Macular Degeneration: Dunaief JL

Glazer-Hockstein C, Dunaief JL. · No affiliation provided · Retina. · Pubmed #16395131 No free full text.

Abstract: Epidemiologic and experimental evidence suggests that blue light-blocking lenses could theoretically benefit patients with age-related macular degeneration. Clinical trials are needed to determine the effect of yellow lenses in preventing the progression of age-related macular degeneration.

Wong RW, Richa DC, Hahn P, Green WR, Dunaief JL. · F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, USA. · Retina. · Pubmed #18040235 No free full text.

Abstract: While it has been known for years that iron overload is associated with retinal degeneration in the context of ocular siderosis, intraocular hemorrhage, and the hereditary diseases aceruloplasminemia and pantothenate kinase associated neurodegeneration, recent evidence suggests that age-related macular degeneration (AMD) may also be exacerbated by retinal iron overload. In the retina, iron is necessary for normal cellular function. Iron overload, however, can cause retinal toxicity through the generation of oxygen free radicals. Histopathology of eyes with macular degeneration has shown elevated levels of iron in the retinal pigment epithelium, Bruch membrane, and within drusen, some of which was chelatable in vitro with deferoxamine. In this review, the authors summarize the evidence that iron overload may contribute to AMD pathogenesis. It is hoped that continued investigation of the role of iron and iron associated proteins in the retina will uncover clues to AMD pathogenesis and lead to new preventative or therapeutic options.

He X, Hahn P, Iacovelli J, Wong R, King C, Bhisitkul R, Massaro-Giordano M, Dunaief JL. · F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, 305 Stellar-Chance Labs, 422 Curie Boulevard, Philadelphia, PA 19104, USA. · Prog Retin Eye Res. · Pubmed #17921041 links to  free full text

Abstract: Iron is essential for many metabolic processes but can also cause damage. As a potent generator of hydroxyl radical, the most reactive of the free radicals, iron can cause considerable oxidative stress. Since iron is absorbed through diet but not excreted except through menstruation, total body iron levels buildup with age. Macular iron levels increase with age, in both men and women. This iron has the potential to contribute to retinal degeneration. Here we present an overview of the evidence suggesting that iron may contribute to retinal degenerations. Intraocular iron foreign bodies cause retinal degeneration. Retinal iron buildup resulting from hereditary iron homeostasis disorders aceruloplasminemia, Friedreich's ataxia, and panthothenate kinase-associated neurodegeneration cause retinal degeneration. Mice with targeted mutation of the iron exporter ceruloplasmin have age-dependent retinal iron overload and a resulting retinal degeneration with features of age-related macular degeneration (AMD). Post mortem retinas from patients with AMD have more iron and the iron carrier transferrin than age-matched controls. Over the past 10 years much has been learned about the intricate network of proteins involved in iron handling. Many of these, including transferrin, transferrin receptor, divalent metal transporter-1, ferritin, ferroportin, ceruloplasmin, hephaestin, iron-regulatory protein, and histocompatibility leukocyte antigen class I-like protein involved in iron homeostasis (HFE) have been found in the retina. Some of these proteins have been found in the cornea and lens as well. Levels of the iron carrier transferrin are high in the aqueous and vitreous humors. The functions of these proteins in other tissues, combined with studies on cultured ocular tissues, genetically engineered mice, and eye exams on patients with hereditary iron diseases provide clues regarding their ocular functions. Iron may play a role in a broad range of ocular diseases, including glaucoma, cataract, AMD, and conditions causing intraocular hemorrhage. While iron deficiency must be prevented, the therapeutic potential of limiting iron-induced ocular oxidative damage is high. Systemic, local, or topical iron chelation with an expanding repertoire of drugs has clinical potential.

Loh A, Hadziahmetovic M, Dunaief JL. · F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, 305 Stellar-Chance Labs, 422 Curie Boulevard, Philadelphia, PA 19104, USA. · Biochim Biophys Acta. · Pubmed #19059309 No free full text.

