Oral communication, iL3

Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011

Physicochemical changes of retinal pigment epithelium melanin with aging and photoaging monitored by advanced EPR techniques

SPEAKER T. Sarna #whois submiter ?
AUTHOR(s) G. Szewczyk, A. Pilat, M. Zareba, J.M. Burke, T. Sarna

Melanin in the human retinal pigment epithelium (RPE) is formed early in fetal development and thereafter shows little metabolic turnover. Being exposed to intense visible light from focal irradiation and high oxygen tension RPE melanin may undergo oxidative modifications that can alter its physicochemical properties and biological functions. In this study, we analyzed changes in paramagnetic, redox and metal-ion binding properties of human RPE melanin with aging and bovine RPE melanosomes subjected to experimental photoaging. RPE cells, obtained from human donors of different age, and purified porcine or bovine RPE melanosomes, with selected degree of photo-bleaching, where analyzed by 95 GHz (W-band) continuous wave (CW) and saturation recovery (SR) EPR spectroscopy at different pH. Redox properties of human RPE melanin and animal RPE melanosomes were tested by monitoring photo-reduction of an appropriate nitroxide spin probe, and the ability of melanin to form complexes with multivalent metal ions was determined by X-band CW and SR EPR spectroscopy. Our results indicate distinct changes in paramagnetic properties of RPE melanin with aging and RPE melanosomes with photoaging. Partially photo-bleached bovine and porcine RPE melanosomes, in comparison with untreated melanosomes, exhibit higher efficiency to photo-reduce nitroxide spin probe. Aged human RPE melanin and experimentally photo-aged animal RPE melanosomes bind multivalent metal ions less tightly than young human RPE and untreated bovine and porcine RPE melanosomes. The data suggest substantial changes in key physiochemical properties of RPE melanin that occur with aging, which, to some degree, can be modeled by photo-bleaching of animal RPE melanosomes, and are monitored by advanced EPR spectroscopy. Supported by Poland Ministry of Science and Higher Education (grant: 2661/B/P01/2010/39) and NIH (grants: R01EY013722, R01EY019664).



Advertisement from our sponsor:
Astellas Pharma Worldwide

Université de Bordeaux 2 & Conseil Régional Aquitaine