'Liver let die': oxidative DNA damage and hepatotropic viruses

DHCR24 in Tumor Diagnosis and Treatment: A Comprehensive Review

As an important nutrient in the human body, cholesterol can not only provide structural components for the body's cells, but also can be transformed into a variety of active substances to regulate cell signaling pathways. As an important cholesterol synthase, DHCR24 participates in important regulatory processes in the body. The application of DHCR24 in tumor clinical diagnosis and treatment also attracts much attention. This article reviews the structure and regulatory characteristics of DHCR24, and the research of DHCR24 on tumor progression. We summarize the possible mechanisms of DHCR24 promoting tumor progression through reactive oxygen species (ROS), p53, Ras and PI3K-AKT pathways. Through our review, we hope to provide more research ideas and reference value for the application of DHCR24 in tumor prevention and treatment.

The role of Traditional Chinese medicine in anti-HBV: background, progress, and challenges

Chronic hepatitis B (CHB) remains a major world's most serious public health issues. Despite the remarkable effect of nucleos(t)ide analogues (NAs) in inhibiting hepatitis B virus (HBV) deoxyribonucleic acid (DNA) as the first-line drug, there are several limitations still, such as poor antigen inhibition, drug resistance, low-level viremia, restricting patients' functional cure. Due to the constraints of NAs, traditional medicines, such as traditional Chinese medicine (TCM), have become more prevalently used and researched in the clinical treatment of CHB as complementary alternative therapies. As a consequence, the review focuses on the background based on HBV's life cycle as well as the NAs' limitations, progress based on direct and indirect pathway of targeting HBV of TCM, and challenges of TCM. We found TCMs play an increasingly important role in anti-HBV. In a direct antiviral way, they regulate HBV infection, replication, assembly, and other aspects of the HBV life cycle. As for indirect way, TCMs can exert anti-HBV effects through targeting the host, including immune regulation, apoptosis, autophagy, oxidative stress, etc. Especially, TCMs have the advantages of strong antigenic inhibition compared to NAs. Specifically, we can combine the benefits of TCMs in strong HBV antigen inhibition with the benefits of NAs in targeted antiviral effects, in order to find a suitable combination of "TCM + NAs" to contribute to Chinese knowledge of the realisation of the "global elimination of HBV by 2030" goal of the World Health Organization.

SARS-CoV-2 and the DNA damage response

The recent coronavirus disease 2019 (COVID-19) pandemic was caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is characterized by respiratory distress, multiorgan dysfunction and, in some cases, death. The virus is also responsible for post-COVID-19 condition (commonly referred to as 'long COVID'). SARS-CoV-2 is a single-stranded, positive-sense RNA virus with a genome of approximately 30 kb, which encodes 26 proteins. It has been reported to affect multiple pathways in infected cells, resulting, in many cases, in the induction of a 'cytokine storm' and cellular senescence. Perhaps because it is an RNA virus, replicating largely in the cytoplasm, the effect of SARS-Cov-2 on genome stability and DNA damage responses (DDRs) has received relatively little attention. However, it is now becoming clear that the virus causes damage to cellular DNA, as shown by the presence of micronuclei, DNA repair foci and increased comet tails in infected cells. This review considers recent evidence indicating how SARS-CoV-2 causes genome instability, deregulates the cell cycle and targets specific components of DDR pathways. The significance of the virus's ability to cause cellular senescence is also considered, as are the implications of genome instability for patients suffering from long COVID.

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.

Single cell and bulk transcriptome analysis identified oxidative stress response-related features of Hepatocellular Carcinoma

Background: Hepatocellular Carcinoma (HCC) is a common lethal digestive system tumor. The oxidative stress mechanism is crucial in the HCC genesis and progression. Methods: Our study analyzed single-cell and bulk sequencing data to compare the microenvironment of non-tumor liver tissues and HCC tissues. Through these analyses, we aimed to investigate the effect of oxidative stress on cells in the HCC microenvironment and identify critical oxidative stress response-related genes that impact the survival of HCC patients. Results: Our results showed increased oxidative stress in HCC tissue compared to non-tumor tissue. Immune cells in the HCC microenvironment exhibited higher oxidative detoxification capacity, and oxidative stress-induced cell death of dendritic cells was attenuated. HCC cells demonstrated enhanced communication with immune cells through the MIF pathway in a highly oxidative hepatoma microenvironment. Meanwhile, using machine learning and Cox regression screening, we identified PRDX1 as a predictor of early occurrence and prognosis in patients with HCC. The expression level of PRDX1 in HCC was related to dysregulated ribosome biogenesis and positively correlated with the expression of immunological checkpoints (PDCD1LG2, CTLA4, TIGIT, LAIR1). High PRDX1 expression in HCC patients correlated with better sensitivity to immunotherapy agents such as sorafenib, IGF-1R inhibitor, and JAK inhibitor. Conclusion: In conclusion, our study unveiled variations in oxidative stress levels between non-tumor liver and HCC tissues. And we identified oxidative stress gene markers associated with hepatocarcinogenesis development, offering novel insights into the oxidative stress response mechanism in HCC.

Hydrogen Peroxide Inhibits Hepatitis B Virus Replication by Downregulating HBx Levels via Siah-1-Mediated Proteasomal Degradation in Human Hepatoma Cells

The hepatitis B virus (HBV) is constantly exposed to significant oxidative stress characterized by elevated levels of reactive oxygen species (ROS), such as H2O2, during infection in hepatocytes of patients. In this study, we demonstrated that H2O2 inhibits HBV replication in a p53-dependent fashion in human hepatoma cell lines expressing sodium taurocholate cotransporting polypeptide. Interestingly, H2O2 failed to inhibit the replication of an HBV X protein (HBx)-null HBV mutant, but this defect was successfully complemented by ectopic expression of HBx. Additionally, H2O2 upregulated p53 levels, leading to increased expression of seven in absentia homolog 1 (Siah-1) levels. Siah-1, an E3 ligase, induced the ubiquitination-dependent proteasomal degradation of HBx. The inhibitory effect of H2O2 was nearly abolished not only by treatment with a representative antioxidant, N-acetyl-L-cysteine but also by knockdown of either p53 or Siah-1 using specific short hairpin RNA, confirming the role of p53 and Siah-1 in the inhibition of HBV replication by H2O2. The present study provides insights into the mechanism that regulates HBV replication under conditions of oxidative stress in patients.

