Reduction of a vascular endothelial growth factor receptor, fetal liver kinase-1, by antisense oligonucleotides induces motor neuron death in rat spinal cord exposed to hypoxia.
Vascular endothelial growth factor (VEGF) is reported to play a neuroprotective role through a VEGF receptor, fetal liver kinase-1 (Flk-1) in vitro. We investigated whether reduction of Flk-1 could induce motor neuron loss in rat spinal cord by inhibiting the expression of Flk-1 in rat spinal cord using antisense oligodeoxynucleotides (ODNs) against the Flk-1 receptor. Rat spinal cord was repetitively exposed to 12% hypoxia, and the change of the phosphatidylinositol 3-kinase (PI3-K)/Akt pathway and the mitogen-activated protein kinase kinase (MEK)/extracellular-signal-regulated kinase (ERK) pathway was examined. Intrathecal infusion of Flk-1 antisense ODNs for 7 days suppressed almost completely Flk-1 expression in the lumbar segment of the spinal cord and was followed by a hypoxic challenge with 12% oxygen for 1 h that was repeated for 7 more days. In the lumbar segment, we observed that reduced Flk-1 expression and hypoxic challenge for 7 days resulted in approximately 50% loss of motor neurons, in which the activation of Akt and ERK, that is, increased levels of phosphorylated-Akt and of phosphorylated-ERK by hypoxia, was markedly inhibited. In contrast, the reduction of Flk-1 expression alone did not induce motor neuron loss. These results suggest that VEGF exerts its protective effect on motor neurons against hypoxia-induced toxicity by the Flk-1 receptor through the PI3-K/Akt and the MEK/ERK signaling pathways.
Shiote
M
M
Department of Neurology, Okayama University Graduate School of Medicine and Dentistry, 2-5-1 Shikata-cho, Okayama, 700-8558 Okayama, Japan.
Nagano
I
I
Ilieva
H
H
Murakami
T
T
Narai
H
H
Ohta
Y
Y
Nagata
T
T
Shoji
M
M
Abe
K
K
D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D000860:Hypoxia / Q000378:metabolism* / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D009046:Motor Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009410:Nerve Degeneration / Q000378:metabolism* / Q000473:pathology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013116:Spinal Cord / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
D048049:Extracellular Signal-Regulated MAP Kinases; D016376:Oligonucleotides, Antisense; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; C494920:Akt1 protein, rat