1
|
Wölkart G, Kollau A, Russwurm M, Koesling D, Schrammel A, Mayer B. Varied effects of tobacco smoke and e-cigarette vapor suggest that nicotine does not affect endothelium-dependent relaxation and nitric oxide signaling. Sci Rep 2023; 13:15833. [PMID: 37739972 PMCID: PMC10517138 DOI: 10.1038/s41598-023-42750-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 09/14/2023] [Indexed: 09/24/2023] Open
Abstract
Chronic smoking causes dysfunction of vascular endothelial cells, evident as a reduction of flow-mediated dilation in smokers, but the role of nicotine is still controversial. Given the increasing use of e-cigarettes and other nicotine products, it appears essential to clarify this issue. We studied extracts from cigarette smoke (CSE) and vapor from e-cigarettes (EVE) and heated tobacco (HTE) for their effects on vascular relaxation, endothelial nitric oxide signaling, and the activity of soluble guanylyl cyclase. The average nicotine concentrations of CSE, EVE, and HTE were 164, 800, and 85 µM, respectively. At a dilution of 1:3, CSE almost entirely inhibited the relaxation of rat aortas and porcine coronary arteries to acetylcholine and bradykinin, respectively, while undiluted EVE, with a 15-fold higher nicotine concentration, had no significant effect. With about 50% inhibition at 1:2 dilution, the effect of HTE was between CSE and EVE. Neither extract affected endothelium-independent relaxation to an NO donor. At the dilutions tested, CSE was not toxic to cultured endothelial cells but, in contrast to EVE, impaired NO signaling and inhibited NO stimulation of soluble guanylyl cyclase. Our results demonstrate that nicotine does not mediate the impaired endothelium-dependent vascular relaxation caused by smoking.
Collapse
Affiliation(s)
- Gerald Wölkart
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Universität Graz, Humboldtstraße 46, 8010, Graz, Austria
| | - Alexander Kollau
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Universität Graz, Humboldtstraße 46, 8010, Graz, Austria
| | - Michael Russwurm
- Department of Pharmacology and Toxicology, Ruhr-Universität Bochum, MA N1-39, 44780, Bochum, Germany
| | - Doris Koesling
- Department of Pharmacology and Toxicology, Ruhr-Universität Bochum, MA N1-39, 44780, Bochum, Germany
| | - Astrid Schrammel
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Universität Graz, Humboldtstraße 46, 8010, Graz, Austria
| | - Bernd Mayer
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Universität Graz, Humboldtstraße 46, 8010, Graz, Austria.
| |
Collapse
|
2
|
Wölkart G, Kollau A, Stessel H, Russwurm M, Koesling D, Schrammel A, Schmidt K, Mayer B. Effects of flavoring compounds used in electronic cigarette refill liquids on endothelial and vascular function. PLoS One 2019; 14:e0222152. [PMID: 31498828 PMCID: PMC6733504 DOI: 10.1371/journal.pone.0222152] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 08/18/2019] [Indexed: 12/26/2022] Open
Abstract
Electronic cigarette refill liquids are commercially provided with a wide variety of flavoring agents. A recent study suggested that several common flavors may scavenge nitric oxide (NO) and cause endothelial dysfunction. It was the aim of the present study to investigate the effects of these flavors on NO/cyclic GMP-mediated signaling and vascular relaxation. We tested the flavoring agents for effects on Ca2+-induced cGMP accumulation and NO synthase activation in cultured endothelial cells. NO scavenging was studied with NO-activated soluble guanylate cyclase and as NO release from a NO donor, measured with a NO electrode. Blood vessel function was studied with precontracted rat aortic rings in the absence and presence of acetylcholine or a NO donor. Cinnamaldehyde inhibited Ca2+-stimulated endothelial cGMP accumulation and NO synthase activation at ≥0.3 mM. Cinnamaldehyde and diacetyl inhibited NO-activated soluble guanylate cyclase with IC50 values of 0.56 (0.54–0.58) and 0.29 (0.24–0.36) mM, respectively, and caused moderate NO scavenging at 1 mM that was not mediated by superoxide anions. The other compounds did not scavenge NO at 1 mM. None of the flavorings interfered with acetylcholine-induced vascular relaxation, but they caused relaxation of pre-contracted aortas. The most potent compounds were eugenol and cinnamaldehyde with EC50 values of ~0.5 mM. Since the flavors did not affect endothelium-dependent vascular relaxation, NO scavenging by cinnamaldehyde and diacetyl does not result in impaired blood vessel function. Although not studied in vivo, the low potency of the compounds renders it unlikely that the observed effects are relevant to humans inhaling flavored vapor from electronic cigarettes.
Collapse
Affiliation(s)
- Gerald Wölkart
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-Universität Graz, Graz, Austria
| | - Alexander Kollau
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-Universität Graz, Graz, Austria
| | - Heike Stessel
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-Universität Graz, Graz, Austria
| | - Michael Russwurm
- Department of Pharmacology and Toxicology, Ruhr-Universität Bochum, Bochum, Germany
| | - Doris Koesling
- Department of Pharmacology and Toxicology, Ruhr-Universität Bochum, Bochum, Germany
| | - Astrid Schrammel
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-Universität Graz, Graz, Austria
| | - Kurt Schmidt
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-Universität Graz, Graz, Austria
| | - Bernd Mayer
- Department of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-Universität Graz, Graz, Austria
- * E-mail:
| |
Collapse
|
3
|
Lee M, Rey K, Besler K, Wang C, Choy J. Immunobiology of Nitric Oxide and Regulation of Inducible Nitric Oxide Synthase. Results Probl Cell Differ 2017; 62:181-207. [PMID: 28455710 DOI: 10.1007/978-3-319-54090-0_8] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Nitric oxide (NO) is a bioactive gas that has multiple roles in innate and adaptive immune responses. In macrophages, nitric oxide is produced by inducible nitric oxide synthase upon microbial and cytokine stimulation. It is needed for host defense against pathogens and for immune regulation. This review will summarize the role of NO and iNOS in inflammatory and immune responses and will discuss the regulatory mechanisms that control inducible nitric oxide synthase expression and activity.
Collapse
Affiliation(s)
- Martin Lee
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Kevin Rey
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Katrina Besler
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Christine Wang
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada
| | - Jonathan Choy
- Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
| |
Collapse
|
4
|
Tryptophan versus nitric oxide, nitrogen dioxide and carbonate radicals: differences in reactivity and implications for oxidative damage to proteins. Theor Chem Acc 2016. [DOI: 10.1007/s00214-016-1913-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|
5
|
Alesutan I, Feger M, Tuffaha R, Castor T, Musculus K, Buehling SS, Heine CL, Kuro-O M, Pieske B, Schmidt K, Tomaschitz A, Maerz W, Pilz S, Meinitzer A, Voelkl J, Lang F. Augmentation of phosphate-induced osteo-/chondrogenic transformation of vascular smooth muscle cells by homoarginine. Cardiovasc Res 2016; 110:408-418. [DOI: 10.1093/cvr/cvw062] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
|
6
|
Chang J, Taylor RD, Davidson RA, Sharmah A, Guo T. Electron Paramagnetic Resonance Spectroscopy Investigation of Radical Production by Gold Nanoparticles in Aqueous Solutions Under X-ray Irradiation. J Phys Chem A 2016; 120:2815-23. [DOI: 10.1021/acs.jpca.6b01755] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joan Chang
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Ryan D. Taylor
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - R. Andrew Davidson
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Arjun Sharmah
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Ting Guo
- Department of Chemistry, University of California, Davis, California 95616, United States
| |
Collapse
|
7
|
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.
Collapse
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.
| |
Collapse
|
8
|
Gambaryan S, Tsikas D. A review and discussion of platelet nitric oxide and nitric oxide synthase: do blood platelets produce nitric oxide from L-arginine or nitrite? Amino Acids 2015; 47:1779-93. [PMID: 25929585 DOI: 10.1007/s00726-015-1986-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 04/09/2015] [Indexed: 02/07/2023]
Abstract
The NO/sGC/cGMP/PKG system is one of the most powerful mechanisms responsible for platelet inhibition. In numerous publications, expression of functional NO synthase (NOS) in human and mouse platelets has been reported. Constitutive and inducible NOS isoforms convert L-arginine to NO and L-citrulline. The importance of this pathway in platelets and in endothelial cells for the regulation of platelet function is discussed since decades. However, there are serious doubts in the literature concerning both expression and functionality of NOS in platelets. In this review, we aim to present and critically evaluate recent data concerning NOS expression and function in platelets, and to especially emphasise potential pitfalls of detection of NOS proteins and measurement of NOS activity. Prevailing analytical problems are probably the main sources of contradictory data on occurrence, activity and function of NOS in platelets. In this review we also address issues of how these problems can be resolved. NO donors including organic nitrites (RONO) and organic nitrate (RONO2) are inhibitors of platelet activation. Endogenous inorganic nitrite (NO2 (-)), the product of NO autoxidation, and exogenous inorganic nitrite are increasingly investigated as NO donors in the circulation. The role of platelets in the generation of NO from nitrite is also discussed.
Collapse
Affiliation(s)
- Stepan Gambaryan
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, 44 Thorez Prosp, St. Petersburg, 194223, Russia,
| | | |
Collapse
|
9
|
Kolesnik B, Heine CL, Schmidt R, Schmidt K, Mayer B, Gorren ACF. Aerobic nitric oxide-induced thiol nitrosation in the presence and absence of magnesium cations. Free Radic Biol Med 2014; 76:286-98. [PMID: 25236749 PMCID: PMC4647830 DOI: 10.1016/j.freeradbiomed.2014.08.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Revised: 08/13/2014] [Accepted: 08/25/2014] [Indexed: 12/29/2022]
Abstract
Although different routes for the S-nitrosation of cysteinyl residues have been proposed, the main in vivo pathway is unknown. We recently demonstrated that direct (as opposed to autoxidation-mediated) aerobic nitrosation of glutathione is surprisingly efficient, especially in the presence of Mg(2+). In the present study we investigated this reaction in greater detail. From the rates of NO decay and the yields of nitrosoglutathione (GSNO) we estimated values for the apparent rate constants of 8.9 ± 0.4 and 0.55 ± 0.06 M(-1)s(-1) in the presence and absence of Mg(2+). The maximum yield of GSNO was close to 100% in the presence of Mg(2+) but only about half as high in its absence. From this observation we conclude that, in the absence of Mg(2+), nitrosation starts by formation of a complex between NO and O2, which then reacts with the thiol. Omission of superoxide dismutase (SOD) reduced by half the GSNO yield in the absence of Mg(2+), demonstrating O2(-) formation. The reaction in the presence of Mg(2+) seems to involve formation of a Mg(2+)•glutathione (GSH) complex. SOD did not affect Mg(2+)-stimulated nitrosation, suggesting that no O2(-) is formed in that reaction. Replacing GSH with other thiols revealed that reaction rates increased with the pKa of the thiol, suggesting that the nucleophilicity of the thiol is crucial for the reaction, but that the thiol need not be deprotonated. We propose that in cells Mg(2+)-stimulated NO/O2-induced nitrosothiol formation may be a physiologically relevant reaction.
