Role of oxidative stress and antioxidant therapy in alcoholic and nonalcoholic liver diseases

Effect of dietary epigallocatechin-3-gallate on cytochrome P450 2E1-dependent alcoholic liver damage: enhancement of fatty acid oxidation

This study was designed to determine whether dietary epigallocatechin-3-gallate (EGCG), the most abundant catechin polyphenol in green tea, can protect the liver from cytochrome P450 2E1 (CYP2E1)-dependent alcoholic liver damage. Compared with an ethanol group, when EGCG was present in the ethanol diet, the formation of a fatty liver was significantly reduced and the serum aspartate transaminase (AST) and alanine transaminase (ALT) levels were much lower. Ethanol treatment significantly elevated hepatic CYP2E1 expression while simultaneously reducing hepatic phospho-acetyl CoA carboxylase (p-ACC) and carnitine palmitoyl-transferase 1 (CPT-1) levels. While EGCG markedly reversed the effect of ethanol on hepatic p-ACC and CPT-1 levels, it had no effect on the ethanol-induced elevation in CYP2E1 expression. EGCG prevents ethanol-induced hepatotoxicity and inhibits the development of a fatty liver. These effects were associated with improvements in p-ACC and CPT-1 levels. The use of EGCG might be useful in treating patients with an alcoholic fatty liver.

Zinc inhibits ethanol-induced HepG2 cell apoptosis

Alcohol consumption produces a variety of metabolic alterations in liver cells, associated with ethanol oxidation and with nonoxidative metabolism of ethanol, among others apoptosis of hepatocytes. As zinc is known as a potent antioxidant and an inhibitor of cell apoptosis, the aim of this paper was to investigate whether zinc supplementation could inhibit ethanol-induced HepG2 apoptosis, and whether this inhibition was connected with attenuation of oxidative stress and modulation of FasR/FasL system expression. The results indicated that zinc supplementation significantly inhibited ethanol-induced HepG2 cell apoptosis (measured by cytochrome c release from mitochondria and caspase-3 activation) by attenuation of reactive oxygen species (ROS) production, increase in the cellular level of GSH, inhibition of ethanol-induced sFasR and FasL overexpression and caspase-8 activation. These results indicate that zinc can inhibit ethanol-induced hepatocyte apoptosis by several independent mechanisms, among others by an indirect antioxidative effect and probably by inhibition of caspase-8 and caspase-9 activation.

Maternal chronic hepatitis B virus is implicated with low neonatal paraoxonase/arylesterase activities

BACKGROUND

Paraoxonase/arylesterase activities are closely implicated with liver function and antiatherogenetic process.

AIM

To evaluate whether maternal chronic hepatitis B virus, disease (HBV) affect serum neonatal paraoxonase/arylesterase activities.

PATIENTS AND METHODS

28 pregnant women with HBV and 28 healthy pregnant women (controls) in the delivery room and their newborns (cord blood) underwent laboratory examinations. Serological virus tests and liver function tests and paraoxonase (PON 1) activities were measured with the Siemens Advia 1650 Clinical Chemistry System, while total antioxidant capacity (TAC) levels and paraoxonase-arylesterase (PON-aryl) activities were measured spectrophotometrically.

RESULTS

Serological HBV tests and HBV DNA showed chronic HBV (precore mutant G1896A) in the diseased mothers whereas anti-HBc and anti-HBe were detected in their neonates. Liver function parameters were found normal in controls and both groups of newborns. Moderately increased transaminase levels were measured in HBV mothers, whereas TAC levels were decreased in hepatic mothers and their newborns. Interestingly albumin levels did not differ among the studied groups. PON 1 and PON-aryl activities in the diseased mothers (148+/-14 U/mL/min, 130+/-16 KU/mL/min) and their infants (32+/-6 U/mL/min, 24+/-5 KU/mL/min) were significantly lower as compared to those of control mothers (217+/-16 U/mL/min, 196+/-14 KU/mL/min p<0.001) and their newborns (57+/-6 U/mL/min, 48+/-8 UK mL/min p<0.001). Inverse significant correlations were found between the studied enzyme activities and liver enzymes in all the groups of study except in infants born from HBV mothers and positive with TAC in all the studied groups.

CONCLUSIONS

Decreased PON 1 and PON-aryl activities were measured in infants born from hepatic mothers probably as a consequence of their low TAC. Infants born from HBV mothers are at risk for developing LDL oxidation perinatally.

Reciprocal effects of micro-RNA-122 on expression of heme oxygenase-1 and hepatitis C virus genes in human hepatocytes

BACKGROUND & AIMS

Heme oxygenase-1 (HO-1) is an antioxidant defense and key cytoprotective enzyme, which is repressed by Bach1. Micro-RNA-122 (miR-122) is specifically expressed and highly abundant in human liver and required for replication of hepatitis C virus (HCV) RNA. This study was to assess whether a specific miR-122 antagomir down-regulates HCV protein replication and up-regulates HO-1.

METHODS

We transfected antagomir of miR-122, 2'-O-methyl-mimic miR-122, or nonspecific control antagomir, into wild-type (WT) Huh-7 cells or Huh-7 stably replicating HCV subgenomic protein core through nonstructural protein 3 of HCV (NS3) (CNS3 replicon cells) or NS3-5B (9-13 replicon cells).

RESULTS

Antagomir of miR-122 reduced the abundance of HCV RNA by 64% in CNS3 and by 84% in 9-13 cells. Transfection with 2'-O-methlyl-mimic miR-122 increased HCV levels up to 2.5-fold. Antagomir of miR-122 also decreased Bach1 and increased HO-1 mRNA levels in CNS3, 9-13, and WT Huh-7 cells. Increasing HO-1 by silencing Bach1 with 50 nmol/L Bach1-short interfering RNA or by treatment with 5 mumol/L cobalt protoporphyrin or heme (known inducers of HO-1) decreased HCV RNA and protein by 50% in HCV replicon cells.

CONCLUSIONS

Down-regulation of HCV replication using an antagomir targeted to miR-122 is effective, specific, and selective. Increasing HO-1, by silencing the Bach1 gene or by treatment with cobalt protoporphyrin or heme, decreases HCV replication. Thus, miR-122 plays an important role in the regulation of HCV replication and HO-1/Bach1 expression in hepatocytes. Down-regulation of miR-122 and up-regulation of HO-1 may be new strategies for anti-HCV intervention and cytoprotection.

Inhibition of the renin-angiotensin system attenuates the development of liver fibrosis and oxidative stress in rats

1. The present study was designed to investigate the potential antifibrotic and anti-oxidant effects of lisinopril, fosinopril and losartan in an experimental rat model of liver injury using carbon tetrachloride (CCl(4)). 2. First, the potential hepatoprotective dose of each drug was screened against CCl(4)-induced acute hepatotoxicity. Then, we chose the minimum hepatoprotective dose of each drug to further investigate the mechanisms involved in the hepatoprotection using a chronic model of hepatotoxicity induced by CCl(4). 3. Liver function was assessed in addition to histopathological examination. Furthermore, oxidative stress markers (reduced glutathione (GSH) and lipid peroxides levels) and markers of fibrosis (hydroxyproline content and liver fibrosis area) were assessed. 4. It was found that treatment of animals with different drugs concomitantly with CCl(4) significantly counteracted the changes in liver function induced by CCl(4) (except fosinopril). In addition, the drugs ameliorated the histopathological changes induced by CCl(4). All drugs significantly counteracted lipid peroxidation and GSH depletion (except fosinopril) compared with the CCl(4)-intoxicated group. Moreover, the drugs studied significantly reduced liver hydroxyproline levels and the area of fibrosis compared with the CCl(4)-intoxicated group. 5. In conclusion, the present study provides evidence for the hepatoprotective effect of lisinopril, fosinopril and losartan. Both lisinopril and losartan was found to have better hepatoprotective potential than fosinopril against CCl(4)-induced hepatotoxicity. These hepatoprotective effects can be explained on the basis of anti-oxidant and antifibrotic mechanisms, mainly enhancement of GSH and reduction of lipid peroxidation and fibrosis.

