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Updating NO •/HNO interconversion under physiological conditions: A biological implication overview. J Inorg Biochem 2020; 216:111333. [PMID: 33385637 DOI: 10.1016/j.jinorgbio.2020.111333] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 11/13/2020] [Accepted: 12/05/2020] [Indexed: 12/12/2022]
Abstract
Azanone (HNO/NO-), also called nitroxyl, is a highly reactive compound whose biological role is still a matter of debate. A key issue that remains to be clarified regarding HNO and its biological activity is that of its endogenous formation. Given the overlap of the molecular targets and reactivity of nitric oxide (NO•) and HNO, its chemical biology was perceived to be similar to that of NO• as a biological signaling agent. However, despite their closely related reactivity, NO• and HNO's biochemical pathways are quite different. Moreover, the reduction of nitric oxide to azanone is possible but necessarily coupled to other reactions, which drive the reaction forward, overcoming the unfavorable thermodynamic barrier. The mechanism of this NO•/HNO interplay and its downstream effects in different contexts were studied recently, showing that more than fifteen moderate reducing agents react with NO• producing HNO. Particularly, it is known that the reaction between nitric oxide and hydrogen sulfide (H2S) produces HNO. However, this rate constant was not reported yet. In this work, firstly the NO•/H2S effective rate constant was measured as a function of the pH. Then, the implications of these chemical (non-enzymatic), biologically compatible, routes to endogenous HNO formation was discussed. There is no doubt that HNO could be (is?) a new endogenously produced messenger that mediates specific physiological responses, many of which were attributed yet to direct NO• effects.
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The Physiological Implications of S-Nitrosoglutathione Reductase (GSNOR) Activity Mediating NO Signalling in Plant Root Structures. Antioxidants (Basel) 2020; 9:antiox9121206. [PMID: 33266126 PMCID: PMC7760381 DOI: 10.3390/antiox9121206] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 11/22/2020] [Accepted: 11/27/2020] [Indexed: 12/12/2022] Open
Abstract
Nitrogen remains an important macronutrient in plant root growth due to its application in amino acid production, in addition to its more elusive role in cellular signalling through nitric oxide (NO). NO is widely accepted as an important signalling oxidative radical across all organisms, leading to its study in a wide range of biological pathways. Along with its more stable NO donor, S-nitrosoglutathione (GSNO), formed by NO non-enzymatically in the presence of glutathione (GSH), NO is a redox-active molecule capable of mediating target protein cysteine thiols through the post translational modification, S-nitrosation. S-nitrosoglutathione reductase (GSNOR) thereby acts as a mediator to pathways regulated by NO due to its activity in the irreversible reduction of GSNO to oxidized glutathione (GSSG) and ammonia. GSNOR is thought to be pleiotropic and often acts by mediating the cellular environment in response to stress conditions. Under optimal conditions its activity leads to growth by transcriptional upregulation of the nitrate transporter, NRT2.1, and through its interaction with phytohormones like auxin and strigolactones associated with root development. However, in response to highly nitrosative and oxidative conditions its activity is often downregulated, possibly through an S-nitrosation site on GSNOR at cys271, Though GSNOR knockout mutated plants often display a stunted growth phenotype in all structures, they also tend to exhibit a pre-induced protective effect against oxidative stressors, as well as an improved immune response associated with NO accumulation in roots.
