By: Aimee Cunningham of Science
A method that gives mice a tan without using ultraviolet radiation now works in human skin samples. It’s an early step in developing a lotion or cream that might provide fair-skinned folk with protection against skin cancer.
As reported June 13 in Cell Reports, a topical drug penetrated and tanned laboratory samples of live human skin, absent the sun. Unlike self-tanning lotions that essentially stain skin brown and provide minimal sun protection, the drug activates the production of the dark form of the skin pigment melanin, which absorbs UV radiation and diminishes damage to skin cells.
The team behind this study had worked with a different drug, the plant extract forskolin, in a 2006 study. The researchers used mice with skin like that of red-haired, fair-skinned people, who don’t tan because of a nonfunctioning protein on the surface of the skin cells that make melanin. Applying forskolin to these mice stimulated production of the dark form of melanin. When exposed to UV rays, the mice with dark pigment had less DNA damage and sunburn, as well as fewer skin tumors, compared with untreated mice (SN: 9/23/06, p. 196).
“There was an obvious interest in asking, could this be applied to human skin?” says David Fisher, a cancer biologist at Massachusetts General Hospital in Boston. But the human epidermis, the outermost layer of skin, is about five times thicker in humans than in mice, he says, which means that many drugs “simply can’t get in.” Sure enough, this was true for forskolin.
So Fisher and colleagues looked at another way to activate pigmentation, focusing on a different enzyme than the one forskolin had targeted. Another research group had shown that an enzyme called salt-inducible kinase inhibits melanin production in mice and that animals lacking the gene for this enzyme developed darkened fur. This provided the opportunity to “try to target that inhibitor, block it and thereby stimulate pigmentation” with a drug, Fisher says.