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Effects on human skin of repetitive ultraviolet-A1 (UVA1) irradiation and visible light
D W Edström1, A Porwit, A M Ros
1Department of Dermatology, Karolinska Hospital, Stockholm, Sweden. desiree.edstrom@ks.se
Background:
Ultraviolet radiation (UVR) has a variety of effects on human skin. Best known are the effects of UVB (290-320 nm) and UVA2 (320-340 nm), which cause DNA damage and increased risk of cancer. However, the effects of UVA1 (340-400 nm) have been not completely investigated.
Methods:
The effects of repetitive low doses of UVA1 and visible light were studied in 12 healthy individuals. A part of the buttock was exposed to 20 J/cm2 UVA1 and another part of 126 J/cm2 of visible light three times a week for 4 weeks. Repeated punch biopsies were taken during the 4 weeks of treatment and also 2 weeks after the last irradiation. The avidin-biotin-immunoperoxidase technique was used to investigate the expression of p53, p21WAF, bcl-2, Ki67 and cyclin A.
Results:
By comparison to untreated skin, an increased expression of p53 but not p21WAF in keratinocytes was seen. The bcl-2 protein expression increased slightly after both UVA1 and visible light. An increased staining with Ki67 and cyclin A after UVA1 but not after visible light was observed as a sign of increased proliferation.
Conclusion:
These results suggest that suberythemal doses of UVA1 and even visible light may cause DNA damage.
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