Abstract: BACKGROUND: Iron is necessary for life, but excess iron can be toxic to tissues. Iron is thought to damage tissues primarily by generating oxygen free radicals through the Fenton reaction. METHODS: We present an overview of the evidence supporting iron's potential contribution to a broad range of eye disease using an anatomical approach. RESULTS: Iron can be visualized in the cornea as iron lines in the normal aging cornea as well as in diseases like keratoconus and pterygium. In the lens, we present the evidence for the role of oxidative damage in cataractogenesis. Also, we review the evidence that iron may play a role in the pathogenesis of the retinal disease age-related macular degeneration. Although currently there is no direct link between excess iron and development of optic neuropathies, ferrous iron's ability to form highly reactive oxygen species may play a role in optic nerve pathology. Lastly, we discuss recent advances in prevention and therapeutics for eye disease with antioxidants and iron chelators. GENERAL SIGNIFICANCE: Iron homeostasis is important for ocular health.

Charkoudian LK, Dentchev T, Lukinova N, Wolkow N, Dunaief JL, Franz KJ. · Department of Chemistry, Duke University, Durham, NC 27708-0346, USA. · J Inorg Biochem. · Pubmed #18835041 No free full text.

Abstract: Dysregulation of localized iron homeostasis is implicated in several degenerative diseases, including Parkinson's, Alzheimer's, and age-related macular degeneration, wherein iron-mediated oxidative stress is hypothesized to contribute to cell death. Inhibiting toxic iron without altering normal metal-dependent processes presents significant challenges for standard small molecule chelating agents. We previously introduced BSIH (isonicotinic acid [2-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-benzylidene]-hydrazide) prochelators that are converted by hydrogen peroxide into SIH (salicylaldehyde isonicotinoyl hydrazone) chelating agents that inhibit iron-catalyzed hydroxyl radical generation. Here, we show that BSIH protects a cultured cell model for retinal pigment epithelium against cell death induced by hydrogen peroxide. BSIH is more stable than SIH in cell culture medium and is more protective during long-term experiments. Repetitive exposure of cells to BSIH is nontoxic, whereas SIH and desferrioxamine induce cell death after repeated exposure. Combined, our results indicate that cell protection by BSIH involves iron sequestration that occurs only when the cells are stressed by hydrogen peroxide. These findings suggest that prochelators discriminate toxic iron from healthy iron and are promising candidates for neuro- and retinal protection.

Bhisitkul RB, Winn BJ, Lee OT, Wong J, Pereira Dde S, Porco TC, He X, Hahn P, Dunaief JL. · Department of Ophthalmology, Epidemiology and Biostatistics Division, University of California at San Francisco, School of Medicine, San Francisco, California, USA. · Invest Ophthalmol Vis Sci. · Pubmed #18421081 No free full text.

Abstract: PURPOSE: To study photoreceptor apoptosis and iron migration as mechanisms of retinotoxicity in a rabbit model of subretinal hemorrhage (SRH) and to assess intravitreal triamcinolone acetonide (IVTA) for anti-apoptotic and neuroprotective effects. METHODS: In adult rabbits, eyes were studied histologically after subretinal injection of autologous blood. For comparisons of control eyes with eyes injected with 2 mg IVTA, morphometric analysis was performed with light microscopy, whereas apoptosis was quantified with terminal dUTP nick end labeling (TUNEL) and fluorescence microscopy. Localization of retinal iron was assessed with Perls' stain. RESULTS: Photoreceptor degeneration was initiated 48 hours after exposure to subretinal blood and progressed over 7 days. Increased TUNEL positivity demonstrating apoptotic cell death was associated with SRH and photoreceptor loss. VIP-Perls staining demonstrated iron in the photoreceptor layer and retinal pigment epithelium that correlated with photoreceptor degeneration. Treatment with IVTA enhanced photoreceptor cell survival by 11% at 48 hours and by 45% at 72 hours (P = 0.01) and reduced photoreceptor apoptosis ratios by 25% at 48 hours (P = 0.006). CONCLUSIONS: Photoreceptor toxicity caused by SRH occurs at least in part by apoptosis and is associated with iron migration to the photoreceptor layer. Treatment with IVTA reduced photoreceptor loss and apoptosis, indicating a neuroprotective action. Therapies to target SRH may augment anti-VEGF treatments in exudative age-related macular degeneration and other diseases of choroidal neovascularization.

