Tnf Alpha Is Required For Late Brb Breakdown In Diabetic Retinopathy, And Its Inhibition Prevents Leukostasis And Protects Vessels And Neurons From Apoptosis

PURPOSE. Blood-retinal barrier [BRB] breakdown, characteristic of diabetic retinopathy (DR), is believed to depend on inflammation and apoptosis. Retinal inflammation is almost completely suppressed in the absence of TNF alpha, which is also associated with apoptosis. This study was conducted to determine the role of TNF alpha in these diabetic complications.METHODS. Diabetes was induced with streptozotocin in Tnfa knockout (KO) mice, to provide a chemical model of diabetes, and Tnfa (KO) mice were crossed with Ins2(AKita) mice to generate a genetic model, with both models being devoid of TNF alpha The BRB was assessed at 1, 1.5, 3, and 6 months. Leukostasis was assessed using FITC-conjugated ConA to label leukocytes. Apoptosis was assessed with RAM. and activated caspase-3 staining. PECAM1 identified endothelial cells, and SMA identified pericytes.RESULTS. At 1 month of diabetes, the absence of TNF alpha had no effect on DR-associated BRB breakdown, even though it prevented retinal leukostasis, demonstrating that neither TNF alpha nor inflammation is essential for early BRB breakdown in DR in either model of diabetes. At 3 months of diabetes, BRB breakdown was significantly suppressed and at 6 months, it was completely prevented in the absence of TNF alpha in both models, showing that TNF alpha is essential for progressive BRB breakdown. DR-mediated apoptosis in the retina, which appears to involve endothelial cells, pericytes, and neurons, was inhibited in the absence of TNF alpha in both models.CONCLUSIONS. Although neither TNFa nor inflammation is necessary for early BRB breakdown in DR, TNF alpha is critical for later complications and would be a good therapeutic target for the prevention of the progressive BRB breakdown, retinal leukostasis, and apoptosis associated with DR. (Invest Ophthalmol Vis Sci. 2011;52:1336-1344) DOI:10.1.1.67/iovs.10-5768