Iron inactivates the RNA polymerase NS5B and suppresses subgenomic replication of hepatitis C Virus

Heme oxygenase-1 is an equid alphaherpesvirus 8 replication restriction host protein and suppresses viral replication via the PKCβ/ERK1/ERK2 and NO/cGMP/PKG pathway

Equid alphaherpesvirus 8 (EqHV-8) is one of the most economically important viruses that is known to cause severe respiratory disease, abortion, and neurological syndromes in equines. However, no effective vaccines or therapeutic agents are available to control EqHV-8 infection. Heme oxygenase-1 (HO-1) is an antioxidant defense enzyme that displays significant cytoprotective effects against different viral infections. However, the literature on the function of HO-1 during EqHV-8 infection is little. We explored the effects of HO-1 on EqHV-8 infection and revealed its potential mechanisms. Our results demonstrated that HO-1 induced by cobalt-protoporphyrin (CoPP) or HO-1 overexpression inhibited EqHV-8 replication in susceptible cells. In contrast, HO-1 inhibitor (zinc protoporphyria) or siRNA targeting HO-1 reversed the anti-EqHV-8 activity. Furthermore, biliverdin, a metabolic product of HO-1, mediated the anti-EqHV-8 effect of HO-1 via both the protein kinase C (PKC)β/extracellular signal-regulated kinase (ERK)1/ERK2 and nitric oxide (NO)-dependent cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) signaling pathways. In addition, CoPP protected the mice by reducing the EqHV-8 infection in the lungs. Altogether, these results indicated that HO-1 can be developed as a promising therapeutic strategy to control EqHV-8 infection.IMPORTANCEEqHV-8 infections have threatened continuously donkey and horse industry worldwide, which induces huge economic losses every year. However, no effective vaccination strategies or drug against EqHV-8 infection until now. Our present study found that one host protien HO-1 restrict EqHV-8 replication in vitro and in vivo. Furthermore, we demonstrate that HO-1 and its metabolite biliverdin suppress EqHV-8 relication via the PKCβ/ERK1/ERK2 and NO/cGMP/PKG pathways. Hence, we believe that HO-1 can be developed as a promising therapeutic strategy to control EqHV-8 infection.

The Role of the NRF2 Pathway in the Pathogenesis of Viral Respiratory Infections

In humans, acute and chronic respiratory infections caused by viruses are associated with considerable morbidity and mortality. Respiratory viruses infect airway epithelial cells and induce oxidative stress, yet the exact pathogenesis remains unclear. Oxidative stress activates the transcription factor NRF2, which plays a key role in alleviating redox-induced cellular injury. The transcriptional activation of NRF2 has been reported to affect both viral replication and associated inflammation pathways. There is complex bidirectional crosstalk between virus replication and the NRF2 pathway because virus replication directly or indirectly regulates NRF2 expression, and NRF2 activation can reversely hamper viral replication and viral spread across cells and tissues. In this review, we discuss the complex role of the NRF2 pathway in the regulation of the pathogenesis of the main respiratory viruses, including coronaviruses, influenza viruses, respiratory syncytial virus (RSV), and rhinoviruses. We also summarize the scientific evidence regarding the effects of the known NRF2 agonists that can be utilized to alter the NRF2 pathway.

Iron metabolism in the cell as a target in the development of potential antimicrobial and antiviral agents

The search and creation of innovative antimicrobial drugs, acting against resistant and multiresistant strains of bacteria and fungi, are one of the most important tasks of modern bioorganic chemistry and pharmaceuticals. Since iron is essential for the vital activity of almost all organisms, including mammals and bacteria, the proteins involved in its metabolism can serve as potential targets in the development of new promising antimicrobial agents. Such targets include endogenous mammalian biomolecules, heme oxygenases, siderophores, protein 24p3, as well as bacterial heme oxygenases and siderophores. Other proteins that are responsible for the delivery of iron to cells and its balance between bacteria and the host organism also attract certain particular interest. The review summarizes data on the development of inhibitors and inducers (activators) of heme oxygenases, selective for mammals and bacteria, and considers the characteristic features of their mechanisms of action and structure. Based on the reviewed literature data, it was concluded that the use of hemin, the most powerful hemooxygenase inducer, and its derivatives as potential antimicrobial and antiviral agents, in particular against COVID-19 and other dangerous infections, would be a promising approach. In this case, an important role is attributed to the products of hemin degradation formed by heme oxygenases in vitro and in vivo. Certain attention has been paid to the data on the antimicrobial action of iron-free protoporphyrinates, namely complexes with Co, Ga, Zn, Mn, their advantages and disadvantages compared to hemin. Modification of the well-known antibiotic ceftazidime with a siderophore molecule increased its effectiveness against resistant bacteria.

Relationship between iron overload caused by abnormal hepcidin expression and liver disease: A review

Iron is essential to organisms, the liver plays a vital role in its storage. Under pathological conditions, iron uptake by the intestine or hepatocytes increases, allowing excess iron to accumulate in liver cells. When the expression of hepcidin is abnormal, iron homeostasis in humans cannot be regulated, and resulting in iron overload. Hepcidin also regulates the release of iron from siderophores, thereby regulating the concentration of iron in plasma. Important factors related to hepcidin and systemic iron homeostasis include plasma iron concentration, body iron storage, infection, inflammation, and erythropoietin. This review summarizes the mechanism and regulation of iron overload caused by hepcidin, as well as related liver diseases caused by iron overload and treatment.

A Journey into the Clinical Relevance of Heme Oxygenase 1 for Human Inflammatory Disease and Viral Clearance: Why Does It Matter on the COVID-19 Scene?

Heme oxygenase 1 (HO-1), the rate-limiting enzyme in heme degradation, is involved in the maintenance of cellular homeostasis, exerting a cytoprotective role by its antioxidative and anti-inflammatory functions. HO-1 and its end products, biliverdin, carbon monoxide and free iron (Fe²⁺), confer cytoprotection against inflammatory and oxidative injury. Additionally, HO-1 exerts antiviral properties against a diverse range of viral infections by interfering with replication or activating the interferon (IFN) pathway. Severe cases of coronavirus disease 2019 (COVID-19), an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), are characterized by systemic hyperinflammation, which, in some cases, leads to severe or fatal symptoms as a consequence of respiratory failure, lung and heart damage, kidney failure, and nervous system complications. This review summarizes the current research on the protective role of HO-1 in inflammatory diseases and against a wide range of viral infections, positioning HO-1 as an attractive target to ameliorate clinical manifestations during COVID-19.

Role of NRF2 and Sirtuin activators in COVID-19

COVID-19 is a pandemic requiring immediate solution for treatment because of its complex pathophysiology. Exploration of novel targets and thus treatment will be life savers which is the need of the hour. 2 host factors- TMPRSS2 and ACE2 are responsible for the way the virus will enter and replicate in the host. Also NRF2 is an important protein responsible for its anti-inflammatory role by multiple mechanisms of action like inhibition of NF-kB, suppression of pro-inflammatory genes, etc. NRF2 is deacetylated by Sirtuins and therefore both have a direct association. Absence of SIRT indicates inhibition of NRF2 expression and thus no anti-oxidative and anti-inflammatory protection for the cell. Therefore, we propose that NRF2 activators and/or SIRT activators can be evaluated to check their efficacy in ameliorating the symptoms of COVID-19.

