HCV proteins increase expression of heme oxygenase-1 (HO-1) and decrease expression of Bach1 in human hepatoma cells

Pathophysiological role of BACH transcription factors in digestive system diseases

BTB and CNC homologous (BACH) proteins, including BACH1 and BACH2, are transcription factors that are widely expressed in human tissues. BACH proteins form heterodimers with small musculoaponeurotic fibrosarcoma (MAF) proteins to suppress the transcription of target genes. Furthermore, BACH1 promotes the transcription of target genes. BACH proteins regulate physiological processes, such as the differentiation of B cells and T cells, mitochondrial function, and heme homeostasis as well as pathogenesis related to inflammation, oxidative-stress damage caused by drugs, toxicants, or infections; autoimmunity disorders; and cancer angiogenesis, epithelial-mesenchymal transition, chemotherapy resistance, progression, and metabolism. In this review, we discuss the function of BACH proteins in the digestive system, including the liver, gallbladder, esophagus, stomach, small and large intestines, and pancreas. BACH proteins directly target genes or indirectly regulate downstream molecules to promote or inhibit biological phenomena such as inflammation, tumor angiogenesis, and epithelial-mesenchymal transition. BACH proteins are also regulated by proteins, miRNAs, LncRNAs, labile iron, and positive and negative feedback. Additionally, we summarize a list of regulators targeting these proteins. Our review provides a reference for future studies on targeted drugs in digestive diseases.

Hepatitis C, systemic inflammation and oxidative stress: correlations with metabolic diseases

Introduction: Hepatitis C chronic infection has long been correlated with numerous systemic diseases, such as diabetes mellitus and hepatic steatosis. Recent studies have also revealed an association with atherosclerosis.Areas covered: An analysis is presented on the mechanisms through which the hepatitis C viral infection can lead to a systemic increase in pro-inflammatory markers, especially tumor necrosis factor-a and interleukin-6. The immunological imbalance created may, through different mechanisms, act on the metabolic pathways that contribute to the development of insulin resistance, the accumulation of lipids in the liver, and even the formation of atherosclerotic plaques. Moreover, an additional contributing factor to the above-mentioned metabolic derangements is the unopposed oxidative stress observed in chronic hepatitis C viral infection. The virus itself contributes to the formation of oxidative stress, through alterations in the trace metal homeostasis and its effect on pro-inflammatory cytokines, such as tumor necrosis factor-a.Expert opinion: The scope of this review is to emphasize the importance of the metabolic manifestations of hepatitis C viral infection and to elucidate the pathophysiological mechanisms behind their emergence.

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.

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.

Sulforaphane Suppresses Hepatitis C Virus Replication by Up-Regulating Heme Oxygenase-1 Expression through PI3K/Nrf2 Pathway

Hepatitis C virus (HCV) infection-induced oxidative stress is a major risk factor for the development of HCV-associated liver disease. Sulforaphane (SFN) is an antioxidant phytocompound that acts against cellular oxidative stress and tumorigenesis. However, there is little known about its anti-viral activity. In this study, we demonstrated that SFN significantly suppressed HCV protein and RNA levels in HCV replicon cells and infectious system, with an IC50 value of 5.7 ± 0.2 μM. Moreover, combination of SFN with anti-viral drugs displayed synergistic effects in the suppression of HCV replication. In addition, we found nuclear factor erythroid 2-related factor 2 (Nrf2)/HO-1 induction in response to SFN and determined the signaling pathways involved in this process, including inhibition of NS3 protease activity and induction of IFN response. In contrast, the anti-viral activities were attenuated by knockdown of HO-1 with specific inhibitor (SnPP) and shRNA, suggesting that anti-HCV activity of SFN is dependent on HO-1 expression. Otherwise, SFN stimulated the phosphorylation of phosphoinositide 3-kinase (PI3K) leading Nrf2-mediated HO-1 expression against HCV replication. Overall, our results indicated that HO-1 is essential in SFN-mediated anti-HCV activity and provide new insights in the molecular mechanism of SFN in HCV replication.

Heme Oxygenase-1 Suppresses Bovine Viral Diarrhoea Virus Replication in vitro

Viral cycle progression depends upon host-cell processes in infected cells, and this is true for bovine viral diarrhoea virus (BVDV), the causative agent of BVD that is a worldwide threat to the bovine industry. Heme oxygenase-1 (HO-1) is a ubiquitously expressed inducible isoform of the first and rate-limiting enzyme for heme degradation. Recent studies have demonstrated that HO-1 has significant antiviral properties, inhibiting the replication of viruses such as ebola virus, human immunodeficiency virus, hepatitis C virus, and porcine reproductive and respiratory syndrome virus. However, the function of HO-1 in BVDV infection is unclear. In the present study, the relationship between HO-1 and BVDV was investigated. In vitro analysis of HO-1 expression in BVDV-infected MDBK cells demonstrated that a decrease in HO-1 as BVDV replication increased. Increasing HO-1 expression through adenoviral-mediated overexpression or induction with cobalt protoporphyrin (CoPP, a potent HO-1 inducer), pre- and postinfection, effectively inhibited BVDV replication. In contrast, HO-1 siRNA knockdown in BVDV-infected cells increased BVDV replication. Therefore, the data were consistent with HO-1 acting as an anti-viral factor and these findings suggested that induction of HO-1 may be a useful prevention and treatment strategy against BVDV infection.

