Isoviolanthin suppresses IL-1β-induced inflammatory and catabolic responses in chondrocytes

Knee osteoarthritis (KOA) is characterized by the progressive degeneration of articular cartilage, necessitating novel therapeutic strategies to halt disease progression. Isoviolanthin, a natural flavonoid glycoside, has an unclear mechanism of action in KOA.

We employed network pharmacology and molecular docking, supported by in vitro assays, to investigate the mechanisms of isoviolanthin in KOA. Predicted targets of isoviolanthin were intersected with KOA-related genes from public databases, and the resulting gene set underwent Gene Ontology and KEGG enrichment analyses, followed by molecular docking. Primary rat chondrocytes were stimulated with interleukin-1β (IL-1β) to establish an in vitro model of inflammation. Using a CCK-8 viability assay, we determined a working concentration of 25 μM at 24 h that did not significantly affect cell viability. The effects of isoviolanthin on inflammatory mediators, extracellular matrix metabolism, and the activation of key proteins in the PI3K-AKT and MAPK pathways were then evaluated by Western blot, RT-qPCR, and immunofluorescence.

Network pharmacology identified 141 overlapping targets. KEGG enrichment analysis revealed the PI3K-AKT and MAPK signaling pathways as among the most significantly enriched. Molecular docking indicated that isoviolanthin exhibits favorable binding affinities to core targets, including AKT1, MAPK1, and EGFR. In IL-1β-stimulated rat chondrocytes, 25 μM isoviolanthin significantly reduced the expression of inflammatory mediators (CXCL3, CXCL6, IL-6, iNOS, TNF-α, IL-1β, COX2) and promoted the anabolism of extracellular matrix components (collagen II, ACAN, SOX9). The treatment also suppressed matrix-degrading enzymes (MMP3, MMP9, MMP13) and attenuated the IL-1β-induced phosphorylation of PI3K-AKT and MAPK family members. Furthermore, isoviolanthin reversed the IL-1β-induced alterations in RXFP1 expression at both the mRNA and protein levels.

These findings demonstrate that isoviolanthin exerts anti-inflammatory and ECM-protective effects in IL-1β-stimulated chondrocytes, likely by inhibiting PI3K-AKT and MAPK signaling and modulating RXFP1 expression. Further validation in human cells and in vivo osteoarthritis models is required to confirm target engagement and assess translational relevance.