AB prepress abstract   -  DOI: https://doi.org/10.3354/ab00770

ABSTRACT: Polysaccharides exhibit a multitude of biological activities, including antioxidant, antitumor, immunoregulation, hepatoprotective and anti-inflammatory effects, but it is not known whether such effects occur in fish as well. Head kidney macrophages from turbot Scophthalmus maximus L. were isolated and cultured to examine the responsiveness of natural polysaccharides as potential immune stimulators. Polysaccharides that were used in the research included Echinacea purpurea polysaccharides (EPP), Astragalus polysaccharide (APS), Lentinan (LNT), seaweed polysaccharides (SPS) and Laminarin (LAM). The test compounds were added to the cultures, and assessed for their effects on the growth and immunomodulatory functions of the cells. Based on the results of cell activity assay, reactive oxygen species assay, and NO assay of macrophages, Astragalus polysaccharides (APS) were selected as an immune stimulator. After APS was added to the culture medium, a comprehensive proteomic analysis was conducted to identify signaling pathways responsible for immune effects of macrophages. Up-regulation of specific immune pathway proteins in cells due to the addition of APS including macrophage migration inhibitory factor, myosin-α, metalloproteinase inhibitor, and collagenase type III. In particular, compared with macrophages not stimulated by APS, the expression level of TLR22 receptor in stimulated macrophages was significantly increased (p < 0.01). A KEGG pathway analysis indicated that relevant pathways were activated and included TNF, PI3K-Akt, and NF- kappa B signaling pathways. ELISA and qRT-PCR analysis also indicated APS reduced IL-1β and TNF-α levels in the cells following LPS stimulation. These data suggest that APS provided an immunoprotective effect on the head kidney macrophages of turbot at 800 ug/mL, and enhance the cell proliferation. Our results provide evidence for anti-inflammatory properties of APS. As such, APS could be a candidate immunopotentiating agent for fish.