Investigating the role of pyroptotic monocytes and macrophages in citrullinated autoantigen generation for rheumatoid arthritis 3417

Abstract Description Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by inflammation of synovial joints. Anti-citrullinated protein antibodies are present in up to 80% of RA patients, are associated with more severe disease, and target citrullination on self-proteins. Citrullination is an irreversible post-translational modification catalyzed by calcium-dependent peptidylarginine deiminase (PAD) enzymes; this process is dysregulated in RA resulting in broad hypercitrullination of proteins and generation of immunostimulatory neoself-antigens. We propose that monocytes, major infiltrators of the RA joint with high expression of PAD enzymes, are uniquely poised to undergo hypercitrullination due to their high susceptibility to pyroptosis, a pore-mediated form of inflammatory cell death. In this study, monocytes were treated with multiple pyroptotic stimuli and calcium. Using the anti-modified citrulline assay, we found that monocytes undergo hypercitrullination during pyroptosis, and citrullinated proteins are expelled from these cells. Moreover, monocyte-derived macrophages generated in vitro were treated with pyroptotic stimuli and calcium; immunofluorescence imaging showed that these cells also undergo hypercitrullination during pyroptosis. We theorize that gasdermin D pores facilitate the influx of PAD-activating calcium and efflux of citrullinated antigens with inflammatory cytokines in monocytes and macrophages, which may be a mechanism of autoantigen generation in RA. Topic Categories Basic Autoimmunity (BA)