Role of phospholipases A2 in diabetic retinopathy: In vitro and in vivo studies

Diabetic retinopathy is one of the leading causes of blindness and the most common complication of diabetes with no cure available. We investigated the role of phospholipases A(2) (PLA(2)) in diabetic retinopathy using an in vitro blood retinal barrier model (BRB) and an in vivo streptozotocin (STZ)-induced diabetic model. Mono- and co-cultures of endothelial cells (EC) and pericytes (PC), treated with high or fluctuating concentrations of glucose, to mimic the diabetic condition, were used. PLA(2) activity, VEGF and PGE(2) levels and cell proliferation were measured, with or without PLA(2) inhibition. Diabetes was induced in rats by STZ injection and PLA(2) activity along with VEGF, TNF alpha and ICAM-1 levels were measured in retina. High or fluctuating glucose induced BRB breakdown, and increased PLA(2) activity, PGE(2) and VEGF in EC/PC co-cultures; inhibition of PLA(2) in mono- or co-cultures treated with high or fluctuating glucose dampened PGE(2) and VEGF production down to the levels of controls. High or fluctuating glucose increased EC number and reduced PC number in co-cultures; these effects were reversed after transfecting EC with small interfering RNA targeted to PLA(2). PLA(2) and COX-2 protein expressions were significantly increased in microvessels from retina of diabetic rats. Diabetic rats had also high retinal levels of VEGF, ICAM-1 and TNF alpha that were reduced by treatment with a cPLA(2) inhibitor. In conclusion, the present findings indicate that PLA(2) upregulation represents an early step in glucose-induced alteration of BRB, possibly upstream of VEGF; thus, PLA(2) may be an interesting target in managing diabetic retinopathy. (C) 2013 Elsevier Inc. All rights reserved.