Redox regulation of hepatitis C in nonalcoholic and alcoholic liver

Hepatitis C virus (HCV) is an RNA virus of the Flaviviridae family that is estimated to have infected 170 million people worldwide. HCV can cause serious liver disease in humans, such as cirrhosis, steatosis, and hepatocellular carcinoma. HCV induces a state of oxidative/nitrosative stress in patients through multiple mechanisms, and this redox perturbation has been recognized as a key player in HCV-induced pathogenesis. Studies have shown that alcohol synergizes with HCV in the pathogenesis of liver disease, and part of these effects may be mediated by reactive species that are generated during hepatic metabolism of alcohol. Furthermore, reactive species and alcohol may influence HCV replication and the outcome of interferon therapy. Alcohol consumption has also been associated with increased sequence heterogeneity of the HCV RNA sequences, suggesting multiple modes of interaction between alcohol and HCV. This review summarizes the current understanding of oxidative and nitrosative stress during HCV infection and possible combined effects of HCV, alcohol, and reactive species in the pathogenesis of liver disease.

Hepatitis C core protein inhibits induction of heme oxygenase-1 and sensitizes hepatocytes to cytotoxicity

Hepatitis C virus (HCV) core protein is a transcriptional modifier whose expression is associated with increased levels of prooxidants in hepatocytes in vivo and in vitro. We previously reported that HCV-infected liver biopsies and core protein-expressing hepatocytes show diminished levels of heme oxygenase-1 (HO-1), which is an important oxidative defense enzyme. The objective of these studies was to test the hypothesis that the expression of core protein sensitizes hepatocytes to toxic injury and inhibits the induction of HO-1 in response to stress. The effects of core protein were tested in two different human hepatocyte cell lines, HepG2 and Huh7, which show increased prooxidative activity and cytotoxicity after treatment with heme, heavy metals, and peroxides compared to control cells. HO-1 is upregulated in response to these treatments in control cells, while the induction is attenuated in core protein-expressing cells. The effects of core protein on HO-1 expression are not accounted for by differences in HO-1 mRNA turnover or by the known effects of core protein on cellular proliferation. Collectively, these data suggest that HCV core protein may contribute to hepatocellular injury by increasing both steady-state levels of prooxidants and the susceptibility of hepatocytes to damage by impairing their response to other sources of oxidative stress.

Protective effect of soy isoflavones and activity levels of plasma paraoxonase and arylesterase in the experimental nonalcoholic steatohepatitis model

Nonalcoholic steatohepatitis (NASH) is characterized by diffuse fatty infiltration in the liver and ballooning degeneration and inflammation in hepatocytes. We aimed to study the protective effect of soy isoflavones on experimental NASH and their effects on plasma paraoxanese and arylesterase levels in rats. Twenty-eight male rats were divided into four groups: Group 1 (n=7) received an isocaloric normal diet for 8 weeks, Group 2 (n=7) was fed an isocaloric basal diet plus oral soy isoflavone for 8 weeks (100 mg/kg in diet), Group 3 (n=7) received a special diet that was methionine and choline deficient (MCD) and rich in fat for 8 weeks, and Group 4 (n=7) was fed a special diet that was MCD and rich in fat plus oral soy isoflavone for 8 weeks (100 mg/kg in diet). Blood samples were collected to measure plasma malondialdehyde (MDA), paraoxanese, and arylesterase and biochemical parameters. Tissue samples were duly taken for histopathological examination and measurement of tissue MDA levels. Plasma MDA levels were higher in Group 3 than in Groups 1, 2, and 4 (P <0.01, P <0.05, and P <0.05 respectively). Liver tissue MDA levels were also significantly higher in Group 3 compared to Groups 1, 2, and 4 (P <0.001, P <0.001, and P <0.05 respectively). A significant decrease was found in the plasma and liver tissue MDA levels in Group 4 compared to Group 3 (P <0.05 and P <0.05, respectively). The activity levels of plasma paraoxanase and arylesterase were significantly higher in Group 2 than in Groups 1 and 3 (P <0.05 and P <0.01, respectively). Also, the plasma paraoxanase and arylesterase levels were significantly higher in Group 4 compared to Groups 1 and 3 (P <0.05 and P <0.01, respectively). A significant reduction was observed in Group 4 in steatosis, inflammation, necrosis, and fibrosis compared to Group 3 (P <0.05 for each). We conclude that soy isoflavones seem to be effective in preventing liver damage by decreasing lipid peroxidation in the NASH model induced by a MCD diet. They stimulate and increase the activity of the antioxidative paraoxanase enyzme while decreasing the total cholesterol and triglyceride levels.

Hepatic glutathione mediated antioxidant system in ethanol treated rats: Decline with age

Alcoholism is a pervasive problem. The aim of the present study was to clarify the effect of ethanol on the hepatic glutathione antioxidant system in young and elderly rats. Male albino Wistar rats of two age groups (3 months and 18 months old) were divided into two experimental groups. The first group of untreated rats served as controls (C; young n=6 and old n=6) and second group received ethanol (Et; young n=6 and old n=6) 2g of ethanol/kg b.w. for 2 months. After the completion of last treatment glutathione (GSH) and antioxidant enzymes glutathione peroxidase (GSH-Px), glutathione reductase (GR) and glutathione-S-transferase (GST) were determined. All these parameters including GST were remarkably decreased in the liver with advancing of age. The ethanol treatment decreased GSH, GSH-Px and GR, whereas, GST was increased in both age groups. The decrease of hepatic antioxidant status with ethanol and aging may be due to over production of free radicals. The changes of parameters studied were greater in the older than in the young rats. In conclusion, ethanol stress exhibited age dependent response on glutathione mediated antioxidant system in the liver.

Ebselen prevents chronic alcohol-induced rat hippocampal stress and functional impairment

BACKGROUND

Most of the previously published data suggest a role for oxidative or nitrosative stress in ethanol-induced nervous system damage. Moreover, ethanol is able to impair learning abilities in adult mammalian brain, a process suggested to be directly related to hippocampal neurogenesis. Ebselen, a synthetic compound with antioxidant properties, is able to prevent ethanol-induced impairment of neurogenesis in adult rats. The aim of the present work was to further demonstrate the ability of ebselen to prevent biochemical alterations, and preserve long-term potentiation (LTP) and learning abilities, in the hippocampus of chronic alcoholic adult rats.

METHODS

Biochemical markers of oxidative stress (glutathione and malondialdehyde) were assayed in hippocampi of control rats and animals fed a liquid alcoholic diet (Lieber-De Carli) supplemented or not with ebselen. Long-term potentiation and hippocampal-dependent tests were studied in all animal groups.

RESULTS

The hippocampal concentrations of glutathione and malondialdehyde were decreased and increased, respectively, in alcohol-treated animals, and did not differ from those of the control and the alcohol+ebselen groups. Long-term potentiation in hippocampal slices from ethanol-treated animals was prevented, when compared with controls, and occurred with a similar profile in control animals and in the alcohol+ebselen groups. Learning ability was tested with the Morris water maze test. Escape latencies were higher in ethanol-treated rats than in control animals or the ones treated with ethanol+ebselen.

CONCLUSIONS

The results herein strongly suggest that oxidative mechanisms may underlie the hippocampal effects of ethanol in adult rats, in view of the protective effect of ebselen.

Effect of hepatitis C virus core shadow protein expressed in human hepatoma cell line on human gene expression profiles

BACKGROUND AND AIMS

The hepatitis C virus (HCV) C region has been reported to have overlapping genes or regions, and may encode a core shadow protein that has a role in HCV self-replication, pathogenesis and carcinogenesis. The aim of this study was to identify the effect of HCV core shadow protein expressed in a human hepatoma (Huh-7) cell line on human gene expression profiles.

METHODS

Recombinants for expression of HCV genotype 1b core shadow protein and genotype 1b core protein were constructed, and an Huh-7 cell line was established that could express the shadow protein and the core protein constitutively. Affymetrix human gene chip, HG-U133 A and B microarray analysis and semiquantitative RT-PCR were employed to identify the expression profiles of two kinds of core proteins in the Huh-7 cell line.

RESULTS

The microarray analysis showed that the core shadow protein caused expression of more genes to be up/down-regulation than the core protein, including signal transduction, protease activity, molecular transport and, particularly, immune responses genes. Surprisingly, the core shadow protein could increase/decrease expression of apoptosis and anti-apoptosis genes simultaneously. The expression profiles of three up-regulated genes were confirmed by semiquantitative RT-PCR, with results similar to the microarray analysis.

CONCLUSIONS

Hepatitis C virus core shadow protein may play an important role in inhibiting or stimulating host cells apoptosis processing and carcinogenesis, which is useful for the understanding of HCV core shadow protein biological functions in vivo and in vitro.

