title: Inhibition of vascular endothelial growth factor (VEGF) is sufficient to completely restore barrier malfunction induced by growth factors in microvascular retinal endothelial cells.
abstract: BACKGROUND
  Deregulated expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) or insulin-like growth factor-1 (IGF-1) is associated with the pathogenesis of diabetic retinopathy. The VEGF(165)-induced increase in permeability of retinal endothelial cells (REC), probably resulting in diabetic macular oedema (DME), could be completely restored by the VEGF-binding Fab fragment ranibizumab in vitro. We investigated whether bFGF and IGF-1 as single factors or in combination with VEGF(165) influence permeability and tight junctions in immortalised bovine REC (iBREC) and if these effects could be restored by inhibition of VEGF.
  
  
  METHODS
  As a measure of changes in cellular permeability, transendothelial electrical resistance (TER) was monitored during long-term treatment of iBREC with growth factors in the absence or presence of ranibizumab or KRN951 (an inhibitor of VEGF receptors). Expression of claudin-1, as an indicator of functional tight junctions, was assessed by western blot analysis.
  
  
  RESULTS
  Whereas VEGF(165) decreased TER and expression of claudin-1 in a concentration-dependent manner, long-term treatment of iBREC with 10-100 ng/ml bFGF or/and IGF-1 did not. Changes in claudin-1 expression or TER, induced by 25 ng/ml VEGF(165), were slightly enhanced by bFGF and/or IGF-1 and were accompanied by a slightly increased secretion of VEGF. Complete reversion of these effects was achieved by prolonged treatment with ranibizumab and partly by exposure to KRN951.
  
  
  CONCLUSIONS
  Our findings indicate that VEGF(165), but not IGF-1 or bFGF, is mainly responsible for changes in cellular permeability observed in REC. This supports VEGF targeting as a therapeutic concept for DME.
authors.affiliation: Department of Ophthalmology, University of Ulm Medical School, Prittwitzstrasse 43, D-89075 Ulm, Germany. heidrun.deissler@uniklinik-ulm.de
authors.forename: Heidrun L
authors.initials: HL
authors.lastname: Deissler
authors.forename: Helmut
authors.initials: H
authors.lastname: Deissler
authors.forename: Gabriele E
authors.initials: GE
authors.lastname: Lang
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology; D002417:Cattle; D002461:Cell Line, Transformed; D062445:Claudin-1; D004347:Drug Interactions; D017097:Electric Impedance; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism*; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D010671:Phenylurea Compounds / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology*; D000069579:Ranibizumab; D040262:Receptors, Vascular Endothelial Growth Factor / Q000037:antagonists & inhibitors / Q000378:metabolism; D012171:Retinal Vessels / Q000166:cytology* / Q000378:metabolism; D019108:Tight Junctions / Q000187:drug effects / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors* / Q000494:pharmacology
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; C568108:CLDN1 protein, human; D062445:Claudin-1; D008565:Membrane Proteins; D010671:Phenylurea Compounds; D011804:Quinolines; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D016222:Fibroblast Growth Factor 2; C553176:tivozanib; D007334:Insulin-Like Growth Factor I; D040262:Receptors, Vascular Endothelial Growth Factor; D000069579:Ranibizumab