97th DOG Annual Meeting 1999
V686
DOES THE LIPOFUSCIN FLUOROPHOR A2-E ACT
AS A PHOTOSENSIBILISATOR IN HUMAN RPE-CELLS?
F. Schütt1, S. Davies2, J. Kopitz1, M. Boulton2, F. G. Holz1
A2-E (N-retinylidene-N-retinylethanolamine) was identified as a fluorophor of lipofuscin (Eldred and Lasky 1993) which accumulates in the lysosomal compartment of postmitotic RPE cells with age or in association with various retinal diseases. A2-E interferes with lysosomal degradation of biomolecules in human RPE cells (Schütt et al. ARVO 1998). We investigated a possible role of A2-E as a photosensitizer and a generator of free radicals in vitro.
Methods: After coupling all-trans-retinaldehyde and ethanolamine (2:1) A2-E was introduced as a complex with LDL into the lysosomal compartment of primary cultivated human RPE cells. A2-E treated cells and controls were exposed to light for 144 hours in a light box (350-550 nm, 2,8 mW/cm2, Boulton et al. 1993) or maintained as controls in the incubator. Cell viability was assessed using the MTT test. Furthermore, lipid peroxidation products were measured with a colorimetric assay.
Results: After 48 and 144 hours light exposition, respectively, RPE-cells without A2-E showed a reduction of cell viability by 25 versus 50 %. This effect was not enhanced by A2-E. After A2-E treatment the content of lipid peroxidation products was not changed in light exposed cells or dark maintained controls.
Conclusions: The results indicate that A2-E is not a photosensitizer or a generator of free radicals. However, A2-E has been shown to impair lysosomal functions in human RPE cells by mechanisms other than light toxicity (Holz et al. 1999, in press), therefore, A2-E may be of pathophysiological relevance in retinal degenerations including age related macular degeneration.
Department of Ophthalmology, University of Heidelberg1, INF 400, 69120 Heidelberg, Germany
Manchester Royal Eye Hospital2, Manchester M13 9 WH, UK
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