OBJECTIVE To explore the mechanism by which Xinfeng Capsule (XFC) improve the immune inflammation of rheumatoid arthritis (RA) of spleen deficiency and dampness excess type.

METHODS Sixty patients with active RA of spleen deficiency and dampness excess were selected and divided into a treatment group and a control group, with 30 patients in each group. The treatment group received oral XFC, while the control group received oral methotrexate. Both groups were treated continuously for 12 weeks, and there were no dropouts during the treatment period. Before and after treatment, the TCM syndrome scores and 28 joint disease activity scores (DAS-28) were observed in two groups of patients. The changes in the levels of erythrocyte sedimentation rate (ESR), rheumatoid factor (RF), high-sensitivity C-reactive protein (hs-CRP), and anti-cyclic citrullinated antibody (anti-CCP) were measured in the laboratory. The serum levels of pro-inflammatory factors interferon-γ (IFN-γ), interleukin-1β (IL-1β), interleukin-18 (IL-18), and tumor necrosis factor-α (TNF-α) were detected by ELISA. Molecular docking was used to verify the interaction between the key active ingredient of XFC and the core target polypyrimidine binding protein 1 (PTBP1) protein. The mRNA expression levels of PTBP1, NOD-like receptor heat protein domain-associated protein 3 (NLRP3), apoptosis-associated granule-like protein (ASC), caspase-1, and GSDMD were detected by real-time quantitative PCR (qPCR). Western blot analysis was performed to detect the protein levels of PTBP1, NLRP3, ASC, caspase-1, and GSDMD. Adverse reactions and routine safety indicators were observed in both groups during treatment to assess drug safety.

RESULTS After treatment, the TCM syndrome score and DAS28 score in the treatment group were significantly reduced (P<0.05), and the levels of ESR, hs-CRP, and serum IFN-γ, IL-1β, IL-18, and TNF-α were also significantly decreased (P<0.05). The mRNA expression of PTBP1, NLRP3 inflammasomes, and their downstream pyroptosis key molecules (ASC, caspase-1, and GSDMD) was significantly reduced in the treatment group (P<0.05), and the protein levels of PTBP1, NLRP3, ASC, caspase-1, and GSDMD were significantly reduced (P<0.05). Molecular docking results showed that XFC could directly act on PTBP1. There were no significant abnormalities in routine safety indicators such as blood routine and liver and kidney function in both groups before and after treatment. No treatment-related adverse events occurred in either group during the treatment period.

CONCLUSION XFC can effectively improve the inflammatory response in RA patients. Its therapeutic mechanism may be related to the regulation of PTBP1 levels, inhibition of NLRP3 activation and its mediated pyroptosis.