Enhanced type I interferon signature induces neutrophil extracellular traps enriched in mitochondrial DNA in adult-onset Still's disease.

Adult-onset Still's disease (AOSD) is a rare but clinically well-known auto-inflammatory disorder. Cytokine storm, the hallmark of AOSD, is mediated by neutrophil hyperactivation and enhanced neutrophil extracellular trap (NET) formation. Type I interferons (IFNs), having a primary role in the initiation of proinflammation responses, can induce subsequent inflammatory cytokine production. However, the role of type I IFNs in AOSD is unclear. Indeed, high levels of IFN-α and IFN-β expression are presented by AOSD patients. In this investigation, hierarchical unsupervised clustering was performed on IFN-α and IFN-β data to identify a cluster of AOSD patients who had a serious condition. Neutrophils from treatment-naïve active AOSD patients showed very strong enrichment in their IFN-α response, as shown by RNA-seq and confirmed by the IFN score. Whether IFN-α stimulates NET formation was also tested. IFN-α had the ability to form NETs that contained oxidized mitochondrial DNA (ox-mtDNA). Moreover, the JAK inhibitor could be used to dampen type I IFN-induced NET formation and eventually control ox-mtDNA release. Our results demonstrated the important roles of type I IFNs in the pathogenesis of AOSD through their promotion of NET formation, as characterized by the enhanced level of ox-mtDNA. The findings open up new avenues of research into therapeutic approaches for AOSD.