Granulocyte-macrophage colony-stimulating factor (GM-CSF) regulates cytokine induction by 1,3-beta-D-glucan SCG in DBA/2 mice in vitro

Effects of Sparassis latifolia neutral polysaccharide on immune activity via TLR4-mediated MyD88-dependent and independent signaling pathways in RAW264.7 macrophages

Background

Sparassis latifolia (S. latifolia) is a precious edible fungus with multiple biological activities. To date, no study has been investigated the underlying molecular mechanism of immunoregulation caused by the neutral polysaccharide of S. latifolia.

Materials and methods

To investigate immunomodulatory mechanism of S. latifolia neutral polysaccharide (SLNP), SLNP was obtained from S. latifolia and its structure, immune receptors and regulation mechanism were studied.

Results

S. latifolia neutral polysaccharide consisted of arabinose, galactose, glucose, xylose, and mannose with a molar ratio of 6:12:63:10:5. SLNP was a pyran polysaccharide with a relative molecular weight of 3.2 × 105 Da. SLNP promoted the proliferation of RAW264.7, which further induced the secretions of nitric oxide, TNF-α, IL-6, and IFN-β, and upregulated the immune receptor TLR4 expression. Moreover, SLNP increased remarkably the levels of TRAF6, IRF3, JNK, ERK, p38, and p38 mRNA and protein mediated by TLR4.

Conclusion

S. latifolia neutral polysaccharide regulated the immune function of RAW264.7 through MyD88-dependent and -independent signaling pathways mediated by TLR4 receptor, which suggests that SLNP is a new immunomodulator.

Medicinal, nutritional, and nutraceutical potential of Sparassis crispa s. lat.: a review

Sparassis crispa is an edible mushroom exhibiting a wide range of medicinal properties. It is recognized for therapeutic value because of the high β-glucan content in the basidiomes. The broad range of its reported curative effects include anti-tumour, anti-cancer, immune-enhancing, hematopoietic, anti-angiogenic, anti-inflammatory, anti-diabetic, wound-healing, antioxidant, anti-coagulant, and anti-hypertensive properties. However, most of the studies are conducted on immunomodulatory and anticancer activities. Besides this, it also exhibits anti-microbial properties due to the presence of sparassol. Technology is now available for the cultivation of S. crispa on coniferous sawdust. This review is an attempt to focus on its distribution, taxonomy, chemical composition, medicinal properties, potential applications, and artificial cultivation.

[Fungal Beta-glucans: Structure and Effect on Host Immune Responses]

Fungi are eukaryotic microorganisms that show complex life cycles, including both anamorph and teleomorph stages. Beta-1,3-1,6-glucans (BGs) are major cell wall components in fungi. BGs are also found in a soluble form and are secreted by fungal cells. Studies of fungal BGs extensively expanded from 1960 to 1990 due to their applications in cancer immunotherapy. However, progress in this field slowed down due to the low efficacy of such therapies. In the early 21st century, the discovery of C-type lectin receptors significantly enhanced the molecular understanding of innate immunity. Moreover, pathogen-associated molecular patterns (PAMPs) and pattern recognition receptors (PRRs) were also discovered. Soon, dectin-1 was identified as the PRR of BGs, whereas BGs were established as PAMPs. Then, studies on fungal BGs focused on their participation in the development of deep-seated mycoses and on their role as a source of functional foods. Fungal BGs may have numerous and complex linkages, making it difficult to systematize them even at the primary structure level. Moreover, elucidating the structure of BGs is largely hindered by the multiplicity of genes involved in cell wall biosynthesis, including those for BGs, and by fungal diversity. The present review mainly focused on the characteristics of fungal BGs from the viewpoint of structure and immunological activities.

Genome sequence of the cauliflower mushroom Sparassis crispa (Hanabiratake) and its association with beneficial usage

Sparassis crispa (Hanabiratake) is a widely used medicinal mushroom in traditional Chinese medicine because it contains materials with pharmacological activity. Here, we report its 39.0-Mb genome, encoding 13,157 predicted genes, obtained using next-generation sequencing along with RNA-seq mapping data. A phylogenetic analysis by comparison with 25 other fungal genomes revealed that S. crispa diverged from Postia placenta, a brown-rot fungus, 94 million years ago. Several features specific to the genome were found, including the A-mating type locus with the predicted genes for HD1 and HD2 heterodomain transcription factors, the mitochondrial intermediate peptidase (MIP), and the B-mating type locus with seven potential pheromone receptor genes and three potential pheromone precursor genes. To evaluate the benefits of the extract and chemicals from S. crispa, we adopted two approaches: (1) characterization of carbohydrate-active enzyme (CAZyme) genes and β-glucan synthase genes and the clusters of genes for the synthesis of second metabolites, such as terpenes, indoles and polyketides, and (2) identification of estrogenic activity in its mycelial extract. Two potential β-glucan synthase genes, ScrFKS1 and ScrFKS2, corresponding to types I and II, respectively, characteristic of Agaricomycetes mushrooms, were newly identified by the search for regions homologous to the reported features of β-glucan synthase genes; both contained the characteristic transmembrane regions and the regions homologous to the catalytic domain of the yeast β-glucan synthase gene FKS1. Rapid estrogenic cell-signaling and DNA microarray-based transcriptome analyses revealed the presence of a new category of chemicals with estrogenic activity, silent estrogens, in the extract. The elucidation of the S. crispa genome and its genes will expand the potential of this organism for medicinal and pharmacological purposes.

