High Concentrations Of Nitric Oxide Research Articles

Nitric oxide-enhanced Shiga toxin production was regulated by Fur and RecA in enterohemorrhagic Escherichia coli O157.

Enterohemorrhagic Escherichia coli (EHEC) produces Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2). Nitric oxide (NO), which acts as an antimicrobial defense molecule, was found to enhance the production of Stx1 and Stx2 in EHEC under anaerobic conditions. Although EHEC O157 has two types of anaerobic NO reductase genes, an intact norV and a deleted norV, in the deleted norV‐type EHEC, a high concentration of NO (12–29 μmol/L, maximum steady‐state concentration) is required for enhanced Stx1 production and a low concentration of NO (~12 μmol/L, maximum steady‐state concentration) is sufficient for enhanced Stx2 production under anaerobic conditions. These results suggested that different concentration thresholds of NO elicit a discrete set of Stx1 and Stx2 production pathways. Moreover, the enhancement of Shiga toxin production in the intact norV‐type EHEC required treatment with a higher concentration of NO than was required for enhancement of Shiga toxin production in the deleted norV‐type EHEC, suggesting that the specific NorV type plays an important role in the level of enhancement of Shiga toxin production in response to NO. Finally, Fur derepression and RecA activation in EHEC were shown to participate in the NO‐enhanced Stx1 and Stx2 production, respectively.

A role of nitrite reductase (NirBD) for NO homeostatic regulation in Streptomyces coelicolor A3(2).

Although nitric oxide (NO) is an important signaling molecule in bacteria and higher organisms, excessive intracellular NO is highly reactive and dangerous. Therefore, living cells need strict regulation systems for cellular NO homeostasis. Recently, we discovered that Streptomyces coelicolor A3(2) retains the nitrogen oxide cycle (NO3-→NO2-→NO→NO3-) and nitrite removal system. The nitrogen oxide cycle regulates cellular NO levels, thereby controlling secondary metabolism initiation (red-pigmented antibiotic, RED production) and morphological differentiation. Nitrite induces gene expression in neighboring cells, suggesting another role for this cycle as a producer of transmittable intercellular communication molecules. Here, we demonstrated that ammonium-producing nitrite reductase (NirBD) is involved in regulating NO homeostasis in S. coelicolor A3(2). NirBD was constitutively produced in culture independently of GlnR, a known transcriptional factor. NirBD cleared the accumulated nitrite from the medium. Nir deletion mutants showed increased NO-dependent gene expression at later culture stages, whereas the wild-type M145 showed decreased expression, suggesting that high NO concentration was maintained in the mutant. Moreover, the nir deletion mutant produced more RED than that produced by the wild-type M145. These results suggest that NO2- removal by NirBD is important to regulate NO homeostasis and to complete NO signaling in S. coelicolor.

Nitrosothiol formation and S-nitrosation signaling through nitric oxide synthases

Nitric oxide (NO) is a gaseous signaling molecule impacting many biological pathways. NO is produced in mammals by three nitric oxide synthase (NOS) isoforms: neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). nNOS and eNOS produce low concentrations of NO for paracrine signaling; NO produced and released from one cell diffuses to a neighboring cell where it binds and activates soluble guanylyl cyclase (sGC). iNOS produces high concentrations of NO using NO toxicity to amplify the innate immune response. Recent work has also defined protein cysteine S-nitrosation as a pathway of sGC-independent NO signaling. Though many studies have shown that S-nitrosation regulates the activity of NOS isoforms and other proteins in vivo, many issues need to be resolved to establish S-nitrosation as a viable signaling mechanism. Several chemical mechanisms result in S-nitrosation including transition metal-catalyzed pathways, NO oxidation followed by thiolate reaction, and thiyl radical recombination with NO. Once formed, nitrosothiols can be transferred between cellular cysteine residues via transnitrosation reactions. However, it is largely unclear how these chemical processes result in selective S-nitrosation of specific cellular cysteine residues. S-nitrosation site selectivity may be imparted via direct interactions or colocalization with NOS isoforms that focus chemical or transnitrosation mechanisms of nitrosothiol formation or transfer. Here, we discuss chemical mechanisms of nitrosothiol formation, S-nitrosation of NOS isoforms, and potential S-nitrosation signaling cascades resulting from NOS S-nitrosation.

