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Glazier AN. Proposed Role for Internal Lens Pressure as an Initiator of Age-Related Lens Protein Aggregation Diseases. Clin Ophthalmol 2022; 16:2329-2340. [PMID: 35924184 PMCID: PMC9342656 DOI: 10.2147/opth.s369676] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 07/13/2022] [Indexed: 11/23/2022] Open
Abstract
The process that initiates lens stiffness evident in age-related lens protein aggregation diseases is thought to be mainly the result of oxidation. While oxidation is a major contributor, the exposure of lens proteins to physical stress over time increases susceptibility of lens proteins to oxidative damage, and this is believed to play a significant role in initiating these diseases. Accordingly, an overview of key physical stressors and molecular factors known to be implicated in the development of age-related lens protein aggregation diseases is presented, paying particular attention to the consequence of persistent increase in internal lens pressure.
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Affiliation(s)
- Alan N Glazier
- Optometry, KeplrVision, Rockville, MD, USA
- Correspondence: Alan N Glazier, Email
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2
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Fan X, Monnier VM. Protein posttranslational modification (PTM) by glycation: Role in lens aging and age-related cataractogenesis. Exp Eye Res 2021; 210:108705. [PMID: 34297945 DOI: 10.1016/j.exer.2021.108705] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 07/09/2021] [Accepted: 07/17/2021] [Indexed: 01/11/2023]
Abstract
Crystallins, the most prevalent lens proteins, have no turnover throughout the entire human lifespan. These long-lived proteins are susceptible to post-synthetic modifications, including oxidation and glycation, which are believed to be some of the primary mechanisms for age-related cataractogenesis. Thanks to high glutathione (GSH) and ascorbic acid (ASA) levels as well as low oxygen content, the human lens is able to maintain its transparency for several decades. Aging accumulates substantial changes in the human lens, including a decreased glutathione concentration, increased reactive oxygen species (ROS) formation, impaired antioxidative defense capacity, and increased redox-active metal ions, which induce glucose and ascorbic acid degradation and protein glycation. The glycated lens crystallins are either prone to UVA mediated free radical production or they attract metal ion binding, which can trigger additional protein oxidation and modification. This vicious cycle is expected to be exacerbated with older age or diabetic conditions. ASA serves as an antioxidant in the human lens under reducing conditions to protect the human lens from damage, but ASA converts to the pro-oxidative role and causes lens protein damage by ascorbylation in high oxidation or enriched redox-active metal ion conditions. This review is dedicated in honor of Dr. Frank Giblin, a great friend and superb scientist, whose pioneering and relentless work over the past 45 years has provided critical insight into lens redox regulation and glutathione homeostasis during aging and cataractogenesis.
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Affiliation(s)
- Xingjun Fan
- Department of Cellular Biology and Anatomy, Medical College of Georgia at Augusta University, Augusta, GA, United States.
| | - Vincent M Monnier
- Department of Pathology, United States; Biochemistry, Case Western Reserve University, Cleveland, OH, United States
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3
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Hemmler D, Gonsior M, Powers LC, Marshall JW, Rychlik M, Taylor AJ, Schmitt‐Kopplin P. Simulated Sunlight Selectively Modifies Maillard Reaction Products in a Wide Array of Chemical Reactions. Chemistry 2019; 25:13208-13217. [PMID: 31314140 PMCID: PMC6856810 DOI: 10.1002/chem.201902804] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Indexed: 11/30/2022]
Abstract
The photochemical transformation of Maillard reaction products (MRPs) under simulated sunlight into mostly unexplored photoproducts is reported herein. Non-enzymatic glycation of amino acids leads to a heterogeneous class of intermediates with extreme chemical diversity, which is of particular relevance in processed and stored food products as well as in diabetic and age-related protein damage. Here, three amino acids (lysine, arginine, and histidine) were reacted with ribose at 100 °C in water for ten hours. Exposing these model systems to simulated sunlight led to a fast decay of MRPs. The photodegradation of MRPs and the formation of new compounds have been studied by fluorescence spectroscopy and nontargeted (ultra)high-resolution mass spectrometry. Photoreactions showed strong selectivity towards the degradation of electron-rich aromatic heterocycles, such as pyrroles and pyrimidines. The data show that oxidative cleavage mechanisms dominate the formation of photoproducts. The photochemical transformations differed fundamentally from "traditional" thermal Maillard reactions and indicated a high amino acid specificity.
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Affiliation(s)
- Daniel Hemmler
- Comprehensive Foodomics Platform, Analytical Food ChemistryTechnical University MunichMaximus-von-Imhof-Forum 285354FreisingGermany
- Research Unit Analytical BioGeoChemistry (BGC)Helmholtz Zentrum MünchenIngolstädter Landstrasse 185764NeuherbergGermany
| | - Michael Gonsior
- University of Maryland Center for Environmental ScienceChesapeake Biological LaboratorySolomonsUSA
| | - Leanne C. Powers
- University of Maryland Center for Environmental ScienceChesapeake Biological LaboratorySolomonsUSA
| | - James W. Marshall
- The Waltham Centre for Pet NutritionMars Petcare (UK)Waltham-on-the-WoldsLeicestershireLE14 4RTUK
| | - Michael Rychlik
- Comprehensive Foodomics Platform, Analytical Food ChemistryTechnical University MunichMaximus-von-Imhof-Forum 285354FreisingGermany
| | - Andrew J. Taylor
- The Waltham Centre for Pet NutritionMars Petcare (UK)Waltham-on-the-WoldsLeicestershireLE14 4RTUK
| | - Philippe Schmitt‐Kopplin
- Comprehensive Foodomics Platform, Analytical Food ChemistryTechnical University MunichMaximus-von-Imhof-Forum 285354FreisingGermany
- Research Unit Analytical BioGeoChemistry (BGC)Helmholtz Zentrum MünchenIngolstädter Landstrasse 185764NeuherbergGermany
- University of Maryland Center for Environmental ScienceChesapeake Biological LaboratorySolomonsUSA
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4
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Wu PT, Lin CL, Lin CW, Chang NC, Tsai WB, Yu J. Methylene-Blue-Encapsulated Liposomes as Photodynamic Therapy Nano Agents for Breast Cancer Cells. NANOMATERIALS (BASEL, SWITZERLAND) 2018; 9:E14. [PMID: 30583581 PMCID: PMC6359461 DOI: 10.3390/nano9010014] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 12/18/2018] [Accepted: 12/18/2018] [Indexed: 01/16/2023]
Abstract
Methylene blue (MB) is a widely used dye and photodynamic therapy (PDT) agent that can produce reactive oxygen species (ROS) after light exposure, triggering apoptosis. However, it is hard for the dye to penetrate through the cell membrane, leading to poor cellular uptake; thus, drug carriers, which could enhance the cellular uptake, are a suitable solution. In addition, the defective vessels resulting from fast vessel outgrowth leads to an enhanced permeability and retention (EPR) effect, which gives nanoscale drug carriers a promising potential. In this study, we applied poly(12-(methacryloyloxy)dodecyl phosphorylcholine), a zwitterionic polymer-lipid, to self-assemble into liposomes and encapsulate MB (MB-liposome). Its properties of high stability and fast intracellular uptake were confirmed, and the higher in vitro ROS generation ability of MB-liposomes than that of free MB was also verified. For in vivo tests, we examined the toxicity in mice via tail vein injection. With the features found, MB-liposome has the potential of being an effective PDT nano agent for cancer therapy.
