To clarify the mechanism of Xinfeng Capsule (XFC) in treating rheumatoid arthritis (RA), this study explores whether it inhibits ferroptosis by regulating the Nrf2/SLC7A11/GPX4 pathway, thus suppressing the inflammatory response of RA.

A clinical study involving forty patients evaluated XFC's therapeutic efficacy in RA by comparing changes in clinical indicators and disease activity scores before and after treatment. Nrf2 levels in the peripheral blood of RA patients were measured to determine differential expression, and correlation with inflammatory indicators was analyzed. Cell transfection regulated Nrf2 and SLC7A11 expression, and cell viability, apoptosis, ferroptosis-related indicators (ROS, MDA, LDH), and inflammatory factor levels were detected. Lipid peroxidation levels were assessed, and rescue experiments used the ferroptosis inhibitor Ferrostatin1. Coimmunoprecipitation assays combined with bioinformatics analysis were used to investigate the interaction between Nrf2 and SLC7A11. Adjuvant arthritis (AA) rats were treated with XFC-containing serum. Joint pathology and synovial cell ultrastructure were examined via haematoxylin and eosin staining and transmission electron microscopy. Expression of Nrf2, SLC7A11, and GPX4, along with markers of ferroptosis, macrophage polarization, and inflammatory cytokines, were assessed.

Clinically, XFC treatment significantly reduced inflammatory indicators (RF, CRP, ESR) DAS28 scores, and VAS scores in RA patients. Nrf2 expression in the peripheral blood of RA patients was significantly higher than controls and positively correlated with RF, CRP, ESR, CCP, etc. Cell experiments showed that Nrf2 overexpression increased ROS, MDA, and LDH levels in RA-FLS, enhanced lipid peroxidation, and promoted pro-inflammatory factor (IL-8, IL-33, IL-37) secretion. Nrf2 knockdown had the opposite effect. Ferrostatin-1 reversed the ferroptogenic effect of Nrf2 overexpression. Co-immunoprecipitation confirmed that Nrf2 directly bound to SLC7A11, and bioinformatics analysis indicated a negative correlation. SLC7A11 overexpression reduced ROS, MDA, and LDH levels in RA-FLS, decreased lipid peroxidation, and inhibited pro-inflammatory factor secretion. In animal experiments, XFC alleviated synovial hyperplasia and inflammatory infiltration in AA rat joints, reduced Nrf2 expression, increased SLC7A11 and GPX4 levels, and downregulated ferroptosis indicators (MDA and ROS). Combination with Ferrostatin-1 had a more significant effect. XFC regulated macrophage polarization towards M2, reducing the M1/M2 ratio and pro-inflammatory factor levels.

Xinfeng Capsule effectively improves clinical symptoms and inflammatory responses in RA patients, potentially by inhibiting Nrf2 expression, relieving negative regulation of the SLC7A11/GPX4 pathway, suppressing ferroptosis in RA-FLS, modulating macrophage polarization, and alleviating inflammatory injury in RA.