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MacFarlane ER, Donaldson PJ, Grey AC. UV light and the ocular lens: a review of exposure models and resulting biomolecular changes. FRONTIERS IN OPHTHALMOLOGY 2024; 4:1414483. [PMID: 39301012 PMCID: PMC11410779 DOI: 10.3389/fopht.2024.1414483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/09/2024] [Accepted: 08/12/2024] [Indexed: 09/22/2024]
Abstract
UV light is known to cause damage to biomolecules in living tissue. Tissues of the eye that play highly specialised roles in forming our sense of sight are uniquely exposed to light of all wavelengths. While these tissues have evolved protective mechanisms to resist damage from UV wavelengths, prolonged exposure is thought to lead to pathological changes. In the lens, UV light exposure is a risk factor for the development of cataract, which is a condition that is characterised by opacity that impairs its function as a focusing element in the eye. Cataract can affect spatially distinct regions of the lens. Age-related nuclear cataract is the most prevalent form of cataract and is strongly associated with oxidative stress and a decrease in the antioxidant capacity of the central lens region. Since UV light can generate reactive oxygen species to induce oxidative stress, its effects on lens structure, transparency, and biochemistry have been extensively investigated in animal models in order to better understand human cataract aetiology. A review of the different light exposure models and the advances in mechanistic understanding gained from these models is presented.
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Affiliation(s)
- Emily R MacFarlane
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Paul J Donaldson
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
| | - Angus C Grey
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
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2
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Mothersill C, Seymour C, Cocchetto A, Williams D. Factors Influencing Effects of Low-dose Radiation Exposure. HEALTH PHYSICS 2024; 126:296-308. [PMID: 38526248 DOI: 10.1097/hp.0000000000001816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
ABSTRACT It is now well accepted that the mechanisms induced by low-dose exposures to ionizing radiation (LDR) are different from those occurring after high-dose exposures. However, the downstream effects of these mechanisms are unclear as are the quantitative relationships between exposure, effect, harm, and risk. In this paper, we will discuss the mechanisms known to be important with an overall emphasis on how so-called "non-targeted effects" (NTE) communicate and coordinate responses to LDR. Targeted deposition of ionizing radiation energy in cells causing DNA damage is still regarded as the dominant trigger leading to all downstream events whether targeted or non-targeted. We regard this as an over-simplification dating back to formal target theory. It ignores that last 100 y of biological research into stress responses and signaling mechanisms in organisms exposed to toxic substances, including ionizing radiation. We will provide evidence for situations where energy deposition in cellular targets alone cannot be plausible as a mechanism for LDR effects. An example is where the energy deposition takes place in an organism not receiving the radiation dose. We will also discuss how effects after LDR depend more on dose rate and radiation quality rather than actual dose, which appears rather irrelevant. Finally, we will use recent evidence from studies of cataract and melanoma induction to suggest that after LDR, post-translational effects, such as protein misfolding or defects in energy metabolism or mitochondrial function, may dominate the etiology and progression of the disease. A focus on such novel pathways may open the way to successful prophylaxis and development of new biomarkers for better risk assessment after low dose exposures.
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Affiliation(s)
- Carmel Mothersill
- Department of Biology, McMaster University, 1280 Main St., Hamilton, ON, Canada L8S 4L8
| | - Colin Seymour
- Department of Biology, McMaster University, 1280 Main St., Hamilton, ON, Canada L8S 4L8
| | - Alan Cocchetto
- The National CFIDS Foundation, 285 Beach Ave., Hull, MA 02045
| | - David Williams
- Cambridge University, The Old Schools, Trinity Lane, Cambridge CB2 1TN, United Kingdom
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3
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Quint WH, van Buuren R, Kokke NCCJ, Meester-Smoor MA, Willemsen R, Broersma R, Iglesias AI, Lucassen M, Klaver CCW. Exposure to cyan or red light inhibits the axial growth of zebrafish eyes. Exp Eye Res 2023; 230:109437. [PMID: 36924981 DOI: 10.1016/j.exer.2023.109437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 03/01/2023] [Accepted: 03/10/2023] [Indexed: 03/18/2023]
Abstract
Myopia, or nearsightedness, is the most common type of refractive error and is characterized by a mismatch between the optical power and ocular axial length. Light, and more specifically the spectral composition of light, has been known to influence myopic axial growth. In this pilot study, we exposed zebrafish to illuminations that vary in spectral composition and screened for changes in axial length. The illumination spectra included narrow band ultra-violet A (UVA) (peak wavelength 369 nm), violet (425 nm), cyan (483 nm), green/yellow (557 nm), and red (633 nm) light, as well as broad band white light (2700 K and 6500 K), dim white light and broad spectrum (day) light. We found that rearing zebrafish in cyan or red light leads to a reduction of the ocular axial length. The results of this pilot study may contribute to new perspectives on the role of light and lighting as an intervention strategy for myopia control.
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Affiliation(s)
- Wim H Quint
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Renee van Buuren
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Nina C C J Kokke
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Magda A Meester-Smoor
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Epidemiology, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Rob Willemsen
- Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, the Netherlands
| | - Rémy Broersma
- Signify Research, Signify, Eindhoven, the Netherlands
| | - Adriana I Iglesias
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Clinical Genetics, Erasmus Medical Center, Rotterdam, the Netherlands
| | | | - Caroline C W Klaver
- Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Epidemiology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Ophthalmology, Radboud University Medical Center, Nijmegen, the Netherlands; Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland.
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4
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Giblin FJ, Anderson DMG, Han J, Rose KL, Wang Z, Schey KL. Acceleration of age-induced proteolysis in the guinea pig lens nucleus by in vivo exposure to hyperbaric oxygen: A mass spectrometry analysis. Exp Eye Res 2021; 210:108697. [PMID: 34233175 PMCID: PMC8429224 DOI: 10.1016/j.exer.2021.108697] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 06/21/2021] [Accepted: 06/30/2021] [Indexed: 11/19/2022]
Abstract
Hyperbaric oxygen (HBO) treatment of animals or ocular lenses in culture recapitulates many molecular changes observed in human age-related nuclear cataract. The guinea pig HBO model has been one of the best examples of such treatment leading to dose-dependent development of lens nuclear opacities. In this study, complimentary mass spectrometry methods were employed to examine protein truncation after HBO treatment of aged guinea pigs. Quantitative liquid chromatography-mass spectrometry (LC-MS) analysis of the membrane fraction of guinea pig lenses showed statistically significant increases in aquaporin-0 (AQP0) C-terminal truncation, consistent with previous reports of accelerated loss of membrane and cytoskeletal proteins. In addition, imaging mass spectrometry (IMS) analysis spatially mapped the acceleration of age-related αA-crystallin truncation in the lens nucleus. The truncation sites in αA-crystallin closely match those observed in human lenses with age. Taken together, our results suggest that HBO accelerates the normal lens aging process and leads to nuclear cataract.