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Oszajca M, Wądołek A, Hooper J, Brindell M, van Eldik R, Stochel G. Urban Particulate Matter-Induced Decomposition of S-Nitrosoglutathione Relevant to Aberrant Nitric Oxide Biological Signaling. CHEMSUSCHEM 2019; 12:661-671. [PMID: 30427595 DOI: 10.1002/cssc.201802201] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Revised: 11/12/2018] [Indexed: 06/09/2023]
Abstract
Exposure to airborne particulate matter (PM) is associated with hazardous effects on human health. Soluble constituents of PM may be released in biological fluids and disturb the precisely tuned nitric oxide signaling processes. The influence of aqueous extracts from two types of airborne urban PM (SRM 1648a, a commercially available sample, and KR PM2.5, a sample collected "in-house" in Krakow, Poland) on the stability of S-nitrosoglutathione (GSNO) was investigated. The particle interfaces had no direct effect on the studied reaction, but extracts obtained from both samples facilitated NO release from GSNO. The effectiveness of NO release was significantly affected by glutathione (GSH) and ascorbic acid (AscA). Examination of the combined influence of Cu2+ , Fe3+ , and reductants on GSNO stability revealed copper to be the main GSNO decomposing species. Computational models of nitrosothiols interacting with metal oxide substrates and solvated metal ions support these claims. The study stresses the importance of the interplay between metal ions and biological reductants in S-nitrosothiols decomposition.
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Affiliation(s)
- Maria Oszajca
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - Anna Wądołek
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - James Hooper
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - Małgorzata Brindell
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
| | - Rudi van Eldik
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
- Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, Egerlandstr. 1, 91058, Erlangen, Germany
| | - Grażyna Stochel
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Krakow, Poland
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Benhar M. Roles of mammalian glutathione peroxidase and thioredoxin reductase enzymes in the cellular response to nitrosative stress. Free Radic Biol Med 2018; 127:160-164. [PMID: 29378334 DOI: 10.1016/j.freeradbiomed.2018.01.028] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 01/22/2018] [Accepted: 01/23/2018] [Indexed: 10/18/2022]
Abstract
Mammalian cells employ elaborate antioxidant systems to effectively handle reactive oxygen and nitrogen species (ROS and RNS). At the heart of these systems operate two selenoprotein families consisting of glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) enzymes. Although mostly studied in the context of oxidative stress, considerable evidence has amassed to indicate that these selenoenzymes also play important roles in nitrosative stress responses. GPx and TrxR, together with their redox partners, metabolize nitrosothiols and peroxynitrite, two major RNS. As such, these enzymes play active roles in the cellular defense against nitrosative stress. However, under certain conditions, these enzymes are inactivated by nitrosothiols or peroxynitrite, which may exacerbate oxidative and nitrosative stress in cells. The selenol groups in the active sites of GPx and TrxR enzymes are critically involved in these beneficial and detrimental processes. Further elucidation of the biochemical interactions between distinct RNS and GPx/TrxR will lead to a better understanding of the roles of these selenoenzymes in cellular homeostasis and disease.
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Affiliation(s)
- Moran Benhar
- Department of Biochemistry, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa 31096, Israel.
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5
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Strumillo J, Nowak KE, Krokosz A, Rodacka A, Puchala M, Bartosz G. The role of resveratrol and melatonin in the nitric oxide and its oxidation products mediated functional and structural modifications of two glycolytic enzymes: GAPDH and LDH. Biochim Biophys Acta Gen Subj 2018; 1862:877-885. [DOI: 10.1016/j.bbagen.2017.12.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 12/06/2017] [Accepted: 12/27/2017] [Indexed: 11/25/2022]
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6
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Monteiro HP, Ogata FT, Stern A. Thioredoxin promotes survival signaling events under nitrosative/oxidative stress associated with cancer development. Biomed J 2017; 40:189-199. [PMID: 28918907 PMCID: PMC6136292 DOI: 10.1016/j.bj.2017.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 06/05/2017] [Accepted: 06/05/2017] [Indexed: 02/07/2023] Open
Abstract
Accumulating mutations may drive cells into the acquisition of abnormal phenotypes that are characteristic of cancer cells. Cancer cells feature profound alterations in proliferation programs that result in a new population of cells that overrides normal tissue construction and maintenance programs. To achieve this goal, cancer cells are endowed with up regulated survival signaling pathways. They also must counteract the cytotoxic effects of high levels of nitric oxide (NO) and of reactive oxygen species (ROS), which are by products of cancer cell growth. Accumulating experimental evidence associates cancer cell survival with their capacity to up-regulate antioxidant systems. Elevated expression of the antioxidant protein thioredoxin-1 (Trx1) has been correlated with cancer development. Trx1 has been characterized as a multifunctional protein, playing different roles in different cell compartments. Trx1 migrates to the nucleus in cells exposed to nitrosative/oxidative stress conditions. Trx1 nuclear migration has been related to the activation of transcription factors associated with cell survival and cell proliferation. There is a direct association between the p21Ras-ERK1/2 MAP Kinases survival signaling pathway and Trx1 nuclear migration under nitrosative stress. The expression of the cytoplasmic protein, the thioredoxin-interacting protein (Txnip), determines the change in Trx1 cellular compartmentalization. The anti-apoptotic actions of Trx1 and its denitrosylase activity occur in the cytoplasm and serve as important regulators of cell survival. Within this context, this review focuses on the participation of Trx1 in cells under nitrosative/oxidative stress in survival signaling pathways associated with cancer development.
