Background: Anti-vascular endothelial growth factor (anti-VEGF) therapy has revolutionized the treatment of severe diabetic retinopathy (DR) , but significant subset of patients showed inadequate response to anti-VEGF. We have previously reported that retinol binding protein 3 (RBP3) prevented hyperglycemia induced retinal pathologies and progression to severe DR. Hypothesis: RBP3 and Anti-VEGF have differential protective profiles in preventing retinal dysfunctions induced by diabetes.
Methods and Results: Recombinant human RBP3 (rhRBP3, 5ug/ml) and anti-VEGF (Avastin, 250mg/ml) inhibited VEGF-induced retinal vascular permeability (RVP) by 70% when intravitreal injections were given together in Lewis rats (P < 0.01) . After 2 months of diabetes induced by streptozotocin (STZ) , intravitreal injection of rhRBP3 and anti-VEGF for 3 days suppressed RVP by 64% and 53% (P < 0.01) in Lewis rats. This was accompanied by reductions of VEGF levels by both proteins. Electroretinogram (ERG) amplitudes of A wave, B wave, C wave were decreased in rats after 2 months of diabetes (P < 0.01) . rhRBP3 increased amplitudes of C wave (P < 0.01) , while anti-VEGF did not improve any waveforms. Furthermore, rhRBP3 decreased retinal mRNA expression of Cd11b and Tnfa (P =0.1) in diabetic rats. In cultured primary bovine Müller cells, rhRBP3 decreased mRNA expressions of Tnfa and Il-6 induced by high glucose (25mM) (P < 0.01) , whereas, anti-VEGF showed no effect. Metabolic function studies using Seahorse assays showed that isolated retina from intravitreal rhRBP3 treated rats exhibited reduced glycolysis rate in ECAR while anti-VEGF treatments had no effects.
Conclusions: Both intravitreal anti-VEGF and RBP3 treatments normalized retinal vascular dysfunctions caused by diabetes. However, only RBP3 reversed abnormal neural-retinal dysfunctions and elevated inflammatory cytokines induced by hyperglycemia, possible by decreasing glucose uptake and glycolysis levels in retinal cells.
Q.Li: None. S.Onizuka: None. K.Park: None. H.Park: None. Q.Li: None. W.Fickweiler: None. J.Fu: None. I.Wu: None. G.L.King: Advisory Panel; Medtronic, Research Support; Janssen Pharmaceuticals, Inc.