Project Summary: Inflammation underlies the disabling manifestations and co-morbidities of rheumatoid arthritis (RA). Treatment regimens for RA patients aim to control inflammation and progressive joint damage mediated by inflammatory cytokines including TNFα, IL-1β, and IL-6. Recent studies demonstrate that humans possess four genes coding Pyrin-only proteins (POPs) that limit NF-B signaling and inflammasome activation pathways, events critical for elaboration of the cytokines mediating inflammation. TNF, IL-1β, and IL-6 are critically regulated by NF-B transcription factors. We have previously described the anti-inflammatory properties of POP2 in-vitro and in-vivo. Here we propose proof-of-concept studies to evaluate how POP2 and POP2-derived peptides impact experimentally induced RA when administered exogenously, using a murine preclinical model. POP2 peptide therapy represents a novel therapeutic approach to ameliorating excessive inflammation through dual inhibition of both NF-B signaling and inflammasome pathways. The immunological and molecular basis for our hypotheses stems from our published and preliminary data showing the naturally expressed, non-toxic POP2 peptide dampens cytokine production in inflammatory responses without compromising host immunity. Our studies will provide insight into how treatment regimens based on POP2 peptide therapy may be utilized or improved upon. In vitro characterization, dose-escalation studies and in-vivo assessment of disease parameters will inform approaches to develop POP2 peptides as a novel therapeutic.