Role of nitric oxide in pathogenesis of herpes simplex virus encephalitis in rats

Neurotropic EV71 causes encephalitis by engaging intracellular TLR9 to elicit neurotoxic IL12-p40-iNOS signaling

Brainstem encephalitis, a manifestation of severe enterovirus 71 (EV71) infection, is an acute excessive inflammatory response. The mechanisms underlying its development remain poorly understood. Usually neurotropic viruses trigger acute host immune response by engaging cell surface or intracellular receptors. Here, we show that EV71 engagement with intracellular receptor TLR9 elicits IL-12p40-iNOS signaling causing encephalitis in mice. We identified IL-12p40 to be the only prominent cytokine-induced at the early infection stage in the brainstem of mice subjected to a lethal dose of EV71. The upregulated IL-12p40 proteins were expressed in glial cells but not neuronal cells. To better understand the role of IL-12p40 in severe EV71 infection, we treated the EV71-infected mice with an antibody against IL-12p40 and found the mortality rate, brainstem inflammation, and gliosis to be markedly reduced, suggesting that the acute IL-12p40 response plays a critical role in the pathogenesis of brainstem encephalitis. Mechanistically, intracellular TLR9 was found essential to the activation of the IL-12p40 response. Blocking TLR9 signaling with CpG-ODN antagonist ameliorated IL-12p40 response, brainstem inflammation, and limb paralysis in mice with EV71-induced encephalitis. We further found the glial IL-12p40 response might damage neurons by inducing excess production of neurotoxic NO by iNOS. Overall, EV71 engagement with intracellular TLR9 was found to elicit a neurotoxic glial response via IL12p40-iNOS signaling contributing to the neurological manifestation of EV71 infection. This pathway could potentially be targeted for the treatment of brainstem encephalitis.

The Establishment of a Noninvasive Bioluminescence-Specific Viral Encephalitis Model by Pseudorabies Virus-Infected NF-κBp-Luciferase Mice

Encephalitis is a rare brain inflammation that is most commonly caused by a viral infection. In this study, we first use an in vivo imaging system (IVIS) to determine whether NF-κBp-luciferase expression could be detected in the brain of pseudorabies virus (PRV)-infected NF-κBp-luciferase mice and to evaluate proinflammatory mediators in a well-described mouse model of PRV encephalitis. In in vitro studies, we used murine microglia (BV-2) cells to demonstrate the PRV-induced encephalitis model entailing the activation of microglia cells. The results indicate that PRV-induced neuroinflammation responses through the induction of IL-6, TNF-α, COX-2, and iNOS expression occurred via the regulation of NF-κB expression in BV-2 cells. In in vivo studies, compared with MOCK controls, the mice infected with neurovirulent PRV exhibited significantly elevated NF-κB transcription factor activity and luciferase protein expression only in the brain by IVIS. Mild focal necrosis was also observed in the brain. Further examination revealed biomarkers of inflammation, including inducible cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS), and tumor necrosis factor (TNF)-α and interleukin (IL)-6, both of which constituted proinflammatory cytokines. PRV infection stimulated inflammation and COX-2 and iNOS expression of IL-6 and TNF-α. The presented results herein suggest that PRV induces iNOS and COX-2 expression in the brain of NF-κBp–luciferase mice via NF-κB activation. In conclusion, we used NF-κBp-luciferase mice to establish a specific virus-induced encephalitis model via PRV intranasal infection. In the future, this in vivo model will provide potential targets for the development of new therapeutic strategies focusing on NF-κB inflammatory biomarkers and the development of drugs for viral inflammatory diseases.

Innate Immune Signaling and Role of Glial Cells in Herpes Simplex Virus- and Rabies Virus-Induced Encephalitis

The environment of the central nervous system (CNS) represents a double-edged sword in the context of viral infections. On the one hand, the infectious route for viral pathogens is restricted via neuroprotective barriers; on the other hand, viruses benefit from the immunologically quiescent neural environment after CNS entry. Both the herpes simplex virus (HSV) and the rabies virus (RABV) bypass the neuroprotective blood-brain barrier (BBB) and successfully enter the CNS parenchyma via nerve endings. Despite the differences in the molecular nature of both viruses, each virus uses retrograde transport along peripheral nerves to reach the human CNS. Once inside the CNS parenchyma, HSV infection results in severe acute inflammation, necrosis, and hemorrhaging, while RABV preserves the intact neuronal network by inhibiting apoptosis and limiting inflammation. During RABV neuroinvasion, surveilling glial cells fail to generate a sufficient type I interferon (IFN) response, enabling RABV to replicate undetected, ultimately leading to its fatal outcome. To date, we do not fully understand the molecular mechanisms underlying the activation or suppression of the host inflammatory responses of surveilling glial cells, which present important pathways shaping viral pathogenesis and clinical outcome in viral encephalitis. Here, we compare the innate immune responses of glial cells in RABV- and HSV-infected CNS, highlighting different viral strategies of neuroprotection or Neuroinflamm. in the context of viral encephalitis.

Exocellular polysaccharides extracted from mangrove fungus Paecilomyces Lilacinuson present anti-HSV-1 activity in mice

This study examined the anti-HSV-1 activity of EPS extracts isolated from mangrove fungus Paecilomyces Lilacinuson after intraperitoneal administration in mice. Mice were experimentally infected with HSV-1 intracranially and treated intraperitoneally with three different doses of EPS extract (6 g/Kg, 8 g/Kg, and 10 g/Kg) for 7 days. One group of 15 mice was infected with HSV-1 but did not receive any treatment, while another group of 15 mice was mock-infected to remain a control group. Animals were observed twice a day for 14 days after virus infection, searching for clinical signs of weight loss, piloerection, isolation, or retardation movement. Compared with the mock-infected group, mortality was significantly increased (p < 0.05) in the virus-infected group and the groups that received 6 g/Kg and 8 g/Kg EPS extract. Interestingly, no significant differences in mortality were found between the 10 g/Kg EPS extract and the mock-infected group. Mortality in the 10 g/Kg EPS extract group was substantially improved compared with virus-infected(p < 0.05). Additionally, EPS extracts inhibited HSV-1 replication in the mice brain in a dose-dependent manner. Furthermore, the extracts decreased NF-κB protein and mRNA expression and the production of TNF-α in HSV-1-infected mice brain tissue. These effects were also dose-dependent. Our findings suggest that the EPS extract may be a potential candidate for developing an antiviral drug against HSV-1.

The 35th Anniversary of the Discovery of EPR Effect: A New Wave of Nanomedicines for Tumor-Targeted Drug Delivery-Personal Remarks and Future Prospects

This Special Issue on the enhanced permeability and retention (EPR) effect commemorates the 35th anniversary of its discovery, the original 1986 Matsumura and Maeda finding being published in Cancer Research as a new concept in cancer chemotherapy. My review here describes the history and heterogeneity of the EPR effect, which involves defective tumor blood vessels and blood flow. We reported that restoring obstructed tumor blood flow overcomes impaired drug delivery, leading to improved EPR effects. I also discuss gaps between small animal cancers used in experimental models and large clinical cancers in humans, which usually involve heterogeneous EPR effects, vascular abnormalities in multiple necrotic foci, and tumor emboli. Here, I emphasize arterial infusion of oily formulations of nanodrugs into tumor-feeding arteries, which is the most tumor-selective drug delivery method, with tumor/blood ratios of 100-fold. This method is literally the most personalized medicine because arterial infusions differ for each patient, and drug doses infused depend on tumor size and anatomy in each patient. Future developments in EPR effect-based treatment will range from chemotherapy to photodynamic therapy, boron neutron capture therapy, and therapies for free radical diseases. This review focuses on our own work, which stimulated numerous scientists to perform research in nanotechnology and drug delivery systems, thereby spawning a new cancer treatment era.

