Evaluation of the Antioxidant Effects of Berberine against Sodium Nitriteinduced Oxidative Injury in the Rat Liver

OBJECTIVES

Berberine is a plant derived alkaloid present in many plants that may has ameliorating potential influences against inflammatory and oxidative conditions. The current study aimed to evaluate the possible protective activity of berberine and investigate its probable mechanisms against sodium nitrite toxicity in the liver.

METHODS

Forty male rats were divided into five groups. Group one, as the control group, received normal saline, group two received berberine (100 mg.kg-1), and group three received sodium nitrite (80 mg.kg-1). Groups four and five received berberine in doses of 50 and 100 mg.kg-1, respectively, and sodium nitrite (80 mg.kg-1) was given orally. All the doses were orally administrated for two months. Then, at the end of the 60th day, the animals were sacrificed, and the liver homogenate was prepared. For evaluating the oxidative injury the levels of albumin (ALB) and aspartate transaminase (AST) in the serum and oxidative stress parameters in the liver were analyzed.

RESULTS

Treatment of rats with sodium nitrite considerably increased the levels of serum AST and liver superoxide anion and significantly reduced the levels of serum ALB, hepatic superoxide dismutase (SOD), total antioxidant capacity (TAC), and catalase (CAT) activity in the liver tissue. Berberine treatment could ameliorate all these parameters dose dependently. Berberine at a dose of 100 mg.kg-1 had the best impact and reached the values of oxidative stress parameters to the normal level.

CONCLUSION

Our results demonstrated that berberine in a dose-dependent manner offered protection against sodium nitrite-induced oxidative injury in liver, which possibly reflects the antioxidant abilities of this alkaloid.

Ameliorative effect of Odontonema cuspidatum extract against testicular damage induced by sodium nitrite in rats

Background

Sodium nitrite (NaNO2) is a chemical substance used to enhance taste, add color, and keep food products fit for consumption for a longer time. NaNO2 gives rise to a negative adverse effect on male reproductive function. Odontonema cuspidatum (OC) is a natural plant that possesses antioxidant capacity.

Aim

Our research evaluates the potential beneficial effect of OC extract on the harmful effects caused by NaNO2 on the testicular tissue and sperm characteristics of male rats.

Methods

Four groups with a total of forty rats: the control, the NaNO2-received group, the OC-administered group, and the fourth group received both NaNO2 and OC. All groups were administered daily for two months. Sperm characteristics, testicular antioxidant status, qRT-PCR, and histopathological changes were evaluated.

Results

Coadministration of NaNO2 and OC, in comparison with NaNO2 alone, contributed to a notable enhancement in acrosomal integrity, decreasing sperm abnormalities and restoring serum testosterone levels. Moreover, such coadministration reduced the oxidative stress marker, malondialdehyde (MDA), and increased superoxide dismutase (SOD) in testicular tissue, lowering TNF-α gene expression, and increasing the expression of P450scc and StAR genes. In addition, the NaNO2 and OC combination decreased the testicular histopathological changes and the Caspase-3 and Proliferating cell nuclear antigen (PCNA) immunoexpression in seminiferous tubules compared with the NaNO2 group.

Conclusion

The extract of OC exhibited the ability to decrease oxidative stress and ameliorate the detrimental effects caused by NaNO2.

Pennisetum glaucum Protein Extract Protects RBC, Liver, Kidney, Small Intestine from Oxidative Damage and Exhibits Anticoagulant, Antiplatelet Activity

High level of exogenous ROS in the circulation affects RBC membrane integrity which facilitates the generation of endogenous RBC ROS, implicated in series of physiological changes primarily associated with thrombosis and vital tissue damage. Although, Pennisetum glaucum (pearl millet) stores abundance of proteins, their therapeutic potential is least explored. Thus, the purpose of this study is to examine the role of Pennisetum Glaucum Protein Extract (PGE) on oxidative stress induced cell/tissue damage and thrombosis. In this investigation, protein characterization was done by using SDS-PAGE, Native-PAGE, PAS-staining and HPLC. In-vitro oxidative stress was induced in RBC using sodium nitrite. While, in-vivo oxidative stress was induced in experimental rats using diclofenac. Stress markers and biochemical parameters were evaluated. Role of PGE on thrombosis was assessed by using, in-vitro plasma recalcification time, activated partial thromboplastin time, prothrombin time, mouse tail bleeding time (In-vivo) and platelet aggregation. PGE revealed varied range of molecular weight proteins on SDS-PAGE. PGE normalized the sodium nitrite induced oxidative damage of RBC and diclofenac induced oxidative damage in liver, kidney and small intestine. PGE exhibited anticoagulant effect by increasing the coagulation time of both PRP and PPP and mouse tail bleeding time. Furthermore, PGE prolonged the clotting time of only APTT but did not affect PT. PGE inhibited agonists ADP and epinephrine induced platelet aggregation. Our findings suggest, PGE could be a better contender in the management of oxidative stress and its associated diseases.

ABBREVIATIONS

PGEPennisetum Glaucum protein ExtractAPPTActivated Partial Thromboplastin TimePTProthrombin TimeROSReactive Oxygen SpeciesPRPPlatelet Rich PlasmaPPPPlatelet Poor PlasmaSDS-PAGESodium Dodecyl Sulfate-Polyacrylamide Gel ElectrophoresisPASPeriodic Acid-schiff StainingODOptical DensityINRInternational Normalized RatioPBSPhosphate Buffered SalineSODSuperoxide DismutaseTCATrichloro Acetatic AcidDTNBDi-Thio-bis-NitroBenzoic acidSGOTSerum Glutamate Oxaloacetate TransaminaseSGPTSerum Glutamate Pyruvate TransaminaseALPAlkaline PhosphataseDFCDiclofenacSylSilymarinMEDMinimum Edema DoseMHDMinimum Hemorrhagic Dose.

Protective Effect of Selenium on the Oxidative Damage of Kidney Cells Induced by Sodium Nitrite in Grass Carp (Ctenopharyngodon idellus)

The present study was conducted to investigate the protective effects of selenium on the oxidative damage of kidney cells (CIK) caused by nitrite exposure in grass carp (Ctenopharyngodon idella). Cells were pre-incubated by Na₂SeO₃ (10 μmol/L) for 12 h and then exposed to NaNO₂ (25 mg/L) for 24 h, the cell viability, apoptosis, gene expression, and antioxidant enzyme activity were assayed. The results show that nitrite reduced cell viability and induced apoptosis, and the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) as well as the sod, cat, and gpx genes reduced (p < 0.05), while the intracellular calcium ion concentration increased (p < 0.05). Interestingly, selenium treatment significantly alleviated the nitrite induced changes in cell growth, apoptosis, and calcium influx. The cell viability after low-concentration selenium treatment is higher than that of normal cells (p < 0.05). CIK cells were pre-incubated with Na₂SeO₃ and then exposed to NaNO₂, the antioxidant indicators could be maintained at normal levels. And compared with nitrite exposure, intracellular calcium ion concentration and apoptotic rate of selenium-incubated still decreased. The expressions of Nrf2 and Keap1 genes increased significantly in CIK cells treated with sodium selenite for 12 h, and the same trend as the enzyme activities of this group. The results show that the supplement of selenium can enhance the cell's resistance to sodium nitrite exposure to a certain extent, by alleviating the antioxidant imbalance, high apoptosis rate, and intracellular calcium ion disturbance caused by nitrite exposure. And the Nrf2-Keap1 pathway may play an important role in the process.

Stress Induces Release of Extracellular Vesicles by Trypanosoma cruzi Trypomastigotes

All extracellular forms of Trypanosoma cruzi, the causative agent of Chagas disease, release extracellular vesicles (EVs) containing major surface molecules of the parasite. EV release depends on several mechanisms (internal and external). However, most of the environmental conditions affecting this phenomenon are still unknown. In this work, we evaluated EV release under different stress conditions and their ability to be internalized by the parasites. In addition, we investigated whether the release conditions would affect their immunomodulatory properties in preactivated bone marrow-derived macrophages (BMDM). Sodium azide and methyl-cyclo-β-dextrin (CDB) reduced EV release, indicating that this phenomenon relies on membrane organization. EV release was increased at low temperatures (4°C) and acidic conditions (pH 5.0). Under this pH, trypomastigotes differentiated into amastigotes. EVs are rapidly liberated and reabsorbed by the trypomastigotes in a concentration-dependent manner. Nitrosative stress caused by sodium nitrite in acid medium or S-nitrosoglutathione also stimulated the secretion of EVs. EVs released under all stress conditions also maintained their proinflammatory activity and increased the expression of iNOS, Arg 1, IL-12, and IL-23 genes in IFN-γ and LPS preactivated BMDM. In conclusion, our results suggest a budding mechanism of release, dependent on the membrane structure and parasite integrity. Stress conditions did not affect functional properties of EVs during interaction with host cells. EV release variations under stress conditions may be a physiological response against environmental changes.