Hepatitis C virus triggers mitochondrial permeability transition with production of reactive oxygen species, leading to DNA damage and STAT3 activation

Hepatitis C virus (HCV) infection is frequently associated with the development of hepatocellular carcinomas and non-Hodgkin's B-cell lymphomas. Previously, we reported that HCV infection causes cellular DNA damage and mutations, which are mediated by nitric oxide (NO). NO often damages mitochondria, leading to induction of double-stranded DNA breaks (DSBs) and accumulation of oxidative DNA damage. Here we report that HCV infection causes production of reactive oxygen species (ROS) and lowering of mitochondrial transmembrane potential (DeltaPsi(m)) in in vitro HCV-infected cell cultures. The changes in membrane potential could be inhibited by BCL-2. Furthermore, an inhibitor of ROS production, antioxidant N-acetyl-L-cysteine (NAC), or an inhibitor of NO, 1,400W, prevented the alterations of DeltaPsi(m). The HCV-induced DSB was also abolished by a combination of NO and ROS inhibitors. These results indicated that the mitochondrial damage and DSBs in HCV-infected cells were mediated by both NO and ROS. Among the HCV proteins, core, E1, and NS3 are potent ROS inducers: their expression led to DNA damage and activation of STAT3. Correspondingly, core-protein-transgenic mice showed elevated levels of lipid peroxidation and oxidatively damaged DNA. These HCV studies thus identified ROS, along with the previously identified NO, as the primary inducers of DSBs and mitochondrial damage in HCV-infected cells.

Hepatitis C infection in hemodialysis patients: Protective against oxidative stress?

Hepatitis C virus (HCV) infection is a common problem that increases morbidity and mortality in hemodialysis patients. These patients are also at risk of increased oxidative stress. The aim of this study was to evaluate possible interactions between HCV infection and oxidative stress indicators in a group of hemodialysis patients awaiting transplantation. We evaluated 73 patients (29 women, 44 men; ages, 49.3 +/- 13.3 years; dialysis duration, 81.7 +/- 48.8 months; Kt/V > or = 1.3). Indicators of plasma oxidative status were monitored at the beginning of a clinically stable hemodialysis session. Measurements were performed for plasma superoxide dismutase (SOD), glutathione peroxidase (GPX), and malonyldialdehyde (MDA) by spectrophotometric methods. We retrospectively recorded the prior year's monthly laboratory values for alanine aminotransferase (ALT), C-reactive protein (CRP), albumin, lipids, homocysteine, Lp(a), calcium, phosphorus, intact parathyroid hormone, and predialysis blood urea nitrogen (BUN) creatinine, as well as clinical findings of body mass index and pre- and postdialysis blood pressures. We excluded patients with chronic inflammation (mean CRP levels > or = 10 mg/L) or HCV infection of duration <12 months or clinically advanced liver failure. Twenty-six patients had HCV. The sex distribution, mean age, and dialysis duration were similar between groups. HCV-infected patients showed significantly lower levels of MDA, albumin, total cholesterol, triglyceride, predialysis creatinine, and phosphorus. Antioxidative indicator levels were also higher in the HCV group, but they were not statistically significant. In conclusion, HCV infection in dialysis patients is associated with decreased levels of plasma oxidative load.

Paraoxonase-1 is associated with oxidative stress, fibrosis and FAS expression in chronic liver diseases

BACKGROUND/AIMS

We previously reported that paraoxonase-1 activity measurement may be useful for the evaluation of liver diseases. Because oxidative stress plays a role in liver apoptosis, and lipid peroxides are hydrolyzed by paraoxonase-1, we have extended our studies to explore the relationships between this enzyme and oxidative stress, fibrosis and apoptosis.

METHODS

We measured paraoxonase-1 activity and concentration, soluble FAS concentration, serum fibrosis markers, and total peroxides in a group of patients with minimal hepatic changes (n=25), chronic hepatitis (n=51), or liver cirrhosis (n=17). We also measured the Knodell activity index in liver biopsies and performed FAS and PON1 immunostaining.

RESULTS

Patients with liver diseases showed an increase in soluble FAS, fibrosis markers and paraoxonase-1 concentrations, as well as a decrease in PON1 activity. Paroxonase-1 activity and concentration were correlated with soluble FAS (r=-0.43, P<0.001 and r=0.27, P=0.007, respectively). Paraoxonase-1 concentration showed a significant inverse association with FAS immunostaining (P=0.013) and a direct association with PON1 immunostaining (P<0.001).

CONCLUSIONS

These results suggest an active role of PON1 in the regulation of oxidative stress, fibrosis and hepatic cell apoptosis in chronic liver diseases.

Hepatoprotective effect of flavonol glycosides rich fraction from Egyptian Vicia calcarata Desf. against CCl4-induced liver damage in rats

The hepatoprotective activity of flavonol glycosides rich fraction (F-2), prepared from 70% alcohol extract of the aerial parts of V. calcarata Desf., was evaluated in a rat model with a liver injury induced by daily oral administration of CCl4 (100 mg/kg, b.w) for four weeks. Treatment of the animals with F-2 using a dose of (25 mg/kg, b.w) during the induction of hepatic damage by CCl4 significantly reduced the indices of liver injuries. The hepatoprotective effects of F-2 significantly reduced the elevated levels of the following serum enzymes: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH). The antioxidant activity of F-2 markedly ameliorated the antioxidant parameters including glutathione (GSH) content, glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), plasma catalase (CAT) and packed erythrocytes glucose-6-phosphate dehydrogenase (G6PDH) to be comparable with normal control levels. In addition, it normalized liver malondialdehyde (MDA) levels and creatinine concentration. Chromatographic purification of F-2 resulted in the isolation of two flavonol glycosides that rarely occur in the plant kingdom, identified as quercetin-3, 5-di-O-beta-D-diglucoside (5) and kaempferol-3, 5-di-O-beta-D-diglucoside (4) in addition to the three known compounds identified as quercetin-3-O-alpha-L-rhamnosyl- (1-->6)-beta-D-glucoside [rutin, 3], quercetin-3-O-beta-D-glucoside [isoquercitrin, 2] and kaempferol-3-O-beta-D-glucoside [astragalin, 1]. These compounds were identified based on interpretation of their physical, chemical, and spectral data. Moreover, the spectrophotometric estimation of the flavonoids content revealed that the aerial parts of the plant contain an appreciable amount of flavonoids (0.89%) calculated as rutin. The data obtained from this study revealed that the flavonol glycosides of F-2 protect the rat liver from hepatic damage induced by CCl4 through inhibition of lipid peroxidation caused by CCl4 reactive free radicals.

Intestinal permeability and oxidative stress in patients with alcoholic pellagra

BACKGROUND & AIMS

Increased intestinal permeability is one of the grastointestinal changes observed in alcoholic patients. However, there are no objective definitions as yet of how alcohol induces pathological changes in the various organs. The action of oxygen-free radicals during ethanol metabolism has been considered a determinant factor of these alterations. The present study was undertaken to determine the effect of niacin supplementation on intestinal permeability and oxidative stress in patients with alcoholic pellagra.

METHODS

The study was divided into two phases: in Phase 1 we studied ten patients with pellagra before treatment with niacin, and in Phase 2 we studied the same patients after 27 days of treatment with niacin. Intestinal permeability was assessed by the (51)CrEDTA test and the antioxidant action of niacin supplementation was assessed by the determination of lipid peroxidation (plasma malondialdehyde, MDA), protein oxidation (plasma carbonyl group) and of the antioxidants plasma vitamin E and erythrocyte glutathione peroxidase.

RESULTS

Comparison of intestinal permeability by the (51)CrEDTA test before and after niacin treatment showed a significant decrease in permeability from 4.29+/-1.92% to 1.90+/-1.19% (P<0.05). Assessment of oxidative stress showed a significant decrease (P<0.05) in lipid and protein peroxidation (MDA: 1.19+/-0.40-0.89+/-0.27 micromol/l; carbonyl groups: 2.22+/-0.36-1.84+/-0.40 nmol/mg protein).

CONCLUSIONS

The results suggest that niacin and vitamin E deficiency in patients with pellagra could be important factors in increased intestinal permeability and decreased antioxidant conditions, recovering to normal values after treatment with niacin, associated to alcohol abstinence and a balanced diet.

