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Timsina R, Hazen P, Trossi-Torres G, Khadka NK, Kalkat N, Mainali L. Cholesterol Content Regulates the Interaction of αA-, αB-, and α-Crystallin with the Model of Human Lens-Lipid Membranes. Int J Mol Sci 2024; 25:1923. [PMID: 38339200 PMCID: PMC10855794 DOI: 10.3390/ijms25031923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 01/28/2024] [Accepted: 02/03/2024] [Indexed: 02/12/2024] Open
Abstract
α-Crystallin (αABc) is a major protein comprised of αA-crystallin (αAc) and αB-crystallin (αBc) that is found in the human eye lens and works as a molecular chaperone by preventing the aggregation of proteins and providing tolerance to stress. However, with age and cataract formation, the concentration of αABc in the eye lens cytoplasm decreases, with a corresponding increase in the membrane-bound αABc. This study uses the electron paramagnetic resonance (EPR) spin-labeling method to investigate the role of cholesterol (Chol) and Chol bilayer domains (CBDs) in the binding of αAc, αBc, and αABc to the Chol/model of human lens-lipid (Chol/MHLL) membranes. The maximum percentage of membrane surface occupied (MMSO) by αAc, αBc, and αABc to Chol/MHLL membranes at a mixing ratio of 0 followed the trends: MMSO (αAc) > MMSO (αBc) ≈ MMSO (αABc), indicating that a higher amount of αAc binds to these membranes compared to αBc and αABc. However, with an increase in the Chol concentration in the Chol/MHLL membranes, the MMSO by αAc, αBc, and αABc decreases until it is completely diminished at a mixing ratio of 1.5. The Ka of αAc, αBc, and αABc to Chol/MHLL membranes at a mixing ratio of 0 followed the trend: Ka (αBc) ≈ Ka (αABc) > Ka (αAc), but it was close to zero with the diminished binding at a Chol/MHLL mixing ratio of 1.5. The mobility near the membrane headgroup regions decreased with αAc, αBc, and αABc binding, and the Chol antagonized the capacity of the αAc, αBc, and αABc to decrease mobility near the headgroup regions. No significant change in membrane order near the headgroup regions was observed, with an increase in αAc, αBc, and αABc concentrations. Our results show that αAc, αBc, and αABc bind differently with Chol/MHLL membranes at mixing ratios of 0 and 0.5, decreasing the mobility and increasing hydrophobicity near the membrane headgroup region, likely forming the hydrophobic barrier for the passage of polar and ionic molecules, including antioxidants (glutathione), creating an oxidative environment inside the lens, leading to the development of cataracts. However, all binding was completely diminished at a mixing ratio of 1.5, indicating that high Chol and CBDs inhibit the binding of αAc, αBc, and αABc to membranes, preventing the formation of hydrophobic barriers and likely protecting against cataract formation.
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Affiliation(s)
- Raju Timsina
- Department of Physics, Boise State University, Boise, ID 83725, USA; (R.T.); (N.K.K.)
| | - Preston Hazen
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.); (N.K.)
| | - Geraline Trossi-Torres
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.); (N.K.)
| | - Nawal K. Khadka
- Department of Physics, Boise State University, Boise, ID 83725, USA; (R.T.); (N.K.K.)
| | - Navdeep Kalkat
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.); (N.K.)
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID 83725, USA; (R.T.); (N.K.K.)
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.); (N.K.)
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2
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Khadka NK, Hazen P, Haemmerle D, Mainali L. Interaction of β L- and γ-Crystallin with Phospholipid Membrane Using Atomic Force Microscopy. Int J Mol Sci 2023; 24:15720. [PMID: 37958704 PMCID: PMC10649403 DOI: 10.3390/ijms242115720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/26/2023] [Accepted: 10/27/2023] [Indexed: 11/15/2023] Open
Abstract
Highly concentrated lens proteins, mostly β- and γ-crystallin, are responsible for maintaining the structure and refractivity of the eye lens. However, with aging and cataract formation, β- and γ-crystallin are associated with the lens membrane or other lens proteins forming high-molecular-weight proteins, which further associate with the lens membrane, leading to light scattering and cataract development. The mechanism by which β- and γ-crystallin are associated with the lens membrane is unknown. This work aims to study the interaction of β- and γ-crystallin with the phospholipid membrane with and without cholesterol (Chol) with the overall goal of understanding the role of phospholipid and Chol in β- and γ-crystallin association with the membrane. Small unilamellar vesicles made of Chol/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (Chol/POPC) membranes with varying Chol content were prepared using the rapid solvent exchange method followed by probe tip sonication and then dispensed on freshly cleaved mica disk to prepare a supported lipid membrane. The βL- and γ-crystallin from the cortex of the bovine lens was used to investigate the time-dependent association of βL- and γ-crystallin with the membrane by obtaining the topographical images using atomic force microscopy. Our study showed that βL-crystallin formed semi-transmembrane defects, whereas γ-crystallin formed transmembrane defects on the phospholipid membrane. The size of semi-transmembrane defects increases significantly with incubation time when βL-crystallin interacts with the membrane. In contrast, no significant increase in transmembrane defect size was observed in the case of γ-crystallin. Our result shows that Chol inhibits the formation of membrane defects when βL- and γ-crystallin interact with the Chol/POPC membrane, where the degree of inhibition depends upon the amount of Chol content in the membrane. At a Chol/POPC mixing ratio of 0.3, membrane defects were observed when both βL- and γ-crystallin interacted with the membrane. However, at a Chol/POPC mixing ratio of 1, no association of γ-crystallin with the membrane was observed, which resulted in a defect-free membrane, and the severity of the membrane defect was decreased when βL-crystallin interacted with the membrane. The semi-transmembrane or transmembrane defects formed by the interaction of βL- and γ-crystallin on phospholipid membrane might be responsible for light scattering and cataract formation. However, Chol suppressed the formation of such defects in the membrane, likely maintaining lens membrane homeostasis and protecting against cataract formation.
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Affiliation(s)
- Nawal K. Khadka
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (D.H.)
| | - Preston Hazen
- Biomolecular Sciences Graduate Program, Boise State University, Boise, ID 83725, USA;
| | - Dieter Haemmerle
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (D.H.)
| | - Laxman Mainali
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (D.H.)
- Biomolecular Sciences Graduate Program, Boise State University, Boise, ID 83725, USA;
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3
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Hazen P, Trossi-Torres G, Khadka NK, Timsina R, Mainali L. Binding of β L-Crystallin with Models of Animal and Human Eye Lens-Lipid Membrane. Int J Mol Sci 2023; 24:13600. [PMID: 37686406 PMCID: PMC10487507 DOI: 10.3390/ijms241713600] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 08/30/2023] [Accepted: 08/31/2023] [Indexed: 09/10/2023] Open
Abstract
Several discoveries show that with age and cataract formation, β-crystallin binds with the lens membrane or associates with other lens proteins, which bind with the fiber cell plasma membrane, accompanied by light scattering and cataract formation. However, how lipids (phospholipids and sphingolipids) and cholesterol (Chol) influence β-crystallin binding to the membrane is unclear. This research aims to elucidate the role of lipids and Chol in the binding of β-crystallin to the membrane and the membrane's physical properties (mobility, order, and hydrophobicity) with β-crystallin binding. We used electron paramagnetic resonance (EPR) spin-labeling methods to investigate the binding of βL-crystallin with a model of porcine lens-lipid (MPLL), model of mouse lens-lipid (MMLL), and model of human lens-lipid (MHLL) membrane with and without Chol. Our results show that βL-crystallin binds with all of the investigated membranes in a saturation manner, and the maximum parentage of the membrane surface occupied (MMSO) by βL-crystallin and the binding affinity (Ka) of βL-crystallin to the membranes followed trends: MMSO (MPLL) > MMSO (MMLL) > MMSO (MHLL) and Ka (MHLL) > Ka (MMLL) ≈ Ka (MPLL), respectively, in which the presence of Chol reduces the MMSO and Ka for all membranes. The mobility near the headgroup regions of the membranes decreases with an increase in the binding of βL-crystallin; however, the decrease is more pronounced in the MPLL and MMLL membranes than the MHLL membrane. In the MPLL and MMLL membranes, the membranes become slightly ordered near the headgroup with an increase in βL-crystallin binding compared to the MHLL membrane. The hydrophobicity near the headgroup region of the membrane increases with βL-crystallin binding; however, the increase is more pronounced in the MPLL and MMLL membranes than the MHLL membrane, indicating that βL-crystallin binding creates a hydrophobic barrier for the passage of polar molecules, which supports the barrier hypothesis in cataract formation. However, in the presence of Chol, there is no significant increase in hydrophobicity with βL-crystallin binding, suggesting that Chol prevents the formation of a hydrophobic barrier, possibly protecting against cataract formation.
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Affiliation(s)
- Preston Hazen
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.)
| | - Geraline Trossi-Torres
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.)
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
| | - Nawal K. Khadka
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
| | - Raju Timsina
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
| | - Laxman Mainali
- Biomolecular Sciences Graduate Programs, Boise State University, Boise, ID 83725, USA; (P.H.); (G.T.-T.)
- Department of Physics, Boise State University, Boise, ID 83725, USA; (N.K.K.); (R.T.)
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4
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Rodriguez J, Tan Q, Šikić H, Taber LA, Bassnett S. The effect of fibre cell remodelling on the power and optical quality of the lens. J R Soc Interface 2023; 20:20230316. [PMID: 37727073 PMCID: PMC10509584 DOI: 10.1098/rsif.2023.0316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 08/22/2023] [Indexed: 09/21/2023] Open
Abstract
Vertebrate eye lenses are uniquely adapted to form a refractive index gradient (GRIN) for improved acuity, and to grow slowly in size despite constant cell proliferation. The mechanisms behind these adaptations remain poorly understood. We hypothesize that cell compaction contributes to both. To test this notion, we examined the relationship between lens size and shape, refractive characteristics and the cross-sectional areas of constituent fibre cells in mice of different ages. We developed a block-face imaging method to visualize cellular cross sections and found that the cross-sectional areas of fibre cells rose and then decreased over time, with the most significant reduction occurring in denucleating cells in the adult lens cortex, followed by cells in the embryonic nucleus. These findings help reconcile differences between the predictions of lens growth models and empirical data. Biomechanical simulations suggested that compressive forces generated from continuous deposition of fibre cells could contribute to cellular compaction. However, optical measurements revealed that the GRIN did not mirror the pattern of cellular compaction, implying that compaction alone cannot account for GRIN formation and that additional mechanisms are likely to be involved.
