Oxidative damage in dengue fever

Selenium-More than Just a Fortuitous Sulfur Substitute in Redox Biology

Living organisms use selenium mainly in the form of selenocysteine in the active site of oxidoreductases. Here, selenium's unique chemistry is believed to modulate the reaction mechanism and enhance the catalytic efficiency of specific enzymes in ways not achievable with a sulfur-containing cysteine. However, despite the fact that selenium/sulfur have different physicochemical properties, several selenoproteins have fully functional cysteine-containing homologues and some organisms do not use selenocysteine at all. In this review, selected selenocysteine-containing proteins will be discussed to showcase both situations: (i) selenium as an obligatory element for the protein's physiological function, and (ii) selenium presenting no clear advantage over sulfur (functional proteins with either selenium or sulfur). Selenium's physiological roles in antioxidant defence (to maintain cellular redox status/hinder oxidative stress), hormone metabolism, DNA synthesis, and repair (maintain genetic stability) will be also highlighted, as well as selenium's role in human health. Formate dehydrogenases, hydrogenases, glutathione peroxidases, thioredoxin reductases, and iodothyronine deiodinases will be herein featured.

Dengue Vaccination: Towards a New Dawn of Curbing Dengue Infection

Dengue is an infectious disease caused by dengue virus (DENV) and is a serious global burden. Antibody-dependent enhancement and the ability of DENV to infect immune cells, along with other factors, lead to fatal Dengue Haemorrhagic Fever and Dengue Shock Syndrome. This necessitates the development of a robust and efficient vaccine but vaccine development faces a number of hurdles. In this review, we look at the epidemiology, genome structure and cellular targets of DENV and elaborate upon the immune responses generated by human immune system against DENV infection. The review further sheds light on various challenges in development of a potent vaccine against DENV which is followed by presenting a current account of different vaccines which are being developed or have been licensed.

Maternal Immune Response to ZIKV Triggers High-Inflammatory Profile in Congenital Zika Syndrome

The immunological mechanisms involved in the development of congenital Zika syndrome (CZS) have yet to be fully clarified. This study aims to assess the immuno-inflammatory profile of mothers and their children who have been diagnosed with CZS. Blood samples, which were confirmed clinically using the plaque reduction neutralization test (PRNT), were collected from children with CZS and their mothers (CZS+ group). Samples were also collected from children who did not develop CZS and had a negative PRNT result and from their mothers (CZS- group). The data demonstrated a correlation between the leukocyte profile of CZS+ children and their mothers, more evident in monocytes. Monocytes from mothers of CZS+ children showed low expression of HLA and elevated hydrogen peroxide production. CZS+ children presented standard HLA expression and a higher hydrogen peroxide concentration than CZS- children. Monocyte superoxide dismutase activity remained functional. Moreover, when assessing the monocyte polarization, it was observed that there was no difference in nitrite concentrations; however, there was a decrease in arginase activity in CZS+ children. These data suggest that ZIKV infection induces a maternal immuno-inflammatory background related to the child's inflammatory response after birth, possibly affecting the development and progression of congenital Zika syndrome.

Critically ill septic patients have elevated oxidative stress biomarkers: lack of attenuation by parenteral vitamin C

Patients with septic shock are under an intense inflammatory burden, which is closely associated with increased oxidative stress and depletion of antioxidants such as vitamin C. We hypothesized that patients with septic shock would present with elevated oxidative stress (assessed as F₂-isoprostanes) and that administration of parenteral vitamin C to these patients would attenuate F₂-isoprostane concentrations. We recruited 40 critically ill patients with septic shock into a randomized placebo-controlled trial and assessed the effect of short-term (4-day) parenteral vitamin C administration (100 mg/kg/d) on 8-isoprostane F_2α concentrations, which were measured using enzyme-linked immunosorbent assays. Sources of sepsis and intensive care unit severity scores were recorded. Smokers (n = 20) and nonsmoking controls (n = 50) were assessed for comparison. The median baseline 8-isoprostane F_2α concentration in the septic patients was 3.95 (interquartile range [Q1, Q3] 2.1, 6.63) ng/mg creatinine; this was higher than smokers 1.61 [1.25, 2.82] P = .007 ng/mg creatinine; P = .005) and nonsmoking controls 1.12 [0.76, 1.57] ng/mg creatinine; P < .0001). The 8-isoprostane F_2α concentrations in the placebo group did not vary significantly over the duration of the study. Although parenteral vitamin C administration significantly increased the vitamin C status of the patients within 24 hours, this did not affect their 8-isoprostane F_2α concentrations. In conclusion, patients with septic shock have elevated 8-isoprostane F_2α excretion, which short-term parenteral vitamin C administration is unable to attenuate. If vitamin C is to work by antioxidant mechanisms, then early administration, before the development of shock, may be required. This trial was registered at anzctr.org.au (ACTRN12617001184369).

Essential Oils and COVID-19

Herbal products are a major source of herbal medicines and other medicines. Essential oils have shown various pharmacological activities, such as antiviral activity, and therefore are proposed to have potential activity against SARS-CoV-2. Due to their lipophilicity, essential oils can easily penetrate the viral membrane and cause the viral membrane to rupture. In addition, crude essential oils usually have many active constituents that can act on different parts of the virus including its cell entry, translation, transcription, and assembly. They have further beneficial pharmacological effects on the host's respiratory system, including anti-inflammatory, immune regulation, bronchiectasis, and mucolytics. This review reported potential essential oils which could be promising drugs for COVID-19 eradication. Essential oils have many advantages because they are promising volatile antiviral molecules, making them potential drug targets for the prevention and treatment of COVID-19, whether used alone or in combination with other chemotherapeutic drugs. The aim of the current review is to shed light on the potential essential oils against enveloped viruses and their proposed activity against SARS-CoV-2 which is also an enveloped virus. The objectives were to present all data reflecting the promising activities of diverse essential oils against enveloped viruses and how they could contribute to the eradication of COVID disease, especially in indoor places. The data collected for the current review were obtained through the SciFinder database, Google scholar, PubMed, and Mendeley database. The data of the current review focused on the most common essential oils which are available in the pharmaceutical market and showed noticeable activities against enveloped viruses such as HSV and influenza.

Heme oxygenase-1 inhibits DENV-induced endothelial hyperpermeability and serves as a potential target against dengue hemorrhagic fever

Dengue virus (DENV) is a cause of vascular endothelial dysfunction and vascular leakage, which are characterized as hallmarks of dengue hemorrhagic fever or dengue shock syndrome, which become a severe global health emergency with substantial morbidity and mortality. Currently, there are still no promising therapeutics to alleviate the dengue-associated vascular hemorrhage in a clinical setting. In the present study, we first observed that heme oxygenase-1 (HO-1) expression level was highly suppressed in severe DENV-infected patients. In contrast, the overexpression of HO-1 could attenuate DENV-induced pathogenesis, including plasma leakage and thrombocytopenia, in an AG129 mouse model. Our data indicate that overexpression of HO-1 or its metabolite biliverdin can maintain endothelial integrity upon DENV infection in vitro and in vivo. We further characterized the positive regulatory effect of HO-1 on the endothelial adhesion factor vascular endothelial-cadherin to decrease DENV-induced endothelial hyperpermeability. Subsequently, we confirmed that two medicinal plant-derived compounds, andrographolide, and celastrol, widely used as a nutritional or medicinal supplement are useful to attenuate DENV-induced plasma leakage through induction of the HO-1 expression in DENV-infected AG129 mice. In conclusion, our findings reveal that induction of the HO-1 signal pathway is a promising option for the treatment of DENV-induced vascular pathologies.

