A method for the solubilization of a (1----3)-beta-D-glucan isolated from Saccharomyces cerevisiae

Behavior of a fenhexamid photoproduct during the alcoholic fermentation of Saccharomyces cerevisiae

The fungicide fenhexamid [N-(2,3-dichloro-4-hydroxyphenyl)-1-methylcyclohexanecarboxamide] degraded rapidly by UV or sunlight irradiation, yielding 7-chloro-6-hydroxy-2-(1-methylcyclohexyl)-1,3-benzoxazole (CHB) as a main photoproduct. CHB was isolated, and its effect on alcoholic fermentation of Saccharomyces cerevisiae was studied. The results indicate that the presence of CHB does not affect the extent of alcohol production. After 12 days, the amount of CHB in the fermentation medium decreased by ca. 65%. Only 25% of the missing CHB was recovered unchanged from yeasts, most likely because it was adsorbed on the yeast wall cell. The remaining part degraded during the fermentation process. Glucan and chitin, two potential adsorbents, which constitute yeast cell walls, exhibited affinity for CHB.

The solubilization and biological activities ofAspergillusβ-(1→3)-d-glucan

We have recently demonstrated that the cell wall beta-glucan of Candida albicans could be solubilized by sodium hypochlorite, followed by dimethylsulfoxide-extraction (NaClO-DMSO method). In this study, applying this method to Aspergillus spp., we prepared mycelial cell wall beta-glucan and examined its physical properties and immunotoxicological activity. The acetone-dried mycelia of Aspergillus spp. were oxidized by the NaClO-DMSO method. An analysis of (13)C NMR spectra revealed the preparations to be composed of alpha-(1 --> 3) and beta-(1 --> 3)-D-glucan. Also, the proportion of alpha-(1 --> 3) and beta-(1 --> 3)-D-glucan varied. Furthermore, a solubilized Aspergillus beta-glucan (ASBG) was prepared from OX-Asp by urea-autoclave treatment. ASBG showed limulus activity similar to Candida solubilized beta-glucan (CSBG), and there was little difference in the activity of ASBG between various Aspergillus spp. ASBG affected the production of IL-8 by human peripheral blood mononuclear cells (PBMC). ASBG should be useful for analyzing the clinical role of beta-glucan.

Pharmacokinetics of fungal (1–3)-β-d-glucans following intravenous administration in rats

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.

Carbohydrates--the renewable raw materials of high biotechnological value

Carbohydrates are the potential biomolecules derived from nature. Their molecular diversity has led to a bewildering variety of species, structures and characteristics all performing a large array of functions of great significance. Biologically they are vital as message (immunological) carriers, physiologically they are useful as energy (nutritional) reserves, and technologically they are needed for altering the texture and consistency (functional) of foods. Recent advances in glycobiology have opened up a new understanding of the role of sugars in biology and medicine. Noncellulosic beta-(1-3)-linked D-glucans, a group of polysaccharides found as constituents of fungi, algae, and higher plants, exhibit many interesting properties, depending on their molecular conformation. They are excellent 'biological response modifiers' and show significant immunomodulatory activities. They elicit a variety of host defense biological responses, for example, potent antitumor activity. On the other hand, the mixed-linkage ((1-3/1-4)-beta-linked) glucans are important constituents of cereal cell walls, where they perform properties of physiological importance, such as water holding capacity, porosity, and plasticity, which are useful at different stages of growth/development of plants. Of late, carbohydrate-based therapeutics are becoming the promise against many chronic diseases of today and tomorrow. Some of the characteristic features, structural attributes, functional significance, and applications of a selected few carbohydrate species are the subject matter of this review.

Anterior pituitary cells express pattern recognition receptors for fungal glucans: implications for neuroendocrine immune involvement in response to fungal infections

OBJECTIVES

Hormones and cytokines are known to act as regulatory messengers between the neuroendocrine and immune systems. The innate immune system identifies infectious agents by means of pattern-recognition receptors. These receptors recognize pathogen-specific macromolecules called pathogen-associated molecular patterns. Fungal cell wall glucans nonspecifically stimulate various aspects of innate immunity via interaction with membrane receptors on immune-competent cells. Glucans are also released into the systemic circulation of patients with fungal infections. Recent evidence confirms the existence of glucan-specific receptors on cells outside the immune system. We hypothesized that glucans may directly interact with pituitary cells as an early signaling event in fungal infections.

METHODS

We characterized the receptor-mediated interaction of glucan derived from Candida albicans with pituitary cells using surface plasmon resonance. Prolactin levels were assayed by commercial ELISA. TLR2, TLR4 and CD14 mRNA levels were assessed by RT-PCR.

RESULTS

A single glucan-specific binding site was identified on rodent somatomammotroph (K(D) = 3.9 microM) and human folliculostellate cell (K(D) = 3.6 microM) membranes. Coincubation of glucan with somatomammotroph cells for 72 h significantly (p < 0.01) increased prolactin accumulation by 56-62% over that observed in cells treated with media alone. Glucan also increased TLR4 and CD14 gene expression in human folliculostellate cells.

