Nitrite Treatment Research Articles

Contribution of amylose-procyanidin complexes to slower starch digestion of red-colored rice prepared by cooking with adzuki bean

Combining high-carbohydrate food with polyphenol-rich food is a possible way of producing slowly digestible starch with beneficial health properties. In Japan, non-glutinous and glutinous rice are cooked with adzuki bean and the colour of the cooked rice is pale red. In this article, we show that (1) the red colour of rice could be attributed to the oxidation of adzuki bean procyanidins, (2) pancreatin-induced starch digestion of the red-coloured non-glutinous rice was slower than white rice and (3) the digestion of amylose and potato starch but not amylopectin became slower by heating with procyanidin B2. Furthermore, the rate of starch digestion of red-coloured rice was not affected by nitrite treatment under simulated gastric conditions. The above results show that procyanidins could bind to amylose independent of the starch source by heating and could suppress starch digestion by α-amylase in the intestine.

Pd and Pd,In nanoparticles supported on polymer fibres as catalysts for the nitrate and nitrite reduction in aqueous media

The presence of high concentrations of nitrate and nitrite ions in water sources is an actual environmental problem. Nowadays, there are several technologies for nitrate and nitrite treatment, but most of them involve the concentration of the ions which are later necessary to be decomposed in a second step. The catalytic elimination of nitrates and nitrites from water is a very promising method because the ions are transformed into the harmless N2(g). Two types of synthetic polymeric fibers were proposed as supports of palladium and indium catalytic species with low metallic loading (Pd:In = 1:0.25 wt.%). They were synthesized by electrospinning method with a Pd/In weight ratio 1:0.25. PdInDA catalyst was prepared by dissolving poly (methyl methacrylate) (PMMA) with a mixture of acetone/dimethylformamide, whereas the polymer (PMMA) was dissolved in pure dimethylformamide for the synthesis of PdD and PdInD catalysts. Both bimetallic solids gave rise to good selectivity to N2(g). However, the PdInDA reached middle nitrate conversions (around 50 %) with low ammonia production (under 0.1Nppm). The characterization results suggested that the active sites remained unchanged after the reaction. This proposal involves a green chemical method with low consumption of reactants and producing a small quantity of waste.

Effects of sodium nitrite treatment on the fermentation quality of red clover-grass silage harvested at two dry matter concentrations and inoculated with clostridia

Legumes are particularly susceptible to clostridial fermentation when ensiled because of their high buffering capacity and water-soluble carbohydrate contents. The aim of the study was to investigate if a sodium nitrite treatment (900 g t-1 herbage in fresh matter [FM]) impairs butyric acid fermentation of red clover-timothy-meadow fescue silage compared with formic acid-treated (4 l t-1 FM) and untreated silage. The sward was harvested after wilting at low dry matter (DM) (LDM, 194 g kg-1) and high DM (HDM, 314 g kg-1) concentrations and half of the herbage batches were inoculated with Clostridium tyrobutyricum spores before additive treatments. No butyric acid fermentation was observed in HDM silages probably because of the relatively high DM and nitrate contents of the herbage mixture. In LDM silage butyric acid was detected only in formic acid-treated silage, and the number of clostridia copies was higher in formic acid-treated than in sodium nitrite treated silage. Sodium nitrite treatment was superior to FA treatment in suppressing clostridial fermentation in the LDM silages.

Nitrite Improves Heart Regeneration in Zebrafish.

Aims: Nitrite is reduced to nitric oxide (NO) under physiological and pathological hypoxic conditions to modulate angiogenesis and improve ischemia-reperfusion injury. Although adult mammals lack the ability to regenerate the heart after injury, this is preserved in neonates and efforts to reactivate this process are of great interest. Unlike mammals, the adult zebrafish maintain the innate ability to regenerate their hearts after injury, providing an important model to study cardiac regeneration. We thus explored the effects of physiological levels of nitrite on cardiac and fin regeneration and downstream cellular and molecular signaling pathways in response to amputation and cryoinjury. Results: Nitrite treatment of zebrafish after ventricular amputation or cryoinjury to the heart in hypoxic water (∼3 parts per million of oxygen) increases cardiomyocyte proliferation, improves angiogenesis, and enhances early recruitment of thrombocytes, macrophages, and neutrophils to the injury. When tested in a fin regeneration model, neutrophil recruitment to the injury site was found to be dependent on NO. Innovation: This is the first study to evaluate effects of physiological levels of nitrite on cardiac regeneration in response to cardiac injury, with the observation that nitrite in water accelerates zebrafish heart regeneration. Conclusion: Physiological and therapeutic levels of nitrite increase thrombocyte, neutrophil, and macrophage recruitment to the heart after amputation and cryoinjury in zebrafish, resulting in accelerated cardiomyocyte proliferation and angiogenesis. Translation of this finding to mammalian models of injury during early development may provide an opportunity to improve outcomes during intrauterine fetal or neonatal cardiac surgery.

