title: Isatin, an endogenous monoamine oxidase inhibitor, triggers a dose- and time-dependent switch from apoptosis to necrosis in human neuroblastoma cells.
abstract: Isatin is an endogenous indole that is increased in stress, inhibits monoamine oxidase (MAO) B and improves bradykinesia and striatal dopamine levels in rat models of Parkinson's disease. Consequently, it has been suggested that isatin might be a possible treatment for Parkinson's disease although little is known about its effects on neural cell growth and survival. The aim of this study was to investigate the survival of dopaminergic human neuroblastoma (SH-SY5Y) cells following treatment with increasing concentrations of isatin. SH-SY5Y cells were exposed to isatin for defined time points, after which cell survival was determined by MTT assay. A combination of Annexin V binding and propidium iodide (PI) exclusion was used to distinguish apoptosis from necrosis in flow cytometry experiments and FACS profiles of permeabilised PI-labelled cells were employed for the assessment of cell cycle distribution. Isatin treatment (1-400 microM) for 24h induced a significant dose-dependent increase in MTT metabolism by SH-SY5Y cells in culture, but this was not due to an increase in cell division. At the higher concentrations (200-400 microm) isatin triggered cell death, although MTT metabolism was still increased in the culture, suggesting that surviving cells were hypermetabolic. Following a longer (48 h) exposure, isatin was found to cause cell death in a dose-dependent manner; at lower concentrations (50 microM), the predominant mode of cell death was apoptosis while at the highest concentration (400 microm) increasing numbers of necrotic cells were also evident. Thus, in dopaminergic SH-SY5Y cells isatin induces cell death in dose- and time-dependent manner. This death occurred as a continuum of survival, apoptosis and necrosis. Our results re-emphasise that caution should be exercised when considering high doses of isatin as a putative anti-Parkinson's disease therapeutic.
authors.affiliation: Weston Laboratory, Institute of Reproductive and Developmental Biology, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK.
authors.forename: N
authors.initials: N
authors.lastname: Igosheva
authors.forename: C
authors.initials: C
authors.lastname: Lorz
authors.forename: E
authors.initials: E
authors.lastname: O'Conner
authors.forename: V
authors.initials: V
authors.lastname: Glover
authors.forename: H
authors.initials: H
authors.lastname: Mehmet
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D000978:Antiparkinson Agents / Q000627:therapeutic use / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002463:Cell Membrane Permeability / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004298:Dopamine / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007510:Isatin / Q000627:therapeutic use / Q000633:toxicity*; D008996:Monoamine Oxidase Inhibitors / Q000627:therapeutic use / Q000633:toxicity*; D009336:Necrosis / Q000139:chemically induced / Q000378:metabolism; D009447:Neuroblastoma; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000627:therapeutic use / Q000633:toxicity; D010300:Parkinson Disease / Q000188:drug therapy / Q000378:metabolism / Q000503:physiopathology; D011419:Propidium; D013778:Tetrazolium Salts; D013844:Thiazoles; D013997:Time Factors
chemical_list: D017304:Annexin A5; D000978:Antiparkinson Agents; D008996:Monoamine Oxidase Inhibitors; D009498:Neurotoxins; D013778:Tetrazolium Salts; D013844:Thiazoles; D011419:Propidium; D007510:Isatin; C022616:thiazolyl blue; D004298:Dopamine