CONCLUSIONS

Pituitary cells directly recognize and respond to fungal cell wall glucans resulting in stimulation of pituitary cell TLR4 and CD14 gene expression. In addition, glucan stimulates secretion of prolactin, a hormone that plays an important role in the response to infection.

Modulation of the Phosphoinositide 3-Kinase Pathway Alters Innate Resistance to Polymicrobial Sepsis

We examined the effect of modulating phosphoinositide 3-kinase (PI3K) activity in a murine model of cecal ligation and puncture-induced polymicrobial sepsis. Inhibition of PI3K activity with wortmannin increased serum cytokine levels and decreased survival time in septic mice. We have reported that an immunomodulator, glucan phosphate, induces protection in murine polymicrobial sepsis. We observed that glucan stimulated tissue PI3K activity, which positively correlated with increased survival in septic mice. We investigated the effect of PI3K inhibition on survival in septic mice treated with glucan. Treatment of mice with the PI3K inhibitors, wortmannin and LY294002, completely eliminated the protective effect of glucan, indicating that protection against septic mortality was mediated through PI3K. Inhibition of PI3K resulted in increased serum levels of IL1-beta, IL-2, IL-6, IL-10, IL-12, and TNF-alpha in septic mice. Apoptosis is thought to play a central role in the response to septic injury. We observed that inhibition of PI3K activity in septic mice resulted in increased splenocyte apoptosis and a change in the anatomic distribution of splenocyte apoptosis. We conclude that PI3K is a compensatory mechanism that suppresses proinflammatory and apoptotic processes in response to sepsis and/or inflammatory injury. Thus, PI3K may play a pivotal role in the maintenance of homeostasis and the integrity of the immune response during sepsis. We also observed that glucan phosphate decreased septic morbidity and mortality through a PI3K-dependent mechanism. This suggests that stimulation of the PI3K pathway may be an effective approach for preventing or treating sepsis and/or septic shock.

Interaction between fenhexamid and yeasts during the alcoholic fermentation of Saccharomyces cerevisiae

The behavior of the fungicide fenhexamid, N-(2,3-dichloro-4-hydroxyphenyl)-1-methyl-cyclohexanecarboxamide, has been studied at concentrations corresponding to the limits fixed for grapes (3 mg kg(-1)), or higher, during the alcoholic fermentation. The presence of the fungicide did not affect the amount of alcohol produced. The amount of fenhexamid in the liquid phase decreased by ca. 15%, but the missing fenhexamid was recovered unchanged from yeasts. This suggests that the fungicide is not degraded during the fermentation process, but adsorbed by yeasts. Two constituents of Saccharomyces cerevisiae cell wall, chitin and glucan, tested as potential adsorbents, exhibited affinity for fenhexamid.

Modulation of tissue Toll-like receptor 2 and 4 during the early phases of polymicrobial sepsis correlates with mortality

OBJECTIVE

To determine whether there was a correlation between induction of polymicrobial sepsis, modulation of tissue Toll-like receptor (TLR) gene, and protein expression and survival outcome.

DESIGN

Prospective, randomized animal study.

SETTING

University medical school research laboratory.

SUBJECTS

Age- and weight-matched ICR/HSD mice.

INTERVENTIONS

Sepsis was induced by cecal ligation and puncture (CLP). No-surgery and sham (laparotomy)-operated mice were controls. We also examined tissue TLR2 and TLR4 messenger RNA and TLR4 protein levels in mice treated with an immunomodulator that increases survival in polymicrobial sepsis. In the immunomodulator study, mice were treated with glucan phosphate (50 mg/kg, intraperitoneally) 1 hr before CLP. No-surgery, sham surgery, glucan + no-surgery, sham surgery + glucan, and CLP groups were employed as controls.

MEASUREMENTS AND MAIN RESULTS

Total RNA was isolated from liver, lung, and spleen at 0, 1, 3, 6, 8, and 24 hrs after CLP. TLR gene expression was assessed by reverse transcription-polymerase chain reaction. Tissue TLR4 protein levels were evaluated at 24 hrs by Western blot and immunohistochemistry. CLP sepsis increased (p <.05) liver and lung TLR2 and TLR4 gene expression compared with controls. TLR4 protein concentrations also were increased. Increased TLR2/4 gene and TLR4 protein expression correlated with mortality. Immunoprophylaxis with glucan phosphate increased (p <.001) long-term survival (20% vs. 70%) but inhibited (p <.05) CLP-induced increases in tissue TLR2 and TLR4 messenger RNA expression as well as TLR4 protein expression.

CONCLUSIONS

Early increases in TLR2/4 gene and TLR4 protein expression correlated with mortality, whereas blunting TLR gene and protein expression correlated with improved long-term survival. This suggests that early up-regulation of tissue TLR2/4 may play a role in the proinflammatory response and pathophysiology of polymicrobial sepsis.

