title: Identification of a biphasic signaling pathway involved in ischemic resistance of the hippocampal dentate gyrus.
abstract: Dentate gyrus is usually assumed to be resistant to ischemia. However, the mechanisms underlying this functional plasticity are not fully understood. Herein, we aimed at identifying a neuroprotective mechanism in the dentate gyrus of the adult rat after global ischemia. Cyclic AMP response element (CRE)-binding protein (CREB), brain-derived neurotrophic factor (BDNF) and calcium/calmodulin-dependent protein kinase IV (CaMKIV) are known to be mediators of neuronal survival and plasticity. Involvement of CaMKIV, BDNF and CREB in ischemic resistance was therefore examined using intracerebroventricular injections of pharmacological agents such as inhibitors, antibodies and consensus oligonucleotides followed by immunohistochemical and Western blot analysis. We provide evidence that ischemia triggers activation of a biphasic pathway during the resistance period of dentate neurons: (1) CaMKIV mediates the early phosphorylation of CREB which drives a prominent synthesis of BDNF; (2) this BDNF synthesis, in turn, induces a second peak of CREB phosphorylation which is required for the maintenance of BDNF synthesis. In addition, we show that: (1) impairment of these transduction signals by the pharmacological agents causes tissular damages and apoptotic deaths in the post-ischemic dentate gyrus; (2) some similar disturbances also occur beyond the resistance period in the dentate gyrus of untreated ischemic rats; (3) these disturbing effects are mainly observed in the suprapyramidal dentate subfield. Collectively, the present results suggest that activation of the CaMKIV/CREB/BDNF pathway plays principally an early protective role in the suprapyramidal subfield of the dentate gyrus.
authors.affiliation: Laboratoire Développement et Vieillissement du Système Nerveux, UMR 7102 CNRS-UPMC, Neurobiologie des Processus Adaptatifs, Université P. and M. Curie, 9 Quai Saint-Bernard, Paris, France. pierre.blanquet@snv.jussieu.fr
authors.forename: Pierre R
authors.initials: PR
authors.lastname: Blanquet
authors.forename: Jean
authors.initials: J
authors.lastname: Mariani
authors.forename: Betty
authors.initials: B
authors.lastname: Fournier
mesh_terms: D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D019208:Brain-Derived Neurotrophic Factor / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018891:Dentate Gyrus / Q000473:pathology / Q000503:physiopathology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D020287:In Situ Nick-End Labeling / Q000379:methods; D007276:Injections, Intraventricular / Q000379:methods; D002546:Ischemic Attack, Transient / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D008954:Models, Biological; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009841:Oligonucleotides / Q000494:pharmacology; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015424:Reperfusion / Q000379:methods; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
chemical_list: D000906:Antibodies; D019208:Brain-Derived Neurotrophic Factor; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D009841:Oligonucleotides; D011494:Protein Kinases; D054734:Calcium-Calmodulin-Dependent Protein Kinase Type 4; C517686:Camk4 protein, rat; D010751:Phosphopyruvate Hydratase