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Ramírez Ortega D, Ugalde Muñiz PE, Blanco Ayala T, Vázquez Cervantes GI, Lugo Huitrón R, Pineda B, González Esquivel DF, Pérez de la Cruz G, Pedraza Chaverrí J, Sánchez Chapul L, Gómez-Manzo S, Pérez de la Cruz V. On the Antioxidant Properties of L-Kynurenine: An Efficient ROS Scavenger and Enhancer of Rat Brain Antioxidant Defense. Antioxidants (Basel) 2021; 11:antiox11010031. [PMID: 35052535 PMCID: PMC8773258 DOI: 10.3390/antiox11010031] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 12/18/2021] [Accepted: 12/20/2021] [Indexed: 02/07/2023] Open
Abstract
L-kynurenine (L-KYN) is an endogenous metabolite, that has been used as a neuroprotective strategy in experimental models. The protective effects of L-KYN have been attributed mainly to kynurenic acid (KYNA). However, considering that L-KYN is prone to oxidation, this redox property may play a substantial role in its protective effects. The aim of this work was to characterize the potential impact of the redox properties of L-KYN, in both synthetic and biological systems. First, we determined whether L-KYN scavenges reactive oxygen species (ROS) and prevents DNA and protein oxidative degradation in synthetic systems. The effect of L-KYN and KYNA (0.1–100 µM) on redox markers (ROS production, lipoperoxidation and cellular function) was compared in rat brain homogenates when exposed to FeSO4 (10 µM). Then, the effect of L-KYN administration (75 mg/kg/day for 5 days) on the GSH content and the enzymatic activity of glutathione reductase (GR) and glutathione peroxidase (GPx) was determined in rat brain tissue. Finally, brain homogenates from rats pretreated with L-KYN were exposed to pro-oxidants and oxidative markers were evaluated. The results show that L-KYN is an efficient scavenger of ●OH and ONOO−, but not O2●– or H2O2 and that it prevents DNA and protein oxidative degradation in synthetic systems. L-KYN diminishes the oxidative effect induced by FeSO4 on brain homogenates at lower concentrations (1 µM) when compared to KYNA (100 µM). Furthermore, the sub-chronic administration of L-KYN increased the GSH content and the activity of both GR and GPx, and also prevented the oxidative damage induced by the ex vivo exposure to pro-oxidants. Altogether, these findings strongly suggest that L-KYN can be considered as a potential endogenous antioxidant.
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Affiliation(s)
- Daniela Ramírez Ortega
- Neurochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico; (D.R.O.); (T.B.A.); (G.I.V.C.); (D.F.G.E.)
| | - Perla Eugenia Ugalde Muñiz
- Laboratorio de Neuroendocrinología, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), Mexico City 04510, Mexico;
| | - Tonali Blanco Ayala
- Neurochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico; (D.R.O.); (T.B.A.); (G.I.V.C.); (D.F.G.E.)
| | - Gustavo Ignacio Vázquez Cervantes
- Neurochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico; (D.R.O.); (T.B.A.); (G.I.V.C.); (D.F.G.E.)
| | - Rafael Lugo Huitrón
- Laboratorio de Neurobiología Conductual, Facultad de Medicina, Universidad Nacional Autónoma de México (UNAM), Mexico City 04510, Mexico;
| | - Benjamín Pineda
- Neuroimmunology Department, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico;
| | - Dinora Fabiola González Esquivel
- Neurochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico; (D.R.O.); (T.B.A.); (G.I.V.C.); (D.F.G.E.)
| | - Gonzalo Pérez de la Cruz
- Department of Mathematics, Faculty of Sciences, Universidad Nacional Autónoma de México (UNAM), Mexico City 04510, Mexico;
| | - José Pedraza Chaverrí
- Department of Biology, Faculty of Chemistry, Universidad Nacional Autónoma de México (UNAM), Mexico City 04510, Mexico;
| | - Laura Sánchez Chapul
- Neuromuscular Diseases Laboratory, National Institute of Rehabilitation “Luis Guillermo Ibarra Ibarra”, Mexico City 14389, Mexico;
| | - Saúl Gómez-Manzo
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico;
| | - Verónica Pérez de la Cruz
- Neurochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico; (D.R.O.); (T.B.A.); (G.I.V.C.); (D.F.G.E.)
