circulating microvesicles, are now being recognized as increasingly important in HCC pathogenesis. This review will outline aspects of the HCC microenvironment, including the potential role of GIT microflora and microvesicles, in providing new insights into tumourigenesis and identifying potential novel targets in the treatment of HCC.

Increased circulatory asymmetric dimethylarginine and multiple organ failure: bile duct ligation in rat as a model

Bile duct ligation (BDL)-treated rats exhibit cholestasis, increased systemic oxidative stress, and liver fibrosis, which ultimately lead to liver cirrhosis. Asymmetric dimethylarginine (ADMA) is a competitive inhibitor of nitric oxide synthase that can decrease the synthesis of nitric oxide. BDL rats have higher plasma and hepatic ADMA levels, which may be due to increased hepatic protein arginine methyltransferase-1 and decreased dimethylarginine dimethylaminohydrolase expression. BDL rats also exhibit renal and brain damage characterized by increased tissue ADMA concentrations. The increased plasma ADMA levels and multiple organ damages seen here are also observed following multiple organ failures associated with critical illness. This review discusses the dysregulation of ADMA in major organs in BDL rats and the role of increased ADMA in multiple organ damages.

Hepatic Injury Correlates With Apoptosis, Regeneration, and Nitric Oxide Synthase Expression in Canine Chronic Liver Disease

Assessment of the clinical severity, pathogenesis, and prognosis of canine chronic liver disease poses significant challenges to clinicians and pathologists, relating in part to a lack of standardized terminology and assessment methods and also to a lack of understanding of the pathogenesis of chronic liver disease in the dog. This study graded the severity of necroinflammatory activity in chronic liver disease in dogs using a modification of Ishak’s grading scheme for human chronic liver disease and examined the association of grade score with hepatocellular apoptosis, regeneration, nitric oxide synthase isoform expression, copper and iron accumulation, and indicators of oxidative stress. Formalin-fixed, paraffin-embedded hematoxylin and eosin (HE)–stained liver biopsies from 45 dogs with chronic liver disease and 55 healthy control dogs were graded for various morphologic components of liver injury and response. The cumulative score for grade of necroinflammatory activity was strongly and significantly correlated with immunoreactive labels for hepatocellular proliferation (Ki-67); apoptosis (cleaved caspase-3); inducible nitric oxide synthase (iNOS) in lobular, portal, and septal stromal cells; endothelial nitric oxide synthase (eNOS) in hepatocytes and lobular, portal, and septal stromal cells; and total stainable hepatic iron. A weaker significant correlation was found between grade and accumulation of hepatocellular copper. No significant correlation was found between grade and immunoreactivity for malondialdehyde-protein adducts. These results document a method for grading of the severity of necroinflammatory disease in canine liver biopsies and show an association with increased iNOS and eNOS expression.

Nitro-oxidative stress after neuronal ischemia induces protein nitrotyrosination and cell death

Ischemic stroke is an acute vascular event that obstructs blood supply to the brain, producing irreversible damage that affects neurons but also glial and brain vessel cells. Immediately after the stroke, the ischemic tissue produces nitric oxide (NO) to recover blood perfusion but also produces superoxide anion. These compounds interact, producing peroxynitrite, which irreversibly nitrates protein tyrosines. The present study measured NO production in a human neuroblastoma (SH-SY5Y), a murine glial (BV2), a human endothelial cell line (HUVEC), and in primary cultures of human cerebral myocytes (HC-VSMCs) after experimental ischemia in vitro. Neuronal, endothelial, and inducible NO synthase (NOS) expression was also studied up to 24 h after ischemia, showing a different time course depending on the NOS type and the cells studied. Finally, we carried out cell viability experiments on SH-SY5Y cells with H₂O₂, a prooxidant agent, and with a NO donor to mimic ischemic conditions. We found that both compounds were highly toxic when they interacted, producing peroxynitrite. We obtained similar results when all cells were challenged with peroxynitrite. Our data suggest that peroxynitrite induces cell death and is a very harmful agent in brain ischemia.

In vivo modulation of iNOS pathway in hepatocellular carcinoma by Nigella sativa

OBJECTIVE

Nitric oxide (NO) and inducible nitric oxide synthase enzyme (iNOS) have been implicated in various tumors. Hepatocellular carcinoma is a highly aggressive form of solid tumor. The lack of effective therapy necessitates the introduction of novel therapeutic strategies to counter this disease. Nigella sativa (NS) has been shown to have specific health benefits. The aim of this study was to investigate the in vivo modulation of the iNOS pathway by NS ethanolic extract (NSEE) and the implications of this effect as an antitumor therapeutic approach against diethylnitrosamine (DENA)-induced hepatocarcinogenesis.

METHODS

Rats were divided into four groups, normal control, NSEE control, cancer control, and NSEE-DENA groups. The diagnosis of cancer was based on alpha-fetoprotein (AFP) levels and histological variations. Serum NO, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels and serum iNOS activity were measured. Liver iNOS expression was investigated by reverse transcriptase (RT)-PCR and western blot assays.

RESULTS

Serum AFP, NO, TNF-α, and IL-6 levels and iNOS enzyme activity were significantly increased in rats treated with DENA. Significant up-regulation of liver iNOS mRNA and protein expression was also observed. Subsequent treatment with NSEE significantly reversed these effects and improved the histopathological changes in malignant liver tissue which appeared after treatment with DENA, without any toxic effect when given alone.

