Oxidative stress-related molecules and liver fibrosis

Oxidative stress stimulates proliferation and invasiveness of hepatic stellate cells via a MMP2-mediated mechanism

Experimental evidence indicates that reactive oxygen species (ROS) are involved in the development of hepatic fibrosis; they induce hepatic stellate cells (HSC) proliferation and collagen synthesis. To address the role of matrix metalloproteinase (MMP)-2 in promoting HSC proliferation during hepatic injury, we investigated whether oxidative stress modulates the growth and invasiveness of HSC by influencing MMP-2 activation. Cell invasiveness and proliferation, which were studied using Boyden chambers and by counting cells under a microscope, were evaluated after treatment with a superoxide-producing system, xanthine plus xanthine oxidase (X/XO), in the presence or absence of antioxidants and MMP inhibitors. Expression and activation of MMP-2 were evaluated via gel zymography, immunoassay, and ribonuclease protection assay. The addition of X/XO induced proliferation and invasiveness of human HSC in a dose-dependent manner. The addition of antioxidants as well as MMP-2-specific inhibitors impaired these phenomena. X/XO treatment increased MMP-2 expression and secretion appreciably and significantly induced members of its activation complex, specifically membrane-type 1 MMP and tissue inhibitor metalloproteinase 2. To study the intracellular signaling pathways involved in X/XO-induced MMP-2 expression, we evaluated the effects of different kinase inhibitors. The inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) and phosphatidyl inositol 3-kinase (PI3K) abrogated X/XO-elicited MMP-2 upregulation and completely prevented X/XO-induced growth and invasiveness of HSC. In conclusion, our findings suggest that MMP-2 is required for the mitogenic and proinvasive effects of ROS on HSC and demonstrate that ERK1/2 and PI3K are the main signals involved in ROS-mediated MMP-2 expression.

Systemic infusion of angiotensin II exacerbates liver fibrosis in bile duct-ligated rats

Recent evidence indicates that the renin-angiotensin system (RAS) plays a major role in liver fibrosis. Here, we investigate whether the circulatory RAS, which is frequently activated in patients with chronic liver disease, contributes to fibrosis progression. To test this hypothesis, we increased circulatory angiotensin II (Ang II) levels in rats undergoing biliary fibrosis. Saline or Ang II (25 ng/kg/h) were infused into bile duct-ligated rats for 2 weeks through a subcutaneous pump. Ang II infusion increased serum levels of Ang II and augmented bile duct ligation-induced liver injury, as assessed by elevated liver serum enzymes. Moreover, it increased the hepatic concentration of inflammatory proteins (tumor necrosis factor alpha and interleukin 1beta) and the infiltration of CD43-positive inflammatory cells. Ang II infusion also favored the development of vascular thrombosis and increased the procoagulant activity of tissue factor in the liver. Livers from bile duct-ligated rats infused with Ang II showed increased transforming growth factor beta1 content, collagen deposition, accumulation of smooth muscle alpha-actin-positive cells, and lipid peroxidation products. Moreover, Ang II infusion stimulated phosphorylation of c-Jun and p42/44 mitogen-activated protein kinase and increased proliferation of bile duct cells. In cultured rat hepatic stellate cells (HSCs), Ang II (10(-8) mol/L) increased intracellular calcium and stimulated reactive oxygen species formation, cellular proliferation and secretion of proinflammatory cytokines. Moreover, Ang II stimulated the procoagulant activity of HSCs, a newly described biological function for these cells. In conclusion, increased systemic Ang II augments hepatic fibrosis and promotes inflammation, oxidative stress, and thrombogenic events.

Levels of serum vitamin A, alpha-tocopherol and malondialdehyde in patients with non-alcoholic steatohepatitis: relationship with histopathologic severity

The aims of our study were to estimate serum levels of malondialdehyde (MDA), serum levels of vitamin A and alpha-tocopherol as antioxidants and determine relationship of these with histopathologic severity in patients with non-alcoholic steatohepatitis (NASH). Twenty-nine patients with biopsy-proven NASH were included to study. NASH were histopathologically scored for grading and staging. Serum MDA and vitamin A levels were increased in patients with NASH and simple steatosis as compared to healthy control group. Serum alpha-tocopherol levels measured in simple steatosis and NASH were significantly lower than in healthy control group. There was no significant difference between grade/stage 0-1 and grade/stage 2-3 in terms of MDA, vitamin A and alpha-tocopherol levels. Serum MDA and vitamin A levels are increased in simple steatosis and NASH. MDA, vitamin A and alpha-tocopherol levels in NASH were not associated with the histopathologic severity.

Alcohol in hepatocellular cancer

Hepatocellular cancer accounts for almost half a million cancer deaths a year, with an escalating incidence in the Western world. Alcohol has long been recognized as a major risk factor for cancer of the liver and of other organs including oropharynx, larynx, esophagus, and possibly the breast and colon. There is compelling epidemiologic data confirming the increased risk of cancer associated with alcohol consumption, which is supported by animal experiments. Cancer of the liver associated with alcohol usually occurs in the setting of cirrhosis. Alcohol may act as a cocarcinogen, and has strong synergistic effects with other carcinogens including hepatitis B and C, aflatoxin, vinyl chloride, obesity, and diabetes mellitus. Acetaldehyde, the main metabolite of alcohol, causes hepatocellular injury, and is an important factor in causing increased oxidant stress, which damages DNA. Alcohol affects nutrition and vitamin metabolism, causing abnormalities of DNA methylation. Abnormalities of DNA methylation, a key pathway of epigenetic gene control, lead to cancer. Other nutritional and metabolic effects, for example on vitamin A metabolism, also play a key role in hepatocarcinogenesis. Alcohol enhances the effects of environmental carcinogens directly and by contributing to nutritional deficiency and impairing immunological tumor surveillance. This review summarizes the epidemiologic evidence for the role of alcohol in hepatocellular cancer, and discusses the mechanisms involved in the promotion of cancer.

Effect of ginkgo biloba extract on livers in aged rats

AIM: To investigate the protective effect of ginkgo biloba extract (GBE) on livers of aged rats and the associated mechanisms.

METHODS: Two-mo- and 20-mo-old rats were treated with GBE/saline for 3 mo. Liver tissue samples from 5-mo-old rats treated with saline (group Y) and 23-mo-old rats treated with GBE (group E) or saline (group N) were used for histopathological examinations (hematoxylin-eosin and Masson staining, Lipofuscin staining-Schmorl staining) and determination of expression of tissue inhibitor-1 of metalloproteinase (TIMP-1) and the level of malondialdehyde (MDA), glutathione peroxidase (GPx) and superoxide dismutase (SOD). Blood samples were collected for determination of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL) and albumin.

RESULTS: Microscopic studies with Masson staining revealed mild liver fibrosis in aged rats (group N), while the livers of aged rats receiving GBE (group E) showed amelioration in fibrosis (2.2±0.1 vs 2.8±0.1, P<0.01) and deposition of lipofuscin (33.7±5.3 vs 62.8±5.7, P<0.01). The expression of TIMP-1 and the level of liver MDA (1.0±0.1 vs 1.2±0.2, P<0.05) also decreased but the activity of GPx (97.1±15.3 vs 61.8±14.5, P<0.01) increased in group E. Compared with group Y, the level of liver MDA (0.8±0.1 vs 1.2±0.2, P<0.01), lipofuscin (32.4±6.0 vs 62.8±5.7, P<0.01) and TIMP-1 expression were increased, while the activity of GPx (103.2±17.6 vs 61.8±14.5, P<0.01) and SOD (16.7±4.4 vs 11.8±3.9, P<0.05) was decreased in group N. There was no difference in liver function among these three groups.

CONCLUSION: GBE has protective effects on aging liver. The possible mechanisms might be its antioxidant activity and inhibition of TIMP-1 expression.

