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Hu Z, Feng L, Jiang Q, Wang W, Tan B, Tang X, Yin Y. Intestinal tryptophan metabolism in disease prevention and swine production. ANIMAL NUTRITION (ZHONGGUO XU MU SHOU YI XUE HUI) 2023; 15:364-374. [PMID: 38058568 PMCID: PMC10695851 DOI: 10.1016/j.aninu.2023.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Revised: 07/05/2023] [Accepted: 08/11/2023] [Indexed: 12/08/2023]
Abstract
Tryptophan (Trp) is an essential amino acid that cannot be synthesized by animals. It has been characterized into two different isomers, levorotation-Trp (L-Trp) and dextrorotation-Trp (D-Trp), based on their distinct molecule orientation. Intestinal epithelial cells and gut microbiota are involved in metabolizing L-Trp in the gut via the activation of the kynurenine, serotonin, and indole pathways. However, knowledge regarding D-Trp metabolism in the gut remains unclear. In this review, we briefly update the current understanding of intestinal L/D-Trp metabolism and the function of their metabolites in modulating the gut physiology and diseases. Finally, we summarize the effects of Trp nutrition on swine production at different stages, including growth performance in weaned piglets and growing pigs, as well as the reproduction performance in sows.
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Affiliation(s)
- Zhenguo Hu
- Laboratory of Animal Nutritional Physiology and Metabolic Process, Institute of Subtropical Agriculture, Chinese Academy of Science, Changsha, Hunan 410125, China
| | - Luya Feng
- Animal Nutritional Genome and Germplasm Innovation Research Center, College of Animal Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
| | - Qian Jiang
- Animal Nutritional Genome and Germplasm Innovation Research Center, College of Animal Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
| | - Wenliang Wang
- Animal Nutritional Genome and Germplasm Innovation Research Center, College of Animal Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
| | - Bi'e Tan
- Animal Nutritional Genome and Germplasm Innovation Research Center, College of Animal Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
| | - Xiongzhuo Tang
- Animal Nutritional Genome and Germplasm Innovation Research Center, College of Animal Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
| | - Yulong Yin
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, National Center of Technology Innovation for Synthetic Biology, Tianjin 300308, China
- Animal Nutritional Genome and Germplasm Innovation Research Center, College of Animal Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
- Laboratory of Animal Nutritional Physiology and Metabolic Process, Institute of Subtropical Agriculture, Chinese Academy of Science, Changsha, Hunan 410125, China
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Sherin PS, Vyšniauskas A, López-Duarte I, Ogilby PR, Kuimova MK. Visualising UV-A light-induced damage to plasma membranes of eye lens. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2021; 225:112346. [PMID: 34736070 DOI: 10.1016/j.jphotobiol.2021.112346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 10/01/2021] [Accepted: 10/19/2021] [Indexed: 01/16/2023]
Abstract
An eye lens is constantly exposed to the solar UV radiation, which is considered the most important external source of age-related changes to eye lens constituents. The accumulation of modifications of proteins and lipids with age can eventually lead to the development of progressive lens opacifications, such as cataracts. Though the impact of solar UV radiation on the structure and function of proteins is actively studied, little is known about the effect of photodamage on plasma membranes of lens cells. In this work we exploit Fluorescence Lifetime Imaging Microscopy (FLIM), together with viscosity-sensitive fluorophores termed molecular rotors, to study the changes in viscosity of plasma membranes of porcine eye lens resulting from two different types of photodamage: Type I (electron transfer) and Type II (singlet oxygen) reactions. We demonstrate that these two types of photodamage result in clearly distinct changes in viscosity - a decrease in the case of Type I damage and an increase in the case of Type II processes. Finally, to simulate age-related changes that occur in vivo, we expose an intact eye lens to UV-A light under anaerobic conditions. The observed decrease in viscosity within plasma membranes is consistent with the ability of eye lens constituents to sensitize Type I photodamage under natural irradiation conditions. These changes are likely to alter the transport of metabolites and predispose the whole tissue to the development of pathological processes such as cataracts.
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Affiliation(s)
- Peter S Sherin
- Chemistry Department, Molecular Sciences Research Hub, Imperial College London, 82 Wood Lane, London W12 0BZ, UK; International Tomography Center SB RAS, Institutskaya street 3A, Novosibirsk 630090, Russia.
| | - Aurimas Vyšniauskas
- Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius LT-10257, Lithuania; Chemistry Department, Vilnius University, Naugarduko st. 24, Vilnius LT-03225, Lithuania
| | - Ismael López-Duarte
- Chemistry Department, Molecular Sciences Research Hub, Imperial College London, 82 Wood Lane, London W12 0BZ, UK
| | - Peter R Ogilby
- Department of Chemistry, Aarhus University, Langelandsgade 140, Aarhus DK-8000, Denmark
| | - Marina K Kuimova
- Chemistry Department, Molecular Sciences Research Hub, Imperial College London, 82 Wood Lane, London W12 0BZ, UK.
