Immunomodulatory activity of polysaccharide from Arca granosa Linnaeus via TLR4/MyD88/NFκB and TLR4/TRIF signaling pathways

The immune effect and the underlying molecular mechanisms of AGP_p, a purified polysaccharide extracted from Arca granosa, have been studied in RAW264.7 in vitro. The results showed that AGP_p could increase the relative quantity of macrophages, enhance the phagocytosis, and improve the secretion of nitric oxide (NO) and cytokines. Moreover, the results of cell surface receptors screening found that AGP_p could bind to the toll-like receptor 4 (TLR4) receptor which on the surface of the RAW264.7 cell membrane. Finally, mechanism studies showed that, AGP_p promoted the expression of TLR4 pathway-related proteins, which included MyD88 dependent and TRIF-dependent. However, when TLR4 inhibitor was added, the protein expression and downstream factors in these two pathways were significantly changed. In a word, these results exhibited that AGP_p could be a promising functional food in immune-modulation, and this effect was mainly related to the mediating of TLR4/MyD88/NFκB and TLR4/TRIF signaling pathways.