Enhancement effect of Sagittaria sagittifolia polysaccharide on immune function of macrophages through mTOR signal pathway

Objective To study the role of mammalian target of rapamycin (mTOR) signaling pathway in enhancement effect of Sagittaria sagittifolia polysaccharide on immune function of macrophage with Raw 264.7 cells.Methods RAW 264.7 cells were incubated with Dulbecco's modified Eagle's medium (DMEM) in vitro.The effects of different dose Sagittaria sagittifolia polysaccharide (5,50,and 500 μg/mL) and lentinan (100 μg/mL) on interleukin-2 (IL-2),tumor necrosis factor α (TNF-α),and nitric oxide (NO) secretions of Raw 264.7 cells were determined with enzyme-linked immunosorbent assay (ELISA) and Griess method.The expressions of mTOR/phosphatase and tensin homologdeleted on chromosome ten (PTEN) mRNA and protein were measured with real time PCR (RT-PCR) and Western blot.Results The IL-2 level was 68.216±1.609,70.850±6.669,89.634±8.399,84.367±8.165 pg/ml in low,moderate,and high dose Sagittaria sagittifolia polysaccharide group and lentinan group;the TNF-α level was 46.989±7.895,70.739±7.452,and 48.125±6.757 pg/ml in moderage and high dose Sagittaria sagittifolia polysaccharide group and lentinan group;the NO level was 7.199±1.242 μmol/L in high dose Sagittaria sagittifolia polysaccharide group;and all the levels were significantly higher compared to those of the model group (IL-2:50.661±5.006 pg/ml,TNF-α:23.788±4.093 pg/ml,NO:2.950±0.723 μmol/L)(all P<0.01).The expressions of mTOR mRNA in RAW 264.7 cells cultured with moderate and high dose Sagittaria sagittifolia polysaccharide were significantly lower than that of the negative control group (P=0.021,P=0.003).The expressions of mTOR protein in RAW 264.7 cells cultured with high dose Sagittaria sagittifolia polysaccharide and lentinan declined significantly compared to that of the negative control group (P=0.003,P=0.049).Conclusion Sagittaria sagittifolia polysaccharide could enhance the activity of phagocytosis of macrophages through mTOR signal pathway.