Investigating the Mechanism of Emodin in Rheumatoid Arthritis Through the HIF-1α/NLRP3 Pathway and Mitochondrial Autophagy

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In this study, we investigated the inhibitory effects of emodin on pyroptosis in rheumatoid arthritis (RA) synovial cells by modulating the HIF-1α/NLRP3 inflammasome pathway and mitochondrial autophagy. By employing a chemically induced hypoxia model with CoCl2, we established experimental groups including normal control, model group, and emodin-treated groups at different concentrations (5 μM, 10 μM, and 20 μM). We optimized the CoCl2 concentration via CCK-8 assay to ensure cell viability. ELISA, Western blotting, transmission electron microscopy, and immunofluorescence were employed to assess HIF-1α, IL-1β, and IL-18 levels, pyroptosis-related proteins, autophagy markers, and NLRP3 fluorescence intensity. Statistical analysis revealed that increased CoCl2 concentrations led to a significant cell viability reduction (p < 0.05), with 300 μM CoCl2 causing ~50% inhibition at 24 h. Transmission electron microscopy confirmed autophagosome formation in emodin-treated groups, while Western blotting showed dose-dependent downregulation of HIF-1α, NLRP3, BNIP3, and related proteins. Immunofluorescence revealed reduced NLRP3 fluorescence intensity with increasing emodin doses (p < 0.05), alongside dose-dependent cell viability recovery (p < 0.05). Our findings demonstrate that emodin alleviates RA synovitis through dual mechanisms: inhibition of mitochondrial autophagy to regulate the balance between mitochondrial autophagy and pyroptosis, and suppression of HIF-1α/NLRP3-mediated pyroptosis signaling, thereby reducing IL-1β and IL-18 release and inhibiting synovial cell proliferation. This study provides innovative approaches for targeted RA therapy.