CONCLUSION

These results provide evidence that attenuation of the iNOS pathway and suppression of the inflammatory response mediated by TNF-α, and IL-6 could be implicated in the antitumor effect of NSEE. As such, our findings hold great promise for the utilization of NS as an effective natural therapeutic agent in the treatment of hepatocarcinogenesis.

Nitric oxide, ammonia, and CRP levels in cirrhotic patients with hepatic encephalopathy: is there a connection?

GOALS

Comparison of nitric oxide (NO) levels in cirrhotic patients with and without hepatic encephalopathy (HE), evaluation of possible correlation between HE and other clinical or laboratory characteristics, and estimation of utilization of NO levels in clinical practice.

BACKGROUND

HE is a neuropsychiatric complication of cirrhosis. The exact pathogenetic mechanisms underlying the presence of HE are not known. However, dysfunction of the NO pathway and ammonia detoxification are thought to play a major role.

STUDY

Sixty-seven cirrhotic patients, 36 (53.7%) without HE, and 31 (46.3%) with HE were included in the study. Eighteen healthy individuals were used as control group. Clinical and laboratory data, including ammonia and stable end products of NO using Griess reaction, were collected.

RESULTS

NOx levels were statistically significantly higher in cirrhotic patients (225.5 μmol/L) than in control group [(67.94 μmol/L) (P=0.000)]. NOx levels were, also, statistically significantly higher in patients with HE compared with patients without HE (324.67 μmol/L vs. 141.96 μmol/L, P=0.000). Significant correlation between the presence of HE and NOx, ammonia, C-reactive protein, albumin, Model for End-Stage Liver Disease score, and Child-Pugh classification revealed. NOx levels also correlated with severity of HE. NOx and ammonia are independent factors predicting HE according to regression analysis. Diagnostic accuracy for the diagnosis of HE using a combination of NOx and ammonia was superior compared with standalone NOx or ammonia utilization.

CONCLUSIONS

NOx levels are correlated with the presence and severity of HE. NOx levels determination, in addition to ammonia levels, could contribute in diagnosis of HE.

Protective effect of L-carnitine and coenzyme Q10 on CCl₄-induced liver injury in rats

This study provides an information about the mechanisms of liver injury induced by CCl(4), and determines the influence of administration of L-carnitine or/and CoQ10 as prophylactic agents against CCl(4) deteriorative effect. The study was carried out on 80 adult male albino rats divided into eight groups, 10 animals each, as follows: four normal groups (control, treated with L-carnitine, treated with CoQ10, and treated with a combination of Lcarnitine and CoQ10) and four liver injury groups treated with CCl(4) (control, treated with L-carnitine, treated with CoQ10, and treated with a combination of L-carnitine and CoQ10). Liver injury was induced by s.c. injection of a single dose of CCl(4) (1 ml/kg). L-carnitine (50 mg/kg/day) was given i.p. for four successive days 24 hours before CCl(4) injection, and CoQ10 (200 mg/kg) was given as a single i.p. dose 24 hours before CCl(4) injection. Animals were sacrificed 24 hours after CCl(4) injection, blood samples were withdrawn and liver tissue samples were homogenized. The levels of the following parameters were determined: hepatic reduced glutathione, serum ALT and AST, hepatic lipid peroxides, hepatic vitamin C, hepatic and serum total protein, serum albumin, serum sialic acid, serum nitrite, and serum and hepatic total LDH activities and LDH isoenzymes. The obtained data revealed that CCl(4) injection produced a significant decrease in reduced glutathione content, vitamin C, total protein and albumin levels. However, there was a significant increase in serum ALT and AST activities, lipid peroxides, sialic acid, nitric oxide, serum and hepatic total LDH activities. On the other hand, groups treated with L-carnitine or/and CoQ10 prior to CCl(4) injection showed an improvement in most parameters when compared with cirrhotic control group. It has been concluded that L-carnitine and coenzyme Q10 have a pronounced prophylactic effect against liver damage induced by halogenated alkanes such as carbon tetrachloride.

Spinal motoneuron synaptic plasticity after axotomy in the absence of inducible nitric oxide synthase

Background

Astrocytes play a major role in preserving and restoring structural and physiological integrity following injury to the nervous system. After peripheral axotomy, reactive gliosis propagates within adjacent spinal segments, influenced by the local synthesis of nitric oxide (NO). The present work investigated the importance of inducible nitric oxide synthase (iNOS) activity in acute and late glial responses after injury and in major histocompatibility complex class I (MHC I) expression and synaptic plasticity of inputs to lesioned alpha motoneurons.

Methods

In vivo analyses were carried out using C57BL/6J-iNOS knockout (iNOS^-/-) and C57BL/6J mice. Glial response after axotomy, glial MHC I expression, and the effects of axotomy on synaptic contacts were measured using immunohistochemistry and transmission electron microscopy. For this purpose, 2-month-old animals were sacrificed and fixed one or two weeks after unilateral sciatic nerve transection, and spinal cord sections were incubated with antibodies against classical MHC I, GFAP (glial fibrillary acidic protein - an astroglial marker), Iba-1 (an ionized calcium binding adaptor protein and a microglial marker) or synaptophysin (a presynaptic terminal marker). Western blotting analysis of MHC I and nNOS expression one week after lesion were also performed. The data were analyzed using a two-tailed Student's t test for parametric data or a two-tailed Mann-Whitney U test for nonparametric data.

