title: Free insulin-like growth factor binding protein-3 (IGFBP-3) reduces retinal vascular permeability in association with a reduction of acid sphingomyelinase (ASMase).
abstract: OBJECTIVE
  To examine the effect of free insulin-like growth factor (IGF) binding protein-3 (IGFBP-3), independent of the effect of insulin-like growth factors, in modulating retinal vascular permeability.
  
  
  METHODS
  We assessed the ability of a form of IGFBP-3 that does not bind IGF-1 (IGFBP-3NB), to regulate the blood retinal barrier (BRB) using two distinct experimental mouse models, laser-induced retinal vessel injury and vascular endothelial growth factor (VEGF)-induced retinal vascular permeability. Additionally, in vitro studies were conducted. In the animal models, BRB permeability was quantified by intravenous injection of fluorescein labeled serum albumin followed by digital confocal image analysis of retinal flat-mounts. Claudin-5 and vascular endothelial-cadherin (VE-cadherin) localization at interendothelial junctions was studied by immunofluorescence. In vitro changes in transendothelial electrical resistance (TEER) and flux of fluorescent dextran in bovine retinal endothelial monolayers (BREC) were measured after IGFBP-3NB treatment. Acid (ASMase) and neutral (NSMase) sphingomyelinase mRNA levels and activity were measured in mouse retinas.
  
  
  RESULTS
  Four days postinjury, laser-injured mouse retinas injected with IGFBP-3NB plasmid demonstrated reduced vascular permeability compared with retinas of laser-injured mouse retinas injected with control plasmid. IGFBP-3NB administration resulted in a significant decrease in laser injury-associated increases in ASMase and NSMase mRNA and activity when compared with laser alone treated mice. In vivo, intravitreal injection of IGFBP-3NB reduced vascular leakage associated with intravitreal VEGF injection. IGFBP-3NB partially restored VEGF-induced in vivo permeability and dissociation of claudin-5 and VE-cadherin at junctional complexes. When IGFBP-3NB was applied basally to bovine retinal endothelial cells (BREC) in vitro, TEER increased and macromolecular flux decreased.
  
  
  CONCLUSIONS
  Intravitreal administration of IGFBP-3NB preserves junctional integrity in the presence of VEGF or laser injury by reducing BRB permeability in part by modulating sphingomyelinase levels.
authors.affiliation: Departments of Pharmacology and Therapeutics, University of Florida, Gainesville, Florida 32610-0267, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Kielczewski
authors.forename: Sergio
authors.initials: S
authors.lastname: Li Calzi
authors.forename: Lynn C
authors.initials: LC
authors.lastname: Shaw
authors.forename: Jun
authors.initials: J
authors.lastname: Cai
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Qi
authors.forename: Qing
authors.initials: Q
authors.lastname: Ruan
authors.forename: Lin
authors.initials: L
authors.lastname: Wu
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.forename: Ping
authors.initials: P
authors.lastname: Hu
authors.forename: Tailoi
authors.initials: T
authors.lastname: Chan-Ling
authors.forename: Robert N
authors.initials: RN
authors.lastname: Mames
authors.forename: Sue
authors.initials: S
authors.lastname: Firth
authors.forename: Robert C
authors.initials: RC
authors.lastname: Baxter
authors.forename: Patric
authors.initials: P
authors.lastname: Turowski
authors.forename: Julia V
authors.initials: JV
authors.lastname: Busik
authors.forename: Michael E
authors.initials: ME
authors.lastname: Boulton
authors.forename: Maria B
authors.initials: MB
authors.lastname: Grant
mesh_terms: D022005:Adherens Junctions / Q000378:metabolism; D000818:Animals; D001813:Blood-Retinal Barrier / Q000187:drug effects* / Q000502:physiology; D002199:Capillary Permeability / Q000187:drug effects / Q000502:physiology; D002417:Cattle; D004195:Disease Models, Animal; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D007834:Lasers / Q000009:adverse effects; D008028:Light Coagulation; D051379:Mice; D008810:Mice, Inbred C57BL; D010957:Plasmids / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D012160:Retina / Q000187:drug effects / Q000293:injuries* / Q000378:metabolism*; D012171:Retinal Vessels / Q000187:drug effects* / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000378:metabolism*; D019108:Tight Junctions / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism / Q000494:pharmacology
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; C112980:acid sphingomyelinase-1; D013108:Sphingomyelin Phosphodiesterase