Japanese encephalitis virus stimulates superoxide dismutase activity in rat glial cultures

Molecular and Cellular Mechanisms Underlying Neurologic Manifestations of Mosquito-Borne Flavivirus Infections

Flaviviruses are a family of enveloped viruses with a positive-sense RNA genome, transmitted by arthropod vectors. These viruses are known for their broad cellular tropism leading to infection of multiple body systems, which can include the central nervous system. Neurologic effects of flavivirus infection can arise during both acute and post-acute infectious periods; however, the molecular and cellular mechanisms underlying post-acute sequelae are not fully understood. Here, we review recent studies that have examined molecular and cellular mechanisms that may contribute to neurologic sequelae following infection with the West Nile virus, Japanese encephalitis virus, Zika virus, dengue virus, and St. Louis encephalitis virus. Neuronal death, either from direct infection or due to the resultant inflammatory response, is a common mechanism by which flavivirus infection can lead to neurologic impairment. Other types of cellular damage, such as oxidative stress and DNA damage, appear to be more specific to certain viruses. This article aims to highlight mechanisms of cellular damage that are common across several flavivirus members and mechanisms that are more unique to specific members. Our goal is to inspire further research to improve understanding of this area in the hope of identifying treatment options for flavivirus-associated neurologic changes.

Japanese Encephalitis virus infection in astrocytes modulate microglial function: Correlation with inflammation and oxidative stress

BACKGROUND

Japanese Encephalitis Virus (JEV) is a neurotropic virus which has the propensity to infect neuronal and glial cells of the brain. Astrocyte-microglia crosstalk leading to the secretion of various factors plays a major role in controlling encephalitis in brain. This study focused on understanding the role of astrocytic mediators that further shaped the microglial response towards JEV infection.

METHODS

After establishing JEV infection in C8D1A (mouse astrocyte cell line) and primary astrocyte enriched cultures (PAEC), astrocyte supernatant was used for preparation of conditioned media. Astrocyte supernatant was treated with UV to inactivate JEV and the supernatant was added to N9 culture media in ratio 1:1 for preparation of conditioned media. N9 microglial cells post treatment with astrocyte conditioned media and JEV infection were checked for expression of various inflammatory genes by qRT-PCR, levels of secreted cytokines in N9 cell supernatant were checked by cytometric bead array. N9 cell lysates were checked for expression of proteins - pNF-κβ, IBA-1, NS3 and RIG-I by western blotting. Viral titers were measured in N9 supernatant by plaque assays. Immunocytochemistry experiments were done to quantify the number of infected microglial cells after astrocyte conditioned medium treatment. Expression of different antioxidant enzymes was checked in N9 cells by western blotting, levels of reactive oxygen species (ROS) was detected by fluorimetry using DCFDA dye.

RESULTS

N9 microglial cells post treatment with JEV-infected astrocyte conditioned media and JEV infection were activated, showed an upsurge in expression of inflammatory genes and cytokines both at the transcript and protein levels. These N9 cells showed a decrease in quantity of viral titers and associated viral proteins in comparison to control cells (not treated with conditioned media but infected with JEV). Also, N9 cells upon conditioned media treatment and JEV infection were more prone to undergo oxidative stress as observed by the decreased expression of antioxidant enzymes SOD-1, TRX-1 and increased secretion of reactive oxygen species (ROS).

CONCLUSION

Astrocytic mediators like TNF-α, MCP-1 and IL-6 influence microglial response towards JEV infection by promoting inflammation and oxidative stress in them. As a result of increased microglial inflammation and secretion of ROS, viral replication is lessened in conditioned media treated and JEV infected microglial cells as compared to control cells with no conditioned media treatment but only JEV infection.

Metabolic response to CNS infection with flaviviruses

Flaviviruses are arthropod-borne RNA viruses found worldwide that, when introduced into the human body, cause diseases, including neuroinfections, that can lead to serious metabolic consequences and even death. Some of the diseases caused by flaviviruses occur continuously in certain regions, while others occur intermittently or sporadically, causing epidemics. Some of the most common flaviviruses are West Nile virus, dengue virus, tick-borne encephalitis virus, Zika virus and Japanese encephalitis virus. Since all the above-mentioned viruses are capable of penetrating the blood-brain barrier through different mechanisms, their actions also affect the central nervous system (CNS). Like other viruses, flaviviruses, after entering the human body, contribute to redox imbalance and, consequently, to oxidative stress, which promotes inflammation in skin cells, in the blood and in CNS. This review focuses on discussing the effects of oxidative stress and inflammation resulting from pathogen invasion on the metabolic antiviral response of the host, and the ability of viruses to evade the consequences of metabolic changes or exploit them for increased replication and further progression of infection, which affects the development of sequelae and difficulties in therapy.

Fundamental neurochemistry review: Glutamatergic dysfunction as a central mechanism underlying flavivirus-induced neurological damage

The Flaviviridae family comprises positive-sense single-strand RNA viruses mainly transmitted by arthropods. Many of these pathogens are especially deleterious to the nervous system, and a myriad of neurological symptoms have been associated with infections by Zika virus (ZIKV), West Nile virus (WNV), and Japanese encephalitis virus (JEV) in humans. Studies suggest that viral replication in neural cells and the massive release of pro-inflammatory mediators lead to morphological alterations of synaptic spine structure and changes in the balance of excitatory/inhibitory neurotransmitters and receptors. Glutamate is the predominant excitatory neurotransmitter in the brain, and studies propose that either enhanced release or impaired uptake of this amino acid contributes to brain damage in several conditions. Here, we review existing evidence suggesting that glutamatergic dysfunction-induced by flaviviruses is a central mechanism for neurological damage and clinical outcomes of infection. We also discuss current data suggesting that pharmacological approaches that counteract glutamatergic dysfunction show benefits in animal models of such viral diseases.