A novel S-nitrosocaptopril monohydrate for pulmonary arterial hypertension: H2O and -SNO intermolecular stabilization chemistry

S-nitrosocaptopril (CapNO) possesses dual capacities of both Captopril and an NO donor with enhanced efficacy and reduced side effects. CapNO crystals are difficult to make due to its unstable S-NO bond. Here, we report a novel stable S-nitrosocaptopril monohydrate (CapNO·H₂O) that is stabilized by intermolecular five-membered structure, where one H of H₂O forms a hydrogen bond with O^- of the stable resonance zwitterion Cap-S⁺=N-O^-, and the O in H₂O forms the dipole-dipole interaction with S⁺ through two unpaired electrons. With the chelation and common ion effect, we synthesized and characterized CapNO·H₂O that is stable at 4 °C for 180 days and thereafter without significant degradation. Compared to Captopril, CapNO showed direct vasorelaxation and beneficial effect on PAH rats, and could be self-assembled in rat stomach when Captopril and NaNO₂ were given separately. This novel CapNO·H₂O with low entropy paves an avenue for its clinical trials and commercialization.

Potential secondary poisoning risks to non-targets from a sodium nitrite toxic bait for invasive wild pigs

BACKGROUND

An acute and orally delivered toxic bait containing micro-encapsulated sodium nitrite (MESN), is under development to provide a novel and humane technology to help curtail damage caused by invasive wild pigs (Sus scrofa). We evaluated potential secondary risks for non-target species by: testing whether four different types of micro-encapsulation coatings could reduce vomiting by invasive wild pigs, testing the levels of residual sodium nitrite (SN) in tissues of invasive wild pigs, testing the environmental persistence of SN in vomitus, and conducting a risk assessment for scavengers.

RESULTS

Micro-encapsulation coatings did not affect the frequency of vomiting. We identified no risk of secondary poisoning for non-target scavengers that consume muscle, eyes, and livers of invasive wild pig carcasses because residual SN from the toxic bait was not detected in those tissues. The risk of secondary poisoning from consuming vomitus appeared low because ∼90% of the SN was metabolized or broken down prior to vomiting, and continued to degrade after being exposed to the environment. Secondary poisoning could occur for common scavengers that consume approximately ≥15% of their daily dietary requirements of digestive tract tissues or undigested bait from carcasses of invasive wild pigs in a rapid, single-feeding event. The likelihood of this occurring in a natural setting is unknown. The digestive tracts of poisoned invasive wild pigs contained an average of ∼4.35 mg/g of residual SN.

CONCLUSION

Data from this study suggest no risks of secondary poisoning for non-target species (including humans) that consume muscle, liver, or eyes of invasive wild pigs poisoned with a MESN toxic bait. More species-specific testing for scavengers that consume digestive tract tissues and undigested bait is needed to reduce uncertainty about these potential risks. © 2017 Society of Chemical Industry.

Volatile organic compounds released from Microcystis flos-aquae under nitrogen sources and their toxic effects on Chlorella vulgaris

Eutrophication promotes massive growth of cyanobacteria and algal blooms, which can poison other algae and reduce biodiversity. To investigate the differences in multiple nitrogen (N) sources in eutrophicated water on the emission of volatile organic compounds (VOCs) from cyanobacteria, and their toxic effects on other algal growth, we analyzed VOCs emitted from Microcystis flos-aquae with different types and concentrations of nitrogen, and determined the effects under Normal-N and Non-N conditions on Chlorella vulgaris. M. flos-aquae released 27, 22, 20, 27, 19, 25 and 17 compounds, respectively, with NaNO₃, NaNO₂, NH₄Cl, urea, Ser, Lys and Arg as the sole N source. With the reduction in N amount, the emission of VOCs was increased markedly, and the most VOCs were found under Non-N condition. C. vulgaris cell propagation, photosynthetic pigment and Fv/Fm declined significantly following exposure to M. flos-aquae VOCs under Non-N condition, but not under Normal-N condition. When C. vulgaris cells were treated with two terpenoids, eucalyptol and limonene, the inhibitory effects were enhanced with increasing concentrations. Therefore, multiple N sources in eutrophicated water induce different VOC emissions from cyanobacteria, and reduction in N can cause nutrient competition, which can result in emissions of more VOCs. Those VOCs released from M. flos-aquae cells under Non-N for nutrient competition can inhibit other algal growth. Among those VOCs, eucalyptol and limonene are the major toxic agents.

Optimization of inorganic carbon sources to improve the carbon fixation efficiency of the non-photosynthetic microbial community with different electron donors

As the non-photosynthetic microbial community (NPMC) isolated from seawaters utilized inorganic carbon sources for carbon fixation, the concentrations and ratios of Na2CO3, NaHCO3, and CO2 were optimized by response surface methodology design. With H2 as the electron donor, the optimal carbon sources were 270 mg/L Na2CO3, 580 mg/L NaHCO3, and 120 mg/L CO2. The carbon fixation efficiency in response to total organic carbon (TOC) was up to 30.59 mg/L with optimal carbon sources, which was about 50% higher than that obtained with CO2 as the sole carbon source. The mixture of inorganic carbon sources developed a buffer system to prevent acidification or alkalization of the medium caused by CO2 or Na2CO3, respectively. Furthermore, CO2 and HCO3(-), the starting points of carbon fixation in the pathways of Calvin-Benson-Bassham and 3-hydroxypropionate cycles, were provided by the carbon source structure to facilitate carbon fixation by NPMC. However, in the presence of mixed electron donors composed of 1.25% Na2S, 0.50% Na2S2O3, and 0.457% NaNO2, the carbon source structure did not exhibit significant improvement in the carbon fixation efficiency, when compared with that achieved with CO2 as the sole carbon source. The positive effect of mixed electron donors on inorganic carbon fixation was much higher than that of the carbon source structure. Nevertheless, the carbon source structure could be used as an alternative to CO2 when using NPMC to fix carbon in industrial processes.

Detection of methemoglobin in whole blood based on confocal micro-Raman spectroscopy and multivariate statistical techniques

Raman spectroscopy has been shown to have the potential for revealing oxygenated and spin ability of hemoglobin. In this study, confocal micro-Raman spectroscopy is developed to monitor the effect of sodium nitrite on oxyhemoglobin (HbO2 ) in whole blood. We observe that the band at 1,638 cm(-1) which is sensitive to the oxidation state decreases dramatically, while the 1,586 cm(-1) (low-spin state band) reduces both in methemoglobin (MetHb) and poisoning blood. Our results show that adding in sodium nitrite lead to the transition from HbO2 (Fe(2+) ) to MetHb (Fe(3+) ) in whole blood, and the iron atom converts from the low spin state to the high spin state with a delocalization from porphyrin plane. Moreover, multivariate statistical techniques, including principal components analysis (PCA) and linear discriminant analysis (LDA) are employed to develop effective diagnostic algorithms for classification of spectra between pure blood and poisoning blood. The diagnostic algorithms based on PCA-LDA yield a diagnostic sensitivity of 100% and specificity of 100% for separating poisoning blood from normal blood. Receiver operating characteristic (ROC) curve further confirms the effectiveness of the diagnostic algorithm based on PCA-LDA technique. The results from this study demonstrate that Raman spectroscopy combined with PCA-LDA algorithms has tremendous potential for the non-invasive detection of nitrite poisoning blood.