Mitochondria as Functional Targets of Proteins Coded by Human Tumor Viruses

Molecular analyses of tumor virus-host cell interactions have provided key insights into the genes and pathways involved in neoplastic transformation. Recent studies have revealed that the human tumor viruses Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpesvirus (KSHV), human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV), and human T-cell leukemia virus type 1 (HTLV-1) express proteins that are targeted to mitochondria. The list of these viral proteins includes BCL-2 homologues (BHRF1 of EBV; KSBCL-2 of KSHV), an inhibitor of apoptosis (IAP) resembling Survivin (KSHV K7), proteins that alter mitochondrial ion permeability and/or membrane potential (HBV HBx, HPV E[wedge]14, HCV p7, and HTLV-1 p13(II)), and K15 of KSHV, a protein with undefined function. Consistent with the central role of mitochondria in energy production, cell death, calcium homeostasis, and redox balance, experimental evidence indicates that these proteins have profound effects on host cell physiology. In particular, the viral BCL-2 homologues BHRF1 and KSBCL-2 inhibit apoptosis triggered by a variety of stimuli. HBx, p7, E1[wedge]4, and p13(II) exert powerful effects on mitochondria either directly due to their channel-forming activity or indirectly through interactions with endogenous channels. Further investigation of these proteins and their interactions with mitochondria will provide important insights into the mechanisms of viral replication and tumorigenesis and could aid in the discovery of new targets for anti-tumor therapy.

PPARalpha ligands activate antioxidant enzymes and suppress hepatic fibrosis in rats

Oxidative stress is a major pathogenetic factor in hepatic fibrosis. Peroxisome proliferator-activated receptor alpha (PPARalpha) is a nuclear receptor which is known to affect oxidative stress and PPARalpha ligands may have rescue effects on hepatic fibrosis. We tested this hypothesis using rat thioacetamide (TAA) models of liver cirrhosis. Rats were given intraperitoneal injection of TAA and treated with a diet containing one of the two PPARalpha ligands, Wy-14,643 (WY) or fenofibrate. WY treatment dramatically reduced hepatic fibrosis and also prevented the inhibition catalase of mRNA expression caused by TAA. Correspondingly, catalase activity increased in the TAA+WY group but decreased in the control TAA group. The antifibrotic action of fenofibrate in the TAA model was comparable with that of WY. PPARalpha ligands have an antifibrotic action in the rat TAA model of liver cirrhosis, probably due to an antioxidant effect of enhanced catalase expression and activity in the liver.

Oxidative Stress in Nonalcoholic Fatty Liver Disease: Pathogenesis and Antioxidant Therapies

Nonalcoholic fatty liver disease is a common cause of chronic liver disease, a common finding on liver biopsy in those patients with abnormal blood transaminase levels, and a common cause of cryptogenic cirrhosis in the United States. The prevalence of this disorder is expected to rise with the increase in obesity, and the clinical spectrum can range from simple steatosis (fatty liver) to cirrhosis of the liver. Insulin resistance is thought to be pivotal for the development of steatosis, and oxidative stress may be a potential factor that can promote hepatic necroinflammation and fibrosis. Preliminary studies have examined the role of oxidative stress and antioxidants in animal and human studies of this disorder. Efforts to improve the hepatic antioxidant system could be achieved by optimizing the patient's diet, by supplementation with precursors for antioxidants, or by supplementation with essential metals and/or antioxidants. Randomized, controlled trials are required to examine these potential approaches using patients with this disorder.

Curcumin inhibits NF-kappaB activation and reduces the severity of experimental steatohepatitis in mice

BACKGROUND/AIMS

While oxidative stress is a feature of non-alcoholic steatohepatitis, the causal link between oxidative stress and inflammatory recruitment has yet to be demonstrated. We analysed the role of NF-kappaB redox-sensitive signalling pathway of inflammatory recruitment in experimental steatohepatitis.

METHODS

Mice were fed the methionine and choline deficient (MCD) or the control diet, with or without curcumin, an NF-kappaB inhibitor, for up to 4 weeks. Histopathology, lipoperoxides, NF-kappaB/DNA binding and expression of NF-kappaB-regulated genes were assessed.

RESULTS

MCD-fed mice developed steatohepatitis accompanied by dramatic accumulation of hepatic lipoperoxides, activation of NF-kappaB and induction of pro-inflammatory ICAM-1, COX-2, MCP-1 and CINC mRNA. Curcumin significantly reduced MCD-induced inflammation but had no effect on steatosis or on the level of hepatic lipid peroxides. Curcumin prevented the MCD-induced activation of NF-kappaB and decreased downstream induction of ICAM-1, COX-2 and MCP-1. However, it failed to reduce activation of AP-1, MAPK pathways or CINC expression.

CONCLUSIONS

Curcumin alleviates the severity of hepatic inflammation in experimental steatohepatitis induced by the MCD diet, an effect likely to be mediated via inhibition of NF-kB activation and dependent pro-inflammatory genes. The NF-kappaB pathway is one among several possible signalling pathways by which inflammation is recruited in experimental steatohepatitis.

Oxidative status in chronic hepatitis C: the influence of antiviral therapy and prognostic value of serum hydroperoxide assay

The effect of alpha-interferon (alpha-IFN) and ribavirin (RBV) treatment on oxidative status in chronic hepatitis C (CHC) is unknown.

AIM

To study the time course of oxidative status in patients with CHC during alpha-IFN and RBV administration, and to evaluate the role of oxidative status in order to predict the therapeutic response.

PATIENTS AND METHODS

Fifty one patients with CHC were studied. All received a combination of alpha-IFN and RBV for 6 or 12 months in relation to the type of response. The hydroperoxides concentration in serum test samples by D-ROM test was measured in all of the patients before therapy. In 27 patients, hydroperoxides were also measured during the treatment and during the 12 subsequent months.

RESULTS

Cross-sectional analysis demonstrates that patients with a successive long-term response had a lower basal serum hydroperoxide concentration than non-responders (280 +/- 40.8 vs 337 +/- 83 CARR Units, p < 0.05). This resulted to be an independent factor predictive of long-term response in the multi-varied analysis. Longitudinal observation on 27 patients showed that the mean hydroperoxide concentration decreased significantly during treatment (T0 329 +/- 79.2 vs T12 272 +/- 34.5 CARR Units) and that the decrease in the mean values was mainly due to variations in the relapsers group.

CONCLUSIONS

Normal basal hydroperoxide concentration helps to predict long-term response to combination therapy. The D-ROM test may be used for screening patients before treatment.

Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is a well-recognized form of chronic liver disease affecting both children and adults that has gained increased recognition. Recently NAFLD has been associated with insulin resistance and its incidence and prevalence is likely increasing, paralleling the rise in obesity and diabetes mellitus in the United States. The article includes current thoughts on the natural history and pathogenesis of NAFLD and describes current trends in the diagnosis and treatment of this condition.

Antioxidant activity of fermented soybean extract

Free radicals are considered to be important causative factors in the development of cancer and cardiovascular diseases. This relationship has led to interest in evaluating the antioxidant capacities of many dietary supplements. Fermented soybean extract is produced by symbiotic fermentation of organic soybean with 20 types of Lactobacillus and yeast. In vitro and in vivo models are used in this study to evaluate the antioxidant effect of fermented soybean extract. Several in vitro models are used to detect the antioxidant capacity of the fermented soybean extract, which is compared to vitamin C and Trolox. The results demonstrate that the fermented soybean extract has strong antioxidant activity against unsaturated fatty acid peroxidation compared to vitamin C and Trolox. By the means of the test system developed by Y. Toshiki et al., it is shown that the fermented soybean extract can function both as an antioxidant and as a free radical acceptor that can convert free radicals into harmless substances through an energy-decreasing procedure. An in vivo study examines the effects of fermented soybean extract on the activity of antioxidant enzymes. The activities of the antioxidant enzymes (AOE) including total superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) are measured in liver, kidney, and brain from male Sprague-Dawley rats. The activities of CAT, SOD, and GPX are increased in the liver. However, the SOD activity is decreased in the kidney. SOD and GPX activities are decreased in the brain. These results lead to the conclusion that fermented soybean extract not only has antioxidant activity but also has an effect on the activity of antioxidant enzymes in liver.

