Immunomodulation by orally administered beta-glucan in mice

Exploring β-glucan as a micro-nano system for oral delivery targeted the colon

The critical role of oral colon-specific delivery systems (OCDDS) is important for delivering active agents to the colon and rectum specifically via the oral route. The use of micro/nanostructured OCDDS further improves drug stability, bioavailability, and retention time, leading to enhanced therapeutic effects. However, designing micro/nanoscale OCDDSs is challenging due to pH changes, enzymatic degradation, and systemic absorption and metabolism. Biodegradable natural polysaccharides are a promising solution to these problems, and β-glucan is one of the most promising natural polysaccharides due to its unique structural features, conformational flexibility, and specific processing properties. This review covers the diverse chemical structures of β-glucan, its benefits (biocompatibility, easy modification, and colon-specific degradation), and various β-glucan-based micro/nanosized OCDDSs, as well as their drawbacks. The potential of β-glucan offers exciting new opportunities for colon-specific drug delivery.

[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.

Antitumor effect of soluble β-glucan as an immune stimulant

β-glucans are linear polysaccharides of d-glucose monomers linked through β-glycosidic bonds and are widely present in nature. Different sources lead to their structural differences. β-glucan has long been acknowledged to be a safe and functional component. Its biological activities include lipid-lowering, hypoglycemic, antitumor and immune regulation etc. A large number of studies have shown that soluble β-glucan can bind to their receptors on the surface of immune cells, activates the pro-inflammatory response of innate immune cells, and enhances the host's antitumor defense. A variety of soluble β-glucans have been widely used in clinical antitumor studies as an immunostimulant to treat the cancer patient. In this paper, we reviewed the molecular structure, antitumor immune activities, structure-activity relationship and clinical trials of soluble β-glucans in order to provide the overall scene of β-glucans as immunostimulant to fight the cancer.

Dynamics of Structural and Functional Changes in Gut Microbiota during Treatment with a Microalgal β-Glucan, Paramylon and the Impact on Gut Inflammation

Previously, we have shown that oral administration of yeast derived β-1,3/1,6-d-glucan enhances immune regulation and alters the composition of the gut microbiota. However, it is not known if other structurally distinct β-glucans have similar properties. Here, using C57BL/6 mice, we show the potential of a microalgae derived β-1,3-d-glucan, paramylon (PM), in shaping the gut microbiota and modulating the susceptibility to colitis. The community structure within the gut microbiota showed progressive changes including selective enrichment of specific communities and lowered community richness and diversity during prolonged oral treatment with PM. Compared to control mice, the gut microbiota of PM-treated mice had significantly higher abundance of Verrucomicrobia and lower abundance of Firmicutes. Specific taxa that were significantly more abundant in PM-treated mice include Akkermansia muciniphila and several Bacteroides members. Predictive functional analysis revealed overrepresentation of carbohydrate metabolism function in the fecal microbiota of PM recipients compared to controls, and this function was linked to Bacteroides spp. Prolonged pretreatment with PM not only diminished susceptibility to dextran sulfate sodium induced colitis severity, but also caused enhanced immune regulation. Overall, this study demonstrates the prebiotic properties of PM and the potential benefits of its prolonged oral consumption to gut health.

Pretreatment with Yeast-Derived Complex Dietary Polysaccharides Suppresses Gut Inflammation, Alters the Microbiota Composition, and Increases Immune Regulatory Short-Chain Fatty Acid Production in C57BL/6 Mice

BACKGROUND

β-Glucans (BGs), a group of complex dietary polysaccharides (CDPs), are available as dietary supplements. However, the effects of orally administered highly purified BGs on gut inflammation are largely unknown.

OBJECTIVES

The aim of this study was to investigate the impact of orally administering highly purified, yeast-derived BG (YBG; β-1,3/1,6-d-glucan) on susceptibility to colitis.

METHODS

Eight-week-old C57BL/6 (B6) mice were used in a series of experiments. Experiment (Expt) 1: male and female mice were treated every day, for 40 d, with saline (control) or 250 μg YBG, followed by 2.5% (wt:vol) dextran sulfate sodium (DSS) in drinking water during days 30-35; and colitis severity and intestinal immune phenotype were determined. Expt 2: female B6 mice were treated with saline or YBG for 30 d and intestinal immune phenotype, gut microbiota composition, and fecal SCFA concentrations were determined. Expt 3: female B6 mice were treated as in Expt 2, given drinking water with or without antibiotics [Abx; ampicillin (1 g/L), vancomycin (0.5 g/L), neomycin (1 g/L), and metronidazole (1 g/L)] during days 16-30, and gut immune phenotype and fecal SCFA concentrations were determined. Expt 4: female B6 Foxp3-green fluorescent protein (-GFP) reporter mice were treated as in Expt 3, and intestinal T-regulatory cell (Treg) frequencies and immune phenotypes were determined. Expt 5: female mice were treated as in Expt 1, given drinking water with or without antibiotics during days 16-40, and colitis severity and intestinal cytokine production were determined.

RESULTS

Compared with controls, the YBG group in Expt 1 exhibited suppressive effects on features of colitis, such as loss of body weight (by 47%; P < 0.001), shortening of colon (by 24%; P = 0.016), and histopathology severity score (by 45%; P = 0.01). The YBG group of Expt 2 showed a shift in the abundance of gut microbiota towards Bacteroides (by 16%; P = 0.049) and Verrucomicrobia (mean ± SD: control = 7.8 ± 0.44 vs. YBG = 21.0 ± 9.6%) and a reduction in Firmicutes (by 66%; P < 0.001). The YBG group also showed significantly higher concentrations of fecal SCFAs such as acetic (by 37%; P = 0.016), propionic (by 47%; P = 0.026), and butyric (by 57%; P = 0.013) acids. Compared with controls, the YBG group of Expt 2 showed higher frequencies of Tregs (by 32%; P = 0.043) in the gut mucosa. Depletion of gut microbiota in the YBG group of mice caused diminished fecal SCFA concentrations (Expt 3) and intestinal Treg frequencies (Expt 4). Compared with the YBG group, the YBG-(Abx) group of Expt 5 showed aggravated colitis features including loss of body weight (by >100%; P < 0.01) and colonic inflammation score (by 42%; P = 0.04).