Effects of different concentrations of nitric oxide on liver cancer cell line HepG2 and peripheral blood mononuclear cells in indirect co-culture system

Objective To study the effects of different concentrations of nitric oxide (NO) on liver cancer cell line HepG2 and peripheral blood mononuclear cells (PBMC). Methods Different rates of PBMC/HepG2 and drugs were arranged to regulate the concentrations of NO. Activity changes of the two kinds of cells were measured in cells cultured alone and co-cultured, which were compared with control group. Results The activity of PBMCs in co-cultured system was harmed only when the concentration of NO was more than 120 μmol/L, however, the activity of HepG2 cells in co-cultured system was suppressed when the concentration of NO was less than that of control group or was more than 241 μmol/L; moreover, the activity of co-cultured HepG2 cells was higher than that of HepG2 cells cultured alone in different concentrations of NO. In co-cultured system, with the increase of PBMC/HepG2 ratio, the concentration of NO was decreased, but the activity of HepG2 cells was increased. Conclusions The results have shown that HepG2 cells are damaged by high or low concentration of NO, and PBMC are only damaged by high concentration of NO, however, the low concentration of NO has few influences on PBMC. Moreover, the indirect contact of PBMC can promote the growth of the HepG2 cells. Key words: Liver neoplasms; Co-culture; Nitric oxide; Immunotherapy

Sputum is a surrogate for bronchoalveolar lavage for monitoring Mycobacterium tuberculosis transcriptional profiles in TB patients

Pathogen-targeted transcriptional profiling in human sputum may elucidate the physiologic state of Mycobacterium tuberculosis (M. tuberculosis) during infection and treatment. However, whether M. tuberculosis transcription in sputum recapitulates transcription in the lung is uncertain. We therefore compared M. tuberculosis transcription in human sputum and bronchoalveolar lavage (BAL) samples from 11 HIV-negative South African patients with pulmonary tuberculosis. We additionally compared these clinical samples with invitro log phase aerobic growth and hypoxic non-replicating persistence (NRP-2). Of 2179M. tuberculosis transcripts assayed in sputum and BAL via multiplex RT-PCR, 194 (8.9%) had a p-value <0.05, but none were significant after correction for multiple testing. Categorical enrichment analysis indicated that expression of the hypoxia-responsive DosR regulon was higher in BAL than in sputum. M. tuberculosis transcription in BAL and sputum was distinct from both aerobic growth and NRP-2, with a range of 396-1020 transcripts significantly differentially expressed after multiple testing correction. Collectively, our results indicate that M. tuberculosis transcription in sputum approximates M. tuberculosis transcription in the lung. Minor differences between M. tuberculosis transcription in BAL and sputum suggested lower oxygen concentrations or higher nitric oxide concentrations in BAL. M. tuberculosis-targeted transcriptional profiling of sputa may be a powerful tool for understanding M. tuberculosis pathogenesis and monitoring treatment responses invivo.

