Journal articles on the topic 'Nitrite metabolism'
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Shi, Jiayang. "Nitrite Toxicity: Chemical Analysis, Metabolism, and Health Effects." Highlights in Science, Engineering and Technology 19 (November 17, 2022): 210–15. http://dx.doi.org/10.54097/hset.v19i.2852.
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Nitrites can be formed from and away by the nitrate-nitrite-nitric oxide pathway. The properties of nitrite oxidation and metHb formation are carefully studied in mechanism, forming either N-binding or O-binding structures. Apart from nitrate and nitric oxide, nitrites can also form carcinogenic nitrosamines in acidic environments. MetHb can cause hypoxia and vasodilation, while symptoms are revealed in different degrees under recalled or present hypoxic conditions. The study thoroughly studied nitrite’s metabolic properties, chemical pathways, and dosage effects on health. The cancer risks of consuming dietary nitrite need more statistical support, while its metabolite N-nitrosodimethylamine and NDMA concentration are well considered with increasing cancer risks. ED50 of human vasodilation is identified, and lethal doses on juvenile pike-perch can be further utilized to predict related doses for humans. More studies should be done to investigate relative nitrite doses to boost utilization and studies about this chemical.
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Curtis, Erin, Lewis L. Hsu, Yuen Yi Hon, Lisa Geary, Audrey C. Noguchi, and Sruti Shiva. "Nitrite Oxidase Activities of Cytochrome P450 and Mitochondria." Blood 118, no. 21 (November 18, 2011): 5310. http://dx.doi.org/10.1182/blood.v118.21.5310.5310.
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Abstract Abstract 5310 Once dismissed as an inert byproduct of nitric oxide (NO) auto-oxidation, nitrite (NO2−) is now accepted as an endocrine reserve of NO that elicits a number of fundamental biological responses in all major organ systems. While it is known that tissue nitrite is derived from both oxidation of NO and from dietary nitrite and nitrate, much less is known about how nitrite is metabolized by tissue or about the factors that influence this metabolism. Here we investigate the rates and mechanisms by which nitrite is metabolized by tissue over a range of oxygen tensions in rats and mice. We show that the rate of nitrite metabolism differs in heart, liver, lung and brain tissue. Further, oxygen regulates the rate and products of nitrite metabolism in each of these tissues. In hypoxic tissue, nitrite is predominantly reduced to NO, with significant formation of iron-nitrosyl heme proteins and S-nitrosothiols. Interestingly, this hypoxic nitrite metabolism is mediated by different sets of nitrite reductase enzymes in each tissue. In contrast, tissue consumption of nitrite is more rapid in normoxia and the major end product is nitrate. While cytochrome P450s and myoglobin contributed in the liver and heart respectively, mitochondrial cytochrome c oxidase played a significant role in this normoxic nitrite oxidation, which could be completely inhibited by cyanide in all tissues. We used cyanide-based nitrite preservation solution to measure the pharmacokinetics of oral and intraperitoneally administered nitrite in vivo. Using this methodology, we measured basal levels of nitrite in the major tissues and confirm that the heart contains the greatest concentration of nitrite, followed by the liver and finally the lung. We demonstrate that intraperitoneal administration of nitrite to mice increases nitrite levels most significantly in the liver and heart, where nitrite uptake is rapid (5–10 min) and steadily decreases thereafter, such that levels are back to baseline by 30 min. Little to no increase was observed in the lung. In these studies, changes in nitrate were difficult to detect due to the high levels of basal nitrate present in vivo and low concentration of nitrite administered. However, the rapid metabolism of nitrite in the tissue suggests that oxidation is at least partially responsible. In contrast to intraperitoneal nitrite, oral nitrite increased nitrite levels in all organs of mice, an effect which peaked in all organs except liver at 3 days. Collectively, these data provide insight into the fate of nitrite in tissue, the enzymes involved in hypoxic and normoxic nitrite metabolism and the role of oxygen in regulating these processes. Disclosures: No relevant conflicts of interest to declare.
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González-Soltero, Rocío, María Bailén, Beatriz de Lucas, Maria Isabel Ramírez-Goercke, Helios Pareja-Galeano, and Mar Larrosa. "Role of Oral and Gut Microbiota in Dietary Nitrate Metabolism and Its Impact on Sports Performance." Nutrients 12, no. 12 (November 24, 2020): 3611. http://dx.doi.org/10.3390/nu12123611.
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Nitrate supplementation is an effective, evidence-based dietary strategy for enhancing sports performance. The effects of dietary nitrate seem to be mediated by the ability of oral bacteria to reduce nitrate to nitrite, thus increasing the levels of nitrite in circulation that may be further reduced to nitric oxide in the body. The gut microbiota has been recently implicated in sports performance by improving muscle function through the supply of certain metabolites. In this line, skeletal muscle can also serve as a reservoir of nitrate. Here we review the bacteria of the oral cavity involved in the reduction of nitrate to nitrite and the possible changes induced by nitrite and their effect on gastrointestinal balance and gut microbiota homeostasis. The potential role of gut bacteria in the reduction of nitrate to nitrite and as a supplier of the signaling molecule nitric oxide to the blood circulation and muscles has not been explored in any great detail.
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Bueno, E., N. Gómez-Hernández, L. Girard, E. J. Bedmar, and M. J. Delgado. "Function of the Rhizobium etli CFN42 nirK gene in nitrite metabolism." Biochemical Society Transactions 33, no. 1 (February 1, 2005): 162–63. http://dx.doi.org/10.1042/bst0330162.
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Rhizobium etli CFN42 is not capable of growing anaerobically with nitrate but it grows with nitrite as a terminal electron acceptor. This bacterium contains the nirK gene encoding the copper-containing Nir (nitrite reductase), which is located on the cryptic plasmid pCFN42f. Mutational analysis has demonstrated that a nirK deficient mutant was not capable of growing under nitrite-respiring conditions. Moreover, microaerobic growth of this mutant was inhibited by the presence of nitrite. Nir activity and nitrite uptake were highly diminished in a nirK mutant, compared with the wild-type levels after incubation under anaerobic conditions. Our results suggest that the copper-containing Nir may have both a respiratory and a nitrite-detoxifying role in R. etli.
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Weiss, Bernard. "Evidence for Mutagenesis by Nitric Oxide during Nitrate Metabolism in Escherichia coli." Journal of Bacteriology 188, no. 3 (February 1, 2006): 829–33. http://dx.doi.org/10.1128/jb.188.3.829-833.2006.
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ABSTRACT In Escherichia coli, nitrosative mutagenesis may occur during nitrate or nitrite respiration. The endogenous nitrosating agent N2O3 (dinitrogen trioxide, nitrous anhydride) may be formed either by the condensation of nitrous acid or by the autooxidation of nitric oxide, both of which are metabolic by-products. The purpose of this study was to determine which of these two agents is more responsible for endogenous nitrosative mutagenesis. An nfi (endonuclease V) mutant was grown anaerobically with nitrate or nitrite, conditions under which it has a high frequency of A:T-to-G:C transition mutations because of a defect in the repair of hypoxanthine (nitrosatively deaminated adenine) in DNA. These mutations could be greatly reduced by two means: (i) introduction of an nirB mutation, which affects the inducible cytoplasmic nitrite reductase, the major source of nitric oxide during nitrate or nitrite metabolism, or (ii) flushing the anaerobic culture with argon (which should purge it of nitric oxide) before it was exposed to air. The results suggest that nitrosative mutagenesis occurs during a shift from nitrate/nitrite-dependent respiration under hypoxic conditions to aerobic respiration, when accumulated nitric oxide reacts with oxygen to form endogenous nitrosating agents such as N2O3. In contrast, mutagenesis of nongrowing cells by nitrous acid was unaffected by an nirB mutation, suggesting that this mutagenesis is mediated by N2O3 that is formed directly by the condensation of nitrous acid.
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Casella, Sergio, Anita Toffanin, Stefania Ciompi, Nora Rossi, and W. J. Payne. "Metabolism of nitrogen oxides and hydroxylamine in cells of true denitrifiers and Rhizobium "hedysari" HCNT1." Canadian Journal of Microbiology 40, no. 1 (January 1, 1994): 1–5. http://dx.doi.org/10.1139/m94-001.
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Cells of several copper-protein denitrifiers that produce nitrite reductase reduced nitrate to gaseous products but were completely or strongly inhibited by the copper chelator diethyldithiocarbamate (DDC), which did not comparably inhibit cells of cytochrome ed1 nitrite reductase producers. Both types of true denitrifiers released NO while reducing nitrite anaerobically in the presence of the uncoupler 3-chlorophenylhydrazonepropanedinitrile (CCCP), as seen previously only in Paracoccus denitrificons. In contrast, the pseudodenitrifier Rhizobium "hedysari" HCNT1, which grows as neither adenitrifier nor a fermenter, failed to reduce nitrate or nitrite or to nitrify ammonia when grown aerobically but reduced nitrite to N2O after growth at low oxygen tension even without any nitrogen oxide in the culture medium. Such oxygen-limited cells also formed N2O when incubated anaerobically with NO and hydroxylamine, and with nitrite and hydroxylamine as well, but not when anaerobic nitrite reduction (i.e., apparent production of NO) was inhibited by DDC. Rhizobium "hedysari" HCNT1 cells released no NO while reducing nitrite even in the presence of CCCP. The use of CCCP may permit differentiation of respiratory from nitrite-detoxifying denitrifying bacteria. Under aeration, but not anoxia, NO and hydroxylamine reacted to form N2O even in the absence of cells, providing a possible indicator of NO production assayable by gas chromatography.Key words: nitrite, nitric oxide, diethyldithiocarbamate (DDC), hydroxylamine, 3-chlorophenylhydrazonepropanedinitrile (CCCP).