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Zhuravleva YS, Sherin PS. Influence of pH on radical reactions between kynurenic acid and amino acids tryptophan and tyrosine. Part II. Amino acids within the protein globule of lysozyme. Free Radic Biol Med 2021; 174:211-224. [PMID: 34363946 DOI: 10.1016/j.freeradbiomed.2021.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/29/2021] [Accepted: 08/01/2021] [Indexed: 12/20/2022]
Abstract
An acidosis, a decrease of pH within a living tissue, may alter yields of radical reactions if participating radicals undergo partial or complete protonation. One of photosensitizers found in the human eye lens, kynurenic acid (KNA-), possesses pKa 5.5 for its radical form that is close to physiological pH 6.89 for a healthy lens. In this work we studied the influence of pH on mechanisms and products of photoinduced radical reactions between KNA- and amino acids tryptophan (Trp) and tyrosine (Tyr) within a globule of model protein, Hen White Egg Lysozyme (HEWL). Our results show that the rate constant of back electron transfer from kynurenyl to HEWL• radicals with the restoration of initial reagents - the major decay pathway for these radicals - does not change in the pH 3-7. The quantum yield of HEWL degradation is also pH independent, however a shift of pH from 7 to 5 completely changes the outcome of photoinduced damage to HEWL from intermolecular cross-linking to oxygenation. HPLC-MS analysis has shown that four of six Trp and all Tyr residues of HEWL are modified in different extents at all pH, but the lowering of pH from 7 to 5 significantly changes the direction of main photodamage from Trp62 to Trp108 located at the entrance and bottom of enzymatic center, respectively. A decrease of intermolecular cross-links via Trp62 is followed by an increase in quantities of intramolecular cross-links Tyr20-Tyr23 and Tyr23-Tyr53. The obtained results point out the competence of cross-linking and oxygenation reactions for Trp and Tyr radicals within a protein globule and significant increase of oxygenation to the total damage of protein in the case of cross-linking deceleration by coulombic repulsion of positively charged protein globules.
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Affiliation(s)
- Yuliya S Zhuravleva
- International Tomography Center SB RAS, Institutskaya street 3a, Novosibirsk, Russia; Novosibirsk State University, Pirogova street 2, Novosibirsk, Russia
| | - Peter S Sherin
- International Tomography Center SB RAS, Institutskaya street 3a, Novosibirsk, Russia; Novosibirsk State University, Pirogova street 2, Novosibirsk, Russia.
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Zhuravleva YS, Sherin PS. Influence of pH on radical reactions between kynurenic acid and amino acids tryptophan and tyrosine. Part I. Amino acids in free state. Free Radic Biol Med 2021; 172:331-339. [PMID: 34146664 DOI: 10.1016/j.freeradbiomed.2021.06.015] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 06/14/2021] [Indexed: 01/06/2023]
Abstract
In the human eye lens the endogenous chromophores of UV-A light (315-400 nm) are able to sensitize radical reactions leading to protein modifications during normal aging and the cataract progression. Kynurenic acid (KNA-) is the most photochemically active dye of the human eye lens reported to date with pKa(KNAH2•) 5.5 for its radical form. Cataract is thought to develop under oxidative stress which could be accompanied by acidosis, an acidification of the intracellular environment. Protonation of kynurenyl radicals at mildly acidic conditions may change the outcome of radical reactions leading to additional damage to proteins. In this work we investigated the influence of pH on the degradation of initial reagents and the formation of products in photoinduced radical reactions between KNA- and amino acids tryptophan (Trp) and tyrosine (Tyr) in free states. Our results have shown that pH variation has minor influence on kinetics of reagent decay and accumulation of products in reactions between tyrosyl and kynurenic acid radicals. However in the case of Trp a two-fold decrease of the reagent degradation without visible changes in the composition of formed products was observed with pH decrease from 7 to 3. Time-resolved measurements have shown similar acidification-induced two-fold acceleration of decay of kynurenyl and tryptophanyl radicals via Back Electron Transfer (BET) with the restoration of initial reagents. Experiments with tryptophan derivatives with different pKa values for their radical forms point out the protonation of tryptophanyl radical as the driving force for BET acceleration at low pH. Our results demonstrate that the protonation of kynurenyl radical does not change its reactivity towards amino acids radicals but the total yield of radical photodamage decreases with the protonation of tryptophanyl radicals. It could be expected that radical induced damage to proteins will depend on the pKa of tryptophanyl radicals within a protein globule.