Treatment with Nitrate, but Not Nitrite, Lowers the Oxygen Cost of Exercise and Decreases Glycolytic Intermediates While Increasing Fatty Acid Metabolites in Exercised Zebrafish

ABSTRACTBackgroundDietary nitrate improves exercise performance by reducing the oxygen cost of exercise, although the mechanisms responsible are not fully understood.ObjectivesWe tested the hypothesis that nitrate and nitrite treatment would lower the oxygen cost of exercise by improving mitochondrial function and stimulating changes in the availability of metabolic fuels for energy production.MethodsWe treated 9-mo-old zebrafish with nitrate (sodium nitrate, 606.9 mg/L), nitrite (sodium nitrite, 19.5 mg/L), or control (no treatment) water for 21 d. We measured oxygen consumption during a 2-h, strenuous exercise test; assessed the respiration of skeletal muscle mitochondria; and performed untargeted metabolomics on treated fish, with and without exercise.ResultsNitrate and nitrite treatment increased blood nitrate and nitrite levels. Nitrate treatment significantly lowered the oxygen cost of exercise, as compared with pretreatment values. In contrast, nitrite treatment significantly increased oxygen consumption with exercise. Nitrate and nitrite treatments did not change mitochondrial function measured ex vivo, but significantly increased the abundances of ATP, ADP, lactate, glycolytic intermediates (e.g., fructose 1,6-bisphosphate), tricarboxylic acid (TCA) cycle intermediates (e.g., succinate), and ketone bodies (e.g., β-hydroxybutyrate) by 1.8- to 3.8-fold, relative to controls. Exercise significantly depleted glycolytic and TCA intermediates in nitrate- and nitrite-treated fish, as compared with their rested counterparts, while exercise did not change, or increased, these metabolites in control fish. There was a significant net depletion of fatty acids, acyl carnitines, and ketone bodies in exercised, nitrite-treated fish (2- to 4-fold), while exercise increased net fatty acids and acyl carnitines in nitrate-treated fish (1.5- to 12-fold), relative to their treated and rested counterparts.ConclusionsNitrate and nitrite treatment increased the availability of metabolic fuels (ATP, glycolytic and TCA intermediates, lactate, and ketone bodies) in rested zebrafish. Nitrate treatment may improve exercise performance, in part, by stimulating the preferential use of fuels that require less oxygen for energy production.

Sucrose enhances colour formation in dry sausages by up-regulating gene expression of nitric oxide synthase in Staphylococcus vitulinus

The effects of glucose and sucrose on the gene expression of nitric oxide synthase (NOS) in Staphylococcus vitulinus and colour formation in dry sausages were investigated. The results showed that sucrose addition promoted nitric oxide (NO) production in media when compared with glucose. In addition, sucrose could up-regulate nos (encoding NOS) and katA (encoding catalase KatA) gene expression by enhancing oxidative stress levels. In the sausages inoculated with S. vitulinus, a*-values (indicating redness) of the sausages with added sucrose were higher than those of samples with added glucose (P < 0.05) but did not differ from those in the nitrite treatment group (P > 0.05). The UV–vis spectra results showed that nitrosylmyoglobin (NO-Mb) was formed in the sausages with either S. vitulinus or nitrite added. In the S. vitulinus-inoculated sausages, sucrose addition led to a higher NO-Mb content than that after glucose addition, which was attributed to up-regulation of the nos gene. This study provides a potential method to enhance NO yield in S. vitulinus and colour formation in dry sausages without nitrite addition.

