Saccharum Alhagi polysaccharide-1 and -2 promote the immunocompetence of RAW264.7 macrophages in vitro

: The in vitro immune activities of Saccharum Alhagi polysaccharides (SAP) have been previously studied. The present study aimed to investigate the effects of SAP-1 and SAP-2 on the activity of RAW264.7 mouse macrophages. RAW264.7 cells were treated with 150, 300 and 600 mg/l concentrations of SAP-1 (a 50% alcohol precipitation) and SAP-2 (an 80% alcohol precipitation) or with 10 mg/l lipopolysaccharide. Untreated cells were used as a negative control. An MTT assay was used to detect the proliferation of the cells, and Hoechst 33528 staining was conducted in order to visualize the cell nuclei. Additionally, the Griess method was used to measure nitric oxide (NO) levels. A neutral red uptake assay was performed to determine the phagocytic activity of the macrophages, and ELISAs were performed to detect cytokine levels. Furthermore, reverse transcription-quantitative polymerase chain reaction was used to measure the mRNA expression of certain cytokines. The results demonstrated that SAP increased the proliferative activity and activated the immune function of RAW264.7 cells, and was lacking in cytotoxicity. In addition, SAP-1 exhibited a stronger effect in promoting RAW264.7 cell proliferation than did SAP-2. Furthermore, SAP-1 and SAP-2 significantly increased the level of NO, with the effect of SAP-1 being stronger than that of SAP-2. SAP-1 increased the phagocytic activity of RAW264.7 cells and promoted the secretion of the cytokines interleukin (IL)-1β, IL-2 and tumor necrosis factor (TNF)-α by RAW264.7 cells, with an effect that was stronger than that of SAP-2. Finally, different concentrations of SAP-1 or SAP-2 had distinct effects in upregulating the expression of TNF-α, IL-1β, nuclear factor-κB and inducible nitric oxide synthase mRNA. The results of the present study demonstrate that SAP is capable of enhancing the immune activity of mouse macrophages.