Dietary nitrite improves insulin signaling through GLUT4 translocation

Diabetes mellitus type 2 is a syndrome of disordered metabolism with inappropriate hyperglycemia owing to a reduction in the biological effectiveness of insulin. Type 2 diabetes is associated with an impaired nitric oxide (NO) pathway that probably serves as the key link between metabolic disorders and cardiovascular disease. Insulin-mediated translocation of GLUT4 involves the PI3K/Akt kinase signal cascade that results in activation of endothelial NO synthase (eNOS). eNOS is dysfunctional during diabetes. We hypothesize that loss of eNOS-derived NO terminates the signaling cascade and therefore cannot activate GLUT4 translocation and that dietary nitrite may repair this pathway. In this study, we administered 50mg/L sodium nitrite to db/db diabetic mice for 4 weeks. After 4 weeks treatment, the db/db mice experienced less weight gain, improved fasting glucose levels, and reduced insulin levels. Cell culture experiments using CHO-HIRc-myc-GLUT4eGFP cell lines stably expressing insulin receptor and myc-GLUT4eGFP protein, as well as L6 skeletal muscle cells stably expressing rat GLUT4 with a Myc epitope (L6-GLUT4myc), showed that NO, nitrite, and GSNO stimulate GLUT4 translocation independent of insulin, which is inhibited by NEM. Collectively our data suggest that nitrite improves insulin signaling through restoration of NO-dependent nitrosation of GLUT4 signaling translocation. These data suggest that NO-mediated nitrosation of GLUT4 by nitrite or other nitrosating agents is necessary and sufficient for GLUT4 translocation in target tissue. Description of this pathway may justify a high-nitrate/nitrite diet along with the glycemic index to provide a safe and nutritional regimen for the management and treatment of diabetes.

[Study on eliminating sodium nitrite and blocking nitrosamine synthesis by anthocyanin from skin of Alpinia galanga]

This study was performed to determine the ability of eliminating sodium nitrite and blocking nitrosamine synthesis by anthocyanin from the skin of Alpinia galanga. purified by macroporous resin. The test was conducted under the condition of the simulated human gastric juice (pH 3.0, 37 degrees C) with VitC as positive control. The results showed that the max capability of eliminating sodium nitrite was 87.14%, which is 1.6 times sronger than that of VitC, and the max capability of blocking nitrosamine synthesis was 97.82%, which is 8 times sronger than that of VitC.

Nitrite supplementation reverses vascular endothelial dysfunction and large elastic artery stiffness with aging

We tested the hypothesis that short-term nitrite therapy reverses vascular endothelial dysfunction and large elastic artery stiffening with aging, and reduces arterial oxidative stress and inflammation. Nitrite concentrations were lower (P < 0.05) in arteries, heart, and plasma of old (26-28 month) male C57BL6 control mice, and 3 weeks of sodium nitrite (50 mg L(-1) in drinking water) restored nitrite levels to or above young (4-6 month) controls. Isolated carotid arteries of old control mice had lower acetylcholine (ACh)-induced endothelium-dependent dilation (EDD) (71.7 ± 6.1% vs. 93.0 ± 2.0%) mediated by reduced nitric oxide (NO) bioavailability (P < 0.05 vs. young), and sodium nitrite restored EDD (95.5 ± 1.6%) by increasing NO bioavailability. 4-Hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPOL), a superoxide dismutase (SOD) mimetic, apocynin, a nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) inhibitor, and sepiapterin (exogenous tetrahydrobiopterin) each restored EDD to ACh in old control, but had no effect in old nitrite-supplemented mice. Old control mice had increased aortic pulse wave velocity (478 ± 16 vs. 332 ± 12 AU, P < 0.05 vs. young), which nitrite supplementation lowered (384 ± 27 AU). Nitrotyrosine, superoxide production, and expression of NADPH oxidase were ∼100-300% greater and SOD activity was ∼50% lower in old control mice (all P < 0.05 vs. young), but were ameliorated by sodium nitrite treatment. Inflammatory cytokines were markedly increased in old control mice (P < 0.05), but reduced to levels of young controls with nitrite supplementation. Short-term nitrite therapy reverses age-associated vascular endothelial dysfunction, large elastic artery stiffness, oxidative stress, and inflammation. Sodium nitrite may be a novel therapy for treating arterial aging in humans.

Reactions of nitrite in erythrocyte suspensions measured by membrane inlet mass spectrometry

The reactions of nitrite with deoxygenated human erythrocytes were examined using membrane inlet mass spectrometry to detect the accumulation of NO in an extracellular solution. In this method an inlet utilizing a silicon rubber membrane is submerged in cell suspensions and allows NO to pass from the extracellular solution into the mass spectrometer. This provides a direct, continuous, and quantitative determination of nitric oxide concentrations over long periods without the necessity of purging the suspension with inert gas. We have not observed accumulation of NO compared with controls on a physiologically relevant time scale and conclude that, within the limitations of the mass spectrometric method and our experimental conditions, erythrocytes do not generate a net efflux of NO after the addition of millimolar concentrations of nitrite. Moreover, there was no evidence at the mass spectrometer of the accumulation of a peak at mass 76 that would indicate N(2)O(3), an intermediate that decays into NO and NO(2). Inhibition of red cell membrane anion exchangers and aquaporins did not affect these processes.

Nitrite therapy after cardiac arrest reduces reactive oxygen species generation, improves cardiac and neurological function, and enhances survival via reversible inhibition of mitochondrial complex I

BACKGROUND

Three-fourths of cardiac arrest survivors die before hospital discharge or suffer significant neurological injury. Except for therapeutic hypothermia and revascularization, no novel therapies have been developed that improve survival or cardiac and neurological function after resuscitation. Nitrite (NO(2)(-)) increases cellular resilience to focal ischemia/reperfusion injury in multiple organs. We hypothesized that nitrite therapy may improve outcomes after the unique global ischemia/reperfusion insult of cardiopulmonary arrest.

METHODS AND RESULTS

We developed a mouse model of cardiac arrest characterized by 12 minutes of normothermic asystole and a high cardiopulmonary resuscitation rate. In this model, global ischemia and cardiopulmonary resuscitation were associated with blood and organ nitrite depletion, reversible myocardial dysfunction, impaired alveolar gas exchange, neurological injury, and an approximately 50% mortality. A single low dose of intravenous nitrite (50 nmol=1.85 micromol/kg=0.13 mg/kg) compared with blinded saline placebo given at cardiopulmonary resuscitation initiation with epinephrine improved cardiac function, survival, and neurological outcomes. From a mechanistic standpoint, nitrite treatment restored intracardiac nitrite and increased S-nitrosothiol levels, decreased pathological cardiac mitochondrial oxygen consumption resulting from reactive oxygen species formation, and prevented oxidative enzymatic injury via reversible specific inhibition of respiratory chain complex I.

CONCLUSIONS

Nitrite therapy after resuscitation from 12 minutes of asystole rapidly and reversibly modulated mitochondrial reactive oxygen species generation during early reperfusion, limiting acute cardiac dysfunction, death, and neurological impairment in survivors.

Dietary nitrite prevents hypercholesterolemic microvascular inflammation and reverses endothelial dysfunction

The nitrite anion is an endogenous product of mammalian nitric oxide (NO) metabolism, a key intermediate in the nitrogen cycle in plants, and a constituent of many foods. Research over the past 6 years has revealed surprising biological and cytoprotective activity of this anion. Hypercholesterolemia causes a proinflammatory phenotype in the microcirculation. This phenotype appears to result from a decline in NO bioavailability that results from a reduction in NO biosynthesis, inactivation of NO by superoxide, or both. Since nitrite has been shown to be potently cytoprotective and restore NO biochemical homeostasis, we investigated if supplemental nitrite could attenuate microvascular inflammation caused by a high cholesterol diet. C57Bl/6J mice were fed either a normal diet or a high cholesterol diet for 3 wk to induce microvascular inflammation. Mice on the high cholesterol diet received either nitrite-free drinking water or supplemental nitrite at 33 or 99 mg/l ad libitum in their drinking water. The results from this investigation reveal that mice fed a cholesterol-enriched diet exhibited significantly elevated leukocyte adhesion to and emigration through the venular endothelium as well as impaired endothelium-dependent relaxation in arterioles. Administration of nitrite in the drinking water inhibited the leukocyte adhesion and emigration and prevented the arteriolar dysfunction. This was associated with sparing of reduced tetrahydrobiopterin and decreased levels of C-reactive protein. These data reveal novel anti-inflammatory properties of nitrite and implicate the use of nitrite as a new natural therapy for microvascular inflammation and endothelial dysfunction associated with hypercholesterolemia.

