Structural characterization, immunomodulatory effect and immune-mediated antitumor activity of a novel polysaccharide from the rhizome of Atractylodis macrocephala Koidz

A novel polysaccharide (WAMPa) was purified from Atractylodis macrocephala Koidz. WAMPa was characterized with molecular weight (MW) distribution, infrared spectrum, monosaccharide composition, methylation and nuclear magnetic resonance spectra. The backbone of WAMPa was → 2)-β-D-Glcp-(1 → interspersed with a small amount of → 5)-α-D-Araf-(1→, and the branches were the terminal α-D-Glcp-(1 → and β-D-Glcp-(1→. The immunomodulatory activities of WAMPa were investigated on two levels experiments including in vitro RAW264.7 cells and in vivo zebrafish. Meanwhile, the immune-mediated antitumor activity was evaluated by the inhibitory effect of the culture medium from WAMPa-treated RAW264.7 cells on human breast cancer cell line MCF-7. Bioactivity assays showed that WAMPa increased mRNA expression levels of TNF-α, IL-6 and iNOS, enhanced the levels of NO, and promoted the phosphorylation of ERK, p38 and JNK. Taken together, these findings revealed that WAMPa exhibited immunomodulatory effects by regulating MAPK signaling pathway. The antitumor experiments showed that WAMPa did not show a significant growth inhibition ratio on MCF-7 cells, but WAMPa-treated RAW264.7 macrophages could significantly inhibit the growth of MCF-7 cells. Thus, the antitumor activity of WAMPa was mediated mainly through the activation of macrophages. These results suggested that WAMPa could be considered as potential immunomodulatory and antitumor supplements.