Sickle cell disease subjects and mouse models have elevated nitrite and cGMP levels in blood compartments

The hypothesis of decreased nitric oxide (NO) bioavailability in sickle cell disease (SCD) proposes that multiple factors leading to decreased NO production and increased consumption contributes to vaso-occlusion, pulmonary hypertension, and pain. The anion nitrite is central to NO physiology as it is an end product of NO metabolism and serves as a reservoir for NO formation. However, there is little data on nitrite levels in SCD patients and its relationship to pain phenotype. We measured nitrite in SCD subjects and examined its relationship to SCD pain. In SCD subjects, median whole blood, red blood cell and plasma nitrite levels were higher than in controls, and were not associated with pain burden. Similarly, Townes and BERK homozygous SCD mice had elevated blood nitrite. Additionally, in red blood cells and plasma from SCD subjects and in blood and kidney from Townes homozygous mice, levels of cyclic guanosine monophosphate (cGMP) were higher compared to controls. In vitro, hemoglobin concentration, rather than sickle hemoglobin, was responsible for nitrite metabolism rate. In vivo, inhibition of NO synthases and xanthine oxidoreductase decreased nitrite levels in homozygotes but not in control mice. Long-term nitrite treatment in SCD mice further elevated blood nitrite and cGMP, worsened anemia, decreased platelets, and did not change pain response. These data suggest that SCD in humans and animals is associated with increased nitrite/NO availability, which is unrelated to pain phenotype. These findings might explain why multiple clinical trials aimed at increasing NO availability in SCD patients failed to improve pain outcomes.

Incubation with sodium nitrite attenuates fatigue development in intact single mouse fibres at physiological .

Dietary nitrate supplementation increases plasma nitrite concentration, which provides an oxygen-independent source of nitric oxide and can delay skeletal muscle fatigue. Nitrate supplementation has been shown to increase myofibre calcium release and force production in mouse skeletal muscle during contractions at a supra-physiological oxygen tension, but it is unclear whether nitrite exposure can delay fatigue development and improve myofibre calcium handling at a near-physiological oxygen tension. Single mouse muscle fibres acutely treated with nitrite had a lower force and cytosolic calcium concentration during single non-fatiguing contractions at a near-physiological oxygen tension. Nitrite treatment delayed fatigue development during repeated fatiguing isometric contractions at near-physiological, but not at supra-physiological, oxygen tension in combination with better maintenance of myofilament calcium sensitivity and sarcoplasmic reticulum calcium pumping. These findings improve understanding of the mechanisms by which increased skeletal muscle nitrite exposure might be ergogenic and imply that this is related to improved calcium handling. Dietary nitrate (NO3- ) supplementation, which increases plasma nitrite (NO2- ) concentration, has been reported to attenuate skeletal muscle fatigue development. Sarcoplasmic reticulum (SR) calcium (Ca2+ ) release is enhanced in isolated single skeletal muscle fibres following NO3- supplementation or NO2- incubation at a supra-physiological but it is unclear whether NO2- incubation can alter Ca2+ handling and fatigue development at a near-physiological . We hypothesised that NO2- treatment would improve Ca2+ handling and delay fatigue at a physiological in intact single mouse skeletal muscle fibres. Each muscle fibre was perfused with Tyrode solution pre-equilibrated with either 20% ( ∼150Torr) or 2% O2 ( =15.6Torr) in the absence and presence of 100µM NaNO2 . At supra-physiological (i.e. 20% O2 ), time to fatigue was lowered by 34% with NaNO2 (control: 257±94 vs. NaNO2 : 159±46s, Cohen's d=1.63, P<0.05), but extended by 21% with NaNO2 at 2% O2 (control: 308±217 vs. NaNO2 : 368±242s, d=1.14, P<0.01). During the fatiguing contraction protocol completed with NaNO2 at 2% O2 , peak cytosolic Ca2+ concentration ([Ca2+ ]c ) was not different (P>0.05) but [Ca2+ ]c accumulation between contractions was lower, concomitant with a greater SR Ca2+ pumping rate (P<0.05) compared to the control condition. These results demonstrate that increased exposure to NO2- blunts fatigue development at near-physiological, but not at supra-physiological, through enhancing SR Ca2+ pumping rate in single skeletal muscle fibres. These findings extend our understanding of the mechanisms by which increased NO2- exposure can mitigate skeletal muscle fatigue development.

Nitrite pharmacokinetics, safety and efficacy after experimental ventricular fibrillation cardiac arrest

