Yam glycoprotein mediated the immunomodulation of macrophages by targeting TLR4

Background: Yam is a medicinal plant and previous studies have demonstrated that the yam glycoprotein (GLP1) possessed immunomodulatory bioactivity. However, how GLP1 exerted immunomodulatory effect and the molecular mechanism is unclear. To investigate the underlying mechanisms, the immunoregulation of GLP1 on macrophages are examined. Methods and Results: The composition of GLP1 was investigated using high-performance liquid chromatography (HPLC) and UV visible spectrophotometer (UV-Vis). The activity of macrophages was detected, and the effects of GLP1 on macrophages were studied using immunofluorescence, flow cytometry, Enzyme-linked immunosorbent assay (ELISA), and Western blotting. Results indicated that GLP1, as a biomolecule, contained abundant monosaccharides and possessed O-glycopeptide bonds. GLP1 bound to pattern recognition receptors (PRRs) and was internalized by macrophages via toll-like receptor 4 (TLR4), thereby exerting its immunomodulatory effects. Further experimental studies revealed that GLP1 promoted RAW264.7 cells proliferation by advancing cells from G0/G1 phase to S phase. Additionally, GLP1 stimulated the secretion of reactive oxygen species (ROS) from mitochondria and induced macrophage polarization toward the M1 phenotype. Conclusion: GLP1 is a functional protein and has the capacity to regulate macrophages immune responses via the TLR4/NF-κB pathway. The findings highlighted the potential of GLP1 might as a dietary immunostimulant at the molecular level.