Supplementary Material for: High Vitreous Concentration of IL-6 and IL-8, but Not of Adhesion Molecules in Relation to Plasma Concentrations in Proliferative Diabetic Retinopathy

Background/Aim: Inflammatory markers have been observed in proliferative diabetic retinopathy (PDR). We assessed vitreous concentrations of adhesion molecules and cytokines in PDR and non-diabetic controls and plasma concentrations to differentiate local inflammation from the breakdown of the blood-retina barrier. Methods: 38 patients with PDR and 16 controls with macular hole or epiretinal membrane underwent vitrectomy. Vitreous and plasma soluble adhesion molecules [sE-selectin, intercellular adhesion molecule (sICAM)-1 and -3, platelet-endothelial cell adhesion molecule (sPECAM)-1, sP-selectin, vascular cell adhesion molecule (sVCAM)-1] and cytokines [interleukin (IL)-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12 (p70), tumour necrosis factor-α and -β, γ-interferon] were detected by the multiplex assay. Results: Levels of IL-6 and IL-8 were 26-fold (p = 0.001) and 6-fold higher (p = 0.001) in vitreous than in plasma in PDR. Vitreous IL-10 (p = 0.004), sPECAM-1, sE-selectin, sICAM-1 and sVCAM-1 were higher in PDR than controls (p = 0.001 for all). Adhesion molecule concentrations in vitreous in PDR were less than 10% of those in plasma. IL-10 was lower in vitreous than plasma (3.0 vs. 12.8 pg/ml, p = 0.007), and the vitreous IL-10/IL-8 ratio was significantly lower in PDR than in controls (0.10 vs. 0.55 pg/ml, p = 0.003). Conclusion: The elevated IL-6 and IL-8 levels in vitreous, but not in plasma, are evidence favouring local over systemic inflammation in PDR. Furthermore, there was imbalance between inflammatory and anti-inflammatory cytokines in the vitreous.