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Delehedde C, Culcasi M, Ricquebourg E, Cassien M, Siri D, Blaive B, Pietri S, Thétiot-Laurent S. Novel Sterically Crowded and Conformationally Constrained α-Aminophosphonates with a Near-Neutral p Ka as Highly Accurate 31P NMR pH Probes. Application to Subtle pH Gradients Determination in Dictyostelium discoideum Cells. Molecules 2022; 27:molecules27144506. [PMID: 35889385 PMCID: PMC9320275 DOI: 10.3390/molecules27144506] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Revised: 07/10/2022] [Accepted: 07/12/2022] [Indexed: 11/16/2022] Open
Abstract
In order to discover new 31P NMR markers for probing subtle pH changes (<0.2 pH unit) in biological environments, fifteen new conformationally constrained or sterically hindered α-aminophosphonates derived from diethyl(2-methylpyrrolidin-2-yl)phosphonate were synthesized and tested for their pH reporting and cytotoxic properties in vitro. All compounds showed near-neutral pKas (ranging 6.28−6.97), chemical shifts not overlapping those of phosphorus metabolites, and spectroscopic sensitivities (i.e., chemical shifts variation Δδab between the acidic and basic forms) ranging from 9.2−10.7 ppm, being fourfold larger than conventional endogenous markers such as inorganic phosphate. X-ray crystallographic studies combined with predictive empirical relationships and ab initio calculations addressed the inductive and stereochemical effects of substituents linked to the protonated amine function. Satisfactory correlations were established between pKas and both the 2D structure and pyramidalization at phosphorus, showing that steric crowding around the phosphorus is crucial for modulating Δδab. Finally, the hit 31P NMR pH probe 1b bearing an unsubstituted 1,3,2-dioxaphosphorinane ring, which is moderately lipophilic, nontoxic on A549 and NHLF cells, and showing pKa = 6.45 with Δδab = 10.64 ppm, allowed the first clear-cut evidence of trans-sarcolemmal pH gradients in normoxic Dictyostelium discoideum cells with an accuracy of <0.05 pH units.
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Affiliation(s)
- Caroline Delehedde
- Aix Marseille Univ, CNRS, ICR, UMR 7273, SMBSO, 13397 Marseille, France; (C.D.); (M.C.); (E.R.); (B.B.); (S.P.)
| | - Marcel Culcasi
- Aix Marseille Univ, CNRS, ICR, UMR 7273, SMBSO, 13397 Marseille, France; (C.D.); (M.C.); (E.R.); (B.B.); (S.P.)
| | - Emilie Ricquebourg
- Aix Marseille Univ, CNRS, ICR, UMR 7273, SMBSO, 13397 Marseille, France; (C.D.); (M.C.); (E.R.); (B.B.); (S.P.)
| | - Mathieu Cassien
- Yelen Analytics, 10 Boulevard Tempête, 13820 Ensuès-la-Redonne, France;
| | - Didier Siri
- Aix Marseille Univ, CNRS, ICR, UMR 7273, CT, 13397 Marseille, France;
| | - Bruno Blaive
- Aix Marseille Univ, CNRS, ICR, UMR 7273, SMBSO, 13397 Marseille, France; (C.D.); (M.C.); (E.R.); (B.B.); (S.P.)
| | - Sylvia Pietri
- Aix Marseille Univ, CNRS, ICR, UMR 7273, SMBSO, 13397 Marseille, France; (C.D.); (M.C.); (E.R.); (B.B.); (S.P.)
| | - Sophie Thétiot-Laurent
- Aix Marseille Univ, CNRS, ICR, UMR 7273, SMBSO, 13397 Marseille, France; (C.D.); (M.C.); (E.R.); (B.B.); (S.P.)
- Correspondence: ; Tel.: +33-(0)4-13-94-58-07
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Petrocchi C, Thétiot-Laurent S, Culcasi M, Pietri S. Novel Mitochondria-Targeted Triphenylphosphonium Conjugates of Linear β-Phosphorylated Nitrones : Preparation, 31P NMR Mitochondrial Distribution, EPR Spin Trapping Reporting, and Site-Directed Antiapoptotic Properties. Methods Mol Biol 2021; 2275:65-85. [PMID: 34118032 DOI: 10.1007/978-1-0716-1262-0_5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The mitochondrion can be considered as the metabolic powerhouse of the cell, having a key impact on energy production, cell respiration, and intrinsic cell death. Mitochondria are also the main source of endogenous reactive oxygen species , including free radicals (FR), which are physiologically involved in signaling pathways but may promote cell damage when unregulated or excessively formed in inappropriate locations. A variety of chronic pathologies have been associated with FR-induced mitochondrial dysfunctions , such as cancer, age-related neurodegenerative diseases, and metabolic syndrome.In recent years drug design based on specific mitochondria-targeted antioxidants has become a very attractive therapeutic strategy and, among target compounds, nitrones have received growing attention because of their specific affinity toward FR. Here, we describe protocols dealing with the preparation, mitochondria permeation assessment, electron paramagnetic resonance (EPR) spin trapping setting, and antiapoptotic properties evaluation of a series of new linear nitrones vectorized by a triphenylphosphonium cation and labeled with a diethoxyphosphoryl moiety as 31P nuclear magnetic resonance (NMR) reporter with antioxidant property.