The flavonoid naringenin inhibits dimethylnitrosamine-induced liver damage in rats

Naringenin, a phytoalexin found in grapefruits and tomatoes, has been reported to exhibit a wide range of pharmacological properties. In this study, we investigated the protective effect of naringenin on hepatic injury induced by dimethylnitrosamine (DMN) in rats. Oral administration of naringenin (20 and 50 mg/kg daily for 4 weeks) remarkably prevented the DMN-induced loss in body and liver weights and inhibited the elevation of serum alanine transaminase, aspartate transaminase, alkaline phosphatase, and bilirubin levels. Naringenin also restored serum albumin and total protein levels, and reduced the hepatic level of malondialdehyde. Furthermore, DMN-induced collagen accumulation, as estimated by histological analysis of liver tissue stained with Sirius red, was reduced in the naringenin-treated rats. A reduction in hepatic stellate cell activation, as assessed by alpha-smooth muscle actin staining, was associated with naringenin treatment. In conclusion, these results demonstrate that naringenin exhibited in vivo hepatoprotective and anti-fibrogenic effects against DMN-induced liver injury. It suggests that naringenin may be useful in preventing the development of hepatic fibrosis.

A new approach to drug therapy in non-alcoholic steatohepatitis (NASH)

Liver steatosis is a common human disease, most often caused by long-term alcohol consumption. Non-alcoholic steatohepatitis (NASH) is characterized by similar histopathological features to those observed in alcoholic liver disease, but occurs in the absence of significant alcohol consumption. Several aetiological factors contribute to NASH: obesity, type 2 diabetes mellitus, hyperlipidaemia, pregnancy, different chemical intoxications, parenteral nutrition, jejeuno-ileal bypass, chronic inflammatory bowel disease, nutritional protein deficiency and congenital metabolic disorders. Biochemically, oxidative stress and lipid peroxidation and their ensuing damage are implicated in the pathogenesis of NASH and alcoholic steatohepatitis (probably resulting from free fatty acids in the mitochondria, and induction of the cytochrome P450 isoform CYP2E1 in hepatocytes and Kupffer's cells). This paper deals with the pathomechanisms, clinical findings and currently available therapies for NASH. The potential use of metadoxine in the treatment of NASH is also discussed.

Increased risk of hepatocellular carcinoma and liver cirrhosis in vinyl chloride workers: synergistic effect of occupational exposure with alcohol intake

Hepatocellular carcinoma (HCC) and liver cirrhosis (LC) are not well-established vinyl chloride monomer (VCM)-induced diseases. Our aim was to appraise the role of VCM, alcohol intake, and viral hepatitis infection, and their interactions, in the etiology of HCC and LC. Thirteen cases of HCC and 40 cases of LC were separately compared with 139 referents without chronic liver diseases or cancer in a case-referent study nested in a cohort of 1,658 VCM workers. The odds ratios (ORs) and the 95% confidence intervals (CIs) were estimated by common methods and by fitting models of logistic regression. We used Rothman's synergy index (S) to evaluate interactions. By holding the confounding factors constant at logistic regression analysis, each extra increase of 1,000 ppm times years of VCM cumulative exposure was found to increase the risk of HCC by 71% (OR = 1.71; 95% CI, 1.28-2.44) and the risk of LC by 37% (OR = 1.37; 95% CI, 1.13-1.69). The joint effect of VCM exposure above 2,500 ppm times years and alcohol intake above 60 g/day resulted in ORs of 409 (95% CI, 19.6-8,553) for HCC and 752 (95% CI, 55.3-10,248) for LC; both S indexes suggested a synergistic effect. The joint effect of VCM exposure above 2,500 ppm times years and viral hepatitis infection was 210 (95% CI, 7.13-6,203) for HCC and 80.5 (95% CI, 3.67-1,763) for LC; both S indexes suggested an additive effect. In conclusion, according to our findings, VCM exposure appears to be an independent risk factor for HCC and LC interacting synergistically with alcohol consumption and additively with viral hepatitis infection.

Oxidant stress in type I autoimmune hepatitis: the link between necroinflammation and fibrogenesis?

Autoimmune hepatitis (AIH) is a chronic liver disease of unknown aetiology characterized by circulating autoantibodies, hyperglobulinaemia and interface hepatitis. The mechanisms of progression from initial autoimmune attack to fibrosis and cirrhosis are unclear but oxidant stress may be involved. Markers of lipid peroxidation, antioxidant status, hepatic fibrogenesis and liver function were measured in blood and urine in 35 controls and in 33 patients with type-1 AIH; histology was assessed in 18 patients. In AIH, markers of lipid peroxidation were significantly elevated (8-isoprostane in both plasma and urine P < 0.001; plasma malondialdehyde P = 0.017). Total antioxidant capacity in protein-free serum and total glutathione in both whole blood and plasma were significantly reduced (P = 0.007, P = 0.037, P < 0.001, respectively). The antioxidants selenium, vitamin A and vitamin E were significantly decreased (P = 0.007, P < 0.001, P = 0.025, respectively); vitamin C was unchanged. Urinary 8-isoprostane correlated positively with interface hepatitis and necroinflammatory score and with hepatic fibrogenesis (type III procollagen peptide). Interface hepatitis correlated negatively with vitamin A and whole blood total glutathione. Oxidant stress, as reflected in blood and urine by a wide range of pro- and antioxidant markers, is a significant feature of AIH and provides a probable mechanism linking hepatic necroinflammation to fibrogenesis and disease progression.

The antioxidant and antifibrogenic effects of the glycosaminoglycans hyaluronic acid and chondroitin-4-sulphate in a subchronic rat model of carbon tetrachloride-induced liver fibrogenesis

Hepatic fibrosis involves the interplay of many factors including reactive oxygen species. Recent reports described antioxidant properties of glycosaminoglycans (GAGs). Since several findings have shown that hyaluronic acid (HYA) and chondroitin-4-sulphate (C4S) may act as antioxidant molecules, the aim of this research was to evaluate the antioxidant effects of HYA and C4S treatment in a rat model of liver fibrosis. The effect on tissue inhibitors of metalloproteinases (TIMPs) was also studied. Liver fibrosis was induced in rats by eight intraperitoneal injections of CCl4, twice a week for 6 weeks. HYA or C4S alone (25 mg/kg) or HYA and C4S in combination (12.5 + 12.5 mg/kg) were administered daily by the same route during the 6 weeks. At the end of the 6-week treatment period (24 h after the last dose of GAGs), the following parameters were evaluated: (1) serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, as index of hepatic cell disruption; (2) hepatic conjugated dienes (CD), as index of lipid peroxidation; (3) hepatic TIMPs activity and expression; (4) hepatic superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, as index of endogenous defences; (5) hepatic hydroxyproline, as index of collagen deposition. CCl4-induced liver fibrosis enhanced lipid peroxidation and TIMPs activation, increased ALT and AST, depleted antioxidants SOD and GPx, and caused collagen deposition in liver tissue. Treatment with GAGs, especially when in combination, successfully reduced ALT and AST rise, lipid peroxidation by evaluating conjugated dienes, TIMPs activation and mRNA expression, partially restored SOD and GPx activities, and limited collagen deposition in the hepatic tissue. The data obtained showed that these molecules were able to limit hepatic injury induced by chronic CCl4 intoxication and especially limited liver fibrosis. They also confirm that HYA and C4S may exert antioxidant mechanism, while reduction of TIMPs expression suggests that GAGs may influence MMPs and TIMPs imbalance in liver fibrosis.