Activation of AP-1 and SP1 correlates with wound growth factor gene expression in glucan-treated human fibroblasts

Glucan is a natural product immunomodulator that has been reported to enhance early wound repair. The mechanism of glucan-stimulated wound repair was thought to be indirect via macrophage release of wound growth factors. However, recent data indicate that there are glucan-specific receptors on human fibroblasts that can modulate cellular function following interaction with the glucan ligand. In this study we examined the effect of glucan on activation of the transcription factors activator protein-1 (AP-1) and specificity protein-1 (Sp1) in normal human dermal fibroblasts. AP-1 and Sp1 are involved in the regulation of cytokine and procollagen genes. In addition, we evaluated the effect of glucan on wound growth factor and vascular endothelial growth factor (VEGF) mRNA expression in primary cultures of normal human dermal fibroblasts. Glucan (1 microg/ml) stimulated fibroblast AP-1 and Sp1 activation in a time-dependent manner, although the temporal kinetics varied between the two transcription factors. AP-1 binding activity was increased (p<0.05) at early time intervals (1, 2, 4, 8 and 12 h), while Sp1 nuclear binding activity was increased (p<0.05) at later time intervals (12, 24, 36 and 48 h). Glucan (1 microg/ml) stimulated fibroblast expression of neurotrophin 3 (NT-3), platelet derived growth factor A (PDGF-A), platelet derived growth factor B (PDGF-B), fibroblast growth factor acidic (aFGF), fibroblast growth factor basic (bFGF), transforming growth factor alpha (TGFalpha), transforming growth factor beta (TGFbeta) and VEGF mRNA at 8 h.

Human Vascular Endothelial Cells Express Pattern Recognition Receptors for Fungal Glucans Which Stimulates Nuclear Factor κB Activation and Interleukin 8 Production

Fungal cell wall glucans nonspecifically stimulate various aspects of innate immunity via interaction with membrane receptors on macrophages, neutrophils, and natural killer cells. We investigated the binding of water-soluble glucans in primary cultures of normal human coronary or dermal vascular endothelial cells (VECs). Membranes from VECs exhibited saturable binding. Competition studies demonstrated the presence of at least two glucan binding sites on VECs. Glucan phosphate competed for all binding sites with a KD of 3.7 μm for coronary VECs and 11 μm for dermal VECs, respectively. Laminarin, a low molecular weight glucan, competed for 47 to 51 per cent of binding ( KD = 2.8–2.9 μm), indicating the presence of at least two binding sites. Glucan (1 μg/mL) stimulated VEC nuclear factor κB nuclear binding activity and Interleukin 8 expression—but not that of vascular endothelial growth factor—in a time-dependent manner. This is the first report of pattern recognition receptors for glucan on human VECs. It also provides the first evidence that glucans can directly modulate the functional activity of VECs by stimulating cytokine gene. These results provide new insights into the mechanisms by which the host recognizes and responds to fungal cell wall products and suggests that the response to glucans may not be confined to leukocytes.

Glucan stimulates human dermal fibroblast collagen biosynthesis through a nuclear factor-1 dependent mechanism

Glucan, an immunomodulator, has been reported to increase collagen deposition and tensile strength in experimental models of wound repair. Previous data suggest that glucan modulates wound healing via an indirect mechanism in which macrophages are stimulated to release growth factors and cytokines. However, recent data have shown the presence of glucan receptors on normal human dermal fibroblasts, suggesting that glucans may be able to directly stimulate fibroblast collagen biosynthesis. To test this hypothesis, we examined the effect of glucan on collagen biosynthesis in normal human dermal fibroblasts. We assessed nuclear factor-1 (NF-1) activation, procollagen mRNA expression, collagen biosynthesis, and whether there was a causal link between glucan treatment, NF-1 activation, and collagen expression. Glucan (1 microg/ml) increased NF-1 binding activity by 46% (8 hours), 64% (24 hours), 215% (36 hours), and 119% (48 hours) in cultured normal human dermal fibroblasts. Alpha 1(I) and alpha1 (III) procollagen mRNA were increased in glucan-treated normal human dermal fibroblasts when compared with the untreated fibroblasts. Collagen synthesis was increased at 24 hours and 48 hours following glucan treatment of normal human dermal fibroblasts. Down-regulation of NF-1 by pentifylline inhibited glucan-induced procollagen mRNA expression. These data indicate that glucan can directly stimulate human fibroblast collagen biosynthesis through an NF-1-dependent mechanism.

