VEGFR-2-mediated increased proliferation and survival in response to oxygen and glucose deprivation in PlGF knockout astrocytes.
In hypoxic/ischemic conditions, astrocytes are involved in neuroprotection and angiogenesis. Vascular endothelial growth factor (VEGF) induces angiogenesis and exhibits neuroprotective and neurotrophic properties. However, the role of placental growth factor (PlGF), a VEGF homolog, in these processes is unclear. Therefore, proliferation and survival studies were performed on PlGF knockout (PlGF-/-) and wild-type (PlGF+/+) mouse astrocytes. A significant increase in cell proliferation and survival to oxygen and glucose deprivation (OGD) was observed in PlGF-/- compared to PlGF+/+ astrocytes. Interestingly, no PlGF protein expression was detected in PlGF+/+ astrocytes and no changes in VEGF protein levels were observed between the two genotypes. Real-time PCR and immunocytochemistry showed over-expression of VEGF receptor-2 (VEGFR-2) in PlGF-/- compared with PlGF+/+ astrocytes. Confocal microscopy revealed nuclear, membrane, and cytoplasmic localization of VEGFR-2. In vivo over-expression of VEGFR-2 mRNA was also detected in PlGF-/- compared with PlGF+/+ astrocytes. Stimulation with VEGF165 resulted in increased proliferation in PlGF-/- compared with PlGF+/+ astrocytes. This effect was blocked by the VEGFR-2 antagonist, VEGF165b. The enhanced proliferation of PlGF-/- astrocytes correlated with increased phospho-extracellular-signal-regulated kinase-1/2 levels, while the resistance to OGD was independent of the phosphatidylinositol 3'-kinase/Akt pathway. These results suggest that VEGFR-2 mediates the enhanced proliferative/OGD resistant phenotype observed in PlGF-/- astrocytes.
Freitas-Andrade
Moises
M
Cerebrovascular Research Group, Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario, Canada.
Carmeliet
Peter
P
Stanimirovic
Danica B
DB
Moreno
Maria
M
D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000473:pathology; D015153:Blotting, Western; D002545:Brain Ischemia / Q000378:metabolism; D015687:Cell Hypoxia / Q000502:physiology; D049109:Cell Proliferation; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D020869:Gene Expression Profiling; D005947:Glucose / Q000172:deficiency; D007150:Immunohistochemistry; D007834:Lasers; D051379:Mice; D018345:Mice, Knockout; D042282:Microdissection; D018613:Microscopy, Confocal; D010100:Oxygen / Q000378:metabolism; D000072483:Placenta Growth Factor; D011257:Pregnancy Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
C000608037:Pgf protein, mouse; D011257:Pregnancy Proteins; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D000072483:Placenta Growth Factor; D040301:Vascular Endothelial Growth Factor Receptor-2; D005947:Glucose; D010100:Oxygen