Oxidative DNA damage in circulating leukocytes occurs as an early event in chronic HCV infection

Impact of amino acid substitutions in hepatitis C virus core region on the severe oxidative stress

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease, leading to liver steatosis, fibrosis, and hepatocellular carcinoma (HCC). Despite the accumulation of clinical data showing the impact of amino acid substitutions at positions 70 (R70Q/H) and/or 91 (L91M) in the HCV core protein in progressive liver diseases, including HCC, the underlying mechanisms have not been elucidated. We analyzed 72 liver biopsy specimens from patients with chronic HCV genotype 1b (HCV-1b) infection prior to antiviral treatment. Levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nuclear factor erythroid 2-related factor 2 (NRF2) in the nucleus were quantified using liver tissue immunohistochemistry. The effects of amino acid substitutions in the HCV core region on hepatocellular oxidative stress were investigated using wild-type or double-mutant (R70Q/H+L91M) HCV-1b core transfection and stable expression in human hepatoma HuH-7 cells. Overall, 24, 19, 11, and 18 patients had the wild-type, R70Q/H, L91M, and R70Q/H+L91M genotypes, respectively, in the HCV core. A significantly higher accumulation of hepatocellular 8-OHdG and a lower NRF2/8-OHdG ratio were observed in patients with R70Q/H+L91M than in those with the wild-type disease. Increased levels of intracellular superoxide and hydrogen peroxide in the cytoplasm and mitochondria, mRNA expression of enzymes generating oxidative stress, and nuclear expression of nicotinamide adenine dinucleotide phosphate oxidase 4 were augmented in cells treated with R70Q+L91M. HCV core proteins harboring either or both substitutions of R70Q/H or L91M enhanced hepatocellular oxidative stress in vivo and in vitro. These amino acid substitutions may affect HCC development by enhancing hepatic oxidative stress in patients with chronic HCV-1b infection.

Utility of comet assay of DNA damage in the detection of malignant transformation of chronic liver cirrhosis

Early detection of hepatocellular carcinoma (HCC) remains a great challenge in laboratory medicine. This study aimed to assess the ability to use the degree of DNA damage (using the comet assay) for the early detection of malignant transformation of liver cirrhosis (LC) to HCC. We used alkaline comet assay for measuring DNA damage in peripheral blood lymphocytes in 50 patients with chronic LC and 50 patients with HCC. Fifty healthy individuals served as a control group. We compared the results of comet assay parameters with alpha fetoprotein as a relevant traditional marker. The HCC group was associated with a significantly higher tail intensity (p=.004), tail moment (p=.016), total area (p=.003), total intensity (p=.010), width (p=.005), and a significantly lower head intensity (.004) when compared to the LC group. Good areas under the curve (AUCs) were found for total area (0.890), head intensity (0.880) and tail intensity (0.880), making it useful for discrimination between HCC and LC groups. Lower head intensity, higher tail intensity, tail moment, total area and width were found to be independent risk factors for HCC on top of LC. Measuring DNA damage using the Alkaline comet assay technique can be considered a sensitive and reliable diagnostic tool for early neoplastic transformation of advanced LC.

Detecting free radicals post viral infections

Free radical generation plays a key role in viral infections. While free radicals have an antimicrobial effect on bacteria or fungi, their interplay with viruses is complicated and varies greatly for different types of viruses as well as different radical species. In some cases, radical generation contributes to the defense against the viruses and thus reduces the viral load. In other cases, radical generation induces mutations or damages the host tissue and can increase the viral load. This has led to antioxidants being used to treat viral infections. Here we discuss the roles that radicals play in virus pathology. Furthermore, we critically review methods that facilitate the detection of free radicals in vivo or in vitro in viral infections.

Hepatitis C virus eradication by direct antiviral agents abates oxidative stress in patients with advanced liver fibrosis

BACKGROUND AND AIMS

HCV eradication improves non-hepatic outcomes such as cardiovascular diseases, although without clearly defined mechanisms. In this study we aimed to assess whether improvement of carotid atherosclerosis may be linked to a reduction in systemic oxidative stress after viral clearance.

METHODS

We studied a retrospective cohort of 105 patients (age 62.4 ± 11.2 years; 62 men) with F3/F4 fibrosis, characterized by carotid ultrasonography at baseline and at sustained virologic response (SVR) follow-up. Levels of 8-iso-prostaglandin F_2α (F₂ -isoprostanes) and other oxidative stress markers were measured on frozen sera. Association between change (denoted as Δ) in oxidative stress markers (exposures) and change in carotid intima-media thickness (cIMT) (outcome) was examined using multiple linear regression.

RESULTS

Subclinical atherosclerosis, defined as the presence of carotid plaque and/or cIMT ≥ 0.9, was present in 72% of the cohort. All patients achieved SVR that led to reduction in cIMT (0.92 ± 0.20 vs 0.83 ± 0.21 mm, P < .001). HCV eradication markedly decreased serum levels of F₂ -isoprostanes (620.5 [143.2; 1904.1] vs 119.51 [63.2; 400.6] pg/mL, P < .0001), lipid hydroperoxides (13.8 [6.3; 20.7] vs 4.9 [2.3; 9.6] nmol/μl, P < .0001) and 8-hydroxy-2'-deoxyguanosine (558.9 [321.0; 6301.2] vs 294.51 [215.31; 408.95] pg/mL, P < .0001), whereas increased serum GPx activity (10.44 [4.6; 16.3] vs 13.75 [9.42; 20.63] nmol/min/mL, P = .001). By multiple linear regression analysis ΔcIMT was independently associated with ΔF₂ -isoprostanes (β: 1.746 [0.948; 2.543]; P < .0001) after adjustment for age, baseline F₂ -isoprostanes and baseline IMT.

CONCLUSIONS

Besides association of lipid peroxidation with severity of liver disease, the reduction in F₂ -isoprostanes may be involved in the improvement of atherosclerosis after HCV eradication.

A decrease in hepatitis C virus RNA to undetectable levels in chronic hepatitis C patients after PegIFNα + RVB or sofosbuvir + NS5A inhibitor treatment is associated with decreased insulin resistance and persistent oxidative stress

Oxidative stress (OS) and insulin resistance (IR) induced by hepatitis C virus (HCV) infection, are involved in the development of chronic hepatitis C (CHC) complications and progression to hepatocellular carcinoma. The aim of this study was to investigate the effect of pegylated interferon alpha (IFNα) + ribavirin (PegIFNα+RVB) or sofosbuvir + NS5A inhibitor (SOF+InNS5A) on IR and the components of OS. HCV was genotyped in 20 CHC patients grouped by treatment with either PegIFNα+RVB (n = 10) or SOF+InNS5A (n = 10). The treatment's effect on OS-induced damage to lipids (HNE-HDL), proteins (advanced glycation end products [AGEs]), and DNA (8-OHdG) as well as the concentrations of proinflammatory cytokines (IL-2, TNFα, IFNγ), ALT, AST, GSH and platelets was determined. Superoxide dismutase (SOD) and catalase activity as well as IR, determined by the HOMA1-IR index, was evaluated. The HCV genotypes (GT) found were GT1b (45%), GT1a (30%), GT2b (20%), and GT2a (5%). Viral RNA became undetectable by week 12 with SOF+InNS5A in 100% of the cases and with PegIFNα+RVB in 70% of the cases. After viral RNA became undetectable, regardless of treatment and GT, a significant increase in the platelet concentration and SOD activity was observed, whereas ALT, insulin, and IR decreased (p < 0.05). However, only for the SOF+InNS5A treated group was there an increase in oxidative damage to lipids (p < 0.017) and proteins (p < 0.05). None of the other parameters demonstrated any differences. These data confirm that OS persisted after treatment with either SOF+InNS5A or PegIFNα+RVB. IR could be considered a response biomarker to treatment with direct-acting antivirals.

