Signaling pathways associated with macrophage-activating polysaccharides purified from fermented barley

Abstract

Barley is commonly used in many food and health products. We have previously demonstrated the macrophage stimulating properties of polysaccharides derived from fermented barley. In this study, three polysaccharide fractions (BF-I-III) were purified from fermented barley and their monosaccharide composition was analyzed. Their immune-stimulatory activities and intracellular signaling pathways were also studied in RAW264.7 cells. Among the three fractions, BF-I exhibited enhanced macrophage activation properties, such as inducing the production of IL-6, IL-12, and TNF-alpha. However, BF-II and BF-III showed moderate effects on RAW 264.7 cells. BF-I treatment led to the phosphorylation of MAPKs, NF-kappa B, and c-Jun (major component of AP-1 transcription factor) and induced the nuclear translocation of p65 in RAW264.7 cells. In addition, experiments with neutralizing antibodies showed that Dectin-1, toll-like receptor (TLR) 4, scavenge receptor (SR), and CD14 were mainly involved in the stimulation of nitric oxide (NO) production by BF-I which was suppressed by the inhibition of JNK phosphorylation. These findings suggest that BF-I, isolated from fermented barley, has an immune potentiation activity on macrophages, where it activates the JNK signaling pathway via several macrophage receptors including dectin-1, TLR4, SR, and CD14. (C) 2019 Elsevier B.V. All rights reserved.