title: Real-time imaging of novel spatial and temporal responses to photodynamic stress.
abstract: Cells subjected to various forms of stress have been shown to induce bystander responses in nontargeted cells, thus extending the stress response to a larger population. However, the mechanism(s) of bystander responses remains to be clearly identified, particularly for photodynamic stress. Oxidative stress and cell viability were studied on the spatial and temporal levels after photodynamic targeting of a subpopulation of EMT6 murine mammary cancer cells in a multiwell plate by computerized time-lapse fluorescence microscopy. In the targeted population a dose-dependent loss of cell viability was observed in accordance with increased oxidative stress. This was accompanied by increased oxidative stress in bystander populations but on different time scales, reaching a maximum more rapidly in targeted cells. Treatment with extracellular catalase, or the NADPH oxidase inhibitor diphenyleneiodinium, decreased production of reactive oxygen species (ROS) in both populations. These effects are ascribed to photodynamic activation of NADPH-oxidase in the targeted cells, resulting in a rapid burst of ROS formation with hydrogen peroxide acting as the signaling molecule responsible for initiation of these photodynamic bystander responses. The consequences of increased oxidative stress in bystander cells should be considered in the overall framework of photodynamic stress.
authors.affiliation: Wellman Center for Photomedicine, Harvard Medical School, Massachusetts General Hospital, Boston, MA 02114, USA.
authors.forename: Noemi
authors.initials: N
authors.lastname: Rubio
authors.forename: Anpuchchelvi
authors.initials: A
authors.lastname: Rajadurai
authors.forename: Kathryn D
authors.initials: KD
authors.lastname: Held
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Prise
authors.forename: Howard L
authors.initials: HL
authors.lastname: Liber
authors.forename: Robert W
authors.initials: RW
authors.lastname: Redmond
mesh_terms: D000818:Animals; D024201:Bystander Effect / Q000187:drug effects / Q000528:radiation effects; D002374:Catalase / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003199:Computer Systems; D003710:Demography; D005260:Female; D015674:Mammary Neoplasms, Animal / Q000473:pathology / Q000628:therapy*; D051379:Mice; D008856:Microscopy, Fluorescence; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors; D009861:Onium Compounds / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects / Q000528:radiation effects; D010778:Photochemotherapy / Q000009:adverse effects; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: D009861:Onium Compounds; D017382:Reactive Oxygen Species; C007517:diphenyleneiodonium; D002374:Catalase; D019255:NADPH Oxidases