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Affiliation(s)
- Hugo P Monteiro
- Department of Biochemistry, Center for Cellular and Molecular Therapy - CTCMol, Paulista Medical School/Federal University of São Paulo, SP, Brazil
| | - Fernando T Ogata
- Department of Biochemistry, Center for Cellular and Molecular Therapy - CTCMol, Paulista Medical School/Federal University of São Paulo, SP, Brazil; Division of Biochemistry, Medical Biochemistry & Biophysics, Karolinska Institutet, Stockholm, Sweden
| | - Arnold Stern
- New York University School of Medicine, New York, NY, USA.
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Dalgliesh AJ, Liu ZZ, Griffiths LG. Magnesium Presence Prevents Removal of Antigenic Nuclear-Associated Proteins from Bovine Pericardium for Heart Valve Engineering. Tissue Eng Part A 2017; 23:609-621. [PMID: 28178887 DOI: 10.1089/ten.tea.2016.0405] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Current heart valve prostheses are associated with significant complications, including aggressive immune response, limited valve life expectancy, and inability to grow in juvenile patients. Animal derived "tissue" valves undergo glutaraldehyde fixation to mask tissue antigenicity; however, chronic immunological responses and associated calcification still commonly occur. A heart valve formed from an unfixed bovine pericardium (BP) extracellular matrix (ECM) scaffold, in which antigenic burden has been eliminated or significantly reduced, has potential to overcome deficiencies of current bioprostheses. Decellularization and antigen removal methods frequently use sequential solutions extrapolated from analytical chemistry approaches to promote solubility and removal of tissue components from resultant ECM scaffolds. However, the extent to which such prefractionation strategies may inhibit removal of antigenic tissue components has not been explored. We hypothesize that presence of magnesium in prefractionation steps causes DNA precipitation and reduces removal of nuclear-associated antigenic proteins. Keeping all variables consistent bar the addition or absence of magnesium (2 mM magnesium chloride hexahydrate), residual BP ECM scaffold antigenicity and removed antigenicity were assessed, along with residual and removed DNA content, ECM morphology, scaffold composition, and recellularization potential. Furthermore, we used proteomic methods to determine the mechanism by which magnesium presence or absence affects scaffold residual antigenicity. This study demonstrates that absence of magnesium from antigen removal solutions enhances solubility and subsequent removal of antigenic nuclear-associated proteins from BP. We therefore conclude that the primary mechanism of action for magnesium removal during antigen removal processes is avoidance of DNA precipitation, facilitating solubilization and removal of nuclear-associated antigenic proteins. Future studies are necessary to further facilitate solubility and removal of nuclear-associated antigenic proteins from xenogeneic ECM scaffolds, in addition to an in vivo assessing of the material.