Effect of chronic dietary ethanol in the promotion of N-nitrosomethylbenzylamine-induced esophageal carcinogenesis in rats

BACKGROUND

The pathogenetic correlation between chronic alcohol consumption and development of esophageal cancer is not clear. The role of alcohol abuse in the carcinogenic action of N-nitrosomethylbenzylamine, which induces tumors in the esophagus, has been evaluated.

METHODS

Twenty male rats were fed liquid diets containing ethanol or carbohydrates for 30 weeks. N-nitrosomethylbenzylamine (0.1 mg/kg, twice a week) was injected i.p. from the 9th to 19th week. The pair feeding was stopped at 9.00 am and N-nitrosomethylbenzylamine was administered at 10.00 am. Ethanol was not detected in the blood at the time of injection. Liquid diets were provided again at 3 pm until 9 am next day. The animals were killed at the end of the 30th week. The esophagi were collected and examined for visible tumors. The tissue sections were stained for histology and CYP2E1expression.

RESULTS

While 5-8 esophageal squamous polyps developed in all rats in the ethanol group, only one polyp each was formed in five out of the 10 rats in the control group. The size of the polyps was significantly larger in the ethanol group, when compared to the control group. Invasive squamous cell carcinoma was also observed in 50% of the animals in the ethanol group. Cytochrome P4502E1 (CYP2E1) staining demonstrated marked expression in the esophageal mucosa in the ethanol group, but not in the control group.

CONCLUSIONS

The increased expression of CYP2E1 induced by chronic ethanol consumption promotes the development of N-nitrosomethylbenzylamine-induced esophageal tumorigenesis. However, the molecular mechanism of the increased production of esophageal tumors during alternative administration of N-nitrosomethylbenzylamine and ethanol is not clear.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

Pathophysiological basis for antioxidant therapy in chronic liver disease

Oxidative stress is a common pathogenetic mechanism contributing to initiation and progression of hepatic damage in a variety of liver disorders. Cell damage occurs when there is an excess of reactive species derived from oxygen and nitrogen, or a defect of antioxidant molecules. Experimental research on the delicately regulated molecular strategies whereby cells control the balance between oxidant and antioxidant molecules has progressed in recent years. On the basis of this evidence, antioxidants represent a logical therapeutic strategy for the treatment of chronic liver disease. Clinical studies with large numbers of patients have not yet been performed. However, results from several pilot trials support this concept and indicate that it may be worth performing multicentre studies, particularly combining antioxidants with anti-inflammatory and/or antiviral therapy. Oxidative stress plays a pathogenetic role in liver diseases such as alcoholic liver disease, chronic viral hepatitis, autoimmune liver diseases and non-alcoholic steatohepatitis. The use of antioxidants (e.g. S-adenosylmethionine [SAMe; ademetionine], tocopherol [vitamin E], polyenylphosphatidylcholine or silymarin) has already shown promising results in some of these pathologies.

Preconditioning-like amelioration of erythropoietin against laparoscopy-induced oxidative injury

BACKGROUND

Laparoscopic surgery has gained wide acceptance for almost every kind of surgical procedure, although it has produced significant oxidative injury to intraabdominal organs depending on the pressure level and the kind of the gas used. The literature describes several preventive measures for decreasing the postlaparoscopic oxidative injury such as low intraabdominal pressure, gasless laparoscopy, and laparoscopic preconditioning. Erythropoietin was shown previously to decrease ischemia-reperfusion injury to the liver. The current study evaluated the effect of erythropoietin against laparoscopy-induced oxidative injury, as compared with laparoscopic preconditioning.

METHODS

For this study, 64 male Spraque-Dawley rats were randomly assigned to one of the following groups. The control group was subjected to a sham operation. The laparoscopy group was subjected to 60 min of pneumoperitoneum. The laparoscopic preconditioning plus laparoscopy group was subjected to 5 min of insufflation and 5 min of desufflation followed by 60 min of pneumoperitoneum. The erythropoietin plus laparoscopy group was subjected to a subcutaneous injection of erythropoietin as a single 1,000-U/kg dose followed by 60 min of pneumoperitoneum. After 45 min of desufflation subsequent to cessation of pneumoperitoneum, blood, liver, and kidney samples were obtained from half of the rats. The other half of the rats were observed for a reperfusion period of 24 h. Tissue and blood samples also were obtained after this period.

RESULTS

Laparoscopy produced significant oxidative injury, as compared with the sham treatment. Laparoscopic preconditioning produced significant amelioration of the ischemic injury. Although erythropoietin administration during the prelaparoscopic period decreased the pneumoperitoneum-induced oxidative injury, the beneficial effect of laparoscopic preconditioning was more pronounced.

CONCLUSION

Laparoscopic preconditioning is more effective than the preischemic administration of erythropoietin in reducing laparoscopy-induced oxidative injury.

HCV-hepatocellular carcinoma: new findings and hope for effective treatment

We present here a comprehensive review of the current literature plus our own findings about in vivo and in vitro analysis of hepatitis C virus (HCV) infection, viral pathogenesis, mechanisms of interferon action, interferon resistance, and development of new therapeutics. Chronic HCV infection is a major risk factor for the development of human hepatocellular carcinoma. Standard therapy for chronic HCV infection is the combination of interferon alpha and ribavirin. A significant number of chronic HCV patients who cannot get rid of the virus infection by interferon therapy experience long-term inflammation of the liver and scarring of liver tissue. Patients who develop cirrhosis usually have increased risk of developing liver cancer. The molecular details of why some patients do not respond to standard interferon therapy are not known. Availability of HCV cell culture model has increased our understanding on the antiviral action of interferon alpha and mechanisms of interferon resistance. Interferons alpha, beta, and gamma each inhibit replication of HCV, and the antiviral action of interferon is targeted to the highly conserved 5'UTR used by the virus to translate protein by internal ribosome entry site mechanism. Studies from different laboratories including ours suggest that HCV replication in selected clones of cells can escape interferon action. Both viral and host factors appear to be involved in the mechanisms of interferon resistance against HCV. Since interferon therapy is not effective in all chronic hepatitis C patients, alternative therapeutic strategies are needed to treat chronic hepatitis C patients not responding to interferon therapy. We also reviewed the recent development of new alternative therapeutic strategies for chronic hepatitis C, which may be available in clinical use within the next decade. There is hope that these new agents along with interferon will prevent the occurrence of hepatocellular carcinoma due to chronic persistent hepatitis C virus infection. This review is not inclusive of all important scientific publications due to space limitation.

Acetaldehyde does not inhibit glutathione peroxidase and glutathione reductase from mouse liver in vitro

Acetaldehyde, the primary ethanol metabolite, has been implicated in the pathogenesis of alcoholic liver disease, but the mechanism involved is still under investigation. This study aims at the search for direct in vitro effects of different concentrations of acetaldehyde (30, 100 and 300microM) on the activities of glutathione reductase (GR), glutathione peroxidase (GPx) from liver supernatants, and the thiol-peroxidase activity of ebselen. They did not change after pre-incubation with acetaldehyde, which suggests that acetaldehyde does not have any direct effect. Nor were direct effects of acetaldehyde toward thiols, such as dithioerythritol and glutathione (GSH), observed either, even though GSH - measured as non-protein thiols from liver supernatants - were oxidized in the presence of acetaldehyde. In addition, acetaldehyde (up to 300microM) significantly oxidized GSH when incubated in the presence of commercially available gamma-glutamyltranspeptidase (GGT), but not in the presence of glutathione-S-transferase. The interaction between ebselen and GSH was also evaluated in an attempt to better understand the possible link between acetaldehyde and nucleophilic selenol groups. The formation and stability of ebselen intermediaries, produced in the chemical interaction between GSH and ebselen, were not affected by acetaldehyde either. Overall, the acetaldehyde oxidation of hepatic low-molecular thiols depends on mouse liver constituents and GGT is proposed as an important enzyme involved in this phenomenon. Thiol depletion, a phenomenon usually observed in the livers of alcoholic patients, can be related to GSH metabolism, and the involvement of GGT may reflect a molecular mechanism involved in thiol oxidation.