(E)-Guggulsterone Inhibits Dengue Virus Replication by Upregulating Antiviral Interferon Responses through the Induction of Heme Oxygenase-1 Expression

Dengue virus (DENV) infection, which causes dengue fever, dengue hemorrhagic fever, and dengue shock syndrome, is a severe global health problem in tropical and subtropical areas. There is no effective vaccine or drug against DENV infection. Thus, the development of anti-DENV agents is imperative. This study aimed to assess the anti-DENV activity of (E)-guggulsterone using a DENV infectious system. A specific inhibitor targeting signal molecules was used to evaluate the molecular mechanisms of action. Western blotting and qRT-PCR were used to determine DENV protein expression and RNA replication, respectively. Finally, an ICR suckling mouse model was used to examine the anti-DENV activity of (E)-guggulsterone in vivo. A dose-dependent inhibitory effect of (E)-guggulsterone on DENV protein synthesis and RNA replication without cytotoxicity was observed. The mechanistic studied revealed that (E)-guggulsterone stimulates Nrf2-mediated heme oxygenase-1 (HO-1) expression, which increases the antiviral interferon responses and downstream antiviral gene expression by blocking DENV NS2B/3B protease activity. Moreover, (E)-guggulsterone protected ICR suckling mice from life-threatening DENV infection. These results suggest that (E)-guggulsterone can be a potential supplement for controlling DENV replication.

Micronutrient Supplementation and Clinical Outcomes in Patients with Dengue Fever

Dengue fever (DF) is a viral infection that is common in tropical countries and represents a significant cause of global morbidity and mortality. Despite its prevalence and severity, treatment options for DF remain limited and consist primarily of supportive measures. Several recent studies have concluded that micronutrient supplementation may improve clinical outcomes in patients with DF, but no review has summarized and synthesized these findings. We conducted a literature review to identify articles investigating the effect of micronutrient supplementation on clinical outcomes among patients with DF. We found several studies which indicated that supplemental vitamin C, vitamin D, vitamin E, and zinc may be useful adjuncts in DF treatment. Folic acid supplementation did not appear to affect clinical outcomes. The reviewed studies have significant limitations including small sample sizes and limited data about the baseline nutritional status of study subjects. We identify a need for additional high-quality randomized trials to elucidate the role of micronutrient supplementation in DF treatment.

Dengue Virus Targets Nrf2 for NS2B3-Mediated Degradation Leading to Enhanced Oxidative Stress and Viral Replication

Dengue virus (DENV) is a mosquito-borne virus that infects upward of 300 million people annually and has the potential to cause fatal hemorrhagic fever and shock. While the parameters contributing to dengue immunopathogenesis remain unclear, the collapse of redox homeostasis and the damage induced by oxidative stress have been correlated with the development of inflammation and progression toward the more severe forms of disease. In the present study, we demonstrate that the accumulation of reactive oxygen species (ROS) late after DENV infection (>24 hpi) resulted from a disruption in the balance between oxidative stress and the nuclear factor erythroid 2-related factor 2 (Nrf2)-dependent antioxidant response. The DENV NS2B3 protease complex strategically targeted Nrf2 for degradation in a proteolysis-independent manner; NS2B3 licensed Nrf2 for lysosomal degradation. Impairment of the Nrf2 regulator by the NS2B3 complex inhibited the antioxidant gene network and contributed to the progressive increase in ROS levels, along with increased virus replication and inflammatory or apoptotic gene expression. By 24 hpi, when increased levels of ROS and antiviral proteins were observed, it appeared that the proviral effect of ROS overcame the antiviral effects of the interferon (IFN) response. Overall, these studies demonstrate that DENV infection disrupts the regulatory interplay between DENV-induced stress responses, Nrf2 antioxidant signaling, and the host antiviral immune response, thus exacerbating oxidative stress and inflammation in DENV infection.IMPORTANCE Dengue virus (DENV) is a mosquito-borne pathogen that threatens 2.5 billion people in more than 100 countries annually. Dengue infection induces a spectrum of clinical symptoms, ranging from classical dengue fever to severe dengue hemorrhagic fever or dengue shock syndrome; however, the complexities of DENV immunopathogenesis remain controversial. Previous studies have reported the importance of the transcription factor Nrf2 in the control of redox homeostasis and antiviral/inflammatory or death responses to DENV. Importantly, the production of reactive oxygen species and the subsequent stress response have been linked to the development of inflammation and progression toward the more severe forms of the disease. Here, we demonstrate that DENV uses the NS2B3 protease complex to strategically target Nrf2 for degradation, leading to a progressive increase in oxidative stress, inflammation, and cell death in infected cells. This study underlines the pivotal role of the Nrf2 regulatory network in the context of DENV infection.

Antiviral potential of garlic (Allium sativum) and its organosulfur compounds: A systematic update of pre-clinical and clinical data

BACKGROUND

Garlic (Allium sativum L.) is a common herb consumed worldwide as functional food and traditional remedy for the prevention of infectious diseases since ancient time. Garlic and its active organosulfur compounds (OSCs) have been reported to alleviate a number of viral infections in pre-clinical and clinical investigations. However, so far no systematic review on its antiviral effects and the underlying molecular mechanisms exists.

SCOPE AND APPROACH

The aim of this review is to systematically summarize pre-clinical and clinical investigations on antiviral effects of garlic and its OSCs as well as to further analyse recent findings on the mechanisms that underpin these antiviral actions. PubMed, Cochrane library, Google Scholar and Science Direct databases were searched and articles up to June 2020 were included in this review.

KEY FINDINGS AND CONCLUSIONS

Pre-clinical data demonstrated that garlic and its OSCs have potential antiviral activity against different human, animal and plant pathogenic viruses through blocking viral entry into host cells, inhibiting viral RNA polymerase, reverse transcriptase, DNA synthesis and immediate-early gene 1(IEG1) transcription, as well as through downregulating the extracellular-signal-regulated kinase (ERK)/mitogen activated protein kinase (MAPK) signaling pathway. The alleviation of viral infection was also shown to link with immunomodulatory effects of garlic and its OSCs. Clinical studies further demonstrated a prophylactic effect of garlic in the prevention of widespread viral infections in humans through enhancing the immune response. This review highlights that garlic possesses significant antiviral activity and can be used prophylactically in the prevention of viral infections.

Could Ergothioneine Aid in the Treatment of Coronavirus Patients?

Infection with SARS-CoV-2 causes the coronavirus infectious disease 2019 (COVID-19), a pandemic that has, at present, infected more than 11 million people globally. Some COVID-19 patients develop a severe and critical illness, spurred on by excessive inflammation that can lead to respiratory or multiorgan failure. Numerous studies have established the unique array of cytoprotective properties of the dietary amino acid ergothioneine. Based on studies in a range of in vitro and in vivo models, ergothioneine has exhibited the ability to modulate inflammation, scavenge free radicals, protect against acute respiratory distress syndrome, prevent endothelial dysfunction, protect against ischemia and reperfusion injury, protect against neuronal damage, counteract iron dysregulation, hinder lung and liver fibrosis, and mitigate damage to the lungs, kidneys, liver, gastrointestinal tract, and testis, amongst many others. When compiled, this evidence suggests that ergothioneine has a potential application in the treatment of the underlying pathology of COVID-19. We propose that ergothioneine could be used as a therapeutic to reduce the severity and mortality of COVID-19, especially in the elderly and those with underlying health conditions. This review presents evidence to support that proposal.