CONCLUSIONS

Studies using B6 mice show that dietary BGs are beneficial for promoting intestinal health when the gut microbiota is intact. However, these CDPs may produce adverse effects if gut microbiota is compromised.

Yeast-Derived β-Glucan in Cancer: Novel Uses of a Traditional Therapeutic

An increased understanding of the complex mechanisms at play within the tumor microenvironment (TME) has emphasized the need for the development of strategies that target immune cells within the TME. Therapeutics that render the TME immune-reactive have a vast potential for establishing effective cancer interventions. One such intervention is β-glucan, a natural compound with immune-stimulatory and immunomodulatory potential that has long been considered an important anti-cancer therapeutic. β-glucan has the ability to modulate the TME both by bridging the innate and adaptive arms of the immune system and by modulating the phenotype of immune-suppressive cells to be immune-stimulatory. New roles for β-glucan in cancer therapy are also emerging through an evolving understanding that β-glucan is involved in a concept called trained immunity, where innate cells take on memory phenotypes. Additionally, the hollow structure of particulate β-glucan has recently been harnessed to utilize particulate β-glucan as a delivery vesicle. These new concepts, along with the emerging success of combinatorial approaches to cancer treatment involving β-glucan, suggest that β-glucan may play an essential role in future strategies to prevent and inhibit tumor growth. This review emphasizes the various characteristics of β-glucan, with an emphasis on fungal β-glucan, and highlights novel approaches of β-glucan in cancer therapy.

Effect of Lentinan on Peyer's patch structure and function in an immunosuppressed mouse model

Lentinan (LNT), a polysaccharide isolated from Lentinus edodes, has been shown to stimulate immune response. Despite its widespread use owing to its health benefits, epidemiologic and experimental studies that address the biological activities of LNT after oral administration to animals or humans are rare. In this study, the effects of LNT on the intestinal mucosal immune system of immunosuppressed mice were investigated. The number and size of the Peyer's patches (PPs), proliferation ability of PP lymphocytes, T and B lymphocyte percentage, and T-cell activation proportion, as well as the number of M-like cells in PPs, were determined. The antigen transfer ability of M-like cells and intestinal secretory immunoglobulin A (IgA) levels were also detected. After oral administration of LNT for 7 days, the number of PPs, lymphocytes in PPs, and the level of intestinal soluble IgA in immunosuppressed mice were increased. LNT maintained the percentage of T and B lymphocytes and upregulated the proportion of activated T cells in PPs. Furthermore, the number of M-like cells, which were differentiated from intestinal epithelial cells, and their antigen transfer ability were enhanced. These results indicate that orally administered LNT can improve the immune status of the intestinal mucosa in immunosuppressed mice.

Complex dietary polysaccharide modulates gut immune function and microbiota, and promotes protection from autoimmune diabetes

The dietary supplement and prebiotic values of β-glucan-rich products have been widely recognized and dietary approaches for modulating autoimmunity have been increasingly explored, we assess the impact of oral administration of high-purity yeast β-glucan (YBG) on gut immune function, microbiota and type 1 diabetes (T1D) using mouse models. Oral administration of this non-digestible complex polysaccharide caused a dectin-1-dependent immune response involving increased expression of interleukin-10 (IL-10), retinaldehyde dehydrogenase (Raldh) and pro-inflammatory cytokines in the gut mucosa. YBG-exposed intestinal dendritic cells induced/expanded primarily Foxp3⁺ , IL-10⁺ and IL-17⁺ T cells, ex vivo. Importantly, prolonged oral administration of low-dose YBG at pre-diabetic stage suppressed insulitis and significantly delayed the appearance of T1D in non-obese diabetic (NOD) mice. Further, prolonged treatment with YBG showed increased Foxp3⁺ T-cell frequencies, and a significant change in the gut microbiota, particularly an increase in the abundance of Bacteroidetes and a decrease in the Firmicute members. Oral administration of YBG, together with Raldh-substrate and β-cell antigen, resulted in better protection of NOD mice from T1D. These observations suggest that YBG not only has a prebiotic property, but also an oral tolerogenic-adjuvant-like effect, and these features could be exploited for modulating autoimmunity in T1D.

Branched mannans from the mushroom Cantharellus cibarius enhance the anticancer activity of natural killer cells against human cancers of lung and colon

Cantharellus cibarius branched mannans increase natural killer cells NK92 viability and proliferation and enhance their cytotoxicity against lung and colon cancer cells A549 and LS180, at the same time they do not affect lung and colon epithelial cells NL20 and CCD841 CoN.

Synergistic antitumor effect of polysaccharide from Lachnum sp. in combination with cyclophosphamide in hepatocellular carcinoma

Combination therapy with chemotherapeutics is attracting increasing attention as an important treatment option for hepatocellular carcinoma (HCC) due to its complex pathological characteristics. In this study, as a new therapy strategy, combination treatment of LEP-2a (a non-toxic polysaccharide from Lachnum sp.) with cyclophosphamide (CTX) was investigated. Results showed that combination treatment with LEP-2a and CTX processed a significantly synergistic anti-tumor effect in H22 tumor-bearing mice through Fas/FasL mediated caspase-dependent death pathway and mitochondria apoptosis pathway. Moreover, our study indicated that LEP-2a played a crucial role in enhancement of immune response, inhibition of tumor angiogenesis and down-regulation of survival associated proteins. Notably, side effects induced by CTX were relieved after LEP-2a treatment. These results support the conception that LEP-2a has the potential as an ideal adjuvant agent for a more effective combination therapy with CTX against HCC.

