In situ detection of oxidative DNA damage, 8-hydroxydeoxyguanosine, in chronic human liver disease

Yellow fever virus infection in human hepatocyte cells triggers an imbalance in redox homeostasis with increased reactive oxygen species production, oxidative stress, and decreased antioxidant enzymes

Yellow fever (YF) presents a wide spectrum of severity, with clinical manifestations in humans ranging from febrile and self-limited to fatal cases. Although YF is an old disease for which an effective and safe vaccine exists, little is known about the viral- and host-specific mechanisms that contribute to liver pathology. Several studies have demonstrated that oxidative stress triggered by viral infections contributes to pathogenesis. We evaluated whether yellow fever virus (YFV), when infecting human hepatocytes cells, could trigger an imbalance in redox homeostasis, culminating in oxidative stress. YFV infection resulted in a significant increase in reactive oxygen species (ROS) levels from 2 to 4 days post infection (dpi). When measuring oxidative parameters at 4 dpi, YFV infection caused oxidative damage to lipids, proteins, and DNA, evidenced by an increase in lipid peroxidation/8-isoprostane, carbonyl protein, and 8-hydroxy-2'-deoxyguanosine, respectively. Furthermore, there was a significant reduction in the activity of the antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx), in addition to a reduction in the ratio of reduced to oxidized glutathione (GSH/GSSG), indicating a pro-oxidant environment. However, no changes were observed in the enzymatic activity of the enzyme catalase (CAT) or in the gene expression of SOD isoforms (1/2/3), CAT, or GPx. Therefore, our results show that YFV infection generates an imbalance in redox homeostasis, with the overproduction of ROS and depletion of antioxidant enzymes, which induces oxidative damage to cellular constituents. Moreover, as it has been demonstrated that oxidative stress is a conspicuous event in YFV infection, therapeutic strategies based on antioxidant biopharmaceuticals may be new targets for the treatment of YF.

Oxidative stress sensor Keap1 recognizes HBx protein to activate the Nrf2/ARE signaling pathway, thereby inhibiting hepatitis B virus replication

IMPORTANCE

The Kelch-like ECH-associated protein 1 (Keap1)/NF-E2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway is one of the most important defense mechanisms against oxidative stress. We previously reported that a cellular hydrogen peroxide scavenger protein, peroxiredoxin 1, a target gene of transcription factor Nrf2, acts as a novel HBV X protein (HBx)-interacting protein and negatively regulates hepatitis B virus (HBV) propagation through degradation of HBV RNA. This study further demonstrates that the Nrf2/ARE signaling pathway is activated during HBV infection, eventually leading to the suppression of HBV replication. We provide evidence suggesting that Keap1 interacts with HBx, leading to Nrf2 activation and inhibition of HBV replication via suppression of HBV core promoter activity. This study raises the possibility that activation of the Nrf2/ARE signaling pathway is a potential therapeutic strategy against HBV. Our findings may contribute to an improved understanding of the negative regulation of HBV replication by the antioxidant response.

Bibliometric study of immunotherapy for hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC), recognized as a significant global health concern, ranks as the sixth most prevalent form of cancer and is the third leading cause of cancer-associated mortality. Over half of HCC patients are diagnosed at advanced stages, an unfortunate phenomenon primarily attributed to the liver's robust compensatory mechanisms. Given the limited availability of donor livers, existing clinical surgical approaches have yet to provide universally applicable treatment strategies offering substantial prognostic improvement for late-stage cancer. Although the past few decades have witnessed significant advancements in chemotherapy and targeted therapy for HCC, the emergence of drug resistance poses a substantial impediment to their successful execution. Furthermore, issues such as diminished quality of life post-treatment and high treatment costs warrant critical attention. Consequently, the imperative for an effective treatment strategy for advanced liver cancer is unequivocal. In recent years, notable progress in the development and application of immunotherapy has sparked a revolution in advanced liver cancer treatment. This study aims to elucidate a more comprehensive understanding of the current landscape, knowledge framework, research focal points, and nascent breakthrough trends in the domain of immunotherapy for hepatocellular carcinoma via bibliometric analysis.

Method

Our study involved conducting a comprehensive literature search spanning from 1999 through December 31, 2022, by utilizing the Science Citation Index Expanded (SCI-Expanded) database. Our aim was to amass all the papers and reviews related to immunotherapy for hepatocellular carcinoma. Our search strategy yielded a total of 4,486 papers. After exclusion of self-citations, we focused our analysis on 68,925 references. These references were cited 119,523 times (excluding 97,941 self-citations), boasting an average citation frequency of 26.64 times per paper, and achieved an h-index of 135. We employed analytical software tools like Citespace and VOSviewer to perform an intricate analysis of the amassed literature, covering various aspects, including geographical location, research institutions, publishing journals, authors, references, and keywords. Our method incorporated timeline analysis, burst detection, and co-occurrence analysis. The application of these tools facilitated a thorough evaluation of research hotspots, knowledge structure, and emerging advancements within the sphere of immunotherapy for hepatocellular carcinoma.

Results

Our bibliometric analysis disclosed a noteworthy escalation in the number of publications in the realm of hepatocellular carcinoma immunotherapy during the years 2021-2022, surpassing the aggregate number of papers published in the preceding decade (2011-2020). This surge underscores a sharp upturn in research interest within this field. Additionally, the research hotspot in hepatocellular carcinoma immunotherapy has perceptibly deviated from the preceding decade's trends. In terms of geographical distribution, China emerged as the leading country, producing 50.08% of the total publications. This was followed by the United States, with 963 papers, and Japan, contributing 335 papers. Among research institutions, Sun Yat-sen University was the most prolific, while Tim F. Greten stood out as the most published author with 42 papers to his credit. A co-reference network examination uncovered a shift in research emphasis within the field of hepatocellular carcinoma immunotherapy, highlighting the evolving nature of this important area of study.

Conclusion

Our bibliometric study highlights the significant evolution and growth in HCC immunotherapy research over the past two decades. Looking ahead, research will focus on improving the microenvironment post-drug resistance from immune combination therapy, harnessing adoptive cellular immunity (as CAR-T), subclassify the population and developing new tumor markers. Incorporation of technologies such as nanotechnology, microbiology, and gene editing will further advance HCC treatments. This progressive trajectory in the field promises a brighter future for individuals suffering from HCC.

MitoQ demonstrates connexin- and p53-mediated cancer chemoprevention in N-nitrosodiethylamine-induced hepatocarcinogenesis rodent model

Cancer chemoprevention is an approach that offers huge potential for preventing/retarding carcinogenesis. MitoQ is well-known and extensively studied mitochondria-targeted antioxidants for its applications in diseases linked with oxidative stress. In the present study chemopreventive potential of mitoQ was studied with a focus on the role of gap-junctions and p53 at an advanced stage of HCC. BALB/c mice model of hepatocarcinogenesis was established using N-nitrosodiethylamine as a carcinogen (200 mg/kg b. w., cumulative dose, intraperitoneally). The chemopreventive effect of mitoQ was studied by pre-protecting animals with mitoQ (0.125 mg/kg b. w., orally once a week) till the termination of the study. The tumors developed in the course of the study were histopathologically analyzed and statistically evaluated. The mechanistic role of mitoQ was investigated in terms of mitochondrial oxidative stress, expression of 8-OHdG, Cx26, Cx32, p53 and status of gap-junctional intercellular communication (GJIC) in tumors. Chemopreventive activity of mitoQ was evident from improved survival of animals, significantly (p ≤ 0.05) lower tumor multiplicity, tumor incidence and a total number of tumors. MitoQ treatment significantly (p ≤ 0.05) decreased mitochondrial oxidative stress as indicated by reduced mtROS and mtLPO. Increased staining intensity of 8-OHdG and internalization of Cx26, Cx32 which was observed in hepatic tumors was reduced upon mitoQ treatment. Furthermore, the expression of Cx26, Cx32 and p53 was significantly increased along with improvement in GJIC in mitoQ treatment group. MitoQ demonstrated its chemopreventive potential probably by regulating mtROS, connexins and p53 in hepatocarcinogenesis.