Modified endotoxin responses in rats pretreated with 1-->3-beta-glucan (zymosan A)

The present study investigates whether 1-->3-beta-glucans (zymosan particles) modify the pulmonary response of rats to endotoxin (lipopolysaccharide, LPS). Initial experiments were conducted to establish appropriate doses of LPS and regimens for exposure to zymosan and LPS. Interaction between zymosan and LPS exposures was determined to be the deviation from the sum of the individual effects of these agents. Treatment with zymosan on Day 1 and LPS on Day 2 modified several indices of pulmonary responsiveness, including tumor necrosis factor-alpha, albumin, and lactate dehydrogenase activity (LDH) in first acellular lavage fluid as well as the levels of chemiluminescence (CL), NO-dependent CL, and nitric oxide production in cultured lavaged alveolar macrophage cells determined 1 day after exposure. No significant deviation from additivity was found for breathing rate increase and polymorphonuclear leukocytes infiltration. Simultaneous administration of zymosan and LPS or administration of LPS before zymosan did not change these indices of pulmonary responsiveness. These data suggest that the inhibitory effect of 1-->3-beta-glucans on pulmonary responsiveness to endotoxin exposure was apparent only when rats were pretreated with 1-->3-beta-glucan. These results suggest that complex interaction of components may exist in exposure to organic dusts. Therefore, hazard may not be defined by measuring endotoxin or 1-->3-beta-glucans alone.

Characterization of the human beta -glucan receptor and its alternatively spliced isoforms

beta-1,3-d-Glucans are biological response modifiers with potent effects on the immune system. A number of receptors are thought to play a role in mediating these responses, including murine Dectin-1, which we recently identified as a beta-glucan receptor. In this study we describe the characterization of the human homologue of this receptor and show that it is structurally and functionally similar to the mouse receptor. The human beta-glucan receptor is a type II transmembrane receptor with a single extracellular carbohydrate recognition domain and an immunoreceptor tyrosine activation motif in its cytoplasmic tail. The human beta-glucan receptor is widely expressed and functions as a pattern recognition receptor, recognizing a variety of beta-1,3- and/or beta-1,6-linked glucans as well as intact yeast. In contrast to the murine receptor, the human receptor mRNA is alternatively spliced, resulting in two major (A and B) and six minor isoforms. The two major isoforms differ by the presence of a stalk region separating the carbohydrate recognition domain from the transmembrane region and are the only isoforms that are functional for beta-glucan binding. The human receptor also binds T-lymphocytes at a site distinct from the beta-glucan binding site, indicating that this receptor can recognize both endogenous and exogenous ligands.

Immune recognition. A new receptor for beta-glucans

The carbohydrate polymers known as beta-1,3-d-glucans exert potent effects on the immune system - stimulating antitumour and antimicrobial activity, for example - by binding to receptors on macrophages and other white blood cells and activating them. Although beta-glucans are known to bind to receptors, such as complement receptor 3 (ref. 1), there is evidence that another beta-glucan receptor is present on macrophages. Here we identify this unknown receptor as dectin-1 (ref. 2), a finding that provides new insights into the innate immune recognition of beta-glucans.

A proton nuclear magnetic resonance method for the quantitative analysis on a dry weight basis of (1-->3)-beta-D-glucans in a complex, solvent-wet matrix

Health benefits of the polysaccharide (1-->3)-beta-D-glucan, reported to induce immunobiological, hypocholesterolemic, and hypoglycemic effects in humans and animals, have made the isolation, characterization, and assay of a viable glucan product critical. A new analytical method, based on internal standard proton NMR analysis, for the assay of solvent-wet samples containing (1-->3)-beta-D-glucan is presented. The method enables glucan identification, provides a solvent-free assay, and improves upon the previous multistep extraction and lyophilization procedure by reducing the 1-2 day analysis time to 1-2 h. NMR offers a rapid method for quantifying the glucan in commercial samples, such as nutraceuticals, as well as industrial samples enabling better evaluation of the efficacy of these carbohydrates in health-related applications.

A (1-->3)-beta-D-linked heptasaccharide is the unit ligand for glucan pattern recognition receptors on human monocytes

Glucans are fungal cell wall polysaccharides which stimulate innate immune responses. We determined the minimum unit ligand that would bind to glucan receptors on human U937 cells using laminarin-derived pentaose, hexaose, and heptaose glucan polymers. When U937 membranes were pretreated with the oligosaccharides and passed over a glucan surface, only the heptasaccharide inhibited the interaction of glucan with membrane receptors at a K(d) of 31 microM (95% CI 20-48 microM) and 100% inhibition. However, the glucan heptasaccharide did not stimulate U937 monocyte NFkappaB signaling, nor did it increase survival in a murine model of polymicrobial sepsis. Laminarin, a larger and more complex glucan polymer (M(w) = 7700 g/mol), only partially inhibited binding (61 +/- 4%) at a K(d) of 2.6 microM (99% CI 1.7-4.2 microM) with characteristics of a single binding site. These results indicate that a heptasaccharide is the smallest unit ligand recognized by macrophage glucan receptors. The data also indicate the presence of at least two glucan-binding sites on U937 cells and that the binding sites on human monocyte/macrophages can discriminate between glucan polymers. The heptasaccharide and laminarin were receptor antagonists, but they were not receptor agonists with respect to activation of NFkappaB-dependent signaling pathways or protection against experimental sepsis.