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Affiliation(s)
- Yuliya S Zhuravleva
- International Tomography Center SB RAS, Institutskaya Street 3a, Novosibirsk, Russia; Novosibirsk State University, Pirogova Street 2, Novosibirsk, Russia
| | - Peter S Sherin
- International Tomography Center SB RAS, Institutskaya Street 3a, Novosibirsk, Russia; Novosibirsk State University, Pirogova Street 2, Novosibirsk, Russia.
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Kynurenic Acid Accelerates Healing of Corneal Epithelium In Vitro and In Vivo. Pharmaceuticals (Basel) 2021; 14:ph14080753. [PMID: 34451850 PMCID: PMC8398234 DOI: 10.3390/ph14080753] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Revised: 07/26/2021] [Accepted: 07/28/2021] [Indexed: 11/17/2022] Open
Abstract
Kynurenic acid (KYNA) is an endogenous compound with a multidirectional effect. It possesses antiapoptotic, anti-inflammatory, and antioxidative properties that may be beneficial in the treatment of corneal injuries. Moreover, KYNA has been used successfully to improve the healing outcome of skin wounds. The aim of the present study is to evaluate the effects of KYNA on corneal and conjunctival cells in vitro and the re-epithelization of corneal erosion in rabbits in vivo. Normal human corneal epithelial cell (10.014 pRSV-T) and conjunctival epithelial cell (HC0597) lines were used. Cellular metabolism, cell viability, transwell migration, and the secretion of IL-1β, IL-6, and IL-10 were determined. In rabbits, after corneal de-epithelization, eye drops containing 0.002% and 1% KYNA were applied five times a day until full recovery. KYNA decreased metabolism but did not affect the proliferation of the corneal epithelium. It decreased both the metabolism and proliferation of conjunctival epithelium. KYNA enhanced the migration of corneal but not conjunctival epithelial cells. KYNA reduced the secretion of IL-1β and IL-6 from the corneal epithelium, leaving IL-10 secretion unaffected. The release of all studied cytokines from the conjunctival epithelium exposed to KYNA was unchanged. KYNA at higher concentration accelerated the healing of the corneal epithelium. These favorable properties of KYNA suggest that KYNA containing topical pharmaceutical products can be used in the treatment of ocular surface diseases.
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Savina ED, Tsentalovich YP, Sherin PS. UV-A induced damage to lysozyme via Type I photochemical reactions sensitized by kynurenic acid. Free Radic Biol Med 2020; 152:482-493. [PMID: 31751763 DOI: 10.1016/j.freeradbiomed.2019.11.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 11/12/2019] [Accepted: 11/13/2019] [Indexed: 02/06/2023]
Abstract
In this work we studied the mechanisms of Type I photodamage to a model protein, hen egg white lysozyme (HEWL), sensitized by kynurenic acid (KNA) - one of the most efficient photosensitizers of the human eye lens present in trace amounts within tissue. The kynurenic acid radical, KNA•-, formed in the quenching of triplet KNA by HEWL, can be readily oxidized by molecular oxygen with the formation of superoxide anion radical O2•-. This leads to two ways of damage to proteins: either via the direct reactions between KNA•- and HEWL• radicals (Type Ia) or via the reactions between superoxide anion O2•- and HEWL• radicals (Type Ib). Our results demonstrate significant degradation of the protein during Type Ia photolysis with the formation of various oligomeric and oxygenated forms of HEWL and several deoxygenated products of KNA. Liquid chromatography-mass spectrometry analysis revealed the cross-linking of HEWL via tryptophan (Trp62) and tyrosine (Tyr23) residues and, for the first time, the covalent binding of KNA to protein via tryptophan (Trp62 and Trp123) residues. It was found that Type Ib reactions lead to substantially smaller damage to HEWL; the degradation quantum yields (Φdeg) of HEWL are 1.3 ± 0.3% and 0.12 ± 0.03% for Type Ia and Ib photolyses, respectively. Low Φdeg values for both types of photolysis indicate the Back Electron Transfer (BET) with the restoration of initial reagents as the main radical decay path with significantly higher BET efficiency in the case of Type Ib reactions. Therefore, in essentially oxygen-free tissues like the eye lens, the direct radical reactions via Type Ia mechanism could induce significantly larger damage to proteins, leading to their cross-linking and oxidation. The accumulation of these modifications can cause the development of various diseases, in particular, cataracts in the eye lens.