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Affiliation(s)
- Po-Ting Wu
- Department of Chemical Engineering, National Taiwan University, Taipei 103, Taiwan.
| | - Chih-Ling Lin
- Department of Chemical Engineering, National Taiwan University, Taipei 103, Taiwan.
| | - Che-Wei Lin
- Department of Chemical Engineering, National Taiwan University, Taipei 103, Taiwan.
| | - Ning-Chu Chang
- Department of Chemical Engineering, National Taiwan University, Taipei 103, Taiwan.
| | - Wei-Bor Tsai
- Department of Chemical Engineering, National Taiwan University, Taipei 103, Taiwan.
| | - Jiashing Yu
- Department of Chemical Engineering, National Taiwan University, Taipei 103, Taiwan.
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5
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Rakete S, Nagaraj RH. UVA Light-mediated Ascorbate Oxidation in Human Lenses. Photochem Photobiol 2017; 93:1091-1095. [PMID: 28084012 DOI: 10.1111/php.12717] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Accepted: 12/05/2016] [Indexed: 12/11/2022]
Abstract
Whether ascorbate oxidation is promoted by UVA light in human lenses and whether this process is influenced by age and GSH levels are not known. In this study, we used paired lenses from human donors. One lens of each pair was exposed to UVA light, whereas the other lens was kept in the dark for the same period of time as the control. Using LC-MS/MS analyses, we found that older lenses (41-73 years) were more susceptible to UVA-induced ascorbate oxidation than younger lenses (18-40 years). Approximately 36% of the ascorbate (relative to control) was oxidized in older lenses compared to ~16% in younger lenses. Furthermore, lenses with higher levels of GSH were less susceptible to UVA-induced ascorbate oxidation compared to those with lower levels, and this effect was not dependent on age. The oxidation of ascorbate led to elevated levels of reactive α-dicarbonyl compounds. In summary, our study showed that UVA light exposure leads to ascorbate oxidation in human lenses and that such oxidation is more pronounced in aged lenses and is inversely related to GSH levels. Our findings suggest that UVA light exposure could lead to protein aggregation through ascorbate oxidation in human lenses.
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Affiliation(s)
- Stefan Rakete
- Department of Ophthalmology, School of Medicine, University of Colorado, Aurora, CO
| | - Ram H Nagaraj
- Department of Ophthalmology, School of Medicine, University of Colorado, Aurora, CO.,Department of Pharmaceutical Sciences, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of Colorado, Aurora, CO
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Fan X, Zhou S, Wang B, Hom G, Guo M, Li B, Yang J, Vaysburg D, Monnier VM. Evidence of Highly Conserved β-Crystallin Disulfidome that Can be Mimicked by In Vitro Oxidation in Age-related Human Cataract and Glutathione Depleted Mouse Lens. Mol Cell Proteomics 2015; 14:3211-23. [PMID: 26453637 DOI: 10.1074/mcp.m115.050948] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Indexed: 01/23/2023] Open
Abstract
Low glutathione levels are associated with crystallin oxidation in age-related nuclear cataract. To understand the role of cysteine residue oxidation, we used the novel approach of comparing human cataracts with glutathione-depleted LEGSKO mouse lenses for intra- versus intermolecular disulfide crosslinks using 2D-PAGE and proteomics, and then systematically identified in vivo and in vitro all disulfide forming sites using ICAT labeling method coupled with proteomics. Crystallins rich in intramolecular disulfides were abundant at young age in human and WT mouse lens but shifted to multimeric intermolecular disulfides at older age. The shift was ∼4x accelerated in LEGSKO lens. Most cysteine disulfides in β-crystallins (except βA4 in human) were highly conserved in mouse and human and could be generated by oxidation with H(2)O(2), whereas γ-crystallin oxidation selectively affected γC23/42/79/80/154, γD42/33, and γS83/115/130 in human cataracts, and γB79/80/110, γD19/109, γF19/79, γE19, γS83/130, and γN26/128 in mouse. Analysis based on available crystal structure suggests that conformational changes are needed to expose Cys42, Cys79/80, Cys154 in γC; Cys42, Cys33 in γD, and Cys83, Cys115, and Cys130 in γS. In conclusion, the β-crystallin disulfidome is highly conserved in age-related nuclear cataract and LEGSKO mouse, and reproducible by in vitro oxidation, whereas some of the disulfide formation sites in γ-crystallins necessitate prior conformational changes. Overall, the LEGSKO mouse model is closely reminiscent of age-related nuclear cataract.
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Affiliation(s)
| | - Sheng Zhou
- ¶State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | | | - Grant Hom
- **Fairview High School, Fairview, Ohio
| | - Minfei Guo
- ‡‡Department of Ophthalmology, the Huichang County People's Hospital, Jiangxi, China
| | - Binbin Li
- §§Department of Ophthalmology, Ganzhou City People's Hospital, Jiangxi, China
| | - Jing Yang
- ¶State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | | | - Vincent M Monnier
- From the ‡Department of Pathology, §Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44120;
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Linetsky M, Raghavan CT, Johar K, Fan X, Monnier VM, Vasavada AR, Nagaraj RH. UVA light-excited kynurenines oxidize ascorbate and modify lens proteins through the formation of advanced glycation end products: implications for human lens aging and cataract formation. J Biol Chem 2014; 289:17111-23. [PMID: 24798334 DOI: 10.1074/jbc.m114.554410] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Advanced glycation end products (AGEs) contribute to lens protein pigmentation and cross-linking during aging and cataract formation. In vitro experiments have shown that ascorbate (ASC) oxidation products can form AGEs in proteins. However, the mechanisms of ASC oxidation and AGE formation in the human lens are poorly understood. Kynurenines are tryptophan oxidation products produced from the indoleamine 2,3-dioxygenase (IDO)-mediated kynurenine pathway and are present in the human lens. This study investigated the ability of UVA light-excited kynurenines to photooxidize ASC and to form AGEs in lens proteins. UVA light-excited kynurenines in both free and protein-bound forms rapidly oxidized ASC, and such oxidation occurred even in the absence of oxygen. High levels of GSH inhibited but did not completely block ASC oxidation. Upon UVA irradiation, pigmented proteins from human cataractous lenses also oxidized ASC. When exposed to UVA light (320-400 nm, 100 milliwatts/cm(2), 45 min to 2 h), young human lenses (20-36 years), which contain high levels of free kynurenines, lost a significant portion of their ASC content and accumulated AGEs. A similar formation of AGEs was observed in UVA-irradiated lenses from human IDO/human sodium-dependent vitamin C transporter-2 mice, which contain high levels of kynurenines and ASC. Our data suggest that kynurenine-mediated ASC oxidation followed by AGE formation may be an important mechanism for lens aging and the development of senile cataracts in humans.
