title: Inhibition of UV radiation-induced DNA damage by a 5-methoxypsoralen tan in human skin.
abstract: Previously untanned buttock skin of 4 volunteers (skin type II; tan with difficulty as they sunburn easily) was treated with various sunscreen preparations and solar--simulated radiation (SSR) or SSR alone for 2 weeks. One week later, the treatment sites were challenged with a DNA-damaging dose of SSR--twice the minimal erythema dose (2 MED). Skin biopsy samples were assayed for the levels of unscheduled DNA synthesis (a measure of DNA damage), melanin distribution, and skin thickening. 5-Methoxypsoralen-containing sunscreen preparations plus SSR or SSR alone induced melanogenesis and increased the stratum corneum thickness, but only the former regimen afforded a high degree of protection against subsequent SSR-induced DNA damage. 5-Methoxypsoralen-free sunscreen preparations plus SSR induced negligible tanning, skin thickening, and photoprotection. These findings are relevant to the risk-benefit analysis of sunscreen preparations, especially in skin type II, as they provide evidence that a 5-methoxypsoralen-induced tan is protective against the DNA-damaging effects of solar UV radiation, and thus has the potential to reduce the carcinogenic risk of exposure to such radiation.
authors.affiliation: Photobiology Unit, Institute of Dermatology, St. Thomas's Hospital, London, UK.
authors.forename: A R
authors.initials: AR
authors.lastname: Young
authors.forename: C S
authors.initials: CS
authors.lastname: Potten
authors.forename: C A
authors.initials: CA
authors.lastname: Chadwick
authors.forename: G M
authors.initials: GM
authors.lastname: Murphy
authors.forename: A J
authors.initials: AJ
authors.lastname: Cohen
mesh_terms: D000078223:5-Methoxypsoralen; D004249:DNA Damage; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D008730:Methoxsalen / Q000494:pharmacology*; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D012867:Skin / Q000187:drug effects / Q000528:radiation effects*; D014466:Ultraviolet Rays
chemical_list: D011837:Radiation-Protective Agents; D000078223:5-Methoxypsoralen; D008730:Methoxsalen