Role of Ocular Melanin in Ophthalmic Physiology and Pathology<sup>†</sup>

Hu, Dan‐Ning; Simon, John D.; Sarna, Tadeusz

doi:10.1111/j.1751-1097.2008.00316.x

Cited by 211 publications

(189 citation statements)

References 65 publications

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“…10,11 This observation is consistent with studies that indicate that pheomelanin is more pro-oxidant than eumelanin. [12][13][14][15][16][17] Determining the quantum efficiency for oxygen activation by these different melanins, however, requires knowing their relative absorption coefficient.…”

Section: Introductionsupporting

confidence: 81%

“…The relative amounts of pheomelanin and eumelanin in tissue varies, and the factors controlling their presence have become increasingly important to understand because the epidemiology of skin and ocular cancers suggests that increasing relative proportions of pheomelanin correlates with an increased risk factor for these diseases. 10,11,48 These epidemiological observations have spurred a significant effort aimed at determining whether pheomelanin plays a causative role in these cancers. To date, no definitive view has been provided because there is currently data that both supports 12,13,17,23,[48][49][50] and refutes [51][52][53][54][55] pheomelanin's role.…”

Section: Discussionmentioning

confidence: 99%

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The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

Peles

Simon

2010

J. Phys. Chem. B

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Uveal melanosomes from the iridal stroma contain both eumelanin and pheomelanin, the ratio of which varies with iris color. Herein, we report the absorption coefficient at λ ) 244 nm for individual human iridal stroma melanosomes from dark brown and blue-green irides. The melanosomes are nearly identical in size, but differ in the relative concentration composition, ranging from a eumelanin/pheomelanin ratio of 14.8:1 (dark brown) to 1.3:1 (blue-green or hazel). The absorption coefficient of the melanosome decreases as its pheomelanin content increases. The origin of this decrease is attributed to a corresponding decrease in the number of UV-absorbing chromophores, reflecting the different molecular volumes of the monomeric building blocks of the two pigments. In agreement with reported data on synthetic pigments, the absorption coefficient of pheomelanin is found to be slightly larger than that for eumelanin at λ ) 244 nm (by a factor of 1.2). On the basis of the reported optical properties of synthetic models, this result suggests that the absorption of pheomelanin is less than eumelanin at wavelengths of biological relevance (∼315-400 nm).

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Section: Introductionsupporting

confidence: 81%

Section: Discussionmentioning

confidence: 99%

The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

Peles

Simon

2010

J. Phys. Chem. B

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“…Interestingly in AMD patients, significantly higher CEP adduct levels were observed in females, consistent with the higher incidence of AMD in females, and in hyperlipidemic individuals, consistent with the lipid source of these adducts. African-Americans with AMD exhibited significantly lower CEP adduct levels than Caucasians, consistent with the lower incidence of AMD in African-Americans and consistent with a greater resistance to oxidative damage perhaps because of the higher levels of ocular melanin in darkly pigmented races and the antioxidant effects of melanin (32). Surprisingly smoking had little impact on plasma CEP adduct levels within either the control or AMD cohorts presumably because of relatively low amounts of DHA in the pulmonary system.…”

Section: Table VII Characteristics Of the Study Populationsupporting

confidence: 52%

Assessing Susceptibility to Age-related Macular Degeneration with Proteomic and Genomic Biomarkers

