Invited review
New trends in photobiology: Properties and function of the ocular melanin — a photobiophysical view

https://doi.org/10.1016/1011-1344(92)85027-RGet rights and content

Abstract

This paper reviews the biosynthesis and physicochemical properties of the ocular melanin. Age-related changes of melanin granules and the corresponding formation of lipofuscin pigments in the retinal pigment epithelium (RPE) are also described. Adverse photoreactions of the eye and, in particular, light-induced damage to the RPE—retina are reviewed in relation to the ocular pigmentation. A hypothesis on the photoprotective role of the RPE melanin is presented that is based on the ability of the cellular melanin to bind redoxactive metal ions. Since bound-to-melanin metal ions are expected to be less damaging to the pigment cells, it is proposed that sequestration of heavy metal ions by the RPE melanin is an efficient detoxifying mechanism. It is postulated that oxidative degradation of RPE melanin may lower its metal-binding capability and decrease its anti-oxidant efficiency. Cellular and environmental factors that may contribute to possible oxidative damage of the RPE melanin are discussed in connection with the etiology of age-related macular degeneration.

References (198)

  • A. Palumbo et al.

    Effect of metal ion on the rearrangement of dopachrome

    Biochim. Biophys. Acta

    (1987)
  • M. Sugumaran et al.

    Formation of a stable quinone methide during tyrosinase-catalyzed oxidation of α-methyl dopa methyl ester and its implication in melanin biosynthesis

    Bioorg. Chem.

    (1990)
  • J.I. Barber et al.

    DOPAchrome oxidoreductase: a new enzyme in the pigment pathway

    J. Invest. Dermatol.

    (1984)
  • M. Sugumaran et al.

    Quinone methide as a new intermediate in eumelanin biosynthesis

    J. Biol. Chem.

    (1991)
  • P. Aroca et al.

    Regulation of mammalian melanogenesis I: partial purification and characterization of a dopachrome converting factor: dopachrome tautomerase

    Biochim. Biophys. Acta

    (1990)
  • J.M. Pawelek

    Dopachrome conversion factor functions as an isomerase

    Biochem. Biophys. Res. Commum.

    (1990)
  • C. Lambert et al.

    A pulse radiolysis investigation of the oxidation of indolic melanin precursors: evidence of indolequinones and subsequent intermediates

    Biochim. Biophys. Acta

    (1989)
  • C. Lambert et al.

    A pulse radiolysis investigation of the oxidation of methoxylated metabolites of indolic melanin precursors

    Biochim. Biophys. Acta

    (1990)
  • B. Kalyanaraman et al.

    Reaction between ortho-semiquinones and oxygen: pulse radiolysis, electron spin resonance, and oxygen uptake studies

    Arch. Biochem. Biophys.

    (1988)
  • H.S. Mason et al.

    Identification by electron spin resonance spectroscopy of the primary product of tryosinase-catalyzed catechol oxidation

    Biochem. Biophys. Res. Commun.

    (1961)
  • Y. Tomita et al.

    Radical production during tyrosinase reaction, dopa-melanin formation, and photoirradiation of dopa-melanin

    J. Invest. Dermatol.

    (1984)
  • W. Korytowski et al.

    Tyrosinase-catalized oxidation of dopa and related catechol(amine)s: a kinetic electron spin resonance investigation using spin-stabilization and spin label oximetry

    Biochim. Biophys. Acta

    (1987)
  • G. Prota

    Recent advances in the chemistry of melanogenesis in mammals

    J. Invest. Dermatol.

    (1980)
  • H.R. Wilson et al.

    Albino spatial vision as an instance of arrested visual development

    Vision Res.

    (1988)
  • D. Van Norren et al.

    Spectral reflectance of the human eye

    Vision Res.

    (1986)
  • M. Boulton et al.

    Age-related changes in the morphology, absorption and fluorescence of melanosomes and liposfuscin granules of the retinal pigment epithelium

    Vision Res.

    (1990)
  • L. Feeney-Burns et al.

    Age-related macular changes in humans over 90 years old

    Am. J. Ophthalmol.

    (1990)
  • G.E. Eldred et al.

    Fluorophores of the human retinal pigment epithelium: separation and spectral characterization

    Exp. Eye Res.

    (1988)
  • G.J. Handelman et al.

    The role of antioxidants in the retina and retinal pigment epithelium and the nature of prooxidant-induced damage

    Adv. Free-Radical Biol. Med.

    (1986)
  • P.E. Kilbride et al.

    Foveal cone pigment density difference in the aging human eye

    Vision Res.

    (1986)
  • W. Hodos et al.

    Age-dependent changes in visual acuity and retinal morphology in pigeons

    Vision Res.

    (1991)
  • W. Froncisz et al.

    Cu2+ probe of metal-ion binding sites in melanin using electron paramagnetic resonance spectrocopy. I. Synthetic melanins

    Arch. Biochem. Biophys.

    (1980)
  • W. Korytowski et al.

    Reaction of superoxide anion with melanins: electron spin resonance and spin trapping studies

    Biochim. Biophys. Acta

    (1986)
  • W. Korytowski et al.

    Bleaching of melanin pigments: role of copper ions and hydrogen peroxide in autooxidation and photooxidation of synthetic dopa-melanin

    J. Biol. Chem.

    (1990)
  • T. Sarna et al.

    Interaction of radicals from water radiolysis with melanin

    Biochim. Biophys. Acta

    (1986)
  • P.R. Crippa et al.

    A band model for melanin deduced from optical absorption and photoconductivity experiments

    Biochim. Biophys. Acta

    (1978)
  • T. Sarna et al.

    Free radicals from eumelanin: quantum yield and wavelength dependence

    Arch. Biochem. Biophys.

    (1984)
  • J. McGinness et al.

    The importance of the fact that melanin is black

    J. Theor. Biol.

    (1973)
  • E.V. Gan et al.

    Electron transfer properties of melanin

    Arch. Biochem. Biophys.

    (1976)
  • J.M. Menter et al.

    Interaction of several mono- and dihydroxybenzene derivatives of various depigmenting potencies with l-3,4-dihydroxyphenylalanine-melanin

    Arch. Biochem. Biophys.

    (1986)
  • M.A. Ostrovsky et al.

    An antioxidative role of ocular screening pigments

    Vision Res.

    (1987)
  • B. Pilas et al.

    The effect of melanin on iron associated decomposition of hydrogen peroxide

    Adv. Free-Radical Biol. Med.

    (1988)
  • F.W. Cope et al.

    Reversible free radical generation in the melanin granules of the eye by visible light

    Arch. Biochem. Biophys.

    (1963)
  • H.S. Mason et al.

    The free radical property of melanins

    Arch. Biochem. Biophys.

    (1960)
  • T. Sarna et al.

    Interaction of melanin with oxygen

    Arch. Biochem. Biophys.

    (1980)
  • F.F. Barr et al.

    Melanin: the organizing molecule

    Med. Hypothesis

    (1986)
  • L. Feeney-Burns

    The pigments of the retinal pigment epithelium

    Curr. Top. Eye Res.

    (1980)
  • G. Prota

    Progress in the chemistry of melanins and related metabolites

    Med. Res. Rev.

    (1988)
  • J. Marshall

    The ageing retina: physiology or pathology

    Eye

    (1987)
  • I.Ben Sira et al.

    Major review. Retinopathy of prematurity

    Surv. Ophthalmol.

    (1988)
  • Cited by (0)

    1

    Also at: Biophysics Section, Medical College of Wisconsin, Milwaukee, WI, USA.

    View full text