IntroductionBesides therapeutic hypothermia or targeted temperature management no novel therapies have been developed to improve outcomes of patients after cardiac arrest (CA). Recent studies suggest that nitrite reduces neurological damage after asphyxial CA. Nitrite is also implicated as a new mediator of remote post conditioning produced by tourniquet inflation-deflation, which is under active investigation in CA. However, little is known about brain penetration or pharmacokinetics (PK). Therefore, to define the optimal use of this agent, studies on the PK of nitrite in experimental ventricular fibrillation (VF) are needed. We tested the hypothesis that nitrite administered after resuscitation from VF is detectable in cerebrospinal fluid (CSF), brain and other organ tissues, produces no adverse hemodynamic effects, and improves neurologic outcome in rats. MethodsAfter return of spontaneous circulation (ROSC) of 5 min untreated VF, adult male Sprague-Dawley rats were given intravenous nitrite (8 μM, 0.13 mg/kg) or placebo as a 5 min infusion beginning at 5 min after CA. Additionally, sham groups with and without nitrite treatment were also studied. Whole blood nitrite levels were serially measured.After 15 min, CSF, brain, heart and liver tissue were collected. In a second series, using a randomized and blinded treatment protocol, rats were treated with nitrite or placebo after arrest. Neurological deficit scoring (NDS) was performed daily and eight days after resuscitation, fear conditioning testing (FCT) and brain histology were assessed. ResultsIn an initial series of experiments, rats (n = 21) were randomized to 4 groups: VF-CPR and nitrite therapy (n = 6), VF-CPR and placebo therapy (n = 5), sham (n = 5), or sham plus nitrite therapy (n = 5). Whole blood nitrite levels increased during drug infusion to 57.14 ± 10.82 μM at 11 min post-resuscitation time (1 min after dose completion) in the VF nitrite group vs. 0.94 ± 0.58 μM in the VF placebo group (p < 0.001). There was a significant difference between the treatment and placebo groups in nitrite levels in blood between 7.5 and 15 min after CPR start and between groups with respect to nitrite levels in CSF, brain, heart and liver. In a second series (n = 25 including 5 shams), 19 out of 20 animals survived until day 8. However, NDS, FCT and brain histology did not show any statistically significant difference between groups. ConclusionsNitrite, administered early after ROSC from VF, was shown to cross the blood brain barrier after a 5 min VF cardiac arrest. We characterized the PK of intravenous nitrite administration after VF and were able to demonstrate nitrite safety in this feasibility study.

Hydrogen sulfide potentiates the favorable metabolic effects of inorganic nitrite in type 2 diabetic rats

ObjectiveDecreased nitric oxide (NO) bioavailability and hydrogen sulfide (H2S) deficiency have been linked with the pathophysiology of type 2 diabetes (T2D). Restoration of NO levels by nitrite have been associated with favorable metabolic effects in T2D. Moreover, H2S can potentiate the effects of NO in the cardiovascular system. The aim of this study was to determine the effects of long-term co-administration of sodium nitrite and sodium hydrosulfide (NaSH) on carbohydrate metabolism in type 2 diabetic rats. MethodsT2D was induced using chronic high fat diet (HFD) feeding combined with low dose streptozotocin (STZ) regimen. Rats were divided into 5 groups (N = 10/group): Control, T2D, T2D + nitrite, T2D + NaSH, and T2D + nitrite + NaSH. Nitrite (50 mg/L in drinking water) and NaSH (0.28 mg/kg, daily i. p. injection) were administered for 9 weeks. Fasting serum glucose, insulin, lipid profile, liver function tests, and oxidative stress indices were measured. Intraperitoneal glucose tolerance test (GTT) was performed at the end of the eighth week, and three days later, intraperitoneal pyruvate tolerance test (PTT) was done. Protein levels and mRNA expression of glucose transporter type 4 (GLUT4) in soleus muscle and epididymal adipose tissue as well as mRNA expression of H2S-producing enzymes in the liver, soleus muscle, and epididymal adipose tissue were measured at the end of the study. ResultsCompared to the controls, HFD and STZ treated rats developed metabolic dysfunction. Nitrite treatment improved carbohydrate metabolism, liver function, and oxidative stress indices whereas NaSH treatment per se had no significant effects. However, co-administration of NaSH and nitrite resulted in further improvement in serum insulin level, GTT, PTT, liver function, oxidative stress, protein level and mRNA expression of GLUT4, as well as mRNA expression of H2S-producing enzymes in diabetic rats. ConclusionLow dose of NaSH per se had no effect on carbohydrate metabolism while it potentiated the favorable metabolic effects of inorganic nitrite in type 2 diabetic rats. These favorable effects were associated with decreased oxidative stress and increased GLUT4 expression in insulin-sensitive tissues as well as improvement of liver function.

