Intensity-dependent direct solar radiation- and UVA-induced radical damage to human skin and DNA, lipids and proteins

Haywood, Rachel, Andrady, Carima, Kassouf, Nick and Sheppard, Nick (2011) Intensity-dependent direct solar radiation- and UVA-induced radical damage to human skin and DNA, lipids and proteins. Photochemistry and Photobiology, 87 (1). pp. 117-130. ISSN 0031-8655

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Abstract

Skin can be exposed to high-intensity UV-radiation in hot countries and during sunbed use; however, the free-radical damage at these intensities is unknown. We used electron spin resonance spectroscopy to measure free-radical generation in ex vivo human skin/substitutes +/- the spin-trap 5,5 dimethyl-1-pyrroline N-oxide (DMPO) exposed to solar-irradiation equivalent to Mediterranean sunlight. Skin-substitutes, model DNA-photosensitizer systems, lipids and proteins were also irradiated with low-intensity UVA/visible light. Without DMPO a broad singlet was detected (using both irradiations) in skin/substitutes, nail-keratin, tendon-collagen, phospholipid and DNA+melanin or riboflavin. In addition to lipid-derived (tentatively tert-alkoxyl/acyl-) and protein radicals detected with DMPO at lower intensities, isotropic carbon-, additional oxygen- and hydrogen-adducts were detected in solar-irradiated skin/substitutes at higher intensities. Carbon-adducts were detected in UVA-irradiated human skin cells, DNA+melanin or riboflavin and soybean-phospholipid. Anisotropic protein-adducts, comparable to adducts in solar-irradiated tendon-collagen, were absent in UVA-irradiated skin fibroblasts suggesting the trapping of extracellular collagen radicals. Absence of hydrogen-adducts in fibroblasts implies formation in the extracellular compartment. We conclude damage at high intensities is part cellular (carbon- and oxygen-radicals) and part extracellular (protein- and hydrogen/H(+)+e(-) ), and skin substitutes are suitable for sunscreen testing. While UVA absorption and lipid-oxidation is direct, DNA and protein-oxidation require photosensitisation.

Item Type: Article
Additional Information: First published: 8 December 2010
Research Areas: A. > School of Science and Technology > Natural Sciences
A. > School of Science and Technology > Natural Sciences > Biomarkers for Cancer group
A. > School of Science and Technology > Natural Sciences > Molecular Biology group
Item ID: 19172
Notes on copyright: Access to full text restricted pending copyright check
Depositing User: Nick Kassouf
Date Deposited: 11 Apr 2016 11:28
Last Modified: 31 May 2019 06:00
URI: https://eprints.mdx.ac.uk/id/eprint/19172

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