Results

A statistical difference was shown with respect to astrogliosis between strains at the different time points studied. Also, MHC I expression by iNOS^-/- microglial cells did not increase at one or two weeks after unilateral axotomy. There was a difference in synaptophysin expression reflecting synaptic elimination, in which iNOS^-/- mice displayed a decreased number of the inputs to alpha motoneurons, in comparison to that of C57BL/6J.

Conclusion

The findings herein indicate that iNOS isoform activity influences MHC I expression by microglial cells one and two weeks after axotomy. This finding was associated with differences in astrogliosis, number of presynaptic terminals and synaptic covering of alpha motoneurons after lesioning in the mutant mice.

Glomerular lesions in patients with sickle cell disease

Sickle cell disease (SCD) is an increasing cause of chronic kidney disease, but the spectrum of glomerular lesions and their underlying mechanisms remain poorly described. We reviewed 18 renal biopsies from patients with SCD and glomerular involvement and studied the expression of hypoxic markers in the biopsy specimens. Four histopathologic variants were distinguished: focal segmental glomerulosclerosis (FSGS) (39%), membranoproliferative glomerulonephritis (28%), thrombotic microangiopathy glomerulopathy (17%), and specific sickle cell disease glomerulopathy (17%). Chronic organ damage and history of acute chest syndrome were associated with the occurrence of SCD glomerulopathy. All patients exhibited macroalbuminuria but only 6 patients displayed impaired renal function. SCD was not associated with a specific FSGS histologic variant. Long-term follow-up analysis revealed that 50% of patients exhibited chronic kidney disease. Regardless of the histologic variants, immunohistochemistry did not reveal a specific induction of hypoxic markers (inducible nitric oxide synthase [iNOS], nitrotyrosine, hypoxia-inducible factor [HIF]-1 alpha) at the time of renal biopsy. This large study shows that a wide spectrum of glomerular lesions is associated with SCD. Whatever lesions are observed, the renal prognosis is poor, and early renoprotective treatment is necessary. Hypoxic state does not seem to play a key role in the progression of glomerular lesions, but its potential role at an early stage of glomerular injury requires further investigation.

Phenotype, compartmental organization and differential vulnerability of nigral dopaminergic neurons

The degeneration of nigral dopaminergic (DA-) neurons is the histopathologic hallmark of Parkinson's disease (PD), but not all nigral DA-cells show the same susceptibility to degeneration. This starts in DA-cells in the ventrolateral and caudal regions of the susbtantia nigra (SN) and progresses to DA-cells in the dorsomedial and rostral regions of the SN and the ventral tegmental area, where many neurons remain intact until the final stages of the disease. This fact indicates a relationship between the topographic distribution of midbrain DA-cells and their differential vulnerability, and the possibility that this differential vulnerability is associated with phenotypic differences between different subpopulations of nigral DA-cells. Studies carried out during the last two decades have contributed to establishing the existence of different compartments of nigral DA-cells according to their neurochemical profile, and a possible relationship between the expression of some factors and the relative vulnerability or resistance of DA-cell subpopulations to degeneration. These aspects are reviewed and discussed here.

Inhibition of inducible nitric oxide synthase activity prevents liver recovery in rat thioacetamide-induced fibrosis reversal

BACKGROUND

Stimulation of nitric oxide (NO) synthesis similar to the application of NO donors could be of benefit in liver fibrosis. Many authors believe that activation of NO synthesis by pharmacological agents is promising in the treatment of liver fibrosis. However, there is considerable controversy in understanding the role of NO in fibrogenesis and fibrolysis. The aims of our study were to evaluate the effects of L-arginine, as an NO metabolic precursor, and those of NO synthase (NOS) inhibitors, L-nitroarginine methyl ester (L-NAME) and aminoguanidine (AG) in rats with thioacetamide (TAA)-induced liver fibrosis reversal.

MATERIALS AND METHODS

Male Wistar rats, 230-240 g, received TAA (200 mg kg(-1), intraperitoneally) twice a week for 3 months. Liver resolution was simulated by withdrawal of TAA administration. Thereafter the animals were subdivided into five groups and treated by intragastric intubation with: L-arginine (100 and 300 mg kg(-1)); L-NAME as an inhibitor of both constitutively expressed NOS (eNOS) and inducible NOS (iNOS) (20 mg kg(-1)), AG as a specific inhibitor of iNOS (100 mg kg(-1)) or placebo. The severity of liver fibrosis was assessed by morphometric evaluation of liver slides stained with Azan-Mallory, hydroxyproline (Hyp) determination and mRNA steady state levels of collagen I, transforming growth factor (TGF)-beta1, metalloproteinases (MMP)-13, -14, tissue inhibitor of MMP (TIMP)-1 and plasminogen activator inhibitor (PAI)-1 were quantified by real time PCR. The activities of serum marker enzyme, alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase, were measured.

RESULTS

TAA treatment during 3 months induced micronodular liver fibrosis with a pronounced deposition of collagen fibres. L-Arginine did not affect this deposition nor did it affect both relative and total liver hydroxyproline content. Both NOS inhibitors significantly increased the square of the liver connective tissue stained by Azan-Mallory and the above parameters characterizing liver hydroxyproline content. Both NOS inhibitors up-regulated procollagen alpha1 (I), MMP-13, TIMP-1 and PAI-1 mRNA expression. The AG effects were more pronounced. than those of L-NAME. AG treatment also increased mRNA expression of TGF-beta1 and PAI-1.

