Effect of intravitreal spironolactone released from PLGA microspheres in diabetic retina of Goto-Kakizaki rat

Abstract

Purpose : Diabetic retinopathy remains a major cause of vision loss worldwide. Mineralocorticoid receptor (MR) is expressed in the retina and its antagonism has anti-inflammatory and anti-angiogenic effects. While MR pathway overactivation is recognized in the pathogenesis of diabetic nephropathy, its role in diabetic retinopathy is unknown. We aimed to evaluate the effect of intravitreal MR antagonist spironolactone in the retina of type2 diabetic Goto-Kakizaki (GK) rat and to establish the link between MR overactivation and diabetic retinopathy.

Methods : Young (3-4 months) and old (≥1 year) GK rats were injected intravitreally with PLGA microspheres controlled releasing spironolactone or non-loaded microspheres. Age and gender matched Wistar rats were used as control. One month later, retinal morphology, immunofluorescence of ion (Kir4.1) and water channels (AQP4) and microglia/macrophages (IBA-1), gene expression of inflammatory factors were analyzed. In old rats, we also assessed the effect of spironolactone on retinal vascular permerbility and a transcriptomic analysis was performed to identify spironolactone-regulated genes and pathways in the diabetic retina. Human ocular media and retina have been used to confirm the relevance.

Results : The sustained local delivery of spironolactone decreased the early and late features of diabetic retinopathy such as retinal inflammation, vascular leakage and retinal edema in diabetic GK rats. The transcriptomic signature of the retina of old diabetic rats treated with spironolactone highlighted the regulation of genes encoding proteins known to intervene in vascular permeability and retinal edema such as Vldlr, Sesn2, Adcyap1, Dusp8, Pten, Slc7a1, Tjp1, Dlg1 and Sema7a. In human diabetic retina, MR expression was enhanced and cortisol was the preferential ligand binding to MR. Lipocalin 2 and galectin 3, two known MR target molecules increased in GK rat retina, were also enhanced in human diabetic retina.

Conclusions : Sustained intravitreal delivery of spironolactone reduces early inflammation and late retinal edema and vascular permeability in the retina of diabetic GK rats, suggesting involvement of MR pathway overactivation in the pathogenesis of diabetic retinopathy. Increase in MR expression, and in its ligand and target molecules in human diabetic retina further confirms the hypothesis.

This is a 2021 ARVO Annual Meeting abstract.