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Affiliation(s)
- Frank J Giblin
- Eye Research Institute, Oakland University, Rochester, MI, 48309, USA
| | - David M G Anderson
- Department of Biochemistry and Mass Spectrometry Research Center, Vanderbilt University, Nashville, TN, 37242, USA
| | - Jun Han
- Genome BC Proteomics Centre, University of Victoria, Victoria, British Columbia, Canada
| | - Kristie L Rose
- Department of Biochemistry and Mass Spectrometry Research Center, Vanderbilt University, Nashville, TN, 37242, USA
| | - Zhen Wang
- Department of Biochemistry and Mass Spectrometry Research Center, Vanderbilt University, Nashville, TN, 37242, USA
| | - Kevin L Schey
- Department of Biochemistry and Mass Spectrometry Research Center, Vanderbilt University, Nashville, TN, 37242, USA.
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Ahmadi M, Barnard S, Ainsbury E, Kadhim M. Early Responses to Low-Dose Ionizing Radiation in Cellular Lens Epithelial Models. Radiat Res 2021; 197:78-91. [PMID: 34324666 DOI: 10.1667/rade-20-00284.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 07/06/2021] [Indexed: 11/03/2022]
Abstract
Cataract is the leading cause of visual impairment which can result in blindness. Cataract formation has been associated with radiation exposure; however, the mechanistic understanding of this phenomenon is still lacking. The goal of this study was to investigate mechanisms of cataract induction in isolated lens epithelial cells (LEC) exposed to ionizing radiation. Human LECs from different genetic backgrounds (SV40 immortalized HLE-B3 and primary HLEC cells) were exposed to varying doses of 137Cs gamma rays (0, 0.1, 0.25 and 0.5 Gy), at low (0.065 Gy/min) and higher (0.3 Gy/min) dose rates. Different assays were used to measure LEC response for, e.g., viability, oxidative stress, DNA damage studies, senescence and changes to telomere length/telomerase activity at two time points (1 h and 24 h, or 24 h and 15 days, depending on the type of assay and expected response time). The viability of cells decreased in a dose-dependent manner within 24 h of irradiation. Measurement of reactive oxygen species showed an increase at 1 h postirradiation, which was alleviated within 24 h. This was consistent with DNA damage results showing high DNA damage after 1 h postirradiation which reduced significantly (but not completely) within 24 h. Induction of senescence was also observed 15 days postirradiation, but this was not attributed to telomere erosion or telomerase activity reduction. Overall, these findings provide a mechanistic understanding of low-dose radiation-induced cataractogenesis which will ultimately help to inform judgements on the magnitude of risk and improve existing radiation protection procedures.
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Affiliation(s)
- Maryam Ahmadi
- Genomic Instability and Cell Communication Research Group, Department of Biological and Medical Science, Oxford Brookes University, Oxford, United Kingdom.,Kidney Genetics Group, Academic Unit of Nephrology, The Medical School, Royal Hallamshire Hospital, Sheffield, United Kingdom
| | - Stephen Barnard
- Public Health England, Centre for Radiation, Chemical and Environmental Hazards, Oxford, United Kingdom
| | - Elizabeth Ainsbury
- Public Health England, Centre for Radiation, Chemical and Environmental Hazards, Oxford, United Kingdom
| | - Munira Kadhim
- Genomic Instability and Cell Communication Research Group, Department of Biological and Medical Science, Oxford Brookes University, Oxford, United Kingdom
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6
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Mondal B, Nagesh J, Reddy G. Double Domain Swapping in Human γC and γD Crystallin Drives Early Stages of Aggregation. J Phys Chem B 2021; 125:1705-1715. [PMID: 33566611 DOI: 10.1021/acs.jpcb.0c07833] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human γD (HγD) and γC (HγC) are two-domain crystallin (Crys) proteins expressed in the nucleus of the eye lens. Structural perturbations in the protein often trigger aggregation, which eventually leads to cataract. To decipher the underlying molecular mechanism, it is important to characterize the partially unfolded conformations, which are aggregation-prone. Using a coarse grained protein model and molecular dynamics simulations, we studied the role of on-pathway folding intermediates in the early stages of aggregation. The multidimensional free energy surface revealed at least three different folding pathways with the population of partially structured intermediates. The two dominant pathways confirm sequential folding of the N-terminal [Ntd] and the C-terminal domains [Ctd], while the third, least favored, pathway involves intermediates where both the domains are partially folded. A native-like intermediate (I*), featuring the folded domains and disrupted interdomain contacts, gets populated in all three pathways. I* forms domain swapped dimers by swapping the entire Ntds and Ctds with other monomers. Population of such oligomers can explain the increased resistance to unfolding resulting in hysteresis observed in the folding experiments of HγD Crys. An ensemble of double domain swapped dimers are also formed during refolding, where intermediates consisting of partially folded Ntds and Ctds swap secondary structures with other monomers. The double domain swapping model presented in our study provides structural insights into the early events of aggregation in Crys proteins and identifies the key secondary structural swapping elements, where introducing mutations will aid in regulating the overall aggregation propensity.