Association of G84A and C276T polymorphism in neuronal nitric oxide synthase (nNOS) gene with herpes simplex encephalitis in eastern Indian population

In this study, a hypothesis that genetic variations in neuronal nitric oxide synthase (nNOS) could influence the susceptibility and outcome of herpes simplex encephalitis was investigated. Polymorphic loci of nNOS gene, G84A and C276T were genotyped in 132 HSE cases (Age 8.2 ± 1.3yr) and 143 in healthy individuals (Age-9.2 ± 1.6yr) of the same ethnic background from Odisha. A significantly increased risk for HSVE was associated with the AG genotype (OR = 1.73, 95%CI = 1.03-2.9, P = 0.03) and AA genotype (OR = 2.96, 95%CI = 1.04-8.4, P = 0.04) of nNOS 84G →A locus. In case of nNOS 276C→T variation, HSVE risk was linked to CT genotype (OR = 1.79, 95%CI = 1.07-3.0, P = 0.03) and TT genotype (OR = 3.6, 95%CI = 1.2-10.8, P = 0.02). Patients with poor outcome either had homo or heterozygous genotype for both SNPs, but separate genotype analysis could not show significance. But combined genotype analysis of both SNPs confirmed that GG + CC was a risk factor for development of poor outcome. (OR = 6.3, CI-1.9-20.7, P = 0.0033). Haplotype analysis of both SNP did show that "at" haplotype was significantly higher and associated with HSVE cases (OR = 2.322,CI: 1.43-3.77, P = 0.00070). The result observed in this study suggested that variation at these loci of nNOS may have decreased its expression and caused low production of NO, which have resulted in risk of HSVE but provided good outcome in these patients.

Nitric Oxide Circumvents Virus-Mediated Metabolic Regulation during Human Cytomegalovirus Infection

Nitric oxide is a versatile and critical effector molecule that can modulate many cellular functions. Although recognized as a regulator of infections, the inhibitory mechanism of nitric oxide against human cytomegalovirus (HCMV) replication remains elusive. We demonstrate that nitric oxide attenuates viral replication by interfering with HCMV-mediated modulation of several cellular processes. Nitric oxide exposure reduced HCMV genome synthesis and infectious viral progeny with cell-type-dependent differences observed. Mitochondrial respiration was severely reduced in both uninfected and HCMV-infected cells during exposure with little impact on ATP levels indicating changes in cellular metabolism. Metabolomics identified significantly altered small molecules in multiple pathways during nitric oxide exposure including nucleotide biosynthesis, tricarboxylic acid (TCA) cycle, and glutamine metabolism. Glutathione metabolites were increased coinciding with a reduction in the glutathione precursor glutamine. This shift was accompanied by increased antioxidant enzymes. Glutamine deprivation mimicked defects in HCMV replication and mitochondrial respiration observed during nitric oxide exposure. These data suggest that nitric oxide limits glutaminolysis by shuttling glutamine to glutathione synthesis. In addition, lipid intermediates were severely altered, which likely contributes to the observed increase in defective viral particles. Nitric oxide disrupts multiple cellular processes, and we had limited success in rescuing replication defects by supplementing with metabolic intermediates. Our studies indicate that nitric oxide attenuation of HCMV is multifactorial with interference in viral manipulation of cellular metabolism playing a central role.IMPORTANCE Human cytomegalovirus is a prevalent pathogen that can cause serious disease in patients with compromised immune systems, including transplant patients and during congenital infection. HCMV lytic replication likely occurs in localized sites of infection with immune cells infiltrating and releasing nitric oxide with other effector molecules. This nonspecific immune response results in both uninfected and infected cells exposed to high levels of nitric oxide. The absence of nitric oxide synthase has been associated with lethal HCMV infection. We demonstrate that nitric oxide inhibition of HCMV replication is multifactorial and cell type dependent. Our results indicate that nitric oxide controls replication by interfering with viral modulation of cellular metabolism while also affecting proliferation and mitochondrial respiration of neighboring uninfected cells. These studies identify the mechanism and contribution of nitric oxide during immune control of HCMV infection and provide insight into its role in other viral infections.

Herpes Simplex Virus-1 in the Brain: The Dark Side of a Sneaky Infection

Herpes simplex virus-1 (HSV-1) establishes latency preferentially in sensory neurons of peripheral ganglia. A variety of stresses can induce recurrent reactivations of the virus, which spreads and then actively replicates to the site of primary infection (usually the lips or eyes). Viral particles produced following reactivation can also reach the brain, causing a rare but severe form of diffuse acute infection, namely herpes simplex encephalitis. Most of the time, this infection is clinically asymptomatic. However, it was recently correlated with the production and accumulation of neuropathological biomarkers of Alzheimer's disease. In this review we discuss the different cellular and molecular mechanisms underlying the acute and long-term damage caused by HSV-1 infection in the brain.

Nitric Oxide Influences HSV-1-Induced Neuroinflammation

Herpes simplex virus type 1 (HSV-1) has the ability to replicate in neurons and glial cells and to produce encephalitis leading to neurodegeneration. Accumulated evidence suggests that nitric oxide (NO) is a key molecule in the pathogenesis of neurotropic virus infections. NO can exert both cytoprotective as well as cytotoxic effects in the central nervous system (CNS) depending on its concentration, time course exposure, and site of action. In this study, we used an in vitro model of HSV-1-infected primary neuronal and mixed glial cultures as well as an intranasal model of HSV-1 in BALB/c mice to elucidate the role of NO and nonapoptotic Fas signalling in neuroinflammation and neurodegeneration. We found that low, nontoxic concentration of NO decreased HSV-1 replication in neuronal cultures together with production of IFN-alpha and proinflammatory chemokines. However, in HSV-1-infected glial cultures, low concentrations of NO supported virus replication and production of IFN-alpha and proinflammatory chemokines. HSV-1-infected microglia downregulated Fas expression and upregulated its ligand, FasL. Fas signalling led to production of proinflammatory cytokines and chemokines as well as induced iNOS in uninfected bystander glial cells. On the contrary, NO reduced production of IFN-alpha and CXCL10 through nonapoptotic Fas signalling in HSV-1-infected neuronal cultures. Here, we also observed colocalization of NO production with the accumulation of β-amyloid peptide in HSV-1-infected neurons both in vitro and in vivo. Low levels of the NO donor increased accumulation of β-amyloid in uninfected primary neuronal cultures, while the NO inhibitor decreased its accumulation in HSV-1-infected neuronal cultures. This study shows for the first time the existence of a link between NO and Fas signalling during HSV-1-induced neuroinflammation and neurodegeneration.

