Abstracts

Aims: Aberrant immune cell activation characterises SLE, in which glucocorticoids (GCs) remain a cornerstone of treatment.However, the unacceptable side effects of GCs have created a pressing need for a similarly broad-acting, but safer, anti-inflammatory agent.The glucocorticoidinduced leucine zipper, GILZ, mediates the anti-inflammatory effects of GCs but is independent of GC-associated metabolic adverse effects.Previously, we showed that GILZ is suppressed in SLE, permitting inappropriate immune cell activation.Therefore, restoring GILZ is a promising therapeutic strategy for reducing inflammation and bypassing the harmful metabolic effects of GCs.We identified "E3-X", a type I IFN-inducible protein which binds to GILZ.Here, we investigated whether inhibition of E3-X would increase GILZ and amplify its anti-inflammatory effects.Methods: We measured GILZ expression in E3-X knockout mice and human cell lines by flow cytometry.To validate the effect of E3-X deletion on inflammatory pathways active in lupus, we performed in vitro inflammatory stimulations of plasmacytoid dendritic cells, bone marrow-derived dendritic cells and T cells from wildtype and E3-X deficient mice.Lastly, to investigate the effect of E3-X deletion on GC-responsiveness, we conducted global proteomic analysis of WT and E3-X knockout A549 cells by mass spectrometry.Results: E3-X deficiency restored GILZ expression in human cell lines and mouse primary cells.In plasmacytoid dendritic cells, absence of E3-X resulted in reduced TNF and IL-6 production and diminished expression of interferon-stimulated genes.E3-X deficient bone marrow-derived dendritic cells demonstrated reduced secretion of Th1 and Th17-inducing cytokines.Likewise, E3-X deficiency attenuated proliferation of T cells in response to Th1-and Th17-inducing cytokines.Absence of E3-X also resulted in amplified GC-induced protein expression and improved GC-sensitivity.Conclusion: E3-X deficiency increased GILZ and reduced inflammation in a host of disease-promoting pathways in SLE.Thus, inhibition of E3-X is an attractive therapeutic strategy for reducing reliance on GCs.