Abstract
Purpose: :
The VEGF/VEGF-receptor system is a promising target for treating diabetic retinopathy because VEGF165 elevates permeability and stimulates proliferation and migration of retinal endothelial cells (REC) and these effects can be completely restored by VEGF-binding Fab-fragment ranibizumab in immortalised bovine REC (iBREC). Whereas ranibizumab has been approved for treatment, the VEGF-specific antibody bevacizumab is also used off-label. However, there is evidence that bevacizumab is taken up by retinal pigment-epithelial cells accumulating in these cells over several days. Here we investigated not only the efficiency of bevacizumab to restore VEGF-induced effects on proliferation, migration and barrier function. We also studied whether both VEGF-inhibitors are taken up by iBREC and whether vital properties of these cells are influenced thereby.
Methods: :
Uptake of ranibizumab and bevacizumab by iBREC with or without pretreatment with VEGF165 was measured by Western-blot analyses of fractionated cellular extracts. In addition, effects of VEGF-inhibitors in the presence and absence of VEGF165 on permeability were determined by measuring the transendothelial resistence (TER). Presence of Claudin-1 as an additional marker for functional tight junctions in iBREC was also determined. Influence of bevacizumab on proliferation and migration rates of iBREC was studied in the presence and absence of VEGF.
Results: :
Uptake of both VEGF inhibitors was detected within 1 h and up to several days after treatment. Bevacizumab was mainly present in the cytoskeleton fraction, ranibizumab in the plasma membrane and organelle fraction, weakly in the cytoskeleton fraction; the amount of bevacizumab was higher compared to ranibizumab. Uptake was not markedly influenced by pretreatment with VEGF165. Both inhibitors stabilized TER up to 6 d of treatment in the absence of VEGF165. However, bevacizumab was less efficient in restoring VEGF-induced effects on barrier function or proliferation. In contrast to ranibizumab, bevacizumab also reduced basal migration rates.
Conclusions: :
Ranibizumab is slightly more efficient than bevacizumab in restoring VEGF-induced processes. Uptake of bevacizumab and ranibizumab seems not to influence vital functions of iBREC.
Keywords: diabetic retinopathy • neovascularization • pump/barrier function