Astragalus polysaccharide promotes the release of mature granulocytes through the L-selectin signaling pathway

BACKGROUND This study aims to investigate the leukogenic effect of astragalus polysaccharide (APS), to compare its effect of increasing the numbers of mature granulocytes with that of granulocyte colony-stimulating factor (G-CSF), and to investigate the mechanism. METHODS Rats were arbitrarily grouped into four groups (control, cyclophosphamide (CTX), CTX + APS, and CTX + G-CSF groups), and each group was then arbitrarily divided into five subgroups according to the time period since CTX infusion (0, 4, 7, 10, and 14 days). The expression of leukocyte selectin (L-selectin), its ligand, and shedding-related protease on granulocytes was analyzed. Leukocyte counts were obtained. Chemotactic capacity of polymorphonuclear leukocytes (PMNLs) was assessed. RESULTS Both APS and G-CSF restored the expression of L-selectin, P-selectin glycoprotein ligand-1 (PSGL-1), CD11b/CD18, and ADAM17 to normal levels (P > 0.05 vs. control group on each time point), with APS eliciting a greater effect than G-CSF (P = 0.005 on day 7, P < 0.001 on day 10 and 14 for L-selectin; P = 0.038 on day 7, P = 0.001 on day 10, P < 0.001 on day 14 for PSGL-1; P < 0.001 on day 7, 10 and 14 for ADAM17; P < 0.001 on day 7, 10, and 14 for CD11b/CD18). The percentages of the bands and segmented bone marrow (BM) cells in myeloid neutrophils were higher in the CTX + APS group than in the CTX group on day 7 (P = 0.030) and reached normal levels on day 10 (P = 0.547) and 14 (P = 0.431) vs. control group. The ability of APS to increase numbers of PMNLs in peripheral blood after chemotherapy was significantly superior to that of G-CSF 7 days after chemotherapy (P = 0.029 on day 10, P = 0.006 on day 14). Moreover, APS more significantly improved the chemotactic ability of PMNLs among mature BM granulocytes and peripheral blood neutrophils after chemotherapy than did G-CSF (P < 0.001 on day 7, P = 0.001 on day 10 and P = 0.005 on day 14). CONCLUSIONS APS promoted the differentiation and chemotactic ability of BM granulocytes via the L-selectin signaling pathway.