SOCS4 expressed by recombinant HSV protects against cytokine storm in a mouse model

Oncolytic viruses are genetically engineered viruses designed for the treatment of solid tumors, and are often coupled with the antitumor immunity of the host. The challenge of using oncolytic herpes simplex virus (oHSV) as an efficacious oncolytic agent is the potential host tissue damage caused by the production of a range of cytokines following intratumoral oHSV injection. An HSV-suppressor of cytokine signaling 4 (SOCS4) recombinant virus was created to investigate whether it inhibits cytokine storm. Recombinant HSV-SOCS4 and HSV-1(F) were used to infect mice, and levels of several representative cytokines, including monocyte chemoattractant protein-1, interleukin (IL)-1β, tumor necrosis factor-α, IL-6 and interferon γ, in serum and bronchoalveolar lavage fluid (BALF) of infected mice were determined, and immune cells in BALF and spleen were enumerated. Lung damage, virus titers in the lung, body weight and survival rates of infected mice were also determined and compared between the two groups. The cytokine concentration of HSV-SOCS4-infected mice was significantly decreased compared with that of HSV-1(F)-infected mice in BALF and serum, and a smaller number of cluster of differentiation (CD)11b⁺ cells of BALF, and CD8⁺CD62L⁺ T cells and CD4⁺CD62L⁺ T cells of the spleen were also identified in HSV-SOCS4-infected mice. HSV-SOCS4-infected mice exhibited slight lung damage, a decrease in body weight loss and a 100% survival rate. The results of the present study indicated that SOCS4 protein may be a useful regulator to inhibit cytokine overproduction, and that HSV-SOCS4 may provide a possible solution to control cytokine storm and its consequences following induction by oncolytic virus treatment.

Mechanisms of Blood-Brain Barrier Disruption in Herpes Simplex Encephalitis

Herpes simplex encephalitis (HSE) is often caused by infection with herpes simplex virus 1 (HSV-1), a neurotropic double-stranded DNA virus. HSE infection always impacts the temporal and frontal lobes or limbic system, leading to edema, hemorrhage, and necrotic changes in the brain parenchyma. Additionally, patients often exhibit severe complications following antiviral treatment, including dementia and epilepsy. HSE is further associated with disruptions to the blood-brain barrier (BBB), which consists of microvascular endothelial cells, tight junctions, astrocytes, pericytes, and basement membranes. Following an HSV-1 infection, changes in BBB integrity and permeability can result in increased movement of viruses, immune cells, and/or cytokines into the brain parenchyma. This leads to an enhanced inflammatory response in the central nervous system and further damage to the brain. Thus, it is important to protect the BBB from pathogens to reduce brain damage from HSE. Here, we discuss HSE and the normal structure and function of the BBB. We also discuss growing evidence indicating an association between BBB breakdown and the pathogenesis of HSE, as well as future research directions and potential new therapeutic targets. Graphical Abstract During herpes simplex encephalitis, the functions and structures of each composition of BBB have been altered by different factors, thus the permeability and integrity of BBB have been broken. The review aim to explore the potential mechanisms and factors in the process, probe the next research targets and new therapeutic targets.

Nitro-fatty acids are formed in response to virus infection and are potent inhibitors of STING palmitoylation and signaling

Several chronic inflammatory conditions have recently been shown to depend on abnormally high activity of the signaling protein stimulator of IFN genes (STING). These conditions include examples from systemic lupus erythematosus, Aicardi–Goutiéres syndrome, and STING-associated vasculopathy with onset in infancy. The involvement of STING in these diseases points to an unmet demand to identify inhibitors of STING signaling, which could form the basis of anti-STING therapeutics. With this report, we identify distinct endogenously formed lipid species as potent inhibitors of STING signaling—and propose that these lipids could have pharmaceutical potential for treatment of STING-dependent inflammatory diseases.

The adaptor molecule stimulator of IFN genes (STING) is central to production of type I IFNs in response to infection with DNA viruses and to presence of host DNA in the cytosol. Excessive release of type I IFNs through STING-dependent mechanisms has emerged as a central driver of several interferonopathies, including systemic lupus erythematosus (SLE), Aicardi–Goutières syndrome (AGS), and stimulator of IFN genes-associated vasculopathy with onset in infancy (SAVI). The involvement of STING in these diseases points to an unmet need for the development of agents that inhibit STING signaling. Here, we report that endogenously formed nitro-fatty acids can covalently modify STING by nitro-alkylation. These nitro-alkylations inhibit STING palmitoylation, STING signaling, and subsequently, the release of type I IFN in both human and murine cells. Furthermore, treatment with nitro-fatty acids was sufficient to inhibit production of type I IFN in fibroblasts derived from SAVI patients with a gain-of-function mutation in STING. In conclusion, we have identified nitro-fatty acids as endogenously formed inhibitors of STING signaling and propose for these lipids to be considered in the treatment of STING-dependent inflammatory diseases.

Herpes Simplex Virus-Type1 (HSV-1) Impairs DNA Repair in Cortical Neurons

Several findings suggest that Herpes simplex virus-1 (HSV-1) infection plays a role in the neurodegenerative processes that characterize Alzheimer’s disease (AD), but the underlying mechanisms have yet to be fully elucidated. Here we show that HSV-1 productive infection in cortical neurons causes the accumulation of DNA lesions that include both single (SSBs) and double strand breaks (DSBs), which are reported to be implicated in the neuronal loss observed in neurodegenerative diseases. We demonstrate that HSV-1 downregulates the expression level of Ku80, one of the main components of non-homologous end joining (NHEJ), a major pathway for the repair of DSBs. We also provide data suggesting that HSV-1 drives Ku80 for proteasomal degradation and impairs NHEJ activity, leading to DSB accumulation. Since HSV-1 usually causes life-long recurrent infections, it is possible to speculate that cumulating damages, including those occurring on DNA, may contribute to virus induced neurotoxicity and neurodegeneration, further suggesting HSV-1 as a risk factor for neurodegenerative conditions.

[Host defense and oxidative stress signaling in bacterial infection ]

Nitric oxide (NO) and reactive oxygen species (ROS) produced during infection are involved critically in host defense mechanisms. It is quite important to physiologically regulate ROS, such as superoxide, and NO. These reactive species produced in excess may cause oxidative damage of biological molecules. An important cytoprotective and antimicrobial function of NO and ROS is mediated by induction of heme oxygenase (HO)-1. The signaling mechanism of this HO-1 induction has remained unclear, however. We discovered in 2007 a unique second messenger, 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP), that mediates electrophilic signal transduction during oxidative stress and other cellular redox signaling in general. 8-Nitro-cGMP is formed via guanine nitration with NO and ROS, and in fact, NO-dependent 8-nitro-cGMP formation and HO-1 induction were identified in Salmonella-infected mice. HO-1 induction was regulated solely by 8-nitro-cGMP formed in cells, and more important, its potent anti-apoptotic function was evident in such a Salmonella infection. 8-Nitro-cGMP has a potent cytoprotective function, of which signaling appears to be mediated via protein sulfhydryls to generate a post-translational modification called protein S-guanylation. 8-Nitro-cGMP specifically S-guanylates Keap1, a negative regulator of transcription factor Nrf2, which in turn up-regulates transcription of HO-1. Our recent study revealed that the autophagy might be involved in the 8-nitro-cGMP-dependent antimicrobial effect. The 8-nitro-cGMP signaling was also found to be regulated by reactive sulfur species that have superior antioxidant activity and unique signaling function. This review will discuss a new paradigm of the host defense that operates via formation of a unique cell signaling molecule, 8-nitro-cGMP, during microbial infections.

