Characterization of a novel polysaccharide from Arca subcrenata and its immunoregulatory activities in vitro and in vivo

Arca subcrenata is an economical edible shellfish. A novel water-soluble alpha-d-glucan (ASPG-1) with a molecular weight of 2.56 x 10(6) Da was purified and characterized from A. subcrenata. Its structure was characterized as a repeating unit consisting of alpha-d-Glcp, (1 -> 6)-alpha-d-Glcp and (1 -> 4,6)-alpha-d-Glcp. ASPG-1 exerted potent immunoregulatory activity by promoting the viability of splenic lymphocytes. Moreover, it enhanced pinocytic capacity, and promoted the secretion of NO and cytokines in RAW264.7 cells. The immunomodulatory mechanism of ASPG-1 involved the activation of the TLR4-MAPK/Akt-NF-kappa B signaling pathway. ASPG-1 inhibited tumor growth in 4T1 breast cancer mice and its combination with doxorubicin increased antitumor efficacy. The ASPG-1 combination with DOX-treated group (64.8%) showed an improved tumor inhibition rate compared to that of the DOX-treated group (53.3%). The antitumor mechanism of ASPG-1 may involve an enhancement of the immune response of mice to tumors. These results indicated that ASPG-1 could be developed as a potential adjuvant in tumor immunotherapy.

Automated summary

A novel water-soluble alpha-d-glucan (ASPG-1) with immunoregulatory activity was purified and characterized from Arca subcrenata. ASPG-1 promoted lymphocyte viability, enhanced pinocytic capacity, and stimulated the secretion of NO and cytokines. It inhibited tumor growth in breast cancer mice and showed improved antitumor efficacy when combined with doxorubicin. Therefore, ASPG-1 has the potential to be developed as an adjuvant in tumor immunotherapy.