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

Petros XE Mouratidis,* Andrew JT George*  Department of Immunology, Imperial College London, London, UK *These authors contributed equally to this work Background: Indoleamine 2,3-dioxygenase (IDO) is an enzyme associated with the regulation of immune responses. Cytokines such as IFNγ 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 IFNγ but not after treatment with TNFα, IL-1β, IL-2, IL-4, IL-6, or IL-10. VEGFβ and heparin negatively regulate IFNγ-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 IFNγ. Heparin and angiogenesis stimulators such as VEGFβ negatively regulate its expression. Keywords: IFNγ, VEGFβ, endothelium, inflammation, HSVE