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Published on: March 24, 2017
UVA1 is skin deep: molecular and clinical implications
Angela Tewari1, Mette M L Grage, Graham I Harrison
1King's College London (KCL), King's College London School of Medicine, Division of Genetics and Molecular Medicine, St John's Institute of Dermatology, London, UK. angela.tewari@kcl.ac.uk
Summary
Long wavelength UVA1 radiation causes DNA damage, specifically cyclobutane pyrimidine dimers (CPD), in deeper skin layers. This suggests increased vulnerability in basal cells, highlighting the need for better UVA1 sun protection.
Area of Science:
- Dermatology
- Photobiology
- Molecular Biology
Background:
- Long wavelength UVA1 (340-400 nm) is a major component of terrestrial UV radiation and is used in phototherapy.
- UVA1's DNA damage was previously attributed to reactive oxygen species (ROS) generation.
- Recent findings indicate UVA1 directly induces cyclobutane pyrimidine dimers (CPD), particularly thymine dimers (T<>T), implicated in skin cancer.
Purpose of the Study:
- To investigate the depth-dependent penetration and DNA damage effects of UVA1 in skin.
- To compare UVA1-induced DNA damage with UVB-induced damage in vivo.
- To assess the vulnerability of deeper skin layers, including the basal layer, to UVA1.
Main Methods:
- In vivo measurement of cyclobutane pyrimidine dimers (CPD) in epidermal and dermal layers after UVA1 and UVB exposure.
- Comparison of UV attenuation by skin for UVB versus UVA1.
- Assessment of DNA damage at different skin depths.
Main Results:
- Skin effectively attenuates UVB, reducing CPD in deeper layers as expected.
- UVA1 penetrates the skin without significant attenuation, with increased CPD observed at greater depths.
- The basal layer, containing stem cells and melanocytes, shows higher UVA1-induced DNA damage than predicted.
Conclusions:
- UVA1 directly induces CPD, posing a significant risk to deeper skin layers, including the basal layer.
- The findings challenge existing models and suggest basal cells are more vulnerable to UVA1 carcinogenesis than previously thought.
- Enhanced UVA1 protection in sunscreens is recommended to mitigate these risks.
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