The association of obesity and severe dengue: possible pathophysiological mechanisms

Dengue virus (DENV) is a medically important flavivirus and the aetiological agent of Dengue, a normally self-resolving febrile illness that, in some individuals, can progress into Severe Dengue (SD), a life-threatening disorder that manifests as organ impairment, bleeding and shock. Many different risk factors have been associated with the development of SD, one of which is obesity. In many countries where DENV is endemic, obesity is becoming more prevalent, therefore SD is becoming an increased public health concern. However, there is a paucity of research on the mechanistic links between obesity and SD. This is a narrative review based on original research and reviews sourced from PubMed and Google Scholar. Four key areas could possibly explain how obesity can promote viral pathogenesis. Firstly, obesity downregulates AMP-Protein Kinase (AMPK), which leads to an accumulation of lipids in the endoplasmic reticulum (ER) that facilitates viral replication. Secondly, the long-term production of pro-inflammatory adipokines found in obese individuals can cause endothelial and platelet dysfunction and can facilitate SD. Thirdly, obesity could also cause endothelial dysfunction in addition to chronic inflammation, through the production of reactive oxygen species (ROS) and possible damage to the glycocalyx found in the endothelium. Finally, obesity has several effects on immunomodulation that reduces NK cell function, B and T cell response and increased pre-disposition to stronger pro-inflammatory cytokine responses after viral infection. Together, these effects can lead to greater viral proliferation and greater tissue damage both of which could contribute to SD. The four mechanisms outlined in this review can be taken as reference starting points for investigating the link between obesity and SD, and to discover potential therapeutic strategies that can potentially reduce disease severity.

MicroRNA-155 inhibits dengue virus replication by inducing heme oxygenase-1-mediated antiviral interferon responses

MicroRNAs (miRNAs) have been reported to directly alter the virus life cycle and virus-host interactions, and so are considered promising molecules for controlling virus infection. In the present study, we observed that miR-155 time-dependently downregulated upon dengue virus (DENV) infection. In contrast, exogenous overexpression of miR-155 appeared to limit viral replication in vitro, suggesting that the low levels of miR-155 would be beneficial for DENV replication. In vivo, overexpression of miR-155 protected ICR suckling mice from the life-threatening effects of DENV infection and reduced virus propagation. Further investigation revealed that the anti-DENV activity of miR-155 was due to target Bach1, resulting in the induction of the heme oxygenase-1 (HO-1)-mediated inhibition of DENV NS2B/NS3 protease activity, ultimately leading to induction of antiviral interferon responses, including interferon-induced protein kinase R (PKR), 2'-5'-oligoadenylate synthetase 1 (OAS1), OAS2, and OAS3 expression, against DENV replication. Collectively, our results provide a promising new strategy to manage DENV infection by modulation of miR-155 expression.

Mayaro Virus Induction of Oxidative Stress is Associated With Liver Pathology in a Non-Lethal Mouse Model

Mayaro virus (MAYV) causes Mayaro fever in humans, a self-limiting acute disease, with persistent arthralgia and arthritis. Although MAYV has a remerging potential, its pathogenic mechanisms remain unclear. Here, we characterized a model of MAYV infection in 3-4-week BALB/c mice. We investigated whether the liver acts as a site of viral replication and if the infection could cause histopathological alterations and an imbalance in redox homeostasis, culminating with oxidative stress. MAYV-infected mice revealed lower weight gain; however, the disease was self-resolving. High virus titre, neutralizing antibodies, and increased levels of aspartate and alanine aminotransferases were detected in the serum. Infectious viral particles were recovered in the liver of infected animals and the histological examination of liver tissues revealed significant increase in the inflammatory infiltrate. MAYV induced significant oxidative stress in the liver of infected animals, as well as a deregulation of enzymatic antioxidant components. Collectively, this is the first study to report that oxidative stress occurs in MAYV infection in vivo, and that it may be crucial in virus pathogenesis. Future studies are warranted to address the alternative therapeutic strategies for Mayaro fever, such as those based on antioxidant compounds.

Oxidative stress response in the pathogenesis of dengue virus virulence, disease prognosis and therapeutics: an update

Dengue virus (DENV) is a mosquito-borne arbovirus that causes febrile illness and can lead to a potentially lethal disease. The mechanism of disease pathogenesis is not completely understood, and there are currently no vaccines or therapeutic drugs available to protect against all four serotypes of DENV. Although many reasons have been suggested for the development of the disease, dengue studies have shown that, during DENV infection, there is an imbalance between oxidants and antioxidants that disrupts homeostasis. An increase in reactive oxygen species (ROS) levels triggers the sudden release of cytokines, which can lead to plasma leakage and other severe symptoms. In the present review, we give an overview of the oxidative stress response and its effect on the progression of dengue disease. We also discuss the role of oxidative-stress-associated molecules in disease prognostic and therapeutics.

Selenium, Selenoproteins and Viral Infection

Reactive oxygen species (ROS) are frequently produced during viral infections. Generation of these ROS can be both beneficial and detrimental for many cellular functions. When overwhelming the antioxidant defense system, the excess of ROS induces oxidative stress. Viral infections lead to diseases characterized by a broad spectrum of clinical symptoms, with oxidative stress being one of their hallmarks. In many cases, ROS can, in turn, enhance viral replication leading to an amplification loop. Another important parameter for viral replication and pathogenicity is the nutritional status of the host. Viral infection simultaneously increases the demand for micronutrients and causes their loss, which leads to a deficiency that can be compensated by micronutrient supplementation. Among the nutrients implicated in viral infection, selenium (Se) has an important role in antioxidant defense, redox signaling and redox homeostasis. Most of biological activities of selenium is performed through its incorporation as a rare amino acid selenocysteine in the essential family of selenoproteins. Selenium deficiency, which is the main regulator of selenoprotein expression, has been associated with the pathogenicity of several viruses. In addition, several selenoprotein members, including glutathione peroxidases (GPX), thioredoxin reductases (TXNRD) seemed important in different models of viral replication. Finally, the formal identification of viral selenoproteins in the genome of molluscum contagiosum and fowlpox viruses demonstrated the importance of selenoproteins in viral cycle.

Flaviviridae Viruses and Oxidative Stress: Implications for Viral Pathogenesis

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

Avocado (Persea americana) fruit extract (2R,4R)-1,2,4-trihydroxyheptadec-16-yne inhibits dengue virus replication via upregulation of NF-κB-dependent induction of antiviral interferon responses

Dengue virus (DENV) caused millions of infections around the world annually. Co-infection with different serotypes of DENV is associated with dengue hemorrhagic shock syndrome, leading to an estimate of 50% death rate. No approved therapies are currently available for the treatment of DENV infection. Hence, novel anti-DENV agents are urgently needed for medical therapy. Here we demonstrated that a natural product (2 R,4 R)-1,2,4-trihydroxyheptadec-16-yne (THHY), extracted from avocado (Persea americana) fruit, can inhibit DENV-2 replication in a concentration-dependent manner and efficiently suppresses replication of all DENV serotypes (1–4). We further reveal that the NF-κB-mediated interferon antiviral response contributes to the inhibitory effect of THHY on DENV replication. Using a DENV-infected ICR suckling mouse model, we found that THHY treatment caused an increased survival rate among mice infected with DENV. Collectively, these findings support THHY as a potential agent to control DENV infection.

