Regulation of indoleamine 2,3-dioxygenase in primary human saphenous vein endothelial cells

Background: Indoleamine 2,3-dioxygenase (IDO) is an enzyme associated with the regulation of immune responses. Cytokines such as IFN gamma induce its expression in endothelial cells originating from immune-privileged sites. In this study, we investigate regulators of IDO in primary endothelial cells from a non-immune-privileged site and determine whether IDO expression affects immune cell behavior. Methods: IDO expression was determined using real-time quantitative polymerase chain reaction and immunoblotting. IDO activity was estimated using an IDO enzyme assay. Primary cells were transfected using microporation, and T-cell migration was determined using a cell transmigration assay. Results: IDO is expressed in human saphenous vein endothelial cells after stimulation with IFN gamma but not after treatment with TNF alpha, IL-1 beta, IL-2, IL-4, IL-6, or IL-10. VEGF beta and heparin negatively regulate IFN gamma-driven increases in IDO. Overexpression of IDO in endothelial cells does not affect transmigration of T-cells. Conclusion: IDO is expressed in human saphenous vein endothelial cells after stimulation with IFN gamma. Heparin and angiogenesis stimulators such as VEGF beta negatively regulate its expression.