Acute tolerance and metabolic responses of Chinese mitten crab (Eriocheir sinensis) juveniles to ambient nitrite

The lethal concentration of nitrite to the Chinese mitten crab Eriocheir sinensis was tested by exposing the animals to 17.78, 23.71, 31.62, 42.17, and 56.23 mg NaNO2 L(-1) at 20 degrees C for 24, 48, 72, and 96 h. The corresponding LC50 value for each time exposure was 43.87 (38.70-51.70), 40.24 (34.88-46.01), 38.87 (33.72-46.01) and 38.87 (33.72-46.01) mg NaNO2 L(-1) or 29.25 (25.80-34.47), 26.83 (23.25-30.67), 25.91(22.48-30.67), 25.91(22.48-30.67) mg NO2-N L(-1), respectively. The physiological response of the crab to nitrite toxicity was further investigated by exposing the crab to 0, 10, 20, 30 and 40 mg NaNO2 L(-1) for 2 d. The changes of nitrogenous compounds in haemolymph, oxyhemocyanin and metabolism were measured at 3, 6, 24 and 48 h upon exposure. Haemolymph nitrite was significantly enhanced by the increase of nitrite from 10 to 40 mg NaNO2 L(-1) during the 2-day exposure. The concentrations of nitrate, urea and glutamate in haemolymph increased concomitantly with the exposing time and ambient nitrite levels, suggesting that the formation of nitrate, urea and glutamine may be the possible end products of nitrite detoxification in crabs. The diffusion of nitrite caused a reduction of oxyhemocyanin, resulting to hypoxia in tissues. Under a hypoxia condition, crabs increased energy demand for metabolism as indicated by the elevated levels of glucose and lactate in haemolymph. Our data showed that ambient nitrite could affect oxygen carrying capacity through oxyhemocyanin reduction and the increase of energy catabolism in crabs. This study suggests that nitrite could be detoxified through the pathway of nitrate, urea and glutamine formation in crabs.

Characterization of a diesel-degrading strain isolated from a hydrocarbon-contaminated site

A diesel-degrading bacterium has been isolated from a diesel-polluted site. The isolate was tentatively identified as Staphylococcus aureus strain DRY11 based on partial 16S rDNA molecular phylogeny and Biolog GP microplate panels and Microlog database. Isolate 11 showed an almost linear increase in cellular growth with respect to diesel concentrations with optimum growth occurring at 4% (v/v) diesel concentration. Optimization studies using different nitrogen sources showed that the best nitrogen source was potassium nitrite. Sodium nitrite was optimum at 1.2 g l(-1) and higher concentrations were strongly inhibitory to cellular growth. The optimal pH that supported growth of the bacterium was between 7.5 to 8.0 and the isolate exhibited optimal broad temperature supporting growth on diesel from 27 to 37 degrees C. An almost complete removal of diesel components was seen from the reduction in hydrocarbon peaks observed using Solid Phase Microextraction Gas Chromatography analysis after 5 days of incubation. The characteristics of this bacterium suggest that it is suitable for bioremediation of diesel spills and pollutions in the tropics.

Leucopaxillus giganteus mycelium: effect of nitrogen source on organic acids and alkaloids

The aim of this work was to find the most useful inorganic nitrogen source to enable Leucopaxillus giganteus to become a more nutritious mushroom, regarding organic acid and phenolic composition and total alkaloids content. For these, the influence of NH 4NO 3,NaNO 2, KNO 3,, and (NH 4) 2HPO 4 on the organic acid production was determined by HPLC-UV and total alkaloid content was assessed by a spectrophotometric method, after precipitation by Dragendorff's reagent. The results showed that L. giganteus presented an organic acid profile composed of oxalic, cis-aconitic, citric, and fumaric acids, citric acid being the major one. The quantitative organic acid profile and total alkaloid content were affected by the nitrogen source and depended on the developmental stage of mycelium and nitrogen availability. Despite being present in all samples, no phenolic compound could be identified.

Nitric oxide formation from nitrite in zebrafish

Nitrite is a potential nitric oxide (NO) donor and may have important biological functions at low concentrations. The present study tests the hypothesis that nitrite accumulation across the gills in fish will cause a massive NO production from nitrite. Zebrafish were exposed to three different nitrite levels for variable time periods, and changes in blood nitrosylhemoglobin (HbNO), methemoglobin (metHb), oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (deoxyHb) were evaluated by spectral deconvolution. Blood HbNO (a biomarker of internal NO production) was low in controls, increased to a stable level around 3.7% of total Hb in fish exposed to 0.6 mmol l(-1) nitrite, and to 12.1% (at day 2) in fish exposed to 2 mmol l(-1) nitrite. The very high HbNO levels testify to an extensive conversion of nitrite to NO. With deoxyHb-mediated reduction of nitrite being a major NO-producing mechanism, the data reveal the significance of this mechanism, when hemoglobin cycles between full and intermediate oxygen saturations in the arterial-venous circulation. Fish exposed to 0.6 mmol l(-1) nitrite for up to 5 days could be divided into responding (with elevated metHb) and non-responding individuals. Exposure to 2 mmol l(-1) nitrite caused a time-dependent increase in metHb to 59% of total Hb within 2 days. Taking HbNO into account, the functional (potential O2 carrying) Hb was reduced to 29% at this stage. Total blood [Hb] was also significantly decreased. In spite of the reduced blood O2 capacitance, and the possibility that excess NO may inhibit mitochondrial respiration, whole animal routine oxygen consumption was not depressed.

Presence of a functional nitrate assimilation pathway in Mycobacterium smegmatis

Ability of Mycobacterium smegmatis to assimilate nitrate was evaluated in its active and dormant phase. Nitrate (10 mM), nitrite (0.5 mM) and ammonia (10mM) allowed growth of M. smegmatis concomitant with their complete depletion from the culture in 144, 120 and 96 h, respectively, when used as sole nitrogen source. Azide (50 microM) stopped the growth of M. smegmatis when nitrate was used as sole nitrogen source. l-methionine-S-sulfoximine (l-MSO), which is a well-known inhibitor of glutamine synthetase, an enzyme also involved in nitrogen metabolic pathway, when applied at 10 microg/ml concentration, completely inhibited the growth of the organism when nitrate or nitrite was used as sole nitrogen source. There was no effect of either azide or l-MSO at above concentrations on the growth of the organism when asparagine or ammonia was used as sole nitrogen source. More significantly, utilization of nitrate, nitrite and ammonia continued even in oxygen depletion induced dormant culture at the rates of 289, 25 and 354 microM/day, respectively. These rates were 5-8 times slower than the rates of 1966, 127 and 2890 microM/day, respectively, in active replicating phase. In the presence of azide (50 microM) and l-MSO (10 microg/ml), 2.1 and 1.51 logs reduction in viability of dormant M. smegmatis was observed using nitrate and nitrite, respectively, as sole nitrogen source. Altogether, the results indicated the presence of nitrate assimilation pathway operating in both active and dormant stage of M. smegmatis.

Formation of DNA-damaging N-nitroso compounds from the interaction of calcium-channel blockers with nitrite

A large number of drugs have been shown to react with nitrite to give genotoxic-carcinogenic N-nitroso compounds (NOC). However, the majority of drugs remain to be examined in this respect, among which calcium-channel blockers, all theoretically nitrosatable and widely used in the therapy of hypertension and other cardiovascular diseases. In this preliminary investigation, seven calcium-channel blockers have been examined either for their in vitro nitrosation according to the procedure recommended by the WHO, or for occurrence of liver DNA fragmentation, as detected by the Comet assay, in rats given by gavage 1/2 LD50 of the drug and 80 mg/kg of sodium nitrite. After 6h incubation the yields of NOC formed in vitro from nicardipine, nifedipine, nimodipine and nitrendipine ranged from 37 to 45% of the theoretical one, whereas the yields of NOC formed from diltiazem, gallopamil and verapamil ranged from 2 to 5%. In vivo, as compared with the effect of the same dose of the drug alone, a significant increase of both tail length and tail moment, indicative of an increased frequency of DNA single-strand breaks and alkali-labile sites, was produced in rat liver DNA by the administration with nitrite of gallopamil, nifedipine, nimodipine and nitrendipine, the ratio [tail length of drug+NaNO(2)/tail length of drug alone] being 3.2 for nimodipine, 3.1 for gallopamil 2.2 for nifedipine, and 2.1 for nitrendipine. Even if present, the increase in the degree of DNA fragmentation did not reach the statistical significance in rats given with nitrite nicardipine, diltiazem and verapamil. Further studies should be performed to investigate the formation of NOC in conditions simulating those occurring in the stomach of humans treated with a therapeutic dose, and to quantitate their genotoxic potency.