Barley β-glucan in poultry diets

There has been an increased interest in the use of immunomodulators as substitutes for antibiotics in food animal production. Beta-glucans from yeast and fungi may be ideal substitutes because of their positive effects on the avian immune system without adversely affecting poultry performance. Barley β-glucans, however, have not shown this potential due to the adverse effects dietary inclusion of barley has on poultry performance.

Immune-modulatory effects of dietary Yeast Beta-1,3/1,6-D-glucan

Beta-glucans are a heterogeneous group of natural polysaccharides mostly investigated for their immunological effects. Due to the low systemic availability of oral preparations, it has been thought that only parenterally applied beta-glucans can modulate the immune system. However, several in vivo and in vitro investigations have revealed that orally applied beta-glucans also exert such effects. Various receptor interactions, explaining possible mode of actions, have been detected. The effects mainly depend on the source and structure of the beta-glucans. In the meantime, several human clinical trials with dietary insoluble yeast beta-glucans have been performed. The results confirm the previous findings of in vivo studies. The results of all studies taken together clearly indicate that oral intake of insoluble yeast beta-glucans is safe and has an immune strengthening effect.

β-Glucans are involved in immune-modulation of THP-1 macrophages

SCOPE

We aimed to examine different immunological aspects of β-glucans derived from different food sources (oat, barley and shiitake) on phorbol myristate acetate (PMA)-differentiated THP-1 macrophages. Commercially purified barley β-glucan (commercial BG) and lentinan were included to compare β-glucans from the same origin but different degree of purity and processing.

METHODS AND RESULTS

Chemical composition and molecular weight distribution of β-glucan samples were determined. Inflammation-related gene expression kinetics (IL-1β, IL-8, nuclear factor kappa B [NF-κB] and IL-10) after 3, 6 and 24 h of stimulation with 100 μg/mL β-glucan were investigated. All tested β-glucans mildly upregulated the observed inflammation-related genes with differential gene expression patterns. Similar gene expression kinetics, but different fold induction values, was found for the crude β-glucan extracts and their corresponding commercial forms. Pre-incubation of THP-1 macrophages with β-glucans prior to lipopolysaccharide (LPS) exposure decreased the induction of inflammation-related genes compared to LPS treatment. No production of nitric oxide (NO) and hydrogen peroxide (H₂O₂) was detected in β-glucan stimulated THP-1 macrophages. Phagocytic activity was not different after stimulation by β-glucan samples.

CONCLUSION

Based on these in vitro analyses, it can be concluded that the analysed β-glucans have varying levels of immunomodulating properties, which are likely related to structure, molecular weight and compositional characteristic of β-glucan.

Intestinal and systemic immune development and response to vaccination are unaffected by dietary (1,3/1,6)-β-D-glucan supplementation in neonatal piglets

Infants are susceptible to infections in early life and must rely on their innate immune system for protection. β-Glucans potentiate immune responses. Therefore, we evaluated the influence of purified yeast (1,3/1,6)-β-d-glucan (Wellmune WGP, here referred to as WGP) on the development of the gastrointestinal tract and the intestinal and systemic immune systems in neonatal piglets. Piglets were fed formula containing 0 (control), 1.8, 18, or 90 mg WGP/kg body weight (BW) and were vaccinated against human influenza. Piglets were euthanized at 7 or 21 days of age. Piglet weight and small intestinal length and weight were unaffected by dietary WGP. In addition, WGP did not affect ileal crypt depth, villus height, or ascending colon cuff depth. Immune parameters not affected by WGP supplementation included T cell phenotypes, cytokine gene expression, and cell proliferation. However, vaccination and developmental effects were seen. Overall, the doses of 1.8, 18, and 90 mg/kg BW of dietary WGP had no effect on intestinal or immune development and did not improve the antibody response to vaccination in neonatal piglets.

Immunomodulatory dietary polysaccharides: a systematic review of the literature

BACKGROUND

A large body of literature suggests that certain polysaccharides affect immune system function. Much of this literature, however, consists of in vitro studies or studies in which polysaccharides were injected. Their immunologic effects following oral administration is less clear. The purpose of this systematic review was to consolidate and evaluate the available data regarding the specific immunologic effects of dietary polysaccharides.

METHODS

Studies were identified by conducting PubMed and Google Scholar electronic searches and through reviews of polysaccharide article bibliographies. Only articles published in English were included in this review. Two researchers reviewed data on study design, control, sample size, results, and nature of outcome measures. Subsequent searches were conducted to gather information about polysaccharide safety, structure and composition, and disposition.

RESULTS

We found 62 publications reporting statistically significant effects of orally ingested glucans, pectins, heteroglycans, glucomannans, fucoidans, galactomannans, arabinogalactans and mixed polysaccharide products in rodents. Fifteen controlled human studies reported that oral glucans, arabinogalactans, heteroglycans, and fucoidans exerted significant effects. Although some studies investigated anti-inflammatory effects, most studies investigated the ability of oral polysaccharides to stimulate the immune system. These studies, as well as safety and toxicity studies, suggest that these polysaccharide products appear to be largely well-tolerated.

CONCLUSIONS

Taken as a whole, the oral polysaccharide literature is highly heterogenous and is not sufficient to support broad product structure/function generalizations. Numerous dietary polysaccharides, particularly glucans, appear to elicit diverse immunomodulatory effects in numerous animal tissues, including the blood, GI tract and spleen. Glucan extracts from the Trametes versicolor mushroom improved survival and immune function in human RCTs of cancer patients; glucans, arabinogalactans and fucoidans elicited immunomodulatory effects in controlled studies of healthy adults and patients with canker sores and seasonal allergies. This review provides a foundation that can serve to guide future research on immune modulation by well-characterized polysaccharide compounds.