Pauer

Yue

et al. 2009

Molecular & Cellular Proteomics

115

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,f,i and the Clinical Genomic and Proteomic AMD Study Group Age-related macular degeneration (AMD) is a progressive disease and major cause of severe visual loss. Toward the discovery of tools for early identification of AMD susceptibility, we evaluated the combined predictive capability of proteomic and genomic AMD biomarkers. We quantified plasma carboxyethylpyrrole (CEP) oxidative protein modifications and CEP autoantibodies by ELISA in 916 AMD and 488 control donors. CEP adducts are uniquely generated from oxidation of docosahexaenoate-containing lipids that are abundant in the retina. Mean CEP adduct and autoantibody levels were found to be elevated in AMD plasma by ϳ60 and ϳ30%, respectively. The odds ratio for both CEP markers elevated was 3-fold greater or more in AMD than in control patients. Genotyping was performed for AMD risk polymorphisms associated with age-related maculopathy susceptibility 2 (ARMS2), high temperature requirement factor A1 (HTRA1), complement factor H, and complement C3, and the risk of AMD was predicted based on genotype alone or in combination with the CEP markers. The AMD risk predicted for those exhibiting elevated CEP markers and risk genotypes was 2-3-fold greater than the risk based on genotype alone. AMD donors carrying the ARMS2 and HTRA1 risk alleles were the most likely to exhibit elevated CEP markers. The results compellingly demonstrate higher mean CEP marker levels in AMD plasma over a broad age range. Receiver operating characteristic curves suggest that CEP markers alone can discriminate between AMD and control plasma donors with ϳ76% accuracy and in combination with genomic markers provide up to ϳ80% discrimination accuracy. Plasma CEP marker levels were altered slightly by several demographic and health factors that warrant further study. We conclude that CEP plasma biomarkers, particularly in combination with genomic markers, offer a potential early warning system for assessing susceptibility to this blinding, multifactorial disease. Molecular & Cellular Proteomics 8:1338 -1349, 2009. Age-related macular degeneration (AMD)1 is the most common cause of legal blindness in the elderly in developed countries (1). It is a complex, progressive disease involving multiple genetic and environmental factors that can result in severe visual loss. Early risk factors include the macular deposition of debris (drusen) on Bruch membrane, the extracellular matrix separating the choriocapillaris from the retinal pigment epithelium (RPE). Later stages of "dry" AMD involve the degeneration of photoreceptor and RPE cells resulting in geographic atrophy. In "wet" AMD, abnormal blood vessels grow from the choriocapillaris through Bruch membrane (choroidal neovascularization (CNV)). CNV occurs in 10 -15% of AMD cases yet accounts for over 80% of debilitating visual loss in AMD. Anti-vascular endothelial growth factor treatments can effectively inhibit the progression of CNV (1), and antioxidant vitamins and zinc can slow dry AMD progression for select individuals (2). However, there a...

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“…Eumelanin and pheomelanin biopolymers are known [1][2][3][4][5][6][7]. Chemical structures of eumelanin and pheomelanin were shown in Figure 1 [1].…”

Section: Introductionmentioning

confidence: 99%

“…Eumelanin mainly exists in the human organism [1,2]. Melanin was found in skin [3,4], hair [5,6], eye [7], and liver cells [8].…”

Section: Introductionmentioning

confidence: 99%

Application of Electron Paramagnetic Resonance Spectroscopy to Examine Free Radicals in Melanin Polymers and the Human Melanoma Malignum Cells

Pilawa¹,

Zdybel²,

Chodurek³

2017

Melanin

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The studies of free radicals in melanin and the human melanoma malignum cells by an X-band (9.3 GHz) electron paramagnetic resonance (EPR) spectroscopy were presented. The original results were compared with those published earlier. The aim of this work was application of the advanced spectral analysis to determine free radical properties in melanin biopolymers obtained from diferent melanotic tumor cells and free radicals existing in the human melanoma cells. Magnetic spin-latice interactions in melanin samples were tested. The evolution of lineshape of tumor cells with increasing of microwave power was determined to conirm their complex free radical system. The useful shape parameters were proposed. The shape of melanotic tumor cells was analyzed. EPR spectra of free radicals in the melanin isolated from diferent tumor cells measured in the wide range of microwave power were analyzed. The melanins were obtained from the control tumor cells and the cells cultured with the several antitumor substances. The usefulness of the electron paramagnetic resonance spectroscopy was conirmed.

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Role of Ocular Melanin in Ophthalmic Physiology and Pathology^†

Cited by 211 publications

References 65 publications

The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

Assessing Susceptibility to Age-related Macular Degeneration with Proteomic and Genomic Biomarkers

Application of Electron Paramagnetic Resonance Spectroscopy to Examine Free Radicals in Melanin Polymers and the Human Melanoma Malignum Cells

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Role of Ocular Melanin in Ophthalmic Physiology and Pathology†

Cited by 211 publications

References 65 publications

The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

The Ultraviolet Absorption Coefficient of Melanosomes Decreases with Increasing Pheomelanin Content

Assessing Susceptibility to Age-related Macular Degeneration with Proteomic and Genomic Biomarkers

Application of Electron Paramagnetic Resonance Spectroscopy to Examine Free Radicals in Melanin Polymers and the Human Melanoma Malignum Cells

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Role of Ocular Melanin in Ophthalmic Physiology and Pathology^†