Inactivation of anthracyclines by serum heme proteins

We have previously shown that the anticancer agent doxorubicin undergoes oxidation and inactivation when exposed to myeloperoxidase-containing human leukemia HL-60 cells, or to isolated myeloperoxidase, in the presence of hydrogen peroxide and nitrite. In the current study we report that commercial fetal bovine serum (FBS) alone oxidizes doxorubicin in the presence of hydrogen peroxide and that nitrite accelerates this oxidation. The efficacy of inactivation was dependent on the concentration of serum present; no reaction was observed when hydrogen peroxide or serum was omitted. Peroxidase activity assays, based on oxidation of 3,3',5,5'-tetramethylbenzidine, confirmed the presence of a peroxidase in the sera from several suppliers. The peroxidative activity was contained in the >10000 MW fraction. We also found that hemoglobin, a heme protein likely to be present in commercial FBS, is capable of oxidizing doxorubicin in the presence of hydrogen peroxide and that nitrite further stimulates the reaction. In contrast to intact doxorubicin, the serum + hydrogen peroxide + nitrite treated drug appeared to be nontoxic for PC3 human prostate cancer cells. Together, this study shows that (pseudo)peroxidases present in sera catalyze oxidation of doxorubicin by hydrogen peroxide and that this diminishes the tumoricidal activity of the anthracycline, at least in in vitro settings. Finally, this study also points out that addition of H2O2 to media containing FBS will stimulate peroxidase-type of reactions, which may affect cytotoxic properties of studied compounds.

Red blood cells prevent inhibition of hypoxic pulmonary vasoconstriction by nitrite in isolated, perfused rat lungs

Nitrite reduction to nitric oxide (NO) may be potentiated by a nitrite reductase activity of deoxyHb and contribute to systemic hypoxic vasodilation. The effect of nitrite on the pulmonary circulation has not been well characterized. We explored the effect of nitrite on hypoxic pulmonary vasoconstriction (HPV) and the role of the red blood cell (RBC) in nitrite reduction and nitrite-mediated vasodilation. As to method, isolated rat lungs were perfused with buffer, or buffer with RBCs, and subjected to repeated hypoxic challenges, with or without nitrite. As a result, in buffer-perfused lungs, HPV was reduced at nitrite concentrations of 7 muM and above. Nitrite inhibition of HPV was prevented by excess free Hb and RBCs, suggesting that vasodilation was mediated by free NO. Nitrite-inhibition of HPV was not potentiated by mild acidosis (pH = 7.2) or xanthine oxidase activity. RBCs at 15% but not 1% hematocrit prevented inhibition of HPV by nitrite (maximum nitrite concentration of approximately 35 muM) independent of perfusate Po(2). Degradation of nitrite was accelerated by hypoxia in the presence of RBCs but not during buffer perfusion. In conclusion, low micromolar concentrations of nitrite inhibit HPV in buffer-perfused lungs and when RBC concentration is subphysiological. This effect is lost when RBC concentration approaches physiological levels, despite enhanced nitrite degradation in the presence of RBCs. These data suggest that, although deoxyHb may generate NO from nitrite, insufficient NO escapes the RBC to cause vasodilation in the pulmonary circulation under the dynamic conditions of blood flow through the lungs and that RBCs are net scavengers of NO.

Improvement of NaNO2-oxidizing activity in Nitrobacter vulgaris by coentrapment in polyacrylamide containing polydimethylsiloxane copolymer and DEAE-sephadex

Removal of nitrite and nitrate from drinking water has attracted great attention in recent years because of the human health risk induced by the exposure to contaminated groundwater and surface water. We have therefore tested a model nitrite oxidation system by coentrapping the NaNO2 oxidizer Nitrobacter vulgaris with polydimethylsiloxane (PDMS) copolymer and DEAE-Sephadex in a polyacrylamide gel. The copolymer and the anion exchanger facilitate the diffusion of oxygen and NaNO2, respectively, into the gel matrix. To test the nitrite-oxidizing activity, the entrapped cells were coupled to a thermal sensor. Coentrapment of 5% (wt/vol) DEAE-Sephadex with Nitrobacter vulgaris increased the nitrite-oxidizing activity by a factor of 3.7 compared to entrapped cells alone, and by the addition of 0.86% (wt/vol) artificial oxygen carrier PDMS copolymer increased the activity further to 4.3 times higher. Operational and storage stability of the coentrapped N.vulgaris also improved. This suggests that this enhanced immobilized cell system can also be used for nitrite oxidation to nitrate in drinking water as an on-line thermally monitored bioreactor.

NO-Generating Compounds Modify Tumoritoxic Effect of Doxorubicin

The effects of NO-generating compounds on the tumoritoxic effect of doxorubicin was evaluated by changes in DNA synthesis and apoptotic death of Ehrlich adenocarcinoma cells in vitro. NO donors significantly inhibited the cytotoxic effect of doxorubicin, which manifested in activation of DNA synthesis and decreased induction of apoptosis. Presumably, NO acts a factor protecting tumor cell DNA from the damaging effect of doxorubicin.

Fatty acids profile of Spirulina platensis grown under different temperatures and nitrogen concentrations

The influence of culture temperature and the concentration of sodium nitrate (NaNO3) on the gas-chromatographic profile of the fatty acids of the filamentous cyanobacterium Spirulina platensis was evaluated. We found that temperature was the most important factor and that the greatest amount of gamma-linolenic acid (GLA) was obtained at 30 degrees C, the fatty acid profile of the Spirulina cultivated showing that (in order of abundance) palmitic, linolenic and linoleic acids were most prevalent.

Quantitative interaction effects of carbon dioxide, sodium chloride, and sodium nitrite on neurotoxin gene expression in nonproteolytic Clostridium botulinum type B

The effects of carbon dioxide, sodium chloride, and sodium nitrite on type B botulinum neurotoxin (BoNT/B) gene (cntB) expression in nonproteolytic Clostridium botulinum were investigated in a tryptone-peptone-yeast extract (TPY) medium. Various concentrations of these selected food preservatives were studied by using a complete factorial design in order to quantitatively study interaction effects, as well as main effects, on the following responses: lag phase duration (LPD), growth rate, relative cntB expression, and extracellular BoNT/B production. Multiple linear regression was used to set up six statistical models to quantify and predict these responses. All combinations of NaCl and NaNO(2) in the growth medium resulted in a prolonged lag phase duration and in a reduction in the specific growth rate. In contrast, the relative BoNT/B gene expression was unchanged, as determined by the cntB-specific quantitative reverse transcription-PCR method. This was confirmed when we measured the extracellular BoNT/B concentration by an enzyme-linked immunosorbent assay. CO(2) was found to have a major effect on gene expression when the cntB mRNA levels were monitored in the mid-exponential, late exponential, and late stationary growth phases. The expression of cntB relative to the expression of the 16S rRNA gene was stimulated by an elevated CO(2) concentration; the cntB mRNA level was fivefold greater in a 70% CO(2) atmosphere than in a 10% CO(2) atmosphere. These findings were also confirmed when we analyzed the extracellular BoNT/B concentration; we found that the concentrations were 27 ng x ml(-1). unit of optical density(-1) in the 10% CO(2) atmosphere and 126 ng x ml(-1). unit of optical density(-1) in the 70% CO(2) atmosphere.

Relative neurotoxin gene expression in clostridium botulinum type B, determined using quantitative reverse transcription-PCR

A quantitative reverse transcription-PCR (qRT-PCR) method was developed to monitor the relative expression of the type B botulinum neurotoxin (BoNT/B) gene (cntB) in Clostridium botulinum. The levels of cntB mRNA in five type B strains were accurately monitored by using primers specific for cntB and for the reference gene encoding the 16S rRNA. The patterns and relative expression of cntB were different in the different strains. Except for one of the strains investigated, an increase in cntB expression was observed when the bacteria entered the early stationary growth phase. In the proteolytic strain C. botulinum ATCC 7949, the level of cntB mRNA was four- to fivefold higher than the corresponding levels in the other strains. This was confirmed when we quantified the production of extracellular BoNT/B by an enzyme-linked immunosorbent assay and measured the toxicity of BoNT/B by a mouse bioassay. When the effect of exposure to air on cntB expression was investigated, no decline in the relative expression was observed in spite of an 83% reduction in the viable count based on the initial cell number. Instead, the level of cntB mRNA remained the same. When there was an increase in the sodium nitrite concentration, the bacteria needed a longer adjustment time in the medium before exponential growth occurred. In addition, there was a reduction in the expression of cntB compared to the expression of the 16S rRNA gene at higher sodium nitrite concentrations. This was most obvious in the late exponential growth phase, but at the highest sodium nitrite concentration investigated, 45 ppm, a one- to threefold decline in the cntB mRNA level was observed in all growth phases.