Human dendritic cells activated via dectin-1 are efficient at priming Th17, cytotoxic CD8 T and B cell responses

Background

Dendritic cells capture antigens through PRRs and modulate adaptive immune responses. The type of adaptive immune T cell response generated is dependent upon the type of PRR activated by the microbes. Dectin-1 is a C-type lectin receptor present on dendritic cells.

Methodology/Principal Findings

Here we show that selective dectin-1 agonist Curdlan can activate human DCs and induce the secretion of large amounts of IL-23, IL-1β, IL-6 and low levels of IL-12p70 as determined by ELISA. The Curdlan-stimulated DCs are efficient at priming naïve CD4 cells to differentiate into Th17 and Th1 cells. Furthermore, these CD4 T cells induce differentiation of B cells to secrete IgG and IgA. In addition, Curdlan-stimulated DCs promote the expansion and differentiation of Granzyme and perforin expressing cytotoxic T lymphocyte that display high cytolytic activity against target tumor cells in vitro.

Conclusions/Significance

These data demonstrate that DCs stimulated through Dectin-1 can generate efficient Th, CTL and B cell responses and can therefore be used as effective mucosal and systemic adjuvants in humans.

Effect of Sophy β-glucan on immunity and growth performance in broiler chicken

This study was carried out to determine the effect of Sophy β-glucan on immunity and growth performance in broilers. One group was treated with 1% β-glucan ad libitum with water and the other group was kept as the control. Vaccination for Infectious Bursal Disease was carried out on days 16 and 21. Blood samples were collected from birds, and antibody titres against IBD were measured. The mean body weight of the β-glucan treated group was significantly (P<0.05) higher than that of the control group. The mean antibody titres measured on days 25, 36 and 42 were significantly (P<0.05) higher in 1% β-glucan treated group than that of the control group, suggesting the presence of immune stimulating effect of β-glucan.

Benefits of oat β-glucan and sucrose feedings on infection and macrophage antiviral resistance following exercise stress

Oat β-glucan can counteract the exercise-induced increased risk for upper respiratory tract infection (URTI) in mice, which is at least partly mediated by its effects on lung macrophages. Substantial evidence in humans indicates that carbohydrate-containing sports drinks can offset the decreased immune function associated with stressful exercise. However, no studies in animals or humans have directly examined their effects on URTI using a controlled virus-challenge model. We examined the effects of sucrose feedings alone and in combination with oat β-glucan on susceptibility to infection and on macrophage antiviral resistance in mice following stressful exercise. These effects were also examined in rested, nonimmunocompromised control mice. Mice were assigned to one of four groups: H2O (water), sucrose (S), oat β-glucan (OβG), and sucrose + oat β-glucan (S+OβG). OβG and S treatments consisted of a solution of 50% OβG and 6% sucrose, respectively, and were administered in drinking water for 10 consecutive days. Exercise consisted of a treadmill run to fatigue performed on three consecutive days. Mice were then intranasally inoculated with a standardized dose of herpes simplex virus 1 (HSV-1) and monitored for morbidity and mortality for 21 days. Additional mice were used to determine macrophage antiviral resistance. In the exercise experiment, S, OβG, and S+OβG all reduced morbidity ( P < 0.05), while only S+OβG reduced mortality ( P < 0.05). Macrophage antiviral resistance was also increased in S, OβG, and S+OβG treatments ( P < 0.05). In resting controls, S and S+OβG reduced morbidity and mortality ( P < 0.05) and showed a trend toward increased macrophage antiviral resistance. There was no significant additive effect of S and OβG in either control or exercised animals. These data extend our previous work on the benefits of oat β-glucan to show that sucrose feedings have similar effects on susceptibility to respiratory infection and macrophage antiviral resistance in both resting controls and following exercise stress.

The influence of beta-glucan on immune responses in broiler chicks

Beta-1,3/1,6-glucan (beta-glucan) was tested as a possible immunomodulator. Chicken macrophages from a macrophage cell line MQ-NCSU and from abdominal exudate of broiler chickens were exposed to various concentrations of beta-glucan in vitro. In addition, day-old broiler chicks were fed a diet containing 0, 20, and 40 mg/kg beta-glucan in the starter and 0, 20, and 20 mg/kg in the grower diet. Several baseline immune parameters were examined following such exposures. The results showed that beta-glucan exposure increased nitrite and interleukin-1 (IL-1) production as well as induced macrophage to proliferate in culture. However, IL-6 production was not affected. Dietary beta-glucan supplementation increased the macrophage phagocytic activity, anti-sheep red blood cells antibody response post-boost, as well as the PHAP-mediated lymphoproliferative response measured as a toe-web swelling. The percentage of CD4+, CD8+, and CD4+/CD8+ double positive lymphocytes in the intestinal intraepithelial leukocytes was increased in beta-glucan supplemented chicks. Furthermore, the primary and secondary lymphoid organs such as bursa of Fabricius, thymus and spleen were larger in beta-glucan-supplemented chicks as compared to the chicks on basal diet. The findings of these studies which showed that beta-glucan improves several baseline immune responses in the chicken imply that beta-glucan can be used as a possible immunomodulator in food animals such as the chicken.

Effect of beta-glucans on an ETEC infection in piglets

The effect of orally administered beta-glucans in protecting pigs against an ETEC infection after weaning was analysed in this study. Three beta-glucans that differed in origin (Saccharomyces cerevisiae (MCG (Macrogard) and G2) or Sclerotium rolfsii (G3)) and/or extraction procedure were tested. Pigs fed for 2 weeks after weaning with these glucans were less susceptible to an F4+ ETEC infection in comparison with the control group. This was evidenced by a reduction in the faecal excretion of F4+ Escherichia coli as well as a reduced F4-specific serum antibody response. This decrease in faecal excretion was statistically significant for pigs fed with the MCG glucan in a first experiment and with the G3 glucan in a second experiment; diarrhoea was milder in the glucan-supplemented groups and was significantly reduced in the MCG-supplemented group. Furthermore, a lower amount of F4-specific IgM antibody-secreting cells (ASC) was found in the lymphoid tissues of pigs fed with G2 or G3 glucans in comparison with the control pig, as well as lower F4-specific IgA ASC in G3-fed pigs in comparison with the control pig. This study showed that beta-glucans can protect against an ETEC infection. Both MCG from S. cerevisiae and G3 from S. rolfsii, resulted in significant effects. To our knowledge, this is the first in vivo study, in which the use of beta-glucans as feed ingredient for just-weaned piglets was tested for their protective effects against ETEC infection.

