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Casey Stottrup, Sumon Roy, Lucien Rizzo, Rafael Simo, Sayon Roy; Effect of Fenofibrate on Overexpression of Extracellular Matrix Components, COX-2, and Barrier Permeability Associated with Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2012;53(14):5415.
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In the Fenofibrate (FA) Intervention and Event Lowering in Diabetes (FIELD) study, FA, a lipid-lowering drug, has been shown to significantly reduce macular edema in diabetic patients. In this study, we investigated whether FA reduces vascular permeability by inhibiting cyclooxygenase-2 (COX-2), a critical mediator of inflammation, and reducing overexpression of fibronectin (FN) and collagen IV (Coll IV), two basement membrane (BM) components upregulated in diabetic retinopathy.
Rat retinal endothelial cells (RRECs) were grown in normal (5 mM glucose) or high (30 mM glucose) medium with or without FA for 7 days. Total protein isolated from these cells was assessed for FN, Coll IV, COX-2 and zonula occludens-1 (ZO-1), a tight junction protein using Western blot analysis. In addition, the distribution and localization of ZO-1 was determined by immunofluorescence microscopy, and cell monolayer permeability was studied by in vitro permeability (IVP) assay.
RRECs grown in HG medium showed significant increase in FN, Coll IV, and COX-2 expression (75%, 42%, 39% of N respectively), and a decrease in ZO-1 expression (30% of N) compared to those of N cells. Cells grown in HG medium supplemented with FA significantly reduced FN, Coll IV, and COX-2 expression by 45%, 32%, 34% respectively, with concomitant increase in ZO-1 expression by 16%. In parallel studies, IVP assays showed a significant increase (39% of N) in cell monolayer permeability in RRECs grown in HG medium, which was significantly reduced with FA treatment. Additionally, immunostaining results indicated FA prevents HG-induced downregulation of ZO-1.
The findings indicate that the beneficial effect of FA in reducing excess permeability is mediated, at least in part, by downregulating abnormal overexpression of BM components and inflammatory factors and preventing compromised tight junctions associated with diabetic retinopathy.
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