Aims: To determine the intra-vitreous levels of two pro-inflammatory cytokines [interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1)] and the anti-inflammatory cytokine interleukin-10 (IL-10) in patients with proliferative diabetic retinopathy (PDR). In addition, the relationship between the profile of cytokines and PDR activity has also been evaluated.
Patients and methods: The study included 22 consecutive diabetic patients with PDR (4 Type 1 and 18 Type 2) on whom a vitrectomy was performed. Sixteen age-matched non-diabetic patients with other conditions requiring vitrectomy, but in which the retina was not directly affected by neovascularization served as a control group. IL-8, MCP-1 and IL-10 were measured by enzyme-linked immunosorbent assay (ELISA).
Results: The vitreal levels of both IL-8 and MCP-1 were strikingly higher in diabetic patients with PDR in comparison with the control group [173.5 (64-1670) vs. 49 pg/ml (25-145), P < 0.001, and 2171 (388-6155) vs. 438 pg/ml (207-1344), P < 0.001, respectively]. In addition, the vitreous concentrations of IL-8 and MCP-1 were higher in patients with active PDR than in those patients with quiescent PDR [324.5 (80-1670) vs. 173.5 pg/ml (64-487), P = 0.06 and 3596 (1670-6155) vs. 1143 pg/ml (388-2500), P = 0.01, respectively]. However, vitreal levels of IL-10 in diabetic patients were similar to that obtained in the control group [2.89 (1.55-5.50) vs. 2.46 pg/ml (2.2-5.41), P = NS].
Conclusions: The pro-inflammatory cytokines IL-8 and MCP-1 are increased in the vitreous fluid of PDR patients without an increase in the anti-inflammatory cytokine IL-10. In addition, both IL-8 and MCP-1 intra-vitreous levels correlated with PDR activity, thus suggesting that these cytokines may be pathogenically important in PDR.