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Karwowska, Małgorzata, and Anna Kononiuk. "Nitrates/Nitrites in Food—Risk for Nitrosative Stress and Benefits." Antioxidants 9, no. 3 (March 16, 2020): 241. http://dx.doi.org/10.3390/antiox9030241.
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In the context of impact on human health, nitrite/nitrate and related nitrogen species such as nitric oxide (NO) are a matter of increasing scientific controversy. An increase in the content of reactive nitrogen species may result in nitrosative stress—a deleterious process, which can be an important mediator of damage to cell structures, including lipids, membranes, proteins and DNA. Nitrates and nitrites are widespread in the environment and occur naturally in foods of plant origin as a part of the nitrogen cycle. Additionally, these compounds are used as additives to improve food quality and protect against microbial contamination and chemical changes. Some vegetables such as raw spinach, beets, celery and lettuce are considered to contain high concentrations of nitrates. Due to the high consumption of vegetables, they have been identified as the primary source of nitrates in the human diet. Processed meats are another source of nitrites in our diet because the meat industry uses nitrates/nitrites as additives in the meat curing process. Although the vast majority of consumed nitrates and nitrites come from natural vegetables and fruits rather than food additives, there is currently a great deal of consumer pressure for the production of meat products free of or with reduced quantities of these compounds. This is because, for years, the cancer risks of nitrates/nitrites have been considered, since they potentially convert into the nitrosamines that have carcinogenic effects. This has resulted in the development and rapid expansion of meat products processed with plant-derived nitrates as nitrite alternatives in meat products. On the other hand, recently, these two ions have been discussed as essential nutrients which allow nitric oxide production and thus help cardiovascular health. Thus, this manuscript reviews the main sources of dietary exposure to nitrates and nitrites, metabolism of nitrites/nitrates, and health concerns related to dietary nitrites/nitrates, with particular emphasis on the effect on nitrosative stress, the role of nitrites/nitrates in meat products and alternatives to these additives used in meat products.
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Ilma, Qoriatul, Achmad Dinoto, Ninu Setianingrum, Mulyadi Mulyadi, Dwi Agustyani, Nani Radiastuti, and Heddy Julistiono. "ISOLATION AND IDENTIFICATION OF BACTERIA REMOVING NITRITE, NITRATE, AND AMMONIUM FROM BIOBALLS FILTER." Indonesian Aquaculture Journal 17, no. 1 (June 29, 2022): 13. http://dx.doi.org/10.15578/iaj.17.1.2022.13-22.
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The presence of effective bacteria removing nitrite, nitrate, and ammonia in a recirculating aquaculture system (RAS) is necessary to attenuate their toxicity to fish. The research was conducted to find bacteria that can be cultured and reduce nitrite, nitrate, and ammonium. Sixteen bacterial colonies were isolated from bioballs of RAS biofilter and tested for their ability to reduce nitrite or nitrate concentrations. Using a simple indicator paper for nitrite and nitrate, four isolates that reduced nitrite and nitrate concentrations, namely K1NA3, K2NA3, CNA1, and PRO4NA1 were selected. The four isolates were then evaluated for the metabolism of nitrate, nitrite, and ammonium compounds using the spectrophotometry method. Results showed that the isolates K1NA3, CNA1, and PRO4NA1 reduced nitrite concentration but produced ammonium, whereas K1NA3 isolate was able to reduce nitrate concentration but produced both nitrite and ammonium. Experiments in reducing ammonium levels in the synthetic waste media showed the ability of four isolates to reduce ammonium levels after six days despite producing nitrite. Based on the 16S rRNA gene analysis, these isolates have a close relationship to Pseudomonas otitidis (KINA3 and K2NA3), Acinetobacter cumulans (CNA1), and Vogesella perlucida (PRO 4NA1).
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Truong, Phuoc Thien Hoang, Huynh Dan Do, Tran Quoc Thang Vo, and Phu Hoa Nguyen. "Isolation and selection of nitrite metabolising bacteria from the bottom mud of lobster culture area in Xuan Dai bay, Phu Yen province." Ministry of Science and Technology, Vietnam 63, no. 9 (September 25, 2021): 59–64. http://dx.doi.org/10.31276/vjst.63(9).59-64.
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The study had isolated and selected groups of bacteria that metabolise nitrite from the bottom mud of lobster cages in Xuan Dai bay, Phu Yen province. Analysis results from 21 sludge samples taken from 11 cages of lobster farming area isolated 16 strains of bacteria capable of nitrite metabolism. After investigating biological characteristics and nitrite metabolism of bacteria strains, 10 strains of bacteria were collected with the ability to metabolise nitrite over 95% in 72 hours. In addition, 10 strains of bacteria with the highest NO2- treatment efficiency, identified by genetic analysis and looked up on BLAST, defined as Stenotrophomonas pavanii, Chryseobacterium gleum, Stenotrophomonas maltophilia, Delftia lacustris, Acinetobacter junii
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van Bezooijen, RL, I. Que, AG Ederveen, HJ Kloosterboer, SE Papapoulos, and CW Lowik. "Plasma nitrate+nitrite levels are regulated by ovarian steroids but do not correlate with trabecular bone mineral density in rats." Journal of Endocrinology 159, no. 1 (October 1, 1998): 27–34. http://dx.doi.org/10.1677/joe.0.1590027.
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Nitric oxide (NO) is a mediator of bone metabolism and its production is under the control of gender hormones in several cell types or tissues. Changes in endogenous NO production, measured as plasma nitrate+nitrite levels, may therefore contribute to ovariectomy (OVX)-induced bone loss. We studied plasma nitrate+nitrite levels and trabecular bone mineral density (TBMD) 4 weeks after sham-operation or OVX in rats receiving various hormonal treatments. OVX decreased plasma nitrate+nitrite levels significantly and this was accompanied by a significant decrease in TBMD. Treatment with oral ethinyl oestradiol (EE) and subcutaneous 17beta-oestradiol dose-dependently prevented the decrease in plasma nitrate+nitrite levels after OVX, but treatment with oral 17beta-oestradiol did not. Oestrogen treatment, 17beta-oestradiol (s. c. or orally) or EE (orally), prevented the OVX-induced decrease in TBMD. Treatment of sham-operated rats with the anti-oestrogen ICI164, 384 induced a significant decrease in TBMD that corresponded to 54% of the decrease observed after OVX, but did not affect plasma nitrate+nitrite levels. Treatment of ovariectomized rats with Org 2058, a pure progestagen, did not prevent bone loss, but prevented the decrease in plasma nitrate+nitrite levels dose-dependently. Treatment with tibolone, a synthetic steroid with combined weak oestrogenic, progestagenic, and androgenic properties, or with progestagen in combination with EE completely prevented bone loss after OVX. These treatments, however, only partly prevented the OVX-induced decrease in plasma nitrate+nitrite levels. In conclusion, OVX decreased both TBMD and plasma nitrate+nitrite levels. Although plasma nitrate+nitrite levels were under the control of both oestrogen and progesterone, TBMD was affected by oestrogen only. Decreased systemic production of NO is, therefore, not involved in OVX-induced bone loss in rats.
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Xia, D. S., D. J. Deng, and S. L. Wang. "Destruction of Parotid Glands Affects Nitrate and Nitrite Metabolism." Journal of Dental Research 82, no. 2 (February 2003): 101–5. http://dx.doi.org/10.1177/154405910308200205.
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Davenport, Susie, Pascaline Le Lay, and Juan Pablo Sanchez-Tamburrrino. "Nitrate metabolism in tobacco leaves overexpressing Arabidopsis nitrite reductase." Plant Physiology and Biochemistry 97 (December 2015): 96–107. http://dx.doi.org/10.1016/j.plaphy.2015.09.013.
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Mur, Luis A. J., Aprajita Kumari, Yariv Brotman, Jurgen Zeier, Julien Mandon, Simona M. Cristescu, Frans Harren, Werner M. Kaiser, Alisdair R. Fernie, and Kapuganti Jagadis Gupta. "Nitrite and nitric oxide are important in the adjustment of primary metabolism during the hypersensitive response in tobacco." Journal of Experimental Botany 70, no. 17 (April 10, 2019): 4571–82. http://dx.doi.org/10.1093/jxb/erz161.
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Abstract Nitrate and ammonia deferentially modulate primary metabolism during the hypersensitive response in tobacco. In this study, tobacco RNAi lines with low nitrite reductase (NiRr) levels were used to investigate the roles of nitrite and nitric oxide (NO) in this process. The lines accumulate NO2–, with increased NO generation, but allow sufficient reduction to NH4+ to maintain plant viability. For wild-type (WT) and NiRr plants grown with NO3–, inoculation with the non-host biotrophic pathogen Pseudomonas syringae pv. phaseolicola induced an accumulation of nitrite and NO, together with a hypersensitive response (HR) that resulted in decreased bacterial growth, increased electrolyte leakage, and enhanced pathogen resistance gene expression. These responses were greater with increases in NO or NO2– levels in NiRr plants than in the WT under NO3– nutrition. In contrast, WT and NiRr plants grown with NH4+ exhibited compromised resistance. A metabolomic analysis detected 141 metabolites whose abundance was differentially changed as a result of exposure to the pathogen and in response to accumulation of NO or NO2–. Of these, 13 were involved in primary metabolism and most were linked to amino acid and energy metabolism. HR-associated changes in metabolism that are often linked with primary nitrate assimilation may therefore be influenced by nitrite and NO production.
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Lillo, Cathrine. "Signalling cascades integrating light-enhanced nitrate metabolism." Biochemical Journal 415, no. 1 (September 12, 2008): 11–19. http://dx.doi.org/10.1042/bj20081115.
