Mechanism and regulation of ferrous heme-nitric oxide (NO) oxidation in NO synthases

Abstract Background: Endothelial function is impaired in hypercholesterolemia and atherosclerosis. Based on mostly indirect evidence, this impairment is attributed to reduced synthesis or impaired biological activity of endothelium-derived nitric oxide (NO). It was the aim of this study to directly estimate and compare whole-body NO production in normo- and hypercholesterolemia by applying a nonradioactive stable isotope dilution technique in vivo. Methods: We enrolled 12 normocholesterolemic and 24 hypercholesterolemic volunteers who were all clinically healthy. To assess whole-body NO synthesis, we intravenously administered l-[guanidino-(15N2)]-arginine and determined the urinary excretion of 15N-labeled nitrate, the specific end product of NO oxidation in humans, by use of gas chromatography-mass spectrometry. In addition, we measured flow-mediated vasodilation (FMD) of the brachial artery, expression of endothelial NOS (eNOS) in platelets, plasma concentration of the endogenous NOS inhibitor asymmetric dimethylarginine (ADMA), and urinary excretion of 8-isoprostaglandin F2α (8-iso-PGF2α). Results: After infusion of l-[guanidino-(15N2)]-arginine, cumulative excretion of 15N-labeled-nitrate during 48 h was 40% [95% CI 15%–66%] lower in hypercholesterolemic than normocholesterolemic volunteers [mean 9.2 (SE 0.8) μmol vs 15.4 (2.3) μmol/l, P = 0.003]. FMD was on average 36% [4%–67%] lower in hypercholesterolemic than normocholesterolemic volunteers [6.3 (4.0)% vs 9.4 (4.6)%, P = 0.027]. Normalized expression of NOS protein in platelets was also significantly lower in hypercholesterolemic volunteers, whereas there were no significant differences in plasma ADMA concentration or urinary excretion of 8-iso-PGF2α between the 2 groups. Conclusions: This study provides direct evidence for a decreased whole body NO synthesis rate in healthy people with hypercholesterolemia.

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Single-atom iron catalyst with single-vacancy graphene-based substrate as a novel catalyst for NO oxidation: a theoretical study

Catalysis Science & Technology ◽

10.1039/c8cy01225c ◽

2018 ◽

Vol 8 (16) ◽

pp. 4159-4168 ◽

Cited By ~ 32

Author(s):

Weijie Yang ◽

Zhengyang Gao ◽

Xiaoshuo Liu ◽

Xiang Li ◽

Xunlei Ding ◽

...

Keyword(s):

Nitric Oxide ◽

Power Plants ◽

Theoretical Study ◽

Iron Catalyst ◽

No Oxidation ◽

Single Atom ◽

Single Vacancy ◽

Novel Catalyst

Nitric oxide (NO) emitted from coal-fired power plants has raised global concerns.

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Hypoxia inhibits nitric oxide synthesis in isolated rabbit lung

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1997.272.6.l1167 ◽

1997 ◽

Vol 272 (6) ◽

pp. L1167-L1173 ◽

Cited By ~ 13

Author(s):

S. P. Kantrow ◽

Y. C. Huang ◽

A. R. Whorton ◽

E. N. Grayck ◽

J. M. Knight ◽

...

Keyword(s):

Nitric Oxide ◽

Competitive Inhibitor ◽

Oxidation Products ◽

No Oxidation ◽

Severe Hypoxia ◽

No Production ◽

Rabbit Lung ◽

Vasoconstrictor Response ◽

Hypoxic Vasoconstriction ◽

Oxide Synthase

Nitric oxide (NO.) has been proposed to modulate hypoxic vasoconstriction in the lung. The activity of nitric oxide synthase (NOS) can be inhibited by hypoxia because molecular oxygen is a necessary substrate for the enzyme. On the basis of this mechanism, we hypothesized that NOS activity has a key role in regulation of pulmonary vascular tone during hypoxia. We measured oxidation products of NO. released into the vasculature of isolated buffer-perfused rabbit lung ventilated with normoxic (21% O2), moderately hypoxic (5% O2), or anoxic (0% O2) gas using two methods. Mean PO2 in perfusate exiting the lung was 25 Torr during anoxic ventilation and 47 Torr during moderately hypoxic ventilation. We found that the amount of the NO. oxidation product nitrite released into the perfusate was suppressed significantly during ventilation with anoxic but not moderately hypoxic gas. During normoxic ventilation, nitrite release was inhibited by pretreatment with NG-monomethyl-L-arginine, a competitive inhibitor of NOS. To confirm that changes in nitrite concentration reflected changes in NO. release into the perfusate, major oxidation products of NO. (NOx) were assayed using a method for reduction of these products to NO. by vanadium(III) Cl. Release of NOx into the perfusate was suppressed by severe hypoxia (anoxic ventilation), and this effect was reversed by normoxia. Pulmonary vasoconstriction was observed during severe but not moderate hypoxia and was related inversely to the rate of nitrite release. These observations provide evidence that decreased NO. production contributes to the pulmonary vasoconstrictor response during severe hypoxia.