- Correspondence: ; Tel.: +52-55-56063822 (ext. 2006)
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Dahmani M, Anderson JF, Sultana H, Neelakanta G. Rickettsial pathogen uses arthropod tryptophan pathway metabolites to evade reactive oxygen species in tick cells. Cell Microbiol 2020; 22:e13237. [PMID: 32562372 DOI: 10.1111/cmi.13237] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Revised: 06/10/2020] [Accepted: 06/13/2020] [Indexed: 12/16/2022]
Abstract
Reactive oxygen species (ROS) that are induced upon pathogen infection plays an important role in host defence. The rickettsial pathogen Anaplasma phagocytophilum, which is primarily transmitted by Ixodes scapularis ticks in the United States, has evolved many strategies to escape ROS and survive in mammalian cells. However, little is known on the role of ROS in A. phagocytophilum infection in ticks. Our results show that A. phagocytophilum and hemin induce activation of l-tryptophan pathway in tick cells. Xanthurenic acid (XA), a tryptophan metabolite, supports A. phagocytophilum growth in tick cells through inhibition of tryptophan dioxygenase (TDO) activity leading to reduced l-kynurenine levels that subsequently affects build-up of ROS. However, hemin supports A. phagocytophilum growth in tick cells by inducing TDO activity leading to increased l-kynurenine levels and ROS production. Our data reveal that XA and kynurenic acid (KA) chelate hemin. Furthermore, treatment of tick cells with 3-hydroxyl l-kynurenine limits A. phagocytophilum growth in tick cells. RNAi-mediated knockdown of kynurenine aminotransferase expression results in increased ROS production and reduced A. phagocytophilum burden in tick cells. Collectively, these results suggest that l-tryptophan pathway metabolites influence A. phagocytophilum survival by affecting build up of ROS levels in tick cells.
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Affiliation(s)
- Mustapha Dahmani
- Department of Biological Sciences, Old Dominion University, Norfolk, Virginia, USA.,Department of Veterinary Medicine, University of Maryland, College Park, Maryland, USA
| | - John F Anderson
- Department of Entomology, Connecticut Agricultural Experiment Station, New Haven, Connecticut, USA
| | - Hameeda Sultana
- Department of Biological Sciences, Old Dominion University, Norfolk, Virginia, USA.,Center for Molecular Medicine, Old Dominion University, Norfolk, VA, USA
| | - Girish Neelakanta
- Department of Biological Sciences, Old Dominion University, Norfolk, Virginia, USA.,Center for Molecular Medicine, Old Dominion University, Norfolk, VA, USA
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González Esquivel D, Ramírez-Ortega D, Pineda B, Castro N, Ríos C, Pérez de la Cruz V. Kynurenine pathway metabolites and enzymes involved in redox reactions. Neuropharmacology 2017; 112:331-345. [DOI: 10.1016/j.neuropharm.2016.03.013] [Citation(s) in RCA: 71] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 02/28/2016] [Accepted: 03/06/2016] [Indexed: 11/27/2022]
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Reyes Ocampo J, Lugo Huitrón R, González-Esquivel D, Ugalde-Muñiz P, Jiménez-Anguiano A, Pineda B, Pedraza-Chaverri J, Ríos C, Pérez de la Cruz V. Kynurenines with neuroactive and redox properties: relevance to aging and brain diseases. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2014; 2014:646909. [PMID: 24693337 PMCID: PMC3945746 DOI: 10.1155/2014/646909] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 12/12/2013] [Accepted: 12/15/2013] [Indexed: 11/18/2022]
Abstract
The kynurenine pathway (KP) is the main route of tryptophan degradation whose final product is NAD(+). The metabolism of tryptophan can be altered in ageing and with neurodegenerative process, leading to decreased biosynthesis of nicotinamide. This fact is very relevant considering that tryptophan is the major source of body stores of the nicotinamide-containing NAD(+) coenzymes, which is involved in almost all the bioenergetic and biosynthetic metabolism. Recently, it has been proposed that endogenous tryptophan and its metabolites can interact and/or produce reactive oxygen species in tissues and cells. This subject is of great importance due to the fact that oxidative stress, alterations in KP metabolites, energetic deficit, cell death, and inflammatory events may converge each other to enter into a feedback cycle where each one depends on the other to exert synergistic actions among them. It is worth mentioning that all these factors have been described in aging and in neurodegenerative processes; however, has so far no one established any direct link between alterations in KP and these factors. In this review, we describe each kynurenine remarking their redox properties, their effects in experimental models, their alterations in the aging process.