Proteome analysis by bio-active ceramic water in rat liver: contribution to antioxidant enzyme expression, SOD I

The purpose of this study was to investigate the protective effect of bio-active ceramic water on rat liver. Male Wistar rats were divided into 4 groups of 15 animals each. Groups 1 and 2 were fed bio-active ceramic water and tap water for 4 months, respectively. Groups 3 and 4 were treated with the same condition for 12 months. The changes of protein expression of these four groups were investigated using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight mass spectrometry. Eleven proteins were significantly up-regulated in bio-active ceramic water treated rat liver including aldehyde dehydrogenase I and II, albumin, fructose-1,6-bisphosphatase, and superoxide dismutase I (SOD I). The most highly expressed protein, SOD I with up-regulated enzyme activity, was confirmed by immunoblots as a major antioxidant capable of detoxifying normally generated reactive oxygen species. These data suggest that modified protein expression of the liver contributes to enhance liver function.

Effect of a load of Vitamin A after acute thioacetamide intoxication on dolichol, dolichol isoprenoids and retinol content in isolated rat liver cells

This study examines how treatment with a single dose of thioacetamide, a known experimental hepatotoxin, alters the content of dolichol, dolichol isoprene units and retinol in isolated rat parenchymal and non-parenchymal liver cells at different times and when the animals are supplemented with Vitamin A. Thioacetamide (300 mg/kg i.p.) was administered in a single injection to rats, sacrificed at intervals of 0.5, 1, 2, 3, 4, 15 and 30 days. Rats supplemented, following thioacetamide, with Vitamin A, 3 days before sacrifice showed increased mortality and cellular necrosis on the third and fourth days. Parameters indicating tissue necrosis returned to normal values in surviving animals. Dolichol and retinol content showed a variable, reversible decrease, with normal levels being restored in 15-30 days. After Vitamin A, dolichol content only in hepatic stellate cells (HSC) was lower then the controls 3 and 4 days after thioacetamide treatment, in parallel with the decrease of retinol storage. The percentage of dolichol-18 is not modified by thioacetamide alone. When supplemented with Vitamin A the percentage of dolichol-18 always decreased after thioacetamide, showing that damage was still present. Mechanisms that might be operative in liver cells are briefly discussed. This approach would provide an indication to investigate how the length of the dolichol chain is determined.

Nitric oxide synthase inhibitors modulate lipopolysaccharide-induced hepatocyte injury: dissociation between in vivo and in vitro effects

Effects of endotoxemia-induced NO production on rat liver and hepatocytes in culture were investigated. Rats were treated intraperitoneally with saline, lipopolysaccharide (LPS, 10 mg/kg), L-nitroarginine methyl ester (L-NAME)+LPS, aminoguanidine (AG)+LPS, FK 506+LPS, S-nitroso-N-acetyl penicillamine (SNAP)+L-NAME+LPS and SNAP+FK 506+LPS. Mortality, hepatocyte viability and liver function test were estimated. Liver morphology was observed by light and electron microscopy. Hepatocyte cultures were treated with LPS, cytokine mixture (CM) with or without FK 506, L-NAME or AG. Hepatocyte function and inducible form of NOS (iNOS) expression were evaluated. Twenty-four hours after treatments with saline, LPS, L-NAME+LPS, AG+LPS, FK 506+LPS, SNAP+L-NAME+LPS and SNAP+FK 506+LPS, rat mortalities were 0%, 10%, 48%, 8%, 20%, 38% and 0%, and hepatocyte viabilities were 93+/-3%, 80+/-3%, 52+/-8%, 88+/-1%, 70+/-3%, 80+/-4% and 82+/-3%, respectively. AG+LPS or L-NAME+LPS administration was followed by excessive vacuolization of hepatocytes with lesions in the intermediary lobule zone characterized by features of secondary necrosis as a continuation of apoptotic processes. SNAP+L-NAME+LPS resulted in a well-preserved structure of central vein lobules with sparse signs of apoptosis. Treatment with LPS or CM increased iNOS expression in hepatocyte culture, which was inhibited by L-NAME, FK 506 or AG. AG reduced LPS-induced rise in alanine aminotransferase leakage. LPS-induced NO exerts cytoprotective effects in vivo, while LPS-induced NO in vitro appears to be toxic. Based on the data of this report, one cannot use in vitro results to predict in vivo responses to LPS-induced NO production. The pharmacological modulation of iNOS expression or NO production in vivo or in vitro, therefore, by the development of specific NO donors or inhibitors is promising for improvement of hepatocyte functions under the two experimental conditions, respectively.

Total Antioxidant Status and Erythrocyte Superoxide Dismutase Activity in Patients with Chronic Hepatitis B and C

Damage of hepatitis B virus (HBV) and hepatitis C virus (HCV)-infected hepatocytes is mediated by both a direct cytopathic effect of the viruses and by immunologic response of T-cells, However, other mechanisms such as oxidative stress, may also be involved in cellular damage. We conducted a study to investigate the status of superoxide dismutase activity (SOD) and the total antioxidant status (TAS) in a consecutive cohort of patients infected with HBV and HCV infections, including HBV patients in the chronic inactive state of the disease. The latter were included in an attempt to determine whether antioxidant status is affected even in cases where an obvious viral activity is absent. TAS and SOD were measured in 55 patients (43 HBV, 12 HCV) and 25 healthy controls. 17 out of 43 patients had chronic inactive HBV state, 15 had chronic hepatitis Band 11 had HBV-related cirrhosis. In the HCV group, 6 patients had chronic hepatitis C and 6 HCV-related cirrhosis. Erythrocyte SOD activity was determined in haemolysate from red blood cells using a kinetic spectrophotometer method. TAS was measured by a colorimetric assay. The mean TAS and SOD values in the total number of patients (1.20±0.12 mmol/L and 1040±255 Ulg Hb, respectively) were significantly lower (p<0.001) compared to healthy controls (1.57±0.13 mmol/L and 1491±420 D/g Hb), Comparisons between groups showed significantly lower (p<0.001) TAS and SOD values in each subgroup of patients compared to healthy controls. A significant positive correlation was found between TAS and SOD in the total number ofpatients (n= 55, p<0.01), in the chronic hepatitis group (n=21, p=0.01) and in the total group of HBV patients (n=43, p<0.01). We demonstrated a significant reduced antioxidant capacity in patients with chronic HBV and HCV as indicated by low TAS and SOD. These findings were independent of the virological, biochemical and clinical status of the patients, including those with chronic inactive HBV state. This could suggest that the tissue-related consequences of oxidative stress might start from the inactive stage of liver viral diseases. However, our observations should be viewed with caution and need to be tested in a larger numbers of patients in order to determine prospectively whether these findings have pathophysiological and/or clinical significance.

