title: Insulin-like growth factor binding protein-3 inhibits monocyte adhesion to retinal endothelial cells in high glucose conditions.
abstract: OBJECTIVE
  Insulin-like growth factor binding protein-3 (IGFBP-3) is cytoprotective in the retina. The goal of this study was to investigate whether IGFBP-3 inhibits monocyte-endothelial cell adhesion associated with hyperglycemia.
  
  
  METHODS
  Human retinal vascular endothelial cells (RECs) were grown in normal (5 mM), medium (15 mM), or high glucose medium (25 mM) for 72 h. After 48 h, cells were transfected with endothelial-cell-specific, non-IGF binding IGFBP-3 plasmid DNA (IGFBP-3NB) at 1 μg/ml for 24 h. Cells were serum starved for 16 h and treated with tumor necrosis factor-alpha (TNF-α; 10 ng/ml) for 4 h. Cell proteins were extracted and analyzed for intercellular adhesion molecule-1 (ICAM-1) expression with enzyme-linked immunosorbent assay. Additional RECs were plated onto attachment factor-coated slides, grown to 90% confluence in high glucose medium, and transfected with IGFBP-3 NB plasmid DNA or ICAM-1 small interfering RNA before treatment with or without TNF-α (10 ng/ml) for 4 h. Slides were then mounted in a parallel-plate flow chamber and subjected to a continuous flow of U937 human monocytes (10(5)/ml) in culture medium at shear stresses of 2 dynes/cm(2), with continual exposure to TNF-α.
  
  
  RESULTS
  In high ambient glucose, overexpression of IGFBP-3 in RECs significantly decreased ICAM-1 expression when compared to the TNF-α-treated samples, whereas TNF-α increased monocyte-endothelial cell adhesion. IGFBP-3 significantly decreased monocyte adhesion to RECs in the high glucose condition. RECs transfected with ICAM-1 siRNA also had a decreased number of monocytes attached compared with the scrambled siRNA control.
  
  
  CONCLUSIONS
  Data suggest that IGFBP-3 reduces monocyte-endothelial cell adhesion through decreased ICAM-1 levels in a hyperglycemic environment. This is the first demonstration of the role of IGFBP-3 in inhibiting monocyte-endothelial cell adhesion.
authors.affiliation: Department of Ophthalmology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
authors.forename: Qiuhua
authors.initials: Q
authors.lastname: Zhang
authors.forename: Youde
authors.initials: Y
authors.lastname: Jiang
authors.forename: Jordan J
authors.initials: JJ
authors.lastname: Toutounchian
authors.forename: Carl
authors.initials: C
authors.lastname: Soderland
authors.forename: C Ryan
authors.initials: CR
authors.lastname: Yates
authors.forename: Jena J
authors.initials: JJ
authors.lastname: Steinle
mesh_terms: D002448:Cell Adhesion / Q000187:drug effects; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D012160:Retina / Q000166:cytology*; D015398:Signal Transduction / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D020298:U937 Cells
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; D005947:Glucose