Chronic and cyclical neuronal loss in hippocampal slice cultures following transient inhibition of the type 1 isoform of superoxide dismutase.
Increased oxidative stress contributes to chronic neurodegenerative diseases, yet the underlying mechanisms are poorly understood. Hippocampal slice cultures prepared from 20-30-day-old mice or rats were used to model chronic neuronal loss following oxidative stress. Neuronal loss was initiated by inhibition of the antioxidant enzyme, superoxide dismutase type 1 (SOD1), using the copper chelator diethyldithiocarbamate (DDC). Continuous DDC treatment of slice cultures induced delayed neuronal loss beginning at 9 days of treatment that lasted for over 4 weeks. Neuronal loss was not uniform, rather it was cyclic: peaking at days 9-13 and at days 19-21 after DDC exposure. Neuronal loss was significantly attenuated in slice cultures that overexpress SOD1, suggesting that SOD1 inhibition was responsible. Inhibitors of nitric oxide synthase also attenuated DDC-induced neuronal loss. Chronic neuronal loss, however, did not require continuous SOD1 inhibition. Application of DDC for 13 days resulted in loss of SOD1 activity. Removal of DDC restored SOD1 activity, yet the cycles of cell loss continued until no neurons remained. Astrocyte activation was observed following the second peak of neuronal loss. Media conditioned by cultures following DDC removal induced neuronal loss and microglial activation in recipient cultures. These data suggest that slice cultures released soluble neurotoxic factor(s) following DDC removal. These data also suggest that a transient reduction of SOD1 activity leads to chronic loss of hippocampal neurons. This neuronal loss may be mediated by soluble neurotoxic factor(s) and microglial activation. Cyclical neuronal loss may also underlie chronic neurodegeneration in vivo.
Moskowitz
S I
SI
Department of Physiology and Pharmacology, State University of New York, Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA.
Basu
S B
SB
Bergold
P J
PJ
D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004050:Ditiocarb / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D015870:Gene Expression / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains / Q000378:metabolism; D017628:Microglia / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D019636:Neurodegenerative Diseases / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D014266:Trientine / Q000494:pharmacology
D002614:Chelating Agents; D017077:Culture Media, Conditioned; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D004050:Ditiocarb; D019001:Nitric Oxide Synthase; C000606291:Sod1 protein, mouse; C000606292:Sod1 protein, rat; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D014266:Trientine