Liver fibrosis: from the bench to clinical targets

Progressive liver fibrosis is the main cause of organ failure in chronic liver diseases of any aetiology. Fibrosis develops with different spatial patterns and is a consequence of different prevalent mechanisms according to the diverse causes of parenchymal damage. Indeed, fibrosis, observed as a consequence of chronic viral infection is initially concentrated within and around the portal tract, while fibrosis secondary to toxic/metabolic damage is located mainly in the centrolobular areas. In addition, it is increasingly evident that different cell types are involved in the deposition of fibrillar extracellular matrix during active hepatic fibrogenesis: hepatic stellate cells are mainly involved when hepatocellular damage is limited or concentrated within the liver lobule, whereas portal myofibroblasts and fibroblasts provide a predominant contribution when the damage is located in the proximity of the portal tracts. In the later stages of evolution (septal fibrosis) it is likely that all extracellular matrix-producing cells contribute to fibrogenesis. Recruitment and activation of extracellular matrix-producing cells to the site of tissue damage can be due to different major mechanisms: (1) Chronic activation of the tissue repair process. In this case, as a consequence of the reiterated damage, accumulation of fibrillar extracellular matrix reflects the impossibility of an effective remodelling and regeneration. (2) Effect of oxidative stress products, including reactive oxygen intermediates and reactive aldehydes. These products, whose concentration become critical in toxic/metabolic liver injury, are able to induce the synthesis of fibrillar extracellular matrix even in the absence of significant hepatocyte damage and inflammation. (3) Derangement of normal the epithelial/mesenchymal interaction. This typically occurs in all conditions characterised by cholangiocyte damage/proliferation, where a consensual proliferation of extracellular matrix-producing cells and progressive fibrogenesis is commonly observed. A major advancement towards the understanding of the molecular mechanisms of fibrogenesis is derived from a consistent number of in vitro studies investigating the biological role of growth factors/cytokines and other soluble factors and their intracellular signalling pathways. The relevance of these factors has been confirmed by studies performed on animal models and by studies performed on pathological human liver. Along these lines, the elucidation of a consistent number of cellular and molecular mechanisms responsible for the progression of liver fibrosis has provided sound basis for the development of pharmacological strategies able to modulate this important pathophysiological process. Finally, there are several clinically relevant issues that need re-evaluation and/or further investigation, and in particular: (1) the need of an accurate and effective monitoring of the fibrotic progression of chronic liver diseases and of the effectiveness of the currently proposed treatments; (2) the identification of general or individual factors potentially relevant for a faster progression of the disease.

Effects of estradiol on liver estrogen receptor-α and its mRNA expression in hepatic fibrosis in rats

AIM: Estradiol treatment regulates estrogen receptor (ER) level in normal rat liver. However, little information is available concerning the role of estrogen in regulating liver ER in hepatic fibrosis in rats. The present study was conducted to determine whether estradiol treatment in CCl₄-induced liver fibrosis of female and ovariectomized rats altered liver ERα and its mRNA expression, and to investigate the possible mechanisms.

METHODS: Seventy female rats were divided into seven groups with ten rats in each. The ovariectomy groups were initiated with ovariectomies and the sham operation groups were initiated with just sham operations. The CCl₄ toxic fibrosis groups received 400 mL/L CCl₄ subcutaneously at a dose of 2 mL/kg twice weekly. Estrogen groups were treated subcutaneously with estradiol 1 mg/kg, the normal control group and an ovariectomy group received injection of peanut oil vehicle twice weekly. At the end of 8 weeks, all the rats were killed to detect their serum and hepatic indicators, their hepatic collagen content, and liver ER and ER mRNA expression.

RESULTS: Estradiol treatment in both ovariectomy and sham ovariectomy groups reduced liver levels of ALT (from 658 ± 220 nkat/L to 311 ± 146 nkat/L and 540 ± 252 nkat/L to 314 ± 163 nkat/L, P < 0.05) and AST (from 697 ± 240 nkat/L to 321 ± 121 nkat/L and 631 ± 268 nkat/L to 302 ± 153 nkat/L, P < 0.05), increased serum nitric oxide (NO) level (from 53.7 ± 17.1 μmol/L to 93.3 ± 24.2 μmol/L and 55.3 ± 23.1 μmol/L to 87.5 ± 23.6 μmol/L, P < 0.05) and hepatic nitric oxide synthase (NOS) activity (from 1.73 ± 0.71 KU/g to 2.49 ± 1.20 KU/g and 1.65 ± 0.46 KU/g to 2.68 ± 1.17 KU/g, P < 0.05), diminished the accumulation of hepatic collagen, decreased centrolobular necrotic areas as well as the inflammatory reaction in rats subjected to CCl₄. The positive signal of ER and ER mRNA distributed in parenchymal and non-parenchymal hepatic cells, especially near the hepatic centrolobular and periportal areas. Ovariectomy decreased ER level (from 10.2 ± 3.2 to 4.3 ± 1.3) and ER mRNA expression (from 12.8 ± 2.1 to 10.9 ± 1.3) significantly (P < 0.05). Hepatic ER and ER mRNA concentrations were elevated after treatment with estradiol in both ovariectomy (15.8 ± 2.4, 20.8 ± 3.1) and sham ovariectomy (18.7 ± 3.8, 23.1 ± 3.7) fibrotic groups (P < 0.05).

CONCLUSION: The increase in hepatic ER and mRNA expression may be part of the molecular mechanisms underlying the suppressive effect of estradiol on liver fibrosis induced by CCl₄ administration.

4-Hydroxynonenal as a selective pro-fibrogenic stimulus for activated human hepatic stellate cells

BACKGROUND/AIMS

4-Hydroxynonenal (HNE) is a putative pro-fibrogenic product of oxidative stress able to elicit apoptosis and cytotoxicity in several cell types. This study has been performed to evaluate its 'in vivo' levels in injured liver and whether HNE may induce apoptosis and/or affect selected phenotypic responses in activated human hepatic stellate cells (HSC/MF).

METHODS/RESULTS

During the development of acute liver injury induced by CCl(4), liver tissue HNE levels were in the range 0.5-10 microM, as shown by high performance liquid chromatography analysis. Cultured human HSC/MF, developed cytotoxicity only if exposed to very high HNE concentrations (25-50 microM) without any sign of induction of classic, caspase-dependent apoptosis, as assessed by evaluating morphology and biochemical parameters of cell death. HNE, at non-cytotoxic doses, up-regulated procollagen type I and tissue inhibitor of metalloproteinases-1 gene expression and/or protein synthesis without significantly affecting chemotaxis (wound healing and haptotaxis assay), matrix metalloproteinases 1 and 2 mRNA expression and activity as well as basal DNA synthesis.

CONCLUSIONS

HNE, at concentrations compatible with those detected in vivo, does not elicit HSC/MF classic apoptosis but, rather, may act as a potent pro-fibrogenic stimulus for the expression of genes involved in excess extracellular matrix deposition and proposed as survival signals for HSC/MF.

NADPH oxidase signal transduces angiotensin II in hepatic stellate cells and is critical in hepatic fibrosis

Angiotensin II (Ang II) is a pro-oxidant and fibrogenic cytokine. We investigated the role of NADPH oxidase in Ang II-induced effects in hepatic stellate cells (HSCs), a fibrogenic cell type. Human HSCs express mRNAs of key components of nonphagocytic NADPH oxidase. Ang II phosphorylated p47phox, a regulatory subunit of NADPH oxidase, and induced reactive oxygen species formation via NADPH oxidase activity. Ang II phosphorylated AKT and MAPKs and increased AP-1 DNA binding in a redox-sensitive manner. Ang II stimulated DNA synthesis, cell migration, procollagen alpha1(I) mRNA expression, and secretion of TGF-beta1 and inflammatory cytokines. These effects were attenuated by N-acetylcysteine and diphenylene iodonium, an NADPH oxidase inhibitor. Moreover, Ang II induced upregulation of genes potentially involved in hepatic wound-healing response in a redox-sensitive manner, as assessed by microarray analysis. HSCs isolated from p47phox-/- mice displayed a blunted response to Ang II compared with WT cells. We also assessed the role of NADPH oxidase in experimental liver fibrosis. After bile duct ligation, p47phox-/- mice showed attenuated liver injury and fibrosis compared with WT counterparts. Moreover, expression of smooth muscle alpha-actin and expression of TGF-beta1 were reduced in p47phox-/- mice. Thus, NADPH oxidase mediates the actions of Ang II on HSCs and plays a critical role in liver fibrogenesis.