Collapse
Affiliation(s)
- Bernd Kolesnik
- Department of Pharmacology & Toxicology, Karl-Franzens-Universität Graz, A-8010 Graz, Austria
| | - Christian L Heine
- Department of Pharmacology & Toxicology, Karl-Franzens-Universität Graz, A-8010 Graz, Austria
| | - Renate Schmidt
- Department of Pharmacology & Toxicology, Karl-Franzens-Universität Graz, A-8010 Graz, Austria
| | - Kurt Schmidt
- Department of Pharmacology & Toxicology, Karl-Franzens-Universität Graz, A-8010 Graz, Austria
| | - Bernd Mayer
- Department of Pharmacology & Toxicology, Karl-Franzens-Universität Graz, A-8010 Graz, Austria
| | - Antonius C F Gorren
- Department of Pharmacology & Toxicology, Karl-Franzens-Universität Graz, A-8010 Graz, Austria.
| |
Collapse
|
10
|
Kolesnik B, Palten K, Schrammel A, Stessel H, Schmidt K, Mayer B, Gorren AC. Efficient nitrosation of glutathione by nitric oxide. Free Radic Biol Med 2013; 63:51-64. [PMID: 23660531 PMCID: PMC3734348 DOI: 10.1016/j.freeradbiomed.2013.04.034] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Revised: 01/24/2013] [Accepted: 04/27/2013] [Indexed: 02/07/2023]
Abstract
Nitrosothiols are increasingly regarded as important participants in a range of physiological processes, yet little is known about their biological generation. Nitrosothiols can be formed from the corresponding thiols by nitric oxide in a reaction that requires the presence of oxygen and is mediated by reactive intermediates (NO₂ or N₂O₃) formed in the course of NO autoxidation. Because the autoxidation of NO is second order in NO, it is extremely slow at submicromolar NO concentrations, casting doubt on its physiological relevance. In this paper we present evidence that at submicromolar NO concentrations the aerobic nitrosation of glutathione does not involve NO autoxidation but a reaction that is first order in NO. We show that this reaction produces nitrosoglutathione efficiently in a reaction that is strongly stimulated by physiological concentrations of Mg(2+). These observations suggest that direct aerobic nitrosation may represent a physiologically relevant pathway of nitrosothiol formation.
Collapse
|
11
|
Liu X, Zweier JL. Application of Electrode Methods in Studies of Nitric Oxide Metabolism and Diffusion Kinetics. J Electroanal Chem (Lausanne) 2013; 688:32-39. [PMID: 23730264 DOI: 10.1016/j.jelechem.2012.09.038] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitric oxide (NO) has many important physiological roles in the body. Since NO electrodes can directly measure NO concentration in the nM range and in real time, NO electrode methods have been generally used in laboratories for measuring NO concentration in vivo and in vitro. This review focuses on the application of electrode methods in studies of NO diffusion and metabolic kinetics. We have described the physical and chemical properties that need to be considered in the preparation of NO stock solution, discussed the effect of several interfering factors on the measured curves of NO concentration that need to be eliminated in the experimental setup for NO measurements, and provided an overview of the application of NO electrode methods in measuring NO diffusion and metabolic kinetics in solution and in biological systems. This overview covers NO metabolism by oxygen (O2), superoxide, heme proteins, cells and tissues. Important conclusions and physiological implication of these studies are discussed.
Collapse
Affiliation(s)
- Xiaoping Liu
- Davis Heart and Lung Research Institute, Department of Internal Medicine, The Ohio State University College of Medicine, 473 West 12th Avenue, Columbus, OH 43210, USA
| | | |
Collapse
|
12
|
Schmidt K, Neubauer A, Kolesnik B, Stasch JP, Werner ER, Gorren ACF, Mayer B. Tetrahydrobiopterin protects soluble guanylate cyclase against oxidative inactivation. Mol Pharmacol 2012; 82:420-7. [PMID: 22648973 DOI: 10.1124/mol.112.079855] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Tetrahydrobiopterin (BH4) is a major endogenous vasoprotective agent that improves endothelial function by increasing nitric oxide (NO) synthesis and scavenging of superoxide and peroxynitrite. Therefore, administration of BH4 is considered a promising therapy for cardiovascular diseases associated with endothelial dysfunction and oxidative stress. Here we report on a novel function of BH4 that might contribute to the beneficial vascular effects of the pteridine. Treatment of cultured porcine aortic endothelial cells with nitroglycerin (GTN) or 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxaline-1-one (ODQ) resulted in heme oxidation of soluble guanylate cyclase (sGC), as evident from diminished NO-induced cGMP accumulation that was paralleled by increased cGMP response to a heme- and NO-independent activator of soluble guanylate cyclase [4-([(4-carboxybutyl)[2-(5-fluoro-2-([4'-(trifluoromethyl)biphenyl-4-yl]methoxy)phenyl)ethyl]amino]methyl)benzoic acid (BAY 60-2770)]. Whereas scavenging of superoxide and/or peroxynitrite with superoxide dismutase, tiron, Mn(III)tetrakis(4-benzoic acid)porphyrin, and urate had no protective effects, supplementation of the cells with BH4, either by application of BH4 directly or of its precursors dihydrobiopterin or sepiapterin, completely prevented the inhibition of NO-induced cGMP accumulation by GTN and ODQ. Tetrahydroneopterin had the same effect, and virtually identical results were obtained with RFL-6 fibroblasts, suggesting that our observation reflects a general feature of tetrahydropteridines that is unrelated to NO synthase function and not limited to endothelial cells. Protection of sGC against oxidative inactivation may contribute to the known beneficial effects of BH4 in cardiovascular disorders associated with oxidative stress.
Collapse
Affiliation(s)
- Kurt Schmidt
- Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, Graz, Austria.
| | | | | | | | | | | | | |
Collapse
|
13
|
Wenzl MV, Beretta M, Griesberger M, Russwurm M, Koesling D, Schmidt K, Mayer B, Gorren ACF. Site-directed mutagenesis of aldehyde dehydrogenase-2 suggests three distinct pathways of nitroglycerin biotransformation. Mol Pharmacol 2011; 80:258-66. [PMID: 21536753 DOI: 10.1124/mol.111.071704] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
To elucidate the mechanism underlying reduction of nitroglycerin (GTN) to nitric oxide (NO) by mitochondrial aldehyde dehydrogenase (ALDH2), we generated mutants of the enzyme lacking the cysteines adjacent to reactive Cys302 (C301S and C303S), the glutamate that participates as a general base in aldehyde oxidation (E268Q) or combinations of these residues. The mutants were characterized regarding acetaldehyde dehydrogenation, GTN-triggered enzyme inactivation, GTN denitration, NO formation, and soluble guanylate cyclase activation. Lack of the cysteines did not affect dehydrogenase activity but impeded GTN denitration, aggravated GTN-induced enzyme inactivation, and increased NO formation. A triple mutant lacking the cysteines and Glu268 catalyzed sustained formation of superstoichiometric amounts of NO and exhibited slower rates of inactivation. These results suggest three alternative pathways for the reaction of ALDH2 with GTN, all involving formation of a thionitrate/sulfenyl nitrite intermediate at Cys302 as the initial step. In the first pathway, which predominates in the wild-type enzyme and reflects clearance-based GTN denitration, the thionitrate apparently reacts with one of the adjacent cysteine residues to yield nitrite and a protein disulfide. The predominant reaction catalyzed by the single and double cysteine mutants requires Glu268 and results in irreversible enzyme inactivation. Finally, combined lack of the cysteines and Glu268 shifts the reaction toward formation of the free NO radical, presumably through homolytic cleavage of the sulfenyl nitrite intermediate. Although the latter reaction accounts for less than 10% of total turnover of GTN metabolism catalyzed by wild-type ALDH2, it is most likely essential for vascular GTN bioactivation.
Collapse
Affiliation(s)
- M Verena Wenzl
- Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, Universitätsplatz 2, A-8010, Austria.
| | | | | | | | | | | | | | | |
Collapse
|
14
|
Labinskyy N, Hicks S, Grijalva J, Edwards J. The Contrary Impact Of Diabetes And Exercise On Endothelial Nitric Oxide Synthase Function. WEBMEDCENTRAL 2010; 1. [PMID: 27683619 DOI: 10.9754/journal.wmc.2010.00137] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
15
|
Thakor AS, Herrera EA, Serón-Ferré M, Giussani DA. Melatonin and vitamin C increase umbilical blood flow via nitric oxide-dependent mechanisms. J Pineal Res 2010; 49:399-406. [PMID: 20958954 DOI: 10.1111/j.1600-079x.2010.00813.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Inadequate umbilical blood flow leads to intrauterine growth restriction, a major killer in perinatal medicine today. Nitric oxide (NO) is important in the maintenance of umbilical blood flow, and antioxidants increase NO bioavailability. What remains unknown is whether antioxidants can increase umbilical blood flow. Melatonin participates in circadian, seasonal, and reproductive physiology, but has also been reported to act as a potent endogenous antioxidant. We tested the hypothesis that treatment during pregnancy with melatonin increases umbilical blood flow via NO-dependent mechanisms. This was tested in pregnant sheep by investigating in vivo the effects on continuous measurement of umbilical blood flow of melatonin before and after NO blockade with a NO clamp. These effects of melatonin were compared with those of the traditional antioxidant, vitamin C. Under anesthesia, 12 pregnant sheep and their fetuses (0.8 of gestation) were fitted with catheters and a Transonic probe around an umbilical artery, inside the fetal abdomen. Following 5 days of recovery, cardiovascular variables were recorded during fetal i.v. treatment with either melatonin (n=6, 0.5±0.1 μg/kg/min) or vitamin C (n=6, 8.9±0.4 mg/kg/min) before and after fetal NO blockade with the NO clamp. Fetal treatment with melatonin or vitamin C increased umbilical blood flow, independent of changes in fetal arterial blood pressure. Fetal NO blockade prevented the increase in umbilical blood flow induced by melatonin or vitamin C. Antioxidant treatment could be a useful clinical tool to increase or maintain umbilical blood flow in complicated pregnancy.
