Nitric Oxide-Induced Nitrative Stress Involved in Microbial Pathogenesis

An anti-virulence drug targeting the evolvability protein Mfd protects against infections with antimicrobial resistant ESKAPE pathogens

The increasing incidence of antibiotic resistance and the decline in the discovery of novel antibiotics have resulted in a global health crisis, particularly, for the treatment of infections caused by Gram-negative bacteria, for which therapeutic dead-ends are alarming. Here, we identify and characterize a molecule, NM102, that displays antimicrobial activity exclusively in the context of infection. NM102 inhibits the activity of the non-essential Mutation Frequency Decline (Mfd) protein by competing with ATP binding to its active site. Inhibition of Mfd by NM102 sensitizes pathogenic bacteria to the host immune response and blocks infections caused by the clinically-relevant bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa, without inducing host toxicity. Finally, NM102 inhibits the mutation and evolvability function of Mfd, thus reducing the bacterial capacity to develop antimicrobial resistance. These data provide a potential roadmap for the development of drugs to combat antimicrobial resistance.

Copper Nanoparticle Decorated Multilayer Nanocoatings for Controlled Nitric Oxide Release and Antimicrobial Performance with Biosafety

Biomedical device-related bacterial infections are a leading cause of mortality, and traditional antibiotics contribute to resistance. Various surface modification strategies have been explored, but effective clinical solutions remain limited. This study introduces a novel antibacterial nanocoating with copper nanoparticles (CuNPs) that triggers localized nitric oxide (NO) release. The multilayered nanocoating is created using branched polyethylenimine (BPEI) and poly(acrylic acid) (PAA) via a Layer-by-Layer assembly method. CuNP-decorated nanocoatings are formed by reducing copper ions coordinated with amine/carboxylic acid groups. In a physiological environment, CuNPs oxidize to Cu(I), promoting NO release from endogenous NO donors. The nanocoating's thickness is adjustable to regulate amount of CuNPs and NO flux. The optimal thickness for effective NO release against Staphylococcus aureus and Pseudomonas aeruginosa is identified, preventing microbial adhesion and biofilm formation. Importantly, the coating remains cytocompatible due to minimal CuNPs, physiological NO levels, and stable coating properties under physiological conditions.

Isolation of Latilactobacillus curvatus with Enhanced Nitric Oxide Synthesis from Korean Traditional Fermented Food and Investigation of Its Probiotic Properties

Nitric oxide (NO) is a free radical associated with physiological functions such as blood pressure regulation, cardiovascular health, mitochondrial production, calcium transport, oxidative stress, and skeletal muscle repair. This study aimed to isolate Latilactobacillus curvatus strains with enhanced NO production from the traditional Korean fermented food, jangajji, and evaluate their probiotic properties for industrial purposes. When cells were co-cultured with various bacterial stimulants, NO production generally increased, and NO synthesis was observed in the range of 20-40 mg/mL. The selected strains of Lat. curvatus were resistant to acid and bile conditions and with variable effectiveness (1-14%) in adhering to Caco-2 cells. Most bacterial strains can inhibit the growth of various pathogens. In addition, they are capable of reducing cholesterol levels via assimilation of cholesterol at 10-50%. Among the selected NO synthases from Lat. curvatus strains, the strain JBCC38 showed the highest capacity to scavenge ABTS (30.1%) and DPPH radicals (39.4%). Moreover, these strains exhibited immunomodulatory properties. The production of TNF-α and IL-6 in the macrophages treated with various bacterial stimulants was induced in all the selected strains.

Impact of Protein Nitration on Influenza Virus Infectivity and Immunogenicity

Influenza viruses are deadly respiratory pathogens of special importance due to their long history of global pandemics. During influenza virus infections, the host responds by producing interferons, which activate interferon-stimulated genes (ISGs) inside target cells. One of these ISGs is inducible nitric oxide synthase (iNOS). iNOS produces nitric oxide (NO) from arginine and molecular oxygen inside the cell. NO can react with superoxide radicals to form reactive nitrogen species, principally peroxynitrite. While much work has been done studying the many roles of nitric oxide in influenza virus infections, the direct effect of peroxynitrite on influenza virus proteins has not been determined. Manipulations of NO, either by knocking out iNOS or chemically inhibiting NO, produced no change in virus titers in mouse models of influenza infection. However, peroxynitrite has a known antimicrobial effect on various bacteria and parasites, and the reason for its lack of antimicrobial effect on influenza virus titers in vivo remains unclear. Therefore, we wished to test the direct effect of nitration of influenza virus proteins. We examined the impact of nitration on virus infectivity, replication, and immunogenicity. We observed that the nitration of influenza A virus proteins decreased virus infectivity and replication ex vivo. We also determined that the nitration of influenza virus hemagglutinin protein can reduce antibody responses to native virus protein. However, our study also suggests that nitration of influenza virus proteins in vivo is likely not extensive enough to inhibit virus functions substantially. These findings will help clarify the role of peroxynitrite during influenza virus infections. IMPORTANCE Nitric oxide and peroxynitrite produced during microbial infections have diverse and seemingly paradoxical functions. While nitration of lung tissue during influenza virus infection has been observed in both mice and humans, the direct effect of protein nitration on influenza viruses has remained elusive. We addressed the impact of nitration of influenza virus proteins on virus infectivity, replication, and immunogenicity. We observed that ex vivo nitration of influenza virus proteins reduced virus infectivity and immunogenicity. However, we did not detect nitration of influenza virus hemagglutinin protein in vivo. These results contribute to our understanding of the roles of nitric oxide and peroxynitrite in influenza virus infections.

Reactive nitrogen species from free nitrous acid (FNA) cause cell lysis

Free nitrous acid (FNA, i.e. HNO₂) has been demonstrated to have broad biocidal effects on a range of microorganisms, which has direct implications for wastewater management. However, the biocidal mechanisms still remain largely unknown. This study aims to test the hypothesis that FNA will induce cell lysis via cell membrane perforations, and consequently cause cell death via proteolysis, through the use of two model organisms namely Escherichia coli K12 and Pseudomonas putida KT2440. A combination of analytical techniques that included viability assays, atomic force microscopy (AFM), protein abundance assays and proteomic analysis using Quadruple-Orbitrap™ Mass spectrometry was used to evaluate the extent of cell death and possible cell lysis mechanisms. FNA treatment at 6.09 mg/L for 24 h (conditions typically applied in applications) induced 36 ± 4.2% and 91 ± 3.5% cell death/lysis of E. coli and P. putida, respectively. AFM showed that the lysis of cells was observed via perforations in the cell membrane; cells also appeared to shrink and become flat following FNA treatment. By introducing a reactive nitrogen species (RNS) scavenger to act as a treatment control, we further revealed that it was the nitrosative decomposition species of FNA, such as ^.NO that caused the cell lysis through the destruction of protein macromolecules found in the cell membrane (proteolysis). Subsequently, the RNS went on to cause the destruction of protein macromolecules within the cells. The death of these model organisms E. coli and P. putida following exposure to FNA treatment provides insights into the use of FNA as an antimicrobial agent in wastewater treatment.

Biochemical Pathways of 8-Aminoguanine Production In Sprague-Dawley and Dahl Salt-Sensitive Rats

BACKGROUND

8-Aminoguanine exerts natriuretic and antihypertensive activity. Whether and how "free" 8-aminoguanine exists in vivo is unclear. Because 8-nitroguanosine is naturally occurring, we tested the hypothesis that 8-aminoguanine can arise from: pathway 1, 8-nitroguanosine→8-aminoguanosine→8-aminoguanine; and pathway 2, 8-nitroguanosine→8-nitroguanine→8-aminoguanine.

