by Dr J. Borovansky
INTERNATIONAL SYMPOSIUM ON PHOTOPROTECTION
Krakow, Poland, May 19 -22, 2001
The symposium was organized by the European Society for Photobiology (ESP) and Jagiellonian University with two main organizers - Prof. Tadeusz Sarna and Prof. T.George Truscott. The cooperation between the European Society for Pigment Cell Research and the European Society for Photobiology dates from the 8th ESPCR Meeting in Prague 1998 where the ESP prepared a special session also devoted to photoprotection. Although this time the ESPCR was not an official partner, the symposium attracted many ESPCR members, particularly to Session I.
Session I "Natural Sunscreens" was opened by Prof. P.A.
Riley who presented a plenary lecture "Photoprotection: Melanin, Mechanisms &
Myths". In his brilliant concise style he summarized factors involved in
photoprotection, with a special emphasis on melanin properties. Simon described the
structural organization of eumelanin based on atomic force microscopy measurements and
discussed the role of pigment aggregation in the photogeneration of ROS (reactive oxygen
species). Sarna et al. reviewed the antioxidant properties of melanin; the ability
of melanin to sequester redox active metal ions and to neutralize ROS are of key
importance in melanin photoprotection. Ramsden in his lecture "Mechanistic
Studies of Tyrosinase Oxidation" demonstrated that tyrosinase oxidizes phenols to
o-quinones in one step and not via intermediate catechols as was widely claimed. Pavel
and Smit ("The Role of Melanin in Protection against UV Radiation")
discussed the leakage of reactive melanin precursors and showed that these compounds could
liberate iron from its ferritin stores, which could substantially increase the cytotoxic
effect of UV radiation. Schallreuter ("Thioredoxin Reductase - Its Role in
Epidermal Redox Status) emphasized that UVB-generated H2O2 in the
epidermis is involved in the control of thioredoxin reductase and showed that oxidation of
6-tetrahydrobiopterin to 6-biopterin by hydrogen peroxide could lead to a cytotoxic
environment for epidermal melanocytes. Leszczynski & Pastilla reported that UVA
radiation enhanced metastatic properties of B16 melanoma cells probably due to an
alteration in expression of adhesion molecules. Haywood & Linge spoke on
thermolysis of hair melanin induced by the 694nm ruby laser. Borovansky & Elleder
characterized in detail the autofluorescence of synthetic and natural eu-, pheo- and
neuromelanins, which can be induced in vitro by UV and near UV-light with
production of hydrogen peroxide, associated with photodegradation of pigment structures.
The principal speaker in Session II "Commercial Sunscreens" was Prof. Urbach who gave the plenary lecture "The Historical Aspects of Sunscreens".
Session III "Dietary and Enzymic Aspects" concentrated mainly on photoprotection by dietary ß-carotene and lycopene. Picardo et al. studied the role of antioxidant enzymes in photoprotection in melanocyte cultures and in biological samples from subjects with different phototypes and from melanoma patients.
Session IV dealt with "Photoprotection of the eye". Boulton characterized photodamage to the RPE as an oxygen dependent phenomenon which involves the photoinduction of ROS from a chromophore(s) located within the RPE. He suggested that lipofuscin and not melanin is the major chromophore responsible for the ensuing cytotoxicity.
In the Poster Session Land and Riley exhibited a poster "Spontaneous Redox Reactions of Dopaquinone and the Balance between the Eumelanic and Phaeomelanic Pathways", Jastrzebska et al. contributed "Photoconductivity of Synthetic Dopa Melanin" and Smit et al. showed a poster devoted to elemental analysis of cultured melanocytes.
The symposium was partly situated in the picturesque historical buildings of the Jagiellonian University. The organization was perfect and the well set up programme was enjoyed by more than 70 scientists from four continents. Many participants left Krakow with a desire to return in the near future, e.g. on the occasion of an ESPCR Meeting.