Induction of HOXA3 by PRRSV inhibits IFN-I response through negatively regulation of HO-1 transcription

Type I interferons (IFN-I) play a key role in the host defense against virus infection, but porcine reproductive and respiratory syndrome virus (PRRSV) infection does not effectively activate IFN-I response, and the underlying molecular mechanisms are poorly characterized. In this study, a novel transcription factor of the heme oxygenase-1 (HO-1) gene, homeobox A3 (HOXA3), was screened and identified. Here, we found that HOXA3 was significantly increased during PRRSV infection. We demonstrated that HOXA3 promotes PRRSV replication by negatively regulating the HO-1 gene transcription, which is achieved by regulating type I interferons (IFN-I) production. A detailed analysis showed that PRRSV exploits HOXA3 to suppress beta interferon (IFN-β) and IFN-stimulated gene (ISG) expression in host cells. We also provide direct evidence that the activation of IFN-I by HO-1 depends on its interaction with IRF3. Then we further proved that deficiency of HOXA3 promoted the HO-1-IRF3 interaction, and subsequently enhanced IRF3 phosphorylation and nuclear translocation in PRRSV-infected cells. These data suggest that PRRSV uses HOXA3 to negatively regulate the transcription of the HO-1 gene to suppress the IFN-I response for immune evasion. IMPORTANCE Porcine reproductive and respiratory syndrome (PRRS), caused by PRRSV, leads the pork industry worldwide to significant economic losses. HOXA3 is generally considered to be an important molecule in the process of body development and cell differentiation. Here, we found a novel transcription factor of the HO-1 gene, HOXA3, can negatively regulate the transcription of the HO-1 gene and play an important role in the suppression of IFN-I response by PRRSV. PRRSV induces the upregulation of HOXA3, which can negatively regulate HO-1 gene transcription, thereby weakening the interaction between HO-1 and IRF3 for inhibiting the type I IFN response. This study extends the function of HOXA3 to the virus field for the first time and provides new insights into PRRSV immune evasion mechanism.

Heme Oxygenase-1 Exerts Antiviral Activity against Hepatitis A Virus In Vitro

Hepatitis A virus (HAV), the causative pathogen of hepatitis A, induces severe acute liver injuries in humans and is a serious public health concern worldwide. However, appropriate therapeutics have not yet been developed. The enzyme heme oxygenase-1 (HO-1) exerts antiviral activities in cells infected with several viruses including hepatitis B and C viruses. In this study, we demonstrated for the first time the suppression of virus replication by HO-1 in cells infected with HAV. Hemin (HO-1 inducer) induced HO-1 mRNA and protein expression, as expected, and below 50 mM, dose-dependently reduced the viral RNA and proteins in the HAV-infected cells without cytotoxicity. Additionally, HO-1 protein overexpression using a protein expression vector suppressed HAV replication. Although ZnPP-9, an HO-1 inhibitor, did not affect HAV replication, it significantly inhibited hemin-induced antiviral activity in HAV-infected cells. Additionally, FeCl3, CORM-3, biliverdin, and the HO-1 inducers andrographolide and CoPP inhibited HAV replication in the HAV-infected cells; andrographolide and CoPP exhibited a dose-dependent effect. In conclusion, these results suggest that HO-1 effectively suppresses HAV infection in vitro, and its enzymatic products appear to exert antiviral activity. We expect that these results could contribute to the development of a new antiviral drug for HAV.

Metabolic reprogramming and immune regulation in viral diseases

The recent outbreak and transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) worldwide and the ensuing coronavirus disease 2019 (COVID-19) pandemic has left us scrambling for ways to contain the disease and develop vaccines that are safe and effective. Equally important, understanding the impact of the virus on the host system in convalescent patients, healthy otherwise or with co-morbidities, is expected to aid in developing effective strategies in the management of patients afflicted with the disease. Viruses possess the uncanny ability to redirect host metabolism to serve their needs and also limit host immune response to ensure their survival. An ever-increasingly powerful approach uses metabolomics to uncover diverse molecular signatures that influence a wide array of host signalling networks in different viral infections. This would also help integrate experimental findings from individual studies to yield robust evidence. In addition, unravelling the molecular mechanisms harnessed by both viruses and tumours in their host metabolism will help broaden the repertoire of therapeutic tools available to combat viral disease.

Heme oxygenase-1 modulation: A potential therapeutic target for COVID-19 and associated complications

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to infect hundred thousands of people every day worldwide. Since it is a novel virus, research continues to update the possible therapeutic targets when new evidence regarding COVID-19 are gathered. This article presents an evidence-based hypothesis that activating the heme oxygenase-1 (HO-1) pathway is a potential target for COVID-19. Interferons (IFNs) have broad-spectrum antiviral activity including against SARS-CoV-2. Induction of HO-1 and increase in the heme catabolism end-product confer antiviral activity. IFN activation results in inhibition of viral replication in various viral infections. COVID-19 induced inflammation as well as acute respiratory distress syndrome (ARDS), and coagulopathies are now known major causes of mortality. A protective role of HO-1 induction in inflammation, inflammation-induced coagulation, and ARDS has been reported. Based on an association of HO-1 promoter polymorphisms and disease severity, we propose an evaluation of the status of these polymorphisms in COVID-19 patients who become severely ill. If an association is established, it might be helpful in identifying patients at high risk. Hence, we hypothesize that HO-1 pathway activation could be a therapeutic strategy against COVID-19 and associated complications.

Can Activation of NRF2 Be a Strategy against COVID-19?

Acute respiratory distress syndrome (ARDS) caused by SARS-CoV-2 is largely the result of a dysregulated host response, followed by damage to alveolar cells and lung fibrosis. Exacerbated proinflammatory cytokines release (cytokine storm) and loss of T lymphocytes (leukopenia) characterize the most aggressive presentation. We propose that a multifaceted anti-inflammatory strategy based on pharmacological activation of nuclear factor erythroid 2 p45-related factor 2 (NRF2) can be deployed against the virus. The strategy provides robust cytoprotection by restoring redox and protein homeostasis, promoting resolution of inflammation, and facilitating repair. NRF2 activators such as sulforaphane and bardoxolone methyl are already in clinical trials. The safety and efficacy information of these modulators in humans, together with their well-documented cytoprotective and anti-inflammatory effects in preclinical models, highlight the potential of this armamentarium for deployment to the battlefield against COVID-19.

The Cytoprotective Enzyme Heme Oxygenase-1 Suppresses Pseudorabies Virus Replication in vitro

Pseudorabies virus (PRV) infection brings about great economic losses to the swine industry worldwide, as there are currently no effective therapeutic agents or vaccines against this disease, and mutations in endemic wild virulent PRV strains result in immune failure of traditional vaccines. Heme oxygenase-1 (HO-1) catalyzes the conversion of heme into biliverdin (BV), iron and carbon monoxide (CO), all of which have been demonstrated to protect cells from various stressors. However, the role of HO-1 in PRV replication remains unknown. Thus, the present study aimed to investigate the effect of HO-1 on PRV replication and determine its underlying molecular mechanisms. The results demonstrated that induction of HO-1 via cobalt-protoporphyrin (CoPP) markedly suppressed PRV replication, while HO-1 specific small interfering RNA or inhibitor zinc-protoporphyrin partially reversed the inhibitory effect of CoPP on PRV replication. Furthermore, overexpression of HO-1 notably inhibited PRV replication, while knockdown of endogenous HO-1 expression promoted PRV replication. Mechanism analyses indicated that the HO-1 downstream metabolites, CO and BV/BR partially mediated the virus suppressive effect of HO-1. Taken together, the results of the present study suggest that HO-1 may be developed as a novel endogenous antiviral factor against PRV, and the HO-1/BV/CO system may constitute a unique antiviral protection network during PRV infection and interaction with host cells.

Metalloprotoporphyrin Inhibition of HCV NS3-4A Protease: Structure-Activity Relationships

Background

Antiviral actions of tetrapyrroles have been described in a number of systems. Our goal was to evaluate antagonism of the HCV NS3-4A protease by a variety of common porphyrins and characterize structure-activity relationships that may be useful for future drug design of HCV and related Flaviviruses.

Methods

Using fluorometric assays, common metalloprotoporphyrins (MPP) all inhibited NS3-4A protease with IC₅₀ values in low micromolar ranges [CoPP (1.4 µM) < ZnPP = MnPP = SnPP < CuPP < FePP (6.5 µM) = protoporphyrin].