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Affiliation(s)
- J. Rodriguez
- Department of Basic Sciences, University of Health Sciences and Pharmacy in St. Louis, 1 Pharmacy Place, St. Louis, MO 63110, USA
| | - Q. Tan
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave, Campus Box 8096, St. Louis, MO 63110, USA
| | - H. Šikić
- Department of Mathematics, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - L. A. Taber
- Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA
| | - S. Bassnett
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave, Campus Box 8096, St. Louis, MO 63110, USA
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5
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Cantrell LS, Gletten RB, Schey KL. Proteome Remodeling of the Eye Lens at 50 Years Identified With Data-Independent Acquisition. Mol Cell Proteomics 2022; 22:100453. [PMID: 36470534 PMCID: PMC9800634 DOI: 10.1016/j.mcpro.2022.100453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 11/03/2022] [Accepted: 11/20/2022] [Indexed: 12/12/2022] Open
Abstract
The eye lens is responsible for focusing and transmitting light to the retina. The lens does this in the absence of organelles, yet maintains transparency for at least 5 decades before onset of age-related nuclear cataract (ARNC). It is hypothesized that oxidative stress contributes significantly to ARNC formation. It is in addition hypothesized that transparency is maintained by a microcirculation system that delivers antioxidants to the lens nucleus and exports small molecule waste. Common data-dependent acquisition methods are hindered by dynamic range of lens protein expression and provide limited context to age-related changes in the lens. In this study, we utilized data-independent acquisition mass spectrometry to analyze the urea-insoluble membrane protein fractions of 16 human lenses subdivided into three spatially distinct lens regions to characterize age-related changes, particularly concerning the lens microcirculation system and oxidative stress response. In this pilot cohort, we measured 4788 distinct protein groups, 46,681 peptides, and 7592 deamidated sequences, more than in any previous human lens data-dependent acquisition approach. Principally, we demonstrate that a significant proteome remodeling event occurs at approximately 50 years of age, resulting in metabolic preference for anaerobic glycolysis established with organelle degradation, decreased abundance of protein networks involved in calcium-dependent cell-cell contacts while retaining networks related to oxidative stress response. Furthermore, we identified multiple antioxidant transporter proteins not previously detected in the human lens and describe their spatiotemporal and age-related abundance changes. Finally, we demonstrate that aquaporin-5, among other proteins, is modified with age by post-translational modifications including deamidation and truncation. We suggest that the continued accumulation of each of these age-related outcomes in proteome remodeling contribute to decreased fiber cell permeability and result in ARNC formation.
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Affiliation(s)
- Lee S. Cantrell
- Vanderbilt University Mass Spectrometry Research Center, Nashville, Tennessee, USA,Vanderbilt University Chemical and Physical Biology Program, Nashville, Tennessee, USA
| | - Romell B. Gletten
- Vanderbilt University Mass Spectrometry Research Center, Nashville, Tennessee, USA,Vanderbilt University Department of Biochemistry, Nashville, Tennessee, USA
| | - Kevin L. Schey
- Vanderbilt University Mass Spectrometry Research Center, Nashville, Tennessee, USA,Vanderbilt University Chemical and Physical Biology Program, Nashville, Tennessee, USA,Vanderbilt University Department of Biochemistry, Nashville, Tennessee, USA,For correspondence: Kevin L. Schey
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6
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Cantrell LS, Schey KL. Data-Independent Acquisition Mass Spectrometry of the Human Lens Enhances Spatiotemporal Measurement of Fiber Cell Aging. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:2755-2765. [PMID: 34705440 PMCID: PMC9685647 DOI: 10.1021/jasms.1c00193] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The ocular lens proteome undergoes post-translational and progressive degradation as fiber cells age. The oldest fiber cells and the proteins therein are present at birth and are retained through death. Transparency of the lens is maintained in part by the high abundance Crystallin family proteins (up to 300 mg/mL), which establishes a high dynamic range of protein abundance. As a result, previous data-dependent analysis (DDA) measurements of the lens proteome are less equipped to identify the lowest abundance proteins. To probe more deeply into the lens proteome, we measured the insoluble lens proteome of an 18-year-old human with DDA and data-independent analysis (DIA) methods. By applying more recent library-free DIA search methods, 5,161 protein groups, 50,386 peptides, and 4,960 deamidation sites were detected: significantly outperforming the quantity of identifications in using DDA and pan-human DIA library searches. Finally, by segmenting the lens into multiple fiber cell-age-related regions, we uncovered cell-age-related changes in proteome composition and putative function.
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Affiliation(s)
- Lee S Cantrell
- Chemical and Physical Biology Program, Vanderbilt University, Nashville, Tennessee 37212, United States
| | - Kevin L Schey
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee 37212, United States
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7
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Sherin PS, Vyšniauskas A, López-Duarte I, Ogilby PR, Kuimova MK. Visualising UV-A light-induced damage to plasma membranes of eye lens. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2021; 225:112346. [PMID: 34736070 DOI: 10.1016/j.jphotobiol.2021.112346] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 10/01/2021] [Accepted: 10/19/2021] [Indexed: 01/16/2023]
Abstract
An eye lens is constantly exposed to the solar UV radiation, which is considered the most important external source of age-related changes to eye lens constituents. The accumulation of modifications of proteins and lipids with age can eventually lead to the development of progressive lens opacifications, such as cataracts. Though the impact of solar UV radiation on the structure and function of proteins is actively studied, little is known about the effect of photodamage on plasma membranes of lens cells. In this work we exploit Fluorescence Lifetime Imaging Microscopy (FLIM), together with viscosity-sensitive fluorophores termed molecular rotors, to study the changes in viscosity of plasma membranes of porcine eye lens resulting from two different types of photodamage: Type I (electron transfer) and Type II (singlet oxygen) reactions. We demonstrate that these two types of photodamage result in clearly distinct changes in viscosity - a decrease in the case of Type I damage and an increase in the case of Type II processes. Finally, to simulate age-related changes that occur in vivo, we expose an intact eye lens to UV-A light under anaerobic conditions. The observed decrease in viscosity within plasma membranes is consistent with the ability of eye lens constituents to sensitize Type I photodamage under natural irradiation conditions. These changes are likely to alter the transport of metabolites and predispose the whole tissue to the development of pathological processes such as cataracts.
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Affiliation(s)
- Peter S Sherin
- Chemistry Department, Molecular Sciences Research Hub, Imperial College London, 82 Wood Lane, London W12 0BZ, UK; International Tomography Center SB RAS, Institutskaya street 3A, Novosibirsk 630090, Russia.
| | - Aurimas Vyšniauskas
- Center for Physical Sciences and Technology, Saulėtekio av. 3, Vilnius LT-10257, Lithuania; Chemistry Department, Vilnius University, Naugarduko st. 24, Vilnius LT-03225, Lithuania
| | - Ismael López-Duarte
- Chemistry Department, Molecular Sciences Research Hub, Imperial College London, 82 Wood Lane, London W12 0BZ, UK
| | - Peter R Ogilby
- Department of Chemistry, Aarhus University, Langelandsgade 140, Aarhus DK-8000, Denmark
| | - Marina K Kuimova
- Chemistry Department, Molecular Sciences Research Hub, Imperial College London, 82 Wood Lane, London W12 0BZ, UK.
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8
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Glarin RK, Nguyen BN, Cleary JO, Kolbe SC, Ordidge RJ, Bui BV, McKendrick AM, Moffat BA. MR-EYE: High-Resolution MRI of the Human Eye and Orbit at Ultrahigh Field (7T). Magn Reson Imaging Clin N Am 2021; 29:103-116. [PMID: 33237011 DOI: 10.1016/j.mric.2020.09.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Ultrahigh-field (7T) MRI provides improved contrast and a signal-to-noise gain compared with lower magnetic field strengths. Here, we demonstrate feasibility and optimization of anatomic imaging of the eye and orbit using a dedicated commercial multichannel transmit and receive eye coil. Optimization of participant setup techniques and MRI sequence parameters allowed for improvements in the image resolution and contrast, and the eye and orbit coverage with minimal susceptibility and motion artifacts in a clinically feasible protocol.
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Affiliation(s)
- Rebecca K Glarin
- The Melbourne Brain Centre Imaging Unit, Department of Medicine and Radiology, The University of Melbourne, Parkville, Victoria 3010, Australia; Department of Radiology, Royal Melbourne Hospital, Parkville, Victoria 3010, Australia.
| | - Bao N Nguyen
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Jon O Cleary
- The Melbourne Brain Centre Imaging Unit, Department of Medicine and Radiology, The University of Melbourne, Parkville, Victoria 3010, Australia; Department of Radiology, Guy's and St. Thomas' NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK
| | - Scott C Kolbe
- Department of Neuroscience, Central Clinical School, Monash University, Prahran, Victoria 3181, Australia
| | - Roger J Ordidge
- The Melbourne Brain Centre Imaging Unit, Department of Medicine and Radiology, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Bang V Bui
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Allison M McKendrick
- Department of Optometry and Vision Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Bradford A Moffat
- The Melbourne Brain Centre Imaging Unit, Department of Medicine and Radiology, The University of Melbourne, Parkville, Victoria 3010, Australia
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9
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Lie AL, Pan X, White TW, Vaghefi E, Donaldson PJ. Age-Dependent Changes in Total and Free Water Content of In Vivo Human Lenses Measured by Magnetic Resonance Imaging. Invest Ophthalmol Vis Sci 2021; 62:33. [PMID: 34293079 PMCID: PMC8300047 DOI: 10.1167/iovs.62.9.33] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Purpose To use magnetic resonance imaging (MRI) to measure age-dependent changes in total and free water in human lenses in vivo. Methods Sixty-four healthy adults aged 18 to 86 years were recruited, fitted with a 32-channel head receiver coil, and placed in a 3 Tesla clinical MR scanner. Scans of the crystalline lens were obtained using a volumetric interpolated breath-hold examination sequence with dual flip angles, which were corrected for field inhomogeneity post-acquisition using a B1-map obtained using a turbo-FLASH sequence. The spatial distribution and content of corrected total (ρlens) and free (T1) water along the lens optical axis were extracted using custom-written code. Results Lens total water distribution and content did not change with age (all P > 0.05). In contrast to total water, a gradient in free water content that was highest in the periphery relative to the center was present in lenses across all ages. However, this initially parabolic free water gradient gradually developed an enhanced central plateau, as indicated by increasing profile shape parameter values (anterior: 0.067/y, P = 0.004; posterior: 0.050/y, P = 0.020) and central free water content (1.932 ms/y, P = 0.022) with age. Conclusions MRI can obtain repeatable total and free water measurements of in vivo human lenses. The observation that the lens steady-state free, but not total, water gradient is abolished with age raises the possibility that alterations in protein-water interactions are an underlying cause of the degradation in lens optics and overall vision observed with aging.
