Abstract: BACKGROUND: Rheumatoid arthritis is a common autoimmune disease that mainly affects the joints and is characterized by persistent synovial inflammation. Studies have suggested that proinflammatory pyroptosis is closely related to the occurrence and development of rheumatoid arthritis.
OBJECTIVE: To investigate the expression levels of pyroptosis-related factors NOD-like receptor protein 3, cysteine aspartic acid-specific protease-1 (caspase-1), interleukin-18 and interleukin-1β in serum and articular fluid of patients with rheumatoid arthritis and their clinical significance. 
METHODS: From January 2021 to January 2022, 24 patients with rheumatoid arthritis admitted to the Rheumatology Department of Luoyang Orthopedic-Traumatological Hospital of Henan Province (Henan Provincial Orthopedic Hospital) were selected as rheumatoid arthritis group. Thirty osteoarthritis patients with knee joint effusion were selected as osteoarthritis group. Forty healthy subjects were selected as control group. C-reactive protein level, erythrocyte sedimentation rate, anti-cyclic citrullinated peptide antibody level, rheumatoid factor levels, and disease activity score in 28 joints were measured and recorded. NOD-like receptor protein 3, caspase-1, interleukin-18 and interleukin-1β levels in serum and joint fluid were determined by enzyme-linked immunosorbent assay (ELISA) to analyze the correlation between their expression levels and the clinical indicators of patients with rheumatoid arthritis. 
RESULTS AND CONCLUSION: The serum levels of NOD-like receptor protein 3, caspase-1, interleukin-18 and interleukin-1β in the rheumatoid arthritis group were significantly higher than those in the control group (P < 0.0001), while the articular fluid levels of NOD-like receptor protein 3, caspase-1, interleukin-18 and interleukin-1β in the rheumatoid arthritis group were significantly higher than those in the osteoarthritis group (P < 0.05-0.01). The expression levels of NOD-like receptor protein 3, caspase-1, interleukin-18 and interleukin-1β in serum and articular fluid of patients with rheumatoid arthritis were positively correlated with D disease activity score in 28 joints, C-reactive protein level, and erythrocyte sedimentation rate. To conclude, pyroptosis-related factors are significantly increased in patients with rheumatoid arthritis and correlated with disease activity, suggesting that pyroptosis may play a role in the pathogenesis of rheumatoid arthritis.

Key words: rheumatoid arthritis, pyroptosis, serum, joint fluid, inflammatory cytokine, disease activity