An arabinogalactan from Bupleurum chinense DC. attenuates LPS-induced inflammation in RAW264.7 macrophages

Inflammation is a fundamental defense mechanism of the human body, but its dysregulation can lead to chronic disease. Therefore, identifying natural compounds with anti-inflammatory potential has become particularly important. Natural polysaccharides have received increased interest due to their immunomodulatory and anti-inflammatory effects. In this study, we characterized the structure of an arabinogalactan (BCP-WB) derived from Bupleurum chinense DC. (Apiaceae family) with a widely used medicinal plant. Its molecular weight was determined to be 34.4 kDa. Its backbone is predominantly made up of →6)-β-D-Galp-(1→, →3,6)-β-D-Galp-(1 → and →6)-α-D-Glcp-(1 → linkages, while the side chains are formed by α-L-Araf-(1→, →5)-α-L-Araf-(1 → and →3,5)-α-L-Araf-(1 → linkages. The anti-inflammatory activities of BCP-WB were evaluated in LPS-induced RAW264.7 cells and CuSO₄-induced zebrafish. BCP-WB significantly alleviates inflammatory reaction, including neutrophil dispersion, NO release, and inflammatory cytokine production. Mechanistically, RNA-seq analysis revealed that BCP-WB induces extensive transcriptional reprogramming in macrophages, including downregulation of NF-κB, TNF, and cell cycle pathways. Guided by these findings, BCP-WB was further demonstrated to bind directly to TLR4, as validated by molecular docking and SPR assays, which provided kinetic evidence of receptor engagement. This interaction ultimately suppresses the activation of NF-κB and MAPK signaling cascades, thereby attenuating inflammatory responses at multiple levels.