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Affiliation(s)
- Alyssa L Lie
- School of Optometry and Vision Science, New Zealand National Eye Centre, University of Auckland, New Zealand
| | - Xingzheng Pan
- School of Optometry and Vision Science, New Zealand National Eye Centre, University of Auckland, New Zealand.,Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, New Zealand
| | - Thomas W White
- Department of Physiology and Biophysics, Stony Brook University, Stony Brook, New York, United States
| | - Ehsan Vaghefi
- School of Optometry and Vision Science, New Zealand National Eye Centre, University of Auckland, New Zealand
| | - Paul J Donaldson
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, New Zealand
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10
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Gong XD, Wang Y, Hu XB, Zheng SY, Fu JL, Nie Q, Wang L, Hou M, Xiang JW, Xiao Y, Gao Q, Bai YY, Liu YZ, Li DWC. Aging-dependent loss of GAP junction proteins Cx46 and Cx50 in the fiber cells of human and mouse lenses accounts for the diminished coupling conductance. Aging (Albany NY) 2021; 13:17568-17591. [PMID: 34226295 PMCID: PMC8312418 DOI: 10.18632/aging.203247] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Accepted: 06/12/2021] [Indexed: 06/13/2023]
Abstract
The homeostasis of the ocular lens is maintained by a microcirculation system propagated through gap junction channels. It is well established that the intercellular communications of the lens become deteriorative during aging. However, the molecular basis for this change in human lenses has not been well defined. Here, we present evidence to show that over 90% of Cx46 and Cx50 are lost in the fiber cells of normal human lenses aged 50 and above. From transparent to cataractous lenses, while Cx43 was upregulated, both Cx46 and Cx50 were significantly down-regulated in the lens epithelia. During aging of mouse lenses, Cx43 remained unchanged, but both Cx46 and Cx50 were significantly downregulated. Under oxidative stress treatment, mouse lenses develop in vitro cataractogenesis. Associated with this process, Cx43 was significantly upregulated, in contrast, Cx46 and Cx50 were sharply downregulated. Together, our results for the first time reveal that downregulation in Cx46 and Cx50 levels appears to be the major reason for the diminished coupling conductance, and the aging-dependent loss of Cx46 and Cx50 promotes senile cataractogenesis.
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Affiliation(s)
- Xiao-Dong Gong
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Yan Wang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Xue-Bin Hu
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Shu-Yu Zheng
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Jia-Ling Fu
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Qian Nie
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Ling Wang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Min Hou
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Jia-Wen Xiang
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Yuan Xiao
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Qian Gao
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Yue-Yue Bai
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - Yi-Zhi Liu
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
| | - David Wan-Cheng Li
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou, Guangdong 510230, China
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11
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Stahnke T, Lindner T, Guthoff R, Stachs O, Wree A, Langner S, Niendorf T, Grabow N, Glass Ä, Beller E, Polei S. Ultrahigh field MRI determination of water diffusion rates in ex vivo human lenses of different age. Quant Imaging Med Surg 2021; 11:3029-3041. [PMID: 34249632 PMCID: PMC8250020 DOI: 10.21037/qims-20-1124] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 02/18/2021] [Indexed: 12/16/2022]
Abstract
BACKGROUND The development of presbyopia is correlated with increased lens stiffness. To reveal structural changes with age, ultrahigh field magnetic resonance imaging (UHF-MRI) was used to analyze water diffusion in differently aged human lenses ex vivo. METHODS After enucleation lens extractions were performed. Lenses were photographed, weighed, and embedded in 0.5% agarose dissolved in culture medium. UHF-MRI was conducted to analyze anatomical characteristics of the lens using T2-weighted Turbo-RARE imaging and to obtain apparent diffusion coefficients (ADC) measurements. A Gaussian fit routine was used to examine the ADC histograms. RESULTS An age-dependent increase in lens wet weight, lens thickness, and lens diameter was found (P<0.001). T2-weighted images revealed a hyperintense lens cortex and a gradually negative gradient in signal intensity towards the nucleus. ADC histograms of the lens showed bimodal distributions (lower ADC values mainly located in the nucleus and higher ADC values mainly located in the cortex), which did not change significantly with age [βPeak1=1.96E-7 (-20E-7, 10E-7), P=0.804 or βPeak2=15.4E-7 (-10E-7, 40E-7), P=0.276; respectively]. CONCLUSIONS Clinically relevant age dependent lens hardening is probably not correlated with ADC changes within the nucleus, which could be confirmed by further measurements.
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Affiliation(s)
- Thomas Stahnke
- Department of Ophthalmology, Rostock University Medical Center, Rostock, Germany
| | - Tobias Lindner
- Core Facility Multimodal Small Animal Imaging, Rostock University Medical Center, Rostock, Germany
| | - Rudolf Guthoff
- Department of Ophthalmology, Rostock University Medical Center, Rostock, Germany
| | - Oliver Stachs
- Department of Ophthalmology, Rostock University Medical Center, Rostock, Germany
| | - Andreas Wree
- Institute of Anatomy, Rostock University Medical Center, Rostock, Germany
| | - Sönke Langner
- Institute of Diagnostic and Interventional Radiology, Rostock University Medical Center, Rostock, Germany
| | - Thoralf Niendorf
- Berlin Ultrahigh Field Facility, Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Niels Grabow
- Institute of Biomedical Engineering, Rostock University Medical Center, Friedrich- Rostock, Germany
| | - Änne Glass
- Institute for Biostatistics and Informatics in Medicine and Ageing Research, Rostock University Medical Center, Rostock, Germany
| | - Ebba Beller
- Institute of Diagnostic and Interventional Radiology, Rostock University Medical Center, Rostock, Germany
| | - Stefan Polei
- Core Facility Multimodal Small Animal Imaging, Rostock University Medical Center, Rostock, Germany
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12
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Affiliation(s)
- Robert C Augusteyn
- Institute for Eye Research and the Vision Cooperative Research Centre, University of New South Wales, Sydney, Australia, and Biochemistry Department, LaTrobe University, Bundoora, Australia
E‐mail:
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13
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Cantrell LS, Schey KL. Proteomic characterization of the human lens and Cataractogenesis. Expert Rev Proteomics 2021; 18:119-135. [PMID: 33849365 DOI: 10.1080/14789450.2021.1913062] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
INTRODUCTION The goal of this review is to highlight the triumphs and frontiers in measurement of the lens proteome as it relates to onset of age-related nuclear cataract. As global life expectancy increases, so too does the frequency of age-related nuclear cataracts. Molecular therapeutics do not exist for delay or relief of cataract onset in humans. Since lens fiber cells are incapable of protein synthesis after initial maturation, age-related changes in proteome composition and post-translational modification accumulation can be measured with various techniques. Several of these modifications have been associated with cataract onset. AREAS COVERED We discuss the impact of long-lived proteins on the lens proteome and lens homeostasis as well as proteomic techniques that may be used to measure proteomes at various levels of proteomic specificity and spatial resolution. EXPERT OPINION There is clear evidence that several proteome modifications are correlated with cataract formation. Past studies should be enhanced with cutting-edge, spatially resolved mass spectrometry techniques to enhance the specificity and sensitivity of modification detection as it relates to cataract formation.
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Affiliation(s)
- Lee S Cantrell
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
| | - Kevin L Schey
- Department of Biochemistry, Vanderbilt University, Nashville, TN, United States
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14
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Cheng C, Parreno J, Nowak RB, Biswas SK, Wang K, Hoshino M, Uesugi K, Yagi N, Moncaster JA, Lo WK, Pierscionek B, Fowler VM. Age-related changes in eye lens biomechanics, morphology, refractive index and transparency. Aging (Albany NY) 2019; 11:12497-12531. [PMID: 31844034 PMCID: PMC6949082 DOI: 10.18632/aging.102584] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Accepted: 11/26/2019] [Indexed: 04/09/2023]
Abstract
Life-long eye lens function requires an appropriate gradient refractive index, biomechanical integrity and transparency. We conducted an extensive study of wild-type mouse lenses 1-30 months of age to define common age-related changes. Biomechanical testing and morphometrics revealed an increase in lens volume and stiffness with age. Lens capsule thickness and peripheral fiber cell widths increased between 2 to 4 months of age but not further, and thus, cannot account for significant age-dependent increases in lens stiffness after 4 months. In lenses from mice older than 12 months, we routinely observed cataracts due to changes in cell structure, with anterior cataracts due to incomplete suture closure and a cortical ring cataract corresponding to a zone of compaction in cortical lens fiber cells. Refractive index measurements showed a rapid growth in peak refractive index between 1 to 6 months of age, and the area of highest refractive index is correlated with increases in lens nucleus size with age. These data provide a comprehensive overview of age-related changes in murine lenses, including lens size, stiffness, nuclear fraction, refractive index, transparency, capsule thickness and cell structure. Our results suggest similarities between murine and primate lenses and provide a baseline for future lens aging studies.
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Affiliation(s)
- Catherine Cheng
- School of Optometry, Indiana University, Bloomington, IN 47405, USA
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Justin Parreno
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Roberta B. Nowak
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Sondip K. Biswas
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA 30303, USA
| | - Kehao Wang
- School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom
| | - Masato Hoshino
- Japan Synchrotron Radiation Research Institute (Spring-8), Sayo-cho, Sayo-gun, Hyogo, Japan
| | - Kentaro Uesugi
- Japan Synchrotron Radiation Research Institute (Spring-8), Sayo-cho, Sayo-gun, Hyogo, Japan
| | - Naoto Yagi
- Japan Synchrotron Radiation Research Institute (Spring-8), Sayo-cho, Sayo-gun, Hyogo, Japan
| | - Juliet A. Moncaster
- Department of Radiology, Boston University School of Medicine, Boston, MA 02118, USA
| | - Woo-Kuen Lo
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, GA 30303, USA
| | - Barbara Pierscionek
- School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom
| | - Velia M. Fowler
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
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15
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Schey KL, Wang Z, Friedrich MG, Garland DL, Truscott RJW. Spatiotemporal changes in the human lens proteome: Critical insights into long-lived proteins. Prog Retin Eye Res 2019; 76:100802. [PMID: 31704338 DOI: 10.1016/j.preteyeres.2019.100802] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/24/2019] [Accepted: 10/30/2019] [Indexed: 12/15/2022]
Abstract
The ocular lens is a unique tissue that contains an age gradient of cells and proteins ranging from newly differentiated cells containing newly synthesized proteins to cells and proteins that are as old as the organism. Thus, the ocular lens is an excellent model for studying long-lived proteins (LLPs) and the effects of aging and post-translational modifications on protein structure and function. Given the architecture of the lens, with young fiber cells in the outer cortex and the oldest cells in the lens nucleus, spatially-resolved studies provide information on age-specific protein changes. In this review, experimental strategies and proteomic methods that have been used to examine age-related and cataract-specific changes to the human lens proteome are described. Measured spatio-temporal changes in the human lens proteome are summarized and reveal a highly consistent, time-dependent set of modifications observed in transparent human lenses. Such measurements have led to the discovery of cataract-specific modifications and the realization that many animal systems are unsuitable to study many of these modifications. Mechanisms of protein modifications such as deamidation, racemization, truncation, and protein-protein crosslinking are presented and the implications of such mechanisms for other long-lived proteins in other tissues are discussed in the context of age-related neurological diseases. A comprehensive understanding of LLP modifications will enhance our ability to develop new therapies for the delay, prevention or reversal of age-related diseases.