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Affiliation(s)
- Consuelo Petrocchi
- Aix Marseille Univ, CNRS, ICR, UMR 7273, Sondes Moléculaires en Biologie et Stress Oxydant, Marseille, France
| | - Sophie Thétiot-Laurent
- Aix Marseille Univ, CNRS, ICR, UMR 7273, Sondes Moléculaires en Biologie et Stress Oxydant, Marseille, France
| | - Marcel Culcasi
- Aix Marseille Univ, CNRS, ICR, UMR 7273, Sondes Moléculaires en Biologie et Stress Oxydant, Marseille, France
| | - Sylvia Pietri
- Aix Marseille Univ, CNRS, ICR, UMR 7273, Sondes Moléculaires en Biologie et Stress Oxydant, Marseille, France.
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On the vasoprotective mechanisms underlying novel β-phosphorylated nitrones: Focus on free radical characterization, scavenging and NO-donation in a biological model of oxidative stress. Eur J Med Chem 2016; 119:197-217. [PMID: 27162124 DOI: 10.1016/j.ejmech.2016.04.067] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2016] [Revised: 04/26/2016] [Accepted: 04/27/2016] [Indexed: 01/02/2023]
Abstract
A series of new hybrid 2-(diethoxyphosphoryl)-N-(benzylidene)propan-2-amine oxide derivatives with different aromatic substitution (PPNs) were synthesized. These molecules were evaluated for their EPR spin trapping potential on eleven different radicals and NO-donation properties in vitro, cytotoxicity and vasoprotective effect on precontracted rat aortic rings. A subfamily of the new PPNs featured an antioxidant moiety occurring in natural phenolic acids. From the experimental screening of these hydroxyphenyl- and methoxyphenyl-substituted PPNs, biocompatible nitrones 4d, and 4g-4i deriving from caffeic, gallic, ferulic and sinapic acids, which combined improved EPR probing of ROS formation, vasorelaxant action and antioxidant potency, might be potential drug candidate alternatives to PBN and its analogues.
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Translation of TRO40303 from myocardial infarction models to demonstration of safety and tolerance in a randomized Phase I trial. J Transl Med 2014; 12:38. [PMID: 24507657 PMCID: PMC3923730 DOI: 10.1186/1479-5876-12-38] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 01/28/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Although reperfusion injury has been shown to be responsible for cardiomyocytes death after an acute myocardial infarction, there is currently no drug on the market that reduces this type of injury. TRO40303 is a new cardioprotective compound that was shown to inhibit the opening of the mitochondrial permeability transition pore and reduce infarct size after ischemia-reperfusion in a rat model of cardiac ischemia-reperfusion injury. METHODS In the rat model, the therapeutic window and the dose effect relationship were investigated in order to select the proper dose and design for clinical investigations. To evaluate post-ischemic functional recovery, TRO40303 was tested in a model of isolated rat heart. Additionally, TRO40303 was investigated in a Phase I randomized, double-blind, placebo controlled study to assess the safety, tolerability and pharmacokinetics of single intravenous ascending doses of the compound (0.5 to 13 mg/kg) in 72 healthy male, post-menopausal and hysterectomized female subjects at flow rates from 0.04 to 35 mL/min (EudraCT number: 2010-021453-39). This work was supported in part by the French Agence Nationale de la Recherche. RESULTS In the vivo model, TRO40303 reduced infarct size by 40% at 1 mg/kg and by 50% at 3 and 10 mg/kg given by intravenous bolus and was only active when administered before reperfusion. Additionally, TRO40303 provided functional recovery and reduced oxidative stress in the isolated rat heart model.These results, together with pharmacokinetic based allometry to human and non-clinical toxicology data, were used to design the Phase I trial. All the tested doses and flow rates were well tolerated clinically. There were no serious adverse events reported. No relevant changes in vital signs, electrocardiogram parameters, laboratory tests or physical examinations were observed at any time in any dose group. Pharmacokinetics was linear up to 6 mg/kg and slightly ~1.5-fold, hyper-proportional from 6 to 13 mg/kg. CONCLUSIONS These data demonstrated that TRO40303 can be safely administered by the intravenous route in humans at doses expected to be pharmacologically active. These results allowed evaluating the expected active dose in human at 6 mg/kg, used in a Phase II proof-of-concept study currently ongoing.
