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Β-Glucans, History, and the Present: Immunomodulatory Aspects and Mechanisms of Action

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Β-Glucans, History, and the Present: Immunomodulatory Aspects and Mechanisms of Action Journal of Immunotoxicology ISSN: 1547-691X (Print) 1547-6901 (Online) Journal homepage: http://www.tandfonline.com/loi/iimt20 β-Glucans, History, and the Present: Immunomodulatory Aspects and Mechanisms of Action M. Novak & V. Vetvicka To cite this article: M. Novak & V. Vetvicka (2008) β-Glucans, History, and the Present: Immunomodulatory Aspects and Mechanisms of Action, Journal of Immunotoxicology, 5:1, 47-57, DOI: 10.1080/15476910802019045 To link to this article: https://doi.org/10.1080/15476910802019045 Published online: 09 Oct 2008. Submit your article to this journal Article views: 2885 Citing articles: 107 View citing articles Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=iimt20 Journal of Immunotoxicology, 5:47–57, 2008 Copyright c Informa Healthcare USA, Inc. ISSN: 1547-691X print / 1547-6901 online DOI: 10.1080/15476910802019045 REVIEW ARTICLE β-Glucans, History, and the Present: Immunomodulatory Aspects and Mechanisms of Action M. Novak Institute of Chemical Technology, Prague, Czech Republic V. Vetvicka Department of Pathology, University of Louisville, Louisville, Kentucky, USA similar or nearly identical immune reactions in macroorganisms, The present paper represents a comprehensive up-to-date can differ in origin as well as in their primary, secondary, or review of β-glucans, their chemical and biological properties, tertiary structures or their solubility in water or alkalies. Due and their role in immunological reactions. β-D-Glucans belong to these factors, numerous discrepancies can be found in the to a group of physiologically active compounds called biological literature. Some sources of β-glucans are listed in Table 1. response modifiers and represent highly conserved structural β− components of cell walls in yeast, fungi, or seaweed. Despite almost Glucans show notable physiological effects; this is their 150 years of research, the exact mechanisms of their action remain most important quality and the reason why so much atten- unclear. The present review starts with the history of glucans. tion has been devoted to them. They belong to a group of Next, attention is focused on sources and structure, comparing the physiologically active compounds, collectively termed biolog- effects of physicochemical properties, and sources on biological ical response modifiers (BRM). According to their effects, effects. As glucans belong to natural products useful in preventing various diseases, they have been highly sought after throughout BRM can be classified into two groups – cytokines, respon- human history. Based on extensive recent research, this paper sible for communication between immune system cells and explains the various mechanisms of effects and the ways glucans regulation of the system, and immuno-modulators. The im- mediate their effects on defense reactions against infections. munomodulators are able to positively (i.e., immunopotentia- Despite the fact that predominately pharmacological effects of tion) or negatively (i.e., immunosuppression) manipulate the glucans are positive, their unfavorable and potentially toxic side effects were not overlooked. In addition, attention was focused immune system. Different known immunomodulators can be on the future research, possible alternatives such as synthetic classified into three groups (Werner, 1987): 1) Intact microbes oligosaccharides, and on clinical applications. (e.g., Bacille Calmette-Guerin´ ) and components of microbial cells (e.g., endotoxin of Gram-negative microorganisms (LPS), Keywords defense, glucan, history, immunity muramyldipeptide (MDP), fungal polysaccharides (zymosan, β- glucans), polynucleotides, bestatine); 2) Natural components of 1. INTRODUCTION a normal immune system (e.g., thymic hormones, lymphokines, Generally, β-glucan is a chemical name of a polymer of β- monokines); and, 3) Synthetic compounds (e.g., levamisole, iso- glucose. There are more of such polymers, differing in glycosidic prinosine, diethyldithiocarbamate). bond position. Cellulose, (1→4)-β-D-glucan, is an example. The Thus far, among many known and tested immunomodulators following data refer to homopolymers of glucose having a linear of the first group, polysaccharides isolated from different mi- molecule with (1→3)-β-D-glycosidic linkages or a branched croorganisms and plants are the most important. A large number one, with side chains bound by (1→6)-β-D-glycosidic linkages. of such polysaccharides, which act only as immunpotentiators, β Although chemically heterogeneous, these polysaccharides are is known (Whistler et al., 1976). As mentioned earlier, -glucans usually termed by common name “β-glucans.” It