(1-->3)-beta-D-Glucans exhibit a variety of biological and immunopharmacological activities, and the significance of these activities is dependent on the structure of the glucans such as molecular weight, degree of branching, and conformation. Based on the generally accepted evidence that the conformation of clinically used Sonifilan (SPG) is a triple helix, we prepared alkaline treated SPG (SPG-OH) as a single helix conformer. In this report, we examined (A) the antitumor effect on a solid form tumor in vivo, (B) hematopoietic response on cyclophosphamide induced leukopenia, (C) antagonistic effect for zymosan mediated-hydrogen peroxide synthesis on peritoneal macrophage (PM), (D) priming effect of lipopolysaccharide (LPS) triggered tumor necrosis factor (TNF) synthesis, (E) nitric oxide synthesis of PM in vivo, and (F) hydrogen peroxide synthesis of PM in vivo. Both SPG and SPG-OH showed a significant effect on (A) and (B). The activity on (C) was stronger in SPG than SPG-OH. The activities of (D), (E), and (F) were stronger in SPG-OH. These facts strongly suggested that the glucan-mediated immunopharmacological activities were dependent on the helical conformation, and the conformation dependency varied dependent on the assays used.

No abstract

It has been reported that the biological activities of several beta-glucans vary due to differences in their physicochemical properties. In this study we investigated the ability of beta-glucans to trigger H2O2 production and activate signaling pathway on peritoneal macrophages. The most effective beta-glucan tested on H2O2 production was zymocel which was a particulate preparation from the yeast cell wall. In contrast, gel-forming beta-glucans which are known as immunoenhancers did not trigger the H2O2 production by macrophages at all. To identify the related signaling pathway for the particulate beta-glucans-triggered H2O2 production, several inhibitors were applied. Hydrogen peroxide production triggered with phorbol myristate acetate was inhibited by pretreatment of macrophages with H-7, a protein kinase C inhibitor. However, beta-glucans-triggered H2O2 production was not affected by H-7. The results suggested that genistein-sensitive tyrosine kinase and bromophenacyl bromide-sensitive phospholipase A2 participated in the particulate beta-glucans-triggered H2O2 production, although the phagocytosis of particulate beta-glucans was not inhibited by either reagents. In conclusion, gel-forming (1-->3)-beta-D-glucans-induced activation was not sufficient to trigger H2O2 on macrophages, and pathways for particulate beta-glucans-triggered H2O2 production were regulated differently from those for phagocytosis of beta-glucans.

Although it has been established that soluble glucan in fungi is important to host defence against infection, the importance of insoluble glucans is not clear. We have examined the in-vivo immunopharmacological activity of the insoluble glucan, zymocel. Administration of zymocel increased peritoneal exudate cell number and spleen weight, and enhanced: phagocytic activity, hydrogen peroxide production, and nitric oxide production of peritoneal exudate cells; the extravascular release of Evans blue (which might reflect vascular permeability); lipopolysaccharide-triggered synthesis of tumour necrosis factor (TNF); and recovery of white blood cell number in cyclophosphamide-induced leukopenia. Zymocel also showed anti-tumour activity against sarcoma 180 in mice and also enhanced TNF synthesis and hydrogen peroxide production by macrophage-like cell line in-vitro, i.e. resulted in direct macrophage activation. These results show that zymocel shows varied immunopharmacological activity; it is suggested that the administration of insoluble glucan induces the inflammatory response, the subsequent activation of the immune systems via the cytokine network, and direct macrophage activation.

Small molecular weight (MW) glucan derivatives could be a useful tool for studying the mechanisms of beta-glucan mediated biological activity, especially as antagonists for a beta-glucan receptor. This paper described the stability of various (1-->6) branched (1-->3)-beta-D-glucans to formolysis in the preparation of small MW derivatives. The glucans used were curdlan (linear), pachyman (few branches), GRN (one branch in every third main chain unit; 2/6), SPG (2/6), SSG (3/6), and OL-2 (4/6). Curdlan and pachyman were easily degraded to oligosaccharides by degradation for 20 min at 100 degrees C by 90% formic acid. However, branched glucans, especially the highly branched glucans, SSG and OL-2, were significantly resistant to degradation, and the majority remained high MW. SSG required a longer period and/or a higher temperature (121 degrees C treatment) to produce small MW derivatives. Branched glucans were also resistant to zymolyase (an endo-(1-->3)-beta-D-glucan hydrolase) digestion. These facts suggest that the (1-->6)-beta-D-branched residues contribute to the glucans' resistance to formic acid degradation and zymolyase digestion.