Direct participation of DNA in the formation of singlet oxygen and base damage under UVA irradiation.
UVA light is hardly absorbed by the DNA molecule, but recent works point to a direct mechanism of DNA lesion by these wavelengths. UVA light also excite endogenous chromophores, which causes DNA damage through ROS. In this study, DNA samples were irradiated with UVA light in different conditions to investigate possible mechanisms involved in the induction of DNA damage. The different types of DNA lesions formed after irradiation were determined through the use of endonucleases, which recognize and cleave sites containing oxidized bases and cyclobutane pyrimidine dimers (CPDs), as well as through antibody recognition. The formation of 8-oxo-7,8-dihydro-2'-deoxyguanine (8-oxodG) was also studied in more detail using electrochemical detection. The results show that high NaCl concentration and concentrated DNA are capable of reducing the induction of CPDs. Moreover, concerning damage caused by oxidative stress, the presence of sodium azide and metal chelators reduce their induction, while deuterated water increases the amounts of oxidized bases, confirming the involvement of singlet oxygen in the generation of these lesions. Curiously, however, high concentrations of DNA also enhanced the formation of oxidized bases, in a reaction that paralleled the increase in the formation of singlet oxygen in the solution. This was interpreted as being due to an intrinsic photosensitization mechanism, depending directly on the DNA molecule to absorb UVA and generate singlet oxygen. Therefore, the DNA molecule itself may act as a chromophore for UVA light, locally producing a damaging agent, which may lead to even greater concerns about the deleterious impact of sunlight.
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Teiti
T
Yagura
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil; Departamento de Bioquímica e Biologia Molecular, Centro de Ciências Naturais e Exatas, Universidade Federal de Santa Maria, 97110-970 Santa Maria, RS, Brazil.
André Passaglia
AP
Schuch
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil; Núcleo de Pesquisa em Ciências Biológicas & Departamento de Ciências Biológicas, Instituto de Ciências Exatas e Biológicas, Universidade Federal de Ouro Preto, 35400-000 Ouro Preto, MG, Brazil.
Camila Carrião Machado
CCM
Garcia
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Clarissa Ribeiro Reily
CRR
Rocha
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Natália Cestari
NC
Moreno
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
José Pedro Friedmann
JPF
Angeli
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Davi
D
Mendes
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Divinomar
D
Severino
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Angelica
A
Bianchini Sanchez
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Paolo
P
Di Mascio
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
Marisa Helena Gennari
MHG
de Medeiros
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil. Electronic address: cfmmenck@usp.br.
Carlos Frederico Martins
CFM
Menck
D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D000974:Antibodies, Antinuclear / Q000378:metabolism; D002417:Cattle; D002474:Cell-Free System; D004247:DNA / Q000737:chemistry* / Q000276:immunology / Q000528:radiation effects; D004249:DNA Damage; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D018384:Oxidative Stress; D010787:Photosensitivity Disorders; D011740:Pyrimidine Dimers / Q000737:chemistry; D026082:Singlet Oxygen / Q000737:chemistry*; D012965:Sodium Chloride / Q000378:metabolism; D013472:Sunlight; D013950:Thymus Gland / Q000502:physiology*; D014466:Ultraviolet Rays / Q000009:adverse effects
D000974:Antibodies, Antinuclear; D011740:Pyrimidine Dimers; D026082:Singlet Oxygen; D012965:Sodium Chloride; D000080242:8-Hydroxy-2'-Deoxyguanosine; D004247:DNA; D003849:Deoxyguanosine
DNA damage; Singlet oxygen; Ultraviolet radiation