CONCLUSIONS

Both NOS inhibitors developed a clear pro-fibrotic effect in the liver. Aminoguanidine was more fibrotic than L-NAME. Our data suggest a significant anti-fibrotic role for iNOS rather than for eNOS. L-Arginine did not show any anti-fibrotic properties in the TAA-model used.

Effect of Prometheus liver assist system on systemic hemodynamics in patients with cirrhosis: A randomized controlled study

AIM: To evaluate treatment safety and hemodynamic changes during a single 6-h treatment with the Prometheus™ liver assist system in a randomized, controlled study.

METHODS: Twenty-four patients were randomized to either the study group or to one of two control groups: Fractionated Plasma Separation Adsorption and Dialysis, Prometheus™ system (Study group; n = 8); Molecular Adsorbent Recirculation System (MARS)™ (Control group 1, n = 8); or hemodialysis (Control group 2; n = 8). All patients included in the study had decompensated cirrhosis at the time of the inclusion into the study. Circulatory changes were monitored with a Swan-Ganz catheter and bilirubin and creatinine were monitored as measures of protein-bound and water-soluble toxins.

RESULTS: Systemic hemodynamics did not differ between treatment and control groups apart from an increase in arterial pressure in the MARS group (P = 0.008). No adverse effects were observed in any of the groups. Creatinine levels significantly decreased in the MARS group (P = 0.03) and hemodialysis group (P = 0.04). Platelet count deceased in the Prometheus group (P = 0.04).

CONCLUSION: Extra-corporal liver support with Prometheus is proven to be safe in patients with end-stage liver disease but does not exert the beneficial effects on arterial pressure as seen in the MARS group.

Short- and long-term outcomes after hepatic resection for hepatocellular carcinoma with concomitant esophageal varices in patients with cirrhosis

BACKGROUND

Hepatic resection for hepatocellular carcinoma (HCC) in cirrhotic patients with esophageal varices (EV) is often avoided because of poor liver function reserve. Outcomes of resection in such cases have not been fully investigated.

METHODS

We conducted a retrospective study of 134 cirrhotic patients (Child-Pugh class A or B) who underwent hepatic resection for HCC, comparing short- and long-term outcomes in patients with EV (n = 31) to those in patients without EV (n = 103).

RESULTS

Patients with EV had higher tumor differentiation, fewer instances of portal invasion, lower liver function reserve, and more limited resections than did patients without EV. Of 31 patients with EV, four died of postoperative complication, and nine of liver failure, seven of HCC, two of ruptured EV, and two of other causes. Median survival time for patients who died of liver failure was 59 months. Mortality and morbidity rates after hepatic resection did not differ between patients with and without EV. The 5-year overall survival rate was significantly higher in patients with EV (70.1%) than in those without EV (47.5%, P = 0.045) but did not differ between patients without portal invasion with and without EV (P = 0.55). Presence of EV was not an independent predictor for survival.

CONCLUSIONS

Short- and long-term outcomes of hepatic resection in HCC patients with and without EV are similar. Limited hepatic resection for early-stage tumor is an option for Child-Pugh class A or B patients with EV.

New strategy for the antifibrotic therapy with oral administration of FR260330 (a selective inducible nitric oxide synthase inhibitor) in rat experimental liver cirrhosis

Inducible nitric oxide synthase (iNOS) activity is significantly elevated in viral hepatitis, alcoholic cirrhosis, and cholestasis. However, there are few reports on the relationship between iNOS and cirrhosis. Here, we investigated the effects of a new iNOS inhibitor that has been developed for oral administration in an experimental rat liver cirrhosis model. A cirrhotic rat model was developed by long-term administration of thioacetamide injections. FR260330 is a new, rationally designed, selective iNOS inhibitor that can be administered orally. After 12 weeks of treatment with FR260330, the rats showed inhibition of progressions of cirrhosis, ascites, and splenomegaly as well as a significant reduction in the proportions of connective tissue in the liver. The expression of nitrotyrosine, which indicates the existence of peroxynitrite and nuclear factor-kappaB activation, was remarkably decreased in the FR260330 treatment group. In addition, immunohistochemical and Western blot analyses showed that the expression of transforming growth factor-beta1 was remarkably decreased in this group. The present study demonstrates that FR260330 reduces liver fibrosis by the inhibition of transforming growth factor-beta1 and retards the development of cirrhosis. This oral iNOS inhibitor will be a new strategy for the treatment of cirrhosis.

Enhanced iNOS Gene Expression in the Steatotic Rat Liver after Normothermic Ischemia

BACKGROUND

Impaired hepatic microcirculation in the steatotic liver has been identified as a considerable factor for increased vulnerability after ischemia/reperfusion (I/R). Changes in regulation and synthesis of vasoactive mediators, such as nitric oxide (NO) and endothelin (ET-1), may result in functional impairment of postischemic sinusoidal perfusion. The aim of the current study was to assess the impact of I/R injury on postischemic gene expression of NO and ET-1 in steatotic livers.

MATERIALS AND METHODS

Male Sprague-Dawley rats with or without hepatic steatosis (induced by carbon tetrachloride treatment) were subjected to normothermic I/R injury. Steady-state mRNA levels were assessed using RT-PCR to study the expression of genes encoding ET-1, NO synthase (endothelial cell NO synthase and inducible NO synthase, iNOS). Immunohistochemistry was performed for detection of iNOS.