The Depletion of Sodium Nitrite by Lactic Acid Bacteria Isolated from Kimchi

Nitrites, whether added or naturally occurring in foods, are potential carcinogens, and controlling their concentrations is important for maintaining a safe food supply. In this study we investigated the depletion of sodium nitrite (150 microg/mL) during the fermentation in Lactobacilli MRS broth at 5, 10, 15, 20, 25, 30, and 36 degrees C by lactic acid bacteria (LAB-A, -B, -C, and -D) isolated from kimchi and Leuconostoc mesenteroides strain KCTC3100. The four species of lactic acid bacteria isolated from kimchi were identified as L. mesenteroides, and all produced depletion of less than 20% of sodium nitrite after 10 days of incubation at 5 degrees C. There was less than 40% depletion after 9 days at 10 degrees C, 86.4-92.8% after 7 days at 15 degrees C, 81.4-87.8% after 4 days and more than 90.0% after 5 days at 20 degrees C, 76.3-85.7% after 3 days and more than 90.0% after 5 days at 25 degrees C, and more than 90.0% after 2 days at 30 and 36 degrees C. The depletion by LAB isolates was similar or higher than that by L. mesenteroides strain KCTC3100, and in particular, the LAB-D strain showed the highest depletion effect of all the strains tested, up to 15 degrees C. From these results, the strains isolated from kimchi were very effective for the depletion of sodium nitrite at high temperature, and all sodium nitrite was depleted at the initial period of incubation (1-2 days) at 30 and 36 degrees C. But as the temperature was lowered, the depletion effect of sodium nitrite was decreased in all the strains tested from kimchi. This illustrates that the depletion of nitrite by each strain is subject to the influence of temperatures.

In vitro evaluation of a new treatment for urinary tract infections caused by nitrate-reducing bacteria

Dietary and endogenous nitrates are excreted in urine, and during infection with nitrate-reducing bacteria they are reduced to nitrite. At a low pH nitrite is converted to a variety of nitrogen oxides that are toxic to bacteria. We hypothesized that acidification of nitrite-rich infected urine would result in the killing of the nitrate-reducing bacteria. An Escherichia coli control strain and a mutant lacking nitrate reductase activity were preincubated in urine supplemented with sodium nitrate (0 to 10 mM) at pH 7.0. Then, the nitrite-containing bacterial culture was transferred (and diluted 1/10) to slightly acidic urine (pH 5 and 5.5) containing ascorbic acid (10 mM) and growth was monitored. The control strain produced nitrite in amounts related to the amount of nitrate added. This strain was killed when the culture was transferred to acidic urine. In contrast, the mutant that did not produce nitrite retained full viability. When control bacteria were grown in acidic urine with nitrate and ascorbic acid present from the start of the experiment, no inhibition of growth was noted. The MICs and minimal bactericidal concentrations of sodium nitrite-ascorbic acid in acidic urine were comparable to those of conventional antibiotics. Preincubation of nitrate-reducing E. coli in nitrate-rich urine leads to the accumulation of nitrite. Subsequent acidification of the urine results in generation of nitrogen oxides that are bactericidal. Killing, however, requires a sequential procedure in which the bacteria are first allowed to grow in a nitrate-rich neutral environment, later followed by acidification. We speculate that ingestion of nitrate followed some hours later by acidification of urine could be a new therapeutic strategy for the treatment of urinary tract infections.

Compensatory increase in ahpC gene expression and its role in protecting Burkholderia pseudomallei against reactive nitrogen intermediates

In the human pathogen Burkholderia pseudomallei, katG encodes the antioxidant defense enzyme catalase-peroxidase. Interestingly, a B. pseudomallei mutant, disrupted in katG, is hyperresistant to organic hydroperoxide. This hyperresistance is due to the compensatory expression of the alkyl hydroperoxide reductase gene ( ahpC) and depends on a global regulator OxyR. The KatG-deficient mutant is also highly resistant to reactive nitrogen intermediates (RNI). When overproduced, the B. pseudomallei AhpC protein, protected cells against killing by RNI. The levels of resistance to both organic peroxide and RNI returned to those of the wild-type when the katG mutant was complemented with katG. These studies establish the partially overlapping defensive activities of KatG and AhpC.

Candidatus “Scalindua brodae”, sp. nov., Candidatus “Scalindua wagneri”, sp. nov., Two New Species of Anaerobic Ammonium Oxidizing Bacteria

Anaerobic ammonium oxidation (anammox) is both a promising process in wastewater treatment and a long overlooked microbial physiology that can contribute significantly to biological nitrogen cycling in the world's oceans. Anammox is mediated by a monophyletic group of bacteria that branches deeply in the Planctomycetales. Here we describe a new genus and species of anaerobic ammonium oxidizing planctomycetes, discovered in a wastewater treatment plant (wwtp) treating landfill leachate in Pitsea, UK. The biomass from this wwtp showed high anammox activity (5.0 +/- 0.5 nmol/mg protein/min) and produced hydrazine from hydroxylamine, one of the unique features of anammox bacteria. Eight new planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass. Four of these were affiliated to known anammox 16S rRNA gene sequences, but branched much closer to the root of the planctomycete line of descent. Fluorescence in situ hybridization (FISH) with oligonucleotide probes specific for these new sequences showed that two species (belonging to the same genus) together made up > 99% of the planctomycete population which constituted 20% of the total microbial community. The identification of these organisms as typical anammox bacteria was confirmed with electron microscopy and lipid analysis. The new species, provisionally named Candidatus "Scalindua brodae" and "Scalindua wagneri" considerably extend the biodiversity of the anammox lineage on the 16S rRNA gene level, but otherwise resemble known anammox bacteria. Simultaneously, another new species of the same genus, Candidatus "Scalindua sorokinii", was detected in the water column of the Black Sea, making this genus the most widespread of all anammox bacteria described so far.

The presence of 4-hydroxyphenylacetic acid in human saliva and the possibility of its nitration by salivary nitrite in the stomach

Human saliva contained 4-hydroxyphenylacetic acid (HPA) (2-10 microM) and nitrite (60-300 microM). HPA was nitrated to 4-hydroxy-3-nitrophenylacetic acid (NO2HPA) when HPA and sodium nitrite were mixed at pH 1.0. NO2HPA was also formed when saliva was incubated under acidic conditions. These results suggest that salivary HPA is nitrated to NO2HPA when saliva is swallowed into the stomach.

Trypanosoma cruzi dihydrolipoamide dehydrogenase is inactivated by myeloperoxidase-generated "reactive species"

Dihydrolipoamide dehydrogenase (LADH) from Trypanosoma cruzi was inactivated by treatment with myeloperoxidase (MPO)-dependent systems. With MPO/H2O2/NaCl, LADH lipoamide reductase and diaphorase activities significantly decreased as a function of incubation time. Iodide, bromide, thiocyanide and chloride effectively supplemented the MPO/H2O2 system, KI and NaCl being the most and the least effective supplements, respectively. LADH inactivation by MPO/H2O2/NaCl and by NaOCl was similarly prevented by thiol compounds such as GSH, L-cysteine, N-acetylcysteine, penicillamine and N-(2-mercaptopropionyl-glycine) in agreement with the role of HOCI in LADH inactivation by MPO/H2O2/NaCl. LADH was also inactivated by MPO/NADH/halide, MPO/H2O2/NaNO2 and MPO/NADH/NaNO2 systems. Catalase prevented the action of the NADH-dependent systems, thus supporting H2O2 production by NADH-supplemented LADH. MPO inhibitors (4-aminobenzoic acid hydrazide, and isoniazid), GSH, L-cysteine, L-methionine and L-tryptophan prevented LADH inactivation by MPO/H2O2/NaNO2. Other MPO systems inactivating LADH were (a) MPO/H2O2/chlorpromazine; (b) MPO/H2O2/monophenolic systems, including L-tyrosine, serotonin and acetaminophen and (c) MPO/H2O2/di- and polyphenolic systems, including norepinephrine, catechol, nordihydroguaiaretic acid, caffeic acid, quercetin and catechin. Comparison of the above effects and those previously reported with pig myocardial LADH indicates that both enzymes were similarly affected by the MPO-dependent systems, allowance being made for T. cruzi LADH diaphorase inactivation and the greater sensitivity of its LADH lipoamide reductase activity towards the MPO/H2O2/NaCl system and NaOCl.