Flaviviridae Viruses and Oxidative Stress: Implications for Viral Pathogenesis

Oxidative stress is induced once the balance of generation and neutralization of reactive oxygen species (ROS) is broken in the cell, and it plays crucial roles in a variety of natural and diseased processes. Infections of Flaviviridae viruses trigger oxidative stress, which affects both the cellular metabolism and the life cycle of the viruses. Oxidative stress associated with specific viral proteins, experimental culture systems, and patient infections, as well as its correlations with the viral pathogenesis attracts much research attention. In this review, we primarily focus on hepatitis C virus (HCV), dengue virus (DENV), Zika virus (ZIKV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and tick-borne encephalitis virus (TBEV) as representatives of Flaviviridae viruses and we summarize the mechanisms involved in the relevance of oxidative stress for virus-associated pathogenesis. We discuss the current understanding of the pathogenic mechanisms of oxidative stress induced by Flaviviridae viruses and highlight the relevance of autophagy and DNA damage in the life cycle of viruses. Understanding the crosstalk between viral infection and oxidative stress-induced molecular events may offer new avenues for antiviral therapeutics.

An intronic single nucleotide polymorphism in the MUTYH gene is associated with increased risk for HCV-induced hepatocellular carcinoma

BACKGROUND & AIMS

The role of base excision repair genes in human hepatocarcinogenesis has not yet been explored. Here, we investigated relationships between variants of these genes and the risk of developing hepatocellular carcinoma (HCC).

METHODS

Nineteen tagging SNPs in base excision repair genes (including MUTYH, OGG1 and MTH1) were genotyped using iPLEX assays; one significant SNP was found and confirmed in Japanese patients with chronic hepatitis C (CHC) (n = 38 HCC and 55 controls). The effects of modifying the intronic variants were determined by luciferase assays. MUTYH-null mice were used to examine the involvement of oxidative stress and DNA repair enzymes in hepatocarcinogenesis.

RESULTS

Significant associations were found for a single intron SNP (rs3219487) in the MUTYH gene. The risk of developing HCC in patients with A/A or G/A genotypes was higher than in those with the G/G genotype (OR = 9.27, 95% CI = 2.39 -32.1, P = 0.0005). MUTYH mRNA levels in both peripheral mononuclear cells were significantly lower in G/A or A/A genotyped subjects (P = 0.0157 and 0.0108, respectively). We found that -2000 in the MUTYH promoter region is involved in enhanced expression of MUTYH by insertion of a major allele sequence of rs3219487. Liver tumors were observed in MUTYH-null mice after 12 months´ high iron diet, but no tumors developed when dietary anti-oxidant (N-Acetyl-L-cysteine) was also provided.

CONCLUSIONS

CHC patients with the rs3219487 adenine allele had a significantly increased risk of developing HCC. MUTYH-null mice with iron-associated oxidative stress were susceptible to development of liver tumors unless prevented by dietary anti-oxidants.

Oxidative stress, a trigger of hepatitis C and B virus-induced liver carcinogenesis

Virally induced liver cancer usually evolves over long periods of time in the context of a strongly oxidative microenvironment, characterized by chronic liver inflammation and regeneration processes. They ultimately lead to oncogenic mutations in many cellular signaling cascades that drive cell growth and proliferation. Oxidative stress, induced by hepatitis viruses, therefore is one of the factors that drives the neoplastic transformation process in the liver. This review summarizes current knowledge on oxidative stress and oxidative stress responses induced by human hepatitis B and C viruses. It focuses on the molecular mechanisms by which these viruses activate cellular enzymes/systems that generate or scavenge reactive oxygen species (ROS) and control cellular redox homeostasis. The impact of an altered cellular redox homeostasis on the initiation and establishment of chronic viral infection, as well as on the course and outcome of liver fibrosis and hepatocarcinogenesis will be discussed The review neither discusses reactive nitrogen species, although their metabolism is interferes with that of ROS, nor antioxidants as potential therapeutic remedies against viral infections, both subjects meriting an independent review.

The Relationship Between Single-Nucleotide Polymorphisms, the Expression of DNA Damage Response Genes, and Hepatocellular Carcinoma in a Polish Population

The molecular mechanism of hepatocellular carcinoma (HCC) is related to DNA damage caused by oxidative stress products induced by hepatitis B virus (HBV) or C (HCV) infection and exposure to environmental pollutants. Single-nucleotide polymorphisms (SNPs) of DNA damage response (DDR) genes may influence individual susceptibility to environmental risk factors and affect DNA repair efficacy, which, in turn, can influence the risk of HCC. The study evaluates a panel of 15 SNPs in 11 DDR genes (XRCC1, XRCC3, XPD, MUTYH, LIG1, LIG3, hOGG1, PARP1, NFIL1, FEN1, and APEX1) in 65 HCC patients, 50 HBV- and 50 HCV-infected non-cancerous patients, and 50 healthy controls. It also estimates the mRNA expression of nine DDR genes in cancerous and adjacent healthy liver tissues. Two of the investigated polymorphisms (rs1052133 and rs13181) were associated with HCC risk. For all investigated genes, the level of mRNA was significantly lower in HCC cancer tissue than in non-cancerous liver tissue. Seven of the investigated polymorphisms were statistically related to gene expression in cancer tissues. The disruption of DDR genes may be responsible for hepatocellular transformation in HCV-infected patients.

Implications of oxidative stress on viral pathogenesis

Reactive species are frequently formed after viral infections. Antioxidant defences, including enzymatic and non-enzymatic components, protect against reactive species, but sometimes these defences are not completely adequate. An imbalance in the production of reactive species and the body's inability to detoxify these reactive species is referred to as oxidative stress. The aim of this review is to analyse the role of oxidative stress in the pathogenesis of viral infections and highlight some major therapeutic approaches that have gained importance, with regards to controlling virus-induced oxidative injury. Attention will be focused on DNA viruses (papillomaviruses, hepadnaviruses), RNA viruses (flaviviruses, orthomyxoviruses, paramyxoviruses, togaviruses) and retroviruses (human immunodeficiency virus). In general, viruses cause an imbalance in the cellular redox environment, which depending on the virus and the cell can result in different responses, e.g. cell signaling, antioxidant defences, reactive species, and other processes. Therefore, the modulation of reactive species production and oxidative stress potentially represents a novel pharmacological approach for reducing the consequences of viral pathogenesis.