Induction of Heme Oxygenase-1 Deficiency and Associated Glutamate-Mediated Neurotoxicity Is a Highly Conserved HIV Phenotype of Chronic Macrophage Infection That Is Resistant to Antiretroviral Therapy

Expression of the cytoprotective enzyme heme oxygenase-1 (HO-1) is significantly reduced in the brain prefrontal cortex of HIV-positive individuals with HIV-associated neurocognitive disorders (HAND). Furthermore, this HO-1 deficiency correlates with brain viral load, markers of macrophage activation, and type I interferon responses. In vitro, HIV replication in monocyte-derived macrophages (MDM) selectively reduces HO-1 protein and RNA expression and induces production of neurotoxic levels of glutamate; correction of this HO-1 deficiency reduces neurotoxic glutamate production without an effect on HIV replication. We now demonstrate that macrophage HO-1 deficiency, and the associated neurotoxin production, is a conserved feature of infection with macrophage-tropic HIV-1 strains that correlates closely with the extent of replication, and this feature extends to HIV-2 infection. We further demonstrate that this HO-1 deficiency does not depend specifically upon the HIV-1 accessory genes nef, vpr, or vpu but rather on HIV replication, even when markedly limited. Finally, antiretroviral therapy (ART) applied to MDM after HIV infection is established does not prevent HO-1 loss or the associated neurotoxin production. This work defines a predictable relationship between HIV replication, HO-1 loss, and neurotoxin production in MDM that likely reflects processes in place in the HIV-infected brains of individuals receiving ART. It further suggests that correcting this HO-1 deficiency in HIV-infected MDM could provide neuroprotection above that provided by current ART or proposed antiviral therapies directed at limiting Nef, Vpr, or Vpu functions. The ability of HIV-2 to reduce HO-1 expression suggests that this is a conserved phenotype among macrophage-tropic human immunodeficiency viruses that could contribute to neuropathogenesis.

IMPORTANCE

The continued prevalence of HIV-associated neurocognitive disorders (HAND) underscores the need for adjunctive therapy that targets the neuropathological processes that persist in antiretroviral therapy (ART)-treated HIV-infected individuals. To this end, we previously identified one such possible process, a deficiency of the antioxidative and anti-inflammatory enzyme heme oxygenase-1 (HO-1) in the brains of individuals with HAND. In the present study, our findings suggest that the HO-1 deficiency associated with excess glutamate production and neurotoxicity in HIV-infected macrophages is a highly conserved phenotype of macrophage-tropic HIV strains and that this phenotype can persist in the macrophage compartment in the presence of ART. This suggests a plausible mechanism by which HIV infection of brain macrophages in ART-treated individuals could exacerbate oxidative stress and glutamate-induced neuronal injury, each of which is associated with neurocognitive dysfunction in infected individuals. Thus, therapies that rescue the HO-1 deficiency in HIV-infected individuals could provide additional neuroprotection to ART.

Hepatic HMOX1 expression positively correlates with Bach-1 and miR-122 in patients with HCV mono and HIV/HCV coinfection

Aim

To analyze the expression of HMOX1 and miR-122 in liver biopsy samples obtained from HCV mono-and HIV/HCV co-infected patients in relation to selected clinical parameters, histological examination and IL-28B polymorphism as well as to determine whether HMOX1 expression is dependent on Bach-1.

Materials and Methods

The study group consisted of 90 patients with CHC: 69 with HCV mono and 21 with HIV/HCV co-infection. RT-PCR was used in the analysis of HMOX1, Bach-1 and miR-122 expression in liver biopsy samples and in the assessment of IL-28B single-nucleotide polymorphism C/T (rs12979860) in the blood. Moreover in liver biopsy samples an analysis of HO-1 and Bach-1 protein level by Western Blot was performed.

Results

HCV mono-infected patients, with lower grading score (G<2) and higher HCV viral load (>600000 IU/mL) demonstrated higher expression of HMOX1. In patients with HIV/HCV co-infection, the expression of HMOX1 was lower in patients with lower lymphocyte CD4 count and higher HIV viral load. IL28B polymorphism did not affect the expression of either HMOX1 or miR-122. Higher HMOX1 expression correlated with higher expression of Bach-1 (Spearman’s ρ = 0.586, p = 0.000001) and miR-122 (Spearman’s ρ = 0.270, p = 0.014059).

Conclusions

HMOX1 and miR-122 play an important role in the pathogenesis of CHC in HCV mono-and HIV/HCV co-infected patients. Reduced expression of HMOX1 in patients with HIV/HCV co-infection may indicate a worse prognosis in this group. Our results do not support the importance of Bach-1 in repression of HMOX1 in patients with chronic hepatitis C.