Hadziahmetovic M, Dentchev T, Song Y, Haddad N, He X, Hahn P, Pratico D, Wen R, Harris ZL, Lambris JD, Beard J, Dunaief JL. · FM Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, Pennsylvania, USA. · Invest Ophthalmol Vis Sci. · Pubmed #18326691 links to  free full text

Abstract: PURPOSE: Iron is an essential element in human metabolism but also is a potent generator of oxidative damage with levels that increase with age. Several studies suggest that iron accumulation may be a factor in age-related macular degeneration (AMD). In prior studies, both iron overload and features of AMD were identified in mice deficient in the ferroxidase ceruloplasmin (Cp) and its homologue hephaestin (Heph) (double knockout, DKO). In this study, the location and timing of iron accumulation, the rate and reproducibility of retinal degeneration, and the roles of oxidative stress and complement activation were determined. METHODS: Morphologic analysis and histochemical iron detection by Perls' staining was performed on retina sections from DKO and control mice. Immunofluorescence and immunohistochemistry were performed with antibodies detecting activated complement factor C3, transferrin receptor, L-ferritin, and macrophages. Tissue iron levels were measured by atomic absorption spectrophotometry. Isoprostane F2alpha-VI, a specific marker of oxidative stress, was quantified in the tissue by gas chromatography/mass spectrometry. RESULTS: DKOs exhibited highly reproducible age-dependent iron overload, which plateaued at 6 months of age, with subsequent progressive retinal degeneration continuing to at least 12 months. The degeneration shared some features of AMD, including RPE hypertrophy and hyperplasia, photoreceptor degeneration, subretinal neovascularization, RPE lipofuscin accumulation, oxidative stress, and complement activation. CONCLUSIONS: DKOs have age-dependent iron accumulation followed by retinal degeneration modeling some of the morphologic and molecular features of AMD. Therefore, these mice are a good platform on which to test therapeutic agents for AMD, such as antioxidants, iron chelators, and antiangiogenic agents.

Metelitsina TI, Grunwald JE, DuPont JC, Ying GS, Brucker AJ, Dunaief JL. · Department of Ophthalmology, Scheie Eye Institute, School of Medicine, University of Pennsylvania, 51 North 39th Street, Philadelphia, PA 19104, USA. · Invest Ophthalmol Vis Sci. · Pubmed #18172113 links to  free full text

Abstract: PURPOSE: To investigate in a longitudinal study whether foveolar choroidal blood flow changes are associated with the development of choroidal neovascularization (CNV) in AMD. METHODS: Relative foveolar choroidal blood velocity (ChBVel), volume (ChBVol), and flow (ChBFlow) were assessed in 135 patients with AMD, at baseline and then annually with laser Doppler flowmetry. All study eyes had visual acuity of 20/40 or better and no CNV at the time of enrollment. Comparison of foveolar choroidal circulatory measurements at baseline and their change before the development of CNV was made between eyes that had CNV and those that did not. RESULTS: CNV developed in 28 eyes during the study. Baseline average foveolar ChBVol and ChBFlow in these eyes were 24% (P < 0.0001) and 20% (P = 0.0007) lower than that observed in the 165 eyes in which CNV did not develop. In the eyes with CNV, foveolar ChBVol and ChBFlow decreased by 9.6% and 11.5% before the formation of CNV, whereas in the eyes that did not, they increased by 6.7% (P = 0.006) and 2.8% (P = 0.004), respectively. Eyes with lower baseline foveolar ChBFlow were more likely (risk ratio = 3.47, 95% CI: 1.24-8.70) to show visual loss of three or more lines than were eyes with a higher baseline ChBFlow (P = 0.005). CONCLUSIONS: The development of CNV and visual loss are associated with lower choroidal circulatory parameters at baseline. In addition, the results suggest that decreases in the foveolar choroidal circulation precede the development of CNV in AMD and may play some role in its development.

Chowers I, Wong R, Dentchev T, Farkas RH, Iacovelli J, Gunatilaka TL, Medeiros NE, Presley JB, Campochiaro PA, Curcio CA, Dunaief JL, Zack DJ. · Department of Ophthalmology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel. · Invest Ophthalmol Vis Sci. · Pubmed #16639025 links to  free full text