Oxidative stress correlates with Wolbachia-mediated antiviral protection in Wolbachia-Drosophila associations

Wolbachia mediates antiviral protection in insect hosts and is being developed as a potential biocontrol agent to reduce the spread of insect-vectored viruses. Definition of the molecular mechanism that generates protection is important for understanding the tripartite interaction between host insect, Wolbachia, and virus. Elevated oxidative stress was previously reported for a mosquito line experimentally infected with Wolbachia, suggesting that oxidative stress is important for Wolbachia-mediated antiviral protection. However, Wolbachia experimentally introduced into mosquitoes impacts a range of host fitness traits, some of which are unrelated to antiviral protection. To explore whether elevated oxidative stress is associated with antiviral protection in Wolbachia-infected insects, we analyzed oxidative stress of five Wolbachia-infected Drosophila lines. In flies infected with protective Wolbachia strains, hydrogen peroxide concentrations were 1.25- to 2-fold higher than those in paired fly lines cured of Wolbachia infection. In contrast, there was no difference in the hydrogen peroxide concentrations in flies infected with nonprotective Wolbachia strains compared to flies cured of Wolbachia infection. Using a Drosophila mutant that produces increased levels of hydrogen peroxide, we investigated whether flies with high levels of endogenous reactive oxygen species had altered responses to virus infection and found that flies with high levels of endogenous hydrogen peroxide were less susceptible to virus-induced mortality. Taken together, these results suggest that elevated oxidative stress correlates with Wolbachia-mediated antiviral protection in natural Drosophila hosts.

Increased DNA damage in hepatitis C virus-related hepatocellular carcinoma

One consequence of hepatitis C virus (HCV) infection is an elevated cancer risk. During chronic viral infection, deoxyribonucleic acid (DNA) damage is being induced by reactive oxygen and nitrogen species, which may play a pathogenic role in HCV-induced carcinogenesis. The study investigated DNA damage in peripheral blood lymphocytes from patients with hepatocellular carcinoma (HCC) and those with HCV infection with and without associated cirrhosis and normal controls. As a measure for genomic damage, the comet assay (single cell gel electrophoresis) was applied, which detects single- and double-strand breaks and alkali-labile sites through electrophoretic mobility of the resulting fragments. The levels of DNA damage were significantly higher in HCC and HCV-associated cirrhosis compared to HCV without cirrhosis and the control group. Patients presenting with DNA damage more than mean+two standard deviation of the controls had a 3.6-fold risk of having HCC more than those with undamaged DNA. HCV disease progression was the only discriminator predicting the extent of DNA damage. The accumulation of DNA damage is important in HCC evolution. DNA damage indicating intracellular oxidative and nitrative stress may lead to mutagenesis and consequently malignant transformation, which emphasizes the need to optimize the therapy for reducing the degree of genomic damage.

Oxidative stress and hepatic Nox proteins in chronic hepatitis C and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common liver cancer and a leading cause of cancer-related mortality in the world. Hepatitis C virus (HCV) is a major etiologic agent of HCC. A majority of HCV infections lead to chronic infection that can progress to cirrhosis and, eventually, HCC and liver failure. A common pathogenic feature present in HCV infection, and other conditions leading to HCC, is oxidative stress. HCV directly increases superoxide and H2O2 formation in hepatocytes by elevating Nox protein expression and sensitizing mitochondria to reactive oxygen species generation while decreasing glutathione. Nitric oxide synthesis and hepatic iron are also elevated. Furthermore, activation of phagocytic NADPH oxidase (Nox) 2 of host immune cells is likely to exacerbate oxidative stress in HCV-infected patients. Key mechanisms of HCC include genome instability, epigenetic regulation, inflammation with chronic tissue injury and sustained cell proliferation, and modulation of cell growth and death. Oxidative stress, or Nox proteins, plays various roles in these mechanisms. Nox proteins also function in hepatic fibrosis, which commonly precedes HCC, and Nox4 elevation by HCV is mediated by transforming growth factor β. This review summarizes mechanisms of oncogenesis by HCV, highlighting the roles of oxidative stress and hepatic Nox enzymes in HCC.

Myeloperoxidase gene polymorphism predicts fibrosis severity in women with hepatitis C

Oxidative stress plays an important role on liver fibrosis progression in the course of hepatitis C virus (HCV) infection. Myeloperoxidase (MPO) is an enzyme released by neutrophils and macrophages, responsible for generating hypochlorous acid and reactive oxygen species (ROS) that may lead to liver injury in HCV infection. On the other hand, antioxidant enzymes such as manganese superoxide dismutase (SOD) controls ROS-mediated damage. The aim of the present study was to investigate the influence of MPO G-463A and SOD2 Ala16Val polymorphisms in the severity of liver fibrosis in individuals with chronic HCV infection. The present study included 270 patients with chronic HCV recruited from the Gastrohepatology Service of the Oswaldo Cruz University Hospital/Liver Institute of Pernambuco (Recife, Northeastern Brazil). All patients underwent liver biopsy, which was classified according METAVIR score. The SNPs were determined by real-time PCR. After multivariate analysis adjustment, the GG genotype of MPO and the presence of metabolic syndrome were independently associated with fibrosis severity in women (P = 0.025 OR 2.25 CI 1.10-4.59 and P = 0.032 OR 2.32 CI 1.07-5.01, respectively). The presence of the GG genotype seems to be a risk factor for fibrosis severity in women with HCV.

Increased frequency of micronuclei in the lymphocytes of patients chronically infected with hepatitis B or hepatitis C virus

In this study, we analysed the frequency of micronuclei (MN), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) and evaluated mutagen-induced sensitivity in the lymphocytes of patients chronically infected with hepatitis B virus (HBV) or hepatitis C virus (HCV). In total, 49 patients with chronic viral hepatitis (28 HBV-infected and 21 HCV-infected patients) and 33 healthy, non-infected blood donor controls were investigated. The frequencies (‰) of MN, NPBs and NBUDs in the controls were 4.41 ± 2.15, 1.15 ± 0.97 and 2.98 ± 1.31, respectively. The frequencies of MN and NPBs were significantly increased (p < 0.0001) in the patient group (7.01 ± 3.23 and 2.76 ± 2.08, respectively) compared with the control group. When considered separately, the HBV-infected patients (7.18 ± 3.57) and HCV-infected patients (3.27 ± 2.40) each had greater numbers of MN than did the controls (p < 0.0001). The HCV-infected patients displayed high numbers of NPBs (2.09 ± 1.33) and NBUDs (4.38 ± 3.28), but only the HBV-infected patients exhibited a significant difference (NPBs = 3.27 ± 2.40, p < 0.0001 and NBUDs = 4.71 ± 2.79, p = 0.03) in comparison with the controls. Similar results were obtained for males, but not for females, when all patients or the HBV-infected group was compared with the controls. The lymphocytes of the infected patients did not exhibit sensitivity to mutagen in comparison with the lymphocytes of the controls (p = 0.06). These results showed that the lymphocytes of patients who were chronically infected with HBV or HCV presented greater chromosomal instability.

Insulin resistance is associated with DNA damage in peripheral blood cells in non-diabetic patients with genotype 1 chronic hepatitis C

BACKGROUND

In chronic liver diseases of different etiologies, including viral hepatitis, genotoxic effects of oxidative stress have been shown, both in clinical and in experimental conditions, suggesting that this mechanism may contribute to the evolution of the disease.

AIM

To evaluate DNA damage in the peripheral blood of untreated non-diabetic patients with chronic hepatitis C and control subjects, and its correlation with demographic, anthropometric, biochemical, and histological parameters in the patient sample.

PATIENTS AND METHODS

This study comprised 100 subjects of both genders, 60 of whom were treatment-naïve patients with positive serology for genotype 1 hepatitis C. The remaining 40 were blood donors with negative serology for hepatitis who were used as control subjects, and matched by gender, age, weight, and BMI. DNA damage was determined using the comet assay in the total peripheral blood.

