In vivo imaging of reactive oxygen species specifically associated with thioflavine S-positive amyloid plaques by multiphoton microscopy.
Amyloid-beta, the primary constituent of senile plaques in Alzheimer's disease, is hypothesized to cause neuronal damage and cognitive failure, but the mechanisms are unknown. Using multiphoton imaging, we show a direct association between amyloid-beta deposits and free radical production in vivo in live, transgenic mouse models of Alzheimer's disease and in analogous ex vivo experiments in human Alzheimer tissue. We applied two fluorogenic compounds, which become fluorescent only after oxidation, before imaging with a near infrared laser. We observed fluorescence associated with dense core plaques, but not diffuse plaques, as determined by subsequent addition of thioflavine S and immunohistochemistry for amyloid-beta. Systemic administration of N-tert-butyl-alpha-phenylnitrone, a free radical spin trap, greatly reduced oxidation of the probes. These data show directly that a subset of amyloid plaques produces free radicals in living, Alzheimer's models and in human Alzheimer tissue. Antioxidant therapy neutralizes these highly reactive molecules and may therefore be of therapeutic value in Alzheimer's disease.
McLellan
Megan E
ME
Massachusetts General Hospital, Department of Neurology/Alzheimer's Disease Research Laboratory, Charlestown, Massachusetts 02129, USA.
Kajdasz
Stephen T
ST
Hyman
Bradley T
BT
Bacskai
Brian J
BJ
D000544:Alzheimer Disease / Q000175:diagnosis* / Q000378:metabolism*; D016229:Amyloid beta-Peptides / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D052160:Benzothiazoles; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism; D003497:Cyclic N-Oxides; D004195:Disease Models, Animal; D005456:Fluorescent Dyes / Q000378:metabolism; D016166:Free Radical Scavengers / Q000494:pharmacology; D005609:Free Radicals / Q000378:metabolism; D007259:Infrared Rays; D007834:Lasers; D051379:Mice; D008822:Mice, Transgenic; D036641:Microscopy, Fluorescence, Multiphoton; D009589:Nitrogen Oxides / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D058225:Plaque, Amyloid / Q000145:classification / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism*; D013844:Thiazoles / Q000378:metabolism*
D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; D000975:Antioxidants; D052160:Benzothiazoles; D003497:Cyclic N-Oxides; D005456:Fluorescent Dyes; D016166:Free Radical Scavengers; D005609:Free Radicals; D009589:Nitrogen Oxides; D017382:Reactive Oxygen Species; D013844:Thiazoles; C009462:thioflavin T; C029217:phenyl-N-tert-butylnitrone