A novel mechanism for macrophage pyroptosis in rheumatoid arthritis induced by Pol β deficiency

Rheumatoid arthritis (RA) is a chronic and inflammatory autoimmune disease. Macrophage pyroptosis, a proinflammatory form of cell death, is critically important in RA; however, the detailed mechanism underlying pyroptosis induction is not yet well understood. Here, we report that DNA polymerase β (Pol β), a key enzyme in base excision repair, plays a pivotal role in RA pathogenesis. Our data shows that Pol β expression is significantly decreased in peripheral blood mononuclear cells (PBMCs) from active RA patients and collagen-induced arthritis (CIA) mice, and Pol β deficiency increases the incidence of RA, macrophage infiltration, and bone destruction in CIA mouse models. In vitro, experiments showed that Pol β deficiency exacerbated macrophage pyroptosis induced by LPS plus ATP, while overexpression of Pol β inhibited macrophage pyroptosis. Further characterization revealed that Pol β knockout resulted in DNA damage accumulation and cytosolic dsDNA leakage, which activated the cGAS-STING-NF-κB signaling pathway and upregulated the expression of NLRP3, IL-1 β, and IL-18. In conclusion, our findings clarify the influence of Pol β on the development of RA and provide a detailed explanation for the STING-NF-κB pathway to induce macrophage pyroptosis.