Abstract: PURPOSE: Iron can cause oxidative stress, and elevated iron levels have been associated with several neurodegenerative diseases including age-related macular degeneration (AMD). Transferrin, an iron transport protein, is expressed at high levels in the retina. The purpose of this study was to assess transferrin involvement in AMD by determining the expression profile of transferrin in retinas with AMD compared with retinas without evidence of disease. METHODS: Postmortem retinas were obtained from AMD and non-AMD eyes. Expression of transferrin was assessed in a microarray dataset from 33 retinas of unaffected donors and 12 retinas of patients with AMD (six with neovascular AMD and six with non-neovascular AMD). Quantitative real-time RT-PCR (QPCR) was used to confirm the microarray results. Transferrin protein expression was assessed by semiquantitative Western blot analysis and immunohistochemistry. RESULTS: In comparison to unaffected retinas, mean transferrin mRNA levels, as measured by microarray analysis were elevated 3.5- and 2.1-fold in non-neovascular and neovascular AMD retinas, respectively. Semiquantitative Western blot analysis demonstrated a 2.1-fold increase in transferrin protein in AMD eyes. Immunohistochemistry showed more intense and widespread transferrin label in AMD maculas, particularly in large drusen, Müller cells, and photoreceptors. CONCLUSIONS: These data demonstrate that transferrin expression is increased in the retinas of patients with AMD relative to those of healthy control patients of comparable age. Along with previous studies that have demonstrated elevated iron levels in AMD retinas, early onset drusen formation in a patient with retinal iron overload resulting from aceruloplasminemia, and retinal degeneration with some features of macular degeneration in the iron-overloaded retinas of ceruloplasmin/hephestin knockout mice, the present study suggests that altered iron homeostasis is associated with AMD.

Dentchev T, Hahn P, Dunaief JL. · No affiliation provided · Arch Ophthalmol. · Pubmed #16344450 No free full text.

This publication has no abstract.

Dunaief JL, Richa C, Franks EP, Schultze RL, Aleman TS, Schenck JF, Zimmerman EA, Brooks DG. · F. M. Kirby Center for Molecular Ophthalmology, Philadelphia, Pennsylvania, USA. · Ophthalmology. · Pubmed #15882908 No free full text.

Abstract: PURPOSE: To provide the first ophthalmic case report of a Caucasian patient with the rare autosomal recessive disease aceruloplasminemia, which results in iron overload in the retina, brain, and pancreas. DESIGN: Single observational case report. METHODS: Perls' staining of a conjunctival biopsy was used to detect elevated iron levels in the conjunctival epithelium. Fundus photography, fluorescein angiography, and electroretinography were used to document retinal appearance and function. RESULTS: Unlike a report of a Japanese patient with aceruloplasminemia, who had midperipheral retinal pigment epithelium (RPE) cell atrophy and yellowish discoloration of the fundus, our Caucasian patient had a maculopathy. Beginning at age 47, he had development and progression of multiple subretinal yellowish-white lesions and RPE cell atrophy. To confirm tissue iron overload in our patient, we took the novel approach of a conjunctival biopsy, which showed Perls' Prussian blue-positive epithelial cells. CONCLUSIONS: Given our recent finding of elevated iron levels in the RPE of patients with age-related macular degeneration (AMD), it is interesting that retinal iron overload in aceruloplasminemia is associated with a maculopathy that clinically resembles AMD. This finding supports the hypothesis that retinal iron homeostasis is essential for normal retinal function. Disruption of iron homeostasis could contribute to the pathogenesis of AMD.

Howes KA, Liu Y, Dunaief JL, Milam A, Frederick JM, Marks A, Baehr W. · Moran Eye Center, University of Utah Health Science Center, Salt Lake City, UT 84112, USA. · Invest Ophthalmol Vis Sci. · Pubmed #15452081 links to  free full text

Abstract: PURPOSE: Advanced glycation end products (AGE) exacerbate disease progression through two general mechanisms: modifying molecules and forming nondegradable aggregates, thus impairing normal cellular/tissue functions, and altering cellular function directly through receptor-mediated activation. In the present study receptor for AGE (RAGE)-mediated cellular activation was evaluated in the etiology of human retinal aging and disease. METHODS: The maculas of human donor retinas from normal eyes and eyes with early age-related macular degeneration (AMD) and advanced AMD with geographic atrophy (GA) were assayed for AGE and RAGE by immunocytochemistry. Cultured ARPE-19 cells were challenged with known ligands for RAGE, AGE, and S100B, to test for activation capacity. Immunocytochemistry, real-time RT-PCR, immunoblot analysis, and the TUNEL assay were used to determine the consequences of RPE cellular activation. RESULTS: Little to no immunolabeling for AGE or RAGE was found in photoreceptor and RPE cell layers in normal retinas. However, when small drusen were present, AGE and RAGE were identified in the RPE or both the RPE and photoreceptors. In early AMD and GA, the RPE and remnant photoreceptor cells showed intense AGE and RAGE immunolabeling. Both AGE and S100B activated cultured RPE cells, as revealed by upregulated expression of RAGE, NFkappaB nuclear translocation, and apoptotic cell death. CONCLUSIONS: Immunolocalization of RAGE in RPE and photoreceptors coincided with AGE deposits and macular disease in aged, early AMD, and GA retinas. Further, AGE stimulated RAGE-mediated activation of cultured ARPE-19 cells in a dose-dependent fashion. AGE accumulation, as occurs with normal aging and in disease, may induce receptor-mediated activation of RPE/photoreceptor cells, contributing to disease progression in the aging human retinas.