RESULTS

The DNA damage evaluated by the comet assay revealed higher values in the group of patients with hepatitis compared with that in the control group. The relationships of the comet assay with the studied variables were assessed using multivariate analysis; significant correlations were only identified with insulin (r = 0.343, p = 0.008) and Homeostasis Model Assessment Insulin Resistance (HOMA-IR) (r = 0.331, p = 0.011).

CONCLUSION

Patients with genotype 1 chronic hepatitis C have higher rates of DNA damage, as determined by comet assay and this alteration is correlated with the HOMA index of insulin resistance.

Effects of coffee consumption in chronic hepatitis C: a randomized controlled trial

BACKGROUND

Coffee is associated with a reduced risk of hepatocellular carcinoma in patients with chronic C hepatitis. This prospective trial was aimed at assessing the mechanisms underlying coffee-related protective effects.

METHODS

Forty patients with chronic hepatitis C were randomized into two groups: the first consumed 4 cups of coffee/day for 30 days, while the second remained coffee "abstinent". At day 30, the groups were switched over for a second month.

RESULTS

At baseline, aspartate aminotransferase and alanine aminotransferase were lower in patients drinking 3-5 (Group B) than 0-2 cups/day (Group A) (56 ± 6 vs 74 ± 11/60 ± 3 vs 73 ± 7 U/L p=0.05/p=0.04, respectively). HCV-RNA levels were significantly higher in Group B [(6.2 ± 1.5) × 10(5)vs (3.9 ± 1.0) × 10(5)UI/mL, p=0.05]. During coffee intake, 8-hydroxydeoxyguanosine and collagen levels were significantly lower than during abstinence (15 ± 3 vs 44 ± 16 8-hydroxydeoxyguanosine/10(5)deoxyguanosine, p=0.05 and 56 ± 9 vs 86 ± 21 ng/mL, p=0.04). Telomere length was significantly higher in patients during coffee intake (0.68 ± 0.06 vs 0.48 ± 0.04 Arbitrary Units, p=0.006). Telomere length and 8-hydroxydeoxyguanosine were inversely correlated.

CONCLUSION

In chronic hepatitis C coffee consumption induces a reduction in oxidative damage, correlated with increased telomere length and apoptosis, with lower collagen synthesis, factors that probably mediate the protection exerted by coffee with respect to disease progression.

Theoretical basis of a beneficial role for vitamin D in viral hepatitis

Abnormal bone metabolism and dysfunction of the calcium-parathyroid hormone-vitamin D axis have been reported in patients with viral hepatitis. Some studies suggested a relationship between vitamin D and viral hepatitis. Genetic studies have provided an opportunity to identify the proteins that link vitamin D to the pathology of viral hepatitis (i.e., the major histocompatibility complex class II molecules, the vitamin D receptor, cytochrome P₄₅₀, the renin-angiotensin system, apolipoprotein E, liver X receptor, toll-like receptor, and the proteins regulated by the Sp1 promoter gene). Vitamin D also exerts its effects on viral hepatitis via non-genomic factors, i.e., matrix metalloproteinase, endothelial vascular growth factor, prostaglandins, cyclooxygenase-2, and oxidative stress. In conclusion, vitamin D could have a beneficial role in viral hepatitis. Calcitriol is best used for viral hepatitis because it is the active form of the vitamin D₃ metabolite.

Oxidative stress, endogenous antioxidants, alcohol, and hepatitis C: pathogenic interactions and therapeutic considerations

Hepatitis C virus (HCV) is a blood-borne pathogen that was identified as an etiologic agent of non-A, non-B hepatitis in 1989. HCV is estimated to have infected at least 170 million people worldwide. The majority of patients infected with HCV do not clear the virus and become chronically infected, and chronic HCV infection increases the risk for hepatic steatosis, cirrhosis, and hepatocellular carcinoma. HCV induces oxidative/nitrosative stress from multiple sources, including inducible nitric oxide synthase, the mitochondrial electron transport chain, hepatocyte NAD(P)H oxidases, and inflammation, while decreasing glutathione. The cumulative oxidative burden is likely to promote both hepatic and extrahepatic conditions precipitated by HCV through a combination of local and more distal effects of reactive species, and clinical, animal, and in vitro studies strongly point to a role of oxidative/nitrosative stress in HCV-induced pathogenesis. Oxidative stress and hepatopathogenesis induced by HCV are exacerbated by even low doses of alcohol. Alcohol and reactive species may have other effects on hepatitis C patients such as modulation of the host immune system, viral replication, and positive selection of HCV sequence variants that contribute to antiviral resistance. This review summarizes the current understanding of redox interactions of HCV, outlining key experimental findings, directions for future research, and potential applications to therapy.

Role of nitrative and oxidative DNA damage in inflammation-related carcinogenesis

Chronic inflammation induced by biological, chemical, and physical factors has been found to be associated with the increased risk of cancer in various organs. We revealed that infectious agents including liver fluke, Helicobacter pylori, and human papilloma virus and noninfectious agents such as asbestos fiber induced iNOS-dependent formation of 8-nitroguanine and 8-oxo-7, 8-dihydro-2′-deoxyguanosine (8-oxodG) in cancer tissues and precancerous regions. Our results with the colocalization of phosphorylated ATM and γ-H2AX with 8-oxodG and 8-nitroguanine in inflammation-related cancer tissues suggest that DNA base damage leads to double-stranded breaks. It is interesting from the aspect of genetic instability. We also demonstrated IL-6-modulated iNOS expression via STAT3 and EGFR in Epstein-Barr-virus-associated nasopharyngeal carcinoma and found promoter hypermethylation in several tumor suppressor genes. Such epigenetic alteration may occur by controlling the DNA methylation through IL-6-mediated JAK/STAT3 pathways. Collectively, 8-nitroguanine would be a useful biomarker for predicting the risk of inflammation-related cancers.

Hepatitis C virus-induced oxidative stress and mitochondrial dysfunction: a focus on recent advances in proteomics

The natural history of chronic hepatitis C virus (HCV) infection presents two major aspects. On one side, the illness is by itself benign, whereas, on the other side, epidemiological evidence clearly identifies chronic HCV infection as the principal cause of cirrhosis, hepatocellular carcinoma, and extrahepatic diseases, such as autoimmune type II mixed cryoglobulinemia and some B cell non-Hodgkin's lymphomas. The mechanisms responsible for the progression of liver disease to severe liver injury are still poorly understood. Nonetheless, considerable biological data and studies from animal models suggest that oxidative stress contributes to steatohepatitis and that the increased generation of reactive oxygen and nitrogen species, together with the decreased antioxidant defense, promotes the development of hepatic and extrahepatic complications of HCV infection. The principal mechanisms causing oxidative stress in HCV-positive subjects have only been partially elucidated and have identified chronic inflammation, iron overload, ER stress, and a direct activity of HCV proteins in increasing mitochondrial ROS production, as key events. This review summarizes current knowledge regarding mechanisms of HCV-induced oxidative stress with its long-term effects in the context of HCV-related diseases, and includes a discussion of recent contributions from proteomics studies.