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Affiliation(s)
- Mikhail Linetsky
- From the Departments of Chemistry, Ophthalmology and Visual Sciences,
| | | | - Kaid Johar
- the Iladevi Cataract and IOL Research Center, Gurukul Road, Memnagar, Ahmedabad, Gujarat-380052, India
| | | | - Vincent M Monnier
- Pathology, and Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106 and
| | - Abhay R Vasavada
- the Iladevi Cataract and IOL Research Center, Gurukul Road, Memnagar, Ahmedabad, Gujarat-380052, India
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8
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UV light phototransduction activates transient receptor potential A1 ion channels in human melanocytes. Proc Natl Acad Sci U S A 2013; 110:2383-8. [PMID: 23345429 DOI: 10.1073/pnas.1215555110] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Human skin is constantly exposed to solar ultraviolet radiation (UVR), the most prevalent environmental carcinogen. Humans have the unique ability among mammals to respond to UVR by increasing their skin pigmentation, a protective process driven by melanin synthesis in epidermal melanocytes. The molecular mechanisms used by melanocytes to detect and respond to long-wavelength UVR (UVA) are not well understood. We recently identified a UVA phototransduction pathway in melanocytes that is mediated by G protein-coupled receptors and leads to rapid calcium mobilization. Here we report that in human epidermal melanocytes physiological doses of UVR activate a retinal-dependent current mediated by transient receptor potential A1 (TRPA1) ion channels. The TRPA1 photocurrent is UVA-specific and requires G protein and phospholipase C signaling, thus contributing to UVA-induced calcium responses to mediate downstream cellular effects and providing evidence for TRPA1 function in mammalian phototransduction. Remarkably, TRPA1 activation is required for the UVR-induced and retinal-dependent early increase in cellular melanin. Our results show that TRPA1 is essential for a unique extraocular phototransduction pathway in human melanocytes that is activated by physiological doses of UVR and results in early melanin synthesis.
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Morosini V, Bastogne T, Frochot C, Schneider R, François A, Guillemin F, Barberi-Heyob M. Quantum dot–folic acid conjugates as potential photosensitizers in photodynamic therapy of cancer. Photochem Photobiol Sci 2011; 10:842-51. [DOI: 10.1039/c0pp00380h] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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10
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The pathogenic role of Maillard reaction in the aging eye. Amino Acids 2010; 42:1205-20. [DOI: 10.1007/s00726-010-0778-x] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2010] [Accepted: 08/25/2010] [Indexed: 12/31/2022]
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11
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Kaji Y, Kiuchi T, Oshika T. Carteolol hydrochloride suppresses the generation of reactive oxygen species and rescues cell death after ultraviolet irradiation of cultured lens epithelial cells. Open Ophthalmol J 2010; 4:60-5. [PMID: 21283534 PMCID: PMC3031156 DOI: 10.2174/1874364101004010060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 08/13/2010] [Accepted: 08/17/2010] [Indexed: 11/22/2022] Open
Abstract
Introduction: Anti-oxidant activities of adrenergic β-blockers are proposed in various organs. The aim of the present study was to investigate the effect of carteolol hydrochloride, an adrenergic β-blocker, on the production of reactive oxygen species (ROS) and the viable cell number after ultraviolet irradiation of cultured lens epithelial cells (LECs). Materials and Methodology: Cultured LECs were exposed to 0, 10–5, 10–4, and 10–3 M carteolol hydrochloride for 30 min followed by ultraviolet B (UVB) irradiation at intensity of 100, 200, or 400 mJ/cm2. The amount of ROS in the LECs was measured using dichlorodihydrofluorescein at 30 min after exposure to UVB. In addition, the number of living LECs was counted at 15 h after exposure to UVB. Results: Exposure to 10–3 M carteolol hydrochloride significantly decreased the amount of ROS after exposure to UVB at intensities of 100, 200, and 400 mJ/cm2. In addition, 10–3 M carteolol hydrochloride significantly increased the viable cell number after exposure to UVB at 400 mJ/cm2. However, 10–4 and 10–5M carteolol hydrochloride had no significant effect on ROS or the viable cell number in LECs. Discussions: Carteolol hydrochloride protects LECs against UVB irradiation by inhibiting the intracellular production of ROS.
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Affiliation(s)
- Yuichi Kaji
- Department of Ophthalmology, University of Tsukuba Institute of Clinical Medicine, Tennoudai 1-1-1, Tsukuba, Ibaraki 305-8575, Japan
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Fuentealba D, Friguet B, Silva E. Advanced Glycation Endproducts Induce Photocrosslinking and Oxidation of Bovine Lens Proteins Through Type-I Mechanism. Photochem Photobiol 2009; 85:185-94. [DOI: 10.1111/j.1751-1097.2008.00415.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Simpanya MF, Ansari RR, Leverenz V, Giblin FJ. Measurement of lens protein aggregation in vivo using dynamic light scattering in a guinea pig/UVA model for nuclear cataract. Photochem Photobiol 2008; 84:1589-95. [PMID: 18627516 DOI: 10.1111/j.1751-1097.2008.00390.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The role of UVA radiation in the formation of human nuclear cataract is not well understood. We have previously shown that exposing guinea pigs for 5 months to a chronic low level of UVA light produces increased lens nuclear light scattering and elevated levels of protein disulfide. Here we have used the technique of dynamic light scattering (DLS) to investigate lens protein aggregation in vivo in the guinea pig/UVA model. DLS size distribution analysis conducted at the same location in the lens nucleus of control and UVA-irradiated animals showed a 28% reduction in intensity of small diameter proteins in experimental lenses compared with controls (P < 0.05). In addition, large diameter proteins in UVA-exposed lens nuclei increased five-fold in intensity compared to controls (P < 0.05). The UVA-induced increase in apparent size of lens nuclear small diameter proteins was three-fold (P < 0.01), and the size of large diameter aggregates was more than four-fold in experimental lenses compared with controls. The diameter of crystallin aggregates in the UVA-irradiated lens nucleus was estimated to be 350 nm, a size able to scatter light. No significant changes in protein size were detected in the anterior cortex of UVA-irradiated lenses. It is presumed that the presence of a UVA chromophore in the guinea pig lens (NADPH bound to zeta crystallin), as well as traces of oxygen, contributed to UVA-induced crystallin aggregation. The results indicate a potentially harmful role for UVA light in the lens nucleus. A similar process of UVA-irradiated protein aggregation may take place in the older human lens nucleus, accelerating the formation of human nuclear cataract.