Hepatitis B Virus-Associated Hepatocellular Carcinoma

Hepatitis B virus (HBV) is DNA-based virus, member of the Hepadnaviridae family, which can cause liver disease and increased risk of hepatocellular carcinoma (HCC) in infected individuals, replicating within the hepatocytes and interacting with several cellular proteins. Chronic hepatitis B can progressively lead to liver cirrhosis, which is an independent risk factor for HCC. Complications as liver decompensation or HCC impact the survival of HBV patients and concurrent HDV infection worsens the disease. The available data provide evidence that HBV infection is associated with the risk of developing HCC with or without an underlying liver cirrhosis, due to various direct and indirect mechanisms promoting hepatocarcinogenesis. The molecular profile of HBV-HCC is extensively and continuously under study, and it is the result of altered molecular pathways, which modify the microenvironment and lead to DNA damage. HBV produces the protein HBx, which has a central role in the oncogenetic process. Furthermore, the molecular profile of HBV-HCC was recently discerned from that of HDV-HCC, despite the obligatory dependence of HDV on HBV. Proper management of the underlying HBV-related liver disease is fundamental, including HCC surveillance, viral suppression, and application of adequate predictive models. When HBV-HCC occurs, liver function and HCC characteristics guide the physician among treatment strategies but always considering the viral etiology in the treatment choice.

Influencing Factors and Molecular Pathogenesis of Sarcopenia and Osteosarcopenia in Chronic Liver Disease

The liver plays a pivotal role in nutrient/energy metabolism and storage, anabolic hormone regulation, ammonia detoxification, and cytokine production. Impaired liver function can cause malnutrition, hyperammonemia, and chronic inflammation, leading to an imbalance between muscle protein synthesis and proteolysis. Patients with chronic liver disease (CLD) have a high prevalence of sarcopenia, characterized by progressive loss of muscle mass and function, affecting health-related quality of life and prognosis. Recent reports have revealed that osteosarcopenia, defined as the concomitant occurrence of sarcopenia and osteoporosis, is also highly prevalent in patients with CLD. Since the differentiation and growth of muscles and bones are closely interrelated through mechanical and biochemical communication, sarcopenia and osteoporosis often progress concurrently and affect each other. Osteosarcopenia further exacerbates unfavorable health outcomes, such as vertebral fracture and frailty. Therefore, a comprehensive assessment of sarcopenia, osteoporosis, and osteosarcopenia, and an understanding of the pathogenic mechanisms involving the liver, bones, and muscles, are important for prevention and treatment. This review summarizes the molecular mechanisms of sarcopenia and osteosarcopenia elucidated to data in hopes of promoting advances in treating these musculoskeletal disorders in patients with CLD.

Plasma pentosidine levels are associated with prevalent fractures in patients with chronic liver disease

Aim

Osteoporotic fractures negatively impact health-related quality of life and prognosis. Advanced glycation end products (AGEs) impair bone quality and reduce bone strength. The aim of this study was to determine the relationship between plasma levels of pentosidine, a surrogate marker for AGEs, and prevalent fractures in patients with chronic liver disease (CLD).

Methods

This cross-sectional study included 324 patients with CLD. Vertebral fractures were evaluated using lateral thoracolumbar spine radiographs. Information on prevalent fractures was obtained through a medical interview, medical records, and/or radiography. The patients were classified into low (L), intermediate (I), and high (H) pentosidine (Pen) groups based on baseline plasma pentosidine levels.

Results

Of the 324 patients, 105 (32.4%) had prevalent fractures. The prevalence of liver cirrhosis (LC) and prevalent fractures significantly increased stepwise with elevated pentosidine levels. The H-Pen group had the highest prevalence of LC (88.6%, p < 0.001) and prevalent fractures (44.3%, p = 0.007), whereas the L-Pen group had the lowest prevalence of LC (32.1%, p < 0.001) and prevalent fractures (21.0%, p = 0.007). Multiple logistic regression analysis identified pentosidine as a significant independent factor related to prevalent fractures (odds ratio = 1.069, p < 0.001). Pentosidine levels increased stepwise and correlated with liver disease severity. They were markedly high in patients with decompensated LC. In multiple regression analysis, liver functional reserve factors (total bilirubin, albumin, and prothrombin time-international normalized ratio) significantly and independently correlated with pentosidine levels.

Conclusions

Plasma pentosidine was significantly associated with prevalent fractures and liver functional reserve in patients with CLD. Pentosidine may be useful in predicting fracture risk and should be closely followed in CLD patients with advanced disease.

β-Sitosterol attenuates liver injury in a rat model of chronic alcohol intake

Liver disease associated with long-term drinking is one of the leading causes of death. There is an urgent need for more effective drugs to reduce alcoholic liver damage. Yin Chen Hao, a traditional Chinese herbal medicine, is widely used for liver diseases. Here, we aimed to explore the protective effect of β-sitosterol (the active ingredient of Artemisia spp.) on alcoholic liver injuries. We treated the rats with alcohol and different dosages of β-sitosterol to detect the expression levels of liver function indicators in serum. The functions of β-sitosterol were evaluated based on variations in histology, liver function indicators and DNA oxidative damages. The underlying mechanism was investigated by measuring lipid peroxidation, the antioxidant, the expression of cytochrome P450 2E1 and the expression of apoptosis related genes. The results showed that β-sitosterol could improve liver histology and suppress biochemical indicators caused by alcohol in serum. In addition, β-sitosterol alleviates alcohol-induced oxidative stress, such as restoring erythrocyte membrane fluidity, reducing glutathione depletion, restoring antioxidant enzyme activity and reducing malondialdehyde overproduction. Furthermore, β-sitosterol downregulated the expression of apoptosis-related genes through the PI3K/Akt pathway. In conclusion, β-sitosterol has a protective effect on chronic alcoholism and has broad clinical application prospects in the treatment of alcohol-induced liver damage.

Molecular mechanisms of viral hepatitis induced hepatocellular carcinoma

Chronic infection with viral hepatitis affects half a billion individuals worldwide and can lead to cirrhosis, cancer, and liver failure. Liver cancer is the third leading cause of cancer-associated mortality, of which hepatocellular carcinoma (HCC) represents 90% of all primary liver cancers. Solid tumors like HCC are complex and have heterogeneous tumor genomic profiles contributing to complexity in diagnosis and management. Chronic infection with hepatitis B virus (HBV), hepatitis delta virus (HDV), and hepatitis C virus (HCV) are the greatest etiological risk factors for HCC. Due to the significant role of chronic viral infection in HCC development, it is important to investigate direct (viral associated) and indirect (immune-associated) mechanisms involved in the pathogenesis of HCC. Common mechanisms used by HBV, HCV, and HDV that drive hepatocarcinogenesis include persistent liver inflammation with an impaired antiviral immune response, immune and viral protein-mediated oxidative stress, and deregulation of cellular signaling pathways by viral proteins. DNA integration to promote genome instability is a feature of HBV infection, and metabolic reprogramming leading to steatosis is driven by HCV infection. The current review aims to provide a brief overview of HBV, HCV and HDV molecular biology, and highlight specific viral-associated oncogenic mechanisms and common molecular pathways deregulated in HCC, and current as well as emerging treatments for HCC.

Effect of Hepatitis Viruses on the Nrf2/Keap1-Signaling Pathway and Its Impact on Viral Replication and Pathogenesis

With respect to their genome and their structure, the human hepatitis B virus (HBV) and hepatitis C virus (HCV) are complete different viruses. However, both viruses can cause an acute and chronic infection of the liver that is associated with liver inflammation (hepatitis). For both viruses chronic infection can lead to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). Reactive oxygen species (ROS) play a central role in a variety of chronic inflammatory diseases. In light of this, this review summarizes the impact of both viruses on ROS-generating and ROS-inactivating mechanisms. The focus is on the effect of both viruses on the transcription factor Nrf2 (nuclear factor erythroid 2 (NF-E2)-related factor 2). By binding to its target sequence, the antioxidant response element (ARE), Nrf2 triggers the expression of a variety of cytoprotective genes including ROS-detoxifying enzymes. The review summarizes the literature about the pathways for the modulation of Nrf2 that are deregulated by HBV and HCV and describes the impact of Nrf2 deregulation on the viral life cycle of the respective viruses and the virus-associated pathogenesis.

Dietary iron restriction leads to a reduction in hepatic fibrosis in a rat model of non-alcoholic steatohepatitis

Iron overload in the liver causes oxidative stress and inflammation, which result in organ dysfunction, making it a risk factor for non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma. We aimed to evaluate the effect of dietary iron restriction on disease progression in rats fed a choline-deficient L-amino acid-defined (CDAA) diet. Male F344 rats were fed a choline-sufficient amino acid-defined (control) diet, a CDAA diet or an iron-restricted CDAA diet for 4, 8 and 12 weeks. At each time point, hepatic iron levels, oxidative stress, inflammation and fibrosis were evaluated by immunohistochemistry. The iron-restricted CDAA diet significantly decreased serum iron levels for 12 weeks compared with the CDAA diet. Histological analysis confirmed that feeding with the CDAA diet induced hepatic iron overload and that this was associated with oxidative stress (number of 8-hydroxydeoxyguanosine-positive cells), inflammation (CD68 positive area) and fibrosis (Sirius Red positive area). Iron restriction with the CDAA diet significantly led to a reduction in the hepatic iron levels, oxidative stress, inflammation and fibrosis. Therefore, dietary iron restriction could be a useful therapeutic approach for NASH patients with hepatic iron overload.