METHODS

8-Aminoguanine biosynthesis was explored in rats using renal microdialysis, mass spectrometry and enzyme kinetics.

RESULTS

In Sprague-Dawley rats, 8-nitroguanosine infusions increased kidney levels of 8-nitroguanine, 8-aminoguanosine and 8-aminoguanine; 8-nitroguanine infusions increased 8-aminoguanine. Purine nucleoside phosphorylase (PNPase) converted 8-nitroguanosine to 8-nitroguanine and 8-aminoguanosine to 8-aminoguanine. Forodesine (PNPase inhibitor) reduced metabolism of 8-nitroguanosine by pathway 2 and shunted metabolism of 8-nitroguanosine to 8-aminoguanosine. In Dahl salt-sensitive rats, 8-nitroguanosine infusions increased kidney levels of 8-nitroguanine, 8-aminoguanosine and 8-aminoguanine. These results indicate that both pathways 1 and 2 participate in the biosynthesis of 8-aminoguanine in Sprague-Dawley and Dahl rats. Endogenous 8-aminoguanine in kidneys and urine were elevated many-fold in Dahl, compared to Sprague-Dawley, rats. The increased levels of 8-aminoguanine in Dahl rats were not due to alterations in pathways 1 and 2 but were associated with increased urine levels of endogenous 8-nitroguanosine suggesting that the "upstream" production of 8-nitroguanosine was increased in Dahl rats. Dahl rats are known to have high levels of peroxynitrite, and peroxynitrite is known to nitrate guanosine in biomolecules. Here we confirm that a peroxynitrite donor increases kidney levels of 8-aminoguanine.

CONCLUSION

8-Aminoguanine occurs naturally via two distinct pathways and kidney levels of 8-aminoguanine are increased in Dahl rats, likely due to increased production of 8-nitroguanosine, a by-product of peroxynitrite chemistry.

Monoterpene Alkaloids from Incarvillea delavayi Bureau et Franchet and Their Inhibition against LPS Induced NO Production in BV2 Cells

Three new monoterpene alkaloids, delavatines C-E (1-3), along with five known ones (4-8), were separated from the whole plants of Incarvillea delavayi. All compounds were deduced by interpretation of comprehensive NMR spectral data and X-Ray single crystal diffraction, in combination with a quantum chemical calculation of NMR chemical shift coupled with an advanced statistical procedure DP4+. Compounds 1-8 were assessed NO suppressive effect in LPS-stimulated BV2 microglia cells. Compounds 2, 3, 6, and 8 exhibited significant inhibition against NO production in LPS-induced BV2 cells with IC₅₀ values of 25.62, 17.29, 19.94 and 23.88 μM, stronger than or comparable to the positive control (AG) with IC₅₀ value of 26.13 μM.

The pathogenic biomarker alcohol dehydrogenase protein is involved in Bacillus cereus virulence and survival against host innate defence

Bacillus cereus is a spore forming bacteria recognized among the leading agents responsible for foodborne outbreaks in Europe. B. cereus is also gaining notoriety as an opportunistic human pathogen inducing local and systemic infections. The real incidence of such infection is likely underestimated and information on genetic and phenotypic characteristics of the incriminated strains is generally scarce. We have recently analyzed a large strain collection of varying pathogenic potential. Screening for biomarkers to differentiate among clinical and non-clinical strains, a gene encoding an alcohol dehydrogenase-like protein was identified among the leading candidates. This family of proteins has been demonstrated to be involved in the virulence of several bacterial species. The relevant gene was knocked out to elucidate its function with regards to resistance to host innate immune response, both in vitro and in vivo. Our results demonstrate that the adhB gene plays a significant role in resistance to nitric oxide and oxidative stress in vitro, as well as its pathogenic ability with regards to in vivo toxicity. These properties may explain the pathogenic potential of strains carrying this newly identified virulence factor.

Structural elucidation of spiro cyclohexandienonyl naphthalenes with potential anti-neuroinflammatory activities from Caragana acanthophylla Kom

Four undescribed spiro cyclohexandienonyl naphthalenes (acanthophyllas A-D) and a revised compound were isolated from the roots of Caragana acanthophylla Kom. (Fabaceae). They were identified using extensive spectroscopic data and via chemical methods. Three of them were resolved into their enantiomers, and their absolute configurations were confirmed by comparing the experimental and calculated electronic circular dichroism spectra. Moreover, the anti-inflammatory activities of the compounds were investigated by evaluating their inhibitory effects on nitric oxide production in lipopolysaccharide-stimulated BV-2 cells. Some compounds showed significant inhibitory activities with IC50 values of 8.8-13.4 μM (minocycline, IC50 7.8 μM), indicating that they might serve as potential therapeutic agents for neurodegenerative diseases.

Eudesmane-type and agarospirane-type sesquiterpenes from agarwood of Aquilaria agallocha

Eleven previously unreported sesquiterpenes, including nine eudesmane-type (agalleudesmanol A-I) and two agarospirane-type sesquiterpenes (agarospiranic aldehyde A-B), together with eight known sesquiterpenes, were isolated from the agarwood of Aquilaria agallocha Roxb. The structures were established based on extensive spectroscopic analyses, including infrared (IR), high-resolution electrospray ionisation mass spectrometry (HRESIMS), nuclear magnetic resonance (NMR), X-ray diffraction, quantum chemical calculations based on empirical electronic circular dichroism (ECD) data, and DP4+ probability analysis. The bioactivity of these undescribed compounds against lipopolysaccharide (LPS)-induced NO production in RAW 264.7 cells was evaluated. Compounds 1 and 2 exhibited significant anti-inflammatory activities, with IC₅₀ values of 5.46-14.07 μM (aminoguanidine as positive control, IC₅₀ 20.33 ± 1.08 μM).

Effects of dietary supplementation of Vitamins E and C on oxidative stress induced by a Nigerian velogenic strain of the Newcastle disease virus (KUDU 113) in the brain and bursa of Fabricius of broiler chickens

Background and Aim:

Newcastle disease (ND) is widely recognized as an extremely harmful and contagious disease of birds. Therefore, the present study aims to evaluate the effect of oxidative stress induced by the virulent ND virus (NDV) (KUDU 113) on the plasma, brain, bursa of Fabricius, NDV antibody response, and hematology as well as the ameliorative effect of the individual or combined use of Vitamins E and C on the clinical signs of NDV-infected chickens.

Materials and Methods:

In this study, a total of 150 broiler chickens were included and divided into five groups: Group 1, nonsupplemented and unchallenged chickens (UCC); Group 2, nonsupplemented and challenged chickens (ICC); Group 3, Vitamin C-supplemented + challenged chickens; Group 4, Vitamin E-supplemented + challenged chickens; and Group 5, Vitamins E and C-supplemented + challenged chickens. Groups 3, 4, and 5 were supplemented with Vitamins E and C (33 and 400 mg/kg/day, respectively). Virus challenge was done with 0.1 ml of KUDU 113 7 days after the start of vitamin inclusion in their diet. Concentrations of glutathione (GSH), malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), and catalase (CAT) were analyzed in the plasma, brain, and bursa on days 0, 3, and 7 post-infection (pi) using the biochemical method. The blood samples were randomly collected from five chickens in each group for antibody response and hematological analyses on day 0 previtamin treatment and at 0, 3, 7, 10, 14, and 21 days pi (dpi).

Results:

A significant increase in the concentrations of MDA and NO in the NDV-challenged chickens was observed when compared with the UCCs. Moreover, a significant decrease in GSH concentration was observed in the NDV-challenged chickens when compared with the UCCs. The activities of CAT and SOD were reduced markedly in the NDV-challenged chickens. Increases in the mean antibody titers were observed in the NDV-challenged group when compared with the UCCs from days 3 to 21 pi. The mortality rates of groups 1, 2, 3, 4, and 5 were 0%, 30%, 3.3%, 3.3%, and 26.6%, respectively.

