Anti-inflammatory activity and underlying mechanism against sepsis-induced acute lung injury of a low-molecular-weight polysaccharide from the root of Stemona tuberosa Lour

The root of Stemona tuberosa Lour has been used to treat tuberculosis, scabies, and eczema. Polysaccharides are among its main bioactive ingredients. A low-molecular-weight (1819 Da) polysaccharide (SPS2-A) was obtained from the root of S. tuberosa Lour by optimizing three-phase partitioning, purified using an ion chromatography column, and its effects and mechanisms were investigated. Structural analysis revealed that SPS2-A contained arabinose, galactose (Gal), glucose (Glc), xylose, and mannose. The SPS2-A backbone structure comprised sugar residues →4)-α-D-Glcp-(1→, →4)-α-D-Galp-(1→, and →4,6)-β-D-Galp-(1→, while the side chain primarily comprised α-D-Glcp-(1 → connected to the O-6 position of the residue →4,6)-β-D-Galp-(1→. In vitro, SPS2-A downregulated the expression of interleukin-6 in lipopolysaccharide-induced RAW264.7 macrophages. In vivo, SPS2-A significantly downregulated the expression of myeloperoxidase, interleukin-6, interleukin-1β, and tumor necrosis factor-α in bronchoalveolar lavage fluid and lung tissue. Western blotting analysis indicated that SPS2-A reduced lung inflammation in mice with sepsis-induced acute lung injury by activating the nuclear factor κB pathway. These results suggest that SPS2-A is a potential anti-inflammatory candidate for the treatment of sepsis-induced acute lung injury.