Circulating Biomarkers and their Possible Role in Pathogenesis of Chronic Hepatitis B and C Viral Infections

The present study evaluated the plausible role of circulating biomarkers in immune pathogenesis of chronic hepatitis considered a priority in clinical hepatology. Total viral load of chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) patients was quantified and correlation studies were performed with circulating levels of Th1/Th2 cytokines; C reactive protein and circulating nucleosomes; glutathione reductase (GR) and superoxide dismutase. To our knowledge, the study is first among its kind that validates strong positive correlation of viral load with IL-4, IL-6, GR in HBV and IL-6, IL-10, GR in HCV infections. Although, multi-centric studies including large cohorts are required for translating our findings to clinical practice, however, role of these biomarkers with potential diagnostic or prognostic significance might be helpful in clinical assessment of high-risk individuals, thereby, designing interventional strategies, towards development of personalized medicare. The results of our study also offer valuable insights of immune signaling mediators engaged in development of hepatocellular carcinoma.

Chronic hepatitis virus infection in patients with multiple myeloma: clinical characteristics and outcomes

OBJECTIVES

Cytotoxic agents and steroids are used to treat lymphoid malignancies, but these compounds may exacerbate chronic viral hepatitis. For patients with multiple myeloma, the impact of preexisting hepatitis virus infection is unclear. The aim of this study is to explore the characteristics and outcomes of myeloma patients with chronic hepatitis virus infection.

METHODS

From 2003 to 2008, 155 myeloma patients were examined to determine their chronic hepatitis virus infection statuses using serologic tests for the hepatitis B (HBV) and C viruses (HCV). Clinical parameters and outcome variables were retrieved via a medical chart review.

RESULTS

The estimated prevalences of chronic HBV and HCV infections were 11.0% (n = 17) and 9.0% (n = 14), respectively. The characteristics of patients who were hepatitis virus carriers and those who were not were similar. However, carrier patients had a higher prevalence of conventional cytogenetic abnormalities (64.3% vs. 25.0%). The cumulative incidences of grade 3-4 elevation of the level of alanine transaminase, 30.0% vs. 12.0%, and hyperbilirubinemia, 20.0% vs. 1.6%, were higher in carriers as well. In a Kaplan-Meier analysis, carrier patients had worse overall survival (median: 16.0 vs. 42.4 months). The prognostic value of carrier status was not statistically significant in the multivariate analysis, but an age of more than 65 years old, the presence of cytogenetic abnormalities, a beta-2-microglobulin level of more than 3.5 mg/L, and a serum creatinine level of more than 2 mg/ dL were independent factors associated with poor prognosis.

CONCLUSION

Myeloma patients with chronic hepatitis virus infections might be a distinct subgroup, and close monitoring of hepatic adverse events should be mandatory.

Protective effects of Rhodiola sachalinensis A. Bor on liver fibrosis: recent advances

Liver fibrosis is a common chronic liver disease and may progress to hepatic cirrhosis. The research on early blockade of early liver fibrosis has become a hot topic. Recently, there has been a considerable amount of research concentrated on the pathogenesis of liver fibrosis. Great achievements have been achieved in the treatment of liver fibrosis with Chinese medicine. Some studies have demonstrated that Rhodiola sachalinensis A. Bor can resist hypoxia, ageing and fibrosis. Here we give a brief review on the protective effects of Rhodiola sachalinensis A. Bor on experimental liver fibrosis.

Impact of amino acid substitutions in the hepatitis C virus genotype 1b core region on liver steatosis and hepatic oxidative stress in patients with chronic hepatitis C

BACKGROUND

Liver steatosis and hepatic oxidative stress are the histopathological features of chronic hepatitis C. Hepatitis C virus (HCV) genotype 1 core protein induces hepatic steatosis and reactive oxygen species production in transgenic mice. The amino acid substitutions in the HCV core region appear to be related to hepatocarcinogenesis.

AIMS

The aim of this study was to clarify the impact of mutations in the HCV core region on oxidative stress and lipid metabolism in patients with chronic hepatitis C.

METHODS

Sixty-seven patients (35 men, 32 women; mean age, 58.4 +/- 10.2 years) with chronic hepatitis C with high titres (>5 log IU/ml) were enrolled. Substitutions in amino acids 70, 75 and 91 of the HCV genotype 1b core region, the percentage of hepatic steatosis, and hepatic 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels were investigated in all patients. Urinary 8-OHdG levels were measured in 35 patients.

RESULTS

Body mass index, alanine aminotransferase, gamma-glutamyl transferase, and triglyceride levels and substitutions of amino acid 70/Q (glutamine) were significantly associated with the presence of steatosis on univariate analysis. Multivariate analysis showed that substitution of amino acid 70 of glutamine and triglyceride levels were the independent factors related to liver steatosis. Hepatic and urinary 8-OHdG levels were significantly higher in patients with methionine at amino acid 91 of the HCV core region than in those with leucine.

CONCLUSION

Substitutions in the amino acids of the HCV genotype1b core region are associated with hepatic steatosis and oxidative stress in patients with chronic hepatitis C.

Role of dietary antioxidants in the prevention of in vivo oxidative DNA damage

Epidemiological evidence consistently shows that diets high in fresh fruit and vegetables significantly lower cancer risk. Given the postulated role of oxidative DNA damage in carcinogenesis, the assumption has been made that it is the antioxidant properties of food constituents, such as vitamin C, E and carotenoids, which confer protection. However, epidemiological studies with specific antioxidants, either singly or in combination, have not, on the whole, supported this hypothesis. In contrast, studies examining the in vitro effect of antioxidants upon oxidative DNA damage have generally been supportive, in terms of preventing damage induction. The same, however, cannot be said for the in vivo intervention studies where overall the results have been equivocal. Nevertheless, recent work has suggested that some dietary antioxidants may confer protective properties through a novel mechanism, unrelated to their conventional free-radical scavenging abilities. Upregulation of antioxidant defence, xenobiotic metabolism, or DNA-repair genes may all limit cellular damage and hence promote maintenance of cell integrity. However, until further work has clarified whether dietary supplementation with antioxidants confers a reduced risk of cancer and the mechanism by which this effect is exerted, the recommendation for a diet rich in fruit and vegetables remains valid empirically.

Role of free radicals in liver diseases

Reactive oxygen and nitrogen species (ROS and RNS) are produced by metabolism of normal cells. However, in liver diseases, redox is increased thereby damaging the hepatic tissue; the capability of ethanol to increase both ROS/RNS and peroxidation of lipids, DNA, and proteins was demonstrated in a variety of systems, cells, and species, including humans. ROS/RNS can activate hepatic stellate cells, which are characterized by the enhanced production of extracellular matrix and accelerated proliferation. Cross-talk between parenchymal and nonparenchymal cells is one of the most important events in liver injury and fibrogenesis; ROS play an important role in fibrogenesis throughout increasing platelet-derived growth factor. Most hepatocellular carcinomas occur in cirrhotic livers, and the common mechanism for hepatocarcinogenesis is chronic inflammation associated with severe oxidative stress; other risk factors are dietary aflatoxin B(1) consumption, cigarette smoking, and heavy drinking. Ischemia-reperfusion injury affects directly on hepatocyte viability, particularly during transplantation and hepatic surgery; ischemia activates Kupffer cells which are the main source of ROS during the reperfusion period. The toxic action mechanism of paracetamol is focused on metabolic activation of the drug, depletion of glutathione, and covalent binding of the reactive metabolite N-acetyl-p-benzoquinone imine to cellular proteins as the main cause of hepatic cell death; intracellular steps critical for cell death include mitochondrial dysfunction and, importantly, the formation of ROS and peroxynitrite. Infection with hepatitis C is associated with increased levels of ROS/RNS and decreased antioxidant levels. As a consequence, antioxidants have been proposed as an adjunct therapy for various liver diseases.