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Affiliation(s)
- Balaka Mondal
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
| | - Jayashree Nagesh
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
| | - Govardhan Reddy
- Solid State and Structural Chemistry Unit, Indian Institute of Science, Bengaluru, Karnataka, India 560012
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7
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Anbaraki A, Ghahramani M, Muranov KO, Kurganov BI, Yousefi R. Structural and functional alteration of human αA-crystallin after exposure to full spectrum solar radiation and preventive role of lens antioxidants. Int J Biol Macromol 2018; 118:1120-1130. [PMID: 29964111 DOI: 10.1016/j.ijbiomac.2018.06.136] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Revised: 06/06/2018] [Accepted: 06/26/2018] [Indexed: 12/31/2022]
Abstract
The chronically exposure of eye lenses to ultra violet and visible light of the solar radiation is an important risk factor for development of the senile cataract diseases. Various photosensitizer molecules including riboflavin (RF) play a significant role in photo-oxidative damages of lens proteins underlying development of opacity in the lenticular tissues. In the current study, RF-mediated photo-oxidation of human αA-crystallin (αA-Cry) was assessed using SDS-PAGE analysis, dynamic light scattering and other spectroscopic assessments. The RF-photosensitized reactions led to non-disulfide covalent cross-linking, oligomerization and significant structural changes in αA-Cry. The photo-damaging of αA-Cry under solar radiation was also accompanied by the reduction in both Trp and Tyr fluorescence intensities which followed by the formation of new photosensitizer chromophores. The solvent exposed hydrophobic patches, secondary structures and chaperone-like activity of αA-Cry were significantly altered after exposure to the solar radiation in the presence of RF. Although glutathione and ascorbate were capable to partially protect the photo-induced structural damages of human αA-Cry, they also disrupted its chaperone function when co-exposed with this protein to the solar radiation. Also, the most promising data were obtained with cysteine which its availability in the lenticular tissues is a rate limiting factor for the biosynthesis of glutathione. Overall our results suggest that glutathione and ascorbate, as the major anti-oxidant compounds within lenticular tissues, demonstrate controversial effect on structure and chaperone-like activity of human αA-Cry. Elucidation of this effect may demand further experiments.
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Affiliation(s)
- Afrooz Anbaraki
- Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran
| | - Maryam Ghahramani
- Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran
| | - Konstantin O Muranov
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Kosygin str. 4, Moscow 119991, Russia
| | - Boris I Kurganov
- Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, 33, bld. 2 Leninsky Ave., Moscow 119071, Russia
| | - Reza Yousefi
- Protein Chemistry Laboratory (PCL), Department of Biology, College of Sciences, Shiraz University, Shiraz, Iran.
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8
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Sormacheva ED, Sherin PS, Tsentalovich YP. Dimerization and oxidation of tryptophan in UV-A photolysis sensitized by kynurenic acid. Free Radic Biol Med 2017; 113:372-384. [PMID: 29024806 DOI: 10.1016/j.freeradbiomed.2017.10.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/04/2017] [Accepted: 10/05/2017] [Indexed: 11/24/2022]
Abstract
Photoinduced generation of radicals in the eye lens may play an important role in the modification of proteins leading to their coloration, aggregation, and insolubilization. The radicals can be formed via the reactions of photoexcited endogenous chromophores of the human lens with lens proteins, in particular with tryptophan residues. In the present work we studied the reactions induced by UV-A (315-400nm) light between kynurenic acid (KNA), an effective photosensitizer present in the human lens, and N-acetyl-L-tryptophan (NTrpH) under aerobic and anaerobic conditions. Our results show that the reaction mechanism strongly depends on the presence of oxygen in solution. Under aerobic conditions, the generation of singlet oxygen is the major channel of the effective NTrpH oxidation. In argon-bubbled solutions, the quenching of triplet KNA by NTrpH results in the formation of KNA•- and NTrp• radicals. Under laser pulse irradiation, when the radical concentration is high, the main pathway of the radical decay is the back electron transfer with the restoration of initial reagents. Other reactions include (i) the radical combination yielding NTrp dimers and (ii) the oxygen atom transfer from KNA•- to NTrp• with the formation of oxidized NTrp species and deoxygenated KNA products. In continuous-wave photolysis, even trace amounts of molecular oxygen are sufficient to oxidize the majority of KNA•- radicals with the rate constant of (2.0 ± 0.2) × 109M-1s-1, leading to the restoration of KNA and the formation of superoxide radical O2•-. The latter reacts with NTrp• via either the radical combination to form oxidized NTrp (minor pathway), or the electron transfer to restore NTrpH in the ground state (major pathway). As the result, the quantum yields of the starting compound decomposition under continuous-wave anaerobic photolysis are rather low: 1.6% for NTrpH and 0.02% for KNA. The photolysis of KNA with alpha-crystallin yields the same deoxygenated KNA products as the photolysis of KNA with NTrpH, indicating the similarity of the photolysis mechanisms. Thus, inside the eye lens KNA can sensitize both protein photooxidation and protein covalent cross-linking with the minor self-degradation. This may play an important role in the lens protein modifications during the normal aging and cataract development.
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Affiliation(s)
- Ekaterina D Sormacheva
- International Tomography Center SB RAS, Institutskaya str. 3A, 630090 Novosibisrk, Russia
| | - Peter S Sherin
- International Tomography Center SB RAS, Institutskaya str. 3A, 630090 Novosibisrk, Russia; Novosibirsk State University, Pirogova str. 2, 630090 Novosibisrk, Russia.
| | - Yuri P Tsentalovich
- International Tomography Center SB RAS, Institutskaya str. 3A, 630090 Novosibisrk, Russia; Novosibirsk State University, Pirogova str. 2, 630090 Novosibisrk, Russia
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9
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Zinflou C, Rochette PJ. Ultraviolet A-induced oxidation in cornea: Characterization of the early oxidation-related events. Free Radic Biol Med 2017; 108:118-128. [PMID: 28342848 DOI: 10.1016/j.freeradbiomed.2017.03.022] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 03/08/2017] [Accepted: 03/20/2017] [Indexed: 11/18/2022]
Abstract
Exposure to sunlight ultraviolet-A (UVA), the main component of solar UV reaching the eyes, is suspected to play an important part in the onset of ocular pathologies. UVA primary biological deleterious effects arise from the photo-induction of oxidative stress in cells. However, the molecular bases linking UVA-induced oxidation to UVA toxicity in eyes remain poorly understood, especially with regards to the cornea. To shed some light on this issue, we have investigated the susceptibility and response potential of the different corneal cellular layers (epithelium, stroma and endothelium) to UVA-induced oxidation. We have monitored UVA-induced immediate effects on cellular redox balance, on mitochondrial membrane potential, on 8-Hydroxy-2'-deoxyguanosine (8-OHdG) accumulation in cellular DNA and on S-glutathionylated proteins (PSSG) levels along whole rabbit corneas. Higher redox imbalance was observed in the posterior part of the cornea following irradiation. Conversely, UVA-altered mitochondrial membrane potentials were observed only in anterior portions of the cornea. UVA-induced 8-OHdG were found in nuclear DNA of epithelia, while they were found in both nuclear and mitochondrial DNA in stromal and endothelial cells. Finally, significantly higher levels of cytosolic PSSG were measured in epithelia and endothelia immediately after UVA exposure, but not in stromas. Taken together, our findings indicate that while corneal epithelial cells are subjected to important modifications in response to UVA exposure, they efficiently limit the early manifestations of UVA-induced toxicity. On the other hand, the corneal endothelium is more susceptible to UVA-induced oxidation-related toxicity.