Hepatitis C virus-core and non structural proteins lead to different effects on cellular antioxidant defenses

Chronic hepatitis C virus (HCV) infection leads to increased oxidative stress in the liver. Hepatic antioxidant enzymes provide an important line of defense against oxidative injury. To understand the antioxidant responses of hepatocytes to different HCV proteins, we compared changes in antioxidative enzymes in HCV-core and HCV-nonstructural protein expressing hepatocyte cell lines. We found that expression of HCV-core protein in hepatocyte cell lines leads to increased oxidative stress as determined by increased in the oxidant-sensitive probe 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-DCFH(2)) fluorescence, decreased reduced glutathione (GSH), and increased oxidation of thioredoxin (Trx). Although the expression of HCV-nonstructural (HCV-NS) proteins led to increased oxidative stress as well, the antioxidant enzymatic responses were different. Over-expression of HCV-NS proteins increased antioxidant enzymes (MnSOD and catalase), heme oxygenase-1 (HO-1), and GSH, indicating different mechanism(s) of prooxidative activity than HCV-core protein. Our findings show that different HCV proteins induce different antioxidant defense responses in hepatocytes. These findings may facilitate understanding the interaction of different HCV proteins with infected liver cells and help identify possible factors contributing to hepatocyte damage during HCV infection.

F2-isoprostanes stimulate collagen synthesis in activated hepatic stellate cells: a link with liver fibrosis?

Carbon tetrachloride (CCl4)-induced hepatic fibrosis has been considered to be linked to oxidative stress and mediated by aldehydic lipid peroxidation products. In the present study, we investigated whether collagen synthesis is induced by F2-isoprostanes, the most proximal products of lipid peroxidation and known mediators of important biological effects. By contrast with aldehydes, F2-isoprostanes act through receptors able to elicit definite signal transduction pathways. In a rat model of CCl4-induced hepatic fibrosis, plasma F2-isoprostanes were markedly elevated for the entire experimental period; hepatic collagen content also increased. When hepatic stellate cells (HSCs) from normal liver were cultured with F2-isoprostanes in the concentration range found in the in vivo studies (10(-9)-10(-8) M), a striking increase in DNA synthesis (reversed by the thromboxane A2 antagonist SQ 29 548), in cell proliferation and in collagen synthesis was observed. Total collagen content was similarly increased. Moreover, F2-isoprostanes markedly increased the production of transforming growth factor-beta1 by U937 cells, considered a model of liver macrophages. The data provide evidence for the possibility that F2-isoprostanes generated by lipid peroxidation in hepatocytes mediate HSC proliferation and collagen production seen in hepatic fibrosis.

Differential contribution of hepatitis C virus NS5A and core proteins to the induction of oxidative and nitrosative stress in human hepatocyte-derived cells

BACKGROUND/AIMS

We aimed to explore the effects of hepatitis C virus (HCV) core and NS5A proteins on reactive oxygen (ROS) and nitrogen species (RNS) formation and on gene expression profile of iNOS in human hepatocyte-derived cells.

METHODS

Production of ROS and RNS and nitrotyrosine residues accumulation were determined by flow cytometry and fluorescent microscopy as well as by Western blot, respectively, in NS5A- and core-transfected cells. Northern blot, Western blot, real-time PCR, and luciferase assays were used to assess iNOS gene expression in both transfectants.

RESULTS

Cytokine-activated NS5A- and core-transfected cells induced ROS and RNS production but an earlier and more marked increase was observed in NS5A-expressing cells. Superoxide production was also augmented, showing a similar temporal pattern of appearance in both NS5A- and core-transfected cells. Although both NS5A and core HCV proteins were able to up-regulate iNOS gene expression, accompanied by a nitrotyrosine-containing proteins accumulation, an earlier iNOS overexpression was observed in NS5A-expressing cells, suggesting a different time course of iNOS activation pattern for core and NS5A HCV proteins.

CONCLUSIONS

Our results indicate a differential contribution of both HCV proteins to oxidative and nitrosative stress generation.

Effects of N-acetylcysteine on ethanol-induced hepatotoxicity in rats fed via total enteral nutrition

The effects of the dietary antioxidant N-acetylcysteine (NAC) on alcoholic liver damage were examined in a total enteral nutrition (TEN) model of ethanol toxicity in which liver pathology occurs in the absence of endotoxemia. Ethanol treatment resulted in steatosis, inflammatory infiltrates, occasional foci of necrosis, and elevated ALT in the absence of increased expression of the endotoxin receptor CD 14, a marker of Kupffer cell activation by LPS. In addition, ethanol treatment induced CYP 2 E1 and increased TNFalpha and TGFbeta mRNA expression accompanied by suppressed hepatic IL-4 mRNA expression. Ethanol treatment also resulted in the hepatic accumulation of malondialdehyde (MDA) and hydroxynonenal (HNE) protein adducts, decreased antioxidant capacity, and increased antibody titers toward serum hydroxyethyl radical (HER), MDA, and HNE adducts. NAC treatment increased cytosolic antioxidant capacity, abolished ethanol-induced lipid peroxidation, and inhibited the formation of antibodies toward HNE and HER adducts without interfering with CYP 2 E1 induction. NAC also decreased ethanol-induced ALT release and inflammation and prevented significant loss of hepatic GSH content. However, the improvement in necrosis score and reduction of TNFalpha mRNA elevation did not reach statistical significance. Although a direct correlation was observed among hepatic MDA and HNE adduct content and TNFalpha mRNA expression, inflammation, and necrosis scores, no correlation was observed between oxidative stress markers or TNFalpha and steatosis score. These data suggest that ethanol-induced oxidative stress can contribute to inflammation and liver injury even in the absence of Kupffer cell activation by endotoxemia.

Production of reactive oxygen species following acute ethanol or acetaldehyde and its reduction by acamprosate in chronically alcoholized rats

The salicylate trap method, combined with microdialysis, has been used to validate whether reactive oxygen species, particularly hydroxyl radicals, ((*)OH), are generated in the hippocampus of male Wistar rats after acute intraperitoneal administration of either ethanol, 2 and 3 g/kg, or acetaldehyde, 200 mg, or during the initial stages of ethanol withdrawal after chronic ethanol intoxication. Salicylate (5 mM) was infused into the hippocampus via the microdialysis probe and the products of its metabolism by hydroxyl radical, particularly 2,3-dihydroxybenzoic acid (2,3-DHBA) as well as 2,5-dihydroxybenzoic acid (2,5-DHBA) assayed by HPLC (High Pressure Liquid Chromatography). Acetaldehyde, 200 mg/kg, and the higher acute dose of ethanol, 3 g/kg, induced transitory increases in 2,3-DHBA and 2,5-DHBA microdialysate content. At the cessation of four weeks of chronic ethanol intoxication, (by the vapour inhalation method), the mean blood alcohol level was 1.90 g/l. Significant increases of microdialysate 2,3-DHBA and 2,5-DHBA levels were assayed 3 h after alcohol withdrawal which were sustained for a further 5 and 1 h 40 min respectively. Oral administration of Acamprosate, 400 mg/kg/day, during the chronic ethanol intoxication procedure prevented the increased formation of 2,3- and 2,5-DHBA by comparison to rats chronically ethanol intoxicated alone.

Antioxidant levels in peripheral blood, disease activity and fibrotic stage in chronic hepatitis C

BACKGROUND

This study addressed the suggested association between levels of the antioxidants glutathione (GSH), vitamin C and vitamin E in peripheral blood and the histological activity and fibrosis stage in chronic hepatitis C (CHC). We then determined whether regular antioxidant supplementation influenced these antioxidant levels or disease severity.

METHODS

Clinical, biochemical, histological and demographic data were collected from 247 CHC patients at the time of liver biopsy. Whole blood total GSH, plasma vitamin C and E were assessed by high-performance liquid chromatography. Statistical analyses were performed to test for associations between the variables and to identify independent predictors for hepatic necroinflammatory and fibrosis scores.

RESULTS

GSH and vitamin C, but not vitamin E correlated with both portal/periportal activity (r = -0.19, P = 0.004; r = -0.19, P = 0.009 respectively) and fibrosis stage (r = -0.18, P = 0.007; r = -0.18, P = 0.009 respectively). GSH was an independent negative predictor of portal/periportal inflammation (P = 0.02) and fibrosis (P = 0.01). Vitamin C was an independent negative predictor of fibrosis stage (P = 0.02). Antioxidant intake was associated with higher vitamin C (P < 0.0001) and vitamin E (P = 0.005) levels, but not GSH.

CONCLUSIONS

Whole blood GSH and plasma vitamin C are negatively associated with hepatic portal/periportal inflammation and fibrosis stage in CHC. Controlled intervention studies with vitamin C and agents that boost endogenous GSH levels are warranted.

