Fenofibric Acid Reduces Fibronectin and Collagen Type IV Overexpression in Human Retinal Pigment Epithelial Cells Grown in Conditions Mimicking the Diabetic Milieu: Functional Implications in Retinal Permeability

Abstract

To determine whether fenofibric acid (FA) reduces high glucose (HG)-induced basement membrane component overexpression and hyperpermeability in human retinal pigment epithelial (RPE) cells. Retinal pigment epithelial cells (ARPE-19) were cultured for 18 days in normal glucose (5 mM) or HG (25 mM) medium and studied for the effects of FA on fibronectin (FN) and collagen IV (Coll IV) expression. During last 3 days of the experiment, 100 μM FA was added to cells grown in HG medium or in HG medium plus IL-1β (HG + IL-1β) to mimic, at least in part, the inflammatory aspect of the diabetic milieu. Real-time RT-PCR was performed to determine FN and Coll IV mRNA levels, whereas protein levels were assessed by Western blot analyses. Cell monolayer morphology and barrier function were analyzed by confocal microscopy using specific antibodies against tight junction proteins, ZO-1, and claudin-1 and by measuring apical-basolateral movements of FITC-dextran, respectively. FN and Coll IV expression were significantly increased in RPE cells grown in HG or HG + IL-1β medium compared with cells grown in normal medium. When cells grown in HG or HG + IL-1β medium were treated with FA, significant reductions in FN and Coll IV expression were observed. In addition, exposure to FA decreased excess permeability in a dose-dependent manner in cells grown in HG + IL-1β medium. This effect was unrelated to changes in tight junction protein content. Findings from this study suggest that the downregulation of basement membrane components by FA may have a protective effect against outer blood-retinal barrier leakage associated with diabetic retinopathy.