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Oka T, Yamashita S, Midorikawa M, Saiki S, Muroya Y, Kamibayashi M, Yamashita M, Anzai K, Katsumura Y. Spin-Trapping Reactions of a Novel Gauchetype Radical Trapper G-CYPMPO. Anal Chem 2011; 83:9600-4. [DOI: 10.1021/ac2023926] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Toshitaka Oka
- Advanced Science Research Center, Japan Atomic Energy Agency (JAEA), Tokai-mura, Ibaraki 319−1195, Japan
| | - Shinichi Yamashita
- Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA), Takasaki, Gunma 370−1292, Japan
| | | | - Seiichi Saiki
- Quantum Beam Science Directorate, Japan Atomic Energy Agency (JAEA), Takasaki, Gunma 370−1292, Japan
| | - Yusa Muroya
- School of Engineering, The University of Tokyo, Tokai-mura, Ibaraki 319−1188, Japan
| | - Masato Kamibayashi
- Pharmaceutical Manufacturing Chemistry, Kyoto Pharmaceutical University, Kyoto, Kyoto 607−8414, Japan
| | - Masayuki Yamashita
- Pharmaceutical Manufacturing Chemistry, Kyoto Pharmaceutical University, Kyoto, Kyoto 607−8414, Japan
| | - Kazunori Anzai
- School of Pharmaceutical Sciences, Nihon Pharmaceutical University, Kitaadachi, Saitama 362−0806, Japan
| | - Yosuke Katsumura
- School of Engineering, The University of Tokyo, Bunkyo, Tokyo 113−8656, Japan
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Han Y, Liu Y, Rockenbauer A, Zweier JL, Durana G, Villamena FA. Lipophilic beta-cyclodextrin cyclic-nitrone conjugate: synthesis and spin trapping studies. J Org Chem 2009; 74:5369-80. [PMID: 19530689 PMCID: PMC2736355 DOI: 10.1021/jo900856x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Nitrone spin traps are commonly employed as probes for the identification of transient radicals in chemical and biological systems using electron paramagnetic resonance (EPR) spectroscopy. Nitrones have also found applications as therapeutic agent in the treatment of radical-mediated diseases. Therefore, a spin trap that incorporates high reactivity to superoxide radical anion (O2(*-)), more persistent superoxide adduct, enhanced bioavailability, and selective targeting in one molecular design is desirable. In this work, the synthesis of a nitrone spin trap, 4, that is tethered via amide bonds to a beta-cyclodextrin (beta-CD) and a dodecyl chain was achieved with the expectation that the beta-cyclodextrin would lead to increased reactivity to O2(*-) and persistent O2(*-) adduct while the lipophilic chain would impart membrane targeting property. The two constitutional racemic isomers, 4a and 4b, were separated using preparative HPLC, and structural analysis and self-aggregation properties were carried out using NMR, induced circular dichroism, dynamic light scattering, transmission electron microscopy, and computational approach. EPR spin trapping of O2(*-) by 4a and 4b was only successful in DMSO and not in an aqueous system, due most likely to the amphiphilic character of 4 that can favor conformations (or aggregation) hindering radical addition to nitrone. Kinetics of formation and decay of the 4a-O2H adduct in polar aprotic solvents show faster reactivity to O2(*-) and more persistent O2(*-) adduct compared to nitrones not conjugated to beta-CD. Computational analysis of 4a and 4b as well as 4a-OOH and 4b-OOH adducts were carried out, and results show that isomerism, both constitutional and stereochemical, affects the orientations of aminoxyl-NO and/or hydroperoxyl groups relative to the beta-CD annulus for optimal H-bond interaction and stability.
