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Late Calcium EDTA Rescues Hippocampal CA1 Neurons from Global Ischemia-Induced Death

2004; Society for Neuroscience; Volume: 24; Issue: 44 Linguagem: Inglês

10.1523/jneurosci.1713-04.2004

1529-2401

Agata Calderone, Teresa Jover, Toshihiro Mashiko, Kyung‐Min Noh, Hidenobu Tanaka, Michael V. L. Bennett, R. Suzanne Zukin,

Neuroscience and Neuropharmacology Research

Transient global ischemia induces a delayed rise in intracellular Zn 2+ , 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 Zn 2+ toxicity in vivo are not well delineated. Here we show the striking finding that intraventricular injection of the high-affinity Zn 2+ 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 ∼50% (late CaEDTA) to 75% (early CaEDTA) of animals. We also show that Zn 2+ acts via temporally distinct mechanisms to promote neuronal death. Early CaEDTA attenuated ischemia-induced GluR2 mRNA and protein downregulation (and, by inference, formation of Zn 2+ -permeable AMPARs), the delayed rise in Zn 2+ , and neuronal death. These findings suggest that Zn 2+ acts at step(s) upstream from GluR2 gene downregulation and implicate Zn 2+ 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), p75 NTR 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 Zn 2+ , p75 NTR 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.