The immunobiology of mushrooms

There has been enormous interest in the biologic activity of mushrooms and innumerable claims have been made that mushrooms have beneficial effects on immune function with subsequent implications for inhibition of tumor growth. The majority of these observations are anecdotal and often lack standardization. However, there remains considerable data on both in vitro and in vivo effects that reflect on the potential of mushroom compounds to influence human immunity. A number of these effects are beneficial but, unfortunately, many responses are still characterized based on phenomenology and there is more speculation than substance. With respect to tumor biology, although many neoplastic lesions are immunogenic, tumor antigens frequently are self antigens and induce tolerance and many patients with cancer exhibit suppressed immune responses, including defective antigen presentation. Therefore, if and when mushroom extracts are effective, they more likely function as a result of improved antigen presentation by dendritic cells than by a direct cytopathic effect. In this review we attempt to place these data in perspective, with a particular focus on dendritic cell populations and the ability of mushroom extracts to modulate immunity. There is, at present, no scientific basis for the use of either mushrooms or mushroom extracts in the treatment of human patients but there is significant potential for rigorous research to understand the potential of mushrooms in human disease and thence to focus on appropriate clinical trials to demonstrate effectiveness and/ or potential toxicity.

Benefits of oat beta-glucan on respiratory infection following exercise stress: role of lung macrophages

Exercise stress is associated with an increased risk for upper respiratory tract infection (URTI). We have shown that consumption of the soluble oat fiber beta-glucan (ObetaG) can offset the increased risk for infection and decreased macrophage antiviral resistance following stressful exercise; however, the direct role of macrophages is unknown. This study examined the effect of macrophage depletion on the benefits of orally administered ObetaG on susceptibility to infection (morbidity, symptom severity, and mortality) following exercise stress. CL(2)MDP (Ex- H(2)O-CL(2)MDP, Ex-ObetaG-CL(2)MDP, Con-H(2)O-CL(2)MDP, Con-ObetaG-CL(2)MDP)-encapsulated liposomes were administered intranasally to deplete macrophages, and PBS (Ex-H(2)O-PBS, Ex-ObetaG-PBS, Con-H(2)O-PBS, Con-ObetaG-PBS)-encapsulated liposomes were given to macrophage-intact groups. Ex mice ran to volitional fatigue on a treadmill for 3 consecutive days, and ObetaG mice were fed a solution of 50% ObetaG in their drinking water for 10 consecutive days before infection. Fifteen minutes following the final bout of Ex or rest, mice were intranasally inoculated with 50 microl of a standardized dose of herpes simplex virus-1. Ex increased morbidity (P < 0.001) and symptom severity (P < 0.05) but not mortality (P = 0.09). The increase in morbidity and symptom severity was blocked by ObetaG consumption for 10 consecutive days before exercise and infection [morbidity (P < 0.001) and symptom severity (P < 0.05)]. Depletion of macrophages negated the beneficial effects of ObetaG on reducing susceptibility to infection following exercise stress, as evidenced by an increase in morbidity (P < 0.01) and symptom severity (P < 0.05). Results indicate that lung macrophages are at least partially responsible for mediating the beneficial effects of ObetaG on susceptibility to respiratory infection following exercise stress.

Oat beta-glucan effects on neutrophil respiratory burst activity following exercise

Fatiguing exercise has been associated with a decrease in certain functions of neutrophils, whereas moderate exercise has generally been associated with an increase. Consumption of oat beta-glucan (ObetaG), a soluble fiber and mild immune system enhancer, may offset the immunosuppression associated with intense training and perhaps further enhance the benefits of moderate exercise.

PURPOSE

To test the effects of ObetaG consumption on neutrophil function and number after both moderate and fatiguing exercise.

METHODS

Male mice were assigned to one of six treatment groups. Fatiguing exercise mice (Ftg-ObetaG and Ftg-H2O) ran to volitional fatigue on a treadmill for three consecutive days, and moderate exercise mice (Mod-ObetaG and Mod-H2O) ran for six consecutive days for 1 h. Control mice (Con-ObetaG and Con-H2O) were exposed to the treadmill environment but did not run. ObetaG was consumed in the drinking water (approximately 0.6 mL x d(-1)) for 10 consecutive days. After rest or exercise on the last day of training, mice were given a 1-mL i.p. injection of thioglycollate. Mice were sacrificed 3 h later; neutrophils were harvested from the peritoneal cavity and counted, and their respiratory burst activity was measured using flow cytometry.

RESULTS

Both moderate exercise and ObetaG increased neutrophil burst activity, whereas fatiguing exercise had no effect. Neutrophil number was increased by fatiguing exercise and ObetaG, but not moderate exercise. There were no additive effects of exercise and ObetaG on either of these variables.

CONCLUSION

These data suggest that although not additive in their effects, both ObetaG and exercise can alter overall neutrophil respiratory burst activity (number and/or function), but only ObetaG increased both number and function, which may have important ramifications for defense against infection.

