Effects of mushroom-derived b-glucan-rich polysaccharide extracts on nitric oxide production by bone marrow-derived macrophages and nuclear factor-kB transactivation in Caco-2 reporter cells: Can effects be explained by structure?

Mushrooms are known for their immune-modulating and anti-tumour properties. The polysaccharide fraction, mainly -glucans, is responsible for the immune-modulating effects. Fungal -glucans have been shown to activate leukocytes, which depend on structural characteristics of -glucans. As edible mushrooms come in contact with the intestinal immune system, effects on enterocytes are also interesting. Our aim was to evaluate the effect of mushroom polysaccharide extracts varying in -glucan structure on nitric oxide production by bone marrow-derived macrophages (BMMs) from mice and on nuclear factor-B transactivation in human intestinal Caco-2 cells. We demonstrated that extracts from Agaricus bisporus stimulated nitric oxide production by BMM, whereas extracts from Coprinus comatus and spores of Ganoderma lucidum had only minor effects. Furthermore, extracts of A. blazei Murill and Phellinus linteus had no effect at all. Almost all mushroom extracts lowered nuclear factor-B transactivation in Caco-2 cells. Structural analysis of A. bisporus compared with A. blazei Murill suggests that branching of the -glucan chain is essential for immune-stimulating activity. In conclusion, extracts from A. bisporus activate BMM, without activating enterocytes. These characteristics make A. bisporus an attractive candidate as a nutritional compound to stimulate the immune response in depressed states of immunity.