e, f Whole-cell lysates from (c) and (d) were analysed by immunoblotting for antiviral signaling with Vinculin (VCL) as loading control. and is inducible by a cell-permeable derivative of the TCA-cycle-derived metabolite itaconate (4-octyl-itaconate, 4-OI). Additionally, engagement of this pathway by 4-OI or the Nrf2 inducer sulforaphane is sufficient to repress STING expression and type I IFN production in cells from patients with STING-dependent interferonopathies. We propose Nrf2 inducers as a future treatment option in STING-dependent inflammatory diseases. Introduction Nrf2 (Nuclear factor (erythroid-derived 2) -like 2) is a member of the capncollar basic leucine zipper family of transcription factors characterized structurally by the presence of Nrf2-ECH homology domains1. At steady state, Nrf2 is kept inactive in the cytosol by its inhibitor protein Keap1 (Kelch-like ECH-associated protein 1), which targets Nrf2 for proteasomal degradation2. In response to oxidative stress, Keap1 is inactivated and Nrf2 is released to induce the transcription of Nrf2-responsive genes. In general, the genes under the control of Nrf2 protect against stress-induced cell death and Nrf2 has thus been suggested as the master regulator of tissue damage during infection3. Furthermore, Nrf2 is also an important regulator of the inflammatory response4,5 and was recently identified to function as a transcriptional repressor of inflammatory genes in murine macrophages6. Type I IFNs (IFN and -) are central to immune-protection against infection with virus. Production of IFN/ in response to infection CA-224 is highly dependent on innate recognition of cytosolic viral nucleic acids by cellular pathogen recognition receptors (PRRs). These receptors include the RNA sensors RIG-I and MDA-5, which signal through the adaptor MAVS7,8, and the DNA sensor cGAS which signals through the adaptor STING9C12. In both signaling pathways, binding of viral nucleic acids to their respective sensors leads to recruitment and phosphorylation of the kinase TBK1 (Tank Binding Kinase 1), which in turn activates the IRF3 transcription factor by phosphorylation13C15. Whereas a balanced production of type I IFNs is necessary for protection against virus, excessive production hereof is a CA-224 powerful driver of pathology. This has recently been demonstrated in influenza A virus infections16 as well as in a series of auto-inflammatory disorders such as systemic lupus erythematosus17,18 and in the more recently discovered disease STING-associated vasculopathy with onset in infancy (SAVI)19. In the latter case, gain-of-function mutations in STING drives a systemic and debilitating inflammatory condition19. Tight regulation of type I IFNs is thus necessary to avoid excessive immune mediated tissue damage in infection as well as in homeostasis. If and CA-224 how Nrf2 affects type I IFN responses induced by antiviral cytosolic sensing and if the Nrf2/Keap1 axis is a potential target for treating STING-dependent interferonopathies is, however, not currently known. The role of biochemistry has recently gained a newfound foothold in innate immunology. Studies dating back from the 1970s showed that microbial products, such as LPS (lipopolysaccharide), negatively regulate respiration of macrophages by inhibiting complexes in oxidative phosphorylation20,21. These early discoveries have now formed the basis of a completely new area of immunology referred to as immunometabolism22. Metabolic reprogramming is now known to include an increase in glycolysis and a two-point interruption of the tricarboxylic acid (TCA) cycle23,24. Recent work has now demonstrated that an important result of metabolic reprogramming, induced through stimulation with LPS, is the accumulation of distinct TCA-cycle derived metabolitesin particular succinate and itaconate25,26. Earlier work demonstrated that succinate operates as a pro-inflammatory agent and is important for the release of IL-125. The anti-inflammatory effect of endogenous itaconate was initially described in Irg1 deficient murine macrophages that lack itaconate production27. Further, itaconate has been demonstrated to have anti-inflammatory properties by inhibiting the enzymatic activity of succinate dehydrogenase (SDH) to accumulate succinate25C27. Moreover, a recent report demonstrated that a cell-permeable derivative of itaconate (4-octyl-itaconate, 4-OI) blunts transcription of IL-1 through activation of the transcription factor Nrf2, which acts as a repressor of IL-1 transcription28. Altogether, these reports contribute to a growing body of evidence for a dependency on metabolic reprogramming for the control of pro-inflammatory cytokine release. No reports have so far demonstrated a link between cellular accumulation of metabolites and regulation of antiviral cytosolic sensing. In this study, we demonstrate that CA-224 Nrf2 represses antiviral Mouse monoclonal to CD31 cytosolic sensing by suppressing the expression of.