Objective: To explore the effects of polysaccharide from Lepidium meyenii raizomel(PLR) on the immune organs in subacute aging mice induced by D-galactose

and investigate its action mechanism. Method: Fifty ICR mice were randomly divided into five groups:normal group

D-galactose model group

and PLR low-

middle-

and high-dose groups. 500 mg·kg-1 of D-galactose was given to the mice by ih administration to produce aging models. The mice in PLR groups were given with PLR solution (75

150

300 mg·kg-1) by ig administration. The drugs were given for 56 days

and then the activities of superoxide dismutase(SOD)

catalase(CAT)

glutathion peroxidase(GSH-Px)

monoamine oxidase(MAO) and the content of malondialdehyde(MDA) in mice serum or liver tissues were detected; the thymus ultrastructural changes were observed under TEM; the mRNA expression levels of SOD

CAT and p53 in the spleen were determined by qPCR. Result: As compared with the normal group

splenic sinusoid was extended in cells of model group

with large perinuclear space and chromatin margination; apoptosis was present in some cells; the SOD and CAT activities in serum of model group mice were significantly decreased; p53 mRNA expression in spleen tissues was significantly increased; SOD2 and CAT mRNA expressions were significantly decreased (P<0.05

P<0.01). As compared with the model group

distribution of lymphocytes in thymus was even in PLR middle dose and high dose groups; with clear perinuclear boundaries; no vacuoles in the cytoplasm; PLR could enhance the activities of SOD

CAT

GSH-Px

and reduce the content of MDA and activity of MAO. PLR high dose group significantly down-regulated the expression of p53 mRNA in spleen; middle dose and high dose groups significantly increased CAT mRNA expression; high dose group significantly increased SOD2 mRNA level (P<0.05

P<0.01). Conclusion: PLR has a protective effect on the immune organs of aging mice models

and the mechanism may be associated with increasing antioxidant enzyme activity and antioxidant enzyme mRNA expression

and decreasing aging-related enzyme activity.