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In higher plants, light is crucial for regulation of nitrate uptake, translocation and assimilation into organic compounds. Part of this metabolism is tightly coupled to photosynthesis because the enzymes involved, nitrite reductase and glutamate synthase, are localized to the chloroplasts and receive reducing power from photosynthetic electron transport. However, important enzymes in nitrate acquisition and reduction are localized to cellular compartments other than chloroplasts and are also up-regulated by light, i.e. transporters in cell and organellar membranes and nitrate reductase in the cytosol. This review describes the different light-dependent signalling cascades regulating nitrate metabolism at the transcriptional as well as post-transcriptional level, and how reactions in different compartments of the cell are co-ordinated. Essential players in this network are phytochrome and HY5 (long hypocotyls 5)/HYH (HY5 homologue)-dependent signalling pathways, the energy-related AMPK (AMP-activated protein kinase) protein kinase homologue SNRK1 (sucrose non-fermenting kinase 1-related kinase), chloroplastic thioredoxins and the prokaryotically originated PII protein. A complex light-dependent network of regulation emerges, which appears to be necessary for optimal nitrogen assimilation and for avoiding the accumulation of toxic intermediates and side products, such as nitrite and reactive oxygen compounds.
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Iino, Toju, Yong Wang, Keisuke Miyauchi, Daisuke Kasai, Eiji Masai, Takeshi Fujii, Naoto Ogawa, and Masao Fukuda. "Specific Gene Responses of Rhodococcus jostii RHA1 during Growth in Soil." Applied and Environmental Microbiology 78, no. 19 (July 27, 2012): 6954–62. http://dx.doi.org/10.1128/aem.00164-12.
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ABSTRACTTranscriptome analysis ofRhodococcus jostiiRHA1 during growth in sterilized soil was performed. A total of 165 soil-specific genes were identified by subtracting genes upregulated in late growth phases and on solid medium from 264 genes commonly upregulated during growth on biphenyl or pyruvate in sterilized soil. Classification of the 165 genes into functional categories indicated that this soil-specific group is rich in genes for the metabolism of fatty acids, amino acids, carbohydrates, and nitrogen and relatively poor in those for cellular processes and signaling. The ro06365–ro06369 gene cluster, in which ro06365 to ro06368 were highly upregulated in transcriptome analysis, was characterized further. ro06365 and ro06366 show similarity to a nitrite/nitrate transporter and a nitrite reductase, respectively, suggesting their involvement in nitrogen metabolism. A strain with an ro06366 deletion, D6366, showed growth retardation when we used nitrate as the sole nitrogen source and no growth when we used nitrite. A strain with a deletion of ro06365 to ro06368, DNop, utilized neither nitrite nor nitrate and recovered growth using nitrite and nitrate by introduction of the deleted genes. Both of the mutants showed growth retardation in sterilized soil, and the growth retardation of DNop was more significant than that of D6366. When these mutants were cultivated in medium containing the same proportions of ammonium, nitrate, and nitrite ions as those in the sterilized soil, they showed growth retardation similar to that in the soil. These results suggest that the ro06365–ro06369 gene cluster has a significant role in nitrogen utilization in sterilized soil.
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Nakano, Michiko M., Tamara Hoffmann, Yi Zhu, and Dieter Jahn. "Nitrogen and Oxygen Regulation of Bacillus subtilis nasDEF Encoding NADH-Dependent Nitrite Reductase by TnrA and ResDE." Journal of Bacteriology 180, no. 20 (October 15, 1998): 5344–50. http://dx.doi.org/10.1128/jb.180.20.5344-5350.1998.
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ABSTRACT The nitrate and nitrite reductases of Bacillus subtilishave two different physiological functions. Under conditions of nitrogen limitation, these enzymes catalyze the reduction of nitrate via nitrite to ammonia for the anabolic incorporation of nitrogen into biomolecules. They also function catabolically in anaerobic respiration, which involves the use of nitrate and nitrite as terminal electron acceptors. Two distinct nitrate reductases, encoded bynarGHI and nasBC, function in anabolic and catabolic nitrogen metabolism, respectively. However, as reported herein, a single NADH-dependent, soluble nitrite reductase encoded by the nasDE genes is required for both catabolic and anabolic processes. The nasDE genes, together with nasBC(encoding assimilatory nitrate reductase) and nasF(required for nitrite reductase siroheme cofactor formation), constitute the nas operon. Data presented show that transcription of nasDEF is driven not only by the previously characterized nas operon promoter but also from an internal promoter residing between the nasC andnasD genes. Transcription from both promoters is activated by nitrogen limitation during aerobic growth by the nitrogen regulator, TnrA. However, under conditions of oxygen limitation,nasDEF expression and nitrite reductase activity were significantly induced. Anaerobic induction of nasDEFrequired the ResDE two-component regulatory system and the presence of nitrite, indicating partial coregulation of NasDEF with the respiratory nitrate reductase NarGHI during nitrate respiration.
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Liu, Ying, Hongrui Ding, Yuan Sun, Yan Li, and Anhuai Lu. "Genome Analysis of a Marine Bacterium Halomonas sp. and Its Role in Nitrate Reduction under the Influence of Photoelectrons." Microorganisms 8, no. 10 (October 5, 2020): 1529. http://dx.doi.org/10.3390/microorganisms8101529.
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The solar light response and photoelectrons produced by widespread semiconducting mineral play important roles in biogeochemical cycles on Earth’s surface. To explore the potential influence of photoelectrons generated by semiconducting mineral particles on nitrate-reducing microorganisms in the photic zone, a marine heterotrophic denitrifier Halomonas sp. strain 3727 was isolated from seawater in the photic zone of the Yellow Sea, China. This strain was classified as a Halomonadaceae. Whole-genome analysis indicated that this strain possessed genes encoding the nitrogen metabolism, i.e., narG, nasA, nirBD, norZ, nosB, and nxr, which sustained dissimilatory nitrate reduction, assimilatory nitrate reduction, and nitrite oxidation. This strain also possessed genes related to carbon, sulfur, and other metabolisms, hinting at its substantial metabolic flexibility. A series of microcosm experiments in a simulative photoelectron system was conducted, and the results suggested that this bacterial strain could use simulated photoelectrons with different energy for nitrate reduction. Nitrite, as an intermediate product, was accumulated during the nitrate reduction with limited ammonia residue. The nitrite and ammonia productions differed with or without different energy electron supplies. Nitrite was the main product accounting for 30.03% to 68.40% of the total nitrogen in photoelectron supplement systems, and ammonia accounted for 3.77% to 8.52%. However, in open-circuit systems, nitrite and ammonia proportions were 26.77% and 11.17%, respectively, and nitrogen loss in the liquid was not observed. This study reveals that photoelectrons can serve as electron donors for nitrogen transformation mediated by Halomonas sp. strain 3727, which reveals an underlying impact on the nitrogen biogeochemical cycle in the marine photic zone.
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Florin, T. H. J., G. Neale, and J. H. Cummings. "The effect of dietary nitrate on nitrate and nitrite excretion in man." British Journal of Nutrition 64, no. 2 (September 1990): 387–97. http://dx.doi.org/10.1079/bjn19900040.
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Dietary nitrate and nitrite may affect colonic pathophysiology. These anions influence fermentation, and nitrite has been shown to augment sodium absorption by the colon and participate in the formation ofN-nitroso compounds. There is, however, no general agreement as to how much dietary nitrate and nitrite reaches the colon. To help resolve this question, balance studies were performed on six healthy ileostomy subjects who were given diets that varied in nitrate content from 0.83 to 5.20 mmol/d. Nitrate and nitrite excretion in ileal effluent and urine were measured by anion-exchange chromatography with conductivity detection. There was no significant nitrite in the diets, urine, or ideal effluent. Dietary nitrate was largely excreted in urine (1.31–4.25 mmol/d). The urinary excretion findings indicated net synthesis of nitrate at low dietary intakes and net catabolism of nitrate at high intakes. Nitrate losses in ileal effluent were very low (0.03–0.05 mmol/d, 0.03–0.06 mmol/kg) and unrelated to intake for all the diets. It is concluded that dietary nitrate and nitrite do not enter the colon from the small intestine in amounts that would affect fermentation and mucosal metabolism in man. The possibility of significant amounts of nitrate reaching the colon via blood in normal subjects has not been excluded.
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Kern, Melanie, Christine Winkler, and Jörg Simon. "Respiratory nitrogen metabolism and nitrosative stress defence in ϵ-proteobacteria: the role of NssR-type transcription regulators." Biochemical Society Transactions 39, no. 1 (January 19, 2011): 299–302. http://dx.doi.org/10.1042/bst0390299.
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ϵ-Proteobacteria form a globally ubiquitous group of ecologically significant organisms and comprise a diverse range of host-associated and free-living species. To grow by anaerobic respiration, many ϵ-proteobacteria reduce nitrate to nitrite followed by either nitrite ammonification or denitrification. Using the ammonifying model organisms Wolinella succinogenes and Campylobacter jejuni, the electron transport chains of nitrate respiration, respiratory nitrite ammonification and even N2O (nitrous oxide) respiration have been characterized in recent years, but knowledge on nitrosative stress defence, nitrogen compound-sensing and corresponding signal transduction pathways is limited. The potentially dominant role of NssR (nitrosative stress-sensing regulator)-type transcription regulators in ϵ-proteobacterial nitrogen metabolism is discussed.
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Leiva Eriksson, Nélida, Brandon J. Reeder, Michael T. Wilson, and Leif Bülow. "Sugar beet hemoglobins: reactions with nitric oxide and nitrite reveal differential roles for nitrogen metabolism." Biochemical Journal 476, no. 14 (July 31, 2019): 2111–25. http://dx.doi.org/10.1042/bcj20190154.