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Affiliation(s)
- Ekaterina D Savina
- International Tomography Center SB RAS, Institutskaya str. 3A, 630090, Novosibirsk, Russia; Novosibirsk State University, Pirogova str. 2, 630090, Novosibirsk, Russia
| | - Yuri P Tsentalovich
- International Tomography Center SB RAS, Institutskaya str. 3A, 630090, Novosibirsk, Russia; Novosibirsk State University, Pirogova str. 2, 630090, Novosibirsk, Russia
| | - Peter S Sherin
- International Tomography Center SB RAS, Institutskaya str. 3A, 630090, Novosibirsk, Russia; Novosibirsk State University, Pirogova str. 2, 630090, Novosibirsk, Russia.
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Matysik-Woźniak A, Paduch R, Turski WA, Maciejewski R, Jünemann AG, Rejdak R. Effects of tryptophan, kynurenine and kynurenic acid exerted on human reconstructed corneal epithelium in vitro. Pharmacol Rep 2017; 69:722-729. [DOI: 10.1016/j.pharep.2017.02.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 02/21/2017] [Accepted: 02/24/2017] [Indexed: 11/28/2022]
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Sherin PS, Zelentsova EA, Sormacheva ED, Yanshole VV, Duzhak TG, Tsentalovich YP. Aggregation of α-crystallins in kynurenic acid-sensitized UVA photolysis under anaerobic conditions. Phys Chem Chem Phys 2016; 18:8827-39. [DOI: 10.1039/c5cp06693j] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Extensive protein aggregation is the major outcome of kynurenic acid-sensitized photolysis of α-crystallin under anaerobic conditions. The main lens antioxidants ascorbate and glutathione effectively inhibit the protein aggregation.
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Affiliation(s)
- P. S. Sherin
- International Tomography Center of Siberian Branch of Russian Academy of Science
- Novosibirsk
- Russia
- Novosibirsk State University
- Novosibirsk
| | - E. A. Zelentsova
- International Tomography Center of Siberian Branch of Russian Academy of Science
- Novosibirsk
- Russia
- Novosibirsk State University
- Novosibirsk
| | - E. D. Sormacheva
- International Tomography Center of Siberian Branch of Russian Academy of Science
- Novosibirsk
- Russia
- Novosibirsk State University
- Novosibirsk
| | - V. V. Yanshole
- International Tomography Center of Siberian Branch of Russian Academy of Science
- Novosibirsk
- Russia
- Novosibirsk State University
- Novosibirsk
| | - T. G. Duzhak
- International Tomography Center of Siberian Branch of Russian Academy of Science
- Novosibirsk
- Russia
- Novosibirsk State University
- Novosibirsk
| | - Yu. P. Tsentalovich
- International Tomography Center of Siberian Branch of Russian Academy of Science
- Novosibirsk
- Russia
- Novosibirsk State University
- Novosibirsk
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Rejdak R, Oleszczuk A, Rummelt C, Turski WA, Choragiewicz T, Nowomiejska K, Ksiazek K, Thaler S, Zarnowski T, Okuno E, Grieb P, Zrenner E, Kruse F, Junemann AGM. Presence and distribution of L-kynurenine aminotransferases immunoreactivity in human cataractous lenses. Acta Ophthalmol 2013; 91:e450-5. [PMID: 23590420 DOI: 10.1111/aos.12138] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE To investigate the presence and distribution of l-kynurenine aminotransferases immunoreactivity in human and animal lenses during cataract formation. METHODS Immunohistochemistry was conducted using polyclonal antibodies against KAT I, KAT II and KAT III on sections of 26 anterior capsules from patients undergoing surgical treatment of anterior subcapsular cataract (ASC) and 22 cataractous lenses from human eyes enucleated because of choroidal malignant melanoma. Additionally, the eyes of 11-month-old DBA/2J mice (6 eyes) were investigated (with KAT I and II). Ten clear human lenses and four BL6 mice lenses were used as controls. Spatial immunoreactivity patterns of enzymes were compared with Periodic Acid - Schiff (PAS)-stained sections. RESULTS Immunohistochemical analysis revealed presence of KAT I, KAT II and KAT III in extracellular structures of all studied types of cataract in human eyes showing specific pattern of the stain. In cortical cataract, immunoreactivity was observed on cortical lens fibres. In nuclear cataract, KAT II revealed stronger and diffused staining than KAT I. Additionally, both KAT showed more pronounced staining at the edge of small clefts. In normal human lenses, KAT I, II and III, immunoreactivity was not observed. Presence of KAT I and KAT II in the intercellular substance of DBA/2J mice cataract was observed. In BL6 mice lenses without cataract, only weak KAT I and KAT II staining was observed. CONCLUSIONS Presence of l-kynurenine aminotransferases in extracellular matrix (ECM) during human cataract formation suggests that products of l-kynurenine pathway might be involved in mechanisms of cataractogenesis.