The features of lipid peroxidation and the antioxidant system of blood under the influence of different concentrations of nitric oxide in a chronic experiment

This paper presents the results of the study of oxidative metabolism of the blood of intact animals subjected to prolonged exposure to nitric oxide at concentrations of 20, 50, and 100 ppm. The experiment was carried out with Wistar rats. NO inhalation was performed for 30 days. The state of blood oxidative metabolism was evaluated after inhalation and a 30-day-long recovery period after discontinuation of NO oxidative stress. The intensity of lipid peroxidation was studied in plasma and erythrocytes by induced biochemiluminescence and the measurement of the level of malondialdehyde. The activity of superoxide dismutase was determined in the hemolysate of erythrocytes. It was established that the optimal dose of inhaled NO is 20 ppm: a maximum increase in the total antioxidant activity after 30 days and normalization of lipid peroxidation in the blood after the completion of the recovery period were observed at this concentration. High concentrations of nitric oxide (50 and 100 ppm) initiated lipid peroxidation in erythrocytes and plasma after discontinuation of NO oxidative stress (after the completion of the recovery period) thus enhancing catalytic properties of superoxide dismutase.

A Preliminary Assessment of the Role of Ambient Nitric Oxide Exposure in Hospitalization with Respiratory Syncytial Virus Bronchiolitis.

Some in vitro studies have indicated a possible link between respiratory syncytial virus (RSV) infection and exposure to Nitric Oxide (NO). However, these studies used much higher NO concentrations than normally found in the ambient environment. This preliminary study explored whether an association was present with short-term exposure to NO in the environment. RSV-related admission data between November 2011 and February 2012 were obtained from Sheffield Children’s Hospital. The dates of admission were linked to contemporaneous ambient NO derived from sentinel air monitors. The case-crossover design was used to study the relationship between daily RSV admissions and NO, controlling for temperature and relative humidity. We found little evidence of association between daily RSV admission rates and exposure to ambient NO at different lags or average exposure across several lags. The findings should, however, be viewed with caution due to the low number of events observed during the time frame. It is possible that the apparent lack of association may be accounted for by the timing of the seasonal RSV epidemic in relation to peaks in NO concentrations. A larger study incorporating a wider range of RSV and NO peaks would determine whether said peaks enhanced the number of RSV hospitalizations in children.

Characterizations of Substrate Delivery Pathways in the Nitric Oxide Reductase

Nitric oxide reductase (NOR), a structurally homologous enzyme of the heme-copper oxidoreductase superfamily and an integral membrane protein, carries out the intermediate step of denitrification by reducing nitric oxide (NO) to nitrous oxide (N2O). The reduction reaction occurs at the buried heme-iron complex. However, experiments demonstrated that the NO binds NOR at a rate near the diffusion limit (5×108 M−1s−1), and that NOR requires only a few nanomolar of NO to reach its half-maximal reduction activity. To provide atomistic and quantitative descriptions of the NO delivery mechanism, molecular dynamics (MD) simulations have been performed, using the crystal structure of cytochrome-c dependent NOR (cNOR) from Pseumonas aeruginosa as the starting model. Independent explicit ligand sampling simulations with high NO concentration have been carried out to accelerate the sampling of NO within the simulation timescale. The results indicate that substrate NO enters the enzyme via three membrane-accessible hydrophobic tunnels, two of which correspond to the observed xenon-bound hydrophobic tunnel of B-type HCO from Thermus thermophilus (cytochrome ba3) by X-ray crystallography. All three tunnels merge into one pathway. Two bottlenecks of NO migration, composed of highly conserved residues, are identified. One is at residues I65 and W209, located 15A from the reduction site, while the other is at residue V206, located 6-8A from the reduction site. Umbrella sampling simulations and in silico mutations have also been performed to characterize the free energy of NO insertion along the pathway and confirm the identified bottlenecks. Alanine substitutions of the bottleneck residues result a decrease in the free-energy barriers, and result in an increase of NO delivery events. The study demonstrates that pathways facilitate the delivery of small gases, such as NO, in enzymes.

