title: Role for extracellular signal-responsive kinase-1 and -2 in retinal angiogenesis.
abstract: OBJECTIVE
  Vascular endothelial growth factor (VEGF) is a potent mitogen for micro- and macrovascular endothelial cells (ECs). Evidence points to a possible role for two mitogen-activated protein (MAP) kinases, the extracellular-signal responsive kinases (ERK)-1 and -2, in VEGF signaling in ECs. This study was undertaken to begin to define the precise role of MAP kinases in VEGF signal transduction related to angiogenesis.
  
  
  METHODS
  Bovine retinal microvascular endothelial cells (BRMECs) and a well-established rat model of retinopathy of prematurity (ROP) were used to investigate the role of ERK-1/2 in EC proliferation and tube formation and in retinal angiogenesis in vivo.
  
  
  RESULTS
  Administration of VEGF to BRMEC cultures increased ERK-1/2 phosphorylation, cell proliferation, and tube formation in a dose-dependent manner. Phosphorylation of retinal ERK-1/2 also was increased in the ROP model. An inhibitor of ERK, AG126, and an inhibitor of ERK kinase (MEK), PD98059, exhibited a dose-dependent reduction of ERK phosphorylation and EC proliferation, but not tube formation, in VEGF-stimulated BRMECs. In the ROP model, intravitreous injection of 10 micro M AG126 or PD98059 reduced the retinal neovascular area by 71% and 48%, respectfully. No effect was seen on intraretinal blood vessel growth.
  
  
  CONCLUSIONS
  These experiments point to a critical role for ERK and MEK in proliferation of ECs, but not in tube formation. Furthermore, inhibition of either of these two signal intermediates can significantly retard retinal neovascularization. This suggests that the MAPK pathway may provide rational targets for therapeutic intervention in ocular and other diseases with an angiogenic component.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Bullard
authors.forename: Xiang
authors.initials: X
authors.lastname: Qi
authors.forename: John S
authors.initials: JS
authors.lastname: Penn
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D016228:Endothelial Growth Factors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D007231:Infant, Newborn; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D008222:Lymphokines / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D015861:Retinal Neovascularization / Q000201:enzymology* / Q000209:etiology / Q000517:prevention & control; D012171:Retinal Vessels / Q000166:cytology*; D012178:Retinopathy of Prematurity / Q000201:enzymology; D020032:Tyrphostins / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D016228:Endothelial Growth Factors; D004791:Enzyme Inhibitors; D005419:Flavonoids; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D020032:Tyrphostins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C069028:AG 127; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one