RESULTS

I/R injury was followed by increased iNOS gene expression (RT-PCR/immunohistochemistry) in animals with hepatic steatosis, predominately in hepatocytes with fatty degeneration. A mild increase in mRNA levels for ET-1 was found in steatotic rat livers. I/R induced a further increase in ET-1 gene expression in some but not all reperfused steatotic livers.

CONCLUSIONS

We show an enhanced gene expression of iNOS in postischemic steatotic rat livers. Hepatocytes with fatty degeneration appear to be the major source for NO generation. Furthermore, I/R may also induce ET-1 gene expression. Dysregulation of sinusoidal perfusion by NO and ET-1 is therefore likely to contribute to I/R injury of the steatotic liver.

Oxidative stress and DNA hypermethylation status in renal cell carcinoma arising in patients on dialysis

Renal cell carcinoma (RCC) is more frequently observed in patients on dialysis than in patients with normal renal function. However, the mechanism underlying carcinogenesis in RCC patients on dialysis is still unclear. We hypothesized that oxidative stress affects patients on dialysis and generates new neoplasms, and therefore analysed the correlation between the influences of various markers of oxidative stress and carcinogenesis in those patients. We evaluated the immunohistochemical expression of oxidative stress markers, such as iNOS, 8-OHdG, and COX-2 in 42 cases on dialysis and 51 cases with normal renal function as a control. The methylation status of p16INK4a, p14ARF, VHL, and RASSF1A was analysed together with clinicopathological factors. Histologically, the papillary type was observed more frequently in dialysis RCC than in sporadic RCC. Immunohistochemically, overexpression of iNOS (p < 0.0001) and COX-2 (p = 0.0002) was more frequently observed in dialysis RCC. Furthermore, the 8-OHdG labelling index was significantly higher in dialysis RCC than in sporadic RCC. Hypermethylation of p16INK4a was more frequently found in dialysis RCC (p < 0.05). However, no significant correlations between oxidative stress markers and DNA hypermethylation status were observed. The overexpression of iNOS, COX-2, and 8-OHdG in dialysis RCC suggests that patients on dialysis are affected by oxidative stress and that this effect plays an important role in the genesis of dialysis RCC.

Inducible nitric oxide synthase activity does not contribute to the maintenance of peripheral vascular tone in patients with heart failure

Enhanced iNOS (inducible nitric oxide synthase) activity may contribute to vascular dysfunction in patients with heart failure. In the present study, we aimed to determine whether iNOS activity contributes to the maintenance of vascular tone in patients with symptomatic heart failure with the use of the highly selective iNOS inhibitor 1400W {N-[3-(aminomethyl)benzyl] acetamidine}. Bilateral forearm blood flow was measured using venous occlusion plethysmography in 12 patients with New York Heart Association class II-IV heart failure and eight matched healthy control subjects during intra-brachial infusion of 1400W (0.1-1 micromol/min), L-NMMA (N(G)-monomethyl-L-arginine; a non-selective NOS inhibitor; 2-8 micromol/min) and noradrenaline (control vasoconstrictor; 60-480 pmol/min). In both patients and controls, intra-brachial infusion of L-NMMA and noradrenaline caused a dose-dependent reduction in infused forearm blood flow (P<0.05 for both): peak reduction of 32+/-6% and 37+/-4% during L-NMMA and 52+/-6% and 49+/-5% during noradrenaline respectively (P values were not significant when patients were compared with controls). In contrast, 1400W had no effect on blood flow at 1 micromol/min [-3+/-4% in patients (95% confidence intervals, -11 to 5%) and 3+/-8% in controls; P value was not significant]. In conclusion, we have demonstrated that intrabrachial selective iNOS inhibition does not influence forearm blood flow in patients with heart failure. We conclude that iNOS activity does not contribute to peripheral vascular tone in patients with symptomatic heart failure.

Effect of adamantylamide dipeptide as adjuvant therapy to praziquantel in mice infected with different S. mansoni isolates

This work investigated the possible use of AdDP as adjuvant therapy to praziquantel (PZQ) in mice infected with PZQ-insusceptible Schistosoma mansoni isolate in a trial to increase the susceptibility of this isolate to the drug. Two batches of C57 BL/6 mice were infected with PZQ-susceptible and -insusceptible S. mansoni isolates, and each batch was divided into five groups. Seven weeks postinfection, the experimental group received AdDP (5 mg/kg) in addition to PZQ in reduced dose (3x100 mg/kg). Three of the remaining four groups were treated controls; they received AdDP, PZQ in reduced dose and in full dose (2x500 mg/kg), and the fourth group was infected untreated. In mice infected with PZQ-susceptible or -insusceptible S. mansoni isolate, praziquantel alone, and in addition to AdDP, reduced worm and egg loads and increased percentage dead eggs. Also, they improved the histopathological changes (reduction in granuloma diameter, percentage fibrotic area with increased percentage degenerated eggs). Inducible nitric oxide synthase (iNOS), nitric oxide (NO) in culture of peritoneal macrophages, and number of CD68-positive cells were decreased with improved alanine amino transaminase. In mice receiving combined therapy AdDP+PZQ, the antischistosomal efficacy and the reductions in the inflammatory granulomatous reactions, NO in cultured peritoneal macrophages, percentage fibrotic areas recorded, were comparable to that in mice receiving full dose of PZQ, with significantly higher reduction in CD68 cells denoting enhanced antischistosomal efficacy and healing of the inflammatory reactions in the liver.