Immunomodulating and anticancer agents in the realm of macromycetes fungi (macrofungi)

Nowadays macrofungi are distinguished as important natural resources of immunomodulating and anticancer agents and with regard to the increase in diseases involving immune dysfunction, cancer, autoimmune conditions in recent years, applying such immunomodulator agents especially with the natural original is vital. These compounds belong mainly to polysaccharides especially beta-d-glucan derivates, glycopeptide/protein complexes (polysaccharide-peptide/protein complexes), proteoglycans, proteins and triterpenoids. Among polysaccharides, beta(1-->3)-d-glucans and their peptide/protein derivates and among proteins, fungal immunomodulatory proteins (Fips) have more important role in immunomodulating and antitumor activities. Immunomodulating and antitumor activity of these metabolites related to their effects to act of immune effecter cells such as hematpoietic stem cells, lymphocytes, macrophages, T cells, dendritic cells (DCs), and natural killer (NK) cells involved in the innate and adaptive immunity, resulting in the production of biologic response modifiers. In this review we have introduced the medicinal mushrooms' metabolites with immunomoduling and antitumor activities according to immunological evidences and then demonstrated their effects on innate and adaptive immunity and also the mechanisms of activation of immune responses and signaling cascade. In addition, their molecular structure and their relation to these activities have been shown. The important instances of these metabolites along with their immunomodulating and/or antitumor activities isolated from putative medicinal mushrooms are also introduced.

A Polysaccharide Extracted from Rice Bran Fermented with Lentinus edodes Enhances Natural Killer Cell Activity and Exhibits Anticancer Effects

The objective of this study was to investigate the activation of natural killer (NK) cells and anticancer effects of exo-biopolymer from rice bran cultured with Lentinus edodes [rice bran exo-biopolymer (RBEP)]. Oral administration of RBEP induced the activation of NK cells in a dose-dependent manner. RBEP also prolonged the life spans of mice transplanted with Sarcoma-180 cells and inhibited growing Sarcoma-180 cells in intraperitoneum. Solid tumor growth was also suppressed by oral administration of RBEP in C57/Bl6 mice transplanted with B16/Bl6 melanoma. Intraperitoneal injection of RBEP was more effective than oral administration at the same dosage in mice with transplanted tumor cells. According to this result, when RBEP directly contacts immune cells, the anticancer activity is higher than by indirectly inducing an immune response through oral administration. Therefore, we suggest that the administration of RBEP may be effective for preventing and/or treating cancer through NK cell activation. However, further studies are needed to elucidate the possible mechanisms of the anticancer activity and to investigate the other beneficial effects of RBEP for the development of a new biological response modifier.

Effects of supplementation of β-glucans on growth performance, nutrient digestibility, and immunity in weanling pigs

Two experiments were conducted to evaluate the efficacy of beta-glucan on growth performance, nutrient digestibility, and immunity in weanling pigs. In Exp. 1, 210 weanling pigs (6.38 +/- 0.92 kg of BW) were fed dietary beta-glucan (0, 0.01, 0.02, 0.03, or 0.04%) for 5 wk. In Exp. 2, 168 pigs (6.18 +/- 1.31 kg of BW) were fed no beta-glucan or antibiotics (T1), 0.02% beta-glucan (T2), only antibiotics (T3), or 0.02% beta-glucan with antibiotics (T4) for 8 wk. In Exp. 2, the antibiotics fed were apramycin and carbadox in phase I (0 to 2 wk) and carbadox and chlortetracycline in phase II (3 to 8 wk). During Exp. 2, the performance study was conducted for 5 wk, and the immune response was tested until 8 wk. In Exp. 1, there was a trend for a linear increase (P = 0.068) in ADG as the dietary beta-glucan concentration increased in the diet. The digestibilities of DM, GE, CP, ether extract, Ca, and P increased linearly (P < 0.05) in the beta-glucan-supplemented pigs. In Exp. 2, the overall ADG was greater (P < 0.05) in treatment T4 compared with the control group (T1). Also, except for P, this group showed greater (P < 0.05) nutrient digestibilities than the control group. In Exp. 2, at d 15, 24, and 46 antibody titers were measured by ELISA against Pasteurella multocida type A and D after vaccination with atrophic rhinitis, and they differed significantly (P < 0.05) with no particular trend. Flow cytometry was used to determine porcine lymphocyte subpopulations at 4 and 8 wk of Exp. 2. There was an increase in CD4 cells (P < 0.05) and a trend for an increase in CD8 cells (P < 0.10) at 8 wk in pigs fed the T2 diet compared with the other groups. Overall, increasing the dietary concentrations of beta-glucan did not improve ADG without antibiotic, and in weanling pigs antibiotics seem to be more effective in improving nutrient digestibilities and growth performance than beta-glucan.

Effects of supplementation of beta-glucan on the growth performance and immunity in broilers

Two experiments were conducted to evaluate the efficacy of beta-glucan on commercial broilers. In experiment 1, one hundred and forty-four broiler chicks were employed in a 2x3 factorial design with cage and open floor housing with three levels of beta-glucan viz. 0%, 0.02% and 0.04%. In experiment 2, ninety-six broilers were used with 4 treatments: No beta-glucan and antibiotic (T1), beta-glucan 0.03% (T2), antibiotic (T3), and beta-glucan 0.03% + antibiotic (T4) for 34 d with 3 replicates of 8 chicks each in both studies. During experiment 1 there was no significant effect of the feeding system or the beta-glucan levels on the performance from 0 to 17 d but during 18-34 days birds housed on the open floor had significantly (p<0.0001) higher weight gain compared with those in cages. In experiment 2, no significant effect was noticed on the weight gains when the effect of beta-glucan, antibiotic or their interaction were tested. The retention of dry matter increased in both experiments with beta-glucan supplementation. The CD8 and TCR 1 cells were significantly higher in the 0.04% beta-glucan group at 42 days as compared with the control. It could be concluded that beta-glucan supplementation was beneficial for broilers.