Conclusion:

The findings of this study suggest that KUDU 113 causes oxidative stress in the brain and bursa of Fabricius of chickens. Individual supplementation with Vitamin E or C was found to be more effective in ameliorating oxidative stress, improving the immune response, and reducing mortality in KUDU 113 infections than the combined supplementation of Vitamins C and E.

Anti-proliferative and anti-inflammatory prenylated isoflavones and coumaronochromones from the fruits of Ficus altissima

Ficus altissima, an evergreen arbor belonging to the Moraceae family, is mainly cultivated in the tropics and subtropics of South and Southeast Asia with the characteristic of exuberant vitality and luxuriant foliage. In this article, four new prenylated isoflavones (1-4), along with ten previously described isoflavones (5-14) and two known prenylated coumaronochromones (15 and 16) were firstly obtained from the fruits of F. altissima. Their structures were identified by various spectroscopic techniques including specific optical rotation, HR-ESI-MS and NMR. The isolated products were evaluated for their anti-proliferative activities against three human tumor cell lines (HepG2, MCF-7 and MDA-MB-231) through MTT assay. Compounds 2, 3 and 16 exhibited obvious anti-proliferative activities against MDA-MB-231 cell line and compounds 3, 13 and 16 showed effective cytotoxic effects on HepG2 cell line in a concentration-dependent manner, as verified by the colony formation assay, cell and nucleus morphological assessment and apoptosis assay. Meanwhile, compounds 5 and 12 exhibited significant inhibition activities on NO production in LPS-stimulated RAW 264.7 cell line compared with positive control indometacin. The phytochemical investigation of the fruits of F. altissima in this study could provide the evidence for the discovery of lead compounds.

Implication of a Key Region of Six Bacillus cereus Genes Involved in Siroheme Synthesis, Nitrite Reductase Production and Iron Cluster Repair in the Bacterial Response to Nitric Oxide Stress

Bacterial response to nitric oxide (NO) is of major importance for bacterial survival. NO stress is a main actor of the eukaryotic immune response and several pathogenic bacteria have developed means for detoxification and repair of the damages caused by NO. However, bacterial mechanisms of NO resistance by Gram-positive bacteria are poorly described. In the opportunistic foodborne pathogen Bacillus cereus, genome sequence analyses did not identify homologs to known NO reductases and transcriptional regulators, such as NsrR, which orchestrate the response to NO of other pathogenic or non-pathogenic bacteria. Using a transcriptomic approach, we investigated the adaptation of B. cereus to NO stress. A cluster of 6 genes was identified to be strongly up-regulated in the early phase of the response. This cluster contains an iron-sulfur cluster repair enzyme, a nitrite reductase and three enzymes involved in siroheme biosynthesis. The expression pattern and close genetic localization suggest a functional link between these genes, which may play a pivotal role in the resistance of B. cereus to NO stress during infection.

Acceleration of Nitric Oxide Release in Multilayer Nanofilms through Cu(II) Ion Intercalation for Antibacterial Applications

Implant-derived bacterial infection is a prevalent cause of diseases, and no antibacterial coating currently exists that is biocompatible and that does not induce multidrug resistance. To this end, nitric oxide (NO) has been emerging as an effective antimicrobial agent that acts on a broad range of bacteria and elicits no known resistance. Here, a method for accelerating NO release from multilayered nanofilms has been developed for facilitating antibacterial activity. A previously reported multilayered nanofilm (nbi film) was fabricated by alternative deposition of branched polyethyleneimine (BPEI) and alginate via the layer-by-layer assembly method. N-Diazeniumdiolate, a chemical NO donor, was synthesized at the secondary amine moiety of BPEI within the film (nbi/NO film). Cu(II) ions can be incorporated into the film by forming chelating compounds with unreacted amines that have not been converted to NO donors. The increase of the amine protonation state in the chelate caused destabilization of the NO donor by reducing hydrogen bonding between the deprotonated amine and the NO donor. Thus, the Cu(II) ion-embedding film presented accelerated NO release and was further subjected to antibacterial testing to demonstrate the correlation between the NO release rate and the antibacterial activity. This study aimed to establish a novel paradigm for NO-releasing material design based on multilayered nanofilms by presenting the correlation between the NO release rate and the antibacterial effect.

Rosanortriterpenes A-B, Two Promising Agents from Rosa laevigata var. leiocapus, Alleviate Inflammatory Responses and Liver Fibrosis in In Vitro Cell Models

Rosanortriterpenes A–B (RTA and RTB), two nortriterpenoids, are characteristic constituents in the fruits of Rosa laevigata var. leiocapus. However, pharmacological studies on these compounds are still scarce. In the present study, we aim to investigate the anti-inflammatory mechanisms associated with the effects of RTA–B in RAW264.7 macrophages and LO₂ cells by detecting cell viabilities, nitric oxide (NO) production, tumour necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) production. Simultaneously, the anti-inflammatory action mechanisms of these two compounds were illustrated through western blot assay. Besides, the antihepatic fibrosis activities of these compounds have also been explored. The results demonstrated that RTA and RTB inhibited the production of NO, TNF-α, and IL-6 and suppressed liver fibrosis. RTA and RTB treatment also greatly inhibited the activation of NF-kappaB (NF-κB) pathway. Our study confirmed the promising anti-inflammatory and anti-liver fibrosis actions of RTA–B, suggesting that they might be developed as alternative and promising drugs for the treatment of hepatic inflammatory and fibrotic diseases.

Nitric oxide-releasing cyclodextrins as biodegradable antibacterial scaffolds: a patent evaluation of US2019343869(A1)

INTRODUCTION

Antimicrobial resistance is one of the major scourges for health care worldwide; therefore, novel investigational approaches are needed to potentiate and preserve the current antibacterial arsenal. Cyclodextrins are known to improve the formulability of several different therapeutic agents. When functionalized with nitric oxide (NO) releasing groups, and suitably loaded with an antibacterial or antitumoral agents, they can exert additive activity, especially toward certain bacterial strains and cell cancer lines.

AREAS COVERED

US2019343869 describes NO-releasing cyclodextrins, a method for their synthesis, a composition that is based on them, and their application as anticancer or antibacterial agents, especially toward planktonic P. aeruginosa and the biofilm resulting from infection. Anticancer activity is measured against A549 cells. The amount of NO released is in the range of 0.5 μmol to 2.5 μmol per milligram of functionalized cyclodextrin with a half-life for NO release in a range of between about 0.7-4.2 hours.

EXPERT OPINION

The results support the use of NO-releasing cyclodextrins as a matrix for the delivery of antibacterial and anticancer drugs in a suitable formulation. However, antibacterial activity seems to be weak, and more focused studies are needed.

Sesquiterpenoids from the roots of Daphne genkwa Siebold et Zucc. With potential anti-inflammatory activity

Six undescribed sesquiterpenoids, including three acorane-type sesquiterpenoids (daphneaines A-C), three guaiane-type sesquiterpenoids (daphneaines E-G) and three known analogues were isolated from the roots of Daphne genkwa Siebold et Zucc. Their gross structures were elucidated by comprehensive spectroscopic analyses. The relative configurations of daphneaines A-C were determined by NOESY experiments. In addition, the relative configuration of daphneaine G was elucidated by performing a quantum chemical calculation of the NMR chemical shifts coupled with an advanced statistical procedure DP4+. The comparison of experimental and calculated electronic circular dichroism (ECD) data led to the establishment of the absolute configurations of daphneaines A-G. All isolates were tested for their inhibitory activity towards the LPS-induced NO production in RAW 264.7 macrophages, and daphneaine F showed inhibitory effect on NO production with an IC₅₀ value of 35.68 ± 3.18 μM.

