UVA DNA damage: lower epidermal cell nuclei are redder indicating more damage
New research has discovered that damage caused by UVA1 – the primary waveband emitted by sun beds – may be more carcinogenic than previously thought.
Although the sun’s UVB rays are generally considered the major cause of skin cancer, a new BRC-funded study reports that UVA radiation is also highly damaging. UVA is 20 times more abundant than UVB in sunshine.
Published online today in the Journal of Investigative Dermatology, the research highlights the need for broader spectrum sun protection and may influence future public health policies.
UV damage
The mutations found in skin cancers are commonly thought to be caused by UVB rays. These cause photochemical reactions, resulting in molecular changes in thymine or cytosine bases in DNA.
The study
Angela Tewari and colleagues at King’s College London, compared the DNA damaging effects of UVA1 (approx 75% of the sun’s UV radiation) and UVB rays in the skin of 12 healthy young volunteers.
They found that UVA1 causes DNA damage called thymine dimers (TT). UVB radiation also cause TT – at a higher level than UVA1 – as well as another type of DNA damage called pyrimidine (6-4) pyrimidone photoproducts.
The UVA1 DNA damage was greatest in the lowest (basal) layer of the epidermis (outer layer of skin). In contrast the UVB damage was greatest in the upper layers.
This suggests that the basal layer of the epidermis may be particularly vulnerable to UVA1-induced damage. This is important because the basal layer is where cell division in the skin takes place and some types of skin cancer originate.
Implications
This study is the first to compare the effects of UVA1 to equivalent sunburning doses of UVB. It:
-
Demonstrates that UVA1 induces damage which – if unrepaired – has the potential to cause skin cancer
-
Indicates that UVA1, the primary waveband emitted by sun-beds, may be more carcinogenic than previously thought
A Tewari et al, J Investigative Derm, Oct 2011
Posted on Friday 7th October 2011