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Affiliation(s)
- Jazmin Reyes Ocampo
- Departamento de Neuroquímica, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A., Insurgentes Sur 3877, 14269 México, DF, Mexico
- Área de Neurociencias, Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana-Iztapalapa, 09340 México, DF, Mexico
| | - Rafael Lugo Huitrón
- Departamento de Neuroquímica, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A., Insurgentes Sur 3877, 14269 México, DF, Mexico
| | - Dinora González-Esquivel
- Departamento de Neuroquímica, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A., Insurgentes Sur 3877, 14269 México, DF, Mexico
| | - Perla Ugalde-Muñiz
- Departamento de Neuroquímica, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A., Insurgentes Sur 3877, 14269 México, DF, Mexico
| | - Anabel Jiménez-Anguiano
- Área de Neurociencias, Departamento de Biología de la Reproducción, Universidad Autónoma Metropolitana-Iztapalapa, 09340 México, DF, Mexico
| | - Benjamín Pineda
- Laboratorio de Neuroinmunología, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A., 14269 México, DF, Mexico
| | - José Pedraza-Chaverri
- Departamento de Biología, Facultad de Química, Universidad Nacional Autónoma de México, 04510 México, DF, Mexico
| | - Camilo Ríos
- Departamento de Neuroquímica, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A., Insurgentes Sur 3877, 14269 México, DF, Mexico
| | - Verónica Pérez de la Cruz
- Departamento de Neuroquímica, Instituto Nacional de Neurología y Neurocirugía Manuel Velasco Suárez, S.S.A., Insurgentes Sur 3877, 14269 México, DF, Mexico
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Identification of (L)-3-hydroxykynurenine O-sulfate in the buccal gland secretion of the parasitic lamprey, Lethenteron japonicum. Amino Acids 2012; 43:2505-12. [PMID: 22648634 DOI: 10.1007/s00726-012-1331-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 05/22/2012] [Indexed: 10/28/2022]
Abstract
Parasitic lampreys are known to secrete proteins having anticoagulant and vasodilator activities from the buccal glands during feeding on their host's blood. However, small molecules in the secretion have never been explored in detail. We examined the secretion of Japanese liver lamprey (Lethenteron japonicum) for small molecules and found an intensely fluorescent substance upon gel filtration. After purification by anion-exchange chromatography and reversed-phase HPLC, structure of the compound was determined to be L-3-hydroxykynurenine O-sulfate by NMR- and UV-spectrometry, complemented with enzymatic and chemical degradation. In vertebrates, the sulfate ester of 3-hydroxykynurenine is a compound that has been regarded as a urinary metabolite of tryptophan but not reported from normal tissues to date. Although the function of this molecule in the buccal glands remains to be elucidated, it is remarkable that the same substance was described in 1960s from two species of blood-sucking insects, Rhodnius prolixus and Triatoma infestans, suggesting its potential role in blood-feeding.
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Tsentalovich YP, Yanshole VV, Polienko YF, Morozov SV, Grigor’ev IA. Deactivation of Excited States of Kynurenine Covalently Linked to Nitroxides. Photochem Photobiol 2010; 87:22-31. [DOI: 10.1111/j.1751-1097.2010.00841.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Antioxidative properties of nitroxyl radicals and hydroxyamines in reactions with triplet and deaminated kynurenine. Russ Chem Bull 2010. [DOI: 10.1007/s11172-010-0046-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Snytnikova O, Sherin P, Tsentalovich Y. Biphotonic ionization of kynurenine and 3-hydroxykynurenine. J Photochem Photobiol A Chem 2007. [DOI: 10.1016/j.jphotochem.2006.08.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Tsentalovich YP, Snytnikova OA, Sherin PS, Forbes MDE. Photochemistry of Kynurenine, a Tryptophan Metabolite: Properties of the Triplet State. J Phys Chem A 2005; 109:3565-8. [PMID: 16839022 DOI: 10.1021/jp045142k] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photolysis of aqueous kynurenine (KN) solutions results in the formation of triplet kynurenine TKN. In low pH solutions, triplet formation occurs with almost 100% efficiency, while in neutral solutions the triplet quantum yield is PhiT = 0.018 +/- 0.004. The dissociation constant of TKN, which is attributed to deprotonation of the anilino group, has a pKa value of 4.7. Similar triplet absorption spectra were obtained under direct and acetone-sensitized photolysis. The large difference in quantum yields as a function of pH is attributed to excited-state properties of the first excited singlet state of KN. The rate constant quenching for TKN by oxygen is kq = 2 x 10(9) M(-1) s(-1).