TROSATIVE STRESS PARAMETERS IN COLON CANCER TUMOR, ADJACENT AND HEALTHY TISSUE

Colorectal cancer is one of the most frequent human malignant diseases and one of the most common causes of malignant diseases death. Oxidative and nitrosative stress have an important role in cancer initiation and propagation. That is why this study is focused on the determination of oxidative and nitrosative stress markers in tumor, adjacent and health tissue, which are important for the estimation of tumor proliferative and angiogenic potential. The study encompassed 50 patients who underwent surgery due to colorectal cancer. In the tissue samples from resected colon preparation (tumor, adjacent and healthy tissue, at least 10 cm distant from tumor), oxidative and nitrosative stress markers, malondialdehyde (MDA) and nitric oxide (NO) were determined. The obtained results prove the presence of oxidative stress in tumor tissue. Highly significantly (p<0.001) increased MDA concentrations in both tumor and adjacent tissue (12.43±9.39 and 11.57±5.56 nmol/mg proteins) compared to healthy one (7.25±5.52) reflect higher tumor aggressiveness and metastatic capacity. Higher NO concentrations in adjacent tissue (85.100±37.972 nmol/mg prot.) compared to the tumor one (58.608±22.789) point out high angiogenic potential of tumor surrounding tissue, which could have the clinical importance in the assessment of tumor invasiveness and the probability of local recurrence. In conclusion, the determination of the intensity of reactive oxygen and nitrogen species generation in tumor and adjacent colon tissue of patients with colorectal carcinoma could be useful in the estimation of the cancer invasive and metastatic capacity related to the prognosis of the disease and the choice of adjuvant therapy.

Nitric oxide donor hybrid compounds as promising anticancer agents.

Nitric oxide (NO) plays important roles in cardiovascular regulation, nerve transmission delivery and immune responses. In the last semicenturry, it has been proved that though low concentration of NO is tumor-promoting, high concentration of NO could exhibit multiple antitumor effects, which led to the research and development of kinds of NO donors and NO donor hybrid compounds as antitumor agents. Herein, the recent development of NO donor hybrid compounds is briefly reviewed.

一氧化氮和天然抗氧化剂对阿尔茨海默症的潜在防治作用

本文以转基因细胞和线虫体系为模型，研究了一氧化氮(nitric oxide, NO)和天然抗氧化剂的合理搭配组合对阿尔茨海默症(Alzheimer’s disease, AD)的防治作用。结果发现，低浓度的NO可以通过降低细胞内活性氧的水平保护神经细胞，防止APPsw和ApoE4过量表达引起的损伤作用；而高浓度的NO可以通过增强活性氧(reactive oxygen species, ROS)的产生加剧神经细胞损伤。适量NO和天然抗氧化剂都对Abeta转基因诱导的线虫瘫痪行为具有抑制作用。NO和天然抗氧化剂的合理搭配组合既可以通过显著清除ROS抑制ApoE4和APPsw转基因引起的细胞活力降低，又可以更好的延缓Abeta转基因诱导的线虫瘫痪行为。这些结果说明，NO和天然抗氧化剂合理搭配可以在AD细胞和线虫模型中抑制转基因引起的细胞和线虫的损伤，有可能对AD具有一定的防治作用。 In this study, the preventive and therapeutic potential of nitric oxide (NO) and natural antioxidants on Alzheimer’s disease (AD) were studied using transgenic cells and C. elegans models. It was found that low concentration of NO protected neuronal cells by reducing the production of reactive oxygen species (ROS). In contrast, high concentration of NO aggravated the cell damage by producing more ROS. Low concentration of NO and natural antioxidant could protect C. elegans against paralysis induced by expression of transgenic Abeta gene. It was found that a formulation of L-arginine and natural antioxidants increased the viability of N2a cells overexpressing APPsw and ApoE4 by scavenging ROS. This formula also protected C. elegans against paralysis caused by transgenic Abeta gene. These results suggest that this formulation of NO precursor and natural antioxidants may have a potential for prevention and treatment of AD.

Nitric Oxide Up-Regulates RUNX2 in LNCaP Prostate Tumours: Implications for Tumour Growth In Vitro and In Vivo.