Redox Imbalance and Viral Infections in Neurodegenerative Diseases

Reactive oxygen species (ROS) are essential molecules for many physiological functions and act as second messengers in a large variety of tissues. An imbalance in the production and elimination of ROS is associated with human diseases including neurodegenerative disorders. In the last years the notion that neurodegenerative diseases are accompanied by chronic viral infections, which may result in an increase of neurodegenerative diseases progression, emerged. It is known in literature that enhanced viral infection risk, observed during neurodegeneration, is partly due to the increase of ROS accumulation in brain cells. However, the molecular mechanisms of viral infection, occurring during the progression of neurodegeneration, remain unclear. In this review, we discuss the recent knowledge regarding the role of influenza, herpes simplex virus type-1, and retroviruses infection in ROS/RNS-mediated Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS).

Heme oxygenase-1 dysregulation in the brain: implications for HIV-associated neurocognitive disorders

Heme oxygenase-1 (HO-1) is a highly inducible and ubiquitous cellular enzyme that subserves cytoprotective responses to toxic insults, including inflammation and oxidative stress. In neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and multiple sclerosis, HO-1 expression is increased, presumably reflecting an endogenous neuroprotective response against ongoing cellular injury. In contrast, we have found that in human immunodeficiency virus (HIV) infection of the brain, which is also associated with inflammation, oxidative stress and neurodegeneration, HO-1 expression is decreased, likely reflecting a unique role for HO-1 deficiency in neurodegeneration pathways activated by HIV infection. We have also shown that HO-1 expression is significantly suppressed by HIV replication in cultured macrophages which represent the primary cellular reservoir for HIV in the brain. HO-1 deficiency is associated with release of neurotoxic levels of glutamate from both HIV-infected and immune-activated macrophages; this glutamate-mediated neurotoxicity is suppressed by pharmacological induction of HO-1 expression in the macrophages. Thus, HO-1 induction could be a therapeutic strategy for neuroprotection against HIV infection and other neuroinflammatory brain diseases. Here, we review various stimuli and signaling pathways regulating HO-1 expression in macrophages, which could promote neuronal survival through HO-1-modulation of endogenous antioxidant and immune modulatory pathways, thus limiting the oxidative stress that can promote HIV disease progression in the CNS. The use of pharmacological inducers of endogenous HO-1 expression as potential adjunctive neuroprotective therapeutics in HIV infection is also discussed.

Animal models and pharmacology of herpetic and postherpetic pain

Varicella-zoster virus (VZV) causes varicella upon primary infection and subsequently becomes latent in the sensory ganglia. Reactivation of latent VZV in the sensory ganglion results in herpes zoster, which usually begins with pain and dysesthesia. Pain that persists long after healing of the rash is termed postherpetic neuralgia. VZV inoculation into rats induces mechanical allodynia and thermal hyperalgesia without causing herpes zoster. As with VZV, herpes simplex virus 1 (HSV1) is an alphaherpesvirus. HSV1 also becomes latent in the sensory ganglia after primary infection, and reactivation of latent HSV1 in the sensory ganglion results in herpes simplex. HSV1 inoculation into mice causes zoster-like skin lesions together with mechanical allodynia and mechanical hyperalgesia. A marked difference between the two rodent models is whether the herpes virus proliferates in the nervous system after inoculation. VZV-inoculated rats are useful for investigating mechanical allodynia induced by latent infection with herpes virus. HSV1-inoculated mice are useful for investigating mechanical allodynia induced by the proliferation of herpes virus in sensory neurons and for assessing the effects of acute herpetic pain on the incidence of postherpetic allodynia.

Infectious agents and neurodegeneration

A growing body of epidemiologic and experimental data point to chronic bacterial and viral infections as possible risk factors for neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease and amyotrophic lateral sclerosis. Infections of the central nervous system, especially those characterized by a chronic progressive course, may produce multiple damage in infected and neighbouring cells. The activation of inflammatory processes and host immune responses cause chronic damage resulting in alterations of neuronal function and viability, but different pathogens can also directly trigger neurotoxic pathways. Indeed, viral and microbial agents have been reported to produce molecular hallmarks of neurodegeneration, such as the production and deposit of misfolded protein aggregates, oxidative stress, deficient autophagic processes, synaptopathies and neuronal death. These effects may act in synergy with other recognized risk factors, such as aging, concomitant metabolic diseases and the host’s specific genetic signature. This review will focus on the contribution given to neurodegeneration by herpes simplex type-1, human immunodeficiency and influenza viruses, and by Chlamydia pneumoniae.

Protective activity of the ethanol extract of Cynanchum paniculatum (BUNGE) Kitagawa on treating herpes simplex encephalitis

To date there has been no valid treatment for herpes simplex encephalitis (HSV). This study explores the protective activity of ethanol extract of Cynanchum paniculatum (bunge) kitagawa for treatment of HSV. Cell models and animal models were established and divided into 4 groups: normal group, virus group, cynanchum paniculatum group and Dexamethasone group. Flow cytometry was employed to detect apoptosis of cell model and TUNEL assay was chosen to detect apoptosis of animal tissues. The survival time of the animal models was observed. ELISA was used to measure TNF-alpha expression and the Greiss method to measure Nitric Oxide (NO) expression in the mouse brain. As a result, it was found that extract of Cynanchum paniculatum can improve the survival rate of HSV-infected mice. The extract could prevent apoptosis in the neuron cell model and reduce apoptosis rate in brain tissue after HSV infection. With the extract intervention, TNF-alpha and NO levels in brain tissue were significantly decreased in the animal model. In conclusion, the extract of Cynanchum paniculatum can prevent HSV-inducing impairment in the cell and animal model of HSE.

Beneficial actions of melatonin in the management of viral infections: a new use for this "molecular handyman"?

Melatonin (N‐acetyl‐5‐methoxytryptamine) is a multifunctional signaling molecule that has a variety of important functions. Numerous clinical trials have examined the therapeutic usefulness of melatonin in different fields of medicine. Clinical trials have shown that melatonin is efficient in preventing cell damage under acute (sepsis, asphyxia in newborns) and chronic states (metabolic and neurodegenerative diseases, cancer, inflammation, aging). The beneficial effects of melatonin can be explained by its properties as a potent antioxidant and antioxidant enzyme inducer, a regulator of apoptosis and a stimulator of immune functions. These effects support the use of melatonin in viral infections, which are often associated with inflammatory injury and increases in oxidative stress. In fact, melatonin has been used recently to treat several viral infections, which are summarized in this review. The role of melatonin in infections is also discussed herein. Copyright © 2012 John Wiley & Sons, Ltd.

Molecular cloning and expression profiles of nitric oxide synthase (NOS) in mud crab Scylla paramamosain

The importance of the nitric oxide synthase (NOS) gene family is demonstrated by many studies in vertebrates and invertebrates in recent years. However, it keeps unknown of nitric oxide (NO) system and NOS gene family in mud crab Scylla paramamosain, an important cultured commercial crustacean in China and Pacific area. In this report, the cDNA of NOS containing full-length ORF was cloned from mud crab, S. paramamosain. It was of 4424 bp, including a 5'-terminal untranslated region (UTR) of 239 bp, a 3'-terminal UTR of 540 bp, which contained two ATTTA motifs, and an open reading frame (ORF) of 3645 bp encoding a polypeptide of 1214 amino acids. Structural analysis indicated that NOS contained a typical NO synthase domain at the N-terminal, next to a flavodoxin 1 domain, a flavin adenine dinucleotide (FAD) binding domain, respectively, and a conservative nicotinamide adenine dinucleotide (NAD) binding domain structure at the C-terminal. Quantitative real-time PCR analysis revealed S. paramamosain NOS (SpNOS) to be expressed in all tissues examined, with the highest expression in midintestine and the weakest level in heart and eyestalk. The expression profiles of SpNOS indicated that the NOS expression levels were significantly induced in midintestine, hepatopancrease and hemocytes after challenged with Vibrio Parahaemolyticus, the synthetic double-stranded RNA polyinosinic polycytidylic acid (poly I:C) and lipopolysaccharides (LPS). The NOS activity in hemocytes showed significant increase during at 24 h-48 h time period after immune challenges with V. Parahaemolyticus, poly I:C and LPS. Results here may suggest that the inducible NOS play an important role in mud crab's defense against pathogenic infection.

