Development of a DNA-dosimeter system for monitoring the effects of solar-ultraviolet radiation

Abstract

Solar radiation sustains and affects all life forms on Earth. In recent years, the increase in environmental levels of solar-UV radiation due to depletion of the stratospheric ozone layer, as a result of anthropogenic emission of destructive chemicals, has highlighted serious issues of social concern. This becomes still more dramatic in tropical and subtropical regions, where the intensity of solar radiation is higher. To better understand the impact of the harmful effects of solar-UV radiation on the DNA molecule, we developed a reliable biological monitoring system based on the exposure of plasmid DNA to artificial UV lamps and sunlight. The determination and quantification of different types of UV photoproducts were performed through the use of specific DNA repair enzymes and antibodies. As expected, a significant number of CPDs and 6-4PPs was observed when the DNA-dosimeter system was exposed to increasing doses of UVB radiation. Moreover, CPDs could also be clearly detected in plasmid DNA when this system was exposed to either UVA or directly to sunlight. Interestingly, although less abundant, 6-4PPs and oxidative DNA damage were also generated after exposure to both UVA and sunlight. These results confirm the genotoxic potential of sunlight, reveal that UVA may also produce CPDs and 6-4PPs directly in naked DNA and demonstrate the applicability of a DNA-dosimeter system for monitoring the biological effects of solar-UV radiation.

Molecular and sensory mechanisms to mitigate sunlight-induced DNA damage in treefrog tadpoles

“…However, studies indicate that UVA radiation induces CPDs directly on DNA more readily than it induces oxidized bases, suggesting that UVA may be more mutagenic than previously assumed (Jiang et al, 2009;Schuch et al, 2009). Additionally, although UVA absorption by DNA is poor, the presence of 6,4PPs in purified DNA samples and in human cell cultures after irradiation with UVA light has been demonstrated (Cortat et al, 2013;Schuch et al, 2009).…”

“…The direct absorption of UVB photons, mainly by the pyrimidine bases cytosine (C) and thymine (T), leads to the formation of distortive DNA lesions known as pyrimidine dimers. The main DNA photoproducts are cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6,4) pyrimidone photoproducts (6,4PPs) (Rastogi et al, 2010;Schuch et al, 2009). However, sunlight can also indirectly damage DNA after photon absorption by other chromophores, thereby generating reactive oxygen species.…”

Resposta a danos no DNA após exposição à luz ultravioleta: apagando o fogo antes do incêndio celular

“…3B). A proporção de fotoprodutos de DNA formados, tanto por luz UVC e UVB, é de 75% de CPD e 25% de 6-4PPs (Kobayashi et al, 2001;Schuch et al, 2009). Porém, enquanto CPD é formado de maneira aleatória na cromatina, 6-4PP apresentam diferente distribuição com formação preferencial em regiões entre nucleossomos (Mitchell et al, 1990).…”

Plasmid DNA damage induced by singlet molecular oxygen released from the naphthalene endoperoxide DHPNO2 and photoactivated methylene blue

“…The enzymes were tested up to saturation, so that all lesions were cleaved, but in amounts where no non-specific cleavage was observed. 28 Damaged plasmid DNA samples were subject to electrophoresis in 0.8% agarose gels already stained with ethidium bromide (0.5 µg/ mL) in a Tris-borate buffer (pH 7.5). After migration, the DNA was visualized under UV light using an Image Quant 300 (GE Healthcare, USA), to obtain digital images of the stained gels.…”