Collapse
Affiliation(s)
- Avnesh S Thakor
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | | | | | | |
Collapse
|
16
|
Schmidt K, Martens-Lobenhoffer J, Meinitzer A, Graier WF, Torres CM, Venema RC, Mayer B. Activation of endothelial nitric oxide synthase by the pro-apoptotic drug embelin: Striking discrepancy between nitric oxide-mediated cyclic GMP accumulation and L-citrulline formation. Nitric Oxide 2010; 22:281-9. [PMID: 20144727 DOI: 10.1016/j.niox.2010.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2009] [Revised: 01/14/2010] [Accepted: 02/01/2010] [Indexed: 01/18/2023]
Abstract
The benzoquinone derivative embelin is a multifunctional drug that not only induces apoptosis by inhibiting XIAP, the X chromosome-linked inhibitor of apoptosis protein, but also blocks nuclear factor-kappaB signaling pathways, thereby leading to down-regulation of a variety of gene products involved in tumor cell survival, proliferation, invasion, angiogenesis, and inflammation. Here, we report that embelin activates and modulates l-arginine/nitric oxide/cyclic GMP signaling in cultured endothelial cells. Embelin elicited a rapid increase of intracellular free Ca(2+), leading to activation of endothelial nitric oxide synthase (eNOS) and NO-induced cGMP accumulation. While the cGMP response was comparable to that caused by other Ca(2+)-mobilizing agents, the stimulatory effect of embelin on l-citrulline formation (approximately 4-fold) was substantially lower than that observed upon activation of eNOS with the Ca(2+) ionophore A23187 (approximately 18-fold), the receptor agonist ATP (approximately 16-fold) or the sarco-endoplasmic reticulum Ca(2+)-ATPase inhibitor thapsigargin (approximately 14-fold). The apparent discrepancy between NO/cGMP and l-citrulline formation in embelin-treated cells was not due to enhanced metabolism and/or efflux of l-citrulline, increased NO bioavailability, inhibition of cGMP hydrolysis, sensitization of soluble guanylate cyclase (sGC) to NO, or enhanced formation of a sGC/eNOS complex. Our puzzling observations suggest that embelin improves coupling of endothelial NO synthesis to sGC activation through mobilization of an as yet unrecognized signaling pathway.
Collapse
Affiliation(s)
- Kurt Schmidt
- Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, Austria.
| | | | | | | | | | | | | |
Collapse
|
17
|
Beretta M, Gorren ACF, Wenzl MV, Weis R, Russwurm M, Koesling D, Schmidt K, Mayer B. Characterization of the East Asian variant of aldehyde dehydrogenase-2: bioactivation of nitroglycerin and effects of Alda-1. J Biol Chem 2009; 285:943-52. [PMID: 19906643 PMCID: PMC2801295 DOI: 10.1074/jbc.m109.014548] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The East Asian variant of mitochondrial aldehyde dehydrogenase (ALDH2) exhibits significantly reduced dehydrogenase, esterase, and nitroglycerin (GTN) denitrating activities. The small molecule Alda-1 was reported to partly restore low acetaldehyde dehydrogenase activity of this variant. In the present study we compared the wild type enzyme (ALDH2*1) with the Asian variant (ALDH2*2) regarding GTN bioactivation and the effects of Alda-1. Alda-1 increased acetaldehyde oxidation by ALDH2*1 and ALDH2*2 approximately 1.5- and 6-fold, respectively, and stimulated the esterase activities of both enzymes to similar extent as the coenzyme NAD. The effect of NAD was biphasic with pronounced inhibition occurring at > or = 5 mM. In the presence of 1 mM NAD, Alda-1 stimulated ALDH2*2-catalyzed ester hydrolysis 73-fold, whereas the NAD-stimulated activity of ALDH2*1 was inhibited because of 20-fold increased inhibitory potency of NAD in the presence of the drug. Although ALDH2*2 exhibited 7-fold lower GTN denitrating activity and GTN affinity than ALDH2*1, the rate of nitric oxide formation was only reduced 2-fold, and soluble guanylate cyclase (sGC) activation was more pronounced than with wild type ALDH2 at saturating GTN. Alda-1 caused slight inhibition of GTN denitration and did not increase GTN-induced sGC activation in the presence of either variant. The present results indicate that Alda-1 stimulates established ALDH2 activities by improving NAD binding but does not improve the GTN binding affinity of the Asian variant. In addition, our data revealed an unexpected discrepancy between GTN reductase activity and sGC activation, suggesting that GTN denitration and bioactivation may reflect independent pathways of ALDH2-catalyzed GTN biotransformation.
Collapse
Affiliation(s)
- Matteo Beretta
- Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, 8010 Graz, Austria
| | | | | | | | | | | | | | | |
Collapse
|
18
|
Zeller A, Wenzl MV, Beretta M, Stessel H, Russwurm M, Koesling D, Schmidt K, Mayer B. Mechanisms underlying activation of soluble guanylate cyclase by the nitroxyl donor Angeli's salt. Mol Pharmacol 2009; 76:1115-22. [PMID: 19720727 DOI: 10.1124/mol.109.059915] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nitroxyl (HNO) may be formed endogenously by uncoupled nitric-oxide (NO) synthases, enzymatic reduction of NO or as product of vascular nitroglycerin bioactivation. The established HNO donor Angeli's salt (trioxodinitrate, AS) causes cGMP-dependent vasodilation through activation of soluble guanylate cyclase (sGC). We investigated the mechanisms underlying this effect using purified sGC and cultured endothelial cells. AS (up to 0.1 mM) had no significant effect on sGC activity in the absence of superoxide dismutase (SOD) or dithiothreitol (DTT). In the presence of SOD, AS caused biphasic sGC activation (apparent EC(50) approximately 10 nM, maximum at 1 microM) that was accompanied by the formation of NO. DTT (2 mM) inhibited the effects of <10 microM AS but led to sGC activation and NO release at 0.1 mM AS even without SOD. AS had no effect on ferric sGC, excluding activation of the oxidized enzyme by HNO. The NO scavenger carboxy-PTIO inhibited endothelial cGMP accumulation induced by AS in the presence but not in the absence of SOD (EC(50) approximately 50 nM and approximately 16 microM, respectively). Carboxy-PTIO (0.1 mM) inhibited the effect of <or=10 microM AS in the presence of SOD but caused NO release from 0.1 mM AS in the absence of SOD. These data indicate that AS activates sGC exclusively via NO, formed either via SOD-catalyzed oxidation of HNO or through a minor AS decomposition pathway that is unmasked in the presence of HNO scavenging thiols.
Collapse
Affiliation(s)
- Andreas Zeller
- Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, Graz, Austria
| | | | | | | | | | | | | | | |
Collapse
|
19
|
Wenzl MV, Beretta M, Gorren ACF, Zeller A, Baral PK, Gruber K, Russwurm M, Koesling D, Schmidt K, Mayer B. Role of the general base Glu-268 in nitroglycerin bioactivation and superoxide formation by aldehyde dehydrogenase-2. J Biol Chem 2009; 284:19878-86. [PMID: 19506075 PMCID: PMC2740413 DOI: 10.1074/jbc.m109.005652] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Mitochondrial aldehyde dehydrogenase-2 (ALDH2) plays an essential role in nitroglycerin (GTN) bioactivation, resulting in formation of NO or a related activator of soluble guanylate cyclase. ALDH2 denitrates GTN to 1,2-glyceryl dinitrate and nitrite but also catalyzes reduction of GTN to NO. To elucidate the relationship between ALDH2-catalyzed GTN bioconversion and established ALDH2 activities (dehydrogenase, esterase), we compared the function of the wild type (WT) enzyme with mutants lacking either the reactive Cys-302 (C302S) or the general base Glu-268 (E268Q). Although the C302S mutation led to >90% loss of all enzyme activities, the E268Q mutant exhibited virtually unaffected rates of GTN denitration despite low dehydrogenase and esterase activities. The nucleotide co-factor NAD caused a pronounced increase in the rates of 1,2-glyceryl dinitrate formation by WT-ALDH2 but inhibited the reaction catalyzed by the E268Q mutant. GTN bioactivation measured as activation of purified soluble guanylate cyclase or release of NO in the presence of WT- or E268Q-ALDH2 was markedly potentiated by superoxide dismutase, suggesting that bioavailability of GTN-derived NO is limited by co-generation of superoxide. Formation of superoxide was confirmed by determination of hydroethidine oxidation that was inhibited by superoxide dismutase and the ALDH2 inhibitor chloral hydrate. E268Q-ALDH2 exhibited approximately 50% lower rates of superoxide formation than the WT enzyme. Our results suggest that Glu-268 is involved in the structural organization of the NAD-binding pocket but is not required for GTN denitration. ALDH2-catalyzed superoxide formation may essentially contribute to oxidative stress in GTN-exposed blood vessels.
Collapse
Affiliation(s)
- M Verena Wenzl
- Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, A-8010 Graz, Austria
| | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Mayer B, Kleschyov AL, Stessel H, Russwurm M, Münzel T, Koesling D, Schmidt K. Inactivation of Soluble Guanylate Cyclase by Stoichiometric S-Nitrosation. Mol Pharmacol 2008; 75:886-91. [DOI: 10.1124/mol.108.052142] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
21
|
Mitochondrial nitrite reduction coupled to soluble guanylate cyclase activation: lack of evidence for a role in the bioactivation of nitroglycerin. Nitric Oxide 2008; 20:53-60. [PMID: 18951990 DOI: 10.1016/j.niox.2008.09.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 09/26/2008] [Accepted: 09/30/2008] [Indexed: 11/20/2022]
Abstract
Reduction of nitrite to nitric oxide (NO) by components of the mitochondrial respiratory chain may link nitroglycerin biotransformation by mitochondrial aldehyde dehydrogenase (ALDH2) to activation of soluble guanylate cyclase (sGC). We used purified sGC as detector for NO-like bioactivity generated from nitrite and GTN by isolated heart and liver mitochondria. Exogenous NADH caused a pronounced increase in oxygen consumption that was completely inhibited by myxothiazol and cyanide. Oxygen depletion of cardiac mitochondria by NADH was accompanied by activation of sGC and cyanide-sensitive formation of NO. Mitochondrial biotransformation of nitroglycerin was sensitive to ALDH2 inhibitors and coupled to sGC activation but not affected by respiratory substrates or inhibitors. Our data suggest that cytochrome c oxidase catalyzes reduction of nitrite to NO at low O(2) tension but argue against the involvement of this pathway in mitochondrial bioactivation of nitroglycerin.
