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

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 DIVA 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/cm(2) UVA1 and another part to 126 J/cm(2) 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, p21(WAF), bcl-2, Ki67 and cyclin A. Results: By comparison tea untreated skin, an increased expression of p53 but not p21(WAF) 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.