The Role of Tissue Oxygen Tension in Dengue Virus Replication

Low oxygen tension exerts a profound effect on the replication of several DNA and RNA viruses. In vitro propagation of Dengue virus (DENV) has been conventionally studied under atmospheric oxygen levels despite that in vivo, the tissue microenvironment is hypoxic. Here, we compared the efficiency of DENV replication in liver cells, monocytes, and epithelial cells under hypoxic and normoxic conditions, investigated the ability of DENV to induce a hypoxia response and metabolic reprogramming and determined the underlying molecular mechanism. In DENV-infected cells, hypoxia had no effect on virus entry and RNA translation, but enhanced RNA replication. Overexpression and silencing approaches as well as chemical inhibition and energy substrate exchanging experiments showed that hypoxia-mediated enhancement of DENV replication depends on the activation of the key metabolic regulators hypoxia-inducible factors 1α/2α (HIF-1α/2α) and the serine/threonine kinase AKT. Enhanced RNA replication correlates directly with an increase in anaerobic glycolysis producing elevated ATP levels. Additionally, DENV activates HIF and anaerobic glycolysis markers. Finally, reactive oxygen species were shown to contribute, at least in part through HIF, both to the hypoxia-mediated increase of DENV replication and to virus-induced hypoxic reprogramming. These suggest that DENV manipulates hypoxia response and oxygen-dependent metabolic reprogramming for efficient viral replication.

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.

Low density lipopolyprotein inhibits flavivirus acquisition in Aedes aegypti

Aedes aegypti is the primary vector of a number of human pathogens including dengue virus (DENV) and Zika virus (ZIKV). Ae. aegypti acquires these viruses during the processing of bloodmeals obtained from an infected vertebrate host. Vertebrate blood contains a number of factors that have the potential to modify virus acquisition in the mosquito. Interestingly, low density lipopolyprotein (LDL) levels are decreased during severe DENV infection. Accordingly, we hypothesized that LDL is a modifiable factor that can influence flavivirus acquisition in the mosquito. We found that LDL is endocytosed by Ae. aegypti cells in a dynamin-dependent manner. LDL is also endocytosed by midgut epithelial cells and accumulates at the luminal midgut epithelium during bloodmeal digestion. Importantly, pretreatment with LDL, but not high density lipopolyprotein (HDL), significantly inhibited both DENV and ZIKV infection in vitro, and LDL inhibited ZIKV infection in vivo. This study identifies human LDL or 'bad cholesterol' as a modifiable factor that can inhibit flavivirus acquisition in Ae. aegypti. Identification of modifiable blood factors and critical cellular interactions that mediate pathogen acquisition may lead to novel strategies to disrupt the transmission cycle of vector-borne diseases.

Meta-analysis of biomarkers for severe dengue infections

BACKGROUND

Dengue viral infection is an acute infection that has the potential to have severe complications as its major sequela. Currently, there is no routine laboratory biomarker with which to predict the severity of dengue infection or monitor the effectiveness of standard management. Hence, this meta-analysis compared biomarker levels between dengue fever (DF) and severe dengue infections (SDI) to identify potential biomarkers for SDI.

METHODS

Data concerning levels of cytokines, chemokines, and other potential biomarkers of DF, dengue hemorrhagic fever, dengue shock syndrome, and severe dengue were obtained for patients of all ages and populations using the Scopus, PubMed, and Ovid search engines. The keywords "(IL1* or IL-1*) AND (dengue*)" were used and the same process was repeated for other potential biomarkers, according to Medical Subject Headings terms suggested by PubMed and Ovid. Meta-analysis of the mean difference in plasma or serum level of biomarkers between DF and SDI patients was performed, separated by different periods of time (days) since fever onset. Subgroup analyses comparing biomarker levels of healthy plasma and sera controls, biomarker levels of primary and secondary infection samples were also performed, as well as analyses of different levels of severity and biomarker levels upon infection by different dengue serotypes.

RESULTS

Fifty-six studies of 53 biomarkers from 3,739 dengue cases (2,021 DF and 1,728 SDI) were included in this meta-analysis. Results showed that RANTES, IL-7, IL-8, IL-10, IL-18, TGF-b, and VEGFR2 levels were significantly different between DF and SDI. IL-8, IL-10, and IL-18 levels increased during SDI (95% CI, 18.1-253.2 pg/mL, 3-13 studies, n = 177-1,909, I2 = 98.86%-99.75%). In contrast, RANTES, IL-7, TGF-b, and VEGFR2 showed a decrease in levels during SDI (95% CI, -3238.7 to -3.2 pg/mL, 1-3 studies, n = 95-418, I2 = 97.59%-99.99%). Levels of these biomarkers were also found to correlate with the severity of the dengue infection, in comparison to healthy controls. Furthermore, the results showed that IL-7, IL-8, IL-10, TGF-b, and VEGFR2 display peak differences between DF and SDI during or before the critical phase (day 4-5) of SDI.

DISCUSSION

This meta-analysis suggests that IL-7, IL-8, IL-10, TGF-b, and VEGFR2 may be used as potential early laboratory biomarkers in the diagnosis of SDI. This can be used to predict the severity of dengue infection and to monitor the effectiveness of treatment. Nevertheless, methodological and reporting limitations must be overcome in future research to minimize variables that affect the results and to confirm the findings.

Dengue in the elderly: a review

INTRODUCTION

Changing dengue epidemiological trends have resulted in a shift in the disease burden to the adult population. Older adults suffer from poorer outcomes as compared to their younger counterparts, making clinical management of this sub-population particularly challenging. Areas covered: We present a review of the current literature on the changing epidemiology of dengue in the elderly, the atypical features of the clinical disease in this population with emphasis on severe disease presentations and challenges in the current management strategies. Expert commentary: Dengue in the elderly is an increasingly important yet greatly understudied area. There is an urgent need to refine the current diagnostic criteria to improve diagnosis, classification of disease severity and identify individuals in this population who are likely to progress to severe disease. Management strategies in this population would have to be adjusted to account for the increased number of co-morbidities. The role of the available dengue vaccines in this group is uncertain, and more studies into their safety and efficacy are critically needed.

Garlic Organosulfur Compounds Reduce Inflammation and Oxidative Stress during Dengue Virus Infection

Dengue virus (DENV) is a mosquito-borne flavivirus that causes significant global human disease and mortality. One approach to develop treatments for DENV infection and the prevention of severe disease is through investigation of natural medicines. Inflammation plays both beneficial and harmful roles during DENV infection. Studies have proposed that the oxidative stress response may be one mechanism responsible for triggering inflammation during DENV infection. Thus, blocking the oxidative stress response could reduce inflammation and the development of severe disease. Garlic has been shown to both reduce inflammation and affect the oxidative stress response. Here, we show that the garlic active compounds diallyl disulfide (DADS), diallyl sulfide (DAS) and alliin reduced inflammation during DENV infection and show that this reduction is due to the effects on the oxidative stress response. These results suggest that garlic could be used as an alternative treatment for DENV infection and for the prevention of severe disease development.