Antioxidant and antihypertensive responses to oral nitrite involves activation of the Nrf2 pathway

Impaired redox balance contributes to the cardiovascular alterations of hypertension and activation of nuclear factor erythroid 2–related factor 2 (Nrf2) pathway may counteract these alterations. While nitrite recycles back to NO and exerts antioxidant and antihypertensive effects, the mechanisms involved in these responses are not fully understood. We hypothesized that nitrite treatment of two-kidney, one-clip (2K1C) hypertensive rats activates the Nrf2 pathway, promotes the transcription of antioxidant genes, and improves the vascular redox imbalance and dysfunction in this model. Two doses of oral nitrite were studied: 15 mg/kg and the sub-antihypertensive dose of 1 mg/kg. Nitrite 15 mg/kg (but not 1 mg/kg) decreased blood pressure and increased circulating plasma nitrite and nitrate. Both doses blunted hypertension-induced increases in mesenteric artery reactive oxygen species concentrations assessed by DHE technique and restored the impaired mesenteric artery responses to acetylcholine. While 2K1C hypertension decreased nuclear Nrf2 accumulation, both doses of nitrite increased nuclear Nrf2 accumulation and mRNA expression of Nrf2-regulated genes including superoxide dismutase-1 (SOD1), catalase (CAT), glutathione peroxidase (GPX), thioredoxin-1(TRDX-1) and -2 (TRDX-2). To further confirm nitrite-mediated antioxidant effects, we measured vascular SOD and GPX activity and we found that nitrite at 1 or 15 mg/kg increased the activity of both enzymes (P < 0.05). These results suggest that activation of the Nrf2 pathway promotes antioxidant effects of nitrite, which may improve the vascular dysfunction in hypertension, even when nitrite is given at a sub-antihypertensive dose. These findings may have many clinical implications, particularly in the therapy of hypertension and other cardiovascular diseases.

Sodium nitrite improves hypertension-induced myocardial dysfunction by mechanisms involving cardiac S-nitrosylation

Although nitrite improves vascular function and lowers blood pressure, its cardiac effects are not completely known. We investigated whether nitrite improves the cardiac function in normotensive and in hypertensive rats. Two-kidney, one-clip hypertension model (2K1C) was induced in Wistar rats. Blood pressure was evaluated by tail-cuff plethysmography over 6 weeks. By the end of week 2, hypertensive and normotensive rats received nitrite (daily dose of 1 or 15 mg/kg) by gavage for 4 weeks. Cardiac morphology and function were performed by transthoracic echocardiography. Intrinsic heart function was evaluated using the isolated heart model (Langendorff's preparation). Starling curves were generated under nitrite (1 μmol/L) and/or ascorbate (1 mmol/L) or vehicle. Cardiac tissue was collected and snap frozen for biochemical analysis. Nitrite treatment (15 mg/kg) lowered both systolic blood pressure and the increases in left ventricular (LV) mass found in 2K1C rats (P < .05). In addition, nitrite treatment restored the decreased cardiac output in 2K1C rats (P < .05) and improved the cardiac function. These findings were associated with increased nitrite, S-nitrosothiols, and protein S-nitrosylation (all P < .05) assessed in heart tissue. The cardiac effects of nitrite were further investigated in the isolated heart model, and nitrite infusion (1 μmol/L) enhanced cardiac contractility and relaxation. This infusion increased S-nitrosothiols concentrations and protein S-nitrosylation in the heart. Ascorbate completely blunted all nitrite-induced effects. These findings show that treatment with oral nitrite improves cardiac function by mechanisms involving increased S-nitrosothiols generation and S-nitrosylation of cardiac proteins. Pharmacological strategies promoting cardiac S-nitrosylation may be useful to improve myocardial function in heart diseases.

NADPH oxidase is a primary target for antioxidant effects by inorganic nitrite in lipopolysaccharide-induced oxidative stress in mice and in macrophage cells

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and oxidative stress is usually considered as an important factor to the pathogenesis of various diseases. Inorganic nitrite, previously viewed as a harmful substance in our diet or inert metabolites of endogenous NO, is recently identified as an important biological NO reservoir in vasculature and tissues. Stimulation of a nitrite-NO pathway shows organ-protective effects on oxidative stress and inflammation, but the mechanisms or target are not clear. In this study, the hypothesis that inorganic nitrite attenuated lipopolysaccharide (LPS)-induced oxidative stress in mice and in macrophage cells by modulating NADPH oxidase activity and NO bioavailability were investigated. We showed that nitrite treatment, in sharp contrast with the worsening effect of NO synthases inhibition, significantly attenuated aortic oxidative stress, endothelial dysfunction and mortality in LPS-induced shock in mice. Mechanistically, protective effects of nitrite were abolished by NO scavenger and xanthine oxidase inhibitor, and inhibition of NADPH oxidase with apocynin attenuated LPS-induced oxidative stress similar to that of nitrite. In the presence of nitrite, no further effect of apocynin was observed, suggesting NADPH oxidase as a possible target. In LPS-activated macrophage cells, nitrite reduced NADPH oxidase activity and oxidative stress and these effects of nitrite were also abolished by NO scavenger and xanthine oxidase inhibitor, where xanthine oxidase-mediated reduction of nitrite attenuated NADPH oxidase activity in activated macrophages via a NO-dependent mechanism. In conclusion, these novel findings position NADPH oxidase in the inflammatory vasculature as a prime target for the antioxidant effects of inorganic nitrite, and open a new direction to modulate the inflammatory response.