NADPH oxidase signal transduces angiotensin II in hepatic stellate cells and is critical in hepatic fibrosis

Angiotensin II (Ang II) is a pro-oxidant and fibrogenic cytokine. We investigated the role of NADPH oxidase in Ang II-induced effects in hepatic stellate cells (HSCs), a fibrogenic cell type. Human HSCs express mRNAs of key components of nonphagocytic NADPH oxidase. Ang II phosphorylated p47phox, a regulatory subunit of NADPH oxidase, and induced reactive oxygen species formation via NADPH oxidase activity. Ang II phosphorylated AKT and MAPKs and increased AP-1 DNA binding in a redox-sensitive manner. Ang II stimulated DNA synthesis, cell migration, procollagen alpha1(I) mRNA expression, and secretion of TGF-beta1 and inflammatory cytokines. These effects were attenuated by N-acetylcysteine and diphenylene iodonium, an NADPH oxidase inhibitor. Moreover, Ang II induced upregulation of genes potentially involved in hepatic wound-healing response in a redox-sensitive manner, as assessed by microarray analysis. HSCs isolated from p47phox-/- mice displayed a blunted response to Ang II compared with WT cells. We also assessed the role of NADPH oxidase in experimental liver fibrosis. After bile duct ligation, p47phox-/- mice showed attenuated liver injury and fibrosis compared with WT counterparts. Moreover, expression of smooth muscle alpha-actin and expression of TGF-beta1 were reduced in p47phox-/- mice. Thus, NADPH oxidase mediates the actions of Ang II on HSCs and plays a critical role in liver fibrogenesis.

Prolonged infusion of angiotensin II into normal rats induces stellate cell activation and proinflammatory events in liver

Recent evidence indicates that angiotensin II (ANG II) plays an important role in liver fibrogenesis. However, the underlying mechanisms are largely unknown. In advanced chronic liver diseases, circulating levels of ANG II are frequently elevated. We investigated the hepatic effects of prolonged systemic infusion of ANG II in normal rats. Saline or ANG II at subpressor and pressor doses (15 and 50 ng.kg-1.min-1, respectively) were infused to normal rats for 4 wk through a subcutaneous osmotic pump. Infusion of ANG II resulted in liver injury, as assessed by elevated serum liver enzymes. Livers from ANG II-perfused rats showed activation of JNK and ERK as well as increased NF-kappaB and activating protein-1 DNA-binding activity. Moreover, ANG II perfusion induced oxidative stress, increased concentration of proinflammatory cytokines, and upregulated the inflammatory proteins inducible nitric oxide synthase and cyclooxygenase-2. Histological examination of the livers from ANG II-infused rats showed mild portal inflammation as well as thickening and thrombosis of small hepatic vessels. ANG II-treated livers showed accumulation of CD43-positive inflammatory cells and activated hepatic stellate cells (HSCs) at the pericentral areas. A slight increase in collagen synthesis was observed, as assessed by Sirius red staining and hepatic hydroxyproline. All of these effects were observed when ANG II was perfused at subpressor and pressor doses. ANG II also accelerated the activation of primary cultured rat HSCs. In conclusion, increased systemic ANG II can induce liver injury by promoting proinflammatory events and vascular damage. ANG II-induced hepatic effects are not dependent on increase in arterial pressure.

Ascorbic acid concentrations in dimethylnitrosamine-induced hepatic fibrosis in rats

BACKGROUND

Ascorbic acid is a potent antioxidant and is involved in many metabolic activities including collagen biosynthesis. In the present investigation, ascorbic acid and lipid peroxides were monitored in the blood and liver samples during the progression of experimentally induced hepatic fibrosis.

METHODS

Liver injury was induced by intraperitoneal injections of dimethylnitrosamine (DMN) on three consecutive days of every week over a period of 21 days. The progression of fibrosis was assessed by histopathological examination and by monitoring of the collagen content of the liver tissue. Ascorbic acid and lipid peroxides were monitored in both blood and liver samples on days 0, 7, 14, and 21 after the start of DMN administration. The liver total protein was also measured during the investigation.

RESULTS

Histopathological examination demonstrated centrilobular necrosis, fibrosis, and early cirrhosis during DMN treatment. The collagen content increased four-fold on the 21st day of investigation. Lipid peroxides were elevated significantly in both blood and liver specimens on days 7, 14, and 21. A drastic decrease was observed in the ascorbic acid concentrations in both liver and blood samples on all days after the start of DMN administration. Liver total protein concentrations were significantly reduced during DMN administration.

CONCLUSIONS

The exact mechanism of the decrease of ascorbic acid during DMN-induced hepatic fibrosis is not clear. The most probable reason for the decreased blood and liver ascorbic acid during DMN-induced hepatic fibrosis is the increased utilization of ascorbic acid for free radical scavenging in order to reduce the highly elevated oxidative stress.

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.

HTS Compatible Assay for Antioxidative Agents Using Primary Cultured Hepatocytes

We have used primary cultured rat hepatocytes to establish a system that is compatible with HTS for screening substance libraries for biologically active compounds. The hepatocytes were treated with t-BHP to induce oxidative stress, leading to the formation ROS. The involvement of ROS in oxidative stress and pathological alterations has been of major interest in recent years, and there is great demand to identify new compounds with antioxidant potential. In most HTS programs each compound is tested in duplicate, and may only be tested once. Because of this it is important to develop assays that can identify candidate compounds accurately and with high confidence. Using newly available cell-based assay systems, we have developed a system that can detect active compounds (hits) with a high degree of confidence. As an example of an agent that can be detected from a substance library, we analyzed the effect of fisetin as an antioxidative compound using this system. All measurements were performed using the newly developed and highly versatile Multilabel-Reader Mithras LB 940 (Berthold Technologies, Bad Wildbad, Germany). The data presented show that all Z' factors determined were highly reliable. Although the protocol is primarily designed to screen for substances with antioxidative potential, it can easily be adapted to screen for other biologically active substances.

The metabolic and microcirculatory impact of orthotopic liver transplantation on the obese Zucker rat

BACKGROUND

The purpose of this study was to investigate the metabolic alterations in the recipient and microcirculatory changes to the graft in the first 3 months after orthotopic liver transplantation (OLT) of nonsteatotic liver grafts from lean rats into obese Zucker rats.

METHODS

Body weight and plasma lipids were measured for 3 months post-OLT. Graft perfusion (hepatic microcirculatory perfusion [HMP]) and vascular structure were measured in vivo at 3 months. Liver biopsy specimens were obtained throughout for morphologic analysis. Sham-operation obese and lean Zucker rats acted as controls.

RESULTS

Plasma cholesterol levels were elevated from 2 months after OLT, whereas plasma triglyceride levels were reduced (P<0.05). Plasma high-density lipoprotein cholesterol concentrations increased from the first month after OLT (P<0.05). HMP in OLT animals (137+/-3 perfusion units [PU]) (P<0.05) was intermediate between lean (221+/-11 PU) and obese controls (113+/-5 PU). Hepatic cord width in the OLT group was similar to that in lean controls. Mean liver-to-body weight ratios in OLT animals (4.12%+/-0.39%) were significantly higher than in lean controls (3.25%+/-0.1%). The number of viable hepatocytes per high-power field in the OLT animals was lower than in the lean animals but higher than in obese controls (P<0.05). The transplanted livers showed moderate to marked microvesicular fatty change (MIFC) and glycogen deposition at 3 months after OLT.

CONCLUSIONS

Transplantation of a nonsteatotic liver into an obese Zucker rat initially has a positive effect on lipid metabolism. However, 3 months after OLT, the donor liver became steatotic with MIFC changes and reduced perfusion. The authors' results emphasize the importance of the recipient's metabolic status in the maintenance of liver graft function after OLT.

8-Isoprostaglandin F2a and ascorbic acid concentration in the aqueous humour of patients with exfoliation syndrome

BACKGROUND/AIMS

The authors investigated the concentrations of 8-isoprostaglandin F(2a), a marker of oxidative stress in vivo, and ascorbic acid, a protectant against oxidative damage, in the aqueous humour of patients with exfoliation syndrome (XFS) and cataract and compared the results with those in age matched patients with cataract, but without XFS, to determine whether XFS is associated with increased oxidative stress.