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Affiliation(s)
- Kevin L Schey
- Department of Biochemistry, Vanderbilt University, USA.
| | - Zhen Wang
- Department of Biochemistry, Vanderbilt University, USA
| | - Michael G Friedrich
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
| | | | - Roger J W Truscott
- Illawarra Health and Medical Research Institute, University of Wollongong, Australia
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16
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Schey KL, Petrova RS, Gletten RB, Donaldson PJ. The Role of Aquaporins in Ocular Lens Homeostasis. Int J Mol Sci 2017; 18:E2693. [PMID: 29231874 PMCID: PMC5751294 DOI: 10.3390/ijms18122693] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 12/08/2017] [Accepted: 12/08/2017] [Indexed: 12/13/2022] Open
Abstract
Abstract: Aquaporins (AQPs), by playing essential roles in the maintenance of ocular lens homeostasis, contribute to the establishment and maintenance of the overall optical properties of the lens over many decades of life. Three aquaporins, AQP0, AQP1 and AQP5, each with distinctly different functional properties, are abundantly and differentially expressed in the different regions of the ocular lens. Furthermore, the diversity of AQP functionality is increased in the absence of protein turnover by age-related modifications to lens AQPs that are proposed to alter AQP function in the different regions of the lens. These regional differences in AQP functionality are proposed to contribute to the generation and directionality of the lens internal microcirculation; a system of circulating ionic and fluid fluxes that delivers nutrients to and removes wastes from the lens faster than could be achieved by passive diffusion alone. In this review, we present how regional differences in lens AQP isoforms potentially contribute to this microcirculation system by highlighting current areas of investigation and emphasizing areas where future work is required.
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Affiliation(s)
- Kevin L Schey
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA.
| | - Rosica S Petrova
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, Auckland 1023, New Zealand.
| | - Romell B Gletten
- Department of Biochemistry, Vanderbilt University, Nashville, TN 37240, USA.
| | - Paul J Donaldson
- Department of Physiology, School of Medical Sciences, New Zealand National Eye Centre, University of Auckland, Auckland 1023, New Zealand.
- School of Optometry and Vison Sciences, New Zealand National Eye Centre, University of Auckland, Auckland 1023, New Zealand.
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17
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Dubicanac M, Radespiel U, Zimmermann E. A review on ocular findings in mouse lemurs: potential links to age and genetic background. Primate Biol 2017; 4:215-228. [PMID: 32110707 PMCID: PMC7041539 DOI: 10.5194/pb-4-215-2017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 09/18/2017] [Indexed: 12/14/2022] Open
Abstract
Mouse lemurs, the world's smallest primates, inhabit forests in
Madagascar. They are nocturnal, arboreal and dependent on vision
for their everyday lives. In the last decades, the grey mouse
lemur became increasingly important for biomedical research, in particular
aging research. Experiments which require the combination of visual
fitness and old age consequently depend on a solid knowledge of
ocular pathologies. Although ocular diseases in mouse lemurs have
been described as being common, they have not received much
attention so far. Yet it is important to know when and why ocular
diseases in captive mouse lemurs may occur. This review aims to
provide a comprehensive overview of known ocular findings in mouse
lemurs. It summarizes the frequency of ocular findings in captive
mouse lemur colonies and points to their likely causes and treatment
options based on the evidence available from other animals and
humans. In addition, it shall be discussed whether age or genetic
background may affect their development. This review may be used as
a reference for future studies which require an assessment of visual
performance in mouse lemurs and help to evaluate observed clinical
signs and ocular diseases. Furthermore, the high incidence of
specific diseases may provide new perspectives and set the groundwork
for a new animal model for ocular research.
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Affiliation(s)
- Marko Dubicanac
- Institute of Zoology, University of Veterinary Medicine Hannover, Buenteweg 17, 30559 Hannover, Germany
| | - Ute Radespiel
- Institute of Zoology, University of Veterinary Medicine Hannover, Buenteweg 17, 30559 Hannover, Germany
| | - Elke Zimmermann
- Institute of Zoology, University of Veterinary Medicine Hannover, Buenteweg 17, 30559 Hannover, Germany
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18
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Dubicanac M, Strueve J, Mestre-Frances N, Verdier JM, Zimmermann E, Joly M. Photoperiodic regime influences onset of lens opacities in a non-human primate. PeerJ 2017; 5:e3258. [PMID: 28484672 PMCID: PMC5420196 DOI: 10.7717/peerj.3258] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 03/30/2017] [Indexed: 11/24/2022] Open
Abstract
Background Opacities of the lens are typical age-related phenomena which have a high influence on photoreception and consequently circadian rhythm. In mouse lemurs, a small bodied non-human primate, a high incidence (more than 50% when >seven years) of cataracts has been previously described during aging. Previous studies showed that photoperiodically induced accelerated annual rhythms alter some of mouse lemurs’ life history traits. Whether a modification of photoperiod also affects the onset of age dependent lens opacities has not been investigated so far. The aim of this study was therefore to characterise the type of opacity and the mouse lemurs’ age at its onset in two colonies with different photoperiodic regimen. Methods Two of the largest mouse lemur colonies in Europe were investigated: Colony 1 having a natural annual photoperiodic regime and Colony 2 with an induced accelerated annual cycle. A slit-lamp was used to determine opacities in the lens. Furthermore, a subset of all animals which showed no opacities in the lens nucleus in the first examination but developed first changes in the following examination were further examined to estimate the age at onset of opacities. In total, 387 animals were examined and 57 represented the subset for age at onset estimation. Results The first and most commonly observable opacity in the lens was nuclear sclerosis. Mouse lemurs from Colony 1 showed a delayed onset of nuclear sclerosis compared to mouse lemurs from Colony 2 (4.35 ± 1.50 years vs. 2.75 ± 0.99 years). For colony 1, the chronological age was equivalent to the number of seasonal cycles experienced by the mouse lemurs. For colony 2, in which seasonal cycles were accelerated by a factor of 1.5, mouse lemurs had experienced 4.13 ± 1.50 seasonal cycles in 2.75 ± 0.99 chronological years. Discussion Our study showed clear differences in age at the onset of nuclear sclerosis formation between lemurs kept under different photoperiodic regimes. Instead of measuring the chronological age, the number of seasonal cycles (N = four) experienced by a mouse lemur can be used to estimate the risk of beginning nuclear sclerosis formation. Ophthalmological examinations should be taken into account when animals older than 5–6 seasonal cycles are used for experiments in which unrestricted visual ability has to be ensured. This study is the first to assess and demonstrate the influence of annual photoperiod regime on the incidence of lens opacities in a non-human primate.
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Affiliation(s)
- Marko Dubicanac
- Institute of Zoology, Tierärztliche Hochschule Hannover, Hanover, Lower Saxony, Germany
| | - Julia Strueve
- Clinic for Small Animals, Tierärztliche Hochschule Hannover, Hanover, Lower Saxony, Germany
| | - Nadine Mestre-Frances
- Department of Molecular Mechanisms in Neurodegenerative Diseases Inserm U1198, Univ. Montpellier, Montpellier, France
| | - Jean-Michel Verdier
- Department of Molecular Mechanisms in Neurodegenerative Diseases Inserm U1198, Univ. Montpellier, Montpellier, France
| | - Elke Zimmermann
- Institute of Zoology, Tierärztliche Hochschule Hannover, Hanover, Lower Saxony, Germany
| | - Marine Joly
- Centre for Comparative and Evolutionary Psychology, University of Portsmouth, Portsmouth, United Kingdom
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19
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Sherin PS, López-Duarte I, Dent MR, Kubánková M, Vyšniauskas A, Bull JA, Reshetnikova ES, Klymchenko AS, Tsentalovich YP, Kuimova MK. Visualising the membrane viscosity of porcine eye lens cells using molecular rotors. Chem Sci 2017; 8:3523-3528. [PMID: 28580097 PMCID: PMC5435988 DOI: 10.1039/c6sc05369f] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Accepted: 02/14/2017] [Indexed: 12/15/2022] Open
Abstract
The plasma membranes of cells within the eye lens play an important role in metabolite transport within the avascular tissue of the lens, maintaining its transparency over the entire lifespan of an individual. Here we use viscosity-sensitive 'molecular rotors' to map the microscopic viscosity within these unusual cell membranes, establishing that they are characterised by an unprecedentedly high degree of lipid organisation.
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Affiliation(s)
- Peter S Sherin
- International Tomography Center SB RAS , Institutskaya Street 3A , 630090 , Novosibirsk , Russia .
- Department of Natural Sciences , Novosibirsk State University , Pirogova Street 2 , 630090 , Novosibirsk , Russia
| | - Ismael López-Duarte
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - Michael R Dent
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - Markéta Kubánková
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - Aurimas Vyšniauskas
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - James A Bull
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
| | - Evdokiya S Reshetnikova
- Institute of Molecular and Cellular Biology SB RAS , 8/2 Lavrentiev Avenue , 630090 , Novosibirsk , Russia
| | - Andrey S Klymchenko
- Laboratoire de Biophotonique et Pharmacologie , UMR 7213 CNRS , Faculté de Pharmacie , Université de Strasbourg , 74 Route du Rhin , 67401 ILLKIRCH Cedex , France
| | - Yuri P Tsentalovich
- International Tomography Center SB RAS , Institutskaya Street 3A , 630090 , Novosibirsk , Russia .
- Department of Natural Sciences , Novosibirsk State University , Pirogova Street 2 , 630090 , Novosibirsk , Russia
| | - Marina K Kuimova
- Department of Chemistry , Imperial College London , Exhibition Road , London , SW7 2AZ , UK .
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20
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Donaldson PJ, Grey AC, Maceo Heilman B, Lim JC, Vaghefi E. The physiological optics of the lens. Prog Retin Eye Res 2017; 56:e1-e24. [DOI: 10.1016/j.preteyeres.2016.09.002] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 09/09/2016] [Accepted: 09/13/2016] [Indexed: 11/17/2022]
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21
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Pescosolido N, Barbato A, Giannotti R, Komaiha C, Lenarduzzi F. Age-related changes in the kinetics of human lenses: prevention of the cataract. Int J Ophthalmol 2016; 9:1506-1517. [PMID: 27803872 DOI: 10.18240/ijo.2016.10.23] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2015] [Accepted: 01/13/2016] [Indexed: 12/12/2022] Open
Abstract
The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina and, by changing shape, it adjusts focal distance (accommodation). The three classes of structural proteins found in the lens are α, β, and γ crystallins. These proteins make up more than 90% of the total dry mass of the eye lens. Other components which can be found are sugars, lipids, water, several antioxidants and low weight molecules. When ageing changes occur in the lens, it causes a gradual reduction in transparency, presbyopia and an increase in the scattering and aberration of light waves as well as a degradation of the optical quality of the eye. The main changes that occur with aging are: 1) reduced diffusion of water from the outside to the inside of the lens and from its cortical to its nuclear zone; 2) crystalline change due to the accumulation of high molecular weight aggregates and insoluble proteins; 3) production of advanced glycation end products (AGEs), lipid accumulation, reduction of reduced glutathione content and destruction of ascorbic acid. Even if effective strategies in preventing cataract onset are not already known, good results have been reached in some cases with oral administration of antioxidant substances such as caffeine, pyruvic acid, epigallocatechin gallate (EGCG), α-lipoic acid and ascorbic acid. Furthermore, methionine sulfoxide reductase A (MSRA) over expression could protect lens cells both in presence and in absence of oxidative stress-induced damage. Nevertheless, promising results have been obtained by reducing ultraviolet-induced oxidative damage.
