title: Melanin reduces ultraviolet-induced DNA damage formation and killing rate in cultured human melanoma cells.
abstract: Epidermal melanin pigment is believed to prevent development of ultraviolet (UV)-induced skin cancer by shielding cell nuclei and reducing DNA damage formation. It has not been experimentally proved, however, whether melanin reduces UV-induced DNA damage, because published experiments have been inconclusive. The present study was carried out to determine whether intracellular melanin protected cultured cells against UV-induced DNA damage and killing. Three human melanoma cell lines containing different amounts of melanin were used. Absorption spectrum, subcellular localization of melanin, and melanin concentration were examined in the three cell lines. Two types of DNA damage, cyclobutane pyrimidine dimers and (6-4)photoproducts, were detected by an enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies specific for these photolesions. We found that melanin reduced the induction rates of both types of DNA damage in pigmented cells irradiated with low doses of UV in a melanin concentration-dependent manner. Almost no differences in repair capacity for the two types of photolesions were observed among the three melanoma cell lines. We also found that the more highly melanotic melanoma cell lines were more UV resistant than the less melanotic melanoma cell lines. These results suggest that intracellular melanin plays an important role in preventing UV-induced cell killing by reducing the formation of two types of DNA damage.
authors.affiliation: Department of Dermatology, Nara Medical University, Japan.
authors.forename: N
authors.initials: N
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Muramatsu
authors.forename: Y
authors.initials: Y
authors.lastname: Yamashina
authors.forename: T
authors.initials: T
authors.lastname: Shirai
authors.forename: T
authors.initials: T
authors.lastname: Ohnishi
authors.forename: T
authors.initials: T
authors.lastname: Mori
mesh_terms: D002470:Cell Survival / Q000528:radiation effects; D004249:DNA Damage; D004260:DNA Repair; D006801:Humans; D008543:Melanins / Q000032:analysis / Q000502:physiology*; D008545:Melanoma / Q000235:genetics / Q000473:pathology*; D011835:Radiation Protection; D014407:Tumor Cells, Cultured; D014466:Ultraviolet Rays
chemical_list: D008543:Melanins