METHODS

Aqueous humour was aspirated at the beginning of phacoemulsification cataract surgery from 27 eyes of 27 cataract patients with XFS and 27 eyes of 27 age matched cataract patients without XFS. 8-Isoprostaglandin F(2a)concentration in the aqueous was determined with a commercial immunoassay; ascorbic acid concentration was measured with a microplate assay method.

RESULTS

The mean concentration of 8-isoprostaglandin F(2a)in the aqueous from patients with XFS (2429 (SD 2940) pg/ml; range 400-10500 pg/ml) was significantly higher than that measured in the aqueous of age matched control patients (529.1 (226.8) pg/ml; range 325-1000 pg/ml); (p = 0.0028). Furthermore, mean ascorbic acid concentration in XFS patients (0.75 (0.39) mM; range 0.28-1.70 mM) was significantly lower than that found in control patients (1.19 (0.47) mM; range 0.53-2.4 mM); (p = 0.0005). There was a reverse correlation between 8-isoprostaglandin F(2a)and ascorbic acid concentration.

CONCLUSION

8-Isoprostaglandin F(2a)was significantly increased in the aqueous of patients with XFS, and ascorbic acid was decreased, providing evidence of a role for free radical induced oxidative damage in the pathobiology of XFS.

Genetic polymorphisms and the progression of liver fibrosis: a critical appraisal

Liver fibrosis is a highly dynamic process in which multiple genes interact with environmental factors. Recent human epidemiologic studies have identified possible polymorphisms in a number of candidate genes that influence the progression of liver fibrosis. These genetic factors could explain the broad spectrum of responses to the same etiologic agent found in patients with chronic liver diseases. Polymorphisms in genes encoding immunoregulatory proteins, proinflammatory cytokines, and fibrogenic factors may influence disease progression in patients with alcohol-induced liver disease, primary biliary cirrhosis, or chronic hepatitis C. However, some of the studies have yielded contradictory results. For example, conflicting results have been obtained in studies assessing the role of mutations in the hemochromatosis gene on fibrosis progression in patients with chronic hepatitis C. Large-scale, well-designed studies are required to clarify the actual role of this factor and other genetic variants in liver fibrosis.

Up-regulation of transforming growth factor-beta 1 in the spleen of aniline-treated rats

Aniline exposure produces selective toxicity to the spleen, leading to a variety of sarcomas in rats following chronic exposure. Fibrosis appears to be an important preneoplastic lesion of the spleen. However, early molecular events leading to splenic fibrosis are not known. Earlier studies have shown that aniline exposure in rats leads to excessive deposition of iron and increased lipid peroxidation in the spleen, which may produce changes in the expression of fibrogenic cytokines, such as transforming growth factor-beta 1 (TGF-beta 1), leading to splenic fibrosis. Therefore, this study was designed to establish whether aniline exposure leads to induction/overexpression of TGF-beta 1 and association of such induction with lipid peroxidation (oxidative stress) in the spleen. To achieve this, male Sprague-Dawley rats were given 1 mmol/kg/day aniline hydrochloride in water by gavage for 7 days, while controls received water only. Aniline treatment resulted in significant increases in spleen weight (97%), spleen-to-body weight ratios (104%), and splenocyte population (25%). Malondialdehyde-protein adducts, quantitated by a competitive ELISA, showed a 56% increase in the spleen of aniline-treated rats. TGF-beta 1, measured in the supernatants of cultured splenocytes by an ELISA specific for TGF-beta 1, showed a significant increase (60%) in the total TGF-beta 1 from aniline-treated rats. These increases were further confirmed by Western blot analysis, which showed approximately 2.5-fold increase in cell-associated TGF-beta 1 protein expression in aniline-treated rats. Furthermore, determination of TGF-beta 1 mRNA expression showed a 4-fold increase in the spleens of aniline-treated rats. These results suggest an association between formation of MDA-protein adducts and overexpression of TGF-beta 1 as a result of aniline insult, which together could promote splenic injury and fibrogenesis.

Chronic ethanol treatment: dolichol and retinol distribution in isolated rat liver cells

The aim of this study was to use chronic ethanol intoxication for 2 and 4 months as a means of studying the distribution of dolichol and retinol in isolated rat liver parenchymal cells, Kupffer cells, sinusoidal endothelial cells, and two subfractions of hepatic stellate cells: Ito 1 and Ito 2. Dolichol and retinol were studied in two batches of rats: on normal nutrition and after a load of vitamin A given 3 d before sacrifice. New observations reported are: (i) on normal nutrition, after 2 months of treatment, dolichol in HC seems to be the first target of chronic ethanol, while retinol is the first target in hepatic stellate cells; (ii) the various types of liver cells are differently affected by chronic ethanol, which highlights the importance of studying each type of sinusoidal cell; (iii) a load of vitamin A given when the damage has already occurred restores dolichol content in HC while retinol decreases; and, (iv) a link between dolichol and vitamin A metabolism might be supposed after the load of vitamin A: the percentage distribution of dolichol with 18 isoprene units (Dolichol -18) increases in all the control cells but decreases after chronic ethanol treatment. A different role of this dolichol and/or a different compartmentalization within the cell need to be further investigated.

Measurement of oxysterols and alpha-tocopherol in plasma and tissue samples as indices of oxidant stress status

Oxidant stress seems to play a role in several setting of human pathology, such as atherosclerosis, cancer, and aging. The study of oxidant stress in human disease should be based on the evaluation of either sensitive and specific markers of enhanced oxidant stress, such as oxysterols, or antioxidant defense, by measuring alpha-tocopherol. We have developed a rapid method to measure the oxysterols 7beta-hydroxycholesterol and 7-ketocholesterol in plasma (50 healthy subjects) and tissue as an index of oxidant stress in vivo, and from the same sample alpha-tocopherol content. The mean plasma concentration of 7beta-hydroxycholesterol and 7-ketocholesterol was 4.6+/-1.1 and 13.4+/-7.6 ng/mL, respectively. Plasma alpha-tocopherol concentration was 5.8+/-1.0 micromol/mol cholesterol. Samples from atherosclerotic plaques contained 20 times more cholesterol, about 45 times higher oxysterols levels, and 600 times more alpha-tocopherol compared to normal arteries. No significant difference in cholesterol and oxysterol content was observed between cirrhotic and normal liver. However, cirrhotic liver contained significantly smaller concentration of alpha-tocopherol compared to normal liver. In conclusion, we have developed a rapid and reliable method for the assay of cholesterol oxidation products and alpha-tocopherol in plasma and tissue useful for estimation of oxidant stress/antioxidant balance.

Advances in the Understanding and Treatment of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a well recognised form of chronic liver disease that has recently gained greater recognition. Originally described in the late 1950s, NAFLD is currently considered the leading cause of abnormal liver enzyme levels in the US, closely paralleling the increase in obesity and diabetes mellitus. NAFLD has a worldwide distribution, affecting both adults and children, and typically is seen in association with obesity, diabetes, hypertension and hypertriglyceridaemia. Most patients are asymptomatic and usually present with mild elevations in aminotransferases. The natural history of NAFLD is not clearly defined but progression to cirrhosis and end-stage liver disease is well recognised in some patients. The accumulation of hepatic steatosis is thought to occur initially, primarily through hepatic and peripheral insulin resistance, which leads to altered glucose and free fatty acid metabolism. The progression from simple fatty liver to more severe forms of NAFLD (nonalcoholic steatohepatitis and cirrhosis) is much less clear but evidence suggests that oxidative stress may preferentially enhance proinflammatory cytokines, which leads to cellular adaptations and dysfunction followed by development of inflammation, necrosis and fibrosis. Therapeutic modalities remain limited and are largely focused on correcting the underlying insulin resistance or reducing oxidative stress. However, at the present time, there are several limitations to the current potential therapies, mainly because of the lack of large-scale, prospective, randomised studies, as well as clearly defined histological endpoints. Ultimately, the future for potential therapeutic modalities to treat this disease are quite promising, but further research is needed to clearly demonstrate which therapy or therapies will be effective at eliminating fatty liver disease and its potential complications.

