Diabetic Retinopathy in the Spontaneously Diabetic Torii Rat: Pathogenetic Mechanisms and Preventive Efficacy of Inhibiting the Urokinase-Type Plasminogen Activator Receptor System

Abstract

The spontaneously diabetic Torii (SDT) rat is of increasing preclinical interest because of its similarities to human type 2 diabetic retinopathy (DR). The system formed by urokinase-type plasminogen activator (uPA) and its receptor (uPAR) is a player in blood-retinal barrier (BRB) breakdown in DR. Here, we investigated whether in SDT rats, preventive administration of UPARANT, an inhibitor of the uPAR pathway, counteracts the retinal impairment in response to chronic hyperglycemia. Electroretinogram (ERG) monitoring was followed over time. Fluorescein-dextran microscopy, CD31 immunohistochemistry, quantitative PCR, ELISA, Evans blue perfusion, and Western blot were also used. UPARANT prevented ERG dysfunction, upregulation of vascular endothelial growth factor and fibroblast growth factor-2, BRB leakage, gliosis, and retinal cell death. The mechanisms underlying UPARANT benefits were studied comparing them with the acute streptozotocin (STZ) model in which UPARANT is known to inhibit DR signs. In SDT rats, but not in the STZ model, UPARANT downregulated the expression of uPAR and its membrane partners. In both models, UPARANT reduced the levels of transcription factors coupled to inflammation or inflammatory factors themselves. These findings may help to establish the uPAR system as putative target for the development of novel drugs that may prevent type 2 DR.

The urokinase‐type plasminogen activator system as drug target in retinitis pigmentosa: New pre‐clinical evidence in the rd10 mouse model

“…The uPA system provides an integrated multimolecular complex that exerts pleiotropic functions including an important role in angiogenesis and inflammation . In the diseased retina, the inhibition of the uPA system has been shown to block critical processes involved in both angiogenesis and inflammation, but no information is available in the rd10 model of RP. As shown by the present findings, targeting the uPA system with UPARANT results in major anti‐inflammatory action including reduction of Müller cell gliosis, as characterized by decreased up‐regulation of both GFAP and pro‐inflammatory markers.…”

“…This dose was based on previous findings obtained in our laboratory. In rats, for instance, subcutaneously administered UPARANT at 20 mg/kg was found to effectively reach the retina, whereas in either streptozotocin (STZ)‐treated rats or spontaneously diabetic Torii rats, UPARANT at 8 mg/kg was shown to efficiently ameliorate the pathological signs of diabetic retinopathy . In addition, UPARANT at 8 mg/kg was found to improve diabetic kidney lesion in STZ‐treated rats .…”

Inhibiting the urokinase‐type plasminogen activator receptor system recovers STZ‐induced diabetic nephropathy

“…Four weeks after diabetes induction, three control or three STZ rats were used for the pharmacokinetics (PK) and the tissue distribution study. To this aim, rats received a single dose of UPARANT succinate dissolved in PBS (vehicle) at 20 mg/kg via subcutaneous injection according to a previous study . To investigate a possible therapeutic role of UPARANT, the drug was administered at 1 or 8 mg/kg daily for 5 days in 15 rats for each concentration used.…”

“…In all experiments, no differences were observed between untreated and vehicle‐treated rats. UPARANT dose and regimen were in line with those used in previous studies . The rats were kept individually in metabolic cages for 24 hours to collect urine for the measurement of urine output.…”

“…The uPAR‐derived tetrapeptide Ac‐L‐Arg‐Aib‐L‐Arg‐L‐Cα(Me)PheNH 2 (UPARANT, recently designated as Cenupatide in the International Nonproprietary Names nomenclature) has been designed to compete with N‐formyl‐Met‐Leu‐Phe peptide for binding to FPRs . It is endowed with a significant anti‐inflammatory and antiangiogenic activity both in vitro and in vivo and has been shown to protect the retina from pathologic changes induced by diabetic retinopathy (DR) in animal models . In this scenario, the possibility that dysregulated uPAR pathway participates to the pathogenic mechanisms of DN may add further value to the possible development of UPARANT as valuable therapy against diabetes complications.…”