Results

Lineweaver-Burk plots confirmed that MPP: NS3 inhibition was basically competitive. All tested MPPs inhibited HCV genotype 1A, 1B, 2A and 3A recombinant proteases with the same fidelity suggesting wide antagonistic capabilities. However, when the MPPs were tested in cellular incubations with HCV replicons only Zn, Fe and free-base protoporphyrin showed comparable EC₅₀ and IC₅₀ values suggesting that there may be critical differences in MPP uptake and intracellular availability. Meso, deutero, and isohematoporphyrin derivatives, with or without metal substitution, all showed less anti-protease and antiviral activities as compared to protoporphyrins, suggesting that the planar, vinyl side chains are important for protease active site binding. MPPs were also active against three common protease mutants (T54A, A156T, and V36M) with equivalent or better IC₅₀ values as compared to wild type enzyme.

Conclusion

These findings document the versatility of MPPs as antiviral agents with an expanded sensitivity for HCV genotypes and resistance to some common viral mutations. The results also suggest that further study of MPP structure and function will be useful for the development of new antiviral agents.

Regulation of the Transferrin Receptor Recycling in Hepatitis C Virus-Replicating Cells

After binding of its ligand transferrin, the transferrin receptor (TfR) is internalized via early endosomes. Ligand and receptor can be recycled. α-Taxilin was identified as an essential factor for TfR recycling. Apart from its role for iron uptake, TfR is a coreceptor for hepatitis C virus (HCV) infection. In HCV-replicating cells, the amount of a-taxilin is decreased. This study aims to investigate the effect of decreased α-taxilin levels in HCV-replicating cells on recycling of TfR, its amount on the cell surface, on iron uptake, and the impact of a disturbed TfR recycling on HCV superinfection exclusion. TfR amount and localization were determined by CLSM and surface biotinylation. α-taxilin expression was modulated by CRISPR-Cas9 knockout, siRNA, and stable or transient overexpression. For analysis of HCV superinfection fluorophor-tagged reporter viruses were used. The amount of α-taxilin is decreased in HCV-infected cells. In accordance to this, the protein amount of TfR is significant lower in HCV-positve cells as compared to the control, while TfR expression is not affected. Due to the impaired recycling, internalized TfR is degraded by the endosomal/lysosomal system. The significant lower number of TfR molecules on the cell surface is reflected by reduced transferrin binding/internalization and strong reduction of intracellular iron level. Overexpression of α-taxilin in HCV-replicating cells rescues TfR recycling, augments TfR on the cell surface, and restores transferrin binding. The block of superinfection in HCV-replicating cells could be overcome by overexpression of α-taxilin. Taken together, the diminished level of α-taxilin in HCV-replicating cells prevents recycling of TfR leading to decreased transferrin binding and iron uptake. Disappearance of TfR from the cell surface could be a factor contributing to the exclusion of superinfection by HCV.

The Use of Antimalarial Drugs against Viral Infection

In recent decades, drugs used to treat malaria infection have been shown to be beneficial for many other diseases, including viral infections. In particular, they have received special attention due to the lack of effective antiviral drugs against new emerging viruses (i.e., HIV, dengue virus, chikungunya virus, Ebola virus, etc.) or against classic infections due to drug-resistant viral strains (i.e., human cytomegalovirus). Here, we reviewed the in vitro/in vivo and clinical studies conducted to evaluate the antiviral activities of four classes of antimalarial drugs: Artemisinin derivatives, aryl-aminoalcohols, aminoquinolines, and antimicrobial drugs.

Genome-wide Integrative Analysis of Zika-Virus-Infected Neuronal Stem Cells Reveals Roles for MicroRNAs in Cell Cycle and Stemness

Zika virus (ZIKV) infection is implicated in severe fetal developmental disorders, including microcephaly. MicroRNAs (miRNAs) post-transcriptionally regulate numerous processes associated with viral infection and neurodegeneration, but their contribution to ZIKV pathogenesis is unclear. We analyzed the mRNA and miRNA transcriptomes of human neuronal stem cells (hNSCs) during infection with ZIKV MR766 and Paraiba strains. Integration of the miRNA and mRNA expression data into regulatory interaction networks showed that ZIKV infection resulted in miRNA-mediated repression of genes regulating the cell cycle, stem cell maintenance, and neurogenesis. Bioinformatics analysis of Argonaute-bound RNAs in ZIKV-infected hNSCs identified a number of miRNAs with predicted involvement in microcephaly, including miR-124-3p, which dysregulates NSC maintenance through repression of the transferrin receptor (TFRC). Consistent with this, ZIKV infection upregulated miR-124-3p and downregulated TFRC mRNA in ZIKV-infected hNSCs and mouse brain tissue. These data provide insights into the roles of miRNAs in ZIKV pathogenesis, particularly the microcephaly phenotype.

The Role of Micronutrients in the Infection and Subsequent Response to Hepatitis C Virus

Micronutrient deficiencies develop for a variety of reasons, whether geographic, socioeconomic, nutritional, or as a result of disease pathologies such as chronic viral infection. As micronutrients are essential for a strong immune response, deficiencies can significantly dampen both the innate and the adaptive arms of antiviral immunity. The innate immune response in particular is crucial to protect against hepatitis C virus (HCV), a hepatotropic virus that maintains chronic infection in up to 80% of individuals if left untreated. While many micronutrients are required for HCV replication, an overlapping group of micronutrients are also necessary to enact a potent immune response. As the liver is responsible for the storage and metabolism of many micronutrients, HCV persistence can influence the micronutrients' steady state to benefit viral persistence both directly and by weakening the antiviral response. This review will focus on common micronutrients such as zinc, iron, copper, selenium, vitamin A, vitamin B12, vitamin D and vitamin E. We will explore their role in the pathogenesis of HCV infection and in the response to antiviral therapy. While chronic hepatitis C virus infection drives deficiencies in micronutrients such as zinc, selenium, vitamin A and B12, it also stimulates copper and iron excess; these micronutrients influence antioxidant, inflammatory and immune responses to HCV.

Review article: iron disturbances in chronic liver diseases other than haemochromatosis - pathogenic, prognostic, and therapeutic implications

BACKGROUND

Disturbances in iron regulation have been described in diverse chronic liver diseases other than hereditary haemochromatosis, and iron toxicity may worsen liver injury and outcome.

AIMS

To describe manifestations and consequences of iron dysregulation in chronic liver diseases apart from hereditary haemochromatosis and to encourage investigations that clarify pathogenic mechanisms, define risk thresholds for iron toxicity, and direct management METHODS: English abstracts were identified in PubMed by multiple search terms. Full length articles were selected for review, and secondary and tertiary bibliographies were developed.

RESULTS

Hyperferritinemia is present in 4%-65% of patients with non-alcoholic fatty liver disease, autoimmune hepatitis, chronic viral hepatitis, or alcoholic liver disease, and hepatic iron content is increased in 11%-52%. Heterozygosity for the C282Y mutation is present in 17%-48%, but this has not uniformly distinguished patients with adverse outcomes. An inappropriately low serum hepcidin level has characterised most chronic liver diseases with the exception of non-alcoholic fatty liver disease, and the finding has been associated mainly with suppression of transcriptional activity of the hepcidin gene. Iron overload has been associated with oxidative stress, advanced fibrosis and decreased survival, and promising therapies beyond phlebotomy and oral iron chelation have included hepcidin agonists.

CONCLUSIONS

Iron dysregulation is common in chronic liver diseases other than hereditary haemochromatosis, and has been associated with liver toxicity and poor prognosis. Further evaluation of iron overload as a co-morbid factor should identify the key pathogenic disturbances, establish the risk threshold for iron toxicity, and promote molecular interventions.