Hepatitis C virus-induced mitochondrial dysfunctions

Chronic hepatitis C is characterized by metabolic disorders and a microenvironment in the liver dominated by oxidative stress, inflammation and regeneration processes that lead in the long term to hepatocellular carcinoma. Many lines of evidence suggest that mitochondrial dysfunctions, including modification of metabolic fluxes, generation and elimination of oxidative stress, Ca²⁺ signaling and apoptosis, play a central role in these processes. However, how these dysfunctions are induced by the virus and whether they play a role in disease progression and neoplastic transformation remains to be determined. Most in vitro studies performed so far have shown that several of the hepatitis C virus (HCV) proteins localize to mitochondria, but the consequences of these interactions on mitochondrial functions remain contradictory, probably due to the use of artificial expression and replication systems. In vivo studies are hampered by the fact that innate and adaptive immune responses will overlay mitochondrial dysfunctions induced directly in the hepatocyte by HCV. Thus, the molecular aspects underlying HCV-induced mitochondrial dysfunctions and their roles in viral replication and the associated pathology need yet to be confirmed in the context of productively replicating virus and physiologically relevant in vitro and in vivo model systems.

Expression of Biliverdin Reductase A in peripheral blood leukocytes is associated with treatment response in HCV-infected patients

BACKGROUND AND AIMS

Hepatitis C virus (HCV) infection is associated with systemic oxidative stress. Since the heme catabolic pathway plays an important role in antioxidant protection, we attempted to assess the gene expression of key enzymes of heme catabolism, heme oxygenase 1 (HMOX1), heme oxygenase 2 (HMOX2), and biliverdin reductase A (BLVRA) in the liver and peripheral blood leukocytes (PBL) of patients chronically infected with HCV.

METHODS

Gene expressions (HMOX1, HMOX2, BLVRA) and HCV RNA were analyzed in PBL of HCV treatment naïve patients (n = 58) and controls (n = 55), with a subset of HCV patients having data on hepatic gene expression (n = 35). Based upon the therapeutic outcome, HCV patients were classified as either responders (n = 38) or treatment-failure patients (n = 20). Blood samples in HCV patients were collected at day 0, and week 12, 24, 36, and 48 after the initiation of standard antiviral therapy.

RESULTS

Compared to the controls, substantially increased BLVRA expression was detected in PBL (p<0.001) of therapeutically naïve HCV patients. mRNA levels of BLVRA in PBL closely correlated with those in liver tissue (r2 = 0.347,p = 0.03). A marked difference in BLVRA expression in PBL between the sustained responders and patients with treatment failure was detected at week 0 and during the follow-up (p<0.001). Multivariate analysis revealed that BLVRA basal expression in PBL was an independent predictor for sustained virological response (OR 15; 95% CI 1.05-214.2; P = 0.046). HMOX1/2 expression did not have any effect on the treatment outcome.

CONCLUSION

Our results suggest that patients with chronic HCV infection significantly upregulate BLVRA expression in PBL. The lack of BLVRA overexpression is associated with non-responsiveness to standard antiviral therapy; whereas, HMOX1/2 does not seem to have any predictive potential.

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

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

Heme oxygenase-1 mRNA expression in egyptian patients with chronic liver disease

BACKGROUND

Chronic liver disease (CLD) is a global medical problem. This disease is associated with increased hepatic oxidative stress. One of the antioxidant enzymes that protect cells against this stress is heme oxygenase-1 (HO-1).

OBJECTIVES

This study aimed to investigate the mRNA expression of HO-1 in Egyptian patients with CLD and its relation to oxidative stress biomarkers.

PATIENTS AND METHODS

Levels of serum ferritin, carboxyhemoglobin, malondialdehyde (MDA), and erythrocyte-reduced glutathione (GSH) were measured, and HO-1 mRNA expression was detected in 45 CLD patients (15 with nonalcoholic steatohepatitis [NASH], 15 with chronic hepatitis C, and 15 with liver cirrhosis) and 15 healthy controls.

RESULTS

HO-1 mRNA expression was increased in patients with NASH, chronic hepatitis C, and liver cirrhosis compared to controls. The expression in cirrhotic patients was significantly higher than that in patients with NASH and chronic hepatitis C. Compared to controls, patients with NASH, chronic hepatitis C, and liver cirrhosis had higher levels of ferritin, carboxyhemoglobin, and MDA and lower levels of GSH. HO-1 mRNA expression was positively correlated with levels of carboxyhemoglobin, serum ferritin, and serum MDA and negatively correlated with levels of erythrocyte GSH in CLD patients.

CONCLUSIONS

HO-1 mRNA expression was significantly increased in CLD patients, and the increase reflected the severity of the disease. The significant relationship between the increased HO-1 expression and oxidative stress biomarkers in patients with CLD suggests that HO-1 may play an important role in protecting the liver from oxidative stress-dependent damage. Therefore, induction of HO-1 could be a novel therapeutic option for CLD.

