title: Late calcium EDTA rescues hippocampal CA1 neurons from global ischemia-induced death.
abstract: Transient global ischemia induces a delayed rise in intracellular Zn2+, which may be mediated via glutamate receptor 2 (GluR2)-lacking AMPA receptors (AMPARs), and selective, delayed death of hippocampal CA1 neurons. The molecular mechanisms underlying Zn2+ toxicity in vivo are not well delineated. Here we show the striking finding that intraventricular injection of the high-affinity Zn2+ chelator calcium EDTA (CaEDTA) at 30 min before ischemia (early CaEDTA) or at 48-60 hr (late CaEDTA), but not 3-6 hr, after ischemia, afforded robust protection of CA1 neurons in approximately 50% (late CaEDTA) to 75% (early CaEDTA) of animals. We also show that Zn2+ acts via temporally distinct mechanisms to promote neuronal death. Early CaEDTA attenuated ischemia-induced GluR2 mRNA and protein downregulation (and, by inference, formation of Zn2+-permeable AMPARs), the delayed rise in Zn2+, and neuronal death. These findings suggest that Zn2+ acts at step(s) upstream from GluR2 gene downregulation and implicate Zn2+ in transcriptional regulation and/or GluR2 mRNA stability. Early CaEDTA also blocked mitochondrial release of cytochrome c and Smac/DIABLO (second mitochondria-derived activator of caspases/direct inhibitor of apoptosis protein-binding protein with low pI), caspase-3 activity (but not procaspase-3 cleavage), p75NTR induction, and DNA fragmentation. These findings indicate that CaEDTA preserves the functional integrity of the mitochondrial outer membrane and arrests the caspase death cascade. Late injection of CaEDTA at a time when GluR2 is downregulated and caspase is activated inhibited the delayed rise in Zn2+, p75NTR induction, DNA fragmentation, and cell death. The finding of neuroprotection by late CaEDTA administration has striking implications for intervention in the delayed neuronal death associated with global ischemia.
authors.affiliation: Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
authors.forename: Agata
authors.initials: A
authors.lastname: Calderone
authors.forename: Teresa
authors.initials: T
authors.lastname: Jover
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Mashiko
authors.forename: Kyung-min
authors.initials: KM
authors.lastname: Noh
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Tanaka
authors.forename: Michael V L
authors.initials: MV
authors.lastname: Bennett
authors.forename: R Suzanne
authors.initials: RS
authors.lastname: Zukin
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins; D002545:Brain Ischemia / Q000378:metabolism / Q000473:pathology*; D002352:Carrier Proteins / Q000378:metabolism; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology*; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004492:Edetic Acid / Q000494:pharmacology*; D005849:Gerbillinae; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D009474:Neurons / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020800:Receptor, Nerve Growth Factor; D018091:Receptors, AMPA / Q000378:metabolism / Q000502:physiology; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism; D013997:Time Factors; D015032:Zinc / Q000378:metabolism / Q000502:physiology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D002352:Carrier Proteins; D002614:Chelating Agents; C489013:DIABLO protein, rat; D024101:Mitochondrial Proteins; D020800:Receptor, Nerve Growth Factor; D018091:Receptors, AMPA; D017475:Receptors, Nerve Growth Factor; D045304:Cytochromes c; D004492:Edetic Acid; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D015032:Zinc; C104722:glutamate receptor ionotropic, AMPA 2