Effects of Sparassis crispa in Medical Therapeutics: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

In this study, we investigated the therapeutic potential and medical applications of Sparassis crispa (S. crispa) by conducting a systematic review of the existing literature and performing a meta-analysis. The original efficacy treatment of the mushroom extract is considered primarily and searched in electronic databases. A total of 623 articles were assessed, 33 randomized controlled experiments were included after the manual screening, and some papers, review articles, or editorials that did not contain data were excluded. A comparative standard means difference (SMD) and a funnel plot between control and S. crispa groups were used as parameters to demonstrate the beneficial effects of S. crispa for diabetes and cancer treatment, as well as anti-inflammatory, anti-fungal and antioxidant activities. The meta-analysis was carried out using Review Manager 5.1 software. Although for therapeutic diabetes there was heterogeneity in the subgroup analysis (I² = 91.9%), the overall results showed statistically significant SMDs in major symptoms that decreased serum insulin levels (SMD = 1.92, 95% CI (1.10, 2.75), I² = 0%), wound rates (SMD = 3.55 (2.56, 4.54), I² = 40%) and contributions to an increase in nutrient intake content (SMD = 0.32 (−0.15, 0.78), I² = 0%). Simultaneously, the study confirmed the utility of S. crispa treatment in terms of not only anti-cancer activity (reduction of tumor activity and survival of cancer cells I² = 42 and 34%, respectively) but also anti-inflammatory, anti-fungal and antioxidant activities (I² = 50, 44, and 10%, respectively). Our findings suggest that S. crispa extracts are useful for prevention and treatment of human diseases and might be the best candidates for future medicines.

Effects of Natural and Chemically Defined Nutrients on Candida albicans Water-soluble Fraction (CAWS) Vasculitis in Mice

Kawasaki disease (KD) is an inflammatory disease that was identified by Professor Tomisaku Kawasaki in 1961. Candida albicans-derived substances, such as C. albicans water-soluble fraction (CAWS) , induce coronary arteritis similar to KD in mice. CAWS functions as a pathogen-associated molecular pattern (PAMP) by acting as a ligand for dectin-2. A gut-associated immunological system has developed specifically to segregate advantageous and detrimental stimuli, and the microbial flora has been found to markedly affect the development and severity of diseases. We herein investigated whether diet affects the onset and progression of CAWS vasculitis in mice. A standard diet, CE-2, and chemically defined diet, AIN93G, which is free of β-glucan, were used. Although all mice administered with CAWS died, the mean number of survival days was smaller in the AIN93G group because vasculitis was induced earlier than in the CE-2 group. Bacteroides, which are inflammatory flora, were enriched in the microbial flora of the AIN93G group. The results of the present study suggest that diet quality affects not only microbial flora changes, but also the progression of systemic disease.

Molecular Analysis of a Short-term Model of β-Glucans-Trained Immunity Highlights the Accessory Contribution of GM-CSF in Priming Mouse Macrophages Response

β-Glucans (BGs) are glucose polymers present in the fungal cell wall (CW) and, as such, are recognized by innate immune cells as microbial-associated pattern through Dectin-1 receptor. Recent studies have highlighted the ability of the pathogenic yeast Candida albicans or its CW-derived β(1,3) (1,6)-glucans to increase human monocytes cytokine secretion upon secondary stimulation, a phenomenon now referred as immune training. This ability of monocytes programming confers BGs an undeniable immunotherapeutic potential. Our objective was to determine whether BGs from Saccharomyces cerevisiae, a non-pathogenic yeast, are endowed with such a property. For this purpose, we have developed a short-term training model based on lipopolysaccharide re-stimulation of mouse bone marrow-derived macrophages primed with S. cerevisiae BGs. Through a transcriptome analysis, we demonstrated that BGs induced a specific gene expression signature involving the PI3K/AKT signaling pathway as in human monocytes. Moreover, we showed that over-expression of Csf2 (that encodes for GM-CSF) was a Dectin-1-dependent feature of BG-induced priming of macrophages. Further experiments confirmed that GM-CSF up-regulated Dectin-1 cell surface expression and amplified macrophages response along BG-mediated training. However, the blockade of GM-CSFR demonstrated that GM-CSF was not primarily required for BG-induced training of macrophages although it can substantially improve it. In addition, we found that mouse macrophages trained with BGs upregulated their expression of the four and a half LIM-only protein 2 (Fhl2) in a Dectin-1-dependent manner. Consistently, we observed that intracellular levels of FHL2 increased after stimulation of macrophages with BGs. In conclusion, our experiments provide new insights on GM-CSF contribution to the training of cells from the monocytic lineage and highlights FHL2 as a possible regulator of BG-associated signaling.