Oxidative stress in viral and alcoholic hepatitis

Liver damage ranges from acute hepatitis to hepatocellular carcinoma, through apoptosis, necrosis, inflammation, immune response, fibrosis, ischemia, altered gene expression and regeneration, all processes that involve hepatocyte, Kupffer, stellate, and endothelial cells. Reactive oxygen and nitrogen species (ROS, RNS) play a crucial role in the induction and in the progression of liver disease, independently from its etiology. They are involved in the transcription and activation of a large series of cytokines and growth factors that, in turn, can contribute to further production of ROS and RNS. The main sources of free radicals are represented by hepatocyte mitochondria and cytochrome p450 enzymes, by endotoxin-activated macrophages (Kupffer cells), and by neutrophils. The consequent alteration of cellular redox state is potentiated by the correlated decrease of antioxidant and energetic reserves. Indices of free radical-mediated damage, such as the increase of malondialdehyde, 4-hydroxynonenal, protein-adducts, peroxynitrite, nitrotyrosine, etc., and/or decrease of glutathione, vitamin E, vitamin C, selenium, etc., have been documented in patients with viral or alcoholic liver disease. These markers may contribute to the monitoring the degree of liver damage, the response to antiviral therapies and to the design of new therapeutic strategies. In fact, increasing attention is now paid to a possible "redox gene therapy." By enhancing the antioxidant ability of hepatocytes, through transgene vectors, one could counteract oxidative/nitrosative stress and, in this way, contribute to blocking the progression of liver disease.

Oxidative burst of Kupffer cells: target for liver injury treatment

Liver injury, and frequent consequent fibrosis, is the focus of a number of research groups ranging from molecular biologists to clinicians. It encompasses many aspects and approaches. Among biochemical events the role of Kupffer cells, oxidative stress and pro-inflammatory mediators are eminent. In this review we focus on recent findings into use of natural substances for the modulation of oxidative burst as well as production of inflammatory mediators by Kupffer cells.

DLPC decreases TGF-beta1-induced collagen mRNA by inhibiting p38 MAPK in hepatic stellate cells

Dilinoleoylphosphatidylcholine (DLPC), the active component of polyenylphosphatidylcholine extracted from soybeans, decreases collagen accumulation induced by TGF-beta1 in cultured hepatic stellate cells (HSCs). Because DLPC exerts antioxidant effects and TGF-beta1 generates oxidative stress, we evaluated whether the antifibrogenic effect of DLPC is linked to its antioxidant action. In passage 1 culture of rat HSCs, TGF-beta1 induced a concentration-dependent increase in procollagen-alpha(1)(I) mRNA levels and enhanced intracellular H(2)O(2) and superoxide anion formation and lipid peroxidation but decreased GSH levels. These changes were prevented by DLPC. Upregulation of collagen mRNA by TGF-beta1 was likewise inhibited by catalase and p38 MAPK inhibitor SB-203580, suggesting involvement of H(2)O(2) and p38 MAPK signaling in this process. TGF-beta1 or addition of H(2)O(2) to HSCs activated p38 MAPK with a rise in procollagen mRNA level; these changes were blocked by catalase and SB-203580 and likewise by DLPC. alpha-Smooth muscle actin abundance in HSCs was not altered by TGF-beta1 treatment (with or without DLPC), indicating that downregulation of procollagen mRNA by DLPC was not due to alteration in HSC activation. These results demonstrate that DLPC prevents TGF-beta1-induced increase in collagen mRNA by inhibiting generation of oxidative stress and associated H(2)O(2)-dependent p38 MAPK activation, which explains its antifibrogenic effect. DLPC, an innocuous phospholipid, may be considered for prevention and treatment of liver fibrosis.

Estrogen reduces CCL4- induced liver fibrosis in rats

AIM: Chronic liver diseases, such as fibrosis or cirrhosis, are more common in men than in women. This gender difference may be related to the effects of sex hormones on the liver. The aim of the present work was to investigate the effects of estrogen on CCL₄-induced fibrosis of the liver in rats.

METHODS: Liver fibrosis was induced in male, female and ovariectomized rats by CCL₄ administration. All the groups were treated with estradiol (1 mg/kg) twice weekly. And tamoxifen was given to male fibrosis model. At the end of 8 wk, all the rats were killed to study serum indicators and the livers.

RESULTS: Estradiol treatment reduced aspartate aminotransferase (AST), alanine aminotransferase (ALT), hyaluronic acid (HA) and type IV collagen (CIV) in sera, suppressed hepatic collagen content, decreased the areas of hepatic stellate cells (HSC) positive for α-smooth muscle actin (α-SMA), and lowered the synthesis of hepatic type I collagen significantly in both sexes and ovariectomy fibrotic rats induced by CCL₄ administration. Whereas, tamoxifen had the opposite effect. The fibrotic response of the female liver to CCL₄ treatment was significantly weaker than that of male liver.

CONCLUSION: Estradiol reduces CCL₄-induced hepatic fibrosis in rats. The antifibrogenic role of estrogen in the liver may be one reason for the sex associated differences in the progression from hepatic fibrosis to cirrhosis.

Oxidative stress in chronic hepatitis C: not just a feature of late stage disease

BACKGROUND/AIMS

Chronic hepatitis C infection is a major world-wide problem, frequently progressing to cirrhosis, liver failure or hepatoma. The pathological mechanisms of disease progression are unclear but oxidant stress may play a role.

METHODS

Markers of lipid peroxidation, antioxidant status, hepatic fibrogenesis and liver function were measured in blood or urine from 42 chronic hepatitis C patients. Fibrosis was graded histologically in a subgroup of 33 patients.

RESULTS

The lipid peroxidation marker 8-isoprostane and the ratio of oxidized to reduced glutathione were significantly elevated (P<0.001, P=0.006). The antioxidants glutathione, selenium and vitamins A, C and E were significantly decreased (all P<0.001) compared to age and sex matched controls. Abnormal values were more marked in cirrhotics, but significant changes were also observed in the non-cirrhotic group. The fibrosis score correlated positively with urinary 8-isoprostane and type III procollagen peptide and negatively with vitamin A.

CONCLUSIONS

Oxidant stress, as reflected in blood and urine by a wide range of pro- and antioxidant markers, is a significant feature of hepatitis C infection. Although more severe in the cirrhotic group, there was clear evidence of oxidant stress in non-cirrhotic patients. Antioxidant therapy may therefore have a role in slowing disease progression to cirrhosis.

Hepatobiliary pathology

Technologic advances using cDNA microarray hybridization, liver diseases characterized by mitochondrial DNA depletion, and new work characterizing bile salt transport problems in familial intrahepatic cholestasis syndromes were some of the major highlights of this past year. Analysis of normal livers by cDNA microarrays disclosed 2418 unique gene transcripts encoding a host of cellular structural and functional proteins. This technique was also applied to hepatocellular carcinoma, where enhanced expression of a number of genes involved in antiapoptosis and cell transformation may shed additional light on the process of hepatocarcinogenesis. Mitochondrial DNA depletion seen in Navajo neurohepatopathy and in respiratory chain disorders of infancy was associated with cholestasis and cirrhosis in the former and microvesicular steatosis and oncocytic transformation (mitochondrial hyperplasia) in the latter. Pathologists who routinely examine liver biopsies after liver or bone marrow transplantation should be aware of unusual biopsy features that mimic other diseases, such as the autoimmune hepatitis-like syndrome that may follow liver transplantation and chronic graft-versus-host disease that clinically and pathologically resembles acute hepatitis.