Neutrophil Extracellular Traps Induce PANoptosis and Inflammatory Responses in Fibroblast-Like Synoviocytes of Rheumatoid Arthritis.

INTRODUCTION

Neutrophil extracellular traps (NETs) significantly contribute to rheumatoid arthritis (RA) pathogenesis, though their exact mechanisms remain unclear. In this research, we explored how NETs influence RA development through the PANoptosis core molecule AIM2.

METHODS

Enzyme-linked immunosorbent assay and Quant-iT Pico Green measured AIM2 and cell-free DNA (cfDNA) levels in synovial fluid. Immunohistochemistry examined the levels of AIM2 in synovial tissues. In vitro, the CCK-8 assay evaluated cell proliferation. Western blot detected the expression changes of AIM2, PANoptosis-related proteins, and NF-κB pathway-related proteins. Real-time quantitative PCR measured mRNA levels of IL-1β, IL-18, and IL-6. Immunofluorescence quantified AIM2, Caspase-8, GSDMD, and p-MLKL fluorescence intensity and cfDNA/AIM2 co-localization. An AIM2-silenced cell model was established to examine changes in the AIM2, PANoptosis-related proteins, and NF-κB pathway-related proteins (Western blot), fluorescence intensity (IF), inflammatory cytokine transcription (RT-qPCR), and RA-FLS migration (scratch and transwell assays).

RESULTS

Our results showed an increase in AIM2 expression in RA synovial fluid and tissues, which correlates with both cfDNA high levels and clinical disease activity scores. In vitro, in RA fibroblast-like synoviocytes (RA-FLSs), NETs elevated AIM2 and PANoptosis-related protein levels, activated the NF-κB signaling pathway, and enhanced the release of inflammatory cytokines. Treatment with DNase1 and AIM2 silencing resulted in lower levels of PANoptosis proteins and AIM2, inhibited NF-κB signaling, and decreased cytokine production.

CONCLUSION

This is the first time exploring the pathogenic mechanism of NETs-induced PANoptosis in RA, and targeting AIM2 may represent a potential new therapeutic approach for RA.