Association of filamin A and vimentin with hepatitis C virus proteins in infected human hepatocytes

Chronic hepatitis C (CHC) infection caused by hepatitis C virus (HCV) is a major cause of liver disease and remains a major therapeutic challenge. A variety of host proteins interact with HCV proteins. The definitive role of cytoskeletal (CS) proteins in HCV infection remains to be determined. In this study, our aim was to determine the expression profile of differentially regulated and expressed selected CS proteins and their association with HCV proteins in infected hepatocytes as possible therapeutic targets. Using proteomics, qRT-PCR, Western blot and immunofluorescence techniques, we revealed that filamin A (fila) and vimentin (vim) were prominently increased proteins in HCV-expressing human hepatoma cells compared with parental cells and in liver biopsies from patients with CHC vs controls. HCV nonstructural (NS) 3 and NS5A proteins were associated with fila, while core protein partially with fila and vim. Immunoprecipitation showed interactions among fila and NS3 and NS5A proteins. Cells treated with interferon-α showed a dose- and time-dependent decrease in CS and HCV proteins. NS proteins clustered at the perinuclear region following cytochalasin b treatment, whereas disperse cytoplasmic and perinuclear distribution was observed in the no-treatment group. This study demonstrates and signifies that changes occur in the expression of CS proteins in HCV-infected hepatocytes and, for the first time, shows the up-regulation and interaction of fila with HCV proteins. Association between CS and HCV proteins may have implications in future design of CS protein-targeted therapy for the treatment for HCV infection.

Legalon-SIL downregulates HCV core and NS5A in human hepatocytes expressing full-length HCV

AIM

To determine the effect of Legalon-SIL (LS) on hepatitis C virus (HCV) core and NS5A expression and on heme oxygenase-1 (HMOX-1) and its transcriptional regulators in human hepatoma cells expressing full length HCV genotype 1b.

METHODS

CON1 cells were treated with 50 μmol/L or 200 μmol/L LS. Cells were harvested after 2, 6 and 24 h. HCV RNA and protein levels were determined by quantitative real-time polymerase chain reaction and Western blotting, respectively.

RESULTS

HCV RNA (core and NS5A regions) was decreased after 6 h with LS 200 μmol/L (P < 0.05). Both 50 and 200 μmol/L LS decreased HCV RNA levels [core region (by 55% and 88%, respectively) and NS5A region (by 62% and 87%, respectively) after 24 h compared with vehicle (dimethyl sulphoxide) control (P < 0.01). Similarly HCV core and NS5A protein were decreased (by 85%, P < 0.01 and by 65%, P < 0.05, respectively) by LS 200 μmol/L. Bach1 and HMOX-1 RNA were also downregulated by LS treatment (P < 0.01), while Nrf2 protein was increased (P < 0.05).

CONCLUSION

Our results demonstrate that treatment with LS downregulates HCV core and NS5A expression in CON1 cells which express full length HCV genotype 1b, and suggests that LS may prove to be a valuable alternative or adjunctive therapy for the treatment of HCV infection.

Targeting oxidative stress in cancer

IMPORTANCE OF THE FIELD

Reactive oxygen species (ROS) occur as natural by-products of oxygen metabolism and have important cellular functions. Normally, the cell is able to maintain an adequate balance between the formation and removal of ROS either via anti-oxidants or through the use specific enzymatic pathways. However, if this balance is disturbed, oxidative stress may occur in the cell, a situation linked to the pathogenesis of many diseases, including cancer.

AREAS COVERED IN THIS REVIEW

HDACs are important regulators of many oxidative stress pathways including those involved with both sensing and coordinating the cellular response to oxidative stress. In particular aberrant regulation of these pathways by histone deacetylases may play critical roles in cancer progression.

WHAT THE READER WILL GAIN

In this review we discuss the notion that targeting HDACs may be a useful therapeutic avenue in the treatment of oxidative stress in cancer, using chronic obstructive pulmonary disease (COPD), NSCLC and hepatocellular carcinoma (HCC) as examples to illustrate this possibility.

TAKE HOME MESSAGE

Epigenetic mechanisms may be an important new therapeutic avenue for targeting oxidative stress in cancer.

Immunoregulatory properties of heme oxygenase-1

Heme oxygenase-1 (HO-1) is one of the three isoforms of the heme oxygenase enzyme that catabolyzes the degradation of heme into biliverdin with the production of free iron and CO. HO-1 is induced by its substrate and by other stimuli, including agents involved in oxidative stress and proinflammatory cytokines as well as several anti-inflammatory stimuli. A growing body of evidence points toward the capacity of this molecule to inhibit immune reactions and the pivotal role of HO-1 in inflammatory diseases. We will first review the physiological role of HO-1 as determined by the analysis of HO-1-deficient individuals. This will be followed by an examination of the effect of HO-1 within immunopathological contexts such as immune disorders (autoimmunity and allergy) or infections. A section will be devoted to the use of an HO-1 inducer as an immunosuppressive molecule in transplantation. Finally, we will review the molecular basis of HO-1 actions on different immune cells.

Biliverdin inhibits hepatitis C virus nonstructural 3/4A protease activity: mechanism for the antiviral effects of heme oxygenase?