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Affiliation(s)
- Robert Rejdak
- Department of Ophthalmology, University of Erlangen-Nuernberg, Germany
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Zelentsova EA, Sherin PS, Snytnikova OA, Kaptein R, Vauthey E, Tsentalovich YP. Photochemistry of aqueous solutions of kynurenic acid and kynurenine yellow. Photochem Photobiol Sci 2013; 12:546-58. [DOI: 10.1039/c2pp25357g] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Rejdak R, Junemann A, Grieb P, Thaler S, Schuettauf F, Chorągiewicz T, Zarnowski T, Turski WA, Zrenner E. Kynurenic acid and kynurenine aminotransferases in retinal aging and neurodegeneration. Pharmacol Rep 2012; 63:1324-34. [PMID: 22358081 DOI: 10.1016/s1734-1140(11)70697-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 06/24/2011] [Indexed: 10/25/2022]
Abstract
The kynurenine aminotransferases (KATs) KAT I and KAT II are pivotal to the synthesis of kynurenic acid (KYNA), the only known endogenous glutamate receptor antagonist and neuroprotectant. KAT I and II have been found in avian, rodent, and human retina. Expression of KAT I in Müller cell endfeet and KAT II in retinal ganglion cells has been documented. Developmental changes in KAT expression and KYNA concentration in the avian and rodent retina have also been found. Studies of retinal neurodegeneration have shown alterations in KYNA synthesis in the retina in response to retinal ganglion cell loss. In DBA/2J mice, a model of ocular hypertension, an age-dependent decrease of retinal KYNA and KATs was found. In the corpora amylacea in the human retina intensive KAT I and II immunoreactivity was demonstrated. In summary, these findings point to the potential involvement of KYNA in the mechanisms of retinal aging and neurodegeneration.
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Affiliation(s)
- Robert Rejdak
- Centre for Ophthalmology, University of Tübingen, Roentgenweg 11, D-72076 Tübingen, Germany.
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Inhibitory effects of kynurenic acid, a tryptophan metabolite, and its derivatives on cytosolic sulfotransferases. Biochem J 2009; 422:455-62. [DOI: 10.1042/bj20090168] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
KYNA (kynurenic acid) is an endogenous metabolite of tryptophan in the kynurenine pathway and has been characterized as an antagonist of ionotropic glutamate receptors. In addition, we have reported this endogenous compound as a potent inhibitor of SULTs (cytosolic sulfotransferases). In the present study we characterized the inhibitory effects of KYNA on several human (h) and mouse (m) recombinant SULTs. No sulfate metabolite of KYNA was detected with mouse and human SULTs examined under the conditions used, suggesting that it is a bona fide inhibitor of SULTs. Among the mouse enzymes examined, KYNA exhibited selective inhibitory effects on Sult1b1-mediated sulfation of various compounds with IC50 values in the low micromolar range (2.9–4.9 μM). KYNA also exerted an inhibitory activity towards hSULT1A1 and hSULT1B1. The inhibitory potency of KYNA for mSult1b1 was stronger than that of 2,6-dichloro-4-nitrophenol, a known non-specific SULT inhibitor, whereas the potencies of these two inhibitors for hSULT1B1 were comparable. The inhibitory characteristics of KYNA were clearly distinct from those of mefenamic acid, a selective inhibitor of SULT1A enzymes. The KYNA derivatives 5,7-dichlorokynurenic acid and L689,560 exhibited preferential inhibitory effects on hSULT1A1 and hSULT1B1 respectively. Interestingly, gavestinel, another KYNA derivative, was found to be an extremely potent inhibitor of hSULT1B1. Finally, we have demonstrated that the mechanism underlying the KYNA inhibition varied depending on the enzyme and substrate involved. Taken together, the present results unveil another distinct aspect of KYNA and its derivatives as an inhibitor of SULTs.