Antiviral activity of bone morphogenetic proteins and activins

Understanding the control of viral infections is of broad importance. Chronic hepatitis C virus (HCV) infection causes decreased expression of the iron hormone hepcidin, which is regulated by hepatic bone morphogenetic protein (BMP)/SMAD signalling. We found that HCV infection and the BMP/SMAD pathway are mutually antagonistic. HCV blunted induction of hepcidin expression by BMP6, probably via tumour necrosis factor (TNF)-mediated downregulation of the BMP co-receptor haemojuvelin. In HCV-infected patients, disruption of the BMP6/hepcidin axis and genetic variation associated with the BMP/SMAD pathway predicted the outcome of infection, suggesting that BMP/SMAD activity influences antiviral immunity. Correspondingly, BMP6 regulated a gene repertoire reminiscent of type I interferon (IFN) signalling, including upregulating interferon regulatory factors (IRFs) and downregulating an inhibitor of IFN signalling, USP18. Moreover, in BMP-stimulated cells, SMAD1 occupied loci across the genome, similar to those bound by IRF1 in IFN-stimulated cells. Functionally, BMP6 enhanced the transcriptional and antiviral response to IFN, but BMP6 and related activin proteins also potently blocked HCV replication independently of IFN. Furthermore, BMP6 and activin A suppressed growth of HBV in cell culture, and activin A inhibited Zika virus replication alone and in combination with IFN. The data establish an unappreciated important role for BMPs and activins in cellular antiviral immunity, which acts independently of, and modulates, IFN.

Host heme oxygenase-1: Friend or foe in tackling pathogens?

Infectious diseases are a major challenge in management of human health worldwide. Recent literature suggests that host immune system could be modulated to ameliorate the pathogenesis of infectious disease. Heme oxygenase (HMOX1) is a key regulator of cellular signaling and it could be modulated using pharmacological reagents. HMOX1 is a cytoprotective enzyme that degrades heme to generate carbon monoxide (CO), biliverdin, and molecular iron. CO and biliverdin (or bilirubin derived from it) can restrict the growth of a few pathogens. Both of these also induce antioxidant pathways and anti-inflammatory pathways. On the other hand, molecular iron can induce proinflammatory pathway besides making the cellular environment oxidative in nature. Since microbial infections often induce oxidative stress in host cells/tissues, role of HMOX1 has been analyzed in the pathogenesis of number of infections. In this review, we have described the role of HMOX1 in pathogenesis of bacterial infections caused by Mycobacterium species, Salmonella and in microbial sepsis. We have also provided a succinct overview of the role of HMOX1 in parasitic infections such as malaria and leishmaniasis. In the end, we have also elaborated the role of HMOX1 in viral infections such as AIDS, hepatitis, dengue, and influenza. © 2018 IUBMB Life, 70(9):869-880, 2018.

More insights into the pharmacological effects of artemisinin

Artemisinin is one of the most widely prescribed drugs against malaria and has recently received increased attention because of its other potential biological effects. The aim of this review is to summarize recent discoveries of the pharmaceutical effects of artemisinin in basic science along with its mechanistic action, as well as the intriguing results of recent clinical studies, with a focus on its antitumor activity. Scientific evidence indicates that artemisinin exerts its biological activity by generating reactive oxygen species that damage the DNA, mitochondrial depolarization, and cell death. In the present article review, scientific evidence suggests that artemisinin is a potential therapeutic agent for various diseases. Thus, this review is expected to encourage interested scientists to conduct further preclinical and clinical studies to evaluate these biological activities.

Carbon monoxide and biliverdin suppress bovine viral diarrhoea virus replication

Bovine viral diarrhoea virus (BVDV) causes significant economic losses to the cattle industry worldwide. Previously, we demonstrated that heme oxygenase-1 (HO-1) can inhibit BVDV replication via an unknown molecular mechanism. To elucidate the mechanism involved, we assess whether the HO-1 downstream metabolites carbon monoxide (CO), biliverdin (BV) and iron affect BVDV replication. We treated Madin-Darby bovine kidney (MDBK) cells with an exogenous CO donor, CORM-2. We found that CORM-2 but not its inactive form (iCORM-2) inhibited BVDV replication in a dose-dependent and time duration-dependent manner, suggesting a CO-specific mediation of the CORM-2 antiviral effect. Direct incubation of BVDV with high-dose CORM-2 reduced virus titres, suggesting that CORM-2 attenuates BVDV growth by both physically inactivating virus particles in the extracellular environment and affecting intracellular BVDV replication, but mainly via an intracellular mechanism. Exogenous BV treatment, both post-infection and co-incubation with BVDV, inhibited BVDV replication in a dose-dependent manner, indicating that BV has potent antiviral activity against BVDV. Direct incubation of BVDV with BV had no significant effect on virus titres, indicating that BV is not virucidal and attenuates BVDV growth by affecting intracellular BVDV replication. Furthermore, BV was found to affect BVDV penetration but not attachment. However, increased iron via addition of FeCl3 did not interfere with BVDV replication. Collectively, the results of the present study demonstrate that the HO-1 metabolites BV and CO, but not iron, inhibit BVDV replication. These findings not only provide new insights into the molecular mechanism of HO-1 inhibition of BVDV replication but also suggest potential new control measures for future BVDV infection.

Pharmacological Induction of Heme Oxygenase-1 Impairs Nuclear Accumulation of Herpes Simplex Virus Capsids upon Infection

Heme oxygenase-1 (HO-1) is an inducible enzyme that is expressed in response to physical and chemical stresses, such as ultraviolet radiation, hyperthermia, hypoxia, reactive oxygen species (ROS), as well as cytokines, among others. Its activity can be positively modulated by cobalt protoporphyrin (CoPP) and negatively by tin protoporphirin (SnPP). Once induced, HO-1 degrades iron-containing heme into ferrous iron (Fe²⁺), carbon monoxide (CO) and biliverdin. Importantly, numerous products of HO-1 are cytoprotective with anti-apoptotic, anti-oxidant, anti-inflammatory, and anti-cancer effects. The products of HO-1 also display antiviral properties against several viruses, such as the human immunodeficiency virus (HIV), influenza, hepatitis B, hepatitis C, and Ebola virus. Here, we sought to assess the effect of modulating HO-1 activity over herpes simplex virus type 2 (HSV-2) infection in epithelial cells and neurons. There are no vaccines against HSV-2 and treatment options are scarce in the immunosuppressed, in which drug-resistant variants emerge. By using HSV strains that encode structural and non-structural forms of the green fluorescent protein (GFP), we found that pharmacological induction of HO-1 activity with CoPP significantly decreases virus plaque formation and the expression of virus-encoded genes in epithelial cells as determined by flow cytometry and western blot assays. CoPP treatment did not affect virus binding to the cell surface or entry into the cytoplasm, but rather downstream events in the virus infection cycle. Furthermore, we observed that treating cells with a CO-releasing molecule (CORM-2) recapitulated some of the anti-HSV effects elicited by CoPP. Taken together, these findings indicate that HO-1 activity interferes with the replication cycle of HSV and that its antiviral effects can be recapitulated by CO.

Relationship between Hepatitis C Virus Infection and Iron Overload

Objective:

The aim of this study was to summarize the interactions between hepatitis C virus (HCV) infection and iron overload, and to understand the mechanisms of iron overload in chronic hepatitis C (CHC) and the role iron plays in HCV life cycle.

Data Sources:

This review was based on data in articles published in the PubMed databases up to January 28, 2017, with the keywords “hepatitis C virus”, “iron overload”, “iron metabolism”, “hepcidin”, “translation”, and “replication”.

Study Selection:

Articles related to iron metabolism, iron overload in patients with CHC, or the effects of iron on HCV life cycle were selected for the review.