Toll-like receptor 4-related immunostimulatory polysaccharides: Primary structure, activity relationships, and possible interaction models

Toll-like receptor (TLR) 4 is an important polysaccharide receptor; however, the relationships between the structures and biological activities of TLR4 and polysaccharides remain unknown. Many recent findings have revealed the primary structure of TLR4/MD-2-related polysaccharides, and several three-dimensional structure models of polysaccharide-binding proteins have been reported; and these models provide insights into the mechanisms through which polysaccharides interact with TLR4. In this review, we first discuss the origins of polysaccharides related to TLR4, including polysaccharides from higher plants, fungi, bacteria, algae, and animals. We then briefly describe the glucosidic bond types of TLR4-related heteroglycans and homoglycans and describe the typical molecular weights of TLR4-related polysaccharides. The primary structures and activity relationships of polysaccharides with TLR4/MD-2 are also discussed. Finally, based on the existing interaction models of LPS with TLR4/MD-2 and linear polysaccharides with proteins, we provide insights into the possible interaction models of polysaccharide ligands with TLR4/MD-2. To our knowledge, this review is the first to summarize the primary structures and activity relationships of TLR4-related polysaccharides and the possible mechanisms of interaction for TLR4 and TLR4-related polysaccharides.

Mechanism of Enhanced Hematopoietic Response by Soluble β-Glucan SCG in Cyclophosphamide-Treated Mice

SCG is a major 6-branched 1,3-beta-D-glucan in Sparassis crispa Fr. SCG shows antitumor activity and also enhances the hematopoietic response in cyclophosphamide (CY)-treated mice. In the present study, the molecular mechanism of the enhancement of the hematopoietic response was investigated. The levels of interferon-(IFN-)gamma, tumor necrosis factor-(TNF-)alpha, granulocyte-macrophage-colony stimulating factor (GM-CSF), interleukin-(IL-) 6 and IL-12p70 were significantly increased by SCG in CY-treated mice. GM-CSF production in the splenocytes from the CY-treated mice was higher than that in normal mice regardless of SCG stimulation. Neutralizing GM-CSF significantly inhibited the induction of IFN-gamma, TNF-alpha and IL-12p70 by SCG. The level of cytokine induction by SCG was regulated by the amount of endogenous GM-CSF produced in response to CY treatment in a dose-dependent manner. The expression of beta-glucan receptors, such as CR3 and dectin-1, was up-regulated by CY treatment. Blocking dectin-1 significantly inhibited the induction of TNF-alpha and IL-12p70 production by SCG. Taken together, these results suggest that the key factors in the cytokine induction in CY-treated mice were the enhanced levels of both endogenous GM-CSF production and dectin-1 expression.

Generation and Evaluation of High β-Glucan Producing Mutant Strains of Sparassis crispa

A chemical mutagenesis technique was employed for development of mutant strains of Sparassis crispa targeting the shortened cultivation time and the high β-glucan content. The homogenized mycelial fragments of S. crispa IUM4010 strain were treated with 0.2 vol% methyl methanesulfonate, an alkylating agent, yielding 199 mutant strains. Subsequent screening in terms of growth and β-glucan content yielded two mutant strains, B4 and S7. Both mutants exhibited a significant increase in β-glucan productivity by producing 0.254 and 0.236 mg soluble β-glucan/mg dry cell weight for the B4 and S7 strains, respectively, whereas the wild type strain produced 0.102 mg soluble β-glucan/mg dry cell weight. The results demonstrate the usefulness of chemical mutagenesis for generation of mutant mushroom strains.

Natural products and biological activity of the pharmacologically active cauliflower mushroom Sparassis crispa

Sparassis crispa, also known as cauliflower mushroom, is an edible mushroom with medicinal properties. Its cultivation became popular in Japan about 10 years ago, a phenomenon that has been attributed not only to the quality of its taste, but also to its potential for therapeutic applications. Herein, I present a comprehensive summary of the pharmacological activities and mechanisms of action of its bioactive components, such as beta-glucan, and other physiologically active substances. In particular, the immunomodulatory mechanisms of the beta-glucan components are presented herein in detail.

