Characterization and macrophages immunomodulatory activity of two water-soluble polysaccharides from Abrus cantoniensis

The study aims to elucidate the physicochemical properties and immunomodulatory activity of two polysaccharides (ACP(t0) and ACP(t2)) from Abrus cantoniensis. Results revealed that ACP(t0) with a molecular weight of 26.0 kDa, was mainly composed of glucose (83.1%) and galactose (6.1%), and that ACP(t2) with a molecular weight of 145.6/8.9 kDa, consisted of galactose (25.6%), galacturonic acid (22.2%), arabinos (16.6%) and galactose (11.0%) respectively. AFM and Congo red experiments suggested that ACP(t0) and ACP(t2) might be spherical particles with triple-helix conformation in aqueous solution. ACP(t0) and ACP(t2) exhibited immunomodulatory activity by promoting the proliferation, augmenting pinocytic and phagocytic capacities, releasing immunoactive molecules such as ROS, NO, iNOS, TNF-α, IL-6 and IL-1β, upregulation of the mRNA levels of corresponding cytokines in macrophages. Moreover, ACP(t0) and ACP(t2) were recognized by toll-like receptor 4 (TLR4) and exerted immunomodulatory effects via activating Myeloid differentiation factor 88 (MyD88), mitogen-activated protein kinases (MAPKs) and serine/threonine kinase (Akt) signaling pathways in macrophages. Notably, ACP(t2) had higher immunomodulatory activity than ACP(t0). Based on the present findings, ACP(t0) and ACP(t2) could be explored as an active component of immunomodulators in the food and pharmaceutical fields.