Normal human fibroblasts express pattern recognition receptors for fungal (1-->3)-beta-D-glucans

Fungal cell wall glucans nonspecifically stimulate various aspects of innate immunity. Glucans are thought to mediate their effects via interaction with membrane receptors on macrophages, neutrophils, and NK cells. There have been no reports of glucan receptors on nonimmune cells. We investigated the binding of a water-soluble glucan in primary cultures of normal human dermal fibroblasts (NHDF). Membranes from NHDF exhibited saturable binding with an apparent dissociation constant (K(D)) of 8.9 +/- 1.9 microg of protein per ml and a maximum binding of 100 +/- 8 resonance units. Competition studies demonstrated the presence of at least two glucan binding sites on NHDF. Glucan phosphate competed for all binding sites, with a K(D) of 5.6 microM (95% confidence interval [CI], 3.0 to 11 microM), while laminarin competed for 69% +/- 6% of binding sites, with a K(D) of 3.7 microM (95% CI, 1.9 to 7.3 microM). Glucan (1 microg/ml) stimulated fibroblast NF-kappaB nuclear binding activity and interleukin 6 (IL-6) gene expression in a time-dependent manner. NF-kappaB was activated at 4, 8, and 12 h, while IL-6 mRNA levels were increased by 48% at 8 h. This is the first report of pattern recognition receptors for glucan on human fibroblasts and the first demonstration of glucan binding sites on cells other than leukocytes. It also provides the first evidence that glucans can directly modulate the functional activity of NHDF. These results provide new insights into the mechanisms by which the host recognizes and responds to fungal (1-->3)-beta-D-glucans and suggests that the response to glucans may not be confined to cells of the immune system.

Immunostimulant oxidized β-glucan conjugates

beta-Glucans are polysaccharides that act as nonspecific immune system stimulants. However, many beta-Glucans are sparingly soluble in water. This work describes an oxidative procedure, which solubilizes the beta-Glucan from Saccharomyces cerevisiae and maintains its immunostimulatory properties. Furthermore, the carboxylates at the site of oxidation allow for the conjugation of small molecule immunostimulants. Both the parent oxidized beta-glucan and its conjugates with O-beta-alanyl-5-[6-(N,N'-dimethylamino)purin-9-yl]pentanol stimulate cytotoxic T-lymphocytes (CTLs), B cells and macrophages. In addition, they both stimulate natural killer (NK) cells, a property which the small molecule purine does not possess.

Glucans exhibit weak antioxidant activity, but stimulate macrophage free radical activity

Polymeric carbohydrates have been reported to modulate inflammatory responses in vitro and in vivo. Previous reports suggest that certain carbohydrate polymers, such as (1-->3)-beta-D-glucans, may possess free radical scavenging activity. If glucans are free radical scavengers then it might explain, in part, the ability of these ligands to modulate inflammatory responses. The present study examined the free radical scavenging activity of a variety of carbohydrate polymers and the effect of the polymers on free radical levels in a murine macrophage cell line. All of the carbohydrates exhibited concentration dependent antioxidant effects (EC(50) range = 807 to 43 microg/ml). However, the antioxidant activity for the carbohydrates was modest in comparison with PDTC (EC(50) = 0.13 microg/ml) and the carbohydrate concentration required for antioxidant activity was high (x EC(50) = 283 microg/ml). The antioxidant ability of the polymers was greater (p < .05) than their monosaccharide constituents, i.e., dextrose EC(50) = 807 vs. glucan sulfate EC(50) = 43 microg/ml. Coincubation of glucans with murine J774a.1 cells increased free radical levels when compared to controls. Therefore, the weak free radical scavenging activity of glucan polymers cannot explain their modulatory effect on inflammatory responses in tissue culture and/or disease models of inflammation.

Structural characterization of beta-D-(1 --> 3, 1 --> 6)-linked glucans using NMR spectroscopy