Effect of total flavonoids of Spatholobus suberectus Dunn on PCV2 induced oxidative stress in RAW264.7 cells

Background

This study was carried out to investigate the effect of total flavonoids of Spatholobus suberectus Dunn (TFSD) on PCV2 induced oxidative stress in RAW264.7 cells.

Methods

Oxidative stress model was established in RAW264.7 cells by infecting with PCV2. Virus infected cells were then treated with various concentrations (25 mg/ml, 50 mg/ml and 100 mg/ml) of TFSD. The levels of oxidative stress related molecules (NO, ROS, GSH and GSSG) and activities of associated enzymes (SOD, MPO and XOD were analyzed using ultraviolet spectrophotometry, fluorescence method and commercialized detection kits.

Results

PCV2 infection induced significant increase of NO secretion, ROS generation, GSSG content, activities of both XOD and MPO, and dramatically decrease of GSH content and SOD activity in RAW264.7 cells (P < 0.05). After treating with TFSD, PCV2 induced alteration of oxidative stress related molecule levels and enzyme activities were recovered to a level similar to control.

Conclusion

Our findings indicated that TFSD was able to regulate oxidative stress induced by PCV2 infection in RAW264.7 cells, which supports the ethnomedicinal use of this herb as an alternative or complementary therapeutic drug for reactive oxygen-associated pathologies.

Classifying oxidative stress by F2-isoprostane levels across human diseases: A meta-analysis

The notion that oxidative stress plays a role in virtually every human disease and environmental exposure has become ingrained in everyday knowledge. However, mounting evidence regarding the lack of specificity of biomarkers traditionally used as indicators of oxidative stress in human disease and exposures now necessitates re-evaluation. To prioritize these re-evaluations, published literature was comprehensively analyzed in a meta-analysis to quantitatively classify the levels of systemic oxidative damage across human disease and in response to environmental exposures.

In this meta-analysis, the F₂-isoprostane, 8-iso-PGF_2α, was specifically chosen as the representative marker of oxidative damage. To combine published values across measurement methods and specimens, the standardized mean differences (Hedges’ g) in 8-iso-PGF_2α levels between affected and control populations were calculated.

The meta-analysis resulted in a classification of oxidative damage levels as measured by 8-iso-PGF_2α across 50 human health outcomes and exposures from 242 distinct publications. Relatively small increases in 8-iso-PGF_2α levels (g<0.8) were found in the following conditions: hypertension (g=0.4), metabolic syndrome (g=0.5), asthma (g=0.4), and tobacco smoking (g=0.7). In contrast, large increases in 8-iso-PGF_2α levels were observed in pathologies of the kidney, e.g., chronic renal insufficiency (g=1.9), obstructive sleep apnoea (g=1.1), and pre-eclampsia (g=1.1), as well as respiratory tract disorders, e.g., cystic fibrosis (g=2.3).

In conclusion, we have established a quantitative classification for the level of 8-iso-PGF_2α generation in different human pathologies and exposures based on a comprehensive meta-analysis of published data. This analysis provides knowledge on the true involvement of oxidative damage across human health outcomes as well as utilizes past research to prioritize those conditions requiring further scrutiny on the mechanisms of biomarker generation.

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Oxidative damage is highly variable in human conditions as measured by F₂-isoprostanes.

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Respiratory tract and urogenital diseases have the highest F₂-isoprostanes.

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Cancer and cardiovascular diseases have surprisingly low F₂-isoprostanes.

Influence of demographics on clinical outcome of dengue: a cross-sectional study of 6703 confirmed cases in Vitória, Espírito Santo State, Brazil

Dengue presents a wide clinical spectrum of signs and symptoms, with characteristics of the host potentially influencing the disease evolution. Therefore, the purpose of this study was to evaluate the influence of gender and age on dengue clinical outcomes in a recent outbreak situation in Brazil, applying a cross-sectional design and including 6703 dengue cases with laboratory confirmation, occurring in Vitória, Espírito Santo State, Brazil, between 2007 and 2013. Data were obtained from the Information System for Notifiable Diseases. Overall, 11·3% of the sample presented with severe dengue, which affected 13·0% of males, 10·0% of females, 8·8% of children, 12·5% of adolescents, 10·5% of adults and 15·5% of the elderly. Age was higher in the severe dengue group (P = 0·03). Severe dengue was associated with males and the elderly (P < 0·01); however, considering only severe cases, children presented haemorrhage and plasma leakage more frequently than older age groups. The results emphasize the importance of a differentiated protocol for management of dengue cases, taking into consideration host factors like age. These findings also suggest the elderly and children as priority groups for immunization in a future implementation of a vaccine.

Interplay between Inflammation and Cellular Stress Triggered by Flaviviridae Viruses

The Flaviviridae family comprises several human pathogens, including Dengue, Zika, Yellow Fever, West Nile, Japanese Encephalitis viruses, and Hepatitis C Virus. Those are enveloped, single-stranded positive sense RNA viruses, which replicate mostly in intracellular compartments associated to endoplasmic reticulum (ER) and Golgi complex. Virus replication results in abundant viral RNAs and proteins, which are recognized by cellular mechanisms evolved to prevent virus infection, resulting in inflammation and stress responses. Virus RNA molecules are sensed by Toll-like receptors (TLRs), RIG-I-like receptors (RIG-I and MDA5) and RNA-dependent protein kinases (PKR), inducing the production of inflammatory mediators and interferons. Simultaneously, the synthesis of virus RNA and proteins are distinguished in different compartments such as mitochondria, ER and cytoplasmic granules, triggering intracellular stress pathways, including oxidative stress, unfolded protein response pathway, and stress granules assembly. Here, we review the new findings that connect the inflammatory pathways to cellular stress sensors and the strategies of Flaviviridae members to counteract these cellular mechanisms and escape immune response.

Human heme oxygenase 1 is a potential host cell factor against dengue virus replication

Dengue virus (DENV) infection and replication induces oxidative stress, which further contributes to the progression and pathogenesis of the DENV infection. Modulation of host antioxidant molecules may be a useful strategy for interfering with DENV replication. In this study, we showed that induction or exogenous overexpression of heme oxygenase-1 (HO-1), an antioxidant enzyme, effectively inhibited DENV replication in DENV-infected Huh-7 cells. This antiviral effect of HO-1 was attenuated by its inhibitor tin protoporphyrin (SnPP), suggesting that HO-1 was an important cellular factor against DENV replication. Biliverdin but not carbon monoxide and ferrous ions, which are products of the HO-1 on heme, mediated the HO-1-induced anti-DENV effect by non-competitively inhibiting DENV protease, with an inhibition constant (Ki) of 8.55 ± 0.38 μM. Moreover, HO-1 induction or its exogenous overexpression, rescued DENV-suppressed antiviral interferon response. Moreover, we showed that HO-1 induction by cobalt protoporphyrin (CoPP) and andrographolide, a natural product, as evidenced by a significant delay in the onset of disease and mortality, and virus load in the infected mice’s brains. These findings clearly revealed that a drug or therapy that induced the HO-1 signal pathway was a promising strategy for treating DENV infection.