Expression of inducible nitric oxide (NO) synthase but not prevention by its gene ablation of hepatocarcinogenesis with fibrosis caused by a choline-deficient, L-amino acid-defined diet in rats and mice

Expression of inducible nitric oxide synthase (iNOS) and effects of iNOS gene ablation on the hepatocarcinogenesis associated with fibrosis caused by a choline-deficient, L-amino acid-defined (CDAA) diet, were examined in male F344 rats and C57BL/6J wild-type and iNOS-/- mice. Western blot, RT-PCR and immunohistochemical analyses revealed increased expression of iNOS protein and mRNA in the livers of rats and wild-type mice fed a CDAA diet for 12-80 weeks, associated with elevated serum NO(x) and liver nitrotyrosine levels. iNOS-/- mice demonstrated greater liver injury and fibrosis in the early stage than their wild-type counterparts, but this did not significantly affect the incidence and multiplicity of altered foci, adenomas and hepatocellular carcinomas in spite of immunohistochemical iNOS expression in these lesions. Results suggested no major determinant roles of the expressed iNOS in the development of liver tumors caused by the CDAA diet.

Conservation of whole body nitric oxide metabolism in human alcoholic liver disease: implications for nitric oxide production

OBJECTIVE

Patients with advanced liver diseases tend to develop a hyperdynamic circulation which complicates cirrhosis. Impairment of nitric oxide (NO) metabolism has been implicated in the pathogenesis of portal hypertension. The aim of this study was to determine nitric oxide synthase (NOS)-dependent whole body NO production in patients with decompensated liver cirrhosis and portal hypertension.

MATERIAL AND METHODS

Ten patients with decompensated alcoholic liver disease and portal hypertension (Child-Pugh Classifications B and C with no signs of infection) and 10 age- and gender-matched control subjects received an intravenous infusion of L-[15N]2-arginine (50 micromol/min for 30 min). Urine and serum nitrite and nitrate concentrations were determined using ion chromatography-mass spectrometry.

RESULTS

NOS-dependent whole body NO synthesis was estimated by the conversion of [15N]guanidino nitrogen of arginine to urine 15N-nitrite and 15N-nitrate. The amount of 15N-nitrite and 15N-nitrate in the urine of patients and control subjects was significantly correlated with the amount of urine nitrite and nitrate over 36 h (r=0.91 and 0.77, respectively, p<0.0001). However, neither a median of 12 h 15N-nitrite and 15N-nitrate nor nitrite and nitrate excretion in the urine was different between patients and control subjects, 46.4 (9.4-152.2) versus 98.7 (29.9-146.5) nmol/mmol creatinine and 20.6 (2.1-69.0) versus 40.0 (27.0-70.1) micromol/mmol creatinine, respectively. No differences were found in serum nitrite and nitrate concentrations and glomerular filtration rates between patients and control subjects, 111.4 (73.2-158.8) versus 109.3 (83.5-176.4) micromol/l.

CONCLUSION

Our results contraindicate a greater basal NOS-dependent whole body NO production in patients with decompensated liver disease and portal hypertension.

Nitric oxide synthase and heme oxygenase expressions in human liver cirrhosis

AIM: Portal hypertension is a common complication of liver cirrhosis. Intrahepatic pressure can be elevated in several ways. Abnormal architecture affecting the vasculature, an increase in vasoconstrictors and increased circulation from the splanchnic viscera into the portal system may all contribute. It follows that endogenous vasodilators may be able to alleviate the hypertension. We therefore aimed to investigate the levels of endogenous vasodilators, nitric oxide (NO) and carbon monoxide (CO) through the expression of nitric oxide synthase (NOS) and heme oxygenase (HO).

METHOD: Cirrhotic (n = 20) and non-cirrhotic (n = 20) livers were obtained from patients who had undergone surgery. The mRNA and protein expressions of the various isoforms of NOS and HO were examined using competitive PCR, Western Blot and immunohistochemistry.

RESULTS: There was no significant change in either inducible NOS (iNOS) or neuronal NOS (nNOS) expressions while endothelial NOS (eNOS) was up-regulated in cirrhotic livers. Concomitantly, caveolin-1, an established down-regulator of eNOS, was up-regulated. Inducible HO-1 and constitutive HO-2 were found to show increased expression in cirrhotic livers albeit in different localizations.

CONCLUSION: The differences of NOS expression might be due to their differing roles in maintaining liver homeostasis and/or involvement in the pathology of cirrhosis. Sheer stress within the hypertensive liver may induce increased expression of eNOS. In turn, caveolin-1 is also increased. Whether this serves as a defense mechanism against further cirrhosis or is a consequence of cirrhosis, is yet unknown. The elevated expression of HO-1 and HO-2 suggest that CO may compensate in its role as a vasodilator albeit weakly. It is possible that CO and NO have parallel or coordinated functions within the liver and may work antagonistically in the pathophysiology of portal hypertension.

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.