Japanese Encephalitis Virus Infection Causes an Imbalance in the Activation of Mitochondrial Fusion/Fission Genes and Triggers the Activation of NOX2-mediated Oxidative Stress and Neuronal Cell Death

Mitochondria dysfunction may be an important contributor to Japanese encephalitis (JE) viral infection disease pathogenesis. In the current study, we define whether changes in mitochondrial DNA copy number (which is the biomarker for mitochondrial function) and alteration in mitochondria dynamics (fusion and fission) contribute to the pathology of the JE virus in vivo mice model. We found decreased mitochondria copy number, reduced activation of mitochondrial fission (FIS1/DRP1), and increased activation of mitochondrial fusion (MFN1/MFN2/OPA1) genes that are associated with increased NOX2-mediated ROS generation and neuronal cell death following JE virus infection. Furthermore, we found that antioxidant glutathione level decreases. In summary, the following study demonstrates that JE viral infection causes an imbalance in mitochondrial fission/fusion gene activation and promotes NOX2-mediated oxidative stress and cell death, suggesting that intervention in mitochondrial dynamics might be a potential therapeutic strategy for combating oxidative stress and inflammatory process in JE viral infection.

Japanese Encephalitis Virus-Infected Cells

RNA virus infections have been a leading cause of pandemics. Aided by global warming and increased connectivity, their threat is likely to increase over time. The flaviviruses are one such RNA virus family, and its prototypes such as the Japanese encephalitis virus (JEV), Dengue virus, Zika virus, West Nile virus, etc., pose a significant health burden on several endemic countries. All viruses start off their life cycle with an infected cell, wherein a series of events are set in motion as the virus and host battle for autonomy. With their remarkable capacity to hijack cellular systems and, subvert/escape defence pathways, viruses are able to establish infection and disseminate in the body, causing disease. Using this strategy, JEV replicates and spreads through several cell types such as epithelial cells, fibroblasts, monocytes and macrophages, and ultimately breaches the blood-brain barrier to infect neurons and microglia. The neurotropic nature of JEV, its high burden on the paediatric population, and its lack of any specific antivirals/treatment strategies emphasise the need for biomedical research-driven solutions. Here, we highlight the latest research developments on Japanese encephalitis virus-infected cells and discuss how these can aid in the development of future therapies.

Host cell stress response as a predictor of COVID-19 infectivity and disease progression

The coronavirus disease (COVID-19) caused by a coronavirus identified in December 2019 has caused a global pandemic. COVID-19 was declared a pandemic in March 2020 and has led to more than 6.3 million deaths. The pandemic has disrupted world travel, economies, and lifestyles worldwide. Although vaccination has been an effective tool to reduce the severity and spread of the disease there is a need for more concerted approaches to fighting the disease. COVID-19 is characterised as a severe acute respiratory syndrome . The severity of the disease is associated with a battery of comorbidities such as cardiovascular diseases, cancer, chronic lung disease, and renal disease. These underlying diseases are associated with general cellular stress. Thus, COVID-19 exacerbates outcomes of the underlying conditions. Consequently, coronavirus infection and the various underlying conditions converge to present a combined strain on the cellular response. While the host response to the stress is primarily intended to be of benefit, the outcomes are occasionally unpredictable because the cellular stress response is a function of complex factors. This review discusses the role of the host stress response as a convergent point for COVID-19 and several non-communicable diseases. We further discuss the merits of targeting the host stress response to manage the clinical outcomes of COVID-19.

Pathobiology of Japanese encephalitis virus infection

Japanese encephalitis virus (JEV) is a flavivirus, spread by the bite of carrier Culex mosquitoes. The subsequent disease caused is Japanese encephalitis (JE), which is the leading global cause of virus-induced encephalitis. The disease is predominant in the entire Asia-Pacific region with the potential of global spread. JEV is highly neuroinvasive with symptoms ranging from mild fever to severe encephalitis and death. One-third of JE infections are fatal, and half of the survivors develop permanent neurological sequelae. Disease prognosis is determined by a series of complex and intertwined signaling events dictated both by the virus and the host. All flaviviruses, including JEV replicate in close association with ER derived membranes by channelizing the protein and lipid components of the ER. This leads to activation of acute stress responses in the infected cell-oxidative stress, ER stress, and autophagy. The host innate immune and inflammatory responses also enter the fray, the components of which are inextricably linked to the cellular stress responses. These are especially crucial in the periphery for dendritic cell maturation and establishment of adaptive immunity. The pathogenesis of JEV is a combination of direct virus induced neuronal cell death and an uncontrolled neuroinflammatory response. Here we provide a comprehensive review of the JEV life cycle and how the cellular stress responses dictate the pathobiology and resulting immune response. We also deliberate on how modulation of these stress pathways could be a potential strategy to develop therapeutic interventions, and define the persisting challenges.

