title: Cytotoxic responses to 405nm light exposure in mammalian and bacterial cells: Involvement of reactive oxygen species.
abstract: Light at wavelength 405 nm is an effective bactericide. Previous studies showed that exposing mammalian cells to 405 nm light at 36 J/cm(2) (a bactericidal dose) had no significant effect on normal cell function, although at higher doses (54 J/cm(2)), mammalian cell death became evident. This research demonstrates that mammalian and bacterial cell toxicity induced by 405 nm light exposure is accompanied by reactive oxygen species production, as detected by generation of fluorescence from 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate. As indicators of the resulting oxidative stress in mammalian cells, a decrease in intracellular reduced glutathione content and a corresponding increase in the efflux of oxidised glutathione were observed from 405 nm light treated cells. The mammalian cells were significantly protected from dying at 54 J/cm(2) in the presence of catalase, which detoxifies H2O2. Bacterial cells were significantly protected by sodium pyruvate (H2O2 scavenger) and by a combination of free radical scavengers (sodium pyruvate, dimethyl thiourea (OH scavenger) and catalase) at 162 and 324 J/cm(2). Results therefore suggested that the cytotoxic mechanism of 405 nm light in mammalian cells and bacteria could be oxidative stress involving predominantly H2O2 generation, with other ROS contributing to the damage.
authors.affiliation: University of Strathclyde, Department of Biomedical Engineering, Wolfson Centre, 106 Rottenrow, Glasgow, Scotland G4 0NW, United Kingdom.
authors.forename: Praveen
authors.initials: P
authors.lastname: Ramakrishnan
authors.affiliation: University of Strathclyde, Department of Biomedical Engineering, Wolfson Centre, 106 Rottenrow, Glasgow, Scotland G4 0NW, United Kingdom; University of Strathclyde, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, 204 George street, Glasgow, Scotland G1 1XW, United Kingdom.
authors.forename: Michelle
authors.initials: M
authors.lastname: Maclean
authors.affiliation: University of Strathclyde, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, 204 George street, Glasgow, Scotland G1 1XW, United Kingdom.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: MacGregor
authors.affiliation: University of Strathclyde, The Robertson Trust Laboratory for Electronic Sterilisation Technologies, 204 George street, Glasgow, Scotland G1 1XW, United Kingdom.
authors.forename: John G
authors.initials: JG
authors.lastname: Anderson
authors.affiliation: University of Strathclyde, Department of Biomedical Engineering, Wolfson Centre, 106 Rottenrow, Glasgow, Scotland G4 0NW, United Kingdom. Electronic address: m.h.grant@strath.ac.uk.
authors.forename: M Helen
authors.initials: MH
authors.lastname: Grant
mesh_terms: D000818:Animals; D002374:Catalase / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D016166:Free Radical Scavengers / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D008027:Light; D050296:Microbial Viability / Q000187:drug effects / Q000528:radiation effects; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects; D011773:Pyruvates / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D013212:Staphylococcus epidermidis / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D016166:Free Radical Scavengers; D011773:Pyruvates; D017382:Reactive Oxygen Species; C038983:1,3-dimethylthiourea; D002374:Catalase; D005978:Glutathione; D013890:Thiourea; D019803:Glutathione Disulfide
keywords: 405nm light; Bactericide; Cytotoxic mechanisms; Osteoblasts; Reactive oxygen species; Scavengers