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Affiliation(s)
- Ailsa J Dalgliesh
- 1 Department of Veterinary Medicine, Medicine and Epidemiology, University of California , Davis, Davis, California.,2 Department of Cardiovascular Diseases, Mayo Clinic , Rochester, Minnesota
| | - Zhi Zhao Liu
- 1 Department of Veterinary Medicine, Medicine and Epidemiology, University of California , Davis, Davis, California
| | - Leigh G Griffiths
- 1 Department of Veterinary Medicine, Medicine and Epidemiology, University of California , Davis, Davis, California.,2 Department of Cardiovascular Diseases, Mayo Clinic , Rochester, Minnesota
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Lancaster JR. How are nitrosothiols formed de novo in vivo? Arch Biochem Biophys 2016; 617:137-144. [PMID: 27794428 DOI: 10.1016/j.abb.2016.10.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Revised: 10/23/2016] [Accepted: 10/25/2016] [Indexed: 02/07/2023]
Abstract
The biological mechanisms of de novo formation of cellular nitrosothiols (as opposed to transnitrosation) are reviewed. The approach is to introduce chemical foundations for each mechanism, followed by evidence in biological systems. The general categories include mechanisms involving nitrous acid, NO autoxidation and oxidant stress, redox active and inactive metal ions, and sulfide/persulfide. Important conclusions/speculations are that de novo cellular thiol nitrosation (1) is an oxidative process, and so should be considered within the family of other thiol oxidative modifications, (2) may not involve a single dominant process but depends on the specific conditions, (3) does not involve O2 under at least some conditions, and (4) may serve to provide a "substrate pool" of protein cysteine nitrosothiol which could, through subsequent enzymatic transnitrosation/denitrosation, be "rearranged" to accomplish the specificity and regulatory control required for effective post-translational signaling.
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Affiliation(s)
- Jack R Lancaster
- Department of Pharmacology & Chemical Biology, University of Pittsburgh School of Medicine, United States; Department of Medicine, University of Pittsburgh School of Medicine, United States; Department of Surgery, University of Pittsburgh School of Medicine, United States
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Wynia-Smith SL, Smith BC. Nitrosothiol formation and S-nitrosation signaling through nitric oxide synthases. Nitric Oxide 2016; 63:52-60. [PMID: 27720836 DOI: 10.1016/j.niox.2016.10.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 08/31/2016] [Accepted: 10/03/2016] [Indexed: 12/16/2022]
Abstract
Nitric oxide (NO) is a gaseous signaling molecule impacting many biological pathways. NO is produced in mammals by three nitric oxide synthase (NOS) isoforms: neuronal (nNOS), endothelial (eNOS), and inducible (iNOS). nNOS and eNOS produce low concentrations of NO for paracrine signaling; NO produced and released from one cell diffuses to a neighboring cell where it binds and activates soluble guanylyl cyclase (sGC). iNOS produces high concentrations of NO using NO toxicity to amplify the innate immune response. Recent work has also defined protein cysteine S-nitrosation as a pathway of sGC-independent NO signaling. Though many studies have shown that S-nitrosation regulates the activity of NOS isoforms and other proteins in vivo, many issues need to be resolved to establish S-nitrosation as a viable signaling mechanism. Several chemical mechanisms result in S-nitrosation including transition metal-catalyzed pathways, NO oxidation followed by thiolate reaction, and thiyl radical recombination with NO. Once formed, nitrosothiols can be transferred between cellular cysteine residues via transnitrosation reactions. However, it is largely unclear how these chemical processes result in selective S-nitrosation of specific cellular cysteine residues. S-nitrosation site selectivity may be imparted via direct interactions or colocalization with NOS isoforms that focus chemical or transnitrosation mechanisms of nitrosothiol formation or transfer. Here, we discuss chemical mechanisms of nitrosothiol formation, S-nitrosation of NOS isoforms, and potential S-nitrosation signaling cascades resulting from NOS S-nitrosation.
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Affiliation(s)
- Sarah L Wynia-Smith
- Department of Biochemistry and Redox Biology Program, Medical College of Wisconsin, Milwaukee, WI, USA
| | - Brian C Smith
- Department of Biochemistry and Redox Biology Program, Medical College of Wisconsin, Milwaukee, WI, USA.