Summary: We reveal that dietary iron restriction leads to a reduction in hepatic inflammation, oxidative stress and fibrosis in rats fed a choline-deficient L-amino acid-defined (CDAA) diet.

Liver-enriched transcription factor expression relates to chronic hepatic failure in humans

The mechanisms by which the liver fails in end-stage liver disease remain elusive. Disruption of the transcription factor network in hepatocytes has been suggested to mediate terminal liver failure in animals. However, this hypothesis remains unexplored in human subjects. To study the relevance of transcription factor expression in terminal stages of chronic liver failure in humans, we analyzed the expression of liver-enriched transcription factors (LETFs) hepatocyte nuclear factor (HNF)4α, HNF1α, forkhead box protein A2 (FOXA2), CCAAT/enhancer-binding protein (CEBP)α, and CEBPβ. We then selected downstream genes responsible for some hepatic functions (ornithine transcarbamylase [OTC], cytochrome P450 3A4 [CYP3A4], coagulation factor VII [F7], cadherin 1 [CDH1], phospho-ezrin (Thr567)/radixin (Thr564)/moesin (Thr558) [p-ERM], phospho-myosin light chain [p-MLC], low-density lipoprotein receptor-related protein 1 [LRP1]) in liver tissue from patients at different stages of decompensated liver function based upon Child-Pugh classification, Model for End-Stage Liver Disease score, and degree of inflammatory activity/fibrosis. We first examined differential expression of LETF and determined whether a relationship exists between transcript and protein expression, and liver function. We found HNF4α expression was down-regulated and correlated well with the extent of liver dysfunction (P = 0.001), stage of fibrosis (P = 0.0005), and serum levels of total bilirubin (P = 0.009; r = 0.35), albumin (P < 0.001; r = 0.52), and prothrombin time activity (P = 0.002; r = 0.41). HNF4α expression also correlated with CYP3A4, OTC, and F7 as well as CDH1 RNA levels. The Rho/Rho-associated protein kinase pathways, which have been implicated in the regulation of HNF4α, were also differentially expressed, in concert with LRP1, a reported upstream regulator of RhoA function. Conclusion: HNF4α and other members of the LETFs appear to be important regulators of hepatocyte function in patients with chronic hepatic failure. (Hepatology Communications 2018;2:582-594).

Detection of a lipid peroxidation-induced DNA adduct across liver disease stages

Background

Oxidative stress and chronic inflammation can increase cellular levels of reactive oxygen species and lipid peroxidation (LPO) when associated with the pathogenesis of hepatocellular carcinoma (HCC), which can develop following the progression of steatosis, fibrosis and cirrhosis. Using a monoclonal antibody for cyclic γ-hydroxy-1, N² -propanodeoxyguanosine (γ-OHPdG), a promutagenic DNA adduct formed endogenously by LPO, we examined its formation across liver disease stages to understand it's potential role in HCC development.

Methods

Formalin-fixed paraffin embedded (FFPE) liver tissue samples from 49 patients representing normal, steatosis, fibrosis, cirrhosis and HCC were stained for γ-OHPdG and 8-hydroxydeoxyguanosine (8-oxo-dG), an oxidative damage biomarker. Quantification of immunohistochemical (IHC) staining was performed using histological scoring of intensity and distribution. Using primary human hepatocytes (HH) and a stellate cell (SC) co-culture, immunocytochemical staining of γ-OHPdG and Nile Red was performed to determine if the formation of γ-OHPdG was consistent between the clinical sample disease stages and the in vitro steatotic and fibrotic conditions.

Results

γ-OHPdG levels varied significantly between the stages of normal and steatosis, steatosis and fibrosis, and steatosis and cirrhosis (P≤0.005). There was a trend, although not significant, of increased levels of γ-OHPdG in HCC compared to the other groups. A strong correlation was observed (Pearson's, R² =0.85) between levels of γ-OHPdG and 8-oxo-dG across the disease spectrum. The increase of γ-OHPdG in steatosis and decrease in fibrosis was a pattern confirmed in an in vitro model using primary HH co-cultured with human SCs.

Conclusions

γ-OHPdG was detected in FFPE liver tissues of patients with different stages of liver disease and in vitro studies, demonstrating that its formation is consistent with LPO in early stages of liver disease and suggesting that it may be a source of mutagenic DNA damage in liver disease progression.

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.

Constitutive gp130 activation rapidly accelerates the transformation of human hepatocytes via an impaired oxidative stress response

Pro-inflammatory signaling pathways, especially interleukin 6 (IL-6), and reactive oxygen species (ROS) promote carcinogenesis in the liver. In order to elucidate the underlying oncogenic mechanism, we activated the IL-6 signal transducer glycoprotein 130 (gp130) via stable expression of a constitutively active gp130 construct (L-gp130) in untransformed telomerase-immortalized human fetal hepatocytes (FH-hTERT). As known from hepatocellular adenomas, forced gp130 activation alone was not sufficient to induce malignant transformation. However, additional challenge of FH-hTERT L-gp130 clones with oxidative stress resulted in 2- to 3-fold higher ROS levels and up to 6-fold more DNA-double strand breaks (DSB). Despite increased DNA damage, ROS-challenged FH-hTERT L-gp130 clones displayed an enhanced proliferation and rapidly developed colony growth capabilities in soft agar. As driving gp130-mediated oncogenic mechanism, we detected a decreased expression of antioxidant genes, in particular glutathione peroxidase 3 and apolipoprotein E, and an absence of P21 upregulation following ROS-conferred induction of DSB. In summary, an impaired oxidative stress response in hepatocytes with gp130 gain-of-function mutations, as detected in dysplastic intrahepatic nodules and hepatocellular adenomas, is one of the central oncogenic mechanisms in chronic liver inflammation.

Genistein mediates the selective radiosensitizing effect in NSCLC A549 cells via inhibiting methylation of the keap1 gene promoter region

Non-small cell lung cancer (NSCLC) cells often possess a hypermethylated Keap1 promoter, which decreases Keap1 mRNA and protein expression levels, thus impairing the Nrf2-Keap1 pathway and thereby leading to chemo- or radio-resistance. In this study, we showed that genistein selectively exhibited a radiosensitizing effect on NSCLC A549 cells but not on normal lung fibroblast MRC-5 cells. Genistein caused oxidative stress in A549 cells rather than MRC-5 cells, as determined by the oxidation of the ROS-sensitive probe DCFH-DA and oxidative damage marked by MDA, PCO or 8-OHdG content. In A549 instead of MRC-5 cells, genistein reduced the level of methylation in the Keap1 promoter region, leading to an increased mRNA expression, thus effectively inhibited the transcription of Nrf2 to the nucleus, which suppressed the Nrf2-dependent antioxidant and resulted in the upregulation of ROS. Importantly, when combined with radiation, genistein further increased the ROS levels in A549 cells whereas decreasing the radiation-induced oxidative stress in MRC-5 cells, possibly via increasing the expression levels of Nrf2, GSH and HO-1. Moreover, radiation combined with genistein significantly increased cell apoptosis in A549 but not MRC-5 cells. Together, the results herein show that the intrinsic difference in the redox status of A549 and MRC-5 cells could be the target for genistein to selectively sensitize A549 cells to radiation, thereby leading to an increase in radiosensitivity for A549 cells.

Redox proteomics screening cellular factors associated with oxidative stress in hepatocarcinogenesis

Liver cancer is a major global health problem being the sixth most common cancer and the third cause of cancer-related death, with hepatocellular carcinoma (HCC) representing more than 90% of primary liver cancers. Mounting evidence suggests that, compared with their normal counterparts, many types of cancer cell have increased levels of ROS. Therefore, cancer cells need to combat high levels of ROS, especially at early stages of tumor development. Recent studies have revealed that ROS-mediated regulation of redox-sensitive proteins (redox sensors) is involved in the pathogenesis and/or progression of many human diseases, including cancer. Unraveling the altered functions of redox sensors and the underlying mechanisms in hepatocarcinogenesis is critical for the development of novel cancer therapeutics. For this reason, redox proteomics has been developed for the high-throughput screening of redox sensors, which will benefit the development of novel therapeutic strategies for the treatment of HCC. In this review, we will briefly introduce several novel redox proteomics techniques that are currently available to study various oxidative modifications in hepatocarcinogenesis and summarize the most important discoveries in the study of redox processes related to the development and progression of HCC.