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Ávila F, Matus A, Fuentealba D, Lissi E, Friguet B, Silva E. Autosensitized oxidation of glycated bovine lens proteins irradiated with UVA-visible light at low oxygen concentration. Photochem Photobiol Sci 2008; 7:718-24. [DOI: 10.1039/b719167g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15
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Dubinina EE, Pustygina AV. Free radical processes in aging, neurodegenerative diseases and other pathological states. BIOCHEMISTRY (MOSCOW) SUPPLEMENT SERIES B: BIOMEDICAL CHEMISTRY 2007. [DOI: 10.1134/s1990750807040026] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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16
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Cheng R, Feng Q, Ortwerth BJ. LC-MS display of the total modified amino acids in cataract lens proteins and in lens proteins glycated by ascorbic acid in vitro. Biochim Biophys Acta Mol Basis Dis 2006; 1762:533-43. [PMID: 16540295 DOI: 10.1016/j.bbadis.2006.01.009] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2005] [Revised: 01/22/2006] [Accepted: 01/23/2006] [Indexed: 10/25/2022]
Abstract
We previously reported chromatographic evidence supporting the similarity of yellow chromophores isolated from aged human lens proteins, early brunescent cataract lens proteins and calf lens proteins ascorbylated in vitro [Cheng, R. et al. Biochimica et Biophysica Acta 1537, 14-26, 2001]. In this paper, new evidence supporting the chemical identity of the modified amino acids in these protein populations were collected by using a newly developed two-dimensional LC-MS mapping technique supported by tandem mass analysis of the major species. The pooled water-insoluble proteins from aged normal human lenses, early stage brunescent cataract lenses and calf lens proteins reacted with or without 20 mM ascorbic acid in air for 4 weeks were digested with a battery of proteolytic enzymes under argon to release the modified amino acids. Aliquots equivalent to 2.0 g of digested protein were subjected to size-exclusion chromatography on a Bio-Gel P-2 column and four major A330nm-absorbing peaks were collected. Peaks 1, 2 and 3, which contained most of the modified amino acids were concentrated and subjected to RP-HPLC/ESI-MS, and the mass elution maps were determined. The samples were again analyzed and those peaks with a 10(4) - 10(6) response factor were subjected to MS/MS analysis to identify the daughter ions of each modification. Mass spectrometric maps of peaks 1, 2 and 3 from cataract lenses showed 58, 40 and 55 mass values, respectively, ranging from 150 to 600 Da. Similar analyses of the peaks from digests of the ascorbylated calf lens proteins gave 81, 70 and 67 mass values, respectively, of which 100 were identical to the peaks in the cataract lens proteins. A total of 40 of the major species from each digest were analyzed by LC-MS/MS and 36 were shown to be identical. Calf lens proteins incubated without ascorbic acid showed several similar mass values, but the response factors were 100 to 1000-fold less for every modification. Based upon these data, we conclude that the majority of the major modified amino acids present in early stage brunescent Indian cataract lens proteins appear to arise as a result of ascorbic acid modification, and are presumably advanced glycation end-products.
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Affiliation(s)
- Rongzhu Cheng
- Mason Eye Institute, University of Missouri-Columbia, 404 Portland St. Columbia, MO 65201, USA.
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17
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Azzam N, Dovrat A. Long-term lens organ culture system to determine age-related effects of UV irradiation on the eye lens. Exp Eye Res 2004; 79:903-11. [PMID: 15642328 DOI: 10.1016/j.exer.2004.06.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2004] [Accepted: 06/21/2004] [Indexed: 10/26/2022]
Abstract
Aging of the eye lens represents the life-long accumulation of damage. Factors responsible for age-related cataract are unknown because medical evaluations of aged populations demonstrate a wide range of systemic diseases and medical disorders. There are some main suspected factors, which may contribute to accumulated age-related damage in the eye lens. (1) Diseases, such as diabetes, substantially increase the probability of cataract formation in the age group from 40 to 49, and double or triple this probability for ages 50 to 69. (2) Drugs, including systemic medications such as steroids. (3) Environmental factors, such as UV radiation, heat and electromagnetic radiation. Our study represents an effort to determine the effects of suspected cataractogenic factors on the eye lens. The experiments are performed using a unique long-term lens organ culture system of bovine lenses. In our system it is possible to give controlled amounts of insult and monitor changes in lens optical quality throughout the culture period of 8-15 days. The optical properties, monitored in association with biochemical analysis of lens epithelium, cortex and nuclear samples, help in determining the mechanisms of cataract formation. The present study investigates mechanisms by which UV-A radiation at 365 nm causes damage to the lens. It is believed that solar radiation is one of the major environmental factors involved in lens cataractogenesis. Bovine lenses were placed in our special culture cells for pre-incubation of 24 hr followed by irradiation of 29 or 33 J cm(-2). The lenses were maintained in the cells during irradiation. After irradiation, lens optical quality was monitored throughout the culture period and lens epithelium was taken for enzyme analysis. Using the culture system we learned that: (a) young lenses (less than one-year-old) are less sensitive to UV radiation than 3-year-old lenses; (b) the lenses have the ability to recover in organ culture conditions; (c) applying the insult in one step results in less damage than dividing the same insult in 4 steps with 24 hr interval between each one; and (d) the damage from UV is greater if the intervals between each irradiation stage are insufficient to permit full recovery.
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Affiliation(s)
- Naiel Azzam
- B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
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18
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Abstract
Epidemiological studies have indicated that ultraviolet radiation (UVR) is one of the main factors leading to senile cataract formation. We investigated morphological changes in the eye lens caused by UVR-A. Twenty three pairs of lenses obtained from 23 one-year-old calves were used for this study. For each pair, one lens was exposed to 44 J/m(2) UVR in the 365 nm wavelength region while the contralateral lens was not exposed and served as a control. The lenses were placed in specially designed organ culture containers for pre-incubation. Lenses were exposed to UVR after one day in culture. After irradiation, lens optical quality was monitored throughout additional 15 days of the culture period and lenses were taken for morphological analysis by scanning electron microscopy. Damage to lens optical quality was evident as early as day 8 after the irradiation and increased with time in culture. We found irregularity of fiber morphology in lenses exposed to UV-A irradiation (but not in control lenses), similar to that reported previously for aged lenses. At the end of the culture period (day 16), lens fiber membranes also showed holes in fiber membranes. We conclude that UVR-A caused damage to cell membranes of the lens and alterations in lens optics, which may subsequently lead to senile cataract formation.
