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UVA-induced carbon-centred radicals in lightly pigmented cells detected using ESR spectroscopy

Kassouf, N; Kay, CWM; Volkov, A; Chiang, S-C; Birch-Machin, MA; El-Khamisy, SF; Haywood, RM; (2018) UVA-induced carbon-centred radicals in lightly pigmented cells detected using ESR spectroscopy. Free Radical Biology and Medicine , 126 pp. 153-165. 10.1016/j.freeradbiomed.2018.07.019. Green open access

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Abstract

Ultraviolet-A and melanin are implicated in melanoma, but whether melanin in vivo screens or acts as a UVA photosensitiser is debated. Here, we investigate the effect of UVA-irradiation on non-pigmented, lightly and darkly pigmented melanocytes and melanoma cells using electron spin resonance (ESR) spectroscopy. Using the spin trap 5,5 Dimethyl-1-pyrroline N-oxide (DMPO), carbon adducts were detected in all cells. However, higher levels of carbon adducts were detected in lightly pigmented cells than in non-pigmented or darkly pigmented cells. Nevertheless, when melanin levels were artificially increased in lightly pigmented cells by incubation with L-Tyrosine, the levels of carbon adducts decreased significantly. Carbon adducts were also detected in UVA-irradiated melanin-free cell nuclei, DNA-melanin systems, and the nucleoside 2'-deoxyguanosine combined with melanin, whereas they were only weakly detected in irradiated synthetic melanin and not at all in irradiated 2'-deoxyguanosine. The similarity of these carbon adducts suggests they may be derived from nucleic acid- guanine - radicals. These observations suggest that melanin is not consistently a UVA screen against free-radical formation in pigmented cells, but may also act as a photosensitizer for the formation of nucleic acid radicals in addition to superoxide. The findings are important for our understanding of the mechanism of damage caused by the UVA component of sunlight in non-melanoma and melanoma cells, and hence the causes of skin cancer.

Type: Article
Title: UVA-induced carbon-centred radicals in lightly pigmented cells detected using ESR spectroscopy
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.freeradbiomed.2018.07.019
Publisher version: https://doi.org/10.1016/j.freeradbiomed.2018.07.01...
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Ultraviolet-A, electron-spin-resonance spectroscopy, free radicals, melanocyte, melanoma
UCL classification: UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology
URI: http://discovery.ucl.ac.uk/id/eprint/10054126
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