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Gilbert R, Peto T, Lengyel I, Emri E. Zinc Nutrition and Inflammation in the Aging Retina. Mol Nutr Food Res 2019; 63:e1801049. [PMID: 31148351 DOI: 10.1002/mnfr.201801049] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 04/18/2019] [Indexed: 12/16/2022]
Abstract
Zinc is an essential nutrient for human health. It plays key roles in maintaining protein structure and stability, serves as catalytic factor for many enzymes, and regulates diverse fundamental cellular processes. Zinc is important in affecting signal transduction and, in particular, in the development and integrity of the immune system, where it affects both innate and adaptive immune responses. The eye, especially the retina-choroid complex, has an unusually high concentration of zinc compared to other tissues. The highest amount of zinc is concentrated in the retinal pigment epithelium (RPE) (RPE-choroid, 292 ± 98.5 µg g-1 dry tissue), followed by the retina (123 ± 62.2 µg g-1 dry tissue). The interplay between zinc and inflammation has been explored in other parts of the body but, so far, has not been extensively researched in the eye. Several lines of evidence suggest that ocular zinc concentration decreases with age, especially in the context of age-related disease. Thus, a hypothesis that retinal function could be modulated by zinc nutrition is proposed, and subsequently trialled clinically. In this review, the distribution and the potential role of zinc in the retina-choroid complex is outlined, especially in relation to inflammation and immunity, and the clinical studies to date are summarized.
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Affiliation(s)
- Rosie Gilbert
- Moorfields Eye Hospital NHS Foundation Trust, City Road, London, EC1V 2PD, UK.,UCL Institute of Ophthalmology, Bath Street, London, EC1V 2EL, UK
| | - Tunde Peto
- School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Ireland
| | - Imre Lengyel
- UCL Institute of Ophthalmology, Bath Street, London, EC1V 2EL, UK.,School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Ireland
| | - Eszter Emri
- School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, Ireland
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Zarfoss MK, Klauss G, Newkirk K, Kiupel M, Jones Y, Colitz CMH, Dubielzig RR. Uveal Spindle Cell Tumor of Blue-Eyed Dogs: An Immunohistochemical Study. Vet Pathol 2016; 44:276-84. [PMID: 17491068 DOI: 10.1354/vp.44-3-276] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Immunohistochemical techniques were used to investigate the origin of a spindle cell tumor in the anterior uveal tract of dogs and the influence of ultraviolet radiation on the development of this tumor. Thirteen tumors were identified from the 4,007 canine ocular samples examined at the Comparative Ocular Pathology Laboratory of Wisconsin between 1978 and 2005. Siberian Husky and Siberian Husky mix dogs were overrepresented (10/13 dogs, overall median age 10 years). Light microscopic evaluation (all dogs) and electron microscopy (2 dogs) were performed. Immunohistochemical staining included alpha-smooth muscle actin (SMA), vimentin, S-100, desmin, glial fibrillary acidic protein (GFAP), Melan A, microphthalmic transcription factor (MITF-1), protein gene product 9.5 (PGP 9.5), laminin, gadd45, p53, proliferating cell nuclear antigen (PCNA), anti-UVssDNA (antibody for detection of (6–4)-dipyrimidine photoproducts), and telomerase reverse transcriptase (TERT). All tumors occurred in the iris with or without ciliary body involvement and were composed of spindle cells arranged in fascicles and whorls (variable Antoni A and B behavior). All tumors were positive when immunostained for vimentin and S-100. Nine of 13 tumors exhibited GFAP immunopositivity. All tumors were negative for SMA, desmin, Melan A, and MITF-1. Tumors were variably positive for PGP 9.5, laminin, gadd45, p53, PCNA, anti-UVssDNA, and TERT. Electron microscopy revealed intermittent basal laminae between cells. These tumors are morphologically and immunohistochemically most consistent with schwannoma. The relationship between spindle cell tumors of the anterior uvea of dogs, altered neural crest, blue iris color, and ultraviolet radiation has not yet been fully elucidated.
