title: Melanin photosensitization and the effect of visible light on epithelial cells.
abstract: Protecting human skin from sun exposure is a complex issue that involves unclear aspects of the interaction between light and tissue. A persistent misconception is that visible light is safe for the skin, although several lines of evidence suggest otherwise. Here, we show that visible light can damage melanocytes through melanin photosensitization and singlet oxygen (1O2) generation, thus decreasing cell viability, increasing membrane permeability, and causing both DNA photo-oxidation and necro-apoptotic cell death. UVA (355 nm) and visible (532 nm) light photosensitize 1O2 with similar yields, and pheomelanin is more efficient than eumelanin at generating 1O2 and resisting photobleaching. Although melanin can protect against the cellular damage induced by UVB, exposure to visible light leads to pre-mutagenic DNA lesions (i.e., Fpg- and Endo III-sensitive modifications); these DNA lesions may be mutagenic and may cause photoaging, as well as other health problems, such as skin cancer.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Orlando
authors.initials: O
authors.lastname: Chiarelli-Neto
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Alan Silva
authors.initials: AS
authors.lastname: Ferreira
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Waleska Kerllen
authors.initials: WK
authors.lastname: Martins
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Christiane
authors.initials: C
authors.lastname: Pavani
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Divinomar
authors.initials: D
authors.lastname: Severino
authors.affiliation: Departamento de Análises Clínicas, Faculdade de Ciências Farmacêuticas-USP, São Paulo, Brazil.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Faião-Flores
authors.affiliation: Departamento de Análises Clínicas, Faculdade de Ciências Farmacêuticas-USP, São Paulo, Brazil.
authors.forename: Silvya Stuchi
authors.initials: SS
authors.lastname: Maria-Engler
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba, Brazil.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Aliprandini
authors.affiliation: Departamento de Bioquímica e Biologia Molecular, Setor de Ciências Biológicas, Universidade Federal do Paraná, Curitiba, Brazil.
authors.forename: Glaucia R
authors.initials: GR
authors.lastname: Martinez
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Paolo
authors.initials: P
authors.lastname: Di Mascio
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Marisa H G
authors.initials: MH
authors.lastname: Medeiros
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Maurício S
authors.initials: MS
authors.lastname: Baptista
mesh_terms: D017209:Apoptosis / Q000528:radiation effects; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects*; D020552:Comet Assay; D006801:Humans; D008027:Light / Q000009:adverse effects*; D008543:Melanins / Q000378:metabolism* / Q000528:radiation effects; D008544:Melanocytes / Q000378:metabolism / Q000528:radiation effects*; D010084:Oxidation-Reduction; D026082:Singlet Oxygen / Q000378:metabolism
chemical_list: D008543:Melanins; D026082:Singlet Oxygen