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Kollau A, Russwurm M, Neubauer A, Rechberger G, Schmidt K, Koesling D, Fassett J, Schrammel A, Mayer B. Scavenging of nitric oxide by hemoglobin in the tunica media of porcine coronary arteries. Nitric Oxide 2016; 54:8-14. [PMID: 26805578 PMCID: PMC5933522 DOI: 10.1016/j.niox.2016.01.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 01/19/2016] [Accepted: 01/20/2016] [Indexed: 11/23/2022]
Abstract
Scavenging of nitric oxide (NO) often interferes with studies on NO signaling in cell-free preparations. We observed that formation of cGMP by NO-stimulated purified soluble guanylate cyclase (sGC) was virtually abolished in the presence of cytosolic preparations of porcine coronary arteries, with the scavenging activity localized in the tunica media (smooth muscle layer). Electrochemical measurement of NO release from a donor compound and light absorbance spectroscopy showed that cytosolic preparations contained a reduced heme protein that scavenged NO. This protein, which reacted with anti-human hemoglobin antibodies, was efficiently removed from the preparations by haptoglobin affinity chromatography. The cleared cytosols showed only minor scavenging of NO according to electrochemical measurements and did not decrease cGMP formation by NO-stimulated sGC. In contrast, the column flow-through caused a nearly 2-fold increase of maximal sGC activity (from 33.1 ± 1.6 to 54.9 ± 2.2 μmol × min(-1) × mg(-1)). The proteins retained on the affinity column were identified as hemoglobin α and β subunits. The results indicate that hemoglobin, presumably derived from vasa vasorum erythrocytes, is present and scavenges NO in preparations of porcine coronary artery smooth muscle. Selective removal of hemoglobin-mediated scavenging unmasked stimulation of maximal NO-stimulated sGC activity by a soluble factor expressed in vascular tissue.
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Affiliation(s)
- Alexander Kollau
- Institute of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of Graz, Austria
| | - Michael Russwurm
- Department of Pharmacology and Toxicology, Ruhr University Bochum, Germany
| | - Andrea Neubauer
- Institute of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of Graz, Austria
| | - Gerald Rechberger
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, Austria; Omics-Center, BioTechMed-Graz, Austria
| | - Kurt Schmidt
- Institute of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of Graz, Austria
| | - Doris Koesling
- Department of Pharmacology and Toxicology, Ruhr University Bochum, Germany
| | - John Fassett
- Institute of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of Graz, Austria
| | - Astrid Schrammel
- Institute of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of Graz, Austria
| | - Bernd Mayer
- Institute of Pharmaceutical Sciences, Department of Pharmacology and Toxicology, University of Graz, Austria.
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11
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Postprandial lipids accelerate and redirect nitric oxide consumption in plasma. Nitric Oxide 2016; 55-56:70-81. [PMID: 27021272 DOI: 10.1016/j.niox.2016.03.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2015] [Revised: 03/16/2016] [Accepted: 03/17/2016] [Indexed: 02/03/2023]
Abstract
Nitric oxide (NO) and O2 are both three-to four-fold more soluble in biological lipids than in aqueous solutions. Their higher concentration within plasma lipids accelerates NO autoxidation to an extent that may be of importance to overall NO bioactivity. This study was undertaken to test the hypothesis that increased plasma lipids after a high-fat meal appreciably accelerate NO metabolism and alter the byproducts formed. We found that plasma collected from subjects after consumption of a single high-fat meal had a higher capacity for NO consumption and consumed NO more rapidly compared to fasting plasma. This increased NO consumption showed a direct correlation with plasma triglyceride concentrations (p = 0.006). The accelerated NO consumption in postprandial plasma was reversed by removal of the lipids from the plasma, was mimicked by the addition of hydrophobic micelles to aqueous buffer, and could not be explained by the presence of either free hemoglobin or ceruloplasmin. The products of NO consumption were shifted in postprandial plasma, with 55% more nitrite (n = 12, p = 0.002) but 50% less SNO (n = 12, p = 0.03) production compared to matched fasted plasma. Modeling calculations indicated that NO autoxidation was accelerated by about 48-fold in the presence of plasma lipids. We conclude that postprandial triglyceride-rich lipoproteins exert a significant influence on NO metabolism in plasma.
