Dietary polyphenol ellagic acid suppresses NF-κB signaling pathway in human synovial fibroblasts by disrupting the binding of TNF-α to its receptors: Insights from molecular interactions

Tumor necrosis factor-α (TNF-α) is a key proinflammatory cytokine that drives rheumatoid arthritis (RA) pathogenesis by sustaining synovial inflammation and joint destruction via binding to its receptors (TNFR1 and TNFR2), making this interaction a core therapeutic target. Ellagic acid (EA), a dietary polyphenol naturally abundant in pomegranates, berries, and nuts, is well known for its anti-inflammatory and antioxidant properties. In this study, we investigated whether EA targets the TNF-α pathway using a combination of molecular interaction analyses and cellular assays. Surface plasmon resonance (SPR) revealed that EA binds directly to TNF-α (K_D = 3.588 × 10^-6 M), TNFR1 (K_D = 6.488 × 10^-6 M), and TNFR2 (K_D = 7.952 × 10^-6 M) with high affinity. Molecular dynamics simulations and competitive SPR assays demonstrated that EA disrupts the TNF-α–TNFR interaction. Functionally, EA (0.625–2.5 μM) suppressed TNF-α-induced apoptosis in L929 cells and inhibited TNF-α-triggered NF-κB activation in 293-TNF-α Res (NF-κB) cells. In RA-relevant cell models using human synovial fibroblasts (HFLS and MH7A), EA attenuated TNF-α-stimulated NF-κB signaling by reducing phosphorylation of IKKα/β, IκBα, and p65, and by blocking p65 nuclear translocation. Notably, EA did not inhibit LPS-induced NF-κB activation, indicating pathway selectivity. These findings demonstrate that EA inhibits NF-κB activation by directly targeting the TNF-α–TNFR interaction, highlighting its potential as a food-derived functional ingredient for managing RA and related inflammatory conditions.