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Affiliation(s)
- Corinne Zinflou
- Axe Médecine Régénératrice, Centre de Recherche du CHU de Québec - Université Laval, Hôpital du Saint-Sacrement, Québec, QC, Canada; Centre de Recherche en Organogénèse Expérimentale de l'Université Laval/LOEX, Université Laval, Québec, QC, Canada
| | - Patrick J Rochette
- Axe Médecine Régénératrice, Centre de Recherche du CHU de Québec - Université Laval, Hôpital du Saint-Sacrement, Québec, QC, Canada; Centre de Recherche en Organogénèse Expérimentale de l'Université Laval/LOEX, Université Laval, Québec, QC, Canada; Département d'Ophtalmologie et ORL - chirurgie cervico-faciale, Université Laval, Québec, QC, Canada.
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10
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Zelentsova EA, Yanshole LV, Fursova AZ, Tsentalovich YP. Optical properties of the human lens constituents. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2017. [PMID: 28624737 DOI: 10.1016/j.jphotobiol.2017.06.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
The absorption and fluorescence properties of the metabolomic (MET), water-soluble and urea-soluble protein fractions from the middle-age, aged, and cataractous human lenses have been measured. At 280nm and 300nm the major lens absorbers are crystallins, which absorb more than 90% of light in the UV-B region (280-315nm). In middle-aged lenses, the absorption at 360nm is mostly provided by UV filters contained in the MET fraction. With aging, and especially with the cataract development, the absorption of MET fraction in UV-A region (315-400nm) decreases due to the drop of the UV filter concentration, while the absorption of protein fractions increases due to the accumulation of post-translational modifications. Consequently, the contribution of the MET fraction into the total lens absorption at 360nm decays from 63% in middle-aged lenses to 25% in aged lenses to 3% in cataractous lenses. The fluorescence yield of the MET fraction from cataractous lenses also significantly increases. Therefore, the protection of the lens tissue against UV radiation in aged and cataractous lenses weakens: the absorption of UV-A light is mostly provided by modified crystallins and non-UV-filter metabolites, which are photochemically more active than the UV filters. The obtained data indicate that the aged and cataractous human lenses are more vulnerable to UV-A light than the middle-aged lenses.
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Affiliation(s)
- Ekaterina A Zelentsova
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
| | - Lyudmila V Yanshole
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
| | - Anjella Zh Fursova
- Novosibirsk State Regional Clinical Hospital, Nemirovicha-Danchenko 130, Novosibirsk 630087, Russia
| | - Yuri P Tsentalovich
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
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11
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Zaman M, Zakariya SM, Nusrat S, Khan MV, Qadeer A, Ajmal MR, Khan RH. Surfactant-mediated amyloidogenesis behavior of stem bromelain; a biophysical insight. J Biomol Struct Dyn 2016; 35:1407-1419. [DOI: 10.1080/07391102.2016.1185040] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Masihuz Zaman
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202002, India
| | - Syed Mohammad Zakariya
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202002, India
| | - Saima Nusrat
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202002, India
| | - Mohsin Vahid Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202002, India
| | - Atiyatul Qadeer
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202002, India
| | - Mohammad Rehan Ajmal
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202002, India
| | - Rizwan Hasan Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP 202002, India
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12
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Lim JC, Umapathy A, Donaldson PJ. Tools to fight the cataract epidemic: A review of experimental animal models that mimic age related nuclear cataract. Exp Eye Res 2016; 145:432-443. [DOI: 10.1016/j.exer.2015.09.007] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/07/2015] [Accepted: 09/14/2015] [Indexed: 12/22/2022]
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13
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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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14
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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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15
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Zheng XY, Xu J, Chen XI, Li W, Wang TY. Attenuation of oxygen fluctuation-induced endoplasmic reticulum stress in human lens epithelial cells. Exp Ther Med 2015; 10:1883-1887. [PMID: 26640566 DOI: 10.3892/etm.2015.2725] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 05/28/2015] [Indexed: 12/31/2022] Open
Abstract
Cataractogenic stresses are associated with the induction of endoplasmic reticulum (ER) stress. However, little is known about oxygen (O2)-induced ER stress in the lens. Cataract research has focused on elevated levels of O2 in lens epithelial cells (LECs). Excessive levels or a lack of O2 are known to induce ER stress whereas chronic ER stress activates the unfolded protein response (UPR). The present study investigated the hypothesis that the fluctuation of O2 levels induces a UPR, and may be controlled by maintaining human LECs (hLECs) in a specific concentration of O2. Human LECs were cultured in different atmospheric levels of O2. Hypoxic conditions were determined by the level of hypoxia-inducible factor (HIF)-1α. 2',7'-Dichlorodihydrofluorescein diacetate and ethidium homodimer-1 staining were conducted to detect reactive oxygen species (ROS) and cell death, respectively. Protein blot analyses were performed with antibodies specific to antioxidant and UPR-specific proteins. Reverse transcription-quantitatative polymerase chain reaction assays were performed to quantify the mRNA levels of activated NF-E2-related factor 2 (Nrf2) and kelch-like ECH-associated protein 1 (Keap1). The treatment of human LECs with 0 and 20% atmospheric O2 activated Nrf2/Keap1. The LECs shifted to 1% atmospheric O2 from 0, 4 or 20% for 24 h showed decreased levels of Keap1. By contrast, hLECs cultured in 1% atmospheric O2 for 24 h and then shifted to 0, 4 or 20% O2 exhibited a significant upregulation of Nrf2. These results suggest that oxidative stress proteins were not expressed in a 1% O2 environment. The O2 levels in the culture medium were equilibrated within 2 h in the cell culture plates. These results showed that an appropriate oxygen environment for the culture of LECs is ~1 % atmospheric O2. Either 0 or 20% of atmospheric O2 activated the UPR and the Nrf2/Keap1-mediated antioxidant system in LECs and chronic exposure to O2 fluctuation led to ROS production and cell death. This study revealed that O2 fluctuation-induced UPR/ER stress could be prevented by maintaining the cells in a 1% O2 environment.
