Oyster mushrooms are an interesting source of biologically active glucans and other polysaccharides. This work is devoted to the isolation and structural characterization of polysaccharides from basidiocarps of the cultivated oyster mushroom, Pleurotus ostreatus. Five polysaccharidic fractions were obtained by subsequent extraction with cold water, hot water and two subsequent extractions with 1 m sodium hydroxide. Branched partially methoxylated mannogalactan and slightly branched (1→6)-β-d-glucan predominated in cold- and hot-water-soluble fractions, respectively. Alternatively, these polysaccharides were obtained by only hot water extraction and subsequent two-stage chromatographic separation. The alkali-soluble parts originating from the first alkali extraction were then fractionated by dissolution in dimethyl sulfoxide (DMSO). The polysaccharide insoluble in DMSO was identified as linear (1→3)-α-d-glucan, while branched (1→3)(1→6)-β-d-glucans were found to be soluble in DMSO. The second alkaline extract contained the mentioned branched β-d-glucan together with some proteins. Finally, the alkali insoluble part was a cell wall complex of chitin and β-d-glucans.

For centuries human civilization has cultivated oats, and now they are consumed in various forms of food, from instant breakfasts to beverages. They are a nutrient-rich food containing linear mixed-linkage (1 → 3) (1 → 4)-β-d-glucans, which are relatively well soluble in water and responsible for various biological effects: the regulation of the blood cholesterol level, as well as being anti-inflammatory, prebiotic, antioxidant, and tumor-preventing. Numerous studies, especially in the last two decades, highlight the differences in the biological properties of the oat β-d-glucan fractions of low, medium, and high molecular weight. These fractions differ in their features due to variations in bioavailability related to the rheological properties of these polysaccharides, and their association with food matrices, purity, and mode of preparation or modification. There is strong evidence that, under different conditions, the molecular weight may determine the potency of oat-extracted β-d-glucans. In this review, we intend to give a concise overview of the properties and studies of the biological activities of oat β-d-glucan preparations depending on their molecular weight and how they represent a prospective ingredient of functional food with the potential to prevent or modulate various pathological conditions.

Dictyosphaerium chlorelloides is a green microalga from the Chlorella clade that produces highly viscous exocellular polysaccharides. The cell wall polysaccharides of this alga have not been studied in detail. In this article, water-soluble polysaccharides from D. chlorelloides biomass were extracted with hot water and purified by preparative chromatography. The composition, structural features and molecular masses of subsequently eluted fractions F1, F2, F3, F4 and F5 (minor) were determined. Three high-yield products F1, F3 and F4 consisted mainly of galactopyranosyl, 2-O-methyl-galactopyranosyl, rhamnopyranosyl and mannopyranosyl units at different proportions, while F2 was rich in glucose. Immunoactivity of these fractions was evidenced in a mixed population of immune cells derived from mice spleens after incubation with polysaccharides by flow cytometry, MTT and Immunospot assays. These fractions, except F2, demonstrated selective immunostimulant activity, and the F1 fraction induced the most potent effect, closely followed by the F3 and F4 fractions. The in vivo mechanism of their action is associated with the activation of innate immunity and shapes the immune response to the Th1 type.

Dendritic cells (DCs) play an important role in the immune response against cancer. Numerous studies indicate that tumor microenvironment affects the phenotype and function of DCs. The aim of the work was to determine how three-dimensional (3D) versus two-dimensional (2D) mixed-cells tumor models (mouse CT26 colon cancer cells mixed with mouse 3T3 fibroblasts) can impact on DCs maturation. Three-days old spheroids of 200μm diameter were used, formed by mixing CT26 and 3T3 cells cultivated in 3D Petri DishTM (microtissuesTM) molds. DCs were isolated from BALB/c mouse femurs and added to mixed-cell 3D spheroids and 2D mixed-cell monolayer, in coculture. DCs control group and Wnt-inhibited DCs (by XAV939) were also used. After 48 hours of coculture, half of the DCs were collected and analyzed by flow cytometry. Splenocytes were added to the remaining half of the DCs, cocultured for another 48 hours, and T-cell activation analysis was performed by flow cytometry. Here we show that mixed colorectal carcinoma spheroids have significantly higher immunoinhibitory properties than 2D mixed cell culture. Inhibition of Wnt signaling pathway doesn't affect the maturation of DCs but decreases the expression of checkpoint molecules (PD-1, Tim3) on CD4+ T-cells primed by XAV939-treated DCs. Acknowledgments: Institutional Grant RVO 61388971 (CZ), The National Institute for Cancer Research Project (EXCELES, ID Project No. LX22NPO5102) funded by the European Union - Next Generation EU, the Ministry of Health of the Czech Republic project NU23-08-00071; the Generali/Česká pojišťovna a.s. (CZ), and UniCredit Bank CZ&SK a.s., Praha (CZ) sponsorships.