Improving wastewater management using free nitrous acid (FNA)

Free nitrous acid (FNA), the protonated form of nitrite, has historically been an unwanted substance in wastewater systems due to its inhibition on a wide range of microorganisms. However, in recent years, advanced understanding of FNA inhibitory and biocidal effects on microorganisms has led to the development of a series of FNA-based applications that improve wastewater management practices. FNA has been used in sewer systems to control sewer corrosion and odor; in wastewater treatment to achieve carbon and energy efficient nitrogen removal; in sludge management to improve the sludge reduction and energy recovery; in membrane systems to address membrane fouling; and in wastewater algae systems to facilitate algae harvesting. This paper aims to comprehensively and critically review the current status of FNA-based applications in improving wastewater management. The underlying mechanisms of FNA inhibitory and biocidal effects are also reviewed and discussed. Knowledge gaps and current limitations of the FNA-based applications are identified; and perspectives on the development of FNA-based applications are discussed. We conclude that the FNA-based technologies have great potential for enhancing the performance of wastewater systems; however, further development and demonstration at larger scales are still required for their wider applications.

Metabolic host response and therapeutic approaches to influenza infection

Based on available metabolomic studies, influenza infection affects a variety of cellular metabolic pathways to ensure an optimal environment for its replication and production of viral particles. Following infection, glucose uptake and aerobic glycolysis increase in infected cells continually, which results in higher glucose consumption. The pentose phosphate shunt, as another glucose-consuming pathway, is enhanced by influenza infection to help produce more nucleotides, especially ATP. Regarding lipid species, following infection, levels of triglycerides, phospholipids, and several lipid derivatives undergo perturbations, some of which are associated with inflammatory responses. Also, mitochondrial fatty acid β-oxidation decreases significantly simultaneously with an increase in biosynthesis of fatty acids and membrane lipids. Moreover, essential amino acids are demonstrated to decline in infected tissues due to the production of large amounts of viral and cellular proteins. Immune responses against influenza infection, on the other hand, could significantly affect metabolic pathways. Mainly, interferon (IFN) production following viral infection affects cell function via alteration in amino acid synthesis, membrane composition, and lipid metabolism. Understanding metabolic alterations required for influenza virus replication has revealed novel therapeutic methods based on targeted inhibition of these cellular metabolic pathways.

Increased Resistance of Nitrite-Admixed Concrete to Microbially Induced Corrosion in Real Sewers

Microbially induced concrete corrosion is a major deterioration process in sewers, causing a huge economic burden, and improved mitigating technologies are required. This study reports a novel and promising effective solution to attenuate the corrosion in sewers using calcium nitrite-admixed concrete. This strategy aims to suppress the development and activity of corrosion-inducing microorganisms with the antimicrobial free nitrous acid, which is generated in situ from calcium nitrite that is added to the concrete. Concrete coupons with calcium nitrite as an admixture were exposed in a sewer manhole, together with control coupons that had no nitrite admixture, for 18 months. The corrosion process was monitored by measuring the surface pH, corrosion product composition, concrete corrosion loss, and the microbial community on the corrosion layer. During the exposure, the corrosion loss of the admixed concrete coupons was 30% lower than that of the control coupons. The sulfide uptake rate of the admixed concrete was also 30% lower, leading to a higher surface pH (0.5-0.6 unit), in comparison to that of the control coupons. A negative correlation between the calcium nitrite admixture in concrete and the abundance of sulfide-oxidizing microorganisms was determined by DNA sequencing. The results obtained in this field study demonstrated that this novel use of calcium nitrite as an admixture in concrete is a promising strategy to mitigate the microbially induced corrosion in sewers.

Cytonemes Versus Neutrophil Extracellular Traps in the Fight of Neutrophils with Microbes

Neutrophils can phagocytose microorganisms and destroy them intracellularly using special bactericides located in intracellular granules. Recent evidence suggests that neutrophils can catch and kill pathogens extracellularly using the same bactericidal agents. For this, live neutrophils create a cytoneme network, and dead neutrophils provide chromatin and proteins to form neutrophil extracellular traps (NETs). Cytonemes are filamentous tubulovesicular secretory protrusions of living neutrophils with intact nuclei. Granular bactericides are localized in membrane vesicles and tubules of which cytonemes are composed. NETs are strands of decondensed DNA associated with histones released by died neutrophils. In NETs, bactericidal neutrophilic agents are adsorbed onto DNA strands and are not covered with a membrane. Cytonemes and NETs occupy different places in protecting the body against infections. Cytonemes can develop within a few minutes at the site of infection through the action of nitric oxide or actin-depolymerizing alkaloids of invading microbes. The formation of NET in vitro occurs due to chromatin decondensation resulting from prolonged activation of neutrophils with PMA (phorbol 12-myristate 13-acetate) or other stimuli, or in vivo due to citrullination of histones with peptidylarginine deiminase 4. In addition to antibacterial activity, cytonemes are involved in cell adhesion and communications. NETs play a role in autoimmunity and thrombosis.

Macrocyclic Diterpenoids from Euphorbia helioscopia and Their Potential Anti-inflammatory Activity

Guided by ¹H NMR spectroscopic experiments using the aromatic protons as probes, 11 macrocyclic diterpenes (1-11) were isolated from the aerial parts of Euphorbia helioscopia. Their full three-dimensional structures, including absolute configurations, were established unambiguously by spectroscopic analysis and single-crystal X-ray crystallographic experiments. Among the isolated compounds, compound 1 is the third member thus far of a rare class of Euphorbia diterpenes featuring an unusual 5/10 fused ring system, and 2-4 are new jatrophane diterpenes. Based on the NMR data of the jatrophane diterpenes obtained in this study as well as those with crystallographic structures reported in the literature, the correlations of the chemical shifts of the relevant carbons and the configurations of C-2, C-13, and C-14 of their flexible macrocyclic ring were considered. Moreover, the anti-inflammatory activities of 1-11 were investigated by monitoring their inhibitory effects on nitric oxide production in lipopolysaccharide-stimulated RAW 264.7 cells. Compound 1 showed an IC₅₀ of 7.4 ± 0.6 μM, which might be related to the regulation of the NF-κB signaling pathway by suppressing the translocation of the p65 subunit and the consequent reduction of IL-6 and TNF-α secretions.

Roles of Toll-Like Receptors in Nitroxidative Stress in Mammals

Free radicals are important antimicrobial effectors that cause damage to DNA, membrane lipids, and proteins. Professional phagocytes produce reactive oxygen species (ROS) and reactive nitrogen species (RNS) that contribute towards the destruction of pathogens. Toll-like receptors (TLRs) play a fundamental role in the innate immune response and respond to conserved microbial products and endogenous molecules resulting from cellular damage to elicit an effective defense against invading pathogens, tissue injury, or cancer. In recent years, several studies have focused on how the TLR-mediated activation of innate immune cells leads to the production of pro-inflammatory factors upon pathogen invasion. Here, we review recent findings that indicate that TLRs trigger a signaling cascade that induces the production of reactive oxygen and nitrogen species.

Zanamivir Diminishes Lung Damage in Influenza A Virus-infected Mice by Inhibiting Nitric Oxide Production

BACKGROUND/AIM

Severe pulmonary influenza A virus (IAV) infection causes lung inflammation and expression of inducible nitric oxide synthase (iNOS), leading to overproduction of nitric oxide (NO). We studied whether zanamivir reduces pulmonary inflammation through inhibition of NO production in mice.

