Topical applications of iron chelators in photosensitization.

Generation of the reactive oxygen species (ROS) in skin by exposure to ultraviolet (UV) radiation induces a number of cutaneous pathologies such as skin cancer, photosensitization, and photoaging among others. Skin iron catalyzes UV generation of ROS. Topical application of iron chelators reduces erythema, epidermal and dermal hypertrophy, wrinkle formation, tumour appearance. It has been proposed that iron chelators can be useful agents against damaging effects of both short- and long-term UV exposure. A better understanding of the action mechanisms of iron chelators, might be useful to developing effective anticancer and antiphotoaging cosmetic products. Iron chelators may lead to accumulation of protoporphyrin IX (PpIX), a strong photosensitizer. The action of iron chelators in skin, related to PpIX increase has not yet been thoroughly studied. Therefore, we have investigated the formation of PpIX in normal mouse skin after topical application of creams containing metal chelators. The amount and distribution of porphyrins formed was determined by means of non-invasive fluorescence spectroscopy. Deferoxamine (DF), ethylenediaminetetraacetic acid (EDTA), 1,2-diethyl-3-hydroxypyridin-4-one (CP94), but not meso-2,3-dimercaptosuccinic acid (DMSA), caused increased accumulation of endogenous porphyrins in the skin. Fluorescence excitation and emission spectroscopy confirmed that PpIX was the main fluorescent species. The amount of PpIX accumulated in skin under the present conditions was not large enough to produce any significant erythema after light exposure. Further studies are needed to evaluate the role of PpIX induced by iron chelators used, against photoaging and cancer prevention.