Nitric oxide and redox regulation in the liver: Part I. General considerations and redox biology in hepatitis

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are created in normal hepatocytes and are critical for normal physiologic processes, including oxidative respiration, growth, regeneration, apoptosis, and microsomal defense. When the levels of oxidation products exceed the capacity of normal antioxidant systems, oxidative stress occurs. This type of stress, in the form of ROS and RNS, can be damaging to all liver cells, including hepatocytes, Kupffer cells, stellate cells, and endothelial cells, through induction of inflammation, ischemia, fibrosis, necrosis, apoptosis, or through malignant transformation by damaging lipids, proteins, and/or DNA. In Part I of this review, we will discuss basic redox biology in the liver, including a review of ROS, RNS, and antioxidants, with a focus on nitric oxide as a common source of RNS. We will then review the evidence for oxidative stress as a mechanism of liver injury in hepatitis (alcoholic, viral, nonalcoholic). In Part II of this review, we will review oxidative stress in common pathophysiologic conditions, including ischemia/reperfusion injury, fibrosis, hepatocellular carcinoma, iron overload, Wilson's disease, sepsis, and acetaminophen overdose. Finally, biomarkers, proteomic, and antioxidant therapies will be discussed as areas for future therapeutic interventions.

Peripheral blood gene expression profile associated with sustained virologic response after peginterferon plus ribavirin therapy for chronic hepatitis-C genotype 1

We investigated the relationship between global gene expression in peripheral blood mononuclear cells (PBMCs) during the first 4 weeks of peginterferon alfa and ribavirin therapy and long-term eradication of hepatitis-C genotype 1 infections in 23 patients. A sustained virologic response (SVR), defined as an undetected serum HCV ribonucleic acid (RNA) at week 72, was the virologic response endpoint. PBMC RNA was prepared at week 0 and week 4 from 23 patients (17 black and 6 white Americans), and hybridized to Affymetrix GeneChip HG-U133 plus 2.0 arrays. Compared to week 0, 269 genes were differentially expressed at week 4 of treatment, including many genes regulated by alpha interferons and associated with host immunity (p<0.0001), cell signal transduction (p<0.001) and cellular protein metabolism (p<0.001). Expression of these 269 genes at week 0 and week 4 did not differ significantly between patients with and without a SVR. In contrast, SVR was associated with differential expression of 98 genes at week 4 (false discovery rate <0.01). Many of the genes have been implicated in control of HCV lifecycle and thus may play important roles in HCV clearance during peginterferon and ribavirin therapy.

DNA oxidative damage and strand breaks in young healthy individuals: A gender difference and the role of life style factors

The aim of this study was to analyze background levels of DNA damage in young (19-31 years) non-smoking individuals and to correlate damage to gender and life style. DNA single strand breaks (SSB) and alkali labile sites (ALS) were measured in 99 subjects living in Stockholm, Sweden. Further, oxidative DNA damage was analyzed using the DNA repair glycosylase FPG as well as HPLC-ECD for specific analysis of 8-oxo-7,8-dihydro-2'deoxyguanosine (8-oxodG). We found that males had higher (P < 0.001) levels of SSB + ALS than females, but no difference was seen for oxidative lesions. There was no correlation between FPG sites and 8-oxodG. For females, there was a positive correlation between FPG levels and body mass index and a negative correlation between SSB + ALS and fruit intake. We conclude that the background level of oxidative DNA damage, analyzed with improved methods, is low and that gender, fruit intake and BMI can affect DNA damage.

Ribavirin in the treatment of chronic hepatitis C

BACKGROUND AND AIM

Current practice guidelines recommend that individuals chronically infected with the hepatitis C virus (HCV) be treated with pegylated interferon plus ribavirin. Ribavirin, however, is associated with serious adverse events (AE), especially anemia. We review its mechanism of action, its importance in treating chronic hepatitis C (CHC) patients, the AE associated with its use, and techniques used to lessen these AE.

METHODS

Medline searches were performed using the keywords ribavirin and hepatitis, together with the keywords mechanism, anemia, liver transplant, renal function, pharmacokinetics, and dose reduction. Searches of abstracts of recent Digestive Diseases Week, American Association for the Study of Liver Diseases, and European Association for the Study of Liver Diseases meetings were also performed.

RESULTS

Ribavirin may be effective in treating CHC by affecting the virus or the host; for example by inducing viral mutations, blocking cellular enzymes, or affecting the host immune response. Although the pegylated interferons are the primary drugs used to treat CHC, a combination with ribavirin is more effective than pegylated interferon alone. Ribavirin-associated AE may be lessened by ribavirin dose reductions and by maintenance of the hematocrit.

CONCLUSIONS

Treatments of ribavirin toxicities, especially anemia, can allow patients to continue full-dose combination therapy with peginterferon and ribavirin, enhancing their probability of attaining a sustained virologic response (SVR). Treatment of CHC should be tailored to individual patients, especially those with renal dysfunction, and should include agents that treat the side-effects of CHC treatment. Monitoring of plasma ribavirin concentrations during treatment may help in the future.

DNA damage in peripheral blood lymphocytes of patients with cirrhosis related to alcohol abuse or to hepatitis B and C viruses

BACKGROUND

Both alcohol abuse and hepatitis B or C virus infections are implicated in the development of hepatocellular carcinoma, but it is still controversial whether the pathogenetic mechanism is epigenetic or genotoxic.

AIM

Considering that alcohol promotes the generation of reactive oxygen species and both viruses infect peripheral lymphocytes, in this study we investigated the occurrence of DNA fragmentation in peripheral blood lymphocytes from patients with alcoholic cirrhosis and from patients with cirrhosis related to B and C viruses, and analyzed the correlation between the degree of DNA fragmentation and the Child-Pugh score used to assess the degree of hepatic insufficiency.

METHODS

The study population consisted of two groups: group I involved 12 patients with alcoholic cirrhosis; group II involved 25 patients with hepatic B virus or hepatic C virus cirrhosis. The control group involved 20 healthy individuals. The degree of DNA fragmentation in peripheral blood lymphocytes was determined with the alkaline Comet assay that provides two indexes of the frequency of DNA single-strand breaks and alkali-labile sites, the tail length and the tail moment.

RESULTS

Mean values of both tail length and tail moment were significantly increased (P<0.001) in lymphocytes from 12 patients with alcoholic cirrhosis and in lymphocytes from 25 patients with HBV or HCV cirrhosis, as compared with average tail length and tail moment values of lymphocytes from 20 healthy individuals. A significant positive correlation was found to exist between the degree of DNA fragmentation present in lymphocytes of each of the 37 patients with alcoholic or viral cirrhosis and the corresponding value of the Child-Pugh score.

CONCLUSION

The occurrence of DNA fragmentation in peripheral blood lymphocytes reflects a direct genotoxic effect of either alcohol or HBV and HCV and suggests that the same genotoxic effect may operate in the liver and contribute to hepatocarcinogenesis.