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Affiliation(s)
- Naiel Azzam
- B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, 7 Efron St., P.O. Box 9649, Haifa 31096, Israel
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19
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Morgan PE, Dean RT, Davies MJ. Protective mechanisms against peptide and protein peroxides generated by singlet oxygen. Free Radic Biol Med 2004; 36:484-96. [PMID: 14975451 DOI: 10.1016/j.freeradbiomed.2003.11.021] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2003] [Revised: 10/16/2003] [Accepted: 11/14/2003] [Indexed: 10/26/2022]
Abstract
Reaction of certain amino acids, peptides, and proteins with singlet oxygen yields substrate-derived peroxides. Recent studies have shown that these species are formed within intact cells and can inactivate key cellular enzymes. This study examines potential mechanisms by which cells might remove or detoxify such peroxides. It is shown that catalase, horseradish peroxidase, and Cu/Zn superoxide dismutase do not react rapidly with these peroxides. Oxymyoglobin and oxyhemoglobin, but not the met (Fe3+) forms of these proteins, react with peptide but not protein, peroxides with oxidation of the heme iron. Glutathione peroxidase, in the presence of reduced glutathione (GSH) rapidly removes peptide, but not protein, peroxides, consistent with substrate size being a key factor. Protein thiols, GSH, other low-molecular-weight thiols, and the seleno-compound ebselen react, in a nonstoichiometric manner, with both peptide and protein peroxides. Cell lysate studies show that thiol consumption and peroxide removal occur in parallel; the stoichiometry of these reactions suggests that thiol groups are the major direct, or indirect, reductants for these species. Ascorbic acid and some derivatives can remove both the parent peroxides and radicals derived from them, whereas methionine and the synthetic phenolic antioxidants Probucol and BHT show little activity. These studies show that cells do not have efficient enzymatic defenses against protein peroxides, with only thiols and ascorbic acid able to remove these materials; the slow removal of these species is consistent with protein peroxides playing a role in cellular dysfunction resulting from oxidative stress.
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Affiliation(s)
- Philip E Morgan
- Free Radical Group, The Heart Research Institute, Camperdown, Sydney, NSW, Australia
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20
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Boileau TWM, Bray TM, Bomser JA. Ultraviolet radiation modulates nuclear factor kappa B activation in human lens epithelial cells. J Biochem Mol Toxicol 2004; 17:108-13. [PMID: 12717744 DOI: 10.1002/jbt.10067] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Exposure to ultraviolet radiation (UVR) is a known risk factor for cataract, but the molecular mechanisms involved have not been elucidated. We hypothesized that exposure to UVR would modulate the activation of nuclear factor kappa-B (NF-kappa B) within the human lens epithelium, since NF-kappa B is a key regulator of cellular responses to UVR stress in other cell types. Human lens epithelial (HLE) cells were exposed to acute physiological doses of ultraviolet A (UVAR), B (UVBR), C (UVCR) radiation, or interleukin-1 beta (IL-1 beta) and NF-kappa B activation was measured by electrophoretic shift assay (EMSA). Phosphorylation of I kappa B in response to UVAR was measured by Western blotting. Irradiation of HLE cells with UVAR (0-1100 J/m(2)) did not reduce cell survival, while UVBR (400-1600 J/m(2)) and UVCR (300-900 J/m(2)) significantly reduced HLE cell survival. EMSA analysis of HLE nuclear proteins indicated activation of NF-kappa B, but not activator protein-1 (AP-1), by UVAR. The effects of UVBR and UVCR were less pronounced. Exposure of HLE cells to UVAR (0-900 J/m(2)) followed by a 30-min incubation resulted in a dose-dependent activation of NF-kappa B. UVAR-induced NF-kappa B activation in HLE cells was evident 10 min postirradiation, maximal at 60 min and returned to control levels by 120 min. Western blot analysis of phosphorylation of the NF-kappa B inhibitory protein, I kappa B, revealed that UVAR activates NF-kappa B via a mechanism involving the phosphorylation of I kappa B-alpha; this effect was dose-dependent. Supershift analysis demonstrated that UVAR and IL-1 beta activate the transcriptionally active p65/p50 NF-kappa B dimer. These studies demonstrate that UVAR activates NF-kappa B in HLE cells in a time- and dose-dependent manner via signaling through I kappa B-alpha. The activation of NF-kappa B in HLE cells by UVAR may have implications for the development and progression of cataract and other related ocular disorders.
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Affiliation(s)
- Thomas W-M Boileau
- Department of Human Nutrition, The Ohio State University, Columbus, OH 43210, USA
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21
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de La Rochette A, Birlouez-Aragon I, Silva E, Morlière P. Advanced glycation endproducts as UVA photosensitizers of tryptophan and ascorbic acid: consequences for the lens. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1621:235-41. [PMID: 12787919 DOI: 10.1016/s0304-4165(03)00072-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Upon aging, the lens accumulates brown fluorophores, mainly derived from the Maillard reaction between vitamin C oxidation products and crystallins lysine residues. At the same time, the concentration of UVA filters decreases, allowing some radiation to be absorbed by lenticular advanced glycation endproducts (AGEs). This paper quantifies the photosensitizing activity of AGEs at various oxygen pressures, and compares it to that of lenticular riboflavin (RF). Solutions containing the sensitizer and the substrates tryptophan (Trp) and ascorbate (AH(-)) were irradiated at 365 nm. We show that the AGEs-photosensitized Trp oxidation rate increases with AGEs concentration and is optimal at 5% oxygen, the pressure in the lens. By contrast, for AH(-), the photooxidation rate increases with oxygen concentration. Despite the higher quantum yield of RF-depending reactions, its low concentration as compared to that of AGEs in aging lenses induces significantly higher Trp and AH(-) photodegradation rates with AGEs than with RF. As ascorbate is more rapidly photodegraded than Trp, the antioxidant competitively protects Trp from oxidation up to 1 mM, although not absolutely. We conclude that in the aging lens, AH(-) exerts a strong UVA protecting activity, but does not impede some Trp residue to be photodegraded proportionally to the AGEs concentration.
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Affiliation(s)
- Arnauld de La Rochette
- Laboratoire de Chimie Analytique, Institut National Agronomique Paris-Grignon, 16 rue Claude Bernard, 75231 Paris Cedex 05, France
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22
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Abstract
Light damage to the retina occurs through three general mechanisms involving thermal, mechanical, or photochemical effects. The particular mechanism activated depends on the wavelength and exposure duration of the injuring light. The transitions between the various light damage mechanism may overlap to some extent. Energy confinement is a key concept in understanding or predicting the type of damage mechanism produced by a given light exposure. As light energy (either from a laser or an incoherent source) is deposited in the retina, its penetration through, and its absorption in, various tissue compartments is determined by its wavelength. Strongly absorbing tissue components will tend to "concentrate" the light energy. The effect of absorbed light energy largely depends on the rate of energy deposition, which is correlated with the exposure duration. If the rate of energy deposition is too low to produce an appreciable temperature increase in the tissue, then any resulting tissue damage necessarily occurs because of chemical (oxidative) reactions induced by absorption of energetic photons (photochemical damage). If the rate of energy deposition is faster than the rate of thermal diffusion (thermal confinement), then the temperature of the exposed tissue rises. If a critical temperature is reached (typically about 10 degrees C above basal), then thermal damage occurs. If the light energy is deposited faster than mechanical relaxation can occur (stress confinement), then a thermoelastic pressure wave is produced, and tissue is disrupted by shear forces or by cavitation-nonlinear effects. Very recent evidence suggests that ultrashort laser pulses can produce tissue damage through nonlinear and photochemical mechanisms; the latter because of two-photon excitation of cellular chromophores. In addition to tissue damage caused directly by light absorption, light toxicity can be produced by the presence of photosensitizing agents. Drugs excited to reactive states by ultraviolet (UV) or visible light produce damage by type I (free radical) and type II (oxygen dependent) mechanisms. Some commonly used drugs, such as certain antibiotics, nonsteroidal anti-inflammatory drugs (NSAIDs), and psychotherapeutic agents, as well as some popular herbal medicines, can produce ocular phototoxicity. Specific cellular effects and damage end points characteristic of light damage mechanisms are described.