MATERIALS AND METHODS

We treated IAV-infected mice daily with intranasal zanamivir. Controls were infected and either placebo-treated or untreated, or not infected and placebo-treated. Mice were weighed daily. After euthanasia on day 3, lungs were excised and bronchoalveolar lavage was performed and fluid nitrite concentration was determined. Lungs were analyzed microscopically. iNOS and IAV RNA levels in lungs were assessed using quantitative reverse transcription-polymerase chain reaction (RT-qPCR).

RESULTS

Mice undergoing zanamivir treatment had less weight loss, viral replication, and lung damage, as well as significant reductions of local NO and iNOS mRNA synthesis (p<0.05).

CONCLUSION

Zanamivir is associated with an anti-inflammatory effect mediated through inhibition of NO production in IAV-infected mice.

Feline calicivirus- and murine norovirus-induced COX-2/PGE2 signaling pathway has proviral effects

Cyclooxygenases (COXs)/prostaglandin E₂ (PGE₂) signaling pathways are known to modulate a variety of homeostatic processes and are involved in various pathophysiological conditions. COXs/PGE₂ signaling pathways have also been demonstrated to have proviral or antiviral effects, which appeared different even in the same virus family. A porcine sapovirus Cowden strain, a member of genus Sapovirus within the Caliciviridae family, induces strong COX-2/PGE₂ but transient COX-1/PGE₂ signaling to enhance virus replication. However, whether infections of other viruses in the different genera activate COXs/PGE₂ signaling, and thus affect the replication of viruses, remains unknown. In the present study, infections of cells with the feline calicivirus (FCV) F9 strain in the genus Vesivirus and murine norovirus (MNV) CW-1 strain in the genus Norovirus only activated the COX-2/PGE₂ signaling in a time-dependent manner. Treatment with pharmacological inhibitors or transfection of small interfering RNAs (siRNAs) against COX-2 enzyme significantly reduced the production of PGE₂ as well as FCV and MNV replications. The inhibitory effects of these pharmacological inhibitors against COX-2 enzyme on the replication of both viruses were restored by the addition of PGE₂. Silencing of COX-1 via siRNAs and inhibition of COX-1 via an inhibitor also decrease the production of PGE₂ and replication of both viruses, which can be attributed to the inhibition COX-1/PGE₂ signaling pathway. These data indicate that the COX-2/PGE₂ signaling pathway has proviral effects for the replication of FCV and MNV, and pharmacological inhibitors against these enzymes serve as potential therapeutic candidates for treating FCV and MNV infections.

Mangiferin alleviates hypertension induced by hyperuricemia via increasing nitric oxide releases

Mangiferin, a natural glucosyl xanthone, was confirmed to be an effective uric acid (UA)- lowering agent with dual action of inhibiting production and promoting excretion of UA. In this study, we aimed to evaluate the effect of mangiferin on alleviating hypertension induced by hyperuricemia. Mangiferin (30, 60, 120 mg/kg) was administered intragastrically to hyperuricemic rats induced by gavage with potassium oxonate (750 mg/kg). Systolic blood pressure (SBP), serum levels of UA, nitric oxide (NO), C-reactionprotein (CRP) and ONOO^- were measured. The mRNA and protein levels of endothelial nitric oxide synthase (eNOS), intercellular adhesion molecule-1 (ICAM-1), CRP were also analyzed. Human umbilical vein endothelial cells (HUVECs) were used in vitro studies. Administration of mangiferin significantly decreased the serum urate level and SBP at 8 weeks and last to 12 weeks. Further more, mangiferin could increase the release of NO and decrease the level of CRP in blood. In addition, mangiferin reversed the protein expression of eNOS, CRP, ICAM-1 and ONOO^- in aortic segments in hyperuricemic rats. The results in vitro were consistent with the observed results in vivo. Taken together, these data suggested that mangiferin has played an important part in alleviating hypertension induced by hyperuricemia via increasing NO secretion and improving endothelial function.

Vitamin E Supplementation Ameliorates Newcastle Disease Virus-Induced Oxidative Stress and Alleviates Tissue Damage in the Brains of Chickens

Newcastle disease (ND), characterized by visceral, respiratory, and neurological pathologies, causes heavy economic loss in the poultry industry around the globe. While significant advances have been made in effective diagnosis and vaccine development, molecular mechanisms of ND virus (NDV)-induced neuropathologies remain elusive. In this study, we report the magnitude of oxidative stress and histopathological changes induced by the virulent NDV (ZJ1 strain) and assess the impact of vitamin E in alleviating these pathologies. Comparative profiling of plasma and brains from mock and NDV-infected chicken demonstrated alterations in several oxidative stress makers such as nitric oxide, glutathione, malondialdehyde, total antioxidant capacity, glutathione S-transferase, superoxide dismutase, and catalases. While decreased levels of glutathione and total antioxidant capacity and increased concentrations of malondialdehyde and nitric oxide were observed in NDV-challenged birds at all time points, these alterations were eminent at latter time points (5 days post infection). Additionally, significant decreases in the activities of glutathione S-transferase, superoxide dismutase, and catalase were observed in the plasma and brains collected from NDV-infected chickens. Intriguingly, we observed that supplementation of vitamin E can significantly reduce the alteration of oxidative stress parameters. Under NDV infection, extensive histopathological alterations were observed in chicken brain including neural inflammation, capillary hyperemia, necrosis, and loss of prominent axons, which were reduced with the treatment of vitamin E. Taken together, our findings highlight that neurotropic NDV induces extensive tissue damage in the brain and alters plasma oxidative stress profiles. These findings also demonstrate that supplementing vitamin E ameliorates these pathologies in chickens and proposes its supplementation for NDV-induced stresses.

The Inflammasome: Regulation of Nitric Oxide and Antimicrobial Host Defence

Nitric oxide (NO) is a gaseous signalling molecule that plays diverse physiological functions including antimicrobial host defence. During microbial infection, NO is synthesized by inducible NO synthase (iNOS), which is expressed by host immune cells through the recognition of microbial pattern molecules. Therefore, sensing pathogens or their pattern molecules by pattern recognition receptors (PRRs), which are located at the cell surface, endosomal and phagosomal compartment, or in the cytosol, is key in inducing iNOS and eliciting antimicrobial host defence. A group of cytosolic PRRs is involved in inducing NO and other antimicrobial molecules by forming a molecular complex called the inflammasome. Assembled inflammasomes activate inflammatory caspases, such as caspase-1 and caspase-11, which in turn process proinflammatory cytokines IL-1β and IL-18 into their mature forms and induce pyroptotic cell death. IL-1β and IL-18 play a central role in immunity against microbial infection through activation and recruitment of immune cells, induction of inflammatory molecules, and regulation of antimicrobial mediators including NO. Interestingly, NO can also regulate inflammasome activity in an autocrine and paracrine manner. Here, we discuss molecular mechanisms of inflammasome formation and the inflammasome-mediated regulation of host defence responses during microbial infections.

Homocysteine, Infections, Polyamines, Oxidative Metabolism, and the Pathogenesis of Dementia and Atherosclerosis

Hyperhomocysteinemia is a risk factor for development of dementia and Alzheimer's disease (AD), and low blood levels of folate and cobalamin are associated with hyperhomocysteinemia and AD. In elderly subjects with cognitive decline, supplementation with folate, cobalamin, and pyridoxal demonstrated reduction of cerebral atrophy in gray matter regions vulnerable to the AD process. Multiple pathogenic microbes are implicated as pathogenic factors in AD and atherosclerosis, and the deposition of amyloid-β (Aβ), phosphorylation of tau protein, neuronal injury, and apoptosis in AD are secondary to microbial infection. Glucose utilization and blood flow are reduced in AD, and these changes are accompanied by downregulation of glucose transport, Na, K-ATPase, oxidative phosphorylation, and energy consumption. Thioretinaco ozonide, the complex formed from thioretinamide, cobalamin, ozone, and oxygen is proposed to constitute the active site of oxidative phosphorylation, catalyzing synthesis of adenosine triphosphate (ATP) from nicotinamide adenine dinucleotide (NAD+) and phosphate. Pathogenic microbes cause synthesis of polyamines in host cells by increasing the transfer of aminopropyl groups from adenosyl methionine to putrescine, resulting in depletion of intracellular adenosyl methionine concentrations in host cells. Depletion of adenosyl methionine causes dysregulation of methionine metabolism, hyperhomocysteinemia, reduced biosynthesis of thioretinamide and thioretinaco ozonide, decreased oxidative phosphorylation, decreased production of nitric oxide and peroxynitrite, and impaired host response to infectious microbes, contributing to the pathogenesis of dementia and atherosclerosis.

