title: Actions of bevacizumab and ranibizumab on microvascular retinal endothelial cells: similarities and differences.
abstract: BACKGROUND
  Retinal endothelial cells are crucially involved in the genesis of diabetic retinopathy which is treated with vascular endothelial growth factor (VEGF) inhibitors. Of these, ranibizumab can completely restore VEGF-induced effects on immortalised bovine retinal endothelial cells (iBREC). In most experiments supporting diabetic retinopathy therapy with bevacizumab, only non-retinal EC or retinal pigment epithelial cells have been used. Also, bevacizumab but not ranibizumab can accumulate in retinal pigment epithelial cells.
  
  
  OBJECTIVE
  To investigate the effects of bevacizumab on VEGF-induced changes of iBREC properties and potential uptake and accumulation of both inhibitors.
  
  
  METHODS
  Uptake of VEGF inhibitors by iBREC with or without pretreatment with VEGF(165) was visualised by immunofluorescence staining and western blot analyses. Measured transendothelial resistance (TER) of iBREC (±VEGF(165)) showed effects on permeability, indicated also by the western blot-determined tight junction protein claudin-1. The influence of bevacizumab on proliferation and migration of iBREC was studied in the presence and absence of VEGF(165).
  
  
  RESULTS
  Bevacizumab strongly inhibited VEGF-stimulated and basal migration, but was less efficient than ranibizumab in inhibiting VEGF-induced proliferation or restoring the VEGF-induced decrease of TER and claudin-1. This ability was completely lost after storage of bevacizumab for 4 weeks at 4°C. Ranibizumab and bevacizumab were detectable in whole cell extracts after treatment for at least 1 h; bevacizumab accumulated during prolonged treatment. Ranibizumab was found in the membrane/organelle fraction, whereas bevacizumab was associated with the cytoskeleton.
  
  
  CONCLUSIONS
  Both inhibitors had similar effects on retinal endothelial cells; however, some differences were recognised. Although barrier properties were not affected by internalised bevacizumab in vitro, potential adverse effects due to accumulation after repetitive intravitreal injections remain to be investigated.
authors.affiliation: Department of Ophthalmology, University of Ulm, 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 / Q000493:pharmacokinetics / Q000494:pharmacology*; D000818:Animals; D061067:Antibodies, Monoclonal, Humanized / Q000493:pharmacokinetics / Q000494:pharmacology*; D000068258:Bevacizumab; D015153:Blotting, Western; D002199:Capillary Permeability; D002417:Cattle; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D017097:Electric Impedance; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D000069579:Ranibizumab; D011994:Recombinant Proteins; D012171:Retinal Vessels / Q000166:cytology*; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors / Q000633:toxicity
chemical_list: D020533:Angiogenesis Inhibitors; D061067:Antibodies, Monoclonal, Humanized; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D000068258:Bevacizumab; D000069579:Ranibizumab