Reduction of retinal albumin leakage by the antioxidant calcium dobesilate in streptozotocin-diabetic rats

Abstract

Calcium dobesilate stabilizes blood–retinal barrier in patients with diabetic retinopathy and possesses antioxidant properties in the retinas of rats with streptozotocin-induced diabetes, exposed ex vivo to ischemia–reperfusion. Here we investigated the action of calcium dobesilate on retinal albumin leakage in streptozotocin-diabetic rats, together with relevant in vivo retinal antioxidant and permeability markers, i.e., carboxymethyl-lysine-advanced glycation end product (CML-AGE) formation and vascular endothelial cell growth factor (VEGF) overexpression. Twenty days after streptozotocin administration, diabetic rats were treated for 10 days with calcium dobesilate (100 mg/kg/day per os) or vehicle. Retinal albumin leakage, CML-AGE formation, and VEGF overexpression were evaluated by immunohistochemistry of frozen eye sections. Diabetic rats exhibited dramatic increases in: (i) retinal albumin leakage (31% of positive vessels vs. 0.2% in nondiabetic rats, P<0.008), (ii) CML-AGE retinal occurrence (40±3% vs. undetectable positive vessels), and (iii) retinal VEGF protein expression (14.6±1.1 vs. 3.5±0.5 VEGF-positive spots/field, P<10 −4). Calcium dobesilate significantly reduced: (i) retinal albumin leakage (by 70%, P<0.008), (ii) retinal CML-AGEs contents (by 62%, P<0.008), and (iii) retinal VEGF expression (by 69.4%, P<0.008). In conclusion, calcium dobesilate orally given to diabetic rats markedly reduced retinal hyperpermeability, CML-AGE contents, and VEGF overexpression. These results strongly suggest that calcium dobesilate stabilizes blood–retinal barrier in diabetic retinopathy via an in situ antioxidant action. Further studies in patients are required to confirm such view.