Effects of tumor necrosis factor-α and interleukin-1β on human retinal endothelial cells

Uveitis, or intraocular inflammation, is a potentially blinding condition that mostly affects the working-age population. The cytokines, tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 beta, play a role in the pathogenesis of non-infectious uveitis and have been linked to the breakdown of the inner blood-retinal barrier, composed mainly of retinal endothelial cells, leading to macular oedema and vascular leakage. However, the effects of TNF alpha and IL-1 beta on human retinal endothelial function are not fully understood. In this work, we investigated the impact of TNF-alpha and IL-1 beta on several aspects of human retinal endothelial cell biology. Through a real-time biosensor, the impact of TNF-alpha and IL-1 beta on formation of a retinal endothelial cell barrier was analyzed. Changes in junctional components were assessed via RT-qPCR and immunolabelling. Cell survival, necrosis and apoptosis were appraised via cell proliferation and flow cytometric studies. Tumor necrosis factor-alpha and IL-1 beta impaired the electrical resistance of the retinal endothelial cell barrier, while the addition of a potentially barrierimpairing cytokine, IL-6, did not enhance the effect of TNF-alpha and IL-1 beta. Level of the gene transcript encoding zonula occludens (ZO)-1 was diminished, while ZO-1 protein configuration was changed by TNF-alpha and IL-1 beta. Both cytokines affected human retinal endothelial cell proliferation and viability, while only TNF-alpha increased rates of necrosis. These results indicate that TNF-alpha and IL-1 beta are important drivers of retinal endothelial dysfunction in non-infectious uveitis, suggesting that targeting these cytokines is critical when treating complications of uveitis, such as macular oedema and vascular leakage.