Genotoxicity, mutagenicity and cytotoxicity of carotenoids extracted from ionic liquid in multiples organs of Wistar rats

The ionic liquid or melted salt 1-Butyl-3-methylimidazolium is an alternative process to extract natural pigments, such as carotenoids. Lycopene represents 80-90% of total of carotenoids presents in tomatoes and it has been widely studied due its potent antioxidant action. The aim of this study was to evaluate genotoxicity, mutagenicity and cytotoxicity of carotenoids extracted from ionic liquid using experimental model in vivo. For this purpose, a total of 20 male Wistar rats were distributed into four groups (n=5), as follows: control group; received a corresponding amount of corn oil for 7days by intragastric gavage (i.g.), ionic liquid group, received 10mgkg^-1 body weight for 7days by gavage; 10mg carotenoids group, received 10mgkg^-1 bw dissolved in corn oil for 7days by gavage and 500mg carotenoids group, received 500mgkg^-1 bw dissolved in corn oil for 7days by gavage. Rat liver treated with ionic liquid exhibited moderate histopathological changes randomly distributed in the parenchyma, such as cytoplasmic eosinophilia, apoptotic bodies, inflammatory infiltrate and focal necrosis. DNA damage was found in peripheral blood and liver cells of rats treated with ionic liquid or carotenoids at 500mg. An increase of micronucleated cells and 8-OhDG immunopositive cells were also detected in rats treated with carotenoids at 500mg. In summary, our results demonstrate that recommended dose for human daily intake of carotenoids extracted by ionic liquid did not induce genotoxicity, mutagenicity and cytotoxicity in multiple organs of rats.

Hepatitis B and its Relationship With Oxidative Stress

CONTEXT

Despite the great breakthroughs we have witnessed in the last 50 years in the prevention, diagnosis, and treatment of hepatitis B, we are still far from eradicating or even curing the disease. Achieving further progress in controlling this disease will not be possible without discovering the exact pathogenesis behind it. One prime suspect in the pathogenesis of various diseases is oxidative stress. This review will exclusively explore hepatitis B in the context of oxidative stress to obtain a more comprehensive clinical perspective on its pathogenesis and eventual medical therapy.

EVIDENCE ACQUISITION

We systematically searched PubMed, Google Scholar, Web of Science, EMBASE, and Scopus using an extensive list of keywords in the following three categories: 1) Hepatitis B and oxidation 2) Hepatitis B and antioxidant system 3) Effects of approved anti-hepatitis B drugs on redox status. All relevant articles were obtained and reviewed carefully after the exclusion criteria were deployed.

RESULTS

There is great evidence indicating extensive oxidative stress occurs in hepatitis B. This oxidative stress takes place on multiple levels, including lipid peroxidation, DNA oxidation, protein oxidation, and reactive oxygen and nitrogen species production. However, there are also conflicting results with regard to antioxidant therapy and antioxidant status in hepatitis B, some of which may be explained by the concept of "compensatory gaps." Nevertheless, further studies are indicated to reach a more thorough judgment.

CONCLUSIONS

Despite the presence of vast oxidative stress in hepatitis B, antioxidant therapy is not always effective as a treatment strategy, especially considering that antioxidants can act as "double-edged swords" or antioxidants; if not used at the right time or place or in the right combination, these substances can easily become pro-oxidants. Therefore, several studies will be needed to determine suitable antioxidant therapies. We propose the "2-step Combined Antioxidant Adjuvant Therapy for hepatitis B (2CAAT Hep B)" as a new strategy for antioxidant adjuvant therapy. We also suggest developing an international platform and database for antioxidant adjuvant therapy in hepatitis B (IPAATH and IDAATH) to canalize this field of research in a standardized direction, especially when complexity is a problem.

Value of the 8-oxodG/dG ratio in chronic liver inflammation of patients with hepatocellular carcinoma

The aim of this study was to examine the role of oxidative DNA damage in chronic liver inflammation in the evolution of hepatocellular carcinoma. The accumulated data demonstrated that oxidative DNA damage and chronic liver inflammation are involved in the transformation of normal hepatocytes and their evolution towards hepatocellular carcinoma. However, the levels of 8-oxy-2'-deoxy-guanosine (8-oxodG), a biomarker of oxidative DNA damage, were overestimated and underestimated in previous reports due to various technical limitations. The current techniques are not suitable to analyze the 8-oxodG levels in the non-malignant liver tissues and tumors of hepatocellular carcinoma patients unless they are modified. Therefore, in this study, the protocols for extraction and hydrolysis of DNA were optimized using 54 samples from hepatocellular carcinoma patients with various risk factors, and the 8-oxodG and 2'-deoxyguanosine (dG) levels were measured. The patients enrolled in the study include 23 from The Princess Alexandra Hospital and The Royal Brisbane and Women's Hospitals, Brisbane, Australia, and 31 from South Africa. This study revealed that the 8-oxodG/dG ratios tended to be higher in most non-malignant liver tissues compared to hepatocellular carcinoma tissue (p=0.2887). It also appeared that the ratio was higher in non-malignant liver tissue from Southern African patients (p=0.0479), but there was no difference in the 8-oxodG/dG ratios between non-malignant liver tissues and tumors of Australian hepatocellular carcinoma patients (p=0.7722). Additionally, this study also revealed a trend for a higher 8-oxodG/dG ratio in non-malignant liver tissues compared to tumoural tissues of patients with HBV. Significant differences were not observed in the 8-oxodG/dG ratios between non-cirrhotic and cirrhotic non-malignant liver tissues.

Loss of c-Met signaling sensitizes hepatocytes to lipotoxicity and induces cholestatic liver damage by aggravating oxidative stress

Recent studies confirmed a critical importance of c-Met signaling for liver regeneration by modulating redox balance. Here we used liver-specific conditional knockout mice (MetKO) and a nutritional model of hepatic steatosis to address the role of c-Met in cholesterol-mediated liver toxicity. Liver injury was assessed by histopathology and plasma enzymes levels. Global transcriptomic changes were examined by gene expression microarray, and key molecules involved in liver damage and lipid homeostasis were evaluated by Western blotting. Loss of c-Met signaling amplified the extent of liver injury in MetKO mice fed with high-cholesterol diet for 30days as evidenced by upregulation of liver enzymes and increased synthesis of total bile acids, aggravated inflammatory response and enhanced intrahepatic lipid deposition. Global transcriptomic changes confirmed the enrichment of networks involved in steatosis and cholestasis. In addition, signaling pathways related to glutathione and lipid metabolism, oxidative stress and mitochondria dysfunction were significantly affected by the loss of c-Met function. Mechanistically, exacerbation of oxidative stress in MetKO livers was corroborated by increased lipid and protein oxidation. Western blot analysis further revealed suppression of Erk, NF-kB and Nrf2 survival pathways and downstream target genes (e.g. cyclin D1, SOD1, gamma-GCS), as well as up-regulation of proapoptotic signaling (e.g. p53, caspase 3). Consistent with the observed steatotic and cholestatic phenotype, nuclear receptors RAR, RXR showed increased activation while expression levels of CAR, FXR and PPAR-alpha were decreased in MetKO. Collectively, our data provide evidence for the critical involvement of c-Met signaling in cholesterol and bile acids toxicity.

Purple carrot extract protects against cadmium intoxication in multiple organs of rats: Genotoxicity, oxidative stress and tissue morphology analyses

The aim of this study was to investigate if purple carrot extract is able to protect against the noxious activities induced by cadmium exposure in multiple organs of rats. For this purpose, histopathological analysis, genotoxicity and oxidative status were investigated in this setting. A total of twenty Wistar rats weighing 250g on the average, and 8 weeks age were distributed into four groups (n=5), as follows: Control group (non-treated group, CTRL); Cadmium group (Cd) and Purple carrot extract groups at 400mg/L or 800mg/L. Histopathological analysis revealed that liver from animals treated with purple carrot extract improved tissue degeneration induced by cadmium intoxication. Genetic damage was reduced in blood and hepatocytes as depicted by comet and micronucleus assays in animals treated with purple carrot extract. SOD-CuZn and cytocrome C gene expression increased in groups treated with purple carrot extract. Purple carrot extract also reduced the 8OHdG levels in liver cells when compared to cadmium group. Taken together, our results demonstrate that purple carrot extract is able to protect against cadmium intoxication by means of reducing tissue regeneration, genotoxicity and oxidative stress in multiple organs of Wistar rats.

