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UVA1 Induces Thymine Dimers in DNA of Human Skin in Vivo

UVA1 induces thymine dimers but not pyrimidine (6-4) pyrimidone photoproducts in skin epidermis

FRIDAY, Oct. 7 (HealthDay News) -- Ultraviolet A1 (UVA1) rays induce thymine dimers (TTs) but not pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) in the DNA of human epidermis in vivo, and the level of induced TTs increases with the epidermal depth, according to a study published online Oct. 6 in the Journal of Investigative Dermatology.

Angela Tewari, M.B.B.S., from King's College London, and colleagues investigated the induction of TTs and 6-4PPs in human skin in vivo by broadband UVA1, and compared it with similar erythemal doses of monochromatic UVB (300 nm).

The investigators found that UVB induced both TTs and 6-4PPs, while UVA1 induced TTs, but not 6-4PPs in the epidermis of healthy volunteers in vivo. For the same level of erythema, UVB induced more TTs than UVA1. With increasing epidermal depth, there was an increase in the level of UVA1-induced TTs, in contrast to a decrease in UVB-induced TTs. The rate of repair of UVA1-induced and UVB-induced TTs in epidermal cells was similar.

"We have demonstrated that erythemally equivalent doses of UVA1 and UVB induce TTs in human buttock skin in vivo, but that 6-4PPs are induced by UVB only," the authors write.

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