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Affiliation(s)
- M K Zarfoss
- Department of Pathobiological Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
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Gonzalez-Iglesias H, Alvarez L, García M, Petrash C, Sanz-Medel A, Coca-Prados M. Metallothioneins (MTs) in the human eye: a perspective article on the zinc-MT redox cycle. Metallomics 2014; 6:201-8. [PMID: 24419560 DOI: 10.1039/c3mt00298e] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Metallothioneins (MTs) are zinc-ion-binding proteins with a wide range of functions, among which are neuroprotection, maintenance of cellular zinc homeostasis, and defense against oxidative damage and inflammation. The human eye is enriched in MTs, and multiple isoforms may contribute to distinct antioxidant defense mechanisms in various ocular tissues. Zinc is a main regulator of MT gene and protein expression, and we recently applied bioanalytical techniques to address key questions on its relationship with MTs, including the stoichiometry of zinc-MT, the fate of zinc tracers ((nat)Zn and (68)Zn) in MTs during activation by exogenous zinc and cytokines, and the concentration of MTs in human ocular cells. We found that exogenously introduced zinc induced a potent de novo synthesis of MTs as well as a strong inhibition of pro-inflammatory cytokines. Zinc and cytokines also promote a stoichiometric transition of the MT complex from Zn6Cu1-MT to Zn7-MT, suggesting that MTs may interact more effectively with reactive oxygen species to decrease potential oxidative damage. Levels of MTs decrease with aging and disease, which may result in zinc release that is potentially cytotoxic. This state is also observed with increased oxidative stress and inflammation, suggesting that the antioxidant function of MTs has been impaired. In this review we propose a working model of the "zinc-metallothionein redox cycle" to regenerate and enhance the antioxidant function of MTs with the aim of combating the progression of these disease states.
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Affiliation(s)
- Héctor Gonzalez-Iglesias
- Fundación de Investigación Oftalmológica, Instituto Oftalmológico Fernández-Vega, Avda. Dres. Fernandez-Vega, 34, 33012, Oviedo, Spain.
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Biesemeier A, Julien S, Kokkinou D, Schraermeyer U, Eibl O. A low zinc diet leads to loss of Zn in melanosomes of the RPE but not in melanosomes of the choroidal melanocytes. Metallomics 2012; 4:323-32. [DOI: 10.1039/c2mt00187j] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Julien S, Biesemeier A, Kokkinou D, Eibl O, Schraermeyer U. Zinc deficiency leads to lipofuscin accumulation in the retinal pigment epithelium of pigmented rats. PLoS One 2011; 6:e29245. [PMID: 22216222 PMCID: PMC3245262 DOI: 10.1371/journal.pone.0029245] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 11/23/2011] [Indexed: 11/19/2022] Open
Abstract
Background Age-related macular degeneration (AMD) is associated with lipofuscin accumulation whereas the content of melanosomes decreases. Melanosomes are the main storage of zinc in the pigmented tissues. Since the elderly population, as the most affected group for AMD, is prone to zinc deficit, we investigated the chemical and ultrastructural effects of zinc deficiency in pigmented rat eyes after a six-month zinc penury diet. Methodology/Principal Findings Adult Long Evans (LE) rats were investigated. The control animals were fed with a normal alimentation whereas the zinc-deficiency rats (ZD-LE) were fed with a zinc deficient diet for six months. Quantitative Energy Dispersive X-ray (EDX) microanalysis yielded the zinc mole fractions of melanosomes in the retinal pigment epithelium (RPE). The lateral resolution of the analysis was 100 nm. The zinc mole fractions of melanosomes were significantly smaller in the RPE of ZD-LE rats as compared to the LE control rats. Light, fluorescence and electron microscopy, as well as immunohistochemistry were performed. The numbers of lipofuscin granules in the RPE and of infiltrated cells (Ø>3 µm) found in the choroid were quantified. The number of lipofuscin granules significantly increased in ZD-LE as compared to control rats. Infiltrated cells bigger than 3 µm were only detected in the choroid of ZD-LE animals. Moreover, the thickness of the Bruch's membrane of ZD-LE rats varied between 0.4–3 µm and thin, rangy ED1 positive macrophages were found attached at these sites of Bruch's membrane or even inside it. Conclusions/Significance In pigmented rats, zinc deficiency yielded an accumulation of lipofuscin in the RPE and of large pigmented macrophages in the choroids as well as the appearance of thin, rangy macrophages at Bruch's membrane. Moreover, we showed that a zinc diet reduced the zinc mole fraction of melanosomes in the RPE and modulated the thickness of the Bruch's membrane.
