title: Subtoxic N-methyl-D-aspartate delayed neuronal death in ischemic brain injury through TrkB receptor- and calmodulin-mediated PI-3K/Akt pathway activation.
abstract: Previous studies have shown that subtoxic NMDA moderated the neuronal survival in vitro and vivo. We performed this experiment to clarify the precise mechanism underlie subtoxic NMDA delayed neuronal death in ischemic brain injury. We found that pretreatment of NMDA (100 mg/kg) increased the number of the surviving CA1 pyramidal cells of hippocampus at 5 days of reperfusion. This dose of NMDA could also enhance Akt activation after ischemia/reperfusion (I/R). Here, we examined the possible mechanism that NMDA induced Akt activation. On the one hand, we found NMDA receptor-mediated Akt activation was associated with increased expression of BDNF (brain-derived neurotrophic factor) and activation of its high-affinity receptor TrkB after I/R in the hippocampus CA1 region, which could be held down by TrkB receptor antagonist K252a. On the other hand, we found that NMDA enhanced the binding of Ca2+-dependent calmodulin (CaM) to p85 (the regulation subunit of PI-3K), which led to the activation of Akt. W-13, an active CaM inhibitor, prevented the combination of CaM and p85 and subsequent Akt activation. Furthermore, NMDA receptor-mediated Akt activation was reversed by combined treatment with LY294002, the specific blockade of PI-3K. Taken together, our results suggested that subtoxic NMDA exerts the neuroprotective effect via activation of prosurvival PI-3K/Akt pathway against ischemic brain injury, and BDNF-TrkB signaling and Ca2+-dependent CaM cascade might contribute to NMDA induced activation of PI-3K/Akt pathway.
authors.affiliation: Research Center for Biochemistry and Molecular Biology, The Jiangsu Key Laboratory of Brain Disease Bioinformation, Xuzhou Medical College, Jiangsu, People's Republic of China.
authors.forename: Jing
authors.initials: J
authors.lastname: Xu
authors.forename: Quan-Guang
authors.initials: QG
authors.lastname: Zhang
authors.forename: Chong
authors.initials: C
authors.lastname: Li
authors.forename: Guang-Yi
authors.initials: GY
authors.lastname: Zhang
mesh_terms: D000818:Animals; D020520:Brain Infarction / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology; D002545:Brain Ischemia / Q000378:metabolism* / Q000503:physiopathology; D019208:Brain-Derived Neurotrophic Factor / Q000187:drug effects / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002147:Calmodulin / Q000378:metabolism*; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D008297:Male; D016202:N-Methylaspartate / Q000378:metabolism / Q000494:pharmacology*; D009410:Nerve Degeneration / Q000188:drug therapy* / Q000503:physiopathology / Q000517:prevention & control; D018696:Neuroprotective Agents / Q000378:metabolism / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021122:Protein Subunits / Q000187:drug effects / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020813:Receptor, trkB / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015427:Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
chemical_list: D019208:Brain-Derived Neurotrophic Factor; D002147:Calmodulin; D004791:Enzyme Inhibitors; D016202:N-Methylaspartate; D018696:Neuroprotective Agents; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D021122:Protein Subunits; D051057:Proto-Oncogene Proteins c-akt; D020813:Receptor, trkB