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Affiliation(s)
- Xiao-Yu Zheng
- Department of Ophthalmology, The Children's Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Jia Xu
- Department of Ophthalmology, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - X I Chen
- The Central Laboratory, The Children's Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Wei Li
- The Central Laboratory, The Children's Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
| | - Ting-Yan Wang
- Department of Ophthalmology, The Children's Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang 310003, P.R. China
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16
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Hamada N, Fujimichi Y, Iwasaki T, Fujii N, Furuhashi M, Kubo E, Minamino T, Nomura T, Sato H. Emerging issues in radiogenic cataracts and cardiovascular disease. JOURNAL OF RADIATION RESEARCH 2014; 55:831-46. [PMID: 24824673 PMCID: PMC4202294 DOI: 10.1093/jrr/rru036] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 04/01/2014] [Accepted: 04/06/2014] [Indexed: 05/26/2023]
Abstract
In 2011, the International Commission on Radiological Protection issued a statement on tissue reactions (formerly termed non-stochastic or deterministic effects) to recommend lowering the threshold for cataracts and the occupational equivalent dose limit for the crystalline lens of the eye. Furthermore, this statement was the first to list circulatory disease (cardiovascular and cerebrovascular disease) as a health hazard of radiation exposure and to assign its threshold for the heart and brain. These changes have stimulated various discussions and may have impacts on some radiation workers, such as those in the medical sector. This paper considers emerging issues associated with cataracts and cardiovascular disease. For cataracts, topics dealt with herein include (i) the progressive nature, stochastic nature, target cells and trigger events of lens opacification, (ii) roles of lens protein denaturation, oxidative stress, calcium ions, tumor suppressors and DNA repair factors in cataractogenesis, (iii) dose rate effect, radiation weighting factor, and classification systems for cataracts, and (iv) estimation of the lens dose in clinical settings. Topics for cardiovascular disease include experimental animal models, relevant surrogate markers, latency period, target tissues, and roles of inflammation and cellular senescence. Future research needs are also discussed.
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Affiliation(s)
- Nobuyuki Hamada
- Radiation Safety Research Center, Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 2-11-1 Iwado-kita, Komae, Tokyo 201-8511, Japan
| | - Yuki Fujimichi
- Radiation Safety Research Center, Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 2-11-1 Iwado-kita, Komae, Tokyo 201-8511, Japan
| | - Toshiyasu Iwasaki
- Radiation Safety Research Center, Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 2-11-1 Iwado-kita, Komae, Tokyo 201-8511, Japan
| | - Noriko Fujii
- Kyoto University Research Reactor Institute (KURRI), 2 Asashiro-nishi, Kumatori-cho, Sennan-gun, Osaka 590-0494, Japan
| | - Masato Furuhashi
- Department of Cardiovascular, Renal and Metabolic Medicine, Sapporo Medical University School of Medicine, S-1, W-16, Chuo-ku, Sapporo, Hokkaido 060-8543, Japan
| | - Eri Kubo
- Department of Ophthalmology, Kanazawa Medical University, 1-1 Daigaku, Kahoku, Ishikawa 920-0293, Japan
| | - Tohru Minamino
- Department of Cardiovascular Biology and Medicine, Niigata University Graduate School of Medical and Dental Sciences, 1-754 Asahimachidori, Chuo-ku, Niigata 951-8510, Japan
| | - Takaharu Nomura
- Radiation Safety Research Center, Nuclear Technology Research Laboratory, Central Research Institute of Electric Power Industry (CRIEPI), 2-11-1 Iwado-kita, Komae, Tokyo 201-8511, Japan
| | - Hitoshi Sato
- Department of Radiological Sciences, Ibaraki Prefectural University of Health Sciences, 4669-2 Ami, Inashiki, Ibaraki 300-0394, Japan
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17
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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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18
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Khan JM, Chaturvedi SK, Rahman SK, Ishtikhar M, Qadeer A, Ahmad E, Khan RH. Protonation favors aggregation of lysozyme with SDS. SOFT MATTER 2014; 10:2591-2599. [PMID: 24647567 DOI: 10.1039/c3sm52435c] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Different proteins have different amino acid sequences as well as conformations, and therefore different propensities to aggregate. Electrostatic interactions have an important role in the aggregation of proteins as revealed by our previous report (J. M. Khan et al., PLoS One, 2012, 7, e29694). In this study, we designed and executed experiments to gain knowledge of the role of charge variations on proteins during the events of protein aggregation with lysozyme as a model protein. To impart positive and negative charges to proteins, we incubated lysozyme at different pH values of below and above the pI (∼11). Negatively charged SDS was used to 'antagonize' positive charges on lysozyme. We examined the effects of pH variations on SDS-induced amyloid fibril formation by lysozyme using methods such as far-UV circular dichroism, Rayleigh scattering, turbidity measurements, dye binding assays and dynamic light scattering. We found that sub-micellar concentrations of SDS (0.1 to 0.6 mM) induced amyloid fibril formation by lysozyme in the pH range of 10.0-1.0 and maximum aggregation was observed at pH 1.0. The morphology of aggregates was fibrillar in structure, as visualized by transmission electron microscopy. Isothermal titration calorimetry studies demonstrated that fibril formation is exothermic. To the best of our current understanding of the mechanism of aggregation, this study demonstrates the crucial role of electrostatic interactions during amyloid fibril formation. The model proposed here will help in designing molecules that can prevent or reverse the amyloid fibril formation or the aggregation.
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Affiliation(s)
- Javed M Khan
- Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India.
