title: Modulation of VEGF-induced retinal vascular permeability by peroxisome proliferator-activated receptor-β/δ.
abstract: OBJECTIVE
  Vascular endothelial growth factor (VEGF)-induced retinal vascular permeability contributes to diabetic macular edema (DME), a serious vision-threatening condition. Peroxisome proliferator-activated receptor β/δ (PPARβ/δ) antagonist/reverse agonist, GSK0660, inhibits VEGF-induced human retinal microvascular endothelial cell (HRMEC) proliferation, tubulogenesis, and oxygen-induced retinal vasculopathy in newborn rats. These VEGF-induced HRMEC behaviors and VEGF-induced disruption of endothelial cell junctional complexes may well share molecular signaling events. Thus, we sought to examine the role of PPARβ/δ in VEGF-induced retinal hyperpermeability.
  
  
  METHODS
  Transendothelial electrical resistance (TEER) measurements were performed on HRMEC monolayers to assess permeability. Claudin-1/Claudin-5 localization in HRMEC monolayers was determined by immunocytochemistry. Extracellular signal-regulated protein kinases 1 and 2 (Erk 1/2) phosphorylation, VEGF receptor 1 (VEGFR1) and R2 were assayed by Western blot analysis. Expression of VEGFR1 and R2 was measured by quantitative RT-PCR. Last, retinal vascular permeability was assayed in vivo by Evans blue extravasation.
  
  
  RESULTS
  Human retinal microvascular endothelial cell monolayers treated with VEGF for 24 hours showed decreased TEER values that were completely reversed by the highest concentration of GSK0660 (10 μM) and PPARβ/δ-directed siRNA (20 μM). In HRMEC treated with VEGF, GSK0660 stabilized tight-junctions as evidenced by Claudin-1 staining, reduced phosphorylation of Erk1/2, and reduced VEGFR1/2 expression. Peroxisome proliferator-activated receptor β/δ siRNA had a similar effect on VEGFR expression and Claudin-1, supporting the specificity of GSK0660 in our experiments. Last, GSK0660 significantly inhibited VEGF-induced retinal vascular permeability and reduced retinal VEGFR1and R2 levels in C57BL/6 mice.
  
  
  CONCLUSIONS
  These data suggest a protective effect for PPARβ/δ antagonism against VEGF-induced vascular permeability, possibly through reduced VEGFR expression. Therefore, antagonism/reverse agonism of PPARβ/δ siRNA may represent a novel therapeutic methodology against retinal hyperpermeability and is worthy of future investigation.
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States.
authors.forename: Sandra
authors.initials: S
authors.lastname: Suarez
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, United States.
authors.forename: Gary W
authors.initials: GW
authors.lastname: McCollum
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States.
authors.forename: Colin A
authors.initials: CA
authors.lastname: Bretz
authors.affiliation: Department of Ophthalmology and Visual Sciences, Vanderbilt University School of Medicine, Nashville, Tennessee, United States.
authors.forename: Rong
authors.initials: R
authors.lastname: Yang
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, United States.
authors.forename: Megan E
authors.initials: ME
authors.lastname: Capozzi
authors.affiliation: Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, Tennessee, United States.
authors.forename: John S
authors.initials: JS
authors.lastname: Penn
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002199:Capillary Permeability / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D062445:Claudin-1 / Q000032:analysis; D062507:Claudin-5 / Q000032:analysis; D017097:Electric Impedance; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D047492:Peroxisome Proliferator-Activated Receptors / Q000037:antagonists & inhibitors / Q000502:physiology*; D040262:Receptors, Vascular Endothelial Growth Factor / Q000378:metabolism; D012160:Retina / Q000378:metabolism; D012171:Retinal Vessels / Q000187:drug effects*; D013450:Sulfones / Q000494:pharmacology; D013876:Thiophenes / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D062445:Claudin-1; D062507:Claudin-5; C529769:GSK0660; D047492:Peroxisome Proliferator-Activated Receptors; D013450:Sulfones; D013876:Thiophenes; D042461:Vascular Endothelial Growth Factor A; D040262:Receptors, Vascular Endothelial Growth Factor; D048049:Extracellular Signal-Regulated MAP Kinases
keywords: vascular permeability, PPARβ; δ, VEGF