GSDMD-dependent neutrophil extracellular traps formation contributes to fibroblast-like synoviocyte activation in rheumatoid arthritis

Objective: The activation of NLRP3 inflammasome is critical for rheumatoid arthritis (RA), however, the role of gasdermin D (GSDMD), a newly identified pyroptosis executioner downstream of NLRP3/ASC/Caspase-1, in RA has not been well defined. Methods Genetically susceptible mice (DBA/1J) are immunized with a type II bovine collagen emulsion in complete Freund's adjuvant (CFA). Peripheral blood neutrophils were isolated from healthy volunteers and RA patients; cells were treated with serum from RA patients. The activation of GSDMD was analyzed by confocal and western blot. Proinflammatory cytokines in joint of mice were detected by qPCR and ELISA. Results The expression of cleaved GSDMD-N terminal in peripheral blood neutrophils from RA patients and the expression of GSDMD-N was positively correlated with the level of IL-1β and IL-18 from RA patients. GSDMD was required for the pathogenesis of RA, and GSDMD inhibition disulfiram significantly suppressed proinflammatory cytokines production and joint damage, leading to reduced arthritis severity score and loss of cartilage in collagen-induced arthritis (CIA) mouse model. Mechanistically, the activation of GSDMD significantly promotes neutrophil extracellular traps (NETs), which are highly immunogenic and decorated with HMGB1 and MMPs. Furthermore, GSDMD-dependent NETs formation facilitated fibroblast-like synoviocytes (FLS) activation and proliferation, driving cartilage and bone destruction, and promoting disease activity in RA. Conclusions GSDMD-dependent NETs formation promotes FLS activation during RA pathogenesis.