Collapse
|
22
|
Beretta M, Gruber K, Kollau A, Russwurm M, Koesling D, Goessler W, Keung WM, Schmidt K, Mayer B. Bioactivation of nitroglycerin by purified mitochondrial and cytosolic aldehyde dehydrogenases. J Biol Chem 2008; 283:17873-80. [PMID: 18450747 PMCID: PMC2440601 DOI: 10.1074/jbc.m801182200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Metabolism of nitroglycerin (GTN) to 1,2-glycerol dinitrate (GDN) and nitrite by mitochondrial aldehyde dehydrogenase (ALDH2) is essentially involved in GTN bioactivation resulting in cyclic GMP-mediated vascular relaxation. The link between nitrite formation and activation of soluble guanylate cyclase (sGC) is still unclear. To test the hypothesis that the ALDH2 reaction is sufficient for GTN bioactivation, we measured GTN-induced formation of cGMP by purified sGC in the presence of purified ALDH2 and used a Clark-type electrode to probe for nitric oxide (NO) formation. In addition, we studied whether GTN bioactivation is a specific feature of ALDH2 or is also catalyzed by the cytosolic isoform (ALDH1). Purified ALDH1 and ALDH2 metabolized GTN to 1,2- and 1,3-GDN with predominant formation of the 1,2-isomer that was inhibited by chloral hydrate (ALDH1 and ALDH2) and daidzin (ALDH2). GTN had no effect on sGC activity in the presence of bovine serum albumin but caused pronounced cGMP accumulation in the presence of ALDH1 or ALDH2. The effects of the ALDH isoforms were dependent on the amount of added protein and, like 1,2-GDN formation, were sensitive to ALDH inhibitors. GTN caused biphasic sGC activation with apparent EC50 values of 42 ± 2.9 and 3.1 ± 0.4 μm in the presence of ALDH1 and ALDH2, respectively. Incubation of ALDH1 or ALDH2 with GTN resulted in sustained, chloral hydrate-sensitive formation of NO. These data may explain the coupling of ALDH2-catalyzed GTN metabolism to sGC activation in vascular smooth muscle.
Collapse
Affiliation(s)
- Matteo Beretta
- Department of Pharmacology and Toxicology, Karl-Franzens-Universität Graz, Graz, Austria
| | | | | | | | | | | | | | | | | |
Collapse
|
23
|
Arakawa H, Masuda K, Tajima N, Maeda M. Chemiluminescence assay for tetrahydrobiopterin based on the generation of hydrogen peroxide using isoluminol-microperoxidase in the presence of 1-methoxy PMS. LUMINESCENCE 2007; 22:245-50. [PMID: 17285567 DOI: 10.1002/bio.958] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We developed a novel highly sensitive chemiluminescence (CL) method for BH(4). The principle of the proposed method is based on active oxygen formation induced by 1-methoxy-5-methyl phenazinium methyl sulphate (1-methoxy PMS) in the presence of dissolved oxygen. Furthermore, active oxygen is determined by a CL assay involving the luminol reaction with microperoxidase. In this report, we examined the mechanism of formation and identified the reactive oxygen species derived from BH(4) employing 1-methoxy PMS. Additionally, optimum conditions for the CL assay of BH(4) were established.
Collapse
Affiliation(s)
- Hidetoshi Arakawa
- School of Pharmaceutical Sciences, Showa University, Tokyo 142-8555, Japan.
| | | | | | | |
Collapse
|
24
|
Valent S, Tóth M. Activation energy determinations suggest that thiols reverse autooxidation of tetrahydrobiopterin by a different mechanism than ascorbate. Int J Biochem Cell Biol 2006; 38:1786-93. [PMID: 16777471 DOI: 10.1016/j.biocel.2006.04.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2005] [Revised: 04/21/2006] [Accepted: 04/25/2006] [Indexed: 11/22/2022]
Abstract
In neutral aqueous solutions tetrahydrobiopterin is oxidized by dioxygen in a reaction that is succinctly described as autooxidation. Ascorbate and thiols moderate this reaction by reversing the oxidative process. In the present study the effect of various thiols on the apparent Arrhenius activation energy of tetrahydrobiopterin autooxidation was characterized and compared to that of ascorbate determined previously. We observed that - in sharp contrast to ascorbate - the efficiency of thiols to protect tetrahydrobiopterin decreased with the elevation of temperature from 22 to 37 degrees C. Accordingly, the apparent Arrhenius activation energies (in kJ/mol) measured in the presence of thiols were consistently greater than the value determined with tetrahydrobiopterin alone (59.6 +/- 1.4) or in the presence of ascorbate (59.9 +/- 2.8). Thus, the energy values were 88.8+/-1.1 with glutathione, 87.6 +/- 2.1 with N-acetylcysteine, 79.2 +/- 1.6 with cysteine, 75.1 +/- 2.4 with dithiotreitol and 70.3 +/- 0.9 with homocysteine. Since thiols are as potent reducing agents as ascorbate, these findings suggest that thiols and ascorbate protect tetrahydrobiopterin from oxidation acting at different steps of the oxidation process. It is likely that thiols reduce quinoidal dihydrobiopterin, whereas ascorbate scavenges the trihydrobiopterin radical to tetrahydrobiopterin. Furthermore, the results indicate that thiols are excellent tools to protect tetrahydrobiopterin from autooxidative decomposition in laboratory experiments conducted at relatively low temperatures, whereas the protective effect diminishes at 37 degrees C, i.e. under physiological conditions.
Collapse
Affiliation(s)
- Sándor Valent
- Department of Medical Chemistry, Molecular Biology and Pathobiochemistry, Semmelweis University, Puskin utca 9, 1088 Budapest, Hungary
| | | |
Collapse
|
25
|
Hara Y, Teramoto K, Ishidate K, Arii S. Cytoprotective function of tetrahydrobiopterin in rat liver ischemia/reperfusion injury. Surgery 2006; 139:377-84. [PMID: 16546503 DOI: 10.1016/j.surg.2005.08.019] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2005] [Revised: 08/18/2005] [Accepted: 08/19/2005] [Indexed: 11/23/2022]
Abstract
BACKGROUND Tetrahydrobiopterin (BH(4)) is a key coenzyme of nitric oxide synthase (NOS), which is associated with a cytoprotective function in various ischemia-reperfusion (I/R) injury models. There have been a few reports on the efficacy of BH(4) in the treatment of I/R injury in other organs; therefore, the aim of this study was to investigate the effect of BH(4) related with NOS reaction in hepatic I/R injury. METHODS A model of 70% liver I/R injury with a 100-minute ischemic time was created in rats, and the non-ischemic lobes were then resected. The rats were given BH(4) (BH(4) group) or saline solution (saline group) before reperfusion. The specific inducible NOS blocker 1400W was used to evaluate the effect of endogenous inducible NOS in the I/R hepatic injury. Survival, nitric oxide products (nitrate and nitrite), NOS expression, and nitrotyrosine (ie, the peroxynitrite product) were measured after reperfusion. RESULTS On day 7, the survival rate was 62.5% in the BH(4) group, as opposed to 14.3% in the saline group (P = .0004); 1400W administration to the BH(4) group decreased the survival rate to 0% (P = .003). BH(4) prevented the significant increase in total bilirubin levels (P < .01) after 12-hour reperfusion. The increases in serum alanine transaminase levels (after 3 hours and 12 hours of reperfusion) were significantly (P < .01) attenuated in the BH(4) group. BH(4) increased the nitrate/nitrite concentrations in liver tissue (P < .05) and reduced nitrotyrosine production, and the protein assay showed that BH(4) increased inducible NOS and endothelial NOS expression. Histologic examination of the liver revealed that BH(4) mitigated the damage that was caused by liver I/R. CONCLUSION Exogenous BH(4) increased nitric oxide production, which attenuated the hepatic I/R injury.
Collapse
Affiliation(s)
- Yuzuru Hara
- Department of Surgery, School of Medicine, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan
| | | | | | | |
Collapse
|
26
|
Liu X, Liu Q, Gupta E, Zorko N, Brownlee E, Zweier JL. Quantitative measurements of NO reaction kinetics with a Clark-type electrode. Nitric Oxide 2005; 13:68-77. [PMID: 15964224 DOI: 10.1016/j.niox.2005.04.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2005] [Revised: 04/26/2005] [Accepted: 04/30/2005] [Indexed: 11/23/2022]
Abstract
Nitric oxide (NO) plays important physiological roles in the body. Knowledge regarding the kinetics of NO catabolism is important for understanding the biological functions of NO. Clark-type NO electrodes have been frequently employed in measuring the kinetics of NO reactions; however, the slow response time of these electrodes can cause measurement errors and limit the application of the electrode in measurements of fast NO reactions. In this study, a simplified diffusion model is given for describing the response process of the NO electrode to the change of NO concentration. The least-square method is used in fitting the currents calculated from the diffusion equation to the experimental curves for determining the diffusion parameters and rate constants. The calculated currents are in excellent accordance with the experimental curves for different NO reaction kinetics. It has been demonstrated that when using an NO electrode with a response time of approximately 6 s to measure fast NO reactions with a half-life of approximately 1s, the response currents of the electrode have large differences compared to the curve of actual NO concentration in the solution; however, the rate constant of NO decay can still be accurately determined by computer simulations with the simplified diffusion model. Theoretical analysis shows that an NO electrode with a response time of 6 s (D/L2=0.06 s-1) and the lowest detection limit of 1 nM NO can be used in measuring kinetics of extremely rapid NO reactions with a half-life below 10 ms.
Collapse
Affiliation(s)
- Xiaoping Liu
- Davis Heart and Lung Research Institute and Division of Cardiovascular Medicine, Department of Internal Medicine, The Ohio State University, Columbus, OH 43210, USA.
| | | | | | | | | | | |
Collapse
|
27
|
Thoeni G, Stoitzner P, Brandacher G, Romani N, Heufler C, Werner-Felmayer G, Werner ER. Tetrahydro-4-aminobiopterin attenuates dendritic cell-induced T cell priming independently from inducible nitric oxide synthase. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2005; 174:7584-91. [PMID: 15944258 DOI: 10.4049/jimmunol.174.12.7584] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Formation of NO by NO synthases (NOSs) strictly depends on tetrahydrobiopterin. Its structural analog, tetrahydro-4-aminobiopterin, is an inhibitor of all NOS isoenzymes, which prolongs allograft survival in acute murine cardiac rejection and prevents septic shock in the rat. In this study, we show that murine bone marrow-derived dendritic cells treated with tetrahydro-4-aminobiopterin had a reduced capacity to prime alloreactive murine T cells in oxidative mitogenesis. Checking for a possible influence on LPS-induced dendritic cell maturation, we found that tetrahydro-4-aminobiopterin down-regulated MHC class II expression and counteracted LPS-induced down-regulation of ICOS ligand, while expression of CD40, CD86, CD80, B7-H1, and B7-DC remained unchanged. Tetrahydro-4-aminobiopterin also reduced activation of CD4(+) T cells isolated from mice overexpressing an OVA-specific TCR by OVA-loaded murine bone marrow-derived dendritic cells, thus indicating that its effect on MHC class II expression is involved in attenuating T cell activation. In line with affecting dendritic cell function and T cell activation, tetrahydro-4-aminobiopterin impaired production of proinflammatory cytokines and the Th1 response. With regard to cell survival, tetrahydro-4-aminobiopterin induced efficient apoptosis of murine T cells but not of murine dendritic cells. Experiments with cells from inducible NOS (iNOS) knockout mice and with N(6)-(1-iminoethyl)-L-lysine, a specific inhibitor of iNOS, ruled out participation of iNOS in any of the observed effects. These findings characterize attenuation of T cell stimulatory capacity of murine bone marrow-derived dendritic cells as an immunosuppressive mechanism of tetrahydro-4-aminobiopterin that is not related to its iNOS-inhibiting properties.