Nitrite Disruption in Olfaction and Internal Physiology in Goldfish (Carassius auratus)

Freshwater ecosystems have experienced a dramatic increase of nitrogenous compounds as a result of farming and industrial activity. Nitrite accumulates by bacterial denitrification/nitrification in freshwater and saltwater ecosystems, reaching concentrations of 1 mM and 0.5 μM respectively. Exposure to high nitrite concentrations can disrupt the endocrine system and physiological processes such as ion homeostasis, respiratory, and cardiovascular activity. However, the accumulation of nitrite in different internal tissues and its effect on external sensitive organs, such as the olfactory epithelium, is unknown. This study aimed to determine the physiological effects of nitrite and its accumulation in several organs in goldfish (Carassius auratus). Goldfish were exposed to different nitrite treatments (0 mM, 0.3 mM, 1.0 mM, and 10 mM) for five days. Upon completion of experiment, brain, nose, liver, kidney, and gill samples were obtained for biological and histological analysis. Goldfish in two treatments (1.0 mM and 10 mM) experienced irreversible oxidation of hemoglobin known as metahemoglobemia, marked by browning of the blood and darker tissues. Biochemical analysis showed an increase of nitrite in brain, nose, liver, and gill tissues. Brain and nose tissues (240 ±0.004 μM and 260 ±0.002 μM, respectively) accumulated more nitrite than gill tissue (190 ±0.002 μM) in the lowest treatment (0.3 mM), and this trend continued as treatment concentrations increased. Preliminary statistical analysis demonstrated that both the brain and nose tissue accumulated &gt;30% more nitrite than gill tissue in the 0.3 mM treatment. Histological analysis of the olfactory epithelium showed hyperplasia, an increase in cell size and number; furthermore, we observed an increase in the number of mucus cells and mucus production, collapse of columnar cells, and lamella constriction in both the 1.0 mM and 10 mM treatments. Histological analysis of gills showed lamella fusion and vascular congestion. Histological liver samples exhibited melanomacrophage aggregate, nucleus degeneration, and cytoplasmic vacuolation in 10 mM. Preliminary findings from electro‐olfactograms show that nitrite reduced the ability of a goldfish to detect odors at nitrite exposure as low as 0.1 mM. These results suggest that nitrite is accumulating faster in external sensory tissues than internal organs, affecting essential physiological processes such as olfactory food detection and possibly acting as a neurotoxin.Support or Funding InformationResearch support: Texas State University start‐up funding to Dr. Mar Huertas.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Biomarkers of Neurodegeneration in Goldfish Exposed to Nitrite

Goldfish have been used in numerous studies involving behavior and toxicology, however, their viability as an animal model to study neuropathies remains to be elucidated. We have previously discovered that the nitrite ion (NO2−) acts as an olfactory disruptor in goldfish. We hypothesize that this disruption is due to neurotoxic effects of NO2− in olfactory receptors and the brain. In this study, goldfish were subjected to a subacute, sublethal 1.0 mM sodium nitrite treatment, and had their brains and olfactory tract dissected. The tissues were mounted in paraffin blocks for sectioning and visualized with hematoxylin and eosin (H&amp;E), Alcian blue, terminal deoxynucleotidyl transferase dUTP nick‐end labeling (TUNEL), caspase immunohistochemistry, and Congo red β‐amyloid staining. We discovered that olfactory tissue from treatment fish displayed signs of hyperplasia and hypertrophy when compared to the olfactory tissue from control fish. Furthermore, signs of increased apoptotic processes, in the form of blebbing, were observed in treatment fish. Alcian blue staining for mucosal cells demonstrated that the microvilli lining the epithelia had lost their brush‐like morphology and were covered by a thick layer of mucus in treatment fish. TUNEL, caspase immunohistochemistry, and β‐amyloid stains are currently being analyzed. Our results indicate that NO2− acts as a neurotoxin in subacute, sublethal doses. Because of the similarities in olfactory processing between goldfish and other vertebrates, it is possible that NO2− may also play a similar role in other aquatic vertebrates. The general availability and easy handling of goldfish make it an ideal candidate to study neuropathies.Support or Funding InformationTexas State University start‐up funding for Dr. Mar HuertasThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Combined effect of high pressure and vinegar addition on the control of Clostridium perfringens and quality in nitrite-free emulsion-type sausage