The nitric oxide pathway provides innate antiviral protection in conjunction with the type I interferon pathway in fibroblasts

The innate host response to virus infection is largely dominated by the production of type I interferon and interferon stimulated genes. In particular, fibroblasts respond robustly to viral infection and to recognition of viral signatures such as dsRNA with the rapid production of type I interferon; subsequently, fibroblasts are a key cell type in antiviral protection. We recently found, however, that primary fibroblasts deficient for the production of interferon, interferon stimulated genes, and other cytokines and chemokines mount a robust antiviral response against both DNA and RNA viruses following stimulation with dsRNA. Nitric oxide is a chemical compound with pleiotropic functions; its production by phagocytes in response to interferon-γ is associated with antimicrobial activity. Here we show that in response to dsRNA, nitric oxide is rapidly produced in primary fibroblasts. In the presence of an intact interferon system, nitric oxide plays a minor but significant role in antiviral protection. However, in the absence of an interferon system, nitric oxide is critical for the protection against DNA viruses. In primary fibroblasts, NF-κB and interferon regulatory factor 1 participate in the induction of inducible nitric oxide synthase expression, which subsequently produces nitric oxide. As large DNA viruses encode multiple and diverse immune modulators to disable the interferon system, it appears that the nitric oxide pathway serves as a secondary strategy to protect the host against viral infection in key cell types, such as fibroblasts, that largely rely on the type I interferon system for antiviral protection.

Immunological function in marine invertebrates: responses to environmental perturbation

The inception of ecological immunology has led to an increase in the number of studies investigating the impact of environmental stressors on host immune defence mechanisms. This in turn has led to an increased understanding of the importance of invertebrate groups for immunological research. This review discusses the advances made within marine invertebrate ecological immunology over the past decade. By demonstrating the environmental stressors tested, the immune parameters typically investigated, and the species that have received the greatest level of investigation, this review provides a critical assessment of the field of marine invertebrate ecological immunology. In highlighting the methodologies employed within this field, our current inability to understand the true ecological significance of any immune dysfunction caused by environmental stressors is outlined. Additionally, a number of examples are provided in which studies successfully demonstrate a measure of immunocompetence through alterations in disease resistance and organism survival to a realized pathogenic threat. Consequently, this review highlights the potential to advance our current understanding of the ecological and evolutionary significance of environmental stressor related immune dysfunction. Furthermore, the potential for the advancement of our understanding of the immune system of marine invertebrates, through the incorporation of newly emerging and novel molecular techniques, is emphasized.

APP processing induced by herpes simplex virus type 1 (HSV-1) yields several APP fragments in human and rat neuronal cells

Lifelong latent infections of the trigeminal ganglion by the neurotropic herpes simplex virus type 1 (HSV-1) are characterized by periodic reactivation. During these episodes, newly produced virions may also reach the central nervous system (CNS), causing productive but generally asymptomatic infections. Epidemiological and experimental findings suggest that HSV-1 might contribute to the pathogenesis of Alzheimer's disease (AD). This multifactorial neurodegenerative disorder is related to an overproduction of amyloid beta (Aβ) and other neurotoxic peptides, which occurs during amyloidogenic endoproteolytic processing of the transmembrane amyloid precursor protein (APP). The aim of our study was to identify the effects of productive HSV-1 infection on APP processing in neuronal cells. We found that infection of SH-SY5Y human neuroblastoma cells and rat cortical neurons is followed by multiple cleavages of APP, which result in the intra- and/or extra-cellular accumulation of various neurotoxic species. These include: i) APP fragments (APP-Fs) of 35 and 45 kDa (APP-F35 and APP-F45) that comprise portions of Aβ; ii) N-terminal APP-Fs that are secreted; iii) intracellular C-terminal APP-Fs; and iv) Aβ_1-40 and Aβ_1-42. Western blot analysis of infected-cell lysates treated with formic acid suggests that APP-F35 may be an Aβ oligomer. The multiple cleavages of APP that occur in infected cells are produced in part by known components of the amyloidogenic APP processing pathway, i.e., host-cell β-secretase, γ-secretase, and caspase-3-like enzymes. These findings demonstrate that HSV-1 infection of neuronal cells can generate multiple APP fragments with well-documented neurotoxic potentials. It is tempting to speculate that intra- and extracellular accumulation of these species in the CNS resulting from repeated HSV-1 reactivation could, in the presence of other risk factors, play a co-factorial role in the development of AD.

Bovine herpesvirus 5 induces an overproduction of nitric oxide in the brain of rabbits that correlates with virus dissemination and precedes the development of neurological signs

We herein report an investigation of nitric oxide (NO) levels, a candidate molecule for neuronal toxicity and dysfunction, in the brain of rabbits during experimental neurological infection by bovine herpesvirus 5 (BoHV-5). Spectrophotometry for NO products (NO(2) and NO(3)) revealed that NO levels were significantly increased (F(4, 40) = 3.33; P <.02) in several regions of the brain of rabbits with neurological disease, correlating with moderate to high BoHV-5 titers. Immunohistochemistry of brain regions revealed a group of cells with neuronal and astrocyte morphology expressing the enzyme inducible NO synthase (iNOS) close to virus antigen-positive neurons. In addition, the investigation of nitric oxide levels between 2 and 6 days post infection (d.p.i.) revealed an initial increase in NO levels in the olfactory bulb and cortex (OB/OC) and anterior cortex (AC) at day 3 p.i., correlating with the initial detection of virus. As the infection proceeded, increased NO levels-and infectivity-were progressively being detected in the OB/CO and AC at day 4 p.i. (F(12, 128) = 2.82; P <.003); at day 5 p.i. in several brain regions (P <.003 in the OB/OC); and at day 6 p.i. in all regions (P <.003) but the thalamus. These results show that BoHV-5 replication in the brain of rabbits induces an overproduction of NO. The increase in NO levels in early infection correlated spatially and temporally with virus dissemination within the brain and preceded the development of neurological signs. Thus, the overproduction of NO in the brain of BoHV-5-infected rabbits may be a component of the pathogenesis of BoHV-5-induced neurological disease.

The role of nitric oxide in mycobacterial infections

Although tuberculosis poses a significant health threat to the global population, it is a challenge to develop new and effective therapeutic strategies. Nitric oxide (NO) and inducible NO synthase (iNOS) are important in innate immune responses to various intracellular bacterial infections, including mycobacterial infections. It is generally recognized that reactive nitrogen intermediates play an effective role in host defense mechanisms against tuberculosis. In a murine model of tuberculosis, NO plays a crucial role in antimycobacterial activity; however, it is controversial whether NO is critically involved in host defense against Mycobacterium tuberculosis in humans. Here, we review the roles of NO in host defense against murine and human tuberculosis. We also discuss the specific roles of NO in the central nervous system and lung epithelial cells during mycobacterial infection. A greater understanding of these defense mechanisms in human tuberculosis will aid in the development of new strategies for the treatment of disease.

