Melanin may promote photooxidation of linoleic acid

Randolph D. Glickman, Kwok Wai Lam

Research output: Contribution to journalConference article

5 Scopus citations

Abstract

We have previously shown that laser-exposed melanin granules isolated from the retinal pigment epithelium (RPE) are capable of oxidizing ascorbic acid. We are now characterizing the reactions of light-activated melanin with other cellular components such as linoleic acid, a polyunsaturated fatty acid. Commercial linoleic acid, and melanin granules isolated from bovine RPE cells, are mixed and exposed to the broadband output of a 150 W Xenon arc lamp or the CW output of an Argon laser. Native linoleic acid is separated from its hydroperoxides by HPLC, and the relative amounts of each are detected by UV absorbance at 210 and 232 nm, respectively. Exposure of the linoleic acid alone to the xenon arc source results in production of linoleic hydroperoxides (LHP) in an intensity-dependent reaction that doubles in extent over the temperature range of 0° to 80° C. Addition of melanin granules at a density of 108 granules/mi reduces the production of LHP, probably because of light absorption and self-screening by the melanin. At or below a density of 107 granules/mi, however, the light-driven production of LHP is enhanced, especially during exposure to the blue-green output of the Argon laser. Physiological antioxidants (Vit. C, E) protect the linoleic acid from photooxidation in the presence or absence of melanin. These observations support the hypothesis that light-activated melanin can react with some cellular components and thereby contribute to photochemical damage, especially if endogenous antioxidants are depleted.

Original languageEnglish (US)
Pages (from-to)254-261
Number of pages8
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume2391
DOIs
Publication statusPublished - May 22 1995
EventLaser-Tissue Interaction VI 1995 - San Jose, United States
Duration: Feb 1 1995Feb 8 1995

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Keywords

  • Antioxidants
  • Laser bioeffects
  • Linoleic acid
  • Melanin
  • Photochemical
  • Photooxidative stress

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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