Oral delivery and gastrointestinal absorption of soluble glucans stimulate increased resistance to infectious challenge

Glucans are immunomodulatory carbohydrates found in the cell walls of fungi and certain bacteria. We examined the pharmacokinetics of three water-soluble glucans (glucan phosphate, laminarin, and scleroglucan) after oral administration of 1 mg/kg doses in rats. Maximum plasma concentrations for glucan phosphate occurred at 4 h. In contrast, laminarin and scleroglucan showed two plasma peaks between 0.5 and 12 h. At 24 h, 27 +/- 3% of the glucan phosphate and 20 +/- 7% of the laminarin remained in the serum. Scleroglucan was rapidly absorbed and eliminated. The liver did not significantly contribute to the clearance of plasma glucan. Biological effects were further studied in mice. Following oral administration of 1 mg, glucans were bound and internalized by intestinal epithelial cells and gut-associated lymphoid tissue (GALT) cells. Internalization of glucan by intestinal epithelial cells was not Dectin-dependent. GALT expression of Dectin-1 and toll-like receptor (TLR) 2, but not TLR4, increased following oral administration of glucan. Oral glucan increased systemic levels of interleukin (IL)-12 (151 +/- 15%) in mice. Oral glucan administration also increased survival in mice challenged with Staphylococcus aureus or Candida albicans. These data demonstrate that orally administered water-soluble glucans translocate from the gastrointestinal (GI) tract into the systemic circulation. The glucans are bound by GI epithelial and GALT cells, and they modulate the expression of pattern recognition receptors in the GALT, increase IL-12 expression, and induce protection against infectious challenge.

Immunostimulating properties of intragastrically administered Acetobacter-derived soluble branched (1,4)-beta-D-glucans decrease murine susceptibility to Listeria monocytogenes

We previously found that AC-1, an extracellular polysaccharide, produced by Acetobacter xylinum and composed of (1,4)-beta-D-glucan with branches of glucosyl residues, showed a strong activity to induce production of interleukin-12 (IL-12) p40 and tumor necrosis factor alpha by macrophages in vitro via Toll-like receptor 4 (TLR-4) signaling. In the present study, we examined the effect of oral administration of AC-1 on protective immunity against Listeria monocytogenes. Mice were given AC-1 or phosphate-buffered saline (PBS) intragastrically 2 days before, on the day of, and 2 days after an intraperitoneal inoculation of L. monocytogenes. The survival rate of AC-1-treated mice was significantly improved and bacterial growth in AC-1-treated mice was severely retarded compared to those of PBS-treated mice after infection with L. monocytogenes. IL-12 p40 levels in serum and magnitudes of CD4+ Th1 and CD8+ Tc1 responses against Listeria antigen were significantly higher in AC-1-treated mice than in PBS-treated mice. The effect of AC-1 on antilisterial activity was diminished in C3H/HeJ mice carrying mutated TLR-4. Thus, AC-1, a potent IL-12 inducer through TLR-4, enhanced protective immunity against L. monocytogenes via augmentation of Th1 responses. These results suggest that infectious processes driven by intracellular microorganisms could be prevented to develop by the (1,4)-beta-D-glucan.

Effects of moderate exercise and oat β-glucan on lung tumor metastases and macrophage antitumor cytotoxicity

Both moderate exercise and the soluble fiber β-glucan can have beneficial effects on the initiation and growth of tumors, but the data are limited, and there is no information on their combined effects. This study tested the independent and combined effects of short-term moderate-exercise training and the soluble oat fiber β-glucan (OβG) on the metatastic spread of injected tumor cells and macrophage antitumor cytotoxicity. Male C57BL/6 mice were assigned to one of four groups: exercise (Ex)-H2O, Ex-OβG, control (Con)-H2O, or Con-OβG. OβG was fed in the drinking water for 10 days before tumor administration and death. Exercise consisted of treadmill running (1 h/day) for 6 days. After rest or exercise on the last day of training, syngeneic B16 melanoma cells (2 × 105) were administered via intravenous injection ( n = 8–11 per group). Lungs were removed 14 days later, and tumor foci were counted. Additional mice ( n = 8 per group) were killed, and peritoneal macrophages were assayed for cytotoxicity against the same mouse tumor cell line at various effector-to-target ratios. Both moderate exercise and OβG decreased lung tumor foci and increased macrophage cytotoxicity. However, there were no differences in lung tumor foci and macrophage cytotoxicity between Ex-OβG and either Ex-H2O or Con-OβG. These data suggest that, although not additive in their effects, both short-term moderate-exercise training and consumption of the soluble OβG can decrease the metatastic spread of injected B16 melanoma cells, and these effects may be mediated in part by an increase in macrophage cytotoxicity to B16 melanoma.

Mechanism by which orally administered beta-1,3-glucans enhance the tumoricidal activity of antitumor monoclonal antibodies in murine tumor models

Antitumor mAb bind to tumors and activate complement, coating tumors with iC3b. Intravenously administered yeast beta-1,3;1,6-glucan functions as an adjuvant for antitumor mAb by priming the inactivated C3b (iC3b) receptors (CR3; CD11b/CD18) of circulating granulocytes, enabling CR3 to trigger cytotoxicity of iC3b-coated tumors. Recent data indicated that barley beta-1,3;1,4-glucan given orally similarly potentiated the activity of antitumor mAb, leading to enhanced tumor regression and survival. This investigation showed that orally administered yeast beta-1,3;1,6-glucan functioned similarly to barley beta-1,3;1,4-glucan with antitumor mAb. With both oral beta-1,3-glucans, a requirement for iC3b on tumors and CR3 on granulocytes was confirmed by demonstrating therapeutic failures in mice deficient in C3 or CR3. Barley and yeast beta-1,3-glucan were labeled with fluorescein to track their oral uptake and processing in vivo. Orally administered beta-1,3-glucans were taken up by macrophages that transported them to spleen, lymph nodes, and bone marrow. Within the bone marrow, the macrophages degraded the large beta-1,3-glucans into smaller soluble beta-1,3-glucan fragments that were taken up by the CR3 of marginated granulocytes. These granulocytes with CR3-bound beta-1,3-glucan-fluorescein were shown to kill iC3b-opsonized tumor cells following their recruitment to a site of complement activation resembling a tumor coated with mAb.

