Transcription Factor NRF2 is Activated by Erythrophagocytosis of Oxidized Red Blood Cell Products and Suppresses the IL-12-IFNg-IL-10 Axis in a Murine Model of Hyperinflammatory Disease

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Hyperinflammatory diseases including macrophage activation syndrome (MAS) and hemophagocytic lymphohistocytosis (HLH) are characterized by multi-lineage cytopenias, hypercytokinemia, and tissue hemophagocytosis. However, the mechanisms by which erythrophagocytosis mediates iron metabolism and regulates the hyperactive immune response remain unclear. The transcription factor NRF2 is an important sensor for inflammatory and redox distress. The targets of NRF2 are antioxidant response elements responsible for transcription of genes related to restoration of redox homeostasis within the cell. Here we demonstrate that mice with CpG-induced MAS have evidence of systemic oxidative and nitrosative distress – including increased serum nitric oxide and elevated systemic lipid peroxidation. In this model, NRF2 knockout mice develop significantly worse organomegaly, hypercytokinemia, and reticulocytosis. NRF2 knockout mice have unexpected exacerbation in the cytokines that are central to hyperinflammatory physiology – namely IL-12, IFN gamma (IFNg), and IL-10. In vitro we demonstrate that oxidized red blood cell products and heme itself suppress IL-12 protein production and transcription from bone marrow derived dendritic cells in a NRF2-dependent manner. Together our studies demonstrate that erythrophagocytosis of oxidized red blood cell products suppresses the Il-12-IFNg-IL-10 axis which drives hyperinflammation in murine hyperinflammation. Graphical abstract Created with BioRender