ROS/RNS Balancing, Aerobic Fermentation Regulation and Cell Cycle Control - a Complex Early Trait ('CoV-MAC-TED') for Combating SARS-CoV-2-Induced Cell Reprogramming

In a perspective entitled 'From plant survival under severe stress to anti-viral human defense' we raised and justified the hypothesis that transcript level profiles of justified target genes established from in vitro somatic embryogenesis (SE) induction in plants as a reference compared to virus-induced profiles can identify differential virus signatures that link to harmful reprogramming. A standard profile of selected genes named 'ReprogVirus' was proposed for in vitro-scanning of early virus-induced reprogramming in critical primary infected cells/tissues as target trait. For data collection, the 'ReprogVirus platform' was initiated. This initiative aims to identify in a common effort across scientific boundaries critical virus footprints from diverse virus origins and variants as a basis for anti-viral strategy design. This approach is open for validation and extension. In the present study, we initiated validation by experimental transcriptome data available in public domain combined with advancing plant wet lab research. We compared plant-adapted transcriptomes according to 'RegroVirus' complemented by alternative oxidase (AOX) genes during de novo programming under SE-inducing conditions with in vitro corona virus-induced transcriptome profiles. This approach enabled identifying a major complex trait for early de novo programming during SARS-CoV-2 infection, called 'CoV-MAC-TED'. It consists of unbalanced ROS/RNS levels, which are connected to increased aerobic fermentation that links to alpha-tubulin-based cell restructuration and progression of cell cycle. We conclude that anti-viral/anti-SARS-CoV-2 strategies need to rigorously target 'CoV-MAC-TED' in primary infected nose and mouth cells through prophylactic and very early therapeutic strategies. We also discuss potential strategies in the view of the beneficial role of AOX for resilient behavior in plants. Furthermore, following the general observation that ROS/RNS equilibration/redox homeostasis is of utmost importance at the very beginning of viral infection, we highlight that 'de-stressing' disease and social handling should be seen as essential part of anti-viral/anti-SARS-CoV-2 strategies.

Stress proteins: the biological functions in virus infection, present and challenges for target-based antiviral drug development

Stress proteins (SPs) including heat-shock proteins (HSPs), RNA chaperones, and ER associated stress proteins are molecular chaperones essential for cellular homeostasis. The major functions of HSPs include chaperoning misfolded or unfolded polypeptides, protecting cells from toxic stress, and presenting immune and inflammatory cytokines. Regarded as a double-edged sword, HSPs also cooperate with numerous viruses and cancer cells to promote their survival. RNA chaperones are a group of heterogeneous nuclear ribonucleoproteins (hnRNPs), which are essential factors for manipulating both the functions and metabolisms of pre-mRNAs/hnRNAs transcribed by RNA polymerase II. hnRNPs involve in a large number of cellular processes, including chromatin remodelling, transcription regulation, RNP assembly and stabilization, RNA export, virus replication, histone-like nucleoid structuring, and even intracellular immunity. Dysregulation of stress proteins is associated with many human diseases including human cancer, cardiovascular diseases, neurodegenerative diseases (e.g., Parkinson’s diseases, Alzheimer disease), stroke and infectious diseases. In this review, we summarized the biologic function of stress proteins, and current progress on their mechanisms related to virus reproduction and diseases caused by virus infections. As SPs also attract a great interest as potential antiviral targets (e.g., COVID-19), we also discuss the present progress and challenges in this area of HSP-based drug development, as well as with compounds already under clinical evaluation.

Progressive Rotavirus Infection Downregulates Redox-Sensitive Transcription Factor Nrf2 and Nrf2-Driven Transcription Units

Eukaryotic cells adopt highly tuned stress response physiology under threats of exogenous stressors including viruses to maintain cellular homeostasis. Not surprisingly, avoidance of cellular stress response pathways is an essential facet of virus-induced obligatory host reprogramming to invoke a cellular environment conducive to viral perpetuation. Adaptive cellular responses to oxidative and electrophilic stress are usually taken care of by an antioxidant defense system, core to which lies the redox-responsive transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and Nrf2-driven transcriptional cascade. Deregulation of host redox balance and redox stress-sensitive Nrf2 antioxidant defense have been reported for many viruses. In the current study, we aimed to study the modulation of the Nrf2-based host cellular redox defense system in response to Rotavirus (RV) infection in vitro. Interestingly, we found that Nrf2 protein levels decline sharply with progression of RV infection beyond an initial upsurge. Moreover, Nrf2 decrease as a whole was found to be accompanied by active nuclear vacuity of Nrf2, resulting in lowered expression of stress-responsive Nrf2 target genes heme oxygenase-1 (HO-1), NAD(P)H quinone dehydrogenase 1, and superoxide dismutase 1 both in the presence and absence of Nrf2-driven transcriptional inducers. Initial induction of Nrf2 concurred with RV-induced early burst of oxidative stress and therefore was sensitive to treatments with antioxidants. Reduction of Nrf2 levels beyond initial hours, however, was found to be independent of the cellular redox status. Furthermore, increasing the half-life of Nrf2 through inhibition of the Kelch-like erythroid cell-derived protein with CNC homology- (ECH-) associated protein 1/Cullin3-RING Box1-based canonical Nrf2 turnover pathway could not restore Nrf2 levels post RV-SA11 infection. Depletion of the Nrf2/HO-1 axis was subsequently found to be sensitive to proteasome inhibition with concurrent observation of increased K48-linked ubiquitination associated with Nrf2. Together, the present study describes robust downregulation of Nrf2-dependent cellular redox defense beyond initial hours of RV infection, justifying our previous observation of potent antirotaviral implications of Nrf2 agonists.