Nondestructive structural analysis of a series of beta-D-(1 --> 3, 1 --> 6)-linked glucans (laminaran, curdlan, yeast glucan, scleroglucan, etc.) was performed using two-dimensional NMR spectroscopy. The relative ratios of H-1 at different AGUs provided the information about DPn and DB. The alpha-, and beta-anomeric protons on reducing terminals were assigned at 5.02 to approximately 5.03 ppm (J 3.6 to approximately 3.7 Hz), and 4.42 to approximately 4.43 ppm (J 7.6 to approximately 7.9 Hz), respectively, whereas the H-1 protons of internal AGUs and beta-(1 --> 6)-branched AGUs appeared at 4.56 to approximately 4.59 ppm (J 7.6 to approximately 7.8 Hz), and 4.26 to approximately 4.28 ppm (J 7.6 to approximately 10.6 Hz), respectively, in a mixed solvent of 6:1 Me2SO-d6-D2O at 80 degrees C. In the solvent, the OH peaks were eliminated from the spectra allowing the H-1 protons to appear clearly. In addition, the nonreducing terminal H-1 and H-1 at the AGU next to reducing terminal could be assigned at 4.45 to approximately 4.46 ppm (J 7.8 to approximately 7.9 Hz), and 4.51 to approximately 4.53 ppm (J 7.8 Hz), respectively. The DPn of the laminaran was 33 (polydispersity 1.12) and the DB was 0.07. The number of glucosyl units in the side chain of laminaran is more than one. The DPn and DB of the water-insoluble yeast glucan were 228 and 0.003, respectively. However the DPn of water soluble yeast glucan phosphate and curdlan was changed upon the number of freeze-drying processes and the content of water in the mixed solvent, respectively. And the DB of those were calculated as 0.02 and 0, respectively. The DB of scleroglucan was precisely calculated as 0.33, compared with the previously reported data. The H-1s at different AGUs of the various beta-D-(1 --> 3, 1 --> 6)-linked glucans having different DB can be exactly assigned by their chemical shifts in the mixed solvent system. This NMR analysis can be effectively used to determine the DP and DB of polysaccharides in a simple and non-destructive manner.

The influence of glucan polymer structure and solution conformation on binding to (1-->3)-beta-D-glucan receptors in a human monocyte-like cell line

Glucans are (1-3)-beta-D-linked polymers of glucose that are produced as fungal cell wall constituents and are also released into the extracellular milieu. Glucans modulate immune function via macrophage participation. The first step in macrophage activation by (1-3)-beta-D-glucans is thought to be the binding of the polymer to specific macrophage receptors. We examined the binding/uptake of a variety of water soluble (1-3)-beta-D-glucans and control polymers with different physicochemical properties to investigate the relationship between polymer structure and receptor binding in the CR3- human promonocytic cell line, U937. We observed that the U937 receptors were specific for (1-->3)-beta-D-glucan binding, since mannan, dextran, or barley glucan did not bind. Scleroglucan exhibited the highest binding affinity with an IC(50)of 23 nM, three orders of magnitude greater than the other (1-->3)-beta-D-glucan polymers examined. The rank order competitive binding affinities for the glucan polymers were scleroglucan>>>schizophyllan > laminarin > glucan phosphate > glucan sulfate. Scleroglucan also exhibited a triple helical solution structure (nu = 1.82, beta = 0.8). There were two different binding/uptake sites on U937 cells. Glucan phosphate and schizophyllan interacted nonselectively with the two sites. Scleroglucan and glucan sulfate interacted preferentially with one site, while laminarin interacted preferentially with the other site. These data indicate that U937 cells have at least two non-CR3 receptor(s) which specifically interact with (1-->3)-beta-D-glucans and that the triple helical solution conformation, molecular weight and charge of the glucan polymer may be important determinants in receptor ligand interaction.

Protective effect of the yeast glucomannan against cyclophosphamide-induced mutagenicity

Glucomannan (GM) isolated from Candida utilis with molecular weight 30 kDa was administered either intraperitoneally or orally prior to cyclophosphamide (CP) injection and its effect on the frequency of micronuclei was evaluated in polychromatic erythrocytes of mouse bone marrow. GM administration by either route decreased significantly (p<0.002) the clastogenic effect of CP. The protective effect was concentration-dependent, with a higher decrease achieved by 200 mg/kg than by 100 mg/kg b. wt. (body weight). The fact that GM was effective also at oral administration is indicative of the passage of GM molecules through the wall of the gastrointestinal tract. The important characteristics of GM isolated from C. utilis, such as good water solubility, relatively small molecular weight (30 kDa), and antimutagenic effect exerted also at oral administration, appear to be promising features for its prospective use as a natural protective agent.

Inhibiting early activation of tissue nuclear factor-kappa B and nuclear factor interleukin 6 with (1-->3)-beta-D-glucan increases long-term survival in polymicrobial sepsis

BACKGROUND

Recent data implicate the activation of nuclear factor-kappa B (NF-kappa B) and nuclear factor interleukin 6 (NF-IL6) as important steps in the pathophysiologic mechanisms of adult respiratory distress syndrome and systemic inflammatory response syndrome.

METHODS

This study evaluated the effect of immunomodulating polysaccharides on transcription factor activation, cytokine expression, and mortality in a murine cecal ligation and puncture (CLP) model. ICR/HSD mice were treated with glucan (50 mg/kg) 1 hour before or 15 minutes after CLP. Liver and lung tissue were harvested at 3 hours and mortality trends were observed for 20 days.

