Sun-worshippers beware: Most sunscreen products offer inadequate protection against the harmful effects of the sun's ultraviolet radiation.
But there is hope, says a University of Illinois researcher who developed a technique to peer into the skin and study how it is affected by ultraviolet radiation. The addition of antioxidants such as vitamins E or C can help prevent skin cancer and keep skin firm and young looking.
"Ultraviolet radiation is known to cause several forms of skin cancer, including basal cell carcinoma, squamous cell cancer and deadly melanoma," said Kerry Hanson, a postdoctoral research scientist in the UIs Laboratory for Fluorescence Dynamics. "But many important questions remain, such as in which layers of the skin, and in which parts of skin cells, the initial damage occurs."
Sunscreens with a sun protection factor of 15 can block up to 94 percent of the ultraviolet light, Hanson said, but the residual light that does penetrate the skin can create free radicals - highly reactive molecules that can weaken or destroy cell membranes. Free radicals can also damage DNA, create age spots and wrinkles, and depress the immune system, increasing the risk of skin cancer.
To study the effects of ultraviolet radiation on free radical generation and the role this plays in skin damage, Hanson employs a two-photon laser fluorescence-imaging microscope. She images the skin at varying depths after ultraviolet exposure, looking for fluorescent tags that reveal the presence of free radicals. She also looks for resulting damage in the skin cells.
Using the technique, Hanson found that the stratum corneum - the skin's main protective barrier against environmental assault - generated a tremendous number of free radicals when exposed to ultraviolet light.
"These free radicals caused considerable damage to both the cytoplasm and the lipid matrix," she said. "The cytoplasm of the lower epidermis was also dramatically damaged."
While typical sunscreens offer no protection against free radical damage, the addition of antioxidants could significantly reduce the generation of free radicals. In a recent study, Hanson examined the quenching effectiveness of three antioxidants: vitamin E acetate, vitamin E alcohol and sodium ascorbyl phosphate (stable vitamin C).
"Vitamin C was by far the best quencher," she said. "There are natural enzymes in your skin that cleave the phosphate group and form a reservoir of vitamin C. The best results were achieved after multiple applications of the antioxidants when a significant amount of vitamin C accumulated within the skin. Any free radicals that are generated will be quenched by the vitamin C stored in your skin."
Skin cancer - caused by repeated sunburn - can develop over a lifetime, Hanson says. "So, the next time you are going out to bake in the sun, wear plenty of sunscreen. And use one that has an antioxidant."
Hanson presented her findings at the Eighth Biennial Sunscreen Symposium held Sep. 13-16 in Orlando, Fla. The Cancer Research Foundation of America and the Skin Cancer Foundation funded the work. - By James E. Kloeppel
[Contact: James E. Kloeppel]