title: Antioxidant enzymes and the mechanism of the bystander effect induced by ultraviolet C irradiation of A375 human melanoma cells.
abstract: Irradiated cells generate dynamic responses in non-irradiated cells; this signaling phenomenon is known as the bystander effect (BE). Factors secreted by the irradiated cells communicate some of these signals. Conditioned medium from UVC-irradiated A375 human melanoma cells was used to study the BE. Exposure of cells to conditioned medium induce cell-cycle arrest at the G2/M transition. Although conditioned medium treatment, by itself, did not alter cell viability, treated cells were more resistant to the lethal action of UVC or H2O2. This protective effect of conditioned medium was lost within 8h. Apoptotic or autophagic cell death was not involved in this resistance. Exposure to conditioned medium did not influence the rate of DNA repair, as measured by NAD(+) depletion. The activities of catalase and superoxide dismutase were elevated in cells exposed to conditioned medium, but returned to normal levels by 8h post-treatment. These results indicate a close correlation between BE-stimulated antioxidant activity and cellular sensitivity. Cell-cycle arrest and stimulation of antioxidant activity may account for the resistance to killing that was observed in bystander cells exposed to UVC or H2O2 treatment and are consistent with the role of the BE as a natural defense function triggered by UVC irradiation.
authors.affiliation: Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal, India. Electronic address: ritadg2001@yahoo.co.in.
authors.forename: Rita
authors.initials: R
authors.lastname: Ghosh
authors.forename: Dipanjan
authors.initials: D
authors.lastname: Guha
authors.forename: Sudipta
authors.initials: S
authors.lastname: Bhowmik
authors.forename: Sayantani
authors.initials: S
authors.lastname: Karmakar
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D024201:Bystander Effect / Q000187:drug effects* / Q000528:radiation effects; D002450:Cell Communication / Q000187:drug effects / Q000528:radiation effects; D059447:Cell Cycle Checkpoints / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008545:Melanoma / Q000473:pathology*; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D006861:Hydrogen Peroxide
keywords: AO; AVO; Antioxidant defense; BE; Bystander effect; CAT; Cell cycle arrest; Cell death; Cu–Zn superoxide dismutase; FITC; GPx; HGPRT; Mutation; NAD+; NAD+ assay; PI; SD; SOD; TUNEL; UV; acidic vesicular organelles; acridine orange; bystander effect; catalase; fluorescein-isothiocyanate; glutathione peroxidase; hypoxanthine guanine phosphoribosyl transferase; nicotinamide adenine dinucleotide; propidium iodide; standard deviation; terminal deoxynucleotidyl transferase dUTP nick end labeling; ultra-violet light