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Affiliation(s)
- Sylvie Julien
- Section of Experimental Vitreoretinal Surgery, Centre of Ophthalmology, Institute for Ophthalmic Research, Tuebingen, Germany
| | - Antje Biesemeier
- Section of Experimental Vitreoretinal Surgery, Centre of Ophthalmology, Institute for Ophthalmic Research, Tuebingen, Germany
| | - Despina Kokkinou
- Section of Experimental Vitreoretinal Surgery, Centre of Ophthalmology, Institute for Ophthalmic Research, Tuebingen, Germany
| | - Oliver Eibl
- Institute of Applied Physics, Eberhard Karls University of Tuebingen, Tuebingen, Germany
| | - Ulrich Schraermeyer
- Section of Experimental Vitreoretinal Surgery, Centre of Ophthalmology, Institute for Ophthalmic Research, Tuebingen, Germany
- * E-mail:
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Rousselet E, Martelli A, Chevallet M, Diemer H, Van Dorsselaer A, Rabilloud T, Moulis JM. Zinc adaptation and resistance to cadmium toxicity in mammalian cells: molecular insight by proteomic analysis. Proteomics 2008; 8:2244-55. [PMID: 18452231 DOI: 10.1002/pmic.200701067] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
To identify proteins involved in cellular adaptive responses to zinc, a comparative proteome analysis between a previously developed high zinc- and cadmium-resistant human epithelial cell line (high zinc-resistant HeLa cells, HZR) and the parental HeLa cells has been carried out. Differentially produced proteins included cochaperones, proteins associated with oxido-reductase activities, and ubiquitin. Biochemical pathways to which these proteins belong were probed for their involvement in the resistance of both cell lines against cadmium toxicity. Among ER stressors, thapsigargin sensitized HZR cells, but not HeLa cells, to cadmium toxicity more acutely than tunicamycin, implying that these cells heavily relied on proper intracellular calcium distribution. The similar sensitivity of both HeLa and HZR cells to inhibitors of the proteasome, such as MG-132 or lactacystin, excluded improved proteasome activity as a mechanism associated with zinc adaptation of HZR cells. The enzyme 4-hydroxyphenylpyruvate dioxygenase (HPPD) was overproduced in HZR cells as compared to HeLa cells. It transforms HPP to homogentisate in the second step of tyrosine catabolism. Inhibition of HPPD decreased the resistance of HZR cells against cadmium, but not that of HeLa cells, suggesting that adaptation to zinc overload and increased HPP removal are linked in HZR cells.
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Affiliation(s)
- Estelle Rousselet
- CEA, DSV, IRTSV, Laboratoire de Chimie et Biologie des Métaux, Grenoble, France
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Biesemeier A, Kokkinou D, Julien S, Heiduschka P, Berneburg M, Bartz-Schmidt KU, Schraermeyer U. UV-A induced oxidative stress is more prominent in naturally pigmented aged human RPE cells compared to non-pigmented human RPE cells independent of zinc treatment. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2007; 90:113-20. [PMID: 18203614 DOI: 10.1016/j.jphotobiol.2007.11.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Revised: 11/23/2007] [Accepted: 11/23/2007] [Indexed: 11/29/2022]
Abstract
To investigate the effects of zinc supplementation on human amelanotic (ARPE-19) and native pigmented retinal pigment epithelial cells (hRPE) under normal light conditions and after ultraviolet A light exposure. hRPE cells, containing both melanin and lipofuscin granules, were prepared from human donor eyes of 60-70 year old patients. Cells of the amelanotic ARPE-19 cell line and pigmented hRPE cells were treated with zinc chloride and subjected to oxidative stress by UV-A irradiation. Intracellular H(2)O(2) formation was measured using a fluorescence oxidation assay. Additionally, apoptosis and viability assays were performed. Control cells were treated identically except for irradiation and zinc supplementation. Under normal light conditions, zinc treated hRPE cells produced less H(2)O(2) than unsupplemented hRPE cells. Viability and apoptosis events did not change. After UV-A irradiation, ARPE and hRPE cells were greatly impaired in all tests performed compared to the non-irradiated controls. No differences were found after zinc supplementation. hRPE cells showed a higher apoptosis and mortality rate than non-pigmented cells when stressed by UV-A light. ARPE cells never showed any zinc related effects. In contrast, without irradiation, zinc supplementation reduced H(2)O(2) production in pigmented hRPE cells slightly. We did not find any zinc effect in irradiated hRPE cells. After UV light exposure, pigmented cells showed a higher apoptosis and mortality than cells lacking any pigmentation. We conclude that cells with pigmentation consisting of melanin and lipofuscin granules have more prooxidative than antioxidative capacity when stressed by UV light exposure compared to cells lacking any pigmentation.