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19
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Schafheimer N, Wang Z, Schey K, King J. Tyrosine/cysteine cluster sensitizing human γD-crystallin to ultraviolet radiation-induced photoaggregation in vitro. Biochemistry 2014; 53:979-90. [PMID: 24410332 PMCID: PMC3954642 DOI: 10.1021/bi401397g] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
![]()
Ultraviolet
radiation (UVR) exposure is a major risk factor for
age-related cataract, a protein-aggregation disease of the human lens
often involving the major proteins of the lens, the crystallins. γD-Crystallin
(HγD-Crys) is abundant in the nucleus of the human lens, and
its folding and aggregation have been extensively studied. Previous
work showed that HγD-Crys photoaggregates in vitro upon exposure
to UVA/UVB light and that its conserved tryptophans are not required
for aggregation. Surprisingly, the tryptophan residues play a photoprotective
role because of a distinctive energy-transfer mechanism. HγD-Crys
also contains 14 tyrosine residues, 12 of which are organized as six
pairs. We investigated the role of the tyrosines of HγD-Crys
by replacing pairs with alanines and monitoring photoaggregation using
light scattering and SDS-PAGE. Mutating both tyrosines in the Y16/Y28
pair to alanine slowed the formation of light-scattering aggregates.
Further mutant studies implicated Y16 as important for photoaggregation.
Mass spectrometry revealed that C18, in contact with Y16, is heavily
oxidized during UVR exposure. Analysis of multiple mutant proteins
by mass spectrometry suggested that Y16 and C18 likely participate
in the same photochemical process. The data suggest an initial photoaggregation
pathway for HγD-Crys in which excited-state Y16 interacts with
C18, initiating radical polymerization.
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Affiliation(s)
- Nathaniel Schafheimer
- Department of Biology, Massachusetts Institute of Technology , 68-330, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States
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20
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Schafheimer N, King J. Tryptophan cluster protects human γD-crystallin from ultraviolet radiation-induced photoaggregation in vitro. Photochem Photobiol 2013; 89:1106-15. [PMID: 23683003 PMCID: PMC3823069 DOI: 10.1111/php.12096] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 05/12/2013] [Indexed: 11/30/2022]
Abstract
Exposure to ultraviolet radiation (UVR) is a significant risk factor for age-related cataract, a disease of the human lens and the most prevalent cause of blindness in the world. Cataract pathology involves protein misfolding and aggregation of the primary proteins of the lens, the crystallins. Human γD-crystallin (HγD-Crys) is a major γ-crystallin in the nucleus of the human lens. We report here analysis of UVR-induced damage to HγD-Crys in vitro. Irradiation of solutions of recombinant HγD-Crys with UVA/UVB light produced a rise in solution turbidity due to polymerization of the monomeric crystallins into higher molecular weight aggregates. A significant fraction of this polymerized protein was covalently linked. Photoaggregation of HγD-Crys required oxygen and its rate was protein concentration and UVR dose dependent. To investigate the potential roles of individual tryptophan residues in photoaggregation, triple W:F mutants of HγD-Crys were irradiated. Surprisingly, despite reducing UVR absorbing capacity, multiple W:F HγD-Crys mutant proteins photoaggregated more quickly and extensively than wild type. The results reported here are consistent with previous studies that postulated that an energy transfer mechanism between the highly conserved pairs of tryptophan residues in HγD-Crys could be protective against UVR-induced photodamage.
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21
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A Class I UV-blocking (senofilcon A) soft contact lens prevents UVA-induced yellow fluorescence and NADH loss in the rabbit lens nucleus in vivo. Exp Eye Res 2012; 102:17-27. [PMID: 22766154 DOI: 10.1016/j.exer.2012.06.007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2012] [Revised: 06/19/2012] [Accepted: 06/21/2012] [Indexed: 11/21/2022]
Abstract
It is known that fluorescence, much of it caused by UVA light excitation, increases in the aging human lens, resulting in loss of sharp vision. This study used an in vivo animal model to investigate UVA-excited fluorescence in the rabbit lens, which contains a high level of the UVA chromophore NADH, existing both free and bound to λ-crystallin. Also, the ability of a Class I (senofilcon A) soft contact lens to protect against UVA-induced effects on the rabbit lens was tested. Rabbit eyes were irradiated with UVA light in vivo (100 mW/cm(2) on the cornea) for 1 h using monochromatic 365 nm light. Irradiation was conducted in the presence of either a senofilcon A contact lens, a minimally UV-absorbing lotrafilcon A contact lens, or no contact lens at all. Eyes irradiated without a contact lens showed blue 365 nm-excited fluorescence initially, but this changed to intense yellow fluorescence after 1 h. Isolated, previously irradiated lenses exhibited yellow fluorescence originating from the lens nucleus when viewed under 365 nm light, but showed normal blue fluorescence arising from the cortex. Previously irradiated lenses also exhibited a faint yellow color when observed under visible light. The senofilcon A contact lens protected completely against the UVA-induced effects on fluorescence and lens yellowing, whereas the lotrafilcon A lens showed no protection. The UVA-exposure also produced a 53% loss of total NADH (free plus bound) in the lens nucleus, with only a 13% drop in the anterior cortex. NADH loss in the nucleus was completely prevented with use of a senofilcon A contact lens, but no significant protection was observed with a lotrafilcon A lens. Overall, the senofilcon A lens provided an average of 67% protection against UVA-induced loss of four pyridine nucleotides in four different regions of the lens. HPLC analysis with fluorescence detection indicated a nearly six-fold increase in 365 nm-excited yellow fluorescence arising from lens nuclear λ-crystallin after the in vivo UVA exposure. It is concluded that UVA-induced loss of free NADH (which fluoresces blue) may have allowed the natural yellow fluorescence of λ-crystallin and other proteins in the lens nucleus to become visible. Increased fluorescence exhibited by UVA-exposed λ-crystallin may have been the result of a UVA-induced change in the conformation of the protein occurring during the initial UVA-exposure in vivo. The results demonstrate the greater susceptibility of the lens nucleus to UVA-induced stress, and may relate to the formation of human nuclear cataract. The senofilcon A contact lens was shown to be beneficial in protecting the rabbit lens against effects of UVA light, including changes in fluorescence, increased yellowing and loss of pyridine nucleotides.
