Modelling Macular Edema: The Effect of IL-6 and IL-6R Blockade on Human Blood–Retinal Barrier Integrity In Vitro

Abstract

PurposeMacular edema (ME) is a leading cause of visual loss in a range of retinal diseases and despite the use of antivascular endothelial growth factor (anti-VEGF) agents, its successful treatment remains a major clinical challenge. Based on the indirect clinical evidence that interleukin-6 (IL-6) is a key additional candidate mediator of ME, we interrogated the effect of IL-6 on blood–retinal barrier (BRB) integrity in vitro.MethodsHuman retinal pigment epithelial cell (ARPE-19) and human retinal microvascular endothelial cell (HRMEC) monolayers were used to mimic the outer and inner BRB, respectively. Their paracellular permeability was assessed by measuring the passive permeation of 40 kDa fluorescein isothiocyanate (FITC)-dextran across confluent cells in the presence of IL-6. Transendothelial/epithelial electrical resistance (TEER) then was measured and the distribution of the tight junction protein ZO-1 was assessed by immunofluorescence using confocal microscopy.ResultsTreatment with IL-6 for 48 hours significantly increased the diffusion rate of FITC-dextran, decreased TEER, and disrupted the distribution of ZO-1 in ARPE-19 cells, which constitutively express the IL-6 transmembrane receptor, and this was reversed with IL-6R blockade. In contrast, IL-6 did not affect the paracellular permeability, TEER, or ZO-1 distribution in HRMECs.ConclusionsThese in vitro data support the hypothesis that IL-6 reversibly disrupts the integrity of ARPE-19 cells, but it does not affect HRMECs.Translational RelevanceIL-6 is a candidate therapeutic target in the treatment of outer BRB driven ME.

Glycolysis is integral to histamine‐induced endothelial hyperpermeability

“…Moreover, considering the role of histamine as a neurotransmitter, 44 it seems reasonable that brain and retinal endothelial cells should be able to maintain their vascular integrity in the presence of histamine. Other reports have noted that HRMEC do increase permeability similarly to other endothelial cell types in response to some factors, such as VEGF, but are unresponsive to others, such as IL‐6 45‐47 . Hence, the distinct responses to histamine of HRMEC, compared to endothelial cells from other vascular beds, provides further evidence for the heterogeneity of vascular endothelial cells from different tissues 48 …”

The role of IL-6-174 G/C polymorphism and intraocular IL-6 levels in the pathogenesis of ocular diseases: a systematic review and meta-analysis

“…On closer examination, it was found that patients with MO secondary to CRVO or BRVO showed a higher IL-6 concentration than patients with CRVO or BRVO alone. Indeed, the administration of IL-6 disrupts the integrity of human retinal pigment epithelial cells (ARPE-19) leading to increased cellular permeability concomitant with a low trans endothelial electrical resistance (TEER) 260 . This indicates the potential use of IL-6 as a biomarker and therapeutic target of retinal vascular diseases.…”

Cytokines and Growth Factors as Predictors of Response to Medical Treatment in Diabetic Macular Edema

“…Its levels have been shown to be increased in several number of other retinal diseases such as retinal vein occlusions and uveitic macular edema. In uveitic macular edema, systemic inhibition of IL-6 has shown benefits (Mesquida et al, 2019). However, an in vitro model has shown that IL-6 can lead to break down of the outer retinal blood brain barrier, but not of the inner blood-retinal brain barrier (Mesquida et al, 2019).…”

“…In uveitic macular edema, systemic inhibition of IL-6 has shown benefits (Mesquida et al, 2019). However, an in vitro model has shown that IL-6 can lead to break down of the outer retinal blood brain barrier, but not of the inner blood-retinal brain barrier (Mesquida et al, 2019). However, even though both barriers are affected in DME, the latter is the main one involved.…”