The action of pro‐inflammatory cytokines on retinal endothelial cell barrier permeability: protective effect of corticosteroids

Abstract Purpose The pro‐inflammatory cytokines interleukin‐1β (IL‐1β) and tumor necrosis factor‐alpha (TNF‐α) were found to be increased in the vitreous of diabetic patients and in diabetic rat retinas, and increased cytokine levels were correlated with elevated retinal vascular permeability. In this work, we investigated the mechanisms underlying IL‐1β‐ and TNF‐α‐induced retinal endothelial cell permeability and evaluated the ability of a glucocorticoid, dexamethasone (DEX), to prevent changes in permeability. Methods Primary cultures of bovine retinal endothelial cells (BRECs) were grown on transwell filters and exposed to IL‐1β and TNF‐α. BRECs permeability to 70 kDa RITC‐dextran was measured. The content and localization of tight junction proteins was assessed by Western blotting and immunocytochemistry. Results IL‐1β and TNF‐α increased retinal endothelial cell permeability in a concentration‐ and time‐dependent manner, but TNF‐α was more effective (increased permeability at a lower dose and shorter time‐point). The increase in permeability was not due to changes in cell viability. IL‐1β and TNF‐α altered ZO‐1 and claudin‐5 content. TNF‐α also decreased ZO‐1 staining at the cell border. Pre‐treatment with DEX prevented TNF‐α‐induced cell permeability, and the protective effect of DEX was partially abolished by the glucocorticoid receptor antagonist RU486. Conclusion These data demonstrate that TNF‐α and IL‐1β potently induce endothelial cell permeability through alterations in tight junctions. Also, the study supports the potential therapeutic use of glucocorticoids to reduce retinal vascular permeability. Support: FCT (Portugal), NIH, JDRF and Allergan