Molecular Design, Synthesis, and Biological Evaluation of 2-Hydroxy-3-Chrysino Dithiocarbamate Derivatives

A series of 2-hydroxy-3-chrysino dithiocarbamate derivatives (3a–k) were designed, synthesized, and characterized for their structure determination by ¹H NMR, ¹³C NMR, and HRMS (ESI) spectral data. They were screened for their in vitro biological activities against a panel of selected bacterial and fungal strains. These antimicrobial studies indicate that some of the analogues manifested significant activity compared to standard drugs. Among the synthetic analogues (3a–k), compounds 3d, 3f, and 3j exhibited very good antibacterial activity and compounds 3d, 3f, and 3h showed very good antifungal activity compared to the standard drugs penicillin and itrazole, respectively. The compounds 3e, 3g, and 3h showed moderate antibacterial activity and the compounds 3j and 3k showed moderate antifungal activity. Molecular docking studies were performed and the experimental antimicrobial screening results were also correlated with the binding energy values obtained by molecular docking. The synthesized chrysin analogues (3a–k) have obeyed Lipinski’s “rule of five” and have drug-likeness.

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.

A study of glutamate levels, NR1, NR2A, NR2B receptors and oxidative stress in rat model of Japanese encephalitis

There is paucity of studies on the role of glutamate excitotoxicity in cell damage in Japanese encephalitis. In this study the glutamate levels and its NMDA receptors, and oxidative stress markers in different brain regions have been evaluated and correlated with neurobehavioral changes at different time points. Twelve day old Wistar rats were inoculated with 3×10⁶pfu/ml intracerebrally. The neurobehavioral effects were evaluated by spontaneous locomotor activity (SLA), grip strength and rota rod test on 10, 33 and 48days post inoculation (dpi). Glutamate level was evaluated by enzyme linked immunosorbent assay, mRNA gene expression of ionotropic glutamate receptors N-methyl d-aspartate (NMDA) receptor 1, 2A and 2B (NR1, NR2A and NR2B) were evaluated by real time PCR. Malondialdehyde (MDA), glutathione (GSH) and glutathione peroxidase (GPx) levels were measured by spectrophotometer in different brain regions of JEV infected rats on 10, 33 and 48dpi. There was significant increase in motor deficit, grip strength and decreased locomotor activity on 10 and 33dpi. Glutamate levels were increased in thalamus, midbrain, frontal cortex, striatum and cerebellum on 10 and 33dpi and were followed by a recovery on 48dpi. Glutamate NMDR receptors NR1, NR2A and NR2B were reduced in thalamus, midbrain, frontal cortex, striatum and cerebellum on 10dpi which was followed by recovery after 33dpi. A significant increase in MDA level in thalamus, midbrain, frontal cortex, striatum and cerebellum was noted on 10 and 33dpi. The antioxidant GSH and GPx were significantly reduced in these brain regions on 10 and 33dpi. Glutamate, MDA, GSH and GPx correlated in different brain regions as the disease progress. Increased Glutamate level may be related to oxidative stress and may be responsible for behavioral alterations in rat model of Japanese encephalitis.

Implications of oxidative stress on viral pathogenesis

Reactive species are frequently formed after viral infections. Antioxidant defences, including enzymatic and non-enzymatic components, protect against reactive species, but sometimes these defences are not completely adequate. An imbalance in the production of reactive species and the body's inability to detoxify these reactive species is referred to as oxidative stress. The aim of this review is to analyse the role of oxidative stress in the pathogenesis of viral infections and highlight some major therapeutic approaches that have gained importance, with regards to controlling virus-induced oxidative injury. Attention will be focused on DNA viruses (papillomaviruses, hepadnaviruses), RNA viruses (flaviviruses, orthomyxoviruses, paramyxoviruses, togaviruses) and retroviruses (human immunodeficiency virus). In general, viruses cause an imbalance in the cellular redox environment, which depending on the virus and the cell can result in different responses, e.g. cell signaling, antioxidant defences, reactive species, and other processes. Therefore, the modulation of reactive species production and oxidative stress potentially represents a novel pharmacological approach for reducing the consequences of viral pathogenesis.

Dengue Virus-Induced Reactive Oxygen Species Production in Rat Microglial Cells

Encephalitis has been described worldwide as a severe complication in patients infected by dengue virus. Reactive oxygen species (ROS) production is a key mechanism involved in the neuronal damage caused by viral encephalitis. In the present study, the capability of dengue virus serotypes 2 (DENV2) and DENV4 to induce ROS production was investigated in a rat microglial cell line, HAPI cells. The cells were infected with DENV2 and DENV4 at a multiplicity of infection of 0.1 for a 2-h adsorption period. Japanese encephalitis virus (JEV) was used as the reference. DENV2- and DENV4-induced microglial activation and significantly increased ROS production corresponded to decreased cell viability. The activity of DENV4 was significantly higher than the activities of DENV2 and JEV at 48 and 72 h post infection. DENV4 partly induced ROS production via an iron-induced Fenton reaction, as demonstrated by the treatment with an iron chelator, deferiprone. Despite the induction of increased inducible nitric oxide synthase expression and nitric oxide (NO) production by JEV, DENV2, and DENV4 did not induce NO production, suggesting the activation of different pathways in response to infections by different viruses. In conclusion, DENV2 and DENV4 have the capability to induce ROS production and activate microglia, which have been reported as the key components of neuronal damage.