Dengue Virus Immunopathogenesis: Lessons Applicable to the Emergence of Zika Virus

Dengue is the leading mosquito-transmitted viral infection in the world. There are more than 390 million new infections annually; while the majority of infected individuals are asymptomatic or develop a self-limited dengue fever, up to 1 million clinical cases develop severe manifestations, including dengue hemorrhagic fever and shock syndrome, resulting in ~25,000 deaths annually, mainly in children. Gaps in our understanding of the mechanisms that contribute to dengue infection and immunopathogenesis have hampered the development of vaccines and antiviral agents. Some of these limitations are highlighted by the explosive re-emergence of another arthropod-borne flavivirus-Zika virus-spread by the same vector, the Aedes aegypti mosquito, that also carries dengue, yellow fever and chikungunya viruses. This review will discuss the early virus-host interactions in dengue infection, with emphasis on the interrelationship between oxidative stress and innate immune pathways, and will provide insight as to how lessons learned from dengue research may expedite therapeutic strategies for Zika virus.

Lower Low-Density Lipoprotein Cholesterol Levels Are Associated with Severe Dengue Outcome

Dengue virus (DENV) is a flavivirus of worldwide importance, with approximately 4 billion people across 128 countries at risk of infection, and up to 390 million infections and 96 million clinically apparent cases estimated annually. Previous in vitro studies have shown that lipids and lipoproteins play a role in modifying virus infectivity. However, the relationship between development of severe dengue and total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C), respectively, is unclear. We analyzed data from 789 laboratory-confirmed dengue cases and 447 other febrile illnesses (OFI) in a prospective pediatric hospital-based study in Managua, Nicaragua between August 2005 and January 2013, using three different classifications of dengue severity: World Health Organization (WHO) 1997, WHO 2009, and standardized intervention categories. Total serum cholesterol and LDL-C levels decreased over the course of illness and were generally lower with increasing dengue severity, regardless of classification scheme. Greater decreases in LDL-C than HDL-C were observed among dengue-positive patients compared to patients with OFI and among severe dengue compared to mild dengue cases. Furthermore, daily cholesterol levels declined with daily albumin blood levels. To examine the effect of cholesterol at presentation on subsequent risk of development of severe dengue, relative risks and 95% confidence intervals were calculated using multivariable modified Poisson models. We found that lower total serum cholesterol and LDL-C levels at presentation were associated with subsequent risk of developing dengue hemorrhagic fever/dengue shock syndrome using the WHO 1997 dengue severity classification, and thus that the reduction in LDL-C is likely driving the decreases observed in total serum cholesterol levels among dengue-positive patients. Our results suggest that cholesterol blood levels are important correlates of dengue pathophysiology and should be explored as part of a prognostic biomarker panel for severe dengue.

Assessment of biochemical and antioxidative status in patients suffering from dengue fever

A multi-centred study was designed to collect dengue epidemiologic data from government and registered private hospitals/clinics and maintained archive of frozen specimens in bio-bank to be used for future dengue epidemic control program, and assess the epidemiology of dengue fever (DF) by evaluating biochemical and oxidative status of patients. ELISA IgM antibodies test was done to confirm DF. From August 2010 to December 2011, 101 confirmed blood samples of DF patients referred to pathology lab of Jinnah Hospital Lahore were subjected to the epidemiologic assessment by evaluating the biochemical and physiological indices and alterations of circulating antioxidants. Clinical features of DF patients and effect of fever on blood components and serum proteins of liver were recorded. The hospital stay in DF, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) showed significant difference. Significant increases in serum alanine amino transferase (ALT) (P=0.000), aspartate amino transferase (AST) (P=0.000), alkaline phosphatase (ALP) (P=0.000), malondialdehyde (MDA) along with significant decreases in total protein (TP) (P=0.000), reduced glutathione (GSH) (P=0.000), superoxide dismutase (SOD), catalase (CAT) (P=0.000), and sialic acid contents (P=0.016) were observed. A positive correlation existed between bound sialic acid levels, liver enzymes and circulating antioxidants (r=0.656, P=0.016). In the present study, alterations of circulating antioxidants in DF suggest that DF might be a metabolic response to an acute, self-limiting tropical viral infection, and a consequence of the viral inflammatory process.

Cellular oxidative stress response controls the antiviral and apoptotic programs in dengue virus-infected dendritic cells

Dengue virus (DENV) is a re-emerging arthropod borne flavivirus that infects more than 300 million people worldwide, leading to 50,000 deaths annually. Because dendritic cells (DC) in the skin and blood are the first target cells for DENV, we sought to investigate the early molecular events involved in the host response to the virus in primary human monocyte-derived dendritic cells (Mo-DC). Using a genome-wide transcriptome analysis of DENV2-infected human Mo-DC, three major responses were identified within hours of infection - the activation of IRF3/7/STAT1 and NF-κB-driven antiviral and inflammatory networks, as well as the stimulation of an oxidative stress response that included the stimulation of an Nrf2-dependent antioxidant gene transcriptional program. DENV2 infection resulted in the intracellular accumulation of reactive oxygen species (ROS) that was dependent on NADPH-oxidase (NOX). A decrease in ROS levels through chemical or genetic inhibition of the NOX-complex dampened the innate immune responses to DENV infection and facilitated DENV replication; ROS were also essential in driving mitochondrial apoptosis in infected Mo-DC. In addition to stimulating innate immune responses to DENV, increased ROS led to the activation of bystander Mo-DC which up-regulated maturation/activation markers and were less susceptible to viral replication. We have identified a critical role for the transcription factor Nrf2 in limiting both antiviral and cell death responses to the virus by feedback modulation of oxidative stress. Silencing of Nrf2 by RNA interference increased DENV-associated immune and apoptotic responses. Taken together, these data demonstrate that the level of oxidative stress is critical to the control of both antiviral and apoptotic programs in DENV-infected human Mo-DC and highlight the importance of redox homeostasis in the outcome of DENV infection.

Dengue virus (DENV), the leading arthropod-borne viral infection in the world, represents a major human health concern with a global at risk population of over 3 billion people. Currently, there are no antivirals or vaccines available to treat patients with dengue fever, nor is it possible to predict which patients will progress to life-threatening severe dengue fever. Markers associated with oxidative stress responses have been reported in patients with severe DENV infection, suggesting a relationship between oxidative stress and viral pathogenesis. In order to uncover biological processes that determine the outcome of disease in patients, we utilized human dendritic cells, the primary target of DENV infection, in an in vitro model. Transcriptional analysis of pathways activated upon de novo DENV infection revealed a major role for cellular oxidative stress in the induction of antiviral, inflammatory, and cell death responses. We also demonstrated that antioxidant mechanisms play a critical role in controlling antiviral and cell death responses to the virus, acting as feedback regulators of the oxidative stress response. This report highlights the importance of oxidative stress responses in the outcome of DENV infection, and identifies this pathway as a potential new entry-point for treating dengue-associated diseases.

Does influenza A infection increase oxidative damage?