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Abstract In contrast with human hemoglobin (Hb) in red blood cells, plant Hbs do not transport oxygen, instead research points towards nitrogen metabolism. Using comprehensive and integrated biophysical methods we characterized three sugar beet Hbs: BvHb1.1, BvHb1.2 and BvHb2. Their affinities for oxygen, CO, and hexacoordination were determined. Their role in nitrogen metabolism was studied by assessing their ability to bind NO, to reduce nitrite (NiR, nitrite reductase), and to form nitrate (NOD, NO dioxygenase). Results show that BvHb1.2 has high NOD-like activity, in agreement with the high nitrate levels found in seeds where this protein is expressed. BvHb1.1, on the other side, is equally capable to bind NO as to form nitrate, its main role would be to protect chloroplasts from the deleterious effects of NO. Finally, the ubiquitous, reactive, and versatile BvHb2, able to adopt ‘open and closed forms’, would be part of metabolic pathways where the balance between oxygen and NO is essential. For all proteins, the NiR activity is relevant only when nitrite is present at high concentrations and both NO and oxygen are absent. The three proteins have distinct intrinsic capabilities to react with NO, oxygen and nitrite; however, it is their concentration which will determine the BvHbs’ activity.
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Marino, Marco, Hugo Cruz Ramos, Tamara Hoffmann, Philippe Glaser, and Dieter Jahn. "Modulation of Anaerobic Energy Metabolism of Bacillus subtilis by arfM(ywiD)." Journal of Bacteriology 183, no. 23 (December 1, 2001): 6815–21. http://dx.doi.org/10.1128/jb.183.23.6815-6821.2001.
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ABSTRACT Bacillus subtilis grows under anaerobic conditions utilizing nitrate ammonification and various fermentative processes. The two-component regulatory system ResDE and the redox regulator Fnr are the currently known parts of the regulatory system for anaerobic adaptation. Mutation of the open reading frame ywiDlocated upstream of the respiratory nitrate reductase operonnarGHJI resulted in elimination of the contribution of nitrite dissimilation to anaerobic nitrate respiratory growth. Significantly reduced nitrite reductase (NasDE) activity was detected, while respiratory nitrate reductase activity was unchanged. Anaerobic induction of nasDE expression was found to be significantly dependent on intact ywiD, while anaerobicnarGHJI expression was ywiD independent. Anaerobic transcription of hmp, encoding a flavohemoglobin-like protein, and of the fermentative operonslctEP and alsSD, responsible for lactate and acetoin formation, was partially dependent on ywiD. Expression of pta, encoding phosphotransacetylase involved in fermentative acetate formation, was not influenced byywiD. Transcription of the ywiD gene was anaerobically induced by the redox regulator Fnr via the conserved Fnr-box (TGTGA-6N-TCACT) centered 40.5 bp upstream of the transcriptional start site. Anaerobic induction of ywiDby resDE was found to be indirect viaresDE-dependent activation of fnr. TheywiD gene is subject to autorepression and nitrite repression. These results suggest a ResDE → Fnr → YwiD regulatory cascade for the modulation of genes involved in the anaerobic metabolism of B. subtilis. Therefore,ywiD was renamed arfM for anaerobic respiration and fermentation modulator.
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Ronen, Zeev, and Jean-Marc Bollag. "Pyridine metabolism by a denitrifying bacterium." Canadian Journal of Microbiology 37, no. 10 (October 1, 1991): 725–29. http://dx.doi.org/10.1139/m91-125.
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A denitrifying bacterium capable of pyridine degradation was isolated from contaminated soil. The Gram-negative bacterium, which was identified as an Alcaligenes sp., rapidly metabolized pyridine under anaerobic conditions with nitrate as electron acceptor. [14C]Pyridine was converted to 14CO2, unidentified polar metabolic products, and labeled biomass. During pyridine metabolism, nitrate was reduced to nitrogen gas via nitrite and nitrous oxide. The molar ratio of pyridine to nitrate strongly affected pyridine metabolism. Maximum pyridine degradation occurred at a nitrate concentration above 5 mM, a temperature of 22–36 °C, and a pH of 6.8–8.0. Key words: pyridine, anaerobic metabolism, denitrifying bacteria, Alcaligenes sp.
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Weitzberg, Eddie, Michael Hezel, Jon O. Lundberg, and David S. Warner. "Nitrate-Nitrite-Nitric Oxide Pathway." Anesthesiology 113, no. 6 (December 1, 2010): 1460–75. http://dx.doi.org/10.1097/aln.0b013e3181fcf3cc.
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The gaseous radical nitric oxide is involved in numerous physiologic and pathophysiological events important in anesthesiology and intensive care. Nitric oxide is endogenously generated from the amino acid l-arginine and molecular oxygen in reactions catalyzed by complex nitric oxide synthases. Recently, an alternative pathway for nitric oxide generation was discovered, wherein the inorganic anions nitrate (NO3) and nitrite (NO2), most often considered inert end products from nitric oxide generation, can be reduced back to nitric oxide and other bioactive nitrogen oxide species. This nitrate-nitrite-nitric oxide pathway is regulated differently than the classic l-arginine-nitric oxide synthase nitric oxide pathway, and it is greatly enhanced during hypoxia and acidosis. Several lines of research now indicate that the nitrate-nitrite-nitric oxide pathway is involved in regulation of blood flow, cell metabolism, and signaling, as well as in tissue protection during hypoxia. The fact that nitrate is abundant in our diet gives rise to interesting nutritional aspects in health and disease. In this article, we present an overview of this field of research with emphasis on relevance in anesthesiology and intensive care.
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Loyola-Vargas, Victor Manuel, Irene Gómez, Ma Eugenia López, Jorge Reyes, Miriam Fierro, and Manuel L. Robert. "Changes in the activity of the enzymes involved in nitrogen metabolism in Catharanthus roseus depending on different nitrogen sources." Canadian Journal of Botany 64, no. 9 (September 1, 1986): 2052–56. http://dx.doi.org/10.1139/b86-268.
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The activities of the enzymes nitrate reductase (EC 1.6.6.1) and nitrite reductase (EC 1.7.99.3) were measured in the leaves and roots of whole plants of Catharanthus roseus grown in different nitrogen sources: water (control), 20 mM KNO3, 2 mM NH4Cl, and a mixture of nitrate and ammonium. The activities of these enzymes were also measured in leaf explants incubated in the same nitrogen sources. The results indicate that nitrate reductase and nitrite reductase in leaves behaved very differently from those in roots. Activity of leaf nitrate reductase measured in vitro decreased with nitrate and increased with ammonium, while in the root, it only decreased when the mixture of both nitrogen sources was employed. In contrast, nitrite reductase from roots was modified by the nitrogen source while the enzyme from the leaves was not. The amino acid pool was increased by all of the nitrogen sources in both whole plants and explants.
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Felix-Portillo, Monserrath, Elizabeth Latham, Ruth Lisbeth Armendariz-Rivas, Jaime Salinas-Chavira, Claudio Arzola, and Robin Anderson. "PSXIV-16 Comparative in vitro effects of spray-dried and freshly-harvested Paenibacillus fortis strain 79R4 on rumen methane, nitrate, nitrite and ammonia metabolism." Journal of Animal Science 97, Supplement_3 (December 2019): 439. http://dx.doi.org/10.1093/jas/skz258.869.
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Abstract Nitrate supplementation into the ruminant diet can decrease ruminal methane emissions, but amounts needed to achieve appreciable decreases can risk ruminal accumulations of nitrite with potential for methemoglobinemia. A denitrifying rumen Paenibacillus fortis strain 79R4 (79R4) selected for enhanced nitrite-metabolizing ability has shown promise as a probiotic to decrease risks of nitrite toxicosis. Presently, a spray-dried prototype of this spore-forming, facultative anaerobe was tested during anaerobic culture (10 mL/tube) of rumen fluid freshly-collected from an alfalfa hay-fed cannulated Jersey cow. Cultures supplemented with 22 mM sodium nitrate and without or with inoculations of freshly-harvested (FH) cells or spray dried (SP) 79R4 spores (3 tubes/treatment; 108 cells/spores per tube) were cultured anaerobically (39oC for 24 h with 100% CO2). The FH- and SP- cells were grown aerobic, 72 h in tryptic soy broth, SP- cells were then processed and spray-dried. Nitrate-supplementation decreased (P = 0.0006; SEM = 0.31) methane production by the cultures, but this decrease was unaffected by 79R4 inoculation (2.57 µmol CH4/mL with no nitrate/no inoculum versus 0.15 µmol CH4/mL with nitrate/inoculum). Nitrate-metabolizing activity in nitrate-treated cultures were unaffected by 79R4 inoculations (P = 0.17; SEM = 0.15), rates being 0.95, 0.63 and 0.50 µmol nitrate/mL h-1 FH-, SP- and non-inoculated cultures, respectively. Nitrite accumulation rates (P = 0.10; SEM = 0.06) and peak nitrite concentrations (P = 0.06; SEM = 0.75) tended to be lower in SP- than in FH- and non-inoculated cultures (0.29, 0.47 and 0.47 µmol nitrite/mL h-1 and 3.33, 5.67 and 5.66 µmol/mL, respectively). Rates of ammonia accumulation were more rapid (P = 0.01; SEM = 0.01) in SP- and FH- than in non-inoculated cultures (0.16 and 0.15 versus 0.06 µmol/mL h-1, respectively). Results provide evidence that 79R4 prototype may aid rumen populations in detoxifying nitrite, therefore enhancing the abilities of high nitrate diets.
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Cheng, K. J., R. C. Phillippe, and W. Majak. "Identification of rumen bacteria that anaerobically degrade nitrite." Canadian Journal of Microbiology 34, no. 9 (September 1, 1988): 1099–102. http://dx.doi.org/10.1139/m88-193.