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Affiliation(s)
- Nicola Pescosolido
- Department of Cardiovascular, Respiratory, Nephrologic, Anesthesiologic and Geriatric Sciences, Sapienza University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy
| | - Andrea Barbato
- Department of Sense Organs, Sapienza University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy
| | - Rossella Giannotti
- Department of Sense Organs, Sapienza University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy
| | - Chiara Komaiha
- Department of Sense Organs, Sapienza University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy
| | - Fiammetta Lenarduzzi
- Department of Sense Organs, Sapienza University of Rome, Piazzale Aldo Moro 5, Rome 00185, Italy
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22
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Gutierrez DB, Garland DL, Schwacke JH, Hachey DL, Schey KL. Spatial distributions of phosphorylated membrane proteins aquaporin 0 and MP20 across young and aged human lenses. Exp Eye Res 2016; 149:59-65. [PMID: 27339748 DOI: 10.1016/j.exer.2016.06.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 06/16/2016] [Accepted: 06/17/2016] [Indexed: 11/26/2022]
Abstract
In the human ocular lens it is now realized that post-translational modifications can alter protein function and/or localization in fiber cells that no longer synthesize proteins. The specific sites of post-translational modification to the abundant ocular lens membrane proteins AQP0 and MP20 have been previously identified and their functional effects are emerging. To further understand how changes in protein function and/or localization induced by these modifications alter lens homeostasis, it is necessary to determine the spatial distributions of these modifications across the lens. In this study, a quantitative LC-MS approach was used to determine the spatial distributions of phosphorylated AQP0 and MP20 peptides from manually dissected, concentric layers of fiber cells from young and aged human lenses. The absolute amounts of phosphorylation were determined for AQP0 Ser235 and Ser229 and for MP20 Ser170 in fiber cells from the lens periphery to the lens center. Phosphorylation of AQP0 Ser229 represented a minor portion of the total phosphorylated AQP0. Changes in spatial distributions of phosphorylated APQ0 Ser235 and MP20 Ser170 correlated with regions of physiological interest in aged lenses, specifically, where barriers to water transport and extracellular diffusion form.
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Affiliation(s)
- Danielle B Gutierrez
- Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, BSB 358 MSC 509, 173 Ashley Ave., Charleston, SC 29425, USA
| | - Donita L Garland
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - John H Schwacke
- Department of Biostatistics and Epidemiology, Medical University of South Carolina, Cannon Place 303C, 135 Cannon St., Charleston, SC 29425, USA
| | - David L Hachey
- Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Suite 9160 MRBIII, 465 21st Ave. So., Nashville, TN 37240-7916, USA
| | - Kevin L Schey
- Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Suite 9160 MRBIII, 465 21st Ave. So., Nashville, TN 37240-7916, USA.
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23
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Anterior lens epithelium in intumescent white cataracts - scanning and transmission electron microscopy study. Graefes Arch Clin Exp Ophthalmol 2015; 254:269-76. [PMID: 26573390 DOI: 10.1007/s00417-015-3220-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 09/30/2015] [Accepted: 11/05/2015] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Our purpose was to study the structure of the lens epithelial cells (LECs) of intumescent white cataracts (IC) in comparison with nuclear cataracts (NC) in order to investigate possible structural reasons for development of IC. METHODS The anterior lens capsule (aLC: basement membrane and associated LECs) were obtained from cataract surgery and prepared for scanning electron microscopy (SEM) and transmission electron microscopy (TEM). RESULTS We observed by SEM that in IC, LEC swelling was pronounced with the clefts surrounding the groups of LECs. Another structural feature was spherical formations, that were observed on the apical side of LEC's, towards the fibre cell layer, both by SEM and TEM. Development of these structures, bulging out from the apical cell membrane of the LEC's and disrupting it, could be followed in steps towards the sphere formation. The degeneration of the lens epithelium and the structures of the aLC in IC similar to Morgagnian globules were also observed. None of these structural changes were observed in NC. CONCLUSIONS We show by SEM and TEM that, in IC, LECs have pronounced structural features not observed in NC. This supports the hypothesis that the disturbed structure of LECs plays a role in water accumulation in the IC lens. We also suggest that, in IC, LECs produce bulging spheres that represent unique structures of degenerated material, extruded from the LEC.
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Avila F, Friguet B, Silva E. Photosensitizing Activity of Endogenous Eye Lens Chromophores: An Attempt to Unravel Their Contributions to Photo-Aging and Cataract Disease. Photochem Photobiol 2015; 91:767-79. [DOI: 10.1111/php.12443] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 02/20/2015] [Indexed: 11/28/2022]
Affiliation(s)
- Felipe Avila
- Escuela de Nutrición y Dietética; Facultad de Ciencias de la Salud; Universidad de Talca; Talca Chile
- Programa de Investigación de Excelencia Interdisciplinario en Envejecimiento Saludable (PIEI-ES); Universidad de Talca; Talca Chile
| | - Bertrand Friguet
- UPMC Univ. Paris 06; CNRS UMR 8256; INSERM U1164; Adaptation Biologique et Vieillissement; Institute of Biology Paris-Seine; Paris France
| | - Eduardo Silva
- Departamento de Química Física; Facultad de Química; Pontifícia Universidad Católica de Chile; Santiago Chile
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Tsentalovich YP, Verkhovod TD, Yanshole VV, Kiryutin AS, Yanshole LV, Fursova AZ, Stepakov DA, Novoselov VP, Sagdeev RZ. Metabolomic composition of normal aged and cataractous human lenses. Exp Eye Res 2015; 134:15-23. [PMID: 25773987 DOI: 10.1016/j.exer.2015.03.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 03/06/2015] [Accepted: 03/11/2015] [Indexed: 10/23/2022]
Abstract
Quantitative metabolomic profiles of normal and cataractous human lenses were obtained with the combined use of high-frequency nuclear magnetic resonance (NMR) and high-performance liquid chromatography with high-resolution mass-spectrometric detection (LC-MS) methods. The concentration of more than fifty metabolites in the lens cortex and nucleus has been determined. For the majority of metabolites, their concentrations in the lens cortex and nucleus are similar, which confirms low metabolic activity in the lens core. The difference between the metabolite levels in the cortex and nucleus of the normal lens is observed for antioxidants and UV filters, which demonstrates the activity of redox processes in the lens. A huge difference is found between the metabolomic compositions of normal and age-matched cataractous lenses: the concentrations of almost all metabolites in the normal lens are higher than in the cataractous one. The most pronounced difference is observed for compounds playing a key role in the lens cell protection and metabolic activity, including antioxidants, UV filters, and osmolytes. The results obtained imply that the development of the age-related cataracts might originate from the metabolic dysfunction of the lens epithelial cells.
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Affiliation(s)
- Yuri P Tsentalovich
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia.
| | - Timofey D Verkhovod
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia
| | - Vadim V Yanshole
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
| | - Alexey S Kiryutin
- International Tomography Center SB RAS, Institutskaya 3a, 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
| | - Denis A Stepakov
- Novosibirsk Regional Clinical Bureau of Forensic Medical Examination, Nemirovicha-Danchenko 134, Novosibirsk 630087, Russia
| | - Vladimir P Novoselov
- Novosibirsk Regional Clinical Bureau of Forensic Medical Examination, Nemirovicha-Danchenko 134, Novosibirsk 630087, Russia
| | - Renad Z Sagdeev
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk 630090, Russia; Novosibirsk State University, Pirogova 2, Novosibirsk 630090, Russia
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Abdelkader H, Alany RG, Pierscionek B. Age-related cataract and drug therapy: opportunities and challenges for topical antioxidant delivery to the lens. J Pharm Pharmacol 2015; 67:537-50. [DOI: 10.1111/jphp.12355] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 10/26/2014] [Indexed: 01/21/2023]
Abstract
Abstract
Objectives
The search for anticataract drugs has been continuing for decades; some treatments no longer exist but antioxidants are still of much interest.
Key findings
The primary function of the human lens, along with the cornea, is to refract light so that it is correctly focused onto the retina for optimum image quality. With age, the human lens undergoes morphological, biochemical and physical changes leading to opacification. Age-related or senile cataract is one of the main causes of visual impairment in the elderly; given the lack of access to surgical treatment in many parts of the world, cataract remains a major cause of sight loss. Surgical treatment is the only means of treating cataract; this approach, however, has limitations and complications.
Summary
This review discusses the anatomy and physiology of the lens and the changes that are understood to occur with ageing and cataract formation to identify potential areas for effective therapeutic intervention. Experimental techniques and agents used to induce cataract in animal models, the advantages and disadvantages of potential pharmacological treatments specific barriers to delivery of exogenous antioxidants to the lens and the prospects for future research are discussed.
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Affiliation(s)
- Hamdy Abdelkader
- Drug Discovery, Delivery and Patient Care (DDDPC) Theme, School of Pharmacy and Chemistry, Kingston University London, London, UK
- Pharmaceutics Department, Faculty of Pharmacy, Minia University, Mina, Egypt
| | - Raid G Alany
- Drug Discovery, Delivery and Patient Care (DDDPC) Theme, School of Pharmacy and Chemistry, Kingston University London, London, UK
- School of Pharmacy, The University of Auckland, Auckland, New Zealand
| | - Barbara Pierscionek
- Vision Cognition and Neuroscience Theme, Faculty of Science, Engineering and Computing, Kingston University London, London, UK
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Intact and N- or C-terminal end truncated AQP0 function as open water channels and cell-to-cell adhesion proteins: end truncation could be a prelude for adjusting the refractive index of the lens to prevent spherical aberration. Biochim Biophys Acta Gen Subj 2014; 1840:2862-77. [PMID: 24821012 DOI: 10.1016/j.bbagen.2014.05.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 04/30/2014] [Accepted: 05/02/2014] [Indexed: 11/20/2022]
Abstract
BACKGROUND Investigate the impact of natural N- or C-terminal post-translational truncations of lens mature fiber cell Aquaporin 0 (AQP0) on water permeability (Pw) and cell-to-cell adhesion (CTCA) functions. METHODS The following deletions/truncations were created by site-directed mutagenesis (designations in parentheses): Amino acid residues (AA) 2-6 (AQP0-N-del-2-6), AA235-263 (AQP0-1-234), AA239-263 (AQP0-1-238), AA244-263 (AQP0-1-243), AA247-263 (AQP0-1-246), AA250-263 (AQP0-1-249) and AA260-263 (AQP0-1-259). Protein expression was studied using immunostaining, fluorescent tags and organelle-specific markers. Pw was tested by expressing the respective complementary ribonucleic acid (cRNA) in Xenopus oocytes and conducting osmotic swelling assay. CTCA was assessed by transfecting intact or mutant AQP0 into adhesion-deficient L-cells and performing cell aggregation and adhesion assays. RESULTS AQP0-1-234 and AQP0-1-238 did not traffic to the plasma membrane. Trafficking of AQP0-N-del-2-6 and AQP0-1-243 was reduced causing decreased membrane Pw and CTCA. AQP0-1-246, AQP0-1-249 and AQP0-1-259 mutants trafficked properly and functioned normally. Pw and CTCA functions of the mutants were directly proportional to the respective amount of AQP0 expressed at the plasma membrane and remained comparable to those of intact AQP0 (AQP0-1-263). CONCLUSIONS Post-translational truncation of N- or C-terminal end amino acids does not alter the basal water permeability of AQP0 or its adhesive functions. AQP0 may play a role in adjusting the refractive index to prevent spherical aberration in the constantly growing lens. GENERAL SIGNIFICANCE Similar studies can be extended to other lens proteins which undergo post-translational truncations to find out how they assist the lens to maintain transparency and homeostasis for proper focusing of objects on to the retina.