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.

Oxidative stress in murine Theiler's virus-induced temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of acquired epilepsy that can be caused by several inciting events including viral infections. However, one-third of TLE patients are pharmacoresistant to current antiepileptic drugs and therefore, there is an urgent need to develop antiepileptogenic therapies that prevent the development of the disease. Oxidative stress and redox alterations have recently been recognized as important etiological factors contributing to seizure-induced neuronal damage. The goal of this study was to determine if oxidative stress occurs in the TMEV (Theiler's murine encephalomyelitis virus) model of temporal lobe epilepsy (TLE). C57Bl/6 mice were injected with TMEV or with PBS intracortically and observed for acute seizures. At various time points after TMEV injection, hippocampi were analyzed for levels of reduced glutathione (GSH), oxidized glutathione (GSSG) and 3-nitrotyrosine (3 NT). Mice infected with TMEV displayed behavioral seizures between days 3 and 7 days post-infection (dpi). The intensity of seizures increased over time with most of the seizures being a stage 4 or 5 on the Racine scale at 6 days p.i. Mice exhibiting at least one seizure during the observation period were utilized for the biochemical analyses. The levels of GSH were significantly depleted in TMEV infected mice at 3, 4 and 14 days p.i. with a concomitant increase in GSSH levels as well as an impairment of the redox status. Additionally, there was a substantial increase in 3 NT levels in TMEV infected mice at these time points. These redox changes correlated with the occurrence of acute seizures in this model. Interestingly, we did not see changes in any of the indices in the cerebellum of TMEV-infected mice at 3 dpi indicating that these alterations are localized to the hippocampus and perhaps other limbic regions. This is the first study to demonstrate the occurrence of oxidative stress in the TMEV model of infection-induced TLE. The redox alterations were observed at time points coinciding with the appearance of acute behavioral seizures suggesting that these changes might be a consequence of seizure activity. Our results support the hypothesis that redox changes correlate with seizure activity in acquired epilepsies, regardless of the inciting insults, and suggest oxidative stress as a potential therapeutic target for their treatment.

Oxidative stress influences positive strand RNA virus genome synthesis and capping

Flaviviruses are 5′ capped positive-stranded RNA viruses that replicate their genomes within endoplasmic reticulum-derived vesicles. Flaviviruses are well known to induce oxidative stress late in infection but it is unknown if oxidative stress plays a positive role in the viral RNA replication cycle. We therefore examined how oxidation affects flavivirus RNA replication. We found that antioxidant treatment reduced virus production, reduced the viral positive-to-negative strand RNA ratio, and resulted in the accumulation of uncapped positive-sense viral RNAs. Treatment of the NS5 RNA capping enzyme in vitro with oxidizing agents enhanced guanylyltransferase activity, indicating that the guanylyltransferase function of the flavivirus NS5 RNA capping enzyme is activated by oxidative conditions. Antioxidant treatment also reduced alphavirus RNA replication and protein expression while enhancing nsP1 capping activity. These findings suggest that RNA viruses may utilize oxidative stress induced during infection to help temporally control genome RNA capping and genome replication.

Ultrasound-enhanced protective effect of tetramethylpyrazine against cerebral ischemia/reperfusion injury

In traditional Chinese medicine, Ligusticum wallichii (Chuan Xiong) and its bioactive ingredient, tetramethylpyrazine (TMP), have been used to treat cardiovascular diseases and to relieve various neurological symptoms, such as those associated with ischemic injury. In the present study, we investigated whether ultrasound (US) exposure could enhance the protective effect of TMP against cerebral ischemia/reperfusion (I/R) injury. Glutamate-induced toxicity to pheochromocytoma (PC12) cells was used to model I/R injury. TMP was paired with US to examine whether this combination could alleviate glutamate-induced cytotoxicity. The administration of TMP effectively protected cells against glutamate-induced apoptosis, which could be further enhanced by US-mediated sonoporation. The anti-apoptotic effect of TMP was associated with the inhibition of oxidative stress and a change in the levels of apoptosis-related proteins, Bcl-2 and Bax. Furthermore, TMP reduced the expression of proinflammatory cytokines such as TNF-α and IL-8, which likely also contributes to its cytoprotective effects. Taken together, our findings suggest that ultrasound-enhanced TMP treatment might be a promising therapeutic strategy for ischemic stroke. Further study is required to optimize ultrasound treatment parameters.

