Diabetes-induced ROCK activation contributes to outer blood retinal barrier breakdown: implications for diabetic macular edema

Abstract

Purpose : Diabetic macular edema is the main cause of visual loss in diabetic retinopathy, particularly in patients with type 2 diabetes. The mechanisms of blood retinal barrier (BRB) breakdown are not fully elucidated. Rho/Rock1 pathway is activated in diabetes and Rock1 activation induces actin cytoskeleton remodeling and tight-junction destabilization. We hypothesized that Rho/Rock1 diabetes-induced activation could contribute to retinal pigment epithelial cells (RPE) barrier breakdown subsequently altering barrier function and leading to retinal edema.

Methods : We used 12 months old Goto-Kakizaki (GK) type 2 diabetic rat and human diabetic RPE samples. Rho/Rhock1 pathway activation was analyzed in RPE through its sub cellular localization and the phosphorylation of its substrates. Pharmacological Rock inhibition by Fasudil administered into the vitreous was tested in rats in vivo on barrier permeability.

Results : In diabetic rats, Rock1 is activated in RPE cells as shown by its membrane translocation confirmed in human diabetic RPE samples. Severe cytoskeleton remodeling of RPE cells was observed, responsible for cell size polydispersity, apical constriction, stress fibers formation and to intercellular junction opening. RPE barrier breakdown was confirmed in-vivo by intravenous injections of FITC-dextran molecules of 150KDa. Retinal edema was evidenced in the outer retina originating from the choroid. Fasudil treatment deactivates and relocates ROCK-1 into the cytoplasm, preserves morphologic abnormalities of diabetic RPE, improving barrier integrity and preventing barriers hyperpermeability

Conclusions : Our results support a role for the outer BRB in diabetic retinopathy complications and suggest that the Rho/Rock1 pathway is a key player in diabetic-induced RPE barrier breakdown. Local intraocular inhibition by FASUDIL could represent a new therapeutic target in diabetic macular edema.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.