Hepatitis C virus: from oxygen free radicals to hepatocellular carcinoma

Epidemiological evidence clearly identifies chronic infection with hepatitis C virus (HCV) as a major risk factor for the development of hepatocellular carcinoma (HCC). Among the mechanisms that have been implicated in the pro-carcinogenic effect of HCV infection, an increased production of reactive oxygen species in the liver seems to have a major pathogenetic role in leading from chronic inflammation to cancer. Recent data have also demonstrated that HCV is capable of inducing this active production of free radicals per se, not just through inflammation, a feature peculiar to this virus and the specific activity of its core protein. This paper provides an overview of the inter-relationships between HCV, liver damage, free radical production and HCC, describing at least in part the complex network involving DNA oxidative damage, cytokine synthesis, proto-oncogene activation and oestrogen receptor expression, that may all be deeply involved in liver carcinogenesis.

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.

The CD16−/CD56brightSubset of NK Cells Is Resistant to Oxidant-Induced Cell Death

Phagocyte-derived reactive oxygen species ("oxygen radicals") have been ascribed a suppressive role in immunoregulation by inducing dysfunction and apoptotic cell death in lymphocytes. Earlier studies show that human NK cells are exceptionally sensitive to oxygen radical-induced apoptosis and functional inhibition. Two subsets of human CD56(+) NK cells have been identified: the highly cytotoxic CD56(dim) cells which constitute >90% of NK cells in peripheral blood, and the less cytotoxic but efficiently cytokine-producing CD56(bright) cells. In this study, we demonstrate that the CD56(bright) subset of NK cells, in contrast to CD56(dim) cells, remains viable and functionally intact after exposure to phagocyte-derived or exogenously added oxygen radicals. The resistance of CD56(bright) cells to oxidative stress was accompanied by a high capacity of neutralizing exogenous hydrogen peroxide, and by a high cell-surface expression of antioxidative thiols. Our results imply that CD56(bright) NK cells are endowed with an efficient antioxidative defense system that protects them from oxygen radical-induced inactivation.

Oxidative-inflammatory damage in cirrhosis: effect of vitamin E and a fermented papaya preparation

BACKGROUND AND AIM

Oxidative DNA damage occurs as an early event in hepatitis C virus (HCV) infection and is an indication of the potential for carcinogenesis. The aim of this study was to test a novel antioxidant/immunomodulator in patients with HCV-related cirrhosis.

METHODS

The study group consisted of 50 patients with HCV-related cirrhosis with transaminase values less than twofold increased (alanine aminotransferase [ALT] < 80 IU/L). Patients underwent a standardized food-vitamin composition assessment and were assessed for dietary intake, nutritional status and iron level. Patients were randomly allocated into two groups and then given either alpha-tocopherol 900 IU/day or 9 g/day of a fermented papaya preparation (FPP, Immun-Age, Osato Research Institute, Gifu, Japan) at bedtime for 6 months. Ten healthy subjects served as controls. Patients were checked monthly for: routine tests, redox status (reduced glutathione, glutathione peroxidase, oxidized glutathione, malondialdehyde), plasma alpha-tocopherol, 8-hydroxy-deoxy-guanidine (8-OHdG) level in circulating leukocyte DNA and serum levels of cytokines.

RESULTS

Patients with cirrhosis showed a significant imbalance of redox status (low antioxidants/high oxidative stress markers) (P < 0.005 vs controls). Neither treatment regimen affected transaminases as a whole. However, vitamin E supplementation almost normalized ALT only in the limited vitamin-E-deficient subgroup. A significant improvement of redox status was obtained by both regimens. However, only FPP significantly decreased 8-OHdG and the improvement of cytokine balance with FPP was significantly better than with vitamin E treatment (P < 0.05).

CONCLUSIONS

Although the present data seem to suggest a potential supportive role of antioxidants/immunomodulators as FPP in HCV patients, more studies are needed to substantiate their effect on the natural history of the disease.

Activation of the ER stress gene gadd153 by hepatitis C virus sensitizes cells to oxidant injury

HCV induces endoplasmic reticulum (ER) stress which correlates with transcriptional induction of ER stress genes. Previously, we reported that expression of HCV structural proteins activates the ER stress and pro-apoptotic gene gadd153 which plays a relevant role in cell death induced by oxidative stress. In the present study, using human hepatic cell lines Huh7 carrying a full-length HCV replicon, we demonstrated that replication and expression of the complete set of HCV proteins were associated with elevated expression of gadd153. Analysis of gadd153 promoter activity revealed that both the ATF4 and the ATF6 pathways, which are typically induced during ER stress response, contribute to the induction of gadd153 in HCV replicon cells. Activation of the ATF4 pathway was confirmed by identification of increased levels of ATF4 protein in replicon cells. Importantly, we showed that, following H2O2 treatment, gadd153 gene reached higher levels of expression in replicon cells. Consistent with the marked induction of the pro-apoptotic gene gadd153, HCV replicon cells showed an increased vulnerability to oxidant injury. Treatment of replicon cells with a specific small interfering RNA, targeted to gadd153 gene, reduced basal expression of gadd153 and decreased cell death following H2O2. These findings suggest that gadd153 may play a major role in sensitivity of HCV replicon cell to oxidative stress.

Role of cell-cycle turnover and oxidative stress in telomere shortening and cellular senescence in patients with chronic hepatitis C

BACKGROUND

In addition to the telomere shortening that occurs with cell division, oxidative stress can damage or shorten telomeres and induce a condition termed premature senescence, possibly before telomeres become critically short. We investigated the effects of cell-cycle turnover and oxidative stress on cellular senescence in hepatitis C virus (HCV)-related chronic liver injury.

METHOD

Using quantitative fluorescence in situ hybridization, the telomere lengths of hepatocytes in biopsy specimens from HCV-positive patients were estimated. We assessed clinicopathological parameters that reflect cell-cycle turnover, including Ki-67 positive index, serum alanine aminotransferase (ALT) level and degree of fibrosis, and also oxidative stress-related parameters, such as 8-hydroxy-2'-deoxyguanosine (8-OHdG) expression. Nuclear size and DNA content of hepatocytes were measured as morphological features of senescence.

RESULTS

Telomere shortening correlated with the degree of cell turnover, hepatic fibrosis and morphological features of aging cells. Furthermore, the rate of telomere shortening per year was positively correlated with fibrosis progression. In cases of no or mild fibrosis, telomere lengths of positive patients were generally shorter than those of 8-OHdG-negative patients, and this trend achieved statistical significance in advanced-stage fibrosis. HCV carriers with persistently normal serum ALT level (PNAL) showed significantly longer telomeres than patients with active hepatitis and mild fibrosis. There was no significant difference in telomere lengths between HCV carriers with PNAL and normal controls.

CONCLUSIONS

Cell-cycle turnover is the primary mechanism of telomere shortening, and can induce fibrosis progression and cellular senescence. However, oxidative stress can be an accelerator of senescence, especially in advanced-stage fibrosis.