Collapse
Affiliation(s)
- Guntram Thoeni
- Biocenter, Division of Biological Chemistry, Department of Dermatology and Venerology, Innsbruck Medical University, Innsbruck, Austria
| | | | | | | | | | | | | |
Collapse
|
28
|
Kinsella JP, Parker TA, Davis JM, Abman SH. Superoxide dismutase improves gas exchange and pulmonary hemodynamics in premature lambs. Am J Respir Crit Care Med 2005; 172:745-9. [PMID: 15947289 PMCID: PMC2718553 DOI: 10.1164/rccm.200501-146oc] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
RATIONALE Oxidant stress may increase the severity of respiratory distress syndrome (RDS) after premature birth by altering vasoreactivity and increasing lung edema, but the acute effects of superoxide dismutase (SOD) treatment on gas exchange, lung compliance (CL), and pulmonary vascular resistance in premature animals with RDS are unknown. OBJECTIVE We studied the effects of intratracheal recombinant human SOD treatment (rhSOD) on gas exchange, CL, and pulmonary hemodynamics in 46 premature lambs with RDS. METHODS After C-section delivery, lambs were randomly assigned to treatment with SOD (2.5-10 mg/kg) with or without inhaled nitric oxide (iNO, 5 ppm), and mechanically ventilated for 4 hours. At the end of the study, pressure-volume curves and wet-dry lung weights were measured to assess CL and edema, respectively. MAIN RESULTS Despite an initial rise in Pa(O(2)), Pa(O(2)) in control animals progressively declined over the 4-hour treatment period (Pa(O(2)) = 25.0 +/- 7.5 mm Hg at 4 hours). In comparison with control animals, early treatment with SOD at 5 and 10 mg/kg improved Pa(O(2)) at 4 hours (167 +/- 44 and 269 +/- 33 mm Hg, respectively; p < 0.05 vs. control), but did not decrease lung edema or improve CL. In contrast, late treatment with SOD did not improve Pa(O(2)). Treatment with iNO increased Pa(O(2)) (196 +/- 22 vs. 25 +/- 8 mm Hg, control animals; p < 0.01), but the response to iNO was not augmented by combined therapy (SOD + iNO). After 4 hours of ventilation with FI(O(2)) = 1.00, rhSOD treatment lowered pulmonary vascular resistance compared with control animals. CONCLUSIONS Early intratracheal rhSOD treatment improves oxygenation in premature lambs with RDS and prevents the development of pulmonary hypertension.
Collapse
Affiliation(s)
- John P Kinsella
- Department of Pediatrics, Pediatric Heart-Lung Center, Section of Neonatology, University of Colorado School of Medicine, Denver, Colorado, USA.
| | | | | | | |
Collapse
|
29
|
Abstract
Endothelial-derived relaxing factor (EDRF) is secreted by different endothelia in vivo. It is synthesised by endothelial NO-synthase (eNOS). Despite numerous works, its identity is not fully understood. Here the production of NA, a nitroso-arginine, which was shown to be synthesised by brain NO-synthase (bNOS), was studied in eNOS preparations. NA was quantified by reductive differential pulse voltammetry (RDPV) during its irreversible electrochemical transformation to N-hydroxy-arginine (NHA). Using microelectrodes, NA and nitrite were simultaneously measured in pure recombinant eNOS giving similar enzyme activity. NA was detected at the surface of human endothelial cells (HUVEC) and disappeared when D-arginine was introduced in the culture medium. NA production by endothelium tissue was studied in rat corpus cavernosum using voltammetric microelectrodes. NA concentration at the endothelium surface was linked to vasodilatation measured by laser Doppler induced by acetylcholine injection. LNMA ic injection induced NA disappearance. These preliminary new experiments suggested that NA could be the endogenous nitroso-compound presented early as EDRF.
Collapse
Affiliation(s)
- Alain Meulemans
- Laboratoire de Biophysique, Faculté de Médecine Xavier-Bichat, 46, rue Henri-Huchard, 75018 Paris, France.
| |
Collapse
|
30
|
Mochizuki S, Sipkema P, Goto M, Hiramatsu O, Nakamoto H, Toyota E, Kajita T, Shigeto F, Yada T, Ogasawara Y, Kajiya F. Exogenous NO suppresses flow-induced endothelium-derived NO production because of depletion of tetrahydrobiopterin. Am J Physiol Heart Circ Physiol 2005; 288:H553-8. [PMID: 15471981 DOI: 10.1152/ajpheart.00408.2004] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Exogenous nitric oxide (NO) suppresses endothelium-derived NO production. We were interested in determining whether this is also the case in flow-induced endothelium-derived NO production. If so, then is the mechanism because of intracellular depletion of tetrahydrobiopterin [BH4; a cofactor of NO synthase (NOS)], which results in superoxide production by uncoupled NOS? Isolated canine femoral arteries were perfused with 100 microM S-nitroso-N-acetylpenicillamine (SNAP; an NO donor) and/or 64 microM BH4. Perfusion of SNAP suppressed flow-induced NO production, which was evaluated as a change in the slope of the linear relationship between perfusion rate and NO production rate (P < 0.02 vs. control; n = 7). Subsequent BH4 perfusion returned the slope to the control level. Concomitant perfusion of SNAP and BH4 retained the control-level NO production (n = 7). Concomitant perfusion of SNAP and 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron; 1 mM; a membrane-permeable superoxide scavenger) also retained the control-level NO production (n = 7), whereas perfusion of Tiron after SNAP could not return the NO production to the control level (P < 0.02 vs. control; n = 7). We also found a significant decrease in BH4 concentration in the endothelial cells after SNAP perfusion. In conclusion, these results indicate that exogenous NO suppresses the flow-induced, endothelium-derived NO production by superoxide released from uncoupled NOS because of intracellular BH4 depletion.
Collapse
Affiliation(s)
- Seiichi Mochizuki
- Department of Medical Engineering, Kawasaki Medical School, Kurashiki, Okayama, Japan.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
31
|
Fujimoto Y, Ohtsuka S, Miyashita H, Sakuma S. Effect of Tetrahydrobiopterin on Copper-Mediated DNA Oxidation: Its Prooxidant Property. J Clin Biochem Nutr 2005. [DOI: 10.3164/jcbn.36.51] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
32
|
Lowe ER, Everett AC, Lee AJ, Lau M, Dunbar AY, Berka V, Tsai AL, Osawa Y. Time-dependent inhibition and tetrahydrobiopterin depletion of endothelial nitric-oxide synthase caused by cigarettes. Drug Metab Dispos 2005; 33:131-8. [PMID: 15470159 DOI: 10.1124/dmd.104.001891] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Smoking causes a dysfunction in endothelial nitric-oxide synthase (eNOS), which is ameliorated, in part, by administration of tetrahydrobiopterin (BH(4)). The exact mechanism by which the nitric oxide deficit occurs is unknown. We have previously shown that aqueous extracts of chemicals in cigarettes (CE) cause the suicide inactivation of neuronal NO synthase (nNOS) by interacting at the substrate-binding site. In the current study, we have found that CE directly inactivates eNOS by a process that is not affected by the natural substrate l-arginine and is distinct from the mechanism of inactivation of nNOS. We discovered that CE causes a time-, concentration-, and NADPH-dependent inactivation of eNOS in an in vitro system containing the purified enzyme, indicating a metabolic component to the inactivation. The CE-treated eNOS but not nNOS was nearly fully reactivated upon incubation with excess BH(4), suggesting that BH(4) depletion is a potential mechanism of inactivation. Moreover, in the presence of CE, eNOS catalyzed the oxidation of BH(4) to dihydrobiopterin and biopterin by a process attenuated by high concentrations of superoxide dismutase but not catalase. We speculate that a redox active component in CE, perhaps a quinone compound, causes oxidative uncoupling of eNOS to form superoxide, which in turn oxidizes BH(4). The discovery of a direct inactivation of eNOS by a compound(s) present in tobacco provides a basis not only for further study of the mechanisms responsible for the biological effects of tobacco but also a search for a potentially novel inactivator of eNOS.
Collapse
Affiliation(s)
- Ezra R Lowe
- Department of Pharmacology, University of Michigan Medical School, 1301 Medical Science Research Building III, Ann Arbor, MI 48109-0632, USA
| | | | | | | | | | | | | | | |
Collapse
|
33
|
Koshimura K, Murakami Y, Tanaka J, Yamamoto M, Kato Y. Effect of tetrahydrobiopterin on nitric oxide synthase-containing cells in the rat hippocampus. Neurosci Res 2004; 50:161-7. [PMID: 15380323 DOI: 10.1016/j.neures.2004.06.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Accepted: 06/21/2004] [Indexed: 11/24/2022]
Abstract
We have observed that tetrahydrobiopterin (BH4), a cofactor of nitric oxide synthase (NOS), acts as a self-protection factor against nitric oxide (NO) toxicity in PC12 cells. To further investigate the self-protection action of BH4 in vivo, the effect of deletion of endogenous BH4 on NO-producing cells was examined in the rat hippocampus. Following the peripheral infusion of 50 mM 2,4-diamino-6-hydroxypyrimidine (DAHP), an inhibitor of GTP cyclohydrolase I, using a miniosmotic pump for 14 days, BH4 content in the hippocampus decreased as compared with the control group administered with vehicle solution, which had no effect on brain BH4 content. When the rats were administered with 50 mM DAHP and 10 mM BH4, the DAHP-induced decrease in BH4 content was prevented. The extracellular concentration of NO metabolites remained unchanged following DAHP administration, suggesting that DAHP-induced decrease in BH4 content had no effect on NO production. The number of NOS-positive cells decreased following DAHP administration in the hippocampal regions, while the number of NOS-negative cells remained unchanged. The DAHP-induced decrease in the NOS-positive cell number was prevented by the administration of 10 mM BH4 and DAHP. These results suggest that endogenous BH4 may affect NOS-positive cell number in the rat hippocampus.