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Affiliation(s)
- Yuri P Tsentalovich
- International Tomography Center, Institutskaya 3a, Novosibirsk, Russia 630090, Novosibirsk State University, 630090 Novosibirsk, Russia.
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Abstract
The tryptophan metabolite xanthurenic acid (Xan) has been isolated from aged human cataractous lenses. The photophysical properties of Xan were examined to determine if it is a potential chromophore for age-related cataractogenesis. We found that Xan produces singlet oxygen (psi delta = 0.17 in CD3OD) with the same efficiency as the lenticular chromophore N-formyl kynurenine and quenches singlet oxygen at a rate similar (2.1 x 10(7); CD3OD) to other tryptophan metabolites found in the eye. As the mechanisms of induction of cataracts may also involve redox reactions, the interactions of hydrated electrons (e(aq)-), the azide radical (N3*) and hydroxyl radical (OH*) with Xan were studied using the technique of pulse radiolysis. The reaction rate constants of e(aq)-, N3* and OH* with Xan were found to be of the same order of magnitude as other tryptophan metabolites. The rate constant for reaction of Xan with e(aq)- solvated electrons was found to be diffusion controlled (k = 1.43 x 10(10) M(-1) s(-1); the reaction with N3* was very fast (k = 4.0 x 10(9) M(-1) s(-1)); and with OH* was also near diffusion controlled (k = 1.0 x 10(10) M(-1) s(-1)). Superoxide O2*- production by irradiated Xan in methanol was detected by electron paramagnetic resonance and substantiated by determining that the enhanced rate of oxygen consumption of Xan irradiated in the presence of furfuryl alcohol was lowered by superoxide dismutase.
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Affiliation(s)
- J E Roberts
- Fordham University, New York City, NY 10023, USA.
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Vazquez S, Garner B, Sheil MM, Truscott RJ. Characterisation of the major autoxidation products of 3-hydroxykynurenine under physiological conditions. Free Radic Res 2000; 32:11-23. [PMID: 10625213 DOI: 10.1080/10715760000300021] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
3-Hydroxykynurenine (3-OHKyn) is a tryptophan metabolite that is readily autoxidised to products that may be involved in protein modification and cytotoxicity. The oxidation of 3-OHKyn has been studied here with a view to characterising the major products as well as determining their relative rates of formation and the role that H2O2 and hydroxyl radical (HO*) may play in modifying the autoxidation process. Oxidation of 3-OHKyn generated several compounds. Xanthommatin (Xan), formed by the oxidative dimerisation of 3-OHKyn, was the major product formed initially. It was, however, found to be unstable, particularly in the presence of H2O2, and degraded to other products including the p-quinone, 4,6-dihydroxyquinolinequinonecarboxylic acid (DHQCA). A compound that has a structure consistent with that of hydroxyxanthommatin (OHXan) was also formed in addition to at least two minor species that we were unable to identify. Hydrogen peroxide was formed rapidly upon oxidation of 3-OHKyn, and significantly influenced the relative abundance of the different autoxidation species. Increasing either pH (from pH 6 to 8) or temperature (from 25 degrees C to 35 degrees C) accelerated the rate of autoxidation but had little impact on the relative abundance of the autoxidation species. Using electron paramagnetic resonance (EPR) spectroscopy, a clear phenoxyl radical signal was observed during 3-OHKyn autoxidation and this was attributed to xanthommatin radical (Xan*). Hydroxyl radicals were also produced during 3-OHKyn autoxidation. The HO* EPR signal disappeared and the Xan* EPR signal increased when catalase was added to the autoxidation mixture. The HO* did not appear to play a role in the formation of the autoxidation products as evidenced using HO* traps/scavengers. We propose that the cytotoxicity of 3-OHKyn may be explained by both the generation of H2O2 and by the formation of reactive 3-OHKyn autoxidation products such as the Xan* and DHQCA.