Redox modulation of the hepatitis C virus replication complex is calcium dependent

Reactive species and perturbation of the redox balance have been implicated in the pathogenesis of many viral diseases, including hepatitis C. Previously, we made a surprising discovery that concentrations of H(2)O(2) that are nontoxic to host cells disrupted the hepatitis C virus (HCV) replication complex (RC) in Huh7 human hepatoma cells in a manner that suggested signaling. Here, we show that H(2)O(2) and interferon-gamma have comparable effects on the HCV subgenomic and genomic RNA replication in Huh7 cells. H(2)O(2) induced a gradual rise in the intracellular calcium concentration ([Ca(2+)](i)). Both rapid and sustained suppression of HCV RNA replication by H(2)O(2) depended on this calcium elevation. The peroxide-induced [Ca(2+)](i) elevation was independent of extracellular calcium and derived, at least in part, from the endoplasmic reticulum. Likewise, the suppression of the HCV RC by H(2)O(2) was independent of extracellular calcium but required an intracellular calcium source. Other agents that elevated [Ca(2+)](i) could also suppress the HCV RC, suggesting that calcium elevation might be sufficient to suppress HCV RNA replication. In conclusion, oxidants may modulate the HCV RC through calcium. Effects on the infectivity and the morphogenesis of HCV remain to be determined. These findings suggest possible regulatory roles for redox and calcium signaling during viral infections.

Oxidative stress inhibits IFN-alpha-induced antiviral gene expression by blocking the JAK-STAT pathway

BACKGROUND/AIMS

Unresponsiveness to IFN-alpha is common in chronic hepatitis C. Since conditions associated with an increased oxidative stress (advanced age, steatosis, fibrosis, iron overload, and alcohol consumption) reduce the likelihood of response, we hypothesized that oxidative stress may affect the antiviral actions of IFN-alpha.

METHODS

We examined in a human hepatocellular carcinoma cell line (Huh-7) the effect of hydrogen peroxide (H2O2), as a generator of oxidative stress, on the IFN-alpha signaling pathway.

RESULTS

Pretreatment of Huh-7 cells with 0.5-1 mM H2O2 resulted in the suppression of the IFN-alpha-induced antiviral protein MxA and of IRF-9 mRNA expression. The reduced expression of these genes was associated to H2O2 -mediated suppression of the IFN-alpha-induced assembly of signal transducer and activator of transcription (STAT) factors to specific promoter motifs on IFN-alpha-inducible genes. This was accomplished by preventing the IFN-alpha-induced tyrosine phosphorylation of STAT-1 and STAT-2 through the inactivation of the upstream receptor associated tyrosine kinases, JAK-1 and Tyk-2. The suppression was fast, occurring within 5mins of pretreatment with H2O2, and did not require protein synthesis.

CONCLUSIONS

In conclusion, oxidative stress impairs IFN-alpha signaling and might cause resistance to the antiviral action of IFN-alpha in chronically HCV infected patients with high level of oxidative stress in the liver.

Oxidative damage, pro-inflammatory cytokines, TGF-α and c-myc in chronic HCV-related hepatitis and cirrhosis

AIM: To assess whether a correlation exists between oxidative DNA damage occurring in chronic HCV-related hepatitis and expression levels of pro-inflammatory cytokines, TGF-α and c-myc.

METHODS: The series included 37 patients with chronic active HCV-related hepatitis and 11 with HCV-related compensated cirrhosis. Eight-hydroxydeoxyguanosine in liver biopsies was quantified using an electrochemical detector. The mRNA expression of TNF-α, IL-1β, TGF-α and c-myc in liver specimens was detected by semi-quantitative comparative RT-PCR.

RESULTS: TNF-α levels were significantly higher in hepatitis patients than in cirrhosis patients (P = 0.05). IL-1β was higher in cirrhosis patients (P = 0.05). A significant correlation was found between TNF-α and staging (P = 0.05) and between IL-1β levels and grading (P = 0.04). c-myc showed a significantly higher expression in cirrhosis patients (P = 0.001). Eight-hydroxydeoxyguanosine levels were significantly higher in cirrhosis patients (P = 0.05) and in HCV genotype 1 (P = 0.03). Considering all patients, 8-hydroxydeoxyguanosine levels were found to be correlated with genotype (P = 0.04) and grading (P = 0.007). Also multiple logistic regression analysis demonstrated a significant correlation among the number of DNA adducts, TNF-α expression and HCV genotype (P = 0.02).

CONCLUSION: In chronic HCV-related liver damage, oxidative DNA damage correlates with HCV genotype, grading and TNF-α levels. As HCV-related liver damage progresses, TNF-α levels drop while IL-1β and c-myc levels increase, which may be relevant to liver carcinogenesis.

Hepatitis C virus core protein inhibits deoxycholic acid-mediated apoptosis despite generating mitochondrial reactive oxygen species

BACKGROUND

Hepatitis C virus (HCV) core protein is known to cause oxidative stress and alter apoptosis pathways. However, the apoptosis results are inconsistent, and the real significance of oxidative stress is not well known. The aim of this study was twofold. First, we wanted to confirm whether core-induced oxidative stress was really significant enough to cause DNA damage, and whether it induced cellular antioxidant responses. Second, we wanted to evaluate whether this core-induced oxidative stress and the antioxidant response to it was responsible for apoptosis changes.

METHODS

HCV core protein was expressed under control of the Tet-Off promoter in Huh-7 cells and HeLa cells. We chose to use deoxycholic acid (DCA) as a model because it is known to produce both reactive oxygen species (ROS) and apoptosis.

RESULTS

Core expression uniformly increased ROS and 8-hydroxy-2'-deoxyguanosine (8-OHdG) under basal and DCA-stimulated conditions. Core protein expression also increased manganese superoxide dismutase levels. Core protein inhibited DCA-mediated mitochondrial membrane depolarization and DCA-mediated activation of caspase-9 and caspase-3, despite the increase in ROS by DCA. Core protein inhibited DCA-mediated apoptosis by increasing Bcl-x(L) protein and decreasing Bax protein, without affecting the proportion of Bax between mitochondria and cytosol, resulting in suppression of cytochrome c release from mitochondria into cytoplasm.

CONCLUSIONS

HCV core protein induces oxidative DNA damage, whereas it inhibits apoptosis that is accompanied by enhancement of ROS production. Thus, oxidative stress and apoptosis modulation by core protein are independent of each other.

Expression of oxidative stress-related molecules in circulating leukocytes and urine in patients with chronic viral hepatitis

AIMS

Oxidative stress plays a role in pathogenesis of chronic viral hepatitis. Expression of oxidative stress-related molecules remains to be clarified.

METHODS

4-hydroxy-2-nonenal (4-HNE), 4-hydroxy-2-hexenal (4-HHE), catalase, superoxide dismutase-1 (SOD-1), glutathione peroxidase-1, thioredoxin (TRX) in leukocytes and urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) were examined in 164 persons, including 130 chronic viral hepatitis patients and 34 normal individuals, by Western blot analysis and enzyme-linked immunosorbent assay, respectively. Hepatic expression of these proteins was immunohistochemically examined in 12 patients with chronic viral hepatitis, compared with three persons without liver damage.

RESULTS

The 4-HNE/beta-actin ratios in chronic viral hepatitis were significantly higher than those in normal individuals (P<0.01), and were significantly correlated with asparate aminotransferase (AST) and alanine aminotransferase (ALT) (P<0.01, each). The catalase/beta-actin and SOD-1/beta-actin ratios in chronic viral hepatitis were higher than those in normal individuals, and were significantly correlated with 4-HNE/beta-actin ratios (P<0.01, each). Hepatic expression of 4-HNE, 4-HHE, catalase, SOD-1 and TRX in chronic viral hepatitis was higher than that without liver damage. Urinary excretion of 8-OHdG was not changed in chronic viral hepatitis.

CONCLUSIONS

The results of the present study suggest that expression of oxidative stress-related molecules in leukocytes is upregulated in relation to serum aminotransferase levels.