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Zarnowski T, Rejdak R, Zielinska-Rzecka E, Zrenner E, Grieb P, Zagórski Z, Junemann A, Turski WA. Elevated concentrations of kynurenic acid, a tryptophan derivative, in dense nuclear cataracts. Curr Eye Res 2007; 32:27-32. [PMID: 17364732 DOI: 10.1080/02713680601090965] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE Kynurenines and their glycoside derivatives in the ocular lens absorb ultraviolet radiation and thus possibly help protect the retina from ultraviolet light. The current study analysed kynurenine aminotransferase I (KAT I) activity and kynurenic acid (KYNA) concentrations in human senile cataractous lenses and in experimentally induced cataracts in diabetic rats treated with streptozotocin (STZ). METHODS KYNA levels and KAT I activity were investigated with HPLC and detected fluorimetrically in the nuclei of 91 human cataractous lenses collected during planned extracapsular extraction. The lenses were classified on the Lens Opacity Classification System III scale and compared with clear lenses regarding KYNA concentrations. Cataractous lenses from STZ-treated rats were compared with control lenses. RESULTS KYNA concentration was 0.95 +/- 0.22 in human NC0 (nuclear color) control lenses, 0.8 +/- 0.72 in NC1, 1.18 +/- 0.88 in NC2, 1.31 +/- 0.70 in NC3, 1.78 +/- 0.92 in NC4, 8.80 +/- 8.28 (p < 0.05 vs. NC0) in NC5, and 14.0 +/- 11.1 (p < 0.05 vs. NC0) in NC6. A correlation was found between KYNA concentrations and the grade of cataract (r = 0.047, p < 0.001). KAT I activity in human cataracts was 0.44 +/- 0.16 pmol/mg protein- 1 hr- 1. Elevated KYNA concentrations in rat cataractous lenses were also observed (p < 0.05). CONCLUSIONS KYNA levels are elevated in senile nuclear human cataracts and in cataractous lenses of rats with experimentally induced diabetes.
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Affiliation(s)
- Tomasz Zarnowski
- Tadeusz Krwawicz Chair of Ophthalmology and 1st Eye Hospital, Medical University of Lublin. Lublin, Poland.
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Sapko MT, Guidetti P, Yu P, Tagle DA, Pellicciari R, Schwarcz R. Endogenous kynurenate controls the vulnerability of striatal neurons to quinolinate: Implications for Huntington's disease. Exp Neurol 2005; 197:31-40. [PMID: 16099455 DOI: 10.1016/j.expneurol.2005.07.004] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2005] [Revised: 07/05/2005] [Accepted: 07/07/2005] [Indexed: 11/24/2022]
Abstract
Excessive activation of NMDA receptors results in excitotoxic nerve cell loss, which is believed to play a critical role in the pathophysiology of Huntington's disease (HD) and several other catastrophic neurodegenerative diseases. Kynurenic acid (KYNA), a neuroinhibitory tryptophan metabolite, has neuroprotective properties and may serve as an endogenous anti-excitotoxic agent. This hypothesis was tested in the striatum, using mice with a targeted deletion of kynurenine aminotransferase II (KAT II), a major biosynthetic enzyme of KYNA in the mammalian brain. On post-natal day (PND) 14, the striatum of mkat-2-/- mice showed a reduction in KYNA levels but contained normal concentrations of the metabolically related neurotoxins 3-hydroxykynurenine and quinolinic acid (QUIN). Intrastriatal injections of QUIN, a NMDA receptor agonist, caused significantly larger lesions in these immature mutant mice than in age-matched wild-type animals. This lesion enlargement was not observed when mkat-2-/- mice were acutely pre-treated with the kynurenine 3-hydroxylase inhibitor UPF 648, which counteracted the striatal KYNA deficit. Moreover, no increased vulnerability to QUIN was observed in 2-month-old mkat-2-/- mice, which present with normal brain KYNA levels. Intrastriatal injections of the non-NMDA receptor agonist kainate caused similar lesion sizes in both genotypes regardless of age. These results indicate that endogenous KYNA preferentially controls the vulnerability of striatal neurons to QUIN. Our data suggest that timely pharmacological interventions resulting in an up-regulation of brain KYNA levels may benefit patients suffering from HD or other neurodegenerative diseases.
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Affiliation(s)
- Michael T Sapko
- Maryland Psychiatric Research Center, University of Maryland School of Medicine, P.O. Box 21247, Baltimore, MD 21228, USA
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