New insight into the structure-dependent two-way immunomodulatory effects of water-soluble yeast β-glucan in macrophages

The immunomodulatory effects and signalling pathways of five water-soluble yeast β-glucan fractions (WYG1-5) with different molecular weights (Mw) and chain conformations were investigated in RAW264.7 macrophages. All five WYG fractions were shown to increase nitric oxide (NO) production, phagocytosis activity and cytokine secretion compared with the normal group. The incubation of cells with WYG for 2 h and then with lipopolysaccharide (LPS) for 24 h showed an inhibition of NO production, phagocytosis activity, cytokine secretion, and the expression of inducible nitric oxide synthase (iNOS) and cytokine mRNA compared with the LPS group. The results showed a two-way immunomodulatory effect of WYG on inflammatory factors, with the best effect for WYG-2 having a Mw of 2830 × 103 g/mol and spherical conformation. Furthermore, both mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-κB) signalling pathways were triggered in the two-way immunomodulation. This study reveals the structure-activity relationship and provides a pharmacological basis for controlling inflammatory disorders with WYG.