Vascular endothelial growth factor regulates primate choroid-retinal endothelial cell proliferation and tube formation through PI3K/Akt and MEK/ERK dependent signaling

Mol Cell Biochem. 2013 Sep;381(1-2):267-72. doi: 10.1007/s11010-013-1710-y. Epub 2013 Jun 8.

Abstract

Vascular endothelial growth factor (VEGF) is a hypoxia-induced angiogenic protein that exhibits a broad range of biological and pathological effects in wet age-related macular degeneration and proliferative diabetic retinopathy. However, its specific mechanism is still not fully understood. Here, we examined the effects of VEGF on choroid-retinal endothelial cells (RF/6A) proliferation and tube formation, and the underlying signal pathways responsible in this process. RF/6A cells were pretreated with MEK inhibitor or PI3K inhibitor, and then incubated in a hypoxia chamber. Real-time PCR and Western blot analysis were carried out to explore VEGF expression on mRNA and protein levels. Hypoxia inducible factor-1α (HIF-1α) and VEGFR2 expression levels were also investigated in the presence and absence of hypoxic conditions. CCK-8 analysis and tube formation assay were tested under hypoxia, exogenous recombinant VEGF, and different signal pathway inhibitors, respectively. Mean while, the PI3K/Akt and MEK/ERK pathways in this process were also investigated. Our results showed that VEGF, HIF-1α, VEGFR2, p-ERK, and p-Akt were up-regulated in RF/6A cells under hypoxic conditions. MEK inhibitor (PD98059) and PI3K inhibitor (LY294002) decreased ERK and Akt activity, respectively, and reduced VEGF expression. VEGF-induced RF/6A proliferation and tube formation requires MEK/ERK and PI3K/Akt signaling, and both of the two pathways were needed in regulating VEGF expression. These suggest that VEGF plays an important role in RF/6A proliferation and tube formation, and MEK/ERK and PI3K/Akt pathway may be responsible for this process.

MeSH terms

  • Animals
  • Blotting, Western
  • Cell Hypoxia / drug effects
  • Cell Line
  • Cell Proliferation / drug effects
  • Choroid / cytology*
  • Collagen / metabolism
  • Down-Regulation / drug effects
  • Drug Combinations
  • Endothelial Cells / cytology*
  • Endothelial Cells / drug effects
  • Endothelial Cells / enzymology
  • Enzyme Activation / drug effects
  • Hypoxia-Inducible Factor 1, alpha Subunit / metabolism
  • Intracellular Space / drug effects
  • Intracellular Space / enzymology
  • Laminin / metabolism
  • MAP Kinase Signaling System* / drug effects
  • Macaca mulatta / metabolism*
  • Neovascularization, Physiologic* / drug effects
  • Phosphatidylinositol 3-Kinases / metabolism
  • Protein Kinase Inhibitors / pharmacology
  • Proteoglycans / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Real-Time Polymerase Chain Reaction
  • Retina / cytology*
  • Up-Regulation / drug effects
  • Vascular Endothelial Growth Factor A / metabolism*
  • Vascular Endothelial Growth Factor A / pharmacology
  • Vascular Endothelial Growth Factor Receptor-2 / metabolism

Substances

  • Drug Combinations
  • Hypoxia-Inducible Factor 1, alpha Subunit
  • Laminin
  • Protein Kinase Inhibitors
  • Proteoglycans
  • Vascular Endothelial Growth Factor A
  • matrigel
  • Collagen
  • Phosphatidylinositol 3-Kinases
  • Vascular Endothelial Growth Factor Receptor-2
  • Proto-Oncogene Proteins c-akt