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28
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Magnetic resonance imaging (MRI) study of the water content and transport in rat lenses. Exp Eye Res 2013; 113:162-71. [DOI: 10.1016/j.exer.2013.06.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 06/07/2013] [Indexed: 11/20/2022]
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Robciuc A, Hyötyläinen T, Jauhiainen M, Holopainen JM. Ceramides in the pathophysiology of the anterior segment of the eye. Curr Eye Res 2013; 38:1006-16. [PMID: 23885886 DOI: 10.3109/02713683.2013.810273] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
PURPOSE Sphingolipid (SL) research reached a peak in the past years. Yet this positive trend was not evident for eye research as the relative number of studies centered on SLs is decreasing. Our aim is to encourage the inclusion of SL metabolites in studies of ocular pathophysiology by summarizing recent findings and current awareness concerning ceramides in the anterior segment of the eye. METHODS Review of literature relating to ceramides as bioactive lipids and the extent to which their particular nature was investigated in ocular pathophysiology. RESULTS Ceramides are rare but indispensable lipids that influence cellular responses through their effects on membrane biophysical properties or direct interaction with target proteins. Their biological significance is increased by variability and adaptability as there are tens of enzymes designed to modulate their function. The eye offers a set of unique environments where ceramides or other SLs have not been extensively studied. Not surprisingly, ceramides were associated with apoptosis in the metabolically active tissues, while little is known about its effects on the biophysical properties of the tears or lens lipids. More so, there are still aspects of the ocular homeostasis control where SLs contribution has not been investigated to date (e.g. pathogen aggression). CONCLUSIONS Ceramides and SL metabolism still receive increasing attention and have proven to be a significant metabolite in many research fields (e.g. cancer, stress response and inflammation) and there are yet many questions that they will aid answer. With the present work, we seek to increase awareness of these lipids also in eye research and to highlight their importance as common regulators of various diseases.
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Affiliation(s)
- Alexandra Robciuc
- Department of Ophthalmology, University of Helsinki, Helsinki Eye Lab, Helsinki, Finland
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Morgan JT, Murphy CJ, Russell P. What do mechanotransduction, Hippo, Wnt, and TGFβ have in common? YAP and TAZ as key orchestrating molecules in ocular health and disease. Exp Eye Res 2013; 115:1-12. [PMID: 23792172 DOI: 10.1016/j.exer.2013.06.012] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 06/03/2013] [Accepted: 06/10/2013] [Indexed: 01/09/2023]
Abstract
Cells in vivo are exposed to a complex signaling environment. Biochemical signaling modalities, such as secreted proteins, specific extracellular matrix domains and ion fluxes certainly compose an important set of regulatory signals to cells. However, these signals are not exerted in isolation, but rather in concert with biophysical cues of the surrounding tissue, such as stiffness and topography. In this review, we attempt to highlight the biophysical attributes of ocular tissues and their influence on cellular behavior. Additionally, we introduce the proteins YAP and TAZ as targets of biophysical and biochemical signaling and important agonists and antagonists of numerous signaling pathways, including TGFβ and Wnt. We frame the discussion around this extensive signaling crosstalk, which allows YAP and TAZ to act as orchestrating molecules, capable of integrating biophysical and biochemical cues into a broad cellular response. Finally, while we draw on research from various fields to provide a full picture of YAP and TAZ, we attempt to highlight the intersections with vision science and the exciting work that has already been performed.
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Affiliation(s)
- Joshua T Morgan
- Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, 1 Shields Ave., Davis, CA 95616, USA
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31
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Blakely EA. Lauriston S. Taylor Lecture on radiation protection and measurements: what makes particle radiation so effective? HEALTH PHYSICS 2012; 103:508-28. [PMID: 23032880 PMCID: PMC3507469 DOI: 10.1097/hp.0b013e31826a5b85] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
The scientific basis for the physical and biological effectiveness of particle radiations has emerged from many decades of meticulous basic research. A diverse array of biologically relevant consequences at the molecular, cellular, tissue, and organism level have been reported, but what are the key processes and mechanisms that make particle radiation so effective, and what competing processes define dose dependences? Recent studies have shown that individual genotypes control radiation-regulated genes and pathways in response to radiations of varying ionization density. The fact that densely ionizing radiations can affect different gene families than sparsely ionizing radiations, and that the effects are dose- and time-dependent, has opened up new areas of future research. The complex microenvironment of the stroma and the significant contributions of the immune response have added to our understanding of tissue-specific differences across the linear energy transfer (LET) spectrum. The importance of targeted versus nontargeted effects remains a thorny but elusive and important contributor to chronic low dose radiation effects of variable LET that still needs further research. The induction of cancer is also LET-dependent, suggesting different mechanisms of action across the gradient of ionization density. The focus of this 35th Lauriston S. Taylor Lecture is to chronicle the step-by-step acquisition of experimental clues that have refined our understanding of what makes particle radiation so effective, with emphasis on the example of radiation effects on the crystalline lens of the human eye.
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Affiliation(s)
- Eleanor A Blakely
- Lawrence Berkeley National Laboratory, One Cyclotron Road, MS 977, Berkeley, CA 94720, USA.
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Vaghefi E, Malcolm DTK, Jacobs MD, Donaldson PJ. Development of a 3D finite element model of lens microcirculation. Biomed Eng Online 2012; 11:69. [PMID: 22992294 PMCID: PMC3494564 DOI: 10.1186/1475-925x-11-69] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 08/10/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND It has been proposed that in the absence of a blood supply, the ocular lens operates an internal microcirculation system. This system delivers nutrients, removes waste products and maintains ionic homeostasis in the lens. The microcirculation is generated by spatial differences in membrane transport properties; and previously has been modelled by an equivalent electrical circuit and solved analytically. While effective, this approach did not fully account for all the anatomical and functional complexities of the lens. To encapsulate these complexities we have created a 3D finite element computer model of the lens. METHODS Initially, we created an anatomically-correct representative mesh of the lens. We then implemented the Stokes and advective Nernst-Plank equations, in order to model the water and ion fluxes respectively. Next we complemented the model with experimentally-measured surface ionic concentrations as boundary conditions and solved it. RESULTS Our model calculated the standing ionic concentrations and electrical potential gradients in the lens. Furthermore, it generated vector maps of intra- and extracellular space ion and water fluxes that are proposed to circulate throughout the lens. These fields have only been measured on the surface of the lens and our calculations are the first 3D representation of their direction and magnitude in the lens. CONCLUSION Values for steady state standing fields for concentration and electrical potential plus ionic and fluid fluxes calculated by our model exhibited broad agreement with observed experimental values. Our model of lens function represents a platform to integrate new experimental data as they emerge and assist us to understand how the integrated structure and function of the lens contributes to the maintenance of its transparency.
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Affiliation(s)
- Ehsan Vaghefi
- Department of Optometry and Vision Sciences, University of Auckland, Building 502, Level 4, 85 Park Road, Grafton, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Duane TK Malcolm
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Marc D Jacobs
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Paul J Donaldson
- Department of Optometry and Vision Sciences, University of Auckland, Building 502, Level 4, 85 Park Road, Grafton, Auckland, New Zealand
- School of Medical Sciences, University of Auckland, Auckland, New Zealand
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Sousounis K, Tsonis PA. Patterns of gene expression in microarrays and expressed sequence tags from normal and cataractous lenses. Hum Genomics 2012; 6:14. [PMID: 23244575 PMCID: PMC3563465 DOI: 10.1186/1479-7364-6-14] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Accepted: 05/14/2012] [Indexed: 11/30/2022] Open
Abstract
In this contribution, we have examined the patterns of gene expression in normal and cataractous lenses as presented in five different papers using microarrays and expressed sequence tags. The purpose was to evaluate unique and common patterns of gene expression during development, aging and cataracts.
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Affiliation(s)
- Konstantinos Sousounis
- Department of Biology and Center for Tissue Regeneration and Engineering, University of Dayton, Dayton, OH 45469-2320, USA
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Hughes JR, Deeley JM, Blanksby SJ, Leisch F, Ellis SR, Truscott RJW, Mitchell TW. Instability of the cellular lipidome with age. AGE (DORDRECHT, NETHERLANDS) 2012; 34:935-47. [PMID: 21894448 PMCID: PMC3682067 DOI: 10.1007/s11357-011-9293-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2010] [Accepted: 07/25/2011] [Indexed: 05/31/2023]
Abstract
The human lens nucleus is formed in utero, and from birth onwards, there appears to be no significant turnover of intracellular proteins or membrane components. Since, in adults, this region also lacks active enzymes, it offers the opportunity to examine the intrinsic stability of macromolecules under physiological conditions. Fifty seven human lenses, ranging in age from 12 to 82 years, were dissected into nucleus and cortex, and the nuclear lipids analyzed by electrospray ionization tandem mass spectrometry. In the first four decades of life, glycerophospholipids (with the exception of lysophosphatidylethanolamines) declined rapidly, such that by age 40, their content became negligible. In contrast the level of ceramides and dihydroceramides, which were undetectable prior to age 30, increased approximately 100-fold. The concentration of sphingomyelins and dihydrosphingomyelins remained unchanged over the whole life span. As a consequence of this marked alteration in composition, the properties of fiber cell membranes in the centre of young lenses are likely to be very different from those in older lenses. Interestingly, the identification of age 40 years as a time of transition in the lipid composition of the nucleus coincides with previously reported macroscopic changes in lens properties (e.g., a massive age-related increase in lens stiffness) and related pathologies such as presbyopia. The underlying reasons for the dramatic change in the lipid profile of the human lens with age are not known, but are most likely linked to the stability of some membrane lipids in a physiological environment.
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Affiliation(s)
- Jessica R. Hughes
- />Graduate School of Medicine, University of Wollongong, Wollongong, 2522 NSW Australia
| | - Jane M. Deeley
- />ARC Centre of Excellence for Free Radical Chemistry, School of Chemistry, University of Wollongong, Wollongong, 2522 NSW Australia
| | - Stephen J. Blanksby
- />ARC Centre of Excellence for Free Radical Chemistry, School of Chemistry, University of Wollongong, Wollongong, 2522 NSW Australia
| | - Friedrich Leisch
- />Institute of Applied Statistics and Computing, University of Natural Resources and Life Sciences, 1180 Vienna, Austria
| | - Shane R. Ellis
- />ARC Centre of Excellence for Free Radical Chemistry, School of Chemistry, University of Wollongong, Wollongong, 2522 NSW Australia
| | - Roger J. W. Truscott
- />Save Sight Institute, University of Sydney, Macquarie Street, Sydney, NSW 2001 Australia
| | - Todd W. Mitchell
- />School of Health Sciences, University of Wollongong, Wollongong, 2522 NSW Australia
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The gradient index lens of the eye: an opto-biological synchrony. Prog Retin Eye Res 2012; 31:332-49. [PMID: 22465790 DOI: 10.1016/j.preteyeres.2012.03.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Revised: 03/02/2012] [Accepted: 03/04/2012] [Indexed: 11/22/2022]
Abstract
The refractive power of a lens is determined largely by its surface curvatures and the refractive index of its medium. These properties can also be used to control the sharpness of focus and hence the image quality. One of the most effective ways of doing this is with a gradient index. Eye lenses of all species, thus far, measured, are gradient index (GRIN) structures. The index gradation is one that increases from the periphery of the lens to its centre but the steepness of the gradient and the magnitudes of the refractive index vary so that the optics of the lens accords with visual demands. The structural proteins, the crystallins, which create the index gradient, also vary from species to species, in type and relative distribution across the tissue. The crystallin classes do not contribute equally to the refractive index, and this may be related to their structure and amino acid content. This article compares GRIN forms in eye lenses of varying species, the relevance of these forms to visual requirements, and the relationship between refractive index and the structural proteins. Consideration is given to the dynamics of a living lens, potential variations in the GRIN form with physiological changes and the possible link between discontinuities in the gradient and growth. Finally, the property of birefringence and the characteristic polarisation patterns seen in highly ordered crystals that have also been observed in specially prepared eye lenses are described and discussed.