Antioxidants: potential antiviral agents for Japanese encephalitis virus infection

Japanese encephalitis (JE) is prevalent throughout eastern and southern Asia and the Pacific Rim. It is caused by the JE virus (JEV), which belongs to the family Flaviviridae. Despite the importance of JE, little is known about its pathogenesis. The role of oxidative stress in the pathogenesis of viral infections has led to increased interest in its role in JEV infections. This review focuses mainly on the role of oxidative stress in the pathogenesis of JEV infection and the antiviral effect of antioxidant agents in inhibiting JEV production. First, this review summarizes the pathogenesis of JE. The pathological changes include neuronal death, astrocyte activation, and microglial proliferation. Second, the relationship between oxidative stress and JEV infection is explored. JEV infection induces the generation of oxidants and exhausts the supply of antioxidants, which activates specific signaling pathways. Finally, the therapeutic efficacy of a variety of antioxidants as antiviral agents, including minocycline, arctigenin, fenofibrate, and curcumin, was studied. In conclusion, antioxidants are likely to be developed into antiviral agents for the treatment of JE.

TNF-α and IL-1β mediate Japanese encephalitis virus-induced RANTES gene expression in astrocytes

Infection with Japanese encephalitis virus (JEV) causes neuroinfection and neuroinflammation characterized by profound neuronal destruction/dysfunction, concomitant microgliosis/astrogliosis, and production of various molecules that initiate the recruitment of immune cells to the sites of infection. Previously, we reported that glial cells expressed RANTES (regulated upon activation, normal T cell expressed and secreted) with chemotactic activity in response to JEV infection. In this study, we further demonstrated that JEV-infected microglia had an additional activity in regulating RANTES production. Both astrocytes and microglia responded to JEV infection by releasing RANTES through a process likely related to viral replication. Independent of infectious virus, supernatants of JEV-infected microglia, but not JEV-infected astrocytes, caused additional RANTES production from astrocytes. Antibody neutralization studies suggested the potential involvement of tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) in mediating additional RANTES production. Treatment of astrocyte cultures with TNF-α and IL-1β caused activation of several signaling molecules and transcription factors crucial to RANTES gene expression, including reactive oxygen species, extracellular signal-regulated kinase, NF-κB, and NF-IL6, increased RANTES gene promoter activity, and provoked RANTES production. As with RANTES, neutralization of bioactive TNF-α and IL-1β caused an attenuation of chemotactic activity from supernatants of mixed glia containing astrocytes and microglia during the course of JEV infection. In conclusion, TNF-α and IL-1β produced by JEV-infected microglia might trigger another mechanism which induces a secondary wave of RANTES gene expression by activating astrocytes. The released RANTES from glial cells might play a role in the recruitment of immune cells during JEV infection.

Increased mitochondrial superoxide dismutase expression and lowered production of reactive oxygen species during rotavirus infection

Rotaviruses are responsible for severe diarrhea in infants and substantial economic losses in animal husbandry worldwide. We investigated the oxidant/antioxidant status in rotavirus-infected human colon adenocarcinoma (Caco-2) cell line. Our results show that within the initial 48 h of infection the expression of the mitochondrial superoxide dismutase (MnSOD) is significantly increased, which correlates with a decrease in reactive oxygen species production, and with a lack of cellular glutathione depletion. During this period the mitochondria display a hyperpolarization of the inner membrane, which leads to an increased mitochondrial membrane potential. No increase in apoptosis was detected in the infected cultures. In contrast to many viral infections which cause redox imbalance in host cells, the described virus-host interaction suggests that rotavirus infection does not lead to an induction of oxidative stress, possibly to prolong cell survival and to allow for accumulation of viral particles before cell destruction and virus release.

Japanese encephalitis virus infection activates caspase-8 and -9 in a FADD-independent and mitochondrion-dependent manner

Japanese encephalitis virus (JEV), a mosquito-borne flavivirus, replicates primarily at the endoplasmic reticulum and thereby triggers apoptosis of infected cells. This study investigated the hierarchical activation of the caspase network induced by JEV infection. It was found that JEV activated the initiators caspase-8 and -9, as well as effector caspase-3, in infected baby hamster kidney and mouse neuroblastoma (N18) cells. In neuronal N18 cells, JEV infection triggered cytochrome c release from mitochondria, which in turn activated caspase-9 and -3. Treatment of JEV-infected N18 cells with cyclosporin A or ruthenium red, which attenuate mitochondrial injuries, blocked activation of caspase-9 or -3, typifying that, in neuronal cells, this apoptosis involves the mitochondrial pathway. Alternatively, in caspase-3-deficient MCF-7 cells, JEV persisted and readily triggered a typical apoptotic response, including cytochrome c release and full activation of caspase-9 and -8 along with caspase-6, indicating that JEV did not require caspase-3 to manifest caspase-8 activation and apoptosis. Interestingly, a Fas-associated death-domain-containing protein (FADD) dominant-negative mutant, which interfered with transmission of the extracellular death signals into cells through the Fas/tumour necrosis factor (TNF) receptor, failed to block JEV-induced apoptosis and caspase-8 activation, implying that receptor oligomerization of the Fas/TNF pathway might not participate in JEV-induced apoptosis. Taken together, these results illustrate that JEV infection triggers caspase cascades involving the initiators caspase-8 and -9, probably through FADD-independent but mitochondrion-dependent pathways.