Aberrant expression of the transcription factor RUNX2 in prostate cancer has a number of important consequences including increased resistance to apoptosis, invasion and metastasis to bone. We previously demonstrated that hypoxia up-regulated RUNX2 in tumour cells, which in turn up-regulated the anti-apoptotic factor Bcl-2. Here, we investigate the impact of nitric oxide (NO) on RUNX2 and Bcl-2 expression in prostate cancer and further, how RUNX2 over-expression can impact tumour growth, angiogenesis and oxygenation in vivo. The effect of NO levels on RUNX2 and thus Bcl-2 expression was examined in prostate cancer cells in vitro using methods including gene and protein expression analyses, nitrite quantitation, protein-DNA interaction assays (ChIP) and viability assays (XTT). The effect of RUNX2 over-expression on tumour physiology (growth, oxygenation and angiogenesis) was also assessed in vivo using LNCaP xenografts. A low (but not high) concentration of NO (10 μM) induced expression of RUNX2 and Bcl-2, conferring resistance to docetaxel. These effects were induced via the ERK and PI3K pathways and were dependent on intact AP-1 binding sites in the RUNX2 promoter. RUNX2 over-expression in LNCaP tumours in vivo decreased the time to tumour presentation and increased tumour growth. Moreover, these tumours exhibited improved tumour angiogenesis and oxygenation. Low levels of NO increase expression of RUNX2 and Bcl-2 in LNCaP prostate tumour cells, and in vivo up-regulation of RUNX2 created tumours with a more malignant phenotype. Collectively, our data reveals the importance of NO-regulation of key factors in prostate cancer disease progression.

Commentary: “Nitric oxide releases Cl− from acidic organelles in retinal amacrine cells”

In their recent article (Krishnan and Gleason, 2015) Vijai Krishnan and Evanna Gleason investigate the cellular mechanisms underlying the shift in the GABA reversal potential upon application of nitric oxide (NO). Functional alteration in GABAergic signaling by alterations in the GABA reversal potential has been identified as an important mechanism of plasticity (Raimondo et al., 2012) and NO is clearly one key substance involved in plasticity (Prast and Philippu, 2001). Therefore, the investigation of the mechanisms behind the NO induced shift in GABAergic effects is an important issue. However, in my opinion the authors neglected a possible explanation of their observations in the discussion section of their recent article. The detailed investigation in the present article was based on the seminal observation by the same group that moderate concentrations of NO donors induced a slight increase in GABAA receptor mediated responses without affecting the reversal potential, while the application of a saturated NO solution (resulting in “hundreds of nanomolar to low micromolar” NO concentrations) led to a significant shift in the GABA reversal potential (Hoffpauir et al., 2006). The latter effect was independent of the soluble guanylate cyclase, which is elementary for the classical NO signaling pathway, and persisted in nominally Cl−-free extracellular solution, suggesting that NO may trigger a Cl− release from intracellular stores (Hoffpauir et al., 2006). Further experiments by the authors suggest that a NO-induced intracellular acidification triggers the release of Cl− from intracellular compartments (McMains and Gleason, 2011). In the present study they used nominally Cl−-free extracellular and intracellular (pipette-) solutions to “wash out both cytosolic and protein-bound Cl−” and thereby isolate Cl− stores “contained within an intracellular membrane-bound compartment” (Krishnan and Gleason, 2015). These experiments demonstrated that application of NO or NO-donors re-established GABAergic currents under nominally Cl−-free conditions, and that this effect was attenuated in the presence of the V-type ATPase inhibitor bafilomycin and was abolished by the uncoupling agent FCCP. From these experimental findings they came to the well supported conclusion, that acidic compartments are a possible source for the NO-induced increase in intracellular Cl− anions. However, when such high NO concentrations are used, it should be considered that the mitochondrial cytochrome c oxidase can reduce NO to nitrite (NO2-), although no information about the maximal rates for this process is available (Sarti et al., 2012). The permeability of NO2- through GABAA receptors is higher than their Cl− permeability (Bormann et al., 1987). Thus the intracellular generation of NO2- might contribute to the re-occurrence of inward currents after NO application under nominally Cl−-free solutions. Notably, the oxidation of NO to NO2- relies on functional oxidative phosphorylation (Sarti et al., 2012). Thus, the reduction of NO-induced GABA currents by bafilomycin and its abolishment by FCCP (Krishnan and Gleason, 2015) may be caused by the fact, that both substances induce mitochondrial dysfunction via uncoupling (Zhdanov et al., 2012). Therefore, I suggest that the authors should consider the formation of NO2- as an additional hypothesis to explain their observations. To differentiate between both hypotheses, a conclusive experiment would be to test whether the NO-induced GABA currents in nominally Cl−-free intra- and extra-cellular solutions are depletable (indicating a limited intracellular reservoir of Cl− ions) or whether repetitive NO applications induced sustained GABA currents (indicating a NO-dependent generation of anions permeable via the GABAA receptor).

