A polysaccharide purified from Radix Adenophorae promotes cell activation and pro-inflammatory cytokine production in murine RAW264.7 macrophages

Radix Adenophorae, a traditional Chinese medicine, has been reported to have a variety of biological functions. In the present study, a polysaccharide component, Radix Adenophorae Polysaccharide （RAPS）, was purified from Radix Adenophorae by decoloring with ADS-7 macroporous adsorption resin, DEAE-52 cellulose ion-exchange chromatography, and Sephacryl S-300HR gel chromatography, with the purity of 98.3% and a molecular weight of 1.8 × 104 Da. The cell viability assay and microscopic examination revealed that RAPS promoted the proliferation and activation of macrophages. At 400 μg·mL-1, RAPS stimulated RAW264.7 cell proliferation by 1.91-fold compared with the control. Meanwhile, RAPS significantly increased the secretion of pro-inflammatory cytokines （TNF-a and IL-6） in a dose-dependent manner in the supernatant of RAW264.7 cell culture as determined by ELISA. At 400 μg·mL-1, the production of TNF-a was 20.8-fold higher than that of the control. Simultaneously, the production of nitric oxide （NO） and the expression of inducible nitric oxide synthase （iNOS） were increased in RAW264.7 cells incubated with RAPS, as measured by Griess assay and Western blot analysis. The NO production of cells treated with RAPS （400 μg·mL-1） reached 15.8 μmol·L-L, which was 30.4-fold higher than that of the control （0.53 μmol·L-1）. These data suggested that RAPS may enhance the immune function and protect against exogenous pathogens by activating macrophages.