Phenolic Compounds in Salicornia spp. and Their Potential Therapeutic Effects on H1N1, HBV, HCV, and HIV: A Review

Despite public health risk mitigation measures and regulation efforts by many countries, regions, and sectors, viral outbreaks remind the world of our vulnerability to biological hazards and the importance of mitigation actions. The saltwater-tolerant plants in the Salicornia genus belonging to the Amaranthaceae family are widely recognized and researched as producers of clinically applicable phytochemicals. The plants in the Salicornia genus contain flavonoids, flavonoid glycosides, and hydroxycinnamic acids, including caffeic acid, ferulic acid, chlorogenic acid, apigenin, kaempferol, quercetin, isorhamnetin, myricetin, isoquercitrin, and myricitrin, which have all been shown to support the antiviral, virucidal, and symptom-suppressing activities. Their potential pharmacological usefulness as therapeutic medicine against viral infections has been suggested in many studies, where recent studies suggest these phenolic compounds may have pharmacological potential as therapeutic medicine against viral infections. This study reviews the antiviral effects, the mechanisms of action, and the potential as antiviral agents of the aforementioned phenolic compounds found in Salicornia spp. against an influenza A strain (H1N1), hepatitis B and C (HBV/HCV), and human immunodeficiency virus 1 (HIV-1), as no other literature has described these effects from the Salicornia genus at the time of publication. This review has the potential to have a significant societal impact by proposing the development of new antiviral nutraceuticals and pharmaceuticals derived from phenolic-rich formulations found in the edible Salicornia spp. These formulations could be utilized as a novel strategy by which to combat viral pandemics caused by H1N1, HBV, HCV, and HIV-1. The findings of this review indicate that isoquercitrin, myricetin, and myricitrin from Salicornia spp. have the potential to exhibit high efficiency in inhibiting viral infections. Myricetin exhibits inhibition of H1N1 plaque formation and reverse transcriptase, as well as integrase integration and cleavage. Isoquercitrin shows excellent neuraminidase inhibition. Myricitrin inhibits HIV-1 in infected cells. Extracts of biomass in the Salicornia genus could contribute to the development of more effective and efficient measures against viral infections and, ultimately, improve public health.

Possible spread of SARS-CoV-2 in domestic and wild animals and body temperature role

The COVID-19 pandemic was officially announced in March 2020 and is still moving around the world. Virus strains, their pathogenicity and infectivity are changing, but the ability is fast to spread and harm people's health remained, despite the seasonality seasons and other circumstances. Most likely, humanity is doomed for a long time to coexistence with this emergent pathogen, since it is already circulating not only among the human population, but and among fauna, especially among wild animals in different regions of the planet. Thus, the range the virus has expanded, the material and conditions for its evolution are more than enough. The detection of SARS-CoV-2 in known infected fauna species is analyzed and possible spread and ongoing circulation of the virus in domestic and wild animals are discussed. One of the main focus of the article is the role of animal body temperature, its fluctuations and the presence of entry receptors in the susceptibility of different animal species to SARS-CoV-2 infection and virus spreading in possible new ecological niches. The possibility of long-term circulation of the pathogen among susceptible organisms is discussed.

Garlic (Allium sativum L.): Its Chemistry, Nutritional Composition, Toxicity and Anticancer Properties

The current review discuss the chemistry, nutritional composition, toxicity, and biological functions of garlic and its bioactive compounds against various types of cancers via different anticancer mechanisms. Several scientific documents were found in reliable literature and searched in databases viz Science Direct, PubMed, Web of Science, Scopus and Research Gate were carried out using keywords such as "garlic", "garlic bioactive compounds", "anticancer mechanisms of garlic", "nutritional composition of garlic", and others. Garlic contains several phytoconstituents with activities against cancer, and these compounds such as diallyl trisulfide (DATS), allicin, and diallyl disulfide (DADS), diallyl sulfide (DAS), and allyl mercaptan (AM). The influence of numerous garlic-derived products, phytochemicals, and nanoformulations on the liver, oral, prostate, breast, gastric, colorectal, skin, and pancreatic cancers has been studied. Based on our search, the bioactive molecules in garlic were found to inhibit the various phases of cancer. Moreover, the compounds in this plant also abrogate the peroxidation of lipids, activity of nitric oxide synthase, epidermal growth factor (EGF) receptor, nuclear factor-kappa B (NF-κB), protein kinase C, and regulate cell cycle and survival signaling cascades. Hence, garlic and its bioactive molecules exhibit the aforementioned mechanistic actions and thus, they could be used to inhibit the induction, development and progression of cancer. The review describes the nutritional Composition of garlic, its bioactive molecules, and nanoformulations against various types of cancers, as well as the potential for developing these agents as antitumor drugs.

Sirt1 deficiency upregulates glutathione metabolism to prevent hepatocellular carcinoma initiation in mice

Sirtuin-1 (SIRT1) is involved in various metabolic pathways, including fatty acid synthesis and gluconeogenesis in the liver. However, its role in initiation and progression of liver cancer remains unclear. Studying Sirt1 liver-specific knockout (LKO) mice in combination with diethylnitrosamine (DEN) treatment, we demonstrated that loss of Sirt1 rendered mice resistant to DEN-induced hepatocellular carcinoma (HCC) development. RNA-seq revealed that livers from LKO mice exhibited an enrichment in glutathione metabolism eight months after DEN challenge. Sirt1 deficiency elevated the expression of glutathione-s-transferase family genes by increasing the level of Nrf2, a key regulator of glutathione metabolism. Hence, LKO livers displayed a reductive environment with an increased ratio of GSH to GSSG and an elevated GSH level. Furthermore, using CRISPR knockout techniques, we confirmed that the impairment of HCC formation in LKO mice is mainly dependent on NRF2 signaling. Meanwhile, HCC induced by DEN could be blocked by the administration of N-acetyl cysteine (NAC) when administered one month after DEN challenge. However, NAC treatment starting five months after DEN injection was not able to prevent tumor development. In conclusion, our findings indicate that a reductive environment orchestrated by glutathione metabolism at an early stage can prevent the initiation of HCC.

Liver-specific over-expression of Cripto-1 in transgenic mice promotes hepatocyte proliferation and deregulated expression of hepatocarcinogenesis-related genes and signaling pathways

In this study, we investigated the role of embryonic gene Cripto-1 (CR-1) in hepatocellular carcinoma (HCC) using hepatocyte-specific CR-1-overexpressing transgenic mice. The expression of truncated 1.7-kb CR-1 transcript (SF-CR-1) was significantly higher than the full-length 2.0-kb CR-1 transcript (FL-CR-1) in a majority of HCC tissues and cell lines. Moreover, CR-1 mRNA and protein levels were significantly higher in HCC tissues than adjacent normal liver tissues. Hepatocyte-specific over-expression of CR-1 in transgenic mice enhanced hepatocyte proliferation after 2/3 partial hepatectomy (2/3 PHx). CR-1 over-expression significantly increased in vivo xenograft tumor growth of HCC cells in nude mice and in vitro HCC cell proliferation, migration, and invasion. CR-1 over-expression in the transgenic mouse livers deregulated HCC-related signaling pathways such as AKT, Wnt/β-catenin, Stat3, MAPK/ERK, JNK, TGF-β and Notch, as well as expression of HCC-related genes such as CD5L, S100A8, S100A9, Timd4, Orm2, Orm3, PDK4, DMBT1, G0S2, Plk2, Plk3, Gsta1 and Gsta2. However, histological signs of precancerous lesions, hepatocyte dysplasia or HCC formation were not observed in the livers of 3-, 6- or 8-month-old hepatocyte-specific CR-1-overexpressing transgenic mice. These findings demonstrate that liver-specific CR-1 overexpression in transgenic mice deregulates signaling pathways and genes associated with HCC.

