Chemiexcitation of melanin derivatives induces DNA photoproducts long after UV exposure

TLDR

Melanin’s protective role may also harbor a dark side, posing risks beyond the immediate DNA damage during sun exposure. The study explores whether adding quenchers to sunscreens could dissipate the delayed energy that drives DNA damage. A chemiexcitation model proposes that UV‑induced reactive oxygen and nitrogen species excite electrons in melanin fragments, transferring energy to DNA. The authors found that melanin mediates delayed DNA photoproduct formation, with reactive species generating the same UV‑like damage hours after sunlight exposure. Science, this issue p.

Abstract

The dark side of melanin exposed Sun worshippers may have more to worry about than the DNA damage that occurs while they're relaxing on the beach. It seems that the DNA photoproducts responsible for cancer-causing mutations in skin cells continue to be generated for hours after sunlight exposure. Premi et al. find that a key mediator of this delayed damage is melanin, a pigment thought to protect against cancer (see the Perspective by Taylor). They propose a “chemiexcitation” model in which reactive oxygen and nitrogen species induced by ultraviolet light excite an electron in melanin fragments. This energy is then transferred to DNA, inducing the same damage as ultraviolet light, but in the dark. Conceivably, this energy could be dissipated by adding quenchers to sunscreens. Science , this issue p. 842 ; see also p. 824