RESULTS

CLP increased liver and lung NF-kappa B and NF-IL6 nuclear binding activity as well as tumor necrosis factor-alpha and interleukin 6 messenger RNA levels at 3 hours. Pretreatment or posttreatment with glucans inhibited tissue NF-kappa B and NF-IL6 nuclear binding activity and tissue cytokine messenger RNA levels. Prophylaxis with glucan phosphate or scleroglucan increased (P < .001) long-term survival (20% CLP vs 65% glucan phosphate, 75% scleroglucan). Posttreatment with glucan phosphate also increased (P < .05) long-term survival (20% vs 65%).

CONCLUSIONS

Pretreatment or posttreatment with biologic response modifiers decreased tissue transcription factor nuclear binding activity and cytokine message in liver and lung of septic mice. Inhibiting early transcription factor activation and cytokine message expression correlates with improved outcome in polymicrobial sepsis as denoted by increased long-term survival.

Generation of Recombinant Fragments of CD11b Expressing the Functional β-Glucan-Binding Lectin Site of CR3 (CD11b/CD18)

CR3 (Mac-1; αMβ2 integrin) functions as both a receptor for the opsonic iC3b fragment of C3 triggering phagocytosis or cytotoxicity and an adhesion molecule mediating leukocyte diapedesis. Recent reports have suggested that a CR3 lectin site may be required for both cytotoxic responses and adhesion. Cytotoxic responses require dual recognition of iC3b via the I domain of CD11b and specific microbial surface polysaccharides (e.g., β-glucan) via a separate lectin site. Likewise, adhesion requires a lectin-dependent membrane complex between CR3 and CD87. To characterize the lectin site further, a recombinant baculovirus (rBv) system was developed that allowed high level expression of rCD11b on membranes and in the cytoplasm of Sf21 insect cells. Six rBv were generated that contained truncated cDNA encoding various CD11b domains. Immunoblotting of rBv-infected Sf21 cells showed that some native epitopes were expressed by five of six rCD11b fragments. Lectin activity of rCD11b proteins was evaluated by both flow cytometry with β-glucan-FITC and radioactive binding assays with [125I]β-glucan. Sf21 cells expressing rCD11b that included the C-terminal region, with or without the I-domain, exhibited lectin activity that was inhibited by unlabeled β-glucan or anti-CR3 mAbs. The smallest rCD11b fragment exhibiting lectin activity included the C-terminus and part of the divalent cation binding region. The β-glucan binding affinities of the three C-terminal region-containing rCD11bs expressed on Sf21 cell membranes were not significantly different from each other and were similar to that of neutrophil CR3. These data suggest that the lectin site may be located entirely within CD11b, although lectin site-dependent signaling through CD18 probably occurs with the heterodimer.

A novel carbohydrate-glycosphingolipid interaction between a beta-(1-3)-glucan immunomodulator, PGG-glucan, and lactosylceramide of human leukocytes

The immunomodulator Betafectin(R) PGG-glucan is a homopolymer of glucose derived from yeast cell walls which has been demonstrated to enhance leukocyte anti-infective activity in vitro and in vivo, without the induction of proinflammatory cytokines. We report here the purification of a PGG-glucan-binding element from human leukocytes and its identification as lactosylceramide, a major glycosphingolipid of neutrophils, which includes the CDw17 epitope. The binding of radiolabeled PGG-glucan to purified lactosylceramide was saturable, specific, and time- and temperature-dependent. Lactosylceramides from human leukocytes were fractionated by high performance liquid chromatography in order to analyze the effect of ceramide structure on binding. A variety of fatty acid chain lengths with varying degrees of unsaturation were found to support binding to radiolabeled PGG-glucan. However, DL-lactosylceramides containing dihydrosphingosine did not bind. Radiolabeled PGG-glucan bound several other neutral glycosphingolipids with a terminal galactose, including galactosylceramide, globotriaosylceramide, and gangliotetraosylceramide. The binding of radiolabeled PGG-glucan to lactosylceramide was not inhibited by glycogen, dextran, mannan, pustulan, laminarin, or a low molecular weight beta-(1-3)-glucan, but was inhibited by high molecular weight beta-(1-3)-glucans and by a monoclonal antibody to lactosylceramide. Although this glycosphingolipid has been shown in numerous reports to bind various microorganisms, this represents the first report of lactosylceramide binding to a macromolecular carbohydrate.

Ligand binding to the (1 --> 3)-beta-D-glucan receptor stimulates NFkappaB activation, but not apoptosis in U937 cells

Recent data suggest that sepsis stimulates macrophage apoptosis (Ao) with subsequent induction of macrophage dysfunction. Nuclear factor-kappaB (NFkappaB) activation has been linked to Ao in either a pro- or antiapoptotic role. Glucans are biological response modifiers which exert antisepsis activity. This investigation examined the effect of (1-3)-beta-D-glucan receptor binding by a high affinity ligand on Ao and NFkappaB activation in U937 cells in the presence or absence of LPS. A high affinity glucan ligand (IC50 = 23 nM) activated NFkappaB, but did not induce Ao or significantly alter LPS induced U937 Ao. These data indicate that: i) modulation of the macrophage (1-3)-beta-D-glucan receptor stimulates NFkappaB; ii) does not induce Ao or significantly diminish LPS induced Ao and iii) activation of the U937 FAS receptor does not alter the relative Ao responses in glucan and LPS treated cells.