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Basal and stimulated nitric oxide in control of kidney function in the aging rat

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1997.272.6.r1747 ◽

1997 ◽

Vol 272 (6) ◽

pp. R1747-R1753 ◽

Cited By ~ 8

Author(s):

C. Hill ◽

A. M. Lateef ◽

K. Engels ◽

L. Samsell ◽

C. Baylis

Keyword(s):

Nitric Oxide ◽

Vascular Resistance ◽

Pressor Response ◽

Renal Vascular Resistance ◽

Oxidation Products ◽

No Oxidation ◽

No Production ◽

Sprague Dawley ◽

Vasoconstrictor Response ◽

Renal Vascular

To investigate the activity of nitric oxide (NO) in control of renal hemodynamics during aging, studies were conducted on conscious Sprague-Dawley rats aged 3-5 mo (young, Y) and 18-22 mo (old, O). Blood pressure (BP) and renal vascular resistance (RVR) were higher in O vs. Y in control, and acute systemic NO synthesis inhibition (NOSI) increased BP and RVR, with an enhanced renal vasoconstrictor response in O. Infusion of the NO substrate L-arginine produced similar, selective renal vasodilation in both groups. The endothelium-dependent vasodilator acetylcholine caused similar falls in BP and RVR, whereas sodium nitroprusside produced an exaggerated depressor response in O vs. Y without falls in RVR in either age group. Urinary excretion of the stable NO oxidation products (NOx) decreased with age, suggesting a decline in the overall somatic NO production. In conclusion, basal tonically produced NO has a more pronounced role in maintenance of renal perfusion in aging, whereas L-arginine- and agonist-stimulated renal vasodilation is not impaired with age. NO production from some source may be reduced with aging, as indicated by falls in 24-h NOX excretion, although the similarity in pressor response and enhanced renal vasoconstrictor response to NOSI suggests that the role of NO in control of total peripheral and renal vascular resistance is maintained.

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Taming NO oxidation efficiency by γ-MnO2 morphology regulation

Catalysis Science & Technology ◽

10.1039/d0cy00573h ◽

2020 ◽

Vol 10 (17) ◽

pp. 5996-6005

Author(s):

Lei Chen ◽

Jinping Zhang ◽

Yuxin Li ◽

Xiaomei Wu ◽

Zaoxiao Zhang ◽

...

Keyword(s):

Nitric Oxide ◽

Fossil Fuels ◽

No Oxidation ◽

Global Concern ◽

Oxidation Efficiency ◽

Oxidation Of No

Nitric oxide (NO) emitted from the combustion of fossil fuels has drawn global concern, and the oxidation of NO contributes greatly to the DeNOx process.

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Acute effect of insulin on nitric oxide synthesis in humans: a precursor-product isotopic study

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00481.2006 ◽

2007 ◽

Vol 293 (3) ◽

pp. E776-E782 ◽

Cited By ~ 15

Author(s):

Paolo Tessari ◽

Anna Coracina ◽

Lucia Puricelli ◽

Monica Vettore ◽

Alessandra Cosma ◽

...

