UVB irradiation changes genotoxic potential of nonylphenolpolyethoxylates- remarkable generation ofç-H2AX with degradation of chemical structure

This study examined the genotoxicity of UVB-irradiated nonylphenolpolyethoxylates (NPEO)s having ethylene oxide units 15 and 70 in a human breast adenocarcinoma cell line, MCF-7, based on the phosphorylation of histone H2AX (ç-H2AX), a sensitive marker for DNA damage. The study clarified that UVB irradiation drastically changed the genotoxic potential of NPEOs: NPEO(15)’s ability to generate ç-H2AX was significantly reduced, whereas non-genotoxic NPEO(70) became able to generate ç-H2AX. Flow cytometric analysis showed that the ç-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 sidechain like NPEO(15) was the cause of the ç-H2AX generation. This study suggested the importance of taking the genotoxicity of photodegraded intermediates into consideration when conducting risk assessments of environmental pollutants.