Hyperhomocysteinemia, Suppressed Immunity, and Altered Oxidative Metabolism Caused by Pathogenic Microbes in Atherosclerosis and Dementia

Many pathogenic microorganisms have been demonstrated in atherosclerotic plaques and in cerebral plaques in dementia. Hyperhomocysteinemia, which is a risk factor for atherosclerosis and dementia, is caused by dysregulation of methionine metabolism secondary to deficiency of the allosteric regulator, adenosyl methionine. Deficiency of adenosyl methionine results from increased polyamine biosynthesis by infected host cells, causing increased activity of ornithine decarboxylase, decreased nitric oxide and peroxynitrate formation and impaired immune reactions. The down-regulation of oxidative phosphorylation that is observed in aging and dementia is attributed to deficiency of thioretinaco ozonide oxygen complexed with nicotinamide adenine dinucleotide and phosphate, which catalyzes oxidative phosphorylation. Adenosyl methionine biosynthesis is dependent upon thioretinaco ozonide and adenosine triphosphate (ATP), and the deficiency of adenosyl methionine and impaired immune function in aging are attributed to depletion of thioretinaco ozonide from mitochondrial membranes. Allyl sulfides and furanonaphthoquinones protect against oxidative stress and apoptosis by increasing the endogenous production of hydrogen sulfide and by inhibiting electron transfer to the active site of oxidative phosphorylation. Diallyl trisulfide and napabucasin inhibit the signaling by the signal transducer and activator of transcription 3 (Stat3), potentially enhancing immune function by effects on T helper lymphocytes and promotion of apoptosis. Homocysteine promotes endothelial dysfunction and apoptosis by the unfolded protein response and endoplasmic reticulum stress through activation of the N-methyl D-aspartate (NMDA) receptor, causing oxidative stress, calcium influx, apoptosis and endothelial dysfunction. The prevention of atherosclerosis and dementia may be accomplished by a proposed nutritional metabolic homocysteine-lowering protocol which enhances immunity and corrects the altered oxidative metabolism in atherosclerosis and dementia.

Activation of COX-2/PGE2 Promotes Sapovirus Replication via the Inhibition of Nitric Oxide Production

Enteric caliciviruses in the genera Norovirus and Sapovirus are important pathogens that cause severe acute gastroenteritis in both humans and animals. Cyclooxygenases (COXs) and their final product, prostaglandin E₂ (PGE₂), are known to play important roles in the modulation of both the host response to infection and the replicative cycles of several viruses. However, the precise mechanism(s) by which the COX/PGE₂ pathway regulates sapovirus replication remains largely unknown. In this study, infection with porcine sapovirus (PSaV) strain Cowden, the only cultivable virus within the genus Sapovirus, markedly increased COX-2 mRNA and protein levels at 24 and 36 h postinfection (hpi), with only a transient increase in COX-1 levels seen at 24 hpi. The treatment of cells with pharmacological inhibitors, such as nonsteroidal anti-inflammatory drugs or small interfering RNAs (siRNAs) against COX-1 and COX-2, significantly reduced PGE₂ production, as well as PSaV replication. Expression of the viral proteins VPg and ProPol was associated with activation of the COX/PGE₂ pathway. We observed that pharmacological inhibition of COX-2 dramatically increased NO production, causing a reduction in PSaV replication that could be restored by inhibition of nitric oxide synthase via the inhibitor N-nitro-l-methyl-arginine ester. This study identified a pivotal role for the COX/PGE₂ pathway in the regulation of NO production during the sapovirus life cycle, providing new insights into the life cycle of this poorly characterized family of viruses. Our findings also reveal potential new targets for treatment of sapovirus infection.

IMPORTANCE

Sapoviruses are among the major etiological agents of acute gastroenteritis in both humans and animals, but little is known about sapovirus host factor requirements. Here, using only cultivable porcine sapovirus (PSaV) strain Cowden, we demonstrate that PSaV induced the vitalization of the cyclooxygenase (COX) and prostaglandin E₂ (PGE₂) pathway. Targeting of COX-1/2 using nonsteroidal anti-inflammatory drugs (NSAIDs) such as the COX-1/2 inhibitor indomethacin and the COX-2-specific inhibitors NS-398 and celecoxib or siRNAs targeting COXs, inhibited PSaV replication. Expression of the viral proteins VPg and ProPol was associated with activation of the COX/PGE₂ pathway. We further demonstrate that the production of PGE₂ provides a protective effect against the antiviral effector mechanism of nitric oxide. Our findings uncover a new mechanism by which PSaV manipulates the host cell to provide an environment suitable for efficient viral growth, which in turn can be a new target for treatment of sapovirus infection.

The Bacterial Mfd Protein Prevents DNA Damage Induced by the Host Nitrogen Immune Response in a NER-Independent but RecBC-Dependent Pathway

Production of reactive nitrogen species is an important component of the host immune defence against bacteria. Here, we show that the bacterial protein Mfd (Mutation frequency decline), a highly conserved and ubiquitous bacterial protein involved in DNA repair, confers bacterial resistance to the eukaryotic nitrogen response produced by macrophage cells and during mice infection. In addition, we show that RecBC is also necessary to survive this stress. The inactivation of recBC and mfd genes is epistatic showing that Mfd follows the RecBC repair pathway to protect the bacteria against the genotoxic effect of nitrite. Surprisingly given the role of Mfd in transcription-coupled repair, UvrA is not necessary to survive the nitrite response. Taken together, our data reveal that during the eukaryotic nitrogen response, Mfd is required to maintain bacterial genome integrity in a NER-independent but RecBC-dependent pathway.

[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.

The bacterial DNA repair protein Mfd confers resistance to the host nitrogen immune response

Production of reactive nitrogen species (NO) is a key step in the immune response following infections. NO induces lesions to bacterial DNA, thus limiting bacterial growth within hosts. Using two pathogenic bacteria, Bacillus cereus and Shigella flexneri, we show that the DNA-repair protein Mfd (Mutation-Frequency-Decline) is required for bacterial resistance to the host-NO-response. In both species, a mutant deficient for mfd does not survive to NO, produced in vitro or by phagocytic cells. In vivo, the ∆mfd mutant is avirulent and unable to survive the NO-stress. Moreover, NO induces DNA-double-strand-breaks and point mutations in the Δmfd mutant. In overall, these observations demonstrate that NO damages bacterial DNA and that Mfd is required to maintain bacterial genomic integrity. This unexpected discovery reveals that Mfd, a typical housekeeping gene, turns out to be a true virulence factor allowing survival and growth of the pathogen in its host, due to its capacity to protect the bacterium against NO, a key molecule of the innate immune defense. As Mfd is widely conserved in the bacterial kingdom, these data highlight a mechanism that may be used by a large spectrum of bacteria to overcome the host immune response and especially the mutagenic properties of NO.

