The role of proteinases in the alteration of blood retinal barrier permeability

Abstract

Abstract: : Purpose: The blood–retinal barrier (BRB) is maintained by tight junctions between either capillary endothelial cells or the retinal pigment epithelium (RPE). The breakdown of tight junction proteins may result in altered retinal permeability. The aim of this study is to determine the role of proteinases in the alteration of the BRB through the proteolysis of the tight junction protein occludin. Methods: Transepithelial electrical resistance (TEER) was performed to quantify tight junction integrity and cellular permeability on confluent human retinal pigmented epithelial cells (ARPE–19) or endothelial cells (HUVEC). Cells were treated with PMA or purified MMP–9, with or without an MMP inhibitor. Western blot analysis for the protein occludin was performed. Results: RPE cells treated with PMA demonstrated a significant decrease in TEER. Treating RPE cells with purified MMP–9 demonstrated a dose dependent decrease in resistance. These effects were partially prevented by co–treatment with an MMP inhibitor. Western blot analysis revealed alterations in the occludin protein from RPE cells treated with MMP–9, which could be prevented by treatment with an MMP inhibitor. Conclusions: Increased expression of proteinases may play a role in the alteration of the BRB through their action on the tight junction protein occludin, and may be important in the pathophysiology of altered BRB permeability.

Keywords: proteolysis • retina • diabetic retinopathy