Transcriptional Up-Regulation of APE1/Ref-1 in Hepatic Tumor: Role in Hepatocytes Resistance to Oxidative Stress and Apoptosis

Objective

Human Hepatocellular Carcinoma (HCC) is the fifth most frequent neoplasm worldwide and the most serious complication of long-standing chronic liver diseases (CLD). Its development is associated with chronic inflammation and sustained oxidative stress. Deregulation of apurinic apyrimidinic endonuclease 1/redox effector factor 1 (APE1/Ref-1), a master regulator of cellular response to oxidative stress, has been associated with poor prognosis in several cancers including HCC.

Design

In the present study we investigated the APE1/Ref-1 mRNA levels in cirrhotic and HCC tissues obtained during HCC resection. The possible protective role of APE1/Ref-1 against oxidative stress and apoptosis was evaluated in vitro in immortalized human hepatocytes (IHH) over-expressing APE1/Ref-1.

Results

APE1/Ref-1 was up-regulated in HCC, regulation occurring at the transcriptional level. APE1/Ref-1 mRNA content increased with the progression of liver disease with the transcriptional up-regulation present in cirrhosis significantly increased in HCC. The up-regulation was higher in the less differentiated cancers. In vitro, over-expression of APE1/Ref-1 in normal hepatocytes conferred cell protection against oxidative stress and it was associated with BAX inhibition and escape from apoptosis.

Conclusion

APE1/Ref-1 is up-regulated in HCC and this over-expression correlates with cancer aggressiveness. The up-regulation occurs at the transcriptional level and it is present in the earliest phases of hepatocarcinogenesis. The APE-1/Ref-1 over-expression is associated with hepatocyte survival and inhibits BAX activation and apoptosis. These data suggest a possible role of APE1/Ref-1 over-expression both in hepatocyte survival and HCC development calling attention to this molecule as a promising marker for HCC diagnosis and treatment.

Cellular stress responses in hepatitis C virus infection: Mastering a two-edged sword

Hepatitis C virus (HCV) infection affects chronically more than 150 million humans worldwide. Chronic HCV infection causes severe liver disease and hepatocellular carcinoma. While immune response-mediated events are major players in HCV pathogenesis, the impact that viral replication has on cellular homeostasis is increasingly recognized as a necessary contributor to pathological manifestations of HCV infection such as steatosis, insulin-resistance or liver cancer. In this review, we will briefly overview the different cellular stress pathways that are induced by hepatitis C virus infection, the response that the cell promotes to attempt regaining homeostasis or to induce dysfunctional cell death, and how the virus co-opts these response mechanisms to promote both viral replication and survival of the infected cell. We will review the role of unfolded protein and oxidative stress responses as well as the role of auto- and mitophagy in HCV infection. Finally, we will discuss the recent discovery of a cellular chaperone involved in stress responses, the sigma-1 receptor, as a cellular factor required at the onset of HCV infection and the potential molecular events underlying the proviral role of this cellular factor in HCV infection.

Resetting the transcription factor network reverses terminal chronic hepatic failure

The cause of organ failure is enigmatic for many degenerative diseases, including end-stage liver disease. Here, using a CCl4-induced rat model of irreversible and fatal hepatic failure, which also exhibits terminal changes in the extracellular matrix, we demonstrated that chronic injury stably reprograms the critical balance of transcription factors and that diseased and dedifferentiated cells can be returned to normal function by re-expression of critical transcription factors, a process similar to the type of reprogramming that induces somatic cells to become pluripotent or to change their cell lineage. Forced re-expression of the transcription factor HNF4α induced expression of the other hepatocyte-expressed transcription factors; restored functionality in terminally diseased hepatocytes isolated from CCl4-treated rats; and rapidly reversed fatal liver failure in CCl4-treated animals by restoring diseased hepatocytes rather than replacing them with new hepatocytes or stem cells. Together, the results of our study indicate that disruption of the transcription factor network and cellular dedifferentiation likely mediate terminal liver failure and suggest reinstatement of this network has therapeutic potential for correcting organ failure without cell replacement.

Transforming growth factor-β and toll-like receptor-4 polymorphisms are not associated with fibrosis in haemochromatosis

AIM: To investigate the role of genetic polymorphisms in the progression of hepatic fibrosis in hereditary haemochromatosis.

METHODS: A cohort of 245 well-characterised C282Y homozygous patients with haemochromatosis was studied, with all subjects having liver biopsy data and DNA available for testing. This study assessed the association of eight single nucleotide polymorphisms (SNPs) in a total of six genes including toll-like receptor 4 (TLR4), transforming growth factor-beta (TGF-β), oxoguanine DNA glycosylase, monocyte chemoattractant protein 1, chemokine C-C motif receptor 2 and interleukin-10 with liver disease severity. Genotyping was performed using high resolution melt analysis and sequencing. The results were analysed in relation to the stage of hepatic fibrosis in multivariate analysis incorporating other cofactors including alcohol consumption and hepatic iron concentration.

RESULTS: There were significant associations between the cofactors of male gender (P = 0.0001), increasing age (P = 0.006), alcohol consumption (P = 0.0001), steatosis (P = 0.03), hepatic iron concentration (P < 0.0001) and the presence of hepatic fibrosis. Of the candidate gene polymorphisms studied, none showed a significant association with hepatic fibrosis in univariate or multivariate analysis incorporating cofactors. We also specifically studied patients with hepatic iron loading above threshold levels for cirrhosis and compared the genetic polymorphisms between those with no fibrosis vs cirrhosis however there was no significant effect from any of the candidate genes studied. Importantly, in this large, well characterised cohort of patients there was no association between SNPs for TGF-β or TLR4 and the presence of fibrosis, cirrhosis or increasing fibrosis stage in multivariate analysis.

CONCLUSION: In our large, well characterised group of haemochromatosis subjects we did not demonstrate any relationship between candidate gene polymorphisms and hepatic fibrosis or cirrhosis.

Oxidative stress and epigenetic instability in human hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is a major cause of cancer death, and its development is influenced by the status of inflammation and oxidative stress in the liver. Although oxidative stress might induce genetic changes and play a role in HCC development, many epigenetic alterations have also been reported in this type of tumor, suggesting the importance of epigenetic instability in hepatocarcinogenesis. Epigenetic instability results in 2 types of DNA alterations: hypermethylation of the promoter of tumor suppressor genes (TSGs), and hypomethylation of nonpromoter CpG, such as repetitive elements and satellite DNA. The former causes transcriptional inactivation of TSGs, while the latter reportedly induces chromosomal instability and an abnormal activation of oncogenes as well as mobile genetic elements. Oxidative stress could induce epigenetic instability and inactivate TSGs through the recruitment of the polycomb repressive complex to the promoter sequence carrying DNA damage induced by oxidation. Inflammatory cytokines from immune cells also reportedly induce expression of several histone and DNA modulators. On the other hand, DNA oxidation could lead to activation of DNA repair pathways and affect the binding of methyl cytosine-binding protein to DNA, which could cause DNA hypomethylation. The decrease of the level of methyl group donors also contributes to the alteration in the methylation status. These mechanisms should act in concert and induce epigenetic instability, leading to HCC.

Oxidative stress and hepatitis C virus

The disproportionate imbalance between the systemic manifestation of reactive oxygen species and body’s ability to detoxify the reactive intermediates is referred to as oxidative stress. Several biological processes as well as infectious agents, physiological or environmental stress, and perturbed antioxidant response can promote oxidative stress. Oxidative stress usually happens when cells are exposed to more electrically charged reactive oxygen species (ROS) such as H2O2 or O2-. The cells’ ability to handle such pro-oxidant species is impeded by viral infections particularly within liver that plays an important role in metabolism and detoxification of harmful substances. During liver diseases (such as hepatocellular or cholestatic problems), the produced ROS are involved in transcriptional activation of a large number of cytokines and growth factors, and continued production of ROS and Reactive Nitrogen Species (RNS) feed into the vicious cycle. Many human viruses like HCV are evolved to manipulate this delicate pro- and antioxidant balance; thus generating the sustainable oxidative stress that not only causes hepatic damage but also stimulates the processes to reduce treatment of damage. In this review article, the oxidant and antioxidant pathways that are perturbed by HCV genes are discussed. In the first line of risk, the pathways of lipid metabolism present a clear danger in accumulation of viral induced ROS. Viral infection leads to decrease in cellular concentrations of glutathione (GSH) resulting in oxidation of important components of cells such as proteins, DNA and lipids as well as double strand breakage of DNA. These disorders have the tendency to lead the cells toward cirrhosis and hepatocellular carcinoma in adults due to constant insult. We have highlighted the importance of such pathways and revealed differences in the extent of oxidative stress caused by HCV infection.