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Affiliation(s)
- Randolph D Glickman
- Department of Ophthalmology, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA.
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23
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Cheng R, Lin B, Ortwerth BJ. Rate of formation of AGEs during ascorbate glycation and during aging in human lens tissue. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1587:65-74. [PMID: 12009426 DOI: 10.1016/s0925-4439(02)00069-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The similarity of the yellow chromophores isolated from human cataracts with those from ascorbic acid modified calf lens proteins was recently published [Biochim. Biophys. Acta 1537 (2001) 14]. The data presented here additionally quantify age-dependent increases in individual yellow chromophores and fluorophores in the water-insoluble fraction of normal human lens. The water-insoluble fraction of individual normal human lens was isolated, solubilized by sonication and digested with a battery of proteolytic enzymes under argon to prevent oxidation. The level of A(330)-absorbing yellow chromophores, 350/450 nm fluorophores and total water-insoluble (WI) protein were quantified in each lens. The total yellow chromophores and fluorophores accumulated in parallel with the increase in the water-insoluble protein fraction during aging. The digest from each single human lens was then subjected to Bio-Gel P-2 size-exclusion chromatography. The fractions obtained were further separated by a semi-preparative prodigy C-18 high-performance liquid chromatography (RP-HPLC). Bio-Gel P-2 chromatography showed four major fractions, each of which increased with age. RP-HPLC of the amino acid peak resolved five major A(330)-absorbing peaks and eight fluorescent peaks, and each peak increased coordinately with age. A late-eluting peak, which contained hydrophobic amino acids increased significantly after age 60. Aliquots from an in vitro glycation of calf lens proteins by ascorbic acid were removed and subjected to the same enzymatic digestion. Ascorbic acid-modified calf lens protein digests showed an almost identical profile of chromophores, which also increased in a time-dependent manner. The late-eluting peak, however, did not increase with the time of glycation and may not be an advanced glycation endproduct (AGE) product. The data indicate that the total water-insoluble proteins, individual yellow chromophores and fluorophores increased equally both with aging in normal human lens and during ascorbate glycation in vitro. The major protein modifications, which accumulate during aging, therefore, appear to be AGEs. Whereas the late-eluting peak, which showed poor correlation to ascorbylation, may represent UV filter compounds bound to lens proteins.
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Affiliation(s)
- Rongzhu Cheng
- Mason Eye Institute, The University of Missouri, 404 Portland St., Columbia 65201, USA.
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24
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Sorg O, Tran C, Carraux P, Didierjean L, Falson F, Saurat JH. Oxidative stress-independent depletion of epidermal vitamin A by UVA. J Invest Dermatol 2002; 118:513-8. [PMID: 11874492 DOI: 10.1046/j.0022-202x.2002.01674.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
In hairless mice, epidermal vitamin A (retinol and retinyl esters) is strongly decreased following a single exposure to UVB. Here, using the same mouse model, we studied the effects of UVA on epidermal vitamin A content, lipid peroxidation, and CRBP-I expression, as well as the putative prevention of vitamin A depletion or lipid peroxidation by topical alpha-tocopherol. An acute exposure to UVA completely depleted epidermal vitamin A with EC50 of 0.25 and 0.5 J per cm2 for retinyl esters and retinol, respectively; these values were 0.1 J per cm2 for both retinoids under UVB exposure. CRBP-I expression was increased 2-fold 8 h following UVA exposure (10 J per cm2), and this increase persisted for at least 16 h. A single UVA exposure induced a concentration-dependent epidermal lipid peroxidation (EC50 = 3.5 J per cm2) giving rise to 55.4 +/- 4.2 nmol lipid peroxides per g at 20 J per cm2, whereas UVB, up to 1 J per cm2, did not increase the basal concentration of 6.7 +/- 0.9 nmol lipid peroxides per g. On the other hand, topical menadione induced a concentration-dependent lipid peroxidation, but did not affect vitamin A content. Pretreatment with alpha-tocopherol (i) did not inhibit UV-induced vitamin A depletion, (ii) completely inhibited the increased lipid peroxidation induced by UVA or menadione, and (iii) accelerated reconstitution of epidermal vitamin A after UVB but not UVA induced depletion. Thus acute UVA induced both epidermal vitamin A depletion and lipid peroxidation, UVB induced only vitamin A depletion, and menadione induced only a lipid peroxidation; topical alpha-tocopherol prevented lipid peroxidation but not vitamin A depletion. These observations indicate (i) that CRBP-I neither provides protection to UVB- and UVA-induced epidermal vitamin A depletion, nor interferes significantly with reconstitution, and (ii) that the UV-induced vitamin A depletion and lipid peroxidation in mouse epidermis are unrelated processes. UV light does not destroy epidermal vitamin A through an oxidative stress but probably by a photochemical reaction in which UV radiations at about 325 nm give the corresponding activation energy.
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Affiliation(s)
- Olivier Sorg
- Department of Dermatology, University Hospital, Geneva, Switzerland.
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25
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Cheng R, Lin B, Lee KW, Ortwerth BJ. Similarity of the yellow chromophores isolated from human cataracts with those from ascorbic acid-modified calf lens proteins: evidence for ascorbic acid glycation during cataract formation. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1537:14-26. [PMID: 11476959 DOI: 10.1016/s0925-4439(01)00051-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Chromatographic evidence supporting the similarity of the yellow chromophores isolated from aged human and brunescent cataract lenses and calf lens proteins ascorbylated in vitro is presented. The water-insoluble fraction from early stage brunescent cataract lenses was solubilized by sonication (WISS) and digested with a battery of proteolytic enzymes under argon to prevent oxidation. Also, calf lens proteins were incubated with ascorbic acid for 4 weeks in air and submitted to the same digestion. The percent hydrolysis of the proteins to amino acids was approximately 90% in every case. The content of yellow chromophores was 90, 130 and 250 A(330) units/g protein for normal human WISS, cataract WISS and ascorbate-modified bovine lens proteins respectively. Aliquots equivalent to 2.0 g of digested protein were subjected to size-exclusion chromatography on a Bio-Gel P-2 column. Six peaks were obtained for both preparations and pooled. Side by side thin-layer chromatography (TLC) of each peak showed very similar R(f) values for the long wavelength-absorbing fluorophores. Glycation with [U-(14)C]ascorbic acid, followed by digestion and Bio-Gel P-2 chromatography, showed that the incorporated radioactivity co-eluted with the A(330)-absorbing peaks, and that most of the fluorescent bands were labeled after TLC. Peaks 2 and 3 from the P-2 were further fractionated by preparative Prodigy C-18 reversed-phase high-performance liquid chromatography. Two major A(330)-absorbing peaks were seen in peak 2 isolated from human cataract lenses and 5 peaks in fraction 3, all of which eluted at the same retention times as those from ascorbic acid glycated calf lens proteins. HPLC fractionation of P-2 peaks 4, 5 and 6 showed many A(330)-absorbing peaks from the cataract WISS, only some of which were identical to the asorbylated proteins. The major fluorophores, however, were present in both preparations. These data provide new evidence to support the hypothesis that the yellow chromophores in brunescent lenses represent advanced glycation endproducts (AGEs) probably due to ascorbic acid glycation in vivo.