Induction of heme oxygenase-1 (HO-1) inhibits hepatitis C virus (HCV) replication. Of the products of the reaction catalyzed by HO-1, iron has been shown to inhibit HCV ribonucleic acid (RNA) polymerase, but little is known about the antiviral activity of biliverdin (BV). Herein, we report that BV inhibits viral replication and viral protein expression in a dose-dependent manner in replicons and cells harboring the infectious J6/JFH construct. Using the SensoLyte 620 HCV Protease Assay with a wide wavelength excitation/emission (591 nm/622 nm) fluorescence energy transfer peptide, we found that both recombinant and endogenous nonstructural 3/4A (NS3/4A) protease from replicon microsomes are potently inhibited by BV. Of the tetrapyrroles tested, BV was the strongest inhibitor of NS3/4A activity, with a median inhibitory concentration (IC(50)) of 9 μM, similar to that of the commercial inhibitor, AnaSpec (Fremont, CA) #25346 (IC(50) 5 μM). Lineweaver-Burk plots indicated mixed competitive and noncompetitive inhibition of the protease by BV. In contrast, the effects of bilirubin (BR) on HCV replication and NS3/4A were much less potent. Because BV is rapidly converted to BR by biliverdin reductase (BVR) intracellularly, the effect of BVR knockdown on BV antiviral activity was assessed. After greater than 80% silencing of BVR, inhibition of viral replication by BV was enhanced. BV also increased the antiviral activity of α-interferon in replicons.

CONCLUSION

BV is a potent inhibitor of HCV NS3/4A protease, which likely contributes to the antiviral activity of HO-1. These findings suggest that BV or its derivatives may be useful in future drug therapies targeting the NS3/4A protease.

Parallel microRNA and mRNA expression profiling of (genotype 1b) human hepatoma cells expressing hepatitis C virus

BACKGROUND & AIMS

MicroRNAs (miRNAs) are members of a class of small noncoding functional RNAs that modulate gene regulation at the post-transcriptional level in a sequence specific manner. miRNA dysfunction has been linked to the pathophysiology of human diseases including those resulting from viral infections. The objective of this study was to investigate changes in miRNA profiles that occur in hepatoma cells expressing hepatitis C virus (HCV) and identify anticorrelated mRNAs, which may be their regulatory targets.

METHODS

Microarrays were used to perform global miRNA and mRNA expression analysis. Fold changes and pairwise statistics were computed for the resulting datasets. Hierarchical cluster and pathway analyses were performed to assess the degree of differential expression and identify regulatory networks. Bioinformatics tools were used to integrate mRNA profiling results with miRNA target predictions.

RESULTS

Replication of the Con1 strain of HCV virus in hepatoma cells elicited extensive differential expression of both miRNAs and mRNAs. Forty-three differentially expressed miRNAs (P≤0.001) were identified by microarray analysis in HCV expressing cells. Six thousand eight hundred and fifteen differentially expressed mRNAs (P≤0.05) were identified. Computational analyses revealed anticorrelated miRNA:mRNA pairs for each target prediction algorithm used. Pathway analysis generated a filtered pathway with 120 entities, including seven major regulators and nine major targets potentially under the control of at least 11 miRNAs.

CONCLUSIONS

The expression of a number of anticorrelated miRNAs:mRNA pairs are affected by the presence of HCV. These miRNAs and their putative targets are attractive candidates for being involved in the pathogenesis and/or progression of HCV-induced chronic hepatitis.

Heme oxygenase-1 as a therapeutic target in inflammatory disorders of the gastrointestinal tract

Heme oxygenase (HO)-1 is the inducible isoform of the first and rate-limiting enzyme of heme degradation. HO-1 not only protects against oxidative stress and apoptosis, but has received a great deal of attention in recent years because of its potent anti-inflammatory functions. Studies with HO-1 knockout animal models have led to major advances in the understanding of how HO-1 might regulate inflammatory immune responses, although little is known on the underlying mechanisms. Due to its beneficial effects the targeted induction of this enzyme is considered to have major therapeutic potential for the treatment of inflammatory disorders. This review discusses current knowledge on the mechanisms that mediate anti-inflammatory protection by HO-1. More specifically, the article deals with the role of HO-1 in the pathophysiology of viral hepatitis, inflammatory bowel disease, and pancreatitis. The effects of specific HO-1 modulation as a potential therapeutic strategy in experimental cell culture and animal models of these gastrointestinal disorders are summarized. In conclusion, targeted regulation of HO-1 holds major promise for future clinical interventions in inflammatory diseases of the gastrointestinal tract.

Hepatitis C virus core protein compromises iron-induced activation of antioxidants in mice and HepG2 cells

One of the characteristics of hepatitis C virus (HCV) infection is the unusual augmentation of oxidative stress, which is exacerbated by iron accumulation in the liver, as observed frequently in hepatitis C patients. Using a transgenic mouse model, the core protein of HCV was shown previously to induce the overproduction of reactive oxygen species (ROS) in the liver. In the present study, the impact of iron overloading on the oxidant/antioxidant system was examined using this mouse model and cultured cells. Iron overloading caused the induction of ROS as well as antioxidants. However, the augmentation of some antioxidants, including heme oxygenase-1 and NADH dehydrogenase, quinone 1, was compromised by the presence of the core protein. The attenuation of iron-induced augmentation of heme oxygenase-1 was also confirmed in HepG2 cells expressing the core protein. This attenuation was not dependent on the Nrf2 transcription factor. Thus, HCV infection not only induces oxidative stress but also hampers the iron-induced antioxidant activation in the liver, thereby exacerbating oxidative stress that would facilitate hepatocarcinogenesis.