Dietary rational targeting of redox-regulated genes

Nutrigenomics is the study of how food and associated nutrients affect gene expression. This field sits at the intersection of diet, the genome and health with the ultimate goal of exploiting its understanding to design a precision nutrition strategy for humans. We have studied diet and nutrigenomics in the context of something we call "dietary rational gene targeting." Here, healthy diet is used to alter disease-causing gene expression back toward the normal to treat various diseases and conditions while lowering treatment cost and toxicity. In this paper, we discuss the use of this strategy to modulate the expression of redox-associated genes to improve human health. Most human disorders are associated, at least to some extent, with oxidative stress and so treatments (including diet) that target redox-related genes have major potential clinical significance. Healthy dietary options here are wide-ranging and include whole foods and botanical-based beverages. In some cases, botanical supplements may also be useful gene modulators although their health benefits are less clear. Key redox gene targets for these dietary agents include antioxidant genes, related transcription factors, detoxification genes, and DNA repair genes. Other important considerations include bioavailability, the contribution of the microbiome, and advancing technologies. In this review, specific examples of redox associated genes and pathologies and their potential treatment with healthy diet are presented to illustrate our approach. This will also serve as a foundation for the design of future clinical studies to improve diet-related health.

Pre-Senescence Induction in Hepatoma Cells Favors Hepatitis C Virus Replication and Can Be Used in Exploring Antiviral Potential of Histone Deacetylase Inhibitors

Recent evidence suggests that fibrotic liver injury in patients with chronic hepatitis C correlates with cellular senescence in damaged liver tissue. However, it is still unclear how senescence can affect replication of the hepatitis C virus (HCV). In this work, we report that an inhibitor of cyclin-dependent kinases 4/6, palbociclib, not only induced in hepatoma cells a pre-senescent cellular phenotype, including G1 arrest in the cell cycle, but also accelerated viral replicon multiplication. Importantly, suppression of HCV replication by direct acting antivirals (DAAs) was barely affected by pre-senescence induction, and vice versa, the antiviral activities of host-targeting agents (HTAs), such as inhibitors of human histone deacetylases (HDACi), produced a wide range of reactions-from a dramatic reduction to a noticeable increase. It is very likely that under conditions of the G1 arrest in the cell cycle, HDACi exhibit their actual antiviral potency, since their inherent anticancer activity that complicates the interpretation of test results is minimized.

The rationale for a multi-step therapeutic approach based on antivirals, drugs and nutrients with immunomodulatory activity in patients with coronavirus-SARS2-induced disease of different severities

In December 2019, a novel human-infecting coronavirus, named Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2), was recognised to cause a pneumonia epidemic outbreak with different degrees of severity in Wuhan, Hubei Province in China. Since then, this epidemic has spread worldwide; in Europe, Italy has been involved. Effective preventive and therapeutic strategies are absolutely required to block this serious public health concern. Unfortunately, few studies about SARS-CoV-2 concerning its immunopathogenesis and treatment are available. On the basis of the assumption that the SARS-CoV-2 is genetically related to SARS-CoV (about 82 % of genome homology) and that its characteristics, like the modality of transmission or the type of the immune response it may stimulate, are still poorly known, a literature search was performed to identify the reports assessing these elements in patients with SARS-CoV-induced infection. Therefore, we have analysed: (1) the structure of SARS-CoV-2 and SARS-CoV; (2) the clinical signs and symptoms and pathogenic mechanisms observed during the development of acute respiratory syndrome and the cytokine release syndrome; (3) the modification of the cell microRNome and of the immune response in patients with SARS infection; and (4) the possible role of some fat-soluble compounds (such as vitamins A, D and E) in modulating directly or indirectly the replication ability of SARS-CoV-2 and host immune response.

Liver Cirrhosis in Chronic Hepatitis B Patients Is Associated with Genetic Variations in DNA Repair Pathway Genes

Simple Summary

As DNA repair enzymes affect dynamics of liver damage and are involved in HBV viral replication, this study focused on the role of genetic variations within genes representing key DNA-repair pathways in HBV-induced liver cirrhosis. The obtained results have demonstrated that SNPs within XRCC1, ERCC2 genes may confer susceptibility to liver cirrhosis in chronic hepatitis B patients.

Abstract

Liver cirrhosis (LC), contributing to more than 1 million of deaths annually, is a major healthcare concern worldwide. Hepatitis B virus (HBV) is a major LC etiological factor, and 15% of patients with chronic HBV infection (CHB) develop LC within 5 years. Recently, novel host genetic determinants were shown to influence HBV lifecycle and CHB course. DNA repair enzymes can affect dynamics of liver damage and are involved in HBV covalently closed circular DNA (cccDNA) formation, an essential step for viral replication. This study aimed to evaluate the possible role of genes representing key DNA-repair pathways in HBV-induced liver damage. MALDI-TOF MS genotyping platform was applied to evaluate variations within XRCC1, XRCC4, ERCC2, ERCC5, RAD52, Mre11, and NBN genes. Apart from older age (p < 0.001), female sex (p = 0.021), portal hypertension (p < 0.001), thrombocytopenia (p < 0.001), high HBV DNA (p = 0.001), and high aspartate aminotransferase (AST) (p < 0.001), we found that G allele at rs238406 (ERCC2, p = 0.025), T allele at rs25487 (XRCC1, p = 0.012), rs13181 GG genotype (ERCC2, p = 0.034), and C allele at rs2735383 (NBN, p = 0.042) were also LC risk factors. The multivariate logistic regression model showed that rs25487 CC (p = 0.005) and rs238406 TT (p = 0.027) were independently associated with lower risk of LC. This study provides evidence for the impact of functional and potentially functional variations in key DNA-repair genes XRCC1 and ERCC2 in HBV-induced liver damage in a Caucasian population.

Salivary Antioxidant and Oxidative Stress Marker Levels in HIV-Positive Individuals

BACKGROUND

HIV infections are a worldwide health problem. HIV infection reduces CD4+ cell counts. Oxidative stress might play an important role in the stimulation of virus replication and immunodeficiency. Saliva might be the first line of defense against oxidative stress.

OBJECTIVE

The aim of this study was to evaluate the oxidative stress marker and antioxidant levels of saliva in HIV-infected patients by measuring total antioxidant capacity and malondialdehyde level.

METHODS

A total of 49 HIV-positive patients and 49 healthy HIV-negative individuals were randomly selected. All the patients were clinically examined. Five mL of unstimulated whole saliva was collected and evaluated by spectrophotometric assay. Data were analyzed with STATA 11.

RESULTS

Mean ages of the case and control groups were 28 and 33 years, respectively. Salivary malondialdehyde levels were significantly higher in the HIV-positive group (3.68±2.26) compared to the healthy control group (2.79±1.91). Levels of salivary total antioxidant capacity were significantly lower in the HIV-positive group (0.20± 0.09) compared to the control group (0.27±0.10).