Collapse
Affiliation(s)
- Kunio Koshimura
- Department of Endocrinology, Metabolism and Hematology, Shimane University School of Medicine, Izumo, Japan.
| | | | | | | | | |
Collapse
|
34
|
Abstract
This review focuses on the role of oxidative processes in atherosclerosis and its resultant cardiovascular events. There is now a consensus that atherosclerosis represents a state of heightened oxidative stress characterized by lipid and protein oxidation in the vascular wall. The oxidative modification hypothesis of atherosclerosis predicts that low-density lipoprotein (LDL) oxidation is an early event in atherosclerosis and that oxidized LDL contributes to atherogenesis. In support of this hypothesis, oxidized LDL can support foam cell formation in vitro, the lipid in human lesions is substantially oxidized, there is evidence for the presence of oxidized LDL in vivo, oxidized LDL has a number of potentially proatherogenic activities, and several structurally unrelated antioxidants inhibit atherosclerosis in animals. An emerging consensus also underscores the importance in vascular disease of oxidative events in addition to LDL oxidation. These include the production of reactive oxygen and nitrogen species by vascular cells, as well as oxidative modifications contributing to important clinical manifestations of coronary artery disease such as endothelial dysfunction and plaque disruption. Despite these abundant data however, fundamental problems remain with implicating oxidative modification as a (requisite) pathophysiologically important cause for atherosclerosis. These include the poor performance of antioxidant strategies in limiting either atherosclerosis or cardiovascular events from atherosclerosis, and observations in animals that suggest dissociation between atherosclerosis and lipoprotein oxidation. Indeed, it remains to be established that oxidative events are a cause rather than an injurious response to atherogenesis. In this context, inflammation needs to be considered as a primary process of atherosclerosis, and oxidative stress as a secondary event. To address this issue, we have proposed an "oxidative response to inflammation" model as a means of reconciling the response-to-injury and oxidative modification hypotheses of atherosclerosis.
Collapse
Affiliation(s)
- Roland Stocker
- Centre for Vascular Research, University of New South Wales, Sydney, New South Wales, Australia.
| | | |
Collapse
|
35
|
Reif A, Shutenko ZV, Feelisch M, Schmidt HHHW. Superoxide dismutase and catalase are required to detect (.-)NO from both coupled and uncoupled neuronal no synthase. Free Radic Biol Med 2004; 37:988-97. [PMID: 15336315 DOI: 10.1016/j.freeradbiomed.2004.07.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2004] [Revised: 05/20/2004] [Accepted: 07/01/2004] [Indexed: 10/26/2022]
Abstract
Despite numerous approaches to measuring nitric oxide ((.-)NO) formation from purified NO synthase (NOS), it is still not clear whether (.-)NO is a direct or indirect product of the NO synthase reaction. The direct detection of catalytically formed (.-)NO is complicated by side reactions with reactive oxide species like H(2)O(2) and superoxide. The aim of the present study was therefore to reinvestigate these reactions both electrochemically and by chemiluminescence detection with particular emphasis on the requirement for cofactors and their interference with (.-)NO detection. Flavins were found to generate large amounts of H(2)O(2) and were therefore excluded from subsequent incubations. Under conditions of both coupled and uncoupled catalysis, SOD was absolutely required to detect (.-)NO from NOS. H(2)O(2) formation took place also in the presence of SOD and gave a smaller yet significant interfering signal. Similar data were obtained when the proposed intermediate N(omega)-hydroxy-l-arginine was utilized as substrate. In conclusion, standard Clark-type ()NO electrodes are cross-sensitive to H(2)O(2) and therefore both SOD and catalase are absolutely required to specifically detect (.-)NO from NOS.
Collapse
Affiliation(s)
- A Reif
- Department of Psychiatry and Psychotherapy, Julius-Maximilians-University Würzburg, D-97078 Würzburg, Germany.
| | | | | | | |
Collapse
|
36
|
Sorlie M, Gorren ACF, Marchal S, Shimizu T, Lange R, Andersson KK, Mayer B. Single-turnover of nitric-oxide synthase in the presence of 4-amino-tetrahydrobiopterin: proposed role for tetrahydrobiopterin as a proton donor. J Biol Chem 2003; 278:48602-10. [PMID: 14514694 DOI: 10.1074/jbc.m305682200] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tetrahydrobiopterin (BH4) is an essential cofactor of nitric-oxide synthase (NOS) that serves as a one-electron donor to the oxyferrous.heme complex. 4-Aminotetrahydrobiopterin (4-amino-BH4) is a potent inhibitor of NO synthesis, although it mimics all allosteric and structural effects of BH4 and exhibits comparable redox properties. We studied the reaction of reduced endothelial NOS oxygenase domain with O2 in the presence of 4-amino-BH4 at -30 degrees C by optical and electron paramagnetic resonance (EPR) spectroscopy. With Arg as the substrate, we observed a trihydropteridine radical with a corresponding heme species that was oxyferrous, with a Soret maximum at 428 nm and no EPR signal. With NG-hydroxy-l-arginine (NHA) no pterin radical appeared, whereas an axial ferrous heme.NO complex was formed. The corresponding optical spectra, with Soret bands at 417/423 nm, suggest that the proximal sulfur ligand is protonated. Accordingly, 4-amino-BH4 serves as a one-electron donor to Fe(II).O2 with both Arg and NHA, but the reaction cycle cannot be completed with either substrate. We propose that protonation of Fe(II)O2- is inhibited in the presence of 4-amino-BH4. With Arg, dissociation of O2- and binding of O2 yields Fe(II).O2 and a pteridine radical; with NHA, reaction of the substrate with heme-bound O2- eventually yields Fe(II).NO and reduced 4-amino-BH4. These results suggest that BH4 donates a proton to Fe(II).O2- during catalysis and that inhibition by 4-amino-BH4 may be due to its inability to support this essential protonation step.
Collapse
Affiliation(s)
- Morten Sorlie
- Department of Chemistry and Biotechnology, Agricultural University of Norway, PO Box 5040, N-1432 As, Norway
| | | | | | | | | | | | | |
Collapse
|
37
|
Kirsch M, Korth HG, Stenert V, Sustmann R, de Groot H. The autoxidation of tetrahydrobiopterin revisited. Proof of superoxide formation from reaction of tetrahydrobiopterin with molecular oxygen. J Biol Chem 2003; 278:24481-90. [PMID: 12714605 DOI: 10.1074/jbc.m211779200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It has been known for quite some time that tetrahydrobiopterin (H4B) is prone to autoxidation in the presence of molecular oxygen. Evidence has been presented that in this process superoxide radicals may be released, although their intermediacy never has been directly proven. In the present study, the autoxidation of H4B was reinvestigated with the aim to find direct evidence for superoxide formation. By means of two specific assays, namely elicitation of luminescence from lucigenin and ESR-spectrometric detection of the DEPMPO-OOH radical adduct, the release of free superoxide radicals was unequivocally demonstrated. The production of superoxide radicals was further corroborated by interaction with nitric oxide. The kinetics of the autoxidation process was established. Our data fully confirm earlier conclusions that the direct reaction between H4B and oxygen serves as an initiation reaction for the further, rapid reaction of the thus formed superoxide with H4B, thereby very likely establishing a chain reaction process involving reduction of molecular oxygen by the intermediary tetrahydrobiopterin radical. Conclusively, because H4B can per se induce oxidative stress, an in vivo overproduction of this pterin, as is evident in various diseases, may be responsible for the observed acceleration of pathophysiological pathways.
Collapse
Affiliation(s)
- Michael Kirsch
- Institut für Physiologische Chemie, Universitätsklinikum, Hufelandstrasse 55, D-45122 Essen, Germany.
| | | | | | | | | |
Collapse
|
38
|
Pannirselvam M, Anderson TJ, Triggle CR. Endothelial cell dysfunction in type I and II diabetes: The cellular basis for dysfunction. Drug Dev Res 2003. [DOI: 10.1002/ddr.10127] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
39
|
Yang D, Levens N, Zhang JN, Vanhoutte PM, Félétou M. Specific potentiation of endothelium-dependent contractions in SHR by tetrahydrobiopterin. Hypertension 2003; 41:136-42. [PMID: 12511543 DOI: 10.1161/01.hyp.0000047669.93078.a7] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
This study was designed to determine the effect of pteridines, R- and S-tetrahydrobiopterin, sepiapterin, and dihydrobiopterin on endothelium-dependent contractions to acetylcholine in isolated aortas from spontaneously hypertensive rat and normotensive Wistar-Kyoto rat. The noncumulative addition of redox-active pteridines R- and S-tetrahydrobiopterin (but not the oxidized analogues sepiapterin and dihydrobiopterin) produced a concentration-dependent transient contraction in isolated aortic rings from both normotensive and hypertensive rats. R- and S-tetrahydrobiopterin (but not sepiapterin or dihydrobiopterin) potentiated the endothelium-dependent contractions to acetylcholine but only in aortas from hypertensive rats and in the presence of N(G)-nitro-L-arginine. In these aortas, the generation of oxygen-derived free radicals by the combination of xanthine plus xanthine oxidase also potentiated the endothelium-dependent contractions to acetylcholine. The presence of R-tetrahydrobiopterin did not alter the characteristics of the endothelium-dependent contractions because they were inhibited by valeryl salicylate, an inhibitor of cyclooxygenase-1, by S18886, a TP-receptor antagonist or by Tiron, a cell permeable superoxide anion scavenger. However, the contractions to acetylcholine, which are unaffected by the combination of superoxide dismutase and catalase, become significantly inhibited by these two scavengers in the presence of R-tetrahydrobiopterin. In the presence of N(G)-nitro-L-arginine, R-tetrahydrobiopterin did not affect the contractions to phenylephrine, U 46619, or to oxygen-derived free radicals generated by xanthine plus xanthine oxidase. These results indicate that the production of superoxide by the autoxidation of tetrahydrobiopterin selectively enhances endothelium-dependent contractions in the spontaneously hypertensive rat when nitric oxide synthase is inhibited.
