Effects on human skin of repetitive ultraviolet-A1 (UVA1) irradiation and visible light
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 to 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.