Human retinal endothelial cells express functional interleukin-6 receptor

Mechanisms of blood-retinal barrier disruption related to intraocular inflammation and malignancy

Blood-retinal barrier (BRB) disruption is a common accompaniment of intermediate, posterior and panuveitis causing leakage into the retina and macular oedema resulting in vision loss. It is much less common in anterior uveitis or in patients with intraocular lymphoma who may have marked signs of intraocular inflammation. New drugs used for chemotherapy (cytarabine, immune checkpoint inhibitors, BRAF inhibitors, EGFR inhibitors, bispecific anti-EGFR inhibitors, MET receptor inhibitors and Bruton tyrosine kinase inhibitors) can also cause different types of uveitis and BRB disruption. As malignant disease itself can cause uveitis, particularly from breast, lung and gastrointestinal tract cancers, it can be clinically difficult to sort out the cause of BRB disruption. Immunosuppression due to malignant disease and/or chemotherapy can lead to infection which can also cause BRB disruption and intraocular infection. In this paper we address the pathophysiology of BRB disruption related to intraocular inflammation and malignancy, methods for estimating the extent and effect of the disruption and examine why some types of intraocular inflammation and malignancy cause BRB disruption and others do not. Understanding this may help sort and manage these patients, as well as devise future therapeutic approaches.

Relationship between vitreous interleukin-6 levels and vitreous particles findings on widefield optical coherence tomography in posterior uveitis

PURPOSE

To investigate relationship between vitreous interleukin-6 levels and vitreous particles findings on widefield optical coherence tomography in posterior uveitis.

METHODS

This retrospective study examined vitreous inflammatory cells (hyperreflective particles) of posterior uveitis on widefield optical coherence tomography (WOCT). We examined the number of hyperreflective particles (possibility of vitreous inflammatory cells) observed on WOCT and the correlations with interleukin-6 (IL-6) levels. The relationship between vitreous IL-6 levels and image findings from WOCT from 37 eyes (34 patients) with posterior uveitis were analyzed. Mean patient age was 63.4±15.7 years. (Mean± standard deviation) IL-6 concentration in vitreous humor was 79.9±7380.9 pg/mL Uveitis was infectious in 9 cases and non-infectious in 28 cases with multiplex polymerase chain reaction system. We measured the number and size of vitreous cells in the posterior vitreous, defined as the space between the upper vitreous and the internal limiting membrane on WOCT at the macular, upper, and lower regions. Image analysis software was also used for cell counting.

RESULTS

A strong correlation was seen between human and software counts. Pearson's correlation coefficient (PCC) was performed to compare categorial variables (on macular +0.866; upper cavity +0.713; lower cavity +0.568; total vitreous cavity +0.834; P<0.001 each). IL-6 levels correlated with both vitreous cell counts and cell counts observed on macular WOCT (human-counted group +0.339, P = 0.04; software-counted group +0.349, P = 0.03). Infectious uveitis showed higher IL-6 levels (P = 0.016) and high cell counts compared with non-infectious uveitis (P = 0.04).

CONCLUSIONS

Vitreous number of hyperreflective particles (cells) findings on WOCTcorrelated well with human and software cell counts. Vitreous cells findings on WOCT also correlated with IL-6 concentrations on macular.

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)-α and interleukin (IL)-1β, 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-α and IL-1β on human retinal endothelial function are not fully understood. In this work, we investigated the impact of TNF-α and IL-1β on several aspects of human retinal endothelial cell biology. Through a real-time biosensor, the impact of TNF-α and IL-1β 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-α and IL-1β impaired the electrical resistance of the retinal endothelial cell barrier, while the addition of a potentially barrier-impairing cytokine, IL-6, did not enhance the effect of TNF-α and IL-1β. Level of the gene transcript encoding zonula occludens (ZO)-1 was diminished, while ZO-1 protein configuration was changed by TNF-α and IL-1β. Both cytokines affected human retinal endothelial cell proliferation and viability, while only TNF-α increased rates of necrosis. These results indicate that TNF-α and IL-1β 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.

Inflammatory cytokines as mediators of retinal endothelial barrier dysfunction in non-infectious uveitis

Characterised by intraocular inflammation, non-infectious uveitis includes a large group of autoimmune and autoinflammatory diseases that either involve the eye alone or have both ocular and systemic manifestations. When non-infectious uveitis involves the posterior segment of the eye, specifically the retina, there is substantial risk of vision loss, often linked to breakdown of the inner blood-retinal barrier. This barrier is formed by non-fenestrated retinal vascular endothelial cells, reinforced by supporting cells that include pericytes, Müller cells and astrocytes. Across the published literature, a group of inflammatory cytokines stand out as prominent mediators of intraocular inflammation, with effects on the retinal endothelium that may contribute to breakdown of the inner blood-retinal barrier, namely tumour necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, IL-17 and chemokine C-C motif ligand (CCL)2. This article reviews the function of each cytokine and discusses the evidence for their involvement in retinal endothelial barrier dysfunction in non-infectious uveitis, including basic laboratory investigations, studies of ocular fluids collected from patients with non-infectious uveitis, and results of clinical treatment trials. The review also outlines gaps in knowledge in this area. Understanding the disease processes at a molecular level can suggest treatment alternatives that are directed against appropriate biological targets to protect the posterior segment of eye and preserve vision in non-infectious uveitis.