SYNERGISTIC TOPICAL PHOTOPROTECTION BY A COMBINATION OF THE IRON CHELATOR 2-FURILDIOXIME AND SUNSCREEN

Background: Iron is a factor in skin photodamage, apparently by way of its participation in oxygen radical production. Certain topical iron chelators are photoprotective. Objective: Our purpose was to determine the level of topical photoprotection provided by the iron chelator 2- furildioxime (FDO) in combination with sunscreen in short- and long-te rm photoprotection models. Methods: Guinea pigs were treated topically with EDO, sunscreen, and a combination of the two and were then expos ed to varying doses of UV radiation to determine the sun protection fa ctor (SPF). Hairless mice were treated topically with FDO, sunscreen, and a combination of the two and then subjected to long-term, exposure to a suberythemal dose of UV radiation. The mice were evaluated for s kin wrinkling and skin tumors. Results: In guinea pigs, topical FDO co mbined with sunscreen provided more than additive protection; 5% FDO a lone provides approximately SPF 3, whereas 5% FDO combined with an SPF 4 sunscreen product yielded an SPF of more than 30. In hairless mice exposed long term to UV radiation, 5% FDO and sunscreen delayed tumor onset by a mean of 8 and 12 weeks, respectively. The combination of FD O and sunscreen delayed tumor onset by a mean of 58 weeks. A similar m ore than additive level of protection was observed for skin wrinkling. Conclusion: Topical FDO combined with sunscreen is a potent photoprot ection system against both short- and long-term UV radiation exposure.