MicroRNA-196 represses Bach1 protein and hepatitis C virus gene expression in human hepatoma cells expressing hepatitis C viral proteins

Hepatitis C virus (HCV) directly induces oxidative stress and liver injury. Bach1, a basic leucine zipper mammalian transcriptional repressor, negatively regulates heme oxygenase 1 (HMOX1), a key cytoprotective enzyme that has antioxidant and anti-inflammatory activities. microRNAs (miRNAs) are small noncoding RNAs ( approximately 22 nt) that are important regulators of gene expression. Whether and how miRNAs regulate Bach1 or HCV are largely unknown. The aims of this study were to determine whether miR-196 regulates Bach1, HMOX1, and/or HCV gene expression. HCV replicon cell lines (Con1 and 9-13) of the Con1 isolate and J6/JFH1-based HCV cell culture system were used in this study. The effects of miR-196 mimic on Bach1, HMOX1, and HCV RNA, and protein levels were measured by way of quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting, respectively. The Dual Glo Luciferase Assay System was used to determine reporter activities. miR-196 mimic significantly down-regulated Bach1 and up-regulated HMOX1 gene expression and inhibited HCV expression. Dual luciferase reporter assays demonstrated that transfection of miR-196 mimic resulted in a significant decrease in Bach1 3'-untranslated region (UTR)-dependent luciferase activity but not in mutant Bach1 3'-UTR-dependent luciferase activity. Moreover, there was no detectable effect of mutant miR-196 on Bach1 3'-UTR-dependent luciferase activity.

CONCLUSION

miR-196 directly acts on the 3'-UTR of Bach1 messenger RNA and translationally represses the expression of this protein, and up-regulates HMOX1. miR-196 also inhibits HCV expression in HCV replicon cell lines (genotype 1b) and in J6/JFH1 (genotype 2a) HCV cell culture system. Thus, miR-196 plays a role in both HMOX1/Bach1 expression and the regulation of HCV expression in human hepatocytes. Overexpression of miR-196 holds promise as a potential novel strategy to prevent or ameliorate hepatitis C infection, and to protect against liver injury in chronic HCV infection.

The heme oxygenase 1 product biliverdin interferes with hepatitis C virus replication by increasing antiviral interferon response

The anti-inflammatory and antiapoptotic heme degrading enzyme heme oxygenase-1 (HO-1) has been shown recently to interfere with replication of hepatitis C virus (HCV). We investigated the effect of HO-1 products carbon monoxide (CO), iron and biliverdin on HCV replication using the replicon cell lines Huh-5-15 and LucUbiNeo-ET, stably expressing HCV proteins NS3 through NS5B. Incubation of these cell lines in the presence of the CO donor methylene chloride transiently reduced HCV replication, whereas an increase of iron in cell culture by administration of FeCl(3) or iron-saturated lactoferrin did not interfere with HCV replication. Likewise, depletion of iron by deferoxamine during induction of HO-1 by cobalt-protoporphyrin IX did not restore HCV replication. The most prominent effect was observed after incubation of replicon cell lines in the presence of biliverdin. Biliverdin seems to interfere with HCV replication-mediated oxidative stress by inducing expression of antiviral interferons, such as interferon alpha2 and alpha17.

CONCLUSION

The antioxidant biliverdin reduces HCV replication in vitro by triggering the antiviral interferon response and might improve HCV therapy in the future.

Iron increases HMOX1 and decreases hepatitis C viral expression in HCV-expressing cells

AIM: To investigate effects of iron on oxidative stress, heme oxygenase-1 (HMOX1) and hepatitis C viral (HCV) expression in human hepatoma cells stably expressing HCV proteins.

METHODS: Effects of iron on oxidative stress, HMOX1, and HCV expression were assessed in CON1 cells. Measurements included mRNA by quantitative reverse transcription-polymerase chain reaction, and protein levels by Western blots.

RESULTS: Iron, in the form of ferric nitrilotriacetate, increased oxidative stress and up-regulated HMOX1 gene expression. Iron did not affect mRNA or protein levels of Bach1, a repressor of HMOX1. Silencing the up-regulation of HMOX1 nuclear factor-erythroid 2-related factor 2 (Nrf2) by Nrf2-siRNA decreased FeNTA-mediated up-regulation of HMOX1 mRNA levels. These iron effects were completely blocked by deferoxamine (DFO). Iron also significantly decreased levels of HCV core mRNA and protein by 80%-90%, nonstructural 5A mRNA by 90% and protein by about 50% in the Con1 full length HCV replicon cells, whereas DFO increased them.

CONCLUSION: Excess iron up-regulates HMOX1 and down-regulates HCV gene expression in hepatoma cells. This probably mitigates liver injury caused by combined iron overload and HCV infection.