Results:

Iron overload is common in patients with CHC. The mechanisms involve decreased hepcidin levels caused by HCV through signal transducer and activator of transcription 3, mitogen-activated protein kinase, or bone morphogenetic protein/SMAD signaling pathways, and the altered expression of other iron-metabolism-related genes. Some studies found that iron increases HCV replication, while other studies found the opposite result. Most of the studies suggest the positive role of iron on HCV translation, the mechanisms of which involve increased expression levels of factors associated with HCV internal ribosome entry site-dependent translation, such as eukaryotic initiation factor 3 and La protein.

Conclusion:

The growing literature demonstrates that CHC leads to iron overload, and iron affects the HCV life cycle in turn. Further research should be conducted to clarify the mechanism involved in the complicated interaction between iron and HCV.

Impact of iatrogenic iron overload on the course of hepatitis C in the dialysis population: A plea for caution

About 2.5% of the world population, corresponding to about 177 million individuals, are infected by hepatitis C virus (HCV), a small, single-stranded RNA virus. The prevalence of HCV infection among dialysis patients in Japan, Europe, and North America during the 2012 to 2015 period was found to be 8.7% in the DOPPS study. Nosocomial HCV spread in hemodialysis facilities still occurs. Increased hepatic tissue iron has been shown to play a deleterious role in the course of hepatitis C, favor development of fibrosis and cirrhosis and possibly increase the risk of liver cancer in the general population. Regular loss of blood in the hemodialysis circuit, in routine blood sampling for laboratory tests (for uremia monitoring), and in gut due to uremic enteropathy, invariably results in iron deficiency for which patients are commonly treated with intravenous (IV) iron preparations. Data on the effects of IV iron in hemodialysis patients with hepatitis C are limited (2 studies) and strongly suggest that parenteral iron may contribute to hepatocellular injury. Iatrogenic iron overload is extremely prevalent among hemodialysis population worldwide. Iron overload and toxicity has emerged as one of the most controversial topic in the management of anemia in dialysis patients. Given the known impact of iron in promoting growth and virulence of HCV and the associated liver disease, it is necessary to use iron therapy cautiously and closely monitor plasma markers of iron metabolism and liver iron stores non-invasively by means of MRI to avoid iron overload in this vulnerable population.

Modulation of Antiviral Immunity by Heme Oxygenase-1

Heme oxygenase-1 (HO-1) is a stress-inducible, anti-inflammatory, and cytoprotective enzyme expressed in most cell types in the organism. Under several stress stimuli, HO-1 expression and activity is up-regulated to catalyze the rate-limiting enzymatic step of heme degradation into carbon monoxide, free iron, and biliverdin. Besides its effects on cell metabolism, HO-1 is also capable of modulating host innate and adaptive immune responses in response to sepsis, transplantation, and autoimmunity, and preventing oxidative damage associated with inflammation. In addition, recent studies have reported that HO-1 can exert a significant antiviral activity against a wide variety of viruses, including HIV, hepatitis C virus, hepatitis B virus, enterovirus 71, influenza virus, respiratory syncytial virus, dengue virus, and Ebola virus, among others. Herein, we address the current understanding of the functional significance of HO-1 against a variety of viruses and its potential as a therapeutic strategy to prevent and control viral infections. Furthermore, we review the most important features of the immunoregulatory functions for this enzyme.

Molecular pathogenesis and clinical consequences of iron overload in liver cirrhosis

BACKGROUND

The liver, as the main iron storage compartment and the place of hepcidin synthesis, is the central organ involved in maintaining iron homeostasis in the body. Excessive accumulation of iron is an important risk factor in liver disease progression to cirrhosis and hepatocellular carcinoma. Here, we review the literature on the molecular pathogenesis of iron overload and its clinical consequences in chronic liver diseases.

DATA SOURCES

PubMed was searched for English-language articles on molecular genesis of primary and secondary iron overload, as well as on their association with liver disease progression. We have also included literature on adjuvant therapeutic interventions aiming to alleviate detrimental effects of excessive body iron load in liver cirrhosis.

RESULTS

Excess of free, unbound iron induces oxidative stress, increases cell sensitivity to other detrimental factors, and can directly affect cellular signaling pathways, resulting in accelerated liver disease progression. Diagnosis of liver cirrhosis is, in turn, often associated with the identification of a pathological accumulation of iron, even in the absence of genetic background of hereditary hemochromatosis. Iron depletion and adjuvant therapy with antioxidants are shown to cause significant improvement of liver functions in patients with iron overload. Phlebotomy can have beneficial effects on liver histology in patients with excessive iron accumulation combined with compensated liver cirrhosis of different etiology.

CONCLUSION

Excessive accumulation of body iron in liver cirrhosis is an important predictor of liver failure and available data suggest that it can be considered as target for adjuvant therapy in this condition.

Alterations in the iron homeostasis network: A driving force for macrophage-mediated hepatitis C virus persistency

Mechanisms that favor Hepatitis C virus (HCV) persistence over clearance are unclear, but involve defective innate immunity. Chronic infection is characterized by hepatic iron overload, hyperferraemia and hyperferittinaemia. Hepcidin modulates iron egress via ferroportin and its storage in ferritin. Chronic HCV patients have decreased hepcidin, while HCV replication is modified by HAMP silencing. We aimed to investigate interactions between HCV and hepcidin, during acute and chronic disease, and putative alterations in cellular iron homeostasis that enhance HCV propagation and promote viral persistence. Thus, we used HCV JFH-1-infected co-cultures of Huh7.5 hepatoma and THP-1 macrophage cells, HCV patients' sera and Huh7 hepcidin-expressing cells transfected with HCV replicons. Hepcidin levels were elevated in acutely infected patients, but correlated with viral load in chronic patients. HAMP expression was up-regulated early in HCV infection in vitro, with corresponding changes in ferritin and FPN. Hepcidin overexpression enhanced both viral translation and replication. In HCV-infected co-cultures, we observed increased hepcidin, reduced hepatoma ferritin and a concurrent rise in macrophaghic ferritin over time. Altered iron levels complemented amplified replication in hepatoma cells and one replication round in macrophages. Iron-loading of macrophages led to enhancement of hepatic HCV replication through reversed ferritin "flow." Viral transmissibility from infected macrophages to naïve hepatoma cells was induced by iron. We propose that HCV control over iron occurs both by intracellular iron sequestration, through hepcidin, and intercellular iron mobilisation via ferritin, as means toward enhanced replication. Persistence could be achieved through HCV-induced changes in macrophagic iron that enhances viral replication in these cells.

Liver hepcidin expression is down-regulated in patients with chronic hepatitis B or hepatitis C

AIM: To explore the mechanism underlying the interaction between inflammatory reaction and iron metabolism regulation in patients with chronic hepatitis B (CHB) or chronic hepatitis C (CHC).

METHODS: Forty-five patients with CHB, 45 patient with CHC, and 90 healthy volunteers were included. Serum levels of hepcidin, interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α) were measured by ELISA. Serum levels of alanine transaminase (ALT), aspartate aminotransferases (AST), and iron (Fe) were also measured. Liver and duodenum specimens were taken from 15 CHC patients, 12 CHB patients, and 12 normal controls to detect the expression of hepcidin and ferroportin by immunohistochemistry and liver iron by iron blue staining.

RESULTS: Serum and hepatic hepcidin levels in the CHC and CHB groups were significantly lower than those of the control group (P < 0.05). Compared with the control group, ferroportin expression in the duodenum was significantly increased (P < 0.05) and the positive rate of liver iron blue staining was significantly higher in the CHC and CHB groups (P < 0.05), especially in the CHC group. There was a negative correlation between ferroportin expression in the duodenum and hepatic (r = -0.638, P < 0.05; r = -0.538, P < 0.05) and serum levels of hepcidin (r = -0.407, P < 0.05; r = -0.519, P < 0.05) in CHC and CHB patients. There was a positive correlation between ferroportin expression in the duodenum and serum iron (r = 0.611, P < 0.05; r = 0.637, P < 0.05) in CHC and CHB patients, between serum hepcidin and IL-6 and TNF-α in CHB patients (r = -0.510, P < 0.05; r = -0.450, P < 0.05), and between serum hepcidin and IL-6 in CHB patients (r = -0.620, P < 0.05). There was a positive correlation between serum hepcidin and TNF-α in CHB patients (r = 0.243, P < 0.05).

