The use of endogenous antioxidants to improve photoprotection.

The skin possesses an elaborate antioxidant defence system to deal with UV-induced oxidative stress. However, excessive exposure to UV can overwhelm the cutaneous antioxidant capacity, leading to oxidative damage and ultimately to skin cancer, immunosuppression and premature skin aging. Therefore, an interesting strategy for photoprotection is the support of the endogenous antioxidant system. This can be accomplished by induction or transdermal delivery of the various antioxidant enzymes, such as glutathione peroxidase, catalase, or superoxide dismutase. Supplementation of non-enzymatic antioxidants such as glutathione, alpha-tocopherol, ascorbate and beta-carotene was also found to be very effective in photoprotection. Although treatments with single components of the antioxidant system were successful against a wide variety of photodamage, the balance between the different antioxidants in the skin is very important. In some studies, it was found that too much of a single component could even have deleterious effects. The most promising results were obtained in studies combining several compounds, often resulting in synergism of the protective effects.