Formation of N-nitrosamines and N-nitramines by the reaction of secondary amines with peroxynitrite and other reactive nitrogen species: comparison with nitrotyrosine formation

Reactive nitrogen species, including nitrogen oxides (N(2)O(3) and N(2)O(4)), peroxynitrite (ONOO(-)), and nitryl chloride (NO(2)Cl), have been implicated as causes of inflammation and cancer. We studied reactions of secondary amines with peroxynitrite and found that both N-nitrosamines and N-nitramines were formed. Morpholine was more easily nitrosated by peroxynitrite at alkaline pH than at neutral pH, whereas its nitration by peroxynitrite was optimal at pH 8.5. The yield of nitrosomorpholine in this reaction was 3 times higher than that of nitromorpholine at alkaline pH, whereas 2 times more nitromorpholine than nitrosomorpholine was formed at pH <7.5. For the morpholine-peroxynitrite reaction, nitration was enhanced by low concentrations of bicarbonate, but was inhibited by excess bicarbonate. Nitrosation was inhibited by excess bicarbonate. On this basis, we propose a free radical mechanism, involving one-electron oxidation by peroxynitrite of secondary amines to form amino radicals (R(2)N(*)), which react with nitric oxide ((*)NO) or nitrogen dioxide ((*)NO(2)) to yield nitroso and nitro secondary amines, respectively. Reaction of morpholine with NO(*) and superoxide anion (O(2)(*)(-)), which were concomitantly produced from spermine NONOate and by the xanthine oxidase systems, respectively, also yielded nitromorpholine, but its yield was <1% of that of nitrosomorpholine. NO(*) alone increased the extent of nitrosomorpholine formation in a dose-dependent manner, and concomitant production of O(2)(*)(-) inhibited its formation. Reactions of morpholine with nitrite plus HOCl or nitrite plus H(2)O(2), with or without addition of myeloperoxidase or horseradish peroxidase, also yielded nitration and nitrosation products, in yields that depended on the reactants. Tyrosine was nitrated easily by synthetic peroxynitrite, by NaNO(2) plus H(2)O(2) with myeloperoxidase, and by NaNO(2) plus H(2)O(2) under acidic conditions. Nitrated secondary amines, e.g., N-nitroproline, could be identified as specific markers for endogenous nitration mediated by reactive nitrogen species.

Measurement of total nitric oxide metabolite (NO(x)(-)) levels in vivo

The measurement of the total level of nitric oxide (NO) metabolite (NO(x)(-)) by microdialysis has recently been used to assess the production of NO in the in vivo brain [D. Luo, S. Knezevich, S.R. Vincent, N-Methyl-D-aspartate-induced nitric oxide release: an in vivo microdialysis study, Neuroscience, 57 (1993), 897-900; K. Ohta, N. Arai, M. Shibata, J. Hamada, S. Komatsumoto, K. Shimazu, Y. Fukuuchi, A novel in vivo system for consecutive measurement of brain nitric oxide production combined with the microdialysis technique, Neurosci. Lett., 176 (1994), 165-168; K. Shintani, S. Kanba, T. Nakai, K. Sato, G. Yagi, R. Kato, M. Arai, Measurement by in vivo microdialysis of nitric oxide release in the rat cerebellum, J. Psychiatr. Neurosci., 3 (1994), 217-221; H. Togashi, K. Mori, K. Ueno, M. Matsumoto, N. Suda, H. Saito, M. Yoshika, Consecutive evaluation of nitric oxide production after transient cerebral ischemia in the rat hippocampus using in vivo brain microdialysis, Neurosci. Lett., 240 (1998), 53-57]. Although several methods are available for detecting NO(x)(-) levels in dialysates, these methods are either not sensitive enough or require expensive experimental equipment. The method described herein provides a convenient and sensitive procedure for determining NO(x)(-) levels in dialysates. This method is useful for the in vivo study of NO production from various brain regions in various pathological conditions, and can be applied to other tissues.

In vitro survival and germination of Candida albicans in the presence of nitrogen compounds

The in vitro effect of nitric oxide (NO) and nitrite on blastoconidia and hyphae of Candida albicans was studied. Sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) were used as NO donors. Both minimal and complex media at two pH values, 7.0 and 4.5, were used for the assays. Blastoconidia were more susceptible than hyphae to NO. The NO effect on blastoconidia was greater at acidic pH. Nitrite affected the viability of blastoconidia in complex medium. The percentage germination and the relative rate of elongation of hyphae were both enhanced when NO was present in acidic conditions.

Inactivation of myocardial dihydrolipoamide dehydrogenase by myeloperoxidase systems: effect of halides, nitrite and thiol compounds

Dihydrolipoamide dehydrogenase (LADH) lipoamide reductase activity decreased whereas enzyme diaphorase activity increased after LADH treatment with myeloperoxidase (MPO) dependent systems (MPO/H2O2/halide, MPO/NADH/halide and MPO/H2O2/nitrite systems. LADH inactivation was a function of the composition of the inactivating system and the incubation time. Chloride, iodide, bromide, and the thiocyanate anions were effective complements of the MPO/H2O2 system. NaOCl inactivated LADH, thus supporting hypochlorous acid (HOCl) as putative agent of the MPO/H2O2/NaCl system. NaOCl and the MPO/H2O2/NaCl system oxidized LADH thiols and NaOCl also oxidized LADH methionine and tyrosine residues. LADH inactivation by the MPO/NADH/halide systems was prevented by catalase and enhanced by superoxide dismutase, in close agreement with H2O2 production by the LADH/NADH system. Similar effects were obtained with lactoperoxidase and horse-radish peroxidase supplemented systems. L-cysteine, N-acetylcysteine, penicillamine, N-(2-mercaptopropionylglycine), Captopril and taurine protected LADH against MPO systems and NaOCl. The effect of the MPO/H2O2/NaNO2 system was prevented by MPO inhibitors (sodium azide, isoniazid, salicylhydroxamic acid) and also by L-cysteine, L-methionine, L-tryptophan, L-tyrosine, L-histidine and reduced glutathione. The summarized observations support the hypothesis that peroxidase-generated "reactive species" oxidize essential thiol groups at LADH catalytic site.

[Effect of carnosine on the transformation of sodium nitrite in vitro in the presence of catalase]

It was shown that carnosine changes the compacting of ferment's globe. On the one hand, that action is causes with the connecting of haem. On the other hand, carnosine influences on the hydrate's membrane around protein. Dipeptide influences also on the interaction of catalase with sodium nitrite, which intensity depends on sequence of introducing HNO2 and carnosine into the medium.

Some aspects of beta-lactoglobulin structural properties in solution studied by fluorescence quenching

The technique of protein fluorescence quenching by acrylamide and sodium nitrite (NO2-) was used to study some structural aspects of beta-lactoglobulin in solution. The degree of exposure and the micro-environments of the two tryptophanyl residues (Trp-19 and Trp-61) present in this ruminant milk protein were sensed, and the influence of the pH and the binding of palmitic acid in their accessibilities were analyzed. The results obtained showed that Trp-19 has an accessibility to the quenchers higher than could be supposed from its structural location. The binding of palmitic acid, on the other hand, increases the accessibility of both tryptophanyl residues, a fact that could be associated with a slight conformational change of the protein.

Xanthine oxidoreductase catalyses the reduction of nitrates and nitrite to nitric oxide under hypoxic conditions

Xanthine oxidoreductase (XOR) catalyses the reduction of the therapeutic organic nitrate, nitroglycerin (glyceryl trinitrate, GTN), as well as inorganic nitrate and nitrite, to nitric oxide (NO) under hypoxic conditions in the presence of NADH. Generation of nitric oxide is not detectable under normoxic conditions and is inhibited by the molybdenum site-specific inhibitors, oxypurinol and (-)BOF 4272. These enzymic reactions provide a mechanism for generation of NO under hypoxic conditions where nitric oxide synthase does not function, suggesting a vasodilatory role in ischaemia.