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Affiliation(s)
- Yongbin Han
- Department of Pharmacology, The Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210
| | - Yangping Liu
- Center for Biomedical EPR Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210
| | - Antal Rockenbauer
- Chemical Research Center, Institute of Structural Chemistry, H-1025 Budapest, Pusztaszeri 59, Hungary
| | - Jay L. Zweier
- Center for Biomedical EPR Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210
| | - Grégory Durana
- Laboratoire de Chimie BioOrganique et des Systèmes Moléculaires Vectoriels, Faculté des Sciences, Université d’Avignon et des Pays de Vaucluse, 33 Rue Louis Pasteur, 84000 Avignon, France
| | - Frederick A. Villamena
- Department of Pharmacology, The Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210
- Center for Biomedical EPR Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University, Columbus, OH 43210
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Durand G, Choteau F, Pucci B, Villamena FA. Reactivity of superoxide radical anion and hydroperoxyl radical with alpha-phenyl-N-tert-butylnitrone (PBN) derivatives. J Phys Chem A 2009; 112:12498-509. [PMID: 18998656 DOI: 10.1021/jp804929d] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitrones have exhibited pharmacological activity against radical-mediated pathophysiological conditions and as analytical reagents for the identification of transient radical species by electron paramagnetic resonance (EPR) spectroscopy. In this work, competitive spin trapping, stopped-flow kinetics, and density functional theory (DFT) were employed to assess and predict the reactivity of O(2)(*-) and HO(2)(*) with various para-substituted alpha-phenyl-N-tert-butylnitrone (PBN) spin traps. Rate constants of O(2)(*-) trapping by nitrones were determined using competitive UV-vis stopped-flow method with phenol red (PR) as probe, while HO(2)(*) trapping rate constants were calculated using competition kinetics with 5,5-dimethylpyrroline N-oxide (DMPO) by employing EPR spectroscopy. The effects of the para substitution on the charge density of the nitronyl-carbon and on the free energies of nitrone reactivity with O(2)(*-) and HO(2)(*) were computationally rationalized at the PCM/B3LYP/6-31+G(d,p)//B3LYP/6-31G(d) level of theory. Theoretical and experimental data show that the rate of O(2)(*-) addition to PBN derivatives is not affected by the polar effect of the substituents. However, the reactivity of HO(2)(*) follows the Hammett equation and is increased as the substituent becomes more electron withdrawing. This supports the conclusion that the nature of HO(2)(*) addition to PBN derivatives is electrophilic, while the addition of O(2)(*-) to PBN-type compounds is only weakly electrophilic.
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Affiliation(s)
- Grégory Durand
- Laboratoire de Chimie Bioorganique et des Systèmes Moléculaires Vectoriels, Université d'Avignon et des Pays de Vaucluse, Faculté des Sciences, 33 rue Louis Pasteur, 84000 Avignon, France.
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Zuo L, Chen YR, Reyes LA, Lee HL, Chen CL, Villamena FA, Zweier JL. The radical trap 5,5-dimethyl-1-pyrroline N-oxide exerts dose-dependent protection against myocardial ischemia-reperfusion injury through preservation of mitochondrial electron transport. J Pharmacol Exp Ther 2009; 329:515-23. [PMID: 19201989 DOI: 10.1124/jpet.108.143479] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Free radicals are important mediators of myocardial ischemia-reperfusion injury. Nitrone spin traps have been shown to scavenge free radicals. The cardioprotective effect of the spin trap, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), was investigated in an isolated heart model of global ischemia and reperfusion. Rat hearts were perfused and subjected to global ischemia for 30 min followed by reperfusion with four treatment groups of varying DMPO concentration (0.5-10 mM) administered before induction of ischemia. DMPO treatment improved the recovery of left ventricular (LV) function and coronary flow over the 30-min period of reperfusion compared with untreated hearts. Enhanced recovery was observed for all doses studied but was highest with 1 mM treatment with 2.4-fold higher recovery of LV developed pressure and 37% reduction in infarct size. Superoxide was measured by tissue fluorometry using the O(2)* probe hydroethidine. Hearts treated with 1 mM DMPO showed a significant reduction in O(2)* production compared with control hearts both over the first 5 min of ischemia and upon reperfusion after 30 min of global ischemia. Studies of mitochondrial function demonstrated that 1 mM DMPO increased the recovery of function of complexes I, II/III, and IV after 30 min of reperfusion. Immunoblotting with antibodies against complexes I, II, and IV further revealed marked up-regulation of mitochondrial proteins, suggesting that DMPO prevents their ischemic degradation via scavenging oxygen radicals generated during ischemia/reperfusion. Thus, DMPO functions as a protective agent against ischemic and postischemic injury via radical scavenging, conferring robust dose-dependent protection with salvage of mitochondrial function and redox homeostasis.