Abstract We evaluated the combined effect of high pressure (HP) and vinegar addition on control of Clostridium perfringens and quality in emulsion-type pork sausages. Sausages were manufactured with different levels of commercial white distilled vinegar made with jasmine tea extract (0, 1, and 2%) and sodium nitrite (0.02%, control). The sausages except for sodium nitrite treatment were subjected to HP at 500 MPa (four cycles and each for 3 min). After storage, the combined treatment of HP and vinegar showed the lowest number of C. perfringens vegetative cells (4.8-log CFU/g reduction) among the all treatments. The combined treatment also inhibited the growth of C. perfringens spores for five weeks (stored at 4 °C for two weeks followed by at 20 °C for three weeks). Among all treatment combinations, the best pH, water-holding capacity and chewiness, were found with the HP-vinegar sausage. In addition, vinegar treatment inhibited the lipid oxidation of sausage throughout the storage. Use of HP and vinegar addition inhibited growth of C. perfringens without observed adverse effects on quality of the emulsion-type sausage. Industrial relevance Currently, the use of natural additives and novel processing technologies for replacing sodium nitrite in meat products is gaining attention owing to increase in consumer demand for nitrite-free and safe meat products. The study showed that the addition of 1% (w/v) of vinegar and pressure treatment at 500 MPa (four cycles and each for 3 min) can replace sodium nitrite to inhibit growth of C. perfringens in emulsion-type sausages.

Nitrite Protects Neurons Against Hypoxic Damage Through S-nitrosylation of Caspase-6.

Aims: The coordination of neurons to execute brain functions requires plenty of oxygen. Thus, it is not surprising that the chronic hypoxia resulting from chronic obstructive pulmonary diseases (COPD) can cause neuronal damage. Injury in the cortex can give rise to anxiety and cognitive dysfunction. This study investigated what causes hypoxia-induced neuronal injury and what strategies might be used to protect neurons against such damage. Results: This study found that hypoxia in primary cortical neurons caused neurite retraction, a caspase-6-dependent process. The hypoxic stress activated caspase-6 within the neurite, leading to microtubule disassembly and neurite retraction. The effect of hypoxia on caspase-6 activation, microtubule disassembly, and neurite retraction was alleviated by nitrite treatment. The protective role of nitrite was further supported by the observation that the active-site Cys146 of caspase-6 was S-nitrosylated in hypoxic neuro-2a cells treated with nitrite. We further validated the beneficial effect of nitrite on neuronal function against hypoxic stress in vivo. Using the wild-type or Apo E-/- mice exposed to chronic hypoxia as a model, we demonstrated that supplementing drinking water with nitrite suppressed active caspase-6 in the cortex of the brain, concomitant with the prevention of hypoxia-induced anxiety in the animals. Innovation: These results are the first evidence of a new pathway for the activation of caspase-6 and the first to indicate that nitrite can protect neurons against chronic hypoxic insult. Conclusion: Our findings suggest that nitrite holds great potential for the treatment of diseases such as COPD associated with hypoxia-induced neuronal injury.

The design of a polyaniline-decorated three dimensional W18O49 composite for full solar spectrum light driven photocatalytic removal of aqueous nitrite with high N2 selectivity

Photocatalysis using solar energy is the most promising green technology for nitrite removal. However, effective photocatalytic performance is often challenged by the limited light absorption, utilization of expensive noble metals and undesired products (nitrate and ammonium). Here, we report for the first time that a full solar light response polyaniline-decorated three dimensional W18O49 composite (PANI@W18O49), a noble metal-free photocatalyst, possesses excellent photocatalytic activity for aqueous nitrite removal with high N2 selectivity. The prepared sample was thoroughly identified via XRD, Raman, FTIR, SEM, TEM, UV–vis DRS and PL. The catalytic results demonstrated that over 80% N2 selectivity (initial concentration 1.0 mM) was achieved through the PANI@W18O49 without sacrificial agent under 300 W Xe lamp irradiation for 60 min. Such advantages were attributed to the built-in junction between n-type W18O49 and p-type PANI, offering suitable redox levels of electron-hole pairs for NO2− reaction. The modification of PANI also benefited the light harvesting ability and activated carriers migration, the calculated rate constant of PANI@W18O49 is about four times as high as that of W18O49. The current study not only prepared a promising photocatalyst, but also provides new insights into improving the photocatalytic activity and N2 selectivity for nitrite treatment.