The physiology and pathophysiology of nitric oxide in the brain

Nitric oxide (NO) is a molecule with pleiotropic effects in different tissues. NO is synthesized by NO synthases (NOS), a family with four major types: endothelial, neuronal, inducible and mitochondrial. They can be found in almost all the tissues and they can even co-exist in the same tissue. NO is a well-known vasorelaxant agent, but it works as a neurotransmitter when produced by neurons and is also involved in defense functions when it is produced by immune and glial cells. NO is thermodynamically unstable and tends to react with other molecules, resulting in the oxidation, nitrosylation or nitration of proteins, with the concomitant effects on many cellular mechanisms. NO intracellular signaling involves the activation of guanylate cyclase but it also interacts with MAPKs, apoptosis-related proteins, and mitochondrial respiratory chain or anti-proliferative molecules. It also plays a role in post-translational modification of proteins and protein degradation by the proteasome. However, under pathophysiological conditions NO has damaging effects. In disorders involving oxidative stress, such as Alzheimer's disease, stroke and Parkinson's disease, NO increases cell damage through the formation of highly reactive peroxynitrite. The paradox of beneficial and damaging effects of NO will be discussed in this review.

The role of nitric oxide in the pathogenesis of systemic and splanchnic vasodilation in cirrhotic rats before and after the onset of ascites

BACKGROUND

The role of nitric oxide (NO) in the pathogenesis of splanchnic arterial vasodilation in cirrhosis has been recently debated by some experimental studies.

AIMS

We investigated the role of NO in the pathogenesis of the splanchnic arterial vasodilation along the course of CCl(4)-induced experimental cirrhosis.

METHODS

We analyzed the effect on mean arterial pressure (MAP), cardiac output (CO), total peripheral resistance (TPR), and resistance in the superior mesenteric artery (RSMA), before and after the administration of a unspecific NO synthase (NOS) inhibitor (Nomega-nitro-L-arginine-methyl-ester, L-NAME) and a specific NOS2 inhibitor (L-N-(1-iminoethyl)-lysine, L-NIL) to cirrhotic rats with and without ascites, and to control rats. NOS2 and NOS3 protein expression was also assessed in systemic and splanchnic arteries of these animals.

RESULTS

L-NAME in cirrhotic rats markedly improved MAP, and TPR and decreased CO regardless of whether they had ascites or not. L-NIL did not produce any significant effect on systemic haemodynamics in control and cirrhotic rats. NOS3 overexpression in the aorta of cirrhotic animals paralleled the progression of the liver disease. L-NAME increased RSMA in cirrhotic rats, but this effect was much less intense in rats with ascites. L-NIL had an effect only on RSMA in rats with ascites, which was of a similar extent to that produced by L-NAME. Western blot experiment showed a faint overexpression of NOS3 in the mesenteric artery of cirrhotic rats with and without ascites and a clear induction of NOS2 only in the mesenteric artery of rats with ascites.

CONCLUSIONS

These results indicate that NO contributes significantly to the pathogenesis of arterial splanchnic circulation in the early stages of experimental cirrhosis but has only a minor role in its maintenance after the development of ascites. Furthermore, the expression of the different NOS isoforms varies along the course of the liver disease.

Antioxidant effects of insulin-like growth factor-I (IGF-I) in rats with advanced liver cirrhosis

Background

The exogenous administration of Insulin-like Growth Factor-I (IGF-I) induces hepatoprotective and antifibrogenic actions in experimental liver cirrhosis. To better understand the possible pathways behind the beneficial effect of IGF-I, the aim of this work was to investigate severe parameters involved in oxidative damage in hepatic tissue from cirrhotic animals treated with IGF-I (2 μg. 100 g^-1. day^-1). Iron and copper play an important role in oxidative mechanisms, producing the deleterious hydroxyl radical (*OH) that peroxides lipid membranes and damages DNA. Myeloperoxidase (MPO) and nitric oxide (NO) are known sources of free radicals and induce reduction of ferritin-Fe³⁺ into free Fe²⁺, contributing to oxidative damage.

Methods

Liver cirrhosis was induced by CCl₄ inhalation in Wistar male rats for 30 weeks. Healthy controls were studied in parallel (n = 10). Fe and Cu were assessed by atomic absoption spectrometry and iron content was also evaluated by Perls' staining. MPO was measured by ELISA and transferrin and ferritin by immunoturbidimetry. iNOS expression was studied by immuno-histochemistry.

Results

Liver cirrhosis was histologically proven and ascites was observed in all cirrhotic rats. Compared to controls untreated cirrhotic rats showed increased hepatic levels of iron, ferritin, transferrin (p < 0.01), copper, MPO and iNOS expression (p < 0.01). However, IGF-treatment induced a significant reduction of all these parameters (p < 0.05).

Conclusion

the hepatoprotective and antifibrogenic effects of IGF-I in cirrhosis are associated with a diminution of the hepatic contents of several factors all of them involved in oxidative damage.