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Affiliation(s)
- S Vazquez
- Australian Cataract Research Foundation, Wollongong NSW, Australia
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Chiarugi A, Rapizzi E, Moroni F, Moroni F. The kynurenine metabolic pathway in the eye: studies on 3-hydroxykynurenine, a putative cataractogenic compound. FEBS Lett 1999; 453:197-200. [PMID: 10403402 DOI: 10.1016/s0014-5793(99)00724-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The rabbit lens has an elevated content of 3-hydroxykynurenine (30HKYN) in spite of a very low activity of the enzymes leading to its synthesis. The iris/ciliary body, on the contrary, has very high activity of 30HKYN synthesizing enzymes but a content of 30HKYN lower than that of the lens. These observations suggest that 30HKYN is formed in the iris/ ciliary body, released into the aqueous humor and then taken up into the lens where it may be used for the synthesis of UV filtering products. An excessive accumulation of 30HKYN in the lens has been associated with cataract formation. We found that available selective inhibitors of kynurenine hydroxylase reduced 30HKYN synthesis in both the lens and the iris/ciliary body.
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Affiliation(s)
- A Chiarugi
- Department of Preclinical and Clinical Pharmacology, University of Florence, Italy
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Reszka KJ, Bilski P, Chignell CF, Dillon J. Free radical reactions photosensitized by the human lens component, kynurenine: an EPR and spin trapping investigation. Free Radic Biol Med 1996; 20:23-34. [PMID: 8903676 DOI: 10.1016/0891-5849(95)02018-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have undertaken electron paramagnetic resonance and spin trapping investigations of the photochemistry of kynurenine (KN), a natural component of the human eye and close analog of the principal chromophore in the young human lens 3-OH-kynurenine O-glucoside (3HKG). 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) was employed as a spin trap. We found that upon UV irradiation (> 300 nm) KN photoreduces oxygen to superoxide radical (in DMSO) and nitromethane (CH3NO2) to a nitromethane radical anion (CH3NO2.-) (in air-free buffers, pH 7 and 9.5). KN also sensitized photooxidation of cysteine, NADH, EDTA, azide, and ascorbate; oxygen greatly accelerated this process. Oxidation of cysteine, NADH, and EDTA was accompanied by superoxide radical formation. Cysteinyl and azidyl radicals were detected as DMPO adducts. We also observed that KN undergoes photodegradation to a product(s) whose photosensitizing capacity is greater than that of KN itself. We postulate that: (i) 3HKG may be able to photoinitiate free radical reactions in vivo, and (ii) oxygen is an important factor determining the yields of free radical processes initiated by lenticular chromophores.
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Affiliation(s)
- K J Reszka
- Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, NC, USA.
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Ellozy AR, Wang RH, Dillon J. Model studies on the photochemical production of lenticular fluorophores. Photochem Photobiol 1994; 59:479-84. [PMID: 8022892 DOI: 10.1111/j.1751-1097.1994.tb05068.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
With aging, human lens proteins accumulate fluorophores having blue and green emissions. Model studies were undertaken to determine the role of 3-hydroxykynurenine (3-HK) and its glucoside (3-HKG) in the photochemical production of those fluorophores. Experiments were carried out using 10(-3) M 3-HK solutions in the presence or absence of glycine (1 M), which was used to mimic the environment of the lens. The solutions were photolyzed (transmission above 295 nm) for various periods of time while the loss of starting material and the formation of fluorescent photoproducts (blue emission at 470 nm, and green emission at 520 nm) were monitored using fluorescence and UV-visible spectroscopy and thin-layer and high-pressure liquid chromatography analysis. Several parameters were varied such as oxygen tension and the addition of the free radical scavenger, penicillamine. The photolytic loss of 3-HK in the absence of glycine occurred approximately 5-10 times faster than in its presence. Conversely, blue and green fluorophores formed in irradiated solutions containing glycine but not with the photolysis of 3-HK alone. The blue fluorophore was formed first and appeared then to be photochemically converted to the green one, with the rate of formation of the latter increasing with an increase in UV dosage or oxidizing conditions. The addition of penicillamine drastically reduced the photochemical formation of both fluorophores. Both the blue and green fluorophores appear to result from the photochemically induced covalent attachment of 3-HK to glycine.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- A R Ellozy
- College at Lincoln Center, Fordham University, New York, NY 10023
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