scleroglucan and laminaran

(1-->3)-beta-D-Glucans, a cell wall component in most microfungi, are suggested to play a role in the development of respiratory and general symptoms in organic dust-related diseases. The mechanisms by which they induce these effects are, however, not clear. In the present study, mediator release and its potentiation by the (1-->3)-beta-D-glucan as well as by the (1-->6)-beta-D-glucan found in yeast and other fungi were therefore examined. Blood leucocytes from healthy volunteers and from patients allergic to house dust mite were incubated with (1-->3)-beta-D-glucans with increasing 1,6-branchings: curdlan [a linear (1-->3)-beta-D-glucan], laminarin and scleroglucan, and furthermore with pustulan, a linear (1-->6)-beta-D-glucan. Histamine release was not observed on exposure to the glucans only, but in the presence of anti-immunoglobulin E (IgE) antibody or specific antigens, all the glucans investigated led to an enhancement of the IgE-mediated histamine release. The glucans induced a significant potentiation of the mediator release when present at concentrations in the range of 2-5 x 10(-5) M. These results suggest that (1-->3)-beta-D-glucan as well as (1-->6)-beta-D-glucan aggravates IgE-mediated histamine release. Knowledge concerning the effects of glucans on immune responses may be of importance for understanding and treating inflammatory and allergic diseases.

Topics: Adult; Air Pollution, Indoor; Allergens; beta-Glucans; Cell Wall; Dust; Environmental Exposure; Fungi; Glucans; Histamine; Humans; Immunoglobulin E; In Vitro Techniques; Leukocytes; Middle Aged; Polysaccharides; Respiratory Hypersensitivity

Glucans are microbial cell wall carbohydrates that are shed into the circulation of patients with infections. Glucans are immunomodulatory and have structures that are influenced by bacterial or fungal species and growth conditions. We developed a method to covalently label carbohydrates with a fluorophore on the reducing terminus, and used the method to study the pharmacokinetics following intravenous administration of three highly purified and characterized glucans (glucan phosphate, laminarin and scleroglucan) that varied according to molecular size, branching frequency and solution conformation. Elimination half-life was longer (3.8+/-0.8 vs. 2.6+/-0.2 and 3.1+/-0.6 h) and volume of distribution lower (350+/-88 ml/kg vs. 540+/-146 and 612+/-154 ml/kg) for glucan phosphate than for laminarin and scleroglucan. Clearance was lower for glucan phosphate (42+/-6 ml/kg h) than for laminarin (103+/-17 ml/kg h) and scleroglucan (117+/-19 ml/kg h). Since plasma levels at steady state are inversely related to clearance, these differences suggest that pharmacokinetics could favor higher blood levels of glucans with certain physicochemical properties.

Topics: Animals; Area Under Curve; beta-Glucans; Glucans; Half-Life; Injections, Intravenous; Limulus Test; Linear Models; Male; Polysaccharides; Rats; Rats, Sprague-Dawley

The appearance of beta-1,3-glucanases in supernatants of Sclerotium glucanicum cultures was followed by SDS-PAGE and shown to be dependent on cultivation time. Three beta-1,3-glucanases were isolated and purified. Glucanase I and III appeared homogeneous on SDS-PAGE with molecular masses of 85 and 33.5 kDa, respectively. Enzyme I was an endo-splitting beta-1,3-glucanase. In hydrolyzing laminarin it released glucose, laminaritriose and laminaribiose as major endproducts and smaller amounts of higher oligosaccharides. Enzyme III was an exo-beta-1,3-glucanase removing glucose from laminarin and gentiobiose and glucose from scleroglucan. For laminarin as substrate the Km of enzyme I and III was 2.5 and 3.33 mg/ml, respectively. Enzyme II was only partially purified and found to be also an exo-beta-1,3-glucanase, releasing glucose as the only hydrolysis product from laminarin. It did not attack scleroglucan. Its molecular weight was determined to be 78 kDa. Optimum pH and temperature of the three enzymes were determined. The three activities were significantly inhibited by 1 mM Hg2+.

Topics: beta-Glucosidase; Electrophoresis, Polyacrylamide Gel; Fungi; Glucan 1,3-beta-Glucosidase; Glucan Endo-1,3-beta-D-Glucosidase; Glucans; Kinetics; Molecular Weight; Polysaccharides; Substrate Specificity