Neurotrophic effects of vascular endothelial growth factor on organotypic cortical explants and primary cortical neurons.
Vascular endothelial growth factor (VEGF) is well known to play an important regulatory role in vascular growth and development. Because gene knock-outs of VEGF and its receptors flk-1 and flt-1 result in early embryonic lethality, determining roles for VEGF in CNS development has been particularly difficult. Recent studies have shown that VEGF is upregulated after various injuries to the adult brain and that the cytokine affords protection to cultured neurons affected by oxidative or excitotoxic stress. The present study demonstrates, for the first time, that VEGF is directly neurotrophic to CNS neurons in culture. We applied VEGF to normoxic fetal organotypic cortical explants as a model of CNS neuropil, in addition to primary cortical neurons, to assess direct growth effects absent vascular or astroglial activity. We found that VEGF provided a significant dose-responsive increase in the neuronal microtubule markers TUJ1 and MAP-2, as well as mRNA for MAP-2 and flk-1. Antisense oligodeoxynucleotides to flk-1, but not flt-1, inhibited neuritic outgrowth, whereas inhibitors of the signaling pathways MEK1 and P13-AKT both abrogated VEGF-induced growth. VEGF applied to primary cortical neurons produced significant increases in neuronal cell body diameter and the number of emerging neurites mediated by flk-1. Possibly, VEGF achieves its effects by acting on the neuronal microtubular content, which is involved with growth, stability and maturation. Several studies have now shown that VEGF is neurotrophic and neuroprotective independent of a vascular component; we suggest that VEGF plays seminal pleiotrophic roles in CNS development and repair.
Rosenstein
Jeffrey M
JM
Department of Anatomy and Cell Biology, The George Washington University Medical Center, Washington, DC 20037, USA. anajmr@gwumc.edu
Mani
Nina
N
Khaibullina
Alfia
A
Krum
Janette M
JM
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000196:embryology; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D066298:In Vitro Techniques; D020935:MAP Kinase Signaling System / Q000502:physiology; D009414:Nerve Growth Factors / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D016501:Neurites / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D014404:Tubulin / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism
D016895:Culture Media, Serum-Free; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D014404:Tubulin; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; C488416:Tubb3 protein, rat; C494920:Akt1 protein, rat