Predicting disease onset in clinically healthy people

Virtually all human disease is induced by oxidative stress. Oxidative stress, which is caused by toxic environmental exposure, the presence of disease, lifestyle choices, stress, chronic inflammation or combinations of these, is responsible for most disease. Oxidative stress from all sources is additive and it is the total oxidative stress from all sources that induces the onset of most disease. Oxidative stress leads to lipid peroxidation, which in turn produces Malondialdehyde. Serum malondialdehyde level is an additive parameter resulting from all sources of oxidative stress and, therefore, is a reliable indicator of total oxidative stress which can be used to predict the onset of disease in clinically asymptomatic individuals and to suggest the need for treatment that can prevent much human disease.

Sendai virus intra-host population dynamics and host immunocompetence influence viral virulence during in vivo passage

In vivo serial passage of non-pathogenic viruses has been shown to lead to increased viral virulence, and although the precise mechanism(s) are not clear, it is known that both host and viral factors are associated with increased pathogenicity. Under- or overnutrition leads to a decreased or dysregulated immune response and can increase viral mutant spectrum diversity and virulence. The objective of this study was to identify the role of viral mutant spectra dynamics and host immunocompetence in the development of pathogenicity during in vivo passage. Because the nutritional status of the host has been shown to affect the development of viral virulence, the diet of animal model reflected two extremes of diets which exist in the global population, malnutrition and obesity. Sendai virus was serially passaged in groups of mice with differing nutritional status followed by transmission of the passaged virus to a second host species, guinea pigs. Viral population dynamics were characterized using deep sequence analysis and computational modeling. Histopathology, viral titer and cytokine assays were used to characterize viral virulence. Viral virulence increased with passage and the virulent phenotype persisted upon passage to a second host species. Additionally, nutritional status of mice during passage influenced the phenotype. Sequencing revealed the presence of several non-synonymous changes in the consensus sequence associated with passage, a majority of which occurred in the hemagglutinin-neuraminidase and polymerase genes, as well as the presence of persistent high frequency variants in the viral population. In particular, an N1124D change in the consensus sequences of the polymerase gene was detected by passage 10 in a majority of the animals. In vivo comparison of an 1124D plaque isolate to a clone with 1124N genotype indicated that 1124D was associated with increased virulence.

The Campylobacter jejuni MarR-like transcriptional regulators RrpA and RrpB both influence bacterial responses to oxidative and aerobic stresses

The ability of the human intestinal pathogen Campylobacter jejuni to respond to oxidative stress is central to bacterial survival both in vivo during infection and in the environment. Re-annotation of the C. jejuni NCTC11168 genome revealed the presence of two MarR-type transcriptional regulators Cj1546 and Cj1556, originally annotated as hypothetical proteins, which we have designated RrpA and RrpB (regulator of response to peroxide) respectively. Previously we demonstrated a role for RrpB in both oxidative and aerobic (O2) stress and that RrpB was a DNA binding protein with auto-regulatory activity, typical of MarR-type transcriptional regulators. In this study, we show that RrpA is also a DNA binding protein and that a rrpA mutant in strain 11168H exhibits increased sensitivity to hydrogen peroxide oxidative stress. Mutation of either rrpA or rrpB reduces catalase (KatA) expression. However, a rrpAB double mutant exhibits higher levels of resistance to hydrogen peroxide oxidative stress, with levels of KatA expression similar to the wild-type strain. Mutation of either rrpA or rrpB also results in a reduction in the level of katA expression, but this reduction was not observed in the rrpAB double mutant. Neither the rrpA nor rrpB mutant exhibits any significant difference in sensitivity to either cumene hydroperoxide or menadione oxidative stresses, but both mutants exhibit a reduced ability to survive aerobic (O2) stress, enhanced biofilm formation and reduced virulence in the Galleria mellonella infection model. The rrpAB double mutant exhibits wild-type levels of biofilm formation and wild-type levels of virulence in the G mellonella infection model. Together these data indicate a role for both RrpA and RrpB in the C. jejuni peroxide oxidative and aerobic (O2) stress responses, enhancing bacterial survival in vivo and in the environment.

Chlamydia trachomatis inhibits inducible NO synthase in human mesenchymal stem cells by stimulating polyamine synthesis

Chlamydia trachomatis is considered the most common agent of sexually transmitted disease worldwide. As an obligate intracellular bacterium, it relies on the host for survival. Production of NO is an effective antimicrobial defense mechanism of the innate immune system. However, whether NO is able to arrest chlamydial growth remains unclear. Similarly, little is known about the mechanisms underlying subversion of cellular innate immunity by C. trachomatis. By analyzing protein and mRNA expression in infected human mesenchymal stem cells, combined with RNA interference and biochemical assays, we observed that infection with C. trachomatis led to downregulated expression of inducible NO synthase (iNOS) in human mesenchymal stem cells in vitro. Furthermore, infection upregulated the expression of the rate-limiting enzyme in the polyamine biosynthetic pathway, ornithine decarboxylase, diverting the iNOS substrate l-arginine toward the synthesis of polyamines. Inhibition of ornithine decarboxylase activity using small interfering RNA or the competitive inhibitor difluoromethylornithine restored iNOS protein expression and activity in infected cells and inhibited chlamydial growth. This inhibition was mediated through tyrosine nitration of chlamydial protein by peroxynitrite, an NO metabolite. Thus, Chlamydia evades innate immunity by inhibiting NO production through induction of the alternative polyamine pathway.

Innate immunity to influenza virus: implications for future therapy

Innate immunity is critical in the early containment of influenza virus infection. The innate response is surprisingly complex. A variety of soluble innate inhibitors in respiratory secretions provide an initial barrier to infection. Dendritic cells, phagocytes and natural killer cells mediate viral clearance and promote further innate and adaptive responses. Toll-like receptors 3 and 7 and cytoplasmic RNA sensors are critical for activating these responses. In general, the innate response restricts viral replication without injuring the lung; however, the 1918 pandemic and H5N1 strains cause more profound, possibly harmful, innate responses. In this review, we discuss the implications of burgeoning knowledge of innate immunity for therapy of influenza.

Respiratory Viral Infections and Subversion of Cellular Antioxidant Defenses

Reactive oxygen species (ROS) formation is part of normal cellular aerobic metabolism, due to respiration and oxidation of nutrients in order to generate energy. Low levels of ROS are involved in cellular signaling and are well controlled by the cellular antioxidant defense system. Elevated levels of ROS generation due to pollutants, toxins and radiation exposure, as well as infections, are associated with oxidative stress causing cellular damage. Several respiratory viruses, including respiratory syncytial virus (RSV), human metapneumovirus (hMPV) and influenza, induce increased ROS formation, both intracellularly and as a result of increased inflammatory cell recruitment at the site of infection. They also reduce antioxidant enzyme (AOE) levels and/or activity, leading to unbalanced oxidative-antioxidant status and subsequent oxidative cell damage. Expression of several AOE is controlled by the activation of the nuclear transcription factor NF-E2-related factor 2 (Nrf2), through binding to the antioxidant responsive element (ARE) present in the AOE gene promoters. While exposure to several pro-oxidant stimuli usually leads to Nrf2 activation and upregulation of AOE expression, respiratory viral infections are associated with inhibition of AOE expression/activity, which in the case of RSV and hMPV is associated with reduced Nrf2 nuclear localization, decreased cellular levels and reduced ARE-dependent gene transcription. Therefore, administration of antioxidant mimetics or Nrf2 inducers represents potential viable therapeutic approaches to viral-induced diseases, such as respiratory infections and other infections associated with decreased cellular antioxidant capacity.