CONCLUSION: In CHC and CHB patients, lowered hepcidin level and increased ferroportin expression may cause an increase in serum and liver iron accumulation. Hepatic iron accumulation is more obvious in CHC patients.

Induction of heme oxygenase-1 contributes to survival of Mycobacterium abscessus in human macrophages-like THP-1 cells

Mycobacterium abscessus (M.abs) is a rapidly growing mycobacterial species that infects macrophages, and is an important pathogen in patients with cystic fibrosis. We studied the early stages of M.abs infection of macrophages, with emphasis on the role of heme-oxygenase-1 (HO-1) in this infection. THP-1 cells were activated using TPA into macrophage-like cells and infected with M.abs for different time points. M.abs infection robustly induced HO-1 expression in the THP-1 cells. Production of HO-1 was p38 MAPK-dependent, as p38 inhibitors suppressed HO-1 induction. Pretreatment with HO-1 inhibitors tin-protoporphyrin (SnPP) significantly inhibited M.abs growth inside macrophages. Furthermore, inhibiting HO-1 using HO-1 siRNA or the HO-1 upstream signaling molecule; Nrf2 using Nrf2 siRNA resulted in similar inhibition of M.abs. In contrast, inducing HO-1 did not increase M.abs intracellular growth above control. Products of HO-1 metabolism of heme are bilirubin, biliverdin, carbon monoxide (CO) and iron. The addition of either bilirubin or biliverdin, but not CO, completely restored the SnPP inhibitory effect and partially that with HO-1 siRNA. To understand the mechanisms, we used Syto-62 labeled M.abs to infect macrophages. Interestingly, HO-1 inhibition promoted M.abs-containing phagosome fusion with lysosomes, which should enhance M.abs killing. M.abs infection enhanced THP-1 ROS production as demonstrated by increased DHE, DCF fluorescence, and EPR signal. HO-1 inhibition further increased ROS production in infected macrophages. Our results indicate that HO-1 induction is important for M.abs growth during the early stages of infection, and that the HO-1 products bilirubin and biliverdin, perhaps through modulation of intracellular ROS levels, may be involved.

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HO-1 induction is important for Mycobacterium abscessus growth inside infected macrophages during the early stages of infection.

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Reducing HO-1 products may enhance the ability of the macrophage to control Mycobacterium abscessus infection.

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HO-1 inhibition increases phagosome–lysosome fusion and thus Mycobacterium abscessus killing.

Spike-in SILAC proteomic approach reveals the vitronectin as an early molecular signature of liver fibrosis in hepatitis C infections with hepatic iron overload

Hepatitis C virus (HCV)-induced iron overload has been shown to promote liver fibrosis, steatosis, and hepatocellular carcinoma. The zonal-restricted histological distribution of pathological iron deposits has hampered the attempt to perform large-scale in vivo molecular investigations on the comorbidity between iron and HCV. Diagnostic and prognostic markers are not yet available to assess iron overload-induced liver fibrogenesis and progression in HCV infections. Here, by means of Spike-in SILAC proteomic approach, we first unveiled a specific membrane protein expression signature of HCV cell cultures in the presence of iron overload. Computational analysis of proteomic dataset highlighted the hepatocytic vitronectin expression as the most promising specific biomarker for iron-associated fibrogenesis in HCV infections. Next, the robustness of our in vitro findings was challenged in human liver biopsies by immunohistochemistry and yielded two major results: (i) hepatocytic vitronectin expression is associated to liver fibrogenesis in HCV-infected patients with iron overload; (ii) hepatic vitronectin expression was found to discriminate also the transition between mild to moderate fibrosis in HCV-infected patients without iron overload.

Association of hepcidin mRNA expression with hepatocyte iron accumulation and effects of antiviral therapy in chronic hepatitis C infection

BACKGROUND

Iron overload is frequently observed in patients with chronic hepatitis C (CHC) and is associated with the increased risk of liver fibrosis and carcinogenesis. Hepcidin is a regulator of iron homeostasis and a component of innate immunity. Based on experimental studies, iron overload might be a result of low hepcidin synthesis in CHC.

OBJECTIVES

The aim of this case-control study was to assess hepcidin mRNA expression in liver tissue of patients with CHC in terms of iron metabolism parameters, hemochromatosis (HFE) gene mutations, disease activity, and efficacy of antiviral treatment with pegylated interferon and ribavirin.

PATIENTS AND METHODS

A total of 31 patients with CHC, who were qualified for antiviral therapy, were compared with 19 patients with chronic hepatitis B (CHB). In both groups, liver function tests and serum iron parameters were assayed and hepcidin mRNA expression was measured in liver specimens using real time PCR with normalization to reference genes mRNA of stable expression.

RESULTS

Patients with CHC had lower hepcidin mRNA expression and more frequently iron deposits in hepatocytes than subjects with CHB did. In CHC group, hepcidin mRNA expression was positively correlated with alanine aminotransferase activity and serum iron concentration. Low expression of hepcidin had no correlation with tissue iron overload in those with CHC. In univariate analysis, HCV viral load and efficacy of antiviral treatment were not significantly associated with hepcidin mRNA expression.

CONCLUSIONS

Further studies on the role of hepcidin in pathogenesis of CHC are needed to assess the potency of its use in antiviral treatment.

Duodenal ferroportin is up-regulated in patients with chronic hepatitis C

Hepatitis C virus (HCV) infection is a leading cause of liver-related mortality. Chronic hepatitis C (CHC) is frequently associated with disturbances in iron homeostasis, with serum iron and hepatic iron stores being elevated. Accumulating evidence indicates that chronic HCV infection suppresses expression of hepatic hepcidin, a key mediator of iron homeostasis, leading to iron overload conditions. Since hepcidin mediates degradation of ferroportin, a basolateral transporter involved in the release of iron from cells, diminished hepcidin expression probably leads to up-regulation of ferroportin-1 (Fpn1) in patients with CHC. In this study, we determined the protein levels of duodenal Fpn1, and found that its expression was significantly up-regulated in patients with CHC. The expression of duodenal Fpn1 is negatively correlated with mRNA levels of hepcidin, and positively correlated with serum iron parameters. Although iron is a critical factor for growth of a variety of pathogenic bacteria, our results suggest that iron overload in blood does not increase the infection rate of bacteria in patients with CHC.

Iron homeostasis and its regulators over the course of chronic hepatitis C

ABSTRACT: 

Chronic infection with HCV has been diagnosed in approximately 170 million people worldwide. It is an important cause of chronic, progressive liver fibrosis. Late consequences of chronic HCV infection, including liver cirrhosis and hepatocellular carcinoma, have become the major indications for liver transplantation in developed countries. Particular attention is being paid to iron accumulation in chronic hepatitis C and its relation to the current antiviral therapy's efficacy and safety, risk of exacerbation of oxidative stress, development of metabolic disorders and hepatocarcinogenesis. HCV infection disrupts the synthesis of hepcidin, which regulates extracellular iron content. This article discusses the impact of iron on HCV multiplication and the involvement of impaired iron homeostasis in chronic hepatitis C in terms of the pathogenesis of insulin resistance, fatty liver and hepatocarcinogenesis.