is necessary to belong to this group. take into account that these compounds, which otherwise caused 2. HISTORY At the beginning of the 18th Century, it was already known Received 12 September 2007; accepted 7 October 2007 that certain infectious diseases showed a therapeutic effect Address correspondence to Professor Vaclav Vetvicka, Univer- sity of Louisville, Department of Pathology, 511 S. Floyd, MDR on malignant processes. Purposeful use of such therapy dates th Bldg., Rm. 224, Louisville, KY 40202, USA; e-mail: Vaclav.vetvicka@ approximately from the middle of the 19 Century, when louisville.edu Bush (Bush, 1850) performed experiments in curing sarcoma 47 48 NOVAK AND VETVICKA TABLE 1 In time, other polysaccharide immunomodulators were Some β-glucans with immunomodulatory effects sought and among them were β-glucans. Their investigation be- gan in the 1960s and 1970s. Two lines can be traced in β-glucan Character history, each based on different starting points but gradually Name Source of polymer converging. The first took place chiefly in the United States and Curdlan Alcaligenes faecalis linear Europe, the second in Asia, primarily in Japan. Research on laminaran Laminaria sp. linear β-glucans in the Euro-American milieu was based on knowl- pachymaran Poria cocos linear edge of immunomodulatory effects of zymosan, a mixture of lentinan Lentinus edodes branched polysaccharides isolated from the cell walls of Saccharomyces Pleuran (HA-glucan) Pleurotus ostreatus branched cerevisiae. Zymosan was for the first time prepared and investi- schizophyllan Schizophyllum commune branched gated by Pillemer and Ecker (1941) in the 1940s and since that sclerotinan (SSG) Sclerotinia sclerotiorum branched time, it has been used in many physiological and immunologi- scleroglucan Sclerotium glucanicum, branched cal studies. Zymosan is potent stimulator especially of alveolar S. rolfsii macrophages and, among others, it induces the release of a series grifolan Grifola frondosa branched of cytokines, mainly interleukin (IL-8), from human neutrophils. T-4-N, T-5-N Dictyophora indusiata branched Although zymosan was able to stimulate non-specific im- yeast glucan Saccharomyces cerevisiae branched mune response, at the onset it was not clear what component of this rather crude composition is responsible for that activity. When zymosan was examined in detail, β-glucan was identified by infecting patients with erysipelas, i.e., with β-hemolytic as the component of primary effect. It was subsequently isolated streptococci of the Group A. These therapeutical procedures and its immunological effects were investigated. This research were repeated toward the end of the 19th Century by Coley was pioneered by Nicholas R. DiLuzio (i.e., see DiLuzio and (Coley, 1894), who applied less dangerous extracts of microbial Riggi, 1970, Williams et al., 1980) at Tulane University in New cultures, in this case from cultures of Bacillus prodigiosus (now Orleans. Serratia marcescens). This extract was at these times known as The arrival of β-glucan in Japan was different. In Asian “Coley’s toxin,” and was lately determined as interleukin IL-12 medicine, consumption of different medicinal mushrooms (e.g., (Tsung and Norton, 2006). shiitake, maitake, reishi, etc.) has a long tradition. In detailed However, Coley does not have priority in this regard. At studies of the biological effects of these mushrooms, especially the time, it was already known that certain components of mi- the anticancer actions, β-glucans were again found to be a main croorganisms caused in macroorganisms, especially mammalian cause of non-specific immunomodulation. The source of this ones, ferocious reactions comparable to pathophysiological con- investigation is associated with Goro Chihara from Teikyo Uni- ditions during infection by intact microbes. It is likely that the versity in Kawasaki, who isolated β-glucan, named by him lenti- first investigated substance with these properties was LPS of nan, from mushroom shiitake (Lentinus edodes,nowLentinula Gram-negative bacteria (e.g., Escherichia, Salmonella, Shigella, edodes) (Chihara et al., 1969). Pseudomonas, Neisseria, and Haemophilus spp.); a paper de- All sufficiently-purified polysaccharidic immunomodulators scribing the endotoxin was published in 1865 (Billroth, 1865). distinguish themselves by very low toxicity (e.g., lentinan has In both humans and experimental animals, LPS induces in- an LD50(mouse) > 1600 mg/kg [Chihara et al., 1982]). Time in- creased phagocytosis with a potential protective effect for host. corporation of β-glucans in the history of immunomodulation However, its toxic effects (such as fever, diarrhea, hypotensive is shown in Table 2. shock, intravascular coagulation, multiple organ dysfunctions) The history of the investigation of the chemical composi- completely predominate.
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