The etiology of alcohol-induced breast cancer

Breast cancer is the most common cancer in women in the United States, and it is second among cancer deaths in women. Results of most epidemiologic studies, as well as of most experimental studies in animals, have shown that alcohol intake is associated with increased breast cancer risk. Alcohol consumption may cause breast cancer through different mechanisms, including through mutagenesis by acetaldehyde, through perturbation of estrogen metabolism and response, and by inducing oxidative damage and/or by affecting folate and one-carbon metabolism pathways. Alcohol-metabolizing enzymes are present in human breast tissue. Acetaldehyde is a known, although weak, mutagen. However, results of some studies with human subjects implicate this agent in the context of genetic susceptibilities to increased ethanol metabolism. Reactive oxygen species, resulting from ethanol metabolism, may be involved in breast carcinogenesis by causing damage, as well as by generating DNA and protein adducts. Alcohol interferes with estrogen pathways in multiple ways, influencing hormone levels and effects on the estrogen receptors. With regard to one-carbon metabolism, alcohol can negatively affect folate levels, and the folate perturbation affects DNA methylation and DNA synthesis, which is important in carcinogenesis. Some study results indicate that genetic variants of one-carbon metabolism genes might increase alcohol-related breast cancer risk. For all these pathways, genetic polymorphisms might play a role in increasing further a woman's risk for breast cancer. Additional studies are needed to determine the relative importance of these pathways, as well as the modifying influence by genetic variation.

Exposure to ethanol induces oxidative damage in the pituitary gland

Chronic exposure of pubertal male rats to ethanol results in a decline in serum testosterone and decreased or inappropriately normal serum luteinizing hormone (LH) and follicle stimulating hormone (FSH) levels suggesting a functional defect in the pituitary. The molecular mechanisms behind this disorder are undefined. A role for ethanol-induced oxidative damage in the pathophysiology is supported by studies in liver, muscle, and heart of experimental animals, but there is limited evidence in the pituitary. We examined markers of oxidative damage to lipids and proteins in pituitaries from rats consuming ethanol for 5, 10, 20, 30, and 60 days in addition to markers of damage to nucleic acids in pituitaries after 60 days of ethanol exposure. There were increases in 8-oxo-deoxyguanosine immunoreactivity, a marker of oxidative damage to nucleic acids, and an overall increase in malondialdehyde and 4-hydroxynonenal, markers of lipid peroxidation. Protein carbonylation and protein nitrotyrosination, markers of protein oxidation, were significantly increased after 30 days and 60 days of ethanol consumption, respectively. After 60 days of ethanol exposure, TUNEL assay revealed that cell death in the ethanol-treated pituitaries was not significantly different from that in the pair-fed controls at the time of examination. We also measured serum testosterone, FSH, and LH after ethanol consumption for 5, 10, 20, 30, and 60 days. Through 5 to 60 days of ethanol exposure, testosterone levels were consistently lower whereas LH and FSH were inappropriately unchanged, suggesting pituitary malfunction. These results provide evidence for ethanol-induced oxidative damage at the pituitary level, which may contribute to pituitary dysfunction.

Antioxidant properties of black tea in alcohol intoxication

Food ingredients such as alcohol may modify cellular redox state. Ethanol metabolism is accompanied by generation of free radicals that can damage cell components especially when antioxidant mechanisms are no able to neutralize them. However black tea is a source of polyphenol antioxidants that may enhance cellular antioxidant abilities. The aim of this study was to investigate the effect of black tea on antioxidant abilities of the liver, blood serum and brain of 12-months old rats sub-chronically (for 28 days) intoxicated with ethanol. Administration of black tea alone caused increase in the activity and concentration of antioxidant parameters more extensively in the liver and serum than in the brain. Alcohol caused decrease in the liver glutathione peroxidase and reductase and catalase activity but increase in activity of superoxide dismutase. Moreover, decrease in the level of non-enzymatic antioxidants, such as reduced glutathione, vitamin C, A and E and beta-carotene was observed. The activity of serum glutathione peroxidase and reductase decreased while superoxide dismutase activity was not changed. The level of non-enzymatic antioxidants in serum was also decreased. However brain activity/level of all examined antioxidants enzymatic as well as non-enzymatic was decreased after ethanol intoxication. Black tea considerably prevented antioxidant parameters against changes caused by ethanol. These results indicate beneficial antioxidant effect of black tea regarding all examined tissues, but especially the liver.

The "Tuebingen desiccator" system, a tool to study oxidative stress in vivo and inhalation toxicokinetics

The "Tuebingen desiccator," a gas-tight all-glass closed chamber system (CCS), has been established in Herbert Remmer's Institute of Toxicology, University of Tuebingen, to investigate the mechanisms underlying the exhalation of endogenous volatile hydrocarbons in rats under oxidative stress. Remmer and associates confirmed the former view that ethane and n-pentane were derived from polyunsaturated fatty acids, and they demonstrated that propane, n-butane and isobutane were released from amino acids. Hydrocarbons exhaled following acute ethanol treatment of rats resulted predominantly from ethanol-dependent inhibition of their metabolism and partly from oxidation of proteins. Exhalation of alkanes in carbon tetrachloride exposed rats did not reflect liver damage, which was, however, directly linked to the amount of carbon tetrachloride metabolized. As has first been shown in Herbert Remmer's institute by investigating the fate of inhaled vinyl chloride in rats, the CSS proved to be also an excellent tool for studying toxicokinetics of inhaled gaseous xenobiotics by means of gas uptake experiments. Based on results gained by such studies, it was recently demonstrated that knowledge of compound-specific physicochemical and species-specific physiological parameters are often sufficient to predict important toxicokinetic properties of inhaled chemicals such as tissue burdens at steady state. By means of the CCS, not only kinetics of a parent gaseous substance but also of gaseous metabolites can be investigated in vivo, as exemplified for ethylene oxide and 1, 2-epoxy-3-butene, metabolites of ethylene and 1,3-butadiene, respectively. Gas uptake studies in closed chamber systems are now worldwide used for determining toxicokinetic parameters relevant for physiological toxicokinetic modeling.

A high-fat diet leads to the progression of non-alcoholic fatty liver disease in obese rats

Fatty livers of obese fa/fa rats are vulnerable to injury when challenged by insults such as endotoxin, ischemia-reperfusion or acute ethanol treatment. The objective of this study was to evaluate whether a high-fat diet can act as a "second hit" and cause progression to liver injury in obese fa/fa rats compared with lean Fa/? rats. Accordingly, obese fa/fa rats and their lean littermates were fed a diet low in fat (12% of total calories) or a diet with 60% calories as lard for 8 weeks. Hyperglycemia and steatohepatitis occurred in the fa/fa rats fed the high-fat diet. This was accompanied by liver injury as assessed by alanine aminotransferase, hematoxilin and eosin staining, increased TNFalpha and stellate cell-derived TGFbeta, collagen deposition, and up-regulation of alpha-smooth muscle actin. Active MMP13 decreased in fa/fa rats independently of the diet, and TIMP1 expression increased with the high-fat diet, especially in fa/fa rats. Although UCP2 expression was higher in fa/fa rats regardless of the diet, minor changes in ATP levels were observed. Oxidative stress occurred in the fa/fa rats fed the high-fat diet as lipid peroxidation and protein carbonyls were elevated, while glutathione and antioxidant enzymes were very low. Expression and activity of cytochrome P450 2E1 and xanthine oxidase activity were down-regulated in fa/fa compared with Fa/? rats, and no effect was seen by the high-fat diet. However, NADPH oxidase activity increased 2.5-fold in fa/fa rats fed with the high-fat diet. In summary, a high-fat diet induces liver injury in fa/fa rats leading to periportal fibrosis. A role for oxidative stress is suggested via increased NADPH oxidase activity, lipid peroxidation, protein carbonyl formation, and low antioxidant defense.

Free radicals in cell biology

In aerobic cells, free radicals are constantly produced mostly as reactive oxygen species. Once produced, free radicals are removed by antioxidant defenses including enzyme catalase, glutathione peroxidase, and superoxide dismutase. Reactive oxygen species, including nitric oxide and related species, commonly exert a series of useful physiological effects. However, imbalance between prooxidant and antioxidant defenses in favor of prooxidants results in oxidative stress associated with the oxidative modification of biomolecules such as lipids, proteins, and nucleic acids. Alone or in combination with primary ethiological factors, free radicals are involved in a pathogenesis of more than a hundred diseases. This chapter reviews the basic science of some of the potential sources and characteristics of free radicals, as well as antioxidant enzymes. Special attention is paid to the role of free radicals in the pathogenesis of atherosclerosis and immunology-mediated inflammatory reaction.