Therapeutic strategies by modulating oxygen stress in cancer and inflammation

Oxygen is the essential molecule for all aerobic organisms, and plays predominant role in ATP generation, namely, oxidative phosphorylation. During this process, reactive oxygen species (ROS) including superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)) are produced as by-products, while it seems indispensable for signal transduction pathways that regulate cell growth and reduction-oxidation (redox) status. However, during times of environmental stress ROS levels may increase dramatically, resulting in significant damage to cell structure and functions. This cumulated situation of ROS is known as oxidative stress, which may, however, be utilized for eradicating cancer cells. It is well known that oxidative stress, namely over-production of ROS, involves in the initiation and progression of many diseases and disorders, including cardiovascular diseases, inflammation, ischemia-reperfusion (I/R) injury, viral pathogenesis, drug-induced tissue injury, hypertension, formation of drug resistant mutant, etc. Thus, it is reasonable to counter balance of ROS and to treat such ROS-related diseases by inhibiting ROS production. Such therapeutic strategies are described in this article, that includes polymeric superoxide dismutase (SOD) (e.g., pyran copolymer-SOD), xanthine oxidase (XO) inhibitor as we developed water soluble form of 4-amino-6-hydroxypyrazolo[3,4-d]pyrimidine (AHPP), heme oxygenase-1 (HO-1) inducers (e.g., hemin and its polymeric form), and other antioxidants or radical scavengers (e.g., canolol). On the contrary, because of its highly cytotoxic nature, ROS can also be used to kill cancer cells if one can modulate its generation selectively in cancer. To achieve this goal, a unique therapeutic strategy was developed named as "oxidation therapy", by delivering cytotoxic ROS directly to the solid tumor, or alternatively inhibiting the antioxidative enzyme system, such as HO-1 in tumor. This anticancer strategy was examined by use of O(2)(-) or H(2)O(2)-generating enzymes (i.e., XO and d-amino acid oxidase [DAO] respectively), and by discovering the inhibitor of HO-1 (i.e., zinc protoporphyrin [ZnPP] and its polymeric derivatives). Further for the objective of tumor targeting and thus reducing side effects, polymer conjugates or micellar drugs were prepared by use of poly(ethylene glycol) (PEG) or styrene maleic acid copolymer (SMA), which utilize EPR (enhanced permeability and retention) effect for tumor-selective delivery. These macromolecular drugs further showed superior pharmacokinetics including much longer in vivo half-life, particularly tumor targeted accumulation, and thus remarkable antitumor effects. The present review concerns primarily our own works, in the direction of "Controlling oxidative stress: Therapeutic and delivery strategy" of this volume.

Neuropatogênese experimental da infecção pelo herpesvírus bovino tipo 5 em coelhos

Vários aspectos da biologia do herpesvírus bovino tipo 5 (BoHV-5) têm sido estudados em coelhos, que desenvolvem infecção aguda e doença neurológica após inoculação experimental. A infecção aguda é seguida pelo estabelecimento de infecção latente, que pode ser reativada natural ou artificialmente. Os primeiros experimentos nesta espécie estabeleceram um protocolo de inoculação e monitoramento da infecção, e caracterizaram os principais aspectos virológicos, clínicos e patológicos da infecção aguda. A patogenia da infecção aguda, desde a replicação viral nos sítios de inoculação, vias e cinética de transporte viral até o encéfalo, distribuição e replicação viral no sistema nervoso central (SNC), tropismo celular e tecidual, manifestações clínicas e patologia no SNC foram detalhadamente estudados nestes animais. Posteriormente, vários aspectos biológicos e moleculares da infecção latente também foram elucidados a partir de inoculações de coelhos. Os coelhos também têm sido utilizados para estudar o fenótipo (neuroinvasividade, neurovirulência) de isolados de campo e de cepas vacinais recombinantes, proteção por imunidade passiva, proteção vacinal, eficácia de drogas anti-virais e terapêuticas de suporte da infecção neurológica. Este modelo experimental também foi utilizado para o estudo da origem e distribuição dos estímulos elétricos produzidos durante as convulsões - uma característica da infecção neurológica pelo BoHV-5 -, e para testes de medicamentos anti-convulsivantes. Ressalvadas as diferenças que certamente existem entre bovinos - os hospedeiros naturais - e coelhos, as observações oriundas deste modelo experimental tem contribuído sobremaneira para o conhecimento da biologia do BoHV-5. O presente trabalho apresenta uma coletânea de resultados e observações, publicadas ou não pelo grupo, ao longo de mais de uma década, envolvendo inoculações de coelhos para estudar diversos aspectos da infecção pelo BoHV-5.

The aryl hydrocarbon receptor is a modulator of anti-viral immunity

Although immune modulation by AhR ligands has been studied for many years, the impact of AhR activation on host defenses against viral infection has not, until recently, garnered much attention. The development of novel reagents and model systems, new information regarding anti-viral immunity, and a growing appreciation for the global health threat posed by viruses have invigorated interest in understanding how environmental signals affect susceptibility to and pathological consequences of viral infection. Using influenza A virus as a model of respiratory viral infection, recent studies show that AhR activation cues signaling events in both leukocytes and non-immune cells. Functional alterations include suppressed lymphocyte responses and increased inflammation in the infected lung. AhR-mediated events within and extrinsic to hematopoietic cells has been investigated using bone marrow chimeras, which show that AhR alters different elements of the immune response by affecting different tissue targets. In particular, suppressed CD8(+) T cell responses are due to deregulated events within leukocytes themselves, whereas increased neutrophil recruitment to and IFN-gamma levels in the lung result from AhR-regulated events extrinsic to bone marrow-derived cells. This latter discovery suggests that epithelial and endothelial cells are overlooked targets of AhR-mediated changes in immune function. Further support that AhR influences host cell responses to viral infection are provided by several studies demonstrating that AhR interacts directly with viral proteins and affects viral latency. While AhR clearly modulates host responses to viral infection, we still have much to understand about the complex interactions between immune cells, viruses, and the host environment.

Primary target cells of herpes simplex virus type 1 in the hippocampus

Herpes simplex virus type 1 (HSV-1) causes fatal and sporadic encephalitis in human. The encephalitis-survivors frequently suffer from symptoms of memory deficits. It remains unclear how HSV-1 induces tissue damages in memory formation-associated brain tissues such as the hippocampus. In this study, we examined HSV-1 infection in the hippocampus using a rat HSV-1 infection model. We found profound pathological changes in the hippocampus and large numbers of HSV-1 antigen-positive cells in the dentate gyrus (DG) subfield of HSV-1-infected rats. To understand the precise mechanism of HSV-1-induced tissue damages in the hippocampus, we employed rat organotypic hippocampal slice cultures (OHC) as an in vitro HSV-1 infection model. In OHC, HSV-1 infection predominated in neuronal cells and the infected neuronal cells were severely damaged. Longitudinal analysis indicated that granule cells in DG subfield were extremely vulnerable to HSV-1 infection among neuronal cells in the hippocampus. Since DG granule cells play a crucial role in memory formation, disruption of these cells may be a primary step leading to memory deficits.