Herpes simplex virus type 1 infection induces oxidative stress and the release of bioactive lipid peroxidation by-products in mouse P19N neural cell cultures

To determine whether herpes simplex virus type 1 (HSV-1) infection causes oxidative stress and lipid peroxidation in cultured neural cells, mouse P19 embryonal carcinoma cells were differentiated into cells with neural phenotypes (P19N cells) by retinoic acid and were then infected with HSV-1. Cellular levels of reactive oxygen species (ROS) and the release of lipid peroxidation by-products into the tissue culture medium were then measured by the generation of fluorescent markers hydroxyphenyl fluorescein and a stable chromophore produced by lipid peroxidation products, malondialdehyde (MDA) and hydroxyalkenals (4-HAEs; predominantly 4-hydroxy-2-nonenal [HNE]), respectively. HSV-1 infection increased ROS levels in neural cells as early as 1 h post infection (p.i.) and ROS levels remained elevated at 24 h p.i. This viral effect required viral entry and replication as heat- and ultraviolet light-inactivated HSV-1 were ineffective. HSV-1 infection also was associated with increased levels of MDA/HAE in the culture medium at 2 and 4 h p.i., but MDA/HAE levels were not different from those detected in mock infected control cultures at 1, 6, and 24 h p.i. HSV-1 replication in P19N cells was inhibited by the antioxidant compound ebselen and high concentrations of HNE added to the cultures, but was increased by low concentrations of HNE. These findings indicate that HSV-1 infection of neural cells causes oxidative stress that is required for efficient viral replication. Furthermore, these observations raise the possibility that soluble, bioactive lipid peroxidation by-products generated in infected neural cells may be important regulators of HSV-1 pathogenesis in the nervous system.

Proinflammatory mediators released by activated microglia induces neuronal death in Japanese encephalitis

While a number of studies have documented the importance of microglia in central nervous system (CNS) response to injury, infection and disease, little is known regarding its role in viral encephalitis. We therefore, exploited an experimental model of Japanese Encephalitis, to better understand the role played by microglia in Japanese Encephalitis Virus (JEV) infection. Lectin staining performed to assess microglial activation indicated a robust increase in reactive microglia following infection. A difference in the topographic distribution of activated, resting, and phagocytic microglia was also observed. The levels of various proinflammatory mediators, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (Cox-2), IL-6, IL-1beta, TNF-alpha, and MCP-1 that have been implicated in microglial response to an activational state was significantly elevated following infection. These cytokines exhibited region selective expression in the brains of infected animals, with the highest expression observed in the hippocampus. Moreover, the expression of neuronal specific nuclear protein NeuN was markedly downregulated during progressive infection indicating neuronal loss. In vitro studies further confirmed that microglial activation and subsequent release of various proinflammatory mediators induces neuronal death following JEV infection. Although initiation of immune responses by microglial cells is an important protective mechanism in the CNS, unrestrained inflammatory responses may result in irreparable brain damage. Our findings suggest that the increased microglial activation following JEV infection influences the outcome of viral pathogenesis. It is likely that the increased microglial activation triggers bystander damage, as the animals eventually succumb to infection.

Oxidative stress in vero cells infected with vesicular stomatitis virus

Viral-induced apoptosis might be mediated by oxidative stress. It has already been described that cell death in vesicular stomatitis virus (VSV)-infected cells occurs by apoptosis. In this study, oxidative stress parameters present in VSV-infected Vero cells were analyzed. Lipid peroxides (LP) were evaluated in cellular extracts and expressed as thiobarbituric acid-reactive substances. LP levels exhibited a rise at different times post infection, according to the multiplicity of infection (MOI), while the presence of cycloheximide determined a reduction on LP. Also, an increase in protein degradation products and a decrease in polyunsaturated fatty acids content was observed, indicating that cellular proteins and lipids began to be susceptible to degradation during VSV infection. In addition, we analyzed cell viability of VSV-infected Vero cells, which were incubated in the presence of butylated hydroxyanisole. This antioxidant was able to protect Vero cells, at least at MOIs assayed in this study, and to reduce viral yield only when VSV infection was done at MOI 0.05. Further, superoxide dismutases, which occupy the first step within the antioxidant enzyme cascade, also exhibit a rise in VSV-infected Vero cells, at different MOI. These results suggest that both an oxidative stress and an antioxidative cell response precede the induction of apoptosis by VSV.

Antiviral effect of dehydroepiandrosterone on Japanese encephalitis virus infection

Japanese encephalitis virus (JEV), which causes neurological disorders, completes its life cycle and triggers apoptotic cell death in infected cells. Dehydroepiandrosterone (DHEA), an adrenal-derived steroid, has been implicated in protection against neurotoxicity and protection of animals from viral-induced encephalitis, resulting in an increased survival rate of the animals. Currently, the mechanisms underlying the beneficial effects of DHEA against the virus are largely unknown. In this study, DHEA suppression of JEV replication and virus-induced apoptosis in murine neuroblastoma (N18) cells was investigated. It was found that DHEA suppressed JEV-induced cytopathic effects, JEV-induced apoptotic cell death and JEV propagation in a concentration-dependent manner. Antiviral activity was more efficient in cultures treated with DHEA immediately after viral adsorption compared with that in cultures receiving delayed administration after adsorption or transient exposure before adsorption. JEV-induced cytotoxicity was accompanied by the inactivation of extracellular signal-regulated protein kinase (ERK). Inactivation of ERK by JEV infection was reversed by DHEA. When cells were treated with the ERK inhibitor U0126, DHEA lost its antiviral effect. Activation of ERK by anisomycin mimicked the action of DHEA in suppressing JEV-induced cytotoxicity. DHEA-related compounds, such as its sulfate ester (DHEAS) and pregnenolone, were unable to suppress JEV-induced cytotoxicity and ERK inactivation. The hormone-receptor antagonists ICI 182780 and flutamide failed to abrogate the antiviral effect of DHEA. These findings suggest that the antiviral effect of DHEA is not linked directly to the genomic steroid-receptor pathways and suggest that the signalling pathways of ERK play a role in the antiviral action of DHEA.