Coinfection with HIV-1 alleviates iron accumulation in patients with chronic hepatitis C virus infection

Most chronically-infected hepatitis C virus (HCV) patients have increased levels of iron in the liver. Iron overload reduces sustained responses to antiviral therapy, leading to more rapid progression to liver cirrhosis and the development of hepatocellular carcinoma. However, it is still unclear how HIV-1 infection affects iron status in patients chronically infected with HCV. The present study recruited 227 patients from a village in central China. These patients were either monoinfected with HCV (n = 129) or coinfected with HCV/HIV-1 (n = 98). Healthy controls (n = 84) were also recruited from the same village. Indicators of iron status, such as serum levels of iron, ferritin, and transferrin, total iron-binding capacity (TIBC), transferrin saturation (Tfs), and hepcidin, were analyzed and compared across the three groups. The results showed that serum levels of iron (p = 0.001) and ferritin (p = 0.009) and the Tfs (p = 0.002) were significantly higher in HCV-monoinfected patients than in the healthy controls; however, there were no differences in iron levels and Tfs between HCV/HIV-1 coinfected patients and healthy controls. Additionally, although serum hepcidin levels in HCV-monoinfected and HCV/HIV-1-coinfected patients were lower (p<0.001) than those in health controls, the levels in coinfected patients were higher (p = 0.025) than those in HCV-monoinfected patients. Serum iron and ferritin levels in HCV-monoinfected patients were positively correlated with serum ALT/AST. Serum transferrin levels were negatively correlated with ALT/AST levels. The levels of iron in the serum of coinfected patients with a CD4+T-cell count <500/µl were lower than those in patients with a CD4+T-cell count ≥500/µl, whereas serum hepcidin levels showed the opposite trend. Taken together, these results suggest that coinfection with HIV-1 alleviates iron accumulation caused by chronic HCV infection. Our study indicated that determining the status of serum iron and other iron-associated parameters will be helpful to understand the complexity of alternations in iron distribution in HCV/HIV-1-coinfected patients.

Hepcidin and the iron enigma in HCV infection

An estimated 30-40% of patients with chronic hepatitis C have elevated serum iron, transferrin saturation, and ferritin levels. Clinical data suggest that iron is a co-morbidity factor for disease progression following HCV infection. Iron is essential for a number of fundamental metabolic processes in cells and organisms. Mammalian iron homeostasis is tightly regulated and this is maintained through the coordinated action of sensory and regulatory networks that modulate the expression of iron-related proteins at the transcriptional and/or posttranscriptional levels. Disturbances of iron homeostasis have been implicated in infectious disease pathogenesis. Viruses, similarly to other pathogens, can escape recognition by the immune system, but they need iron from their host to grow and spread. Hepcidin is a 25-aa peptide, present in human serum and urine and represents the key peptide hormone, which modulates iron homeostasis in the body. It is synthesized predominantly by hepatocytes and its mature form is released in circulation. In this review, we discuss recent advances in the exciting crosstalk of molecular mechanisms and cell signaling pathways by which iron and hepcidin production influences HCV-induced liver disease.

Inhibition of replication of porcine reproductive and respiratory syndrome virus by hemin is highly dependent on heme oxygenase-1, but independent of iron in MARC-145 cells

Current vaccines against porcine reproductive and respiratory syndrome virus (PRRSV) have failed to provide sustainable disease control, and development of new antiviral strategies is of great importance. The present study investigated the mechanism of the antiviral effect of hemin during PRRSV infection in MARC-145 cells. Hemin, a commercial preparation of heme, is used as an iron donor or heme oxygenase 1 (HO-1) inducer, and has been shown to provide antiviral activity in many studies. In the current study, the anti-PRRSV activity of hemin was identified through suppressing PRRSV propagation. The 50% inhibitory concentration (IC50) of hemin antiviral activity was estimated to be 32μM, and the 50% cytotoxic concentration (CC50) of hemin was found to be higher than 125μM. Further study showed that the antiviral activity of hemin is independent of iron. In addition, after treatment with Protoporphyrin IX zinc (II) (ZnPP) or Sn (IV) Protoporphyrin IX dichloride (SnPP), inhibitors of HO-1, the inhibition of viral replication by hemin was partially reversed. Additionally, it was confirmed that hemin and N-acetyl cysteine were able to significantly reduce reactive oxygen species (ROS) in MARC-145 cells infected with virus. N-acetyl-L-cysteine (NAC), however, did not produce a reduction in viral load or promote expression of HO-1. Taken together, these data indicate that the effect of hemin on the inhibition of PRRSV propagation via HO-1 induction, as well as the antiviral mechanism of HO-1, is not dependent on decreased levels of ROS. In conclusion, these data demonstrate that hemin had antiviral activity against PRRSV and may serve as a useful antiviral agent inhibiting PRRSV replication.

Specific sequence of a Beta turn in human la protein may contribute to species specificity of hepatitis C virus

Human La protein is known to be an essential host factor for translation and replication of hepatitis C virus (HCV) RNA. Previously, we have demonstrated that residues responsible for interaction of human La protein with the HCV internal ribosomal entry site (IRES) around the initiator AUG within stem-loop IV form a β-turn in the RNA recognition motif (RRM) structure. In this study, sequence alignment and mutagenesis suggest that the HCV RNA-interacting β-turn is conserved only in humans and chimpanzees, the species primarily known to be infected by HCV. A 7-mer peptide corresponding to the HCV RNA-interacting region of human La inhibits HCV translation, whereas another peptide corresponding to the mouse La sequence was unable to do so. Furthermore, IRES-mediated translation was found to be significantly high in the presence of recombinant human La protein in vitro in rabbit reticulocyte lysate. We observed enhanced replication with HCV subgenomic and full-length replicons upon overexpression of either human La protein or a chimeric mouse La protein harboring a human La β-turn sequence in mouse cells. Taken together, our results raise the possibility of creating an immunocompetent HCV mouse model using human-specific cell entry factors and a humanized form of La protein.

IMPORTANCE

Hepatitis C virus is known to infect only humans and chimpanzees under natural conditions. This has prevented the development of a small-animal model, which is important for development of new antiviral drugs. Although a number of human-specific proteins are responsible for this species selectivity and some of these proteins--mostly entry factors--have been identified, full multiplication of the virus in mouse cells is still not possible. In this study, we show that a turn in the human La protein that is responsible for the interaction with the viral RNA is highly specific for the human sequence. Replacement of the corresponding mouse sequence with the human sequence allows the mouse La to behave like its human counterpart and support viral growth in the mouse cell efficiently. This observation, in combination with previously identified cell entry factors, should open up the possibility of creating a mouse model of hepatitis C.

Hepatitis C virus infection causes iron deficiency in Huh7.5.1 cells

Patients with chronic hepatitis C virus (HCV) infection frequently develop systemic iron overload, which exacerbates morbidity. Nevertheless, iron inhibits HCV replication in cell culture models and thereby exerts antiviral activity. We hypothesized that the cellular iron status is crucial for the establishment of HCV infection. We show that HCV infection of permissive Huh7.5.1 hepatoma cells promotes an iron deficient phenotype. Thus, HCV leads to increased iron regulatory protein (IRP) activity, accumulation of IRP2 and suppression of transferrin receptor 1 (TfR1) and divalent metal transporter 1 (DMT1) in the host. These data suggest that HCV regulates cellular iron levels to bypass iron-mediated inhibition in viral replication.

Artemisinin analogues as potent inhibitors of in vitro hepatitis C virus replication

We reported previously that Artemisinin (ART), a widely used anti-malarial drug, is an inhibitor of in vitro HCV subgenomic replicon replication. We here demonstrate that ART exerts its antiviral activity also in hepatoma cells infected with full length infectious HCV JFH-1. We identified a number of ART analogues that are up to 10-fold more potent and selective as in vitro inhibitors of HCV replication than ART. The iron donor Hemin only marginally potentiates the anti-HCV activity of ART in HCV-infected cultures. Carbon-centered radicals have been shown to be critical for the anti-malarial activity of ART. We demonstrate that carbon-centered radicals-trapping (the so-called TEMPO) compounds only marginally affect the anti-HCV activity of ART. This provides evidence that carbon-centered radicals are not the main effectors of the anti-HCV activity of the Artemisinin. ART and analogues may possibly exert their anti-HCV activity by the induction of reactive oxygen species (ROS). The combined anti-HCV activity of ART or its analogues with L-N-Acetylcysteine (L-NAC) [a molecule that inhibits ROS generation] was studied. L-NAC significantly reduced the in vitro anti-HCV activity of ART and derivatives. Taken together, the in vitro anti-HCV activity of ART and analogues can, at least in part, be explained by the induction of ROS; carbon-centered radicals may not be important in the anti-HCV effect of these molecules.