Effects of silymarin on hepatitis C virus and haem oxygenase-1 gene expression in human hepatoma cells

BACKGROUND/AIMS

Hepatitis C virus (HCV) infection is a global medical problem. The current standard treatment of chronic hepatitis C (CHC), pegylated interferon plus ribavirin, is prolonged, expensive, has serious side effects and, at best, is only 50% effective. Silymarin (SI) is a natural antioxidant often used by patients with CHC, although its efficacy for decreasing HCV levels or ameliorating CHC remains uncertain. HCV infection is associated with increased hepatic oxidative stress, and one of the antioxidant enzymes that protect cells against this stress is haem oxygenase-1 (HO-1).

METHODS

We investigated effects of SI on HCV and HO-1 gene expression in Huh-7 cells, CNS3 and 9-13 cells (the latter two stably expressing HCV-proteins).

RESULTS

Silymarin significantly downregulated HCV core mRNA (by 20%-36%) and protein (by 30%-60%) in CNS3 cells. In contrast, SI did not decrease HCV NS5A mRNA or protein expression in 9-13 cells. HO-1 mRNA was upregulated (60%-400%) by SI in Huh-7, CNS3 and 9-13 cells, whereas BTB and CNC homology 1 and nuclear factor erythroid related factor 2 mRNA levels were not affected. The effect of SI to downregulate HCV core was not related to changes in the Janus-activated tyrosine kinases-signal transducer and activators of transcription signalling pathway.

CONCLUSIONS

Silymarin may be of benefit in CHC, although prospective, randomized, controlled trials are needed to be certain.

Heme oxygenase-1 suppresses hepatitis C virus replication and increases resistance of hepatocytes to oxidant injury

Oxidative injury to hepatocytes occurs as a result of hepatitis C virus (HCV) infection and replication. Modulation of host cell antioxidant enzymes such as heme oxygenase-1 (HO-1) may be useful therapeutically to minimize cellular injury, reduce viral replication, and attenuate liver disease. In this report, we evaluated the effects of HO-1 overexpression on HCV replication and hepatocellular injury. Full-length (FL) (Con1) or nonstructural (NS) replicons (I 389 NS3-3') were transfected with complete human HO-1 sequences or empty vector for control. Cell lines overexpressing HO-1 (twofold to sixfold above basal values) or empty vector were isolated, and their HCV RNA synthesis, pro-oxidant levels, and resistance to oxidative injury were assessed. HO-1 overexpression decreased HCV RNA replication in both FL and NS replicons without affecting cellular growth or DNA synthesis. The attenuation of HCV replication was significantly reversed in both replicon systems with HO-1 small interfering RNA (siRNA) knockdown. Both FL and NS replicons that overexpress HO-1 showed reduced prooxidant levels at baseline and increased resistance to oxidant-induced cytotoxicity. HO-1 induction with hemin also markedly decreased HCV replication in both parental FL and NS replicon cell lines. Conversely, knockdown of HO-1 messenger RNA (mRNA) by siRNA in parental FL or NS replicons did not significantly affect HCV replication, suggesting that less than basal levels of HO-1 had minimal effect on HCV replication.

CONCLUSION

Overexpression or induction of HO-1 results in decreased HCV replication as well as protection from oxidative damage. These findings suggest a potential role for HO-1 in antiviral therapy and therapeutic protection against hepatocellular injury in HCV infection.

Natural heme oxygenase-1 inducers in hepatobiliary function

Many physiological effects of natural antioxidants, their extracts or their major active components, have been reported in recent decades. Most of these compounds are characterized by a phenolic structure, similar to that of α-tocopherol, and present antioxidant properties that have been demonstrated both in vitro and in vivo. Polyphenols may increase the capacity of endogenous antioxidant defences and modulate the cellular redox state. Changes in the cellular redox state may have wide-ranging consequences for cellular growth and differentiation. The majority of in vitro and in vivo studies conducted so far have attributed the protective effect of bioactive polyphenols to their chemical reactivity toward free radicals and their capacity to prevent the oxidation of important intracellular components. However, in recent years a possible novel aspect in the mode of action of these compounds has been suggested; that is, the ultimate stimulation of the heme oxygenase-1 (HO-1) pathway is likely to account for the established and powerful antioxidant/anti-inflammatory properties of these polyphenols. The products of the HO-catalyzed reaction, particularly carbon monoxide (CO) and biliverdin/bilirubin have been shown to exert protective effects in several organs against oxidative and other noxious stimuli. In this context, it is interesting to note that induction of HO-1 expression by means of natural compounds contributes to protection against liver damage in various experimental models. The focus of this review is on the significance of targeted induction of HO-1 as a potential therapeutic strategy to protect the liver against various stressors in several pathological conditions.

Differential regulation of human ALAS1 mRNA and protein levels by heme and cobalt protoporphyrin

5-Aminolevulinic acid synthase 1 (ALAS1) is the first and rate-controlling enzyme of heme biosynthesis. This study was to determine the effects of heme and selected nonheme metalloporphyrins on human ALAS1 gene expression in hepatocytes. We found that, upon heme and cobalt protoporphyrin (CoPP) treatments, ALAS1 mRNA levels were down-regulated significantly by ca. 50% or more. Measurement of mRNA in the presence of actinomycin D showed that these down-regulations were due to the decreases in mRNA half-lives. Furthermore, the levels of mitochondrial mature ALAS1 protein were down-regulated by 60-70%, but those of the cytosolic precursor protein were up-regulated by 2-5-fold. Measurement of protein in the presence of cycloheximide (CHX) suggests that elevation of the precursor form is due to the increase in protein half-lives. These results provide novel insights into the mechanisms of heme repressional effects on ALAS1 and provide a rationale for further investigation of CoPP as a therapeutic agent for acute porphyric syndromes.