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Affiliation(s)
- R Cheng
- Mason Eye Institute, The University of Missouri, 404 Portland Street, Columbia, MO 65201, USA
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26
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Glickman RD. The origin of photo-oxidative stress in the aging eye. PROGRESS IN BRAIN RESEARCH 2001; 131:699-712. [PMID: 11420981 DOI: 10.1016/s0079-6123(01)31054-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Affiliation(s)
- R D Glickman
- Department of Ophthalmology, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
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27
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Wright A, Hawkins CL, Davies MJ. Singlet oxygen-mediated protein oxidation: evidence for the formation of reactive peroxides. Redox Rep 2001; 5:159-61. [PMID: 10939303 DOI: 10.1179/135100000101535573] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Affiliation(s)
- A Wright
- EPR Group, Heart Research Institute, Sydney, New South Wales, Australia
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28
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Shamsi FA, Sharkey E, Creighton D, Nagaraj RH. Maillard reactions in lens proteins: methylglyoxal-mediated modifications in the rat lens. Exp Eye Res 2000; 70:369-80. [PMID: 10712823 DOI: 10.1006/exer.1999.0800] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The nonenzymatic Maillard reaction is thought to contribute to aging and cataract formation in the lens. As levels of methylglyoxal (MG) and glutathione (GSH) affect the reaction, we examined the relationship of these factors and determined the effect of a glyoxalase I inhibitor on the Maillard reaction. Rat lens cultures were maintained for up to 3 days in TC-199 medium with or without 20 m m glyceraldehyde (GLD) and 250 microm S-[N-hydroxy-N-(4-chlorophenyl) carbamoyl] glutathione diethyl ester (HCCG diester). We measured GSH, MG, D-lactate, glyoxalase I activity, immunoreactive MG-derived advanced glycation endproducts (MG-AGEs) and imidazolysine in organ cultured rat lenses. In vitro experiments with isolated rat lens proteins revealed that HCCG alone inhibited glyoxalase I activity in a dose-dependent manner. In organ cultured rat lens protein, GLD increased MG levels 24-fold, and the addition of HCCG diester further increased it by about two-fold. GSH levels fell sharply in the presence of GLD and this was prevented to some extent by the presence of HCCG diester. D-lactate production in the lens was suppressed by HCCG diester treatment. Dialysed lens proteins retained glyoxalase I activity, indicating that the enzyme was unaltered during incubation. MG-AGEs and imidazolysine levels were significantly higher (P<0.05) in GLD-treated lenses, but a combination of HCCG diester and GLD lowered immunoreactive MG-AGEs and imidazolysine levels compared to GLD alone. HCCG had no significant effect on MG-AGE formation in lens proteins incubated with GLD or MG. We conclude that exogenous GLD enhances MG and MG-AGE levels in the rat lens and that this increase is accompanied by a loss in GSH. In addition, inhibition of glyoxalase I promotes MG accumulation.
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Affiliation(s)
- F A Shamsi
- Center for Vision Research, Department of Ophthalmology, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, OH 44106, USA
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29
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Lee KW, Meyer N, Ortwerth BJ. Chromatographic comparison of the UVA sensitizers present in brunescent cataracts and in calf lens proteins ascorbylated in vitro. Exp Eye Res 1999; 69:375-84. [PMID: 10504271 DOI: 10.1006/exer.1999.0709] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The water-insoluble (WI) fraction from aged human lenses contains yellow chromophoric sensitizers, which generate reactive oxygen species (ROS) when irradiated with UVA light. The WI proteins from type I to V brunescent cataract lenses were assayed for UVA-dependent superoxide anion synthesis. Rates varied from 8.4-15 nMol h(-1)mg protein(-1), but there was no significant difference in specific activity between cataract types. When calf lens soluble proteins were incubated with ascorbic acid for 4 weeks and dialyzed, they were capable of generating 30-40 nMol h(-1)mg protein(-1)superoxide anion when irradiated with UVA light. Two preparations each of brunescent cataract WI proteins and bovine lens proteins ascorbylated in vitro were extensively digested with proteolytic enzymes and the released amino acids separated by normal phase HPLC. The elution profiles of the digests were very similar based upon the absorbance at 330 nm and fluorescence at 350 nm excitation/450 nm emission. Each peak was pooled and analyzed for the UVA-dependent generation of both superoxide anion and singlet oxygen. Every peak exhibited sensitizer activity, and the UVA-dependent ROS generation was roughly proportional to the absorbance at 330 nm. In addition, the ratio of superoxide anion to singlet oxygen generated was similar with both preparations. These data argue that it is the brown, fluorescent compounds which accumulate during aging and cataract formation that are responsible for the UVA-dependent ROS formation, and that these browning products may be similar to the advanced glycation endproducts produced by ascorbylation of lens proteins under oxidative conditions. This work also presents an initial report of a chromatographic method to separate the UVA-sensitizers present in each of these protein preparations without the use of acid or base hydrolysis.
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Affiliation(s)
- K W Lee
- Mason Eye Institute, University of Missouri, Columbia, MO 65212, USA
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30
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Alegrı́a AE, Ferrer A, Santiago G, Sepúlveda E, Flores W. Photochemistry of water-soluble quinones. Production of the hydroxyl radical, singlet oxygen and the superoxide ion. J Photochem Photobiol A Chem 1999. [DOI: 10.1016/s1010-6030(99)00138-0] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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31
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Linetsky M, James HL, Ortwerth BJ. Spontaneous generation of superoxide anion by human lens proteins and by calf lens proteins ascorbylated in vitro. Exp Eye Res 1999; 69:239-48. [PMID: 10433859 DOI: 10.1006/exer.1999.0710] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The proteins isolated from aged human lenses and brunescent cataracts exhibit extensive disulfide bond formation. Diabetic rat lenses similarly contain disulfide-bonded protein aggregates. These observations are consistent with the known link between diabetes, glycation and oxidative damage, and suggest a role for reactive oxygen species (ROS) in this process. To assess whether the glycation-related modifications in human lens proteins spontaneously generate ROS, superoxide anion formation was measured using both cataractous lens proteins and calf lens proteins glycated in vitro with ascorbic acid (ascorbylated). The water-insoluble fraction from aged normal human lenses generated 0.3-0.6 nmol superoxide h(-1)mg protein(-1), whereas the activity increased to 0.5-1.8 nmol h(-1)mg protein(-1)with the WI fraction from brunescent cataracts, and 2.3 nmol h(-1)mg protein(-1)with calf lens proteins ascorbylated for 4 weeks in vitro. The activity in the human lens proteins was observed in both the water-soluble and water-insoluble fractions, and was completely dependent upon the presence of oxygen. The pH optimum curve for superoxide formation increased from pH 6.5 to 10 with both the cataract and ascorbylated proteins. The superoxide-generating activity in human lens was completely bound to a boronate affinity column, but only partially bound with the ascorbylated proteins. The superoxide anion produced by a 5 m m solution of purified N(epsilon)-fructosyl-lysine was barely detectable, and therefore, could not account for the superoxide formed by any of the lens protein preparations. Also, superoxide formation increased 10-fold at pH 8.8 with fructosyl-lysine, but only 1.3-1.8-fold with human lens proteins. The addition of copper-stimulated superoxide formation with glycated bovine serum albumin, but no stimulation was seen with cataractous proteins. Assays of specific compounds showed that catechol, hydroquinone, 3-OH kynurenine and 3-OH anthranylic acid exhibited the greatest activity for superoxide generation, but had a very short halflife. 2,3-Dihydroxypyridine and 4,5 dihydroxynaphthalene were one and two orders of magnitude less reactive. In long-term incubations at 37 degrees, cataractous proteins retained the potential to produce superoxide anion, losing only half of the initial activity after 6-7 days. Therefore, the water-insoluble fraction from aged human lenses and dark brown cataracts are potentially capable of generating >100 nmol mg protein(-1)and >170 nmol mg protein(-1)of superoxide anion respectively, likely due to the presence of advanced glycation endproducts in human lens proteins. This spontaneous generation of superoxide anion in vivo could account for a major portion of the oxidation of sulfur amino acids seen during aging and cataract formation.
