Inositol 1,4,5-triphosphate receptors and NAD(P)H mediate Ca2+ signaling required for hypoxic preconditioning of hippocampal neurons.
Exposure of neurons to a non-lethal hypoxic stress greatly reduces cell death during subsequent severe ischemia (hypoxic preconditioning, HPC). In organotypic cultures of rat hippocampus, we demonstrate that HPC requires inositol triphosphate (IP3) receptor-dependent Ca2+ release from the endoplasmic reticulum (ER) triggered by increased cytosolic NAD(P)H. Ca2+ chelation with intracellular BAPTA, ER Ca2+ store depletion with thapsigargin, IP3 receptor block with xestospongin, and RNA interference against subtype 1 of the IP3 receptor all blunted the moderate increases in [Ca2+](i) (50-100 nM) required for tolerance induction. Increases in [Ca2+](i) during HPC and neuroprotection following HPC were not prevented with NMDA receptor block or by removing Ca2+ from the bathing medium. Increased NAD(P)H fluorescence in CA1 neurons during hypoxia and demonstration that NADH manipulation increases [Ca2+](i) in an IP3R-dependent manner revealed a primary role of cellular redox state in liberation of Ca2+ from the ER. Blockade of IP3Rs and intracellular Ca2+ chelation prevented phosphorylation of known HPC signaling targets, including MAPK p42/44 (ERK), protein kinase B (Akt) and CREB. We conclude that the endoplasmic reticulum, acting via redox/NADH-dependent intracellular Ca2+ store release, is an important mediator of the neuroprotective response to hypoxic stress.
Bickler
P E
PE
Department of Anesthesia, University of California at San Francisco, 513 Parnassus Avenue, Sciences 255, Box 0542, San Francisco, CA 94143-0542, USA. bicklerp@anesthesia.ucsf.edu
Fahlman
C S
CS
Gray
J
J
McKleroy
W
W
D000818:Animals; D002545:Brain Ischemia / Q000517:prevention & control; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000503:physiopathology*; D002534:Hypoxia, Brain / Q000503:physiopathology*; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000378:metabolism
D017362:Cyclic AMP Response Element-Binding Protein; D053496:Inositol 1,4,5-Trisphosphate Receptors; D016194:Receptors, N-Methyl-D-Aspartate; D009243:NAD; D009249:NADP; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D002118:Calcium