Pathogenesis of hepatitis C-associated hepatocellular carcinoma

Epidemiologic, clinical, and virologic data have shown a close association between chronic infection with hepatitis C virus (HCV) and the development of hepatocellular carcinoma (HCC). In many countries of the developed world, HCV infection accounts for more than half of the cases of HCC. HCC usually arises after 2-4 decades of infection, typically in the context of an underlying cirrhosis. Treatment of hepatitis C with interferon-alfa can lead to sustained clearance of HCV, and small prospective studies as well as larger retrospective analyses suggest that interferon therapy leads to a decrease in the incidence of HCC. Without a reliable tissue culture system or a small animal model of HCV infection, analysis of the mechanisms by which HCV leads to cancer has been difficult. Nevertheless, both in vitro expression systems and in vivo transgenic mice studies suggest that HCV has an inherent carcinogenic potential. Understanding the pathogenesis of HCV-associated HCC is important in developing effective means of prevention and treatment of this highly malignant form of cancer.

Prediagnostic Levels of Serum Micronutrients in Relation to Risk of Gastric Cancer in Shanghai, China

Data on blood levels of specific carotenoids and vitamins in relation to gastric cancer are scarce. Little is known about the relationship between prediagnostic serum levels of carotenoids other than β-carotene and risk of gastric cancer especially in non-Western populations. Prediagnostic serum concentrations of α-carotene, β-carotene, β-cryptoxanthin, lycopene, lutein/zeaxanthin, retinol, α-tocopherol, γ-tocopherol, and vitamin C were determined on 191 cases and 570 matched controls within a cohort of 18,244 middle-aged or older men in Shanghai, China, with a follow-up of 12 years. High serum levels of α-carotene, β-carotene, and lycopene were significantly associated with reduced risk of developing gastric cancer (all Ps for trend ≤ 0.05); the odds ratios (95% confidence intervals) for the highest versus the lowest quartile of α-carotene, β-carotene, and lycopene were 0.38 (0.13-1.11), 0.54 (0.32-0.89), and 0.55 (0.30-1.00), respectively. Increased serum level of vitamin C was significantly associated with reduced risk of gastric cancer among men who neither smoked cigarettes over lifetime nor consumed ≥3 drinks of alcohol per day; the odds ratios (95% confidence intervals) for the second, third, and fourth quartile categories were 0.69 (0.28-1.70), 0.36 (0.14-0.94), and 0.39 (0.15-0.98), respectively, compared with the lowest quartile of vitamin C (P for trend = 0.02). There were no statistically significant relationships of serum levels of β-cryptoxanthin, lutein/zeaxanthin, retinol, α-tocopherol, and γ-tocopherol with gastric cancer risk. The present study implicates that dietary carotenes, lycopene, and vitamin C are potential chemopreventive agents for gastric cancer in humans.

Effects of beta-carotene on cell viability and antioxidant status of hepatocytes from chronically ethanol-fed rats

The purpose of the present study was to evaluate the effects of beta-carotene on the cell viability and antioxidant status of hepatocytes from chronically ethanol-fed rats. Rats in the ethanol group were given an ethanol-containing liquid diet that provided 36 % of total energy as ethanol, while rats in the control group were fed an isoenergetic diet without ethanol. After 4 weeks, hepatocytes were taken out and cultured for 24 h. Hepatocytes from the rats in the control and ethanol groups were cultured in medium without (HC, HE) or with beta-carotene (HC+B, HE+B). The results showed that lactate dehydrogenase leakage was significantly increased in the HE compared with that in the HC group. However, lactate dehydrogenase leakage of the HE+B group was similar to that of the HC group. When compared with the HC group, activities of glutathione peroxidase and catalase in the HE group were significantly decreased by 54 and 31 %, respectively. Catalase activity in the HE+B group was significantly increased by 61 % compared with that in the HE group. However, activities of glutathione reductase and superoxide dismutase showed no difference among the groups. The level of glutathione in the HC+B and HE+B groups was significantly increased to 155 and 143 % compared with those in the HC and HE groups, respectively. The concentration of lipid peroxides showed no difference among the groups. The present results demonstrate that beta-carotene improved the cell viability of hepatocytes, and increased catalase activities and glutathione levels in hepatocytes from chronically ethanol-fed rats.

Mechanisms of non-alcoholic steatohepatitis

In 1980, the term non-alcoholic steatohepatitis was coined to describe a new syndrome occurring in patients who usually were obese (often diabetic) females who had a liver biopsy picture consistent with alcoholic hepatitis, but who denied alcohol use. The causes of this syndrome were unknown, and there was no defined therapy. More than two decades later, this clinical syndrome is only somewhat better understood, and still there is no Food and Drug Administration-approved or even generally accepted drug therapy. Patients with primary non-alcoholic steatohepatitis typically have the insulin resistance syndrome (synonymous with the metabolic syndrome, syndrome X, and so forth), which is characterized by obesity, diabetes, hyperlipidemia, hypertension, and, in some instances, other metabolic abnormalities such as polycystic ovary disease. Secondary non-alcoholic steatohepatitis may be caused by drugs such as tamoxifen, certain industrial toxins, rapid weight loss, and so forth. The cause of non-alcoholic steatohepatitis remains elusive, but most investigators agree that a baseline of steatosis requires a second hit capable of inducing inflammation, fibrosis, or necrosis for non-alcoholic steatohepatitis to develop. Our research group has focused its efforts on the interactions of nutritional abnormalities, cytokines, oxidative stress with lipid peroxidation, and mitochondrial dysfunction in the induction of steatohepatitis, both alcoholic and non-alcoholic in origin. Research findings from other laboratories also support the role of increased cytokine activity, oxidative stress, and mitochondrial dysfunction in the pathogenesis of non-alcoholic steatohepatitis. The objectives of this article are to review the (1) definition and clinical features of non-alcoholic steatohepatitis, (2) potential mechanisms of non-alcoholic steatohepatitis, and (3) potential therapeutic interventions in non-alcoholic steatohepatitis.

Alcoholic muscle disease and biomembrane perturbations (review)

Excessive alcohol ingestion is damaging and gives rise to a number of pathologies that influence nutritional status. Most organs of the body are affected such as the liver and gastrointestinal tract. However, skeletal muscle appears to be particularly susceptible, giving rise to the disease entity alcoholic myopathy. Alcoholic myopathy is far more common than overt liver disease such as cirrhosis or gastrointestinal tract pathologies. Alcohol myopathy is characterised by selective atrophy of Type II (anaerobic, white glycolic) muscle fibres: Type I (aerobic, red oxidative) muscle fibres are relatively protected. Affected patients have marked reductions in muscle mass and impaired muscle strength with subjective symptoms of cramps, myalgia and difficulty in gait. This affects 40-60% of chronic alcoholics (in contrast to cirrhosis, which only affects 15-20% of chronic alcohol misuers).Many, if not all, of these features of alcoholic myopathy can be reproduced in experimental animals, which are used to elucidate the pathological mechanisms responsible for the disease. However, membrane changes within these muscles are difficult to discern even under the normal light and electron microscope. Instead attention has focused on biochemical and other functional studies. In this review, we provide evidence from these models to show that alcohol-induced defects in the membrane occur, including the formation of acetaldehyde protein adducts and increases in sarcoplasmic-endoplasmic reticulum Ca(2+)-ATPase (protein and enzyme activity). Concomitant increases in cholesterol hydroperoxides and oxysterol also arise, possibly reflecting free radical-mediated damage to the membrane. Overall, changes within muscle membranes may reflect, contribute to, or initiate the disturbances in muscle function or reductions in muscle mass seen in alcoholic myopathy. Present evidence suggest that the changes in alcoholic muscle disease are not due to dietary deficiencies but rather the direct effect of ethanol or its ensuing metabolites.