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Affiliation(s)
- M Linetsky
- Mason Eye Institute, University of Missouri, Columbia, MO, 65212, USA
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32
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Abstract
A multifunctional cell surface protein with NADH oxidase (NOX) activity and capable of oxidizing hydroquinones is located at the exterior of the cell and is shed in soluble form into sera. The oxidase appears to function as a terminal oxidase of a trans plasma membrane electron transport chain consisting of a NAD(P)H-ubiquinone reductase at the cytosolic membrane surface, possibly a b-type cytochrome, ubiquinone and the oxidase. Hyperactivity or conditions that interrupt ordered 2H+ + 2e- transport from NAD(P)H or hydroquinone to molecular oxygen and other acceptors at the external cell surface may result in the generation of superoxide. The latter may serve to propagate aging-related redox changes both to adjacent cells and circulating blood components. A circulating NOX activity form associated with aging and the reduction of cytochrome c by sera of aged patients that is partially inhibited by ubiquinone are described.
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Affiliation(s)
- D J Morré
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
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33
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Ortwerth BJ, Coots A, James HL, Linetsky M. UVA irradiation of human lens proteins produces residual oxidation of ascorbic acid even in the presence of high levels of glutathione. Arch Biochem Biophys 1998; 351:189-96. [PMID: 9515056 DOI: 10.1006/abbi.1997.0549] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The oxidation products of ascorbic acid (AscH-) can rapidly glycate and crosslink lens proteins in vitro, producing fluorophores and browning products similar to those present in cataractous lenses. The accumulation of AscH- oxidation products, however, would largely be prevented by the millimolar levels of glutathione (GSH) present in human lens. Here we investigate whether protein aggregation could allow the oxidation of AscH- by UVA-induced reactive oxygen species in the presence of physiological levels of GSH. The metal-catalyzed oxidation of 1.0 mM AscH- by 50 microM Cu(II) was almost complete after 1 h, but no oxidation was seen in the presence of GSH concentrations as low as 0.5 mM. UVA irradiation of protein aggregates from human lens, which accumulated more than 2.0 mM singlet oxygen after 1 h, caused a 50-60% oxidation of 1.0 mM AscH-. The addition of 204 mM GSH, however, decreased AscH- oxidation by less than half, and 30% of the AscH- was oxidized even in the presence of 15 mM GSH. This diminished protection may be due, in part, to the ability of AscH-, but not GSH, to penetrate to the sites of singlet oxygen generation located within the protein. Consistent with this hypothesis, greater GSH protection was seen when a proteolytic digest of the human proteins was subjected to the same irradiation or when singlet oxygen was chemically generated from 3-(4-methyl-1-naphthyl)propionic acid endoperoxide (MNPAE) at 37 degrees C in the medium. The addition of 50 microM Cu(II) had no effect on the rate of degradation of dehydroascorbic acid (DHA). Singlet oxygen, either UVA- or MNPAE-generated, increased the rate of DHA loss. This secondary oxidation of DHA by singlet oxygen would allow the accumulation of AscH- oxidation products was not reducible by GSH. Therefore, the data presented here argue that the protein aggregation seen in older human lenses may permit oxidized AscH--induced crosslinking to occur even at physiological GSH levels.
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Affiliation(s)
- B J Ortwerth
- Mason Eye Institute, University of Missouri, Columbia, Missouri 65212, USA
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Photodynamic action of phycobiliproteins: in situ generation of reactive oxygen species. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 1997. [DOI: 10.1016/s0005-2728(97)00021-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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García J, Silva E. Flavin-sensitized photooxidation of amino acids present in a parenteral nutrition infusate: Protection by ascorbic acid. J Nutr Biochem 1997. [DOI: 10.1016/s0955-2863(97)00024-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Ortwerth BJ, Prabhakaram M, Nagaraj RH, Linetsky M. The relative UV sensitizer activity of purified advanced glycation endproducts. Photochem Photobiol 1997; 65:666-72. [PMID: 9114742 DOI: 10.1111/j.1751-1097.1997.tb01909.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The oxidation products of ascorbic acid react with lens proteins to form advanced glycation endproducts (AGE) that are capable of generating reactive oxygen species when irradiated with UVA light. L-Threose, the most active of these oxidation products, was reacted with N-acetyl lysine and six AGE peaks were isolated by RP-HPLC. Each peak exhibited fluorescence and generated superoxide anion and singlet oxygen in response to UV light. Solutions of these AGE peaks (50 micrograms/mL) generated 5-10 nmol/mL of superoxide anion during a 30 min irradiation. This activity was 100-fold less than the superoxide anion generated by kynurenic acid and 400-fold less than riboflavin. Ultraviolet irradiation generated from 1.2 to 2.7 mumol/mL of singlet oxygen with the purified threose AGE compounds. This activity was similar to that seen with other purified AGE compounds (pentosidine, LM-1 and Ac-FTP) and with kynurenine and 3-OH kynurenine. This considerable singlet oxygen formation, however, was still 40-fold less than that obtained with kynurenic acid and 100-fold less than riboflavin under the same irradiation conditions. In spite of this lower sensitizer efficiency, the purified AGE generated 20-60-fold more singlet oxygen on a weight basis than either crude ascorbic acid glycated proteins or a preparation of water-insoluble proteins from aged normal human lenses. On a molar basis, therefore, AGE could account for the sensitizer activity in these protein preparations if they represented less than 1% of the total amino acids.
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Affiliation(s)
- B J Ortwerth
- Mason Eye Institute, University of Missouri, Columbia 65212, USA.
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