Elucidation of regulatory mechanisms in the activation of dendritic cells by combined stimuli with PRR ligands and sulfated polysaccharide fucoidan

Abstract

Abstract Fucoidan, a series of natural high-molecular weight sulfated polysaccharides derived from brown algae, has been reported to have various physiological effects such as antitumor, antiviral, and immunomodulatory activities. In a previous study, we demonstrated that fucoidan from Cladosiphon okamuranus (Okinawamozuku) was effectively activate murine macrophage-like cell line RAW264 in synergistic action with dectin-1-stimulating beta-glucan from Saccharomyces cerevisiae. In this study, we further examined their synergistic mode of action of Okinawamozuku-derived fucoidan in cooperate with pathogen stimulation in terms of dendritic cell activation. After myeloid dendritic cells (mDC) and plasmacytoid dendritic cells (pDC) were differentiated by culturing bone marrow cells isolated from C57BL/6J mice with Flt3 ligand, cytokine production upon stimulation with fucoidan and various pathogen components (pattern recognition receptor, PRR ligands) was measured. As the results, fucoidan alone enhanced the production of interferon (IFN)-gamma by the Flt3-L-induced mixed BMDCs, and besides, fucoidan synergistically augmented IFN-gamma production with Pam3CSK4 (bacterial TLR1/TLR2 ligand) or Poly(I:C)/LyoVec (viral RIG-I ligand). On the other hand, their IFN-alpha productions were reinforced with Poly(I:C) (viral TLR3 ligand), ODN1585 (viral TLR9 ligand) and Poly(I:C)/LyoVec, although no synergic enhancement by fucoidan was observed. These results suggested that fucoidan was extremely effective in activating dendritic cells, which play a central role in the regulation of immune function to eliminate infectious pathogens. Supported by grants from JSPS KAKENHI (JP21K05423)