A polysaccharide from Strongylocentrotus nudus eggs protects against myelosuppression and immunosuppression in cyclophosphamide-treated mice.

To assess the chemoprotective properties of a polysaccharide from Strongylocentrotus nudus eggs (SEP), myelosuppressed and immunosuppressed mouse models were generated by administration of cyclophosphamide (Cy) and then treated with SEP. SEP (16 mg/kg/d) remarkably increased spleen and thymus indices, activated the proliferation of leukocytes and erythrocytes and platelets from peripheral blood, and exhibited co-mitogenic activity on ConA- or LPS-stimulated splenocytes in a dose-dependent manner. An increased percentage of CD34(+) cells in bone marrow of Cy-treated mice was also observed. Furthermore, SEP elevated CD4(+) T lymphocyte counts as well as the CD4/CD8 ratio dose-dependently, and it increased interleukin-2 (IL-2), IgA, IgM, and IgG levels in the sera of Cy-treated mice. Pre-incubation with TLR2 and TLR4 blocking antibodies inhibited splenocyte proliferation and its IL-2 secretion. Finally, SEP significantly induced Akt phosphorylation in splenocytes from Cy-treated mice, suggesting that chemoprotection by SEP was mediated through the PI3K/Akt signaling pathway. These findings indicate that SEP plays an important role in the protection against myelosuppression and immunosuppression in Cy-treated mice and could be a potential immunomodulatory agent.