Revised model for aerobic growth of Shigella flexneri to extend the validity of predictions at temperatures between 10 and 19 degrees C

Although Shigella is a major foodborne pathogen, its growth in foods has received little attention. Growth of S. flexneri 5348 inoculated into commercially available sterile foods (canned broths, meat, fish, UHT milk, baby foods) was studied at 10 to 37 degrees C. S. flexneri was enumerated by surface-plating on Tryptic Soy Agar and growth curves were fitted by means of the Gompertz equation. Observed growth kinetics values and values calculated using a previously developed response surface model compared favorably for growth at 19 to 37 degrees C, but not at < 19 degrees C. To refine the model, additional data were collected for growth at 10 to 19 degrees C. A total of 844 tests in BHI broth, representing 197 variable combinations of temperature (10-37 degrees C), pH (5.0-7.5), NaCl (0.5-5.0%) and NaNO2 (0-1000 ppm) was used for the revised model. The revised model, developed in BHI, gave significantly better agreement of calculated growth kinetics values with those observed in foods at 10 to 19 degrees C.

Gaseous nitrogen dioxide increases the endogenous synthesis of carcinogenic N-nitrosodimethylamine in animals

Inhalation of nitrogen dioxide (NO2) by mice administered orally amidopyrine (AP) and sodium nitrite resulted in increased biosynthesis of N-nitrosodimethylamine (NDMA), as determined by analysis using gas chromatography with thermal energy analyzer detector. These results were also confirmed indirectly in chronic experiments on rats using the system of biomarkers of NDMA formation (single-stranded DNA liver damages, alanine-aminotransferase, glutathione-S-transferase, and liver S9 fraction activity). The inhibition of NDMA metabolism by 4-methylpyrazol (4-MP) administration increases the sensitivity of NDMA biosynthesis assay in frozen whole-mouse powder. The results confirm that NO2 can serve as the precursor of nitrosamines.

In vitro studies of interactions of NO. donor drugs with superoxide and hydroxyl radicals

Nitric oxide (NO.) is a free radical characterized by a high spontaneous chemical reactivity with many other molecules including the superoxide radical (O2.-). This complex interaction may generate a peroxynitrite anion (ONOO-), which behaves as an important mediator of oxidative stress in many pathological states. In the present study, in vitro experiments were performed to assess directly the O2.- and hydroxyl (.OH) radical scavenging effects of various NO. donor drugs, i.e. sodium nitroprusside (SNP), sodium nitrite (NaNO2), molsidomine and SIN 1, at pH 7.4, 7 or 6. Concentrations of NO. in the incubation medium containing the different NO. donor drugs were measured by the assay based on the reaction of Fe-N-methyl-D-glucamine dithiocarbamate (MGD) with NO. that yields a stable spin-adduct measured by electron paramagnetic resonance (EPR). O2.- and .OH generation was characterized by EPR spin trapping techniques, using the spin trap 5,5-dimethyl-1-pyrroline-1-oxide (DMPO). These free radicals were generated from the enzymatic system xanthine-xanthine oxidase, in phosphate buffer adjusted at pH 7.4, 7 and 6. Under these experimental conditions, SNP exhibited the strongest superoxide scavenging properties, characterized by IC50 values expressed in the micromolar range, which decreased at low pH. Addition of SNP (800 microM) to solution containing MGD and Fe2+ (5:1) at pH 7 4 produced a three line EPR spectrum which is identified to [(MGD)2-Fe2+-NO]. In control experiments no EPR signal was observed. We obtained the same results with NaNO2 and an augmentation of the spin-adduct level was noted with the prolongation of the incubation period. In return, molsidomine (2 mM) did not produce, in our conditions, a detectable production of NO.. NaNO2 displayed a significant superoxide scavenging effect only at pH 6, whilst neither molsidomine nor SIN 1 had any effect. Therefore, the superoxide scavenging properties of SNP, NaNO2, and molsidomine appeared to be closely related to their potential for NO release, which partially depends on the pH conditions. The behaviour of SIN 1 is more complicated, the speed of oxygen diffusion probably acting as a limiting factor in NO. formation in our conditions. The production of NO. was detected in presence of SIN 1. The intensity of the complex is comparable with the signal founded with NaNO2. By contrast, all molecules exhibited hydroxyl radical scavenging properties, highlighting the capacity of .OH to react with a wide range of molecules. In conclusion, considering the poor chemical reactivity of O2.-, the NO. donor drugs/O2.- interactions suggest a special relationship between these two radical species, which, in certain pathological states, could lead to the generation of cytotoxic end-products with strong oxidizing properties.

Leishmania spp.: mechanisms of toxicity of nitrogen oxidation products

Intracellular killing of Leishmania parasites within activated murine macrophages is thought to result from the toxic activities of nitrogen oxidation products (referred to as NO) released by the activated cells. In order to determine possible mechanisms of NO toxicity for these microorganisms, promastigotes of Leishmania major and Leishmania enriettii were exposed to NO generated chemically from acidified nitrite, S-nitrosocysteine, diethylamine NONOate, or nitroprusside. Treatment with these agents led to loss of viability (as determined from decreased motility and inhibition of [3H]TdR uptake upon reincubation in NO-free medium) with kinetics characteristic for each compound L. major was less sensitive to these effects than L. enriettii, and amastigotes displayed the same sensitivity as promastigotes of the same species. The early effects of NO toxicity could be detected within minutes of exposure to the NO donors; they included decreased respiration rate and inhibition of glucose, proline, and adenine incorporation. Inhibition of the activities of glyceraldehyde 3-phosphate dehydrogenase and of aconitase were also evidenced. In order to determine whether these phenomena reflected the mechanisms of toxicity of bona fide NO generated by macrophages, promastigotes were exposed to IFN-gamma + LPS-activated macrophages across permeable membranes. This resulted in marked inhibition of proline and adenine uptake in the parasites, which was restored, however, to control levels when macrophages were activated in the presence of the nitric oxide synthase inhibitor NGMMA. These results indicate that several cellular targets may be subject to NO toxicity in Leishmania parasites, including enzymes of glycolysis and respiratory metabolism as well as trans-membrane transport systems.

Binding of nitric oxide to thiols and hemes in hemoglobin H: implications for alpha-thalassemia and hypertension

Our earlier studies suggested an association between alpha-thalassemia and hypertension. We postulated that this association might involve trapping of the vasodilator nitric oxide (NO) by hemoglobin (Hb). Hb A has recently been shown to carry NO on its sulfhydryl groups in addition to its hemes. In this report we studied the interaction of purified Hb H as well as Hb A with NO. The number of reactive sulfhydryls were determined spectrophotometrically with bis-dithionitrobenzoate. Spectral studies and nitrosothiol measurements after treatment with NO or nitrosothiols indicated that all eight reactive sulfhydryls of Hb H were capable of binding NO. Hb A, however, was only able to bind and transfer two molecules of NO per tetramer. These findings support the biochemical basis for the association between alpha-thalassemia and hypertension.

Fatal methemoglobinemia caused by liniment solutions containing sodium nitrite

We describe a case of fatal methemoglobinemia (MetHb-emia) resulting from application of liniment solution containing large quantities of sodium nitrite. As a remedial treatment of atopic dermatitis, the liniment solution was applied all over the boy's body. Autopsy findings showed no significant macroscopic or microscopic findings except blood tinted chocolate brown color and chronic atopic dermatitis over the whole surface of the body. Quantitation of the methemoglobin (MetHb) in the blood was performed using spectrophotometer; MetHb concentration of the blood was 76%. Ion chromatographic determination revealed a nitrite concentration of 1 mg/L in the serum. Such a liniment solution is not authorized by the Ministry of Public Welfare.

Mutagenicity of soy sauce treated with nitrite in the presence of ethanol or alcoholic beverages

The mutagenicity induced by soy sauce after reaction with 50 mM nitrite at pH 3, 37 degrees C, for 60 min in the presence of 1.25-10% ethanol was reduced in proportion to the ethanol concentration. The mutagenicity of soy sauce treated with nitrite was also reduced in the presence of commercial alcoholic beverages, Japanese sake, wine, 'shochu', whiskey and brandy, but not beer, in proportion to the concentration. The mutagenicity of nitrite-treated tyramine, which is a major precursor of a mutagen in soy sauce treated with nitrite, was strongly reduced in the presence of ethanol, n-propanol or isopropanol and more strongly reduced in the presence of methanol, but was increased twofold in the presence of the sugars glucose or sucrose. The reduction of the mutagenicity of nitrite-treated tyramine required simultaneous treatment of tyramine with ethanol and nitrite. The mutagenicity of tyramine treated with nitrite was clearly reduced in the presence of shochu and whiskey, similarly to ethanol. Analysis by high-performance liquid chromatography revealed that the reduction of the mutagenicity of nitrite-treated tyramine in the presence of ethanol resulted from the reduced production of mutagenic 3-diazotyramine from tyramine.