title: Effects on human skin of repetitive ultraviolet-A1 (UVA1) irradiation and visible light.
abstract: 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.
  
  
  CONCLUSIONS
  These results suggest that suberythemal doses of UVA1 and even visible light may cause DNA damage.
authors.affiliation: Department of Dermatology, Karolinska Hospital, Stockholm, Sweden. desiree.edstrom@ks.se
authors.forename: D W
authors.initials: DW
authors.lastname: Edström
authors.forename: A
authors.initials: A
authors.lastname: Porwit
authors.forename: A M
authors.initials: AM
authors.lastname: Ros
mesh_terms: D000328:Adult; D019925:Cyclin A / Q000032:analysis; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000032:analysis; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000032:analysis; D008027:Light; D008297:Male; D008875:Middle Aged; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D012867:Skin / Q000737:chemistry / Q000528:radiation effects*; D016159:Tumor Suppressor Protein p53 / Q000032:analysis; D014466:Ultraviolet Rays
chemical_list: C493956:CDKN1A protein, human; D019925:Cyclin A; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D019394:Ki-67 Antigen; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53