Antioxidant properties of melanin in retinal pigment epithelial cells

Photochem Photobiol. 2006 Mar-Apr;82(2):474-9. doi: 10.1562/2005-10-21-RA-725.


The retinal pigment epithelium (RPE) is a monolayer of highly pigmented cells lining the inner aspect of Bruch's membrane. This pigmentation is due to eumelanin and a possible antioxidant role of melanin is reported here. The photo-oxidation of A2E, a constituent of RPE lipofuscin, leads to the sequential addition of up to nine oxygen atoms and/or the addition or loss of two hydrogen atoms. These photo-oxidations were investigated in the presence and absence of either calf or human RPE melanin in A2E-laden RPE cells. It was found that calf melanin was protective against the photo-oxidation of A2E, with an inhibition of oxidation of up to 50% in the case of the addition of two oxygen atoms. Calf melanin was also protective against blue light-induced damage to RPE cells. In addition this ability appears to decrease in humans as they grow older. With aging, a melanin-lipofuscin complex called melanolipofuscin forms. It is suggested that the oxidation or photo-oxidation of A2E in vivo may contribute to the age-related deterioration of the anti-oxidant role of RPE melanin and lead to various retinal disorders, such as age-related macular degeneration.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / metabolism*
  • Cattle
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Dose-Response Relationship, Radiation
  • Humans
  • Light*
  • Lipofuscin / chemistry
  • Lipofuscin / metabolism
  • Macular Degeneration / pathology
  • Melanins / metabolism*
  • Oxidation-Reduction
  • Pigment Epithelium of Eye / cytology
  • Pigment Epithelium of Eye / metabolism*
  • Pigment Epithelium of Eye / pathology
  • Retinal Diseases / pathology
  • Time Factors


  • Antioxidants
  • Lipofuscin
  • Melanins