Lipofuscin component A2E does not reduce antioxidant activity of DOPA-melanin

Bull Exp Biol Med. 2013 Mar;154(5):624-7. doi: 10.1007/s10517-013-2015-6.

Abstract

We studied the capacity of DOPA-melanin (natural eumelanin analog) to bind chromophore A2E of retinal pigmented epithelial cell lipofuscin granule into complexes. DOPA-melanin bound up to 200 nm A2E per 1 mg polymer; antioxidant activity of the resultant complexes was evaluated. Luminol chemiluminescence quenching in the presence of hydrogen peroxide showed that the chemiluminescence latency/concentration constants were virtually the same for DOPA-melanin and its A2E complexes. Comparison of the inhibitory effects of DOPA-melanin and DOPA-A2E complexes by rate of UV-induced peroxidation of the outer segments of photoreceptor cells showed higher inhibitory activity of the complexes in comparison with pure DOPA-melanin. Antioxidant activity of DOPA-A2E complexes towards Fe(2+)-ascorbate-induced peroxidation of the outer segments of photoreceptor cells was also higher than that of DOPA-melanin. The results indicated that chromophore A2E of lipofuscin granules in the studied concentrations did not attenuate the antioxidant effects of DOPA-melanin and even potentiated it. This suggested that A2E excess in retinal pigmented epithelium cells could be bound by melanosome melanin and lose its toxicity.

MeSH terms

  • Animals
  • Antioxidants / chemistry
  • Antioxidants / metabolism*
  • Cattle
  • Cells, Cultured
  • Dihydroxyphenylalanine / analogs & derivatives*
  • Dihydroxyphenylalanine / chemistry
  • Dihydroxyphenylalanine / metabolism
  • Epithelial Cells / chemistry
  • Epithelial Cells / metabolism
  • Lipofuscin / chemistry
  • Melanins / metabolism
  • Melanosomes / metabolism
  • Oxidation-Reduction
  • Pigment Epithelium of Eye / metabolism*
  • Pyridinium Compounds / metabolism*
  • Retina / cytology
  • Retinoids / metabolism*

Substances

  • A2-E (N-retinylidene-N-retinylethanolamine)
  • Antioxidants
  • Lipofuscin
  • Melanins
  • Pyridinium Compounds
  • Retinoids
  • Dihydroxyphenylalanine
  • DOPA melanin