Targeting Leukostasis for the Treatment of Early Diabetic Retinopathy

Leukocyte-endothelial interaction plays an important role in the early phase of the development of diabetic retinopathy. It has been studied extensively linking inflammatory processes to its development conducted to date in rats and mice, and have focused on insulin-deficient models. The molecular and functional changes that are characteristics of inflammation have been detected in retinas from diabetic animals and humans with involvement of multiple pathways that results in the final sequelae of increased permeability of the blood retinal barrier and finally ischemia that drives angiogenesis. Increased expression of Intracellular adhesion molecules heralds the onset of changes that results in attraction of leucocytes such as neutrophils. The consequent release of cytokines and growth factors such as vascular endothelial growth factor (VEGF), tumor necrosis factor-alpha, and interleukin 1-Beta results in increased permeability and retinal edema. Other indirect mediators involved include pathways such as the protein kinase C (PKC), renin-angiotensin system, enzymes such as the poly ADP-ribose polymerase, 3-hydroxy-3-methylglutaryl-coenzyme A reductase, nitric oxide synthetase and finally advanced glycation products. Therapy for early diabetic retinopathy may inhibit one or more of these pathways using drugs that can be given systemically, with local ocular applications having a more direct effect as in other eye diseases.