Abstract:

Objective  To study the inhibitory effect of  water-soluble polysaccharide  alkali-extracted from Pleurotus ostreatus and to clarify its mechanism.Methods The water-soluble polysaccharide WPOP-N1 from Pleurotus ostreatus were obtained by alkaline extraction,ethanol precipitation,and joint deproteinized and column chromatography methods.Forelimbs of BalB/C mice were subcutaneously injected with S-180 sarcoma cells to establish mouse tumor  models.60 BalB/C mice were randomly divided into normal control group,model control group,cyclophosphamide (positive control) group,WPOP-N1 low,medium,high doses groups（100,200 and
400 mg/kg）,and there were 10 mice in each group.Besidesnormal control group,the mice in the other groups were subcutaneously injected with S-180 sarcoma cells suspensions,and the mice in normal control group were given saline and the mice in model control group were given lipopolysaccharide.The levels of serum TNF-α secreted  were detected by ELISA method.The effects of  WPOP-N1 on macrophage phagocytic function and the levels of NO and TNF-α were estimated.Results The tumor weights of mice in WPOP-N1 low,medium and high doses groupswere (2.38±0.55),(1.79±0.64),and (1.37±0.51) g,respectively,which were lower than that in normal control group (3.71 g±0.81 g) (P<0.05);the anti-tumor rates of WPOP-N1 low,medium and high doses groups were 35.8%,51.8%,and 63.1%;the serum TNF-α levels of mice in WPOP-N1 medium and high doses groups were higher than that in  normal control group (P<0.05 or P<0.01);the phagocytic activities of peritoneal macrophages of mice in WPOP-N1 medium and high doses groups were higherthan that in  normal control group (P<0.05 or P<0.01);the NO and TNF-α levels secreted by  murine peritoneal macrophages in WPOP-N1 low,medium and high doses groups were increased (P<0.05) and had a dose-response.Conclusion WPOP-N1 has a significantly  inhibitory effect on tumor in vivo and its mechanism may be related to activating macrophages to secrete NO and TNF-α,and enhancing the phagocytic activities of macrophages.

Key words: Pleurotus ostreatus;polysaccharide;immunomodulation;macrophage