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Fifty-one pure strains of rumen bacteria, representing 15 genera, were tested for their ability to metabolize nitrite. Twenty-five of the strains, belonging to eight genera, were capable of growth and nitrite metabolism in nitrite-containing medium sterilized by autoclaving. An additional 10 strains showed growth and nitrite metabolism in medium that was autoclaved before the addition of filter-sterilized nitrite. Nitrite metabolism was not observed in the remaining 16 strains, and these were also incapable of growth in the presence of nitrite. Ammonia was produced during nitrite reduction by Megasphaera elsdenii J1. In agreement with previous studies, abiotic losses of nitrite were observed during autoclaving and storage of media, but losses of nitrite due to bacterial metabolism were much greater.
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Nebl, Josefine, Kathrin Drabert, Sven Haufe, Paulina Wasserfurth, Julian Eigendorf, Uwe Tegtbur, Andreas Hahn, and Dimitrios Tsikas. "Exercise-Induced Oxidative Stress, Nitric Oxide and Plasma Amino Acid Profile in Recreational Runners with Vegetarian and Non-Vegetarian Dietary Patterns." Nutrients 11, no. 8 (August 13, 2019): 1875. http://dx.doi.org/10.3390/nu11081875.
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This study investigated the exercise-induced changes in oxidative stress, nitric oxide (NO) metabolism and amino acid profile in plasma of omnivorous (OMN, n = 25), lacto-ovo-vegetarian (LOV, n = 25) and vegan (VEG, n = 23) recreational runners. Oxidative stress was measured as malondialdehyde (MDA), NO as nitrite and nitrate, and various amino acids, including homoarginine and guanidinoacetate, the precursor of creatine. All analytes were measured by validated stable-isotope dilution gas chromatographic-mass spectrometric methods. Pre-exercise, VEG had the highest MDA and nitrate concentrations, whereas nitrite concentration was highest in LOV. Amino acid profiles differed between the groups, with guanidinoacetate being highest in OMN. Upon acute exercise, MDA increased in the LOV and VEG group, whereas nitrate, nitrite and creatinine did not change. Amino acid profiles changed post-exercise in all groups, with the greatest changes being observed for alanine (+28% in OMN, +21% in LOV and +28% in VEG). Pre-exercise, OMN, LOV and VEG recreational runners differ with respect to oxidative stress, NO metabolism and amino acid profiles, in part due to their different dietary pattern. Exercise elicited different changes in oxidative stress with no changes in NO metabolism and closely comparable elevations in alanine. Guanidinoacetate seems to be differently utilized in OMN, LOV and VEG, pre- and post-exercise.
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Balint, B., L. E. Donnelly, T. Hanazawa, S. A. Kharitonov, and P. J. Barnes. "Increased nitric oxide metabolites in exhaled breath condensate after exposure to tobacco smoke." Thorax 56, no. 6 (June 1, 2001): 456–61. http://dx.doi.org/10.1136/thx.56.6.456.
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BACKGROUNDCigarette smoking reduces the level of exhaled nitric oxide (NO) in healthy subjects, although the mechanism is unclear. NO is a highly reactive molecule which can be oxidised or complexed with other biomolecules, depending on the microenvironment. The stable oxidation end products of NO metabolism are nitrite and nitrate. This study investigated the effect of smoking on NO metabolites in exhaled breath condensate.METHODSFifteen healthy current smokers were recruited together with 14 healthy non-smokers. Measurement of exhaled NO, lung function, and collection of exhaled breath condensate were performed. Nitrite, nitrite + nitrate, S-nitrosothiols, and nitrotyrosine levels were measured. The effect of inhaling two cigarettes in smokers was also evaluated. The mean level of exhaled NO in smokers was significantly lower than in non-smokers (4.3 (0.3) ppb v 5.5 (0.5) ppb, p<0.05).RESULTSThere was no difference in the levels of nitrite, nitrite + nitrate, S-nitrosothiols, and nitrotyrosine in the exhaled breath condensate at the baseline visit between smokers and non-smokers. After smoking, nitrite + nitrate levels were significantly but transiently increased (from 20.2 (2.8) μM to 29.8 (3.4) μM, p<0.05). There was no significant change in the levels of exhaled NO, nitrite, S-nitrosothiols, or nitrotyrosine 30 and 90 minutes after smoking.CONCLUSIONSThese findings suggest that acute smoking can increase the level of nitrate, but not nitrite, S-nitrosothiols, or nitrotyrosine in breath condensate. The deleterious effect of oxidant radicals induced by smoking may contribute to the epithelial damage of airways seen in smokers.
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Curtis, Erin, Lewis L. Hsu, Audrey C. Noguchi, Lisa Geary, and Sruti Shiva. "Oxygen Regulates Tissue Nitrite Metabolism." Antioxidants & Redox Signaling 17, no. 7 (October 2012): 951–61. http://dx.doi.org/10.1089/ars.2011.4242.
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Oliveira-Paula, Gustavo H., and Jose E. Tanus-Santos. "Nitrite-stimulated Gastric Formation of S-nitrosothiols As An Antihypertensive Therapeutic Strategy." Current Drug Targets 20, no. 4 (January 25, 2019): 431–43. http://dx.doi.org/10.2174/1389450119666180816120816.
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Hypertension is usually associated with deficient nitric oxide (NO) bioavailability, and therefore stimulating NO activity is an important antihypertensive strategy. Recently, many studies have shown that both nitrite and nitrate anions are not simple products of NO metabolism and indeed may be reduced back to NO. While enzymes with nitrite-reductase activity capable of generating NO from nitrite may contribute to antihypertensive effects of nitrite, another mechanism involving the generation of NO-related species in the stomach from nitrite has been validated. Under the acidic conditions of the stomach, nitrite generates NO-related species that form S-nitrosothiols. Conversely, drugs that increase gastric pH may impair the gastric formation of S-nitrosothiols, which may mediate antihypertensive effects of oral nitrite or nitrate. Therefore, it is now becoming clear that promoting gastric formation of S-nitrosothiols may result in effective antihypertensive responses, and this mechanism opens a window of opportunity in the therapy of hypertension. In this review, we discuss the recent studies supporting the gastric generation of S-nitrosothiols as a potential antihypertensive mechanism of oral nitrite. We also highlight some drugs that increase S-nitrosothiols bioavailability, which may also improve the responses to nitrite/nitrate therapy. This new approach may result in increased nitrosation of critical pharmacological receptors and enzymes involved in the pathogenesis of hypertension, which tend to respond less to their activators resulting in lower blood pressure.
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Priego, Teresa, Miriam Granado, Estibaliz Castillero, Ana Isabel Martín, M. Ángeles Villanúa, and Asunción López-Calderón. "Nitric oxide production by hepatocytes contributes to the inhibitory effect of endotoxin on insulin-like growth factor I gene expression." Journal of Endocrinology 190, no. 3 (September 2006): 847–56. http://dx.doi.org/10.1677/joe.1.06938.
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We tested whether endotoxin (lipopolysaccharide, LPS) inhibits IGF-I gene expression in hepatocytes and the possible role of Kupffer cells and nitric oxide (NO) in this effect. LPS decreased IGF-I mRNA in hepatocyte cultures and increased the nitrite + nitrate levels in the culture medium. Furthermore, there was a negative correlation between the IGF-I mRNA and the nitrite+nitrate levels. When hepatocytes were cocultured with Kupffer cells, the inhibitory effect of LPS on IGF-I mRNA was higher than in hepatocyte cultures, but the stimulatory effect on nitrite+nitrate was similar in both conditions. The exogenous NO donated by S-nitroso-n-acetyl-d,l-penicillamide also decreased the IGF-I gene expression in hepatocyte cultures. In addition, two specific inducible NO synthase (iNOS) inhibitors, l-N6-(1-iminoethyl)lysine (l-NIL) and aminoguanidine, prevented the effect of LPS on nitrite+nitrate levels and on IGF-I gene expression in hepatocyte cultures. These data indicate that iNOS-derived NO may cause downregulation of IGF-I gene expression in hepatocytes. However, in cocultures, the iNOS inhibitor l-NIL prevented the effect of LPS on nitrite+nitrate levels, but only attenuated the LPS-induced decrease in IGF-I gene expression. We conclude that in hepatocytes, LPS-induced decrease in IGF-I is mainly due to induction of iNOS, whereas in the presence of Kupffer cells LPS inhibits IGF-I through NO release and through other inhibitory pathways.
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Pijuan, M., L. Ye, and Z. Yuan. "Could nitrite/free nitrous acid favour GAOs over PAOs in enhanced biological phosphorus removal systems?" Water Science and Technology 63, no. 2 (January 1, 2011): 345–51. http://dx.doi.org/10.2166/wst.2011.062.
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Enhanced biological phosphorus removal (EBPR) normally occurs together with nitrogen removal in wastewater treatment plants (WWTPs). In recent years, efforts have been devoted to remove nitrogen via the nitrite pathway (oxidation of ammonia to nitrite and reduction of nitrite to nitrogen gas without going through nitrate), reducing the requirement for carbon and oxygen in the plant. However nitrite and free nitrous acid (FNA), the protonated species of nitrite, have been shown to cause EBPR deterioration under certain concentrations. This study provides a direct comparison between the different levels of FNA inhibition in the aerobic processes of polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) by reviewing the studies published in this area. Also, new data is presented assessing the FNA effect on the anaerobic metabolism of these two groups of bacteria. Overall, FNA has shown inhibitory effects on most of the processes involved in the metabolism of PAOs and GAOs. However, the inhibition-initiation levels are different between different processes and, even more importantly between the two groups. In general, PAOs appear to be more affected than GAOs at the same level of FNA, thus giving GAOs competitive advantage over PAOs in EBPR systems when nitrite is present.