Agaricus brasiliensis-derived β-glucans exert immunoenhancing effects via a dectin-1-dependent pathway

Agaricus brasiliensis is a well-known medicinal mushroom. We have previously demonstrated that Agaricus-derived polysaccharides exhibit potent antitumor effects; however, the underlying mechanism(s) have not been elucidated yet. In this study, we examined the immunoenhancing activities of Agaricus extracts. Agaricus-derived polysaccharides were characterized as 1,6-β-glucan with a small amount of 1,3-β-glucan using anti-β-glucan antibody and nuclear magnetic resonance analysis. These polysaccharides strongly induced the production of various cytokines from both murine splenocytes and bone marrow-derived dendritic cells in the presence of exogenous granulocyte-macrophage colony-stimulating factor. Polysaccharide-induced cytokine production was significantly reduced in bone marrow-derived dendritic cells derived from dectin-1-deficient mice. Furthermore, a binding assay revealed that the Agaricus-derived polysaccharides can be recognized by dectin-1, a pivotal receptor for 1,3-β-glucan. Taken together, our results clearly indicate that the immunostimulation induced by Agaricus-derived polysaccharides is exerted, at least in part, via dectin-1 in combination with granulocyte-macrophage colony-stimulating factor.

The effect of enzymatically polymerised polyphenols on CD4 binding and cytokine production in murine splenocytes

High-molecular weight polymerised polyphenols have been shown to exhibit anti-influenza virus, anti-HIV, and anti-cancer activities. The purpose of this study was to evaluate the immunomodulating activities of enzymatically polymerised polyphenols, and to clarify the underlying mechanisms of their effects. The cytokine-inducing activity of the enzymatically polymerised polyphenols derived from caffeic acid (CA), ferulic acid (FA), and p-coumaric acid (CoA) was investigated using murine splenocytes. Polymerised polyphenols, but not non-polymerised polyphenols, induced cytokine synthesis in murine splenocytes. Polymerised polyphenols induced several cytokines in murine splenocytes, with interferon-γ (IFN-γ) and granulocyte-macrophage colony-stimulating factor (GM-CSF) being the most prominent. The underlying mechanisms of the effects of the polymerised polyphenols were then studied using neutralising antibodies and fluorescent-activated cell sorting (FACS) analysis. Our results show that polymerised polyphenols increased IFN-γ and GM-CSF production in splenocytes. In addition, the anti-CD4 neutralised monoclonal antibody (mAb) inhibited polymerised polyphenol-induced IFN-γ and GM-CSF secretion. Moreover, polymerised polyphenols bound directly to a recombinant CD4 protein, and FACS analysis confirmed that interaction occurs between polymerised polyphenols and CD4 molecules expressed on the cell surface. In this study, we clearly demonstrated that enzymatic polymerisation confers immunoactivating potential to phenylpropanoic acids, and CD4 plays a key role in their cytokine-inducing activity.

Effect of Agaricus brasiliensis-derived cold water extract on Toll-like receptor 2-dependent cytokine production in vitro

Agaricus brasiliensis (Agaricus blazei Murrill) is well known as a medicinal mushroom. Fruit body of A. brasiliensis is rich in β-glucan and has shown benefits for various diseases. Both hot and cold water extraction are traditional methods for intake of this mushroom extract. In the present study, we prepared cold water extract of the fruit body of A. brasiliensis (ACWS). The 1,3-β-glucan segment of this fraction was too small and did not interact with the 1,3-β-glucan receptor, dectin-1. However, ACWS could induce production of various cytokines including IL-6 from murine splenocytes. Therefore, we aimed to identify the receptor that modulates IL-6 production using ACWS. We focused our attention on Toll-like receptors (TLRs) and examined them as follows. (i) The interaction between TLRs and ACWS was screened using HEK293 cells transfected with TLR plasmid. (ii) IL-6 production from splenocytes induced by ACWS was inhibited by treatment of anti-TLR antibodies. (iii) Direct binding activity between TLR protein and ACWS was assessed by ELISA-like assay. ACWS was found to activate HEK293 cells via TLR2, 4 and 5. However, only anti-TLR2 monoclonal antibody suppressed IL-6 production from splenocytes. In addition, ACWS has the ability to bind directly to TLR2 protein. Accordingly, we suggest that fruit body of A. brasiliensis has some water-soluble TLR ligand complexes, and TLR2 on splenocytes strongly induces IL-6 production.

[Gene expression in murine splenocytes induced by soluble beta-glucan]

SCG is a 6-branched 1,3-β-D-glucan, and is a major cell wall structural component in fungi. The leukocytes from DBA/1 and DBA/2 mice are highly sensitive to SCG, producing cytokines, such as GM-CSF, IFN-γ and TNF-α. GM-CSF plays a key biological role in this activity. We analyzed factors induced by SCG in splenocytes from DBA/2 mice by DNA microarray analysis on the condition of high sensitivity to β-glucan. Splenocytes were stimulated with SCG at 0, 24 or 30 h, and then supernatant was collected at 48 h to measure cytokines. SCG stimulated splenocytes to produce GM-CSF, IFN-γ and TNF-α in all the supernatants of 0, 24, and 30 h. The amount of IFN-γ production thus stimulated at 24 h was comparable to that at 0 h. Cytokine induction was observed at 4 h after SCG-stimulation even in the splenocytes pre-cultured for 36 h. The gene expression induced by SCG was analyzed with DNA microarray in the splenocytes in this condition. SCG up-regulated the expression of genes including Edn1 and Ptgs2 as well as genes associated with cytokine and chemokine. PGE(2) was detected in the medium of splenocytes stimulated with SCG. Taken together, these results indicated that splenocytes enhanced the sensitivity to SCG in earlier culture periods, and then responded to SCG to induce not only the cytokines but also various other factors.