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Affiliation(s)
- Li Zuo
- Center for Biomedical Electron Paramagnetic Resonance Spectroscopy and Imaging, The Davis Heart and Lung Research Institute, Ohio State University, Columbus, OH 43210-1252, USA
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Gosset G, Martel S, Clément JL, Blaive B, Olive G, Culcasi M, Rosas R, Thévand A, Pietri S. Nouveaux marqueurs de pH utilisables en RMN du 31P. Détermination de la relaxation longitudinale en fonction de la structure chimique, de la température, du pH et du milieu biologique. CR CHIM 2008. [DOI: 10.1016/j.crci.2007.08.016] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Burgett RA, Bao X, Villamena FA. Superoxide Radical Anion Adduct of 5,5-Dimethyl-1-pyrroline N-Oxide (DMPO). 3. Effect of Mildly Acidic pH on the Thermodynamics and Kinetics of Adduct Formation. J Phys Chem A 2008; 112:2447-55. [DOI: 10.1021/jp7107158] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Randy A. Burgett
- Department of Pharmacology and Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210
| | - Xiaofeng Bao
- Department of Pharmacology and Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210
| | - Frederick A. Villamena
- Department of Pharmacology and Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210
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Pietri S, Mercier A, Mathieu C, Caffaratti S, Culcasi M. Hemodynamic and metabolic effects of the beta-phosphorylated nitroxide 2-diethoxyphosphoryl-2,5,5-trimethylpyrrolidinoxyl during myocardial ischemia and reperfusion. Free Radic Biol Med 2003; 34:1167-77. [PMID: 12706497 DOI: 10.1016/s0891-5849(03)00069-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In vitro, the stable six-membered ring nitroxide 2,2,6,6-tetramethyl-1-piperidine-N-oxyl (TEMPO) is known to protect the ischemic and reperfused myocardium through a mechanism likely to involve the limitation of free radical damage. In vivo, TEMPO's high rate of reduction into diamagnetic nonactive compounds could limit its pharmacological use and its potential as an ESR probe in oxymetry studies. Recently, beta-phosphorylated nitrones and pyrrolidines have been reported to protect against myocardial reperfusion injury better than their nonphosphorylated analogs. Using hemodynamic, metabolic, and enzymatic indices of reperfusion injury, the efficacy of 2-diethoxyphosphoryl-2,5,5-trimethylpyrrolidinoxyl (TMPPO), a five-membered ring beta-phosphorylated nitroxide, has been compared to that of TEMPO when added at a nontoxic concentration (1 mM) in buffer-perfused isolated rat hearts during low-flow ischemia, total ischemia, and reflow. TMPPO, which is five times as hydrophilic and eight times as resistant to reduction in a biological medium as TEMPO, was more effective in reducing postischemic contracture and myocardial enzymatic leakage. Since a diamagnetic analog of TMPPO was far less protective and both nitroxides showed an antilipoperoxidant effect and acted mainly when administered only at reflow, it was proposed that beta-phosphorylated nitroxides such as TMPPO could be interesting alternatives in pharmacological and ESR applications.
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Affiliation(s)
- Sylvia Pietri
- Laboratoire Structure et Réactivité des Espèces Paramagnétiques UMR 6517 du Centre National de la Recherche Scientifique, Universités d'Aix-Marseille I et III, France.
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Pietri S, Miollan M, Martel S, Le Moigne F, Blaive B, Culcasi M. alpha - and beta -phosphorylated amines and pyrrolidines, a new class of low toxic highly sensitive 31P NMR pH indicators. Modeling of pKa and chemical shift values as a function of substituents. J Biol Chem 2000; 275:19505-12. [PMID: 10748044 DOI: 10.1074/jbc.m001784200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fourteen linear and cyclic alpha- and beta-aminophosphonates in which the P-atom is substituted by alkoxy groups have been synthesized and evaluated as (31)P NMR pH markers in Krebs-Henseleit buffer. pK(a) values varied with substitution in the range 1.3-9.1, giving potentially access to a wide range of pH. Temperature had a weak influence on pH and a dramatic increase in ionic strength slightly modified the pK(a) of the pyrrolidine diethyl(2-methylpyrrolidin-2-yl)phosphonate (DEPMPH). All compounds displayed a 4-fold better NMR sensitivity than inorganic phosphate or other commonly used phosphonates, as assessed by differences delta(b)-delta(a) between the chemical shifts of the protonated and the unprotonated forms. In isolated perfused rat hearts, a non-toxic concentration window of 1.5-15 mm was determined for three representative compounds. Using empirical linear relationships, the experimental values of pK(a), delta(a), and delta(b) have been correlated with the two-dimensional structure, i.e. the chemical nature of substituents bonded to the secondary amine and P-atom. The data suggest that DEPMPH and its cyclic and linear variants are ideal versatile (31)P NMR probes for the study of tenuous pH changes in biological processes.
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Affiliation(s)
- S Pietri
- Structure et Réactivité des Espèces Paramagnétiques, CNRS-UMR 6517, France.
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