Considerable data implicate oxidative damage in influenza pathogenesis. We examined temporal changes in oxidative damage using accurate biomarkers in an adult cohort with acute influenza infection and their relationships with clinical parameters. Clinical information and blood samples were collected during their acute illness and 3 months later. A fatigue questionnaire was administered 3 months following influenza infection. Thirty-five patients (mean age, 34 years) with polymerase chain reaction-confirmed influenza A infection were included; all patients returned for follow-up assessments. Adjusted levels of plasma F2-isoprostanes, total hydroxyeicosatetraenoic products (HETEs), 7β-hydroxycholesterol and 7-ketocholesterol, serum gamma-glutamyltransferase, and high-sensitivity C-reactive protein (hsCRP) were increased during the acute illness compared with age-matched controls. Despite clinical recovery, levels of these biomarkers remained higher at month 3 compared with controls. A proportion of patients had persistent symptoms such as fatigue (23%), myalgia (14%), and arthralgia (11%) at month 3. Patients with significant fatigue had higher baseline levels of plasma F2-isoprostanes, F4-neuroprostanes, and total HETEs compared to those without fatigue. By contrast, patients with persistent arthralgia and myalgia had higher baseline levels of serum hsCRP compared to those without these symptoms. Our observations lead to the hypothesis that oxidative damage participates in the pathogenesis of influenza infection and postinfectious fatigue.

Association between proinflammatory cytokines and lipid peroxidation in patients with severe dengue disease around defervescence

OBJECTIVES

Proinflammatory cytokines and the oxidative stress response are reported to be involved in dengue viral disease. The present study investigated the correlation of proinflammatory cytokines and lipid peroxidation with dengue severity.

METHODS

Clinical samples from 27 dengue fever (DF) cases, 30 dengue haemorrhagic fever (DHF) cases, and 24 dengue shock syndrome (DSS) cases were studied around defervescence, along with samples from 30 healthy controls. Plasma samples were analysed for tumour necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) by ELISA and for malondialdehyde (MDA) by thiobarbituric acid assay.

RESULTS

Dengue-infected individuals had significantly higher levels of TNF-α, IFN-γ, and MDA in comparison to controls. The ratio of TNF-α to IFN-γ was significantly higher in DHF and DSS than in DF. A TNF-α/IFN-γ ratio value of 5.69 around defervescence predicted DHF and DSS with moderate accuracy and thus may serve as an indicator to study dengue severity. The study observed a significant positive correlation of lipid peroxides with TNF-α levels and the TNF-α/IFN-γ ratio in severe dengue cases.

CONCLUSIONS

We propose that the oxidative stress response induced by the dengue virus may trigger the inflammatory cytokine responses in dengue severity and thereby contributes to the pathogenesis of the disease; however the interplay between the oxidative response and inflammatory activity in disease virulence needs further study.

Augmentation of 5-lipoxygenase activity and expression during dengue serotype-2 infection

BACKGROUND

Leukotriene B4, a 5-lipoxygenase product of arachidonic acid with potent chemotactic effects on neutrophils, has not been assessed in dengue patients. In this study, plasma leukotriene B4 and serum high-sensitivity C-reactive protein levels were determined in adult patients during the febrile, convalescent and defervescent stages of dengue serotype-2 (DENV-2) infection, and compared with those of age-matched healthy and non-dengue febrile subjects. In vitro studies were performed to examine the effects of live and heat-inactivated DENV-2 on the activities and expression of 5-lipoxygenase in human neutrophils.

RESULTS

Plasma leukotriene B4 was elevated during the febrile stages of dengue infection compared to levels during convalescence and in study controls. Plasma leukotriene B4 also correlated with serum high-sensitivity C-reactive protein in dengue patients (febrile, r = 0.91, p < 0.001; defervescence, r = 0.87, p < 0.001; convalescence, r = 0.87, p < 0.001). Exposure of human neutrophils to DENV-2 resulted in a significant rise in leukotriene B4; the extent of increase, however, did not differ between exposure to live and heat-inactivated DENV-2. Pre-incubation of either live or heat-inactivated DENV-2 resulted in reduced leukotriene B4 release by neutrophils, indicating that contact with dengue antigens (and not replication) triggers the neutrophil response. Production of leukotriene B4 was associated with an increase in 5-lipoxygenase expression in human neutrophils; addition of MK886 (a 5-lipoxygenase activating protein inhibitor) attenuated further increase in leukotriene B4 production.

CONCLUSION

These findings provide important clinical and mechanistic data on the involvement of 5-lipoxygenase and its metabolites in dengue infection. Further studies are needed to elucidate the therapeutic implications of these findings.

Differential oxidative stress induced by dengue virus in monocytes from human neonates, adult and elderly individuals

Changes in immune response during lifespan of man are well known. These changes involve decreased neonatal and elderly immune response. In addition, it has been shown a relationship between immune and oxidative mechanisms, suggesting that altered immune response could be associated to altered oxidative response. Increased expression of nitric oxide (NO) has been documented in dengue and in monocyte cultures infected with different types of dengue virus. However, there is no information about the age-dependent NO oxidative response in humans infected by dengue virus. In this study, monocyte cultures from neonatal, elderly and adult individuals (n = 10 each group) were infected with different dengue virus types (DENV- 1 to 4) and oxidative/antioxidative responses and apoptosis were measured at days 1 and 3 of culture. Increased production of NO, lipid peroxidation and enzymatic and nonenzymatic anti-oxidative responses in dengue infected monocyte cultures were observed. However, neonatal and elderly monocytes had lower values of studied parameters when compared to those in adult-derived cultures. Apoptosis was present in infected monocytes with higher values at day 3 of culture. This reduced oxidant/antioxidant response of neonatal and elderly monocytes could be relevant in the pathogenesis of dengue disease.

Serum metabolome and lipidome changes in adult patients with primary dengue infection

Background

Dengue virus (DENV) is the most widespread arbovirus with an estimated 100 million infections occurring every year. Endemic in the tropical and subtropical areas of the world, dengue fever/dengue hemorrhagic fever (DF/DHF) is emerging as a major public health concern. The complex array of concurrent host physiologic changes has hampered a complete understanding of underlying molecular mechanisms of dengue pathogenesis.

Methodology/Principle Findings

Systems level characterization of serum metabolome and lipidome of adult DF patients at early febrile, defervescence, and convalescent stages of DENV infection was performed using liquid chromatography- and gas chromatography-mass spectrometry. The tractability of following metabolite and lipid changes in a relatively large sample size (n = 44) across three prominent infection stages allowed the identification of critical physiologic changes that coincided with the different stages. Sixty differential metabolites were identified in our metabolomics analysis and the main metabolite classes were free fatty acids, acylcarnitines, phospholipids, and amino acids. Major perturbed metabolic pathways included fatty acid biosynthesis and β-oxidation, phospholipid catabolism, steroid hormone pathway, etc., suggesting the multifactorial nature of human host responses. Analysis of phospholipids and sphingolipids verified the temporal trends and revealed association with lymphocytes and platelets numbers. These metabolites were significantly perturbed during the early stages, and normalized to control levels at convalescent stage, suggesting their potential utility as prognostic markers.

Conclusions/Significance

DENV infection causes temporally distinct serum metabolome and lipidome changes, and many of the differential metabolites are involved in acute inflammatory responses. Our global analyses revealed early anti-inflammatory responses working in concert to modulate early pro-inflammatory processes, thus preventing the host from development of pathologies by excessive or prolonged inflammation. This study is the first example of how an omic- approach can divulge the extensive, concurrent, and dynamic host responses elicited by DENV and offers plausible physiological insights to why DF is self limiting.