Induction of dendritic cell maturation by β-glucan isolated from Sparassis crispa

Sparassis crispa is a medicinal mushroom containing high 6-branched 1,3-β-D-glucan (sparan) content, which exhibits immune-mediated antitumor activity. In the present study, we investigated the stimulating effect of sparan on phenotypic and functional maturation of dendritic cells (DCs). Phenotypic maturation was confirmed by the elevated expressions of CD40, CD80, CD86, and MHC-I/II molecules. Functional activation was proved by increased cytokine production of IL-12, IL-1β, TNF-α, and IFN-α/β, enhanced IL-2 production and proliferation of allogenic T cells, and decreased endocytosis. The role of toll-like receptor 4 (TLR4) as a membrane receptor of sparan was proved by the impaired maturation of DCs generated from bone marrow cells of tlr4⁻/⁻ knock-out mice and TLR4-mutated C3H/HeJ mice, and by using anti-MD-2/TLR4 neutralizing antibody. Sparan increased phosphorylation of ERK, p38, and JNK, and enhanced nuclear translocation of NF-κB p50/p65 in DCs. These results indicate that sparan activates DCs via MAPK and NF-κB signaling pathways, which are signaling molecules downstream of TLR4.

Granulocyte macrophage colony-stimulating factor is required for cytokine induction by a highly 6-branched 1,3-β-D-glucan from Aureobasidium pullulans in mouse-derived splenocytes

We have previously obtained and elucidated the precise structure of a highly branched 1,3-β-D-glucan (with 6-monoglucopyranosyl side chains), Aureobasidium pullulans-fermented β-D-glucan (AP-FBG), from the fungus A. pullulans. However, the mechanism(s) of the effects of AP-FBG on in vitro mouse primary cells have not been analyzed in detail. Herein, we report that the induction of cytokines by AP-FBG was dependent on the existence of a granulocyte macrophage colony-stimulating factor (GM-CSF); this is similar way to be a typical 1,3-β-D-glucan from Sparassis crispa (SCG), which is a 1,3-β-D-glucopyranosyl backbone with single 1,6-β-D-glucopyranosyl side branching units every three residues. In other words, the production of cytokines in DBA/2-mouse-derived splenocytes by AP-FBG was completely hampered by an anti-GM-CSF neutralizing monoclonal antibody. Furthermore, the addition of exogenous GM-CSF to C57BL/6-derived splenocytes, which are less sensitive to AP-FBG, induced the production of cytokines by AP-FBG. Therefore, GM-CSF is indispensable for the induction of cytokines by AP-FBG in mouse-derived splenocytes. This finding has provided a new insight into our understanding of the actions of β-D-glucan but will also aid in the design and development of more effective β-D-glucan agents.

A highly branched 1,3-beta-D-glucan extracted from Aureobasidium pullulans induces cytokine production in DBA/2 mouse-derived splenocytes

We recently elucidated the structure of a highly branched 1,3-beta-D-glucan with 6-monoglucopyranosyl side chains, extracted from Aureobasidium pullulans (AP-FBG). Although the biological effects of beta-D-glucans are known to depend on their structures, the effects of a highly branched 1,3-beta-D-glucan on the production of cytokines by leukocytes in mice have not yet been elucidated. In this study, we found that AP-FBG strongly induced the production of various cytokines, especially Th1 cytokines (e.g., IFN-gamma and IL-12p70) and Th17 cytokines (e.g., IL-17A), but did not induce the production of IL-4, IL-10, and TNF-alpha in DBA/2 mouse-derived splenocytes in vitro.

Anti-angiogenic and anti-metastatic effects of beta-1,3-D-glucan purified from Hanabiratake, Sparassis crispa

Sparassis crispa (SC), Hanabiratake in Japanese, is an edible mushroom with medicinal properties, that contains more than 40% beta-D-glucan. It was concluded from results of the methylation study that beta-D-glucan from SC (SBG) was composed of a backbone of beta-(1-->3)-linked D-glucopyranosyl residues, and had beta-D-glucopyranosyl groups joined through O-6 and O-2 of D-glucose of the backbone. We purified SBG and investigated its anti-angiogenic functions and anti-metastatic effects on neoplasm using different animal models. The oral administration of the purified SBG suppressed B16-F10 cell-induced angiogenesis in the dorsal air sac assay using female ICR mice as well as vascular endothelial growth factor induced neovascularization in the Matrigel plug assay using female C57BL/6J mice. Furthermore, it suppressed the growth and numbers of the metastatic tumor foci in lung, along with the primary tumor growth in the spontaneous metastatic model using female C57BL/6J mice. From these results, it is apparent that the oral administration of SBG results in suppressive effect on tumor growth and metastasis in lung through the inhibition of tumor induced-angiogenesis. These effects are not a result of direct action on the endothelial cells because cell growth, migration and capillary-like tube formation were not affected in the human umbilical vein endothelial cells by SBG application. This is the first report showing that the oral administration of SBG is capable of suppressing angiogenesis and metastasis.