Keyword(s):

Nitric Oxide ◽

Acute Effect ◽

Oxidation Products ◽

No Oxidation ◽

Metabolic Effects ◽

Whole Body ◽

Fasting State ◽

Isotopic Study ◽

Euglycemic Hyperinsulinemic Clamp

Nitric oxide (NO) is a key regulatory molecule with wide vascular, cellular, and metabolic effects. Insulin affects NO synthesis in vitro. No data exist on the acute effect of insulin on NO kinetics in vivo. By employing a precursor-product tracer method in humans, we have directly estimated the acute effect of insulin on intravascular NOx (i.e., the NO oxidation products) fractional (FSR) and absolute (ASR) synthesis rates in vivo. Nine healthy male volunteers were infused iv with l-[15N2-guanidino]arginine ([15N2]arginine) for 6 h. Timed measurements of 15NOx and [15N2]arginine enrichments in whole blood were performed in the first 3 h in the fasting state and then following a 3-h euglycemic-hyperinsulinemic clamp (with plasma insulin raised to ≈1,000 pmol/l). In the last 60 min of each experimental period, at ≈steady-state arginine enrichment, a linear increase of 15NOx enrichment (mean r = 0.9) was detected in both experimental periods. In the fasting state, NOx FSR was 27.4 ± 4.3%/day, whereas ASR was 0.97 ± 0.36 mmol/day, accounting for 0.69 ± 0.27% of arginine flux. Following hyperinsulinemia, both FSR and ASR of NOx increased (FSR by ≈50%, to 42.4 ± 6.7%/day, P < 0.005; ASR by ≈25%, to 1.22 ± 0.41 mmol/day, P = 0.002), despite a ≈20–30% decrease of arginine flux and concentration. The fraction of arginine flux used for NOx synthesis was doubled, to 1.13 ± 0.35% ( P < 0.003). In conclusion, whole body NOx synthesis can be directly measured over a short observation time with stable isotope methods in humans. Insulin acutely stimulates NOx synthesis from arginine.

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Ascorbic Acid Catalyzes Nitric Oxide Production from Nitrite Ions.

Blood ◽

10.1182/blood.v108.11.1574.1574 ◽

2006 ◽

Vol 108 (11) ◽

pp. 1574-1574 ◽

Cited By ~ 2

Author(s):

Nathawut Sibmooh ◽

Barbora Piknova ◽

Alan N. Schechter

Keyword(s):

Nitric Oxide ◽

Ascorbic Acid ◽

Rate Constant ◽

Dehydroascorbic Acid ◽

Nitrite Reduction ◽

Erythrocyte Membranes ◽

No Production ◽

Ferrous Ions ◽

Physiological Conditions ◽

Ferrous Heme

Abstract We have previously shown that nitrite ions can be reduced by hemoglobin to nitric oxide (NO), a ubiquitous signaling molecule and potent vasodilator. Nitrite serves as a stable tissue and vascular source for NO production; the reduction reaction is maximal at about 50% oxygen saturation values and is enhanced at low pH but little is known about other effectors of this reaction. In the current work, we studied the effect of ascorbic acid on nitrite reduction under physiological conditions using chemiluminescence to quantify NO production. In physiological buffer, this reaction has a rate constant of about 1×10−5 M−1.s−1. Thus, a significant production of NO would likely occur in plasma only at pharmacological levels of ascorbic acid (> 1 mM) although lowering pH below 7.0 markedly enhances this reaction. Loading human erythrocytes with 0.5 mM dehydroascorbic acid, which is in redox equilibrium with ascorbic acid and which can significantly raise intracellular ascorbic acid levels, increased basal levels of nitrite ions from 42±9.0 nM to 98±56 nM. Uptake of nitrite ions into erythrocytes by incubation in 10 μM nitrite was increased about 1.5 fold by dehydroascorbic acid and the half-time of nitrite loss was slowed to the same extent. Ascorbic acid also reduced free ferric heme in erythrocytes and plasma to ferrous heme which catalyzed the reduction of nitrite to NO with a rate constant of 2.3×103 M−1.s−1 under physiological conditions. However, free ferrous ions did not significantly produce NO in physiological buffer (rate constant = 1.8×10−2 M−1.s−1). The reaction of ferrous heme with nitrite was not affected by heme binding to proteins such as hemopexin and albumin, or erythrocyte membranes. These results suggest that physiological levels of ascorbic acid (20–80 μM in plasma and erythrocytes) may act to catalyze NO production in the blood by promoting the reduction of nitrite ions by free ferrous heme and by increasing intra-erythrocytic levels of nitrite ions which can be reduced to NO by deoxyhemoglobin.

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Pulmonary alveolar epithelial inducible NO synthase gene expression: regulation by inflammatory mediators

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1995.268.3.l501 ◽

1995 ◽

Vol 268 (3) ◽

pp. L501-L508 ◽

Cited By ~ 18

Author(s):

H. H. Gutierrez ◽

B. R. Pitt ◽

M. Schwarz ◽

S. C. Watkins ◽

C. Lowenstein ◽

...