Lactobacillus fermentum CJL-112 protects mice against influenza virus infection by activating T-helper 1 and eliciting a protective immune response

We have previously reported that nasally administered Lactobacillus fermentum CJL-112 (CJL-112) efficiently improves resistance against lethal influenza infection in both mice and chicken. The aim of the present study was to understand the underlying mechanisms of the significant anti-influenza activity of this lactobacilli strain. In vitro, co-culturing of the chicken macrophage cell line HD-11 with CJL-112 significantly increased nitric oxide (NO) production. In vivo, CJL-112 was nasally administered to BALB/c mice for 21 days prior to influenza A/NWS/33 (H1N1) virus (IFV) infection. Significant up-regulation of T-helper 1 (Th1) cytokines (IL-2, IFN-γ) was observed, while the levels of T-helper 2 (Th2) cytokines (IL-4, IL-5, IL-10) was either reduced or unchanged than that in control mice were. Furthermore, IgA and specific anti-influenza IgA levels increased significantly in the treated mice than those in untreated mice. Therefore, CJL-112 likely protects the mice against lethal IFV infection via stimulation of macrophages, activation of Th1 and augmentation of IgA production, when directly delivered into the respiratory tract.

Biological nitric oxide signalling: chemistry and terminology

Biological nitrogen oxide signalling and stress is an area of extreme clinical, pharmacological, toxicological, biochemical and chemical research interest. The utility of nitric oxide and derived species as signalling agents is due to their novel and vast chemical interactions with a variety of biological targets. Herein, the chemistry associated with the interaction of the biologically relevant nitrogen oxide species with fundamental biochemical targets is discussed. Specifically, the chemical interactions of nitrogen oxides with nucleophiles (e.g. thiols), metals (e.g. hemeproteins) and paramagnetic species (e.g. dioxygen and superoxide) are addressed. Importantly, the terms associated with the mechanisms by which NO (and derived species) react with their respective biological targets have been defined by numerous past chemical studies. Thus, in order to assist researchers in referring to chemical processes associated with nitrogen oxide biology, the vernacular associated with these chemical interactions is addressed.

Inducible nitric oxide contributes to viral pathogenesis following highly pathogenic influenza virus infection in mice

Highly pathogenic influenza A viruses, including avian H5N1 viruses and the 1918 pandemic virus, cause severe respiratory disease in humans and animals. Virus infection is followed by intense pulmonary congestion due to an extensive influx of macrophages and neutrophils, which can release large quantities of reactive oxygen species potentially contributing to the pathogenesis of lung disease. Here, the role of nitric oxide (NO), a potent signaling molecule in inflammation, was evaluated following highly pathogenic influenza virus challenge in mice. We observed higher levels of NO in mice infected with H5N1 and 1918 viruses as compared to a seasonal H1N1 virus. Mice deficient in inducible NO synthase (NOS2(-/-)) exhibited reduced morbidity, reduced mortality, and diminished cytokine production in lung tissue following H5N1 and 1918-virus challenge, compared with wild-type control mice. Furthermore, systemic treatment of mice with the NOS inhibitor NG-monomethyl-l-arginine delayed weight loss and death among 1918 virus infected mice compared to untreated control animals. This study demonstrates that NO contributes to the pathogenic outcome of H5N1 and 1918 viral infections in the mouse model.

Respiratory syncytial virus infection: mechanisms of redox control and novel therapeutic opportunities

Respiratory syncytial virus (RSV) is one of the most important causes of upper and lower respiratory tract infections in infants and young children, for which no effective treatment is currently available. Although the mechanisms of RSV-induced airway disease remain incompletely defined, the lung inflammatory response is thought to play a central pathogenetic role. In the past few years, we and others have provided increasing evidence of a role of reactive oxygen species (ROS) as important regulators of RSV-induced cellular signaling leading to the expression of key proinflammatory mediators, such as cytokines and chemokines. In addition, RSV-induced oxidative stress, which results from an imbalance between ROS production and airway antioxidant defenses, due to a widespread inhibition of antioxidant enzyme expression, is likely to play a fundamental role in the pathogenesis of RSV-associated lung inflammatory disease, as demonstrated by a significant increase in markers of oxidative injury, which correlate with the severity of clinical illness, in children with RSV infection. Modulation of ROS production and oxidative stress therefore represents a potential novel pharmacological approach to ameliorate RSV-induced lung inflammation and its long-term consequences.

Paradox of schizophrenia genetics: is a paradigm shift occurring?

BACKGROUND

Genetic research of schizophrenia (SCZ) based on the nuclear genome model (NGM) has been one of the most active areas in psychiatry for the past two decades. Although this effort is ongoing, the current situation of the molecular genetics of SCZ seems disappointing or rather perplexing. Furthermore, a prominent discrepancy between persistence of the disease at a relatively high prevalence and a low reproductive fitness of patients creates a paradox. Heterozygote advantage works to sustain the frequency of a putative susceptibility gene in the mitochondrial genome model (MGM) but not in the NGM.

METHODS

We deduced a criterion that every nuclear susceptibility gene for SCZ should fulfill for the persistence of the disease under general assumptions of the multifactorial threshold model. SCZ-associated variants listed in the top 45 in the SZGene Database (the version of the 23rd December, 2011) were selected, and the distribution of the genes that could meet or do not meet the criterion was surveyed.

RESULTS

19 SCZ-associated variants that do not meet the criterion are located outside the regions where the SCZ-associated variants that could meet the criterion are located. Since a SCZ-associated variant that does not meet the criterion cannot be a susceptibility gene, but instead must be a protective gene, it should be linked to a susceptibility gene in the NGM, which is contrary to these results. On the other hand, every protective gene on any chromosome can be associated with SCZ in the MGM. Based on the MGM we propose a new hypothesis that assumes brain-specific antioxidant defenses in which trans-synaptic activations of dopamine- and N-methyl-d-aspartate-receptors are involved. Most of the ten predictions of this hypothesis seem to accord with the major epidemiological facts and the results of association studies to date.

CONCLUSION

The central paradox of SCZ genetics and the results of association studies to date argue against the NGM, and in its place the MGM is emerging as a viable option to account for genomic and pathophysiological research findings involving SCZ.

Regulation of Influenza Virus-Caused Oxidative Stress by Kegan Liyan Oral Prescription, as Monitored by Ascorbyl Radical ESR Signals

To study the oxidative stress level of the influenza virus A FM1 subset-infected mouse in intranasal inhalation as a model, we employ an ascorbyl radical's ESR (electron spin resonance) spectrum as an oxidative stress biomarker. These infected mice were pretreated with Ribavirin, ascorbic acid, superoxide dismutase (SOD) or Kegan Liyan oral prescription (KGLY, proprietary Chinese medicine for influenza and common cold) in the stomach tube for 3 days, and then followed by the virus-infecting for 4 days. On the 4th day, samples were collected. It is recognized the strength of ascorbyl radical's ESR signal ( A -.) (a H4 = 0.177 Gauss, g = 2.00517) denotes oxidative stress level in vivo and in vitro. The magnitude of ESR spectrum (28.65 ± 10.71 AU) in mice infected with influenza virus was significantly higher than those of healthy control mice (19.10 ± 3.61 AU). Serum A -. in mice treated with Ribavirin, ascorbic acid, SOD and KGLY declined to 19.70 ± 6.05, 18.50 ± 2.93 and 16.25 ± 3.59, 18.40 ± 2.14 AU respectively. It is close to A -. signal height in healthy controls via down-regulation of the influenza virus-caused oxidative stress level getting decline in the lung index of pneumonia as compare to those of untreated healthy and the influenza virus infected mice pneumonia. It is well known that SOD can prevent the influenza virus pneumonia enhancing mouse survival rate; Ribavirin can treat viral diseases. Data from this study suggested that KGLY may indirectly relieve influenza virus-infected pneumonia via down- regulation of virus caused oxidative stress coupled with a redox reaction cascade as ribavirin, ascorbic acid and SOD.