The application of various protic acids in the extraction of (1-->3)-beta-D-glucan from Saccharomyces cerevisiae

Glucans are (1-->3)-beta-linked glucose polymers which have immune-stimulating capability. The extraction of water-insoluble (1-->3)-beta-D-glucan form Saccharomyces cerevisiae employs hydrochloric acid. Hydrochloric acid is difficult to employ in the large-scale pharmaceutical extraction of glucans due to its corrosive nature and toxicity. To address these concerns, we determined whether acetic, formic or phosphoric acid can be substituted for hydrochloric acid in the process for the isolation of (1-->3)-beta-D-glucan. The resulting microparticulate glucans were employed as the starting material for the production of (1-->3)-beta-D-glucan phosphate. 13C NMR analysis of the glucan phosphates derived from the acetic, formic or phosphoric acid-extracted microparticulate glucan show excellent correspondence to hydrochloric acid extracted glucan and laminarin, a (1-->3)-beta-D-glucan standard, indicating that the primary structure is not altered by the acid used for extraction. Glucan phosphate prepared from hydrochloric acid had a Mw of 7.2 x 10(4) g/mol, rmsz of 17.7 nm, of 1.50 and (eta) of 49.0 mL/g. Glucan phosphate prepared from acetic acid had a primary polymer peak with a Mw of 1.4 x 10(6) g/mol, rmsz of 23.6 nm, I of 1.93 and (eta) of 62.4 mL/g. Glucan phosphate prepared from formic acid had a main polymer peak with a Mw of 1.2 x 10(6) g/mol, rmsz 27.1 nm, I of 1.56 and (eta) of 89.0 mL/g. Glucan phosphate prepared from phosphoric acid had a primary polymer peak with a Mw of 6.6 x 10(5) g/mol, rmsz of 32.3 nm, I of 2.70 and (eta) of 91.3 mL/g. These data indicate that the molecular mass, size, polydispersity and intrinsic viscosity of the glucan phosphate obtained is influenced by the pKa of protic acid employed to extract the microparticulate glucan. However, the primary structure and side-chain branching are not substantially altered regardless of the acid employed.

Comparison of the carbohydrate biological response modifiers Krestin, schizophyllan and glucan phosphate by aqueous size exclusion chromatography with in-line argon-ion multi-angle laser light scattering photometry and differential viscometry detectors

A major barrier to the development, preclinical and clinical application of natural carbohydrate biological response modifiers has been the difficulty involved in accurately characterizing carbohydrate polymers with molecular masses ranging from 10(4) to 10(7) g/mol. Herein, we employed size exclusion chromatography with multi-angle laser light scattering and differential viscometry to compare and contrast structural properties of the biological response modifiers Krestin, schizophyllan and glucan phosphate. Krestin, schizophyllan and glucan phosphate exhibit significant differences in molecular mass moments, molecular mass distribution, polymer sizes, intrinsic viscosity and perhaps their solution behaviour. This knowledge of precise physicochemical data is required for a better understanding of the properties and higher structure of complex carbohydrate biological response modifiers.

Development of a water-soluble, sulfated (1-->3)-beta-D-glucan biological response modifier derived from Saccharomyces cerevisiae

This report describes a method for the solubilization of micro-particulate (1-->3)-beta-D-glucan. Insoluble glucan is dissolved in methyl sulfoxide and urea (8 M) and partially sulfated at 100 degrees. The resulting water-soluble product is called glucan sulfate. The conversion rate is 98%, and the preparation is endotoxin free as determined by the Limulus lysate procedure. Glucan sulfate is composed of 34.06% C, 6.15% H, 50.30% O, 5.69% S and 3.23% N, and has a repeating unit empirical formula of (C6H10O5)8.3 SO3NH4+.4 H2O, suggesting that, on the average, a sulfate group is substituted on every third glucose subunit along the polymer. Molecular weight averages, polydispersity, and intrinsic viscosity were determined by aqueous high-performance size-exclusion chromatography (HPSEC). Two polymer peaks were resolved. Peak 1 (Mw = 1.25 x 10(6) g/mol) represents < 1% of the total polymer mass. Peak 2 (Mw = 1.45 x 10(4) g/mol) comprises > 99% of polymers. 13C NMR spectroscopy confirmed the beta-(1-->3) interchain linkage. In solution, glucan sulfate polymers self-associate in a triple helix. Glucan sulfate stimulates murine bone marrow proliferation following intravenous administration. The ability to prepare a immunologically active, water-soluble (1-->3)-beta-D-glucan preparation will greatly enhance the clinical utility of this class of compounds.