Collapse
Affiliation(s)
- Di Yang
- Jiangsu Province Hospital, First Affiliated Hospital of Nanjing Medical University, Nanjing, Peoples Republic of China
| | | | | | | | | |
Collapse
|
40
|
Fink B, Bassenge E. Association between vascular tolerance and platelet upregulation: comparison of nonintermittent administration of pentaerithrityltetranitrate and glyceryltrinitrate. J Cardiovasc Pharmacol 2002; 40:890-7. [PMID: 12451322 DOI: 10.1097/00005344-200212000-00010] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Enhanced formation of oxygen-derived radicals O plays a dominant role in the development of nitrate tolerance. In 18 healthy subjects, this study tested the effect of additional vitamin C (Vit-C) administration (1 g three times daily) on glyceryltrinitrate (GTN)-induced hemodynamic changes during 3 days of nonintermittent transdermal administration of GTN (0.4 mg/h) in comparison with administration of pentaerithrityltetranitrate (PETN, 40 mg three times daily, orally). GTN caused an immediate significant rise in arterial conductivity (a/b ratio of dicrotic pulse pressure, from 2.33 +/- 0.06 to 2.52 +/- 0.06). Within 2 days of GTN administration, the a/b ratio progressively decreased and reached pre-GTN control levels, documenting tolerance. However, the administration of GTN along with Vit-C or with PETN alone induced changes in the a/b ratio and in the orthostatic reaction, which were fully maintained for the period of treatment. This vascular tolerance seen after GTN treatment was paralleled by an upregulation of ex vivo platelet activity, which was evident from a rise in aggregation from 29.2 +/- 2.8% at control day to 85.4 +/- 8.5% at day 3, and additionally from thrombin-induced increases of intracellular Ca concentration from 494 +/- 60 nM at control day to 741 +/- 37 nM at day 3. This upregulation was not observed during PETN or GTN; with additional Vit-C administration. Administration of PETN or GTN, the latter supplemented by Vit-C, induced neither vascular tolerance nor the upregulation of washed platelet activity during nonintermittent administration, in contrast to GTN without Vit-C. This is explained by a diminished formation of reactive oxygen species when PETN or when GTN along with Vit-C is used.
Collapse
Affiliation(s)
- Bruno Fink
- Institute of Applied Physiology, University of Freiburg, Germany [corrected].
| | | |
Collapse
|
41
|
Sharma P, Barthwal MK, Dikshit M. NO synthesis and its regulation in the arachidonic-acid-stimulated rat polymorphonuclear leukocytes. Nitric Oxide 2002; 7:119-26. [PMID: 12223181 DOI: 10.1016/s1089-8603(02)00100-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Nitric oxide (NO) synthesis and free radical generation from polymorphonuclear leukocytes (PMNs) play an important role in several pathological conditions. In the present study, regulation of NO synthesis has been investigated in the unstimulated and arachidonic-acid (AA)-stimulated rat PMNs. L-Citrulline formation or nitrite content was used as a marker of NO synthesis, while AA-induced free radical generation was assessed by flow cytometry using a dye, 2('),7(')-dichlorofluoreseindiacetate. L-Citrulline formation in the unstimulated PMNs increased in a time-dependent manner for up to 120 min. The increase was significantly less (25-55%) in AA-stimulated PMNs at all the time points. AA-induced free radical generation was maximum during the first 15 min followed by a time-dependent decrease. Interestingly, similar experiments under hyperoxic conditions did not exhibit any decrease in L-citrulline and nitrite formation after AA stimulation even though the free radical generation further increased. Scavenging or inhibition of free radicals by several types of interventions increased NO generation from AA-stimulated PMNs. The results of the present study suggest that the availability of oxygen, a common substrate for both NADPH oxidase and NOS, can inversely affect the synthesis of NO and PMNs seem to prefer oxygen utilization over NO synthesis for free radical generation.
Collapse
Affiliation(s)
- Prashant Sharma
- Division of Pharmacology, Central Drug Research Institute, Lucknow 226001, India
| | | | | |
Collapse
|
42
|
Pannirselvam M, Verma S, Anderson TJ, Triggle CR. Cellular basis of endothelial dysfunction in small mesenteric arteries from spontaneously diabetic (db/db -/-) mice: role of decreased tetrahydrobiopterin bioavailability. Br J Pharmacol 2002; 136:255-63. [PMID: 12010774 PMCID: PMC1573335 DOI: 10.1038/sj.bjp.0704683] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2002] [Revised: 02/14/2002] [Accepted: 02/18/2002] [Indexed: 02/07/2023] Open
Abstract
1. Endothelium-dependent and -independent regulation of vascular tone in small mesenteric arteries (SMA) from control (db/db +/?) and diabetic (db/db -/-) mice was compared. 2. Phenylephrine-induced maximum contraction, but not sensitivity, of SMA in db/db -/- compared to db/db +/? was enhanced. 3. Acetylcholine (ACh), but not sodium nitroprusside (SNP), -induced relaxation was reduced in SMA from db/db -/- compared to db/db +/?. 4. ACh-induced relaxation of SMA was inhibited by a combination of N(omega)-nitro-L-arginine and indomethacin in db/db +/?, but not in db/db -/-. 5. Acute incubation of SMA with tetrahydrobiopterin (BH(4), 10 microM) and sepiapterin (100 microM) enhanced ACh-induced relaxation in SMA from db/db -/-, but not from db/db +/? 2,4-diamino-6-hydroxypyrimidine, an inhibitor of GTP cyclohydrolase I, (10 mM), impaired the sensitivity of SMA from db/db +/? to ACh, which was restored by co-incubation with BH(4) (10 microM). 6. BH(4) and superoxide dismutase (SOD, 150 u ml(-1)), either alone or in combination, had no effect on either ACh or SNP-induced relaxation in SMA from eNOS -/- mice. 7. Incubation of SMA with SOD (150 iu ml(-1)), catalase (200 iu ml(-1)) and L-arginine (1 mM) had no effect on ACh-induced relaxation of SMA. However, the combination of polyethylene glycol-SOD (200 iu ml(-1)) and catalase (80 u ml(-1)) improved the sensitivity of ACh-induced relaxation in db/db -/-, but not in db/db +/?. 8. These data suggest that increased production of superoxide anions and decreased availability of BH(4) result in an 'uncoupling' of nitric oxide synthase and endothelial dysfunction in SMA from db/db -/- mice.
Collapse
MESH Headings
- Animals
- Biological Availability
- Biopterins/analogs & derivatives
- Biopterins/pharmacokinetics
- Diabetes Mellitus, Type 2/genetics
- Diabetes Mellitus, Type 2/metabolism
- Diabetes Mellitus, Type 2/physiopathology
- Dose-Response Relationship, Drug
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Endothelium, Vascular/physiopathology
- Male
- Mesenteric Arteries/drug effects
- Mesenteric Arteries/metabolism
- Mice
- Mice, Inbred C57BL
- Mice, Mutant Strains
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Leptin
- Vasodilation/drug effects
- Vasodilation/genetics
- Vasodilation/physiology
Collapse
Affiliation(s)
- Malarvannan Pannirselvam
- Department of Pharmacology and Therapeutics and Smooth Muscle Research group, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| | - Subodh Verma
- Division of Cardiac Surgery, University of Toronto, Toronto, ON, Canada
| | - Todd J Anderson
- Division of Cardiology, Foothills Hospital, Calgary, Alberta, Canada
| | - Chris R Triggle
- Department of Pharmacology and Therapeutics and Smooth Muscle Research group, Faculty of Medicine, University of Calgary, Calgary, Alberta T2N 4N1, Canada
| |
Collapse
|
43
|
Koshimura K, Tanaka J, Murakami Y, Kato Y. Involvement of nitric oxide in glucose toxicity on differentiated PC12 cells: prevention of glucose toxicity by tetrahydrobiopterin, a cofactor for nitric oxide synthase. Neurosci Res 2002; 43:31-8. [PMID: 12074839 DOI: 10.1016/s0168-0102(02)00016-0] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Effects of high concentrations of glucose on cell survival of differentiated PC12 cells were examined. Seven day-culture with D-glucose (9.0-27.0 mg/ml as 2-6-fold of the optimal level) induced cell death in a dose-related manner but 3-day culture with high concentrations of glucose had no effect on cell viability. L-glucose had no effect on viability of PC12 cells, suggesting that D-glucose toxicity was independent of its osmolarity effect. Seven-day culture with D-glucose (13.5 mg/ml as 3-fold of the optimal level) increased nitric oxide metabolites (NOx) in the culture medium. Glucose-induced increase in NOx was eliminated by 0.1 mM L-nitro-arginine methylester (L-NAME), a nitric oxide synthase (NOS) inhibitor. Intracellular Ca(2+) concentration was increased by D-glucose in a dose-related manner, suggesting that D-glucose activated NOS by increasing intracellular Ca(2+) concentration in PC12 cells. Glucose-induced cell death was blunted by 0.1 mM L-NAME, showing that nitric oxide (NO) was involved in the glucose toxicity to PC12 cells. Tetrahydrobiopterin (BH(4)), a cofactor for NOS, attenuated both glucose-induced cell death and NOx production at 1 microM but not at 10 microM. The effects of BH(4) on glucose-induced cell death and NOx production were not mimicked by reducing agents such as ascorbate and cysteine. These results taken together suggest that high concentrations of glucose induced cell death via NO production and that low concentration of BH(4) had a protective effect against glucose neurotoxicity in differentiated PC12 cells.
Collapse
Affiliation(s)
- Kunio Koshimura
- Department of Medicine, First Division, Shimane Medical University, Izumo, Japan.
| | | | | | | |
Collapse
|
44
|
Strizhak PE, Khavrus VO, Bar-Eli K. Effect of NO, CO, and Cl2 on Mixed-Mode Regimes in the Belousov−Zhabotinskyi Oscillating Chemical Reaction in a CSTR. J Phys Chem A 2002. [DOI: 10.1021/jp011774k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Peter E. Strizhak
- L.V. Pysarzhevsky Institute of Physical Chemistry of the National Academy of Sciences of Ukraine, pr. Nauki 31, Kiev, 03039, Ukraine, and Tel-Aviv University, Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel-Aviv, 69978, Israel
| | - Vyacheslav O. Khavrus
- L.V. Pysarzhevsky Institute of Physical Chemistry of the National Academy of Sciences of Ukraine, pr. Nauki 31, Kiev, 03039, Ukraine, and Tel-Aviv University, Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel-Aviv, 69978, Israel
| | - Kedma Bar-Eli
- L.V. Pysarzhevsky Institute of Physical Chemistry of the National Academy of Sciences of Ukraine, pr. Nauki 31, Kiev, 03039, Ukraine, and Tel-Aviv University, Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel-Aviv, 69978, Israel
| |
Collapse
|
45
|
Saram KD, McNeill KL, Khokher S, Ritter JM, Chowienczyk PJ. Divergent effects of vitamin C on relaxations of rabbit aortic rings to acetylcholine and NO-donors. Br J Pharmacol 2002; 135:1044-50. [PMID: 11861333 PMCID: PMC1573205 DOI: 10.1038/sj.bjp.0704541] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
1. Vitamin C may influence NO-dependent relaxation independently of effects on oxidant stress. 2. We investigated effects of vitamin C (0.1 -- 10 mmol l(-1)) on relaxation of pre-constricted rabbit aortic rings to acetylcholine (ACh), authentic NO and the NO-donors glyceryl trinitrate (GTN), nitroprusside (NP) and S-nitroso-N-acetyl-penicillamine (SNAP). DETCA (2 -- 6 mmol l(-1)), a cell permeable inhibitor of endogenous Cu-Zn superoxide dismutase (SOD) was used to increase intracellular superoxide anion (O(2)(-)). 3. Vitamin C reduced the response to ACh (71 +/- 7% inhibition of maximum relaxation at 10 mmol l(-1)) and inhibited relaxation to authentic NO. Vitamin C inhibited relaxation to GTN but potentiated relaxations to NP and SNAP, causing a parallel shift to a lower concentration range of the log dose-response curve by approximately one log unit at the highest dose. 4. Vitamin C increased the concentration of NO in bath solution (plus EDTA, 1.0 mmol l(-1)) following the addition of SNAP from 53 +/- 14 to 771 +/- 101 nmol l(-1) over the range 0.1-3.0 mmol l(-1). 5. DETCA inhibited relaxation to ACh (71 +/- 9% inhibition of maximum relaxation). This inhibition was abolished by a cell permeable SOD mimetic, but not by vitamin C. DETCA inhibited relaxation to SNAP but not that to NP nor to GTN. 6. Vitamin C inhibits endothelium-dependent relaxations of rabbit aortic rings to ACh and authentic NO and does not reverse impaired relaxation resulting from increased intracellular oxidant stress. Vitamin C potentiates relaxation to the NO-donors NP and SNAP by a mechanism that could involve release of NO from nitrosothiols.
