Differences in anti-inflammatory properties of water soluble and insoluble bioactive polysaccharides in lipopolysaccharide-stimulated RAW264.7 macrophages

beta-Linked polysaccharides including beta-glucans are well known to be important functional ingredients, and are known to possess immunomodulatory and anti-tumor activities. This study aimed to investigate the anti-inflammatory properties and participating receptor of water soluble and insoluble bioactive polysaccharides from Grifola frondosa (GFP, non-digestible water soluble polysaccharides), Laminaria digitata (laminarin, a water soluble beta-glucan) and Saccharomyces cerevisiae (zymosan, a water insoluble beta-glucan) in lipopolysaccharide (LPS)-stimulated parental and Dectin-1 highly expressing RAW264.7 macrophages. Results showed that GFP and laminarin significantly inhibited nitric oxide and prostaglandin E2 production, but only the GFP with high molecular weight exhibited strong inhibition on pro-inflammatory cytokine (TNF-alpha and IL-6) secretion in a concentration-dependent manner. The activation of NF-kappa B was also significantly down-regulated by GFP treatment as compared with cells treated with LPS alone. Although GFP and laminarin were able to bind to beta-glucan receptor Dectin-1, there was no relationship between the inhibitory potency and the content of beta-glucans in GFP, and these inhibitory effects were not affected by the expression level of Dectin-1 in macrophage cells. In contrast, zymosan significantly intensified LPS-induced inflammatory responses through Dectin-1. In conclusion, these results suggest that the inhibitory effects of water soluble polysaccharides on LPS-induced pro-inflammatory mediator production in murine macrophages may not involve beta-glucan receptor Dectin-1.