Differential expression of hepatic apurinic/apyrimidinic endonuclease 1, a DNA repair enzyme, in chronic hepatitis

AIM: To determine hepatic expression of apurinic/apyrimidinic endonuclease 1 (APE-1) and 8-hydroxydeoxyguanosine (8-OHdG) in patients with chronic hepatitis B and C.

METHODS: Liver biopsies were obtained from 27 patients with chronic hepatitis B virus (HBV), 30 with chronic hepatitis C virus (HCV), 6 with autoimmune hepatitis (AIH), and 6 with primary biliary cirrhosis (PBC). Normal liver tissue was obtained from surgical resection specimens of four patients. Hepatic APE-1 protein and mRNA expression were assayed by Western blot and by real-time polymerase chain reaction, respectively. Hepatocellular APE-1 and 8-OHdG expression were determined by immunohistochemistry.

RESULTS: The staining intensity of hepatocellular nuclear APE-1 was lower in the HBV group than in the other groups (P < 0.05). Hepatic APE-1 protein levels were reduced in the HBV group relative to the other groups. Hepatic APE-1 mRNA levels were also lower in the HBV group. The proportion of hepatocytes with 8-OHdG-positive nuclei was increased in the HCV, AIH and PBC groups (P < 0.05), but not in the HBV group. Hepatocellular nuclear APE-1 levels were positively correlated with hepatocellular 8-OHdG levels in both the HBV and HCV groups (HBV, r = 0.34, P < 0.05; HCV, r = 0.54, P < 0.01).

CONCLUSION: An imbalance between oxidative DNA damage and APE-1 expression may contribute to hepatocarcinogenesis in chronic viral hepatitis.

HCV and oxidative stress in the liver

Hepatitis C virus (HCV) is the etiological agent accounting for chronic liver disease in approximately 2-3% of the population worldwide. HCV infection often leads to liver fibrosis and cirrhosis, various metabolic alterations including steatosis, insulin and interferon resistance or iron overload, and development of hepatocellular carcinoma or non-Hodgkin lymphoma. Multiple molecular mechanisms that trigger the emergence and development of each of these pathogenic processes have been identified so far. One of these involves marked induction of a reactive oxygen species (ROS) in infected cells leading to oxidative stress. To date, markers of oxidative stress were observed both in chronic hepatitis C patients and in various in vitro systems, including replicons or stable cell lines expressing viral proteins. The search for ROS sources in HCV-infected cells revealed several mechanisms of ROS production and thus a number of cellular proteins have become targets for future studies. Furthermore, during last several years it has been shown that HCV modifies antioxidant defense mechanisms. The aim of this review is to summarize the present state of art in the field and to try to predict directions for future studies.

Oxidative stress-induced 1, N6-ethenodeoxyadenosine adduct formation contributes to hepatocarcinogenesis

Numerous studies have found that oxidative stress-derived 1, N⁶-ethenodeoxyadenosine (ɛ-dA) can act as a driving force towards hepatocellular carcinoma (HCC) in cancer-prone liver diseases. The aim of the present study was to determine the oxidative stress status and the occurrence of ɛ-dA in HCC and adjacent non-tumor liver tissue, and to clarify whether the occurrence of ɛ-dA is related to liver inflammatory activity, fibrosis and mutant p53 expression. Oxidative stress-related parameters were examined in tumor and (or) non-tumor liver tissues of 32 patients with HCC. ɛ-dA, mutant p53 and proliferating cell nuclear antigen (PCNA) were immunohistochemically investigated in control, HCC and non-tumor liver tissues. The total antioxidant capacity and total superoxide dismutase activity of HCC tissues were lower compared to those of non-tumor tissues (P<0.05 vs. P<0.001). The prevalence of ɛ-dA in HCC was significantly higher compared to control (P<0.0001) and non-tumor liver tissues (P<0.001). A significant correlation between the positive rate of ɛ-dA and mutant p53 was observed (r=0.5162, P<0.01). The positive rate of PCNA in HCC was significantly higher compared to control (P<0.0001) and non-tumor liver tissues (P<0.0001). There was a possible link between the formation of ɛ-dA and chronic inflammation and fibrosis. Therefore, ɛ-dA lesions may gradually accumulate in chronic liver diseases, and partially contribute to mutant p53 overexpression and excessive cell proliferation, making it a potential mechanism in oxidative stress-mediated hepatocarcinogenesis.

Oxidative stress induces itch via activation of transient receptor potential subtype ankyrin 1 in mice

OBJECTIVE

To investigate the role of oxidative stress in itch-indicative scratching behavior in mice, and furthermore, to define the cellular and molecular mechanisms underlying oxidative stress-mediated itch.

METHODS

Scratching behavior was induced by intradermal injection of the oxidants hydrogen peroxide (H₂O₂) or tert-butylhydroperoxide (tBHP) into the nape of the neck in mice. The mice were observed for 30 min.

RESULTS

Intradermal H₂O₂ (0.03%-1%) or tBHP (1-30 μmol) elicited robust scratching behavior, displaying an inverted U-shaped dose-response curve. Naloxone, an opioid receptor antagonist, but not morphine, largely suppressed the oxidant-induced scratching. Chlorpheniramine, a histamine H1 receptor antagonist, blocked histamine- but not oxidant-induced scratching, indicating the involvement of a histamine-independent mechanism in oxidant-evoked itch. Further, resiniferatoxin treatment abolished oxidant-induced scratching, suggesting an essential role of C-fibers. Notably, blockade of transient receptor potential subtype ankyrin 1 (TRPA1) with the selective TRPA1 antagonist HC-030031, or genetic deletion of Trpa1 but not Trpv1 (subfamily V, member 1) resulted in a profound reduction in H₂O₂-evoked scratching. Finally, systemic administration of the antioxidant N-acetyl-L-cysteine or trolox (a water-soluble vitamin E analog) attenuated scratching induced by the oxidants.

CONCLUSION

Oxidative stress by different oxidants induces profound scratching behavior, which is largely histamine- and TRPV1-independent but TRPA1-dependent. Antioxidants and TRPA1 antagonists may be used to treat human itch conditions associated with oxidative stress.

Oxidative stress and liver disease

In humans, oxidative stress and antioxidant defenses are the sum of a complicated network of enzymatic and non-enzymatic processes. Depending on the stage and severity of diseases, a patient's antioxidant armamentarium may increase as an appropriate response to an oxidant challenge, whereas others may decrease as an indication of unbalanced consumption. In some cases, the formation of reactive oxygen species is a requisite and healthy event. In fact, free radicals can affect intracellular signal transduction and gene regulation, resulting in cytokine production essential to the inflammatory process. In many other cases, especially liver diseases, excessive oxidative stress undoubtedly contributes to the progression and pathological findings of disease and serves as a prognostic indicator. Reactive oxygen species are highly reactive molecules that are naturally generated in small amounts through metabolism and could damage cellular molecules such as lipids, proteins or DNA. Oxidative stress plays a major role in many liver diseases. In this review, we summarize the biological character of free radicals and some antioxidants, and the related methods of analysis. Then, we discusses the association of oxidative stress to many types of liver diseases.

Bile acids: from digestion to cancers

Bile acids (BAs) are cholesterol metabolites that have been extensively studied these last decades. BAs have been classified in two groups. Primary BAs are synthesized in liver, when secondary BAs are produced by intestinal bacteria. Recently, next to their ancestral roles in digestion and fat solubilization, BAs have been described as signaling molecules involved in many physiological functions, such as glucose and energy metabolisms. These signaling pathways involve the activation of the nuclear receptor FXRα or of the G-protein-coupled receptor TGR5. These two receptors have selective affinity to different types of BAs and show different expression patterns, leading to different described roles of BAs. It has been suggested for long that BAs could be molecules linked to tumor processes. Indeed, as many other molecules, regarding analyzed tissues, BAs could have either protective or pro-carcinogen activities. However, the molecular mechanisms responsible for these effects have not been characterized yet. It involves either chemical properties or their capacities to activate their specific receptors FXRα or TGR5. This review highlights and discusses the potential links between BAs and cancer diseases and the perspectives of using BAs as potential therapeutic targets in several pathologies.