Keyword(s):

Nitric Oxide ◽

Gene Expression Regulation ◽

Interleukin 1 ◽

Alveolar Epithelium ◽

Cell Types ◽

Oxidation Products ◽

No Oxidation ◽

Target Cells ◽

Cell Permeabilization ◽

Necrosis Factor Alpha

Nitric oxide (.NO) is a short-lived mediator that can be induced by different cytokines and lipopolysaccharide (LPS) in a variety of cell types and produces many physiological and metabolic changes in target cells. In the current study, we show that a combination of cytokines, LPS, and zymosan-activated serum (ZAS; called for convenience cytomix Z) induces production of high concentrations of the NO oxidation products nitrite (NO2-) and nitrate (NO3-) by cultured rat fetal lung epithelial type II cells in a time-dependent fashion. Interferon-gamma and tumor necrosis factor-alpha alone did not significantly affect .NO synthesis, whereas ZAS, LPS, and interleukin-1 beta caused only a modest increase in formation of .NO oxidation products. Production of NO2- and NO3- was inhibited by NG-monomethyl-L-arginine and cyclohexmide. After exposure of these cells to a combination of the above cytokines, Escherichia coli LPS, and ZAS (cytomix Z), enhanced inducible nitric oxide synthase (iNOS) expression was indicated by an elevation in steady-state mRNA specific for iNOS (via Northern blot analysis) and increased immunofluorescence for iNOS after cell permeabilization, incubation with anti-iNOS antibody, and treatment with Cy3.18-conjugated rabbit-specific antibody. The extent of inflammatory mediator-induced.NO production by alveolar epithelium, which exceeds that of other lung cell types, reveals new insight into mechanisms of pulmonary host defense and pathways of free radical-mediated lung injury.

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Cytokine-induced metabolic effects in human adipocytes are independent of endogenous nitric oxide

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00374.2005 ◽

2006 ◽

Vol 290 (6) ◽

pp. E1068-E1077 ◽

Cited By ~ 9

Author(s):

Philippe Linscheid ◽

Dalma Seboek ◽

Henryk Zulewski ◽

Arnaud Scherberich ◽

Nenad Blau ◽

...

Keyword(s):

Nitric Oxide ◽

Adipose Tissue ◽

Metabolic Regulation ◽

Oxidation Products ◽

No Oxidation ◽

Metabolic Effects ◽

Inos Mrna ◽

Peroxisome Proliferator ◽

Human Adipocytes ◽

Nos Inhibitors

Nitric oxide (NO) has been recognized as a potential mediator of inflammation-induced metabolic alterations, including insulin resistance. However, expression mechanisms and potential roles of endothelial and inducible NO synthases (eNOS and iNOS, respectively) in human adipocytes are poorly understood. In the present study, we aimed to analyze several aspects of NO-related gene expression and metabolite synthesis in basal and inflammation-activated human adipocyte models. eNOS mRNA was highly expressed in omental and to a lesser extent in human subcutaneous adipose tissue biopsies, but not in purified adipocytes, in mesenchymal stem cell (MSC)- and in preadipocyte-derived adipocytes, respectively. Trace amounts of iNOS mRNA were detected in adipose tissue samples of donors with abdominal infection, as opposed to noninfected subjects. Interferon-γ, in combination with interleukin-1β or lipopolysaccharide, evoked a transient (4 h < time < 24 h) iNOS mRNA expression in human MSC and preadipocyte-derived adipocytes, respectively. This induction was preceded by cytokine-specific mRNAs. In addition, it was accompanied by an activation of the tetrahydrobiopterin synthesis pathway and by inhibition of peroxisome proliferator-activated receptor-γ2. In contrast to murine 3T3-L1-derived adipocytes, iNOS protein and NO oxidation products remained undetectable in iNOS mRNA-positive human adipocytes. Accordingly, coadministration of NOS inhibitors (i.e., Nω-nitro-l-arginine methyl ester, Nω-monomethyl-l-arginine, and 1400W) had no effects on insulin-mediated glucose uptake and lipolysis. We conclude that, in human adipocytes, endogenous NO is not involved in metabolic regulation during either basal or cytokine-activated conditions.

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