Contribution of dectin-1 and granulocyte macrophage-colony stimulating factor (GM-CSF) to immunomodulating actions of beta-glucan

beta-Glucans are major cell wall structural components in fungi. As they are not found in animals, these carbohydrates are considered to be classic pathogen-associated molecular patterns (PAMPs), and are recognized by the innate immune system. Although their immunomodulating activities have been shown to be associated with the recognition of some fungi, and with their medicinal properties in the field of cancer immunotherapy, it is still unclear how beta-glucans mediate their effects. Recent studies have started to shed some light on their cellular receptors, such as dectin-1, and their molecular mechanisms of action. We have extensively investigated the response of leukocytes to beta-glucan, focusing on cytokine induction by SCG, which is a major 6-branched 1,3-beta-d-glucan in Sparassis crispa Fr. There is a strain difference in the reactivity of mice to SCG, and DBA/1 and DBA/2 mice are highly sensitive strains. In the process of research on cytokine induction by SCG in DBA/2 mice, we found that GM-CSF plays a key biological role in this activity. Cytokine induction by SCG was completely abolished in dendritic cells from dectin-1 knockout mice. On the other hand, controlling the level of endogenous GM-CSF production and/or dectin-1 expression could regulate the reactivity to beta-glucan. These results indicate that the key factors in the responsiveness to beta-glucan are GM-CSF production and dectin-1 expression. In this review, we describe how the key molecules related to the expression of the immunomodulating activities of beta-glucan were identified, and how the response to beta-glucan is controlled.

NMR characterization of the structure of a beta-(1-->3)-D-glucan isolate from cultured fruit bodies of Sparassis crispa

SCG, a purified beta-d-glucan, obtained from Sparassis crispa, exhibits various biological activities including an antitumor effect, enhancement of the hematopoietic response in cyclophosphamide-induced leukopenic mice, and induction of the production of cytokines. The mechanisms of these effects have been extensively investigated; however, an unambiguous structural characterization of SCG is yet to be achieved. It is well accepted that the biological effects of beta-glucan depend on its primary structures, conformation, and molecular weight. In the present study, we examine the difference of biological effects among beta-glucans, elucidate the primary structure of SCG, and compare with SPG from Schizophyllum commune using NMR spectroscopy. Our data reveal that SCG but not SPG induce cytokine production from bone marrow-derived dendritic cells (BMDCs) and their major structural units are a beta-(1-->3)-d-glucan backbone with single beta-(1-->6)-d-glucosyl side branching units every three residues.

A novel role of glia maturation factor: induction of granulocyte-macrophage colony-stimulating factor and pro-inflammatory cytokines

The glia maturation factor (GMF), which was discovered in our laboratory, is a highly conserved protein predominantly localized in astrocytes. GMF is an intracellular regulator of stress-related signal transduction. We now report that the overexpression of GMF in astrocytes leads to the destruction of primary oligodendrocytes by interactions between highly purified cultures of astrocytes, microglia, and oligodendrocytes. We infected astrocytes with a replication-defective adenovirus carrying the GMF cDNA. The overexpression of GMF caused the activation of p38 MAP kinase and transcription factor NF-kappaB, as well as the induction of granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA and protein in astrocytes. Small interfering RNA-mediated GMF knockdown completely blocked the GMF-dependent activation of p38 mitogen-activated protein kinase (MAPK), NF-kappaB, and enhanced expression of GM-CSF by astrocytes. Inhibition of p38 MAPK or NF-kappaB by specific inhibitors prevented GM-CSF production. The cell-free conditioned medium from overexpressing GMF astrocytes contained 320 +/- 33 pg/mL of GM-CSF, which was responsible for enhanced production and secretion of TNF-alpha, IL-1beta, IL-6, and IP-10 by microglia. Presence of these inflammatory cytokines in the conditioned medium from microglia efficiently destroyed oligodendrocytes in culture. These results suggest that GMF-induced production of GM-CSF in astrocytes is depending on p38 MAPK and NF-kappaB activation. The GM-CSF-dependent expression and secretion of inflammatory cytokine/chemokine, TNF-alpha, IL-1beta, IL-6, and IP-10, is cytotoxic to oligodendrocytes, the myelin-forming cells in the central nervous system, and as well as neurons. Our results suggest a novel pathway of GMF-initiated cytotoxicity of brain cells, and implicate its involvement in inflammatory diseases such as multiple sclerosis.