Hahn P, Qian Y, Dentchev T, Chen L, Beard J, Harris ZL, Dunaief JL. · The F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA. · Proc Natl Acad Sci U S A. · Pubmed #15365174 links to  free full text

Abstract: Mechanisms of brain and retinal iron homeostasis have become subjects of increased interest after the discovery of elevated iron levels in brains of patients with Alzheimer's disease and retinas of patients with age-related macular degeneration. To determine whether the ferroxidase ceruloplasmin (Cp) and its homolog hephaestin (Heph) are important for retinal iron homeostasis, we studied retinas from mice deficient in Cp and/or Heph. In normal mice, Cp and Heph localize to Müller glia and retinal pigment epithelium, a blood-brain barrier. Mice deficient in both Cp and Heph, but not each individually, had a striking, age-dependent increase in retinal pigment epithelium and retinal iron. The iron storage protein ferritin was also increased in Cp-/-Heph-/Y retinas. After retinal iron levels had increased, Cp-/-Heph-/Y mice had age-dependent retinal pigment epithelium hypertrophy, hyperplasia and death, photoreceptor degeneration, and subretinal neovascularization, providing a model of some features of the human retinal diseases aceruloplasminemia and age-related macular degeneration. This pathology indicates that Cp and Heph are critical for CNS iron homeostasis and that loss of Cp and Heph in the mouse leads to age-dependent retinal neurodegeneration, providing a model that can be used to test the therapeutic efficacy of iron chelators and antiangiogenic agents.

Hahn P, Dentchev T, Qian Y, Rouault T, Harris ZL, Dunaief JL. · F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Philadelphia, PA, USA. · Mol Vis. · Pubmed #15354085 links to  free full text

Abstract: PURPOSE: CNS iron accumulation is associated with several neurodegenerative diseases, including age-related macular degeneration. Intracellular overload of free iron is prevented, in part, by the iron export protein, ferroportin, and the iron storage protein, ferritin. The purpose of this study was to assess retinal localization and regulation of ferroportin and ferritin. METHODS: Normal murine retinas were analyzed by immunohistochemistry to localize ferroportin, cytosolic ferritin, and mitochondrial ferritin, with double-labeling using cell-specific markers to identify cell types. Retinas deficient in the ferroxidases, ceruloplasmin and hephaestin, accumulate iron in their retinas and RPE, while retinas deficient in iron regulatory proteins (IRPs) lack the ability to regulate several proteins involved in iron metabolism; retinas from these knockout mice along with their age matched wild type littermates were also examined to study regulation of ferritin and ferroportin. To enable visualization of label in the retinal pigment epithelial cells, sections from pigmented mice were bleached with H2O2 prior to IHC, a novel use of this technique for study of the RPE. RESULTS: In normal retinas, cytosolic ferritins were found predominantly in rod bipolar cells and photoreceptors. Ferroportin was found in RPE and Müller cells. Iron accumulation in mice deficient in ceruloplasmin and hephaestin was associated with upregulation of ferritin and ferroportin. Mice deficient in IRPs showed upregulation of ferritin and ferroportin, likely because of their inability to repress translation. CONCLUSIONS: Normal retinas contain ferritin and ferroportin, whose levels are regulated by iron-responsive, iron regulatory proteins. Ferroportin colocalizes with ceruloplasmin and hephaestin to RPE and Müller cells, supporting a potential cooperation between these ferroxidases and the iron exporter. Cytosolic ferritin accumulates in rod bipolar synaptic terminals, suggesting that ferritin may be involved in axonal iron transport. Mitochondrial ferritin increases with iron accumulation, suggesting a role in iron storage.

Chen L, Wu W, Dentchev T, Wong R, Dunaief JL. · F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA. · Exp Eye Res. · Pubmed #15325575 No free full text.

