Yagura Teiti, Schuch André Passaglia, Garcia Camila Carrião Machado, Rocha Clarissa Ribeiro Reily, Moreno Natália Cestari, Angeli José Pedro Friedmann, Mendes Davi, Severino Divinomar, Bianchini Sanchez Angelica, Di Mascio Paolo, de Medeiros Marisa Helena Gennari, Menck Carlos Frederico Martins
Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, 05508-000 São Paulo, SP, Brazil.
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.
Free Radic Biol Med. 2017 Jul;108:86-93. doi: 10.1016/j.freeradbiomed.2017.03.018. Epub 2017 Mar 18.
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.
紫外线A（UVA）几乎不被DNA分子吸收，但最近的研究指出这些波长会通过直接机制造成DNA损伤。UVA还会激发内源性发色团，通过活性氧（ROS）导致DNA损伤。在本研究中，对处于不同条件下的DNA样本进行UVA照射，以探究DNA损伤诱导过程中可能涉及的机制。照射后形成的不同类型DNA损伤通过使用能识别并切割含有氧化碱基和环丁烷嘧啶二聚体（CPD）位点的核酸内切酶以及抗体识别来确定。还使用电化学检测更详细地研究了8-氧代-7,8-二氢-2'-脱氧鸟嘌呤（8-氧代dG）的形成。结果表明，高氯化钠浓度和浓缩的DNA能够减少CPD的诱导。此外，关于氧化应激造成的损伤，叠氮化钠和金属螯合剂的存在会减少其诱导，而重水会增加氧化碱基的量，这证实了单线态氧参与了这些损伤的产生。然而，奇怪的是，高浓度的DNA也会增强氧化碱基的形成，这一反应与溶液中单线态氧形成的增加平行。这被解释为是由于一种内在的光敏化机制，直接取决于DNA分子吸收UVA并产生单线态氧。因此，DNA分子本身可能充当UVA的发色团，在局部产生一种损伤剂，这可能会引发对阳光有害影响的更大担忧。