Blocking Effect of Anti-Dectin-1 Antibodies on the Anti-tumor Activity of 1,3-.BETA.-Glucan and the Binding of Dectin-1 to 1,3-.BETA.-Glucan

Schizophyllan (SPG) is used to treat cervical cancer in combination with irradiation to enhance the immunological surveillance system. Dectin-1 is a cell surface receptor for 1,3-beta-glucan. In this study, we prepared two anti-Dectin-1 monoclonal antibodies, 4B2 and SC30 having a K(D) of 7.04 x 10(-8) M and 1.55 x 10(-7) M, respectively, and evaluated the role of Dectin-1 in SPG-induced anti-tumor activity in mice. Expression of Dectin-1 on peritoneal macrophages and binding of SPG to the cells were decreased by administration of 4B2 and SC30. SPG-mediated anti-tumor activity was inhibited by 4B2 and SC30. 4B2 and SC30 inhibited the binding of SPG to splenocytes from mice. The binding of SPG-biotin to Dectin-1-transfected HEK293 cells was inhibited by 4B2, but not SC30. 4B2 and SC30 differ in their influence on Dectin-1 between primary cells and transduced cells, and Dectin-1 effects 1,3-beta-glucan-mediated anti-tumor activity in mice by binding to SPG.

F1 hybrid mice (BALB/c x DBA/1) are resistant to collagen-induced arthritis with beta-glucan as an adjuvant

Collagen-induced arthritis (CIA) is an experimental model of rheumatoid arthritis (RA) used for studying the clinical, immunological and genetic factors of the disease. Many studies of genetic susceptibility to CIA have been performed, usually with two strains of mice, DBA/1 and B10.RIII, since they are highly susceptible to CIA. Furthermore, F1 hybrid mice of susceptible and resistant strains reportedly develop arthritis. Recently, we reported that particles of beta-glucan, OX-CA, prepared from Candida albicans by NaClO-oxidation, acted as an adjuvant for CIA. Although, there have been many studies about the relationship between antigen and the major histocompatibility complex (MHC) in F1 hybrid mice, little is known argument about susceptibility to adjuvants. Therefore, we checked the susceptibility of F1 hybrids to CIA using OX-CA as an adjuvant. BALB/c and DBA/1 were mated to generate F1 hybrids which were then immunized with type II collagen (CII) plus Freund's complete adjuvant (FCA) or OX-CA. The results showed that F1 hybrids injected with CII plus FCA developed severe arthritis at an incidence ratio 80%, versus only 20% in mice injected with CII plus OX-CA. Furthermore, levels of anti-CII antibody, especially of the IgG2a subclass, in sera from mice treated with CII plus OX-CA were significantly low. Susceptibility to CIA might depend on not only MHC but also the adjuvant used for immunoactivation.

Lethal and severe coronary arteritis in DBA/2 mice induced by fungal pathogen, CAWS, Candida albicans water-soluble fraction

CAWS is a microbial pathogen-associated molecular patterns (PAMPs) produced by Candida albicans. CAWS is a mannoprotein-beta-glucan complex and secreted into the culture supernatant. CAWS has various biological effects, causing acute shock and disrupting vascular permeability. Intraperitoneal administration of CAWS induces coronary arteritis in various strains of inbred mice. The CAWS-induced coronary arteritis is strain-dependent and most severe in DBA/2 mice with a significant number of these animals expiring with cardiomegaly during the observation period. In vivo and in vitro, splenocytes of DBA/2 mice produced various cytokines, such as IL-6, TNF-alpha, and IFN-gamma in response to CAWS. GM-CSF was also produced in response to CAWS. The production of cytokines was significantly enhanced in the presence of recombinant GM-CSF. In contrast, anti-GM-CSF significantly reduced the production of TNF-alpha and IFN-gamma. Augmented production of cytokines in response to CAWS would be a key to the severity of coronary arteritis.

Cell to Cell Contact Through ICAM-1-LFA-1 and TNF-α Synergistically Contributes to GM-CSF and Subsequent Cytokine Synthesis in DBA/2 Mice Induced by 1,3-β-D-Glucan SCG