Arcobacter butzleri Induce Colonic, Extra-Intestinal and Systemic Inflammatory Responses in Gnotobiotic IL-10 Deficient Mice in a Strain-Dependent Manner.

BackgroundThe immunopathological impact of human Arcobacter (A.) infections is under current debate. Episodes of gastroenteritis with abdominal pain and acute or prolonged watery diarrhea were reported for A. butzleri infected patients. Whereas adhesive, invasive and cytotoxic capacities have been described for A. butzleri in vitro, only limited information is available about the immunopathogenic potential and mechanisms of infection in vivo.Methodology/Principal FindingsGnotobiotic IL-10-/- mice were generated by broad-spectrum antibiotic treatment and perorally infected with the A. butzleri strains CCUG 30485 and C1 shown to be invasive in cell culture assays. Bacterial colonization capacities, clinical conditions, intestinal, extra-intestinal and systemic immune responses were monitored at day six and 16 postinfection (p.i.). Despite stable intestinal A. butzleri colonization at high loads, gnotobiotic IL-10-/- mice were virtually unaffected and did not display any overt symptoms at either time point. Notably, A. butzleri infection induced apoptosis of colonic epithelial cells which was paralleled by increased abundance of proliferating cells. Furthermore A. butzleri infection caused a significant increase of distinct immune cell populations such as T and B cells, regulatory T cells, macrophages and monocytes in the colon which was accompanied by elevated colonic TNF, IFN-γ, nitric oxide (NO), IL-6, IL-12p70 and MCP-1 concentrations. Strikingly, A. butzleri induced extra-intestinal and systemic immune responses as indicated by higher NO concentrations in kidney and increased TNF, IFN-γ, IL-12p70 and IL-6 levels in serum samples of infected as compared to naive mice. Overall, inflammatory responses could be observed earlier in the course of infection by the CCUG 30485 as compared to the C1 strain.Conclusion/SignificancePeroral A. butzleri infection induced not only intestinal but also extra-intestinal and systemic immune responses in gnotobiotic IL-10-/- mice in a strain-dependent manner. These findings point towards an immunopathogenic potential of A. butzleri in vertebrate hosts.

Identification of new inhibitors of soluble guanylyl cyclase activity

Objective Soluble guanylyl cyclase, (sGC) is an enzyme that can be activated endogenously by nitric oxide (NO). As its particulate counterparts, the role of the cytoplasmic sGC inside the cell is to convert GTP to the second messenger, cGMP. NO is produced by nitric oxide synthase during the conversion of l-arginine to l-citrulline. NO binds to the ferrous heme of sGC and activates the enzyme, augmenting the production of cGMP which leads to the activation of cGMP-dependent targets. The activation of various proteins through elevated cGMP production by sGC produces physiological functions like vasodilation, inhibition of platelet aggregation, photosensitivity, and cell growth. However, studies have indicated that during pathophysiological conditions like sepsis and cancer, the inhibition of sGC activity could potentially be beneficial in achieving a desired cellular and pharmaceutical response. In addition, a common inhibitor of sGC, ODQ, only inhibits NO-stimulated sGC, not basal, and ODQ also does not work well under high NO concentrations thus furthering the need to develop novel sGC inhibitors.