Isoprostanes and the liver

The liver has been central to our understanding of the physiology and biology of the F2-isoprostanes. The discovery of F2-IsoPs and the initial demonstration that they could be used to localize oxidative stress was first demonstrated in a rat model of oxidative liver injury (carbon tetrachloride), and the first demonstration that plasma concentrations are increased in a human disease was in patients with liver failure and the hepatorenal syndrome [J. Clin. Invest. 90 (6) (1992b) 2502; J. Lipid Mediat. 6 (1/3) (1993) 417]. This article will cover the measurement of F2-IsoPs as markers of lipid peroxidation in vivo in liver disease, and review their biological activity as mediators of disease.

Green tea protects against ethanol-induced lipid peroxidation in rat organs

Ethanol metabolism is accompanied by generation of free radicals, which stimulates lipid peroxidation. Natural antioxidants are particularly useful in such a situation. The current study was designed to investigate the efficacy of green tea, as a source of water-soluble antioxidants (catechins), on lipid peroxidation in liver, brain, and blood induced by chronic (4 weeks) ethanol intoxication in rats. Feeding of ethanol led to a significant increase in lipid peroxidation, as measured by increased concentrations of lipid hydroperoxides, 4-hydroxynonenal, and malondialdehyde. Feeding of ethanol also changed the glutathione-dependent lipid hydroperoxide decomposition system, resulting in a decrease in both reduced glutathione concentration and activity of glutathione peroxidase. Observed changes were statistically significant in all examined tissues. Enhancement in lipid peroxidation was associated with disruption of hepatocyte cell membranes, as observed through electron microscopic evaluation. Green tea protects phospholipids from enhanced peroxidation and prevents changes in biochemical parameters and morphologic changes observed after ethanol consumption. These results support the suggestion that green tea protects membranes from peroxidation of lipids associated with ethanol consumption.

Effect of prenatal exposure to ethanol on hepatic elongation factor-2 and proteome in 21 d old rats: protective effect of folic acid

In this article, we study the effects of ethanol intake during pregnancy and lactation on hepatic and pancreatic elongation factor-2 (EF-2) of 21 d old progeny. At the same time, the effect of ethanol on the level of other relevant hepatic proteins was determined using proteomic analysis. The results show that ethanol not only produces a general increase of protein oxidation, but also produces an important depletion of EF-2 and several other proteins. Among the hepatic proteins affected by ethanol, the concomitant supplementation with folic acid to alcoholic mother rats prevented EF-2, RhoGDI-1, ER-60 protease, and gelsolin depletion. This protective effect of folic acid may be related to its antioxidant properties and suggests that this vitamin may be useful in minimizing the effect of ethanol in the uterus and lactation exposure of the progeny.

Virgin olive and fish oils enhance the hepatic antioxidant defence system in atherosclerotic rabbits

BACKGROUND & AIMS

In this study we report the effects of sunflower, virgin olive and fish oils on the lipid profile and antioxidant defence system in liver mitochondria from rabbits with experimental atherosclerosis.

METHOD

An atherogenic control group were fed for 50 days on a diet containing 3% lard and 1.3% cholesterol. Four groups were fed for an additional period of 30 days with a diet enriched in different oils: sunflower oil, virgin olive oil, refined olive oil and fish oil. A control group was fed with a standard chow.

RESULTS

The atherogenic diet caused important changes in the hepatic mitochondria lipid profile and in the enzymatic and non-enzymatic antioxidant defence system accompanied with an increase in the content of hydroperoxides in liver mitochondria. The administration of virgin olive and fish oils showed a better profile in the antioxidant system as well as decrease in the content of hydroperoxides.

CONCLUSIONS

The intake of cholesterol- and lard-enriched diet leads to a high impairment in the hepatic antioxidant defence system. However, the replacement of that diet by other unsaturated fat-enriched diets using virgin olive, sunflower and fish oil enhances hepatic antioxidant defence system, virgin olive and fish oil diet provide the best results.

Role of naringin supplement in regulation of lipid and ethanol metabolism in rats

The current study was performed to investigate the effect of naringin supplements on the alcohol, lipid, and antioxidant metabolism in ethanol-treated rats. Male Sprague-Dawley rats were randomly divided into six groups (n = 10) based on six dietary categories: ethanol and naringin-free, ethanol (50 g/L) plus low-naringin (0.05 g/L), ethanol plus high-naringin (0.125 g/L), and three corresponding pair-fed groups. The pair-fed control rats received an isocaloric diet containing dextrin-maltose instead of ethanol for 5 wks. Among the ethanol treated groups, the naringin supplements significantly lowered the plasma ethanol concentration with a simultaneous increase in the ADH and/or ALDH activities. However, among the ethanol-treated groups, naringin supplementation resulted in a significant decrease in the hepatic triglycerides and plasma and hepatic total cholesterol compared to that in the naringin-free group. Naringin supplementation significantly increased the HDL-cholesterol and HDL-C/total-C ratio, while lowering the AI value among the ethanol-treated groups. Hepatic lipid accumulation was also significantly reduced in the naringin-supplemented groups compared to the naringin-free group among the ethanol-treated groups, while no differences were found among the pair-fed groups. Among the ethanol-treated groups, the low-naringin supplementation resulted in a significant decrease in the levels of plasma and hepatic TBARS, whereas it resulted in higher SOD and GSH-Px activities and gluthathion levels in the liver. Accordingly, naringin would appear to contribute to alleviating the adverse effect of ethanol ingestion by enhancing the ethanol and lipid metabolism as well as the hepatic antioxidant defense system.

Inflammatory cytokine response to Vibrio vulnificus elicited by peripheral blood mononuclear cells from chronic alcohol users is associated with biomarkers of cellular oxidative stress

Vibrio vulnificus is the leading cause of death in the United States associated with the consumption of raw seafood, particularly oysters. In epidemiological studies, primary septicemia and inflammation-mediated septic shock caused by V. vulnificus is strongly associated with liver disease, often in the context of chronic alcohol abuse. The present study was undertaken to determine whether clinical biomarkers of liver function or cellular oxidative stress are associated with peripheral blood mononuclear cell inflammatory cytokine responses to V. vulnificus. Levels of interleukin-1 beta (IL-1 beta), IL-6, IL-8, and tumor necrosis factor alpha elicited in response to V. vulnificus and measured in cell supernatants were not associated with the liver biomarkers aspartate aminotransferase (AST) or alanine aminotransferase (ALT) or the AST/ALT ratio. In contrast, reduced glutathione (GSH) levels were associated with the release of all four cytokines (IL-1 beta [R(2) = 0.382; P = 0.006], IL-6 [R(2) = 0.393; P = 0.005], IL-8 [R(2) = 0.487; P = 0.001], and TNF-alpha [R(2) = 0.292; P = 0.021]). Those individuals with below-normal GSH levels produced significantly less proinflammatory cytokines in response to V. vulnificus. We hypothesize that persons with markers for cellular oxidative stress have increased susceptibility to V. vulnificus septicemia.

Increased NAD(P)H fluorescence with decreased blood flow in the steatotic liver of the obese Zucker rat

The steatotic liver is characterized by deranged intrahepatic microvasculature that is believed to predispose it to ischemia-reperfusion injury. The aim of this study was to investigate the distorted hepatic hemodynamics and its impact on the redox status of the steatotic liver. Hepatic hemodynamic parameters, hepatic microcirculatory perfusion (HMP), and in vivo reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] autofluorescence, which reflects the mitochondrial redox status and tissue oxygen levels, were measured in obese (n = 7) and lean Zucker rats (n = 7). Portal venous and total hepatic blood flow per unit of liver weight were found to exhibit a 37.9% and 35.9% reduction, respectively, in the steatotic liver compared to the nonsteatotic liver of the lean group (P < 0.0001) as was HMP (obese, 96.1 +/- 18.1 PU; lean, 143.8 +/- 12.0 PU, P < 0.05) that showed a 33.2% decrease in the former. Hepatic arterial resistance, however, was 38.7% lower in the obese rat (83.1 +/- 9.1 mmHg. ml(-1). min) than in the lean rat (135.5 +/- 15.8 mmHg. ml(-1). min) (P < 0.05). NAD(P)H fluorescence intensity was significantly elevated in the steatotic liver (0.16 +/- 0.001 aU) compared with the lean one (0.14 +/- 0.007 aU) (P = 0.014). Our results suggest that, in response to a reduced portal venous blood flow, there is a significant decrease in hepatic arterial resistance that, nevertheless, cannot completely compensate for the drop in overall hepatic perfusion and oxygenation of the microvascular bed in the steatotic liver of the obese Zucker rat.