Effects of Oat ??-Glucan on Innate Immunity and Infection after Exercise Stress

PURPOSE

To test the effects of oat beta-glucan (ObetaG) on respiratory infection, macrophage antiviral resistance, and NK cytotoxicity.

METHODS

Mice were randomly assigned to one of four groups: Ex-H2O, Ex-ObetaG, Con-H2O, or Con-ObetaG. ObetaG was fed in the drinking water for 10 d before intranasal inoculation of HSV-1 or sacrifice. Exercise consisted of treadmill running to volitional fatigue (approximately 140 min) for three consecutive days. Fifteen minutes after the last bout of exercise or rest, mice (N = 24) were intranasally inoculated with a standardized dose of HSV-1. Mice were monitored twice daily for morbidity and mortality. Additional mice were sacrificed after exercise, peritoneal macrophages were obtained via i.p. lavage and assayed for antiviral resistance to HSV-1 (N = 18), and spleens were harvested and assayed for NK cell cytotoxicity (N = 12).

RESULTS

Exercise stress was associated with a 28% increase in morbidity (P = 0.036) and 18% increase in mortality (P = 0.15). Ingestion of ObetaG before infection prevented this increase in morbidity (P = 0.048) and mortality (P = 0.05). Exercise stress was associated with a decrease in macrophage antiviral resistance (P = 0.007), which was blocked by ingestion of ObetaG (P < 0.001). There were no effects of exercise or ObetaG on NK cytotoxicity.

CONCLUSION

These data suggest that daily ingestion of ObetaG may offset the increased risk of URTI associated with exercise stress, which may be mediated, at least in part, by an increase in macrophage antiviral resistance.

Effects of moderate exercise and oat β-glucan on innate immune function and susceptibility to respiratory infection

Both moderate exercise and the soluble oat fiber β-glucan can increase immune function and decrease risk of infection, but no information exists on their possible combined effects. This study tested the effects of moderate exercise and oat β-glucan on respiratory infection, macrophage antiviral resistance, and natural killer (NK) cell cytotoxicity. Mice were assigned to four groups: exercise and water, exercise and oat β-glucan, control water, or control oat β-glucan. Oat β-glucan was fed in the drinking water for 10 days before intranasal inoculation of herpes simplex virus type 1 (HSV-1) or euthanasia. Exercise consisted of treadmill running (1 h/day) for 6 days. Macrophage resistance to HSV-1 was increased with both exercise and oat β-glucan, whereas NK cell cytotoxicity was only increased with exercise. Exercise was also associated with a 45 and 38% decrease in morbidity and mortality, respectively. Mortality was also decreased with oat β-glucan, but this effect did not reach statistical significance. No additive effects of exercise and oat β-glucan were found. These data confirm a positive effect of both moderate exercise and oat β-glucan on immune function, but only moderate exercise was associated with a significant reduction in the risk of upper respiratory tract infection in this model.

Repeated dose oral toxicological evaluation of concentrated barley beta-glucan in CD-1 mice including a recovery phase

The cholesterol-lowering effect observed following consumption of oats and barley is attributable to the beta-glucan component of the soluble fiber fraction of these cereal grains. beta-Glucan has also been reported to modulate immune activity, however, few studies have evaluated the hematological effects of beta-glucan following oral exposure. In the current study, a concentrated beta-glucan (64%) preparation from barley (Barley Betafiber) was blended into mouse feed at concentrations of 1, 5, or 10% (corresponding to approximately 0.7, 3.5, and 7% beta-glucan) and evaluated in CD-1 mice. Plasma was collected for clinical chemistry and hematological measurements at the initiation of the study and again following 14 and 28 days of exposure. Plasma was also collected from animals that consumed the same diets for 28-days but were switched to control diet (containing no supplemental beta-glucan) for an additional 14-day period to evaluate reversibility or delayed occurrence of treatment-related changes. Half of the animals were sacrificed for histopathologic analysis following the 28-day exposure period and the other half were evaluated following the recovery period. Histopathologic analysis focused on primary lymphoid organs and lymph nodes proximal and distal to the route of exposure. An additional group of untreated animals (nai;ve) was bled and sacrificed at day 0, 14, 27 and 41 for comparison of the hematology parameters with those of the control group because it was not known if multiple blood draws would affect hematology parameters. Compared to animals consuming the control diet, no treatment-related adverse effects were observed in hematological or clinical chemistry measurements or in organ weights and immunopathology in either sex following consumption of concentrated barley beta-glucan for 28-days or following the recovery period. Likewise, no differences were observed between the nai;ve and control groups. Results from this study showed that consumption of concentrated barley beta-glucan did not cause treatment-related inflammatory or other adverse effects in CD-1 mice.

Botanical medicines for the treatment of cancer: rationale, overview of current data, and methodological considerations for phase I and II trials

There appears to be exceptional and growing public enthusiasm for botanical, or "herbal", medicines, especially amongst cancer patients. This has recently begun to be matched by increasing scientific attention. Whilst it is known that plant extracts are active against cancer, the standard approach has been to isolate, synthesize and administer the single chemical compound thought responsible for this effect. However, different components in a botanical may have synergistic activities. There is also some evidence that the presence of multiple compounds in a botanical extract can buffer the toxic effects of a single constituent. Though many of the botanicals popular among patients are probably not of benefit (e.g. Mistletoe, Pau D'arco), several botanicals have shown promise in Phase III (Sho-saiko-to, PSK) or Phase II (PC-SPES) trial. Quality control of botanicals poses significant challenges: small differences in genetics, soil, temperature, moisture and time of harvesting can lead to significant differences in the concentration of important constituents. Phase I and II methodology is also problematic: botanicals have low toxicity and are unlikely to cause rapid tumor regression. There is currently minimal regulation of botanical medicines.