The Urokinase Receptor-Derived Peptide UPARANT Recovers Dysfunctional Electroretinogram and Blood–Retinal Barrier Leakage in a Rat Model of Diabetes

PURPOSE. The activation of the urokinase-type plasminogen activator and its receptor system is associated with retinal diseases. Among peptide inhibitors of this system, UPARANT acts by preventing the onset of pathological signs of neovascular ocular diseases. We investigated whether systemic UPARANT may act in a therapeutic regimen by suppressing the retinal damage that characterizes diabetic retinopathy using a rat model of streptozotocin-induced diabetes. METHODS. In healthy rats, plasma, eye, and retina concentrations of UPARANT were evaluated by mass spectrometry. In rat models of streptozotocin-induced diabetes, the appearance of diabetic retinopathy was assessed by electroretinogram (ERG). UPARANT was then administered at different dosages and daily regimens. ERG recording, Evans blue perfusion, and real-time PCR were used to evaluate UPARANT efficacy. UPARANT safety was also determined. RESULTS. UPARANT was found in plasma, eye, and retina soon after its administration and remained detectable after 24 hours. Between the 4th and the 5th week after diabetes onset, UPARANT at 8 mg/kg (daily for 5 days) was effective in recovering dysfunctional ERG. Threeday treatments at 8 mg/kg or a half dose for 5 days were ineffective. ERG recovery lasted about 2 weeks. ERG recovery was accompanied by restored blood–retinal barrier integrity and inhibition of inflammatory and angiogenic responses. UPARANT showed a safety profile. CONCLUSIONS. These data suggest that targeting the urokinase-type plasminogen activator and its receptor system by systemic UPARANT is a potential therapeutic approach for the treatment of early diabetic retinopathy, thus providing a potential alternative approach to delay disease progression in humans.