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Affiliation(s)
- Antje Biesemeier
- Section of Experimental Vitreoretinal Surgery, University Eye Hospital Tuebingen, Schleichstr. 12/1, 72076 Tuebingen, Germany.
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Abstract
Melanin is the main chromophore of the human iris. This pigment is considered to be the most important factor that determines the color of the irides. Previous studies based mainly on chemical degradation methods showed that brown irides contain more melanin than blue ones. In our study, we used electron spin resonance (ESR) spectroscopy to detect and characterize melanin free radical centers and associated iron in human irides. Based on this method, we determined the amount of melanin in the irides and the relative content of iron in iridial melanin as a function of their color, shade, and the age of their donors. Chemical degradation of iridial homogenates enabled us to characterize the structure of eumelanin and determine the content of pheomelanin present in human and bovine irides. The ESR amplitude, the normalized intensity obtained by double integration of the ESR signal of melanin, and the content of the pigment in the irides depended on color and shade of the eyes being 40% higher in the brown group of the irides compared with all other groups. On the other hand, the relative iron content normalized to the melanin content in light blue irides showed a small decrease with age of donors. Melanin in human and bovine irides was mostly composed of eumelanin, and pheomelanin content was of the order of a few percent. Although some differences in the structure of eumelanin present in the human and bovine irides are possible, the results obtained in this study suggest that human irides contain eumelanin with very similar chemical properties.
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Affiliation(s)
- Albert R Wielgus
- Department of Biophysics, Faculty of Biotechnology, Jagiellonian University, ul. Gronostajowa 7, 30-387 Krakow, Poland
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Kokkinou D, Kasper HU, Schwarz T, Bartz-Schmidt KU, Schraermeyer U. Zinc uptake and storage: the role of fundus pigmentation. Graefes Arch Clin Exp Ophthalmol 2005; 243:1050-5. [PMID: 15906061 DOI: 10.1007/s00417-005-1197-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Accepted: 02/23/2005] [Indexed: 10/25/2022] Open
Abstract
BACKGROUND Age-related macular degeneration (AMD) is associated with lower melanin pigmentation and is more prevalent among the elderly Caucasian population than among Africans. A correlation between light iris colour, fundus pigmentation and the incidence of AMD is reported. Moreover, melanin represents the main storage of zinc in the eye. Zinc enhances antioxidant capacity through its function as a cofactor of important enzymes or by influencing gene expression of regulatory elements in the eye. In this study, we investigated the uptake and storage of zinc in the human choroid/retinal pigment epithelium (RPE) complexes in dependence on the fundus pigmentation as judged by the iris colour. MATERIAL AND METHODS Choroid/RPE complexes of blue and brown human eyes were used. Tissues without any substitution served as controls. Specimens from choroid/RPE complexes were incubated with 100 microM zinc chloride for 24 h. After incubation, pieces of the complexes were stored to investigate the uptake of zinc. The rest of the tissues were kept for 3 and 7 days in culture medium (DMEM) for storage examination. The concentration of zinc was measured by inductively coupled plasma mass spectrometry. RESULTS After 24 h of zinc treatment the concentration of zinc in the choroid/RPE complexes of blue eyes was not significantly increased. The concentration of zinc in highly pigmented tissues (brown eyes) was increased by the factor 5.1 after 24 h and remained at high levels after 3 days (factor 4.4) and 7 days (factor 2.8). CONCLUSIONS Zinc uptake in the choroid/RPE complex correlates to the iris colour. Alterations of the degree of iris pigmentation result in differences of zinc uptake and storage in the choroids. A potential protective role of zinc may be more prominent in dark- than in light-coloured eyes.
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Affiliation(s)
- Despina Kokkinou
- Section of Experimental Vitreoretinal Surgery, University of Tuebingen, Schleichstrasse 12/1, 72076, Tuebingen, Germany.
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