Abstract: Oxidative stress plays a role in human age-related macular degeneration and in the light damage model of retinal degeneration. Metallothionein (MT), an antioxidant, has been reported to protect retinal pigment epithelial cells against apoptosis and oxidative stress. The purpose of this study was to evaluate changes in MT expression level and retinal localization following light damage. To accomplish this, Balb/c mice were exposed to cool white fluorescent light (10,000 lx) for 7 hr. In three independent experiments, at several intervals after the light injury, retinal MTs were studied at the protein level by immunohistochemistry (IHC) and Western analysis, and at the mRNA level by quantitative PCR with isoform-specific primers. Western analysis and IHC indicated an increase in metallothionein protein following light damage. MT localized to the retinal pigment epithelium and several layers of neural retina. Quantitative PCR identified the expression of MT I-III isoforms, not the MT IV isoform in the mouse retina, and, following light damage, showed increased expression of retinal MT-I and MT-II mRNAs by 8- and 22-fold, respectively. Increased expression of the antioxidant MT in the light damaged mouse retina suggests that upregulation of MT is an important acute retinal response to photo-oxidative stress.

Chen L, Wu W, Dentchev T, Zeng Y, Wang J, Tsui I, Tobias JW, Bennett J, Baldwin D, Dunaief JL. · F.M. Kirby Center for Molecular Ophthalmology Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA. · Exp Eye Res. · Pubmed #15325571 No free full text.

Abstract: Oxidative stress plays a role in the light damage model of retinal degeneration as well as in age-related macular degeneration. The purpose of this study is to identify retinal genes induced by acute photo-oxidative stress, which may function as mediators of apoptosis or as survival factors. To accomplish this, Balb/c mice were exposed to bright cool white fluorescent light for 7 hr. Retinas were then isolated for total RNA preparation followed by Affymetrix DNA microarray analysis to compare gene expression in light damaged mice to unexposed controls. Three independent light damage experiments were carried out and statistical filters were applied to detect genes with expression changes averaging at least two-fold. Quantitative PCR was carried out to confirm altered gene expression. Seventy genes were upregulated at least two-fold immediately following light damage. QPCR confirmed upregulation of all 10 genes tested. The upregulated genes fall into several categories including antioxidants: ceruloplasmin, metallothionein, and heme oxygenase; antiapoptotic gene: bag3, chloride channels: clic1 and clic4; transcription factors: c-fos, fra1, junB, stat1, krox-24 and c/ebp; secreted signaling molecules: chitinase 3-like protein 1 and osteopontin; inflammation related genes: MCP-1 and ICAM1 and others. Upregulation of five interferon-gamma responsive genes suggests elevated interferon levels after light damage. Upregulation of three components of the AP-1 transcription factor is consistent with previous evidence implicating AP-1 in light damage pathogenesis. Four copper or iron binding proteins were upregulated, suggesting that photo-oxidative stress may affect metal homeostasis. The genes found upregulated by light damage may affect the survival of photoreceptors subjected to photo-oxidative stress.

King A, Gottlieb E, Brooks DG, Murphy MP, Dunaief JL. · F.M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA. · Photochem Photobiol. · Pubmed #15191057 No free full text.

Abstract: Throughout the lifetime of an individual, light is focused onto the retina. The resulting photooxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration (AMD), the leading cause of legal blindness in the developed world, involves oxidative stress and death of the retinal pigment epithelium (RPE) followed by death of the overlying photoreceptors. Evidence suggests that damage due to exposure to light plays a role in AMD and other age-related eye diseases. In this work a system for light-induced damage and death of the RPE, based on the human ARPE-19 cell line, was used. Induction of mitochondria-derived reactive oxygen species (ROS) is shown to play a critical role in the death of cells exposed to short-wavelength blue light (425 +/- 20 nm). ROS and cell death are blocked either by inhibiting the mitochondrial electron transport chain or by mitochondria-specific antioxidants. These results show that mitochondria are an important source of toxic oxygen radicals in blue light-exposed RPE cells and may indicate new approaches for treating AMD using mitochondria-targeted antioxidants.

Hahn P, Milam AH, Dunaief JL. · F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA. · Arch Ophthalmol. · Pubmed #12912686 No free full text.