Nitric oxide is required for the auxin-induced activation of NADPH-dependent thioredoxin reductase and protein denitrosylation during root growth responses in arabidopsis.

Auxin is the main phytohormone controlling root development in plants. This study uses pharmacological and genetic approaches to examine the role of auxin and nitric oxide (NO) in the activation of NADPH-dependent thioredoxin reductase (NTR), and the effect that this activity has on root growth responses in Arabidopsis thaliana. Arabidopsis seedlings were treated with auxin with or without the NTR inhibitors auranofin (ANF) and 1-chloro-2, 4-dinitrobenzene (DNCB). NTR activity, lateral root (LR) formation and S-nitrosothiol content were measured in roots. Protein S-nitrosylation was analysed by the biotin switch method in wild-type arabidopsis and in the double mutant ntra ntrb. The auxin-mediated induction of NTR activity is inhibited by the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CPTIO), suggesting that NO is downstream of auxin in this regulatory pathway. The NTR inhibitors ANF and DNCB prevent auxin-mediated activation of NTR and LR formation. Moreover, ANF and DNCB also inhibit auxin-induced DR5 : : GUS and BA3 : : GUS gene expression, suggesting that the auxin signalling pathway is compromised without full NTR activity. Treatment of roots with ANF and DNCB increases total nitrosothiols (SNO) content and protein S-nitrosylation, suggesting a role of the NTR-thioredoxin (Trx)-redox system in protein denitrosylation. In agreement with these results, the level of S-nitrosylated proteins is increased in the arabidopsis double mutant ntra ntrb as compared with the wild-type. The results support for the idea that NTR is involved in protein denitrosylation during auxin-mediated root development. The fact that a high NO concentration induces NTR activity suggests that a feedback mechanism to control massive and unregulated protein S-nitrosylation could be operating in plant cells.

An in vivo safety and efficacy demonstration of a topical liposomal nitric oxide donor treatment for Staphylococcus aureus biofilm–associated rhinosinusitis

The burden of drug resistance emerges in the wake of chronic and repeated antibiotic use. This underpins the importance of discovering alternatives to current antibiotic regimens. In chronic rhinosinusitis (CRS), topical therapy such as nasal douches and steroid sprays is the mainstay of treatment. However, bacterial sinusitis such as those with Staphylococcus aureus biofilm infection point to more recalcitrant CRS subtypes, focusing research efforts into topical antimicrobial therapies. In the sinuses, both local mucosal and systemic effects must be considered in designing any new topical medication. Nitric oxide (NO), an endogenous antimicrobial agent, is found at extremely low levels in CRS sinuses and high levels in healthy sinuses. As a novel treatment modality, we have designed a liposomal formulation of an NO donor (LFNO) using isosorbide mononitrate, as a topical sinus wash in a sheep model of S. aureus biofilm rhinosinusitis. Heart rate (HR), blood pressure, mean arterial pressure (MAP), and histologic and ciliary analyses were assessed in the safety component. Efficacy was assessed by quantifying biofilm biomass post-treatment. LFNO-treated sheep had lesser inflammation (P = 0.02), and comparable ciliary preservation (P = 0.86) than the control group. A transient increase in HR and decrease in MAP were observed in the LFNO group (P < 0.05), but this was not accompanied by observable side effects. LFNO sheep had significantly lower biofilm biomass vs controls (P = 0.044). Our findings demonstrate the localized and systemic safety of LFNO in an animal model despite using high NO concentrations, thus warranting further investigation for its possible therapeutic role in CRS.