Pharmacological and clinical aspects of heme oxygenase

This review is intended to stimulate interest in the effect of increased expression of heme oxygenase-1 (HO-1) protein and increased levels of HO activity on normal and pathological states. The HO system includes the heme catabolic pathway, comprising HO and biliverdin reductase, and the products of heme degradation, carbon monoxide (CO), iron, and biliverdin/bilirubin. The role of the HO system in diabetes, inflammation, heart disease, hypertension, neurological disorders, transplantation, endotoxemia and other pathologies is a burgeoning area of research. This review focuses on the clinical potential of increased levels of HO-1 protein and HO activity to ameliorate tissue injury. The use of pharmacological and genetic probes to manipulate HO, leading to new insights into the complex relationship of the HO system with biological and pathological phenomena under investigation, is reviewed. This information is critical in both drug development and the implementation of clinical approaches to moderate and to alleviate the numerous chronic disorders in humans affected by perturbations in the HO system.

Bach1 Repression of Ferritin and Thioredoxin Reductase1 Is Heme-sensitive in Cells and in Vitro and Coordinates Expression with Heme Oxygenase1, β-Globin, and NADP(H) Quinone (Oxido) Reductase1

Ferritin gene transcription is regulated by heme as is ferritin mRNA translation, which is mediated by the well studied mRNA.IRE/IRP protein complex. The heme-sensitive DNA sequence in ferritin genes is the maf recognition/antioxidant response element present in several other genes that are induced by heme and repressed by Bach1. We now report that chromatin immunoprecipitated with Bach1 antiserum contains ferritin DNA sequences. In addition, overexpression of Bach1 protein in the transfected cells decreased ferritin expression, indicating insufficient endogenous Bach1 for full repression; decreasing Bach1 with antisense RNA increased ferritin expression. Thioredoxin reductase1, a gene that also contains a maf recognition/antioxidant response element but is less studied, responded similarly to ferritin, as did the positive controls heme oxygenase1 and NADP(H) quinone (oxido) reductase1. Bach1-DNA promoter interactions in cells were confirmed in vitro with soluble, recombinant Bach1 protein and revealed a quantitative range of Bach1/DNA stabilities: ferritin L approximately ferritin H approximately beta-globin, beta-globin approximately 2-fold >heme oxygenase1 = quinone reductase beta-globin approximately 4-fold >thioredoxin reductase1. Such results indicate the possibility that modulation of cellular Bach1 concentrations will have variable effects among the genes coordinately regulated by maf recognition/antioxidant response elements in iron/oxygen/antioxidant metabolism.

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

BACKGROUND & AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Redox regulation of hepatitis C in nonalcoholic and alcoholic liver

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

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

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

Homeostatic response under carcinogen withdrawal, heme oxygenase 1 expression and cell cycle association

Background

Chronic injury deregulates cellular homeostasis and induces a number of alterations leading to disruption of cellular processes such as cell cycle checkpoints and apoptosis, driving to carcinogenesis. The stress protein heme oxygenase-1 (HO-1) catalyzes heme degradation producing biliverdin, iron and CO. Induction of HO-1 has been suggested to be essential for a controlled cell growth. The aim of this work was to analyze the in vivo homeostatic response (HR) triggered by the withdrawal of a potent carcinogen, p-dimethylaminoazobenzene (DAB), after preneoplastic lesions were observed. We analyzed HO-1 cellular localization and the expression of HO-1, Bcl-2 and cell cycle related proteins under these conditions comparing them to hepatocellular carcinoma (HC).

Methods

The intoxication protocol was designed based on previous studies demonstrating that preneoplastic lesions were evident after 89 days of chemical carcinogen administration. Male CF1 mice (n = 18) were used. HR group received DAB (0.5 % w/w) in the diet for 78 days followed by 11 days of carcinogen deprivation. The HC group received the carcinogen and control animals the standard diet during 89 days. The expression of cell cycle related proteins, of Bcl-2 and of HO-1 were analyzed by western blot. The cellular localization and expression of HO-1 were detected by immnunohistochemistry.

Results

Increased expression of cyclin E/CDK2 was observed in HR, thus implicating cyclin E/CDK2 in the liver regenerative process. p21^cip1/waf1 and Bcl-2 induction in HC was restituted to basal levels in HR. A similar response profile was found for HO-1 expression levels, showing a lower oxidative status in the carcinogen-deprived liver. The immunohistochemical studies revealed the presence of macrophages surrounding foci of necrosis and nodular lesions in HR indicative of an inflammatory response. Furthermore, regenerative cells displayed changes in type, size and intensity of HO-1 immunostaining.

Conclusion

These results demonstrate that the regenerative capacity of the liver is still observed in the pre-neoplastic tissue after carcinogen withdrawal suggesting that reversible mechanism/s to compensate necrosis and to restitute homeostasis are involved.