SCG is a major 6-branched 1,3-beta-D-glucan in Sparassis crispa Fr. showing antitumor activity. We recently found that the splenocytes from naive DBA/1 and DBA/2 mice are potently induced by SCG to produce interferon- gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), granulocyte-macrophage colony-stimulating factor (GM-CSF), and interleukin-12p70 (IL-12p70), and that GM-CSF plays a key biologic role among these cytokines. In this study, we investigated the contribution of cell-cell contact and soluble factors to cytokine induction by SCG in DBA/2 mice. Cell-cell contact involving intercellular adhesion molecule-1 (ICAM-1) and lymphocyte function-associated antigen-1 (LFA-1) was an essential step for the induction of GM-CSF and IFN-gamma by SCG but not for the induction of TNF-alpha or IL-12p70 by SCG. SCG directly induced adherent splenocytes to produce TNF-alpha and IL-12p70. GM-CSF was required for the induction of TNF-alpha by SCG, and in turn, TNF-alpha enhanced the release of GM-CSF and thereby augmented the induction of IL-12p70 and IFN-gamma by SCG. Neutralization of IL-12 significantly inhibited the induction of IFN-gamma by SCG. We concluded that induction of GM-CSF production by SCG was mediated through ICAM-1 and LFA-1 interaction, GM-CSF subsequently contributed to further cytokine induction by SCG, and reciprocal actions of the cytokines were essential for enhancement of the overall response to SCG in DBA/2 mice.

Soy isoflavone aglycone modulates a hematopoietic response in combination with soluble beta-glucan: SCG

Soy isoflavone aglycones (IFAs) have a wide range of biological actions that suggest they may be of use in cancer prevention. On the other hand, a branched beta-glucan from Sparassis crispa (SCG) is a major 6-branched 1,3-beta-D-glucan in an edible/medicinal mushroom: Sparassis crispa showing antitumor activity. We have previously reported that both oral and intraperitoneal administration of SCG enhanced the hematopoietic response in cyclophosphamide (CY)-induced leukopenic mice. In this study, we investigated the hematopoietic response due to IFA in combination with SCG in CY-induced leukopenic mice. The oral administration of IFA in combination with SCG synergistically enhanced the number of white blood cells, and increased spleen weight. Analyzing the leukocyte population by flow cytometry, the combination of IFA and SCG increased the number of monocytes and granulocytes in the spleen. Taken together, the combination of IFA and SCG synergistically provides the hematopoietic responses that are enhanced over IFA or SCG alone.

Effect of Candida albicans cell wall glucan as adjuvant for induction of autoimmune arthritis in mice

Collagen-induced arthritis (CIA) is an experimental model of rheumatoid arthritis (RA) and has aided research into the pathogenesis of inflammatory joint disease. Typically, Type II collagen (CII) emulsified with Freund's complete adjuvant (FCA) is injected into DBA/1 mice. After a booster injection, the mice develop inflammation of the paws. But the fact that the immunization of CII alone does not induce arthritis suggests that activation of the immune system by an adjuvant is necessary for induction of the arthritis. In the present study, we investigated the ability of beta-glucans derived from Candida albicans to act as an adjuvant to induce autoimmune arthritis. DBA/1 mice were injected with CII emulsified with FCA or particulate beta-glucan, OX-CA, on day 0 and given a booster at day 21. Mice immunized with CII plus OX-CA developed arthritis at around 7-10 days after the booster injection. Similarly, mice administered CII emulsified with FCA developed arthritis with the same time course. The mice immunized with CII and OX-CA had a more severe arthritis than those immunized with CII and FCA. Histological changes and production of anti-CII antibody were observed regardless of the type of injection. In addition, components of C. albicans were also tested for their ability to induce arthritis as an adjuvant. The results showed that CSBG, which is a soluble beta-glucan, acted as an adjuvant for CIA but CAWS, which is a mannoprotein-beta-glucan complex, did not. In conclusion, beta-glucan derived from C. albicans acted as an adjuvant and the injection with CII resulted in arthritis with the production of anti-CII autoantibody. The results strongly suggested that fungal metabolites such as beta-glucans have the capacity to induce and exacerbate autoimmune diseases such as RA.

Effect of Nitric Oxide on .BETA.-Glucan/Indomethacin-Induced Septic Shock

We have previously shown that repeated administration of nonsteroidal anti-inflammatory drugs (NSAIDs) to mice treated with beta-glucan, a biological response modifier, induced severe lethality. The lethality would be strongly related to the translocation of enterobacterial flora to the peritoneal cavity and disruption of the cytokine network. Reports suggest that nitric oxide (NO) can have an effective or detrimental role in septic shock. In the present study, we examined the effect of NO, an inflammatory mediator, on beta-glucan/indomethacin (IND)- induced septic shock by inhibiting its synthesis with N(G)-nitro-L-arginine methyl ester (L-NAME), a nonselective NO synthase (NOS) inhibitor. Nitrite concentration was used as an indicator of NO generation. Mortality in beta-glucan/IND-treated mice was increased by administering L-NAME. Numbers of bacteria in various organs of mice treated with beta-glucan/IND rose significantly within a couple of days of the administration of L-NAME. Additionally, TNF-alpha, IL-1beta, and IL-6 concentrations were enhanced in peritoneal exuded cells in culture. These results suggest a significant loss of the bactericidal activity of macrophages on the administration of a NOS inhibitor which enhanced the rate of enterobacterial invasion to the peritoneal cavity, resulting in systemic inflammatory response syndrome. The production of NO, therefore, provides a protective effect in beta-glucan/IND-induced sepsis.