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36
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Functions of cholesterol and the cholesterol bilayer domain specific to the fiber-cell plasma membrane of the eye lens. J Membr Biol 2011; 245:51-68. [PMID: 22207480 DOI: 10.1007/s00232-011-9412-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 11/29/2011] [Indexed: 10/14/2022]
Abstract
The most unique feature of the eye lens fiber-cell plasma membrane is its extremely high cholesterol content. Cholesterol saturates the bulk phospholipid bilayer and induces formation of immiscible cholesterol bilayer domains (CBDs) within the membrane. Our results (based on EPR spin-labeling experiments with lens-lipid membranes), along with a literature search, have allowed us to identify the significant functions of cholesterol specific to the fiber-cell plasma membrane, which are manifest through cholesterol-membrane interactions. The crucial role is played by the CBD. The presence of the CBD ensures that the surrounding phospholipid bilayer is saturated with cholesterol. The saturating cholesterol content in fiber-cell membranes keeps the bulk physical properties of lens-lipid membranes consistent and independent of changes in phospholipid composition. Thus, the CBD helps to maintain lens-membrane homeostasis when the membrane phospholipid composition changes significantly. The CBD raises the barrier for oxygen transport across the fiber-cell membrane, which should help to maintain a low oxygen concentration in the lens interior. It is hypothesized that the appearance of the CBD in the fiber-cell membrane is controlled by the phospholipid composition of the membrane. Saturation with cholesterol smoothes the phospholipid-bilayer surface, which should decrease light scattering and help to maintain lens transparency. Other functions of cholesterol include formation of hydrophobic and rigidity barriers across the bulk phospholipid-cholesterol domain and formation of hydrophobic channels in the central region of the membrane for transport of small, nonpolar molecules parallel to the membrane surface. In this review, we provide data supporting these hypotheses.
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37
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Truscott RJW, Comte-Walters S, Ablonczy Z, Schwacke JH, Berry Y, Korlimbinis A, Friedrich MG, Schey KL. Tight binding of proteins to membranes from older human cells. AGE (DORDRECHT, NETHERLANDS) 2011; 33:543-554. [PMID: 21181282 PMCID: PMC3220407 DOI: 10.1007/s11357-010-9198-9] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2010] [Accepted: 11/16/2010] [Indexed: 05/30/2023]
Abstract
The lens is an ideal model system for the study of macromolecular aging and its consequences for cellular function, since there is no turnover of lens fibre cells. To examine biochemical processes that take place in the lens and that may also occur in other long-lived cells, membranes were isolated from defined regions of human lenses that are synthesised at different times during life, and assayed for the presence of tightly bound cytosolic proteins using quantitative iTRAQ proteomics technology. A majority of lens beta crystallins and all gamma crystallins became increasingly membrane bound with age, however, the chaperone proteins alpha A and alpha B crystallin, as well as the thermally-stable protein, βB2 crystallin, did not. Other proteins such as brain-associated signal protein 1 and paralemmin 1 became less tightly bound in the older regions of the lens. It is evident that protein-membrane interactions change significantly with age. Selected proteins that were formerly cytosolic become increasingly tightly bound to cell membranes with age and are not removed even by treatment with 7 M urea. It is likely that such processes reflect polypeptide denaturation over time and the untoward binding of proteins to membranes may alter membrane properties and contribute to impairment of communication between older cells.
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38
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Gutierrez DB, Garland D, Schey KL. Spatial analysis of human lens aquaporin-0 post-translational modifications by MALDI mass spectrometry tissue profiling. Exp Eye Res 2011; 93:912-20. [PMID: 22036630 DOI: 10.1016/j.exer.2011.10.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 10/17/2011] [Accepted: 10/17/2011] [Indexed: 10/16/2022]
Abstract
Aquaporin-0 (AQP0), the major integral membrane protein in lens fiber cells, becomes highly modified with increasing age. The functional consequences of these modifications are being revealed, and the next step is to determine how these modifications affect the ocular lens, which is directly related to their abundances and spatial distributions. The aim of this study was to utilize matrix-assisted laser desorption ionization (MALDI) direct tissue profiling methods, which produce spatially-resolved protein profiles, to map and quantify AQP0 post-translational modifications (PTMs). Direct tissue profiling was performed using frozen, equatorial human lens sections of various ages prepared by conditions optimized for MALDI mass spectrometry profiling of membrane proteins. Modified forms of AQP0 were identified and further investigated using liquid chromatography tandem mass spectrometry (LC-MS/MS). The distributions of unmodified, truncated, and oleoylated forms of AQP0 were examined with a maximum spatial resolution of 500 μm. Direct tissue profiling of intact human lens sections provided high quality, spatially-resolved, relative quantitative information of AQP0 and its modified forms indicating that 50% of AQP0 is truncated at a fiber cell age of 24 ± 1 year in all lenses examined. Furthermore, direct tissue profiling also revealed previously unidentified AQP0 modifications including N-terminal acetylation and carbamylation. N-terminal acetylation appears to provide a protective effect against N-terminal truncation.
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Affiliation(s)
- Danielle B Gutierrez
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, MD, USA
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39
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Vaghefi E, Pontre BP, Jacobs MD, Donaldson PJ. Visualizing ocular lens fluid dynamics using MRI: manipulation of steady state water content and water fluxes. Am J Physiol Regul Integr Comp Physiol 2011; 301:R335-42. [DOI: 10.1152/ajpregu.00173.2011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies using various MRI techniques have shown that a water-protein concentration gradient exists in the ocular lens. Because this concentration is higher in the core relative to the lens periphery, a gradient in refractive index is established in the lens. To investigate how the water-protein concentration profile is maintained, bovine lenses were incubated in different solutions, and changes in water-protein concentration ratio monitored using proton density weighted (PD-weighted) imaging in the absence and presence of heavy water (D2O). Lenses incubated in artificial aqueous humor (AAH) maintained the steady state water-protein concentration gradient, but incubating lenses in high extracellular potassium (KCl-AAH) or low temperature (Low T-AAH) caused a collapse of the gradient due to a rise in water content in the core of the lens. To visualize water fluxes, lenses were incubated in D2O, which acts as a contrast agent. Incubation in KCl-AAH and low T-AAH dramatically slowed the movement of D2O into the core but did not affect the movement of D2O into the outer cortex. D2O seemed to preferentially enter the lens cortex at the anterior and posterior poles before moving circumferentially toward the equatorial regions. This directionality of D2O influx into the lens cortex was abolished by incubating lenses in high KCl-AAH or low T-AAH, and resulted in homogenous influx of D2O into the outer cortex. Taken together, our results show that the water-protein concentration ratio is actively maintained in the core of the lens and that water fluxes preferentially enter the lens at the poles.
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Affiliation(s)
- Ehsan Vaghefi
- Department of Optometry and Vision Sciences, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Beau P. Pontre
- Centre for Advanced MRI, University of Auckland, Auckland, New Zealand; and
| | - Marc D. Jacobs
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Paul J. Donaldson
- Department of Optometry and Vision Sciences, New Zealand National Eye Centre, University of Auckland, Auckland, New Zealand
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40
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Dahm R, van Marle J, Quinlan RA, Prescott AR, Vrensen GFJM. Homeostasis in the vertebrate lens: mechanisms of solute exchange. Philos Trans R Soc Lond B Biol Sci 2011; 366:1265-77. [PMID: 21402585 DOI: 10.1098/rstb.2010.0299] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The eye lens is avascular, deriving nutrients from the aqueous and vitreous humours. It is, however, unclear which mechanisms mediate the transfer of solutes between these humours and the lens' fibre cells (FCs). In this review, we integrate the published data with the previously unpublished ultrastructural, dye loading and magnetic resonance imaging results. The picture emerging is that solute transfer between the humours and the fibre mass is determined by four processes: (i) paracellular transport of ions, water and small molecules along the intercellular spaces between epithelial and FCs, driven by Na(+)-leak conductance; (ii) membrane transport of such solutes from the intercellular spaces into the fibre cytoplasm by specific carriers and transporters; (iii) gap-junctional coupling mediating solute flux between superficial and deeper fibres, Na(+)/K(+)-ATPase-driven efflux of waste products in the equator, and electrical coupling of fibres; and (iv) transcellular transfer via caveoli and coated vesicles for the uptake of macromolecules and cholesterol. There is evidence that the Na(+)-driven influx of solutes occurs via paracellular and membrane transport and the Na(+)/K(+)-ATPase-driven efflux of waste products via gap junctions. This micro-circulation is likely restricted to the superficial cortex and nearly absent beyond the zone of organelle loss, forming a solute exchange barrier in the lens.
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Affiliation(s)
- Ralf Dahm
- Center for Brain Research, Medical University of Vienna, Spitalgasse 4, A-1090 Vienna, Austria.
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41
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Zhu X, Korlimbinis A, Truscott RJ. Age-Dependent Denaturation of Enzymes in the Human Lens: A Paradigm for Organismic Aging? Rejuvenation Res 2010; 13:553-60. [DOI: 10.1089/rej.2009.1009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Xiangjia Zhu
- Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai 200031, China
- Save Sight Institute, University of Sydney, NSW, 2001, Australia
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42
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43
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Deeley JM, Hankin JA, Friedrich MG, Murphy RC, Truscott RJW, Mitchell TW, Blanksby SJ. Sphingolipid distribution changes with age in the human lens. J Lipid Res 2010; 51:2753-60. [PMID: 20547889 PMCID: PMC2918457 DOI: 10.1194/jlr.m007716] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Revised: 06/07/2010] [Indexed: 11/20/2022] Open
Abstract
The formation of an internal barrier to the diffusion of small molecules in the lens during middle age is hypothesized to be a key event in the development of age-related nuclear (ARN) cataract. Changes in membrane lipids with age may be responsible. In this study, we investigated the effect of age on the distribution of sphingomyelins, the most abundant lens phospholipids. Human lens sections were initially analyzed by MALDI mass spectrometry imaging. A distinct annular distribution of the dihydrosphingomyelin, DHSM (d18:0/16:0), in the barrier region was observed in 64- and 70-year-old lenses but not in a 23-year-old lens. An increase in the dihydroceramide, DHCer (d18:0/16:0), in the lens nucleus was also observed in the older lenses. These findings were supported by ESI mass spectrometry analysis of lipid extracts from lenses dissected into outer, barrier, and nuclear regions. A subsequent analysis of 18 lenses ages 20-72 years revealed that sphingomyelin levels increased with age in the barrier region until reaching a plateau at approximately 40 years of age. Such changes in lipid composition will have a significant impact on the physical properties of the fiber cell membranes and may be associated with the formation of a barrier.
