ABSTRACT: The aim of this study is to determine the effects of silver nanoparticles (Ag-NP) on vascular endothelial growth factor (VEGF)-and interleukin-1 beta (IL-1beta)-induced vascular permeability, and to detect the underlying signaling mechanisms involved in endothelial cells. Porcine retinal endothelial cells (PRECs) were exposed to VEGF, IL-1beta and Ag-NP at different combinations and endothelial cell permeability was analyzed by measuring the flux of RITC-dextran across the PRECs monolayer. We found that VEGF and IL-1beta increase flux of dextran across a PRECs monolayer, and Ag-NP block solute flux induced by both VEGF and IL-1beta. To explore the signalling pathway involved VEGF- and IL-1beta-induced endothelial alteration, PRECs were treated with Src inhibitor PP2 prior to VEGF and IL-1beta treatment, and the effects were recorded. Further, to clarify the possible involvement of the Src pathways in endothelial cell permeability, plasmid encoding dominant negative(DN) and constitutively active(CA) form of Src kinases were transfected into PRECs, 24 h prior to VEGF and IL-1beta exposure and the effects were recorded. Overexpression of DN Src blocked both VEGF-and IL-1beta-induced permeability, while overexpression of CA Src rescues the inhibitory action of Ag-NP in the presence or absence of VEGF and IL-1beta. Further, an in vitro kinase assay was performed to identify the presence of the Src phosphorylation at Y419. We report that VEGF and IL-1beta-stimulate endothelial permeability via Src dependent pathway by increasing the Src phosphorylation and Ag-NP block the VEGF-and IL-1beta-induced Src phosphorylation at Y419. These results demonstrate that Ag-NP may inhibit the VEGF-and IL-1beta-induced permeability through inactivation of Src kinase pathway and this pathway may represent a potential therapeutic target to inhibit the ocular diseases such as diabetic retinopathy.