Massive nitrous oxide emissions from the tropical South Pacific Ocean

Nitrous oxide is a potent greenhouse gas and a key compound in stratospheric ozone depletion. In the ocean, nitrous oxide is produced at intermediate depths through nitrification and denitrification, in particular at low oxygen concentrations. Although a third of natural emissions of nitrous oxide to the atmosphere originate from the ocean, considerable uncertainties in the distribution and magnitude of the emissions still exist. Here we present high-resolution surface measurements and vertical profiles of nitrous oxide that include the highest reported nitrous oxide concentrations in marine surface waters, suggesting that there is a hotspot of nitrous oxide emissions in high-productivity upwelling ecosystems along the Peruvian coast. We estimate that off Peru, the extremely high nitrous oxide supersaturations we observed drive a massive efflux of 0.2–0.9 Tg of nitrogen emitted as nitrous oxide per year, equivalent to 5–22% of previous estimates of global marine nitrous oxide emissions. Nutrient and gene abundance data suggest that coupled nitrification–denitrification in the upper oxygen minimum zone and transport of resulting nitrous oxide to the surface by upwelling lead to the high nitrous oxide concentrations. Our estimate of nitrous oxide emissions from the Peruvian coast surpasses values from similar, highly productive areas.

Expression of the tetrahydrofolate-dependent nitric oxide synthase from the green alga Ostreococcus tauri increases tolerance to abiotic stresses and influences stomatal development in Arabidopsis.

Nitric oxide (NO) is a signaling molecule with diverse biological functions in plants. NO plays a crucial role in growth and development, from germination to senescence, and is also involved in plant responses to biotic and abiotic stresses. In animals, NO is synthesized by well-described nitric oxide synthase (NOS) enzymes. NOS activity has also been detected in higher plants, but no gene encoding an NOS protein, or the enzymes required for synthesis of tetrahydrobiopterin, an essential cofactor of mammalian NOS activity, have been identified so far. Recently, an NOS gene from the unicellular marine alga Ostreococcus tauri (OtNOS) has been discovered and characterized. Arabidopsis thaliana plants were transformed with OtNOS under the control of the inducible short promoter fragment (SPF) of the sunflower (Helianthus annuus) Hahb-4 gene, which responds to abiotic stresses and abscisic acid. Transgenic plants expressing OtNOS accumulated higher NO concentrations compared with siblings transformed with the empty vector, and displayed enhanced salt, drought and oxidative stress tolerance. Moreover, transgenic OtNOS lines exhibited increased stomatal development compared with plants transformed with the empty vector. Both in vitro and in vivo experiments indicate that OtNOS, unlike mammalian NOS, efficiently uses tetrahydrofolate as a cofactor in Arabidopsis plants. The modulation of NO production to alleviate abiotic stress disturbances in higher plants highlights the potential of genetic manipulation to influence NO metabolism as a tool to improve plant fitness under adverse growth conditions.

Controllable Generation of Nitric Oxide by Near‐Infrared‐Sensitized Upconversion Nanoparticles for Tumor Therapy

NaYbF4:Tm@NaYF4:Yb/Er upconversion nanoparticles are synthesized and then integrated with light‐sensitive nitric oxide (NO) donors (Roussin's black salt) to construct a novel near‐infrared (NIR)‐triggered on‐demand NO delivery platform. This nanocompound can absorb 980 nm NIR photons, convert them into higher energy photons and then transfer the energy to the NO donors, resulting in an efficient release of NO. By manipulating the output power of the 980‐nm NIR light, NO‐concentration‐dependent biological effects for cancer therapy can be fine‐tuned, which is investigated and confirmed in vitro. High concentrations of NO can directly kill cancer cells and low concentrations of NO can act as a potent P‐glycoprotein (P‐gp) modulator to overcome multi‐drug resistance (MDR) if combined with chemotherapy.