Inducible Nitric Oxide Synthase Activity and Expression in Liver and Hepatocytes of Diabetic Rats

Inducible nitric oxide synthase (iNOS) is expressed by the liver in a number of physiological and pathophysiological conditions. The aim of this study was to investigate the relationship between the diabetic state, iNOS and oxidative stress in the rat liver and isolated hepatocytes. Hepatic iNOS expression and activity was measured in both healthy and streptozotocin-induced diabetic rats and determined in hepatocytes in the presence and absence of insulin. Cu/Zn superoxide dismutase (SOD) and phosphatidylinositol-3-kinase (PI3K) were also measured. In a separate experiment lasting 3 weeks, diabetic rats received either no treatment, two daily injections of insulin or aminoguanidine in the drinking water. Diabetes led to increased activity (45%) and expression (70%) of liver iNOS, an effect that was attenuated by insulin treatment both in vitro and in whole animals. Hepatocyte iNOS expression increased by 56%. Hepatic SOD expression was elevated in the diabetic state, but activity levels were similar to healthy controls. Insulin treatment in vivo led to increased enzyme activity but expression was not modified. Levels of PI3K protein were significantly lower in diabetic rats while insulin treatment markedly increased expression. Aminoguanidine did not inhibit hepatic iNOS in this study. Glycemic control via insulin administration was able to downregulate enhanced hepatic iNOS activity and expression in the liver observed in the diabetic state and improve SOD activity, responses that can potentially reduce the free radical damage associated with diabetes.

Inhibition of inducible nitric oxide synthase protects against liver injury induced by mycobacterial infection and endotoxins

BACKGROUND/AIMS

Bacillus Calmette Guerin (BCG) infection causes hepatic injury following granuloma formation and secretion of cytokines which render mice highly sensitive to endotoxin-mediated hepatotoxicity. This work investigates the role of inducible nitric oxide synthase (iNOS) in liver damage induced by BCG and endotoxins in BCG-infected mice.

METHODS

Liver injury and cytokine activation induced by BCG and by LPS upon BCG infection (BCG/LPS) were compared in wild-type and iNOS-/- mice.

RESULTS

iNOS-/- mice infected with living BCG are protected from hepatic injury when compared to wild-type mice which express iNOS protein in macrophages forming hepatic granulomas. In addition, iNOS-/- mice show a decrease in BCG-induced IFN-gamma serum levels. LPS challenge in BCG-infected mice strongly activates iNOS in the liver and spleen of wild-type mice which show important liver damage associated with a dramatic increase in TNF and IL-6 and also Th1 type cytokines. In contrast, iNOS-/- mice are protected from liver injury after BCG/LPS challenge and their TNF, IL-6 and Th1 type cytokine serum levels raise moderately.

CONCLUSIONS

These results demonstrate that nitric oxide (NO) from iNOS is involved in hepatotoxicity induced by both mycobacterial infection and endotoxin effects upon BCG infection and that inhibition of NO from iNOS protects from liver injuries.

Nitric oxide from rat liver sinusoidal endothelial cells induces apoptosis in IFN gamma-sensitized CC531s colon carcinoma cells

BACKGROUND/AIMS

Investigation of apoptosis is pivotal in searching for mechanisms that eliminate colon cancer cells getting trapped in liver sinusoids at the time of surgical removal of the primary tumor. This study focuses on nitric oxide (NO), Fas/FasL and the involvement of interferon-gamma (IFNgamma) in liver sinusoidal endothelial cells (LSECs) and in the colon carcinoma cell line CC531s.

METHODS

Apoptosis was quantified and visualized in vitro by specific DNA fragmentation, specific staining and electron microscopy. In vivo experiments were also conducted.

RESULTS

In co-cultures of LSECs with CC531s, apoptosis of CC531s was observed only when they were pre-treated with IFNgamma, and was unaffected by blocking the Fas/FasL pathway. However, LSECs continuously produced NO, and apoptosis was inhibited by NO-inhibitors (NMMA and dexamethasone). When IFNgamma-sensitized CC531s were injected into rats, liver weight was lower, in contrast to control conditions where liver weight was higher.

CONCLUSIONS

(i) LSECs induce apoptosis in IFNgamma-sensitized CC531s in vitro; (ii) LSECs express FasL; (iii) Fas on CC531s becomes active after IFNgamma-treatment; however, (iv) blocking the Fas/FasL pathway had no effect; (v) apoptosis was inhibited by NO-inhibitors; (vi) the immune system uses this IFNgamma-activated pathway to support LSECs in killing tumor cells.

Distribution of constitutive (COX-1) and inducible (COX-2) cyclooxygenase in postviral human liver cirrhosis: a possible role for COX-2 in the pathogenesis of liver cirrhosis

AIMS

Prostaglandins produced by the action of cyclooxygenases (COX) are important mediators of systemic vasodilatation and inflammation in liver cirrhosis. The aim of this study was to investigate the distribution of COX-1 and COX-2 in postviral cirrhosis.

METHODS

The immunohistochemical expression of the constitutive (COX-1) and the inducible (COX-2) isoenzymes was investigated in 15 patients with cirrhosis after hepatitis B and C infection; three normal control livers were also analysed.

RESULTS

COX-2 was absent from normal liver but was highly expressed in cirrhosis, mainly in the inflammatory, sinusoidal, vascular endothelial, and biliary epithelial cells. Low amounts of COX-1 were expressed in both normal and cirrhotic livers, exclusively in sinusoidal and vascular endothelial cells, with no differences seen between normal and cirrhotic livers.

CONCLUSIONS

COX-2 is overexpressed in liver cirrhosis, and possibly contributes to prostaglandin overproduction, which may be a major component of the inflammation and hyperdynamic circulation associated with cirrhosis. Because COX-2 is thought to contribute to tumour development, high COX-2 production could be a contributor to hepatocellular carcinoma development in cirrhosis. The finding of COX-2 and not COX-1 upregulation in cirrhosis could provide a possible new role for selective COX-2 inhibitors in reducing inflammation and minimising the occurrence of hepatocellular carcinoma in patients with cirrhosis.