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22
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Moreau KL, King JA. Protein misfolding and aggregation in cataract disease and prospects for prevention. Trends Mol Med 2012; 18:273-82. [PMID: 22520268 DOI: 10.1016/j.molmed.2012.03.005] [Citation(s) in RCA: 296] [Impact Index Per Article: 24.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 03/01/2012] [Accepted: 03/14/2012] [Indexed: 11/16/2022]
Abstract
The transparency of the eye lens depends on maintaining the native tertiary structures and solubility of the lens crystallin proteins over a lifetime. Cataract, the leading cause of blindness worldwide, is caused by protein aggregation within the protected lens environment. With age, covalent protein damage accumulates through pathways thought to include UV radiation, oxidation, deamidation, and truncations. Experiments suggest that the resulting protein destabilization leads to partially unfolded, aggregation-prone intermediates and the formation of insoluble, light-scattering protein aggregates. These aggregates either include or overwhelm the protein chaperone content of the lens. Here, we review the causes of cataract and nonsurgical methods being investigated to inhibit or delay cataract development, including natural product-based therapies, modulators of oxidation, and protein aggregation inhibitors.
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Affiliation(s)
- Kate L Moreau
- Massachusetts Institute of Technology, Department of Biology, 77 Massachusetts Avenue, 68-330, Cambridge, MA 02139, USA
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23
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Low glucose under hypoxic conditions induces unfolded protein response and produces reactive oxygen species in lens epithelial cells. Cell Death Dis 2012; 3:e301. [PMID: 22513875 PMCID: PMC3358018 DOI: 10.1038/cddis.2012.40] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Aging is enhanced by hypoxia and oxidative stress. As the lens is located in the hypoglycemic environment under hypoxia, aging lens with diabetes might aggravate these stresses. This study was designed to examine whether low glucose under hypoxic conditions induces the unfolded protein response (UPR), and also if the UPR then generates the reactive oxygen species (ROS) in lens epithelial cells (LECs). The UPR was activated within 1 h by culturing the human LECs (HLECs) and rat LECs in <1.5 mM glucose under hypoxic conditions. These conditions also induced the Nrf2-dependent antioxidant-protective UPR, production of ROS, and apoptosis. The rat LECs located in the anterior center region were the least susceptible to the UPR, whereas the proliferating LECs in the germinative zone were the most susceptible. Because the cortical lens fiber cells are differentiated from the LECs after the onset of diabetes, we suggest that these newly formed cortical fibers have lower levels of Nrf2, and are then oxidized resulting in cortical cataracts. Thus, low glucose and oxygen conditions induce the UPR, generation of ROS, and expressed the Nrf2 and Nrf2-dependent antioxidant enzymes at normal levels. But these cells eventually lose reduced glutathione (GSH) and induce apoptosis. The results indicate a new link between hypoglycemia under hypoxia and impairment of HLEC functions.
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24
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Löfgren S, Michael R, Söderberg PG. Impact of iris pigment and pupil size in ultraviolet radiation cataract in rat. Acta Ophthalmol 2012; 90:44-8. [PMID: 20346084 DOI: 10.1111/j.1755-3768.2010.01871.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE To investigate the effect of iris pigment and pupil size in ultraviolet radiation (UVR)-induced cataract. METHODS Brown-Norway rats (pigmented) and Fischer-344 rats (non-pigmented) were unilaterally exposed in vivo to 5 kJ/m(2) UVR. Each strain was split into two groups, each receiving either mydriatic (tropicamide) or miotic (pilocarpine) eye-drops. One week after exposure, the degree of ocular inflammation and damage in the anterior segment was determined. The lenses were extracted, photographed and the degree of forward light scattering (cataract) was quantified. RESULTS The cataract types differed between the two strains. All Fischer rats developed macroscopically identifiable UVR cataract while only 41% of Brown-Norway rats did so. All groups except the miotic Brown-Norway developed significant light scattering. The Fischer rats developed 3-4-fold more lens light scattering than the Brown-Norway rats. The miotic Fischer group exhibited significantly more light scattering than the mydriatic Fischer group. There was no significant difference in light scattering between the two Brown-Norway groups. There was a correlation between ocular inflammation and degree of light scattering, with Brown-Norway rats exhibiting less inflammation and lens light scattering. CONCLUSIONS Pigmented rats develop less UVR cataract and less ocular inflammation than non-pigmented rats. Pupil size plays a smaller role in UVR cataract development in pigmented rats than in non-pigmented. The role of UVR-induced ocular inflammation in cataract development is still ambiguous.
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Affiliation(s)
- Stefan Löfgren
- Karolinska Institutet, St. Erik's Eye Hospital, Stockholm, Sweden.
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25
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Abstract
Photo-induced damage to proteins occurs via multiple pathways. Direct damage induced by UVB (λ 280-320 nm) and UVA radiation (λ 320-400 nm) is limited to a small number of amino acid residues, principally tryptophan (Trp), tyrosine (Tyr), histidine (His) and disulfide (cystine) residues, with this occurring via both excited state species and radicals. Indirect protein damage can occur via singlet oxygen ((1)O(2)(1)Δ(g)), with this resulting in damage to Trp, Tyr, His, cystine, cysteine (Cys) and methionine (Met) residues. Although initial damage is limited to these residues multiple secondary processes, that occur both during and after radiation exposure, can result in damage to other intra- and inter-molecular sites. Secondary damage can arise via radicals (e.g. Trp, Tyr and Cys radicals), from reactive intermediates generated by (1)O(2) (e.g. Trp, Tyr and His peroxides) and via molecular reactions of photo-products (e.g. reactive carbonyls). These processes can result in protein fragmentation, aggregation, altered physical and chemical properties (e.g. hydrophobicity and charge) and modulated biological turnover. Accumulating evidence implicates these events in cellular and tissue dysfunction (e.g. apoptosis, necrosis and altered cell signaling), and multiple human pathologies.
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Affiliation(s)
- David I Pattison
- The Heart Research Institute, 7 Eliza Street, Newtown, Sydney, NSW 2042, Australia
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26
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Weiss NG, Hayes MA, Garcia AA, Ansari RR. Isoelectric focusing in a drop. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:494-8. [PMID: 21117663 PMCID: PMC3025497 DOI: 10.1021/la104085t] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A novel approach to molecular separations is investigated using a technique termed droplet-based isoelectric focusing. Drops are manipulated discretely on a superhydrophobic surface, subjected to low voltages for isoelectric focusing, and split-resulting in a preparative separation. A universal indicator dye demonstrates the generation of stable, reversible pH gradients (3-10) in ampholyte buffers, and these gradients lead to protein focusing within the drop length. Focusing was visually characterized, spectroscopically verified, and assessed quantitatively by noninvasive light scattering measurements. It was found to correlate with a quantitative model based on 1D steady-state theory. This work illustrates that molecular separations can be deployed within a single open drop, and the differential fractions can be separated into new discrete liquid elements.