Microglia are the major cellular source of inducible nitric oxide synthase during experimental herpes encephalitis

Although production of reactive nitrogen and reactive oxygen species (RNS and ROS) is a component of innate defense against viral infection, their overproduction in the brain may also lead to deleterious consequences. To investigate potential immunopathologic roles of oxidative stress during herpes encephalitis, the authors examined the expression kinetics of inducible nitric oxide synthase (iNOS) as well as heme oxygenase-1 (HO-1), a marker of oxidative stress, and evaluated infection-induced oxidative brain damage. Results from these studies showed that both iNOS and HO-1 gene expression were highly elevated in the brain within 7 days post infection (d.p.i.) and remained elevated through 21 d.p.i. Real-time bioluminescence imaging of HO-1 promoter-luciferase transgenic mice confirmed HO-1 promoter activity in the brains of HSV-1-infected animals within 3 d.p.i., which peaked between 5 and 7 d.p.i. Immunohistochemical staining for both 3-nitrotyrosine and 8-hydroxydeoxyguanosine (8-OH-dG), as well as quantitative assessment of 8-isoprostane levels, demonstrated the presence of viral infection-induced oxidative brain damage. In addition, when brain leukocytes obtained from animals with experimental herpes encephalitis were sorted using fluorescence-activated cell sorting (FACS) and the individual cell populations analyzed, CD45(int)/CD11b(+) resident microglia were found to be the major cellular source of iNOS expression.

Subconjunctival antisense oligonucleotides targeting TNF-alpha influence immunopathology and viral replication in murine HSV-1 retinitis

BACKGROUND

To investigate the role of tumor necrosis factor-alpha (TNF-alpha) in immunopathology and viral replication in the contralateral eye in the von Szily model of herpes simplex virus (HSV)-1 acute retinitis.

METHODS

In vivo distribution was analyzed after subconjunctival injection of FITC-labeled antisense oligonucleotides (ASON). After HSV-1 (KOS) was injected in the right anterior chamber (AC) in BALB/c mice, the course of the contralateral retinitis was evaluated. The left eyes were treated with either TNF-alpha ASON, sequence-unspecific control (CON), or buffer. The ocular TNF-alpha content was quantified by ELISA. The delayed-type hypersensitivity (DTH) reaction, uptake of [3H]thymidine from regional lymph nodes (rln)- and spleen cells, serum-neutralizing antibodies, and viral titer in the eyes were evaluated.

RESULTS

After subconjunctival injection, FITC-labeled ASON were found in the choroid and retina. In the TNF-alpha ASON-treated eyes, TNF-alpha expression and the incidence and severity of retinitis were reduced on day 8 postinfection (PI) (p < 0.05). On day 10 PI, higher viral titers were only seen in the eyes of the TNF-alpha ASON group (p < 0.05), and retinitis was slightly more severe on day 12 PI. While the HSV-1 specific [3H]thymidine uptake from rln cells was higher in the TNF-alpha ASON mice (p < 0.05), the [3H]thymidine uptake from spleen cells, the DTH response, and the neutralizing-antibody titers did not differ between the groups.

CONCLUSIONS

After regional blockade of TNF-alpha in experimental HSV-1 retinitis TNF-alpha seems to possess an antiviral capacity against HSV-1 in the contralateral eye and participates in the immunopathology of HSV-1-induced acute retinitis.

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.

Defensive effects of a fucoidan from brown alga Undaria pinnatifida against herpes simplex virus infection

Fucoidan, a sulfated polysaccharide isolated from an edible brown alga Undaria pinnatifida, was previously shown to be a potent inhibitor of the in vitro replication of herpes simplex virus type 1 (HSV-1). HSV-1 is a member of herpes viruses that cause infections ranging from trivial mucosal ulcers to life-threatening disorders in immunocompromised hosts. In the in vivo conditions, the replication of HSV-1 is controlled under the immunoresponse coordinated by both the innate and adaptive immune systems. In the present study, the effects of the fucoidan were examined on in vivo viral replication and the host's immune defense system. Oral administration of the fucoidan protected mice from infection with HSV-1 as judged from the survival rate and lesion scores. Phagocytic activity of macrophages and B cell blastogenesis in vitro were significantly stimulated by the fucoidan, while no significant change in the release of NO(2)(-) by macrophages was observed. In in vivo studies, oral administration of the fucoidan produced the augmentation of NK activity in HSV-1-infected mice immunosuppressed by 5-fluorouracil treatment. CTL activity in HSV-1-infected mice was also enhanced by oral administration of the fucoidan. The production of neutralizing antibodies in the mice inoculated with HSV-1 was significantly promoted during the oral administration of the fucoidan for 3 weeks. These results suggested that oral intake of the fucoidan might take the protective effects through direct inhibition of viral replication and stimulation of both innate and adaptive immune defense functions.

The immune response to herpes simplex virus encephalitis in mice is modulated by dietary vitamin E

Herpes simplex virus encephalitis (HSE) is the most common fatal sporadic encephalitis in humans. HSE is primarily caused by herpes simplex virus (HSV)-1 infection of the brain. HSE results in increased levels of oxidative stress, including the production of reactive oxygen species, free radicals, and neuroinflammation. The most biologically active form of vitamin E (VE) is alpha-tocopherol (alpha-TOC). In cellular membranes, alpha-TOC prevents lipid peroxidation by scavenging free radicals and functioning as an antioxidant. Supplementation with VE has been shown to decrease immunosenescence, improve immune function, and may be neuroprotective. To determine how VE deficiency and VE supplementation would alter the pathogenesis of HSE, we placed weanling male BALB/cByJ mice on VE-deficient (VE-D), VE-adequate (VE-A), or 10x VE-supplemented diets for 4 wk, and then infected the mice intranasally with HSV-1. VE-D mice had more severe symptoms of encephalitis than VE-A mice, including weight loss, keratitis, hunched posture, and morbidity. VE-D mice had increased cytokine and chemokine expression in the brain and increased viral titers. In contrast, VE supplementation failed to decrease cytokine production and had no effect on viral titer. We demonstrated that adequate levels of VE are important in limiting HSE pathology and that 10x supplementation does not enhance protection.

Tumor-targeted induction of oxystress for cancer therapy

Reactive oxygen species (ROS), such as superoxide anion radicals (O.-2) and hydrogen peroxide (H2O2) are potentially harmful by-products of normal cellular metabolism that directly affect cellular functions. ROS is generated by all aerobic organisms and it seems to be indispensable for signal transduction pathways that regulate cell growth and reduction-oxidation (redox) status. However, overproduction of these highly reactive oxygen metabolites can initiate lethal chain reactions, which involve oxidation and damage to structures that are crucial for cellular integrity and survival. In fact, many antitumor agents, such as vinblastine, cisplatin, mitomycin C, doxorubicin, camptothecin, inostamycin, neocarzinostatin and many others exhibit antitumor activity via ROS-dependent activation of apoptotic cell death, suggesting potential use of ROS as an antitumor principle. Thus, a unique anticancer strategy named "oxidation therapy" has been developed by inducing cytotoxic oxystress for cancer treatment. This goal could be achieved mainly by two methods, namely, (i) inducing the generation of ROS directly to solid tumors and (ii) inhibiting the antioxidative enzyme (defense) system of tumor cells. Since 1950s, many strategies have been employed based on the first method, namely, administration of ROS per se (e.g. H2O2) or ROS generating enzyme to tumor bearing animals. However no successful and practical results were obtained probably because of the lack of tumor selective ROS delivery and hence resulting in subsequent induction of severe side effects. To overcome these obstacles, we developed polyethylene glycol (PEG) conjugated O.-2 or H2O2-generating enzymes, xanthine oxidase (XO) and D-amino acid oxidase (DAO) (PEG-DAO) respectively. More recently, a pegylated (PEG) zinc protoporphyrin (PEG-ZnPP) and a highly water soluble micellar formulation of ZnPP based on amphiphilic styrene maleic acid (SMA) copolymer, SMA-ZnPP, are prepared, which are potent inhibitors of heme oxygenase-1 (HO-1). HO-1 is a major antioxidative enzyme of tumors, that is different in mechanism of catalase or superoxide dismutase (SOD). Consequently, both PEG-enzymes and PEG-ZnPP exhibited superior in vivo pharmacokinetics than their parental molecules, particularly in tumor delivery by taking advantage of the EPR effect of macromolecular nature, and thus showed remarkable antitumor effects suggesting the potentials of this anticancer therapeutic for clinical application. Furthermore, it has been well known that many antioxidative enzymes such as catalase, SOD are down-regulated in most solid tumors in vivo. On the contrary, HO-1 is highly upregulated and it plays a very important role of antioxidation, because HO-1 generates biliverdin, which being converted to bilirubin exhibits a very potent antioxidative effect, and hence antiapoptosis in tumors. Thus this oxidation therapy, by inhibiting this HO-1 dependent antioxidant (bilirubin) formation by ZnPP, and by enhancing ROS generation, is expected to offer a powerful therapeutic modality for future anticancer therapy.