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Muller, Claudia M., Annette Scierka, Richard L. Stiller, Yong-Myeong Kim, Ryan D. Cook, Jack R. Lancaster, Charles W. Buffington, and David W. Watkins. "Nitric Oxide Mediates Hepatic Cytochrome P450 Dysfunction Induced by Endotoxin." Anesthesiology 84, no. 6 (June 1, 1996): 1435–42. http://dx.doi.org/10.1097/00000542-199606000-00020.
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Background Animals subjected to immunostimulatory conditions (sepsis) exhibit decreased total cytochrome P450 content and decreased P450-dependent drug metabolism. Cytochrome P450 function is of clinical significance because it mediates the metabolism of some opioid and hypnotic drugs. The authors tested the hypothesis that reduced P450 function and decreased drug metabolism in sepsis are mediated by endotoxin-enhanced synthesis of nitric oxide. Methods Hepatic microsomes were prepared from male Sprague-Dawley rats in nontreated rats, rats pretreated with phenobarbital and rats receiving aminoguanidine or NG-L-monomethyl-arginine alone. Nitric oxide synthesis was augmented for 12 h with a single injection of bacterial lipopolysaccharides. Nitric oxide synthase was inhibited with aminoguanidine or N(G)-L-monomethyl-arginine during the 12 h of endotoxemia in some animals. Plasma nitrite and nitrate concentrations were measured in vivo, and total microsomal P450 content, and metabolism of ethylmorphine and midazolam in vitro. Results Administration of endotoxin increased plasma nitrite and nitrate concentrations, decreased total cytochrome P450 content, and decreased metabolism of ethylmorphine and midazolam. Inhibition of nitric oxide formation by aminoguanidine or N(G)-L-monomethyl-arginine partially prevented the endotoxin-induced effects in the nontreated and phenobarbital-treated groups. Aminoguanidine or N(G)-L-monomethyl-arginine alone did not have an effect on either total cytochrome P450 content or P450-dependent drug metabolism. Plasma nitrite and nitrate concentrations correlated significantly negatively with P450 content (nontreated r = -0.88, phenobarbital r = -0.91), concentrations of formed formaldehyde (nontreated r = -0.87, phenobarbital r = -0.95), and concentrations of midazolam metabolites (4-OH midazolam nontreated r = -0.88, phenobarbital r = -0.93, and 1'-OH midazolam nontreated r = -0.88, phenobarbital r = -0.97). Conclusions Altered hepatic microsomal ethylmorphine and midazolam metabolism during sepsis is mediated in large part by nitric oxide.
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Llorens, Nuria, Lluís Arola, Cinta Bladé, and Albert Mas. "Nitrogen metabolism in a grapevine in vitro system." OENO One 36, no. 3 (September 30, 2002): 157. http://dx.doi.org/10.20870/oeno-one.2002.36.3.968.
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<p style="text-align: justify;">Ammonium, nitrate, nitrite, protein and individual and total amino acid contents were determined in grapevine (cv Sauvignon) cultured <em>in vitro</em>. The enzyme activities of nitrate and nitrite reductases, glutamine synthetase, glutamate synthetase and dehydrogenase were also determined. The nitrogen taken up by the plants was 70% of the total nitrogen in the medium after 75 days of <em>in vitro</em> culture. Most of the nitrogen taken up was recovered in the leaves, yet only ammonia and amino acid concentrations were significantly higher in leaves. In roots, glutamine was the most abundant amino acid. In leaves, the most abundant amino acids were aspartate, glutamate, glutamine, alanine, arginine and g-aminobutirate. All enzyme activities were higher in roots than in leaves. These results suggest that both roots and leaves incorporate inorganic nitrogen into organic forms.</p>
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Wu, Fan, Xiaobo Sun, Xingfeng Hu, Bingzhang Zou, Nengqing Lin, Jingquan Lin, and Kongshu Ji. "Response of Nitrogen Metabolism in Masson Pine Needles to Elevated CO2." Forests 11, no. 4 (April 1, 2020): 390. http://dx.doi.org/10.3390/f11040390.
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To explore the response of nitrogen metabolism in Masson pine (Pinus massoniana) to high CO2 concentrations, needles from one-year-old seedlings were used as materials to detect key enzyme activities, gene expression and different forms of nitrogen metabolites after CO2 stress for different durations (0 h, 6 h, 12 h, 24 h). The results show that elevated CO2 affected the efficiency of nitrogen metabolism in Masson pine needles, inhibiting the expression of key genes involved in nitrogen metabolism, including glutamate synthase (GOGAT), nitrite reductase (NiR), glutamine synthase (GS), nitrate reductase (NR) and glutamate dehydrogenase (GDH), and decreasing the activities of GOGAT, NiR, and GS. The decrease in enzyme activities and gene expression caused a decrease in different forms of nitrogen metabolites, including total nitrogen, ammonium, nitrite and specific amino acids. With prolonged stress, the nitrate content increased first and then decreased. In this study, the response pattern of nitrogen metabolism to CO2 stress in Masson pine needles was described, which may aid future research on nitrogen utilization in Masson pine.
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JI, Yanbin, Theodorus P. M. AKERBOOM, and Helmut SIES. "Microsomal formation of S-nitrosoglutathione from organic nitrites: possible role of membrane-bound glutathione transferase." Biochemical Journal 313, no. 2 (January 15, 1996): 377–80. http://dx.doi.org/10.1042/bj3130377.
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The formation of S-nitrosoglutathione (GSNO) from amyl nitrite and n-butyl nitrite was studied in rat liver microsomes, employingN-ethylmaleimide (MalNEt) as an activator and indomethacin as an inhibitor of microsomal glutathione S-transferase (GST). Rates were compared with GST activity measured with 1-chloro-2,4-dinitrobenzene(CDNB) as a substrate. MalNEt stimulated GST activity and the formation of GSNO from amyl nitrite and n-butyl nitrite about 10-fold. Increasing concentrations of indomethacin inhibited both reactions in parallel. N-Acetyl-L-cysteine but not L-cysteine could substitute for GSH. It is concluded that rat liver microsomal GST catalyses the formation of GSNO from amyl nitrite and n-butyl nitrite. The activity of the MalNEt-stimulated microsomal GST is calculated to be about 17 units/mg of enzyme with the alkyl nitrites and about 16 units/mg of enzyme with CDNB as a substrate, assuming that 3% of microsomal protein is GST. These rates are comparable with those obtained for cytosolic GSTs. Thus microsomal GST may play a significant role in the metabolism of alkyl nitrites in biological membranes.
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Brizzolari, Andrea, Michele Dei Cas, Danilo Cialoni, Alessandro Marroni, Camillo Morano, Michele Samaja, Rita Paroni, and Federico Maria Rubino. "High-Throughput Griess Assay of Nitrite and Nitrate in Plasma and Red Blood Cells for Human Physiology Studies under Extreme Conditions." Molecules 26, no. 15 (July 28, 2021): 4569. http://dx.doi.org/10.3390/molecules26154569.
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The metabolism of nitric oxide plays an increasingly interesting role in the physiological response of the human body to extreme environmental conditions, such as underwater, in an extremely cold climate, and at low oxygen concentrations. Field studies need the development of analytical methods to measure nitrite and nitrate in plasma and red blood cells with high requirements of accuracy, precision, and sensitivity. An optimized spectrophotometric Griess method for nitrite–nitrate affords sensitivity in the low millimolar range and precision within ±2 μM for both nitrite and nitrate, requiring 100 μL of scarcely available plasma sample or less than 50 μL of red blood cells. A scheduled time-efficient procedure affords measurement of as many as 80 blood samples, with combined nitrite and nitrate measurement in plasma and red blood cells. Performance and usefulness were tested in pilot studies that use blood fractions deriving from subjects who dwelt in an Antarctica scientific station and on breath-holding and scuba divers who performed training at sea and in a land-based deep pool facility. The method demonstrated adequate to measure low basal concentrations of nitrite and high production of nitrate as a consequence of water column pressure-triggered vasodilatation in deep-water divers.
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Keller, Rosa, Laura Beaver, Patrick Reardon, and Norman Hord. "Nitrate and Nitrite Treatment Modulate Performance and Available Fuel Sources In Zebrafish Muscle and Liver." Current Developments in Nutrition 4, Supplement_2 (May 29, 2020): 1758. http://dx.doi.org/10.1093/cdn/nzaa066_013.
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Abstract Objectives Treatment with nitrate, but not nitrite, improves exercise performance but the mechanisms responsible are not fully understood. Thus, we tested the hypothesis that nitrate and nitrite treatment alter exercise performance through regulation of genes related to glucose and lipid metabolism in skeletal muscle and liver. Furthermore, we tested the hypothesis that nitrate treatment caused increased abundance and utilization of metabolic fuels in muscle that require less oxygen for energy production. Methods Adult zebrafish fish were exposed to sodium nitrate (606.9 mg NaNO3/L water), sodium nitrite (19.5 mg NaNO2/L of water), or control water for 21 days (n = 9–12/treatment). Liver and muscle gene expression were analyzed by quantitative real-time PCR and liver and muscle metabolomes were assessed by 1H-NMR untargeted metabolomics. Results Nitrite treatment significantly increased carnitine palmitoyl transferase 1b (cpt1b) expression in the liver and significantly decreased acetyl-CoA carboxylase (acaca) expression in skeletal muscle. Nitrate treatment significantly increased expression of peroxisome proliferator activated receptor-γ (pparg) muscle while acaca significantly decreased in skeletal muscle. Nitrate treatment also induced significant increases in metabolic fuels, such as ATP and creatine phosphate, and fuel sources including β-hydroxybutyrate and glycolytic intermediates in rested skeletal muscle. After a graded exercise test, these metabolites decreased in skeletal muscle of nitrate-treated fish while they increased with exercise in the skeletal muscle of control-treated zebrafish. Conclusions Our data are consistent with the hypothesis that nitrate treatment altered lipid and carbohydrate metabolism of zebrafish, in part, through a pparg mediated mechanism in the liver, and may improve exercise performance through utilization of fuel sources that require less oxygen during exercise. In contrast, our data indicate that nitrite may attenuate exercise performance, in part, by promoting dependence on fatty acid oxidation in the liver of zebrafish. These mechanisms may mediate improved exercise tolerance in populations with cardiovascular disease. Funding Sources Celia Strickland and G. Kenneth Austin III Endowment and National Institutes of Health.