CONCLUSION

The antioxidant defense system in HIV-positive individuals was low and oxidative stress was high in this population. Saliva might be used as a diagnostic tool for antioxidant changes in HIV-positive patients in the future. There were changes in salivary antioxidant defense system and oxidative stress in HIV-positive individuals. Antioxidant supplements might help local salivary and general health statuses.

Predicting hepatocellular carcinoma recurrences: A data-driven multiclass classification method incorporating latent variables

Hepatocellular carcinoma (HCC), a malignant form of cancer, is frequently treated with surgical resections, which have relatively high recurrence rates. Effective recurrence predictions enable physicians' timely detections and adequate therapeutic measures that can greatly improve patient care and outcomes. Toward that end, predictions of early versus late HCC recurrences should be considered separately to reflect their distinct onset time horizons, clinical causes, underlying clinical etiology, and pathogenesis. We propose a novel Bayesian network-based method to predict different HCC recurrence outcomes by considering the respective recurrence evolution paths. Typical patient information obtained in early stages is insufficiently informative to predict recurrence outcomes accurately, due to the lack of subsequent patient progression information. Our method alleviates such information deficiency constraints by incorporating an independent latent variable, dominant recurrence type, to regulate recurrence outcome predictions (early, late, or no recurrence). We use a real-world HCC data set to evaluate the proposed method, relative to three prevalent benchmark techniques. Overall, the results show that our method consistently and significantly outperforms all the benchmark techniques in terms of accuracy, precision, recall, and F-measures. For increased robustness, we use another data set to perform an out-of-sample evaluation and obtain similar results. This study thus contributes to HCC recurrence research and offers several implications for clinical practice.

The Biological Function of Hepatitis B Virus X Protein in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the major malignant tumors that lead to death. Chronic hepatitis B virus infection is an important risk factor for HCC initiation. HBx protein, encoded by the HBV X gene, is a significant factor that promotes HBV-related HCC, although the exact molecular mechanism remains unclear. This article summarizes the pathological roles and related mechanisms of HBx in HCC. HBx plays a carcinogenic role by promoting cell proliferation, metastasis, and angiogenesis and inhibiting apoptosis in HCC. A detailed study of the biological functions of HBx will help to elucidate the mechanism of hepatocarcinogenesis and lead to the development of novel therapeutic targets for the treatment of HBV-related HCC.

The Immunogenicity in Mice of HCV Core Delivered as DNA Is Modulated by Its Capacity to Induce Oxidative Stress and Oxidative Stress Response

HCV core is an attractive HCV vaccine target, however, clinical or preclinical trials of core-based vaccines showed little success. We aimed to delineate what restricts its immunogenicity and improve immunogenic performance in mice. We designed plasmids encoding full-length HCV 1b core and its variants truncated after amino acids (aa) 60, 98, 152, 173, or up to aa 36 using virus-derived or synthetic polynucleotides (core191/60/98/152/173/36_191v or core152s DNA, respectively). We assessed their level of expression, route of degradation, ability to trigger the production of reactive oxygen species/ROS, and to activate the components of the Nrf2/ARE antioxidant defense pathway heme oxygenase 1/HO-1 and NAD(P)H: quinone oxidoreductase/Nqo-1. All core variants with the intact N-terminus induced production of ROS, and up-regulated expression of HO-1 and Nqo-1. The capacity of core variants to induce ROS and up-regulate HO-1 and Nqo-1 expression predetermined their immunogenicity in DNA-immunized BALB/c and C57BL/6 mice. The most immunogenic was core 152s, expressed at a modest level and inducing moderate oxidative stress and oxidative stress response. Thus, immunogenicity of HCV core is shaped by its ability to induce ROS and oxidative stress response. These considerations are important in understanding the mechanisms of viral suppression of cellular immune response and in HCV vaccine design.

Dysregulation of Nrf2 in Hepatocellular Carcinoma: Role in Cancer Progression and Chemoresistance

The liver executes versatile functions and is the chief organ for metabolism of toxicants/xenobiotics. Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and the third foremost cause of cancer death worldwide. Oxidative stress is a key factor related with the development and progression of HCC. Nuclear factor erythroid 2 [NF-E2]-related factor 2 (Nrf2) is a cytosolic transcription factor, which regulates redox homeostasis by activating the expression of an array of antioxidant response element-dependent genes. Nrf2 displays conflicting roles in normal, healthy liver and HCC; in the former, Nrf2 offers beneficial effects, whereas in the latter it causes detrimental effects favouring the proliferation and survival of HCC. Sustained Nrf2 activation has been observed in HCC and facilitates its progression and aggressiveness. This review summarizes the role and mechanism(s) of action of Nrf2 dysregulation in HCC and therapeutic options that can be employed to modulate this transcription factor.

CD4+ memory T cells infected with latent HIV-1 are susceptible to drugs targeting telomeres

The population of HIV reservoir in infected person is very small, but extremely long-lived and is a major obstacle for an HIV cure. We previously showed that cells with established HIV latency have deficiencies in DNA damage response (DDR). Here, we investigated ability of HIV-1 to interfere with telomere maintenance, and the effects of targeting telomeres on latently infected cells. Our results show that telomeres are elongated in cultured primary memory CD4 + T cells (T_CM) after HIV-1 infection and when virus latency is established. Similarly, much longer telomeres were found in several Jurkat-derived latently infected cell lines, indicating that virus stimulates telomere elongation. Exposing primary CD4+ T_CM cells to BRACO19, an agent targeting telomeres, resulted in a higher rate of apoptosis for infected cultures at day 3 post-infection, during HIV-1 latency and for PMA-stimulated cultures with low level of HIV-1 reactivation. Importantly, BRACO19 induced apoptosis in infected cells with potency similar to etoposide and camptothecin, whereas uninfected cells were less affected by BRACO19. We also determined that apoptosis induced by BRACO19 is not caused by telomeres shortening, but is related to formation of gamma-H2AX, implicating DNA damage or uncapping of telomeres, which triggers genome instability. In conclusion, our results indicate that HIV-1 stimulates telomere elongation during latency, suggesting that HIV reservoir has greater capacity for clonal expansion and extended lifespan. Higher rates of apoptosis in response to BRACO19 treatment suggest that HIV reservoirs are more susceptible to targeting telomere maintenance and to inhibitors targeting DDR, which is also involved in stabilizing telomeres.

