Role of interleukin-1 in the pathogenesis of diabetic retinopathy

Aim: To examine the role of cytokine interleukin-1β (IL-1β) in retinal capillary cell death in diabetes. Methods: The effect of glucose on the expression of IL-1β was measured in the bovine retinal endothelial cells. The role of IL-1β in the accelerated endothelial cell loss was determined by investigating the effect of human recombinant IL-1β on their apoptosis in normal and high glucose conditions, and was confirmed using interleukin-1 receptor antagonist (IL-1ra). Results: High glucose increased IL-1β expression by 60% compared with cells incubated in 5 mM glucose (p<0.05). Incubation of cells with IL-1β increased NO levels by about 80% and activated NF-κB by 40%. In the same cells apoptosis was increased by 70% and caspase-3 activity was increased by 40%. Supplementation of IL-1β in 20 mM glucose medium further increased nitric oxide and NF-κB, and accelerated apoptosis, and addition of IL-1ra significantly decreased glucose induced abnormalities and apoptosis. Conclusions: IL-1β accelerates apoptosis of retinal capillary cells via activation of NF-κB, and the process is exacerbated in high glucose conditions. These studies suggest a possible role of IL-1β in the development of retinopathy in diabetes, and offer a possible rationale to test IL-1β receptor antagonists to inhibit the development of diabetic retinopathy.