Restoration of type I interferon expression by heme and related tetrapyrroles through inhibition of NS3/4A protease

BACKGROUND

Tetrapyrrole substrates and products of heme oxygenase are potent inhibitors of hepatitis C virus (HCV) replication. It is not clear whether this occurs through primary induction of type I interferon (IFN), inhibition of viral NS3/4A protease, or a combination of these mechanisms. We studied the antiviral actions of tetrapyrroles and their potential influence on type I IFN induction.

METHODS

The effects of tetrapyrrole on NS3/4A protease activity and type I IFN induction were assessed in HCV-permissive cells, replicons, or human embryonic kidney (HEK) 293 cells transfected with NS3/4A protease. Activation of innate immune signaling was determined after transfection of double-strand surrogate nucleic acid antigens or infection with defined sequence HCV cell culture (HCVcc) RNA.

RESULTS

Tetrapyrroles failed to directly induce IFN expression at concentrations that inhibited HCV replication and NS3/4A protease activity. However, they potently restored IFN induction after attenuation with NS3/4A protease, a process accompanied by preservation of the adapter protein, mitochondrial antiviral signaling protein, nuclear localization of IFN regulatory factor 3, and augmentation of IFN-stimulated gene products.

CONCLUSIONS

Tetrapyrroles do not directly induce IFN, but they dramatically restore type I IFN signaling pathway after attenuation with NS3/4A protease. They show immunomodulatory as well as antiprotease activity and may be useful for treatment of HCV infection.

Human La protein interaction with GCAC near the initiator AUG enhances hepatitis C Virus RNA replication by promoting linkage between 5' and 3' untranslated regions

Human La protein has been implicated in facilitating the internal initiation of translation as well as replication of hepatitis C virus (HCV) RNA. Previously, we demonstrated that La interacts with the HCV internal ribosome entry site (IRES) around the GCAC motif near the initiator AUG within stem-loop IV by its RNA recognition motif (RRM) (residues 112 to 184) and influences HCV translation. In this study, we have deciphered the role of this interaction in HCV replication in a hepatocellular carcinoma cell culture system. We incorporated mutation of the GCAC motif in an HCV monocistronic subgenomic replicon and a pJFH1 construct which altered the binding of La and checked HCV RNA replication by reverse transcriptase PCR (RT-PCR). The mutation drastically affected HCV replication. Furthermore, to address whether the decrease in replication is a consequence of translation inhibition or not, we incorporated the same mutation into a bicistronic replicon and observed a substantial decrease in HCV RNA levels. Interestingly, La overexpression rescued this inhibition of replication. More importantly, we observed that the mutation reduced the association between La and NS5B. The effect of the GCAC mutation on the translation-to-replication switch, which is regulated by the interplay between NS3 and La, was further investigated. Additionally, our analyses of point mutations in the GCAC motif revealed distinct roles of each nucleotide in HCV replication and translation. Finally, we showed that a specific interaction of the GCAC motif with human La protein is crucial for linking 5' and 3' ends of the HCV genome. Taken together, our results demonstrate the mechanism of regulation of HCV replication by interaction of the cis-acting element GCAC within the HCV IRES with human La protein.

Short communication: atazanavir-based therapy is associated with higher hepatitis C viral load in HIV type 1-infected subjects with untreated hepatitis C

We assessed the relationship between atazanavir (ATV)-based antiretroviral treatment (ART) and plasma hepatitis C virus (HCV) viral load in a population of HIV/HCV-coinfected patients. HIV/HCV-coinfected patients who received ART based on a protease inhibitor (PI) or nonnucleoside reverse transcriptase inhibitor (NNRTI) were included. Patients were stratified by ART drug [ATV/rtv, lopinavir (LPV/rtv), efavirenz (EFV), nevirapine (NVP), and other PIs], HCV genotype (1/4 and 2/3), and IL28B genotype (CC and non-CC). The Kruskal-Wallis test and chi-squared test were used to compare continuous and categorical variables, respectively. Multivariate analysis consisted of a stepwise linear regression analysis. Six hundred and forty-nine HIV/HCV-coinfected patients were included. HCV genotype 1/4 patients who received ATV had higher HCV RNA levels [6.57 (5.9-6.8) log IU/ml] than those who received LPV [6.1 (5.5-6.5) log IU/ml], EFV [6.1 (5.6-6.4) log IU/ml], NVP [5.8 (5.5-5.9) log IU/ml], or other PIs [6.1 (5.7-6.4) log IU/ml] (p=0.014). This association held for the IL28B genotype (CC versus non-CC). The association was not found in patients carrying HCV genotypes 2/3. The linear regression model identified the IL28B genotype and ATV use as independent factors associated with HCV RNA levels. ATV-based therapy may be associated with a higher HCV RNA viral load in HIV/HCV-coinfected patients.

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.

Heme and HO-1 Inhibition of HCV, HBV, and HIV

Hepatitis C virus, human immunodeficiency virus, and hepatitis B virus are chronic viral infections that cause considerable morbidity and mortality throughout the world. In the decades following the identification and sequencing of these viruses, in vitro experiments demonstrated that heme oxygenase-1, its oxidative products, and related compounds of the heme oxygenase system inhibit replication of all 3 viruses. The purpose of this review is to critically evaluate and summarize the seminal studies that described and characterized this remarkable behavior. It will also discuss more recent work that discovered the antiviral mechanisms and target sites of these unique antiviral agents. In spite of the fact that these viruses are diverse pathogens with quite profound differences in structure and life cycle, it is significant that heme and related compounds show striking similarity for viral target sites across all three species. Collectively, these findings strongly indicate that we should move forward and develop heme and related tetrapyrroles into versatile antiviral agents that could be used therapeutically in patients with single or multiple viral infections.

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.

Alternative ferritin mRNA translation via internal initiation

Ferritin stores and detoxifies an excess of intracellular iron, and thereby plays an important role in the metabolism of this metal. As unshielded iron promotes oxidative stress, ferritin is crucial in maintaining cellular redox balance and may also modulate cell growth, survival, and apoptosis. The expression of ferritin is controlled by transcriptional and post-transcriptional mechanisms. In light of the well-established transcriptional induction of ferritin by inflammatory signals, we examined how ferritin mRNA translation responds to stress conditions. We first used HT1080 fibrosarcoma cells engineered for coumermycin-inducible expression of PKR, a stress kinase that inhibits protein synthesis in virus-infected cells by phosphorylating eIF2α. In this setting, iron triggered partial ferritin mRNA translation despite a PKR-induced global shutdown in protein synthesis. Moreover, iron-mediated ferritin synthesis was evident in cells infected with an attenuated strain of poliovirus; when eIF4GI was cleaved, eIF2α was phosphorylated, and host protein synthesis was inhibited. Under global inhibition of protein synthesis or specific inhibition of ferritin mRNA translation in cells overexpressing PKR or IRP1, respectively, we demonstrate association of ferritin mRNA with heavy polysomes. Further experiments revealed that the 5' untranslated region (5' UTR) of ferritin mRNA contains a bona fide internal ribosomal entry site (IRES). Our data are consistent with the existence of an alternative, noncanonical mechanism for ferritin mRNA translation, which may primarily operate under stress conditions to protect cells from oxidative stress.