Oxidative stress is bane in chronic liver diseases: Clinical and experimental perspective

Oxidative stress plays an important role in the pathogenesis of various chronic liver diseases (CLD) and increasing evidence have confirmed the contributory role of oxidative stress in the pathogenesis of drugs and chemical-induced CLD. Chronic liver injury is manifested as necrosis, cholestasis, fibrosis, and cirrhosis. Chronic administration of anti-tubercular, anti-retroviral, immunosuppressive drugs is reported to induce free radical generation during their biotransformation in the liver. Further, these reactive intermediates are said to induce profibrogenic cytokines, several inflammatory markers, collagen synthesis during the progression of hepatic fibrosis. Oxidative stress and free radicals are reported to induce activation and proliferation of hepatic stellate cells in the injured liver leading to the progression of CLD. Hence, to counteract or to scavenge these reactive intermediates, several plant-derived antioxidant principles have been effectively employed against oxidative stress and came out with promising results in human and experimental models of CLD. This review summarizes the relationships between oxidative stress and different liver pathogenesis induced by drugs and xenobiotics, focusing upon different chronic liver injury induced by alcohol, antitubercular drugs and hyperactivity of antiretroviral drugs in HIV patients, viral hepatitis infection induced oxidative stress.

Beneficial effects of naringenin in liver diseases: Molecular mechanisms

Liver diseases are caused by different etiological agents, mainly alcohol consumption, viruses, drug intoxication or malnutrition. Frequently, liver diseases are initiated by oxidative stress and inflammation that lead to the excessive production of extracellular matrix (ECM), followed by a progression to fibrosis, cirrhosis and hepatocellular carcinoma (HCC). It has been reported that some natural products display hepatoprotective properties. Naringenin is a flavonoid with antioxidant, antifibrogenic, anti-inflammatory and anticancer properties that is capable of preventing liver damage caused by different agents. The main protective effects of naringenin in liver diseases are the inhibition of oxidative stress, transforming growth factor (TGF-β) pathway and the prevention of the transdifferentiation of hepatic stellate cells (HSC), leading to decreased collagen synthesis. Other effects include the inhibition of the mitogen activated protein kinase (MAPK), toll-like receptor (TLR) and TGF-β non-canonical pathways, the inhibition of which further results in a strong reduction in ECM synthesis and deposition. In addition, naringenin has shown beneficial effects on nonalcoholic fatty liver disease (NAFLD) through the regulation of lipid metabolism, modulating the synthesis and oxidation of lipids and cholesterol. Moreover, naringenin protects from HCC, since it inhibits growth factors such as TGF-β and vascular endothelial growth factor (VEGF), inducing apoptosis and regulating MAPK pathways. Naringenin is safe and acts by targeting multiple proteins. However, it possesses low bioavailability and high intestinal metabolism. In this regard, formulations, such as nanoparticles or liposomes, have been developed to improve naringenin bioavailability. We conclude that naringenin should be considered in the future as an important candidate in the treatment of different liver diseases.

The Pivotal Role of DNA Repair in Infection Mediated-Inflammation and Cancer

Pathogenic and commensal microbes induce various levels of inflammation and metabolic disease in the host. Inflammation caused by infection leads to increased production of reactive oxygen species (ROS) and subsequent oxidative DNA damage. These in turn cause further inflammation and exacerbation of DNA damage, and pose a risk for cancer development. Helicobacter pylori-mediated inflammation has been implicated in gastric cancer in many previously established studies, and Fusobacterium nucleatum presence has been observed with greater intensity in colorectal cancer patients. Despite ambiguity in the exact mechanism, infection-mediated inflammation may have a link to cancer development through an accumulation of potentially mutagenic DNA damage in surrounding cells. The multiple DNA repair pathways such as base excision, nucleotide excision, and mismatch repair that are employed by cells are vital in the abatement of accumulated mutations that can lead to carcinogenesis. For this reason, understanding the role of DNA repair as an important cellular mechanism in combatting the development of cancer will be essential to characterizing the effect of infection on DNA repair proteins and to identifying early cancer biomarkers that may be targeted for cancer therapies and treatments.

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.

Viral Oncology: Molecular Biology and Pathogenesis

Oncoviruses are implicated in approximately 12% of all human cancers. A large number of the world's population harbors at least one of these oncoviruses, but only a small proportion of these individuals go on to develop cancer. The interplay between host and viral factors is a complex process that works together to create a microenvironment conducive to oncogenesis. In this review, the molecular biology and oncogenic pathways of established human oncoviruses will be discussed. Currently, there are seven recognized human oncoviruses, which include Epstein-Barr Virus (EBV), Human Papillomavirus (HPV), Hepatitis B and C viruses (HBV and HCV), Human T-cell lymphotropic virus-1 (HTLV-1), Human Herpesvirus-8 (HHV-8), and Merkel Cell Polyomavirus (MCPyV). Available and emerging therapies for these oncoviruses will be mentioned.

Chronic viral hepatitis and its association with liver cancer

Chronic infection with hepatitis viruses represents the major causative factor for end-stage liver diseases, including liver cirrhosis and primary liver cancer (hepatocellular carcinoma, HCC). In this review, we highlight the current understanding of the molecular mechanisms that drive the hepatocarcinogenesis associated with chronic hepatitis virus infections. While chronic inflammation (associated with a persistent, but impaired anti-viral immune response) plays a major role in HCC initiation and progression, hepatitis viruses can also directly drive liver cancer. The mechanisms by which hepatitis viruses induce HCC include: hepatitis B virus DNA integration into the host cell genome; metabolic reprogramming by virus infection; induction of the cellular stress response pathway by viral gene products; and interference with tumour suppressors. Finally, we summarise the limitations of hepatitis virus-associated HCC model systems and the development of new techniques to circumvent these shortcomings.

Analysis of the Mitochondrial 4977 Bp Deletion in Patients with Hepatocellular Carcinoma

Mutations in the mitochondrial (mt) genome that result in mt dysfunction, have long been proposed to play important roles in the pathogenesis of hepatocellular carcinoma (HCC). Among these, the common mtDNA 4977 bp deletion is one of the most frequent mutations observed in various cancers. To understand the relationship between the mtDNA 4977 bp deletion and HCC, we performed mutational screening for the presence of this deletion in 105 HCC patients and 69 unrelated healthy subjects. After nested-polymerase chain reaction (nested-PCR) amplification, we found that there were 10 patients carrying the mtDNA 4977 bp deletion, and this deletion was absent in control subjects. Moreover, HCC patients carrying this deletion showed a marked increase in reactive oxygen species (ROS) level and mtDNA copy number when compared with the healthy controls. Taken together, our data indicated that the mtDNA 4977 bp deletion may play important role in the carcinogenesis of HCC, possibly via the alternation of mtDNA copy number and oxidative stress.

The NADPH Oxidase Inhibitor Apocynin Suppresses Preneoplastic Liver Foci of Rats

Reactive oxygen species (ROS) have been revealed to be important factors for carcinogenesis and tumor progression. Therefore, we focused on an ROS-generating protein, nicotinamide adenine dinucleotide phosphate oxidase, and evaluated whether its inhibitor, apocynin, could suppress hepatocarcinogenesis in a medium-term rat liver bioassay. The number and size of glutathione S-transferase placental form (GST-P)-positive foci were significantly reduced by apocynin in a dose-dependent manner. The reduction of ROS generation by apocynin was confirmed by dihydroethidium staining. Apocynin treatment also significantly reduced Ki-67 positivity, downregulated cyclooxygenase 2, and suppressed the activation of the c-Myc pathway. Meanwhile, ROS generation was not different between GST-P-positive foci and surrounding GST-P-negative areas of the liver. In conclusion, the present data suggest that apocynin possesses a potential antihepatocarcinogenic property.

