title: Photosensitization of DNA damage by glycated proteins.
abstract: Photosensitized DNA damage in skin is thought to be an important mechanism of UV phototoxicity. Here we demonstrate that proteins modified by advanced glycation endproducts (AGE-proteins) are photosensitizers of DNA damage and show that multiple mechanisms are involved in AGE-sensitization. AGE-chromophores accumulate on long-lived skin proteins such as collagen and elastin as a consequence of glycation, the spontaneous amino-carbonyl reaction of protein-bound lysine and arginine residues with reactive carbonyl species. AGE-proteins accumulate in both the nucleus and the cytoplasm of mammalian cells. To test the hypothesis that protein-bound AGEs in close proximity to DNA are potent UV-photosensitizers, a simple plasmid DNA cleavage assay was established. Irradiation of supercoiled phiX 174 DNA with solar simulated light in the presence of AGE-modified bovine serum albumin or AGE-modified RNAse A induced DNA single strand breaks. The sensitization potency of the glycated protein correlated with increased AGE-modification and the unmodified protein displayed no photosensitizing activity. AGE-sensitized formation of reactive oxygen species was not fully responsible for the observed DNA damage and other mechanisms such as direct electron transfer interaction between photoexcited AGE and DNA are likely to be involved. Glycated proteins in skin may equally function as potent photosensitizers of DNA damage with implications for photoaging and photocarcinogenesis.
authors.affiliation: Department of Pharmacology and Toxicology, College of Pharmacy, Arizona Cancer Center, University, of Arizona, Tucson, AZ, USA.
authors.forename: Georg T
authors.initials: GT
authors.lastname: Wondrak
authors.forename: Elaine L
authors.initials: EL
authors.lastname: Jacobson
authors.forename: Myron K
authors.initials: MK
authors.lastname: Jacobson
mesh_terms: D000818:Animals; D002417:Cattle; D004247:DNA / Q000737:chemistry / Q000528:radiation effects*; D004249:DNA Damage; D017127:Glycation End Products, Advanced / Q000737:chemistry* / Q000633:toxicity; D006031:Glycosylation; D006861:Hydrogen Peroxide / Q000138:chemical synthesis; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000633:toxicity; D010957:Plasmids / Q000528:radiation effects; D017382:Reactive Oxygen Species / Q000737:chemistry; D012259:Ribonuclease, Pancreatic / Q000737:chemistry* / Q000633:toxicity; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000633:toxicity; D013050:Spectrometry, Fluorescence; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods; D013472:Sunlight / Q000009:adverse effects*; D013481:Superoxides / Q000138:chemical synthesis; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D017127:Glycation End Products, Advanced; D017319:Photosensitizing Agents; D017382:Reactive Oxygen Species; D013481:Superoxides; D012710:Serum Albumin, Bovine; D004247:DNA; D006861:Hydrogen Peroxide; D012259:Ribonuclease, Pancreatic