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Affiliation(s)
- Jane M. Deeley
- Schools of Chemistry, University of Wollongong, Wollongong, Australia
| | - Joseph A. Hankin
- Department of Pharmacology, University of Colorado Health Sciences Centre, Aurora, CO
| | | | - Robert C. Murphy
- Department of Pharmacology, University of Colorado Health Sciences Centre, Aurora, CO
| | | | - Todd W. Mitchell
- Health Sciences, University of Wollongong, Wollongong, Australia
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Abstract
Not only are human lenses different in many ways from those of non-primates, they also undergo dramatic changes with age. These age-dependent alterations lead to perturbations in the properties of older lenses, and ultimately to disturbances in visual function, which typically become apparent at middle age. Recent data suggest that many, if not all, of these age-dependent features can be traced to the lack of macromolecular turnover in the lens and to the inexorable modifications to proteins and membrane components over a period of decades. Exposure of lenses to heat can reproduce many of these alterations, suggesting that long-term incubation at body temperature may be an important factor in aging the human lens. Two conclusions flow from this. Firstly, the human lens may be an ideal tissue for studying macromolecular aging in man. Secondly, it will be extremely challenging to examine the origin of human age-related conditions, such as presbyopia and nuclear cataract, using traditional laboratory animals. Characterising the unfolding and decomposition of long-lived macromolecules appears to provide the key to understanding the two most common human lens disorders: presbyopia and age-related nuclear cataract.
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45
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Beebe DC, Truscott RJW. Counterpoint: The lens fluid circulation model--a critical appraisal. Invest Ophthalmol Vis Sci 2010; 51:2306-10; discussion 2310-2. [PMID: 20435605 DOI: 10.1167/iovs.10-5350a] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- David C Beebe
- Department of Ophthalmology and Vision Sciences, Washington University, St. Louis, MO 63110, USA.
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46
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Stella DR, Floyd KA, Grey AC, Renfrow MB, Schey KL, Barnes S. Tissue localization and solubilities of αA-crystallin and its numerous C-terminal truncation products in pre- and postcataractous ICR/f rat lenses. Invest Ophthalmol Vis Sci 2010; 51:5153-61. [PMID: 20435586 DOI: 10.1167/iovs.10-5302] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To investigate the tissue distribution and solubilities of various αA-crystallin truncation products in the cataractous ICR/f rat model. METHODS Rat lenses from precataractous (21-day) and postcataractous (100-day) ICR/f rats were sectioned and applied to a matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) target plate. Mass spectrometry images were collected to obtain a macromolecular profile of the abundant lens proteins. Separately, age-matched lenses were extracted into water-soluble (WS) and water-insoluble/urea-soluble (WI-US) fractions and subjected to MALDI-TOF mass spectrometry to correlate the protein solubilities with the imaging data. Protein identities were assigned by using a top-down proteomics approach on a high-resolution mass spectrometer. RESULTS Ten novel αA-crystallin truncation products were identified, along with six previously known αA-crystallin truncation products. Nearly all truncations exhibited nuclear localization, with larger truncated products displaying a ringlike localization that progressed outward toward the extranuclear, cortical region. The distributions were similar in both ages with the only significant difference being the amount of tissue area encompassed by a particular species with increasing age. Almost all nuclear products fractionated into the WI-US fraction, whereas the five largest extranuclear species exhibited mixed solubility. CONCLUSIONS A successful methodology for the sectioning and imaging of pre- and postcataractous ICR/f rat lenses has been established. Data collected from these analyses indicate that there are multiple αA-crystallin truncation products present in both pre- and postcataractous rats. Furthermore, these species have defined lenticular localizations and unique solubilities that may be a consequence of lens development and protein function within the lens environment.
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Affiliation(s)
- David R Stella
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
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47
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Friedrich MG, Truscott RJW. Large-scale binding of α-crystallin to cell membranes of aged normal human lenses: a phenomenon that can be induced by mild thermal stress. Invest Ophthalmol Vis Sci 2010; 51:5145-52. [PMID: 20435594 DOI: 10.1167/iovs.10-5261] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE With age, large amounts of crystallins become associated with fiber cell membranes in the human lens nucleus, and it has been proposed that this binding of protein may lead to the obstruction of membrane pores and the onset of a barrier to diffusion. This study focused on membrane binding within the barrier region and the outermost lens cortex. METHODS Human lenses across the age range were used, and the interaction of crystallins with membranes was examined using sucrose density gradient centrifugation, two-dimensional gel electrophoresis, and amine-reactive isobaric tagging technology. Lipids were quantified using shotgun lipidemics. RESULTS Binding of proteins to cell membranes in the barrier region was found to be different from that in the lens nucleus because in the barrier and outer cortical regions, only one high-density band formed. Most of the membrane-associated protein in this high-density band was α-crystallin. Mild thermal stress of intact young lenses led to pronounced membrane binding of proteins and yielded a sucrose density pattern in all lens regions that appeared to be identical with that from older lenses. CONCLUSIONS α-Crystallin is the major protein that binds to cell membranes in the barrier region of lenses after middle age. Exposure of young human lenses to mild thermal stress results in large-scale binding of α-crystallin to cell membranes. The density gradient profiles of such heated lenses appear to be indistinguishable from those of older normal lenses. The data support the hypothesis that temperature may be a factor responsible for age-related changes to the human lens.
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48
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Augusteyn RC. On the growth and internal structure of the human lens. Exp Eye Res 2010; 90:643-54. [PMID: 20171212 DOI: 10.1016/j.exer.2010.01.013] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 01/25/2010] [Accepted: 01/29/2010] [Indexed: 11/27/2022]
Abstract
Growth of the human lens and the development of its internal features are examined using in vivo and in vitro observations on dimensions, weights, cell sizes, protein gradients and other properties. In vitro studies have shown that human lens growth is biphasic, asymptotic until just after birth and linear for most of postnatal life. This generates two distinct compartments, the prenatal and the postnatal. The prenatal growth mode leads to the formation of an adult nuclear core of fixed dimensions and the postnatal, to an ever-expanding cortex. The nuclear core and the cortex have different properties and can readily be physically separated. Communication and adhesion between the compartments is poor in older lenses. In vivo slit lamp examination reveals several zones of optical discontinuity in the lens. Different nomenclatures have been used to describe these, with the most common recognizing the embryonic, foetal, juvenile and adult nuclei as well as the cortex and outer cortex. Implicit in this nomenclature is the idea that the nuclear zones were generated at defined periods of development and growth. This review examines the relationship between the two compartments observed in vitro and the internal structures revealed by slit lamp photography. Defining the relationship is not as simple as it might seem because of remodeling and cell compaction which take place, mostly in the first 20 years of postnatal life. In addition, different investigators use different nomenclatures when describing the same regions of the lens. From a consideration of the dimensions, the dry mass contents and the protein distributions in the lens and in the various zones, it can be concluded that the juvenile nucleus and the layers contained within it, as well as most of the adult nucleus, were actually produced during prenatal life and the adult nucleus was completed within 3 months after birth, in the final stages of the prenatal growth mode. Further postnatal growth takes place entirely within the cortex. It can also be demonstrated that the in vitro nuclear core corresponds to the combined slit lamp nuclear zones. In view of the information presented in this review, the use of the terms foetal, juvenile and adult nucleus seems inappropriate and should be abandoned.
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Affiliation(s)
- Robert C Augusteyn
- The Vision Cooperative Research Centre, School of Optometry, University of NSW, Sydney, NSW 2052, Australia.
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49
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Kopylova LV, Snytnikova OA, Chernyak EI, Morozov SV, Forbes MDE, Tsentalovich YP. Kinetics and mechanism of thermal decomposition of kynurenines and biomolecular conjugates: ramifications for the modification of mammalian eye lens proteins. Org Biomol Chem 2009; 7:2958-66. [PMID: 19582306 DOI: 10.1039/b903196k] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Thermal degradation reactions of kynurenine (KN), 3-hydroxykynurenine (3OHKN), and several adducts of KN, to amino acids and reduced glutathione (GSH) have been studied at physiological temperature. These compounds are all implicated in age-related mammalian eye lens cataract formation at the molecular level. The main reaction pathway for both KN and 3OHKN is deamination via beta-elimination to carboxyketoalkenes CKA and 3OHCKA. These reactions show a weak pH dependence below pH values of approximately 8, and a strong pH dependence above this value. The 3OHKN structure deaminates at a faster rate than KN. A mechanism for the deamination reaction is proposed, involving an aryl carbonyl enol/enolate ion, that is strongly supported by the structural, kinetic, and pH data. The degradation of Lys, His, Cys and GSH adducts of the CKA moieties was also studied. The Lys adduct was found to be relatively stable over 200 h at 37 degrees C, while significant degradation was observed for the other adducts. The results are discussed in terms of known post-translational modification reactions of the lens proteins and compared to incubation studies involving KN and related compounds in the presence of proteins.
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Affiliation(s)
- Lyudmila V Kopylova
- International Tomography Center SB RAS, Institutskaya 3a, Novosibirsk, 630090, Russia
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Lim LS, Tai ES, Aung T, Tay WT, Saw SM, Seielstad M, Wong TY. Relation of age-related cataract with obesity and obesity genes in an Asian population. Am J Epidemiol 2009; 169:1267-74. [PMID: 19329528 DOI: 10.1093/aje/kwp045] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Obesity shows an inconsistent association with cataract. Causality has not been established. Polymorphisms at the fat mass- and obesity-associated (FTO) locus are associated with obesity and offer an opportunity to examine the obesity-cataract association using a mendelian randomization approach. The authors conducted a population-based study among Singaporean Malay adults (2004-2006) in which nuclear, cortical, and posterior subcapsular (PSC) cataracts were assessed and defined by slit-lamp examination using Lens Opacity Classification System III. Obesity was defined as body mass index (weight (kg)/height (m)(2)) > or =30. The study included 3,000 subjects, of whom 1,339 (44.6%) had cataract (848 (28.3%) nuclear, 939 (31.3%) cortical, and 285 (9.5%) PSC). After multivariable adjustment for age, gender, diabetes, hypertension, smoking, and education, obesity was significantly associated with cortical (odds ratio (OR) = 1.31, 95% confidence interval (CI): 1.01, 1.71) and PSC (OR = 1.60, 95% CI: 1.10, 2.32) cataracts but not nuclear cataract. FTO single nucleotide polymorphisms known to be associated with obesity in this study population were not associated with cortical or PSC cataract but were associated with nuclear cataract (OR = 1.33, 95% CI: 1.11, 1.58), even in multivariate analyses controlling additionally for body mass index, diabetes, hypertension, and smoking (OR = 1.30, 95% CI: 1.08, 1.55). These results do not support a causal association between obesity and cortical or PSC cataract. The FTO gene may be involved in the pathogenesis of nuclear cataract.
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