Collapse
Affiliation(s)
- K de Saram
- Department of Clinical Pharmacology, St Thomas' Hospital, Centre for Cardiovascular Biology and Medicine, King's College, London SE1 7EH
| | - K L McNeill
- Department of Clinical Pharmacology, St Thomas' Hospital, Centre for Cardiovascular Biology and Medicine, King's College, London SE1 7EH
| | - S Khokher
- Department of Clinical Pharmacology, St Thomas' Hospital, Centre for Cardiovascular Biology and Medicine, King's College, London SE1 7EH
| | - J M Ritter
- Department of Clinical Pharmacology, St Thomas' Hospital, Centre for Cardiovascular Biology and Medicine, King's College, London SE1 7EH
| | - P J Chowienczyk
- Department of Clinical Pharmacology, St Thomas' Hospital, Centre for Cardiovascular Biology and Medicine, King's College, London SE1 7EH
- Author for correspondence:
| |
Collapse
|
46
|
David-Dufilho M, Brunet A, Privat C, Devynck MA. Analysis of agonist-evoked nitric oxide release from human endothelial cells: role of superoxide anion. Clin Exp Pharmacol Physiol 2001; 28:1015-9. [PMID: 11903306 DOI: 10.1046/j.1440-1681.2001.03565.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. Dichlorofluorescein oxidation and electrochemical monitoring of in situ nitric oxide (NO) release from cultured human endothelial cells reveals that agonists such as thrombin and histamine simultaneously stimulate transient superoxide production. 2. The duration of *NO release was increased only in the simultaneous presence of extracellular L-arginine and exogenous superoxide dismutase. In contrast, the inhibition of membrane reduced nicotinamide adenine dinucleotide (phosphate) oxidases, the major source of *O2- in endothelial cells, did not prolong *NO release, although extracellular L-arginine was also present. Comparison of these two experimental conditions suggested that H2O2 was involved in the extension of the *NO signal. 3. The present study demonstrates that, in the absence of external L-arginine, *O2- production does not constitute the major pathway controlling the duration of agonist-induced *NO signal. These results suggest that L-arginine and H2O2 act jointly to maintain nitric oxide synthase in an activated form.
Collapse
Affiliation(s)
- M David-Dufilho
- Département de Pharmacologie, UMR 8604, Université René Descartes, Faculté de Médecine Necker, Paris, France
| | | | | | | |
Collapse
|
47
|
Kwon S, Newcomb RL, George SC. Mechanisms of synergistic cytokine-induced nitric oxide production in human alveolar epithelial cells. Nitric Oxide 2001; 5:534-46. [PMID: 11730360 DOI: 10.1006/niox.2001.0387] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitric oxide (NO) derived from inducible NO synthase (iNOS) at sites of inflammation is closely related to host defense against infection and airway inflammation. Cytokines are known to stimulate NO production in human alveolar epithelial cells in a synergistic (nonlinear or nonadditive) manner. The mechanism of this synergy is not known. We measured the activation of the transcription factor NF-kappaB, the iNOS protein, and NO production in A549 monolayers (human alveolar epithelial cell line) in response to different combinations of IL-1beta, INF-gamma, and TNF-alpha (100 ng/ml), and the cofactors FMN, FAD, and BH4. We found that both IL-1beta and TNF-alpha could independently activate cytosolic NF-kappaB, direct its translocation into the nucleus, and induce iNOS monomer synthesis. In addition, different combinations of cytokines produced synergistic amounts of iNOS monomers. Exogenous BH4 (0.1 microM) had no impact on NO production induced by cytokine combinations that included IL-1beta, but significantly enhanced NO production in the presence of INF-gamma and TNF-alpha, and allowed TNF-alpha independently to produce NO. We conclude that there are at least three mechanisms of synergistic cytokine-induced NO production: (1) the biosynthesis of iNOS monomer due to nonlinear interactions by transcription factors, (2) synergistic cytosolic activation of NF-kappaB, and (3) parallel biosynthesis of BH4 in the presence of cytokine combinations that include IL-1beta.
Collapse
Affiliation(s)
- S Kwon
- Department of Chemical and Biochemical Engineering and Materials Science, University of California, Irvine, California 92697-2575, USA
| | | | | |
Collapse
|
48
|
Davidson C, Gow AJ, Lee TH, Ellinwood EH. Methamphetamine neurotoxicity: necrotic and apoptotic mechanisms and relevance to human abuse and treatment. BRAIN RESEARCH. BRAIN RESEARCH REVIEWS 2001; 36:1-22. [PMID: 11516769 DOI: 10.1016/s0165-0173(01)00054-6] [Citation(s) in RCA: 403] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Research into methamphetamine-induced neurotoxicity has experienced a resurgence in recent years. This is due to (1) greater understanding of the mechanisms underlying methamphetamine neurotoxicity, (2) its usefulness as a model for Parkinson's disease and (3) an increased abuse of the substance, especially in the American Mid-West and Japan. It is suggested that the commonly used experimental one-day methamphetamine dosing regimen better models the acute overdose pathologies seen in humans, whereas chronic models are needed to accurately model human long-term abuse. Further, we suggest that these two dosing regimens will result in quite different neurochemical, neuropathological and behavioral outcomes. The relative importance of the dopamine transporter and vesicular monoamine transporter knockout is discussed and insights into oxidative mechanisms are described from observations of nNOS knockout and SOD overexpression. This review not only describes the neuropathologies associated with methamphetamine in rodents, non-human primates and human abusers, but also focuses on the more recent literature associated with reactive oxygen and nitrogen species and their contribution to neuronal death via necrosis and/or apoptosis. The effect of methamphetamine on the mitochondrial membrane potential and electron transport chain and subsequent apoptotic cascades are also emphasized. Finally, we describe potential treatments for methamphetamine abusers with reference to the time after withdrawal. We suggest that potential treatments can be divided into three categories; (1) the prevention of neurotoxicity if recidivism occurs, (2) amelioration of apoptotic cascades that may occur even in the withdrawal period and (3) treatment of the atypical depression associated with withdrawal.
Collapse
Affiliation(s)
- C Davidson
- Department of Psychiatry, Box 3870, Duke University Medical Center, Durham, NC 27710, USA
| | | | | | | |
Collapse
|
49
|
Ishibashi T, Gödecke A, Schrader J. Protein kinase A- and C-dependent modulation of murine inducible nitric oxide synthase. TOHOKU J EXP MED 2001; 194:75-90. [PMID: 11642342 DOI: 10.1620/tjem.194.75] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Effects of pharmacological modulation of protein kinase A, C and G (PKA, PKC and PKG) were examined on inducible form of nitric oxide synthase (iNOS) expressed in COS cells to elucidate regulatory mechanism of iNOS by protein kinases. Formation of nitric oxide (NO), as an index of NOS activity, was assessed by measurement of nitrite in incubation medium in long term observation and by hemoglobin assay method in kinetic study. In long term observation (18 hours), activation of PKA by 8-Br-cAMP increased NO formation that was inhibited by N-(2-[p-bromocinnamylamino] ethyl)-5-isoquinolinesulfonamide (H89). Though activation of PKC by 12-O-tetradecanoyl phorbol-13-acetate (TPA) decreased NO formation, PKC inhibitor, chelerythrine, failed to inhibit the decrease. Activation of PKG with 8-Br-cGMP and inhibition with KT5823 resulted in no change in NO formation. Western blot analysis revealed that neither 8-Br-cAMP nor TPA affect iNOS expression. In kinetic study (short term perfusion study), no change in NO formation was observed by 8-Br-cAMP and TPA. These results indicate that, in living cells, PKG does not play a regulatory role in iNOS activity and that PKA and PKC do not directly modulate iNOS activity. However, PKA and PKC would possibly modify NOS activity indirectly via cofactors necessary for NO formation.
Collapse
Affiliation(s)
- T Ishibashi
- Institut für Herz- und Kreislaufphysiologie, Heinrich-Heine-Universität Düsseldorf, Federal Republic of Germany.
| | | | | |
Collapse
|
50
|
Reif A, Zecca L, Riederer P, Feelisch M, Schmidt HH. Nitroxyl oxidizes NADPH in a superoxide dismutase inhibitable manner. Free Radic Biol Med 2001; 30:803-8. [PMID: 11275480 DOI: 10.1016/s0891-5849(01)00477-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Nitric oxide synthases (NOS) convert L-arginine and N(omega)-hydroxy-L-arginine to nitric oxide (*NO) and/or nitroxyl (NO(-)) in a NADPH-dependent fashion. Subsequently, *NO/superoxide (O(2-)-derived peroxynitrite (ONOO(-)) consumes one additional mol NADPH. The related stoichiometry of NO(-) and NADPH is unclear. We here describe that NO(-) also oxidizes NADPH in a concentration-dependent manner. In the presence of superoxide dismutase (SOD), which also converts NO(-) to *NO, nitrite accumulation was almost doubled and no oxidation of NADPH was observed. Nitrate yield from NO(-) was low, arguing against intermediate ONOO(-) formation. Thus, biologically formed NO(-) may function as an effective pro-oxidant unless scavenged by SOD and affect the apparent NADPH stoichiometry of the NOS reaction.
Collapse
Affiliation(s)
- A Reif
- Clinical Neurochemistry, Department of Psychiatry and Psychotherapy, Julius-Maximilians-University, Würzburg, Germany.
| | | | | | | | | |
Collapse
|