Dengue virus is the most widespread arbovirus and a major public health threat in the tropical and subtropical areas of the world. As yet, little is known about the molecular mechanisms underlying infection, and there is no specific treatment or vaccine that is currently effective against the disease. Metabolomics and lipidomics provide global views of metabolome and lipidome landscapes and implicate metabolic to disease phenotype. We performed serum metabolic and lipidomic profiling on a cohort of dengue patients with three sampling time points at early febrile, defervescence, and convalescent stages via mass spectrometry-based analytical platforms. Compared with healthy subjects, approximately two hundred metabolites showed significant difference in dengue patients, and 60 were identified. This study revealed that in primary dengue infection, the host metabolome is tightly regulated, with active, early anti-inflammatory processes modulating the pro-inflammatory processes, suggesting the self-limiting phenotype of dengue fever. Major perturbed metabolic pathways included fatty acid biosynthesis, fatty acid β-oxidation, phospholipid catabolism, steroid hormone pathway, etc. This represents a first report on the characterization of the serum metabolome and significantly advances our understanding on host and dengue virus interactions. These differential metabolites have the potential as biomarkers for disease monitoring and evaluation of therapeutic interventions.

Inhibitory effect of glutathione on oxidative liver injury induced by dengue virus serotype 2 infections in mice

The pathogenesis of dengue virus (DV) infection has not been completely defined and change of redox status mediated by depletion of glutathione (GSH) in host cell is a common result of viral infection. Our previous study has demonstrated that DV serotype 2 (DV2) infection alters host intracellular GSH levels, and exogenous GSH inhibits viral production by modulating the activity of NF-κB in HepG2 cells. GSH is the most powerful intracellular antioxidant and involved in viral infections. Thus, this study was to investigate whether DV2 infection can induce alteration in redox balance and effect of GSH on the disease in HepG2 xenografts SCID mice. Our results revealed that mice infected with DV2 showed alterations in oxidative stress by increasing the level of malondialdehyde (MDA), an end product of lipid peroxidation, and GSSG/GSH ratio. DV2-infected mice also showed a decrease in the activity of catalase (CAT) and total superoxide dismutase (T-SOD) in the serum and/or observed organs, especially the liver. Moreover, DV2 infection resulted in elevated serum levels of the cytokines tumor necrosis factor-α and interlukin-6 and obvious histopathological changes in the liver. The administration of exogenous GSH significantly reversed all of the aforementioned pathological changes and prevented significant liver damage. Furthermore, in vitro treatment of HepG2 cells with antioxidants such as GSH inhibited viral entry as well as the production of reactive oxygen species in HepG2 cells. These results suggest that GSH prevents DV2-induced oxidative stress and liver injury in mice by inhibiting proinflammatory cytokine production, and GSH and may be a promising therapeutic agent for prevention of oxidative liver damage during DV infection.

Reactive oxygen species regulate the replication of porcine circovirus type 2 via NF-κB pathway

Intracellular redox state has been suggested to have various effects on the replication of different viruses within host cells. The aim of the present study was to investigate the influence of reactive oxygen species (ROS) on replication of porcine circovirus type 2 (PCV2), in PK15 cells. Following PCV2 infection there was a time-dependent increase in ROS. Antioxidant N-acetyl-l-cysteine treatment of cells resulted in lower ROS levels and lower PCV2 replication. In contrast, treatment by buthionine sulfoximine (BSO), a GSH synthesis inhibitor, resulted in elevation of ROS levels and increased PCV2 replication. Furthermore, inhibiting the activity of NF-κB, a redox-responsive transcription factor, suppressed BSO-mediated increase of PCV2 replication, indicating that increased PCV2 replication likely occurs via ROS activation of NF-κB. Taken together, our results indicate that the generation of ROS during PCV2 infection is involved in its replication and this progression is associated with the alteration in NF-κB activity induced by ROS.

Oral zinc supplementation does not improve oxidative stress or vascular function in patients with type 2 diabetes with normal zinc levels

OBJECTIVE

There is considerable controversy about what constitutes optimal zinc intakes in patients with type 2 diabetes mellitus. Several studies suggest that higher zinc intakes improve vascular function and decrease oxidative damage. We aimed to assess the effects of zinc supplementation using a range of reliable biomarkers of oxidative damage and vascular function in patients with type 2 diabetes.

METHODS

Forty male type 2 diabetic patients were supplemented either with 240 mg/day of zinc as zinc gluconate (n=20) or with placebo (n=20) for 3 months. Blood and spot urine samples were taken at baseline, days 3 and 7, months 1, 2 and 3 during supplementation and 1 month after cessation. Serum zinc, reliable biomarkers of oxidative damage (F(2)-isoprostanes, neuroprostanes, cholesterol oxidation products, allantoin) as well as hydroxyeicosatetraenoic acid products and vascular-related indices (augmentation index, pulse wave velocity and aortic pressure) were measured.

RESULTS

Despite significantly higher levels of serum zinc in the treatment group, markers of oxidative damage, levels of hydroxyeicosatetraenoic acid products and vascular indices were unchanged by zinc supplementation during the four-month study period.

CONCLUSION

Improving the zinc status in patients with type 2 diabetes with normal zinc levels did not have any impact on oxidative damage and vascular function, and such supplementation may not be generally beneficial in these individuals.

Biomarkers of oxidative damage in cigarette smokers: which biomarkers might reflect acute versus chronic oxidative stress?

Cigarette smoking predisposes to the development of multiple diseases involving oxidative damage. We measured a range of oxidative damage biomarkers to understand which differ between smokers and nonsmokers and if the levels of these biomarkers change further during the act of smoking itself. Despite overnight abstinence from smoking, smokers had higher levels of plasma total and esterified F(2)-isoprostanes, hydroxyeicosatetraenoic acid products (HETEs), F(4)-neuroprostanes, 7-ketocholesterol, and 24- and 27-hydroxycholesterol. Levels of urinary F(2)-isoprostanes, HETEs, and 8-hydroxy-2'-deoxyguanosine were also increased compared with age-matched nonsmokers. Several biomarkers (plasma free F(2)-isoprostanes, allantoin, and 7β-hydroxycholesterol and urinary F(2)-isoprostane metabolites) were not elevated. The smokers were then asked to smoke a cigarette; this acute smoking elevated plasma and urinary F(2)-isoprostanes, plasma allantoin, and certain cholesterol oxidation products compared to presmoking levels, but not plasma HETEs or urinary 8-hydroxy-2'-deoxyguanosine. Smokers showed differences in plasma fatty acid composition. Our findings confirm that certain oxidative damage biomarkers are elevated in smokers even after a period of abstinence from smoking, whereas these plus some others are elevated after acute smoking. Thus, different biomarkers do not measure identical aspects of oxidative stress.

Using isoprostanes as biomarkers of oxidative stress: some rarely considered issues

The measurement of F2-isoprostanes by methods utilizing mass spectrometry is widely regarded as the best currently available biomarker of lipid peroxidation. F2-isoprostanes and their metabolites can be measured accurately in plasma, urine, and other body fluids using mass spectrometric techniques, and detailed protocols have been published in several papers. However, many clinical studies and intervention studies with diets or supplements, have employed single "spot" measurements of F2-isoprostanes on either plasma/serum or urine to estimate "oxidative stress." This review examines the validity of the common assumption that plasma and urinary F2-isoprostane measurements are equivalent. It identifies scenarios where they may not be and where "spot" measurements can be misleading, with examples from the literature. We also discuss the controversial issue of whether and how F2-isoprostane levels in plasma should be standardized against lipids, and, if so, which lipids to use.