Tetramethylpyrazine reduces ischemic brain injury in rats

Tetramethylpyrazine (TMP), which is widely used in the treatment of ischemic stroke by Chinese herbalists, is one of the most important active ingredients of the traditional Chinese herbal medicine, Ligusticum wallichii Franchat (Chung Xiong). However, the mechanism by which TMP protects the brain is still not clear. We examined neuroprotective effects of TMP after transient focal cerebral ischemia using common carotid artery and middle cerebral artery occlusion model in rats and evaluated the involvement of anti-inflammation. TMP administrated intraperitoneally significantly protected the brain against ischemic insult as evidenced by the reduction in infarction volume, preservation of neurons, and decrease in brain edema. TMP markedly reduced cerebral ischemia/reperfusion-induced inflammatory cell activation and proinflammatory mediator production. Moreover, TMP suppressed lipopolysaccharide/interferon-gamma-induced inflammation and prostaglandin E(2) production in cultured glial cells. Our findings suggest that one of neuroprotective effects of TMP against ischemic brain injury might involve its anti-inflammatory potential.

Upregulation of RANTES gene expression in neuroglia by Japanese encephalitis virus infection

Infection with Japanese encephalitis virus (JEV) causes cerebral inflammation and stimulates inflammatory cytokine expression. Glial cells orchestrate immunocyte recruitment to focal sites of viral infection within the central nervous system (CNS) and synchronize immune cell functions through a regulated network of cytokines and chemokines. Since immune cell infiltration is prominent, we investigated the production of a responding chemoattractant, RANTES (regulated upon activation, normal T-cell expressed and secreted), in response to JEV infection of glial cells. Infection with JEV was found to elicit the production of RANTES from primary neurons/glia, mixed glia, microglia, and astrocytes but not from neuron cultures. The production of RANTES did not seem to be directly responsible for JEV-induced neuronal death but instead contributed to the recruitment of immune cells. RANTES expression required viral replication and the activation of extracellular signal-regulated kinase (ERK) as well as transcription factors, including nuclear factor kappa B (NF-kappaB) and nuclear factor IL-6 (NF-IL-6). The induction of RANTES expression by JEV infection in glial cells needed the coordinate activation of NF-kappaB and NF-IL-6. Using enzymatic inhibitors, we demonstrated a strong correlation between the ERK signaling pathway and RANTES expression. However, JEV replication was not dependent on the activation of ERK, NF-kappaB, and NF-IL-6. Altogether, these results demonstrated that infection of glial cells by JEV provided the early ERK-, NF-kappaB-, and NF-IL-6-mediated signals that directly activated RANTES expression, which might be involved in the initiation and amplification of inflammatory responses in the CNS.

The two faces of L-DOPA: benefits and adverse side effects in the treatment of Encephalitis lethargica, Parkinson’s disease, multiple sclerosis and amyotrophic lateral sclerosis

Parkinson's disease, encephalitis lethargica, multiple sclerosis and amyotrophic lateral sclerosis patients all display two distinct types of symptoms. Some of these are due directly to a deficiency of dopamine and are quickly reduced by laevodihydroxyphenylalanine (L-DOPA). The second set, however, are the result of neurological damage caused by metabolites of dopamine, which include dopachrome and other chrome indoles that are both hallucinogenic and neurotoxic. If this hypothesis is correct, three corollaries follow. Patients of all four disorders should display excessive oxidative stress, natural methyl acceptors should delay development and elevated antioxidant supplementation, given with L-DOPA, ought to prolong the "honeymoon" period in which the benefits of the drug out weigh its subsequent disadvantages. A literature review suggests that all three corollaries are probably correct.

Common host genes are activated in mouse brain by Japanese encephalitis and rabies viruses

This study identified nine genes whose expression is upregulated in the central nervous system (CNS) of mice during Japanese encephalitis virus (JEV) infection. These include: cathepsin S, oligoadenylate synthetase (OAS), GARG49/IRG2, lymphocyte antigen-6A (Ly-6A), macrophage activation gene-2 (Mpa2), early growth response gene1 (Egr1), pyrimidine 5'-nucleotidase (P5N), apolipoprotein D (ApoD) and STAT1. Activation of all nine genes during JEV infection was confirmed by Northern blot analysis. JEV replication was inhibited in the majority of mice immunized with Biken JEV vaccine, and these mice also exhibited reduced expression of JEV-inducible CNS genes. Thus, there is a good correlation between virus load and upregulation of host CNS genes. It was also demonstrated that all the CNS genes activated by JEV are also upregulated during rabies virus infection. In addition, GARG49, STAT1, cathepsin S and ApoD are known to be upregulated in the CNS by Sindbis virus, an alphavirus, and this supports the proposal that common host cell pathways are activated in the CNS by different neurotropic viruses.