Tularemia progression accompanied with oxidative stress and antioxidant alteration in spleen and liver of BALB/c mice

Francisella tularensis is the causative agent of tularemia. It is an intracellular pathogen with the ability to survive within phagosomes and induce pyroptotic cell death. In this study, we attempted to prove whether oxidative imbalance plays a significant role in tularemia pathogenesis. In our experimental model, we subcutaneously infected female BALB/c mice (dose 10(5) CFU of F. tularensis LVS). Liver, spleen, and blood were collected from mice at regular intervals from days 1-15 after infection. The bacterial burden was assessed by a cultivation test. The burden was unchanging from the 2(nd) to 6(th) day after infection. The bacterial burden corresponded to the plasmatic level of IFN-γ, IL-6, and liver malondialdehyde. After the phase of acute bacteraemia and the innate immunity reaction, the levels of reduced glutathione and total low molecular weight antioxidants decreased significantly and the activity of caspase-3 increased in the liver. The level of reduced glutathione decreased to 25% of the original level, and the total level of low molecular weight antioxidants was less than 50% of the initial amount. The demonstrated effects of tularemia-induced pathology had a more extensive impact on the liver than on the spleen.

Farnesoid X receptor protects hepatocytes from injury by repressing miR-199a-3p, which increases levels of LKB1

BACKGROUND & AIMS

Hepatocyte injury occurs during liver fibrogenesis. MicroRNAs (miRNA) regulate some of these processes, and some are regulated by the farnesoid X receptor (FXR). We investigated the effect of repression of specific miRNAs by FXR in hepatocyte injury using fibrotic liver tissue from patients and hepatocytes.

METHODS

We used immunohistochemistry or real-time polymerase chain reaction to analyze proteins and miRNAs in human and mouse liver samples. HepG2 cells were transfected with pre-miRNA, antisense oligonucleotides, small interfering RNAs, the 3'-untranslated region of liver kinase B1 (LKB1) (STK11), or constructs for overexpression, and analyzed.

RESULTS

Liver tissue from patients with severe fibrosis had lower levels of FXR and greater amounts of hepatocyte death than samples from patients with mild disease. Levels of several miRNAs changed when FXR expression was disrupted in the liver; one of these, miR-199a-3p, was significantly up-regulated in patients with severe fibrosis. Activation of FXR by its ligand reduced the level of miR-199a-3p in HepG2 cells. LKB1 messenger RNA was identified as a target of miR-199a-3p, and its expression was reduced in human fibrotic liver tissue. Overexpression of FXR or incubation of cultured hepatocytes with the FXR ligand up-regulated LKB1; LKB1 was not induced in cells transfected with miR-199a-3p. Incubation of HepG2 cells with FXR ligand, or injection of the ligand into mice, protected hepatocytes from injury and increased levels of LKB1; levels of miR-199a-3p were reduced compared with cells that were not incubated with the FXR ligand. Activation of FXR reduced mitochondrial dysfunction and oxidative stress and increased hepatocyte survival.

CONCLUSIONS

In hepatocytes, FXR represses production of miR-199a-3p. In fibrotic livers of humans and mice, FXR expression is reduced, increasing levels of miR-199a-3p, which reduces levels of LKB1. FXR therefore protects hepatocytes from injury by repressing miR-199a-3p and thereby increasing levels of LKB1.

Immunochemical detection of oxidatively damaged DNA

Oxidatively damaged DNA is implicated in various diseases, including neurodegenerative disorders, cancer, diabetes, cardiovascular and inflammatory diseases as well as aging. Several methods have been developed to detect oxidatively damaged DNA. They include chromatographic techniques, the Comet assay, (32)P-postlabelling and immunochemical methods that use antibodies to detect oxidized lesions. In this review, we discuss the detection of 8-oxo-7,8-dihydro-29-deoxyguanosine (8-oxodG), the most abundant oxidized nucleoside. This lesion is frequently used as a marker of exposure to oxidants, including environmental pollutants, as well as a potential marker of disease progression. We concentrate on studies published between the years 2000 and 2011 that used enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry to detect 8-oxodG in humans, laboratory animals and in cell lines. Oxidative damage observed in these organisms resulted from disease, exposure to environmental pollutants or from in vitro treatment with various chemical and physical factors.

Microfluidic tool based on the antibody-modified paramagnetic particles for detection of 8-hydroxy-2'-deoxyguanosine in urine of prostate cancer patients

Guanosine derivatives are important for diagnosis of oxidative DNA damage including 8-hydroxy-2'-deoxyguanosine (8-OHdG) as one of the most abundant products of DNA oxidation. This compound is commonly determined in urine, which makes 8-OHdG a good non-invasive marker of oxidation stress. In this study, we optimized and tested the isolation of 8-OHdG from biological matrix by using paramagnetic particles with an antibody-modified surface. 8-OHdG was determined using 1-naphthol generated by alkaline phosphatase conjugated with the secondary antibody. 1-Naphthol was determined by stopped flow injection analysis (SFIA) with electrochemical detector using a glassy carbon working electrode and by stationary electrochemical detection using linear sweep voltammetry. A special modular electrochemical SFIA system which needs only 10  μL of sample including working buffer for one analysis was completely designed and successfully verified. The recoveries in different matrices and analyte concentration were estimated. Detection limit (3 S/N) was estimated as 5  pg/mL of 8-OHdG. This method promises to be very easily modified to microfluidic systems as "lab on valve". The optimized method had sufficient selectivity and thus could be used for determination of 8-OHDG in human urine and therefore for estimation of oxidative DNA damage as a result of oxidation stress in prostate cancer patients.

Enhanced hepatic Nrf2 activation after ursodeoxycholic acid treatment in patients with primary biliary cirrhosis

The cytoprotective mechanisms of ursodeoxycholic acid (UDCA) in primary biliary cirrhosis (PBC) have not been fully clarified. UDCA has some antioxidant properties. Nuclear factor-E2-related factor-2 (Nrf2) plays a critical role in protecting a variety of tissues against oxidative stress. Therefore, to investigate the potential antioxidant effects of UDCA in PBC, we determined the intracellular status of both oxidant stress and antioxidant defenses in paired pre- and posttreatment liver biopsies from 13 PBC patients by immunodetection of 8-hydroxydeoxyguanosine (8-OHdG), Nrf2-, and Nrf2-mediated antioxidant proteins. After UDCA treatment, the number of 8-OHdG-positive hepatocytes or bile duct cells decreased with improvement of hepatic injury. The hepatic levels of both total and phosphorylated Nrf2 protein were increased, along with upregulation of nuclear phosphorylated Nrf2 expression in bile duct cells. In addition, the levels of both thioredoxin (TRX) and thioredoxin reductase 1 (TrxR1) protein were increased in the liver after UDCA. The upregulation of hepatic TRX or TrxR1 protein expression positively correlated with that of total Nrf2 protein expression. In conclusion, UDCA treatment can enhance hepatic Nrf2 activation and upregulate hepatic TRX and TrxR1 protein expression. Hepatic Nrf2 activation may play a role in the therapeutic response to UDCA in PBC.

Characteristic expression pattern of oxidative stress in livers with cryptogenic hepatocellular carcinoma

The mechanism responsible for the development of hepatocellular carcinoma (HCC) in the setting of oxidative stress has yet to be clearly defined. We studied the role of oxidative stress in hepatocarcinogenesis in subjects without underlying chronic viral hepatitis. The subjects were 24 patients negative for serum hepatitis B surface antigen and hepatitis C antibody tests, who underwent hepatic resection for HCC (Group N). Subjects were excluded if diagnosed with liver disease predisposing to HCC. Immunohistochemical staining for oxidative stress-related markers was performed on non-cancerous liver regions. Resected liver tissues adjacent to HCC from 24 patients with chronic hepatitis B (Group B) and 21 patients with chronic hepatitis C (Group C) were also examined. The percentage of 8-hydroxydeoxyguanosine-positive hepatocytes in Group N was significantly lower than that in Group B and that in the combined population of Groups B and C. The percentage of the area positive for 4-hydroxynonenal in Group N was significantly higher than that in Groups B or C. Meanwhile, the percentage of the area positive for manganese superoxide dismutase in Group N was not different from that in Groups B and C. In conclusion, the mechanism of hepatocarcinogenesis through oxidative stress for patients without known liver disease predisposing to HCC may differ from that for patients with chronic viral hepatitis.

Hydroxyoctadecadienoic acid as a potential biomarker for oxidative stress in patients with chronic hepatitis C

BACKGROUND AND AIM

The possible involvement of oxidative stress in hepatitis C virus (HCV)-induced liver damage and hepatocarcinogenesis has been reported. We have recently developed a novel method to measure total hydroxyoctadecadienoic acid (tHODE) and have proposed its usefulness as a biomarker for lipid peroxidation. The present study was undertaken to evaluate oxidative stress in HCV-infected liver diseases by several potential oxidative stress markers including tHODE and further to validate the biomarkers for evaluating the efficacy of iron reduction therapy.

METHODS

Total hydroxyoctadecadienoic acid, total 8-iso-prostagrandin F(2alpha) (t8-iso-PGF(2alpha)), selenoprotein P and other antioxidant compounds were measured in the plasma and erythrocytes obtained from 42 healthy controls and 78 HCV patients. Plasma levels of biomarkers and antioxidants were also assessed during the iron reduction therapy for 16 weeks in 12 HCV patients.