Abstract: OBJECTIVE: To investigate whether iron is involved in the pathogenesis of age-related macular degeneration (AMD). METHODS: Postmortem AMD-affected (nonexudative or exudative) and healthy maculas were studied using the 3,3'-diaminobenzidine-enhanced Perls Prussian blue stain. The Perls Prussian blue stain was quantified by computer-assisted analysis of digital images. To determine whether the iron was chelatable, sections treated with the iron chelator deferoxamine were compared with adjacent, nonchelated sections. RESULTS: Compared with healthy maculas, AMD-affected maculas had statistically significant increases in the total iron level. Some of this iron was chelatable. The iron was present in retinal pigment epithelium and Bruch's membrane in maculas from patients who had drusen only, geographic atrophy, and exudative AMD in pathologic areas and, occasionally, in relatively healthy areas. CONCLUSIONS: Oxidative stress has been implicated in the pathogenesis of AMD by the Age-Related Eye Disease Study. Increased concentrations of iron, which generate highly reactive hydroxyl radicals via the Fenton reaction, may induce oxidative stress in the macula and lead to AMD. As the increased iron concentrations in AMD-affected eyes consist in part of a chelatable iron pool, treatment of patients who have AMD with iron chelators might be considered a potential therapy. While there are, as yet, no clinical data indicating that the treatment of patients who have AMD with iron chelators is beneficial, data presented herein indicate that further investigation of iron concentrations in postmortem tissues and the mechanisms of iron transport in the retina is warranted.

Dentchev T, Milam AH, Lee VM, Trojanowski JQ, Dunaief JL. · F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Philadelphia, PA, USA. · Mol Vis. · Pubmed #12764254 links to  free full text

Abstract: PURPOSE: Age-related macular degeneration (AMD) is the most common cause of irreversible vision loss in the elderly. Increased understanding of the pathogenesis is necessary. Amyloid-beta (Abeta), a major extracellular deposit in Alzheimer's disease plaques, has recently been found in drusen, the hallmark extracellular deposit in AMD. The goal of this study was to characterize the distribution and frequency of Abeta deposits in drusen from AMD and normal post mortem human retinas to gain additional insight about the potential role of Abeta in AMD patho genesis. METHODS: Immunocytochemistry was performed with three Abeta antibodies on sections from 9 normal and 9 AMD (3 early, 3 geographic atrophy, 3 exudative AMD) retinas. Five sections from each eye were evaluated. Abeta positive deposits in drusen were identified using epifluorescence and confocal microscopy. Antibodies were pre-adsorbed with Abeta peptide to verify specificity. Some sections were stained with PAS-hematoxylin to aid in evaluation of morphology. RESULTS: To test and optimize immunocytochemistry, Abeta was detected in amyloid plaques from Alzheimer's brains. Abeta label was blocked by pre-adsorption of antibody with Abeta peptide, verifying specificity. Four of the 9 AMD retinas and none of the 9 normal retinas had Abeta positive drusen. Two of the early AMD eyes had a few A[beta] positive drusen, each with a few Abeta-containing vesicles, and 2 of the geographic atrophy (GA) eyes had many Abeta positive drusen with many Abeta containing vesicles. CONCLUSIONS: Abeta was present in 4 of 9 AMD eyes. Within these eyes, Abeta localized to a subset of drusen. None of the 9 normal eyes surveyed, some of which had small drusen, were A beta positive. Abetapositive vesicles were most numerous in GA eyes at the edges of atrophy, the region at risk for further degeneration. These results suggest that Abeta in drusen correlates with the location of degenerating photoreceptors and retinal pigment epithelium (RPE) cells. Further work will be necessary to determine whether Abeta deposition in drusen may contribute to or result from retinal degeneration.

Chen L, Dentchev T, Wong R, Hahn P, Wen R, Bennett J, Dunaief JL. · F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA, USA. · Mol Vis. · Pubmed #12724641 links to  free full text