Hepatitis C virus induces a prediabetic state by directly impairing hepatic glucose metabolism in mice

Virus-related type 2 diabetes is commonly observed in individuals infected with the hepatitis C virus (HCV); however, the underlying molecular mechanisms remain unknown. Our aim was to unravel these mechanisms using FL-N/35 transgenic mice expressing the full HCV ORF. We observed that these mice displayed glucose intolerance and insulin resistance. We also found that Glut-2 membrane expression was reduced in FL-N/35 mice and that hepatocyte glucose uptake was perturbed, partly accounting for the HCV-induced glucose intolerance in these mice. Early steps of the hepatic insulin signaling pathway, from IRS2 to PDK1 phosphorylation, were constitutively impaired in FL-N/35 primary hepatocytes via deregulation of TNFα/SOCS3. Higher hepatic glucose production was observed in the HCV mice, despite higher fasting insulinemia, concomitant with decreased expression of hepatic gluconeogenic genes. Akt kinase activity was higher in HCV mice than in WT mice, but Akt-dependent phosphorylation of the forkhead transcription factor FoxO1 at serine 256, which triggers its nuclear exclusion, was lower in HCV mouse livers. These findings indicate an uncoupling of the canonical Akt/FoxO1 pathway in HCV protein-expressing hepatocytes. Thus, the expression of HCV proteins in the liver is sufficient to induce insulin resistance by impairing insulin signaling and glucose uptake. In conclusion, we observed a complete set of events leading to a prediabetic state in HCV-transgenic mice, providing a valuable mechanistic explanation for HCV-induced diabetes in humans.

A Role for the Host DNA Damage Response in Hepatitis B Virus cccDNA Formation-and Beyond?

Chronic hepatitis B virus (HBV) infection puts more than 250 million people at a greatly increased risk to develop end-stage liver disease. Like all hepadnaviruses, HBV replicates via protein-primed reverse transcription of a pregenomic (pg) RNA, yielding an unusually structured, viral polymerase-linked relaxed-circular (RC) DNA as genome in infectious particles. Upon infection, RC-DNA is converted into nuclear covalently closed circular (ccc) DNA. Associating with cellular proteins into an episomal minichromosome, cccDNA acts as template for new viral RNAs, ensuring formation of progeny virions. Hence, cccDNA represents the viral persistence reservoir that is not directly targeted by current anti-HBV therapeutics. Eliminating cccDNA will thus be at the heart of a cure for chronic hepatitis B. The low production of HBV cccDNA in most experimental models and the associated problems in reliable cccDNA quantitation have long hampered a deeper understanding of cccDNA molecular biology. Recent advancements including cccDNA-dependent cell culture systems have begun to identify select host DNA repair enzymes that HBV usurps for RC-DNA to cccDNA conversion. While this list is bound to grow, it may represent just one facet of a broader interaction with the cellular DNA damage response (DDR), a network of pathways that sense and repair aberrant DNA structures and in the process profoundly affect the cell cycle, up to inducing cell death if repair fails. Given the divergent interactions between other viruses and the DDR it will be intriguing to see how HBV copes with this multipronged host system.

Hepatitis C Virus Indirectly Disrupts DNA Damage-Induced p53 Responses by Activating Protein Kinase R

Many DNA tumor viruses promote cellular transformation by inactivating the critically important tumor suppressor protein p53. In contrast, it is not known whether p53 function is disrupted by hepatitis C virus (HCV), a unique, oncogenic RNA virus that is the leading infectious cause of liver cancer in many regions of the world. Here we show that HCV-permissive, liver-derived HepG2 cells engineered to constitutively express microRNA-122 (HepG2/miR-122 cells) have normal p53-mediated responses to DNA damage and that HCV replication in these cells potently suppresses p53 responses to etoposide, an inducer of DNA damage, or nutlin-3, an inhibitor of p53 degradation pathways. Upregulation of p53-dependent targets is consequently repressed within HCV-infected cells, with potential consequences for cell survival. Despite this, p53 function is not disrupted by overexpression of the complete HCV polyprotein, suggesting that altered p53 function may result from the host response to viral RNA replication intermediates. Clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9-mediated ablation of double-stranded RNA (dsRNA)-activated protein kinase R (PKR) restored p53 responses while boosting HCV replication, showing that p53 inhibition results directly from viral activation of PKR. The hepatocellular abundance of phosphorylated PKR is elevated in HCV-infected chimpanzees, suggesting that PKR activation and consequent p53 inhibition accompany HCV infection in vivo. These findings reveal a feature of the host response to HCV infection that may contribute to hepatocellular carcinogenesis.

Chronic infection with hepatitis C virus (HCV) is the leading cause of liver cancer in most developed nations. However, the mechanisms whereby HCV infection promotes carcinogenesis remain unclear. Here, we demonstrate that HCV infection inhibits the activation of p53 following DNA damage. Contrary to previous reports, HCV protein expression is insufficient to inhibit p53. Rather, p53 inhibition is mediated by cellular protein kinase R (PKR), which is activated by HCV RNA replication and subsequently suppresses global protein synthesis. These results redefine our understanding of how HCV infection influences p53 function. We speculate that persistent disruption of p53-mediated DNA damage responses may contribute to hepatocellular carcinogenesis in chronically infected individuals.

Deficiency in DNA damage response, a new characteristic of cells infected with latent HIV-1

Viruses can interact with host cell molecules responsible for the recognition and repair of DNA lesions, resulting in dysfunctional DNA damage response (DDR). Cells with inefficient DDR are more vulnerable to therapeutic approaches that target DDR, thereby raising DNA damage to a threshold that triggers apoptosis. Here, we demonstrate that 2 Jurkat-derived cell lines with incorporated silent HIV-1 provirus show increases in DDR signaling that responds to formation of double strand DNA breaks (DSBs). We found that phosphorylation of histone H2AX on Ser139 (gamma-H2AX), a biomarker of DSBs, and phosphorylation of ATM at Ser1981, Chk2 at Thr68, and p53 at Ser15, part of signaling pathways associated with DSBs, are elevated in these cells. These results indicate a DDR defect even though the virus is latent. DDR-inducing agents, specifically high doses of nucleoside RT inhibitors (NRTIs), caused greater increases in gamma-H2AX levels in latently infected cells. Additionally, latently infected cells are more susceptible to long-term exposure to G-quadruplex stabilizing agents, and this effect is enhanced when the agent is combined with an inhibitor targeting DNA-PK, which is crucial for DSB repair and telomere maintenance. Moreover, exposing these cells to the cancer drug etoposide resulted in formation of DSBs at a higher rate than in un-infected cells. Similar effects of etoposide were also observed in population of primary memory T cells infected with latent HIV-1. Sensitivity to these agents highlights a unique vulnerability of latently infected cells, a new feature that could potentially be used in developing therapies to eliminate HIV-1 reservoirs.