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12
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Nitric oxide and the thioredoxin system: a complex interplay in redox regulation. Biochim Biophys Acta Gen Subj 2015; 1850:2476-84. [DOI: 10.1016/j.bbagen.2015.09.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2015] [Revised: 08/26/2015] [Accepted: 09/15/2015] [Indexed: 12/11/2022]
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Heine CL, Schmidt R, Geckl K, Schrammel A, Gesslbauer B, Schmidt K, Mayer B, Gorren ACF. Selective Irreversible Inhibition of Neuronal and Inducible Nitric-oxide Synthase in the Combined Presence of Hydrogen Sulfide and Nitric Oxide. J Biol Chem 2015; 290:24932-44. [PMID: 26296888 PMCID: PMC4599001 DOI: 10.1074/jbc.m115.660316] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Indexed: 11/06/2022] Open
Abstract
Citrulline formation by both human neuronal nitric-oxide synthase (nNOS) and mouse macrophage inducible NOS was inhibited by the hydrogen sulfide (H2S) donor Na2S with IC50 values of ∼2.4·10−5 and ∼7.9·10−5m, respectively, whereas human endothelial NOS was hardly affected at all. Inhibition of nNOS was not affected by the concentrations of l-arginine (Arg), NADPH, FAD, FMN, tetrahydrobiopterin (BH4), and calmodulin, indicating that H2S does not interfere with substrate or cofactor binding. The IC50 decreased to ∼1.5·10−5m at pH 6.0 and increased to ∼8.3·10−5m at pH 8.0. Preincubation of concentrated nNOS with H2S under turnover conditions decreased activity after dilution by ∼70%, suggesting irreversible inhibition. However, when calmodulin was omitted during preincubation, activity was not affected, suggesting that irreversible inhibition requires both H2S and NO. Likewise, NADPH oxidation was inhibited with an IC50 of ∼1.9·10−5m in the presence of Arg and BH4 but exhibited much higher IC50 values (∼1.0–6.1·10−4m) when Arg and/or BH4 was omitted. Moreover, the relatively weak inhibition of nNOS by Na2S in the absence of Arg and/or BH4 was markedly potentiated by the NO donor 1-(hydroxy-NNO-azoxy)-l-proline, disodium salt (IC50 ∼ 1.3–2.0·10−5m). These results suggest that nNOS and inducible NOS but not endothelial NOS are irreversibly inhibited by H2S/NO at modest concentrations of H2S in a reaction that may allow feedback inhibition of NO production under conditions of excessive NO/H2S formation.
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Affiliation(s)
| | | | - Kerstin Geckl
- From the Departments of Pharmacology and Toxicology and
| | | | - Bernd Gesslbauer
- Pharmaceutical Chemistry, Institute of Pharmaceutical Sciences, Karl Franzens University Graz, A-8010 Graz, Austria
| | - Kurt Schmidt
- From the Departments of Pharmacology and Toxicology and
| | - Bernd Mayer
- From the Departments of Pharmacology and Toxicology and
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Śpiewak K, Stochel G, Brindell M. Influence of redox activation of NAMI-A on affinity to serum proteins: transferrin and albumin. J COORD CHEM 2015. [DOI: 10.1080/00958972.2015.1067692] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- K. Śpiewak
- Faculty of Chemistry, Department of Inorganic Chemistry, Jagiellonian University, Krakow, Poland
| | - G. Stochel
- Faculty of Chemistry, Department of Inorganic Chemistry, Jagiellonian University, Krakow, Poland
| | - M. Brindell
- Faculty of Chemistry, Department of Inorganic Chemistry, Jagiellonian University, Krakow, Poland
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