RESULTS

The concentrations of tHODE in the plasma and erythrocytes and t8-iso-PGF(2alpha) in the plasma of chronic HCV-infected patients were significantly higher than those of healthy controls. Plasma levels of vitamin E and vitamin C of HCV-infected patients were lower than those of the controls. Furthermore, the plasma tHODE significantly correlated with serum aminotransferases and type IV collagen-7S domain in chronic HCV-infected patients. During the iron reduction therapy, the plasma levels of tHODE but not t8-iso-PGF(2alpha) decreased and inversely its stereo-isomer ratio (ZE/EE) increased in parallel with the decreases of serum alanine aminotransferase, ferritin and alpha-fetoprotein.

CONCLUSION

The levels of tHODE in chronic HCV-infected patients can be a useful biomarker for the evaluation of oxidative stress in chronic hepatitis C.

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.

Redox mechanisms in hepatic chronic wound healing and fibrogenesis

Reactive oxygen species (ROS) generated within cells or, more generally, in a tissue environment, may easily turn into a source of cell and tissue injury. Aerobic organisms have developed evolutionarily conserved mechanisms and strategies to carefully control the generation of ROS and other oxidative stress-related radical or non-radical reactive intermediates (that is, to maintain redox homeostasis), as well as to 'make use' of these molecules under physiological conditions as tools to modulate signal transduction, gene expression and cellular functional responses (that is, redox signalling). However, a derangement in redox homeostasis, resulting in sustained levels of oxidative stress and related mediators, can play a significant role in the pathogenesis of major human diseases characterized by chronic inflammation, chronic activation of wound healing and tissue fibrogenesis. This review has been designed to first offer a critical introduction to current knowledge in the field of redox research in order to introduce readers to the complexity of redox signalling and redox homeostasis. This will include ready-to-use key information and concepts on ROS, free radicals and oxidative stress-related reactive intermediates and reactions, sources of ROS in mammalian cells and tissues, antioxidant defences, redox sensors and, more generally, the major principles of redox signalling and redox-dependent transcriptional regulation of mammalian cells. This information will serve as a basis of knowledge to introduce the role of ROS and other oxidative stress-related intermediates in contributing to essential events, such as the induction of cell death, the perpetuation of chronic inflammatory responses, fibrogenesis and much more, with a major focus on hepatic chronic wound healing and liver fibrogenesis.

Protective effects of N-acetylcysteine and Ginkgo biloba extract on ischaemia-reperfusion-induced hepatic DNA damage in rats

Hepatic ischaemia-reperfusion injury is a serious problem that occurs during various surgical operations such as liver transplantation, surgical revascularization, and partial organ resection. Different pharmacological agents have been used for the protection of organ function and for extending the tolerable ischaemic interval after the ischaemic insult. We aimed to determine the presence of 8-hydroxydeoxyguanosine (8-OHdG) in the DNA from liver undergoing ischaemia-reperfusion, and also to evaluate the protective effects of N-acetylcysteine (NAC) and EGb761 (Ginkgo biloba extract) against hepatic oxidative DNA damage. A total of 40 rats were divided into four groups of 10 animals each (sham-operation group, control group, NAC group, and EGb761 group). Oxidative damage to DNA was evaluated by measuring the increase in 8-OHdG formation in liver tissue and also the effects of NAC and EGb761 pretreatment. Hepatic ischaemia for 90 min followed by reperfusion caused a marked increase in tissue levels of 8-OHdG, thiobarbituric acid-reactive substance, serum ALT, AST and LDH activities compared to sham-operated group. Pretreatment with both NAC and EGb761 clearly diminished 8-OHdG formation and lipid peroxidation. These findings suggest that antioxidant molecules such as NAC and EGb761 may be useful in preventing postischaemic reperfusion injury in hepatic tissue.

8-Hydroxy-2'-deoxy-guanosine is a risk factor for development of hepatocellular carcinoma in patients with chronic hepatitis C virus infection

BACKGROUND AND AIM

Increased production of reactive oxygen species, which cause oxidative DNA damage, is considered to be related to hepatocarcinogenesis. 8-Hydroxy-2'-deoxy-guanosine (8-OHdG) is a useful marker of DNA damage induced by oxidative stress. The aim of this study was to determine whether expression of 8-OHdG is a risk factor for the development of hepatocellular carcinoma (HCC) in patients with hepatitis C virus (HCV) infection.

METHODS

The expression of 8-OHdG in liver biopsy specimens was assessed immunohistochemically. In total, 104 patients with chronic HCV infection who were diagnosed on liver biopsy between January 1987 and December 2002 were studied retrospectively. Univariate and multivariate analyses using age, gender, habitual drinking, tobacco exposure, diabetes mellitus, serum alanine aminotransferase level, HCV genotype, hepatic fibrosis, inflammation, steatosis, and 8-OHdG expression in liver biopsy specimens were conducted to identify factors related to the development of HCC.

RESULTS

On multivariate analysis, 8-OHdG and fibrosis were independent and significant risk factors for HCC development (relative risk, 2.48; P = 0.023; relative risk, 5.35; P = 0.001, respectively). Furthermore, the cumulative incidence rate of HCC in 39 patients with high 8-OHdG expression levels was significantly greater than that in 65 patients with low 8-OHdG expression levels (P = 0.043). In addition, liver 8-OHdG expression was correlated with hepatic inflammation.

CONCLUSIONS

8-OHdG is a risk factor for the development of HCC in patients with chronic HCV infection. Patients with chronic HCV who express 8-OHdG should be monitored carefully for the development of HCC.

Serum paraoxonase and arylesterase activities for the evaluation of patients with chronic hepatitis

The sensitivity of standard biochemical tests for liver function is low and insufficient for a reliable determination of the presence or absence of liver disease. The aim of the present study was to investigate serum paraoxonase and arylesterase activities and lipid hydroperoxide (LOOH) levels, and to find out that whether the measurement of serum paraoxonase and arylesterase activities would be useful as an index of liver function status in chronic hepatitis (CH). Fourty-four patients with CH (24 CHB and 20 CHC) and 38 controls were enrolled. Serum paraoxonase and arylesterase activities were detected spectrophotometrically. LOOH levels were measured by the FOX-2 assay. Serum paraoxonase and arylesterase activities were significantly lower in patients with CH than controls (p < 0.001 for both), while LOOH levels were significantly higher (p < 0.001). Paraoxonase and arylesterase activities were inversely correlated with LOOH levels (r = -0.394, p < 0.05; r =-0.362, p < 0.05, respectively). Fibrosis scores of CH patients were significantly correlated with paraoxonase and arylesterase activities and LOOH levels (r =-0.276, p < 0.05; r = -0.583, p < 0.001 and r = 0.562, p < 0.001, respectively). Our results indicated that decrease in the activities paraoxonase and arylesterase may play a role in the pathogenesis of CH. In addition, serum paraoxonase and arylesterase activities measurement may add a significant contribution to the liver function tests.

Cytoplasmic fine granular expression of 8-hydroxydeoxyguanosine reflects early mitochondrial oxidative DNA damage in nonalcoholic fatty liver disease

To clarify the possible role of oxidative stress in hepatocytes in nonalcoholic fatty liver disease, the hepatic expression of 8-hydroxydeoxyguanosine (8-OHdG), a good marker of oxidative DNA damage, was immunohistochemically investigated in nonalcoholic steatohepatitis (NASH) and steatosis. In double immunostaining, the cytoplasmic fine granular 8-OHdG expression was considered to reflect 8-OHdG-positive mitochondrial DNA affecting oxidation stress. In steatosis, 4 of 8 cases showed cytoplasmic 8-OHdG, 1 case showed nuclear 8-OHdG and 1 case showed both cytoplasmic and nuclear 8-OHdG. In contrast, 8-OHdG expression was more frequently detected in NASH (12 of 13 cases, 92%). Immunoreactivity for 8-OHdG was observed only in the cytoplasm with a fine granular pattern (1 of 13 cases, 8%), only in the nucleus (6 of 13 cases, 46%), and in both the cytoplasm and the nucleus (5 of 13 cases, 38%). Megamitochondria also exhibited 8-OHdG intensely. We indicate that 8-OHdG expression in the cytoplasm with a fine granular pattern reflects oxidative damage to the mitochondrial DNA of hepatocytes in both NASH and steatosis. We propose herein that the evaluation of cytoplasmic 8-OHdG may be a sensitive diagnostic marker of early nonalcoholic fatty liver disease events.