The Paradoxical Effects of Different Hepatitis C Viral Loads on Host DNA Damage and Repair Abilities

Hepatitis C virus (HCV)-induced hepatic stress is associated with increased oxidative DNA damage and has been implicated in hepatic inflammation. However, HCV infection and replication are uneven and vary among individual hepatocytes. To investigate the effect of the viral load on host DNA damage, we used an Enhanced Yellow Fluorescent Protein gene (EYFP)-tagged HCV virus to distinguish between HCV intracellular high viral load (HVL) cells and low viral load (LVL) cells. The cell sorting efficiency was confirmed by the high expression of the HCV polyprotein. We found DNA damage γ-H2AX foci in the HVL population. Comet assays demonstrated that HVL was related to the extent of the DNA strand breaks. Surprisingly, the DNA qPCR arrays and western blotting showed that the damage-related genes GPX2, MRE11, phospho-ATM, and OGG1 were significantly up-regulated in LVL cells but inversely down-regulated or consistently expressed in HVL cells. The colony survival assay to examine the repair abilities of these cells in response to irradiation showed that the LVL cells were more resistant to irradiation and had an increased ability to repair radiation-induced damage. This study found that intracellular viral loads drove cellular DNA damage levels but suppressed damage-related gene expression. However, the increase in damage-related gene expression in the LVL cells may be affected by ROS from the HVL cells. These findings provide new insights into the distinct DNA damage and repair responses resulting from different viral loads in HCV-infected cells.

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.

Hepatitis B and Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death worldwide, and its incidence has been increasing in the last decade largely in parallel to the incidence and duration of exposure to hepatitis B and C. The widespread implementation of hepatitis B vaccine, hepatitis B antivirals, and the introduction of direct antiviral therapies for hepatitis C virus may have a substantial impact in reducing the incidence of HCC. This report reviews the risk factors and underlying mechanisms associated with the development of HCC in hepatitis B, along with advances in the diagnosis, imaging, and management of HCC.

Oxidative Stress during HIV Infection: Mechanisms and Consequences

It is generally acknowledged that reactive oxygen species (ROS) play crucial roles in a variety of natural processes in cells. If increased to levels which cannot be neutralized by the defense mechanisms, they damage biological molecules, alter their functions, and also act as signaling molecules thus generating a spectrum of pathologies. In this review, we summarize current data on oxidative stress markers associated with human immunodeficiency virus type-1 (HIV-1) infection, analyze mechanisms by which this virus triggers massive ROS production, and describe the status of various defense mechanisms of the infected host cell. In addition, we have scrutinized scarce data on the effect of ROS on HIV-1 replication. Finally, we present current state of knowledge on the redox alterations as crucial factors of HIV-1 pathogenicity, such as neurotoxicity and dementia, exhaustion of CD4+/CD8+ T-cells, predisposition to lung infections, and certain side effects of the antiretroviral therapy, and compare them to the pathologies associated with the nitrosative stress.

Circulating predictive and diagnostic biomarkers for hepatitis B virus-associated hepatocellular carcinoma

Chronic hepatitis B virus (HBV) infected patients have an almost 100-fold increased risk to develop hepatocellular carcinoma (HCC). HCC is the fifth most common and third most deadly cancer worldwide. Up to 50% of newly diagnosed HCC cases are attributed to HBV infection. Early detection improves survival and can be achieved through regular screening. Six-monthly abdominal ultrasound, either alone or in combination with alpha-fetoprotein serum levels, has been widely endorsed for this purpose. Both techniques however yield limited diagnostic accuracy, which is not improved when they are combined. Alternative circulating or histological markers to predict or diagnose HCC are therefore urgently needed. Recent advances in systems biology technologies have enabled the identification of several new putative circulating biomarkers. Although results from studies assessing combinations of these biomarkers are promising, evidence for their clinical utility remains low. In addition, most of the studies conducted so far show limitations in design. Attention must be paid for instance to different ethnicities and different etiologies when studying biomarkers for hepatocellular carcinoma. This review provides an overview on the current understandings and recent progress in the field of diagnostic and predictive circulating biomarkers for hepatocellular carcinoma in chronically infected HBV patients and discusses the future prospects.

Hepatitis C virus promotes hepatocellular carcinogenesis by targeting TIPE2, a new regulator of DNA damage response

Infection of hepatitis C virus (HCV) is associated with primary hepatocellular carcinoma (HCC). However, its underlying molecular mechanisms remain enigmatic. Tumor necrosis factor-α-induced protein 8-like 2 (TIPE2), a new negative regulator of immunity, plays significant roles in modulating inflammation and tumorigenesis. We hypothesized that TIPE2 might be involved in the development of HCV-induced HCC. To test this hypothesis, the expression of TIPE2 was determined by Western blot in the tumor and pericarcinomatous tissues collected from ten HCV-positive HCC patients; the interaction between TIPE2 and HCV-encoded non-structural proteins was analyzed by immunoprecipitation and immunofluorescence assays, and tumorigenesis and its mechanisms were studied in cell models and nude mice. Our results demonstrated that the expression of TIPE2 was significantly reduced in HCC tissues compared to that in the paracarcinoma tissues. HCV-encoded non-structural protein NS5A could specifically interact with TIPE2 and induce its degradation. Downregulation of TIPE2 by shRNA in cell lines increased genomic DNA damage and promoted cell colony formation in vitro and tumorigenesis in nude mice. In contrast, overexpression of TIPE2 had an opposite effect. Downregulation of TIPE2 by NS5A is associated with genomic DNA instability and HCV-induced HCC development. Thus, TIPE2 may be a new therapeutic target for the treatment of HCV-associated HCC.

Inverse Association of Plasma Level of Glutathione Peroxidase with Liver Fibrosis in Chronic Hepatitis B: Potential Role of Iron

BACKGROUND

Oxidative stress has a major pathogenic role for liver damage following chronic hepatitis B. Glutathione peroxidase (Gpx) is necessary in oxidative state mechanism that is generally down-regulated by Hepatitis B virus (HBV) infection. On the other hand, disorders of iron homeostasis have been found out in HBV infected patients. Therefore, the objective of this study was to assess the interplay of Gpx and serum iron on clinical and virological features of patients with chronic HBV infection.

METHODS

One hundred and fifty adult, treatment-naïve, patients with chronic hepatitis B were randomly designated from an ongoing cohort of patients with HBV. Plasma Gpx1 concentration and HBV DNA quantity were measured. Liver stiffness was measured by transient elastography.

RESULTS

Serum iron had a positive association with HBV DNA count in the total population. Serum iron was not associated with liver stiffness. However, HBV DNA was significantly associated with liver stiffness only in male patients. Serum Gpx was inversely associated with liver stiffness. Serum iron and Gpx had indirect effects on liver stiffness via HBV DNA count. We observed dissimilar effects of serum iron on HBV DNA and Gpx on liver stiffness in male and female patients.

