TNF and diabetic retinopathy: Free radicals as reactive oxygen species (ROS) are a strong stimulus for the release of proinflammatory cytokines, such as tumor necrosis factor-α(TNF-α) and interleukin 1β (IL-1β), which damage endothelial cells and play an important role in the pathogenesis of DR [10], and it has been reported that anti-inflammatory drugs could prevent early diabetic retinopathy via suppression of proinflammatory cytokines like TNF-α [11].