AMD1 regulates cysteine metabolism and ferroptosis sensitivity in rheumatoid arthritis fibroblast-like synoviocytes.

BACKGROUND: Rheumatoid arthritis (RA) is characterized by synovial inflammation and hyperplasia, with fibroblast-like synoviocytes (FLS) playing a key pathogenic role. Cysteine metabolism is central to redox homeostasis and ferroptosis regulation, yet its mechanisms in RA-FLS remain poorly understood. This study investigates the role of AMD1, a polyamine metabolism enzyme, in regulating cysteine metabolism and ferroptosis sensitivity in RA-FLS. METHODS: Transcriptomic (GSE89408) and single-cell RNA-seq datasets (GSE200815, GSE246416) were analyzed using differential expression, WGCNA, and machine learning (LASSO, Random Forest, SVM). RA-FLS were subjected to AMD1 knockdown or overexpression, with functional assays for proliferation, migration, redox status, and ferroptosis markers. Rescue experiments used exogenous cysteine or Ferrostatin-1 (Fer-1). A collagen-induced arthritis (CIA) mouse model with local AAV-mediated AMD1 knockdown was used for in vivo validation. RESULTS: AMD1 was significantly upregulated in RA synovium and showed prominent expression in FLS. AMD1 knockdown reduced RA-FLS proliferation and migration, decreased polyamine and glutathione levels, increased ROS and lipid peroxidation, and promoted ferroptosis, as evidenced by reduced SLC7A11 and GPX4 expression, increased ACSL4 expression, and Fe2+ accumulation. Exogenous cysteine or Fer-1 partially reversed these effects. In CIA mice, local AMD1 knockdown alleviated joint swelling, cartilage destruction, and synovitis, while modulating ferroptosis-related protein expression. CONCLUSIONS: AMD1 regulates cysteine metabolism and ferroptosis susceptibility in RA-FLS, representing a promising therapeutic target for RA.