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Wang, Henian, Ching-Ping Tseng, and Robert P. Gunsalus. "The napF and narG Nitrate Reductase Operons in Escherichia coli Are Differentially Expressed in Response to Submicromolar Concentrations of Nitrate but Not Nitrite." Journal of Bacteriology 181, no. 17 (September 1, 1999): 5303–8. http://dx.doi.org/10.1128/jb.181.17.5303-5308.1999.
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ABSTRACT Escherichia coli synthesizes two biochemically distinct nitrate reductase enzymes, a membrane-bound enzyme encoded by thenarGHJI operon and a periplasmic cytochromec-linked nitrate reductase encoded by thenapFDAGHBC operon. To address why the cell makes these two enzymes, continuous cell culture techniques were used to examinenapF and narG gene expression in response to different concentrations of nitrate and/or nitrite. Expression of thenapF-lacZ and narG-lacZ reporter fusions in strains grown at different steady-state levels of nitrate revealed that the two nitrate reductase operons are differentially expressed in a complementary pattern. The napF operon apparently encodes a “low-substrate-induced” reductase that is maximally expressed only at low levels of nitrate. Expression is suppressed under high-nitrate conditions. In contrast, the narGHJI operon is only weakly expressed at low nitrate levels but is maximally expressed when nitrate is elevated. The narGHJI operon is therefore a “high-substrate-induced” operon that somehow provides a second and distinct role in nitrate metabolism by the cell. Interestingly, nitrite, the end product of each enzyme, had only a minor effect on the expression of either operon. Finally, nitrate, but not nitrite, was essential for repression of napF gene expression. These studies reveal that nitrate rather than nitrite is the primary signal that controls the expression of these two nitrate reductase operons in a differential and complementary fashion. In light of these findings, prior models for the roles of nitrate and nitrite in control ofnarG and napF expression must be reconsidered.
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Fedtke, I., A. Kamps, B. Krismer, and F. Götz. "The Nitrate Reductase and Nitrite Reductase Operons and the narT Gene of Staphylococcus carnosus Are Positively Controlled by the Novel Two-Component System NreBC." Journal of Bacteriology 184, no. 23 (December 1, 2002): 6624–34. http://dx.doi.org/10.1128/jb.184.23.6624-6634.2002.
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ABSTRACT In Staphylococcus carnosus, the nreABC (for nitrogen regulation) genes were identified and shown to link the nitrate reductase operon (narGHJI) and the putative nitrate transporter gene narT. An nreABC deletion mutant, m1, was dramatically affected in nitrate and nitrite reduction and growth. Transcription of narT, narGHJI, and the nitrite reductase (nir) operon was severely reduced even when cells were cultivated anaerobically without nitrate or nitrite. nreABC transcripts were detected when cells were grown aerobically or anaerobically with or without nitrate or nitrite. NreA is a GAF domain-containing protein of unknown function. In vivo and in vitro studies showed that NreC is phosphorylated by NreB and that phospho-NreC specifically binds to a GC-rich palindromic sequence to enhance transcription initiation. This binding motif was found at the narGHJI, nir, and narT promoters but not at the moeB promoter. NreB is a cytosolic protein with four N-terminal cysteine residues. The second cysteine residue was shown to be important for NreB function. In vitro autophosphorylation of NreB was not affected by nitrate, nitrite, or molybdate. The nir promoter activity was iron dependent. The data provide evidence for a global regulatory system important for aerobic and anaerobic metabolism, with NreB and NreC forming a classical two-component system and NreB acting as a sensor protein with oxygen as the effector molecule.
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Brandão, Andrea D., and Ladaslav Sodek. "Nitrate uptake and metabolism by roots of soybean plants under oxygen deficiency." Brazilian Journal of Plant Physiology 21, no. 1 (2009): 13–23. http://dx.doi.org/10.1590/s1677-04202009000100003.
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Nitrate is reported to improve tolerance of plants towards oxygen deficiency enabled by waterlogging of the root system, but the mechanism underlying the phenomenon remains poorly understood. We studied the metabolism of nitrate in roots exposed to hypoxia, using soybean plants growing in a hydroponic system after suspending aeration and covering the surface of the nutrient solution with mineral oil. Nitrate depletion from the medium was more intense under hypoxia than normoxia, but in the presence of chloramphenicol, consumption under hypoxia was significantly reduced. Nitrite accumulated in the medium in the state of hypoxia and this effect was partially eliminated by chloramphenicol. Nitrate consumption sensitive to chloramphenicol was attributed to bacterial activity. Endogenous root nitrate was strongly reduced under hypoxia indicating mobilization. Although the transport of nitrate to the shoot via the xylem was also reduced under hypoxia, the severity of this reduction was dependent on the concentration of nitrate in the medium, suggesting that at least some of the nitrate in the xylem came from the medium. Root nitrate reductase was also strongly reduced under hypoxia, but recovered rapidly on return to normoxia. Overall, the data are consistent with two main metabolic fates for chloramphenicol-insensitive nitrate depletion under hypoxia: the reduction of some nitrate to nitrite (despite the reduced nitrate reductase activity) followed by its release to the medium (at least one-third of the nitrate consumed followed this route), and the transport of nitrate to the shoot. Nevertheless, it is highly unlikely that these metabolic routes account for all the nitrate consumed.
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May, James M., Zhi-Chao Qu, Li Xia, and Charles E. Cobb. "Nitrite uptake and metabolism and oxidant stress in human erythrocytes." American Journal of Physiology-Cell Physiology 279, no. 6 (December 1, 2000): C1946—C1954. http://dx.doi.org/10.1152/ajpcell.2000.279.6.c1946.
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Nitric oxide, when released into the bloodstream, is quickly scavenged by Hb in erythrocytes or oxidized to nitrite. Nitrite can also enter erythrocytes and oxidize Hb. The goals of this work were to determine the mechanism of erythrocyte nitrite uptake and whether this uptake causes oxidant stress in these cells. Erythrocytes took up 0.8 mM nitrite with a half-time of 11 min. Nitrite uptake was sensitive to temperature and to the pH and ionic composition of the medium but was not inhibited by the specific anion-exchange inhibitor DIDS. About 25% of nitrite uptake occurred on the sodium-dependent phosphate transporter and the rest as diffusion of nitrous acid or other species across the plasma membrane. Methemoglobin formation increased in proportion to the intracellular nitrite concentration. Nitrite reacted with erythrocyte ascorbate, but ascorbate loading of cells decreased nitrite-induced methemoglobin formation only at high nitrite concentrations. In conclusion, nitrite rapidly enters erythrocytes and reacts with oxyhemoglobin but does not exert a strong oxidant stress on these cells.
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Anjum, Muna F., Tânia M. Stevanin, Robert C. Read, and James W. B. Moir. "Nitric Oxide Metabolism in Neisseria meningitidis." Journal of Bacteriology 184, no. 11 (June 1, 2002): 2987–93. http://dx.doi.org/10.1128/jb.184.11.2987-2993.2002.
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ABSTRACT Neisseria meningitidis, the causative agent of meningococcal disease in humans, is likely to be exposed to nitrosative stress during natural colonization and disease. The genome of N. meningitidis includes the genes aniA and norB, predicted to encode nitrite reductase and nitric oxide (NO) reductase, respectively. These gene products should allow the bacterium to denitrify nitrite to nitrous oxide. We show that N. meningitidis can support growth microaerobically by the denitrification of nitrite via NO and that norB is required for anaerobic growth with nitrite. NorB and, to a lesser extent, the cycP gene product cytochrome c′ are able to counteract toxicity due to exogenously added NO. Expression of these genes by N. meningitidis during colonization and disease may confer protection against exogenous or endogenous nitrosative stress.
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Ye, Rick W., Wang Tao, Laura Bedzyk, Thomas Young, Mario Chen, and Liao Li. "Global Gene Expression Profiles of Bacillus subtilis Grown under Anaerobic Conditions." Journal of Bacteriology 182, no. 16 (August 15, 2000): 4458–65. http://dx.doi.org/10.1128/jb.182.16.4458-4465.2000.
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ABSTRACT Bacillus subtilis can grow under anaerobic conditions, either with nitrate or nitrite as the electron acceptor or by fermentation. A DNA microarray containing 4,020 genes from this organism was constructed to explore anaerobic gene expression patterns on a genomic scale. When mRNA levels of aerobic and anaerobic cultures during exponential growth were compared, several hundred genes were observed to be induced or repressed under anaerobic conditions. These genes are involved in a variety of cell functions, including carbon metabolism, electron transport, iron uptake, antibiotic production, and stress response. Among the highly induced genes are not only those responsible for nitrate respiration and fermentation but also those of unknown function. Certain groups of genes were specifically regulated during anaerobic growth on nitrite, while others were primarily affected during fermentative growth, indicating a complex regulatory circuitry of anaerobic metabolism.
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Qu, X. M., Z. F. Wu, B. X. Pang, L. Y. Jin, L. Z. Qin, and S. L. Wang. "From Nitrate to Nitric Oxide." Journal of Dental Research 95, no. 13 (October 8, 2016): 1452–56. http://dx.doi.org/10.1177/0022034516673019.
