title: UVB irradiation changes genotoxic potential of nonylphenolpolyethoxylates--remarkable generation of γ-H2AX with degradation of chemical structure.
abstract: Nonylphenolpolyethoxylates (NPEOs) are non-ionic surfactants widely used for industrial and household purposes. In actual environments, NPEOs can be biodegraded, but the products are reported to be more persistent and toxic than the parent compounds. NPEOs are also exposed to sunlight and degraded. Studies on the photodegradation of NPEOs have focused mainly on chemical changes after exposure to light. Toxic changes of photodegraded products correlating to the chemical changes are not completely understood. In this study, we examined the genotoxicity of UVB-irradiated NPEOs having ethylene oxide units 15 and 70 in a human breast adenocarcinoma cell line, MCF-7, based on the phosphorylation of histone H2AX (γ-H2AX), a sensitive marker for DNA damage. We clarified that UVB irradiation drastically changed the genotoxic potential of NPEOs: NPEO(15)'s ability to generate γ-H2AX was significantly reduced, whereas non-genotoxic NPEO(70) became able to generate γ-H2AX. Flow cytometric analysis showed that the γ-H2AX generated by UVB-irradiated NPEO(70)was produced independent of cell cycle phases. In addition, its production involved the activation of ATM or DNA-PK, a general signalling pathway in response to DNA double strand breaks. High-performance liquid chromatography analysis indicated that the formation of NPEO intermediates with a short side-chain like NPEO(15) was the cause of the γ-H2AX generation. This study suggests the importance of taking the genotoxicity of photodegraded intermediates into consideration when conducting risk assessments of environmental pollutants.
authors.affiliation: Institute for Environmental Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka-shi, Shizuoka 422-8526, Japan.
authors.forename: Tatsushi
authors.initials: T
authors.lastname: Toyooka
authors.forename: Toru
authors.initials: T
authors.lastname: Kubota
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ibuki
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D045744:Cell Line, Tumor; D002851:Chromatography, High Pressure Liquid; D004249:DNA Damage / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D006657:Histones / Q000378:metabolism*; D006801:Humans; D009152:Mutagenicity Tests / Q000379:methods; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism; D013501:Surface-Active Agents / Q000737:chemistry / Q000528:radiation effects* / Q000633:toxicity*; D014466:Ultraviolet Rays
chemical_list: D015415:Biomarkers; C468783:H2AX protein, human; D006657:Histones; D017382:Reactive Oxygen Species; D013501:Surface-Active Agents