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Affiliation(s)
- Noah G. Weiss
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ
| | - Mark A. Hayes
- Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ
| | - Antonio A. Garcia
- School of Biological and Health Systems Engineering, Arizona State University, Tempe, AZ
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27
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Short-chain peptides as a promising class of chaperone-like anticataract agents: Molecular mechanism of inhibition of crystallin aggregation by pantethine. Russ Chem Bull 2010. [DOI: 10.1007/s11172-010-0066-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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28
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Expression and purification of his-tagged recombinant mouse zeta-crystallin. Protein Expr Purif 2009; 69:147-52. [PMID: 19679188 DOI: 10.1016/j.pep.2009.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2009] [Revised: 08/04/2009] [Accepted: 08/05/2009] [Indexed: 11/20/2022]
Abstract
Zeta-crystallin is an NADPH-binding protein consisting of four identical 35kD subunits. The protein possesses quinone oxidoreductase activity, and is present in large amounts in the lenses of camelids, certain hystricomorphic rodents, and the Japanese tree frog, and in lower catalytic amounts in certain tissues of various species. In this study, recombinant methods were used to produce substantial quantities of his-tagged recombinant mouse zeta-crystallin, which was then purified to homogeneity. The yield of pure recombinant mouse zeta-crystallin was five times that obtained previously for purification of recombinant guinea pig zeta-crystallin. The quinone oxidoreductase activity of purified his-tagged recombinant mouse zeta-crystallin was comparable to that of purified native guinea pig lens zeta-crystallin, and to that previously reported for recombinant guinea pig zeta-crystallin. The method permits production of substantial amounts of recombinant zeta-crystallin for conducting studies on the biological role of this interesting protein, which exists in such high concentration in the lenses of certain species.
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Ainsbury EA, Bouffler SD, Dörr W, Graw J, Muirhead CR, Edwards AA, Cooper J. Radiation cataractogenesis: a review of recent studies. Radiat Res 2009; 172:1-9. [PMID: 19580502 DOI: 10.1667/rr1688.1] [Citation(s) in RCA: 245] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The lens of the eye is recognized as one of the most radiosensitive tissues in the human body, and it is known that cataracts can be induced by acute doses of less than 2 Gy of low-LET ionizing radiation and less than 5 Gy of protracted radiation. Although much work has been carried out in this area, the exact mechanisms of radiation cataractogenesis are still not fully understood. In particular, the question of the threshold dose for cataract development is not resolved. Cataracts have been classified as a deterministic effect of radiation exposure with a threshold of approximately 2 Gy. Here we review the combined results of recent mechanistic and human studies regarding induction of cataracts by ionizing radiation. These studies indicate that the threshold for cataract development is certainly less than was previously estimated, of the order of 0.5 Gy, or that radiation cataractogenesis may in fact be more accurately described by a linear, no-threshold model.
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Affiliation(s)
- E A Ainsbury
- Health Protection Agency, Radiation Protection Division, Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot, Oxfordshire OX11 0RQ, United Kingdom.
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Simpanya MF, Wistow G, Gao J, David LL, Giblin FJ, Mitton KP. Expressed sequence tag analysis of guinea pig (Cavia porcellus) eye tissues for NEIBank. Mol Vis 2008; 14:2413-27. [PMID: 19104676 PMCID: PMC2605723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Accepted: 12/11/2008] [Indexed: 11/04/2022] Open
Abstract
PURPOSE To characterize gene expression patterns in guinea pig ocular tissues and identify orthologs of human genes from NEIBank expressed sequence tags. METHODS RNA was extracted from dissected eye tissues of 2.5-month-old guinea pigs to make three unamplified and unnormalized cDNA libraries in the pCMVSport-6 vector for the lens, retina, and eye minus lens and retina. Over 4,000 clones were sequenced from each library and were analyzed using GRIST for clustering and gene identification. Lens crystallin EST data were validated using two-dimensional electrophoresis (2-DE), matrix assisted laser desorption (MALDI), and electrospray ionization mass spectrometry (ESIMS). RESULTS Combined data from the three libraries generated a total of 6,694 distinctive gene clusters, with each library having between 1,000 and 3,000 clusters. Approximately 60% of the total gene clusters were novel cDNA sequences and had significant homologies to other mammalian sequences in GenBank. Complete cDNA sequences were obtained for many guinea pig lens proteins, including alphaA/alphaAinsert-, gammaN-, and gammaS-crystallins, lengsin and GRIFIN. The ratio of alphaA- to alphaB-crystallin on 2-DE gels was 8: 1 in the lens nucleus and 6.5: 1 in the cortex. Analysis of ESTs, genome sequence, and proteins (by MALDI), did not reveal any evidence for the presence of gammaD-, gammaE-, and gammaF-crystallin in the guinea pig. Predicted masses of many guinea pig lens crystallins were confirmed by ESIMS analysis. For the retina, orthologs of human phototransduction genes were found, such as Rhodopsin, S-antigen (Sag, Arrestin), and Transducin. The guinea-pig ortholog of NRL, a key rod photoreceptor-specific transcription factor, was also represented in EST data. In the 'rest-of-eye' library, the most abundant transcripts included decorin and keratin 12, representative of the cornea. CONCLUSIONS Genomic analysis of guinea pig eye tissues provides sequence-verified clones for future studies. Guinea pig orthologs of many human eye specific genes were identified. Guinea pig gene structures were similar to their human and rodent gene counterparts. Surprisingly, no orthologs of gammaD-, gammaE-, and gammaF-crystallin were found in EST, proteomic, or the current guinea pig genome data.
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Affiliation(s)
| | - Graeme Wistow
- Section on Molecular Structure and Functional Genomics, National Eye Institute, National Institutes of Health, Bethesda, MD
| | - James Gao
- Section on Molecular Structure and Functional Genomics, National Eye Institute, National Institutes of Health, Bethesda, MD
| | - Larry L. David
- Department of Biochemistry and Molecular Biology of the School of Medicine, Oregon Health Sciences University, Portland, OR
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