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The salivary glands and oral bacteria play an essential role in the conversion process from nitrate (NO3-) and nitrite (NO2-) to nitric oxide (NO) in the human body. NO is, at present, recognized as a multifarious messenger molecule with important vascular and metabolic functions. Besides the endogenous L-arginine pathway, which is catalyzed by complex NO synthases, nitrate in food contributes to the main extrinsic generation of NO through a series of sequential steps (NO3--NO2--NO pathway). Up to 25% of nitrate in circulation is actively taken up by the salivary glands, and as a result, its concentration in saliva can increase 10- to 20-fold. However, the mechanism has not been clearly illustrated until recently, when sialin was identified as an electrogenic 2NO3-/H+ transporter in the plasma membrane of salivary acinar cells. Subsequently, the oral bacterial species located at the posterior part of the tongue reduce nitrate to nitrite, as catalyzed by nitrate reductase enzymes. These bacteria use nitrate and nitrite as final electron acceptors in their respiration and meanwhile help the host to convert nitrate to NO as the first step. This review describes the role of salivary glands and oral bacteria in the metabolism of nitrate and in the maintenance of NO homeostasis. The potential therapeutic applications of oral inorganic nitrate and nitrite are also discussed.
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Spryn, K. R., M. V. Sabadashka, and N. O. Sybirna. "Effects of agmatine and red wine concentrate, enriched with polyphenolic compounds, on L-arginine / nitrogen oxide system in the brain of rats with experimental diabetes mellitus." Studia Biologica 15, no. 2 (2021): 25–34. http://dx.doi.org/10.30970/sbi.1502.655.
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Background. Diabetes mellitus is a chronic endocrine metabolic disease with absolute or relative insufficiency of insulin, accompanied by impaired metabolism. Endogenous bioamine agmatine may become a basis of new antidiabetic drugs, as it is capable to induce the release of some peptide hormones, in particular insulin, and can regulate NO synthesis. Natural polyphenols are potential multifunctional agents that also can reduce the risk of diabetes and diabetic complications. The aim of the study was to evaluate the effect of agmatine and red wine concentrate, enriched with polyphenolic compounds, on NO-synthase activity and the content of NO stable metabolites under experimental diabetes mellitus. Materials and Methods. The experiments were conducted on white Wistar male rats. Diabetes was induced by intra-abdominal injection of streptozotocin. From the 14th day after the induction of diabetes, agmatine was injected intramuscularly or red wine concentrate, enriched with polyphenolic compounds was administrated orally to animals for 14 days. Rats were decapitated under ether anesthesia on the 28th day of the experiment. In the brain of rats, the activity of constitutive (Ca2+-dependent) and inducible (Ca2+-independent) isoforms of NO-synthase and the content of nitrite and nitrate anions were determined. Results and Discussion. The activities of constitutive and inducible isoforms of NO-synthase were increased in the brain of diabetic rats. The administration of both agmatine and red wine concentrate, enriched with polyphenolic compounds, caused the reduction of the activities of NO-synthase isoforms. In the case of diabetes, the administration of agmatine contributes to the increase of nitrite and nitrate content in brain cells compared to diabetes. The administration of red wine concentrate, enriched with polyphenolic compounds, also promotes nitrite levels but does not affect the nitrate level. Conclusion. We found that the red wine concentrate, enriched with polyphenolic compounds, has a stronger effect on the activity of Ca2+-dependent and Ca2+-independent isoforms of NO-synthase, as well as the content of nitrites and nitrates in brain of rats with experimental diabetes mellitus, compared to the effect of agmatine.
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Bir, Shyamal C., Christopher B. Pattillo, Sibile Pardue, Gopi K. Kolluru, John Docherty, Dave Goyette, Peter Dvorsky, and Christopher G. Kevil. "Nitrite anion stimulates ischemic arteriogenesis involving NO metabolism." American Journal of Physiology-Heart and Circulatory Physiology 303, no. 2 (July 15, 2012): H178—H188. http://dx.doi.org/10.1152/ajpheart.01086.2010.
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Nitric oxide (NO) is a potential regulator of ischemic vascular remodeling, and as such therapies augmenting its bioavailability may be useful for the treatment of ischemic tissue diseases. Here we examine the effect of administering the NO prodrug sodium nitrite on arteriogenesis activity during established tissue ischemia. Chronic hindlimb ischemia was induced by permanent unilateral femoral artery and vein ligation. Five days postligation; animals were randomized to control PBS or sodium nitrite (165 μg/kg) therapy twice daily. In situ vascular remodeling was measured longitudinally using SPY angiography and Microfil vascular casting. Delayed sodium nitrite therapy rapidly increased ischemic limb arterial vessel diameter and branching in a NO-dependent manner. SPY imaging angiography over time showed that nitrite therapy enhanced ischemic gracillis collateral vessel formation from the profunda femoris to the saphenous artery. Immunofluorescent staining of smooth muscle cell actin also confirmed that sodium nitrite therapy increased arteriogenesis in a NO-dependent manner. The NO prodrug sodium nitrite significantly increases arteriogenesis and reperfusion of established severe chronic tissue ischemia.
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Granger, D. L., J. B. Hibbs, and L. M. Broadnax. "Urinary nitrate excretion in relation to murine macrophage activation. Influence of dietary L-arginine and oral NG-monomethyl-L-arginine." Journal of Immunology 146, no. 4 (February 15, 1991): 1294–302. http://dx.doi.org/10.4049/jimmunol.146.4.1294.
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Abstract Murine macrophage oxidation of L-arginine guanidino nitrogen to nitrite/nitrate yields an intermediate effector, possibly nitric oxide, with antimicrobial activity. Total body nitrogen oxidation metabolism (NOM) was measured in vivo by determining the urinary nitrate excretion of mice ingesting a chemically defined nitrite/nitrate-free diet. As reported previously, mycobacterial infection with bacillus Calmétte-Guerin led to a large increase in urinary nitrate excretion. This increase was temporally related to macrophage activation in vivo. The substrate for macrophage nitrogen oxidation metabolism in vitro, L-arginine, was deleted from the diet without ameliorating the urinary nitrate excretion response induced by BCG. This suggested that L-arginine was synthesized endogenously because there are no other known natural substrates for NOM. A competitive inhibitor of NOM, the L-arginine analog, NG-monomethyl-L-arginine was fed to mice in their drinking water. NG-monomethyl-L-arginine ingestion blocked both basal and bacillus Calmétte-Guerin-induced urinary nitrate excretion over a 2-4 week time span. These experimental conditions should prove useful for further investigation on the role of macrophage NOM in host defense against intracellular microorganisms.
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CHENG, K. J., R. C. PHILLIPPE, G. C. KOZUB, W. MAJAK, and J. W. COSTERTON. "INDUCTION OF NITRATE AND NITRITE METABOLISM IN BOVINE RUMEN FLUID AND THE TRANSFER OF THIS CAPACITY TO UNTREATED ANIMALS." Canadian Journal of Animal Science 65, no. 3 (September 1, 1985): 647–52. http://dx.doi.org/10.4141/cjas85-076.
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Nitrate, given intraruminally (0.1 g NO−3 per kg of body weight) to cattle, stimulated the capacity of the rumen microflora to degrade nitrite (NO−2) and nitrate in vitro. Threefold to fourfold increases in rates of NO−2 and NO−3 reduction were observed during NO−3 treatment. The treatment also appeared to stimulate nitropropanol degradation but this effect was less pronounced. The enhanced capacity of rumen microbes to degrade NO−2 and NO−3 was transferred to noninduced (untreated) animals housed in adjacent pens. The transfer of induced metabolism was not observed when induced animals were widely separated from the noninduced ones. This apparent transfer of microbial activities between adjacent animals may complicate studies in which treated and control animals are not separately housed. Key words: Nitrate, nitrite, nitropropanol, induction, degradation, cattle
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Afshar, Sepideh, Christopher Kim, Harold G. Monbouquette, and Imke Schröder. "Effect of Tungstate on Nitrate Reduction by the Hyperthermophilic Archaeon Pyrobaculum aerophilum." Applied and Environmental Microbiology 64, no. 8 (August 1, 1998): 3004–8. http://dx.doi.org/10.1128/aem.64.8.3004-3008.1998.
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ABSTRACT Pyrobaculum aerophilum, a hyperthermophilic archaeon, can respire either with low amounts of oxygen or anaerobically with nitrate as the electron acceptor. Under anaerobic growth conditions, nitrate is reduced via the denitrification pathway to molecular nitrogen. This study demonstrates that P. aerophilumrequires the metal oxyanion WO4 2− for its anaerobic growth on yeast extract, peptone, and nitrate as carbon and energy sources. The addition of 1 μM MoO4 2−did not replace WO4 2− for the growth ofP. aerophilum. However, cell growth was completely inhibited by the addition of 100 μM MoO4 2−to the culture medium. At lower tungstate concentrations (0.3 μM and less), nitrite was accumulated in the culture medium. The accumulation of nitrite was abolished at higher WO4 2−concentrations (<0.7 μM). High-temperature enzyme assays for the nitrate, nitrite, and nitric oxide reductases were performed. The majority of all three denitrification pathway enzyme activities was localized to the cytoplasmic membrane, suggesting their involvement in the energy metabolism of the cell. While nitrite and nitric oxide specific activities were relatively constant at different tungstate concentrations, the activity of nitrate reductase was decreased fourfold at WO4 2− levels of 0.7 μM or higher. The high specific activity of the nitrate reductase enzyme observed at low WO4 2− levels (0.3 μM or less) coincided with the accumulation of nitrite in the culture medium. This study documents the first example of the effect of tungstate on the denitrification process of an extremely thermophilic archaeon. We demonstrate here that nitrate reductase synthesis inP. aerophilum occurs in the presence of high concentrations of tungstate.