Different roles of nitric oxide synthase-1 and -2 between herpetic and postherpetic allodynia in mice

We investigated using the mice role of nitric oxide synthase (NOS) in the spinal dorsal horn in herpetic and postherpetic pain, especially allodynia, which was induced by transdermal inoculation of the hind paw with herpes simplex virus type-1 (HSV-1). The virus inoculation induced NOS2 expression in the lumbar dorsal horn of mice with herpetic allodynia, but not postherpetic allodynia. There were no substantial alternations in the expression level of NOS1 at the herpetic and postherpetic stages. Herpetic allodynia was significantly inhibited by i.p. administration of the selective NOS2 inhibitor S-methylisothiourea, but not the selective NOS1 inhibitor 7-nitroindazole. NOS2 expression was observed around HSV-1 antigen-immunoreactive cells. On the other hand, postherpetic allodynia was significantly inhibited by i.p. administration of 7-nitroindazole, but not S-methylisothiourea. The activity of reduced nicotinamide adenine dinucleotide phosphate diaphorase, an index of NOS1 activity, significantly increased in the laminae I and II of the lumbar dorsal horn of mice with postherpetic allodynia, but not mice without postherpetic allodynia. The expression level of NOS1 mRNA in the dorsal root ganglia was similar between mice with and without postherpetic allodynia. The results suggest that herpetic and postherpetic allodynia is mediated by nitric oxide in the dorsal horn and that NOS2 and NOS1 are responsible for herpetic and postherpetic allodynia, respectively. It may be worth testing the effects of NOS2 and NOS1 inhibitors on herpetic pain and postherpetic neuralgia in human subjects, respectively.

Immunoregulatory and antimicrobial effects of nitrogen oxides

The therapeutic effects of inhaled nitric oxide (NO) therapy are thought to be restricted to the pulmonary vasculature because of rapid inactivation of NO by hemoglobin in the bloodstream. However, recent data suggest that inhaled NO may not only be scavenged by the heme iron of hemoglobin but also may react with protein thiols in the bloodstream, including cysteine-93 of the hemoglobin B subunit. Reaction of NO with protein or peptide thiols is termed S-nitrosylation and results in the formation of relatively stable protein S-nitrosothiols that carry NO bioactivity to distal organs. Thus, inhaled NO-induced protein S-nitrosylation may allow inhaled NO to have multiple as yet undiscovered physiologic and pathophysiologic effects outside of the lung. Here we review the immunoregulatory and antimicrobial functions of NO and the potential effects of inhaled NO therapy on host defense.

The effects of aminoguanidine on primary and recurrent ocular herpes simplex virus infection

In primary ocular herpes simplex virus (HSV) infection, nitric oxide may function to control viral replication and herpetic stromal keratitis (HSK) lesions. Recurrent HSK, manifested as corneal opacity and neovascularization, is the potentially blinding sequel to primary infection. Here, we assess the effects of nitric oxide synthase inhibition on a mouse model of recurrent HSK. In preliminary primary infection experiments, NIH inbred mice treated with aminoguanidine, an inhibitor of inducible nitric oxide synthase (iNOS), experienced no changes in post-infection tear, brain, or ganglia virus titers, but encephalitis-related mortality was elevated. After UV-B stimulated viral reactivation, iNOS inhibition did not affect virus shedding or clinical disease. In contrast to primary HSK, there was no exacerbation of mortality in recurrent disease. Our findings indicate that nitric oxide can be neuroprotective without antiviral effects in primary HSK, and does not play a significant role in the pathogenesis of recurrent HSK. Compared with data from other mouse strains, this work suggests that there may be a genetic component to the importance of NO in controlling ocular HSV infection.

Nitrative stress through formation of 8-nitroguanosine: insights into microbial pathogenesis

Reactive oxygen and nitrogen species, respectively, mediate oxidative and nitrative stresses by means of oxidation and nitration of various biomolecules including proteins, lipids, and nucleic acids. We have observed nitric oxide (NO)-dependent formation of 8-nitroguanosine and 3-nitrotyrosine during microbial infection, and we determined that both 8-nitroguanosine and 3-nitrotyrosine are useful biomarkers of nitrative stress. Of importance, however, is the great difference in biological characteristics of these two nitrated compounds. 8-Nitroguanosine has unique biochemical and pharmacological properties such as redox activity and mutagenic potential, which 3-nitrotyrosine does not. In this review, we discuss the mechanism of nitrative stress occurring during microbial infections, with special emphasis on biological functions of 8-nitroguanosine formed via NO during the host response to pathogens. These findings provide insights into NO-mediated pathogenesis not only of viral infections but also of many other diseases.

Reovirus infection of the CNS enhances iNOS expression in areas of virus-induced injury

Nitric oxide (NO) has been implicated as a contributor to the host's innate defense against viral infections including those affecting the CNS. Reovirus infection of the CNS is a classic experimental system for understanding the pathogenesis of neurotropic viral infection. Infection with serotype 3 strains is associated with perturbations in various cellular signaling pathways including NF-kappaB and NO plays a regulatory role in many of these same pathways. We therefore examined whether NO production is dysregulated following reovirus serotype 3 strain Abney (T3A) infection of the mouse CNS. Nitric oxide synthase (NOS) activity was significantly higher in brain homogenates from T3A-infected animals compared to mock infected. Increased NOS activity correlated with inducible NOS (iNOS) expression in brain homogenates of T3A-infected animals. Expression of iNOS was confined to areas of viral infection and injury. T3A infection of primary neuronal and glial cultures was also associated with enhanced expression of iNOS. Immunocytochemical studies of primary glial cultures demonstrated that, in addition to its known neuronotropism, T3A was also capable of infecting immature microglial cells. T3A infection did not alter expression of either neuronal or endothelial NOS isoforms in neuronal or glial cultures or in mouse brain. The NO donor S-Nitroso-N-acetyl penicillamine (SNAP) significantly inhibited T3A growth in neuronal cultures, conversely the NOS inhibitor N-omega-Nitro-L-arginine methyl ester hydrochloride (L-NAME) augmented viral growth. Our findings provide the first evidence of reovirus-induced iNOS expression and the first demonstration that NO inhibits mammalian reovirus replication, suggesting that NO may play an antiviral role during reovirus infection.