CONCLUSION

We identified interplay of serum iron and Gpx1 in relation to level of liver fibrosis in patients with chronic hepatitis B. Our results propose that oxidative stress and serum iron are differentially implicated in the progression of chronic hepatitis B in male and female patients.

HCV-Induced Oxidative Stress: Battlefield-Winning Strategy

About 150 million people worldwide are chronically infected with hepatitis C virus (HCV). The persistence of the infection is controlled by several mechanisms including the induction of oxidative stress. HCV relies on this strategy to redirect lipid metabolism machinery and escape immune response. The 3β-hydroxysterol Δ24-reductase (DHCR24) is one of the newly discovered host markers of oxidative stress. This protein, as HCV-induced oxidative stress responsive protein, may play a critical role in the pathogenesis of HCV chronic infection and associated liver diseases, when aberrantly expressed. The sustained expression of DHCR24 in response to HCV-induced oxidative stress results in suppression of nuclear p53 activity by blocking its acetylation and increasing its interaction with MDM2 in the cytoplasm leading to its degradation, which may induce hepatocarcinogenesis.

Increased Oxidative Stress and RUNX3 Hypermethylation in Patients with Hepatitis B Virus-Associated Hepatocellular Carcinoma (HCC) and Induction of RUNX3 Hypermethylation by Reactive Oxygen Species in HCC Cells

Promoter hypermethylation of the runt-related transcription factor 3 (RUNX3) gene is associated with increased risk of hepatocellular carcinoma (HCC). Oxidative stress plays a vital role in both carcinogenesis and progression of HCC. However, whether oxidative stress and RUNX3 hypermethylation in HCC have a cause- and-effect relationship is not known. In this study, plasma protein carbonyl and total antioxidant capacity (TAC) in patients with hepatitis B virus (HBV)-associated HCC (n=60) and age-matched healthy subjects (n=80) was determined. RUNX3 methylation in peripheral blood mononuclear cells (PBMC) of subjects was measured by methylation-specific PCR. Effect of reactive oxygen species (ROS) on induction of RUNX3 hypermethylation in HCC cells was investigated. Plasma protein carbonyl content was significantly higher, whereas plasma TAC was significantly lower, in HCC patients than healthy controls. Based on logistic regression, increased plasma protein carbonyl and decreased plasma TAC were independently associated with increased risk for HCC. PBMC RUNX3 methylation in the patient group was significantly greater than in the healthy group. RUNX3 methylation in hydrogen peroxide (H2O2)-treated HepG2 cells was significantly higher than in untreated control cells. In conclusion, increase in oxidative stress in Thai patients with HBV-associated HCC was demonstrated. This oxidative increment was independently associated with an increased risk for HCC development. RUNX3 in PBMC was found to be hypermethylated in the HCC patients. In vitro, RUNX3 hypermethylation was experimentally induced by H2O2. Our findings suggest that oxidative stress is a cause of RUNX3 promoter hypermethylation in HCC cells.

Interaction of hepatitis B virus X protein with PARP1 results in inhibition of DNA repair in hepatocellular carcinoma

Hepatitis B virus X protein (HBx) contributes to the development of hepatocellular carcinoma (HCC), probably by regulating activities of many host or viral proteins through protein-protein interactions. In this study, we identified poly(ADP-ribose) polymerase (PARP1), a crucial factor in DNA repair, as an HBx-interacting protein using a proteomics approach. Coimmunoprecipitation and proximity ligation assays confirmed the binding and colocalization of HBx and PARP1 in the nucleus. The carboxyl-terminus of HBx protein bound to the catalytic domain of PARP1, and this binding reduced the enzymatic activity of PARP1 in both in vitro and in vivo assays. HBx interrupted the binding of PARP1 to Sirt6, which catalyzes the mono-ADP-ribosylation required for DNA repair. Consistently, overexpression of HBx inhibited the clearance of γH2AX DNA repair foci generated under oxidative stress in Chang liver cells. Recruitment of the DNA repair complex to the site-specific double-strand breaks was inhibited in the presence of HBx, when measured by laser microirradiation assay and damage-specific chromatin immunoprecipitation assays. Consequently, HBx increased signs of DNA damage such as accumulation of 8-hydroxy-2'-deoxyguanosine and comet formation, which were reversed by overexpression of PARP1 and/or Sirt6. Finally, the interaction between PARP1 and Sirt6 was markedly lower in the livers of HBx-transgenic mice and specimens obtained from HCC patients to compare with the corresponding control. Our data suggest that the physical interaction of HBx and PARP1 accelerates DNA damage by inhibiting recruitment of the DNA repair complex to the damaged DNA sites, which may lead to the onset of hepatocarcinogenesis.

Significance of hepatitis virus infection in the oncogenic initiation of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer-related death worldwide. Chronic infection of hepatitis B virus (HBV) and/or hepatitis C virus (HCV) is a major risk factor in the development of the HCC, independently from excessive alcohol abuse and metabolic disease. Since the biology of HBV and HCV is different, their oncogenic effect may go through different mechanisms, direct and/or indirect. Viral hepatitis infection is associated with cellular inflammation, oxidative stress, and DNA damage, that may lead to subsequent hepatic injuries such as chronic hepatitis, fibrosis, cirrhosis, and finally HCC. Direct oncogenic properties of these viruses are related with their genotypic characteristics and the ability of viral proteins to interact with host proteins, thus altering the molecular pathways balance of the cells. In addition, the integration of HBV DNA, especially the gene S and X, in a particular site of the host genome can disrupt chromosomal stability and may activate various oncogenic mechanisms, including those in hematopoietic cells. Recently, several studies also had demonstrated that viral hepatitis could trigger the population of hepatic cancer stem cells. This review summarize available pre-clinical and clinical data in literature regarding oncogenic properties of HBV and HCV in the early initiation of HCC.

Activation of the DNA Damage Response by RNA Viruses

RNA viruses are a genetically diverse group of pathogens that are responsible for some of the most prevalent and lethal human diseases. Numerous viruses introduce DNA damage and genetic instability in host cells during their lifecycles and some species also manipulate components of the DNA damage response (DDR), a complex and sophisticated series of cellular pathways that have evolved to detect and repair DNA lesions. Activation and manipulation of the DDR by DNA viruses has been extensively studied. It is apparent, however, that many RNA viruses can also induce significant DNA damage, even in cases where viral replication takes place exclusively in the cytoplasm. DNA damage can contribute to the pathogenesis of RNA viruses through the triggering of apoptosis, stimulation of inflammatory immune responses and the introduction of deleterious mutations that can increase the risk of tumorigenesis. In addition, activation of DDR pathways can contribute positively to replication of viral RNA genomes. Elucidation of the interactions between RNA viruses and the DDR has provided important insights into modulation of host cell functions by these pathogens. This review summarises the current literature regarding activation and manipulation of the DDR by several medically important RNA viruses.