Cytokines and adhesion molecules in proliferative diabetic retinopathy: High vitreous concentration of IL‐6 and IL‐8, but not of adhesion molecules in relation to plasma concentrations

Purpose Inflammatory markers have been observed in vitreous in diabetic retinopathy, but the increases may be predominantely due to leakage than due to intraocular production. We assessed vitreous concentrations of adhesion molecules and cytokines in proliferative diabetic retinopathy (PDR) and non‐diabetic controls (C) in correlation to corresponding plasma levels. The purpose of the study is to differentiate intraocular production from breakdown of the blood retinal barrier. Methods The study population was 38 patients with PDR undergoing vitrectomy. Group C consisted of 16 subjects vitrectomized for macular hole or epiretinal membrane. Vitreous and plasma concentrations of six adhesion molecules (sE‐Selectin, sICAM‐1, sICAM‐3, sPECAM‐1, sP‐Selectin, sVCAM‐1) and eleven cytokines (IL‐1β, IL‐2, IL‐4, IL‐5, IL‐6, IL‐8, IL‐10, IL‐12(p70), TNF‐α, TNF‐β, IFN‐γ) were detected by the flow‐cytometry based Multiplex assay (Bender). Results IL‐6 and IL‐8 were 26‐fold and 6‐fold higher in vitreous than in plasma in PDR, respectively. Vitreous concentrations of IL‐10, sPECAM‐1, sE‐selectin, sICAM‐1 and sVCAM‐1 were higher in PDR than C. However, concentrations of adhesion molecules in vitreous in PDR were less than 10 % of corresponding concentrations in plasma. Also anti‐inflammatory IL‐10 was lower in vitreous than in plasma and vitreous IL‐10/IL‐8 ratio significantly lower in PDR than in C. Conclusion There is an active role of cytokines IL‐6 and IL‐8 in proliferative diabetic retinopathy, which might be due to their intraocular production. Furthermore, there is an imbalance between inflammatory and anti‐inflammatory cytokines in vitreous.