AMP-activated protein kinase activation and NADPH oxidase inhibition by inorganic nitrate and nitrite prevent liver steatosis

Advanced age and unhealthy dietary habits contribute to the increasing incidence of obesity and type 2 diabetes. These metabolic disorders, which are often accompanied by oxidative stress and compromised nitric oxide (NO) signaling, increase the risk of adverse cardiovascular complications and development of fatty liver disease. Here, we investigated the therapeutic effects of dietary nitrate, which is found in high levels in green leafy vegetables, on liver steatosis associated with metabolic syndrome. Dietary nitrate fuels a nitrate-nitrite-NO signaling pathway, which prevented many features of metabolic syndrome and liver steatosis that developed in mice fed a high-fat diet, with or without combination with an inhibitor of NOS (l-NAME). These favorable effects of nitrate were absent in germ-free mice, demonstrating the central importance of host microbiota in bioactivation of nitrate. In a human liver cell line (HepG2) and in a validated hepatic 3D model with primary human hepatocyte spheroids, nitrite treatment reduced the degree of metabolically induced steatosis (i.e., high glucose, insulin, and free fatty acids), as well as drug-induced steatosis (i.e., amiodarone). Mechanistically, the salutary metabolic effects of nitrate and nitrite can be ascribed to nitrite-derived formation of NO species and activation of soluble guanylyl cyclase, where xanthine oxidoreductase is proposed to mediate the reduction of nitrite. Boosting this nitrate-nitrite-NO pathway results in attenuation of NADPH oxidase-derived oxidative stress and stimulation of AMP-activated protein kinase and downstream signaling pathways regulating lipogenesis, fatty acid oxidation, and glucose homeostasis. These findings may have implications for novel nutrition-based preventive and therapeutic strategies against liver steatosis associated with metabolic dysfunction.

Nitrite treatment downregulates vascular MMP-2 activity and inhibits vascular remodeling in hypertension independently of its antihypertensive effects

Hypertension is associated with cardiovascular remodeling. Given that impaired redox state activates matrix metalloproteinase (MMP)− 2 and promotes vascular remodeling, we hypothesized that nitrite treatment at a non-antihypertensive dose exerts antioxidant effects and attenuates both MMP-2 activation and vascular remodeling of hypertension. We examined the effects of oral sodium nitrite at antihypertensive (15 mg/kg) or non-antihypertensive (1 mg/kg) daily dose in hypertensive rats (two kidney, one clip; 2K1C model). Sham-operated and 2K1C hypertensive rats received vehicle or nitrite by gavage for four weeks. Systolic blood pressure decreased only in hypertensive rats treated with nitrite 15 mg/Kg/day. Both low and high nitrite doses decreased 2K1C-induced vascular remodeling assessed by measuring aortic cross-sectional area, media/lumen ratio, and number of vascular smooth muscle cells/aortic length. Both low and high nitrite doses decreased 2K1C-induced vascular oxidative stress assessed in situ with the fluorescent dye DHE and with the lucigenin chemiluminescence assay. Vascular MMP-2 expression and activity were assessed by gel zymography, Western blot, and in situ zymography increased with hypertension. While MMP-2 levels did not change in response to both doses of nitrite, both doses completely prevented hypertension-induced increases in vascular MMP activity. Moreover, incubation of aortas from hypertensive rats with nitrite at 1–20 μmol/L reduced gelatinolytic activity by 20–30%. This effect was fully inhibited by the xanthine oxidase (XOR) inhibitor febuxostat, suggesting XOR-mediated generation of nitric oxide (NO) from nitrite as a mechanism explaining the responses to nitrite. In vitro incubation of aortic extracts with nitrite 20 μmol/L did not affect MMP-2 activity. These results show that nitrite reverses the vascular structural alterations of hypertension, independently of anti-hypertensive effects. This response is mediated, at least in part, by XOR and is attributable to antioxidant effects of nitrite blunting vascular MMP-2 activation. Our findings suggest nitrite therapy to reverse structural alterations of hypertension.