Abstract: PURPOSE: Oxidative stress plays a role in the photic injury model of retinal degeneration and in age-related macular degeneration. Our preliminary microarray analysis of retinal gene expression upon photic injury suggested increased expression of ceruloplasmin, a ferroxidase that could reduce retinal oxidative stress. Patients with acerul oplasminemia have retinal degeneration, indicating that ceruloplasmin is necessary for maintenance of retinal health. The purpose of this study was to determine whether retinal ceruloplasmin is upregulated following photo-oxidation, to localize ceruloplasmin protein, and to determine which ceruloplasmin isoform is present in the retina. METHODS: Balb/c mice were exposed to bright white light for seven hours. TUNEL labeling was used to detect photoreceptor apoptosis. At several intervals after the light injury, retinal ceruloplasmin was studied by quantitative PCR, immunohistochemistry, and western analysis. Expression of the secreted and expression of the membrane-anchored glycosyl phosphatidyl inositol (GPI) linked forms of ceruloplasmin were assesed in rat retina using primers specific for each form. Vitreous ceruloplasmin was detected by immunohistochemistry in Balb/c mouse eyes and by western analysis of aspirated vitreous from post-mortem human eyes. RESULTS: Retinal ceruloplasmin mRNA was upregulated eight-fold following photic injury. Ceruloplasmin protein was detected throughout normal retinas by immunohistochemistry, with a specific increase in Muller cell labeling following photic injury. Western analysis confirmed an increase in ceruloplasmin protein following photic injury and revealed eight-fold more ceruloplasmin protein in normal retina than in brain. The mRNAs for both the secreted and GPI linked forms of ceruloplasmin were detected by RT-PCR in the retina. Ceruloplasmin protein was detected by western analysis of normal human vitreous and was increased in mouse vitreous following photic injury. CONCLUSIONS: Ceruloplasmin, a retinal ferroxidase, is upregulated at the mRNA and protein levels upon light damage. The increased protein is primarily in Muller cells. Ceruloplasmin is considerably more abundant in retina than in brain. The retina expresses both the GPI-linked and secreted forms of ceruloplasmin, and since vitreous ceruloplasmin increases following photic injury, some of the retinal ceruloplasmin may be secreted into the vitreous. Ceruloplasmin may protect the retina from oxidative stress by decreasing the amount of ferrous iron available to produce reactive oxygen species.

Dunaief JL, Dentchev T, Ying GS, Milam AH. · 305 Stellar Chance Labs, University of Pennsylvania, Philadelphia, PA 19104, USA. · Arch Ophthalmol. · Pubmed #12427055 No free full text.

Abstract: OBJECTIVE: To investigate apoptosis in human age-related macular degeneration (AMD). METHODS: Postmortem retinas with AMD and normal retinas were studied by terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) to identify dying cells, and by immunocytochemistry with cell-specific antibodies to identify rods and cones. Sections were also labeled for Fas, a cell surface receptor that triggers apoptosis in other cell types. The maculas with AMD had geographic atrophy (GA) or exudative AMD. RESULTS: Maculas with AMD had statistically significant increases in TUNEL-positive cells in the inner choroid, retinal pigment epithelium (RPE), photoreceptors, and inner nuclear layers compared with normal retinas. In eyes with GA, TUNEL-positive rod and RPE cell nuclei were present near edges of RPE atrophy. Photoreceptors in the maculas of eyes with AMD were strongly Fas-positive, while normal photoreceptors were only weakly labeled. CONCLUSIONS: Evidence in this study suggests that in human AMD, RPE, photoreceptors, and inner nuclear layer cells die by apoptosis. Most TUNEL-positive RPE and photoreceptor cells were at edges of atrophy, correlating with clinically observed expansion of atrophic areas with vision loss in patients with GA. Increased Fas labeling in AMD photoreceptors indicates that the Fas/Fas ligand system may be involved in photoreceptor apoptosis. This information is essential for developing rational therapy for AMD.

Dunaief JL. · F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, University of Pennsylvania, 305 Stellar-Chance Labs, 422 Curie Boulevard, Philadelphia, PA 19104, USA. · Invest Ophthalmol Vis Sci. · Pubmed #17065470 links to  free full text

Abstract: Iron is a potent generator of oxidative damage whose levels increase with age, potentially exacerbating age-related diseases. Several lines of evidence suggest that iron accumulation may be a factor in age-related macular degeneration (AMD). AMD retinas have more iron within the photoreceptors, RPE, and drusen than do age-matched control retinas. Accelerated AMD-like maculopathy develops in patients with retinal iron overload from the hereditary disease aceruloplasminemia. Mice with retinal iron overload resulting from knockout of ceruloplasmin and its homologue hephaestin exhibit retinal degeneration with some features of AMD, including subretinal neovascularization, accumulation of RPE lipofuscin and sub-RPE deposits, and RPE/photoreceptor death. Increased understanding of the mechanisms of retinal iron homeostasis may help in the development of therapies to prevent iron overload. For example, herein it is shown that one regulator of systemic iron homeostasis, HFE, is expressed in the RPE. Thus, patients with the common disease hereditary hemochromatosis, which is often caused by an HFE mutation, may have retinal iron overload predisposing to AMD. Preliminary data suggest that iron chelation can reduce RPE iron overload in mice and protect them from degeneration, suggesting that iron-binding drugs may one day prove useful in reducing RPE oxidative stress and decreasing the risk of AMD progression.