Photomicronucleus assay of phototoxic and pseudophotoclastogenic chemicals in human keratinocyte NCTC2544 cells

Mayumi Horinouchi, Sakae Arimoto-Kobayashi

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16 Citations (Scopus)


Photochemical genotoxicity was evaluated in human keratinocyte NCTC2544 cells. The cells were pre-treated with photogenotoxic or pseudophotoclastogenic chemicals and irradiated with a solar-simulator for 50min at a total UV dose of 5J/cm2 or placed in the dark for the same period. After washing, the cells were cultured for 1.5-2 cell cycles with fresh culture medium. At the end of culturing, slide specimens were prepared and examined for micronucleus formation. 8-Methoxypsoralen, a photogenotoxic chemical, strongly induced micronucleated cells with UV irradiation but not under non-irradiation conditions. Therefore, NCTC2544 cells were subjected to further investigation to evaluate the possible photogenotoxicity of other chemicals. 6-Methylcoumarin, 3,3′,4′,5-tetrachlorosalicylanilide and protoporphyrin IX disodium salt, which are all known phototoxic substances, induced micronucleated cells with irradiation but not in the non-irradiation state. These phototoxic substances were confirmed to be photogenotoxic. Tetrabenzoporphine and 5-aminolevulinic acid, which are used for photodynamic therapy, showed phototoxicity. However, these chemicals did not induce micronucleated cells in the irradiated or non-irradiated state, suggesting a lack of photogenotoxicity. Among 3 pseudophotoclastogenic chemicals having no light absorbance at 290-700nm, neither cycloheximide nor disulfoton induced micronucleated cells with or without irradiation; zinc oxide induced micronucleated cells with irradiation and, to a lesser extent, without irradiation. Based on the results of the photogenotoxicity assays of these 9 chemicals, NCTC2544 cells are considered to be a suitable test system to evaluate the photogenotoxic potential of chemicals.

Original languageEnglish
Pages (from-to)43-50
Number of pages8
JournalMutation Research - Genetic Toxicology and Environmental Mutagenesis
Issue number1
Publication statusPublished - Jul 14 2011


  • Human keratinocyte
  • NCTC2544 cells
  • Photogenotoxicity
  • Photomicronucleus assay

ASJC Scopus subject areas

  • Genetics
  • Health, Toxicology and Mutagenesis


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